Electrode assemblies, battery cells, batteries, and power consumption devices

Abstract

The present invention provides electrode assemblies, battery cells, batteries, and power consumption devices that can improve safety. [Solution] Embodiments of the present invention provide an electrode assembly (10), a battery cell, a battery, and a power consumption device. The electrode assembly comprises a positive electrode sheet (11), a negative electrode sheet (12), and an isolation assembly (13) for isolating the positive electrode sheet and the negative electrode sheet. At least a portion of the isolation assembly is set up as a multi-layer structure region (13a), and at least a portion of the multi-layer structure region is located between adjacent positive electrode sheets and negative electrode sheets. The multi-layer structure region corresponds to a position on the negative electrode sheet where lithium is likely to be deposited. By blocking lithium dendrites, the multi-layer structure region reduces the probability of electrical conductivity between the positive electrode sheet and the negative electrode sheet, effectively reducing the risk of short circuits and improving the service life and safety of the electrode assembly.

Description

[Technical Field]

[0001] This application claims priority to Chinese Patent Application No. 202111062600.7, filed on September 10, 2021, with the title of the invention "Electrode Assembly and Related Battery Cells, Batteries, Apparatus and Method of Manufacturing Thereof," the entire contents of which are incorporated herein by reference.

[0002] This application relates to the technology of batteries, and more specifically to electrode assemblies, battery cells, batteries, and power consumption devices. [Background technology]

[0003] Battery cells are widely used in electronic devices such as mobile phones, laptop computers, electric scooters, electric vehicles, electric airplanes, electric boats, electric toy cars, electric toy boats, electric toy airplanes, and power tools. Battery cells may include cadmium nickel battery cells, nickel hydrogen battery cells, lithium-ion battery cells, and secondary alkali zinc manganese battery cells.

[0004] In the development of battery technology, improving the safety of battery cells is a key area of ​​focus in battery technology research. [Overview of the project]

[0005] This application provides an electrode assembly, battery cell, battery, and power consumption device that can improve safety.

[0006] In a first embodiment, an embodiment of the present application provides an electrode assembly comprising a positive electrode sheet, a negative electrode sheet, and an isolation assembly for separating the positive electrode sheet and the negative electrode sheet. At least a portion of the isolation assembly is configured as a multi-layer structure region, and at least a portion of the multi-layer structure region is located between adjacent positive electrode sheets and negative electrode sheets.

[0007] In the above proposed technology, the multi-layer structure region corresponds to a position on the negative electrode sheet where lithium is easily deposited. By blocking lithium dendrites, the multi-layer structure region reduces the probability of electrical conductivity between the positive electrode sheet and the negative electrode sheet, effectively reducing the risk of short circuits and improving the service life and safety of the electrode assembly.

[0008] In some embodiments, a positive electrode sheet, an isolation assembly, and a negative electrode sheet are wound together to form a folded region, and at least a portion of the multi-layer structure region is placed in the folded region.

[0009] Lithium deposition is likely to occur in the folded region. In the above proposed technology, at least a portion of the multi-layer structure region is placed in the folded region. Therefore, even if lithium deposition occurs in the folded region, the multi-layer structure region blocks the lithium dendrites, reducing the probability of electrical conductivity between the positive electrode sheet and the negative electrode sheet. This effectively reduces the risk of short circuits and improves the service life and safety of the electrode assembly.

[0010] In some embodiments, at least a portion of the multi-layer structure region is located adjacent to the first fold of the positive electrode sheet.

[0011] The curvature of the first bend of the positive electrode sheet is large, and during charging, the negative electrode sheet adjacent to the first bend of the positive electrode sheet is prone to lithium deposition problems. In the above proposed technology, by placing at least a portion of the multi-layer structure region adjacent to the first bend of the positive electrode sheet, the risk of electrical conductivity between the first bend of the positive electrode sheet and the lithium dendrite can be reduced, thereby improving the safety of the battery cell.

[0012] In some embodiments, multi-layer structures are provided on both sides of the first fold of the positive electrode sheet, and the number of layers in the multi-layer structure located inside the first fold of the positive electrode sheet is greater than or equal to the number of layers in the multi-layer structure located outside the first fold of the positive electrode sheet. This reduces the risk of electrical conductivity between the first fold of the positive electrode sheet and the lithium dendrite, thereby improving the safety of the battery cell.

[0013] In some embodiments, at least a portion of the multi-layer structure region is located adjacent to the second bend of the positive electrode sheet.

[0014] The curvature of the second bend of the positive electrode sheet is large, making it prone to lithium deposition problems on the negative electrode sheet adjacent to the second bend of the positive electrode sheet during charging. In the above proposed technology, by placing at least a portion of the multi-layer structure region adjacent to the second bend of the positive electrode sheet, the risk of electrical contact between the second bend of the positive electrode sheet and the lithium dendrite can be reduced, thereby improving the safety of the battery cell.

[0015] In some embodiments, the number of layers in the multi-layer structure region located inside the first folded portion of the positive electrode sheet is equal to or greater than the number of layers in the multi-layer structure region located inside the second folded portion of the positive electrode sheet. This reduces the risk of electrical conductivity between the first folded portion of the positive electrode sheet and the lithium dendrite, thereby improving the safety of the battery cell.

[0016] In some embodiments, a portion of the isolation assembly is configured as a single-layer structure region, and the single-layer and multi-layer structures are arranged along the winding direction. At least a portion of the single-layer structure region is located between adjacent positive and negative electrode sheets.

[0017] In the above proposed technology, the single-layer structure region corresponds to a position on the negative electrode sheet where lithium is less likely to be deposited. The single-layer structure region has a small number of layers, thus reducing the amount of isolation assembly used and improving the energy density of the battery cell.

[0018] In some embodiments, the positive electrode sheet, isolation assembly, and negative electrode sheet are wound together to form a flat region, which is then connected to a folded region. At least a portion of the single-layer structure region is located within the flat region.

[0019] In the above proposed technology, lithium deposition problems are less likely to occur on the negative electrode sheet in the flat region compared to the folded region. Therefore, even when the single-layer structure region is installed in the flat region, the insulation between the positive and negative electrode sheets can be improved, and the risk of short circuits can be reduced. The volume of the single-layer structure region is small, which can improve the energy density of the electrode assembly.

[0020] In some embodiments, the ends of the multi-layer structure region along the winding direction are located in a flat region.

[0021] In some embodiments, both the multi-layer structure regions and the single-layer structure regions are installed in multiple locations, and the multiple multi-layer structure regions and the multiple single-layer structure regions are installed alternately along the winding direction.

[0022] In the above proposed technology, each of the multiple multi-layer structural regions corresponds to a multiple folded portion of the positive electrode sheet, thereby reducing the risk of short circuits occurring at the multiple folded portions of the positive electrode sheet and improving safety.

[0023] In some embodiments, the number of layers in multiple multi-layer structural regions gradually decreases from the inside to the outside along the winding direction.

[0024] In the above technical solution, the number of layers of the multi-layer structure region is increased in the region with a high short-circuit risk, and the number of layers of the multi-layer structure region is decreased in the region with a low short-circuit risk, so that the safety can be improved and the usage amount of the isolation assembly can be saved.

[0025] In some embodiments, in the winding direction, the whole of the multi-layer structure region is located on the side closer to the starting end of the winding of the isolation assembly of the single-layer structure region. The multi-layer structure region can pass through the folded portion of the innermost circumference of the positive electrode sheet to reduce the short-circuit risk and improve the safety.

[0026] In some embodiments, at least a part of the multi-layer structure region is installed adjacent to the folded portion of the last turn of the positive electrode sheet, thereby reducing the risk of conduction between the folded portion of the last turn of the positive electrode sheet and the lithium dendrite, and improving the safety of the battery cell.

[0027] In some embodiments, the isolation assembly includes a first isolation layer for insulatingly isolating the positive electrode sheet and the negative electrode sheet, and a second isolation layer at least a part of which is located between the positive electrode sheet and the negative electrode sheet and is laminated with the first isolation layer. The region where the first isolation layer overlaps with the second isolation layer and the second isolation layer form the multi-layer structure region of the isolation assembly.

[0028] In the above technical solution, by separately adding a second isolation layer to the electrode assembly, a multi-layer structure region can be formed in the isolation assembly, the short-circuit risk caused by lithium precipitation can be reduced, and the safety can be improved.

[0029] In some embodiments, in the multi-layer structure region, the number of layers of the second isolation layer is 1 to 10.

[0030] In some embodiments, the thickness of the second isolation layer is not greater than the thickness of the first isolation layer.

[0031] <e In the above proposed technology, since the first and second isolation layers can function as multi-layer protection, the thickness of the added second isolation layer can be made less than or equal to the thickness of the first isolation layer, thereby reducing the amount of the second isolation layer used.

[0032] In some examples, the thickness of the first isolation layer is 2 μm to 30 μm, and the thickness of the second isolation layer is 1 μm to 25 μm.

[0033] In some embodiments, the first isolation layer includes a first base film and an insulating layer applied to the surface of the first base film, while the second isolation layer includes a second base film, the second base film of which no insulating layer is applied.

[0034] In the above proposed technology, the second isolation layer primarily serves to isolate the lithium dendrite from the positive electrode sheet. The requirements for other performance aspects of the second isolation layer in the electrode assembly are low, and it is not necessary to install an insulating layer in the second isolation layer. This simplifies the structure of the second isolation layer, saves costs, and improves energy density.

[0035] In some embodiments, the thickness of the second base film is greater than the thickness of the first base film. The second base film having greater thickness can effectively isolate the lithium dendrite from the cathode sheet, thereby improving safety.

[0036] In some embodiments, in the stacking direction between the first isolation layer and the second isolation layer, at least a portion of the second isolation layer is installed separately from the first isolation layer.

[0037] When the first isolation layer is stretched by the pressure of the lithium layer, the influence of the first isolation layer on the separation portion between the second isolation layer and the first isolation layer is small, resulting in a small degree of stretching of the second isolation layer and a low risk of defects. Therefore, the above technical proposal can effectively reduce the risk of lithium dendrites passing through the first and second isolation layers and improve safety.

[0038] In some embodiments, a positive electrode sheet, an isolation assembly, and a negative electrode sheet are wound together to form a bent region and a flat region connected to the bent region. A portion of the second isolation layer is located in the bent region, and the other portion of the second isolation layer is located in the flat region. In the bent region, the second isolation layer is installed separately from the first isolation layer, and in the flat region, the second isolation layer is attached to the first isolation layer.

