Electrochemical accumulator with bipolar architecture incorporating a particular structure

Abstract

The present invention relates to an accumulator with a bipolar architecture, comprising two end current collectors between which a stack of n electrochemical cells is arranged, where n is an integer at least equal to 2: each electrochemical cell comprises a positive electrode, a negative electrode, and an ion-conducting membrane interposed between the positive and negative electrodes, and a liquid electrolyte contained within the electrodes and the ion-conducting membrane; and the n electrochemical cells are separated from each other by n-1 bipolar current collectors, characterized in that the positive and negative electrodes of each electrochemical cell are gel electrodes comprising a composite material comprising a polymer matrix made from at least one gelling polymer (FF), an electrode active material, and optionally one or more electronically conductive additives, the polymer matrix trapping the liquid electrolyte, and the one or more gelling polymers (FF) selected from fluorinated polymers comprising at least one repeating unit derived from the polymerization of a fluorinated monomer and at least one repeating unit derived from the polymerization of a monomer comprising at least one carboxylic acid group, optionally in the form of a salt. Applications: Any of the fields in which accumulators with bipolar architecture are likely to be used, in particular in the production of electric or hybrid vehicles, devices for the stationary storage of energy, and portable electronic devices (telephones, touch tablets, computers, cameras, video cameras, etc.).

Description

[Technical Field]

[0001] The present invention relates to the field of electrochemical accumulators with bipolar architecture, which encompasses a particular structure that does not specifically require the application of seals between adjacent cells forming these accumulators.

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

[0003] Electrochemical accumulators work on the principle of an electrochemical cell that can deliver an electric current due to the presence of a pair of electrodes (respectively a positive and a negative electrode) separated by an electrolyte in each of them. The electrodes contain specific materials that can react according to an oxidation-reduction reaction, which results in the production of electrons that give rise to an electric current and the production of ions that will be transported from one electrode to the other by the electrolyte.

[0004] From accumulators according to this principle, the following can be mentioned: - Lead-acid accumulators using lead and lead oxide PbO2 as the electrode active material; - Ni-MH accumulators using metal hydrides and nickel oxyhydroxide as electrode active materials; - accumulators using nickel or nickel-based compounds to constitute at least one active material of the electrodes, such as Ni-MH accumulators, in particular using metal hydrides and nickel oxyhydroxide as electrode active materials; Ni-Cd accumulators, using cadmium and nickel oxyhydroxide as electrode active materials, or nickel-zinc accumulators, using nickel hydroxide and zinc oxide as electrode active materials; and - accumulators that function on the principle of intercalation-deintercalation of alkali or alkaline earth elements acting on the electrodes (more specifically on the electrode active material). Accumulators that follow this principle and are currently used are lithium-ion type accumulators that use lithium materials, in whole or in part, to constitute the electrode active material.

[0005] Due to the continuous improvement of the performance of Li-ion accumulators in terms of energy density, these Li-ion accumulators have supplanted the other accumulators mentioned above a few years ago, as they are now superior to Ni-MH and Ni-Cd accumulators (which have capacities of 50 and 100 Wh kg -1 ) as well as lead-acid accumulators (these can range from 30 to 35 Wh·kg -1 These have significantly better energy densities in terms of mass and volume than those found in -1 This is because it allows for the acquisition of a larger number of points (which may be greater than the number of points).

[0006] Currently, the lithium-ion accumulator market is dominated by the so-called "monopolar" architecture, i.e., the accumulator contains only one electrochemical cell. This uses, for example, a positive electrode based on lithium cobalt oxide (LiCoO2) and a negative electrode based on graphite, separated from each other by an electrolyte that conducts lithium ions. These accumulators have a nominal voltage of around 3.6 V.

[0007] Thus, in such architectures, to obtain high voltages, it is necessary to connect multiple single-cell accumulators in series via external connections.

[0008] In contrast to this monopolar architecture, a new generation of accumulators with so-called bipolar architecture has been the subject of research for many years.

[0009] When the accumulator is a lithium-ion accumulator, the accumulator with bipolar architecture is an electrochemical cell (C1, C2, ..., C3) comprising two terminal current collecting substrates 1, 3, each of which has a positive electrode 5 and a negative electrode 7, and a separator 9 interposed between the positive and negative electrodes, in the presence of an electrolyte conducting lithium ions, as illustrated in the accompanying FIG. 1 . n ) in which the electrochemical cells are separated from each other by current collecting substrates called bipolar current collecting substrates 11, which are in the form of foils, one side of which is in contact with the negative electrode of an electrochemical cell and the other side of which is in contact with the positive electrode of an adjacent electrochemical cell.

[0010] In this way, the bipolar architecture allows for the serial connection of several accumulators by means of so-called bipolar current collecting substrates. This makes it possible to dispense with the external connections that would be necessary to assemble monopolar accumulators in series. This therefore leads to a lighter system than would result from the assembly of monopolar accumulators in series, thus increasing the energy density. In addition, depending on the number of cells that make up the stack, the final voltage of the accumulator can be easily adjusted and, if desired, can be very high.

[0011] Nevertheless, an essential problem of bipolar technology is the difficulty of confining the liquid electrolyte within each cell in order to have an assembly containing cells in series that are identical but remain independent of each other. This is because if the liquid electrolyte contained in a cell does not remain confined therein but spreads into adjacent cells, the phenomenon of ionic short-circuiting can occur. This can cause instability of the stack and in particular failure of all or some of the cells, thus causing rapid deterioration of the assembly.

[0012] To avoid these drawbacks, sealing can be provided by creating a physical barrier to the movement of the electrolyte. This physical barrier can be obtained, for example, by the following means: a seal made from a thermosetting resin of the epoxy resin type or an adhesive of the acrylic adhesive type, which is deposited on the periphery of the stack of electrochemical cells, as described for example in patent application WO 2005 / 024994 and illustrated in FIG. 1 by reference number 13; - a soft and flexible adhesive film, which is bonded to the periphery of the bipolar current collector as described in patent application WO 2005 / 024999; - A fluorinated polymer barrier, as described in US Patent No. 5,649, 1999, is provided around the periphery of the bipolar current collector, lined with an air- and liquid-tight seal made from a polymer arranged on the outside of this barrier.

[0013] However, the use of physical barriers to the diffusion of liquid electrolytes is not entirely sufficient, as none of them are completely resistant to the electrolyte solvents typically used in liquid electrolytes, which can ultimately cause ionic short-circuiting.

[0014] Another alternative could consist in omitting the use of liquid electrolyte, for example by replacing it by the following solution: - Glasses or ceramics that conduct lithium ions in pure solid form, for example thin layers deposited by chemical vapor deposition (CVD), such as a layer of LIPON, or a polymer matrix made, for example, from polyvinylidene fluoride and Li7La3Zr2O 12 and a filler comprising lithium oxide, such as: - A dry solid electrolyte consisting of a polyethylene oxide (POE) type polymer and a lithium salt such as lithium trifluorosulfonylimide (LiTFSI).

[0015] However, these various solutions currently all have a number of drawbacks.

[0016] Regarding the use of glasses or ceramics that conduct lithium ions, this requires packaging or synthesis techniques that are very complex to develop in an industrial context, which may prove prohibitive for the production of accumulators on a large scale.

[0017] As for dry solid electrolytes, their ionic conductivities are generally around 10 -5 S cm -1 In conventional liquid electrolytes, the ionic conductivity is less than 10 -3 S cm -1 before and after, or even 10 -2 S cm -1 In fact, it may prove necessary to use accumulators containing dry electrolyte at temperatures higher than ambient temperature, for example in the range of 60 to 80° C., in order to aid the diffusion of lithium ions in the electrolyte.

[0018] Finally, with the ion-conducting membranes currently used, it is not possible to completely dispense with the use of impermeable resins at the periphery of the electrochemical cell to ensure total impermeability. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] International Publication No. 03 / 047021 Brochure [Patent Document 2] U.S. Patent No. 7,220,516 [Patent Document 3] U.S. Patent No. 7,097,937 Summary of the Invention [Problem to be solved by the invention]

[0020] Thus, in light of existing solutions and the drawbacks resulting from their use, the inventor set himself the goal of proposing a new accumulator with a bipolar architecture that uses a liquid electrolyte, the leakage of which is prevented without having to resort to the use of a physical barrier to flow, such as a seal placed around the periphery of the electrochemical cell. Moreover, the inventor set himself the goal of proposing a new accumulator with a bipolar architecture that, apart from good confinement of the electrolyte, has electrochemical performance that is effective and stable even after a large number of operating cycles (or in other words, charge-discharge cycles). [Means for solving the problem]

[0021] The authors of the present invention have been able to achieve the aforementioned goal by installing gel electrodes in an accumulator with a bipolar architecture, which make it possible to confine the liquid electrolyte without compromising its conductivity properties and without the risk of its leakage.

