Positive pole piece, preparation method of positive pole piece, lithium ion battery, battery device and power utilization device

Abstract

The invention belongs to the technical field of batteries, and particularly discloses a positive pole piece, a preparation method of the positive pole piece, a lithium ion battery, a battery device and a power utilization device. The battery device comprises a lithium ion battery and a battery management system, the lithium ion battery comprises a positive pole piece, a separator and a negative pole piece, the positive pole piece comprises a positive pole material, the positive pole material has a core-shell structure, the core of the core-shell structure comprises a positive pole active material, and the shell layer comprises a lithium element, a sulfur element and a silicon element; the charging cut-off voltage of the battery device arranged in the battery management system is greater than 4.5 V. The lithium ion battery designed by the invention has the advantages of high energy density, good cycling stability and good rate capability.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to a positive electrode sheet and its preparation method, as well as lithium-ion batteries, battery devices, and power-consuming devices. Background Technology

[0002] Secondary batteries are widely used in various consumer electronics and electric vehicles due to their outstanding characteristics such as light weight, no pollution, and no memory effect. Among them, lithium-ion batteries have a very wide range of applications in portable electronic devices and electric vehicles.

[0003] As the application of rechargeable batteries becomes more and more widespread, the requirements for battery performance are also becoming higher and higher. Summary of the Invention

[0004] In view of the above problems, this application provides a positive electrode sheet and its preparation method, as well as a lithium-ion battery, battery device, and power-consuming device. It improves the cycle stability of the battery by increasing the structural stability of the positive electrode active material.

[0005] In a first aspect, this application provides a battery device, including a lithium-ion battery and a battery management system; the lithium-ion battery includes a positive electrode, a separator and a negative electrode stacked together, the positive electrode includes a positive electrode material, the positive electrode material has a core-shell structure, the core-shell structure includes a core and a shell layer, the shell layer is located on at least a portion of the surface of the core;

[0006] The core contains positive electrode active material;

[0007] The outer shell contains lithium, sulfur, and silicon.

[0008] The charging cutoff voltage of the aforementioned battery device is set to be greater than 4.5V in the battery management system.

[0009] In some embodiments of this application, the mass percentage content of lithium in the outer shell layer is 10.0% to 15.5%;

[0010] and / or;

[0011] The mass percentage of sulfur in the outer shell is 5.0% to 9.2%.

[0012] and / or;

[0013] The mass percentage content of silicon in the outer shell is 7.3% to 14.9%.

[0014] In some embodiments of this application, the outer shell layer of the core-shell structure further includes carbon and oxygen elements, wherein the mass percentage content of carbon in the outer shell layer is 15.1% to 20.8%;

[0015] and / or;

[0016] The mass percentage of oxygen in the outer shell is 50.1% to 58.9%;

[0017] The balance contains hydrogen and essential impurity elements.

[0018] In some embodiments of this application, the outer shell layer of the core-shell structure comprises an organosilicon resin, which has a mesh structure.

[0019] The outer shell layer also contains lithium sulfate, which is distributed within the network structure.

[0020] In some embodiments of this application, the silicone resin includes polyalkyl silicone resin.

[0021] In some embodiments of this application, the silicone resin includes one or more of polymethyl silicone resin, polyethyl silicone resin, and polyvinyl silicone resin.

[0022] In some embodiments of this application, the volumetric particle size distribution Dv50 of the positive electrode active material is 5.1 μm to 9.0 μm.

[0023] In some embodiments of this application, the thickness of the outer shell layer is <0.5μm, preferably 0.05μm to 0.45μm.

[0024] In some embodiments of this application, the positive electrode active material includes any one or more of the following: lithium-rich solid solution positive electrode material, nickel-manganese spinel positive electrode material, high-nickel positive electrode material, polyanionic positive electrode material, and modified lithium cobalt oxide positive electrode material.

[0025] In some embodiments of this application, the positive electrode includes a positive electrode film layer, the compaction density of which is greater than or equal to 2.9 g / cm³. 3 The preferred value is 2.9 g / cm³. 3 ~3.4g / cm 3 .

[0026] In some embodiments of this application, the lithium-ion battery further includes an electrolyte, which comprises one or more of fluorocarbonates, sulfones, and nitrile compounds.

[0027] A second aspect of this application is to provide a lithium-ion battery, which includes a positive electrode, a separator, and a negative electrode stacked together.

[0028] The aforementioned positive electrode sheet includes a positive electrode material having a core-shell structure, the core-shell structure including a core and an outer shell layer, the outer shell layer being located on at least a portion of the surface of the core;

[0029] The core contains positive electrode active material;

[0030] The outer shell contains lithium, sulfur, and silicon.

[0031] A third aspect of this application is to provide a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode film layer located on at least one side surface of the positive current collector;

[0032] The positive electrode film layer contains a positive electrode material, which has a core-shell structure, including a core and an outer shell layer, with the outer shell layer located on at least a portion of the surface of the core.

[0033] The core contains positive electrode active material;

[0034] The outer shell contains lithium, sulfur, and silicon.

[0035] The fourth aspect of this application is to provide a method for preparing a positive electrode sheet, comprising the following steps:

[0036] Preparation of composite materials: Lithium-containing compounds, sulfur-containing compounds and silicon-containing organic compounds are pulverized and mixed to obtain composite materials;

[0037] Preparation of positive electrode slurry: Take positive electrode active material and composite material, mix them evenly and disperse them in an organic solvent to form positive electrode slurry;

[0038] Preparation of positive electrode sheet: The positive electrode slurry is coated on at least one side of the surface of the positive electrode current collector to form a positive electrode film layer.

[0039] In some embodiments of this application, the lithium-containing compound includes any one or more of lithium oxalate, lithium squaric acid, lithium carbonate, lithium hydroxide, lithium oxide, lithium nitrate, and lithium silicate.

[0040] and / or;

[0041] Sulfur-containing substances include any one or more of elemental sulfur, sodium sulfide, and sodium sulfite;

[0042] and / or;

[0043] Silicon-containing organic compounds include silicone resins, which include polyalkyl silicone resins, wherein the average degree of substitution of hydrocarbon groups in the polyalkyl silicone resin is ≤1.

[0044] In some embodiments of this application, the silicone-containing organic material includes one or more of polymethyl silicone resin, polyethyl silicone resin, and polyvinyl silicone resin.

[0045] In some embodiments of this application, the mass ratio of lithium element in lithium-containing compounds, sulfur element in sulfur-containing compounds, and silicon element in silicon-containing organic compounds is (10.0%–15.5%):(5.0%–9.2%):(7.3%–14.9%).

[0046] In some embodiments of this application, the composite material further includes a conductive agent;

[0047] The conductive agent has a mass percentage content of 8% to 15% in the above composite material;

[0048] The conductive agent includes one or more of graphite, superconducting carbon, carbon black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0049] In some embodiments of this application, the mass percentage content of the composite material in the above-mentioned positive electrode film layer is 2% to 6%.

[0050] The fifth aspect of this application is to provide an electrical device comprising the battery device described in the first aspect, the lithium-ion battery described in the second aspect, the positive electrode sheet described in the third aspect, or the positive electrode sheet prepared by the preparation method described in the fourth aspect.

[0051] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0052] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0053] Figure 1 This is a schematic diagram of the battery structure of some embodiments of this application;

[0054] Figure 2 This is an exploded structural diagram of a battery according to some embodiments of this application;

[0055] Figure 3 This is a schematic diagram of the vehicle structure according to some embodiments of this application;

[0056] Figure 4 This is a schematic diagram of the battery pack structure according to some embodiments of this application;

[0057] Figure 5 This is a schematic diagram of the electrical connection between the battery pack and the battery management system in some embodiments of this application;

[0058] Figure 6 This is a schematic diagram of the structure of the positive electrode active material in some embodiments of this application;

[0059] Figure 7A , Figure 7B , Figure 8 These are test diagrams for some embodiments of this application;

[0060] The reference numerals in the detailed embodiments are as follows:

[0061] 10000, vehicles;

[0062] 1000, Battery; 2000, Controller; 3000, Motor;

[0063] 100. Battery cell;

[0064] 200. Box body; 210. First part; 220. Second part;

[0065] 10. Secondary batteries;

[0066] 300. Battery Management System;

[0067] 101. Housing; 102. Electrode assembly; 103. Cover plate;

[0068] 1. Core-shell structure; 11. Core; 12. Outer shell. Detailed Implementation

[0069] The following detailed description, with appropriate reference to the accompanying drawings, discloses the positive electrode sheet of this application, its preparation method, and embodiments of lithium-ion batteries, battery devices, and power-consuming devices. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0070] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is also expected that ranges of 60–110 and 80–120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0071] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0072] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0073] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0074] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0075] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0076] Unless otherwise specified, in this application, the terms "first," "second," etc., are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features.

[0077] Unless otherwise specified, in this application, the term "multiple" means two or more (including two), similarly, "multiple sets" means two or more (including two sets), and "multiple pieces" means two or more (including two pieces).

[0078] Unless otherwise specified, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0079] Lithium-ion batteries have been widely used in various products due to their advantages such as high energy density, long cycle life, and safety and reliability. In recent years, with the significant increase in demand for lithium-ion batteries as an energy source, higher requirements have been placed on their performance, such as energy density and cycle stability.

[0080] Employing high-voltage cathode materials is a crucial way to improve the energy density of lithium-ion batteries, such as nickel-manganese spinel cathode materials, high-nickel cathode materials, and lithium-rich cathode materials. However, at high voltages, the cathode material structure becomes unstable and prone to collapse, and side reactions between the cathode material and the electrolyte can cause a decline in the electrochemical performance of lithium-ion batteries. Furthermore, the difference in electronic and ionic conductivity between high-voltage cathode materials leads to defects in rate performance and cycle performance.

[0081] To overcome the aforementioned defects, current solutions primarily involve elemental doping and surface coating of the cathode material. This approach mitigates, to some extent, the collapse of the cathode material and the oxidative decomposition of the electrolyte under high voltage. Currently, coating materials mainly include metals and their oxides, which can effectively suppress side reactions between the cathode material and the electrolyte. However, these methods typically suffer from uneven coating, high processing temperatures, and poor ionic conductivity, making it difficult to achieve ideal coating results. Polymers, especially conductive polymers, are also frequently used to coat cathode materials, improving conductivity while protecting the cathode material structure. However, conductive polymers have poor ionic conductivity, and the coating layer is detrimental to Li... + The rapid transmission has a limited impact on the overall battery performance.

[0082] Based on the above considerations, in order to improve the rate performance and cycle performance of lithium-ion batteries containing high-voltage positive electrode active materials, this application discloses a positive electrode sheet and its preparation method, as well as a lithium-ion battery, battery device, and power consumption device.

[0083] First, this application discloses a battery device including a lithium-ion battery and a battery management system. The lithium-ion battery includes a positive electrode, a separator, and a negative electrode, wherein the positive electrode, separator, and negative electrode are sequentially stacked to form a wound cell or a stacked cell. Meanwhile, the positive electrode includes a positive electrode material having a core-shell structure, comprising a core and an outer shell layer, with the outer shell layer located on at least a portion of the surface of the core. The core contains a positive electrode active material. The outer shell layer of the core-shell structure contains lithium, sulfur, and silicon. Furthermore, the charging cutoff voltage of the battery device in the battery management system is greater than 4.5V.

[0084] The cathode material provided in this application has a core-shell structure, which includes a core and an outer shell layer located on at least a portion of the surface of the core. The core contains a cathode active material, and the outer shell layer isolates the cathode active material from the outside world, thereby reducing the ion dissolution of the cathode active material to a certain extent, alleviating the structural collapse of the cathode active material and its oxidative decomposition with the electrolyte, and thus improving the cycle stability of the lithium-ion battery.

[0085] Meanwhile, the lithium element in the outer shell layer acts as a lithium replenishment material, primarily supplying lithium ions to the negative electrode to compensate for the lithium ions consumed during SEI film formation, thereby improving the initial efficiency of the lithium-ion battery. The sulfur element in the outer shell layer reacts with lithium to form a CEI film, which is part of the outer shell layer and exhibits strong oxidation resistance, serving as a protective film for the positive electrode active material. Silicon is filled between the CEI film and the positive electrode active material, and this silicon-containing material supports the CEI film. Furthermore, the sulfur element in the outer shell layer serves two purposes: firstly, to regulate the kinetics of lithium delithiation in the replenishment material to improve the battery's rate performance; and secondly, to contribute to the formation of a high-quality SEI layer to reduce irreversible lithium loss. Therefore, the lithium-ion battery designed in this application possesses advantages such as high energy density and good cycle stability, and also improves the battery's rate performance to a certain extent.

[0086] Therefore, the lithium-ion battery provided in this application is beneficial for improving the cycle stability and rate capability of the battery under high-voltage operating conditions, thereby enhancing the user experience. As a type of rechargeable battery, the lithium-ion battery may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte composed of the aforementioned lithium-ion battery. The outer packaging of the lithium-ion battery can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging of the lithium-ion battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic, including but not limited to polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0087] This application does not impose any particular limitation on the shape of the secondary battery containing lithium-ion batteries; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 10.

[0088] According to some embodiments of this application, reference is made to Figure 2 The outer packaging may include a housing 101 and a cover plate 103. The housing 101 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 101 has an opening communicating with the receiving cavity, and the cover plate 103 can be placed over the opening to close the receiving cavity. Positive electrode sheets, negative electrode sheets, and separators may be formed into electrode assemblies 102 through a winding process or a stacking process. The electrode assembly 102 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 102. The secondary battery 10 may contain one or more electrode assemblies 102, which can be selected by those skilled in the art according to specific practical needs.

[0089] The electrode assembly 102 provided in this application is beneficial to improving the performance of a secondary battery when applied in a secondary battery. The secondary battery can be a power source for an electrical device or an energy storage unit for an electrical device. The electrical device is applied in the power field, such as mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited to the above fields.

[0090] For ease of explanation, some embodiments of this application are illustrated using a vehicle as an example of an electrical device.

[0091] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the structure of a vehicle 10000 provided in some embodiments of this application. The vehicle 10000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery 1000 is disposed inside the vehicle 10000, and the battery 10000 can be located at the bottom, front, or rear of the vehicle 10000. The battery 10000 can be used to power the vehicle 10000; for example, the battery 10000 can serve as the operating power source for the vehicle 10000. The vehicle 10000 may also include a controller 2000 and a motor 3000. The controller 2000 is used to control the battery 10000 to supply power to the motor 3000, for example, to meet the power needs of the vehicle 10000 during startup, navigation, and driving.

[0092] In some embodiments of this application, the battery 1000 can not only serve as the operating power source for the vehicle 10000, but also as the driving power source for the vehicle 10000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 10000.

[0093] Please refer to Figure 4 , Figure 4 This is an exploded view of a battery 1000 provided in some embodiments of this application. The battery 1000 includes a housing 200 and a battery cell 100. A conventional battery cell includes a primary battery or a secondary battery. This application specifically protects a secondary battery 10. The battery cell 100 is housed within the housing 200. The housing 200 provides space for the battery cell 100, and the housing 200 can adopt various structures.

[0094] In some embodiments, the housing 200 may include a first portion 210 and a second portion 220, which overlap each other, and together define a receiving space for accommodating the secondary battery 100. The second portion 220 may be a hollow structure with one open end, and the first portion 210 may be a plate-like structure, with the first portion 210 covering the open side of the second portion 220 so that the first portion 210 and the second portion 220 together define the receiving space; alternatively, the first portion 210 and the second portion 220 may both be hollow structures with one open side, with the open side of the first portion 210 covering the open side of the second portion 220. Of course, the housing 200 formed by the first portion 210 and the second portion 220 may be of various shapes, such as a cylinder, a cuboid, etc.

[0095] In battery 1000, there can be multiple battery cells 100, which can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 100 are connected in both series and parallel configurations. Multiple battery cells 100 can be directly connected in series, parallel, or in a mixed manner, and then the entire assembly of the multiple battery cells 100 is housed within housing 200. Alternatively, battery 1000 can also be composed of multiple battery cells 100 first connected in series, parallel, or in a mixed manner to form battery modules, and then these modules are connected in series, parallel, or in a mixed manner to form a whole, which is also housed within housing 200. Battery 1000 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 100.

