Electrode assembly, battery cell, battery and power consuming device

Abstract

The embodiments of the present application provide an electrode assembly, a battery cell, a battery, and a power consuming device. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and an isolation assembly for isolating the positive electrode sheet and the negative electrode sheet. The isolation assembly includes a base region and a reinforcing region connected to the base region, and the thickness of the reinforcing region is greater than the thickness of the base region. At least a portion of the reinforcing region is located between the adjacent positive electrode sheet and the negative electrode sheet. The reinforcing region corresponds to a position of the negative electrode sheet where lithium is likely to be deposited, so that when the negative electrode sheet deposits lithium, the reinforcing region can effectively separate the positive electrode sheet and the negative electrode sheet, reducing the risk of lithium dendrites passing through the isolation assembly, and improving the service life and safety. The base region can have a smaller thickness than the reinforcing region. In this way, the amount of isolation assembly used can be reduced, the cost can be reduced, and the energy density of the electrode assembly can be improved.

Description

[Technical Field]

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

[0002] The present application relates to the technical field of batteries, and more particularly to electrode assemblies, battery cells, batteries, and power consuming devices. [Background technology]

[0003] Battery cells are widely used in electronic devices such as mobile phones, laptops, electric scooters, electric cars, electric airplanes, electric boats, toy cars, toy boats, toy airplanes, and power tools, etc. Battery cells may include cadmium-nickel battery cells, nickel-metal hydride battery cells, lithium-ion battery cells, and secondary alkaline zinc-manganese battery cells, etc.

[0004] With the development of battery technology, how to improve the safety of battery cells has become a direction of study in battery technology. Summary of the Invention

[0005] The present application provides an electrode assembly, a battery cell, a battery, and a power consuming device that can improve safety.

[0006] In a first aspect, the present invention provides an electrode assembly including a positive electrode sheet, a negative electrode sheet, and a separator assembly for separating the positive electrode sheet and the negative electrode sheet. The separator assembly includes a base region and a reinforcing region connected to the base region, the reinforcing region having a thickness greater than the thickness of the base region. At least a portion of the reinforcing region is located between adjacent positive and negative electrode sheets.

[0007] In the above technical solution, the reinforcing region corresponds to the position of the negative electrode sheet where lithium is likely to be deposited. When lithium is deposited on the negative electrode sheet, the reinforcing region effectively separates the positive electrode sheet from the negative electrode sheet, reducing the risk of lithium dendrites passing through the separator assembly and improving service life and safety. The substrate region can have a smaller thickness than the reinforcing region. This reduces the amount of separator assembly used, reduces costs, and improves the energy density of the electrode assembly.

[0008] In some embodiments, the thickness of the reinforced region is between 2 μm and 100 μm.

[0009] The thinner the thickness of the reinforcing region, the higher the energy density of the electrode assembly, but the higher the risk of lithium dendrites passing through the reinforcing region. The thicker the reinforcing region, the lower the energy density of the electrode assembly, but the lower the risk of lithium dendrites passing through the reinforcing region, thereby improving the safety of the electrode assembly. In the above technical proposal, the thickness of the reinforcing region is limited to 2 μm to 100 μm, thereby achieving a balance between the energy density and safety of the electrode assembly.

[0010] In some embodiments, the positive electrode sheet, the separator assembly, and the negative electrode sheet are rolled to form a folding region, and at least a portion of the reinforcement region is disposed in the folding region.

[0011] In the above technical solution, at least a portion of the reinforcing region is located in the bending region where lithium is likely to precipitate. Even if lithium does precipitate in the bending region, the reinforcing region blocks the lithium dendrites, thereby reducing the probability of electrical conduction 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.

[0012] In some embodiments, the positive electrode sheet includes a first fold portion located in the fold region and adjacent to the reinforcement region, and the negative electrode sheet includes a second fold portion adjacent to the first fold portion. The reinforcement region includes multiple fold layers located in the fold region and stacked between the first fold portion and the second fold portion.

[0013] In the above technical solution, the multiple folded layers can block lithium dendrites when lithium is precipitated at the second folded portion, thereby reducing the risk of lithium dendrites coming into contact with the first folded portion and improving safety.

[0014] In some embodiments, a reinforced region and a second folded portion are located at least inside the first folded portion.

[0015] Because the curvature of the second bent portion located inside the first bent portion is greater than that of the first bent portion, the second bent portion is more likely to lose active material during bending, i.e., the second bent portion located inside the first bent portion is more likely to experience lithium deposition. The reinforced region of the above technical solution can separate the first bent portion from the second bent portion located inside the first bent portion. Even if lithium deposits in the second bent portion, the probability of lithium dendrites passing through the reinforced region is reduced, reducing the risk of short circuits and improving safety.

[0016] In some embodiments, the first folded portion includes a first current collector and a first active material layer disposed on the surface of the first current collector, and the thickness of the first active material layer is h1. The second folded portion includes a second current collector and a second active material layer disposed on the surface of the second current collector, and the thickness of the second active material layer is h2, the thickness of the folded layer is h3, and the thickness of the second current collector is h4. In the thickness direction of the first folded portion, the maximum distance between the first folded portion and the second folded portion is X. The number of folded layers located between the first folded portion and the second folded portion is Y, and Y is a positive integer greater than 1. The active material capacity per unit area of ​​the first active material layer is A1, and the active material capacity per unit area of ​​the second active material layer is A2, where A2 / A1≧1. h1, h2, h3, h4, X, and Y are Meets JPEG0007749108000001.jpg28161.

[0017] The fewer the number of folded layers in the reinforced region, the higher the risk of lithium dendrites passing through the reinforced region. The more folded layers in the reinforced region, the more complex the structure of the separator assembly becomes, and the lower the energy density of the electrode assembly. In the above technical solution, the number of folded layers is set based on the above formula, thereby balancing the safety and energy density of the electrode assembly.

[0018] In some embodiments, the first folded portion includes a first current collector and a first active material layer disposed on the surface of the first current collector, the first active material layer having a thickness of h1. The second folded portion includes a second current collector and a second active material layer disposed on the surface of the second current collector, the second active material layer having a thickness of h2, the folded layer having a thickness of h3, and the second current collector having a thickness of h4. The maximum distance between the first folded portion and the second folded portion in the thickness direction of the first folded portion is X. The number of folded layers located between the first folded portion and the second folded portion is Y, where Y is a positive integer greater than 1. The active material capacity per unit area of ​​the first active material layer is A1, and the active material capacity per unit area of ​​the second active material layer is A2, where A2 / A1<1. h1, h2, h3, h4, X, and Y are Meet JPEG0007749108000002.jpg27140.

[0019] In the above technical solution, the number of folded layers is set based on the above formula, thereby achieving a balance between the safety and energy density of the electrode assembly.

[0020] In some embodiments, the value of h3 is between 1 μm and 20 μm to balance the safety and energy density of the electrode assembly.

[0021] In some embodiments, the value of X is between 10 μm and 5000 μm.

[0022] In some embodiments, the positive electrode sheet includes a plurality of positive electrode folds arranged along the winding direction, and the positive electrode fold formed by at least the first fold of the positive electrode sheet is arranged as the first fold.

[0023] The positive electrode fold formed by the first fold of the positive electrode sheet has a large curvature, which makes it easy for lithium deposition problems to occur on the negative electrode sheet adjacent to the positive electrode fold formed by the first fold of the positive electrode sheet during charging.In the above technical solution, the positive electrode fold formed by the first fold of the positive electrode sheet is set as the first fold, and the reinforcing area effectively isolates the positive electrode fold formed by the first fold of the positive electrode sheet from lithium dendrites, reducing the risk of short circuits and improving safety.

[0024] In some embodiments, the positive electrode fold formed by folding the positive electrode sheet a second time is also designated as the first fold.

[0025] In the above technical solution, the positive electrode fold formed by the second fold of the positive electrode sheet is set as the first fold, and the reinforced area effectively isolates the positive electrode fold formed by the second fold of the positive electrode sheet from the lithium dendrite, thereby reducing the risk of short circuit and improving safety.

[0026] In some embodiments, the total thickness of the reinforcement region located inside the positive electrode fold formed by the first folding of the positive electrode sheet is T1, and the total thickness of the reinforcement region located inside the positive electrode fold formed by the second folding of the positive electrode sheet is T2, where T1≧T2.

[0027] In the above technical proposal, by making T1≧T2, the risk of the positive electrode fold formed by the first fold of the positive electrode sheet becoming conductive with lithium dendrites is reduced, improving the safety of the battery cell.

[0028] In some embodiments, a reinforced region and a second folded region are disposed on both sides of the first folded region, and the total thickness of the reinforced region located inside the first folded region is equal to or greater than the total thickness of the reinforced region located outside the first folded region, thereby reducing the risk of the first folded region becoming electrically conductive to lithium dendrites and improving the safety of the battery cell.

[0029] In some embodiments, the positive electrode sheet includes a plurality of positive electrode folds arranged along the winding direction, and at least the positive electrode fold formed by the last fold of the positive electrode sheet is arranged as the first fold, thereby reducing the risk of electrical conduction between the positive electrode fold formed by the last fold of the positive electrode sheet and lithium dendrites and improving the safety of the battery cell.

[0030] In some embodiments, the positive electrode sheet, the separator assembly, and the negative electrode sheet are wound to further form a flat region, the flat region being connected to the folded region, and at least a portion of the substrate region being disposed on the flat region.

[0031] The positive electrode sheet and the negative electrode sheet located in the flat region are both in a flat state, so the active material in the flat region is less likely to fall off, and the negative electrode sheet located in the flat region is less likely to have lithium deposition problems. Therefore, even if the substrate region is installed in the flat region, the above technical solution can improve the insulation between the positive and negative electrode sheets and reduce the risk of short circuits.

[0032] In some embodiments, a plurality of reinforcing regions and a plurality of base regions are provided, and the plurality of reinforcing regions and the plurality of base regions are provided alternately along the winding direction.

[0033] In the above technical solution, the multiple reinforcing regions respectively correspond to the multiple positive electrode bending portions of the positive electrode sheet, thereby reducing the risk of short circuits occurring at the multiple positive electrode bending portions of the positive electrode sheet and improving safety.

[0034] In some embodiments, the thickness of the reinforced regions gradually decreases from the inside to the outside along the winding direction.

[0035] Along the winding direction, the curvature of the positive electrode folded from the inside to the outside of the positive electrode sheet gradually decreases, and the risk of contact with lithium dendrites also gradually decreases. In the above technical solution, the thickness of the reinforced region can be increased in areas with a high risk of short circuiting and decreased in areas with a low risk of short circuiting. This improves safety and reduces the amount of isolation assemblies used.

[0036] In some embodiments, the difference in thickness between adjacent reinforced regions along the winding direction is between 0.5 μm and 10 μm.

[0037] In some embodiments, the reinforcement region is provided as a multi-layer structure and the substrate region is provided as a single layer structure.

[0038] In the above technical solution, when the thickness is the same, the reinforced region with a multi-layer structure can more effectively block lithium dendrites, reduce the risk of short circuits, and improve safety compared to the reinforced region with a single-layer structure. As long as the strength requirements are met, the reinforced region with a multi-layer structure can have a smaller thickness compared to the reinforced region with a single-layer structure. This reduces the amount of separator assemblies used and improves the energy density of the electrode assembly.

[0039] In some embodiments, the separator assembly includes a first separator layer and a second separator layer, the first separator layer is used to electrically isolate the positive electrode sheet from the negative electrode sheet, and at least a portion of the second separator layer is located between the positive electrode sheet and the negative electrode sheet and laminated with the first separator layer, where the area of ​​the first separator layer overlapping with the second separator layer and the second separator layer form a reinforcement region of the separator assembly, and the area of ​​the first separator layer not overlapping with the second separator layer forms a substrate region.

