WO2024144720A1

WO2024144720A1 - Method to produce cathode material for energy storage devices

Info

Publication number: WO2024144720A1
Application number: PCT/TR2023/051754
Authority: WO
Inventors: Servet Turan; Semih ENGUN; Tayfun KOCAK; Nuran AY; Zhang XIOGANG
Original assignee: Bulent Ecevit Universitesi; Eskisehir Teknik Universitesi
Current assignee: Bulent Ecevit Universitesi; Eskisehir Teknik Universitesi
Priority date: 2022-12-29
Filing date: 2023-12-27
Publication date: 2024-07-04
Anticipated expiration: 2025-06-29

Abstract

The invention relates to a method of producing cathode material developed for the production of cathode materials having high energy capacity and high cyclic stability in the field of electrochemical energy storage, and to the cathode material obtained by this method. The manufacturing method of the invention, in its most general form, comprises the process step of homogeneous coating at least one cathode active material comprising at least one of the group of layered oxide-based cathode active material, spinel-based cathode active material, olivine-based cathode active material or combinations thereof with at least one coating material containing boron nitride.

Description

METHOD TO PRODUCE CATHODE MATERIAL FOR ENERGY STORAGE DEVICES

Field of the Invention

The invention relates to a method of producing cathode material developed for the production of cathode materials having high energy capacity and high cyclic stability in the field of electrochemical energy storage , and to the cathode material obtained by this method .

State of the Art

Nowadays , the need for energy is increasing due to the increasing population, technological developments , and industrialization . The ever-growing energy demand and the necessity to reduce carbon emissions create various challenges . This situation requires a focus on renewable energy sources and efficient storage of energy . Battery technology offers a solution for the need for high power density, long life , and cost-effective storage devices for the generated energy .

Li-ion batteries are devices that store chemical energy and are now widely used in energy storage devices , portable electronic devices , and electric vehicles . In the most general form, Li- ion batteries consist of four main components : anode , cathode , electrolyte , and separator . Li-ion, Na-ion or F-ion batteries work on the principle of transporting ions between the anode and cathode through the electrolyte and converting the electrons released to ensure charge balance into electrical energy while moving from the anode to the cathode through the currentconducting cable .

The first lithium-ion battery was produced by Goodenough and Mizushima in 1981 with lithium cobalt oxide (LiCo0₂ ) as a positive electrode and a voltage of 4V was obtained against lithium metal. By 1991, with the commercialization of the first rechargeable lithium-ion battery by Sony, LiCo02 has become one of the most widely used cathode materials to date. However, today, the widespread use of electronic devices and studies to increase the range of electric cars continue intensively. One of these studies is the use of cathode materials with high redox voltage (LiNio.5Mn1.5O4, NMC811, and LiNiPO4, etc. ) .

By using cathode materials with a high voltage range, solvents such as conventional EC, DMC, and DC, and salts such as LiFPg cause the chemical bonds in the battery to break down. These impurities adhere to the surface of the anode and cathode active materials, increasing the internal resistance of the battery and shortening its life. Therefore, surface coating technology has developed and many studies on the coating of different cathode materials with different coating materials have been published in the literature.

High voltage NMC811, NMC622, and LNMO (LiNio.5Mn .5O4) cathode materials, which are widely used in lithium-ion batteries, undergo chemical degradation because they are outside the operating range of conventional liquid electrolytes. The decomposed liquid electrolyte and LiPF_e salt decompose into PF₅ and LiF and PF₅ reacts with water in the liquid electrolyte to form HF acid and PF₃O, Li_xPF_Y/ and Li_xPF_yO_z impurities. Surface analysis by the XPS characterization method conducted by Duncan et al., it was shown that inorganic impurities such as LiF and Li_xPF_yO_z and organic impurities such as polyethers and carbonates form residues on the surface as a result of degradation. (H. Duncan, D. Duguay, Y. Abu-Lebdeh, and I. J. Davidson, "Study of the LiNio.5Mn1.5O4 Electrolyte Interface at Room Temperature and 60°C," J. Electrochem. Soc. , vol. 158, no. 5, p. A537, 2011. )

Coating materials ' ionic and electrical conductivity, resistance to HF acid, thickness, and homogeneity of the coating layer have a significant effect on battery performance . Ionically and electrically non-conductive coating materials increase the ionic and electron resistance of the battery and adversely affect the battery ' s performance . A higher thickness of the coating material than the optimum thickness also leads to a decrease in electronic and ionic conductivity . As a result of inhomogeneous coating of the coating materials , the cathode surface is not fully protected and the interaction between the liquid electrolyte and the cathode surface continues . This leads to degradation of the liquid electrolyte during cycling and unwanted impurities coating the surface ( SEI ) , reducing the discharge capacity of the battery .

