Fluoropolymer binder for lithium-ion secondary battery anode

Abstract

The present invention provides core-shell structure fluoropolymer for use as an anode binder in a Li-ion battery electrode comprising a high molecular weight fibrillatable PTFE core and a shell comprising a shell monomer which increases the lowest unoccupied molecular orbital (LUMO) of the core shell structure fluoropolymer which results in higher reduction stability and better battery performance compared with non-modified PTFE.

Description

TITLE OF THE INVENTIONFLUOROPOLYMER BINDER FOR LITHIUM-ION SECONDARY BATTERY ANODECROSS REFERENCE TO RELATED APPLICATIONS

[0001] This Application claims the priority benefit of US provisional patent application no. 63 / 532,992, filed on August 16, 2023, the disclosure of which is hereby incorporated by reference in its entirety.FIELD

[0002] Fluoropolymer binders used in an anode electrode having improved reductive stability and performance in a secondary lithium-ion battery.BACKGROUND

[0003] It is recognized that multiple factors can contribute to the electrochemical stability of a fluoropolymer binder in an electrode. These include, but are not limited to, the composition and molecular structure. Further, the relationship of molecular weight and fibrillation is critical in the preparation of fluoropolymers for use. The control and regulation of fibrillation is critical to obtain required performance criteria in products. It is well known in the art that expanded polytetrafluoroethylene (ePTFE) can achieve a high tensile strength via long range fibrillation of extruded PTFE materials. This increased ePTFE strength is made possible via ultra-high molecular weight polymer chains. By comparison, PTFE fine powder products with molecular weights in this range will undergo fibrillation upon even gentle mixing. This shows the importance to effect fibrillation, as desired, to obtain the designated and required characteristics of the material.

[0004] US 8,637,144 provides commentary on various techniques to polymerize tetrafluoroethylene (‘TFE”) alone or in combination. Dispersion polymerization of TFE produces a resin that has come to be known as “fine powder”. Generally, a sufficient dispersing agent is introduced into a water carrier such that, upon addition of tetrafluoroethylene monomer in the presence of a suitable polymerization initiator and, upon agitation and under autogenous tetrafluoroethylene pressure, thepolymerization proceeds until the level of colloidally dispersed polymer particles is reached and the reaction is then stopped. In particular, the ‘144 patent provides a TFE copolymer, of the fine powder type, which is expandable, to produce expanded TFE copolymeric products, providing combinations of various amount ranges of monomers with TFE. This procedure to make “expanded” TFE recognizes the importance of the relationship of characteristics e.g., fibrillation, to obtain the physical and chemical qualities needed for an intended use. For applications where high- shear is required to fibrillate PTFE to provide adhesion and cohesion for solvent free electrode fabrication materials with such high molecular weights often fibrillate to an extent that leads to inefficient mixing with other electrode components and undesired agglomeration of PTFE particles.

[0005] JP Patent No. 5434753 provides an organosol composition which includes a non-fibril-forming modified tetrafluoroethylene particle and a melt-processable perfluoropolymer dispersed in an organic solvent. It can be used in electrode mixtures in the manufacture of the lithium battery electrodes. The non-fibril-forming modified tetrafluoroethylene particles are core-shell composite particles having a fibril-forming tetrafluoroethylene core and a non-fibril-forming resin shell, The 753 provides any monomer other than a fluorine-containing monomer that can be substantially copolymerized with TFE and having a modification amount of 2 wt.% or less can also achieve the required invention. These are useful in the latter half of the polymerization to adjust the molecular weight of PTFE in the shell part by the amount added, and the fibrillation capacity of the modified PTFE particles can be adjusted to prevent flocculation during mixing of organosol preparation. However, the 753 is devoid of any results or any instructions on obtaining organosol including the necessary core-shell polymer for use with the active element of a slurry processed electrode to obtain the performance characteristics required. Having distinguishing manufacturing process, components, and different amounts comonomer.

[0006] PTFE binders are electrochemically stable in lithium-ion battery cathodes, but it can be reduced in the lithium-ion battery anode resulting in electrochemical and mechanical degradation [Ladislav Kavan, Chem. Rev. 1997, 97, 3061-3082; Guobao Li, Rongjian Xue, Liquan Chen, Solid State Ionics, 1996, 90, 221-225], The deterioration of binding force (fibrils) of PTFE will cause battery performance and cycling failure.

[0007] What is needed in the industry is the recognition of multiple factors in the design of perfluoropolymer which are coordinated to obtain the required properties, including but not limited to, control of fibrillation, with the composition and architecture of the fluoropolymer. This recognition will provide reductively stable and fibrillating fluoropolymers which can be used as binders in anode electrodes of secondary lithium-ion batteries.SUMMARY

[0008] The present invention provides compositions and fabrication methods for a core-shell structure fluoropolymer for use as an anode binder in a Li-ion battery electrode having a high molecular weight fibrillatable PTFE core and a shell comprising a shell monomer which increases the lowest unoccupied molecular orbital (LUMO) of the core shell structure fluoropolymer which results in higher reduction stability compared with non-modified PTFE fluoropolymer for improved electrochemical stability. The fibrillation characteristics of these binders allows them to be used in a dry, solvent free electrode formation process and modification of the architecture of the core-shell structure of fluoropolymer results in improved performance characteristics.

[0009] In a first embodiment, the present invention is directed to a core-shell structure fluoropolymer for use as an anode binder in a Li-ion battery electrode having a high molecular weight fibrillatable PTFE core and a shell including a shell monomer which increases the lowest unoccupied molecular orbital (LUMO) of the core shell structure fluoropolymer which results in higher reduction stability compared with non-modified PTFE.

[0010] In another embodiment, the invention is directed to method to manufacture a core-shell structure fluoropolymer for use in an electrode composition including the steps of polymerizing TFE monomer in a pressurized reactor to form a core portion of the fluoropolymer, modifying reactor conditions, adding a shell monomer, polymerizing under required reactor conditions in the absence of any wax to ensure phase compatibility, and adding additional TFE monomer with the shell monomer providing a core-shell structure fluoropolymer, wherein the core portion of the fluoropolymer has a molecular weight to provide fibrillation and the shell monomer increases the lowest unoccupied molecular orbital (LUMO) of the core shell structurefluoropolymer which results in higher reduction stability compared with non-modified PTFE.

[0011] In another embodiment, the present invention is directed to an electrode composition for use in a secondary lithium-ion battery anode film, having anode active particles, a fibri Hated core-shell structure fluoropolymer having a high molecular weight fibrillatable PTFE core and a shell having shell monomer which increases the lowest unoccupied molecular orbital (LIIMO) of the core shell structure fluoropolymer which results in higher reduction stability compared with non-modified PTFE.

[0012] In another embodiment, the present invention is directed to a method for manufacturing an electrode composition for use in a lithium-ion secondary battery anode, including the steps of mixing anode active and conductive particles together with a fluoropolymer whereby the fluoropolymer binder is fibrillated. The fluoropolymer has a high molecular weight fibrillatable PTFE core and a shell having a shell monomer which increases the lowest unoccupied molecular orbital (LUMO) of the core shell structure fluoropolymer, which results in higher reduction stability compared with non-modified PTFE, conducted substantially free of solvent.