[0096] In some embodiments of this application, such as Figure 5 The battery device includes the aforementioned housing 200, and also includes a battery management system 300 electrically connected to the housing 200. The battery management system 300 is used to control or adjust the operating state or operating parameters of the individual battery cells 100 inside the housing 200. For example, in some embodiments of this application, the charging cutoff voltage of the battery device is set in the battery management system to be greater than 4.5V.

[0097] Battery device

[0098] This application discloses a battery device in some embodiments, the battery device including a lithium-ion battery and a battery management system; the lithium-ion battery includes a positive electrode, a separator and a negative electrode stacked together, the positive electrode includes a positive electrode material, the positive electrode material has a core-shell structure, the core-shell structure includes a core and a shell layer, the shell layer is located on at least a portion of the surface of the core; the core contains a positive electrode active material; the shell layer contains lithium, sulfur and silicon; the charging cut-off voltage of the battery device in the battery management system is greater than 4.5V.

[0099] The core-shell structure of this application is as follows: Figure 6 The core-shell structure 1 includes a core 11 and an outer shell layer 12 covering the surface of the core 11. The outer shell layer 12 is located on at least a portion of the surface of the core 11. Here, "at least a portion" includes a portion of the surface, such as the outer shell layer 12 being located on the surface of the core 11 in a point-like manner, and also includes the outer shell layer 12 being located on all surfaces of the core 11.

[0100] The outer shell layer 12 of this application isolates the core positive electrode active material from the outside world, which reduces the ion dissolution of the positive electrode active material to a certain extent and alleviates the structural collapse of the positive electrode active material under high voltage and the degree of oxidative decomposition between it and the electrolyte.

[0101] The battery management system of this application is used to control or adjust the operating status or operating parameters of a lithium-ion battery.

[0102] The battery management system of this application sets the charging cutoff voltage of the aforementioned battery device to be greater than 4.5V. This charging cutoff voltage indicates the voltage at which charging of the battery stops. Actual battery charging methods include constant current and constant voltage charging, where constant current charging refers to a charging method that maintains a constant current value throughout the entire charging process or a portion of the time. Constant voltage charging refers to a charging method that maintains a constant battery voltage during charging. Constant current and constant voltage charging is a charging method that combines constant current charging and constant voltage charging. In the initial stage of charging, a small charging rate (e.g., less than 0.1C) is selectively used to charge the battery based on its voltage. After the battery reaches a preset voltage, constant current charging is initiated, where the charging current is constant and the battery voltage gradually increases. After the battery reaches the preset charging cutoff voltage, it enters the constant voltage charging stage, where the charging current gradually decreases and the battery voltage remains constant. When the charging current decreases to below the preset charging cutoff current, the charging process ends.

[0103] The outer shell layer 12 of this application contains lithium, sulfur, and silicon. The method for determining these elements involves bombarding the outer shell layer sample or a cross-sectional sample of the outer shell layer with an electron beam generated by an energy-dispersive X-ray spectrometer. Since different elements emit characteristic X-rays with different energies, various different elements can be identified.

[0104] The lithium element in the outer shell layer 12 of this application serves as a lithium replenishment material, primarily supplying lithium ions to the negative electrode to compensate for the lithium ions consumed during SEI film formation, thereby improving the battery's initial efficiency or cycle life. The sulfur element in the outer shell layer 12 reacts with lithium ions to form a CEI film, which is part of the outer shell layer and exhibits strong oxidation resistance, serving as a protective film for the positive electrode active material. Silicon is filled between the CEI film and the positive electrode active material, and this silicon-containing material supports the CEI film. The sulfur element in the outer shell layer 12 serves two purposes: firstly, to regulate the kinetics of lithium removal from the replenishment material to improve the battery's rate performance; and secondly, to contribute to the formation of a high-quality SEI layer to reduce irreversible lithium loss.

[0105] The lithium-ion battery provided in this application isolates the core positive electrode active material from the external environment through the outer shell layer itself and the CEI film formed by the reaction between the elements in the outer shell layer and the electrolyte. This reduces ion dissolution of the positive electrode active material to a certain extent, alleviates the structural collapse of the positive electrode active material under high voltage and the degree of oxidative decomposition between it and the electrolyte, thus improving the cycle stability of the battery. At the same time, the lithium element in the outer shell layer acts as a lithium replenishing material, mainly used to supply lithium ions to the negative electrode to replenish the lithium ions consumed during the formation of the SEI film, thereby improving the first-time efficiency of the lithium-ion battery. In addition, some elements in the outer shell layer can be used to adjust the kinetic performance of lithium removal from the replenishing material to improve the rate performance of the battery, and can also form a high-quality SEI layer to reduce irreversible lithium loss. Therefore, the lithium-ion battery provided in this application improves the first-time efficiency, energy density, and cycle stability of the battery by increasing the structural stability of the positive electrode active material under high voltage, and improves the rate performance of the battery by utilizing the role of sulfur element in the outer shell layer in adjusting the kinetic performance of lithium removal from the replenishing material.

[0106] In some embodiments of this application, it is disclosed that the mass percentage content of lithium in the aforementioned outer shell layer is 10.0% to 15.5%. The specific determination method includes SEM-EDS, and the testing steps include: using a FESEM instrument (JEOL JSM-7900F) at an accelerating voltage of 5 kV to perform EDS mapping at a rate of x10,000 times to determine the content of sulfur, silicon, carbon, and oxygen, with the remainder being lithium or other elements.

[0107] In these embodiments, this application discloses that the mass percentage content of lithium element in the aforementioned outer shell layer is any one of 10.0% to 10.5%, 10.0% to 11.0%, 10.0% to 11.5%, 11.5% to 12%, 12.0% to 15.5%, or any one of the aforementioned ranges.

[0108] In these embodiments, this application discloses that the mass percentage content of lithium in the aforementioned outer shell layer is 10.0%, 10.1%, 10.2%, 10.3%, 10.4%, 10.5%, 10.6%, 10.7%, 10.8%, 10.9%, 11.0%, 11.1%, 11.2%, 11.3%, 11.4%, 11.5%, 11.6%, 11.7%, 11.8%, 11.9%, 12.0%, 12.1%, 12.2%, 12.3%, 12.4%, 12.5%, and 12.6%. The lithium content is 12.7%, 12.8%, 12.9%, 13.0%, 13.1%, 13.2%, 13.3%, 13.4%, 13.5%, 13.6%, 13.7%, 13.8%, 13.9%, 14.0%, 14.1%, 14.2%, 14.3%, 14.4%, 14.5%, 14.6%, 14.7%, 14.8%, 14.9%, 15.0%, 15.1%, 15.2%, 15.3%, 15.4%, or 15.5%, or any value within the range described above. The method for testing the lithium content in this application is the same as described above and will not be repeated here.

[0109] In some embodiments, this application discloses that the sulfur content in the outer shell layer is 5.0% to 9.2% by mass.

[0110] In these embodiments, this application discloses that the mass percentage content of sulfur in the aforementioned outer shell layer is any one of 5.0%–6%, 5.0%–7%, 5.0%–8%, 5.0%–9%, ​​5.0%–10%, 5.0%–10%, 5.5%–10%, 6.5%–10%, 7.5%–10%, 8.5%–10%, or 9.5%–10%, or any one of the aforementioned ranges.

[0111] In these embodiments, this application discloses that the mass percentage content of sulfur in the aforementioned outer shell layer is any one of 5.0%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7.0%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, 8.0%, 8.1%, 8.2%, 8.3%, 8.4%, 8.5%, 8.6%, 8.7%, 8.8%, 8.9%, 9.0%, 9.1%, and 9.2%, or any one of the above-mentioned ranges. The test method for sulfur content in this application is the same as above, and will not be repeated here.

[0112] In some embodiments, this application discloses that the mass percentage content of silicon in the aforementioned outer shell layer is 7.3% to 14.9%.

[0113] In these embodiments, this application discloses that the mass percentage content of silicon element in the aforementioned outer shell layer is any one of 7.3%–8%, 7.3%–9%, ​​7.3%–10%, 7.3%–11%, 7.3%–12%, 7.3%–13%, 7.3%–14%, 7.3%–15%, 7%–14.9%, 8%–14.9%, 9%–14.9%, 10%–14.9%, 11%–14.9%, 12%–14.9%, 13%–14.9%, and 14%–14.9%, or any one of the aforementioned ranges.

[0114] In these embodiments, this application discloses that the mass percentage content of silicon in the aforementioned outer shell layer is 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11.0, 11.1, and 11.2. The silicon content is determined by any one of the following values: 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 12.0, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.8, 12.9, 13.0, 13.1, 13.2, 13.3, 13.4, 13.5, 13.6, 13.7, 13.8, 13.9, 14.0, 14.1, 14.2, 14.3, 14.4, 14.5, 14.6, 14.7, 14.8, 14.9, or any one of the values ​​within the above range. The method for testing the silicon content in this application is the same as described above and will not be repeated here.

[0115] This application discloses in some embodiments that the outer shell of the core-shell structure further includes carbon and oxygen elements, and the mass percentage content of carbon in the outer shell is 17% to 20.8%.

[0116] In some embodiments, this application discloses that the mass percentage content of carbon element in the aforementioned outer shell layer is any one of 17%–18%, 17%–19%, 17%–20%, 17%–21%, 18%–20.8%, 19%–20.8%, 20%–20.8%, or any one of the aforementioned ranges.

[0117] In these embodiments, this application discloses that the mass percentage content of carbon element in the aforementioned outer shell layer is any one of 17%, 17.1%, 17.2%, 17.3%, 17.4%, 17.5%, 17.6%, 17.7%, 17.8%, 17.9%, 18.0%, 18.1%, 18.2%, 18.3%, 18.4%, 18.5%, 18.6%, 18.7%, 18.8%, 18.9%, 19.0%, 19.1%, 19.2%, 19.3%, 19.4%, 19.5%, 19.6%, 19.7%, 19.8%, 19.9%, 20.0%, 20.1%, 20.2%, 20.3%, 20.4%, 20.5%, 20.6%, 20.7%, and 20.8%, or any one of the aforementioned ranges. The method for testing the carbon element content in this application is the same as described above and will not be repeated here.

[0118] In some embodiments, this application discloses that the oxygen content in the outer shell layer is 45% to 59% by mass.

[0119] In some embodiments, this application discloses that the mass percentage content of oxygen in the aforementioned outer shell layer is any one of 45% to 50%, 50% to 59%, or any one of the aforementioned ranges.

[0120] In these embodiments, this application discloses that the mass percentage content of oxygen in the aforementioned outer shell layer is any one of 45%, 45.5%, 46%, 46.5%, 47%, 47.5%, 48%, 48.5%, 49%, 49.5%, 50%, 50.5%, 51%, 51.5%, 52%, 52.5%, 53%, 53.5%, 54%, 54.5%, 55%, 55.5%, 56%, 56.5%, 57%, 57.5%, 58%, 58.5%, and 59%, or any one of the above ranges. The method for testing the oxygen content in this application is the same as above, and will not be repeated here.

[0121] In some embodiments, this application discloses that the outer shell layer of the core-shell structure comprises an organosilicon resin having a network structure; the outer shell layer contains lithium sulfate, which is distributed in the network structure.

[0122] The organosilicon resin of this application, also known as polysiloxane, is a class of polymers with a network structure composed of alternating silicon and oxygen atoms, and various organic groups linked to silicon atoms. Organosilicon resins contain both "organic groups" and "inorganic structures," a unique composition and molecular structure that combines the properties of organic and inorganic substances. One of the most prominent properties of organosilicon resins is their excellent thermal oxidation stability. They also possess outstanding weather resistance, thus the organosilicon resin provided in this application has advantages such as resistance to electrolyte corrosion and resistance to softening under heating. The characterization method for the network structure of this organosilicon resin includes sampling the outer shell layer and then obtaining its network structure using high-magnification electron microscopy (SEM, two-dimensional image) or atomic force microscopy (AFM, three-dimensional image). In this application, lithium sulfate is distributed within the network structure of the organosilicon resin. This network structure provides channels for lithium-ion transport, which helps to reduce the impact of the outer shell layer on the lithium-ion conductivity caused by the core coating. Meanwhile, the sulfur element in lithium sulfate can also regulate the kinetics of lithium ions to improve the rate performance of the battery. Therefore, the core-shell structure provided in this application is beneficial to improving the ionic conductivity of the cathode material under high voltage operation, thereby improving the rate performance of the battery. Furthermore, the organosilicon resin in this application possesses excellent thermal oxidation stability. Its coating on the surface of the cathode active material further forms a CEI film with good stability and high oxidation resistance. Therefore, this CEI film isolates the cathode active material from the external environment, reducing ion dissolution to a certain extent and alleviating the structural collapse of the cathode active material and its oxidative decomposition with the electrolyte.

[0123] This application discloses in some embodiments that the silicone resin includes a polyalkyl silicone resin having an average degree of substitution of hydrocarbon groups DS≤1.

[0124] Based on the different organic substituents on the silicon atoms in the siloxane chain, the organosilicon resins in this application can be basically divided into three categories: polyalkyl organosilicon resins, polyaryl organosilicon resins, and polyalkylaryl organosilicon resins. This application selects polyalkyl organosilicon resins, and the average degree of substitution (DS) of the hydrocarbon groups in the polyalkyl organosilicon resin is ≤1. The average degree of substitution (DS) in this application refers to the average number of hydrocarbon groups (ester hydrocarbons) attached to each silicon atom in the organosilicon polymer, and its calculation formula is as follows: DS = ∑(molar fraction of a monomer component × number of hydrocarbon groups in that monomer molecule) / 100. The selection of a polyalkyl organosilicon resin with an average degree of substitution (DS) ≤1 indicates a relatively high degree of crosslinking, mainly a network structure. This network structure is not easily softened under heating and is not easily dissolved in organic solvents. After separating the organosilicon resin for the positive electrode sheet, the functional groups can be determined by infrared spectroscopy, and the elements can be conveniently determined by EDS. Given the type of organosilicon resin, the type and content of the monomers can be known, thus facilitating the calculation of DS.

[0125] This application discloses in some embodiments that the aforementioned organosilicon resin comprises any one or more of polymethyl silicone resin, polyethyl silicone resin, and polyvinyl silicone resin.

[0126] The polymethyl silicone resin in this application is generally composed of SiO₂. 3 / 2 CH3SiO 3 / 2 (CH3)3SiO 2 / 2 (CH)SiO 1 / 2 A copolymer composed of siloxane units, wherein the methyl content is 0.2–0.5 mol / 100g.

[0127] The polyethyl silicone resin used in this application generally refers to a copolymer containing ethyl groups in the polysiloxane chain. The ethyl content is 0.077 to 0.101 mol / 100g.

[0128] The polyvinyl silicone resin used in this application generally refers to a copolymer containing vinyl groups in the polysiloxane chain. The vinyl content is 0.05 mol to 0.1 mol / 100g. In these embodiments, this application provides vinyl content of any one of 0.05 mol / 100g, 0.06 mol / 100g, 0.07 mol / 100g, 0.08 mol / 100g, 0.09 mol / 100g, and 0.1 mol / 100g, or any value within the aforementioned range.

[0129] The types of silicone resins listed in this application have the advantages of high heat resistance and strong oxidation resistance.

[0130] This application discloses in some embodiments that the volumetric particle size distribution Dv50 of the positive electrode active material is 5.1 μm to 9.0 μm.

[0131] The volumetric particle size distribution Dv50 in this application includes particles larger than its diameter accounting for 50% of the total volume, and particles smaller than its diameter also accounting for 50% of the total volume. Also known as the median diameter, it is typically used to represent the average particle size. It can be measured using conventional methods in the art, such as using a particle size analyzer to determine the particle size distribution and then obtaining the result statistically. In these embodiments, this application selects to measure it using laser diffraction particle size analysis, specifically referring to standard GB / T19077-2016 to obtain the particle size distribution map, and then calculating the result.

[0132] In these embodiments, this application discloses that the volumetric particle size distribution Dv50 of the positive electrode active material is any one of 5.1μm~6.0μm, 5.1μm~6.5μm, 5.1μm~7.0μm, 5.1μm~7.5μm, 5.1μm~8.0μm, 5.1μm~8.5μm, 5.1μm~9.0μm, 6.0μm~9.0μm, 7.0μm~9.0μm, 8.0μm~9.0μm, or any one of the above range values.

