Electrochemical device and electronic device

Abstract

The present application provides an electrochemical device and an electronic device. The electrochemical device comprises a positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, the positive electrode active material layer comprises conductive fibers, and the conductive fibers comprise at least one of antimony-doped tin oxide (SnO)x1(Sb2O3)x2 or aluminum-doped zinc oxide (ZnO)y1(Al2O3)y2, where the ratio of x1 to x2 ranges from 80:20 to 95:5, and the ratio of y1 to y2 ranges from 85:15 to 99:1. The antimony-doped tin oxide (SnO)x1(Sb2O3)x2 and the aluminum-doped zinc oxide (ZnO)y1(Al2O3)y2 have a good electrical conductivity and a poor adsorption capacity. The above arrangement is beneficial for improving the electrical conductivity of the conductive fibers and reducing the enrichment of side reaction products on the surface of the conductive fibers, and therefore the cycle performance of the electrochemical device is improved.

Description

An electrochemical device and an electronic device

[0001] This application claims priority to Chinese Patent Application No. 202410284550.4, filed on March 12, 2024, entitled "An Electrochemical Device and an Electronic Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of electrochemical technology, and in particular to an electrochemical device and an electronic device. Background Technology

[0003] Lithium-ion batteries (electrochemical devices) have advantages such as high energy density, long cycle life, and no memory effect, and are widely used in consumer electronics, power batteries, and energy storage batteries. With the widespread application of lithium-ion batteries in these fields, the market demands increasingly higher electrochemical performance from them.

[0004] Carbon fiber, as a commonly used conductive agent in lithium-ion batteries, possesses excellent electrical conductivity. However, carbon fiber also exhibits strong adsorption properties. During the charging and discharging process of lithium-ion batteries, this leads to the accumulation of by-reaction products on its surface, resulting in an increase in the diameter of the carbon fiber. This affects the conductivity of the carbon fiber and consequently impacts the cycle performance of the lithium-ion battery. Summary of the Invention

[0005] The purpose of this application is to provide an electrochemical device to improve the cycle performance of lithium-ion batteries. The specific technical solution is as follows:

[0006] The first aspect of this application provides an electrochemical device comprising a positive electrode, the positive electrode comprising a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer comprising conductive fibers, the conductive fibers comprising antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 At least one of the following, wherein the ratio of x1:x2 ranges from 80:20 to 95:5, and the ratio of y1:y2 ranges from 85:15 to 99:1. Antimony-doped tin oxide (SnO) x1 (Sb2O3) x2 And aluminum-doped zinc oxide (ZnO) y1 (Al2O3) y2 It possesses good electrical conductivity and poor adsorption capacity, which can improve the conductivity of conductive fibers and reduce the accumulation of by-reaction products on the surface of conductive fibers. Conductive fibers include antimony-doped tin oxide (SnO). x1 (Sb2O3) x2Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 Using at least one of the following, and adjusting the values ​​of x1:x2 and y1:y2 within the scope of this application, is beneficial to improving the conductivity of the conductive fiber, thereby improving the cycle performance of the electrochemical device.

[0007] In some embodiments of this application, the conductive fiber includes carbon fiber and antimony-doped tin oxide (SnO) disposed on the surface of the carbon fiber. x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 The above configuration helps to improve the conductivity of the conductive fibers and enhance the cycle performance of the electrochemical device.

[0008] In some embodiments of this application, the conductive fiber has a diameter of D nm and is doped with antimony-tin oxide (SnO). x1 (Sb2O3) x2 And / or aluminum-doped zinc oxide (ZnO) y1 (Al2O3) y2 The conductive fiber has a thickness of T nm on its surface and meets at least one of the following characteristics: (1) T / D ≤ 50%; (2) 2 nm ≤ D ≤ 800 nm; (3) 0.1 nm ≤ T ≤ 50 nm. Meeting at least one of these characteristics is beneficial for the conductive fiber to exert its conductive effect and improve the cycle performance of the electrochemical device.

[0009] In some embodiments of this application, the conductive fiber has a diameter of D nm and is doped with antimony-tin oxide (SnO). x1 (Sb2O3) x2 And / or aluminum-doped zinc oxide (ZnO) y1 (Al2O3) y2 The thickness on the conductive fiber surface is T nm, where 0.5 nm ≤ T ≤ 20 nm. Antimony-doped tin oxide (SnO) x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 It can improve the stiffness of conductive fibers. By adjusting the T value within the range of this application, the conductive fibers can have appropriate stiffness, making them less prone to tangling and allowing them to be evenly dispersed between the positive electrode active material particles. It can also avoid the conductive fibers being difficult to adhere to the surface of the positive electrode active material particles due to excessive stiffness, thereby improving the utilization rate of conductive fibers, improving the conductive network in the positive electrode sheet, and improving the cycle performance of the electrochemical device.

[0010] In some embodiments of this application, the conductive fiber is antimony-doped tin oxide (SnO). x1(Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 Fibers. The above arrangement helps to improve the conductivity of the conductive fibers and enhance the cycle performance of the electrochemical device.

[0011] In some embodiments of this application, the mass percentage of conductive fibers in the positive electrode active material layer is 0.1% to 5%. By adjusting the mass percentage of conductive fibers within the range of this application, it is beneficial to improve the conductivity of the positive electrode and improve the cycle performance of the electrochemical device.

[0012] In some embodiments of this application, the positive electrode active material layer includes a positive electrode active material, and the particle size of the positive electrode active material and the length L of the conductive fiber satisfy at least one of the following characteristics: (1) 0.3 μm ≤ L ≤ 30 μm; (2) 0.1 ≤ Dv10 / L ≤ 5, 1.5 ≤ Dv90 / L ≤ 50; (3) 0.5 μm ≤ Dv10 ≤ 10 μm, 15 μm ≤ Dv90 ≤ 50 μm. Satisfying at least one of the above characteristics is beneficial to leveraging the long-range conductivity of the conductive fiber, and is beneficial to the gradation between the conductive fiber and the positive electrode active material particles, further improving the cycle performance of the electrochemical device.

[0013] In some embodiments of this application, the length of the conductive fiber is L μm, where 3 μm ≤ L ≤ 15 μm. By adjusting the length of the conductive fiber within the range specified in this application, it is beneficial for the conductive fiber to be uniformly dispersed in the positive electrode sheet, and it is also beneficial for the long-range conductivity of the conductive fiber to be utilized, thereby further improving the cycle performance of the electrochemical device.

