Battery cell, battery device, and electric device

Abstract

The application provides a battery monomer, a battery device and a power utilization device, and belongs to the battery field. The battery monomer comprises one or more wound electrode assemblies, the electrode assembly comprises a flat area and a corner area; the wound electrode assembly comprises a pole piece, the pole piece comprises a composite current collector; the composite current collector comprises a support layer and a conductive layer located on at least one side surface of the support layer; the porosity of the support layer in the bending area is Q1, the porosity of the support layer in the flat area is Q2, and 1Q1 / Q23; the conductive layer is provided with a through hole in the bending area, and the through hole is provided in the thickness direction of the conductive layer. The battery monomer provided by the application can reduce the lithium precipitation of the wound battery monomer in the bending area, and can also consider the energy density of the battery.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to a battery cell, a battery device, and an electrical device. Background Technology

[0002] With the development of new energy technologies, batteries are being used more and more widely, such as in mobile phones, laptops, electric vehicles, electric cars, energy storage devices, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools. This places increasingly higher demands on battery performance. Summary of the Invention

[0003] This application provides a battery cell, a battery device, and an electrical device. The battery cell is beneficial for improving the battery's cycle life and energy density.

[0004] A first aspect of this application is to provide a battery cell including one or more wound electrode assemblies, the wound electrode assembly including a flat region and a bent region, the wound electrode assembly including an electrode sheet, the electrode sheet including a composite current collector and an active material layer disposed on at least one side of the composite current collector; the composite current collector includes a support layer and a conductive layer located on at least one surface of the support layer.

[0005] The porosity of the support layer in the bending region is Q1, and the porosity of the support layer in the straight region is Q2, satisfying 1 < Q1 / Q2 ≤ 3;

[0006] The conductive layer has a through hole in the bending area, and the through hole extends through the conductive layer along its thickness direction.

[0007] The composite current collector provided in this application, without affecting its own conductivity, also has liquid absorption and storage functions. Furthermore, by setting differentiated porosity in the bending and straight areas of the support layer of the composite current collector, the storage capacity of the electrode assembly in the bending area is increased within a certain range, effectively solving the lithium plating problem in the bending area. Moreover, the conductive layer is provided with through holes in the bending area, which improves the wettability of the electrolyte to the active material and facilitates the rapid flow of electrolyte from the support layer to the conductive layer. In addition, the electrolyte squeezed out during the cycle expansion of the battery cell can also flow back to the interior of the electrode assembly more quickly, keeping the active material in an electrolyte-wetted state, thereby improving the cycle performance of the battery by reducing lithium plating.

[0008] At the same time, this design does not affect the amount of active material added in the bending region, especially the smooth insertion and extraction of the positive electrode active material, thus also taking into account the energy density of the battery.

[0009] In some embodiments, the porosity Q1 of the support layer in the bending region is 20% to 40%, and the porosity Q2 of the support layer in the straight region is 10% to 20%.

[0010] In these embodiments, this application selects specific values ​​of the porosity of the support layer in the aforementioned bending and straight regions to facilitate its cooperation with the through holes provided on the conductive layer, while not affecting the load on the active material. Therefore, it is beneficial to balance the energy density and cycle performance of the battery.

[0011] In some embodiments, the conductive layer has a plurality of first through holes in the bending region and a plurality of second through holes in the straight region, wherein the average diameter of the first through holes is greater than or equal to the average diameter of the second through holes.

[0012] The average pore size of the first through hole is 1 μm to 10 μm, and the average pore size of the second through hole is 100 nm to 1 μm.

[0013] and / or;

[0014] The spacing between two adjacent first through holes and / or the spacing between two adjacent second through holes is 0.08mm to 1.2mm.

[0015] In some embodiments, this application further selects to provide through holes in the conductive layer. These through holes extend along the thickness direction of the conductive layer. This design facilitates the smooth flow of electrolyte stored in the support layer to the active material layer, and further increases the wetting of the active material layer by the electrolyte. As mentioned above, the technical problem this application actually aims to solve is the lithium plating problem that occurs in the bending area of ​​the wound cell due to electrolyte extrusion. The electrolyte extruded during the cyclic expansion of the battery cell can also flow back to the electrode assembly more quickly, keeping the active material in an electrolyte-wetted state. This application selects that the average pore size of the first through hole in the bending area of ​​the conductive layer is larger than the average pore size of the second through hole in the straight area. Since the pore size of the through hole in the bending area is relatively larger and matches the porosity of the support layer, it facilitates better improvement of the wetting of the active material layer by the electrolyte in the bending area of ​​the wound cell, thus further improving the lithium plating problem.

[0016] In some embodiments, the conductive layer is provided with a plurality of through holes in the bending region, the average diameter of the through holes being 100 nm to 10 μm, and the spacing between two adjacent through holes being 0.08 mm to 1.2 mm.

[0017] Furthermore, the conductive layer does not have through holes in the aforementioned flat area.

[0018] In some embodiments, this application discloses that the conductive layer has multiple through holes in the bending region, while the conductive layer does not have through holes in the straight region. This design reduces the impact of small-diameter particles in the active material clogging the through holes. Furthermore, it matches the porosity of the support layer, facilitating better improvement of electrolyte wetting of the active material layer in the bending region of the wound cell, thus further improving the lithium plating problem.

[0019] In some embodiments, the electrode sheet includes a negative electrode sheet, which includes the composite current collector and a negative electrode film layer located on at least one side surface of the composite current collector, the negative electrode film layer including a negative electrode active material.

[0020] The average particle size of the aforementioned negative electrode active material in the aforementioned bending region is smaller than the average particle size of the aforementioned straight region.

[0021] In these embodiments, this application discloses that the negative electrode sheet includes a composite current collector having the characteristics of a support layer with different porosities and / or a conductive layer with through-holes of different pore sizes. In these embodiments, the current collector of the positive electrode sheet can be any type of current collector conventional in the art, or it can be the composite current collector described above. When both the negative electrode sheet and the positive electrode sheet include the composite current collector described above, it is relatively optimal for improving the lithium plating problem and taking into account the battery energy density.

[0022] In these embodiments, the present application selects negative electrode active materials with different average particle sizes in the bending region and the straight region. In the bending region, negative electrode active materials with relatively smaller average particle sizes are selected. Generally speaking, the smaller the average particle size, the larger its specific surface area, which facilitates the shuttle of electrolyte ions in the electrolyte without affecting the energy density of the active material.

[0023] In some embodiments, the average particle size of the negative electrode active material in the bending region is 5 μm to 12 μm; and the average particle size of the negative electrode active material in the straight region is 10 μm to 20 μm.

[0024] In some embodiments, the negative electrode film layer includes a conductive agent, and the mass percentage content of the conductive agent in the bending region is greater than the mass percentage content in the straight region based on the total mass of the negative electrode film layer.

[0025] The conductive agent has a mass percentage content of 1.0% to 1.5% in the bending region and a mass percentage content of 0.5% to 1.0% in the straight region.

[0026] In some embodiments, the negative electrode film layer includes an adhesive, and the mass percentage content of the adhesive in the bending region is less than the mass percentage content in the straight region based on the total mass of the negative electrode film layer.

[0027] The adhesive has a mass percentage content of 1.0% to 1.5% in the bending area and a mass percentage content of 1.5% to 2.5% in the straight area.

[0028] In these embodiments, the present application further uses conductive agents and binders with different contents to reduce the impact on the amount of negative electrode active material used, so that the active material can be inserted and removed more quickly and smoothly in the bending area. Therefore, this design method is also conducive to ensuring the energy density of the battery.

[0029] In some embodiments, the thickness of the support layer is 3 μm to 5 μm, and the thickness of the conductive layer is 5 μm to 10 μm;

[0030] The aforementioned support layer includes any one or more of the following: polyterephthalate, polyethylene, polypropylene, epoxy resin, polyamide, polyimide, polyester, polyolefin, polyacetylene, siloxane polymer, polyether, polyol, polysulfone, polysaccharide polymer, amino acid polymer, polysulfide polymer, and aromatic ring polymer.

[0031] The conductive layer described above includes a metal, which includes one or more of aluminum, aluminum alloys, copper, copper alloys, nickel, nickel alloys, iron, iron alloys, titanium, titanium alloys, silver, and silver alloys.

[0032] A second aspect of this application is to provide a battery device comprising the battery cell described in the first aspect.

[0033] A third aspect of this application is to provide an electrical device that includes the battery device described in the second aspect. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the battery structure of some embodiments of this application;

[0036] Figure 2 This is an exploded structural diagram of a battery according to some embodiments of this application;

[0037] Figure 3 This is a schematic diagram of the vehicle structure according to some embodiments of this application;

[0038] Figure 4 This is a schematic diagram of the battery pack structure according to some embodiments of this application;

[0039] Figure 5 This is a schematic diagram of the structure of a wound electrode assembly according to some embodiments of this application;

[0040] Figure 6A This is a schematic diagram of the composite current collector with a wound structure according to some embodiments of this application;

[0041] Figure 6B for Figure 6A A schematic diagram of the structure after the current collector is deployed.

[0042] 10000, vehicles;

[0043] 1000, Battery; 2000, Controller; 3000, Motor;

[0044] 100. Battery cell;

[0045] 200. Box body; 210. First part; 220. Second part;

[0046] 10. Secondary batteries;

[0047] 101. Housing; 102. Winded electrode assembly; 103. Cover plate; 102a. Straight area of ​​electrode assembly; 102b. Bending area of ​​electrode assembly;

[0048] 20. Composite current collector; 20a. Straight section of current collector; 20b. Bend section of current collector;

[0049] 21. Support layer; 22. Conductive layer.

