DENDRITE-FREE ANODES AND CURRENT COLLECTORS FOR LITHIUM METAL BATTERIES AND LITHIUM-ION BATTERIES STATEMENT OF GOVERNMENT INTEREST [0001] This invention was made with government support under DE-EE0009649 awarded by the Department of Energy (DOE). The government has certain rights in the invention. CROSS REFERENCE TO RELATED PATENT APPLICATIONS [0002] This patent application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63/533,998 entitled “DENDRITE-FREE ANODES AND CURRENT COLLECTORS FOR LITHIUM METAL BATTERIES AND LITHIUM-ION BATTERIES”, filed in the U.S. Patent Trademark Office on August 22, 2023, the contents of which is incorporated herein in its entirety. FIELD OF THE INVENTION [0003] The disclosed concept pertains to the identification, design, fabrication and methods of preparing multi-component alloy (MCA) systems with body-centered cubic (bcc) crystal structures as anodes and current collectors for lithium metal and lithium-ion batteries, that prevent the formation of lithium dendrites known to adversely affect performance of the batteries. BACKGROUND OF THE INVENTION [0004] The rapid advancement of portable electronics, electric vehicles, and renewable energy systems has driven the demand for batteries with higher energy density, faster charging capabilities, and enhanced safety. Lithium-ion batteries (LIBs) have been at the forefront of this technological revolution for decades, owing to their favorable energy density, long cycle life, and reliability. However, as the drive for more powerful and longer-lasting energy storage devices intensifies, the limitations of traditional LIBs become increasingly apparent. Specifically, the energy density of LIBs is approaching its theoretical maximum, prompting researchers to explore alternative battery chemistries and architectures. Lithium metal batteries (LMBs) have garnered significant attention as a promising successor to LIBs in recent years, primarily due to the superior theoretical capacity of lithium metal (3,860 mAh/g) and its low electrochemical potential (-3.04 V vs. standard hydrogen electrode). The large theoretical specific capacity of Li metal and mainly, the ability to potentially harness it has been the main reason for the recent interest. Metallic lithium has always been the center of interest ever since the concept of rechargeable Li-ion batteries came
into vogue in the mid-1970s. However, the immense reactivity of metallic lithium to atmospheric air and the hazardous flammability and explosive nature of the exothermic oxidation reaction to air and moisture severely thwarted the use of metallic lithium. The advent of intercalation concept and the consequent ability of storing ionized lithium, Li
+, into the carbon and graphite layers offered a good and excellent alternative solution to the use of metallic lithium completely avoiding the risk of fire and explosion with use of metallic Li. However, carbon and graphite anodes can only store 1 Li for every 6 carbons limiting the theoretical specific capacity to 372 mAh/g which is 1/10
th of that afforded by metallic Li. Renewed interest in Li has therefore made it imperative to explore avenues to protect metallic Li during fabrication of the electrode thereby preventing any contact with air and moisture and thus circumventing the possibility of fire and explosion. With the higher theoretical specific capacity, the use of lithium metal as an anode material has the potential to revolutionize energy storage by significantly boosting energy density, thereby extending the range of electric vehicles and the lifespan of portable devices. Despite these advantages, the practical implementation of lithium metal anodes is fraught with challenges, the most critical of which is the formation of pernicious lithium dendrites. [0005] Dendrites are needle-like or mossy lithium structures that emerge on the surface of the lithium metal anode due to inhomogeneous nucleation and growth of Li during repeated charge and discharge cycles. Consequently, there is uneven deposition of lithium resulting in initiation and propagation of these needle-like structures emanating from the electrode surface like the branches of a tree. The formation of dendrites and uneven deposition of metallic Li from the lithium ions can be exacerbated by factors such as high current densities, localized ion flux, and the intrinsic instability of the lithium metal-electrolyte interface. The growth of dendrites not only reduces the efficiency of the battery by consuming active lithium but also poses serious safety risks. As dendrites puncture and extend across the separator, they can cause internal short circuits, leading to thermal runaway resulting in an abrupt spike in temperature leading to fires, or explosions with the temperatures exceeding the flash point and flammability regime of the organic electrolytes. These safety concerns have been a major impediment to the commercialization of lithium metal batteries, necessitating the development of strategies to inhibit dendrite formation. [0006] In recent years, considerable research efforts have been devoted to addressing the dendrite issue and enhancing the performance of lithium metal anodes. A variety of approaches have been explored to achieve dendrite-free lithium deposition, with a focus on both innovation of material
and electrode design. One promising strategy involves the use of protective coatings on the lithium metal anode. These coatings, such as solid electrolyte interphases (SEIs) and artificial passivation layers, act as barriers that stabilize the interface between the lithium metal and the electrolyte, thereby reducing the likelihood of dendrite formation. However, the stability of these coatings during vast and abrupt variations in current densities during operation is always questionable, which can lead to delamination with plating and stripping of the metallic lithium thereby leading to dendrite formation once the coatings are compromised. [0007] Another approach involves the development of three-dimensional (3D) structured current collectors, which provide a more uniform distribution of lithium ions and accommodate the volumetric changes of the anode during cycling. This not only enhances the mechanical stability of the electrode but also promotes even lithium deposition, thereby mitigating dendrite growth. However, the efficient engineering and design of the 3D framework or confinement structures for the entire life of the battery eliminating dendrite formation is a challenge. This is because most of these 3D structures involve creation of a porous architecture enabling Li to be deposited within the pores. However, even if the 3D architecture and the confinement can be engineered meticulously to house the metallic Li, these 3D structures and confinement systems present the risk of deposited Li coalescing and filling the confinement structures and the porous channels. Thereby eventually leading to dendrite formation once the voids and channels are completely covered and filled with metallic Li. [0008] Moreover, electrolyte engineering has emerged as a critical factor in preventing dendrite formation. The design of advanced electrolytes with optimized ionic conductivity, solvent composition, and additive selection has been shown to influence lithium-ion transport and deposition. For instance, the incorporation of certain additives can modify the lithium metal surface and facilitate the formation of a stable SEI, which is crucial for suppressing dendrite growth. The ability of these additives to curtail the formation of dendrites during the entire life of the Li-ion battery and the current surges experienced during operation of the Li-ion battery presents unique challenges for efficient and effective electrolyte design. [0009] Additionally, solid-state electrolytes (SSEs) are being investigated for their potential to eliminate dendrites by providing a mechanically rigid medium that impedes dendrite penetration. However, although SSEs eliminate the use of organic liquid electrolytes and the potential risks of low flashpoints and temperatures exceeding the boiling temperatures and ignition temperatures of
the organic solvents, the inherent risk of inhomogeneous Li deposition and stripping of Li remains. Thereby presenting the possibility of dendrites forming and eventually migrating through and shorting the cell. Most of the SSEs are either ceramic or polymer or polymer-ceramic composites that tend to be mechanically brittle. Hence, there is the risk of the dendrites penetrating the brittle and thin SSE layer causing undesired short circuits leading to failure and rupturing of the cell. Thus, leaving the metallic Li exposed to air and moisture. This exposure combined with temperature excursions arising, owing to the short circuit and increase in resistance, cannot eliminate the possibility of dangerous explosions and fire. Therefore, there is a need for a transformative approach that addresses the root cause of formation of dendrites at the metallic electrode itself, which is the basis of the disclosed concept. [0010] As described above, there have been major advances in the coating areas, 3D electrode design and advent of SSEs. Despite these advancements, several challenges remain in fully realizing dendrite-free Li-metal anodes that are both practical and scalable for commercial applications due to the traditional approach of storing the Li-ions. Typically, as mentioned above, Li-ions tend to plate onto the surface of Li-metal and form uneven deposits leading to the formation of dendrites that can compromise battery safety and performance. [0011] Thus, there is a need in the art to design and develop anodes, current collectors, and methods related thereto, to effectively mitigate dendritic growth in lithium metal batteries and lithium-ion batteries. [0012] The disclosed concept relates to addressing the issue of dendrite formation at the grass roots level of metal alloy development and modification of the anode. The highly efficient anodes, current collectors and methods of the disclosed concept are effective for reversibly storing and cycling lithium absent of dendritic growth that can provide high power and high- energy density lithium-anode and lithium-ion based batteries. SUMMARY OF THE INVENTION [0013] In one aspect, the disclosed concept includes a lithium-ion or lithium metal battery including an anode-free current collector, including a multi-component alloy, including 40 atom % iron; 40 atom % aluminum or gallium; and 20 atom % magnesium, or 10 atom % iron; 40 atom % aluminum or gallium; and 50 atom % magnesium; or 50 atom % iron; 40 atom % aluminum or gallium; and 10 atom % magnesium; a cathode comprising lithium; and an
electrolyte, wherein the lithium-ion or lithium metal battery is dendrite free throughout the charge and discharge process of the battery. [0014] The electrolyte may include polymer gel. [0015] The cathode may be selected from the group consisting of LiCoO
2, LiNiO
2,and LiNi0.8Co0.1Mn0.1O2 as well as LiNi1-xCoxO2(0<x<1), and LiNi1-x-yMnxCoyO2(0< x + y <1). [0016] The multi-component alloy may include a body-centered cubic crystal structure maintained throughout the charge and discharge processes of the battery. [0017] The multi-component alloy may exhibit optimal interfacial energy for alloying with lithium. [0018] In another aspect, the disclosed concept includes a lithium-ion or lithium metal battery including a Li-containing anode including a multi-component alloy in a solid solution form, the multi-component alloy including a multi-component alloy, including 40 atom % iron; 40 atom % aluminum or gallium; and 20 atom % magnesium; or 10 atom % iron; 40 atom % aluminum or gallium; and 50 atom % magnesium; or 50 atom % iron; 40 atom % aluminum or gallium; and 10 atom % magnesium; a cathode; and an electrolyte, wherein the lithium-ion or lithium metal battery is dendrite free throughout the charge and discharge processes of the battery. [0019] In another aspect, the disclosed concept includes a method of preparing an anode-free current collector including preparing a multi-component alloy, including obtaining each of iron, aluminum or gallium, and magnesium in a dry form; blending or mixing the dry form of iron, aluminum or gallium, and magnesium according to an alloy composition selected from the following: 40 atom % iron; 40 atom % aluminum or gallium; and 20 atom % magnesium, or 10 atom % iron; 40 atom % aluminum or gallium; and 50 atom% magnesium; or 50 atom % iron; 40 atom % aluminum or gallium; and 10 atom % magnesium; subjecting the alloy composition to high energy milling to form a high energy milled composition; and forming a current collector including the high energy milled composition, wherein the lithium-ion or lithium metal battery is dendrite free throughout the charge and discharge processes of the battery. [0020] This method may further include forming pellets comprising the high energy milled composition prior to forming the current collector. In certain embodiments, the forming pellets may include cold pressing, cold isostatic pressing and cold-uniaxial pressing at moderate temperatures of about 100 to about 150
oC. Further, in certain embodiments, the method may include cold rolling the pellets to form foils for direct use as a current collector.
[0021] In yet another aspect, the disclosed concept includes a method of preparing a Li- containing anode including preparing a multi-component alloy, including obtaining each of iron, aluminum or gallium, and magnesium in a dry form; blending or mixing the dry form of iron, aluminum or gallium, and magnesium according to an alloy composition selected from the following: 40 atom % iron; 40 atom % aluminum or gallium; and 20 atom % magnesium, or 10 atom % iron; 40 atom % aluminum or gallium; and 50 atom % magnesium; or 50 atom % iron; 40 atom % aluminum or gallium; and 10 atom % magnesium; subjecting the alloy composition to high energy milling to form a high energy milled composition; and applying or depositing the high energy milled composition on a current collector to form a solid solution, wherein the lithium-ion or lithium metal battery is dendrite free throughout the charge and discharge processes of the battery. [0022] This method may further include forming pellets comprising the high energy milled composition; forming a slurry comprising the pellets; and applying the slurry to a current collector to form a solid solution. [0023] In this method, the dry form may be powder. [0024] In this method, the powder-to-milling ball ratio may be constant at 1:1. [0025] In this method, the solid solution may include a body-centered cubic crystal structure. [0026] In this method the forming the slurry may include adding polyvinylidene fluoride as a binder. BRIEF DESCRIPTION OF THE DRAWINGS [0027] FIG.1 is an in-situ XRD measurement of pure pellet PPFAM442 with 0.25 mA/cm
2 for 15 hours for Li-ion insertion into the alloy showing no formation of metallic Li and related Li-phases, according to certain embodiments of the disclosed concept. [0028] FIG.2 illustrates an electrochemical evaluation of slurry-coated FAM145 electrodes for Li storage at various charge rates ranging from 1 mAh to 20 mAh for 31 cycles each, according to certain embodiments of the disclosed concept. [0029] FIGS. 3a-3f illustrate electrochemical evaluations of FAM145 electrodes for Li storage at 1 and 5 mAh charge rates for 31 cycles each: a) voltage profiles and areal capacity, b-c) voltage profiles of 1
st and 31
st cycle at 1 mAh; d) voltage profiles and areal capacity, e-f) voltage profiles of 1
st and 31
st cycle at 5 mAh, according to certain embodiments of the disclosed concept.
