Method for manufacturing an electrode comprising a polymer matrix entrapping an electrolyte - Patent Application 20070122997

Abstract

The present invention relates to a method for manufacturing an electrode comprising a polymer matrix enclosing an electrolyte, the method comprising the steps of: a) preparing a composition comprising components intended to be included in the construction of the electrode; and b) forming an electrode from the composition on a support, the composition being such that the composition prepared in step a) is 0.1 s -1 a composition in paste form having a kinematic viscosity of more than 5000 Pa.s measured at a shear gradient of 0.15 mm and at ambient temperature; - a preparation step consisting of introducing the components intended to be included in the construction of an electrode into a mixer equipped with two co-rotating intermeshing screws rotating in a closed sleeve and mixing the components therein, characterized in that the preparation step is carried out at a temperature below 100°C.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an electrode comprising a polymer matrix enclosing an electrolyte, more particularly a liquid electrolyte capable of forming a gel with the polymer matrix (in this case the electrode can be referred to as an ion gel electrode), which electrode is provided for incorporation into an electrochemical accumulator (secondary battery).

[0002] The general technical field of the present invention can be defined as that of energy storage devices, and in particular that of electrochemical accumulators. [Background technology]

[0003] Electrochemical accumulators operate on the principle of an electrochemical cell suitable for delivering an electric current by virtue of the presence in each of them of a pair of electrodes (respectively an anode and a cathode) separated by an electrolyte, the electrodes containing specific substances suitable for reacting by oxidation-reduction reactions, whereby there is an exchange of electrons in the source of the electric current and an exchange of ions that flow from one electrode to the other through the intermediary of the electrolyte.

[0004] Among the accumulators employing this principle, those operating on the principle of intercalation / deintercalation of metal elements occurring at the electrode (and more specifically on the electrode active material) and known by the term metal-ion accumulators (e.g. Li-ion, Na-ion, K-ion, Ca-ion, Mg-ion or Al-ion) have replaced other types of accumulators, such as lead-acid accumulators and Ni-MH accumulators, in particular due to their performance in terms of energy density. In fact, M-ion accumulators, such as Li-ion accumulators, are more expensive than Ni-MH and Ni-Cd accumulators (50-100 Wh kg -1 range) and lead-acid (30-35Wh·kg -1 (which may be in the range of 180Wh kg) -1This allows us to obtain a larger

[0005] From a functional standpoint, in a metal ion accumulator, the reaction at the source of current generation (i.e., when the accumulator is in discharge mode) involves the transfer of metal cations from the cathode through an electrolyte that conducts metal ions, which are plugged into an acceptor network at the anode, while electrons from the reaction at the cathode provide an external circuit to which the anode and cathode are connected.

[0006] More specifically, in the case of a Li-ion accumulator, the anode may contain, as the lithium insertion material, a lithium-based phosphate material (e.g., LiFePO4), an optionally substituted lithiated manganese oxide (e.g., LiMn2O4), a lithium-nickel-manganese-cobalt-based material, LiNi x Mn y Co z O2, where x+y+z=1 (also known by the abbreviation NMC) (e.g., LiNi 0.33 Mn 0.33 Co 0.33 O2 or LiNi 0.6 Mn 0.2 Co 0.2 O2), lithium-nickel-cobalt-aluminum based material LiNi x Co y Al z O2, where x+y+z=1 (also known by the abbreviation NCA) (e.g., LiNi 0.8 Co 0.15 Al 0.05 O2).

[0007] As a lithium insertion material, the cathode may be made of a carbon material such as graphite, silicon carbide (SiC), or silicon oxide (SiO). x Silicon-based compounds such as Li4Ti5O 12 Lithium-ion-doped lithium-ion intercalation materials may include lithiated titanium oxides such as lithium-germanium alloys, or mixtures of several of these lithium intercalation materials, such as mixtures including graphite and silicon-based compounds.

[0008] As mentioned above, an electrolyte is disposed between the cathode and anode, which allows for the movement of ions (typically from metal salts present in the electrolyte) from the anode to the cathode during charging and conversely, discharging.

[0009] The electrolyte may be in the form of a liquid and typically comprises one or more organic solvents (e.g., a mixture of carbonate ester solvents) in which one or more metal salts (e.g., one or more lithium salts if the accumulator is a lithium ion accumulator) are dissolved.

[0010] However, the use of liquid electrolytes has several drawbacks, including: - Problems with liquid electrolyte leaking from batteries; - In the event of thermal runaway in a battery containing an electrolyte, the liquid electrolyte may chemically react with the oxygen in the active material of the anode, which may generate large amounts of gas, which may result in the battery catching fire or even exploding.

[0011] To overcome these drawbacks, an alternative consists in eliminating the use of liquid electrolytes, for example by replacing them with the following solutions: - glass or ceramic lithium ion conductors in purely solid form, for example thin layers deposited by chemical vapor deposition (CVD), for example a layer of LIPON, or a polymer matrix, for example a polymer matrix of poly(vinylidene fluoride), and a lithiated oxide, for example Li7La3Zr2O 12 a layer of a filler-containing composite material comprising: - A dry polymer solid electrolyte made of a polyoxyethylene (POE) type polymer and a lithium salt, for example lithium bis(trifluorosulfonyl)imidide (LiTFSI).

[0012] However, all of these various solutions currently suffer from a number of drawbacks.

[0013] Regarding the use of glass or ceramic lithium-ion conductors, these require implementation or synthesis techniques that are very complex to develop in an industrial context, which may prove to be an obstacle for large-scale production of accumulators.

[0014] For solid dry polymer electrolytes, their ionic conductivities at room temperature are generally in the range of 10 -5 S cm -1 In conventional liquid electrolytes, the ionic conductivity is less than 10 -3 S cm -1 , or 10 -2 S cm -1 This may justify the need to use accumulators containing dry polymer electrolytes at temperatures higher than room temperature, for example in the range of 60-80°C, in order to promote the diffusion of lithium ions in the electrolyte.

[0015] In order to mitigate the drawbacks linked to the use of liquid electrolytes and those of solid electrolytes mentioned above, a new technology developed and illustrated in WO 2015 / 169835 consists in trapping a liquid electrolyte in a polymer matrix to form an integral part of the anode and cathode (these electrodes can be called ion gel electrodes), this technology making it possible to obtain, at room temperature, electrochemical performances comparable to those of lithium ion accumulators comprising a liquid electrolyte not confined in a polymer matrix.