[0050] The accompanying drawings may not be drawn to scale. Detailed Implementation

[0051] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the positive electrode composite current collector, battery cell, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0052] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the content of this application.

[0054] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the content of this application.

[0055] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0056] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0057] In the description of the embodiments of this application, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0058] Unless otherwise stated, the test temperature for all parameters mentioned in this application is 25°C.

[0059] Batteries, with their advantages of high energy density, long cycle life, and safety and reliability, have been widely used in various products. In recent years, with the significant increase in demand for batteries as an energy source, higher requirements have been placed on battery performance, such as cycle life.

[0060] During charge-discharge cycles, irreversible reactions occur simultaneously with the extraction and insertion of positive and negative electrode materials. These reaction products, as insoluble byproducts, deposit on the electrode surface, easily causing irreversible swelling of the battery. This leads to the squeezing out of the electrolyte in the bending areas of the wound cell, resulting in poor electrolyte wetting and lithium plating in the bending areas. Furthermore, due to the winding process, the area of ​​the positive electrode facing the winding axis (also known as the concave positive electrode surface) in the outermost bending area is larger than the area of ​​the negative electrode facing away from the winding core (also known as the convex negative electrode surface). This may result in the concave positive electrode surface having a greater delithiation capacity than the convex negative electrode surface, causing lithium plating on the convex negative electrode surface and thus affecting the battery's cycle performance.

[0061] In related technologies, by making the unit area capacity of the positive active material in the bending region of the positive electrode sheet smaller than that in the straight region of the positive electrode sheet, and by making the surface density of the bending region of the positive electrode sheet smaller than that in the straight region of the positive electrode sheet during coating, it is possible to reduce the lithium delithiation capability of the positive electrode in the bending region and improve the lithium insertion capability of the negative electrode, thereby ultimately reducing the lithium plating problem in the bending region.

[0062] However, while these methods can improve lithium plating to some extent, they sacrifice the battery's energy density.

[0063] In view of this, this application provides a battery cell, a battery device, and an electrical device, wherein the battery cell is advantageous in balancing the battery's cycle performance and energy density.

[0064] A battery cell includes one or more wound electrode assemblies, each wound electrode assembly including a flat region and a bent region; the wound electrode assembly includes an electrode sheet, the electrode sheet including a composite current collector and an active material layer disposed on at least one side of the composite current collector; the composite current collector includes a support layer and a conductive layer located on at least one surface of the support layer; the support layer has a porosity of Q1 in the bent region and a porosity of Q2 in the flat region, satisfying 1 < Q1 / Q2 ≤ 3; the conductive layer has a through hole in the bent region, the through hole being disposed along the thickness direction of the conductive layer.

[0065] The composite current collector provided in this application, without affecting its conductivity, also possesses liquid absorption and storage functions. Furthermore, by setting differentiated porosities in the bending and straight regions of the support layer of the composite current collector, the amount of electrolyte stored in the electrode assembly in the bending region is increased within a certain range, effectively solving the lithium plating problem in the bending region. Moreover, the through-holes in the conductive layer in the bending region improve the wettability of the electrolyte to the active material, facilitating the rapid flow of electrolyte from the support layer to the conductive layer. Furthermore, the electrolyte squeezed out during the cycle expansion of the battery cell can also flow back to the interior of the electrode assembly more quickly, keeping the active material in an electrolyte-wetted state, thereby improving battery cycle performance by reducing lithium plating. At the same time, this design does not affect the amount of active material used in the bending region, especially the smooth insertion / extraction of the positive electrode active material, thus also considering the battery's energy density.

[0066] Electrode assembly

[0067] A single battery cell typically includes an electrode assembly. This assembly comprises a positive electrode, a negative electrode, and a separator, with the separator positioned between the positive and negative electrodes. During the charging and discharging process of the battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits while allowing active ions to pass through.

[0068] Battery device

[0069] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0070] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0071] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0072] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0073] As an example, the battery cell assembly can be a battery module, and the battery cell assembly can be housed in the housing by fixing the battery module in the housing.

[0074] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0075] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0076] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0077] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0078] The battery cell of this application may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte composed of the aforementioned battery cell. The outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging of the battery cell can also be a flexible package, such as a pouch-type flexible package. The material of the flexible package can be plastic, including but not limited to polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0079] This application does not impose any particular limitation on the shape of the battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 10.

[0080] According to some embodiments of this application, reference is made to Figure 2The outer packaging may include a housing 101 and a cover plate 103. The housing 101 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 101 has an opening communicating with the receiving cavity, and the cover plate 103 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator can be formed into a wound electrode assembly 102 by a winding process. The wound electrode assembly 102 is encapsulated within the receiving cavity. Electrolyte is immersed in the wound electrode assembly 102. The secondary battery 10 may contain one or more wound electrode assemblies 102, which can be selected by those skilled in the art according to specific practical needs.

[0081] The wound electrode assembly 102 provided in this application is beneficial to improving the performance of a battery cell when applied in a battery cell. The battery cell can be used as a power source for an electrical device or as an energy storage unit for an electrical device. The electrical device is used in the power field, such as mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited to the above fields.

[0082] For ease of explanation, some embodiments of this application are illustrated using a vehicle as an example of an electrical device.

[0083] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the structure of a vehicle 10000 provided in some embodiments of this application. The vehicle 10000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery 1000 is disposed inside the vehicle 10000, and the battery 10000 can be located at the bottom, front, or rear of the vehicle 10000. The battery 10000 can be used to power the vehicle 10000; for example, the battery 10000 can serve as the operating power source for the vehicle 10000. The vehicle 10000 may also include a controller 2000 and a motor 3000. The controller 2000 is used to control the battery 10000 to supply power to the motor 3000, for example, to meet the power needs of the vehicle 10000 during startup, navigation, and driving.

[0084] In some embodiments of this application, the battery 1000 can not only serve as the operating power source for the vehicle 10000, but also as the driving power source for the vehicle 10000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 10000.

[0085] Please refer to Figure 4 , Figure 4This is an exploded view of a battery 1000 provided in some embodiments of this application. The battery 1000 includes a housing 200 and a battery cell 100. A conventional battery cell includes a primary battery or a secondary battery. This application specifically protects a secondary battery 10. The battery cell 100 is housed within the housing 200. The housing 200 provides space for the battery cell 100, and the housing 200 can adopt various structures.

[0086] In some embodiments, the housing 200 may include a first portion 210 and a second portion 220, which overlap each other, and together define a receiving space for accommodating the battery cell 100. The second portion 220 may be a hollow structure with one open end, and the first portion 210 may be a plate-like structure, with the first portion 210 covering the open side of the second portion 220 so that the first portion 210 and the second portion 220 together define the receiving space; alternatively, the first portion 210 and the second portion 220 may both be hollow structures with one open side, with the open side of the first portion 210 covering the open side of the second portion 220. Of course, the housing 200 formed by the first portion 210 and the second portion 220 may be of various shapes, such as a cylinder, a cuboid, etc.

[0087] In battery 1000, there can be multiple battery cells 100, which can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 100 are connected in both series and parallel configurations. Multiple battery cells 100 can be directly connected in series, parallel, or in a mixed manner, and then the entire assembly of the multiple battery cells 100 is housed within housing 200. Alternatively, battery 1000 can also be composed of multiple battery cells 100 first connected in series, parallel, or in a mixed manner to form battery modules, and then these modules are connected in series, parallel, or in a mixed manner to form a whole, which is also housed within housing 200. Battery 1000 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 100.

[0088] battery cell

[0089] This application discloses a battery cell in some embodiments, the battery cell including one or more wound electrode assemblies, the wound electrode assembly including a flat region and a bent region; the wound electrode assembly includes an electrode sheet, the electrode sheet including a composite current collector and an active material layer disposed on at least one side of the composite current collector; the composite current collector includes a support layer and a conductive layer located on at least one surface of the support layer; the support layer has a porosity of Q1 in the bent region and a porosity of Q2 in the flat region, satisfying Q1 > Q2 and further, 1 < Q1 / Q2 ≤ 3; the conductive layer has a through hole in the bent region, the through hole being disposed along the thickness direction of the conductive layer.

[0090] The wound electrode assembly of this application includes an electrode sheet and a separator film, which are wound around a winding axis to form a wound electrode assembly.

[0091] The winding axis of this application includes conventional concepts in the art, such as the common practice of winding a negative electrode, a separator, and a positive electrode together to form an electrode assembly, and the winding axis includes the central axis of the winding needle.

[0092] The wound electrode assembly 102 formed by winding in this application includes a straight region 102a and a bent region 102b. The straight region 102a is the straight portion, and the bent region 102b is the arc-shaped portion formed after the wound electrode assembly 102 is wound. Figure 5 Schematic diagram: The straight region 102a of the electrode assembly is located in the middle of the bent region 102b of the electrode assembly, and the bent region 102b is located at both ends of the straight region 102a of the electrode assembly. Meanwhile, the length of the straight region 102a of the electrode assembly refers to... Figure 5 The schematic L1 refers to the distance between the two ends of the straight region 102a of the electrode assembly; the length of the bent region 102b of the electrode assembly refers to... Figure 5 The schematic L2 refers to the normal distance from the intersection of the straight area 102a and the bent area 102b of the electrode assembly to the tangential surface at the farthest end of the bent area 102b of the electrode assembly.

[0093] like Figure 6A As shown, the composite current collector 20 provided in this application extends from the starting end of the winding along the winding direction to the ending end of the winding, forming a straight current collector region 20a and a bent current collector region 20b; the straight current collector region 20a includes multiple straight portions, and the bent current collector region 20b includes multiple bent portions.

