Battery monomer, battery, electric equipment, pole piece and pole piece preparation method

Abstract

The invention provides a battery monomer, a battery, electric equipment, a pole piece and a pole piece preparation method. The battery monomer comprises at least two pole pieces and at least two isolating membranes, the at least two pole pieces comprise a positive pole piece and a negative pole piece, and the positive pole piece, the isolating membranes and the negative pole piece are sequentially laminated and wound into an electrode assembly with a multi-layer winding structure with a corner region and a flat region; each pole piece comprises a plurality of transition pole piece parts located at the junction area of the corner area and the flat area after being wound and an edge pole piece part located at the end part of the outermost layer of the pole piece, at least two pole pieces comprise at least one reinforced pole piece part, and at least one side surface of the reinforced pole piece part is provided with a reinforced layer, and the at least one reinforced pole piece part comprises at least one transition pole piece part of the at least one pole piece. According to the battery monomer, the risk of cracking of the pole piece at the transition pole piece part after the electrode assembly is used for a long time is reduced, so that the failure risk and the potential safety hazard of the battery monomer are reduced.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell, a battery, an electrical device, a pole piece, and a method for preparing the pole piece. Background Art

[0002] During the hot pressing process after winding, the negative electrode sheets and positive electrode sheets (collectively referred to as electrode sheets) of the battery cells with wound electrode assemblies are prone to cracking in the corner areas, which may cause electrode sheet failure and safety hazards.

[0003] In the related art, the strength of the pole piece in the corner area is enhanced by attaching a film to the corner area of ​​the pole piece, in order to solve the failure and safety hazard problems caused by the easy cracking of the pole piece in the corner area during the hot pressing process, but the factors that may easily cause the pole piece to crack during use are not considered.

[0004] The above statements are only used to provide background information related to the present application and do not necessarily constitute prior art. Summary of the invention

[0005] The purpose of the present application is to provide a battery cell, a battery, an electrical device, a pole piece and a method for preparing the pole piece, aiming to solve the failure and safety hazard problems caused by local cracking of the pole piece after long-term use of the electrode assembly.

[0006] The first aspect of the present application provides a battery cell, comprising at least two pole sheets and at least two separators, the at least two pole sheets comprising a positive pole sheet and a negative pole sheet, the positive pole sheet, the separator and the negative pole sheet are sequentially stacked and wound into an electrode assembly with a multi-layer winding structure having a corner area and a flat area, each pole sheet comprising a plurality of transition pole sheet portions located at the junction area of ​​the corner area and the flat area after winding and an edge pole sheet portion located at the end of its outermost layer, at least two pole sheets comprising at least one strengthening pole sheet portion, at least one side of the strengthening pole sheet portion being provided with a strengthening layer, wherein at least one strengthening pole sheet portion comprises at least one transition pole sheet portion of at least one pole sheet, and, along the length direction of the pole sheet, two ends of the strengthening layer provided at the transition pole sheet portion are respectively located at the corner area and the flat area of ​​the transition pole sheet portion where the strengthening layer is located.

[0007] The battery cell provided in the present application has a reinforcing layer on the side of at least one of the transition pole piece portions of the pole piece of its electrode assembly located at the junction area of ​​the corner area and the flat area of ​​the electrode assembly. Along the length direction of the pole piece, the two ends of the reinforcing layer provided on the transition pole piece portion are respectively located in the corner area and the flat area of ​​the transition pole piece portion where the transition pole piece portion is located. The strength of at least one transition pole piece portion where the stress concentration phenomenon of the pole piece is more significant can be strengthened, and the tensile strength of the pole piece in the transition pole piece portion can be increased, which is beneficial to reducing the risk of cracking of the pole piece in the transition pole piece portion after long-term use of the electrode assembly, thereby helping to reduce the risk of failure of the battery cell and safety hazards.

[0008] In some embodiments of the battery cell, at least one strengthening pole sheet portion includes at least the transition pole sheet portions located in the outermost layer of the multi-layer winding structure; or at least one strengthening pole sheet portion includes at least the transition pole sheet portions of the positive pole sheet and the negative pole sheet located in the respective outermost layers; or at least one strengthening pole sheet portion includes at least the transition pole sheet portions of each pole sheet.

[0009] During the use of the electrode assembly of the battery cell, as the expansion force increases, due to the characteristics of the multi-layer winding structure itself and the influence of the friction force after the electrode assembly abuts against the shell of the battery cell, there is a stress concentration phenomenon in the transition pole piece portion at the junction of the flat area and the corner area. As the electrode assembly continues to age, the expansion force increases, and the stress concentration phenomenon in the transition pole piece portion becomes more significant, especially in the transition pole piece portion of the outermost layer of the multi-layer winding structure, where the stress concentration phenomenon is most significant. Each transition pole piece portion located at the outermost layer of the multi-layer winding structure is provided with a reinforcement layer, so that the tensile strength of at least the outermost transition pole piece portion of the multi-layer winding structure is improved, which is beneficial to reduce the risk of cracking in multiple transition pole piece portions of the outermost layer of the electrode sheet after long-term use of the electrode assembly, thereby helping to reduce the risk of battery cell failure and safety hazards.

[0010] The transition electrode parts of the positive electrode sheet and the negative electrode sheet located at their respective outermost layers are provided with a reinforcement layer, so that the tensile strength of the transition electrode parts of at least the outermost layers of the multi-layer winding structure is improved, which is beneficial to reducing the risk of cracking of the multiple transition electrode parts of at least the outermost layers of the electrode sheet after long-term use of the electrode assembly, thereby helping to further reduce the risk of battery cell failure and safety hazards.

[0011] Each transition pole piece portion of each pole piece is provided with a reinforcement layer, so that the tensile strength of each transition pole piece portion of each layer of the multi-layer winding structure is improved, which is beneficial to reducing the risk of cracking of multiple transition pole piece portions of at least the outermost two layers of the pole piece after long-term use of the electrode assembly, thereby helping to further reduce the risk of battery cell failure and safety hazards.

[0012] In the battery cell of some embodiments, the at least one reinforcing pole piece portion further includes at least one edge pole piece portion of the pole piece.

[0013] Since the edge pole piece is located at the outermost layer after the pole piece is wound and the pole piece has a certain thickness, the edge pole piece is also susceptible to stress concentration and is easily damaged. The strengthening layer is arranged at the edge pole piece of the pole piece, which is beneficial to effectively improve the tensile strength of the edge pole piece where the strengthening layer is located.

[0014] In the battery cell of some embodiments, along the length direction of the pole piece, the length range of the reinforcement layer provided at the transition pole piece portion in the corner area and the flat area of ​​the transition pole piece portion where the reinforcement layer is located is 1 / 8πR~1 / 2πR, wherein R is the radius of the portion of the transition pole piece portion where the reinforcement layer is located in the corner area; and / or the reinforcement layer provided at the transition pole piece portion is in a multi-layer winding structure, and the greater the number of layers from the inside to the outside, the larger the size along the length direction of the pole piece and / or the greater the thickness.

[0015] The length range of the strengthening layer arranged at the transition pole piece portion in the corner area and the flat area of ​​the transition pole piece portion where the strengthening layer is located is 1 / 8πR~1 / 2πR. On the basis of effectively improving the tensile strength of the transition pole piece portion where the strengthening layer is located, the thickness of the pole piece occupied by the strengthening layer can be reasonably controlled, which is beneficial to reducing the material cost of the strengthening layer and reducing the adverse effects caused by the setting of the strengthening layer, such as the reduction of the area of ​​the active material layer on the surface of the pole piece and the reduction of the energy density.

[0016] In the multi-layer winding structure of the electrode assembly, the greater the number of layers from the inside to the outside, the greater the stress concentration on the transition pole piece. Therefore, the transition pole piece closer to the outer layer is more likely to crack. The greater the number of layers from the inside to the outside of the reinforcement layer provided in the transition pole piece in the multi-layer winding structure, the greater the size and / or thickness along the length direction of the pole piece. This makes the transition pole piece closer to the outer layer more strongly protected by the reinforcement layer, which is beneficial to effectively prevent the pole piece from cracking while minimizing the impact of the increased cost and reduced energy density caused by the provision of the reinforcement layer.

[0017] In the battery cell of some embodiments, the strengthening layer is located at least in the middle of the strengthening electrode sheet portion where the strengthening layer is located along the width direction of the electrode sheet.

[0018] The probability of cracking in the middle of the reinforced pole piece in the width direction of the pole piece is higher than that at the two ends of the pole piece in the width direction. The reinforcement layer is at least located in the middle of the reinforced pole piece along the width direction of the pole piece, which is beneficial for the reinforcement layer to effectively reinforce the reinforced pole piece.

[0019] In the battery cells of some embodiments, along the width direction of the pole piece, at least one end of the reinforcement layer provided on at least one side of the reinforcement pole piece portion is spaced from the edge of the corresponding end of the reinforcement pole piece portion where it is located; and / or along the width direction of the pole piece, at least one end of the reinforcement layer provided on at least one side of the reinforcement pole piece portion is flush with the edge of the corresponding end of the reinforcement pole piece portion where it is located; and / or along the width direction of the pole piece, at least one end of the reinforcement layer provided on at least one side of the reinforcement pole piece portion exceeds the edge of the corresponding end of the reinforcement pole piece portion where it is located; and / or at least one reinforcement pole piece portion also includes at least one edge pole piece portion of the pole piece, and along the length direction of the pole piece, the outer end of the reinforcement layer provided on at least one side of the edge pole piece portion is flush with the outer end edge of the edge pole piece portion where it is located; and / or at least one reinforcement pole piece portion also includes at least one edge pole piece portion of the pole piece, and along the length direction of the pole piece, the outer end of the reinforcement layer provided on at least one side of the edge pole piece portion exceeds the outer end edge of the edge pole piece portion where it is located.

[0020] Along the width direction of the pole piece, the strengthening layer on at least one side is spaced from the edge of at least one end of the strengthening pole piece portion where it is located, which is beneficial to effectively prevent the pole piece from cracking while minimizing the impact of increased costs and reduced energy density caused by setting up the strengthening layer.

[0021] Along the width direction of the pole piece, the strengthening layer on at least one side is flush with the edge of at least one end of the strengthening pole piece portion where it is located, which is beneficial to effectively prevent the pole piece from cracking while reducing the impact of increased costs and reduced energy density caused by setting up the strengthening layer.

[0022] Along the width direction of the pole piece, at least one end of the strengthening pole piece portion where the strengthening layer is located exceeds the edge of the corresponding end of the strengthening pole piece portion where it is located, which is beneficial to more effectively prevent the pole piece from cracking.