[0013] In another embodiment, the present invention is directed to a lithium-ion secondary battery having an anode with an anode electrode layer adhered to a metal current collector, the anode electrode layer having an anode electrode composition including anode active particles; core-shell structure fluoropolymer binder having a high molecular weight fibrillatable PTFE core and a shell having a shell monomer which increases the lowest unoccupied molecular orbital (LUMO) of the core shell structure fluoropolymer which results in higher reduction stability compared with nonmodified PTFE. The battery further includes a cathode and a separator between the cathode and anode, with an electrolyte in communication with the cathode, anode and separator.DETAILED DESCRIPTION OF THE DRAWNGS

[0014] FIG. 1 is cyclic voltammetry of graphite anode fabricated using various core-shell fluoropolymer binders.

[0015] FIG. 2 is the first cycle coulombic efficiency of graphite anode fabricated using various core-shell fluoropolymer binders.

[0016] FIG. 3 is of half-cell cycling performance graphite anode fabricated using various core-shell fluoropolymer binders.

[0017] FIG 3A is of half-cell cycling performance graphite anode fabricated using example 3 binder and comparative example B binder.

[0018] FIG. 4 is full cell Cycling performance of graphite anode fabricated using example 3 binder and comparative example A binder, respectively.

[0019] FIG. 5 is SEM images of graphite anode fabricated using example 1 binder at 5K magnification before (top row) and after (bottom row) 1 cycle.

[0020] FIG. 6 is SEM images of graphite anode fabricated using example 3 binder at 5K magnification before (top row) and after (bottom row) 1 cycle.

[0021] FIG. 7 is SEM images of the surface of the graphite anode fabricated using example 5 binder at 2K (top row) and 5K (bottom row) magnification after 120 cycles.DETAILED DESCRIPTION

[0022] The materials and methods of the present invention provide a core-shell fluoropolymer with the physical and chemical properties required for use in a designated product. The structure of these core-shell polymers provides properties which are useful in other applications. For example, the selection of shell monomer may be such as to provide either compatibility or reactivity with similar organic polymers or fluids such that the nanometer sized primary particles or micrometer sized polymer particle agglomerates may be uniformly dispersed in the matrix of choice, thus imparting some fluoropolymer characteristics to other organic substrates. In applications such as coatings or films, design of these core-shell polymer particles may give rise to controlled stratification of PTFE across the film thickness, hence, for example, tunable surface properties or regulated UV transparency.

[0023] A core concept of the present invention is an appreciation of the components and structural design of a core-shell fluoropolymer containing tetrafluoroethylene core and a shell comprising a shell monomer which increases the lowest unoccupied molecular orbital (LUMO) of the core shell structure fluoropolymer which results in higher reduction stability compared with non-modified PTFE,resulting improved reduction stability for secondary lithium-ion battery anode electrode application. In addition, the fluoropolymer has a molecular weight so that the fluoropolymer fine powder samples retain the ability to undergo eventual interparticle fibrillation (for example during film calendaring) without premature fibrillation during the initial mixing processes with other electrode components recognizing the importance to effect initiation and termination of fibrillation, as required for the intended use of the fluoropolymer.

[0024] In a first embodiment, the invention is directed to a core-shell structure fluoropolymer for use as an anode binder in a Li-ion battery electrode having a high molecular weight fibrillatable PTFE core and a shell having a shell monomer which increases the lowest unoccupied molecular orbital (LIIMO) of the core shell structure fluoropolymer, which results in higher reduction stability compared with non-modified PTFE.

[0025] The core of the fluoropolymer of the present invention must include a fibrillatable constituent, most commonly PTFE, which could be alone or be combined with a second constituent to an amount which would not prohibit required fibrillation for the desired use. The shell monomer has a structure of alkene, hydrofluoroolefin, or perfluoro(alkyl vinyl ether) (PAVE) and most commonly is selected from group of ethylene, VF2, PMVE, PEVE and PPVE. The shell may further include a second monomer, commonly TFE. However, one skilled in the art recognizes that the shell portion could be exclusively a constituent which increases the lowest unoccupied molecular orbital (LUMO) of the core shell structure fluoropolymer.

[0026] In the present invention, the amounts of the constituents in the core and the shell vary and are dictated by required properties such as the necessary amount of fibrillation needed for a particular use. For example, the amount of fibrillatable TFE in the core depends on the fibrillation of shell; if the shell constituents do not fibril late, an increased amount of fibrillating constituent, e.g. high molecular weight TFE, are required in the core. The fundamental principle in polymer design is to maximize polymer LUMO without unacceptably reducing the propensity of the polymer to fibrillate, a requirement for polymer function in the end use application. In a coreshell polymer, this may be accomplished in several ways: (1 ) by judicious selection of a LUMO increasing shell monomer or monomers, (2) by increasing theconcentration of shell monomer in the shell, (3) by increasing the proportion of polymer shell in the bulk polymer.

[0027] Recognizing this principle of the invention, the fibrillatable constituent in the core could be from 1 to 100% which the shell could include a shell monomer in the range of 1 to 100 wt% and the second monomer is in the range of 1 to 90%.

[0028] In another embodiment, the invention is directed to method to manufacture a core-shell structure fluoropolymer for use in an electrode composition including the steps of polymerizing TFE monomer in a pressurized reactor to form a core portion of the fluoropolymer, modifying reactor conditions; adding a shell monomer; and polymerizing under required reactor conditions in the absence of any wax to ensure phase compatibility. Thereafter, additional TFE monomer is added with the shell monomer, providing a core-shell structure fluoropolymer. The core portion of the fluoropolymer has a molecular weight to provide fibrillation and the shell monomer increases the lowest unoccupied molecular orbital (LIIMO) of the core shell structure fluoropolymer which results in higher reduction stability compared with non-modified PTFE.

[0029] Molecular orbital energy level of LIIMO can be calculated by using Gaussian 16™ with the Hartree-Fock level of theory. Geometric optimizations were performed using the 6-311 +g basis set and solvation was accounted for using the SMD model with Ethylene Carbonate parameters. This configuration was chosen based on the qualitative and quantitative match of orbital energies found in reference (Masaki Yoshio, Ralph J. Brodd, Akiya Kozawa (Eds.), Lithium-Ion Batteries, 2009, Chapter 6). The calculation results of LUMO level of PTFE and copolymer of TFE and PPVE (10 wt%) are shown in the Chart 1. 10% PPVE monomer could increase the LUMO of copolymer from 2.94 eV (PTFE homopolymer) to 3.17 eV. The LUMO is lowest unoccupied molecular orbital. Regarding electrochemical reactions, reduction is to add electrons to LUMO. The increase of LUMO make it is more difficult for electrons to be added. And therefore, it leads to a better reduction stability.

