COMPOSITE ELECTRODE COMPRISING A METAL AND A POLYMER MEMBRANE, MANUFACTURING METHOD AND BATTERY CONTAINING SAME

Abstract

A composite negative electrode based on pure metallic lithium, pure metallic sodium or one of their alloys and a polymer membrane, a method for manufacturing such an electrode, as well as an electrical energy storage system, in particular an electrochemical accumulator such as a secondary (rechargeable) lithium or sodium battery comprising at least one such negative electrode. It is particularly applicable to Lithium-Metal-Polymer or LMP™ batteries.

Claims

1. A negative electrode in the form of a composite material, comprising: (i) at least one metallic layer based on pure lithium, pure sodium or an alloy of lithium or of sodium; (ii) at least one polymer membrane comprising at least one polymer, said polymer membrane having two faces; said polymer membrane is non-porous and is in direct physical contact, by at least one of its two faces, with said metallic layer; said at least one polymer is selected from: (a) electrically non-conducting polymers selected from the group comprising polyolefins; homopolymers and copolymers of ethylene oxide, of methylene oxide, of propylene oxide, of epichlorohydrin or of allylglycidyl ether, and mixtures thereof; halogenated polymers; homopolymers and copolymers of styrene and mixtures thereof; vinyl polymers; anionic polymers; polyacrylates; and one of the mixtures thereof; and (b) electrically conducting polymers selected from the group comprising polyaniline, polypyrroles, polyfluorenes, polypyrenes, polyazulenes, polynaphthalenes, polycarbazoles, polyindoles, polyazepines, polythiophenes, poly(p-phenylene sulfides), polyacetylenes and poly(p-phenylene vinylenes).

2. The electrode according to claim 1, characterized in that the electrically non-conducting polymer or polymers are selected from homopolymers and copolymers of ethylene oxide, copolymers of vinylidene fluoride and hexafluoropropylene (PVdF-co-HFP) and mixtures thereof.

3. The electrode according to claim 1, characterized in that the polymer membrane is an electrically conducting membrane and in that it comprises: either one or more electrically non-conducting polymers and at least one electron conduction additive; or at least one electrically conducting polymer optionally in the presence of at least one electron conduction additive.

4. The electrode according to claim 1, characterized in that the polymer membrane additionally contains at least one salt comprising at least one anion and at least one metal cation M.

5. The electrode according to claim 4, characterized in that said salts are selected from MBF.sub.4, MPF.sub.6, CF.sub.3SO.sub.3M, a bis(trifluoromethylsulfonyl)imide of a metal cation M, a bis(fluorosulfonyl)imide of a metal cation M, a bis(pentafluoroethylsulfonyl)imide of a metal cation M, MAsF.sub.6, MCF.sub.3SO.sub.3, MSbF.sub.6, MSbCl.sub.6, M.sub.2TiCl.sub.6, M.sub.2SeCl.sub.6, M.sub.2B.sub.10Cl.sub.10, M.sub.2B.sub.12Cl.sub.12, MNO.sub.3, McIO.sub.4, a trifluoroimidazole of a metal cation M, a tetrafluoroborate of a metal cation M, a bis(oxalato)borate of a metal cation M, M.sub.3PO.sub.4, M.sub.2CO.sub.3, and Na.sub.2SO.sub.4, M being selected from lithium, beryllium, sodium, magnesium, aluminium, potassium, calcium, silver, rubidium, strontium, caesium, barium, radium and francium cations.

6. The electrode according to claim 1, characterized in that the polymer membrane has a thickness from 2 to 50 μm, and in that the metallic layer has a thickness from 1 to 50 μm.

7. The electrode according to claim 1, characterized in that it further comprises at least one second metallic layer, said second metallic layer being in direct physical contact with the other face of said non-porous polymer membrane.

8. The electrode according to claim 7, characterized in that the first metallic layer is identical to the second metallic layer.

9. The electrode according to claim 1, characterized in that the non-porous polymer membrane is electrically conducting and in that said electrode further comprises a current collector, said current collector being in direct physical contact with said membrane.