[0023] Along the length direction of the pole piece, the outer end of the reinforcement layer provided on at least one side of the edge pole piece is flush with the outer edge of the edge pole piece where it is located; and / or along the length direction of the pole piece, the outer end of the reinforcement layer provided on at least one side of the edge pole piece exceeds the outer edge of the edge pole piece where it is located, both of which are beneficial to more effectively prevent the edge pole piece from cracking.

[0024] In the battery cells of some embodiments, along the width direction of the pole piece, at least one end of the reinforcement layer provided on both sides of the reinforcement pole piece portion is connected to wrap the edge of the corresponding end of the reinforcement pole piece portion where it is located; and / or along the length direction of the pole piece, the outer ends of the reinforcement layer provided on both sides of the edge pole piece portion are connected to wrap the outer end edge of the edge pole piece portion where it is located.

[0025] Along the width direction of the pole piece, at least one end of the strengthening layer arranged on both sides of the strengthening pole piece portion is connected to wrap the edge of the corresponding end of the strengthening pole piece portion where it is located, which is beneficial to strengthen the strengthening effect of the strengthening layer on the strengthening pole piece portion where it is located.

[0026] Along the length direction of the pole piece, the outer ends of the strengthening layers arranged on both sides of the edge pole piece are connected to wrap the outer end edges of the edge pole piece where they are located, which is beneficial to strengthen the strengthening effect of the strengthening layer on the edge pole piece where it is located.

[0027] In some embodiments of the battery cell, the elastic modulus of the reinforcement layer is greater than the elastic modulus of the reinforcement pole piece; and / or the tensile strength of the reinforcement layer is greater than the tensile strength of the reinforcement pole piece; and / or the elongation at break of the reinforcement layer is greater than the elongation at break of the reinforcement pole piece.

[0028] The elastic modulus of the strengthening layer is greater than the elastic modulus of the strengthening pole piece, the tensile strength of the strengthening layer is greater than the tensile strength of the strengthening pole piece, and the elongation at break of the strengthening layer is greater than the elongation at break of the strengthening pole piece. All of these are beneficial for the strengthening layer to enhance the tensile strength of the strengthening pole piece and prevent it from cracking. Even if the strengthening piece breaks in extreme cases, the force applied to the electrode assembly usually only breaks the strengthening pole piece but not the strengthening layer. The strengthening layer can wrap up the debris generated by the breaking of the strengthening pole piece, which is beneficial for preventing the debris from piercing the isolation membrane and causing the risk of internal short circuit.

[0029] In the battery cells of some embodiments, adjacent reinforcement layers on the same side of the same pole piece are spaced apart along the length direction of the pole piece; and / or the reinforcement layer is bonded to the reinforcement pole piece portion where it is located by coating; and / or the reinforcement layer includes polyurea material, polyurethane material, polyamide material or acrylic resin material; and / or the reinforcement layer includes a main body area with uniform thickness.

[0030] Along the length direction of the pole piece, the adjacent strengthening layers on the same side of the same pole piece are arranged at intervals, which is conducive to effectively preventing the pole piece from cracking while minimizing the impact of the increased cost and reduced energy density caused by the setting of the strengthening layer. In addition, for the pole piece portion in the corner area where the strengthening layer is not set, due to the existence of the two adjacent transition pole piece portions, there are more gaps around the pole piece portion where the strengthening layer is not set, which is conducive to reducing the mutual squeezing of the adjacent layer pole piece portions, thereby also helping to reduce the possibility of cracking of the pole piece portion where the strengthening layer is not set.

[0031] The strengthening layer is combined with the strengthening pole piece portion where it is located by coating, which is conducive to the strengthening layer and the strengthening pole piece portion being firmly combined into one, so that the strengthening layer can better maintain its strengthening effect when the pole piece is severely stretched, which is conducive to effectively preventing the pole piece from cracking.

[0032] The reinforcement layer includes polyurea material, polyurethane material, polyamide material or acrylic resin material, which is beneficial for the reinforcement layer to have higher strength, thereby effectively improving the tensile strength of the reinforcement pole piece portion, which is beneficial for effectively preventing the pole piece from cracking.

[0033] The strengthening layer includes a main body region with uniform thickness, which is beneficial for the strengthening layer to uniformly strengthen the part of the strengthening pole piece where the main body region is set, so that the strengthening effect of the corresponding part is better.

[0034] In the battery cell of some embodiments, the thickness of the main region is 5-150 μm.

[0035] The thickness of the main area is 5~150μm, which is beneficial to ensure the strengthening effect of the strengthening layer on the strengthening electrode sheet while avoiding the problem of insufficient local electrolyte content and reduced charge and discharge rate capacity due to the large interlayer gap between the positive electrode sheet and the negative electrode sheet caused by setting the strengthening layer too thick.

[0036] In the battery cell of some embodiments, the thickness of the main region is 5-100 μm.

[0037] The thickness of the main area is 5~100μm, so that the interlayer gap between the positive electrode sheet and the negative electrode sheet can be within a reasonable range, which is conducive to avoiding insufficient local electrolyte content and reduced charge and discharge rate capacity due to the large interlayer gap between the positive electrode sheet and the negative electrode sheet caused by setting the strengthening layer too thick.

[0038] In the battery cell of some embodiments, the strengthening layer further includes a thinning region whose thickness gradually decreases from the main region toward a direction away from the main region.

[0039] Since the film is attached to the corner area of ​​the pole piece in the related art, a step is generated at the edge of the film, and the step will also cause secondary stress concentration in the pole piece near the step. The strengthening layer also includes a thinning area whose thickness gradually decreases from the main area to the direction away from the main area, which is conducive to reducing the secondary stress concentration caused by the setting of the strengthening layer.

[0040] In the battery cells of some embodiments, the cross-section of the thinning zone perpendicular to the length direction and / or width direction of the pole piece is a straight line or a smooth convex curve on the side away from the reinforcing pole piece portion; and / or thinning zones are provided at both ends of the main region along the length direction of the pole piece; and / or thinning zones are provided at both ends of the main region along the width direction of the pole piece.

[0041] The cross section of the thinning zone perpendicular to the length and / or width direction of the pole piece is a straight line away from the reinforced pole piece portion, which is conducive to effectively alleviating the secondary stress concentration phenomenon. The thinning zone can be obtained by cutting the edge of the reinforcement layer.

[0042] The cross section of the thinning zone perpendicular to the length and / or width direction of the pole piece and away from the reinforced pole piece portion is a smooth convex curve, which is conducive to effectively alleviating the secondary stress concentration phenomenon. At the same time, the thinning zone can be obtained by gradually reducing the amount of material at the edge of the strengthening layer when processing the strengthening layer.

[0043] Both ends of the main body region along the length direction of the pole piece are provided with thinning areas; and / or both ends of the main body region along the width direction of the pole piece are provided with thinning areas, which is beneficial to the secondary stress concentration phenomenon at the corresponding edges of the strengthening layer.

[0044] A second aspect of the present application provides a battery, comprising the battery cell of the first aspect of the present application.

[0045] The battery of the embodiment of the present application has the advantages of the battery cell of the embodiment of the present application.

[0046] A third aspect of the present application provides an electrical device, comprising the battery of the second aspect of the present application, and the battery is used to provide power to the electrical device.

[0047] The electrical equipment of the embodiment of the present application has the advantages of the battery of the embodiment of the present application.

[0048] A fourth aspect of the present application provides a pole piece for an electrode assembly having a multi-layer winding structure with a corner area and a flat area, the pole piece comprising a plurality of transition pole piece portions and an edge pole piece portion, the transition pole piece portion being located at the junction of the corner area and the flat area after the pole piece is wound, the edge pole piece portion being located at the end of the outermost layer after the pole piece is wound, the pole piece comprising at least one reinforcing pole piece portion, at least one side of the reinforcing pole piece portion being provided with a reinforcing layer, and at least one reinforcing pole piece portion of the pole piece comprising at least one transition pole piece portion.

[0049] In some embodiments of the pole piece, along the length direction of the pole piece, the length range of the reinforcement layer provided in the transition pole piece portion in the corner area and the flat area of ​​the transition pole piece portion where the reinforcement layer is located is 1 / 8πR~1 / 2πR, wherein R is the radius of the portion of the transition pole piece portion where the reinforcement layer is located that will be in the corner area; and / or the reinforcement layer provided in the transition pole piece portion is in a multi-layer winding structure, and the larger the number of layers from the inside to the outside, the larger the size along the length direction of the pole piece and / or the larger the thickness; and / or the reinforcement layer is at least located in the middle of the reinforcement pole piece portion where it is located along the width direction of the pole piece; and / or adjacent reinforcement layers on the same side of the pole piece are spaced apart; and / or the reinforcement layer is bonded to the reinforcement pole piece portion where it is located by coating; and / or the reinforcement layer includes polyurea material, polyurethane material, polyamide material or acrylic resin material; and / or the reinforcement layer includes a main body area with uniform thickness and a thinning area in which the thickness gradually decreases from the main body area to the direction away from the main body area.

[0050] The pole piece of the embodiment of the present application has the corresponding advantages of the corresponding battery cell of the embodiment of the present application.

[0051] A fourth aspect of the present application provides a method for preparing a pole piece of the fourth aspect of the present application, comprising: providing a strengthening layer on at least one side of at least one strengthening pole piece portion of the pole piece.

[0052] In some embodiments of the pole piece preparation method, the pole piece preparation method includes: along the length direction of the pole piece, the length range of the strengthening layer provided in the transition pole piece portion in the corner area and the flat area of ​​the transition pole piece portion where the strengthening layer is located is 1 / 8πR~1 / 2πR, wherein R is the radius of the portion of the transition pole piece portion where the strengthening layer is located that will be in the corner area; and / or the strengthening layer provided in the transition pole piece portion is in a multi-layer winding structure, and the larger the number of layers from the inside to the outside, the larger the size along the length direction of the pole piece and / or the larger the thickness; and / or the strengthening layer is at least provided in the middle part of the strengthening pole piece portion where the strengthening layer is located along the width direction of the pole piece; and / or the adjacent strengthening layers on the same side of the pole piece are spaced apart; and / or the strengthening layer is coated on the strengthening pole piece portion where the strengthening layer is located; and / or the strengthening layer is prepared using polyurea material, polyurethane material, polyamide material or acrylic resin material; and / or the strengthening layer forms a main body area with uniform thickness and a thinning area with a thickness gradually decreasing from the main body area to the direction away from the main body area.

[0053] The pole piece preparation method of the embodiment of the present application has the advantages of the pole piece of the embodiment of the present application.

[0054] Other features and advantages of the present application will become apparent from the following detailed description of exemplary embodiments of the present application with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0056] Figure 1 This is a schematic diagram of the structure of electrical equipment in some embodiments of the present application.

[0057] Figure 2 Schematic diagram of the exploded structure of batteries according to some embodiments of the present application.