[0030] The addition of wax in the preparation of core-shell fluoropolymer limits the amount and type of shell monomer as polymer produced with the shell monomer may compatibilize the core-shell fluoropolymer with the wax phase and produce a substance which is not usable for various uses, including binder for lithium batteries. The method of the present invention does not include wax and therefore allows a higher amount and wider variety of shell monomers, thus efficiently increasing the LUMO by interrupting the CF2-CF2 bonds of TFE, and therefore provides a structure which reduces degradation. In the present embodiment, one example using an ethylene monomer as the shell monomer, provides multiple CH2-CH2 spacers in the polymer shell. In contrast to the existing art which provides that hydrocarbons in the shell leads to thermal and chemical weakness in the typical PTFE applications, the method of the present invention allows for a higher amount of the CH2-CH2 spacers which result in reduction stability and better battery performance. Use of the coreshell structure in this manner preserves the fribrillatable nature of the polymer while imparting reduction stability. An illustration of a PTFE core and TFE-ethylene shell fluoropolymer is provided in illustration 1.Illustration 1

[0031] The core-shell structure fluoropolymer manufactured by the method wherein the core portion of the fluoropolymer has a molecular weight to provide fibrillation. The core-shell structure has a structure of alkene, hydrofluoroolefin, of perfluoro(alkyl vinyl ether) (PAVE), wherein the shell monomer is selected from group comprising ethylene, VF2, PMVE, PEVE and PPVE.

[0032] In another embodiment the invention is directed to an electrode composition for use in a secondary lithium-ion battery anode film having anode active particles and a fibrillated core-shell structure fluoropolymer having a high molecular weight fibrillatable PTFE core and a shell having a shell monomer which increases the lowest unoccupied molecular orbital (LIIMO) of the core shell structure fluoropolymer which results in higher reduction stability compared with non-modified PTFE.

[0033] The shell of the core-shell structure fluoropolymer can have a second monomer, which is usually TFE. The shell monomer has a structure of alkene, hydrofluoroolefin, or perfluoro(alkyl vinyl ether) (PAVE) and most commonly is selected from group of ethylene, VF2, PMVE, PEVE and PPVE. The shell may further include a second monomer, commonly TFE. The shell portion could be exclusively a constituent which increases the lowest unoccupied molecular orbital(LUMO) of the core shell structure fluoropolymer. As described previously herein, in the present invention, the amounts of the constituents in the core and the shell vary, and are dictated, by required properties such as the necessary amount of fibrillation needed for a particular use.

[0034] Referring again to Illustration 1 , The position of the shell is proximal to the active e.g. graphite, during mixing / milling processes no matter if the shell is fibrillatable or not. If shell is fibrillatable, the beginning of fibrils with shell composition which has improved reduction stability is proximal to the active e.g. graphite in the electrode. The fibrils with core composition are not attached to graphite and thus there is no electron to reduce them. Therefore, the shell protects a non-modified PTFE core from reduction which results in better battery performance. If shell is not fibrillatable, it also protects the fibrils of PTFE core from contacting with graphite and therefor eliminates the reduction and leads to better battery performance.

[0035] The fluoropolymer is substantially free from solvent, creating an electrode binder to enable more sustainable solvent-free electrode manufacturing processes. Dry processing technology is more cost-efficient and greener compared to conventional solvent-based electrode casting technology, which uses toxic organic solvents. Also, it has advantage for energy density enhancement because it avoids the electrode particles sedimentation for wet electrode during drying process.

[0036] Cyclic voltammetry shows the oxidation and reduction features from the electrode components. The reduction signal between 0.9 to 0.3 is assigned to the degradation of the fluoropolymer and electrolyte reduction. Electrolyte reduction is similar for all the cells. The signal (reduction) around 0.1V represents the graphite lithiation. The oxidation signal around 0.2V represents the graphite de-lithiation. PTFE reduction is irreversible (there is no corresponding oxidation reaction) process while graphite reduces and oxidizes reversibly while switching negative current to positive current. PTFE reduction causes the capacity loss and decreases the binding property of PTFE thereby leading to poor battery performance. In order to quantify the fluoropolymer reduction (or degradation), the integrated area under the X-axis is calculated by multiplying voltage and normalized current and adding them in the voltage range of 0.9 and 0.3V. Referring to Fig. 1 and Table 2, the core-shellstructure fluoropolymer in cyclic voltammetry test degradation in the anode composition is diminished by > / = 7% compared to PTFE homopolymer, as determined by the integrated intensity in the 0.3 to 0.9 V region using the formula 100 * (1- (integrated current of fluoropolymer) / integrated current of non-modified PTFE.

[0037] Chart 2 provides the estimated amount of shell monomer in the core shell structures made by the method of the present invention.Chart 2

[0038] In the present embodiment, the electrode composition contains from about 0.2 to about 10 weight percent fluoropolymer binder and from about 90 to about 99.8 weight percent anode active particles.

[0039] In another embodiment the invention is directed to a method for manufacturing an electrode composition for use in a lithium-ion secondary battery anode, comprising, mixing anode active and conductive particles together with a fluoropolymer whereby said fluoropolymer binder is fibrillated. The fluoropolymer has a high molecular weight fibrillatable PTFE core and a shell having a shell monomer which increases the lowest unoccupied molecular orbital (LUMO) of the core shell structure fluoropolymer which results in higher reduction stability compared with nonmodified PTFE. The method is conducted substantially free from solvent.

[0040] The method provides a core-shell fluoropolymer for use as binder in an electrode for a secondary lithium-ion battery anode, the fluoropolymer has the physical property to provide fibrillation. This provides fibrillation characteristics which complement the chemical and physical properties necessary for the anode, most specifically, reduced degradation, improved columbic efficiency and better cycling life.

[0041] The fluoropolymer obtained for the method to manufacture a core shell fluoropolymer has advantageous characteristics. Table 1 provides the combinations with “shell” components with various amount in mol% by NMR. Referring to FIG. 1 , the cyclic voltammetry curves are provided to illustrate the reversible oxidationreduction reaction. The upward peak indicates the oxidation of the active species and the downward peak indicates the species' reduction. This technique is used to appreciate the redox features of electrode components.

[0042] In another embodiment, the invention is directed to a composition for use in a secondary lithium-ion battery anode film, having anode active particles; conductive additives and a fibrillated fluoropolymer binder with core-shell structure. The composition contains from about 0.2 to about 10 weight percent fluoropolymer binder and from about 90 to about 99.8 weight percent anode active particles.

[0043] The present anode active particles are selected from conventional materials known in this field, for example, graphite, graphene, metal oxides, metal alloy, lithium titanate, Sn, and silicon, silicon oxides or silicon-containing materials.

[0044] In one embodiment, the anode electrode composition is prepared by milling the anode active particles and dry agglomerates comprising core-shell fluoropolymer. The milling is carried out substantially free from solvent. For example, free from water, and organic solvents such as N-methyl-2-pyrrolidone (NMP) commonly used as carriers in battery binder manufacturing processes.

[0045] In another embodiment, the present invention is directed to a secondary lithium-ion battery having an anode with an anode electrode layer adhered to a metal current collector, the anode electrode layer having an anode electrode composition including anode active particles, conductive additive, fluoropolymer binder, a cathode electrode, a separator between the cathode and said anode; and an electrolyte in communication with the cathode, anode and separator.

[0046] The electrode composition for the anode film includes anode active particles and a fibril lated core-shell structure fluoropolymer having a high molecular weight fibrillatable PTFE core and a shell having a shell monomer which increases the lowest unoccupied molecular orbital (LUMO) of the core shell structure fluoropolymer which results in higher reduction stability compared with non-modified PTFE.

