Method for manufacturing a treated positive electrode for a battery

Abstract

The present invention relates to a method for manufacturing a treated positive electrode for a battery comprising the following steps: a) mixing at least one active material for a positive electrode, at least one binder with at least one solution comprising at least one lithium salt comprising boron and fluorine; b) depositing the mixture obtained at the end of step a) onto a support; c) applying to said mixture: i) at least one solution comprising at least one compound C comprising at least one nitrogen atom and at least one polymerizable group; or ii) a polymer resulting from the polymerization of a compound C comprising at least one nitrogen atom and at least one polymerizable group; d) when i) is carried out, polymerizing said compound C.

Description

Title of the invention: Method for manufacturing a treated positive electrode for a battery. Technical field

[0001] The present invention relates to the field of batteries. More particularly, the present invention relates to a method for manufacturing a treated positive electrode for a battery. The invention also relates to said treated positive electrode for a battery. The present invention also relates to a battery cell comprising said treated positive electrode for a battery or the treated positive electrode for a battery that can be obtained by the manufacturing method according to the invention, a battery comprising said battery cell, and a vehicle comprising said battery. Prior Arts

[0002] An electrochemical cell of an electric battery comprises a positive electrode called the "cathode", a negative electrode called the "anode", an electrolyte allowing the circulation of ions between the anode and the cathode, and anodic and cathodic current collectors carrying, respectively, the anode and the cathode and connecting them to the external circuit.

[0003] The positive electrodes generally comprise a positive electrode active material that plays an essential role in an electrochemical cell. Specifically, it enables the insertion and deinsertion of lithium ions during the charging and discharging processes. The positive electrode active material is generally an oxide comprising lithium and at least one transition metal.

[0004] The performance of a battery depends on its ionic and electronic transport properties. Thermodynamic reactions are initiated during the first charging cycle of the electrochemical cell, and the first ion exchanges between the electrodes take place.

[0005] During these exchanges, the transition metals present in an active material for a positive electrode can be dissolved in an electrolyte at high temperatures, thus causing a reduction in the capacity and lifespan of rechargeable batteries.

[0006] Various approaches have been explored to address this problem.

[0007] Among these approaches, we can notably mention studies consisting of intervening on the electrolyte, for example by adding an additive to the electrolyte to improve electrochemical stability.

[0008] Other studies have sought to enhance electrochemical performance by manipulating the positive electrode. For example, the use of a ligand can be cited. multi dentate containing nitrogen atony in a positive electrode, or the formation of a protective layer on the positive electrode.

[0009] However, not all of these solutions are entirely satisfactory.

[0010] There is therefore a need to continue developing research, for example by developing a manufacturing process for a positive electrode that improves the electrochemical performance of a battery. Description of the invention

[0011] The invention therefore relates to a method for manufacturing a treated positive electrode for a battery comprising the following steps:

[0012] a) mix at least one active material for positive electrode, at least one binder with at least one solution comprising at least one lithium salt comprising boron and fluorine;

[0013] b) deposit the mixture obtained at the end of step a) onto a support;

[0014] c) apply to said mixture:

[0015] i) at least one solution comprising at least one compound C comprising at least one nitrogen atom and at least one polymerizable group; or

[0016] ii) a polymer resulting from the polymerization of a compound C comprising at least one nitrogen atom and at least one polymerizable group;

[0017] d) when i) is carried out, polymerize said compound C.

[0018] The manufacturing process for the treated positive electrode for a battery according to the invention makes it possible to obtain a treated positive electrode comprising a layer of a particular material. This layer is a protective layer for the positive electrode, preventing the transition metals of the active material for the positive electrode from dissolving in the electrolyte during battery operation, thereby improving the electrochemical performance of said battery. Thus, the manufacturing process according to the invention makes it possible to improve the lifespan of the batteries.

[0019] The invention also relates to a treated positive electrode for a battery. Another object of the invention is a battery cell comprising at least one treated positive electrode for a battery according to the invention or capable of being obtained by the manufacturing process according to the invention, a battery comprising at least one battery cell according to the invention, as well as a vehicle comprising at least one battery according to the invention.