[0058] Figure 3 This is a schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application.

[0059] Figure 4 This is a schematic cross-sectional structural diagram of an electrode assembly of a battery cell in some embodiments of the present application in a wound state.

[0060] Figure 5 Schematic diagram of the cross-sectional structure of the electrode assembly of the battery cell in some other embodiments of the present application in a wound state.

[0061] Figure 6 Schematic diagram of the partial structure of the pole piece of some embodiments of the present application.

[0062] Figure 7Schematic diagram of the partial structure of pole pieces in other embodiments of the present application.

[0063] Figure 8 Schematic diagram of the partial structure of pole pieces in other embodiments of the present application.

[0064] Fig. 9 Schematic diagram of the partial structure of pole pieces in other embodiments of the present application.

[0065] Fig.10 This is a schematic structural diagram of a cross-section of a strengthening layer of a pole piece in some embodiments of the present application that is perpendicular to the length direction of the pole piece.

[0066] Fig.11 Schematic diagram of the structure of the cross section of the strengthening layer of the pole piece perpendicular to the length direction of the pole piece in some other embodiments of the present application.

[0067] Fig.12 A schematic diagram of the partial structure of a cross section perpendicular to the width direction of the pole piece in which a reinforcement layer is provided at the edge pole piece portion of some other embodiments of the present application.

[0068] Figures 1 to 12 In the figure, each reference numeral represents: D. Vehicles; B. Battery; 1. Box body; 11. Box shell; 12. Box cover; 2. Battery pack; 20. Battery cells; 21 end cover assembly; 211, end cover; 212, positive terminal; 213, negative terminal; 214, explosion-proof valve; 215, insulation board; 22. Positive electrode connecting piece; 23. Negative electrode connecting piece; 24. Electrode assembly; C, corner area; S, flat area; L, straight line; 240. Electrode assembly body; 241, positive electrode plate; 241A, positive electrode curved section; 241B, positive electrode flat section; 2413, positive electrode ear; 242, isolation membrane; 242A, isolation curved section; 242B, isolation plane section; 243, negative electrode plate; 243A, negative electrode curved section; 243B, negative electrode flat section; 2433, negative electrode ear; 24B, transition pole piece; 24S, strengthening layer; 24S1, main area; 24S2, thinning area; 24F, edge pole piece; 25. Shell. DETAILED DESCRIPTION

[0069] The following detailed description and drawings of the embodiments of the present application are used to illustrate the principles of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0070] In the description of the present application, it should be noted that, unless otherwise specified, "multiple" means more than two; the terms "upper", "lower", "left", "right", "inside", "outside", etc., indicating the orientation or positional relationship, are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. "Vertical" is not strictly vertical, but is within the allowable error range. "Parallel" is not strictly parallel, but is within the allowable error range.

[0071] The directional words appearing in the following description are all directions shown in the figures, and do not limit the specific structure of this application. In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0072] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0073] Although in the lithium-ion battery of the related art, the strength of the pole piece in the corner area can be enhanced by attaching a film in the middle of the corner area of ​​the pole piece, which is helpful to alleviate the problem of easy cracking of the corner area of ​​the pole piece during the hot pressing process. However, in the process of forming this application, the inventor found that: during the use of the electrode assembly of the battery cell, as the expansion force increases, due to the characteristics of its own multi-layer winding structure and the friction force after the electrode assembly and the battery cell shell are abutted, there is a stress concentration phenomenon in the transition pole piece part at the junction of the flat area and the corner area. As the electrode assembly continues to age, the expansion force increases, and the stress concentration phenomenon in the transition pole piece part is more significant.

[0074] Therefore, if Figures 3 to 11As shown, the present application provides a battery cell 20, wherein the side of the transitional electrode piece portion 24B of the electrode assembly 24 located at the junction area between the corner area C and the flat area S of the electrode assembly 24 is provided with a strengthening layer 24S, which can strengthen the area where the stress concentration phenomenon of the electrode piece is more significant after the electrode assembly is used for a long time, increase the tensile strength of the electrode piece in the transitional electrode piece portion 24B, and reduce the risk of cracking of the electrode piece. Furthermore, the present application also provides a battery having the battery cell and an electrical device having the battery.

[0075] The embodiment of the present application provides an electric device that uses a battery as a power source, and the battery is configured to provide electrical energy to the electric device. The electric device may be, but is not limited to, a mobile phone, a portable device, a laptop computer, an electric vehicle, an electric car, a ship, a spacecraft, an electric toy, an electric tool, and the like. For example, a spacecraft includes an airplane, a rocket, a space shuttle, and a spacecraft, and the like. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like. Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools, and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers.

[0076] The battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery module or a battery pack. The battery generally includes a box for encapsulating one or more battery cells. The box can prevent liquid or other foreign matter from affecting the charging or discharging of the battery cells.

[0077] In the present application, battery cells may include lithium-ion batteries, sodium-ion batteries, sodium-lithium-ion batteries, lithium metal batteries, sodium metal batteries, lithium-sulfur batteries, magnesium-ion batteries, nickel-hydrogen batteries, nickel-cadmium batteries, lead-acid batteries, etc., which are not limited in the embodiments of the present application. Battery cells may be flat, rectangular, or in other shapes, which are not limited in the embodiments of the present application. Battery cells are generally packaged as square battery cells and soft-pack battery cells, which are not limited in the embodiments of the present application.

[0078] The battery cell mainly includes a battery core, a shell and an end cap assembly. The battery core may include one or two or more electrode assemblies. The battery core is encapsulated in the housing space of the shell through the end cap of the end cap assembly, and the housing space is filled with electrolyte. The electrode assembly is arranged in the housing space of the shell. The electrode assembly is the component in the battery cell where the electrochemical reaction occurs.

[0079] The shell is a component used to provide a space for accommodating the electrode assembly, electrolyte and other components. The shell can be in various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the shell can be determined according to the specific shape and size of the electrode assembly. The material of the shell can be selected from copper, iron, aluminum, stainless steel, aluminum alloy, plastic and other materials.

[0080] The end cap refers to a component that covers the opening of the shell to isolate the internal environment of the battery cell from the external environment. The shape of the end cap can be adapted to the shape of the shell to match the shell. Optionally, the end cap can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap is not easily deformed when squeezed and collided, so that the battery cell can have a higher structural strength and the safety performance can also be improved. Functional components such as electrode terminals can be provided on the end cap. The electrode terminal can be used to electrically connect to the electrode assembly for outputting or inputting electrical energy of the battery cell. In some embodiments, the end cap can also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell reaches a threshold. The pressure relief mechanism is, for example, an explosion-proof valve. The material of the end cap can also be a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., which is not limited in the embodiments of the present application.

[0081] The shell and the end cover may be independent components, and an opening is provided on the shell, and the end cover is closed at the opening to form the internal environment of the battery cell. Without limitation, the end cover and the shell may be integrated, and specifically, the end cover and the shell may form a common connection surface before other components are installed into the shell, and when the interior of the shell needs to be encapsulated, the end cover is closed with the shell, and the shell and the end cover are encapsulated as one.

[0082] In some embodiments of the battery cell, an insulating member may be provided inside the end cap, and the insulating member may be used to isolate the electrical connection components in the housing from the end cap to reduce the risk of short circuit. For example, the insulating member may be an insulating plate, which may be made of materials such as plastic and rubber.

[0083] The end cap and various components arranged on the end cap, such as electrode terminals, explosion-proof valves, insulating plates, etc., form an end cap assembly.

[0084] The electrode assembly is mainly composed of a positive electrode sheet, a negative electrode sheet and a separator. The battery cell mainly relies on the movement of metal ions between the positive electrode sheet and the negative electrode sheet to work.

[0085] The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is coated on the surface of the positive electrode current collector. The positive electrode current collector not coated with the positive electrode active material layer protrudes from the positive electrode current collector coated with the positive electrode active material layer, and the positive electrode current collector not coated with the positive electrode active material layer serves as a positive electrode tab. The positive electrode current collector coated with the positive electrode active material layer and the positive electrode active material layer thereon constitute the plate body of the positive electrode plate. Taking lithium-ion batteries as an example, the material of the positive electrode current collector can be aluminum, and the positive electrode active material can be at least one or more of lithium-containing phosphate-based positive electrode materials such as lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide, and nickel-containing lithium transition metal oxides.

[0086] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is coated on the surface of the negative electrode current collector. The negative electrode current collector not coated with the negative electrode active material layer protrudes from the negative electrode current collector coated with the negative electrode active material layer, and the negative electrode current collector not coated with the negative electrode active material layer serves as a negative electrode tab. The negative electrode current collector coated with the negative electrode active material layer and the negative electrode active material layer thereon constitute the main body of the negative electrode sheet. The material of the negative electrode current collector can be copper, and the negative electrode active material can be carbon or silicon, etc.

[0087] In order to ensure that a large current can pass without melting, the number of positive electrode tabs is generally multiple and stacked together, and the number of negative electrode tabs is generally multiple and stacked together.

[0088] The material of the isolation film can be polypropylene (PP) or polyethylene (PE) and the like.

[0089] like Figures 3 to 12 As shown, an embodiment of the present application provides a battery cell 20. The battery cell 20 includes at least two pole pieces and at least two separators 242. The at least two pole pieces include a positive pole piece 241 and a negative pole piece 243. The positive pole piece 241, the separator 242 and the negative pole piece 243 are sequentially stacked and wound into an electrode assembly 24 having a multi-layer winding structure with a corner area C and a flat area S. Each pole piece includes a plurality of transition pole piece portions 24B located at the junction area of ​​the corner area C and the flat area S after winding and an edge pole piece portion 24F located at the end of the outermost layer thereof. At least two pole pieces include at least one strengthening pole piece portion, and at least one side of the strengthening pole piece portion is provided with a strengthening layer 24S, wherein at least one strengthening pole piece portion includes at least one transition pole piece portion 24B of at least one pole piece, and along the length direction X of the pole piece, the two ends of the strengthening layer 24S provided in the transition pole piece portion 24B are respectively located in the corner area C and the flat area S of the transition pole piece portion 24B where it is located.

[0090] In the battery cell of the embodiment of the present application, a reinforcing layer 24S is provided on the side of at least one of the transition pole piece portions 24B of the pole piece of the electrode assembly 24 located at the junction area of ​​the corner area C and the flat area S of the electrode assembly 24. Along the length direction X of the pole piece, the two ends of the reinforcing layer 24S provided at the transition pole piece portion 24B are respectively located at the corner area C and the flat area S of the transition pole piece portion 24B where it is located, so as to strengthen the strength of at least one transition pole piece portion 24B where the stress concentration phenomenon of the pole piece is more significant, increase the tensile strength of the pole piece in the transition pole piece portion 24B, and help reduce the risk of cracking of the pole piece in the transition pole piece portion 24B after long-term use of the electrode assembly, thereby helping to reduce the failure risk and safety hazards of the battery cell 20.

