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WO2024130260A1 - Sélection d'additif de type fibre revêtue de métal pour réduction de résistance dans une batterie et matériaux de batterie - Google Patents

Sélection d'additif de type fibre revêtue de métal pour réduction de résistance dans une batterie et matériaux de batterie Download PDF

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WO2024130260A1
WO2024130260A1 PCT/US2024/010608 US2024010608W WO2024130260A1 WO 2024130260 A1 WO2024130260 A1 WO 2024130260A1 US 2024010608 W US2024010608 W US 2024010608W WO 2024130260 A1 WO2024130260 A1 WO 2024130260A1
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Prior art keywords
metal
battery
cathode
anode
coated
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George Hansen
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Battery Electron Transport Associates Inc
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Battery Electron Transport Associates Inc
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Priority claimed from US18/079,811 external-priority patent/US20230123858A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/626—Metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes

Definitions

  • the present invention relates to increasing the conductivity of battery cathodes and anodes to enhance battery performance. More specifically, the present invention relates to methods and systems for enhancing the performance of batteries by lowering the electrical resistance both across and particularly through the active films, thus increasing conductivity to increase discharge and charge rates, and ultimately to increase both power and energy density.
  • Various exemplary embodiments of the present invention are described below. Use of the term “exemplary” means illustrative or by way of example only, and any reference herein to “the invention” is not intended to restrict or limit the invention to exact features or steps of any one or more of the exemplary embodiments disclosed in the present specification.
  • references to “exemplary embodiment,” “one embodiment,” “an embodiment,” “some embodiments,” “various embodiments,” and the like, may indicate that the embodiment s) of the invention so described may include a particular structure, feature, property, or characteristic, but not every embodiment necessarily includes the particular structure, feature, property, or characteristic. Further, repeated use of the phrase “in one embodiment,” or “in an exemplary embodiment,” does not necessarily refer to the same embodiment, although they may.
  • a battery is simply a device in which the anode (negatively charged or reducing electrode) may be loaded with electrons through an electrochemical galvanic process, and a cathode (positively charged or oxidizing electrode), where the electrochemical galvanic reaction is reversed and the stored electron is discharged to a circuit, thus providing an electrical current. Batteries where these reactions are singularly non-reversible are called primary batteries, which are non-rechargeable. Batteries where these reactions can be reversed multiple times are called secondary batteries, or rechargeable. Though the examples described in this disclosure are secondary in nature, those skilled in the art will understand that the concepts herein described may apply to both primary and secondary systems.
  • Battery design and choice of materials are a function of the galvanic potential between the materials and their ability to provide a designed voltage potential to drive a current to a circuit to supply electrical power.
  • a battery is an electrochemical cell having a series of resistors, comprising an anode current collector and tabs, an anode active material coating, the electrolyte (providing ionic transport), a separator (which electrically isolates the anode and the cathode), a cathode current collector and tabs, and an active cathode material coating.
  • the current collectors and tabs typically being metal foil, and the anode, often being carbon, are each fairly to highly conductive.
  • the cathode usually being an oxide, is non-conductive.
  • the cathode may be rendered conductive enough to transport electrons by adding a small percentage of conductive carbon powder.
  • cathodic resistance or more formally, cathodic impedance
  • the resistance of the cathode is a primary driver in the discharge performance of the battery. For instance, a person of ordinary skill in the art may design the cathode (usually in film form) for power discharge by making the film thin and increasing the amount of conductive carbon in the film so that the poor electron transport is compensated by having more paths and a short distance to the current collector.
  • the cathode may be made much thicker, with less conductive carbon, thus increasing the amount of active cathode material contained in the film and cell.
  • This design increases the cell’s energy, but at the cost of a poor discharge rate.
  • This thick film/less conductive carbon design would be an energy cell.
  • those skilled in the art may design a power cell with low capacity, or an energy cell with reduced power; but not both.
  • An important aspect of any battery design is the method by which the electrical current is collected and distributed. While the examples described herein principally apply to lithium-ion rechargeable batteries, the concepts disclosed herein (methods and materials that significantly improve current collection) translate and apply to all batteries (z.e., non-lithium- ion batteries) that use a current collector. For the purposes of this disclosure, all battery systems containing lithium will be identified as lithium-ion batteries. The choice of materials used to improve the current collection by methods described herein must be compatible with the electrochemical galvanic reactions of the selected battery, such that the selected materials do not become an active corrosion product of that battery at the operating voltage of the battery.
  • the exemplary embodiments described herein involve a lithium-ion secondary battery, specifically a lithium iron phosphate or a lithium nickel manganese cobalt oxide cathode and a carbon powder anode.
  • a lithium-ion secondary battery specifically a lithium iron phosphate or a lithium nickel manganese cobalt oxide cathode and a carbon powder anode.
  • the concepts taught herein may apply to any battery where the materials, methods and techniques described would provide the described improvements.
  • the relationship of the voltage, current and resistance is defined by Ohms law. If the anode is more conductive, the electrical resistance is lowered, thus reducing the required applied voltage to run a given current, or conversely, to run a higher current at a given voltage. This reduction in resistance also results in reducing the resistive heating losses. Likewise, increased conductivity will permit thicker anodic film to be employed, thus increasing capacity.
