Functionalized binders and electrode made thereafter

Abstract

Disclosed is a fluoropolymer composition comprising an alloy of PTFE and functionalized PVDF. The alloy can be in the form of a scaffold. Further disclosed is an anode film comprising PTFE and functionalized PVDF which is free of solvent residue.

Description

FUNCTIONALIZED BINDERS AND ELECTRODE MADE THEREAFTER

[0001] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This application was made with United States Government support under DE-EE0009109 awarded by the Department of Energy of the United States. The United States Government has certain rights in the invention.

[0003] FIELD OF THE INVENTION

[0004] The present invention relates generally to the field of energy storage devices. More particularly, the present invention relates to structures and methods for making dry fluoropolymer based binders and films for energy storage devices.

[0005] BACKGROUND OF THE INVENTION

[0006] PVDF-based polymers are semi-crystalline polymers used for many different applications such as extrusion, injection molding, fiber spinning, extrusion blow molding, blown film, and scaffolds to form articles. Scaffolds are generally made via electrospinning of polymer solutions which often requires using toxic and flammable solvents. Fabricating scaffolds without using any solvent / liquid is advantageous especially when they are free of any residual solvent. The ultimate tensile strength property of articles made from scaffolds is an important parameter for the purpose of handling, processing, and durability of the film. The ultimate tensile strength of the articles made from scaffolds depends on the strength and quality of the scaffold, for example, electrode ultimate tensile strength and mechanical properties are important to ensure that the roll-to-roll process is feasible.

[0007] The first cycle efficiency (FCE) in lithium-ion batteries (LIBs) and in Sodium-ion batteries (NIBs) refers to the percentage of charge that can be stored and then retrieved during the initial charging and discharging cycle. It’s an important metric because it impacts the overall performance and longevity of the battery. Therefore, having a high FCE is very desirable.

[0008] DOI: 10.1002 / ente.202200732 (Energy Technol. 2022, 10, 2200732) describes a solvent-free graphite anode using a PTFE and PVDF binder. The synergistic effect of PVDF and PTFE binder increased the first cycle efficiency and kept the integrity of electrode even after PTFE is reduced in the first lithiation process. This article demonstrate that the free-standing electrode film was formed when the dry mixture was hot rolled at 160 °C using a calendar machine. The hot roll is needed because it failed to produce PVDF-PTFE scaffolds and consequently needed high temperature to melt / soften PVDF.

[0009] U.S. Pat. No.11876230B2 describes a method of fabricating anodes for an energy storage device combining an active material and at least one composite binder material. The composite binder material comprises polytetrafluoroethylene (PTFE) material and at least one of polyvinylidene fluoride (PVDF), a PVDF co-polymer, or polyethylene oxide (PEO).

[0010] U.S. Pat. No. US20190237748A1 describes a dry electrode film comprising active material, and dry binder, wherein the dry binder comprises at least one of polytetrafluoroethylene (PTFE), carboxymethylcellulose (CMC), and polyvinylidene fluoride (PVDF).

[0011] WO2024072861A2 describes a binder for lithium-ion secondary battery electrode, comprising dry friable agglomerates comprising i) a first polymer comprising a tetrafluoroethylene polymer having a melt creep viscosity of at least about 0.5 x 1011 poise, and ii) a second polymer different from said first polymer.

[0012] The PVDF-PTFE scaffold, a 3-dimensional porous structure, of this invention exist a single phase of material which has not been previously described or suggested. The PVDF-PTFE scaffolds of this invention is a single-phase material meaning the PVDF and PTFE is not distinguishable from one another based on their morphology according to high-resolution SEM images. The PVDF-PTFE scaffolds of this invention do not exhibit microscopic phase separation, and PVDF is blended into the PTFE during shearing. By “do not exhibit microscopic phase separation” we mean that under SEM (2000X magnification) in a 25X25 micron view there are less than 5 particle agglomerates of greater than 5 microns visible (number average particle size). Figure 5 shows particle agglomerates. These unique scaffolds were made by using functionalized PVDF in combination with expandable PTFE.

[0013] This invention further relates to a scaffold structure comprising functionalized PVDF and PTFE that can be used in battery anode manufacturing. The use of the scaffold structure comprising a functionalized PVDF and PTFE, increases the ultimate tensile strength of the film and allows for a wider processing window as compared to the PVDF homopolymer / PTFE mixture.

[0014] This invention further relates to an anode film comprising functionalized PVDF and PTFE and a method of making the anode film. The anode film can be free standing or supported by a current collector or substrate.

[0015] Using functionalized PVDF-PTFE has not been previously described or suggested.

[0016] BRIEF DESCRIPTION OF FIGURES

[0017] Figure 1 is a picture of the functionalized PVDF (of example1) and PTFE alloy.

[0018] Figure 2 is a SEM picture of the PVDF-PTFE scaffold material of Example 5

[0019] Figure 3 is a picture of a porous mat made with the functionalized PVDF of example 1 and PTFE

[0020] Figure 4 illustrates the first discharge voltage profile of anode half cells with and without the PVDF of example 1.

[0021] Figure 5 is a picture of Kynar 741-PTFE blend (counter example 1).

[0022] Figure 6 is a SEM picture of Kynar 741-PTFE blend (counter example 1).

[0023] Figure 7 is a picture of porous mats made with Kynar741-PTFE shows the porous mat of counter example 2.

[0024] SUMMARY OF THE INVENTION

[0025] This invention discloses a process for transforming functionalized PVDF-based powder and expandable PTFE powder into PVDF-PTFE scaffolds at room temperature, the temperature of the processing is not critical as long as it is done 20°C or more below the melting point of the functionalized PVDF. Generally, the temperature range can be from 20°C and up to about 130°C, as long as the polymers do not melt, without the use of any solvent. The PVDF-PTFE scaffold of this invention is comprised of a functionalized polyvinylidene fluoride (PVDF) where the functionalized PVDF powders having primary particle size between 50 to 300 nm for emulsion grade, and 2 µm to 200 µm for suspension grade PVDF. The scaffold made according to this invention, exhibits higher ultimate tensile strength and lower extractable as compared to a PVDF and PTFE mixture using commercial homopolymer PVDF such as Kynar 761 or Kynar HSV900. The functionalized PVDF-PTFE scaffold of this invention can be transformed into a plaque or unwoven mat at a temperatures as low 15°C and greater, preferably between 15°C to 120°C. The scaffold can be used either alone to form articles or with the particulate matters to form composites.

[0026] This invention also discloses electrode compositions for energy storage devices using PVDF-PTFE scaffolds which are made using PTFE and functionalized PVDF. These anodes are processed without any solvent / liquid and are free of any residual solvent. The anode of this invention is comprised of scaffolds containing functionalized PVDF, at least 0.1 wt% PTFE, and anode forming materials. The functionalized PVDF powder used in the invention contains at least 0.1 wt % functional groups. Preferably the functionalized PVDF has a number average primary particle size diameter (by SEM) of between 50 to 500 nm for emulsion grade PVDF, and 2 to 200 µm for suspension grade PVDF. Emulsion grade is preferred for the invention. The anodes made using functionalized polyvinylidene fluoride / PTFE scaffolds of this invention exhibit much higher ultimate tensile strength compared to those made with non-functionalized- PVDF. In addition, the functionalized PVDF allows ease of processing as compared to those having no functionality. Ease of process mean there is high flowability and low cohesion between particles (asmeasure by ASTM D7891). The anodes made using the functionalized PVDF / PTFE binder have higher first cycle efficiency as compared to the electrodes made using only expandable PTFE as a binder.

