Battery pole piece and preparation method thereof, secondary battery and electric equipment

Abstract

The invention discloses a battery pole piece, a preparation method of the battery pole piece, a secondary battery and electric equipment. Wherein the active layer of the battery pole piece comprises an electrode active material, a binder, a conductive agent and an additive; the melting point of the additive is higher than the manufacturing temperature and the working temperature of an applied battery cell and lower than the thermal runaway temperature of the battery cell, and the additive has electrolyte insolubility and is used for reducing the porosity of a pole piece. According to the battery pole piece provided by the embodiment of the invention, the additive which does not reach the melting point is uniformly distributed in the pole piece in the form of solid particles in the normal assembling and manufacturing process of the battery cell and the cyclic operation process of the battery cell. When the battery cell applied by the battery pole piece tends to generate thermal runaway in the circulating process, the temperature in the battery cell gradually rises to reach the melting point of the additive, and the additive is molten and fills the pores of the pole piece to block the pore channels of the pole piece and cut off the transmission channel of ions, so that the battery thermal runaway is effectively prevented from continuing to generate, and the risk of thermal runaway of the battery cell is reduced; the safety performance of the battery cell is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and specifically to a battery pole piece and a preparation method thereof, a secondary battery, and an electrical device. Background Art

[0002] A secondary battery is a rechargeable battery that mainly relies on the movement of metal ions such as lithium between the positive and negative electrodes to work. When charging, metal ions are deintercalated from the positive electrode of the battery and embedded in the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; the opposite is true when discharging. In recent years, pure electric vehicles have become an important development direction for electric vehicles because they can truly achieve "zero emissions", and secondary batteries have become an ideal power source for the new generation of electric vehicles due to their excellent performance.

[0003] Secondary batteries are composed of diaphragms, electrolytes, positive and negative electrode materials, and other parts. Secondary batteries are prone to thermal runaway under electrical, thermal, and mechanical failures such as internal and external short circuits, overcharging, thermal abuse, and mechanical abuse, releasing large amounts of heat and explosive gases, causing fires and explosions. In recent years, fires and explosions caused by thermal runaway of secondary batteries such as lithium-ion batteries have been reported frequently, and the safety issues of secondary batteries have become one of the main factors hindering their large-scale commercial application in the power supply industry. During the thermal runaway of the battery cell, a series of chemical reactions will occur inside the battery. These reactions generate a large amount of heat, accompanied by the generation of a lot of flammable gases, which eventually lead to thermal runaway of the battery. Safety accidents such as fires and explosions are caused, resulting in huge social impacts such as huge property losses and casualties.

[0004] At present, the main solutions to the thermal runaway problem of batteries include: improving explosion-proof valves, or using water cooling devices to transfer heat in time. However, these methods are taken after thermal runaway occurs, and they cannot handle and reduce the risk of thermal runaway in time. Summary of the invention

[0005] In view of the above problems, the embodiments of the present application provide a battery electrode and a method for preparing the same, a secondary battery, and an electrical device to solve the current technical problem of battery thermal runaway affecting safety.

[0006] In a first aspect, the present application provides an embodiment of a battery electrode, wherein the active layer of the battery electrode comprises an electrode active material, a binder, a conductive agent and an additive; the melting point of the additive is higher than the manufacturing temperature and the operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell, the additive is insoluble in the electrolyte, and the additive is used to reduce the porosity of the battery electrode.

[0007] In the technical solution of the embodiment of the present application, the melting point of the additive introduced into the provided battery pole piece is higher than the manufacturing temperature of the applied battery cell and the operating temperature of the battery cell, and the additive is insoluble in the electrolyte and will not be dissolved by the electrolyte in the battery cell. The melting point of the additive is not reached during the normal assembly and manufacturing of the battery cell and the cyclic operation of the battery cell, and the additive introduced into the battery pole piece is evenly distributed in the pole piece in the form of solid particles. In addition, the melting point of the additive is lower than the thermal runaway temperature of the battery cell. Therefore, when the battery cell applied to the battery pole piece tends to thermal runaway during the cycle, as the temperature in the battery cell gradually rises to the melting point of the additive, the additive in the battery pole piece will become molten and fill in the pores of the pole piece, blocking the pole piece pores, thereby reducing the porosity of the battery pole piece, cutting off the transmission channel of the ions, effectively preventing the battery cell from further releasing heat, preventing the battery thermal runaway from continuing to occur, and reducing the risk of thermal runaway of the battery cell.

[0008] In some embodiments, the melting point of the additive is 66 to 120°C. The melting point of the additive is higher than the operating temperature of conventional lithium-ion batteries and higher than the manufacturing temperature of the battery pole piece assembled into the battery cell. Therefore, the melting point of the additive is not reached during the normal assembly and manufacturing of the battery cell and the cycle operation of the battery cell. The additive introduced into the battery pole piece is evenly distributed in the pole piece in the form of solid particles. In addition, the melting point of the additive is lower than the temperature of thermal runaway of the battery. Therefore, when the battery cell used in the battery pole piece tends to have thermal runaway during the cycle, the additive will become molten and fill in the pores of the pole piece to block the pole piece pores, reduce the porosity of the battery pole piece, cut off the ion transmission channel, effectively prevent the battery thermal runaway from continuing to occur, and improve the safety of the battery cell.

[0009] In some embodiments, the mass percentage of the additive in the active layer of the battery pole piece is 2-8wt%. This mass percentage not only ensures the control effect of the additive on the battery pole piece in the case of thermal runaway, but also ensures the charge and discharge performance of the battery pole piece, is conducive to the embedding and de-embedding of ions in the pole piece, and ensures the electrochemical properties of the battery pole piece, such as rate performance and capacity.

[0010] In some embodiments, the additives include: at least one of non-metallic substances, thiazoles, sulfenamides, thiurams, thioformates, azobenzenes, guanidines, and thioureas. These additives not only have a relatively low melting point, which can satisfy the requirement that the melting point is higher than the manufacturing temperature and operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell; but also contain elements such as sulfur, which participate in the formation of the film material during the SEI film formation process, play a role in enhancing the toughness of the SEI film, and prevent the SEI film from breaking during the cycle process.

[0011] In some embodiments, the non-metallic substance includes at least one of sulfide and elemental sulfur.

[0012] In some embodiments, the thiazoles include at least one of 2-mercaptobenzothiazole and dibenzothiazole disulfide.

[0013] In some embodiments, the sulfenamides include at least one of N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, and N,N'-dicyclohexyl-2-benzothiazole sulfenamide.

[0014] In some embodiments, the thiurams include at least one of tetramethylthiuram disulfide, tetramethylthiuram monosulfide, tetraethylthiuram disulfide, and pentamethylenethiuram hexasulfide.

[0015] In some embodiments, the thioformate salts include at least one of zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, and zinc dimethyldithiocarbamate.

[0016] In some embodiments, the guanidines include at least one of diphenylguanidine.

[0017] In some embodiments, the thioureas include at least one of thiourea dioxide and thiourea.

[0018] In the above embodiments of the present application, the additives specifically used all have suitable melting points, which can effectively prevent the battery thermal runaway from continuing to occur and reduce the risk of thermal runaway of the battery cell. In addition, the additives such as sulfide, sulfur, sulfonamide, thiazole, thiourea, thioformate, and thiuram also contain S element, which participates in the formation of the film material during the SEI film formation process, plays a role in enhancing the toughness of the SEI film, and prevents the SEI film from breaking during the cycle process.

[0019] In some embodiments, the additive includes at least two of non-metallic substances, thiazoles, sulfenamides, thiurams, thioformates, azobenzenes, guanidines, and thioureas. Through the compounding of multiple additives with different melting points, the electrode pores can be better blocked after melting, the ion transmission channels can be better cut off, and the battery thermal runaway can be effectively prevented from continuing to occur, so that the additives can play a better role in blocking thermal runaway in the battery electrode.

[0020] In some embodiments, the additive includes an additive containing sulfur. The additive containing sulfur can participate in the reaction to form sulfonic acid groups during the film formation process on the negative electrode surface, participate in the film formation reaction of SEI, enhance the toughness of the SEI film, prevent the SEI film from breaking during the cycle, and help the stability of the battery.

[0021] In some embodiments, the mass percentage of the sulfur-containing additive in the additive is 40-60wt%, based on the total mass of the additive being 100%. This ensures that the sulfur element in the additive participates in the film-forming reaction of the SEI and has a sufficient strengthening effect on the toughness of the SEI film, which is beneficial to improving the stability of the battery, and also ensures that the additive has a barrier effect on ion transmission in the battery pole piece when the battery cell is in thermal runaway.

[0022] In some embodiments, the additive is distributed in a gradient manner in the active layer along the thickness direction of the active layer.

[0023] In some embodiments, the content of the additive in the active layer is distributed in an increasing manner along the active layer toward the current collector contained in the battery pole piece. The additive content on the side of the active layer close to the diaphragm is low, which is beneficial to improve the insertion and extraction of ions during the normal cycle of the battery cell and ensure the charging and discharging efficiency of the battery cell. The additive content on the side of the active layer close to the current collector is high, but when thermal runaway occurs, it can better reduce the porosity of the battery pole piece, cut off ion transmission, prevent the battery thermal runaway from continuing to occur, and reduce the risk of thermal runaway of the battery cell.

