Dry powder binder compositions for lithium ion batteries

Abstract

A method for making a fibrillatable dry powder binder composition for a lithium ion battery includes forming an agglomerate by co-coagulating a fibrillatable fluoropolymer with particles of a fluoroelastomer having a Dv50 particle size (i.e., median particle diameter) of less than 300 nm. The fibrillatable fluoropolymer comprises a tetrafluoroethylene (TFE)-based polymer. The fluoroelastomer is present in the dry powder binder composition in a weight percentage of greater than zero and 10 wt.% or less. The fluoroelastomer has a higher reduction stability than the fibrillatable fluoropolymer.

Description

Atorney Docket No.: FL0702-W001TITLE OF THE INVENTIONDRY POWDER BINDER COMPOSITIONS FOR LITHIUM ION BATTERIESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority benefit of US provisional patent application no. 63 / 754,750, filed on February 6, 2025, the disclosure of which is hereby incorporated by reference in its entirety.FIELD OF THE INVENTION

[0002] The present disclosure relates to dry friable fluoropolymer agglomerate compositions for use as binder in lithium-ion secondary battery electrodes, methods for the dry manufacture of such compositions, electrode compositions and electrodes, and lithium-ion batteries utilizing such electrodes.BACKGROUND OF THE INVENTION

[0003] Electrodes for lithium ion batteries typically include an electrode active material, such as graphite, metal, or metal oxide, that undergoes an electrochemical reaction associated with energy storage; a binder, that mechanically supports and binds the active component and attaches the electrode to a current collector; and optionally an electrically conductive additive (or conductive agent), such as carbon black, that increases the electrical conductivity of the electrode.

[0004] Recent advances in lithium-ion battery manufacturing have increasingly leveraged the unique properties of polytetrafluoroethylene (PTFE) in solvent-free electrode fabrication. By removing organic solvents from the process, manufacturers can significantly reduce production costs and environmental impact, aligning with global sustainability goals. PTFE’s exceptional ability to form fibrils under mechanical stress is critical to this approach, as it enables robust, interconnected networks among electrode components — including active materials and conductive additives such as carbon black. The dry method not only simplifies processing and mitigates solvent recovery challenges but also allows for the construction of much thickerAttorney Docket No.: FL0702-W001electrodes with higher active mass, directly boosting the energy density and capacity of next-generation battery cells.

[0005] Despite these benefits, limitations emerge when PTFE homopolymer are used as binders in anode electrodes. Unlike their stable performance in cathodes, PTFE binders are prone to reduction reactions at the anode’s operating potential. The degradation of PTFE could lead to poor adhesion between electrode materials and current collectors, as well as diminished internal cohesion, which eventually causes electrochemical failure. The electrochemical reduction of PTFE also results in a loss of cell capacity and a lower first coulombic efficiency (ICE) due to the loss of cyclable or reversible lithium. Thus, there is a significant need for an approach to stabilize PTFE-based polymers within lithium-ion battery electrodes. Effective stabilization would mitigate the reduction of PTFE, thereby preventing mechanical degradation of the electrode and improving the initial coulombic efficiency and cycle life performance.

[0006] Co-coagulation of PTFE and TFE-based polymers with polymers such as fluoroelastomers or perfluoroelastomers (e.g., FKM or FKKM) has been disclosed in international patent application publication no. WO2024 / 072861 A2 to Aryal etal.. Co-coagulation using FKM dispersions having a particle size of less than 300 nm is not described.

[0007] It has been found that a commercially-viable, large-scale production process based on co-coagulating a fibrillatable fluoropolymer (e.g., PTFE) with a fluoroelastomer (e.g. FKM) is significantly impacted by the stability of the fluoroelastomer dispersion over extended periods of time. Hence, there is a need to create fibrillatable (dry) powders suitable for use as binder in dry battery electrode production containing a fibrillatable fluoropolymer and FKM, where the FKM is derived from dispersions which are more stable overextended times.SUMMARY OF THE INVENTION

[0008] This disclosure relates to fibrillatable dry powder binder compositions for use in lithium ion battery electrodes, e.g., negative or positive electrodes. These dry binder compositions are formed by co-coagulating particles of a fibrillatable fluoropolymer with small particles of a fluoroelastomer having a higher reductionAttorney Docket No.: FL0702-W001stability than the fibrillatable fluoropolymer. The small particle size fluoroelastomer dispersion (Dv50 particle size of less than 300 nm) prior to co-coagulation was found to be a stable dispersion. The resulting fibrillatable dry powder binder compositions were used to prepare electrodes having several improved properties. The fibrillatable dry powder binder compositions that result from this co-coagulation have good stability against electrochemical reduction. When these binders are used in negative electrodes for lithium ion batteries, the resulting electrodes are robust against electrochemical and mechanical degradation and contribute to long cycle life of the batteries.

[0009] In a first aspect, a method of making a fibrillatable dry powder binder composition for a lithium ion battery includes co-coagulating particles of a fibrillatable fluoropolymer with particles of a fluoroelastomer. The particles of the fluoroelastomer have a Dv50 particle size of less than 300 nm. The fibrillatable fluoropolymer includes a tetrafluoroethylene (TFE)-based polymer, and wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of greater than zero and less than 10 wt.%.

[0010] In a second aspect, a fibrillatable dry powder binder composition is provided comprising agglomerates of a fibrillatable fluoropolymer and a fluoroelastomer. The agglomerates were produced by co-coagulating particles of the fibrillatable fluoropolymer with particles of the fluoroelastomer having a Dv50 particle size of less than about 300 nm (particle size of fluoroelastomer particles measured in dispersion prior to co-coagulation), and wherein the fluoroelastomer is present in the powder in a weight percentage of greater than zero and 10 wt% or less.

[0011] In a third aspect, a method of making an electrode composition for a lithium ion battery is provided comprising co-coagulating particles of a fibrillatable fluoropolymer with particles of a fluoroelastomer to form a dry powder binder composition and mixing the dry powder binder composition with an electrode active material to form an electrode composition. The particles of the fluoroelastomer have a Dv50 particle size of less than 300 nm. The fibrillatable fluoropolymer includes a tetrafluoroethylene (TFE)-based polymer, such as polytetrafluoroethylene (PTFE) homopolymers and modified PTFE. The fibrillatable fluoropolymer includes a tetrafluoroethylene (TFE)-based polymers, such as polytetrafluoroethylene (PTFE)Attorney Docket No.: FL0702-W001homopolymers and modified PTFE. The fluoroelastomer is present in the dry powder binder composition in a weight percentage of greater than zero and 10 wt.% or less.

[0012] In a fourth aspect, a method of making an electrode composition for a lithium ion battery is provided comprising mixing a dry powder binder composition with particles of an electrode active material to form an electrode composition. The fibrillatable dry powder binder composition has been formed by co-coagulating particles of a fibrillatable fluoropolymer with particles of a fluoroelastomer having a Dv50 particle size of less than about 300 nm. The fluoropolymer includes a tetrafluoroethylene (TFE)-based polymer. The fluoroelastomer is present in the dry powder binder composition in a weight percentage of greater than zero and less than about 10 wt.%

[0013] In a fifth aspect, an electrode composition for an electrode of a lithium ion battery is provided comprising particles of an electrode active material and a binder composition. The binder composition is formed by co-coagulating particles of a fibrillatable fluoropolymer with particles of a fluoroelastomer having a Dv50 particle size of less than about 300 nm. The fibrillatable fluoropolymer includes a tetrafluoroethylene (TFE)-based polymer, such as PTFE. The fluoroelastomer is present in the dry powder binder composition in a weight percentage of greater than zero and less than 10 wt.%. fluoropolymer.

[0014] In a sixth aspect, an electrode film includes the electrode composition of the fifth aspect.

[0015] In a seventh aspect, a negative electrode for a lithium ion battery includes a film including the electrode composition of the fifth aspect.

