Electrode formulations for li-ion batteries and methods of making solvent-free electrodes

Abstract

To provide an electrode for a Li-ion battery by a solvent-free deposition technique on a metal substrate.SOLUTION: A Li-ion battery electrode comprising an active filler for an anode or a cathode, an electronically conductive filler and a fluoropolymer binder, said binder consisting of a mixture of two fluoropolymers: a non-functional fluoropolymer A and a fluoropolymer B having at least one functionality, wherein said fluoropolymers A and B contain at least one fluoromonomer selected from vinyl fluoride; vinylidenefluoride (VDF); trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE) and the like, and wherein said fluoropolymer B comprises a monomer unit having at least one carboxylic functional group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates generally to the field of electrical energy storage in rechargeable secondary batteries of the Li-ion type. More specifically, the present invention relates to an electrode formulation for Li-ion batteries, which comprises a binder based on a mixture of fluoropolymers. The present invention also relates to a method for preparing an electrode using said formulation by the technique of solvent-free deposition on a metal substrate. The present invention finally relates to the electrode obtained by this method, and to a Li-ion storage battery comprising at least one such electrode. [Background technology]

[0002] A Li-ion battery comprises at least one negative electrode or anode bonded to a copper current collector, a positive electrode or cathode bonded to an aluminum current collector, a separator, and an electrolyte, which consists of a lithium salt, typically lithium hexafluorophosphate, mixed with a solvent that is a mixture of organic carbonates selected to optimize ion transport and dissociation.

[0003] Rechargeable or secondary batteries have advantages over primary (non-rechargeable) batteries because the associated chemical reactions that occur at the battery's positive and negative electrodes are reversible. The electrodes of secondary batteries can be regenerated multiple times by the application of an electrical charge. Many advanced electrode systems have been developed to store electrical charge. In parallel, significant efforts have been put into developing electrolytes that can improve the capacity of electrochemical cells.

[0004] For its part, the electrode generally comprises at least one current collector on which is deposited, in the form of a film, a composite consisting of a material called the active material because it is electrochemically active towards lithium, a polymer acting as a binder, plus one or more conductive additives, generally carbon black or acetylene black, and, optionally, a surfactant.

[0005] Binders are counted among the so-called inactive components because they do not directly contribute to the cell's capacity. However, their important role in electrode processing and their significant impact on the electrode's electrochemical performance have been widely documented. The main relevant physical and chemical properties of binders are thermal stability, chemical and electrochemical stability, tensile strength (strong adhesiveness and cohesion), and flexibility. The main purpose of using binders is to form a stable network (cohesion) of the electrode's solid components, i.e., the active material and the conductive agent. The binder must also ensure adhesion (adhesion) between the composite electrode and the current collector.

[0006] Polyvinylidene fluoride (PVDF) is the most commonly used binder in lithium-ion batteries due to its excellent electrochemical stability, good adhesion capacity, and strong adhesion to electrode and current collector materials. However, PVDF can only be dissolved in certain organic solvents, such as N-methylpyrrolidone (NMP), which is volatile, flammable, explosive, and highly toxic, posing serious environmental problems. The use of organic solvents requires significant investment in production, recycling, and purification facilities. If lithium-ion battery electrodes could be produced using a solvent-free process, the carbon footprint and production costs would be significantly reduced while still complying with the same specifications.

[0007] A paper by Wang et al. (J. Electrochem. Soc. 2019 166(10):A2151-A2157) analyzed the effect of several properties of PVDF binders on electrodes fabricated by dry powder coating (electrostatic spray deposition). To improve adhesion to the metal substrate and cohesion of the electrode, a heat treatment step at 200°C for 1 hour was performed. The electrodes contained 5% by weight of binder. Two binders with different viscosities were used: HSV900 (50 kpoise) and Alfa Aesar grade (25 kpoise).

[0008] Fluid binders provide the best adhesion but worse high discharge rate behavior than viscous binders (under these conditions, capacity retention improves from 17% to 50% without compromising bond strength and long-term cycling performance). The porosity of the binder layer increases with the molecular weight of the PVDF.

