Electrode sheets, electrode assemblies, battery cells, batteries and electrical devices

Abstract

This application discloses an electrode sheet, an electrode assembly, a battery cell, a battery, and an electrical device. The electrode sheet includes: a current collector; and an active material layer deposited on the surface of the current collector; the average compaction density of the portion of the active material layer deposited in the middle of the current collector is less than the average compaction density of the portion deposited at the edge of the current collector. The electrode sheet, electrode assembly, battery cell, battery, and electrical device provided in this application can improve the performance of the electrode assembly.

Description

Technical Field

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

[0002] Energy conservation and emission reduction are key to the sustainable development of the automotive industry. In this context, electric vehicles, due to their energy-saving and environmentally friendly advantages, have become an important component of the automotive industry's sustainable development. And for electric vehicles, battery technology is a crucial factor in their development.

[0003] The overall manufacturing process of batteries is lengthy and complex, involving a series of steps such as coating, sheet fabrication, assembly, laser welding, and electrolyte injection. Among these, the processing of the electrode components inside the battery cell is particularly crucial, directly impacting the cell's processing efficiency and performance. Therefore, improving the processing efficiency and performance of electrode components is a pressing technical challenge that needs to be addressed. Summary of the Invention

[0004] This application provides an electrode sheet, an electrode assembly, a battery cell, a battery, and an electrical device, which can improve the performance of the electrode assembly.

[0005] In a first aspect, an electrode is provided, comprising: a current collector; an active material layer disposed on the surface of the current collector; wherein the average compaction density of the portion of the active material layer disposed in the middle of the current collector is less than the average compaction density of the portion disposed at the edge of the current collector.

[0006] Therefore, in the electrode of this embodiment, by setting the average compaction density of the active material layer in the middle of the current collector to be less than the average compaction density of the portion laid at the edge of the current collector, the porosity of the active material layer in the middle is greater than that in the portion at the edge. This allows the middle region to hold more electrolyte, effectively solving the problem of lithium plating caused by electrolyte extrusion in the middle region, thus effectively reducing lithium plating and improving the performance and cycle life of the battery cell.

[0007] In some embodiments, the average thickness of the active material layer laid in the middle portion of the current collector is greater than the average thickness of the portion laid at the edge of the current collector. By setting the average thickness of the active material layer in the middle portion to be larger and the average thickness of the edge portion to be smaller, it is easy to achieve the effect that the average compaction density of the active material layer laid in the middle portion of the current collector is smaller and the average compaction density of the portion laid at the edge of the current collector is larger, which facilitates processing.

[0008] In some embodiments, the current collector has a first groove with an opening facing the active material layer in the middle. The average thickness of the bottom wall of the first groove is less than the average thickness of the edge of the current collector. Through the first groove, the average thickness of the portion of the active material layer laid in the middle of the current collector can be greater than the average thickness of the portion laid in the edge of the current collector.

[0009] In some embodiments, the electrode further includes a base coating layer disposed in at least a portion of the spacer between the current collector and the active material layer. The base coating layer can be used to connect and fix the current collector and the active material layer, and can also be used to increase the conductivity of the electrode.

[0010] In some embodiments, the center of the current collector is in direct contact with the active material layer, and the base coating is disposed between the edge of the current collector and the active material layer. Thus, regardless of whether the center of the current collector has a first groove, since the edge of the current collector has an additional base coating layer compared to the center, the average thickness of the middle portion of the active material layer is greater than the average thickness of its edge portion, thereby facilitating a lower average compaction density in the middle portion of the active material layer compared to its edge portion.

[0011] In some embodiments, the base coating is provided over the entire area between the current collector and the active material layer. This base coating can more effectively connect and fix the current collector and the active material layer, and can also increase the conductivity of the electrode, thereby improving the stability and performance of the electrode.

[0012] In some embodiments, the portion of the base coating corresponding to the middle of the current collector is provided with a second groove with an opening facing the active material layer. The middle portion of the active material layer is located within the second groove, so that the average thickness of the middle portion of the active material layer is greater than the average thickness of its edge portion, and further, the average compaction density of the portion of the active material layer laid in the middle of the current collector is less than the average compaction density of the portion of the active material layer laid in the edge of the current collector.

[0013] In some embodiments, the average thickness of the bottom wall of the second groove is less than the average thickness of the portion of the base coating corresponding to the edge of the current collector. Thus, regardless of whether the first groove is provided in the middle of the current collector, and regardless of whether the average thickness of the bottom wall of the second groove exceeds the depth of the first groove, the average thickness of the middle portion of the active material layer is greater than the average thickness of its edge portion. Furthermore, the average compaction density of the portion of the active material layer laid in the middle of the current collector is less than the average compaction density of the portion of the active material layer laid in the edge of the current collector. This design is simple and easy to implement.

[0014] In some embodiments, the edge of the current collector includes a first portion and a second portion, the first portion being located at one end of the current collector in the width direction of the electrode, the second portion being located at the other end of the current collector in the width direction of the electrode, and the middle portion of the current collector being located between the first portion and the second portion.

[0015] The current collector is positioned at the midpoint of the electrode's width. After the electrode is processed into an electrode assembly, whether it's a wound or stacked electrode assembly, the midpoint of the current collector corresponds to the midpoint of the electrode assembly. The portion of the active material layer laid in the midpoint of the current collector also corresponds to the midpoint of the electrode assembly. Especially for wound electrode assemblies, taking the figure as an example, when the compaction density of the portion of the active material layer laid in the midpoint of the current collector is high, the porosity of this portion is relatively low, allowing it to hold more electrolyte. This effectively solves the problem of electrolyte extrusion and lithium plating in the midpoint region, thus effectively reducing lithium plating and improving the performance and cycle life of the battery cell.

[0016] In some embodiments, the edge of the current collector includes a third portion and a fourth portion, the third portion being located at one end of the current collector in the length direction of the electrode; the fourth portion being located at the other end of the current collector in the length direction of the electrode; and the middle portion of the current collector being located between the third portion and the fourth portion, so as to be applicable to different types of electrode assemblies. For example, it can be applied to stacked electrode assemblies to effectively reduce lithium plating in stacked electrode assemblies, thereby improving the performance and cycle life of the battery cell.

[0017] In some embodiments, along the width direction of the electrode, the ratio of the average width W1 of the middle portion of the current collector to the average width W2 of the electrode ranges from [1 / 3, 2 / 3]. If the ratio of W1 to W2 is too small, for example, less than 1 / 3, the width W1 of the middle portion of the current collector will be too small, and the width W1 of the portion of the active material layer deposited in the middle portion of the current collector will also be too small. That is, only a small area can achieve the effect of increasing compaction density, correspondingly only reducing the lithium plating problem in a small area, and the effect of improving the performance and cycle life of the battery cell will not be significant. Conversely, if the ratio of W1 to W2 is too large, for example, greater than 2 / 3, the width W1 of the middle portion of the current collector will be too large, that is, the width W1 of the portion of the active material layer deposited in the middle portion of the current collector will also be too large. Although it can effectively solve the lithium plating problem of the electrode, it will increase the cost of the electrode assembly and increase the processing difficulty of the electrode assembly.

[0018] In some embodiments, the ratio of the average width of the middle portion of the current collector to the average width of the electrode is in the range of [40%, 60%] along the width direction of the electrode, so that the width of the portion of the active material layer laid in the middle portion of the current collector is not too large or too small. This can effectively solve the lithium plating problem of the electrode and also keep the processing difficulty and cost of the electrode assembly from being too high, thereby improving the processing efficiency of the battery cell.

[0019] In some embodiments, along the thickness direction of the electrode, the ratio of the difference H1-H2 between the average thickness H1 of the portion of the active material layer deposited in the middle of the current collector and the average thickness H2 of the portion deposited at the edge of the current collector, to the average thickness H2 of the portion of the active material layer deposited at the edge of the current collector, ranges from [1% to 3%.] If the ratio between the thickness difference H1-H2 and the average thickness H2 is too small, the value of the difference H1-H2 of the electrode will be set too small, corresponding to the difference between the average compaction density of the portion of the active material layer deposited in the middle of the current collector and the average compaction density of the portion of the active material layer deposited at the edge of the current collector will also be too small, which may affect the performance of the electrode and fail to effectively solve the lithium plating problem. Conversely, if the ratio between the thickness difference H1-H2 and the average thickness H2 is too large, the value of the difference H1-H2 of the electrode will be set too large, which will increase the processing difficulty of the electrode and may also affect the structural strength of the electrode, thereby affecting the processing efficiency of the electrode assembly and the battery cell.

[0020] In some embodiments, along the thickness direction of the electrode, the difference between the average thickness of the portion of the active material layer deposited in the middle of the current collector and the average thickness of the portion deposited at the edge of the current collector is H, where H is in μm, and the average compaction density of the portion of the active material layer deposited in the middle of the current collector is Y, where Y is in g / cm³. 3 H and Y satisfy Y = KH, where the value of K ranges from [0.1, 0.4].

[0021] Considering that the average compaction density of the active material layer laid in the middle of the current collector has a certain range, if the proportional coefficient K is too high, the thickness difference H will be too large. In this case, on the one hand, the average thickness of the active material layer laid in the middle of the current collector may be too large, which will make the electrode too thick and thus affect the energy density of the battery cell formed by the electrode. On the other hand, the average thickness of the active material layer laid at the edge of the current collector may be too small, which will result in weaker structural strength of the electrode and affect the performance of the electrode.