[0022] Thus, an accumulator having a bipolar architecture according to the present invention can be defined as follows: An accumulator having a bipolar architecture, These include two terminal current collectors between which is disposed a stack of n electrochemical cells, where n is an integer at least equal to 2: - each electrochemical cell comprises a positive electrode, a negative electrode, an ion-conducting membrane interposed between the positive and negative electrodes, and a liquid electrolyte contained within the electrodes (i.e., the positive and negative electrodes) and the ion-conducting membrane; - the n electrochemical cells are isolated from one another by n-1 bipolar current collectors; and they are characterized in that the positive electrode and the negative electrode of each electrochemical cell are gel electrodes comprising a composite material comprising a polymer matrix made from at least one gelling polymer (FF), an electrode active material and optionally one or more electronically conductive additives, the polymer matrix trapping the liquid electrolyte, and the gelling polymer(s) (FF) are selected from fluorinated polymers comprising 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 comprising at least one carboxylic acid group, preferably optionally in the form of a salt.

[0023] Before going into any more detail of the description, the following definitions are provided. Positive electrode conventionally means above and below in this specification the electrode that acts as a cathode when the accumulator is delivering current (i.e., when it is in the process of discharging) and as an anode when the accumulator is in the process of charging. Negative electrode is conventionally used herein above and below to refer to the electrode that acts as an anode when the accumulator is delivering current (i.e., when it is in the process of discharging) and as a cathode when the accumulator is in the process of charging. Repeat unit is conventionally used herein above and below to mean a divalent unit that results from the polymerization of monomers and repeats in the polymer.

[0024] According to the present invention, our accumulator comprises as essential elements gel electrodes (i.e., the positive and negative electrodes of each compartment) comprising (or even consisting of) a composite material comprising (or even consisting of) a polymer matrix made from at least one gelling polymer (FF), an electrode active material and optionally one or more electronically conductive additives, the polymer matrix trapping the liquid electrode, and the gelling polymer(s) (FF) being chosen 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.

[0025] These gel electrode attachments trap liquid electrolyte, providing the following benefits: - Because the liquid electrolyte is confined in the gel electrodes, there is no leakage of electrolyte between the compartments of the bipolar accumulator, which allows to obtain stable cycling behavior under all conditions, including low-speed conditions, and for a large number of cycles; - Due to the confinement of the liquid electrolyte in the gel electrode, it is not necessary to have an impermeable seal specifically around the periphery of the electrode; - when the bipolar accumulator is manufactured, it is not necessary to carry out a step of filling the electrolyte for each of the stacked cells, nor before closing the outer casing, as the liquid electrolyte is already contained in the gel electrode(s), which leads to a time-saving and easy operation of the manufacturing method; Due to their affinity for liquid electrolytes, these gel electrodes may also prevent leakage of liquid electrolytes from membranes in contact with the gel electrodes.

[0026] Advantageously, according to the invention, the components constituting the positive and negative electrodes are identical, except for the nature of the electrode active material.

[0027] The gelling polymer(s) (FF) are chosen from fluorinated polymers comprising 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, preferably optionally in salt form.

[0028] It is understood that the repeat unit(s) resulting from the polymerization of a fluorinated monomer and the repeat unit(s) resulting from the polymerization of a monomer comprising at least one carboxylic acid group, optionally in the form of a salt, if applicable, are chemically different repeat units, and in particular the repeat unit(s) resulting from the polymerization of a fluorinated monomer do not comprise a carboxylic acid group, optionally in the form of a salt.

[0029] In the gelling polymer (FF), the repeat unit(s) resulting from the polymerization of a fluorinated monomer may more particularly be one or more repeat units resulting from the polymerization of one or more ethylenic monomers containing at least one fluorine atom and optionally one or more other halogen atoms. Examples of monomers of this type are: - C2-C8 perfluoroolefins, such as tetrafluoroethylene or hexafluoropropene (also known by the abbreviation HFP); - C2-C8 hydrogenated fluoroolefins, such as vinylidene fluoride, vinyl fluoride, 1,2-difluoroethylene, and trifluoroethylene; - Formula CH2=CHR 1 perfluoroalkylethylene of the formula R 1 is a C1-C6 perfluoroalkyl group; - C2-C6 fluoroolefins containing one or more other halogen atoms (e.g., chlorine, bromine, or iodine), such as chlorotrifluoroethylene; - Formula CF2=CFOR 2 (per)fluoroalkyl vinyl ethers of the formula: 2 is a C1-C6 fluoro or perfluoroalkyl group, such as CF3, C2F5, or C3F7; - Formula CF2=CFOR 3 wherein R 3 is C1-C 12 Alkyl groups, C1-C 12 Alkoxy group, or C1-C 12 (per)fluoroalkoxy groups, such as perfluoro-2-propoxypropyl groups; and / or - Formula CF2=CFOCF2OR 4 wherein R 4 is a C1-C6 fluoro or perfluoroalkyl group, such as CF2, C2F5, or C3F7, or a C1-C6-fluoro or perfluoroalkoxy group, such as -C2F5-O-CF3.

[0030] More specifically, said gelling polymer(s) (FF) may comprise, as repeating unit(s) resulting from the polymerization of fluorinated monomers, repeating units resulting from the polymerization of monomers of the C2-C8 perfluoroolefin category, such as hexafluoropropene, and repeating units resulting from the polymerization of monomers of the C2-C8 hydrogenated fluoroolefin category, such as vinylidene fluoride.

[0031] The repeat unit(s) resulting from the polymerization of a unit comprising at least one carboxylic acid group, optionally in salt form, may more particularly be one or more repeat units resulting from the polymerization of a monomer of formula (I): [ka] (I) In the formula, R 5 From R 7 represent independently a hydrogen atom or a C1-C3 alkyl group, and R 8 represents a hydrogen atom or a monovalent cation (for example, an alkali or ammonium cation), and specific examples of this type of monomer are acrylic acid or methacrylic acid.

[0032] A gelling polymer (FF) that may be specifically used in the context of the present invention may be a polymer containing 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 specifically, repeating units resulting from the polymerization of hexafluoropropene).

[0033] Again, more specifically, the gelling polymers (FF) that may be used in the context of the present invention are gelling polymers whose aforementioned repeating units result from the polymerization of: - at least 70 mol % of C2-C8 hydrogenated fluoroolefins, preferably vinylidene fluoride; - 0.1 to 15 mol % of a C2-C8 perfluoroolefin, preferably hexafluoropropene; and - 0.01 to 20 mol % of a monomer of the aforementioned formula (I), preferably acrylic acid.

[0034] Moreover, the gelling polymer(s) (FF) advantageously have an intrinsic viscosity, measured in N,N-dimethylformamide at 25° C., ranging from 0.1 to 1.0 l / g, preferably from 0.25 to 0.45 l / g.

[0035] More specifically, the intrinsic viscosity is determined by the following equation based on the fall 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

[0036] Each of the electrodes includes an electrode active material, i.e., a material that can insert and deintercalate metal ions into its structure, such as alkali ions (e.g., lithium when the accumulator is a lithium accumulator, sodium when the accumulator is a sodium accumulator, or potassium when the accumulator is a potassium accumulator), alkaline earth ions (e.g., when the accumulator is a magnesium accumulator), or the like.

[0037] Naturally, the nature of the active material will depend on its purpose, ie whether it is intended for a positive or negative electrode.

[0038] Examples of electrode active materials that can form part of the positive electrode of the lithium accumulator may include: - metal chalcogenides of formula LiMQ2, where M is at least a transition metal element, for example a metal element selected from Co, Ni, Fe, Mn, Cr, V, and Q is a chalcogen such as O or S; preferred metal chalcogenides are those of formula LiMO2, where M is as defined above, for example, LiCoO2, LiNiO2, LiNi x Co 1-x O2(0 <x<1)、またはLiMn2O4; - Formula M1M2(JO4) f E 1-fwherein M1 is lithium, which may be partially substituted by another alkali element to a degree of substitution of at least 20%, M2 is a transition metal element having an oxidation degree of +2 selected from Fe, Mn, Ni, and combinations thereof, which may be partially substituted by one or more other additional metal elements having an oxidation degree between +1 and +5 to a degree of substitution of at least 35%, JO4 is an oxyanion, wherein J is 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, generally between 0.75 and 1 inclusive.

[0039] More specifically, the lithiated or partially lithiated materials may advantageously be based on phosphorus (which means, in other words, that the oxyanion conforms to the formula PO4) and may have an ordered or modified olivine-type structure.

[0040] Preferably, the lithiated or partially lithiated material has the specific formula Li 3-x M' y M'' 2-y (JO4)3, where 0≦x≦3, 0≦y≦2, M′ and M″ represent 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, and J is selected from S, V, Si, Nb, Mo, and combinations thereof.