[0016] These electrodes are prepared in a conventional manner by a method comprising the following steps in succession: - preparing an ink (i.e. a liquid dispersion containing the solid components of the electrode in suspension) by mixing the various components intended to be incorporated into the structure of the electrode, the components being the active material, the electronically conductive additive(s), a fluorinated (co)polymer allowing the confinement of the liquid electrolyte, at least one solvent for the fluorinated copolymer (e.g. acetone), a lithium salt, one or more electrolyte solvents (such as carbonate solvents) to solubilize the lithium salt; - depositing the ink once obtained, generally by spreading it on a substrate constituting a current collector; - evaporation of the solvent(s) of the fluorinated (co)polymer and, optionally, subsequent calendering (whereby the desired electrodes are present).

[0017] Typically, ink preparation processes carried out in conventional mixers, such as dispersers or planetary mixers, require a high proportion of solvent(s), which limits the percentage of solids mass in the ink. More specifically, the percentage of solids mass relative to the total mass of the ink typically constitutes 35-49% by mass, while the mass of the liquid electrolyte (salt + electrolyte solvent(s)) constitutes 6-13% of the total mass of the ink, and the solvent(s) of the fluorinated (co)polymer constitutes 45-57% of the total mass of the ink.

[0018] The presence of such amounts of solvent constitutes a limiting factor for the implementation of such a process, in particular on an industrial scale, since it implies providing for the management of the effluents (in this case the solvent or solvents used in large amounts), both in terms of safety (in particular due to the potential flammability of the selected solvent(s) and / or the toxicity of the selected solvent(s)) and solvent removal, which in turn leads to high implementation costs for the process. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] International Publication No. 2015 / 169835 [Patent Document 2] U.S. Patent No. 6,203,944 [Patent Document 3] International Publication No. 00 / 03444 Summary of the Invention [Problem to be solved by the invention]

[0020] In this context, the inventors set out as an objective to provide a new method for manufacturing electrodes comprising a polymer matrix incorporating an electrolyte, which makes it possible to limit or even eliminate the use of large amounts of solvent, and thus is cheaper and limits the drawbacks associated with the use of large amounts of solvent. [Means for solving the problem]

[0021] Towards that end, the inventors have developed a method for manufacturing electrodes that no longer involves the pre-preparation of an ink, but rather the pre-preparation of a composition in the form of a paste containing the ingredients that are to be supplied to go into the structure of the electrode, this preparation being made possible by the use of a specific mixer during this process.

[0022] More specifically, according to the present invention, a method for producing an electrode comprising a polymer matrix trapping an electrolyte comprises the following steps: a) preparing a composition containing ingredients adapted to be incorporated into the structure of an electrode; b) forming an electrode on a substrate from the composition; Including, - the composition prepared in step a) is 0.1 s -1 a composition in the form of a paste having a kinematic viscosity greater than 5000 Pa s measured at a shear rate of 1000 Pa s and at room temperature; and - the preparation step consists in introducing and mixing the components prepared to enter the structure of the electrode into a mixer equipped with two co-rotary interpenetrating screws rotating in a closed sleeve, said preparation step being carried out at a temperature below 100°C.

[0023] The use of this particular mixer makes it possible to use less solvent than methods using conventional mixers, thus limiting the drawbacks associated with effluent management. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a graph showing the variation of voltage U (in V) as a function of capacity C (in mAh / g) for a cathode obtained by the method of Example 1, curve a) for the first cycle and curve b) for the second cycle. [Figure 2] FIG. 2 is a graph showing the variation of voltage U (in V) as a function of capacity C (in mAh / g) for an anode obtained by the method of Example 3, curve a) for the first cycle and curve b) for the second cycle. [Figure 3] FIG. 3 is a cross-sectional view of a particular bi-screw mixer, previously described, that can be used in connection with the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] First, the method of the present invention comprises the step of preparing a composition in the form of a paste containing the components constituting the electrode by introducing and mixing the components into a mixer equipped with two co-rotating intermeshing screws rotating in a closed sleeve.

[0026] The introduction of the components may be simultaneous or sequential, and the introduction may be - closure sleeve 1; - two intermeshing screws 3 and 5; - first component introduction zone 7 (called zone A); a second component introduction zone 9 (called zone B), and - outlet 11 for discharging the formed composition; - a motor 13 connected to the screw, which causes the screw to rotate This may be done in separate locations (e.g., introduction of solid components in a first introduction zone via one or more inlets of the mixer, and introduction of liquid components in a second introduction zone via one or more inlets of the mixer), such as with the mixer illustrated in FIG. 3 attached hereto, which includes

[0027] More specifically, this composition contains, as components constituting the electrode, - at least one electrode active material; - at least one polymer is prepared, which is incorporated into the polymer matrix; - electrolytes, Including, - optionally at least one electronically conductive additive, may also include:

[0028] The electrode active material is a material suitable for inserting and deintercalating metal ions into its structure, and the metal ions are, for example, alkali ions (e.g., lithium ions when the accumulator (secondary battery) is a lithium accumulator, sodium ions when the accumulator is a sodium accumulator, and potassium ions when the accumulator is a potassium accumulator), alkaline earth ions (e.g., magnesium ions when the accumulator is a magnesium accumulator, and calcium ions when the accumulator is a calcium accumulator), or metal ions (e.g., aluminum ions when the accumulator is an aluminum ion accumulator).

[0029] The properties of the active material, of course, vary depending on its purpose, i.e., whether it is supplied for the anode or the cathode.