[0040] In the above technical solution, by adding a second isolation layer to the electrode assembly, a reinforced area with a large thickness is formed in the isolation assembly, which can reduce the risk of short circuit caused by lithium deposition and improve safety.

[0041] In some embodiments, the thickness of the second insulating layer is less than or equal to the thickness of the first insulating layer.

[0042] In the above technical solution, the first and second isolation layers can function as multi-layer protection, so that the added second isolation layer can be made thinner than the first isolation layer, thereby reducing the amount of second isolation layer used.

[0043] In some embodiments, at least a portion of the second isolation layer is disposed separately from the first isolation layer in the stacking direction of the first isolation layer and the second isolation layer.

[0044] When the first isolating layer is stretched by the pressure of the lithium layer, the impact of the first isolating layer on the separation between the second isolating layer and the first isolating layer is small, the degree of stretching of the second isolating layer is small, and the risk of defects is low. The above technical solution can effectively reduce the risk of lithium dendrites passing through the first and second isolating layers, thereby improving safety.

[0045] In some embodiments, the positive electrode sheet, the separator assembly, and the negative electrode sheet are wound to form a folded region and a flat region, and the flat region is connected to the folded region. A portion of the second separator layer is located in the folded region, and another portion of the second separator layer is located in the flat region. In the folded region, the second separator layer is disposed separately from the first separator layer. In the flat region, the second separator layer is attached to the first separator layer.

[0046] In the above technical solution, the risk of lithium deposition is high in the bent region, and by separating the second isolation layer from the first isolation layer in the bent region, the risk of lithium dendrites passing through the first isolation layer and the second isolation layer can be effectively reduced, improving safety.In the flat region, the second isolation layer is attached to the first isolation layer, reducing the movement width of the second isolation layer along the winding direction and reducing the risk of misalignment of the second isolation layer.

[0047] In some embodiments, the second isolation layer is formed by folding over an end of the first isolation layer.

[0048] In the above technical solution, 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, which makes the winding process more convenient and improves the integrity of the electrode assembly.

[0049] In some embodiments, the positive electrode sheet, the separator assembly, and the negative electrode sheet are wound and installed, the electrode assembly including a starting segment along the winding direction, and the end of the first separator layer is located at the starting segment.

[0050] In the above technical solution, the second separator extends from the starting segment along the winding direction and passes through the positive electrode fold formed by the first fold of the positive electrode sheet, thereby reducing the risk of lithium dendrites simultaneously passing through the first separator and the second separator and coming into contact with the positive electrode fold of the positive electrode sheet, thereby improving safety, and further reducing the length that the second separator needs to extend, thereby saving usage and reducing costs.

[0051] In some embodiments, the positive electrode sheet, the separator assembly, and the negative electrode sheet are rolled to form a folding region, the folding region including a first folding portion adjacent to the start segment along the rolling direction, a first separator layer and a second separator layer disposed at the first folding portion, and the second separator layer extending from an end of the first separator layer and beyond the first folding portion.

[0052] In the above technical solution, the bending curvature of the positive and negative electrode sheets is greatest at the first bending portion, which is the area most susceptible to lithium deposition on the negative electrode sheet during charging. The second separator extends beyond the first bending portion, and the first and second separators protect at least the first bending portion, where lithium deposition is most likely to occur, while also reducing the amount of second separator used. This saves costs and improves the safety and service life of the electrode assembly.

[0053] In some embodiments, the positive electrode sheet, the separator assembly, and the negative electrode sheet are rolled to form a folding region, the folding region includes a plurality of folding portions disposed along the rolling direction, the electrode assembly includes a plurality of second separator layers, and the first separator layer and the plurality of second separator layers are disposed in at least one of the plurality of folding portions.

[0054] In the above technical solution, by installing a second isolation layer at some or all of the positions of the multiple bending parts, the risk of short circuit at the bending parts can be effectively reduced and safety can be improved.

[0055] In some embodiments, a plurality of second isolation layers are spaced apart along the winding direction.

[0056] The above technical solution allows for more flexible installation of the second isolation layer, i.e., the second isolation layer can be installed arbitrarily where the number of isolation layers needs to be increased, while reducing waste caused by adding second isolation layers where the number of isolation layers does not need to be increased, and improving energy density.

[0057] In some embodiments, the electrode assembly includes a start segment along a winding direction, the plurality of fold portions include a first fold portion and a second fold portion, the first fold portion being closer to the start segment than the second fold portion along the winding direction, and the thickness of the second isolation layer provided at the first fold portion is greater than the thickness of the second isolation layer provided at the second fold portion.

[0058] The above technical solution strengthens protection at the first bent portion, which is more susceptible to short circuits, thereby improving safety and reducing the amount of second isolation layer used.

[0059] In some embodiments, the first separator includes two surfaces along its thickness direction, and multiple second separators are located on the same surface of the first separator. This reduces the effect of the second separator on the gap between the positive electrode sheet and the negative electrode sheet when the first separator is tensioned, thereby reducing the risk of lithium deposition and improving safety.

[0060] In some embodiments, multiple second isolation layers are adhered to the surface of the first isolation layer, thereby reducing the risk of the second isolation layers being displaced during the charge and discharge process of the electrode assembly and ensuring the isolation effect of the second isolation layers.

[0061] In a second aspect, embodiments of the present application provide a battery cell including a housing and the electrode assembly of any of the embodiments of the first aspect, the electrode assembly being contained within the housing.

[0062] In a third aspect, embodiments of the present application provide a battery including a plurality of battery cells of the second aspect.

[0063] In a fourth aspect, embodiments of the present application provide a power consumption device including a battery cell of the second aspect, the battery cell being adapted to supply electrical energy.

[0064] In order to more clearly explain the technical solutions of the embodiments of the present application, the following briefly describes the drawings necessary for the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can further obtain other drawings based on the drawings without any creative work. [Brief explanation of the drawings]

[0065] [Figure 1] 1 is a schematic diagram of a vehicle according to some embodiments of the present application.

[0066] [Figure 2] 1 is an exploded schematic view of a battery according to some embodiments of the present application; FIG.

[0067] [Figure 3] FIG. 1 is an exploded schematic view of a battery cell according to some embodiments of the present application.

[0068] [Figure 4] 1 is a schematic diagram of an electrode assembly according to some embodiments of the present application.

[0069] [Figure 5] FIG. 5 is an enlarged schematic view of a portion of the electrode assembly shown in FIG. 4.

[0070] [Figure 6] FIG. 6 is an enlarged schematic view of block P in FIG. 5.

[0071] [Figure 7] FIG. 5 is a schematic diagram of the electrode assembly shown in FIG. 4 before winding.

[0072] [Figure 8] FIG. 8 is a schematic diagram of the isolation assembly shown in FIG. 7.

[0073] [Figure 9] 10 is a schematic diagram of the configuration of an isolation assembly of an electrode assembly according to some other embodiments of the present application before winding. FIG.

[0074] [Figure 10] 10A and 10B are schematic diagrams illustrating the configuration of an electrode assembly according to still other embodiments of the present application.

[0075] [Figure 11] FIG. 11 is an enlarged schematic view of a portion of the electrode assembly shown in FIG.

[0076] [Figure 12] FIG. 11 is a schematic diagram of the electrode assembly shown in FIG. 10 before winding.

[0077] [Figure 13] FIG. 10 is a schematic diagram of the structure of an electrode assembly according to still other embodiments of the present application before winding.

[0078] [Figure 14] 10A and 10B are schematic diagrams illustrating the configuration of an electrode assembly according to still other embodiments of the present application.

[0079] The symbols of specific embodiments are as follows:

[0080] 1 vehicle 2 batteries 3 Controller 4 motors 5. Cabinet 5a First housing part 5b Second housing part 5c Containment Space 6 battery cells 10 Electrode Assembly 100 Starting Segment 20. Housing 21 cases 22 End cover 30 electrode terminal 11 Positive electrode sheet 111 first bending portion 1111 First current collecting part 1112 First active material layer 11a Positive electrode bent part 12 Negative electrode sheet 121 Second bending part 1211 Second current collector 1212 Second active material layer 13 Isolation Assembly 131 First Isolation Layer 132 Second Isolation Layer 133 Base Film 134 Insulating Layer 13a Reinforcement area 13b Base area 14 Folding layer A Flat area B. Folding area B1 First bending point B2 Second bending point W Winding direction DETAILED DESCRIPTION OF THE INVENTION

[0081] In order to clarify the objectives, technical solutions and advantages of the embodiments of the present application, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without any creative work are all within the scope of protection of the present application.

[0082] Unless otherwise defined, all technical and technical terms used herein have the same meaning as commonly understood by those skilled in the art of this application. The terms used herein are merely intended to describe specific embodiments and are not intended to limit the present application. The terms "comprise," "have," and any variations thereof in the specification, claims, and drawings of this application are intended to cover a non-exclusive inclusion. The terms "first," "second," etc. in the specification, claims, and drawings of this application are used to distinguish between different objects and are not used to describe a specific order or a subordinate relationship.

[0083] In the description of this application, orientations or positional relationships indicated by terms such as "center," "lateral," "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" are orientations or positional relationships shown in the drawings, and are intended to facilitate and simplify the description of this application. They do not indicate or imply that the devices or elements shown have a particular orientation or must be constructed or operated in a particular orientation, and therefore should not be construed as limiting this application.

[0084] In the description of this application, unless otherwise clearly specified or limited, the terms "mounted," "connected," "coupled," and "attached" should be understood in a broad sense. For example, they may refer to a fixed connection, a detachable connection, or an integral connection, and may also refer to a direct connection, an indirect connection via an intermediate medium, or internal communication between two elements. Those skilled in the art can understand the specific meanings of the above terms in this application according to specific circumstances.

[0085] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described with reference to the embodiment may be included in at least one embodiment of the present application. The appearance of the term in each location in the specification does not necessarily refer to the same embodiment, nor is it an independent or potential embodiment that is mutually exclusive with other embodiments. Those skilled in the art will understand, both explicitly and implicitly, that the embodiments described herein can be combined with other embodiments.

[0086] The term "and / or" in this specification simply describes the relationship between related objects and can indicate the existence of three types of relationships. For example, A and / or B can indicate three situations: A only exists, A and B both exist, and B only exists. In addition, in this specification, the symbol " / " generally indicates that the related objects before and after it are in an "or" relationship.

[0087] As used herein, "plurality" refers to two or more (including two); similarly, "sets" refers to two or more (including two sets); and "plurality" refers to two or more (including two).

[0088] In the present application, the battery cells may include, but are not limited to, 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. The battery cells may be cylindrical, flat, rectangular, or have other shapes, but are not limited to these. Battery cells are generally divided into cylindrical battery cells, prismatic battery cells, and soft-pack battery cells based on their packaging, but are not limited to these.

[0089] The battery cell includes an electrode assembly and an electrolyte, and the electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. The battery cell operates primarily by relying on the movement of metal ions between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer is coated on the surface of the positive electrode current collector, and the current collector without the positive electrode active material layer protrudes from the current collector with the positive electrode active material layer coated thereon, and the current collector without the positive electrode active material layer is called a positive electrode tab. Taking a lithium-ion battery as an example, the positive electrode current collector may be made of aluminum, and the positive electrode active material may be lithium cobalt oxide, lithium iron phosphate, ternary lithium, lithium manganese oxide, etc. The negative electrode sheet includes 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, and the current collector without the negative electrode active material layer protrudes from the current collector coated with the negative electrode active material layer. The current collector without the negative electrode active material layer is called a negative electrode tab. 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 high current flow without melting, multiple positive electrode tabs are stacked, and multiple negative electrode tabs are stacked. The separator may be made of polypropylene (PP) or polyethylene (PE), etc. The electrode assembly may have a wound structure or a stacked structure, and the embodiments of the present application are not limited thereto. The development of battery technology requires simultaneous consideration of multiple design factors, such as performance parameters such as energy density, cycle life, discharge capacity, and charge / discharge ratio, as well as battery safety.

