Positive electrode material, positive plate comprising positive electrode material, electrochemical device and electronic equipment

Abstract

The invention discloses a positive electrode material, a positive plate comprising the positive electrode material, an electrochemical device and electronic equipment, and relates to the technical field of electrochemical energy storage. According to the present invention, the positive electrode material is formed by mixing the lithium cobalt oxide and the silicate material, such that the capacity of the positive electrode material can be well improved, the safety performance, the compaction density and the energy density of the positive electrode material are improved, and the overall material cost is reduced. By reducing the particle size and carbon coating of the silicate material, the conductivity and cyclic reversibility of the silicate material are improved; the bulk phase structure of the silicate material is improved through Al element doping, and the cycle reversibility is improved. When the particle size ratio of the lithium cobalt oxide to the silicate material is controlled to be more than or equal to 20 and less than or equal to 6000000 and the A / C is more than or equal to 1 and less than or equal to 100, the conductivity and the cyclic reversibility can meet the requirements. The positive electrode material is good in stability, high in gram volume and high in safety, the cycle life of a battery cell is prolonged, the structural stability and the thermal stability are improved, and the positive electrode material has extremely high application value.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, and in particular to a cathode material and a cathode sheet, electrochemical device and electronic device including the cathode material. Background Technology

[0002] In the field of rechargeable batteries, the choice of cathode material directly affects the battery's performance, cost, and safety. Currently, one of the most widely used cathode materials for rechargeable batteries is lithium cobalt oxide (LiCoO2), whose core advantages lie in its top-tier volumetric energy density (which can be increased to 240 Wh / kg through elemental doping and surface coating) and stable high-voltage platform (4.5V and above), exhibiting excellent electrochemical performance. However, lithium cobalt oxide has certain drawbacks in terms of cycle stability: 1) Insufficient structural stability: a) Layered structure collapse: During deep charge and discharge (especially at high voltages > 4.3V), repeated lithium-ion intercalation and deintercalation lead to lattice oxygen precipitation, causing the structure to transform from layered to spinel phase, accelerating capacity decay; b) Inferior cycle life: Traditional 4.2V products show a significant decrease in capacity retention after 500 cycles, and although the improved 4.5V products optimized by doping / coating achieve 800~1200 cycles, they are still significantly lower than lithium iron phosphate (>4000 cycles) or ternary materials (>1500 cycles). 2) Poor thermal stability and prominent safety risks: a) High temperature oxygen release: Lithium cobalt oxide decomposes its crystal structure at >180℃, releasing oxygen and reacting violently with the electrolyte; b) Thermal runaway chain reaction: Oxygen fuels the combustion of the electrolyte, leading to battery fire / explosion, making its safety far lower than that of lithium iron phosphate (LFP decomposition temperature >500℃).

[0003] Therefore, it is of great significance to solve the problems of insufficient structural stability, poor cycle life, poor thermal stability, and prominent safety risks of lithium cobalt oxide in current cathode materials. Summary of the Invention

[0004] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a cathode material and a cathode sheet, electrochemical device, and electronic device including the cathode material, aiming to solve the problems of insufficient structural stability, poor cycle life, poor thermal stability, and prominent safety risks of current cathode materials such as lithium cobalt oxide.

[0005] A first aspect of this application proposes a cathode material comprising lithium cobalt oxide and a silicate material; wherein the median particle size Dv of the lithium cobalt oxide is... 50 The median particle size Dv of the silicate material is X μm. 50 The mass content of Al in the lithium cobalt oxide is Appm, and the mass content of Al in the silicate material is Cppm; wherein, 20≤CX / Y≤6000000, 1≤A / C≤100.

[0006] The cathode material according to the embodiments of this application has at least the following beneficial effects: This application proposes a cathode material, which is a composite cathode material composed of lithium cobalt oxide and silicate materials. The silicate material added to the lithium cobalt oxide material in this application has a theoretical specific capacity of ~330 mAh / g, and the raw materials are readily available and low in cost. Blending it with conventional lithium cobalt oxide materials can significantly improve the capacity of the composite cathode material. Compared with pure lithium cobalt oxide materials, the composite cathode material formed through blending exhibits improved safety performance, compaction density, and energy density, while simultaneously reducing the overall material cost. Furthermore, to improve the conductivity and cycle reversibility of the silicate material, this application increases the conductivity by reducing the particle size and carbon coating of the silicate material; and improves the bulk structure of the silicate material by doping with Al elements, thereby enhancing cycle reversibility. This application finds that controlling the particle size ratio of lithium cobalt oxide to silicate materials to be 20≤CX / Y≤6000000 and 1≤A / C≤100 is beneficial to the structural stability of the materials. Furthermore, controlling the particle size distribution reduces side reactions between the cathode material and the electrolyte. Simultaneously, 1≤A / C≤100 can balance the Li content of the lithium cobalt oxide and silicate materials. + The insertion / extraction rate ensures that both conductivity and cycle reversibility meet the requirements, and the small particle size of the silicate material reduces Li... + The transmission path is improved, impedance is reduced, and thus conductivity is increased; within this range, Al doping can stabilize the silicate bulk structure, which is more conducive to Li... + Deintercalation and deintercalation of lithium cobalt oxide (Li) + Balancing the insertion / extraction rates improves cycle reversibility. Ultimately, the cathode material provided in this application exhibits good stability, high specific capacity, and high safety, improving the cycle life of the cell while also enhancing structural and thermal stability, making it highly valuable for applications in the secondary battery field.

[0007] In some embodiments, the mass content of Ti in the lithium cobalt oxide is Bppm, wherein 3≤A / B≤100.