[0030] Also, when the method of the present invention is a method for manufacturing an anode, examples of electrode active materials that can be incorporated into the structure of the anode of a lithium accumulator include the following: - Metal chalcogenides of the formula LiMQ2 (where M is at least one metal element selected from metal elements such as Co, Ni, Fe, Mn, Cr, V, Al, and Q is a chalcogen such as O or S), preferably metal chalcogenides of the formula LiMO2 (where M is as defined above), for example, preferably LiCoO2, LiNiO2, LiNi x Co 1-x O2 (0 < x < 1), substances based on lithium-nickel-manganese-cobalt LiNi x Mn y Co z O2 (where x + y + z = 1) (also known by the abbreviation NMC), for example, LiNi 0.33 Mn 0.33 Co 0.33 O2, or substances based on lithium-nickel-cobalt-aluminum LiNi x Co y Al z O2 (where x + y + z = 1) (also known by the abbreviation NCA), for example, LiNi 0,8 Co 0.15 Al 0.05 O2; - Chalcogenides with a spinel structure, such as LiMn2O4; - Of the formula M1M2(JO4) f E 1-fwherein M1 is lithium which may be partially substituted with another alkali element to a degree of substitution of less than 20%, M2 is a transition metal element in the oxidation state +2 selected from Fe, Mn, Ni and combinations thereof, which may be partially substituted with one or more additional metal elements in the oxidation states +1 to +5 to a degree of substitution of less than 35%, and JO4, where J is an oxyanion selected from P, S, V, Si, Nb, Mo and combinations thereof, E is a fluoride, hydroxide, or chloride anion, and f is the mole fraction of the oxyanion JO4 and is typically comprised between 0.75 and 1, inclusive.

[0031] More specifically, the lithiated or partially lithiated materials may be phosphorus-based (which in turn means that the oxyanions satisfy the formula PO4) and may have an ordered or modified olivine structure.

[0032] Lithiated or partially lithiated materials have the specific formula Li 3-x M' y M'' 2-y (JO4)3 (wherein 0≦x≦3, 0≦y≦2, M′ and M″ are the same or different metal elements, at least one of M′ and M″ is a transition metal element, and JO4 is preferably PO4, which may be partially substituted with another oxyanion having J selected from S, V, Si, Nb, Mo, and combinations thereof).

[0033] Lithiated or partially lithiated materials have the formula Li(Fe x Mn 1-x )PO4, where 0≦x≦1, and preferably x is equal to 1 (which in turn means that the corresponding material is LiFePO4).

[0034] When the method of the present invention is a method for producing a negative electrode, examples of electrode active materials that can be incorporated into the structure of the negative electrode of the lithium accumulator include: carbonaceous materials, such as graphitic carbon, which are suitable for intercalating lithium and which may typically be present in the form of powders, flakes, fibers or spheres (for example mesocarbon microbeads); silicon-based compounds, such as silicon carbide SiC or silicon oxide SiO x ; - metallic lithium; lithium alloys, such as those described in US Pat. No. 6,203,944 and / or WO 00 / 03444; lithiated titanium oxide, for example of the formula Li (4-x) M x Ti5O 12 or Li4M y Ti (5-y) O 12 (wherein x and y are in the range of 0 to 0.2, and M is an element selected from Na, K, Mg, Nb, Al, Ni, Co, Zr, Cr, Mn, Fe, Cu, Zn, Si, and Mo, and a specific example is Li4Ti5O 12 These oxides, after lithium is inserted, are lithium insertion materials with low thermal expansion; - non-lithiated titanium oxides, for example, TiO2; - Formula M y Ti (5-y) O 12 wherein y is in the range of 0 to 0.2 and M is an element selected from Na, K, Mg, Nb, Al, Ni, Co, Zr, Cr, Mn, Fe, Cu, Zn, Si, and Mo; lithium-germanium alloys, for example of the formula Li 4.4 containing a crystalline phase of Ge; or - Mixtures thereof, for example mixtures containing graphite and silicon-based compounds.

[0035] The polymer or polymers suitable for incorporating into the structure of the polymer matrix are advantageously selected from gelling polymers suitable for gelling in contact with an electrolyte, thereby trapping the electrolyte (the resulting electrode thus forms what are commonly referred to as "ion gel electrodes"), and may more particularly be selected from fluorinated polymers comprising at least one repeating unit resulting from the polymerization of a fluorinated monomer and preferably at least one repeating unit resulting from the polymerization of a monomer comprising at least one carboxylic acid group, optionally in the form of a salt.

[0036] It should be understood that the repeat units resulting from the polymerization of fluorinated monomers and the repeat units resulting from the polymerization of monomers comprising at least one carboxylic acid group, optionally in the form of a salt, if any, are chemically distinct repeat units, and in particular the repeat unit(s) resulting from the polymerization of fluorinated monomers do not comprise any carboxylic acid group, optionally in the form of a salt.

[0037] For gelling polymers (gelling polymers), the repeating units resulting from the polymerization of a fluorinated monomer may more particularly be one or more repeating units resulting from the polymerization of one or more ethylene monomers containing at least one fluorine atom and optionally one or more other halogen atoms; examples of this type of monomer are: - C2-C8 perfluoroolefins, such as tetrafluoroethylene and hexafluoropropene (also known as HFP); - C2-C8 hydrogenated fluoroolefins, such as vinylidene fluoride, vinyl fluoride, 1,2-difluoroethylene, and trifluoroethylene; - Formula CH2=CHR 1 (In the formula, R 1 is a C1-C6 perfluoroalkyl group); - C2-C6 fluoroolefins containing one or more other halogen atoms (chlorine, bromine, iodine, etc.), such as chlorotrifluoroethylene; - Formula CF2=CFOR 2 (In the formula, R 2 is a C1-C6 fluoro- or perfluoroalkyl group, for example, CF3, C2F5, C3F7), (per)fluoroalkyl vinyl ethers; - Formula CF2=CFOR 3 (In the formula, R 3 is C1~C 12 Alkyl groups, C1-C 12 Alkoxy group or C1-C 12 and / or monomers of (per)fluoroalkoxy groups, such as perfluoro-2-propoxypropyl groups; and / or - Formula CF2=CFOCF2OR 4 (In the formula, R 4 is a fluoro- or perfluoro-C1-C6-alkyl group, for example, CF2, C2F5, C3F7, or a fluoro- or perfluoro-C1-C6-alkoxy group, for example, -C2F5-O-CF3).

[0038] More particularly, the gelling polymer may contain, as repeating units resulting from the polymerization of fluorinated monomers, repeating units resulting from the polymerization of monomers from the category of C2-C8 perfluoroolefins, such as hexafluoropropene, and repeating units resulting from the polymerization of monomers from the category of C2-C8 hydrogenated fluoroolefins, such as vinylidene fluoride.