[0024] In some embodiments, the electrode active material is selected from a positive electrode active material or a negative electrode active material.

[0025] In a second aspect, the present application provides a method for preparing a battery electrode sheet, comprising the following steps:

[0026] Obtaining an additive, and preparing an electrode slurry by combining the additive with an electrode active material, a binder, and a conductive agent;

[0027] The electrode slurry is made into a battery electrode; in the battery electrode, the melting point of the additive is higher than the manufacturing temperature and operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell, the additive is insoluble in the electrolyte, and the additive is used to reduce the porosity of the battery electrode.

[0028] The preparation method of the battery pole piece provided in the embodiment of the present application has a simple preparation process and is suitable for industrial large-scale production and application. The prepared battery pole piece contains an additive whose melting point is higher than the manufacturing temperature and operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell. And the additive is insoluble in the electrolyte and will not be dissolved by the electrolyte in the battery cell. Therefore, during the normal assembly and manufacturing of the battery cell and the cycle operation of the battery cell, the additive that has not reached the melting point is evenly distributed in the pole piece in the form of solid particles. When the battery cell used in the battery pole piece tends to thermal runaway during the cycle, as the temperature in the battery cell gradually rises to the melting point of the additive, the additive melts and fills the pores in the pole piece to block the pole piece pores, reduce the porosity of the battery pole piece, cut off the ion transmission channel, effectively prevent the battery thermal runaway from continuing to occur, reduce the risk of thermal runaway of the battery cell, and improve the safety performance of the battery cell.

[0029] In some embodiments, the melting point of the additive is 66 to 120°C. The melting point of the additive is higher than the operating temperature of conventional lithium-ion batteries, and is also higher than the manufacturing temperature of the battery pole piece assembled into the battery cell. Therefore, the melting point of the additive is not reached during the normal assembly and manufacturing of the battery cell and the cycle operation of the battery cell. The additive introduced into the battery pole piece is evenly distributed in the pole piece in the form of solid particles. In addition, the melting point of the additive is lower than the temperature of thermal runaway of the battery. Therefore, when the battery cell used in the battery pole piece tends to have thermal runaway during the cycle, the additive will become molten and fill in the pores of the pole piece to block the pole piece pores, reduce the porosity of the battery pole piece, cut off the ion transmission channel, effectively prevent the battery thermal runaway from continuing to occur, and improve the safety of the battery cell.

[0030] In some embodiments, in the electrode slurry, the mass of the additive accounts for 2-8wt% of the total mass of the additive, the electrode active material, the binder and the conductive agent. This mass percentage not only ensures the control effect of the additive on the battery pole piece under thermal runaway, when the temperature of the battery cell rises and tends to thermal runaway, the additive can melt and fill and block the pole piece pores in time to prevent further deterioration of thermal runaway; at the same time, it ensures the charge and discharge performance of the battery pole piece, is conducive to the embedding and de-embedding of ions in the pole piece, and ensures the electrochemical properties of the battery pole piece such as rate performance and capacity.

[0031] In some embodiments, the additive includes at least one of non-metallic substances, thiazoles, sulfenamides, thiurams, thioformates, azobenzene, guanidines, and thioureas.

[0032] In some embodiments, the non-metallic substance includes at least one of sulfide and elemental sulfur.

[0033] In some embodiments, the thiazoles include at least one of 2-mercaptobenzothiazole and dibenzothiazole disulfide.

[0034] In some embodiments, the sulfenamides include at least one of N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, and N,N'-dicyclohexyl-2-benzothiazole sulfenamide.

[0035] In some embodiments, the thiurams include at least one of tetramethylthiuram disulfide, tetramethylthiuram monosulfide, tetraethylthiuram disulfide, and pentamethylenethiuram hexasulfide.

[0036] In some embodiments, the thioformate salts include at least one of zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, and zinc dimethyldithiocarbamate.

[0037] In some embodiments, the guanidines include at least one of diphenylguanidine.

[0038] In some embodiments, the thioureas include at least one of thiourea dioxide and thiourea.

[0039] The additives in the above embodiments of the present application not only have a relatively low melting point, which can satisfy the requirement that the melting point is higher than the manufacturing temperature and operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell; but also these additives have little effect on the ion embedding and extraction efficiency of the battery pole piece. Moreover, these additives also contain elements such as sulfur, which participate in the formation of the film material during the SEI film formation process, play a role in enhancing the toughness of the SEI film, and prevent the SEI film from breaking during the cycle process.

[0040] In some embodiments, the electrode active material is selected from a positive electrode active material or a negative electrode active material. When the electrode active material is a positive electrode active material, the battery electrode sheet is a positive electrode sheet, and when the electrode active material is a negative electrode active material, the battery electrode sheet is a negative electrode sheet.

[0041] In a third aspect, the present application provides a secondary battery, which includes an electrode, wherein the electrode includes the above-mentioned battery electrode sheet or the battery electrode sheet prepared by the above-mentioned method.

[0042] In the secondary battery provided in the embodiment of the present application, the electrode includes the above-mentioned battery electrode, which contains an additive with a melting point higher than the manufacturing temperature and operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell, which can effectively prevent the deterioration of the thermal runaway of the battery and reduce the risk of thermal runaway of the battery cell, thereby improving the safety performance of the secondary battery.

[0043] In some embodiments, the secondary battery includes at least one of a battery cell, a battery module, and a battery pack.

[0044] In a fourth aspect, the present application provides an electrical device, which includes the above-mentioned secondary battery.

[0045] The electrical equipment provided in the embodiment of the present application includes the secondary battery with high safety performance, thereby improving the safety and stability of electricity consumption of the electrical equipment.

[0046] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0048] Figure 1 Schematic diagram of the distribution of additives in the battery pole piece of the present application embodiment Figure 1 ;

[0049] Figure 2 Schematic diagram of the distribution of additives in the battery pole piece of the present application embodiment Figure 2 ;

[0050] Figure 3 Schematic diagram of the distribution of additives in the battery pole piece of the present application embodiment Figure 3 ;

[0051] Figure 4 A schematic diagram of a process for preparing a battery electrode according to an embodiment of the present application;

[0052] Figure 5 This is a schematic structural diagram of an implementation of a battery cell according to an embodiment of the present application;

[0053] Figure 6 for Figure 5 An exploded schematic diagram of the battery cell shown;

[0054] Figure 7 This is a schematic structural diagram of an implementation scheme of a battery module according to an embodiment of the present application;

[0055] Figure 8 This is a schematic structural diagram of an implementation scheme of a battery pack according to an embodiment of the present application;

[0056] Fig. 9 for Figure 8 A schematic diagram of the exploded structure of the battery pack shown;

[0057] Fig.10 A schematic diagram of an embodiment of an electric device including a secondary battery of an embodiment of the present application as a power source;

[0058] Fig.11 This is a sample picture after the heating test of the secondary battery in Example 1 of the present application;

[0059] Fig.12 This is a sample picture of the secondary battery of Comparative Example 1 after the heating test;

[0060] Fig.13 This is a sample picture after the secondary battery of Example 1 of the present application is subjected to a needle puncture test;

[0061] Fig.14 This is a sample picture of the secondary battery of Comparative Example 1 after the needle penetration test.

[0062] The reference numerals in the specific implementation manner are as follows:

[0063] 1. Battery pole piece;

[0064] 2. Additives;

[0065] 3. Current collector;

[0066] 4. Battery cell, 41. Shell, 42. Electrode assembly, 43. Cover plate;

[0067] 5. Battery module;

[0068] 6. battery pack, 61. upper box, 62. lower box. DETAILED DESCRIPTION

[0069] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0071] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0072] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0073] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0074] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0075] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0076] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0077] From the perspective of the development of the market situation, lithium-ion batteries are currently being used on a large scale in both power batteries and energy storage batteries, and people are still terrified by the spontaneous combustion and explosion of batteries, and battery safety issues are still a topic that the industry cannot avoid. Thermal runaway is the main object of research on improving the safety of lithium-ion batteries. Battery thermal runaway refers to a chain reaction phenomenon caused by various inducements. The large amount of heat and harmful gases emitted by thermal runaway can cause battery fire and explosion. Battery thermal runaway often starts with the decomposition of the negative electrode SEI film in the battery cell, followed by the decomposition and melting of the diaphragm, resulting in a reaction between the negative electrode and the electrolyte, followed by the decomposition of the positive electrode and the electrolyte, which causes a large-scale internal short circuit, causing the electrolyte to burn, and then spread to other cells, causing serious thermal runaway, causing the entire battery pack to spontaneously combust. During the thermal runaway of the battery cell, a series of chemical reactions will occur inside the battery, which will generate a large amount of heat, accompanied by the generation of a lot of flammable gases, and ultimately cause thermal runaway of the battery. It causes safety accidents such as fire and explosion, causing huge property losses and social impacts such as casualties.

