Secondary battery and electric device

Abstract

The invention provides a secondary battery and an electric device. The secondary battery comprises a positive pole piece, a negative pole piece, electrolyte and an isolating membrane arranged between the positive pole piece and the negative pole piece, the isolating membrane comprises an additive, and the additive comprises at least one selected from a pyridine compound and a phosphine compound; the positive pole piece comprises a positive active material, the positive active material comprises an inner core and a carbon coating layer, the carbon coating layer at least covers part of the surface of the inner core, and the inner core comprises a phosphate material.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and more particularly to a secondary battery and an electrical device. Background Technology

[0002] Secondary batteries have advantages such as high energy density, high operating voltage, low self-discharge rate, small size, and light weight, and are widely used in the consumer electronics field.

[0003] With the rapid development of electric vehicles and mobile electronic devices, people have increasingly higher requirements for the safety performance of secondary batteries. How to reduce the possibility of gas generation during battery cycling and improve battery safety performance is a scientific and technological problem that urgently needs to be solved in the field of secondary battery applications. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a secondary battery and an electrical device, wherein the separator of the secondary battery contains specific additives that can remove acidic substances in the battery system, thereby reducing the possibility of acidic substances undergoing a reduction reaction at the negative electrode to produce hydrogen gas, reducing the possibility of gas production during battery cycling, and improving the safety performance of the battery.

[0005] A first aspect of this application provides a secondary battery, including a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode, wherein the separator includes an additive, the additive including at least one selected from pyridine compounds and phosphine compounds;

[0006] The positive electrode sheet includes a positive active material, which includes a core and a carbon coating layer. The carbon coating layer covers at least a portion of the surface of the core, and the core includes a phosphate material.

[0007] Phosphate materials, with their advantages of long lifespan and good safety performance, have become a hot research topic in the industry. However, their poor conductivity limits their development in high-power applications. Carbon coating can improve their electrochemical performance; however, the carbon coating layer contains hydrophilic oxygen-containing functional groups, making it prone to adsorbing water molecules. These adsorbed water molecules are difficult to remove completely during cell manufacturing, resulting in a high water content within the cell. The electrolyte in the battery system is extremely sensitive to the presence of moisture. LiPF6 in the electrolyte is prone to hydrolysis in the presence of trace amounts of moisture, generating acidic substances such as phosphorus pentafluoride and hydrogen fluoride. These acidic substances easily migrate to the negative electrode during battery cycling, where they undergo reduction reactions to produce hydrogen gas, affecting battery safety.

[0008] To address the aforementioned issues, this application introduces pyridine and phosphine compounds as additives in the separator of a lithium manganese iron phosphate battery system with carbon-coated positive electrode active material. These pyridine and phosphine compounds contain Lewis basic groups. During battery charging and discharging, through Lewis acid-base neutralization reactions, the additives can react with or form complexes with acidic substances in the battery system. This reduces the content of acidic substances in the electrolyte, lowers the likelihood of hydrogen generation from the reduction of acidic substances at the negative electrode, reduces the possibility of gas generation during battery cycling, and improves battery safety performance.

[0009] In any embodiment, the separator includes a substrate and a coating comprising inorganic and / or organic particles disposed on at least one surface of the substrate.

[0010] The additive is located between inorganic and / or organic particles in the coating or as a separate layer between the substrate and the coating.

[0011] Additives are placed between inorganic and / or organic particles in the inorganic and / or organic particle layer, or placed as a separate layer between the substrate and the inorganic and / or organic particle layer. This reduces the possibility of premature additive failure due to direct contact between the additive and the positive and negative electrodes. It achieves the purpose of removing acidic substances from the system and reducing gas generation. At the same time, compared with acidic substances, the reaction byproducts obtained after the additive reacts or combines with acidic substances are larger in size, so they are less likely to diffuse through the inorganic and / or organic particle layer into the electrolyte. This reduces the impact of reaction byproducts on the interface impedance of the positive or negative electrode, improves the high-temperature cycle performance and high-temperature storage performance of the battery, and extends the battery's service life.

[0012] In any embodiment, based on the mass of the electrolyte, the mass content of the additive is less than or equal to 0.3%.

[0013] By controlling the mass content of additives in the electrolyte to be less than or equal to 0.3%, meaning that the additives are basically present in the separator and little or no additives are present in the electrolyte, the possibility of additives in the electrolyte coming into direct contact with the positive and negative electrodes and thus failing prematurely is reduced. This achieves the purpose of removing acidic substances from the system, which can reduce the possibility of acidic substances undergoing reduction reactions at the negative electrode to produce hydrogen gas, reduce the possibility of gas generation during battery cycling, and improve the safety performance of the battery.

[0014] In any embodiment, the viscosity of the electrolyte at 25°C is less than or equal to 3 mPa·s.

[0015] As mentioned earlier, additives in the separator can react with acidic substances in the system, reducing the impact of acidic substances on gas generation in the battery. However, additives and their reaction byproducts can remain in the pores of the separator, reducing its ionic conductivity and affecting the battery's kinetic performance.

[0016] By controlling the viscosity of the electrolyte to be less than or equal to 3 mPa·S, the migration rate and conductivity of active ions in the electrolyte can be improved, alleviating the kinetic problems caused by the blockage of pores by additives and their reaction byproducts in the separator, and improving the kinetic performance and cycle performance of the battery.

[0017] In any embodiment, the electrolyte comprises a first solvent having a viscosity of less than 0.65 mPa·s at 25°C.

[0018] Adding a first solvent with a viscosity of less than 0.65 mPa·S to the electrolyte can reduce the electrolyte viscosity, thereby increasing the mobility and conductivity of active ions in the electrolyte and improving the battery's kinetic and cycle performance.

[0019] In any embodiment, the first solvent includes one or more of dimethyl carbonate, methyl formate, ethyl formate, methyl acetate, ethyl acetate, ethyl propionate, ethyl butyrate, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, 1,2-dimethoxyethane, acetonitrile, methyl nonafluorobutyl ether, and ethyl nonafluorobutyl ether.

[0020] In any embodiment, based on the mass of the electrolyte, the mass content of the first solvent is 10%-80%.

[0021] In any embodiment, based on the mass of the electrolyte, the mass content of the first solvent is 30%-70%.

[0022] Controlling the mass content of the first solvent within a suitable range can improve the migration rate of active ions, increase the ionic conductivity of the electrolyte, and enhance the kinetic and rate performance of the battery. At the same time, it can prevent excessive low-viscosity first solvent from affecting the oxidation resistance of the electrolyte, reduce gas generation and / or lithium plating caused by oxidation, and improve the cycle performance and safety performance of the battery.

[0023] In any embodiment, the pyridine compound includes at least one selected from compounds shown in Formula I, Formula II, and Formula III.

[0024]

[0025] The phosphine compounds include at least one selected from the compounds shown in Formula IV.

[0026]

[0027] Where R1~R 13 and R 15 ~R 17 Each independently includes any one of the following: alkyl groups having 1-20 carbon atoms, alkenyl groups having 2-20 carbon atoms, aryl groups having 6-26 carbon atoms, aryloxy groups having 6-26 carbon atoms, and groups formed by substitution of these groups with F, Cl, Br, sulfonic acid groups, or sulfonyl groups, H, F, Cl, Br, R 14 It includes any one of the following groups selected from alkyl groups having 1-20 carbon atoms, alkenyl groups having 2-20 carbon atoms, aryl groups having 7-26 carbon atoms, aryloxy groups having 7-26 carbon atoms, and groups formed by substituting them with F, Cl, Br, sulfonic acid group or sulfonyl group, where n is an integer greater than or equal to 2.

[0028] In any embodiment, the pyridine compound includes at least one selected from isonicotinate, 2-hydroxypyridine-4-carboxylate, and 2,2'-bipyridine-4,4'-dicarboxylate.

