Battery

Abstract

The invention relates to the technical field of batteries, and provides a battery which comprises a shell, a battery cell and an explosion-proof structure, the battery cell comprises a positive plate and a negative plate, a positive active material layer is formed on the positive plate, a negative active material layer is formed on the negative plate, the negative active material layer comprises a silicon-carbon composite material, and the silicon-carbon composite material is a silicon-carbon composite material. The explosion-proof structure is connected to the shell and covers the outer side of the first through hole in a sealing mode, the explosion-proof structure comprises a base body layer and a hot melt adhesive layer, the overlapping area of the base body layer and the hot melt adhesive layer is S1 mm < 2 >, the mass ratio percentage content of silicon of the negative electrode active material layer is D, and S1 and D meet the relational expression that S1 / D is larger than or equal to 10 and smaller than or equal to 80. According to the battery provided by the embodiment of the invention, the purpose of ensuring that the battery has enough safety on the premise of improving the energy density can be achieved.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and in particular, to a battery. Background Art

[0002] Lithium-ion batteries are widely used in many fields such as consumer electronics, wearable electronic devices, and new energy vehicles due to their advantages of high energy density, high cycle life, and high charging efficiency. During the charge and discharge cycle of a lithium-ion battery, expansion and contraction phenomena will occur due to changes in the internal temperature of the battery. When the temperature is too high or even in a thermal runaway situation, the high-temperature gas inside the lithium-ion battery needs to open the pressure relief valve to play a pressure relief role, preventing safety accidents such as fire or explosion, thereby ensuring the safety of the lithium-ion battery.

[0003] With the continuous improvement of the energy density of lithium-ion batteries, the safety problems of lithium-ion batteries in terms of thermal runaway are becoming more and more serious. At present, high-energy-density lithium-ion batteries have design defects, resulting in safety problems such as easy thermal runaway of lithium-ion batteries. Summary of the Invention

[0004] The present application provides a battery, which can achieve the purpose of ensuring sufficient safety of the battery on the premise of improving the energy density.

[0005] A first aspect of the present application provides a battery, including:

[0006] A housing having a receiving cavity and a first through hole communicating with the receiving cavity;

[0007] A battery cell disposed in the receiving cavity. The battery cell includes a positive electrode sheet and a negative electrode sheet. A positive electrode active material layer is formed on the positive electrode sheet, and a negative electrode active material layer is formed on the negative electrode sheet. The negative electrode material layer includes a silicon-carbon composite material;

[0008] And an explosion-proof structure connected to the housing and sealingly covering the outside of the first through hole. The explosion-proof structure includes a base layer and a hot melt adhesive layer. The base layer includes a sealing layer and a covering layer. The sealing layer sealingly covers the outside of the first through hole. The sealing layer has a second through hole communicating with the first through hole. The hot melt adhesive layer is connected to the sealing layer. The hot melt adhesive layer has a third through hole communicating with the second through hole. The covering layer is connected to the hot melt adhesive layer. The covering layer seals the third through hole; the overlapping area of the base layer and the hot melt adhesive layer is S1 mm 2 , and the mass percentage content of silicon element in the negative electrode active material layer is D. The S1 and the D satisfy the relationship:

[0009] 10 ≤ S1 / D ≤ 80.

[0010] According to the battery described in the first aspect of the present application, by providing an explosion-proof structure and a negative electrode active material layer including a silicon-carbon composite material, within the normal temperature range under normal conditions, the hot melt adhesive layer of the explosion-proof structure can be tightly connected to the housing to seal the first through hole, ensuring the normal use of the battery under normal conditions. When the temperature is too high, such as in the case of thermal runaway, etc., through the heat conduction of the metal housing, the hot melt adhesive layer is heated and gradually loses its viscosity. At the same time, the gas formed by the expansion of the negative electrode active material layer including the silicon-carbon composite material forms a greater impact force, assisting in breaking through the hot melt adhesive layer to achieve the purpose of pressure relief, reducing the risk of safety problems such as explosion and fire of the battery, improving the thermal sensitivity of the pressure relief of the explosion-proof structure, improving the reliability of pressure relief, and further increasing the passing rate of the thermal box of the battery.

[0011] In the battery according to the embodiment of the present application, the design of including a silicon-carbon composite material in the negative electrode active material layer can improve the energy density of the battery, and the design of the explosion-proof structure and its hot melt adhesive layer can cooperate with the impact force formed during the charge and discharge cycle of the silicon-carbon composite material, thereby achieving the purpose of ensuring sufficient safety of the battery while improving the energy density.

[0012] In a possible implementation manner, the graphite orientation degree of the negative electrode sheet is X, and X satisfies the relationship: 3 ≤ X ≤ 35.

[0013] In a possible implementation manner, the mass percentage content D of silicon element in the negative electrode active material layer is 5 - 50%, and / or, the overlapping area S1 of the matrix layer and the hot melt adhesive layer is 3 - 10 mm 2 。

[0014] In a possible implementation manner, the aperture of the first through hole is d1, the aperture of the second through hole is d2, and the aperture of the third through hole is d3, and d1, d2, and d3 satisfy the relationship: d1 < d2 < d3.

[0015] In a possible implementation manner, the outer diameter of the sealing layer is d4, the outer diameter of the hot melt adhesive layer is d5, and the outer diameter of the covering layer is d6, and d4, d5, and d6 satisfy the relationship: d4 > d5 > d6.

[0016] In a possible implementation manner, the overlapping area of the sealing layer, the hot melt adhesive layer, and the covering layer is S2, and S2 satisfies the relationship:

[0017] 0.1mm 2 ≤ S2 ≤ 3mm 2 。

[0018] In a possible implementation manner, the area of the covering layer is S3, and S2 and S3 satisfy the relationship: S2 / S3 = 0.1 to 0.75.

[0019] In a possible implementation manner, the hot melt adhesive layer includes:

[0020] A skeleton layer;

[0021] A sticky layer, the sticky layer is connected to both sides of the skeleton layer, the thickness of the skeleton layer is greater than the thickness of the sticky layer, and the melting point of the skeleton layer is higher than the melting point of the sticky layer;

[0022] And a passivation layer, the passivation layer is arranged between the skeleton layer and the sticky layer.

[0023] In a possible implementation manner, the glass transition temperature Tg of the hot melt adhesive layer satisfies the relationship: Tg = 95°C - 135°C.

[0024] In a possible implementation manner, the negative electrode sheet is arranged on both sides of the positive electrode sheet, the negative electrode sheet is a single-sided negative electrode sheet, and a sticker layer is coated on the outer periphery of the negative electrode sheet, and the width L1 of the sticker layer satisfies the relationship: L1 ≥ 5 mm.

[0025] In a possible implementation manner, the average sphericity H of the silicon-carbon composite material satisfies the relationship: H = 0.1 to 1.