[0078] At present, the main solutions to the thermal runaway problem of batteries include: explosion venting and isolation. Among them, for explosion venting, once the battery cell has thermal runaway, a large amount of high-temperature gas will be quickly generated. If the gas cannot be effectively released, the high-temperature gas (and the molten material) will heat the surrounding battery cells, which may cause thermal runaway of other battery cells; at the same time, there may be serious consequences such as explosion. Therefore, effective explosion-proof discharge paths and discharge ports are designed in the battery box, and the explosion-proof valve is improved to guide the high-temperature gas reasonably. In addition, for isolation, the purpose of isolation is to block the spread, which includes isolation inside the battery pack and isolation outside the battery pack. Among them, the isolation inside the battery pack includes the use of longitudinal and transverse beams to isolate the modules and the use of fire-resistant insulation materials for isolation. Isolation outside the battery pack includes measures such as timely transfer of heat using water cooling devices. However, these methods are all taken after the thermal runaway occurs, and they cannot be handled in time and reduce the risk of thermal runaway.

[0079] In order to alleviate the current problem of battery thermal runaway affecting safety, research has found that the focus of thermal runaway of battery cells should be on prevention. Once thermal runaway occurs, there is no good way to stop it. For the prevention of thermal runaway, on the one hand, we can start from the outside and use a safe and efficient thermal management system to suppress the temperature rise of lithium-ion batteries. Passive cooling strategies such as adding fins, embedding foam metals, and coating phase change materials improve the safety of lithium-ion battery applications. In addition, the best way is to solve the thermal runaway problem at the source. Before thermal runaway, physical isolation methods should be used to block the transmission of metal ions and prevent further heat release, which can minimize the risk.

[0080] Based on the above considerations, a battery pole piece is proposed, in which an additive with a low melting point is introduced into the active layer of the battery pole piece; the melting point of the additive is higher than the manufacturing temperature and operating temperature of the applied battery cell, and the melting point of the additive is lower than the thermal runaway temperature of the battery cell.

[0081] In such a battery pole piece, due to the addition of an additive with a low melting point, the melting point of the additive is higher than the manufacturing temperature and the operating temperature of the battery cell used, ensuring the normal assembly and manufacturing of the battery cell and the cyclic operation of the battery cell. When the battery cell used in the battery pole piece has thermal runaway during the cycle, as the temperature in the battery cell gradually rises to the melting point of the additive, the additive in the battery pole piece will become molten and fill in the pores of the pole piece, blocking the pores of the pole piece, thereby reducing the porosity of the battery pole piece, cutting off the transmission channel of ions, effectively preventing the battery cell from further releasing heat, and reducing the risk of thermal runaway of the battery cell.

[0082] For the convenience of explanation, the following embodiments of the present application are described by taking a battery electrode and a preparation method thereof, a secondary battery, and an electrical device as examples.

[0083] In the description of the embodiments of the present application, the term "operating temperature of the battery cell" refers to the operating temperature of a conventional lithium-ion battery between -20°C and 60°C. However, generally, the performance of the lithium battery will decrease below 0°C, and the discharge capacity will decrease accordingly. Therefore, the operating temperature at which the lithium-ion battery fully performs is commonly between 0 and 40°C.

[0084] In the description of the embodiments of the present application, the term "battery cell manufacturing temperature" refers to the battery cell manufacturing process which can be divided into a front-end electrode manufacturing process, a middle-end battery cell synthesis process, and a back-end formation and packaging process. The battery cell manufacturing temperature includes the temperature values ​​involved in the front-end, middle-end and back-end processes.

[0085] In the description of the embodiments of the present application, the term "thermal runaway temperature of the battery cell" takes the large-scale dissolution of the diaphragm as the breakthrough point, and the thermal runaway can be divided into three stages. The first stage, the self-heating stage (50℃-140℃), is also called the heat accumulation stage, which starts with the dissolution of the SEI film; the second stage, the thermal runaway stage (140℃-850℃), the large-scale melting temperature of the diaphragm starts at 140℃, after the temperature exceeds 140℃, the positive and negative electrode materials join the ranks of the electrochemical reaction, and the increase in the mass of the reactants makes the temperature rise faster; the third stage, the thermal runaway termination stage (850℃-normal temperature), once thermal runaway occurs, it can only be terminated by the complete combustion of the reactants. Only when the reactants are exhausted can the thermal runaway process terminate naturally.

[0086] In the description of the embodiments of the present application, the term "SEI" is an abbreviation of "Solid Electrolyte Interphase", which means an interface protective film or a solid electrolyte interface (film), and refers to a passivation film layer with solid electrolyte properties. Specifically, the SEI film is a passivation film generated by the reaction of the negative electrode material and the electrolyte during the first charging formation of the lithium battery. Its function is to coat the negative electrode material on the one hand to protect its structure from damage; on the other hand, it allows lithium ions to pass through and embed into the negative electrode material.

[0087] In the description of the embodiments of the present application, the term "electrolyte insoluble" means that the additives in the battery electrode will not be dissolved by the electrolyte.

[0088] In the first aspect, an embodiment of the present application provides a battery electrode 1, the active layer of which includes an electrode active material, a binder, a conductive agent and an additive 2; the melting point of the additive 2 is higher than the manufacturing temperature and the operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell; the additive 2 is insoluble in the electrolyte, and the additive is used to reduce the porosity of the battery electrode 1.

[0089] Thus, the active layer of the battery pole piece 1 provided in the embodiment of the present application contains an electrode active material, a binder, a conductive agent and an additive 2. Among them, the melting point of the additive 2 introduced into the battery pole piece 1 is higher than the manufacturing temperature of the applied battery cell and the operating temperature of the battery cell, and the additive 2 is insoluble in the electrolyte and will not be dissolved by the electrolyte in the battery cell. The melting point of the additive 2 is not reached during the normal assembly and manufacturing of the battery cell and the cycle operation of the battery cell, and the additive 2 introduced into the battery pole piece 1 is evenly distributed in the pole piece in the form of solid particles. In addition, the melting point of the additive 2 is lower than the thermal runaway temperature of the battery cell. Therefore, when the battery cell used in the battery pole piece 1 tends to have thermal runaway during the cycle, as the temperature in the battery cell gradually rises to the melting point of the additive 2, the additive 2 in the battery pole piece 1 will become molten and fill in the pores of the pole piece, blocking the pole piece pores, thereby reducing the porosity of the battery pole piece 1, cutting off the transmission channel of the ions, effectively preventing the battery cell from further releasing heat, preventing the battery thermal runaway from continuing to occur, and reducing the risk of thermal runaway of the battery cell.

[0090] After the battery pole piece 1 of the embodiment of the present application is applied to the battery cell, during the normal assembly and manufacturing of the battery cell and the cycle operation of the battery cell, the distribution of the additive 2 in the battery pole piece 1 includes at least the following situations:

[0091] In the embodiment, as shown in the attached Figure 1As shown, the additive 2 in the battery pole piece 1 is evenly distributed in the pole piece in the form of solid particles, and further, the additive 2 is evenly distributed in the pores of the battery pole piece 1. In this case, when the battery cell tends to have thermal runaway during the cycle process, as the temperature in the battery cell gradually rises to the melting point of the additive 2, the additive 2 evenly distributed in the battery pole piece 1 will become molten and evenly fill the pores of the pole piece, fully blocking the pores of the pole piece, thereby reducing the porosity of the battery pole piece 1, cutting off the transmission channel of ions, effectively preventing the battery thermal runaway from continuing to occur, and reducing the risk of thermal runaway of the battery cell.

[0092] In the embodiment, the additive 2 of the battery electrode 1 is distributed in a gradient manner in the active layer along the thickness direction of the active layer. Figure 2 As shown, the additive 2 is distributed in a gradient along the thickness direction of the active layer in the form of solid particles. In this case, when the battery cell tends to thermal runaway during the cycle, as the temperature in the battery cell gradually rises to the melting point of the additive 2, the additive 2 in the battery pole piece 1 melts to form a gradient blockage along the thickness direction of the active layer, effectively preventing the battery thermal runaway from continuing to occur and reducing the risk of thermal runaway of the battery cell.

[0093] In the embodiment, as shown in the attached Figure 3 As shown, the battery pole piece 1 also includes a current collector 3, and the content of the additive 2 in the active layer is distributed in an increasing manner along the direction from the active layer to the current collector 3. Specifically, the additive 2 is in the form of solid particles in the active layer, and is distributed in an increasing manner along the direction from the active layer to the current collector 3. In this case, the additive 2 is distributed in an increasing manner along the direction from the active layer to the current collector 3, and the content of the additive 2 on the side close to the diaphragm in the active layer is low, which is conducive to improving the embedding and extraction of ions during the normal cycle of the battery cell, and ensuring the charging and discharging efficiency of the battery cell. In addition, the content of the additive 2 on the side close to the current collector 3 in the active layer is high. When the battery cell tends to have thermal runaway during the cycle, as the temperature in the battery cell gradually rises to the melting point of the additive 2, the additive 2 in the battery pole piece 1 melts on the side close to the current collector 3 to form a denser and more comprehensive blocking effect, which can better reduce the porosity of the battery pole piece, cut off ion transmission, prevent the battery thermal runaway from continuing to occur, and reduce the risk of thermal runaway of the battery cell.

