Positive electrode material and preparation method thereof, positive plate, secondary battery and electric device

Abstract

The invention discloses a positive electrode material and a preparation method thereof, a positive plate, a secondary battery and a power utilization device, and relates to the technical field of batteries, the positive electrode material comprises a positive electrode active material and a first coating layer at least partially coating the surface of the positive electrode active material, and the first coating layer comprises titanium carbide and lithium borate; the positive electrode active material comprises at least one of ternary lithium positive electrode active materials. Lithium borate is a fast ion conductor, the first discharge capacity is increased, the impedance is reduced, titanium carbide has the advantages of oxidation resistance, good conductivity and the like, lithium ion reduction and electrolyte corrosion can be inhibited when the surface of the ternary lithium positive electrode active material is coated with the titanium carbide, the electrolyte is prevented from being oxidized to generate hydrofluoric acid and H3PO4, and corrosion of the positive electrode active material is reduced.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a positive electrode material and its preparation method, a positive electrode sheet, a secondary battery, and an electrical device. Background Technology

[0002] Lithium nickel cobalt manganese oxide ternary cathode materials possess advantages such as high energy density, long cycle life, and low environmental pollution, and their fabrication process is relatively simple, leading to their wide application in mobile electronic devices, high-power electric vehicles, and electric trucks. However, with the rapid development of modern society, people have increasingly higher requirements for battery performance, making research on lithium-ion batteries extremely important, especially focusing on the cycle and power performance of materials. However, the impedance problem of cathode materials cannot be well solved; excessive impedance will affect the cycle rate and power performance of the material. Summary of the Invention

[0003] This application provides a positive electrode material and its preparation method, a positive electrode sheet, a secondary battery, and an electrical device to reduce impedance and improve cycle performance.

[0004] In a first aspect, this application provides a positive electrode material, comprising a positive electrode active material and a first coating layer at least partially coated on the surface of the positive electrode active material, wherein: The materials of the first coating layer include titanium carbide and lithium borate; The positive electrode active material includes at least one of ternary lithium positive electrode active materials.

[0005] This application utilizes the advantages of lithium borate, a fast ion conductor, which increases initial discharge capacity and reduces impedance, and titanium carbide, which possesses advantages such as oxidation resistance and good conductivity. Coating the surface of the ternary lithium cathode active material with titanium carbide can inhibit lithium-ion reduction and electrolyte corrosion, suppress electrolyte oxidation to form hydrofluoric acid and H3PO4, and reduce corrosion of the cathode active material. Some titanium is doped into the crystal lattice, replacing Ni / Co / Mn or Ni / Co / Al elements in the ternary lithium cathode active material. Titanium doping can balance Ni... 2+ The resulting inversion defects suppress Ni 2+ Migrating to the lithium layer reduces lithium-nickel mixing; the Ti-O bond energy is 662 kJ / mol, while the Ni-O bond energy is 382 kJ / mol. The Ti-O bond energy is significantly greater than the Ni-O bond energy. Titanium doping not only improves the structural stability of the material but also lowers the lithium intercalation voltage, promoting more lithium intercalation / deintercalation under a fixed overpotential, thus improving discharge capacity and capacity retention. Using lithium borate as a coating agent enhances the initial discharge capacity of the cathode material, while lithium borate also acts as a dispersant for titanium carbide. The combined use of both not only improves the coating effect but also enhances the cycle performance and rate performance of the cathode material.

[0006] In some embodiments, the mass ratio of the material of the first coating layer to the positive electrode active material is (0.3~3.5):100. This mass ratio, within this range, can improve the cycle performance and rate performance of the ternary lithium positive electrode active material while reducing its impact on the specific capacity, lowering impedance, and minimizing the impact on lithium-ion transport while also reducing the impact on the proportion of active material; and / or, The mass ratio of titanium carbide to lithium borate is (0.05~7.5):1. Within this range, the mass ratio of titanium carbide to lithium borate can have a synergistic effect. Too little lithium borate will not disperse the titanium carbide, while too much lithium borate will result in a thick coating layer, affecting lithium-ion transport. Too little titanium carbide will have an insignificant effect, while too much titanium carbide will reduce the proportion of active material and affect the specific capacity.

[0007] In some embodiments, the positive electrode material further includes a second coating layer that at least partially covers the surface of the first coating layer, wherein: The materials of the second coating layer include titanium oxide and lithium borate.

[0008] Titanium oxide can react with alkali to form lithium titanate compounds during battery use, which enhances the structural stability of the cathode material, improves the material's conductivity, and reduces impedance.

[0009] In some embodiments, the thickness ratio of the first coating layer to the second coating layer is (4~9):1. This thickness ratio allows for maximizing the ionic conductivity of the material without compromising its electronic conductivity.

[0010] Secondly, this application provides a method for preparing a cathode material, comprising the following steps: The positive electrode active material is mixed with titanium carbide and a borate-containing compound to obtain a first mixture; The first mixture is sintered to obtain the positive electrode material; The positive electrode material includes a positive electrode active material and a first coating layer that at least partially covers the surface of the positive electrode active material; The materials of the first coating layer include titanium carbide and lithium borate; The positive electrode active material includes at least one of ternary lithium positive electrode active materials.

[0011] At high temperatures, borate compounds are molten and can coat the surface of positive electrode active materials. After reacting with alkali, these compounds generate lithium borate and other related compounds. Titanium carbide is soluble in borate compounds, allowing it to disperse within them and then coat the substrate surface as particles, driven by the borate compounds. Lithium borate is a fast ion conductor, increasing initial discharge capacity and reducing impedance. Titanium carbide possesses advantages such as oxidation resistance and good conductivity. Coating the surface of ternary lithium positive electrode active materials can inhibit lithium ion reduction and electrolyte corrosion, suppress electrolyte oxidation to form hydrofluoric acid and H3PO4, and reduce corrosion of the positive electrode active material. Some titanium is doped into the crystal lattice, replacing Ni / Co / Mn or Ni / Co / Al elements in the ternary lithium positive electrode active material. Titanium doping can balance Ni... 2+ The resulting inversion defects suppress Ni 2+ Migrating to the lithium layer reduces lithium-nickel mixing; the Ti-O bond energy is 662 kJ / mol, while the Ni-O bond energy is 382 kJ / mol. The Ti-O bond energy is significantly greater than the Ni-O bond energy. Titanium doping not only improves the structural stability of the material but also lowers the lithium intercalation voltage, promoting more lithium intercalation / deintercalation under a fixed overpotential, thus improving discharge capacity and capacity retention. Using lithium borate as a coating agent enhances the initial discharge capacity of the cathode material, while lithium borate also acts as a dispersant for titanium carbide. The combined use of both not only improves the coating effect but also enhances the cycle performance and rate performance of the cathode material.

