Battery, preparation method for battery, protective layer and electric device

Abstract

A battery, a preparation method for a battery, a protective layer (2) and an electric device (3). The protective layer (2) is arranged between adjacent battery cells (1), and by means of the arrangement of the protective layer (2), a bonding layer can be separated from the battery cells (1), such that the influence the bonding layer introduced between adjacent battery cells (1) has on the battery cells (1) is reduced, and the cycle performance of a battery can thus be improved.

Description

Battery, preparation method, protective layer and electrical device Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery, a preparation method, a protective layer, and an electrical device. Background Art

[0002] Batteries are typically constructed by arranging multiple battery cells in a box. During battery use, the volume expansion of the battery cells may affect the battery's cycle performance.

[0003] Summary of the Invention

[0004] In a first aspect, the present application provides a battery, comprising: a battery unit, wherein the battery unit comprises a plurality of battery cells arranged along a first direction, the battery cell having a first surface parallel to the first direction and a second surface parallel to a second direction, the second direction intersecting with the first direction, the second surface connected to the first surface, and the area of ​​the second surface being greater than or equal to the area of ​​the first surface; a case, wherein the case is used to accommodate the battery unit; an adhesive layer, wherein the adhesive layer is located between the case and the battery unit for connecting the case to the battery unit; and a protective layer, wherein the protective layer is located between the second surfaces opposite to each other of two adjacent battery cells for isolating the adhesive layer from extending to the central area of ​​the second surface.

[0005] When the battery cell is assembled into the box, the protective layer can separate the adhesive, reducing the risk of the adhesive penetrating into the central area of ​​the second surface of the adjacent battery cell, thereby reducing the inhibition of the adhesive layer on the expansion of the battery cell and reducing the risk of stress concentration in the central area of ​​the second surface, so that the electrolyte squeezed out during the expansion process can be better absorbed back to the middle of the electrode assembly, thereby maintaining better cycle performance of the battery.

[0006] In some embodiments, the protective layer covers at least the central region of the second surfaces between two adjacent battery cells. Covering at least the central region of the second surfaces reduces the risk of adhesive penetrating into the central region of the second surfaces, reduces the effect of the adhesive layer on expansion at the central region of the second surfaces, promotes smooth expansion of the battery cells, and further maintains good battery cycle performance.

[0007] In some embodiments, the distance between the protective layer and the outer edge of the battery cell is less than or equal to 15 mm. In this case, the protective layer can better isolate the second surface of the battery cell from the adhesive layer, further reducing the effect of the adhesive layer on the expansion of the second surface of the battery cell, thereby promoting the battery to maintain good cycle performance. Optionally, the protective layer covers the entire second surface.

[0008] In some embodiments, between the second surfaces of two adjacent battery cells, the edge of the protective layer wraps around the edge of the second surface to form a closed structure. The closed structure encloses a hollow region, and the central region of the battery cell is located in the hollow region. The central region of the battery cell is located in the hollow region. When the battery cell expands in volume, the hollow region can serve as a buffer for the volume expansion of the battery cell, reducing the risk of compression between adjacent battery cells due to expansion, thereby further improving the battery's cycle performance.

[0009] In some embodiments, the width of the enclosed structure is 1 mm to 15 mm. Within this width range, the protective layer can have a hollow area of ​​appropriate size to adequately buffer the volume expansion of the battery cells. Furthermore, the protective layer and the battery cells can have a relatively appropriate contact area, which can better reduce the risk of adhesive penetrating into the hollow area during battery assembly. This can further stably separate the battery cells from the adhesive layer and improve the battery's cycling performance.

[0010] In some embodiments, the distance between the edge of the hollowed-out area and the outer edge of the battery cell is 1 mm to 15 mm. In this case, the protective layer can better isolate the second surface of the battery cell from the adhesive layer, further reducing the effect of the adhesive layer on the expansion of the second surface of the battery cell, thereby promoting the battery to maintain good cycle performance.

[0011] In some embodiments, the second surface includes a first edge, a second edge, a third edge, and a fourth edge connected in sequence end to end; the first edge is configured as an outer side surface of the opening of the battery cell, and the third edge is arranged opposite to the first edge; at the first edge, the distance between the edge of the hollow area and the outer edge of the battery cell is 1mm-10mm.

[0012] In some embodiments, a distance between an edge of the hollow area and an outer edge of the battery cell is 1 mm to 15 mm.

[0013] In some embodiments, at the third edge, a distance between an edge of the hollow area and an outer edge of the battery cell is 1 mm-10 mm.

[0014] In some embodiments, at the fourth edge, a distance between an edge of the hollow area and an outer edge of the battery cell is 1 mm to 15 mm.

[0015] In some embodiments, the thickness of the protective layer is 0.5 mm to 10 mm. The thickness of the protective layer within this range can ensure that the protective layer has a relatively suitable volume, thereby maintaining a relatively suitable volume of the battery, which is conducive to maintaining a high energy density of the battery.

[0016] In some embodiments, the protective layer has a rebound rate of 50% to 100%. A protective layer with a rebound rate within this range has good resilience, can further cushion the volume expansion of the battery cells, and further improve the battery's cycling performance. Alternatively, the protective layer has a rebound rate of 95% to 98%.

[0017] In some embodiments, the compression modulus of the protective layer is 1 MPa-10 MPa. A large compression modulus of the protective layer can provide the protective layer with good strength while maintaining good resilience, reducing the risk of excessive deformation of the protective layer when squeezed, helping the protective layer maintain relatively stable resilience, and further improving the cycle performance of the battery.

[0018] In some embodiments, the bonding strength between the protective layer and the battery cells is 0.1 MPa-2.2 MPa. Due to the good bonding performance, the protective layer can be more stably positioned between adjacent battery cells, stably exerting its rebound properties and further improving the battery's cycle performance.

[0019] In some embodiments, the material of the protective layer includes a thermoplastic elastomer. Thermoplastic elastomer has good elasticity, which can enable the protective layer to better buffer the expansion of the battery cell, further improving the cycle performance of the battery.

[0020] In some embodiments, the thermoplastic elastomer comprises a linear polymer. The linear polymer has good plasticity and can be remelted by heating after solidification, which can facilitate the processing and recycling of the protective layer and lay the foundation for the reuse of the thermoplastic elastomer.

[0021] In some embodiments, the thermoplastic elastomer has a melting temperature of 140° C. to 240° C. A thermoplastic elastomer with a melting temperature within this range can maintain a relatively stable structure during battery use and has good processing properties, facilitating the processing and molding of the protective layer.

[0022] In some embodiments, the thermoplastic elastomer includes one or more of styrene-based thermoplastic elastomer, olefin-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polyester-based thermoplastic elastomer, and polyamide-based thermoplastic elastomer.

[0023] In some embodiments, the styrenic thermoplastic elastomer includes one or more of a styrene-butadiene-styrene triblock copolymer, a hydrogenated styrene-butadiene-styrene triblock copolymer, a styrene-isoprene-styrene triblock copolymer, and a hydrogenated styrene-isoprene-styrene triblock copolymer.

[0024] In some embodiments, the styrene-based thermoplastic elastomer includes a styrene-butadiene-styrene triblock copolymer and a styrene-isoprene-styrene triblock copolymer, and the mass ratio of the styrene-butadiene-styrene triblock copolymer to the styrene-isoprene-styrene triblock copolymer is 3:7-1:9.

[0025] In some embodiments, the material of the protective layer further comprises a tackifying resin. The use of the tackifying resin can further improve the bonding performance between the protective layer and the battery cells, which is conducive to maintaining a more stable bonding structure between adjacent battery cells.

[0026] In some embodiments, the tackifying resin comprises 15%-30% by mass of rosin and 5%-10% by mass of petroleum resin, based on the mass percentage of the thermoplastic elastomer.

[0027] In some embodiments, the protective layer material further includes inorganic particles. The inorganic particle filler can provide support for the protective layer, ensuring that the protective layer has good strength while maintaining good resilience, reducing the risk of excessive deformation of the protective layer when squeezed, and facilitating a relatively stable bonding structure between adjacent battery cells.