[0090] The battery referred to in the embodiments of this application refers to a single physical module that includes one or more battery cells to provide higher voltage and capacity. For example, the battery referred to in this application may include a battery module or a battery pack. The battery generally includes a housing for sealing one or more battery cells. The housing can prevent liquids or other foreign objects from affecting the charging or discharging of the battery cells.

[0091] The separator, which has electronic insulation properties, is placed between the positive electrode sheet and the negative electrode sheet. Its main role is to prevent the positive electrode sheet and the negative electrode sheet from coming into contact with each other and causing an internal short circuit in the electrode assembly. The separator has a large number of through-holes, ensuring the free passage of electrolyte ions. In particular, the separator has good permeability to lithium ions. For example, the separator may include an isolation substrate and a functional layer located on the surface of the isolation substrate. The isolation substrate 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.

[0092] The separator occupies a very important position in the electrode assembly, and can directly cause phenomena such as short circuit of the electrode assembly, reducing its performance and service life.

[0093] During charging of a battery cell, metal ions desorb from the positive electrode active material layer and intercalate into the negative electrode active material layer. However, some abnormal situations may occur, resulting in metal ion precipitation. Taking a lithium-ion battery cell as an example, due to insufficient lithium intercalation space in the negative electrode active material layer, excessive resistance to lithium ion intercalation into the negative electrode active material layer, or excessively rapid deintercalation of lithium ions from the positive electrode active material layer, the deintercalated lithium ions cannot intercalate equally into the negative electrode active material layer of the negative electrode sheet. The lithium ions that cannot intercalate into the negative electrode sheet gain electrons only on the surface of the negative electrode sheet, thereby forming metallic lithium. This phenomenon is called lithium precipitation. Lithium precipitation not only reduces the performance of the battery cell, but also significantly shortens the cycle life and limits the fast charging capacity of the battery cell. Furthermore, if lithium is deposited in a battery cell, the deposited lithium metal is highly reactive and reacts with the electrolyte at a low temperature, causing a decrease in the self-heating onset temperature (Tonset) of the battery cell and an increase in the self-heating rate, which seriously endangers the safety of the battery cell. Furthermore, if lithium deposition is severe, the desorbed lithium ions form a lithium layer on the surface of the negative electrode sheet, and lithium dendrites from the lithium layer may pass through the separator and cause a short circuit between the adjacent positive and negative electrode sheets, potentially posing a safety risk.

[0094] The inventors have attempted to increase the overall thickness of the separator to reduce the risk of lithium dendrites penetrating the separator, however, increasing the separator thickness reduces the energy density of the electrode assembly.

[0095] The inventors have discovered that during charge and discharge, serious lithium deposition is likely to occur only in a portion of the negative electrode sheet, in other words, lithium deposition is unlikely to occur or only slight lithium deposition occurs in a portion of the negative electrode sheet, and there is no need to thicken the separator facing this portion.

[0096] In light of these issues, the inventors of the present application provide an electrode assembly including a positive electrode sheet, a negative electrode sheet, and an isolating assembly for isolating the positive and negative electrode sheets. The isolating assembly includes a substrate region and a reinforcing region connected to the substrate region, with the reinforcing region having a thickness greater than the thickness of the substrate region. At least a portion of the reinforcing region is located between the adjacent positive and negative electrode sheets. The reinforcing region corresponds to a position on the negative electrode sheet where lithium deposition is likely to occur. Thus, when lithium deposits on the negative electrode sheet, the reinforcing region effectively separates the positive and negative electrode sheets, reducing the risk of lithium dendrites passing through the isolating assembly and improving service life and safety. The substrate region has a smaller thickness than the reinforcing region. This reduces the amount of isolating assembly used, lowering costs and improving the energy density of the electrode assembly.

[0097] For ease of explanation, the following embodiment will be described by taking an example in which the power consuming device is a vehicle.

[0098] 1 is a schematic diagram of a vehicle according to some embodiments of the present application. As shown in FIG. 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 may be used as the operating power source for the vehicle 1.

[0099] The vehicle 1 further comprises a controller 3 and a motor 4, and the controller 3 is used to control the supply of power from the battery 2 to the motor 4, for example, for the power consumption required for starting the vehicle 1, navigation, and operation while driving.

[0100] In some embodiments of the present application, the battery 2 may not only serve as the operating power source for the vehicle 1, but also as the driving power source for the vehicle 1, replacing or partially replacing fuel oil or natural gas to provide driving force for the vehicle 1.

[0101] 2 is a schematic exploded view of a battery according to some embodiments of the present application. As shown in FIG. 2, the battery 2 includes a housing 5 and a battery cell 6 housed within the housing 5.

[0102] The housing 5 is used to house the battery cells 6 and may have various structures. In some embodiments, the housing 5 includes a first housing portion 5a and a second housing portion 5b, which are coupled to each other and cover each other, and together define a housing space 5c for housing the battery cells 6. The second housing portion 5b may have a hollow structure with one end open, and the first housing portion 5a has a plate-like structure, and the first housing portion 5a is covered by the open side of the second housing portion 5b, thereby forming the housing 5 having the housing space 5c. Both the first housing portion 5a and the second housing portion 5b may have a hollow structure with one end open, and the open side of the first housing portion 5a is covered by the open side of the second housing portion 5b, thereby forming the housing 5 having the housing space 5c. Naturally, the first housing part 5a and the second housing part 5b may have various shapes, such as a cylindrical body or a rectangular parallelepiped.

[0103] In order to improve the sealing performance after the first housing part 5a and the second housing part 5b are connected, a sealing material such as a sealant or a seal ring may be installed between the first housing part 5a and the second housing part 5b.

[0104] When the first housing part 5a is covered on top of the second housing part 5b, the first housing part 5a may be called the upper housing and the second housing part 5b may be called the lower housing.

[0105] The battery 2 includes a plurality of battery cells 6. The plurality of battery cells 6 may be connected in series, parallel, or series-parallel, and series-parallel refers to the plurality of battery cells 6 being connected in both series and parallel. The plurality of battery cells 6 may be directly connected in series, parallel, or series-parallel, and the entire configuration of the plurality of battery cells 6 may be housed within a housing 5. Naturally, a battery module may be formed by first connecting the plurality of battery cells 6 in series, parallel, or series-parallel, and the plurality of battery modules may then be further connected in series, parallel, or series-parallel to form an integrated unit and housed within a housing 5.

[0106] FIG. 3 is a schematic exploded view of a battery cell according to some embodiments of the present application.

[0107] The battery cell 6 refers to the smallest unit constituting the battery 2. As shown in Figure 3, the battery cell 6 includes a housing 20, an electrode assembly 10, and other functional members, and the electrode assembly 10 is housed in the housing 20.

[0108] In some embodiments, the housing 20 may include an end cover 22 and a case 21 .

[0109] The end cover 22 is a member 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 adapted to fit the shape of the case 21, but is not limited to this. Optionally, the end cover 22 may be made of a material (e.g., aluminum alloy) with a certain hardness and strength. In this way, the end cover 22 is less likely to deform when subjected to a pressure collision, allowing the battery cell 6 to have higher structural strength and improved safety performance. The end cover 22 may be provided with functional members such as electrode terminals 30. The electrode terminals 30 are electrically connected to the electrode assembly 10 and are used to output or input electrical energy to or from the battery cell 6.

[0110] In some embodiments, the end cover 22 may further include a pressure release mechanism for releasing internal pressure when the internal pressure or temperature of the battery cells 6 reaches a threshold. The end cover 22 may be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., but the embodiments of the present application are not particularly limited thereto.

[0111] In some embodiments, an insulating member may be further installed inside the end cover 22. The insulating member isolates the electrical connection members in the case 21 from the end cover 22, thereby reducing the risk of short circuits. Illustratively, the insulating member may be made of plastic, rubber, or the like.

[0112] The case 21 is an assembly that mates with the end cover 22 to form an internal environment for the battery cell 6. The internal environment is used to accommodate the electrode assembly 10, electrolyte, and other components. The case 21 and the end cover 22 may be separate components, or an opening may be provided in the case 21, and the end cover 22 covers the opening to form the internal environment for the battery cell 6. Alternatively, 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 inserted into the case. If the interior of the case 21 needs to be sealed, the end cover 22 may then cover the case 21. The case 21 may have various shapes and sizes, such as a rectangular parallelepiped, cylindrical, or hexagonal prism. Specifically, the shape of the case 21 can be determined depending on the specific shape and dimensions of the electrode assembly 10. The case 21 may be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., but the embodiment of the present application is not particularly limited to these.

[0113] The electrode assembly 10 is a component in the battery cell 6 that is infiltrated with the electrolyte to cause an electrochemical reaction. One or more electrode assemblies 10 may be contained within the case 21. The electrode assembly 10 is primarily formed by winding a positive electrode sheet and a negative electrode sheet, and a separator is typically placed between the positive and negative electrode sheets. The portions of the positive and negative electrode sheets that have active material constitute the main body of the electrode assembly 10, and the portions of the positive and negative electrode sheets that do not have active material constitute tabs, respectively. The positive and negative electrode tabs may be commonly located at one end of the main body, or may be located at both ends of the main body. During the charge and discharge process of the battery cell 6, the positive and negative electrode active materials react with the electrolyte, and the tabs are connected to electrode terminals 30 to form a current circuit.

[0114] Fig. 4 is a schematic diagram of an electrode assembly according to some embodiments of the present application. Fig. 5 is a partially enlarged schematic diagram of the electrode assembly shown in Fig. 4. Fig. 6 is an enlarged schematic diagram of block P in Fig. 5. Fig. 7 is a schematic diagram of the electrode assembly shown in Fig. 4 before winding. Fig. 8 is a schematic diagram of the isolation assembly shown in Fig. 7.

[0115] 4 to 8 , an electrode assembly 10 according to an embodiment of the present invention includes a positive electrode sheet 11, a negative electrode sheet 12, and a separator assembly 13. The separator assembly 13 is used to separate the positive electrode sheet 11 from the negative electrode sheet 12. The separator assembly 13 includes a base region 13b and a reinforcing region 13a connected to the base region 13b, and the thickness of the reinforcing region 13a is greater than the thickness of the base region 13b. At least a portion of the reinforcing region 13a is located between the adjacent positive electrode sheet 11 and negative electrode sheet 12.

[0116] The electrode assembly 10 may have a variety of shapes; for example, the electrode assembly 10 may be cylindrical, flat, prismatic (eg, triangular, square, or hexagonal), or other shapes.

[0117] The separator assembly 13 may be one or more. For example, two separator assemblies 13 are provided, and in the present application, one separator assembly 13, a negative electrode sheet 12, another separator assembly 13, and a positive electrode sheet 11 are stacked in this order and then wound two or more times to form a wound structure. When multiple separator assemblies 13 are provided, the reinforcing region 13a may be provided in only one separator assembly 13, or in each separator assembly 13.

[0118] The separator assembly 13 is an assembly including an insulating film and is used to separate the positive electrode sheet 11 from the negative electrode sheet 12. Such an insulating film has a large number of through-holes and can ensure the free passage of metal ions. Illustratively, the insulating film has good permeability to lithium ions and cannot substantially block the passage of lithium ions.