[0012] In some embodiments, the borate-containing compound includes at least one of boric acid, metaboric acid, lithium borate, and lithium metaborate. At least one of the aforementioned borate-containing compounds can be coated onto the surface of the positive electrode active material. After reacting with an alkali, the borate-containing compound generates a series of compounds such as lithium borate. Titanium carbide is soluble in the borate-containing compound, allowing it to disperse within the compound and, driven by the borate-containing compound, coat the substrate surface as coated particles; and / or, The positive electrode active material includes at least one of ternary lithium positive electrode active materials, wherein the chemical formula of the ternary lithium positive electrode active material may be LiNixCoyMn(1-xy)O2, wherein 0.1≤x≤1, 0.1≤y≤1, 0≤z<0.1, x+y+z≤1, and M is one or more doping elements selected from Zr, Sr, Al, V, Ta, Mo, Nb, B, Y, La, and Nb; and / or, The mass ratio of the material of the first coating layer to the positive electrode active material is (0.3~3.5):100. Within this range, the mass ratio of the first coating layer material to the positive electrode active material can have a synergistic effect, reducing the impact on lithium-ion transport, the proportion of active material, and the specific capacity; and / or, The mass ratio of titanium carbide to lithium borate is (0.05~7.5):1. Within this range, the titanium carbide and lithium borate have a synergistic effect. Too little lithium borate will not effectively disperse the titanium carbide, while too much will result in an excessively thick coating, affecting lithium-ion transport. Too little titanium carbide will have an insignificant effect, while too much will reduce the proportion of active material, affecting the specific capacity. And / or, The sintering temperature is 300~900℃. The sintering temperature should not be too high or too low. Excessive temperature will cause boron and titanium to enter the bulk phase, forming bulk doping and reducing the surface coating effect; excessive temperature will result in a loose coating layer that is prone to detachment, leading to poor surface protection. Controlling the sintering temperature within the above range helps to form a coating layer of suitable thickness and density on the core surface of the ternary cathode material; and / or, The sintering time is 5-15 hours. The sintering time should not be too long or too short. Too long a time will cause boron and titanium elements to enter the bulk phase, forming bulk doping and reducing the surface coating effect; too short a time will result in a loose coating layer that is easy to detach, leading to poor surface protection. Controlling the time within the above range helps to form a coating layer of suitable thickness and density on the core surface of the ternary cathode material.

[0013] In some embodiments, sintering the first mixture to obtain the cathode material includes: The first mixture was sintered in an oxygen-containing atmosphere to obtain the cathode material; The positive electrode material further includes a second coating layer that at least partially covers the surface of the first coating layer; The materials of the second coating layer include titanium oxide and lithium borate.

[0014] Titanium carbide sintering in an atmosphere with an oxygen concentration of 0.1-1% can undergo an oxidation reaction to generate titanium oxide. Titanium oxide can react with alkali to generate lithium titanate compounds, which enhance the structural stability of the material, improve its conductivity, and reduce its impedance.

[0015] Thirdly, this application provides a positive electrode sheet, including a positive current collector and at least a positive active layer disposed on one side of the positive current collector, wherein the positive active layer is prepared from the positive electrode material described in the first aspect, or from the positive electrode material prepared by the method described in the second aspect.

[0016] Fourthly, this application provides a secondary battery, including a negative electrode, a separator, and the positive electrode described in the third aspect.

[0017] Fifthly, this application provides an electrical device including the secondary battery described in the fourth aspect. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0019] Lithium nickel cobalt manganese oxide ternary cathode materials possess advantages such as high energy density, long cycle life, and low environmental pollution, and their fabrication process is relatively simple, leading to their wide application in mobile electronic devices, high-power electric vehicles, and electric trucks. However, with the rapid development of modern society, people have increasingly higher requirements for battery performance, making research on lithium-ion batteries extremely important, especially focusing on the cycle and power performance of materials. However, the impedance problem of cathode materials cannot be well solved; excessive impedance will affect the cycle rate and power performance of the material.

[0020] In view of this, this application provides a positive electrode material and its preparation method, a positive electrode sheet, a secondary battery and an electrical device, so as to reduce impedance and improve cycle performance.

[0021] In a first aspect, this application provides a positive electrode material, comprising a positive electrode active material and a first coating layer at least partially coated on the surface of the positive electrode active material, wherein: The materials of the first coating layer include titanium carbide and lithium borate; The positive electrode active material includes at least one of ternary lithium positive electrode active materials.

[0022] This application utilizes the advantages of lithium borate, a fast ion conductor, which increases initial discharge capacity and reduces impedance, and titanium carbide, which possesses advantages such as oxidation resistance and good conductivity. Coating the surface of the ternary lithium cathode active material with titanium carbide can inhibit lithium-ion reduction and electrolyte corrosion, suppress electrolyte oxidation to form hydrofluoric acid and H3PO4, and reduce corrosion of the cathode active material. Some titanium is doped into the crystal lattice, replacing Ni / Co / Mn or Ni / Co / Al elements in the ternary lithium cathode active material. Titanium doping can balance Ni... 2+ The resulting inversion defects suppress Ni 2+Migrating to the lithium layer reduces lithium-nickel mixing; the Ti-O bond energy is 662 kJ / mol, while the Ni-O bond energy is 382 kJ / mol. The Ti-O bond energy is significantly greater than the Ni-O bond energy. Titanium doping not only improves the structural stability of the material but also lowers the lithium intercalation voltage, promoting more lithium intercalation / deintercalation under a fixed overpotential, thus improving discharge capacity and capacity retention. Using lithium borate as a coating agent enhances the initial discharge capacity of the cathode material, while lithium borate also acts as a dispersant for titanium carbide. The combined use of both not only improves the coating effect but also enhances the cycle performance and rate performance of the cathode material.

