Pole piece, Battery cell, Battery, and Electric device

Abstract

Embodiments of the present application provide a pole piece, a battery monomer, a battery and an electric device. The pole piece includes an insulating base, a conductive layer and an active material layer. The conductive layer is arranged on the surface of the insulating base. The active material layer is coated on the surface of the conductive layer away from the insulating base. The conductive layer includes a first part coated with the active material layer and a second part not coated with the active material layer. The first part and the second part are arranged along a first direction. The resistivity of the conductive layer is p1, the specific heat capacity of the conductive layer is C, the density of the conductive layer is p2, and the constant K = p1 / (C p2). The thickness of the conductive layer is d1, the size of the first part along the first direction is W, and d1, W and K satisfy: 0.001 J / (Ω mm 4 ·℃)≤d1 / (K W)≤0.0075 J / (Ω mm 4 ·℃). The present application limits the value of d1 / (K W) to 0.001 J / (Ω mm 4 ·℃)-0.0075 J / (Ω mm 4 ·℃), balancing the cycle life and energy density of the battery monomer.

Description

Technical Field

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

[0002] Battery cells are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools. Battery cells can include nickel-cadmium battery cells, nickel-metal hydride battery cells, lithium-ion battery cells, and rechargeable alkaline zinc-manganese battery cells, among others.

[0003] In the development of battery technology, improving the safety of individual battery cells is a key research direction. Summary of the Invention

[0004] This application provides an electrode, a battery cell, a battery, and an electrical device that can improve the safety of the battery cell.

[0005] In a first aspect, embodiments of this application provide an electrode sheet comprising an insulating substrate, a conductive layer, and an active material layer. The conductive layer is disposed on the surface of the insulating substrate. The active material layer is coated on the surface of the conductive layer opposite to the insulating substrate. The conductive layer includes a first portion coated with the active material layer and a second portion uncoated with the active material layer, the first portion and the second portion being arranged along a first direction. The resistivity of the conductive layer is ρ1, the specific heat capacity of the conductive layer is C, the density of the conductive layer is ρ2, and the constant K = ρ1 / (C·ρ2). The thickness of the conductive layer is d1, and the dimension of the first portion along the first direction is W. d1, W, and K satisfy: 0.001 J / (Ω·mm²). 4 ·℃)≤d1 / (K·W)≤0.0075J / (Ω·mm 4 ·℃).

[0006] In the above technical solution, the conductive layer has a small thickness. When the conductive layer is punctured by an external structure, the burrs generated at the puncture site are small. This reduces the risk of burrs puncturing the separator, thereby reducing the possibility of short circuits and improving the safety of the battery cell.

[0007] The smaller the value of d1 / (K·W), the more heat is generated by the conductive layer during charging and discharging, the higher the temperature, the faster the active material layer coated on the conductive layer ages, and the faster the capacity of the battery cell decreases. If d1 / (K·W) is too large, the thickness d1 of the conductive layer will be over-designed, resulting in a lower energy density of the battery cell. The above technical solution limits the value of d1 / (K·W) to 0.001 J / (Ω·mm²). 4 ·℃)-0.0075J / (Ω·mm 4•℃) to balance the energy density and cycle life of individual battery cells.

[0008] In some implementations, d1, W, and K satisfy: 0.002 J / (Ω·mm 4 ·℃)≤d1 / (K·W)≤0.003J / (Ω·mm 4 ·℃).

[0009] In some implementations, d1 is 0.5 μm-5 μm.

[0010] In some embodiments, the electrode further includes a tab, which is welded to the second portion to form a first welded portion; in a first direction, one end of the tab opposite to the active material layer protrudes from the second portion. The portion of the tab protruding from the second portion in the first direction can be used to connect to the electrode lead-out structure of the battery cell.

[0011] In some implementations, the thickness of the tab is d2, where d2 is greater than d1. The thickness of the tab is greater than the thickness of the conductive layer to improve the tab's current-carrying capacity.

[0012] In some implementations, d2 is 1 μm-100 μm.

[0013] The smaller d2 is, the smaller the current-carrying area of ​​the tab, and the weaker the current-carrying capacity. The larger d2 is, the larger the volume and weight of the tab, the more heat is generated during the welding of the tab to the conductive layer, and the more prone the tab and conductive layer are to welding defects. The above technical solution limits the value of d2 to 1μm-100μm to ensure that the tab meets the current-carrying requirements and reduces the heat generated by the tab during the welding process.