[0091] The strengthening layer 24S can be arranged on one side of the transition pole piece 24B where it is located, which is beneficial to simplify the processing steps and save the material used for the strengthening layer 24S on the basis of effectively improving the tensile strength of the transition pole piece 24B where the strengthening layer 24S is located.

[0092] like Figures 3 to 9 As shown, the strengthening layer 24S may also be disposed on both sides of the transition pole piece portion 24B where the strengthening layer 24S is located, so as to more effectively improve the tensile strength of the transition pole piece portion 24B where the strengthening layer 24S is located.

[0093] like Figure 4 and Figure 5 As shown, in some embodiments of the battery cell 20, at least one reinforcing pole piece portion includes at least transition pole piece portions 24B located at the outermost layer of the multi-layer winding structure.

[0094] During the use of the electrode assembly 24 of the battery cell 20, as the expansion force increases, due to the characteristics of its own multi-layer winding structure and the influence of friction after the electrode assembly 24 abuts against the shell 25 of the battery cell 20, there is a stress concentration phenomenon in the transition pole piece portion at the junction of the flat area S and the corner area C. As the electrode assembly 24 continues to age, the expansion force increases, and the stress concentration phenomenon in the transition pole piece portion 24B is more significant, especially in the transition pole piece portion 24B of the outermost layer of the multi-layer winding structure, where the stress concentration phenomenon is most significant. Each transition pole piece portion 24B located at the outermost layer of the multi-layer winding structure is provided with a strengthening layer 24S, so that at least the outermost transition pole piece portion 24B of the multi-layer winding structure has improved tensile strength, which is beneficial to reduce the risk of cracking of multiple transition pole piece portions 24B of the outermost layer of the electrode sheet after long-term use of the electrode assembly, thereby helping to reduce the failure risk and safety hazards of the battery cell 20.

[0095] like Figure 4 and Figure 5As shown, in some embodiments of the battery cell 20 , at least one reinforcing electrode piece portion includes at least a positive electrode piece 241 and a negative electrode piece 243 , each of which is located at the outermost layer of each transition electrode piece portion 24B.

[0096] The transition electrode parts 24B of the positive electrode sheet 241 and the negative electrode sheet 243 located at their respective outermost layers are provided with a reinforcement layer 24S, so that the tensile strength of the transition electrode parts 24B of at least the outermost two layers of the multi-layer winding structure is improved, which is beneficial to reducing the risk of cracking of the multiple transition electrode parts 24B of at least the outermost two layers of the electrode sheet after long-term use of the electrode assembly, thereby helping to further reduce the failure risk and safety hazards of the battery cell 20.

[0097] like Figure 5 As shown, in some embodiments of the battery cell 20 , at least one reinforcing pole piece portion includes at least each transition pole piece portion 24B of each pole piece.

[0098] Each transition pole piece portion 24B of each pole piece is provided with a reinforcement layer 24S, so that the tensile strength of each transition pole piece portion 24B of each layer of the multi-layer winding structure is improved, which is beneficial to reducing the risk of cracking of multiple transition pole piece portions 24B of the pole piece in at least the outermost two layers after long-term use of the electrode assembly, thereby helping to further reduce the failure risk and safety hazards of the battery cell 20.

[0099] In the battery cell 20 of some embodiments, the at least one reinforcing pole piece portion further includes at least one pole piece edge pole piece portion 24F.

[0100] Since the edge pole piece portion 24F is located at the outermost layer after the pole piece is wound and the pole piece has a certain thickness, the edge pole piece portion 24F is also susceptible to stress concentration and is easily damaged. The strengthening layer is arranged at the edge pole piece portion 24F of the pole piece, which is beneficial to effectively improve the tensile strength of the edge pole piece portion 24F where the strengthening layer is located.

[0101] In the battery cell 20 of some embodiments, along the length direction X of the pole piece, the length range of the strengthening layer 24S provided in the transition pole piece portion 24B in the corner area C and the flat area S of the transition pole piece portion 24B where it is located is 1 / 8πR~1 / 2πR, wherein R is the radius of the portion of the transition pole piece portion 24B where the strengthening layer 24S is located in the corner area C.

[0102] The strengthening layer 24S provided in the transition pole piece portion 24B has a length range of 1 / 8πR~1 / 2πR in the corner area C and the flat area S of the transition pole piece portion 24B where the strengthening layer 24S is located. On the basis of effectively improving the tensile strength of the transition pole piece portion 24B where the strengthening layer 24S is located, the thickness of the pole piece occupied by the strengthening layer 24S can be reasonably controlled, which is beneficial to reducing the material cost of the strengthening layer 24S and reducing the adverse effects caused by the provision of the strengthening layer 24S, such as the reduction in the area of ​​the active material layer on the pole piece surface and the reduction in energy density.

[0103] like Figure 4 and Figure 5 As shown, the reinforcing layer 24S provided in the transition pole piece portion 24B is in a multi-layer winding structure. The larger the number of layers from the inside to the outside, the larger the size and / or the thickness along the length direction X of the pole piece.

[0104] In the multi-layer winding structure of the electrode assembly 24, the greater the number of layers from the inside to the outside, the greater the stress concentration on the transition pole piece portion 24B. Therefore, the transition pole piece portion 24B closer to the outer layer is more likely to crack. The greater the number of layers from the inside to the outside of the reinforcement layer 24S provided in the transition pole piece portion 24B in the multi-layer winding structure, the greater the size and / or thickness along the length direction X of the pole piece. Therefore, the transition pole piece portion 24B closer to the outer layer is more strongly protected by the reinforcement layer 24S, which is beneficial to effectively prevent the pole piece from cracking while minimizing the impact of the increased cost and reduced energy density caused by the provision of the reinforcement layer 24S.

[0105] like Figures 6 to 9 As shown, in some embodiments of the battery cell 20 , the strengthening layer 24S is at least located in the middle of the strengthening electrode sheet portion along the width direction Y of the electrode sheet.

[0106] The probability of cracking in the middle of the reinforced pole piece in the width direction Y of the pole piece is higher than that at the two ends of the pole piece in the width direction Y. The reinforcement layer 24S is at least located in the middle of the reinforced pole piece along the width direction Y of the pole piece, which is beneficial for the reinforcement layer 24S to effectively reinforce the reinforced pole piece portion where it is located.

[0107] In some embodiments of the battery cell 20, in some embodiments of the battery cell 20, as Figure 6 As shown, along the width direction Y of the pole piece, at least one end of the strengthening layer 24S provided on at least one side of the strengthening pole piece portion is spaced from the edge of the corresponding end of the strengthening pole piece portion where it is located; and / or as Figure 7 As shown, along the width direction Y of the pole piece, at least one end of the strengthening layer 24S provided on at least one side of the strengthening pole piece portion is flush with the edge of the corresponding end of the strengthening pole piece portion where it is located; and / or Figure 8 and Fig. 9 As shown, along the width direction Y of the pole piece, at least one end of the strengthening layer 24S provided on at least one side of the strengthening pole piece portion exceeds the edge of the corresponding end of the strengthening pole piece portion where it is located; and / or, at least one strengthening pole piece portion further includes at least one edge pole piece portion 24F of the pole piece, and along the length direction X of the pole piece, the outer end of the strengthening layer 24S provided on at least one side of the edge pole piece portion 24F is flush with the outer end edge of the edge pole piece portion 24F where it is located; and / or as Fig.12The at least one reinforcing pole piece portion shown also includes at least one edge pole piece portion 24F of the pole piece. Along the length direction X of the pole piece, the outer end of the reinforcing layer 24S arranged on at least one side of the edge pole piece portion 24F exceeds the outer end edge of the edge pole piece portion 24F where it is located.

[0108] Along the width direction Y of the pole piece, the strengthening layer 24S on at least one side is spaced from the edge of at least one end of the strengthening pole piece portion where it is located, which is beneficial to effectively prevent the pole piece from cracking while minimizing the impact of increased costs and reduced energy density caused by setting up the strengthening layer 24S.

[0109] Along the width direction Y of the pole piece, the strengthening layer 24S on at least one side is flush with the edge of at least one end of the strengthening pole piece portion where it is located, which is beneficial to effectively prevent the pole piece from cracking while reducing the impact of increased costs and reduced energy density caused by setting the strengthening layer 24S.

[0110] Along the width direction of the pole piece, at least one end of the strengthening pole piece portion where the strengthening layer is located exceeds the edge of the corresponding end of the strengthening pole piece portion where it is located, which is beneficial to more effectively prevent the pole piece from cracking.

[0111] Along the length direction X of the pole piece, the outer end of the strengthening layer 24S provided on at least one side of the edge pole piece portion 24F is flush with the outer edge of the edge pole piece portion 24F where it is located; and / or along the length direction X of the pole piece, the outer end of the strengthening layer 24S provided on at least one side of the edge pole piece portion 24F exceeds the outer edge of the edge pole piece portion 24F where it is located, both of which are beneficial to more effectively prevent the edge pole piece portion 24F from cracking.

[0112] In some embodiments of the battery cell 20, along the width direction Y of the pole piece, at least one end of the reinforcement layer 24S provided on both sides of the reinforcement pole piece portion is connected to wrap the edge of the corresponding end of the reinforcement pole piece portion where it is located; and / or along the length direction X of the pole piece, the outer ends of the reinforcement layer 24S provided on both sides of the edge pole piece portion 24F are connected to wrap the outer end edge of the edge pole piece portion 24F where it is located.

[0113] Along the width direction Y of the pole piece, at least one end of the strengthening layer 24S arranged on both sides of the strengthening pole piece portion is connected to wrap the edge of the corresponding end of the strengthening pole piece portion where it is located, which is beneficial to strengthen the strengthening effect of the strengthening layer on the strengthening pole piece portion where it is located.

[0114] Along the length direction X of the pole piece, the outer ends of the strengthening layers 24S arranged on both sides of the edge pole piece portion 24F are connected to wrap the outer end edges of the edge pole piece portion 24F where they are located, which is beneficial to strengthen the strengthening effect of the strengthening layer on the edge pole piece portion 24F.

[0115] In some embodiments of the battery cell 20, the elastic modulus of the reinforcement layer 24S is greater than the elastic modulus of the reinforcement pole piece portion; and / or the tensile strength of the reinforcement layer 24S is greater than the tensile strength of the reinforcement pole piece portion; and / or the elongation at break of the reinforcement layer 24S is greater than the elongation at break of the reinforcement pole piece portion.