[0041] Even more preferably, the lithiated or partially lithiated material has the formula Li(Fe x Mn 1-x )PO4, where 0≦x≦1, preferably x is equal to 1 (which in turn means that the corresponding material is LiFePO4).

[0042] Examples of electrode active materials that can form part of the negative electrode of the lithium accumulator may include: - carbon materials, such as graphitic carbons suitable for lithium intercalation, which may typically be present in the form of powders, flakes, fibers, or spheres (e.g. mesocarbon microbeads); - 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 range from 0 to 0.2 and M represents an element selected from Na, K, Mg, Nb, Al, Ni, Co, Zr, Cr, Mn, Fe, Cu, Zn, Si, and Mo, one particular example being Li4Ti5O 12 and these oxides are lithium insertion materials that have a low level of physical expansion after lithium insertion; - non-lithiated titanium oxides, e.g. TiO2; - 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-silicon alloys, commonly known by the term lithium silicides, advantageously having a high Li / Si ratio, for example Li 4,4 Si; - lithium-germanium alloys, such as those of the formula Li 4,4 Contains a crystalline phase of Ge.

[0043] Furthermore, whether it is a positive or negative electrode, it may contain electronically conductive additives, i.e. additives capable of conferring electronic conductivity to the electrode in which they are incorporated. These additives may be, for example, carbon materials such as carbon black, carbon nanotubes, carbon fibers (in particular carbon fibers obtained in the gas phase known by the abbreviation VGCF), graphite in powder form, graphite fibers, and mixtures thereof.

[0044] However, when the negative electrode includes a carbon material such as graphite as the active material, the negative electrode may advantageously be free of any electronically conductive additive(s).

[0045] Advantageously, all of the negative electrodes of the accumulator conform to the same specifications (ie, in terms of composition and dimensions), just as all of the positive electrodes of the accumulator also conform to the same specifications in terms of composition and dimensions.

[0046] Furthermore, whether positive or negative electrodes, they contain a liquid electrolyte trapped in a polymer matrix.

[0047] The liquid electrolyte trapped in the membrane is conventionally an ion-conducting electrolyte, which may comprise (or even consist of) at least one organic solvent, at least one metal salt, and optionally a compound of the vinyl compound family.

[0048] The organic solvent(s) may be carbonate solvents, more particularly: cyclic carbonate solvents, such as ethylene carbonate (abbreviated as EC), propylene carbonate (abbreviated as PC), butylene carbonate, vinylene carbonate, fluoroethylene carbonate, fluoropropylene carbonate, and mixtures thereof; linear carbonate solvents, such as diethyl carbonate (abbreviated as DEC), dimethyl carbonate (abbreviated as DMC), ethyl methyl carbonate (abbreviated as EMC), and mixtures thereof; It could be.

[0049] The organic solvent(s) can also be an ester solvent (such as ethyl propionate or n-propyl propionate), a nitrile solvent (such as acetonitrile), or an ether solvent (such as dimethyl ether or 1,2-dimethoxyethane).

[0050] The organic solvent(s) may also be ionic liquids, i.e., compounds formed by the combination of conventionally positively charged cations and negatively charged anions, which are in the liquid state at temperatures below 100° C. at atmospheric pressure.

[0051] More specifically, the ionic liquid may include: - a cation chosen from imidazolium, pyridinium, pyrrolidinium, or piperidinium cations, said cations being optionally substituted with at least one alkyl group containing from 1 to 30 carbon atoms; - an anion selected from a halide anion, a perfluorinated anion, or a borate anion.

[0052] Even more specifically, the cation may be selected from the following cations: a pyrrolidinium cation of the following formula (II): [ka] (II) [In the formula, R 13 and R 14 represent independently a C1-C8 alkyl group, R 15 , R 16 , R 17 , and R 18 are independently hydrogen atoms or C1-C 30Alkyl groups, preferably C1-C 18 alkyl group, again preferably a C1-C8 alkyl group]; a piperidinium cation of formula (III): [ka] (III) [In the formula, R 19 and R 20 represent independently a C1-C8 alkyl group, R 21 , R 22 , R 23 , R 24 , and R 25 are independently hydrogen atoms or C1-C 30 Alkyl groups, preferably C1-C 18 represents an alkyl group, again preferably a C1-C8 alkyl group].

[0053] In particular, the positively charged cations may be selected from the following cations: a pyrrolidinium cation of the following formula (II-A): [ka] a piperidinium cation of the following formula (III-A): [ka]

[0054] Specifically, the negatively charged ions may be selected from: - 4,5-dicyano-2-(trifluoromethyl)imidazole (known by the abbreviation TDI); - bis(fluorosulfonyl)imide (known by the abbreviation FSI); - Formula (SO2CF3)2N - bis(trifluoromethylsulfonyl)imide; - Formula PF6 - of hexafluorophosphate; - Formula BF4 -of tetrafluoroboric acid; - oxaloboric acid of the formula: [ka]

[0055] Particular ionic liquids that can be used in accordance with the present invention are those comprising a cation of formula (II-A) as defined above and a cation of formula (SOCF)N - , PF6 - , or BF4 - and an anion of

[0056] The metal salt(s) may be selected from salts of the following formulae: MeI, Me(PF6) n , Me(BF4)n, Me(ClO4) n , Me(bis(oxalato)boronic acid) n (This is an abbreviation for Me(BOB) n (which may be referred to as MeCF3SO3, Me[N(FSO2)2] n , Me[N(CF3SO2)2] n , Me[N(C2F5SO2)2] n , R F is a -C2F5, -C4F9, or -CF3OCF2CF3 group, Me[N(CF3SO2)(R F SO2)] n , Me(AsF6) n , Me[C(CF3SO2)3] n , Me2S n, Me(CFN) (where CFN corresponds to 4,5-dicyano-2-(trifluoromethyl)imidazole, and when Me is Li, the salt corresponds to lithium 4,5-dicyano-2-(trifluoromethyl)imidazole, which salt is known by the abbreviation LiTDI), where Me is a metal element, preferably a transition metal element, an alkali element, or an alkaline earth element, again preferably Me is Li (particularly when the accumulator of the present invention is a lithium ion or lithium-air accumulator). accumulator), Na (particularly when the accumulator is a sodium ion accumulator), K (particularly when the accumulator is a potassium ion accumulator), Cs, Mg (particularly when the accumulator is a Mg ion accumulator), Ca (particularly when the accumulator is a calcium ion accumulator), and Al (particularly when the accumulator is an aluminum ion accumulator), where n corresponds to the valence of the metal element (typically 1 or 2).

[0057] When Me is Li, the salt is preferably LiPF6.

[0058] The concentration of metal salt in the liquid electrolyte is advantageously at least 0.01M, preferably at least 0.025M, again preferably at least 0.05M, and advantageously not more than 5M, preferably not more than 2M, again preferably not more than 1M.

[0059] Furthermore, the liquid electrolyte may contain an additive belonging to the category of vinyl compounds, such as vinylene carbonate, in a proportion not exceeding 5% by weight of the total weight of the electrolyte.

[0060] A liquid electrolyte that can be used in the accumulator of the present invention, particularly when it is the case for a lithium-ion accumulator, is an electrolyte comprising a mixture of carbonate solvents (e.g. a mixture of cyclic carbonate solvents, such as ethylene carbonate and propylene carbonate, for example present in equal volumes), a lithium salt, such as LiPF6 (e.g. 1 M), and vinylene carbonate (e.g. present in an amount of up to 2% by weight relative to the total weight of the liquid electrolyte).

[0061] Furthermore, the positive electrode(s) and / or negative electrode(s) may have a thickness ranging from 2 to 500 μm, preferably from 10 to 400 μm, again preferably from 50 to 300 μm.

[0062] The gelled nature of the electrode allows for greater thickness to be achieved than conventional non-gelled electrodes, which allows for the incorporation of more active material and thus greater energy content.

[0063] Furthermore, each electrochemical cell contains a membrane disposed between the positive and negative electrodes, thus allowing physical separation between them. In this way, it can also be called a separator. This membrane also allows ionic conduction in the conventional manner (i.e., the passage of ions from the negative electrode to the positive electrode and vice versa, depending on whether a charging or discharging process is taking place). This allows it to be called an ionically conductive membrane. Furthermore, it advantageously allows the containment of a liquid electrolyte, which advantageously conforms to the same specifications as that forming part of the gel electrode.

[0064] More specifically, each membrane advantageously comprises an organic portion comprising (or consisting of) at least one fluorinated polymer (F) comprising 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 comprising at least one hydroxyl group, optionally in the form of a salt, and an inorganic portion formed wholly or partly by one or more oxides of at least one element M chosen from Si, Ti and Zr, and combinations thereof, and furthermore comprises a liquid electrolyte, which is advantageously the same as that contained in the gel electrode.

