Battery monomer and preparation method thereof, battery device and power utilization device

Abstract

The invention is suitable for the technical field of batteries, and provides a battery monomer, a preparation method thereof, a battery device and a power utilization device. The battery monomer comprises an electrode assembly, and the electrode assembly comprises a positive pole piece, a negative pole piece, a diaphragm and a porous insulating layer; the positive pole piece, the diaphragm and the negative pole piece are stacked and wound; at least part of the porous insulating layer is arranged in the bending area of the electrode assembly, and the porous insulating layer is arranged between the positive pole piece and the diaphragm and / or between the negative pole piece and the diaphragm; the porous insulating layer comprises a base body layer and a reinforcing layer arranged on the base body layer. According to the battery monomer and the preparation method thereof, the battery device and the power utilization device provided by the invention, the internal short circuit risk of the battery monomer can be reduced.

Description

Technical Field

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

[0002] At least one electrode assembly is usually arranged inside a battery cell. The electrode assembly can be processed into a roll structure by winding a positive electrode sheet, a negative electrode sheet, and a separator separating the positive electrode sheet and the negative electrode sheet. The electrode assembly has a main body area and a bending area arranged at the end side of the main body area. However, during the use of the battery cell, the bending area of ​​the electrode assembly is prone to metal precipitation. As time goes by, dendrites are prone to grow in the bending area. The dendrites are prone to cause internal short circuits in the battery cell, affecting the safety of the battery cell. Summary of the invention

[0003] In view of the above problems, the present application provides a battery cell and a preparation method thereof, a battery device and an electrical device, aiming to reduce the risk of internal short circuit of the battery cell.

[0004] In a first aspect, an embodiment of the present application provides a battery cell, the battery cell includes an electrode assembly, the electrode assembly includes a positive electrode sheet, a negative electrode sheet, a separator and a porous insulating layer; the positive electrode sheet, the separator and the negative electrode sheet are stacked and wound; at least a portion of the porous insulating layer is arranged in a bending area of ​​the electrode assembly, and is arranged between the positive electrode sheet and the separator and / or between the negative electrode sheet and the separator; the porous insulating layer includes a base layer and a reinforcement layer arranged on the base layer.

[0005] The battery cell provided in the embodiment of the present application has a porous insulating layer arranged between the positive electrode plate and the diaphragm, or between the negative electrode plate and the diaphragm, and the porous insulating layer includes a base layer and a reinforcement layer. By reasonably selecting the material and setting method of the base layer, as well as the material and setting method of the reinforcement layer, the porous insulating layer is not prone to cracks, splitting, curling and other problems when the electrode assembly is being shaped, so that the porous insulating layer has better performance and can block dendrites on the side away from the positive electrode plate or the negative electrode plate, so that the dendrites are always spaced apart from the positive electrode plate or the negative electrode plate, so that the dendrites cannot contact the positive electrode plate and the negative electrode plate at the same time, thereby reducing the risk of internal short circuit in the battery cell to a certain extent, improving the protection against lithium plating in the bending zone, and improving the safety of the battery cell.

[0006] In some embodiments, the pores of the porous insulating layer have a pore size of [0.03 μm, 1 μm]. By adopting the above scheme, on the one hand, the air permeability of the porous insulating layer can be ensured to be moderate, and the reactants can be ensured to freely and normally penetrate the pores of the porous insulating layer. On the other hand, during the use of the battery cell, the porous insulating layer can be guaranteed to have a barrier effect on dendrites growing from defects in the diaphragm, and the risk of dendrites growing from the pores of the porous insulating layer can be reduced, thereby correspondingly extending the service life of the battery cell and correspondingly improving the safety of the battery cell.

[0007] In some embodiments, the porosity of the porous insulating layer is [35%, 55%]. The porosity of the porous insulating layer is 35% to 55%, which allows the reactants to pass through quickly, thereby reducing the adverse effect of the porous insulating layer on the electrochemical reaction rate in the battery cell.

[0008] In some embodiments, the air permeability value of the porous insulating layer is less than or equal to 350s / 100cc. The air permeability value of the porous insulating layer is less than or equal to 350s / 100cc. A smaller air permeability value indicates that the porous insulating layer has better air permeability, which allows the reaction substances to pass smoothly and quickly, and the electrochemical reaction rate in the battery cell is less adversely affected by the setting of the porous insulating layer.

[0009] In some embodiments, the material of the substrate layer includes polyethylene. The substrate layer is made of a material including polyethylene, which has good toughness, so that the porous insulating layer is not easily pierced by dendrites, so that the dendrites cannot contact the positive electrode sheet and the negative electrode sheet at the same time, thereby reducing the risk of internal short circuit of the battery cell to a certain extent.

[0010] In some embodiments, the material of the reinforcement layer includes at least one of polyimide fiber, para-aramid fiber, meta-aramid fiber, polyacrylonitrile fiber and ceramic. The reinforcement layer adopts the solution provided in this embodiment, so that the reinforcement layer has good resistance to heat shrinkage and resistance to thermoplastic deformation. When the material of the base layer is polyethylene, the reinforcement layer adopts the solution provided in this embodiment, so that the porous insulating layer has high tensile strength, elongation at break and impact strength, does not crack during the hot pressing process of the bare battery cell (Jelly Roll, JR), and has good resistance to heat shrinkage and resistance to thermoplastic deformation, and is not prone to curling and other problems.

[0011] In some embodiments, the reinforcement layer is arranged in the base layer or on the side of the base layer close to the diaphragm or on the side of the base layer close to the pole piece. As mentioned above, in some embodiments, the heat resistance of the base layer is poor, and the heat resistance of the reinforcement layer is good. In this way, the solution provided by this embodiment, whether the reinforcement layer is arranged in the base layer, or on the side of the base layer close to the diaphragm, or on the side of the base layer close to the pole piece, can improve the heat resistance of the porous insulating layer to a certain extent, reduce the risk of curling and other problems during use, and facilitate preparation.

[0012] In some embodiments, the porous insulating layer further includes a hot melt adhesive layer, which is located on the side of the combined structure of the base layer and the reinforcement layer facing the pole piece, and the combined structure is bonded to the pole piece through the hot melt adhesive layer. The combined structure of the base layer and the reinforcement layer is bonded to the positive pole piece or the negative pole piece through the hot melt adhesive layer. Compared with bonding with ordinary adhesive layers, the hot melt adhesive layer can withstand high temperatures, so that when the electrode assembly is formed by hot pressing, the adhesive layer between the base layer and the pole piece is not easy to melt, so that it will not overflow to other areas of the electrode assembly, and it is not easy to cause bonding between the pole piece and the diaphragm, as well as blocking of the embedded ion channel on the positive pole piece or the negative pole piece, which helps the normal operation of the electrode assembly.

[0013] In some embodiments, the hot melt adhesive layer is formed by heating and curing hot melt adhesive particles. The hot melt adhesive layer is formed by heating and curing hot melt adhesive particles, which can make the surface area of ​​the hot melt adhesive layer relatively large, absorb heat faster when heated, accelerate the melting process, shorten the heating time, and at the same time, the setting of the hot melt adhesive particles can achieve accurate measurement, reduce excess adhesive waste, and reduce production costs.

[0014] In some embodiments, the softening temperature of the hot melt adhesive particles is [110°C, 150°C]. Since the electrode assembly is different according to the material, the hot pressing temperature during the shaping of the electrode assembly is also different, such as the hot pressing temperature of lithium-ion batteries is 80°C to 120°C, and the hot pressing temperature of lithium iron phosphate batteries is 80°C to 110°C. The softening temperature of the hot melt adhesive particles is [110°C, 150°C]. During design, the composition of the material of the hot melt adhesive particles can be adjusted according to the material of the specific electrode assembly, so that the softening temperature of the hot melt adhesive particles is higher than the hot pressing temperature during the shaping of the electrode assembly. In this way, when used, the hot melt adhesive layer is not easy to soften when the electrode assembly is shaped, so that it is not easy to overflow to other areas of the electrode assembly, and it is not easy to cause the adhesion of the electrode sheet and the diaphragm, as well as the blocking of the embedded ion channel on the positive electrode sheet or the negative electrode sheet, which is conducive to the normal operation of the electrode assembly.

[0015] In some embodiments, the particle size of the hot melt adhesive particles is [0.4 μm, 0.7 μm]. The particle size of the hot melt adhesive particles is [0.4 μm, 0.7 μm], which is small in size and has high fluidity after melting, and is easier to be evenly distributed on the surface to be bonded, which helps to improve the uniformity and reliability of bonding between the pole piece and the substrate layer.

[0016] In some embodiments, the material of the hot melt adhesive particles includes polyolefin resin. Polyolefin resin has many advantages such as good thermal stability, chemical stability, mechanical properties, wide range of adhesive properties, fast curing, environmental safety, easy processing, cost-effectiveness and customization possibilities. The material of the hot melt adhesive particles includes polyolefin resin, which is easy to process and has good thermal stability, chemical stability, mechanical properties, wide range of adhesive properties and other advantages.

[0017] In some embodiments, the material of the polyolefin resin includes at least one of polypropylene, polyethylene, polybutadiene rubber, ethylene-propylene acetate copolymer, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, maleic anhydride modified polyolefin, poly (butadiene-acrylonitrile), and styrene-maleic anhydride copolymer. The polyolefin resin in this embodiment can be composed of any of the above materials, or a mixture of multiple materials, which can be determined according to the needs of use. Regardless of which setting method is adopted, the polyolefin resin has good thermal stability and mechanical properties, which can make the structure of the hot melt adhesive layer stable and not easy to overflow, thereby reducing the risk of adhesion between the diaphragm and the pole piece and the diaphragm blocking the embedded ion channel on the pole piece.

[0018] In some embodiments, the material of the hot melt adhesive particles is maleic anhydride modified polypropylene. The material of the hot melt adhesive particles is maleic anhydride modified polypropylene, which can make the hot melt adhesive layer have a higher softening temperature and higher bonding strength.