[0026] In a possible implementation manner, the particle size distribution of the silicon-carbon composite material is: Dv10 = 3 - 6 μm; Dv50 = 6 - 12 μm; Dv90 = 12 - 25 μm.

[0027] In a possible implementation manner, the porosity K of the negative electrode sheet satisfies the relationship: K = 5% to 50%.

[0028] In a possible implementation manner, the peak intensity ratio g range of the characteristic peaks of the dO / Dv curve of the carbon-silicon composite material at 0.25 V to 0.3 V and at 0.4 V to 0.45 V satisfies the relationship: g = 1 to 3. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1Shows an explosion schematic diagram of a battery provided according to an embodiment of the present application;

[0031] Figure 2 Shows a structural schematic diagram of a housing provided according to an embodiment of the present application;

[0032] Figure 3 Shows a connection schematic diagram of an explosion-proof structure and a housing provided according to an embodiment of the present application.

[0033] Reference numerals:

[0034] 100 - housing; 101 - receiving cavity; 102 - first through hole; 110 - positive electrode post; 120 - negative electrode post; 130 - upper cover; 140 - bottom case;

[0035] 200 - battery cell; 201 - positive electrode tab; 202 - negative electrode tab;

[0036] 300 - explosion-proof structure; 301 - hollow area; 302 - overlapping area; 310 - hot melt adhesive layer; 320 - sealing layer; 330 - covering layer; 321 - second through hole; 311 - third through hole. Detailed implementation manners

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0038] Lithium-ion batteries are widely used in multiple fields such as consumer electronic products, wearable electronic devices, and new energy vehicles due to their advantages such as high energy density, high cycle life, and high charging efficiency. With the continuous upgrade of the market's requirements for the performance of lithium-ion batteries, for example, new energy vehicles need to have better endurance and higher charging rates, which makes the requirements for the energy density of lithium-ion batteries higher and higher. Currently, lithium-ion batteries can be improved in many aspects to enhance their energy density. These improvements include both structural design and material selection. The former can be, for example, the design of the edge structure of the battery cell, and the latter can be, for example, the upgrade of the materials of lithium-ion batteries.

[0039] During the charge and discharge cycles of a lithium-ion battery with a high energy density, expansion and contraction phenomena occur due to temperature changes inside the battery. During charging, the lithium-ion battery expands, and during discharging, the lithium-ion battery contracts. The frequent expansion and contraction of the lithium-ion battery act on the battery housing. To prevent impact damage to the housing, the housing of the lithium-ion battery can be made of steel. The steel housing has the advantages of high structural strength and strong impact resistance, enabling the lithium-ion battery to have high safety and reliability. Of course, in some cases, the housing can also be made of a soft-pack aluminum-plastic film. In some special cases, when the internal temperature of the lithium-ion battery is too high or even in a thermal runaway situation, the high-temperature gas inside the lithium-ion battery needs to blow open the pressure relief valve (a type of explosion-proof structure) to relieve pressure and prevent safety accidents such as fire or explosion, thus ensuring the safety of the lithium-ion battery.

[0040] In the above-mentioned special situations encountered by the lithium-ion battery, to ensure the safety of the lithium-ion battery, the gas needs to blow open the pressure relief valve in a timely manner. To ensure the normal use of the lithium-ion battery, it is also necessary to ensure that the lithium-ion battery has sufficient structural stability (for example, it needs to have sufficient structural strength and impact resistance). In the related art, it is difficult for a lithium-ion battery to achieve a reasonable balance between safety in the above-mentioned special situations and structural stability during normal use. Moreover, the higher the energy density of the lithium-ion battery, the more difficult it is to achieve this balance.

[0041] With the continuous improvement of the energy density of lithium-ion batteries, the above-mentioned steel structure is usually used to form the housing of the lithium-ion battery. However, the overall design of the lithium-ion battery is getting closer to the limit, and the safety problems of the lithium-ion battery in terms of thermal runaway are becoming more and more serious, resulting in the lithium-ion battery being prone to safety problems such as thermal runaway.

[0042] Specifically, taking the design of the steel structure as an example, the steel structure usually includes specific structural design, dimension design, etc. The former, for example, includes the transition of each connection surface of the steel structure and the connection design of each connection surface. The dimension design mainly includes the thickness design of the steel structure. It can be understood that when the various designs adopted by the steel structure enable it to have excellent structural stability, the steel structure can ensure the normal use of the lithium-ion battery under normal conditions. However, in the above-mentioned special situations, there may be a risk of difficult pressure relief. On the contrary, when the various designs adopted by the steel structure enable it to relieve pressure in a timely manner, the structural stability of the steel structure may be difficult to support the normal use of the lithium-ion battery. When designing a lithium-ion battery with a high energy density, as the design criterion in the related art, usually, on the premise of ensuring that the lithium-ion battery has a high energy density, the structural stability of the steel structure is improved as much as possible. This method is likely to cause the lithium-ion battery to be difficult to relieve pressure in a timely manner and prone to safety problems such as thermal runaway.

[0043] In summary, the lithium-ion batteries in the related art can further improve the energy density, but it is difficult to achieve the purpose of ensuring sufficient safety of the lithium-ion battery while improving the energy density. The lithium-ion battery is prone to safety problems such as thermal runaway.

[0044] Based on the above status quo and problems, the present application provides a battery, which can be a lithium-ion battery. The battery can achieve a balance in terms of material selection and structural design. Based on material selection, the energy density of the battery can be improved. Based on structural design, the normal use of the battery under normal conditions and the safety of the battery under special conditions can be ensured, and the purpose of ensuring sufficient safety of the battery while improving the energy density can be achieved.

[0045] In terms of material selection, the battery in the embodiment of the present application mainly improves the negative electrode active material. The negative electrode active material is a silicon-based material, mainly including a silicon-carbon composite material, which can effectively improve the energy density of the battery. Of course, in the following embodiments of the present application, it can also be recognized that the present application also designs aspects such as the ratio and particle design of the silicon-carbon composite material, which can improve the comprehensive performance of the battery on the premise of ensuring the energy density. Here, the comprehensive performance includes structural stability, service life, cycle life, etc. In terms of structural design, the battery in the embodiment of the present application adopts an explosion-proof structure different from the traditional technology. The explosion-proof structure can make full use of the changes brought about by the use of the silicon-carbon composite material as the negative electrode active material. This change mainly refers to the change in the impact force during the charge and discharge cycle of the battery, and the impact force will become larger. The explosion-proof structure can adapt to the increased impact force. The explosion-proof structure can ensure that the inside of the battery is in a sealed state under normal conditions, thus ensuring the normal use of the battery. In special cases, the explosion-proof structure can timely open the pressure relief channel to prevent safety problems such as thermal runaway.