[0116] The elastic modulus of the strengthening layer 24S is greater than the elastic modulus of the strengthening pole piece where it is located, the tensile strength of the strengthening layer 24S is greater than the tensile strength of the strengthening pole piece where it is located, and the elongation at break of the strengthening layer 24S is greater than the elongation at break of the strengthening pole piece where it is located, which are all conducive to the strengthening layer 24S enhancing the tensile strength of the strengthening pole piece where it is located, and preventing the strengthening pole piece from cracking. Even if the strengthening pole piece breaks in extreme cases, the force applied to the electrode assembly 24 usually only causes the strengthening pole piece to break while the strengthening layer 24S does not break. The strengthening layer 24S can wrap up the debris generated by the breaking of the strengthening pole piece, which is conducive to preventing the debris from piercing the isolation film 242 and causing the risk of internal short circuit.

[0117] In some embodiments of the battery cell 20, as Figure 4 and Figure 5 As shown, along the length direction X of the pole piece, adjacent reinforcing layers 24S on the same side of the same pole piece are arranged at intervals; and / or the reinforcing layer 24S is combined with the reinforcing pole piece portion where it is located by coating; and / or the reinforcing layer 24S includes polyurea material, polyurethane material, polyamide material or acrylic resin material; and / or as Figures 4 to 12 As shown, the strengthening layer 24S includes a main body region 24S1 having a uniform thickness.

[0118] Along the length direction X of the pole piece, adjacent strengthening layers 24S on the same side of the same pole piece are arranged at intervals, which is conducive to effectively preventing the pole piece from cracking while minimizing the impact of increased costs and reduced energy density caused by the setting of the strengthening layer 24S. In addition, the pole piece portion in the corner area C where no strengthening layer is set has more gaps around the pole piece portion where no strengthening layer is set due to the presence of the two adjacent transition pole piece portions 24B, which is conducive to reducing the mutual squeezing of the adjacent layer pole piece portions, thereby also helping to reduce the possibility of cracking of the pole piece portion where no strengthening layer is set.

[0119] The strengthening layer 24S is combined with the strengthening pole piece portion where it is located by coating, which is conducive to the strengthening layer 24S and the strengthening pole piece portion being firmly combined into one, so that the strengthening layer 24S can better maintain its strengthening effect when the pole piece is severely stretched, which is conducive to effectively preventing the pole piece from cracking.

[0120] The reinforcement layer 24S includes polyurea material, polyurethane material, polyamide material or acrylic resin material, which is beneficial for the reinforcement layer 24S to have higher strength, thereby effectively improving the tensile strength of the reinforcement pole piece portion, and effectively preventing the pole piece from cracking.

[0121] The strengthening layer 24S includes a main body region 24S1 with uniform thickness, which is beneficial for the strengthening layer 24S to uniformly strengthen the portion of the strengthening pole piece where the main body region 24S1 is set, thereby achieving a better strengthening effect on the corresponding portion.

[0122] In the battery cell 20 of some embodiments, the thickness of the body region 24S1 is 5-150 μm.

[0123] The thickness of the main area 24S1 is 5~150μm, which is beneficial to ensure the strengthening effect of the strengthening layer 24S on the strengthening electrode sheet where it is located, while avoiding the problem of insufficient local electrolyte content and reduced charge and discharge rate capability due to the large interlayer gap between the positive electrode sheet 241 and the negative electrode sheet 243 caused by setting the strengthening layer 24S to be too thick.

[0124] In the battery cell 20 of some embodiments, the thickness of the body region 24S1 is 5-100 μm.

[0125] The thickness of the main region 24S1 is 5 to 100 μm, so that the interlayer gap between the positive electrode sheet 241 and the negative electrode sheet 243 can be within a reasonable range, which helps to avoid insufficient local electrolyte content and reduced charge and discharge rate capability due to the large interlayer gap between the positive electrode sheet 241 and the negative electrode sheet 243 caused by setting the reinforcement layer 24S to be too thick.

[0126] like Fig.10 and Fig.12 As shown, in the battery cell 20 of some embodiments, the strengthening layer 24S further includes a thinning region 24S2 whose thickness gradually decreases from the main region 24S1 toward a direction away from the main region 24S1 .

[0127] Since the film is attached to the corner area of ​​the pole piece in the related art, a step is generated at the edge of the film, and the step will also cause secondary stress concentration in the pole piece part near the step. The strengthening layer 24S also includes a thinning area 24S2 whose thickness gradually decreases from the main area 24S1 to the direction away from the main area 24S1, which is conducive to reducing the secondary stress concentration caused by the setting of the strengthening layer.

[0128] In the battery cell 20 of some embodiments, the cross section of the thinned region 24S2 perpendicular to the length direction X and / or the width direction Y of the pole piece away from the reinforcing pole piece portion is as follows: Fig.10 and Fig.12 The straight line shown or Fig.11 The smooth convex curve shown; and / or Fig.10 and Fig.12 As shown, both ends of the main region 24S1 along the length direction X of the pole piece are provided with thinning regions 24S2; and / or both ends of the main region 24S1 along the width direction Y of the pole piece are provided with thinning regions 24S2.

[0129] The cross section of the thinned area 24S2 perpendicular to the length and / or width direction of the pole piece and away from the strengthened pole piece portion is a straight line, which is conducive to effectively alleviating the secondary stress concentration phenomenon. The thinned area 24S2 can be obtained by cutting the edge of the strengthening layer 24S.

[0130] The cross section of the thinning zone 24S2 perpendicular to the length and / or width direction of the pole piece and away from the reinforcing pole piece portion is a smooth convex curve, which is beneficial to effectively alleviate the secondary stress concentration phenomenon. At the same time, the thinning zone 24S2 can be obtained by gradually reducing the amount of material at the edge of the strengthening layer 24S when processing the strengthening layer 24S.

[0131] Both ends of the main area 24S1 along the length direction X of the pole piece are provided with thinning areas 24S2 and / or both ends of the main area 24S1 along the width direction Y of the pole piece are provided with thinning areas 24S2, which is beneficial to the secondary stress concentration phenomenon at the corresponding edges of the strengthening layer 24S.

[0132] The embodiment of the present application further provides a battery, comprising the battery cell 20 of the first aspect of the present application.

[0133] The battery of the embodiment of the present application has the advantages of the battery cell of the embodiment of the present application.

[0134] An embodiment of the present application also provides an electrical device, including the battery of the second aspect of the present application, and the battery is used to provide power to the electrical device.

[0135] The electrical equipment of the embodiment of the present application has the advantages of the battery of the embodiment of the present application.

[0136] The embodiment of the present application also provides a pole piece. The pole piece is used for an electrode assembly 24 having a multi-layer winding structure with a corner area C and a flat area S. The pole piece includes a plurality of transition pole piece portions 24B and an edge pole piece portion 24F, and the transition pole piece portion 24B is located at the junction area of ​​the corner area C and the flat area S after the pole piece is wound. The edge pole piece portion 24F is located at the end of the outermost layer after the pole piece is wound. The pole piece includes at least one strengthening pole piece portion, and at least one side of the strengthening pole piece portion is provided with a strengthening layer 24S. At least one strengthening pole piece portion of the pole piece includes at least one transition pole piece portion 24B.

[0137] The electrode piece may be a positive electrode piece 241 or a negative electrode piece 243 .

[0138] In the pole piece of some embodiments, along the length direction X of the pole piece, the length range of the strengthening layer 24S provided in the transition pole piece portion 24B in the corner area C and the flat area S of the transition pole piece portion 24B where it is located is 1 / 8πR~1 / 2πR, wherein R is the radius of the portion of the transition pole piece portion 24B where the strengthening layer 24S is located that will be in the corner area C; and / or the strengthening layer 24S provided in the transition pole piece portion 24B is in a multi-layer winding structure, the greater the number of layers from the inside to the outside, the larger the size and / or the thickness along the length direction X of the pole piece; and / or The reinforcement layer 24S is at least located in the middle of the reinforcement pole piece portion where it is located along the width direction Y of the pole piece; and / or adjacent reinforcement layers 24S on the same side of the pole piece are arranged at intervals; and / or the reinforcement layer 24S is combined with the reinforcement pole piece portion where it is located by coating; and / or the reinforcement layer 24S includes polyurea material, polyurethane material, polyamide material or acrylic resin material; and / or the reinforcement layer 24S includes a main body area 24S1 with uniform thickness and a thinning area 24S2 with a thickness gradually decreasing from the main body area 24S1 to a direction away from the main body area 24S1.

[0139] The pole piece of the embodiment of the present application has the corresponding advantages of the corresponding battery cell of the embodiment of the present application.

[0140] The embodiment of the present application further provides a method for preparing a pole piece of the fourth aspect of the present application. The method for preparing a pole piece includes: providing a strengthening layer 24S on at least one side surface of at least one strengthening pole piece portion of the pole piece.

[0141] In some embodiments of the pole piece preparation method, the pole piece preparation method includes: along the length direction X of the pole piece, the strengthening layer 24S provided in the transition pole piece portion 24B is in the range of 1 / 8πR to 1 / 2πR in the corner area C and the flat area S of the transition pole piece portion 24B where it is located, wherein R is the radius of the portion of the transition pole piece portion 24B where the strengthening layer 24S is located that will be in the corner area C; and / or the strengthening layer 24S provided in the transition pole piece portion 24B is in a multi-layer winding structure, the larger the number of layers from the inside to the outside, the larger the size along the length direction X of the pole piece and / or the thickness. The greater the degree; and / or the strengthening layer 24S is arranged at least in the middle of the strengthening pole piece portion where it is located along the width direction Y of the pole piece; and / or the adjacent strengthening layers 24S on the same side of the pole piece are arranged at intervals; and / or the strengthening layer 24S is coated on the strengthening pole piece portion where it is located; and / or the strengthening layer 24S is prepared by using polyurea material, polyurethane material, polyamide material or acrylic resin material; and / or the strengthening layer 24S forms a main body area 24S1 with uniform thickness and a thinning area 24S2 with a thickness gradually decreasing from the main body area 24S1 to a direction away from the main body area 24S1.

[0142] The following combination Figures 1 to 12 The battery cells, batteries, electrical equipment, pole pieces and pole piece preparation methods of some embodiments of the present application are described in detail.

[0143] The electrical equipment in the embodiment of the present application is a vehicle D. Please refer to Figure 1 The vehicle D may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended range vehicle. Figure 2 The vehicle D is provided with a battery B inside, and the battery B can be provided at the bottom, head or tail of the vehicle D. The battery B can be used for powering the vehicle D, for example, it can be used as an operating power source of the vehicle D.

[0144] In some embodiments of the present application, battery B can not only serve as an operating power source for vehicle D, but also serve as a driving power source for vehicle D, replacing or partially replacing fuel or natural gas to provide driving power for vehicle D.