[0027] The anode film of this invention can be free standing or supported by a substrate such as an current collector and is made by a dry fabrication process

[0028] This invention describes a process for fabricating articles at temperatures at about or below the melting point of functionalized PVDF, preferably below 120 ˚C, preferably less than 80C, using functionalized PVDF / PTFE scaffolds. i.e., non-woven mat or solid plaques. The mat / plaque has improved properties such as higher ultimate tensile strength, compared to the those made with the corresponding non-functionalized PVDF / PTFE mixture under identical conditions. The scaffolds of this invention and objects made thereafter are free of any trace solvent.

[0029] Some Embodiments of the Invention:

[0030] Embodiment 1: A fluoropolymer composition comprising an alloy of functionalized PVDF and PTFE wherein the weight ratio of functionalized PVDF to PTFE is 10:90 to 95:5, wherein the functionalized PVDF comprises a functional group, and wherein the fluoropolymer composition is absent of solvent residue.

[0031] Embodiment 2: The fluoropolymer composition of embodiment 1, wherein the weight ratio is from 25:75 to 90:10.

[0032] Embodiment 3: The fluoropolymer composition of embodiment 1 or 2, wherein the functionalized PVDF comprises HFP monomer units.

[0033] Embodiment 4: The fluoropolymer composition of any one or more of embodiments 1-4, wherein the functional group comprises a carboxylic group or salt or ester thereof.

[0034] Embodiment 5: The fluoropolymer composition of any one or more of embodiments 1-4, wherein the functional group comprises a phosphate or sulfonate.

[0035] Embodiment 6: The fluoropolymer composition of any one or more of embodiments 1-4, wherein the functional group comprises a hydroxyl group or ether group

[0036] Embodiment 7: The fluoropolymer composition of any one or more of embodiments 1-6, wherein the amount of functional groups is at least 0.1 mole percent to 10 mole percent, preferably 0.2 to 5 mole percent based on VDF monomer units.

[0037] Embodiment 8: The fluoropolymer composition of any one or more of embodiments 1-7, wherein fluoropolymer binder comprising the PTFE and the functionalized PVDF is in the form of a scaffold.

[0038] Embodiment 9: An anode film comprising an anode composition comprising an anode active material and a fluoropolymer binder comprising PTFE and functionalized PVDF , wherein the weight ratio of functionalized PVDF to PTFE in the anode is 10:90 to 95:5, wherein the functionalized PVDF comprisesa functional group; , and wherein the film is free of solvent residue, and wherein the total fluoropolymer binder amount is from 1 wt% to 10 wt% of the anode composition.

[0039] Embodiment 10: The anode film of embodiment 9, wherein the weight ratio of functionalized PVDF to PTFE is from 25:75 to 90:10.

[0040] Embodiment 11: The anode film of embodiment 9 or 10, wherein the functionalized PVDF comprises HFP monomer units.

[0041] Embodiment 12: The anode film of any one or more of embodiments 9-11, wherein the functional group comprises a carboxylic group or salt or ester thereof.

[0042] Embodiment 13: The anode film of any one or more of embodiments 9-11, wherein the functional group comprises an ether group or hydroxyl group.

[0043] Embodiment 14 The anode film of any one or more of embodiments 9-11, wherein the functional group comprises a phosphate or sulfonate.

[0044] Embodiment 15: The anode film of any one or more of embodiments 9-14, wherein the anode film comprises from 1 weight % to 6 weight % of the fluoropolymer binder based on the weight of the anode film.

[0045] Embodiment 16: The anode film of any one or more of embodiments 9-15, wherein the amount of functional groups is equal to or greater than 0.1 mole percent in the fluoropolymer binder.

[0046] Embodiment 17: The anode film of any one or more of embodiments 9-16, wherein fluoropolymer binder comprising the PTFE and the functionalized PVDF is in the form of a scaffold.

[0047] Embodiment 18: The anode film of any one or more of embodiments 9-17, wherein the anode active material is selected from the group consisting of synthetic graphite, natural graphite, hard carbon, graphene, graphene oxide, amorphous silicon, semi crystalline silicon, silicon oxides, silicon nanowires, silicon-carbon composite, tin, tin oxides, germanium, lithium titanate, or mixtures thereof.

[0048] Embodiment 19: The anode film of any one or more of embodiments 9-18, wherein the anode film comprises a conductive carbon.

[0049] Embodiment 20: An energy storage device comprising the anode film of any one or more of embodiments 9-19, wherein the energy storage device comprises a lithium-ion battery or a sodium ion battery or a lithium containing-sulfur battery.

[0050] Embodiment 21: A method of fabricating an anode film for an energy storage device, comprising: a) combining an anode active material and functionalized PVDF to form a first mixture, b) adding PTFE to the first mixture to form a second mixture; andc) subjecting the second mixture to a shearing to form a dry anode film forming mixture comprising PTFE and functionalized PVDF, and wherein no liquid is used in the process.

[0051] Embodiment 22: The method of embodiment 21 or 22, wherein the shearing comprises jet- milling.

[0052] Embodiment 23: The method of embodiment 21 or 22, wherein the shearing comprises ball- milling and uses milling media.

[0053] Embodiment 24: The method of embodiment 21, wherein each of the combining and the adding steps comprises blending at a temperature of between 10° C to 120° C.

[0054] Embodiment 25: The method of any one or more of embodiments 21-24, wherein combining further comprises combining a conductive carbon additive with the active material and the functionalized PVDF to form the first mixture.

[0055] Embodiment 26: The method of any one or more of embodiments 21-25, further comprising calendaring the dry anode film forming mixture to form an anode film.

[0056] Embodiment 27: The method of embodiment 26, further comprising the step of disposing the anode film over a current collector to form the anode.

[0057] Embodiment 28: The method of embodiment 27, wherein the disposing comprises laminating the anode film to the current collector.

[0058] Embodiment 29: The method of any one or more of embodiments 21-28, wherein the weight ratio of functionalized PVDF to PTFE is 10:90 to 95:5.

[0059] Embodiment 30: The method of any one or more of embodiments 21-29, wherein the anode active material comprises at least one of synthetic graphite, natural graphite, hard carbon, soft carbon, graphene, graphene oxide, silicon, silicon oxides, tin, tin oxides, germanium, lithium titanate, or mixtures thereof.

[0060] Embodiment 31: The method of any one or more of embodiments 21-29, wherein the anode active material comprises at least one of synthetic graphite, natural graphite, or combinations thereof.

[0061] Embodiment 32: A method of fabricating an energy storage device comprising affixing the anode film of any one or more of embodiments 9 to 19, to a current collector to form an anode, inserting the anode, a cathode and a separator within a housing, wherein the separator is positioned between the anode and the cathode.

[0062] Embodiment 33: An energy storage device, comprising the anode film of any one or more of embodiments 9 to 19, a cathode and a separator within a housing, wherein the separator is positioned between the anode film and the cathode.

[0063] Embodiment 34: The energy storage device of embodiment 33, wherein the energy storage device is selected from the group consisting of a lithium-ion battery, a lithium-ion capacitor, a sodium- ion battery, or a lithium containing-sulfur battery.

[0064] Embodiment 35: An article comprising: the fluoropolymer composition of any one or more of embodiments 1 to 8.

[0065] DETAILED DESCRIPTION OF THE INVENTION

[0066] The references cited in this application are incorporated herein by reference.

[0067] Percentages, as used herein are weight percentages (wt%), unless noted otherwise, Amounts expressed in “ppm” are weight by weight based.

[0068] The term “fluoropolymer” refers to polymers and copolymers (including polymers having two or more different monomers, including for example terpolymers) containing at least 50 mole percent of fluoromonomer units. The copolymers may be homogeneous, heterogeneous, or random, and may have a gradient distribution of co-monomer units.