[0094] In some possible embodiments, the melting point of additive 2 is 66-120°C. In this case, the melting point of additive 2 is higher than the operating temperature of conventional lithium-ion batteries (-20°C to 60°C), and is also higher than the manufacturing temperature of the battery pole piece 1 assembled into the battery cell, specifically higher than the normal temperature aging temperature of the battery cell by about 25°C, and the high temperature aging temperature by 38-45°C. Therefore, the melting point of additive 2 is not reached during the normal assembly and manufacturing of the battery cell and the cycle operation of the battery cell, and the additive 2 introduced into the battery pole piece 1 is evenly distributed in the pole piece in the form of solid particles. However, the melting point of additive 2 is lower than the temperature of thermal runaway of the battery (140-850°C). Therefore, when the battery cell used in the battery pole piece 1 tends to have thermal runaway during the cycle, as the temperature in the battery cell gradually rises to the melting point of additive 2, the additive 2 in the battery pole piece 1 will become molten and fill in the pores of the pole piece to block the pole piece pores, reduce the porosity of the battery pole piece, cut off the transmission channel of ions, effectively prevent the battery thermal runaway from continuing to occur, and improve the safety of the battery cell. Illustratively, the melting point of the additive 2 may be 66-70°C, 70-75°C, 75-80°C, 80-90°C, 90-100°C, 100-110°C, 110-120°C, or the like.

[0095] In some possible embodiments, the mass percentage of additive 2 in the active layer of the battery pole piece 1 is 2-8wt%. This mass percentage of additive 2 in the battery pole piece 1 ensures that additive 2 controls the battery pole piece 1 in the case of thermal runaway. When the temperature of the battery cell rises and tends to thermal runaway, additive 2 can melt, fill and block the pole piece pores in time to prevent further deterioration of thermal runaway; at the same time, it ensures the charge and discharge performance of the battery pole piece 1, is conducive to the embedding and de-embedding of ions in the pole piece, and ensures the electrochemical properties of the battery pole piece 1, such as rate performance and capacity. Exemplarily, the mass percentage of additive 2 in the active layer of the battery pole piece 1 can be 2-3wt%, 3-4wt%, 4-5wt%, 5-6wt%, 6-7wt%, 7-8wt%, etc.

[0096] In some possible embodiments, the additive 2 includes: at least one of non-metallic substances, thiazoles, sulfonamides, thiurams, thioformates, azobenzenes, guanidines, and thioureas. These additives 2 used in the embodiments of the present application not only have a relatively low melting point, but also can meet the requirement that the melting point is higher than the manufacturing temperature and operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell; and these additives 2 will not be dissolved by the electrolyte in the battery cell, and these additives 2 have little effect on the ion insertion and extraction efficiency of the battery pole piece 1. In addition, these additives 2 also contain elements such as sulfur. During the film formation process on the negative electrode surface, the S element will also participate in the reaction to form a sulfonic acid group, and participate in the formation of the membrane material during the SEI film formation process, which plays a role in enhancing the toughness of the SEI film and preventing the SEI film from breaking during the cycle.

[0097] In some possible implementations, the non-metallic substance includes at least one of sulfide and elemental sulfur.

[0098] In some possible embodiments, the thiazoles include at least one of 2-thiolbenzothiazole (M) and dibenzothiazyl disulfide (DM).

[0099] In some possible embodiments, the sulfenamides include at least one of N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N-tert-butyl-2-benzothiazole sulfenamide (TBBS), N-oxydiethylene-2-benzothiazole sulfenamide (NOBS), and N,N'-dicyclohexyl-2-benzothiazole sulfenamide (DZ).

[0100] In some possible embodiments, the thiurams include at least one of tetramethylthiuram disulfide (TMTD), tetramethylthiuram monosulfide (TMTM), tetraethylthiuram disulfide (TETD), and pentamethylenethiuram hexasulfide (DPTT).

[0101] In some possible embodiments, the thioformate salts include at least one of zinc diethyldithiocarbamate (ZDC), zinc dibutyldithiocarbamate (BZ), and zinc dimethyldithiocarbamate (PZ).

[0102] In some possible embodiments, the guanidines include at least one of diphenylguanidine (D).

[0103] In some possible embodiments, the thioureas include at least one of thiourea dioxide and thiourea.

[0104] In the above embodiments of the present application, non-metallic substances, thiazoles, sulfonamides, thiurams, thioformates, azobenzene, guanidines, thioureas and other additives 2 are specifically used. On the one hand, these additives 2 all have a suitable melting point, and the additives 2 have little effect on the electrochemical properties of the battery cells during the normal assembly and manufacturing of the battery cells and the circulation operation of the battery cells; and when the battery cells used in the battery pole pieces 1 tend to have thermal runaway during the circulation process, the additives 2 are heated to become molten state and fill in the pores of the pole pieces, blocking the pole piece pores, reducing the porosity of the battery pole pieces 1, cutting off the ion transmission channel, and effectively preventing the battery thermal runaway from continuing to occur, thereby reducing the risk of thermal runaway of the battery cells. On the other hand, additives such as sulfides, elemental sulfur, sulfonamides, thiazoles, thioureas, thioformates, and thiurams also contain the element S. During the film formation process on the negative electrode surface, the element S will also participate in the reaction to form sulfonic acid groups, and participate in the composition of the membrane material during the SEI film formation process, thereby enhancing the toughness of the SEI film and preventing the SEI film from rupturing during the cycle.

[0105] In some possible embodiments, the additive 2 includes at least two of non-metallic substances, thiazoles, sulfonamides, thiurams, thioformates, azobenzenes, guanidines, and thioureas. In this case, by adding two or more additives 2 to the battery pole piece 1 at the same time, different types of additives 2 will have a certain degree of difference in melting point, particle shape, size, etc. When the battery cell used in the battery pole piece 1 tends to have thermal runaway during the cycle process, through the compounding effect of multiple additives 2 with different melting points, after melting, the pole piece pores can be better blocked, the ion transmission channel can be better cut off, and the battery thermal runaway can be effectively prevented from continuing to occur, so that the additive 2 can play a better role in blocking thermal runaway in the battery pole piece 1.

[0106] In some possible embodiments, the additive 2 includes at least two of non-metallic substances, thiazoles, sulfenamides, thiurams, thioformates, azobenzenes, guanidines, and thioureas; and the additive 2 includes a sulfur-containing additive 2. In this case, not only can two or more additives 2 be compounded to better prevent thermal runaway in the battery pole piece 1, but also the sulfur-containing additive 2 can participate in the reaction to form sulfonic acid groups during the film formation process on the negative electrode surface, participate in the film formation reaction of SEI, play a role in enhancing the toughness of the SEI film, prevent the SEI film from breaking during the cycle process, and help the stability of the battery.

[0107] In some possible embodiments, the mass percentage of the additive 2 containing sulfur element in the additive 2 is 40-60wt%, based on the total mass of the additive 2 being 100%. In this case, the mass percentage of the additive 2 containing sulfur element in the additive 2 is 40-60wt%, which not only ensures that the sulfur element in the additive 2 participates in the film-forming reaction of SEI, and has a sufficient strengthening effect on the toughness of the SEI film, which is beneficial to improving the battery stability, but also ensures that the additive 2 has a barrier effect on the ion transmission in the battery pole piece 1 when the battery cell is thermally runaway. Exemplarily, based on the total mass of the additive 2 being 100%, the mass percentage of the additive 2 containing sulfur element in the additive 2 can be 40-45wt%, 45-50wt%, 50-55wt%, 55-60wt%, etc.

[0108] In the battery pole piece 1 of the embodiment of the present application, the electrode active material is selected from the positive electrode active material or the negative electrode active material. In lithium-ion batteries, the positive electrode active material plays the role of providing a lithium source. It not only provides Li ions that travel back and forth between the positive and negative electrodes during the reversible charge and discharge process, but also provides Li ions consumed when the SEI film is formed on the surface of the negative electrode during the first charge and discharge process; at the same time, it provides a higher electrode potential, and the voltage platform is stable during the charge and discharge process. The positive electrode active material has a small electrochemical equivalent, a large amount of reversible lithium insertion and extraction, a high lithium ion diffusion coefficient, a high ionic and electronic conductivity, and good structural stability during the charge and discharge process. The negative electrode active material is the carrier of lithium ions and electrons during the charging process of the battery, and plays a role in storing and releasing energy. The insertion redox potential of lithium ions in the negative electrode matrix is ​​as low as possible, close to the potential of metallic lithium, so that the input voltage of the battery is high; a large amount of lithium in the matrix can be reversibly embedded and de-embedded to obtain high capacity; the redox potential should change as little as possible with the insertion and de-embedding of Li, so that the battery voltage does not change significantly and can maintain relatively stable charging and discharging; during the embedding / de-embedding process, the main structure of the negative electrode does not change or changes very little, which is conducive to maintaining the cycle stability of the battery cell.

