Method for manufacturing an electrode comprising a polymer matrix that confines an electrolyte

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 (in this case, the electrode can be called an ion gel electrode) including a polymer matrix that confines a liquid electrolyte capable of forming a gel with the polymer matrix, and the electrode is provided for incorporation into an electrochemical accumulator (secondary battery).

[0002] The general technical field of the present invention can be defined as the field of energy storage devices, particularly electrochemical accumulators.

Background Art

[0003] An electrochemical accumulator operates on the principle of a suitable electrochemical cell by the presence of a pair of electrodes (an anode and a cathode, respectively) separated by an electrolyte, and the electrodes contain specific substances suitable for the reaction by redox reaction, whereby there is an exchange of electrons at the source of the current and an exchange of ions flowing from one electrode to the other through the intervention of the electrolyte.

[0004] Among the accumulators adopting this principle, accumulators operating on the principle of insertion / extraction of metal elements occurring at the electrodes (and more specifically, on the electrode active material), known by the term metal ion accumulators (e.g., Li ions, Na ions, K ions, Ca ions, Mg ions, or Al ions), are replacing other types of accumulators such as lead-acid accumulators and Ni-MH accumulators, particularly due to their performance regarding energy density. In fact, M-ion accumulators such as Li-ion accumulators have significantly higher weight and volumetric energy densities (180 Wh·kg -1 which can be in the range of) than those of Ni-MH and Ni-Cd accumulators (which can be in the range of 50 - 100 Wh·kg -1 and lead-acid (which can be in the range of 30 - 35 Wh·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 described above, an electrolyte is disposed between the cathode and the anode, which enables the movement of ions (generally derived from metal salts present in the electrolyte) from the anode to the cathode during charging and conversely during discharging.

[0009] This electrolyte may take the form of a liquid and usually can contain 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 of the following drawbacks, including the following: - The problem of leakage of the liquid electrolyte from the battery; - In the case of thermal runaway occurring in a battery containing the electrolyte, the liquid electrolyte may chemically react with the oxygen of the anode active material, which may generate a large volume of gas, and as a result, the battery may catch fire or even explode.

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

[0012] However, all of these various solutions currently have several drawbacks.

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

[0014] Regarding solid dry polymer electrolytes, their ionic conductivity at room temperature is generally -5 S·cm -1 less than that of conventional liquid electrolytes, where the ionic conductivity is -3 S·cm -1 or even on the order of -2 S·cm -1 at room temperature. This can prove that in order to promote the diffusion of lithium ions in the electrolyte, accumulators containing dry polymer electrolytes need to be used at temperatures higher than room temperature, for example, in the range of 60 to 80 °C.

[0015] To mitigate the drawbacks associated with the use of liquid electrolytes and the drawbacks of the solid electrolytes described above, the new technology developed and exemplified in International Publication No. WO 2015 / 169835 consists of trapping a liquid electrolyte in a polymer matrix and forming the essential parts of the anode and cathode (these electrodes can be called ion gel electrodes), and this technology enables obtaining electrochemical performance equivalent to that of a lithium ion accumulator containing a liquid electrolyte not trapped in a polymer matrix at room temperature.

[0016] These electrodes are prepared by a method that conventionally continuously includes the following steps: - A process of manufacturing an ink (i.e., a liquid dispersion containing solid components of an electrode) by mixing various components prepared to enter into the structure of the electrode, wherein the components are an active material, one or more electron-conducting additives, a fluorinated (co)polymer enabling confinement of a liquid electrolyte, at least one solvent of the fluorinated copolymer (e.g., acetone), a lithium salt, and one or more electrolyte solvents (such as carbonate ester solvents) for solubilizing the lithium salt; - Once the ink is obtained, depositing it, generally by spreading the ink on a substrate constituting a current collector; - Evaporating one or more solvents of the fluorinated (co)polymer and, optionally in some cases, subsequently calendaring (thereby resulting in the presence of a predetermined electrode).

[0017] Typically, the ink manufacturing process, which is usually carried out in a conventional mixer, such as a disperser or a planetary mixer, requires a high proportion of solvent(s), which limits the percentage of the solid mass in the ink. More specifically, the percentage of the solid mass with respect to the total mass of the ink usually constitutes 35 - 49% by mass, while the mass of the liquid electrolyte (salt + one or more electrolyte solvents) constitutes 6 - 13% of the total mass of the ink, and one or more solvents of the fluorinated (co)polymer constitute 45 - 57% of the total mass of the ink.