[0030] FIGS. 4a-4f illustrate electrochemical evaluations of FAM145 electrodes for Li storage at 12 and 18 mAh charge rates for 31 cycles each: a) voltage profiles and areal capacity, b-c) voltage profiles of 1
st and 31
st cycle at 12 mAh; d) voltage profiles and areal capacity, e-f) voltage profiles of 1
st and 31
st cycle at 18 mAh, according to certain embodiments of the disclosed concept. [0031] FIGS. 5a-5i illustrate electrochemical evaluations of FAM541 electrodes for Li storage at 1, 2 and 4 mAh charge rates for 30 cycles each: a) voltage profiles and areal capacity, b-c) voltage profiles of 1
st and 30
st cycle at 1 mAh; d) voltage profiles and areal capacity, e-f) voltage profiles of 1
st and 30
st cycle at 2 mAh, g) voltage profiles and areal capacity, h-i) voltage profiles of 1
st and 30
st cycle at 4 mAh, according to certain embodiments of the disclosed concept. [0032] FIG. 6 illustrates electrochemical evaluation of slurry-coated FAM442 electrodes for Li storage at various charge rates ranging from 1 mAh to 18 mAh, according to certain embodiments of the disclosed concept. [0033] FIGS. 7a-7i illustrate electrochemical evaluations of FAM442 in coin cell configuration for Li storage at 1, 12 and 15 mAh charge rates for 31 and 200 cycles each, respectively: a) voltage profiles and areal capacity, b-c) voltage profiles of 1
st and 31
st cycle at 1 mAh; d) voltage profiles and areal capacity, e-f) voltage profiles of 325
th and 525
th cycle at 12 mAh, g) voltage profiles and areal capacity, h-i) voltage profiles of 525
th and 725
th cycle at 15 mAh, according to certain embodiments of the disclosed concept. [0034] FIG. 8 illustrates electrochemical evaluation of FAM442 electrodes in single-layer pouch cell for Li storage at 9 mAh charge rate for 100 cycles: a) voltage profiles and areal capacity; and b-c) voltage profiles of 1
st and 100
th cycle at 9 mAh charge, according to certain embodiments of the disclosed concept. [0035] FIG. 9 illustrates electrochemical evaluation of FAM442 pellet prepared using Ga as sintering agent (PFAM442-G) as a current collector for Li storage at various charge rates ranging from 1 mAh to 8 mAh in coin cell configuration, according to certain embodiments of the disclosed concept. [0036] FIG. 10 illustrates electrochemical evaluations of PFAM442-G pellet in coin cell configuration for Li storage at 1, 4 and 8 mAh charge rates for 110 cycles each, respectively: a) voltage profiles and areal capacity, b-c) voltage profiles of 1
st and 110
th cycle at 1 mAh; d) voltage profiles and areal capacity, e-f) voltage profiles of 221
st and 330
th cycle at 4 mAh, g) voltage
profiles and areal capacity, h-i) voltage profiles of 441
st and 550
th cycle at 8 mAh, according to certain embodiments of the disclosed concept. [0037] FIG. 11 illustrates electrochemical evaluation of pure pristine pellet of FAM442 (PPFAM442) in coin cell configuration for Li storage at 1 mA/cm
2 current density to realize 5 mAh/cm
2 areal capacity for 250 cycles: a) voltage profiles and areal capacity for 250 cycles; and b-f) voltage profiles of 1
st, 109
th, 152
nd, 174
th, and 250
th cycles, according to certain embodiments of the disclosed concept. [0038] FIG. 12 illustrates electrochemical evaluation of pre-lithiated pure pristine pellet of FAM442 (PPFAM442) as Li reservoir at 2 mA/cm
2 current density to realize 6 mAh/cm
2 areal capacity for 300 cycles: a) sequential scheme pre-lithiation of PPFAM442 to 15 mAh/cm
2 at CCCV; b) voltage profiles and areal capacity of 6 mAh/cm
2 for 300 cycles where Li-ions are cycled from PPFAM442 to counter Li-metal; and c-e) voltage profiles of 1
st, 153
rd, and 300
th cycles, according to certain embodiments of the disclosed concept. DETAILED DESCRIPTION [0039] This disclosed concept relates to a formation of solid solution including preserving the crystallographic symmetry with metallic lithium (Li), namely preserving the body-centered cubic (bcc) crystal structure, isostructural to metallic Li, as well as lowering the interfacial energy to an optimal value that will lead to complete solid solution formation without inducing any phase separation or intermetallic alloy or intermediate structure formation. As a result, there is no deposition or plating and stripping of Li, rather an alloy formation is observed throughout the charge and discharge processes completely eliminating dendrite formation arising from deposition or plating of Li on the surface of the alloy. The preservation of the lattice structure of Li and the optimal enthalpy and interfacial energy of mixing results in eliminating any perturbation of the interface leading to a desired planar interface rather than a morphologically perturbed interface causing the infamous and deleterious dendrites. [0040] Various alloys have been identified called multi-component alloys (MCAs), that are all isostructural to metallic Li, preserving and maintaining the bcc symmetry. These alloys exhibit solubility limit of metallic Li as high as 62 at. % resulting in solid solution alloy formation causing up to 18 mAh/cm
2 of areal capacity of Li (~100 microns of Li) to be alloyed with the MCA system. These are also lightweight alloys with densities more than 50% lower than that of copper, the conventionally used anode current collector.
[0041] The disclosed concept transforms the existing technology which uses copper foil as the current collector and metallic Li foil as the anode. The disclosed concept uses MCA alloys directly as a Li-containing solid solution MCA anode and as a non-Li containing MCA current collector. The solid solution formation offers the potential to replace copper current collectors with an equivalent thickness of MCA alloy giving identical capacities of 100-micron Li used as the anode. Thus, capacities of 3861 mAh/g identical to Li metal can be achieved as solid solution in these novel MCA alloys with densities more than 50% lower than metallic copper resulting in lightweight structures presenting a complete transformation in the Li metal and lithium-ion battery anodes without forming dendrites. [0042] The MCA alloys can be made containing Li or without Li. Non-lithiated MCAs serve as anode-free current collectors to cycle batteries that have Li containing cathodes, such as LiCoO
2 in current Li-ion batteries, including LiNi1-xCoxO2(0<x<1), LiNi1-x-yMnxCoyO2(0< x + y <1), and LiNi0.8Co0.1Mn0.1O2 (NMC-811) also used in some commercial systems, as well as LiNiO2, and emerging systems such as Li-S utilizing Li
2S as cathodes or as pre-lithiated alloys to serve directly as Li containing current collectors for cycling batteries that have non-lithium containing cathodes, such as sulfur in Li-S batteries and also in Li-air batteries. [0043] The MCA systems will thus replace the use of copper as current collector and use of separate Li metal foil thereby causing significant weight savings resulting in higher energy densities. [0044] The design of the MCA systems with bcc crystal structures are analogous to metallic Li that can dissolve Li into the solid lattice forming a solid-solution rather than plating on the surface. The disclosed concept includes the identification of such MCA systems that have a bcc crystal structure with optimal interfacial energy and enthalpy of mixing for Li to dissolve in its structure and form a solid solution. Thereby preventing uneven deposition and the subsequent growth of dendrites. This concept eliminates the possibility of Li plating on the surface since the Li ions during discharge will dissolve into the alloy and during charge will subsequently get ionized and leave the solid solution alloy leaving behind the non-Li containing alloy. As a result, there is no possibility of Li plating. Even with current surges during operation, the Li ions will always either dissolve into the alloy forming the solid solution or exit the alloy in ionized form. Thereby eliminating any plating possibility and the ensuing risks associated with plating and consequent formation of dendrites with growth of the plated or deposited Li layers. This disclosed concept
not only enhances the safety and reliability of lithium metal batteries but also paves the way for their broader application in next-generation energy storage systems. With respect to mitigating or precluding dendrite formation, preserving the crystallographic symmetry with metallic Li, namely preserving the body centered cubic crystal structure (bcc) isostructural to metallic Li and maintaining the optimal enthalpy of mixing and interfacial energy at the electrode-electrolyte interface have been identified as the primary factors. [0045] The MCA systems provide a direct current collector in Li-ion and Li-metal batteries. In certain embodiments, the MCA systems represent an anode-free current collector. The MCA systems are a substitute for copper (e.g., copper foil) as current collectors and metallic Li foil as the anode. The MCA systems are suitable for use directly as a Li-containing solid solution MCA anode and as a non-Li containing MCA current collector. In certain embodiments, the density of the MCA systems is about 50% less than copper. Thereby, reducing the weight of the battery by 50%. Such MCA systems of the disclosed concept include the following features: (i) same iso- structure as Li, (ii) interfacial energy close to zero, i.e., to form a solid solution, and (iii) less than 5% volume expansion. [0046] Li metal has a bcc crystal lattice, and the MCAs are designed to have similar crystallographic symmetry with optimal interfacial energy and enthalpy of mixing such that Li dissolves into the MCAs and forms a solid solution instead of plating over it. Furthermore, the MCA anodes have bcc crystal structure which is the same as pure metallic lithium to maintain a lattice coherence during Li alloying and/or plating at the surface. According to the disclosed concept, the formation of solid solution preserving the crystallographic symmetry with metallic Li, namely preserving the body centered cubic crystal structure (bcc) isostructural to metallic Li as well as lowering the interfacial energy to an optimal value that leads to complete solid solution formation without inducing any phase separation or intermetallic alloy or intermediate structure formation. The alloys identified as MCA systems are all isostructural to metallic Li preserving and maintaining the bcc symmetry. [0047] The MCA systems include alloys of iron, aluminum, and magnesium. In certain embodiments, the MCA system alloy includes 40 atom percent iron, 40 atom percent aluminum, and 20 atom percent magnesium, based on total atomic weight of the alloy. In other embodiments, the MCA system alloy includes 10 atom percent iron, 40 atom percent aluminum, and 50 atom
percent magnesium. In further embodiments, the MCA system alloy includes 50 atom percent iron, 40 atom percent aluminum, and 10 atom percent magnesium. [0048] The MCA systems also include alloys of iron, gallium, and magnesium. In certain embodiments, the MCA system alloy includes 40 atom percent iron, 40 atom percent gallium, and 20 atom percent magnesium, based on total atomic weight of the alloy. In other embodiments, the MCA system alloy includes 10 atom percent iron, 40 atom percent gallium, and 50 atom percent magnesium. In further embodiments, the MCA system alloy includes 50 atom percent iron, 40 atom percent gallium, and 10 atom percent magnesium. [0049] Preparation of the MCA system alloys includes obtaining the iron, aluminum and magnesium in dry, e.g., powder or particle, form and executing high energy mechanical milling. The milled alloy powder is then fabricated into the form of a pellet, and the pellet is, optionally, cold rolled to a foil. [0050] In certain embodiments, the MCAs are synthesized by a simple and scalable high-energy mechanical milling and alloying (HEMM/HEMA) process. For example, the elemental Fe, Al, and Mg powders (or elemental Fe, Ga, and Mg powders) are obtained in their atomic ratios and loaded in milling jars. The powder-to-milling ball ratio is kept constant at 1:1. A solvent (e.g., 10 ml of toluene) is added to the jar containing the powder and milling balls to facilitate wet milling, followed by HEMM/HEMA for about 5 hours with an about 20-minute rest after each consecutive hour of milling. After milling, the jars are kept open in a fume hood overnight to remove the solvent. The MCA powders are then dried in a vacuum oven (e.g., at 60 ℃ for 6 hours) and stored in a vacuum desiccator. [0051] The HEMM/HEMA process facilitates the formation of the metastable solid solution due to repeated fracturing, welding, and rewelding of powder particles in a high-energy ball mill promoting rapid diffusion. The repeated high-energy collisions between the balls and the powder particles result in the mixing of different elements at an atomic level enabling facile diffusion of the elements, leading to the formation of a metastable solid solution alloy of the desired composition. The intense mechanical deformation allows atoms of one element to dissolve into the crystal lattice of another, forming a homogeneous solid solution. The HEMM/HEMA of Fe, Al, and Mg elemental powders or Fe, Ga, and Mg elemental powders involves intense mechanical forces and high-energy collisions resulting in the mixing of their atoms forming a metastable solid solution with a body-centered cubic (bcc) crystal structure. The different crystal sizes of Fe, Al,
Ga, and Mg result in the formation of nanocrystalline structures which further stabilizes the bcc phase. [0052] In certain embodiments, the following MCAs are prepared by taking the elemental powders in their atomic ratio: Fe
0.4Al
0.4Mg
0.2 (FAM442), Fe
0.5Al
0.4Mg
0.1 (FAM541), and Fe
0.1Al
0.4Mg
0.5 (FAM145). These developed MCA systems offer a significant reduction in density, e.g., over 50% lower than traditional copper (Cu = ~9 g/cc) current collectors (for example, FAM442 = ~4.6 g/cc, FAM541 = ~5.2 g/cc, FAM145 = ~2.7 g/cc). [0053] Further, in certain embodiments, the powder samples of MCAs are used as an active material with polyvinylidene fluoride (PVDF) as a binder during slurry preparation and utilized as an anode versus Li-metal as a counter electrode. The MCAs are used as an anode material for various Li-based batteries. Furthermore, MCA pellets are effective as current collectors in anode- free systems. In certain embodiments, MCA powders of the aforementioned alloys (Fe/Al/Mg and Fe/Ga/Mg) are formed into dense pellets using an uniaxial cold press. Based on the electrochemical response, the MCAs demonstrate effectiveness as a current collector in Li battery operation. In certain embodiments, Fe0.4Al0.4Mg0.2 (FAM442) has superior performance as a reliable and efficient current collector in advanced Li-based battery technologies, particularly, in innovative configurations like anode-free systems. [0054] Electrodes may be prepared using a standard slurry coating method on a Cu foil. A slurry is prepared by mixing the MCA powders as an active material with a binder, and a solvent. The slurry is coated on the Cu foil using a conventional technique. The slurry-coated foil is then dried. In certain embodiments, the slurry is obtained by mixing 95% MCA powders and 5% PVDF, using NMP as a solvent. The slurry is coated on Cu foil using a doctor’s blade. The slurry-coated foil is dried in a vacuum oven at about 80 ℃ for about 12 hours. [0055] In certain embodiments, the lithium ion or lithium metal battery includes a gel polymer electrolyte. In other embodiments, an electrolyte solution is used, which includes Lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt (e.g., 1.0 M) in a 1:1 (v/v) mixture of solvent (e.g., Dioxolane (DOL) and Dimethoxyethane, with LiNO
3 (2 wt.%) as an additive. [0056] The MCA systems of the disclosed concept include one or more of the following advantages: (i) Lightweight and reduces the weight of the battery since the MCA alloys eliminate use of a separate current collector and anode;
(ii) Eliminates dendrite formation that is prone to form in current batteries using copper current collectors and metallic Li foil as the anode; (iii) Realization or gain in gravimetric and volumetric capacity; and (iv) Achieving more than 500 cycles with no dendrite formation for MCA alloy anode and current collectors. EXAMPLES Example 1 Section I: Theoretical Studies related to the multicomponent alloy anodes (MCAs) [0057] The study involved three components.1. To identify the optimal MCA alloy anode system, 2. Determine the solubility limit for the alloying Li, 3. Determine the interfacial energy of the alloying Li with the MCA, 4. Volume expansion of the MCA with formation of solid solution with alloying of Li, and 5. Identification of elements enhancing the diffusion of Li ions in the MCA. These studies are described below. Computational study to identify optimal MCA anodes [0058] An extensive ab-initio study was conducted for identification of different compositions of multicomponent alloy (MCA) anodes with high Li solubility and improved Li-ion conductivity. 1. Phase stability of the solid solution MCAs [0059] Since the MCA anodes must have bcc crystal structure which is the same as pure metallic lithium to maintain a lattice coherence during Li alloying and/or plating at the surface, the phase stability of the bcc solid solution phase was studies. The total energies of the three possible fully disordered bcc, fcc, and hcp solid solution structures, respectively, were studies for each specific composition of the alloys. A phase with the lowest energy would be considered as the most stable crystal structure among the all the three different crystallographic phases. [0060] A metastable bcc solid solution phase of Fe