  • the lithium iron phosphate (hereafter LFP) and the lithium nickel manganese cobalt oxide (hereafter NMC) are non-conductive insulators.
  • LFP lithium iron phosphate
  • NMC lithium nickel manganese cobalt oxide
  • these materials are combined with small amounts of a polymer binder and a conductive sub-micron carbon and then spread thinly onto an aluminum foil substrate.
  • the cathode film is about twice the thickness of the anode film.
  • the volume resistivity of the cathode film is about one to two orders of magnitude less than the volume resistivity of the anode.
  • cathode resistance is the most prohibitive limiting factor for battery discharge rate or capacity.
  • the cathode must be made thinner so that the electron is more proximate to the current collecting foil.
  • making the film thinner reduces the capacity of the battery.
  • the capacity of the battery may be increased by increasing the thickness of the cathode film, but then the discharge rate is commensurately reduced.
  • any measure which increases the conductivity of the anode, or the cathode will result in a lower resistance, or impedance, across the entire battery system, increasing the voltage or amperage, and increasing either rate or capacity or both.
  • An increase in conductivity also results in less joule heating.
  • a decrease in joule heating is a very important factor for two reasons. First, the reduction in joule heating results in this energy being manifest in greater capacity. Second, reduced heating results in a cooler and safer battery.
  • the present disclosure describes developments responsive to the present state of the art, and in particular, a response to the problems and needs in the art that have not yet been fully solved by currently available electrodes.
  • the electrodes of the present disclosure are easily implemented and provide significant advances in both power density and energy density.
  • the exemplary’ electrodes may be used in batteries in a full range of sizes and weights for use in small electronic devices such as cell phones and laptop computers to electric vehicles such as golf carts and automobiles, to very large-scale centralized batteries for renewable energy storage, for example.
  • Improvements in conductivity in both the anode and the cathode are desirable and beneficial.
  • the larger benefit comes from the ability to improve the conductivity of the cathode.
  • the anode is moderately conductive, typically about 0.1 ohm-cm in volume resistivity; the cathode has a volume resistivity of about 1 to 10 ohm-cm. Due to the poor conductivity of cathodic films, the discharge energy capacity of the battery is limited by the inability of the cathode film to conduct electrons through its thickness to the aluminum foil current collector. Conversely, if more power is desired, then the film must be made thinner to facilitate faster electron transport to the foil, thus sacrificing capacity.
  • a more conductive cathodic film will result in a faster discharge rate.
  • a film with less resistivity can be laid down thicker at an equal resistance, thus increasing capacity at the same power rate.
  • the energy density may be increased approximately by the ratio of the thicknesses.
  • a significant improvement in the conductivity of either the anode or the cathode leads to lower resistivity, not only across or through the respective cathodic or anodic film, but also generally across the entire battery cell.
  • a lower resistance leads to higher voltage to move a given current or move a higher current at a given voltage. This, in turn, leads to faster charging or discharging, or the ability to move an electron at greater ease through thicker films, thus increasing capacity.
  • This disclosure describes various exemplary methods by which electrical conductivity of the cathode and/or the anode may be improved.
  • the magnitude of the improvement may be by a fractional margin (e.g., such as 25% or 50%), or an integral margin, such as doubling, or tripling or better.
  • This disclosure also describes improvements in the operation of a complete lithium-ion cell. Additionally, this disclosure describes methodology for designing improvements into the operation of non-lithium-ion batteries.
  • Described in this disclosure are exemplary conductive additives for the anode and the cathode, and their respective effects on the performance of these members. Further, a battery cell fabricated from these materials is described. Although optimal performance is yet to be determined, this disclosure clearly demonstrates the efficacy of these exemplary materials in achieving significant improvements.
  • Exemplary conductive additive materials were evaluated for increasing conductivity performance. It should be understood, this disclosure is not limited to only these exemplary materials and methods. Those skilled in the art, armed with the disclosures herein, will understand that the exemplary materials described exemplify the broader concepts.
  • a conductive metal-coated fiber or a conductive metallic additive to the active cathode material and/or active anode material to decrease the impedance of the cathode and/or the anode depends on 1) the ability to disperse the conductive additive within the active cathode material and/or the active anode material, and 2) whether the conductive additive is able to survive the voltage potential created in the battery (whether an lithium-ion battery or not).
  • the operating voltage potential of a battery is derived by determining the voltage potential of the chosen cathode material against the electrolyte cation (for instance a positively charged lithium ion) and determining the voltage potential of the chosen anode material against the electrolyte cation, and then taking the difference between these two voltages.
  • the voltage potential of the conductive additive against the electrolyte cation is also determined. If the operating voltage of the battery is greater than the voltage potential of the additive against the electrolyte cation, then the additive will corrode; if the operating voltage is less, then it will not corrode.
  • each cathode material and each anode material, and each conductive additive will create potentials particular to each material combination, according to the laws of electrochemistry.
