Dry electrode compositions for lithium-ion batteries

Abstract

An electrode film formed from a dry process is provided having an elongation of at least 8 % is provided, wherein said film comprises at least 95 wt% electrode active material having a small particle size (D50 of 3 µm or less). Compositions and methods related to preparing the electrode film are provided as well as electrodes and lithium-ion batteries comprises these materials.

Description

Attorney Docket No.: FP0033-W001TITLE OF THE INVENTIONDRY ELECTRODE COMPOSITIONS FOR LITHIUM-ION BATTERIESCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority benefit of US provisional patent application no. 63 / 683,404, filed on August 15, 2024, the disclosure of which is hereby incorporated by reference in its entirety.BACKGROUND OF THE INVENTION

[0002] Electrodes for an electrochemical storage device typically include an active component (or active material), such as graphite, metal, or metal oxide, that undergoes an electrochemical reaction associated with energy storage; a binder, such as polyvinylidene fluoride (PVDF), 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.

[0003] In a “dry” or “solvent-free” process, an electrode film is formed by compaction of an electrode power in a calendering process, without requiring a slurry material and corresponding solvent drying process. The electrode film can then be bonded / laminated to a current collector.

[0004] Small particle size electrode active materials, such as lithium iron phosphate (“LFP”) with having a Dso value of 3 pm or less, can present challenges when forming dry processed electrode films having a total binder content of 5 wt% or less. These films often have insufficient mechanical properties (such as elongation values below 8%) and issues with insufficient mixing of the active filler particles (electrode active materials, conductive particles, etc.). As such, there is a need to provide self-supporting electrode films having an elongation of at least 8%; wherein the electrode films comprise at least 95 wt% of an electrode active material having an average particle size (or median particle; D50 value) of 3 pm or less; preferably less than 2 pm), a binderAttorney Docket No.: FP0033-W001 content of 5 wt% or less. Typically, these films should self-supporting and having an average thickness from 100 pm to 500 pm, preferably about 200 pm to about 500 pm.SUMMARY OF THE INVENTION

[0005] This disclosure relates to compositions and methods for preparing a self-supporting electrode film for lithium-ion batteries formed using a dry process, wherein the electrode films comprise at least 95 wt% of an electrode active material having a D50 particle size of 3 pm or less, 5 wt% or less of a fibrillatable binder, and up to 3 wt% of electrically conductive particles; wherein the electrode film comprises an elongation of at least 8%, preferably at least 9%, and most preferable at least 10% as measured using the methods described herein. In a preferred aspect, the electrode film is used in a cathode and the electrode active material is lithium iron phosphate (“LFP”).

[0006] In another embodiment, dry electrode compositions for use in solventless fabrication of electrode (e.g., cathode) films for lithium-ion batteries are also provided. In some embodiments, the electrode compositions described herein include a dry powder binder composition that includes a first fluoropolymer that is co-coagulated with a second fluoropolymer. In one embodiment, the first fluoropolymer is more fibrillizable than the second fluoropolymer and the second fluoropolymer is more friable than the first fluoropolymer, providing cocoagulated binder compositions (agglomerates) that are both fibrillizable and friable. The electrode compositions also include small particles of an electrode active material, such as a cathode active material. In some embodiments, the fibrillizable and friable nature of the binder compositions promote homogeneous mixing with the cathode active materials in the electrode compositions and generally enables better mechanical properties of the resulting cathodes, e.g., providing robust elongation.

[0007] In a first aspect, an electrode composition for a lithium-ion battery includes a dry powder binder composition and an electrode active material having a D50 particle size of less than 3 pm. In one aspect, the dry powderAttorney Docket No.: FP0033-W001 binder composition includes a first fluoropolymer co-coagulated with a second fluoropolymer, wherein the first fluoropolymer is more fibrill izable than the second fluoropolymer, and wherein the second fluoropolymer is more friable than the first fluoropolymer.

[0008] Embodiments can include one or any combination of two or more of the following features.

[0009] In some embodiments, the molecular weight of the first fluoropolymer is greater than the molecular weight of the second fluoropolymer.

[0010] The first and second fluoropolymers have different melt creep viscosity (MCV) values. In some cases, the first fluoropolymer has a mean MCV of at least 0.5 x 101° poise (0.5 x 109Pa-S). In some cases, the first fluoropolymer has a mean MCV of at least 0.5 x 1011poise (0.5 x 101° Pa-S). In some cases, the first fluoropolymer has a higher mean MCV than the second fluoropolymer.

[0011] In one embodiment, the first fluoropolymer is a homopolymer.

[0012] In another embodiment, the second fluoropolymer is a copolymer.

[0013] Each of the first and second fluoropolymers includes a tetrafluoroethylene (TFE)-based polymer. In some cases, at least one of the first fluoropolymer or the second fluoropolymer includes a modified PTFE. In some cases, at least one of the first fluoropolymer or the second fluoropolymer includes a TFE-based copolymer.

[0014] In one embodiment, at least one of the first fluoropolymer or the second fluoropolymer includes a co-coagulate of PTFE with another fluoropolymer.

[0015] In another embodiment, at least one of the first fluoropolymer or the second fluoropolymer is a core-shell polymer. In some cases, a core portion of the core-shell polymer has a different molecular weight than a shell portion of the core-shell polymer. In some cases, the composition of the core portion of the core-shell polymer differs from the composition of the shell portion of the core-Attorney Docket No.: FP0033-W001 shell polymer. In some cases, the second fluoropolymer includes a core-shell copolymer, wherein the core portion includes a first TFE-based copolymer and the shell portion includes a second TFE-based copolymer.

[0016] In one embodiment, the binder includes equal to or greater than 50% by weight of the second fluoropolymer.

[0017] In another embodiment, the binder includes equal to or greater than 50% by weight of the first fluoropolymer.

[0018] In another embodiment, the binder includes approximately equal amounts by weight of the first and second fluoropolymers.

[0019] In one embodiment, the electrode active material includes a lithium transition metal phosphate. In some cases, the electrode active material includes lithium iron phosphate (also known as lithium ferrous phosphate or “LFP”).

[0020] In one embodiment, the electrode active material has a (median) D50 particle size of between 1.0 and 1.5 pm.

[0021] In another embodiment, the electrode composition includes a conductive additive such as a conductive carbon additive.

[0022] The electrode composition is in the form of an electrode film that has an elongation of at least 1 % when measured on a 20 mm x 5.3 mm sample (having a thickness of approximately 350 pm) at an applied tensile strain rate of 10% per minute at room temperature (~ 22 °C). In some cases, the electrode film has an elongation of between 1% and 15%. In some cases, the electrode film has an elongation of between 1% and 10%. In some cases, the electrode film has an elongation of at least 8, 9 or 10%. As used herein, elongation is defined as the strain (in %) at the ultimate tensile strength.

[0023] In one embodiment, the dry powder binder composition is fibrillizable.

[0024] In another embodiment, the dry powder binder composition is friable.Attorney Docket No.: FP0033-W001

[0025] The dry powder binder composition, prior to mixing with the electrode active material, has an average particle size of between 10 pm and 200 pm as measured by laser diffraction after application of 60 pounds per square inch (psi) (-414 kPa) of pressure to the dry powder binder composition.

[0026] The dry powder binder composition, prior to mixing with the electrode active material, has a particle size that is greater than the particle size of the first fluoropolymer and less than the particle size of the second fluoropolymer, as measured by laser diffraction after application of 60 psi (-414 kPa) of pressure to the dry powder binder composition.

[0027] The second fluoropolymer has a particle size of less than 100 pm, as measured by laser diffraction after application of 60 psi (-414 kPa) of pressure to the dry powder binder composition; and the first fluoropolymer has a particle size greater than the particle size of the second fluoropolymer.

[0028] In one embodiment, the electrode composition includes 5 wt% or less of the binder composition, preferably from 1.0 to 4.0 wt% based on the total weight of the electrode composition.

[0029] In a second aspect, combinable with the first aspect, an electrode for a lithium-ion battery includes a film including a binder composition and an electrode active material having a Dso particle size of less than 3 pm, 2 pm, 1 .5 pm, or 1.0 pm, preferably from about 0.5 to about 2.0 pm or from about 1 .0 to about 1 .5 pm. In one embodiment, the binder composition includes a first fluoropolymer co-coagulated with a second fluoropolymer, wherein the first fluoropolymer is more fibrillizable than the second fluoropolymer, and wherein the second fluoropolymer is more friable than the first fluoropolymer; and

[0030] Embodiments can include one or any combination of two or more of the following features.