[0016] In an eighth aspect, a lithium ion battery includes the negative electrode of the seventh aspect, a positive electrode, and an electrolyte in contact with the negative electrode and the positive electrode.

[0017] In a ninth aspect, a fibrillatable dry powder composition is provided for use as a binder in an electrode, said composition comprising agglomerates of fibrillatable fluoropolymer particles and fluoroelastomer particles, said fluoroelastomer particles having a Dv50 particle size of 300 nm or less; wherein said agglomerates have a Dv50 particle size of 300 pm or less; wherein the weight percent (wt%) of theAttorney Docket No.: FL0702-W001fluoroelastomer within fibrillatable dry powder composition is more than 0 wt% and no more than 10 wt%. In one embodiment, the fibrillatable dry powder composition comprises fibrillatable polytetrafluoroethylene (PTFE) homopolymer, fibrillatable modified PTFE ora combination thereof.

[0018] In a tenth aspect, an electrode composition is provided comprising: particles of an electrode active material; and the fibrillatable dry powder binder composition of the ninth aspect. In one embodiment of the tenth aspect, the fibrillatable fluoropolymer is partially or fully fi bril lated . In another embodiment of the tenth aspect, the electrode composition further comprises particles of at least one conductive additive.

[0019] In an eleventh aspect, an electrode film is provided comprising the electrode composition of the tenth aspect. In a further embodiment to the eleventh aspect, the electrode film is self-supporting. In a further embodiment to the eleventh aspect, the electrode film further comprises at least one current collect. The current collector is a laminated layer in the electrode film.

[0020] In a twelfth aspect, an electrode is provided comprising the electrode film of the eleventh aspect. In one embodiment of the twelfth aspect, the electrode film is a negative electrode. In one embodiment of the twelfth aspect, the integrated area of the reduction peak of the electrode between 0.2 V and 0.9 V, as characterized by cyclic voltammetry in a half-cell configuration vs. Li / Li+, is less than an integrated area of a comparative electrode having a binder composition without fluoroelastomer. In another embodiment of the twelfth aspect, the integrated area of the reduction peak of the electrode between 0.2 V and 0.9 V, as characterized by cyclic voltammetry in a half-cell configuration vs. Li / Li+, is less than an integrated area of a comparative electrode having a binder composition comprising a fluoroelastomer having a particle size greater than 300 nm, preferably greater than 800 nm, most preferably greater than 2 pm. In another embodiment of the twelfth aspect, the integrated area of the reduction peak of the electrode is at least 10% less than the integrated area of the reduction peak of the comparative electrode. In another embodiment of the twelfth aspect, the integrated area of the reduction peak of the electrode between 0.2 V and 0.9 V, as characterized by cyclic voltammetry in a half-cell configuration vs. Li / Li+, is less than an integrated area of a comparativeAttorney Docket No.: FL0702-W001electrode having a binder composition formed by co-coagulating particles of the fibrillatable fluoropolymer with particles of the fluoroelastomer having a Dv50 particle size of greater than about 300 nm. In another embodiment of the twelfth aspect, the integrated area of the reduction peak of the electrode is at least 10% less than the integrated area of the reduction peak of the comparative electrode.

[0021] In a thirteenth aspect, a lithium ion battery is provided comprising:the negative electrode of the twelfth aspect;a positive electrode; and an electrolyte in contact with the negative electrode and the positive electrode.

[0022] Embodiments of any of the foregoing aspects can include one or any combination of two or more of the following features.

[0023] The fluoroelastomer has a higher reduction stability than the fluoropolymer. The co-coagulating produces agglomerates of the fluoropolymer and the fluoroelastomer, the agglomerates having a Dv50 particle size of less than 300 pm when measured by particle size distribution at 20 pounds per square inch (PSI)(~138 kPa).

[0024] Co-coagulating particles of the fibrillatable fluoropolymer with particles of the fluoroelastomer includes mixing an aqueous dispersion of the particles of the fibrillatable fluoropolymer with an aqueous dispersion of the particles of the fluoroelastomer. Co-coagulating the particles of the fibrillatable fluoropolymer with particles of the fluoroelastomer includes producing agglomerates of the fibrillatable fluoropolymer and the fluoroelastomer. The agglomerates of the fluoropolymer and the fluoroelastomer are friable.

[0025] The agglomerates have a Dv50 particle size of between about 200 pm and about 1000 pm. The agglomerates have a Dv50 particle size of between about 200 pm and about 500 pm.

[0026] The method of any of the foregoing aspects includes separating the agglomerates and drying the agglomerates to form the fibrillatable dry powder binder composition. The particles of the fluoroelastomer have a Dv50 particle size of between about 50 nm and about 300 nm, preferably between about 200 nm andAttorney Docket No.: FL0702-W001about 300 nm. In the fibrillatable dry powder binder composition, the fibrillatable fluoropolymer is substantially unfibrillated .

[0027] The fibrillatable fluoropolymer includes polytetrafluoroethylene (PTFE). The fibrillatable fluoropolymer includes PTFE homopolymers, modified PTFE or any combination thereof. The fibrillatable fluoropolymer has a melt creep viscosity of at least about 0.1 x 1011poise (0.1 x 1010Pa S). The fluoroelastomer includes a copolymer including vinylidene fluoride. The fluoroelastomer includes a copolymer of vinylidene fluoride and hexafluoropropylene (HFP). The fluoroelastomer is present in the fibrillatable dry powder binder composition in a weight percentage of greater than zero and less than about 5 wt.%.

[0028] The fluoroelastomer is present in the fibrillatable dry powder binder composition in a weight percentage of between about 1 wt.% and about 5 wt.%. The fluoroelastomer is present in the fibrillatable dry powder binder composition in a weight percentage of between about 1 wt.% and about 4 wt.%. The fluoroelastomer is present in the fibrillatable dry powder binder composition in a weight percentage of between about 1 wt.% and about 3 wt.%.

[0029] The fluoroelastomer is present in the fibrillatable dry powder binder composition in a weight percentage of greater than zero and less than about 4 wt.%. The fluoroelastomer is present in the fibrillatable dry powder binder composition in a weight percentage of greater than zero and less than about 3 wt.%. The fluoroelastomer is present in the fibrillatable dry powder binder composition in a weight percentage of about 2 wt.%.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 is a diagram of a battery.

[0031] FIG. 2 shows cyclic voltammetry results.

[0032] FIG. 3 shows particle size measurement results.DETAILED DESCRIPTION OF THE INVENTION

[0033] This disclosure relates to dry powder binder compositions for lithium ion battery electrodes, such as negative or positive electrodes. These binderAttorney Docket No.: FL0702-W001compositions are formed by co-coagulating particles of a fluoropolymer with small particles of a fluoroelastomer (i.e. having a Dv50 particle size of less than 300 nm). The fluoroelastomer has a higher reduction stability than the fibrillatable fluoropolymer. For instance, the dry powder binder compositions that result from this co-coagulation have good stability against electrochemical reduction in the context of anode electrodes for lithium ion batteries.

[0034] Generally, due to their electronic structure, fibrillatable fluoropolymers such as polytetrafluoroethylene (PTFE) (homopolymers and modified PTFE) are easily reduced when used as binders in negative electrodes of lithium ion batteries. Over time, as such a battery is cycled, reduction of PTFE in lithium ion battery anode electrodes causes the binder material to deteriorate, which can compromise the mechanical integrity of the electrode, e.g., causing a degradation in adhesion of the electrode to the current collector of the battery and / or internal cohesion of components of the electrode. Without being bound by theory, it is believed that PTFE may produce Li F along with a reduced or partial ly / fully fluorinated product, which can also result in a loss of cell capacity due to loss of cyclable lithium.