50Zn
40Mg
10 (FZM541) alloy was synthesized, thus proving that the synthesis of this kind of metastable structures is realistic and experimentally feasible. [0061] The alloy FZM541 was chosen as a benchmark to gage the energy differences between various phases, while other four MCA compounds, such as Fe
50Al
40Mg
10, Fe
40Al
40Mg
20, Fe10Al40Mg50, Fe10Ga40Mg50 were taken as the main MCA anodes used for experimental synthesis and characterization. In the original Fe-based composition, FZM541, Fe and Zn are relatively
heavy elements, thus, to improve the gravimetric specific capacity there was a compelling notion to replace Zn for Al as lighter element and, also to decrease the Fe contents in the alloying compositions. The element, Ga was chosen due to its softness which can improve the Li-diffusivity through the compound. [0062] The following equation was used for estimating the phase stability: ΔG
f = [Etot(MCAfcc)] – Etot(MCAbcc) ΔG
f = [E
tot(MCA
hcp)] – E
tot(MCA
bcc) ΔG
f = [E
tot(MCA
bcc)] – E
tot(MCA
bcc) = 0 If: ΔG
f < 0 – phase is more stable than bcc ΔG
f > 0 – phase is less stable than bcc [0063] For computational ease instead of 100 atoms, there were chosen 96 atom supercells consisting of 48 bcc and hcp elementary cells (2 at. per each cell), namely: 4x4x3=48 cells and 24 fcc cubic cells (4 at. per cell): 2x3x4=24 cells. All the 96 atoms were randomly distributed over the 96 sites of the supercell with the following atomic ratios: for nominal 10 at% of concentration there were chosen 10 atoms, for 20% - 20 atoms, for 40% - 38 atoms, and for 50% - 48 atoms. It should be noted that such slight deviations of model compositions from the actual experimental compounds did not change much the general trends found from the computational study. [0064] The computational method in this work is based on DFT using the projector augmented wave (PAW) formalism. The PAW basis and projector functions were constructed by Vienna Ab- initio Simulation Package (VASP). The exchange-correlation functional was used in the generalized gradient approximation (GGA) form. The Monkhorst-Pack scheme has been used to sample the Brillouin zone and create the k-point grid for all the MCA compounds used in the current study. The selection of appropriate numbers of k-points in the irreducible parts of the Brillouin zone was made on the grounds limiting the convergence of the total energy to 0.1 meV/atom. The relaxation procedure was used to optimize the internal positions as well as the lattice parameters of atoms within the supercell. [0065] The relative phase stability of bcc, fcc, and hcp was calculated for all the five alloying compositions. Not one composition including the experimentally synthesized FZM541 had a ground state with the much-needed bcc structure. This finding implied that all the alloys should be metastable and therefore, synthesized by carefully crafted and specially engineered approaches
maintaining specific temperature regimes during their production ensuring the stability of the metastable phases. [0066] However, a comparison of the phase stability between the already synthesized FZM541 phase as a benchmark and the other four proposed MCAs demonstrated similarities in the ΔG values between bcc and the most stable crystal structures. Three MCAs, such as Fe50Al40Mg10, Fe40Al40Mg20, and Fe10Ga40Mg50 demonstrated ΔG equal or even smaller than that for FZM541, implying that all these compounds also could be synthesized in the bcc phase, similar to FZM541. Only Fe10Al40Mg50 shows ΔG slightly larger than that of FZM541, which however, would not create a significant obstacle for the experimental synthesis of this compound as demonstrated and shown by our experiments discussed in the experimental section (Section II). 2. Li-solubility in the MCA anodes [0067] The ab-initio approach was also applied to study the Li solubility in all the five metastable compositions. For these purposes 250-atom [5x5x5] bcc supercell has been chosen and the following relationship was used to evaluate the Li-solubility limit in the compositions studied: ΔG
f = Etot(MCA1-xLix) – [(1-x)Etot(MCA) + xEtot(Li
bcc)] ΔG
f < 0 – solid solution, ΔG
f > 0 – phase separation. [0068] The calculated ΔG for different MCAs as a function of Li content revealed that in Fe
50Zn
40Mg
10 (FZM541) alloy may homogeneously dissolve only ~33 at. % of Li corresponding to ~21 mAh/cm
2 areal capacity of Li into the structure for an equivalent mass of 100-micron thick copper, the preferred current collector in traditional Li-ion batteries. However, there were developed solid solution alloys exhibiting even higher solubility of Li demonstrating the possibility of achieving even higher areal capacities for the lithiated alloy structure without inducing any phase separation. [0069] Calculations of Li solubility in the Fe50Al40Mg10 and Fe40Al40Mg20 structures indicated that up to 53 and 62 at. % of Li can be dissolved into the Fe
40Al
40Mg
20 and Fe
50Al
40Mg
10 alloys, respectively. [0070] Therefore, these two alloys have higher Li-solubility as well as lower atomic weights than FZM541, which will likely contribute to achieving even higher specific capacities for the anode.
These alloys can therefore serve as current collectors and anodes for next generation high energy density Li-ion batteries. [0071] Furthermore, Fe10Ga40Mg50 (density ~4g/cc), Fe40Al40Mg20 (density ~5.2 g/cc), and Fe
10Al
40Mg
50 (density ~2.74 g/cc), are much lighter than Fe
50Zn
40Mg
10 (~7g/cc) and Cu (~9 g/cc). These alloys can be used to significantly lower the weight of the finally packaged batteries which is another added advantage over the currently used Li-ion batteries. 3. Interfacial energy at the MCA alloys: [0072] One of the main conditions for dendrite free anodes is the interfacial energy of the surface between metal Li layer and alloyed metallic surface with various MCA compositions denoted as A
xB
yC
1-x-y. The macroscopic atom model was used to estimate such an interfacial from the following equation: ^^
^ ^^ ^
^ ^^ ^
^ ^
^ ^^^^^ = ^ ^^ ^^ ^^^ ^^ ∆^
^ ^^ ^
^ ^^ ^
^ + ^ ∆^
^ ^^ ^
^ ^^ ^
^ + ^1 − ^ − ^^∆^
^ ^^ ^
^ ^^ ^
^ (1)
$ ∆^
^^^^ =
! & % 9 + /−0
^Δ2
^ + 5 '^6
& 4 ^^^^^ "# ∗ 4 7
8 : , ; – partial interfacial energy of Li with metal A.
metal A. VLi − atomic volume of Li, P = 14.2 kJ/(mol cm
2 V
2 (density unit)
1/3) and Q = 133.5 kJ/(mol cm
2 9 (density unit)). '6
& 7
8 : , and 2
^ ∗ are tabulated and available in the literature or can also be calculated from first principles for elements not documented in the public sources. [0073] For 5 at. % of Li, the interfacial energies ΔH
int in all considered non-lithiated MCA alloys are collected in Table 1. The lowest ΔH
int are for Fe
10Al
40Mg
50 and Fe
10Ga
40Mg
50, which makes them the most optimal compounds in terms of suppression of the dendrite formation. [0074] For calculation of the interfacial energy of Li above the solubility limit Xlim, the equation will be slightly modified as shown below: ^^
^ ^^ ^
^ ^^ ^
^ ^
^A^^ ^^^^^ = ^
^ ^^ ^^ ^^^^^^^^1 − B C^D^^^
^ ^^ ^
^ ^^ ^
^ ^
^ ^^^^^ + ^^^
^ ^^ ^
^ ^^ ^
^ ^
^^^^^ ; ^^
^ ^^ ^
^ ^^ ^
^ ^
^^^^^ =0 (2)
on the surface of the Li-saturated alloy interface. For 5 at. % of Li above the solubility limit, the ∆H
int
are also collected in Table 1. In comparison to non-lithiated alloys, the alloys saturated with lithium up to the solubility limit drastically decrease the interfacial energy at the surface with metallic Li further plated on top of this alloyed surface. This happens due to presence of substantial amount of Li in the solid solution, which increases the affinity of the alloying surface to pure plated Li and thus, decreases the interfacial energy. As a result, the higher solubility limit Xlim leads to lower interfacial energy due to the (1 - Xlim) term in Equation (2) and thus, allowing to plate higher amount of Li beyond the solid solubility limit of Li on the surface maintaining relatively low interfacial energy needed to ensure dendrite free Li deposition. Table 1. Calculated interfacial energies: for non-lithiated MCAs lithiated up to the solubility limits, and Li solubility limit values. MCA Composition delta H
int for c
Li=5 at. % delta H
int for c
Li=5 at.% X
lim in non-lithiated MCAs above solubility limit (at.%) (in kJ/mol) in Li-saturated MCAs (in kJ/mol) Fe
50Zn
40Mg
10 +1.5 +1.0 33 Fe50Al40Mg10 +1.8 +0.68 62 Fe40Al40Mg20 +1.4 +0.66 53 Fe
10Al
40Mg
50 +0.07 +0.044 37 Fe
10Ga
40 Mg
50 -0.3 -0.16 45 4. Volume expansion of the lithiated MCA anodes [0075] The volume expansion of the lithiated alloy vs. non-lithiated alloy depends on the atomic radii of the metallic components of the alloy and an atomic radius of Li. For example, in Fe40Al40Mg20 the atomic metallic radii for Fe, Al, and Mg are 1.26Å, 1.43 Å, and 1.60 Å, respectively. Thus, the average atomic radius of Fe
40Al
40Mg
20, R
av, is [1.26
3x0.4 + 1.43
3x0.4 + 1.6
3]
1/3 = 1.41 Å. Taking into account the atomic radius of Li, RLi = 1.52 Å, the volume expansion during alloying of Li into the alloy will be: [Rav
3 (1-x) + RLi
3 x] / Rav
3(1-x) = 1 + 1.258x/(1-x), where x is Li content. The percentage change in volume will thus be given by: %Volume expansion ΔV: [1.258x/(1-x)] * 100%. [0076] With respect to this function and the corresponding relation, a high content of Li (50 at%) the volume expansion ΔV reaches 126%, which is quite large (the total volume increases more than twice). However, at lower Li content ~20at% ΔV is within ~30-31%. Furthermore, in
experimental observations of the synthesized alloy of Fe
40Al
40Mg
20 as described in Section II, to achieve a desired areal capacity of Li of 6 mAh/cm
2 which corresponds to 1.5 mg of Li since 1 mg of Li results in an areal capacity of 4 mAh/cm
2. With a fabricated dense pellet of Fe40Al40Mg20 of 183 mg with the atomic mass of 38-gram atoms/mole, the mole percent of alloyed Li is 4.3 mole% which would correspond to a volume change of ~5.6%, which can be easily endured by the system without causing any phase separation, accompanying volume expansion related decrepitation of the electrode and additionally, preserving the original bcc crystal structure. Even with a higher amount of Li alloyed into the system, the volume change will likely be ~5-10% that can be easily endured by the alloy and will not result in any decrepitation or cracking that is typically seen in Zintl alloy phases encountered in Si and Sn anodes that result in colossal volume change of 300- 400%. This is another attribute of the present invention and the identified multicomponent component alloys (MCAs). 5. Li-ion mobility in MCA anodes [0077] Li-ion mobility in MCA anodes is one of the critical characteristics of the compound needed for efficient cycling of the electrode. Hindered mobility of Li ions in the anode can result in a very poor cyclability. For estimation of the Li-ion mobility in various MCAs there is a need to calculate the activation energy barriers during hopping of the lithium atoms between two neighbor unit cells of the crystal lattice via the vacancy hopping diffusion mechanism. [0078] The computational model for calculating the activation barriers consisted of two body centered cubic (bcc) elementary unit cells with alternate atomic layers of Li and probed metal layer. In model (a), a Li-atom located in the center of the cubic bcc unit cell moves to the neighbor Li-vacancy through the intermediate atomic layer. At the same time the Li-vacancy moves in the opposite direction. In model (b), in the case of pure Li metal, the intermediate layer consists of only Li atoms. For calculation of the activation energies, E
a of Li-ion in pure Li and in other metal components of the studied MCAs, models (a) an (b) were used. All the computations were executed using the climbing image nudged elastic band method (CINEB) also implemented in VASP computational package within the projector-augmented wave (PAW) method and the generalized gradient approximation (GGA) for the exchange-correlation energy functional in a form known in the art. The total path of the Li-ion between both centers of the adjacent unit cells was divided in eight equal intervals with calculations of the total energies of the system in each consecutive point from start to the end of this path. For all calculations, a 2x2x2 supercell was
considered consisting of eight elementary bcc unit cells, and containing one Li vacancy, seven Li atoms, and eight atoms of other metals that was constructed. For pure Li metal, the structure contained 1 vacancy and 15 Li atoms. The Monkhorst-Pack scheme has been used to sample the Brillouin zone and create the k-point grid for all the Li alloys used in the current study. The selection of appropriate numbers of k-points in the irreducible parts of the Brillouin zone was made on the grounds limiting the convergence of the total energy to 0.1 meV/atom. [0079] The calculated potential energy profiles for the different alloying elements were derived. All the potential energy graphs have similar profiles with maximum energy values located at the middle of the Li hopping path which correspond to the activation barriers for each specific alloying element. According to these results, the Li-mobility in the modeled Mg and Zn bcc metals are even slightly higher (E
a barriers are lower) than in pure Li-bcc most likely due to lower cohesive energy of pure Mg and Zn compared to pure Li which enables the Li-atom easier to diffuse through the Mg and Zn plane and, thus, results in a facile overall Li-ion conductivity/mobility in pure Mg and Zn metals. Also, this graph shows that Na decreases the activation barrier for Li-movement through the lattice even more compared to that of metallic Mg and Zn. [0080] Whereas, Fe, Al, and Ga increase the activation barriers for Li-ion hopping pathway. It happens due to higher Fe-Fe, Al-Al, and Ga-Ga interatomic bonding within the corresponding intermediate layer. [0081] Also, collected in Table 2 are the average activation barriers, Ea for all MCAs considered in the study. One can see that the lowest E
a av (the highest Li-mobility) are demonstrated by Fe
50Zn
40Mg
10, Fe
10Ga
40Mg
50 and Fe
10Al
40Mg
50, MCA systems. Table 2. Calculated average Ea
av for different MCAs Alloy Ea average (eV) Fe
50Zn
40Mg
10 0.150 Fe50Al40Mg10 0.166 Fe40Al40M20 0.163 Fe
10Al
40Mg
50 0.153 Fe10Ga40Mg50 0.152 [0082] Thus, this computational study was useful in estimating different physical properties of various MCA anodes. These properties include phase stability, interfacial energy, Li solubility limits, volume expansion and Li-ion mobility through the MCAs. The theoretical studies described
above formed the basis of the experimental studies that were executed to validate the findings of the theoretical and computational studies which are described in Section II below. Section II: Experimental Studies of Dendrite-free Novel Multi-Component Alloy (MCA) Anodes and Current Collectors for Li-ion Batteries [0083] This study comprises all the experimental studies conducted on the three MCA systems identified by the theoretical studies described above in Section I. Experimental section: [0084] The MCAs were synthesized by a high-energy mechanical milling and alloying (HEMM/HEMA) process. The elemental Fe, Al, and Mg powders were taken in their atomic ratios and loaded in the milling jars. The powder-to-milling ball ratio was kept constant at 1:1. A 10 ml of toluene as solvent was added to the jar containing the powder and milling balls to facilitate wet milling followed by HEMM/HEMA for 5 hours with a 20 min rest after each consecutive hour of milling. After milling, the jars were kept open in the fume hood overnight to remove the solvent. The MCA powders were then dried in a vacuum oven at 60 ℃ for 6 hours and stored in a vacuum desiccator. Various MCAs (Fe0.4Al0.4Mg0.2 (FAM442), Fe0.5Al0.4Mg0.1 (FAM541), and Fe0.1Al0.4Mg0.5 (FAM145)) were prepared by taking the elemental powders in their atomic ratio. These developed MCA systems offer a significant reduction in density, over 50% lower than traditional copper (Cu = ~9 g/cc) current collectors (FAM442 = ~4.6 g/cc, FAM541 = ~5.2 g/cc, FAM145 = ~2.7 g/cc). [0085] The powder samples of MCAs were used as an active material with PVDF as a binder during slurry preparation and utilized as an anode versus Li-metal as a counter electrode in their initial electrochemical testing. This demonstrated their promise to be used as an anode material for various Li-based batteries. MCA pellets were prepared and utilized for electrochemical testing to evaluate the effectiveness of MCA as potential current collectors in anode-free systems. The MCA powders were formed into a dense pellet using a uniaxial cold press. FAM442 was selected as the representative material of the various MCA materials tested to further investigate its potential as a current collector. Based on the preliminary electrochemical response of the MCAs, FAM442 indicated a superior performance compared to other MCAs and thus, was considered to demonstrate its effectiveness as a current collector in the battery operation. FAM442 powder was made into pellets and investigated to serve as a reliable and efficient current collector in advanced Li-based battery technologies, particularly in innovative configurations like anode-free systems.