[0028] In some embodiments, the inorganic particles include one or more of inorganic particles having a dielectric constant of 5 or greater, inorganic particles capable of transporting active ions, and inorganic particles capable of electrochemical oxidation and reduction.

[0029] In some embodiments, the inorganic particles include first particles and second particles, wherein the Dv50 of the first particles is greater than the Dv50 of the second particles. The larger Dv50 of the first particles can reinforce the protective layer, further improving the strength of the protective layer. The smaller Dv50 of the second particles can be more evenly dispersed in the protective layer, further improving the support effect of the protective layer.

[0030] In some embodiments, the first particles have a Dv50 of 20 μm to 50 μm.

[0031] In some embodiments, the second particles have a Dv50 of 20 nm to 50 nm.

[0032] In some embodiments, the mass ratio of the second particles to the first particles is 1:1 to 5:1. The mass ratio of the second particles to the first particles within this range can better match the second particles to the first particles and more substantially improve the strength of the protective layer.

[0033] In some embodiments, the mass percentage of the first particles is 3% to 10% of the mass percentage of the thermoplastic elastomer. The mass percentage of the first particles within this range can provide a relatively suitable weight for the protective layer while providing good support, thereby helping the battery maintain a high energy density.

[0034] In some embodiments, the mass percentage of the second particles is 10%-30% based on the mass percentage of the thermoplastic elastomer. The mass percentage of the second particles within this range can provide a relatively suitable weight for the protective layer while providing good support, thereby helping the battery maintain a high energy density.

[0035] In some embodiments, the material of the protective layer further includes a wetting agent. In this case, the components of the protective layer can be mixed more evenly, which is beneficial to improving the uniformity of the protective layer and further improving the bonding stability between adjacent battery cells.

[0036] In some embodiments, the wetting agent includes one or more of a polyethylene resin and a polypropylene resin.

[0037] In some embodiments, the mass percentage of the wetting agent is 15%-25% based on the mass percentage of the thermoplastic elastomer.

[0038] In some embodiments, the material of the protective layer includes a styrene-based thermoplastic elastomer, a tackifying resin, inorganic particles, a wetting agent, a plasticizer, and an antioxidant; the inorganic particles include first particles and second particles, the Dv50 of the first particles is greater than the Dv50 of the second particles; the mass percentage of the first particles is 3%-10% based on the mass percentage of the thermoplastic elastomer, the mass percentage of the second particles is 10%-30% based on the mass percentage of the thermoplastic elastomer; the mass percentage of the first particles is 10%-20% based on the mass percentage of the thermoplastic elastomer; the mass percentage of the second particles is 10%-30% based on the mass percentage of the thermoplastic elastomer; the mass percentage of the first particles is 3%-10% based on the mass percentage of the thermoplastic elastomer; the mass percentage of the second particles is 10%-20% based on the mass percentage of the thermoplastic elastomer; the mass percentage of the first particles is 3%-10% based on the mass percentage of the thermoplastic elastomer; the mass percentage of the second particles is 10%-30% based on the mass percentage of the thermoplastic elastomer. Calculated by mass percentage of the styrene-based thermoplastic elastomer, the tackifying resin includes 15%-30% of rosin and 5%-10% of petroleum resin; calculated by mass percentage of the thermoplastic elastomer, the wetting agent has a mass percentage of 15%-25%; calculated by mass percentage of the thermoplastic elastomer, the plasticizer has a mass percentage of 0.1%-0.5%; and calculated by mass percentage of the thermoplastic elastomer, the antioxidant has a mass percentage of 0.1%-1%.

[0039] A second aspect of the present application provides a method for preparing a battery, comprising the following steps:

[0040] A plurality of battery cells are arranged along a first direction, and a protective layer is provided between two adjacent battery cells to form a battery unit; the battery cells have a first surface parallel to the first direction and a second surface parallel to a second direction, the second direction intersecting the first direction, the second surface connected to the first surface, and the area of ​​the second surface is greater than or equal to the area of ​​the first surface; the protective layer is located between the opposing second surfaces of the two adjacent battery cells;

[0041] The box body is connected to the battery unit through an adhesive layer, and the protective layer is used to isolate the adhesive layer and extends to the central area of ​​the second surface.

[0042] In some embodiments, providing the protective layer includes the following steps: applying a protective layer material to the surface of the battery cell, covering another battery cell on the surface of the protective layer material, and shaping the protective layer material to form the protective layer.

[0043] In some embodiments, applying the protective layer material includes applying the protective layer material to an edge of a surface of the battery cell to form a ring-shaped protective layer material.

[0044] In some embodiments, a starting point and an end point for applying the protective layer material are located on the same side of the surface of the battery cell, with a gap between the starting point and the end point.

[0045] In some embodiments, the gap between the application start point and the application end point is less than or equal to 10 mm.

[0046] In some embodiments, the protective layer is defined as the protective layer in the battery.

[0047] A third aspect of the present application provides a protective layer, which is defined as the protective layer in the battery described in the first aspect.

[0048] A fourth aspect of the present application provides an electrical device comprising the battery of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes currently understood for these applications. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the accompanying drawings:

[0050] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0051] FIG. 2 is an exploded view of the battery cell according to one embodiment of the present application shown in FIG. 1 .

[0052] FIG3 is a schematic diagram showing the positions of the battery cells and the protective layer in one embodiment of the present application.

[0053] FIG4 is a schematic diagram showing the positions of battery cells and a protective layer in another embodiment of the present application.

[0054] FIG5 is a schematic diagram showing the position of a protective layer on a battery cell in another embodiment of the present application.

[0055] FIG6 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0056] Description of reference numerals:

[0057] 1. Battery cell; 11. Casing; 111. First surface; 112. Second surface; 1121. First edge; 1122. Second edge; 1123. Third edge; 1124. Fourth edge; 12. Electrode assembly; 13. Cover plate; 14. Electrode terminal; 2. Protective layer; 3. Electrical device. DETAILED DESCRIPTION

[0058] To facilitate understanding of the present application, a more comprehensive description of the present application will be provided below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0060] The "ranges" disclosed in this application can be defined in the form of lower limits and upper limits. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. Ranges defined in this way can be inclusive or exclusive of the end values, any end value can be included or excluded independently, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4, and 5 are also listed, the following ranges are all expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to listing the parameter as, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and so on. For example, when a parameter is expressed as an integer selected from "2-10," this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0061] In this application, "a plurality of" or "a plurality of" refers to a number greater than or equal to 2 unless otherwise specified. For example, "one or more" means one or more than or equal to two.

[0062] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0063] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0064] Those skilled in the art will appreciate that, in the methods of each embodiment or example, the order in which the steps are written does not imply a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, it is mentioned that the method may also include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0065] In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0066] In this application, the terms "optionally," "optional," and "optional" are optional and refer to either option being present or absent. If a technical solution contains multiple "options," each option is considered independent unless otherwise specified and there are no conflicts or constraints.

[0067] In this application, unless otherwise specified, a "battery cell" refers to a basic unit that can achieve the mutual conversion of chemical energy and electrical energy. Further, generally speaking, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the battery's charge and discharge process, active ions are embedded in and out of the positive and negative electrode plates. The electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0068] During the battery assembly process, the battery cells are connected to the casing using an adhesive in the casing. During this process, the adhesive may penetrate between adjacent battery cells and solidify. The solidified adhesive restricts the expansion of the battery cells, causing stress concentration in the battery cells where the adhesive solidified. This stress concentration increases the resistance to electrolyte reabsorption, making it difficult for the electrolyte squeezed out during the expansion process to be fully absorbed back into the electrode assembly. This reduces the wettability of the electrolyte in the battery cells to the electrode assembly, thereby affecting the battery cell's cycling performance.

