Method for manufacturing a treated positive electrode for a battery

Abstract

The present invention relates to a method for producing a treated positive electrode for a battery, the method comprising the following steps: a) mixing at least one active material for a positive electrode and 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) on a support; c) applying to the mixture: i) at least one solution comprising at least one compound C comprising at least one nitrogen atom and at least one polymerisable group; or ii) a polymer resulting from the polymerisation of a compound C comprising at least one nitrogen atom and at least one polymerisable group; d) when i) is carried out, polymerising the compound C.

Description

[0001] Method for manufacturing a treated positive electrode for a battery

[0002] technical field

[0003] 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 further relates to a battery cell comprising said treated positive electrode for a battery or the treated positive electrode for a battery obtainable by the manufacturing method according to the invention, a battery comprising said battery cell, and a vehicle comprising said battery.

[0004] Previous techniques

[0005] 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.

[0006] Positive electrodes typically contain a positive electrode active material, which plays a crucial role in an electrochemical cell. This material facilitates the insertion and removal of lithium ions during charging and discharging. The positive electrode active material is usually an oxide containing lithium and at least one transition metal.

[0007] 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.

[0008] During these exchanges, the transition metals present in an active material for the positive electrode can dissolve in an electrolyte at high temperatures, thus causing a reduction in the capacity and lifespan of rechargeable batteries.

[0009] Various approaches have been explored to address this problem.

[0010] Among these approaches, we can notably mention studies involving intervention on the electrolyte, for example by adding an additive to the electrolyte to improve electrochemical stability.

[0011] Other studies have sought to enhance electrochemical performance by modifying the positive electrode. Examples include the use of a multi-dentate ligand containing a nitrogen atom in the positive electrode, or the formation of a protective layer on the positive electrode.

[0012] However, not all of these solutions are entirely satisfactory.

[0013] 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.

[0014] Description of the invention

[0015] The invention therefore 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.

[0016] The manufacturing process for the treated positive electrode for batteries 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.

[0017] 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.

[0018] Other advantages and features of the invention will become clearer upon examination of the detailed description. It is specified that the expression "from... to..." used in this description of the invention shall be understood as including each of the limits mentioned.

[0019] As stated above, the manufacturing process for the treated battery support according to the invention comprises: a) mixing at least one active material for the positive electrode, at least one binder with at least one solution comprising at least one lithium salt comprising boron and fluorine.

[0020] The battery can be any type of battery, including a Li-ion battery.

[0021] The active material for the positive electrode can be any active material for a positive electrode suitable for use in a battery.

[0022] Advantageously, the active material for the positive electrode is chosen from a material with the formula LiMn2Û4, a material with the formula LiNi w Mn2- w O4, in which 0 < w < 0.5 and a material of formula LiNi x Co y Mn z O2 in which 0.2 < x < 0.8, 0.1 < y < 0.4, 0.1 < z < 0.4, with x + y + z = 1.

[0023] Examples of active materials for positive electrodes that can be used in the context of the invention include the material with the formula LiNio.5Mn1.5O4, the material with the formula LiNii / sCoi / sMni / sCL, the material with the formula LiNio.6Coo.2Mno.2O2, the material with the formula LiNio.6Coo.2Mno.2O2, or the material with the formula LiNio.8Coo.1Mno.1O2.

[0024] Advantageously, the binder is chosen from polybutadiene-styrene latex, polyesters, polyethers, carboxymethyl cellulose, polyvinyl acetates or polyacrylate acetates, polyvinylidene fluoride, and mixtures thereof.

[0025] Preferably, the binder is polyvinylidene fluoride.

[0026] The mixture may further include at least one conductive compound, which may be chosen from carbon black, carbon nanotubes, conductive polymers, such as PEDOT:PSS, etc.

[0027] 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.

[0028] Particularly preferred, the lithium salt comprising boron and fluorine is lithium tetrafluoroborate.

[0029] During this step (a), the lithium salt containing 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 containing 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 compound can be added to the solution containing the lithium salt containing boron and fluorine. The mixture can then be combined.

[0030] As previously stated, the manufacturing process according to the invention comprises: b) depositing the mixture obtained at the end of step a) onto a support.

[0031] 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.

[0032] The mixture can be applied to the substrate by any method known to a person skilled in the art. For example, it can be applied using a conventional wet application method.