[0086] Initially, gallium (Ga) was explored as a chemical additive to obtain a thick and dense pellet. A 5 wt.% of Ga (10 mg) was added with 95 wt.% of FAM442 (190 mg) powder in a mortar pestle and kept in an oven at 60 ℃ and mixed to get a homogenous powder mixture. This powder mixture was then loaded into a pellet-making die (1.3 cm diameter, 1.32 cm
2) and placed in the uniaxial cold press at 40 ℃ for 1 hour at various pressures. Ga was used as a low-temperature liquid phase sintering agent as its melting point is less than 30 ℃. Consequently, a dense pellet (PFAM442-G) was obtained using 5 wt.% Ga at the optimized processing parameters of holding the cold press at 40 ℃, 250 psi pressure for 2 hours. When the PFAM442-G pellet was tested for its Li-ion storage capability, it was observed that the Ga which is used as a sintering agent to form a pellet tends to form intermetallic with the Li-ions and thus, influences the electrochemical performance of the pellet for initial cycles. Thus, avoiding the usage of any sintering agent affecting the electrochemical performance of the MCA pellets, the pure pellet of 100% FAM442 (PPFAM442) was synthesized. The processing conditions of the uniaxial press to synthesize the pellet were optimized. Generally, 200 mg of FAM442 powder synthesized by HEMM/HEMA was weighed and transferred into a pellet-making die. The die was then loaded into the uniaxial press which was held at a temperature and pressure of 110 ℃ and 6750 psi respectively, for 5 hours to yield a dense pellet of FAM442. The pellet was then collected and stored in a vacuum desiccator until its electrochemical testing. PPFAM442 pellets were prepared for in-situ XRD measurements using the optimized pellet-making processing condition with an areal loading of 116 mg /cm
2 with a 0.5 cm
2 surface area and 200 – 400 µm thickness. Structural and electrochemical characterization: [0087] The phase structure characterization of the samples was obtained by X-ray diffractometer (XRD) (Empyrean: Malvern Panalytical) using Co radiation. The wavelength correction was performed to convert the pattern to depict Cu Kα radiation. The electrochemical performance of various MCA alloys was evaluated in both coin cell and pouch cell configurations. Electrodes were prepared by a standard slurry coating method on a Cu foil. A slurry was obtained by mixing 95% MCA powders as active material and 5% PVDF as a binder using NMP as a solvent and coated on Cu foil using a doctor’s blade. The slurry-coated foil was dried in a vacuum oven at 80 ℃ for 12 h. Electrodes for testing in coin cell configuration were obtained by punching circular discs of 0.5- inch diameter (1.26 cm
2). Coin cells were fabricated using CR2032 employing the electrodes of various MCAs (FAM541, FAM442, and FAM145) as a working electrode, a polypropylene
separator disc, and Li foil as a reference and counter electrode. The electrolyte solution was prepared by dissolving 1.0 M Lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt in a 1:1 (v/v) mixture of Dioxolane (DOL) and Dimethoxyethane as solvents with 2 wt.% of LiNO3 as an additive. The electrolyte amount was maintained constant throughout the electrochemical testing in coin cells at 60 μL. [0088] Coin cells were also fabricated using dense pellets of pure FAM442 and with Ga as a sintering agent with an areal loading of 135 - 142mg/cm
2 and 145.4 mg/cm
2 respectively, versus Li foil as a counter electrode. The electrolyte amount used was kept constant at 60 µL leading to an extremely lean electrolyte-to-active material ratio. [0089] For a single-layer pouch cell fabrication, the FAM442 electrodes were cut into a rectangular shape (4 cm and 5 cm) with an area of 20 cm
2 using an electrode cutter machine. The areal loading of the active material (FAM442) in the pouch cell electrodes was 9.2 mg/cm
2. The single-layer electrodes were enclosed with a PP separator. The pouch cell bag (multi-layer laminate material) was prepared by cutting and heat-sealing which creates a cavity that will hold the electrode assembly. Li foil (50 µm in thickness) was used as a counter and reference electrode for the pouch cell testing. A 400 µL of the electrolyte was used for the pouch cell testing leading to an extremely lean electrolyte to active material ratio. The MCA electrodes enclosed in separators were assembled against the Li foil and this assembly was then loaded in the pouch cell bag before electrolyte filling and sealing the pouch cell. The as-fabricated pouch cell was allowed to rest for 24 hours before electrochemical testing. The electrochemical performance of the various MCA electrodes was measured by using Arbin Potentiostat (Electrochemical workstation). Results and discussion: [0090] The HEMM/HEMA facilitates the formation of the metastable solid solution due to repeated fracturing, welding, and rewelding of powder particles in a high-energy ball mill. The repeated high-energy collisions between the balls and the powder particles result in the mixing of different elements at an atomic level, leading to the formation of a solid solution. The intense mechanical deformation allows atoms of one element to dissolve into the crystal lattice of another, forming a homogeneous solid solution. The HEMM/HEMA of Fe, Al, and Mg elemental powders involves intense mechanical forces and high-energy collisions resulting in the mixing of their atoms forming a solid solution with a body-centered cubic (bcc) crystal structure. The different crystal sizes of Fe, Al, and Mg result in the formation of nanocrystalline structures which further
stabilizes the bcc phase. The XRD patterns of all the synthesized MCAs in powder and pellet form were obtained. The XRD patterns of the powder samples of Fe0.4Al0.4Mg0.2 (FAM442) and Fe0.5Al0.4Mg0.1 (FAM541) respectively, after milling showed two peaks around the 2θ values of 44.5
o and 65
o corresponding to the nanocrystalline bcc phase confirming the formation of solid solution during HEMM/HEMA. Li metal has a bcc crystal lattice, and the MCAs are designed to have similar crystallographic symmetry with optimal interfacial energy and enthalpy of mixing such that Li dissolves into the MCAs and forms a solid solution instead of plating over it. The XRD pattern of Fe0.1Al0.4Mg0.5 (FAM145) showed a small hump around 2θ value of 44.5
o demonstrating the initiation of the formation of bcc phase after 5 hours of HEMM/HEMA, although all the elements had not fully reacted. The formation of the bcc phase shows that the approach is conducive to formation of the metastable structure to demonstrate the feasibility and validity of the disclosed concept. The XRD pattern of the pellets synthesized using Ga as a sintering agent (PFAM442-G) and pure powder of FAM442 (PPFAM442), respectively, showed two peaks around the 2θ values of 44.5
o and 65
o, indicating the presence of the nanocrystalline bcc phase, suggesting that the processing parameters for synthesizing the pellet via uniaxial cold press have no adverse effects on the material structure. [0091] The in situ XRD measurements of the PPFAM442 were carried out during cell operation to examine whether Li plates over the surface of the FAM442 pellet or forms a solid solution with the alloy. A special EL-cell was fabricated of these measurements in the glove box with Li-foil (0.785 cm
2 area and 600 µm thickness). The PPFAM442 in the EL-cell was charged with a current density of 0.25 mA/cm
2 to realize 3.75 mAh/cm
2 areal capacity. XRD measurements were carried out at intervals of 15 min during cell operation. The XRD pattern of the pellet was collected over 15 hours while Li-ions were being charged into it and presented in FIG. 1. There was no evidence of any peak corresponding to the metallic Li or any Li-related alloy or compound even after 15 hours of cycling (3.75 mAh/cm
2 which is equivalent to approximately 1 mg of Li) from FIG. 1, suggesting that the Li-ions formed a solid solution with the FAM442 pellet. A. Electrochemical evaluation of slurry-coated MCAs as dendrite-free anode for Li-based batteries 1) Fe
0.1Al
0.4Mg
0.5 (FAM145) [0092] FIG. 2 shows the electrochemical Li-ion storage in the slurry-coated FAM145 electrodes with Li foil as a counter and reference electrode in a coin cell. The FAM145 electrodes (1.26 cm
2)
with active material loading of 2-3 mg/cm
2 were presented with the Li-ion at various charge rates ranging from 1 mAh to 20 mAh for 31 cycles each. Initially, the electrodes were cycled at 1 mA current for 31 cycles beginning with 1h charge/discharge with sequential increments of 1h to 10h following which the cells were also cycled at 3 mA current for 4h and 5h for 31 cycles, respectively. Additionally, to examine the limits of the solid solution alloy of MCA with Li, the charge rates of the electrodes were then increased to realize 18 mAh and 20 mAh for 31 cycles each. The FAM145 electrodes demonstrated the ability to not only store high Li charge storage via solid solution formation but also long cyclic stability at low and high charge rates. The FAM145 displayed the promise to be utilized as an alternative anode material for advanced energy storage batteries with a longer and more stable lifespan devoid of dendrite formation. The electrodes were subjected to over 4500 hours of continuous electrochemical evaluation for lithium charge storage. The electrodes showed the ability to store Li up to 20 mAh which is equivalent to ~5 mg of Li without showing any signs of dendrites. [0093] Initially, the energy efficiency of the FAM145 electrodes was relatively lower which could be attributed to the SEI formation and the initial diffusion barrier for Li-ion to get into the bcc phase of the MCA solid solution. Additionally, the XRD pattern of FAM145 confirmed that it consists of a mixed phase of bcc and a metallic elemental phase corresponding to the unreacted elements which could also have contributed to the lower coulombic efficiency. However, as the cycling progressed further, Li-ions paved their pathway, stabilizing the system and opened the crystal lattice of the MCA alloy facilitating the diffusion of Li ions to form the solid solution. As a result, the energy efficiency of the FAM145 electrodes is 100% from 5 mAh charge storage of Li-ions. The computational studies indicated that FAM145 has the most optimal interfacial energy (0.07 kJ/mol) along with 37 at. % Li solubility and partial bcc crystal lattice, thus, these electrodes showed stable and reversible Li cycling over the higher charged rates. [0094] FIG. 3 shows the Li charge storage response of FAM145 electrodes at 1 mAh (FIG. 3a-c) and 5 mAh (FIG. 3d-f) charge rates. FIG. 3a and 3d display the voltage profile curves and areal capacities of FAM145 electrodes with an electrode surface area of 1.26 cm
2 for 31 cycles at 1 mAh and 5 mAh charge, respectively. FIG.3b-c and Fig.3e-f show the 1
st and 31
st cycle voltage profiles of the electrodes at 1 mAh and 5 mAh charge, respectively. The 1
st voltage profile of FAM145 at 1 mAh charge shows a diffusive curve displaying the resistance faced by Li-ions during their initial insertion into the FAM145 structure. The overpotential of the coin cells in the initial cycles is
higher (~0.34 V) due to this initial diffusion resistance to the Li-ions, and due to the formation of the solid electrolyte interphase (SEI) layer on the electrode surface (FIG. 3b). However, the overpotential decreases with cycling showing ~0.16 V after 31 (FIG. 3c) cycles of continuous charge and discharge of the cell. As the cycling continues with 5 mAh the overpotential further reduces to (~0.1 V) after the 31
st cycle of 5 mAh charge (FIG. 3f). [0095] FIG. 4 shows the electrochemical evaluation of FAM145 electrodes at higher charge rates of 12 mAh and 18 mAh. Before connecting at these charge rates, the cells had already cycled for more than 3400 hours at different charge rates as shown in FIG. 2. FIG. 4a-c and 4d-f show the Li-storage of FAM145 at higher charge storage rates of 12 mAh and 18 mAh. It is evident from these curves that FAM145 can reversibly store Li even at higher charge storage rates with 100% energy efficiency, although with higher overpotential possibly due to electrolyte consumption and an increase in the overall impedance of the cells. [0096] Computational studies revealed that the solubility limit for FAM145 to form a solid solution with Li-ions was 37 at.%. With the loading of the 2-3 mg/cm
2, FAM145 alloy at charge storage rate of 18 mAh had surpassed the solubility limit, and yet the electrodes could reversibly cycle Li-ions at much higher rates. The computational studies further revealed that the interfacial energy of the FAM145 at the Li solubility limit and above, is even more favorable for uniform Li deposition without forming any dendrites (Table 1). As a result, the FAM145 electrodes can plate the Li-ions beyond their solubility limits and store Li ions via solid solution formation and uniform Li deposition over it. The electrodes demonstrated long-term stability, cycling for over 4,500 hours during electrochemical evaluation, successfully storing up to 20 mAh (equivalent to ~5 mg of Li) without exhibiting any signs of dendrite formation. These results of the electrochemical studies demonstrated FAM145 as a potential anode material that offers high capacity and stability and ensures the safe and reliable operation of lithium metal batteries. 2. Fe0.5Al0.4Mg0.1 (FAM541) [0097] FIG.5 shows the Li-ion storage performance of FAM541 electrodes that showed complete formation of pure bcc phase and has an optimal interfacial energy of 1.8 kJ/mol. Computational studies predicted that FAM541 exhibits the highest Li solubility of 62 at. % to form a solid solution. FIGS. 5a, 5d, and 5f display the voltage profile curves and areal capacities of FAM541 electrodes with an electrode surface area of 1.26 cm
2 for 30 cycles at 1, 2, and 4 mAh charge, respectively. FIGS. 5b-c, 5e-f, and Fig. 5h-i show the 1
st and 30
th cycle voltage profiles of the
electrodes at 1, 2and 4 mAh charge, respectively. Similar to FAM145, the 1