[0109] In some possible embodiments, the negative electrode active materials can be divided into two categories: carbon-based and non-carbon-based negative electrode materials according to the different negative electrode active substances. Among them, carbon-based materials can be divided into carbon-based negative electrode materials such as graphite, hard carbon, soft carbon (such as coke, etc.) and graphene. Among them, graphite negative electrode materials can be further divided into natural graphite, artificial graphite, composite graphite and mesophase carbon microspheres. Natural graphite and artificial graphite are the most widely used. Non-carbon materials are divided into silicon-based negative electrode materials, lithium titanate, nitride, tin-based oxide, tin-based oxide, tin alloy and other non-carbon materials. Among them, silicon-based negative electrode materials include silicon alone, compounds formed by silicon and non-metals, compounds formed by silicon and metals, etc.

[0110] In some possible embodiments, the positive electrode active material includes, but is not limited to, metal oxides, such as lithium cobalt oxide, lithium nickel oxide, nickel cobalt manganese ternary materials, lithium nickel cobalt aluminum oxide, lithium-rich manganese-based materials, lithium manganate, lithium nickel manganate, ferroferric oxide, lithium vanadate, etc. Phosphates, silicates, sulfates, borates, titanates and other polyanion salts, such as lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium nickel phosphate, lithium iron silicate, lithium fluorosulfate, lithium iron borate, lithium iron titanate, etc. And fluorides, sulfides, selenides and other types, such as iron trifluoride, cobalt trifluoride, nickel trifluoride (NiF3), titanium disulfide, iron disulfide, molybdenum disulfide, niobium triselenide, etc.

[0111] In the battery pole piece 1 of the embodiment of the present application, the binder is an inactive component in the battery electrode, and mainly plays a connecting role between the active material, the conductive agent and the current collector 3, so that they have integrity and reduce the electrode impedance. At the same time, the battery pole piece 1 has good mechanical properties and processing properties, which can meet the needs of actual production.

[0112] In some possible embodiments, the binder includes, but is not limited to, at least one of polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), methyl cellulose (MC), polyvinyl alcohol (PVA), styrene-butadiene latex (SBR), polyacrylic acid (PAA), polyacrylonitrile (PAN) and polyacrylate. Among them, PVDF is the first widely used lithium-ion battery electrode binder, which has strong electrochemical corrosion resistance and can be applied to positive electrode materials. The solid content of SBR binder is generally 49% to 51%, and it is easily soluble in water and polar solvents. It has high bonding strength and good mechanical stability and operability. It is used as a binder in the battery industry, and the binder has good effect and stable quality. Aqueous binders with polyacrylic acid (PAA) and polyacrylonitrile (PAN) as main components. PAA has many oxygen-containing groups (-COOH) and can form hydrogen bonds with the surface of silicon-carbon active materials, giving strong binding force between active particles and current collector 3; it can alleviate the volume expansion of silicon-based materials, improve the cycle performance of batteries, and increase the life of batteries; it can form a more uniform SEI film-like coating layer on the Si surface than CMC, inhibiting the decomposition of electrolyte. Polyacrylonitrile (PAN) is a polymer obtained by polymerization of monomer acrylonitrile, with good antioxidant and anti-reduction capabilities; PAN has strong polarity and can form stable hydrogen bonds with silicon and current collector 3, which is conducive to the uniform dispersion of the binder; compared with PVDF binder, polyacrylonitrile (PAN) has less swelling, which can prevent the active material from falling off during the use of lithium batteries; no thickener and organic solvent are required during use, which can effectively reduce costs and environmental pollution. In some specific embodiments, the lithium battery binder is divided into two categories: oil-soluble and water-soluble. The positive electrode uses an oil-soluble binder and the negative electrode uses a water-based binder. The oil-soluble binder is most widely used in polyvinylidene fluoride (PVDF) homopolymers and copolymers, and an organic solvent is used as a dispersant; the water-soluble binder is widely used in styrene-butadiene (SBR) emulsion binder, and water is used as a dispersant.

[0113] In order to ensure that the battery pole piece 1 has good charge and discharge performance, a certain amount of conductive agent is added to the battery pole piece 1 in the embodiment of the present application, which plays a role in collecting microcurrents between the electrode active materials and between the active materials and the current collector 3, reduces the contact resistance of the electrode, accelerates the movement rate of electrons, and improves the electronic conductivity. In addition, the conductive agent can also improve the processability of the battery pole piece 1, promote the infiltration of the electrolyte into the pole piece, and can also effectively increase the migration rate of lithium ions in the electrode material, reduce polarization, thereby improving the charge and discharge efficiency of the electrode and the service life of the lithium battery.

[0114] In some possible implementations, the conductive agent includes, but is not limited to, amorphous carbon, carbon nanotubes, carbon fibers, graphene, etc. This is only an exemplary description and is not specifically limited herein.

[0115] In some possible implementations, in the battery pole piece 1, the mass ratio of the electrode active material, the conductive agent, and the binder is (80-99): (1-5): (2-10). Under this ratio, the bonding stability and conductivity of each component in the battery pole piece 1 are ensured at the same time, thereby ensuring the electrochemical performance of the battery pole piece 1.

[0116] In some specific embodiments, the battery electrode 1 is a negative electrode, and the active layer of the negative electrode includes negative electrode active materials, binders, conductive agents and additives 2. The additives 2 are evenly distributed in the pores of negative electrode materials such as graphite in the negative electrode, and the melting point of the additives 2 is higher than the manufacturing temperature and operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell. When the battery cell has thermal runaway during the cycle, the temperature rises to the melting point of the additives 2, and these additives 2 will become molten to block the pores of negative electrode materials such as graphite, block the transmission channel of metal ions, and prevent the battery cell from further releasing heat.

[0117] In some possible implementations, the negative electrode current collector in the negative electrode sheet may be a metal foil, such as copper foil, gold foil, platinum foil, etc. This is only for illustrative purposes and is not specifically limited here.

[0118] In some specific embodiments, the battery electrode 1 is a positive electrode, and the active layer of the positive electrode includes a positive electrode active material, a binder, a conductive agent and an additive 2. The additive 2 is evenly distributed in the pores of the positive electrode, and the melting point of the additive 2 is higher than the manufacturing temperature and operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell. When the battery cell has thermal runaway during the cycle, the temperature rises to the melting point of the additive 2, and the additive 2 will become molten to block the pores of the positive electrode, blocking the transmission channel of the metal ions and preventing the battery cell from further releasing heat.

[0119] In some possible implementations, the positive electrode current collector in the positive electrode sheet may be a metal foil, such as aluminum foil, gold foil, platinum foil, etc. This is only for illustrative purposes and is not specifically limited here.

[0120] The battery pole piece 1 of the above embodiment of the present application can be manufactured by the following embodiment method.

[0121] Second, as attached Figure 4 As shown, the embodiment of the present application provides a method for preparing a battery electrode 1, comprising the following steps:

[0122] S10. Obtaining additive 2, and preparing electrode slurry by mixing additive 2 with electrode active material, binder and conductive agent;

[0123] S20. The electrode slurry is made into a battery electrode 1; in the battery electrode, the melting point of the additive 2 is higher than the manufacturing temperature and the operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell; the additive 2 is insoluble in the electrolyte, and the additive 2 is used to reduce the porosity of the battery electrode 1.

[0124] The preparation method of the battery pole piece 1 provided in the embodiment of the present application, after preparing the electrode slurry containing the additive 2 and the electrode active material, the binder, and the conductive agent, the electrode slurry is made into the battery pole piece 1. The preparation process is simple and suitable for industrial large-scale production and application. The prepared battery pole piece 1 contains the additive 2 whose melting point is higher than the manufacturing temperature and operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell. And the additive 2 is electrolyte insoluble and will not be dissolved by the electrolyte in the battery cell. Therefore, during the normal assembly and manufacturing of the battery cell and the cycle operation of the battery cell, the additive 2 that has not reached the melting point is evenly distributed in the pole piece in the form of solid particles. When the battery cell used in the battery pole piece 1 tends to have thermal runaway during the cycle, as the temperature in the battery cell gradually rises to the melting point of the additive 2, the additive 2 melts and fills in the pole piece pores to block the pole piece pores, reduce the porosity of the battery pole piece 1, cut off the ion transmission channel, effectively prevent the battery thermal runaway from continuing to occur, reduce the risk of thermal runaway of the battery cell, and improve the safety performance of the battery cell.

[0125] In the above step S10, the preparation steps of the electrode slurry include but are not limited to: mixing the additive 2 with the electrode active material, the binder, the conductive agent and the solvent, so that each component is fully dissolved / dispersed in the solvent to form a uniformly dispersed and stable mixed slurry, i.e., the electrode slurry.

[0126] In some possible implementations, the viscosity of the electrode slurry is 7000-8000 cps. Under this viscosity condition, the electrode slurry is conducive to the subsequent preparation of a uniform and smooth electrode active layer. Exemplarily, the viscosity of the electrode slurry can be 7000-7200 cps, 7200-7500 cps, 7500-7800 cps, 7800-8000 cps, etc.