[0046] Figure 1 Shows an explosion schematic diagram of a battery provided according to an embodiment of the present application; Figure 2 Shows a structural schematic diagram of a housing provided according to an embodiment of the present application; Figure 3 Shows a connection schematic diagram of an explosion-proof structure and a housing provided according to an embodiment of the present application.

[0047] In the embodiment of the present application, please refer to Figures 1 to 3 , the battery pack may include a housing 100, a battery cell 200, and an explosion-proof structure 300.

[0048] The housing 100 may be a steel structure, that is, each component of the housing 100 is made of steel. The housing 100 is an external protection structure of the battery and can protect the internal structure of the battery. The housing 100 has a receiving cavity 101 and a first through hole 102 communicating with the receiving cavity 101.

[0049] The housing 100 can be designed in various shapes, such as circular, square, etc. For the sake of simplicity in description and understanding, in this application, the housing 100 with a square structure is mainly described. Correspondingly, the battery cell 200 in this application is also mainly described as a battery cell 200 with a square structure.

[0050] The housing 100 may include an upper cover 130 and a bottom case 140. The upper cover 130 can be covered on the bottom case 140 to enclose the above-mentioned receiving cavity 101.

[0051] In the embodiment of this application, the battery cell 200 is disposed in the receiving cavity 101. The battery cell 200 includes a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet. A positive electrode active material layer is formed on the positive electrode sheet. For example, the positive electrode active material layer can be formed on the surface of the positive electrode current collector by coating. A negative electrode active material layer is formed on the negative electrode sheet. For example, the negative electrode active material layer can be formed on the surface of the negative electrode current collector by coating. The negative electrode active material layer includes a silicon-carbon composite material.

[0052] In some exemplary embodiments, the positive electrode current collector can be made of aluminum foil. Of course, other positive electrode current collectors commonly used in the art can also be used. The thickness of the positive electrode current collector can be 1 μm to 200 μm. The positive electrode active material layer can be disposed on one surface or two opposite surfaces of the positive electrode current collector. Further, in the thickness direction of the positive electrode plate, the positive electrode active material layer can be coated only on a partial area of the positive electrode current collector. The thickness of the positive electrode active material layer can be 10 μm to 500 μm.

[0053] The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes LiCoO2, LiNiO2, LiMn2O4, LiCo1-yMyO2, LiNi1-yMyO2, LiMn2-yMyO4, LiNixCoyMnzM1-x-y-zO2, where M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and 0≤y≤1, 0≤x≤1, 0≤z≤1, x + y + z≤1. Exemplarily, the positive electrode active material may include at least one of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate or lithium nickel manganate. The above positive electrode active material may be subjected to doping and / or coating treatment. The positive electrode active material layer further includes a binder and a conductive agent. Exemplarily, the binder in the positive electrode active material layer may include at least one of polyvinylidene fluoride, copolymer of vinylidene fluoride - hexafluoropropylene, styrene - acrylate copolymer, styrene - butadiene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene; the conductive agent in the positive electrode active material layer may include at least one of conductive carbon black, acetylene black, Ketjen black, flake graphite, graphene, carbon nanotubes or carbon fibers.

[0054] In some exemplary embodiments, the negative electrode current collector may be at least one of copper foil, aluminum foil, nickel foil or carbon - based current collector; the thickness of the negative electrode current collector may be from 1 μm to 200 μm. The negative electrode active material layer may be disposed on one surface or two opposite surfaces of the negative electrode current collector. Further, in the thickness direction of the negative electrode plate, the negative electrode active material layer may be coated only on a partial area of the negative electrode current collector. Exemplarily, the thickness of the negative electrode active material layer may be from 10 μm to 500 μm.

[0055] The negative electrode active material layer includes a negative electrode active material. Exemplarily, the negative electrode active material includes at least one of lithium metal, natural graphite, artificial graphite or silicon - based materials, and the silicon - based materials include at least one of silicon, silicon oxide compounds, silicon carbide compounds or silicon alloys. The negative electrode active material layer may further include a conductive agent and / or a binder. Exemplarily, the conductive agent in the negative electrode active material layer may include at least one of carbon black, acetylene black, Ketjen black, flake graphite, graphene, carbon nanotubes, carbon fibers or carbon nanowires; the binder in the negative electrode active material layer may include at least one of carboxymethyl cellulose CMC, polyacrylic acid, polyacrylate salt, polyacrylate, polyvinylpyrrolidone, polyaniline, polyimide, polyamideimide, polysiloxane, styrene - butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene.

[0056] In some exemplary embodiments, the separator includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, the polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene. In particular, polyethylene and polypropylene have a good effect on preventing short circuits and can improve the stability of the electrode assembly through the shut-off effect. The thickness of the separator 50 ranges from about 3 μm to 500 μm.

[0057] In the embodiments of the present application, the battery cell 200 can be a stacked structure or a wound core structure. When it adopts a stacked structure, the number of positive electrode sheets and negative electrode sheets is set according to actual needs.

[0058] The positive electrode sheet of the battery cell 200 further forms a positive electrode tab 201, and the negative electrode sheet further forms a negative electrode tab 202. The positive electrode tab 201 can be connected to the positive electrode post 110 on the housing 100, and the negative electrode tab 202 can be connected to the negative electrode post 120 on the housing 100. The positive electrode post 110 and the negative electrode post 120 can serve as the positive and negative terminals of the battery, respectively.

[0059] For the above-mentioned battery cell 200, since the negative electrode active material layer includes a silicon-carbon composite material, the proportion of the silicon material in the silicon-carbon composite material is relatively high, and it can even exceed 10 times that of the graphite material. Therefore, the energy density of the battery can be improved. During the charge and discharge cycle of the battery, due to the increase in the silicon content in the negative electrode active material layer, the thermal expansion coefficient of silicon is relatively high, and a large impact force will be formed inside the battery.

[0060] The housing 100 is further provided with a first through hole 102, which is the pressure relief hole of the battery. The first through hole 102 is communicated with the pressure relief channel inside the battery. The explosion-proof structure 300 is connected to the housing 100 and hermetically covers the outside of the first through hole 102. The explosion-proof structure 300 includes a hot melt adhesive layer 310, and the hot melt adhesive layer 310 can change from a solid state to a molten state at a predetermined temperature.

[0061] The explosion-proof structure 300 includes a base layer and a hot melt adhesive layer 310, and the overlapping area of the base layer and the hot melt adhesive layer 310 is S1 mm 2 , and the mass percentage content of silicon element in the negative electrode active material layer is D. S1 and D satisfy the relationship:

[0062] 10 ≤ S1 / D ≤ 80.