[0035] The fibrillatable dry powder binder compositions described here include small particles of a fluoroelastomer, co-coagulated with a fibrillatable fluoropolymer such as a tetrafluoroethylene (TFE)-based polymer. The presence of the small particles of fluoroelastomer within the co-coagulated structure of the binder contributes to better stability of the binder against electrochemical reduction when formulated in an anode electrode of a lithium ion battery.Fluoropolymer and fluoroelastomer compositions

[0036] The dry powder binder materials described here are formed by cocoagulating a fibrillatable fluoropolymer with a fluoroelastomer. In one embodiment, the fluoroelastomer is a perfluoroelastomer. Co-coagulation is discussed further infra and in international patent application publication no. WO2024 / 072861 A2 to Aryal etal., published April 4, 2024.

[0037] The fibrillatable fluoropolymer is a tetrafluoroethylene (TFE)-based polymer. A fi brillatable TFE-based fluoropolymer refers to a fibrillatable polymer, at least a portion of which has repeating units arising from TFE monomer. In oneAttorney Docket No.: FL0702-W001embodiment, the fibrillatable fluoropolymer is fibrillatable polytetrafluoroethylene (PTFE) (i.e. PTFE homopolymer, modified PTFE or any combination thereof).

[0038] In some examples, the fibrillatable fluoropolymer is a TFE-based copolymer that includes repeating units arising from TFE monomer and repeating units arising from another monomer. One example of a class of TFE-based copolymer is perfluoroalkoxy alkanes (PFAs), which are copolymers of TFE and perfluoroethers. Another example of a class of TFE-based copolymers is “modified PTFE”, which refers to PTFE having a small concentration of a comonomer (e.g., 1 wt.% or less, preferably less than 0.5 wt.%, more preferably between 0.05 wt% and 0. 5 wt.%, and most preferably 0.01 wt% and 0.5 wt% of the comonomer). For instance, the concentration of comonomer in a modified PTFE can be small enough that the molecular weight of the resulting polymer is not substantially reduced below that of homopolymer PTFE. Examples of comonomers in modified PTFE include, e.g., perfluoroolefins such as hexafluoropropylene (HFP) or perfluoro(alkyl vinyl ether) (PAVE), where the alkyl group contains 1 to 5 carbon atoms, e.g., perfluoro(ethylvinyl ether) (PEVE), perfluoro(propyl vinyl ether) (PPVE), chlorotrifluoroethylene (CTFE), perfluorobutyl ethylene (PFBE), or other similar monomers that introduce relatively sterically bulky side groups into the PTFE polymer chain.

[0039] The fluoropolymer has a melt creep viscosity that is sufficiently high such that the fluoropolymer does not flow in the molten state and is not melt-processable. For instance, the fluoropolymer has a melt creep viscosity of at least about 0.1 x 1011poise (0.1 x 1010Pa-S), between about 0.1 x 1011poise (0.1 x 1010Pa S) and about 6.0 x 1011poise (6.0 x 1010Pa S), e.g., about 1.0 x 1011poise (1.0 x 1010Pa S), about 1.5 x 1011poise (1.5 x 1010Pa S), about 2.0 x 1011poise (2.0 x 1010Pa S), about 2.5 x io11poise (2.5 x 1010Pa S), about 3.0 x 1O11poise (3.0 x 1010Pa S), about 3.5 x 1011poise (3.5 x 1010Pa S), about 4.0 x 1011poise (4.0 x 1010Pa S), about 4.5 x 1011poise (4.5 x 1010Pa S), about 5.0 x 1011poise (5.0 x 1010Pa S), about 5.5 x 1011poise (5.5 x 1010Pa S), or about 6.0 x 1011poise (6.0 x 1010Pa S). Melt creep viscosity (MCV) is measured by the method described in Ebnesajjad, Sina, (2015), in Fluoroplastics, Volume 1 - Non-Melt Processible Fluoropolymers - The Definitive User's Guide and Data Book (2nd Edition), Appendix 5, Melt CreepAttorney Docket No.: FL0702-W001Viscosity of Polytetrafluoroethylene, pp. 660-661, with reference to U.S. Patent no.3,819,594.

[0040] The TFE-based polymer is a fluoropolymer that is fibril lizable. A fibrillizable polymer is a polymer that is capable of forming fibrils when subjected to shear forces. Once fibrillized, the fibrils help to durably enmesh one or more active fillers within the fi bri Hated matrix and help to form more durable structures such as self- supporting composite films / sheets (e.g. electrode films). Fibrils have at least one dimension in the nanoscale (e.g., < 100 nm) and can vary in length from submicrometer to tens of micrometers.

[0041] The particles of the fibrillatable fluoropolymer are capable of forming a stable aqueous dispersion, which is mixed with an aqueous dispersion of small particles of the fluoroelastomer (discussed below) to co-coagulate the two polymers. Aqueous dispersions of TFE-based polymers can be manufactured by known methods. Dispersion processes for polymerizing fluorinated monomers in aqueous media are described in U.S. Patent No. 6,429,258, PCT patent application publication no. W02008 / 060461 A1, and U.S. patent application publication no. 2009 / 0281241 A1. Aqueous dispersion processes for manufacture of tetrafluoroethylene polymer typically employ a surfactant, also referred to as dispersant, to provide dispersion stability and permit the fluoromonomer polymerization to be carried to commercially acceptable solids concentrations at commercially acceptable production rates.

[0042] As used herein, the term “fluoroelastomer” includes both fluoroelastomers (FKM) or perfluoroelastomers (FFKM). The fluoroelastomer and has a reduction stability that is higher than the reduction stability of the fibrillatable fluoropolymer (e.g. PTFE). In one aspect, the fluoroelastomer is FKM. The presence of small fluoroelastomer particles with higher reduction stability in the dry powder binder composition provides electrochemical stability against reduction to lithium ion battery negative electrodes that are formed from the dry powder binder composition.

[0043] For instance, the fluoroelastomer can be a copolymer including hexafluoropropylene (HFP), e.g., vinylidene fluoride / hexafluoropropylene copolymer (VDF / HFP); vinylidene fluoride / hexafluoropropylene / tetrafluoroethylene copolymer (VDF / HFP / TFE); vinylidene fluoride / perfluoro(methyl vinyl ether) / tetrafluoroethyleneAttorney Docket No.: FL0702-W001copolymer (VDF / PMVE / TFE); tetrafluoroethylene / perfluoro(methyl vinyl ether) copolymer (TFE / PMVE); tetrafluoroethylene / propylene copolymer (TFE / P); and ethylene / tetrafluoroethylene / perfluoro(methyl vinyl ether) copolymer (E / TFE / PMVE). In a specific example, the fluoroelastomer is a copolymer including 60 wt.% VDF and 40 wt.% HFP. In some embodiments the fluoroelastomer does not include TFE as a monomer.

[0044] In an example, fluoroelastomers used in forming the binder compositions described here can be described as:(A) vinylidene fluoride-based (VDF) fluoroelastomers, in which VDF is copolymerized with at least one additional comonomer selected from the group consisting of:(i) C2-C8 perfluoroolefins, such as tetrafluoroethylene (TFE), hexafluoropropylene (HFP);(ii) hydrogen-containing C2-C8 olefins, such as vinyl fluoride (VF), trifluoroethylene, hexafluoroisobutene, perfluoroalkyl ethylenes of formula CH2=CH- Rf, wherein Rt is a Ci-Ce perfluoroalkyl group;(iii) C2-C8 fluoroolefins comprising at least one of iodine, chlorine and bromine, such as chlorotrifluoroethylene (CTFE);(iv) (per)fluoroalkylvinylethers (PAVE) of formula CF2=CFORf, wherein Rf is a Ci-Ce (per)fluoroalkyl group, preferably -CF3, -C2F5, -C3F7;(v) (per)fluoro-oxy-alkylvinylethers of formula CF2=CFOX, wherein X is a Ci- C12 ((per)fluoro)-oxyalkyl comprising catenary oxygen atoms, e g. the perfluoro- 2-propoxypropyl group;(vi) (per)fluorodioxoles;(vii) (per)fluoro-methoxy-vinylethers having formula: CF2=CFOCF2ORf2, wherein Rf2 is selected from the group consisting of Ci-Ce (per)fluoroalkyls; Cs-Ce cyclic (per)fluoroalkyls; and C2-C6 (per)fluorooxyalkyls, comprising at least one catenary oxygen atom; Rf2 is preferably -CF2CF3; -CF2CF2OCF3; or-CFs;(viii) C2-C8 non-fluorinated olefins, for example ethylene and propylene; andAttorney Docket No.: FL0702-W001(B) TFE-based fluoroelastomers, in which TFE is copolymerized with at least one additional comonomer selected from the group consisting of (i) through (viii) as described immediately above.