[0039] The repeat unit resulting from the polymerization of a monomer comprising at least one carboxylic acid group, optionally in the form of a salt, may more particularly be one or more repeat units resulting from the polymerization of a monomer of formula (I): [ka] [In the formula, R 5 ~R 7are each independently a hydrogen atom or a C1-C3 alkyl group, and R 8 is a hydrogen atom or a monovalent cation (eg, an alkali cation, an ammonium cation), and specific examples of this type of monomer are acrylic acid or methacrylic acid].

[0040] A particular gelling polymer that can be used in connection with the present invention may be a polymer comprising repeating units resulting from the polymerization of vinylidene fluoride, repeating units resulting from the polymerization of a monomer containing at least one carboxylic acid group, such as acrylic acid, and optionally repeating units resulting from the polymerization of a fluorinated monomer other than vinylidene fluoride (more particularly repeating units resulting from the polymerization of hexafluoropropene).

[0041] Even more particularly, gelling polymers that can be used in the context of the present invention are gelling polymers in which the repeating units mentioned above result from the polymerization of: - at least 70 mol % of hydrogenated C2-C8 fluoroolefin, preferably vinylidene fluoride; - 0.1 to 15 mol % of a C2 to C8 perfluoroolefin, preferably hexafluoropropene; and - 0.01 to 20 mol % of a monomer of formula (I) above, preferably acrylic acid.

[0042] Furthermore, the gelling polymer(s) advantageously have an intrinsic viscosity measured in N,N-dimethylformamide at 25° C. in the range of 0.1 to 1.0 L / g, preferably 0.25 to 0.45 L / g.

[0043] More specifically, the intrinsic viscosity is determined using an Ubbelohde viscometer based on the fall time at 25°C of a solution of the polymer in a solvent (N,N-dimethylformamide) at a concentration of approximately 0.2 g / dL, according to the following formula:

number

[0044] The electrolyte is advantageously a liquid electrolyte and more particularly a liquid electrolyte capable of gelling on contact with a polymer matrix, in which case the latter comprises one or more gelling polymers (gelling polymers).

[0045] The liquid electrolyte may comprise (or may consist of) at least one organic solvent, at least one metal salt, and optionally an additive belonging to the category of carbonaceous compounds (which additive is then understood to be different from the carbonate ester solvent that may be contained in the electrolyte).

[0046] The one or more organic solvents may be carbonate solvents, and more particularly: - cyclic carbonate solvents, such as ethylene carbonate (symbolized by the abbreviation EC), propylene carbonate (symbolized by the abbreviation PC), butylene carbonate, vinylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate, and mixtures thereof; - Linear carbonate solvents, such as diethyl carbonate (symbolized by the abbreviation DEC), dimethyl carbonate (symbolized by the abbreviation DMC), ethyl methyl carbonate (symbolized by the abbreviation EMC), and mixtures thereof. It may be.

[0047] The one or more organic solvents may be an ester solvent (eg, ethyl propionate or n-propyl propionate), a nitrile solvent (eg, acetonitrile), or an ether solvent (eg, dimethyl ether or 1,2-dimethoxyethane).

[0048] The organic solvent(s) may be an ionic liquid, i.e., a compound formed by the combination of a positively charged cation and a negatively charged anion that is conventionally in the liquid state at temperatures below 100°C under atmospheric pressure.

[0049] More specifically, the ionic liquid is - cations selected from imidazolium, pyridinium, pyrrolidinium, piperidinium, quaternary ammonium, quaternary phosphonium, pyrazolium, which cations may be optionally substituted, for example by at least one alkyl group containing 1 to 30 carbon atoms; an anion selected from halide anions, perfluorinated anions, and borate anions, may include:

[0050] More specifically, the cation may be selected from the following cations: - Below formula (II): [ka] [In the formula, R 13 and R 14 are each independently a C1-C8 alkyl group, and R 15 , R 16 , R 17 , and R 18 are each independently a hydrogen atom or a C1-C 30 Alkyl groups, preferably C1-C 18 alkyl group, more preferably a C1 to C8 alkyl group. pyrrolidinium cation; - Below formula (III): [ka] [In the formula, R 19 and R 20 are each independently a C1-C8 alkyl group, and R 21 , R 22 , R 23 , R 24 , and R 25 are each independently a hydrogen atom or a C1-C 30 Alkyl groups, preferably C1-C 18 alkyl group, more preferably a C1 to C8 alkyl group. piperidinium cation; - quaternary ammonium cations; - quaternary phosphonium cations; - imidazolium cation; and - Pyrazolium cation.

[0051] In particular, the positively charged cation may be selected from the following cations: - Below formula (II-A): [ka] a pyrrolidinium cation of - Below formula (III-A): [ka] piperidinium cation.

[0052] When the cation is a quaternary ammonium cation, it may be a tetraalkylammonium cation, a trialkylarylammonium cation, or a tetraarylammonium cation, and the alkyl groups, if present, may be the same or different and may be straight-chain or branched alkyl groups containing 4 to 12 carbon atoms, preferably 4 to 6 carbon atoms, and the aryl groups, if present, may be the same or different and may be phenyl, benzyl, or naphthyl groups. More specifically, the cation may be a tetraethylammonium cation, a tetrapropylammonium cation, a tetrabutylammonium cation, a trimethylbenzylammonium cation, a methyltributylammonium cation, a N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium cation, a N,N-dimethyl-N-ethyl-N-(3-methoxypropyl)ammonium cation, a N,N-dimethyl-N-ethyl-N-benzylammonium cation, a N,N-dimethyl-N-ethyl-N-phenylethylammonium cation, a N-tributyl-N-methylammonium cation, a N-trimethyl-N-butylammonium cation, a N-trimethyl-N-hexylammonium cation, or a N-trimethyl-N-propylammonium cation.

[0053] When the cation is a quaternary phosphonium cation, it may be a tetraalkylphosphonium cation, a trialkylarylphosphonium cation, or a tetraarylammonium cation, in which the alkyl groups, if present, may be the same or different and may be linear or branched alkyl groups containing 4 to 12 carbon atoms, preferably 4 to 6 carbon atoms, and the aryl groups, if present, may be the same or different and may be phenyl, benzyl, or naphthyl groups. More specifically, the cation is a trihexyl(tetradecyl)phosphonium cation or a tetrabutylphosphonium cation.