[0018] The presence of such an amount of solvent constitutes a limiting factor for the implementation of such a method, especially on an industrial scale, because it implies providing management of the effluent (in this case, one or more solvents used in large quantities) from the viewpoints of both safety (especially due to the potential flammability and / or toxicity of the one or more selected solvents) and solvent removal, which further results in high implementation costs for this method.

Prior Art Documents

Patent Documents

[0019]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0020] Under such circumstances, the inventors of the present invention set as an object to provide a new method for manufacturing an electrode including a polymer matrix incorporating an electrolyte, which makes it possible to limit or, if possible, eliminate the use of a large amount of solvent, thereby being less expensive and limiting the drawbacks associated with the use of a large amount of solvent.

Means for Solving the Problems

[0021] Towards that end, the inventors of the present invention have developed a method for manufacturing an electrode that no longer includes preparing the ink in advance, but rather preparing the composition in the form of a paste containing components supplied to enter the structure of the electrode, this preparation being made possible by using a specific mixer during this step.

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

[0023] By using this specific mixer, it is possible to use a smaller amount of solvent compared to the method of using a conventional mixer, and thus limit the drawbacks associated with the management of the effluent.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

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

[0026] The introduction of the components may be simultaneous or sequential, and the introduction is - a closed sleeve 1; - two interpenetrating screws 3 and 5; - The first component introduction zone 7 (referred to as zone A); - The second component introduction zone 9 (referred to as zone B), and - An outlet 11 for discharging the formed composition; - A motor 13 connected to the screw that causes the screw to rotate It may be carried out at separate positions, as in the case of using the mixer illustrated in FIG. 3 attached to this specification (for example, introduction of solid constituent components in the first introduction zone through one or more inlets of the mixer, and introduction of liquid constituent components in the second introduction zone through one or more inlets of the mixer).

[0027] More specifically, this composition, as a component constituting an electrode, - At least one electrode active material; - At least one prepared polymer incorporated into the structure of the polymer matrix; - An electrolyte, includes - Optionally, at least one electronic conduction additive, may be included.

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

[0029] The nature of the active material will of course vary depending on its purpose, ie whether it is provided for the anode or cathode.

[0030] Furthermore, when the method of the present invention is a method for producing a positive electrode, examples of electrode active materials that can be incorporated into the structure of the positive electrode of the lithium accumulator include: - metal chalcogenides of formula LiMQ2, where M is a metal element, for example at least one metal element selected from Co, Ni, Fe, Mn, Cr, V, Al, and Q is a chalcogen, for example O or S, preferred metal chalcogens are those of formula LiMO2, where M is as defined above, for example, preferably LiCoO2, LiNiO2, LiNi x Co 1-x O2(0 <x<1)、リチウム-ニッケル-マンガン-コバルトに基づく物質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 the 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; - chalcogenides with spinel structure, for example LiMn2O4; - Formula M1M2(JO4) f E 1-fThe lithiumated or partially lithiumated substance (wherein M1 is lithium which may be partially substituted by another alkali element to a substitution degree of less than 20%, M2 is a transition metal element with an oxidation state of +2 selected from Fe, Mn, Ni and combinations thereof, which may be partially substituted by one or more additional metal elements with oxidation states of +1 to +5 to a substitution degree of less than 35%, JO4 is an oxyanion where J is selected from P, S, V, Si, Nb, Mo, and combinations thereof, E is an anion of fluoride, hydroxide, or chloride, f is the mole fraction of the oxyanion JO4, and is usually included in the range of 0.75 to 1 (including 0.75 and 1)).

[0031] More specifically, the lithiumated or partially lithiumated substance may be phosphorus-based (which means, in other words, that the oxyanion satisfies the formula PO4), and can have a regular or modified olivine-type structure.

[0032] The lithiumated or partially lithiumated substance has a specific formula Li 3-x M’ y M’’ 2-y (JO4)3 (where 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, JO4 is preferably PO4, which may be partially substituted by another oxyanion having J selected from S, V, Si, Nb, Mo and combinations thereof).

[0033] The lithiumated or partially lithiumated substance may satisfy the formula Li(Fe x Mn 1-x )PO4, where 0 ≤ x ≤ 1, and preferably x is equal to 1 (which means, in other words, that the corresponding substance is LiFePO4).