[0045] The particles (i.e., a Dv50 of less than 300 nm) of the fluoroelastomer are capable of forming a stable aqueous dispersion. As used herein, a “stable aqueous dispersion” of the fluoroelastomer particles will refer to a shelf stable aqueous dispersion that can be redispersed with substantially no settling of the fluoroelastomer particles after sitting at rest at room temperature (~22 °C) at atmospheric pressure (1 bar; 100 kPa) for at least 1 month, preferably at least 2 months and most preferably at least 3 months under these conditions. Without being bound by theory, it is believed that small size of the fluoroelastomer particles contributes the long-term shelf stability of the dispersions. Aqueous solutions of fluoroelastomer that have long-term shelf stability are advantageous, e.g., rendering the solutions transportable such that they can be manufactured at a different location than the fabrication of the dry powder binder compositions.Formation of binder compositions

[0046] A fibrillatable dry powder binder composition is formed by co-coagulating particles of fibrillatable fluoropolymer with small particles (i.e. Dv50 < 300 nm) of the fluoroelastomer to produce a free-flowing powder composed of friable agglomerates containing both fibrillatable fluoropolymer and fluoroelastomer. A free-flowing powder is a powder in which the constituent components (here, the agglomerates containing fluoropolymer and fluoroelastomer) are substantially free to move relative to one another.

[0047] The small particles of the fluoroelastomer in the aqueous dispersion prior to co-coagulation with the fluoropolymer have a Dv50 particle size (median particle diameter) of less than 300 nm, e.g., between about 50 nm and about 300 nm, between about 5 nm and about 250 nm, between about 50 nm and about 250 nm, or between about 200 nm and about 300 nm; as measured by laser light scattering (discussed in detail below).

[0048] The particles of the fluoropolymer in the aqueous dispersion prior to cocoagulation with the fluoroelastomer have a Dv50 median particle diameter of between about 100 nm and about 300 nm, e.g., between about 100 nm and aboutAttorney Docket No.: FL0702-W001250 nm, between about 100 nm and about 200 nm, or between about 200 nm and about 300 nm; as measured by laser light scattering.

[0049] In one embodiment, co-coagulating the fibrillatable fluoropolymer and the fluoroelastomer includes forming an aqueous dispersion or solution containing particles of the fluoropolymer and an aqueous dispersion or solution containing particles of the fluoroelastomer, and combining the two dispersions or solutions to co-coagulate the fluoropolymer and the fluoroelastomer, thereby forming agglomerates including co-coagulates of the fluoropolymer and the fluoroelastomer. Further discussion of co-coagulation is provided in international patent application publication no. WO2024 / 072861 A2 to Aryal etal., published April 4, 2024, and in U.S. patent no. 7,947,775, issued May 24, 2011.

[0050] Co-coagulation can be carried out by various mixing processes, such as by vigorously agitating and / or stirring the mixture, optionally supplemented by addition of electrolyte and / or water-immiscible solvent having low surface tension, and / or by freeze-thaw procedures. In some examples, the co-coagulation process includes diluting the mixture of the aqueous dispersions to a polymer concentration of about 10 wt% to about 20 wt% and optionally adjusting the pH to neutral or basic. In some examples, a coagulating agent such as a water-soluble organic compound, an inorganic salt, or acid is included in the mixture.

[0051] The vigorous agitation and / or stirring causes co-coagulation of the fibrillatable fluoropolymer and the fluoroelastomer, which “crash out” in the form of a powder including agglomerates of the fibrillatable fluoropolymer and the fluoroelastomer co-coagulated with one another. Crashing out can be spontaneous or aided, e.g., by freezing to initiate precipitation. The fibrillatable powder, which includes co-coagulated agglomerates, can be separated from the aqueous phase by conventional techniques, such as skimming and / or filtration. Drying of the agglomerates can be carried out by vacuum, high frequency, and / or heated air, such that the wet powder is not excessively fluidized. Excessive friction or contact between the particles during drying, especially at a high temperature, may adversely affect the agglomerates due to fibrillation and resulting loss of particulate structure leading to potentially poorer properties of electrode compositions and films madeAttorney Docket No.: FL0702-W001from the agglomerates. In some implementations, the powder is dried at drying temperature(s) in a range from 100°C to 180°C.

[0052] The agglomerates that result from co-coagulation of the fibrillatable fluoropolymer particles and the fluoroelastomer particles have a Dv50 particle size (median particle diameter) of between about 200 pm and about 1000 pm, e.g., between about 200 pm and about 5000 pm. In the agglomerates, the fibrillatable fluoropolymer particles and the fluoroelastomer particles are physically intermixed with one another with domains on the micron scale or smaller.

[0053] In the co-coagulated agglomerates, the fibrillatable fluoropolymer is substantially unfibrillated, and the agglomerates themselves are both friable and fi bri llizable. Friability of a polymer refers to the ability of agglomerates of the polymer to be deagglomerated and comminuted, e.g., through application of shear force (e.g., in a mixing process) without substantially fibrillating the polymer. Friability of a polymer can be quantified by applying an external pressure to the polymer, causing the polymer agglomerates to break down into smaller agglomerates. The particle size of the resulting smaller agglomerates is an indication of the friability of the polymer: smaller size of the agglomerates indicates a more friable polymer. For instance, when measured after application of 60 pounds per square inch (60 PSI; - 414 kPa) of external pressure, the smaller agglomerates have a Dv50 particle size (median particle diameter) of 30 - 100 pm.

[0054] Friability of the agglomerates can be measured quantitatively using variable shear air jets. Specifically, the agglomerates are exposed to varying levels of dispersion energy from pressurized air jets, and particle size distribution is measured by laser diffraction. When measured in this variable shear air jet process, the agglomerates have a Dv50 particle size (median particle diameter) of less than about 300 pm when measured at 20 PSI (-138 kPa).

[0055] The fluoroelastomer is present in the agglomerates in a weight percentage of greater than zero (for example, greater than 0.01 wt%) and 10 weight percent (wt.%) or less, less than 8 wt.%, less than 6 wt.%, less than 5 wt.%, less than 4 wt.%, or less than 3 wt.%, e.g., between 0.01 wt% and 10 wt%, 1 wt.% and 10 wt.% or between about 1 wt.% and 5 wt.%, e.g., between 1 wt.% and 4 wt.% or between 1 wt.% and 3 wt.%, e.g. 2 wt.% In some instances, agglomerates formed by coAttorney Docket No.: FL0702-W001coagulation containing more than 10 weight percent or more than 5 weight percent of fluoroelastomer resulted in dry powder binder compositions that are rubbery and generally not free-flowing or fibrillizable.

[0056] The agglomerate structure formed by co-coagulation and its properties differ from the structure and properties that would result from a simple physical mixing / blending of the fibrillatable fluoropolymer and the fluoroelastomer. For instance, physical mixtures of the fibrillatable fluoropolymer and the fluoroelastomer include large domains of the fibrillatable fluoropolymer and the fluoroelastomer, large particle sizes, agglomerations of the fluoropolymer and the fluoroelastomer, etc. By contrast, the co-coagulated agglomerate structure is a homogenous or substantially homogenous mixture with the micron or submicron domain sizes noted above.