[0054] When the cation is an imidazolium cation, it may be a 1,3-dimethylimidazolium cation, a 1-(4-sulfobutyl)-3-methylimidazolium cation, a 1-allyl-3H-imidazolium cation, a 1-butyl-3-methylimidazolium cation, a 1-ethyl-3-methylimidazolium cation, a 1-hexyl-3-methylimidazolium cation, a 1-octyl-3-methylimidazolium cation.

[0055] Specifically, the negatively charged anion may be selected from the following: - 4,5-dicyano-2-(trifluoromethyl)imidazole (known by the abbreviation TDI); - bis(fluorosulfonyl)imidide (known as FSI); - Formula (SO2CF3)2N - Bis(trifluoromethylsulfonyl)imidide; - Formula PF6 - hexafluorophosphate; - Formula BF4 - tetrafluoroborate; - Below formula (IV): [ka] of oxaloborate.

[0056] Specific ionic liquids that can be used in accordance with the present invention are those having a cation of formula (II-A) as defined above and a cation of formula (SOCF)N - , PF6 - , or BF4 - The ionic liquid may be an ionic liquid consisting of an anion of

[0057] The metal salt(s) may be salts of the following formulae: MeI, Me(PF6) n , Me(BF4) n , Me(ClO4) n , Me(bis(oxalato)borate) n (Abbreviation Me(BOB) n(which can be represented by MeCF3SO3, Me[N(FSO2)2] n , Me[N(CF3SO2)2] n , Me[N(C2F5SO2)2] n , Me[N(CF3SO2)(R F SO2)] n (In the formula, R F is -C2F5, -C4F9, or -CF3OCF2CF3), Me(AsF6) n , Me[C(CF3SO2)3] n , Me2S n , Me(CFN) (wherein CFN is 4,5-dicyano-2-(trifluoromethyl)imidazole, and when Me is Li, the salt is lithium 4,5-dicyano-2-(trifluoromethyl)imidazole, which salt is known by the abbreviation LiTDI), in which Me is a metal element, preferably a transition metal element, an alkali metal element, or an alkaline earth metal element, more preferably Me is Li (especially when the accumulator of the present invention is a lithium ion or a lithium-air ion). accumulator), Na (especially if the accumulator is a sodium ion accumulator), K (especially if the accumulator is a potassium ion accumulator), Mg (especially if the accumulator is a Mg ion accumulator), Ca (especially if the accumulator is a calcium ion accumulator), and Al (especially if the accumulator is an aluminum ion accumulator), and n is the valence level of the metal element (typically 1, 2, or 3).

[0058] When Me is Li, the salt is preferably LiPF6.

[0059] The concentration of the metal salt in the liquid electrolyte is advantageously at least 0.01M, preferably at least 0.025M, more preferably at least 0.05M, and advantageously at most 5M, preferably at most 2M, and more preferably at most 1M.

[0060] Furthermore, the liquid electrolyte may contain at least one additive from the group of carbonaceous compounds (this additive being understood to be different from the carbonate solvent or solvents contained in the electrolyte, if any), such as vinylene carbonate or fluoroethylene carbonate, in an amount not exceeding 5% by weight of the total weight of the electrolyte.

[0061] A liquid electrolyte that can be used, particularly when the electrode produced by the method of the present invention is for a lithium ion accumulator, is an electrolyte comprising a mixture of carbonate ester solvents (e.g., a mixture of cyclic carbonates, such as a mixture of ethylene carbonate and propylene carbonate, or a mixture of cyclic carbonate and linear carbonate solvents, such as a mixture of ethylene carbonate, propylene carbonate, and dimethyl carbonate), a lithium salt, such as LiPF6 (e.g., 1M), and optionally an additive, such as vinylene carbonate or fluoroethylene carbonate.

[0062] As mentioned above, the composition may comprise at least one electronically conductive additive, i.e. an additive capable of imparting electronic conductivity to the electrode in which it is incorporated; for example, this additive may be chosen from carbonaceous materials, such as carbon black, carbon nanotubes, carbon fibers (in particular vapor-grown carbon fibers, known by the abbreviation VGCF), graphite in powder form, graphite fibers, graphene, and mixtures thereof.

[0063] Furthermore, the composition may contain at least one solvent (optionally separate from the organic solvent of the electrolyte) for the polymer provided to be incorporated into the structure of the polymer matrix, and when the one or more polymers are selected from the class of fluorinated polymers comprising at least one repeating unit resulting from the polymerization of a fluorinated monomer and preferably at least one repeating unit resulting from the polymerization of a monomer comprising at least one carboxylic acid group, optionally in the form of a salt, this solvent may be a solvent from the class of ketones (e.g., acetone). Thanks to the use of a specific mixer, the one or more solvents can be used in smaller amounts than in methods using conventional mixers.

[0064] When the composition comprises at least one solvent as described above, the method advantageously comprises, after the formation step, an evaporation step, which evaporation is selective for the solvent or solvents for the polymer or polymers provided to enter into the structure of the polymer matrix, for example by in-line drying with selective evaporation.

[0065] The preparation step is carried out at a temperature below 100°C, preferably below 80°C, even more preferably below 70°C, and preferably at a temperature above 5°C, more preferably above 10°C, even more preferably above 15°C.

[0066] More particularly, the preparation step can be carried out at ambient temperature (i.e., the temperature at which the preparation step is carried out without heating by any heating element, for example, a temperature in the range of 15 to 35°C, more particularly, a temperature equal to 25°C), or at a temperature higher than ambient temperature, for example, higher than ambient temperature but lower than 100°C. More particularly, the preparation step can be carried out at a temperature higher than ambient temperature but lower than the boiling temperature of the solvent(s) for the polymer(s) provided to enter into the structure of the polymer matrix, if one or more solvents are present in the composition, or higher than room temperature but lower than the melting temperature of the polymer(s) provided to enter into the structure of the polymer matrix, if one or more solvents are not present (it being understood that the temperature at which the preparation step is carried out is always lower than 100°C).