10. A method for preparing a negative electrode as defined in claim 1, comprising at least one step of application of a non-porous polymer membrane based on at least one polymer on at least one metallic layer based on pure lithium, pure sodium or an alloy of lithium or of sodium, said polymer being selected from: (a) the electrically non-conducting polymers selected from the group comprising polyolefins; homopolymers and copolymers of ethylene oxide, of methylene oxide, of propylene oxide, of epichlorohydrin or of allylglycidyl ether, and mixtures thereof; halogenated polymers; homopolymers and copolymers of styrene and mixtures thereof; vinyl polymers; anionic polymers; polyacrylates; and one of the mixtures thereof; and (b) electrically conducting polymers selected from the group comprising polyaniline, polypyrroles, polyfluorenes, polypyrenes, polyazulenes, polynaphthalenes, polycarbazoles, polyindoles, polyazepines, polythiophenes, poly(p-phenylene sulfides), polyacetylenes and poly(p-phenylene vinylenes).

11. The method according to claim 10, for preparing a negative electrode composed of at least three layers, namely, in this order, a first metallic layer, a layer of non-porous polymer membrane comprising two faces, and at least one second metallic layer, said method being characterized in that said electrode is obtained by the complexing of first and second metallic layers respectively on each of the faces of said non-porous polymer membrane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The attached drawings illustrate the invention:

[0060] FIG. 1 shows the change of the relative capacity and of the efficiency of the battery from Example 3 compared to a control battery, as a function of the number of cycles;

[0061] FIG. 2 shows the change of the internal resistance of the battery from Example 3, compared to a control battery, as a function of the number of cycles;

[0062] FIG. 3 shows the change of the relative capacity and of the efficiency of the battery from Example 4, compared to a control battery, as a function of the number of cycles;

[0063] FIG. 4 shows the change of the internal resistance of the battery from Example 4, compared to a control battery, as a function of the number of cycles;

[0064] FIG. 5 shows the change of the relative capacity and of the efficiency of the battery from Example 6, compared to a control battery, as a function of the number of cycles;

[0065] FIG. 6 shows the change of the internal resistance of the battery from Example 6, compared to a control battery, as a function of the number of cycles;

[0066] FIG. 7 is a diagrammatic view of a composite negative electrode according to the invention comprising 5 layers (five-layer composites): lithium/conductive polymer membrane/copper collector/conductive polymer membrane/lithium;

[0067] FIG. 8 shows the change of the relative capacity and of the efficiency of the battery from Example 8, compared to a control battery, as a function of the number of cycles;

[0068] FIG. 9 shows the change of the internal resistance of the battery from Example 8, compared to a control battery, as a function of the number of cycles.

EXAMPLES

Example 1: Preparation of a Lithium Composite Negative Electrode Comprising an Electrically Conducting Polymer Membrane

[0069] 1st Step: Preparation of an Electrically Conducting Polymer Membrane

[0070] A polymer composition was prepared by mixing 90% by weight of polyethylene oxide sold under reference PEO 1 L by the company Sumitomo Seika and 10% by weight of carbon black with the trade name Ketjenblack EC600JD from the company Akzo Nobel using a Plastograph® (Brabender), at a temperature of 100° C., at a speed of 80 revolutions per minute.

[0071] The mixture obtained was then laminated at 110° C. in the form of a membrane having a thickness of 10 μm.

[0072] 2nd Step: Preparation of the Composite Negative Electrode

[0073] Two lithium strips with a thickness of 35 μm were laminated on either side of the polymer membrane obtained above in the preceding step to obtain a lithium/polymer membrane/lithium three-layer composite electrode (three-layer composite). Lamination was carried out under a pressure of 5.Math.10.sup.5 Pa and at a temperature of 80° C.

[0074] The three-layer composite thus obtained was then laminated between two rollers, using two co-rolling films of polyethylene terephthalate (PET), at ambient temperature and under a pressure of 5.Math.10.sup.3 Pa to obtain three-layer negative electrode films having a total thickness of 15-20 μm, which corresponds to approximately 7 μm of lithium on each face of the polymer membrane, the latter having a thickness of approximately 5 μm.

Example 2: Preparation of a Lithium Composite Negative Electrode Comprising an Electrically Conducting Polymer Membrane

[0075] In this example, a composite negative electrode was prepared according to the method described above in Example 1, in all points identical to that of Example 1 above, except that in this example the thickness of the polymer membrane was fixed at 30 μm. A negative electrode was thus obtained, composed of two sheets of lithium with a thickness of approximately 11 μm arranged on either side of the polymer membrane (about 30 μm), which corresponds to a total thickness of the electrode of approximately 52 μm.