[0029] In any embodiment, the isonicotinate comprises at least one selected from lithium isonicotinate, sodium isonicotinate, potassium isonicotinate, aluminum isonicotinate, magnesium isonicotinate, calcium isonicotinate, iron isonicotinate, cobalt isonicotinate, nickel isonicotinate, and manganese isonicotinate; and / or;

[0030] The 2-hydroxypyridine-4-carboxylate includes at least one selected from lithium 2-hydroxypyridine-4-carboxylate, sodium 2-hydroxypyridine-4-carboxylate, potassium 2-hydroxypyridine-4-carboxylate, aluminum 2-hydroxypyridine-4-carboxylate, magnesium 2-hydroxypyridine-4-carboxylate, calcium 2-hydroxypyridine-4-carboxylate, iron 2-hydroxypyridine-4-carboxylate, cobalt 2-hydroxypyridine-4-carboxylate, nickel 2-hydroxypyridine-4-carboxylate, and manganese 2-hydroxypyridine-4-carboxylate; and / or,

[0031] The 2,2'-bipyridine-4,4'-dicarboxylate includes at least one selected from sodium 2,2'-bipyridine-4,4'-dicarboxylate, potassium 2,2'-bipyridine-4,4'-dicarboxylate, aluminum 2,2'-bipyridine-4,4'-dicarboxylate, magnesium 2,2'-bipyridine-4,4'-dicarboxylate, calcium 2,2'-bipyridine-4,4'-dicarboxylate, ferric 2,2'-bipyridine-4,4'-dicarboxylate, cobalt 2,2'-bipyridine-4,4'-dicarboxylate, nickel 2,2'-bipyridine-4,4'-dicarboxylate, and manganese 2,2'-bipyridine-4,4'-dicarboxylate.

[0032] In any embodiment, the phosphine compound includes at least one selected from diethylphenylphosphine, trihexylphosphine, tributylphosphine, 1,6-bis(diphenylphosphine)hexane, tri(o-methoxyphenyl)phosphine, tri-n-octylphosphine, diphenylcyclohexylphosphine, diphenyl-2-pyridinylphosphine, 2-(dicyclohexylphosphine)biphenyl, 2-(di-tert-butylphosphine)biphenyl, diphenylethoxyphosphine, tri(2-furanyl)phosphine, tricyclopentylphosphine, and diethylphenylphosphine.

[0033] In any embodiment, the loading of the additive on the separator membrane is 0.01 g / m³. 2 -10g / m 2 .

[0034] By controlling the amount of additives loaded on the separator within a suitable range, the content of acidic substances in the battery system can be effectively reduced, thereby reducing the possibility of acidic substances undergoing reduction reactions at the negative electrode to produce hydrogen gas, reducing the possibility of gas generation during battery cycling, improving battery safety performance, and also avoiding the impact of excessive additives on the gas permeability of the separator and the internal resistance of the battery, thus comprehensively improving the battery's dynamic performance and cycle performance.

[0035] In any implementation, the chemical formula of the kernel is:

[0036] Li m A a Fe x Mn b D d P y E e O z G g ,

[0037] Wherein, A includes at least one element selected from Al, Na, K, and Mg;

[0038] The D includes at least one element selected from Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, Ti, and V;

[0039] The E includes at least one element selected from B, S, Si, and N;

[0040] The G includes at least one element selected from S, F, Cl, and Br;

[0041] The value of m is selected from the range of 0.95 to 1.15;

[0042] The a is selected from the range of 0 to 0.1;

[0043] The x is selected from the range of 0.1 to 1;

[0044] The value of b is selected from the range of 0.1 to 0.9;

[0045] The d is selected from the range of 0 to 0.1;

[0046] The value of y is selected from the range of 0.95 to 1;

[0047] The value of e is selected from the range of 0 to 0.1;

[0048] The z is selected from the range of 3.5 to 4;

[0049] The value of g is selected from the range of 0 to 0.1.

[0050] By simultaneously doping specific elements at specific amounts at the Li, Mn, P, and O sites of the core material, significantly improved rate performance can be obtained, while significantly reducing the dissolution of Mn and Mn-site dopants, resulting in significantly improved cycle performance and storage performance. Furthermore, the specific capacity and compaction density of the material can also be obtained.

[0051] In any embodiment, the thickness of the carbon coating layer is less than or equal to 10 nm.

[0052] In any embodiment, the thickness of the carbon coating layer is 5 nm to 7.5 nm.

[0053] Controlling the thickness of the carbon coating layer on the surface of the core within a suitable range can improve the conductivity of the positive electrode active material, reduce the structural degradation of the positive electrode active material during cycling, reduce the dissolution of manganese metal, and also prevent excessive carbon coating layer thickness from introducing too much trace water into the system. It also reduces the impact of carbon coating layer thickness on the extraction and insertion of lithium ions in the core.

[0054] In any embodiment, the thickness of the coating is 0.1 μm to 10 μm.

[0055] In any embodiment, the thickness of the coating is 0.5 μm to 5 μm.

[0056] By controlling the coating thickness within a suitable range, contact between the additives and the positive and negative electrode interfaces can be effectively isolated, reducing the possibility of premature additive failure and thus lowering the likelihood of acidic substances undergoing reduction reactions at the negative electrode to generate hydrogen gas. On the other hand, it also avoids the coating thickness affecting the permeability of the separator and the internal resistance of the battery, comprehensively improving the battery's kinetic and cycle performance.

[0057] In any embodiment, the inorganic particles comprise at least one selected from the group consisting of silicon dioxide, aluminum oxide, boehmite, magnesium oxide, titanium dioxide, zinc oxide, and magnesium aluminate; and / or, the organic particles comprise at least one selected from the group consisting of polyethylene oxide particles, polyvinylidene chloride particles, polyacrylonitrile particles, polyvinylidene fluoride particles, polymethyl methacrylate particles, and polyvinylidene fluoride-hexafluoropropylene copolymer particles.

[0058] A second aspect of this application provides an electrical device comprising the secondary battery described in the first aspect. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application;

[0060] Figure 2 yes Figure 1 An exploded view of a secondary battery according to an embodiment of this application is shown.

[0061] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application;

[0062] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0063] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown;

[0064] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0065] Figure label:

[0066] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Casing; 52 Electrode assembly; 53 Cover plate. Detailed Implementation

[0067] The embodiments of the secondary battery and power-consuming device of this application are hereby disclosed in detail with appropriate reference to the accompanying drawings. 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 making the following description unnecessarily lengthy 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.

[0068] 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 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 "ab" 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.

[0069] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0070] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0071] 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.

[0072] 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.

[0073] 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).

[0074] Phosphate materials possess advantages such as good safety performance, wide availability of raw materials, and long cycle life, making them a hot research topic in the industry. However, these materials inherently suffer from poor conductivity, hindering their development in high-power applications. Carbon coating can improve their electrochemical performance; however, the carbon coating layer contains hydrophilic oxygen-containing functional groups, making it prone to adsorbing water molecules, which are difficult to completely remove during cell manufacturing, resulting in a significant water content within the cell. The electrolyte in the battery system is extremely sensitive to the presence of moisture. LiPF6 in the electrolyte is prone to hydrolysis in the presence of trace amounts of moisture, generating acidic substances such as phosphorus pentafluoride and hydrogen fluoride. These acidic substances can then undergo reduction reactions at the negative electrode, producing hydrogen gas, leading to gas generation and affecting battery safety.

[0075] [Rechargeable Battery]

[0076] This application provides a secondary battery, including a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode. The separator includes an additive, which includes at least one selected from pyridine compounds and phosphine compounds.

[0077] The positive electrode sheet includes a positive active material, which includes a core and a carbon coating layer. The carbon coating layer covers at least a portion of the surface of the core, and the core includes a phosphate material.

[0078] The additives in the separator, such as pyridine and phosphine compounds, contain Lewis basic groups. During battery charging and discharging, through Lewis acid-base neutralization reactions, the additives can react with or form complexes with acidic substances in the battery system. This reduces the content of acidic substances in the electrolyte, decreases the possibility of acidic substances in the battery system undergoing reduction reactions at the negative electrode to generate hydrogen gas, reduces the possibility of gas generation during battery cycling, and improves battery safety performance.