[0069] “Copolymer” is used to mean a polymer having two or more different monomer units, including terpolymers and higher degree polymers. “Polymer” is used to mean both homopolymer and copolymers.

[0070] “PVDF” means polyvinylidene fluoride, this includes both homopolymer and copolymers unless otherwise noted. “VDF” means vinylidene fluoride.

[0071] Dispersion means a dispersion or suspension of polymer particles in water. No oil phase or other organic phase is present.

[0072] “Solids content” means the matter that remains after drying of the dispersion. The solids content of the aqueous dispersion was measured by means of gravimetry method. A HG63 moisture analyzer from Mettler Toledo can be used to measure solids content. A known quantity of the latex is dried and the change in weight is measured.

[0073] Melt viscosity are measured according to ASTM D3835 by a capillary rheometry at 230°C, and at shear rate of 100 sec-1.

[0074] Thermogravimetric Analysis (TGA) is used to measure the 5% weight decomposition temperature. TGA was carried out from room temperature to 800 ˚C at a heating rate of 20 ˚C / min under steady state flow of nitrogen.

[0075] Lower extractable means the portion of polymer dissolved in a good solvent. For example, in a mixture of PVDF / PTFE alloy, the amount of PVDF that dissolved in NMP

[0076] Number average particle size can be determined using scanning electron microscope (“SEM”). The PVDF particles are symmetrical under SEM. The diameter is measured.

[0077] The infrared spectra to determine the crystalline phase and phase ratios, were obtained using a Fourier transform infrared (FTIR) spectrometer (Nicolet iS50, Thermo-Fisher Scientific), equipped with a Thunderdome Diamond ATR accessory. The spectra were collected with a resolution of 4 cm-1with 32 scans per spectrum. For the analysis, the regions 837-840 cm-1(CH2and CF2vibrations) as containing high contribution from non-α and 763-765 cm-1(CF2and CCC vibrations) as containing mainly α contributions are selected. For each spectrum, the maximum peak height (the highest peak within the respective range) are determined (the two selected regions) and a ratio is calculated.

[0078] The ultimate tensile strength (tensile at break, psi) and through plane resistivity of the films were measured using Instron 3343 series instrument. The tensile bar was a dog bone, as described in ASTM D1708. The speed used for this experiment was 12.7 mm / min. The samples were processed at room temperature and the ultimate tensile strength was measured in a controlled environment, where the dew point was kept at -5 ˚C. The samples were not conditioned before the ultimate tensile test.

[0079] PVDF exhibits three main crystalline phases (α, β, and γ). As a result, PVDF can have various characteristics (solution viscosity, Tm, Tc and etc.) depending on the crystalline structure and ratio of crystalline phases. Changing the PVDF crystalline phase induces unique properties. For example, β phase induces piezoelectric, and pyroelectric properties. Also changing the PVDF crystalline phase from α to non-α, could improve adhesion properties of this semicrystalline polymer when used as a binder for battery electrodes. In some embodiments of the invention, the percentage of non-α phase of functionalized PVDF is higher than 70% after shearing with PTFE. The percentage of non-α phase increases by shearing PVDF with PTFE. Even after shearing with PTFE, the non-α phase is preferably higher than 70% for the functionalized PVDF. In contrast for non-functionalized PVDF we find non-α phase to be lower than 70% even after being blended with PTFE. Percent of crystalline phases are determined using FTIR spectra.

[0080] Scaffold means a 3-dimensional porous fibrous web structure or matrix formed by the polymer alloy when they are fibrillized by shearing. The scaffold appears as a fibrous web under SEM.

[0081] Polymers and polymer alloys capable of fibrillization are commonly referred to as “fibrillizable binders' or “fibril-forming binders.” Fibril-forming binders find use with other powder like materials. Fibrillization of the binder particles produces fibrils that eventually allow formation of a matrix or lattice for supporting a resulting composition of matter. In the prior art, solvents, and / or other liquids, are added so that subsequent shear forces applied to a resulting mixture are sufficient to fibrillize theparticles which are not desirable due to the use of toxic solvent. In the present invention, no solvents or liquids are used to create the alloy in the form of a scaffold.

[0082] By alloy we mean is a single-phase homogeneous physical blend of materials that exhibits a single phase composition of PVDF-PTFE scaffolds according to SEM imaging.

[0083] The PTFE used in the present invention is expandable PTFE also called fibrillizable PTFE, meaning it can be expanded or fibrillized by stretching it in one or more direction, usually through shearing without melting. See for example US11527747 or US3962153.

[0084] The invention provides a composition comprising an alloy of a functionalized PVDF and PTFE. Preferably the alloy is in the form of a scaffold.

[0085] The invention provides an article comprising the inventive composition.

[0086] This composition can be used in forming an anode for a lithium ion or sodium ion battery.

[0087] The invention provides an anode film comprising the alloy of PTFE with a functionalized PVDF. Preferably the alloy is in the form of a scaffold.

[0088] The invention provides a method of making an anode film comprising the alloy of a functionalized PVDF and PTFE, preferably the alloy is in the form of a scaffold. The method is a dry method where all the component materials used are dry powder materials. No solvents are used in the method.

[0089] The anode film of this invention is free of solvent residuals.

[0090] PVDF-based material

[0091] The term “vinylidene fluoride polymer” or “polyvinylidene fluoride” used herein includes homopolymers, copolymers, and functionalized polymers within its meaning. Such copolymers include those containing at least 50 mole percent of vinylidene fluoride , preferably greater than 65 mole percent or 90 mole percent or greater, copolymerized with at least one comonomer selected from the group consisting of tetrafluoroethylene (TFE), trifluoroethylene (TrFE), chlorotrifluoroethylene (CTFE), perfluorobutylethylene (PFBE), hexafluoropropene (HFP), vinyl fluoride (VF), pentafluoropropene, 2,3,3,3-tetrafluoropropene, trifluoropropene, fluorinated (alkyl) vinyl ethers, such as, perfluoroethyl vinyl ether (PEVE), and perfluoro-2-propoxypropyl vinyl ether, perfluoromethyl vinyl ether (PMVE), perfluoropropyl vinyl ether (PPVE), perfluorobutylvinyl ether (PBVE), longer chain perfluorinated vinyl ethers, one or more of partly or fully fluorinated alpha-olefins such as 3,3,3-trifluoro-1-propene, 2- trifluoromethyl-3,3,3-trifluoropropene, 1,2,3,3,3-pentafluoropropene, 3,3,3,4,4-pentafluoro-1-butene, hexafluoroisobutylene (HFIB), fluorinated dioxoles, such as perfluoro(1,3-dioxole) and perfluoro(2,2- dimethyl-1,3-dioxole) (PDD), partially- or per-fluorinated alpha olefins of C4 and higher, partially- or per-fluorinated cyclic alkenes of C3 and higher, partly fluorinated allylic, or fluorinated allylic monomers, and combinations thereof.

[0092] Functionalized PVDF

[0093] The present invention uses functionalized PVDF as a component of the invention.

[0094] Fluoropolymers, for example those based on vinylidene fluoride CF2=CH2 (VDF) or tetrafluoroethylene CF2=CF2 (TFE) are known to have excellent mechanical stability properties, very great chemical inertness, low surface energy, electrochemical stability, and good aging resistance. These qualities are exploited in various end-use applications.

[0095] Unfortunately, the excellent properties provided by fluoropolymers can also limit the applications in which they can be used. For example, it is difficult to bond fluoropolymers or combine them with other materials or alloy them with each other.