[0039] In the above proposed technology, the bending region has a high risk of lithium deposition. By installing the second isolation layer in the bending region separately from the first isolation layer, the risk of lithium dendrites passing through the first and second isolation layers can be effectively reduced, thereby improving safety. In the flat region, by attaching the second isolation layer to the first isolation layer, the amount of movement of the second isolation layer along the winding direction can be reduced, thereby reducing the risk of displacement of the second isolation layer.

[0040] In some embodiments, the porosity of the second isolation layer is smaller than that of the first isolation layer.

[0041] In the above proposed technology, since the second isolation layer has a low porosity, after the lithium dendrite passes through the first isolation layer, it is difficult for the lithium dendrite to pass through the pores in the second isolation layer. This reduces the risk of electrical contact between the lithium dendrite and the positive electrode sheet, thereby improving safety.

[0042] In some embodiments, the second isolation layer has a porous structure, and the pore size of the pores in the second isolation layer is 1 μm or less.

[0043] In the above proposed technology, the pore diameter of the holes in the second isolation layer is small, making it difficult for lithium dendrites to pass through. This reduces the risk of electrical conductivity between the lithium dendrites and the positive electrode sheet, thereby improving safety.

[0044] In some embodiments, the elongation rate of the second isolation layer along the winding direction is greater than the elongation rate of the first isolation layer along the winding direction.

[0045] In the above proposed technology, the second isolation layer has a high elongation rate, so when the second isolation layer is subjected to pressure from the lithium layer, defects are less likely to occur during the stretching process, thereby reducing the risk of lithium dendrites passing through the second isolation layer and improving safety.

[0046] In some embodiments, the second isolation layer is formed by folding the edges of the first isolation layer.

[0047] In the above proposed technology, the second isolation layer extends directly from the end of the first isolation layer, eliminating the need to add and fix the second isolation layer separately. This makes the winding process more convenient and improves the overall integrity of the electrode assembly.

[0048] In some embodiments, the positive electrode sheet, isolation assembly, and negative electrode sheet are wound and installed, and the electrode assembly has a starting segment along the winding direction, with the end of the first isolation layer located at the starting segment.

[0049] In the above proposed technology, the second isolation layer extends from the starting segment along the winding direction and passes through the first bend of the positive electrode sheet, thereby reducing the risk of lithium dendrites simultaneously penetrating both the first and second isolation layers and coming into contact with the first bend of the positive electrode sheet, thereby improving safety. At the same time, it reduces the required length of the second isolation layer, saving material and lowering costs.

[0050] In some embodiments, a positive electrode sheet, an isolation assembly, and a negative electrode sheet are wound to form a bent region, the bent region having a first bent portion adjacent to a starting segment along the winding direction, a first isolation layer and a second isolation layer are installed in the first bent portion, the second isolation layer extends from the end of the first isolation layer and extends beyond the first bent portion.

[0051] At the first bending point, the curvature of the bending between the positive electrode sheet and the negative electrode sheet is greatest, and the risk of lithium deposition on the negative electrode sheet during charging is highest. In the above proposed technology, the second isolation layer extends beyond the first bending point, and the first and second isolation layers can protect at least the first bending point where lithium deposition problems are likely to occur, while simultaneously saving on the amount of the second isolation layer used, thereby saving costs and improving the safety and service life of the electrode assembly.

[0052] In some embodiments, a positive electrode sheet, an isolation assembly, and a negative electrode sheet are wound together to form a bent region. The bent region comprises a plurality of bent portions located along the winding direction, the electrode assembly comprises a plurality of second isolation layers, and the first isolation layer and the plurality of second isolation layers are located in at least one of the plurality of bent portions.

[0053] In the above proposed technology, by installing a second isolation layer at some or all of the multiple bending points, the risk of short circuits at the bending points can be effectively reduced and safety can be improved.

[0054] In some embodiments, multiple second isolation layers are spaced apart along the winding direction. The portions of the first isolation layer that overlap with the multiple second isolation layers and the multiple second isolation layers form multiple multi-layer structural regions.

[0055] In the above proposed technology, the method of installing the second isolation layer can be made more flexible, meaning that the second isolation layer can be arbitrarily installed in locations where it is necessary to increase the number of isolation layers, and at the same time, waste caused by adding the second isolation layer in locations where it is not necessary to increase the number of isolation layers can be reduced, thereby improving energy density.

[0056] In some embodiments, the electrode assembly includes a starting segment along the winding direction. Multiple bends include a first bend and a second bend, and along the winding direction, the first bend is closer to the starting segment than the second bend. The thickness of the second isolation layer installed at the first bend is greater than the thickness of the second isolation layer installed at the second bend, thereby reinforcing protection at the first bend, which is more prone to short circuits, improving safety, and saving on the amount of the second isolation layer used.

[0057] In some embodiments, the first isolation layer includes two surfaces along its own thickness direction, and multiple second isolation layers are located on the same surfaces of the first isolation layer. This reduces the impact on the spacing between the positive and negative electrode sheets of the second isolation layer when the first isolation layer is tensioned, thereby reducing the risk of lithium deposition and improving safety.

[0058] In some embodiments, multiple second isolation layers are bonded to the surface of the first isolation layer, thereby reducing the risk of displacement of the second isolation layer during the charging and discharging process of the electrode assembly and ensuring the isolation effect of the second isolation layer.

[0059] In a second embodiment, an embodiment of the present application provides a battery cell comprising a housing and an electrode assembly of any one embodiment of the first embodiment, wherein the electrode assembly is housed within the housing.

[0060] In a third embodiment, the embodiment of the present application provides a battery comprising a plurality of battery cells of a second embodiment.

[0061] In a fourth embodiment, the present invention provides a power consumption device comprising a battery cell for supplying electrical energy according to the second embodiment.

[0062] To more clearly explain the technical concept of the embodiments of this application, the following is a brief description of the drawings necessary for the embodiments of this application. Clearly, the drawings described below represent only a few embodiments of this application, and those skilled in the art can obtain further drawings based on these drawings, even without any creative work. [Brief explanation of the drawing]

[0063] [Figure 1] This is a schematic diagram of the configuration of a vehicle according to several embodiments of the present invention.

[0064] [Figure 2] This is a schematic diagram of the exploded three-dimensional structure of a battery according to several embodiments of the present invention.

[0065] [Figure 3] This is a schematic diagram of the exploded three-dimensional structure of a battery cell according to some embodiments of the present invention.

[0066] [Figure 4] This is a schematic diagram of the configuration of an electrode assembly according to several embodiments of the present application.

[0067] [Figure 5] Figure 4 is a partially enlarged schematic diagram of the electrode assembly shown.

[0068] [Figure 6] Figure 4 is a schematic diagram of the electrode assembly before winding.

[0069] [Figure 7] Figure 6 is a schematic diagram of the configuration of some of the isolated assemblies.

[0070] [Figure 8] This is a schematic diagram of the configuration of an electrode assembly according to some other embodiments of the present invention.

[0071] [Figure 9] Figure 8 is a schematic diagram of a part of the electrode assembly shown.

[0072] [Figure 10] Figure 8 is a schematic diagram of the electrode assembly before winding.

[0073] [Figure 11] This is a schematic diagram of the configuration of an electrode assembly before winding, according to several further embodiments of the present application.

[0074] [Figure 12] This is a schematic diagram of the configuration of an electrode assembly according to several further embodiments of the present invention.

[0075] Explanation of the symbols

[0076] 1 Vehicle, 2 Battery, 3 Controller, 4 Motor, 5 Housing, 5a First housing section, 5b Second housing section, 5c Housing space, 6 Battery cell, 10 Electrode assembly, 100 Starting segment, 20 Housing, 21 Case, 22 End cover, 30 Electrode terminals, 11 Positive electrode sheet, 111 First bend section, 112 Second bend section, 113 Final bend section, 12 Negative electrode sheet, 13 Isolation assembly, 131 First isolation layer, 131a First base film, 131b Insulating layer, 132 Second isolation layer, 132a Second base film, 13a Multi-layer structure region, 13b Single-layer structure region, 13c Winding start end, A Flat region, B Bending region, B1 First bend section, B2 Second bend section, W Winding direction. [Modes for carrying out the invention]

[0077] To further clarify the purpose, technical concept and advantages of the embodiments of this application, the technical concept of the embodiments of this application will be clearly and completely described below with reference to the drawings of the embodiments of this application, and it is clear that the embodiments described are some embodiments of this application, not all embodiments. All other embodiments obtained based on the embodiments of this application, without creative work by a person skilled in the art, are all within the scope of protection of this application.

[0078] Unless otherwise specified, all technical terms and technical descriptions used herein have the same meaning as those generally understood by those skilled in the art of this application. The terms used herein are intended solely to describe specific embodiments and are not intended to limit this application. The terms “equipped,” “having,” and any variations thereof in the description of the specification, claims, and drawings of this application are intended to cover non-exclusive inclusion. Terms such as “first,” “second,” etc., in the specification, claims, or drawings of this application are used to distinguish different subjects and are not used to describe a particular order or hierarchical relationship.

[0079] Furthermore, in the description of this application, the directional or positional relationships indicated by terms such as "center," "lateral direction," "length," "width," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," "axial direction," "radial direction," and "circumferential direction" are the directional or positional relationships shown in the drawings. These are intended to facilitate and simplify the description of this application and do not indicate or imply that the shown device or element has a specific direction or must be constructed or operated in a specific direction. Therefore, they should not be understood as limiting this application.

[0080] In this description, unless otherwise specified or limited, the terms “attachment,” “connection,” “linking,” and “mounting” should be understood in a broad sense. For example, it may be a fixed connection, a removable connection, or an integral connection; it may be a direct connection, an indirect connection via an intermediate medium, or internal communication between two elements. A person skilled in the art will be able to understand the specific meaning of the above terms in this application depending on the specific circumstances.

[0081] As used herein, “Examples” means that certain features, structures, or properties described with reference to the Examples may be included in at least one Example of the Application. The appearance of the term at each location in the Specification does not necessarily mean the same Example, nor does it mean an independent or candidate Example that is mutually exclusive with the other Examples. The Examples described herein can be combined with other Examples, as will be understood explicitly and implicitly by those skilled in the art.

[0082] In this specification, the terms "and / or" simply describe the relationship between related objects and can indicate that three types of relationships exist. For example, A and / or B can indicate three situations: A exists alone, A and B exist simultaneously, or B exists alone. In this specification, the symbol " / " generally indicates that the preceding and following related objects are in an "or" relationship.

[0083] In this application, "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more sets (including two sets), and "multiple sheets" refers to two or more sheets (including two sheets).