[0063] The value of D can represent the mass percentage of silicon element in the negative electrode active material layer, and further can represent the energy density of the battery. When the value of D is larger, the energy density is higher. During the charge and discharge process of the battery, the expansion degree of the negative electrode sheet will be more intense. The overlapping area S1 of the substrate layer and the hot melt adhesive layer 310 can, to a certain extent, represent the force required to break through the hot melt adhesive layer. It can be understood that the larger the overlapping area S1, the stronger the bonding force between the substrate layer and the hot melt adhesive layer, and the stronger the sealing performance of the hot melt adhesive layer. At the same time, it also means that when thermal runaway occurs, a greater impact force needs to be formed inside the battery to complete pressure relief.

[0064] In the above embodiments, designing D and S1 according to the above dimensions can ensure timely pressure relief under thermal runaway and also achieve the sealing performance at normal temperature, and can isolate water vapor and the like from entering the battery to affect the performance of the battery, thereby ensuring the safety performance of the battery on the basis of improving the energy density. Specifically, when S1 / D is less than 10, that is, when there is too much silicon element in the negative electrode active material layer, during the normal charge and discharge process, due to the excessive expansion of the negative electrode sheet doped with silicon carbide, the entire battery cell is prone to expand. The expansion of the battery cell displaces the gas towards the first through hole, and the gas is likely to break through the hot melt adhesive layer, resulting in premature leakage of gas and liquid. In addition, if S1 / D is too large, it means that the overlapping area of the substrate layer and the hot melt adhesive layer 310 is relatively large. Although it can ensure the sealing inside the battery during the normal charge and discharge process, it is likely to cause a situation where the impact force of the gas is insufficient to break through the hot melt adhesive layer to achieve pressure relief and lead to explosion or fire in the case of actual thermal runaway.

[0065] It should be noted that during the process of the hot melt adhesive layer 310 changing from a solid state to a molten state, the temperature inside the battery is continuously rising. At this time, the battery is in a high-temperature and high-humidity environment. Designing the overlapping area and the mass percentage content of silicon element into the above relationship can prevent water vapor and the like from entering the battery during the process of the hot melt adhesive changing from a solid state to a molten state.

[0066] In specific design, S1 / D can be equal to 80, and this S1 / D can also be equal to 10.

[0067] It should be pointed out that when D is too large, the expansion degree of the negative electrode sheet will be too intense. Then, during the normal charge and discharge process, the negative electrode sheet is prone to expand too much and top against the inner side wall of the housing 100, and the negative electrode sheet is prone to bend and contact the positive electrode sheet to cause a short circuit. When D is too small, it is difficult to break through the hot melt adhesive layer and the pressure relief is not timely. In some embodiments, D = 5 - 50%, and this D can be 5%, 10%, 20%, 30%, 40%, 50%, 60%, 80% or the range composed of any two of them. Thereby, the battery can be protected and the pressure relief can be completed in time.

[0068] In some embodiments, the overlapping area S1 between the base layer and the hot melt adhesive layer 310 is 3 to 10 mm 2 . Specifically, in the design, it can be 3 mm 2 , 4 mm 2 , 5 mm 2 , 6 mm 2 , 7 mm 2 , 8 mm 2 , 9 mm 2 , 10 mm 2 or the range formed by any two of them. When S1 is too small, it is difficult to ensure that the gas formed by the expansion of the silicon-doped negative electrode sheet during the normal charge and discharge process can ensure the sealing of the battery; when S1 is too large, during the thermal runaway process, the adhesive force is too large, making it difficult for the gas to break through the hot melt adhesive, reducing the sensitivity of the battery.

[0069] In some embodiments, the base layer here is mainly a structure that plays functions such as a supporting role and an insulating role in the explosion-proof structure 300. For example, in the following embodiments, the base layer may include a sealing layer 320 and a covering layer 330. The hot melt adhesive layer 310 can be bonded to the base layer, and the overlapping area formed by the hot melt adhesive layer 310 and the base layer can be combined Figure 3 understood in the orientation shown, in Figure 3 , the area of the base layer projected onto the housing 100 in the Z direction and the area of the hot melt adhesive layer 310 projected onto the housing 100 in the Z direction have an overlapping region 302, and the area of this overlapping region 302 is the overlapping area.

[0070] In some embodiments, the base layer and the hot melt adhesive layer 310 can be distributed in a layered structure. Generally, the hot melt adhesive layer 310 can be arranged on the lower side of the base layer or inside the base layer, that is, the hot melt adhesive layer 310 is located between the base layer and the housing 100 or the hot melt adhesive layer 310 is located between different components of the base layer. For example, when the base layer includes a sealing layer 320 and a covering layer 330, the hot melt adhesive layer 310 can be located between the sealing layer 320 and the covering layer 330.

[0071] In some other embodiments, the base layer and the hot melt adhesive layer 310 can also form a coating structure, that is, the base layer coats the outer edge of the hot melt adhesive layer 310 at the outer edge, so that the explosion-proof structure 300 has better structural strength as a whole.

[0072] In the embodiments where the above coating structure is formed, for the convenience of pressure relief, the base layer can be provided with a weak link at the position corresponding to the hot melt adhesive layer 310 at its edge. This weak link can be realized by setting a thinner base layer, or through holes can also be opened on the base layer. Thus, when phenomena such as thermal runaway occur, the impact force can break through the hot melt adhesive layer to achieve pressure relief.

[0073] Within the normal temperature range under normal conditions, the hot melt adhesive layer 310 is in a solid state, and the above-mentioned large impact force cannot break through the explosion-proof structure 300. The explosion-proof structure 300 can be tightly connected to the housing 100 to seal the first through hole 102, ensuring the normal use of the battery under normal conditions. In special cases, when the temperature is too high, such as in the case of thermal runaway, the above-mentioned impact force further increases. At the same time, the hot melt adhesive layer 310 can change from a solid state to a molten state, and the greater impact force formed by the high-temperature gas inside the battery can break through the hot melt adhesive layer 310 to achieve the purpose of pressure relief, ensuring the safety of the battery in special cases and preventing safety problems such as thermal runaway.

[0074] In the embodiment of the present application, the design of including silicon-carbon composite material in the negative electrode active material layer can improve the energy density of the battery. The design of the explosion-proof structure 300 and its hot melt adhesive layer 310 can cooperate with the impact force formed during the charge and discharge cycle of the silicon-carbon composite material, thereby achieving the purpose of ensuring sufficient safety of the battery on the premise of improving the energy density.

[0075] For the battery in the embodiment of the present application, the housing 100 based on steel structure is beneficial to the control of the overall size of the battery and can also inhibit the expansion of the battery in the thickness direction.