[0133] In these embodiments, this application discloses that the volumetric particle size distribution Dv50 of the positive electrode active material is 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6.0 μm, 6.1 μm, 6.2 μm, 6.3 μm, 6.4 μm, 6.5 μm, 6.6 μm, 6.7 μm, 6.8 μm, and 6.9 μm. The value can be any one of the following: 7.0μm, 7.1μm, 7.2μm, 7.3μm, 7.4μm, 7.5μm, 7.6μm, 7.7μm, 7.8μm, 7.9μm, 8.0μm, 8.1μm, 8.2μm, 8.3μm, 8.4μm, 8.5μm, 8.6μm, 8.7μm, 8.8μm, 8.9μm, 9.0μm, or any one of the values ​​within the above range.

[0134] This application discloses in some embodiments that the thickness of the outer shell layer is <0.5μm, such as 0.05μm, 0.055μm, 0.1μm, 0.102μm, 0.123μm, 0.156μm, 0.158μm, 0.162μm, 0.165μm, 0.2μm, 0.21μm, 0.25μm, 0.3μm, 0.35μm, 0.38μm, 0.39μm, 0.4μm, 0.41μm, 0.42μm, 0.43μm, 0.44μm, 0.45μm, 0.48μm, etc.

[0135] In some embodiments, this application discloses that the thickness of the outer shell layer is 0.05 μm to 0.45 μm.

[0136] This application discloses in some embodiments that the positive electrode active material includes any one or more of the following: lithium-rich solid solution positive electrode material, nickel-manganese spinel positive electrode material, high-nickel positive electrode material, polyanionic positive electrode material, and modified lithium cobalt oxide positive electrode material.

[0137] The lithium-rich solid solution cathode material in this application has a layered structure, and its composition can be found in...

[0138] Li (Li 1 / 3 Mn 2 / 3)O2—LiCoO2—LiNiO2—LiNi 0.5 Mn 0.5 O2 quaternary phase diagram, and the chemical formula can be written as xLi(Li 1 / 3 Mn 2 / 3 )O2·(1 - x)LiMO2 or Li 1+x M 1-x O2(0 < x < 1). Among them, the component Li(Li 1 / 3 Mn 2 / 3 )O2 (or Li2MnO3) structure belongs to the layered monoclinic system, and LiMO2 (M = one or several of Ni, Co or Mn) belongs to the layered hexagonal system. Their lattice constants are close, and it is easy to form a solid solution. In (1 + x) moles of Li, 1 mole of Li occupies 3a, and x moles of Li and transition metals such as Ni, Mn, and Co occupy the 3b position. Due to the radius of Li + (R Li + = 0.076nm) and the radius of Ni 2+ (R Ni 2+ = 0.069nm) are very close, so Ni 2+ in the transition metal layer is very easy to migrate to the Li + layer, which will hinder the diffusion of Li + in the crystal structure during the charge - discharge process. To a certain extent, it increases the polarization phenomenon of the material and affects the rate performance of the material. To prevent the mixing of Li + / Ni 2+ , when preparing the layered lithium - rich solid - solution cathode material, it is necessary to add more lithium sources than the stoichiometric ratio. Too high lithium content often results in a relatively high total base amount on the surface of the prepared layered lithium - rich material, deteriorating the high - temperature cycle and storage performance. On the other hand, the deterioration of the high - temperature cycle and storage performance of the layered lithium - rich solid - solution material is not only related to the total surface base amount, but also related to the dissolution of surface transition metal ions in the electrolyte or the surface reaction between the material / electrolyte, especially when in a high - charge state (above 4.5V), the dissolution of transition metal ions and the material / electrolyte interface reaction are more significant. The outer shell layer provided by this application is beneficial to alleviating the above problems.

[0139] This application discloses in some embodiments that the general formula of the lithium - rich solid - solution cathode material is

[0140] Li n X m Mn a Co b Ni c M dO2, 1.0≤n≤1.6, 0≤m≤0.3, 0.4≤a≤1, 0.05≤b≤0.2, 0.05≤c≤0.2, 0≤d≤0.2, X includes Na, K, Mg, Ca or Zn, and M includes Fe, Cr, Al, Zr or La. In these embodiments, n includes any one of 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 or any one of the above-mentioned range values. m includes any one of 0, 0.1, 0.2, 0.3 or any one of the above-mentioned range values. a includes any one of 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 or any one of the above-mentioned range values. b includes 0.05, 0.05, ...

[0141] This application discloses, in some embodiments, a nickel-manganese spinel cathode material with the general formula Li. 1+x M y Mn 2-y O 4： M includes one or more of Ni, Mn, Co, Al, V, Cu, and Cr; y = 0 to 1.5, 0 < X ​​≤ 1; wherein, in some embodiments of this application, LiNi is selected as a high-voltage spinel structure cathode material. 0.5 Mn 1.5 O4 (LNMO) is characterized by a voltage plateau of 4.7V (vs. Li / Li+), which is achieved by utilizing nickel (Ni) 2+ / 4+ The total redox capacity of ). Therefore, although its actual capacity is only 120-140 mAh g. -1 However, its energy density can reach 650Wh / kg. -1 above.

[0142] The structure of the nickel-manganese spinel cathode material of this application is closely related to its preparation method, which includes: solid-state method, sol-gel method, high-temperature molten salt method, latex drying method, ultrasonic spray high-temperature decomposition method, polymer high-temperature decomposition method, and precipitation method, etc.

[0143] The chemical formula of the high-nickel cathode material in this application is Li. a Ni x Co y M z O2, wherein M is selected from one or more combinations of Mn, Al, Zr, Ti, V, Mg, Fe, Mo, Ta, W, Nb, Sb, and La, 1≤a≤2; and x+y+z=1, 0.9≤x<1, 0≤y<0.1.

[0144] The polyanionic cathode materials in this application include lithium iron pyrophosphate (LiFePO4), sodium vanadium phosphate (Li3V2(PO4)3), LiM'PO4F (M' is one or more of V, Fe, Mn and Ni), and Li3(VO4)2(PO4)3. y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0145] In these embodiments, this application discloses polyanionic compounds comprising one or more of lithium vanadium trifluorophosphate (Li3V2(PO4)2F3), lithium vanadium fluorophosphate (LiVPO4F), lithium vanadium phosphate (Li3V2(PO4)3), lithium iron pyrophosphate (Na4Fe3(PO4)2(P2O7)), and lithium iron pyrophosphate (LiFePO4).

[0146] This application describes a modified lithium cobalt oxide cathode material comprising a coated lithium cobalt oxide cathode material. The coating material is beneficial for increasing the interfacial stability of lithium cobalt oxide, for example, by utilizing a solid electrolyte material, Li. 1.5 Al 0.5 Ti 1.5 (PO4)3(LATP)-coated lithium cobalt oxide. During the material synthesis process, LATP reacts with lithium cobalt oxide to form a uniform interface layer on the surface with high structural and electrochemical stability and excellent ionic and electronic conductivity, thus effectively solving the surface stability problem of lithium cobalt oxide during high-voltage charging.

[0147] This application discloses in some embodiments that the positive electrode includes a positive electrode film layer, and the compaction density of the positive electrode film layer is greater than or equal to 2.9 g / cm³. 3 .

[0148] The positive electrode film layer in this application is located on one or both surfaces of the positive electrode current collector. Typically, the positive electrode film layer is located on both surfaces of the positive electrode current collector, and its formation methods include coating or deposition. This application will use both sides as examples in the following examples. Meanwhile, the compaction density of the positive electrode film layer in this application can be used to characterize the energy density of the material; however, the compaction density of the positive electrode film layer is used to evaluate the overall compaction density of the positive electrode sheet. The compaction density of the positive electrode film layer = areal density of the positive electrode film layer / thickness of the positive electrode film layer. The thickness of the positive electrode film layer includes the distance between the two end faces of the positive electrode film layer along the thickness direction. The areal density of the positive electrode film layer = weight of a single-sided positive electrode film layer / area of ​​a single-sided positive electrode film layer. The weight of a single-sided positive electrode film layer can be obtained by weighing, and the area of ​​a single-sided positive electrode film layer can be obtained by using an area calculation formula based on the shape of the film layer. In these embodiments, this application lists a positive electrode film layer compaction density greater than or equal to 2.9 g / cm³. 3 The upper limit of the compaction density of the positive electrode film is a conventional value in the art, and will not be elaborated upon in this application.

[0149] This application discloses in some embodiments that the compaction density of the positive electrode film is 2.9 g / cm³. 3 ~3.4g / cm 3 .

[0150] This application discloses in these embodiments that the compaction density of the positive electrode film layer includes 2.9 g / cm³. 3 3.0g / cm 3 3.1g / cm 3 3.2g / cm 3 3.3g / cm 3 3.4g / cm 3 Any one of the above values ​​or any one of the above range values.

[0151] This application discloses in some embodiments that the lithium-ion battery further includes an electrolyte comprising one or more of fluorocarbonates, sulfones, and nitrile compounds.

[0152] The fluorinated carbonates of this application exhibit high electrochemical stability due to the strong electronegativity and weak polarity of the fluorine atom. Replacing the carbonate solvent with fluorine enhances its antioxidant capacity and facilitates the formation of a solid electrolyte interphase (SEI) film on the negative electrode surface. For example, fluoroethylene carbonate (FEC) can also form a protective film on the positive electrode surface, which is beneficial for improving the cycle stability of the electrode.

[0153] In these embodiments, this application discloses an electrolyte comprising carbonates and fluorocarbonates, wherein the fluorocarbonate comprises fluoroethylene carbonate (FEC), and the carbonate comprises one or more of ethylene carbonate (EC), propylene carbonate (PC), ethylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and butyl carbonate (BC).

[0154] The sulfone solvents used in this application exhibit higher thermal stability than conventional carbonate solvents, while also possessing good electrochemical stability; for example, the oxidation potentials of sulfolane (TMS) and methyl ethyl sulfone (EMS) are both above 5V. However, they are generally solids or have high viscosity at room temperature and are typically used in conjunction with existing carbonate solvents to lower their melting point and viscosity. Sulfone solvents cannot form a stable SEI film on graphite surfaces, necessitating the introduction of film-forming additives.

[0155] The sulfone solvents of this application include at least one or more combinations of sulfolane (SF), dimethyl sulfone (MSM), ethyl sulfone (EMS), diethyl sulfone (ESE), and sulfone fluoride (FMES).

[0156] The nitrile solvents of this application exhibit high electrochemical stability; for example, glutaronitrile (GLN) has an oxidation potential as high as 8.3V (vs. Li / Li). + It has higher stability than most aprotic solvents; however, it has poor compatibility with graphite anodes, which can be improved by adding EC, etc.

[0157] The nitrile solvents of this application include one or more of acetonitrile (AN), glutaronitrile (GLN), and adiponitrile (ADN).

[0158] The CEI film on the positive electrode surface of this application is formed by the oxidation of the electrolyte on the positive electrode surface, generally at a relatively high potential. After the positive electrode surface film is formed, it is not stable during charge-discharge cycles, especially under high voltage and high temperature conditions, where it will decompose and regenerate. In order to improve the actual operating voltage of the electrolyte, a positive electrode film-forming additive can be introduced. During charging, this additive preferentially oxidizes and decomposes on the positive electrode surface than the solvent, forming a stable interfacial film on the positive electrode surface. This reduces the catalytic effect of the active sites on the positive electrode surface on the decomposition of the electrolyte, allowing the electrolyte to operate under conditions close to its theoretical oxidation and decomposition voltage.

[0159] The film-forming additives of this application include sulfonate compounds and borate compounds, wherein the sulfonate compounds include one or more of methylene disulfonate (MMDS), 1,3-propane sulfonate lactone (PS), propylene sulfonate lactone (PES), 3-fluoro1,3-propane sulfonate lactone (FPS), and vinyl sulfate (DTD).

[0160] Boronate compounds include one or more of tris(trimethylsilane)borate (TMSB), lithium dioxalate borate (LiBOB), and lithium monooxalate difluoroborate (LiDFOB).

[0161] Lithium-ion batteries

[0162] This application discloses a lithium-ion battery in some embodiments, comprising a positive electrode, a separator, and a negative electrode, wherein the positive electrode, separator, and negative electrode are sequentially stacked together to form the lithium-ion battery using a winding or stacking process. Meanwhile, the positive electrode includes a positive electrode material having a core-shell structure, comprising a core and an outer shell layer, the outer shell layer being located on at least a portion of the surface of the core; the core contains a positive electrode active material, and the outer shell layer of the core-shell structure contains lithium, sulfur, and silicon.

[0163] The core-shell structure of this application is as follows: Figure 6The core-shell structure 1 includes a core 11 and an outer shell layer 12 covering the surface of the core 11. The outer shell layer 12 is located on at least a portion of the surface of the core 11. Here, "at least a portion" includes a portion of the surface, such as the outer shell layer 12 being located on the surface of the core 11 in a point-like manner, and also includes the outer shell layer 12 being located on all surfaces of the core 11.

[0164] The outer shell layer 12 of this application isolates the core positive electrode active material from the outside world, which reduces the ion dissolution of the positive electrode active material to a certain extent and alleviates the structural collapse of the positive electrode active material under high voltage and the degree of oxidative decomposition between it and the electrolyte.

[0165] The outer shell layer 12 of this application contains lithium, sulfur, and silicon. The method for determining these elements involves bombarding the outer shell layer sample or a cross-sectional sample of the outer shell layer with an electron beam generated by an energy-dispersive X-ray spectrometer. Since different elements emit characteristic X-rays with different energies, various different elements can be identified.

[0166] The lithium element in the outer shell layer 12 of this application serves as a lithium replenishment material, primarily supplying lithium ions to the negative electrode to compensate for the lithium ions consumed during SEI film formation, thereby improving the battery's initial efficiency or cycle life. The sulfur element in the outer shell layer 12 reacts with lithium ions to form a CEI film, which is part of the outer shell layer and exhibits strong oxidation resistance, serving as a protective film for the positive electrode active material. Silicon is filled between the CEI film and the positive electrode active material, and this silicon-containing material supports the CEI film. The sulfur element in the outer shell layer 12 serves two purposes: firstly, to regulate the kinetics of lithium removal from the replenishment material to improve the battery's rate performance; and secondly, to contribute to the formation of a high-quality SEI layer to reduce irreversible lithium loss.

[0167] The lithium-ion battery provided in this application isolates the core positive electrode active material from the external environment through the outer shell layer itself and the CEI film formed by the reaction between the elements in the outer shell layer and the electrolyte. This reduces ion dissolution of the positive electrode active material to a certain extent, alleviates the structural collapse of the positive electrode active material under high voltage and the degree of oxidative decomposition between it and the electrolyte, thus improving the cycle stability of the battery. At the same time, the lithium element in the outer shell layer acts as a lithium replenishing material, mainly used to supply lithium ions to the negative electrode to replenish the lithium ions consumed during the formation of the SEI film, thereby improving the first-time efficiency of the lithium-ion battery. In addition, some elements in the outer shell layer can be used to adjust the kinetic performance of lithium removal from the replenishing material to improve the rate performance of the battery, and can also form a high-quality SEI layer to reduce irreversible lithium loss. Therefore, the lithium-ion battery provided in this application improves the first-time efficiency, energy density, and cycle stability of the battery by increasing the structural stability of the positive electrode active material under high voltage, and improves the rate performance of the battery by utilizing the role of sulfur element in the outer shell layer in adjusting the kinetic performance of lithium removal from the replenishing material.

[0168] In some embodiments of this application, it is disclosed that the mass percentage content of lithium in the aforementioned outer shell layer is 10.0% to 15.5%. The specific determination method includes SEM-EDS, and the testing steps include: using a FESEM instrument (JEOL JSM-7900F) at an accelerating voltage of 5 kV to perform EDS mapping at a rate of x10,000 times to determine the content of sulfur, silicon, carbon, and oxygen, with the remainder being lithium or other elements.

[0169] In these embodiments, this application discloses that the mass percentage content of lithium element in the aforementioned outer shell layer is any one of 10.0% to 10.5%, 10.0% to 11.0%, 10.0% to 11.5%, 11.5% to 12%, 12.0% to 15.5%, or any one of the aforementioned ranges.