[0031] The film has a contact thickness of about 200 - 500 pm.

[0032] The film is a free-standing (i.e., self-supporting) film.Attorney Docket No.: FP0033-W001

[0033] The film has an elongation of at least 1% when measured on a 20 mm x 5.3 mm sample (having a thickness of approximately 350 pm) at an applied tensile strain rate of 10% per minute at room temperature (~ 22 °C). In some cases, the film has an elongation of between 1% and 10%. In some cases, the film has an elongation of at least 8, 9 or 10%.

[0034] In a third aspect, combinable with either of the previous aspects, a lithium-ion battery includes a first electrode including an electrode film disposed on a substrate, a second electrode; and an electrolyte in contact with the first electrode and the second electrode. The electrode film of the first electrode includes a binder composition and an electrode active material having a D50 particle size of less than 3 pm. In one embodiment, the binder composition includes a first fluoropolymer co-coagulated with a second fluoropolymer, wherein the first fluoropolymer is more fibrillizable than the second fluoropolymer, and wherein the second fluoropolymer is more friable than the first fluoropolymer.

[0035] In a fourth aspect, combinable with any of the previous aspects, a method of making an electrode for a lithium-ion battery includes mixing a dry powder binder composition with an electrode active material having a D50 particle size of less than 3 pm to form an electrode composition. The dry powder binder composition includes a first fluoropolymer co-coagulated with a second fluoropolymer, wherein the first fluoropolymer is more fibrillizable than the second fluoropolymer, and wherein the second fluoropolymer is more friable than the first fluoropolymer.

[0036] Embodiments can include one or any combination of two or more of the following features.

[0037] The method includes forming an electrode film from the electrode composition.

[0038] The method includes forming the dry powder binder composition, including: mixing an aqueous dispersion of the first fluoropolymer with an aqueous dispersion of the second fluoropolymer to produce the agglomerates;Attorney Docket No.: FP0033-W001 separating the agglomerates; and drying the agglomerates to form the dry powder binder composition.

[0039] In a fifth aspect, a self-supporting electrode film comprising any of the above electrode compositions is also provided.

[0040] In a sixth aspect, a self-supporting electrode film for lithium-ion batteries formed using a dry process is provided, wherein the electrode film comprises at least 95 wt% of an electrode active material having a Dso particle size of 3 pm or less, 5 wt% or less of a fibrillatable binder, and up to 3 wt% of electrically conductive particles; wherein the electrode film comprises an elongation of at least 8%, preferably at least 9%, and most preferable at least 10% when measured on a 20 mm x 5.3 mm sample (preferably having a thickness of approximately 350 pm) at an applied tensile strain rate of 10% per minute at room temperature (~ 22 °C). In a preferred aspect, the self-supporting electrode film is used in a cathode and the electrode active material is lithium iron phosphate (“LFP”).

[0041] In a seventh aspect, the fibrillatable binder comprises at least one fibrillatable polytetrafluoroethylene (PTFE) having a melt creep viscosity of at least 0.5 x 1010poise, preferably 0.5 x 1011poise. In another aspect, the fibrillatable binder is coagulum (i.e. co-coagulated agglomerates / particles) of at least one fibrillatable PTFE having a melt creep viscosity (MCV) of at least 0.5 x 1010poise, preferably at least 0.5 x 1011poise, and a second PTFE that is different from the first PTFE, wherein the second PTFE is more friable and less fibrillatable than the first PTFE. The fibrillizable and friable nature of the binder compositions helps to promote homogeneous mixing with the electrode active materials in the electrode compositions and enables good mechanical properties of the resulting electrode films.

[0042] In another aspect, a cathode is provided comprising a current collector bound / laminated to the self-supporting electrode film described according to any of the previous aspects described above.Attorney Docket No.: FP0033-W001

[0043] In a nineth aspect, a lithium-ion battery is provided comprising the cathode described in the above aspect.

[0044] In a tenth aspect, a method to obtain an electrode film having an elongation of at least 8, 9 or 10 % is provided comprising: a. providing an electrode composition comprising a dry blend of i. at least 95 wt% of an electrode active material particles; ii. 5 wt% or less of a fibrillatable binder; and iii. 0 to 3 wt% of electrically conductive particles; b. mixing under sufficient shear to partially fibrillate the fibrillatable binder and form a free-standing electrode film, wherein the total amount of energy input into the mixing process is no more than 50%, 40%, 30% or 25% of the total energy used to reach a maximum torque for the same electrode composition; wherein the electrode film comprises an elongation of at least 8, 9 or 10%.

[0045] Embodiments of the tenth aspect can include one or any combination of two or more of the following features.

[0046] Elongation % is determined using a 20 mm x 5.3 mm cross section sample of the free-standing electrode film having a thickness of approximately 350 pm and applying a tensile strain to the samples at a 10% per minute pure tensile strain rate at approximately room temperature (~22 °C).

[0047] The electrode active material particles have a D50 (median) particle size of 3 pm or less.

[0048] The electrode active material is lithium iron phosphate (“LFP”).

[0049] The binder is at least one fibrillated polytetrafluoroethylene (PTFE) resin based on a PTFE resin having a melt creep viscosity of at least 0.5 x 1010poise prior to fibrillation, preferably at least 0.5 x 1011poise prior to fibrillation.

[0050] The fibrillated binder was a cocoagulate prior to fibrillation, said cocoagulate comprising at least one fibrillatable PTFE having a melt creepAttorney Docket No.: FP0033-W001 viscosity (MCV) of at least 0.5 x 1010poise, preferably at least 0.5 x 1011poise, and a second PTFE that is different from the first PTFE, wherein the second PTFE is more friable and less fibrillatable than the first PTFE.

[0051] The second PTFE comprises a melt creep viscosity less than the melt creep viscosity of the first PTFE.

[0052] The first PTFE and said second PTFE are independently PTFE homopolymers, modified PTFE polymers, and any combination thereof.

[0053] The weight percent of the first PTFE in the cocoagulate is at least 30, 40, 50, 60, 70, 80, 90% based on the total weight of said cocoagulate.

[0054] The approaches described here can have one or more of the following advantages. The electrode compositions described here are substantially homogeneously mixed and fibrillated, which contributes to good mechanical properties, e.g., elongation and flexibility, of electrode films formed of these electrode compositions.

[0055] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF DRAWINGS

[0056] FIG. 1 is a schematic diagram of a battery.

[0057] FIGS. 2A and 2B are graphs of particle size distributions of polymers prior to application of pressure (FIG. 2A) and after application of 40 psi of external pressure (FIG. 2B).

[0058] FIGS. 3-4 show elongation graphs of electrode films including various binder compositions.

[0059] FIG. 5 is a graph of elongation of electrode films including various binder compositions.Attorney Docket No.: FP0033-W001

[0060] FIG. 6 is a graph of elongation of electrode films including various binder compositions.

[0061] FIG. 7 is a graph of torque evolution for various electrode compositions.

[0062] FIG. 8 is a graph of elongation of electrode films including various binder compositions.

[0063] FIG. 9A is a scanning electron microscopy (SEM) image of small particle lithium iron phosphate (LFP).

[0064] FIG. 9B is an SEM image of an electrode composition including LFP.

[0065] FIG. 10 is a graph of elongation values for various electrode compositions at both 2 wt% and 4 wt% binder loading illustrating that physical blending of fluoropolymer binders is inferior to cocoagulates.DETAILED DESCRIPTION OF THE INVENTION

[0066] This disclosure relates to dry electrode compositions for use in solvent-less fabrication of electrode (e.g., cathode) films for lithium-ion batteries. The electrode compositions described here include a dry powder binder composition that includes a first fluoropolymer that is co-coagulated with a second fluoropolymer. The first fluoropolymer is more fibrillizable than the second fluoropolymer and the second fluoropolymer is more friable than the first fluoropolymer, providing the co-coagulated binder compositions with both fibrillizability and friability. The electrode compositions also include small particles of an electrode active material, such as a cathode active material. The fibrillizable and friable nature of the binder compositions promotes homogeneous mixing with the cathode active materials in the electrode compositions and enables good mechanical properties of the resulting cathodes, e.g., providing robust elongation.

[0067] The electrode active materials used in the electrode compositions described herein are, e.g., small particles of a cathode active material such as a lithium transition metal phosphate, e.g., lithium iron phosphate (LFP). SmallAttorney Docket No.: FP0033-W001 particle cathode active material is advantageous in providing good battery operational characteristics. However, solvent-free manufacturing of cathodes incorporating small particle cathode active material can present challenges, e.g., in terms of binder fibrillation, film mechanical properties such as cohesiveness, and processability.