[0065] The liquid electrolyte is advantageously confined or trapped in the material that makes up the membrane and may follow the same specific characteristics in terms of composition (organic solvents, salts, concentrations, etc.) as those disclosed above for gel electrodes.

[0066] In the fluorinated polymer (F), the repeating unit(s) 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 ethylenic monomers containing at least one fluorine atom and optionally one or more other halogen atoms. Examples of monomers of this type are: C2-C8 perfluoroolefins, such as tetrafluoroethylene or hexafluoropropene (also known by the abbreviation HFP); - C2-C8 hydrogenated fluoroolefins, such as vinylidene fluoride, vinyl fluoride, 1,2-difluoroethylene, and trifluoroethylene; - Formula CH2=CHR 1 perfluoroalkylethylene of the formula R 1 is a C1-C6 perfluoroalkyl group; - C2-C6 fluoroolefins containing one or more other halogen atoms (e.g., chlorine, bromine, or iodine), such as chlorotrifluoroethylene; - Formula CF2=CFOR 2 (per)fluoroalkyl vinyl ethers of the formula:2 is a C1-C6 fluoro or perfluoroalkyl group, such as CF3, C2F5, C3F7; - Formula CF2=CFOR 3 wherein R 3 is C1-C 12 Alkyl groups, C1-C 12 Alkoxy group, or C1-C 12 (per)fluoroalkoxy groups, such as perfluoro-2-propoxypropyl groups; and / or - Formula CF2=CFOCF2OR 4 wherein R 4 is a C1-C6 fluoro or perfluoroalkyl group, such as CF2, C2F5, C3F7, or a C1-C6 fluoro or perfluoroalkoxy group, such as -C2F5-O-CF3.

[0067] More specifically, the fluorinated polymer (F) may contain, as repeating units resulting from the polymerization of fluorinated monomers, repeating units resulting from the polymerization of a monomer in the category of C2-C8 perfluoroolefins, such as hexafluoropropene, and repeating units resulting from the polymerization of a monomer in the category of C2-C8 hydrogenated fluoroolefins, such as vinylidene fluoride.

[0068] It should be noted that for said fluorinated polymer (F), said repeat unit(s) resulting from the polymerization of a monomer comprising at least one hydroxyl group, optionally in the form of a salt, may more specifically be one or more repeat units resulting from the polymerization of a monomer of the following formula (IV): [ka] (IV) In the formula, R 9 From R 11 represent independently a hydrogen atom or a C1-C3 alkyl group, and R 12is a C1-C5 hydrocarbon group containing at least one hydroxyl group, examples of this type of monomer are hydroxyethyl (meth)acrylate monomers and hydroxypropyl (meth)acrylate monomers.

[0069] More specifically, the fluorinated polymer (F) contains, as repeating units resulting from polymerization of monomers containing at least one hydroxyl group, repeating units resulting from polymerization of monomers represented by the following formulae (V) to (VII): [ka] Preferably, it may comprise repeat units resulting from the polymerization of a monomer of formula (V) above, which corresponds to 2-hydroxyethyl acrylate (also known by the abbreviation HEA).

[0070] Thus, specific fluorinated polymers (F) that can be used to form membranes in the context of the present invention can be polymers that contain, as repeating units resulting from the polymerization of fluorinated monomers, repeating units resulting from the polymerization of monomers of the C2-C8 perfluoroolefin category, such as hexafluoropropene, and repeating units resulting from the polymerization of monomers of the C2-C8 hydrogenated fluoroolefin category, such as vinylidene fluoride, and that contain, as repeating units resulting from the polymerization of monomers containing at least one hydroxyl group, repeating units resulting from the polymerization of monomers of formula (IV) as defined above, again more specifically, the aforementioned repeating units resulting from the polymerization of: - at least 70 mol % of C2-C8 hydrogenated fluoroolefins, preferably vinylidene fluoride; - 0.1 to 15 mol % of a C2-C8 perfluoroolefin, preferably hexafluoropropene; and - 0.01 to 20 mol % of a monomer of formula (IV), preferably 2-hydroxyethyl acrylate.

[0071] Advantageously, said inorganic moieties, formed at least in part by one or more oxides of at least one element M chosen from Si, Ti and Zr, and combinations thereof, are chemically bonded to said organic moieties, in whole or in part, via said hydroxyl groups.

[0072] The membranes of the invention advantageously have a surface that completely covers the surface of the negative electrode they contact (so as to ensure a clear separation from the positive electrode), but they do not protrude beyond the face of the current collector that houses the negative electrode, otherwise there would be a risk of creating an ionic short circuit by contacting the membrane of an adjacent cell during the process of assembling the various elements that make up the accumulator.

[0073] The accumulator of the present invention is an accumulator with a bipolar architecture, which assumes the presence of a bipolar current collector between two adjacent cells.

[0074] More specifically, a bipolar current collector (when the accumulator contains only two cells) or a plurality of bipolar current collectors (when the accumulator contains three or more cells) may be defined as a current collector that isolates two adjacent electrochemical cells from each other and supports on a first face an electrode of one of the electrochemical cells and on a second face opposite the first face an electrode of opposite sign to the other one of the electrochemical cells.

[0075] Moreover, an electrochemical cell is considered to be adjacent to another electrochemical cell when it immediately precedes or follows it in the stack, and is thus isolated from it only by a bipolar current collector.

[0076] The accumulator of the invention also comprises a terminal current collector, generally located at the end of the stack and housing on one of its faces an electrode layer belonging to the terminal cell (depending on the required polarity, this electrode layer is a positive or negative electrode layer), which electrode layer has the same construction as that of the electrode layer of the same polarity conventionally associated with a bipolar current collector.

[0077] Moreover, the current collector(s), whether they are terminal or bipolar, may be single-layer (in this case, they preferably consist of an aluminum, copper, or aluminum alloy foil) or double-layer (in this case, they preferably consist of an aluminum foil combined with a copper layer or two foils facing each other (e.g., an aluminum foil facing a copper foil)). They have a thickness of, for example, 20 μm.

[0078] Advantageously, the active material of the positive electrodes, whether they are terminal or bipolar, is LiNi 0.33 Mn 0.33 Co 0.33 O2 and the active material of the negative electrode is Li4Ti5O 12 When the current collector(s) consist of a single layer of foil, such as aluminum foil.

[0079] In particular, the active material of the positive electrode is LiNi 0.33 Mn 0.33 Co 0.33 When the active material of the negative electrode is O2 (the resulting positive electrode is placed on the face of a collector formed by an aluminum foil) and graphite (the resulting negative electrode is placed on the face of a collector formed by a copper foil), they may advantageously be a double layer resulting, for example, from the juxtaposition of an aluminum foil and a copper foil.

[0080] The surface(s) occupied by the electrodes, whether bipolar current collectors or terminal collectors, advantageously have, on their periphery, a free (i.e., not occupied by an electrode) edge and / or at least one tongue that contacts or extends said collector(s), all or part of these free edges and / or tongues being wholly or partially covered by a layer of insulating material. More specifically, each pair of current collectors facing each other via a free edge and / or tongue may, for at least one of them, include a layer of insulating material covering all or part of the free edge and / or tongue. This is because the presence of a layer of insulating material makes it possible to insulate these collectors electronically (and to avoid short circuits, especially if they happen to come into contact with each other due to the pressure of the stack). This insulating material, applied in the form of a layer, performs the insulating function usually entrusted to the seal(s) present in each cell in conventional bipolar accumulators. These seals are not present in the accumulator of the present invention. This is because the liquid electrolyte is well confined by the selection of electrodes and membranes described above.

[0081] The layer of insulating material can be in a variety of locations.

[0082] Thus, according to a first embodiment illustrated in FIG. 2, which shows in side view a bipolar accumulator comprising two cells (reference numerals 15 and 17 respectively illustrate the negative and positive electrodes of each cell, reference numeral 19 the membrane of each cell, reference numerals 21, 23 and 25 respectively the negative terminal current collector, the bipolar current collector and the positive terminal current collector), it is provided that a layer of insulating material (reference numerals 27 and 29 respectively) is attached to the tongues (reference numerals 20 and 24 respectively) or to each terminal current collector on its inner side (i.e. on the sides opposite each other).

[0083] According to a second embodiment illustrated in FIG. 3 , which shows in side view a bipolar accumulator comprising two cells (reference numerals 15 and 17 respectively illustrate the negative and positive electrodes of each cell, reference numeral 19 illustrates the membrane of each cell, reference numerals 21 , 23 and 25 respectively illustrate the negative terminal current collector, the bipolar current collector and the positive terminal current collector): a layer of insulating material (reference number 31) on the free edge portion of the face of the bipolar current collector that accommodates the positive electrode (this free edge portion faces the tongue portion (reference number 33) of the negative terminal current collector); and - a layer of insulating material (reference number 35) on the tongue (reference number 37) of the positive terminal current collector 25 opposite the face of the bipolar current collector; Mounting is provided.