st voltage profile of FAM541 at 1 mAh charge also showed a diffusive curve indicative of the resistance offered during the initial insertion of Li-ions into the FAM541 bcc structure. The overpotential of the coin cells in the initial cycles is higher (~0.285 V) due to this initial diffusion resistance to the Li-ions, and the formation of the solid electrolyte interphase (SEI) layer on the electrode surface which reduces ~0.09V over cycling for 30 cycles. The bcc crystal lattice of FAM541 must open to allow for the Li-ions to occupy the atomic sites of the lattice and thus, offers initial diffusional limitations for Li-ion migration. Once the lattice stabilizes and opens and Li-ions occupy the atomic sites, it creates a pathway for the Li ions to readily diffuse and re-occupy the sites in the subsequent cycles. The FAM541 electrodes show much lower overpotential when cycled to store 2 and 4 mAh of Li- ion charge. Thus, the overpotential of the FAM541 electrodes tends to decrease with cycling as evident from the 1
st and 30
th voltage profiles of the cells at 2 (FIGS.5e-f) and 4 mAh charge (FIGS. 5h-i). The electrodes also show reasonable energy efficiency during cycling and thus, show the potential of the FAM541 to be utilized as anodes for Li-ion storage for advanced battery technologies. 3. Fe0.4Al0.4Mg0.2 FAM442 a. Coin cell performance evaluation [0098] FIG. 6 displays the electrochemical storage performance and response for Li-ion storage at various charge rates of the slurry-coated FAM442 electrodes with 95% and 5% active material and PVDF as the binder, respectively. The electrodes with areal loadings of 2 - 4 mg/cm
2 were tested in a coin cell configuration mode to initially examine their electrochemical performance. The FAM442 showed complete formation of pure bcc phase exhibiting an optimal interfacial energy of 1.4 kJ/mol (Table 1) and a Li solubility limit of 53 at.%. The electrodes were evaluated for their Li storage at various charge rates ranging from 1 mAh to 18 mAh as depicted in FIG. 6. The FAM442 electrodes demonstrated their ability to reversibly store Li-ions by forming a solid solution up to 18 mAh which is equivalent to ~4.5 mg of Li. The electrodes were cycled for 1, 2, 4, and 6 mAh charges for 30 cycles each followed by increasing the charge to 8 mAh and cycling for 100 cycles. The cells showed reasonable charge storage by forming a solid solution with Li- ions. [0099] Afterwards, following these studies to examine the structural robustness of the FAM442, the cells were kept idle for 30 days after testing at 8 mAh charge and resumed their testing at a 10
mAh charge for 200 cycles. The electrodes showed 100% energy efficiency and with no nucleation or growth overpotential indicative of forming a perfect solid solution till the Li solubility limit was reached and thereafter, exhibiting uniform Li plating devoid of forming dendrites due to even lower interfacial energy. Thus, the electrodes were further able to reversibly store Li-ions delivering an areal reversible capacity of 14.5 mAh/cm
2 at an 18 mAh charge. [0100] Similar to previous MCAs, FAM442 also showed an initial diffusion barrier for Li-ions to occupy the atomic sites of the bcc lattice (FIG. 7a-c). Thus, the overpotential of the cells is relatively higher in the initial cycling phase, and the energy efficiency is also lower. However, as the cycling progresses (FIG.7d-f), the crystal lattice of FAM442 is stabilized with the introduction of the Li-ions that paves its way to occupy the atomic sites of the lattice structure leading to the opening of the structure of the alloy facilitating diffusion of Li ions to form the solid solution alloy. Thus, after the crystal lattice is completely opened, the Li-ions readily dissolve into the alloy continuing to form the solid solution without any nucleation and growth overpotential. As a result, the FAM442 electrodes dissolve and extract the Li-ions from its bcc phase at a relatively constant potential as seen in the voltage profiles of the cells in FIG. 7e-f and FIG. 7h-i. [0101] The electrochemical performance evaluation of the FAM442 in coin cell configurations suggested that it is viable for further testing in larger, more complex pouch cell settings. The single- layer pouch cell evaluation of FAM442 at a charge rate of 9 mAh for 100 cycles is presented in FIG. 8. The pouch cell electrodes were cut in a 20 cm
2 area with an areal loading of 9.15 mg/cm
2 and the cell was fabricated in a tandem glovebox with a 400 µL electrolyte amount. The voltage profiles and the areal capacity values for 100 cycles are presented in FIG. 8a and the 1
st and 100
th cycle voltage profiles are displayed in FIG. 8b-c. The pouch cell performance is consistent with the coin cell electrochemical evaluation. The pouch cell showed signs of initial diffusion kinetic barrier for the Li-ions presenting them with the initial resistance to occupy the atomic sites to open the bcc crystal lattice of the FAM442 promoting facile subsequent diffusion of the Li ions. As a result, the energy efficiency is lower in the initial cycles and increases to 97% after 35 cycles. Additionally, the overpotential is relatively higher in the 1
st cycle (~0.08V) which reduces to ~0.072V after 100 cycles. The consistent pouch cell electrochemical evaluation of FAM442 indicates that its properties are consistently reliable across different cell formats. This suggests that the FAM442 alloys maintain their structural integrity, electrochemical stability, and ability to suppress dendrite formation even when scaled up from the smaller, controlled environment of a
coin cell to the more practical and commercially relevant pouch cell configuration. Such consistency implies that FAM442 is suitable for integration into commercial lithium metal batteries without significant performance degradation during scale-up. B. Electrochemical evaluation of FAM442 pellet as a dendrite-free current collector for Li-based batteries [0102] After the successful demonstration of FAM442 as a dendrite-free anode material for advanced Li-based batteries, we evaluated its performance to be utilized in anode-free systems as a current collector. We used a cold uniaxial press to synthesize FAM442 powders into thick (200 – 1000 µm) and dense pellets. Initially, the pellets were prepared using Ga as a liquid phase sintering agent. Additionally, pellets were also prepared using pure FAM442 powders by optimizing the pellet processing conditions. 1) Pellet of FAM442 with Ga as a sintering agent [0103] The XRD pattern of the pure pellet synthesized with Ga is consistent with that of the powder sample suggesting that the crystallographic structure of the material remains intact during the compaction process. FIG. 9 shows the electrochemical performance of the pellet (1.32 cm
2 surface area, 200 – 400 µm thickness) prepared by Ga (PFAM442-G) as a sintering agent with an areal loading of 145.4 mg/cm
2 at various charge rates ranging from 1 mAh to 8 mAh for 110 cycles each. The pellet PFAM442-G was charged with 1, 2, 4, 6, and 8 mAh rates (FIG.9), and the areal capacity and voltage curves for 1, 4, and 8 mAh are shown in FIG. 10a-i. Initially, the pellet prepared using Ga shows low energy efficiency at 1 mAh charge for up to 50 cycles due to Li-ions forming an intermetallic alloy with Ga which can be seen in the voltage profiles in FIG. 10a-c. At this stage, Li-ions not only form a solid solution with the PFAM442 but also form an alloy with Ga (FIG. 10a-c). However, as the cycling progresses, the surface of the pellet stabilizes, and Li- ions tend to dissolve in the PFAM442-G and show no signs of alloying with Ga (FIG. 10d-i). The Li-ions enter and occupy the vacant spaces of the bcc lattice structure of PFAM442-G and form a solid solution. The complete formation of the solid solution of the pellet with Li renders a constant voltage dissolution and extraction of the Li-ions with no nucleation and growth overpotential to overcome during charge and discharge cycles of the cell operation. The overpotential for dissolution and extraction of the Li-ions also reduces with each cycle of the entire cycling performance of the cells. The pellet has been demonstrated to deliver high areal capacities of more than 6 mAh/cm
2 showing long cycling stability for more than 440 cycles. Corresponding to the 53
at. % solubility limit of the FAM442, the pellet can form a solid solution with Li equivalent to an areal capacity of 114-120 mAh/cm
2. The electrochemical performance of PFAM442-G is consistent with that of the powder samples however, Ga which is used as a sintering agent to form a pellet tends to form intermetallic alloy structures with the Li-ions and hence, influences the electrochemical performance of the pellet. Thus, avoiding the usage of any sintering agent affecting the electrochemical performance of the MCA pellets, and to explore the performance of the pure system devoid of any sintering agents, the pure pellet of 100% FAM442 (PPFAM442) was synthesized. 2) Pure pellet of FAM442 [0104] A pure pellet of pristine FAM442 was prepared without any sintering additive by optimizing the processing parameters of the uniaxial press (110 ℃ and 6750 psi for 5 h). The dense and thick PPFAM442 pellet was then used to fabricate a coin cell vs. Li-metal foil to evaluate its promise to be used as a current collector. The pellet exhibited an areal loading of 138.6 mg/cm
2 for 1.32 cm
2 and a thickness of 200 – 400 mm. PPFAM442 exhibits a similar XRD pattern to that of the powder samples corresponding to the formation of the bcc solid solution phase. The electrochemical performance of this pellet is shown in FIG. 11 along with a digital image of the PPFAM442 in the inset of FIG. 11a. The coin cell with the PPFAM442 pellet was charged with a current density of 1 mA/cm
2 to realize an areal capacity of 5 mAh/cm
2 for more than 250 cycles. The energy efficiency of the cell is lower in the initial few cycles due to the resistance offered to the Li-ions to occupy the atomic sites of the bcc crystal lattice of the alloy. Due to this initial kinetic barrier, the cell shows high overpotential during the initial few cycles. However, after the complete solid solution lattice formation of Li-ions with the alloy, the overpotential significantly reduces and the energy efficiency increases to 100% during subsequent dissolution and extraction of the ions for more than 250 cycles. This indicates that the charge-discharge process is highly efficient, with no significant loss of lithium ions due to side reactions or other inefficiencies. FIG. 11b-f displays the voltage profiles of the cell and indicates the evolution of the overpotential with cycling. The overpotential decreases significantly with cycling due to the formation of a complete solid solution resulting in improved electrochemical kinetics leading to faster charge and discharge processes with facile diffusion of Li ions. The results demonstrate that PPFAM442 is highly effective at facilitating reversible lithium storage without losses, degradation, or safety risks and is devoid of any dendrite formation. These results showcase the potential of this MCA system of
FAM442 (Fe
40Al
40Mg
20) to be used as a current collector in advanced Li-ion batteries (LIBs) or lithium metal batteries (LMBs) in anode-free systems. 3) Pre-lithiated pure pellet of FAM442 as Li-ion reservoir [0105] In the above section, the results described the performance of PPFAM442 demonstrating the promise of FAM442 to be used as a current collector in LIBs and LMB. However, the pellet still exhibited an initial kinetic diffusion barrier for Li-ions to occupy the vacant sites of the lattice structure and form a solid solution. To minimize this initial barrier, a new pellet was synthesized (1.32 cm
2 surface area, 140.9 mg/cm
2, 200 – 400 µm) and sequentially subjected to pre-lithiation with constant current and constant voltage (CCCV). The CCCV process is anticipated to force the Li-ions into the atomic vacant sites of the crystal lattice of the alloy enabling it to form a complete solid solution. The pellet was first charged with a constant current (CC) density of 0.5 mA/cm
2 for 1 mAh/cm
2 followed by holding the potential (CV) at -0.2V till the current drops to C/10. Following this, the pellet was again charged with CC of 1mA/cm
2 for 4 mAh/cm
2 and holding the potential at -0.2V till the current drops to C/10. Similarly, the pellet was charged sequentially for 9 and 1 mAh/cm
2 with CCCV to cumulatively charge the pellet with 15 mAh/cm
2 of Li-ions. This pre-lithiated pellet with Li equivalent to 15 mAh/cm
2 (~3.75 mg of Li) dissolved in it was then used as a Li reservoir during cell operation. The Li-ions from the pellet were then cycled at a current density of 2 mA/cm
2 to realize an areal capacity of 6 mAh/cm
2 and deposited over the counter Li-metal anode to showcase the promise of PPFAM442 as a current collector in anode- free systems and the results are presented in FIG.12b. The energy efficiency of the cell is evaluated as striping or dealloying from the solid solution (discharge capacity) over plating or alloying forming the solid solution (charge capacity) during cell operation. Interestingly, the cell displayed a 100% coulombic efficiency in the 1
st cycle and maintained it throughout the 300 cycles. However, the overpotential of the cell (FIG. 12c-e) gradually increases with cycling possibly due to an increase in the internal resistance of the cell or degradation of the interface between the Li- metal used as the counter electrode and the electrolyte. Nevertheless, a 100% coulombic efficiency throughout the 300 cycles signifies that the MCA pellet is highly efficient in lithium cycling. The results shown here demonstrate that Li-containing FAM442 pellet as a lightweight current collector offers a compelling combination of reduced weight, enhanced energy density, structural integrity, and dendrite suppression, positioning it as a promising solution for advanced LIBs and LMBs.