[0068] The use of dry powder binder compositions including a first, more fibril lizable fluoropolymer co-coagulated with a second, more friable fluoropolymer, as described here, helps to mitigate some of these challenges associated with the use of small particle cathode active material. For instance, the co-coagulated nature of the first and second fluoropolymers allows for intimate mixing between the two fluoropolymers than can be achieved by simple physical mixing of the two polymers. This intimate mixing in turn enables the emergence of synergistic effects that take advantage of both the more f ibrill izable nature of the first fluoropolymer and the more friable nature of the second fluoropolymer. These binder compositions have a friability that is between that of the first and second fluoropolymers, while still retaining fibri llizabil ity sufficient to enable fabrication of mechanically robust cathode films.

[0069] Without being bound by theory, it is believed that the presence of the second fluoropolymer contributes friability to the binder composition, allowing agglomerates of the binder composition to break down into small particles when mixed with the small particle cathode active material. The close match between the particle size of the resulting binder particles and the small particle cathode active material facilitates homogeneous mixing in the dry electrode composition. The presence of the second fluoropolymer contributes fibrillizability: those small particles of the binder composition mixed with the small particle cathode active material are readily fibril lizable, yielding a well-dispersed fibrillar network that provides robust mechanical properties to a resulting electrode film.Electrode compositions and electrodes containing co-coagulated binder

[0070] The electrode composition includes small particles of electrode active material, e.g., cathode active material. For instance, the small particle cathodeAttorney Docket No.: FP0033-W001 active material can be a lithium transition metal phosphate, such as lithium iron phosphate, LiFePCU (LFP) or lithium manganese phosphate, LiMnPCU. The cathode active material has a Dso particle size of less than 3 pm or less than 2 pm, e.g., between 1-2 pm or between 1 -1.5 pm (referred to here as “small particle cathode active material”).

[0071] The small particle cathode active material is mixed with a dry powder binder composition including a first, f ibrill izable fluoropolymer co-coagulated with a second, friable fluoropolymer to form the electrode composition. Cocoagulation is discussed further infra and in International Patent Application No. PCT / US2023 / 033819, filed September 27, 2023, publishing as WO2024 / 072861 A1.

[0072] Generally, and as discussed in more detail infra, the first fluoropolymer in the dry powder binder composition is more fibrillizable than the second fluoropolymer and the second fluoropolymer is more friable than the first fluoropolymer. The molecular weight of the first fluoropolymer is greater than the molecular weight of the second fluoropolymer. The first and second fluoropolymers have different melt creep viscosity values.

[0073] The first fluoropolymer is a tetrafluoroethylene (TFE)-based polymer. A TFE-based fluoropolymer refers to a polymer, at least a portion of which has repeating units arising from TFE monomer. In some examples, the first fluoropolymer is polytetrafluoroethylene (PTFE), which is a TFE homopolymer that consists of or consists essentially of repeating units of TFE monomer.

[0074] In some examples, the first 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 a copolymer of TFE with a small concentration of comonomer (e.g., less than 2 weight % (wt.%), less than 1 wt.%, or less than 0.5 wt.%, e.g., between 0.05 and 0.5 wt.% of the comonomer). For instance, theAttorney Docket No.: FP0033-W001 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.

[0075] In some examples, the first fluoropolymer is a TFE-based core-shell polymer. A core-shell polymer is a structured composite polymer that includes a first polymer composition in a core of the polymer and a second, different polymer composition in a shell of the polymer. The core polymer, the shell polymer, or both are TFE-based polymers, e.g., PTFE or a TFE-based copolymer such as PFA or modified PTFE. In some cases, only one of the core polymer and the shell polymer is a TFE-based polymer and the other of the core polymer and the shell polymer is a different fluoropolymer, such as Viton™. In some examples the core polymer and the shell polymer have different molecular weights.

[0076] In some examples, the first fluoropolymer is itself a co-coagulate of a TFE-based polymer (e.g., PTFE or a TFE-based copolymer such as PFA or modified PTFE) with another polymer, such as a different TFE-based polymer or a different fluoropolymer.

[0077] The second fluoropolymer is also a tetrafluoroethylene (TFE)-based polymer and has a composition different from that of the first fluoropolymer. In some examples, the second fluoropolymer is a TFE-based copolymer, such as a PFA or a modified 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),Attorney Docket No.: FP0033-W001 chlorotrifluoroethylene (CTFE), perfluorobutyl ethylene (PFBE), or other similar monomers that introduce relatively sterically bulky side groups into the PTFE polymer chain.

[0078] In some examples, the second fluoropolymer is a TFE-based coreshell polymer. The core polymer, the shell polymer, or both are TFE-based polymers, e.g., PTFE or a TFE-based copolymer such as PFA or modified PTFE. In some cases, only one of the core polymer and the shell polymer is a TFE- based polymer and the other of the core polymer and the shell polymer is a different fluoropolymer. In some examples the core polymer and the shell polymer have different molecular weights.

[0079] In some examples, the second fluoropolymer is itself a co-coagulate of a TFE-based polymer (e.g., PTFE or a TFE-based copolymer such as PFA or modified PTFE) with another polymer, such as a different TFE-based polymer or a different fluoropolymer.

[0080] The first fluoropolymer is fibril lizable, and in particular is more fibril lizable than the second fluoropolymer. A fibri llizable polymer is a polymer that is capable of forming fibrils when subjected to shear forces. Fibrils have at least one dimension in the nanoscale (e.g., < 100 nm) and can vary in length from submicrometer to tens of micrometers.

[0081] The second fluoropolymer is friable, and in particular is more friable than the first fluoropolymer. 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 fibril lating the polymer. Friability of a polymer can be quantified by applying an external pressure to the polymer, causing the polymer to break down into particles. The particle size of the resulting particles is an indication of the friability of the polymer: smaller particles indicate a more friable polymer. For instance, when measured after application of 60 pounds per square inch (psi) (~414 kPa) of external pressure, the second fluoropolymer has a Dso particle size of less than 100 pm or less than 50 pm, e.g., between 5 pm and 100 pm,Attorney Docket No.: FP0033-W001 between 10 pm and 100 pm, between 10 pm and 50 pm, or between 10 pm and 20 pm. The first fluoropolymer particle size when measured after application of 60 psi (414 kPa) of external pressure is larger than that of the second fluoropolymer. For instance, the first fluoropolymer has a Dso particle size of between 100 pm and 300 pm, e.g., between 100 pm and 200 pm, or between 200 pm and 300 pm.

[0082] The first and second fluoropolymers have different melt creep viscosities. For instance, the first fluoropolymer has a melt creep viscosity (MCV) of at least about 0.5 x 1010poise (0.5 x 109Pa S), preferably at least about 0.5 x1011poise (0.5 x 1010Pa S), e.g., between about 0.5 x 1010poise (0.5 x 109Pa S) and about 6.0 x 1011poise (6.0 x 101° Pa S), preferably between about 0.5 x 1011poise (0.5 x 101° Pa S) and about 6.0 x 1011poise (6.0 x 101° Pa 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 1011poise (2.5 x 1010Pa S), about 3.0 x 1011poise (3.0 x 101° Pa S), about 3.5 x 1011poise (3.5 x 101° Pa S), about 4.0 x 1011poise (4.0 x 101° Pa S), about 4.5 x 1011poise (4.5 x 101° Pa 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 1 o11poise (6.0 x 1010Pa S). The second fluoropolymer has anMCV lower than that of the first fluoropolymer, e.g., a melt creep viscosity that is between about 0.5 x 1011poise and about 6.0 x 1011poise and less than the MCV of the first fluoropolymer. MCV is measured by the method described in Ebnesajjad, Sina, (2015), Fluoroplastics, Volume 1 - Non-Melt Processible Fluoropolymers - The Definitive User's Guide and Data Book (2nd Edition), Appendix 5, Melt Creep Viscosity of Polytetrafluoroethylene, pp. 660-661 , with reference to US Patent No. 3,819,594, incorporated here by reference in its entirety.