[0034] When the method of the present invention is a method for manufacturing a cathode, examples of electrode active materials that can be incorporated into the structure of the cathode of a lithium accumulator include the following: - Carbonaceous materials, such as graphite carbon, which are suitable for intercalating lithium and can typically be present in the form of powders, flakes, fibers, or spheres (e.g., mesocarbon microbeads); - Compounds based on silicon, such as silicon carbide SiC or silicon oxide SiO x ; - Metallic lithium; - Lithium alloys, such as those described in U.S. Patent No. 6,203,944 and / or International Publication No. 00 / 03444; - Lithiated titanium oxides, such as the oxides of the formula Li (4-x) M x Ti5O 12 or Li4M y Ti (5-y) O 12 (wherein x and y range from 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 , and these oxides are lithium insertion materials having low thermal expansion after lithium is inserted); - Non-lithiated titanium oxides, such as TiO2; - Oxides of the formula M y Ti (5-y) O 12 (wherein y ranges from 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, such as those containing a crystalline phase of the formula Li 4.4 Ge; or - Mixtures thereof, such as mixtures containing graphite and compounds based on silicon.

[0035] One or more polymers suitable for incorporation into the structure of the polymer matrix are preferably selected from gelling polymers suitable for gelling upon contact with the electrolyte and thereby trapping the electrolyte (thus, the resulting electrodes form electrodes commonly referred to as "ion gel electrodes"), and more specifically, 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 containing at least one carboxylic acid group, optionally in the form of a salt, which may be selected from fluorinated polymers.

[0036] The repeating unit resulting from the polymerization of the fluorinated monomer and, if any, the repeating unit resulting from the polymerization of a monomer containing at least one carboxylic acid group, optionally in the form of a salt, are chemically different repeating units. In particular, it should be understood that the repeating unit(s) resulting from the polymerization of the fluorinated monomer do not contain any carboxylic acid groups, optionally in the form of a salt.

[0037] For the gelling polymer (gel-forming polymer), the repeating unit resulting from the polymerization of the fluorinated monomer may more specifically 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 as follows: - 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; - The perfluoroalkyl ethylene of the formula CH2=CHR 1 (wherein R 1 is a C1 - C6 perfluoroalkyl group); - C2 - C6 fluoroolefins containing one or more other halogen atoms (such as chlorine, bromine, iodine, etc.), for example, chlorotrifluoroethylene; - The formula CF2=CFOR 2 (wherein R 2 is a C1 - C6 fluoro - or perfluoroalkyl group, for example, CF3, C2F5, C3F7) of (per)fluoroalkyl vinyl ether; - The formula CF2=CFOR 3 (wherein R 3 is a C1 - C 12 alkyl group, a C1 - C 12 alkoxy group, or a C1 - C 12 (per)fluoroalkoxy group, for example, perfluoro - 2 - propoxypropyl group) of the monomer; and / or - The formula CF2=CFOCF2OR 4 (wherein R 4 is fluoro - or perfluoro - C1 - C6 - alkyl, for example, CF2, C2F5, C3F7, or fluoro - or perfluoro - C1 - C6 - alkoxy group, for example, - C2F5 - O - CF3) of the monomer.

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

[0039] The repeating units resulting from the polymerization of monomers optionally containing at least one carboxylic acid group, optionally in the form of a salt in some cases, may more specifically be one or more repeating units resulting from the polymerization of monomers of the following formula (I):

Chemical formula

[0040] Certain gelling polymers that can be used in connection with the present invention may be polymers 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 different from vinylidene fluoride (more particularly, repeating units resulting from the polymerization of hexafluoropropene).

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

[0042] Furthermore, one or more gelling polymers advantageously have an intrinsic viscosity in the range of 0.1-1.0 L / g, preferably 0.25-0.45 L / g, as measured in N,N-dimethylformamide at 25°C.

[0043] Even more particularly, the intrinsic viscosity is determined by the following formula based on the drop time at 25°C of a solution obtained by dissolving the polymer in a solvent (N,N-dimethylformamide) at a concentration of approximately 0.2 g / dL using an Ubbelohde viscometer:

Number

[0044] The electrolyte is preferably a liquid electrolyte and, more particularly, a liquid electrolyte that can gel upon contact with the polymer matrix, in which case the latter contains one or more gelling polymers (gelling polymers).

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

[0046] The one or more organic solvents may be carbonic ester solvents and, more particularly, the following: - cyclic carbonic ester 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 carbonic ester 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. may be.