[0008] In some embodiments, the positive electrode material includes at least one of the following (a1) to (a5): (a1) The median particle size Dv of the lithium cobalt oxide 50 The range is 2~20μm; (a2) The median particle size Dv of the silicate material 50 The range is 0.01~10μm; (a3) The mass content of Al element in the lithium cobalt oxide is 3000~10000ppm; (a4) The mass content of Al element in the silicate material is 100~3000ppm; (a5) The mass content of Ti element in the lithium cobalt oxide is 100~1000ppm.

[0009] In some embodiments, the silicate material accounts for 0.5% to 5% of the mass of the positive electrode material.

[0010] In some embodiments, the positive electrode material includes at least one of the following (b1) to (b4): (b1) The silicate material includes Li2(M 1-x Al x SiO4, M is selected from at least one of Fe, Mn, Co, Ni, and Ti, and x ranges from 0.001 to 0.05; (b2) When (b1) is included, the silicate material is selected from Li2Fe. 1-x Al x SiO4, Li2Mn 1-x Al x SiO4, Li2Co 1-x Al x SiO4, Li2Ni 1-x Al x SiO4, Li2Ni 1-x Ti x At least one of SiO4; (b3) The surface of the silicate material includes a carbon coating; (b4) When (b3) is included, the mass content of the carbon coating is 30 to 1000 ppm.

[0011] In some embodiments, the Dv of the positive electrode material 10 Particle size ≥ 2.5 μm, Dv 50 The particle size range is 12~18μm, Dv 90 The particle size range is 20~40μm, and (Dv) 90 -Dv 10 ) / Dv 50 ≤4.

[0012] A second aspect of this application also provides a positive electrode sheet, comprising a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, the positive active material layer comprising the aforementioned positive electrode material.

[0013] A third aspect of this application also proposes a battery cell comprising a negative electrode and the aforementioned positive electrode.

[0014] A fourth aspect of this application also proposes an electrochemical device comprising the aforementioned battery cell.

[0015] A fifth aspect of this application also proposes an electronic device comprising the aforementioned electrochemical device. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. The embodiments of this application may omit unnecessary detailed descriptions. For example, detailed descriptions of well-known matters and repeated descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features. As used herein, the terms “approximately,” “generally,” “substantially,” and “about” are used to describe and indicate small variations. When used in conjunction with an event or situation, the terms may refer to examples in which the event or situation occurred precisely and examples in which the event or situation occurred very approximately. For example, when used in conjunction with numerical values, the terms may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. For example, if the difference between two values ​​is less than or equal to ±10% of the average of the values ​​(e.g., less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%), then the two values ​​can be considered "substantially" the same. Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format in this document. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only the numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified. In the detailed description and claims, a list of items connected by the terms "one of," "among," "a kind of," or other similar terms may mean any of the listed items. For example, if items A and B are listed, then the phrase "one of A and B" means only A or only B. In another example, if items A, B, and C are listed, then the phrase "one of A, B, and C" means only A; only B; or only C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements. In the detailed description and claims, the list of items connected by the term "at least one of" can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. In the following description, all figures disclosed in this application are approximate values, regardless of whether the terms "about" or "approximately" are used in conjunction. They may vary by 1%, 2%, 5%, or sometimes 10% to 20%. Whenever a range of values ​​with a lower limit (RL) and an upper limit (RU) is disclosed, any values ​​falling within that range are specifically disclosed. Specifically, the following values ​​within this range are specifically disclosed: R = RL + k * (RU - RL), where k is a variable ranging from 1% to 100% with a 1% increment, i.e., k is 1%, 2%, 3%, 4%, 5%, ..., 50%, 51%, 52%, ..., 95%, 96%, 97%, 98%, 99%, or 100%. Furthermore, any range of values ​​defined by the two R values ​​as defined above are also specifically disclosed. Throughout this specification, references to "implementation," "partial implementation," "one implementation," "another implementation," "specific method," or "partial method" mean that at least one implementation or embodiment in this application includes the specific features, structures, materials, or characteristics described in that implementation or embodiment. In this application, numerical ranges are involved. Unless otherwise specified, the numerical ranges mentioned above are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form a range not explicitly stated. Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the invention, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the invention.

[0017] The term "polymer" refers to a polymeric compound prepared by polymerizing the same or different types of monomers. The general term "polymer" includes the terms "homopolymer," "copolymer," "trimer," and "interpolymer." The term "coating" refers to one or more layers applied to one or both sides of a porous substrate material. Functional coatings comprise a mixture of at least one organic binder and at least one inorganic filler. In addition to the organic binder and inorganic filler, the protective porous layer may also include one or more additives. Functional coatings can be single-layer, double-layer, or multi-layer structures. The term "binder" refers to a substance used to bond inorganic fillers to or to each other in a porous substrate material. Any organic binder that can bond inorganic fillers to or to each other in a porous substrate material may be used herein. Some non-limiting examples of organic binders include polyesters, polyamides, polyacrylic acid, polyethers, polyimides, polyolefins, rubbers, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, cellulose, cellulose derivatives, latexes, and combinations thereof.

[0018] The term "inorganic filler" refers to a non-conductive material. Some non-limiting examples of inorganic fillers include metal oxides, as well as non-oxide materials and non-metallic materials. Some non-limiting examples of metal oxides include alumina, zirconium oxide, barium titanate, lead zirconate titanate, ferrites, zinc oxide, and combinations thereof. Some non-limiting examples of non-oxide materials and non-metallic materials include silicon carbide, silicon nitride, aluminum nitride, boron nitride, titanium boride, molybdenum silicide, and combinations thereof. The term "water-soluble polymer" refers to a high molecular weight polymer that is soluble in water or uniformly dispersed in water. The term "oil-soluble polymer" refers to a high molecular weight polymer that is soluble in water or uniformly dispersed in an organic polar solvent, including but not limited to N-methylpyrrolidone (NMP) and dimethyl sulfoxide (DMSO).