Studies have shown that thick cerium, alumina , and zirconia coatings have a negative effect on the conductivity of coated samples .

Alumina (AI2O3 ) coating on sodium-ion batteries by atomic layer deposition (ALD) coating technique improves the mechanical adhesion properties of the cathode coating on aluminium foil by reducing the large volumetric changes ( 6% to 300% ) after chargedischarge . A1₂O₃ coating has the advantage , however, that although it is ionically conductive , it is electronically insulating . Consequently, with thicker coatings , the kinetics of A1₂O₃ deteriorates due to its insulating structure , and interfacial charge transfer (between the liquid electrolyte and the active cathode surface ) becomes difficult , resulting in lower charge/discharge capacity and lower charge/discharge performance at high current .

Although A1₂O₃ , which is a widely applied coating material , is more durable than other coating materials (TiO2 , ZnO , and Bi2O3 ) , it has been observed that it is not sufficiently resistant to HF acid and cannot fully provide surface protection as a result of long cycle tests . The art contains many documents dealing with the application of different coating materials to the cathode surface . Examples of the state of the art are documents US20210376310 Al , US20170069907 Al , US20210184209 Al , US8900761 B2 , US10511012 B2 .

US20210376310 Al discloses a lithium borate-carbonate material coating on a cathode material surface using an atomic layer deposition (ALD) technique . US20170069907 Al relates to the coating of the cathode surface with A1₂O₃ . US20210184209 Al relates to the coating of AI2O3 , ZrO₂ , TiO₂ , ZnO, B₂O₃ , MgO, La₂O₃ , LiF or combinations thereof on the surface of LiMPO4 (M=Fe , Cr, Mn, Ni , V) . US8900761 B2 describes the process of coating zinc particles used as anodes in zinc batteries with boron-containing films ( triethyl -boron) by the ALD method . US10511012 B2 describes the oxide , phosphate , and fluorite-based coating process on the surface of energy cycle components .

To eliminate the above-mentioned disadvantages , a cathode material production method has been developed to obtain cathode materials with high ionic and electrical conductivity and durability in the field of electrochemical energy storage .

Detailed Description of the Invention

The invention relates to a method for improving the electrochemical properties of positive active material surfaces used as electrodes in devices based on electrochemical energy storage .

One obj ect of the invention is to provide cathode materials with high energy capacity and high cyclic stability in the field of electrochemical energy storage .

Another obj ective of the invention is to produce cathode materials with high ionic and electronic conductivity and durability . The invention relates to the production of batteries based on electrochemical energy storage by coating cathode materials with boron nitride ( BN) . The cathode material obtained by the method of the invention and the energy storage devices comprising said cathode material are also within the scope of the protection of the invention .

The invention relates to a method of manufacturing a cathode material and, in its most general form, comprises the process step of homogeneous coating at least one cathode active material comprising at least one of the group of layered oxide-based cathode active material , spinel-based cathode active material , olivine based cathode active material or combinations thereof with at least one coating material containing boron nitride .

In an embodiment of the invention, the coating material is coated in nano or micron thickness .

In an embodiment of the invention, the coating material is coated with a thickness of 1 nm-100 pm.

In an embodiment , LiCo0₂ , LiNiO₂ , LiNi_xCo_yMn_z0₂ , and LiNi_xCo_yAl_z are used as layered oxide-based cathode active materials . Wherein x+y+z=l .

In an embodiment of the invention, LiMn₂O₄ is used as the spinelbased cathode active material .

In an embodiment , LiFePO₄ , LiNiPO₄ , and LiCoP0₄ are used as olivine-based cathode active materials .

In an embodiment , the surface of the coating material of the invention is functionalized and/or modified with carbon and/or various compounds on its surface . In an embodiment , the coating material is coated by thermionic vacuum arc plasma, thermal spray, arc sputtering , high- temperature plasma , plasma spray, spray, fluidized bed reactor , colloidal dispersion, precipitation, physical and chemical adsorption, mechanical alloying, mixing , physical vapour deposition, chemical vapour deposition or atomic layer deposition technique .

In an embodiment , the coating material is coated by the sol-gel technique .

In an embodiment , the coating material of the invention is coated by sol-gel technique , wherein the manufacturing method of said embodiment most generally comprises ;

- -mixing the cathode active material , the boron nitridecontaining coating material , and at least one dispersing material to form a solid phase and a liquid phase and mixing until a homogeneous mixture is obtained,

- evaporation of the liquid phase by heating the resulting mixture , and

- the process steps of heating the solid phase and coating the coating material by adhering the coating material to the cathode active material .

In an embodiment of the invention, the mixture is heated at a temperature of 60-120°C .

In an embodiment of the invention, the solid phase is heated at a temperature of 150-500°C .