[0084] In this application, the battery cell may include lithium-ion secondary battery cells, lithium-ion primary battery cells, lithium-sulfur battery cells, sodium lithium-ion battery cells, sodium-ion battery cells, or magnesium-ion battery cells, but the embodiments of this application are not limited to these. The battery cell may be cylindrical, flattened, rectangular, or have other shapes, but the embodiments of this application are not limited to these. Battery cells are generally classified into cylindrical battery cells, prismatic battery cells, and soft-pack battery cells by their packaging method, but the embodiments of this application are not limited to these.

[0085] A battery cell comprises an electrode assembly and an electrolyte, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet, and a separator. The battery cell operates primarily by the movement of metal ions between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer being coated on the surface of the positive electrode current collector, current collectors without the positive electrode active material layer protruding from current collectors with the positive electrode active material layer, and current collectors without the positive electrode active material layer forming a positive electrode tab. Taking a lithium-ion battery as an example, the material of the positive electrode current collector may be aluminum, and the positive electrode active material may be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is coated on the surface of the negative electrode current collector. Current collectors without the negative electrode active material layer protrude from the current collectors with the negative electrode active material layer, and these current collectors without the negative electrode active material layer form negative electrode tabs. The material of the negative electrode current collector may be copper, and the negative electrode active material may be carbon or silicon, etc. To ensure that a large current can be carried without melting, there are multiple positive electrode tabs and the negative electrode tabs are also multiple and stacked. The separator material may be PP (polypropylene) or PE (polyethylene), etc. The electrode assembly may be a wound structure or a stacked structure, and the embodiments of this application are not limited to these. The development of battery technology necessitates the simultaneous consideration of multiple design factors of performance parameters such as energy density, cycle life, discharge capacity, and charge / discharge ratio, as well as the safety of the battery.

[0086] The battery referred to in the embodiments of this application refers to a single physical module that provides higher voltage and capacity by comprising one or more battery cells. For example, the battery referred to in this application may comprise a battery module or a battery pack. The battery generally comprises a housing for enclosing one or more battery cells. The housing can prevent liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0087] A separator is an electronically insulating material placed between a positive electrode sheet and a negative electrode sheet. Its main role is to prevent contact between the positive and negative electrode sheets and to prevent the electrode assembly from developing an internal short circuit. The separator has a large number of through-pores, which can ensure that electrolyte ions can pass through freely. In particular, the separator has good permeability to lithium ions. Exemplarily, the separator may include an isolation base layer and a functional layer located on the surface of the isolation base layer. The isolation base layer may be at least one of polypropylene, polyethylene, ethylene-propylene copolymer, polybutylene terephthalate, etc., and the functional layer may be a mixture layer of ceramic oxide and adhesive.

[0088] Separators play a crucial role in electrode assemblies, and can directly cause short circuits, leading to reduced performance and service life.

[0089] During battery cell charging, metal ions detach from the positive electrode active material layer and are inserted into the negative electrode active material layer. However, several abnormal situations can occur, potentially leading to metal ion deposition. Taking lithium-ion battery cells as an example, if the lithium insertion space in the negative electrode active material layer is insufficient, the resistance to lithium ion insertion into the negative electrode active material layer is too high, or the detachment of lithium ions from the positive electrode active material layer is too rapid, the detached lithium ions cannot be inserted equally into the negative electrode active material layer of the negative electrode sheet. These lithium ions that cannot be inserted into the negative electrode sheet gain electrons only on the surface of the negative electrode sheet, forming elemental metallic lithium. This is known as lithium deposition. Lithium deposition not only degrades the performance of the battery cell, but also significantly shortens the cycle life and limits the rapid charging capacity of the battery cell. Furthermore, if lithium deposits in the battery cell, the deposited lithium metal is highly reactive and reacts with the electrolyte at low temperatures, causing a decrease in the battery cell's tonic temperature (Tonset) and an increase in the rate of self-heating, seriously compromising the safety of the battery cell. Moreover, if lithium deposition is severe, the detached lithium ions can form a lithium layer on the surface of the negative electrode sheet, and this lithium layer can cause a short circuit between adjacent positive and negative electrode sheets, potentially posing a safety risk.

[0090] After diligent research, the inventors discovered that the short circuit was caused by lithium dendrites in the lithium layer passing through the separator. Specifically, after the lithium layer is deposited on the surface of the negative electrode sheet, the lithium layer presses against the separator between the positive and negative electrode sheets, and the separator is stretched by the pressure of the lithium layer. The separator has a porous structure, and when the separator is stretched by force, the pore size of some of the pores in the separator increases, thereby forming a defect region on the separator. When the defect region of the separator faces the lithium layer, the small lithium dendrites in the lithium layer can pass through the larger pores in the defect region, causing the lithium dendrites to come into contact with the positive electrode sheet and potentially causing a short circuit.

[0091] In view of this, the inventors of the present application provide an electrode assembly comprising a positive electrode sheet, a negative electrode sheet, and an isolation assembly for isolating the positive electrode sheet and the negative electrode sheet, wherein at least a portion of the isolation assembly is set up as a multi-layer structure region, and at least a portion of the multi-layer structure region is located between adjacent positive electrode sheets and negative electrode sheets. The multi-layer structure region of the isolation assembly can reduce the risk of short circuits between the positive and negative electrode sheets and improve service life and safety.

[0092] The following embodiments will be explained using the example that the power consumption device is a vehicle, for the sake of clarity.

[0093] Figure 1 is a schematic diagram of the configuration of a vehicle according to some embodiments of the present invention. As shown in Figure 1, a battery 2 is installed inside the vehicle 1, and the battery 2 may be installed at the bottom, head, or tail of the vehicle 1. The battery 2 is used to supply power to the vehicle 1, and for example, the battery 2 can serve as the operating power source for the vehicle 1.

[0094] Vehicle 1 further includes a controller 3 and a motor 4. The controller 3 is used to control the supply of power from the battery 2 to the motor 4, and is used, for example, for the power consumption required for starting, navigation, and driving operations of Vehicle 1.

[0095] In some embodiments of the present invention, the battery 2 may serve not only as the operating power source for the vehicle 1 but also as the driving power source for the vehicle 1, supplying driving force to the vehicle 1 by replacing or partially replacing fuel oil or natural gas.

[0096] Figure 2 is a schematic diagram of the exploded three-dimensional structure of a battery according to some embodiments of the present invention. As shown in Figure 2, the battery 2 comprises a housing 5 and battery cells 6 housed within the housing 5.

[0097] The housing 5 is used to house the battery cells 6, and the housing 5 may have various structures. In some embodiments, the housing 5 comprises a first housing portion 5a and a second housing portion 5b, the first housing portion 5a and the second housing portion 5b covering and joining each other, and together the first housing portion 5a and the second housing portion 5b define a housing space 5c for housing the battery cells 6. The second housing portion 5b may be a hollow structure with one end open, and the first housing portion 5a is a plate-like structure, and the first housing portion 5a is covered on the open side of the second housing portion 5b, thereby forming a housing 5 having a housing space 5c. Both the first housing portion 5a and the second housing portion 5b may be hollow structures with one side open, and the open side of the first housing portion 5a is covered on the open side of the second housing portion 5b, thereby forming a housing 5 having a housing space 5c. Naturally, the first housing portion 5a and the second housing portion 5b may be of various shapes, such as a cylinder or a rectangular parallelepiped.

[0098] To improve the airtightness after connecting the first housing portion 5a and the second housing portion 5b, a sealing material such as a sealant or a sealing ring may be installed between the first housing portion 5a and the second housing portion 5b.

[0099] When the first housing portion 5a is covered by the top of the second housing portion 5b, the first housing portion 5a may be called the upper housing and the second housing portion 5b may be called the lower housing.

[0100] In battery 2, there are multiple battery cells 6. The multiple battery cells 6 may be connected in series, in parallel, or in series-parallel, where series-parallel means that there are both series and parallel connections among the multiple battery cells 6. The multiple battery cells 6 may be directly connected in series, in parallel, or in series-parallel, and the entire assembly composed of multiple battery cells 6 may be housed in the casing 5. Naturally, multiple battery cells 6 may first be connected in series, in parallel, or in series-parallel to form a battery module, and multiple battery modules may be further connected in series, in parallel, or in series-parallel to form a single unit, which may then be housed in the casing 5.

[0101] Figure 3 is a schematic diagram of the exploded three-dimensional structure of a battery cell according to some embodiments of the present application.

[0102] The battery cell 6 represents the smallest unit that makes up the battery 2. As shown in Figure 3, the battery cell 6 comprises a housing 20, an electrode assembly 10, and other functional components, with the electrode assembly 10 housed within the housing 20.

[0103] In some embodiments, the housing 20 may include an end cover 22 and a case 21.

[0104] The end cover 22 is a component that covers the opening of the case 21 and isolates the internal environment of the battery cell 6 from the external environment. The shape of the end cover 22 can be fitted to the case 21 to match the shape of the case 21, but is not limited thereto. Optionally, the end cover 22 may be manufactured from a material having a certain hardness and strength (e.g., an aluminum alloy), so that the end cover 22 is less likely to deform when subjected to pressure impact, allowing the battery cell 6 to have higher structural strength and improving safety performance. Functional components such as electrode terminals 30 may be installed on the end cover 22. The electrode terminals 30 are electrically connected to the electrode assembly 10 and are used to output or input electrical energy to the battery cell 6.

[0105] In some embodiments, the end cover 22 may be further equipped with a pressure release mechanism to release internal pressure when the internal pressure or temperature of the battery cell 6 reaches a threshold. The material of the end cover 22 may be of several types, such as copper, iron, aluminum, stainless steel, aluminum alloy, or plastic, but the embodiments of the present application are not particularly limited to these.

[0106] In some embodiments, an additional insulating member may be installed inside the end cover 22 to isolate the end cover 22 from the electrical connection members inside the case 21, thereby reducing the risk of short circuits. Exemplarily, the insulating member may be made of plastic, rubber, or the like.

[0107] The case 21 is an assembly that fits with the end cover 22 to form the internal environment of the battery cell 6, where the formed internal environment is used to house the electrode assembly 10, electrolyte, and other components. The case 21 and the end cover 22 may be independent components, and the case 21 may have an opening, which is covered by the end cover 22 to form the internal environment of the battery cell 6. Optionally, the end cover 22 and the case 21 may be integrated, specifically, the end cover 22 and the case 21 may first form a common connection surface before other components are placed in the case, and if it is necessary to seal the inside of the case 21, the end cover 22 can further cover the case 21. The case 21 may have various shapes and sizes, such as a rectangular parallelepiped, cylindrical shape, or hexagonal prism shape. Specifically, the shape of the case 21 can be determined according to the specific shape and dimensions of the electrode assembly 10. The material of case 21 may be of several types, such as copper, iron, aluminum, stainless steel, aluminum alloy, or plastic, but the embodiments of the present application are not particularly limited to these.