[0019] In some embodiments, the thickness of the hot melt adhesive layer is less than or equal to 1 μm. Since the thickness of the positive electrode sheet is generally between 50 μm and 200 μm, and the thickness of the negative electrode sheet is generally between 50 μm and 150 μm, the thickness of the hot melt adhesive layer is less than or equal to 1 μm, which is relatively thin and much smaller than the thickness of the positive electrode sheet and the negative electrode sheet. In this way, the setting of the hot melt adhesive layer is not likely to have a significant impact on the spacing between the positive electrode sheet and the negative electrode sheet, so that the winding and electrochemical reaction of the electrode assembly are not easily adversely affected.

[0020] In some embodiments, the electrode assembly has a main body region and a bending region arranged at the end side of the main body region; the porous insulating layer has a bending section arranged in the bending region, and an extension section connected to the end of the bending section and arranged in the main body region.

[0021] By adopting the above solution, compared with the case where the porous insulating layer is only arranged in the bending area of ​​the electrode assembly, the coverage area of ​​the porous insulating layer can be increased, which can reduce the risk of internal short circuit in the battery cell to a certain extent, and at the same time reduce the risk of displacement of the porous insulating layer during the use of the battery cell.

[0022] In some embodiments, in the bending area, at least the innermost circle of the positive electrode sheet is provided with a porous insulating layer. By adopting the above scheme, a porous insulating layer is provided at least on the curved portion of the inner side and / or outer side of the innermost circle of the positive electrode sheet. On the one hand, the dendrites grown from the curved portion of the innermost circle of the negative electrode sheet can be insulated to prevent the dendrites from connecting the positive electrode sheet and the negative electrode sheet, thereby reducing the risk of internal short circuit of the battery cell to a certain extent between the innermost circle of the positive electrode sheet and the innermost circle of the negative electrode sheet where metal precipitation is easy to occur, thereby correspondingly extending the service life of the battery cell and correspondingly improving the safety of the battery cell; on the other hand, the provision of the porous insulating layer can provide insulation for the curved portion of the innermost circle of the positive electrode sheet. The extrusion stress borne by the curved part can be buffered to reduce the risk of a reduction in active material due to a tear defect in the curved part of the innermost circle of the positive electrode plate; the tensile stress borne by the curved part of the innermost circle of the negative electrode plate can even be buffered to reduce the risk of a reduction in active material due to a tear defect in the curved part of the innermost circle of the negative electrode plate, thereby effectively reducing the risk of aggravating metal precipitation due to the reduction in active material, and effectively alleviating the growth rate of dendrites between the innermost circle of the positive electrode plate and the innermost circle of the negative electrode plate, thereby correspondingly extending the service life of the battery cell and correspondingly improving the safety of the battery cell.

[0023] In some embodiments, the size of the porous insulating layer in the length direction of the positive electrode sheet is [10 mm, 24 mm]. Generally, the length of the bending area of ​​the innermost positive electrode sheet is less than 10 mm. The size of the porous insulating layer in the length direction of the positive electrode sheet is [10 mm, 24 mm], which can completely cover the bending area of ​​the innermost positive electrode sheet, reducing the risk of short circuit there.

[0024] In some embodiments, in the width direction of the positive electrode piece, at least one end of the porous insulating layer exceeds the target electrode piece, and the dimension of the target electrode piece is [3mm, 6mm], and the target electrode piece is the electrode piece connected to the porous insulating layer. In this way, the porous insulating layer can cover as large an area of ​​the target electrode piece as possible, so that the dendrite cannot contact the target electrode piece from at least one end of the target electrode piece in the width direction, which can further reduce the risk of internal short circuit of the battery cell.

[0025] In some embodiments, in the width direction of the positive electrode sheet, both ends of the porous insulating layer extend beyond the target electrode sheet, and the dimension extending beyond the target electrode sheet is [3 mm, 6 mm]. By adopting the solution provided in this embodiment, compared with the case where the porous insulating layer only extends beyond the target electrode sheet at one end in the width direction of the positive electrode sheet, the dendrites cannot contact the target electrode sheet from either end in the width direction of the target electrode sheet, and the risk of internal short circuit of the battery cell can be further reduced.

[0026] In some embodiments, the thickness of the porous insulating layer is [10 μm, 20 μm]. By adopting the above scheme, the thickness of the porous insulating layer can be ensured to be moderate, so as to reduce the adverse effects of the porous insulating layer on the energy density of the battery cell and the penetration rate of active ions through the porous insulating layer on the basis of ensuring that the porous insulating layer can form a better insulating barrier effect on the dendrites growing toward it, thereby ensuring the conductivity and the charge and discharge performance of the battery cell. At the same time, the extrusion stress borne by the curved portion of the innermost positive electrode sheet can be buffered to reduce the risk of tearing defects in the curved portion of the innermost positive electrode sheet leading to a reduction in active substances; even the tensile stress borne by the curved portion of the electrode sheet in the corresponding area during hot pressing and shaping of the electrode assembly can be buffered to reduce the risk of tearing defects in the corresponding electrode sheet leading to a reduction in active substances, that is, to reduce the risk of powdering and exposed metal layers in the corresponding electrode sheet, thereby effectively reducing the risk of metal precipitation due to the reduction of active substances, and correspondingly extending the service life of the battery cell and improving the safety of the battery cell.

[0027] In some embodiments, the thickness of the base layer is [7 μm, 16 μm]. The thickness of the base layer is [7 μm, 16 μm], which accounts for about half of the thickness of the insulating layer, or most of it. In this way, when the base layer is made of a material with better toughness such as polyethylene, the insulating layer has greater toughness and is not easily pierced by dendrites, which can reduce the risk of internal short circuits in battery cells.

[0028] In some embodiments, the thickness of the reinforcement layer is [3 μm, 8 μm]. The thickness of the reinforcement layer is [3 μm, 8 μm], which occupies about half or a small part of the thickness of the insulating layer, so that the reinforcement layer can have a reinforcement effect without affecting some excellent properties of the base layer, such as toughness, etc., so that the insulating layer can have the excellent properties of both the base layer and the reinforcement layer.

[0029] In a second aspect, an embodiment of the present application provides a battery device, which includes a battery cell provided by any of the above solutions.

[0030] In a third aspect, an embodiment of the present application provides an electrical device, comprising a battery device or a battery cell provided by any of the above solutions.

[0031] In a fourth aspect, an embodiment of the present application provides a method for preparing a battery cell, and the battery cell provided by any of the above solutions includes: Arranging a porous insulating layer on the positive electrode sheet and / or the negative electrode sheet; The positive electrode sheet, separator and negative electrode sheet are stacked and wound in a preset order.

[0032] The effects of the second to fourth aspects are the same as those of the first aspect and will not be repeated here.

[0033] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings: Figure 1 A schematic diagram of the structure of a vehicle provided in some embodiments of the present application; Figure 2 A schematic diagram of the exploded structure of a battery device provided in some embodiments of the present application; Figure 3 A schematic diagram of the exploded structure of a battery cell provided in some embodiments of the present application; Figure 4 A schematic diagram of the structure of an electrode assembly in a battery cell provided in some embodiments of the present application; Figure 5 A schematic cross-sectional view of a porous insulating layer in a battery cell provided in some embodiments of the present application; Figure 6 A schematic diagram of the local structure of a porous insulating layer in a battery cell provided in some embodiments of the present application before the hot-melt adhesive particles are heated; Figure 7 A schematic diagram of a partial structure of an electrode assembly in a battery cell provided in some embodiments of the present application; Figure 8 A schematic diagram of a partial structure of a combined structure of a positive electrode sheet and a porous insulating layer in a battery cell provided in some embodiments of the present application; Fig. 9 A schematic diagram of a partial structure of a combined structure of a positive electrode sheet and a porous insulating layer in a battery cell provided in some embodiments of the present application; Fig.10A photograph of the combined structure of the positive electrode sheet and the porous insulating layer after the battery cell provided by the embodiment of the present application has been used for a period of time; Fig.11 This is a photo of the negative electrode plate of the battery cell provided by the embodiment of the present application after being used for a period of time.

[0035] The reference numerals in the specific implementation manner are as follows: 1000. Vehicles; 100, battery device; 200, controller; 300, motor; 10. Box body; 11. First part; 12. Second part; 20. Battery cell; 21. End cover; 21a. Electrode terminal; 22. Shell; 23. Electrode assembly; 231. Positive electrode sheet; 232. Negative electrode sheet; 233. Diaphragm; 234. Porous insulating layer; 23a. Main body area; 23b. Bending area; 2341. Base layer; 2342. Reinforcement layer; 2343. Hot melt adhesive layer; 23431. Hot melt adhesive particles; 234a. Bending section; 234b. Extended section; d1, the thickness of the hot melt adhesive layer; d2, the thickness of the porous insulating layer; d3, the thickness of the base layer; d4, the thickness of the reinforcing layer; d5, the size of the porous insulating layer in the length direction of the positive electrode; d6, the size of one end of the porous insulating layer beyond the target electrode; d7, the size of the other end of the porous insulating layer beyond the target electrode; X, length direction; Y, width direction. DETAILED DESCRIPTION

[0036] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0038] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0039] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0040] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0041] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0042] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0043] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0044] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0045] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0046] The electrode assembly is an important component of the battery. According to the preparation method of the electrode assembly, it can be divided into a wound electrode assembly and a laminated electrode assembly. Among them, the wound electrode assembly is widely used because it is relatively simple to operate and easy to control the quality.

[0047] The wound electrode assembly generally includes a negative electrode sheet, a positive electrode sheet and a separator arranged in a preset order. The positive electrode sheet and the negative electrode sheet are generally composed of a current collector and an active material layer coated on the current collector. The wound electrode assembly can be a square structure or a cylindrical structure. Among them, the square wound electrode assembly is widely used due to its advantages such as good heat dissipation and good safety.

[0048] Lithium deposition refers to the phenomenon that during the charging process of lithium-ion batteries, lithium ions fail to be smoothly embedded in the negative electrode plate, but instead form metallic lithium deposition on the surface of the negative electrode plate. This phenomenon not only reduces the capacity and cycle life of the battery, but may also bring safety hazards such as internal short circuit and thermal runaway.