[0079] In some embodiments, the separator includes a substrate and a coating comprising inorganic and / or organic particles disposed on at least one surface of the substrate.

[0080] The additive is located between inorganic and / or organic particles in the coating or as a separate layer between the substrate and the coating.

[0081] In this application, the term "inorganic particles and / or organic particles" refers to individual inorganic particles, individual organic particles, or a mixture of both. For example, the term "inorganic particle and / or organic particle layer" refers to a layer consisting of individual inorganic particles, a layer consisting of individual organic particles, or a mixture of both. Specific examples will be described in detail in the Embodiments section below.

[0082] Additives are placed between inorganic and / or organic particles in the inorganic and / or organic particle layer, or placed as a separate layer between the substrate and the inorganic and / or organic particle layer. This reduces the possibility of premature additive failure due to direct contact between the additive and the positive and negative electrodes. It achieves the purpose of removing acidic substances from the system and reducing gas generation. At the same time, compared with acidic substances, the reaction byproducts obtained after the additive reacts or combines with acidic substances are larger in size, so they are less likely to diffuse through the inorganic and / or organic particle layer into the electrolyte. This reduces the impact of reaction byproducts on the interface impedance of the positive or negative electrode, improves the high-temperature cycle performance and high-temperature storage performance of the battery, and extends the battery's service life.

[0083] In some embodiments, the mass content of the additive is less than or equal to 0.3% based on the mass of the electrolyte.

[0084] In some embodiments, based on the mass of the electrolyte, the mass content of the additive can be selected as 0%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, or a range of any two of the above values.

[0085] The mass content of additives in the electrolyte can be determined using commonly used testing methods in this field, for example: disassemble the battery, obtain the electrolyte, and determine it by separation and detection analysis using ion chromatography and infrared spectroscopy, referring to standards JY / T 020-1996 and GB / T6040-2002.

[0086] By controlling the mass content of additives in the electrolyte to be less than or equal to 0.3%, meaning that the additives are basically present in the separator and little or no additives are present in the electrolyte, the possibility of additives in the electrolyte coming into direct contact with the positive and negative electrodes and thus failing prematurely is reduced. This achieves the purpose of removing acidic substances from the system, which can reduce the possibility of acidic substances undergoing reduction reactions at the negative electrode to produce hydrogen gas, reduce the possibility of gas generation during battery cycling, and improve the safety performance of the battery.

[0087] In some embodiments, the viscosity of the electrolyte at 25°C is less than or equal to 3 mPa·s.

[0088] In some embodiments, the viscosity of the electrolyte at 25°C may be selected as 1.2 mPa·s, 1.5 mPa·s, 2.0 mPa·s, 2.2 mPa·s, 2.4 mPa·s, 2.5 mPa·s, or a range of any two of the above values.

[0089] The viscosity of the electrolyte at 25°C can be determined using commonly used testing methods in this field, for example: the electrolyte is obtained by disassembling the battery and determined by rotational viscosity analysis, which can be referenced in standard GB / T10247.

[0090] As mentioned earlier, additives in the separator can react with acidic substances in the system, reducing the impact of acidic substances on gas generation in the battery. However, additives and their reaction byproducts can remain in the pores of the separator, reducing its ionic conductivity and affecting the battery's kinetic performance.

[0091] By controlling the viscosity of the electrolyte to be less than or equal to 3 mPa·S, the migration rate and conductivity of active ions in the electrolyte can be improved, alleviating the kinetic problems caused by the blockage of pores by additives and their reaction byproducts in the separator, and improving the kinetic performance and cycle performance of the battery.

[0092] In some embodiments, the electrolyte comprises a first solvent having a viscosity of less than 0.65 mPa·s at 25°C. In some embodiments, the viscosity of the first solvent at 25°C may be selected from 0.1 mPa·s, 0.2 mPa·s, 0.3 mPa·s, 0.4 mPa·s, 0.5 mPa·s, 0.6 mPa·s, or a range of any two of the above values.

[0093] Adding a first solvent with a viscosity of less than 0.65 mPa·S to the electrolyte can reduce the electrolyte viscosity, thereby increasing the mobility and conductivity of active ions in the electrolyte and improving the battery's kinetic and cycle performance.

[0094] In some embodiments, the first solvent includes one or more of dimethyl carbonate, methyl formate, ethyl formate, methyl acetate, ethyl acetate, ethyl propionate, ethyl butyrate, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, 1,2-dimethoxyethane, acetonitrile, methyl nonafluorobutyl ether, and ethyl nonafluorobutyl ether.

[0095] In some embodiments, the viscosity of dimethyl carbonate is 0.63 mPa·s at 25°C.

[0096] In some embodiments, the viscosity of methyl acetate is 0.48 mPa·s at 25°C.

[0097] In some embodiments, the viscosity of ethyl acetate is 0.55 mPa·s at 25°C.

[0098] In some embodiments, the viscosity of ethyl propionate is 0.59 mPa·s at 25°C.

[0099] In some embodiments, the viscosity of ethyl butyrate is 0.63 mPa·s at 25°C.

[0100] In some embodiments, the viscosity of tetrahydrofuran is 0.46 mPa·s at 25°C.

[0101] In some embodiments, the viscosity of 2-methyltetrahydrofuran is 0.48 mPa·s at 25°C.

[0102] In some embodiments, the viscosity of 1,2-dimethoxyethane is 0.58 mPa·s at 25°C.

[0103] In some embodiments, the viscosity of acetonitrile is 0.40 mPa·s at 25°C.

[0104] In some embodiments, the viscosity of ethyl nonafluorobutyl ether is 0.46 mPa·s at 25°C.

[0105] The viscosity of the first solvent at 25°C can be determined using commonly used testing methods in this field, as shown in the following example: determined by rotational viscosity analysis, which can be referenced in standard GB / T10247.

[0106] In some embodiments, based on the mass of the electrolyte, the mass content of the first solvent is 10%-80%, optionally 30%-70%.

[0107] In some embodiments, based on the mass meter of the electrolyte, the mass content of the first solvent can be selected as 10%, 30%, 40%, 50%, 60%, 70%, 80%, or a range of any two of the above values.

[0108] Controlling the mass content of the first solvent within a suitable range can improve the migration rate of active ions, increase the ionic conductivity of the electrolyte, and enhance the kinetic and rate performance of the battery. At the same time, it can prevent excessive low-viscosity first solvent from affecting the oxidation resistance of the electrolyte, reduce gas generation and / or lithium plating caused by oxidation, and improve the cycle performance and safety performance of the battery.

[0109] In some embodiments, the pyridine compound includes at least one selected from compounds shown in Formula I, Formula II, and Formula III.

[0110]

[0111] The phosphine compounds include at least one selected from the compounds shown in Formula IV.

[0112]

[0113] Where R1~R 13 and R 15 ~R 17 Each independently includes any one of the following: alkyl groups having 1-20 carbon atoms, alkenyl groups having 2-20 carbon atoms, aryl groups having 6-26 carbon atoms, aryloxy groups having 6-26 carbon atoms, and groups formed by substitution of these groups with F, Cl, Br, sulfonic acid groups, or sulfonyl groups, H, F, Cl, Br, R 14 It includes any one of the following groups selected from alkyl groups having 1-20 carbon atoms, alkenyl groups having 2-20 carbon atoms, aryl groups having 7-26 carbon atoms, aryloxy groups having 7-26 carbon atoms, and groups formed by substituting them with F, Cl, Br, sulfonic acid group or sulfonyl group, where n is an integer greater than or equal to 2.

[0114] In some embodiments, the pyridine compound includes at least one selected from isonicotinate, 2-hydroxypyridine-4-carboxylate, and 2,2'-bipyridine-4,4'-dicarboxylate.

[0115] In some embodiments, the isonicotinate includes at least one selected from lithium isonicotinate, sodium isonicotinate, potassium isonicotinate, aluminum isonicotinate, magnesium isonicotinate, calcium isonicotinate, iron isonicotinate, cobalt isonicotinate, nickel isonicotinate, and manganese isonicotinate.