[0119] Illustratively, isolation assembly 13 may be fabricated using a single insulating film or multiple insulating films.

[0120] The number of reinforcing regions 13a may be one or more. Illustratively, there are multiple reinforcing regions 13a, and adjacent reinforcing regions 13a are connected by a base region 13b.

[0121] The entire reinforcing region 13 a may be located between the positive electrode sheet 11 and the negative electrode sheet 12 , or only a portion of the reinforcing region 13 a may be located between the positive electrode sheet 11 and the negative electrode sheet 12 .

[0122] The reinforcing region 13a corresponds to a position on the negative electrode sheet 12 where lithium is likely to be deposited. Thus, when lithium is deposited on the negative electrode sheet 12, the reinforcing region 13a effectively separates the positive electrode sheet 11 from the negative electrode sheet 12, reducing the risk of lithium dendrites passing through the separator assembly 13 and improving service life and safety. Compared to the reinforcing region 13a, the substrate region 13b can have a smaller thickness. This reduces the amount of separator assembly 13 used, lowering costs and improving the energy density of the electrode assembly 10.

[0123] In some embodiments, the thickness of the reinforced region 13a is between 2 μm and 100 μm. Preferably, the thickness of the reinforced region 13a is 2 μm, 5 μm, 7 μm, 10 μm, 12 μm, 20 μm, 30 μm, 50 μm, 80 μm or 100 μm.

[0124] The thinner the thickness of the reinforcing region 13a, the higher the energy density of the electrode assembly 10, but the higher the risk of lithium dendrites passing through the reinforcing region 13a.The thicker the reinforcing region 13a, the lower the energy density of the electrode assembly 10, but the lower the risk of lithium dendrites passing through the reinforcing region 13a, and the safer the electrode assembly 10.

[0125] In order to strike a balance between the energy density and safety of the electrode assembly 10, the inventors have determined through testing and calculation that the thickness of the reinforced region 13a is limited to 2 μm to 100 μm.

[0126] In some embodiments, the thickness of the reinforced region 13a is between 5 μm and 30 μm.

[0127] In some embodiments, the reinforcement region 13a is provided as a multi-layer structure and the substrate region 13b is provided as a single layer structure.

[0128] In the reinforcement region 13a, multiple separator layers are stacked to form a multilayer structure. The stacking direction of the multiple separator layers is parallel to the stacking direction of the positive electrode sheet 11 and the negative electrode sheet 12. In the reinforcement region 13a, two adjacent separator layers may be connected to each other or may be separated from each other.

[0129] For the reinforced region 13a having a multi-layer structure, the thickness of the reinforced region 13a refers to the sum of the thicknesses of the multiple isolation layers.

[0130] The number of layers in the reinforced region 13a is 2 or more. For example, the number of layers in the reinforced region 13a may be 2 to 15.

[0131] In the base region 13b, the isolation layer is a single layer. There may be one or more base regions 13b. For example, there are multiple base regions 13b and multiple reinforcing regions 13a, and the multiple base regions 13b and multiple reinforcing regions 13a are alternately arranged along the winding direction W.

[0132] The substrate region 13b corresponds to a position on the negative electrode sheet 12 where lithium deposition is difficult. The substrate region 13b has a smaller number of layers, thus reducing the amount of separator assembly 13 used and improving the energy density of the battery cell.

[0133] After the lithium layer is deposited on the surface of the negative electrode sheet 12, the lithium layer presses against the separator layer adjacent to the negative electrode sheet 12 in the reinforcement region 13a, and the separator layer adjacent to the negative electrode sheet 12 is stretched by the pressure of the lithium layer. If the pore size of the separator layer adjacent to the negative electrode sheet 12 increases locally and a defect region is formed, small lithium dendrites in the lithium layer may pass through the defect region. The separator layer away from the negative electrode sheet 12 in the reinforcement region 13a insulates and isolates lithium dendrites passing 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.

[0134] The distance between the separator layer away from the negative electrode sheet 12 and the lithium layer in the reinforcement region 13a is large, so the compressive force it receives from the lithium layer is small, and the risk of it being stretched and developing a defect region due to the compressive force is also low. The position at which the defect region occurs in the separator layer during the stretching process is not constant, and a defect region also occurs in the separator layer away from the negative electrode sheet 12. It is unlikely that a defect region in the separator layer away from the negative electrode sheet 12 and a defect region in the separator layer close to the negative electrode sheet 12 will be exactly opposite each other, making it difficult for lithium dendrites to pass through the reinforcement region 13a at the same time. Therefore, by providing the reinforcement region 13a in the embodiments of the present application, the risk of short circuiting can be effectively reduced and safety can be improved.

[0135] Assuming the thickness is the same, the reinforced region 13a with a multi-layer structure can more effectively block lithium dendrites, reduce the risk of short circuits, and improve safety compared to the reinforced region 13a with a single-layer structure. For example, the protective effect of the reinforced region 13a composed of two 5 μm isolation layers is superior to the protective effect of the reinforced region 13a composed of a single 10 μm isolation layer. In other words, as long as the insulation requirements are met, the reinforced region 13a with a multi-layer structure can be thinner than the reinforced region 13a with a single-layer structure. This reduces the amount of isolation assembly 13 used and improves the energy density of the electrode assembly 10.

[0136] In some embodiments, the positive electrode sheet 11, the separator assembly 13, and the negative electrode sheet 12 are rolled to form a folding region B, and at least a portion of the reinforcement region 13a is located in the folding region B.

[0137] The winding direction W is the direction in which the positive electrode sheet 11, the negative electrode sheet 12, and the separator assembly 13 are wound circumferentially from the inside to the outside. Illustratively, the winding direction W is counterclockwise in the drawing.

[0138] The folding region B is a region of the electrode assembly 10 having a folding structure, and the positive electrode sheet 11, the negative electrode sheet 12, and the separator assembly 13 are all folded in the folding region B. Illustratively, the portion of the positive electrode sheet 11 located in the folding region B is folded in a substantially circular arc shape, and the portion of the negative electrode sheet 12 located in the folding region B is folded in a substantially circular arc shape.

[0139] The winding device winds the positive electrode sheet 11, the negative electrode sheet 12, and the separator assembly 13 multiple times, with each winding constituting several layers. One winding refers to starting the calculation from a certain point on the electrode assembly 10 as the starting point, winding one winding along the winding direction W, and reaching another point as the ending point, with the ending point, the starting point, and the center of this winding being aligned in a straight line, and the starting point being between the ending point and the center of this winding.

[0140] The electrode assembly 10 may have a folded region B over the entire area, or only a portion of the area may have a folded region B. For example, the electrode assembly includes a flat region A and a folded region B, where the folded region B is connected to the flat region A, and the flat region A is a region of the electrode assembly 10 having a flat structure.

[0141] The entire reinforcing region 13a may be provided in the folding region B, or only a portion thereof may be provided in the folding region B.

[0142] The positive electrode sheet 11 and the negative electrode sheet 12 located in the folding region B must be folded. During the folding process, stress concentration easily occurs in the positive electrode active material layer and the negative electrode active material layer, resulting in the detachment of the respective active materials. The detachment of active materials, particularly the active material detachment on the negative electrode sheet 12, can result in fewer lithium intercalation sites in the negative electrode active material layer of the negative electrode sheet 12 than the number of lithium ions available in the positive electrode active material layer of the adjacent positive electrode sheet 11, potentially resulting in lithium deposition. In the present embodiment, at least a portion of the reinforcing region 13a is located in the folding region B. Even if lithium deposits in the folding region B, the reinforcing region 13a blocks lithium dendrites, reducing the likelihood of electrical connection between the positive electrode sheet 11 and the negative electrode sheet 12. This effectively reduces the risk of short circuits and improves the service life and safety of the electrode assembly 10.

[0143] In some embodiments, the positive electrode sheet 11 includes a first folded portion 111 located in the folding region B and adjacent to the reinforcing region 13a, and the negative electrode sheet 12 includes a second folded portion 121 adjacent to the first folded portion 111. The reinforcing region 13a includes a plurality of folded layers 14 located in the folding region B and laminated between the first folded portion 111 and the second folded portion 121.

[0144] The first folded portion 111 being adjacent to the second folded portion 121 means that no other positive electrode sheet layer or no other negative electrode sheet layer is present between them. The reinforced region 13a being adjacent to the first folded portion 111 means that no other positive electrode sheet layer or no other negative electrode sheet layer is present between them.

[0145] The positive electrode sheet 11 includes a plurality of positive electrode folded portions 11a located in the folding region B, and the positive electrode folded portion 11a adjacent to the reinforced region 13a having a multilayer structure is the first folded portion 111. In the positive electrode sheet 11, some of the positive electrode folded portions 11a may be the first folded portions 111, or all of the positive electrode folded portions 11a may be the first folded portions 111.

[0146] The negative electrode sheet 12 includes a plurality of negative electrode folding portions located in the folding region B, and for example, the negative electrode folding portion adjacent to the first folding portion 111 and sandwiching the first folding portion 111 and the reinforcement region 13a therebetween is the second folding portion 121.

[0147] In the electrode assembly 10, the reinforcing region 13a and the second bent portion 121 may be provided only on the inside of the first bent portion 111, or the reinforcing region 13a and the second bent portion 121 may be provided only on the outside of the first bent portion 111, or the reinforcing region 13a and the second bent portion 121 may be provided on both sides of the first bent portion 111.

[0148] The multiple folded layers 14 can block lithium dendrites when lithium is precipitated at the second folded portion 121, reducing the risk of lithium dendrites coming into contact with the first folded portion 111 and improving safety.

[0149] In some embodiments, a reinforced region 13a and a second folded portion 121 are provided at least inside the first folded portion 111.

[0150] The curvature of the second bent portion 121 located inside the first bent portion 111 is greater than the curvature of the first bent portion 111. This makes it more likely that the active material will fall off from the second bent portion 121 during the bending process. In other words, lithium deposition is more likely to occur in the second bent portion 121 located inside the first bent portion 111. The reinforced region 13a can separate the first bent portion 111 from the second bent portion 121 located inside the first bent portion 111. Even if lithium deposits in the second bent portion 121, the probability that lithium dendrites will pass through the reinforced region 13a is reduced, thereby reducing the risk of a short circuit and improving safety.

[0151] In some embodiments, the first folded portion 111 includes a first current collector 1111 and a first active material layer 1112 disposed on the surface of the first current collector 1111, and the first active material layer 1112 has a thickness h1. The second folded portion 121 includes a second current collector 1211 and a second active material layer 1212 disposed on the surface of the second current collector 1211, and the second active material layer 1212 has a thickness h2, the folded layer 14 has a thickness h3, and the second current collector 1211 has a thickness h4. In the thickness direction of the first folded portion 111, the maximum distance between the first folded portion 111 and the second folded portion 121 is X. The number of folded layers 14 located between the first folded portion 111 and the second folded portion 121 is Y, where Y is a positive integer greater than 1. The active material capacity per unit area of ​​first active material layer 1112 is A1, and the active material capacity per unit area of ​​second active material layer 1212 is A2.

[0152] The first current collector 1111 may be part of a positive electrode current collector, and the first active material layer 1112 is part of a positive electrode active material layer. The second current collector 1211 may be part of a negative electrode current collector, and the second active material layer 1212 is part of a negative electrode active material layer.

[0153] In the thickness direction of the first bent portion 111, the maximum distance between the surface of the first bent portion 111 facing the second bent portion 121 and the surface of the second bent portion 121 facing the first bent portion 111 is X. Illustratively, the thickness direction of the first bent portion 111 may be a normal direction to the surface of the first bent portion 111 facing the second bent portion 121.