[0023] In conjunction with the first aspect, in some embodiments provided in this application, the mass ratio of the material of the first coating layer to the positive electrode active material is (0.3~3.5):100. The mass ratio of the material of the first coating layer to the positive electrode active material is within this range, which can improve the cycle performance and rate performance of the ternary lithium positive electrode active material while reducing the impact on the specific capacity of the ternary lithium positive electrode active material, reduce impedance, and reduce the impact on the proportion of active material while reducing the impact on lithium-ion transport.

[0024] In conjunction with the first aspect, in some embodiments provided in this application, the mass ratio of titanium carbide to lithium borate is (0.05~7.5):1. Within this range, the mass ratio of titanium carbide to lithium borate can have a synergistic effect. Too little lithium borate will not effectively disperse the titanium carbide, while too much will result in an excessively thick coating layer, affecting lithium-ion transport. Too little titanium carbide will have an insignificant effect, while too much will reduce the proportion of active material, affecting specific capacity. Preferably, the mass ratio of titanium carbide to lithium borate is (0.5~0.85):1, which can further enhance ion conduction capability and improve discharge capacity and capacity retention.

[0025] In conjunction with the first aspect, in some embodiments provided in this application, the positive electrode material further includes a second coating layer that at least partially covers the surface of the first coating layer, wherein: The materials of the second coating layer include titanium oxide and lithium borate.

[0026] Titanium oxide can react with alkali to form lithium titanate compounds during battery use, which enhances the structural stability of the cathode material, improves the material's conductivity, and reduces impedance.

[0027] In conjunction with the first aspect, in some embodiments provided in this application, the thickness ratio of the first coating layer to the second coating layer is (4~9):1. Within this range, the thickness ratio of the first coating layer to the second coating layer can maximize the ionic conductivity of the material without affecting its electronic conductivity.

[0028] Secondly, this application provides a method for preparing a cathode material, comprising the following steps: The positive electrode active material is mixed with titanium carbide and a borate-containing compound to obtain a first mixture; The first mixture is sintered to obtain the positive electrode material; The positive electrode material includes a positive electrode active material and a first coating layer that at least partially covers the surface of the positive electrode active material; The materials of the first coating layer include titanium carbide and lithium borate; The positive electrode active material includes at least one of ternary lithium positive electrode active materials.

[0029] At high temperatures, borate compounds are molten and can coat the surface of positive electrode active materials. After reacting with alkali, these compounds generate lithium borate and other related compounds. Titanium carbide is soluble in borate compounds, allowing it to disperse within them and then coat the substrate surface as particles, driven by the borate compounds. Lithium borate is a fast ion conductor, increasing initial discharge capacity and reducing impedance. Titanium carbide possesses advantages such as oxidation resistance and good conductivity. Coating the surface of ternary lithium positive electrode active materials can inhibit lithium ion reduction and electrolyte corrosion, suppress electrolyte oxidation to form hydrofluoric acid and H3PO4, and reduce corrosion of the positive electrode active material. Some titanium is doped into the crystal lattice, replacing Ni / Co / Mn or Ni / Co / Al elements in the ternary lithium positive electrode active material. Titanium doping can balance Ni... 2+ The resulting inversion defects suppress Ni 2+ Migrating to the lithium layer reduces lithium-nickel mixing; the Ti-O bond energy is 662 kJ / mol, while the Ni-O bond energy is 382 kJ / mol. The Ti-O bond energy is significantly greater than the Ni-O bond energy. Titanium doping not only improves the structural stability of the material but also lowers the lithium intercalation voltage, promoting more lithium intercalation / deintercalation under a fixed overpotential, thus improving discharge capacity and capacity retention. Using lithium borate as a coating agent enhances the initial discharge capacity of the cathode material, while lithium borate also acts as a dispersant for titanium carbide. The combined use of both not only improves the coating effect but also enhances the cycle performance and rate performance of the cathode material.

[0030] In conjunction with the second aspect, in some embodiments provided in this application, the borate-containing compound includes at least one of boric acid, metaboric acid, lithium borate, and lithium metaborate. At least one of the aforementioned borate-containing compounds can coat the surface of the positive electrode active material. After reacting with an alkali, the borate-containing compound generates a series of compounds such as lithium borate. Titanium carbide is soluble in the borate-containing compound, allowing it to disperse within the compound and, driven by the borate-containing compound, coat the substrate surface as coated particles.

[0031] In conjunction with the second aspect, in some embodiments provided in this application, the positive electrode active material includes at least one of ternary lithium positive electrode active materials. The chemical formula of the ternary lithium positive electrode active material may be LiNixCoyMn(1-xy)O2, wherein 0.1≤x≤1, 0.1≤y≤1, 0≤z<0.1, x+y+z≤1, and M is one or more doping elements selected from Zr, Sr, Al, V, Ta, Mo, Nb, B, Y, La, and Nb.

[0032] In conjunction with the second aspect, in some embodiments provided in this application, the mass ratio of the material of the first coating layer to the positive electrode active material is (0.3~3.5):100. The mass ratio of the material of the first coating layer to the positive electrode active material within this range can play a synergistic role, reducing the impact on lithium-ion transport, reducing the impact on the proportion of active material, and reducing the impact on specific capacity.

[0033] In conjunction with the second aspect, in some embodiments provided in this application, the mass ratio of titanium carbide to lithium borate is (0.05~7.5):1. Within this range, the mass ratio of titanium carbide to lithium borate can play a synergistic role. Too little lithium borate will not disperse the titanium carbide, too much lithium borate will result in a thick coating layer, affecting lithium ion transport. Too little titanium carbide will have an insignificant effect, while too much titanium carbide will reduce the proportion of active material and affect the specific capacity.