[0047] The shell of the core-shell structure fluoropolymer can have a second monomer, which is usually TFE. The shell monomer has a structure of alkene, hydrofluoroolefin, or perfluoro(alkyl vinyl ether) (PAVE) and most commonly is selected from group of ethylene, VF2, PMVE, PEVE and PPVE. The shell may further include a second monomer, commonly TFE. However, one skilled in the art recognizes that the shell portion could be exclusively a constituent which increases the lowest unoccupied molecular orbital (LUMO) of the core shell structure fluoropolymer. The required amount in the core is based on necessary amount of fibrillation needed for the use.EXAMPLESComparative Example A

[0048] To a nominally 10-gallon jacketed, cylindrically-shaped stainless steel reactor with an aspect ratio of 1.5 equipped with a paddle stirrer was charged 600 grams of natural paraffin wax and 4.3 g of succinic acid and the reactor was sealed. After adding 24.1 liters of demineralized water, the reactor was heated to 65 °C, the reactor was agitated at 70 RPM then pressured to 400 PSIG with nitrogen and checked for leaks. After venting, an aqueous solution containing 0.7 g perfluoropolyether acid polymerized from hexafluoropropylene oxide with a number average molecular weight of approximately 1500 Daltons, 147 g of HFPO dimer acid, ammonium salt, and 61.8 g demineralized water was added. The agitator was stopped and the reactor was purged with TFE to greater than 25 PSIG and evacuated to at least -2.0 PSIG three times. The agitator was restarted, and the reactor was charged with TFE until a pressure of 400 PSIG was reached. To start the polymerization, 180 mL of a 0.015% (m / v) aqueous solution of potassium permanganate (KMnO4) were added at a rate of 80 mL / min, then KMnO4 injection continued at 3.5 mL / min until 4.7 kg of TFE had been charged from the start ofKMnO4 injection. Also, at 4.7 kg of TFE charged, the temperature was increased to 85 °C. After a total of 10.9 kg of TFE were added since kickoff, the TFE addition valve was closed, the agitator was stopped, and the reactor was vented slowly over 10 minutes. When the reactor pressure reached 1-2 PSIG, nitrogen was added to give a slow pressure rise to 5 PSIG. The reactor was evacuated for 1 minute then the nitrogen flow was stopped, and the reactor was vented. The reaction time was 130 minutes. The resulting dispersion, containing 33.63% polymer, was discharged from the reactor, and allowed to cool. The dispersion was found to have a raw dispersion particle size of 218.5 nm. After draining the dispersion, 495 g of coagulum, containing water, paraffin wax and polymer, were left behind in the reactor and gave an SSG of 2.1672.

[0049] Polymer was coagulated in a 3L vessel by diluting the dispersion to about 14 wt% solids and by adding about 3.7% by mass (dry weight) of a 20 wt% aqueous ammonium carbonate solution followed by vigorous agitation until the polymer fully separated from the water. The polymer was dried in a static oven at 150 °C for 24 hours.Comparative Example B

[0050] An initiator solution consisting of 3.0 g of 70 wt% active disuccinic acid peroxide and 0.2 g of ammonium persulfate raised to 500 g with deionized, deaerated water is prepared. A 11 .7 liter horizontal reactor is purged with nitrogen and then evacuated. 5400 ml of deionized, deaerated water is charged to the reactor. A surfactant solution consisting of 10.0 g of GX905D surfactant (manufactured by The Chemours Company) raised to 500g with deionized, deaerated water is added to the reactor. Reactor pressure is raised to approximately 30 psig with nitrogen and then evacuated. This procedure for further removing trace oxygen is repeated two more times, leaving the reactor in vacuum. The reactor pressure is raised to approximately 30 psig with tetrafluoroethylene (TFE) and vented to atmospheric pressure 3 times to substantially remove nitrogen. Agitation is commenced at 70 rpm and the reactor content is heated to 70°C. TFE flow is set to 1500 g / hr and ethylene flow is set at 0.0006g of ethylene per gram of TFE.Reactor pressure is raised to 400 psig by adding the above monomer mixture. Once at a pressure of 400 psig, 50 ml of initiator solution is rapidly added to the reactor.The monomer mixture is fed to the reactor at a rate sufficient to maintain reactor pressure at 400 psig. After 1500 g of TFE and 0.9 g of ethylene has been fed since introduction of initiator, TFE & ethylene flow is stopped, agitation is ceased, and reactor is vented to atmospheric pressure. The resulting reactor contents consists of 40.3 g of undispersed polymer and 7447.3 g of fluoropolymer dispersion containing 20.09 wt% polymer with a raw dispersion particle size, Dv(50) as measured by laser light scattering using a Malvern Zetasizer of 170 nm. Total polymer produced is 1536.5 g. Analysis by Differential Scanning Calorimeter (DSC) shows a melting peak on first heat of 341 ,7°C with a heat of fusion of 78.0 J / g. Melting point on second heat is 326.1 °C with a heat of fusion of 44.3 J / g. Bulk composition of the resulting polymer is measured by solid state 19F MAS (Magic Angle Spinning) NMR (Neuclear Magnetic Resonance) and determined to consist of 0.20 mol% ethylene. EXAMPLESPolymerization - Core-Shell Fluoropolymer.Example 1

[0051] An initiator solution consisting of 0.15 g KMnCM and 5.0 g of a 1.4 wt% aqueous (NH4)2HPO4 solution raised to 1000 g with deionized, de-aerated water is prepared. A 11.7 liter horizontal reactor is purged with nitrogen and then evacuated. 5500 ml of deionized water is then charged to the reactor. A surfactant solution consisting of 10.0 g of GX905D surfactant (manufactured by The Chemours Company) and 1 drop of Tomadol 32-1 , raised to 500g with deionized, de-aerated water is added to the reactor. 250 g of an acid solution containing 1.5 g of succinic acid and 0.12 g of oxalic acid is then added to the reactor. Reactor pressure is raised to approximately 100 psig with nitrogen and then evacuated. This procedure for removing trace oxygen is repeated two more times, leaving the reactor in vacuum. The reactor pressure is raised to approximately 30 psig with tetrafluoroethylene (TFE) and vented to atmospheric pressure 3 times to substantially remove nitrogen. Agitation is commenced and the reactor content is heated to 65°C. Reactor pressure is raised to 400 psig by adding TFE. Once at a pressure of 400 psig, 35 ml of initiator solution is rapidly added to the reactor and then a continuous initiator feed of 0.75 ml / min is commenced. TFE is fed to the reactor at a rate sufficient to maintain reactor pressure at 400 psig. After 1250 g of TFE has been fed since introduction of initiator, the polymer core has been producedand if all flows are stopped, agitation ceased and the reactor pressure vented to atmospheric pressure, the resulting weight of polymer produced is 1338.1 g. Analysis of the core polymer by Differential Scanning Calorimeter (DSC) shows a melting peak on first heat of 343.4°C with a heat of fusion of 75.1 J / g. Melting point of second heat is 325.7°C with a heat of fusion of 36.5 J / g.