[0019] Positive electrode active material: As used herein and in the claims, the term "positive electrode active material" (also known as cathode active material) is defined as a material that is electrochemically active in a positive electrode or cathode. Active material should be understood as a material capable of capturing and releasing Li and / or Na ions when subjected to voltage changes over a predetermined time period.

[0020] <Cathode Materials> A first aspect of this application proposes a cathode material comprising lithium cobalt oxide and a silicate material; wherein the median particle size Dv of the lithium cobalt oxide is... 50 The median particle size Dv of the silicate material is X μm. 50 The mass content of Al in the lithium cobalt oxide is Appm, and the mass content of Al in the silicate material is Cppm; wherein, 20≤CX / Y≤6000000, 1≤A / C≤100.

[0021] The cathode material according to the embodiments of this application has at least the following beneficial effects: This application proposes a cathode material, which is a composite cathode material composed of lithium cobalt oxide and silicate materials. The silicate material added to the lithium cobalt oxide material in this application has a theoretical specific capacity of ~330 mAh / g, and the raw materials are readily available and low in cost. Blending it with conventional lithium cobalt oxide materials can significantly improve the capacity of the composite cathode material. Compared with pure lithium cobalt oxide materials, the composite cathode material formed through blending exhibits improved safety performance, compaction density, and energy density, while simultaneously reducing the overall material cost. Furthermore, to improve the conductivity and cycle reversibility of the silicate material, this application increases the conductivity by reducing the particle size and carbon coating of the silicate material; and improves the bulk structure of the silicate material by doping with Al elements, thereby enhancing cycle reversibility. This application finds that controlling the particle size ratio of lithium cobalt oxide to silicate materials to be 20≤CX / Y≤6000000 and 1≤A / C≤100 is beneficial to the structural stability of the materials. Furthermore, controlling the particle size distribution reduces side reactions between the cathode material and the electrolyte. Simultaneously, 1≤A / C≤100 can balance the Li content of the lithium cobalt oxide and silicate materials. + The insertion / extraction rate ensures that both conductivity and cycle reversibility meet the requirements, and the small particle size of the silicate material reduces Li... + The transmission path is improved, impedance is reduced, and thus conductivity is increased; within this range, Al doping can stabilize the silicate bulk structure, which is more conducive to Li... + Deintercalation and deintercalation of lithium cobalt oxide (Li) +Balancing the insertion / extraction rates improves cycle reversibility. Ultimately, the cathode material provided in this application exhibits good stability, high specific capacity, and high safety, improving the cycle life of the cell while also enhancing structural and thermal stability, making it highly valuable for applications in the secondary battery field.

[0022] In some embodiments, 20 ≤ CX / Y ≤ 6,000,000. Exemplarily, the value of CX / Y can be 20, 200, 2000, 20000, 200000, 200000, 3000000, 4000000, 5000000, 6000000, or within any two of the above values. Since silicate materials have lower conductivity than lithium cobalt oxide, mixing them reduces the overall conductivity and cycle reversibility of the material. This application improves the conductivity of silicate materials by reducing the particle size and carbon coating, and simultaneously improves the bulk structure of silicate materials through Al doping, thereby enhancing cycle reversibility. When the particle size ratio of lithium cobalt oxide to silicate materials is controlled at 20 ≤ CX / Y ≤ 6,000,000, the conductivity and cycle reversibility of the cathode material meet the requirements, mainly because the small particle size of the silicate cathode material reduces Li... + The transmission path is improved, impedance is reduced, and thus conductivity is increased. Furthermore, within this range, Al doping can stabilize the silicate bulk structure, which is more conducive to Li... + Deintercalation improves cycle reversibility. If the CX / Y value is <20, it will lead to a deterioration in capacity performance; if the CX / Y value is >6,000,000, it will lead to a difference in compaction density. Larger lithium cobalt oxide particles will affect the coating and rolling processes of electrode preparation, and the specific surface area of ​​silicate particles will increase, resulting in a deterioration in cycle performance.

[0023] In some implementations, 1 ≤ A / C ≤ 100. For example, the value of A / C can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or fall within the range of any two of the above values.

[0024] In some embodiments, the mass content of Al in lithium cobalt oxide is Appm, and the mass content of Ti in lithium cobalt oxide is Bppm, wherein 3 ≤ A / B ≤ 100. For example, the value of A / B can be 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or within any range of two of the above values. When 3 ≤ A / B ≤ 100, the cathode material not only exhibits improved electrochemical performance at high voltage but also better high-temperature performance. If the value of A / B is < 3, it will lead to the formation of a large number of polycrystalline particles; if the value of A / B is > 100, it will result in low capacity and uneven element distribution in the cathode material.

[0025] In some embodiments, the median particle size Dv of lithium cobalt oxide 50 The range is 2~20 μm, meaning the value of X ranges from 2 to 20. For example, the median particle size Dv of lithium cobalt oxide... 50 It can be 2μm, 4μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, or within the range of any two of the above values.

[0026] In some embodiments, the median particle size Dv of the silicate material 50 The range is 0.01~10 μm, that is, the value of Y ranges from 0.01 to 10. For example, the median particle size Dv of silicate materials... 50 It can be 0.01μm, 0.1μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, or within the range of any two of the above values.

[0027] In some embodiments, the mass content of Al in lithium cobalt oxide is 3000~10000 ppm, that is, the value of A is in the range of 3000~10000. For example, the mass content of Al in lithium cobalt oxide can be 3000ppm, 4000ppm, 5000ppm, 6000ppm, 7000ppm, 8000ppm, 9000ppm, 10000ppm, or within any two of the above values.

[0028] In some embodiments, the mass content of Al in the silicate material is 100~3000 ppm, that is, the value of C is in the range of 100~3000. For example, the mass content of Al in the silicate material can be 100ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 2000ppm, 3000ppm, or within any two of the above values.

[0029] In some embodiments, the mass content of Ti in lithium cobalt oxide is 100~1000 ppm, that is, the value of B is in the range of 100~1000. For example, the mass content of Ti in lithium cobalt oxide can be 100ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, or within any two of the above values.