[0154] The active material capacity A1 per unit area of ​​first active material layer 1112 is the ratio of the active material capacity of first active material layer 1112 to the area of ​​the surface of first current collecting portion 1111 to which first active material layer 1112 is applied. The active material capacity A2 per unit area of ​​second active material layer 1212 is the ratio of the active material capacity of second active material layer 1212 to the area of ​​the surface of second current collecting portion 1211 to which second active material layer 1212 is applied.

[0155] The average discharge capacity of the first active material layer 1112 was tested. The positive electrode sheet 11 from each of the above examples was taken and punched using a die to obtain a small wafer containing the first active material layer 1112 on one side. Six identical CR2430 button cell batteries were assembled in an argon-protected glove box using a lithium metal sheet as the counter electrode, a Celgard membrane as the separator, and a solution of EC, DMC, and DEC (ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1) dissolved in LiPF6 (1 mol / L). (1) After assembly, the battery cells were allowed to stand for 12 hours. (2) Constant-current charging was performed at a charging current of 0.1 C until the voltage reached the upper cutoff voltage x 1 V, and then constant-voltage charging was performed until the current reached 50 μA, maintaining the voltage x 1 V. (3) The battery cells were allowed to stand for 5 minutes. (4) Finally, discharge the battery at a constant current of 0.1 C until the voltage reaches the lower cutoff voltage y1V. (5) Allow the battery to stand for 5 minutes. Repeat steps (2) to (5) and record the discharge capacity of the second cycle. The average discharge capacity of the six button batteries is the average discharge capacity of the first active material layer 1112 on one side, which can be defined as the active material capacity A1 per unit area of ​​the first active material layer 1112. For example, if the positive electrode active material is lithium iron phosphate, the upper cutoff voltage x1V = 3.75 V and the lower cutoff voltage y1V = 2 V. If the positive electrode active material is lithium nickel cobalt manganese oxide (NCM), the upper cutoff voltage x1V = 4.25 V and the lower cutoff voltage y1V = 2.8 V.

[0156] The average discharge capacity of the second active material layer 1212 was tested. The negative electrode sheet 12 from each of the above examples was taken and a die was used to cut a small wafer with the same area as the small positive electrode wafer, including the second active material layer 1212 on one side. Six CR2430 button cells were assembled in an argon-protected glove box using a lithium metal sheet as the counter electrode, a Celgard membrane as the separator, and a solution of EC, DMC, and DEC (ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1) dissolved in LiPF6 (1 mol / L) as the electrolyte. (1) After assembly, the cells were allowed to stand for 12 hours. (2) A constant current discharge was performed at a discharge current of 0.05 C until the voltage reached the lower cutoff voltage y2 mV. (3) A constant current discharge was then performed at a discharge current of 50 μA until the voltage reached the lower cutoff voltage y2 mV. (4) The cells were allowed to stand for 5 minutes. (5) Next, perform constant current discharge at a discharge current of 10 μA until the lower cutoff voltage y2 mV is reached. (6) Allow to stand for 5 minutes. (7) Finally, perform constant current charge at a charge current of 0.1 C until the final voltage reaches the upper cutoff voltage x2 V. (8) Allow to stand for 5 minutes. Repeat steps (2) to (8) and record the charge capacity of the second cycle. The average charge capacity of the six button batteries is the average charge capacity of the second active material layer 1212 on one side, which can be defined as the active material capacity A2 per unit area of ​​the second active material layer 1212. For example, if the negative electrode active material is graphite, the upper cutoff voltage x2 V = 2 V and the lower cutoff voltage y2 V = 5 mV. If the negative electrode active material is silicon, the upper cutoff voltage x2 V = 2 V and the lower cutoff voltage y2 V = 5 mV.

[0157] In some embodiments, A2 / A1 ≧ 1. h1, h2, h3, h4, X, and Y satisfy the following formula: JPEG0007749108000003.jpg28150

[0158] The fewer the number of folded layers 14 in the reinforced region 13a, the higher the risk of lithium dendrites passing through the reinforced region 13a. The more the number of folded layers 14 in the reinforced region 13a, the more complex the structure of the separator assembly 13 becomes, and the lower the energy density of the electrode assembly 10. The inventors have conducted tests and calculations to determine the number of folded layers 14 based on the above formula, thereby achieving a balance between the safety and energy density of the electrode assembly 10.

[0159] In some embodiments, A2 / A1<1. h1, h2, h3, h4, X, and Y satisfy the following formula: JPEG0007749108000004.jpg25141

[0160] When A2 / A1<1, the lithium intercalation space in the second active material layer 1212 is insufficient, and lithium ions escaping from the first active material layer 1112 cannot be intercalated in equal amounts into the second active material layer 1212. Lithium ions that cannot be intercalated into the second active material layer 1212 can only obtain electrons on the surface of the second active material layer 1212. This results in lithium deposition. Compared to an electrode assembly 10 where A2 / A1≧1, an electrode assembly 10 where A2 / A1<1 experiences more severe lithium deposition, and therefore requires more folded layers 14 in the reinforcing region 13a.

[0161] The inventors have established a balance between the safety and energy density of the electrode assembly 10 by setting the number of folded layers 14 based on the above formula through tests and calculations.

[0162] In some embodiments, the value of h1 is between 5 μm and 80 μm. Preferably, the value of h1 is 5 μm, 10 μm, 20 μm, 30 μm, 50 μm or 80 μm.

[0163] In some embodiments, the value of h2 is between 10 μm and 100 μm. Preferably, the value of h2 is 10 μm, 20 μm, 30 μm, 50 μm, 80 μm or 100 μm.

[0164] In some embodiments, the value of h3 is between 1 μm and 20 μm. Preferably, the value of h3 is 1 μm, 3 μm, 5 μm, 10 μm, 15 μm or 20 μm.

[0165] Assuming that the isolation effect is satisfied, the smaller the value of h3, the greater the number of folded layers 14 in the reinforced region 13a. If the value of h3 is too small, the number of folded layers 14 in the reinforced region 13a will be too large, making the structure of the isolation assembly 13 complex and difficult to mold. Therefore, the inventors set the value of h3 to 1 μm or more.

[0166] The larger the value of h3, the larger the total thickness of the reinforced region 13a. If the value of h3 is too large, the energy density of the electrode assembly 10 will be low. Therefore, the inventors ensure the energy density of the electrode assembly 10 by setting the value of h3 to 20 μm or less.

[0167] In some embodiments, the value of h4 is between 2 μm and 20 μm, and preferably, the value of h4 may be 2 μm, 3 μm, 5 μm, 10 μm, 15 μm, or 20 μm.

[0168] In some embodiments, the value of X is between 10 μm and 5000 μm. Preferably, the value of X may be 10 μm, 20 μm, 50 μm, 100 μm, 500 μm, 1000 μm, 2000 μm, or 5000 μm.

[0169] In some embodiments, the positive electrode sheet 11 includes a plurality of positive electrode folds 11a arranged along the winding direction W, and at least the positive electrode fold 11a formed by the first folding of the positive electrode sheet 11 is arranged as the first folding portion 111. In other words, the positive electrode fold 11a formed by the first folding of the positive electrode sheet 11 is arranged adjacent to the reinforcing region 13a.

[0170] Each of the positive electrode bent portions 11a of the positive electrode sheet 11 is bent. For example, the positive electrode bent portions 11a are generally arc-shaped.

[0171] The positive electrode folded portion 11a formed by the first folding of the positive electrode sheet 11 refers to the positive electrode folded portion 11a formed by the first folding in the process of winding the positive electrode sheet 11 along the winding direction W.

[0172] The curvature of the positive electrode folded portion 11a formed by the first folding of the positive electrode sheet 11 is large, and during charging, lithium deposition is likely to occur in the negative electrode sheet 12 adjacent to the positive electrode folded portion 11a formed by the first folding of the positive electrode sheet 11. In this embodiment, the positive electrode folded portion 11a formed by the first folding of the positive electrode sheet 11 is set as the first folding portion 111, and the reinforcing region 13a effectively isolates the positive electrode folded portion 11a formed by the first folding of the positive electrode sheet 11 from lithium dendrites, thereby reducing the risk of short circuits and improving safety.

[0173] In some embodiments, the positive electrode folded portion 11a formed by folding the positive electrode sheet 11 a for the second time is also set as the first folded portion 111. That is, the positive electrode folded portion 11a formed by folding the positive electrode sheet 11 a for the second time is also set adjacent to the reinforced region 13a.

[0174] The positive electrode folded portion 11a formed by the second folding of the positive electrode sheet 11 refers to the positive electrode folded portion 11a formed by the second folding in the process of winding the positive electrode sheet 11 along the winding direction W.

[0175] The reinforcing region 13a adjacent to the positive electrode bent portion 11a formed by the first folding of the positive electrode sheet 11 may be integrally connected to the reinforcing region 13a adjacent to the positive electrode bent portion 11a formed by the second folding of the positive electrode sheet 11, or may be installed at an interval along the winding direction W.

[0176] The curvature of the positive electrode folded portion 11a formed by the second folding of the positive electrode sheet 11 is large, and during charging, lithium deposition is likely to occur in the negative electrode sheet 12 adjacent to the positive electrode folded portion 11a formed by the second folding of the positive electrode sheet 11. In this embodiment, the positive electrode folded portion 11a formed by the second folding of the positive electrode sheet 11 is set as the first folded portion 111, and the reinforcing region 13a effectively isolates the positive electrode folded portion 11a formed by the second folding of the positive electrode sheet 11 from lithium dendrites, thereby reducing the risk of short circuits and improving safety.

[0177] In some embodiments, the total thickness of the reinforcing region 13a located inside the positive electrode fold portion 11a formed by the first folding of the positive electrode sheet 11 is T1, and the total thickness of the reinforcing region 13a located inside the positive electrode fold portion 11a formed by the second folding of the positive electrode sheet 11 is T2, where T1≧T2.

[0178] The curvature of the second fold 121 located inside the positive electrode fold 11a formed by the first folding of the positive electrode sheet 11 is larger than the curvature of the second fold 121 located inside the positive electrode fold 11a formed by the second folding of the positive electrode sheet 11, and lithium is more likely to deposit in the second fold 121 located inside the positive electrode fold 11a formed by the first folding of the positive electrode sheet 11. In this embodiment, by making T1≧T2, the risk of the positive electrode fold 11a formed by the first folding of the positive electrode sheet 11 becoming conductive with lithium dendrites can be reduced, thereby improving the safety of the battery cell.

[0179] In some embodiments, the number of layers of the isolation layer in the reinforced region 13a located inside the positive electrode fold portion 11a formed by the first folding of the positive electrode sheet 11 is L1, and the number of layers of the isolation layer in the reinforced region 13a located inside the positive electrode fold portion 11a formed by the second folding of the positive electrode sheet 11 is L2, where L1≧L2.

[0180] In some embodiments, a reinforced region 13a and a second folded region 121 are provided on both sides of the first folded region 111, and the total thickness of the reinforced region 13a located inside the first folded region 111 is greater than or equal to the total thickness of the reinforced region 13a located outside the first folded region 111.

[0181] The reinforced regions 13 a on both sides of the first bent portion 111 may belong to the same isolation assembly 13 , or may belong to two different isolation assemblies 13 .

[0182] The curvature of the second bent portion 121 located inside the first bent portion 111 is greater than the curvature of the second bent portion 121 located outside the first bent portion 111, and lithium deposition is more likely to occur in the second bent portion 121 located inside the first bent portion 111. In this embodiment, by making the thickness of the reinforced region 13a located inside the first bent portion 111 equal to or greater than the thickness of the reinforced region 13a located outside the first bent portion 111, the risk of the first bent portion 111 becoming conductive with lithium dendrites can be reduced, and the safety of the battery cell can be improved.