[0014] In some embodiments, the electrode further includes an adhesive layer that is attached to the tab and covers at least a portion of the first weld.

[0015] In the above technical solution, the adhesive layer can fix at least some of the particles on the first welding part, reducing the risk of particles falling into the electrode assembly and improving safety.

[0016] In some embodiments, a portion of the adhesive layer is located between the active material layer and the tab in a first direction, coated on a second portion, and attached to the active material layer.

[0017] In the above technical solution, the adhesive layer is connected to the active material layer, which can cover the connection between the first part and the second part, reducing the risk of cracking of the conductive layer and ensuring the current carrying capacity of the conductive layer. The adhesive layer can also connect the tab to the conductive layer and the active material layer, thereby reducing the risk of tab detachment.

[0018] In some embodiments, the electrode further includes an insulating layer, at least a portion of which is located on the side of the adhesive layer opposite to the first weld portion and is attached to the adhesive layer.

[0019] In the above technical solution, the insulating layer protects the adhesive layer, reducing the risk of short circuits caused by the weld puncturing the adhesive layer and improving safety. The insulating layer also improves the insulation of the electrode sheets, reducing the risk of short circuits caused by the positive and negative electrode sheets colliding. The adhesive layer further connects the insulating layer to the tabs, reducing the risk of the insulating layer detaching.

[0020] In some embodiments, both the insulating layer and the adhesive layer include an adhesive, the weight ratio of the adhesive in the insulating layer to the insulating layer is N1, and the weight ratio of the adhesive in the adhesive layer to the adhesive layer is N2, where N1 is less than N2.

[0021] In the above technical solution, the adhesive content of the adhesive layer is relatively high, which allows it to adhere better to the first welded part and reduces the risk of separation between the adhesive layer and the first welded part. The insulating layer does not need to be connected to the first welded part and can contain less adhesive. In this way, the insulating layer can be made of more high-strength materials to improve the overall strength of the insulating layer.

[0022] In some embodiments, the insulating layer completely covers the adhesive layer to reduce the exposed area of ​​the adhesive layer and reduce the risk of the adhesive layer separating from the first weld during immersion in the electrolyte.

[0023] In some embodiments, the electrode further includes an insulating layer connected to the tab and the active material layer, and the insulating layer covers at least a portion of the first weld.

[0024] In the above technical solution, the insulating layer can fix at least some of the particles on the first welding part, reducing the risk of particles falling into the electrode assembly and improving safety.

[0025] In some embodiments, the insulating layer comprises ceramic particles and an adhesive, wherein the weight ratio of the adhesive to the insulating layer is greater than or equal to 0.1. A higher adhesive content in the insulating layer allows for better adhesion to the first weld joint, reducing the risk of separation between the insulating layer and the first weld joint.

[0026] In some implementations, in the first direction, the portion of the tab extending beyond the conductive layer is not coated with an insulating layer to reduce the risk of interference between the insulating layer and the electrode lead-out structure.

[0027] In some embodiments, the electrode tab includes a plurality of tab portions spaced apart along a second direction, the second direction being perpendicular to the first direction and the thickness direction of the electrode sheet. In the first direction, the tab portions protrude from the second portions.

[0028] The above technical solution divides the electrode tab into multiple separate electrode tab parts, which makes it easier for the electrode tab parts to be bent after the electrode sheet is wound.

[0029] Secondly, embodiments of this application provide a battery cell including a housing, an electrode assembly, and an electrode lead-out structure. The electrode assembly is housed within the housing. The electrode assembly includes electrode plates as described in any embodiment of the first aspect. The electrode lead-out structure is disposed on the housing and connected to an electrode tab.

[0030] In some embodiments, two conductive layers are provided, one on each side of the insulating substrate. The tabs include a first tab and a second tab, which are respectively welded to the second portion of the two conductive layers. The first tab and the second tab are used to draw current from the two conductive layers.