Conclusion: [0106] Innovative MCA designs: The patent presents a novel approach to creating multicomponent alloy (MCA) systems with a body-centered cubic (bcc) solid solution phase, achieved through advanced computational studies. These MCAs are optimized for interfacial energy and enthalpy of mixing, ensuring superior performance as dendrite-free anodes and current collectors for use in lithium metal and lithium-ion batteries in anode free configurations wherein the Li comes directly from the cathode such as LiCoO
2, LiNiO
2, LiNi
1-xCo
xO
2 (0<x<1), and LiNi
1- x-yMnxCoyO2 (0< x + y <1), as well as emerging systems such as Li-S utilizing Li2S as cathodes. In lithiated forms, the MCA systems can also be used as dendrite free anodes as well as current collectors for lithium-sulfur, Li-S and Li-O
2 batteries. [0107] Lightweight and efficient current collectors: The MCA systems developed in this patent offer a significant reduction in the density, over 50% lower than traditional copper current collectors. This makes them highly attractive as lightweight current collector alternatives, contributing to the overall efficiency and energy density of the battery systems. [0108] Scalable synthesis process: The MCAs are synthesized using a scalable and cost-effective method involving HEMM/HEMA. This process ensures the feasibility of large-scale production, making these materials suitable for industrial applications. Furthermore, the use of cold pressing (CP), cold isostatic pressing (CIP) and cold-uniaxial press (CUP) at moderate temperatures of ~100 – 150
oC ensures the formation of dense pellets that can also be cold rolled to form foils for direct use as current collectors in anode free configurations replacing copper the currently used current collectors in Li-ion batteries. [0109] Solid solution formation with lithium: The MCAs are designed to allow lithium to form a solid solution by occupying the vacant sites within the bcc phase. This unique interaction between lithium and the MCA prevents dendrite formation, enhancing the safety and reliability of the battery. [0110] Versatility of MCA compositions: Various MCA compositions, including FAM145, FAM541, and FAM442, have been synthesized and evaluated. These compositions have shown promising electrochemical performance in both coin and pouch cell configurations, highlighting their potential for use in advanced battery technologies. [0111] Industrial viability of FAM442: Among the tested compositions, FAM442 demonstrated particularly strong electrochemical performance in both coin and pouch cells, indicating its
suitability for industrial and vehicle technology battery applications. Its stability and efficiency make it a viable candidate for integration into commercial battery products, although all compositions have equally demonstrated promise for use as dendrite free anodes and current collectors. [0112] Application in anode-free setups: The MCA systems can be utilized in their pre-lithiated alloyed states for use as anodes and current collectors or as components in anode-free setups with lithium-containing cathodes. This versatility broadens their potential applications in next- generation battery technologies, offering new possibilities for high-performance, lightweight, and safe energy storage solutions.
$ ∆^^^^^ = ! & % 9 + /−0^Δ2 ^ + 5 '^6 & 4 ^^^^^ "# ∗ 4 78 : , ; – partial interfacial energy of Li with metal A.
metal A. VLi − atomic volume of Li, P = 14.2 kJ/(mol cm2 V2 (density unit)1/3) and Q = 133.5 kJ/(mol cm2 9 (density unit)). '6 & 78 : , and 2^ ∗ are tabulated and available in the literature or can also be calculated from first principles for elements not documented in the public sources. [0073] For 5 at. % of Li, the interfacial energies ΔHint in all considered non-lithiated MCA alloys are collected in Table 1. The lowest ΔHint are for Fe10Al40Mg50 and Fe10Ga40Mg50, which makes them the most optimal compounds in terms of suppression of the dendrite formation. [0074] For calculation of the interfacial energy of Li above the solubility limit Xlim, the equation will be slightly modified as shown below: ^^^ ^^ ^^ ^^ ^^ ^^A^^ ^^^^^ = ^ ^ ^^ ^^ ^^^^^^^^1 − B C^D^^^^ ^^ ^^ ^^ ^^ ^^ ^^^^^ + ^^^^ ^^ ^^ ^^ ^^ ^ ^^^^^ ; ^^^ ^^ ^^ ^^ ^^ ^ ^^^^^ =0 (2)
on the surface of the Li-saturated alloy interface. For 5 at. % of Li above the solubility limit, the ∆Hint
are also collected in Table 1. In comparison to non-lithiated alloys, the alloys saturated with lithium up to the solubility limit drastically decrease the interfacial energy at the surface with metallic Li further plated on top of this alloyed surface. This happens due to presence of substantial amount of Li in the solid solution, which increases the affinity of the alloying surface to pure plated Li and thus, decreases the interfacial energy. As a result, the higher solubility limit Xlim leads to lower interfacial energy due to the (1 - Xlim) term in Equation (2) and thus, allowing to plate higher amount of Li beyond the solid solubility limit of Li on the surface maintaining relatively low interfacial energy needed to ensure dendrite free Li deposition. Table 1. Calculated interfacial energies: for non-lithiated MCAs lithiated up to the solubility limits, and Li solubility limit values. MCA Composition delta Hint for cLi=5 at. % delta Hint for cLi=5 at.% Xlim in non-lithiated MCAs above solubility limit (at.%) (in kJ/mol) in Li-saturated MCAs (in kJ/mol) Fe50Zn40Mg10 +1.5 +1.0 33 Fe50Al40Mg10 +1.8 +0.68 62 Fe40Al40Mg20 +1.4 +0.66 53 Fe10Al40Mg50 +0.07 +0.044 37 Fe10Ga40 Mg50 -0.3 -0.16 45 4. Volume expansion of the lithiated MCA anodes [0075] The volume expansion of the lithiated alloy vs. non-lithiated alloy depends on the atomic radii of the metallic components of the alloy and an atomic radius of Li. For example, in Fe40Al40Mg20 the atomic metallic radii for Fe, Al, and Mg are 1.26Å, 1.43 Å, and 1.60 Å, respectively. Thus, the average atomic radius of Fe40Al40Mg20, Rav, is [1.263x0.4 + 1.433x0.4 + 1.63]1/3 = 1.41 Å. Taking into account the atomic radius of Li, RLi = 1.52 Å, the volume expansion during alloying of Li into the alloy will be: [Rav3 (1-x) + RLi3 x] / Rav3(1-x) = 1 + 1.258x/(1-x), where x is Li content. The percentage change in volume will thus be given by: %Volume expansion ΔV: [1.258x/(1-x)] * 100%. [0076] With respect to this function and the corresponding relation, a high content of Li (50 at%) the volume expansion ΔV reaches 126%, which is quite large (the total volume increases more than twice). However, at lower Li content ~20at% ΔV is within ~30-31%. Furthermore, in
experimental observations of the synthesized alloy of Fe40Al40Mg20 as described in Section II, to achieve a desired areal capacity of Li of 6 mAh/cm2 which corresponds to 1.5 mg of Li since 1 mg of Li results in an areal capacity of 4 mAh/cm2. With a fabricated dense pellet of Fe40Al40Mg20 of 183 mg with the atomic mass of 38-gram atoms/mole, the mole percent of alloyed Li is 4.3 mole% which would correspond to a volume change of ~5.6%, which can be easily endured by the system without causing any phase separation, accompanying volume expansion related decrepitation of the electrode and additionally, preserving the original bcc crystal structure. Even with a higher amount of Li alloyed into the system, the volume change will likely be ~5-10% that can be easily endured by the alloy and will not result in any decrepitation or cracking that is typically seen in Zintl alloy phases encountered in Si and Sn anodes that result in colossal volume change of 300- 400%. This is another attribute of the present invention and the identified multicomponent component alloys (MCAs). 5. Li-ion mobility in MCA anodes [0077] Li-ion mobility in MCA anodes is one of the critical characteristics of the compound needed for efficient cycling of the electrode. Hindered mobility of Li ions in the anode can result in a very poor cyclability. For estimation of the Li-ion mobility in various MCAs there is a need to calculate the activation energy barriers during hopping of the lithium atoms between two neighbor unit cells of the crystal lattice via the vacancy hopping diffusion mechanism. [0078] The computational model for calculating the activation barriers consisted of two body centered cubic (bcc) elementary unit cells with alternate atomic layers of Li and probed metal layer. In model (a), a Li-atom located in the center of the cubic bcc unit cell moves to the neighbor Li-vacancy through the intermediate atomic layer. At the same time the Li-vacancy moves in the opposite direction. In model (b), in the case of pure Li metal, the intermediate layer consists of only Li atoms. For calculation of the activation energies, Ea of Li-ion in pure Li and in other metal components of the studied MCAs, models (a) an (b) were used. All the computations were executed using the climbing image nudged elastic band method (CINEB) also implemented in VASP computational package within the projector-augmented wave (PAW) method and the generalized gradient approximation (GGA) for the exchange-correlation energy functional in a form known in the art. The total path of the Li-ion between both centers of the adjacent unit cells was divided in eight equal intervals with calculations of the total energies of the system in each consecutive point from start to the end of this path. For all calculations, a 2x2x2 supercell was
considered consisting of eight elementary bcc unit cells, and containing one Li vacancy, seven Li atoms, and eight atoms of other metals that was constructed. For pure Li metal, the structure contained 1 vacancy and 15 Li atoms. The Monkhorst-Pack scheme has been used to sample the Brillouin zone and create the k-point grid for all the Li alloys used in the current study. The selection of appropriate numbers of k-points in the irreducible parts of the Brillouin zone was made on the grounds limiting the convergence of the total energy to 0.1 meV/atom. [0079] The calculated potential energy profiles for the different alloying elements were derived. All the potential energy graphs have similar profiles with maximum energy values located at the middle of the Li hopping path which correspond to the activation barriers for each specific alloying element. According to these results, the Li-mobility in the modeled Mg and Zn bcc metals are even slightly higher (Ea barriers are lower) than in pure Li-bcc most likely due to lower cohesive energy of pure Mg and Zn compared to pure Li which enables the Li-atom easier to diffuse through the Mg and Zn plane and, thus, results in a facile overall Li-ion conductivity/mobility in pure Mg and Zn metals. Also, this graph shows that Na decreases the activation barrier for Li-movement through the lattice even more compared to that of metallic Mg and Zn. [0080] Whereas, Fe, Al, and Ga increase the activation barriers for Li-ion hopping pathway. It happens due to higher Fe-Fe, Al-Al, and Ga-Ga interatomic bonding within the corresponding intermediate layer. [0081] Also, collected in Table 2 are the average activation barriers, Ea for all MCAs considered in the study. One can see that the lowest Ea av (the highest Li-mobility) are demonstrated by Fe50Zn40Mg10, Fe10Ga40Mg50 and Fe10Al40Mg50, MCA systems. Table 2. Calculated average Eaav for different MCAs Alloy Ea average (eV) Fe50Zn40Mg10 0.150 Fe50Al40Mg10 0.166 Fe40Al40M20 0.163 Fe10Al40Mg50 0.153 Fe10Ga40Mg50 0.152 [0082] Thus, this computational study was useful in estimating different physical properties of various MCA anodes. These properties include phase stability, interfacial energy, Li solubility limits, volume expansion and Li-ion mobility through the MCAs. The theoretical studies described
above formed the basis of the experimental studies that were executed to validate the findings of the theoretical and computational studies which are described in Section II below. Section II: Experimental Studies of Dendrite-free Novel Multi-Component Alloy (MCA) Anodes and Current Collectors for Li-ion Batteries [0083] This study comprises all the experimental studies conducted on the three MCA systems identified by the theoretical studies described above in Section I. Experimental section: [0084] The MCAs were synthesized by a high-energy mechanical milling and alloying (HEMM/HEMA) process. The elemental Fe, Al, and Mg powders were taken in their atomic ratios and loaded in the milling jars. The powder-to-milling ball ratio was kept constant at 1:1. A 10 ml of toluene as solvent was added to the jar containing the powder and milling balls to facilitate wet milling followed by HEMM/HEMA for 5 hours with a 20 min rest after each consecutive hour of milling. After milling, the jars were kept open in the fume hood overnight to remove the solvent. The MCA powders were then dried in a vacuum oven at 60 ℃ for 6 hours and stored in a vacuum desiccator. Various MCAs (Fe0.4Al0.4Mg0.2 (FAM442), Fe0.5Al0.4Mg0.1 (FAM541), and Fe0.1Al0.4Mg0.5 (FAM145)) were prepared by taking the elemental powders in their atomic ratio. These developed MCA systems offer a significant reduction in density, over 50% lower than traditional copper (Cu = ~9 g/cc) current collectors (FAM442 = ~4.6 g/cc, FAM541 = ~5.2 g/cc, FAM145 = ~2.7 g/cc). [0085] The powder samples of MCAs were used as an active material with PVDF as a binder during slurry preparation and utilized as an anode versus Li-metal as a counter electrode in their initial electrochemical testing. This demonstrated their promise to be used as an anode material for various Li-based batteries. MCA pellets were prepared and utilized for electrochemical testing to evaluate the effectiveness of MCA as potential current collectors in anode-free systems. The MCA powders were formed into a dense pellet using a uniaxial cold press. FAM442 was selected as the representative material of the various MCA materials tested to further investigate its potential as a current collector. Based on the preliminary electrochemical response of the MCAs, FAM442 indicated a superior performance compared to other MCAs and thus, was considered to demonstrate its effectiveness as a current collector in the battery operation. FAM442 powder was made into pellets and investigated to serve as a reliable and efficient current collector in advanced Li-based battery technologies, particularly in innovative configurations like anode-free systems.