[0014] In some embodiments of this application, at least a portion of the surface region of the positive electrode active material includes aluminum, and the mass percentage of aluminum in the surface region of the positive electrode active material is 0.1% to 1% based on the mass of the positive electrode active material. This configuration helps to improve the structural stability of the positive electrode material and further improve the cycle performance of the electrochemical device.

[0015] In some embodiments of this application, the internal region of the positive electrode active material includes aluminum, and the mass percentage of aluminum in the internal region of the positive electrode active material is 0.5% to 2% based on the mass of the positive electrode active material. This configuration helps to improve the structural stability of the positive electrode material and further improve the cycle performance of the electrochemical device.

[0016] In some embodiments of this application, the electrochemical device includes an electrolyte comprising fluoroethylene carbonate and fluorocarboxylic acid esters. Based on the mass of the electrolyte, the mass percentage of fluoroethylene carbonate is W1%, and the mass percentage of fluorocarboxylic acid ester is W2%. The electrolyte satisfies at least one of the following conditions: (1) 10% ≤ W2 ≤ 20%; (2) 0.2 ≤ W1 / W2 ≤ 0.5. Satisfying at least one of the above conditions is beneficial for reducing the generation of by-reaction products under high voltage, and also for the adhesion of the electrolyte to the surface of conductive fibers, improving the ion conduction pathway of the positive electrode, thereby improving the cycle performance of the electrochemical device.

[0017] In some embodiments of this application, after the electrochemical device is cycled at 45°C for 501 cycles, the diameter increase rate of the conductive fiber is ≤20%, and the resistance increase rate of the electrochemical device is ≤100%. The fact that the diameter increase rate of the conductive fiber is ≤20% and the resistance increase rate of the electrochemical device is ≤100% indicates that the lithium-ion battery has good cycle performance.

[0018] The second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application. The electrochemical device provided in the first aspect of this application has good cycle performance, thereby providing the electronic device provided in the second aspect of this application with a longer service life.

[0019] The beneficial effects of this application are:

[0020] This application provides an electrochemical device and an electronic device. The electrochemical device includes a positive electrode sheet, which includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector. The positive active material layer includes conductive fibers, and the conductive fibers include antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 At least one of the following, wherein the ratio of x1:x2 ranges from 80:20 to 95:5, and the ratio of y1:y2 ranges from 85:15 to 99:1. Antimony-doped tin oxide (SnO) x1 (Sb2O3) x2 And aluminum-doped zinc oxide (ZnO) y1 (Al2O3) y2 It possesses good electrical conductivity and poor adsorption capacity, which can improve the conductivity of conductive fibers and reduce the accumulation of by-reaction products on the surface of conductive fibers. Conductive fibers include antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2Using at least one of the following, and adjusting the values ​​of x1:x2 and y1:y2 within the scope of this application, is beneficial to improving the conductivity of the conductive fiber, thereby improving the cycle performance of the electrochemical device.

[0021] Of course, it is not necessary to achieve all the advantages described above at the same time when implementing any product or method of the present application. Detailed Implementation

[0022] 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, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0023] It should be noted that, in the specific embodiments of this application, lithium-ion batteries are used as an example of electrochemical devices to explain this application, but the electrochemical devices of this application are not limited to lithium-ion batteries.

[0024] The first aspect of this application provides an electrochemical device comprising a positive electrode, the positive electrode comprising a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer comprising conductive fibers, the conductive fibers comprising antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 At least one of the following, wherein the ratio of x1:x2 ranges from 80:20 to 95:5, and the ratio of y1:y2 ranges from 85:15 to 99:1. For example, antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 In the ratio x1:x2, it can be 80:20, 83:17, 85:15, 87:13, 90:10, 93:7, 95:5, or a range of any two of these values; aluminum-doped zinc oxide (ZnO). y1 (Al2O3) y2 In the range y1:y2, it can be 85:15, 87:13, 90:10, 93:7, 95:5, 99:1, or any two of these values.

[0025] The researchers in this application discovered that antimony-doped tin oxide (SnO) x1 (Sb2O3) x2 And aluminum-doped zinc oxide (ZnO) y1 (Al2O3) y2It possesses good conductivity and poor adsorption capacity, which is beneficial for improving the conductivity of conductive fibers, reducing the accumulation of by-reaction products on the surface of conductive fibers, and decreasing the diameter growth rate of conductive fibers. This, in turn, helps improve the conductivity of the positive electrode and reduce cell polarization. Conductive fibers include antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 Using at least one of the following, and adjusting the values ​​of x1:x2 and y1:y2 within the scope of this application, is beneficial to improving the conductivity of conductive fibers and improving the cycle performance of electrochemical devices.

[0026] In some embodiments of this application, the conductive fiber includes carbon fiber and antimony-doped tin oxide (SnO) disposed on the surface of the carbon fiber. x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 The above configuration improves the conductivity of the conductive fibers and enhances the cycle performance of the electrochemical device. The carbon fiber includes at least one of carbon nanofibers, carbon nanotubes, and graphite fibers.

[0027] In some embodiments of this application, the conductive fiber has a diameter of D nm and is doped with antimony-tin oxide (SnO). x1 (Sb2O3) x2 And / or aluminum-doped zinc oxide (ZnO) y1 (Al2O3) y2 The thickness of the conductive fiber surface is T nm, and the T / D ratio is ≤50%. Preferably, the T / D value is greater than 0% and less than or equal to 50%. For example, the T / D value can be 0.01%, 0.1%, 1%, 20%, 30%, 40%, 50%, or a range of any two of these values. Antimony-doped tin oxide (SnO) x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 It can improve the stiffness of conductive fibers. By adjusting the T / D value within the range of this application, the conductive fibers can have appropriate stiffness, making them less prone to tangling and allowing them to be evenly dispersed between the positive electrode active material particles. It can also avoid the conductive fibers being difficult to adhere to the surface of the positive electrode active material particles due to excessive stiffness, thereby improving the utilization rate of conductive fibers, improving the conductive network in the positive electrode sheet, and improving the cycle performance of the electrochemical device.