[0170] In these embodiments, this application discloses that the mass percentage content of lithium in the aforementioned outer shell layer is 10.0%, 10.1%, 10.2%, 10.3%, 10.4%, 10.5%, 10.6%, 10.7%, 10.8%, 10.9%, 11.0%, 11.1%, 11.2%, 11.3%, 11.4%, 11.5%, 11.6%, 11.7%, 11.8%, 11.9%, 12.0%, 12.1%, 12.2%, 12.3%, 12.4%, 12.5%, and 12.6%. The lithium content is 12.7%, 12.8%, 12.9%, 13.0%, 13.1%, 13.2%, 13.3%, 13.4%, 13.5%, 13.6%, 13.7%, 13.8%, 13.9%, 14.0%, 14.1%, 14.2%, 14.3%, 14.4%, 14.5%, 14.6%, 14.7%, 14.8%, 14.9%, 15.0%, 15.1%, 15.2%, 15.3%, 15.4%, or 15.5%, or any value within the range described above. The method for testing the lithium content in this application is the same as described above and will not be repeated here.

[0171] In some embodiments, this application discloses that the sulfur content in the outer shell layer is 5.0% to 9.2% by mass.

[0172] In these embodiments, this application discloses that the mass percentage content of sulfur in the aforementioned outer shell layer is any one of 5.0%–6%, 5.0%–7%, 5.0%–8%, 5.0%–9%, ​​5.0%–10%, 5.0%–10%, 5.5%–10%, 6.5%–10%, 7.5%–10%, 8.5%–10%, or 9.5%–10%, or any one of the aforementioned ranges.

[0173] In these embodiments, this application discloses that the mass percentage content of sulfur in the aforementioned outer shell layer is any one of 5.0%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7.0%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, 8.0%, 8.1%, 8.2%, 8.3%, 8.4%, 8.5%, 8.6%, 8.7%, 8.8%, 8.9%, 9.0%, 9.1%, and 9.2%, or any one of the above-mentioned ranges. The test method for sulfur content in this application is the same as above, and will not be repeated here.

[0174] In some embodiments, this application discloses that the mass percentage content of silicon in the aforementioned outer shell layer is 7.3% to 14.9%.

[0175] In these embodiments, this application discloses that the mass percentage content of silicon element in the aforementioned outer shell layer is any one of 7.3%–8%, 7.3%–9%, ​​7.3%–10%, 7.3%–11%, 7.3%–12%, 7.3%–13%, 7.3%–14%, 7.3%–15%, 7%–14.9%, 8%–14.9%, 9%–14.9%, 10%–14.9%, 11%–14.9%, 12%–14.9%, 13%–14.9%, and 14%–14.9%, or any one of the aforementioned ranges.

[0176] In these embodiments, this application discloses that the mass percentage content of silicon in the aforementioned outer shell layer is 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11.0, 11.1, and 11.2. The silicon content is determined by any one of the following values: 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 12.0, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.8, 12.9, 13.0, 13.1, 13.2, 13.3, 13.4, 13.5, 13.6, 13.7, 13.8, 13.9, 14.0, 14.1, 14.2, 14.3, 14.4, 14.5, 14.6, 14.7, 14.8, 14.9, or any one of the values ​​within the above range. The method for testing the silicon content in this application is the same as described above and will not be repeated here.

[0177] This application discloses in some embodiments that the outer shell of the core-shell structure further includes carbon and oxygen elements, and the mass percentage content of carbon in the outer shell is 17% to 20.8%.

[0178] In some embodiments, this application discloses that the mass percentage content of carbon element in the aforementioned outer shell layer is any one of 17%–18%, 17%–19%, 17%–20%, 17%–21%, 18%–20.8%, 19%–20.8%, 20%–20.8%, or any one of the aforementioned ranges.

[0179] In these embodiments, this application discloses that the mass percentage content of carbon element in the aforementioned outer shell layer is any one of 17%, 17.1%, 17.2%, 17.3%, 17.4%, 17.5%, 17.6%, 17.7%, 17.8%, 17.9%, 18.0%, 18.1%, 18.2%, 18.3%, 18.4%, 18.5%, 18.6%, 18.7%, 18.8%, 18.9%, 19.0%, 19.1%, 19.2%, 19.3%, 19.4%, 19.5%, 19.6%, 19.7%, 19.8%, 19.9%, 20.0%, 20.1%, 20.2%, 20.3%, 20.4%, 20.5%, 20.6%, 20.7%, and 20.8%, or any one of the aforementioned ranges. The method for testing the carbon element content in this application is the same as described above and will not be repeated here.

[0180] In some embodiments, this application discloses that the oxygen content in the outer shell layer is 45% to 59% by mass.

[0181] In some embodiments, this application discloses that the mass percentage content of oxygen in the aforementioned outer shell layer is any one of 45% to 50%, 50% to 59%, or any one of the aforementioned ranges.

[0182] In these embodiments, this application discloses that the mass percentage content of oxygen in the aforementioned outer shell layer is any one of 45%, 45.5%, 46%, 46.5%, 47%, 47.5%, 48%, 48.5%, 49%, 49.5%, 50%, 50.5%, 51%, 51.5%, 52%, 52.5%, 53%, 53.5%, 54%, 54.5%, 55%, 55.5%, 56%, 56.5%, 57%, 57.5%, 58%, 58.5%, and 59%, or any one of the above ranges. The method for testing the oxygen content in this application is the same as above, and will not be repeated here.

[0183] In some embodiments, this application discloses that the outer shell layer of the core-shell structure comprises an organosilicon resin having a network structure; the outer shell layer contains lithium sulfate, which is distributed in the network structure.

[0184] The organosilicon resin of this application, also known as polysiloxane, is a class of polymers with a network structure composed of alternating silicon and oxygen atoms, and various organic groups linked to silicon atoms. Organosilicon resins contain both "organic groups" and "inorganic structures," a unique composition and molecular structure that combines the properties of organic and inorganic substances. One of the most prominent properties of organosilicon resins is their excellent thermal oxidation stability. They also possess outstanding weather resistance, thus the organosilicon resin provided in this application has advantages such as resistance to electrolyte corrosion and resistance to softening under heating. The characterization method for the network structure of this organosilicon resin includes sampling the outer shell layer and then obtaining its network structure using high-magnification electron microscopy (SEM, two-dimensional image) or atomic force microscopy (AFM, three-dimensional image). In this application, lithium sulfate is distributed within the network structure of the organosilicon resin. This network structure provides channels for lithium-ion transport, which helps to reduce the impact of the outer shell layer on the lithium-ion conductivity caused by the core coating. Meanwhile, the sulfur element in lithium sulfate can also regulate the kinetics of lithium ions to improve the rate performance of the battery. Therefore, the core-shell structure provided in this application is beneficial to improving the ionic conductivity of the cathode material, thereby improving the rate performance of the battery. Furthermore, the organosilicon resin in this application possesses excellent thermal oxidation stability. Its coating on the surface of the cathode active material further forms a CEI film with good stability and high oxidation resistance. This CEI film isolates the cathode active material from the external environment, reducing ion dissolution to a certain extent and alleviating the structural collapse of the cathode active material under high voltage and the degree of oxidative decomposition between it and the electrolyte.

[0185] This application discloses in some embodiments that the silicone resin includes a polyalkyl silicone resin having an average degree of substitution of hydrocarbon groups DS≤1.

[0186] Based on the different organic substituents on the silicon atoms in the siloxane chain, the organosilicon resins in this application can be basically divided into three categories: polyalkyl organosilicon resins, polyaryl organosilicon resins, and polyalkylaryl organosilicon resins. This application selects polyalkyl organosilicon resins, and the average degree of substitution (DS) of the hydrocarbon groups in the polyalkyl organosilicon resin is ≤1. The average degree of substitution (DS) in this application refers to the average number of hydrocarbon groups (ester hydrocarbons) attached to each silicon atom in the organosilicon polymer, and its calculation formula is as follows: DS = ∑(molar fraction of a monomer component × number of hydrocarbon groups in that monomer molecule) / 100. The selection of a polyalkyl organosilicon resin with an average degree of substitution (DS) ≤1 indicates a relatively high degree of crosslinking, mainly a network structure. This network structure is not easily softened under heating and is not easily dissolved in organic solvents. After separating the organosilicon resin for the positive electrode sheet, the functional groups can be determined by infrared spectroscopy, and the elements can be conveniently determined by EDS. Given the type of organosilicon resin, the type and content of the monomers can be known, thus facilitating the calculation of DS.

[0187] This application discloses in some embodiments that the aforementioned organosilicon resin comprises any one or more of polymethyl silicone resin, polyethyl silicone resin, and polyvinyl silicone resin.

[0188] The polymethyl silicone resin in this application is generally composed of SiO₂. 3 / 2 CH3SiO 3 / 2 (CH3)3SiO 2 / 2 (CH)SiO 1 / 2 A copolymer composed of siloxane units, wherein the methyl content is 0.2–0.5 mol / 100g.

[0189] The polyethyl silicone resin used in this application generally refers to a copolymer containing ethyl groups in the polysiloxane chain. The ethyl content is 0.077 to 0.101 mol / 100g.

[0190] The polyvinyl silicone resin used in this application generally refers to a copolymer containing vinyl groups in the polysiloxane chain. The vinyl content is 0.05 mol to 0.1 mol / 100g. In these embodiments, this application provides vinyl content of any one of 0.05 mol / 100g, 0.06 mol / 100g, 0.07 mol / 100g, 0.08 mol / 100g, 0.09 mol / 100g, and 0.1 mol / 100g, or any value within the aforementioned range.

[0191] The types of silicone resins listed in this application have the advantages of high heat resistance and strong oxidation resistance.

[0192] This application discloses in some embodiments that the volumetric particle size distribution Dv50 of the positive electrode active material is 5.1 μm to 9.0 μm.

[0193] The volumetric particle size distribution Dv50 in this application includes particles larger than its diameter accounting for 50% of the total volume, and particles smaller than its diameter also accounting for 50% of the total volume. Also known as the median diameter, it is typically used to represent the average particle size. It can be measured using conventional methods in the art, such as using a particle size analyzer to determine the particle size distribution and then obtaining the result statistically. In these embodiments, this application selects to measure it using laser diffraction particle size analysis, specifically referring to standard GB / T19077-2016 to obtain the particle size distribution map, and then calculating the result.

[0194] In these embodiments, this application discloses that the volumetric particle size distribution Dv50 of the positive electrode active material is any one of 5.1μm~6.0μm, 5.1μm~6.5μm, 5.1μm~7.0μm, 5.1μm~7.5μm, 5.1μm~8.0μm, 5.1μm~8.5μm, 5.1μm~9.0μm, 6.0μm~9.0μm, 7.0μm~9.0μm, 8.0μm~9.0μm, or any one of the above range values.

[0195] In these embodiments, this application discloses that the volumetric particle size distribution Dv50 of the positive electrode active material is 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6.0 μm, 6.1 μm, 6.2 μm, 6.3 μm, 6.4 μm, 6.5 μm, 6.6 μm, 6.7 μm, 6.8 μm, and 6.9 μm. The value can be any one of the following: 7.0μm, 7.1μm, 7.2μm, 7.3μm, 7.4μm, 7.5μm, 7.6μm, 7.7μm, 7.8μm, 7.9μm, 8.0μm, 8.1μm, 8.2μm, 8.3μm, 8.4μm, 8.5μm, 8.6μm, 8.7μm, 8.8μm, 8.9μm, 9.0μm, or any one of the values ​​within the above range.

[0196] This application discloses in some embodiments that the thickness of the outer shell layer is <0.5μm, such as 0.05μm, 0.055μm, 0.1μm, 0.102μm, 0.123μm, 0.156μm, 0.158μm, 0.162μm, 0.165μm, 0.2μm, 0.21μm, 0.25μm, 0.3μm, 0.35μm, 0.38μm, 0.39μm, 0.4μm, 0.41μm, 0.42μm, 0.43μm, 0.44μm, 0.45μm, 0.48μm, etc.

[0197] In some embodiments, this application discloses that the thickness of the outer shell layer is 0.05 μm to 0.45 μm.

[0198] This application discloses in some embodiments that the positive electrode active material includes any one or more of the following: lithium-rich solid solution positive electrode material, nickel-manganese spinel positive electrode material, high-nickel positive electrode material, polyanionic positive electrode material, and modified lithium cobalt oxide positive electrode material.

[0199] The lithium-rich solid solution cathode material in this application has a layered structure, and its composition can be found in...

[0200] Li (Li 1 / 3 Mn 2 / 3)O2—LiCoO2—LiNiO2—LiNi 0.5 Mn 0.5 O2 quaternary phase diagram, and the chemical formula can be written as xLi(Li 1 / 3 Mn 2 / 2 5>)O2·(1-x)LiMO2 or Li 1+x M 1-x O2 (0 < x < 1). Among them, the component Li(Li 1 / 3 Mn 2 / 3 )O2 (or Li2MnO3) structure belongs to the layered monoclinic system, and LiMO2 (M = one or several of Ni, Co or Mn) belongs to the layered hexagonal system. Their lattice constants are close, and it is easy to form a solid solution. Among (1 + x) moles of Li, 1 mole of Li occupies 3a, and x moles of Li and transition metals such as Ni, Mn and Co occupy the 3b position. Due to the radius of Li + (R Li + = 0.076nm) and the radius of Ni 2+ (R Ni 2+ = 0.069nm) are very close, so Ni 2+ in the transition metal layer is very easy to migrate to the Li + layer, which will hinder the diffusion of Li + in the crystal structure during the charge and discharge process. To a certain extent, it increases the polarization phenomenon of the material and affects the rate performance of the material. To prevent the mixing of Li + / Ni 2+ , when preparing the layered lithium-rich solid solution cathode material, it is necessary to add more lithium sources than the stoichiometric ratio. Too high lithium content often results in a relatively high total alkali content on the surface of the prepared layered lithium-rich material, deteriorating the high-temperature cycle and storage performance. On the other hand, the deterioration of the high-temperature cycle and storage performance of the layered lithium-rich solid solution material is not only related to the total surface alkali content, but also related to the dissolution of surface transition metal ions in the electrolyte or the surface reaction between the material / electrolyte. Especially at high charge states (above 4.5V), the dissolution of transition metal ions and the interface reaction between the material / electrolyte are more significant. The outer shell layer provided by this application helps to alleviate the above problems.

[0201] In some embodiments of this application, the general formula of the lithium-rich solid solution cathode material is disclosed as

[0202] Li n X m Mn a Co b Ni c M dO2, 1.0≤n≤1.6, 0≤m≤0.3, 0.4≤a≤1, 0.05≤b≤0.2, 0.05≤c≤0.2, 0≤d≤0.2, X includes Na, K, Mg, Ca or Zn, and M includes Fe, Cr, Al, Zr or La. In these embodiments, n includes any one of 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 or any one of the above-mentioned range values. m includes any one of 0, 0.1, 0.2, 0.3 or any one of the above-mentioned range values. a includes any one of 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 or any one of the above-mentioned range values. b includes 0.05, 0.05, ...

[0203] This application discloses, in some embodiments, a nickel-manganese spinel cathode material with the general formula Li. 1+x M y Mn 2-y O 4： M includes one or more of Ni, Mn, Co, Al, V, Cu, and Cr; y = 0 to 1.5, 0 < X ​​≤ 1; wherein, in some embodiments of this application, LiNi is selected as a high-voltage spinel structure cathode material. 0.5 Mn 1.5 O4 (LNMO) is characterized by a voltage plateau of 4.7V (vs. Li / Li+), which is achieved by utilizing nickel (Ni) 2+ / 4+ The total redox capacity of ). Therefore, although its actual capacity is only 120-140 mAh g. -1 However, its energy density can reach 650Wh / kg. -1 above.

[0204] The structure of the nickel-manganese spinel cathode material of this application is closely related to its preparation method, which includes: solid-state method, sol-gel method, high-temperature molten salt method, latex drying method, ultrasonic spray high-temperature decomposition method, polymer high-temperature decomposition method, and precipitation method, etc.

[0205] The chemical formula of the high-nickel cathode material in this application is Li. a Ni x Co y M z O2, wherein M is selected from one or more combinations of Mn, Al, Zr, Ti, V, Mg, Fe, Mo, Ta, W, Nb, Sb, and La, 1≤a≤2; and x+y+z=1, 0.9≤x<1, 0≤y<0.1.