  • the conditions of and selected combination of anode, cathode, electrolyte cation, and conductive additive may be determined, and survivability predicted. In practice, these predicted values are confirmed empirically.
  • the voltage differential for a LiNMC cathode and a graphite/carbon anode is approximately 4.0V. Because this 4.0V voltage differential is greater than the galvanic potential of nickel against lithium (at 3.8 V), it can be predicted that if nickel is contained in the conductive additive, that the nickel will corrode. A conductive additive with a higher potential must be used, such as aluminum.
  • the voltage differential for the same active LiNMC cathode and graphite/carbon anode is 0.33V less than the voltage differential for a lithium-ion battery, at approximately 3.67V. Because the voltage differential of 3.67V for the sodium-ion battery is less than the galvanic potential of nickel (3.8V), nickel may be used in the conductive additive without a corrosive reaction.
  • the lithium iron phosphate cathode/carbon anode battery its operating voltage is 3.2V.
  • the conductive additive metal may be nickel, as the cell does not reach the 3.8V that would corrode the nickel.
  • the technique for determining whether any particular conductive additive will survive the voltage differentials of a particular cell is to choose an anode and cathode combination and select the conductive metallic additive such that the additive is dispersible within the cathode and/or anode and the selected metal in the conductive additive is greater than the voltage differential for the cell.
  • a person of ordinary skill in electrochemistry and armed with the disclosure herein may design a battery system (lithium- ion or non-lithium-ion) with enhanced performance without corrosion by selecting a cathode and/or an anode in a half-cell and selecting a metallic conductive additive, dispersible within the cathode and/or anode selected, so long as the metal has a galvanic potential greater than the voltage differential for the half cell.
  • the addition of metal-coated fibers to either the anode or the cathode improves conductivity in both films.
  • the metal may be any metal
  • the fiber may be any fiber, so long as the chemical, physical, and mechanical properties of the fiber and metal coating are compatible with each other and compatible with the respective properties of the selected anode or cathode.
  • Minimization of fiber diameter, maximization of length, optimization of length vs dispersibility vs. efficacious concentration, minimization of density, and maximization of conductivity of the fiber are just a few of the highly interrelated properties to be considered.
  • Metal-coated fibers of various types have been items of commerce for many decades. Many metals (nickel, silver, aluminum, gold, iron, copper, chromium, cobalt, molybdenum, to name a few) have been deposited onto a wide variety of fibers (carbon, surface-modified carbon, silicon carbide, silicate, borosilicate, alumina, basalt, quartz, aramid, acrylic, rayon, nylon, cotton, silk, to name a few). A smaller fiber diameter is better, as this increases the available length and specific surface area of fibers for a given unit weight and the available conductive surface area per unit weight for electronic interconnectivity.
  • Deposition processes for coating the fiber include vacuum processes (physical vapor deposition (PVD), sputtering, evaporation, etc.), wet chemistry processes (electroplating, electroless plating) and Chemical Vapor Deposition (CVD) are all known and may be used with varying degrees of conductivity improvement. Though the general conductivity concepts taught in this disclosure are somewhat agnostic (z.e., compatible with many battery types) to the deposition method, some of these methods provide for better coating uniformity and control. This is because the mechanical properties and geometries of the coatings are highly dependent on the deposition method used.
  • Electroplated fibers typically exhibit a complete coating, though the coating tends to be thicker, rough, irregular (non-uniform), and brittle. This is due to the nucleation process of electroplating. Consequently, although electroplated fibers may be used as an additive and may demonstrate enhanced conductivity, some of the physical characteristics of electroplated fibers may affect dispersibility or other physical requirements of certain battery types. For example, the brittleness of the coating may be prone to flaking off when used in batteries that require robustness or the thickness of the coating may add undesired weight or size to the battery.
  • Depositions formed by vacuum coating processes are not uniform, and the lack of uniformity inhibits optimal conductivity enhancement.
  • sputtered coatings show a “half-moon” of coating on opposite sides of each fiber, thus being very non-uniform. Sputtered coatings, however, still may be used to enhance conductivity in batteries that do not require the level of enhancement provided by uniform coatings. But if they could be made uniform, fibers coated using vacuum coating processes may be an attractive option for certain battery designs.
  • Nickel-coated fibers are available for enhancing conductivity.
  • copper is five times as conductive as nickel.
  • the deposition of copper onto fibers by both electroplating and chemical vapor deposition have been demonstrated, though the electroplating process is far more mature.
  • Copper-coated PCF is an excellent alternative.
  • the choice of fiber (substrate) and the choice of metal (coating) must also be compatible with the chemistry of the battery system.
  • the galvanic corrosion potential of the metal-coating with respect to the chosen ionic electrolyte must be greater than the operating voltage of the battery, for if it is less, it will prematurely galvanically corrode, as discussed herein.
  • the volume resistivity of the coated fiber must be less than that of the active film. The wider this improvement is, the greater the increase in performance.
  • the length of the fiber also has importance. Fibers may be cut to very precise and consistent lengths, ranging from 0.1 mm to 1.0 mm to facilitate dispersibility.
  • fibers also may be cut precisely to traditional lengths of several mm.