[0022] Conversely, if the proportionality coefficient K is too small, the thickness difference H will be too small. For example, the thickness difference H may approach zero, which will make the thickness of the active material layer in the middle of the current collector approximately equal to the thickness of the active material layer at the edge of the current collector. Correspondingly, the difference between the average compaction density of the active material layer in the middle of the current collector and the average compaction density of the active material layer at the edge of the current collector will also be too small, which may affect the performance of the electrode and fail to solve the lithium plating problem effectively.

[0023] In some embodiments, the average compaction density of the portion of the active material layer laid in the middle of the current collector is Y, where Y is expressed in g / cm³. 3 The total coating mass of the material laid on the surface of the current collector facing the active material layer is M, where M is in g / 1540.25 mm. 2 Y and M satisfy Y = NM, where N takes values ​​in the range [1, 7].

[0024] When the total coating mass M of the material laid on the surface of the current collector facing the active material layer is constant, if the proportionality coefficient N is too large, the average compaction density Y of the active material layer in the middle of the current collector will be too large. Conversely, the average compaction density of the active material layer at the edge of the current collector will be even larger. This increases the processing difficulty and cost of the electrode. Conversely, if the proportionality coefficient N is too small, the average compaction density Y of the active material layer in the middle of the current collector will be too small, failing to meet the design requirements of the electrode, reducing its performance, and consequently reducing the performance of the electrode assembly formed from it.

[0025] In some embodiments, the average thickness of the middle part of the electrode is substantially equal to the average thickness of the edge of the electrode, making both surfaces of the electrode relatively flat, which facilitates subsequent processing into electrode assemblies. This makes the spacing between different electrode layers in the electrode assembly relatively uniform, reducing lithium plating problems caused by large spacing differences. This not only improves the space utilization and energy density of the battery cell, but also reduces lithium plating during long-term charge-discharge cycles of the battery cell, thereby improving the cycle life and safety of the battery cell.

[0026] In some embodiments, the electrode includes two active material layers, with the current collector located between the two active material layers. The two active material layers are any active material layers with inconsistent compaction densities as described above, to simultaneously reduce lithium plating on both sides of the electrode and further improve the performance of the electrode assembly and the battery cell.

[0027] In a second aspect, an electrode assembly is provided, comprising: a positive electrode and a negative electrode, wherein the positive electrode and / or the negative electrode comprises the electrode of the first aspect or any embodiment of the first aspect.

[0028] In some embodiments, the positive electrode and the negative electrode are wound together to form the electrode assembly.

[0029] In some embodiments, the electrode assembly is a cylinder.

[0030] Thirdly, a battery cell is provided, including: the electrode assembly of the second aspect or any embodiment of the second aspect.

[0031] Fourthly, a battery is provided, comprising a plurality of battery cells, wherein the battery cells include those in the third aspect or any one of the embodiments of the third aspect.

[0032] Fifthly, an electrical device is provided, comprising: a battery as described in the fourth aspect or any one of the embodiments of the fourth aspect, the battery being used to provide electrical energy.

[0033] In some embodiments, the electrical equipment is a vehicle, a ship, or a spacecraft. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of a vehicle according to one embodiment of this application;

[0035] Figure 2 This is an exploded structural diagram of a battery according to an embodiment of this application;

[0036] Figure 3 This is an exploded structural diagram of a battery cell according to an embodiment of this application;

[0037] Figure 4 This is a schematic diagram of the structure of an electrode sheet according to an embodiment of this application;

[0038] Figure 5 This is a schematic diagram of the structure of an electrode sheet according to another embodiment of this application;

[0039] Figure 6 This is a schematic diagram of the electrode structure in another embodiment of this application;

[0040] Figures 7 to 17 These are schematic cross-sectional views of at least a portion of the electrode sheet in different embodiments of this application. Detailed Implementation

[0041] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0042] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

[0044] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0045] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0046] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0047] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0048] In this application, "multiple" refers to two or more (including two), and similarly, "multiple groups" refers to two or more (including two), and "multiple pieces" refers to two or more (including two).

[0049] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0050] The battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and the embodiments of this application are not limited to this.

[0051] In some implementations, the battery cell in this application embodiment can be a metal battery. Specifically, the metal battery may include lithium metal secondary batteries, sodium metal batteries, or magnesium metal batteries, etc. This application embodiment does not limit this.

[0052] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charging and discharging process of a single 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.

[0053] In some embodiments, the positive electrode may be a positive electrode sheet, which may include a positive electrode current collector and a positive electrode active material disposed on at least one surface of the positive electrode current collector.

[0054] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0055] As an example, the positive electrode current collector can be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, it can be silver-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium, etc. Foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. Composite current collectors can include a polymer material base layer and a metal layer. Composite current collectors can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0056] As an example, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0057] In some embodiments, the negative electrode may be a negative electrode sheet, which may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.

[0058] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0059] As an example, the negative electrode current collector can be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, it can be silver-treated aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, or titanium, etc. Composite current collectors can include a polymer material base layer and a metal layer. Foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. Composite current collectors can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0060] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc.

[0061] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0062] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0063] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride, and ceramic.

[0064] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0065] In some embodiments, the battery cell also includes an electrolyte, which acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. The electrolyte can be liquid, gel, or solid.

[0066] In some implementations, the electrode assembly is a wound structure. The positive and negative electrode sheets are wound into a wound structure.

[0067] In some implementations, the electrode assembly is a stacked structure.

[0068] As an example, multiple positive and negative electrodes can be set, and multiple positive and multiple negative electrodes can be stacked alternately.

[0069] As an example, multiple positive electrode plates can be provided, and negative electrode plates can be folded to form multiple stacked folded segments, with a positive electrode plate sandwiched between adjacent folded segments.

[0070] As an example, both the positive and negative electrode plates are folded to form multiple stacked folded segments.

[0071] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0072] As an example, the separators can be continuously arranged, either by folding or rolling between any adjacent positive or negative electrode plates.

[0073] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0074] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0075] In some embodiments, the battery cell may include a housing. The housing is used to encapsulate components such as electrode assemblies and electrolytes. The housing may be made of steel, aluminum, plastic (such as polypropylene), composite metal (such as copper-aluminum composite), or aluminum-plastic film, etc. The housing includes a shell and a cover plate.

[0076] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0077] The battery mentioned in the embodiments of this application may be a single physical module comprising one or more battery cells to provide higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, parallel, or mixed via a busbar.

[0078] In some embodiments, the battery can be a battery module, and when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0079] In some embodiments, the battery can be a battery pack, which includes a housing and individual battery cells, with the individual battery cells or battery modules housed within the housing.

[0080] 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.

[0081] The battery cell in this embodiment has an electrode assembly inside. During the process of injecting electrolyte into the battery cell, the electrode assembly is usually wetted from one end face, for example, from the end face where the tab is located. In this process, the wettability of the middle area of ​​the electrode assembly is worse than that of the edge area. Furthermore, during the subsequent use of the battery cell, after multiple charge-discharge cycles, the middle area of ​​the electrode is more likely to expand, which will squeeze out the electrolyte, increase the resistance to ion movement, and easily cause lithium plating in the middle area of ​​the electrode, thus affecting the performance and service life of the battery cell.

[0082] Therefore, embodiments of this application provide an electrode sheet, electrode assembly, battery cell, battery, and electrical device that can solve the above-mentioned problems. The electrode sheet of this application includes a current collector and an active material layer deposited on the surface of the current collector. The average compaction density of the active material layer deposited in the middle of the current collector is less than the average compaction density of the portion deposited at the edge of the current collector; that is, the porosity of the middle portion of the active material layer is greater than the porosity of the edge portion. In this way, the middle region can accommodate more electrolyte, effectively solving the problem of lithium plating caused by electrolyte extrusion in the middle region, thus effectively reducing lithium plating and improving the performance and cycle life of the battery cell.

[0083] The technical solutions described in the embodiments of this application are applicable to various battery-powered electrical devices.

[0084] Electrical equipment can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the above-mentioned electrical equipment.

[0085] For ease of explanation, the following embodiments use a vehicle as an example of electrical equipment.

[0086] For example, such as Figure 1 The diagram shown is a structural schematic of a vehicle 1 according to one embodiment of this application. Vehicle 1 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 motor 40, a controller 30, and a battery 10 can be installed inside vehicle 1. The controller 30 controls the battery 10 to supply power to the motor 40. For example, the battery 10 can be installed at the bottom, front, or rear of vehicle 1. The battery 10 can be used to power vehicle 1; for example, it can serve as the operating power source for the vehicle 1's electrical system, such as for the power requirements of starting, navigation, and operation. In another embodiment of this application, the battery 10 can not only serve as the operating power source for vehicle 1 but also as the driving power source, replacing or partially replacing gasoline or natural gas to provide driving power to vehicle 1.

[0087] To meet diverse power demands, a battery can comprise multiple individual cells, which can be connected in series, parallel, or a combination of both. A battery can also be called a battery pack. Optionally, multiple individual cells can first be connected in series, parallel, or a combination of both to form a battery module, and then multiple battery modules can be connected in series, parallel, or a combination of both to form a battery. In other words, multiple individual cells can be directly assembled into a battery, or they can first be assembled into battery modules, and then the battery modules can be assembled into a battery.