[0030] In some embodiments, the mass percentage of silicate material in the cathode material is 0.5% to 5% (wt). Exemplarily, it can be 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, or within any two of the above values. When the amount of silicate added is 0.5wt% to 5wt%, with the increase of the added amount, the strong Si-O bond energy exhibits excellent safety performance, gradually increasing the improvement in the safety performance of lithium cobalt oxide and continuously improving the thermal stability of the lithium-ion secondary battery.

[0031] In some embodiments, the silicate material includes Li2(M) 1-x Al x SiO4, M is selected from at least one of Fe, Mn, Co, Ni, and Ti, and x ranges from 0.001 to 0.05, but is not limited thereto. Commonly used silicate cathode materials in this field can be reasonably applied in this application. Among them, silicate cathode materials are a type of lithium-ion battery cathode materials with silicon-oxygen tetrahedra (SiO4) as the structural unit.

[0032] In some embodiments, the silicate material is selected from Li2Fe. 1-x Al x SiO4, Li2Mn 1-x Al x SiO4, Li2Co 1- x Al x SiO4, Li2Ni 1-x Al x SiO4, Li2Ni 1-x Ti x At least one of SiO4, but not limited to this.

[0033] In some embodiments, the surface of the silicate material includes a carbon coating.

[0034] In some embodiments, the carbon coating content is 30 to 1000 ppm by mass. Exemplarily, the carbon coating content can be 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, or within a range of any two of the above values.

[0035] In some implementations, the Dv of the cathode material 10 Particle size ≥ 2.5 μm, Dv 50The particle size range is 12~18μm, Dv 90 The particle size range is 20~40μm, and (Dv) 90 -Dv 10 ) / Dv 50 ≤4. When this condition is met, the cathode material exhibits good crystallinity and structural stability, which improves the capacity, cycle life, and kinetic performance of the cathode material.

[0036] <Positive Electrode Tablets> A second aspect of this application provides a positive electrode sheet, comprising a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, the positive active material layer comprising the aforementioned positive electrode material.

[0037] The cathode sheet according to the embodiments of this application has at least the following beneficial effects: The cathode material of the cathode active material layer provided by this application is a composite cathode material composed of lithium cobalt oxide and silicate materials. In the above scheme, the silicate material added to the lithium cobalt oxide material has a theoretically high specific capacity (~330 mAh / g), and the raw materials are readily available and low in cost. After being blended with conventional lithium cobalt oxide materials, it can significantly improve the capacity of the composite cathode material. Furthermore, compared with pure lithium cobalt oxide materials, the composite cathode material formed through blending improves safety performance, compaction density, and energy density, while reducing the overall material cost. Simultaneously, to improve the conductivity and cycle reversibility of the silicate material, this application improves the conductivity of the silicate material by reducing the particle size and carbon coating; and improves the bulk structure of the silicate material by doping with Al elements, thereby improving cycle reversibility. This application finds that controlling the particle size ratio of lithium cobalt oxide to silicate materials to be 20≤CX / Y≤6000000 and 1≤A / C≤100 is beneficial to the structural stability of the materials. Furthermore, controlling the particle size distribution reduces side reactions between the cathode material and the electrolyte. Simultaneously, 1≤A / C≤100 can balance the Li content of the lithium cobalt oxide and silicate materials. + The insertion / extraction rate ensures that both conductivity and cycle reversibility meet the requirements, and the small particle size of the silicate material reduces Li... + The transmission path is improved, impedance is reduced, and thus conductivity is increased; within this range, Al doping can stabilize the silicate bulk structure, which is more conducive to Li... + Deintercalation and deintercalation of lithium cobalt oxide (Li) + Balancing the insertion / extraction rates improves cycle reversibility. Ultimately, the cathode material provided in this application exhibits good stability, high specific capacity, and high safety, improving the cycle life of the cell while also enhancing structural and thermal stability, making it highly valuable for applications in the secondary battery field.

[0038] In some embodiments, the mass ratio of silicate material to lithium cobalt oxide in the positive electrode active material layer is (0.5~5):(95~99.5).

[0039] In some embodiments, the positive electrode active material layer further includes a positive electrode binder and a positive electrode conductive agent.

[0040] In some embodiments, the mass percentage of each component, taking the positive electrode material, conductive agent, and binder as a whole, is as follows: positive electrode material 80-98%, conductive agent 1-10%, and binder 1-10%.

[0041] In some embodiments, the positive electrode binder includes at least one of polyvinylidene fluoride (PVDF), poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polyvinyl butyral, polyvinylpyrrolidone (PVP), acrylic acid-acrylonitrile-acrylamide copolymer, and acrylic acid-acrylonitrile-acrylate copolymer. The positive electrode binder of this application is not limited to the above materials, but also includes other materials that can be used as battery positive electrode binders. In some embodiments, the positive electrode conductive agent may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon nanotubes, carbon nanotubes, activated carbon, and mesoporous carbon. The positive electrode conductive agent in this application is not limited to the above materials, but also includes other materials that can be used as positive electrode conductive agents in batteries.

[0042] In some embodiments, the positive current collector is a metal foil or a composite current collector. In some embodiments, the metal foil is an aluminum foil. The composite current collector may include a metal foil substrate and a conductive layer disposed on at least one side of the metal foil substrate.

[0043] In some embodiments, the conductive layer may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fiber, carbon nanofiber, graphitized carbon sheet, carbon tube, carbon nanotube, activated carbon, and mesoporous carbon. In some embodiments, the preparation method of the positive electrode sheet includes the following steps: thoroughly mixing the positive electrode material, conductive agent, binder, and solvent according to a mass ratio, coating the mixture onto the positive electrode current collector, and then drying, cold pressing, and slitting to obtain the positive electrode sheet. The preparation method of the positive electrode sheet can adopt conventional methods in the industry, and this application does not limit it.