[0206] The polyanionic cathode materials in this application include lithium iron pyrophosphate (LiFePO4), sodium vanadium phosphate (Li3V2(PO4)3), LiM'PO4F (M' is one or more of V, Fe, Mn and Ni), and Li3(VO4)2(PO4)3. y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0207] In these embodiments, this application discloses polyanionic compounds comprising one or more of lithium vanadium trifluorophosphate (Li3V2(PO4)2F3), lithium vanadium fluorophosphate (LiVPO4F), lithium vanadium phosphate (Li3V2(PO4)3), lithium iron pyrophosphate (Na4Fe3(PO4)2(P2O7)), and lithium iron pyrophosphate (LiFePO4).

[0208] This application describes a modified lithium cobalt oxide cathode material comprising a coated lithium cobalt oxide cathode material. The coating material is beneficial for increasing the interfacial stability of lithium cobalt oxide, for example, by utilizing a solid electrolyte material, Li. 1.5 Al 0.5 Ti 1.5 (PO4)3(LATP)-coated lithium cobalt oxide. During the material synthesis process, LATP reacts with lithium cobalt oxide to form a uniform interface layer on the surface with high structural and electrochemical stability and excellent ionic and electronic conductivity, thus effectively solving the surface stability problem of lithium cobalt oxide during high-voltage charging.

[0209] This application discloses in some embodiments that the positive electrode includes a positive electrode film layer, and the compaction density of the positive electrode film layer is greater than or equal to 2.9 g / cm³. 3 .

[0210] The positive electrode film layer in this application is located on one or both surfaces of the positive electrode current collector. Typically, the positive electrode film layer is located on both surfaces of the positive electrode current collector, and its formation methods include coating or deposition. This application will use both sides as examples in the following examples. Meanwhile, the compaction density of the positive electrode film layer in this application can be used to characterize the energy density of the material; however, the compaction density of the positive electrode film layer is used to evaluate the overall compaction density of the positive electrode sheet. The compaction density of the positive electrode film layer = areal density of the positive electrode film layer / thickness of the positive electrode film layer. The thickness of the positive electrode film layer includes the distance between the two end faces of the positive electrode film layer along the thickness direction. The areal density of the positive electrode film layer = weight of a single-sided positive electrode film layer / area of ​​a single-sided positive electrode film layer. The weight of a single-sided positive electrode film layer can be obtained by weighing, and the area of ​​a single-sided positive electrode film layer can be obtained by using an area calculation formula based on the shape of the film layer. In these embodiments, this application lists a positive electrode film layer compaction density greater than or equal to 2.9 g / cm³. 3 The upper limit of the compaction density of the positive electrode film is a conventional value in the art, and will not be elaborated upon in this application.

[0211] This application discloses in some embodiments that the compaction density of the positive electrode film is 2.9 g / cm³. 3 ~3.4g / cm 3 .

[0212] This application discloses in these embodiments that the compaction density of the positive electrode film layer includes 2.9 g / cm³. 3 3.0g / cm 3 3.1g / cm 3 3.2g / cm 3 3.3g / cm 3 3.4g / cm 3 Any one of the above values ​​or any one of the above range values.

[0213] This application discloses in some embodiments that the lithium-ion battery further includes an electrolyte comprising one or more of fluorocarbonates, sulfones, and nitrile compounds.

[0214] The fluorinated carbonates of this application exhibit high electrochemical stability due to the strong electronegativity and weak polarity of the fluorine atom. Replacing the carbonate solvent with fluorine enhances its antioxidant capacity and facilitates the formation of a solid electrolyte interphase (SEI) film on the negative electrode surface. For example, fluoroethylene carbonate (FEC) can also form a protective film on the positive electrode surface, which is beneficial for improving the cycle stability of the electrode.

[0215] In these embodiments, this application discloses an electrolyte comprising carbonates and fluorocarbonates, wherein the fluorocarbonate comprises fluoroethylene carbonate (FEC), and the carbonate comprises one or more of ethylene carbonate (EC), propylene carbonate (PC), ethylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and butyl carbonate (BC).

[0216] The sulfone solvents used in this application exhibit higher thermal stability than conventional carbonate solvents, while also possessing good electrochemical stability; for example, the oxidation potentials of sulfolane (TMS) and methyl ethyl sulfone (EMS) are both above 5V. However, they are generally solids or have high viscosity at room temperature and are typically used in conjunction with existing carbonate solvents to lower their melting point and viscosity. Sulfone solvents cannot form a stable SEI film on graphite surfaces, necessitating the introduction of film-forming additives.

[0217] The sulfone solvents of this application include at least one or more combinations of sulfolane (SF), dimethyl sulfone (MSM), ethyl sulfone (EMS), diethyl sulfone (ESE), and sulfone fluoride (FMES).

[0218] The nitrile solvents of this application exhibit high electrochemical stability; for example, glutaronitrile (GLN) has an oxidation potential as high as 8.3V (vs. Li / Li). + It has higher stability than most aprotic solvents; however, it has poor compatibility with graphite anodes, which can be improved by adding EC, etc.

[0219] The nitrile solvents of this application include one or more of acetonitrile (AN), glutaronitrile (GLN), and adiponitrile (ADN).

[0220] The CEI film on the positive electrode surface of this application is formed by the oxidation of the electrolyte on the positive electrode surface, generally at a relatively high potential. After the positive electrode surface film is formed, it is not stable during charge-discharge cycles, especially under high voltage and high temperature conditions, where it will decompose and regenerate. In order to improve the actual operating voltage of the electrolyte, a positive electrode film-forming additive can be introduced. During charging, this additive preferentially oxidizes and decomposes on the positive electrode surface than the solvent, forming a stable interfacial film on the positive electrode surface. This reduces the catalytic effect of the active sites on the positive electrode surface on the decomposition of the electrolyte, allowing the electrolyte to operate under conditions close to its theoretical oxidation and decomposition voltage.

[0221] The film-forming additives of this application include sulfonate compounds and borate compounds, wherein the sulfonate compounds include one or more of methylene disulfonate (MMDS), 1,3-propane sulfonate lactone (PS), propylene sulfonate lactone (PES), 3-fluoro1,3-propane sulfonate lactone (FPS), and vinyl sulfate (DTD).

[0222] Boronate compounds include one or more of tris(trimethylsilane)borate (TMSB), lithium dioxalate borate (LiBOB), and lithium monooxalate difluoroborate (LiDFOB).

[0223] [Positive electrode plate]

[0224] This application discloses a positive electrode sheet in some embodiments, the positive electrode sheet comprising a positive current collector and a positive electrode film layer located on at least one side surface of the positive current collector; the positive electrode film layer comprises a positive electrode material having a core-shell structure, the core-shell structure comprising a core and an outer shell layer, the outer shell layer being located on at least a portion of the surface of the core; the core comprises a positive electrode active material, and the outer shell layer comprises lithium, sulfur and silicon.

[0225] The outer shell layer 12 of this application contains lithium, sulfur, and silicon. The method for determining these elements involves bombarding the outer shell layer sample or a cross-sectional sample of the outer shell layer with an electron beam generated by an energy-dispersive X-ray spectrometer. Since different elements emit characteristic X-rays with different energies, various different elements can be identified.

[0226] The lithium element in the outer shell layer 12 of this application serves as a lithium replenishment material, primarily supplying lithium ions to the negative electrode to compensate for the lithium ions consumed during SEI film formation, thereby improving the battery's initial efficiency or cycle life. The sulfur element in the outer shell layer 12 reacts with lithium ions to form a CEI film, which is part of the outer shell layer and exhibits strong oxidation resistance, serving as a protective film for the positive electrode active material. Silicon is filled between the CEI film and the positive electrode active material, and this silicon-containing material supports the CEI film. The sulfur element in the outer shell layer 12 serves two purposes: firstly, to regulate the kinetics of lithium removal from the replenishment material to improve the battery's rate performance; and secondly, to contribute to the formation of a high-quality SEI layer to reduce irreversible lithium loss.

[0227] The lithium-ion battery provided in this application isolates the core positive electrode active material from the external environment through the outer shell layer itself and the CEI film formed by the reaction between the elements in the outer shell layer and the electrolyte. This reduces ion dissolution of the positive electrode active material to a certain extent, alleviates the structural collapse of the positive electrode active material under high voltage and the degree of oxidative decomposition between it and the electrolyte, thus improving the cycle stability of the battery. At the same time, the lithium element in the outer shell layer acts as a lithium replenishing material, mainly used to supply lithium ions to the negative electrode to replenish the lithium ions consumed during the formation of the SEI film, thereby improving the first-time efficiency of the lithium-ion battery. In addition, some elements in the outer shell layer can be used to adjust the kinetic performance of lithium removal from the replenishing material to improve the rate performance of the battery, and can also form a high-quality SEI layer to reduce irreversible lithium loss. Therefore, the lithium-ion battery provided in this application improves the first-time efficiency, energy density, and cycle stability of the battery by increasing the structural stability of the positive electrode active material under high voltage, and improves the rate performance of the battery by utilizing the role of sulfur element in the outer shell layer in adjusting the kinetic performance of lithium removal from the replenishing material.

[0228] In some embodiments of this application, it is disclosed that the mass percentage content of lithium in the aforementioned outer shell layer is 10.0% to 15.5%. The specific determination method includes SEM-EDS, and the testing steps include: using a FESEM instrument (JEOL JSM-7900F) at an accelerating voltage of 5 kV to perform EDS mapping at a rate of x10,000 times to determine the content of sulfur, silicon, carbon, and oxygen, with the remainder being lithium or other elements.

[0229] In these embodiments, this application discloses that the mass percentage content of lithium element in the aforementioned outer shell layer is any one of 10.0% to 10.5%, 10.0% to 11.0%, 10.0% to 11.5%, 11.5% to 12%, 12.0% to 15.5%, or any one of the aforementioned ranges.

[0230] In these embodiments, this application discloses that the mass percentage content of lithium in the aforementioned outer shell layer is 10.0%, 10.1%, 10.2%, 10.3%, 10.4%, 10.5%, 10.6%, 10.7%, 10.8%, 10.9%, 11.0%, 11.1%, 11.2%, 11.3%, 11.4%, 11.5%, 11.6%, 11.7%, 11.8%, 11.9%, 12.0%, 12.1%, 12.2%, 12.3%, 12.4%, 12.5%, and 12.6%. The lithium content is 12.7%, 12.8%, 12.9%, 13.0%, 13.1%, 13.2%, 13.3%, 13.4%, 13.5%, 13.6%, 13.7%, 13.8%, 13.9%, 14.0%, 14.1%, 14.2%, 14.3%, 14.4%, 14.5%, 14.6%, 14.7%, 14.8%, 14.9%, 15.0%, 15.1%, 15.2%, 15.3%, 15.4%, or 15.5%, or any value within the range described above. The method for testing the lithium content in this application is the same as described above and will not be repeated here.

[0231] In some embodiments, this application discloses that the sulfur content in the outer shell layer is 5.0% to 9.2% by mass.

[0232] In these embodiments, this application discloses that the mass percentage content of sulfur in the aforementioned outer shell layer is any one of 5.0%–6%, 5.0%–7%, 5.0%–8%, 5.0%–9%, ​​5.0%–10%, 5.0%–10%, 5.5%–10%, 6.5%–10%, 7.5%–10%, 8.5%–10%, or 9.5%–10%, or any one of the aforementioned ranges.

[0233] In these embodiments, this application discloses that the mass percentage content of sulfur in the aforementioned outer shell layer is any one of 5.0%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7.0%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, 8.0%, 8.1%, 8.2%, 8.3%, 8.4%, 8.5%, 8.6%, 8.7%, 8.8%, 8.9%, 9.0%, 9.1%, and 9.2%, or any one of the above-mentioned ranges. The test method for sulfur content in this application is the same as above, and will not be repeated here.

[0234] In some embodiments, this application discloses that the mass percentage content of silicon in the aforementioned outer shell layer is 7.3% to 14.9%.

[0235] In these embodiments, this application discloses that the mass percentage content of silicon element in the aforementioned outer shell layer is any one of 7.3%–8%, 7.3%–9%, ​​7.3%–10%, 7.3%–11%, 7.3%–12%, 7.3%–13%, 7.3%–14%, 7.3%–15%, 7%–14.9%, 8%–14.9%, 9%–14.9%, 10%–14.9%, 11%–14.9%, 12%–14.9%, 13%–14.9%, and 14%–14.9%, or any one of the aforementioned ranges.

[0236] In these embodiments, this application discloses that the mass percentage content of silicon in the aforementioned outer shell layer is 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11.0, 11.1, and 11.2. The silicon content is determined by any one of the following values: 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 12.0, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.8, 12.9, 13.0, 13.1, 13.2, 13.3, 13.4, 13.5, 13.6, 13.7, 13.8, 13.9, 14.0, 14.1, 14.2, 14.3, 14.4, 14.5, 14.6, 14.7, 14.8, 14.9, or any one of the values ​​within the above range. The method for testing the silicon content in this application is the same as described above and will not be repeated here.

[0237] This application discloses in some embodiments that the outer shell of the core-shell structure further includes carbon and oxygen elements, and the mass percentage content of carbon in the outer shell is 17% to 20.8%.

[0238] In some embodiments, this application discloses that the mass percentage content of carbon element in the aforementioned outer shell layer is any one of 17%–18%, 17%–19%, 17%–20%, 17%–21%, 18%–20.8%, 19%–20.8%, 20%–20.8%, or any one of the aforementioned ranges.

[0239] In these embodiments, this application discloses that the mass percentage content of carbon element in the aforementioned outer shell layer is any one of 17%, 17.1%, 17.2%, 17.3%, 17.4%, 17.5%, 17.6%, 17.7%, 17.8%, 17.9%, 18.0%, 18.1%, 18.2%, 18.3%, 18.4%, 18.5%, 18.6%, 18.7%, 18.8%, 18.9%, 19.0%, 19.1%, 19.2%, 19.3%, 19.4%, 19.5%, 19.6%, 19.7%, 19.8%, 19.9%, 20.0%, 20.1%, 20.2%, 20.3%, 20.4%, 20.5%, 20.6%, 20.7%, and 20.8%, or any one of the aforementioned ranges. The method for testing the carbon element content in this application is the same as described above and will not be repeated here.

[0240] In some embodiments, this application discloses that the oxygen content in the outer shell layer is 45% to 59% by mass.

[0241] In some embodiments, this application discloses that the mass percentage content of oxygen in the aforementioned outer shell layer is any one of 45% to 50%, 50% to 59%, or any one of the aforementioned ranges.

[0242] In these embodiments, this application discloses that the mass percentage content of oxygen in the aforementioned outer shell layer is any one of 45%, 45.5%, 46%, 46.5%, 47%, 47.5%, 48%, 48.5%, 49%, 49.5%, 50%, 50.5%, 51%, 51.5%, 52%, 52.5%, 53%, 53.5%, 54%, 54.5%, 55%, 55.5%, 56%, 56.5%, 57%, 57.5%, 58%, 58.5%, and 59%, or any one of the above ranges. The method for testing the oxygen content in this application is the same as above, and will not be repeated here.

[0243] In some embodiments, this application discloses that the outer shell layer of the core-shell structure comprises an organosilicon resin having a network structure; the outer shell layer contains lithium sulfate, which is distributed in the network structure.

[0244] The organosilicon resin of this application, also known as polysiloxane, is a class of polymers with a network structure composed of alternating silicon and oxygen atoms, and various organic groups linked to silicon atoms. Organosilicon resins contain both "organic groups" and "inorganic structures," a unique composition and molecular structure that combines the properties of organic and inorganic substances. One of the most prominent properties of organosilicon resins is their excellent thermal oxidation stability. They also possess outstanding weather resistance, thus the organosilicon resin provided in this application has advantages such as resistance to electrolyte corrosion and resistance to softening under heating. The characterization method for the network structure of this organosilicon resin includes sampling the outer shell layer and then obtaining its network structure using high-magnification electron microscopy (SEM, two-dimensional image) or atomic force microscopy (AFM, three-dimensional image). In this application, lithium sulfate is distributed within the network structure of the organosilicon resin. This network structure provides channels for lithium-ion transport, which helps to reduce the impact of the outer shell layer on the lithium-ion conductivity caused by the core coating. Meanwhile, the sulfur element in lithium sulfate can also regulate the kinetics of lithium ions to improve the rate performance of the battery. Therefore, the core-shell structure provided in this application is beneficial to improving the ionic conductivity of the cathode material, thereby improving the rate performance of the battery. Furthermore, the organosilicon resin in this application possesses excellent thermal oxidation stability. Its coating on the surface of the cathode active material further forms a CEI film with good stability and high oxidation resistance. This CEI film isolates the cathode active material from the external environment, reducing ion dissolution to a certain extent and alleviating the structural collapse of the cathode active material under high voltage and the degree of oxidative decomposition between it and the electrolyte.