[0009] However, the influence of different PVDF blends on the properties of electrodes fabricated by the dry coating method was not described.

[0010] Compared to the traditional method of producing electrodes in wet suspension, dry (solvent-free) production methods are simpler, eliminate the emission of volatile organic compounds, and offer the possibility of producing electrodes with greater thickness (>120 μm) with higher energy densities in the final energy storage device. While the change in production technique only slightly affects the active material of the electrode, the polymer additives responsible for the electrode's mechanical integrity and its electrical behavior must be suitable for the new manufacturing conditions.

[0011] There remains a need to develop new electrode compositions for Li-ion batteries that are suitable for implementation without the use of organic solvents.

[0012] It is therefore an object of the present invention to provide a Li-ion battery electrode composition that is convertible.

[0013] The present invention also aims to provide a method for producing an electrode for a Li-ion battery using said formulation by the technique of solvent-free deposition on a metal substrate. Finally, the present invention relates to the electrode obtained by this method.

[0014] Finally, the invention aims to provide a rechargeable Li-ion accumulator comprising at least one such electrode. [Prior art documents] [Non-patent literature]

[0015] [Non-Patent Document 1] Wang et al. J.Electrochem.Soc.2019 166(10):A2151-A2157 Summary of the Invention [Problem to be solved by the invention]

[0016] The technical solution proposed by the present invention is an electrode composition for Li-ion batteries comprising a binder based on a mixture of at least two fluoropolymers, one of which has one or more functional groups.

[0017] The present invention relates first to a Li-ion battery electrode for an anode or cathode, comprising an active filler, an electronically conductive filler, and a fluoropolymer binder, characterized in that the binder comprises a mixture of two fluoropolymers: a non-functionalized fluoropolymer A and a fluoropolymer B having at least one functional group.

[0018] The present invention also provides a method for producing a Li-ion battery electrode, comprising the following steps: - mixing the active fillers, the polymer binder and the conductive fillers using solvent-free thermomechanical mixing to obtain an electrode formulation; depositing said electrode formulation on a metal substrate to obtain a Li-ion battery electrode; - consolidating said electrode by heat treatment; The present invention relates to a method, including:

[0019] The present invention also relates to a Li-ion battery electrode produced by the above method.

[0020] The present invention also provides a Li-ion secondary battery comprising a negative electrode, a positive electrode, and a separator, wherein at least one electrode is as described above.

[0021] The present invention makes it possible to overcome the drawbacks of the state of the art. More specifically, the present invention provides: - controlling the distribution of binders and conductive fillers on the surface of the active fillers; Ensuring the cohesion and mechanical integrity of the electrode by ensuring good film formation or compaction of the formulation, which can be difficult to achieve with solvent-free methods; - Creating adhesion on metal substrates, -Ensuring uniformity of electrode composition in thickness and width of the electrode; - Controlling the porosity of the electrode and ensuring its uniformity in thickness and width; - reducing the overall binder content in the electrode, which remains higher than the binder content of standard slurry processes in the case of known solvent-free processes; - To provide a technology that makes it possible to improve the mechanical strength of a self-supporting film of an electrode formulation, where the formulation achieves sufficient mechanical behavior for handling and winding / unwinding steps when the solvent-free electrode production process proceeds through the intermediate step of producing a self-supporting film of the formulation before assembly on a current collector. It means making it possible.

[0022] The advantages of this technique are that it improves the following properties of the electrode: thickness uniformity of composition, porosity uniformity, cohesion, and adhesion to the metal substrate. It also reduces the binder content required for the electrode, and can reduce the heat treatment temperature and / or time to control porosity and improve adhesion. DETAILED DESCRIPTION OF THE INVENTION

[0023] The invention will now be explained in more detail and in a non-limiting manner in the following description.