[0034] In conjunction with the second aspect, in some embodiments provided in this application, the sintering temperature is 300~900℃. The sintering temperature should not be too high or too low. If the temperature is too high, boron and titanium elements will enter the bulk phase, forming bulk doping and reducing the surface coating effect. If the temperature is too low, the coating layer will not be tightly bonded and will easily fall off, resulting in poor surface protection. Controlling the sintering temperature within the above range helps to form a coating layer of suitable thickness and density on the core surface of the ternary cathode material.

[0035] In conjunction with the second aspect, in some embodiments provided in this application, the sintering time is 5-15 hours. The sintering time should not be too long or too short. Excessive time will cause boron and titanium elements to enter the bulk phase, forming bulk doping and reducing the surface coating effect; insufficient time will result in a loosely bonded coating layer that is prone to detachment, leading to poor surface protection. Controlling the time within the above range helps to form a coating layer of suitable thickness and density on the core surface of the ternary cathode material.

[0036] In conjunction with the second aspect, in some embodiments provided in this application, the sintering of the first mixture to obtain the positive electrode material includes: The first mixture was sintered in an oxygen-containing atmosphere to obtain the cathode material; The positive electrode material further includes a second coating layer that at least partially covers the surface of the first coating layer; The materials of the second coating layer include titanium oxide and lithium borate.

[0037] Titanium carbide sintering in an atmosphere with an oxygen concentration of 0.1-1% can undergo an oxidation reaction to generate titanium oxide. Titanium oxide can react with alkali to generate lithium titanate compounds, which enhance the structural stability of the material, improve its conductivity, and reduce its impedance.

[0038] Thirdly, this application provides a positive electrode sheet, comprising a positive current collector and at least one positive active layer disposed on one side of the positive current collector. The positive active layer is prepared from the positive electrode material described in the first aspect, or from the positive electrode material prepared by the method described in the second aspect. The positive electrode sheet possesses all the technical solutions of the positive electrode material or the method for preparing the positive electrode material, and therefore also possesses all the beneficial effects of the positive electrode material or the method for preparing the positive electrode material, which will not be elaborated upon here.

[0039] Fourthly, this application provides a secondary battery, including a negative electrode, a separator, and the positive electrode described in the third aspect. The secondary battery possesses all the technical solutions of the positive electrode material or the method for preparing the positive electrode material, and therefore also possesses all the beneficial effects of the positive electrode material or the method for preparing the positive electrode material, which will not be elaborated upon here.

[0040] Fifthly, this application provides an electrical device including the secondary battery described in the fourth aspect. The electrical device includes, but is not limited to, mobile electronic devices, high-power electric vehicles, and electric trucks. The electrical device possesses all the technical solutions of the positive electrode material or the method for preparing the positive electrode material, and therefore also possesses all the beneficial effects of the positive electrode material or the method for preparing the positive electrode material, which will not be elaborated upon here.

[0041] The technical solutions provided in this application will be described in detail below with reference to the embodiments.

[0042] Example 1 Example 1 of this application provides a cathode material and its preparation method.

[0043] Lithium hydroxide and a ternary precursor (Ni0.8Co0.1Mn0.1(OH)2) were added to a high-speed mixer at a molar ratio of 1.04:1 and mixed at 500 rpm for 20 min. The mixture was then sintered at high temperature in a box furnace at 750°C for 12 h under an oxygen atmosphere. After cooling to room temperature, the material was pulverized using a mechanical mill to obtain the ternary lithium cathode material. Boric acid, titanium carbide, and the ternary lithium cathode material were added to a high-speed mixer at a mass ratio of 0.57:0.42:100 for a secondary mixing process at 300 rpm for 15 min. The mixture was then placed in a box furnace and sintered at 300°C for 12 h under a nitrogen atmosphere with an oxygen concentration of 0.8%. After cooling to room temperature, the mixture was sieved to obtain the cathode material coated with lithium borate and titanium carbide.

[0044] Example 2 Example 2 of this application provides a positive electrode material and its preparation method.

[0045] Lithium hydroxide and a ternary precursor (Ni0.8Co0.1Mn0.1(OH)2) were added to a high-speed mixer at a molar ratio of 1.04:1 and mixed at 500 rpm for 20 min. The mixture was then sintered at high temperature in a box furnace at 750°C for 12 h in an oxygen atmosphere. After cooling to room temperature, the material was pulverized using a mechanical mill to obtain the ternary lithium cathode material. Boric acid, titanium carbide, and the ternary lithium cathode material were added to a high-speed mixer at a mass ratio of 0.2:0.1:100 for a secondary mixing process at 300 rpm for 15 min. The mixture was then placed in a box furnace and sintered at 300°C for 12 h in a nitrogen atmosphere with an oxygen concentration of 0.8%. After cooling to room temperature, the mixture was sieved to obtain the cathode material coated with lithium borate and titanium carbide.

[0046] Example 3 Example 3 of this application provides a positive electrode material and its preparation method.

[0047] Lithium hydroxide and a ternary precursor (Ni0.8Co0.1Mn0.1(OH)2) were added to a high-speed mixer at a molar ratio of 1.04:1 and mixed at 500 rpm for 20 min. The mixture was then sintered at high temperature in a box furnace at 750°C for 12 h in an oxygen atmosphere. After cooling to room temperature, the material was pulverized using a mechanical mill to obtain the ternary lithium cathode material. Boric acid, titanium carbide, and the ternary lithium cathode material were added to a high-speed mixer at a mass ratio of 2:1.5:100 for a secondary mixing process at 300 rpm for 15 min. The mixture was then placed in a box furnace and sintered at 300°C for 12 h in a nitrogen atmosphere with an oxygen concentration of 0.8%. After cooling to room temperature, the mixture was sieved to obtain the cathode material coated with lithium borate and titanium carbide.

[0048] Example 4 Example 4 of this application provides a cathode material and its preparation method.