[0127] In some possible embodiments, the melting point of additive 2 is 66-120°C. In this case, the melting point of additive 2 is higher than the operating temperature of conventional lithium-ion batteries, and is also higher than the manufacturing temperature of the battery pole piece 1 assembled into the battery cell. Therefore, the melting point of additive 2 is not reached during the normal assembly and manufacturing of the battery cell and the cycle operation of the battery cell, and the additive 2 introduced into the battery pole piece 1 is evenly distributed in the pole piece in the form of solid particles. In addition, the melting point of additive 2 is lower than the temperature of thermal runaway of the battery. Therefore, when the battery cell used in the battery pole piece 1 tends to have thermal runaway during the cycle, as the temperature in the battery cell gradually rises to the melting point of additive 2, the additive 2 in the battery pole piece 1 will become molten and fill in the pores of the pole piece to block the pole piece pores, reduce the porosity of the battery pole piece 1, cut off the ion transmission channel, effectively prevent the battery thermal runaway from continuing to occur, and improve the safety of the battery cell.

[0128] In some possible embodiments, the additive 2 includes: at least one of non-metallic substances, thiazoles, sulfonamides, thiurams, thioformates, azobenzenes, guanidines, and thioureas. These additives 2 not only have a relatively low melting point, which can satisfy the requirement that the melting point is higher than the manufacturing temperature and operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell; but also the additives 2 are electrolyte insoluble and will not be dissolved by the electrolyte in the battery cell. These additives 2 have little effect on the ion insertion and extraction efficiency of the battery pole piece 1. In addition, these additives 2 also contain elements such as sulfur, which participate in the formation of the membrane material during the SEI film formation process, play a role in enhancing the toughness of the SEI film, and prevent the SEI film from breaking during the cycle.

[0129] In some possible implementations, the non-metallic substance includes at least one of sulfide and elemental sulfur.

[0130] In some possible embodiments, the thiazoles include at least one of 2-thiolbenzothiazole and dibenzothiazyl disulfide.

[0131] In some possible embodiments, the sulfenamides include at least one of N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, and N,N'-dicyclohexyl-2-benzothiazole sulfenamide.

[0132] In some possible embodiments, the thiurams include at least one of tetramethylthiuram disulfide, tetramethylthiuram monosulfide, tetraethylthiuram disulfide, and pentamethylenethiuram hexasulfide.

[0133] In some possible embodiments, the thioformate salts include at least one of zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, and zinc dimethyldithiocarbamate.

[0134] In some possible embodiments, the guanidines include at least one of diphenylguanidines.

[0135] In some possible embodiments, the thioureas include at least one of thiourea dioxide and thiourea.

[0136] In the above embodiments of the present application, the non-metallic substances, thiazoles, sulfonamides, thiurams, thioformates, azobenzene, guanidines, thioureas and other additives 2 are specifically used. These additives 2 have a suitable melting point and have little effect on the electrochemical performance of the battery cell during the normal assembly and manufacturing of the battery cell and the cyclic operation of the battery cell. When the battery cell used in the battery pole piece 1 tends to have thermal runaway during the cycle, the additive 2 is heated to a molten state and filled in the pores of the pole piece, blocking the pole piece pores, reducing the porosity of the battery pole piece 1, cutting off the transmission channel of ions, and effectively preventing the battery from continuing to have thermal runaway. In addition, sulfides, sulfur, sulfonamides, thiazoles, thioureas, thioformates, thiurams and other additives 2 also contain S elements. In the film formation process on the negative electrode surface, the S element will also participate in the reaction to form sulfonic acid groups, participate in the formation of membrane materials in the SEI film formation process, play a role in enhancing the toughness of the SEI film, and prevent the SEI film from breaking during the cycle.

[0137] In some possible implementations, in the electrode slurry, the mass of the additive 2 accounts for 2-8wt% of the total mass of the additive 2, the electrode active material, the binder and the conductive agent. The mass percentage of the additive 2 in the battery pole piece 1 ensures that the additive 2 has a control effect on the battery pole piece 1 under thermal runaway. When the temperature of the battery cell rises and tends to cause thermal runaway, the additive 2 can melt, fill and block the pole piece pores in time to prevent further deterioration of thermal runaway; at the same time, it ensures the charge and discharge performance of the battery pole piece 1, is conducive to the embedding and de-embedding of ions in the pole piece, and ensures the electrochemical properties of the battery pole piece 1, such as rate performance and capacity.

[0138] In some possible embodiments, the additive 2 includes at least two of non-metallic substances, thiazoles, sulfonamides, thiurams, thioformates, azobenzenes, guanidines, and thioureas. Through the compounding of multiple additives 2 with different melting points, the electrode pores can be better blocked after melting, the ion transmission channels can be better cut off, and the battery thermal runaway can be effectively prevented from continuing to occur, so that the additive 2 can play a better role in blocking thermal runaway in the battery electrode 1.

[0139] In some possible embodiments, the additive 2 includes at least two of non-metallic substances, thiazoles, sulfenamides, thiurams, thioformates, azobenzenes, guanidines, and thioureas; and the additive 2 includes a sulfur-containing additive 2. In this case, not only can two or more additives 2 be compounded to better prevent thermal runaway in the battery pole piece 1, but also the sulfur-containing additive 2 can participate in the reaction to form sulfonic acid groups during the film formation process on the negative electrode surface, participate in the film formation reaction of SEI, play a role in enhancing the toughness of the SEI film, prevent the SEI film from breaking during the cycle process, and help the stability of the battery.

[0140] In some possible implementations, the mass percentage of the sulfur-containing additive 2 in the additive 2 is 40-60wt%, based on the total mass of the additive 2 being 100%. In this case, the mass percentage of the sulfur-containing additive 2 in the additive 2 ensures that the sulfur element in the additive 2 participates in the film-forming reaction of the SEI and has a sufficient strengthening effect on the toughness of the SEI film, which is beneficial to improving the battery stability, and also ensures that the additive 2 has a barrier effect on the ion transmission in the battery pole piece 1 when the battery cell is thermally runaway.

[0141] In some possible embodiments, the electrode active material is selected from a positive electrode active material or a negative electrode active material.

[0142] In some possible embodiments, the negative electrode active material includes but is not limited to carbon materials such as graphite, soft carbon (such as coke, etc.), hard carbon, or nitrides, tin-based oxides, tin-based oxides, tin alloys, and silicon-based negative electrode materials.

[0143] In some possible embodiments, the positive electrode active material includes but is not limited to metal oxides, such as lithium cobalt oxide, lithium nickel oxide, nickel cobalt manganese ternary materials, lithium nickel cobalt aluminum oxide, lithium-rich manganese-based materials, lithium manganate, lithium nickel manganate, ferroferric oxide, lithium vanadate, etc. Phosphates, silicates, sulfates, borates, titanates and other polyanion salts, such as lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium nickel phosphate, lithium iron silicate, lithium fluorosulfate, lithium iron borate, lithium iron titanate, etc. And fluorides, sulfides, selenides and other types, such as iron trifluoride, cobalt trifluoride, nickel trifluoride (NiF3), titanium disulfide, iron disulfide, molybdenum disulfide, niobium triselenide, etc.

[0144] In some possible embodiments, the binder includes but is not limited to at least one of polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), methyl cellulose (MC), polyvinyl alcohol (PVA), styrene-butadiene latex (SBR), polyacrylic acid (PAA), polyacrylonitrile (PAN) and polyacrylate.

[0145] In some possible embodiments, the conductive agent includes, but is not limited to, amorphous carbon, carbon nanotubes, carbon fibers, graphene, and the like.

[0146] In the above step S20, the step of making the electrode slurry into the battery electrode sheet 1 can be to make a positive electrode sheet or a negative electrode sheet.

[0147] In some possible embodiments, the steps of making the negative electrode sheet include: mixing the negative electrode active material with a conductive agent such as conductive carbon black, a binder such as carboxymethyl cellulose and styrene-butadiene rubber, and a solvent such as water in a mass ratio of (80-99):(1-5):(2-10):100 to make a positive electrode mixed slurry, vacuum degassing, discharging, coating on a coating machine, and obtaining a negative electrode sheet after rolling, slitting, and die-cutting.

[0148] In some possible embodiments, the steps of making a positive electrode sheet include: mixing a positive electrode active material with a conductive agent such as conductive carbon black, a binder such as polyvinylidene fluoride, and a solvent such as N-methylpyrrolidone in a mass ratio of (80-99):(1-5):(2-10):100 to make a positive electrode mixed slurry, vacuum degassing, discharging, coating on a coating machine, and obtaining a positive electrode sheet after rolling, slitting, and die-cutting.

[0149] In a third aspect, an embodiment of the present application provides a secondary battery, which includes an electrode, and the electrode includes the above-mentioned battery electrode sheet 1 or the battery electrode sheet 1 prepared by the above-mentioned method.

[0150] In the secondary battery provided in the embodiment of the present application, the electrode includes the above-mentioned battery electrode 1, which contains an additive 2 with a melting point higher than the manufacturing temperature and operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell, which can effectively prevent the deterioration of the thermal runaway of the battery and reduce the risk of thermal runaway of the battery cell, thereby improving the safety performance of the secondary battery.