[0088] For example, Figure 2 A schematic diagram of the structure of a battery 10 according to an embodiment of this application is shown. The battery 10 may include multiple battery cells 20. Figure 2 As shown, the battery 10 may also include a housing 11, which has a hollow interior and houses multiple battery cells 20. Figure 2 This application illustrates one possible implementation of the housing 11, such as... Figure 2 As shown, the housing 11 may include two parts, referred to herein as a first part 111 and a second part 112, which are fastened together. The shapes of the first part 111 and the second part 112 may be determined according to the shape of the combination of multiple battery cells 20 inside, and at least one of the first part 111 and the second part 112 has an opening. For example, as... Figure 2 As shown, both the first part 111 and the second part 112 can be hollow cuboids and each has only one face as an opening. The openings of the first part 111 and the second part 112 are arranged opposite to each other, and the first part 111 and the second part 112 are interlocked to form a box 11 with a closed cavity.

[0089] For example, unlike Figure 2 As shown, in the first part 111 and the second part 112, only one can be a hollow cuboid with an opening, while the other can be plate-shaped to cover the opening. For example, if the second part 112 is a hollow cuboid with only one open face, and the first part 111 is plate-shaped, then the first part 111 covers the opening of the second part 112 to form a box 11 with a closed cavity, which can be used to accommodate multiple battery cells 20. The multiple battery cells 20 are connected in parallel, series, or mixed and placed inside the box 11 formed by the first part 111 and the second part 112.

[0090] Optionally, the battery 10 may also include other structures, which will not be described in detail here. For example, the battery 10 may also include a busbar component for realizing the electrical connection between multiple battery cells 20, such as in parallel, series, or mixed connections. Specifically, the busbar component can realize the electrical connection between battery cells 20 by connecting the electrode terminals 214 of the battery cells 20. Further, the busbar component can be fixed to the electrode terminals 214 of the battery cells 20 by welding. The electrical energy of the multiple battery cells 20 can be further led out through the housing 11 via a conductive mechanism.

[0091] Depending on different power demands, the number of battery cells 20 in battery 10 can be set to any value. Multiple battery cells 20 can be connected in series, parallel, or mixed connections to achieve a larger capacity or power. Since each battery 10 may contain a large number of battery cells 20, for ease of installation, the battery cells 20 can also be grouped, with each group of battery cells 20 forming a battery module. The number of battery cells 20 included in a battery module is unlimited and can be set according to requirements.

[0092] Figure 3 This is a partially exploded structural diagram of a battery cell 20 according to an embodiment of this application. For example, Figure 3 The battery cell 20 shown can be Figure 2 Any single battery cell, 20. (e.g.) Figure 3 As shown, the battery cell 20 in this embodiment may include a housing 21. Specifically, the housing 21 may include a shell 211, which is a hollow structure with at least one opening 2111; a cover plate 212 for covering the opening 2111 of the shell 211; and an electrode assembly 22 housed within the housing 21.

[0093] It should be understood that, in this embodiment of the application, the housing 211 is a component for accommodating the electrode assembly 22, and the housing 211 can be a hollow structure with an opening 2111 at one or more ends. For example, if the housing 211 is a hollow structure with an opening 2111 at one end, then a single cover plate 212 can be provided; as another example, such as Figure 3 As shown, if the shell 211 is a hollow structure with openings 2111 at opposite ends, then the cover plate 212 can be set as two, with the two cover plates 212 respectively covering the openings 2111 at both ends of the shell 211.

[0094] The shell 211 can be of various shapes, such as a cylinder, a cuboid, or other polyhedrons. For example, ... Figure 3 As shown in the embodiments of this application, the shell 211 is mainly described as a cylindrical structure.

[0095] It should be understood that the cover plate 212 in this embodiment is used to cover the opening 2111 of the housing 211 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover plate 212 can be adapted to the shape of the housing 211, such as... Figure 3 As shown, the shell 211 is a cylindrical structure, and the cover plate 212 is a circular plate structure adapted to the shell 211.

[0096] In this embodiment, the shell 211 can be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. The cover plate 212 can also be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. Optionally, the material of the cover plate 212 can be the same as or different from the material of the shell 211.

[0097] It should be understood that the battery cell 20 also includes electrode terminals 214. In this embodiment, the electrode terminals 214 are used for electrical connection with the electrode assembly 22 inside the battery cell 20 to output electrical energy from the battery cell 20. Specifically, the battery cell 20 may include at least two electrode terminals 214, which may include at least one positive electrode terminal and at least one negative electrode terminal. The positive electrode terminal is used for electrical connection with the positive electrode tab of the electrode assembly 22, and the negative electrode terminal is used for electrical connection with the negative electrode tab of the electrode assembly 22. The positive electrode terminal and the positive electrode tab can be directly connected or indirectly connected, and the negative electrode terminal and the negative electrode tab can be directly connected or indirectly connected. For example, the positive electrode terminal can be electrically connected to the positive electrode tab through a connecting member, and the negative electrode terminal can be electrically connected to the negative electrode tab through a connecting member.

[0098] In some embodiments, the at least two electrode terminals 214 included in the battery cell 20 may be located on different walls, or may be located on different walls. For example, as Figure 3 As shown, in the cylindrical battery cell 20 of this application embodiment, the two electrode terminals 214 can be respectively located on two cover plates 212 arranged opposite to each other, so that each electrode terminal 214 is electrically connected to the corresponding tab 221 in the tabs 221 located at both ends of the electrode assembly 22.

[0099] In this battery cell 20, the electrode assembly 22 is the component in which the electrochemical reaction occurs. Depending on actual usage requirements, the electrode assembly 22 within the casing 211 can be one or multiple. For example, as... Figure 3 As shown, an electrode assembly 22 is disposed within the battery cell 20. The type and shape of the electrode assembly 22 can also be configured according to actual usage requirements. For example, the electrode assembly 22 can be a cylinder, a cuboid, etc. For example, as... Figure 3As shown, if the housing 211 is a cylindrical structure, the corresponding electrode assembly 22 can also be a cylindrical structure to improve the internal space utilization and energy density of the battery cell 20; for example, if the housing 211 is a cuboid structure, the electrode assembly 22 can be a cuboid structure or a cylindrical structure, and the embodiments of this application are not limited thereto.

[0100] It should be understood that, such as Figure 3 As shown, the electrode assembly 22 includes tabs 221 and an electrode body 222. The tabs 221 of the electrode assembly 22 may include positive tabs and negative tabs. The positive tabs may be formed by stacking the portions of the positive electrode sheet that are not coated with a positive active material layer, and the negative tabs may be formed by stacking the portions of the negative electrode sheet that are not coated with a negative active material layer. The electrode body 222 may be formed by stacking or winding the positive and negative electrode sheets together.

[0101] The electrode sheet used to form an electrode assembly according to embodiments of this application will now be described with reference to the accompanying drawings. Figure 4 A schematic diagram of the structure of the electrode 3 according to an embodiment of this application is shown. Figure 4 The electrode 3 shown is in its unfolded state. For example... Figure 4 As shown, the electrode 3 includes: a current collector 31; an active material layer 32, which is laid on the surface of the current collector 31; the average compaction density of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 is less than the average compaction density of the portion 322 laid in the edge 312 of the current collector 31.

[0102] In the embodiments of this application, the electrode 3 can be a positive electrode, or it can be a negative electrode. For example, for any electrode assembly 22, the positive electrode included in the electrode assembly 22 can be the electrode 3, and / or the negative electrode can be the electrode 3; and the electrode assembly 22 can be a wound electrode assembly 22 or a stacked electrode assembly 22, and the embodiments of this application are not limited thereto.

[0103] It should be understood that the electrode 3 in this embodiment may include a tab portion 301 and a main body portion 302, wherein the tab portion 301 is used to form the tab 221 of the electrode assembly 22, and the main body portion 302 is used to form the electrode main body portion 222 of the electrode assembly 22. Specifically, the tab portion 301 of the electrode 3 may be formed by stacking the portions of the electrode 3 that are not coated with the active material layer 32. For example, for a positive electrode, the tab portion 301 may be formed by stacking the portions of the positive electrode that are not coated with the positive active material layer; for a negative electrode, the tab portion 301 may be formed by stacking the portions of the negative electrode that are not coated with the negative active material layer. The main body portion 302 of the electrode 3 is used to stack or wind to form the electrode main body portion 222 of the electrode assembly 22.

[0104] For ease of description, the current collector 31 included in the electrode 3 of the embodiment of this application mainly refers to the current collector 31 of the main body portion 302 of the electrode 3; correspondingly, the active material layer 32 of the electrode 3 mainly refers to the active material layer 32 of the main body portion 302 of the electrode 3, and this part of the active material layer 32 is laid on the surface of the corresponding current collector 31.

[0105] For ease of description, the embodiments of this application define a length direction X and a width direction Y for the electrode 3. Specifically, the length direction X of the electrode 3 is the extension direction of the electrode 3, the width direction Y of the electrode 3 is the arrangement direction of the tab portion 301 and the main body portion 302 of the electrode 3, and the length direction X and the width direction Y are perpendicular to each other.

