Battery electrodes and their preparation methods, secondary batteries, electrical equipment

Abstract

This application discloses a battery electrode and its preparation method, a secondary battery, and an electrical device. The active layer of the battery electrode includes an electrode active material, a binder, a conductive agent, and additives. The additives have a melting point higher than the manufacturing and operating temperature of the battery cell but lower than the thermal runaway temperature of the cell. The additives are electrolyte-insoluble and used to reduce the porosity of the electrode. In the battery electrode provided in this application, during normal assembly and manufacturing of the battery cell and during its cycling operation, the additives that have not reached their melting point are uniformly distributed in the electrode as solid particles. When the battery cell tends to experience thermal runaway during cycling, as the temperature inside the cell gradually rises to the melting point of the additives, the additives melt and fill the pores of the electrode, blocking the electrode channels, cutting off the ion transport channels, effectively preventing further thermal runaway, reducing the risk of thermal runaway, and improving the safety performance of the battery cell.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a battery electrode and its preparation method, a secondary battery, and an electrical device. Background Technology

[0002] A secondary battery is a type of rechargeable battery that primarily functions by the movement of metal ions, such as lithium, between the positive and negative electrodes. During charging, metal ions are extracted from the positive electrode, pass through the electrolyte, and embed into the negative electrode, leaving the negative electrode in a lithium-rich state; the process is reversed during discharge. In recent years, pure electric vehicles have become a crucial development direction for electric vehicles due to their ability to truly achieve "zero emissions," and secondary batteries, with their superior performance, have become an ideal power source for the next generation of electric vehicles.

[0003] Secondary batteries consist of a separator, electrolyte, and positive and negative electrode materials. Under electrical, thermal, and mechanical faults such as internal and external short circuits, overcharging, thermal abuse, and mechanical abuse, secondary batteries are prone to thermal runaway, releasing large amounts of heat and explosive gases, leading to fires and explosions. In recent years, fires and explosions caused by thermal runaway of secondary batteries, such as lithium-ion batteries, have been frequently reported. The safety of secondary batteries has become one of the main factors hindering their large-scale commercial application in the power supply industry. During the thermal runaway process of a battery cell, a series of chemical reactions occur inside the battery. These reactions generate a large amount of heat, accompanied by the production of many flammable gases, ultimately leading to thermal runaway. This can cause safety accidents such as fires and explosions, resulting in huge property losses and casualties, among other social impacts.

[0004] Currently, the main solutions to the problem of thermal runaway in batteries include improving explosion-proof valves or using water-cooling devices to transfer heat in a timely manner. However, these methods are all taken after thermal runaway has occurred and cannot address or reduce the risk of thermal runaway in a timely manner. Summary of the Invention

[0005] In view of the above problems, this application provides a battery electrode and its preparation method, a secondary battery, and an electrical device to solve the technical problem of battery thermal runaway affecting safety.

[0006] In a first aspect, this application provides a battery electrode sheet, wherein the active layer of the battery electrode sheet 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 operating temperature of the battery cell to which it is applied and lower than the thermal runaway temperature of the battery cell; the additive is non-soluble in electrolyte; and the additive is used to reduce the porosity of the battery electrode sheet.

[0007] In the technical solution of this application embodiment, the additive introduced into the battery electrode has a melting point higher than the manufacturing temperature and operating temperature of the battery cell, and the additive is electrolyte-insoluble and will not be dissolved by the electrolyte in the battery cell. During normal assembly and manufacturing of the battery cell and during its cycling operation, the melting point of the additive is not reached, and the additive introduced into the battery electrode is uniformly distributed in the electrode in the form of solid particles. Furthermore, the melting point of the additive is lower than the thermal runaway temperature of the battery cell. Therefore, when the battery cell to which the battery electrode is applied tends to experience thermal runaway during cycling, as the temperature inside the battery cell gradually rises to reach the melting point of the additive, the additive in the battery electrode will become molten and fill the pores of the electrode, blocking the electrode channels, thereby reducing the porosity of the battery electrode, cutting off the ion transport channels, effectively preventing further heat release from the battery cell, preventing further thermal runaway, and reducing the risk of battery cell thermal runaway.

[0008] In some embodiments, the additive has a melting point of 66–120°C. This melting point is higher than the operating temperature of conventional lithium-ion batteries and also higher than the manufacturing temperature at which the battery electrodes are assembled into the cell. Therefore, during normal cell assembly and manufacturing, and during cell cycling, the additive's melting point is not reached, and the additive introduced into the battery electrodes is uniformly distributed in the electrode as solid particles. Furthermore, the additive's melting point is lower than the battery's thermal runaway temperature. Therefore, when the cell using the battery electrodes tends to experience thermal runaway during cycling, the additive melts and fills the electrode pores, blocking the electrode channels, reducing the porosity of the battery electrodes, cutting off ion transport channels, effectively preventing further thermal runaway, and improving the cell's safety.

[0009] In some embodiments, the additive has a mass percentage content of 2-8 wt% in the active layer of the battery electrode. This mass percentage content ensures both the control effect of the additive on the battery electrode under thermal runaway conditions and the charge-discharge performance of the battery electrode, which is beneficial for the insertion and extraction of ions in the electrode, and ensures the rate performance, capacity, and other electrochemical performance of the battery electrode.

[0010] In some embodiments, the additives include at least one of the following: non-metallic substances, thiazoles, sulfenamides, thiurams, thiocarbamates, azobenzenes, guanidines, and thioureas. These additives not only have relatively low melting points, meeting the requirement of melting points higher than the manufacturing and operating temperatures of the applied battery cell but lower than the thermal runaway temperature of the battery cell; they also contain elements such as sulfur, which participate in the formation of the membrane material during SEI film formation, enhancing the toughness of the SEI film and preventing it from rupturing during cycling.

[0011] In some embodiments, the nonmetallic substance includes at least one of sulfides and elemental sulfur.

[0012] In some embodiments, the thiazole class includes at least one of 2-thiol benzothiazole and dibenzothiazole disulfide.

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

[0014] In some embodiments, the thiuram class includes at least one of tetramethylthiuram disulfide, tetramethylthiuram monosulfide, tetraethylthiuram disulfide, and pentamethylthiuram hexasulfide.

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

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

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

[0018] In the above embodiments of this application, the additives used all have suitable melting points, which can effectively prevent the continued occurrence of battery thermal runaway and reduce the risk of cell thermal runaway. Furthermore, these additives, including sulfides, elemental sulfur, sulfenamides, thiazoles, thioureas, thiocarbamates, and thiurams, also contain sulfur (S), which participates in the formation of the membrane material during SEI film formation, enhancing the toughness of the SEI film and preventing it from rupturing during cycling.

[0019] In some embodiments, the additive includes at least two of the following: non-metallic substances, thiazoles, sulfenamides, thiurams, thiocarbamates, azobenzenes, guanidines, and thioureas. Through the combined effect of multiple additives with different melting points, the additives, after melting, can better block the electrode pores and cut off ion transport channels, effectively preventing further thermal runaway of the battery. This allows the additives to exert a better effect in preventing thermal runaway in the battery electrode.