[0052] To make the core-shell polymer of interest, after the 1250 g of TFE has been fed as described above, only the TFE flow is stopped, reactor temperature setpoint is increased to 70°C and 80 ml of PEVE [1 , 1 ,2-Trifluoro-2-(1 , 1 ,2,2,2- pentafluoroethoxy)ethene] is rapidly added to the reactor. Polymerization proceeds and once reactor pressure is reduced to 300 psig, all flows are stopped, agitation is ceased, and reactor pressure is vented to atmospheric pressure. The resulting fluoropolymer dispersion contains no undispersed polymer, has an average raw dispersion particle size, Dv(50), of 142 nm as measured by Laser Light Scattering, measures 19.38 wt% polymer, and the total polymer produced is 1537.6g. Thus, the PEVE containing shell on the polymer particle comprises 13 wt% of the total polymer produced. Bulk PEVE content measures 0.67 wt% by Fourier Transform Infrared (FTIR) analysis. PEVE content in the shell is thus calculated as 5.15 wt%. Analysis by DSC shows a melting peak on first heat of 342.8°C with a heat of fusion of 75.0 J / g. Melting point on second heat is 323.8°C with a heat of fusion of 34.1 J / g.Example 2

[0053] The procedure of Example 1 is repeated with the following exceptions: TFE is fed to maintain 400 psig reactor pressure until a total of 1750 g of TFE is fed since introduction of initiator, At this point, the core polymer has been produced and if all flows are stopped, agitation ceased and the reactor pressure vented to atmospheric pressure, the resulting weight of polymer produced is 1764.7 g. Analysis of the core polymer by Differential Scanning Calorimeter (DSC) shows a melting peak on first heat of 345°C with a heat of fusion of 75.2 J / g. Melting point of second heat is 326.7°C with a heat of fusion of 33.4 J / g.

[0054] To make the core-shell polymer of interest, after the 1750 g of TFE has been fed as described above, only the TFE flow is stopped, reactor temperature setpoint is increased to 70°C and 100 ml of PPVE (perfluoro propyl vinyl ether, CAS: 1623-05-8) is rapidly added to the reactor. Once reactor pressure drops to 300 psig,TFE flow is started again to maintain 300 psig run pressure. When shell TFE flow is started, a new initiator precharge of 75 ml of 1.65 wt% aqueous ammonium persulfate (APS) is added. Polymerization proceeds and once 500 additional grams of TFE is added, all flows are stopped, agitation is ceased, and reactor pressure is vented to atmospheric pressure. The resulting fluoropolymer dispersion contains 27 g of undispersed polymer, has an average raw dispersion particle size, Dv(50), of 174 nanometers as measured by Laser Light Scattering, measures 28.59 wt% polymer, and the total polymer produced is 2579.5 g. Thus, the PPVE containing shell on the polymer particle comprises 31 .6 wt% of the total polymer produced. Bulk PPVE content measures 2.87 wt% by Fourier Transform Infrared (FTIR) analysis. PPVE content in the shell is thus calculated as 9.08 wt%. Analysis by DSC shows a melting peak on first heat of 342.3°C with a heat of fusion of 70.4 J / g. Melting point on second heat is 323.3°C with a heat of fusion of 34.8 J / g.Example 3

[0055] An initiator solution consisting of 0.15 g KMnC>4 and 5.0 g of a 1 .4 wt% aqueous (NH4)2HPO4 solution raised to 1000 g with deionized, deaerated water is prepared. A 11.7 liter horizontal reactor is purged with nitrogen and then evacuated. 5400 ml of deionized, deaerated water is then charged to the reactor. A surfactant solution consisting of 10.0 g of GX905D surfactant (manufactured by The Chemours Company) and 1 drop of Tomadol 32-1 , raised to 500g with deionized, deaerated water is added to the reactor. 250 g of an acid solution containing 1.5 g of succinic acid and 0.12 g of oxalic acid is then added to the reactor. Reactor pressure is raised to approximately 100 psig with nitrogen and then evacuated. This procedure for removing trace oxygen is repeated two more times, leaving the reactor in vacuum. The reactor pressure is raised to approximately 30 psig with tetrafluoroethylene (TFE) and vented to atmospheric pressure 3 times to substantially remove nitrogen. Agitation is commenced and the reactor content is heated to 65°C. Reactor pressure is raised to 400 psig by adding TFE. Once at a pressure of 400 psig, 75 ml of initiator solution is rapidly added to the reactor and then a continuous initiator feed of 0.75 ml / min is commenced. TFE is fed to the reactor at a rate sufficient to maintain reactor pressure at 400 psig. After 1000 g of TFE has been fed since introduction of initiator, ethylene is added to the TFE feed at the ratio of 0.028 g of ethylene per g of TFE. This mixture is continuously added at arate to maintain reactor pressure at 400 psig. After a total of 1500 g of TFE has been fed since introduction of initiator, TFE & ethylene flow is stopped, agitation is ceased, and reactor is vented to atmospheric pressure. The resulting fluoropolymer dispersion contains 18.3 g of undispersed polymer and measures 20.66 wt% polymer and has a raw dispersion particle size, Dv(50) as measured by laser light scattering using a Malvern Zetasizer of 168 nm. Total polymer produced is 1640.4 g. Analysis by Differential Scanning Calorimeter (DSC) shows a melting peak on first heat of 343.8°C with a heat of fusion of 74.6 J / g. Melting point on second heat is 325.7°C with a heat of fusion of 34.8 J / g. Bulk composition of the resulting polymer is measured by solid state19F MAS (Magic Angle Spinning) NMR (Neuclear Magnetic Resonance) and determined to consist of 0.21 mol% ethylene (0.06 wt%). Because of monomer delivery system volumes, ethylene does not enter the reactor as soon as flow of that monomer is commenced. However, when ethylene does enter the reactor there is a very noticeable decrease in polymerization rate. Therefore, this point of rate decrease is taken as the point at which shell formation starts. This point occurs at 1369 g of TFE fed and represents a shell size of 8.7 wt%. From this shell size and the bulk composition as measured by19F MAS NMR, the shell composition is calculated to comprise approximately 0.69 wt% ethylene.Example 4

[0056] The procedure described for example 3 is repeated with the following exceptions and results: After 950 g if TFE is added to the reactor since introduction of initiator, addition of 25 g / hr of VF2 (1 ,1 -Difluoroethene, CAS: 75-38-7) is commenced. After 1000 g of TFE is added, TFE flow is stopped and VF2 flow is adjusted to control reactor pressure at 400 psig. After a total of 500 g of VF2 has been fed, VF2 flow is stopped, agitation is ceased, and reactor is vented to atmospheric pressure. The resulting fluoropolymer dispersion contains 13.7 g of undispersed polymer and measures 22.54 wt% polymer and has a raw dispersion particle size, Dv(50) as measured by laser light scattering using a Malvern Zetasizer of 172 nm. Total polymer produced is 1823.7 g. Analysis by Differential Scanning Calorimeter (DSC) shows a melting peak on first heat of 344.4°C with a heat of fusion of 70.4 J / g. Melting point on second heat is 325.7°C with a heat of fusion of 33.9 J / g. Bulk composition of the resulting polymer is measured by solid state19F MAS NMR and determined to consist of 4.33 mol% VF2 (2.8 wt%). As with theintroduction of ethylene , the introduction of VF2 to the reactor also results in a significant decrease in polymerization rate. That decrease occurs at 1387 g of total TFE & VF2 added since introduction of initiator. Thus, the shell on this polymer primary particle consists of 7.5 wt% of the total polymer particle and the resulting VF2 content in the shell is calculated as 37.3 wt%.Example 5