[0108] The electrode assembly 10 is a component in the battery cell 6 that immerses in the electrolyte and undergoes an electrochemical reaction. One or more electrode assemblies 10 can be included in the case 21. The electrode assembly 10 is mainly formed by winding a positive electrode sheet and a negative electrode sheet, and a separator is usually placed between the positive electrode sheet and the negative electrode sheet. The portions of the positive electrode sheet and the negative electrode sheet that have active material constitute the main body of the electrode assembly 10, and the portions of the positive electrode sheet and the negative electrode sheet that do not have active material each constitute a tab. The positive electrode tab and the negative electrode tab may be located in common at one end of the main body, or they may be located at both ends of the main body, respectively. During the charging and discharging process of the battery cell 6, the positive electrode active material and the negative electrode active material react with the electrolyte, and the tabs are connected to the electrode terminals 30 to form an electric current circuit.

[0109] Figure 4 is a schematic diagram of the structure of an electrode assembly according to several embodiments of the present application. Figure 5 is a partially enlarged schematic diagram of the electrode assembly shown in Figure 4. Figure 6 is a schematic diagram of the electrode assembly shown in Figure 4 before winding. Figure 7 is a schematic diagram of the isolation assembly shown in Figure 6.

[0110] As shown in Figures 4 to 7, the electrode assembly 10 of the embodiment of the present invention comprises a positive electrode sheet 11, a negative electrode sheet 12, and an isolation assembly 13 for isolating the positive electrode sheet 11 and the negative electrode sheet 12. At least a portion of the isolation assembly 13 is set up as a multi-layer structure region 13a, and at least a portion of the multi-layer structure region 13a is located between the adjacent positive electrode sheet 11 and the negative electrode sheet 12.

[0111] The electrode assembly 10 may have multiple shapes; for example, the electrode assembly 10 can be a cylinder, a flattened body, a prism (e.g., a triangular prism, a square prism, or a hexagonal prism) or other shapes.

[0112] The isolation assembly 13 may be one or more. For example, two isolation assemblies 13 may be installed. In this application, one isolation assembly 13, the negative electrode sheet 12, the other isolation assembly 13, and the positive electrode sheet 11 can be stacked in order, and then wound around two or more times to form a wound structure. When multiple isolation assemblies 13 are installed, the multi-layer structure region 13a may be installed in only one isolation assembly 13, or the multi-layer structure region 13a may be installed in each of the isolation assemblies 13.

[0113] The isolation assembly 13 is an assembly containing one type of insulating film, used to isolate the positive electrode sheet 11 and the negative electrode sheet 12. Such an insulating film has a large number of permeable pores, which can ensure that metal ions can pass through freely. Exemplarily, the insulating film has good permeability to lithium ions and is essentially unable to block the passage of lithium ions.

[0114] The isolation assembly 13 may be manufactured from a single insulating film or from multiple insulating films.

[0115] The multi-layer structure region 13a is a region of the isolation assembly 13 having a multi-layer structure. Exemplarily, a region in which multiple isolation layers of the isolation assembly 13 are stacked constitutes the multi-layer structure region 13a, and the direction in which the multiple isolation layers are stacked is parallel to the stacking direction of the positive electrode sheet 11 and the negative electrode sheet 12. In the multi-layer structure region 13a, two adjacent isolation layers may be connected to each other or separated from each other.

[0116] The number of layers in the multi-layer structure region 13a is two or more. For example, the number of layers in the multi-layer structure region 13a may be between 2 and 15.

[0117] The isolation assembly 13 may be a multi-layer structure region 13a overall, or only a part of it may be a multi-layer structure region 13a. For example, the isolation assembly 13 may have only a part of it as a multi-layer structure region 13a, or in other words, a part of the isolation assembly 13 may be set up as a single-layer structure region 13b.

[0118] The multi-layer structure region 13a may be one or multiple. For example, there may be multiple multi-layer structure regions 13a, and adjacent multi-layer structure regions 13a are connected by single-layer structure regions 13b.

[0119] The multi-layer structure region 13a may be located entirely between the positive electrode sheet 11 and the negative electrode sheet 12, or only a portion of it may be located between the positive electrode sheet 11 and the negative electrode sheet 12.

[0120] The multi-layer structure region 13a corresponds to a position that facilitates lithium deposition on the negative electrode sheet 12. By blocking lithium dendrites, the multi-layer structure region 13a reduces the probability of electrical conductivity between the positive electrode sheet 11 and the negative electrode sheet 12, effectively reducing the risk of short circuits and improving the service life and safety of the electrode assembly 10.

[0121] Specifically, after the lithium layer is deposited on the surface of the negative electrode sheet 12, the lithium layer presses against the isolation layer adjacent to the negative electrode sheet 12 in the multi-layer structure region 13a, and the isolation layer adjacent to the negative electrode sheet 12 is stretched by the pressure of the lithium layer. If the pore diameter of some of the pores in the isolation layer adjacent to the negative electrode sheet 12 becomes larger and forms a defect region, small lithium dendrites in the lithium layer may pass through the defect region. The isolation layer in the multi-layer structure region 13a, which is far from the negative electrode sheet 12, insulates the lithium dendrites that have passed through the defect region from the positive electrode sheet 11, thereby reducing the risk of lithium dendrites coming into contact with the positive electrode sheet 11 and providing safety.

[0122] In the multi-layer structure region 13a, the isolation layer away from the negative electrode sheet 12 is at a large distance from the lithium layer, resulting in low pressure from the lithium layer and a low risk of stretching and generating defect regions due to the pressure. The position where defect regions are generated in the isolation layer during the stretching process is not constant, and defect regions can also be generated in the isolation layer away from the negative electrode sheet 12. The possibility of a defect region in the isolation layer far from the negative electrode sheet 12 and a defect region in the isolation layer close to the negative electrode sheet 12 directly facing each other is small, making it difficult for lithium dendrites to pass through the multi-layer structure region 13a simultaneously. Therefore, by providing the multi-layer structure region 13a in this embodiment, the risk of short circuits can be effectively reduced and safety can be improved.

[0123] In some embodiments, the positive electrode sheet 11, the isolation assembly 13, and the negative electrode sheet 12 are wound together to form a folded region B, and at least a portion of the multi-layer structure region 13a is placed in the folded region B.

[0124] The winding direction W is the direction in which the positive electrode sheet 11, the negative electrode sheet 12, and the isolation assembly 13 are wound circumferentially from the inside out. Exemplarily, in the figure, the winding direction W is counterclockwise.

[0125] The bending region B is a region in the electrode assembly 10 that has a bending structure, and in this bending region B, the positive electrode sheet 11, the negative electrode sheet 12, and the isolation assembly 13 are all bent. Exemplarily, the portion of the positive electrode sheet 11 located in bending region B is bent in a substantially arc shape, and the portion of the negative electrode sheet 12 located in bending region B is also bent in a substantially arc shape.

[0126] The winding device can wind the positive electrode sheet 11, the negative electrode sheet 12, and the isolation assembly 13 multiple times, forming several layers with each turn. One turn is defined as starting from a point on the electrode assembly 10 as the starting end, completing one turn along the winding direction W, reaching another point as the ending end, with the ending end, starting end, and the center of this turn being in a straight line, and the starting end being between the ending end and the center of this turn.

[0127] The electrode assembly 10 may be entirely a bent region B, or only a portion of it may be a bent region B. Exemplarily, the electrode assembly includes a flat region A and a bent region B, where the bent region B is connected to the flat region A, and the flat region A is the region of the electrode assembly 10 having a flat structure.

[0128] The multi-layer structure region 13a may be entirely installed in the folding region B, or only a portion of it may be installed in the folding region B.

[0129] The positive electrode sheet 11 and negative electrode sheet 12 located in the bending region B need to be bent, and stress concentration is likely to occur in the positive electrode active material layer and the negative electrode active material layer during the bending process, leading to the detachment of the respective active materials. Due to the detachment of active materials, particularly the detachment of active material on the negative electrode sheet 12, the lithium insertion position in the negative electrode active material layer of the negative electrode sheet 12 is less than the number of lithium ions that the positive electrode active material layer of the adjacent positive electrode sheet 11 can provide, which may cause lithium deposition. In the embodiment of the present invention, at least a portion of the multi-layer structure region 13a is placed in the bending region B, and even if lithium is deposited in the bending region B, the multi-layer structure region 13a blocks lithium dendrites, reduces the probability of conductivity between the positive electrode sheet 11 and the negative electrode sheet 12, effectively reduces the risk of short circuits, and improves the service life and safety of the electrode assembly 10.

[0130] In some embodiments, at least a portion of the multi-layer structure region 13a is located adjacent to the first folded portion 111 of the positive electrode sheet 11.

[0131] The fact that the multi-layer structure region 13a is adjacent to the first folded portion 111 of the positive electrode sheet 11 means that the negative electrode sheet 12 is not installed between the multi-layer structure region 13a and the first folded portion 111 of the positive electrode sheet 11.

[0132] The first folded portion 111 of the positive electrode sheet 11 is the portion that is folded for the first time during the process of winding the positive electrode sheet 11 along the winding direction W. Exemplarily, the first folded portion 111 of the positive electrode sheet 11 is approximately arc-shaped.

[0133] The multi-layer structure region 13a adjacent to the first folded portion 111 of the positive electrode sheet 11 may be located inside the first folded portion 111 of the positive electrode sheet 11, or it may be located outside the first folded portion 111 of the positive electrode sheet 11.

[0134] The curvature of the first bend portion 111 of the positive electrode sheet 11 is large, and during charging, the negative electrode sheet 12 adjacent to the first bend portion 111 of the positive electrode sheet 11 is prone to lithium deposition problems. In this embodiment, by placing at least a portion of the multi-layer structure region 13a adjacent to the first bend portion 111 of the positive electrode sheet 11, the risk of electrical conductivity between the first bend portion 111 of the positive electrode sheet 11 and the lithium dendrite can be reduced, thereby improving the safety of the battery cell 6.

[0135] In some embodiments, multi-layer structure regions 13a are provided on both sides of the first folded portion 111 of the positive electrode sheet 11, and the number of layers in the multi-layer structure region 13a located inside the first folded portion 111 of the positive electrode sheet 11 is equal to or greater than the number of layers in the multi-layer structure region 13a located outside the first folded portion 111 of the positive electrode sheet 11.