[0049] Lithium deposition inside the battery is one of the main factors affecting the battery's electrical and safety performance, especially for wound square-shell batteries, where the risk of lithium deposition in the bending area of ​​the electrode assembly is greater. Once lithium deposition occurs in the battery, it will not only reduce the battery's service life, but also, as the amount of lithium deposition accumulates, it is easy to form dendrites on the diaphragm. The dendrites may pierce the diaphragm, connect the positive and negative pole pieces, and cause a short circuit in the battery, posing a safety hazard.

[0050] In order to at least partially improve the above problems, an embodiment of the present application provides a battery cell. The battery cell is provided with a porous insulating layer between the positive electrode sheet and the separator, or between the negative electrode sheet and the separator, and the porous insulating layer includes a base layer and a reinforcement layer. By reasonably selecting the material and setting method of the base layer, and the material and setting method of the reinforcement layer, the porous insulating layer is not prone to cracks, splitting, curling and other problems when the electrode assembly is shaped, so that the porous insulating layer has better performance to block the dendrites on the side away from the positive electrode sheet or the negative electrode sheet, so that the dendrites are always spaced from the positive electrode sheet or the negative electrode sheet, so that the dendrites cannot contact the positive electrode sheet and the negative electrode sheet at the same time, and then the risk of internal short circuit in the battery cell can be reduced to a certain extent, the protection against lithium deposition in the bending zone is improved, and the safety of the battery cell is improved.

[0051] The battery cells disclosed in the embodiments of the present application can be used in battery devices, as well as power-consuming devices that use battery devices as power sources or various energy storage systems that use batteries as energy storage elements. Power-consuming devices may be, but are not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0052] For the convenience of description, the following embodiments are described by taking a vehicle 1000 as an example of an electrical device according to an embodiment of the present application.

[0053] Please refer to Figure 1 , Figure 1 A schematic diagram of the structure of a vehicle 1000 provided for some embodiments of the present application. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery device 100 is provided inside the vehicle 1000, and the battery device 100 may be provided at the bottom, head or tail of the vehicle 1000. The battery device 100 may be used to power the vehicle 1000, for example, the battery device 100 may be used as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery device 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0054] In some embodiments of the present application, the battery device 100 can not only serve as an operating power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0055] Please refer to Figure 2 , Figure 2Schematic diagram of the exploded structure of a battery device provided for some embodiments of the present application. The battery device 100 includes a box 10 and a battery cell 20, and the battery cell 20 is contained in the box 10. Among them, the box 10 is used to provide a storage space for the battery cell 20, and the box 10 can adopt a variety of structures. In some embodiments, the box 10 may include a first part 11 and a second part 12, and the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 jointly define a storage space for accommodating the battery cell 20. The second part 12 can be a hollow structure with one end open, and the first part 11 can be a plate-like structure, and the first part 11 covers the open side of the second part 12, so that the first part 11 and the second part 12 jointly define a storage space; the first part 11 and the second part 12 can also be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12. Of course, the box 10 formed by the first part 11 and the second part 12 can be in a variety of shapes, such as a cylinder, a cuboid, etc.

[0056] In some embodiments, the box 10 can be used as a part of the chassis structure of the vehicle. For example, part of the box 10 can become at least a part of the floor of the vehicle, or part of the box 10 can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0057] In the battery device 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a mixed connection. A mixed connection means that the multiple battery cells 20 are both connected in series and in parallel. The multiple battery cells 20 may be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 20 is accommodated in the box 10; of course, the battery device 100 may also be a battery module formed by connecting multiple battery cells 20 in series, in parallel, or in a mixed connection, and then the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the box 10. The battery device 100 may also include other structures, for example, the battery device 100 may also include a busbar component for realizing electrical connection between the multiple battery cells 20.

[0058] Each battery cell 20 may be a secondary battery or a primary battery, or a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 20 may be cylindrical, flat, rectangular, or in other shapes.

[0059] Please refer to Figure 3 , Figure 3 The schematic diagram of the exploded structure of the battery cell 20 provided in some embodiments of the present application. The battery cell 20 refers to the smallest unit that constitutes the battery. Figure 3 The battery cell 20 includes an end cover 21, a shell 22, an electrode assembly 23 and other functional components.

[0060] The end cap 21 refers to a component that covers the opening of the shell 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 21 can be adapted to the shape of the shell 22 to match the shell 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 21 is not easily deformed when squeezed and collided, so that the battery cell 20 can have a higher structural strength and the safety performance can also be improved. Functional components such as electrode terminals 21a can be provided on the end cap 21. The electrode terminal 21a can be used to electrically connect with the electrode assembly 23 for outputting or inputting electrical energy of the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The material of the end cap 21 can also be a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose special restrictions on this. In some embodiments, an insulating member may be provided inside the end cap 21, and the insulating member may be used to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating member may be plastic, rubber, or the like.

[0061] The shell 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the electrode assembly 23, the electrolyte and other components. The shell 22 and the end cap 21 can be independent components, and an opening can be set on the shell 22, and the internal environment of the battery cell 20 is formed by covering the opening with the end cap 21 at the opening. Without limitation, the end cap 21 and the shell 22 can also be integrated. Specifically, the end cap 21 and the shell 22 can form a common connection surface before other components are put into the shell, and when the interior of the shell 22 needs to be encapsulated, the end cap 21 covers the shell 22. The shell 22 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the shell 22 can be determined according to the specific shape and size of the electrode assembly 23. The material of the shell 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions on this.

[0062] The electrode assembly 23 is a component in the battery cell 20 where electrochemical reactions occur. One or more electrode assemblies 23 may be included in the housing 22. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets. The parts of the positive and negative electrode sheets with active materials constitute the main body of the electrode assembly, and the parts of the positive and negative electrode sheets without active materials each constitute a lug. The positive and negative electrode lugs may be located together at one end of the main body or at both ends of the main body, respectively. During the charge and discharge process of the battery, the positive active material and the negative active material react with the electrolyte, and the lugs connect the electrode terminals to form a current loop.

[0063] like Figures 3 to 5 As shown, Figure 4 A schematic diagram of the structure of an electrode assembly in a battery cell provided in some embodiments of the present application, Figure 5 This is a schematic diagram of a cross-sectional structure of a porous insulating layer in a battery cell provided in some embodiments of the present application. The embodiments of the present application provide a battery cell. The battery cell includes an electrode assembly 23, and the electrode assembly 23 includes a positive electrode sheet 231, a negative electrode sheet 232, a separator 233, and a porous insulating layer 234. The positive electrode sheet 231, the separator 233, and the negative electrode sheet 232 are stacked and wound.

[0064] At least a portion of the porous insulating layer 234 is disposed in the bending region 23 b of the electrode assembly 23 , and the porous insulating layer 234 is disposed between the positive electrode sheet 231 and the separator 233 and / or between the negative electrode sheet 232 and the separator 233 .

[0065] The porous insulating layer 234 includes a base layer 2341 and a reinforcement layer 2342 disposed on the base layer 2341 .

[0066] The electrode assembly 23 in this embodiment includes at least one positive electrode sheet 231 and one negative electrode sheet 232. The negative electrode sheet 232, the separator 233 and the positive electrode sheet 231 are generally stacked in a preset order of the positive electrode sheet 231, the separator 233, the negative electrode sheet 232, the separator 233, or the negative electrode sheet 232, the separator 233, the positive electrode sheet 231, and the separator 233. When the wound battery cell adopts multiple negative electrode sheets 232 and multiple positive electrode sheets 231, the stacking principle is equivalent to the above, which will not be repeated here.

[0067] In addition, the electrode assembly 23 in this embodiment is a winding structure, and a flat multi-turn winding body is formed after winding. Winding means that the diaphragm 233 and at least two pole pieces stacked in a preset order are wound around a virtual axis, and then hot-pressed or cold-pressed to form a flat winding body. The flat winding body is a multi-turn winding structure, such as Figure 4As shown in FIG. 1 , the flat winding body has a main body area and two bending areas. Figure 4 As shown, each pole piece of the flat winding body includes two oppositely arranged straight portions and two curved portions connecting the two adjacent straight portions. It should be noted that in the pole pieces in the same circle, one curved portion is used to connect the two straight portions in the pole piece of the circle, such as Figure 4 The other curved portion is used to connect one of the straight portions in the pole piece of the circle and one of the straight portions in the pole piece of another circle, such as Figure 4 The curved portion on the right side of the electrode assembly. It can be understood that the straight portion is a relatively straight portion relative to the curved portion, and is not absolutely straight, and may be wavy or curved. At the same time, each circle of diaphragm 233 also includes two relatively straight portions and two curved portions connecting two adjacent straight portions. The straight portions of each pole piece and diaphragm 233 are combined into the main body area of ​​the electrode assembly, and the curved portions of each pole piece and diaphragm 233 on the same side are combined into a bending area of ​​the electrode assembly.

[0068] For ease of understanding, Figure 4 As shown, the portion of the electrode assembly between the first reference line L1 and the second reference line L2 is the main area, the portion on the left side of the first reference line L1 is the bending area, and the portion on the right side of the second reference line L2 is the bending area.

[0069] The porous insulating layer 234 has a certain porosity, and the cross-sectional area of ​​a single hole in the porous insulating layer 234 is larger than the cross-sectional area of ​​a single particle of the reactants (including carriers and electrolyte) participating in the electrochemical reaction of the battery cell, and smaller than the cross-sectional area of ​​the dendrite, so that the reactants participating in the electrochemical reaction of the battery cell can pass through, and can block the dendrite from passing through.

[0070] The porous insulating layer 234 is arranged between the positive electrode plate 231 and the diaphragm 233 and / or between the negative electrode plate 232 and the diaphragm 233, including the following situations: first, the porous insulating layer 234 is arranged between the positive electrode plate 231 and the diaphragm 233; second, the porous insulating layer 234 is arranged between the negative electrode plate 232 and the diaphragm 233; third, the porous insulating layer 234 is arranged between the positive electrode plate 231 and the diaphragm 233 and between the negative electrode plate 232 and the diaphragm 233.

[0071] like Figure 5 As shown, the base layer 2341 is the basic structure of the porous insulating layer 234 , and can serve as a basis for preparing the reinforcement layer 2342 , or provide support for the reinforcement layer 2342 .