Example 3: Manufacture of a Lithium Battery According to the Invention

[0076] The composite negative electrode obtained above in Example 1 was used to manufacture a lithium-metal-polymer (LMP™) battery.

[0077] A polymer electrolyte comprising 40% by weight of a copolymer of poly(vinylidene fluoride) and hexafluoropropylene sold under reference PVDF-HFP 21512 by the company Solvay, 48% by weight of polyethylene oxide (PEO 1 L) sold by the company Sumitomo Seika and 12% by weight of LiTFSI (Solvay) was prepared in a Plastograph® Brabender mixer at 130° C., at a speed of 80 revolutions per minute. The resultant mixture was then laminated at 130° C. between two films of siliconized PET. A polymer electrolyte film having a thickness of approximately 20 μm was obtained at the end of lamination.

[0078] A positive electrode comprising 74% by weight of LiFePO.sub.4 (LFP) sold by the company Sumitomo Osaka Cement, 2% by weight of carbon black sold under the trade name Ketjenblack EC600JD by the company Akzo Nobel, 4.8% by weight of LiTFSI (Solvay) and 19.2% by weight of PEO (reference: PEO 1 L Sumitomo Seika) was prepared in a Plastograph® Brabender mixer at 80° C., at a speed of 80 revolutions per minute. The resultant mixture was then laminated at 80° C. on a current collector of coated aluminium (Armor).

[0079] A battery according to the present invention was then assembled by successive laminations of the assembly formed by the composite negative electrode as obtained above in Example 1, the polymer electrolyte film and the positive electrode. Lamination was carried out at a pressure of 5.Math.10.sup.3 Pa and a temperature of 80° C. under air (dew point −40° C.) in small cells of the “pouch cell” type having a volume of approximately 10 cm.sup.3.

[0080] For comparison, a control battery, not according to the invention, was assembled using the same positive electrode, the same polymer electrolyte but using, as negative electrode, a single sheet of lithium with a thickness of 10 μm, fused to a PET supporting film to allow handling thereof. Assembly of the control battery was carried out under the same conditions as for the battery according to the invention.

[0081] These two batteries were then cycled at 80° C. on a Bitrode™ cycling bench with a charge/discharge rate equal to C/10-D/10 for the first cycle and C/4-D/2 for the subsequent cycles in order to evaluate their electrochemical performance.

[0082] The results obtained are given in FIG. 1, where the relative capacity and the efficiency (%) are expressed as a function of the number of cycles for each of the two batteries. In this figure, the grey curves correspond to the change of the relative capacity and of the efficiency of the battery according to the present invention and the black curves correspond to the change of the relative capacity and of the efficiency of the control battery, not according to the present invention. The curves with filled diamonds correspond to the change of the capacity, whereas the curves with empty diamonds correspond to the change of the efficiency.

[0083] The results presented in FIG. 1 demonstrate that the efficiency and the relative capacity of the battery according to the present invention, i.e. comprising the composite negative electrode, are stable for about 120 cycles. The efficiency of the battery according to the invention begins to drop between the 120th cycle and the 150th cycle. In comparison, the control battery not according to the invention, i.e. in which the negative electrode is a single sheet of metallic lithium, has an efficiency and a relative capacity that are only stable for about twenty cycles.

[0084] Moreover, FIG. 2 shows the change of the internal resistance (Ri in ohm.Math.cm.sup.2) as a function of the number of cycles, for the two batteries tested. In this figure, the grey curve corresponds to the change of the internal resistance of the battery according to the invention containing the composite negative electrode, whereas the black curve corresponds to the change of the internal resistance of the control battery, not according to the invention.

[0085] The results presented in FIG. 2 show that the internal resistances of these batteries have different changes. Whereas the battery according to the present invention shows stable internal resistance, the internal resistance of the control battery increases strongly in only 20 cycles. This demonstrates the better properties of the composite electrode according to the present invention with respect to a single sheet of lithium.

Example 4: Manufacture of a Lithium Battery According to the Invention

[0086] The composite negative electrode obtained above in Example 2 was used to manufacture a lithium-metal-polymer (LMP™) battery according to the present invention according to exactly the same method as that described above in Example 3.