[0094] like Figure 6B Indicates that Figure 6A When the schematic composite current collector 20 is unfolded along its length, the length of each straight section of the composite current collector 20 is L. Taking the number of winding layers of a wound battery cell as an example, for example, if the number of winding layers is 1, 2, 3...i, then D1 is the length of the bend corresponding to the first winding layer, D2 is the length of the bend corresponding to the second winding layer, and so on. i Let D1 be the length of the bend corresponding to the i-th layer, and D1 < D2 < D3 < ... < D i .

[0095] This application D1 to D i The method for determining this includes any method conventional in the art, and may specifically take the following forms:

[0096] Assuming the radius of the winding needle is... r The thickness of the negative electrode in the electrode sheet isa The thickness of the positive electrode sheet is b The thickness of the separator is c The gap between the positive and negative electrode plates is g .

[0097] At this point, finding the corner position has... i The length of the bend in the composite current collector corresponding to the layered negative electrode is D. i And D i Satisfy the following mathematical relationship:

[0098]

[0099] Find the corner position with i The length of the bend in the composite current collector corresponding to the layered positive electrode is D. i And D i Satisfy the following mathematical relationship:

[0100] .

[0101] The composite current collector of this application is a structure or component that, compared to existing metal foils, has a multi-layer structure while still retaining the function of collecting current. The composite current collector of this application includes a support layer and a conductive layer located on at least one surface of the support layer, and may also include other film layers.

[0102] The support layer in this application refers to a film layer made of organic polymer material that supports the conductive layer and active material layer. In the event of a battery short circuit, this support layer provides greater resistance, reduces short-circuit current, prevents thermal runaway, and thus improves battery safety. Simultaneously, this support layer also possesses a certain porosity, enabling it to absorb and store a certain amount of electrolyte. This application, by setting differentiated porosities in the bending and straight regions of the support layer of the composite current collector, increases the electrolyte storage capacity of the electrode assembly in the bending region within a certain range, effectively solving the lithium plating problem in the bending region.

[0103] The conductive layer in this application refers to a film layer with conductive capabilities. This conductive layer can collect the current generated by the electrode active material to form a larger current output. At the same time, the active material can be easily coated normally on the side of the conductive layer away from the support layer without affecting the amount of active material added in the bending region, especially without affecting the smooth insertion and extraction of the positive electrode active material, thus also taking into account the energy density of the battery.

[0104] In this application, the through-hole in the conductive layer refers to a through-hole provided along the thickness direction of the conductive layer. This through-hole improves the wettability of the electrolyte to the active material and facilitates the rapid flow of the electrolyte in the support layer to the conductive layer. Furthermore, the electrolyte squeezed out during the cyclic expansion of the battery cell can also flow back to the electrode assembly more quickly, keeping the active material in a state of electrolyte wettability, thereby improving the cycle performance of the battery by reducing lithium plating.

[0105] The porosity in this application refers to the percentage of pore volume in a material to the total volume of the material in its natural state. The porosity is influenced by the shape, structure, and arrangement of the porous structure. Furthermore, the porosity affects the fluid transport performance within the porous medium and the mechanical properties of the material. Generally, the higher the porosity, the more fluid is absorbed within the material, and the faster the fluid transport speed. The porosity determination method in this application includes any method conventional in the art. For example, after physically peeling off the conductive layer from each current collector sample after drying, the remaining support layer is cut into square samples of approximately 20mm × 20mm. The thickness and actual side length are measured using a digital micrometer and vernier calipers, and its volume is calculated as V. Its weight M0 is then measured. The square sample is then immersed in hexadecane reagent and soaked for 2 hours at room temperature and in air atmosphere. After soaking, the surface-adsorbed hexadecane reagent liquid is removed, and its weight M0 is measured. t The porosity of each current collector support layer sample satisfies the following mathematical relationship:

[0106] Porosity = (M) t -M0) / ρ×V×100%;

[0107] In the above mathematical formula, ρ represents the density of the n-hexadecane reagent, in g / mm³. 3 V represents the volume of the square specimen of each current collector support layer sample, in mm. 3 Weights M0 and M t The unit is g, and the weight measuring instrument is a 0.1 / 1000 balance. The models of the 0.1 / 1000 balance, digital micrometer, and vernier caliper include, but are not limited to, any conventional models in this field.

[0108] In some embodiments, the porosity of the support layer in the bending region is Q1, and the porosity of the support layer in the straight region is Q2, where 1 < Q1 / Q2 ≤ 3.

[0109] This application selects a ratio between the porosity Q1 of the support layer in the aforementioned bending region and the porosity Q2 of the support layer in the aforementioned straight region that satisfies the aforementioned numerical range, which is beneficial to both taking into account the function of the support layer itself and solving the lithium plating problem in the bending region.

[0110] In these embodiments, this application discloses that the ratio of the porosity Q1 of the support layer in the bending region to the porosity Q2 of the support layer in the straight region is any one of 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0 or any one of the above two ranges.

[0111] In summary, the composite current collector provided in this application, without affecting its conductivity, also possesses liquid absorption and storage functions. Furthermore, by setting differentiated porosities in the bending and straight regions of the support layer of the composite current collector, the electrolyte storage capacity of the electrode assembly in the bending region is increased to a certain extent, effectively solving the lithium plating problem in the bending region. Moreover, the conductive layer has through-holes in the bending region, which improves the wettability of the electrolyte to the active material, facilitating the rapid flow of electrolyte from the support layer to the conductive layer. Furthermore, the electrolyte squeezed out during the cycle expansion of the battery cell can also flow back to the electrode assembly more quickly, keeping the active material in an electrolyte-wetted state, thereby improving battery cycle performance by reducing lithium plating. At the same time, this design does not affect the amount of active material added in the bending region, especially the smooth insertion / extraction of the positive electrode active material, thus also considering the battery's energy density.

[0112] In some embodiments, the porosity Q1 of the support layer in the bending region is 20% to 40%, and the porosity Q2 of the support layer in the straight region is 10% to 20%.

[0113] This application discloses specific porosity values ​​of the support layer in the aforementioned bending and straight regions in these embodiments. Specifically, the porosity Q1 of the support layer in the aforementioned bending region is any one of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, and 40%, or any one of the ranges of both. Similarly, the porosity Q2 of the support layer in the aforementioned straight region is any one of 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%, or any one of the ranges of both.

[0114] In these embodiments, this application selects specific values ​​of the porosity of the support layer in the aforementioned bending and straight regions to facilitate its cooperation with the through holes provided on the conductive layer, while not affecting the load on the active material. Therefore, it is beneficial to balance the energy density and cycle performance of the battery.

[0115] In some embodiments, the conductive layer has a plurality of first through holes in the bending region and a plurality of second through holes in the straight region, wherein the average diameter of the first through holes is greater than or equal to the average diameter of the second through holes.

[0116] The average pore size of the first through hole is 1 μm to 10 μm, and the average pore size of the second through hole is 100 nm to 1 μm.

[0117] and / or;

[0118] The spacing between two adjacent first through holes and / or the spacing between two adjacent second through holes is 0.08mm to 1.2mm.

[0119] The average aperture of the through holes in the conductive layer of this application refers to the average value of the aperture diameters of the through holes, which can be obtained by scanning electron microscopy.

[0120] In some embodiments, this application further selects to provide through holes in the conductive layer. These through holes extend along the thickness direction of the conductive layer. This design facilitates the smooth flow of electrolyte stored in the support layer to the active material layer, and further increases the wetting of the active material layer by the electrolyte. As mentioned above, the technical problem this application actually aims to solve is the lithium plating problem that occurs in the bending area of ​​the wound cell due to electrolyte extrusion. The electrolyte extruded during the cyclic expansion of the battery cell can also flow back to the electrode assembly more quickly, keeping the active material in an electrolyte-wetted state. This application selects that the average pore size of the first through hole in the bending area of ​​the conductive layer is larger than the average pore size of the second through hole in the straight area. Since the pore size of the through hole in the bending area is relatively larger and matches the porosity of the support layer, it facilitates better improvement of the wetting of the active material layer by the electrolyte in the bending area of ​​the wound cell, thus further improving the lithium plating problem.

[0121] This application discloses the specific dimensions of each through-hole in these embodiments. Specifically, the average aperture of the first through-hole is any one of 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, and 10μm, or any one of the above two ranges. Similarly, the average aperture of the second through-hole is any one of 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, and 1μm, or any one of the above two ranges.

[0122] The spacing between the through holes in this application refers to the straight-line distance between the center points of the through holes, and the method for measuring this distance includes scanning electron microscopy.

[0123] In some embodiments, the conductive layer has a plurality of through holes in the bending region, the average diameter of the through holes is 100 nm to 10 μm, and the spacing between two adjacent through holes is 0.08 mm to 1.2 mm.

[0124] Furthermore, the conductive layer does not have through holes in the aforementioned flat area.

[0125] In some embodiments, this application discloses that the conductive layer has multiple through holes in the bending region, while the conductive layer does not have through holes in the straight region. This design reduces the impact of small-diameter particles in the active material clogging the through holes. Furthermore, it matches the porosity of the support layer, facilitating better improvement of electrolyte wetting of the active material layer in the bending region of the wound cell, thus further improving the lithium plating problem.

[0126] In these embodiments, this application discloses that the average aperture of the through-holes in the conductive layer in the aforementioned bending region is any one of 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm or any one of the above two ranges.

[0127] In some embodiments, the electrode sheet includes a negative electrode sheet, which includes the composite current collector described above.