  • Dispersion efforts show that the precision consistency of fiber length greatly reduces the loading of fiber required for a desired conductivity, thereby reducing viscosity and dispersion issues.
  • fibers that are above 1 mm in length may become entangled and may not disperse well.
  • fibers that are 0.1 mm in length disperse very well, but their shorter aspect ratio mandates that higher loading is required for a desired conductivity. This added material loading adds weight and cost, but more importantly, displaces active battery materials, thereby commensurately reducing the available capacity.
  • 0.5 mm fibers or fibers of about 0.5 mm are particularly suitable for dispersion, and that length may be adjusted upward or downward from 0.5 mm depending on other factors such as diameter or to facilitate dispersion.
  • fiber length and loading There is a tradeoff between fiber length and loading. Fibers of 1.0 mm are very conductive but can be too long to disperse well into certain materials. Fibers of 0.10 mm disperse well in most materials, but a higher loading is required that may displace precious active battery material.
  • Metal-coated fibers having a diameter of from 3 microns to 20 microns with metal coating thickness between 0.1 microns and 3 microns are particularly suitable for dispersion within cathode and anode materials.
  • fibers produced by any known means, may vary in length within the 0.1 mm to 1 mm range mentioned above, it is preferred to use precision-chopped fibers, wherein precision-chopped fibers means that the fibers are uniformly ⁇ 10% of the selected length (e.g., for 0.5 mm fibers, all fibers are between 0.45 and 0.55 mm). At that length, fibers may be dispersed in the active anode and cathode materials up to about 10% by weight. But in practice, dispersions above 10% are difficult to achieve. Dispersion loading percentages may be analyzed to determine whether a given loading percentage contributes to conductivity commensurate with the added weight, cost, or displacement of active material. Higher load percentages still may provide enhanced conductivity sufficient to justify use in some battery designs.
  • Carbon fibers - Carbon fibers, in either continuous woven, felt, or a chopped format have been the subject of extensive battery research, as a current collector, support member, or mechanical reinforcement. However, these fibers do not exhibit sufficient conductivity to achieve the desired conductivity enhancement objectives herein.
  • Nickel-coated carbon fibers - Nickel-coated carbon fibers are an item of commerce. Their small diameter, low density, high aspect ratio, high linear mass yield, excellent electrical conductivity and environmental stability all combine to provide an excellent conductivity network at very low loadings.
  • the corrosion of nickel against lithium occurs at 3.8 volts, and the lithium NMC cathode operates at 4.2 volts, the nickel on the fiber corrodes at 3.8 volts, and a battery thus made will not cycle, but will fail at 3.8 volts.
  • LFP lithium iron phosphate
  • the maximum voltage is 3.6V, and the operating voltage is closer to 3.2V.
  • the nickel -coated fiber works well.
  • Aluminum-coated fiber may be contemplated.
  • Aluminum is coated onto fibers and fabrics usually through a vacuum process or melt process.
  • Applications for these products are usually optical in nature, such as a reflector (optical fibers or mylar balloons) or as a reflector of heat (gloves for high temperature processes). These have been items of commerce for decades.
  • these fibers are large in diameter (usually over 25 microns) and have a density of about 2.7 g/cc. Though they could be a viable candidate, their large diameter and moderate density results in a linear yield that is less than desirable.
  • Aluminum-coated carbon fiber As the carbide of aluminum is easily formed, an aluminum-coated carbon fiber is not a viable option.
  • any fiber that will not form a carbide during or after deposition is a candidate. Examples that have been demonstrated include silicon carbide, silicate, alumina, aluminum borosilicate, basalt, quartz, aramid, and so forth. Each of these fibers have been demonstrated to readily accept a thin aluminum film, but this list is by no means exhaustive.
  • the fiber (substrate) of an aluminum-coated fiber may be selected from the group including carbon, pan ox, silica, quartz, silicates, alumina, aluminosilicates, borosilicates, glass, minerals, carbides, nitrides, borides, polymers, cellulose, inorganic fibers, and organic fibers.
  • the surface of a carbon fiber may be modified to a silicon carbide, after which the aluminum readily coats onto the silicon carbide surface. This fiber provides the smallest diameter and lowest density approach.
  • Powders and filamentary branching metals In the cases where nickel is actively employed for the conductivity, such as in the lithium-ion anode or the LFP cathode, certain types of filamentary nickel powders may act to provide further electrical paths between the metal-coated fibers or act to provide multiple conductive paths through the active mass/polymer/foil current collector interface.
  • the synergistic effects of adding other conductive solid shapes, such as platelets or spheres, are known to increase the interconnectivity between the metal-coated fibers, but not nearly to the extent that filamentary metal powders and structures do.
  • nickel powder of a highly filamentary and branched structure where the main branches of the structure are generally above a micron in diameter, with some branching (such as Inco type 255 powder) may be used.
  • a filamentary branching metal known as “nanostrands” generally has branches below a micron in diameter and exhibits very extensive branching (“nanostrands” are available from Conductive Composites Company of Heber City, Utah).
  • metal-coated fiber and the high-aspect ratio, conductive filamentary structures work together to create a comprehensive network of electron transport pathways.