[0069] One embodiment of the present application provides a battery. The battery includes: a battery unit, the battery unit includes a plurality of battery cells arranged along a first direction, the battery cell has a first surface parallel to the first direction and a second surface parallel to a second direction, the second direction intersects with the first direction, the second surface is connected to the first surface, and the area of ​​the second surface is greater than or equal to the area of ​​the first surface. A casing, the casing is used to accommodate the battery cells. An adhesive layer, the adhesive layer is located between the casing and the battery cells to connect the casing to the battery cells. A protective layer, the protective layer is located between the second surfaces opposite to each other of two adjacent battery cells to isolate the adhesive layer from extending to the central area of ​​the second surface. In the battery of this embodiment, by providing the protective layer, the risk of the adhesive layer extending to the central area of ​​the second surface of the battery cell can be reduced, the inhibition of the adhesive layer on the expansion of the battery cell can be reduced, and the risk of stress concentration in the central area of ​​the second surface can be reduced, so that the electrolyte squeezed out during the expansion process can be better sucked back to the middle of the electrode assembly, thereby maintaining good cycle performance of the battery.

[0070] In some embodiments, the area of ​​the second surface is greater than the area of ​​the first surface. Referring to FIG1 , the battery cell 1 generally includes a first surface 111 (such as a side surface) and a second surface 112 (such as a front surface) connected to each other. It is understandable that the battery cell 1 includes a shell 11, and the shell 11 includes a first surface 111 and a second surface 112 connected to each other. In order to improve the assembly utilization rate of the box space, the second surfaces of adjacent battery cells with larger areas are often arranged relative to each other. At this time, when the battery cell expands, the volume change of the battery cell is mainly manifested as a change in the shape of the second surface. When the battery cell is assembled into the box, the protective layer can separate the adhesive and reduce the risk of the adhesive penetrating into the center area of ​​the second surface of the adjacent battery cell, thereby reducing the influence of the adhesive layer on the deformation of the second surface when the battery cell expands, reducing the inhibition of the adhesive layer on the expansion of the battery cell, reducing the risk of stress concentration in the center area of ​​the second surface, and allowing the battery to maintain good cycle performance.

[0071] In some embodiments, the second direction is perpendicular to the first direction, which can make the battery cells more comprehensively distributed and improve the space utilization of the box.

[0072] In some embodiments, the battery cell is a prismatic battery cell. In the prismatic battery cell, the first surface is optionally a surface bounded by the height and thickness directions of the battery cell, and the second surface is optionally a surface bounded by the length and height directions of the battery cell, with the area of ​​the second surface being greater than the area of ​​the first surface.

[0073] In some embodiments, the battery cell is a cylindrical battery cell. In the cylindrical battery cell, the first surface is optionally the round side of the battery cell, and the second surface is optionally the side surface of the battery cell. Optionally, the area of ​​the second surface is greater than the area of ​​the first surface.

[0074] FIG1 is a battery cell 1 of a square structure as an example. In some embodiments, referring to FIG2 , the battery cell 1 may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The cover plate 13 is provided with an electrode terminal 14. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 1 may be one or more, and those skilled in the art can select according to actual needs.

[0075] In some embodiments, the housing of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the housing of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic. Non-limiting examples of plastic include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0076] In some embodiments, the protective layer covers at least the central area of ​​the second surface between the opposing second surfaces of two adjacent battery cells. When the battery cell expands, the central area of ​​the second surface of the battery cell often has a large deformation. When the battery cell is assembled, if the adhesive penetrates to the center of the second surface, the cured adhesive will produce a relatively obvious stress concentration in the center of the second surface, and the electrolyte squeezed out during the expansion process will be difficult to fully absorb back to the center of the electrode assembly. When the protective layer covers at least the central area of ​​the second surface, the electrolyte squeezed out during the expansion process can be better absorbed back to the center of the electrode assembly, thereby maintaining good cycle performance of the battery.

[0077] It is understandable that the central area of ​​the second surface represents the center of the second surface, and can also represent the area spreading from the center of the second surface to the edge of the second surface. Optionally, the distance between the protective layer and the outer edge of the battery cell is less than or equal to 15 mm. In this case, the protective layer can better separate the second surface of the battery cell from the adhesive layer, so that there is as little adhesive layer as possible between two adjacent battery cells, further reducing the effect of the adhesive layer on the expansion of the second surface of the battery cell, and promoting the battery to maintain better cycle performance. Optionally, the distance between the protective layer and the outer edge of the battery cell can be 15 mm, 14 mm, 13 mm, 12 mm, 11 mm, 10 mm, 9 mm, 8 mm, 7 mm, 6 mm, 5 mm, 4 mm, 3 mm, 2 mm, 1 mm, 0 mm or any value within any range composed of these values.

[0078] Referring to Figure 3, in some embodiments, the battery cell has four edges, and the distances between the protective layer 2 and the outer edges of the battery cell are represented by L1, L2, L3, and L4, respectively. Optionally, L1 ≤ 15 mm, L2 ≤ 15 mm, L3 ≤ 15 mm, and L4 ≤ 15 mm. Further optionally, L1, L2, L3, and L4 are equal. Further optionally, the protective layer 2 completely covers the second surface 112. Complete coverage means that the contact area between the protective layer and the second surface is equal to the area of ​​the second surface. In this case, the distance between the protective layer and the outer edge of the battery cell is 0 mm, that is, L1, L2, L3, and L4 are all 0.

[0079] In some embodiments, between the opposing second surfaces of two adjacent battery cells, the edge of the protective layer wraps around the edge of the second surface to form a closed structure. This closed structure encloses a hollow region, with the center of the battery cell located within the hollow region. When the battery cell expands, the expansion is primarily concentrated in the central region of the second surface of the battery cell. In this case, the hollow region serves as a buffer for the volume expansion of the battery cell, reducing the risk of stress concentration in the center of the second surface of the battery cell, thereby further improving the battery's cycling performance.

[0080] In some embodiments, the width of the closed structure is 1mm-15mm. The width of the closed structure within this range can, on the one hand, allow the protective layer to have a hollow area of ​​appropriate size, fully buffering the volume expansion of the battery cell, and on the other hand, allow the protective layer and the battery cell to have a more appropriate contact area, better reducing the risk of adhesive infiltration into the hollow area during battery assembly, thereby more stably separating the battery cell and the adhesive layer, and further improving the cycle performance of the battery. It will be understood that the width of the closed structure refers to the width of the closed structure in a direction perpendicular to the extension direction of the closed structure. Optionally, the width of the closed structure can be 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm or any value within any range composed of these values.

[0081] In some embodiments, the distance between the edge of the hollowed-out area and the outer edge of the battery cell is 1 mm to 15 mm. This allows for better alignment of the width of the hollowed-out area and the enclosed structure, further reducing the effect of the adhesive layer on the expansion of the second surface of the battery cell and enabling the battery to maintain good cycling performance. Alternatively, the distance between the edge of the hollowed-out area and the outer edge of the battery cell can be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, or any value within any range of these values.

[0082] In some embodiments, the second surface 112 includes a first edge 1121, a second edge 1122, a third edge 1123, and a fourth edge 1124 connected in sequence end to end. The first edge 1121 is configured as an outer side surface of the opening of the battery cell 1, and the third edge 1123 is arranged opposite to the first edge 1121. At the first edge 1121, the distance between the edge of the hollow area and the outer edge of the battery cell is 1 mm-10 mm. Optionally, at the first edge 1121, the distance between the edge of the hollow area and the outer edge of the battery cell can be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, or any value within any range composed of these values.

[0083] Optionally, referring to FIG. 4 , the opening of the battery cell 1 is arranged in the vertical direction. In this case, at the first edge 1121 , the distance between the hollow area and the outer edge of the battery cell is represented by L11 , ie, L11 is 1 mm-10 mm.

[0084] In some embodiments, at the second edge 1122, the distance between the edge of the hollowed-out area and the outer edge of the battery cell is 1 mm - 15 mm. At this time, at the second edge 1122, the distance between the hollowed-out area and the outer edge of the battery cell is represented by L22, that is, L22 is 1 mm - 15 mm. Optionally, at the second edge 1122, the distance between the edge of the hollowed-out area and the outer edge of the battery cell can be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm or any value within any range composed of these values.