[0151] The electrodes in the secondary battery of the embodiment of the present application include a positive electrode and a negative electrode, wherein the positive electrode includes the above-mentioned positive electrode sheet, and the negative electrode includes the above-mentioned negative electrode sheet. The positive electrode sheet includes a positive electrode active layer and a positive electrode current collector arranged in layers, wherein the positive electrode active layer includes a positive electrode active material, a binder, a conductive agent and an additive 2; the positive electrode current collector may be a metal foil, such as aluminum foil, gold foil, platinum foil, etc. The negative electrode sheet includes a negative electrode active layer and a negative electrode current collector arranged in layers, wherein the negative electrode active layer includes a negative electrode active material, a binder, a conductive agent and an additive 2; the negative electrode current collector 3 may be a metal foil, such as copper foil, gold foil, platinum foil, etc.

[0152] The materials such as additives 2, electrode active materials, binders, conductive agents, etc. in the electrode of the secondary battery in the embodiment of the present application can refer to the materials involved in the above-mentioned embodiment of the battery pole piece 1, and will not be repeated here.

[0153] In some possible embodiments, the secondary battery further includes a separator, which can block the passage of electrons and allow the passage of ions. Exemplary separators include but are not limited to single-layer polypropylene (PP), single-layer polyethylene (PE), double-layer PP / PE, double-layer PP / PP, triple-layer PP / PE / PP, and ceramic-coated PE.

[0154] In some possible embodiments, the secondary battery further includes an electrolyte, and the electrolyte includes at least one soluble metal salt. In some specific embodiments, the metal salt includes LiClO4, LiBF4, LiPF6, LiAsF6, LiCF3SO3, LiTDI, Li[(CF3SO2)2N], Li[(FSO2)2N], Li[(C m F 2m+1 SO2)(C n F 2n+1 SO2)N], wherein m and n are natural numbers. These electrolytic salts can ensure high ionic conductivity of the electrolyte, and do not cause harmful side reactions with electrode materials, electrolytes, diaphragms, etc., and have good chemical stability.

[0155] In some possible implementations, the secondary battery includes at least one of a battery cell 4 , a battery module 5 , and a battery pack 6 .

[0156] In some possible implementations, the types of battery cells 4 include lithium-ion batteries, and new types of batteries such as sodium-ion batteries, lithium-air batteries, and lithium metal batteries.

[0157] In some possible implementations, the present application embodiment has no particular limitation on the shape of the battery cell 4, which may be cylindrical, square, or any other shape. Figure 5 The battery cell 4 is a square structure as an example.

[0158] In some embodiments, Figure 6 As shown, the outer packaging of the battery cell 4 may include a shell 41 and a cover plate 43. The shell 41 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a receiving cavity. The shell 41 has an opening connected to the receiving cavity, and the cover plate 43 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 42 through a winding process and / or a lamination process. The electrode assembly 42 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 42. The number of electrode assemblies 42 contained in the battery cell 4 can be one or more, which can be adjusted according to actual needs. Among them, the composite diaphragm of the above embodiment is arranged between the positive electrode sheet and the negative electrode sheet.

[0159] In some possible implementations, the battery cells 4 according to the present application may be assembled into a battery module 5 , and the battery module 5 may contain multiple battery cells 4 , the specific number of which may be adjusted according to the application and capacity of the battery module 5 .

[0160] In a possible implementation, as a schematic diagram of an exemplary battery module 5, as shown in FIG. Figure 7 As shown, in the battery module 5, the plurality of battery cells 4 may be arranged in sequence along the length direction of the battery module 5. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 4 may be fixed by fasteners.

[0161] In a possible implementation, the battery module 5 may further include a housing having a receiving space, and the plurality of battery cells 4 are received in the receiving space.

[0162] In a possible implementation, the battery cells 4 and / or battery modules 5 may also be assembled into a battery pack 6 , and the number of battery cells 4 or battery modules 5 included in the battery pack 6 may be adjusted according to the application and capacity of the battery pack 6 .

[0163] In a possible implementation manner, a schematic diagram of a battery pack 6 is shown as an example. Figure 8 and Fig. 9 As shown, the battery pack 6 may include a battery box and a plurality of battery modules 5 disposed in the battery box. The battery box includes an upper box body 61 and a lower box body 62, wherein the upper box body 61 is used to cover the lower box body 62 and form a closed space for accommodating the battery modules 5. The plurality of battery modules 5 may be arranged in the battery box in any manner.

[0164] In a fourth aspect, an embodiment of the present application provides an electrical device, which includes the secondary battery mentioned above.

[0165] The electrical equipment provided in the embodiment of the present application includes the secondary battery with high safety performance, thereby improving the safety and stability of electricity consumption of the electrical equipment.

[0166] In a possible implementation, the electrical equipment may select the secondary battery such as the battery cell, battery module 5 or battery pack 6 according to its usage requirements.

[0167] In one possible implementation, the electrical device may be, but is not limited to, a mobile device, such as a mobile phone, a laptop computer, etc., or an electric vehicle, such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., or an electric train, a ship and a satellite, an energy storage system, etc.

[0168] In a possible implementation, the electric device may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of such electric devices for high power and high energy density of batteries, the above-mentioned battery pack 6 or battery module 5 may be used.

[0169] In some specific embodiments, as a schematic diagram of an exemplary electrical device, as shown in the attached Fig.10 The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electric device for high power and high energy density, a battery pack 6 or a battery module can be used.

[0170] In some other possible implementations, the electrical device may also be a recorder, a radio, an electronic learning machine, a mobile phone, a tablet computer, a laptop computer, etc. Such electrical devices are usually required to be light and thin, and the battery cell in the above embodiment may be used as a power source.

[0171] Example

[0172] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0173] Example 1

[0174] The present application provides a negative electrode sheet, the preparation of which includes the following steps:

[0175] 1. Add deionized water with a solid content of 40% to graphite, styrene-butadiene rubber SBR / carboxymethyl cellulose CMC, conductive carbon and additive 2 in a mass ratio of 88.5%:2%:1.5%:8% to prepare a negative electrode slurry; wherein additive 2 is composed of azobenzene and S in a mass ratio of 1:1.2;

[0176] 2. Stir the negative electrode slurry in a double planetary mixer for 3 hours. Ensure that the viscosity of the slurry is 7000cps during the stirring process. After vacuum degassing for 30 minutes, discharge the material and coat it on the copper foil current collector 3 on a coating machine. Ensure that the coating temperature is less than the melting point of the additive 2. In order to prevent the coating effect of the current collector 3 from being affected by the temperature drop, add a blasting device. After rolling, slitting and die cutting, the negative electrode sheet is obtained.

[0177] Example 2

[0178] This embodiment provides a negative electrode sheet, the preparation of which includes the following steps:

[0179] 1. Add deionized water with a solid content of 40% to graphite, styrene-butadiene rubber SBR / carboxymethyl cellulose CMC, conductive carbon and additive 2 in a mass ratio of 88.5%:2%:1.5%:8% to prepare a negative electrode slurry; wherein additive 2 is composed of 2-thiolbenzothiazole and S element in a mass ratio of 1:1.2;

[0180] 2. Stir the negative electrode slurry in a double planetary mixer for 3 hours. Ensure that the viscosity of the slurry is 7000cps during the stirring process. After vacuum degassing for 30 minutes, discharge the material and coat it on the copper foil current collector 3 on a coating machine. Ensure that the coating temperature is less than the melting point of the additive 2. In order to prevent the coating effect of the current collector 3 from being affected by the temperature drop, add a blasting device. After rolling, slitting and die cutting, the negative electrode sheet is obtained.

[0181] Example 3

[0182] This embodiment provides a negative electrode sheet, which is different from Embodiment 1 in that the mass ratio of graphite, styrene-butadiene rubber SBR / carboxymethyl cellulose CMC, conductive carbon and additive 2 is 94.5:2:1.5:2.

[0183] Example 4

[0184] This embodiment provides a negative electrode sheet, which is different from Embodiment 1 in that the mass ratio of graphite, styrene-butadiene rubber SBR / carboxymethyl cellulose CMC, conductive carbon and additive 2 is 91.5:2:1.5:5.

[0185] Example 5

[0186] This embodiment provides a negative electrode sheet, which is different from Embodiment 1 in that the mass ratio of graphite, styrene-butadiene rubber SBR / carboxymethyl cellulose CMC, conductive carbon and additive 2 is 95.5:2:1.5:1.

[0187] Example 6

[0188] This embodiment provides a negative electrode sheet, which is different from Embodiment 1 in that the mass ratio of graphite, styrene-butadiene rubber SBR / carboxymethyl cellulose CMC, conductive carbon and additive 2 is 87.5:2:1.5:9.

[0189] Example 7

[0190] This embodiment provides a negative electrode sheet, which is different from the embodiment 1 in that the additive 2 is 2-thiolbenzothiazole.

[0191] Example 8

[0192] This embodiment provides a negative electrode sheet, which is different from the embodiment 1 in that the additive 2 is N-cyclohexyl-2-benzothiazole sulfenamide.

[0193] Example 9

[0194] This embodiment provides a negative electrode sheet, which is different from Embodiment 1 in that the additive 2 is tetramethylthiuram disulfide.