[0116] In some embodiments, the 2-hydroxypyridine-4-carboxylate includes at least one selected from lithium 2-hydroxypyridine-4-carboxylate, sodium 2-hydroxypyridine-4-carboxylate, potassium 2-hydroxypyridine-4-carboxylate, aluminum 2-hydroxypyridine-4-carboxylate, magnesium 2-hydroxypyridine-4-carboxylate, calcium 2-hydroxypyridine-4-carboxylate, iron 2-hydroxypyridine-4-carboxylate, cobalt 2-hydroxypyridine-4-carboxylate, nickel 2-hydroxypyridine-4-carboxylate, and manganese 2-hydroxypyridine-4-carboxylate.

[0117] In some embodiments, the 2,2'-bipyridine-4,4'-dicarboxylate includes at least one selected from sodium 2,2'-bipyridine-4,4'-dicarboxylate, potassium 2,2'-bipyridine-4,4'-dicarboxylate, aluminum 2,2'-bipyridine-4,4'-dicarboxylate, magnesium 2,2'-bipyridine-4,4'-dicarboxylate, calcium 2,2'-bipyridine-4,4'-dicarboxylate, iron 2,2'-bipyridine-4,4'-dicarboxylate, cobalt 2,2'-bipyridine-4,4'-dicarboxylate, nickel 2,2'-bipyridine-4,4'-dicarboxylate, and manganese 2,2'-bipyridine-4,4'-dicarboxylate.

[0118] In some embodiments, the phosphine compound includes at least one selected from diethylphenylphosphine, trihexylphosphine, tributylphosphine, 1,6-bis(diphenylphosphine)hexane, tri(o-methoxyphenyl)phosphine, tri-n-octylphosphine, diphenylcyclohexylphosphine, diphenyl-2-pyridinylphosphine, 2-(dicyclohexylphosphine)biphenyl, 2-(di-tert-butylphosphine)biphenyl, diphenylethoxyphosphine, tri(2-furanyl)phosphine, tricyclopentylphosphine, and diethylphenylphosphine.

[0119] In some embodiments, the additive is loaded onto the separator membrane at a rate of 0.01 g / m³. 2 -10g / m 2 .

[0120] In some embodiments, the additive is loaded onto the separator membrane at a rate of 0.01 g / m³. 2 1g / m 2 2g / m 2 3g / m 2 4g / m 2 5g / m 2 6g / m 2 7g / m 2 8g / m 2 9g / m 2 10g / m 2 Or a range consisting of any two of the above values.

[0121] The loading of additives on the separator membrane can be determined using commonly used testing methods in the field, as shown in the following example: Disassemble the battery to obtain the separator membrane, cut the separator membrane into 3cm*3cm samples, soak the samples in a solvent that can dissolve the additives (such as deionized water) for 5 days, filter and dry the solvent, obtain the mass of additives in the sample, and then calculate the loading of additives on the separator membrane.

[0122] By controlling the amount of additives loaded on the separator within a suitable range, the content of acidic substances in the battery system can be effectively reduced, thereby reducing the possibility of acidic substances undergoing reduction reactions at the negative electrode to produce hydrogen gas, reducing the possibility of gas generation during battery cycling, improving battery safety performance, and also avoiding the impact of excessive additives on the gas permeability of the separator and the internal resistance of the battery, thus comprehensively improving the battery's dynamic performance and cycle performance.

[0123] In some embodiments, the chemical formula of the kernel is:

[0124] Li m A a Fe x Mn b D d P y E e O z G g ,

[0125] Wherein, A includes at least one element selected from Al, Na, K, and Mg;

[0126] The D includes at least one element selected from Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, Ti, and V;

[0127] The E includes at least one element selected from B, S, Si, and N;

[0128] The G includes at least one element selected from S, F, Cl, and Br;

[0129] The value of m is selected from the range of 0.95 to 1.15;

[0130] The a is selected from the range of 0 to 0.1;

[0131] The x is selected from the range of 0.1 to 1;

[0132] The value of b is selected from the range of 0.1 to 0.9;

[0133] The d is selected from the range of 0 to 0.1;

[0134] The value of y is selected from the range of 0.95 to 1;

[0135] The value of e is selected from the range of 0 to 0.1;

[0136] The z is selected from the range of 3.5 to 4;

[0137] The value of g is selected from the range of 0 to 0.1.

[0138] In some implementations, m is 0.95, 1.00, 1.05, 1.10, 1.15, or a range consisting of any two of the above values.

[0139] In some implementations, 'a' is 0, 0.05, 0.1, or a range consisting of any two of the above values.

[0140] In some implementations, x is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or a range consisting of any two of the above values.

[0141] In some implementations, b is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or a range consisting of any two of the above values.

[0142] In some implementations, d is 0, 0.05, 0.1, or a range of any two of the above values.

[0143] In some implementations, y is 0.95, 0.96, 0.97, 0.98, 1, or a range consisting of any two of the above values.

[0144] In some implementations, e is 0, 0.05, 0.1, or a range of any two of the above values.

[0145] In some implementations, z is 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, or a range consisting of any two of the above values.

[0146] In some implementations, g is 0, 0.05, 0.1, or a range of any two of the above values.

[0147] In this application, the doping composition of the positive electrode active material is determined by inductively coupled plasma (ICP) spectroscopy, for example, referring to standards YS / T1006.2-2014, GB / T23367.2-2009, or YS / T1028.5-2015. Specifically, according to the embodiments of this application, an inductively coupled plasma emission spectrometer can be used, and the measurement can be performed according to the instruction manual of the corresponding equipment.

[0148] Selecting an appropriate dopant element D at the Mn site can improve the lattice change rate of lithium manganese iron phosphate during lithium insertion / extraction, enhance the structural stability of the cathode active material, significantly reduce manganese dissolution, and decrease oxygen activity on the particle surface. This can improve the specific capacity of the material, reduce interfacial side reactions between the material and the electrolyte during use, and ultimately improve the cycle performance of the material.

[0149] Choosing an appropriate P-site dopant element E can help change the ease with which the Mn-O bond length changes, thereby improving electronic conductivity and reducing the lithium-ion migration barrier, promoting lithium-ion migration, and improving the rate performance of secondary batteries.

[0150] Appropriate elemental doping with A at the Li site can also improve the lattice change rate of the material and maintain its battery capacity.

[0151] O-site doping with element G can help improve interfacial side reactions between the material and the electrolyte, reduce interfacial activity, and thus improve the cycle performance of the positive electrode active material. Furthermore, doping at the O site can enhance the material's resistance to acid corrosion such as HF, thereby improving its cycle performance and lifespan.

[0152] In some embodiments, the thickness of the carbon coating layer is less than or equal to 10 nm, and can be selected from 5 nm to 7.5 nm. In some embodiments, the thickness of the carbon coating layer can be selected from 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 10 nm, or any range of two of the above values.

[0153] The thickness of the carbon coating can be measured using commonly used methods in this field, as illustrated below: A thin slice of approximately 100 nm thickness is cut from the middle of a single particle of the positive electrode active material using FIB (fiber optics). The slice is then subjected to TEM (thermometry) to obtain the raw TEM image, which is saved in the original image format (xx.dm3). The raw TEM image is opened in DigitalMicrograph software, and the carbon coating is identified using lattice spacing and angle information. The thickness of the carbon coating is then measured. The thickness is measured at three locations on the selected particle, and the average value is taken.

[0154] Controlling the thickness of the carbon coating layer on the surface of the core within a suitable range can improve the conductivity of the positive electrode active material, reduce the structural degradation of the positive electrode active material during cycling, reduce the dissolution of manganese metal, and also prevent excessive carbon coating layer thickness from introducing too much trace water into the system. It also reduces the impact of carbon coating layer thickness on the extraction and insertion of lithium ions in the core.

[0155] In some embodiments, the thickness of the coating is 0.1 μm to 10 μm.

[0156] In some embodiments, the thickness of the coating is 0.1 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a range of any two of the above values.