[0057] Dv50 particle size (median particle diameter) of the raw dispersions of fibrillatable fluoropolymer and fluoroelastomer particles is measured using laser light scattering with a Zetasizer Nano-ZS manufactured by Malvern Instruments (Malvern Panalytical Inc., Westborough, Massachusetts). Samples for analysis are prepared in 10x10x45 mm polystyrene cuvettes, capped and placed in the device for analysis. Preparation of the sample is as follows. Water used to flush the cuvette and used to dilute the dispersion sample is rendered substantially free of particles by drawing deionized, deaerated water into a 10 cc glass hypodermic syringe with locking tip. A Whatman 0.02 micron filter (Cat. No. 6809-2002) is fitted to the locking tip of the syringe and pressure is applied force water through the filter and into the cuvette. Approximately 1.5 ml_ of water is placed in the cuvette, the cuvette is capped, shaken and uncapped. Water is poured out of the cuvette thus assuring the cuvette is free of particles. Approximately 2.5 gm of filtered water is placed in the cuvette. One drop of the dispersion to be analyzed is added to the cuvette. The cuvette is capped and shaken to completely mix the particles in the water. The sample is placed in the Nano-ZS for determination of Dv50. Dv50 is the median particle diameter (also referred to herein as the “particle size” or “median particle size”) based on volumetric particle size distribution, i.e. the particle size below which 50% of the volume of the population resides. Further description of Dv50 particle size measurement can be found in U.S. Patent No. 9,371,405, the entire contents of which incorporated here by reference in its entirety.Attorney Docket No.: FL0702-W001Electrodes and lithium ion batteries

[0058] In some examples, the fibrillatable dry powder binder composition is mixed with small particles of anode active material and, optionally, a conductive additive to form a negative electrode composition. Example anode active particles include, e.g., graphite, graphene, lithium titanate, silicon, silicon-containing materials, or other suitable anode active materials. For instance, the electrode composition contains between about 1 and about 10 wt.% binder composition and between about 90 to about 99 wt.% anode active particles.

[0059] The mixing of the dry powder binder composition with the anode active material particles induces deagglomeration, comminution, and fibrillation of the fibrillatable binder composition, resulting in a substantially homogeneous mixture of the small particle anode active material, the conductive additive, and fibrils of the binder composition. The mixing process is carried out in a solvent-free process, e.g., free from water and organic solvents such as N-methyl-2-pyrrolidone (i.e. a dry process for forming dry battery electrodes).

[0060] In an example, the anode active material particles are mixed together with the dry powder binder composition in a milling process in a solvent-free environment. The milling process is carried out under conditions sufficient for the agglomerates to deagglomerate and comminute to secondary agglomerates having a particle size substantially similar to that of the anode active particles, and for the anode active particles and the secondary agglomerates to be substantially homogeneously mixed. Example milling techniques include jet-milling, pin milling, impact pulverization, and hammer milling, and similar techniques and apparatus. The milling process can be carried out at a temperature of between about 20 °C and about 200 °C, e.g., between about 80 °C and about 150 °C.

[0061] In some examples, the fibrillatable dry powder binder composition is mixed with small particles of cathode active material to form a positive electrode composition. Example cathode active particles include particles of lithium transition metal oxide. Positive electrode compositions can also include conductive additives such as conductive carbon.

[0062] Formation of electrode films using the electrode compositions described here can also be carried out in a solvent-free process, e.g., without requiring a slurry.Attorney Docket No.: FL0702-W001For instance, electrode films can be formed by compacting an electrode composition in a calendering process. The electrode film can be laminated onto a current collector to be used as an electrode in a lithium ion battery. In some examples, the electrode films are free-standing, e.g., able to maintain mechanical integrity when unsupported.

[0063] Anode electrode films including from dry powder binder materials that are prepared by co-coagulating particles of a fibrillatable fluoropolymer with small particles (e.g., Dv50 particle size of less than 300 nm) of a fluoroelastomer have good stability against electrochemical reduction. Specifically, these anode electrode films have a smaller integrated area of the electrochemical reduction peak between 0.2 and 0.9 V, as characterized by cyclic voltammetry in a half-cell configuration versus Li / Li+, than the integrated area of the electrochemical reduction peak of a comparative anode electrode film containing no fluoroelastomer. For instance, these anode electrode films have an integrated reduction peak area that is at least about 10% of the integrated reduction peak area of a comparative anode electrode film containing no fluoroelastomer, e.g., between 10-50%, between 10-40%, between 10- 30%, or between 10-20% of the integrated reduction peak area of the comparative electrode.

[0064] Moreover, these anode electrode films have a smaller integrated area of the electrochemical reduction peak between 0.2 and 0.9 V, as characterized by cyclic voltammetry in a half-cell configuration versus Li / Li+, than the integrated area of the electrochemical reduction peak of a comparative anode electrode film containing binder material prepared by co-coagulating particles of fluoropolymer with particles of fluoroelastomer having a Dv50 particle size of greater than 300 nm. For instance, these anode electrode films have an integrated reduction peak area that is at least 10% of the integrated reduction peak area of a comparative anode electrode film containing fluoroelastomer particles larger than 300 nm, e.g., between 10-50%, between 10-40%, between 10-30%, or between 10-20% of the integrated reduction peak area of the comparative electrode.

[0065] Co-coagulating only 2-5 wt% of small particle fluoroelastomers in the fibrillatable dry powder binder composition for lithium ion battery anodes can lead to a disproportionately large decrease in integrated reduction peak area, e.g., aAttorney Docket No.: FL0702-W001decrease in area of at least 10%, compared to a comparative anode electrode film containing no fluoroelastomers. Without being bound by theory, it is believed that the microstructure formed in the electrode that is formed from such co-coagulated binder material using small particle fluoroelastomer particles contributes to the smaller integrated reduction area.

[0066] Referring to FIG. 1 , a battery 100 or other electrochemical device or energy storage device includes a cathode 104 on a cathode current collector 102 (e.g., laminated onto the cathode current collector 102), an anode 108 on an anode current collector 106, and an electrolyte 110 (e.g., a lithium-based gel or solvent electrolyte) between the electrodes 104, 108. The anode 108 is formed of the electrode composition described here, e.g., formed of anode active material with a binder that is prepared by co-coagulating particles of a fluoropolymer with small particles of a fluoroelastomer.Materials and Methods

[0067] The following polymers are used in these examples.

[0068] PTFE1: PTFE1 is a modified polytetrafluoroethylene polymer, containing 0.128 wt% of copolymerized perfluoro(propyl vinyl ether) (PPVE) as modifier, having a melt creep viscosity of 1.47 x 1010poise (0.147 x 1010Pa S) manufactured by Chemours FC LLC.

[0069] PTFE2: PTFE2 is a polytetrafluoroethylene homopolymer having a melt creep viscosity of 4.0 x 1011poise (4.0 x 1010Pa S) manufactured by Chemours FC LLC.

[0070] FKM1 is a fluoroelastomer dispersion of VF2 / HFP copolymer in water with the Dv50 particle size of at least 800 nm (Table 1).

[0071] FKM2 is a fluoroelastomer dispersion of VF2 / HFP copolymer in water with the Dv50 particle size of less than 300 nm (Table 1).

[0072] Test anodes were prepared by the following procedures:

[0073] Approximately 10 g of a powder mixed was created using 90 % graphite (Amsted Graphite Materials, Anmoore, VA), % Super P carbon black, and 5 wt % ofAttorney Docket No.: FL0702-W001the polymer binder. The graphite and super P carbon black were combined in a mortar and pestle and mixed for approximately 15 minutes.

[0074] This mixture was combined with the fluoropolymer binder into a 250-mL plastic bottle with approximately ten ZrO2 (10 mm in diameter) milling media and rolled for about 30 minutes. The powder was separated from the milling media.

[0075] A free standing film was created by placing 3 g of the mixture onto a small glass mortar and pestle. This material was manually ground until the powder formed a solid flake. The flakes were placed onto a hot plate with a piece of Kapton® film, heated to 100 °C. Using a manual steel rolled, the flake was rolled at 100 °C until a film was formed which was uniform.