[0085] In some embodiments, at the third edge 1123, the distance between the edge of the hollowed-out area and the outer edge of the battery cell is 1 mm - 10 mm. At this time, at the third edge 1123, the distance between the hollowed-out area and the outer edge of the battery cell is represented by L33, that is, L33 is 1 mm - 10 mm. Optionally, at the third edge 1123, the distance between the edge of the hollowed-out area and the outer edge of the battery cell can be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm or any value within any range composed of these values.

[0086] In some embodiments, at the fourth edge 1124, the distance between the edge of the hollowed-out area and the outer edge of the battery cell is 1 mm - 15 mm. At this time, at the fourth edge 1124, the distance between the hollowed-out area and the outer edge of the battery cell is represented by L44, that is, L44 is 1 mm - 15 mm. Optionally, at the fourth edge 1124, the distance between the edge of the hollowed-out area and the outer edge of the battery cell can be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm or any value within any range composed of these values.

[0087] Please refer to FIG. 4 again, where the width of the closed structure is shown. Among them, the width of the closed structure represents the width of the closed structure in the direction perpendicular to the extension direction of the closed structure. The closed structure is in a double-square shape, and W represents the width of the closed structure.

[0088] In some embodiments, please refer to FIG. 5. The openings of the battery cell 1 are provided in the horizontal direction, and the housing of the battery cell has two openings. At this time, the first edge 1121 and the third edge 1123 are respectively configured as the outer sides of the two openings of the battery cell. At this time, L11 is 1 mm - 10 mm, L22 is 1 mm - 15 mm, L33 is 1 mm - 15 mm, and L44 is 1 mm - 10 mm.

[0089] In some embodiments, the thickness of the protective layer is 0.5 mm to 10 mm. The thickness of the protective layer within this range can ensure that the protective layer has a relatively suitable volume, thereby maintaining a relatively suitable volume of the battery, which is conducive to maintaining a high energy density of the battery.

[0090] In some embodiments, the resilience of the protective layer is 50% to 100%. The protective layer with a resilience in this range has good resilience performance, can provide further buffering for the volume expansion of the battery cell, and further improve the cycle performance of the battery. Optionally, the resilience of the protective layer can be 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, 95%, 98%, 100% or any value within any range composed of these values. Further optionally, the resilience of the protective layer is 95%-98%.

[0091] The rebound rate of the protective layer can be tested in the following way: disassemble the battery, separate the two adjacent battery cells, and peel off the protective layer. Cut the peeled protective layer into For a sample, the compression tester's pressure surface completely covers the sample surface. Compress to 50% compression. After unloading, record the rebound thickness and calculate the rebound rate. Rebound rate = (rebound thickness - initial thickness * 50%) / (initial thickness * 50%).

[0092] In some embodiments, the compression modulus of the protective layer is 1MPa-10MPa. The protective layer has a large compression modulus, which can make the protective layer have better strength on the basis of having good rebound performance, reduce the risk of excessive deformation of the protective layer when squeezed, and help the battery cell maintain a more stable structure. Optionally, the compression modulus of the protective layer can be any value within any range of 1MPa, 2MPa, 3MPa, 4MPa, 5MPa, 6MPa, 7MPa, 8MPa, 9MPa, 10MPa or the above values. Further optionally, the compression modulus of the protective layer is 6.8MPa-7.1MPa.

[0093] The compression modulus of the protective layer can be tested in the following way: disassemble the battery, separate the two adjacent battery cells, and peel off the protective layer. Cut the peeled protective layer into Refer to GB / T7757, the compression tester's pressure surface completely covers the sample surface, the compression rate is 2mm / min, the compression is performed to 90% strain, and the slope of the linear part of the compression stress-strain curve is extracted as the compression modulus.

[0094] In some embodiments, the bonding strength between the protective layer and the battery cell is 0.1 MPa-2.2 MPa. In this case, the protective layer can provide good bonding performance between adjacent battery cells, maintaining a relatively stable bonding structure between adjacent battery cells, and maintaining a relatively stable structure of the battery unit. Optionally, the bonding strength between the protective layer and the battery cell can be 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, 1.1 MPa, 1.2 MPa, 1.3 MPa, 1.4 MPa, 1.5 MPa, 1.6 MPa, 1.7 MPa, 1.8 MPa, 1.9 MPa, 2 MPa, 2.1 MPa, 2.2 MPa, or any value within any range of these values. Further optionally, the bonding strength between the protective layer and the battery cell is 1.5 MPa-2.1 MPa.

[0095] The bond strength between the protective layer and the battery cell can be tested by disassembling the battery, removing the electrolyte and electrode assembly from the battery cell, and disassembling the battery cell housing, retaining the surface where the housing and protective layer are connected, to obtain a sample with a housing-protective layer-housing laminate. Referring to GB / T7124, the sample is cut to a size of (25±1.2)5mm×(12.5±0.625)mm. The tensile rate is set to (50±2.5)mm / min to separate the housing and protective layer in the sample. The maximum load at which the sample shears to failure is recorded as the failure load, and the shear strength is calculated as the bond strength.

[0096] In some embodiments, the protective layer comprises a thermoplastic elastomer. Thermoplastic elastomers are polymer materials that combine the properties of rubber and plastic. Thermoplastic elastomers have good elasticity, enabling the protective layer to effectively cushion the expansion of battery cells, further improving the battery's cycling performance. Furthermore, thermoplastic elastomers have good processability, facilitating the processing and molding of the protective layer.

[0097] In some embodiments, the thermoplastic elastomer comprises a linear polymer. Linear polymers have long molecular chains without branches or crosslinks. Linear polymers have good plasticity and can be remelted by heating after solidification. This facilitates processing and recycling of the protective layer and paves the way for the reuse of the thermoplastic elastomer.

[0098] In some embodiments, the melting temperature of the thermoplastic elastomer is 140°C-240°C. Thermoplastic elastomers with a melting temperature within this range can maintain a relatively stable structure during the use of the battery. At the same time, the thermoplastic elastomer has good processing properties, which facilitates the processing and molding of the protective layer. Optionally, the melting temperature of the thermoplastic elastomer can be 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C or any value within any range composed of these values. Optionally, the melting temperature of the thermoplastic elastomer is 160°C-180°C.

[0099] The melting temperature of the thermoplastic elastomer can be measured by using a differential scanning calorimeter at a heating rate of 10°C / min, reading the melting temperature range from the DSC curve, and taking the middle portion as the melting temperature.

[0100] In some embodiments, the thermoplastic elastomer includes one or more of styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, polyester-based thermoplastic elastomers, and polyamide-based thermoplastic elastomers.

[0101] Optionally, the styrene-based thermoplastic elastomer includes one or more of styrene-butadiene-styrene triblock copolymer (SBS), hydrogenated styrene-butadiene-styrene triblock copolymer, styrene-isoprene-styrene triblock copolymer (SIS) and hydrogenated styrene-isoprene-styrene triblock copolymer. Styrene-butadiene-styrene triblock copolymer and hydrogenated styrene-butadiene-styrene triblock copolymer can be melted at a suitable temperature, and can be better characterized when the temperature is reduced, so they are easy to reuse and have a high utilization rate. At the same time, styrene-butadiene-styrene triblock copolymer and hydrogenated styrene-butadiene-styrene triblock copolymer have good elasticity, which is conducive to making the protective layer have a higher rebound rate. Styrene-isoprene-styrene triblock copolymer and hydrogenated styrene-isoprene-styrene triblock copolymer have good elasticity and can also improve the compatibility between the various components in the protective layer, which is conducive to making the protective layer have good bonding properties while maintaining good elasticity.

[0102] In some embodiments, the styrenic thermoplastic elastomer includes a styrene-butadiene-styrene triblock copolymer (SBS) and a styrene-isoprene-styrene triblock copolymer (SIS), with the mass ratio of the SBS to SIS being 3:7 to 1:9. This SBS to SIS mass ratio within this range allows the protective layer to have good resilience while maintaining good adhesion, which facilitates adhesion between adjacent battery cells. Alternatively, the SBS to SIS mass ratio can be 3:7, 2.5:7.5, 2:8, 1.5:8.5, 1:9, or any value within any range comprised of these values.