[0020] In some embodiments, the additive includes a sulfur-containing additive. The sulfur-containing additive can participate in the reaction to form sulfonic acid groups during the film formation process on the negative electrode surface, participating in the SEI film formation reaction, thereby enhancing the toughness of the SEI film, preventing SEI film rupture during cycling, and contributing to battery stability.

[0021] In some embodiments, the sulfur-containing additive comprises 40-60 wt% of the total mass of the additives. This ensures that the sulfur in the additives participates in the SEI film-forming reaction, providing sufficient enhancement to the toughness of the SEI film and thus improving battery stability. It also ensures that the additives block ion transport in the battery electrodes during thermal runaway.

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

[0023] In some embodiments, the additive content in the active layer increases progressively towards the current collector contained in the battery electrode. A lower additive content on the side of the active layer closer to the separator is beneficial for improving ion insertion and extraction during normal cell cycling, ensuring the cell's charge and discharge efficiency. A higher additive content on the side of the active layer closer to the current collector, however, can better reduce the porosity of the battery electrode in the event of thermal runaway, cutting off ion transport and preventing further thermal runaway, thus reducing the risk of cell thermal runaway.

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

[0025] Secondly, this application provides a method for preparing a battery electrode, comprising the following steps:

[0026] Obtain the additives and combine them with electrode active materials, binders, and conductive agents to form an electrode slurry;

[0027] The electrode slurry is used to form a battery electrode sheet; in the battery electrode sheet, the melting point of the additive is higher than the manufacturing temperature and operating temperature of the battery cell and lower than the thermal runaway temperature of the battery cell, the additive is non-soluble in electrolyte, and the additive is used to reduce the porosity of the battery electrode sheet.

[0028] The battery electrode preparation method provided in this application is simple and suitable for large-scale industrial production and application. The prepared battery electrode contains additives with melting points higher than the manufacturing and operating temperatures of the battery cell but lower than its thermal runaway temperature. Furthermore, the additives are electrolyte-insoluble and will not dissolve in the battery cell. Therefore, during normal assembly and manufacturing of the battery cell and during its cycling operation, the additives that have not reached their melting point are uniformly distributed in the electrode as solid particles. When the battery cell tends to experience thermal runaway during cycling, as the temperature inside the cell gradually rises to the melting point of the additives, the additives melt and fill the pores of the electrode, blocking the electrode channels, reducing the porosity of the battery electrode, cutting off ion transport channels, effectively preventing further thermal runaway, reducing the risk of battery thermal runaway, and improving the safety performance of the battery cell.

[0029] In some embodiments, the melting point of the additive is 66–120°C. The melting point of the additive is higher than the operating temperature of conventional lithium-ion batteries, and also higher than the manufacturing temperature at which the battery electrode is assembled into the cell. Therefore, during normal cell assembly and manufacturing, and during cell cycling, the melting point of the additive is not reached, and the additive introduced into the battery electrode is uniformly distributed in the electrode in the form of solid particles. Furthermore, the melting point of the additive is lower than the temperature at which the battery experiences thermal runaway. Therefore, when the cell in which the battery electrode is used tends to experience thermal runaway during cycling, the additive will become molten and fill the pores of the electrode, blocking the electrode channels, reducing the porosity of the battery electrode, cutting off the ion transport channels, effectively preventing further thermal runaway, and improving the safety of the cell.

[0030] In some embodiments, the additive in the electrode slurry accounts for 2-8 wt% of the total mass of the additive, the electrode active material, the binder, and the conductive agent. This mass percentage ensures both the control effect of the additive on the battery electrode under thermal runaway conditions—that is, when the cell temperature rises and tends to cause thermal runaway, the additive can melt and fill and block the electrode pores in time, preventing further deterioration of thermal runaway—and the charge-discharge performance of the battery electrode, which is beneficial for the insertion and extraction of ions in the electrode, ensuring the rate performance, capacity, and other electrochemical performance of the battery electrode.

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

[0032] In some embodiments, the nonmetallic substance includes at least one of sulfides and elemental sulfur.

[0033] In some embodiments, the thiazole class includes at least one of 2-thiol benzothiazole and dibenzothiazole disulfide.

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

[0035] In some embodiments, the thiuram class includes at least one of tetramethylthiuram disulfide, tetramethylthiuram monosulfide, tetraethylthiuram disulfide, and pentamethylthiuram hexasulfide.

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

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

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

[0039] The additives in the above embodiments of this application not only have relatively low melting points, meeting the requirement of melting points higher than the manufacturing and operating temperatures of the applied battery cell but lower than the thermal runaway temperature of the battery cell; but also have little impact on the ion insertion and extraction efficiency of the battery electrode. Furthermore, these additives also contain elements such as sulfur, which participate in the formation 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 cycling.

[0040] In some embodiments, the electrode active material is selected from either 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 is a positive electrode; when the electrode active material is a negative electrode active material, the battery electrode is a negative electrode.

[0041] Thirdly, this application provides a secondary battery, which includes electrodes, the electrodes including the battery electrode sheet described above or the battery electrode sheet prepared by the above method.

[0042] In the secondary battery provided in this application embodiment, the electrode includes the aforementioned battery electrode sheet. The battery electrode sheet contains an additive with a melting point higher than the manufacturing temperature and operating temperature of the applied battery cell but lower than the thermal runaway temperature of the battery cell. This effectively prevents the deterioration of battery thermal runaway and reduces the risk of battery cell thermal runaway, 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] Fourthly, this application provides an electrical device that includes the aforementioned secondary battery.

[0045] The electrical equipment provided in this application embodiment improves the electrical safety and stability of the equipment by including the aforementioned high-safety-performance secondary battery.

[0046] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0047] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0048] Figure 1 This is a schematic diagram of the distribution of additives in the battery electrode sheets of this application embodiment. Figure 1 ;

[0049] Figure 2 This is a schematic diagram of the distribution of additives in the battery electrode sheets of this application embodiment. Figure 2 ;

[0050] Figure 3 This is a schematic diagram of the distribution of additives in the battery electrode sheets of this application embodiment. Figure 3 ;

[0051] Figure 4 This is a schematic flowchart of the method for preparing battery electrode sheets according to an embodiment of this application;

[0052] Figure 5 This is a schematic diagram of the structure of a single battery cell according to an embodiment of this application;

[0053] Figure 6 for Figure 5 The diagram shows an exploded view of a single battery cell.

[0054] Figure 7 This is a schematic diagram of one embodiment of the battery module of this application;

[0055] Figure 8 This is a schematic diagram of one embodiment of the battery pack of this application;

[0056] Figure 9 for Figure 8 The diagram shows the exploded structure of the battery pack.

[0057] Figure 10 This is a schematic diagram of one embodiment of an electrical device that uses a secondary battery as a power source, as described in the present application.

[0058] Figure 11 This is a sample image of the secondary battery of Embodiment 1 of this application after undergoing a heating test;

[0059] Figure 12 This is a sample image of the secondary battery of Comparative Example 1 after a heating test.

[0060] Figure 13 This is a sample image of the secondary battery of Embodiment 1 of this application after undergoing a nail penetration test;

[0061] Figure 14 This is a sample image of the secondary battery of Comparative Example 1 after undergoing a nail penetration test.