[0084] Finally, according to a third embodiment illustrated in FIG. 4 , which shows in side view a bipolar accumulator comprising three cells (reference numerals 15 and 17 respectively illustrate the negative and positive electrodes of each cell, reference numeral 19 illustrates the membrane of each cell, reference numerals 21 , 23 and 25 respectively illustrate the negative terminal current collector, the bipolar current collector and the positive terminal current collector): - a layer of insulating material (reference numeral 31) on the free edge of the face of each bipolar current collector containing a positive electrode; and a layer of insulating material (reference numeral 35) on the tongue (reference numeral 37) of the positive terminal current collector 25 opposite the face of the bipolar current collector containing the negative electrode; Mounting is provided.

[0085] In these various embodiments, which are given merely by way of example and not limitation, it is clear that the layer of insulating material is positioned so as to avoid any direct contact between the metal parts (free edges and / or tongues) of the faces of the current collectors that are located opposite each other.

[0086] The insulating material used may consist of a plastic material such as Kapton® or polypropylene and may be attached to the required part by adhesive bonding, coating, printing or simply contacting.

[0087] Furthermore, the accumulator of the invention may, as its name indicates, comprise a housing intended to encase the various elements that make up the stack.

[0088] This outer casing can be flexible (in this case, for example, it is produced from a laminated film comprising a frame in the form of an aluminum sheet, which is covered on its outer surface by a layer of polyethylene terephthalate (PET) or polyamide, and which is covered on its inner surface by a layer of polypropylene (PP) or polyethylene (PE)) or rigid (in this case, it is made, for example, from a lightweight and inexpensive metal, such as stainless steel, aluminum, or titanium, or from a thermosetting resin, such as an epoxy resin), depending on the type of application sought.

[0089] The number n of electrochemical cells that may comprise the accumulator of the invention is chosen to obtain a total voltage Utot that is sufficient according to the application for which this accumulator is intended, according to the rule Utot = n x Un, where Un corresponds to the voltage of the electrochemical couple employed. Typically, n may be between 2 and 20 in the accumulator of the invention.

[0090] The accumulator of the present invention may find application in the production of electric or hybrid vehicles, stationary energy storage devices, and portable electronic devices (phones, touch tablets, computers, photography equipment, video cameras, portable tools, sensors, etc.).

[0091] Moreover, the accumulator of the present invention can be adapted to various types of formats, such as a planar format, for example of the button cell type; a cylindrical format; a wound or spiral format; a prismatic format.

[0092] The accumulator of the invention can be prepared by a method comprising the step of assembling the basic elements: said bipolar current collector(s) covered on two opposite faces by a positive electrode and a negative electrode, respectively (the number of current collectors to be assembled corresponds to (n-1), where n corresponds to the number of cells of said accumulator), said membrane as defined above, and said terminal current collector, one of whose faces is covered in one case by a negative electrode and in the other case by a positive electrode.

[0093] Each film may be interposed between the positive and negative electrodes of each cell, meaning that it may be present prior to the formation of the stack, or it may be deposited (by any solution deposition technique, such as coating, pouring, or printing) onto one side of one of the positive or negative electrodes of each cell.

[0094] The various basic elements described above, particularly the positive and negative electrodes, may be pre-prepared prior to assembly.

[0095] In this way, in particular, positive and negative electrodes can be produced by depositing a composition comprising the components that make up the electrodes (gelling polymer (FF) as defined above, active material, liquid electrolyte, and optionally at least one electronically conductive additive) onto a current collector by a solution deposition technique (e.g. coating, printing, pouring), followed by drying.

[0096] More specifically, the positive and negative electrodes may be prepared by a method comprising the following steps: (i) Provision of a current collector; (ii) - at least one gelling polymer (FF) as defined above; - at least one electrode active material (it is understood that said electrode active material is a positive electrode active material when said method relates to the preparation of a positive electrode, or a negative electrode active material when said method relates to the preparation of a negative electrode); - liquid electrolyte; - optionally one or more electronically conductive additives; Provision of a composition comprising: (iii) applying the composition of step (ii) to the current collector of step (i), thereby providing an assembly including the current collector covered by at least one layer of the composition; and (iv) drying the assembly resulting from step (iii).

[0097] According to step (iii), the composition can be applied to the current collector by any type of application method, for example by pouring, printing or coating, for example by a roller.

[0098] Step (iii) may be repeated, typically one or more times, depending on the thickness of the electrode required.

[0099] The components of the composition may be the same variations as those already defined for the same components in the context of the description of the electrode itself.

[0100] It should be pointed out that the composition advantageously comprises an organic solvent chosen to allow the solubilization of the gelling polymer(s) (FF). This organic solvent can be that of the liquid electrolyte or can be added in addition to the other components listed above.

[0101] To ensure homogeneous properties for all positive and negative electrodes of the accumulator, these can result from the same deposition layer (with a given composition for the positive electrode and a given composition for the negative electrode) being deposited on a substrate made of the material that constitutes the various current collectors, followed by suitable cutting of this substrate to provide the various coated electrode current collectors.

[0102] As already mentioned above, the various current collectors coated in this way may be provided with metal tongues to provide current pick-up when it is a matter of terminal current collectors or to control the voltage when it is the case of bipolar current collectors, or their free edges and / or tongues may be coated with a layer of insulating material.

[0103] Said membranes, when they comply with the specific definition given above, can be obtained by a method comprising a hydrolysis condensation step of at least one organometallic compound containing a metal element chosen from Si, Ti, Zr and combinations thereof, in the presence of a liquid electrolyte as defined above and a fluorinated polymer (F), advantageously a reaction taking place between the organometallic compound and the fluorinated polymer (F).

[0104] More specifically, according to a specific embodiment, said membrane may be produced by a method comprising the following specific steps: (i) at least one fluorinated polymer (F) as defined above: at least one organometallic compound M1 of the following formula: X 4-m AY m [wherein m is an integer ranging from 1 to 3, A is a metal element selected from Si, Ti, Zr, and combinations thereof, Y is a hydrolyzable group, and X is a hydrocarbon group containing at least one isocyanate group -N=C=O]; - a liquid electrolyte as defined above; optionally at least one organometallic compound M2 of the formula: A'Y' m’ [wherein m' is an integer ranging from 1 to 4, A' is a metal element selected from Si, Ti, Zr, and combinations thereof, and Y' is a hydrolyzable group]; contacting the (ii) reacting at least a portion of the hydroxyl groups of the fluorinated polymer (F) with at least a portion of the compound M1 and optionally with at least a portion of the compound M2, thereby obtaining a composition comprising a fluorinated polymer, wherein at least a portion of the hydroxyl groups are substituted with hydroxyl groups of the formula -O-CO-NH-Z-AY m X 3-m wherein m, Y, A, and X are as defined above and Z is a hydrocarbon group optionally containing at least one group -N=C=O, and optionally at least a portion of said hydroxyl groups are converted to groups of the formula -O-A'Y' m’-1 wherein A', Y', and m' are as defined above; (iii) A step of hydrolytic condensation of the composition obtained in (ii), which forms the inorganic part of the membrane used in the context of the present invention.

[0105] This type of method falls into the category of sol-gel type methods because it involves organometallic compounds containing hydrolyzable groups and a step of hydrolytic condensation of these compounds to form inorganic moieties.

[0106] The hydrolyzable group of compound M1 is preferably selected to allow the formation of an -OA- bond, and can be selected from a halogen atom (preferably chlorine), an alkoxy group, an acyloxy group, and a hydroxyl group.

[0107] More specifically, compound M1 may conform to the formula: O=C=NR A -A-(OR B )3 In the formula, A is a metal element selected from Si, Ti, Zr, and combinations thereof; A is a linear or branched hydrocarbon group containing 1 to 12 carbon atoms, and R B is a hydrocarbon group, more specifically an alkyl group that is straight-chain or branched and contains from 1 to 5 carbon atoms (eg, a methyl or ethyl group).

[0108] Examples of compound M1 may include trimethoxysilylmethyl isocyanate, triethoxysilylmethyl isocyanate, trimethoxysilylethyl isocyanate, triethoxysilylethyl isocyanate, trimethoxysilylpropyl isocyanate, triethoxysilylpropyl isocyanate, trimethoxysilylbutyl isocyanate, triethoxysilylbutyl isocyanate, trimethoxysilylpentyl isocyanate, triethoxysilylpentyl isocyanate, trimethoxysilylhexyl isocyanate, and triethoxysilylhexyl isocyanate.