[0103] In some embodiments, the olefinic thermoplastic elastomer includes one or more of polyolefin, ethylene-propylene copolymer, ethylene-octene copolymer, and ethylene-propylene-diene copolymer.

[0104] In some embodiments, the polyurethane-based thermoplastic elastomer includes one or more of polyester polyurethane and polyether polyurethane.

[0105] In some embodiments, the polyester thermoplastic elastomer includes one or more of a polyester thermoplastic elastomer having polybutylene terephthalate as a hard segment and a polyester thermoplastic elastomer having polyethylene terephthalate as a hard segment.

[0106] In some embodiments, the polyamide-based thermoplastic elastomer includes one or more of polyether block amide, polyether ester amide, and polyester amide block copolymer.

[0107] In some embodiments, the protective layer also includes a tackifying resin. This is a functional resin that increases the viscosity of the protective layer. The use of a tackifying resin can further improve the adhesion between the protective layer and the battery cells, thereby maintaining a more stable bonding structure between adjacent battery cells.

[0108] Optionally, the tackifying resin includes one or more of rosin, petroleum resin, terpene resin, and thermoplastic phenolic resin. Further optionally, the rosin includes one or more of rosin 135 and rosin 145. The petroleum resin includes one or more of C5 petroleum resin and C9 petroleum resin.

[0109] In some embodiments, the tackifying resin comprises 15% to 30% by weight of rosin and 5% to 10% by weight of petroleum resin, based on the mass percentage of the thermoplastic elastomer. Alternatively, the mass percentage of rosin can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or any value within any range consisting of the above values. The mass percentage of petroleum resin can be 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or any value within any range consisting of the above values.

[0110] In some embodiments, the protective layer material further includes inorganic particles. The inorganic particle filler can provide support for the protective layer, ensuring that the protective layer has good strength while maintaining good resilience, reducing the risk of excessive deformation of the protective layer when squeezed, and facilitating a relatively stable bonding structure between adjacent battery cells.

[0111] In some embodiments, the inorganic particles include one or more of inorganic particles having a dielectric constant of 5 or more, inorganic particles having the ability to transport active ions, and inorganic particles capable of electrochemical oxidation and reduction. Alternatively, the inorganic particles having a dielectric constant of 5 or more include one or more of strontium titanate, tin oxide, cerium oxide, magnesium oxide, nickel oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, aluminum oxide, titanium oxide, and silicon carbide. The inorganic particles having the ability to transport active ions include lithium phosphate, lithium titanium phosphate (Li x Ti y (PO4)3, 0<x<2, 0<y<3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0<x<2, 0<y<1, 0<z<3), (LiAlTiP) x O y Type glass (0<x<4, 0<y<13), lithium lanthanum titanate (Li x La y TiO3, 0<x<2, 0<y<3), lithium germanium thiophosphate (Li x Ge y P z S w , 0<x<4, 0<y<1, 0<z<1, 0<w<5), lithium nitride (Li x N y , 0<x<4, 0<y<2), SiS2 type glass (Li x Si y S z, 0<x<3, 0<y<2, 0<z<4) and P2S5 type glass (Li x P y S z , 0<x<3, 0<y<3, 0<z<7) or one or more of the following.

[0112] In some embodiments, the inorganic particles include one or more of calcium carbonate particles, talc particles, clay particles, white carbon black particles, silicon oxide particles, and silicon nitride particles.

[0113] In some embodiments, the inorganic particles include first particles and second particles, wherein the Dv50 of the first particles is greater than the Dv50 of the second particles. The larger Dv50 of the first particles can reinforce the protective layer, further improving the strength of the protective layer. The smaller Dv50 of the second particles can be more evenly dispersed in the protective layer, further enhancing the support effect of the protective layer. Optionally, the first particles include micronized calcium carbonate particles, and the second particles include nanoclay particles.

[0114] In some embodiments, the Dv50 of the first particles is 20 μm to 50 μm. Alternatively, the Dv50 of the first particles can be 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, or any value within any range thereof.

[0115] In some embodiments, the second particles have a Dv50 of 20 nm to 50 nm. Alternatively, the second particles have a Dv50 of 20 nm, 22 nm, 25 nm, 28 nm, 30 nm, 32 nm, 35 nm, 38 nm, 40 nm, 42 nm, 45 nm, 48 nm, 50 nm, or any value within any range thereof.

[0116] The Dv50 of particles is known in the art and represents the particle size at which the cumulative volume distribution percentage reaches 50%. Dv50 can be measured using methods known in the art. For example, it can be measured using a laser particle size analyzer (e.g., Malvern Master Size 3000) in accordance with standard GB / T 19077-2016.

[0117] In some embodiments, the mass ratio of the second particles to the first particles is 1:1-5:1. A mass ratio of the second particles to the first particles within this range can better match the second particles to the first particles, further substantially improving the strength of the protective layer. Alternatively, the mass ratio of the second particles to the first particles can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, or any value within any range consisting of these values.

[0118] In some embodiments, the mass percentage of the first particles is 3%-10% based on the mass percentage of the thermoplastic elastomer. This mass percentage of the first particles within this range allows the protective layer to have a suitable weight while providing good support, thereby helping the battery maintain a high energy density. Alternatively, the mass percentage of the first particles can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value within any range consisting of these values, based on the mass percentage of the thermoplastic elastomer.

[0119] In some embodiments, the mass percentage of the second particles is 10%-30% based on the mass percentage of the thermoplastic elastomer. The mass percentage of the second particles in this range can provide a relatively suitable weight of the protective layer while providing better support, which is beneficial for maintaining a high energy density of the battery. Alternatively, the mass percentage of the second particles can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% or any value within any range consisting of the above values ​​based on the mass percentage of the thermoplastic elastomer.

[0120] In some embodiments, the protective layer material also includes a wetting agent. This allows the various components of the protective layer to mix more evenly, improving the uniformity of the protective layer and further enhancing the bonding stability between adjacent battery cells. Optionally, the wetting agent includes one or more of polyethylene resin and polypropylene resin.

[0121] In some embodiments, the mass percentage of the wetting agent is 15%-25% based on the mass percentage of the thermoplastic elastomer. Alternatively, the mass percentage of the wetting agent is 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or any value within any range thereof, based on the mass percentage of the thermoplastic elastomer.

[0122] In some embodiments, the material of the protective layer further includes a plasticizer. The introduction of the plasticizer can enable the protective layer to maintain good flexibility and compression resilience, and can further enhance the adhesion of the protective layer. Optionally, the plasticizer includes one or more of phthalates, aliphatic dibasic acid esters, phosphate esters, polyol esters, epoxidized oils, stearates, citrates, and alkylbenzenes. Further optionally, the plasticizer includes one or more of dibutyl phthalate (DBP) and dioctyl phthalate (DOP).

[0123] In some embodiments, the mass percentage of the plasticizer is 0.1%-0.5% based on the mass percentage of the thermoplastic elastomer. Alternatively, the mass percentage of the plasticizer is 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, or any value within any range thereof, based on the mass percentage of the thermoplastic elastomer.

[0124] In some embodiments, the material of the protective layer further includes an antioxidant. The antioxidant can improve the stability of the protective layer during the hot melt process, helping to promote the stable formation of the protective layer. Optionally, the antioxidant includes one or more of a phenolic antioxidant, an amine antioxidant, a phosphite antioxidant, and a thioether antioxidant. Further optionally, the antioxidant includes one or more of 2,6-di-tert-butyl-p-cresol and 4,4'-bis(6-tert-butyl-m-phenol) sulfide.

[0125] In some embodiments, the antioxidant is present in an amount of 0.1% to 1% by weight of the thermoplastic elastomer. Alternatively, the antioxidant is present in an amount of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% by weight of the thermoplastic elastomer, or any value within any range thereof.