[0024] According to a first aspect, the present invention relates to a Li-ion battery electrode for an anode or cathode, comprising an active filler, an electronically conductive filler and a fluoropolymer binder. Characteristically, said binder consists of a mixture of two fluoropolymers: a non-functionalized fluoropolymer A and a fluoropolymer B having at least one functional group.

[0025] According to various embodiments, the electrode includes the following features, in combination where appropriate: Contents listed are by weight unless otherwise stated.

[0026] The present invention uses a fluoropolymer. The term "fluoropolymer" means a polymer containing a fluorine group -F. A fluoropolymer contains a vinyl group that can be ring-opened to polymerize, and contains at least one monomer in its chain that is directly bonded to the vinyl group and is selected from compounds containing at least one fluorine atom, a fluoroalkyl group, or a fluoroalkoxy group.

[0027] Examples of fluorinated vinyl monomers include vinyl fluoride; vinylidene fluoride (VDF); trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), 5-perfluoro(ethyl vinyl) ether (PEVE), and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); and perfluoro(2,2-dimethyl-1,3-dioxole) (PDD) with the formula CF2 = CFOCF2CF(CF3)OCF2. Examples of suitable fluoropolymers include: CFX products (wherein X is SOF, COH, CHOH, CHOCN, or CHOPOH); products of the formula CF=CFOCFCFSOF; products of the formula F(CF)CHOCF=CF (wherein n is 1, 2, 3, 4, or 5); products of the formula RCHOCF=CF (wherein R is hydrogen or F(CF) and m is 1, 2, 3, or 4); products of the formula ROCF=CH (wherein R is F(CF) and p is 1, 2, 3, or 4); perfluorobutylethylene (PFBE); 3,3,3-trifluoropropene and 2-trifluoromethyl-3,3,3-trifluoro-1-propene. The fluoropolymer may be a homopolymer or a copolymer, and may also contain non-fluoromonomers such as ethylene.

[0028] The fluoropolymer that is part of each of the compositions of polymers A and B can be a homopolymer, or a copolymer containing two or more of the fluoromonomers listed above, or a mixture of a homopolymer and a copolymer, or a mixture of two copolymers, which can also contain non-fluorocomonomers such as ethylene.Terpolymers such as those based on VDF, TFE and HFP are excluded from the scope of the present invention.

[0029] In the electrode composition according to the present invention, the binder is a mixture of fluoropolymers A and B, and only fluoropolymer B has one or more functional groups that can exhibit adhesion to the metal substrate and good cohesion of the materials that make up the electrode.

[0030] Fluoropolymer B comprises monomer units having at least one carboxylic acid functional group.

[0031] The functional groups are introduced onto the fluoropolymer B by chemical reaction, which may be grafting or copolymerization, of the fluoromonomer with a monomer having at least one -COOH group and a vinyl functional group copolymerizable with the fluoromonomer, according to techniques well known to those skilled in the art.

[0032] According to one embodiment of the fluoropolymer B, the functional groups have carboxylic acid functional groups, which are (meth)acrylic acid type groups selected from acrylic acid, methacrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate and hydroxyethylhexyl (meth)acrylate.

[0033] According to one embodiment, the units with carboxylic acid functionality further contain heteroatoms selected from oxygen, sulfur, nitrogen and phosphorus.

[0034] According to one embodiment, the functional groups are introduced onto the fluoropolymer B by means of a transfer agent used during the synthesis process. The transfer agent is a polymer having a molar mass of less than or equal to 20,000 g / mol and containing carboxylic acid groups. Oligomers of acrylic acid are an example of this type of transfer agent.

[0035] The content of functional groups in polymer B is at least 0.01 mol %, preferably at least 0.1 mol %, and at most 15 mol %, preferably at most 10 mol %.

[0036] The fluoropolymers used in the present invention can be obtained by known polymerization methods such as solution, emulsion or suspension polymerization. According to one embodiment, they are prepared by emulsion polymerization in the absence of fluorinated surfactants.