[0049] Lithium hydroxide and a ternary precursor (Ni0.8Co0.1Mn0.1(OH)2) were added to a high-speed mixer at a molar ratio of 1.04:1 and mixed at 500 rpm for 20 min. The mixture was then sintered at high temperature in a box furnace at 750°C for 12 h in an oxygen atmosphere. After cooling to room temperature, the material was pulverized using a mechanical mill to obtain the ternary lithium cathode material. Boric acid, titanium carbide, and the ternary lithium cathode material were added to a high-speed mixer at a mass ratio of 0.2:1.5:100 for a secondary mixing process at 300 rpm for 15 min. The mixture was then placed in a box furnace and sintered at 300°C for 12 h in a nitrogen atmosphere with an oxygen concentration of 0.8%. After cooling to room temperature, the mixture was sieved to obtain the cathode material coated with lithium borate and titanium carbide.

[0050] Example 5 Example 5 of this application provides a positive electrode material and its preparation method.

[0051] Lithium hydroxide and a ternary precursor (Ni0.8Co0.1Mn0.1(OH)2) were added to a high-speed mixer at a molar ratio of 1.04:1 and mixed at 500 rpm for 20 min. The mixture was then sintered at high temperature in a box furnace at 750°C for 12 h in an oxygen atmosphere. After cooling to room temperature, the material was pulverized using a mechanical mill to obtain the ternary lithium cathode material. Boric acid, titanium carbide, and the ternary lithium cathode material were added to a high-speed mixer at a mass ratio of 2:0.1:100 for a secondary mixing process at 300 rpm for 15 min. The mixture was then placed in a box furnace and sintered at 300°C for 12 h in a nitrogen atmosphere with an oxygen concentration of 0.8%. After cooling to room temperature, the mixture was sieved to obtain the cathode material coated with lithium borate and titanium carbide.

[0052] Example 6 Example 6 of this application provides a positive electrode material and its preparation method.

[0053] Lithium hydroxide and a ternary precursor (Ni0.8Co0.1Mn0.1(OH)2) were added to a high-speed mixer at a molar ratio of 1.04:1 and mixed at 500 rpm for 20 min. The mixture was then sintered at high temperature in a box furnace at 750°C for 12 h under an oxygen atmosphere. After cooling to room temperature, the material was pulverized using a mechanical mill to obtain the ternary lithium cathode material. Boric acid, titanium carbide, and the ternary lithium cathode material were added to a high-speed mixer at a mass ratio of 1.9:1.6:100 for a secondary mixing process at 300 rpm for 15 min. The mixture was then placed in a box furnace and sintered at 300°C for 12 h under a nitrogen atmosphere with an oxygen concentration of 0.8%. After cooling to room temperature, the mixture was sieved to obtain the cathode material coated with lithium borate and titanium carbide.

[0054] Example 7 Example 7 of this application provides a positive electrode material and its preparation method.

[0055] Lithium hydroxide and a ternary precursor (Ni0.8Co0.1Mn0.1(OH)2) were added to a high-speed mixer at a molar ratio of 1.03:1 and mixed at 600 rpm for 30 min. The mixture was then sintered at high temperature in a box furnace at 760°C for 10 h in an oxygen atmosphere. After cooling to room temperature, the material was pulverized using a mechanical mill to obtain the ternary lithium cathode material. Metaboric acid, titanium carbide, and the ternary lithium cathode material were added to a high-speed mixer at a mass ratio of 1.8:1.2:100 for a secondary mixing process at 500 rpm for 30 min. The mixture was then placed in a box furnace and sintered at 900°C for 5 h in a nitrogen atmosphere with a 1% oxygen concentration. After cooling to room temperature, the mixture was sieved to obtain the cathode material coated with lithium borate and titanium carbide.

[0056] Example 8 Example 8 of this application provides a cathode material and its preparation method. Lithium hydroxide and a ternary precursor (Ni0.8Co0.1Mn0.1(OH)2) are added to a high-speed mixer at a molar ratio of 1.02:1 and mixed at 800 rpm for 60 min. The mixture is then sintered at high temperature in a box furnace at 760°C for 10 h in an oxygen atmosphere. After cooling to room temperature, the material is pulverized using a mechanical mill to obtain a ternary lithium cathode material. Lithium metaborate, titanium carbide, and the ternary lithium cathode material are added to a high-speed mixer at a mass ratio of 1.6:1:100 for a secondary mixing process at 800 rpm for 30 min. The mixture is then placed in a box furnace and sintered at 350°C for 12 h in a nitrogen atmosphere with an oxygen concentration of 1.5%. After cooling to room temperature, the mixture is sieved to obtain a cathode material coated with lithium borate and titanium carbide.

[0057] Example 9 Example 9 of this application provides a cathode material and its preparation method. Lithium hydroxide and a ternary precursor (Ni0.8Co0.1Mn0.1(OH)2) are added to a high-speed mixer at a molar ratio of 1.02:1 and mixed at 800 rpm for 60 min. The mixture is then sintered at high temperature in a box furnace at 760°C for 10 h in an oxygen atmosphere. After cooling to room temperature, the material is pulverized using a mechanical mill to obtain a ternary lithium cathode material. Lithium borate, titanium carbide, and the ternary lithium cathode material are added to a high-speed mixer at a mass ratio of 1.6:1:100 for a secondary mixing process at 800 rpm for 30 min. The mixture is then placed in a box furnace and sintered at 350°C in a nitrogen atmosphere for 12 h. After cooling to room temperature, the mixture is sieved to obtain a cathode material coated with lithium borate and titanium carbide.

[0058] Comparative Example 1 Comparative Example 1 of this application provides a cathode material and its preparation method.

[0059] Lithium hydroxide and ternary precursor (Ni0.8Co0.1Mn0.1(OH)2) were added to a high-speed mixer at a molar ratio of 1.04:1 and mixed at 500 rpm for 20 min. The mixture was then sintered at high temperature in a box furnace at 750 °C for 12 h in an oxygen atmosphere. After cooling to room temperature, the material was pulverized and sieved using a mechanical mill to obtain the cathode material.

[0060] Comparative Example 2 Comparative Example 2 of this application provides a cathode material and its preparation method.