[0020] Other advantages and features of the invention will become more apparent upon examination of the detailed description.

[0021] It is specified that the expression "from... to..." used in this description of the invention should be understood as including each of the limits mentioned.

[0022] As indicated above, the manufacturing process for the treated battery support according to the invention comprises:

[0023] a) mix at least one active material for positive electrode, at least one binder with at least one solution comprising at least one lithium salt comprising boron and fluorine.

[0024] The battery can be any battery, including a Li-ion battery.

[0025] The active material for the positive electrode can be any active material for the positive electrode suitable for use in a battery.

[0026] Advantageously, the active material for the positive electrode is chosen from a material of formula LiMn2O4, a material of formula LiNiwMn2 wO4, in which 0 < w < 0.5 and a material of formula LiNixCoyMnzO2 in which 0.2 < x < 0.8, 0.1 < y < 0.4, 0.1 < z < 0.4, with x + y + z = 1.

[0027] Among the active materials for positive electrode that can be used in the context of the invention, examples include the material with formula LiNio^Mn^C^, the material with formula LiNi / 3Coi / 3Mni / 3O2, the material with formula LiNio,6Cooj2Mno>2O2, the material with formula LiNio>6Cooj2MnOj2O2, or the material with formula LiNiO,8CoO,i MnO,iO2.

[0028] Advantageously, the binder is chosen from polybutadiene-styrene latex, polyesters, polyethers, carboxymethyl cellulose, polyvinyl acetates or polyacrylate acetates, polyvinylidene fluoride, and mixtures thereof.

[0029] Preferably, the binder is polyvinylidene fluoride.

[0030] The mixture may further comprise at least one conductive compound, which may be selected from carbon black, carbon nanotubes, conductive polymers, such as PEDOT:PSS, etc.

[0031] Advantageously, the lithium salt comprising boron and fluorine is selected from lithium tetrafluoroborate, lithium bis(malonato)borate (BMB), lithium bis(perfluoropinacolato)borate (BPFPB), lithium bis(oxalato)borate (LiBOB), lithium fluoro(oxalato)borate (LiFOB), lithium difluoro(oxalato)borate (LiDFOB) and mixtures thereof.

[0032] In a particularly preferred manner, the lithium salt comprising boron and fluorine is lithium tetrafluoroborate.

[0033] During this step a), the lithium salt comprising boron and fluorine can be dissolved in a solvent, for example an aprotic solvent, such as tetrahydrofuran or diethyl ether. The molar concentration of the lithium salt comprising boron and fluorine in the solution can range from 0.1 mol / L to 5 mol / L, with a preference for a molar concentration of 2 mol / L. Then, the active material for the positive electrode, the binder, and the Conductive compounds can then be added to the solution containing lithium salt, which includes boron and fluorine. The mixture can then be combined.

[0034] As previously stated, the manufacturing process according to the invention comprises:

[0035] b) deposit the mixture obtained at the end of step a) onto a support.

[0036] Advantageously, the support is a current collector, in particular a cathode ray current collector. An example of a cathode ray current collector is an aluminum foil.

[0037] The mixture can be deposited on the substrate by any method known to those skilled in the art. For example, it can be applied by a conventional wet application method to the substrate.

[0038] The mixture can then be dried, in particular under an inert gas atmosphere in order to avoid, or at least minimize, traces of moisture in the air.

[0039] This drying step makes it possible to eliminate the aprotic solvent as mentioned above.

[0040] The manufacturing process according to the invention also includes:

[0041] c) apply to said mixture:

[0042] i) at least one solution comprising at least one compound C comprising at least one nitrogen atom and at least one polymerizable group; or

[0043] ii) a polymer resulting from the polymerization of a compound C comprising at least one nitrogen atom and at least one polymerizable group;

[0044] d) when i) is carried out, polymerize said compound C.

[0045] Thus, compound C can be any compound as long as it includes at least one nitrogen atom and at least one polymerizable group for the purpose of obtaining a polymer.

[0046] Advantageously, compound C is selected from acrylonitrile, vinyl acetonitrile, the compound of formula (I) following:

[0047] in which -R represents a polymerizable group, preferably -R is chosen from -CH=CH2 and -CN,

[0048] and their mixtures;

[0049] preferably the compound of formula (I).