[0037] According to one embodiment, the binder is a fluoropolymer A comprising a VDF homopolymer and / or at least one copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), a functionalized fluoropolymer B comprising VDF monomer units or VDF and HFP monomer units, the functionalized fluoropolymer B having at least one carboxylic acid function, Contains:

[0038] Preferentially, fluoropolymer A comprises a VDF homopolymer and / or at least one VDF-HFP copolymer with an HFP content of at least 3% by weight, preferably at least 6% by weight, said VDF-HFP copolymer having an HFP content of at most 55%, preferably at most 50%.

[0039] According to one embodiment, the fluoropolymer A is a VDF homopolymer or a mixture of VDF homopolymers.

[0040] According to one embodiment, fluoropolymer A consists of a single VDF-HFP copolymer with an HFP content equal to or greater than 3%.

[0041] According to one embodiment, fluoropolymer A consists of a mixture of two or more VDF-HFP copolymers, each copolymer having an HFP content of at least 3%.

[0042] According to one embodiment, fluoropolymer A consists of a mixture of PVDF homopolymer and VDF-HFP copolymer with an HFP content of 3% or more.

[0043] According to one embodiment, fluoropolymer B comprises VDF and acrylic or methacrylic units.

[0044] According to one embodiment, fluoropolymer B comprises VDF, HFP and acrylic or methacrylic units.

[0045] The polymer binder comprises 10% to 99% by weight of polymer A and 1% to 90% by weight of polymer B.

[0046] According to one embodiment, the mixture comprises: i. a weight content of polymer A between 10% and 99%, preferably between 10% and 95% and advantageously between 10% and 55%, ii. a weight content of polymer B between 1% and 90%, preferably between 5% and 90%, advantageously between 45% and 90%, Includes.

[0047] The active materials in the negative electrode are generally lithium metal, graphite, silicon / carbon composites, silicon, CF with x between 0 and 1. x Fluoro-graphite of the type, and LiTiO 12 It is a type titanate.

[0048] The active material in the positive electrode is generally of the LiMO2 type, LiMPO4 type, Li2MPO3F type, Li2MSiO4 type (M is Co, Ni, Mn, Fe or a combination thereof), LiMn2O4 type or S8 type.

[0049] The conductive fillers are selected from carbon black, natural or synthetic graphite, carbon fibers, carbon nanotubes, metal fibers and powders, and conductive metal oxides, and are preferentially selected from carbon black, natural or synthetic graphite, carbon fibers, and carbon nanotubes.

[0050] Mixtures of these conductive fillers can also be produced, and in particular the use of carbon nanotubes in combination with another conductive filler, such as carbon black, can have the advantage of reducing the conductive filler content in the electrode and reducing the polymer binder content due to their lower specific surface area compared to carbon black.

[0051] According to one embodiment, a polymeric dispersing agent, different from the binder, is used in the mixture with the conductive filler to break up any agglomerates present and aid their dispersion in the final formulation containing the polymeric binder and the active filler. The polymeric dispersing agent is selected from poly(vinylpyrrolidone), poly(phenylacetylene), poly(meta-phenylenevinylidene), polypyrrole, poly(para-phenylenebenzobisoxazole), poly(vinyl alcohol), and mixtures thereof.

[0052] The weight composition of the electrode is 50% to 99%, preferably 50% to 99%, of active fillers, 25% to 0.05%, preferably 25% to 0.5%, of a conductive filler; 25% to 0.05%, preferably 25% to 0.5%, of a polymer binder; - 0-5% of at least one additive selected from the list: plasticizers, ionic liquids, dispersing agents for conductive fillers, flow agents for formulations, fibrillating agents such as polytetrafluoroethylene (PTFE), All these percentages add up to 100%.

[0053] The present invention also provides a method for producing a Li-ion battery electrode, comprising the steps of: - mixing the active fillers, the polymer binder, the conductive fillers and any additives by a method that makes it possible to obtain an electrode formulation that can be applied to a metal support by a solvent-free method; - depositing said electrode formulation on a metal substrate by a "solvent-free" method to obtain a Li-ion battery electrode; - consolidating said electrodes by thermal treatment (application of temperatures in the range of up to 50°C above the melting temperature of the polymer, without mechanical pressure) and / or by thermomechanical treatment such as calendering; The present invention relates to a method, including:

[0054] A "solvent-free" method is understood to mean a method in which no step of evaporating residual solvent downstream of the deposition step is necessary.