[0044] <Battery Cell> A third aspect of this application also proposes a battery cell comprising a negative electrode and the aforementioned positive electrode.

[0045] Since the battery cell adopts all the technical solutions of the positive electrode sheet in the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions in the above embodiments. That is, it effectively suppresses cobalt dissolution from the positive electrode, reduces the cycle decay rate, improves battery cycle stability, improves cell life, and increases specific capacity, thus having extremely broad application prospects.

[0046] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector.

[0047] In some embodiments, the negative current collector is a metal foil or a composite current collector. In some embodiments, the metal foil is a copper foil. The composite current collector may include a metal foil substrate and a conductive layer disposed on at least one side of the metal foil substrate.

[0048] In some embodiments, the conductive layer may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fiber, carbon nanofiber, graphitized carbon sheet, carbon tube, carbon nanotube, activated carbon, and mesoporous carbon.

[0049] In some embodiments, the negative electrode active material layer includes a negative electrode active material, a negative electrode binder, and a negative electrode binder conductive agent.

[0050] In some embodiments, the negative electrode active material may include natural graphite particles, synthetic graphite particles, hard carbon, soft carbon, mesophase carbon microspheres (MCMB), Sn, SnO2, SnO, Li4Ti5O 12 The negative electrode active material is selected from at least one of LTO, Si materials, silicon-carbon (Si-C) composite materials, silicon-nitrogen (Si-N) composite materials, and silicon-oxygen (Si-O) composite materials. The negative electrode active material of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as negative electrode active materials for batteries.

[0051] In some embodiments, the negative electrode binder may include at least one of polyacrylic acid, polymethacrylic acid, polyacrylate, polymethacrylate, polyacrylamide, styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylic acid-acrylonitrile-acrylamide copolymer, acrylic acid-acrylonitrile-acrylate copolymer, acrylonitrile-butadiene rubber, nitrile rubber, acrylonitrile-styrene-butadiene copolymer, acryloyl rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polyepoxychloropropane, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, carboxymethyl chitosan, polyester, polyamide, polyether, polyimide, polycarboxylic acid ester, polycarboxylic acid, polyurethane, alginate, fluorinated polymer, chlorinated polymer, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropylene. The negative electrode binder of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as battery negative electrode binders. In some embodiments, the negative electrode conductive agent may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon nanotubes, carbon nanotubes, activated carbon, and mesoporous carbon. The negative electrode conductive agent of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as battery negative electrode conductive agents.

[0052] In some embodiments, a method for preparing the above-mentioned negative electrode sheet is also provided, including the steps of: thoroughly mixing the negative electrode active material, conductive agent, and binder according to a mass ratio, coating the mixture onto the negative electrode current collector, and then drying, cold pressing, and slitting to obtain the negative electrode sheet. The preparation method of the negative electrode sheet can adopt conventional methods in the industry, and this application does not limit it.

[0053] <Electrochemical Device> A fourth aspect of this application also proposes an electrochemical device comprising the aforementioned battery cell.

[0054] The electrochemical device provided in this application includes any device in which an electrochemical reaction occurs to convert chemical energy into electrical energy and vice versa. Specific, non-limiting examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0055] In some implementations, the electrochemical device includes a lithium-ion battery.

[0056] In some embodiments, the electrochemical device includes a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive and negative electrodes.

[0057] The separator separates the negative and positive electrodes and provides a pathway for lithium-ion migration. The use of the separator is not particularly limited, as long as it is a separator commonly used in lithium-ion secondary batteries. In particular, separators with low resistance to electrolyte ion movement and excellent electrolyte permeability are preferred. Specifically, porous polymer membranes can be used, such as porous polymer membranes formed from polyolefin-based polymers (e.g., ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, ethylene / methacrylate copolymers, etc.) or laminated structures with two or more layers. Alternatively, nonwoven fabrics formed from conventional porous nonwoven fabrics (e.g., glass fibers with high melting points, polyethylene terephthalate fibers, etc.) can be used. Furthermore, coated separators containing ceramic components or polymer materials to ensure heat resistance or mechanical strength can be used, and can optionally be used as single-layer or multi-layer structures. Generally, a diaphragm includes a substrate and a coating applied to the surface of the substrate. In some embodiments, the porous substrate is, but is not limited to, at least one of polyolefins, polyesters, polyacetals, polyamides, polyethylene terephthalate, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, polyacrylonitrile, polyvinylidene fluoride, polyoxymethylene, polyoxymethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, polysulfone, and polymethyl methacrylate. Some non-limiting examples of polyolefins include at least one of polyethylene (PE), ultra-high molecular weight polyethylene (UHMWPE), high-density polyethylene (HDPE), polypropylene (PP), polyethylene-polypropylene copolymer (PE-PP), and polyethylene-polypropylene-polyethylene copolymer. In some embodiments, the coating is disposed on one side of the substrate. In some embodiments, the coating is disposed on both sides of the substrate.

[0058] In some embodiments, the coating includes inorganic fillers and adhesives.

[0059] In some embodiments, the inorganic filler comprises Al2O3, SiO2, TiO2, ZrO2, Mg(OH)2, MgO, SnO2, CaCO3, BaSO4, TiN, AlN, Na2O.mTiO2, K2O.nTiO2, BaO x MTiO3 and combinations thereof, wherein m is 3 or 6, n is 1, 2, 4, 6 or 8, x is 1 or 2, and M is Ba, Sr or Ca. The inorganic filler may be spherical, plate-like, disc-like, needle-like, cylindrical, irregular or other known particle shapes.

[0060] In some embodiments, the inorganic filler includes one or more of alumina, hydrated alumina, boehmite, magnesium hydroxide, magnesium oxide, titanium dioxide, zirconium oxide, and barium sulfate. In some implementations, the binder is a water-soluble polymer.