[0028] In some embodiments of this application, the diameter of the conductive fiber is D nm, where 2 nm ≤ D ≤ 800 nm. For example, the diameter of the conductive fiber can be 2 nm, 10 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, or a range of any two of these values. By adjusting the diameter of the conductive fiber within the range specified in this application, it is beneficial to improve the conductivity of the conductive fiber and enhance the cycle performance of the electrochemical device.

[0029] In some embodiments of this application, antimony-doped tin oxide (SnO) is used. x1 (Sb2O3) x2 And / or aluminum-doped zinc oxide (ZnO) y1 (Al2O3) y2 The thickness of the conductive fiber surface is T nm, where 0.1 nm ≤ T ≤ 50 nm, preferably 0.5 nm ≤ T ≤ 20 nm. For example, the value of T can be 0.1 nm, 1 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, or any range of two such values. Antimony-doped tin oxide (SnO) x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 It can improve the stiffness of conductive fibers. By adjusting the T value within the range of this application, the conductive fibers can have appropriate stiffness, making them less prone to tangling and allowing them to be evenly dispersed between the positive electrode active material particles. It can also avoid the conductive fibers being difficult to adhere to the surface of the positive electrode active material particles due to excessive stiffness, thereby improving the utilization rate of conductive fibers, improving the conductive network in the positive electrode sheet, and improving the cycle performance of the electrochemical device.

[0030] In some embodiments of this application, the conductive fiber is antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 Fibers. The above arrangement helps to improve the conductivity of the conductive fibers and enhance the cycle performance of the electrochemical device.

[0031] In some embodiments of this application, the mass percentage of the conductive fiber in the positive electrode active material layer is 0.1% to 5%. For example, the mass percentage of the conductive fiber can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or a range of any two of these values. By adjusting the mass percentage of the conductive fiber within the range specified in this application, it is beneficial to improve the conductivity of the positive electrode and enhance the cycle performance of the electrochemical device.

[0032] In some embodiments of this application, the length of the conductive fiber is L, satisfying 0.3 μm ≤ L ≤ 30 μm, preferably 3 μm ≤ L ≤ 15 μm. For example, the length of the conductive fiber can be 0.3 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, or a range of any two of these values. By adjusting the length of the conductive fiber within the range of this application, it is beneficial for the conductive fiber to be uniformly dispersed in the positive electrode, and it is also beneficial for the long-range conductivity of the conductive fiber to be utilized, further improving the cycle performance of the electrochemical device.

[0033] In some embodiments of this application, the positive electrode active material layer includes a positive electrode active material, the particle size of which and the length L of the conductive fiber satisfy 0.1 ≤ Dv10 / L ≤ 5, and 1.5 ≤ Dv90 / L ≤ 50. Here, Dv10 refers to the Dv10 of the positive electrode active material, in μm; Dv90 refers to the Dv90 of the positive electrode active material, in μm; and the length L of the conductive fiber is in μm. For example, the value of Dv10 / L can be 0.1, 0.5, 1, 2, 3, 4, 5, or a range of any two of these values; the value of Dv90 / L can be 1.5, 5, 8, 10, 12, 15, 18, 20, 30, 40, 50, or a range of any two of these values. By adjusting the values ​​of Dv10 / L and Dv90 / L within the range of this application, it is beneficial to the gradation between conductive fibers and positive electrode active material particles, avoiding the influence of excessively long conductive fibers on their dispersion in the positive electrode sheet, thus maximizing the conductivity of the conductive fibers and further improving the cycle performance of the electrochemical device. "Dv10" refers to the particle size that reaches 10% of the cumulative volume in the volumetric particle size distribution of the material; "Dv90" refers to the particle size that reaches 90% of the cumulative volume in the volumetric particle size distribution of the material.

[0034] In some embodiments of this application, the positive electrode active material layer includes a positive electrode active material, the particle size of which satisfies 0.5 μm ≤ Dv10 ≤ 10 μm and 15 μm ≤ Dv90 ≤ 50 μm. For example, the value of Dv10 can be 0.5 μm, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, or a range of any two of these values, and the value of Dv90 can be 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or a range of any two of these values. By adjusting the values ​​of Dv10 and Dv90 within the range of this application, it is beneficial to the gradation between the conductive fibers and the positive electrode active material particles, avoiding excessively long conductive fibers that would affect the dispersion of the conductive fibers in the positive electrode sheet, thus maximizing the conductivity of the conductive fibers and further improving the cycle performance of the electrochemical device.

[0035] In some embodiments of this application, at least a portion of the surface region of the positive electrode active material includes aluminum. Based on the mass of the positive electrode active material, the mass percentage of aluminum in the surface region of the positive electrode active material is 0.1% to 1%, for example, the mass percentage of aluminum in the surface region of the positive electrode active material can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or a range of any two of these values. The surface region of the positive electrode active material refers to a region with a thickness of 50 nm from the surface to the interior of the positive electrode active material. By controlling the mass percentage of the surface region of the positive electrode active material within the range of this application, it is beneficial to improve the structural stability of the positive electrode material, reduce the precipitation of transition metal elements in the positive electrode active material, reduce side reactions between the positive electrode active material and the electrolyte, reduce gas production, and further improve the cycle performance of the electrochemical device.

[0036] In some embodiments of this application, the internal region of the positive electrode active material includes aluminum. Based on the mass of the positive electrode active material, the mass percentage of aluminum in the internal region of the positive electrode active material is 0.5% to 2%. For example, the mass percentage of aluminum in the internal region of the positive electrode active material can be 0.5%, 0.7%, 0.9%, 1%, 1.3%, 1.5%, 1.7%, 2%, or a range of any two of these values. The internal region of the positive electrode active material refers to the region with a thickness greater than 50 nm from the surface to the interior of the positive electrode active material. By controlling the mass percentage of aluminum in the internal region of the positive electrode active material within the range of this application, it is beneficial to improve the structural stability of the positive electrode material, reduce the precipitation of transition metal elements in the positive electrode active material, reduce side reactions between the positive electrode active material and the electrolyte, reduce gas production, and further improve the cycle performance of the electrochemical device.