[0245] This application discloses in some embodiments that the silicone resin includes a polyalkyl silicone resin having an average degree of substitution of hydrocarbon groups DS≤1.

[0246] Based on the different organic substituents on the silicon atoms in the siloxane chain, the organosilicon resins in this application can be basically divided into three categories: polyalkyl organosilicon resins, polyaryl organosilicon resins, and polyalkylaryl organosilicon resins. This application selects polyalkyl organosilicon resins, and the average degree of substitution (DS) of the hydrocarbon groups in the polyalkyl organosilicon resin is ≤1. The average degree of substitution (DS) in this application refers to the average number of hydrocarbon groups (ester hydrocarbons) attached to each silicon atom in the organosilicon polymer, and its calculation formula is as follows: DS = ∑(molar fraction of a monomer component × number of hydrocarbon groups in that monomer molecule) / 100. The selection of a polyalkyl organosilicon resin with an average degree of substitution (DS) ≤1 indicates a relatively high degree of crosslinking, mainly a network structure. This network structure is not easily softened under heating and is not easily dissolved in organic solvents. After separating the organosilicon resin for the positive electrode sheet, the functional groups can be determined by infrared spectroscopy, and the elements can be conveniently determined by EDS. Given the type of organosilicon resin, the type and content of the monomers can be known, thus facilitating the calculation of DS.

[0247] This application discloses in some embodiments that the aforementioned organosilicon resin comprises any one or more of polymethyl silicone resin, polyethyl silicone resin, and polyvinyl silicone resin.

[0248] The polymethyl silicone resin in this application is generally composed of SiO₂. 3 / 2 CH3SiO 3 / 2 (CH3)3SiO 2 / 2 (CH)SiO 1 / 2 A copolymer composed of siloxane units, wherein the methyl content is 0.2–0.5 mol / 100g.

[0249] The polyethyl silicone resin used in this application generally refers to a copolymer containing ethyl groups in the polysiloxane chain. The ethyl content is 0.077 to 0.101 mol / 100g.

[0250] The polyvinyl silicone resin used in this application generally refers to a copolymer containing vinyl groups in the polysiloxane chain. The vinyl content is 0.05 mol to 0.1 mol / 100g. In these embodiments, this application provides vinyl content of any one of 0.05 mol / 100g, 0.06 mol / 100g, 0.07 mol / 100g, 0.08 mol / 100g, 0.09 mol / 100g, and 0.1 mol / 100g, or any value within the aforementioned range.

[0251] The types of silicone resins listed in this application have the advantages of high heat resistance and strong oxidation resistance.

[0252] This application discloses in some embodiments that the volumetric particle size distribution Dv50 of the positive electrode active material is 5.1 μm to 9.0 μm.

[0253] The volumetric particle size distribution Dv50 in this application includes particles larger than its diameter accounting for 50% of the total volume, and particles smaller than its diameter also accounting for 50% of the total volume. Also known as the median diameter, it is typically used to represent the average particle size. It can be measured using conventional methods in the art, such as using a particle size analyzer to determine the particle size distribution and then obtaining the result statistically. In these embodiments, this application selects to measure it using laser diffraction particle size analysis, specifically referring to standard GB / T19077-2016 to obtain the particle size distribution map, and then calculating the result.

[0254] In these embodiments, this application discloses that the volumetric particle size distribution Dv50 of the positive electrode active material is any one of 5.1μm~6.0μm, 5.1μm~6.5μm, 5.1μm~7.0μm, 5.1μm~7.5μm, 5.1μm~8.0μm, 5.1μm~8.5μm, 5.1μm~9.0μm, 6.0μm~9.0μm, 7.0μm~9.0μm, 8.0μm~9.0μm, or any one of the above range values.

[0255] In these embodiments, this application discloses that the volumetric particle size distribution Dv50 of the positive electrode active material is 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6.0 μm, 6.1 μm, 6.2 μm, 6.3 μm, 6.4 μm, 6.5 μm, 6.6 μm, 6.7 μm, 6.8 μm, and 6.9 μm. The value can be any one of the following: 7.0μm, 7.1μm, 7.2μm, 7.3μm, 7.4μm, 7.5μm, 7.6μm, 7.7μm, 7.8μm, 7.9μm, 8.0μm, 8.1μm, 8.2μm, 8.3μm, 8.4μm, 8.5μm, 8.6μm, 8.7μm, 8.8μm, 8.9μm, 9.0μm, or any one of the values ​​within the above range.

[0256] This application discloses in some embodiments that the thickness of the outer shell layer is <0.5μm, such as 0.05μm, 0.055μm, 0.1μm, 0.102μm, 0.123μm, 0.156μm, 0.158μm, 0.162μm, 0.165μm, 0.2μm, 0.21μm, 0.25μm, 0.3μm, 0.35μm, 0.38μm, 0.39μm, 0.4μm, 0.41μm, 0.42μm, 0.43μm, 0.44μm, 0.45μm, 0.48μm, etc.

[0257] In some embodiments, this application discloses that the thickness of the outer shell layer is 0.05 μm to 0.45 μm.

[0258] This application discloses in some embodiments that the positive electrode active material includes any one or more of the following: lithium-rich solid solution positive electrode material, nickel-manganese spinel positive electrode material, high-nickel positive electrode material, polyanionic positive electrode material, and modified lithium cobalt oxide positive electrode material.

[0259] The lithium-rich solid solution cathode material in this application has a layered structure, and its composition can be found in...

[0260] Li (Li 1 / 3 Mn 2 / 3)O2—LiCoO2—LiNiO2—LiNi 0.5 Mn 0.5 O2 quaternary phase diagram, and the chemical formula can be written as xLi(Li 1 / 3 Mn 2 / 3 )O2·(1 - x)LiMO2 or Li 1+x M 1-x O2(0 < x < 1). Among them, the component Li(Li 1 / 3 Mn 2 / 3 )O2 (or Li2MnO3) structure belongs to the layered monoclinic system, and LiMO2 (M = one or several of Ni, Co or Mn) belongs to the layered hexagonal system. The lattice constants of the two are close, and it is easy to form a solid solution. Among (1 + x) moles of Li, 1 mole of Li occupies 3a, and x moles of Li and transition metals such as Ni, Mn and Co occupy the 3b position. Due to the radius of Li + (R Li + = 0.076nm) and the radius of Ni 2+ (R Ni 2+ = 0.069nm) are very close, so Ni in the transition metal layer 2+ is very easy to migrate to the Li + layer, which will hinder the diffusion of Li + in the crystal structure during the charge and discharge process. To a certain extent, it increases the polarization phenomenon of the material and affects the rate performance of the material. To prevent the mixing of Li + / Ni 2+ , when preparing the layered lithium-rich solid solution cathode material, it is necessary to add more lithium sources than the stoichiometric ratio. Too high lithium content often results in a relatively high total surface base amount of the prepared layered lithium-rich material, deteriorating the high-temperature cycle and storage performance. On the other hand, the deterioration of the high-temperature cycle and storage performance of the layered lithium-rich solid solution material is not only related to the total surface base amount, but also related to the dissolution of surface transition metal ions in the electrolyte or the surface reaction between the material / electrolyte. Especially at high charge states (above 4.5V), the dissolution of transition metal ions and the material / electrolyte interface reaction are more significant. The outer shell layer provided by this application helps to alleviate the above problems.

[0261] This application discloses in some embodiments that the general formula of the lithium-rich solid solution cathode material is

[0262] Li n X m Mn a Co b Ni c M dO2, 1.0≤n≤1.6, 0≤m≤0.3, 0.4≤a≤1, 0.05≤b≤0.2, 0.05≤c≤0.2, 0≤d≤0.2, X includes Na, K, Mg, Ca or Zn, and M includes Fe, Cr, Al, Zr or La. In these embodiments, n includes any one of 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 or any one of the above-mentioned range values. m includes any one of 0, 0.1, 0.2, 0.3 or any one of the above-mentioned range values. a includes any one of 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 or any one of the above-mentioned range values. b includes 0.05, 0.05, ...

[0263] This application discloses, in some embodiments, a nickel-manganese spinel cathode material with the general formula Li. 1+x M y Mn 2-y O 4： M includes one or more of Ni, Mn, Co, Al, V, Cu, and Cr; y = 0 to 1.5, 0 < X ​​≤ 1; wherein, in some embodiments of this application, LiNi is selected as a high-voltage spinel structure cathode material. 0.5 Mn 1.5 O4 (LNMO) is characterized by a voltage plateau of 4.7V (vs. Li / Li+), which is achieved by utilizing nickel (Ni) 2+ / 4+ The total redox capacity of ). Therefore, although its actual capacity is only 120-140 mAh g. -1 However, its energy density can reach 650Wh / kg. -1 above.

[0264] The structure of the nickel-manganese spinel cathode material of this application is closely related to its preparation method, which includes: solid-state method, sol-gel method, high-temperature molten salt method, latex drying method, ultrasonic spray high-temperature decomposition method, polymer high-temperature decomposition method, and precipitation method, etc.

[0265] The chemical formula of the high-nickel cathode material in this application is Li. a Ni x Co y M z O2, wherein M is selected from one or more combinations of Mn, Al, Zr, Ti, V, Mg, Fe, Mo, Ta, W, Nb, Sb, and La, 1≤a≤2; and x+y+z=1, 0.9≤x<1, 0≤y<0.1.

[0266] The polyanionic cathode materials in this application include lithium iron pyrophosphate (LiFePO4), sodium vanadium phosphate (Li3V2(PO4)3), LiM'PO4F (M' is one or more of V, Fe, Mn and Ni), and Li3(VO4)2(PO4)3. y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0267] In these embodiments, this application discloses polyanionic compounds comprising one or more of lithium vanadium trifluorophosphate (Li3V2(PO4)2F3), lithium vanadium fluorophosphate (LiVPO4F), lithium vanadium phosphate (Li3V2(PO4)3), lithium iron pyrophosphate (Na4Fe3(PO4)2(P2O7)), and lithium iron pyrophosphate (LiFePO4).

[0268] This application describes a modified lithium cobalt oxide cathode material comprising a coated lithium cobalt oxide cathode material. The coating material is beneficial for increasing the interfacial stability of lithium cobalt oxide, for example, by utilizing a solid electrolyte material, Li. 1.5 Al 0.5 Ti 1.5 (PO4)3(LATP)-coated lithium cobalt oxide. During the material synthesis process, LATP reacts with lithium cobalt oxide to form a uniform interface layer on the surface with high structural and electrochemical stability and excellent ionic and electronic conductivity, thus effectively solving the surface stability problem of lithium cobalt oxide during high-voltage charging.

[0269] This application discloses in some embodiments that the positive electrode includes a positive electrode film layer, and the compaction density of the positive electrode film layer is greater than or equal to 2.9 g / cm³. 3 .

[0270] The positive electrode film layer in this application is located on one or both surfaces of the positive electrode current collector. Typically, the positive electrode film layer is located on both surfaces of the positive electrode current collector, and its formation methods include coating or deposition. This application will use both sides as examples in the following examples. Meanwhile, the compaction density of the positive electrode film layer in this application can be used to characterize the energy density of the material; however, the compaction density of the positive electrode film layer is used to evaluate the overall compaction density of the positive electrode sheet. The compaction density of the positive electrode film layer = areal density of the positive electrode film layer / thickness of the positive electrode film layer. The thickness of the positive electrode film layer includes the distance between the two end faces of the positive electrode film layer along the thickness direction. The areal density of the positive electrode film layer = weight of a single-sided positive electrode film layer / area of ​​a single-sided positive electrode film layer. The weight of a single-sided positive electrode film layer can be obtained by weighing, and the area of ​​a single-sided positive electrode film layer can be obtained by using an area calculation formula based on the shape of the film layer. In these embodiments, this application lists a positive electrode film layer compaction density greater than or equal to 2.9 g / cm³. 3 The upper limit of the compaction density of the positive electrode film is a conventional value in the art, and will not be elaborated upon in this application.

[0271] This application discloses in some embodiments that the compaction density of the positive electrode film is 2.9 g / cm³. 3 ~3.4g / cm 3 .

[0272] This application discloses in these embodiments that the compaction density of the positive electrode film layer includes 2.9 g / cm³. 3 3.0g / cm 3 3.1g / cm 3 3.2g / cm 3 3.3g / cm 3 3.4g / cm 3 Any one of the above values ​​or any one of the above range values.

[0273] [Preparation method of positive electrode sheet]

[0274] This application discloses a method for preparing a positive electrode sheet in some embodiments, the method comprising the following steps:

[0275] Preparation of composite materials: Lithium-containing compounds, sulfur-containing compounds and silicon-containing organic compounds are pulverized and mixed to obtain composite materials;

[0276] Preparation of positive electrode slurry: Take positive electrode active material and composite material, mix them evenly and disperse them in an organic solvent to form positive electrode slurry;

[0277] Preparation of positive electrode sheet: The positive electrode slurry is coated on at least one side of the surface of the positive electrode current collector to form a positive electrode film layer.

[0278] This application discloses in some embodiments that the lithium-containing compound includes one or more of lithium oxalate, lithium squaric acid, lithium carbonate, lithium hydroxide, lithium oxide, lithium nitrate, and lithium silicate. The lithium-containing compound provided in this application is mainly used as a lithium replenishment material to supply lithium ions to the negative electrode to replenish the lithium ions consumed during SEI film formation, thereby improving the battery's initial efficiency or cycle life.

[0279] This application discloses in some embodiments that the sulfur-containing material comprises one or more of elemental sulfur, sodium sulfide, and sodium sulfite. The sulfur-containing material of this application is used to provide sulfur element, which reacts with lithium ions to form a CEI film. This CEI film has strong oxidation resistance and is part of the outer shell layer, serving as a protective film for the positive electrode active material. Simultaneously, the sulfur element is used to regulate the kinetics of lithium removal from the lithium replenishment material to improve the battery's rate performance, and also helps to form a high-quality SEI layer to reduce irreversible lithium loss.

[0280] This application discloses in some embodiments that the silicon-containing organic material comprises an organosilicon resin, which comprises a polyalkyl organosilicon resin, wherein the average degree of substitution (DS) of the hydrocarbon groups in the polyalkyl organosilicon resin is ≤1. The silicon-containing organic material of this application is stable and can also serve as a carrier for lithium-containing compounds and sulfur-containing substances, which is beneficial for the uniform distribution of lithium-containing compounds and sulfur-containing substances inside and outside the material.

[0281] This application discloses in some embodiments that the silicone-containing organic material includes one or more of polymethyl silicone resin, polyethyl silicone resin, and polyvinyl silicone resin. The silicone resins listed in this application have the advantages of high heat resistance and strong oxidation resistance.

[0282] In this application, during battery formation and cycling, sulfur is readily oxidized to sulfate. Simultaneously, the sulfate combines with lithium ions to form lithium sulfate, which is distributed within the silicon-containing organic material. As described above, due to the network structure of the silicon-containing organic material, the lithium sulfate is distributed within this network structure. This network structure provides a channel for lithium ion transport, which helps reduce the impact of the outer shell layer on the core coating on lithium-ion conductivity. Furthermore, the sulfur in the lithium sulfate can regulate the kinetics of lithium ions to improve the battery's rate performance. Therefore, the core-shell structure provided in this application helps improve the ionic conductivity of high-voltage cathode materials, thereby improving the battery's rate performance.

[0283] In some embodiments of this application, it is disclosed that the mass ratio of lithium element in lithium-containing compounds, sulfur element in sulfur-containing compounds, and silicon element in silicon-containing organic compounds is (10.0%–15.5%):(5.0%–9.2%):(7.3%–14.9%).