[0061] In some implementations, the water-soluble polymer is a homopolymer or copolymer. In some embodiments, the water-soluble binder includes at least one of polyamide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, polyvinyl alcohol, polyvinyl acetate, polyacrylamide, cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, carboxymethyl cellulose, cyanoethyl cellulose, nitrile rubber (NBR), styrene-butadiene rubber (SBR), and latex.

[0062] In some implementations, the binder is an oil-soluble polymer. In some embodiments, non-limiting examples of oil-soluble polymers include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyester, polyether, polyvinyl compounds, polyolefins, rubber, polyvinylpyrrolidone, polystyrene, nitrile rubber (NBR), styrene-butadiene rubber (SBR), latex, acrylonitrile-styrene-butadiene copolymer, halogenated polymers, fluorinated polymers, chlorinated polymers, unsaturated polymers, conjugated diene polymers, and combinations thereof.

[0063] In some embodiments, the electrolyte may include at least one of a gel electrolyte, a solid electrolyte, and a liquid electrolyte. In some embodiments, the liquid electrolyte may include a non-aqueous solvent and a lithium salt.

[0064] In some embodiments, the lithium salt may include at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and lithium difluoroborate. In some embodiments, the non-aqueous solvent may be at least one of carbonate compounds, carboxylic acid ester compounds, and ether compounds. In some embodiments, the carbonate compound may include at least one of chain carbonate compounds, cyclic carbonate compounds, and fluorocarbonate compounds. In some embodiments, the chain carbonate compound may include diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and combinations thereof. In some embodiments, the cyclic carbonate compound may include ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), vinyl ethylene carbonate (VEC), and combinations thereof. In some embodiments, the fluorocarbonate compound may include at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, and trifluoromethylethylene carbonate. In some embodiments, the carboxylic acid ester compound may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerate lactone, mevalonate lactone, caprolactone, and methyl formate. In some embodiments, the ether compound may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof. In some embodiments, the non-aqueous solvent may also include at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters.

[0065] <Electronic Devices> In a fifth aspect, the present invention provides an electronic device comprising the electrochemical device described above.

[0066] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. The application of the electrochemical device in this application is not particularly limited, and it can be used in any electronic device known in the prior art. Some embodiments of this application include electronic devices such as mobile phones, smartphones, laptops, tablets, wearable devices, smartwatches, smart bracelets, smart glasses, power banks, televisions, game consoles, game controllers, digital cameras, smart speakers, headphones, keyboards, mice, monitors, drones, audio equipment, home appliances, toys, power tools, automobiles, motorcycles, electric bicycles, bicycles, robots, robot dogs, industrial robots, and android robots.

[0067] Unless otherwise specified in the following examples, the techniques or conditions described in the literature in this field or in accordance with the product instructions shall apply. All reagents or instruments without a specified manufacturer are commercially available conventional products.

[0068] Example 1 A lithium-ion secondary battery 1. Preparation of positive electrode sheet 1) Preparation method of lithium cobalt oxide materials: According to the chemical formula LiCo 0.9740 Al 0.0252 Ti 0.0008 The molar ratio of Li, Co, Al, and Ti in O2 added to the raw material Li2CO 3、 Co3O4, Al2O3, and TiO2 were mixed uniformly using a high-speed mixer and then sintered at 950℃ for 5 hours to obtain LiCo with an Al content of 7000 ppm and a Ti content of 400 ppm. 0.9740 Al 0.0252 Ti 0.0008 O2, Dv 50 =20µm.

[0069] 2) Preparation methods of silicate materials: According to the chemical formula Li2Mn 0.9822 Al 0.0178 Li, Mn, and Al molar ratios of Li and Mn were added to raw materials Li₂MnSiO₄ and Al₂O₃ in SiO₄. After homogenization using a high-speed mixer, the mixture was sintered at 800℃ for 5 hours to obtain Li₂MnSiO₄. 0.9822 Al 0.0178 SiO4, with an Al doping content of 3000 ppm, Dv 50 =0.01µm.

[0070] 3) Methods for preparing cathode materials: The lithium cobalt oxide material and silicate material prepared above were mixed evenly at a mass ratio of 0.5% of the total mass of the cathode material, and then passed through a 400-mesh sieve to obtain the cathode material. Dv 50=16.6μm, Dv 90 =36.0μm, Dv 10 =5.5μm.

[0071] 4) Method for preparing the positive electrode: The positive electrode material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 95:3:2. The mixture is then coated onto the positive electrode current collector Al foil, dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0072] 2. Preparation of negative electrode sheet The negative electrode active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are thoroughly mixed in a deionized water solvent system at a mass ratio of 96:1:1.5:1.5. The mixture is then coated onto the negative electrode current collector Cu foil, dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0073] 3. Preparation of the separating membrane Polyethylene (PE) porous polymer film is used as the separator.

[0074] 4. Preparation of electrolyte A solution prepared by mixing lithium salt LiPF6 with a non-aqueous organic solvent (ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC): propyl propionate (PP): ethylene carbonate (VC)) in a mass ratio of 20:30:20:28:2, with a mass ratio of 8:92) is used as the electrolyte for lithium-ion secondary batteries.

[0075] 5. Preparation of lithium-ion secondary batteries The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes for safety isolation. The electrode assembly is then wound to form the final electrode assembly. This assembly is placed in a packaging shell, infused with electrolyte, and sealed to obtain a lithium-ion secondary battery.

[0076] Example 2 The difference from Example 1 is that the Al content of the silicate cathode material in this example is 2000 ppm, and the Dv of the lithium cobalt oxide cathode material is... 50 =10µm, the rest is the same as in Example 1, and will not be repeated.

[0077] Example 3 The difference from Example 1 is that the Al content of the silicate cathode material in this example is 2000 ppm, and the Dv... 50 =0.1µm, lithium cobalt oxide cathode material Dv 50 =10µm, the rest is the same as in Example 1, and will not be repeated.