[0037] In some embodiments of this application, the electrochemical device includes an electrolyte comprising fluoroethylene carbonate and fluorocarboxylic acid esters. Based on the mass of the electrolyte, the mass percentage of fluoroethylene carbonate is W1%, and the mass percentage of fluorocarboxylic acid ester is W2%. The electrolyte satisfies at least one of the following conditions: (1) 10% ≤ W2 ≤ 20%; (2) 0.2 ≤ W1 / W2 ≤ 0.5. For example, the value of W2 can be 10%, 13%, 15%, 17%, 19%, 20%, or a range of any two of these values, and the value of W1 / W2 can be 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, or a range of any two of these values. The electrolyte satisfying at least one of the above conditions is beneficial for reducing the generation of by-reaction products under high voltage, and also for the adhesion of the electrolyte to the surface of conductive fibers, improving the ion conduction pathway of the positive electrode, thereby improving the cycle performance of the electrochemical device.

[0038] In some embodiments of this application, after the electrochemical device is cycled at 45°C for 501 cycles, the diameter increase rate of the conductive fiber is ≤20%, and the resistance increase rate of the electrochemical device is ≤100%. The fact that the diameter increase rate of the conductive fiber is ≤20% and the resistance increase rate of the electrochemical device is ≤100% indicates that the lithium-ion battery has good cycle performance.

[0039] This application does not impose any particular restrictions on the preparation method of conductive fibers, such as the internal arrangement of antimony-doped tin oxide (SnO) on the surface of carbon fibers. x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 The preparation method of conductive fibers may include, but is not limited to, the following steps: First, hydrocarbon substances are deposited by chemical vapor deposition under high temperature and the action of a catalyst to obtain carbon nanofibers. Then, residual catalysts and impurities are removed by washing, centrifugation, filtration, etc., to obtain pure carbon nanofibers. The aforementioned hydrocarbon substances may include, but are not limited to, at least one of acetylene or methane. Commercially available conductive carbon fibers can also be used. Then, the carbon nanofibers are used as a carbon source and dissolved in water with metal salts, oxidants, precipitants, surfactants, etc., to form an aqueous solution. The aqueous solution is transferred to a hydrothermal reactor, sealed, and allowed to react for a period of time under certain temperature and pressure. After filtration, washing, drying, and calcination, conductive fibers are obtained. The synthesized surface contains (SnO). x1 (Sb2O3) x2 The conductive fibers contain metal salts including tin salts and antimony salts. Tin salts may include, but are not limited to, at least one of tin dichloride, tin nitrate, and tin sulfate. Antimony salts may include, but are not limited to, at least one of antimony trichloride, antimony nitrate, and antimony sulfate. The synthesized surface contains (ZnO). y1 (Al2O3) y2 The metal salts of the conductive carbon fibers include zinc salts and aluminum salts. The zinc salts may include, but are not limited to, at least one of zinc dichloride, zinc sulfate, and zinc acetate. The aluminum salts may include, but are not limited to, at least one of aluminum trichloride, aluminum nitrate, and aluminum sulfate. The oxidizing agents mentioned above may include, but are not limited to, at least one of nitric acid and hydrogen peroxide. The precipitating agents mentioned above may include, but are not limited to, at least one of ammonium hydroxide and sodium hydroxide. The surfactants mentioned above may include, but are not limited to, at least one of sodium nitrate and sodium dodecyl sulfate.

[0040] This application does not impose any particular limitations on the reaction temperature, reaction pressure, reaction time, calcination temperature, and calcination time in the hydrothermal reactor, as long as the purpose of this application can be achieved. For example, the reaction temperature in the hydrothermal reactor can be 100°C to 200°C, the reaction pressure in the hydrothermal reactor can be 1 MPa to 5 MPa, the reaction time in the hydrothermal reactor can be 3 h to 10 h, the calcination temperature can be 130°C to 250°C, and the calcination time can be 22 h to 26 h.

[0041] The conductive fiber is antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 The preparation method may include, but is not limited to, the following steps: dissolving a metal source in an acid solution, then co-titting it with an alkaline solution to prepare a metal hydroxide; filtering and washing to remove impurities, and dispersing the metal hydroxide in a solvent to obtain a metal hydroxide dispersion; adding the metal hydroxide to a polymer to prepare a spinning solution, and performing electrospinning to prepare nanofibers; and then heat-treating the above nanofibers to obtain antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 Nanofibers. Synthesis of antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 The metal sources for conductive fibers include tin and antimony sources. Tin sources can include, but are not limited to, at least one of tin dichloride, tin oxide, and stannous oxide. Antimony sources can include, but are not limited to, at least one of antimony trichloride, antimony oxide, and antimony nitrate. Aluminum-doped zinc oxide (ZnO) is synthesized. y1 (Al2O3) y2 The metal source for the conductive fiber includes a zinc source and an aluminum source. The zinc source may include, but is not limited to, at least one of zinc oxide, zinc, and zinc carbonate. The aluminum source may include, but is not limited to, at least one of alumina and aluminum. The acid solution may include, but is not limited to, at least one of hydrochloric acid, sulfuric acid, and nitric acid. The alkaline solution may include, but is not limited to, at least one of sodium hydroxide, potassium hydroxide, and calcium hydroxide. The solvent may include, but is not limited to, at least one of deionized water, acetone, and ethanol. The polymer may include, but is not limited to, at least one of polyethylene terephthalate, polyacrylamide, and poly(p-phenylene glycol).

[0042] This application does not impose any particular limitation on the above heat treatment process, as long as it can achieve the purpose of this application. For example, in an air atmosphere, the temperature is heated from room temperature to 100°C to 400°C and held for 0.1h to 5h, and then heated to 400°C to 900°C and held for 0.1h to 5h.

[0043] This application does not impose any particular limitations on the preparation method of aluminum-containing areas in the surface and internal regions of the positive electrode active material. For example, a primary positive electrode active material (such as lithium cobalt oxide) can be uniformly mixed with an aluminum-containing compound (such as aluminum chloride) and sintered at 600°C to 1000°C for 4 to 12 hours to obtain an aluminum-containing positive electrode active material. When the primary positive electrode active material is mixed with the aluminum-containing compound and sintered, aluminum will undergo thermal diffusion to the internal region of the primary positive electrode active material during sintering at 600°C to 1000°C, resulting in a higher aluminum content in the internal region than in the surface region. Generally, the difference in aluminum content between the surface and internal regions of the positive electrode active material can be controlled by adjusting the sintering temperature or sintering time.