[0076] A TMAX calender was used (Xiamen T max Battery Equipments Limited, Xiamen City, China). The calendering rolls were heated to 50 °C before use for at least 1 hour. The thickness of the free-standing film was measured prior to calendering by using a digital thickness probe. The calendering gap was set at 50- 100 pm below the starting film thickness. For example, if the starting free standing film is 480 pm, the gap distance is initially set to 400 pm. The free standing film was placed on the roller The film was passed through the calendering gap two times. At higher gap distances, the film will fall off the rollers. A piece of paper was held below the rolls to catch the film. The calendering gap was reduced by 50 micron steps. For each step, the film was passed through the calendering rollers two times. Eventually, the film will stick to the rolls, and the film was run through the calendering device in this manner. The calendered gap was continually lowered in 50 micron increments until a final thickness of 70-80 microns was reached.

[0077] Cell configuration: The electrode disks (14 mm in diameter) were punched from the free standing (self-supporting) film and dried at 1200C under vacuum at least for 8 hours. Cell containing a graphite electrode and a lithium metal counterelectrode and a Celgard separator 2325 (Celgard, USA) was assembled a CR2032 coin cell (MSE Supplies LLC, Tucson, AZ). The electrolyte of 1.2M LiPFein ethylene carbonate / diethyl carbonate (EC / DEC) (3:7 by volume) +5% FEC (fluoroethylene carbonate) (Gotion, Fremont, CA) was used.Attorney Docket No.: FL0702-W001

[0078] Cell testing: The coin cells were cycled using a Neware battery tester (Neware Battery USA, Belleville, IL) from 0.01 V- 1.25 V vs. Li / Li+with C / 25 formation for 2 cycles and C / 10 for cycling.1C = 1 hour charge / discharge. All the cells were cycled at room temperature (~ 22 °C).EXAMPLESExamples 1 through 4

[0079] Cyclic voltammetry measurements for electrodes with different binder compositions listed in Table 1 were measured in a Bio-Logic potentiostat (BioLogic, Seyssinet-Pariset, France) using lithium metal half cells. The cyclic voltammetry testing involved scanning from 0 to 1.5 V potential vs Li / Li+at 0.05 mV / sec scan rate. The current is normalized with the mass of active Graphite anode material in the electrode. The graphite anode is composed of 90:5:5 composition of Active Graphite, SP conductive carbon and the fluoropolymer or fluoropolymer-fluoroelastomer binder. 2032 type lithium-ion coin cells were made with the anode in half cell format with lithium metal counter / reference electrode.Table 1 : Composition of binder examplesAttorney Docket No.: FL0702-W001

[0081] In order to quantify the fluoropolymer reduction (or degradation), the integrated area under the X-axis is calculated by multiplying voltage and normalized current and adding them in the voltage range of 0.9 and 0.2V vs. Li / Li+during the first reductive sweep in the cyclic voltammetry measurement. The percentage improvement or diminution in the degradation of the fluoropolymer in the anode composition is calculated using the integrated area in the cyclic voltammetry curves. More explicitly, the % improvement or % decrease in integrated area is 100 * (1- (integrated current of example) / integrated current of comparative example)).

[0082] The numerically integrated area of the reduction peak in the 0.9 to 0.2 V region is shown in Table 2 for examples corresponding to the scans of FIG. 2.Table 2: Integration data of reduction peaks of examples

[0083] As shown in FIG. 2, Comparative Example 1 shows a reduction peak at 0.2 - 0.9 V, which corresponds to the reduction of PTFE. The presence of fluoroelastomer in the binder composition causes the reduction peak to decrease relative to the integrated area of the reduction peak of PTFE alone (Table 2).However, further decrease is achieved by using small particle size fluoroelastomer in the binder. Specifically, reduction peaks of co-coagulated binder compositions formed of co-coagulates of PTFE and small-particle FKM decreased in integrated area relative to the reduction peaks of both comparative examples, indicating that the reduction of PTFE was further suppressed by the incorporation of small particle FKM into the binder composition. In addition, the results show that smaller particle sizes of FKM in the co-coagulated binder compositions provide a better reduction resistance.Attorney Docket No.: FL0702-W001Example 5

[0084] Friability of the binder compositions of Examples 1 through 3 were characterized. The results are shown in FIG. 3. As shown, the agglomerates have a Dv50 size of less than 300 pm when measured at 20 PSI (-138 kPa), which is significantly smaller than the Dv50 particle size of the particles of Comparative Examples 1 and 2.

[0085] A Microtrac MRB S3500 Laser Diffraction Particle Size Analyzer (Microtrac Retsch GmbH, Haan, Germany) was used to characterize the particle size and friability (grindability) of present fluoropolymer composition powders under varying levels of dispersion energy from pressurized air jets. This instrument measures particle size distribution by laser diffraction and offers a quantitative assessment of the friability of the present fluoropolymer compositions as compared with the pure tetrafluoroethylene polymers.

[0086] The key instrument operational settings for these experiments included: Dry Feeder TurboTrac; 95 PSI (-655 kPa) dried air; 0 - 60 PSI (0 kPa - -314 kPa) air to eductor 0-75 LPM (0 kPa - -517 kPa); high shear eductor - gap setting 1 ; 4-6 in H2O vacuum (50 LPM) (Nilfisk GM-80); temperature 22 °C; and relative humidity 40-55%. The key calculation parameters for these experiments included: particle refractive index: 1 .35; particle shape: irregular; and particle transparency: transparent.

[0087] The procedure for the experiments using this instrument included: 1) Samples stored under refrigeration (4 °C) until ready for measurement; 2) set desired pressure on instrument; 3) gently scoop 250 mg - 500 mg fluoropolymer composition onto weigh paper using a spatula. Then pour the sample onto sampling tray.; 4) load sampling tray into the "Turbotrac" and perform measurement through device computer software.

[0088] Procedural notes for the experiments using this instrument: 1) 250 mg up to 500 mg of fluoropolymer composition is measured depending on pressure and flow rate used and sample behavior. Too much fluoropolymer composition powder can clog the eductor system or produce erroneous results from high particle concentration effects. Too little powder will not give sufficient detection signal and give poor results.; 2) Powder may buildup in the eductor, especially when measuring powders of small particle size at high airflowrates. The powder buildup will need toAttorney Docket No.: FL0702-W001be cleaned as powder flow will be stopped.; 3) The air pressure supplied to the eductor is varied to adjust the level of dispersive energy / shear to the fluoropolymer composition particles. High pressures result in more particle breakage, producing smaller particle sizes. A volumetric flow meter was added to measure the air flow rate (in liters per minute; LPM) into the eductor. A pressure of 0 psi (0 kPa) means there is no pressured air fed into the eductor, so the powder flows under vacuum flow.; 4) A secondary air regulator was added in line with the eductor air feed for the 2.3 psi (-16 kPa) pressure.Eductor Air Flow Rate (in liters per minute) at given pressure:

Claims

Attorney Docket No.: FL0702-W001CLAIMSWhat is claimed is:

1. A method for making a fibri llatable dry powder binder composition for a lithium ion battery, the method comprising:co-coagulating particles of a fibrillatable fluoropolymer with particles of a fluoroelastomer, wherein the particles of the fluoroelastomer have a Dv50 particle size (median particle diameter) of less than about 300 nm, wherein the fibrillatable fluoropolymer comprises a tetrafluoroethylene (TFE)-based polymer, andwherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of greater than zero and 10 wt.% or less.

2. The method of claim 1 , wherein the fluoroelastomer has a higher reduction stability than the fibrillatable fluoropolymer.

3. The method of any one of the preceding claims, wherein the co-coagulating produces agglomerates of the fibrillatable fluoropolymer and the fluoroelastomer, the agglomerates having a Dv50 particle size of less than 300 pm when measured by particle size distribution at 20 PSI (138 kPa).