  • the physical nature of metal-coated fibers and the high-aspect ratio, conductive filamentary structure(s) facilitate the creation of an inter-fiber electron transport network for moving electrons between the anode and the current collector interface.
  • the metal -coated fibers act much like logs being elongated linear electron transport conduits and the conductive filamentary structures act much like tumbleweeds that electrically interconnect the logs.
  • anode conductivity is further enhanced.
  • the carbon powder of the anode is already somewhat conductive
  • the spaces between the filamentary network of the conductive filamentary branching structure is about the same dimension and geometry as the carbon powder particle size. Consequently, the filamentary branching structures somewhat three-dimensionally wrap themselves around the carbon particles, like a spider web or a net (hereinafter referred to as a “nanonet”).
  • This “nanonet” phenomenon leads to a much greater level of electrical interconnectivity between the carbon particles, the filamentary branching structures, the metal-coated fibers, and the current collecting foil. This effect is more pronounced for the nanostrands, due to their smaller diameter and larger degree of branching.
  • branching nickel powder and nanostrands may also serve as additives to the anode and/or cathode in battery systems that are nickel compatible. Data is provided below regarding the use of either branching nickel powder or nanostrands as individual additives or in combination with nickel-coated fibers and each demonstrates enhanced conductivity.
  • the amount of metal coating on the fiber is an important parameter in modifying conductivity, as will be demonstrated in the examples provided below in the Detailed Description.
  • FIG. 1 is a schematic depiction of an exemplary embodiment of a discharging lithium-ion battery as generally known in the prior art.
  • Fig. 2 is a schematic depiction of the exemplary embodiment of the lithium-ion battery of Fig. 1 during recharging as generally known in the prior art.
  • FIG. 3 is a representative depiction of a portion of an exemplary embodiment of a cathode as generally known in the prior art showing an active base cathode material.
  • Fig. 4 is a representative depiction of a portion of an exemplary embodiment of an enhanced cathode showing metal-coated fibers dispersed throughout the active base cathode material of Fig. 3.
  • Fig. 5 is a representative depiction of a portion of an exemplary embodiment of an alternative enhanced cathode showing metal-coated fibers and conductive filamentary structures dispersed throughout the active base cathode material of Fig. 3.
  • FIG. 6 is a representative depiction of a portion of an exemplary embodiment of an anode as generally known in the prior art showing an active base anode material.
  • Fig. 7 is a representative depiction of a portion of an exemplary embodiment of an enhanced anode showing metal-coated fibers dispersed throughout the active base anode material of Fig. 6.
  • Fig. 8 is a representative depiction of a portion of an exemplary embodiment of an alternative enhanced anode showing metal -coated fibers and conductive filamentary structures dispersed throughout the active base anode material of Fig. 6.
  • Fig. 9 is a representative depiction of a portion of an exemplary embodiment of an alternative enhanced electrode (anode or cathode) showing conductive filamentary structures dispersed throughout the base electrode material.
  • Fig. 10 is a chart depicting data regarding improving volume resistivity in a cathode by adding various conductors into an LFP battery cathode.
  • FIG. 1 a representative rechargeable lithium-ion battery 10 as known in the prior art that operates with a standard cathode 12 made of an active base cathode material 14 and a standard anode 16 made of an active base anode material 18.
  • the exemplary embodiments of the present invention comprise modified electrodes with increased conductive that separately or together may be components of an enhanced battery.
  • Fig. 1 a representative rechargeable lithium-ion battery 10 as known in the prior art is depicted schematically.
  • the lithium-ion battery 10 comprises the standard cathode 12 made of the active base cathode material 14, the standard anode 16 made of the active base anode material 18, an electrolyte 20, a separation barrier 22, an anode current collector foil 24, and a cathode current collector foil 26 encased within a battery housing 28.
  • the active base cathode material 14 may be any of many cathode compounds known to be of use in batteries; however, for the purposes of this description, the battery 10 is a lithium-ion battery 10 and exemplary active base cathode materials 14 may include lithium iron phosphate (LFP) and the lithium nickel manganese cobalt oxide (NMC) and any other cathode material used in lithium-ion batteries.
  • LFP lithium iron phosphate
  • NMC lithium nickel manganese cobalt oxide
  • the active base anode material 14 may be any of the anode materials known to be of use in batteries; however, for the purposes of this description, the battery 10 is a lithium-ion battery 10 and exemplary active base anode materials 14 may include carbon power, graphite powder, and any other cathode material used in lithium-ion batteries. Such compounds also contain a small amount of a polymer used as a binder. Also, the most used electrolyte 20 in lithium-ion batteries 10 is lithium salt, such as LiPF6 in an organic solution. The key role of electrolyte 20 is transporting positive lithium ions (cations) between the cathode 12 and anode 16.
  • the battery 10 operates to transport electrons through the system of components.
  • the electron transport starts with the anode current collector foil 24, then through the anode foil/active mass interface to the anode active mass (in this case, the standard anode 16).
  • the discharging direction of electron flow (shown by schematic flow path 30) is shown generally at Arrow A from negative to positive.