[0106] It should be understood that, in this embodiment, the active material layer 32 being deposited on the surface of the current collector 31 means that, along the thickness direction of the electrode 3, the current collector 31 includes two opposing surfaces, and the active material layer 32 is deposited on either of these two surfaces. The thickness direction of the electrode 3 is perpendicular to its length direction X and width direction Y; that is, the length direction X, width direction Y, and thickness direction of the electrode 3 are mutually perpendicular.

[0107] In this embodiment, the average compaction density of the portion 321 of the active material layer 32 of the electrode 3, which is laid in the middle 311 of the current collector 31, is less than the average compaction density of the portion 322 laid in the edge 312 of the current collector 31. That is, the porosity of the middle portion 321 of the active material layer 32 is greater than the porosity of the edge portion 322. This allows the middle region of the electrode 3 to hold more electrolyte, effectively solving the problem of lithium plating caused by electrolyte extrusion in the middle region. This effectively reduces lithium plating, thereby improving the performance and cycle life of the battery cell 20.

[0108] In this embodiment of the application, the middle portion 311 of the current collector 31 is closer to the center of the current collector 31 than the edge 312 of the current collector 31. Furthermore, the middle portion 311 of the current collector 31 may refer to the middle portion of the electrode 3 in the length direction X and / or the middle portion of the electrode 3 in the width direction Y.

[0109] In some embodiments, the edge 312 of the current collector 31 includes a first portion 3121, which is located at one end of the current collector 31 in the width direction Y of the electrode 3, and the middle portion 311 of the current collector 31 is located at the other end of the current collector 31 in the width direction Y of the electrode 3. Specifically, with Figure 4For example, in the width direction Y of the electrode 3, the edge 312 of the current collector 31 includes a first part 3121, which can be located on either side of the middle part 311 of the current collector 31, and the middle part 311 of the current collector 31 is closer to the center of the main body 302 than the first part 3121.

[0110] Furthermore, the edge 312 of the current collector 31 also includes a second portion 3122, which is located at the other end of the current collector 31 in the width direction Y of the electrode 3, and the middle portion 311 of the current collector 31 is located between the first portion 3121 and the second portion 3122. Specifically, as Figure 4 As shown, in the width direction Y of the electrode 3, the middle part 311 of the current collector 31 is located between the first part 3121 and the second part 3122. Therefore, the middle part 311 of the current collector 31 is closer to the center of the main body 302 than either the first part 3121 or the second part 3122.

[0111] The middle portion 311 of the current collector 31 is positioned at the midpoint of the electrode sheet 3 in the width direction Y. After the electrode sheet 3 is processed into an electrode assembly 22, whether it is a wound electrode assembly 22 or a stacked electrode assembly 22, the middle portion 311 of the current collector 31 corresponds to the middle position of the electrode assembly 22, and the portion 321 of the active material layer 32 laid in the middle portion 311 of the current collector 31 also corresponds to the middle position of the electrode assembly 22. Especially for the wound electrode assembly 22, Figure 3 For example, if the compaction density of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 is relatively large, the porosity of this portion 321 is relatively small, which can accommodate more electrolyte. This can effectively solve the problem of lithium plating caused by easy extrusion of electrolyte in the middle region, that is, it can effectively reduce lithium plating phenomenon, thereby improving the performance and cycle life of the battery cell 20.

[0112] Figure 5 and Figure 6 Other possible structural schematic diagrams of the electrode 3 according to embodiments of this application are shown respectively. Figure 5 and Figure 6 All electrode plates 3 shown are in their unfolded state. Figure 5 and Figure 6 For example, the middle part 311 of the current collector 31 can include not only the middle part of the width direction Y of the electrode 3, but also the middle part of the length direction X of the electrode 3.

[0113] In some embodiments, the edge 312 of the current collector 31 includes a third portion 3123, which is located at one end of the current collector 31 in the longitudinal direction X of the electrode 3, and the middle portion 311 of the current collector 31 is located at the other end of the current collector 31 in the longitudinal direction X of the electrode 3. Specifically, with Figure 5 and Figure 6 For example, in the length direction X of the electrode 3, the edge 312 of the current collector 31 may include a third part 3123, which may be located on either side of the middle part 311 of the current collector 31, and the middle part 311 of the current collector 31 is closer to the center of the main body 302 than the third part 3123.

[0114] Furthermore, the edge 312 of the current collector 31 also includes a fourth portion 3124, which is located at the other end of the current collector 31 in the longitudinal direction X of the electrode 3, and the middle portion 311 of the current collector 31 is located between the third portion 3123 and the fourth portion 3124. Specifically, as Figure 5 and Figure 6 As shown, in the length direction X of the electrode 3, the middle part 311 of the current collector 31 is located between the third part 3123 and the fourth part 3124. Therefore, the middle part 311 of the current collector 31 is closer to the center of the main body 302 than either the third part 3123 or the fourth part 3124.

[0115] Furthermore, considering that the length direction X of the electrode 3 is the extension direction of the electrode 3, and different types of electrode assemblies 22 use different lengths of the electrode 3, therefore, as Figure 5 and Figure 6 As shown, in the length direction X of the electrode 3, the electrode 3 may include one or more third parts 3123, and correspondingly, it may also include one or more fourth parts 3124. The middle part 311 of the current collector 31 is located between a third part 3123 and a corresponding fourth part 3124.

[0116] Different types of electrodes 3 can be applied to different types of electrode assemblies 2. For example, for... Figure 3 The electrode assembly 22 of the wound cylindrical battery cell 20 shown can typically be, for example, Figure 4 or Figure 5 The electrode 3 shown is positioned such that, along the width Y direction of the electrode 3, or along the height Y direction of the electrode assembly 22, the middle portion 311 of the current collector 31 corresponds to the middle position of the electrode assembly 22. This allows the electrode 3 in this embodiment to effectively reduce lithium plating, thereby improving the performance and cycle life of the battery cell 20. For example, the electrode assembly 22 of a wound prismatic battery cell 20 can also typically employ... Figure 4 or Figure 5The electrode 3 shown can increase the porosity of the central region in the height direction of the electrode assembly 22, thereby reducing lithium plating. In particular, for the wound prismatic battery cell 20, it can also employ... Figure 6 The electrode 3 is shown. For example, in the electrode assembly 22 formed after the electrode 3 is wound, the middle portion 311 of the current collector 31 can be used to form the large surface of the electrode assembly 22, while the edge 312 of the current collector 31 can be used to form the edge portion of the electrode assembly 22. For example, the first portion 3121 and the second portion 3122 can be used to form the end of the electrode assembly 22, while the third portion 3123 and the fourth portion 3124 can be used to form the corner portion or the bent portion of the electrode assembly 22.

[0117] For example, the stacked electrode assembly 22 may include multiple positive electrode plates and multiple negative electrode plates, which are alternately stacked; or, multiple positive electrode plates may be provided, and negative electrode plates are folded to form multiple stacked folded segments, with a positive electrode plate sandwiched between adjacent folded segments; or, both positive and negative electrode plates are folded to form multiple stacked folded segments. Therefore, for the electrode plates in the electrode assembly 22 that are folded to form multiple stacked folded segments, the electrode plates can be used as follows: Figures 4 to 6 Any of the electrode plates 3 shown in the figure, wherein, for example, Figure 6 The electrode 3 shown can be folded in the third part 3123 and the fourth part 3124. For electrode assemblies 22 with multiple electrodes, these multiple electrodes can be arranged as follows: Figure 6 The electrode 3 shown is obtained through processing. For example, the electrode 3 can be cut into the third part 3123 and the fourth part 3124 so that the middle part of each electrode 3 obtained after cutting corresponds to the middle part 311 of the current collector 31 in this embodiment. With the above-described arrangement, the electrode 3 of this embodiment can effectively reduce the lithium plating phenomenon of the stacked electrode assembly 22, thereby improving the performance and cycle life of the battery cell 20, but this embodiment is not limited to this.

[0118] It should be understood that the size of the middle portion 311 of the current collector 31 in this embodiment can be flexibly set according to actual applications. For example, as Figures 4 to 6As shown, along the width direction Y of the electrode 3, the ratio of the average width W1 of the middle portion 311 of the current collector 31 to the average width W2 of the electrode 3 ranges from [1 / 3, 2 / 3]. If the ratio of W1 to W2 is too small, for example, less than 1 / 3, the width W1 of the middle portion 311 of the current collector 31 will be too small, and the width W1 of the portion 321 of the active material layer 32 laid in the middle portion 311 of the current collector 31 will also be too small. That is, only a very small area can achieve the effect of increasing the compaction density, which can only reduce the lithium plating problem in a very small area. The effect of improving the performance and cycle life of the battery cell 20 will not be obvious. Conversely, if the ratio of W1 to W2 is too large, for example, greater than 2 / 3, the width W1 of the middle part 311 of the current collector 31 will be too large, that is, the width W1 of the part 321 of the active material layer 32 laid in the middle part 311 of the current collector 31 will also be too large. Although it can effectively solve the lithium plating problem of the electrode 3, it will increase the cost of the electrode assembly 22 and increase the processing difficulty of the electrode assembly 22.