4. The method of any one of the preceding claims, wherein co-coagulating particles of the fibrillatable fluoropolymer with particles of the fluoroelastomer comprises mixing an aqueous dispersion of the particles of the fibrillatable fluoropolymer with an aqueous dispersion of the particles of the fluoroelastomer.

5. The method of claim 4, wherein co-coagulating the particles of the fibrillatable fluoropolymer with particles of the fluoroelastomer comprises producing agglomerates of the fibrillatable fluoropolymer and the fluoroelastomer.

6. The method of claim 5, wherein the agglomerates of the fibrillatable fluoropolymer and the fluoroelastomer are friable.

7. The method of claim 5 or claim 6, wherein the agglomerates have a Dv50 particle size of between about 200 pm and about 1000 pm.Attorney Docket No.: FL0702-W0018. The method of claim 7, wherein the agglomerates have a Dv50 particle size of between about 200 pm and about 500 pm.

9. The method of any one of claims 5 to 8, comprising:separating the agglomerates; anddrying the separated agglomerates to form the fibrillatable dry powder binder composition.

10. The method of any one of the preceding claims, wherein the particles of the fluoroelastomer have a Dv50 particle size of between about 50 nm and about 250 nm.

11. The method of any one of the preceding claims, wherein the particles of the fluoroelastomer have a Dv50 particle size of between about 200 nm and about 300 nm.

12. The method of any one of the preceding claims, wherein the particles of the fluoropolymer have a Dv50 particle size of between about 100 nm and about 300 nm.

13. The method of any one of the preceding claims, wherein in the dry powder binder composition, the fibrillatable fluoropolymer is substantially unfibrillated.

14. The method of any one of the preceding claims, wherein the fibrillatable fluoropolymer comprises polytetrafluoroethylene (PTFE).

15. The method of any one of the preceding claims, wherein the fibrillatable fluoropolymer comprises a modified PTFE.

16. The method of any one of the preceding claims, wherein the fibrillatable fluoropolymer has a melt creep viscosity of at least about 0.1 x 1011poise (0.1 x 101oPa S).

17. The method of any one of the preceding claims, wherein the fluoroelastomer comprises a copolymer comprising vinylidene fluoride.

18. The method of claim 17, wherein the fluoroelastomer comprises a copolymer of vinylidene fluoride and hexafluoropropylene (HFP).Attorney Docket No.: FL0702-W00119. The method of any one of the preceding claims, wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of greater than zero and less than about 5 wt.%.

20. The method of claim 19, wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of between about 1 wt.% and about 5 wt.%.

21. The method of claim 20, wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of between about 1 wt.% and about 4 wt.%.

22. The method of claim 21 , wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of between about 1 wt.% and about 3 wt.%.

23. The method of any one of the preceding claims, wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of greater than zero and less than about 4 wt.%.

24. The method of claim 23, wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of greater than zero and less than about 3 wt.%.

24. The method of any one of the preceding claims, wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of about 2 wt.%.

26. A fibrillatable dry powder binder composition comprising:a fibrillatable powder comprising agglomerates of a fibrillatable fluoropolymer and a fluoroelastomer, the agglomerates having been produced by cocoagulating particles of the fibrillatable fluoropolymer with particles of the fluoroelastomer having a Dv50 particle size (median particle diameter) of less than about 300 nm, andwherein the fluoroelastomer is present in the powder in a weight percentage of greater than zero and less than about 10 wt.%.Attorney Docket No.: FL0702-W00127. The fibrillatable dry powder binder composition of claim 26, wherein the fluoroelastomer has a higher reduction stability than the fibrillatable fluoropolymer.

28. The fibrillatable dry powder binder composition of claim 26 or 27, wherein the agglomerates have a Dv50 particle size of less than 300 pm when measured by particle size distribution at 20 PSI (138 kPa).

29. The fibrillatable dry powder binder composition of any one of claims 26 to 28, wherein the powder is friable.

30. The fibrillatable dry powder binder composition of any one of claims 26 to 29, wherein in the powder, the fibrillatable fluoropolymer is substantially unfibrillated.

31. The dry powder binder composition of any one of claims 26 to 30, wherein the powder is a free-flowing powder.

32. The dry powder binder composition of any one of claims 26 to 31 , wherein the agglomerates of the fibrillatable fluoropolymer and the fluoroelastomer are friable.

33. The dry powder binder composition of any one of claims 26 to 32, wherein the agglomerates have a Dv50 particle size between about 200 pm and about 1000 pm.

34. The dry powder binder composition of claim 33, wherein the agglomerates have a Dv50 particle size of between about 200 pm and about 500 pm.

35. The dry powder binder composition of any one of claims 26 to 34, wherein the particles of the fluoroelastomer have a Dv50 particle size of between about 50 nm and about 250 nm.

36. The dry powder binder composition of any one of claims 26 to 35, wherein the particles of the fluoroelastomer have a Dv50 particle size of between about 200 nm and about 300 nm.

37. The dry powder binder composition of any one of claims 26 to 36, wherein the particles of the fluoropolymer have a Dv50 particle size of between about 100 nm and about 300 nm.Attorney Docket No.: FL0702-W00138. The dry powder binder composition of any one of claims 26 to 37, wherein in the dry powder binder composition, the fibrillatable fluoropolymer is substantially unfibrillated.

39. The fibrillatable dry powder binder composition of any one of claims 26 to 38, wherein the fibrillatable fluoropolymer comprises polytetrafluoroethylene (PTFE).

40. The dry powder binder composition of any one of claims 26 to 39, wherein the fibrillatable fluoropolymer comprises a modified PTFE.

41. The fibrillatable dry powder binder composition of any one of claims 26 to 40, wherein the fibrillatable fluoropolymer has a melt creep viscosity of at least about 0.1 x 1011poise (0.1 x 1010Pa-S).

42. The fibrillatable dry powder binder composition of any one of claims 26 to 41 , wherein the fluoroelastomer comprises a copolymer comprising vinylidene fluoride.

43. The fibrillatable dry powder binder composition of claim 42, wherein the fluoroelastomer comprises a copolymer of vinylidene fluoride and hexafluoropropylene (HFP).

44. The dry powder binder composition of any one of claims 26 to 43, wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of greater than zero and less than about 5 wt.%.

45. The dry powder binder composition of claim 44, wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of between about 1 wt.% and about 5 wt.%.

46. The dry powder binder composition of claim 45, wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of between about 1 wt.% and about 4 wt.%.

47. The dry powder binder composition of claim 46, wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of between about 1 wt.% and about 3 wt.%.Attorney Docket No.: FL0702-W00148. The dry powder binder composition of any one of claims 26 to 47, wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of greater than zero and less than about 4 wt.%.

49. The dry powder binder composition of claim 48, wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of greater than zero and less than about 3 wt.%.

50. The dry powder binder composition of any one of claims 26 to 49, wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of about 2 wt.%.

51. A method of making an electrode composition for a lithium ion battery, the method comprising:co-coagulating particles of a fibrillatable fluoropolymer, wherein said fibrillatable fluoropolymer comprises a tetrafluoroethylene (TFE)-based polymer with particles of a fluoroelastomer to form a fibrillatable dry powder binder composition, wherein the particles of the fluoroelastomer have a Dv50 particle size (median particle diameter) of less than about 300 nm; and mixing the fibrillatable dry powder binder composition with an electrode active material to form an electrode composition,wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of greater than zero and less than about 10 wt.%.

52. The method of claim 51 , wherein the fluoroelastomer has a higher reduction stability than the fibrillatable fluoropolymer.

53. The method of claim 51 or claim 52, wherein the co-coagulating produces agglomerates of the fibrillatable fluoropolymer and the fluoroelastomer, the agglomerates having a Dv50 particle size of less than 300 pm when measured by particle size distribution at 20 PSI (138 kPa).