[0128] In these embodiments, this application discloses that the negative electrode sheet includes a composite current collector having the characteristics of a support layer with different porosities and / or a conductive layer with through-holes of different pore sizes. In these embodiments, the current collector of the positive electrode sheet can be any type of current collector conventional in the art, or it can be the composite current collector described above. When both the negative electrode sheet and the positive electrode sheet include the composite current collector described above, it is relatively optimal for improving the lithium plating problem and taking into account the battery energy density.

[0129] In some embodiments, the negative electrode sheet includes a negative electrode film layer located on at least one side surface of the composite current collector, the negative electrode film layer including a negative electrode active material;

[0130] The average particle size of the aforementioned negative electrode active material in the aforementioned bending region is smaller than the average particle size of the aforementioned straight region.

[0131] In these embodiments, the present application selects negative electrode active materials with different average particle sizes in the bending region and the straight region. In the bending region, negative electrode active materials with relatively smaller average particle sizes are selected. Generally speaking, the smaller the average particle size, the larger its specific surface area, which facilitates the shuttle of electrolyte ions in the electrolyte without affecting the energy density of the active material.

[0132] In some embodiments, the average particle size of the negative electrode active material in the bending region is 5 μm to 12 μm; and the average particle size of the negative electrode active material in the straight region is 10 μm to 20 μm.

[0133] The average particle size of the negative electrode active material in this application is its volume average particle size Dv50. Referring to GB / T19077-2016, the volumetric particle size distribution curve of the negative electrode active material can be obtained, and the particle size corresponding to the cumulative volume distribution percentage reaching 50% is taken as the average particle size Dv50. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK. Deionized water is used as the solvent. Before testing, the negative electrode active material is ultrasonically treated for 5 minutes, dried, and then directly measured by the instrument.

[0134] In these embodiments, this application discloses that the average particle size of the above-mentioned negative electrode active material in the bending region is any one of 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm or any one of the above two ranges.

[0135] In these embodiments, this application discloses that the average particle size of the above-mentioned negative electrode active material in the above-mentioned flat region is any one of 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm or any one of the above two ranges.

[0136] In some embodiments, the specific surface area of ​​the negative electrode active material in the bending region is greater than that in the straight region.

[0137] In some embodiments, the negative electrode active material has a specific surface area of ​​1.5 m² in the bending region. 2 / g~3.0m 2 / g; the specific surface area of ​​the above-mentioned negative electrode active material in the above-mentioned flat region is 0.5m². 2 / g ~1.5m 2 / g.

[0138] The specific surface area of ​​the negative electrode active material in this application has the conventional meaning in the art. Its determination method follows GB / T19587-2004, employing the nitrogen adsorption specific surface area analysis method, and the specific surface area of ​​the negative electrode active material is calculated using the BET (Brunauer Emmett Teller) method. The testing instrument can be a TRISTAR II 3020 specific surface area and porosity analyzer from Micromeritics, USA.

[0139] This application discloses in these embodiments that the above-mentioned negative electrode active material has a specific surface area of ​​1.5 m² in the bending region. 2 / g, 1.6m 2 / g, 1.7m 2 / g, 1.8m 2 / g, 1.9m 2 / g, 2.0m 2 / g、2.1m 2 / g, 2.2m 2 / g, 2.3m 2 / g, 2.4m 2 / g, 2.5m 2 / g, 2.6m 2 / g, 2.7m 2 / g, 2.8m 2 / g, 2.9m 2 / g, 3.0m 2 Any one of / g or any one of the ranges of the above two.

[0140] This application discloses in these embodiments that the above-mentioned negative electrode active material has a specific surface area of ​​0.5 m² in the above-mentioned flat region. 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 Any one of / g or any one of the ranges of the above two.

[0141] This application discloses in these embodiments that the negative electrode active material comprises one or more of carbonaceous materials, silicon-based materials, silicon-carbon composite materials, tin-based materials, and their alloys. The carbonaceous materials in this application comprise one or more combinations of artificial graphite, natural graphite, soft carbon, and hard carbon. Among them, artificial graphite, natural graphite, soft carbon, and hard carbon encompass any form of material conventional in the art, and include any manufacturer and model conventional in the art. The silicon-based materials in this application comprise one or two of silicon-oxygen materials or silicon-carbon materials, or silicon-carbon composites. The tin-based materials and their alloys in this application include, but are not limited to, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, etc. This application will use artificial graphite as an example for specific description in subsequent detailed embodiments.

[0142] In some embodiments, the negative electrode film layer includes a conductive agent, and the mass percentage content of the conductive agent in the bending region is greater than the mass percentage content in the straight region, based on the total mass of the negative electrode film layer.

[0143] and / or;

[0144] The adhesive has a lower mass percentage content in the bending zone than it has in the straight zone.

[0145] As described above, the average particle size of the negative electrode active material in the bending region is smaller than that in the straight region. In these embodiments, this application further uses conductive agents and binders with different contents to reduce the impact on the amount of negative electrode active material used, so that the active material can be inserted and removed more quickly and smoothly in the bending region. Therefore, this design method is also conducive to ensuring the energy density of the battery.

[0146] The conductive agents and binders used in the bending and straight areas of this application can be the same or different. In these embodiments, this application discloses that the conductive agents include one or more of dot-like, linear, and planar conductive agents. Dot-like conductive agents include, but are not limited to, conductive carbon black (Super P or Super S), acetylene black, conductive graphite (KS-6 or KS-15 or SFG-6 or SFG-15), and Ketjen black. Linear conductive agents include one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon nanofibers. Planar conductive agents include, but are not limited to, graphene. In these embodiments, this application discloses that the binders include, but are not limited to, polyvinyl alcohol, polyethylene glycol, sodium carboxymethyl cellulose, polyethylene oxide, polyacrylic acid, polyacrylamide, sodium alginate, and styrene-butadiene rubber (SBR). Dispersants also include any type conventional in the art, such as cellulose and its salts, specifically including, but not limited to, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, and lithium carboxymethyl cellulose.

[0147] In some embodiments, the conductive agent has a mass percentage content of 1.0% to 1.5% in the bending region and a mass percentage content of 0.5% to 1.0% in the straight region.

[0148] and / or;

[0149] The adhesive has a mass percentage content of 1.0% to 1.5% in the bending area and a mass percentage content of 1.5% to 2.5% in the straight area.

[0150] In these embodiments, this application discloses that the conductive agent has a mass percentage content of 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5% in the bending region, or any one of the above two ranges.

[0151] In these embodiments, this application discloses that the conductive agent has a mass percentage content of 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1.0% in the flat region, or any one of the ranges of both of the above.

[0152] In these embodiments, this application discloses that the adhesive has a mass percentage content of 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5% in the aforementioned bending area, or any one of the ranges of both.

[0153] In these embodiments, this application discloses that the adhesive has a mass percentage content of 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, or 2.5% in the aforementioned flat region, or any one of the ranges of both.

[0154] In some embodiments, this application discloses the components contained in the negative electrode film in the flat region: negative electrode active material: conductive agent: binder: dispersant = (94.5%~96%): (0.5%~1.0%): (1.5%~2.5%): (0.5%~2.0%).

[0155] In some embodiments, this application discloses the components contained in the bending region of the negative electrode film layer, namely, negative electrode active material: conductive agent: binder: dispersant = (95.0%~96.5%): (1.0%~1.5%): (1.0%~1.5%): (0.5%~2.0%).

[0156] The mass percentage content mentioned above in this application is calculated based on the mass of a single-sided negative electrode film layer.

[0157] In some embodiments, the thickness of the support layer is 3μm to 5μm, and the thickness of the conductive layer is 5μm to 10μm;

[0158] The aforementioned support layer includes any one or more of the following: polyterephthalate, polyethylene, polypropylene, epoxy resin, polyamide, polyimide, polyester, polyolefin, polyacetylene, siloxane polymer, polyether, polyol, polysulfone, polysaccharide polymer, amino acid polymer, polysulfide polymer, and aromatic ring polymer.

[0159] The conductive layer described above includes a metal, which includes one or more of aluminum, aluminum alloys, copper, copper alloys, nickel, nickel alloys, iron, iron alloys, titanium, titanium alloys, silver, and silver alloys.

[0160] This application selects a support layer and a conductive layer with appropriate thickness to improve the battery energy density by reducing the influence of the current collector on the coating thickness of the active material.

[0161] In these embodiments, this application discloses that the thickness of the support layer is any one of 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.0 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 4.9 μm, and 5.0 μm, or any one of the above ranges.

[0162] This application discloses conductive layer thicknesses of 5.0 μm, 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6.0 μm, 6.1 μm, 6.2 μm, 6.3 μm, 6.4 μm, 6.5 μm, 6.6 μm, 6.7 μm, 6.8 μm, 6.9 μm, 7.0 μm, 7.1 μm, 7.2 μm, 7.3 μm, 7.4 μm, and 7.5 μm in these embodiments. The values ​​are any one of the following: μm, 7.6μm, 7.7μm, 7.8μm, 7.9μm, 8.0μm, 8.1μm, 8.2μm, 8.3μm, 8.4μm, 8.5μm, 8.6μm, 8.7μm, 8.8μm, 8.9μm, 9.0μm, 9.1μm, 9.2μm, 9.3μm, 9.4μm, 9.5μm, 9.6μm, 9.7μm, 9.8μm, 9.9μm, 10μm, or any one of the values ​​within any two of the above ranges.

[0163] In some embodiments, the conductive layer in this application is formed on the insulating substrate by any one or more of mechanical rolling, bonding, vapor deposition, electroless plating, and electroplating methods.