[0076] The content of silicon element can be tested by thermogravimetric analysis. The specific method is as follows: After discharging the battery to 0% SOC, disassemble and take out the negative electrode sheet, soak it in dimethyl carbonate (DMC) solvent for 12 h, and then rinse it with DMC to remove the lithium salt attached to the negative electrode sheet. After drying, the negative electrode sheet is heat-treated at 400 °C in an inert atmosphere for 2 h (such as in a tubular furnace under nitrogen or argon atmosphere), and the negative electrode active material layer can be peeled off from the negative electrode current collector to obtain the negative electrode active material. In the silicon content test, a thermogravimetric analyzer (such as TGA 550 thermogravimetric analyzer) is used, and the sample amount for testing is 5 - 15 mg. Under air or oxygen atmosphere, the temperature is raised from room temperature to 900 °C at a heating rate of 10 °C / min and held at 900 °C for 40 min, so that the non-silicon components in the negative electrode active material volatilize while silicon can be fully oxidized to silicon dioxide. The weight percentage at the end of the whole test process is the ash content of the negative electrode active material layer. Divide the ash value by the molar mass of silicon dioxide and then multiply by the molar mass of silicon to obtain the percentage of silicon in the negative electrode active material layer.

[0077] In some embodiments, the OI value of the graphite orientation degree of the negative electrode sheet is X, and X satisfies the relationship: 3 ≤ X ≤ 35.

[0078] Within the above range, the expansion of the silicon-carbon composite material during normal charge and discharge cycles can be controlled, while helping to improve the energy density, cycle life and safety of the battery.

[0079] In specific design, the X can be 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 32, 35 or the range composed of any two of them.

[0080] The OI value can be obtained in the following way: After discharging the battery to 0% SOC, disassemble and take out the negative electrode sheet, soak it in dimethyl carbonate (DMC) solvent for 12 h, then rinse it with DMC to remove the lithium salt attached to the negative electrode sheet. After drying, test it with an X-ray powder diffraction instrument (such as Shimadzu XRD-6100 X-ray diffractometer). The diffraction peak appearing at 2θ = 54 - 55° in the obtained diffraction pattern is the (004) peak of graphite, and its intensity is denoted as I004. The diffraction peak appearing at 2θ = 77 - 78° is the (110) peak of graphite, and its intensity is denoted as I110. The OI value of the negative electrode sheet is I004 / I110.

[0081] In some embodiments, please refer to Figure 3 , the explosion-proof structure 300 further includes a sealing layer 320 and a covering layer 330. The sealing layer 320 is hermetically covered outside the first through hole 102. The sealing layer 320 has a second through hole 321 communicating with the first through hole 102. The hot melt adhesive layer 310 is connected to the sealing layer 320. The hot melt adhesive layer 310 has a third through hole 311 communicating with the second through hole 321. The covering layer 330 is connected to the hot melt adhesive layer 310, and the covering layer 330 seals the third through hole 311.

[0082] The sealing layer 320 and the covering layer 330 can form the matrix layer in the foregoing text. The sealing layer 320 and the covering layer 330 can be made of a metal material with relatively high structural strength. The two materials can be the same or different. For the explosion-proof structure 300, taking Figure 3 the shown orientation as an example, in the Z direction, the sealing layer 320, the hot melt adhesive layer 310, and the covering layer 330 are arranged in sequence. The hot melt adhesive layer 310 is located between the sealing layer 320 and the covering layer 330. By reasonably designing the dimensions of the three, the structural stability of the explosion-proof structure 300 under normal conditions can be improved, and the purpose of timely pressure relief in special cases can be achieved.

[0083] Please refer to Figure 3, in the above embodiments, both the sealing layer 320 and the hot melt adhesive layer 310 adopt a through-hole design. A second through-hole 321 is formed in the sealing layer 320, and a third through-hole 311 is formed in the hot melt adhesive layer 310. The second through-hole 321 and the third through-hole 311 are communicated with the first through-hole 102. This design can form a hollow area 301 in the middle area of the explosion-proof structure 300, and the hollow area 301 is communicated with the pressure relief channel in the battery. The high-temperature gas in the battery can act on the side surface of the hot melt adhesive layer 310, thereby improving the realization of the functions of the hot melt adhesive layer 310 in the solid state and the molten state. In the solid state, it can ensure the sealing of the battery and ensure the normal use of the battery. In the molten state, it is convenient for the high-temperature gas to be discharged.

[0084] In some specific embodiments, the first through-hole 102, the second through-hole 321, and the third through-hole 311 are coaxially arranged, thereby improving the structural stability at the edge of the first through-hole 102.

[0085] In some specific embodiments, the aperture of the first through-hole 102 is d1, the aperture of the second through-hole 321 is d2, and the aperture of the third through-hole 311 is d3. d1, d2, and d3 satisfy the relationship: d1 < d2 < d3.

[0086] Thus, at the hollow area 301, the sealing layer 320 is retracted inside the housing 100, the hot melt adhesive layer 310 is retracted inside the sealing layer 320, and there is a distance between the edge of the hot melt adhesive layer 310 and the edges of the sealing layer 320 and the housing 100. This can prevent the hot melt adhesive layer 310 from overflowing and also prevent the hot melt adhesive layer 310 from dripping into the battery interior when it turns into the molten state, thus causing a safety accident.

[0087] In some specific embodiments, a collecting groove can be formed at the edge of the sealing layer 320 close to the hot melt adhesive layer 310. The hot melt adhesive layer 310 can flow into the collecting groove in the molten state, thereby playing a role in collecting the glue liquid. The collecting groove can include multiple layers and be arranged in sequence along the X direction.

[0088] In some specific embodiments, the outer diameter of the sealing layer 320 is d4, the outer diameter of the hot melt adhesive layer 310 is d5, and the outer diameter of the covering layer 330 is d6. d4, d5, and d6 satisfy the relationship: d4 > d5 > d6.

[0089] Thus, at the edge of the explosion-proof structure 300, the sealing layer 320 extends out of the hot melt adhesive layer 310 and the covering layer 330, and the hot melt adhesive layer 310 extends out of the covering layer 330, which can improve the structural stability of the explosion-proof structure 300 at its edge.

[0090] In some embodiments, please refer to Figure 3 , the overlapping area of the sealing layer 320, the hot melt adhesive layer 310, and the covering layer 330 is S2, and S2 satisfies the relationship:

[0091] 0.1 mm 2 ≤ S2 ≤ 3 mm 2 。

[0092] Taking the above aperture relationship and outer diameter relationship as an example, an overlapping area 302 is formed between one side of the hot melt adhesive layer 310 located in the hollow area 301 and the outside of the covering layer 330. The area of the overlapping area 302 is S2. Setting S2 within the above dimensions can ensure that there is sufficient bonding force between the sealing layer 320, the hot melt adhesive layer 310, and the covering layer 330, which can guarantee the safety of the battery under normal conditions and also meet the requirement of bursting open the hot melt adhesive layer 310 under special circumstances.

[0093] In some embodiments, the area of the covering layer 330 is S3, and S2 and S3 satisfy the relationship: S2 / S3 = 0.1 - 0.75.

[0094] With this setting, the bonding force between the sealing layer 320, the hot melt adhesive layer 310, and the covering layer 330 can be further controlled, which can ensure the sealing property while ensuring that high-temperature gas can burst open the hot melt adhesive layer 310 under special circumstances such as thermal runaway.