[0086] Initially, gallium (Ga) was explored as a chemical additive to obtain a thick and dense pellet. A 5 wt.% of Ga (10 mg) was added with 95 wt.% of FAM442 (190 mg) powder in a mortar pestle and kept in an oven at 60 ℃ and mixed to get a homogenous powder mixture. This powder mixture was then loaded into a pellet-making die (1.3 cm diameter, 1.32 cm2) and placed in the uniaxial cold press at 40 ℃ for 1 hour at various pressures. Ga was used as a low-temperature liquid phase sintering agent as its melting point is less than 30 ℃. Consequently, a dense pellet (PFAM442-G) was obtained using 5 wt.% Ga at the optimized processing parameters of holding the cold press at 40 ℃, 250 psi pressure for 2 hours. When the PFAM442-G pellet was tested for its Li-ion storage capability, it was observed that the Ga which is used as a sintering agent to form a pellet tends to form intermetallic with the Li-ions and thus, influences the electrochemical performance of the pellet for initial cycles. Thus, avoiding the usage of any sintering agent affecting the electrochemical performance of the MCA pellets, the pure pellet of 100% FAM442 (PPFAM442) was synthesized. The processing conditions of the uniaxial press to synthesize the pellet were optimized. Generally, 200 mg of FAM442 powder synthesized by HEMM/HEMA was weighed and transferred into a pellet-making die. The die was then loaded into the uniaxial press which was held at a temperature and pressure of 110 ℃ and 6750 psi respectively, for 5 hours to yield a dense pellet of FAM442. The pellet was then collected and stored in a vacuum desiccator until its electrochemical testing. PPFAM442 pellets were prepared for in-situ XRD measurements using the optimized pellet-making processing condition with an areal loading of 116 mg /cm2 with a 0.5 cm2 surface area and 200 – 400 µm thickness. Structural and electrochemical characterization: [0087] The phase structure characterization of the samples was obtained by X-ray diffractometer (XRD) (Empyrean: Malvern Panalytical) using Co radiation. The wavelength correction was performed to convert the pattern to depict Cu Kα radiation. The electrochemical performance of various MCA alloys was evaluated in both coin cell and pouch cell configurations. Electrodes were prepared by a standard slurry coating method on a Cu foil. A slurry was obtained by mixing 95% MCA powders as active material and 5% PVDF as a binder using NMP as a solvent and coated on Cu foil using a doctor’s blade. The slurry-coated foil was dried in a vacuum oven at 80 ℃ for 12 h. Electrodes for testing in coin cell configuration were obtained by punching circular discs of 0.5- inch diameter (1.26 cm2). Coin cells were fabricated using CR2032 employing the electrodes of various MCAs (FAM541, FAM442, and FAM145) as a working electrode, a polypropylene
separator disc, and Li foil as a reference and counter electrode. The electrolyte solution was prepared by dissolving 1.0 M Lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt in a 1:1 (v/v) mixture of Dioxolane (DOL) and Dimethoxyethane as solvents with 2 wt.% of LiNO3 as an additive. The electrolyte amount was maintained constant throughout the electrochemical testing in coin cells at 60 μL. [0088] Coin cells were also fabricated using dense pellets of pure FAM442 and with Ga as a sintering agent with an areal loading of 135 - 142mg/cm2 and 145.4 mg/cm2 respectively, versus Li foil as a counter electrode. The electrolyte amount used was kept constant at 60 µL leading to an extremely lean electrolyte-to-active material ratio. [0089] For a single-layer pouch cell fabrication, the FAM442 electrodes were cut into a rectangular shape (4 cm and 5 cm) with an area of 20 cm2 using an electrode cutter machine. The areal loading of the active material (FAM442) in the pouch cell electrodes was 9.2 mg/cm2. The single-layer electrodes were enclosed with a PP separator. The pouch cell bag (multi-layer laminate material) was prepared by cutting and heat-sealing which creates a cavity that will hold the electrode assembly. Li foil (50 µm in thickness) was used as a counter and reference electrode for the pouch cell testing. A 400 µL of the electrolyte was used for the pouch cell testing leading to an extremely lean electrolyte to active material ratio. The MCA electrodes enclosed in separators were assembled against the Li foil and this assembly was then loaded in the pouch cell bag before electrolyte filling and sealing the pouch cell. The as-fabricated pouch cell was allowed to rest for 24 hours before electrochemical testing. The electrochemical performance of the various MCA electrodes was measured by using Arbin Potentiostat (Electrochemical workstation). Results and discussion: [0090] The HEMM/HEMA facilitates the formation of the metastable solid solution due to repeated fracturing, welding, and rewelding of powder particles in a high-energy ball mill. The repeated high-energy collisions between the balls and the powder particles result in the mixing of different elements at an atomic level, leading to the formation of a solid solution. The intense mechanical deformation allows atoms of one element to dissolve into the crystal lattice of another, forming a homogeneous solid solution. The HEMM/HEMA of Fe, Al, and Mg elemental powders involves intense mechanical forces and high-energy collisions resulting in the mixing of their atoms forming a solid solution with a body-centered cubic (bcc) crystal structure. The different crystal sizes of Fe, Al, and Mg result in the formation of nanocrystalline structures which further
stabilizes the bcc phase. The XRD patterns of all the synthesized MCAs in powder and pellet form were obtained. The XRD patterns of the powder samples of Fe0.4Al0.4Mg0.2 (FAM442) and Fe0.5Al0.4Mg0.1 (FAM541) respectively, after milling showed two peaks around the 2θ values of 44.5o and 65o corresponding to the nanocrystalline bcc phase confirming the formation of solid solution during HEMM/HEMA. Li metal has a bcc crystal lattice, and the MCAs are designed to have similar crystallographic symmetry with optimal interfacial energy and enthalpy of mixing such that Li dissolves into the MCAs and forms a solid solution instead of plating over it. The XRD pattern of Fe0.1Al0.4Mg0.5 (FAM145) showed a small hump around 2θ value of 44.5o demonstrating the initiation of the formation of bcc phase after 5 hours of HEMM/HEMA, although all the elements had not fully reacted. The formation of the bcc phase shows that the approach is conducive to formation of the metastable structure to demonstrate the feasibility and validity of the disclosed concept. The XRD pattern of the pellets synthesized using Ga as a sintering agent (PFAM442-G) and pure powder of FAM442 (PPFAM442), respectively, showed two peaks around the 2θ values of 44.5o and 65o, indicating the presence of the nanocrystalline bcc phase, suggesting that the processing parameters for synthesizing the pellet via uniaxial cold press have no adverse effects on the material structure. [0091] The in situ XRD measurements of the PPFAM442 were carried out during cell operation to examine whether Li plates over the surface of the FAM442 pellet or forms a solid solution with the alloy. A special EL-cell was fabricated of these measurements in the glove box with Li-foil (0.785 cm2 area and 600 µm thickness). The PPFAM442 in the EL-cell was charged with a current density of 0.25 mA/cm2 to realize 3.75 mAh/cm2 areal capacity. XRD measurements were carried out at intervals of 15 min during cell operation. The XRD pattern of the pellet was collected over 15 hours while Li-ions were being charged into it and presented in FIG. 1. There was no evidence of any peak corresponding to the metallic Li or any Li-related alloy or compound even after 15 hours of cycling (3.75 mAh/cm2 which is equivalent to approximately 1 mg of Li) from FIG. 1, suggesting that the Li-ions formed a solid solution with the FAM442 pellet. A. Electrochemical evaluation of slurry-coated MCAs as dendrite-free anode for Li-based batteries 1) Fe0.1Al0.4Mg0.5 (FAM145) [0092] FIG. 2 shows the electrochemical Li-ion storage in the slurry-coated FAM145 electrodes with Li foil as a counter and reference electrode in a coin cell. The FAM145 electrodes (1.26 cm2)
with active material loading of 2-3 mg/cm2 were presented with the Li-ion at various charge rates ranging from 1 mAh to 20 mAh for 31 cycles each. Initially, the electrodes were cycled at 1 mA current for 31 cycles beginning with 1h charge/discharge with sequential increments of 1h to 10h following which the cells were also cycled at 3 mA current for 4h and 5h for 31 cycles, respectively. Additionally, to examine the limits of the solid solution alloy of MCA with Li, the charge rates of the electrodes were then increased to realize 18 mAh and 20 mAh for 31 cycles each. The FAM145 electrodes demonstrated the ability to not only store high Li charge storage via solid solution formation but also long cyclic stability at low and high charge rates. The FAM145 displayed the promise to be utilized as an alternative anode material for advanced energy storage batteries with a longer and more stable lifespan devoid of dendrite formation. The electrodes were subjected to over 4500 hours of continuous electrochemical evaluation for lithium charge storage. The electrodes showed the ability to store Li up to 20 mAh which is equivalent to ~5 mg of Li without showing any signs of dendrites. [0093] Initially, the energy efficiency of the FAM145 electrodes was relatively lower which could be attributed to the SEI formation and the initial diffusion barrier for Li-ion to get into the bcc phase of the MCA solid solution. Additionally, the XRD pattern of FAM145 confirmed that it consists of a mixed phase of bcc and a metallic elemental phase corresponding to the unreacted elements which could also have contributed to the lower coulombic efficiency. However, as the cycling progressed further, Li-ions paved their pathway, stabilizing the system and opened the crystal lattice of the MCA alloy facilitating the diffusion of Li ions to form the solid solution. As a result, the energy efficiency of the FAM145 electrodes is 100% from 5 mAh charge storage of Li-ions. The computational studies indicated that FAM145 has the most optimal interfacial energy (0.07 kJ/mol) along with 37 at. % Li solubility and partial bcc crystal lattice, thus, these electrodes showed stable and reversible Li cycling over the higher charged rates. [0094] FIG. 3 shows the Li charge storage response of FAM145 electrodes at 1 mAh (FIG. 3a-c) and 5 mAh (FIG. 3d-f) charge rates. FIG. 3a and 3d display the voltage profile curves and areal capacities of FAM145 electrodes with an electrode surface area of 1.26 cm2 for 31 cycles at 1 mAh and 5 mAh charge, respectively. FIG.3b-c and Fig.3e-f show the 1st and 31st cycle voltage profiles of the electrodes at 1 mAh and 5 mAh charge, respectively. The 1st voltage profile of FAM145 at 1 mAh charge shows a diffusive curve displaying the resistance faced by Li-ions during their initial insertion into the FAM145 structure. The overpotential of the coin cells in the initial cycles is
higher (~0.34 V) due to this initial diffusion resistance to the Li-ions, and due to the formation of the solid electrolyte interphase (SEI) layer on the electrode surface (FIG. 3b). However, the overpotential decreases with cycling showing ~0.16 V after 31 (FIG. 3c) cycles of continuous charge and discharge of the cell. As the cycling continues with 5 mAh the overpotential further reduces to (~0.1 V) after the 31st cycle of 5 mAh charge (FIG. 3f). [0095] FIG. 4 shows the electrochemical evaluation of FAM145 electrodes at higher charge rates of 12 mAh and 18 mAh. Before connecting at these charge rates, the cells had already cycled for more than 3400 hours at different charge rates as shown in FIG. 2. FIG. 4a-c and 4d-f show the Li-storage of FAM145 at higher charge storage rates of 12 mAh and 18 mAh. It is evident from these curves that FAM145 can reversibly store Li even at higher charge storage rates with 100% energy efficiency, although with higher overpotential possibly due to electrolyte consumption and an increase in the overall impedance of the cells. [0096] Computational studies revealed that the solubility limit for FAM145 to form a solid solution with Li-ions was 37 at.%. With the loading of the 2-3 mg/cm2, FAM145 alloy at charge storage rate of 18 mAh had surpassed the solubility limit, and yet the electrodes could reversibly cycle Li-ions at much higher rates. The computational studies further revealed that the interfacial energy of the FAM145 at the Li solubility limit and above, is even more favorable for uniform Li deposition without forming any dendrites (Table 1). As a result, the FAM145 electrodes can plate the Li-ions beyond their solubility limits and store Li ions via solid solution formation and uniform Li deposition over it. The electrodes demonstrated long-term stability, cycling for over 4,500 hours during electrochemical evaluation, successfully storing up to 20 mAh (equivalent to ~5 mg of Li) without exhibiting any signs of dendrite formation. These results of the electrochemical studies demonstrated FAM145 as a potential anode material that offers high capacity and stability and ensures the safe and reliable operation of lithium metal batteries. 2. Fe0.5Al0.4Mg0.1 (FAM541) [0097] FIG.5 shows the Li-ion storage performance of FAM541 electrodes that showed complete formation of pure bcc phase and has an optimal interfacial energy of 1.8 kJ/mol. Computational studies predicted that FAM541 exhibits the highest Li solubility of 62 at. % to form a solid solution. FIGS. 5a, 5d, and 5f display the voltage profile curves and areal capacities of FAM541 electrodes with an electrode surface area of 1.26 cm2 for 30 cycles at 1, 2, and 4 mAh charge, respectively. FIGS. 5b-c, 5e-f, and Fig. 5h-i show the 1st and 30th cycle voltage profiles of the
electrodes at 1, 2and 4 mAh charge, respectively. Similar to FAM145, the 1st voltage profile of FAM541 at 1 mAh charge also showed a diffusive curve indicative of the resistance offered during the initial insertion of Li-ions into the FAM541 bcc structure. The overpotential of the coin cells in the initial cycles is higher (~0.285 V) due to this initial diffusion resistance to the Li-ions, and the formation of the solid electrolyte interphase (SEI) layer on the electrode surface which reduces ~0.09V over cycling for 30 cycles. The bcc crystal lattice of FAM541 must open to allow for the Li-ions to occupy the atomic sites of the lattice and thus, offers initial diffusional limitations for Li-ion migration. Once the lattice stabilizes and opens and Li-ions occupy the atomic sites, it creates a pathway for the Li ions to readily diffuse and re-occupy the sites in the subsequent cycles. The FAM541 electrodes show much lower overpotential when cycled to store 2 and 4 mAh of Li- ion charge. Thus, the overpotential of the FAM541 electrodes tends to decrease with cycling as evident from the 1st and 30th voltage profiles of the cells at 2 (FIGS.5e-f) and 4 mAh charge (FIGS. 5h-i). The electrodes also show reasonable energy efficiency during cycling and thus, show the potential of the FAM541 to be utilized as anodes for Li-ion storage for advanced battery technologies. 3. Fe0.4Al0.4Mg0.2 FAM442 a. Coin cell performance evaluation [0098] FIG. 6 displays the electrochemical storage performance and response for Li-ion storage at various charge rates of the slurry-coated FAM442 electrodes with 95% and 5% active material and PVDF as the binder, respectively. The electrodes with areal loadings of 2 - 4 mg/cm2 were tested in a coin cell configuration mode to initially examine their electrochemical performance. The FAM442 showed complete formation of pure bcc phase exhibiting an optimal interfacial energy of 1.4 kJ/mol (Table 1) and a Li solubility limit of 53 at.%. The electrodes were evaluated for their Li storage at various charge rates ranging from 1 mAh to 18 mAh as depicted in FIG. 6. The FAM442 electrodes demonstrated their ability to reversibly store Li-ions by forming a solid solution up to 18 mAh which is equivalent to ~4.5 mg of Li. The electrodes were cycled for 1, 2, 4, and 6 mAh charges for 30 cycles each followed by increasing the charge to 8 mAh and cycling for 100 cycles. The cells showed reasonable charge storage by forming a solid solution with Li- ions. [0099] Afterwards, following these studies to examine the structural robustness of the FAM442, the cells were kept idle for 30 days after testing at 8 mAh charge and resumed their testing at a 10