[0072] The reinforcing layer 2342 is a structure capable of improving the mechanical properties of the porous insulating layer 234, and can be arranged inside the base layer 2341, or embedded on the base layer 2341, or arranged on the side of the base layer 2341 away from the positive electrode sheet 231 or the negative electrode sheet 232. The above mechanical properties can be determined according to the mechanical properties to be achieved by the porous insulating layer 234 to be prepared, and the mechanical properties of the base layer 2341. For example, the mechanical properties to be achieved by the above porous insulating layer 234 are generally determined according to the use requirements, such as the mechanical strength of the porous insulating layer 234 in the transverse direction (TD) of the electrode sheet needs to meet certain requirements, so that the porous insulating layer 234 will not have cracks, cracks and other problems when the electrode assembly 23 is shaped, and the heat resistance of the porous insulating layer 234 also needs to meet certain requirements, so that the porous insulating layer 234 will not have warping and curling problems during the preparation process of the electrode assembly 23 (including the hot pressing process). The base layer 2341 can be made of polypropylene, polyethylene, etc. When the base layer 2341 is made of polypropylene, the reinforcement layer can be made of polyethylene, polyurethane, polyamide-imide, etc. to increase the mechanical strength of the porous insulating layer 234 in the TD direction; when the base layer 2341 is made of polyethylene, since polyethylene has high toughness and poor heat resistance, the reinforcement layer can be made of polyimide, ceramic, etc., so as to improve the mechanical strength of the porous insulating layer 234 in the TD direction while making the heat shrinkage resistance of the porous insulating layer 234 meet the use requirements.

[0073] In addition, depending on the setting method of the reinforcement layer 2342 and the use requirements of the porous insulating layer 234 , pores can be set only in the base layer 2341 , or pores can be set in both the base layer 2341 and the reinforcement layer 2342 .

[0074] In the battery cell provided in the embodiment of the present application, a porous insulating layer 234 is arranged between the positive electrode sheet 231 and the diaphragm 233, or between the negative electrode sheet 232 and the diaphragm 233. The porous insulating layer 234 includes a base layer 2341 and a reinforcement layer 2342. By reasonably selecting the material and setting method of the base layer 2341, and the material and setting method of the reinforcement layer 2342, the porous insulating layer 234 is not prone to cracks, splitting, curling and other problems when the electrode assembly 23 is being shaped, so that the porous insulating layer 234 has better performance and can block dendrites on the side away from the positive electrode sheet 231 or the negative electrode sheet 232, so that the dendrites are always spaced from the positive electrode sheet 231 or the negative electrode sheet 232, so that the dendrites cannot contact the positive electrode sheet 231 and the negative electrode sheet 232 at the same time, thereby reducing the risk of internal short circuit in the battery cell to a certain extent, improving the protection against lithium deposition in the bending area 23b, and improving the safety of the battery cell. In some embodiments, the pores of the porous insulating layer 234 have a pore size of [0.03 μm, 1 μm].

[0075] It should be noted that the porous insulating layer 234 has a plurality of pores, and the pore diameter of the porous insulating layer 234 refers to the radial size of each pore of the porous insulating layer 234 .

[0076] It is understandable that the pore sizes of the pores of the porous insulating layer 234 may be completely the same or different. The pore size may refer to the pore size when the pore sizes are the same, or the pore size of any part of the pores when the pore sizes are not completely the same.

[0077] It is understood that the shape of each hole of the porous insulating layer 234 can be circular or other shapes such as rectangular. When the hole is circular, the hole diameter refers to the diameter of the hole; when the hole is rectangular or other shapes, the hole diameter refers to the maximum size of the hole in the radial direction perpendicular to the central axis.

[0078] By adopting the above solution, on the one hand, the air permeability of the porous insulating layer 234 can be ensured to be moderate, and the reactants can freely and normally penetrate the pores of the porous insulating layer 234. On the other hand, during the use of the battery cell, the porous insulating layer 234 can be guaranteed to have a blocking effect on dendrites growing from defects of the diaphragm 233, and reduce the risk of dendrites growing from the pores of the porous insulating layer 234, thereby correspondingly extending the service life of the battery cell and improving the safety of the battery cell.

[0079] In some embodiments, the porosity of the porous insulating layer 234 is [35%, 55%].

[0080] Porosity refers to the ratio of the pore volume to the total volume of the porous insulating layer 234, usually expressed as a percentage. The higher the porosity, the more pores there are in the porous insulating layer 234, and theoretically, the more paths for gas to pass through.

[0081] There are many ways to measure porosity, such as the volume density method and liquid immersion method. The volume density method is to calculate the porosity by measuring the volume mass and theoretical density (i.e., the mass when there are no pores) of the sample. When measuring, the actual mass of the sample is measured first, and then its true volume is determined by the drainage method, and then the porosity is calculated based on the theoretical density of the material. The liquid immersion method is to use liquid to completely fill the pores in the sample, and calculate the porosity by comparing the mass change before and after immersion. When measuring, the sample is immersed in a certain liquid until it is saturated, and then its mass change is measured to infer the pore volume.

[0082] The porosity of the porous insulating layer 234 is 35% to 55%, which allows the reactants to pass through quickly, thereby reducing the adverse effect of the porous insulating layer 234 on the electrochemical reaction rate in the battery cell.

[0083] In some embodiments, the porous insulating layer 234 has an air permeability value less than or equal to 350 s / 100 cc.

[0084] Air permeability refers to the degree to which the porous insulating layer 234 allows gas to pass through, and the value can be obtained by measuring the amount of air permeability per unit volume or cross-section per unit time and specific pressure. The air permeability value is usually expressed in "seconds / 100 cubic centimeters" (s / 100cc), which means the time required for 100 cubic centimeters of air to pass through 1 square centimeter of material under standard conditions. The lower the air permeability value, the better the air permeability of the material.

[0085] The permeability value of the porous insulating layer 234 is less than or equal to 350s / 100cc. A smaller permeability value indicates that the porous insulating layer 234 has better permeability, allowing the reactants to pass through smoothly and quickly, and the electrochemical reaction rate in the battery cell is less adversely affected by the setting of the porous insulating layer 234.

[0086] In some embodiments, the material of base layer 2341 includes polyethylene.

[0087] Polyethylene is a polyolefin polymer, which is a thermoplastic resin obtained by polymerization of ethylene. Polyethylene has excellent chemical stability and electrical insulation, and compared with polypropylene, polyethylene has good flexibility and processing properties, and is suitable for applications that require flexibility.

[0088] In this embodiment, the material of the base layer 2341 may include only polyethylene, or may include other materials in addition to polyethylene, such as polyimide, polypropylene, etc.

[0089] The base layer 2341 is made of a material including polyethylene, which has good toughness, so that the porous insulating layer 234 is not easily pierced by dendrites, thereby preventing the dendrites from contacting the positive electrode plate 231 and the negative electrode plate 232 at the same time, thereby reducing the risk of internal short circuit in the battery cell to a certain extent.

[0090] In some embodiments, the material of the reinforcement layer 2342 includes at least one of polyimide fiber, para-aramid fiber, meta-aramid fiber, polyacrylonitrile fiber, and ceramic.

[0091] Among them, polyimide fiber (PI fiber) is a high-performance fiber made from polyamic acid (PAA) precursors through thermal imidization reaction. Polyimide fiber has extremely high thermal stability and can be used for a long time at temperatures up to 400°C, and can even withstand higher temperatures for a short time. It is not easy to decompose at high temperatures and maintains good mechanical properties. It also has high strength, high modulus, and good tensile resistance, fatigue resistance, impact resistance and wear resistance. It also has good chemical stability, excellent flame retardancy and good electrical insulation properties.

[0092] Para-aramid fiber is a high-performance fiber made by polymerization of terephthaloyl chloride and p-phenylenediamine. Para-aramid fiber has very high tensile strength and modulus, which is five times stronger than steel, but much lighter, with good impact resistance and wear resistance. It can be used for a long time at temperatures up to 200°C, and can even withstand higher temperatures for a short time. It maintains good mechanical properties at high temperatures, does not melt or drip, has high resistance to most acids, alkalis and organic solvents, has strong corrosion resistance, and also has excellent flame retardant properties and good electrical insulation properties.

[0093] Meta-aramid fiber is a high-performance fiber with excellent heat resistance, flame retardancy and chemical stability. Specifically, meta-aramid fiber can be used for a long time at a temperature of up to 220°C, and can even withstand higher temperatures for a short time. It will not melt or drip at high temperatures and maintain good mechanical properties. It can reach UL 94 V-0 rating without adding any flame retardants. It has high resistance to most acids, alkalis and organic solvents. In addition, although the strength and modulus of meta-aramid fiber are slightly lower than those of para-aramid fiber, it still has good tensile and impact resistance. And meta-aramid fiber has good flexibility and fatigue resistance.

[0094] Polyacrylonitrile Fiber (PAN Fiber) is a high-performance synthetic fiber made from acrylonitrile (CH2=CH-CN) monomers through polymerization. Polyacrylonitrile fiber has high tensile strength and modulus, with strength close to that of para-aramid fiber, and good impact resistance and wear resistance. It can be used for a long time at temperatures up to 180°C, and can even withstand higher temperatures for a short time; it has excellent flame retardant properties and can reach UL 94V-0 grade without adding any flame retardant; it has high resistance to most acids, alkalis and organic solvents, strong corrosion resistance, and is suitable for harsh chemical environments; it has good electrical insulation properties, etc.

[0095] Ceramics are a widely used inorganic non-metallic material, which is a solid material made by high-temperature sintering of inorganic non-metallic materials. These materials usually include oxides, nitrides, carbides, etc. Ceramic materials have extremely high heat resistance and can be used at extremely high temperatures, such as above 1000°C, without melting or deformation, and maintaining good mechanical properties; they have high resistance to most acids, alkalis and organic solvents, strong corrosion resistance, and are suitable for harsh chemical environments; they have high hardness, high wear resistance, high strength and high modulus, as well as good electrical insulation properties.

[0096] The ceramic in this embodiment may be common ceramic, or may be at least one of a ceramic coating containing polyimide fibers, a ceramic coating containing aramid fibers, a ceramic coating containing polyacrylonitrile fibers, and the like.