[0095] In some embodiments, the hot melt adhesive layer 310 may include a skeleton layer and an adhesive layer. The adhesive layer is connected to both sides of the skeleton layer. The thickness of the skeleton layer is greater than the thickness of the adhesive layer, and the melting point of the skeleton layer is higher than the melting point of the adhesive layer.

[0096] It can be understood that both the skeleton layer and the adhesive layer can become a molten state at high temperature. The skeleton layer and the adhesive layer can be made of different materials. Among them, by designing the thickness of the skeleton layer to be greater than the thickness of the adhesive layer and the melting point of the skeleton layer to be higher than the melting point of the adhesive layer, the adhesive layer can start to melt first, and then the skeleton layer melts. During the melting process of the hot melt adhesive layer 310, it can proceed gradually and slowly, which can prevent the hot melt adhesive layer 310 from being burst open when the temperature rises slowly and does not reach the limit of thermal runaway, and can improve the accuracy of the battery in dealing with thermal runaway, thereby improving the service life and stability of the battery.

[0097] In some specific embodiments, the thickness of the hot melt adhesive layer 310 may be 5um to 50um, the melting point range of the skeleton layer is set at 110°C to 170°C, and the melting point range of the adhesive layer may be set at 90°C to 135°C. Such a design can be made that when the thickness of the hot melt adhesive layer 310 is relatively thick, its melting point can be made higher. For example, when the thickness of the hot melt adhesive layer 310 is 50um, the melting point of the skeleton layer can be 110°C, and the melting point of the adhesive layer can be 90°C. When the thickness of the hot melt adhesive layer is 5um, the melting point of the skeleton layer can be 170°C, and the melting point of the adhesive layer can be 135°C. Through this matching design, the performance uniformity of the hot melt adhesive layer 310 can be achieved by changing the thickness of the hot melt adhesive layer 310, so that the hot melt adhesive layer 310 can be designed with different thicknesses in different usage scenarios.

[0098] It can be understood that suitable materials can be selected according to the melting points of the skeleton layer and the adhesive layer, and these materials can be EVA, TPR, etc.

[0099] In some embodiments, a passivation layer may also be provided between the skeleton layer and the adhesive layer to achieve reliable connection between the skeleton layer and the adhesive layer.

[0100] In some embodiments, the glass transition temperature Tg of the hot melt adhesive layer 310 satisfies the relationship: Tg = 95°C - 135°C. It can be ensured that the hot melt adhesive layer 310 can smoothly turn into a molten state under thermal runaway (generally greater than 120°C), so as to achieve pressure relief, and can maintain a solid state and isolate water vapor in a conventional high-temperature (generally less than 65°C) and high-humidity environment.

[0101] In some embodiments, the battery cell 200 adopts a stacked structure, the negative electrode sheets are arranged on both sides of the positive electrode sheet, the negative electrode sheets are single-sided negative electrode sheets, that is, a negative electrode active material layer is coated on one side of the negative electrode sheet, and the outer periphery of the negative electrode sheet is coated with an adhesive tape layer, and the width of the adhesive tape layer is L1 and satisfies the relationship: L1 ≥ 5mm.

[0102] The adhesive tape layer can fix the battery cell 200, and the above-mentioned width design of the adhesive tape layer can provide an appropriate pulling force for the negative electrode sheet to prevent the negative electrode sheet from over-expanding.

[0103] It should be noted that when arranging the adhesive tape layer, it can be arranged around the non-tab side of the negative electrode sheet. When the side length of the negative electrode sheet is too long, such as exceeding 30mm, at least one adhesive tape layer can be provided for it to prevent the negative electrode sheet from over-expanding.

[0104] In some embodiments, the average sphericity H of the silicon-carbon composite material satisfies the relationship: H = 0.1 to 1.

[0105] It can be understood that the higher the sphericity of the particles in the silicon-carbon composite material, the closer the shape is to a spherical shape. As a result, when its volume expands, the impact on the negative electrode sheet is smaller, and the overall structural stability of the negative electrode sheet can be maintained during expansion. In addition, spherical particles can improve the mechanical strength and stability of the material, reduce the stress concentration between particles caused by expansion, and effectively reduce the extrusion of the housing 100 during the charge and discharge process under normal conditions.

[0106] The sphericity of the particles can be measured in the following way: After discharging the battery to 0% SOC, disassemble and take out the negative electrode sheet. Immerse it in dimethyl carbonate (DMC) solvent for 12 h, then rinse it with DMC to remove the lithium salts attached to the electrode sheet. Then, rinse the negative electrode active material layer from the electrode sheet with deionized water, centrifuge it after ultrasonic treatment to remove the filtrate, and then dry it. The obtained powder is observed in the backscattering mode of a scanning electron microscope. In this mode, the contrast of the particles is brighter, which can be distinguished from graphite and conductive carbon. Analyze the images of each particle with brighter contrast in the SEM photo at a certain magnification (such as 2500 times) through image processing software (such as Image Pro Plus) to obtain the perimeter and area of each particle. Calculate the perimeter equivalent radius r1 and area equivalent radius r2 of each particle respectively, then the sphericity V of each particle = r2 / r1. Then, perform a quantity-weighted average of the sphericities of each particle to obtain the average sphericity of the silicon-carbon composite material in the negative electrode sheet.

[0107] In some embodiments, the particle size distribution of the silicon-carbon composite material is Dv10 = 3 - 6 μm; Dv50 = 6 - 12 μm; Dv90 = 12 - 25 μm.

[0108] In the system of the silicon-carbon composite material, smaller particles usually exhibit a lower expansion rate because the small particle size can reduce the influence of the volume change of a single particle during the charge and discharge process on the entire particle. In contrast, larger particle sizes may lead to more obvious volume expansion because the volume change of a single silicon particle has a greater impact on the overall particle structure. In the above embodiments, the silicon-carbon particles with a smaller Dv50 can help reduce the mechanical stress and stress concentration of the silicon particles during the charge and discharge process, which helps to maintain the structural stability of the silicon-carbon composite material, reduce the rupture or structural damage of the particles, and thus extend the service life of the battery.

[0109] The particle size distribution can be tested in the following way: Laser particle size test method, for example, using a Malvern particle size tester for measurement. The test steps are as follows: Disperse the silicon-carbon composite material in deionized water containing a dispersant (such as nonylphenol polyoxyethylene ether, with a content of 0.02 - 0.03 wt%), form a mixture, ultrasonically treat the mixture for 2 minutes, and then put it into the Malvern particle size tester for testing.

[0110] In some embodiments, the porosity K of the negative electrode sheet satisfies the relationship: K = 5% to 50%. The porosity within this range can provide more space to accommodate the expansion of the silicon-carbon particles, better absorb the volume change of the silicon-carbon particles caused by charge and discharge, and contribute to maintaining the structural stability and cycle life of the negative electrode sheet.