[0062] The reference numerals in the detailed embodiments are as follows:

[0063] 1. Battery electrode plates;

[0064] 2. Additives;

[0065] 3. Current collector;

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

[0067] 5. Battery module;

[0068] 6. Battery pack, 61. Upper casing, 62. Lower casing. Detailed Implementation

[0069] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0071] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0072] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0073] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0074] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0075] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0076] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0077] From a market perspective, lithium-ion batteries are currently used extensively in both power and energy storage batteries. However, the public remains deeply concerned about battery spontaneous combustion and explosions, and battery safety remains an unavoidable topic in the industry. Thermal runaway is a primary focus of research on improving the safety of lithium-ion batteries. Battery thermal runaway refers to a chain reaction phenomenon triggered by various factors. The large amount of heat and harmful gases released during thermal runaway can cause battery fires and explosions. Battery thermal runaway often begins with the decomposition of the negative electrode SEI film within the battery cell, followed by the decomposition and melting of the separator. This leads to a reaction between the negative electrode and the electrolyte, subsequently causing the positive electrode and electrolyte to decompose, resulting in a large-scale internal short circuit. This causes electrolyte combustion, which then spreads to other cells, leading to severe thermal runaway and ultimately causing the entire battery pack to spontaneously combust. During the thermal runaway process within a battery cell, a series of chemical reactions occur inside the battery. These reactions generate a large amount of heat, accompanied by the production of many flammable gases, ultimately leading to thermal runaway. This can cause safety accidents such as fires and explosions, resulting in significant property damage and personal injury.

[0078] Currently, the main solutions to the problem of thermal runaway in batteries include explosion venting and isolation. Regarding explosion venting, once a battery cell experiences thermal runaway, it rapidly generates a large amount of high-temperature gas. If this gas cannot be effectively released, the high-temperature gas (and molten material) will heat surrounding cells, potentially triggering thermal runaway in other cells; it may also lead to explosions and other serious consequences. Therefore, effective explosion-proof venting paths and outlets are designed into the battery casing, and explosion-proof valves are improved to guide the high-temperature gas appropriately. Regarding isolation, the purpose is to block the propagation of the runaway. This includes isolation within the battery pack and isolation outside the battery pack. Isolation within the battery pack includes using longitudinal and transverse beams to isolate the modules and using fire-resistant and heat-insulating materials. Isolation outside the battery pack includes measures such as using water-cooling devices to promptly transfer heat. However, these methods are all implemented after thermal runaway has occurred and cannot address and reduce the risk of thermal runaway in a timely manner.

[0079] To mitigate the safety risks posed by battery thermal runaway, research has found that prevention is key, as there's little effective way to stop it once it occurs. Prevention can be approached externally by employing safe and efficient thermal management systems to suppress temperature rise in lithium-ion batteries. Passive cooling strategies, such as adding fins, embedding metal foam, and coating with phase change materials, enhance the safety of lithium-ion battery applications. However, the best approach is to address thermal runaway at its source. Before it occurs, physical barriers should be used to block the transport of metal ions, preventing further heat release and minimizing the risk.

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

[0081] In such battery electrodes, the addition of low-melting-point additives—with melting points higher than the manufacturing and operating temperatures of the battery cells—ensures proper assembly and cycling of the cells. When the battery cell experiences thermal runaway during cycling, as the cell's internal temperature gradually rises to the additive's melting point, the additive melts and fills the electrode pores, blocking the channels and reducing the electrode's porosity. This cuts off ion transport channels, effectively preventing further heat generation and mitigating the risk of thermal runaway.

[0082] For ease of explanation, the embodiments in this application use battery electrodes and their preparation methods, secondary batteries, and electrical devices as examples.

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

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

[0085] In the description of the embodiments of this application, the term "thermal runaway temperature of the battery cell" is used as the breakthrough point to divide thermal runaway into three stages. The first stage, the self-heating stage (50℃-140℃), is also called the heat accumulation stage, which begins with the dissolution of the SEI film. The second stage, the thermal runaway stage (140℃-850℃), is when the large-scale melting temperature of the separator starts at 140℃. After the temperature exceeds 140℃, both the positive and negative electrode materials join the electrochemical reaction. The increase in the amount of reactants makes the temperature rise faster. The third stage, the thermal runaway termination stage (850℃-room temperature), is when thermal runaway can only be terminated when all the reactants are burned off. Only when the reactants are exhausted can the thermal runaway process terminate naturally.

[0086] In the description of the embodiments in this application, the term "SEI" is an abbreviation for "Solid Electrolyte Interphase," which refers to an interface protective film or solid electrolyte interface (film), and specifically a passivation film layer with solid electrolyte properties. Specifically, the SEI film is a passivation film formed during the first charging formation of a lithium battery by the reaction of the negative electrode material and the electrolyte. Its function is twofold: firstly, to coat the negative electrode material, protecting its structure from damage; and secondly, to allow lithium ions to pass through and embed into the negative electrode material.

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

[0088] In a first aspect, embodiments of this application provide 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 operating temperature of the battery cell to which it is applied and lower than the thermal runaway temperature of the battery cell; the additive 2 is non-soluble in electrolyte and is used to reduce the porosity of the battery electrode 1.

[0089] Thus, the active layer of the battery electrode 1 provided in this embodiment contains electrode active material, binder, conductive agent, and additive 2. The additive 2 introduced into the battery electrode 1 has a melting point higher than the manufacturing temperature and operating temperature of the battery cell, and is electrolyte-insoluble, meaning it will not dissolve in the battery cell. During normal assembly and manufacturing of the battery cell and during its cycling operation, the melting point of additive 2 is not reached, and additive 2 is uniformly distributed in the electrode as solid particles. Furthermore, the melting point of additive 2 is lower than the thermal runaway temperature of the battery cell. Therefore, when the battery cell using battery electrode 1 tends to experience thermal runaway during cycling, as the temperature inside the cell gradually rises to the melting point of additive 2, additive 2 in the battery electrode 1 melts and fills the pores of the electrode, blocking the pores and reducing the porosity of the battery electrode 1. This cuts off the ion transport channels, effectively preventing further heat release from the battery cell, stopping further thermal runaway, and reducing the risk of thermal runaway.

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

[0091] In the embodiments, as shown in the appendix Figure 1As shown, additive 2 is uniformly distributed in the form of solid particles in battery electrode 1. Furthermore, additive 2 is uniformly distributed in the pores of battery electrode 1. In this case, when the cell tends to experience thermal runaway during cycling, as the temperature inside the cell gradually rises to the melting point of additive 2, the additive 2 uniformly distributed in battery electrode 1 will become molten and uniformly fill the pores of the electrode, fully blocking the electrode channels, thereby reducing the porosity of battery electrode 1, cutting off the ion transport channels, effectively preventing the continued occurrence of battery thermal runaway, and reducing the risk of cell thermal runaway.

[0092] In this embodiment, the additive 2 of the battery electrode 1 is distributed in a gradient along the thickness direction of the active layer. Specifically, as shown in the attached figure... Figure 2 As shown, 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 cell tends to experience thermal runaway during cycling, as the temperature inside the cell gradually rises to the melting point of additive 2, additive 2 melts in the battery electrode 1 and forms a gradient blockage along the thickness direction of the active layer, effectively preventing the battery thermal runaway from continuing and reducing the risk of cell thermal runaway.