[0055] Another embodiment of a method for producing an electrode comprises the following steps: - mixing the active fillers, the polymer binder and the conductive fillers by a method that makes it possible to obtain an electrode formulation in which the components are homogeneously mixed; - producing a self-supporting film of the formulation by a thermomechanical method such as extrusion, calendering or thermocompression; - depositing a self-supporting film on a metal substrate by calendering or thermocompression; - consolidating the electrode by heat treatment and / or thermomechanical treatment, for example calendering, this final step being optional if the preceding steps have already achieved a sufficient level of adhesion and / or porosity; Includes.

[0056] Preparing the electrode formulation Polymers A and B are in powder form, the average particle size of which is between 10 nm and 1 mm, preferentially between 50 nm and 500 μm, and even more preferentially between 50 nm and 50 μm.

[0057] Fluoropolymer powders may be obtained by various methods. Powders can be obtained directly by emulsion or suspension synthesis, by drying by spray drying or freeze drying. Powders can also be obtained by grinding techniques such as cryogenic grinding. Upon completion of the powder production step, the particle size can be adjusted and optimized by selection or screening methods.

[0058] According to one embodiment, polymers A and B are introduced simultaneously with the active and conductive fillers at the time of the mixing step.

[0059] According to another embodiment, polymers A and B are mixed together before being mixed with the active and conductive fillers. For example, a mixture of polymers A and B can be produced by co-spraying the latexes of polymers A and B to obtain a mixture in powder form. The mixture thus obtained can then be mixed with the active and conductive fillers.

[0060] Another embodiment of the mixing step consists in proceeding in two steps. First, either polymer A or polymer B, or both, are mixed with the conductive filler by a solvent-free method or co-spraying. This step makes it possible to obtain a homogeneous mixture of the binder and the conductive filler. Then, in a second step, the premixed binder and conductive filler, as well as any fluoropolymer not yet used, are mixed with the active filler. The active filler is mixed with said homogeneous mixture using a solvent-free mixing method to obtain the electrode formulation.

[0061] Another embodiment of the mixing step consists in proceeding in two stages: first, either polymer A or polymer B, or both, are mixed with the active filler by a solventless method or by spraying a liquid containing the binder and / or conductive filler onto a fluidized powder bed of the active filler. This step makes it possible to obtain a homogeneous mixture of the binder and the active filler. Then, in a second step, the binder, the active filler, and any fluoropolymer not yet used are mixed with the conductive filler.

[0062] Another embodiment of the mixing step consists in proceeding in two steps: first, the active filler is mixed with the conductive filler by a solvent-free method, then in a second step, the two polymers A and B are mixed simultaneously with the premixed active filler and conductive filler, or the polymers A and B are mixed one after the other with the premixed active filler and conductive filler.

[0063] Solvent-free mixing methods for the various components of electrode formulations include, but are not limited to, stirring mixing, air jet mixing, high shear mixing, V-mixer mixing, screw mixer mixing, double cone mixing, drum mixing, conical mixing, double Z-arm mixing, fluidized bed mixing, planetary mixer mixing, mechanofusion mixing, extrusion mixing, calendering mixing, and milling mixing.

[0064] Other mixing methods include mixing options using a liquid such as water, such as spray drying (co-atomization) or spraying a liquid containing a binder and / or conductive filler onto a fluidized powder bed of active filler.

[0065] At the end of this mixing step, the resulting formulation may undergo a final step of milling and / or screening and / or selection to optimize the particle size of the formulation in preparation for the deposition step onto the metal substrate.