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

[0048] The one or more organic solvents may be an ionic liquid, that is, a compound formed by a combination of a cation having a positive charge and an anion having a negative charge that is in a liquid state at a temperature of less than 100 °C under atmospheric pressure as in the prior art.

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

[0050] Even more specifically, the cation can be selected from the following cations: - the following formula (II):

Chemical formula

Chemical formula

[0051] In particular, the cation having a positive charge can be selected from the following cations: - the following formula (II-A): [Chemical formula] of the pyrrolidinium cation, - the following formula (III-A): [Chemical formula] of the piperidinium cation.

[0052] When the cation is a quaternary ammonium cation, it may be a tetraalkylammonium cation, a trialkylarylammonium cation, or a tetraarylammonium cation. 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. Also, the aryl groups, if present, may be the same or different and may be phenyl groups, benzyl groups, or naphthyl groups. More specifically, the cation may be a tetraethylammonium cation, a tetrapropylammonium cation, a tetrabutylammonium cation, a trimethylbenzylammonium cation, a methyltributylammonium cation, an N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium cation, an N,N-dimethyl-N-ethyl-N-(3-methoxypropyl)ammonium cation, an N,N-dimethyl-N-ethyl-N-benzylammonium cation, an N,N-dimethyl-N-ethyl-N-phenylethylammonium cation, an N-tributyl-N-methylammonium cation, an N-trimethyl-N-butylammonium cation, an N-trimethyl-N-hexylammonium cation, or an 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. 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. Also, the aryl groups, if present, may be the same or different and may be phenyl groups, benzyl groups, or naphthyl groups. More specifically, the cation may be 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, or a 1-octyl-3-methylimidazolium cation.

[0055] Specifically, the anion having a negative charge can be selected from the following: - 4,5-dicyano-2-(trifluoromethyl)imidazole (known by the abbreviation TDI); - bis(fluorosulfonyl)imide (known as FSI); - bis(trifluoromethylsulfonyl)imide of the formula (SO2CF3)2N - ; - hexafluorophosphate of the formula PF6 - ; - tetrafluoroborate of the formula BF4 - ; - the following formula (IV):

Chemical formula

[0056] Specific ionic liquids that can be used according to the present invention are ionic liquids composed of the cation of formula (II-A) defined above and an anion of (SO2CF3)2N - , PF6 - , or BF4 - .

[0057] The metal salt(s) is / are salts of the following formula: MeI, Me(PF6) n , Me(BF4) n , Me(ClO4) n , Me(bis(oxalato)borate) n (abbreviation Me(BOB) nwhich 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 (wherein R F is -C2F5, -C4F9, or -CF3OCF2CF3), Me(AsF6) n , Me[C(CF3SO2)3] n , Me2S n , Me(C6F3N4)(C6F3N4 is 4,5-dicyano-2-(trifluoromethyl)imidazole, and when Me is Li, the salt is lithium 4,5-dicyano-2-(trifluoromethyl)imidazole, and this salt is known by the abbreviation LiTDI), can be selected from, in the above formula, 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 lithium-air accumulator), Na (especially when the accumulator is a sodium ion accumulator), K (especially when the accumulator is a potassium ion accumulator), Mg (especially when the accumulator is a Mg ion accumulator), Ca (especially when the accumulator is a calcium ion accumulator), and Al (especially when 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 0.01 M, preferably at least 0.025 M, more preferably at least 0.05 M, and, advantageously, at most 5 M, preferably at most 2 M, and more preferably at most 1 M.

[0060] Furthermore, the liquid electrolyte may contain at least one additive belonging to the group of carbonaceous compounds (it is understood that this additive is different from one or more carbonate solvents contained in the electrolyte, if any), for example, vinylene carbonate or fluoroethylene carbonate, and this additive is contained in the electrolyte in an amount not exceeding 5% by mass of the total mass of the electrolyte.

[0061] The liquid electrolyte that can be used is, in particular, when the electrode produced by the method of the present invention is for a lithium-ion accumulator, a mixture of carbonate solvents (for example, a mixture of cyclic carbonates, for example, a mixture of ethylene carbonate and propylene carbonate, or a mixture of a cyclic carbonate and a linear carbonate solvent, for example, a mixture of ethylene carbonate, propylene carbonate, and dimethyl carbonate), a lithium salt, for example, LiPF6 (for example, 1M), and optionally, in some cases, an additive, for example, vinylene carbonate or fluoroethylene carbonate.