In an embodiment of the invention, the coating material comprises a powder or slurry boron nitride mixture . In an embodiment, the coating material/boron nitride mixture comprises a boron nitride mixture in the cubic or hexagonal crystal structure, in plain form and/or in functionalized form.

In an embodiment of the invention, the coating material/boron nitride mixture comprises at least one surfactant comprising anionic, cationic, or non-ionic organic materials or combinations thereof. Preferably, the boron nitride mixture comprises at least one surfactant in an amount of 0.1-5% by weight of the boron nitride mixture. Preferably contains, but not limited to, cetyltrimethylammonium bromide (CTAB) , cetyltrimethylammonium chloride (CTAC) , Darvan®, Polyethyleneimine, Sodium dodecyl sulfate (SDS) , Triton™ X-100, TEGO®.

In an embodiment of the invention, the coating material/boron nitride mixture comprises at least one binder material. Preferably, the boron nitride mixture comprises 0.1-10% by weight of the binder material. Said binder preferably comprises epoxy, alkyd, and/or acrylic binder.

In an embodiment, at least one of water, alcohol, acetone, or combinations thereof is used as the dispersing material.

In an embodiment of the invention, 0.1-5 percent of the cathode weight of the coating material is used.

In an embodiment of the invention, 0.1-20 percent of the cathode weight of the dispersing material is used.

In an embodiment of the invention, a coating material comprising 0.01-5 wt % boron nitride is used.

The invention provides a method of boron nitride-coated cathode surface modification for obtaining cathode materials with high energy capacity and high cyclic stability in the field of electrochemical energy storage . The surface coating process can be carried out using more than one technique . Said techniques include sol-gel , atomic layer deposition, residue deposition, thermal spray or magnetron sputtering , etc .

The coating techniques of the invention, and in particular the sol-gel technique , provide homogeneous and flawless coating, are suitable for mass production in high quantities , and require low coating process costs and low coating system maintenance .

In an embodiment of the invention, the coating process is carried out by sol-gel technique and the composition of the coating solution used in said method comprises a solid phase comprising 0 . 1-5% of the cathode weight of the coating material and a dispersing phase comprising 1-20% of the cathode weight . Said solid phase material contains a mixture of boron nitride powder or sludge . Said boron nitride mixture is in the cubic or hexagonal crystal structure , in plain form and/or in functionalised form . In an embodiment of the invention, said boron nitride mixture comprises 0 . 1-5 % by weight of surfactant components comprising anionic , cationic , and non-ionic organic materials such as Ctab, Ctac , Darvan®, Polyethyleneimine , Sds , Triton™ X-100 , Tego® and combinations thereof . In an embodiment , said boron nitride mixture comprises , but is not limited to , epoxy, alkyd, and acrylic binders in a ratio of 0 . 1-10% . In an embodiment of the invention, the dispersing phase comprises water, alcohol , acetone , and/or combinations thereof .

In an embodiment of the invention, the sol-gel coating process comprises the steps of mixing the cathode-active material and the coating materials with the dispersing material to form a solid-liquid phase and mixing until a homogeneous structure is formed; evaporation of the liquid phase by heating the mixture at 60-120°C; heating the obtained solid phase to 150-500°C to ensure that the boron nitride coating material adheres on the cathode material continuously or in the form of islets with a thickness of 1 nm -100 microns .

Boron nitride-coated cathode material is converted into batteries by standard battery production methods .

In an embodiment of the invention, the cathode materials include LiNi_xMn_yCo_z0₂ (NMC ) , LiNi_xCo_yAl_z0₂ (NCA) , LiNio .5Mni .5O4 , LiFePO₄ , LiNi_xCo_yMn_zP04 , MnO₂ .

The invention provides a solution to the problems of coating thickness and homogeneity in the art . Coating thickness and homogeneity is an important parameter and Figure la shows a view of the inhomogeneous coating . Figure lb shows a view of a homogenous but too-thick coating . In particular, the sol-gel technique in the method of invention can be used to provide an optimum thickness ( 1 nm-100 pm) and homogeneous surface coating . A view of the said coating is shown in Figure 1c .

Table 1 below shows a cathode material composition ( Example-1 ) without boron nitride coating material . Said cathode material does not use any coating material and can be used as a reference sample .

Table 1 Composition of cathode material without coating material

Table 2 below shows a cathode material composition ( Example-2 ) containing boron nitride coating material . In the aforementioned composition, approximately 1 wt% boron nitride is used .

Table 2 Composition of cathode material containing coating material

Table 3 below shows the capacity conservation of the above- mentioned cathode material compositions comparatively .

Table 3 Comparative capacity retention table

According to the discharge capacity values and capacity conservation in the samples , it is seen that the initial discharge capacity in Sample 2 is 107 mAhg-1 and the capacity conservation after 50 cycles is 77 % . Example 1 is given as an uncoated reference NMC532 composition .