[0066] Compounds in powder form are characterized by their bulk density. It is known in the art that low density compounds are very restrictive in terms of their use and application. The main component contributing to densification is carbon black (0.4 g / cm 3 (bulk density less than 0.1g / cm), carbon nanotubes (bulk density less than 0.1g / cm 3 (bulk density less than 0.9g / cm3) 3The combination of low density components to obtain a polymer binder / electronic conductor / other additive combination is recommended to improve the premixing step downstream of the deposition of the above-mentioned formulation. Such a combination can be achieved by the following methods: a) Dispersion of the ingredients in water or an organic solvent followed by removal of the solvent (co-spraying, freeze drying, extrusion / compounding in the presence of solvent or water, etc.); b) dry or "wet" co-milling using known milling methods such as ball milling or bead milling, followed by an optional drying step; It can be produced by

[0067] Such a method is particularly advantageous for significantly increasing bulk density.

[0068] depositing the electrode formulation on a support According to one embodiment, at the end of the mixing step, the electrode is produced by a solventless powder coating method by depositing the formulation onto a metal substrate by the methods of pneumatic spraying, electrostatic spraying, immersion in a fluidized powder bed, dusting, electrostatic transfer, deposition by a rotating brush, deposition by a rotating metering roll, and calendering.

[0069] According to one embodiment, at the end of the mixing step, the electrode is produced by a two-stage solventless powder coating process. The first step consists of producing a self-supporting film from the premixed formulation by a thermomechanical process such as extrusion, calendering, or thermocompression. This self-supporting film is then assembled with a metal substrate by a combined temperature and pressure process such as calendering or thermocompression.

[0070] The metal support for the electrodes is generally made of aluminum for the cathode and copper for the anode. The metal support may be surface-treated and may have a conductive primer with a thickness of 5 μm or more. The support may also be made of woven or nonwoven carbon fiber fabric.

[0071] Consolidating the electrode formulation The consolidation of the electrode is carried out by heat treatment, by passing through an oven, under an infrared lamp, by passing through a calender with heated rollers, or by passing through a press with heated plates. Another alternative consists of a two-stage process: first, the electrode is subjected to a heat treatment in an oven, under an infrared lamp, or by contacting it with a heated plate without pressure. Then, a compression step at ambient or elevated temperature is carried out by a calender or plate press. This step makes it possible to adjust the porosity of the electrode and improve its adhesion to the metal substrate.

[0072] The present invention also relates to a Li-ion battery electrode produced by the above method.

[0073] According to one embodiment, the electrode is an anode.

[0074] According to one embodiment, the electrode is a cathode.

[0075] The present invention also provides a Li-ion secondary battery comprising a negative electrode, a positive electrode, and a separator, wherein at least one electrode is as described above. [Example]

[0076] The following examples illustrate the scope of the present invention without, however, limiting it.

[0077] product: PVDF1: Vinylidene fluoride homopolymer, 100s -1 and characterized by a melt viscosity of 2500 Pa.s at 230°C.

[0078] PVDF2: A vinylidene fluoride homopolymer having a functionality content of about 1% by weight of carboxylic acid functional groups, -1 and vinylidene fluoride homopolymer characterized by a viscosity of 4000 Pa.s at 230°C.

[0079] Graphite C-NERGY ACTILION GHDR 15-4: Graphite sold by Imerys with a volume mean diameter (Dv50) of 17 μm and a thickness of 4.1 m 2 Graphite characterized by a BET specific surface area of ​​1000 .mu.m / g.

[0080] Preparation of fluoropolymer and graphite blends: Fluoropolymer and graphite blends consisting of 5 wt. % PVDF and 95 wt. % graphite were produced by a dry process using a Minimix mixer sold by Merris International. A mixture of 50 grams of each formulation was prepared in a 250 ml metal jar by shaking in the blender for 1 minute 30 seconds at room temperature.