[0136] The multi-layer structure regions 13a on both sides of the first bent portion 111 of the positive electrode sheet 11 can belong to the same isolation assembly 13, or they can each belong to two different isolation assemblies 13.

[0137] The curvature of the negative electrode sheet 12 located inside the first bend portion 111 of the positive electrode sheet 11 is greater than the curvature of the negative electrode sheet 12 located outside the first bend portion 111 of the positive electrode sheet 11, and lithium is more likely to precipitate on the negative electrode sheet 12 located inside the first bend portion 111 of the positive electrode sheet 11. In this embodiment, by making the number of layers in the multi-layer structure region 13a located inside the first bend portion 111 of the positive electrode sheet 11 greater than or equal to the number of layers in the multi-layer structure region 13a located outside the first bend portion 111 of the positive electrode sheet 11, the risk of electrical conductivity between the first bend portion 111 of the positive electrode sheet 11 and the lithium dendrite can be reduced, and the safety of the battery cell 6 can be improved.

[0138] In some embodiments, the number of layers in the multi-layer structure region 13a located inside the first folded portion 111 of the positive electrode sheet 11 is greater than the number of layers in the multi-layer structure region 13a located outside the first folded portion 111 of the positive electrode sheet 11.

[0139] In some embodiments, at least a portion of the multi-layer structure region 13a is located adjacent to the second folded portion 112 of the positive electrode sheet 11.

[0140] The fact that the multi-layer structure region 13a is adjacent to the second folded portion 112 of the positive electrode sheet 11 means that the negative electrode sheet 12 is not installed between the multi-layer structure region 13a and the second folded portion 112 of the positive electrode sheet 11.

[0141] The second folded portion 112 of the positive electrode sheet 11 is the portion that is folded for the second time during the process of winding the positive electrode sheet 11 along the winding direction W. Exemplarily, the second folded portion 112 of the positive electrode sheet 11 is approximately arc-shaped.

[0142] The multi-layer structure region 13a adjacent to the second folded portion 112 of the positive electrode sheet 11 may be located inside the second folded portion 112 of the positive electrode sheet 11, or it may be located outside the second folded portion 112 of the positive electrode sheet 11.

[0143] The multi-layer structure region 13a adjacent to the second folded portion 112 of the positive electrode sheet 11 may be integrally connected to the multi-layer structure region 13a adjacent to the first folded portion 111 of the positive electrode sheet 11, or they may be installed at intervals along the winding direction W.

[0144] The curvature of the second bend portion 112 of the positive electrode sheet 11 is large, making it prone to lithium deposition problems on the negative electrode sheet 12 adjacent to the second bend portion 112 of the positive electrode sheet 11 during charging. In this embodiment, by placing at least a portion of the multi-layer structure region 13a adjacent to the second bend portion 112 of the positive electrode sheet 11, the risk of electrical conductivity between the second bend portion 112 of the positive electrode sheet 11 and the lithium dendrite can be reduced, thereby improving the safety of the battery cell 6.

[0145] In some embodiments, the number of layers in the multi-layer structure region 13a located inside the first folded portion 111 of the positive electrode sheet 11 is equal to or greater than the number of layers in the multi-layer structure region 13a located inside the second folded portion 112 of the positive electrode sheet 11.

[0146] The curvature of the negative electrode sheet 12 located inside the first bend portion 111 of the positive electrode sheet 11 is greater than the curvature of the negative electrode sheet 12 located inside the second bend portion 112 of the positive electrode sheet 11, and lithium is more likely to precipitate on the negative electrode sheet 12 located inside the first bend portion 111 of the positive electrode sheet 11. In this embodiment, by making the number of layers in the multi-layer structure region 13a located inside the first bend portion 111 of the positive electrode sheet 11 greater than or equal to the number of layers in the multi-layer structure region 13a located inside the second bend portion 112 of the positive electrode sheet 11, the risk of electrical conductivity between the first bend portion 111 of the positive electrode sheet 11 and the lithium dendrite can be reduced, and the safety of the battery cell 6 can be improved.

[0147] In some embodiments, the number of layers in the multi-layer structure region 13a located inside the first folded portion 111 of the positive electrode sheet 11 is equal to the number of layers in the multi-layer structure region 13a located inside the second folded portion 112 of the positive electrode sheet 11.

[0148] In some embodiments, a portion of the isolation assembly 13 is configured as a single-layer structure region 13b, and the single-layer structure region 13b and the multi-layer structure region 13a are configured along the winding direction W. At least a portion of the single-layer structure region 13b is located between adjacent positive electrode sheets 11 and negative electrode sheets 12.

[0149] A single-layer structure region 13b is a region of the isolation assembly 13 that has a single-layer structure. There may be one single-layer structure region 13b or multiple single-layer structure regions 13b. For example, both single-layer structure regions 13b and multi-layer structure regions 13a can be multiple, and the multiple single-layer structure regions 13b and multiple multi-layer structure regions 13a are arranged alternately along the winding direction W.

[0150] The single-layer structure region 13b corresponds to a location on the negative electrode sheet 12 where lithium deposition is less likely. The single-layer structure region 13b has a small number of layers, thus reducing the amount of isolation assembly 13 used and improving the energy density of the battery cell 6.

[0151] In some embodiments, the total thickness of the multi-layer structure region 13a is greater than the thickness of the single-layer structure region 13b.

[0152] In some embodiments, the positive electrode sheet 11, the isolation assembly 13, and the negative electrode sheet 12 are wound together to form a flat region A, which is connected to a folded region B. At least a portion of the single-layer structure region 13b is located in the flat region A.

[0153] Flat region A is a region of the electrode assembly 10 that has a flat structure, and the portions of the positive electrode sheet 11 and the negative electrode sheet 12 located in flat region A are installed almost flat. Exemplarily, the surfaces of the positive electrode sheet and the negative electrode sheet of each layer located in flat region A are both almost flat.

[0154] Both the positive electrode sheet 11 and the negative electrode sheet 12 located in flat region A are in a flat state, making it difficult for the active material in flat region A to fall off, and making it difficult for lithium deposition problems to occur on the negative electrode sheet 12 located in flat region A. Therefore, even if the single-layer structure region 13b is installed in flat region A, the insulation between the positive and negative electrode sheets can be improved, and the risk of short circuits can be reduced.

[0155] In some embodiments, two folding regions B are provided, and the two folding regions B are located at opposite ends of the flat region A.

[0156] In some embodiments, the ends of the multi-layer structure region 13a along the winding direction W are located in the flat region A.

[0157] In some examples, one end of the multi-layer structure region 13a along the winding direction W is located in the flat region A, and the other end is located in the folded region B.

[0158] In another example, both ends of the multi-layer structure region 13a along the winding direction W are located in the flat region A, and in this way the entire multi-layer structure region 13a passes through the folded region B, thereby reducing the risk of short-circuiting the folded region B.

[0159] In some embodiments, in the winding direction W, the entire multi-layer structure region 13a is located on the side closer to the winding start end 13c of the isolation assembly 13 of the single-layer structure region 13b.

[0160] The winding start end 13c of the isolation assembly 13 is the innermost end along the winding direction W of the isolation assembly 13. There is one multi-layer structure region 13a and one single-layer structure region 13b.

[0161] The multi-layer structure region 13a is located close to the winding start end 13c of the isolation assembly 13. This placement allows the multi-layer structure region 13a to pass through the innermost folded portion of the positive electrode sheet 11, thereby reducing the risk of short circuits and improving safety.

[0162] In some embodiments, the isolation assembly 13 includes a first isolation layer 131 and a second isolation layer 132, the first isolation layer 131 being used to electrically isolate the positive electrode sheet 11 and the negative electrode sheet 12, and at least a portion of the second isolation layer 132 being located between the positive electrode sheet 11 and the negative electrode sheet 12 and laminated with the first isolation layer 131. The region of the first isolation layer 131 overlapping with the second isolation layer 132 and the second isolation layer 132 form a multi-layer structure region 13a of the isolation assembly 13.

[0163] Exemplary, the first isolation layer 131 can be understood as a single isolation layer between the positive electrode sheet 11 and the negative electrode sheet 12 in the related technology, i.e., a base isolation layer, and the second isolation layer 132 can be understood as an additional isolation layer, i.e., an additional isolation layer.

[0164] In the isolation assembly 13, the second isolation layer 132 may be one or more.

[0165] The first isolation layer 131 and the second isolation layer 132 may be two parts of an integrated member, or they may be two separate members provided separately.

[0166] The first isolation layer 131 and the second isolation layer 132 may be manufactured from the same material or from different materials.

[0167] In this embodiment, the thickness of the first isolation layer 131 and the thickness of the second isolation layer 132 are not limited; the thickness of the first isolation layer 131 may be greater than or equal to the thickness of the second isolation layer 132, or less than or equal to the thickness of the second isolation layer 132.

[0168] The first isolation layer 131 and the second isolation layer 132 are laminated between the positive electrode sheet 11 and the negative electrode sheet 12. The second isolation layer 132 may be installed independently of the first isolation layer 131, that is, in the lamination direction of the first isolation layer 131 and the second isolation layer 132, the second isolation layer 132 faces the surface of the first isolation layer 131 and there is no adhesive or other connection between it and the first isolation layer 131. Naturally, the second isolation layer 132 may be attached to the surface of the first isolation layer 131, and exemplary, the second isolation layer 132 may be attached entirely to the first isolation layer 131, or only a part of it may be attached to the first isolation layer 131. Attaching means bonding by sticking.

[0169] In the embodiments of the present invention, by additionally installing a second isolation layer 132 on the electrode assembly 10, a multi-layer structure region 13a is formed on the isolation assembly 13, thereby reducing the risk of short circuits due to lithium deposition and improving safety.

[0170] In some embodiments, the number of layers of the second isolation layer 132 in the multi-layer structure region 13a is 1 to 10. For example, the number of layers of the second isolation layer 132 in the multi-layer structure region 13a is 1, 2, 3, 5, or 10. When multiple second isolation layers 132 are installed in one multi-layer structure region 13a, the dimensions of the multiple second isolation layers 132 along the winding direction may be the same or different.

[0171] In some embodiments, there are multiple multi-layer structural regions 13a of the isolation assembly 13, and the number of second isolation layers 132 in the multiple multi-layer structural regions 13a may be the same or different.

[0172] In some embodiments, the thickness of the second isolation layer 132 is less than or equal to the thickness of the first isolation layer 131.