[0096] Some embodiments of the present invention use functionalized PVDF. By “functionalized” or “functional groups” we mean that groups containing at least one atom other than C, H or F are part of at least one monomeric unit of the fluoropolymer. Atoms, in addition to any one or more of C, H or F, in the functional groups include at least one of O, N, S, or P. Useful functional groups that can be incorporated into a fluoropolymer include, but are not limited to, carboxylic, hydroxyl, siloxane, ether, ester, sulfonic, phosphoric, phosphonic, sulfuric, amide, nitrile, epoxy groups, alkylene oxide (such as ethylene oxide or propylene oxide) or a mixture thereof. The carboxylic group includes the acid form, the salt form, the ester form, and anhydride form. In some embodiments the functional group contains an oxygen.

[0097] Carboxylic group includes the acid form, the salt form, the ester form and anhydride form.

[0098] Functionality (functional groups) may be incorporated into a fluoropolymer by different means, such as by copolymerization, post-polymerization grafting and use of low molecular weight functionalized polymer chain transfer agents.

[0099] Direct copolymerization of a monomer having a functional group (“functional monomer”) with the fluoromonomers can result in a functional fluoropolymer. Post-polymerization grafting mechanism, such as the grafting of maleic anhydride onto a polyvinylidene fluoride homopolymer or copolymer, as described in US 7,241,817 can added be used to functionalize a fluoropolymer. WO 2013 / 110740 and US 7,351,498 further describe functionalization of a fluoropolymer by monomer grafting or by copolymerization.

[0100] Low molecular weight functionalized polymer chain transfer agents, as described in US 11,643,484, can be used in the polymerization of fluoromonomers, as a means of both controlling theresulting fluoropolymer molecular weight and providing improved properties to the fluoropolymer. Useful functional chain transfer agents include, but are not limited to, polyacrylic acid, polylactic acid, polyphosphonic acid, polysulfonic acid, and polymaleic acid.

[0101] Functional monomers may include, but are not limited to, an acrylic based glycol ester, preferably the acrylic based glycol ester comprises at least one of polyethylene glycol acrylate (PEGA), polyethylene glycol methacrylate (PEGMA), polypropylene glycol acrylate (PPGA), or polypropylene glycol methacrylate (PPGMA).

[0102] Examples of functional monomers include, but not limited to, ethylenically unsaturated ionic monomer comprising at least one functional group selected from carboxylate, sulfonate, sulfate, phosphate, phosphonate, and / or acids, and / or salts, and / or anhydrides thereof.

[0103] Examples of acid functionalized monomers include ethylenically unsaturated monomers comprising at least one acid functional group. Examples of acid functionalized monomers include (meth) acrylic acid, beta-polycarboxy ethyl acrylate, 4-styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, vinyl phosphonic acid, vinyl sulfonic acid, mono-esters of itaconic acid, maleic acid, fumaric acid, and mixtures thereof.

[0104] Examples of functional monomers further include but are not limited to: i) ethylenically unsaturated ionic monomer comprising at least one functional group ; examples include (meth) acrylic acid, 2-carboxyethyl acrylate, 2-polycarboxy ethyl acrylate, mono-ester of itaconic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, 2-acrylamide-2- methylpropane sulfonic acid, 4-styrenesulfonic acid, vinylsulfonic acid, 2-sulfoethyl methacrylate, phosphate esters of polyalkylene glycol mono(meth)acrylate, polyalkylene glycol allyl ether phosphate, vinylphosphonic acid, 2-(methacryloyloxy)ethyl phosphonic acid; and / or acids, and / or salts, and / or anhydrides thereof; and mixtures thereof. ii) oxyalkylated monomer with ethylenic unsaturation and terminated by a hydrogen or hydrophobic aryl or alkyl chain, having the following formula:oxide units of from 0 and 15, n represents a number of ethylene oxide units of from 5 and 15, q represents a whole number at least equal to 1 or greater, R1 and R2 represent methyl or ethyl, and R′ represents a hydrogen or hydrophobic aryl chain with 5 to 60 carbon atoms or an alkyl chain end with 1 to 5 carbon atoms; R represents a group comprising at least onepolymerizable olefinic unsaturation, preferably a group chosen from acrylate, methacrylate, acrylurethane, methacrylurethane, vinyl, allyl, methallyl, isoprenyl, an unsaturated urethane group, in particular acrylurethane, methacrylurethane, α-α'-dimethyl -isopropenyl-benzylurethane, allylurethane, more preferably a group chosen from acrylate, methacrylate, acrylurethane, methacrylurethane, vinyl, allyl, methallyl and isoprenyl, esters of maleic acid, esters of itaconic acid, esters of crotonic acid, even more preferably a methacrylate group, and mixtures thereof, and iii) N-alkylol(meth)acrylamide, vinyl glycidyl ether, allyl glycidyl ether, glycidyl (meth)acrylate, diacetone acrylamide, acetoacetoxyethyl methacrylate, (meth)acryloxyalkyltrialkoxysilanes, vinyltrialkoxysilanes, and mixtures thereof.

[0105] The functionalized polyvinylidene fluoride comprises polymerized vinylidene fluoride units and preferably from 0.1 to 10 mole percent of functional groups in the polymer. The presence of functional monomer or functional group on the fluoropolymer can be detected by means of NMR.

[0106] The melt viscosity of the functionalized PVDF is at least 5 kPoise, preferably at least 10 kPoise, measured according to ASTM D3835 by a capillary rheometry at 230°C, and at shear rate of at 1001 / s.

[0107] Anode active material

[0108] The anode active material comprises electrochemically active material in the form of a particulates. The anode active materials are selected from conventional materials known in this field, for example, graphite, graphene, lithium titanate, silicon or silicon-containing materials. Examples include, but are not limited to, synthetic graphite, natural graphite, hard carbon, graphene, amorphous silicon, semi crystalline silicon, silicon oxides, silicon nanowires, silicon-carbon composite, tin, tin oxides, germanium, lithium titanate, mixtures or combinations of the aforementioned materials, and / or other materials known in the art or described herein as suitable for use as the anode in a lithium ion, and / or sodium ion batteries.

[0109] Conductive carbon

[0110] The optional conductive carbon materials are widely used in positive and negative electrodes to improve the electronic conductivity of electrodes. Conductive carbon can be used in the anode film. Non- limiting examples of conductive carbon include, but are not limited to, carbon black, submicron (less than 15 microns) graphene powders, activated carbon, fine graphite powder such as submicron (less than 5 microns) graphite powders, furnace black, acetylene black, carbon nanotubes (CNT), carbon nanofibers (CNF), vapor deposited graphite fibers, and Ketjen carbon black. Conductive carbon such as carbon black are essentially formed out of primary carbons which are spherical in shape and arranged into aggregates and agglomerates. However, In the case of Ketjen there is no onion-like structure and this carbon containsa network of disordered graphene-sheets. These conductive carbons are used for enhancing electronic conductivity and therefore lower the charge transfer resistance of the battery cell. The typical loading level of the conductive carbon, when incorporated, relative to the anode forming material in the anode is usually within the range of 0 to 20% by weight, 0.1% by weight to 20% by weight, and more preferably within the range of 0.5% by weight to 10% by weight, based on the total amount of the anode forming materials.

[0111] Anode forming material (Anode active material plus conductive carbon plus binder)

[0112] These particulate anode forming materials include anode active material, i.e., materials capable of intercalating (accepting) lithium or sodium ions, and also conductive carbon, if used, and the fluoropolymer binder. Intercalation refers to insertion of ions between the atoms or molecules or groups of another material. As an example, lithium ion intercalates into graphite to form lithiated graphite. An intercalating material is capable of absorbing and desorbing ions at a given potential.