[0126] In some embodiments, the protective layer comprises a styrene-based thermoplastic elastomer, a tackifying resin, inorganic particles, a wetting agent, a plasticizer, and an antioxidant. The inorganic particles include first particles and second particles, with the Dv50 of the first particles being greater than the Dv50 of the second particles. The first particles comprise 3% to 10% by weight of the thermoplastic elastomer, and the second particles comprise 10% to 30% by weight of the thermoplastic elastomer. The tackifying resin comprises 15% to 30% by weight of rosin and 5% to 10% by weight of petroleum resin, based on the mass percentage of the styrene-based thermoplastic elastomer. The wetting agent comprises 15% to 25% by weight of the thermoplastic elastomer. The plasticizer comprises 0.1% to 0.5% by weight of the thermoplastic elastomer. The antioxidant comprises 0.1% to 1% by weight of the thermoplastic elastomer.

[0127] Another embodiment of the present application provides a method for preparing a battery. The method includes the following steps: arranging a plurality of battery cells along a first direction and providing a protective layer between two adjacent battery cells to form a battery unit; the battery cell having a first surface parallel to the first direction and a second surface parallel to a second direction, the second direction intersecting the first direction, the second surface connected to the first surface, and the area of ​​the second surface being greater than or equal to the area of ​​the first surface; the protective layer being located between the opposing second surfaces of the two adjacent battery cells; and connecting the housing to the battery unit via an adhesive layer, with the protective layer used to isolate the adhesive layer from extending to the center area of ​​the second surface.

[0128] In some embodiments, providing the protective layer includes the following steps: applying a protective layer material to a surface of a battery cell, covering another battery cell on the surface of the protective layer material, and shaping the protective layer material to form the protective layer.

[0129] Optionally, applying the protective layer material includes applying the protective layer material to an edge of a surface of the battery cell to form a ring-shaped protective layer material.

[0130] Furthermore, optionally, the starting point and end point for applying the protective layer material are located on the same side of the battery cell surface, with a gap between them. This facilitates control over the starting and end points for applying the protective layer material. Furthermore, when the starting and end points for applying the protective layer material are located on the same side of the battery cell surface, this helps maintain a relatively single casting direction during the casting process, improving the regularity of the protective layer. Furthermore, the gap between the starting and end points reduces the risk of stringing caused by interference between the protective layer material and the starting point, thereby improving the regularity of the protective layer.

[0131] The protective layer material can be flexibly transferred to the edge of the surface of the battery cell to form an annular protective layer material. After the material is solidified, a protective layer with a hollow structure can be formed, and the hollow area of ​​the protective layer can provide a buffer for the volume expansion of the battery cell, thereby improving the cycle performance of the battery cell. In the process of applying the protective layer material, it is difficult for the application starting point and application end point of the protective layer material to form an ideal connection interface. For example, when the application starting point and application end point of the protective layer material are directly connected, it is necessary to form a certain overlap between the application end point and the application starting point, which will result in an excessive amount of protective layer material applied at the connection position, making the thickness of the protective layer at the connection position greater than other places, thereby causing the protective layer to form a bulge at the connection. The presence of this bulge will increase the force on the battery cell at this location, increase the risk of abnormal extrusion of the battery cell, and thus lead to a decrease in the cycle performance of the battery. In this embodiment, there is a gap between the application starting point and the application end point of the protective layer material. After covering another battery cell, the application starting point and the application end point of the protective layer material are connected through the casting effect. In this way, the protective layer material can form a hollow structure while reducing the risk of bulges in the protective layer, thereby reducing the risk of abnormal squeezing of the battery cell, which is conducive to promoting the maintenance of battery cycle performance.

[0132] In some embodiments, the gap between the application start point and the application end point is less than or equal to 10 mm. For example, the gap between the application start point and the application end point can be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, or any value within any range of these values. Alternatively, the distance between the application start point and the application end point can be determined based on the device for applying the protective layer material. For example, if the protective layer material application device is a dispensing head, the distance between the application start point and the application end point is the wall thickness of the dispensing head.

[0133] In some embodiments, the temperature when applying the protective layer material is 140°C-240°C. This temperature range allows the protective layer material to fully melt, facilitating its application. Furthermore, within this temperature range, the protective layer material is not easily oxidized, allowing the protective layer material to maintain relatively stable properties. Alternatively, the temperature when applying the protective layer material can be 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, or any value within any range thereof.

[0134] In some embodiments, after applying the protective layer material, the protective layer material is cured for 5 to 10 seconds. A curing time within this range is beneficial for obtaining a protective layer with a regular morphology. Alternatively, the curing time of the protective layer material can be any value within any range consisting of 5, 6, 7, 8, 9, or 10 seconds.

[0135] The setting time of the protective layer material can be tested by the following method: after the protective layer material is extruded from the dispensing head, lightly press the surface with a metal sheet every 1 second to observe whether there is any wire drawing, and record the shortest time that the protective layer material remains set.

[0136] In some embodiments, the protective layer is defined as the protective layer in the battery described above.

[0137] In some embodiments, when preparing a battery, the protective layer material is defined as the protective layer material in the battery described above.

[0138] In the traditional battery cell manufacturing process, four rubber strips are usually attached to the four sides of the battery cell, leaving a certain gap between adjacent strips, such as a gap of 2.5mm. Bond another battery cell to the strip. Multiple battery cells are bonded in the same way to obtain a battery cell, and then the battery cell is placed in a box and injected with adhesive. In this way, the adhesive will seep into the gaps between the battery cells through the gaps in the rubber strips, and the adhesive layer formed after curing will produce stress concentration, affecting the infiltration of the electrolyte inside the battery cell into the electrode assembly. In the present application, the protective layer can better separate the battery cell and the adhesive layer, so that the adhesive will not enter between the battery cells, thereby reducing the impact of the stress concentration generated after the adhesive is cured on the battery cell, and thus improving the cycle performance of the battery.

[0139] Another embodiment of the present application provides a protective layer material. The protective layer material is defined as the protective layer material in the battery described above and will not be further described here.

[0140] Another embodiment of the present application provides a protective layer. The protective layer is defined as the protective layer in the battery described above and will not be further described here.

[0141] Another embodiment of the present application provides an electrical device comprising the above-mentioned battery.

[0142] The battery and the electrical device of the present application will be described below with reference to the accompanying drawings as appropriate.

[0143] Typically, a battery cell consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0144] Positive electrode

[0145] The positive electrode sheet includes a positive electrode current collector and a positive electrode active layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active layer includes a positive electrode active material.

[0146] As a non-limiting example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active layer is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0147] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0148] In some embodiments, the positive electrode active material may be a positive electrode active material for a battery that is well known in the art. As a non-limiting example, the positive electrode active material may include one or more of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide (such as LiCoO2), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Non-limiting examples of olivine-structured lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.8 Co 0.15 Al 0.05 O2.

[0149] In some embodiments, the positive electrode active layer may further optionally include a binder. As non-limiting examples, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0150] In some embodiments, the positive electrode active layer may further include a conductive agent. As non-limiting examples, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0151] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on at least one side of the positive electrode current collector, and after drying, cold pressing, and other processes, the positive electrode sheet can be obtained. The type of solvent can be selected from but not limited to any of the aforementioned embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be on a single surface of the positive electrode current collector or on both surfaces of the positive electrode current collector. The surface of the positive electrode current collector coated with the positive electrode slurry can be on a single surface of the positive electrode current collector or on both surfaces of the positive electrode current collector.

[0152] Negative electrode

[0153] The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active layer includes a negative electrode active material.

[0154] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0155] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0156] In some embodiments, the negative electrode active material may adopt negative electrode active materials for batteries that are well known in the art. As non-limiting examples, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0157] In some embodiments, the negative electrode active layer may further optionally include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0158] In some embodiments, the negative electrode active layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0159] In some embodiments, the negative electrode active layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0160] In some embodiments, the negative electrode sheet can be prepared by dispersing the aforementioned components for preparing the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry on at least one side of a negative electrode current collector, and performing drying, cold pressing, and other processes to obtain the negative electrode sheet. The negative electrode current collector surface coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector.