[0061] Lithium hydroxide and a ternary precursor (Ni0.8Co0.1Mn0.1(OH)2) were added to a high-speed mixer at a molar ratio of 1.04:1 and mixed at 500 rpm for 20 min. The mixture was then sintered at high temperature in a box furnace at 750°C for 12 h in an oxygen atmosphere. After cooling to room temperature, the material was pulverized using a mechanical mill to obtain the ternary lithium cathode material. Titanium carbide and the ternary lithium cathode material were then added to a high-speed mixer at a mass ratio of 0.42:100 for a secondary mixing process at 300 rpm for 15 min. The mixture was then placed in a box furnace and sintered at 300°C for 12 h in a nitrogen atmosphere with an oxygen concentration of 0.8%. After cooling to room temperature, the mixture was sieved to obtain the titanium carbide-coated cathode material.

[0062] Comparative Example 3 Comparative Example 3 of this application provides a cathode material and its preparation method.

[0063] Lithium hydroxide and a ternary precursor (Ni0.8Co0.1Mn0.1(OH)2) were added to a high-speed mixer at a molar ratio of 1.04:1 and mixed at 500 rpm for 20 min. The mixture was then sintered at high temperature in a box furnace at 750°C for 12 h in an oxygen atmosphere. After cooling to room temperature, the material was pulverized using a mechanical mill to obtain the ternary lithium cathode material. Boric acid and the ternary lithium cathode material were then added to the high-speed mixer at a mass ratio of 0.57:100 for a secondary mixing process at 300 rpm for 15 min. The mixture was then placed in a box furnace and sintered at 300°C for 12 h in a nitrogen atmosphere with an oxygen concentration of 0.8%. After cooling to room temperature, the mixture was sieved to obtain the lithium borate-coated cathode material.

[0064] Comparative Example 4 Comparative Example 4 of this application provides a cathode material and its preparation method.

[0065] Lithium hydroxide and a ternary precursor (Ni0.8Co0.1Mn0.1(OH)2) were added to a high-speed mixer at a molar ratio of 1.04:1 and mixed at 500 rpm for 20 min. The mixture was then sintered at high temperature in a box furnace at 750°C for 12 h in an oxygen atmosphere. After cooling to room temperature, the material was pulverized using a mechanical mill to obtain the ternary lithium cathode material. Boric acid, titanium carbide, and the ternary lithium cathode material were then added to the high-speed mixer at a mass ratio of 2:0.1:100 for a secondary mixing process at 300 rpm for 15 min to obtain the cathode material.

[0066] Performance testing The cathode materials of Examples 1 to 9 and the cathode materials of Comparative Examples 1 to 4 were subjected to performance tests.

[0067] BET: Sampling: Take dry sample tubes and numbered rubber stoppers, ensuring that each stopper corresponds to a sample tube. Secure the sample tube with a foam pad and seal the opening with the rubber stopper. Weigh the empty sample tube, rubber stopper, and foam pad using an analytical balance and record the mass as m1. Weigh the sample to be tested (50 mg) and use a paper trough to transfer the sample to the bottom of the sample tube, avoiding contact with the tube wall.

[0068] Vacuuming: Insert the sample tube into the vacuum port and secure it. Set the target temperature to 250℃ and begin vacuuming, which typically lasts about 2 hours. After vacuuming is complete, cool the sample tube to room temperature and backfill with gas to eject the sample tube. Weigh the sample tube with the sample, the rubber stopper, and the foam pad again, and record the mass as m2.

[0069] Specific surface area determination: Install the sample tube onto the instrument, ensuring it is inserted vertically and at the same height as the empty tube. Fill the liquid nitrogen bottle with liquid nitrogen, ensuring the liquid nitrogen level is approximately 5 cm below the bottle opening. Open the software, input the mass of the empty tube (m1) and the mass of the sample tube (m2), save the settings, and start the analysis. After the analysis is complete, save the results and copy the data.

[0070] Powder resistor: Sample pretreatment: remove impurities and dry (hygroscopic powders need to be vacuum dried) to ensure uniform particle size. Sample molding: Weigh a fixed amount of powder, press it into shape (record the pressure and holding time), and measure the diameter and thickness of the pressed tablet with calipers. Test preparation: Select a four-probe tester (low resistance), install electrodes to ensure good contact; calibrate the equipment in a constant temperature and humidity environment. Resistance measurement: Connect the wires according to the equipment requirements, set the test parameters (such as current and range), and take the reading after stabilization. Repeat the measurement 3-5 times at the same location and take the average. Data processing: Calculate the volume resistivity using the formula ρ=R×S / L (where S is the cross-sectional area and L is the thickness).

[0071] Results Recording: Record sample information, molding / testing parameters, resistance and resistivity, and analyze errors (such as uneven pressure, poor contact, etc.).

[0072] Charging capacity (mAh / g): The positive electrode materials of Examples 1 to 9 and Comparative Examples 1 to 4 were used as active materials, PVDF as binder, and SP as conductive agent. The ratio of active material: binder: conductive agent was 90:5:5. The materials were dissolved in NMP solvent to prepare a slurry. The slurry was then uniformly coated onto aluminum foil and vacuum dried at 80°C for 2 hours. Finally, it was cut into circular electrode sheets with a diameter of 11 mm using a punch to serve as working electrodes. In a clean glove box filled with Ar (O2 content less than 0.1 ppm, H2O content less than 0.1 ppm), a lithium metal sheet was used as the counter electrode, a Celgard 2400 porous propylene membrane was used as the separator, and 1 mL of electrolyte was used. -1 A lithium hexafluorophosphide (LiPF6) solution was used as the solvent, with a volume ratio of ethylene carbonate (EC): ethyl carbonate (DMC) of 1:1. A button cell (model CR2032) was prepared according to a certain assembly process. After completion, the cell was allowed to stand for 24 hours to allow the electrolyte and electrode materials to be fully wetted. The first charge specific capacity test was conducted at room temperature (25℃±1) and a voltage of 3.0V-4.25V.