[0057] The procedure described for example 9 is repeated with the following exceptions and results: After initiator is added and PTFE polymerization commenced as indicated by a drop in reactor pressure, addition of PMVE (Perfluoro Methy Vinyl Ether, 1 ,1 ,2-trifluoro-2-(trifluoromethoxy)ethene, CAS: 1187-93-5) at the rate of 0.005 g of PMVE per g of TFE fed is commenced and maintained throughout the remaining polymerization. After a total of 2250 g of TFE and 11.1 g of PMVE have been added since commencement of polymerization, agitation is ceased, and reactor is vented to atmospheric pressure. The resulting fluoropolymer dispersion contains 19.2 g of undispersed polymer and measures 26.91 wt% polymer and has a raw dispersion particle size, Dv(50) as measured by laser light scattering using a Malvern Zetasizer of 166 nm. Total polymer produced is 2349.6 g. Analysis by Differential Scanning Calorimeter (DSC) shows a melting peak on first heat of 344.4°C with a heat of fusion of 71.6 J / g. Melting point on second heat is 326.1 °C with a heat of fusion of 35.4 J / g. Bulk composition of the resulting polymer is measured by solid state19F MAS NMR and determined to consist of 0.02 mol% PMVE (0.03 wt%). Experience has shown that due to monomer delivery system volumes, newly introduced monomers enter the reactor after about 400 g of TFE has been fed since the introduction of additional monomers. Thus, the shell on this polymer primary particle comprises approximately 82 wt% of the total polymer particle and the resulting PMVE content in the shell is calculated as 0.04 wt%.

[0058] Table 1 provides the resultant properties and modifier content of the Core Shell Examples.Table 1

[0059] Table 1 provides information regarding Core Shell Examples 1-5, however, one skilled in the art would recognize the present invention includes core-shell polymers with a shell wt% of 1 - 99%, and the second monomer / co-monomer wt% is 0.01 - 50%.TEST METHODSANODE

[0060] Test anodes were prepared using the present fluoropolymer compositions by the following procedures:

[0061] Mixing: 1 . Weigh out material for a 10g batch with a composition of 90% Graphite, 5% Super P conductive carbon, and 5% PTFE (or present inventive fluoropolymer composition).; 2. Combine graphite and Super P in a mortar and pestle for 15 min.; 3. Add graphite and Super P mixture and the PTFE to a 250 ml_ plastic bottle with 10 beads (1 bead / g material).; 4. Set roll mill speed to 55 and place the bottle into the holder and tape the top closed. Put on rollerfor 30 minutes.;5. After 30 minutes, remove the beads from the anode mixture and gently scrape any material stuck to the side of the bottle off.

[0062] Film Formation: 1 . Place 3 g of the mixture in a small glass mortar and pestle.; 2. Grind the material together until it forms a solid flake.; 3. Place the flake onto the hot plate at 100°C on a piece of Kapton® and roll out using a steel roller heated to 100°C. Roll until the film is uniform.Calendering: 1 . Allow the calendering rolls to heat to 50°C for at least an hour and check the temperature with a thermocouple. 2. Measure the thickness of the film and start the calendering gap at 50-100 pm below that. For example, if a film is 480 pm, start the gap distance at 400 pm.; 3. Place the film onto the rolls and turn the roller speed to 150. Pass the film through the gap 2 times. 4. Reduce the gapdistance by 100 m and pass the film through the new gap distance 2 times. 5. Repeat lowering the gap until 100 pm. Pass the film through the gap 5 times at 100 pm and 10 times at 50 pm until a final thickness of 70-80 microns was reached.

[0063] Anode Lamination: 1 . Cut a piece of copper foil, wipe both sides with IPA, and allow to dry.; 2. Pour copper etchant into a glass tray. Place one side of the copper foil into the etchant for 10 seconds.; 3. Transfer copper foil to another glass tray filled with DI water and soak for a minute. Thoroughly rinse the copper foil with DI water and dry on a blue napkin.; 4. Plasma treat etched copper.; 5. Heat a hot press to 300°C. Place the anode film onto the copper foil and in between two sheets of the metal shim. Place the metal shim onto steel backing plates.; 6. Press at 5,000 lbs. for 5 minutes.; 7 Take it off the hot press and allow to cool before removing the metal shims.

[0064] Half cell configuration: Half cell containing a graphite electrode and a lithium metal counter-electrode and a Celgard separator was assembled a CR2032 coin cell. The electrolyte of 1 ,2M LiPFe in EC / DEC (3:7 by volume) +5% PEC was used.

[0065] Half cell testing: The coin cells were cycled using a Neware battery tester from 0.01 V - 1 .25 V vs. Li / Li+with C / 25 formation for 2 cycles and C / 10 for cycling. 1 C = 1 hour charge / discharge. All of the cells were cycled at room temperature.

[0066] The cyclic voltammetry (CV) was measured in a Bio-Logic potentiostat using the lithium metal half cells assembled as described above. The cyclic voltammetry testing is preferably comprises scanning from 0.01V to 1 .5 V potential vs Li / Li+at 0.05 mV / sec scan rate.CathodeTo build the full cells with the dry processed Graphite Anodes with example 3 fluoropolymer binder, commercially available LiNi0.6Mn0.2Co0.2O2 (NMC622) cathode powder was blended with SP carbon and polyvinylidene fluoride (PVDF) binder in N- Methyl-2-pyrrolidone (NMP) solution at 90: 5: 5 by weight composition in Thinky Mixture. The obtained slurry was deposited in carbon coated aluminum foil with a doctor blade. The electrode was dried at 120°C for 12 hours.Full cell assembleSlurry processed NMC 622 was used as cathode and dry processed graphite electrode with example 3 fluoropolymer binder and comparative example A binder as anode, respectively. The anode: cathode capacity ratio was around 1.1. The electrolyte of 1 ,2M LiPFe in EC / DEC (3:7 by volume) +5% EEC was used in the full cells. Full cells were made in the 2032 coin cell format with automatic cell crimper inside the argon gas filled Glove Box.Full cell testThe cells rested for 2 hours before starting to cycle using a Neware battery tester. The cells were charged and discharged at room temperature condition with Galvanostatic cycling of C / 25 (1 C=160 mAh / g) for the first two cycles and at C / 10 for the rest cycles.DISCUSSION OF RESULTS AND TEST METHODS FOR CORE-SHELL EMBODIMENT:Cyclic Voltammetry Measurement:

[0067] The results are shown for the core shell fluoropolymer in the Table 2 below, and graphically illustrated in FIG 1 .Table 2

[0068] As provided herein, the Core Shell embodiment was tested in Cyclic Voltammetry. The % improvement or diminution in the degradation is 100 * (1- (integrated current of example) / integrated current of comparative example)

[0069] The results indicate an improvement or diminution in degradation of the fluoropolymer of the present invention, in the anode electrode, of 7 % or greater.This improvement or diminution in the fluoropolymer degradation will result in improved stability and increased performance the anode electrode when used in an electrochemical device or lithium-ion battery.