[0113] The electrode film of a lithium or sodium-ion capacitor and / or a lithium or sodium-ion battery may comprise from about 80 weight percent up to 99 weight percent of the anode active materials. In any case, the total amount of all materials in the anode film adds up to 100%. These anode forming materials are typically in the form of powders.

[0114] Alloyed scaffold material

[0115] In this invention, the alloy of PVDF-PTFE is a composite material which is not linked covalently. The alloy of PVDF and PTFE polymers is achieved by enhancing the interaction forces between the two polymers. Not bound by any theory, the interaction forces may include: (1) physical attraction due to van der Waals forces, hydrogen bonding and electrostatic attraction which are enhanced by functionalization of the PVDF; (2) mechanical interlocking due to penetration of one polymer in another one by increasing the interfacial areas which is accomplished by producing functionalized PVDF or PTFE; and (3) by diffusion of PVDF into the bulk phase of expandable PTFE which is achieved via the shear forces.

[0116] Preferably the PVDF has a number average primary particle size (by SEM) of less than 120 nm. Scanning Electron Microscopy (SEM) is used to take microscopic images of PVDF powder. The number average primary particle size can be measured by averaging size of over 50 particles in SEM pictures.

[0117] The present invention discloses PVDF-PTFE scaffolds which comprise functionalized PVDF where the scaffolds have higher ultimate tensile strength of at least 25% greater as compared to the ultimate tensile strength of the non functionalized homopolymer PVDF-PTFE mixtures. A solvent-free process can be used to fill this scaffold and form a porous freestanding film or a supported film. The PVDF-PTFEscaffolds can provide a matrix to confine other powdery material. The pores of the scaffold can be filled with powdery material such as anode active material and optionally conductive carbon.

[0118] The most common solvent used for PVDF is N-Methyl-2-pyrrolidone (NMP), which is a hazardous solvent. This scaffold can eliminate the need for NMP-solvent and enable the fabrication of freestanding or supported articles at from 15°C up to at or about melting temperature of functionalized PVDF or in some embodiments from 15°C up to 120°C.

[0119] Functionalized PVDF-PTFE scaffolds can be used in various applications, where forming freestanding or supported films and articles below the melting temperature of the PVDF and without use of any solvent / liquid is desired.

[0120] Manufacture of Alloyed scaffold material Functionalized PVDF-PTFE scaffold

[0121] The PVDF-PTFE scaffold and anode film of this invention are made by dry fabrication processes.

[0122] PVDF-PTFE scaffold is made by combining PVDF comprising functionalized PVDF in powder form and PTFE in powder form, and then shearing the blend at a temperature of between 10°C and the melting temperature of the PVDF, preferably between 15°C and 120°C. For example, the alloy of functionalized PVDF-PTFE can be made by mixing first at low shear followed by high-shear mixing until fibers are formed. For example, at a laboratory scale, the powder was first mixed at 500 rpm for 1 minute, with 2 zirconia beads, followed by shearing at 2000 rpm for 2 mins with total of 7 zirconia beads in a Thinky mixer resulting in formation of functionalized PVDF-PTFE scaffolds, at ambient temperature.

[0123] High Shear mixing or blending is used to alloy the functionalized PVDF and the PTFE together and create a scaffold structure. Batch mixers and in-line mixers can be used. At a laboratory scale, this was accomplished, by ball milling using mixing media. The bulk material is sheared to produce scaffolding in a high-energy ball mill using milling media like balls or beads. There is a variety of milling media materials such as: Steel (chrome steel, and stainless steel, 304SS and 316SS) or Ceramics (agate, alumina, yttria stabilized zirconia, zirconium silicate, zirconia toughened alumina, and tungsten carbide).

[0124] The method of fabricating an anode of an energy storage devices comprises combining an anode active material, optionally conductive carbon material, and functionalized PVDF to form a first mixture, adding PTFE to the first mixture to form a second mixture; and subjecting the second mixture to a shearing process to form a dry anode forming mixture comprising an alloy of PVDF and PTFE in the form of a scaffold intermixed with the anode active material, optionally conductive carbon material. The process is a dry process. No liquid is used in the process. All components are in a powder form.

[0125] The anode active material can be any anode active material described herein.

[0126] The functionalized PVDF can be functionalized PVDF described herein.

[0127] The steps of the method can be performed a temperature of 10° C to at or about melting temperature of functionalized PVDF or in some embodiments from 15°C up to 120° C.

[0128] The shearing can be done via jet -milling.

[0129] The shearing can be done via ball-milling and may use milling media.

[0130] The method may further comprise adding a conductive carbon with the active material and the functionalized PVDF.

[0131] The resulting material may be calendered to form a free-standing anode film or a film supported on a current collector. The free-standing anode film may be disposed over a current collector to form an anode. This may be done by laminating the free-standing anode film to the current collector.

[0132] EXAMPLES

[0133] Melt viscosity of PVDF is measured according to ASTM D3835 by a capillary rheometry at 230°C, and at shear rate of at 1001 / s).

[0134] The solids content of the aqueous dispersion was measured by means of gravimetry method.

[0135] Primary particle size of fluoropolymer is measured by averaging the size of 50 particles in a SEM image. A Hitachi SU 8010 SEM was used for SEM, and the PVDF powder was coated with platinum prior to SEM imaging.

[0136] Melting temperature was measured using a Differential Scanning Calorimeter (DSC). The DSC runs were cycled at 10 ˚C / min from -20 ˚C to 210 ˚C for two cycles with the melting taken from the second cycle.

[0137] Example 1 Production of PVDF with particle size below 100 nm.

[0138] To a 7.5-liter, stainless steel reactor was added 4200 g of water and 0.5 g of non-ionic emulsifiers of Pluronic® 31R1 (from BASF) and 3.5 g of Poly (Propylene Glycol) Monomethacrylate (“PPGMA”). The mixture was purged with nitrogen and agitated for 0.5 hours. The reactor temperature was raised to 105 °C for deoxygenation. The reactor sealed, while agitation was continued, the temperature was set at 100C. The reactor was charged with vinylidene fluoride to a pressure of 650 psig (4.5 MPa); an aqueous initiator solution, comprised of 2 wt. % in potassium persulfate and 2 wt % in sodium triacetate, was charged at 500 g / hr to initiate the polymerization. The initiator solution feed rate was set at about 60 g / h to maintain the reaction throughout the rest of the polymerization. Total initiator was 300 milliliters. The reaction pressure was maintained at 650 psig by adding as needed vinylidene fluoride. After a total of 1500 g ofVDF was added to the reactor, the monomer feed was stopped. For a period of 10 minutes, agitation was continued, and the temperature was maintained. The agitation and heating were discontinued. After cooling to room temperature, surplus gas was vented, and the reactor was emptied of dispersion through a stainless-steel mesh screen (208 micron). The PVDF latex has 29% solid contents. The PVDF powder has a melt viscosity of greater than 27 kPoise. The average primary particle size is 82 nm. Melting temperature was measured to be 164 ˚C

[0139] Example 2 Production of PVDF / HFP copolymer with particle size below 100 nm.