[0284] This application discloses in some embodiments that the composite material further includes a first conductive agent. This application adds a first conductive agent to the composite material to improve its electrical conductivity.

[0285] This application discloses in some embodiments that the first conductive agent includes one or more combinations of graphite, superconducting carbon, carbon black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0286] In some embodiments of this application, it is disclosed that the conductive agent has a mass percentage content of 8% to 15% in the composite material. In these embodiments, it is disclosed that the mass percentage content of the conductive agent in the composite material includes any one of 8%, 9%, 10%, 11%, 12%, 13%, 14%, and 15%, or any one of the above range values.

[0287] This application discloses in some embodiments that the composite material content in the above-mentioned positive electrode film layer is 2% to 6% by mass. In these embodiments, this application discloses that the composite lithium supplementation material content in the positive electrode film layer includes 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, and 3.4% by mass. Any one of the following values: 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6.0%, or any value within the range mentioned above.

[0288] In some embodiments of this application, it is disclosed that the above-mentioned crushing and mixing refer to the ball milling process, which is specifically carried out in a ball mill. In these embodiments, it is disclosed that the rotation speed of the ball mill is controlled at 600 rpm to 800 rpm and the ball milling time is 3h to 6h. Any type of ball mill is within the protection scope of this application.

[0289] This application discloses in some embodiments that an organic solvent, such as NMP, is added during ball milling to improve the thorough and effective mixing of the components.

[0290] This application discloses in some embodiments that the positive electrode film layer further includes a second conductive agent, a binder, etc. The type of the second conductive agent may be the same as or different from the first conductive agent. The second conductive agent includes, but is not limited to, one or more combinations of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black, Super P, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder includes, but is not limited to, one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc.

[0291] This application discloses in some embodiments that the positive electrode current collector can be a metal foil or a composite current collector. The metal foil can be an aluminum foil, and the composite current collector can include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector can be formed by forming a metal material, such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy, on a polymer substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE).

[0292] This application discloses a method for forming a positive electrode film in some embodiments. The method includes coating, for example, dissolving components including the positive electrode active material and other components in an organic solvent to form a positive electrode slurry, coating the positive electrode slurry onto both surfaces of a current collector, and obtaining the positive electrode film after drying and cold pressing. The solvents used to prepare the positive electrode slurry include one or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-diethylformamide (DEF), dimethyl sulfoxide (DMSO), pyridine, and tetrahydrofuran (THF). By selecting these solvents, the stability and dispersion uniformity of the positive electrode active material in the slurry can be improved; at the same time, the solubility of additives in the slurry can be improved, solving problems such as slurry instability, easy stratification, and sedimentation. The selected solvents are non-aqueous systems, which can solve the problem of additive hydrolysis by hot water.

[0293] In some embodiments of this application, the mass ratio of the positive electrode active material, the composite material, the second conductive agent, and the binder is disclosed as (92.5%–95.5%):(2%–4%):(1%–4%):(0.9%–2.2%).

[0294] The specific types of components in the positive electrode sheet of this application are as described above, and will not be repeated here.

[0295] [Negative electrode plate]

[0296] According to some embodiments of this application, as described above, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer located on at least one side surface of the negative electrode current collector. The negative electrode film layer contains a negative electrode active material. The compaction density of the negative electrode active material is as described in the section on lithium-ion batteries above.

[0297] The negative electrode active material in this application comprises carbonaceous materials, including one or more combinations of artificial graphite, natural graphite, soft carbon, and hard carbon. Among these, artificial graphite, natural graphite, soft carbon, and hard carbon encompass any form of material conventional in the art, and include any manufacturer and model conventional in the art. Simultaneously, the negative electrode active material may also comprise silicon-based materials, including one or two of silicon-oxygen materials or silicon-carbon materials. In addition, the negative electrode active material may also comprise silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, TiO2-Li4Ti5O 12 Li-Al alloys are used. However, this application is not limited to these materials; other conventional materials that can be used as negative electrode active materials in lithium-ion batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0298] The method for preparing artificial graphite in this application includes: providing raw materials, crushing and shaping → granulation → graphitization treatment → surface roughening treatment to obtain artificial graphite material. The raw materials in these embodiments of this application can be one or more of raw coke and calcined coke; preferably, the raw materials include one or more of needle-shaped raw petroleum coke, non-needle-shaped raw petroleum coke, needle-shaped coal-based raw coke, non-needle-shaped coal-based raw coke, calcined needle-shaped coke, and calcined petroleum coke. The crushing in this application can be performed using devices and methods known in the art, such as air jet mills, mechanical mills, or roller mills. During the crushing process, a large number of excessively small particles are usually generated, and sometimes excessively large particles are also generated. Therefore, after crushing, grading can be performed as needed to remove excessively small and excessively large particles from the crushed powder. Grading can obtain granular products with a better particle size distribution, which is beneficial for subsequent molding and / or granulation processes. Grading can be performed using devices and methods known in the art, such as grading sieves, gravity classifiers, or centrifugal classifiers. The shaping in this application can be performed using equipment (e.g., molding machines or other molding equipment) and methods known in the art. For example, polishing the edges of the resulting granular product facilitates subsequent operations and improves the stability of the product. The granulation process in this application includes using equipment known in the art, such as a granulator. A granulator typically includes a stirred reactor and a reactor temperature control module. Furthermore, the median particle size of the resulting product can be controlled by adjusting process conditions during granulation, such as stirring speed, heating rate, granulation temperature, and cooling rate. The graphitization process in this application includes high-temperature graphitization and low-temperature graphitization. In some embodiments, one or both of high-temperature and low-temperature graphitization can be appropriately selected for treatment according to specific needs. Alternatively, high-temperature and / or low-temperature graphitization can be repeated. High-temperature graphitization can yield graphite with an appropriate degree of graphitization and interlayer spacing. Graphite prepared at an appropriate graphitization temperature can achieve an appropriate degree of graphitization and interlayer spacing, thereby enabling the composite artificial graphite to obtain high structural stability and specific capacity. The surface roughening process in this application includes using conventional methods in the art, such as physical methods.

[0299] In addition to the negative electrode active material, the negative electrode film layer of this application also includes binders, conductive agents, dispersants, etc. The binders include, but are not limited to, polyvinyl alcohol, polyethylene glycol, sodium carboxymethyl cellulose, polyethylene oxide, polyacrylic acid, polyacrylamide, sodium alginate, styrene-butadiene rubber (SBR), etc. The conductive agents include any type conventional in the art, such as graphite, superconducting carbon, carbon black (e.g., acetylene black, Ketjen black, Super P, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers, or a combination of two or more of these. The dispersants also include any type conventional in the art, such as cellulose and its salts, specifically including, but not limited to, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, etc.

[0300] The method for forming the negative electrode film in this application includes mixing the above-mentioned raw materials with a solvent (such as deionized water) in a certain mass ratio to form a negative electrode slurry, defoaming the negative electrode slurry, and then uniformly coating the negative electrode slurry onto both sides of the negative electrode current collector; controlling the single-sided coating weight to be 0.13g~0.25g / 1540.25mm. 2 Drying and then compacting the material to a certain compaction density using a cold press yields a negative electrode sheet containing a negative electrode film layer.

[0301] [Isolation Component]

[0302] Some embodiments of this application disclose isolation elements. This application does not have any particular restrictions on the type of isolation element, and any known porous structure isolation element with good chemical and mechanical stability can be selected.

[0303] In some embodiments, the separator includes a base film (or a substrate material layer) and a coating disposed on the surface of the substrate material layer; the substrate material layer comprises one or more of polyethylene, polypropylene, poly(p-phenylene terephthalamide), polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, and polyamide; the coating comprises a ceramic coating and / or a polymer coating. The substrate material layer has good lithium-ion permeability, which is beneficial to lithium-ion migration; at least one surface of the substrate material layer is provided with a coating, which comprises one or more of a ceramic adhesive layer or a polymer adhesive layer.

[0304] This application discloses in these embodiments that the ceramic adhesive layer comprises a ceramic material selected from one or more of silicon oxide (such as SiO2), titanium oxide (such as TiO2), zirconium oxide (such as ZrO2), aluminum oxide (such as Al2O3), magnesium oxide (such as MgO), and silicon carbide (such as SiC). In some embodiments, the ceramic adhesive layer optionally further comprises an adhesive selected from one or more of polyvinylidene fluoride (PVDF), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, polyurethane (PU), and styrene-acrylic latex (SA).

[0305] In these embodiments, this application discloses that the polymer adhesive layer refers to a coating containing a polymer adhesive selected from one or more of polyvinylidene fluoride (PVDF), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, polyurethane (PU), and styrene-acrylic latex (SA).

[0306] The base film of this application is made from a matrix material, which includes one or more of polyethylene, polypropylene, poly(p-phenylene terephthalamide), polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, and polyamide. The base film can be a single-layer film or a multilayer composite film, without particular limitation. When the base film is a multilayer composite film, the materials of each layer can be the same or different, without particular limitation. In other embodiments of this application, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multilayer composite film, without particular limitation. When the separator is a multilayer composite film, the materials of each layer can be the same or different, without particular limitation.

[0307] Electrolyte

[0308] Some embodiments of this application disclose an electrolyte comprising an electrolyte salt and an organic solvent. The electrolyte salt includes any type conventional in the art, such as, but not limited to, inorganic metal salts, such as RClO4, RAsF6, RPF6, RBF4, RSbF6, RSO3F, RN(FSO2)2, etc.; fluorinated organometallic salts, such as RCF3SO3, RN(FSO2)(CF3SO2), RN(CF3SO2)2, RN(C2F5SO2)2, cyclic 1,3-hexafluoropropanedisulfonylimide lithium / sodium, cyclic 1,2-tetrafluoroethanedisulfonylimide lithium / sodium, RN(CF3SO2)(C4F5SO2)2, etc. Examples of lithium compounds include lithium ions such as RC(CF3SO2)3, RPF4(CF3)2, RPF4(C2F5)2, RPF4(CF3SO2)2, RPF4(C2F5SO2)2, RBF2(CF3)2, RBF2(C2F5)2, RBF2(CF3SO2)2, and RBF2(C2F5SO2)2; as well as metal salts containing dicarboxylic acid complexes, such as lithium bis(oxalate)borate, lithium difluorooxalate borate, lithium tri(oxalate)phosphate, lithium difluorobis(oxalate)phosphate, and lithium tetrafluoro(oxalate)phosphate. Here, both the metal and R contain lithium ions.

[0309] According to some embodiments of this application, the concentration of the electrolyte salt in the electrolyte is 0.1 mol / L to 4 mol / L. In these embodiments, this application discloses that the concentration of the electrolyte salt is any one of 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.5 mol / L, 2.8 mol / L, 3 mol / L, 3.2 mol / L, 3.5 mol / L, 3.8 mol / L, and 4 mol / L, or any one of the above ranges.

[0310] As described above, the electrolyte of this application contains one or more of fluorocarbonates, sulfones, and nitrile compounds.

[0311] The fluorinated carbonates of this application exhibit high electrochemical stability due to the strong electronegativity and weak polarity of the fluorine atom. Replacing the carbonate solvent with fluorine enhances its antioxidant capacity and facilitates the formation of a solid electrolyte interphase (SEI) film on the negative electrode surface. For example, fluoroethylene carbonate (FEC) can also form a protective film on the positive electrode surface, which is beneficial for improving the cycle stability of the electrode.

[0312] In these embodiments, this application discloses an electrolyte comprising carbonates and fluorocarbonates, wherein the fluorocarbonate comprises fluoroethylene carbonate (FEC), and the carbonate comprises one or more of ethylene carbonate (EC), propylene carbonate (PC), ethylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and butyl carbonate (BC).

[0313] The sulfone solvents used in this application exhibit higher thermal stability than conventional carbonate solvents, while also possessing good electrochemical stability; for example, the oxidation potentials of sulfolane (TMS) and methyl ethyl sulfone (EMS) are both above 5V. However, they are generally solids or have high viscosity at room temperature and are typically used in conjunction with existing carbonate solvents to lower their melting point and viscosity. Sulfone solvents cannot form a stable SEI film on graphite surfaces, necessitating the introduction of film-forming additives.

[0314] The sulfone solvents of this application include at least one or a combination of sulfolane (SF), dimethyl sulfone (MSM), ethyl sulfone (EMS), diethyl sulfone (ESE), and sulfone fluoride (FMES).

[0315] The nitrile solvents of this application exhibit high electrochemical stability; for example, glutaronitrile (GLN) has an oxidation potential as high as 8.3V (vs. Li / Li). + It has higher stability than most aprotic solvents; however, it has poor compatibility with graphite anodes, which can be improved by adding EC, etc.

[0316] The nitrile solvents of this application include one or more of acetonitrile (AN), glutaronitrile (GLN), and adiponitrile (ADN).

[0317] The CEI film on the positive electrode surface of this application is formed by the oxidation of the electrolyte on the positive electrode surface, generally at a relatively high potential. After the positive electrode surface film is formed, it is not stable during charge-discharge cycles, especially under high voltage and high temperature conditions, where it will decompose and regenerate. In order to improve the actual operating voltage of the electrolyte, a positive electrode film-forming additive can be introduced. During charging, this additive preferentially oxidizes and decomposes on the positive electrode surface than the solvent, forming a stable interfacial film on the positive electrode surface. This reduces the catalytic effect of the active sites on the positive electrode surface on the decomposition of the electrolyte, allowing the electrolyte to operate under conditions close to its theoretical oxidation and decomposition voltage.

[0318] The film-forming additives of this application include sulfonate compounds and borate compounds, wherein the sulfonate compounds include one or more of methylene disulfonate (MMDS), 1,3-propane sulfonate lactone (PS), propylene sulfonate lactone (PES), 3-fluoro1,3-propane sulfonate lactone (FPS), and vinyl sulfate (DTD).

[0319] Boronate compounds include one or more of tris(trimethylsilane)borate (TMSB), lithium dioxalate borate (LiBOB), and lithium monooxalate difluoroborate (LiDFOB).

[0320] The lithium-ion battery of this application will be described in detail below with reference to specific embodiments.

[0321] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0322] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0323] This application may employ conventional inorganic chemistry techniques within the art. In the following examples, efforts have been made to ensure the accuracy of the figures used (including quantities, temperatures, reaction times, etc.), but some experimental errors and deviations should be considered. Temperatures (in degrees Celsius) used in the following examples are expressed in °C, and pressures are at or near atmospheric pressure. All reagents were purchased from AR-grade suppliers, and all reactions were carried out under argon protection. Unless otherwise specified, all reagents were obtained commercially. The raw materials are listed below.

[0324] Table 1

[0325] type Manufacturer and Model Lithium oxalate, lithium squartzate, lithium carbonate Shanghai Aladdin Biochemical Technology Co., Ltd., 99.9% Elemental S Shanghai Aladdin Biochemical Technology Co., Ltd., 99.9% <![CDATA[Na2S]]> Shanghai Aladdin Biochemical Technology Co., Ltd., 99.9% Polymethyl silicone resin, polyvinyl silicone resin Shandong Dayi Chemical Co., Ltd., DY-MQ102N <![CDATA[Nickel manganese spinel (LiNi 0.5 Mn 1.5 O4)]]> Ningbo Ronbay New Energy Technology Co., Ltd., SNC1

[0326] Example 1

[0327] A lithium-ion battery is provided, and the specific preparation process is as follows:

[0328] Preparation of positive electrode sheet:

[0329] Li₂C₂O₄, elemental sulfur, and polymethyl silicone resin were mixed in a certain mass ratio (the mass ratio of lithium in Li₂C₂O₄, sulfur in elemental sulfur, and silicon in polymethyl silicone resin was 10.5:6.1:10.6) and placed in a ball mill. Super P (10wt%) was then added as a conductive agent. The ball milling speed was controlled at 800 rpm and the ball milling time was 4 h to obtain the composite material.

[0330] The ball-milled composite material was tested using scanning electron microscopy / X-ray energy dispersive spectroscopy (SEM / EDS). Specifically, morphology was measured using a FESEM (Zeiss Sigma 300) at an accelerating voltage of 5 kV at a rate of 10,000 cycles. Then, elemental analysis was performed using X-ray energy dispersive spectroscopy. Figure 7A ; combination Figure 7A It can be seen that the material after ball milling has been fully and evenly mixed.