[0119] Therefore, the ratio of W1 to W2 should not be too large or too small. For example, along the width direction Y of the electrode 3, the ratio of the average width W1 of the middle portion 311 of the current collector 31 to the average width W2 of the electrode 3 is in the range of [40%, 60%]. This ensures that the width W1 of the portion 321 of the active material layer 32 laid in the middle portion 311 of the current collector 31 is not too large or too small, which can effectively solve the lithium plating problem of the electrode 3 and also keep the processing difficulty and cost of the electrode assembly 22 from being too high, thereby improving the processing efficiency of the battery cell 20. For another example, along the width direction Y of the electrode 3, the ratio of the average width W1 of the middle portion 311 of the current collector 31 to the average width W2 of the electrode 3 can be set to 1 / 3, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, or 2 / 3. The embodiments of this application are not limited to these.

[0120] Similarly, along the length direction X of the electrode 3, the length of the middle portion 311 of the current collector 31 can be flexibly set according to the actual application. For example, it can be determined whether to set a third portion 3123 and the length of the third portion 3123, depending on the actual application; or, it can be determined whether to set a fourth portion 3124 and the length of the fourth portion 3124, depending on the actual application. The embodiments of this application are not limited to these.

[0121] It should be understood that, for ease of description, the embodiments of this application are mainly referred to as follows: Figure 4 The electrode shown in Figure 3 is used as an example for detailed description, but the same description applies to electrodes such as... Figure 5 and Figure 6 Other embodiments shown will not be described in detail here.

[0122] It should be understood that the compaction density in this embodiment represents the density of the electrode 3 after extrusion processing, for example, the density of the electrode 3 after cold pressing. The average compaction density of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 in this embodiment can be set according to actual application, and the range of the average compaction density of this portion 321 can be the same or different for the positive electrode and the negative electrode.

[0123] In some embodiments, if the electrode 3 is a positive electrode, the average compaction density of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 can be in the range of [2.5 g / cm³]. 3 3g / cm 3 Furthermore, the range of this value can be [2.7 g / cm³]. 3 2.8g / cm 3 To meet design requirements and effectively avoid lithium plating, for example, the average compaction density of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 can be specifically set to 2.5 g / cm³. 3 2.6g / cm 3 2.7g / cm 3 2.8g / cm 3 2.9g / cm 3 Or 3g / cm 3 .

[0124] Correspondingly, when the electrode 3 is a positive electrode, the average compaction density of the portion 322 of the active material layer 32 laid on the edge 312 of the current collector 31 can be in the range of [2 g / cm³]. 3 2.6g / cm 3 Furthermore, the range of this value can be [2.3 g / cm³]. 3 2.5g / cm 3 To meet design requirements. For example, the average compaction density of the portion 322 of the active material layer 32 laid at the edge 312 of the current collector 31 can be specifically set to 2 g / cm³. 3 2.1g / cm 3 2.2g / cm 3 2.3g / cm 3 2.4g / cm 3 2.5g / cm 3 Or 2.6g / cm 3 .

[0125] In some embodiments, if the electrode 3 is a negative electrode, the average compaction density of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 can be in the range of [1.2 g / cm³]. 3 1.6g / cm 3 Furthermore, the range of this value can be [1.3 g / cm³]. 3 1.5g / cm 3 To meet design requirements and effectively avoid lithium plating, for example, the average compaction density of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 can be specifically set to 1.2 g / cm³. 3 1.3g / cm 3 1.4g / cm 3 1.5g / cm 3 Or 1.6g / cm 3 .

[0126] Correspondingly, when electrode 3 is a negative electrode, the average compaction density of the portion 322 of the active material layer 32 laid on the edge 312 of the current collector 31 can be in the range of [1.0 g / cm³]. 3 1.7g / cm 3 Furthermore, the range of this value can be [1.3 g / cm³]. 3 1.6g / cm 3 To meet design requirements. For example, the average compaction density of the portion 322 of the active material layer 32 laid at the edge 312 of the current collector 31 can be specifically set to 1.0 g / cm³. 3 1.1g / cm 3 1.2g / cm 3 1.3g / cm 3 1.4g / cm 3 1.5g / cm 3 1.6g / cm 3 Or 1.7g / cm 3 .

[0127] It should be understood that in the embodiments of this application, the average compaction density of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 is less than the average compaction density of the portion 322 laid in the edge 312 of the current collector 31, which can be achieved in various ways. For example, it can be achieved by adjusting the cold pressing process; or, for another example, it can be achieved by setting different thicknesses in different regions.

[0128] Figure 7 and Figure 8 Partial cross-sectional schematic diagrams of the electrode 3 in different embodiments of this application are shown, for example, Figure 7 and Figure 8 It can be like Figures 4 to 6 A possible partial cross-sectional schematic diagram of any electrode 3, the cross-section being perpendicular to the length direction X of electrode 3. For example... Figure 7 and Figure 8 As shown, different compaction densities can be achieved by setting different thicknesses in different regions of the active material layer 32.

[0129] Specifically, the average thickness H1 of the portion 321 of the active material layer 32 located in the middle 311 of the current collector 31 is greater than the average thickness H2 of the portion 322 located at the edge 312 of the current collector 31. Before compaction, when the active material layer 32 is laid on the surface of the current collector 31, the coating thickness in different areas can be the same or different. However, after compaction, by setting the average thickness H1 of the middle portion 321 of the active material layer 32 to be larger and the average thickness H2 of the edge portion 322 to be smaller, it is easier to achieve the effect of a smaller average compaction density in the portion 321 of the middle 311 of the current collector 31 and a larger average compaction density in the portion 322 located at the edge 312 of the current collector 31, which facilitates processing.

[0130] It should be understood that the average thickness H1 of the portion 321 of the active material layer 32 deposited in the middle 311 of the current collector 31 can refer to the average thickness dimension of the portion 321 of the active material layer 32 deposited in the middle 311 of the current collector 31 along the thickness direction Z of the electrode 3. Similarly, the average thickness H2 of the portion 322 of the active material layer 32 deposited in the edge 312 of the current collector 31 can refer to the average thickness dimension of the portion 322 of the active material layer 32 deposited in the edge 312 of the current collector 31 along the thickness direction Z of the electrode 3. In this embodiment, the thickness direction Z of the electrode 3 is perpendicular to the length direction X and the width direction Y of the electrode 3.

[0131] It should be understood that the different thicknesses of different regions of the active material layer 32 in the embodiments of this application can be achieved in various ways. For example, using Figure 7For example, the surface of the active material layer 32 away from the current collector 31 can be uneven to meet the thickness requirements of different areas. Specifically, before the compaction treatment, that is, when the active material layer 32 is laid on the surface of the current collector 31, the coating thickness of different areas can be set to be the same or different. For example, the average thickness H1 of the middle part 321 of the active material layer 32 can be set to be equal or unequal to the average thickness H2 of the edge part 322. However, after a special compaction treatment, the average thickness H1 of the middle part 321 of the active material layer 32 can be larger, while the average thickness H2 of the edge part 322 can be smaller. This results in a lower average compaction density of the portion 321 of the active material layer 32 laid in the middle part 311 of the current collector 31, and a higher average compaction density of the portion 322 laid in the edge part 312 of the current collector 31.

[0132] For example, with Figure 7 Unlike other materials, the surface of the active material layer 32 furthest from the current collector 31 can also be substantially flush, and this can be achieved through different configurations. Specifically, with... Figure 8 For example, the center 311 of the current collector 31 is provided with a first groove 313 with an opening facing the active material layer 32. The average thickness H21 of the bottom wall of the first groove 313 is less than the average thickness H22 of the edge 312 of the current collector 31. Specifically, the bottom wall of the first groove 313 corresponds to the center 311 of the current collector 31. Through the first groove 313, different thicknesses of different regions of the active material layer 32 can be achieved. During the process of laying the active material layer 32 on the surface of the current collector 31, the surface of the active material layer 32 away from the current collector 31 can be set to be basically flush. Due to the first groove 313, the average thickness H1 of the portion 321 of the active material layer 32 laid in the center 311 of the current collector 31 is larger, while the average thickness H2 of the portion 322 laid in the edge 312 of the current collector 31 is smaller. Furthermore, during the compaction process, since the surface of the active material layer 32 away from the current collector 31 is basically flush, special compaction treatment is not required for different areas. After compaction, the surface of the active material layer 32 away from the current collector 31 remains basically flush, facilitating subsequent processing of the electrode sheet 3 and assembly into an electrode assembly. In addition, the first groove 313 ensures that the average compaction density of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 is lower, while the average compaction density of the portion 322 laid at the edge 312 of the current collector 31 is higher.

[0133] It should be understood that, when the surface of the active material layer 32 away from the current collector 31 is substantially flush, the average thickness H1 of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 can be made greater than the average thickness H2 of the portion 322 laid in the edge 312 of the current collector 31 by other means.

[0134] It should be understood that the electrode 3 in this embodiment further includes a base coating 33 disposed in at least a portion of the area between the current collector 31 and the active material layer 32. The base coating 33 can be used to connect and fix the current collector 31 and the active material layer 32, and can also be used to increase the conductivity of the electrode 3. For example, the material of the base coating 33 may include a binder and / or a conductive material. For another example, the base coating 33 may include a conductive material. Taking lithium batteries as an example, commonly used conductive materials for lithium batteries may include traditional conductive agents, such as conductive carbon black (SP), conductive graphite, carbon fiber, etc.; or, it may also include novel conductive agents, such as carbon nanotubes, graphene, and their mixed conductive slurries, etc. For another example, the base coating 33 may include a binder. Still taking lithium batteries as an example, commonly used binders mainly include at least one of the following: polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR) emulsion, carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylonitrile (PAN), and polyacrylate.