[0164] In some embodiments, this application also discloses forming a conductive carbon layer on at least one side of the conductive layer away from the support layer. The conductive carbon layer comprises conductive carbon, and its formation on the surface of the conductive layer includes coating. The conductive carbon layer is positioned in the same manner as the conductive layer in both the bending and straight regions, and the location and arrangement of the openings are also the same. This conductive carbon layer, without affecting the wetting of the electrode by the electrolyte, helps to improve the bonding ability between the conductive layer and the active material layer, and further improves interface stability.

[0165] Preparation method of composite current collector

[0166] Some embodiments of this application disclose a method for preparing a current collector, including the following process:

[0167] Preparation of the support layer: Organic polymer materials are extruded through a twin-screw extruder to obtain a high-temperature melt. This high-temperature melt is accurately metered by a melt pump and fed into a die. The high-temperature melt flowing out of the die slit passes through a chilling roller to obtain an extruded sheet. The extruded sheet is stretched 1-5 times along its width using a bidirectional asynchronous stretching machine. Then, according to the distinction between the straight and bent regions, it is stretched to different degrees along its length to form a straight region support layer and a bent region support layer with different porosities. Specifically, the bent region support layer is stretched 3-6 times along its length, and the straight region support layer is stretched 1-4 times along its length, so that the porosity Q1 of the resulting support layer in the bent region is greater than the porosity Q2 of its straight region.

[0168] The support layer obtained above is placed in a high-temperature shaping device and kept at a certain temperature for a certain period of time to fully remove the film stress, thus obtaining the finished support layer; then it is cut to the required size according to the battery specifications.

[0169] Preparation of conductive layer: After cleaning the above-prepared support layer by acid washing, alkali washing and other methods, place it in a vacuum evaporation chamber, place a mask on any side surface of the support layer, and deposit conductive metal on at least one side surface of the support layer at a high temperature of 1300℃~2000℃. Then, according to actual needs, through holes are set on the conductive metal layer.

[0170] [Negative electrode plate]

[0171] The negative electrode of this application includes a current collector and a negative electrode film layer located on one or both surfaces of the current collector. Generally, the negative electrode film layer is located on both surfaces of the current collector, and is formed by methods such as coating or deposition. In this application, both sides will be used as examples.

[0172] The negative current collector in this application is as described above, and will not be repeated here.

[0173] The method for forming the negative electrode film in this application includes mixing the above-mentioned raw materials with a solvent (such as deionized water) in a certain mass ratio to form a negative electrode slurry; after defoaming the negative electrode slurry, uniformly coating the negative electrode slurry onto both sides of the negative electrode current collector; controlling the coating weight on one side; drying; and compacting it to a certain compaction density (greater than or equal to 1.65 g / cm³) using a cold press. 3 This yields a negative electrode sheet containing a negative electrode film.

[0174] [Positive electrode plate]

[0175] According to some embodiments of this application, as described above, the positive electrode includes a current collector and a positive electrode film layer located on at least one side surface of the current collector. The positive electrode film layer contains a positive electrode active material.

[0176] According to some embodiments of this application, when the positive electrode sheet is applied to a lithium-ion battery, the positive electrode active material includes, but is not limited to, one or more combinations of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium olivine-structured lithium phosphate; wherein, the structural formula of the olivine-structured lithium phosphate is: LiFe 1-x-y Mn x M y PO4, 0≤x≤1, 0≤y<1, 0≤x+y≤1, M contains one or more of the transition metal elements or non-transition metal elements other than Fe and Mn, and M further contains any one or more of Cr, Mg, Ti, Al, Zn, W, Nb, and Zr.

[0177] This application specifically includes, but is not limited to, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM111), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 CO 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 CO 0.1 Mn 0.1 O2(NCM811), LiNi 0.85 CO 0.15 Al 0.05 Any one or more of O2, LiFePO4 (LFP), and LiMnPO4.

[0178] According to some embodiments of this application, when the positive electrode sheet is applied to a sodium-ion battery, the positive electrode active material includes, but is not limited to, at least one of sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. Specifically, in the sodium transition metal oxide, the transition metal can be any one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and the sodium transition metal oxide is, for example, Na. xMO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≤ 1. Polyanionic compounds include sodium vanadium trifluorophosphate (Na3V2(PO4)2F3), sodium vanadium fluorophosphate (NaVPO4F), sodium vanadium phosphate (Na3V2(PO4)3), Na4Fe3(PO4)2P2O7, and NaFePO4, among any one or more of these. Prussian blue compounds are Na... x M1M2(CN)6, wherein M1 and M2 are one or more of Fe, Mn, Co, Ni, Cu, Zn, Cr, Ti, V, Zr, and Ce, and 0 < x ≤ 2.

[0179] According to some embodiments of this application, the positive electrode film layer also includes conductive agents, binders, etc. Conductive agents include, but are not limited to, any one or more of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black, Super P, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Binders include, but are not limited to, any one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc. The positive electrode current collector in this application is as described above, and will not be repeated here.

[0180] The positive current collector in this application is as described above, and will not be repeated here.

[0181] The method for forming the positive electrode film in this application includes mixing the above-mentioned raw materials with a solvent (such as N-methylpyrrolidone) in a certain mass ratio to form a positive electrode slurry, uniformly coating the positive electrode slurry on both sides of the current collector; controlling a certain single-sided coating weight; and after drying, compacting it to a certain compaction density (2.4 g / cm³) using a cold press. 3 ~3.4g / cm 3 This yields a positive electrode sheet containing a positive electrode film.

[0182] [Isolation Component]

[0183] Some embodiments of this application disclose isolation elements. This application does not have any particular restrictions on the type of isolation element, and any known porous structure isolation element with good chemical and mechanical stability can be selected.

[0184] In some embodiments, the separator includes a substrate material layer and a coating disposed on the surface of the substrate material layer; the substrate material of the substrate material layer includes one or more of polyethylene, polypropylene, poly(p-phenylene terephthalamide), polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, and polyamide; the coating includes an inorganic coating and / or an organic coating. The substrate material layer has good permeability to metal ions, which is beneficial to the migration of metal ions; the coating disposed on the surface of the substrate material layer can further improve the mechanical properties of the separator. Further, the inorganic coating includes a ceramic coating, and the ceramic particles in the ceramic coating include one or more of SiO2, Al2O3, AlOOH, CaO, TiO2, MgO, ZnO, ZrO2, Mg(OH)2, and BaSO4. The ceramic coating of this application plays an insulating role, reducing the probability of short circuit due to puncture of the separator. That is, this application uses a separator containing a ceramic coating, which firstly reduces the probability of short circuit, and even if a short circuit occurs, the current collector designed in this application can quickly cut off the short circuit to improve safety.

[0185] In some embodiments, the organic coating includes an organic polymer coating, wherein the polymer material of the organic polymer coating includes one or more of polyethylene (PE), polypropylene (PP), poly(p-phenylene terephthalamide) (PPTA), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polyimide (PI), and polyamide (PA). The polymer coating may be made of the same or different material as the substrate material layer, and the thicknesses of the polymer coating and the substrate material layer may be different; furthermore, the thickness of the polymer coating is less than the thickness of the substrate material layer.

[0186] In other embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0187] [Electrolytes]

[0188] Electrolytes are disclosed in some embodiments of this application. The electrolyte in this application can be liquid, solid, or gel-like. Solid state refers to a solid electrolyte, liquid state to a liquid electrolyte, and gel-like state to a gel electrolyte. The lithium-ion battery of this application uses a liquid electrolyte, i.e., an electrolyte solution. This electrolyte solution contains an electrolyte salt and an organic solvent. The electrolyte salt can be any type conventional in the art, including, but not limited to, inorganic metal salts such as LiClO4, LiAsF6, LiPF6, LiBF4, LiSbF6, LiSO3F, LiN(FSO2)2, etc.; fluorine-containing organometallic salts such as LiCF3SO3, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,3-hexafluoropropane disulfonylimide lithium, cyclic 1,2-tetrafluoroethane disulfonylimide lithium, LiN(CF3SO2)(C4F5SO2)2, etc. LiC(CF3SO2)3, LiPF4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, LiBF2(C2F5SO2)2, etc.; and metal salts containing dicarboxylic acid complexes, such as lithium bis(oxalate)borate, lithium difluorooxalate borate, lithium tri(oxalate)phosphate, lithium difluorobis(oxalate)phosphate, lithium tetrafluoro(oxalate)phosphate, etc.

[0189] According to some embodiments of this application, the concentration of the electrolyte salt in the electrolyte is 0.1 mol / L to 4 mol / L. In these embodiments, this application discloses that the concentration of the electrolyte salt is any one of 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.5 mol / L, 2.8 mol / L, 3 mol / L, 3.2 mol / L, 3.5 mol / L, 3.8 mol / L, and 4 mol / L, or any one of the above ranges.

[0190] As described above, the organic solvent comprises one or more of carboxylic acid esters, carbonates, and ethers. Specifically, the carboxylic acid esters comprise one or more of ethyl acetate (EA), methyl acetate (MA), ethyl propionate (EP), propyl acetate (PA), methyl propionate (MP), methyl butyrate (MB), ethyl butyrate (EB), and 1,4-butyrolactone (GBL); the carbonates comprise one or more of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), and fluoroethylene carbonate (FEC). The ethers comprise at least one of tetrahydrofuran, dimethyl tetrahydrofuran, tetrahydropyran, dimethyl tetrahydropyran, 1,2-dimethoxyethane, dipropylene glycol dimethyl ether, or dimethyl phthalate. The organic solvents of this application also include one or two of nitrile solvents and sulfone solvents. The nitrile solvents include one or more of acetonitrile (AN), glutaronitrile (GLN), and adiponitrile (ADN). The sulfone solvents include at least one or a combination of two of sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0191] In some embodiments, the electrolyte comprises carbonate compounds and carboxylic acid ester compounds, and the volume ratio of carbonate compounds to carboxylic acid ester compounds is (2~8):3.