[0109] In compound M2, in the same manner as compound M1, the hydrolyzable group of compound M2 is preferably selected to allow the formation of an -OA- bond, which group can be selected from a halogen atom (preferably chlorine), an alkoxy group, an acyloxy group, and a hydroxyl group.

[0110] Examples of compounds M2, when A is silicon, may include tetramethoxysilane (known by the abbreviation TMS) or tetraethoxysilane (known by the abbreviation TEOS).

[0111] Reaction step (ii) is generally carried out at a temperature in the range of from 20 to 100°C, preferably from 20 to 90°C, again preferably from 20 to 60°C, and preferably under an inert gas atmosphere (e.g. a stream of argon). This reaction step (ii) and subsequent step (iii) may be carried out in the presence of a condensation catalyst, which may be introduced in step (i).

[0112] The condensation catalyst can be an organotin compound.

[0113] It may be introduced in step (i) to the extent of 0.1% to 50 mol %, preferably 1 to 25 mol %, again preferably 5 to 15 mol %, relative to the total number of moles of compound M1 and, if applicable, compound M2.

[0114] Examples of organotin compounds can include dibutyltin dilaurate, dibutyltin oxide, tributyltin oxide, dioctyltin oxide, tributyltin chloride, and tributyltin fluoride.

[0115] The hydrolysis condensation step (iii) can be carried out at ambient temperature or by heating to a temperature below 100° C. The choice of temperature depends on the boiling point of the liquid electrolyte.

[0116] This hydrolysis and condensation step can be carried out in the presence of an acid catalyst, which can be added in one of steps (i) to (iii), for example, to the extent of 0.5 to 10% by weight, preferably 1 to 5% by weight, based on the total weight of the composition.

[0117] The acid catalyst may in particular be an organic acid such as formic acid.

[0118] Furthermore, the method may comprise a step (iv) of forming the composition into a film, which may be carried out concomitantly with the hydrolysis and condensation step (iii), and which may be carried out by any known technique for film formation involving composite materials, for example, a suitable technique is the extrusion slot deposition technique, or commonly known by the English term "slot die coating".

[0119] Finally, the method for preparing the accumulator of the present invention may include the step of attaching a sheath around the accumulator, which may be performed by heat sealing in the case of a flexible sheath, or by laser welding in the case of a rigid sheath.

[0120] Other advantages and features of the present invention will become apparent from the remainder of the following detailed description, which is given by way of example of the invention and which refers to the accompanying drawings. [Brief explanation of the drawings]

[0121] [Figure 1] FIG. 1, already mentioned, shows a schematic longitudinal cross-sectional view of a conventional example of an accumulator with a bipolar architecture. [Figure 2] FIG. 2, already mentioned, shows a schematic longitudinal cross-sectional view of an accumulator according to the invention. [Figure 3] FIG. 3, already mentioned, shows a schematic longitudinal cross-sectional view of an accumulator according to the invention. [Figure 4] FIG. 4, already mentioned, shows a schematic longitudinal cross-sectional view of an accumulator according to the invention. [Figure 5] FIG. 5 is a graph illustrating the variation of voltage U (in V) as a function of time t (in h), obtained in the context of the test of Example 1, by means of curves a) and b) for the first and second cells of the accumulator and curve c) for the accumulator itself. [Figure 6] FIG. 6 is a graph illustrating the variation of the discharge capacity C (in mAh) as a function of the number of cycles N of an accumulator according to the invention, obtained in the context of the test of Example 1. [Figure 7] FIG. 7 is another graph illustrating the variation of the discharge capacity C (in mAh) as a function of the number of cycles N of an accumulator according to the invention, obtained in the context of the tests of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0122] (Example) Example 1 In this example, the preparation of a lithium accumulator with bipolar structure according to the invention is disclosed, involving the following steps: 1) Preparation of electrodes; 2) membrane preparation; 3) Preparation of the accumulator.

[0123] 1. Preparation of Electrodes The same gelling polymer is used to prepare inks intended for preparing electrodes, whether positive or negative. This is a polymer 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. This polymer is referred to below by the term "Polymer 1." It is incorporated into inks intended for producing electrodes in the form of a solution in acetone, with 10% of Polymer 1 dissolved at 60 °C. The solution is cooled to room temperature and introduced into a glove box under an argon atmosphere (O<2 ppm, H<2 ppm).

[0124] a) Preparation of ink for negative electrode To do this, a mixture of 50% by weight of carbon black C-NERGY® C65 and 50% by weight of carbon fiber "VGCF Fiber" and Li4Ti5O4 was prepared, with a mass ratio of ((VGCF+C65+LTO) / Polymer 1) of 95 / 5 and a mass ratio of (VGCF+C65) / LTO equal to 5.3 / 94.7. 12 (referred to as LTO) was added to the solution of polymer 1 mentioned in the previous paragraph. To the resulting mixture was also added a liquid electrolyte consisting of a mixture (EC:PC) in mass proportions (1:1) (EC designates ethylene carbonate and PC designates propylene carbonate), vinylene carbonate (to the extent of 2% by mass) and lithium salt LiPF6 (1M). The liquid electrolyte was added in a mass ratio (m) equal to 75%. 電解質 / (m 電解質 +m ポリマー1 )) × 100. The whole, placed in a closed flask to avoid evaporation of the acetone, was mixed with a magnetic stirrer for 1 hour.

[0125] b) Preparation of ink for the positive electrode To do this, a mixture of 50% by weight of carbon black C-NERGY® C65 and 50% by weight of carbon fibers obtained in the gas phase, known as "VGCF fibers", and LiNi, was used, so that the mass ratio of ((VGCF+C65+NMC) / polymer 1) was 92.8 / 7.2 and the mass ratio of (VGCF+C65) / NMC was equal to 7.7 / 92.3. 0,33 Mn 0,33 Co 0,33 O2 (referred to as NMC) was added to the solution of polymer 1 mentioned in the paragraph above. To the resulting mixture was also added a liquid electrolyte composed of a mixture (EC:PC) in mass proportions (1:1) (EC designates ethylene carbonate and PC designates propylene carbonate), vinylene carbonate (to the extent of 2% by mass) and lithium salt LiPF6 (1M). The liquid electrolyte was added in a mass ratio (m ) equal to 85.7%. 電解質 / (m 電解質 +m ポリマー1 )) × 100. The whole, placed in a closed flask to avoid evaporation of the acetone, was mixed with a magnetic stirrer for 1 hour.

[0126] c) Preparation of electrodes To ensure that the bipolar cell was constructed from positive and negative electrodes with exactly the same characteristics, the electrode-coated bipolar current collector and the two terminal positive and negative electrodes were prepared from the same strip (hereinafter referred to as the bipolar electrode strip).

[0127] *Preparation of bipolar electrode strips The preparation of bipolar electrode strips by coating was carried out on a laboratory coating table in a dry room (with a dew point temperature of -40°C to 20°C). To do this, an LTO negative electrode strip was produced by coating the ink prepared above onto an aluminum foil (having a thickness of 20 μm) with a width of 100 mm, applying a coating thickness of 320 μm, and drying it in the free air of a dry room for 30 minutes. Its surface capacity was 1.5 mAh / cm. 2 was measured as. Another NMC positive electrode strip was produced by coating the ink prepared above onto the other side of the same aluminum foil behind the LTO coat, preferably at the center, with the same width of 75 mm, applying a coating thickness of 360 μm. It was then dried in free air in a dry room for 30 minutes. Its surface capacity was 1.65 mAh cm. 2 was measured as.

[0128] * Preparation of basic components for electrode-coated bipolar current collectors and preparation of terminating positive and negative electrodes Three 40mm x 60mm rectangles were cut from the 100mm coated bipolar electrode strip using a punch. The edges of each of these rectangles were then cleaned off to leave two opposing positive and negative electrode squares measuring 32mm x 32mm. The square electrodes were thus surrounded on three sides by a 4mm wide strip of bare aluminum and on the fourth side by a 24mm wide strip. The three rectangles prepared in this way constituted the basic components used to produce the bipolar current collector coated with the bipolar accumulator electrodes and the two terminal positive and negative electrodes. To achieve the same densification level for all electrodes, each rectangle was compressed between two metal plates measuring 100 mm x 100 mm with a 2-ton weight.

[0129] *Preparation of the terminating positive electrode The positive terminal electrode is produced from one of the three basic components listed above. Thus, using a specific punch, a square terminal electrode with dimensions 32 mm x 32 mm is cut out, leaving a bare aluminum tongue with dimensions 5 mm x 20 mm for current pickup. On the other side of the square, the negative electrode layer is completely removed, exposing the metal current collector. An aluminium tongue with a sealing ribbon located in the heat sealing zone of the outer sheath is ultrasonically welded onto the current pick-up.