[0073] Discharge capacity (mAh / g): The positive electrode materials of Examples 1 to 9 and Comparative Examples 1 to 4 were used as active materials, PVDF as binder, and SP as conductive agent. The ratio of active material: binder: conductive agent was 90:5:5. The materials were dissolved in NMP solvent to prepare a slurry. The slurry was then uniformly coated onto aluminum foil and vacuum dried at 80°C for 2 hours. Finally, it was cut into circular electrode sheets with a diameter of 11 mm using a punch to serve as working electrodes. In a clean glove box filled with Ar (O2 content less than 0.1 ppm, H2O content less than 0.1 ppm), a lithium metal sheet was used as the counter electrode, a Celgard 2400 porous propylene membrane was used as the separator, and 1 mL of electrolyte was used. -1 A lithium hexafluorophosphide (LiPF6) solution was used as the solvent, with a volume ratio of ethylene carbonate (EC): ethyl carbonate (DMC) of 1:1. A button cell (model CR2032) was prepared according to a certain assembly process. After completion, the cell was allowed to stand for 24 hours to allow the electrolyte and electrode materials to be fully wetted. The first discharge specific capacity test was conducted at room temperature (25℃±1) and a voltage of 3.0V-4.25V.

[0074] First-time efficiency (%): The positive electrode materials of Examples 1 to 9 and Comparative Examples 1 to 4 were used as active materials, PVDF as binder, and SP as conductive agent. The ratio of active material: binder: conductive agent was 90:5:5. The materials were dissolved in NMP solvent to prepare a slurry. The slurry was then uniformly coated onto aluminum foil and vacuum dried at 80°C for 2 hours. Finally, it was cut into circular electrode sheets with a diameter of 11 mm using a punch to serve as working electrodes. In a clean glove box filled with Ar (O2 content less than 0.1 ppm, H2O content less than 0.1 ppm), a lithium metal sheet was used as the counter electrode, a Celgard 2400 porous propylene membrane was used as the separator, and 1 mL of electrolyte was used. -1 A lithium hexafluorophosphide (LiPF6) solution was used as the solvent, with a volume ratio of ethylene carbonate (EC) to ethyl carbonate (DMC) of 1:1. A button cell (model CR2032) was prepared according to a specific assembly process. After completion, the cell was allowed to stand for 24 hours to allow the electrolyte and electrode materials to be fully wetted. The first charge-discharge specific capacity test was conducted at room temperature (25℃±1) and a voltage of 3.0V-4.25V. The first efficiency was calculated as (discharge specific capacity / charge specific capacity) * 100%.

[0075] Cyclic Rct(mΩ): The positive electrode materials of Examples 1 to 9 and Comparative Examples 1 to 4 were used as active materials, PVDF as binder, and SP as conductive agent. The ratio of active material: binder: conductive agent was 90:5:5. The materials were dissolved in NMP solvent to prepare a slurry. The slurry was then uniformly coated onto aluminum foil and vacuum dried at 80°C for 2 hours. Finally, it was cut into circular electrode sheets with a diameter of 11 mm using a punch to serve as working electrodes. In a clean glove box filled with Ar (O2 content less than 0.1 ppm, H2O content less than 0.1 ppm), a lithium metal sheet was used as the counter electrode, a Celgard 2400 porous propylene membrane was used as the separator, and 1 mL of electrolyte was used. -1 A lithium hexafluorophosphide (LiPF6) solution was used as the solvent, with a volume ratio of ethylene carbonate (EC) to ethyl carbonate (DMC) of 1:1. A button cell (model CR2032) was prepared according to a specific assembly process. After completion, the cell was allowed to stand for 24 hours to allow the electrolyte and electrode materials to be fully wetted. At room temperature (25℃±1), the cell was charged at a voltage of 3.0V-4.25V and discharged to 50% SOC. The DCR was calculated after 5C discharge for 5 seconds.

[0076] Cycle retention rate: The positive electrode materials of Examples 1 to 9 and Comparative Examples 1 to 4 were used as active materials, PVDF as binder, and SP as conductive agent. The ratio of active material: binder: conductive agent was 90:5:5. The materials were dissolved in NMP solvent to prepare a slurry. The slurry was then uniformly coated onto aluminum foil and vacuum dried at 80°C for 2 hours. Finally, it was cut into circular electrode sheets with a diameter of 11 mm using a punch to serve as working electrodes. In a clean glove box filled with Ar (O2 content less than 0.1 ppm, H2O content less than 0.1 ppm), a lithium metal sheet was used as the counter electrode, a Celgard 2400 porous propylene membrane was used as the separator, and 1 mL of electrolyte was used. -1 A lithium hexafluorophosphide (LiPF6) solution was used as the solvent, with a volume ratio of ethylene carbonate (EC): ethyl carbonate (DMC) of 1:1. A button cell (model CR2032) was prepared according to a certain assembly process. After completion, the cell was allowed to stand for 24 hours to allow the electrolyte and electrode materials to be fully wetted. At room temperature (25℃±1), the cell was charged and discharged at 1C under a voltage of 3.0V-4.25V.

[0077] The results are shown in Table 1: Table 1 Performance results of Examples 1 to 9 and Comparative Examples 1 to 4

[0078] As shown in Table 1, the BET values ​​of Examples 1 / 3 / 4 / 5 are lower than those of Example 2 because the appropriate amounts of titanium carbide and lithium borate form a coating layer on the particle surface, making the particle surface smoother. The powder resistivity of Examples 1 to 9 is significantly lower than that of Comparative Examples 1 to 4, and the powder resistivity decreases with increasing titanium carbide coating amount, indicating that titanium carbide coating improves the conductivity of the material. Example 9, due to the absence of a second titanium oxide coating layer, exhibits inferior powder resistivity, pre- and post-cycle DCR, and cycle rate performance compared to Examples 1 and 3 to 8.

[0079] Compared to Comparative Examples 1 to 4, Examples 1 / 2 / 3 / 4 / 5, which used titanium carbide and lithium borate coatings, improved the charge / discharge specific capacity of the material. Titanium carbide had little effect on the material's capacity, but because the titanium carbide coating improved the material's conductivity and reduced its impedance, Comparative Example 2 showed a slight improvement in discharge specific capacity and initial efficiency compared to Comparative Example 1. With the increase in titanium carbide coating amount, the charge / discharge specific capacity initially increased and then remained essentially unchanged. This is because the increased coating material thickened the protective layer on the material surface, which negatively impacted lithium-ion transport. However, the increased titanium carbide coating improved the material's conductivity, resulting in minimal change in charge / discharge specific capacity despite the increased coating amount. Although Example 6 also used titanium carbide and borate coatings, the excessive amount of titanium carbide resulted in a less significant increase in specific capacity compared to the other examples.