[0070] Improvement of reduction stability of PTFE using the core-shell structure with a defined composition and molecule design, as provided in the present invention as illustrated in FIG. 1 , confirms the core-shell structure can be used in an electrode. More particularly, the composition is electrochemically stable in the core-shell structure within an electrode.Coulombic Efficiency

[0071] Referring to FIG. 2, the anode incorporating the binder of the present invention provides increased the first cycle coulombic efficiency over the PTFE nonmodified binder. The amount of modifier is variable but, in all amounts, the anode with the binder of the present invention is improved.

[0072] Coulombic efficiency (CE) of an anode as used herein is the percentage ratio of specific charge (delithiation in a half cell) capacity to specific discharge (lithiation in a half cell) capacity. The degradation (reduction) of PTFE binder contributes the capacity loss in the first cycle and leads to the low first cycle coulombic efficiency.Cycling Life

[0073] Referring to FIG. 3, the half-cell cycling performance is illustrated. The core-shell PTFE shows better cycling performance compared with comparative example A, as illustrated in FIG. 3.

[0074] Referring to Table 3, the half-cell cycle life (cycle number at 80% capacity retention) with core-shell PTFE was significantly improved compared with comparative example A at least by 146%.

[0075] Referring to FIG 3A, the half-cell performance of electrode fabricated using Example 3 binder is illustrated in comparison to Comparative Example B binder.The core-shell fluoropolymer binder example 3 shows better cycling performance compared with comparative Example B. Example B is TFE-ethylene copolymer with same amount of ethylene as Example 3 binder, but example B binder is not core-shell structure. All ethylene was distributed to the polymer uniformly. As illustrated in FIG. 3A, polymer with TFE / ethylene shell has half-cell performance of 90% retention @100 cycles. However for comparative example B, ethylene-TFE copolymer (not core-shell structure), cycle life is only 21 cycles. This demonstrated that core-shell structure fluoropolymer has advantage over copolymer (non core-shell structure) with same amount of shell monomer in terms of battery performance.Table 3

[0076] Referring to FIG. 4, the “full cell” cycling performance is illustrated. Full cells were assembled with dry processed graphite anode (example 3 binder) and slurry processed NMC622 cathode. Duplicate cells show similar cycling performance with 70% capacity retention at 200 cycles. As comparison, capacity of full cells with dry processed graphite anode (comparative example A binder) and slurry processed NMC622 cathode dramatically fade in the initial 20 cycles and reach to 70% capacity retention in 80 cycles. Core-shell fluoropolymer Example 3 binder show much better full cell performance compared with non-modified PTFE under same testing conditions.

[0077] Referring to FIGs 5 through 6, SEM images of electrodes fabricated using fluoropolymer Examples 1 and 3 binders are illustrated at 5K magnification (respectively), taken before and after 1 cycle. As illustrated, the varying amount of fibrils coordinate the composition of the samples with the fibrils illustrated. If fibrils remain after cycling, it is evidence that fibrils are reduction resistant. SEM images are the visualized results that validate the present invention both in regard tocomposition and architecture design (core-shell could improve the reduction stability). Fibrils are key to maintain good electrode integrity which is a must-have for good cycling. The improvement of reduction stability is a crucial industry focus in anode binder. As illustrated in FIGs 5 and 6, the presence of the fibrils provides evidence of the improved strength and stability provided by the present invention. Referring to FIG 7, is a surface view of an SEM image of the electrode fabricated using fluoropolymer Example 5 binder illustrated at 2K and 5K magnification (respectively). The half cell with electrode of example 5 was carefully de-crimped after 120 cycles in Argon atmosphere glovebox. The electrode with example 5 binder was gently washed with dimethyl carbonate solvent. The presence of the fibrils after 120 cycles illustrates the stability of fluoropolymer binder after long term cycling and demonstrated the ability of the anode, including the fluoropolymer binder of the present invention, can maintain better cycling life, in addition to other performance criteria.

Claims

CLAIMS1 . A core-shell structure fluoropolymer for use as an anode binder in a Li-ion battery electrode comprising a high molecular weight fibrillatable PTFE core and a shell comprising a monomer which increases the lowest unoccupied molecular orbital (LUMO) of the core shell structure fluoropolymer which results in higher reduction stability compared with non-modified PTFE.

2. The core-shell structure fluoropolymer of claim 1 , wherein the shell further comprises a second monomer.

3. The core-shell structure fluoropolymer of claim 2, wherein the second monomer is a TFE monomer.

4. The core-shell structure fluoropolymer of claim 3, wherein the shell monomer has a structure of alkene, hydrofluoroolefin, or perfluoro(alkyl vinyl ether) (PAVE).

5. The core-shell structure fluoropolymer of claim 4, wherein the shell monomer is selected from group comprising ethylene, VF2, PMVE, PEVE and PPVE.

6. The core-shell structure fluoropolymer of claim 5, wherein the TFE is in the range of 10 to 100% wt.% in the fibrillatable core polymer composition.

7. The core-shell structure fluoropolymer of claim 6, wherein the shell monomer is in the range of 0.01 - 90 wt% in the shell.

8. The core-shell structure fluoropolymer of claim 7, wherein the second monomer is in the range of 0 - 99 wt. %.

9. A method to manufacture a core-shell structure fluoropolymer for use in an electrode composition comprising the steps of: a. polymerizing TFE monomer in a pressurized reactor to form a core portion of the fluoropolymer; b. modifying reactor conditions; c. adding a shell monomer; and d. polymerizing under required reactor conditions in the absence of any wax to ensure phase compatibility, additional TFE monomer with the shell monomer.

10. A core-shell structure fluoropolymer manufactured by the method of 9, wherein the core portion of the fluoropolymer has a molecular weight to provide fibrillation.11 . The core-shell fluoropolymer of claim 10, wherein the fluoropolymer is a core-shell copolymer of TFE and a shell monomer, wherein the shell monomer increases the lowest unoccupied molecular orbital (LIIMO) of the core shell structure fluoropolymer which results in higher reduction stability compared with non-modified PTFE.

12. The core-shell structure fluoropolymer of claim 11 , wherein the shell monomer has a structure of alkene, hydrofluoroolefin, or perfluoro(alkyl vinyl ether) (PAVE).

13. The core-shell structure fluoropolymer of claim 12, wherein the shell monomer is selected from group comprising ethylene, VF2, PMVE, PEVE and PPVE.

14. The core-shell structure fluoropolymer of claim 13, wherein the PTFE is in the range of 10-90 wt. %.

15. The core-shell structure fluoropolymer of claim 14, wherein the TFE is in the range of 10-100 wt. % in the fibrillatable PTFE core.

16. The core-shell structure fluoropolymer of claim 15, wherein the shell monomer is in the range of 10-90 wt.

17. The core-shell structure fluoropolymer of claim 16, wherein the shell monomer is in the range of 0.01-90 wt % in the shell.