[0083] The first fluoropolymer and second fluoropolymers have different molecular weights. For instance, first fluoropolymer has a higher molecular weight than the second fluoropolymer.Attorney Docket No.: FP0033-W001

[0084] In some examples, the first fluoropolymer and second fluoropolymer are present in the dry powder binder in approximately equal amounts, e.g., in a weight ratio of about 50:50. In some examples, the dry powder binder composition contains more of the first fluoropolymer than the second fluoropolymer by weight, e.g., the ratio of the weight of the first fluoropolymer in the dry binder composition to the weight of the second fluoropolymer in the dry powder binder composition is more than 50:50, e.g., between 90:10 and 50:50, e.g., 90:10, 80:20, 70:30, or 60:40. In some examples, the dry powder binder composition contains more of the second fluoropolymer than the first fluoropolymer by weight, e.g., the ratio of the weight of the first fluoropolymer in the dry binder composition to the weight of the second fluoropolymer in the dry powder binder composition is less than 50:50, e.g., 40:60, 30:70, 20:80, or 10:90. The weight ratio can be selected depending on desired characteristics for the dry powder binder composition.

[0085] The dry powder binder composition, prior to mixing with the small particle cathode active material to form the electrode composition, is in the form of agglomerates composed of co-coagulated first and second fluoropolymer. The agglomerates have a size of between about 200 pm and about 1000 pm, e.g., between about 200 pm and about 500 pm. In the agglomerates, the first and second fluoropolymers are physically intermixed with one another with domains on the micron scale or smaller, e.g., with average domain size of 10 pm or less, 1 pm or less, 500 nm or less, or 100 nm or less. The average domain size can be at least 1 nm. The agglomerates are both friable and fibrillizable.

[0086] This co-coagulated structure and its properties differ from a simple physical mixture of the first and second fluoropolymers. For instance, physical mixtures of the first and second fluoropolymers include large domains of the first and second fluoropolymers, large particle sizes, agglomerations of the first and second fluoropolymers, etc. This microstructure has not been observed to provide the mechanical improvements discussed herein. By contrast, the cocoagulated structure is a homogenous or substantially homogenous mixture with the micron or submicron domain sizes noted above.Attorney Docket No.: FP0033-W001

[0087] For instance, the friability of the dry powder binder composition is between that of the first fluoropolymer and that of the second fluoropolymer, i.e., the dry powder binder composition is more friable than the first fluoropolymer alone but less friable than the second fluoropolymer alone. For instance, when measured after application of 60 pounds per square inch (psi) of external pressure, the dry powder binder composition has a Dso particle size of between 10 pm and 200 pm, e.g., between 10 pm and 100 pm or between 100 pm and 200 pm, between 10 pm and 50 pm, between 10 pm and 20 pm, between 50 pm and 100 pm, between 100 pm and 150 pm, or between 150 pm and 200 pm. The particle size of the dry powder binder composition after application of external pressure depends on the relative amounts of the first and second fluoropolymers in the dry powder binder composition: more of the second fluoropolymer in the dry powder binder composition corresponds to smaller particle size, e.g., to a more friable dry powder binder composition.

[0088] In addition, the dry powder binder composition is fibrillizable, e.g., with a fibrillizability between that of the first fluoropolymer and that of the second fluoropolymer: the dry powder binder composition is more fibrillizable than the first fluoropolymer alone but less fibrillizable than the second fluoropolymer alone. The fibrillizability of the dry powder binder composition depends on the relative amounts of the first and second fluoropolymers in the dry powder binder composition: more of the first fluoropolymer in the dry powder binder composition corresponds to a more fibrillizable dry powder binder composition.

[0089] When the dry powder binder composition is mixed with the small particle cathode active material, the friability of the binder composition allows the binder composition to break down into smaller particles. The smaller binder particles have at least one dimension that is generally similar to the size of the small particle cathode active material. These smaller fluoropolymer particles fibrillate, e.g., due to the presence of the fibrillizable first polymer, forming small fibrils. The presence of small particles of the binder composition allows for substantially homogeneous mixing of the binder composition and the small particle cathode active material. Moreover, the fibrillation of these small particlesAttorney Docket No.: FP0033-W001 of the binder composition contributes robust mechanical properties to the electrode composition and ultimately to the resulting electrode film.

[0090] In some examples, the electrode composition further includes a conductive additive such as a conductive carbon, e.g., carbon black, porous carbon, carbon nanotubes, carbon fiber, vapor grown carbon fiber, graphene sheets, acetylene black, or other conductive carbon.

[0091] In one embodiment, the electrode compositions described here contain from 0.5-10 wt.% binder, preferably between 1-5 wt.% binder, e.g., 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.% or 5 wt% binder. The electrode compositions also contain from 95-98 wt.% small particle cathode active material, e.g., 95 wt.%, 96 wt.%, 97 wt.%, or 98 wt.%; and 0-10 wt.%, e.g., 1 -10%, of a conductive additive such as conductive carbon.

[0092] Electrode films prepared from the electrode compositions described here can be fabricated in various thicknesses, , e.g., in a thickness from 200-500 pm, e.g., 300-400 pm, preferably about 350 pm. The fibrillation of the binder composition in the electrode composition and the substantially homogeneous mixing of the constituent components of the binder composition contribute to good mechanical properties of these electrode films, e.g., cohesiveness, mechanical strength, and flexibility.

[0093] For instance, electrode films formed from the electrode compositions described here have an elongation of at least 1 % or at least 10%, e.g., 1 -15%, 1 - 10%, or 10-15%. In a preferred aspect, the electrode films have an elongation of at least 8%, 9% or 10% as measured using the method described herein. The elongation of a film refers to the strain at the ultimate tensile strength of the film. Elongation as used here was measured by cutting samples to a 20 mm x 5.3 mm cross section (preferably having a thickness of approximately 350 pm) and applying a tensile strain to the samples at a 10% per minute pure tensile strain rate at approximately 22 °C (i.e. ambient room temperature)

[0094] Electrode films formed from the electrode compositions described here are flexible. Flexibility can be characterized by a rod test, in which a film isAttorney Docket No.: FP0033-W001 wrapped around a rod of a given diameter. The smaller the diameter of the rod that the film can be wrapped around without cracking, the more flexible the film. The electrode films described here have flexibility characterized by a rod diameter of between 1 mm and 5 mm in such a rod test, e.g., between 1 mm and 4 mm or between 1 mm and 3 mm where the flexible electrode films are capable of being formed around said rods without breakage or substantial cracking.Methods of making electrode compositions and electrodes containing cocoagulated binder

[0095] Methods of making the electrode compositions described above include co-coagulating the first and second fluoropolymers to form a dry powder binder composition composed of agglomerates and mixing the dry powder binder composition with small particle cathode active material and optionally a conductive additive to form an electrode composition.

[0096] Co-coagulating the first and second fluoropolymers includes forming an aqueous dispersion or solution of the first fluoropolymer and an aqueous dispersion or solution of the second polymer and combining the two dispersions or solutions to co-coagulate the first fluoropolymer and the second fluoropolymer, thereby forming agglomerates including co-coagulates of the first fluoropolymer and the second fluoropolymer. Further discussion of co-coagulation is provided in International Patent Application No. PCT / US2023 / 033819, filed September 27, 2023, publishing as WO2024 / 072861 A1 , and in U.S. 7,947,775, issued May 24, 2011 , incorporated herein by reference in its entirety.

[0097] In some examples, the second polymer is in the form of an aqueous dispersion capable of being coagulated, and the aqueous dispersions of the first and second polymers are combined and mixed. Instead of or in addition to aqueous dispersion forms, any other suitable suspended fine particulate form can be used. The resulting mixture of the first and second polymer aqueous dispersions is then co-coagulated. The 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-Attorney Docket No.: FP0033-W001 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 to about 20 weight percent 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.

[0098] The vigorous agitation and / or stirring causes co-coagulation of the first and second fluoropolymers, which “crash out” in the form of a powder including agglomerates of the first and second fluoropolymers co-coagulated with one another. Crashing out can be spontaneous or aided, e.g., by freezing to initiate precipitation. The 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, 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 made from the agglomerates. In some implementations, the powder is dried at drying temperature(s) in a range from 100°C to 180°C.

[0099] The agglomerates of the dry powder binder composition are mixed with small particle cathode active material and, optionally, a conductive additive to form the electrode composition. This mixing induces deagglomeration, comminution, and fibrillation of the binder composition, resulting in a substantially homogeneous mixture of the small particle cathode 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.

[0100] Formation of electrode films using the electrode compositions described here can also be carried out in a solvent-free process, e.g., withoutAttorney Docket No.: FP0033-W001 requiring a slurry. For 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.