[0081] Electrode preparation For electrode fabrication, each fluoropolymer / graphite mixture was manually sprinkled onto the surface of an 18 μm thick copper current collector sold by Hohsen Corp. The basis weight of the resulting deposit was approximately 5 × 5 cm. 2 30 mg / cm on the surface 2 At the end of deposition, the electrodes were consolidated under a hot platen press by placing silicone paper between the deposited coating and the upper platen of the press. Each coating was pressed at 205 °C and 6 bar for 10 minutes. At the end of this pressing step, the electrodes were removed from the press and allowed to cool to ambient temperature. The silicone paper was then removed.

[0082] Electrode evaluation The goal of the manufacturing process is to obtain a coating of approximately 100 microns on the metal substrate with sufficient cohesion to allow operation of the electrode without cracking or splitting of the coating. Therefore, the first thing to check is the ability of the formulation to form a coherent, uniform coating on the surface of the current collector. An indicator of this level of compaction is the amount of powder / formulation that is transferred to and remains attached to the surface of the silicone paper at the end of the pressing step. If no pieces of the coating remain attached to the silicone paper, the coating is considered to have good film coating and compaction within the context of the described protocol.

[0083] Another criterion of good mechanical integrity is the level of adhesion obtained on the current collector, which must avoid any spontaneous delamination of the coating.

[0084] Table 1 shows the composition of the PVDF used in the examples according to the invention.

[0085] [Table 1]

[0086] Table 2 shows the properties of an electrode with a composition of 95 wt. % graphite and 5 wt. % PVDF.

[0087] [Table 2]

Claims

1. 1. A Li-ion battery electrode comprising an active filler for an anode or a cathode, an electronically conductive filler, and a fluoropolymer binder, the binder consists of a mixture of two fluoropolymers: a non-functional fluoropolymer A and a fluoropolymer B having at least one functionality; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro(alkyl vinyl) ethers such as perfluoro(methyl vinyl) ether (PMVE), 5-perfluoro(ethyl vinyl) ether (PEVE), and perfluoro(propyl vinyl) ether (PPVE); perfluoro(1,3-dioxole); perfluoro(2,2-dimethyl-1,3-dioxole) (PDD); ２ = CFOCF ２ CF (CF ３ ) OCF ２ CF ２ X product (wherein X is SO ２ F, CO ２ H, CH ２ OH, CH ２ OCN or CH ２ OPO ３ H); ２ = CFOCF ２ CF ２ SO ２ F product; ２ ) nCH ２ OCF = CF ２ wherein n is 1, 2, 3, 4 or 5; １ CH ２ OCF = CF ２ (wherein R １ is hydrogen or F(CF ２ ) m, where m is equal to 1, 2, 3 or 4; ２ OCF=CH ２ (wherein R ２ is F(CF ２ )p, where p is 1, 2, 3, or 4); perfluorobutylethylene (PFBE); 3,3,3-trifluoropropene, and 2-trifluoromethyl-3,3,3-trifluoro-1-propene; The fluoropolymer B comprises a monomer unit having at least one carboxylic acid functional group; A Li-ion battery electrode.

2. The binder is a fluoropolymer A comprising a VDF homopolymer and / or at least one copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), a functionalized fluoropolymer B comprising VDF monomer units or VDF and HFP monomer units, the functionalized fluoropolymer B having at least one carboxylic acid function; 10. The electrode of claim 1 comprising:

3. 3. An electrode according to claim 1 or 2, wherein the at least one VDF-HFP copolymer forming part of the composition of fluoropolymer A has an HFP content of ≥ 6% and ≤ 55%.

4. 3. The electrode according to claim 1, wherein said fluoropolymer A consists of a single VDF-HFP copolymer having an HFP content of 3% or more.

5. 3. The electrode according to claim 1, wherein said fluoropolymer A consists of a mixture of two or more VDF-HFP copolymers, each copolymer having an HFP content of 3% or more.

6. Electrode according to claims 1 to 4, wherein said fluoropolymer A is a homopolymer of vinylidene fluoride or a mixture of homopolymers of vinylidene fluoride.

7. 7. The electrode according to claim 1, wherein the fluoropolymer B comprises VDF units or VDF and HFP units and acrylic acid units or methacrylic acid units.