[0183] In some embodiments, the number of isolation layers in the reinforced region 13 a located inside the first fold 111 is equal to or greater than the number of isolation layers in the reinforced region 13 a located outside the first fold 111 .

[0184] In some embodiments, the positive electrode sheet 11, the separator assembly 13, and the negative electrode sheet 12 are wound to further form a flat region A, which is connected to a folded region B. At least a portion of the substrate region 13b is disposed on the flat region A.

[0185] The flat region A is a region in which the electrode assembly 10 has a flat structure, and the portions of the positive electrode sheet 11 and the negative electrode sheet 12 located in the flat region A are arranged substantially flat. Illustratively, the surfaces of the positive electrode sheets 11 and the negative electrode sheets 12 located in the flat region A are both essentially flat.

[0186] The positive electrode sheet 11 and the negative electrode sheet 12 located in the flat region A are both in a flat state, the active material in the flat region A is less likely to fall off, and the problem of lithium deposition is less likely to occur in the negative electrode sheet 12 located in the flat region A. Therefore, even if the base region 13b is placed in the flat region A, the insulation between the positive and negative sheets can be improved and the risk of short circuits can be reduced.

[0187] In some embodiments, two folding regions B are provided, and the two folding regions B are provided at both ends of the flat region A, respectively.

[0188] In some embodiments, both ends of the reinforced region 13a along the winding direction W are located in the flat region A, so that the entire reinforced region 13a can pass through the folding region B. This reduces the risk of short circuits in the folding region B.

[0189] In some embodiments, the dimension of the end portion of the reinforced region 13a beyond the folding region B in the winding direction W is 3 mm to 500 mm. Preferably, the dimension of the end portion of the reinforced region 13a beyond the folding region B is 10 mm to 100 mm.

[0190] In some embodiments, the isolation assembly 13 includes a first isolation layer 131 and a second isolation layer 132, where the first isolation layer 131 is 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 is located between the positive electrode sheet 11 and the negative electrode sheet 12 and is laminated with the first isolation layer 131. The area of ​​the first isolation layer 131 that overlaps with the second isolation layer 132 and the second isolation layer 132 form the reinforcement region 13a of the isolation assembly 13, and the area of ​​the first isolation layer 131 that does not overlap with the second isolation layer 132 forms the substrate region 13b.

[0191] For example, the first isolation layer 131 can be understood as an isolation layer between the positive electrode sheet 11 and the negative electrode sheet 12 in the related art, 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.

[0192] In the isolation assembly 13, the number of second isolation layers 132 may be one or more.

[0193] The first isolation layer 131 and the second isolation layer 132 may be two parts of a single piece, or may be two separate pieces provided respectively.

[0194] The first isolation layer 131 and the second isolation layer 132 may be made of the same material or different materials.

[0195] In this embodiment, there is no limitation on the thickness of the first isolation layer 131 and the thickness of the second isolation layer 132, and the thickness of the first isolation layer 131 may be greater than or equal to the thickness of the second isolation layer 132, or may be less than or equal to the thickness of the second isolation layer 132.

[0196] The first isolating layer 131 and the second isolating layer 132 are laminated between the positive electrode sheet 11 and the negative electrode sheet 12. The second isolating layer 132 may be installed independently of the first isolating layer 131, i.e., in the lamination direction of the first isolating layer 131 and the second isolating layer 132, the second isolating layer 132 faces the surface of the first isolating layer 131 and has no connection, such as adhesive, with the first isolating layer 131. Naturally, the second isolating layer 132 may be attached to the surface of the first isolating layer 131. For example, the second isolating layer 132 may be entirely attached to the first isolating layer 131, or only a portion of the second isolating layer 132 may be attached to the first isolating layer 131. Attaching means connecting by sticking.

[0197] In the present embodiment, by adding a second isolation layer 132 to the electrode assembly 10, a reinforced region 13a with a large thickness is formed in the isolation assembly 13, which can reduce the risk of short circuits due to lithium deposition and improve safety.

[0198] In some embodiments, the number of second isolation layers 132 in the reinforced region 13a is 1 to 10. Illustratively, the number of second isolation layers 132 in the reinforced region 13a is 1, 2, 3, 5, or 10. When multiple second isolation layers 132 are provided in one reinforced region 13a, the dimensions of the multiple second isolation layers 132 along the winding direction may be the same or different.

[0199] In some embodiments, the isolator assembly 13 has a plurality of reinforced regions 13a, and the number of layers of the second isolating layers 132 of the plurality of reinforced regions 13a may be the same or different.

[0200] 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 .

[0201] Since the first isolation layer 131 and the second isolation layer 132 can function as multi-layer protection, the added second isolation layer 132 can be made thinner than the first isolation layer 131, thereby reducing the amount of second isolation layer 132 used.

[0202] Optionally, the thickness of the second isolation layer 132 is less than the thickness of the first isolation layer 131 .

[0203] In some embodiments, the second separator layer 132 is disposed on the side of the first separator layer 131 facing the positive electrode sheet 11 .

[0204] In some embodiments, the thickness of the first isolation layer 131 is between 2 μm and 30 μm. Optionally, the thickness of the first isolation layer 131 is 2 μm, 5 μm, 7 μm, 10 μm, 15 μm, 20 μm, or 30 μm.

[0205] In some embodiments, the thickness of the second isolation layer 132 is between 1 μm and 25 μm. Optionally, 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.

[0206] In some embodiments, the porosity of the second isolation layer 132 is smaller than the porosity of the first isolation layer 131. Because the second isolation layer 132 has a small porosity, after the lithium dendrites pass through the first isolation layer 131, the lithium dendrites are less likely to pass through the pores in the second isolation layer 132, thereby reducing the risk of electrical conduction between the lithium dendrites and the positive electrode sheet 11 and improving safety.

[0207] In some embodiments, the second isolation layer 132 has a porous structure, and the pore size of the pores in the second isolation layer 132 is 1 μm or less.

[0208] The pore diameter of the second isolation layer 132 is small, making it difficult for lithium dendrites to pass through, thereby reducing the risk of electrical conduction between the lithium dendrites and the positive electrode sheet 11 and improving safety.

[0209] In some embodiments, the first isolation layer 131 includes a base film 133 and an insulating layer 134 applied to the surface of the base film 133. The base film 133 may be a porous film. Illustratively, the base film 133 is made of an electrically insulating and liquid-retaining polymer material, such as PP (polypropylene), PE (polyethylene), or PVDF (polyvinylidene fluoride).

[0210] The insulating layer 134 is a functional layer provided on the surface of the base film 133. Exemplarily, the insulating layer 134 includes an inorganic material, a polymer adhesive, and a dispersant, where the inorganic material includes at least one of boehmite and silica, the polymer adhesive includes at least one of PVDF and polystyrene-acrylate, and the dispersant can include polyvinyl alcohol. The inorganic material sandwiches the base film 133 and can reduce shrinkage of the base film 133. The polymer adhesive is bonded to the electrode sheet to increase the overall rigidity of the electrode assembly 10.

[0211] The second isolation layer 132 may include only the base film 133, or may include both the base film 133 and the insulating layer 134. Preferably, the base film 133 of the second isolation layer 132 is integrally connected to the base film 133 of the first isolation layer 131.

[0212] In the embodiment of the present application, the number of layers in the reinforced region 13a is determined by the number of layers in the base film 133. In other words, the number of layers in the reinforced region 13a refers to the number of layers in the base film 133 in the reinforced region 13a.

[0213] In some embodiments, the thickness of the insulating layer 134 is 0.5 μm to 10 μm. The particle size of the inorganic material is 0.1 μm to 10 μm. The content of the inorganic material in the insulating layer 134 is 70% to 98%. The content of the polymer adhesive is 1% to 20%. The content of the dispersant is 0.5% to 10%.

[0214] In some embodiments, at least a portion of the second isolation layer 132 is disposed separately from the first isolation layer 131 in the stacking direction of the first isolation layer 131 and the second isolation layer 132 .

[0215] There is no connection, such as adhesion, between at least a portion of the second isolation layer 132 and the first isolation layer 131.

[0216] When the first isolating layer 131 (or the second isolating layer 132) is stretched by the pressure of the lithium layer, the influence of the first isolating layer 131 on the separation portion between the second isolating layer 132 and the first isolating layer 131 is small, the degree of stretching of the second isolating layer 132 is small, and the risk of defects occurring is low. Therefore, in this embodiment, the risk of lithium dendrites passing through the first isolating layer 131 and the second isolating layer 132 can be effectively reduced, thereby improving safety.

[0217] In some embodiments, the positive electrode sheet 11, the separator assembly 13, and the negative electrode sheet 12 are wound to form a folding region B and a flat region A, with the flat region A connected to the folding region B. A portion of the second separator layer 132 is located in the folding region B, and another portion of the second separator layer 132 is located in the flat region A. In the folding region B, the second separator layer 132 is disposed separately from the first separator layer 131. In the flat region A, the second separator layer 132 is attached to the first separator layer 131.

[0218] The folding region B has a high risk of lithium precipitation, and by separating the second isolation layer 132 in the folding 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, improving safety. In the flat region A, the second isolation layer 132 is attached to the first isolation layer 131, thereby reducing the movement width of the second isolation layer 132 along the winding direction W and reducing the risk of the second isolation layer 132 becoming misaligned.

[0219] In some embodiments, the second isolation layer 132 is formed by folding over an end of the first isolation layer 131 .

[0220] Illustratively, the second isolation layer 132 is formed after the end of the first isolation layer 131 is folded, and the folding point is the boundary between the first isolation layer 131 and the second isolation layer 132.

[0221] In this embodiment, the second isolation layer 132 extends directly from the end of the first isolation layer 131, eliminating the need to add and fix the second isolation layer 132 separately, making the winding process more convenient and improving the integrity of the electrode assembly 10.

[0222] In some embodiments, the positive electrode sheet 11, the separator assembly 13, and the negative electrode sheet 12 are wound and installed, and the electrode assembly 10 has a starting segment 100 along the winding direction W, and the end of the first separator layer 131 is located at the starting segment 100.

[0223] The start segment 100 along the winding direction W is the end portion located at the innermost periphery of the electrode assembly 10 .

[0224] The second separator 132 extends from the start segment 100 along the winding direction W and passes through the positive electrode fold 11a formed by the first folding of the positive electrode sheet 11, thereby reducing the risk of lithium dendrites simultaneously passing through the first separator 131 and the second separator 132 and coming into contact with the positive electrode fold 11a of the positive electrode sheet 11, thereby improving safety. At the same time, this embodiment further reduces the length that the second separator 132 needs to extend, saving on usage and reducing costs.

[0225] In some embodiments, the positive electrode sheet 11, the isolation assembly 13, and the negative electrode sheet 12 are rolled to form a folding region B, which includes a first folding portion B1 adjacent to the starting segment 100 along the rolling direction W, and a first isolation layer 131 and a second isolation layer 132 are disposed at the first folding portion B1, with the second isolation layer 132 extending from the end of the first isolation layer 131 and beyond the first folding portion B1.

[0226] The first folding region B1 is a position where the electrode assembly 10 is folded for the first time during winding. For example, at the first folding region B1, the positive electrode sheet 11 is folded for the first time, and the negative electrode sheet 12 is folded for the first time.