[0093] In the embodiments, as shown in the appendix Figure 3 As shown, the battery electrode 1 also includes a current collector 3. Along the direction from the active layer to the current collector 3, the content of additive 2 in the active layer increases progressively. Specifically, additive 2 exists in the active layer in the form of solid particles, progressively distributed along the direction from the active layer to the current collector 3. In this case, the additive 2 is progressively distributed along the direction from the active layer to the current collector 3, with a lower content of additive 2 on the side of the active layer closer to the separator. This is beneficial for improving the insertion and extraction of ions during normal cell cycling, ensuring the cell's charge and discharge efficiency. Furthermore, the higher content of additive 2 on the side of the active layer closer to the current collector 3 means that when the cell tends towards thermal runaway during cycling, as the temperature inside the cell gradually rises to the melting point of additive 2, the additive 2 in the battery electrode 1 melts on the side closer to the current collector 3, forming a denser and more comprehensive blocking effect. This better reduces the porosity of the battery electrode, cuts off ion transport, prevents further thermal runaway, and reduces the risk of cell thermal runaway.

[0094] In some possible implementations, 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 also higher than the manufacturing temperature at which battery electrode 1 is assembled into the cell, specifically about 25°C higher than the cell's room temperature aging temperature and 38–45°C high temperature aging temperature. Therefore, during the normal assembly and manufacturing of the cell and during the cell's cycling operation, the melting point of additive 2 is not reached, and additive 2 introduced into battery electrode 1 is uniformly distributed in the electrode in the form of solid particles. However, the melting point of additive 2 is lower than the temperature at which the battery experiences thermal runaway (140–850°C). Therefore, when the cell in which battery electrode 1 is used tends to experience thermal runaway during cycling, as the temperature inside the cell gradually rises to reach the melting point of additive 2, additive 2 in battery electrode 1 will become molten and fill the pores of the electrode, blocking the electrode channels, reducing the porosity of the battery electrode, cutting off the ion transport channels, effectively preventing the battery from continuing to experience thermal runaway, and improving the safety of the cell. For example, the melting point of additive 2 can be 66-70℃, 70-75℃, 75-80℃, 80-90℃, 90-100℃, 100-110℃, 110-120℃, etc.

[0095] In some possible implementations, the additive 2 has a mass percentage content of 2-8 wt% in the active layer of the battery electrode 1. This mass percentage content of additive 2 in the battery electrode 1 ensures both the control effect of additive 2 on the battery electrode 1 under thermal runaway conditions—when the cell temperature rises and tends to cause thermal runaway, additive 2 can melt and fill and block the electrode channels in time, preventing further deterioration of thermal runaway—and the charge and discharge performance of the battery electrode 1, which is beneficial to the insertion and extraction of ions in the electrode, ensuring the rate performance, capacity, and other electrochemical performance of the battery electrode 1. For example, the mass percentage content of additive 2 in the active layer of the battery electrode 1 can be 2-3 wt%, 3-4 wt%, 4-5 wt%, 5-6 wt%, 6-7 wt%, 7-8 wt%, etc.

[0096] In some possible implementations, additive 2 includes at least one of the following: non-metallic substances, thiazoles, sulfenamides, thiurams, thiocarbamates, azobenzenes, guanidines, and thioureas. The additives 2 used in this application not only have relatively low melting points, meeting the requirement of melting points higher than the manufacturing and operating temperatures of the applied battery cell but lower than the thermal runaway temperature of the cell; moreover, these additives 2 are not dissolved by the electrolyte in the battery cell, and have little impact on the ion insertion and extraction efficiency of the battery electrode 1. In addition, these additives 2 also contain elements such as sulfur. During the film formation process on the negative electrode surface, sulfur participates in the reaction to form sulfonic acid groups, participating in the composition of the film material during SEI film formation, thereby enhancing the toughness of the SEI film and preventing it from rupturing during cycling.

[0097] In some possible implementations, the nonmetallic substance includes at least one of sulfides and elemental sulfur.

[0098] In some possible implementations, the thiazole class includes at least one of 2-thiol-benzothiazole (M) and dibenzothiazole disulfide (DM).

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

[0100] In some possible implementations, the thiuram class includes at least one of tetramethylthiuram disulfide (TMTD), tetramethylthiuram monosulfide (TMTM), tetraethylthiuram disulfide (TETD), and pentamethylthiuram hexasulfide (DPTT).

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

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

[0103] In some possible implementations, thiourea compounds include at least one of thiourea dioxide and thiourea.

[0104] In the above embodiments of this application, the non-metallic substances, thiazoles, sulfenamides, thiurams, thiocarbamates, azobenzenes, guanidines, thioureas, and other additives 2 are specifically used. On the one hand, these additives 2 all have suitable melting points, and during the normal assembly and manufacturing of the battery cell and the cyclic operation of the battery cell, the additives 2 have little impact on the electrochemical performance of the battery cell. On the other hand, when the battery cell to which the battery electrode 1 is used tends to undergo thermal runaway during the cycle, the additives 2 are heated to become molten and fill the pores of the electrode, blocking the electrode channels, reducing the porosity of the battery electrode 1, cutting off the ion transport channels, effectively preventing the battery thermal runaway from continuing to occur, and reducing the risk of battery cell thermal runaway. On the other hand, additives such as sulfides, elemental sulfur, sulfenamides, thiazoles, thioureas, thiocarbamates, and thiurams also contain sulfur. During the film formation process on the negative electrode surface, sulfur will also participate in the reaction to form sulfonic acid groups, which will participate in the composition of the film material during the SEI film formation process, thereby enhancing the toughness of the SEI film and preventing the SEI film from breaking during cycling.

[0105] In some possible implementations, additive 2 includes at least two of the following: non-metallic substances, thiazoles, sulfenamides, thiurams, thiocarbamates, azobenzenes, guanidines, and thioureas. In this case, by simultaneously adding two or more additives 2 to the battery electrode 1, the different types of additives 2 will have certain differences in melting point, particle morphology, and size. When the battery cell to which the battery electrode 1 is used tends to undergo thermal runaway during cycling, the combined effect of multiple additives 2 with different melting points can better block the electrode channels after melting, better cut off the ion transport channels, and effectively prevent the battery thermal runaway from continuing to occur, thereby enabling additive 2 to play a better role in blocking thermal runaway in the battery electrode 1.

[0106] In some possible implementations, additive 2 includes at least two of the following: non-metallic substances, thiazoles, sulfenamides, thiurams, thiocarbamates, azobenzenes, guanidines, and thioureas; and additive 2 includes a sulfur-containing additive 2. In this case, not only can the combination of two or more additives 2 achieve a better effect in preventing thermal runaway in the battery electrode 1, but the sulfur-containing additive 2 can also participate in the reaction to form sulfonic acid groups during the film formation process on the negative electrode surface, participating in the SEI film formation reaction, thereby enhancing the toughness of the SEI film, preventing the SEI film from rupturing during cycling, and contributing to the stability of the battery.