8. Electrode according to any one of claims 1 to 6, wherein said fluoropolymer B comprises maleic anhydride functionality grafted onto the backbone of a VDF homopolymer or a VDF-HFP copolymer.

9. The mixture i. a weight content of polymer A of ≧10%≦99%≦10% and preferably ≧95% and advantageously ≧10% and ≦55%; ii. a weight content of polymer B of ≥ 1% to ≤ 90%, preferably > 5% to ≤ 90%, advantageously ≥ 45% to ≤ 90%, The electrode according to any one of claims 1 to 8, comprising:

10. The active filler may be selected from the group consisting of lithium metal, graphite, silicon / carbon composites, silicon, fluorographite of the CFx type (x is 0 to 1), and LiTi for the negative electrode. ５ O １２ 10. An electrode according to claim 1, wherein the titanates are selected from the group consisting of:

11. The active filler is LiMO for the positive electrode. ２ Type, LiMPO ４ Type, Li ２ MPO ３ F type, Li ２ MSiO ４ type (wherein M is Co, Ni, Mn, Fe or a combination thereof), LiMn ２ O ４ Type or S ８ 11. An electrode according to claim 1, wherein the active material is selected from the group consisting of:

12. 12. The electrode according to any one of claims 1 to 11, wherein the conductive filler is selected from carbon black, natural or synthetic graphite, carbon fibers, carbon nanotubes, metal fibers and powders, conductive metal oxides, or mixtures thereof.

13. Composition by weight: - 50% to 99% active filler; - 0.05% to 25% conductive filler; - 0.05% to 25%, preferably 25% to 0.5%, of a polymer binder; - 0 to 5% of at least one additive selected from the list: plasticizers, ionic liquids, dispersants for fillers, flow agents for formulations, fibrillating agents, Electrode according to any one of claims 1 to 12, wherein the sum of all these percentages is 100%.

14. A method for manufacturing a Li-ion battery electrode according to any one of claims 1 to 13, comprising the following steps: mixing said active fillers, said polymer binder and said fillers by a method that makes it possible to obtain an electrode formulation that can be applied to a metal support by a solvent-free method; - depositing said electrode formulation onto said metal substrate by a solvent-free method to obtain a Li-ion battery electrode; - consolidating said electrode by thermal and / or thermomechanical treatment; A method comprising:

15. The mixing step mixing the conductive filler with the polymer binder using a solventless method or by co-spraying to obtain an intimate mixture; and mixing the active filler with the intimate mixture using a solvent-free mixing method to obtain an electrode formulation; 15. The method of claim 14, wherein the method is carried out in two steps:

16. 16. The method of claim 14 or 15, wherein the mixing step is carried out by stirring, air jet mixing, milling the mixture, high shear mixing, V-mixer mixing, screw mixer mixing, double cone mixing, drum mixing, conical mixing, double Z-arm mixing, mixing in a fluidized bed, planetary mixer, extrusion, calendering, or mechanofusion.

17. 17. The method according to any one of claims 14 to 16, wherein the solventless powder coating process is carried out by depositing the formulation onto the metal substrate by a method selected from the following methods: pneumatic spraying, electrostatic spraying, immersion in a fluidized powder bed, dusting, electrostatic transfer, deposition by a rotating brush, deposition by a rotating metering roll, and calendering.

18. 17. The method according to any one of claims 14 to 16, wherein the solventless powder coating process is carried out in two steps: a first step consisting of producing a self-supporting film from the premixed formulation using a thermomechanical method, and a second step in which the self-supporting film is assembled with the metal substrate by a method combining temperature and pressure such as calendering or hot pressing.

19. 19. The method according to any one of claims 14 to 18, wherein the consolidation of the electrode is carried out by heat treatment in an oven, under an infrared lamp, or by passing through a calender with heated rolls.

20. A secondary Li-ion battery comprising an anode, a cathode, and a separator, wherein at least one of the electrodes has the composition of any one of claims 1 to 12.

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