[0161] electrolytes

[0162] The electrolyte conducts ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0163] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0164] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorodioxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0165] In some embodiments, the solvent may include ethylene carbonate (EC, ), propylene carbonate (PC, ), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate One or more of fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0166] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0167] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), and the like.

[0168] Isolation film

[0169] In some embodiments, the battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0170] In some embodiments, the material of the separator can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0171] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0172] In some embodiments, the housing of the battery cell may be used to accommodate the electrode assembly and the electrolyte.

[0173] In some embodiments, a battery includes at least one battery cell. A battery may include one or more battery cells.

[0174] In some embodiments, the battery may be a battery module or a battery pack.

[0175] A battery module includes at least one battery cell. The number of battery cells contained in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0176] In a battery module, multiple battery cells can be arranged in sequence along the length of the battery module. Of course, they can also be arranged in any other manner. Further, the multiple battery cells can be fixed by fasteners.

[0177] Optionally, the battery module may further include a housing having an accommodation space, wherein the plurality of battery cells are accommodated in the accommodation space.

[0178] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select an appropriate number based on the application and capacity of the battery pack.

[0179] A battery pack may include a battery box and multiple battery modules disposed within the box. The battery box comprises an upper case and a lower case. The upper case can be placed over the lower case to form an enclosed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0180] In addition, the present application also provides an electrical device, which includes the battery provided in the present application. The battery can serve as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc. Among them, mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0181] As an electrical device, a battery can be selected according to its usage requirements.

[0182] Figure 6 shows an example of an electric device 3. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0183] Another example device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0184] In order to make the technical problems, technical solutions and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0185] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0186] Example 1

[0187] In this embodiment, the method for preparing a battery cell includes the following steps:

[0188] (1) Preparation of positive electrode sheet

[0189] The cathode active material, lithium iron phosphate (LiFePO4), the conductive agent Super P, and the binder PVDF are mixed in a weight ratio of 97:1:2 and dissolved in the solvent N-methylpyrrolidone (NMP) to form the cathode slurry. The cathode slurry is then coated on the current collector aluminum foil, dried, and then cold pressed, trimmed, cut, and slit to obtain the cathode sheet.

[0190] (2) Preparation of negative electrode sheet

[0191] Graphite, carbon black (a conductive agent), sodium carboxymethyl cellulose (a thickener), and styrene-butadiene rubber (a binder) are mixed in a weight ratio of 96:1:1.2:1.8 and dissolved in deionized water to create a negative electrode slurry. This is then stirred in a vacuum mixer to create the negative electrode slurry. The negative electrode slurry is then coated onto the current collector copper foil. After drying, the negative electrode sheet is cold pressed, trimmed, cut, and slit.

[0192] (3) Isolation film

[0193] Polypropylene film was used as the separator.

[0194] (4) Preparation of electrolyte

[0195] In an argon atmosphere glove box with a water content of <10 ppm, diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) were mixed in a weight ratio of 1:1:1 to create an organic solvent. LiPF6 was then dissolved in the organic solvent to a LiPF6 concentration of 1.0 mol / L, followed by the addition of vinylene carbonate (VC) to a concentration of 2% of the total electrolyte mass.

[0196] (5) Preparation of battery cells

[0197] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrodes to provide insulation. The electrodes are then wound to form an electrode assembly. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum packaging, resting, forming, and shaping, a battery cell is obtained.

[0198] In this embodiment, the method for preparing the battery includes the following steps:

[0199] The protective layer material is extruded onto the front edge of the battery cell, with the starting and ending points of the protective layer on the same side of the battery cell. Another battery cell is placed on the surface of the protective layer material, and the curing of the protective layer material bonds the adjacent battery cells together. The battery cell is then placed into the casing and the adhesive is injected. The protective layer material comprises: SBS and SIS in a mass ratio of 2:8. The particle size of the calcium carbonate particles is 35 nm. The particle size of the clay particles is 35 μm. As a percentage of the total mass of the SBS and SIS, the mass percentage of the calcium carbonate particles is 15%, and the mass ratio of the calcium carbonate particles to the clay particles is 5:1. As a percentage of the total mass of the SBS and SIS, the mass percentage of 145 rosin is 15%, and the mass ratio of 145 rosin to C5-C9 copolymerized petroleum resin is 3:1. As a percentage of the total mass of the SBS and SIS, the mass percentage of the polypropylene resin is 22.5%. As a percentage of the total mass of the SBS and SIS, the mass percentage of DOP is 0.4%. Calculated as a percentage of the total mass of SBS and SIS, the mass percentage of 2,6-di-tert-butyl-p-cresol is 0.6%.

[0200] Example 2-9: Compared with Example 1, the difference between Example 2-9 is that the material of the protective layer is different. The material of the protective layer is shown in Table 1.

[0201] Comparative Example 1

[0202] The battery manufacturing method in this comparative example includes the following steps: attaching four rubber strips to the four edges of a battery cell, with a gap of 2.5 mm between the strips. Bonding another battery cell to the rubber strips. Placing the battery cell into a box and injecting encapsulating adhesive.

[0203] Test Case

[0204] (1) The adhesion strength, rebound rate, and compression modulus of the adhesive layer between adjacent battery cells in each embodiment were tested, and the results are shown in Table 1. The test methods used were the test methods corresponding to the adhesion strength, rebound rate, and compression modulus described above.

[0205] Table 1

[0206] In Table 1, SBS / SIS represents the mass ratio of SBS to SIS. Polypropylene resin represents the mass percentage of polypropylene resin to the total mass of SBS and SIS. Calcium carbonate / clay represents the mass ratio of calcium carbonate particles to clay particles. The unit of bond strength is MPa. The unit of compression modulus is MPa.

[0207] It can be seen from Examples 1-4 that when the SBS / SIS ratio in the protective layer material is within an appropriate range, the protective layer has a higher rebound rate.

[0208] It can be seen from Examples 1 and 5-6 that when the mass percentage of the polypropylene resin in the protective layer material is within an appropriate range, the protective layer has better bonding strength.

[0209] It can be seen from Examples 1 and 7-9 that when the calcium carbonate / clay ratio in the protective layer material is within an appropriate range, the protective layer has a higher compression modulus.

[0210] (2) The cycle performance of the batteries of Example 1 and Comparative Example 1 was tested. The test method is as follows: the oven temperature is adjusted to 25°C, the battery is placed in the oven and allowed to stand for 60 minutes, and then charged to 3.65V at a constant current of 0.5C, then charged at a constant voltage of 3.65V with a cut-off current of 0.05C (100% SOC), then allowed to stand for 10 minutes, and discharged to 2.5V at 0.2C. The discharge capacity of this step is recorded as C0, and allowed to stand for 10 minutes; the battery is placed in a 25°C oven and allowed to stand for 60 minutes, and then charged to 3.65V at a constant current of 2C, then charged at a constant voltage of 3.65V with a cut-off current of 0.05C (100% SOC), then allowed to stand for 10 minutes, and discharged to 2.5V at 0.5C. The discharge capacity of this step is recorded as Cn. This is one charge-discharge cycle, and the capacity retention rate of the battery = Cn / C0*100%. The battery is charged and discharged according to this method, and the capacity retention rate is tested after 1000 charge-discharge cycles. Among them, the capacity retention rate of the battery in Example 1 after 1000 cycles is 90.2%, and the capacity retention rate of the battery in Comparative Example 1 after 1000 cycles is 83.7%, indicating that the provision of the protective layer in the battery of Example 1 can improve the battery and maintain good cycle performance.

[0211] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0212] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A battery, characterized in that: include: A battery unit, the battery unit comprising a plurality of battery cells arranged along a first direction, the battery cells having a first surface parallel to the first direction and a second surface parallel to a second direction, the second direction intersecting with the first direction, the second surface connected with the first surface, and an area of ​​the second surface being greater than or equal to an area of ​​the first surface; A box body, the box body is used to accommodate the battery unit; an adhesive layer, the adhesive layer being located between the box and the battery cell to connect the box and the battery cell; A protection layer is located between the second surfaces of two adjacent battery cells and is used to isolate the adhesive layer from extending to the center area of ​​the second surface. 2 . The battery according to claim 1 , wherein the protective layer covers at least a central area of ​​the second surfaces between two adjacent second surfaces of the battery cells.