[0157] By controlling the coating thickness within a suitable range, the contact between the additive and the positive and negative electrode interfaces can be effectively isolated, reducing the possibility of premature additive failure. This also reduces the possibility of acidic substances undergoing reduction reactions at the negative electrode to generate hydrogen gas. At the same time, it avoids the impact of excessive coating thickness on the permeability of the separator and the internal resistance of the battery, thereby comprehensively improving the battery's dynamic performance and cycle performance.

[0158] In some embodiments, the inorganic particles comprise at least one selected from the group consisting of silicon dioxide, aluminum oxide, boehmite, magnesium oxide, titanium dioxide, zinc oxide, and magnesium aluminum oxide.

[0159] In some embodiments, the organic particles include at least one selected from the group consisting of polyethylene oxide particles, polyvinylidene chloride particles, polyacrylonitrile particles, polyvinylidene fluoride particles, polymethyl methacrylate particles, and polyvinylidene fluoride-hexafluoropropylene copolymer particles.

[0160] In some embodiments, the substrate can be a substrate commonly used in the art as a separator substrate. The substrate may include at least one selected from polyethylene, polypropylene, cellulose, and polyimide. In this application, the thickness of the substrate can be 1-20 μm. Optionally, the thickness of the substrate can be 2-15 μm, 2-10 μm, 2.5-9 μm, 3-8 μm, 3.5-8 μm, 4-7.5 μm, 4.5-6 μm, and 5-6.5 μm. By adopting the above thicknesses, it is possible to ensure the air permeability of the separator and improve the battery energy density while maintaining insulation.

[0161] [Positive electrode plate]

[0162] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, wherein the positive electrode film layer includes the positive electrode active material in any embodiment.

[0163] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0164] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0165] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0166] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0167] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0168] [Negative electrode plate]

[0169] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0170] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0171] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0172] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0173] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0174] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0175] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0176] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0177] [Electrolytes]

[0178] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0179] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0180] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0181] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0182] [Isolation membrane]

[0183] The separator used in this application is the separator described above. Furthermore, the separator used in this application can be used in combination with other separators commonly used in the art, as needed.

[0184] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0185] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0186] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0187] [Rechargeable Battery]

[0188] In one embodiment of this application, a secondary battery is provided, including a positive electrode, a separator, a negative electrode, and an electrolyte, wherein the binder in the active material layer of the positive electrode includes polymers according to any embodiment of this application.

[0189] In some embodiments, the secondary battery is a lithium-ion battery or a sodium-ion battery. During the charging and discharging process, active ions repeatedly insert and extract between the positive and negative electrode plates. The electrolyte acts as a conductor of ions between the positive and negative electrode plates. A separator is disposed between the positive and negative electrode plates, primarily to prevent short circuits between the positive and negative electrodes, while simultaneously allowing ions to pass through.

[0190] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0191] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0192] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0193] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0194] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0195] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0196] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0197] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0198] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0199] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0200] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, 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.

[0201] As an electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0202] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0203] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0204] Example

[0205] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0206] I. Preparation Method

[0207] Example 1

[0208] 1) Preparation of the separating membrane

[0209] Inorganic material alumina (Al2O3), additive sodium isonicotinate, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) were dissolved in deionized water at a mass ratio of 85:10:1:4 and mixed evenly to obtain a coating slurry. This inorganic slurry was then evenly coated onto a polypropylene base film, dried at 60°C, and subsequently slit to obtain a release film. The coating mass of the slurry was 10 g / m³. 2 The loading amount of additive on the separator membrane is 1 g / m 2 .

[0210] 2) Preparation of positive electrode sheet

[0211] Step S1: Preparation of doped manganese oxalate

[0212] 689.6 g of manganese carbonate and 455.27 g of ferrous carbonate were added to a mixer and mixed thoroughly for 6 hours. The resulting mixture was then transferred to a reaction vessel, and 5 L of deionized water and 1260.6 g of oxalic acid dihydrate were added. The mixture was heated to 80°C and stirred thoroughly at 500 rpm for 6 hours until homogeneous and the reaction was terminated with no more bubbles, yielding a doped manganese oxalate suspension. The suspension was then filtered, dried at 120°C, and milled to obtain manganese oxalate particles with a particle size of 100 nm.

[0213] Step S2: Prepare the doped core

[0214] 1793.1 g of manganese oxalate, 368.3 g of lithium carbonate, 1146.6 g of ammonium dihydrogen phosphate, and 4.9 g of dilute sulfuric acid prepared in S1 were added to 20 L of deionized water and stirred thoroughly. The mixture was then uniformly mixed and reacted at 80 °C for 10 h to obtain a slurry. The slurry was transferred to a spray dryer for spray drying and granulation, and dried at 250 °C to obtain a powder. Under a protective atmosphere (90% nitrogen and 10% hydrogen), the powder was sintered in a roller kiln at 700 °C for 4 h to obtain LiMn. 0.6 Fe 0.4 PO4 core material.

[0215] Step S3: Prepare carbon coating layer

[0216] 37.3 g of sucrose was dissolved in 5000 g of deionized water, then stirred until fully dissolved to obtain a sucrose aqueous solution. 1633.9 g of the core material obtained in S2 was added to the sucrose solution and stirred together for 6 hours. After homogeneity, the mixture was dried in a 150°C oven for 6 hours, and then sintered at 700°C for 10 hours to obtain carbon-coated LiMn. 0.6 Fe 0.4 PO4, and the carbon coating thickness is 5nm.

[0217] Step S4: Prepare the positive electrode sheet

[0218] LiMn coated with carbon as the positive electrode active material 0.6 Fe 0.4 PO4, polyvinylidene fluoride (PVDF) binder, and acetylene black conductive agent are dissolved in N-methylpyrrolidone (NMP) solvent at a mass ratio of 97:2:1 and thoroughly mixed to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated onto the positive electrode current collector, followed by drying, cold pressing, and slitting to obtain the positive electrode sheet.

[0219] 3) Preparation of negative electrode sheet

[0220] The active material artificial graphite, the binder styrene-butadiene rubber (SBR), the thickener sodium carboxymethyl cellulose (CMC), and the conductive agent acetylene black were dissolved in deionized water at a mass ratio of 96.5:2:1:0.5 and mixed evenly to prepare a negative electrode slurry. The negative electrode slurry was then evenly coated onto the negative electrode current collector copper foil, dried, and a negative electrode film was obtained. The film was then cold-pressed and slit to obtain the negative electrode sheet.

[0221] 4) Preparation of electrolyte

[0222] In an argon-atmospheric glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate (EC, solid at 25 °C, viscosity 1.9 mPa·S at 40 °C) and ethyl methyl carbonate (EMC, viscosity 0.78 mPa·S at 25 °C) were mixed uniformly at a mass ratio of 3 / 7. Dimethyl carbonate (DMC, viscosity 0.63 mPa·S at 25 °C) was added as the first solvent to obtain the mixed solvent of the electrolyte. Then, 1 mol / L LiPF6 lithium salt was added and dissolved in the mixed solvent and stirred uniformly to obtain the electrolyte. Based on the mass of the electrolyte, the mass content of the first solvent, dimethyl carbonate, was 50%.

[0223] 5) Battery manufacturing

[0224] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The cells are then wound to obtain a wound battery cell. The wound battery 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.

[0225] Implementation 2-5

[0226] Compared with Example 1, Examples 2-5 adjusted the coating weight of the coating slurry, thereby adjusting the additive loading. The coating weight of the coating slurry in Examples 2-5 was 0.1 g / m³. 2 1 / m 2 50g / m 2 100g / m2 For specific parameters, please refer to Table 1.

[0227] Examples 6-10

[0228] Compared with Example 1, Examples 6-10 have the types of additives adjusted. See Table 1 for specific parameters.