[0050] In a particularly preferred manner, the compound of formula (I) is 4-vinylpyridine.

[0051] Thus, according to the method according to the invention, step i) or step ii) is implemented.

[0052] According to step i), a solution comprising at least one compound C comprising at minus one nitrogen atom and at least one polymerizable group is applied to said mixture, then step d) is carried out d) according to which said compound C is polymerized.

[0053] Said solution may further comprise a solvent, such as tetrahydrofuran, diethyl ether or dichloromethane, and a polymerization initiator, such as AIBN.

[0054] The solution can be applied to said mixture by any method known to a person skilled in the art, for example by chemical vapor deposition (CVD) or by spraying.

[0055] The polymerization of compound C can be any suitable polymerization method within the scope of the present invention. In particular, it can be a radical polymerization or a radical polymerization controlled by reversible addition-fragmentation chain transfer (RAFT). The transfer agents used in these methods can be, for example, thioesters. The degree of polymerization achieved can range from 5 to 50 (the number of monomer units in a polymer). These polymerization methods are well known to those skilled in the art.

[0056] According to step ii), a polymer resulting from the polymerization of a compound C comprising at least one nitrogen atom and at least one polymerizable group is applied to the mixture.

[0057] Thus, a polymer has been previously obtained from said compound C. The polymerization of said compound C can be carried out according to the methods described above. Once the polymer is obtained, it is applied to the mixture.

[0058] Thus, the treated positive electrode for battery is obtained at the end of the manufacturing process according to the invention.

[0059] The treated positive electrode obtained comprises a layer of a material comprising said polymer, and in which a covalent coordination bond is formed between the nitrogen atom, included in compound C, and a boron atom from said lithium salt comprising boron and fluorine.

[0060] Preferably, when compound C has formula (I) and the lithium salt comprising boron and fluorine is lithium tetrafluoroborate, then the polymer comprises at least one monomer motif of the following formula (II):

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069] where -R represents a polymerizable group, preferably -R is chosen from -CH=CH2 and -CN. Preferably, -R represents -CH=CH2. The layer made of this material is a protective layer for the positive electrode, preventing the transition metals of the active material for the positive electrode from dissolving in the electrolyte during battery operation, thus improving the electrochemical performance of said battery. The invention also relates to a treated positive electrode for a battery comprising: - at least a first layer in a mixture comprising at least one active material for positive electrode and at least one binder; - at least a second layer located on at least part of the surface of the first layer, in a material comprising at least one polymer resulting from the polymerization of a compound C comprising at least one nitrogen atom and at least one polymerizable group, and in which a covalent coordination bond is formed between the nitrogen atom and a boron atom from at least one lithium salt comprising boron and fluorine. Preferably, the various embodiments described above for the manufacturing process of the treated positive electrode for battery are also valid for the treated positive electrode for battery, where applicable. Preferably, when compound C has formula (I) and the lithium salt comprising boron and fluorine is lithium tetrafluoroborate, then the polymer comprises at least one monomeric unit of formula (II) as defined above, and in which -R represents a polymerizable group, preferably -R is chosen from -CH=CH2 and -CN. Preferably, -R represents -CH=CH2. Another object of the invention is a battery cell comprising at least one positive electrode treated for battery according to the invention or capable of being obtained by the manufacturing process according to the invention, preferably obtained by the manufacturing process according to the invention. Another object of the present invention is a battery comprising at least one battery cell as defined above.

[0070] The present invention also relates to a vehicle comprising at least one battery as defined above.

[0071] The present invention is illustrated in a non-limiting manner by the following examples. Example

[0072] In this example, lithium tetrafluoroborate is used. It is dissolved in an aprotic solvent, such as tetrahydrofuran or diethyl ether. The molar concentration of lithium tetrafluoroborate in the solution can range from 0.1 mol / L to 5 mol / L, with a preference for a molar concentration of 2 mol / L.