[0135] It should be understood that by using different configurations of the base coating layer 33 and the current collector 31, different thicknesses can be achieved in different regions of the active material layer 32.

[0136] In some embodiments, the base coating 33 may be disposed in a portion of the area between the current collector 31 and the active material layer 32 to achieve different thicknesses in different areas of the active material layer 32. For example, Figure 9 and Figure 10 Partial cross-sectional schematic diagrams of the electrode 3 in different embodiments of this application are shown, for example, Figure 9 and Figure 10 It can be like Figures 4 to 6 A possible partial cross-sectional schematic diagram of any electrode 3, the cross-section being perpendicular to the length direction X of electrode 3.

[0137] like Figure 9 and Figure 10As shown, the middle part 311 of the current collector 31 is in direct contact with the active material layer 32, and a base coating 33 is provided between the edge 312 of the current collector 31 and the active material layer 32. That is, no base coating 33 is provided between the middle part 311 of the current collector 31 and the middle part 321 of the corresponding active material layer 32, so that this part of the current collector 31 is in direct contact with the active material layer 32; while the edge 312 of the current collector 31 and the edge part 322 of the corresponding active material layer 32 are provided with a base coating 33, so that this part of the current collector 31 and the active material layer 32 are indirectly connected through the base coating 33. Thus, regardless of whether the middle portion 311 of the current collector 31 is provided with the first groove 313, since the edge 312 of the current collector 31 is provided with an additional base coating layer 33 compared to the middle portion 311, the average thickness H1 of the middle portion 321 of the active material layer 32 is greater than the average thickness H2 of its edge portion 322, thereby facilitating the realization that the average compaction density of the middle portion 321 of the active material layer 32 is smaller than the average compaction density of its edge portion 322.

[0138] For example, such as Figure 9 As shown, it can be done as follows Figure 8 Based on the electrode 3 shown, a partial undercoating 33 is further provided to achieve different thicknesses in different areas of the active material layer 32. Specifically, based on the first groove 313 provided in the middle 311 of the current collector 31, the undercoating 33 is not provided in the middle 311 of the current collector 31, but is provided at the edge 312 of the current collector 31. In this way, when the surface of the active material layer 32 away from the current collector 31 is basically flush, the difference between the average thickness H1 of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 and the average thickness H2 of the portion 322 of the active material layer 32 laid in the edge 312 of the current collector 31 is equal to the sum of the depth of the first groove 313 in the middle 311 of the current collector 31 and the thickness of the undercoating 33 located at the edge 312 of the current collector 31. Therefore, by adjusting the depth of the first groove 313 in the middle 311 of the current collector 31 and the thickness of the bottom coating 33 located at the edge 312 of the current collector 31, the difference between the average thickness H1 and the average thickness H2 can be adjusted, and the difference between the average compaction density of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 and the average compaction density of the portion 322 of the active material layer 32 laid in the edge 312 of the current collector 31 can also be adjusted.

[0139] For example, such as Figure 10As shown, even without the first groove 313 in the middle 311 of the current collector 31, the thickness of different areas of the active material layer 32 can be achieved by varying the presence or absence of a base coating 33. Specifically, when the surface of the active material layer 32 furthest from the current collector 31 is substantially flush, the difference between the average thickness H1 of the portion 321 of the active material layer 32 in the middle 311 of the current collector 31 and the average thickness H2 of the portion 322 of the active material layer 32 in the edge 312 of the current collector 31 is equal to the thickness of the base coating 33 located at the edge 312 of the current collector 31. Therefore, by adjusting the coating thickness of the base coating 33, the difference between the average thickness H1 and the average thickness H2 can be directly adjusted. Furthermore, the difference between the average compaction density of the portion 321 of the active material layer 32 in the middle 311 of the current collector 31 and the average compaction density of the portion 322 of the active material layer 32 in the edge 312 of the current collector 31 can also be adjusted. The structure is simple and easy to implement.

[0140] In some embodiments, the base coating 33 can also be disposed in the entire area between the current collector 31 and the active material layer 32, thus achieving different thicknesses in different areas of the active material layer 32. For example... Figure 11 and Figure 12 Partial cross-sectional schematic diagrams of the electrode 3 in different embodiments of this application are shown, for example, Figure 11 and Figure 12 It can be like Figures 4 to 6 A possible partial cross-sectional schematic diagram of any electrode 3, the cross-section being perpendicular to the length direction X of electrode 3.

[0141] like Figure 11 and Figure 12 As shown, a base coating 33 is provided over the entire area between the current collector 31 and the active material layer 32. In this way, the base coating 33 can more effectively connect and fix the current collector 31 and the active material layer 32, and can also increase the conductivity of the electrode 3, thereby improving the stability and performance of the electrode 3.

[0142] In some embodiments, the portion 331 of the base coating 33 corresponding to the middle portion 311 of the current collector 31 is provided with a second groove 333 opening toward the active material layer 32. Regardless of whether the middle portion 311 of the current collector 31 is provided with a first groove 313, the portion 331 of the base coating 33 corresponding to the middle portion 311 of the current collector 31 can be provided with a second groove 333. Then, the middle portion 321 of the active material layer 32 is located in the second groove 333, so that the average thickness H1 of the middle portion 321 of the active material layer 32 is greater than the average thickness H2 of its edge portion 322. Furthermore, the average compaction density of the portion 321 of the active material layer 32 laid in the middle portion 311 of the current collector 31 is less than the average compaction density of the portion 322 of the active material layer 32 laid in the edge portion 312 of the current collector 31.

[0143] In some embodiments, the average thickness H31 of the bottom wall of the second groove 333 is less than the average thickness H32 of the portion 332 of the base coating 33 corresponding to the edge 312 of the current collector 31. For example... Figure 11 and Figure 12 As shown, the bottom wall of the second groove 333 corresponds to the middle portion 311 of the current collector 31. Thus, regardless of whether the middle portion 311 of the current collector 31 has the first groove 313, and regardless of whether the average thickness H31 of the bottom wall of the second groove 333 exceeds the depth of the first groove 313, the average thickness H1 of the middle portion 321 of the active material layer 32 is greater than the average thickness H2 of its edge portion 322. Furthermore, the average compaction density of the portion 321 of the active material layer 32 laid in the middle portion 311 of the current collector 31 is less than the average compaction density of the portion 322 of the active material layer 32 laid in the edge portion 312 of the current collector 31. The structure is simple and easy to implement.

[0144] For example, with Figure 11 For example, if the middle part 311 of the current collector 31 is not provided with the first groove 313, then the surface of the bottom wall of the second groove 333 facing the current collector 31 is basically flush with the surface of the portion 332 of the base coating 33 corresponding to the edge 312 of the current collector 31 facing the current collector 31, and the average thickness H31 of the bottom wall of the second groove 333 is less than the average thickness H32 of the portion 332 of the base coating 33 corresponding to the edge 312 of the current collector 31. The structure is simple and easy to process.

[0145] For example, with Figure 12For example, if the middle portion 311 of the current collector 31 is provided with a second groove 313, then the bottom wall of the second groove 333 facing the current collector 31 protrudes beyond the surface of the portion 332 of the base coating 33 corresponding to the edge 312 of the current collector 31. In this case, the average thickness H31 of the bottom wall of the second groove 333 may be less than or equal to or greater than the depth of the first groove 313, and may also be less than or equal to or greater than the average thickness H32 of the portion 332 of the base coating 33 corresponding to the edge 312 of the current collector 31. Both of these conditions can result in the average thickness H1 of the middle portion 321 of the active material layer 32 being greater than the average thickness H2 of its edge portion 322. The embodiments of this application are not limited to this.

[0146] In the embodiments of this application, the above figures mainly use the example of the active material layer 32 being laid on the edge 312 of the current collector 31 with a basically uniform thickness, or, unlike this, the thickness of this portion 322 can also be set as stepped. Specifically, Figure 13 A partial cross-sectional schematic diagram of the electrode 3 according to another embodiment of this application is shown, for example, Figure 13 It can be like Figures 4 to 6 A possible partial cross-sectional schematic diagram of any electrode 3, the cross-section being perpendicular to the length direction X of electrode 3.

[0147] like Figure 13 As shown, the thickness of the active material layer 32 at different locations on the edge 312 portion 322 of the current collector 31 can be unequal. For example, the thickness of the edge portion 322 of the active material layer 32 can be set to gradually increase from near the middle portion 321 to away from the middle portion 321, so that the corresponding compaction density gradually decreases, thereby reducing lithium plating and improving the performance and service life of the electrode assembly 22 and the battery cell 22. Specifically, the thickness difference can be achieved by different arrangements of the first groove 313 and / or the second groove 333. For example, a first groove 313 can be provided in the middle 311 of the current collector 31, and no base coating 33 can be provided in the middle 311; in addition, no base coating 33 can be provided in the area near the middle 311 of the edge 312 of the current collector 31, but a base coating 33 can be provided in the area away from the middle 311, so that the average thickness H1 of the active material layer 32 laid in the middle 311 portion 321 of the current collector 31 is the largest, while the average thickness of the active material layer 32 laid in the edge 312 portion 322 of the current collector 31 is smaller, and in the edge 312 portion 322 of the current collector 31, the average thickness H2' of the active material layer 32 laid in the area near the middle 311 is greater than the average thickness H2 of the area away from the middle 311.