[0044] This application does not impose any particular limitation on the positive electrode sheet, as long as it can achieve the purpose of this application. For example, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector. This application does not impose any particular limitation on the positive current collector, as long as it can achieve the purpose of this application. For example, the positive current collector may include aluminum foil or aluminum alloy foil, etc. The positive active material layer of this application includes a positive active material. This application does not impose any particular limitation on the type of positive active material, as long as it can achieve the purpose of this application. For example, the positive active material may include at least one of lithium nickel cobalt manganese oxide (NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate, preferably at least one of lithium nickel cobalt manganese oxide (NCM811, NCM622, NCM523, NCM111), lithium cobalt oxide (LiCoO2), and lithium manganese oxide. Based on the mass of the positive electrode active material layer, the mass percentage of the positive electrode active material can be from 93% to 99%, for example, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or any combination of two of these values. In this application, there are no particular limitations on the thickness of the positive electrode current collector and the positive electrode active material layer, as long as the purpose of this application is achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, preferably 6 μm to 18 μm. The thickness of the single-sided positive electrode active material layer is 30 μm to 120 μm. In this application, the positive electrode active material layer can be disposed on one surface or on two surfaces in the thickness direction of the positive electrode current collector. It should be noted that the "surface" here can be the entire area of ​​the positive electrode current collector or only a portion thereof; there are no particular limitations in this application, as long as the purpose of this application is achieved. The positive electrode active material layer of this application may further include a positive electrode conductive agent and a positive electrode binder. This application does not impose any particular limitations on the positive electrode conductive agent and the positive electrode binder, as long as they can achieve the purpose of this application. For example, the conductive agent may include at least one of graphene, carbon nanotubes, Ketjen black, graphite fiber, or conductive carbon black (Super P). Based on the mass of the positive electrode active material layer, the mass percentage content of the positive electrode conductive agent may be from 0% to 3%, for example, the mass percentage content of the positive electrode conductive agent may be 0%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, or a range consisting of any two of these values.The positive electrode binder may include at least one of polyacrylic acid, polyvinylidene fluoride (PVDF), polytetrafluoroethylene-hexafluoropropylene, sodium polyacrylate, nitrile rubber, or polyacrylate. Based on the mass of the positive electrode active material layer, the mass percentage content of the positive electrode binder may be 1% to 4%. For example, the mass percentage content of the positive electrode binder is 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or a range composed of any two of these values.

[0045] This application places no particular restrictions on the negative electrode sheet, as long as the purpose of this application can be achieved. For example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. In this application, the negative electrode active material layer may be provided on one surface in the thickness direction of the negative electrode current collector, or may be provided on both surfaces in the thickness direction of the negative electrode current collector. It should be noted that the "surface" here can be the entire area of the negative electrode current collector or a partial area of the negative electrode current collector. This application places no particular restrictions, as long as the purpose of this application can be achieved. This application places no particular restrictions on the negative electrode current collector, as long as the purpose of this application can be achieved. For example, the negative electrode current collector may include, but is not limited to, copper foil, copper alloy foil, nickel foil, titanium foil, nickel foam, copper foam, or composite current collector, etc. The negative electrode active material layer of this application contains a negative electrode active material. This application places no particular restrictions on the type of the negative electrode active material, as long as the purpose of this application can be achieved. For example, the negative electrode active material may include, but is not limited to, natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0 < x ≤ 2) or at least one of metallic lithium, etc. In this application, there are no particular restrictions on the thickness of the negative electrode current collector and the negative electrode active material layer, as long as the purpose of this application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 12 μm, and the thickness of the single-sided negative electrode active material layer is 30 μm to 130 μm. The negative electrode active material layer of this application may also contain a conductive agent and a binder. This application places no particular restrictions on the conductive agent and the binder, as long as the purpose of this application can be achieved. For example, the conductive agent may include at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon nanofibers, graphite fibers, Ketjen black, acetylene black, natural graphite, artificial graphite, flake graphite, or graphene, etc. The binder may include at least one of polyacrylic acid, polyvinyl alcohol, polyacrylate, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyamideimide, nitrile rubber, styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polytetrafluoroethylene-hexafluoropropylene, polyvinyl butyral (PVB), water-based acrylic resin, carboxymethyl cellulose (CMC), or sodium carboxymethyl cellulose (CMC-Na), etc.

[0046] The electrochemical device of this application also includes an electrolyte, which may include lithium salts and organic solvents. This application does not particularly limit the type of lithium salt, as long as it achieves the purpose of this application. For example, the lithium salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(fluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(oxalatoborate)borate (LiBOB), or lithium difluorooxalatoborate (LiDFOB). This application does not limit the content of lithium salt in the electrolyte, as long as it achieves the purpose of this application. This application does not particularly limit the type of organic solvent mentioned above, as long as it achieves the purpose of this application. For example, it may include, but is not limited to, at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents. The carbonate compounds mentioned above may include, but are not limited to, at least one of chain carbonate compounds or cyclic carbonate compounds. The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, or methyl ethyl carbonate. The aforementioned cyclic carbonate compounds may include, but are not limited to, at least one of ethylene carbonate, propylene carbonate, butylene carbonate, or ethylene ethylene carbonate. The aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valproic acid lactone, or caprolactone. The aforementioned ether compounds may include, but are not limited to, at least one of ethylene glycol dimethyl ether, dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The other organic solvents mentioned above may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate.

[0047] The electrochemical device of this application also includes a diaphragm to separate the positive and negative electrode plates, prevent internal short circuits, allow electrolyte ions to pass freely, and not affect the electrochemical charging and discharging process. This application does not impose any particular limitation on the diaphragm, as long as it achieves the purpose of this application. For example, the diaphragm material can be, but is not limited to, at least one of polyethylene (PE), polypropylene (PP), polyolefin (PO) diaphragms primarily composed of polytetrafluoroethylene, polyester membranes (e.g., polyethylene terephthalate (PET) membranes), cellulose membranes, polyimide (PI) membranes, polyamide (PA) membranes, spandex, or aramid membranes. The type of diaphragm can be, but is not limited to, at least one of woven membranes, nonwoven membranes (non-woven fabrics), microporous membranes, composite membranes, rolled membranes, or spun membranes. The diaphragm of this application may have a porous structure, with a porous layer disposed on at least one surface of the diaphragm. The porous layer comprises inorganic particles and a binder. The inorganic particles may include at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder may include at least one of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene. This application does not particularly limit the pore size of the porous structure, as long as it achieves the purpose of this application; for example, the pore size may be from 0.01 μm to 1 μm. In this application, the thickness of the diaphragm is not particularly limited, as long as it achieves the purpose of this application; for example, the thickness may be from 3 μm to 500 μm.