[0097] The reinforcement layer 2342 adopts the solution provided in this embodiment, so that the reinforcement layer 2342 has good resistance to heat shrinkage and heat plastic deformation. When the material of the base layer 2341 is polyethylene, the reinforcement layer 2342 adopts the solution provided in this embodiment, so that the porous insulating layer 234 has high tensile strength, elongation at break and impact strength, does not crack during the hot pressing process of the bare battery cell (Jelly Roll, JR), and has good resistance to heat shrinkage and heat plastic deformation, and is not prone to curling and other problems.

[0098] In some embodiments, the reinforcement layer 2342 is disposed in the base layer 2341 or is located on a side of the base layer 2341 close to the diaphragm 233 or is located on a side of the base layer 2341 close to the pole piece.

[0099] The solution provided in this embodiment includes at least several situations: first, the reinforcement layer 2342 is arranged in the base layer 2341; second, the reinforcement layer 2342 is located on the side of the base layer 2341 close to the separator 233; third, the reinforcement layer 2342 is located on the side of the base layer 2341 close to the pole piece. It can be understood that the pole piece in the third situation refers to when the porous insulating layer 234 is arranged between the positive pole piece 231 and the separator 233, the reinforcement layer 2342 is located on the side of the base layer 2341 close to the positive pole piece 231; when the porous insulating layer 234 is arranged between the negative pole piece 232 and the separator 233, the reinforcement layer 2342 is located on the side of the base layer 2341 close to the negative pole piece 232.

[0100] As mentioned above, in some embodiments, the heat resistance of the base layer 2341 is poor, and the heat resistance of the reinforcement layer 2342 is better. In this way, by adopting the solution provided by this embodiment, no matter the reinforcement layer 2342 is arranged in the base layer 2341, or is located on the side of the base layer 2341 close to the diaphragm 233, or is located on the side of the base layer 2341 close to the pole piece, the heat resistance of the porous insulating layer 234 can be improved to a certain extent, the risk of curling and other problems during use can be reduced, and it is easy to prepare.

[0101] In some embodiments, the porous insulating layer 234 further includes a hot melt adhesive layer 2343. The hot melt adhesive layer 2343 is located on a side of the combined structure of the base layer 2341 and the reinforcement layer 2342 facing the pole piece. The above-mentioned combined structure is bonded to the pole piece through the hot melt adhesive layer 2343.

[0102] The hot melt adhesive layer 2343 is an adhesive layer that melts under heating conditions and solidifies after cooling. The main features of the hot melt adhesive layer 2343 are fast solidification, good bonding performance and easy automated production.

[0103] When hot melt adhesive is heated, it becomes liquid, making it easier to spread and penetrate; after cooling, it quickly solidifies to form a strong bond. Hot melt adhesive can be cured within a few seconds to a few minutes, making it suitable for high-speed production lines.

[0104] The hot melt adhesive layer 2343 may include only a base resin, or may include at least one of a tackifier, a softener, an antioxidant, a filler, etc. in addition to the base resin. Among them, the base resin is used to provide basic bonding properties and thermoplasticity, including but not limited to ethylene-vinyl acetate copolymer, polyethylene, polypropylene, etc. The tackifier is used to improve the bonding strength of the hot melt adhesive, including but not limited to rosin resin, terpene resin, etc. The softener is used to adjust the fluidity and flexibility of the hot melt adhesive, including but not limited to paraffin oil, mineral oil, etc. Antioxidants are used to prevent the hot melt adhesive from oxidative degradation at high temperatures. Fillers are used to improve the physical properties of the hot melt adhesive and reduce costs, including but not limited to calcium carbonate, silica, etc.

[0105] In this embodiment, the hot melt adhesive layer 2343 is located on the side of the combined structure of the base layer 2341 and the reinforcement layer 2342 facing the pole piece, and the above-mentioned combined structure is bonded to the pole piece through the hot melt adhesive layer 2343, which means that when the porous insulating layer 234 is arranged between the positive pole piece 231 and the diaphragm 233, the hot melt adhesive layer 2343 is located on the side of the combined structure of the base layer 2341 and the reinforcement layer 2342 facing the positive pole piece 231, and the above-mentioned combined structure is bonded to the positive pole piece 231 through the hot melt adhesive layer 2343; when the porous insulating layer 234 is arranged between the negative pole piece 232 and the diaphragm 233, the hot melt adhesive layer 2343 is located on the side of the combined structure of the base layer 2341 and the reinforcement layer 2342 facing the negative pole piece 232, and the above-mentioned combined structure is bonded to the negative pole piece 232 through the hot melt adhesive layer 2343.

[0106] The combined structure of the base layer 2341 and the reinforcement layer 2342 is bonded to the positive electrode sheet 231 or the negative electrode sheet 232 through the hot-melt adhesive layer 2343. Compared with bonding with ordinary adhesive layers, the hot-melt adhesive layer 2343 can withstand high temperatures, so that when the electrode assembly 23 is formed by hot pressing, the combined structure of the base layer 2341 and the reinforcement layer 2342 and the adhesive layer between the electrode sheets are not easy to melt, thereby not overflowing to other areas of the electrode assembly 23, and not easily causing adhesion between the electrode sheet and the diaphragm 233, as well as blocking of the embedded ion channels on the positive electrode sheet 231 or the negative electrode sheet 232, which helps the normal operation of the electrode assembly 23.

[0107] like Figure 5 and Figure 6 As shown, Figure 6 A schematic diagram of the local structure of a porous insulating layer in a battery cell before the hot-melt adhesive particles are heated is provided in some embodiments of the present application. In some embodiments, the hot-melt adhesive layer 2343 is formed by heating and curing the hot-melt adhesive particles 23431.

[0108] Hot melt adhesive pellets 23431 are a common form of hot melt adhesive, usually in the form of small particles or beads.

[0109] It can be understood that the hot-melt adhesive particles 23431 in the present embodiment have no stickiness before being heated and are in the form of complete particles. When heated, at least part of the hot-melt adhesive particles 23431 will melt and become sticky so as to bond the corresponding pole pieces and the substrate layer 2341. During and after this process, the hot-melt adhesive particles 23431 will no longer be in the form of complete particles. Adjacent hot-melt adhesive particles 23431 may be adhered together, or adjacent hot-melt adhesive particles 23431 may still be spaced apart, but their shapes have changed compared to when they are not heated.

[0110] The preparation process of the hot melt adhesive layer 2343 in this embodiment can refer to the following operations: Place the hot melt adhesive pellets 23431 into a hot melt glue gun, glue melter or other heating equipment and heat to the melting temperature. Different types of hot melt adhesive pellets 23431 have different melting temperatures, usually between 120°C and 200°C. Use a spray gun, glue dispenser or roller to evenly apply the melted hot melt adhesive to the surface to be bonded (pole piece or substrate layer 2341). Quickly press the two pole pieces and substrate layer 2341 to be bonded together to ensure full contact. Allow the hot melt adhesive to cool and solidify naturally, usually within a few seconds to a few minutes.

[0111] The hot melt adhesive layer 2343 is formed by heating and curing the hot melt adhesive particles 23431, which can make the surface area of ​​the hot melt adhesive layer 2343 relatively large, absorb heat faster when heated, accelerate the melting process, and shorten the heating time. At the same time, the setting of the hot melt adhesive particles 23431 can achieve accurate measurement, reduce excess adhesive waste, and reduce production costs.

[0112] In some embodiments, the softening temperature of the hot melt adhesive particles 23431 is [110° C., 150° C.].

[0113] The softening temperature is the temperature at which the hot melt adhesive particles 23431 begin to become soft and fluid. At this temperature, the hot melt adhesive particles 23431 can be transformed from a solid state to a liquid or semi-liquid state, which is convenient for application and penetration.

[0114] Since the electrode assembly 23 has different materials, the hot pressing temperature during the shaping of the electrode assembly 23 is also different, such as the hot pressing temperature of lithium-ion batteries is 80°C to 120°C, and the hot pressing temperature of lithium iron phosphate batteries is 80°C to 110°C. The softening temperature of the hot melt adhesive particles 23431 is [110°C, 150°C]. During design, the composition of the material of the hot melt adhesive particles 23431 can be adjusted according to the specific material of the electrode assembly 23, so that the softening temperature of the hot melt adhesive particles 23431 is higher than the hot pressing temperature during the shaping of the electrode assembly 23. In this way, when in use, the hot melt adhesive layer 2343 is not easy to soften when the electrode assembly 23 is shaped, so that it is not easy to overflow to other areas of the electrode assembly 23, and it is not easy to cause the adhesion of the electrode sheet and the diaphragm 233, and the blocking of the embedded ion channel on the positive electrode sheet or the negative electrode sheet, which is conducive to the normal operation of the electrode assembly 23.

[0115] In some embodiments, the particle size of the hot melt adhesive particles 23431 is [0.4 μm, 0.7 μm].

[0116] Since the hot melt adhesive particle 23431 is generally spherical, the particle size of the hot melt adhesive particle 23431 is the diameter of the hot melt adhesive particle 23431 .

[0117] When the hot melt adhesive particle 23431 is non-spherical, the particle size of the hot melt adhesive particle 23431 may be the maximum size of the hot melt adhesive particle 23431 in all directions. For example, if the size of the hot melt adhesive particle 23431 in the first direction is a1, the size in the second direction is a2, and the size in the third direction is a3, and a1>a2>a3, then the particle size of the hot melt adhesive particle 23431 is a1, and a1 is [0.4 μm, 0.7 μm].

[0118] The particle size of the hot melt adhesive particles 23431 is [0.4 μm, 0.7 μm], which is small in size and has high fluidity after melting, making it easier to be evenly distributed on the surface to be bonded, which helps to improve the uniformity and reliability of the bonding between the pole piece and the substrate layer 2341.

[0119] In some embodiments, the material of the hot melt adhesive particles 23431 includes polyolefin resin.

[0120] In this embodiment, the material of the hot melt adhesive particles 23431 may include only polyolefin resin, or may include other materials in addition to polyolefin resin, such as at least one of the above-mentioned tackifiers, softeners, antioxidants, fillers, etc., which can be determined according to the needs of use.

[0121] Polyolefin resin has many advantages, such as good thermal stability, chemical stability, mechanical properties, wide range of bonding properties, fast curing, environmental safety, easy processing, cost-effectiveness and customization possibilities. The material of hot melt adhesive particles 23431 includes polyolefin resin, which is easy to process and has good thermal stability, chemical stability, mechanical properties, wide range of bonding properties and other advantages.