  • Positively charged lithium ions 32 travel within the electrolyte 20 (in this case, the lithium accepting an electron at the standard anode 16 when charging), that electron and lithium (of the lithium ions 32) pass across the separation barrier 22 (as shown by Dashed Arrows B) to the standard cathode 12.
  • Fig. 2 shows the battery 10 of Fig. 1 during charging.
  • the charging direction of electron flow (shown by schematic flow path 30) is reversed as shown generally at Arrow C from positive to negative.
  • Positively charged lithium ions 32 travel within the electrolyte 20 from the standard cathode 12 passing across the separation barrier 22 (as shown by Dashed Arrows D) to the standard anode 14.
  • Significant improvement in the conductivity of either the anode or the cathode or both leads to lower resistivity, not only across or through the respective cathodic or anodic film, but also generally across the entire battery cell. As a result, a lower resistance leads to higher voltage to move a given current or move a higher current at a given voltage.
  • exemplary conductive additives 34 for the anode 16 and the cathode 12 that significantly improve conductivity enhancing the performance of these components 12, 16 and the battery 10 within which they are used.
  • the resultant, enhanced cathode 36 and/or enhanced anode 44 exhibit increased conductivity and ion transport within the battery system is facilitated. It is also postulated that the non-carbon surfaces of the highly conductive anode additives may inhibit SEI growth.
  • Fig. 3 is a representative depiction of a portion of an exemplary embodiment of cathode 12 as generally known in the prior art showing an active base cathode material 14 from which the cathode 12 is made.
  • the active base cathode material 14 may be any of many cathode compounds known to be of use in batteries.
  • FIG. 4 An exemplary embodiment of an enhanced cathode 36 showing metal -coated fibers 38 dispersed throughout the active base cathode material 14 is depicted in Fig. 4.
  • the depiction of Fig. 4 is not drawn to scale, nor does it suggest any specific level of loading. Rather, the depiction is merely intended to give context to the dispersion of metal-coated fibers 38 within the active base cathode material 14.
  • Fig. 5 a magnification compared to Fig. 4, depicts an alternative exemplary embodiment of the enhanced cathode 36 showing metal-coated fibers 38 and conductive filamentary structures 42 (which are high aspect ratio conductors 40) dispersed throughout the active base cathode material 14.
  • the structures of the conductive filamentary structures additive 42 are smaller than the metal coated fibers 38 in at least one material physical aspect, such as diameter, weight, or volume and may also exhibit branching.
  • the electrical conductivity between the conductive metal -coated fibers 38 is further enhanced by the addition of the conductive filamentary structures additive 42.
  • the depiction of Fig. 5 is not drawn to scale, nor does it suggest any specific level of loading. Rather, the depiction is merely intended to give context to the dispersion of metal-coated fibers 38 and conductive filamentary structures additive 42 within the active base cathode material 14.
  • Fig. 6 is a representative depiction of a portion of an exemplary embodiment of an anode 16 as generally known in the prior art showing an active base anode material 18 from which the anode 16 is made.
  • the active base anode material 16 may be any of the active anode materials known to be of use in batteries.
  • FIG. 7 An exemplary embodiment of an enhanced anode 44 showing metal-coated fibers 38 dispersed throughout the active base anode material 18 is depicted in Fig. 7.
  • the depiction of Fig. 7 is not drawn to scale, nor does it suggest any specific level of loading. Rather, the depiction is merely intended to give context to the dispersion of metal-coated fibers 38 within the active base anode material 18.
  • Fig. 8 a magnification compared to Fig. 4, depicts an exemplary embodiment of an alternative enhanced anode 44 showing metal-coated fibers 38 and conductive filamentary structures 42 (which are high aspect ratio conductors 40) dispersed throughout the active base anode material 18.
  • the structures of the conductive filamentary structures additive 42 are smaller than the metal coated fibers 38 in at least one material physical aspect, such as diameter, weight, or volume and may also exhibit branching.
  • the electrical conductivity between the conductive metal-coated fibers 38 is further enhanced by the addition of conductive filamentary structures additive 42.
  • FIG. 9 a representative schematic depiction of a portion of an exemplary embodiment of an alternative enhanced electrode (anode or cathode), shows conductive filamentary structures additive 42 dispersed throughout the active base electrode material.
  • Fig. 9 serves a dual function in that the depiction is the same for an exemplary active base cathode material 14 as for an exemplary active base anode material 18 even though such active materials likely differ from one another. Accordingly, reference numbers are provided in the alternative for cathode-related and anode-related references.
  • the purpose of Fig. 9 is to clarify that conductive filamentary structures additive 42 may be used alone as conductive additive or may be used in combination with metal-coated fiber additive 38 as depicted in Figs. 5 and 8.
  • the chart of Fig. 10 shows data regarding improving volume resistivity in a cathode by adding various conductors as additives; namely, PCF (precision chopped fiber) alone, nanostrands alone, NFP or NiFP (nickel filamentary power such as Type 255 powder (and its derivatives)) alone, PCF with nanostrands, and PCF with NiFP into an LFP battery cathode.