[0078] Example 4 The difference from Example 1 is that the Al content of the silicate cathode material in this example is 2000 ppm, and the Dv... 50 =1µm, lithium cobalt oxide cathode material Dv 50 =10µm, the rest is the same as in Example 1, and will not be repeated.

[0079] Example 5 The difference from Example 1 is that the Al content of the silicate cathode material in this example is 100 ppm, and the Dv... 50 =10µm, lithium cobalt oxide cathode material Dv 50 =2µm, the rest is the same as in Example 1, and will not be repeated.

[0080] Example 6 The difference from Example 1 is that the Al content of the lithium cobalt oxide cathode material in this example is 3000ppm, while the rest is the same as in Example 1, and will not be repeated here.

[0081] Example 7 The difference from Example 1 is that the Al content of the silicate cathode material in this example is 140 ppm, while the rest is the same as in Example 1, and will not be repeated here.

[0082] Example 8 The difference from Example 1 is that the Al content of the silicate cathode material in this example is 70 ppm, while the rest is the same as in Example 1, and will not be repeated here.

[0083] Example 9 The difference from Example 1 is that the Al content in the lithium cobalt oxide cathode material in this example is 3000ppm and the Ti content is 1000ppm. The rest is the same as in Example 1 and will not be repeated.

[0084] Example 10 The difference from Example 1 is that the Al content in the lithium cobalt oxide cathode material in this example is 10,000 ppm and the Ti content is 100 ppm. The rest is the same as in Example 1 and will not be repeated.

[0085] Example 11 The difference from Example 1 is that the Al content in the lithium cobalt oxide cathode material in this example is 7000ppm and the Ti content is 140ppm. The rest is the same as in Example 1 and will not be repeated.

[0086] Example 12 The difference from Example 1 is that the Al content in the lithium cobalt oxide cathode material in this example is 7000ppm and the Ti content is 3500ppm. The rest is the same as in Example 1 and will not be repeated.

[0087] Example 13 The difference from Example 1 is that the Al content in the lithium cobalt oxide cathode material in this example is 7000ppm and the Ti content is 69ppm. The rest is the same as in Example 1 and will not be repeated.

[0088] Example 14 The difference from Example 1 is that in this example, lithium cobalt oxide cathode material is obtained by mixing lithium cobalt oxide particles of different sizes. 50 =12.5μm, Dv 90 =60μm, Dv 10 =10μm, (Dv) 90 -Dv 10 ) / Dv 50 =4.0, the rest is the same as in Example 1, and will not be repeated.

[0089] Example 15 The difference from Example 1 is that the mass of the silicate cathode material in this example accounts for 2.0% of the total mass of the material. The rest is the same as in Example 1 and will not be repeated.

[0090] Example 16 The difference from Example 1 is that the mass of the silicate cathode material in this example accounts for 3.0% of the total mass of the material. The rest is the same as in Example 1 and will not be repeated.

[0091] Example 17 The difference from Example 1 is that the mass of the silicate cathode material in this example accounts for 5.0% of the total mass of the material. The rest is the same as in Example 1 and will not be repeated.

[0092] Example 18 The difference from Example 1 is that the mass of the silicate cathode material in this example accounts for 0.1% of the total mass of the material. The rest is the same as in Example 1 and will not be repeated.

[0093] Example 19 The difference from Example 1 is that the mass of the silicate cathode material in this example accounts for 6.0% of the total mass of the material. The rest is the same as in Example 1 and will not be repeated.

[0094] Example 20 The difference from Example 1 is that: in this example, a carbon-coated silicate cathode material is used, with a carbon coating amount of 30 ppm. The rest is the same as in Example 1 and will not be repeated.

[0095] Example 21 The difference from Example 1 is that: in this example, a carbon-coated silicate cathode material is used, with a carbon coating amount of 1000ppm. The rest is the same as in Example 1 and will not be repeated.

[0096] Comparative Example 1 The difference from Example 1 is that the positive electrode sheet in this comparative example is prepared without the addition of silicate positive electrode material. Lithium cobalt oxide, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are then thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 95:3:2. This mixture is then coated onto the positive current collector Al foil, dried, cold-pressed, and slit to obtain the positive electrode sheet. The rest is the same as in Example 1 and will not be repeated.

[0097] Comparative Example 2 The difference from Example 1 is that the silicate cathode material used in this comparative example does not contain Al element. The rest is the same as in Example 1 and will not be repeated.

[0098] Comparative Example 3 The difference from Example 1 is that no Al element was added to the lithium cobalt oxide cathode material in this comparative example. The rest is the same as in Example 1 and will not be repeated.

[0099] Comparative Example 4 The difference from Example 1 is that the Al content of the lithium cobalt oxide cathode material in this comparative example is 500 ppm, while the rest is the same as in Example 1, and will not be repeated here.

[0100] Comparative Example 5 The difference from Example 1 is that the material mixed with the lithium cobalt oxide cathode material is Al2O3, and the mass of Al2O3 accounts for 5% of the total mass of the material. The rest is the same as in Example 1 and will not be repeated.

[0101] Physical and chemical testing 1. Particle size Dv 50 The median particle size (Dv) was measured using a Mastersizer 3000 laser particle size analyzer. 50 .

[0102] Dv 90 Dv 90 Defined as the particle size at 90% of the cumulative volume percentage distribution obtained from Mastersizer 3000.

[0103] Dv 10 Dv 10 Defined as the particle size at 10% of the cumulative volume percentage distribution obtained from Mastersizer 3000.