[0122] In some embodiments, the material of the polyolefin resin includes any one or more of polypropylene, polyethylene, polybutadiene rubber, ethylene-propylene acetate copolymer, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, maleic anhydride modified polyolefin and poly(butadiene-acrylonitrile), and styrene-maleic anhydride copolymer.

[0123] Polypropylene is a commonly used thermoplastic polymer, a high molecular compound formed by the polymerization reaction of propylene monomers. Polypropylene has a high melting point of about 160°C to 170°C, has good thermal stability, chemical stability, mechanical properties, and a wide range of adhesive properties, can achieve rapid curing, easy processing, can improve production efficiency, and reduce production costs.

[0124] Polyethylene is a widely used thermoplastic polymer, a high molecular compound formed by polymerization of ethylene monomers. The melting point of polyethylene is usually between 120°C and 135°C, depending on its density and molecular structure. Polyethylene has good thermal stability, chemical stability, mechanical properties, and a wide range of adhesive properties. It can achieve fast curing and is easy to process, which can improve production efficiency and reduce production costs.

[0125] Polybutadiene rubber is an important synthetic rubber, a high molecular compound formed by the polymerization reaction of butadiene monomers. Polybutadiene rubber has excellent elasticity and resilience, and can quickly recover to its original shape; it has high wear resistance and is suitable for applications that need to withstand wear for a long time; it also has good processing performance and can be processed by extrusion, molding, injection molding and other methods.

[0126] Ethylene-vinyl acetate copolymer is an important thermoplastic polymer, a high molecular compound formed by copolymerization of ethylene (Ethylene) and vinyl acetate (Vinyl Acetate, VA). Ethylene-vinyl acetate copolymer has good flexibility and elasticity, excellent bonding properties, good processing properties, and good chemical resistance.

[0127] Ethylene-Propylene Copolymer (EPC) is a polymer compound formed by copolymerization of ethylene (Ethylene) and propylene (Propylene). It has good flexibility, elasticity, chemical resistance, heat resistance and processing properties.

[0128] Ethylene-Vinyl Acetate Copolymer (EVA) is a polymer compound formed by copolymerization of two monomers, ethylene (Ethylene) and vinyl acetate (Vinyl Acetate, VA). It has good flexibility, elasticity, excellent bonding properties, and good processing properties.

[0129] Maleic Anhydride Grafted Polyolefins (MA-g-PO) are polymer compounds obtained by grafting maleic anhydride (MA) onto polyolefins (such as polyethylene and polypropylene). The introduction of maleic anhydride increases the polarity of the material, improves the compatibility and bonding properties with polar materials. The modified polyolefin has better processing properties, such as better fluidity and lower melt viscosity, and the modified polyolefin has higher strength and toughness.

[0130] Poly(butadiene-acrylonitrile) (NBR) is a polymer compound formed by copolymerization of two monomers, butadiene and acrylonitrile. It has good heat resistance and can be used at higher temperatures. It also has high wear resistance and is suitable for applications that require long-term wear resistance.

[0131] Styrene-Maleic Anhydride Copolymer (SMA) is a polymer compound formed by copolymerization of styrene and maleic anhydride. It has good polarity, excellent thermal stability and good mechanical properties.

[0132] The polyolefin resin in this embodiment can be composed of any of the above materials, or a mixture of multiple materials, depending on the specific needs of use. No matter which setting method is adopted, the polyolefin resin has good thermal stability and mechanical properties, which can make the structure of the hot melt adhesive layer 2343 stable and not easy to overflow, thereby reducing the risk of adhesion between the diaphragm and the electrode and the risk of the diaphragm blocking the embedded ion channel on the electrode.

[0133] In some embodiments, the material of the hot melt adhesive particles 23431 is maleic anhydride modified polypropylene.

[0134] The material of the hot melt adhesive particles 23431 is maleic anhydride-modified polypropylene, which can make the hot melt adhesive layer 2343 have a higher softening temperature and higher adhesion.

[0135] In some embodiments, the thickness of the hot melt adhesive layer 2343 is less than or equal to 1 μm.

[0136] The thickness of the hot melt adhesive layer 2343 refers to the dimension of the hot melt adhesive layer 2343 in the thickness direction of the positive electrode sheet 231 .

[0137] Since the thickness of the positive electrode sheet 231 is generally between 50 μm and 200 μm, and the thickness of the negative electrode sheet 232 is generally between 50 μm and 150 μm, the thickness of the hot melt adhesive layer 2343 is less than or equal to 1 μm, which is relatively thin and much smaller than the thickness of the positive electrode sheet 231 and the negative electrode sheet 232. In this way, the setting of the hot melt adhesive layer 2343 is not likely to cause a significant impact on the distance between the positive electrode sheet 231 and the negative electrode sheet 232, so that the winding and electrochemical reaction of the electrode assembly 23 are not easily adversely affected.

[0138] like Figure 4 and Figure 7 As shown, Figure 7A partial structural schematic diagram of an electrode assembly in a battery cell provided in some embodiments of the present application, in some embodiments, the electrode assembly 23 has a main body region 23a and a bending region 23b disposed at the end side of the main body region 23a. The porous insulating layer 234 has a bending section 234a disposed in the bending region 23b, and an extension section 234b connected to the end of the bending section 234a and disposed in the main body region 23a.

[0139] The electrode assembly 23 is a wound structure. The main body area 23a is a relatively straight portion located in the middle of the wound structure, that is, the area corresponding to the straight portion, and is also Figure 4 The area between the dotted lines L1 and L2, and the bending area 23b is the part of the winding structure that is located at the end side of the main area 23a and is bent, and is also the area corresponding to the above-mentioned bending portion, and is located at Figure 4 The area to the left of the dashed line L1 and Figure 4 The area to the right of the middle dotted line L2.

[0140] The porous insulating layer 234 has a curved section 234a, and the curved section 234a of the porous insulating layer 234 is arranged in the bending area 23b. The porous insulating layer 234 can be provided with one or two extension sections 234b, and the extension section 234b is arranged in the main area 23a. When one extension section 234b is provided, the extension section 234b is only provided at one end of the curved section 234a in the same porous insulating layer 234; when two extension sections 234b are provided, the extension sections 234b are provided at both ends of the curved section 234a in the same porous insulating layer 234, and the extension lengths of the two extension sections 234b can be the same or different.

[0141] By adopting the above solution, compared with the case where the porous insulating layer 234 is only arranged in the bending area of ​​the electrode assembly, the coverage area of ​​the porous insulating layer 234 can be increased, which can reduce the risk of internal short circuit in the battery cell to a certain extent, and at the same time reduce the risk of displacement of the porous insulating layer 234 during the use of the battery cell.

[0142] like Figure 4 And such as Figure 8 As shown, Figure 8 A schematic diagram of the partial structure of the combined structure of the positive electrode sheet and the porous insulating layer in the battery cell provided in some embodiments of the present application. In some embodiments, in the bending area 23b, at least the inner side surface and / or the outer side surface of the innermost circle of the positive electrode sheet 231 is provided with a porous insulating layer 234.

[0143] The inner side refers to the innermost side of the positive electrode sheet 231 facing the center of the electrode assembly. The outer side refers to the side of the positive electrode sheet 231 opposite to the inner side.

[0144] Since the radius of curvature of the electrode sheets becomes smaller as they move toward the innermost circle, the curved portion of the innermost positive electrode sheet 231 and the curved portion of the innermost negative electrode sheet 232 will be subjected to greater bending stress and will be more prone to powder loss. Furthermore, since the curved portion of the innermost positive electrode sheet 231 is relatively located on the outside of the curved portion of the innermost negative electrode sheet 232, lithium deposition problems are easily generated from the curved portion of the innermost negative electrode sheet 232 during the charging process of the battery cell.

[0145] Therefore, by adopting the above scheme, a porous insulating layer 234 is provided at least on the innermost curved portion of the positive electrode sheet 231. On the one hand, the dendrites growing from the innermost curved portion of the negative electrode sheet 232 can be insulated and blocked to prevent the dendrites from connecting the positive electrode sheet 231 and the negative electrode sheet 232, thereby reducing the risk of internal short circuit of the battery cell to a certain extent between the innermost curved portion of the positive electrode sheet 231 and the innermost curved portion of the negative electrode sheet 232 where metal precipitation is easily generated, thereby correspondingly extending the service life of the battery cell and correspondingly improving the safety of the battery cell; on the other hand, the provision of the porous insulating layer 234 can provide insulation for the innermost curved portion of the positive electrode sheet 231. 1 can buffer the extrusion stress borne by the curved portion, so as to reduce the risk of tearing defects in the curved portion of the innermost positive electrode sheet 231 leading to a reduction in active substances; it can even buffer the tensile stress borne by the curved portion of the innermost negative electrode sheet 232, so as to reduce the risk of tearing defects in the curved portion of the innermost negative electrode sheet 232 leading to a reduction in active substances, thereby effectively reducing the risk of aggravating metal precipitation due to the reduction in active substances, and effectively alleviating the growth rate of dendrites between the innermost positive electrode sheet 231 and the innermost negative electrode sheet 232, thereby correspondingly extending the service life of the battery cell and correspondingly improving the safety of the battery cell.

[0146] It is understandable that when the porous insulating layer 234 is located on the inner side or outer side of the outermost pole piece, the porous insulating layer 234 can support the pole piece to reduce the loss of active materials, support the diaphragm to improve diaphragm cracking, etc.

[0147] Figure 8 This is a partial structural diagram of the combined structure of the positive electrode sheet and the porous insulating layer in the battery cell provided in some embodiments of the present application. Figure 8 As shown, in some embodiments, in the length direction X of the positive electrode sheet 231, the size of the porous insulating layer 234 is [10 mm, 24 mm]. That is, the size d5 of the porous insulating layer in the length direction of the positive electrode sheet is [10 mm, 24 mm].

[0148] Generally, the length of the bending area 23b of the innermost positive electrode sheet 231 is less than 10 mm. The size of the porous insulating layer 234 in the length direction X of the positive electrode sheet 231 is [10 mm, 24 mm], which can completely cover the bending area 23b of the innermost positive electrode sheet 231, reducing the risk of short circuit at this location.