[0062] As described above, the composition may contain at least one electron-conducting additive, that is, an additive that can impart electron conductivity to the electrode in which it is incorporated. For example, this additive can be selected 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 include at least one solvent for the polymer supplied to enter into the structure of the polymer matrix (optionally, separate from the organic solvent of the electrolyte). When one or more polymers are selected from the class of fluorinated polymers containing at least one repeating unit resulting from the polymerization of a fluorinated monomer and at least one repeating unit resulting from the polymerization of a monomer containing at least one carboxylic acid group which may preferably be in the form of a salt optionally, this solvent can be a solvent from the class of ketones (such as acetone). Thanks to the use of a specific mixer, this one or more solvents can be used in a small amount compared to the method of using a conventional mixer.

[0064] When the composition contains at least one solvent as described above, the above method preferably includes an evaporation step after the forming step, and the evaporation is selective for one or more solvents for one or more polymers supplied to enter into the structure of the polymer matrix. The evaporation is, for example, by in-line drying by selective evaporation.

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

[0066] More particularly, the preparation process can also be carried out at ambient temperature (i.e., the temperature of the surroundings at which the preparation process is carried out without being heated 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 the ambient temperature, for example, a temperature higher than the ambient temperature and less than 100 °C. More particularly, when one or more solvents are present in the composition, the preparation process is carried out at a temperature higher than the ambient temperature but less than the boiling temperature of the one or more solvents for the one or more polymers supplied to enter the structure of the polymer matrix, and when no one or more solvents are present, it can be carried out at a temperature higher than room temperature but lower than the melting temperature of the one or more polymers supplied to enter the structure of the polymer matrix (it is understood that the temperature at which the preparation process is carried out is always less than 100 °C).

[0067] The preparation process has a very high kinematic viscosity, more particularly, at a shear rate of 0.1 s -1 and measured at ambient temperature, to obtain a homogeneous paste-form composition having a kinematic viscosity higher than 5000 Pa·s, preferably higher than 6000 Pa·s, more preferably higher than 7000 Pa·s.

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

[0069] More particularly, the kinematic viscosity of the composition is measured with 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 with a 150 μm gap between the Peltier support and the movable element. Optionally, when the composition contains at least one solvent of the polymer constituting the polymer matrix, a solvent trap is added to the system to avoid excessive rapid evaporation of the solvent. In the viscometer mode, at 0.1 s -1Perform the measurement over an integration time of 5 seconds at the shear rate and ambient temperature indicated.

[0070] Furthermore, the paste-form composition generally has a kinematic viscosity not exceeding 20,000 Pa·s, preferably not exceeding 18,000 Pa·s, under the conditions as defined above (i.e., at a shear rate of 0.1 s -1 and ambient temperature). Very advantageous results have been obtained when the composition is in the form of a paste having a kinematic viscosity in the range of 7,000 to 12,000 Pa·s under the conditions as defined above (i.e., at a shear rate of 0.1 s -1 and ambient temperature).

[0071] In fact, a particularly advantageous aspect of the method of the present invention lies in its ability to prepare an electrode-forming composition having a very high kinematic viscosity that enables minimizing the use of liquid electrolytes and / or organic solvents. This is advantageous compared to well-established methods for manufacturing electrodes from inks having a kinematic viscosity, measured under the above measurement conditions, of less than 5,000 Pa·s, or even less than 1,000 Pa·s, which are manufactured based on conventional mixers of the disperser or planetary mixer type.

[0072] If the composition contains at least one solvent of a polymer that is supplied such that the polymer enters the structure of the polymer matrix, these compositions may further contain a solids mass of 50 to 80% with respect to the total mass of the composition for the preparation process.

[0073] More particularly, when the composition comprises, as constituents, at least one electrode active material, at least one polymer supplied to enter into the structure of the polymer matrix, an electrolyte, and optionally in some cases at least one electronic conduction additive and at least one solvent of the polymer, the composition further obtained for this preparation step advantageously has a percentage of solid mass, which can be in the range of 50 to 80% with respect to the total mass of the composition (compared to 35 to 49% in the method using a conventional mixer). Further, these compositions may include a mass of electrolyte that is 6 to 11% of the total mass of the composition and a mass of the solvent of the polymer that is 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 lack one or more solvents of one or more polymers supplied to enter into the structure of the polymer matrix. Under these conditions, the composition may further include 83 to 90% of solid mass with respect to the total mass of the composition for the preparation step.