[0048] The electrochemical device of this application also includes a packaging bag for containing the positive electrode, the separator, the negative electrode, and the electrolyte, as well as other components known in the art in the electrochemical device. This application does not limit the scope of these other components. This application does not impose any particular limitation on the packaging bag; it can be any packaging bag known in the art, as long as it achieves the purpose of this application. For example, an aluminum-plastic film packaging bag can be used.

[0049] The electrochemical device described in this application is not particularly limited and may include any device in which an electrochemical reaction occurs. In one embodiment of this application, the electrochemical device may include, but is not limited to, lithium-ion batteries, sodium-ion batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0050] The preparation process of the electrochemical device of this application is well known to those skilled in the art, and this application has no particular limitations. For example, it may include, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain the electrochemical device; or stacking the positive electrode, separator, and negative electrode in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly in a packaging bag; injecting electrolyte into the packaging bag and sealing it to obtain the electrochemical device. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the packaging bag as needed to prevent pressure rise and overcharging / discharging inside the electrochemical device.

[0051] A second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application. The electrochemical device provided in this application has good cycle performance, thereby providing the electronic device with a long service life.

[0052] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries or lithium-ion capacitors, etc.

[0053] Example

[0054] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0055] Test methods and equipment:

[0056] Testing of various characteristic quantities of conductive fibers and positive electrode active materials

[0057] (1) Disassemble the lithium-ion battery to obtain the positive electrode sheet. Soak the positive electrode sheet in dimethyl carbonate (DMC) at 25±5℃ for 30 minutes, then take it out and let it air dry naturally.

[0058] (2) Using a scanning electron microscope (ZEISSSEM) to observe and test the length of 15 conductive fibers of the positive electrode obtained in (1), take the average value and record it as the length L of the conductive fiber; use EDS (energy dispersive X-ray spectroscopy) to test the surface elements of the conductive fiber, the Sn element content is x1, half of the Sb element content is x2, the Zn element content is y1, and half of the Al element content is y2; then use EDS to test the surface elements of the positive electrode active material, the Al element content is the mass percentage of aluminum element in the surface area of ​​the positive electrode active material.

[0059] (3) Cut the positive electrode sheet obtained in (1) under plasma to obtain the cross-section of the positive electrode sheet. Observe and test the diameter of the conductive fiber at 15 locations and the antimony-doped tin oxide (SnO) under a scanning electron microscope. x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 The thickness of the conductive fiber surface is taken as the average value, and is recorded as the diameter D of the conductive fiber and the antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 The thickness T on the surface of the conductive fiber is measured; then EDS testing is used to test the conductive fiber and the internal region of the positive electrode active material respectively. The Al element content measured in the positive electrode active material is recorded as the mass percentage content of aluminum element in the internal region of the positive electrode active material.

[0060] Testing of particle size of positive electrode active material

[0061] (1) Disassemble the lithium-ion battery to obtain the positive electrode sheet. Soak the positive electrode sheet in dimethyl carbonate (DMC) at 25±5℃ for 30 minutes, then take it out and let it air dry naturally.

[0062] (2) The positive electrode sheet obtained in (1) is placed in concentrated sulfuric acid for corrosion, and the remaining particles are the positive electrode active material.

[0063] (3) After washing and dispersing the positive electrode active material particles obtained in (2) with deionized water, the particles were tested using a Malvern laser particle size analyzer to obtain Dv10 and Dv90 of the positive electrode active material.

[0064] Cyclic performance testing

[0065] Place the lithium-ion battery in a 45°C environment for 60 minutes, then discharge it to 3V with a constant current of 0.5C, and let it stand for 5 minutes.

[0066] [Charge at a constant current of 1.5C to 4.5V, then charge at a constant voltage of 4.5V to 0.05C, let stand for 5 minutes, then discharge at a constant current of 0.7C to 3V, and let stand for 5 minutes.]

[0067] The process in brackets [ ] was repeated 49 times, and the internal resistance of the lithium-ion battery was tested at 1 kHz. The results were recorded sequentially as IMP1, IMP2, IMP3...IMP 49 In week 50, the battery was charged to 4.5V at a constant current of 0.5C, then charged to 0.05C at a constant voltage of 4.5V, allowed to rest for 5 minutes, and then discharged to 3V at a constant current of 0.2C. The internal resistance of the lithium-ion battery was measured at 1kHz and recorded as IMP. 50}

[0068] The process in {} is repeated 10 times, and then the process in 【】 is repeated once. The internal resistance of the lithium-ion battery is tested at 1 kHz and recorded as IMP. 501 The internal resistance growth rate of a lithium-ion battery after 501 cycles = [(IMPa) 501 -IMP1) / IMP1]×100%.

[0069] The internal resistance growth rate of lithium-ion batteries is used as an indicator to evaluate the cycle performance of lithium-ion batteries. The smaller the internal resistance growth rate, the better the cycle performance of lithium-ion batteries.

[0070] Test of the growth rate of conductive fiber diameter

[0071] Disassemble unused lithium-ion batteries, remove the positive electrode, clean it with dimethyl carbonate (DMC), and then observe and test the diameter of 15 conductive fibers using a scanning electron microscope (ZEISSSEM). Calculate the average value and record it as D0. Perform the same cycle performance test on lithium-ion batteries under the same conditions. Disassemble lithium-ion batteries that have undergone 501 cycles at 45°C, remove the positive electrode, clean it with DMC, and then observe and test the diameter of 15 conductive fibers using a scanning electron microscope. Calculate the average value and record it as D0. 501 The growth rate of the diameter of conductive fibers = [(D 501 -D0) / D0]×100%.