[0111] The gas displacement method can be used to test the porosity K. The specific method is as follows: After discharging the battery to 0% SOC, disassemble and take out the negative electrode sheet. Immerse it in dimethyl carbonate (DMC) solvent for 12 h, then rinse it with DMC to remove the lithium salt attached to the negative electrode sheet. After drying, use a slicing machine to cut the negative electrode sheet into circular pieces with a diameter of 12 mm. Use a micrometer to measure the thickness of 20 circular pieces, calculate the volume of each piece respectively and sum them up to obtain the total volume V1 of the 20 circular pieces. Subsequently, use a true density meter (such as the JW-M100A full-automatic true density tester of Jingwei Gaobo) to test the true volume V2 of the 20 circular pieces. The test gas is helium, and the test environment temperature is 25 ± 2 °C. Then the porosity of the negative electrode sheet is (V1 - V2) / V1 * 100%.

[0112] In some embodiments, the peak intensity ratio g of the characteristic peak of the dO / Dv curve of the carbon-silicon composite material in the range of 0.25 V to 0.3 V to the characteristic peak in the range of 0.4 V to 0.45 V satisfies the relationship: g = 1 to 3.

[0113] The battery provided by the present invention and its applications will be specifically introduced below through specific embodiments.

[0114] Unless otherwise specified, the reagents, materials, and instruments used in the following embodiments are all conventional reagents, conventional materials, and conventional instruments in the art, and can all be obtained through commercial purchase. The reagents involved can also be synthesized by conventional methods in the art.

[0115] Example 1-1

[0116] This example provides a battery, and its preparation method is as follows:

[0117] 1. Preparation of the housing

[0118] 2. Preparation of the battery cell

[0119] 2.1 Preparation of the positive electrode sheet: The active material lithium cobalt oxide (LiCoO₂), conductive carbon black (Super P), CNT (carbon nanotube), and polyvinylidene fluoride (PVDF) are mixed according to a weight ratio of 97.5:0.5:0.5:1.5. N-methylpyrrolidone (NMP) is added as a solvent to prepare a positive electrode active material with a solid content of 75 wt%, and it is stirred evenly for standby. Aluminum foil is used as the positive electrode current collector. The above-mentioned active material is evenly coated on the surface of one side of the positive electrode current collector using a slot coater, and then dried at 90 °C to obtain a positive electrode sheet with a positive electrode active material layer coated on one side. At this time, the thickness of the positive electrode active material layer is 50 μm. Then, the above coating steps are repeated on the surface of the other side of the positive electrode current collector to obtain a positive electrode sheet with positive electrode active material layers coated on both sides; then the coated positive electrode is cold-pressed. After cold pressing, the thickness of the positive electrode active material layer is 35 μm. The area of the positive electrode current collector that is not covered when the positive electrode active material layer is coated is the empty foil area, and the positive electrode tab is obtained by cutting the empty foil area;

[0120] 2.2 Preparation of the negative electrode sheet: The active materials artificial graphite, silicon-carbon composite material (the mass percentage of silicon element in the negative electrode active material layer is 25%), conductive carbon black (Super P), styrene-butadiene rubber (SBR), and CMC (sodium carboxymethyl cellulose) are mixed according to a weight ratio of 97:0.5:1.3:1.2. Deionized water is added as a solvent to prepare a negative electrode active material with a weight percentage of 50 wt%, and it is stirred evenly for standby. Copper foil with a thickness of 10 μm is used as the negative electrode current collector. The above-mentioned negative electrode active material is evenly coated on the surface of one side of the negative electrode current collector using a coater, and then dried at 110 °C to obtain a negative electrode sheet with a negative electrode active material layer coated on one side. Then the above steps are repeated on the other side of the negative electrode current collector to obtain a negative electrode sheet with negative electrode active material layers coated on both sides. At this time, the thickness of the negative electrode active material layer along the first direction X is 60 μm. Then the coated negative electrode sheet 20 is cold-pressed. After cold pressing, the thickness of the negative electrode active material layer is 40 μm. The area of the negative electrode current collector 21 that is not covered when the negative electrode active material layer 22 is coated is the empty foil area, and the negative electrode tab is obtained by cutting the empty foil area;

[0121] 2.3 Preparation of the separator: A 7-micron-thick polyethylene porous polymer film is used as the separator;

[0122] 2.4 Formation of the battery cell: The positive electrode sheet, separator, and negative electrode sheet are stacked to obtain a stacked battery cell. Or, the positive electrode sheet, separator, and negative electrode sheet are wound to obtain a wound battery cell.

[0123] 3 Preparation of the explosion-proof structure

[0124] Press the sealing layer, hot melt adhesive layer and covering layer together by hot pressing to form an explosion-proof structure. Among them, the overlapping area of the matrix layer and the hot melt adhesive layer in the explosion-proof structure is 6 mm 2 。

[0125] 4. Assembly of the battery

[0126] Place the battery cell into the accommodating cavity of the housing, connect the positive tab to the positive terminal on the housing, connect the negative tab to the negative terminal, connect the upper cover 130 and the bottom case 140. After injecting liquid through the first through hole, cover the explosion-proof structure on the first through hole and connect it to the housing.

[0127] Test examples

[0128] 1. Pass rate of the hot box test

[0129] Test method: After fully charging the battery cell, place the battery cell into the test chamber. The test chamber is heated at a temperature rise rate of (5 ± 2) °C / min. When the temperature inside the chamber reaches 130 °C ± 2 °C, keep it constant for 30 min. The passing standard is that the battery cell completes pressure relief through the pressure relief component 4 and does not catch fire or explode.

[0130] 2. Pass rate of the high temperature and high humidity test

[0131] Test method: Discharge the battery cell for testing, leave it for 5 min, charge it conventionally to the full charge state, and measure the thickness value of the fully charged battery cell. The fully charged battery cell is left open-circuited at (65 ± 2) °C and 90% to 95% humidity for 42 days. Take out the battery cell every 7 days and leave it open-circuited at room temperature for 2 h to measure the cooled thickness. The passing standard is that there is no leakage on the appearance of the battery cell

[0132] 3. Pass rate of the battery short circuit safety test

[0133] Test method: At 25 °C, discharge the battery at a current of 5C until the voltage reaches 3.0V. Then charge it at a constant current of 1C until the voltage reaches 4.25V, and then charge it at a constant voltage of 4.25V until the current reaches 0.05C. Let it stand for 5 min, and then discharge it at a constant current of 5C until the voltage reaches 3.0V. This is one charge and discharge cycle. During the cycle, if the voltage value drops suddenly, especially from the normal value to a level close to zero rapidly, it indicates that a short circuit has occurred inside the battery. Record whether the battery undergoes thermal runaway, catches fire or explodes when the battery is short-circuited.