[0192] In these embodiments, this application discloses that the volume ratio of ester compound to carboxylic acid ester compound is any one of 2:3, 3:3, 4:3, 5:3, 6:3, 7:3, 8:3 or any one of the above ranges.

[0193] According to some embodiments of this application, the electrolyte further comprises a film-forming stabilizer, which includes a positive electrode film-forming stabilizer and a negative electrode film-forming stabilizer. The positive electrode film-forming stabilizer comprises carbonate additives and / or sulfate additives. The carbonate additives include one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), vinyl ethylene carbonate (VEC), and dioctyl carbonate (CC). The sulfate additives include cyclic sulfonate additives and / or sulfated hydrocarbon ester additives; further, the cyclic sulfonate additives include one or more of 1,3-propanesulfonate lactone (PS), propenesulfonate lactone (PES), and 3-fluoro-1,3-propanesulfonate lactone (FPS); the sulfated hydrocarbon ester additives include one or more of vinyl sulfate (DTD), diethyl sulfate (DES), and dimethyl sulfate (DMS).

[0194] In some embodiments, the mass percentage of vinylene carbonate in the electrolyte is greater than zero and less than 4%. This application discloses in these embodiments that the mass percentage of vinylene carbonate in the electrolyte is any one of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, or any one of the ranges for both of the above.

[0195] In some embodiments, the mass percentage of vinyl sulfate in the electrolyte is greater than zero and less than or equal to 1.5%. This application discloses in these embodiments that the mass percentage of vinyl sulfate in the electrolyte is any one of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, and 1.5%, or any one of the ranges for both of the above.

[0196] In some embodiments, the mass percentage of 1,3-propanesulfonate lactone in the electrolyte is less than or equal to 1.5%. This application discloses in these embodiments that the mass percentage of 1,3-propanesulfonate lactone in the electrolyte is any one of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%, or any one of the ranges for both of the above.

[0197] Experimental materials:

[0198] The materials used for the positive electrode active material, negative electrode active material, conductive layer, and support layer are all commercially available.

[0199] Preparation Example 1-1

[0200] A method for preparing a negative electrode composite current collector is provided, the method comprising:

[0201] S100. Preparation of the support layer: Organic polymer material (polypropylene particles) is extruded through a twin-screw extruder at a temperature of 180℃ to obtain a high-temperature melt. The high-temperature melt is accurately metered by a melt pump and fed into a die. The high-temperature melt flowing out of the die slit passes through a chilling roller to obtain an extruded casting. The casting is stretched 3 times along the width direction (perpendicular to the x-axis) using a bidirectional asynchronous stretching machine. Then, the straight and bent areas are stretched separately along the length direction (x-axis) of the casting (2.5 times for the straight area and 5 times for the bent area). The porosity Q1 of the bent area of ​​the support layer is 30%, and the porosity Q2 of the straight area of ​​the support layer is 15%.

[0202] S200. After cleaning the above-prepared support layer using acid washing, alkali washing, etc., it is placed in a vacuum evaporation chamber. A mask with a aperture of 100 nm and a hole spacing of 0.1 mm is placed in the corresponding bending area of ​​the support layer. The temperature is controlled at 1350℃, and a copper conductive layer is deposited on both sides of the support layer. Other aspects are the same as in Example 1-1.

[0203] Preparation Examples 1-2

[0204] A method for preparing a negative electrode composite current collector is provided. This method differs from that in Example 1-1 in that the aperture of the S200 and the mask is 10 μm, and the aperture spacing is 0.1 mm. Other aspects remain the same as in Example 1-1.

[0205] Preparation Examples 1-3

[0206] A method for preparing a negative electrode composite current collector is provided. This method differs from that in Example 1-1 in that the aperture of the S200 and the mask is 5 μm, and the aperture spacing is 0.1 mm. Other aspects remain the same as in Example 1-1.

[0207] Preparation Examples 1-4

[0208] A method for preparing a negative electrode composite current collector is provided. This method differs from the preparation method in Example 1-1 in that the porosity Q1 of the corresponding bent region of the support layer in S100 is 20%, and the porosity Q2 of the straight region of the support layer is 10%.

[0209] In step S200, after cleaning the aforementioned support layer using acid washing and alkali washing, it is placed in a vacuum evaporation chamber. A mask with a aperture of 6.5 μm and a spacing of 0.1 mm is placed in the bending area corresponding to the support layer. The temperature is controlled at 1500℃, and a copper conductive layer is deposited on both sides of the support layer. Other aspects remain the same as in Example 1-1.

[0210] Preparation Examples 1-5

[0211] A method for preparing a negative electrode composite current collector is provided. This method differs from the preparation method in Example 1-1 in that the porosity Q1 of the corresponding bent region of the support layer in S100 is 40%, and the porosity Q2 of the straight region of the support layer is 20%.

[0212] In step S200, after cleaning the aforementioned support layer using acid washing and alkali washing methods, it is placed in a vacuum evaporation chamber. A mask with an aperture of 8.5 μm and a hole spacing of 0.1 mm is placed in the corresponding bending area of ​​the support layer. The temperature is controlled at 1450℃, and a copper conductive layer is deposited on both sides of the support layer. Other aspects remain the same as in Example 1-1.

[0213] Preparation Examples 1-6

[0214] A method for preparing a negative electrode composite current collector is provided. This method differs from Preparation Example 1-1 in that an organic polymer material (polyimide particles) is extruded using a twin-screw extruder at 350°C to obtain a high-temperature melt. This high-temperature melt is accurately metered by a melt pump and fed into a die. The high-temperature melt flowing out of the die slit passes through a chilling roller to obtain an extruded sheet. The sheet is stretched twice its width (perpendicular to the x-axis) using a bidirectional asynchronous stretching machine, and then stretched separately along the length (x-axis) of the sheet in both the straight and bent regions (straight region stretched once, bent region stretched three times). The porosity Q1 of the bent region of the support layer is 30%, and the porosity Q2 of the straight region of the support layer is 15%. All other aspects remain the same as in Preparation Example 1-1.

[0215] Preparation Examples 1-7

[0216] A method for preparing a positive electrode composite current collector and a negative electrode composite current collector is provided, wherein the method for preparing the negative electrode composite current collector is the same as that in Preparation Example 1-1.

[0217] The preparation method of the positive electrode composite current collector includes: forming aluminum conductive layers on both sides of the support layer, and the evaporation temperature of the aluminum conductive layers is different, which is 1310℃, and other aspects are the same as in Example 1-1.

[0218] Preparation Example 2-1

[0219] A method for preparing a negative electrode composite current collector is provided. This method differs from the preparation method in Example 1-1 in that the porosity Q1 of the corresponding bent region of the support layer in S100 is 30%, and the porosity Q2 of the straight region of the support layer is 10%.

[0220] In step S200, after cleaning the aforementioned support layer using acid washing and alkali washing, it is placed in a vacuum evaporation chamber. Masks with different aperture sizes are placed in the bending and straight areas corresponding to the support layer. The aperture size of the mask in the bending area is 10 μm, and the aperture size of the mask in the straight area is 1 μm, with a aperture spacing of 0.1 mm. The temperature is controlled at 1450℃, and copper conductive layers are deposited on both sides of the support layer. Other aspects remain the same as in Example 1-1.

[0221] Preparation Example 2-2

[0222] A method for preparing a negative electrode composite current collector is provided. This method differs from the preparation method in Example 2-1 in that the porosity Q1 of the corresponding bent region of the support layer in S100 is 35%, and the porosity Q2 of the straight region of the support layer is 20%.

[0223] In step S200, after cleaning the aforementioned support layer using acid washing and alkali washing, it is placed in a vacuum evaporation chamber. Masks with different aperture sizes are placed in the bending and straight areas corresponding to the support layer. The aperture size of the mask in the bending area is 5 μm, and the aperture size of the mask in the straight area is 750 nm, with a aperture spacing of 0.1 mm. The temperature is controlled at 1450℃, and copper conductive layers are deposited on both sides of the support layer. Other aspects remain the same as in Example 2-1.

[0224] Preparation Examples 2-3

[0225] A method for preparing a positive electrode composite current collector and a negative electrode composite current collector is provided, wherein the method for preparing the negative electrode composite current collector is the same as that in preparation example 2-2.

[0226] The method for preparing the positive electrode composite current collector includes forming an aluminum conductive layer on both sides of the support layer. Other aspects remain the same as in Example 2-2.

[0227] Preparation Examples 2-4

[0228] A method for preparing a negative electrode composite current collector is provided. This method differs from the preparation method in Example 2-1 in that the porosity Q1 of the corresponding bent region of the support layer in S100 is 22%, and the porosity Q2 of the straight region of the support layer is 20%.

[0229] In step S200, after cleaning the aforementioned support layer using acid washing and alkali washing, it is placed in a vacuum evaporation chamber. Masks with different aperture sizes are placed in the bending and straight areas corresponding to the support layer. The aperture size of the mask in the bending area is 1 μm, and the aperture size of the mask in the straight area is 100 nm, with a aperture spacing of 0.1 mm. The temperature is controlled at 1450℃, and copper conductive layers are deposited on both sides of the support layer. Other aspects remain the same as in Example 2-1.