[0072] Example 1

[0073] <Preparation of the positive electrode>

[0074] Lithium cobalt oxide (LiCoO2), a positive electrode active material, polyvinylidene fluoride (PVDF), a positive electrode binder, conductive fibers, and conductive carbon black (Super P) were mixed in a mass ratio of 97.5:1.4:0.4:0.7. The lithium cobalt oxide (LiCoO2) positive electrode active material had a Dv10 of 5 μm and a Dv90 of 30 μm. The aluminum content in the surface region of the positive electrode active material was 0.4%, and the aluminum content in the internal region was 1%. The conductive fibers had a diameter D of 60 nm and a length of 8 μm, and the surface of the conductive fibers contained (SnO). x1 (Sb2O3) x2 The thickness is 6 nm, where x1:x2 = 90:10. N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75 wt%, and the mixture is stirred evenly. The positive electrode slurry is uniformly coated onto one surface of a 10 μm thick aluminum foil used as a positive electrode current collector, and dried at 110 °C to obtain a single-sided positive electrode sheet with a 100 μm thick active material layer. The above steps are then repeated on the other surface of the positive electrode sheet to obtain a double-sided positive electrode sheet. After coating, the positive electrode sheet is cold-pressed and cut into sheets with a size of 74 mm × 867 mm for later use.

[0075] <Preparation of Negative Electrode Sheets>

[0076] Graphite, styrene-butadiene rubber, and sodium carboxymethyl cellulose (CMC) were mixed at a mass ratio of 97.5:1.3:1.2, and deionized water was added as a solvent to prepare a negative electrode slurry with a solid content of 70 wt%, which was then stirred evenly. The negative electrode slurry was uniformly coated onto one surface of a 10 μm thick copper foil, dried at 110 °C, and cold-pressed to obtain a negative electrode sheet with a single-sided coating of negative electrode active material layer with a thickness of 150 μm. The negative electrode sheet was then cut into sheets with a specification of 74 mm × 875 mm for later use.

[0077] <Preparation of the diaphragm>

[0078] A 5μm thick polyethylene film (supplied by Celgard) is used.

[0079] <Preparation of Electrolyte>

[0080] In a dry argon-atmospheric glove box, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 30:50:20 to obtain a base solvent. Thoroughly dried lithium salt LiPF6 was dissolved in the base solvent, and fluoroethylene carbonate and fluorocarboxylic acid esters were added and mixed thoroughly to obtain an electrolyte. The electrolyte contained in this electrolyte had a mass percentage of 12.5% ​​for lithium salt LiPF6, 5% for fluoroethylene carbonate, and 15% for fluorocarboxylic acid esters, with the remainder being the base solvent.

[0081] <Preparation of Lithium-ion Batteries>

[0082] The positive electrode, separator, and negative electrode are stacked sequentially, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode assembly is then wound to form the electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag, and after dehydration at 80°C, the electrolyte is injected, and the assembly is sealed. Following formation, degassing, and shaping processes, a lithium-ion battery is obtained.

[0083] Examples 2 to 22

[0084] Except for the preparation of the positive electrode sheet, where the parameters of the conductive fiber are adjusted according to Table 1, the rest is the same as in Example 1.

[0085] Example 23

[0086] Except for the preparation of the positive electrode sheet, the parameters of the conductive fiber were adjusted according to Table 1. The conductive fiber is (SnO). x1 (Sb2O3) x2 Except for (ATO), the rest is the same as in Example 1.

[0087] Example 24

[0088] Except for the preparation of the positive electrode sheet, the parameters of the conductive fiber were adjusted according to Table 1. The conductive fiber is (ZnO). y1 (Al2O3) y2 Except for (AZO), the rest is the same as in Example 1.

[0089] Examples 25 to 27

[0090] Except for the <Preparation of Positive Electrode Sheet>, where the mass percentage of conductive fiber is adjusted according to Table 1 and the content of positive electrode active material is changed accordingly, the rest is the same as in Example 1.

[0091] Examples 28 to 31

[0092] Except for the preparation of the positive electrode sheet, which is adjusted according to Table 1, the rest is the same as in Example 1.

[0093] Examples 32 to 35

[0094] Except for the <Preparation of Positive Electrode Sheet>, which adjusts the mass percentage of aluminum in the surface or internal region of the positive electrode active material according to Table 1, the rest is the same as in Example 1.

[0095] Examples 36 to 39

[0096] Except for the preparation of the electrolyte, where the content of fluoroethylene carbonate and fluorocarboxylic acid ester was adjusted according to Table 1, and the content of the base solvent was changed accordingly, the rest was the same as in Example 1.

[0097] Comparative Example 1

[0098] Except for the preparation of the positive electrode sheet, in which carbon fiber (with an average diameter of 60 nm and a length of 8 μm) is used for the conductive fiber, the rest is the same as in Example 1.

[0099] The researchers in this study discovered that conductive fibers doped with antimony tin oxide (SnO) x1 (Sb2O3) x2 x1:x2 and aluminum-doped zinc oxide (ZnO) y1 (Al2O3) y2 The values ​​of y1:y2 affect the cycle performance of lithium-ion batteries. As can be seen from Examples 1 to 6 and Comparative Example 1, the conductive particles include antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 Using at least one of the following, and adjusting the values ​​of x1:x2 and y1:y2 within the scope of this application, is beneficial to improving the conductivity of conductive fibers, reducing the enrichment of by-reaction products on the surface of conductive fibers, and can make the conductive fibers in lithium-ion batteries have a lower diameter growth rate, and make lithium-ion batteries have a lower internal resistance growth rate, indicating that lithium-ion batteries have good cycle performance.

[0100] The researchers in this application discovered that antimony-doped tin oxide (SnO) x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 The thickness of the conductive fiber surface affects the cycle performance of the electrochemical device. As can be seen from Examples 1, 7 to 10, 4, and 15 to 18, the thickness of the conductive fiber surface can be adjusted to control the antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3)y2 Within the range of the conductive fiber surface thickness in this application, the conductive fibers in the lithium-ion battery can have a lower diameter growth rate, resulting in a lower internal resistance growth rate for the lithium-ion battery, indicating that the lithium-ion battery has good cycle performance.

[0101] The researchers of this application discovered that the diameter of conductive fibers affects the cycle performance of electrochemical devices. As can be seen from Examples 1, 11 to 14, 4, 19 to 22, by adjusting the diameter of conductive fibers within the range of this application, the conductive fibers in the lithium-ion battery can have a lower diameter growth rate, resulting in a lower internal resistance growth rate for the lithium-ion battery, indicating that the lithium-ion battery has good cycle performance.

[0102] The researchers of this application discovered that the T / D value affects the cycle performance of the electrochemical device. As can be seen from Examples 1, 4, 7 to 22, by adjusting the T / D value within the range of this application, the conductive fibers in the lithium-ion battery can have a lower diameter growth rate, and the lithium-ion battery can have a lower internal resistance growth rate, indicating that the lithium-ion battery has good cycle performance.