mAh charge for 200 cycles. The electrodes showed 100% energy efficiency and with no nucleation or growth overpotential indicative of forming a perfect solid solution till the Li solubility limit was reached and thereafter, exhibiting uniform Li plating devoid of forming dendrites due to even lower interfacial energy. Thus, the electrodes were further able to reversibly store Li-ions delivering an areal reversible capacity of 14.5 mAh/cm2 at an 18 mAh charge. [0100] Similar to previous MCAs, FAM442 also showed an initial diffusion barrier for Li-ions to occupy the atomic sites of the bcc lattice (FIG. 7a-c). Thus, the overpotential of the cells is relatively higher in the initial cycling phase, and the energy efficiency is also lower. However, as the cycling progresses (FIG.7d-f), the crystal lattice of FAM442 is stabilized with the introduction of the Li-ions that paves its way to occupy the atomic sites of the lattice structure leading to the opening of the structure of the alloy facilitating diffusion of Li ions to form the solid solution alloy. Thus, after the crystal lattice is completely opened, the Li-ions readily dissolve into the alloy continuing to form the solid solution without any nucleation and growth overpotential. As a result, the FAM442 electrodes dissolve and extract the Li-ions from its bcc phase at a relatively constant potential as seen in the voltage profiles of the cells in FIG. 7e-f and FIG. 7h-i. [0101] The electrochemical performance evaluation of the FAM442 in coin cell configurations suggested that it is viable for further testing in larger, more complex pouch cell settings. The single- layer pouch cell evaluation of FAM442 at a charge rate of 9 mAh for 100 cycles is presented in FIG. 8. The pouch cell electrodes were cut in a 20 cm2 area with an areal loading of 9.15 mg/cm2 and the cell was fabricated in a tandem glovebox with a 400 µL electrolyte amount. The voltage profiles and the areal capacity values for 100 cycles are presented in FIG. 8a and the 1st and 100th cycle voltage profiles are displayed in FIG. 8b-c. The pouch cell performance is consistent with the coin cell electrochemical evaluation. The pouch cell showed signs of initial diffusion kinetic barrier for the Li-ions presenting them with the initial resistance to occupy the atomic sites to open the bcc crystal lattice of the FAM442 promoting facile subsequent diffusion of the Li ions. As a result, the energy efficiency is lower in the initial cycles and increases to 97% after 35 cycles. Additionally, the overpotential is relatively higher in the 1st cycle (~0.08V) which reduces to ~0.072V after 100 cycles. The consistent pouch cell electrochemical evaluation of FAM442 indicates that its properties are consistently reliable across different cell formats. This suggests that the FAM442 alloys maintain their structural integrity, electrochemical stability, and ability to suppress dendrite formation even when scaled up from the smaller, controlled environment of a
coin cell to the more practical and commercially relevant pouch cell configuration. Such consistency implies that FAM442 is suitable for integration into commercial lithium metal batteries without significant performance degradation during scale-up. B. Electrochemical evaluation of FAM442 pellet as a dendrite-free current collector for Li-based batteries [0102] After the successful demonstration of FAM442 as a dendrite-free anode material for advanced Li-based batteries, we evaluated its performance to be utilized in anode-free systems as a current collector. We used a cold uniaxial press to synthesize FAM442 powders into thick (200 – 1000 µm) and dense pellets. Initially, the pellets were prepared using Ga as a liquid phase sintering agent. Additionally, pellets were also prepared using pure FAM442 powders by optimizing the pellet processing conditions. 1) Pellet of FAM442 with Ga as a sintering agent [0103] The XRD pattern of the pure pellet synthesized with Ga is consistent with that of the powder sample suggesting that the crystallographic structure of the material remains intact during the compaction process. FIG. 9 shows the electrochemical performance of the pellet (1.32 cm2 surface area, 200 – 400 µm thickness) prepared by Ga (PFAM442-G) as a sintering agent with an areal loading of 145.4 mg/cm2 at various charge rates ranging from 1 mAh to 8 mAh for 110 cycles each. The pellet PFAM442-G was charged with 1, 2, 4, 6, and 8 mAh rates (FIG.9), and the areal capacity and voltage curves for 1, 4, and 8 mAh are shown in FIG. 10a-i. Initially, the pellet prepared using Ga shows low energy efficiency at 1 mAh charge for up to 50 cycles due to Li-ions forming an intermetallic alloy with Ga which can be seen in the voltage profiles in FIG. 10a-c. At this stage, Li-ions not only form a solid solution with the PFAM442 but also form an alloy with Ga (FIG. 10a-c). However, as the cycling progresses, the surface of the pellet stabilizes, and Li- ions tend to dissolve in the PFAM442-G and show no signs of alloying with Ga (FIG. 10d-i). The Li-ions enter and occupy the vacant spaces of the bcc lattice structure of PFAM442-G and form a solid solution. The complete formation of the solid solution of the pellet with Li renders a constant voltage dissolution and extraction of the Li-ions with no nucleation and growth overpotential to overcome during charge and discharge cycles of the cell operation. The overpotential for dissolution and extraction of the Li-ions also reduces with each cycle of the entire cycling performance of the cells. The pellet has been demonstrated to deliver high areal capacities of more than 6 mAh/cm2 showing long cycling stability for more than 440 cycles. Corresponding to the 53
at. % solubility limit of the FAM442, the pellet can form a solid solution with Li equivalent to an areal capacity of 114-120 mAh/cm2. The electrochemical performance of PFAM442-G is consistent with that of the powder samples however, Ga which is used as a sintering agent to form a pellet tends to form intermetallic alloy structures with the Li-ions and hence, influences the electrochemical performance of the pellet. Thus, avoiding the usage of any sintering agent affecting the electrochemical performance of the MCA pellets, and to explore the performance of the pure system devoid of any sintering agents, the pure pellet of 100% FAM442 (PPFAM442) was synthesized. 2) Pure pellet of FAM442 [0104] A pure pellet of pristine FAM442 was prepared without any sintering additive by optimizing the processing parameters of the uniaxial press (110 ℃ and 6750 psi for 5 h). The dense and thick PPFAM442 pellet was then used to fabricate a coin cell vs. Li-metal foil to evaluate its promise to be used as a current collector. The pellet exhibited an areal loading of 138.6 mg/cm2 for 1.32 cm2 and a thickness of 200 – 400 mm. PPFAM442 exhibits a similar XRD pattern to that of the powder samples corresponding to the formation of the bcc solid solution phase. The electrochemical performance of this pellet is shown in FIG. 11 along with a digital image of the PPFAM442 in the inset of FIG. 11a. The coin cell with the PPFAM442 pellet was charged with a current density of 1 mA/cm2 to realize an areal capacity of 5 mAh/cm2 for more than 250 cycles. The energy efficiency of the cell is lower in the initial few cycles due to the resistance offered to the Li-ions to occupy the atomic sites of the bcc crystal lattice of the alloy. Due to this initial kinetic barrier, the cell shows high overpotential during the initial few cycles. However, after the complete solid solution lattice formation of Li-ions with the alloy, the overpotential significantly reduces and the energy efficiency increases to 100% during subsequent dissolution and extraction of the ions for more than 250 cycles. This indicates that the charge-discharge process is highly efficient, with no significant loss of lithium ions due to side reactions or other inefficiencies. FIG. 11b-f displays the voltage profiles of the cell and indicates the evolution of the overpotential with cycling. The overpotential decreases significantly with cycling due to the formation of a complete solid solution resulting in improved electrochemical kinetics leading to faster charge and discharge processes with facile diffusion of Li ions. The results demonstrate that PPFAM442 is highly effective at facilitating reversible lithium storage without losses, degradation, or safety risks and is devoid of any dendrite formation. These results showcase the potential of this MCA system of
FAM442 (Fe40Al40Mg20) to be used as a current collector in advanced Li-ion batteries (LIBs) or lithium metal batteries (LMBs) in anode-free systems. 3) Pre-lithiated pure pellet of FAM442 as Li-ion reservoir [0105] In the above section, the results described the performance of PPFAM442 demonstrating the promise of FAM442 to be used as a current collector in LIBs and LMB. However, the pellet still exhibited an initial kinetic diffusion barrier for Li-ions to occupy the vacant sites of the lattice structure and form a solid solution. To minimize this initial barrier, a new pellet was synthesized (1.32 cm2 surface area, 140.9 mg/cm2, 200 – 400 µm) and sequentially subjected to pre-lithiation with constant current and constant voltage (CCCV). The CCCV process is anticipated to force the Li-ions into the atomic vacant sites of the crystal lattice of the alloy enabling it to form a complete solid solution. The pellet was first charged with a constant current (CC) density of 0.5 mA/cm2 for 1 mAh/cm2 followed by holding the potential (CV) at -0.2V till the current drops to C/10. Following this, the pellet was again charged with CC of 1mA/cm2 for 4 mAh/cm2 and holding the potential at -0.2V till the current drops to C/10. Similarly, the pellet was charged sequentially for 9 and 1 mAh/cm2 with CCCV to cumulatively charge the pellet with 15 mAh/cm2 of Li-ions. This pre-lithiated pellet with Li equivalent to 15 mAh/cm2 (~3.75 mg of Li) dissolved in it was then used as a Li reservoir during cell operation. The Li-ions from the pellet were then cycled at a current density of 2 mA/cm2 to realize an areal capacity of 6 mAh/cm2 and deposited over the counter Li-metal anode to showcase the promise of PPFAM442 as a current collector in anode- free systems and the results are presented in FIG.12b. The energy efficiency of the cell is evaluated as striping or dealloying from the solid solution (discharge capacity) over plating or alloying forming the solid solution (charge capacity) during cell operation. Interestingly, the cell displayed a 100% coulombic efficiency in the 1st cycle and maintained it throughout the 300 cycles. However, the overpotential of the cell (FIG. 12c-e) gradually increases with cycling possibly due to an increase in the internal resistance of the cell or degradation of the interface between the Li- metal used as the counter electrode and the electrolyte. Nevertheless, a 100% coulombic efficiency throughout the 300 cycles signifies that the MCA pellet is highly efficient in lithium cycling. The results shown here demonstrate that Li-containing FAM442 pellet as a lightweight current collector offers a compelling combination of reduced weight, enhanced energy density, structural integrity, and dendrite suppression, positioning it as a promising solution for advanced LIBs and LMBs.
Conclusion: [0106] Innovative MCA designs: The patent presents a novel approach to creating multicomponent alloy (MCA) systems with a body-centered cubic (bcc) solid solution phase, achieved through advanced computational studies. These MCAs are optimized for interfacial energy and enthalpy of mixing, ensuring superior performance as dendrite-free anodes and current collectors for use in lithium metal and lithium-ion batteries in anode free configurations wherein the Li comes directly from the cathode such as LiCoO2, LiNiO2, LiNi1-xCoxO2 (0<x<1), and LiNi1- x-yMnxCoyO2 (0< x + y <1), as well as emerging systems such as Li-S utilizing Li2S as cathodes. In lithiated forms, the MCA systems can also be used as dendrite free anodes as well as current collectors for lithium-sulfur, Li-S and Li-O2 batteries. [0107] Lightweight and efficient current collectors: The MCA systems developed in this patent offer a significant reduction in the density, over 50% lower than traditional copper current collectors. This makes them highly attractive as lightweight current collector alternatives, contributing to the overall efficiency and energy density of the battery systems. [0108] Scalable synthesis process: The MCAs are synthesized using a scalable and cost-effective method involving HEMM/HEMA. This process ensures the feasibility of large-scale production, making these materials suitable for industrial applications. Furthermore, the use of cold pressing (CP), cold isostatic pressing (CIP) and cold-uniaxial press (CUP) at moderate temperatures of ~100 – 150oC ensures the formation of dense pellets that can also be cold rolled to form foils for direct use as current collectors in anode free configurations replacing copper the currently used current collectors in Li-ion batteries. [0109] Solid solution formation with lithium: The MCAs are designed to allow lithium to form a solid solution by occupying the vacant sites within the bcc phase. This unique interaction between lithium and the MCA prevents dendrite formation, enhancing the safety and reliability of the battery. [0110] Versatility of MCA compositions: Various MCA compositions, including FAM145, FAM541, and FAM442, have been synthesized and evaluated. These compositions have shown promising electrochemical performance in both coin and pouch cell configurations, highlighting their potential for use in advanced battery technologies. [0111] Industrial viability of FAM442: Among the tested compositions, FAM442 demonstrated particularly strong electrochemical performance in both coin and pouch cells, indicating its
suitability for industrial and vehicle technology battery applications. Its stability and efficiency make it a viable candidate for integration into commercial battery products, although all compositions have equally demonstrated promise for use as dendrite free anodes and current collectors. [0112] Application in anode-free setups: The MCA systems can be utilized in their pre-lithiated alloyed states for use as anodes and current collectors or as components in anode-free setups with lithium-containing cathodes. This versatility broadens their potential applications in next- generation battery technologies, offering new possibilities for high-performance, lightweight, and safe energy storage solutions.