[0145] Please refer to Figure 2 The battery B is in the form of a battery pack, including a box body 1 and a battery cell 20 contained in the box body 1. The box body 1 includes a box shell 11 and a box cover 12 buckled on the box shell 11, and the box body 1 is used to provide a storage space for the battery cell 20. In the above embodiment, the box body 1 is a rectangular parallelepiped as a whole. In the embodiment not shown in the figure, the box body 1 can also be other shapes, such as a cylinder.

[0146] In the battery B, there are multiple battery cells 20, and the multiple battery cells 20 can be connected in series, in parallel, or in mixed connection. Mixed connection means that the multiple battery cells 20 are both connected in series and in parallel. The multiple battery cells 20 can be directly connected in series, in parallel, or in mixed connection, and then the whole formed by the multiple battery cells 20 is accommodated in the box body 1.

[0147] like Figure 2 As shown, the battery B may be a battery pack 2 formed by connecting a plurality of battery cells 20 in series, in parallel or in mixed connection. The battery pack 2 may be in the form of a battery module. The plurality of battery packs 2 are then connected in series, in parallel or in mixed connection to form a whole, and are accommodated in the box 1. The battery B may also include other structures, for example, the battery B may also include a busbar component for realizing electrical connection between the plurality of battery cells 20.

[0148] The following combination Figures 3 to 12 The battery cell 20 and the positive electrode sheet 241 thereof and the method for preparing the positive electrode sheet 241 according to some embodiments of the present application are described in detail.

[0149] Please refer to Figure 3 . Figure 3 The exploded structural diagram of a battery cell 20 according to an embodiment of the present application is shown in FIG. The battery cell 20 according to the embodiment of the present application comprises an end cap assembly 21 , a housing 25 , and a battery cell, wherein the battery cell comprises two electrode assemblies 24 .

[0150] The end cap assembly 21 includes an end cap 211, a positive terminal 212, a negative terminal 213, an explosion-proof valve 214 and an insulating plate 215. The end cap 211 is used to cooperate with the housing 25 to encapsulate the battery cell in a closed accommodation space formed by the end cap 211 and the housing 25. The electrode assembly 24 includes an electrode assembly body 240, a positive electrode tab 2413 and a negative electrode tab 2433. The positive terminal 212 and the negative terminal 213 can be electrically connected to the positive electrode tab 2413 and the negative electrode tab 2433 of the corresponding electrode assembly 24 through the positive electrode connecting sheet 22 and the negative electrode connecting sheet 23, respectively. During the charge and discharge process of the battery, the positive electrode active material and the negative electrode active material react with the electrolyte, and the positive electrode tab 2413 and the negative electrode tab 2433 are respectively connected to the positive terminal 212 and the negative terminal 213 to form a current loop. The insulating plate 215 is arranged between the end cover 211 and the positive electrode connecting sheet 22 and the negative electrode connecting sheet 23 to achieve insulation between the end cover 211 and the positive electrode connecting sheet 22 and the negative electrode connecting sheet 23 as well as each electrode assembly 24 .

[0151] Please refer to Figure 4 and Figure 5 . Figure 4 It is a schematic cross-sectional structural diagram of an electrode assembly of a battery cell in a wound state according to an embodiment of the present application. Figure 5 It is a schematic cross-sectional structural diagram of an electrode assembly of a battery cell in a wound state according to another embodiment of the present application. Figure 4 and Figure 5 The straight line L in FIG. 2 is intended to distinguish the flat area S from the corner area C, and is not a structure of the electrode assembly 24 .

[0152] like Figures 3 to 12 As shown, the battery cell 20 includes two pole pieces and two separators 242. The two pole pieces include a positive pole piece 241 and a negative pole piece 243. The positive pole piece 241, the separator 242 and the negative pole piece 243 are sequentially stacked and wound into an electrode assembly 24 having a multi-layer winding structure with a corner area C and a flat area S.

[0153] Figures 4 to 11 In the description, the strengthening pole piece portion includes a transition pole piece portion 24B, that is, a strengthening layer 24S is provided on at least one side of the transition pole piece portion 24B. Fig.12 In the description, some embodiments are further described in which the strengthening pole piece portion includes an edge pole piece portion 24F, that is, a strengthening layer 24S is provided on the edge pole piece portion 24F.

[0154] Figure 4 and Figure 5In the embodiment, the electrode assembly 24 is flat. A layer of isolation film 242 is also provided on the side of the negative electrode sheet 243 away from the positive electrode sheet 241. The isolation film 242 and the negative electrode sheet 243 are wound more at the head and tail relative to the positive electrode sheet 241, and the isolation film 242 is wound more at the head and tail relative to the negative electrode sheet 243 to form isolation protection for the electrode assembly 24.

[0155] When the electrode assembly 24 is manufactured, the electrode assembly 24 can be directly wound into a flat shape. The portions of the positive electrode sheet 241 and the negative electrode sheet 243 having active materials constitute the electrode assembly body 240 of the electrode assembly 24, and the portions of the positive electrode sheet 241 and the negative electrode sheet 243 not having active materials respectively constitute the positive electrode tab 2413 and the negative electrode tab 2433. The positive electrode tab 2413 and the negative electrode tab 2433 can be located together at one end of the electrode assembly body 240 or at both ends of the electrode assembly body 240.

[0156] like Figure 4 and Figure 5 As shown, the electrode assembly 24 includes a flat area S and a corner area C located at both ends of the flat area S. The parts of the positive electrode sheet 241, the separator 242 and the negative electrode sheet 243 in the corner area are respectively the positive curved section 241A, the isolated curved section 242A and the negative curved section 243A. The positive curved section 241A, the isolated curved section 242A and the negative curved section 243A can form a roughly circular arc shape, for example. The parts of the positive electrode sheet 241, the separator 242 and the negative electrode sheet 243 in the flat area S are respectively the positive plane section 241B, the isolated plane section 242B and the negative plane section 243B. The positive plane section 241B, the isolated plane section 242B and the negative plane section 243B can be relatively flat surfaces, and are not required to be pure planes. In the electrode assembly 24, the positive electrode sheet 241 can include multiple positive curved sections 241A and multiple positive plane sections 241B. The isolation film 242 may include a plurality of isolation curved segments 242A and a plurality of isolation plane segments 242B. The negative electrode sheet 243 may include a plurality of negative curved segments 243A and a plurality of negative plane segments 243B. Thus, each electrode sheet (positive electrode sheet or negative electrode sheet) includes a plurality of transition electrode sheet portions 24B located at the junction of the corner area C and the flat area S after winding.

[0157] like Figure 4 In the illustrated embodiment, each transition electrode portion 24B located at the outermost layer of the positive electrode sheet 241 and the negative electrode sheet 243 is provided with a strengthening layer 24S, and the remaining layers of the positive electrode sheet 241 and the negative electrode sheet 243 are not provided with a strengthening layer 24S.

[0158] like Figure 5 In the illustrated embodiment, each transition pole piece portion 24B of each pole piece is provided with a strengthening layer 24S.

[0159] exist Figures 4 to 9 In the illustrated embodiment, the strengthening layer 24S is disposed on both sides of the transition pole piece portion 24B where it is located.

[0160] In an embodiment not shown in the figure, the strengthening layer 24S may be disposed only on one side of the transition pole piece portion 24B where it is located, for example, may be disposed on the radial outer side of the transition pole piece portion 24B where it is located.

[0161] Along the length direction X of the pole piece, the length range of the strengthening layer 24S in the corner area C and the flat area S of the transition pole piece portion 24B where it is located is 1 / 8πR~1 / 2πR. R is the radius of the portion of the transition pole piece portion 24B where the strengthening layer 24S is located in the corner area C.

[0162] like Figure 4 and Figure 5 In the illustrated embodiment, the greater the number of layers of the strengthening layer 24S in the multi-layer winding structure from the inside to the outside, the greater the size along the length direction X of the pole piece. For example, the size of the portion of the strengthening layer 24S located on the flat area S is equal to each other, while the size of the portion located on the corner area C is greater the greater the number of layers of the multi-layer winding structure from the inside to the outside, the greater the size along the length direction X of the pole piece.

[0163] like Figures 6 to 9 As shown, the strengthening layer 24S is at least located in the middle of the transition pole piece portion 24B where it is located along the width direction Y of the pole piece. It should be noted that, Figures 6 to 9 The electrode structure shown is applicable to both the positive electrode 241 and the negative electrode 243 .

[0164] like Figure 6 In the illustrated embodiment, the strengthening layer 24S is disposed on both sides of the transition pole piece 24B where it is located. Along the width direction Y of the pole piece, each of the strengthening layers 24S on both sides is spaced from the edges of both ends of the transition pole piece 24B where it is located.

[0165] like Figure 7 In the illustrated embodiment, the strengthening layer 24S is disposed on both sides of the transition pole piece portion 24B where it is located. Along the width direction Y of the pole piece, each of the strengthening layers 24S on both sides is flush with the edges of both ends of the transition pole piece portion 24B where it is located.

[0166] like Figure 8 In the embodiment shown, the strengthening layer 24S is disposed on both sides of the transition pole piece 24B where it is located. Along the width direction Y of the pole piece, one end of the transition pole piece 24B where the strengthening layer 24S is located is disposed, and the other end is flush with the edge of the transition pole piece 24B. The strengthening layer 24S on both sides of the transition pole piece 24B where it is located is connected.

[0167] like Fig. 9In the embodiment shown, the strengthening layer 24S is disposed on both sides of the transition pole piece 24B where it is located. Along the width direction Y of the pole piece, the strengthening layer 24S is disposed at both ends of the transition pole piece 24B where it is located. Each strengthening layer 24S connects the two sides of the transition pole piece 24B where it is located.

[0168] The reinforcing layer 24S connected thereto is made of the same material and / or is formed integrally therewith. In this embodiment, the reinforcing layer 24S and the reinforcing layer 24S are both made of polyurea material and are combined with the corresponding transition pole piece 24B by spraying.

[0169] In an embodiment not shown in the figure, polyurethane material, polyamide material or acrylic resin material can also better meet the material properties required by the strengthening layer 24S, and can be used as the material for making the strengthening layer 24S. And it can also be joined with the transition pole piece 24B by a coating process such as spraying or rolling.

[0170] Figure 4 and Figure 5 In the illustrated embodiment, along the length direction X of the pole piece, adjacent strengthening layers 24S on the same side of the same pole piece are arranged at intervals.

[0171] Figure 10 to Figure 11 In the illustrated embodiment, the strengthening layer 24S includes a main region 24S1 with uniform thickness and a thinning region 24S2 with a thickness gradually decreasing from the main region 24S1 to a direction away from the main region 24S1. Fig.10 and Fig.11 As shown, thinning regions 24S2 are provided at both ends of the main region 24S1 along the length direction X of the pole piece.