[0103] The researchers in this application discovered that the type of internal material of conductive fibers affects the cycle performance of electrochemical devices. As can be seen from Examples 1, 4, 23, and 24, the internal material of the conductive fibers is carbon fiber and antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 One of these methods can result in a lower diameter growth rate of conductive fibers in lithium-ion batteries, leading to a lower internal resistance growth rate and indicating that lithium-ion batteries have good cycle performance.

[0104] The researchers of this application discovered that the mass percentage of conductive fibers in the positive electrode active material layer affects the cycle performance of the electrochemical device. As can be seen from Examples 1, 25 to 27, by adjusting the mass percentage of conductive fibers within the range of this application, the conductive fibers in the lithium-ion battery can have a lower diameter growth rate, resulting in a lower internal resistance growth rate for the lithium-ion battery, indicating that the lithium-ion battery has good cycle performance.

[0105] The researchers of this application discovered that the length of conductive fibers affects the cycle performance of electrochemical devices. As can be seen from Examples 1, 28 to 31, by adjusting the length of conductive fibers within the range of this application, the conductive fibers in the lithium-ion battery can have a lower diameter growth rate, resulting in a lower internal resistance growth rate for the lithium-ion battery, indicating that the lithium-ion battery has good cycle performance.

[0106] The researchers of this application discovered that the values ​​of Dv10 / L, Dv90 / L, Dv10, and Dv90 affect the cycle performance of the electrochemical device. As can be seen from Examples 1, 28 to 31, by adjusting the values ​​of Dv10 / L, Dv90 / L, Dv10, and Dv90 within the range of this application, the conductive fibers in the lithium-ion battery can have a lower diameter growth rate, and the lithium-ion battery can have a lower internal resistance growth rate, indicating that the lithium-ion battery has good cycle performance.

[0107] The researchers of this application discovered that the aluminum content in the surface and internal regions of the positive electrode active material affects the cycle performance of the electrochemical device. As can be seen from Examples 1, 32 to 35, by controlling the aluminum content in the surface and internal regions of the positive electrode active material within the range of this application, the conductive fibers in the lithium-ion battery can have a lower diameter growth rate, and the lithium-ion battery can have a lower internal resistance growth rate, indicating that the lithium-ion battery has good cycle performance.

[0108] The researchers of this application discovered that the values ​​of W2 and W1 / W2 affect the cycle performance of the electrochemical device. As can be seen from Examples 1, 36 to 39, by adjusting the values ​​of W2 and W1 / W2 within the range of this application, the conductive fibers in the lithium-ion battery can have a lower diameter growth rate, and the lithium-ion battery can have a lower internal resistance growth rate, indicating that the lithium-ion battery has good cycle performance.

[0109] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An electrochemical device comprising a positive electrode, the positive electrode comprising a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer comprising conductive fibers, the conductive fibers comprising antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 At least one of them, wherein The ratio of x1:x2 ranges from 80:20 to 95:5, and the ratio of y1:y2 ranges from 85:15 to 99:

1.

2. The electrochemical device according to claim 1, wherein, The conductive fiber comprises carbon fiber and antimony-doped tin oxide (SnO) disposed on the surface of the carbon fiber. x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 .

3. The electrochemical device according to claim 2, wherein, The conductive fiber has a diameter of D nm, and the antimony-doped tin oxide (SnO) x1 (Sb2O3) x2 And / or aluminum-doped zinc oxide (ZnO) y1 (Al2O3) y2 The conductive fiber has a thickness of T nm on its surface and satisfies at least one of the following characteristics: (1) T / D ≤ 50%; (2) 2nm≤D≤800nm; (3) 0.1nm≤T≤50nm.

4. The electrochemical device according to claim 2, wherein, The conductive fiber has a diameter of D nm, and the antimony-doped tin oxide (SnO) x1 (Sb2O3) x2 And / or aluminum-doped zinc oxide (ZnO) y1 (Al2O3) y2 The thickness of the conductive fiber surface is T nm, where 0.5 nm ≤ T ≤ 20 nm.

5. The electrochemical device according to claim 1, wherein, The conductive fiber is antimony-doped tin oxide (SnO). x1 (Sb2O3) x2 Or it can be zinc oxide (ZnO) with aluminum added. y1 (Al2O3) y2 fiber.

6. The electrochemical device according to claim 1, wherein, Based on the mass of the positive electrode active material layer, the mass percentage of the conductive fiber is 0.1% to 5%.

7. The electrochemical device according to any one of claims 1 to 6, wherein, The positive electrode active material layer includes a positive electrode active material, and the particle size of the positive electrode active material and the length L of the conductive fiber satisfy at least one of the following characteristics: (1) 0.3μm≤L≤30μm; (2) 0.1≤Dv10 / L≤5, 1.5≤Dv90 / L≤50; (3) 0.5μm≤Dv10≤10μm, 15μm≤Dv90≤50μm.

8. The electrochemical device according to any one of claims 1 to 6, wherein, The length of the conductive fiber is Lμm, where 3μm≤L≤15μm.

9. The electrochemical device according to claim 7, wherein, At least a portion of the surface region of the positive electrode active material includes aluminum, and the mass percentage of aluminum in the surface region of the positive electrode active material is 0.1% to 1% based on the mass of the positive electrode active material.

10. The electrochemical device according to claim 7, wherein, The internal region of the positive electrode active material includes aluminum, and the mass percentage of aluminum in the internal region of the positive electrode active material is 0.5% to 2% based on the mass of the positive electrode active material.

11. The electrochemical device according to claim 1, wherein, The electrochemical device includes an electrolyte comprising fluoroethylene carbonate and fluorocarboxylic acid esters. Based on the mass of the electrolyte, the mass percentage of fluoroethylene carbonate is W1%, and the mass percentage of fluorocarboxylic acid esters is W2%. The electrolyte satisfies at least one of the following conditions: (1)10％≤W2≤20％； (2) 0.2≤W1 / W2≤0.

5.

12. The electrochemical device according to claim 1, wherein, After the electrochemical device is cycled at 45°C for 501 cycles, the diameter growth rate of the conductive fiber is ≤20%, and the resistance growth rate of the electrochemical device is ≤100%.

13. An electronic device comprising the electrochemical device according to any one of claims 1 to 12.

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