54. The method of any one of claims 51 to 53, wherein mixing the dry powder binder composition with the electrode active material comprises milling particles of the electrode active material with the dry powder binder composition.Attorney Docket No.: FL0702-W00155. The method of claim 54, comprising milling the particles of the electrode active material with the dry powder binder composition at a temperature of between about 20 °C and about 200 °C.

56. The method of claim 55, comprising milling the particles of the electrode active material with the dry powder binder composition at a temperature of between about 80 °C and about 150 °C.

57. The method of any one of claims 51 to 56, comprising mixing the particles of the electrode active material with the dry powder binder composition in an environment free of solvent.

58. The method of any one of claims 51 to 57, wherein mixing the dry powder binder composition with the electrode active material comprises fibrillating the fibrillatable fluoropolymer.

59. The method of any one of claims 51 to 58, wherein in the dry powder binder composition, the fibrillatable fluoropolymer is substantially unfibril lated.

60. The method of any one of claims 51 to 59, wherein the electrode active material comprises a negative electrode active material.

61. The method of any one of claims 51 to 60, comprising forming an electrode film using the electrode composition.

62. A method of making an electrode composition for a lithium ion battery, the method comprising:mixing a fibrillatable dry powder binder composition with particles of an electrode active material to form an electrode composition, the fibrillatable dry powder binder composition having been formed by co-coagulating particles of a fibrillatable fluoropolymer with particles of a fluoroelastomer having a Dv50 particle size (median particle diameter) of less than about 300 nm, wherein the fibrillatable fluoropolymer comprises a tetrafluoroethylene (TFE)-based polymer,wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of greater than zero and less than about 10 wt.%.Attorney Docket No.: FL0702-W00163. The method of claim 62, wherein the fluoroelastomer has a higher reduction stability than the fluoropolymer.

64. The method of claim 62 or claim 63, wherein the dry binder composition comprises co-coagulated agglomerates of the fibrillatable fluoropolymer and the fluoroelastomer, the agglomerates having a Dv50 particle size of less than 300 pm when measured by particle size distribution at 20 PSI (138 kPa).

65. An electrode composition for an electrode of a lithium ion battery, the electrode composition comprising:particles of an electrode active material; anda binder composition, the binder composition having been formed by cocoagulating particles of a fibrillatable fluoropolymer with particles of a fluoroelastomer having a Dv50 particle size (median particle diameter) of less than about 300 nm,wherein the fibrillatable fluoropolymer comprises a tetrafluoroethylene (TFE)-based polymer,wherein the fluoroelastomer is present in the dry powder binder composition in a weight percentage of greater than zero and less than about 10 wt.%.

66. The electrode composition of claim 65, wherein the fluoroelastomer has a higher reduction stability than the fibrillatable fluoropolymer.

67. The electrode composition of claim 65 or claim 66, wherein the binder composition comprises co-coagulated agglomerates of the fibrillatable fluoropolymer and the fluoroelastomer, the agglomerates having a Dv50 particle size of less than 300 pm when measured by particle size distribution at 20 psig (138 kPa).

68. The electrode composition of any one of claims 65 to 67, wherein the fibrillatable fluoropolymer is at least partially fibrillated.

69. The electrode composition of any one of claims 65 to 67, wherein an integrated area of the reduction peak of the electrode composition between 0.2 V and 0.9 V, as characterized by cyclic voltammetry in a half-cell configuration vs. Li / Li+, isAttorney Docket No.: FL0702-W001less than an integrated area of a comparative electrode composition having a binder composition without fluoroelastomer.

70. The electrode composition of claim 69, wherein the integrated area of the reduction peak of the electrode composition is at least 10% less than the integrated area of the reduction peak of the comparative electrode composition.

71. The electrode composition of any one of claims 65 to 70, wherein an integrated area of the reduction peak of the electrode composition between 0.2 V and 0.9 V, as characterized by cyclic voltammetry in a half-cell configuration vs. Li / Li+, is less than an integrated area of a comparative electrode composition having a binder composition formed by co-coagulating particles of the fibrillatable fluoropolymer with particles of the fluoroelastomer having a Dv50 particle size of greater than about 300 nm.

72. The electrode composition of claim 71 , wherein the integrated area of the reduction peak of the electrode composition is at least 10% less than the integrated area of the reduction peak of the comparative electrode composition.

73. The electrode composition of any one of claims 65 to 72, comprising a conductive additive.

74. An electrode film comprising the electrode composition of any one of claims 65 to 73.

75. The electrode film of claim 74, wherein the electrode film is self-supporting.

76. A negative electrode for a lithium ion battery, the negative electrode comprising a film comprising the electrode composition of any one of claims 65 to 73.

77. A lithium ion battery comprising:the negative electrode of claim 76;a positive electrode; andan electrolyte in contact with the negative electrode and the positive electrode.

78. A fibrillatable dry powder composition for use as a binder in an electrode comprising agglomerates of fibrillatable fluoropolymer particles andAttorney Docket No.: FL0702-W001fluoroelastomer particles, said fluoroelastomer particles having a Dv50 particle size (median particle diameter) of 300 nm or less; wherein said agglomerates have a Dv50 particle size (median particle diameter) of 300 pm or less; wherein the weight percent (wt%) of the fluoroelastomer within fibrillatable dry powder composition is more than 0 wt% and no more than 10 wt%.

79. The fibrillatable dry powder composition of claim 78 wherein the fibrillatable fluoropolymer comprises fibrillatable polytetrafluoroethylene (PTFE) homopolymer, fibrillatable modified PTFE ora combination thereof.

80. An electrode composition comprising: particles of an electrode active material;preferably particles of an anode active material, and the fibrillatable dry powder binder composition of claim 78 or claim 79.

81. The electrode composition of claim 80 wherein the fibrillatable fluoropolymer is partially or fully fibril lated .

82. The electrode composition of claim 80 or claim 81 further comprising particles of at least one conductive additive.

83. An electrode film comprising the electrode composition of claim 80, claim 81 or claim 82.

84. The electrode film of clam 83 wherein the electrode film is self-supporting.

85. The electrode film of claim 83 or claim 84 further comprising at least one current collector.

86. An electrode comprising the electrode film of any one of claim 83 to 85.

87. The electrode of claim 86 wherein the electrode is a negative electrode.

88. The electrode of claim 86 or claim 87, wherein an integrated area of the reduction peak of the electrode composition between 0.2 V and 0.9 V, as characterized by cyclic voltammetry in a half-cell configuration vs. Li / Li+, is less than an integrated area of a comparative electrode composition having a binder composition without fluoroelastomer.

89. The electrode of any one of claim 86 to 87 wherein an integrated area of the reduction peak of the electrode composition between 0.2 V and 0.9 V, asAttorney Docket No.: FL0702-W001characterized by cyclic voltammetry in a half-cell configuration vs. Li / Li+, is less than an integrated area of a comparative electrode composition having a binder composition comprising a fluoroelastomer having a particle size greater than 300 nm, preferably greater than 800 nm, most preferably greater than 2 pm.

90. The electrode of claim 88 or claim 89, wherein the integrated area of the reduction peak of the electrode composition is at least 10% less than the integrated area of the reduction peak of the comparative electrode composition.

91. The electrode of claim 86 or claim 87, wherein an integrated area of the reduction peak of the electrode composition between 0.2 V and 0.9 V, as characterized by cyclic voltammetry in a half-cell configuration vs. Li / Li+, is less than an integrated area of a comparative electrode composition having a binder composition formed by co-coagulating particles of the fibrillatable fluoropolymer with particles of the fluoroelastomer having a Dv50 particle size of greater than about 300 nm.

92. The electrode of claim 91 , wherein the integrated area of the reduction peak of the electrode composition is at least 10% less than the integrated area of the reduction peak of the comparative electrode composition.

93. A lithium ion battery comprising:the negative electrode of any one of claims 87 to 92;a positive electrode; andan electrolyte in contact with the negative electrode and the positive electrode.

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