[0107] In some possible implementations, the sulfur-containing additive 2 comprises 40-60 wt% of the total mass of additive 2. In this case, the 40-60 wt% sulfur-containing additive 2 ensures that the sulfur in additive 2 participates in the SEI film-forming reaction, providing sufficient enhancement to the toughness of the SEI film and thus improving battery stability. It also ensures that additive 2 blocks ion transport in the battery electrode 1 during thermal runaway. For example, the sulfur-containing additive 2 may comprise 40-45 wt%, 45-50 wt%, 50-55 wt%, or 55-60 wt% of the total mass of additive 2.

[0108] In the battery electrode 1 of this application embodiment, the electrode active material is selected from either the positive electrode active material or the negative electrode active material. In a lithium-ion battery, the positive electrode active material serves to provide a lithium source. It not only provides Li ions that travel back and forth between the positive and negative electrodes during the reversible charge-discharge process, but also provides the Li ions consumed during the initial charge-discharge process when an SEI film is formed on the surface of the negative electrode; simultaneously, it provides a high electrode potential, ensuring a stable voltage plateau during charge-discharge. The positive electrode active material has a low electrochemical equivalent, a large reversible lithium insertion / extraction capacity, a high lithium-ion diffusion coefficient, high ionic and electronic conductivity, and good structural stability during charge-discharge. The negative electrode active material is the carrier of lithium ions and electrons during battery charging, playing a role in energy storage and release. The redox potential of lithium ions in the negative electrode matrix should be as low as possible, close to the potential of metallic lithium, so as to achieve a high input voltage of the battery; a large number of lithium ions in the matrix can undergo reversible insertion and extraction to obtain high capacity; the redox potential should change as little as possible with the insertion and extraction of Li, so that the battery voltage will not change significantly and can maintain relatively stable charging and discharging; during the insertion / extraction process, the main structure of the negative electrode does not change or changes very little, which is beneficial to maintaining the cycle stability of the cell.

[0109] In some possible implementations, anode active materials can be broadly classified into two categories based on their active substances: carbon-based and non-carbon-based anode materials. Carbon-based materials can be further divided into graphite, hard carbon, soft carbon (such as coke), and graphene, among others. Graphite anode materials can be further subdivided into natural graphite, artificial graphite, composite graphite, and mesophase carbon microspheres. Natural and artificial graphite are the most widely used. Non-carbon-based materials include silicon-based anode materials, lithium titanate, nitrides, tin-based oxides, tin alloys, and other non-carbon materials. Silicon-based anode materials include elemental silicon, compounds formed from silicon and nonmetals, and compounds formed from silicon and metals.

[0110] In some possible implementations, 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 manganese oxide, lithium nickel-manganese oxide, iron tetroxide, and lithium vanadium oxide. Polyanionic salts such as phosphates, silicates, sulfates, borates, and titanates include lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium cobalt phosphate, lithium nickel phosphate, lithium iron phosphate, lithium iron fluoride sulfate, lithium iron borate, and lithium iron titanate. Fluorides, sulfides, and selenides also exist, such as iron trifluoride, cobalt trifluoride, nickel trifluoride (NiF3), titanium disulfide, iron disulfide, molybdenum disulfide, and niobium triselenide.

[0111] In the battery electrode 1 of this application embodiment, the binder is a non-active component in the battery electrode, mainly playing a connecting role between the active material, conductive agent, and current collector 3, making them integral and reducing electrode impedance. At the same time, it gives the battery electrode 1 good mechanical and processing properties, meeting the needs of actual production.

[0112] In some possible implementations, 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 these, PVDF was the first widely used lithium-ion battery electrode binder, exhibiting strong resistance to electrochemical corrosion and suitable for use in cathode materials. SBR binders typically have a solid content of 49%–51%, are readily soluble in water and polar solvents, possess high bonding strength, good mechanical stability, and workability, and are used as binders in the battery industry with good bonding performance and stable quality. Water-based binders with polyacrylic acid (PAA) and polyacrylonitrile (PAN) as main components: PAA has many oxygen-containing groups (-COOH), which can form hydrogen bonds with the surface of silicon-carbon active materials, giving the active particles and current collector 3 a strong binding force; it can alleviate the volume expansion of silicon-based materials, improve the cycle performance of the battery, and increase the battery life; it can form a more uniform SEI-like coating layer on the Si surface than CMC, inhibiting the decomposition of the electrolyte. Polyacrylonitrile (PAN) is a polymer obtained by polymerization of acrylonitrile monomer, with good antioxidant and reduction resistance; PAN has strong polarity and can form stable hydrogen bonds with silicon and current collector 3, which is beneficial 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 lithium battery use; it does not require the addition of thickeners and organic solvents, which can effectively reduce costs and environmental pollution. In some specific embodiments, lithium battery binders are divided into two categories: oil-soluble and water-soluble. Oil-soluble binders are used for the positive electrode, while water-soluble binders are used for the negative electrode. Oil-soluble binders are most widely used in homopolymers and copolymers of polyvinylidene fluoride (PVDF), using organic solvents as dispersants. Water-soluble binders are more widely used in styrene-butadiene rubber (SBR) emulsion binders, using water as a dispersant.

[0113] In this embodiment, to ensure good charge-discharge performance of the battery electrode 1, a certain amount of conductive agent is added to the battery electrode 1. This agent collects microcurrents between the active materials of the electrode and between the active materials and the current collector 3, reducing the contact resistance of the electrode, accelerating the electron mobility, and improving the electronic conductivity. Furthermore, the conductive agent also improves the processability of the battery electrode 1, promotes the wetting of the electrode by the electrolyte, and effectively increases the migration rate of lithium ions in the electrode material, reducing polarization, thereby improving the charge-discharge efficiency of the electrode and the lifespan 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 merely illustrative and does not constitute a specific limitation.

[0115] In some possible implementations, the mass ratio of electrode active material, conductive agent, and binder in battery electrode 1 is (80–99):(1–5):(2–10). This ratio ensures both the bonding stability and conductivity of each component in battery electrode 1, thereby guaranteeing the electrochemical performance of battery electrode 1.

[0116] In some specific embodiments, the battery electrode 1 is a negative electrode. The active layer of the negative electrode includes a negative electrode active material, a binder, a conductive agent, and an additive 2. The additive 2 is uniformly distributed in the pores of the negative electrode material such as graphite. The melting point of the additive 2 is higher than the manufacturing and operating temperature of the battery cell but lower than the thermal runaway temperature of the battery cell. When thermal runaway occurs during battery cell cycling, the temperature rises to the melting point of the additive 2. The additive 2 then melts and blocks the pores of the negative electrode material such as graphite, blocking the transport channels of metal ions and preventing further heat release from the battery cell.

[0117] In some possible implementations, the negative current collector in the negative electrode sheet can be a metal foil, such as copper foil, gold foil, platinum foil, etc. This is merely an illustrative example and is not intended to be specific.

[0118] In some specific embodiments, the battery electrode 1 is a positive electrode. The active layer of the positive electrode includes a positive active material, a binder, a conductive agent, and an additive 2. The additive 2 is uniformly distributed in the channels of the positive electrode. The melting point of the additive 2 is higher than the manufacturing and operating temperature of the battery cell but lower than the thermal runaway temperature of the battery cell. When thermal runaway occurs during battery cell cycling, the temperature rises to the melting point of the additive 2. The additive 2 then melts and blocks the channels of the positive electrode, blocking the transport channels of metal ions and preventing further heat release from the battery cell.