3. The battery according to claim 2, characterized in that The distance between the protective layer and the outer edge of the battery cell is less than or equal to 15 mm.

4. The battery according to claim 2 or 3, characterized in that: The protective layer covers the entire second surface.

5. The battery according to claim 1, characterized in that Between the second surfaces of two adjacent battery cells, the edge of the protective layer is arranged around the edge of the second surface to form a closed structure, the closed structure is surrounded to form a hollow area, and the central area of ​​the battery cell is located in the hollow area.

6. The battery according to claim 5, characterized in that The width of the closed structure is 1 mm-15 mm.

7. The battery according to claim 5 or 6, characterized in that: The distance between the edge of the hollow area and the outer edge of the battery cell is 1 mm-15 mm.

8. The battery according to claim 7, characterized in that The second surface includes a first edge, a second edge, a third edge and a fourth edge connected in sequence end to end; the first edge is configured as an outer side surface of the opening of the battery cell, and the third edge is arranged opposite to the first edge; at the first edge, the distance between the edge of the hollow area and the outer edge of the battery cell is 1mm-10mm.

9. The battery according to claim 8, characterized in that At the second edge, the distance between the edge of the hollow area and the outer edge of the battery cell is 1 mm-15 mm; and / or, At the third edge, the distance between the edge of the hollow area and the outer edge of the battery cell is 1 mm-10 mm; and / or, At the fourth edge, the distance between the edge of the hollow area and the outer edge of the battery cell is 1 mm-15 mm.

10. The battery according to any one of claims 1 to 9, characterized in that The thickness of the protective layer is 0.5 mm to 10 mm.

11. The battery according to any one of claims 1 to 10, characterized in that The resilience of the protective layer is 50% to 100%.

12. The battery according to any one of claims 1 to 11, characterized in that The resilience of the protective layer is 95%-98%.

13. The battery according to any one of claims 1 to 12, characterized in that The compression modulus of the protective layer is 1 MPa-10 MPa.

14. The battery according to any one of claims 1 to 13, characterized in that The bonding strength between the protective layer and the battery cell is 0.1 MPa-2.2 MPa.

15. The battery according to any one of claims 1 to 14, characterized in that The material of the protective layer includes thermoplastic elastomer.

16. The battery according to claim 15, characterized in that The thermoplastic elastomer includes a linear polymer.

17. The battery according to claim 15 or 16, characterized in that: The melting temperature of the thermoplastic elastomer is 140°C-240°C.

18. The battery according to any one of claims 15 to 17, characterized in that: The thermoplastic elastomer includes one or more of styrene-based thermoplastic elastomer, olefin-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polyester-based thermoplastic elastomer and polyamide-based thermoplastic elastomer.

19. The battery according to claim 18, characterized in that The styrene-based thermoplastic elastomer includes one or more of styrene-butadiene-styrene triblock copolymer, hydrogenated styrene-butadiene-styrene triblock copolymer, styrene-isoprene-styrene triblock copolymer and hydrogenated styrene-isoprene-styrene triblock copolymer.

20. The battery according to claim 18 or 19, characterized in that The styrene-based thermoplastic elastomer includes a styrene-butadiene-styrene triblock copolymer and a styrene-isoprene-styrene triblock copolymer, and the mass ratio of the styrene-butadiene-styrene triblock copolymer to the styrene-isoprene-styrene triblock copolymer is 3:7-1:

9.

21. The battery according to any one of claims 15 to 20, characterized in that The material of the protective layer also includes a tackifying resin.

22. The battery according to claim 21, characterized in that Calculated by mass percentage of the thermoplastic elastomer, the tackifying resin includes 15%-30% by mass of rosin and 5%-10% by mass of petroleum resin.

23. The battery according to any one of claims 15 to 22, characterized in that The material of the protective layer also includes inorganic particles.

24. The battery according to claim 23, characterized in that The inorganic particles include one or more of inorganic particles having a dielectric constant of 5 or more, inorganic particles capable of transporting active ions, and inorganic particles capable of electrochemical oxidation and reduction.

25. The battery according to any one of claims 23-24, characterized in that The inorganic particles include first particles and second particles, and Dv50 of the first particles is greater than Dv50 of the second particles.

26. The battery according to claim 25, characterized in that The inorganic particles meet one or more of the following characteristics: (1) The Dv50 of the first particles is 20 μm-50 μm; (2) the Dv50 of the second particles is 20 nm to 50 nm; (3) The mass ratio of the second particles to the first particles is 1:1-5:1; (4) the mass percentage of the first particles is 3% to 10% based on the mass percentage of the thermoplastic elastomer; (5) The mass percentage of the second particles is 10%-30% based on the mass percentage of the thermoplastic elastomer.

27. The battery according to any one of claims 15 to 26, characterized in that The material of the protective layer also includes a wetting agent.

28. The battery according to claim 27, characterized in that The wetting agent meets one or more of the following characteristics: (1) The wetting agent includes one or more of polyethylene resin and polypropylene resin; (2) The mass percentage of the wetting agent in terms of the mass percentage of the thermoplastic elastomer is: 15％-25％。 29. The battery according to any one of claims 15 to 28, characterized in that The material of the protective layer includes styrene-based thermoplastic elastomer, tackifying resin, inorganic particles, wetting agent, plasticizer and antioxidant; The inorganic particles include first particles and second particles, the Dv50 of the first particles is greater than the Dv50 of the second particles; the mass percentage of the first particles is 3%-10% based on the mass percentage of the thermoplastic elastomer, and the mass percentage of the second particles is 10%-30% based on the mass percentage of the thermoplastic elastomer; The tackifying resin comprises 15% to 30% by mass of rosin and 5% to 10% by mass of petroleum resin, based on the mass percentage of the styrene-based thermoplastic elastomer; The mass percentage of the wetting agent is 15%-25% based on the mass percentage of the thermoplastic elastomer; The mass percentage of the plasticizer is 0.1%-0.5% based on the mass percentage of the thermoplastic elastomer; Calculated by the mass percentage of the thermoplastic elastomer, the mass percentage of the antioxidant is 0.1%-1%.

30. A method for preparing a battery, characterized in that: The steps include: Arrange a plurality of battery cells along a first direction, and provide a protective layer between two adjacent battery cells to form a battery unit; the battery cell has a first surface parallel to the first direction and a second surface parallel to a second direction, the second direction intersects with the first direction, the second surface is connected to the first surface, and the area of ​​the second surface is greater than or equal to the area of ​​the first surface; The protective layer is located between the second surfaces opposite to each other of two adjacent battery cells; The box body is connected to the battery unit through an adhesive layer, and the protective layer is used to isolate the adhesive layer extending to the central area of ​​the second surface.

31. The method for preparing a battery according to claim 30, characterized in that: The provision of the protective layer comprises the following steps: A protective layer material is applied to the surface of the battery cell, another battery cell is covered on the surface of the protective layer material, and the protective layer material is shaped to form the protective layer.

32. The method for preparing a battery according to claim 31, characterized in that: The application of the protective layer material comprises the following steps: The protective layer material is applied to the edge of the surface of the battery cell to form a ring-shaped protective layer material.

33. The method for preparing a battery according to claim 32, characterized in that: The application starting point and the application end point of the protective layer material are located on the same side of the surface of the battery cell, and there is a gap between the application starting point and the application end point.

34. The method for preparing a battery according to claim 33, characterized in that: The gap between the application starting point and the application end point is less than or equal to 10 mm.

35. The method for preparing a battery according to any one of claims 30 to 34, characterized in that: The protective layer defines the protective layer in the battery according to any one of claims 1-29.

36. A protective layer, characterized in that: It defines the protective layer in the battery according to any one of claims 10-29.

37. An electrical device, characterized in that: A battery comprising the battery of any one of claims 1-29.

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