[0104] 2. Element content test The amounts of Al and Ti in the cathode active material powder were measured using an Agilent 5800 inductively coupled plasma optical emission spectrometry (ICP-OES) method. Two grams of the powder sample were dissolved in 10 mL of high-purity hydrochloric acid (at least 37 wt% HCl relative to the total weight of the solution) in an Erlenmeyer flask. The flask was covered with a glass cap and heated on a hot plate at 380 °C until the precursor was completely dissolved. After cooling to room temperature, the solution from the Erlenmeyer flask was poured into a 250 mL volumetric flask. The volumetric flask was then filled to the 250 mL mark with deionized water and completely homogenized. Finally, conduct the on-machine test. Enter the analysis interface, select "Lithium Cobalt Oxide Impurity Elements (Standard Addition Method)" for testing, and follow the procedure as follows: Calibration test: Measure the standard solution sequentially from low concentration point to high concentration point, and complete the standard curve plotting. The elemental correlation coefficient should be >0.999; Quality control test: Measure the corresponding quality control sample for this method, check the test results after the test is completed, and the elemental test result deviation should be ≤2%; Sample test: After the calibration test and quality control test meet the requirements, measure the digested and diluted sample.

[0105] The materials and proportions of Examples 1-21 and Comparative Examples 1-5 are shown in Table 1: Table 1

[0106] Performance testing 1. Gram capacity test Five lithium-ion secondary batteries from the comparative example and the embodiment were taken and charged at a constant current rate of 0.1C at room temperature until the voltage reached 4.5V. They were then further charged at a constant voltage of 4.5V until the current dropped below 0.05C, bringing them to a fully charged state at 4.5V. Subsequently, they were discharged at a constant current rate of 0.1C until the voltage reached 3.0V, yielding the 0.1C discharge capacity. The batteries were left to rest for 10 minutes, then charged at a constant current rate of 0.1C at room temperature until the voltage reached 4.5V. They were then further charged at a constant voltage of 4.5V until the current dropped below 0.05C, bringing them to a fully charged state at 4.5V. Subsequently, they were discharged at a constant current rate of 0.2C until the voltage reached 3.0V.

[0107] 0.2C capacity retention rate = (0.2C discharge capacity / first 0.1C discharge capacity) × 100%.

[0108] 2. High-temperature cycling performance test Take three lithium-ion secondary batteries from each of the comparative example and the embodiment, and repeatedly charge and discharge them using the following steps, and calculate the cycle capacity retention rate of the lithium-ion secondary batteries.

[0109] First, in an environment of 45℃, the first charge and discharge cycle was performed. Constant current and constant voltage charging was carried out at a charging current of 0.1C (i.e., the current value that completely discharges the theoretical capacity within 10 hours) until the upper limit voltage is 4.5V. Then, constant current discharge was carried out at a discharge current of 1C until the final voltage is 3V. The discharge capacity of the first cycle was recorded. Then, 100 charge and discharge cycles were performed, and the discharge capacity of the 100th cycle was recorded.

[0110] Cycle capacity retention = (Discharge capacity of the 100th cycle / Discharge capacity of the first cycle) × 100%.

[0111] The test data is shown in Table 2: Table 2

[0112] Comparative examples and comparative examples show that the mixed lithium cobalt oxide cathode material with silicate material that meets the conditions of this application exhibits excellent capacity and high-temperature cycle retention of lithium-ion secondary batteries, and has high thermal stability and safety.

[0113] The embodiments described above are merely examples of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application.

Claims

1. A positive electrode material, characterized in that, Including lithium cobalt oxide and silicate materials; The median particle size Dv of the lithium cobalt oxide 50 The median particle size Dv of the silicate material is X μm. 50 The mass content of Al in the lithium cobalt oxide is Appm, and the mass content of Al in the silicate material is Cppm. Where 20≤CX / Y≤6000000, 1≤A / C≤100.

2. The cathode material according to claim 1, characterized in that, The mass content of Ti in the lithium cobalt oxide is Bppm, where 3≤A / B≤100.

3. The cathode material according to claim 2, characterized in that, Including at least one of the following (a1) to (a5): (a1) The median particle size Dv of the lithium cobalt oxide 50 The range is 2~20μm; (a2) The median particle size Dv of the silicate material 50 The range is 0.01~10μm; (a3) The mass content of Al element in the lithium cobalt oxide is 3000~10000ppm; (a4) The mass content of Al element in the silicate material is 100~3000ppm; (a5) The mass content of Ti element in the lithium cobalt oxide is 100~1000ppm.

4. The cathode material according to claim 1, characterized in that, In the cathode material, the silicate material accounts for 0.5% to 5% of the mass.

5. The cathode material according to any one of claims 1-4, characterized in that, Including at least one of the following (b1) to (b4): (b1) The silicate material includes Li2(M 1-x Al x SiO4, M is selected from at least one of Fe, Mn, Co, Ni, and Ti, and x ranges from 0.001 to 0.05; (b2) When (b1) is included, the silicate material is selected from Li2Fe. 1-x Al x SiO4, Li2Mn 1-x Al x SiO4, Li2Co 1- x Al x SiO4, Li2Ni 1-x Al x SiO4, Li2Ni 1-x Ti x At least one of SiO4; (b3) The surface of the silicate material includes a carbon coating; (b4) When (b3) is included, the mass content of the carbon coating is 30 to 1000 ppm.

6. The cathode material according to claim 1, characterized in that, The positive electrode material Dv 10 Particle size ≥ 2.5 μm, Dv 50 The particle size range is 12~18μm, Dv 90 The particle size range is 20~40μm, and (Dv) 90 -Dv 10 ) / Dv 50 ≤4.

7. A positive electrode plate, characterized in that, It includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, wherein the positive active material layer includes the positive electrode material as described in any one of claims 1-6.

8. A battery cell, characterized in that, It includes a negative electrode and a positive electrode as described in claim 7.

9. An electrochemical device, characterized in that, Including the battery cell as described in claim 8.

10. An electronic device, characterized in that, It includes the electrochemical device as described in claim 9.

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