[0149] Fig. 9 This is a partial structural diagram of the combined structure of the positive electrode sheet and the porous insulating layer in the battery cell provided in some other embodiments of the present application. Fig. 9 As shown, in some embodiments, in the width direction Y of the positive electrode plate 231, at least one end of the porous insulating layer 234 exceeds the target electrode plate, and the dimension exceeding the target electrode plate is [3mm, 6mm], and the target electrode plate is the electrode plate connected to the porous insulating layer 234. Fig. 9 The dimension d6 of one end of the porous insulating layer exceeding the target pole piece is [3mm, 6mm], and the dimension d7 of the other end of the porous insulating layer exceeding the target pole piece is also [3mm, 6mm].

[0150] The width direction of the positive electrode sheet 231 is also the lateral direction of the positive electrode sheet 231 and is also the width direction of the target electrode sheet.

[0151] The porous insulating layer 234 has two ends in the width direction Y of the positive electrode sheet 231. In this embodiment, one or both ends of the porous insulating layer 234 in the width direction of the positive electrode sheet 231 may be set beyond the target sheet, and the exceeding range may be any value in [3mm, 6mm]. In this way, the porous insulating layer 234 can cover as large an area of ​​the target sheet as possible, so that the dendrite cannot contact the target sheet from at least one end of the target sheet in the width direction, which can further reduce the risk of internal short circuit of the battery cell.

[0152] In some embodiments, in the width direction Y of the positive electrode plate 231 , both ends of the porous insulating layer 234 extend beyond the target electrode plate, and the dimension extending beyond the target electrode plate is [3 mm, 6 mm].

[0153] By adopting the solution provided in this embodiment, compared with the porous insulating layer 234 only extending beyond the target electrode at one end in the width direction of the positive electrode plate 231, the dendrites cannot contact the target electrode from either end in the width direction of the target electrode, which can further reduce the risk of internal short circuit in the battery cell.

[0154] like Figure 5 As shown, in some embodiments, the thickness d2 of the porous insulating layer 234 is [10 μm, 20 μm].

[0155] It should be noted that, in theory, the thicker the porous insulating layer 234 is, the better the insulating barrier effect of the porous insulating layer 234 on dendrites is. However, as the thickness of the porous insulating layer 234 increases, the energy density of the battery cell will decrease, and the penetration rate of active ions through the porous insulating layer 234 will deteriorate, thereby causing the conductivity to deteriorate and even causing the metal precipitation phenomenon to intensify.

[0156] Therefore, by adopting the above scheme, the thickness of the porous insulating layer 234 can be ensured to be moderate, so as to ensure that the porous insulating layer 234 can form a better insulating barrier effect on the dendrites growing toward it, and reduce the adverse effects of the porous insulating layer 234 on the energy density of the battery cell and the penetration rate of active ions penetrating the porous insulating layer 234, thereby ensuring the electrical conductivity and the charging and discharging performance of the battery cell. At the same time, the extrusion stress borne by the curved portion of the innermost circle positive electrode plate 231 can be buffered to reduce the risk of tearing defects in the curved portion of the innermost circle positive electrode plate 231 leading to a reduction in active substances; it can even buffer the tensile stress borne by the curved portion of the electrode plate in the corresponding area during hot pressing and shaping of the electrode assembly to reduce the risk of tearing defects in the corresponding electrode plate leading to a reduction in active substances, that is, reduce the risk of powdering and exposed metal layer in the corresponding electrode plate, thereby effectively reducing the risk of metal precipitation due to the reduction in active substances, and correspondingly extending the service life of the battery cell and improving the safety of the battery cell.

[0157] In some embodiments, the thickness d3 of the base layer 2341 is [7 μm, 16 μm].

[0158] The thickness of the base layer 2341 is [7μm, 16μm], which accounts for about half, or most, of the thickness of the insulating layer. In this way, when the base layer 2341 is made of a material with better toughness such as polyethylene, the insulating layer has greater toughness and is not easily pierced by dendrites, thereby reducing the risk of internal short circuit in the battery cell.

[0159] In some embodiments, the thickness d4 of the reinforcement layer 2342 is [3 μm, 8 μm].

[0160] The thickness of the reinforcing layer 2342 is [3μm, 8μm], which occupies about half or a small part of the thickness of the insulating layer. This allows the reinforcing layer 2342 to have a reinforcing effect without affecting some excellent properties of the base layer 2341, such as toughness, so that the insulating layer can have the excellent properties of both the base layer 2341 and the reinforcing layer 2342.

[0161] According to some embodiments of the present application, the present application also provides a battery device, including a battery cell provided by any of the above solutions.

[0162] The battery device provided in the embodiment of the present application, including the above-mentioned battery cell, can achieve the same effect as above, which will not be described in detail here.

[0163] According to some embodiments of the present application, the present application further provides an electrical device, comprising a battery device or a battery cell provided by any of the above solutions. The battery device or the battery cell is used to provide electrical energy.

[0164] The power-consuming device may be any of the aforementioned devices or systems using batteries.

[0165] The electrical device provided in the embodiment of the present application, including the above-mentioned battery device or battery cell, can achieve the same effect as above, which will not be described in detail here.

[0166] According to some embodiments of the present application, the present application further provides a method for preparing a battery cell, which is used to prepare the battery cell provided by any of the above embodiments, comprising at least the following steps: S1. A porous insulating layer is provided on the positive electrode sheet and / or the negative electrode sheet.

[0167] The porous insulating layer in this step can be arranged in the manner proposed in any of the above embodiments, and can be arranged on the positive electrode sheet or the negative electrode sheet according to the use requirements. It is preferably arranged on the innermost curved portion of the positive electrode sheet, and can extend a portion to the straight portion, and can be arranged on both the inner side and the outer side of the positive electrode sheet. In other embodiments, it can also be arranged on other curved portions of the positive electrode sheet and / or the negative electrode sheet.

[0168] S2, stacking the positive electrode sheet, the separator and the negative electrode sheet in a preset order and winding them into shape.

[0169] The preset sequence is as described above, and a diaphragm is provided between any two pole pieces to prevent the positive pole piece and the negative pole piece from directly contacting each other. The winding forming can be performed by means of the winding method in the related art, which will not be described in detail here.

[0170] The method for preparing the battery cell provided in this embodiment can be used to prepare the battery cell provided in any of the above embodiments.

[0171] like Figures 3 to 10 As shown, an embodiment of the present application provides a battery device, which relates to the fields of power batteries, energy storage batteries, mechanical devices, etc. The battery device includes an electrode assembly 23, and the electrode assembly 23 includes a positive electrode sheet 231, a negative electrode sheet 232, a separator 233 and a porous insulating layer 234. The positive electrode sheet 231, the separator 233 and the negative electrode sheet 232 are stacked and wound.

[0172] At least a portion of the porous insulating layer 234 is disposed at the bending region 23 b of the electrode assembly 23 . The porous insulating layer 234 is disposed between the positive electrode sheet 231 and the separator 233 .

[0173] The porous insulating layer 234 includes a base layer 2341, a reinforcement layer 2342 and a hot melt adhesive layer 2343. The reinforcement layer 2342 is disposed on a side of the base layer 2341 close to the separator 233. The base layer 2341 is bonded to the positive electrode sheet 231 through the hot melt adhesive layer 2343.

[0174] The surfaces of the two active material layers of the positive electrode plate 231 are covered with a layer of highly breathable isolation film tape (i.e., the porous insulating layer 234 mentioned above), which allows lithium ion transmission between the positive and negative active material layers. The porous insulating layer 234 has a micro-nano pore size of a conventional diaphragm, with pores distributed between 0.03μm and 1μm, and a porosity between 35% and 55%. The material of the base layer 2341 is PE (polyethylene), and the thickness of the base layer 2341 is 7μm to 16μm.

[0175] The reinforcing layer 2342 is a layer structure, which can be called a reinforcing layer. The reinforcing layer can be a polyimide fiber layer, a para-aramid fiber layer, a meta-aramid fiber layer, a polyacrylonitrile fiber layer, a ceramic coating containing polyimide fiber, a ceramic coating containing aramid fiber, a ceramic coating containing polyacrylonitrile fiber, or a common ceramic coating. The thickness of the reinforcing layer 2342 is 3 μm to 8 μm.

[0176] The hot melt adhesive layer 2343 is a granular island-shaped distribution of hot melt adhesive particles with a thickness of less than 1 μm. The above hot melt adhesive particles can be referred to as glue particles. The particle size Dv50 of the glue particles is 0.4~0.7μm. The glue particles belong to the hot melt adhesive type and have a high softening temperature of 110~150℃. They are not sticky at room temperature, but are sticky when hot melted at high temperature. Therefore, the porous insulating layer 234 can be tightly attached to the positive electrode sheet 231 in the bending area through the process of hot pressing. The glue particles have a high softening temperature, which can avoid the porous insulating layer 234 from being hot-pressed and compounded to the positive electrode sheet in the bending area 23b and the subsequent JR hot pressing process. The phenomenon of overflow and adhesion of the diaphragm 233 can also be avoided to the greatest extent. The dissolution of the glue particles in this area is also avoided to the greatest extent. The enrichment in the opposite negative electrode area, thereby blocking the channel for lithium ion insertion of negative electrode particles.

[0177] The hot melt adhesive type particles are polyolefin resins; the polyolefin resins include any one or more of polypropylene, polyethylene, polybutadiene rubber, ethylene-propylene acetate copolymer, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, maleic anhydride modified polyolefin and poly (butadiene-acrylonitrile), styrene-maleic anhydride copolymer, among which maleic anhydride modified polypropylene has a higher softening temperature and higher adhesion, and is the preferred solution in this case.

[0178] The porous insulating layer 234 can be called an isolation film adhesive tape. The isolation film adhesive tape has high tensile strength, elongation at break and impact strength, and does not crack during the hot pressing process of the bare JR (Jelly Roll). Due to the provision of a reinforcement layer, the heat shrinkage resistance and heat plastic deformation resistance of the PE substrate can be greatly improved; the isolation film adhesive tape has a thickness of 10μm ~20μm and a width of 10 mm ~24mm, completely covering the bending area, and appropriately extending to the large surface area (i.e. the above-mentioned main area), with a height slightly higher than the pole piece height, and both sides exceeding the pole piece by 3mm~6mm.