[0229] Examples 11-14

[0230] Compared with Example 1, Examples 11-14 adjusted steps S1 and S2 in the preparation process of the positive electrode active material, thereby adjusting the core of the positive electrode active material, as follows:

[0231] Example 11

[0232] Step S1: Preparation of doped manganese oxalate

[0233] 689.6 g of manganese carbonate, 457.6 g of ferrous carbonate, and 4.2 g of magnesium carbonate were added to a mixer and mixed thoroughly for 6 hours. The resulting mixture was then transferred to a reaction vessel, and 5 L of deionized water and 1260.6 g of oxalic acid dihydrate were added. The mixture was heated to 80°C and stirred thoroughly at 500 rpm for 6 hours until homogeneous and the reaction was terminated with no further bubble formation, yielding a doped manganese oxalate suspension. The suspension was then filtered, dried at 120°C, and milled to obtain manganese oxalate particles with a particle size of 100 nm.

[0234] Step S2: Prepare the doped core

[0235] 1791.6 g of manganese oxalate, 369.4 g of lithium carbonate, 1150.1 g of ammonium dihydrogen phosphate, and 4.9 g of dilute sulfuric acid prepared in S1 were added to 20 L of deionized water and stirred thoroughly. The mixture was then uniformly mixed and reacted at 80 °C for 10 h to obtain a slurry. The slurry was transferred to a spray dryer for spray drying and granulation, and dried at 250 °C to obtain a powder. Under a protective atmosphere (90% nitrogen and 10% hydrogen), the powder was sintered in a roller kiln at 700 °C for 4 h to obtain LiMn. 0.60 Fe 0.395 Mg 0.005 PO4 core material.

[0236] Example 12

[0237] Step S1: Preparation of doped manganese oxalate

[0238] 689.6 g of manganese carbonate, 457.6 g of ferrous carbonate, 2.4 g of vanadium dichloride, and 3.6 g of nickel carbonate were added to a mixer and mixed thoroughly for 6 hours. The resulting mixture was then transferred to a reaction vessel, and 5 L of deionized water and 1260.6 g of oxalic acid dihydrate were added. The mixture was heated to 80°C and stirred thoroughly at 500 rpm for 6 hours until homogeneous and the reaction was terminated with no more bubbles, yielding a doped manganese oxalate suspension. The suspension was then filtered, dried at 120°C, and then milled to obtain manganese oxalate particles with a particle size of 100 nm.

[0239] Step S2: Prepare the doped core

[0240] 1793.2 g of manganese oxalate, 369.4 g of lithium carbonate, 1150.1 g of ammonium dihydrogen phosphate, and 4.9 g of dilute sulfuric acid prepared in S1 were added to 20 L of deionized water and stirred thoroughly. The mixture was then uniformly mixed and reacted at 80 °C for 10 h to obtain a slurry. The slurry was transferred to a spray dryer for spray drying and granulation, and dried at 250 °C to obtain a powder. Under a protective atmosphere (90% nitrogen and 10% hydrogen), the powder was sintered in a roller kiln at 700 °C for 4 h to obtain LiMn. 0.60 Fe 0.395 V 0.002 Ni 0.003 PO4 core material.

[0241] Example 13:

[0242] Step S1: Preparation of doped manganese oxalate

[0243] 689.6 g of manganese carbonate, 455.3 g of ferrous carbonate, 4.7 g of cobalt sulfate, and 4.9 g of vanadium dichloride were added to a mixer and mixed thoroughly for 6 hours. The resulting mixture was then transferred to a reaction vessel, and 5 L of deionized water and 1260.6 g of oxalic acid dihydrate were added. The mixture was heated to 80°C and stirred thoroughly at 500 rpm for 6 hours until homogeneous and the reaction was terminated with no more bubbles, yielding a doped manganese oxalate suspension. The suspension was then filtered, dried at 120°C, and milled to obtain manganese oxalate particles with a particle size of 100 nm.

[0244] Step S2: Prepare the doped core

[0245] 1793.1 g of manganese oxalate, 369.8 g of lithium carbonate, 1148.9 g of ammonium dihydrogen phosphate, and 0.8 g of silicic acid prepared in S1 were added to 20 L of deionized water and stirred thoroughly. The mixture was then uniformly mixed and reacted at 80 °C for 10 h to obtain a slurry. The slurry was transferred to a spray dryer for spray drying and granulation, and dried at 250 °C to obtain a powder. Under a protective atmosphere (90% nitrogen and 10% hydrogen), the powder was sintered in a roller kiln at 700 °C for 4 h to obtain Li. 1.001 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.999 Si 0.001 O4 core material.

[0246] Example 14

[0247] Step S1: Preparation of doped manganese oxalate

[0248] 689.6 g of manganese carbonate, 455.3 g of ferrous carbonate, 4.7 g of cobalt sulfate, and 4.9 g of vanadium dichloride were added to a mixer and mixed thoroughly for 6 hours. The resulting mixture was then transferred to a reaction vessel, and 5 L of deionized water and 1260.6 g of oxalic acid dihydrate were added. The mixture was heated to 80°C and stirred thoroughly at 500 rpm for 6 hours until homogeneous and the reaction was terminated with no more bubbles, yielding a doped manganese oxalate suspension. The suspension was then filtered, dried at 120°C, and milled to obtain manganese oxalate particles with a particle size of 100 nm.

[0249] Step S2: Prepare the doped core

[0250] 1793.1 g of manganese oxalate, 369.8 g of lithium carbonate, 1146.6 g of ammonium dihydrogen phosphate, and 4.9 g of dilute sulfuric acid prepared in S1 were added to 20 L of deionized water and stirred thoroughly. The mixture was then uniformly mixed and reacted at 80 °C for 10 h to obtain a slurry. The slurry was transferred to a spray dryer for spray drying and granulation, and dried at 250 °C to obtain a powder. Under a protective atmosphere (90% nitrogen and 10% hydrogen), the powder was sintered in a roller kiln at 700 °C for 4 h to obtain Li. 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 O4 core material.

[0251] Examples 15-17

[0252] Compared with Example 1, Examples 15-17 adjusted the concentration of the sucrose solution in step S3, thereby adjusting the thickness of the carbon coating layer, as follows:

[0253] Example 15:

[0254] Step S3: Prepare carbon coating layer

[0255] 56.1 g of sucrose was dissolved in 5000 g of deionized water, then stirred until fully dissolved to obtain a sucrose aqueous solution. 1633.9 g of the core material obtained in S2 was added to the sucrose solution and stirred together for 6 hours. After homogeneity, the mixture was dried in a 150°C oven for 6 hours, and then sintered at 700°C for 10 hours to obtain carbon-coated LiMn. 0.6 Fe 0.4 PO4, and the carbon coating thickness is 7.5 nm.

[0256] Example 16:

[0257] Step S3: Prepare carbon coating layer

[0258] 24.9 g of sucrose was dissolved in 5000 g of deionized water, then stirred until fully dissolved to obtain a sucrose aqueous solution. 1633.9 g of the core material obtained in S2 was added to the sucrose solution and stirred together for 6 hours. After homogeneity, the mixture was dried in a 150°C oven for 6 hours, and then sintered at 700°C for 10 hours to obtain carbon-coated LiMn. 0.6 Fe 0.4 PO4, and the carbon coating thickness is 10 nm.

[0259] Example 17:

[0260] Step S3: Prepare carbon coating layer

[0261] 74.7 g of sucrose was dissolved in 5000 g of deionized water, then stirred until fully dissolved to obtain a sucrose aqueous solution. 1633.9 g of the core material obtained in S2 was added to the sucrose solution and stirred together for 6 hours. After homogeneity, the mixture was dried in a 150°C oven for 6 hours, and then sintered at 700°C for 10 hours to obtain carbon-coated LiMn. 0.6 Fe 0.4 It contains PO4, and the carbon coating thickness is 12.5 nm.

[0262] Example 18

[0263] Compared with Example 1, the preparation method of the separator membrane was adjusted, as follows:

[0264] First, sodium isonicotinate (additive), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) are dissolved in deionized water at a mass ratio of 95:1:4 and mixed evenly to obtain an additive slurry. Then, the additive slurry is coated onto a polypropylene base film using a gravure printing method to obtain an additive layer, with a coating weight of 1.05 g / m². 2 The loading amount of additive on the separator membrane is 1 g / m 2 .