[0173] Since the first isolation layer 131 and the second isolation layer 132 can function as multi-layer protection, the thickness of the added second isolation layer 132 can be made less than or equal to the thickness of the first isolation layer 131, thereby reducing the amount of the second isolation layer 132 used.

[0174] Selectively, the thickness of the second isolation layer 132 is smaller than the thickness of the first isolation layer 131.

[0175] In some embodiments, the second isolation layer 132 is installed on the side of the first isolation layer 131 facing the positive electrode sheet 11.

[0176] In some embodiments, the thickness of the first isolation layer 131 is 2 μm to 30 μm. Selectively, the thickness of the first isolation layer 131 is 2 μm, 5 μm, 7 μm, 10 μm, 15 μm, 20 μm, or 30 μm.

[0177] In some embodiments, the thickness of the second isolation layer 132 is 1 μm to 25 μm. Selectively, the thickness of the second isolation layer 132 is 1 μm, 2 μm, 5 μm, 7 μm, 10 μm, 15 μm, 20 μm, or 25 μm.

[0178] In some embodiments, the porosity of the second isolation layer 132 is smaller than that of the first isolation layer 131. Because the second isolation layer 132 has a smaller porosity, after the lithium dendrites have passed through the first isolation layer 131, they are less likely to pass through the pores in the second isolation layer 132, thereby reducing the risk of electrical contact between the lithium dendrites and the positive electrode sheet 11 and improving safety.

[0179] In some embodiments, the second isolation layer 132 has a porous structure, and the pore diameter of the pores in the second isolation layer 132 is 1 μm or less.

[0180] The small pore size of the holes in the second isolation layer 132 makes it difficult for lithium dendrites to pass through, thereby reducing the risk of electrical contact between the lithium dendrites and the positive electrode sheet 11 and improving safety.

[0181] In some embodiments, the elongation of the first isolation layer 131 along the winding direction W is 30% to 1000%, and the elongation of the second isolation layer 132 along the winding direction W is 30% to 1000%.

[0182] In some embodiments, the elongation rate of the second isolation layer 132 along the winding direction W is greater than the elongation rate of the first isolation layer 131 along the winding direction W.

[0183] The second isolation layer 132 has a high elongation rate, which makes it less likely for defects to occur during the stretching process when the second isolation layer 132 is pressed by the lithium layer. This reduces the risk of lithium dendrites passing through the second isolation layer 132 and improves safety.

[0184] In some embodiments, the axial elongation of the first isolation layer 131 is 30% to 1000%, and the axial elongation of the second isolation layer 132 is 30% to 1000%, with the axial direction being perpendicular to the winding direction W.

[0185] In some embodiments, the tensile strength of the first isolation layer 131 and the second isolation layer 132 along the winding direction is 500 kgf / cm². 2 ~10,000 kgf / cm² 2 The tensile strength along the axial direction of the first isolation layer 131 and the second isolation layer 132 is 500 kgf / cm². 2 ~10,000 kgf / cm² 2 That is the case.

[0186] In some embodiments, after holding at 105°C for one hour, the shrinkage rate of the first isolation layer 131 and the second isolation layer 132 along the winding direction W was 0.01% to 50%, and the shrinkage rate of the first isolation layer 131 and the second isolation layer 132 along the axial direction was 0.01% to 50%.

[0187] In some embodiments, the needling strength of the first isolation layer 131 is 80 gf or more, and the needling strength of the second isolation layer 132 is 80 gf or more.

[0188] In some embodiments, the surface density of the first isolation layer 131 is 30 mg / 10000 mm². 2 ~100mg / 10000mg 2 The surface density of the second isolation layer 132 is 30 mg / 10000 mm². 2 ~100mg / 10000mg 2 That is the case.

[0189] In some embodiments, the air permeability of the first isolation layer 131 is 10 sec / 100cc to 1000 sec / 100cc, and the air permeability of the second isolation layer 132 is 10 sec / 100cc to 1000 sec / 100cc.

[0190] In some embodiments, the first isolation layer 131 includes a first base film 131a and an insulating layer 131b applied to the surface of the first base film 131a, while the second isolation layer 132 includes a second base film 132a, and the insulating layer 131b is not applied to the surface of the second base film 132a.

[0191] The first base film 131a and the second base film 132a are porous films. The first base film 131a and the second base film 132a may be the same type of film layer or different types of film layers. Exemplarily, the base film is made of an electrically insulating and liquid-retaining polymer material, such as PP (polypropylene), PE (polyethylene), or PVDF (polyvinylidene fluoride).

[0192] The insulating layer 131b is a functional layer placed on the surface of the first base film 131a. Exemplarily, the insulating layer 131b comprises an inorganic material, a polymer adhesive, and a dispersant, wherein the inorganic material comprises at least one of boehmite and silica, the polymer adhesive comprises at least one of PVDF and polystyrene-acrylate, and the dispersant may include polyvinyl alcohol. The inorganic material can sandwich the base film and reduce the shrinkage of the base film. The polymer adhesive adheres to the electrode sheet to increase the overall rigidity of the electrode assembly 10.

[0193] The first base film 131a and the second base film 132a may be integrally molded or may be separate structures.

[0194] In the embodiments of this application, the thickness of the first base film 131a and the thickness of the second base film 132a are not limited.

[0195] In the embodiment of the present application, the number of layers in the multi-layer structure region 13a is determined by the number of layers in the base film. In other words, the number of layers in the multi-layer structure region 13a refers to the number of layers in the base film of the multi-layer structure region 13a.

[0196] The second isolation layer 132 primarily serves to isolate the lithium dendrite from the positive electrode sheet 11. The requirements for other performance aspects of the second isolation layer 132 of the electrode assembly 10 are low, and an insulating layer 131b is not provided in the second isolation layer 132. This simplifies the structure of the second isolation layer 132, saves costs, and improves energy density.

[0197] In some examples, the thickness of the insulating layer 131b is 0.5 μm to 10 μm. The particle size of the inorganic material is 0.1 μm to 10 μm. The inorganic material content in the insulating layer 131b is 70% to 98%, and the polymer adhesive content is 1% to 20%. The dispersant content is 0.5% to 10%.

[0198] In some embodiments, the thickness of the second base film 132a is greater than the thickness of the first base film 131a. The second base film 132a, having greater thickness, can effectively isolate the lithium dendrite from the positive electrode sheet 11, thereby improving safety.

[0199] In some embodiments, in the stacking direction of the first isolation layer 131 and the second isolation layer 132, at least a portion of the second isolation layer 132 is installed separately from the first isolation layer 131.

[0200] At least a portion of the second isolation layer 132 does not have any connection relationship, such as adhesion, with the first isolation layer 131.

[0201] When the first isolation layer 131 (or the second isolation layer 132) is stretched by the pressure of the lithium layer, the influence of the first isolation layer 131 on the separation portion between the second isolation layer 132 and the first isolation layer 131 is small, the degree of stretching of the second isolation layer 132 is small, and the risk of defects is low. Therefore, in this embodiment, the risk of lithium dendrites passing through the first isolation layer 131 and the second isolation layer 132 can be effectively reduced, and safety can be improved.

[0202] In some embodiments, the positive electrode sheet 11, the isolation assembly 13, and the negative electrode sheet 12 are wound together to form a bent region B and a flat region A, with the flat region A connected to the bent region B. A portion of the second isolation layer 132 is located in the bent region B, and the other portion of the second isolation layer 132 is located in the flat region A. In the bent region B, the second isolation layer 132 is installed separately from the first isolation layer 131. In the flat region A, the second isolation layer 132 is attached to the first isolation layer 131.

[0203] The bending region B has a high risk of lithium deposition. By separating the second isolation layer 132 in bending region B from the first isolation layer 131, the risk of lithium dendrites passing through the first isolation layer 131 and the second isolation layer 132 can be effectively reduced, thereby improving safety. In the flat region A, attaching the second isolation layer 132 to the first isolation layer 131 reduces the amount of movement of the second isolation layer 132 along the winding direction W, thereby reducing the risk of displacement of the second isolation layer 132.

[0204] In some embodiments, the second isolation layer 132 is formed by folding the edges of the first isolation layer 131.

[0205] For example, the second isolation layer 132 is formed after the edge of the first isolation layer 131 is folded, and the folded area is the boundary between the first isolation layer 131 and the second isolation layer 132.

[0206] In this embodiment, by directly extending the second isolation layer 132 from the end of the first isolation layer 131, it is not necessary to add and fix the second isolation layer 132 separately, making the winding process more convenient and improving the overall integrity of the electrode assembly 10.

[0207] In some embodiments, the positive electrode sheet 11, the isolation assembly 13, and the negative electrode sheet 12 are wound and installed, and the electrode assembly 10 includes a starting segment 100 along the winding direction W, with the end of the first isolation layer 131 located at the starting segment 100.

[0208] The starting segment 100 along the winding direction W is the end located at the innermost circumference of the electrode assembly 10.

[0209] The second isolation layer 132 extends from the starting segment 100 along the winding direction W and passes through the first bend portion 111 of the positive electrode sheet 11, thereby reducing the risk of lithium dendrites simultaneously passing through the first isolation layer 131 and the second isolation layer 132 and coming into contact with the first bend portion 111 of the positive electrode sheet 11, and improving safety. At the same time, this embodiment can further reduce the length that the second isolation layer 132 needs to extend, saving on usage and lowering costs.

[0210] In some embodiments, a positive electrode sheet 11, an isolation assembly 13, and a negative electrode sheet 12 are wound together to form a bent region B, the bent region B includes a first bent portion B1 adjacent to the starting segment 100 along the winding direction W, a first isolation layer 131 and a second isolation layer 132 are provided in the first bent portion B1, the second isolation layer 132 extends from the end of the first isolation layer 131 and extends beyond the first bent portion B1.

[0211] The first bending point B1 is the position where the electrode assembly 10 is bent for the first time during winding molding. For example, at the first bending point B1, the positive electrode sheet 11 is bent for the first time, and the negative electrode sheet 12 is bent for the first time.

[0212] At the first bending portion B1, the curvature of the bending between the positive electrode sheet 11 and the negative electrode sheet 12 is greatest, and the risk of lithium deposition on the negative electrode sheet 12 during charging is highest. The second isolation layer 132 extends beyond the first bending portion B1, and the first isolation layer 131 and the second isolation layer 132 can protect at least the first bending portion B1 where lithium deposition problems are likely to occur, while simultaneously saving on the amount of the second isolation layer 132 used, thereby saving costs and improving the safety and service life of the electrode assembly 10.