[0172] Fig.10 In the illustrated embodiment, the cross section of the thinned region 24S2 perpendicular to the width direction Y of the pole piece is a straight line away from the transition pole piece portion 24B.

[0173] Fig.11 In the illustrated embodiment, the cross section of the thinned region 24S2 perpendicular to the width direction Y of the pole piece is a smooth convex curve on the side away from the transition pole piece portion 24B.

[0174] In an embodiment not shown, if the strengthening layer 24S and the edges of the transition pole piece portion 24B where it is located are spaced apart along the width direction Y of the pole piece, thinning regions 24S2 may also be provided at both ends of the main region 24S1 along the width direction Y of the pole piece.

[0175] The thickness of the main body region 24S1 may be set to 5-150 μm. Preferably, the thickness of the main body region 24S1 is 5-100 μm. The thickness of the main body region 24S1 may be, for example, 5 μm, 15 μm, 30 μm, 40 μm, 55 μm, 80 μm, 95 μm, 108 μm, 128 μm, 135 μm, 150 μm, etc.

[0176] Figures 4 to 11 In the illustrated embodiment, the thickness of the main region 24S1 of the strengthening layer 24S of each transition pole piece portion 24B is the same, and the shape and size of the thinned region 24S2 are the same.

[0177] In the above embodiments of the present application, a strengthening layer 24S is provided at the transition pole piece portion 24B at the junction of the flat area S and the corner area C of the pole piece, which can strengthen the performance of the pole piece in the local area of ​​the transition pole piece portion 24B and alleviate or resolve the safety risks caused by stress concentration in the local area.

[0178] Each strengthening layer 24S is attached to the transition pole piece portion 24B by spraying, and the bonding force is effectively enhanced compared to the method of attaching a film in the related art. The tensile strength and elastic modulus of the strengthening layer 24S are greater than those of the pole piece, which is beneficial to reducing the deformation of the transition pole piece portion 24B at the junction of the flat area S and the corner area C, and can reduce the risk of failure caused by stress concentration at the transition pole piece portion 24B.

[0179] During the use of the electrode assembly, the stress concentration phenomenon of the transition pole piece portion 24B at the junction area between the flat area S and the corner area C of the outermost layer of the multi-layer winding structure is the most serious, and increases with the increase of the expansion force, which is the main weak point of the electrode assembly 24. The risk of stress concentration decreases from the outermost layer to the innermost layer of the multi-layer winding structure. Therefore, if the strengthening layer 24S is only provided at each transition pole piece portion 24B of the outermost layer of the multi-layer winding structure, a better effect of preventing the pole piece from cracking can be achieved at a relatively low cost. Due to fluctuations in the production process, the mechanical properties of the pole pieces in different layers of the multi-layer winding structure are different. It is also possible that stress concentration may occur in the transition pole piece portion 24B of the pole pieces in the layers other than the outermost layer, resulting in a decrease in safety performance. Therefore, a strengthening layer 24S is provided in the transition pole piece portions 24B of more layers. For example, a strengthening layer 24S is provided at each transition pole piece portion 24B of the outermost layer of the positive pole piece 241 and the negative pole piece 243 of the multi-layer winding structure, or a strengthening layer 24S is provided at each transition pole piece portion 24B of each pole piece, which is beneficial to more effectively reduce the risk of failure of the pole piece caused by cracking due to stress concentration.

[0180] Along the length direction X of the pole piece, the length of each strengthening layer 24S in the corner area C and the flat area S of the transition pole piece portion 24B where it is located is too long, which easily causes waste of the manufacturing material of the strengthening layer 24S and reduces the energy density of the electrode assembly 24; if the length is too short, the strengthening layer 24S cannot envelop the stress concentration area of ​​the transition pole piece portion 24B, and the strengthening effect is difficult to meet the requirements. Therefore, it is necessary to reasonably design the length of the strengthening layer 24S. Along the length direction X of the pole piece, the length range of each strengthening layer 24S in the corner area C and the flat area S of the transition pole piece portion 24B where it is located is 1 / 8πR~1 / 2πR. On the basis of effectively improving the tensile strength of the transition pole piece portion 24B where the strengthening layer 24S is located, the thickness of the pole piece occupied by the strengthening layer 24S can be reasonably controlled, which is conducive to reducing the material cost of the strengthening layer 24S and reducing the adverse effects caused by the setting of the strengthening layer 24S, such as the reduction of the area of ​​the active material layer on the pole piece surface and the reduction of the energy density.

[0181] Along the length direction X of the pole piece, the length of each strengthening layer 24S in the corner area C and the flat area S of the transition pole piece portion 24B where it is located can be designed according to the stress concentration degree at each transition pole piece portion 24B. The closer to the outermost layer of the multi-layer winding structure, the greater the stress concentration degree, and the length of the strengthening layer 24S can be appropriately lengthened. The closer to the innermost layer of the multi-layer winding structure, the smaller the stress concentration degree, and the length of the strengthening layer 24S can be appropriately reduced.

[0182] During the expansion of the electrode assembly 24, the electrode sheet will generate compressive stress between the electrode sheets due to its own restraint force and the force applied by the outside world, such as the pressure from the shell 25 of the battery cell 20 and the working environment of the electrode assembly 24. The method of attaching the film or the conventional spraying method in the related technology will cause a step between the strengthening layer 24S and the electrode sheet. Under the action of the compressive stress between the electrode sheets, the electrode sheet will have a serious secondary stress concentration phenomenon at the step position. In order to alleviate or eliminate the secondary stress concentration phenomenon at the step, the edge of the strengthening layer 24S is subjected to transition thinning or the spraying flow rate is reduced relative to the main area 24S1 during edge spraying, and the thickness of the edge of the strengthening layer 24S is gradually reduced to form a thinning area 24S2 whose thickness is gradually thinner than the main area 24S1, so as to alleviate the secondary stress concentration phenomenon.

[0183] When the strengthening ability of the material used to prepare the strengthening layer 24S is strong, a lower value of the lower limit of the thickness can be taken, and when the strengthening ability is weak, a higher value of the lower limit of the thickness can be taken. In order to ensure that the strengthening layer 24S can achieve its strengthening function for the pole piece, and at the same time prevent the thickness from being too large, resulting in a large gap between the positive pole piece 241 and the negative pole piece 243, which causes insufficient local electrolyte content and causes other problems, such as lithium ions cannot be normally transmitted through the gap, causing lithium deposition on the pole piece, reducing the charge and discharge rate capability of the lithium-ion battery, etc., the thickness (single-side thickness) of the main area 24S1 of the strengthening layer 24S can preferably be set to 5~150um, and more preferably, the thickness is 5~100μm.

[0184] The strengthening layer 24S is arranged in the middle area of ​​the transition pole piece portion 24B along the width direction Y of the pole piece. Along the width direction Y of the pole piece, the strengthening layer 24S can be arranged as an open type, that is, Figure 6 and Figure 7 In the embodiment shown, the height of the strengthening layer 24S is less than or equal to the height of the pole piece. Along the width direction Y of the pole piece, the strengthening layer 24S can also be set to be semi-open, that is, Figure 8 In the embodiment shown, one of the two ends of the transition pole piece 24B in the width direction Y is connected to the strengthening layer 24S on both sides, and the other end is open. Along the width direction Y of the pole piece, the strengthening layer 24S can also be set to be fully enclosed, that is, Fig. 9 In the illustrated embodiment, both ends of the transition pole piece portion 24B in the width direction Y are connected by a reinforcement layer 24S at both ends.

[0185] By coating, such as spraying, the strengthening layer 24S is combined with the transition pole piece 24B. During the use of the battery cell 20, the strengthening layer 24S and the pole piece are easy to maintain a good bonding state, which is conducive to maintaining the stability of the strengthening layer 24S in alleviating the local stress concentration effect. Forming the strengthening layer 24S by coating can also enhance the tensile strength of the pole piece, reduce the risk of cracking of the pole piece, and help alleviate or prevent the burrs or debris generated when the transition pole piece 24B cracks and pierce the isolation film 242 to cause safety risks.

[0186] The greater the strength of the material used to make the strengthening layer 24S, the smaller the deformation when under tension, the more it can enhance the tensile strength of the pole piece to which the strengthening layer 24S is attached, the better the protection performance for the pole piece, and the more significant the improvement on the problem of local stress concentration.

[0187] The embodiment of the present application uses polyurea material as the preparation material of the reinforcement layer 24S, which is water-resistant and does not react with the electrolyte, and is suitable for the working environment of the pole piece. The reinforcement layer 24S is made of polyurea material, and the elastic modulus, tensile strength and elongation at break of the reinforcement layer 24S are greater than the elastic modulus, tensile strength and elongation at break of the pole piece made of conventional materials, which can provide better protection for the transition pole piece portion 24B where it is located, enhance its tensile strength, and thus help prevent the pole piece from cracking. Even if the transition pole piece portion 24B breaks in extreme cases, the compressive stress that the electrode assembly 24 is usually subjected to can usually only cause the transition pole piece portion 24B to break while the reinforcement layer 24S is not broken. The reinforcement layer 24S can wrap up the debris generated by the break of the transition pole piece portion 24B to prevent the debris from piercing the isolation membrane 242 and causing the risk of internal short circuit.

[0188] In addition, polyurea material has the characteristics of low density, fast curing speed, high bonding strength, good density, corrosion resistance, and aging resistance. The use of polyurea material to prepare the reinforcement layer 24S has the advantages of less impact on the energy density of the electrode assembly 24, fast production speed of the electrode piece, strong adhesion ability with the electrode piece, and good synergistic effect.

[0189] Fig.12 The schematic diagram of the partial structure of the cross section perpendicular to the width direction of the pole piece is a schematic diagram of the edge pole piece of some embodiments of the present application, in which a strengthening layer is provided. The edge pole piece involved in this embodiment as a strengthening pole piece can be combined with any of the above embodiments to form a corresponding alternative embodiment.

[0190] like Fig.12 In the illustrated embodiment, strengthening layers 24S are provided on both sides of the edge pole piece 24F. Each strengthening layer 24S includes a main body region 24S1 with uniform thickness and a thinning region 24S2 with a thickness gradually decreasing from the main body region 24S1 to a direction away from the main body region 24S1. The side of the cross section of the thinning region 24S2 away from the edge pole piece 24F is a straight line. The main body region 24S1 is provided with thinning regions 24S2 at both ends along the length direction X of the pole piece and at both ends along the width direction Y of the pole piece.