[0119] In some possible implementations, the positive current collector in the positive electrode sheet can be a metal foil, such as aluminum foil, gold foil, platinum foil, etc. This is merely an illustrative example and is not intended to be specific.

[0120] The battery electrode 1 described in the above embodiments of this application can be prepared by the following methods.

[0121] Secondly, as attached Figure 4 As shown in the figure, this application provides a method for preparing a battery electrode 1, including the following steps:

[0122] S10. Obtain additive 2, and combine additive 2 with electrode active material, binder and conductive agent to form electrode slurry;

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

[0124] The battery electrode 1 preparation method provided in this application involves preparing an electrode slurry containing additive 2, electrode active material, binder, and conductive agent, and then forming the battery electrode 1 from the electrode slurry. The preparation process is simple and suitable for large-scale industrial production and application. The prepared battery electrode 1 contains additive 2 with a melting point higher than the manufacturing and operating temperature of the battery cell but lower than the thermal runaway temperature of the battery cell. Furthermore, additive 2 is electrolyte-insoluble and will not dissolve in the battery cell. Therefore, during normal assembly and manufacturing of the battery cell and during its cycling operation, additive 2, which has not reached its melting point, is uniformly distributed in the electrode as solid particles. When the battery cell to which battery electrode 1 is used tends to experience thermal runaway during cycling, as the temperature inside the battery cell gradually rises to the melting point of additive 2, additive 2 melts and fills the pores of the electrode, blocking the electrode channels, reducing the porosity of the battery electrode 1, cutting off the ion transport channels, effectively preventing further thermal runaway, reducing the risk of thermal runaway, and improving the safety performance of the battery cell.

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

[0126] In some possible implementations, the viscosity of the electrode paste is 7000–8000 cps. At this viscosity, the electrode paste is advantageous for subsequent preparation of a uniform and smooth electrode active layer. For example, the viscosity of the electrode paste can be 7000–7200 cps, 7200–7500 cps, 7500–7800 cps, 7800–8000 cps, etc.

[0127] In some possible implementations, 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 also higher than the manufacturing temperature at which battery electrode 1 is assembled into the cell. Therefore, during normal assembly and manufacturing of the cell and during cell cycling, the melting point of additive 2 is not reached, and additive 2 introduced into battery electrode 1 is uniformly distributed in the electrode in the form of solid particles. Furthermore, the melting point of additive 2 is lower than the temperature of battery thermal runaway. Therefore, when the cell in which battery electrode 1 is used tends to experience thermal runaway during cycling, as the temperature inside the cell gradually rises to reach the melting point of additive 2, additive 2 in battery electrode 1 will become molten and fill the pores of the electrode, blocking the electrode channels, reducing the porosity of battery electrode 1, cutting off the ion transport channels, effectively preventing further thermal runaway of the battery, and improving the safety of the cell.

[0128] In some possible implementations, additive 2 includes at least one of the following: non-metallic substances, thiazoles, sulfenamides, thiurams, thiocarbamates, azobenzenes, guanidines, and thioureas. These additives 2 not only have relatively low melting points, meeting the requirement of melting points higher than the manufacturing and operating temperatures of the applied battery cell but lower than the thermal runaway temperature of the cell; but also possess electrolyte-insoluble properties, meaning they are not dissolved in the electrolyte within the battery cell. These additives 2 have minimal impact on the ion insertion and extraction efficiency of the battery electrode 1. Furthermore, these additives 2 also contain elements such as sulfur, which participate in the formation of the membrane material during SEI film formation, enhancing the toughness of the SEI film and preventing it from rupturing during cycling.

[0129] In some possible implementations, the nonmetallic substance includes at least one of sulfides and elemental sulfur.

[0130] In some possible implementations, the thiazole class includes at least one of 2-thiol-benzothiazole and dibenzothiazole disulfide.

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

[0132] In some possible implementations, the thiuram class includes at least one of tetramethylthiuram disulfide, tetramethylthiuram monosulfide, tetraethylthiuram disulfide, and pentamethylthiuram hexasulfide.

[0133] In some possible implementations, thiocarbamates include at least one of zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, and zinc dimethyldithiocarbamate.

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

[0135] In some possible implementations, thiourea compounds include at least one of thiourea dioxide and thiourea.

[0136] In the above embodiments of this application, the non-metallic substances, thiazoles, sulfenamides, thiurams, thiocarbamates, azobenzene, guanidines, thioureas, and other additives 2 are specifically used. These additives 2 all have suitable melting points and have little impact on the electrochemical performance of the battery cell during normal assembly and manufacturing and cyclic operation. When the battery cell using the battery electrode 1 tends to experience thermal runaway during cycling, the additives 2 melt upon heating and fill the pores of the electrode, blocking the electrode channels, reducing the porosity of the battery electrode 1, cutting off the ion transport channels, and effectively preventing further thermal runaway. Furthermore, these additives 2, including sulfides, elemental sulfur, sulfenamides, thiazoles, thioureas, thiocarbamates, and thiurams, also contain sulfur (S). During the film formation process on the negative electrode surface, the sulfur element participates in the reaction to form sulfonic acid groups, participating in the composition of the film material during SEI film formation, enhancing the toughness of the SEI film, and preventing the SEI film from rupturing during cycling.

[0137] In some possible implementations, the mass of additive 2 in the electrode slurry accounts for 2 to 8 wt% of the total mass of additive 2, electrode active material, binder, and conductive agent. This mass percentage of additive 2 in the battery electrode 1 ensures both the control effect of additive 2 on the battery electrode 1 under thermal runaway conditions, allowing additive 2 to melt and fill and block the electrode pores in a timely manner when the cell temperature rises and tends to cause thermal runaway, preventing further deterioration of thermal runaway; and also ensures the charge and discharge performance of the battery electrode 1, facilitating the insertion and extraction of ions in the electrode, and ensuring the rate performance, capacity, and other electrochemical performance of the battery electrode 1.

[0138] In some possible implementations, additive 2 includes at least two of the following: non-metallic substances, thiazoles, sulfenamides, thiurams, thiocarbamates, azobenzenes, guanidines, and thioureas. Through the combined effect of multiple additives 2 with different melting points, after melting, they can better block the electrode pores and better cut off the ion transport channels, effectively preventing further thermal runaway of the battery. This allows additive 2 to exert a better effect in preventing thermal runaway in the battery electrode 1.

[0139] In some possible implementations, additive 2 includes at least two of the following: non-metallic substances, thiazoles, sulfenamides, thiurams, thiocarbamates, azobenzenes, guanidines, and thioureas; and additive 2 includes a sulfur-containing additive 2. In this case, not only can the combination of two or more additives 2 achieve a better effect in preventing thermal runaway in the battery electrode 1, but the sulfur-containing additive 2 can also participate in the reaction to form sulfonic acid groups during the film formation process on the negative electrode surface, participating in the SEI film formation reaction, thereby enhancing the toughness of the SEI film, preventing the SEI film from rupturing during cycling, and contributing to the stability of the battery.