[0087] The polymer electrolyte film and the positive electrode were also the same as those prepared above in Example 3.

[0088] The performance of the LMP™ battery according to the present invention thus obtained was compared against that of a control battery not according to the invention, identical to the control battery prepared in Example 3 above.

[0089] The cycling conditions were also identical to those in Example 3.

[0090] The results obtained are given in FIG. 3, where the relative capacity and the efficiency (%) are expressed as a function of the number of cycles for each of the two batteries. In this figure, the grey curves correspond to the change of the relative capacity and of the efficiency of the battery according to the present invention and the black curves correspond to the change of the relative capacity and of the efficiency of the control battery, not according to the present invention. The curves with filled diamonds correspond to the change of the capacity, whereas the curves with empty diamonds correspond to the change of the efficiency.

[0091] FIG. 4 shows the change of the internal resistance (Ri in ohm.Math.cm.sup.2) as a function of the number of cycles, for the two batteries tested. In this figure, the grey curve corresponds to the change of the internal resistance of the battery according to the invention containing the composite negative electrode, whereas the black curve corresponds to the change of the internal resistance of the control battery, not according to the invention.

[0092] FIG. 3 shows that the change of the efficiency and of the capacity are comparable for the two batteries. However, the results presented in FIG. 4 show that the change of the internal resistances is somewhat different. In fact, the internal resistance of the control battery not according to the present invention increases more quickly than that of the battery according to the present invention, i.e. comprising the composite negative electrode. The operation of the battery according to the present invention is therefore better than that of the control battery.

Example 5: Preparation of a Lithium Composite Negative Electrode Comprising an Electrically Non-Conducting Polymer Membrane

[0093] 1st Step: Preparation of an Electrically Non-Conducting Polymer Membrane

[0094] A polymer composition was prepared by mixing 40% by weight of a copolymer of poly(vinylidene fluoride) and hexafluoropropylene sold under reference PVDF-HFP 21512 by the company Solvay, 48% by weight of polyethylene oxide (PEO 1 L) sold by the company Sumitomo Seika and 12% by weight of LiTFSI (Solvay) using a Plastograph® (Brabender), at a temperature of 130° C., at a speed of 80 revolutions per minute. The resultant mixture was then laminated at 130° C. until a membrane was obtained having a thickness of 14 μm.

[0095] 2nd Step: Preparation of the Composite Negative Electrode

[0096] Two lithium strips with a thickness of 35 μm were laminated on either side of the polymer membrane obtained above in the preceding step to obtain a lithium/polymer membrane/lithium three-layer composite electrode (three-layer composite). Lamination was carried out under a pressure of 5.Math.10.sup.5 Pa and at a temperature of 80° C.

[0097] The three-layer composite thus obtained was then laminated between two rollers, using two co-rolling films of polyethylene terephthalate (PET), at ambient temperature, at a pressure of 5.Math.10.sup.3 Pa to obtain three-layer negative electrode films having a total thickness of 15-20 μm, which corresponds to approximately 7 μm of lithium on each face of the polymer membrane, the latter having a thickness of approximately 2 μm.

Example 6: Manufacture of a Lithium Battery According to the Invention

[0098] The composite negative electrode obtained above in Example 5 was used to manufacture a lithium-metal-polymer (LMP™) battery.

[0099] A polymer electrolyte comprising 40% by weight of a copolymer of poly(vinylidene fluoride) and hexafluoropropylene sold under reference PVDF-HFP 21512 by the company Solvay, 48% by weight of polyethylene oxide (PEO 1 L) sold by the company Sumitomo Seika and 12% by weight of LiTFSI (Solvay) was prepared in a Plastograph® Brabender mixer at 130° C., at a speed of 80 revolutions per minute. The resultant mixture was then laminated at 130° C. between two films of siliconized PET. A polymer electrolyte film having a thickness of approximately 20 μm was obtained at the end of lamination.

[0100] A positive electrode comprising 74% by weight of LiFePO.sub.4 (LFP) sold by the company Sumitomo Osaka Cement, 2% by weight of carbon black sold under the trade name Ketjenblack EC600JD by the company Akzo Nobel, 4.8% by weight of LiTFSI (Solvay) and 19.2% by weight of PEO (reference PEO 1 L; Sumitomo Seika) was prepared in a Plastograph® Brabender mixer at 80° C., at a speed of 80 revolutions per minute. The resultant mixture was then laminated at 80° C. on a current collector of coated aluminium (Armor).