[0067] The preparation process involves the use of very high dynamic viscosities, more particularly, 0.1 s -1 and ambient temperature, it is possible to obtain a composition in the form of a homogeneous paste having a kinematic viscosity, measured at a shear rate of 1000 Pa·s, preferably higher than 6000 Pa·s, more preferably higher than 7000 Pa·s.

[0068] It should be noted that ambient temperature is understood to mean the temperature of the environment in which the kinematic viscosity measurement is carried out without heating by any heating element, for example a temperature in the range of 15 to 35°C, such as a temperature equal to 25°C.

[0069] More specifically, the kinematic viscosity of the composition is measured using a Mavern brand CVO Bohlin rheometer equipped with a Peltier support and a movable cone plate with a diameter of 40 mm and an angle of 4°. For this purpose, the composition is placed between the Peltier support and the movable element with a gap of 150 μm. Optionally, if the composition contains at least one solvent for the polymer that constitutes the polymer matrix, a solvent trap is added to the system to avoid excessively rapid evaporation of the solvent. In viscometer mode, the viscosity is measured at 0.1 s. -1Measurements are carried out at a shear rate of 1000 kJ / min and ambient temperature over an integration time of 5 seconds.

[0070] Furthermore, the composition in paste form is generally prepared under the conditions as defined above (i.e., 0.1 s -1 The composition has a kinematic viscosity at a shear rate of 0.1 s (at ambient temperature) of not more than 20,000 Pa·s, preferably not more than 18,000 Pa·s. -1 Very advantageous results have been obtained when the composition is in the form of a paste having a kinematic viscosity in the range of 7000-12000 Pa·s (at a shear rate of 1000 MPa and ambient temperature).

[0071] Indeed, a particularly advantageous aspect of the method of the present invention is its ability to prepare electrode-forming compositions with very high dynamic viscosities that allow the use of liquid electrolytes and / or organic solvents to be minimized, compared to well-established methods for producing electrodes from inks that are produced based on conventional mixers of the disperser or planetary mixer type and have a dynamic viscosity of less than 5000 Pa·s, or even less than 1000 Pa·s, measured under the above measurement conditions.

[0072] If the composition comprises at least one solvent for the polymer provided so as to enter into the structure of the polymer matrix, these compositions may further comprise, for the preparation process, 50 to 80% by weight of solids relative to the total weight of the composition.

[0073] More particularly, when the composition comprises as components at least one electrode active material, at least one polymer provided to be incorporated into the structure of a polymer matrix, an electrolyte, and optionally at least one electronically conductive additive and at least one solvent for the polymer, the composition obtained further from this preparation step advantageously has a percentage of solids mass that can range from 50 to 80% relative to the total mass of the composition (compared to 35 to 49% in the method using a conventional mixer).Furthermore, these compositions may comprise a mass of electrolyte that amounts to 6 to 11% of the total mass of the composition and a mass of solvent for the polymer that amounts to 11 to 42% of the total mass of the composition (compared to 45 to 57% in the method using a conventional mixer).

[0074] In a particular and advantageous embodiment, the composition may be devoid of one or more solvents for one or more polymers provided to enter the structure of the polymer matrix. In these conditions, the composition may further comprise, for the preparation process, 83 to 90% by weight of solids relative to the total weight of the composition.

[0075] More particularly, when the composition comprises as components at least one electrode active material, at least one polymer provided in a structure of a polymer matrix, an electrolyte, and optionally at least one electronically conductive additive, but lacking one or more solvents for one or more polymers, the percentage of solid mass may be 83-90% of the total mass of the composition, and the mass of the electrolyte may be 10-17% of the total mass of the composition.

[0076] Under these conditions, the solvent evaporation step described above is not necessary.

[0077] The preparation process can be carried out continuously, that is to say that the introduction of the ingredients and their mixing inside the particular mixer is carried out continuously, that is to say over the entire duration of the process.

[0078] Forming an electrode from the composition can be carried out by depositing it through a die, for example a slot die, which conveys the composition onto a substrate through a die whose purpose is to flow the composition from a circular shape to a rectangular shape so as to form a strip on the substrate.

[0079] The composition may optionally be laminated before reaching the substrate so as to reduce its thickness, and the thus laminated composition may be deposited on the substrate by a co-laminating operation with the substrate.

[0080] Before the forming step and after the manufacturing step, the composition can be passed through another mixer, for example a conveying device under pressure, such as a monoscrew conveyor that rotates in a closed sleeve and withstands a higher pressure than the mixture used in the manufacturing step, in which case the forming step can also be carried out through a die, preferably located at the outlet of the other mixer, which die also has the purpose of flowing the composition from a circular shape to a rectangular shape so as to form a strip on the substrate.

[0081] Before being introduced into another mixer, for example a monoscrew conveyor, the composition may be in the form of granules, which are formed at the outlet of a bi-screw mixer used for the manufacturing process to form rods, for example by means of a round die arranged at the outlet from the mixer, this die being equipped with a cutting system arranged at the outlet from the bi-screw mixer.

[0082] After the steps of forming the electrode and optionally the evaporation step, the method may further include the step of calendering the electrode to increase the volumetric energy density.

[0083] The manufacturing method may be a continuous method, i.e., a method that is carried out without interruption throughout its entire implementation period, which means that the electrode is manufactured without interruption throughout the entire implementation period of the method. In other words, this means that steps a) and b) are carried out simultaneously without interruption throughout the entire implementation period of the method, which means that at each time t during the period of the method, a fraction of the composition is subjected to the manufacturing process, while another fraction of the composition is subjected to the forming process. In this case, it should also be understood that all optional steps of the method (e.g., lamination process, drying process), if any, are carried out continuously.

[0084] The invention will now be described in the light of the examples given below by way of non-limiting illustration. [Example]

[0085] This example illustrates the production of a cathode containing 55% by mass of solids relative to the total mass of the electrode by a continuous method according to the invention.