[0265] Then, inorganic material alumina (Al2O3), binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) were dissolved in deionized water at a mass ratio of 95:1:4 and mixed evenly to obtain a slurry. The slurry was then coated onto the additive layer with a coating weight of 8.95 g / m². 2 .

[0266] Example 19

[0267] Compared with Example 1, the preparation method of the electrolyte was adjusted, as follows:

[0268] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), ethylene carbonate and ethyl methyl carbonate are mixed evenly at a mass ratio of 3 / 7 to obtain a mixed solvent for the electrolyte. Then, 1 mol / L LiPF6 lithium salt is added and dissolved in the mixed solvent, and stirred evenly to obtain the electrolyte.

[0269] Examples 20-23

[0270] Compared with Example 1, the mass content of the first solvent, dimethyl carbonate, in the electrolyte was adjusted. Specific parameters are shown in Table 1.

[0271] Example 24

[0272] Compared with Example 1, Example 24 adjusts the types of additives. See Table 1 for specific parameters.

[0273] Example 25

[0274] Compared with Example 1, the difference lies in the preparation method of the separator, as follows:

[0275] Sodium isonicate (additive), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were dissolved in deionized water at a mass ratio of 95:1:4 and mixed evenly to obtain an additive slurry. The additive slurry was then coated onto a polypropylene base film using a gravure printing method to form an additive layer, with a coating weight of 1.05 g / m². 2 The loading amount of additive on the separator membrane is 1 g / m 2 Dry at 60℃, then slit to obtain a release film.

[0276] Comparative Example 1

[0277] Compared with Example 1, the difference lies in the preparation method of the separator, as follows:

[0278] Inorganic alumina (Al2O3), styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC) thickener were dissolved in deionized water at a mass ratio of 95:1:4 and mixed evenly to obtain an inorganic slurry. The inorganic slurry was then uniformly coated onto a polypropylene base film, dried at 60°C, and subsequently slit to obtain a release membrane. The coating mass of the inorganic slurry was 10 g / m³. 2 .

[0279] II. Testing Methods

[0280] 1. Testing the gas production of secondary batteries

[0281] The battery cell was immersed in silicone oil, and the test temperature was controlled at 25°C using a constant temperature water bath method. The mass (Mx) of the battery cell was measured, and the volume change (Vx) was calculated according to Archimedes' principle to obtain the gas production rate. Under the condition of 25°C, the batteries of the examples and comparative examples were charged at a constant current of 0.05C to 4.1V, and then charged at a constant voltage of 4.1V to 0.05C. The changes in volume change (Vx) over time and voltage were recorded to obtain the formation gas production rate per unit capacity at the cutoff voltage.

[0282] 2. Cyclic performance test of secondary batteries at 45℃

[0283] At 45℃, the lithium-ion battery was charged at a constant current of 1C to a voltage of 4.1V, then charged at a constant voltage of 4.1V until the current ≤0.02C. After resting for 2 minutes, the lithium-ion battery was discharged at a constant current of 1C to a voltage of 2.0V. This constitutes one charge-discharge cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. The lithium-ion battery was subjected to multiple charge-discharge cycles using the above method until the discharge capacity of the lithium-ion rechargeable battery decreased to 80%, and the number of cycles was recorded.

[0284] 3. Storage performance test of secondary batteries at 45℃

[0285] At 45℃, the prepared lithium-ion secondary battery was first charged to 4.1V with a constant current of 0.33C, then charged to 0.05C with a constant voltage of 4.1V, and then discharged to 2V with a constant current of 0.33C. The discharge capacity C0 is the discharge capacity of the lithium-ion secondary battery before high-temperature storage. Then, the lithium-ion secondary battery was charged to 4.1V with a constant current of 0.33C, and then charged to 0.05C with a constant voltage of 4.1V to fully charge. The battery was placed in a 45℃ oven for 90 days, then removed and placed in a 25℃ environment for 0.33C discharge. The discharge capacity was recorded as C1; capacity retention rate = (C1 / C0) × 100%.

[0286] 4. Test of transition metal ion dissolution content after the secondary battery is cycled 500 times at 45℃

[0287] The positive electrode was obtained by disassembling the secondary battery after 500 cycles at 45°C. The positive electrode was scraped off with ethylene glycol dimethyl ether, washed, dried, and then digested with 1+1 aqua regia using microwave digestion (high temperature and high pressure ~200°C) for 6 hours. The content of various transition metals in the cathode was determined by inductively coupled plasma atomic emission spectrometry (ICP).

[0288] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0289] Secondary batteries for each embodiment and comparative example were prepared according to the above method, and various parameters were measured. The results are shown in the table below.

[0290] Table 1

[0291]

[0292]

[0293] As shown in the table above, the secondary battery in Examples 1-25 of this application includes a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive and negative electrodes. The separator includes sodium isonicotinic acid, potassium isonicotinic acid, sodium 2-hydroxypyridine-4-carboxylate, sodium 2,2'-bipyridine-4,4'-dicarboxylate, trihexylphosphine, tri-n-octylphosphine, pyridine, and triphenylphosphine additives. The positive electrode includes a positive electrode active material, which includes a core and a carbon coating layer. The carbon coating layer at least covers a portion of the surface of the core. The core includes LiMn. 0.6 Fe 0.4 PO4, LiMn 0.60 Fe 0.395 Mg 0.005 PO4, LiMn 0.60 Fe 0.395 V 0.002 Ni 0.003PO4, Li 1.001 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.999 Si 0.001 O4 or Li 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 O4.

[0294] As can be seen from the comparison between Examples 1-25 and Comparative Example 1, by adding sodium isonicotinic acid, potassium isonicotinic acid, sodium 2-hydroxypyridine-4-carboxylate, sodium 2,2'-bipyridine-4,4'-dicarboxylate, trihexylphosphine, tri-n-octylphosphine, and triphenylphosphine additives to the separator, the gas production volume during battery cycling can be reduced, the gas production phenomenon of the battery can be reduced, and the safety performance of the battery can be improved.

[0295] As can be seen from the comparison between Examples 1 and 18 and Example 25, the sodium isonicotinate additive is located between the inorganic particles and / or organic particles in the coating or in the form of a separate layer between the substrate and the coating, which can further reduce the gas production volume during battery cycling and further improve the safety performance of the battery.

[0296] A comparison of Examples 1, 6-10 and Example 24 shows that, based on the mass of the electrolyte, an additive mass content of less than or equal to 0.3% can further reduce the gas production volume during battery cycling and further improve the battery's safety performance.

[0297] As can be seen from Examples 1-5, the loading amount of sodium isonicotinic acid additive on the separator membrane is 0.01 g / m. 2 -10g / m 2 The battery has low gas production and excellent safety performance.

[0298] Table 2

[0299]

[0300] As can be seen from the comparison between Examples 1, 20-23 and Example 19, the viscosity of the electrolyte at 25°C is less than or equal to 3 mPa·S, which can further improve the high-temperature cycle performance and high-temperature storage performance of the battery and extend the battery's service life.

[0301] As can be seen from Examples 1 and 20-23, based on the mass of the electrolyte, the mass content of the solvent with a viscosity of less than 0.65 mPa·S at 25°C is 10%-80%, and the battery has excellent high-temperature cycling performance and high-temperature storage performance.

[0302] As can be seen from Examples 1, 21-22 and Examples 20, 23, based on the mass of the electrolyte, the mass content of solvent with a viscosity of less than 0.65 mPa·s at 25°C is 30%-70%, which can further improve the high-temperature cycle performance and high-temperature storage performance of the battery and extend the battery's service life.

[0303] Table 3

[0304]

[0305] As can be seen from the comparison between Examples 11-14 and Example 1, compared to Example 1, when the core material is LiMn... 0.6 Fe 0.4 PO4, using LiMn 0.60 Fe 0.395 Mg 0.005 PO4, LiMn 0.60 Fe 0.395 V 0.002 Ni 0.003 PO4, Li 1.001 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.999 Si 0.001 O4 or Li 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 The core material of O4 can further reduce the leaching of transition metals in the positive electrode active material, improve the high-temperature cycle performance and high-temperature storage performance of the battery, and extend the battery's service life.