[0134] 4. Energy density retention rate after 20T cycles

[0135] Test method: Cycle at 25°C, charge at 1C to the cut-off voltage, charge at constant voltage to 0.05C cut-off current, discharge at 1C to the lower limit voltage, and repeat the above charge and discharge steps 200 times. The maximum discharge capacity of the first 3 cycles is denoted as R1, the discharge capacity after 200 cycles is denoted as R2, and the capacity retention rate is calculated as R2 / R1*100%.

[0136] The data in each of the above examples and comparative examples are shown in Table 1.1, and the test results are shown in Table 1.2.

[0137] Table 1.1

[0138]

[0139]

[0140] Table 1.2

[0141]

[0142] The following conclusions can be drawn from the analysis of Table 1.1 and Table 1.2:

[0143] 1) By comparing Example 1-1, Example 1-2, Example 1-3 and each comparative example, it can be seen that when S1 / D is too small, during normal use, due to the expansion of the negative electrode sheet doped with silicon carbide, the impact gas formed easily breaks through the hot melt adhesive layer, resulting in liquid leakage. When S1 / D is too large, during thermal runaway, the overlapping area is too large, making it difficult for the gas formed by thermal runaway inside the housing and the gas formed by the expansion of the negative electrode sheet to break through the hot melt adhesive, reducing the pressure relief sensitivity of the battery.

[0144] 2) By comparing Example 1-4, Example 1-5, Example 1-6, Example 1-7 and each comparative example, it can be seen that when S1 is too small, it is difficult to ensure the gas formed by the expansion of the silicon-doped negative electrode sheet during normal charge and discharge, and it is difficult to ensure the sealing of the battery; when S1 is too large, during thermal runaway, the bonding force is too large, making it difficult for the gas to break through the hot melt adhesive, reducing the sensitivity of the battery.

[0145] 3) By comparing Example 1-8, Example 1-9, Example 1-10 and each comparative example, it can be seen that when the mass ratio percentage content of silicon element is too small, it is difficult to break through the hot melt adhesive; if it is too large, during normal charge and discharge, the expansion of the negative electrode sheet is too large, easily causing the housing to deform or the electrode sheet to break.

[0146] 4) By comparing Example 1-11 and Example 1-12 and each comparative example, it can be seen that the graphite orientation degree affects the energy density of the battery after cycling.

[0147] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present application.

[0148] In the description of the present application, it should be understood that the terms "including" and "having" used in the embodiments of the present application and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0149] Unless otherwise clearly specified and defined, the terms "install", "connect", "couple", "fix", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be directly connected, or indirectly connected through an intermediate medium, which can be the connection inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features.

[0150] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or equivalently replace some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery, characterized in that: include: A shell having a receiving cavity and a first through hole communicating with the receiving cavity; A battery cell is disposed in the receiving cavity, the battery cell comprising a positive electrode sheet and a negative electrode sheet, a positive electrode active material layer is formed on the positive electrode sheet, a negative electrode active material layer is formed on the negative electrode sheet, and the negative electrode material layer comprises a silicon-carbon composite material; and an explosion-proof structure, the explosion-proof structure is connected to the shell and sealed on the outside of the first through hole, the explosion-proof structure includes a base layer and a hot melt adhesive layer, the base layer includes a sealing layer and a covering layer, the sealing layer is sealed on the outside of the first through hole, the sealing layer has a second through hole connected to the first through hole, the hot melt adhesive layer is connected to the sealing layer, the hot melt adhesive layer has a third through hole connected to the second through hole, the covering layer is connected to the hot melt adhesive layer, and the covering layer seals the third through hole; the overlapping area of ​​the base layer and the hot melt adhesive layer is S1mm 2 , the mass percentage of silicon element in the negative electrode active material layer is D, and S1 and D satisfy the relationship: 10≤S1 / D≤80.

2. The battery according to claim 1, characterized in that The graphite orientation degree of the negative electrode sheet is X, and X satisfies the relationship: 3≤X≤35.

3. The battery according to claim 1, characterized in that The mass percentage content D of silicon element in the negative electrode active material layer is 5-50%, and / or the overlapping area S1 of the base layer and the hot melt adhesive layer is 3-10 mm 2 .

4. The battery according to claim 1, characterized in that The aperture of the first through hole is d1, the aperture of the second through hole is d2, the aperture of the third through hole is d3, and d1, d2 and d3 satisfy the relationship: d1<d2<d3, the outer diameter of the sealing layer is d4, the outer diameter of the hot melt adhesive layer is d5, and the outer diameter of the covering layer is d6, and d4, d5 and d6 satisfy the relationship: d4>d5>d6.

5. The battery according to claim 1, characterized in that The overlapping area of ​​the sealing layer, the hot melt adhesive layer and the covering layer is S2, and S2 satisfies the relationship: 0.1mm 2 ≤S2≤3mm 2 , The area of ​​the covering layer is S3, and S2 and S3 satisfy the relationship: S2 / S3=0.1~0.

75.

6. The battery according to any one of claims 1 to 5, characterized in that The hot melt adhesive layer comprises: Skeleton layer; A sticky layer, wherein the sticky layer is connected to both sides of the skeleton layer, the thickness of the skeleton layer is greater than the thickness of the sticky layer, and the melting point of the skeleton layer is higher than the melting point of the sticky layer; and a passivation layer, wherein the passivation layer is disposed between the skeleton layer and the adhesive layer.

7. The battery according to any one of claims 1 to 5, characterized in that The glass transition temperature Tg of the hot melt adhesive layer satisfies the relationship: Tg=95°C-135°C.

8. The battery according to any one of claims 1 to 5, characterized in that The negative electrode sheet is arranged on both sides of the positive electrode sheet. The negative electrode sheet is a single-sided negative electrode sheet. A tape layer is coated on the outer periphery of the negative electrode sheet. The width L1 of the tape layer satisfies the relationship: L1≥5mm.

9. The battery according to any one of claims 1 to 5, characterized in that The average sphericity H of the silicon-carbon composite material satisfies the relationship: H = 0.1 to 1; And / or, the particle size distribution of the silicon-carbon composite material is Dv10=3-6um; and / or Dv50=6-12um; and / or Dv90=12-25um; And / or, the peak intensity ratio g of the characteristic peak at 0.25V to 0.3V and the characteristic peak at 0.4V to 0.45V of the dO / Dv curve of the carbon-silicon composite material satisfies the relationship: g=1-3; And / or, the peak intensity ratio g of the characteristic peak at 0.25V to 0.3V and the characteristic peak at 0.4V to 0.45V of the dO / Dv curve of the carbon-silicon composite material satisfies the relationship: g=1-3.

10. The battery according to any one of claims 1 to 5, characterized in that The porosity K of the negative electrode sheet satisfies the relationship: K=5% to 50%.

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