[0101] 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 cathode 104 is formed of the electrode composition described here, e.g., formed of an electrode composition including small particle cathode active material (e.g., small particle LFP) and a polymeric binder including co-coagulates of the first fluoropolymer and the second fluoropolymer). In some examples, the cathode also includes a conductive additive such as conductive carbon.Controlling Total Energy Input During High Shear Mixing to Obtain Electrode Films with Target Elongation

[0102] Torque data was collected to elucidate the total energy input of a powder mixture. The torque trends were used in understanding how the polymers interact with other constituents, which leads to variability in the fibril network and resulting powder microstructure. Terminating mixing of the electrode composition at different points along the torque curve produces electrode compositions that result in electrodes having different properties, e.g., different elongation; demonstrating the ability to provide a “tunable fibril network”. Relative time points (correlating to the total amount of energy input at each time point during high shearing / fibrillation) were established based on the maximum torque observed for the respective binder / filler particle compositions described herein. It was discovered that to obtain the desired elongation of at least 8% in a free-standing electrode film comprising: a. at least 94 wt% of an electrode active material having a Dso (median) particle size of 3 pm or less;Attorney Docket No.: FP0033-W001 b. 5 wt% or less of a fibri Hated binder; and c. 0 to 3 wt% of electrically conductive particles; one has to limit the total amount of energy input during high shear mixing to a fraction of the total amount of energy input at maximum torque (measured in J / g) for the binder / fil ler particle compositions described herein. That is to say, the total amount of energy input should be no more than 50%, 40%, 30% or preferably 25% of the total amount of energy input (measured at maximum torque - corresponding to maximum fibrillation). Assuming the amount of energy input during high shear mixing is essentially constant, this should also correspond to a time point (“stop point”) that is about 50%, 40%, 30%, or preferably 25% of the time it takes to reach maximum torque (corresponding to the relative degree of fibrillation).

[0103] In one embodiment, electrode films with at least 95% of a small particle size electrode active material (e.g. a Dso of 3 pm or less; preferably in the range of 0.1 to 3 pm, and most preferably from about 0.5 pm to about 2 pm) with a fibrillatable binder content of 5 wt% or less, preferably 4 wt% or less, and most preferably from about 2 wt% to about 4 wt% should only be partially fibri Hated (based on a fraction of the total energy input measured at maximum torque during high shear mixing). In one embodiment, the fibril lated binder with the above compositions should be only partially fibri Hated (correlating to no more than 50%, 40%, 30% or preferably 25% of the total amount of energy input required to achieve a maximum torque during high shear mixing).

[0104] The elongation of a film refers to the strain at the ultimate tensile strength of the film. The present electrode films have an elongation of at least 8%, preferably at least 9%, and most preferably at least 10%. Elongation was measured using a sample of approximately 350 pm thickness which was cut into samples having 20 mm x 5.3 mm cross section and applying a tensile strain to the samples at a 10% per minute tensile strain rate at approximately room temperature (~22 °C). In one embodiment, the elongation % is calculated based on an electrode film comprising:Attorney Docket No.: FP0033-W001 about 94% of an electrode active material having a Dso particle size of 3 pm or less; about 4 wt% of a fibri Hated binder; and about 2 wt% of electrically conductive particles; where the sample of the electrode film used for testing comprises a 20 mm x 5.3 mm cross section having a thickness of approximately 350 pm and applying a tensile strain to the samples at a 10% per minute pure tensile strain rate at approximately room temperature (~22 °C).

[0105] In a first aspect, an electrode film for a lithium-ion battery is provided comprising a. at least 95 wt% of an electrode active material having a Dso (median) particle size of 3 pm or less; b. 5 wt% or less of a fibri Hated binder; and c. 0 to 3 wt% of electrically conductive particles; wherein the electrode film comprises an elongation of at least 8%, 9% or 10% according to the method described herein (using an ~350 pm thick sample having a 20 mm x 5.3 mm cross section and applying a tensile strain to the samples at a 10% per minute pure tensile strain rate at approximately room temperature (~22 °C)).

[0106] In a further aspect to said first aspect, the electrode film is a cathode film and the electrode active material is lithium iron phosphate (“LFP”).

[0107] In a further aspect to any of the above aspects, fibrillated binder is at least one fibrillated polytetrafluoroethylene (PTFE) resin based on a PTFE resin having a melt creep viscosity of at least 0.5 x 1010poise prior to fibrillation, preferably at least 0.5 x 1011poise.

[0108] In a further aspect to any of the above aspects, the fibrillated binder was a cocoagulate prior to fibrillation, said cocoagulate comprising at least one fibrillatable PTFE having a melt creep viscosity (MCV) of at least 0.5 x 1010poise, preferably at least 0.5 x 1011poise, and a second PTFE that is different from the first PTFE, wherein the second PTFE is more friable and less fibrillatable thanAttorney Docket No.: FP0033-W001 the first PTFE. In yet a further aspect, the second PTFE comprises a melt creep viscosity less than the melt creep viscosity of the first PTFE.

[0109] In a further aspect to any of the above aspects, said first PTFE and said second PTFE are independently PTFE homopolymers, modified PTFE polymers, and any combination thereof.

[0110] In a further aspect to any of the above aspects the weight percent of the first PTFE in the cocoagulate is at least 30, 40, 50, 60, 70, 80, 90% based on the total weight of said cocoagulate.

[0111] A method to obtain an electrode film having an elongation of at least 8, 9 or 10 % is also provided comprising: a. providing an electrode composition comprising a dry blend of i. at least 95 wt% of an electrode active material particles; ii. 5 wt% or less of a fibrillatable binder; and iii. 0 to 3 wt% of electrically conductive particles; b. mixing under sufficient shear to partially fibrillate the fibrillatable binder and form a free-standing electrode film, wherein the total amount of energy input into the mixing process is no more than 50%, 40%, 30% or 25% of the total energy used to reach a maximum torque for the same electrode composition; wherein the electrode film comprises an elongation of at least 8, 9 or 10%.

[0112] In a further aspect to the above method, the elongation % is calculated of the free-standing electrode film is measured using a 20 mm x 5.3 mm cross section sample of the free-standing electrode film and applying a tensile strain to the samples at a 10% per minute pure tensile strain rate at approximately room temperature (~22 °C).

[0113] In a further embodiment to the above method, the electrode active material particles have a Dso (median) particle size of 3 pm or less.Attorney Docket No.: FP0033-W001

[0114] In a further embodiment to the above method, the electrode active material is lithium iron phosphate (“LFP”).

[0115] In a further embodiment to the above method, binder is at least one fibrillated polytetrafluoroethylene (PTFE) resin based on a PTFE resin having a melt creep viscosity of at least 0.5 x 1010poise prior to fibrillation, preferably at least 0.5 x 1011poise.

[0116] In a further embodiment to the above method, the fibrillated binder was a cocoagulate prior to fibrillation, said cocoagulate comprising at least one fibrillatable PTFE having a melt creep viscosity (MCV) of at least 0.5 x 1010poise, preferably at least 0.5 x 1011poise, and a second PTFE that is different from the first PTFE, wherein the second PTFE is more friable and less fibrillatable than the first PTFE. In yet a further aspect, the second PTFE comprises a melt creep viscosity less than the melt creep viscosity of the first PTFE.

[0117] In a further embodiment to the above method, said first PTFE and said second PTFE are independently PTFE homopolymers, modified PTFE polymers, and any combination thereof.

[0118] In a further embodiment to the above method, the weight percent of the first PTFE in the cocoagulate is at least 30, 40, 50, 60, 70, 80, 90% based on the total weight of said cocoagulate.Examples

[0119] The following polymers are used in these examples. The polymers are obtainable from a variety of manufacturers including, but not limited to, The Chemours Company, Wilmington, DE.

[0120] PTFE1 : PTFE1 is a PTFE homopolymer having an MCV of about 4.1 x 1011poise, a standard specific gravity (SSG) of about 2.16, a bulk density of 550 g / L, and an average particle size of 500 pm, meeting the requirements of ASTM D4895, Type I, Grade 1 , Class A.

[0121] PTFE2: PTFE2 is a modified PTFE including small concentrations (e.g. < 0.02 wt%) of hexafluoropropylene (HFP) and perfluorobutyl ethyleneAttorney Docket No.: FP0033-W001(PFBE) and having an MCV of about 1.5 x 1011poise, an SSG of 2.16, a bulk density of 550 g / L, and an average particle size of about 500 pm, meeting the requirements of ASTM D4895, Type I, Grade 1 , Class C.