[0148] It should be understood that the above... Figures 7 to 13The embodiments shown are described using the active material layer 32 on either side of the current collector 31 as an example. The active material layer 32 on the other side of the current collector 31 can be flexibly configured according to the actual application.

[0149] Figure 14 A cross-sectional schematic diagram of electrode 3 according to another embodiment of this application is shown, for example, Figure 14 It can be like Figures 4 to 6 A possible cross-sectional schematic diagram of any electrode 3, the cross-section being perpendicular to the length direction X of electrode 3. For example... Figure 14 As shown, one side of the current collector 31 is provided with an active material layer 32 of inconsistent compaction density according to this embodiment of the application. For example, Figure 14 To set as Figure 8 Taking the active material layer 32 shown as an example, but as Figures 7 to 13 Other embodiments shown are also applicable. However, an active material layer 32' with uniform compaction density is provided on the other side of the current collector 31. For example, an active material layer 32' with uniform thickness can be provided on the other side of the current collector 31 to simplify the structure and facilitate processing.

[0150] For example, unlike... Figure 14 The arrangement shown allows for the provision of active material layers 32 with inconsistent compaction densities on both sides of the current collector 31, as described in this application embodiment. Specifically, the electrode 3 includes two active material layers 32, with the current collector 31 located between the two active material layers 32. These two active material layers 32 can be any active material layers 32 with inconsistent compaction densities as described above, thereby reducing lithium plating on both sides of the electrode 3 and further improving the performance of the electrode assembly 22 and the battery cell 20.

[0151] Figure 15 and Figure 16 This application illustrates two possible cross-sectional schematic diagrams of an electrode 3 comprising two active material layers 32, as shown in the embodiments of this application. Figure 15 and Figure 16 They can be respectively as follows Figures 4 to 6 A possible cross-sectional schematic diagram of any electrode 3, the cross-section being perpendicular to the length direction X of electrode 3.

[0152] In some embodiments, active material layers 32 are respectively disposed on both sides of the current collector 31, and are disposed in the same manner, so that the electrode 3 has a symmetrical structure with respect to the plane perpendicular to the thickness direction Z, which facilitates processing and improves processing efficiency. For example, with Figure 15 and Figure 16 For example, Figure 15 To adopt such Figure 8 Taking the current collector 31 and the two active material layers 32 as an example, the following configuration is used. Figure 16 To adopt such Figure 10The example shown illustrates the configuration of the current collector 31, two base coating layers 33, and two active material layers 32, but the embodiments of this application are not limited to this.

[0153] Figure 17 This illustration shows another possible cross-sectional schematic diagram of an electrode 3 comprising two active material layers 32, according to an embodiment of this application. Figure 17 It can be like Figures 4 to 6 A possible cross-sectional schematic diagram of any electrode 3, the cross-section being perpendicular to the length direction X of electrode 3.

[0154] In some embodiments, active material layers 32 are respectively disposed on both sides of the current collector 31, but the disposal method and / or the size of the layers can be different, so that the electrode 3 is an asymmetrical structure relative to the plane perpendicular to the thickness direction Z, which allows for more flexible placement and wider application. For example, as Figure 17 As shown, Figure 17 To adopt respectively, such as Figure 9 and Figure 10 The example shown illustrates the configuration of the current collector 31, two base coating layers 33, and two active material layers 32. Alternatively, any two other configurations shown in the embodiments can be used. Furthermore, the same configuration of the embodiment can be used, but with different thicknesses in the corresponding areas of the two active material layers 32; however, this application is not limited to these configurations.

[0155] In some embodiments, the average thickness of the center of the electrode 3 is substantially equal to the average thickness of the edge of the electrode 3. Specifically, as shown in the figure... Figures 14 to 16 As shown, the middle part of the electrode 3 corresponds to the middle part 311 of the current collector 31, and the edge of the electrode 3 corresponds to the edge 312 of the current collector 31. The average thickness of the middle part of the electrode 3 and the average thickness of the edge of the electrode 3 are both equal to H0, making both surfaces of the electrode 3 relatively flat, which facilitates subsequent processing into the electrode assembly 22. This makes the spacing between different electrode layers in the electrode assembly 22 relatively uniform, reducing the lithium plating problem caused by large spacing differences. This can improve the space utilization and energy density of the battery cell 20, and also reduce lithium plating during the long-term charge and discharge cycle of the battery cell 20, thereby improving the cycle life and safety of the battery cell 20.

[0156] It should be understood that the thickness direction dimensions of different types of electrode sheets 3 in this application embodiment can be flexibly set according to actual applications. For example, along the thickness direction Z of the electrode sheet 3, the ratio of the difference H1-H2 between the average thickness H1 of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 and the average thickness H2 of the portion 322 laid in the edge 312 of the current collector 31, and the average thickness H2 of the portion 322 of the active material layer 32 laid in the edge 312 of the current collector 31, is in the range of [1%, 3%].

[0157] If the ratio between the difference H1-H2 and the average thickness H2 is too small, the value of the difference H1-H2 of the electrode 3 will be set too small. The difference between the average compaction density of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 and the average compaction density of the portion 322 of the active material layer 32 laid in the edge 312 of the current collector 31 will also be too small, potentially affecting the performance of the electrode 3 and failing to effectively solve the lithium plating problem. Conversely, if the ratio between the difference H1-H2 and the average thickness H2 is too large, the value of the difference H1-H2 of the electrode 3 will be set too large, increasing the processing difficulty of the electrode 3 and potentially affecting its structural strength, thereby impacting the processing efficiency of the electrode assembly 22 and the battery cell 20.

[0158] For example, the ratio between the difference H1-H2 and the average thickness H2 can typically be set to 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, or 3%.

[0159] In this embodiment, the difference between the average thickness H1 of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 and the average thickness H2 of the portion 322 of the active material layer 32 laid in the edge 312 of the current collector 31 is equal to H1-H2. In different embodiments, this difference H1-H2 can be flexibly set.

[0160] For example, for such Figure 14 In the embodiment shown with uneven compaction density on one side, the range of the difference H1-H2 for the active material layer 32 on the side with uneven compaction density can be set according to the actual application.

[0161] For example, if electrode 3 is a positive electrode, the range of the difference H1-H2 is typically set to [1μm, 10μm]. For example, the difference H1-H2 can be equal to 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, or 10μm. As another example, if electrode 3 is a negative electrode, the range of the difference H1-H2 is typically set to [1μm, 6μm]. For example, the difference H1-H2 can be equal to 1μm, 2μm, 3μm, 4μm, 5μm, or 6μm.

[0162] For example, for such as Figures 15 to 17 When the compaction densities of the two active material layers 32 shown are not uniform, the range of the difference H1-H2 for each active material layer 32 can be set according to the actual application, and the difference H1-H2 between the two active material layers 32 can be equal or unequal. Here, we take any one active material layer 32 as an example.

[0163] For example, if the electrode 3 is a positive electrode, the range of the difference H1-H2 is typically set to [1μm, 4μm]. For example, the difference H1-H2 can be equal to 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, or 4μm. As another example, if the electrode 3 is a negative electrode, the range of the difference H1-H2 is typically set to [1μm, 3μm]. For example, the difference H1-H2 can be equal to 1μm, 1.5μm, 2μm, 2.5μm, or 3μm. The difference H1-H2 between the active material layers 32 on one side of the electrode 3 should not be too large to meet the structural strength requirements of the electrode 3 and improve its structural stability.

[0164] In some embodiments, the average thickness H1 of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 can be flexibly set according to the actual application; the average thickness H2 of the portion 322 of the active material layer 32 laid in the edge 312 of the current collector 31 can also be flexibly set according to the actual application. For the sake of simplicity, these will not be described in detail here.

[0165] It should be understood that the average thickness H1 of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 and the average thickness H2 of the portion 322 of the active material layer 32 laid in the edge 312 of the current collector 31 in the embodiments of this application may be related to a variety of factors. For example, it may be related to the compaction density of the active material layer 32, or it may be related to the quality of the material on the surface of the current collector 31.

[0166] In some embodiments, along the thickness direction Z of the electrode 3, the difference between the average thickness H1 of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 and the average thickness H2 of the portion 322 laid in the edge 312 of the current collector 31 is H, that is, the difference H is equal to H1-H2, and the unit of H is μm. The average compaction density of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 is Y, and the unit of Y is g / cm³. 3 H and Y satisfy Y = KH, where the value of K ranges from [0.1, 0.4].

[0167] Considering that the average compaction density of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 has a certain range, if the proportional coefficient K is too large, the difference H will be too large. In this case, on the one hand, the average thickness H1 of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 may be too large, which will make the thickness of the electrode 3 too large, thus affecting the energy density of the battery cell 20 formed by the electrode 3. On the other hand, the average thickness H2 of the portion 322 of the active material layer 32 laid in the edge 312 of the current collector 31 may be too small, which will result in a weaker structural strength of the electrode 3 and affect the performance of the electrode 3.

[0168] Conversely, if the proportionality coefficient K is too small, the difference H will be too small. For example, the difference H may approach zero, which will make the thickness H1 of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 approximately equal to the thickness H2 of the portion 322 of the active material layer 32 laid in the edge 312 of the current collector 31. Correspondingly, the difference between the average compaction density of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 and the average compaction density of the portion 322 of the active material layer 32 laid in the edge 312 of the current collector 31 will also be too small, which may affect the performance of the electrode 3 and fail to solve the lithium plating problem effectively.