[0101] A battery according to the present invention was then assembled by successive laminations of the assembly formed by the composite negative electrode as obtained above in Example 5, the polymer electrolyte film and the positive electrode. Lamination was carried out at a pressure of 5.Math.10.sup.3 Pa and at a temperature of 80° C. under air (dew point −40° C.) in pouch cells.

[0102] By way of comparison, a control battery, not according to the invention, was assembled using the same positive electrode, the same polymer electrolyte but using, as negative electrode, a single sheet of lithium with a thickness of 10 μm, fused to a PET supporting film to allow handling thereof. Assembly of the control battery was carried out under the same conditions as for the battery according to the invention.

[0103] These two batteries were then cycled at 80° C. on a Bitrode™ cycling bench with a charge/discharge rate equal to C/10-D/10 for the first cycle and C/4-D/2 for the subsequent cycles in order to evaluate their electrochemical performance.

[0104] The results obtained are given in FIG. 5, where the relative capacity and the efficiency (%) are expressed as a function of the number of cycles for each of the two batteries. In this figure, the grey curves correspond to the change of the relative capacity and of the efficiency of the battery according to the present invention and the black curves correspond to the change of the relative capacity and of the efficiency of the control battery, not according to the present invention. The curves with filled diamonds correspond to the change of the capacity, whereas the curves with empty diamonds correspond to the change of the efficiency.

[0105] The results presented in FIG. 5 show that the efficiency and the capacity of the two batteries are stable and have comparable changes.

[0106] Moreover, FIG. 6 shows the change of the internal resistance (Ri in ohm.Math.cm.sup.2) as a function of the number of cycles, for the two batteries tested. In this figure, the grey curve corresponds to the change of the internal resistance of the battery according to the invention containing the composite negative electrode, whereas the black curve corresponds to the change of the internal resistance of the control battery, not according to the invention.

[0107] The results presented in FIG. 6 show that the internal resistances of these batteries have different changes: the internal resistance of the battery not according to the invention shows a quicker increase than the battery according to the invention comprising the composite negative electrode. This demonstrates the better properties of the composite electrode according to the present invention with respect to a single sheet of lithium.

Example 7: Manufacture of a Lithium Composite Negative Electrode Comprising a Current Collector

[0108] 1st Step: Preparation of an Electrically Conducting Polymer Membrane

[0109] A polymer composition was prepared by mixing 90% by weight of polyethylene oxide sold under reference PEO 1 L by the company Sumitomo Seika and 10% by weight of carbon black with the trade name Ketjenblack EC600JD by the company Akzo Nobel using a Plastograph® (Brabender), at a temperature of 100° C., at a speed of 80 revolutions per minute.

[0110] The mixture obtained was then laminated at 110° C. in the form of a membrane having a thickness of 10 μm.

[0111] 2nd Step: Preparation of the Composite Negative Electrode

[0112] A lithium strip with a thickness of 35 μm was laminated on one of the faces of the polymer membrane obtained above in the preceding step to obtain a two-layer lithium/polymer membrane composite electrode (two-layer composite). Lamination was carried out under a pressure of 5.Math.10.sup.5 Pa and at a temperature of 80° C.

[0113] The two-layer composite thus obtained was then laminated between two rollers, using two co-rolling films of polyethylene terephthalate (PET), at ambient temperature and under a pressure of 5.Math.10.sup.3 Pa to obtain a two-layer composite negative electrode film having a total thickness of 10 μm, which corresponds to approximately 7 μm of lithium on a membrane of 3 μm.

[0114] The two-layer composite thus obtained after this lamination was then applied on each of the two faces of a copper current collector having a thickness of 10 μm, by lamination at 80° C. under a pressure of 5.Math.10.sup.3 Pa, so as to obtain a composite negative electrode with 5 layers (five-layer composites): lithium/conductive polymer membrane/copper collector/conductive polymer membrane/lithium having a total thickness of approximately 30 μm.

Example 8: Manufacture of a Battery According to the Invention Comprising a Lithium Composite Negative Electrode Comprising a Current Collector

[0115] The composite negative electrode obtained above in Example 6 was used for making a lithium-metal-polymer (LMP™) battery.