[0306] A comparison of Examples 1, 15-16 and Example 17 shows that a carbon coating layer thickness of less than or equal to 10 nm in the positive electrode active material can further improve the high-temperature cycle performance and high-temperature storage performance of the battery, and extend the battery's service life.

[0307] As can be seen from the comparison between Examples 1 and 16 and Examples 15 and 17, the thickness of the carbon coating layer of the positive electrode active material is 5nm-7.5nm, which can further reduce the amount of transition metals dissolved in the positive electrode active material, improve the high-temperature cycle performance and high-temperature storage performance of the battery, and extend the battery's service life.

[0308] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A secondary battery, characterized in that, The device includes a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode. The separator includes an additive, which includes at least one selected from pyridine compounds and phosphine compounds. The positive electrode sheet includes a positive active material, which includes a core and a carbon coating layer. The carbon coating layer covers at least a portion of the surface of the core, and the core includes a phosphate material.

2. The secondary battery according to claim 1, characterized in that, The isolation membrane includes a substrate and a coating comprising inorganic and / or organic particles disposed on at least one surface of the substrate. The additive is located between inorganic and / or organic particles in the coating or as a separate layer between the substrate and the coating.

3. The secondary battery according to claim 1 or 2, characterized in that, Based on the mass of the electrolyte, the mass content of the additive is less than or equal to 0.3%.

4. The secondary battery according to any one of claims 1 to 3, characterized in that, The viscosity of the electrolyte at 25°C is less than or equal to 3 mPa·S.

5. The secondary battery according to any one of claims 1 to 4, characterized in that, The electrolyte contains a first solvent, the viscosity of which is less than 0.65 mPa·S at 25°C.

6. The secondary battery according to claim 5, characterized in that, The first solvent includes one or more of dimethyl carbonate, methyl formate, ethyl formate, methyl acetate, ethyl acetate, ethyl propionate, ethyl butyrate, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, 1,2-dimethoxyethane, acetonitrile, methyl nonafluorobutyl ether, and ethyl nonafluorobutyl ether.

7. The secondary battery according to claim 5 or 6, characterized in that, Based on the mass of the electrolyte, the mass content of the first solvent is 10%-80%.

8. The secondary battery according to any one of claims 5 to 7, characterized in that, Based on the mass of the electrolyte, the mass content of the first solvent is 30%-70%.

9. The secondary battery according to any one of claims 1 to 8, characterized in that, The pyridine compounds include at least one selected from compounds shown in Formula I, Formula II, and Formula III. The phosphine compounds include at least one selected from the compounds shown in Formula IV. Where R1~R 13 and R 15 ~R 17 Each independently includes any one of the following: alkyl groups having 1-20 carbon atoms, alkenyl groups having 2-20 carbon atoms, aryl groups having 6-26 carbon atoms, aryloxy groups having 6-26 carbon atoms, and groups formed by substitution of these groups with F, Cl, Br, sulfonic acid groups, or sulfonyl groups, H, F, Cl, Br, R 14 It includes any one of the following groups selected from alkyl groups having 1-20 carbon atoms, alkenyl groups having 2-20 carbon atoms, aryl groups having 7-26 carbon atoms, aryloxy groups having 7-26 carbon atoms, and groups formed by substituting them with F, Cl, Br, sulfonic acid group or sulfonyl group, where n is an integer greater than or equal to 2.

10. The secondary battery according to claim 9, characterized in that, The pyridine compounds include at least one selected from isonicotinate, 2-hydroxypyridine-4-carboxylate, and 2,2'-bipyridine-4,4'-dicarboxylate.

11. The secondary battery according to claim 9 or 10, characterized in that, The isonicotinate comprises at least one selected from lithium isonicotinate, sodium isonicotinate, potassium isonicotinate, aluminum isonicotinate, magnesium isonicotinate, calcium isonicotinate, iron isonicotinate, cobalt isonicotinate, nickel isonicotinate, and manganese isonicotinate; and / or; The 2-hydroxypyridine-4-carboxylate includes at least one selected from lithium 2-hydroxypyridine-4-carboxylate, sodium 2-hydroxypyridine-4-carboxylate, potassium 2-hydroxypyridine-4-carboxylate, aluminum 2-hydroxypyridine-4-carboxylate, magnesium 2-hydroxypyridine-4-carboxylate, calcium 2-hydroxypyridine-4-carboxylate, iron 2-hydroxypyridine-4-carboxylate, cobalt 2-hydroxypyridine-4-carboxylate, nickel 2-hydroxypyridine-4-carboxylate, and manganese 2-hydroxypyridine-4-carboxylate; and / or, The 2,2'-bipyridine-4,4'-dicarboxylate includes at least one selected from sodium 2,2'-bipyridine-4,4'-dicarboxylate, potassium 2,2'-bipyridine-4,4'-dicarboxylate, aluminum 2,2'-bipyridine-4,4'-dicarboxylate, magnesium 2,2'-bipyridine-4,4'-dicarboxylate, calcium 2,2'-bipyridine-4,4'-dicarboxylate, ferric 2,2'-bipyridine-4,4'-dicarboxylate, cobalt 2,2'-bipyridine-4,4'-dicarboxylate, nickel 2,2'-bipyridine-4,4'-dicarboxylate, and manganese 2,2'-bipyridine-4,4'-dicarboxylate.

12. The secondary battery according to any one of claims 8 to 11, characterized in that, The phosphine compounds include at least one selected from diethylphenylphosphine, trihexylphosphine, tributylphosphine, 1,6-bis(diphenylphosphine)hexane, tri(o-methoxyphenyl)phosphine, tri-n-octylphosphine, diphenylcyclohexylphosphine, diphenyl-2-pyridinylphosphine, 2-(dicyclohexylphosphine)biphenyl, 2-(di-tert-butylphosphine)biphenyl, diphenylethoxyphosphine, tri(2-furanyl)phosphine, tricyclopentylphosphine, and diethylphenylphosphine.

13. The secondary battery according to any one of claims 1 to 12, characterized in that, The additive is loaded at a rate of 0.01 g / m² on the separator membrane. 2 -10g / m 2 .

14. The secondary battery according to any one of claims 1 to 13, characterized in that, The chemical formula of the kernel is: Li m A a Fe x Mn b D d P y E e About z G g , Wherein, A includes at least one element selected from Al, Na, K, and Mg; The D includes at least one element selected from Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, Ti, and V; The E includes at least one element selected from B, S, Si, and N; The G includes at least one element selected from S, F, Cl, and Br; The value of m is selected from the range of 0.95 to 1.15; The a is selected from the range of 0 to 0.1; The x is selected from the range of 0.1 to 1; The value of b is selected from the range of 0.1 to 0.9; The d is selected from the range of 0 to 0.1; The value of y is selected from the range of 0.95 to 1; The value of e is selected from the range of 0 to 0.1; The z is selected from the range of 3.5 to 4; The value of g is selected from the range of 0 to 0.

1.

15. The secondary battery according to any one of claims 1 to 14, characterized in that, The thickness of the carbon coating layer is less than or equal to 10 nm.

16. The secondary battery according to any one of claims 1 to 14, characterized in that, The thickness of the carbon coating layer is 5nm-7.5nm.

17. The secondary battery according to any one of claims 2 to 16, characterized in that, The thickness of the coating is 0.1μm-10μm.

18. The secondary battery according to any one of claims 2 to 16, characterized in that, The thickness of the coating is 0.5μm-5μm.

19. The secondary battery according to any one of claims 2 to 18, characterized in that, The inorganic particles include at least one selected from the group consisting of silicon dioxide, aluminum oxide, boehmite, magnesium oxide, titanium dioxide, zinc oxide, and magnesium aluminate; and / or, the organic particles include at least one selected from the group consisting of polyethylene oxide particles, polyvinylidene chloride particles, polyacrylonitrile particles, polyvinylidene fluoride particles, polymethyl methacrylate particles, and polyvinylidene fluoride-hexafluoropropylene copolymer particles.

20. An electrical appliance, characterized in that, The secondary battery includes any one of claims 1 to 19.

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