[0075] More particularly, when the composition comprises, as constituents, at least one electrode active material, at least one polymer supplied to enter into one structure of the polymer matrix, an electrolyte, and optionally in some cases at least one electronic conduction additive, but lacks one or more solvents of one or more polymers, the percentage of the solid mass may be 83 to 90% of the total mass of the composition, and the mass of the electrolyte may be 10 to 17% of the total mass of the composition.

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

[0077] The preparation step can be carried out continuously, that is, the introduction of the components and their mixing inside a specific mixer are carried out continuously, that is, over the entire duration of the implementation of the method.

[0078] The step of forming the electrode from the composition can be carried out by depositing it through a die, for example, a slot die, and conveying the composition onto the substrate through a die whose purpose is to form a strip on the substrate and whose flow of the composition is from a circular shape to a rectangular shape.

[0079] Optionally, the composition may be laminated prior to reaching the substrate so as to reduce its thickness, and the composition thus laminated can be deposited onto the substrate by an operation of co-laminating with the substrate.

[0080] Before the forming step and after the manufacturing step, the composition can be passed through a conveying device under pressure, such as a single-screw conveyor that rotates within another mixer, for example, within a closed sleeve and withstands a higher pressure than the mixture used in the manufacturing step. In this case, the forming step can preferably also be carried out through a die arranged at the outlet of the other mixer, and this die also has the purpose of the flow of 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, inside a single-screw conveyor, the composition may be in the form of granules, and these granules are formed into rods, for example, by a round die arranged at the outlet from the twin-screw mixer used for the manufacturing step, and this die is equipped with a cutting system arranged at the outlet from the twin-screw mixer.

[0082] After the step of forming the electrode and optionally after the evaporation step if any, the method may further include a step of calendering the electrode so as to increase the volumetric energy density.

[0083] The manufacturing method may be a continuous method, that is, a method carried out without interruption over its entire implementation period, which means, in other words, manufacturing the electrodes without interruption throughout the period of implementation of the method. In other words, this means carrying out steps a) and b) simultaneously without interruption over the entire period of the method, which means, in other words, that at each point in time t of the period of the method, while a fraction of the composition is being subjected to the manufacturing process, another fraction of the composition is being subjected to the forming process. In this case, it should also be understood that all optional steps of the method (for example, the lamination step, the drying step), if it exists, are carried out continuously.

[0084] Here, the present invention will be described based on the examples given below as non-limiting illustrations.

Example

[0085] In this example, the production of a cathode containing 55% solid mass relative to the total mass of the electrode by the continuous method according to the present invention is illustrated.

[0086] In the first phase, inside a mixer having two co-rotating meshing screws rotating within a closed sleeve, the components of the electrode were continuously introduced in the presence of acetone and mixed at 25° to prepare an ion gel electrode paste. Their introduction is carried out by first introducing the solid components and then, second, introducing the liquid components. The composition of the paste is as follows: 39.2% by mass of graphite (D 50 = 20 μm) in a mixture of ethylene carbonate and propylene carbonate (1:1) containing 2% by mass of vinyl carbonate, graphite (D 50= 3.5 μm) 13.1 mass%, copolymer constituting the polymer matrix 2.7 mass% (this copolymer is a copolymer containing 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), acetone anhydride 37.5 mass%, and 1M LiPF6 electrolyte 7.5 mass%.

[0087] The kinematic 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 purpose, the paste was placed between the Peltier stage and the movable element with a gap of 150 μm, and a solvent trap was added to the system to avoid excessive rapid evaporation of acetone. In the viscometer mode, the measurement was carried out at a shear rate of 0.1 s -1 and at 25 °C over an integration time of 5 seconds.

[0088] The obtained kinematic viscosity measurement value 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, and then dried and calendared, 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 (3.6 mAh / cm 2 ). The capacity of this electrode was verified with a button-type battery against lithium metal.

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

Example

[0091] In this example, the production of an ion gel electrode paste is illustrated. The paste is prepared according to the production process of the method of the present invention and contains 65% by solid mass relative to the total mass of the electrode.