The microstructural changes of NMC532 powder obtained as a result of boron nitride coating were observed by scanning electron microscopy and are shown in Figure 2a and Figure 2b .

The crystal structure changes of NMC532 powder obtained as a result of boron nitride coating were analysed by X-ray diffractometer and are shown in Figure 3 . In more detail , XRD phase analysis of NMC532 powders with BN surface coating by solgel method is shown in Figure 3 , and data for boron nitride coated NMC532 cathode powders in Figure-3a and uncoated and coated NMC532 cathode powders in Figure 3b are shown .

Figure 4 shows the cycle count-capacity graph of NMC532 powders with boron nitride surface coating by sol-gel method between 2 . 75V-4 . 25 V and 0 . 1C discharge rate . The results in Figure 4 and Table 3 show that the boron nitride coating improves the discharge capacity and capacity conservation .

In summary, the invention provides cathode materials with high energy capacity and high cyclic stability in the field of electrochemical energy storage . Said cathode materials are used in battery applications .

Description of the Figures

Figure la A view of cathode surfaces with an inhomogeneous rough coating

Figure lb A view of cathode surfaces with a homogeneous but thick surface coating

Figure lc A view of cathode surfaces with thin film coating Figure 2a SEM image of NMC532 powder with boron nitride surface coating by sol-gel method

Figure 2b SEM image of NMC532 powder with boron nitride surface coating by sol-gel method Figure 3a XRD phase analysis of NMC532 powders with boron nitride surface coating by sol-gel method

Figure 3b XRD phase analysis of uncoated and boron nitride coated

NMC532 powders by sol-gel method

Figure 4 The cycle count-capacity graph of NMC532 powders with boron nitride surface coating by sol-gel method between 2 . 75V- 4 . 25 V and 0 . 1C discharge rate

Claims

1 . A cathode material production method comprises homogeneous coating of at least one cathode active material selected from the group consisting of at least one of a layered oxide-based cathode active material , spinel-based cathode active material , an olivine-based cathode active material group or combinations thereof with at least one coating material comprising boron nitride .

2 . A method according to claim 1 , wherein the coating material is coated in nano or micron thickness .

3. A method according to claim 2 , wherein the coating material is coated with a thickness of 1 nm-100 pm .

4 . A method according to claim 1 , wherein the layered oxide-based cathode active material is LiCo02 , LiNiO2 , LiNi_xCo_yMn_z02 , LiNi_xCo_vAl_z .

5. A method according to claim 1 , wherein the spinel-based cathode active material is LiMn₂O₄ .

6. A method according to claim 1 , the olivine-based cathode active material is LiFePO₄ , LiNiPO₄ , LiCoP0₄ .

7 . A method according to any one of claims 1 to 6 , wherein the coating material is coated by thermionic vacuum arc plasma , thermal spray, arc spray, high-temperature plasma , plasma spray, spray, fluidised bed reactor , colloidal dispersion, precipitation, physical and chemical adsorption, mechanical alloying, mixing, physical vapour deposition, chemical vapour deposition or atomic layer deposition technique .

8 . A method according to any one of claims 1 to 6 , wherein the coating material is coated by sol-gel technique .

9. A method according to claim 8 , wherein it comprises

- mixing the cathode active material , the boron nitridecontaining coating material , and at least one dispersing material to form a solid phase and a liquid phase and mixing until a homogeneous mixture is obtained,

- evaporation of liquid phase by heating the resulting mixture , and

- heating the solid phase and coating the coating material by adhering the coating material to the cathode active material .

10 . A method according to claim 9 , wherein the mixture is heated at a temperature of 60-120°C .

11 . A method according to claim 9 , wherein the solid phase is heated at a temperature of 150-500°C .

12 . A method according to claim 9 , wherein the coating material comprises a powder or slurry boron nitride mixture .

13 . A method according to claim 9 , wherein the coating material comprises a mixture of boron nitride in a cubic or hexagonal crystal structure , in a plain form and/or in a functionalised structure .

14 . A method according to claim 9 , wherein the coating material comprises at least one surface active material .

15 . A method according to claim 14 , wherein the coating material comprises cetyl trimethylammonium bromide (CTAB ) , cetyl trimethylammonium chloride (CTAC) , Darvan®, Polyethyleneimine, Sodium dodecyl sulphate (SDS) , Triton™ X-100 and/or TEGO®.

16. A method according to claim 1 or 9, wherein the coating material comprises at least one binder.

17. A method according to claim 16, wherein the coating material comprises an epoxy, alkyd, and/or acrylic binder.

18. A method according to claims 1 or 9, wherein the coating material comprises 0.01-5 wt % boron nitride.

19. A cathode material, obtained by a method according to any one of the preceding claims .