[0230] Comparative Preparation Example 1

[0231] A copper foil is provided as the negative current collector and an aluminum foil as the positive current collector.

[0232] Comparative Preparation Example 2

[0233] A method for preparing a negative electrode current collector is provided, which differs from the preparation method in that the conductive layer of S200 does not have through holes.

[0234] Comparative preparation example 3

[0235] A method for preparing a negative electrode current collector is provided, which differs from Preparation Example 1-1 in that: S100, preparation of the support layer: organic polymer material (polypropylene particles) is extruded through a twin-screw extruder at a temperature of 180°C to obtain a high-temperature melt. The high-temperature melt is accurately metered by a melt pump and fed into a die. The high-temperature melt flowing out of the die slit passes through a chilling roller to obtain an extruded casting. The casting is stretched 3 times along the width direction (perpendicular to the x-axis) using a bidirectional asynchronous stretching machine, and then stretched 5 times along the length direction (x-axis), resulting in a porosity of 28% for the support layer. Other aspects remain the same as in Preparation Example 1-1.

[0236] Comparative preparation example 4

[0237] A method for preparing a negative electrode composite current collector is provided, the method comprising:

[0238] S100, Preparation of the support layer: Organic polymer material (polypropylene particles) is extruded through a twin-screw extruder at a temperature of 180℃ to obtain a high-temperature melt. The high-temperature melt is accurately metered by a melt pump and fed into a die. The high-temperature melt flowing out of the die slit passes through a chilling roller to obtain an extruded casting. The casting is stretched 3 times along the width direction (perpendicular to the x-axis) using a bidirectional asynchronous stretching machine. Then, the straight and bent areas are stretched separately along the length direction (x-axis) of the casting (the straight area is stretched 3 times, and the bent area is stretched 1 time). The porosity Q1 of the bent area of ​​the support layer is 12%, and the porosity Q2 of the straight area of ​​the support layer is 27%.

[0239] [Performance Testing of the Preparation Example]

[0240] ① Test the porosity of the support layer:

[0241] After drying, the support membrane samples from each part were cut into square specimens of approximately 20 mm × 20 mm. The thickness and actual side length were measured using a digital micrometer and vernier calipers, and the volume (V) was calculated. The weight (M0) was then measured. The square specimens were then immersed in hexadecane reagent and soaked for 2 hours at room temperature and in air. After soaking, the hexadecane reagent liquid adsorbed on the surface was removed, and the weight (M) was measured.t The porosity of each supporting membrane layer satisfies the following mathematical relationship:

[0242] Porosity = (M) t -M0) / ρ×V×100%;

[0243] In the above mathematical formula, ρ represents the density of the n-hexadecane reagent, in g / mm³. 3 V represents the volume of the square sample supporting each membrane layer, in mm. 3 Weights M0 and M t The unit is g, and the weight measuring instrument is a 0.1 / 1000 balance.

[0244] ② Test the average pore diameter of the through-hole in the conductive layer

[0245] Samples of each part of the conductive layer were obtained.

[0246] The testing instrument used was an ASAP2460 physical adsorption analyzer. Each sample after drying and degassing was placed in liquid nitrogen, and the amount of nitrogen adsorbed was measured by adjusting different test pressures. Adsorption and desorption isotherms were plotted, and the pore volume and specific surface area of ​​each sample were obtained based on the adsorption and desorption isotherms, and then the average pore diameter was calculated.

[0247] The performance of the composite current collector obtained according to the above test method is shown in Table 1 below:

[0248] Table 1 Performance List of Composite Current Collectors

[0249]

[0250] Example 1-1

[0251] A method for preparing a battery cell is provided. The battery cell includes an electrode assembly, which includes a positive electrode, a negative electrode, and a separator wound around a winding axis. The negative electrode includes the composite current collector obtained in Preparation Example 1-1 above, and the positive electrode includes aluminum foil.

[0252] The preparation method of the above-mentioned battery cell includes the following preparation process:

[0253] Preparation of positive electrode sheet:

[0254] Take LiNi 0.5 Co 0.2 Mn 0.3O2 (NCM523), conductive carbon black, and PVDF were mixed in a ratio of 94:4:2. After adding N-methylpyrrolidone solvent and stirring, a positive electrode slurry was formed. This slurry was then coated onto an aluminum foil surface and dried using a multi-section oven with sequential temperature settings of 120℃ / 100℃ / 90℃. Finally, a cold press was used to compact the slurry, resulting in a positive electrode film with a compaction density of 3.4 g / cm³. 3 .

[0255] Preparation of negative electrode sheet:

[0256] Artificial graphite (particle size Dv50 of 11.5 μm) was dispersed in deionized water at a mass ratio of 95.5:1.0:2.0:1.5 with conductive carbon black (conductive agent), carboxymethyl cellulose (stabilizer), and SBR (binder) to form a negative electrode slurry. This negative electrode slurry was uniformly coated onto the surface of the copper conductive layer prepared in Example 1-1 above. The layer was dried in a nine-section oven at sequentially set temperatures of 100℃ / 100℃ / 95℃ / 85℃ / 85℃ / 80℃ / 80℃ / 80℃ / 60℃. The layer was then compacted using a cold press, achieving a compaction density of 1.65 g / cm³. 3 .

[0257] Provide isolation components:

[0258] A porous polypropylene (PP) membrane with a thickness of 10 μm is used as the separator.

[0259] Electrolyte provided:

[0260] In an argon atmosphere glove box with a water content of <10ppm, EC (ethylene carbonate), EA (ethyl acetate), and DMC (dimethyl carbonate) were mixed in a weight ratio of EC:EA:DMC=3:3:3. Then, LiPF6, VC, DTD, and PS were added and stirred until homogeneous to obtain an electrolyte. The concentration of LiPF6 in the lithium-ion battery electrolyte was 1mol / L, and the mass percentages of VC, DTD, and PS were 3%, 1%, and 1%, respectively.

[0261] Assemble individual battery cells:

[0262] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrode to provide isolation. The corresponding components are then assembled to form a wound bare cell. The wound bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a single battery cell is obtained.

[0263] Examples 1-2

[0264] A method for preparing a battery cell is provided. This method differs from Example 1-1 in that the negative electrode current collector is the composite current collector obtained in Example 1-2 above, while other aspects remain the same as in Example 1-1.

[0265] Examples 1-3

[0266] A method for preparing a battery cell is provided. This method differs from Example 1-1 in that the negative electrode current collector is the composite current collector obtained in Example 1-3 above, while other aspects remain the same as in Example 1-1.

[0267] Examples 1-4

[0268] A method for preparing a battery cell is provided. This method differs from Example 1-1 in that the negative electrode current collector is the composite current collector obtained in Example 1-4 above, while other aspects remain the same as in Example 1-1.

[0269] Examples 1-5

[0270] A method for preparing a battery cell is provided. This method differs from that of Example 1-1 in that the negative electrode current collector is the composite current collector obtained in Example 1-5 above, while other aspects remain the same as those of Example 1-1.

[0271] Examples 1-6

[0272] A method for preparing a battery cell is provided. This method differs from that of Example 1-1 in that the negative electrode current collector is the composite current collector obtained in Examples 1-6 above, while other aspects remain the same as those of Example 1-1.

[0273] Examples 1-7

[0274] A method for preparing a battery cell is provided. This method differs from that of Example 1-1 in that the current collector is the composite current collector obtained in Examples 1-7 above, while other aspects remain the same as those in Example 1-1.

[0275] Example 2-1

[0276] A method for preparing a battery cell is provided. This method differs from Example 1-1 in that the negative electrode current collector is the composite current collector obtained in Example 2-1, while other aspects remain the same as in Example 1-1.

[0277] Example 2-2

[0278] A method for preparing a battery cell is provided. This method differs from Example 1-1 in that the negative electrode current collector is the composite current collector obtained in Example 2-2 above, while other aspects remain the same as in Example 1-1.

[0279] Example 2-3

[0280] A method for preparing a battery cell is provided. This method differs from Example 1-1 in that the current collector is the composite current collector obtained in Example 2-3 above, while other aspects remain the same as in Example 1-1.

[0281] Examples 2-4

[0282] A method for preparing a battery cell is provided. This method differs from that of Example 1-1 in that the negative electrode current collector is the composite current collector obtained in Example 2-4 above, while other aspects remain the same as those of Example 1-1.

[0283] Example 3-1

[0284] A method for preparing a battery cell is provided. The method differs from that in Example 2-2 in that the composition of the bending region of the negative electrode sheet is as follows: artificial graphite (particle size Dv50 is 6.5μm) is dispersed in deionized water at a mass ratio of 95.5:1.0:2.0:1.5 with conductive agent conductive carbon black, stabilizer carboxymethyl cellulose and binder SBR to form a first negative electrode slurry.

[0285] The composition of the flat region of the negative electrode sheet is as follows: artificial graphite (particle size Dv50 is 14.5μm) is dispersed in deionized water at a mass ratio of 95.5:1.0:2.0:1.5 with conductive agent conductive carbon black, stabilizer carboxymethyl cellulose and binder SBR to form the second negative electrode slurry; other aspects are the same as in Examples 3-2.

[0286] Example 3-2

[0287] A method for preparing a battery cell is provided. The method differs from that in Example 2-2 in that the composition of the bending region of the negative electrode sheet is as follows: artificial graphite (particle size Dv50 is 12μm) is dispersed in deionized water at a mass ratio of 95.5:1.0:2.0:1.5 with conductive agent conductive carbon black, stabilizer carboxymethyl cellulose and binder SBR to form a first negative electrode slurry.