[0116] A polymer electrolyte comprising 40% by weight of a copolymer of poly(vinylidene fluoride) and hexafluoropropylene sold under reference PVDF-HFP 21512 by the company Solvay, 48% by weight of polyethylene oxide (PEO 1 L) sold by the company Sumitomo Seika and 12% by weight of LiTFSI (Solvay) was prepared in a Plastograph® Brabender mixer at 130° C., at a speed of 80 revolutions per minute. The resultant mixture was then laminated at 130° C. between two films of siliconized PET. A polymer electrolyte film having a thickness of approximately 20 μm was obtained at the end of lamination.

[0117] A positive electrode comprising 74% by weight of LiFePO.sub.4 (LFP) sold by the company Sumitomo Osaka Cement, 2% by weight of carbon black sold under the trade name Ketjenblack EC600JD by the company Akzo Nobel, 4.8% by weight of LiTFSI (Solvay) and 19.2% by weight of PEO (reference: PEO 1 L Sumitomo) was prepared in a Plastograph® Brabender mixer at 80° C., at a speed of 80 revolutions per minute. The resultant mixture was then laminated at 80° C. on a current collector of coated aluminium (Armor).

[0118] A battery according to the present invention was then assembled by successive lamination of an assembly comprising at the centre the negative electrode as prepared above in Example 6, surrounded on either side by two electrolytes and two positive electrodes as illustrated in the attached FIG. 7.

[0119] In this figure, the battery 1 comprises a composite negative electrode 2 comprising a copper current collector 21 comprising on each of its two faces a conductive polymer membrane 22, each of these two conductive polymer membranes 22 being in direct physical contact with a lithium sheet 23. Each lithium sheet 23 is in contact with a polymer electrolyte film 3 on the face opposite to the face that is in contact with the conductive polymer membrane 22, said polymer electrolyte films 3 themselves each being in contact with a positive electrode 4 comprising a layer of positive electrode material 41 in contact with a face of each polymer electrolyte 3, and an aluminium current collector 42.

[0120] Lamination was carried out at a pressure of 5.Math.10.sup.3 Pa and a temperature of 80° C. under air (dew point −40° C.) in pouch cells.

[0121] For comparison, a control battery, not according to the invention, was assembled using a single sheet of lithium with a thickness of 30 μm in place of the composite negative electrode 2, the other constituent elements of the control battery (electrolytes and positive electrodes) being identical, moreover, to those of the battery according to the invention. Assembly of the control battery was carried out under the same conditions as for the battery according to the invention.

[0122] These two batteries were then cycled at 80° C. on a Bitrode™ cycling bench with a charge/discharge rate equal to C/10-D/10 for the first cycle and C/4-D/2 for the subsequent cycles in order to evaluate their electrochemical performance.

[0123] The results obtained are given in FIG. 8, where the relative capacity and the efficiency (%) are expressed as a function of the number of cycles for each of the two batteries. In this figure, the grey curves correspond to the change of the relative capacity and of the efficiency of the battery according to the present invention and the black curves correspond to the change of the relative capacity and of the efficiency of the control battery, not according to the present invention. The curves with filled diamonds correspond to the change of the capacity, whereas the curves with empty diamonds correspond to the change of the efficiency.

[0124] The results presented in FIG. 8 show that the change of the capacity and of the efficiency of the battery according to the present invention, i.e. comprising a 5-layer composite negative electrode 2, is more stable than that of the control battery not according to the invention comprising a single sheet of lithium by way of negative electrode.

[0125] Moreover, FIG. 9 shows the change of the internal resistance (Ri in ohm.Math.cm.sup.2) as a function of the number of cycles, for the two batteries tested. In this figure, the grey curve corresponds to the change of the internal resistance of the battery according to the invention containing the composite negative electrode, whereas the black curve corresponds to the change of the internal resistance of the control battery, not according to the invention.

[0126] The results presented in FIG. 9 show that even if the internal resistance of the battery according to the invention is higher initially than that of the control battery not according to the invention, the internal resistance of the battery according to the invention does not vary during the cycles of charging and discharging, whereas that of the control battery increases, thus reflecting degradation of the electrochemical performance of the battery. Thus, the use of a composite negative electrode according to the present invention leads to better cycling stability of the battery comprising same.