[0191] Along the width direction Y of the pole piece, both ends of the strengthening layer 24S provided on both sides of the edge pole piece portion 24F exceed the edge of the corresponding end of the strengthening pole piece portion where they are located. And the two ends of the strengthening layer 24S provided on both sides of the edge pole piece portion 24F are respectively connected to wrap the edges of both ends of the edge pole piece portion 24F. Along the length direction X of the pole piece, the outer ends of the strengthening layer 24S provided on both sides of the edge pole piece portion 24F exceed the outer end edge of the edge pole piece portion 24F where they are located, and the outer ends of the strengthening layer 24S provided on both sides of the edge pole piece portion 24F are connected to wrap the outer end edge of the edge pole piece portion 24F.

[0192] Fig.12Any parts not described in the illustrated embodiment may refer to the relevant contents of the other embodiments, including but not limited to the structure and material of the strengthening layer 24S, the method of combining it with the strengthening pole piece, the method of forming the thinning area, etc., which will not be repeated here.

[0193] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present application can still be modified or some technical features can be replaced by equivalents, which should all be included in the scope of the technical solution requested for protection in this application.

Claims

1. A battery cell (20), comprising at least two pole pieces and at least two separators (242), wherein the at least two pole pieces comprise a positive pole piece (241) and a negative pole piece (243), wherein the positive pole piece (241), the separator (242) and the negative pole piece (243) are sequentially stacked and wound into an electrode assembly (24) having a multi-layer winding structure with a corner region (C) and a flat region (S), wherein each pole piece comprises a plurality of transition pole piece portions (24B) located at the boundary region between the corner region (C) and the flat region (S) after winding and an edge pole piece portion (24F) located at the outermost end of the pole piece, characterized in that: The at least two pole pieces include at least one reinforcing pole piece portion, and at least one side of the reinforcing pole piece portion is provided with a reinforcing layer (24S), wherein the at least one reinforcing pole piece portion includes at least one transition pole piece portion (24B) of at least one pole piece, and along the length direction (X) of the pole piece, two ends of the reinforcing layer (24S) provided at the transition pole piece portion (24B) are respectively located at the corner area (C) and the flat area (S) of the transition pole piece portion (24B) where it is located.

2. The battery cell (20) according to claim 1, characterized in that: The at least one reinforcing pole piece portion at least comprises the transition pole piece portions (24B) located at the outermost layer of the multi-layer winding structure; or The at least one reinforcing pole piece portion at least includes the transition pole piece portions (24B) of the positive pole piece (241) and the negative pole piece (243) located at the outermost layers of each; or The at least one reinforcing pole piece portion at least includes each of the transition pole piece portions (24B) of each of the pole pieces.

3. The battery cell (20) according to claim 1, characterized in that: The at least one reinforcing pole piece portion also includes the edge pole piece portion (24F) of at least one of the pole pieces.

4. The battery cell (20) according to claim 1, characterized in that: Along the length direction (X) of the pole piece, the length range of the strengthening layer (24S) provided at the transition pole piece portion (24B) in the corner area (C) and the flat area (S) of the transition pole piece portion (24B) where it is located is 1 / 8πR~1 / 2πR, wherein R is the radius of the portion of the transition pole piece portion (24B) where the strengthening layer (24S) is located that is located in the corner area (C); and / or The reinforcing layer (24S) provided in the transition pole piece portion (24B) has a larger dimension and / or a larger thickness along the length direction (X) of the pole piece as the number of layers from the inside to the outside of the multi-layer winding structure increases.

5. The battery cell (20) according to claim 1, characterized in that: The strengthening layer (24S) is located at least in the middle of the strengthening pole piece portion where it is located along the width direction (Y) of the pole piece.

6. The battery cell (20) according to claim 5, characterized in that: Along the width direction (Y) of the pole piece, at least one end of the strengthening layer (24S) provided on at least one side of the strengthening pole piece portion is spaced from an edge of a corresponding end of the strengthening pole piece portion where it is located; and / or Along the width direction (Y) of the pole piece, at least one end of the strengthening layer (24S) provided on at least one side of the strengthening pole piece portion is flush with the edge of the corresponding end of the strengthening pole piece portion where it is located; and / or Along the width direction (Y) of the pole piece, at least one end of the strengthening layer (24S) provided on at least one side of the strengthening pole piece portion exceeds the edge of the corresponding end of the strengthening pole piece portion where it is located; and / or The at least one reinforcing pole piece portion further comprises the edge pole piece portion (24F) of at least one pole piece, and along the length direction (X) of the pole piece, the outer end of the reinforcing layer (24S) provided on at least one side of the edge pole piece portion (24F) is flush with the outer end edge of the edge pole piece portion (24F) where it is located; and / or The at least one reinforcing pole piece portion also includes the edge pole piece portion (24F) of at least one of the pole pieces, and along the length direction (X) of the pole piece, the outer end of the reinforcing layer (24S) arranged on at least one side of the edge pole piece portion (24F) exceeds the outer end edge of the edge pole piece portion (24F) where it is located.

7. The battery cell (20) according to claim 6, characterized in that: Along the width direction (Y) of the pole piece, at least one end of the strengthening layer (24S) provided on both sides of the strengthening pole piece portion is connected to wrap the edge of the corresponding end of the strengthening pole piece portion where it is located; and / or Along the length direction (X) of the pole piece, the outer ends of the reinforcing layers (24S) arranged on both sides of the edge pole piece portion (24F) are connected to wrap the outer end edges of the edge pole piece portion (24F) where they are located.

8. The battery cell (20) according to claim 1, characterized in that: The elastic modulus of the reinforcement layer (24S) is greater than the elastic modulus of the reinforcement pole piece portion where it is located; and / or The tensile strength of the strengthening layer (24S) is greater than the tensile strength of the strengthening pole piece where it is located; and / or The fracture elongation of the strengthening layer (24S) is greater than the fracture elongation of the strengthening pole piece portion where it is located.

9. The battery cell (20) according to any one of claims 1 to 8, characterized in that: Along the length direction (X) of the pole piece, adjacent strengthening layers (24S) on the same side of the same pole piece are arranged at intervals; and / or The strengthening layer (24S) is bonded to the strengthening pole piece portion where it is located by coating; and / or The reinforcing layer (24S) comprises polyurea material, polyurethane material, polyamide material or acrylic resin material; and / or The strengthening layer (24S) comprises a main body region (24S1) with uniform thickness.

10. The battery cell (20) according to claim 9, characterized in that: The thickness of the main region (24S1) is 5-150 μm.

11. The battery cell (20) according to claim 10, characterized in that: The thickness of the main region (24S1) is 5-100 μm.

12. The battery cell (20) according to claim 9, characterized in that: The strengthening layer (24S) further comprises a thinning region (24S2) whose thickness gradually decreases from the main region (24S1) in a direction away from the main region (24S1).

13. The battery cell (20) according to claim 12, characterized in that: The side of the cross section of the thinned area (24S2) away from the reinforcing pole piece portion is a straight line or a smooth convex curve; and / or The thinning area (24S2) is provided at both ends of the main area (24S1) along the length direction (X) of the pole piece; and / or The thinning areas (24S2) are provided at both ends of the main area (24S1) along the width direction (Y) of the pole piece.

14. A battery, characterized in that: A battery cell (20) comprising the battery cell (20) according to any one of claims 1 to 13.

15. An electrical equipment, characterized in that: The battery according to claim 14 is used to provide power to the electrical device.

16. A pole piece for an electrode assembly (24) having a multi-layer winding structure with a corner region (C) and a flat region (S), characterized in that: The pole piece includes a plurality of transition pole piece portions (24B) and an edge pole piece portion (24F), wherein the transition pole piece portion (24B) is located at the boundary area between the corner area (C) and the flat area (S) after the pole piece is wound, and the edge pole piece portion (24F) is located at the end of the outermost layer after the pole piece is wound, and is characterized in that the pole piece includes at least one reinforcing pole piece portion, at least one side of the reinforcing pole piece portion is provided with a reinforcing layer (24S), and the at least one reinforcing pole piece portion of the pole piece includes at least one transition pole piece portion (24B).

17. The pole piece according to claim 16, characterized in that: Along the length direction (X) of the pole piece, the length range of the strengthening layer (24S) provided at the transition pole piece portion (24B) in the corner area (C) and the flat area (S) of the transition pole piece portion (24B) where it is located is 1 / 8πR~1 / 2πR, wherein R is the radius of the portion of the transition pole piece portion (24B) where the strengthening layer (24S) is located that will be in the corner area (C); and / or The reinforcing layer (24S) provided in the transition pole piece portion (24B) has a larger dimension and / or a larger thickness along the length direction (X) of the pole piece as the number of layers from the inside to the outside of the multi-layer winding structure increases; and / or The strengthening layer (24S) is at least located in the middle of the strengthening pole piece portion where it is located along the width direction (Y) of the pole piece; and / or Adjacent strengthening layers (24S) on the same side of the pole piece are arranged at intervals; and / or The strengthening layer (24S) is bonded to the strengthening pole piece portion where it is located by coating; and / or The reinforcing layer (24S) comprises polyurea material, polyurethane material, polyamide material or acrylic resin material; and / or The strengthening layer (24S) comprises a main body region (24S1) with uniform thickness and a thinning region (24S2) with a thickness gradually decreasing from the main body region (24S1) in a direction away from the main body region (24S1).

18. A method for preparing a pole piece according to claim 16 or 17, characterized in that: The method comprises: providing a strengthening layer (24S) on at least one side surface of at least one of the strengthening pole piece portions of the pole piece.

19. The method for preparing a pole piece according to claim 18, characterized in that: include: Along the length direction (X) of the pole piece, the length range of the strengthening layer (24S) provided at the transition pole piece portion (24B) in the corner area (C) and the flat area (S) of the transition pole piece portion (24B) where it is located is 1 / 8πR~1 / 2πR, wherein R is the radius of the portion of the transition pole piece portion (24B) where the strengthening layer (24S) is located that will be in the corner area (C); and / or The reinforcing layer (24S) provided at the transition pole piece portion (24B) is in the multi-layer winding structure, and the larger the number of layers from the inside to the outside, the larger the size along the length direction (X) of the pole piece and / or the larger the thickness; and / or The strengthening layer (24S) is arranged at least in the middle of the strengthening pole piece portion where the strengthening pole piece is located along the width direction (Y) of the pole piece; and / or The adjacent strengthening layers (24S) on the same side of the pole piece are arranged at intervals; and / or The strengthening layer (24S) is applied to the strengthening pole piece portion where it is located; and / or The strengthening layer (24S) is made of polyurea material, polyurethane material, polyamide material or acrylic resin material; and / or The strengthening layer (24S) is formed into a main body region (24S1) with uniform thickness and a thinning region (24S2) with a thickness gradually decreasing from the main body region (24S1) in a direction away from the main body region (24S1).

Images