[0092] This electrode paste is prepared by continuously introducing the components of the electrode into the interior of a mixer having two co-rotating intermeshing screws rotating within a closed sleeve, and mixing at 25° in the presence of acetone. Their introduction is carried out by first introducing the solid components and then, second, introducing the liquid components. The composition of the paste is as follows: graphite (D 50 = 20 μm) 46.4% by mass, graphite (D 50 = 3.5 μm) 15.4% by mass, 3.2% by mass of a copolymer constituting the polymer matrix (this copolymer is a copolymer containing 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°), 24.2% by mass of anhydrous acetone, and 10.8% by mass of a 1M LiPF6 electrolyte in a mixture of ethylene carbonate, propylene carbonate, and dimethyl carbonate (1:1:3) containing 2% by mass of vinyl carbonate.

[0093] Due to too high a kinematic viscosity (substantially exceeding 10000 Pa·s at a shear rate of 0.1 s -1 ), it was impossible to measure the kinematic viscosity of the resulting composition using a Malvern brand CVO Bohlin rheometer.

Example

[0094] In this example, the production of an anode containing 70% by solid mass relative to the total mass of the electrode by a continuous method according to the present invention is illustrated.

[0095] In the first phase, the constituent components of the electrode are continuously introduced into the interior of a mixer having two co-rotating meshing screws rotating within a closed sleeve, and mixed at 25° in the presence of acetone to prepare an ion gel electrode paste. These introductions are carried out by first introducing the solid constituent components and then, second, introducing the liquid constituent components. The composition of this paste is as follows: LiNi 0.33 Mn 0.33 Co 0.33 O2 65.8 mass%, electron conduction additive 2.8 mass%, copolymer constituting the polymer matrix 1.4 mass% (this copolymer is a copolymer containing 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), anhydrous acetone 22.4 mass%, and 7.6 mass% of 1M LiPF6 electrolyte in a mixture of ethylene carbonate and propylene carbonate (1:1) containing 2 mass% of vinyl carbonate.

[0096] The kinematic viscosity of this composition was measured with a Malvern brand CVO Bohlin rheometer equipped with a Peltier stage and a movable cone plane with a diameter of 40 mm and an angle of 4°. For this purpose, the paste was placed with a 150 μm gap between the Peltier stage and the movable element, and a solvent trap was added to the system to avoid excessive rapid evaporation of acetone. In the viscometer mode, measurements were carried out at a shear rate of 0.1 s -1 and at 25°C over an integration time of 5 seconds.

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

[0098] In the second phase, the electrode paste thus formed is applied onto a 20 μm thick aluminum sheet at the outlet of a specific mixer, and then dried and calendared, 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 (2.9 mAh / cm2 ) It is. The capacity of the electrode was verified with a button-type battery against lithium metal. The measured total capacity was 170 mAh / g, and the reversible capacity was 147 mAh / g in the first cycle at C / 20. The reversible capacity was 143 mAh / g in the second cycle at C / 20, and these data are shown in Fig. 2, representing the change in voltage U (V) as a function of capacity C (mAh / g). Curve a) is for the first cycle, and curve b) is for the second cycle.

Example

[0099] In this example, the production of an anode containing 80% solid mass with respect to the total mass of the electrode by the continuous method according to the present invention is illustrated.

[0100] In the first phase, the components of the electrode are continuously introduced into the interior of a mixer having two co-rotating meshing screws rotating within a closed sleeve in the presence of acetone and mixed at 25° to prepare an ion gel electrode paste. These introductions are carried out by first introducing the solid components and then, second, introducing the liquid components. The composition of the paste is as follows: LiNi 0,33 Mn 0,33 Co 0,33 O2 75.2 mass%, electron conduction additive 3.2 mass%, copolymer constituting the polymer matrix 1.6 mass% (this copolymer is a copolymer containing 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 at 25°C in dimethylformamide), 11.3 mass% of anhydrous acetone, and 8.7 mass% of 1M LiPF6 electrolyte in a mixture of ethylene carbonate and propylene carbonate (1:1) containing 2 mass% of vinyl carbonate.

[0101] Too high kinematic viscosity (0.1 s -1At the shear rate (significantly exceeding 10,000 Pa·s), it was impossible 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 prepared is formed into strips through a slot die disposed at the outlet of the mixer, then the strips are laminated to reduce their thickness, and then deposited on an aluminum current collector by co-lamination to form an ion gel electrode.

Example

[0103] This example illustrates the production of an anode containing 90% solid mass relative to the total mass of the electrode by the continuous method according to the present invention.