[0122] PTFE3 is a modified PTFE having a small concentration (~0.038 wt%) of PFBE and having a MCV of about 0.92 x 1011poise, an SSG of about 2.18, a bulk density of 460 g / L, and an average particle size of about 500 pm, meeting the requirements of ASTM D4895, Type I, Grade 3, Class C.Example 1 : Particle Size Characterization of Co-coagulated Agglomerates

[0123] The particle size for various polymer compositions was measured as a function of applied pressure. Pressure ranging from 0-60 pounds per square inch (psi) was applied and particle size was measured by dynamic light scattering using a Microtrac system (Verder Scientific, Haan, Germany). The characterized polymer compositions included fine powder PTFE1 alone, fine powder PTFE2 alone, co-coagulates of PTFE1 and PTFE2 in various weight ratios (20:80 PTFE1 :PTFE2, 50:50, and 80:20) (labeled as “PTFE1 / PTFE2”), and physical mixtures of PTFE1 and PTFE2 (labeled as “PTFE1 + PTFE2”) in a 50:50 weight ratio.

[0124] Table 1 summarizes the Dso (median) particle size (in pm) distribution at applied pressures of 0-60 psi (414 kPa), illustrating the friability of the compositions. The particle size distributions acquired at 0 psi and 40 psi are illustrated in FIGS. 2A and 2B, respectively.Attorney Docket No.: FP0033-W001Table 1Table 1. Dso particle size distribution for polymers of interest for small particleLFP at 0 psi, 2.3 psi, 10 psi, 20 psi, 40 psi, and 60 psi, illustrating the friability of the polymer compositions.

[0125] These results demonstrate that the PTFE1 / PTFE2 co-coagulations show improved friability compared to the physical blends (PTFE1 + PTFE2) of the PTFE powders. Moreover, co-coagulations with greater than or equal to 50 wt% PTFE2 have improved friability, which can be attributed to the greater friability of PTFE2. This friability of the co-coagulates contributes to the ability of dry powder binder compositions including these co-coagulates to mix homogeneously with small particle electrode active material and conductive carbon additives, as demonstrated in the following examples.Attorney Docket No.: FP0033-W001Example 2: Mechanical Characterizations

[0126] Dry powder electrode compositions were fabricated via batch mixing using a Brabender mixer (Anton Paar, Graz, Austria). The quality of the powder mixture that results from a batch mixing process is influenced by the distribution of electrode powder constituents (e.g., dry powder binder, active material particles, conductive additives) and by the degree of fluoropolymer fibrillation. To determine a suitable batch mixer fill factor for achieving a dry powder electrode composition that is usable for calendaring a uniform, flexible cathode with improved elongation, a comprehensive fill factor study was conducted.

[0127] The fill factor quantifies the proportion of the mixing chamber’s volume that is occupied by the material being mixed. The fill factor is calculated using the following equation:

[0128] Electrode compositions were mixed at various fill factors including LFP, Super P, and dry powder binder polymer in weight ratios of 95:3:2. The dry powder binder polymer was a co-coagulate of PTFE1 and PTFE2 in a 50:50 weight ratio (referred to as “Cocoag 2”). The time evolution of the torque of the electrode composition as a function of fill factor was evaluated.

[0129] These fill factor results demonstrated that a fill factor of more than 33% leads to mixtures with hard granules that lack the malleability that is generally required for unispeed roll calendaring. Subsequent examples in this document use a fill factor of 33% in the Brabender PL-2000 Plasti-Corder (Anton Paar, supra) at 100 °C at 30 rpm (revolutions per minute) using the high shear, roller-type blade, in a 40 cm3mixing head.

[0130] Torque data helps to elucidate the total energy input of a powder mixture. Torque trends can be used in understanding how polymers interact with other constituents, which can lead to variability in fibrillation and resulting powderAttorney Docket No.: FP0033-W001 microstructure. Terminating mixing of the electrode composition at different points along the torque curve produces electrode compositions that result in electrodes having different properties, e.g., different elongation values. Electrode compositions mixed at a fill factor of 33% were retrieved at different torque values and formed into electrodes for mechanical testing.

[0131] Specifically in the present example (Example 2), electrode compositions were retrieved from the mixer at two points in time: 50% before the maximum torque (referred to as “stop point A”) and 20% after the maximum torque (referred to as “stop point B”). Each stop point is expected to yield a different degree of fibrillation. These compositions were formed into electrode films using a unispeed roller at 85-90 °C at 140-150 revolutions per minute (rpm). Dynamic mechanical analysis (DMA) was completed to understand the influence of fill factor on the mechanical properties of electrodes formed from the malleable powder electrode composition samples.

[0132] FIG. 3 shows elongation results for electrode films formed from electrode compositions including LFP, Super P, and dry powder binder polymer in weight ratios of 95:3:2, mixed at a 33% fill factor. The dry powder binder polymer was a co-coagulate of PTFE1 and PTFE2 in an 80:20 weight ratio (i.e. 80 wt% PTFE1 :20 wt% PTFE2). The elongation of the electrode film formed from the electrode composition retrieved at stop points A and B was 4.74% ± 1 .76% and 3.06% ± 0.71 %, respectively. Samples were mechanically investigated using a TA Instruments Discovery DMA 850 (TA Instruments, New Castle, DE). Samples were cut to a 20 mm x 5.3 mm cross-section and elongation was evaluated by application of tensile strain at a 10% / min pure tensile strain rate at room temperature (~ 22 °C). This composition exhibits higher elongation at stop point A than a 50:50 PTFE1 / PTFE2 sample (results not shown), demonstrating that the composition of the fluoropolymer binder can lead to differences in the ideal stop point and the energy input required for preferential degree of fibrillation, and thus can impact (e.g., improve) mechanical properties of the resulting electrode film.Attorney Docket No.: FP0033-W001

[0133] FIG. 4 shows elongation results for electrode films formed from electrode compositions including LFP, Super P, and dry powder binder polymer in weight ratios of 95:3:2. The dry powder binder polymer was a co-coagulate of PTFE1 and PTFE2 in a 50:50 weight ratio. Two samples were prepared, one at a 28% fill factor and the other at a 33% fill factor. Statistically similar elongation values were found for electrode films prepared from these two samples: the 28% fill factor sample had an elongation of 1.18% ± 0.71 % and the 33% fill factor sample had an elongation of 1.27% ± 0.17%. These results confirm that the 33% fill factor used in the foregoing experiments is suitable for comparing behavior of various fluoropolymer compositions in the electrode compositions described here.

[0134] Further torque testing was performed for electrode compositions including LFP, Super P, and a binder composition in weight ratios of 95:3:2. The binder compositions tested were the unmixed polymers PTFE1 and PTFE2 and the three PTFE1 / PTFE2 co-coagulates discussed above: co-coagulates of PTFE1 and PTFE2 in weight ratios of 20:80 (“Cocoag 1”), 50:50 (“Cocoag 2”), and 80:20 (“Cocoag 3”). These torque testing experiments illustrated that PTFE1 has the highest maximum torque peak, followed by the three co-coagulates in decreasing order of the amount of PTFE1 contained in the co-coagulate. This trend lends confirmation to the understanding that when PTFE1 and PTFE2 are co-coagulated, synergistic properties such as fibrillation ability are available in solvent-free binder preparation processes.

[0135] Some of the electrode compositions tested in this torque testing experiment were fabricated into electrode films and DMA was performed to determine elongation of the films. The elongation of films prepared with binder compositions of PTFE1 / PTFE2 w / w 50:50, PTFE1 / PTFE2 w / w 80:20, and PTFE1 are 1.27% ± 0.17%, 4.74% ± 1.76%, 5.56% ± 1.37%, respectively, as shown in FIG. 5. These results demonstrate systematic trends in increased elongation values as the amount of PTFE1 in the co-coagulated binder composition increases.Attorney Docket No.: FP0033-W001

[0136] Further torque studies were performed on electrode compositions having different amounts of binder composition. Three electrode compositions were tested, each including LFP, Super P, and PTFE1 / PTFE2 w / w 50:50 binder composition, with weight ratios of 95:3:2, 95:2:3, and 94:2:4. These results demonstrated a systematic increase of the 50% before peak maximum torque value with an increase in the weight percent of the binder in the electrode composition, i.e. , demonstrating that increased amounts of binder lead to faster onset of torque increase. Elongation values for electrode films formed from these three electrode compositions were measured to be 1 .27% ± 0.17%, 5.97% ± 1 .63%, and 5.68% ± 1 .42%, respectively, as shown in FIG. 6. These experiments are relevant because more than 2 wt.%, e.g., between 2-4 wt.%, of binder in electrode compositions containing small particle cathode active material (e.g., small particle LFP) may be necessary to obtain electrode films with target elongation and tensile properties.