[0086] In the first phase, the ion gel electrode paste was prepared by successively introducing the electrode components in the presence of acetone and mixing them at 25° inside a mixer with two co-rotating intermeshing screws rotating in a closed sleeve. The introduction is carried out by first introducing the solid components and then the liquid components. The paste composition is as follows: graphite (D ) in a mixture of ethylene carbonate and propylene carbonate (1:1) containing 2% by weight of vinyl carbonate. 50 = 20 μm) 39.2 mass%, graphite (D 50= 3.5 μm), 2.7% by weight of a copolymer comprising repeating units resulting from the polymerization of vinylidene fluoride (96.7 mol%), acrylic acid (0.9 mol%), and hexafluoropropene (2.4 mol%), and having an intrinsic viscosity of 0.30 L / g in dimethylformamide at 25°C, 37.5% by weight of anhydrous acetone, and 7.5% by weight of 1 M LiPF6 electrolyte.

[0087] The dynamic viscosity of the composition was measured with a Malvern brand CVO Bohlin rheometer equipped with a Peltier stage and a movable cone-plate with a diameter of 40 mm and an angle of 4°. For this, the paste was placed with a gap of 150 μm between the Peltier stage and the movable element, and a solvent trap was added to the system to avoid excessively rapid evaporation of acetone. The dynamic viscosity was measured in viscometer mode for 0.1 s. -1 Measurements are taken at a shear rate of 1000 kJ / min and 25°C over an integration time of 5 seconds.

[0088] The kinematic viscosity measurement obtained is 7200 Pa·s.

[0089] In the second phase, the electrode paste thus formed is spread on a 10 μm thick copper sheet at the outlet of a specific mixer, then dried and calendered, thereby forming an ion-gel graphite electrode. The mass per unit area of ​​the electrode is 11.3 mg / cm for a thickness of 90 μm. 2 (3.6mAh / cm 2 The capacity of this electrode was verified using a button cell battery against lithium metal.

[0090] The measured total capacity is 350 mAh / g, and the reversible capacity is 300 mAh / g for the first cycle at C / 20. The reversible capacity is 350 mAh / g for the second cycle at C / 20. These data are shown in Figure 1, which represents the change in voltage U (in V) as a function of capacity C (in mAh / g), where curve a) is for the first cycle and curve b) is for the second cycle. [Example]

[0091] This example illustrates the production of an ion gel electrode paste, said paste being prepared according to the manufacturing steps of the method of the present invention and containing 65% solids by weight relative to the total weight of the electrode.

[0092] This electrode paste is prepared by successively introducing the constituents of the electrode in the presence of acetone and mixing them at 25° inside a mixer with two co-rotating intermeshing screws rotating in a closed sleeve, the introduction being carried out by first introducing the solid constituents and then the liquid constituents. The composition of the paste is as follows: graphite (D 50 = 20 μm) 46.4 mass%, graphite (D 50 = 3.5 μm), 3.2 wt. % copolymer comprising the polymer matrix (the copolymer contains repeating units resulting from the polymerization of vinylidene fluoride (96.7 mol%), acrylic acid (0.9 mol%), and hexafluoropropene (2.4 mol%) and has an intrinsic viscosity of 0.30 L / g in dimethylformamide at 25°C), 24.2 wt. % anhydrous acetone, and 10.8 wt. % 1 M LiPF electrolyte in a mixture of ethylene carbonate, propylene carbonate, and dimethyl carbonate (1:1:3) containing 2 wt. % vinyl carbonate.

[0093] Too high kinematic viscosity (0.1s -1 Due to the shear rate (well above 10,000 Pa.s at 1000 kJ / min), it was not possible to measure the kinematic viscosity of the resulting composition using a Malvern brand CVO Bohlin rheometer. [Example]

[0094] This example illustrates the production of an anode containing 70% solids mass relative to the total mass of the electrode by a continuous method according to the invention.

[0095] In the first phase, the ion gel electrode paste is prepared by successively introducing the electrode components in the presence of acetone and mixing them at 25° inside a mixer with two co-rotating intermeshing screws rotating in a closed sleeve, first introducing the solid components and then the liquid components. The composition of this paste is as follows: LiNi 0.33 Mn 0.33 Co 0.33 65.8 wt% O2, 2.8 wt% electronically conductive additive, 1.4 wt% copolymer comprising the polymer matrix (the copolymer contains repeating units resulting from the polymerization of vinylidene fluoride (96.7 mol%), acrylic acid (0.9 mol%), and hexafluoropropene (2.4 mol%), and has an intrinsic viscosity of 0.30 L / g in dimethylformamide at 25°C), 22.4 wt% anhydrous acetone, and 7.6 wt% 1M LiPF6 electrolyte in a mixture of ethylene carbonate and propylene carbonate (1:1) containing 2 wt% vinyl carbonate.

[0096] The kinematic viscosity of this composition was measured using a Malvern brand CVO Bohlin rheometer equipped with a Peltier stage and a moving cone plane with a diameter of 40 mm and an angle of 4°. To do so, the paste was placed with a gap of 150 μm between the Peltier stage and the moving element, and a solvent trap was added to the system to avoid excessively rapid evaporation of acetone. The viscosity was measured in viscometer mode for 0.1 s. -1 Measurements are taken at a shear rate of 100 rpm and 25°C over an integration time of 5 seconds.

[0097] The kinematic viscosity measurement obtained is 11000 Pa·s.

[0098] In the second phase, the electrode paste thus formed is applied at the outlet of a specific mixer onto a 20 μm thick aluminum sheet, which is then dried and calendered, thereby forming an ion-gel graphite electrode. The mass per unit area of ​​the electrode is 19.5 mg / cm for a thickness of 95 μm. 2 (2.9mAh / cm2 The capacity of the electrode was verified in a button cell against lithium metal. The measured total capacity was 170 mAh / g, and the reversible capacity was 147 mAh / g for the first cycle at C / 20. The reversible capacity was 143 mAh / g for the second cycle at C / 20. These data are shown in Figure 2, which shows the change in voltage U (V) as a function of capacity C (mAh / g), where curve a) is for the first cycle and curve b) is for the second cycle. [Example]

[0099] This example illustrates the continuous production of an anode according to the invention, containing 80% by weight of solids relative to the total weight of the electrode.