[0033] The mixture can then be dried, particularly under an inert gas atmosphere to avoid, or at least minimize, traces of moisture in the air.

[0034] This drying step allows the aprotic solvent to be eliminated as mentioned above.

[0035] The manufacturing process according to the invention also includes: 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.

[0036] Thus, compound C can be any compound as long as it includes at least one nitrogen atom and at least one polymerizable group in order to obtain a polymer.

[0037] Advantageously, compound C is chosen from acrylonitrile, vinyl acetonitrile, the compound of formula (I) following:

[0038] (I), in which -R represents a polymerizable group, preferably -R is chosen from

[0039] -CH=CH2 and -CN, and their mixtures; preferably the compound of formula (I).

[0040] Particularly preferred, the compound of formula (I) is 4- vinylpyridine.

[0041] Thus, according to the method according to the invention, step i) or step ii) is implemented.

[0042] According to step i), a solution comprising at least one compound C comprising at least one nitrogen atom and at least one polymerizable group is applied to said mixture, and then step d) is carried out d) according to which said compound C is polymerized.

[0043] The said solution may further comprise a solvent, such as tetrahydrofuran, diethyl ether or dichloromethane, and a polymerization initiator, such as AIBN.

[0044] The solution can be applied to the said mixture by any method known to a person skilled in the art, for example by chemical vapor deposition (CVD) or by spraying.

[0045] The polymerization of compound C can be carried out by 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.

[0046] According to step ii), a polymer obtained from the polymerization of a compound C comprising at least one nitrogen atom and at least one polymerizable group is applied to the mixture.

[0047] Thus, a polymer was 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.

[0048] Thus, the treated positive electrode for the battery is obtained at the end of the manufacturing process according to the invention.

[0049] The resulting treated positive electrode comprises a layer of a material comprising said polymer, 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. 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 the following formula (II):

[0050] (Il), where -R represents a polymerizable group, preferably -R is chosen from -CH=CH2 and -CN. Preferably, -R represents -CH=CH2.

[0051] 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.

[0052] The invention also relates to a treated positive electrode for a battery comprising:

[0053] - at least a first layer in a mixture comprising at least one active material for positive electrode and at least one binder;

[0054] - 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.

[0055] 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.

[0056] 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 motif 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 -COCH2.

[0057] 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.

[0058] Another object of the present invention is a battery comprising at least one battery cell as defined above.

[0059] The present invention also relates to a vehicle comprising at least one battery as defined above.

[0060] The present invention is illustrated in a non-limiting manner by the following examples.

[0061] Example

[0062] In this example, lithium tetrafluoroboroate is used. It is dissolved in an aprotic solvent, such as tetrahydrofuran or diethyl ether. The molar concentration of lithium tetrafluoroboroate 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.

[0063] Then, the material with the formula LiNio.sM ^CU, polyvinylidene fluoride (PVdF), and a conductive compound, for example carbon black or carbon nanotubes, are added to the solution containing lithium tetrafluoroboroate. The mixture is then blended, for example, for one hour at room temperature.

[0064] The mixture is then deposited on a cathode current collector, such as an aluminum foil, by any method known to a person skilled in the art, for example by wet application.

[0065] Then, the mixture is dried under an inert gas atmosphere to avoid, or at least minimize, traces of moisture in the air.

[0066] This drying step allows the aprotic solvent to be eliminated.

[0067] 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.

[0068] The solution can be applied to the said mixture by any method known to a person skilled in the art, for example by chemical vapor deposition (CVD) or by spraying.

[0069] The polymerization of compound C can be either radical polymerization or 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. A treated positive electrode is thus obtained. It comprises a layer of a material containing the polymer, in which a covalent coordination bond is formed between the nitrogen atom of 4-vinylpyridine and the BF3 group.

[0070] 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 into the electrolyte during battery operation.

[0071] This allows for improved electrochemical performance of the battery, and consequently its lifespan.

Claims

DEMANDS 1. A process 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 obtained 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 LiMn2U4, a material of formula LiNi w Mn2- wO4, in which 0 < w < 0.5 and a material of formula LiNixCoyMnzCh 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 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.

7. Battery cell comprising at least one battery-treated positive electrode as defined in the preceding claim or obtainable 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.

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