[0213] Figure 8 is a schematic diagram of the configuration of an electrode assembly according to another embodiment of the present application. Figure 9 is a schematic diagram of a part of the electrode assembly shown in Figure 8. Figure 10 is a schematic diagram of the configuration of the electrode assembly shown in Figure 8 before winding.

[0214] As shown in Figures 8 to 10, in some embodiments, both the multi-layer structure region 13a and the single-layer structure region 13b are installed in multiple locations, and the multiple multi-layer structure region 13a and the multiple single-layer structure region 13b are installed alternately along the winding direction W.

[0215] Each of the multiple multi-layer structural regions 13a corresponds to one of the multiple folded portions of the positive electrode sheet 11, thereby creating a short-circuit risk at the multiple folded portions of the positive electrode sheet 11 and improving safety.

[0216] Each multi-layer structure region 13a comprises one or more second isolation layers 132. The number of layers in the multiple multi-layer structure regions 13a may be the same or different.

[0217] In some embodiments, each multi-layer structure region 13a can isolate one folded portion of the positive electrode sheet 11 from the negative electrode sheet 12.

[0218] In some embodiments, both ends of each multi-layer structure region 13a along the winding direction W are located in the flat region A.

[0219] In some embodiments, a positive electrode sheet 11, an isolation assembly 13, and a negative electrode sheet 12 are wound together to form a bent region B. The bent region B includes a plurality of bent portions located along the winding direction W, the electrode assembly 10 comprises a plurality of second isolation layers 132, and the first isolation layer 131 and the plurality of second isolation layers 132 are located in at least one of the plurality of bent portions.

[0220] The bent portion is a point where the electrode assembly 10 is bent during winding molding. For example, a plurality of bent portions include a first bent portion B1 and a second bent portion B2. At the first bent portion B1, both the positive electrode sheet 11 and the negative electrode sheet 12 undergo their first bend, and at the second bent portion B2, both the positive electrode sheet 11 and the negative electrode sheet 12 undergo their second bend.

[0221] In this embodiment, by installing the second isolation layer 132 at some or all of the multiple bending points, the risk of short circuits at the bending points can be effectively reduced and safety can be improved.

[0222] Furthermore, one of the second isolation layers 132 may be installed so as to extend and pass through multiple folding sections, or each second isolation layer 132 may be installed so as to extend and pass through one folding section.

[0223] In some embodiments, multiple second isolation layers 132 are installed at intervals along the winding direction W.

[0224] The fact that multiple second isolation layers 132 are installed at intervals means that the multiple second isolation layers 132 are not connected as a single second isolation layer 132, but are understood to be separate entities. In this embodiment, the installation method of the second isolation layer 132 can be made more flexible, that is, the second isolation layer 132 can be arbitrarily installed in locations where it is necessary to add more isolation layers, and at the same time, the waste caused by adding second isolation layers 132 in locations where it is not necessary to add more isolation layers can be reduced, thereby improving energy density.

[0225] In some embodiments, the electrode assembly 10 includes a starting segment 100 along the winding direction W. The multiple bending portions include a first bending portion B1 and a second bending portion B2, and along the winding direction W, the first bending portion B1 is closer to the starting segment 100 than the second bending portion B2. The thickness of the second isolation layer 132 installed at the first bending portion B1 is greater than the thickness of the second isolation layer 132 installed at the second bending portion B2.

[0226] The risk of lithium deposition in the negative electrode sheet 12 at the first bending portion B1 is higher than the risk of lithium deposition in the negative electrode sheet 12 at the second bending portion B2, and the risk of lithium dendrites passing through the second isolation layer 132 at the first bending portion B1 is higher than the risk of lithium dendrites passing through the second isolation layer 132 at the second bending portion B2. Therefore, in this embodiment, by making the thickness of the second isolation layer 132 installed at the first bending portion B1 greater than the thickness of the second isolation layer 132 installed at the second bending portion B2, protection can be reinforced at the first bending portion B1, which is more prone to short circuits, safety can be improved, and the amount of the second isolation layer 132 used can be saved.

[0227] In some embodiments, multiple second isolation layers 132 are bonded to the surface of the first isolation layer 131, thereby reducing the risk of displacement of the second isolation layers 132 during the charging and discharging process of the electrode assembly 10 and ensuring the isolation effect of the second isolation layers 132.

[0228] The second isolation layer 132 is selectively bonded to the first isolation layer 131 at both ends along the winding direction W, or the second isolation layer 132 is installed separately from the first isolation layer 131 along the central part of the winding direction W.

[0229] In some embodiments, after the electrode assembly 10 is wound and molded, the second isolation layer 132 is bonded to the first isolation layer 131 by hot pressing the electrode assembly 10 from the outside.

[0230] In some embodiments, the first isolation layer 131 includes two surfaces along its own thickness direction, and a plurality of second isolation layers 132 are located on the same surface of the first isolation layer 131.

[0231] If the gap between the positive electrode sheet 11 and the negative electrode sheet 12 is too large, it will affect the lithium insertion process and worsen the lithium deposition phenomenon. By placing multiple second isolation layers 132 on the same surface of the first isolation layer 131, when the first isolation layer 131 is tensioned, the influence of the second isolation layers 132 on the gap between the positive electrode sheet 11 and the negative electrode sheet 12 can be reduced, thereby reducing the risk of lithium deposition and improving safety.

[0232] Figure 11 is a schematic diagram of the pre-winding configuration of an electrode assembly according to some further embodiments of the present application.

[0233] As shown in Figure 11, in some embodiments, the number of layers in the multiple layer structure regions 13a gradually decreases from the inside to the outside along the winding direction W.

[0234] In this embodiment, along the winding direction W, the number of layers in the innermost multi-layer structure region 13a is greater than the number of layers in the outermost multi-layer structure region 13a. The number of layers in two adjacent multi-layer structure regions 13a may be the same or different.

[0235] Along the winding direction W, the curvature of the multiple folded portions of the positive electrode sheet 11 from the inside to the outside gradually decreases, and the risk of contact with the lithium dendrite is also gradually reduced. According to this embodiment, the number of layers in the multi-layer structure region 13a can be increased in areas with a high risk of short circuits, and the number of layers in the multi-layer structure region 13a can be decreased in areas with a low risk of short circuits, thereby improving safety and saving on the amount of isolation assembly 13 used.

[0236] Figure 12 is a schematic diagram of the configuration of an electrode assembly according to some further embodiments of the present application.

[0237] As shown in Figure 12, at least a portion of the multi-layer structure region 13a is located adjacent to the final folded portion 113 of the positive electrode sheet 11.

[0238] The electrode assembly 10 expands during charging and presses against the case 21, and the case 21 applies a reaction force to the electrode assembly 10. The region of the negative electrode sheet 12 facing the final bend portion 113 of the positive electrode sheet 11 is prone to lithium deposition due to the reaction force. In this embodiment, at least a portion of the multi-layer structure region 13a is made adjacent to the final bend portion 113 of the positive electrode sheet 11, thereby reducing the risk of electrical conductivity between the final bend portion 113 of the positive electrode sheet 11 and the lithium dendrite, and improving the safety of the battery cell 6.

[0239] For example, the electrode assembly 10 is cylindrical. Each folded portion of the positive electrode sheet 11 refers to one full turn of the positive electrode sheet.

[0240] According to some embodiments of the present application, the present application further provides a battery cell comprising a housing and an electrode assembly housed within the housing of any of the above embodiments.

[0241] According to some embodiments of the present application, the present application provides a battery comprising a battery cell of any of more than one embodiment.

[0242] According to some embodiments of the present application, the present application further provides a power consumption device comprising a battery cell of any of the above embodiments, wherein the battery cell supplies electrical energy to the power consumption device. The power consumption device may be a device or system to which any of the above battery cells is applied.

[0243] Referring to some embodiments of the present application, specifically Figures 4 to 7, the present application provides an electrode assembly comprising a positive electrode sheet 11, a negative electrode sheet 12, and an isolation assembly 13 for isolating the positive electrode sheet 11 and the negative electrode sheet 12. The isolation assembly 13 comprises a first isolation layer 131 and a second isolation layer 132, the first isolation layer 131 being used to electrically isolate the positive electrode sheet 11 and the negative electrode sheet 12, and at least a portion of the second isolation layer 132 being located between the positive electrode sheet 11 and the negative electrode sheet 12 and laminated with the first isolation layer 131. The region of the first isolation layer 131 overlapping with the second isolation layer 132 and the second isolation layer 132 form a multi-layer structure region 13a of the isolation assembly 13. The region of the first isolation layer 131 not overlapping with the second isolation layer 132 forms a single-layer structure region 13b of the isolation assembly 13. The second isolation layer 132 is formed by folding the edges of the first isolation layer 131.

[0244] The positive electrode sheet 11, the isolation assembly 13, and the negative electrode sheet 12 are wound together to form a folded region B and a flat region A. The flat region A is connected to the folded region B, at least a portion of the multi-layer structure region 13a is placed in the folded region B, and at least a portion of the single-layer structure region 13b is placed in the flat region A. A portion of the multi-layer structure region 13a is placed adjacent to the first folded portion 111 of the positive electrode sheet 11, and another portion of the multi-layer structure region 13a is placed adjacent to the second folded portion 112 of the positive electrode sheet 11.

[0245] The present application will be further described below with reference to the following examples.

[0246] To further clarify the purpose, technical proposal, and beneficial technical effects of the present invention, the present invention will be described in more detail below with reference to examples. However, the examples of the present invention are for interpretation purposes only and not to limit the present invention, and it should be understood that the examples of the present invention are not limited to those described in the specification. Where specific experimental or operating conditions are not specified in the examples, the materials should be manufactured under normal conditions or under conditions recommended by the material provider.

[0247] Example 1 can be manufactured according to the following steps.

[0248] (i) LiNi 0.8 Co 0.1 Mn 0.1 O2, acetylene black as the conductive agent, and PVDF as the adhesive are mixed in a mass ratio of 96:2:2, put into a solvent (NMP), and stirred with a vacuum stirrer until the whole becomes a uniform state to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on an aluminum foil, dried at room temperature, then transferred to an oven for drying, and then, through cold rolling, slitting, and punching, a positive electrode sheet is obtained.

[0249] (ii) Graphite as the negative electrode active material, acetylene black as the conductive agent, CMC as the thickening agent, and SBR as the adhesive are mixed in a mass ratio of 96.4:1:1.2:1.4, then put into deionized water as the solvent, and stirred with a vacuum stirrer until the whole becomes a uniform state to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on a copper foil, dried at room temperature, then transferred to an oven for drying, and then, through cold rolling, slitting, and punching, a negative electrode sheet is obtained.