[0288] The composition of the flat region of the negative electrode sheet is as follows: artificial graphite (particle size Dv50 is 20μm) is dispersed in deionized water at a mass ratio of 95.5:1.0:2.0:1.5 with conductive agent conductive carbon black, stabilizer carboxymethyl cellulose and binder SBR to form the second negative electrode slurry; other aspects are the same as in Examples 3-2.

[0289] Example 3-3

[0290] A method for preparing a battery cell is provided. The method differs from that in Example 2-2 in that the composition of the bending region of the negative electrode sheet is as follows: artificial graphite (particle size Dv50 is 6.5 μm) is dispersed in deionized water at a mass ratio of 95.5:1.5:2.0:1.0 with conductive agent conductive carbon black, stabilizer carboxymethyl cellulose and binder SBR to form a first negative electrode slurry.

[0291] The composition of the flat region of the negative electrode sheet is as follows: artificial graphite (particle size Dv50 is 14.5μm) is dispersed in deionized water at a mass ratio of 95.5:0.5:1.5:2.5 with conductive agent conductive carbon black, stabilizer carboxymethyl cellulose and binder SBR to form the second negative electrode slurry; other aspects are the same as in Examples 3-2.

[0292] Comparative Example 1

[0293] A method for preparing a battery cell is provided, which differs from Example 1-1 in that the negative electrode current collector is the composite current collector obtained in Comparative Preparation Example 1.

[0294] Comparative Example 2

[0295] A method for preparing a battery cell is provided, which differs from that of Examples 1-1 in that the negative electrode current collector is the composite current collector obtained in Comparative Preparation Example 2.

[0296] Comparative Example 3

[0297] A method for preparing a battery cell is provided, which differs from that in Examples 1-1 in that the negative electrode current collector is the composite current collector obtained in Comparative Preparation Example 3.

[0298] Comparative Example 4

[0299] A method for preparing a battery cell is provided, which differs from that of Examples 1-1 in that the negative electrode current collector is the composite current collector obtained in Comparative Preparation Example 4.

[0300] Battery performance testing:

[0301] ③ Test the capacity retention rate of the battery after 500 cycles at 25℃:

[0302] Under constant temperature of 25℃, the capacitor is charged to 4.4V with a constant current of 1C, then charged to 0.05C with a constant voltage of 4.4V, and then discharged to 2.5V with a constant current of 1C. The discharge specific capacity of the first cycle (Cd1) is obtained. This charging and discharging process is repeated until the 500th cycle. The discharge specific capacity after 500 cycles is denoted as Cdn.

[0303] Capacity retention (%) = discharge specific capacity after 500 cycles (Cdn) / discharge specific capacity in the first cycle (Cd1).

[0304] ④ Determination and analysis of lithium deposition on the surface of the negative electrode after the battery has undergone 500 cycles at 25℃:

[0305] After cycling the battery 500 times according to the above cycling method, it was charged to 4.3V with a constant current of 0.33C, and then charged to 0.05C with a constant voltage of 4.3V. The battery was then disassembled, and the positive and negative electrode plates were further separated. The lithium deposition on the surface of the negative electrode plate was observed using a scanning electron microscope, especially the lithium deposition on the surface of the main area of ​​the negative electrode plate.

[0306] The judgment criteria are shown in Table 2 below;

[0307] Table 2 Lithium plating grade standards

[0308]

[0309] Table 2 List of Lithium Plating Grades

[0310] ⑤ Determination of energy density:

[0311] Under constant temperature conditions of 25℃, the battery is charged to 4.4V with a constant current of 0.33C, then charged at a constant voltage of 4.4V until the current drops to 0.05C, and finally discharged to 2.5V with a constant current of 0.33C, yielding the battery discharge energy E. The battery is then weighed to obtain its mass m. The battery's mass energy density Ew can then be obtained using the following formula: Ew = E / m.

[0312] The performance of each embodiment obtained according to the above measurement method is shown in Table 3 below:

[0313] Table 3. List of Performance Tests for Examples and Comparative Examples

[0314]

[0315] As can be seen from Examples 1-1 to 1-5 of this application, and Comparative Examples 1 and 2, the porosity of the current collector support layer in the bending region and the porosity in the straight region, as well as the through-holes in the conductive layer in the bending region, affect the battery cycle performance. As can be seen from Examples 1-1 to 1-3, when the porosity of the support layer in the bending region and the porosity in the straight region remain unchanged, increasing the pore size of the through-holes in the conductive layer in the bending region within a certain range ensures better battery cycle performance while maintaining battery energy density.

[0316] As can be seen from Embodiments 1-1 and 1-6 of this application, changing the material of the support layer has little impact on the cycle life and energy density of the battery.

[0317] As can be seen from Embodiments 1-1, 2-1 to 2-4 of this application, further providing through holes in the flat area of ​​the conductive layer can not only ensure battery cycle performance but also appropriately improve battery energy density.

[0318] As can be seen from Embodiments 1-1, 1-7 and 2-3 of this application, both the positive and negative electrode sheets adopt the current collector designed in this application, which is beneficial to better balance the battery cycle performance and energy density.

[0319] As can be seen from Examples 1-1, 3-1 to 3-3 of this application, based on the improvement of the current collector of this application, the different settings of the negative electrode active material, conductive agent and binder in the bending area and the straight area are also conducive to better balancing battery cycle performance and energy density.

[0320] As can be seen from Comparative Examples 3 and 4 of this application, when the ratio of the porosity of the current collector support layer in the bending region to the porosity in the straight region is not within the protection scope of this application, the cycle performance of the battery cell cannot be guaranteed.

[0321] Therefore, the composite current collector provided in this application, without affecting its own conductivity, also has the functions of liquid absorption and storage. Furthermore, by setting differentiated porosity in the bending and straight areas of the support layer of the composite current collector, the storage capacity of the electrode assembly in the bending area is increased within a certain range, effectively solving the lithium plating problem in the bending area. Moreover, the conductive layer is provided with through holes in the bending area, which improves the wettability of the electrolyte to the active material and facilitates the rapid flow of electrolyte from the support layer to the conductive layer. In addition, the electrolyte squeezed out during the cycle expansion of the battery cell can also flow back to the interior of the electrode assembly more quickly, keeping the active material in a state of electrolyte wetting, thereby improving the cycle performance of the battery by reducing lithium plating.

[0322] At the same time, this design does not affect the amount of active material added in the bending region, especially the smooth insertion and extraction of the positive electrode active material, thus also taking into account the energy density of the battery.

[0323] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, The device includes one or more wound electrode assemblies, each including a flat region and a bent region; the wound electrode assembly includes an electrode sheet, each including a composite current collector and an active material layer disposed on at least one side of the composite current collector; The composite current collector includes a support layer and a conductive layer located on at least one side surface of the support layer; The support layer has a porosity of Q1 in the bending region and a porosity of Q2 in the straight region, satisfying 1 < Q1 / Q2 ≤ 3; The conductive layer has a through hole in the bending area, and the through hole extends through the conductive layer along its thickness direction.

2. The battery cell according to claim 1, characterized in that, The support layer has a porosity Q1 of 20% to 40% in the bending region and a porosity Q2 of 10% to 20% in the straight region.

3. The battery cell according to claim 1, characterized in that, The conductive layer has a plurality of first through holes in the bending region and a plurality of second through holes in the straight region. The average diameter of the first through holes is greater than or equal to the average diameter of the second through holes. The average pore size of the first through hole is 1μm to 10μm, and the average pore size of the second through hole is 100nm to 1µm.

4. The battery cell according to claim 1, characterized in that, The conductive layer has multiple through holes in the bending area, the average diameter of the through holes is 100nm~10μm, and the spacing between two adjacent through holes is 0.08mm~1.2mm. Furthermore, the conductive layer does not have through holes in the flat area.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The electrode includes a negative electrode, the negative electrode includes a negative electrode film layer located on at least one side surface of the composite current collector, and the negative electrode film layer includes a negative electrode active material; The average particle size of the negative electrode active material in the bending region is smaller than that in the straight region. The negative electrode active material has an average particle size of 5μm to 12μm in the bending region; the negative electrode active material has an average particle size of 10μm to 20μm in the straight region.

6. The battery cell according to claim 5, characterized in that, The negative electrode film layer includes a conductive agent and a binder. Based on the total mass of the negative electrode film layer, the mass percentage content of the conductive agent in the bending region is greater than the mass percentage content in the straight region. and / or; The adhesive has a lower mass percentage content in the bending region than it has in the straight region.

7. The battery cell according to claim 6, characterized in that, The conductive agent has a mass percentage content of 1.0% to 1.5% in the bending region and a mass percentage content of 0.5% to 1.0% in the straight region. and / or; The adhesive has a mass percentage content of 1.0% to 1.5% in the bending area and a mass percentage content of 1.5% to 2.5% in the straight area.

8. The battery cell according to any one of claims 1 to 4, characterized in that, The thickness of the support layer is 3μm~5μm, and the thickness of the conductive layer is 5μm~10μm; The support layer comprises any one or more of the following: polyterephthalate, polyethylene, polypropylene, epoxy resin, polyamide, polyimide, polyester, polyolefin, polyyne, siloxane polymer, polyether, polyol, polysulfone, polysaccharide polymer, amino acid polymer, polysulfide polymer, and aromatic ring polymer. The conductive layer comprises a metal, which includes one or more of aluminum, aluminum alloys, copper, copper alloys, nickel, nickel alloys, iron, iron alloys, titanium, titanium alloys, silver, and silver alloys.

9. A battery device, characterized in that, Includes the battery cell according to any one of claims 1 to 8.

10. An electrical device, characterized in that, Includes the battery device as described in claim 9.

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