[0100] In the first phase, the ion gel electrode paste is prepared by successively introducing the electrode components in the presence of acetone and mixing them at 25° inside a mixer with two co-rotating intermeshing screws rotating in a closed sleeve, first introducing the solid components and then the liquid components. The paste has the following composition: LiNi 0,33 Mn 0,33 Co 0,33 75.2 wt% O2, 3.2 wt% electronically conductive additive, 1.6 wt% copolymer comprising the polymer matrix (the copolymer contains repeating units resulting from the polymerization of vinylidene fluoride (96.7 mol%), acrylic acid (0.9 mol%), and hexafluoropropene (2.4 mol%), and has an intrinsic viscosity of 0.30 L / g in dimethylformamide at 25°C), 11.3 wt% anhydrous acetone, and 8.7 wt% 1M LiPF6 electrolyte in a mixture of ethylene carbonate and propylene carbonate (1:1) containing 2 wt% vinyl carbonate.

[0101] Too high kinematic viscosity (0.1s -1Due to the shear rate (well above 10,000 Pa.s at 1000 kJ / min), it was not possible to measure the kinematic viscosity of the resulting composition using a Malvern brand CVO Bohlin rheometer.

[0102] In the second phase, the electrode paste thus produced is formed into a strip through a slot die located at the outlet of the mixer, and then the strip is laminated to reduce its thickness and then deposited onto an aluminum current collector by co-lamination to form an ion gel electrode. [Example]

[0103] This example illustrates the continuous production of an anode according to the invention, containing 90% by weight of solids relative to the total weight of the electrode.

[0104] In the first phase, the ion gel electrode paste is prepared by successively introducing and mixing at 25° the constituents of the electrode in the presence of acetone inside a mixer with two co-rotating intermeshing screws rotating in a closed sleeve, the introduction of which is carried out by first introducing the solid constituents and then the liquid constituents in the second. The composition of the paste is as follows: LiNi 0,33 Mn 0,33 Co 0,33 84.6% by weight of O2, 3.6% by weight of an electronically conductive additive, 1.8% by weight of a copolymer comprising repeating units resulting from the polymerization of vinylidene fluoride (96.7 mol%), acrylic acid (0.9 mol%), and hexafluoropropene (2.4 mol%) to form a polymer matrix (the copolymer has an intrinsic viscosity of 0.30 L / g in dimethylformamide at 25°C), and 10% by weight of 1M LiPF6 electrolyte in a mixture of ethylene carbonate and propylene carbonate (1:1) containing 2% by weight of vinyl carbonate.

[0105] Too high kinematic viscosity (0.1s -1Due to the shear rate (well above 10,000 Pa.s at 1000 kJ / min), it was not possible to measure the kinematic viscosity of the resulting composition using a Malvern brand CVO Bohlin rheometer.

[0106] In the first phase, the electrode paste thus produced is formed into a strip through a slot die located at the outlet of the mixer, and then the strip is laminated to reduce its thickness and then deposited onto an aluminum current collector by co-lamination to form an ion gel electrode. [Explanation of symbols]

[0107] 1 closure sleeve 3 Intermeshing screw 5 Intermeshing screw 7. First ingredient introduction zone 9 Second ingredient introduction zone 11 Exit 13 Motor

Claims

1. 1. A method for making an electrode comprising a polymer matrix entrapping an electrolyte, the method comprising: a) preparing a composition comprising ingredients to be delivered into the structure of an electrode; b) forming an electrode on a substrate from the composition; Including, - the composition prepared in step a) is 0.1 s －１ a composition in the form of a paste having a kinematic viscosity greater than 5000 Pa s measured at a shear rate of 1000 Pa s and at ambient temperature; and - the preparation step consists in introducing and mixing the components to be fed into the structure of the electrode inside a mixer equipped with two co-rotating intermeshing screws rotating in a closed sleeve, said preparation step being carried out at a temperature below 100°C, and The component defined in step a) is at least one electrode active material, - at least one polymer provided in such a way that it is incorporated into the structure of the polymer matrix; and - electrolytes Including, and wherein the electrolyte is a liquid electrolyte containing at least one electrolytic organic solvent and at least one metal salt.

2. A manufacturing method as described in claim 1, wherein the components specified in step a) further include at least one electronic conductive additive.

3. A manufacturing method described in claim 1 or 2, wherein the at least one polymer is selected from gelling polymers suitable for gelling on contact with an electrolyte, thereby trapping the electrolyte.

4. A manufacturing method described in any one of claims 1 to 3, wherein the at least one polymer is selected from fluorinated polymers containing at least one repeating unit resulting from the polymerization of a fluorinated monomer.

5. The manufacturing method described in claim 4, further comprising at least one repeating unit resulting from the polymerization of a monomer containing at least one carboxylic acid group that is not in the form of a salt or that is in the form of a salt.

6. The method according to claim 1 , wherein the electrolyte further comprises an additive belonging to the class of carbonaceous compounds.

7. 7. The method of claim 1, wherein the composition further comprises at least one polymer solvent for the at least one polymer provided so as to enter into the structure of the polymer matrix.

8. 8. The method of claim 7, further comprising the step of evaporating at least one polymer solvent for said at least one polymer provided into the structure of the polymer matrix after the forming step.

9. 7. The method of claim 1, wherein the composition is devoid of at least one polymer solvent for the at least one polymer provided to enter into the structure of the polymer matrix.

10. The method according to any one of claims 1 to 9, wherein the preparation steps are carried out continuously.

11. 10. A process according to claim 7 or 9, wherein the preparation step is carried out at ambient temperature or at a temperature above ambient temperature but below 100°C.

12. 12. The method of any one of claims 7, 9 and 11, wherein the preparation step is carried out at a temperature above ambient temperature but below the boiling point of at least one polymer solvent for at least one polymer provided to be incorporated into the structure of the polymer matrix, if at least one polymer solvent for at least one polymer is present in the composition, or at a temperature above ambient temperature but below the melting temperature of at least one polymer provided to be incorporated into the structure of the polymer matrix, if at least one polymer solvent for at least one polymer is not present.

13. 10. The method according to any one of claims 1, 7 and 9, wherein the composition for the manufacturing process comprises 50% to 80% by weight of solids relative to the total weight of the composition if it further comprises at least one polymer solvent for at least one polymer that is provided in the structure of the polymer matrix, or 83 to 90% by weight of solids relative to the total weight of the composition if it does not comprise a polymer solvent for at least one polymer that is provided in the structure of the polymer matrix.

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