[0195] Example 10

[0196] This embodiment provides a negative electrode sheet, which is different from the embodiment 1 in that the additive 2 is zinc diethyldithiocarbamate.

[0197] Embodiment 11

[0198] This embodiment provides a negative electrode sheet, which is different from Embodiment 1 in that the additive 2 is diphenylguanidine.

[0199] Example 12

[0200] This embodiment provides a negative electrode sheet, which is different from Embodiment 1 in that the additive 2 is thiourea dioxide.

[0201] Comparative Example 1

[0202] This comparative example provides a negative electrode sheet, which is different from Example 1 in that the additive 2 is not introduced.

[0203] Assembling the negative electrode sheets prepared in the above-mentioned embodiments and comparative examples into a battery cell comprises the following steps:

[0204] 1. Positive electrode sheet: Add NMP (N-methylpyrrolidone) solvent at a solid content of 60% to the positive electrode material NCM811, binder PVDF and conductive agent Super-p in a mass ratio of 95:3:2, stir for 3 hours with a double planetary mixer, vacuum degas for 30 minutes, discharge the material, coat it on a coater, and obtain the positive electrode sheet after rolling, slitting and die-cutting.

[0205] 2. Negative electrode sheet: The negative electrode sheets prepared in the above embodiments and comparative examples are respectively used.

[0206] 3. Electrolyte: Ethylene carbonate EC / ethyl methyl carbonate EMC volume ratio 3:7+1M lithium hexafluorophosphate.

[0207] 4. Cell assembly: The commercial PE diaphragm, positive electrode sheet and negative electrode sheet are wound according to the conventional process to make the electrode core, and the electrode core is assembled into the shell, welded and sealed, baked, injected with electrolyte, impregnated, formed, and divided into volumes to obtain the battery cell. The design capacity of the battery cell is 60Ah, and the injection amount is 2.5g / Ah.

[0208] The safety performance of the secondary battery using the negative electrode sheets of the above embodiment and comparative example was tested as follows:

[0209] 1. Acupuncture test, the test method refers to the enterprise standard Q / CATL J010007-20234; heating test, the test method refers to the national standard GB38031;

[0210] 2. Heating test, the test method refers to the national standard GB38031;

[0211] 3. Drop test, the test method refers to the national standard Q / CATL J010007-2023;

[0212] The above test results are shown in Table 1 below:

[0213] Table 1

[0214]

[0215]

[0216] The sample of the secondary battery of Example 1 after the heating test is shown in the attached figure. Fig.11 As shown in the attached figure, the sample of the secondary battery of comparative example 1 after heating test is shown in the attached figure. Fig.12 As shown in the attached figure, the sample of the secondary battery of Example 1 of the present application after the needle puncture test is carried out is shown in the attached figure. Fig.13 As shown in the attached figure, the sample of the secondary battery of comparative example 1 after the needle puncture test is shown in the attached figure. Fig.14 shown.

[0217] It can be seen from the above test results that Examples 1 to 12 of the present application add azobenzene, S single substance, 2-thiol benzothiazole, N-cyclohexyl-2-benzothiazole sulfonamide, tetramethylthiuram disulfide, zinc diethyl dithiocarbamate, diphenylguanidine, thiourea dioxide and other additives with low melting points to the negative electrode of the battery. The melting points of these additives are all higher than the manufacturing temperature of the battery cell and the operating temperature of the battery cell, ensuring the normal assembly and manufacturing of the battery cell and the cycle operation of the battery cell. At the same time, the melting points of these additives are lower than the thermal runaway temperature of the battery cell. When the battery cell has thermal runaway during the cycle, as the temperature in the battery cell gradually rises to the melting point of the additive, the additive in the battery pole piece will become molten and fill in the pores of the pole piece, blocking the pole piece pores, cutting off the transmission channel of the ions, effectively preventing the battery cell from further releasing heat, and reducing the risk of thermal runaway of the battery cell. Therefore, in the needle puncture test, drop test and heating test, the battery cells prepared in the embodiments of the present application all show good stability on the surface, and they do not catch fire or explode. However, the battery cell prepared in Comparative Example 1 without adding an additive with a low melting point to the negative electrode sheet may cause problems such as fire or explosion in the puncture test, drop test and heating test.

[0218] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A battery pole piece, characterized in that: The active layer of the battery pole piece includes an electrode active material, a binder, a conductive agent and an additive; the melting point of the additive is higher than the manufacturing temperature and the operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell, the additive is insoluble in the electrolyte, and the additive is used to reduce the porosity of the battery pole piece.

2. The battery pole piece according to claim 1, characterized in that: The melting point of the additive is 66-120°C.

3. The battery electrode according to any one of claims 1 to 2, characterized in that: The mass percentage of the additive in the active layer of the battery pole piece is 2-8wt%.

4. The battery electrode according to any one of claims 1 to 3, characterized in that: The additives include: at least one of non-metallic substances, thiazoles, sulfenamides, thiurams, thioformates, azobenzene, guanidines, and thioureas.

5. The battery pole piece according to claim 4, characterized in that: The non-metallic substance includes at least one of sulfide and elemental sulfur; and / or, the thiazoles include at least one of 2-thiolbenzothiazole and dibenzothiazole disulfide; And / or, the sulfenamides include at least one of N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, and N,N'-dicyclohexyl-2-benzothiazole sulfenamide; And / or, the thiurams include at least one of tetramethylthiuram disulfide, tetramethylthiuram monosulfide, tetraethylthiuram disulfide, and pentamethylenethiuram hexasulfide; And / or, the thioformate salts include at least one of zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, and zinc dimethyldithiocarbamate; and / or, the guanidines include at least one of diphenylguanidine; And / or, the thioureas include at least one of thiourea dioxide and thiourea.

6. The battery pole piece according to any one of claims 1 to 5, characterized in that: The additives include at least two of non-metallic substances, thiazoles, sulfenamides, thiurams, thioformates, azobenzenes, guanidines, and thioureas.

7. The battery pole piece according to claim 6, characterized in that: The additives include additives containing sulfur elements.

8. The battery pole piece according to claim 7, characterized in that: Taking the total mass of the additive as 100%, the mass percentage of the sulfur-containing additive in the additive is 40-60wt%.

9. The battery pole piece according to any one of claims 1 to 8, characterized in that: The additive is distributed in the active layer in a gradient manner along the thickness direction of the active layer.

10. The battery pole piece according to claim 9, characterized in that: Along the direction from the active layer to the current collector contained in the battery pole piece, the content of the additive in the active layer is distributed in an increasing manner.

11. The battery electrode according to any one of claims 1 to 10, characterized in that: The electrode active material is selected from positive electrode active materials or negative electrode active materials.

12. A method for preparing a battery pole piece, characterized in that: The following steps are involved: Obtaining an additive, and preparing an electrode slurry by combining the additive with an electrode active material, a binder, and a conductive agent; The electrode slurry is made into a battery electrode; in the battery electrode, the melting point of the additive is higher than the manufacturing temperature and operating temperature of the applied battery cell and lower than the thermal runaway temperature of the battery cell, the additive is insoluble in the electrolyte, and the additive is used to reduce the porosity of the battery electrode.

13. The method for preparing a battery pole piece according to claim 12, characterized in that: The melting point of the additive is 66-120°C.

14. The method for preparing a battery pole piece according to any one of claims 12 to 13, characterized in that: In the electrode slurry, the mass of the additive accounts for 2 to 8 wt % of the total mass of the additive, the electrode active material, the binder and the conductive agent.

15. The method for preparing a battery pole piece according to any one of claims 12 to 14, characterized in that: The additives include: at least one of non-metallic substances, thiazoles, sulfenamides, thiurams, thioformates, azobenzene, guanidines, and thioureas.

16. The method for preparing a battery pole piece according to claim 15, characterized in that: The non-metallic substance includes at least one of sulfide and elemental sulfur; and / or, the thiazoles include at least one of 2-thiolbenzothiazole and dibenzothiazole disulfide; And / or, the sulfenamides include at least one of N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, and N,N'-dicyclohexyl-2-benzothiazole sulfenamide; And / or, the thiurams include at least one of tetramethylthiuram disulfide, tetramethylthiuram monosulfide, tetraethylthiuram disulfide, and pentamethylenethiuram hexasulfide; And / or, the thioformate salts include at least one of zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, and zinc dimethyldithiocarbamate; and / or, the guanidines include at least one of diphenylguanidine; And / or, the thioureas include at least one of thiourea dioxide and thiourea.

17. The method for preparing a battery pole piece according to any one of claims 12 to 16, characterized in that: The electrode active material is selected from positive electrode active materials or negative electrode active materials.

18. A secondary battery, characterized in that: The secondary battery comprises an electrode, and the electrode comprises the battery electrode sheet as claimed in any one of claims 1 to 11 or the battery electrode sheet prepared by the method as claimed in any one of claims 12 to 17.

19. The secondary battery according to claim 18, characterized in that: The secondary battery includes at least one of a battery cell, a battery module, and a battery pack.

20. An electrical equipment, characterized in that: The electrical equipment comprises the secondary battery as claimed in any one of claims 18 to 19.

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