[0227] The first folding portion B1 has the largest curvature of the folding between the positive electrode sheet 11 and the negative electrode sheet 12, and is therefore at the highest risk of lithium deposition on the negative electrode sheet 12 during charging. The second separating layer 132 extends beyond the first folding portion B1, so that the first separating layer 131 and the second separating layer 132 can protect at least the first folding portion B1, which is prone to lithium deposition problems, and at the same time, reduce the amount of the second separating layer 132 used, thereby saving costs and improving the safety and service life of the electrode assembly 10.

[0228] FIG. 9 is a schematic diagram of the configuration of an isolation assembly of an electrode assembly according to some other embodiments of the present application before winding.

[0229] 9, in some embodiments, the entire isolator assembly 13 is a single layer structure. The isolator assembly 13 has a reinforcement region 13a and a base region 13b having different thicknesses directly formed therein during molding.

[0230] Fig. 10 is a schematic diagram of the configuration of an electrode assembly according to still other embodiments of the present application. Fig. 11 is a partially enlarged schematic diagram of the electrode assembly shown in Fig. 10. Fig. 12 is a schematic diagram of the configuration of the electrode assembly shown in Fig. 10 before winding.

[0231] As shown in FIGS. 10 to 12, in some embodiments, a plurality of reinforcement regions 13a and a plurality of base regions 13b are provided, and the plurality of reinforcement regions 13a and the plurality of base regions 13b are provided alternately along the winding direction W.

[0232] The multiple reinforcing regions 13a correspond to the multiple positive electrode fold portions 11a of the positive electrode sheet 11, respectively, thereby reducing the risk of short circuits occurring at the multiple positive electrode fold portions 11a of the positive electrode sheet 11 and improving safety.

[0233] Each of the reinforced regions 13a includes one or more second isolation layers 132. The number of layers in the multiple reinforced regions 13a may be the same or different.

[0234] In some embodiments, each reinforcement region 13 a can separate one positive electrode fold 11 a from one negative electrode fold of the negative electrode sheet 12 .

[0235] In some embodiments, the positive electrode sheet 11, the separator assembly 13, and the negative electrode sheet 12 are rolled to form a folding region B. The folding region B includes a plurality of folding positions arranged along the rolling direction W, and the electrode assembly 10 includes a plurality of second separator layers 132, and the first separator layer 131 and the plurality of second separator layers 132 are arranged in at least one of the plurality of folding positions.

[0236] The folding portions are locations where the electrode assembly 10 is folded during winding. Exemplarily, the folding portions include a first folding portion B1 and a second folding portion B2, where the positive electrode sheet 11 and the negative electrode sheet 12 are both folded a first time at the first folding portion B1, and where the positive electrode sheet 11 and the negative electrode sheet 12 are both folded a second time at the second folding portion B2.

[0237] In this embodiment, the second isolation layer 132 is installed at some or all of the positions of the multiple bending portions, which can effectively reduce the risk of short circuits at the bending portions and improve safety.

[0238] In addition, one of the second isolation layers 132 may be installed so as to extend and pass through multiple bending portions, or each of the second isolation layers 132 may be installed so as to extend and pass through one bending portion.

[0239] In some embodiments, the second isolation layers 132 are spaced apart along the winding direction W.

[0240] The phrase "the plurality of second isolation layers 132 are disposed at intervals" can be understood to mean that the plurality of second isolation layers 132 are separate and not connected as a single second isolation layer 132. In this embodiment, the manner of disposing the second isolation layers 132 can be made more flexible, i.e., the second isolation layers 132 can be disposed arbitrarily in positions where additional isolation layers are required, and at the same time, waste caused by adding second isolation layers 132 in positions where additional isolation layers are not required can be reduced, and energy density can be improved.

[0241] In some embodiments, the electrode assembly 10 includes a start segment 100 along the winding direction W. The plurality of fold locations include a first fold location B1 and a second fold location B2, where the first fold location B1 is closer to the start segment 100 than the second fold location B2 along the winding direction W. The thickness of the second isolation layer 132 located at the first fold location B1 is greater than the thickness of the second isolation layer 132 located at the second fold location B2.

[0242] The risk of lithium deposition in the negative electrode sheet 12 at the first fold position B1 is higher than the risk of lithium deposition in the negative electrode sheet 12 at the second fold position B2, and the risk of lithium dendrites passing through the second isolating layer 132 at the first fold position B1 is higher than the risk of lithium dendrites passing through the second isolating layer 132 at the second fold position B2. Therefore, in this embodiment, the thickness of the second isolating layer 132 installed at the first fold position B1 is made thicker than the thickness of the second isolating layer 132 installed at the second fold position B2, thereby providing additional protection at the first fold position B1, which is more susceptible to short circuits, improving safety, and reducing the amount of second isolating layer 132 used.

[0243] In some embodiments, multiple second isolation layers 132 are adhered to the surface of the first isolation layer 131, thereby reducing the risk of the second isolation layers 132 shifting position during the charging and discharging process of the electrode assembly 10 and ensuring the isolation effect of the second isolation layers 132.

[0244] Optionally, both ends of the second isolation layer 132 along the winding direction W are adhered to the first isolation layer 131, and the second isolation layer 132 is positioned separately from the first isolation layer 131 along the center of the winding direction W.

[0245] In some embodiments, after the electrode assembly 10 is rolled, the electrode assembly 10 is externally hot pressed to bond the second isolation layer 132 to the first isolation layer 131 .

[0246] In some embodiments, the first isolation layer 131 includes two surfaces along its thickness direction, and the plurality of second isolation layers 132 are located on the same surface of the first isolation layer 131 .

[0247] 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. Therefore, by installing multiple second isolation layers 132 on the same surface of the first isolation layer 131, when the first isolation layer 131 is tensioned, the impact of the second isolation layer 132 on the gap between the positive electrode sheet 11 and the negative electrode sheet 12 can be reduced, the risk of lithium deposition can be reduced, and safety can be improved.

[0248] FIG. 13 is a schematic diagram of the configuration of an electrode assembly according to still other embodiments of the present application before winding.

[0249] As shown in FIG. 13, in some embodiments, the thickness of the multiple reinforced regions 13a gradually decreases from the inside to the outside along the winding direction W.

[0250] In this embodiment, the thickness of the innermost reinforcing region 13a is greater than the thickness of the outermost reinforcing region 13a along the winding direction W. The thicknesses of two adjacent reinforcing regions 13a may be the same or different.

[0251] Along the winding direction W, the curvature of the positive electrode fold 11a of the positive electrode sheet 11 gradually decreases from the inside to the outside, gradually reducing the risk of contact with lithium dendrites. In this embodiment, the thickness of the reinforced region 13a can be increased in areas with a high risk of short circuiting and decreased in areas with a low risk of short circuiting. This improves safety and reduces the amount of isolation assembly 13 used.

[0252] In some embodiments, the difference in thickness between adjacent reinforcement regions 13a is 0.5 μm to 10 μm along the winding direction W. Preferably, the difference in thickness between adjacent reinforcement regions 13a is 0.5 μm, 1 μm, 2 μm, 5 μm, 7 μm, or 10 μm.

[0253] FIG. 14 is a schematic diagram of an electrode assembly according to still other embodiments of the present application.

[0254] As shown in FIG. 14 , in some embodiments, the positive electrode sheet 11 includes a plurality of positive electrode folds 11a arranged along the winding direction W, and at least the positive electrode fold 11a formed by the last fold of the positive electrode sheet 11 is arranged as the first fold 111.

[0255] During charging, the electrode assembly 10 expands and presses against the case, and the case applies a reaction force to the electrode assembly 10. The reaction force makes it easy for lithium to deposit in the region of the negative electrode sheet 12 facing the positive electrode fold 11a formed by the final fold of the positive electrode sheet 11. In this embodiment, by locating at least a portion of the reinforcing region 13a adjacent to the positive electrode fold 11a formed by the final fold of the positive electrode sheet 11, the risk of the positive electrode fold 11a formed by the final fold of the positive electrode sheet 11 becoming conductive with lithium dendrites is reduced, improving the safety of the battery cell.

[0256] Illustratively, the electrode assembly 10 has a cylindrical shape. Each positive electrode folded portion 11a of the positive electrode sheet 11 corresponds to one turn of the positive electrode sheet.

[0257] According to some embodiments of the present application, the present application further provides a battery cell including a housing and the electrode assembly of any of the above embodiments, wherein the electrode assembly is contained within the housing.

[0258] According to some embodiments of the present application, the present application further provides a battery including a plurality of the battery cells of any of the above embodiments.

[0259] According to some embodiments of the present application, the present application further provides a power consumption device including the 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.

[0260] 4 to 8 , the present application provides an electrode assembly 10 including 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 includes a first isolation layer 131 and a second isolation layer 132. The first isolation layer 131 is 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 is located between the positive electrode sheet 11 and the negative electrode sheet 12 and is laminated with the first isolation layer 131. The area of ​​the first isolation layer 131 overlapping with the second isolation layer 132 and the second isolation layer 132 form a reinforcement area 13a of the isolation assembly 13. The area of ​​the first isolation layer 131 not overlapping with the second isolation layer 132 forms a base area 13b of the isolation assembly 13, and the thickness of the reinforcement area 13a is greater than the thickness of the base area 13b. The second isolation layer 132 is formed by folding the end of the first isolation layer 131 .

[0261] The positive electrode sheet 11, the separator assembly 13, and the negative electrode sheet 12 are wound to form a folding region B and a flat region A, and the flat region A is connected to the folding region B. At least a portion of the reinforcement region 13a is located in the folding region B, and at least a portion of the substrate region 13b is located in the flat region A.

[0262] A part of the reinforcing region 13a is placed adjacent to the positive electrode fold portion 11a formed by the first folding of the positive electrode sheet 11, and another part of the reinforcing region 13a is placed adjacent to the positive electrode fold portion 11a formed by the second folding of the positive electrode sheet 11.

[0263] The present application will now be further described with reference to the following examples.

[0264] In order to clarify the purpose, technical solution and beneficial technical effects of the present invention, the present invention will be described in more detail below with reference to examples. However, it should be understood that the examples are merely for the purpose of interpreting the present invention, and are not intended to limit the present invention, and the examples of the present invention are not limited to the examples described in the specification. When specific experimental conditions or operating conditions are not specified in the examples, they are prepared under normal conditions or under the conditions recommended by the material provider.

[0265] Example 1 can be prepared according to the following steps.

[0266] (i) LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, acetylene black (a conductive agent), and PVDF (an adhesive) are mixed in a mass ratio of 96:2:2, then added to a solvent (NMP) and stirred with a vacuum mixer until the mixture is homogeneous to obtain positive electrode slurry. The positive electrode slurry is then evenly applied to aluminum foil, dried at room temperature, and then transferred to an oven for drying. The resulting mixture is then cold-rolled, slit, and punched to obtain a positive electrode sheet.

[0267] (ii) The negative electrode active material graphite, conductive agent acetylene black, thickener CMC, and adhesive SBR are mixed in a mass ratio of 96.4:1:1.2:1.4, then added to deionized water as a solvent and stirred with a vacuum mixer until the mixture is homogeneous to obtain negative electrode slurry. The negative electrode slurry is then evenly applied to copper foil, dried at room temperature, and then transferred to an oven for drying. The negative electrode sheet is then obtained through cold rolling, slitting, and punching.

[0268] (iii) Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then thoroughly dried lithium salt LiPF6 is dissolved in the mixed organic solvent to prepare an electrolyte solution with a concentration of 1 mol / L.