[0250] (iii) Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed according to a volume ratio of 1:1:1 to obtain an organic solvent. Next, sufficiently dried lithium salt LiPF6 is dissolved in the mixed organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0251] (iv) A 7-μm-thick polyethylene film is folded to form a separator assembly. The separator assembly includes a first separator layer and a second separator layer, and the length of the second separator layer is 652.5 mm.

[0252] (v) The positive electrode sheet, the separator assembly, and the negative electrode sheet are laminated and wound around multiple times, and after winding, it is flattened into a flat shape to manufacture an electrode assembly.

[0253] (vi) The electrode assembly is placed in a rectangular case, and the case and end cover are welded together. Next, a battery cell is obtained through processes such as liquid injection, standing, chemical formation, and shaping. Exemplarily, the capacity of the battery cell is 60 Ah.

[0254] In step (v), lithium deposition of the electrode assembly is accelerated by artificially reducing the gap between the innermost positive electrode sheet and the innermost negative electrode sheet to 200 μm. In the wound electrode assembly, a first isolation layer and a second isolation layer are provided between the innermost positive electrode sheet and the innermost negative electrode sheet.

[0255] Example 2

[0256] The method for manufacturing the battery cell in Example 2 is the same as in Example 1, with the following differences: In step (vi), the gap between the innermost two-turn positive electrode sheet and the innermost two-turn negative electrode sheet is artificially set to 200 μm, the length of the second isolation layer is 873.6 mm, and the first and second isolation layers are simultaneously placed between the second-turn positive electrode sheet and the second-turn negative electrode sheet.

[0257] Comparative Example 1

[0258] The manufacturing method of the battery cell in Comparative Example 1 is the same as in Example 1, with the following differences: The isolation assembly in Comparative Example 1 is not folded, and the isolation assembly has a single-layer structure.

[0259] Comparative Example 2

[0260] The manufacturing method of the battery cell in Comparative Example 2 is the same as in Example 2, with the following differences: The isolation assembly in Comparative Example 2 is not folded, and the isolation assembly has a single-layer structure.

[0261] Eighty battery cells were manufactured and tested according to Example 1, Example 2, Comparative Example 1, and Comparative Example 2.

[0262] Specifically, the battery cells are charged at a 1C multiplier and discharged at a 1C multiplier under normal temperature conditions, and cycle charging and discharging is performed in the high SOC (e.g., 0.9-1) range.

[0263] The 40 battery cells from Example 1 were fully charged after 500 cycles, then left to stand for 24 hours. The voltage drop of each battery cell was detected, and the self-discharge rate of each battery cell was calculated, followed by the average value. The self-discharge rate is voltage drop / time. The remaining 40 battery cells from Example 1 underwent 2000 cycles, and the number of battery cell failures during the cycle process was recorded, and the failure rate was calculated.

[0264] Example 2, Comparative Example 1, and Comparative Example 2 were also tested using the steps described above.

[0265] Table 1 shows the evaluation results for Examples 1 and 2 and Comparative Examples 1 and 2.

[0266] [Table 1]

[0267] Referring to Examples 1-2 and Comparative Examples 1 and 2, by installing a multi-layer structure region between the positive electrode sheet and the negative electrode sheet, the risk of short-circuiting can be reduced and the lifespan of the battery cell can be improved when lithium is deposited on the negative electrode sheet.

[0268] Furthermore, if there are no conflicts, the embodiments and features described herein can be combined with each other.

[0269] Finally, it should be noted that the above embodiments merely illustrate the technical proposal of the present application and do not limit it. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical proposal described in each of the above embodiments or make equivalent substitutions to some of the technical features thereof, but these modifications or substitutions will not cause the essence of the corresponding technical proposal to deviate from the spirit and scope of the technical proposal of each embodiment of the present application.

Claims

1. The system comprises a positive electrode sheet, a negative electrode sheet, and an isolation assembly for separating the positive electrode sheet and the negative electrode sheet. At least a portion of the isolation assembly is installed as a multi-layer structure region, the multi-layer structure region is a region in which multiple isolation layers of the isolation assembly are stacked to form a multi-layer structure region, and at least a portion of the multi-layer structure region is located between adjacent positive electrode sheets and negative electrode sheets. The electrode assembly is a flattened or prismatic body, The positive electrode sheet, the isolation assembly, and the negative electrode sheet are wound together. Multiple multi-layered structures are installed. Along the winding direction, the number of layers in the multiple layered structural regions gradually decreases from the inside to the outside. Electrode assembly.

2. The electrode assembly according to claim 1, wherein the positive electrode sheet, the isolation assembly, and the negative electrode sheet are wound together to form a folded region, and at least a portion of the multi-layer structure region is placed in the folded region.

3. The electrode assembly according to claim 2, wherein at least a portion of the multi-layer structure region is installed adjacent to the first folding portion of the positive electrode sheet.

4. The electrode assembly according to claim 3, wherein the multi-layer structure regions are provided on both sides of the first folded portion of the positive electrode sheet, and the number of layers in the multi-layer structure region located inside the first folded portion of the positive electrode sheet is equal to or greater than the number of layers in the multi-layer structure region located outside the first folded portion of the positive electrode sheet.

5. The electrode assembly according to claim 3, wherein at least a portion of the multi-layer structure region is installed adjacent to the second folding portion of the positive electrode sheet.

6. The electrode assembly according to claim 5, wherein the number of layers in the multi-layer structure region located inside the first folded portion of the positive electrode sheet is equal to or greater than the number of layers in the multi-layer structure region located inside the second folded portion of the positive electrode sheet.

7. A portion of the isolation assembly is installed as a single-layer structural region, and the single-layer structural region and the multi-layer structural region are installed along the winding direction. The electrode assembly according to claim 2, wherein at least a portion of the single-layer structure region is located between adjacent positive electrode sheets and negative electrode sheets.

8. The positive electrode sheet, the isolation assembly, and the negative electrode sheet are wound together to form a flat region that is further connected to the bending region. The electrode assembly according to claim 7, wherein at least a portion of the single-layer structure region is installed in the flat region.

9. The electrode assembly according to claim 8, wherein the ends of the multi-layer structure region along the winding direction are located in the flat region.

10. The electrode assembly according to claim 8, wherein a plurality of the single-layer structural regions are provided, and the plurality of the plurality of the plurality of the multi-layer structural regions and the plurality of the single-layer structural regions are arranged alternately along the winding direction.

11. The isolation assembly comprises a first isolation layer for insulatingly isolating the positive electrode sheet and the negative electrode sheet, and a second isolation layer, at least a portion of which is located between the positive electrode sheet and the negative electrode sheet and is laminated with the first isolation layer. The electrode assembly according to claim 1, wherein the region of the first isolation layer overlapping with the second isolation layer and the second isolation layer form a multi-layer structure region of the isolation assembly.

12. The electrode assembly according to claim 11, wherein the thickness of the second isolation layer is less than or equal to the thickness of the first isolation layer.

13. The electrode assembly according to claim 12, wherein the thickness of the first isolation layer is 2 μm to 30 μm, and the thickness of the second isolation layer is 1 μm to 25 μm.

14. The electrode assembly according to claim 11, wherein the first isolation layer comprises a first base film and an insulating layer applied to the surface of the first base film, and the second isolation layer comprises a second base film, wherein the insulating layer is not applied to the surface of the second base film.

15. The electrode assembly according to claim 14, wherein the thickness of the second base film is greater than the thickness of the first base film.

16. The electrode assembly according to claim 11, wherein, in the stacking direction of the first isolation layer and the second isolation layer, at least a portion of the second isolation layer is installed separately from the first isolation layer.

17. The positive electrode sheet, the isolation assembly, and the negative electrode sheet are wound together to form a bent region and a flat region connected to the bent region. A portion of the second isolation layer is located in the folded region, and the other portion of the second isolation layer is located in the flat region. The electrode assembly according to claim 16, wherein in the bent region, the second isolation layer is installed separately from the first isolation layer, and in the flat region, the second isolation layer is attached to the first isolation layer.

18. The electrode assembly according to claim 11, wherein the porosity of the second isolation layer is smaller than the porosity of the first isolation layer.

19. The electrode assembly according to claim 11, wherein the second isolation layer has a porous structure, and the pore diameter of the pores in the second isolation layer is 1 μm or less.

20. The electrode assembly according to claim 11, wherein the elongation rate of the second isolation layer along the winding direction is greater than the elongation rate of the first isolation layer along the winding direction.

21. The electrode assembly according to claim 11, wherein the second isolation layer is formed by folding the end of the first isolation layer.

22. The electrode assembly according to claim 21, wherein the positive electrode sheet, the isolation assembly, and the negative electrode sheet are wound and installed, the electrode assembly has a starting segment along the winding direction, and the end of the first isolation layer is located at the starting segment.

23. The electrode assembly according to claim 22, wherein the positive electrode sheet, the isolation assembly, and the negative electrode sheet are wound together to form a bent region, the bent region comprises a first bent portion adjacent to the starting segment along the winding direction, the first isolation layer and the second isolation layer are installed in the first bent portion, the second isolation layer extends from the end of the first isolation layer and extends beyond the first bent portion.

24. The positive electrode sheet, the isolation assembly, and the negative electrode sheet are wound together to form a folded region. The electrode assembly according to claim 11, wherein the bending region comprises a plurality of bending portions arranged along the winding direction, the electrode assembly comprises a plurality of second isolation layers, and the first isolation layer and the plurality of second isolation layers are installed in at least one of the plurality of bending portions.

25. The electrode assembly according to claim 24, wherein the plurality of second isolation layers are spaced apart along the winding direction.

26. The electrode assembly comprises a starting segment along the winding direction, and the plurality of bent portions comprises a first bent portion and a second bent portion, and along the winding direction, the first bent portion is closer to the starting segment than the second bent portion. The electrode assembly according to claim 24, wherein the thickness of the second isolation layer installed at the first bending portion is greater than the thickness of the second isolation layer installed at the second bending portion.

27. The electrode assembly according to claim 24, wherein the first isolation layer includes two surfaces along its own thickness direction, and a plurality of the second isolation layers are located on the same surface of the first isolation layer.

28. The electrode assembly according to claim 24, wherein a plurality of the second isolation layers are bonded to the surface of the first isolation layer.

29. A battery cell comprising a housing and an electrode assembly according to any one of claims 1 to 28 housed within the housing.

30. A battery comprising a plurality of battery cells as described in claim 29.

31. A power consumption device comprising a battery cell according to claim 29 for supplying electrical energy.

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