[0331] Further X-ray diffraction (XRD) was used to test the ball-milled composite material. Specifically, the composite powder was placed in a sample trough 0.5 mm deep and 25 mm in diameter and spread evenly. The testing range was 5–90 degrees, and the scan rate was 4° / min. The standard card showed predominantly Li₂C₂O₄ diffraction peaks, indicating that this substance is the main original component of lithium salts and does not contain any elemental sulfur diffraction peaks, suggesting the amorphous nature of the introduced sulfur component. This characteristic of sulfur allows it to rapidly penetrate organosilicon and ultimately adsorb / bind to the outermost surface of the lithium salt, which can be observed from… Figure 7B The distribution of sulfur in the scanning mapping image is supported.

[0332] Take the above-prepared composite material and nickel-manganese spinel (molecular formula LiNi). 0.5 Mn 1.5 O4), conductive carbon black, single-walled carbon nanotubes (diameter 1nm~3nm, BET 1200m) 2 The mixture of (g) and PVDF in a mass ratio of 3:93:1:1:2 was added to the solvent NMP to form a positive electrode slurry with a solid content of 60%. This positive electrode slurry was then coated onto both surfaces of the positive electrode current collector aluminum foil, with a coating width of 70 mm and a coating surface density of 19 mg / cm³. 2 The material is heated and dried using a multi-section oven with temperatures set sequentially at 120℃, 100℃, and 90℃. Then, it is compacted using a cold press to obtain a positive electrode sheet with a compacted density of 2.9 g / cm³. 3 The positive electrode sheet is cut to obtain the positive electrode sheet.

[0333] Preparation of negative electrode sheet:

[0334] Artificial graphite, conductive carbon black (a conductive agent), sodium carboxymethyl cellulose (a stabilizer), and SBR (a binder) were dispersed in deionized water at a mass ratio of 95:2:1.2:1.8 to form a negative electrode slurry. The negative electrode slurry was then uniformly coated onto both sides of the copper foil used as the negative electrode current collector, with a coating width of 75 mm and a coating surface density of 11 mg / cm³. 2 The film was dried using a nine-section drying oven with sequential temperature settings of 100℃ / 100℃ / 95℃ / 85℃ / 85℃ / 80℃ / 80℃ / 80℃ / 60℃, followed by compaction using a cold press to achieve a single-sided coating weight of 0.15g / 1540.25mm for the negative electrode film. 2 .

[0335] Preparation of electrolyte:

[0336] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), non-aqueous organic solvents fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) are mixed at a volume ratio of 1:1 to obtain a first solvent. The first solvent is then mixed with ethylene carbonate (EC) at a volume ratio of 2:1 to form a non-aqueous solvent. Lithium hexafluorophosphate is added to the non-aqueous solvent, followed by a film-forming stabilizer (DTD + TMSB + PS in a molar ratio of 1:1:1) to prepare an electrolyte with a lithium hexafluorophosphate concentration of 1 mol / L. The amount of film-forming stabilizer added is 0.01 wt%, based on the total mass of the electrolyte.

[0337] Provide isolation components:

[0338] Polypropylene film with a thickness of 12μm is used as the separator.

[0339] Preparation of lithium-ion batteries:

[0340] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrode to provide isolation. The corresponding components are then assembled to form a wound cell. The wound cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0341] The ion battery was subjected to three charge-discharge cycles, disassembled, and the positive electrode was tested using the aforementioned scanning electron microscope / X-ray energy dispersive spectroscopy (SEM / EDS). Specifically, a FESEM (Zeiss Sigma 300) was used to perform morphological measurements at a rate of x10,000 times under an accelerating voltage of 5 kV. Then, X-ray energy dispersive spectroscopy was used to determine the elemental composition. Figure 8 ; combination Figure 8 It can be seen that the composite material is coated on the surface of the positive electrode material in the form of a coating, and Mn, Ni, and O are all distributed in the nickel-manganese spinel of the electrode (molecular formula LiNi). 0.5 Mn 1.5 On O4) particles, C, S, and Si are mainly distributed on the edges of LNMO particles.

[0342] Examples 2 to 3

[0343] A lithium-ion battery is provided, which differs from Example 1 in that the amounts of lithium-containing compounds, sulfur-containing substances, and silicon-containing organic substances used are different, while all other aspects remain the same as in Example 1.

[0344] Examples 4 to 5

[0345] A lithium-ion battery is provided, which differs from Example 1 in that it contains a different lithium compound, but is otherwise identical to Example 1.

[0346] Example 6

[0347] A lithium-ion battery is provided, which differs from Example 1 in that it contains different sulfur compounds, but otherwise remains the same as Example 1.

[0348] Example 7

[0349] A lithium-ion battery is provided, which differs from Example 1 in that it contains a different silicon-containing organic material, but is otherwise identical to Example 1.

[0350] Example 8

[0351] A lithium-ion battery is provided, which differs from Example 1 in that the electrolyte is different. The non-aqueous organic solvent sulfolane and diethyl carbonate are mixed in a volume ratio of 1:1 to obtain a first solvent. The first solvent is then mixed with dimethyl carbonate in a volume ratio of 2:1 to form a non-aqueous solvent. All other aspects are the same as in Example 1.

[0352] Examples 9 to 10

[0353] A lithium-ion battery is provided, which differs from Example 1 in that the particle size of the high-voltage positive electrode active material is different, while all other aspects remain the same as in Example 1.

[0354] Example 11

[0355] A lithium-ion battery is provided, which differs from Example 1 in that the positive electrode active material is a lithium-rich solid solution positive electrode material with the chemical formula: Li. 1.4 MnCo 0.2 Ni 0.2 O2, and everything else remains the same as in Example 1.

[0356] Example 12

[0357] A lithium-ion battery is provided, which differs from Example 1 in that the positive electrode active material is a high-nickel positive electrode material with the chemical formula: Li. 1.1 Ni 0.9 Co 0.05 Mn 0.05 O2, and everything else remains the same as in Example 1.

[0358] Comparative Example 1

[0359] A lithium-ion battery is provided, which differs from Example 1 in that it does not include a shell layer formed of a composite material. Nickel-manganese spinel (molecular formula LiNi) is used. 0.5 Mn 1.5 O4), conductive carbon black, single-walled carbon nanotubes (diameter 1nm~3nm, BET 1200m) 2Mix (g) and PVDF at a mass ratio of 96:1:1:2.

[0360] Comparative Example 2

[0361] A lithium-ion battery is provided, which differs from Example 1 in that no sulfur-containing substances are added to the composite material.

[0362] Comparative Example 3

[0363] A lithium-ion battery is provided, which differs from Example 1 in that no silicon-containing organic matter is added to the composite material.

[0364] Comparative Example 4

[0365] A lithium-ion battery is provided, which differs from Example 1 in that no lithium-containing compound is added to the composite material.

[0366] Table 2

[0367]

[0368]

[0369] [Material Parameter Testing]

[0370] ① Test the content of each element in the outer shell:

[0371] The specific measurement method includes SEM-EDS. The test steps include: using an FESEM device (Thermo Fisher Scientific A preo2s) at an accelerating voltage of 20KV, an aperture of 60um, a working distance of 8.5mm, and in-lens mode to collect secondary electron signals (to ensure the highest resolution) to perform EDS mapping to obtain the content of each element in the outer shell.

[0372] ② Test the thickness of the outer shell layer:

[0373] The cross-section of the electrode was treated using ion polishing technology. The sample preparation process was as follows:

[0374] a. Use ceramic scissors to cut the electrode into 6mm*6mm pieces and attach them to the sample stage coated with paraffin, making sure the sample protrudes slightly (<1mm) from the edge of the sample stage;

[0375] b. Set the polishing voltage to 7.5KV and the polishing time to 50min. The resulting electrode cross-section was tested using a field emission scanning electron microscope (FET). The settings were: In-lens mode, voltage: 10KV, aperture: 30um, working distance: 4.5mm. The testing procedure was as follows: 2-3 images were taken at 500x magnification (including both upper and lower active materials and the current collector), and two images were taken at 1000x magnification (including the active material on the current collector side) for both upper and lower layers. High-voltage (30K and 10K) images were taken focusing on the positive electrode active material to obtain a high-magnification electrode. The thickness of the outer shell layer was then measured.

[0376] ③ Test the particle size Dv50 of the high-voltage positive electrode active material:

[0377] The particles of the positive electrode active material were tested using a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK. The volumetric particle size distribution curve of the particles was obtained. The particle size corresponding to the cumulative volume distribution percentage reaching 50% was taken as the average particle size Dv50. For details, please refer to GB / T19077-2016.

[0378] [Battery Performance Test]

[0379] ④ Test the battery's first-cycle coulombic efficiency:

[0380] The lower cell was charged at a constant current rate of 0.5C to a voltage of 3.5V. After resting for 5 minutes, it was charged at a constant current rate of 0.2C to a voltage of 4.9V. After resting for 5 minutes, it was charged at a constant voltage of 4.9V until the current was ≤0.05C. After resting for 30 minutes, the battery capacity at this point was recorded as C1. Then, it was discharged at a constant current rate of 0.5C to the discharge cutoff voltage of 3.5V. After resting for 30 minutes, the battery capacity at this point was recorded as D1. The coulombic efficiency of the battery in the first cycle can be calculated using the formula D1 / C1×100%.

[0381] ⑤ Test the battery's DCR at 25℃:

[0382] The following steps were performed at 25°C:

[0383]

[0384]

[0385] ⑥ Test the battery's capacity retention rate after 1000 cycles at 25℃ and 45℃:

[0386] At 25℃, the battery was charged at a constant current rate of 0.5C to the cutoff voltage of 4.9V, then charged at a constant voltage until the current ≤0.05C, and allowed to stand for 30 minutes. Next, it was discharged at a constant current rate of 1C to the discharge cutoff voltage of 3.5V, and allowed to stand for 30 minutes. The battery capacity at this point was recorded as C0. This method was repeated for 1000 charge-discharge cycles, and the battery capacity after 1000 cycles was recorded as C1. The cycle capacity retention rate at 25℃ can be calculated using the formula C1 / C0 × 100%.

[0387] At 45°C, the battery capacity retention rate was measured and calculated after 1000 cycles according to the above test method.

[0388] Table 3

[0389]

[0390]

[0391] As can be seen from the list, the design method provided in this application is beneficial to improving the first-time efficiency of the battery and can reduce the internal resistance of the battery to a certain extent. In addition, the cycle stability of the battery designed in this application is also improved. Furthermore, the design method provided in this application is applicable to high-voltage positive electrode active materials and is also beneficial to improving the energy density of the battery.

[0392] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery device, characterized in that: Including lithium-ion batteries and battery management systems; The lithium-ion battery includes a positive electrode, a separator, and a negative electrode stacked together. The positive electrode includes a positive electrode material, the positive electrode material having a core-shell structure, the core-shell structure including a core and an outer shell layer, the outer shell layer being located on at least a portion of the surface of the core; The core contains a positive electrode active material; The outer shell layer contains lithium, sulfur, and silicon. The charging cutoff voltage of the battery device is set to be greater than 4.5V in the battery management system.

2. The battery device according to claim 1, characterized in that: The lithium element in the outer shell layer has a mass percentage content of 10.0% to 15.5%; and / or; The sulfur element in the outer shell layer has a mass percentage content of 5.0% to 9.2%; and / or; The silicon element in the outer shell layer has a mass percentage content of 7.3% to 14.9%.

3. The battery device according to claim 2, characterized in that: The outer shell of the core-shell structure also includes carbon and oxygen elements, and the carbon element in the outer shell contains 15.1% to 20.8% by mass. and / or; The oxygen element in the outer shell layer has a mass percentage content of 50.1% to 58.9%; The balance contains hydrogen and essential impurity elements.

4. The battery device according to any one of claims 1 to 3, characterized in that: The outer shell layer of the core-shell structure comprises an organosilicon resin, and the organosilicon resin has a network structure. The outer shell layer also contains lithium sulfate, which is distributed within the mesh structure.

5. The battery device according to claim 4, characterized in that: The silicone resin includes polyalkyl silicone resin.

6. The battery device according to claim 5, characterized in that: The silicone resin includes one or more of polymethyl silicone resin, polyethyl silicone resin, and polyvinyl silicone resin.

7. The battery device according to any one of claims 1 to 6, characterized in that: The volumetric particle size distribution Dv50 of the positive electrode active material is 5.1 μm to 9.0 μm.

8. The battery device according to any one of claims 1 to 7, characterized in that: The thickness of the outer shell layer is <0.5μm, preferably 0.05μm to 0.45μm.

9. The battery device according to any one of claims 1 to 8, characterized in that: The positive electrode active material includes any one or more of the following: lithium-rich solid solution positive electrode material, nickel-manganese spinel positive electrode material, high-nickel positive electrode material, polyanionic positive electrode material, and modified lithium cobalt oxide positive electrode material.

10. The battery device according to any one of claims 1 to 9, characterized in that: The positive electrode sheet includes a positive electrode film layer, and the compaction density of the positive electrode film layer is greater than or equal to 2.9 g / cm³. 3 The preferred value is 2.

9. g / cm 3 ~3.4g / cm 3 。 11. The battery device according to any one of claims 1 to 10, characterized in that: The lithium-ion battery further includes an electrolyte, which contains one or more of fluorinated carbonates, sulfones, and nitrile compounds.

12. A lithium-ion battery, characterized in that: This includes a stacked positive electrode, a separator, and a negative electrode; The positive electrode includes a positive electrode material, the positive electrode material having a core-shell structure, the core-shell structure including a core and an outer shell layer, the outer shell layer being located on at least a portion of the surface of the core; The core contains a positive electrode active material; The outer shell contains lithium, sulfur, and silicon.

13. A positive electrode plate, characterized in that: It includes a positive current collector and a positive electrode film layer located on at least one side surface of the positive current collector; The positive electrode film layer includes a positive electrode material, the positive electrode material having a core-shell structure, the core-shell structure including a core and an outer shell layer, the outer shell layer being located on at least a portion of the surface of the core; The core contains a positive electrode active material; The outer shell contains lithium, sulfur, and silicon.

14. A method for preparing a positive electrode sheet, characterized in that: The process includes the following: Preparation of composite materials: Lithium-containing compounds, sulfur-containing compounds and silicon-containing organic compounds are pulverized and mixed to obtain composite materials; Preparation of positive electrode slurry: Take positive electrode active material and composite material, mix them evenly and disperse them in an organic solvent to form positive electrode slurry; Preparation of positive electrode sheet: The positive electrode slurry is coated on at least one side of the surface of the positive electrode current collector to form a positive electrode film layer.

15. The preparation method according to claim 14, characterized in that: The lithium-containing compound comprises any one or more of lithium oxalate, lithium squaric acid, lithium carbonate, lithium hydroxide, lithium oxide, lithium nitrate, and lithium silicate. and / or; The sulfur-containing substance includes one or more of elemental sulfur, sodium sulfide, and sodium sulfite; and / or; The silicon-containing organic compound includes an organosilicon resin, the organosilicon resin includes a polyalkyl organosilicon resin, and the average degree of substitution of the hydrocarbon groups in the polyalkyl organosilicon resin is DS≤1.

16. The preparation method according to any one of claims 14 to 15, characterized in that: The silicon-containing organic material includes one or more of polymethyl silicone resin, polyethyl silicone resin, and polyvinyl silicone resin.

17. The preparation method according to any one of claims 14 to 16, characterized in that: The mass ratio of lithium in the lithium-containing compound, sulfur in the sulfur-containing compound, and silicon in the silicon-containing organic compound is (10.0%–15.5%):(5.0%–9.2%):(7.3%–14.9%).

18. The preparation method according to any one of claims 14 to 17, characterized in that: The composite material also contains a conductive agent; The conductive agent has a mass percentage content of 8% to 15% in the composite material; The conductive agent includes one or more of graphite, superconducting carbon, carbon black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

19. The preparation method according to any one of claims 14 to 18, characterized in that: The composite material has a mass percentage content of 2% to 6% in the positive electrode film layer.

20. An electrical appliance, characterized in that: The battery device according to any one of claims 1 to 11, the lithium-ion battery according to claim 12, the positive electrode according to claim 13, or the positive electrode prepared by any one of claims 14 to 19.

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