[0137] FIG. 7 shows torque curves for electrode compositions including 4 wt.% binder composition. The tested electrode compositions included LFP, Super P, and a binder composition in weight ratios of 94:2:4. The binder compositions tested were the unmixed polymers PTFE1 and PTFE2, the three PTFE1 / PTFE2 co-coagulates discussed above: co-coagulates of PTFE1 and PTFE2 in weight ratios of 20:80 (“Cocoag 1”), 50:50 (“Cocoag 2”), and 80:20 (“Cocoag 3”) taken at stop points “A” and “B”, and a 50:50 physical mixture PTFE1 + PTFE2. These torque curves illustrate that with increasing amounts of PTFE1 , there is an increase in the maximum torque value. By contrast, as the amount of PTFE2 increases, the onset time to fibrillation increases and the maximum torque value decreases.

[0138] The compositions tested in FIG. 7 were formed into electrode films using a unispeed roller at 85-90 °C at 140-150 rpm. Elongation values for these films, shown in FIG. 8, were measured to be 4.07% ± 0.55% (PTFE1 ), 4.06% ± 0.90% (Cocoag 3), 5.68% ± 1.42% (Cocoag 2), 5.76% ± 0.53% (Cocoag 1 ), and 3.23% ± 1.27% (PTFE2), respectively. The 50:50 physical mixture PTFE1 + PTFE2 had an elongation substantially similar to that of Cocoag 2.Attorney Docket No.: FP0033-W001

[0139] Table 2 summarizes the experimental results discussed above, which demonstrate for small particle LFP electrode compositions, e.g., showing the process-property relationships between total energy input for stop point A and the elongation value at maximum stress for each electrode composition.Table 2. Process-Property Relationships Derived from Total Energy Input for Stop Point A and the Corresponding Elongation PercentagesExample 3: Imaging of Cathode Materials

[0140] Imaging of cathode materials was conducted. FIG. 9A is a scanning electron microscopy (SEM) image of small particle (Dso = 1 pm) LFP. FIG. 9B is an SEM image of an LFP electrode composition including LFP, Super P, and PTFE binder in weight ratios of 95:3:2. Fibrillation of the PTFE binder can be observed in the image.Example 4 - Development of Electrode Films with at least 8% ElongationThis experiment was conducted using similar conditions as described above in Example 2 unless otherwise noted. There were some modifications to theAttorney Docket No.: FP0033-W001Brabender mixing step, including fill factor and stop point required to achieve an excess of 8% elongation. The data in FIG. 10 was obtained using a fill factor of 28% (or ~ 25 g) with a stop point on the torque curve at ~ 75% before the max torque curve (Stop Point “C”). The Brabender experiment was completed at 100 °C. The films were fabricated using 2 rollers on a Saueressig calendering machine (Matthews International Corporation, Pittsburgh, Pennsylvania). The temperature of the rollers was set at 120 °C with a 5 meters / min roller speed with a differential speed of 65% at the gap. The gap was set to 400 pm for the first pass and 300 pm for the second pass with a force of 20 kN.

[0141] FIG. 10 highlights the elongation values at both 2 wt% and 4 wt% binder loading in the electrodes. The 4 wt% binder loading samples have an electrode composition of LFP / Super P / PTFE w / w / w 94:2:4, whereas the 2 wt% binder loading samples have a composition of LFP / Super P / PTFE w / w / w 95:3:2. At 4 wt% binder loading, PTFE1 , PTFE2, Cocoag 3, and Physical Blend 1 have elongation % values of 3.53% ± 0.02%, 6.88% ± 1.08%, 5.21 % ± 0.74%, and 3.4%2 ± 0.87%; respectively. These were inferior to the other materials that exceeded the 8% elongation target. Cocoag 1 , Cocoag 2, and PTFE 3 have elongation % values of 9.73% ± 0.97%, 10.68% ± 0.62%, and 10.32% ± 1.09%; respectively. The key differentiators at 2 wt% binder loading were that the Cocoag 2 achieved an elongation of 8.06% ± 1.19%, whereas the Physical Blend 1 material only achieved an elongation of 4.34% ± 1 .60%. All elongation percentage values for the materials can be found in Table 3. Table 3 also includes the total energy input using the Brabender to achieve the desired fibrillation state of the composite material to achieve the elongation values mentioned herein.Attorney Docket No.: FP0033-W001Table 3. Total Energy Input for Stop Point C and the Corresponding Elongation Percentage valuesExample 5. Flexibility Measured Using Rod Bend TestTo perform the rod test, an electrode with a sample size of 0.35 mm thickness x 0.7 mm width x 30 mm length was taped down to a flat surface. The rod of a specified diameter was then attached to the opposite end of the sample. The sample was then rolled around the rod to meet the taped end, followed by unrolling the rod back to the initial position. If the electrode sample was rolled up around the testing rod without any cracking or structural failure / breakage, then it was qualitatively evaluated as “PASS”. If the electrode led to cracks or breakage after the rolling test, then it was qualitatively evaluated as “FAIL”. The results for a selection of binders are found in the Table 4.Table 4. Flexibility Testing - Rod Bend Test Results

Claims

Attorney Docket No.: FP0033-W001What is claimed is:1 . An electrode composition for a lithium-ion battery, the composition comprising: a dry powder binder composition comprising: a first fluoropolymer co-coagulated with a second fluoropolymer, wherein the first fluoropolymer is more fibril lizable than the second fluoropolymer, and wherein the second fluoropolymer is more friable than the first fluoropolymer; and an electrode active material having a Dso particle size of less than 3 pm.

2. The electrode composition of claim 1 , wherein the molecular weight of the first fluoropolymer is greater than the molecular weight of the second fluoropolymer.

3. The electrode composition of claim 1 or 2, wherein the first and second fluoropolymers have different melt creep viscosity (MCV) values.

4. The electrode composition of claim 3, wherein the first fluoropolymer has a mean MCV of at least 0.5 x 1011poise (0.5 x 1010Pa S).

5. The electrode composition of claim 3 or 4, wherein the first fluoropolymer has a higher mean MCV than the second fluoropolymer.

6. The electrode composition of any of the preceding claims, wherein the first fluoropolymer is a homopolymer.Attorney Docket No.: FP0033-W0017. The electrode composition of any of the preceding claims, wherein the second fluoropolymer is a copolymer.

8. The electrode composition of any of the preceding claims, wherein each of the first and second fluoropolymers comprises a tetrafluoroethylene (TFE)-based polymer.

9. The electrode composition of claim 8, wherein at least one of the first fluoropolymer or the second fluoropolymer comprises a modified PTFE.

10. The electrode composition of claim 8 or 9, wherein at least one of the first fluoropolymer or the second fluoropolymer comprises a TFE-based copolymer.11 . The electrode composition of any of the preceding claims, wherein at least one of the first fluoropolymer or the second fluoropolymer comprises a cocoagulate of PTFE with another fluoropolymer.

12. The electrode composition of any of the preceding claims, wherein at least one of the first fluoropolymer or the second fluoropolymer is a core-shell polymer.

13. The electrode composition of claim 12, wherein a core portion of the coreshell polymer has a different molecular weight than a shell portion of the coreshell polymer.

14. The electrode composition of claim 12 or 13, wherein a composition of the core portion of the core-shell polymer differs from a composition of the shell portion of the core-shell polymer.Attorney Docket No.: FP0033-W00115. The electrode composition of claim 14, wherein the second fluoropolymer comprises a core-shell copolymer, wherein the core portion comprises a first TFE-based copolymer and the shell portion comprises a second TFE-based copolymer.

16. The electrode composition of any one of the preceding claims, wherein the binder comprises equal to or greater than 50% by weight of the second fluoropolymer.

17. The electrode composition of claim 1 , wherein the binder comprises equal to or greater than 50% by weight of the first fluoropolymer.

18. The electrode composition of claim 1 , wherein the binder comprises approximately equal amounts by weight of the first and second fluoropolymers.

19. The electrode composition of any one of the preceding claims, wherein the electrode active material comprises a lithium transition metal phosphate.

20. The electrode composition of claim 19, wherein the electrode active material comprises lithium iron phosphate (LFP).21 . The electrode composition of any one of the preceding claims, wherein the electrode active material has a median particle size of between 1-1 .5 pm.

22. The electrode composition of any of the preceding claims, comprising a conductive additive.

23. The electrode composition of claim 22, wherein the conductive additive comprises a conductive carbon additive.Attorney Docket No.: FP0033-W00124. The electrode composition of any one of the preceding claims, wherein the electrode composition is in the form of an electrode film that has an elongation of at least 1 % when measured on a 20 mm x 5.3 mm sample at an applied tensile strain rate of 10% per minute at room temperature (~22 °C).