[0140] In some possible implementations, the sulfur-containing additive 2 comprises 40–60 wt% of the total mass of additive 2. In this case, the wt% content of the sulfur-containing additive 2 ensures that the sulfur in additive 2 participates in the SEI film-forming reaction, providing sufficient enhancement to the toughness of the SEI film and thus improving battery stability. It also ensures that additive 2 blocks ion transport in the battery electrode 1 during cell thermal runaway.

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

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

[0143] In some possible implementations, 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 manganese oxide, lithium nickel-manganese oxide, iron tetroxide, lithium vanadium oxide, etc.; polyanionic salts such as phosphates, silicates, sulfates, borates, titanates, etc., such as lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium cobalt phosphate, lithium nickel phosphate, lithium iron phosphate, lithium iron fluoride sulfate, lithium iron borate, lithium iron titanate, etc.; and types such as fluorides, sulfides, selenides, etc., such as iron trifluoride, cobalt trifluoride, nickel trifluoride (NiF3), titanium disulfide, iron disulfide, molybdenum disulfide, niobium triselenide, etc.

[0144] In some possible implementations, the adhesive 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 implementations, the conductive agent includes, but is not limited to, amorphous carbon, carbon nanotubes, carbon fibers, graphene, etc.

[0146] In step S20 above, the step of forming the electrode slurry into battery electrode 1 can be either forming a positive electrode or a negative electrode.

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

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

[0149] Thirdly, embodiments of this application provide a secondary battery, which includes an electrode, comprising the battery electrode 1 described above or the battery electrode 1 prepared by the method described above.

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

[0151] The electrodes in the secondary battery of this application embodiment include a positive electrode and a negative electrode. The positive electrode includes the aforementioned positive electrode sheet, and the negative electrode includes the aforementioned negative electrode sheet. The positive electrode sheet includes a stacked positive electrode active layer and a positive electrode current collector. The positive electrode active layer includes a positive electrode active material, a binder, a conductive agent, and additive 2. The positive electrode current collector can be a metal foil, such as aluminum foil, gold foil, platinum foil, etc. The negative electrode sheet includes a stacked negative electrode active layer and a negative electrode current collector. The negative electrode active layer includes a negative electrode active material, a binder, a conductive agent, and additive 2. The negative electrode current collector 3 can be a metal foil, such as copper foil, gold foil, platinum foil, etc.

[0152] The additives 2, electrode active materials, binders, conductive agents, and other materials in the electrodes of the secondary battery in this application embodiment can refer to the materials involved in the above-mentioned battery electrode 1 embodiment, and will not be repeated here.

[0153] In some possible implementations, the secondary battery also includes a separator that blocks electrons from passing through while allowing ions to pass through. 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 separators.

[0154] In some possible implementations, the secondary battery further includes an electrolyte comprising 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], and Li[(C m F 2m+1 SO2)(C n F 2n+1 At least one of SO2(N)[m, n], where m and n are natural numbers. These electrolytic salts can ensure high ionic conductivity of the electrolyte and do not undergo harmful side reactions with electrode materials, electrolyte, diaphragm, etc., and have good chemical stability.

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

[0156] In some possible implementations, the battery cell type 4 includes lithium-ion batteries, as well as novel batteries such as sodium-ion batteries, lithium-air batteries, and lithium metal batteries.

[0157] In some possible implementations, the embodiments of this application do not impose particular limitations on the shape of the battery cell 4; it can be cylindrical, square, or other arbitrary shapes. Figure 5 Here is a square-structured battery cell 4 as an example.

[0158] In some embodiments, such as Figure 6 As shown, the outer packaging of the battery cell 4 may include a housing 41 and a cover plate 43. The housing 41 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 41 has an opening communicating with the receiving cavity, and the cover plate 43 is used to cover the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator may be formed into an electrode assembly 42 by a winding process and / or a stacking process. The electrode assembly 42 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 42. The number of electrode assemblies 42 contained in the battery cell 4 may be one or more, which can be adjusted according to actual needs. The composite separator of the above embodiment is disposed between the positive electrode sheet and the negative electrode sheet.

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

[0160] In one possible implementation, a schematic diagram of battery module 5 as an example is shown below. Figure 7 As shown, in the battery module 5, multiple battery cells 4 can be arranged sequentially along the length of the battery module 5. Of course, they can also be arranged in any other way. Furthermore, these multiple battery cells 4 can be fixed in place using fasteners.

[0161] In one possible implementation, the battery module 5 may further include a housing with a receiving space in which multiple battery cells 4 are received.

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

[0163] In one possible implementation, a schematic diagram of battery pack 6 as an example is shown below. Figure 8 and Figure 9 As shown, the battery pack 6 may include a battery box and multiple battery modules 5 disposed within the battery box. The battery box includes an upper box 61 and a lower box 62. The upper box 61 covers the lower box 62 and forms a closed space for accommodating the battery modules 5. The multiple battery modules 5 can be arranged in the battery box in any manner.

[0164] Fourthly, embodiments of this application provide an electrical device that includes the aforementioned secondary battery.

[0165] The electrical equipment provided in this application embodiment improves the electrical safety and stability of the equipment by including the aforementioned high-safety-performance secondary battery.

[0166] In one possible implementation, the electrical equipment can select the aforementioned secondary batteries, such as battery cells, battery modules 5, or battery packs 6, according to its usage requirements.

[0167] In one possible implementation, the electrical equipment may be, but is not limited to, mobile devices such as mobile phones, laptops, etc., or electric vehicles such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., or electric trains, ships and satellites, energy storage systems, etc.

[0168] In one possible implementation, the electrical device can be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of such electrical devices for batteries, the aforementioned battery pack 6 or battery module 5 can be used.

[0169] In some specific embodiments, a schematic diagram of an example electrical device is shown in the attached figure. Figure 10 As shown. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device, a battery pack 6 or a battery module can be used.

[0170] In other possible implementations, the electrical device can also be a tape recorder, radio, e-learning machine, mobile phone, tablet computer, laptop computer, etc. These types of electrical devices typically require a thin and light design, and can use the battery cells described in the above embodiments as their power source.

[0171] Example

[0172] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0173] Example 1

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

[0175] 1. Graphite, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), conductive carbon, and additive 2 in a mass ratio of 88.5%:2%:1.5%:8% are mixed with deionized water at a solid content of 40% to prepare a negative electrode slurry; wherein, additive 2 is composed of azobenzene and elemental sulfur in a mass ratio of 1:1.2.

[0176] 2. The negative electrode slurry is stirred in a double planetary mixer for 3 hours, ensuring the viscosity remains at 7000 cps during stirring. After vacuum degassing for 30 minutes, the slurry is discharged and coated onto the copper foil current collector 3 using a coating machine. The coating temperature is kept below the melting point of additive 2. To ensure the coating effect of current collector 3 is not affected by temperature drop, a blower is added. 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. Graphite, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), conductive carbon, and additive 2 in a mass ratio of 88.5%:2%:1.5%:8% are mixed with deionized water at a solid content of 40% to prepare a negative electrode slurry; wherein, additive 2 is composed of 2-thiol benzothiazole and elemental sulfur in a mass ratio of 1:1.2.