[0130] *Preparation of the terminating negative electrode The terminating negative electrode is produced by a procedure similar to that of the positive electrode: - Using a blanking punch, cut out a 32mm x 32mm square negative electrode, leaving an aluminum tongue for current pickup; - Thorough cleaning of the positive surface to leave only the bare current collector; - Ultrasonic welding of an aluminium tongue onto the current pick-up that will serve as the negative pole of the battery, with the sealing ribbon positioned in the heat sealing zone of the outer casing.

[0131] *Preparation of electrode-coated bipolar current collectors The bipolar current collector coated with electrodes is produced from the third basic component: a 24 mm wide bare aluminum strip is cut to a length of 25 mm, thus leaving a 15 mm wide tongue. A thinner (5 mm) and longer tongue is then ultrasonically welded to this, which will be used to control the voltage of the electrode. At the end electrode, a sealing ribbon will be placed in the heat sealing zone of the outer sheath. Once assembled, a small strip of Kapton® type adhesive is bonded to each side of a 4 mm bare aluminum strip on the opposite side of the square electrodes to avoid any electrical shorts between the positive, negative, and bipolar electrodes. No seal is placed around the electrodes coating the bipolar current collectors, nor around the terminating electrodes.

[0132] 2. Preparation of Membranes The polymer hybrid membrane consists of an organic / inorganic hybrid copolymer based on modified PVdF-HFP containing methacrylic branches (PVdF-HEA-HFP), in which the sol-gel reaction is carried out using tetraethoxysilane (TEOS). It is obtained by coating a polymer solution onto a polyethylene terephthalate (PET) substrate.

[0133] a) Preparation of polymer solution To do this, 10 g of a copolymer containing repeating units resulting from the polymerization of vinylidene fluoride (VDF), 2-hydroxyethyl acrylate (HEA), and hexafluoropropene (HFP) was introduced into a 300 ml double-walled synthesis reactor previously inerted with argon, followed by the addition of 67 ml of anhydrous acetone with a purity of 99.9%. This polymer was designated PVdF-HEA-HFP (96.8 mol% VDF, 0.8 mol% HEA, and 2.4 mol% HFP) and had an intrinsic viscosity of 0.08 g / L. The mixture was mechanically stirred under a stream of argon at 60°C for 30 minutes. Next, 0.10 g of dibutyltin dilaurate (DBTL) was added, and the resulting mixture was stirred under a stream of argon at 60°C for 30 minutes. Next, 0.40 g of 3-(triethoxysilyl)propyl isocyanate (TSPI) is added, and the mixture is stirred under an argon flow at 60°C for 90 minutes. 37.50 g of electrolyte, having the same composition as that used in the electrodes, is added, and the mixture is stirred under an argon flow at 60°C for 30 minutes. Next, 2.50 g of formic acid is added, and the mixture is stirred under an argon flow at 60°C for 30 minutes. Finally, 3.47 g of tetraethoxysilane is added, and the mixture is stirred under an argon flow at 60°C for 30 minutes.

[0134] b) Preparation of membranes using polymer solutions Once prepared, the polymer solution is transferred into a sealed flask in a dry room (dew point temperature -20 to 22°C). It is then coated by an R2R coating machine ("Roll-to-Roll Slot Die Coating Machine, Ingecal Tailor Made"). The solution is introduced into the machine in a controlled environment at room temperature but with a dew point temperature of -20 to 22°C. The operating parameters of the machine are as follows: - Line speed: 1m / min; - Drying section: 1st and 2nd zones at 40°C; 3rd zone at 50°C, and 4th zone at 60°C; - Opening of the slot during extrusion: 300 μm. This makes it possible to obtain a film of approximately 50 μm deposited on a polyethylene terephthalate (PET) substrate. The membrane strip thus obtained is then stored in a heat-sealed airtight pouch while awaiting further assembly of the bipolar accumulator.

[0135] 3- Preparation of the bipolar accumulator Two membranes measuring 34 mm x 34 mm are cut and deposited on the two sides of a bipolar current collector coated with electrodes. Terminal electrodes are then placed against the membranes, facing the opposite polarity electrodes of the bipolar current collector. The bipolar electrochemical core with its two compartments is then fixed in a flexible sheath made of multilayer aluminum foil. The whole is then heat-sealed. To ensure the sheath is sealed against moisture, the heat-sealing zone must pass through the level of the two terminal electrodes and the sealing ribbon of the bipolar current collector coated with electrodes.

[0136] Considering the characteristics of the electrodes, the expected capacity of the battery is 15.3 mAh. The latter was cycled at room temperature (20 °C) at a current of approximately 100 μA over a potential range [2 to 6 V] with a cutoff voltage per compartment fixed between 1 V and 3 V.

[0137] The tests show that the two compartments function in exactly the same way, as illustrated by Figure 5, which shows the superposition of the voltage curves for all cycles for the first and second cells (curves a) and b) for the first and second cells of the accumulator, and curve c) for the accumulator itself, illustrating the variation of voltage U (by V) as a function of time t (by h).

[0138] Also, stable behavior was demonstrated for the accumulators with the discharge capacity remaining stable over at least 20 cycles, as illustrated in Figure 6, which illustrates the change in discharge capacity C (in mAh) as a function of cycle number N.

[0139] Similarly, stable behavior was demonstrated for the accumulators with discharge capacities remaining stable over at least 40 cycles, as illustrated in FIG. 7 , which illustrates the change in discharge capacity C (in mAh) as a function of cycle number N.

[0140] Having demonstrated the operating principle, a bipolar accumulator similar to that defined above was produced, except that the active material of the negative electrode was replaced by graphite and the bipolar current collector was replaced by a bipolar current collector resulting from joining copper and aluminum foils. The surface occupied by the copper foil housed the negative electrode, and the surface occupied by the aluminum foil housed the positive electrode. The performance of this accumulator is very good, especially in terms of its stability throughout cycling and its similar behavior of the compartments (which proves the absence of ionic leakage).

[0141] Finally, we produced an accumulator similar to the one defined above, except that it contains three cells instead of two, based on an NMC positive electrode and an LTO negative electrode. The performance of this accumulator is also very good, especially in terms of its stability throughout cycling and its similar behavior of the compartments (which proves the absence of ionic leakage).

Claims

1. 1. An accumulator having a bipolar architecture, comprising: It comprises two terminal current collectors between which is disposed a stack of n electrochemical cells, where n is an integer at least equal to 2: each electrochemical cell comprising a positive electrode, a negative electrode, an ion-conducting membrane interposed between said positive electrode and said negative electrode, and a liquid electrolyte contained within said positive electrode, said negative electrode and said ion-conducting membrane; - said n electrochemical cells are isolated from each other by n-1 bipolar current collectors; and characterized in that the positive electrode and the negative electrode of each electrochemical cell are gel electrodes comprising a composite material comprising a polymer matrix made from at least one gelling polymer (FF), an electrode active material and optionally one or more electronically conductive additives, wherein the polymer matrix traps the liquid electrolyte, and the gelling polymer(s) (FF) are selected from fluorinated polymers comprising 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 comprising at least one carboxylic acid group, with the carboxylic acid group optionally being in the form of a salt; for the bipolar current collector(s) and the terminal current collector(s), the surface(s) occupied by the electrodes have, on their periphery, free edge portions, i.e. not occupied by the electrodes, and / or at least one tongue portion contacting or extending the bipolar current collector(s) or the terminal current collector(s), all or part of these free edge portions and / or tongue portions being totally or partially covered by a layer of insulating material, An accumulator with a bipolar architecture.

2. 2. The accumulator of claim 1, wherein said repeat unit(s) resulting from polymerization of a fluorinated monomer result from polymerization of one or more ethylenic monomers containing at least one fluorine atom and optionally one or more other halogen atoms selected from: - C ２ -C ８ perfluoroolefins; - C ２ -C ８ hydrogenated fluoroolefins; - Formula CH ２ = CHR １ perfluoroalkylethylene of the formula R １ is C １ -C ６ is a perfluoroalkyl group; - C containing one or more other halogen atoms ２ -C ６ Fluoroolefins; - Formula CF ２ =CFOR ２ (per)fluoroalkyl vinyl ethers of the formula: ２ is C １ -C ６ is a fluoro or perfluoroalkyl group; - Formula CF ２ =CFOR ３ wherein R ３ is C １ -C １２ Alkyl group, C １ -C １２ an alkoxy group, or C １ -C １２ is a (per)fluoroalkoxy group; and / or - Formula CF ２ = CFOCF ２ OR ４ A monomer of the formula: ４ is C １ -C ６ Fluoro or perfluoroalkyl group or C １ -C ６ It is a fluoro or perfluoroalkoxy group.