[0169] Therefore, the scaling factor K in the embodiments of this application should not be too small. For example, the scaling factor K can be specifically set to 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 or 0.4 to improve the performance of the electrode 3 and effectively solve the problem of lithium plating.

[0170] In some embodiments, the average compaction density of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 is Y, where Y is in g / cm³. 3 The total coating mass of the material laid on the surface of the current collector 31 facing the active material layer 32 is M, where M is in g / 1540.25 mm. 2Y and M satisfy Y = NM, and the value of N is in the range of [1, 7]. The material applied to the surface of the current collector 31 facing the active material layer 32 includes the active material layer 32 applied to one side of the current collector 31 and the base coating layer 33, and the mass of the base coating layer 33 may be zero. That is, if no base coating layer 33 is provided between the current collector 31 and the active material layer 32, the total coating mass of the material applied to the surface of the current collector 31 facing the active material layer 32 includes the total mass of the active material layer 32 applied to one side of the current collector 31; if a base coating layer 33 is provided between the current collector 31 and the active material layer 32, the total coating mass of the material applied to the surface of the current collector 31 facing the active material layer 32 includes the sum of the total mass of the active material layer 32 applied to one side of the current collector 31 and the total mass of the base coating layer 33 applied between the current collector 31 and the active material layer 32.

[0171] It should be understood that, given a fixed total coating mass M of the material laid on the surface of the current collector 31 facing the active material layer 32, if the proportionality coefficient N is too large, the average compaction density Y of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 will be too large. Correspondingly, the average compaction density of the portion 322 of the active material layer 32 laid in the edge 312 of the current collector 31 will be even greater. This will increase the processing difficulty and cost of the electrode 3. Conversely, if the proportionality coefficient N is too small, the average compaction density Y of the portion 321 of the active material layer 32 laid in the middle 311 of the current collector 31 will be too small, failing to meet the design requirements of the electrode 3, reducing the performance of the electrode 3, and consequently reducing the performance of the electrode assembly 22 formed by the electrode 3.

[0172] Therefore, the value of the proportionality coefficient N should not be too large or too small. For example, the proportionality coefficient N can be specifically set to 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5 or 7 to improve the performance of the electrode 3.

[0173] In this embodiment, the total coating mass M of the material laid on the surface of the current collector 31 facing the active material layer 32 can be set according to the actual application. For example, if the electrode 3 is a positive electrode, the range of the total coating mass M can be set to [0.2g / 1540.25mm]. 2 0.4g / 1540.25mm 2 Specifically, the total coating mass M can be set to 0.2g / 1540.25mm. 2 0.23g / 1540.25mm 2 0.25g / 1540.25mm 2 0.28g / 1540.25mm2 0.3g / 1540.25mm 2 0.33g / 1540.25mm 2 0.35g / 1540.25mm 2 0.38g / 1540.25mm 2 Or 0.4g / 1540.25mm 2 For example, if electrode 3 is a negative electrode, then the total coating mass M can be set to a value within the range of [0.1g / 1540.25mm]. 2 0.2g / 1540.25mm 2 Specifically, the total coating mass M can be set to 0.1g / 1540.25mm. 2 0.11g / 1540.25mm 2 0.12g / 1540.25mm 2 0.13g / 1540.25mm 2 0.14g / 1540.25mm 2 0.15g / 1540.25mm 2 0.16g / 1540.25mm 2 0.17g / 1540.25mm 2 0.18g / 1540.25mm 2 0.19g / 1540.25mm 2 or

[0174] 0.2g / 1540.25mm 2 .

[0175] In this embodiment, the average compaction density of the portion 321 of the active material layer 32 of the electrode 3, which is laid in the middle 311 of the current collector 31, is less than the average compaction density of the portion 322 laid in the edge 312 of the current collector 31. That is, the porosity of the middle portion 321 of the active material layer 32 is greater than the porosity of the edge portion 322. This allows the middle region of the electrode 3 to hold more electrolyte, effectively solving the problem of lithium plating caused by electrolyte extrusion in the middle region. This effectively reduces lithium plating, thereby improving the performance and cycle life of the battery cell 20.

[0176] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. An electrode sheet, characterized in that, include: Current collector(31); An active material layer (32) is laid on the surface of the current collector (31); The average compaction density of the portion (321) of the active material layer (32) laid in the middle (311) of the current collector (31) is less than the average compaction density of the portion (322) laid at the edge (312) of the current collector (31); The average thickness of the portion (321) of the active material layer (32) laid in the middle (311) of the current collector (31) is greater than the average thickness of the portion (322) laid in the edge (312) of the current collector (31); The current collector (31) has a first groove (313) with an opening facing the active material layer (32) in the middle (311). The average thickness of the bottom wall of the first groove (313) is less than the average thickness of the edge (312) of the current collector (31).

2. The electrode sheet according to claim 1, characterized in that, The electrode also includes: An undercoating layer (33) is disposed in at least a portion of the area between the current collector (31) and the active material layer (32).

3. The electrode sheet according to claim 2, characterized in that, The middle part (311) of the current collector (31) is in direct contact with the active material layer (32), and the base coating layer (33) is provided between the edge (312) of the current collector (31) and the active material layer (32).

4. The electrode sheet according to claim 2, characterized in that, The base coating layer (33) is provided in the entire area between the current collector (31) and the active material layer (32).

5. The electrode sheet according to claim 4, characterized in that, The portion (331) of the base coating (33) corresponding to the middle (311) of the current collector (31) is provided with a second groove (333) with an opening facing the active material layer (32).

6. The electrode sheet according to claim 5, characterized in that, The average thickness of the bottom wall of the second groove (333) is less than the average thickness of the portion (332) of the base coating (33) corresponding to the edge (312) of the current collector (31).

7. The electrode sheet according to claim 1, characterized in that, The edge (312) of the current collector (31) includes a first part (3121) and a second part (3122), the first part (3121) being located at one end of the current collector (31) in the width direction of the electrode, the second part (3122) being located at the other end of the current collector (31) in the width direction of the electrode, and the middle part (311) of the current collector (31) being located between the first part (3121) and the second part (3122).

8. The electrode sheet according to claim 7, characterized in that, The edge (312) of the current collector (31) includes a third part (3123) and a fourth part (3124), the third part (3123) being located at one end of the current collector (31) along the length of the electrode; the fourth part (3124) being located at the other end of the current collector (31) along the length of the electrode; and the middle part (311) of the current collector (31) being located between the third part (3123) and the fourth part (3124).

9. The electrode sheet according to claim 7, characterized in that, Along the width direction of the electrode, the ratio of the average width of the middle part (311) of the current collector (31) to the average width of the electrode ranges from [1 / 3, 2 / 3].

10. The electrode sheet according to claim 9, characterized in that, Along the width direction of the electrode, the ratio of the average width of the middle part (311) of the current collector (31) to the average width of the electrode ranges from [40%, 60%].

11. The electrode sheet according to any one of claims 1 to 10, characterized in that, Along the thickness direction of the electrode, the difference between the average thickness of the portion (321) of the active material layer (32) laid in the middle (311) of the current collector (31) and the average thickness of the portion (322) laid in the edge (312) of the current collector (31) is [1%, 3%].

12. The electrode sheet according to any one of claims 1 to 10, characterized in that, Along the thickness direction of the electrode, the difference between the average thickness of the portion (321) of the active material layer (32) laid in the middle (311) of the current collector (31) and the average thickness of the portion (322) laid at the edge (312) of the current collector (31) is H, where H is in μm. The average compaction density of the portion (321) of the active material layer (32) laid in the middle (311) of the current collector (31) is Y, where Y is in g / cm³. 3 H and Y satisfy Y = KH, where the value of K ranges from [0.1, 0.4].

13. The electrode sheet according to any one of claims 1 to 10, characterized in that, The average compaction density of the portion (321) of the active material layer (32) laid in the middle (311) of the current collector (31) is Y, where the unit of Y is g / cm³. 3 The total coating mass of the material laid on the surface of the current collector (31) facing the active material layer (32) is M, where M is in g / 1540.25 mm. 2 Y and M satisfy Y = NM, where N takes values ​​in the range [1, 7].

14. The electrode sheet according to any one of claims 1 to 10, characterized in that, The average thickness of the middle part of the electrode is equal to the average thickness of the edge of the electrode.

15. The electrode sheet according to any one of claims 1 to 10, characterized in that, The electrode comprises two active material layers (32), and the current collector (31) is located between the two active material layers (32).

16. An electrode assembly, characterized in that, include: A positive electrode and a negative electrode, wherein the positive electrode and / or the negative electrode comprises an electrode as described in any one of claims 1 to 15.

17. The electrode assembly according to claim 16, characterized in that, The positive electrode and the negative electrode are wound together to form the electrode assembly.

18. The electrode assembly according to claim 17, characterized in that, The electrode assembly is cylindrical.

19. A single battery cell, characterized in that, include: The electrode assembly as described in any one of claims 16 to 18.

20. A battery, characterized in that, include: Multiple battery cells, wherein the battery cells are as described in claim 19.

21. An electrical appliance, characterized in that, include: The battery of claim 20 is used to provide electrical energy.

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