[0080] Compared to Example 1, Example 7 shows an increase in the coating of titanium carbide and boric acid. Since titanium carbide and boric acid do not provide capacity, the discharge specific capacity is reduced. The coating layer is also thicker, which affects lithium-ion transport. During cycling, the impedance increases and the cycling performance decreases.

[0081] Compared to Example 1, Examples 8 and 9 show increased coating of titanium carbide and boric acid. Since titanium carbide and boric acid do not provide capacity, the discharge specific capacity is reduced. In Example 9, the second sintering was carried out in a nitrogen atmosphere, which did not form a second coating layer. As a result, the specific capacity, impedance, and cycle performance of Example 9 are all lower than those of Example 8.

[0082] Comparative Example 1 has poor conductivity due to the lack of coating, resulting in poor rate performance; due to the absence of a coating layer, the ternary material is prone to side reactions with the electrolyte, and the retention rate is only 87.9% after 100 cycles.

[0083] Comparative Example 2 contains only titanium carbide, which cannot be uniformly coated on the surface of the ternary material. Although the conductivity is improved to some extent, the uneven coating of titanium carbide affects the transport of lithium ions, resulting in poor cycle and rate performance of the material in Comparative Example 2.

[0084] Comparative Example 3 contains only boric acid, so only a layer of lithium borate is coated on the surface of the ternary material, which improves the specific capacity to a certain extent, but there is no synergistic effect of titanium carbide. The improvement in powder resistance and DCR before and after cycling is not significant, resulting in poor cycling and rate performance.

[0085] Comparative Example 4 was only a mixture and was not sintered, so the two substances did not play any role and instead affected lithium-ion transport, resulting in a deterioration of BET, powder resistance, specific capacity, DCR before and after cycling, and cycle rate performance.

[0086] In summary, lithium borate, being a fast ion conductor, increases initial discharge capacity and reduces impedance. Titanium carbide, with its advantages of oxidation resistance and good conductivity, can be coated onto the surface of ternary lithium cathode active materials to inhibit lithium-ion reduction and electrolyte corrosion, suppress electrolyte oxidation to form hydrofluoric acid and H3PO4, and reduce corrosion of the cathode active material. Some titanium is doped into the crystal lattice, replacing Ni / Co / Mn or Ni / Co / Al elements in the ternary lithium cathode active material. Titanium doping can balance Ni... 2+ The resulting inversion defects suppress Ni 2+ Migrating to the lithium layer reduces lithium-nickel mixing; the Ti-O bond energy is 662 kJ / mol, while the Ni-O bond energy is 382 kJ / mol. The Ti-O bond energy is significantly greater than the Ni-O bond energy. Titanium doping not only improves the structural stability of the material but also lowers the lithium intercalation voltage, promoting more lithium intercalation / deintercalation under a fixed overpotential, thus improving discharge capacity and capacity retention. Using lithium borate as a coating agent enhances the initial discharge capacity of the cathode material, while lithium borate also acts as a dispersant for titanium carbide. The combined use of both not only improves the coating effect but also enhances the cycle performance and rate performance of the cathode material.

[0087] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0088] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly specified.

[0089] In the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of this application, "multiple" means two or more.

[0090] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A positive electrode material, characterized in that, It includes a positive electrode active material and a first coating layer that at least partially coats the surface of the positive electrode active material, wherein: The materials of the first coating layer include titanium carbide and lithium borate; The positive electrode active material includes at least one of ternary lithium positive electrode active materials.

2. The cathode material as described in claim 1, characterized in that: The mass ratio of the material of the first coating layer to the positive electrode active material is (0.3~3.5):100; and / or, The mass ratio of titanium carbide to lithium borate is (0.05~7.5):

1.

3. The positive electrode material as described in claim 1, characterized in that, The positive electrode material further includes a second coating layer that at least partially covers the surface of the first coating layer, wherein: The materials of the second coating layer include titanium oxide and lithium borate.

4. The cathode material as described in claim 3, characterized in that: The thickness ratio of the first coating layer to the second coating layer is (4~9):

1.

5. A method for preparing a positive electrode material, characterized in that, Includes the following steps: The positive electrode active material is mixed with titanium carbide and a borate-containing compound to obtain a first mixture; The first mixture is sintered to obtain the positive electrode material; The positive electrode material includes a positive electrode active material and a first coating layer that at least partially covers the surface of the positive electrode active material; The materials of the first coating layer include titanium carbide and lithium borate; The positive electrode active material includes at least one of ternary lithium positive electrode active materials.

6. The method for preparing the cathode material as described in claim 5, characterized in that: The borate-containing compound includes at least one selected from boric acid, metaboric acid, lithium borate, and lithium metaborate; and / or, The positive electrode active material includes at least one of ternary lithium positive electrode active materials; and / or, The mass ratio of the material of the first coating layer to the positive electrode active material is (0.3~3.5):100; and / or, The mass ratio of titanium carbide to lithium borate is (0.05~7.5):1; and / or, The sintering temperature is 300~900℃; and / or, The sintering time is 5 to 15 hours.

7. The method for preparing the cathode material as described in claim 5, characterized in that, The sintering of the first mixture to obtain the positive electrode material includes: The first mixture was sintered in an oxygen-containing atmosphere to obtain the cathode material; The positive electrode material further includes a second coating layer that at least partially covers the surface of the first coating layer; The materials of the second coating layer include titanium oxide and lithium borate.

8. A positive electrode plate, characterized in that, It includes a positive current collector and at least one positive active layer disposed on one side of the positive current collector, wherein the positive active layer is prepared from the positive electrode material as described in claim 1, 2, 3 or 4, or from the positive electrode material prepared by the method described in claim 5, 6 or 7.

9. A secondary battery, characterized in that, It includes a negative electrode, a separator, and a positive electrode as described in claim 8.

10. An electrical device, characterized in that, Includes the secondary battery as described in claim 9.

Images