18. An electrode composition for use in a secondary lithium-ion battery anode film, comprising: a. anode active particles; b. a fibrillated core-shell structure fluoropolymer comprising a high molecular weight fibrillatable PTFE core and a shell comprising a shell monomer which increases the lowest unoccupied molecular orbital (LUMO) of the core shell structure fluoropolymer which results in higher reduction stability compared with non-modified PTFE.

19. The electrode composition of claim 18, wherein the core-shell structure fluoropolymer shell further comprises a second monomer.

20. The electrode composition of claim 19, wherein the core-shell structure fluoropolymer second monomer is a TFE monomer.21 . The electrode composition of claim 20, wherein the shell monomer of the core-shell structure fluoropolymer has a structure of alkene, hydrofluoroolefin, or perfluoro(alkyl vinyl ether) (PAVE).

22. The electrode composition of claim 21 , wherein the shell monomer of the core-shell structure fluoropolymer is selected from group comprising ethylene, VF2, PMVE, PEVE and PPVE.

23. The electrode composition of claim 22, wherein the PTFE core of the coreshell structure fluoropolymer is in the range of 10-90 wt. % in the fibrillatable PTFE core.

24. The electrode composition of claim 23, wherein the shell monomer of the core-shell structure fluoropolymer is in the range of 0.01-90%.

25. The electrode composition of claim 24, wherein the second monomer of the core-shell structure fluoropolymer is in the range of 0-99%.

26. The electrode composition of claim 25, wherein the shell of the core-shell structure fluoropolymer is proximal to the anode active particles.

27. The electrode composition of claim 26, wherein the cyclic voltammetry test degradation of the fluoropolymer in the anode composition is diminished by > / = 7% compared to PTFE homopolymer, as determined by the integrated intensity in the 0.3 to 0.9 V region using the formula 100 * (1- (integrated current of fluoropolymer) / integrated current of non-modified PTFE).

28. The electrode composition of claim 27, wherein the amount of the shell monomer is the amount required to obtain the diminished degradation.

29. The electrode composition of claim 28, wherein the amount of the shell monomer does not affect the required fibrillation of the PTFE core or the second monomer.

30. The electrode composition of claim 27, wherein the composition contains from about 0.2 to about 10 weight percent fluoropolymer binder and from about 90 to about 99.8 weight percent anode active particles.31 . A method for manufacturing an electrode composition for use in a lithium-ion secondary battery anode, comprising, mixing anode active and conductive particles together with a fluoropolymer whereby said fluoropolymer binder is fibrillated.

32. The method of claim 29, wherein the fluoropolymer a high molecular weight fibrillated PTFE core and a shell comprising a shell monomer which increases the lowest unoccupied molecular orbital (LIIMO) of the core shell structure fluoropolymer which results in higher reduction stability compared with non-modified PTFE.

33. The method of claim 30, carried out substantially free from solvent.

34. A lithium-ion secondary battery comprising: a. an anode comprising: an anode electrode layer adhered to a metal current collector, said anode electrode layer comprising an anode electrode composition comprising: anode active particles; core-shell structure fluoropolymer binder comprising a high molecular weight fibrillatable PTFE core and a shell comprising a shell monomer which increases the lowest unoccupied molecular orbital (LUMO) of the core shell structure fluoropolymer which results in higher reduction stability compared with non-modified PTFE. b. a cathode; c. a separator between said cathode and said anode; and d. an electrolyte in communication with said cathode, anode and separator,35. The lithium-ion secondary battery of claim 34, wherein the shell monomer of the core-shell structure fluoropolymer has a structure of alkene, hydrofluoroolefin, or perfluoro(alkyl vinyl ether) (PAVE).

36. The lithium-ion secondary battery electrode composition of claim 35, wherein the shell monomer of the core-shell structure fluoropolymer is selected from group comprising ethylene, VF2, PMVE, PEVE and PPVE.

37. The lithium-ion secondary battery of claim 36, wherein the shell of the coreshell structure fluoropolymer is proximal to the anode active particles.

38. The lithium-ion secondary battery of claim 37, wherein the core-shell structure fluoropolymer binder is about 87% core and 13% shell.

39. The lithium-ion secondary battery of claim 38, wherein the PTFE core of the core-shell structure fluoropolymer is 100 wt % fibrilliatable PTFE.

40. The lithium-ion secondary battery of claim 39, wherein the shell monomer PEVE of the core-shell structure fluoropolymer is 5.15 wt% of the shell.41 . The lithium-ion secondary battery of claim 40 having about 146% longer cycle life at a given cycling rate than an identical battery having a non modified PTFE binder.

42. The lithium-ion secondary battery of claim 37, wherein the core-shell structure fluoropolymer binder is about 68.4% core and 31 .6% shell.

43. The lithium-ion secondary battery of claim 42, wherein the PTFE core of the core-shell structure fluoropolymer is 100 wt % fibrillated PTFE.

44. The lithium-ion secondary battery of claim 43, wherein the shell monomer PPVE of the core-shell structure fluoropolymer is 9.08 wt% of the shell.

45. The lithium-ion secondary battery of claim 44 having about 158% longer cycle life at a given cycling rate than an identical battery having a non-modified fluoropolymer binder.

46. The lithium-ion secondary battery of claim 37, wherein the core-shell structure fluoropolymer binder is about 91.3% core and 8.7% shell.

47. The lithium-ion secondary battery of claim 46, wherein the PTFE core of the core-shell structure fluoropolymer is 100 wt % fibrillatable PTFE.

48. The lithium-ion secondary battery of claim 47, wherein the shell monomer ethylene of the core-shell structure fluoropolymer is 0.69 wt% of the shell.

49. The lithium-ion secondary battery of claim 48 having about 333% longer cycle life at a given cycling rate than an identical battery having a non modified fluoropolymer binder.

50. The lithium-ion secondary battery of claim 37, wherein the core-shell structure fluoropolymer binder is about 92.5% core and 7.5% shell.51 . The lithium-ion secondary battery of claim 50, wherein the PTFE core of the core-shell structure fluoropolymer is 100 wt% fibrillatable PTFE .

52. The lithium-ion secondary battery of claim 51 , wherein the shell monomer VF2 of the core-shell structure fluoropolymer is 37.3 wt% of the shell.

53. The lithium-ion secondary battery of claim 52 having about 158% longer cycle life at a given cycling rate than an identical battery having a non-modified fluoropolymer binder.

54. The lithium-ion secondary battery of claim 37, wherein the core-shell structure fluoropolymer binder is about 18% core and 82% shell.

55. The lithium-ion secondary battery of claim 54, wherein the PTFE core of the core-shell structure fluoropolymer is 100 wt% fibrillatable PTFE.

56. The lithium-ion secondary battery of claim 55, wherein the shell monomer PMVE of the core-shell structure fluoropolymer is 0.04 wt% of the shell.

57. The lithium-ion secondary battery of claim 56 having about 342% longer cycle life at a given cycling rate than an identical battery having a non-modified fluoropolymer binder.

58. The secondary lithium-ion battery of claim 37, wherein the fluoropolymer binder has a molecular weight to provide inter-particle fibrillation without initiation of fibrillation until the fluoropolymer binder is homogenously mixed with the other electrode components.

59. The secondary lithium-ion battery of claim 37, wherein said anode electrode composition is prepared by mixing the anode active particles, and fluoropolymer binder substantially free from solvent.

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