  • PCF precision chopped fiber
  • NFP nanostrands
  • NiFP nickel filamentary power such as Type 255 powder (and its derivatives)
  • PCF comprises metal -coated precision chopped fiber
  • the metal may be either nickel or aluminum and the nickel coating may be of any known type including coatings made by vacuum processes (physical vapor deposition (PVD), sputtering, evaporation, etc.), wet chemistry processes (electroplating, electroless plating) and Chemical Vapor Deposition (CVD) and the aluminum coating may be of any known type including coatings made by vacuum processes (physical vapor deposition (PVD), sputtering, evaporation, etc.) and Chemical Vapor Deposition (CVD).
  • PVD physical vapor deposition
  • PVD sputtering
  • evaporation evaporation
  • CVD Chemical Vapor Deposition
  • PCF precision chopped fibers
  • NiFP filamentary nickel powders
  • the nanostrands are a much better “tumbleweeds”, but the filamentary powders are more than adequate.
  • Example #1 Nickel-coated carbon fiber in a cathode.
  • a nickel-coated carbon fiber (7 microns diameter, with 40% nickel coating, or 0.25 micron thick, precision chopped to 0.50 mm) provided excellent conductivity in the cathode.
  • Adding 2% by weight of the described fiber moved the through thickness resistance of a 100 microns film from 3.5 ohms (no fiber) down to 1.5 ohms (2% fiber).
  • the lithium-ion NMC coin cells made from these films would not cycle. It was discovered that the cell corroded at 3.8 volts, before reaching the 4.2 volts operating condition. This is because the half-cell potential of nickel and lithium is 3.8 volts. However, this did demonstrate that the conductivity could be greatly improved and suggested that the nickel-coated fiber should work in systems that remain below about three and a half volts (see LFP cathode examples below).
  • Example #2 Aluminum-coated fiber in a cathode and a coin cell.
  • the half-cell potential of aluminum and lithium is 4.7 volts.
  • an aluminum-coated fiber should survive a cathode having a 4.2-volt operating voltage lithium.
  • a 0.2-micron coating of aluminum was plated over a 0.1 -micron coating of nickel on carbon fiber.
  • the dually coated fiber was chopped to 0.50 mm length. When this fiber was added to the cathode at 3%, by weight, the cell was able to successfully cycle for about a week, before the underlying nickel entered into the reaction.
  • the standard cathode made of an active base cathode material
  • the fiber-loaded cathode active base cathode material metal -coated fiber loaded
  • the table below compares the thickness, resistance, voltage, and capacity of these two cells. (Each value is the average of three samples).
  • the fiber loaded film is 27% thicker than the standard film but exhibits the same resistance indicating lower resistivity.
  • the lower resistivity resulted in a higher voltage.
  • the implication of the higher voltage would manifest a higher rate.
  • the capacity of the fiber-loaded film was increased by 23%.
  • Example #3 Process of coating various fibers with CVD aluminum. Many of the previously mentioned fibers have been coated by an aluminum CVD (chemical vapor deposition) process, precision chopped to 0.5 mm and added to the cathode. Fiber examples include (but are not limited to) silicon carbide, borosilicate, quartz, mineral (basalt), surface modified carbon and organic (aramid-Kevlar). In each of these cases, the addition of 1% to 5% of the precision chopped, aluminum-CVD coated fiber improved the conductivity of the coating by values similar to that of Example #1 above. Each of these fibers will add certain advantages, or disadvantages, unique to that particular fiber, but they all work to improve the conductivity of the cathode.
  • Example #4 Aluminum-coated fibers precision chopped to 0.5 mm. These coated fibers were dispersed into a standard cathode mix at 3% by weight (always reserving a portion of the mix for a control). This was repeated several times, the largest variable being a batch to batch or fiber type variation in the aluminum-coated fiber conductivity.
  • sample set D the samples were calendared and measured for composite
  • CVR Volume Resistivity
  • IR interface resistivity
  • Example # 5 Higher fiber loading in cathode.
  • a standard cathode mixture was loaded with 3%, 4%, 5% and 6% of 0.5 mm precision chopped, nickel-coated fiber having a 40% nickel coating (250 nm thickness). Attempts to mix above 6% resulted in poorer dispersion. However, the following table illustrated the improvement in through thickness volume resistivity when films of equal thickness were pulled from these mixtures.
  • Example #6 Anode with copper-coated carbon fibers. Copper is more conductive than nickel, so copper-coated carbon fiber is more conductive than nickel-coated carbon fiber. Because the current collector of the anode is copper foil, copper-coated carbon fibers may be a viable candidate for anode improvement. In this example, up to 8% of a copper-coated carbon fiber was added to the anode. The copper coating is 40% by weight on an AS4 fiber. The copper coated carbon fiber was obtained from Technical Fiber Products of Schenectady, New York, and precision chopped to 0.50 mm length.
  • Example #7 - Filamentary branching structures Nickel powders produced by chemical vapor decomposition may be produced in two distinct geometrical classes; either spherical (type 1 powders) or filamentary (type 2 powders).