[0140] To a 7.5 liter stainless steel reactor was added 4200 g of water and 0.5 g of non-ionic emulsifiers of Pluronic® 31R1 (from BASF) and 3.5 g PPGMA. The mixture was purged with nitrogen and agitated for 0.5 hours. The reactor temperature was raised to 105 °C for deoxygenation. The reactor sealed, while agitation was continued, the temperature was set at 100°C. The reactor was charged with vinylidene fluoride to a pressure of 650 psig(4.5 MPa); an aqueous initiator solution, comprised of 2 wt. % in potassium persulfate and 2 wt % in sodium triacetate, was charged at 500 g / hr to start the polymerization. The initiator solution feed rate was set at about 60 g / h to maintain the reaction rate throughout the rest of the polymerization. Total initiator was 290 milliliters. The reaction pressure was maintained at 650 psig by adding as needed vinylidene fluoride. After a total of 365 g of VDF was added to the reactor, the VDF feed was stopped and 273 g of HFP monomer is added to reactor and then was topped with VDF to reach 1500 g total of VDF. For a period of 10 minutes, agitation was continued, and the temperature was maintained. Then agitation and heating were discontinued. After cooling to room temperature, surplus gas was vented, and the reactor was emptied of dispersion through a stainless-steel mesh screen (208 micron). The PVDF latex has 31% solid contents. The PVDF powder has a melt viscosity of 25 kPoise (at 1001 / s), a melting temperature of 162 ˚C and primary particle size of 87 nm.

[0141] Example 3 Production of PVDF (with PPGMA and PAA) with particle size below 100 nm.

[0142] To a 7.5 liter, stainless steel reactor was added 3000 g of water and 0.5 g of non-ionic emulsifiers of Pluronic 31R1 (from BASF) and 3.0 g of PPGMA. The mixture was purged with nitrogen and agitated for 0.5 hours. The reactor temperature was raised to 105 °C for deoxygenation. The reactor sealed, while agitation was continued, the temperature was set at 100°C. The reactor was charged with vinylidene fluoride to a pressure of 650 psig(4.5 MPa); an aqueous initiator solution, comprised of 2 wt. % in potassium persulfate and 2wt % in sodium triacetate, was charged at 500 g / hr to start the polymerization. Total initiator was 255 milliliters. The initiator solution feed rate was set at about 60 g / h to maintain the reaction rate throughout the rest of the polymerization. The reaction pressure was maintained at 650 psig by adding as needed vinylidene fluoride. After a total of 800 g of VDF was added to the reactor, a 5wt%solution of polyacrylic acid (Sokalan CP-10 from BASF) having a weight average molecular weight of ~ 4000 in water was fed to the reactor at 200 ml / hr while the feeding of VDF continued. Addition of polyacrylic acid solution was stopped when a total of 195 ml of PAA solution was reached. Addition of VDF was stopped when the total of VDF fed reached 1700 g. For a period of 10 minutes, agitation was continued, and the temperature was maintained. Then agitation and heating were discontinued. After cooling to room temperature, surplus gas was vented, and the reactor was emptied of dispersion through a stainless- steel mesh screen (208 microns). The PVDF latex has 33% solid contents. The PVDF powder has a melt viscosity of 28 kPoise (at 1001 / s), a melting temperature of 164 ˚C and a primary particle size of 95 nm.

[0143] Example 4 Production of PVDF (PPGMA and PAM) with particle size below 100 nm.

[0144] To a 7.5 liter, stainless steel reactor was added 3000 g of water and 0.5 g of non-ionic emulsifiers of Pluronic 31R1 (from BASF) and 3.0 g of PPGMA. The mixture was purged with nitrogen and agitated for 0.5 hours. The reactor temperature was raised to 105 °C for deoxygenation. The reactor sealed, while agitation was continued, the temperature was set at a 100°C. The reactor was charged with vinylidene fluoride to a pressure of 650 psig(4.5 MPa); an aqueous initiator solution, comprised of 2 wt. % in potassium persulfate and 2wt % in sodium triacetate, was charged at 500 g / hr to start the polymerization. Total initiator was 270 milliliters. The initiator solution feed rate was set at about 60 g / h to maintain the reaction rate throughout the rest of the polymerization. The reaction pressure was maintained at 650 psig by adding, as needed, vinylidene fluoride. After a total of 800 g of VDF was added to the reactor, 2% wt / wt of solution of alkyl methacrylate phosphate (Sipomer® PAM 4000 by Solvay) in water and then was fed to the reactor at 100 ml / hr while the feeding of VDF continued for a total of 285 ml of Sipomer® PAM 4000 solution. Addition of VDF and PAM 4000 solution were stop when the total of fed VDF reached 1700 g. For a period of 10 minutes, agitation was continued, and the temperature was maintained. The agitation and heating were discontinued. After cooling to room temperature, surplus gas was vented, and the reactor was emptied of dispersion through a stainless-steel mesh screen. The PVDF latex has 28% solid contents. The PVDF powder has melt viscosity of 29 kPoise (at 1001 / s), a melting temperature of 161 ˚C and an average primary particle size of 78 nm.

[0145] Example 5 Functionalized PVDF-PTFE scaffold

[0146] PVDF-PTFE scaffold was made by shearing 3 g of PVDF functionalized polyvinylidene fluoride fluoropolymer (functionalized with PPGMA) of example 1 and 1 g of PTFE powder (Teflon® PTFE 601X from Chemours) with total of 7 Zirconia beads of 6.5 mm, using a planetary mixer (Thinky ARE-310). The powder was first mixed at 500 rpm for 1 minute, with 2 zirconia beads, followed by shearing at 2000 rpm for 2 minutes with total of 7 zirconia beads resulting in formation of PVDF-PTFE scaffolds, Figure 1. The PVDF-PTFE scaffolds of this example is a fibrous powdery material. Figure 2 is a SEM of the PVDF-PTFE scaffold material of Example 5, based on the SEM pictures, no PVDF spherical particles are observed in the scaffold. This shows that the PVDF is physically alloyed with the PTFE to form the functionalized PVDF-PTFE scaffolds.

[0147] Example 6 Making PVDF-PTFE porous mat

[0148] Functionalized PVDF from examples 1 and 4 with PTFE (PVDF / PTFE: 3 / 1 by weight) scaffolds were made following this process described in example 5. The samples were compression molded using a Carver Press and samples were pressed at six metric ton at room temperature for 10 minutes. The tensile bar has a thickness of ~1000 µm. Figure 3 shows a picture of the porous mat and confirms the uniform color of this article. This shows that the functionalized PVDF and the PTFE form a single phase. Ultimate tensile strength of these mats were measured according to the ASTM D1708 method and the ultimate tensile were corrected for porosities of these mats. The results are reported in Table 1. The porosity (^^^^) of the sample was measured based the measured density of the mat and calculated density of PVDF and PTFE using the following equation: ^^^^ = 1 −^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[0149] Figure 3 shows the porous material exhibits homogeneous color.As seen in the figure 3, the mat has an even color throughout the article, consistent with uniform distribution of PVDF-PTFE in the alloy.

[0150] Example 7 FTIR of functionalized PVDF and alloy of functionalized PVDF-PTFE

[0151] The FTIR spectra of PVDF of example 1 and 4, and porous mats of example 6 were measured and the amount of non-α phase PVDF was calculated. For the analysis, the regions 837-840 cm-1(CH2and CF2vibrations) as containing high contribution from non-α and 763-765 cm-1(CF2and CCC vibrations) as containing mainly α contributions were selected. For each spectrum, the peak heights were determined (the two selected regions) and a ratio was calculated (peak height at 840 divided by the sum of the two peak heights). The percentage of non-α phase is reported in Table 2.

[0152] Example 8 TGA of functionalized PVDF-PTFE

[0153] Thermal degradation of functionalized PVDF of example 1 and 4, functionalized PVDF (Solef 5130, Synesqo), and alloy of functionalized PVDF-PTFE of example 6 was evaluated by TGA. The decomposition temperature at 5% weight loss is reported in Table 3. The decomposition temperature corresponds to 5% weight loss of the initial mass, when the decomposition starts.