[0180] 2. The negative electrode slurry is stirred in a double planetary mixer for 3 hours, ensuring the viscosity remains at 7000 cps during stirring. After vacuum degassing for 30 minutes, the slurry is discharged and coated onto the copper foil current collector 3 using a coating machine. The coating temperature is kept below the melting point of additive 2. To ensure the coating effect of current collector 3 is not affected by temperature drop, a blower is added. After rolling, slitting, and die-cutting, the negative electrode sheet is obtained.

[0181] Example 3

[0182] This embodiment provides a negative electrode sheet, which differs 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 differs 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 differs 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 differs 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 differs from that in Embodiment 1 in that: additive 2 is 2-thiol benzothiazole.

[0191] Example 8

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

[0193] Example 9

[0194] This embodiment provides a negative electrode sheet, which differs from Example 1 in that: additive 2 is tetramethylthiuram disulfide.

[0195] Example 10

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

[0197] Example 11

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

[0199] Example 12

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

[0201] Comparative Example 1

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

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

[0204] 1. Positive electrode sheet: NCM811 positive electrode material, PVDF binder and Super-p conductive agent in a mass ratio of 95:3:2 are added to NMP (N-methylpyrrolidone) solvent at a solid content of 60%. The mixture is stirred for 3 hours with a double planetary mixer, vacuum degassing for 30 minutes, and then discharged. The mixture is coated on a coating machine and then rolled, slit and die-cut to obtain the positive electrode sheet.

[0205] 2. Negative electrode: Negative electrode prepared using the above-described embodiments and comparative examples respectively.

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

[0207] 4. Cell Assembly: Commercial PE separators are wound with positive and negative electrode sheets using conventional processes to form the electrode core. The electrode core is then assembled into the casing, welded and sealed, baked, injected with electrolyte, impregnated, formed, and capacity tested to obtain the battery cell. The designed capacity of the battery cell is 60Ah, with an electrolyte injection rate of 2.5g / Ah.

[0208] The safety performance of the secondary batteries using the negative electrode sheets in the above embodiments and comparative examples was tested as follows:

[0209] 1. Needle penetration test, the test method refers to enterprise standard Q / CATL J010007-2023; 4. Heating test, the test method refers to national standard GB38031.

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

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

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

[0213] Table 1

[0214]

[0215]

[0216] The sample image of the secondary battery in Example 1 after heating test is attached. Figure 11 As shown in the attached image, the secondary battery of Example 1 has undergone a heating test. Figure 12 As shown in the attached figure, a sample image of the secondary battery of Embodiment 1 of this application after undergoing a nail penetration test is obtained. Figure 13 As shown in the attached image, the secondary battery of Example 1 after undergoing a nail penetration test is a sample image. Figure 14 As shown.

[0217] As shown in the test results above, Examples 1-12 of this application added low-melting-point additives such as azobenzene, elemental sulfur (S), 2-thiol-benzothiazole, N-cyclohexyl-2-benzothiazole sulfenamide, tetramethylthiuram disulfide, zinc diethyldithiocarbamate, diphenylguanidine, and thiourea dioxide to the negative electrode of the battery. The melting points of these additives are all higher than the manufacturing temperature and operating temperature of the battery cell, ensuring normal assembly and manufacturing of the cell and its cyclic operation. Simultaneously, the melting points of these additives are lower than the thermal runaway temperature of the battery cell. When thermal runaway occurs during cycling, as the temperature inside the cell gradually rises to the melting point of the additives, the additives in the battery electrode will melt and fill the pores of the electrode, blocking the pores, cutting off the ion transport channels, effectively preventing further heat release from the cell, and reducing the risk of thermal runaway. Therefore, the battery cells prepared in the examples of this application all exhibit good stability in the needle penetration test, drop test, and heating test, and none of them ignite or explode. However, the battery cell prepared in Comparative Example 1 without adding low-melting-point additives to the negative electrode sheet caused problems such as fire or explosion in needle penetration 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 this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery electrode, characterized in that: The active layer of the battery electrode includes electrode active material, binder, conductive agent, and additives; the melting point of the additive is higher than the manufacturing and operating temperature of the battery cell and lower than the thermal runaway temperature of the battery cell; the additive is electrolyte-insoluble; the additive is used to reduce the porosity of the battery electrode; the melting point of the additive is 66–120°C; the mass percentage of the additive in the active layer of the battery electrode is 2–8 wt%; the additive includes at least one of the following: non-metallic substances, thiazoles, sulfenamides, thiurams, thiocarbamates, azobenzene, guanidines, and thioureas; the non-metallic substances include at least one of sulfides and elemental sulfur; the thiazoles include at least one of 2-thiol benzothiazole and dibenzothiazole disulfide; The sulfonamides include at least one of N-cyclohexyl-2-benzothiazole sulfonamide, N-tert-butyl-2-benzothiazole sulfonamide, N-oxadiethylene-2-benzothiazole sulfonamide, and N,N'-dicyclohexyl-2-benzothiazole sulfonamide; the thiurams include at least one of tetramethylthiuram disulfide, tetramethylthiuram monosulfide, tetraethylthiuram disulfide, and pentamethylthiuram hexasulfide; the thiocarbamates include at least one of zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, and zinc dimethyldithiocarbamate; the guanidines include at least one of diphenylguanidine; and the thioureas include at least one of thiourea dioxide and thiourea. The additives are distributed in a gradient along the thickness direction of the active layer in the active layer.

2. The battery electrode according to claim 1, characterized in that: The additives include at least two of the following: non-metallic substances, thiazoles, sulfenamides, thiurams, thiocarbamates, azobenzenes, guanidines, and thioureas.

3. The battery electrode according to claim 2, characterized in that: The additives include those containing sulfur.

4. The battery electrode according to claim 3, characterized in that: Based on the total mass of the additives being 100%, the sulfur-containing additives constitute 40-60 wt% of the total mass of the additives.

5. The battery electrode according to claim 4, characterized in that: Along the direction from the active layer to the current collector contained in the battery electrode, the content of the additive in the active layer increases progressively.

6. The battery electrode sheet according to any one of claims 1 to 5, characterized in that: The electrode active material is selected from positive electrode active materials or negative electrode active materials.

7. A method for preparing a battery electrode sheet as described in any one of claims 1 to 6, characterized in that: Includes the following steps: Obtain the additives and combine them with electrode active materials, binders, and conductive agents to form an electrode slurry; The electrode slurry is used to form a battery electrode sheet; in the battery electrode sheet, the melting point of the additive is higher than the manufacturing temperature and operating temperature of the battery cell and lower than the thermal runaway temperature of the battery cell, the additive is non-soluble in electrolyte, and the additive is used to reduce the porosity of the battery electrode sheet.

8. The method for preparing battery electrode sheets according to claim 7, characterized in that: The additive has a melting point of 66–120°C.

9. The method for preparing the battery electrode according to any one of claims 7 to 8, characterized in that: The electrode active material is selected from positive electrode active materials or negative electrode active materials.

10. A secondary battery, characterized in that, The secondary battery includes electrodes, which include battery electrode sheets as described in any one of claims 1 to 6 or battery electrode sheets prepared by the method described in any one of claims 7 to 9.

11. The secondary battery according to claim 10, characterized in that, The secondary battery includes at least one of the following: a battery cell, a battery module, and a battery pack.

12. An electrical appliance, characterized in that, The electrical device includes a secondary battery as described in any one of claims 10 to 11.

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