[0073] Then, the material with the formula LiNio.5Mn1.5O4, polyvinylidene fluoride (PVdF), and a conductive compound, for example carbon black or carbon nanotubes, are added to the solution comprising lithium tetrafluoroborate. The mixture is then blended, for example, for one hour at room temperature.

[0074] The mixture is then deposited on a cathode current collector, such as an aluminum foil, by any method known to those skilled in the art, for example by wet application.

[0075] Then, the mixture is dried under an inert gas atmosphere in order to avoid, or at least minimize, traces of moisture in the air.

[0076] This drying step allows the aprotic solvent to be eliminated.

[0077] Then, a solution comprising 4-vinylpyridine, a solvent, such as tetrahydrofuran, diethyl ether or dichloromethane, and a polymerization initiator, such as AIBN, is applied to the mixture.

[0078] The solution can be applied to said mixture by any method known to a person skilled in the art, for example by chemical vapor deposition (CVD) or by spraying.

[0079] The polymerization of compound C can be a radical polymerization or a radical polymerization controlled by reversible addition-fragmentation chain transfer (RAFT). The transfer agents used in these methods can be, for example, thioesters. The degree of polymerization achieved can range from 5 to 50.

[0080] Thus, a treated positive electrode is obtained. It comprises a layer of a material comprising said polymer, and in which a covalent coordination bond is formed between the nitrogen atom of the 4-vinylpyridine and the BF3 group.

[0081] This layer is a protective layer for the positive electrode, thus preventing the transition metals of the active material for the positive electrode from dissolving in the electrolyte during battery operation.

[0082] This makes it possible to improve the electrochemical performance of the battery, and consequently its lifespan.

Claims

Demands

1. A method for manufacturing a treated positive electrode for a battery comprising the following steps: a) mixing at least one active material for a positive electrode, at least one binder with at least one solution comprising at least one lithium salt comprising boron and fluorine; b) depositing the mixture obtained at the end of step a) onto a support; c) applying to said mixture: i) at least one solution comprising at least one compound C comprising at least one nitrogen atom and at least one polymerizable group; or ii) a polymer resulting from the polymerization of a compound C comprising at least one nitrogen atom and at least one polymerizable group; d) when i) is carried out, polymerizing said compound C.

2. A method according to claim 1, characterized in that the active material for the positive electrode is selected from a material of formula LiMn2O4, a material of formula LiNiwMn2 wO4, in which 0 < w < 0.5 and a material of formula LiNixCoyMnzO2 in which 0.2 < x < 0.8, 0.1 < y < 0.4, 0.1 < z < 0.4, with x + y + z = 1.

3. A process according to claim 1 or 2, characterized in that the binder is selected from polybutadiene-styrene latex, polyesters, polyethers, carboxymethyl cellulose, polyvinyl acetates or polyacrylate acetates, polyvinylidene fluoride, and mixtures thereof.

4. A process according to any one of the preceding claims, characterized in that the lithium salt comprising boron and fluorine is selected from lithium tetrafluoroborate, lithium bis(malonato)borate, lithium bis(perfluoropinacolato)borate, lithium bis(oxalato)borate, lithium fluoro(oxalato)borate, lithium difluoro(oxalato)borate and mixtures thereof.

5. A process according to any one of the preceding claims, characterized in that compound C is selected from acrylonitrile, vinyl acetonitrile, the compound of formula (I) following: in which -R represents a polymerizable group, preferably -R is chosen from -CH=CH2 and -CN, and their mixtures; preferably the compound of formula (I).

6. Treated positive electrode for battery comprising: - at least a first layer of a mixture comprising at least one active material for positive electrode and at least one binder; - at least a second layer located on at least a part of the surface of the first layer, of a material comprising at least one polymer from the polymerization of a compound C comprising at least one nitrogen atom and at least one polymerizable group, and in which a covalent coordination bond is formed between the nitrogen atom and a boron atom from at least one lithium salt comprising boron and fluorine.

7. Battery cell comprising at least one battery-treated positive electrode as defined in the preceding claim or capable of being obtained by the manufacturing process as defined in any one of claims 1 to 5.

8. Battery comprising at least one battery cell as defined in claim 7.

9. Vehicle comprising at least one battery as defined in claim 8.