[0154] Example 9 Making anode films

[0155] Anode films were made by mixing graphite (GHDR-15-4, Imerys), functionalized PVDF of example 1 (PPGMA functional comonomer) and PTFE (Teflon™ PTFE 601X, Chemours) in a weight ratio of 95: 4: 1 in a Thinky mixer (ARE310). First PVDF and graphite were mixed at 500 rpm with 3 Zirconia beads of 12 mm. After addition of PTFE and 5 beads of 10 mm, the mixture was sheared at 2000 rpm for 2 minutes and the material was turned into a film at room temperature. A film using the same process was made without PVDF and using 5 % PTFE. The films were laminated on a carbon coated copper foil at 80 ˚C and cycled between 0.005-1.5 V (vs Li / Li+) against lithium metal. The electrolyte was 1 M LiPF6 in EC / DEC (ethylene carbonate / diethylene carbonate) and a polyethylene Celgard separator was used. The first cycle efficiency of the cell with and without PVDF binder was 88.5 and 75%, respectively. The higher first cycle efficiency results in a lower irreversible capacity loss and higher discharge capacity in batteries. The first discharge voltage profile for these anodes is shown in Figure 4. The PTFE decomposition plateau appears between 0.6-0.8 V (vs Li / Li+), addition of PVDF in PVDF / PTFE scaffold significantly reduces the amount of decomposition in the anode film. Figure 4 shows the first discharge voltage profile of anode half cells with and without PVDF of example 1. This figure shows that the PTFE decomposition is lower when the functionalized PVDF-PTFE scaffold is used.

[0156] Example 10

[0157] Anode films were made by mixing graphite (GHDR-15-4, Imerys), conductive carbon (Super P, Imerys), functionalized PVDF of example 1, and PTFE in a ratio of 95:1:3:1 in a Thinky mixer. First PVDF and conductive carbon were mixed at 500 rpm, for 90 seconds, with 3 Zirconia beads of 12 mm, then graphite was added to the mixture and mixed at 500 rpm for 90 seconds. After addition of PTFE and 5 beads of 10 mm, the mixture was sheared at 2000 rpm for 2 minutes and the material was turned into a film at room temperature. Different PVDF grades were used to evaluate the ultimate tensile strength (tensile strength at break, kPa) of the films. Table 4 shows the ultimate tensile results of these samples, it is clear from this figure that the functionalized PVDFs provide higher ultimate tensile compared to the non-functionalized PVDF. The ultimate tensile strength of these samples was measured using the ASTM D1708 method. The tensile bar was a dog bone, as described in ASTM D1708. The speed used for this experiment was 12.7 mm / min. The samples were processed at 20°C and the ultimate tensile strength was measured in a controlled environment, where the dew point was kept at 5 ˚C. The samples were not conditioned before the ultimate tensile test.

[0158] Example 11

[0159] Anode film, containing 5% of silicon was made using the process described in example 10, where the silicon was added right before adding the PTFE binder. Ultimate tensile strength (measured using the ASTM D1708 method) of the film was 170 kPa, and film thickness was 204 µm.

[0160] Example 12

[0161] Flow properties of PVDF / carbon / graphite mixture in a ratio of 3 / 1 / 96 wt% is quantified using powder rheology. Functionalized PVDF of example 1, carbon, and graphite were mixed at 500 rpm, for 90 seconds, with 3 zirconia beads of 12 mm. A FT4 powder rheometer was used to determine flow property of the powder. A shear cell was used to quantify the cohesion and flowability index of powders according to ASTM D7891, and the powders were classified according to Jenike DOI 10.1016 / S0260-8774(03)00147- X. Based on the results in Table 5, the mixture with functionalized PVDF of example 1 is classified as an easy-flowing powder, which allows wider operational windows in powder processing and electrode manufacturing.

[0162] Counter Example 1 Homopolymer PVDF-PTFE mixture

[0163] Kynar 741-PTFE mixture was made by shearing 3 g of Kynar 741 PVDF homopolymer and 1 g of PTFE powder at room temperature with total of 7 Zirconia beads of 6.5 mm, using a planetary mixer Thinky ARE-310. The powder was first mixed at 500 rpm for 1 minute, with 2 zirconia beads, followed by shearing at 2000 rpm for 2 mins with total of 7 zirconia beads resulting in formation of PVDF-PTFE blend, Figure 5.

[0164] Figure 6 is an SEM of Counter Example 1 showing that the PVDF homopolymer (Kynar 741) did not form an alloy with the PTFE. The agglomerated PVDF particles can be seen in the SEM.

[0165] Counter Example 2 PVDF-PTFE porous freestanding mat

[0166] Kynar 761 PVDF-PTFE (PVDF / PTFE: 3 / 1 by weight) samples were made following the process of counter example 1. The samples were then pressed at six metric ton at room temperature for 10 minutes using a Carver Press and porous mats were fabricated. The tensile bar has a thickness of ~1000 µm. Ultimate tensile strength of these mats was measured according to the ASTM D1708 method and the ultimate tensile at break were normalized to account for porosities of these mats and reported in Table 1. Table 1 shows that the mats made from the alloy using functionalized PVDF of example 1 and of example 4, have higher ultimate tensile strength compared to the mat made using the Kynar 761 PVDF-PTFE blend.

[0167] Figure 7 shows the porous mat made. The material exhibits a non-homogeneous composition. As seen in the Figure 7, the darker shade areas of the mat indicate areas to be of higher density (less porous) than the lighter shade or white areas which are more porous. This shows that the PVDF and PTFE did not form a uniform alloy.

[0168] Table 1. Ultimate tensile results of PVDF-PTFE porous mats Sample Ultimate Tensile (kPa) ASTM D1708 -PTFE

[0170] The FTIR spectra of Kynar 711, 761, and HSV900 powders, and porous mats of Kynar 711-PTFE, Kynar 761-PTFE, and HSV900-PTFE, made using the process described in counter example 2, were measured and the amount of non-α phase for PVDF was calculated. For the analysis, the regions 837-840 cm-1(CH2and CF2vibrations) as containing high contribution from non-α and 763-765 cm-1(CF2and CCC vibrations) as containing mainly α contributions are selected. For each spectrum, the peak heights were determined (the two selected regions) and a ratio was calculated. The percentage of non-α phase is reported in Table 2. From this table we can conclude that the percentage of non-α phase of functionalized PVDF of example 1 and 4 is higher than 70%. The percentage of non-α phase increases by mixing PVDF with PTFE and then shearing. Even after mixing with PTFE and then shearing, the non-α phase is higher than 70% for the functionalized PVDF of example 1 and 4, while it is still lower than 70% for the nonfunctionalized PVDF-PTFE blend.

[0171] Table 2. FTIR of pure PVDF powder and PVDF / PTFE samples Sample(^^^^^^^^^^^^−^^^^^^^^^^^^^^^^^^^^)(^^^^^^^^^^^^−^^^^^^^^^^^^^^^^^^^^)+(^^^^^^^^^^^^^^^^^^^^) (%) E

[0172] Counter Example 8 TGA of PVDF and PVDF-PTFE

[0173] Thermal degradation of Kynar 761, HSV900 powder and blend of Kynar761-PTFE and HSV900- PTFE, made using the process described in counter example 2, was evaluated by TGA. The decomposition temperature at 5% weight loss is reported in Table 3. The decomposition temperature corresponds to 5% weight loss of the initial mass, when the decomposition starts. Based on these results, the thermal degradation of Kynar 761 is higher than the PVDF of example 1 and example 4. The 5% weight loss temperature of Kynar 761 is higher than the functionalized PVDF of examples 1 and 4, even after mixing with PTFE and then shearing.