[0269] (iv) folding a 7 μm thick polyethylene film to form an isolator assembly, the isolator assembly comprising a first isolator layer and a second isolator layer, the second isolator layer having a length of 652.5 mm, the area of ​​the first isolator layer overlapping with the second isolator layer and the second isolator layer forming a reinforcement area of ​​the isolator assembly, the area of ​​the first isolator layer not overlapping with the second isolator layer forming a base area of ​​the isolator assembly, the reinforcement area having a thickness of 14 μm, and the base area having a thickness of 7 μm.

[0270] (v) The positive electrode sheet, the separator assembly, and the negative electrode sheet are stacked and wound multiple times, and then flattened into a flat shape to produce an electrode assembly.

[0271] (vi) The electrode assembly is placed in a rectangular case, and the case and end cover are welded together. Then, after undergoing processes such as liquid injection, standing, chemical conversion, and shaping, a battery cell is obtained. For example, the battery cell has a capacity of 60 Ah.

[0272] In step (v), the gap between the innermost positive electrode sheet and the innermost negative electrode sheet is artificially set to 200 μm to accelerate lithium deposition in the electrode assembly. In the wound electrode assembly, a first separator and a second separator are disposed between the innermost positive electrode sheet and the innermost negative electrode sheet.

[0273] Example 2

[0274] The manufacturing method of the battery cell of Example 2 is similar to that of Example 1, except for the following: in step (vi), the gap between the innermost two turns of the positive electrode sheet and the innermost two turns of the negative electrode sheet is artificially set to 200 μm, the length of the second separator is 873.6 mm, and a first separator and a second separator are also installed between the second turn of the positive electrode sheet and the second turn of the negative electrode sheet.

[0275] Comparative Example 1

[0276] The manufacturing method of the battery cell of Comparative Example 1 is the same as that of Example 1, with the following differences: The separator assembly of Comparative Example 1 is not folded, and the separator assembly has a single-layer structure.

[0277] Comparative Example 2

[0278] The manufacturing method of the battery cell of Comparative Example 2 is the same as that of Example 2, with the following differences: The separator assembly of Comparative Example 2 is not folded, and the separator assembly has a single-layer structure.

[0279] 80 battery cells are manufactured for each of Example 1, Example 2, Comparative Example 1 and Comparative Example 2, and each battery cell is tested.

[0280] Specifically, in a room temperature environment, the battery cell is charged at 1C and discharged at 1C, and cycle charging and discharging is performed in a high SOC (for example, 0.9 to 1) range.

[0281] The 40 battery cells of Example 1 were fully charged after 500 cycles and then left to stand for 24 hours to detect the voltage drop of the battery cells and calculate the self-discharge rate of each battery cell, and then the average value was calculated. The self-discharge rate is the voltage drop / hour. The remaining 40 battery cells of Example 1 were subjected to 2000 cycles, and the number of battery cell failures during the cycle process was recorded and the failure rate was calculated.

[0282] Example 2, Comparative Example 1, and Comparative Example 2 were also tested using the above steps.

[0283] The evaluation results of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1.

[0284] [Table 1]

[0285] With reference to Examples 1 and 2 and Comparative Examples 1 and 2, when a reinforcing region is provided between the positive electrode sheet and the negative electrode sheet and lithium is deposited on the negative electrode sheet, the risk of short circuiting can be reduced and the service life of the battery cell can be improved.

[0286] In addition, if there is no conflict, the embodiments and features of the embodiments in this application can be combined with each other.

[0287] Finally, it should be noted that the above embodiments are merely for illustrating the technical solutions of the present application, and are not intended to limit the same. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art may still modify the technical solutions described in the above embodiments or make equivalent substitutions for some of the technical features thereof, and it is understood that these modifications or substitutions do not deviate from the essence of the corresponding technical solutions and the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. a positive electrode sheet, a negative electrode sheet, and an isolation assembly for isolating the positive electrode sheet and the negative electrode sheet; the isolation assembly includes a base region and a reinforcement region connected to the base region, the reinforcement region having a thickness greater than a thickness of the base region; At least a portion of the reinforcing region is located between the adjacent positive electrode sheet and the adjacent negative electrode sheet, the positive electrode sheet, the separator assembly, and the negative electrode sheet are wound to form a folding region, and at least a portion of the reinforcing region is disposed in the folding region; the positive electrode sheet includes a first folding portion located in the folding region and adjacent to the reinforcement region, and the negative electrode sheet includes a second folding portion adjacent to the first folding portion; the reinforcement region includes a plurality of folded layers, the plurality of folded layers being located in the folded region and laminated between the first folded portion and the second folded portion; the positive electrode sheet includes a plurality of positive electrode fold portions arranged along a winding direction, and the positive electrode fold portion formed by at least a first fold of the positive electrode sheet is arranged as the first fold portion, the positive electrode folded portion formed by folding the positive electrode sheet a second time is also set as the first folded portion, a total thickness of the reinforcement region located inside the positive electrode folding portion formed by folding the positive electrode sheet a first time is T1, and a total thickness of the reinforcement region located inside the positive electrode folding portion formed by folding the positive electrode sheet a second time is T2, and T1≧T2. Electrode assembly.

2. 2. The electrode assembly according to claim 1, wherein the thickness of the reinforcing region is 2 μm to 100 μm.

3. The electrode assembly according to claim 1 , wherein the reinforcing region and the second bent portion are provided at least inside the first bent portion.

4. the first folded portion includes a first current collecting portion and a first active material layer disposed on a surface of the first current collecting portion, the first active material layer having a thickness h1; the second folded portion includes a second current collecting portion and a second active material layer disposed on a surface of the second current collecting portion, the second active material layer having a thickness h2, the folded layer having a thickness h3, and the second current collecting portion having a thickness h4; a maximum distance X between the first bent portion and the second bent portion in a thickness direction of the first bent portion; the number of the folded layers located between the first folded portion and the second folded portion is Y, where Y is a positive integer greater than 1; the first active material layer has an active material capacity per unit area of ​​A1, the second active material layer has an active material capacity per unit area of ​​A2, and A2 / A1≧1; h1, h2, h3, h4, X and Y are The electrode assembly according to claim 1 , wherein

5. the first folded portion includes a first current collecting portion and a first active material layer disposed on a surface of the first current collecting portion, the first active material layer having a thickness h1; the second folded portion includes a second current collecting portion and a second active material layer disposed on a surface of the second current collecting portion, the second active material layer having a thickness h2, the folded layer having a thickness h3, and the second current collecting portion having a thickness h4; a maximum distance X between the first bent portion and the second bent portion in a thickness direction of the first bent portion; the number of the folded layers located between the first folded portion and the second folded portion is Y, where Y is a positive integer greater than 1; the first active material layer has an active material capacity per unit area of ​​A1, the second active material layer has an active material capacity per unit area of ​​A2, and A2 / A1<1; h1, h2, h3, h4, X and Y are The electrode assembly according to claim 1 , wherein

6. 6. The electrode assembly according to claim 4, wherein the value of h3 is 1 μm to 20 μm.

7. 6. The electrode assembly according to claim 4, wherein the value of X is from 10 μm to 5000 μm.

8. 2. The electrode assembly of claim 1, wherein the reinforcing region and the second reinforcing region are provided on both sides of the first reinforcing region, and the total thickness of the reinforcing region located inside the first reinforcing region is equal to or greater than the total thickness of the reinforcing region located outside the first reinforcing region.

9. 2. The electrode assembly according to claim 1, wherein the positive electrode sheet includes a plurality of positive electrode folds arranged along the winding direction, and at least the positive electrode fold formed by the last fold of the positive electrode sheet is arranged as the first fold.

10. the positive electrode sheet, the separator assembly, and the negative electrode sheet are wound to form a flat region, and the flat region is connected to the folding region; 2. The electrode assembly of claim 1, wherein at least a portion of the base region is disposed on the flat region.

11. The electrode assembly according to claim 10 , wherein a plurality of the reinforcing regions and a plurality of the base regions are provided, and the plurality of the reinforcing regions and the plurality of the base regions are provided alternately along the winding direction.

12. The electrode assembly according to claim 11 , wherein the thickness of the plurality of reinforcing regions gradually decreases from the inside to the outside along the winding direction.

13. 13. The electrode assembly according to claim 12, wherein the difference in thickness of adjacent reinforcing regions along the winding direction is 0.5 μm to 10 μm.

14. 2. The electrode assembly of claim 1, wherein the reinforcement region is provided as a multi-layer structure and the base region is provided as a single-layer structure.

15. the isolation assembly includes a first isolation layer and a second isolation layer, the first isolation layer is used to electrically isolate the positive electrode sheet and the negative electrode sheet, and at least a portion of the second isolation layer is located between the positive electrode sheet and the negative electrode sheet and is laminated with the first isolation layer; 2. The electrode assembly of claim 1, wherein the area of ​​the first isolation layer that overlaps with the second isolation layer and the second isolation layer form the reinforcement area of ​​the isolation assembly, and the area of ​​the first isolation layer that does not overlap with the second isolation layer forms the base area.

16. 16. The electrode assembly of claim 15, wherein the thickness of the second separator layer is less than or equal to the thickness of the first separator layer.

17. 17. The electrode assembly according to claim 15 or 16, wherein at least a portion of the second isolation layer is disposed separately from the first isolation layer in the stacking direction of the first isolation layer and the second isolation layer.

18. the positive electrode sheet, the separator assembly, and the negative electrode sheet are wound to form a folding region and a flat region, and the flat region is connected to the folding region; a portion of the second isolation layer is located in a folding region, and another portion of the second isolation layer is located in a flat region; 18. The electrode assembly of claim 17, wherein the second isolation layer is spaced apart from the first isolation layer in the folded region and the second isolation layer is attached to the first isolation layer in the flat region.

19. The electrode assembly of claim 15 , wherein the second isolation layer is formed by folding an end of the first isolation layer.

20. 20. The electrode assembly of claim 19, wherein the positive electrode sheet, the separator assembly, and the negative electrode sheet are wound and installed, the electrode assembly includes a start segment along the winding direction, and an end of the first separator layer is located at the start segment.

21. 21. The electrode assembly of claim 20, wherein the positive electrode sheet, the separator assembly, and the negative electrode sheet are rolled to form a folding region, the folding region including a first folding portion adjacent to the start segment along the rolling direction, the first separator layer and the second separator layer being disposed at the first folding portion, and the second separator layer extending from an end of the first separator layer and beyond the first folding portion.

22. the positive electrode sheet, the separator assembly, and the negative electrode sheet are rolled to form a folding region; 16. The electrode assembly of claim 15, wherein the folding region includes a plurality of folding portions arranged along the winding direction, the electrode assembly includes a plurality of the second isolation layers, and the first isolation layer and the plurality of the second isolation layers are arranged in at least one of the plurality of folding portions.

23. 23. The electrode assembly of claim 22, wherein the plurality of second isolation layers are spaced apart along the winding direction.

24. the electrode assembly includes a start segment along a winding direction, the plurality of bend portions include a first bend portion and a second bend portion, and the first bend portion is closer to the start segment than the second bend portion along the winding direction; 24. The electrode assembly of claim 22 or 23, wherein the thickness of the second isolation layer provided at the first bent portion is greater than the thickness of the second isolation layer provided at the second bent portion.

25. 23. The electrode assembly of claim 22, wherein the first isolation layer includes two surfaces along its thickness direction, and the plurality of second isolation layers are located on the same surface of the first isolation layer.

26. 23. The electrode assembly of claim 22, wherein a plurality of the second isolation layers are adhered to a surface of the first isolation layer.

27. A battery cell comprising a housing and the electrode assembly of claim 1 , wherein the electrode assembly is contained within the housing.

28. 30. A battery comprising a plurality of the battery cells of claim 27.

29. 30. A power consuming device comprising the battery cell of claim 27 for supplying electrical energy.

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