25. The electrode composition of claim 24, wherein the electrode film has an elongation of between 1 % and 15%.

26. The electrode composition of claim 25, wherein the electrode film has an elongation of between 1 % and 10%.

27. The electrode composition of claim 24, wherein the electrode film has an elongation of at least 10%.

28. The electrode composition of any one of the preceding claims, wherein the dry powder binder composition is fibril lizable.

29. The electrode composition of any one of the preceding claims, wherein the dry powder binder composition is friable.

30. The electrode composition of any one of the preceding claims, wherein the dry powder binder composition, prior to mixing with the electrode active material, has a particle size of between 10 pm and 200 pm as measured by dynamic light scattering after application of 60 psi (414 kPa) of pressure to the dry powder binder composition.Attorney Docket No.: FP0033-W00131 . The electrode composition of any of the preceding claims, wherein the dry powder binder composition, prior to mixing with the electrode active material, has a particle size that is greater than the particle size of the first fluoropolymer and less than the particle size of the second fluoropolymer, as measured by dynamic light scattering after application of 60 psi (414 kPa) of pressure to the dry powder binder composition.

32. The electrode composition of any of the preceding claims, wherein: the second fluoropolymer has a particle size of less than 100 pm, as measured by dynamic light scattering after application of 60 psi (414 kPa) of pressure to the dry powder binder composition; and the first fluoropolymer has a particle size greater than the particle size of the second fluoropolymer.

33. The electrode composition of any of the preceding claims, comprising between about 1 -4 wt.% dry powder binder composition.

34. An electrode for a lithium-ion battery, the electrode comprising: a film comprising: a binder composition comprising: a first fluoropolymer co-coagulated with a second fluoropolymer, wherein the first fluoropolymer is more fibril lizable than the second fluoropolymer, and wherein the second fluoropolymer is more friable than the first fluoropolymer; andAttorney Docket No.: FP0033-W001 an electrode active material having a Dso particle size of less than 3 pm.

35. The electrode of claim 34, wherein the film has a thickness of 200-500 pm.

36. The electrode of claim 34 or 35, wherein the film is a free-standing film.

37. The electrode of any of claims 34 to 36, wherein the film has an elongation of at least 1 % when measured on a 20 mm x 5.3 mm sample at an applied tensile strain rate of 10% per minute at room temperature (~22 °C).

38. The electrode composition of claim 37, wherein the film has an elongation of between 1 % and 10%.

39. The electrode composition of claim 37, wherein the film has an elongation of at least 10%.

40. A lithium-ion battery comprising: a first electrode comprising an electrode film disposed on a substrate, the electrode film comprising: a binder composition comprising: a first fluoropolymer co-coagulated with a second fluoropolymer, wherein the first fluoropolymer is more fibril lizable than the second fluoropolymer, and wherein the second fluoropolymer is more friable than the first fluoropolymer; andAttorney Docket No.: FP0033-W001 an electrode active material having a Dso particle size of less than 3 pm a second electrode; and an electrolyte in contact with the first electrode and the second electrode.41 . A method of making an electrode for a lithium-ion battery, the method comprising: mixing a dry powder binder composition with an electrode active material having a Dso particle size of less than 3 pm to form an electrode composition, wherein the dry powder binder composition comprises: a first fluoropolymer co-coagulated with a second fluoropolymer, wherein the first fluoropolymer is more fibril lizable than the second fluoropolymer, and wherein the second fluoropolymer is more friable than the first fluoropolymer.

42. The method of claim 41 , comprising forming an electrode film from the electrode composition.

43. The method of claim 41 or 42, comprising forming the dry powder binder composition, including: mixing an aqueous dispersion of the first fluoropolymer with an aqueous dispersion of the second fluoropolymer to produce the agglomerates; separating the agglomerates; andAttorney Docket No.: FP0033-W001 drying the agglomerates to form the dry powder binder composition.

44. An electrode film for a lithium-ion battery comprising a. at least 95 wt% of an electrode active material having a Dso particle size of 3 pm or less; b. 5 wt% or less of a fibrillated binder; and c. 0 to 3 wt% of electrically conductive particles; wherein the electrode film comprises an elongation of at least 8%, 9% or 10% according to the method described herein.

45. The electrode film of claim 44 wherein the electrode film is a cathode film and the electrode active material is lithium iron phosphate (“LFP”).

46. The electrode film of claim 44 wherein the fibrillated binder is at least one fibrillated polytetrafluoroethylene (PTFE) resin based on a PTFE resin having a melt creep viscosity of at least 0.5 x 1010poise (0.5 x 109Pa S) prior to fibrillation, preferably at least 0.5 x 1011poise (0.5 x 1010Pa S).

47. The electrode film of claim 46 wherein the fibrillated binder was a cocoagulate prior to fibrillation, said cocoagulate comprising at least one fibrillatable PTFE having a melt creep viscosity (MCV) of at least 0.5 x 1010poise (0.5 x 109Pa S), preferably at least 0.5 x 1011poise (0.5 x 1010Pa S), and a second PTFE that is different from the first PTFE, wherein the second PTFE is more friable and less fibrillatable than the first PTFE.

48. The electrode film of claim 47 wherein the second PTFE comprises a melt creep viscosity less than the melt creep viscosity of the first PTFE.Attorney Docket No.: FP0033-W00149. The electrode film of any one of the preceding claims wherein said first PTFE and said second PTFE are independently PTFE homopolymers, modified PTFE polymers, and any combination thereof.

50. The electrode film of any one of the preceding claims wherein the weight percent of the first PTFE in the cocoagulate is at least 30, 40, 50, 60, 70, 80, 90% based on the total weight of said cocoagulate.51 . An electrode comprising the electrode film of any one of claims 44 to 50 laminated to a current collector.

52. The electrode of claim 51 wherein said electrode is a cathode.

53. A lithium-ion battery comprising the electrode of claim 51 or claim 52.

54. A method to obtain an electrode film having an elongation of at least 8, 9 or 10 % comprising: a. providing an electrode composition comprising a dry blend of i. at least 95 wt% of an electrode active material particles; ii. 5 wt% or less of a fibrillatable binder; and iii. 0 to 3 wt% of electrically conductive particles; b. mixing under sufficient shear to partially fibrillate the fibrillatable binder;Attorney Docket No.: FP0033-W001 and form a free-standing electrode film, wherein the total amount of energy input into the mixing process is no more than 50%, 40%, 30% or 25% of the total energy used to reach a maximum torque for the same electrode composition; wherein the electrode film comprises an elongation of at least 8, 9 or 10%.

55. The method of claim 54 wherein elongation % is determined using a 20 mm x 5.3 mm cross section sample of the free-standing electrode film having a thickness of approximately 350 pm and applying a tensile strain to the samples at a 10% per minute pure tensile strain rate at approximately room temperature (~22 °C).

56. The method of claim 54 or claim 55 wherein the electrode active material particles have a Dso (median) particle size of 3 pm or less.

57. The method of any one of the preceding claims wherein the electrode active material is lithium iron phosphate (“LFP”).

58. The method of any one of the preceding claims wherein the binder is at least one f ibril lated polytetrafluoroethylene (PTFE) resin based on a PTFE resin having a melt creep viscosity of at least 0.5 x 1010poise (0.5 x 109Pa-S) prior to fibrillation, preferably at least 0.5 x 1011poise (0.5 x 1010Pa-S) prior to fibrillation.Attorney Docket No.: FP0033-W00159. The method of any one of the preceding claims wherein the fibri Hated binder was a cocoagulate prior to fibrillation, said cocoagulate comprising at least one fibrillatable PTFE having a melt creep viscosity (MCV) of at least 0.5 x 1010poise (0.5 x 109Pa S), preferably at least 0.5 x 1011poise (0.5 x 1010Pa S), and a second PTFE that is different from the first PTFE, wherein the second PTFE is more friable and less fibrillatable than the first PTFE.

60. The method of any one of the preceding claims wherein second PTFE comprises a melt creep viscosity less than the melt creep viscosity of the first PTFE.61 . The method of any one of the preceding claims wherein said first PTFE and said second PTFE are independently PTFE homopolymers, modified PTFE polymers, and any combination thereof.

62. The method of any one of the preceding claims wherein the weight percent of the first PTFE in the cocoagulate is at least 30, 40, 50, 60, 70, 80, 90% based on the total weight of said cocoagulate.

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