[0179] The air permeability of the fresh separator tape is <250s / 100cc, and the air permeability of the separator after hot pressing is <350s / 100cc. The high-permeability separator tape has a lower air permeability, which allows the positive and negative electrodes in the bending area 23b to perform normal lithium insertion and extraction, and will not significantly deteriorate the analytical window of the tape attachment position.

[0180] The isolation film adhesive tape has a three-layer composite structure. The reinforcement layer greatly improves the heat shrinkage resistance and heat deformation resistance of the PE substrate layer, thereby effectively improving the problems of rewinding and shrinkage that occur during the gluing process.

[0181] The polyolefin polymer material is used as a high-permeability isolation film adhesive tape attached to the positive electrode plate at the bend. The high-permeability adhesive tape is in close contact with the plate. When the anode of the bending area 23b undergoes lithium deposition and pierces the separator 233, the adhesive tape does not extend under the force of the lithium dendrites, which means that the lithium dendrites cannot pierce the adhesive tape, thereby blocking the risk of short-circuit failure caused by the contact between the lithium dendrites and the cathode; the material has high tensile strength and elongation at break, and does not crack during the bare JR (JellyRoll) hot pressing process, which can avoid the loss of protection against lithium deposition in the bending area 23b due to cracks. In addition, the thickness of the isolation film is 10~20μm, which covers the surface of the bent positive electrode plate, which can avoid aluminum leakage and powder loss caused by hot pressing fracture of the plate in this area. In order to alleviate the internal short circuit problem of battery cells in the related art, an insulating layer is set in the bending area of ​​the positive electrode sheet or the negative electrode sheet, and is bonded by an electrolyte-soluble acrylic pressure-sensitive adhesive. The electrode assembly 23 needs to be hot-pressed and shaped during preparation. During this process, the above-mentioned glue layer is easy to overflow under high temperature and pressure. The overflowed glue layer may connect the diaphragm 233 and the positive electrode sheet 231 or the negative electrode sheet 232, so as to achieve the adhesion of the diaphragm 233 and the positive electrode sheet 231 or the negative electrode sheet 232; at the same time, the overflowed glue layer will partially dissolve in the electrolyte to release small molecule chains, covering the surface of the positive and negative electrode sheets, affecting the surface dynamics of the sheets, and may block the ion insertion channels on the negative electrode sheet 232 or the positive electrode sheet 231, which usually affects the normal transmission of active substances such as lithium ions. If the blockage is serious, it may cause physical contact between different components inside the battery, causing local short circuits, causing self-discharge in the battery, and thus causing battery performance degradation. The self-discharge phenomenon refers to the chemical reaction that occurs inside the battery even when there is no external load, resulting in a gradual decrease in power. That is, although the solution provided by the relevant technology can improve the lithium deposition in the bending area 23b, it brings about the problem of adhesion of the diaphragm 233 and self-discharge of the battery. Therefore, how to effectively reduce the risk of internal short circuit caused by lithium deposition in the bending area 23b of the wound electrode assembly 23 or reduce or avoid lithium deposition is still a technical problem that needs to be solved in the process of battery development.

[0182] The battery cell provided in this embodiment uses hot melt adhesive to bond the porous insulating layer to the positive electrode sheet, which can reduce the risk of the above-mentioned diaphragm adhesion and battery self-discharge. In addition, the material of the insulating layer in the related art is polypropylene. The tensile strength of this material in the MD (longitudinal) direction is much higher than the tensile strength in the TD (transverse) direction. This makes the insulating layer tightly attached to the positive electrode in the bending area after hot pressing. When the electrode assembly is shaped, the positive electrode sheet in the bending area will produce TD direction compression and stretching on the insulating layer tightly attached to the positive electrode sheet. The stress there is large and concentrated, which will cause cracks in the insulating layer attached to the positive electrode sheet in the bending area, and even cracking problems. This may cause the lithium dendrites generated by the negative electrode sheet in the bending area to pierce the diaphragm, and the dendrites are easy to overlap the positive electrode sheet from the cracks in the insulating layer, which may lead to the loss of the protection effect of lithium precipitation in the bending area. The porous insulating layer in the battery cell provided in this embodiment is made of polyethylene, which has higher toughness than polypropylene, and can reduce the risk of cracks in the porous insulating layer during the shaping of the electrode assembly, thereby reducing the risk of failure of the porous insulating layer, and allowing it to protect the bending area from lithium deposition for a long time. If the porous insulating layer is made of ethylene only, its softening temperature is low, and it is easy to roll back during the production process, resulting in an unsatisfactory bonding effect of the porous insulating layer on the pole piece. The provision of the reinforcement layer can improve its heat shrinkage resistance, thereby improving the process bonding effect.

[0183] Using the battery cell provided in this embodiment, the separator adhesive tape can be used for normal hot pressing and laminating operation of the positive electrode sheet, and the hard shell prepared by using the above-mentioned electrode sheet is verified by adopting the 60°C floating charge verification scheme to verify the technical effect. The verification results are as follows Fig.10 As shown in the figure, the disassembly found that there was no cracking or powdering problem in the bending area of ​​the positive electrode (i.e. the area where the porous insulating layer was attached), no lithium deposition was found in the bending area of ​​the negative electrode, and no adhesion and lithium deposition of the edge diaphragm was found. This shows that the solution has a good improvement effect on the protection of lithium deposition in the bending area.

[0184] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A battery cell, characterized in that: The battery cell comprises an electrode assembly, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet, a separator and a porous insulating layer; The positive electrode sheet, the separator and the negative electrode sheet are stacked and wound; At least part of the porous insulating layer is disposed in the bending region of the electrode assembly and between the positive electrode sheet and the separator and / or between the negative electrode sheet and the separator; The porous insulating layer includes a base layer and a reinforcement layer disposed on the base layer.

2. The battery cell according to claim 1, characterized in that: The pores of the porous insulating layer have a pore size of [0.03 μm, 1 μm].

3. The battery cell according to claim 1, characterized in that: The porosity of the porous insulating layer is [35%, 55%].

4. The battery cell according to claim 1, characterized in that: The air permeability value of the porous insulating layer is less than or equal to 350s / 100cc.

5. The battery cell according to claim 1, characterized in that: The material of the base layer includes polyethylene.

6. The battery cell according to claim 1, characterized in that: The material of the reinforcement layer includes at least one of polyimide fiber, para-aramid fiber, meta-aramid fiber, polyacrylonitrile fiber and ceramic.

7. The battery cell according to any one of claims 1 to 6, characterized in that: The reinforcement layer is arranged in the base layer or located on a side of the base layer close to the diaphragm or located on a side of the base layer close to the pole piece.

8. The battery cell according to any one of claims 1 to 6, characterized in that: The porous insulating layer further comprises a hot melt adhesive layer, which is located on a side of the combined structure of the base layer and the reinforcement layer facing the pole piece, and the combined structure is bonded to the pole piece via the hot melt adhesive layer.

9. The battery cell according to claim 8, characterized in that: The hot melt adhesive layer is formed by curing hot melt adhesive particles through heating.

10. The battery cell according to claim 9, characterized in that: The softening temperature of the hot melt adhesive particles is [110° C., 150° C.].

11. The battery cell according to claim 9, characterized in that: The particle size of the hot melt adhesive particles is [0.4 μm, 0.7 μm].

12. The battery cell according to claim 9, characterized in that: The material of the hot-melt adhesive particles includes polyolefin resin.

13. The battery cell according to claim 12, characterized in that: The material of the polyolefin resin includes at least one of polypropylene, polyethylene, polybutadiene rubber, ethylene-propylene acetate copolymer, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, maleic anhydride modified polyolefin, poly(butadiene-acrylonitrile), and styrene-maleic anhydride copolymer.

14. The battery cell according to claim 9, characterized in that: The material of the hot melt rubber particles is maleic anhydride modified polypropylene.

15. The battery cell according to claim 8, characterized in that: The thickness of the hot melt adhesive layer is less than or equal to 1 μm.

16. The battery cell according to any one of claims 1 to 6, characterized in that: The electrode assembly comprises a main body region and a bending region arranged at an end side of the main body region; The porous insulating layer has a bending section arranged in the bending area, and an extending section connected to an end of the bending section and arranged in the main body area.

17. The battery cell according to any one of claims 1 to 6, characterized in that: In the bending region, at least the inner side surface and / or the outer side surface of the innermost circle of the positive electrode plate is provided with the porous insulating layer.

18. The battery cell according to claim 17, characterized in that: In the length direction of the positive electrode sheet, the size of the porous insulating layer is [10 mm, 24 mm].

19. The battery cell according to any one of claims 1 to 6, characterized in that: In the width direction of the positive electrode plate, at least one end of the porous insulating layer exceeds the target electrode plate, and the dimension exceeding the target electrode plate is [3mm, 6mm]. The target electrode plate is the electrode plate connected to the porous insulating layer.

20. The battery cell according to claim 19, characterized in that: In the width direction of the positive electrode plate, both ends of the porous insulating layer extend beyond the target electrode plate, and the dimension extending beyond the target electrode plate is [3 mm, 6 mm].

21. The battery cell according to any one of claims 1 to 6, characterized in that: The thickness of the porous insulating layer is [10 μm, 20 μm].

22. The battery cell according to claim 21, characterized in that: The thickness of the base layer is [7 μm, 16 μm].

23. The battery cell according to claim 21, characterized in that: The thickness of the reinforcement layer is [3 μm, 8 μm].

24. A battery device, characterized in that: The battery device comprises the battery cell according to any one of claims 1-23.

25. An electrical device, wherein: The electrical device comprises the battery device according to claim 24, or the battery cell according to any one of claims 1-23.

26. A method for preparing a battery monomer, used for preparing the battery monomer according to any one of claims 1 to 23, characterized in that: include: Arranging the porous insulating layer on the positive electrode sheet and / or the negative electrode sheet; The positive electrode sheet, the separator and the negative electrode sheet are stacked and wound in a preset order.

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