[0174] Table 3. Thermal degradation of PVDF Sample 5% weight loss temperature (˚C) Pure Sheared with 25% PTFE

[0175] Counter Example 9

[0176] Anode films were made by mixing graphite (GHDR-15-4, Imerys), conductive carbon (Super P, Imerys), Kynar 741 PVDF, and PTFE (601X, Chemours) in a ratio of 95:1:3:1 in a Thinky mixer. First PVDF and carbon were mixed at 500 rpm for 90 seconds with 3 Zirconia beads of 12 mm, then graphite was added to the mixture and mixed at 500 rpm for 90 seconds. After addition of PTFE and 5 beads of 10 mm, the mixture was sheared twice at 2000 rpm for 2 minutes and the material was calendared into a film at room temperature. Table 4 shows the ultimate tensile results of these samples. Anode film was made using graphite, conductive carbon, and PTFE in a ratio of 98:1:1 in a Thinky mixer. First graphite and carbon were mixed at 500 rpm with 3 Zirconia beads of 12 mm for 90 seconds. After addition of PTFE and 5 beads of 10 mm, the mixture was sheared twice at 2000 rpm for 2 minutes and the material was turned into a film at room temperature. The ultimate tensile strength of these samples was measured using the ASTM D1708 method. The tensile bar was a dog bone, as described in ASTM D1708. The speed used for this experiment was 12.7 mm / min. The samples were processed at room temperature and the ultimate tensile strength was measured in a controlled environment, where the dew point was kept at -5 ˚C. The samples were not conditioned before the ultimate tensile test.

[0177] Table 4. Ultimate tensile strength of anode films made using dry process (ultimate tensile values are reported as measured) Binder Thickness Ultimate tensile (µm) (kPa)

[0179] Flow properties of PVDF / carbon / graphite mixture in a ratio of 3 / 1 / 96 wt% is quantified using powder rheology. Kynar 741 PVDF / carbon / graphite were mixed at 500 rpm with 3 zirconia beads of 12 mm. A FT4 powder rheometer was used to determine flow property of the powder. A shear cell was used to quantify the cohesion and flowability index of powders, according to ASTM D7891. The powders were classified according to Jenike 10.1016 / S0260-8774(03)00147-X. where flowability index of 4 < flowbility index< 10 is considered easy flowing and from 2< flowability index < 4 is consider cohesive. Based on the results in Table 5, the mixture with Kynar 741 is classified as a cohesive powder.

[0180] Table 5. Powder rheology results of PVDF, carbon, graphite mixture. Blend of Binder w / Carbon and graphite Cohesion Flowability index Classification

[0181] This shows that the functionalized PVDF decreases cohesion and increases flowability of the dry powder compositions.

Claims

CLAIMS 1. A fluoropolymer composition comprising an alloy of functionalized PVDF and PTFE wherein the weight ratio of functionalized PVDF to PTFE is 10:90 to 95:5, wherein the functionalized PVDF comprises a functional group, and wherein the fluoropolymer composition is absent of solvent residue.

2. The fluoropolymer composition of claim 1, wherein the weight ratio is from 25:75 to 90:

10.

3. The fluoropolymer composition of claim 1, wherein the functionalized PVDF comprises HFP monomer units.

4. The fluoropolymer composition of claim 1, wherein the functional group comprises a carboxylic group or salt or ester thereof.

5. The fluoropolymer composition of claim 1, wherein the functional group comprises a phosphate or sulfonate.

6. The fluoropolymer composition of claim 1, wherein the functional group comprises a hydroxyl group or ether group.

7. The fluoropolymer composition of claim 1, wherein the amount of functional groups is at least 0.1 mole percent and up to 10 mole% based on VDF monomer units.

8. The fluoropolymer composition of claim 1, wherein fluoropolymer binder comprising the PTFE and the functionalized PVDF is in the form of a scaffold.

9. An anode film comprising an anode composition comprising an anode active material and a fluoropolymer binder comprising PTFE and functionalized PVDF, wherein the weight ratio of functionalized PVDF to PTFE in the anode is 10:90 to 95:5, wherein the functionalized PVDF comprises a functional group, and wherein the film is free of solvent residue, and wherein the total fluoropolymer binder amount is from 1 wt% to 10 wt% of the anode composition.

10. The anode film of claim 9, wherein the weight ratio of functionalized PVDF to PTFE is from 25:75 to 90:

10.

11. The anode film of claim 9, wherein the functionalized PVDF comprises HFP monomer units.

12. The anode film of claim 9, wherein the functional group comprises a carboxylic group or salt or ester thereof.

13. The anode film of claim 9, wherein the functional group comprises an ether group or hydroxyl group.

14. The anode film of claim 9, wherein the functional group comprises a phosphate or sulfonate.

15. The anode film of claim 9, wherein the anode film comprises from 1 weight % to 6 weight % of the fluoropolymer binder based on the weight of the anode film.

16. The anode film of claim 9, wherein the amount of functional groups is equal to or greater than 0.1 mole percent in the fluoropolymer binder.

17. The anode film of claim 9, wherein fluoropolymer binder comprising the PTFE and the functionalized PVDF is in the form of a scaffold.

18. The anode film of claim 9, wherein the anode active material is selected from the group consisting of synthetic graphite, natural graphite, hard carbon, graphene, graphene oxide, amorphous silicon, semi crystalline silicon, silicon oxides, silicon nanowires, silicon-carbon composite, tin, tin oxides, germanium, lithium titanate, or mixtures thereof.

19. The anode film of claim 9, wherein the anode film comprises a conductive carbon.

20. An energy storage device comprising the anode film of claim 9, wherein the energy storage device comprises a lithium-ion battery or a sodium ion battery or a lithium containing-sulfur battery.

21. A method of fabricating an anode film for an energy storage device, comprising: a) combining an anode active material and functionalized PVDF to form a first mixture, b) adding PTFE to the first mixture to form a second mixture; and c) subjecting the second mixture to a shearing to form a dry anode film forming mixture comprising PTFE and functionalized PVDF, and wherein no liquid is used in the process.

22. The method of claim 21, wherein the shearing comprises jet-milling.

23. The method of claim 21, wherein the shearing comprises ball-milling and uses milling media.

24. The method of claim 21, wherein combining further comprises combining a conductive carbon additive with the active material and the functionalized PVDF to form the first mixture.

25. The method of claim 21, wherein each of the combining and the adding steps comprises blending at a temperature of between 10° C to 120° C.

26. The method of claim 21, further comprising calendering the dry anode film forming mixture to form an anode film.

27. The method of claim 26, further comprising the step of disposing the anode film over a current collector to form the anode.

28. The method of claim 27, wherein the disposing comprises laminating the anode film to the current collector.

29. The method of claim 21, wherein the weight ratio of functionalized PVDF to PTFE is 10:90 to 95:5.

30. The method of claim 21, wherein the anode active material comprises at least one of synthetic graphite, natural graphite, hard carbon, soft carbon, graphene, graphene oxide, silicon, silicon oxides, tin, tin oxides, germanium, lithium titanate, or mixtures thereof.

31. The method of claim 21, wherein the anode active material comprises at least one of synthetic graphite, natural graphite, or combinations thereof.

32. A method of fabricating an energy storage device comprising affixing the anode film of claim 1 to a current collector to form an anode, inserting the anode, a cathode and a separator within a housing, wherein the separator is positioned between the anode and the cathode.

33. An energy storage device, comprising the anode film of claim 9, a cathode and a separator within a housing, wherein the separator is positioned between the anode film and the cathode.

34. The energy storage device of claim 33, wherein the energy storage device is selected from the group consisting of a lithium-ion battery, a lithium-ion capacitor, a sodium-ion battery, or a lithium containing-sulfur battery.

35. An article comprising: the fluoropolymer composition of claim 1.

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