3. The gelling polymer(s) (FF) comprises, as repeating units resulting from the polymerization of fluorinated monomers, C ２ -C ８ Repeating units resulting from the polymerization of monomers of the perfluoroolefin category and C ２ -C ８ 3. The accumulator of claim 1 or 2, comprising repeat units resulting from the polymerization of monomers of the hydrogenated fluoroolefin category.

4. 4. The accumulator of any one of claims 1 to 3, wherein the repeat unit(s) resulting from the polymerization of a monomer comprising at least one carboxylic acid group result from the polymerization of a monomer of the following formula (I): 【Chemistry 9】 （I） [In the formula, R ５ From R ７ are independently a hydrogen atom or C １ -C ３ represents an alkyl group, and R ８ represents a hydrogen atom or a monovalent cation].

5. 5. An accumulator according to any one of claims 1 to 4, wherein said gelling polymer(s) (FF) is a polymer comprising repeating units resulting from the polymerization of vinylidene fluoride, repeating units resulting from the polymerization of a monomer comprising at least one carboxylic acid group, and optionally repeating units resulting from the polymerization of a fluorinated monomer different from vinylidene fluoride.

6. 6. The accumulator according to claim 1, wherein the liquid electrolyte trapped in the ion-conducting membrane is an ion-conducting electrolyte comprising at least one organic solvent, at least one metal salt and optionally a compound of the family of vinyl compounds.

7. 7. The accumulator of claim 6, wherein the organic solvent(s) is a carbonate solvent.

8. 8. The accumulator of claim 6 or 7, wherein the metal salt(s) is / are selected from salts of the following formula: MeI, Me(PF ６ ) ｎ , Me(BF ４ )n, Me(ClO ４ ) ｎ , Me(bis(oxalato)boronic acid) ｎ , MeCF ３ SO ３ , Me[N(FSO ２ ) ２ ] ｎ , Me[N(CF ３ SO ２ ) ２ ] ｎ , Me[N(C ２ F ５ SO ２ ) ２ ] ｎ , R Ｆ Ga-C ２ F ５ , -C ４ F ９ , or -CF ３ OCF ２ CF ３ Me[N(CF ３ SO ２ ) (R Ｆ SO ２ )] ｎ , Me(AsF ６ ) ｎ , Me[C(CF ３ SO ２ ) ３ ] ｎ , Me ２ S ｎ , Me(C ６ F ３ N ４ ) group, wherein Me is a metal element and n corresponds to the valence of the metal element.

9. 9. The accumulator of claim 1, wherein the ion-conducting membrane of each electrochemical cell comprises an organic portion comprising at least one fluorinated polymer (F) comprising at least one repeat unit resulting from the polymerization of a fluorinated monomer and at least one repeat unit resulting from the polymerization of a monomer comprising at least one hydroxyl group, wherein said hydroxyl group is optionally in the form of a salt, and an inorganic portion formed at least in part by one or more oxides of at least one element M selected from Si, Ti, and Zr, and combinations thereof.

10. 10. The accumulator of claim 9, wherein the repeat unit(s) resulting from polymerization of a fluorinated monomer result from polymerization of one or more ethylenic monomers containing at least one fluorine atom and optionally one or more other halogen atoms selected from: - C ２ -C ８ perfluoroolefins; - C ２ -C ８ hydrogenated fluoroolefins; - Formula CH ２ = CHR １ perfluoroalkylethylene of the formula R １ is C １ -C ６ is a perfluoroalkyl group; - C containing one or more other halogen atoms ２ -C ６ Fluoroolefins; - Formula CF ２ =CFOR ２ (per)fluoroalkyl vinyl ethers of the formula: ２ is C １ -C ６ is a fluoro or perfluoroalkyl group; - Formula CF ２ =CFOR ３ wherein R ３ is C １ -C １２ Alkyl group, C １ -C １２ an alkoxy group, or C １ -C １２ is a (per)fluoroalkoxy group; and / or - Formula CF ２ = CFOCF ２ OR ４ A monomer of the formula: ４ is C １ -C ６ Fluoro or perfluoroalkyl group or C １ -C ６ It is a fluoro or perfluoroalkoxy group.

11. The fluorinated polymer (F) contains, as a repeating unit resulting from polymerization of a fluorinated monomer, C ２ -C ８ Repeating units resulting from the polymerization of monomers of the perfluoroolefin category and C ２ -C ８ 11. The accumulator of claim 9 or 10, comprising repeat units resulting from the polymerization of monomers of the category of hydrogenated polyolefins.

12. 12. The accumulator of any one of claims 9 to 11, wherein the repeat unit(s) resulting from the polymerization of a monomer comprising at least one hydroxyl group result from the polymerization of a monomer of the following formula (IV), wherein the hydroxyl group is optionally in the form of a salt: 【Chemistry 10】 (IV) [In the formula, R ９ From R １１ are independently a hydrogen atom or C １ -C ３ represents an alkyl group, and R １２ C containing at least one hydroxyl group １ -C ５ It is a hydrocarbon group.

13. 13. The accumulator according to any one of claims 9 to 12, wherein the fluorinated polymer (F) comprises, as repeating units resulting from the polymerization of a monomer containing at least one hydroxyl group, a repeating unit resulting from the polymerization of one of the monomers of the following formulae (V) to (VII): 【Chemistry 11】

14. The fluorinated polymer (F) contains, as a repeating unit resulting from polymerization of a fluorinated monomer, C ２ -C ８ Repeating units resulting from the polymerization of monomers of the perfluoroolefin category and C ２ -C ８ The accumulator according to any one of claims 9 to 13, which is a polymer comprising repeating units resulting from the polymerization of monomers of the category of hydrogenated fluoroolefins and repeating units resulting from the polymerization of monomers containing at least one hydroxyl group, the repeating units resulting from the polymerization of monomers of formula (IV) according to claim 12.

15. 15. The accumulator according to any one of claims 9 to 14, wherein the inorganic moieties formed at least in part by one or more oxides of at least one element M selected from Si, Ti, and Zr, and combinations thereof, are chemically bonded to the organic moieties, in whole or in part, via the hydroxyl groups.

16. 2. A method for preparing an accumulator according to claim 1, comprising a step of assembling basic elements, which are the bipolar current collector(s) covered on two opposite faces by a positive electrode and a negative electrode, respectively, the ion-conducting membrane, and the terminal current collector, one of whose faces is covered in one case by the negative electrode and in the other case by the positive electrode, wherein the number of bipolar current collectors to be assembled corresponds to (n-1), n ​​corresponding to the number of cells of the accumulator.

17. 17. The method of claim 16, wherein the various building blocks are pre-prepared prior to assembly.

18. 18. The method of claim 17, wherein the positive and negative electrodes are prepared by a method comprising the steps of: (i) Provision of a current collector; (ii) - at least one gelling polymer (FF) according to claims 1 to 5, at least one electrode active material, - liquid electrolyte, - optionally one or more electronically conductive additives, providing a composition comprising: (iii) applying the composition of step (ii) to the current collector of step (i), thereby resulting in an assembly comprising the current collector covered by at least one layer of the composition; and (iv) drying the assembly resulting from step (iii).

19. The method according to claim 17, wherein the ion-conducting membrane is obtained by a method comprising a hydrolysis and condensation step in the presence of the liquid electrolyte according to any one of claims 9 to 15, a fluorinated polymer (F), and at least one organometallic compound containing a metal element selected from Si, Ti, Zr, and a combination thereof.

20. 20. The method of claim 19, wherein the ion-conducting membrane is produced by a method comprising the following specific steps: (i) at least one fluorinated polymer (F): at least one organometallic compound M1 of the following formula: X ４－ｍ AY ｍ [wherein m is an integer ranging from 1 to 3, A is a metal element selected from Si, Ti, Zr, and combinations thereof, Y is a hydrolyzable group, and X is a hydrocarbon group containing at least one isocyanate group -N=C=O]; - a liquid electrolyte as defined above; optionally at least one organometallic compound M2 of the following formula: A'Y' ｍ’ [wherein m' is an integer ranging from 1 to 4, A' is a metal element selected from Si, Ti, Zr, and combinations thereof, and Y' is a hydrolyzable group]; contacting the (ii) reacting at least a portion of the hydroxyl groups of the fluorinated polymer (F) with at least a portion of the compound M1 and optionally with at least a portion of the compound M2, thereby obtaining a composition comprising a fluorinated polymer, wherein at least a portion of the hydroxyl groups are of the formula —O—CO—NH-Z-AY ｍ X ３－ｍ wherein m, Y, A, and X are as defined above and Z is a hydrocarbon group optionally containing at least one group -N=C=O, and optionally at least a portion of said hydroxyl groups are converted to groups of the formula -O-A'Y' ｍ’－１ wherein A', Y', and m' are as defined above; (iii) A step of hydrolysis and condensation of the composition obtained in (ii), thereby forming the inorganic part of the ion-conducting membrane.

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