  • Type 1 powders are of little use in increasing conductivity until loadings are exceptionally high, due to the need for the particles to come in close contact to each other.
  • the filamentary powders become conductive at lower loadings due to the higher aspect ratio, and in part due to filamentary powders generally exhibiting some degree of branching.
  • These powders in larger diameter format are available through Vale or Novamet, notably as Type 255 powder (and its derivatives).
  • Nanostrands are a filamentary branching metal having a smaller diameter with more extensive branching. Nanostrands are available from The Conductive Group, Heber City, Utah.
  • NiPCF fibers Nickel-coated, precisionchopped fibers
  • filamentary branching structures forming a “logs and tumbleweeds” network.
  • the filamentary branching structures not only provide a multiplicity of high aspect ratio paths to the nickel-coated fibers (logs), but they also tend to lay on, or tend to touch the carbon particles in multiple places (each such touching hereinafter being referred to as a “touch point”).
  • touch point Each such touching hereinafter being referred to as a “touch point”.
  • the more open and branched nanostrands they tend to wrap themselves around and envelop the carbon particles, like a spider web or net, creating a nanonet and exhibiting a multiplicity of touch points. It is this fashion of multiple touching and nanonetting that adds significantly more conduction opportunities.
  • Example #8 - Cathodes with branched filamentary structures As these branching filamentary conductors are made of nickel, they can only be applied to LFP cells. Cathodes were made with no additives (control sample) and with NiPCF (chopped to a shorter 0.25 mm, refer to Example #9 below), with the branched Type 255 powder (larger diameter and less branching) alone, with the nanostrands (smaller diameter, more branching) alone, and with combinations thereof, as follows. The volume resistivity of each was reported (volume resistivity is similar, but not the same as CVR).
  • Nanostrands demonstrate tremendous efficacy, both alone and with PCF. Nanostrands may be screened, such as through a 100 mesh.
  • Example #9 - PCF length In some battery embodiments, depending on the type and makeup of the battery, 0.50 mm PCF may prove to be too long and penetrate the separator. There are two immediate solutions to this occurrence; 1) Implement a thicker separator or a double separator (which has been found to work) or 2) make the fiber shorter. As mentioned above, making the fiber shorter may require a greater loading to achieve the same CVR. The IR, however, is not affected as much. These concepts are shown in the following table: [00130]
  • Example #10 The example of a modified cathode is given in Example #6 above.
  • Example #10 demonstrates the performance of two sets of lithium iron phosphate cells, one with a standard cathode and one with an additive loading of 5% by weight of nickel-coated PCF at 40% nickel and precision chopped to a 0.50 mm length. After a successful build and conditioning cycle, each of the cells were cycled to C/10 discharge rates to determine their capacities. Then each population was subjected to a series of increasing discharge rates as follows: C/2. 1C, 2C and 3C. This demonstrated that at any equivalent voltage, the nickel- coated PCF cells discharge 2.1 times faster than the standard cell, which implies that the treated cell will develop 2.1 times the power.
  • any means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.
  • a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures.
  • a construction under Section 112 is not intended. Additionally, it is not intended that the scope of patent protection afforded the present invention be defined by reading into any claim a limitation found herein that does not explicitly appear in the claim itself.

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Abstract

La résistance électrique de films cathodiques et anodiques actifs peut être significativement réduite par ajout de petites fractions d'additifs conducteurs à l'intérieur d'un système de batterie. La diminution de la résistance dans la cathode et/ou l'anode conduit à un transport d'électrons plus facile à travers la batterie, ce qui permet d'augmenter la puissance, la capacité et les vitesses tout en diminuant les pertes de chauffage en joules.
PCT/US2024/010608 2022-12-12 2024-01-07 Sélection d'additif de type fibre revêtue de métal pour réduction de résistance dans une batterie et matériaux de batterie Ceased WO2024130260A1 (fr)

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US18/079,811 US20230123858A1 (en) 2020-06-14 2022-12-12 Metal-Coated Fiber Additive Selection for Resistance Reduction in a Battery and Battery Materials

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20180006330A1 (en) * 2016-06-30 2018-01-04 Wildcat Discovery Technologies, Inc. Electrolyte additives and electrode materials for high temperature and high voltage operation
US20180294474A1 (en) * 2017-04-10 2018-10-11 Nanotek Instruments, Inc. Encapsulated Cathode Active Material Particles, Lithium Secondary Batteries Containing Same, and Method of Manufacturing
US20210391581A1 (en) * 2020-06-14 2021-12-16 George Clayton Hansen Resistance Reduction in a Battery and Battery Materials

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20180006330A1 (en) * 2016-06-30 2018-01-04 Wildcat Discovery Technologies, Inc. Electrolyte additives and electrode materials for high temperature and high voltage operation
US20180294474A1 (en) * 2017-04-10 2018-10-11 Nanotek Instruments, Inc. Encapsulated Cathode Active Material Particles, Lithium Secondary Batteries Containing Same, and Method of Manufacturing
US20210391581A1 (en) * 2020-06-14 2021-12-16 George Clayton Hansen Resistance Reduction in a Battery and Battery Materials

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