[0104] In the first phase, the components of the electrode are continuously introduced inside a mixer having two co-rotating intermeshing screws rotating within a closed sleeve, and mixed at 25° in the presence of acetone to prepare an ion gel electrode paste. Their introduction is carried out by first introducing the solid components and then, second, introducing the liquid components. The composition of the paste is as follows: LiNi 0,33 Mn 0,33 Co 0,33 O2 84.6% by mass, 3.6% by mass of an electron conduction additive, 1.8% by mass of a copolymer constituting the polymer matrix (this copolymer is a copolymer containing 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 at 25 °C in dimethylformamide), 10% by mass of a 1M LiPF6 electrolyte in a mixture of ethylene carbonate and propylene carbonate (1:1) containing 2% by mass of vinyl carbonate.

[0105] Too high kinematic viscosity (0.1 s -1At a shear rate far exceeding 10,000 Pa·s), it was impossible 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 prepared was formed into strips through a slot die placed at the outlet of the mixer, then the strips were laminated to reduce their thickness, and then deposited onto an aluminum current collector by co-lamination to form an ion gel electrode.

Description of Symbols

[0107] 1 Closed sleeve 3 Meshing screw 5 Meshing screw 7 First component introduction zone 9 Second component introduction zone 11 Outlet 13 Motor

Claims

1. A method for manufacturing an electrode comprising a polymer matrix that confines an electrolyte, comprising: a) preparing a composition comprising components to be supplied into the structure of the electrode; b) forming an electrode on a substrate from the composition; comprising: - The composition prepared in step a) is in the form of a paste having a kinematic viscosity greater than 5000 Pa·s as measured at a shear rate of 0.1 s －１ and at ambient temperature; and - The preparation step consists of introducing and mixing components to be supplied into the structure of the electrode into a mixer equipped with two co-rotating intermeshing screws rotating within a closed sleeve, and the preparation step is carried out at a temperature below 100 °C, and the components defined in step a) are - at least one electrode active material, - at least one polymer to be supplied into the structure of the polymer matrix, and - an electrolyte comprising, and the electrolyte is a liquid electrolyte comprising at least one electrolyte organic solvent and at least one metal salt, characterized in that it is a manufacturing method.

2. The manufacturing method according to claim 1, wherein the components defined in step a) further comprise at least one electron-conducting additive.

3. The manufacturing method according to claim 1 or 2, wherein the at least one polymer is selected from polymers that gel upon contact with the electrolyte, thereby confining the electrolyte.

4. The manufacturing method according to any one of claims 1 to 3, wherein the at least one polymer is selected from fluorinated polymers comprising at least one repeating unit resulting from the polymerization of fluorinated monomers.

5. The manufacturing method according to claim 4, wherein the at least one polymer further comprises at least one repeating unit resulting from the polymerization of monomers comprising at least one carboxylic acid group that is not in salt form or is in salt form.

6. The manufacturing method according to any one of claims 1 to 5, wherein the electrolyte further comprises an additive belonging to the class of carbonaceous compounds.

7. The manufacturing method according to any one of claims 1 to 6, wherein the composition further comprises at least one polymer solvent for the at least one polymer to be supplied into the structure of the polymer matrix.

8. The manufacturing method according to claim 7, further comprising a step of evaporating at least one polymer solvent for the at least one polymer to be supplied into the structure of the polymer matrix after the forming step.

9. The production method according to any one of claims 1 to 6, wherein the composition lacks at least one polymer solvent for at least one polymer supplied to enter the structure of the polymer matrix.

10. The production method according to any one of claims 1 to 9, wherein the preparation step is carried out continuously.

11. The production method according to claim 7 or 9, wherein the preparation step is carried out at ambient temperature or at a temperature higher than ambient temperature but lower than 100 °C.

12. When at least one polymer solvent for at least one polymer is present in the composition, the preparation step is carried out at a temperature higher than ambient temperature but lower than the boiling point of at least one polymer solvent for at least one polymer supplied to enter the structure of the polymer matrix, or when no polymer solvent for at least one polymer is present, the preparation step is carried out at a temperature higher than ambient temperature but lower than the melting temperature of at least one polymer supplied to enter the structure of the polymer matrix. The production method according to any one of claims 7, 9, and 11.

13. Furthermore, when the composition for the production step contains at least one polymer solvent for at least one polymer supplied to enter the structure of the polymer matrix, it contains 50% to 80% of solid mass based on the total mass of the composition, or when it does not contain a polymer solvent for at least one polymer supplied to enter the structure of the polymer matrix, it contains 83 to 90% of solid mass based on the total mass of the composition. The production method according to any one of claims 1, 7, and 9.

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