[0031] In some embodiments, the electrode lead-out structure has a connecting portion. In a first direction, the connecting portion is located on the side of the first electrode tab away from the active material layer. The connecting portion abuts and is welded to the first electrode tab and to the second electrode tab. The thickness of the connecting portion is t. The first electrode tab, in its flattened state, extends beyond the first welding portion in the first direction by a dimension h2, where t and h2 satisfy: 2.5 ≤ h2 / t ≤ 10. The second electrode tab, in its flattened state, extends beyond the first welding portion in the first direction by a dimension h3, where t and h3 satisfy: 2.5 ≤ h3 / t ≤ 10.

[0032] In the above technical solution, the larger h2 is, the larger the portion of the first electrode tab that can be welded to the connecting part, but the larger the space occupied by the first electrode tab is also; the smaller the value of t is, the less heat is generated during welding, the lower the connection strength between the first electrode tab and the connecting part, and the smaller the current carrying capacity of the connecting part. The smaller h2 is, the smaller the portion of the first electrode tab that can be welded to the connecting part, but the smaller the space occupied by the first electrode tab is also; the larger the value of t is, the more heat is generated during welding, the more heat is transferred to the first electrode tab and the isolator, and the higher the risk of the electrode tab and the isolator being burned. The above technical solution limits the value of h2 / t to 2.5-10 to ensure the connection strength between the connecting part and the first electrode tab, reduce the risk of the first electrode tab being melted through, and improve the energy density. Similarly, the above technical solution limits the value of h3 / t to 2.5-10 to ensure the connection strength between the connecting part and the second electrode tab, reduce the risk of the second electrode tab being melted through, and improve the energy density.

[0033] In some embodiments, in a first direction, the end of the first electrode tab facing away from the active material layer extends beyond the second electrode tab, and the second electrode tab bends toward the first electrode tab and connects to the first electrode tab. The electrode lead-out structure has a connecting portion, which is located on the side of the first electrode tab facing away from the active material layer in the first direction, and the connecting portion abuts against and is welded to the first electrode tab. The thickness of the connecting portion is t, and the dimension of the first electrode tab extending beyond the first welded portion in the first direction in the flattened state is h2, where t and h2 satisfy: 5 ≤ h2 / t ≤ 20.

[0034] The second electrode tab is not welded to the connecting part. Therefore, the above technical solution limits the value of h2 / t to 5-20 to ensure the connection strength between the connecting part and the first electrode tab, reduce the risk of the first electrode tab being melted through, and improve the energy density. Compared with the solution where both the first and second electrode tabs are welded to the connecting part, the solution where only the first electrode tab is welded to the connecting part requires the first electrode tab to have a larger h2.

[0035] In some embodiments, the electrode is wound in multiple turns. In the radial direction of the electrode assembly, the spacing between two adjacent turns of the electrode is d3, where 0.2 mm ≤ d3 ≤ 0.4 mm.

[0036] In the above technical solution, the electrode sheet is wound into multiple turns, and correspondingly, the electrode tabs are also wound into multiple turns. The larger the value of d3, the greater the distance between two adjacent turns of the electrode tabs, increasing the risk of the laser passing between the tabs during welding of the electrode tabs and electrode lead-out structures. If the value of d3 is too large, the insulating components of the electrode assembly may be burned by the laser, posing a safety risk. Therefore, the above technical solution limits the value of d3 to less than or equal to 0.4 mm to improve safety.

[0037] In some embodiments, the electrode lead-out structure has a connecting portion located on the side of the tab away from the active material layer in a first direction, and the connecting portion abuts against and is welded to the tab. The electrode assembly also includes a spacer, which is stacked and wound with the electrode sheet. In the first direction, the minimum distance between the surface of the connecting portion abutting against the first tab and the spacer is S1, and the thickness of the connecting portion is t, where S1 ≥ 0.75t.

[0038] The larger the value of t, the greater the heat generated between the welded joint and the first electrode tab; the smaller S1, the shorter the heat conduction path between the insulating component and the joint, the more heat is conducted to the insulating component, and the higher the risk of the insulating component being burned. The above technical solution limits S1 to greater than or equal to 0.75t to reduce the heat conducted to the insulating component and reduce the risk of the insulating component being burned.

[0039] In some embodiments, the tab is wound into multiple turns along the winding direction, and the end of the multiple turns of the tab away from the active material layer is flattened to form an end face, and the electrode lead-out structure is welded to the end face.

[0040] In some embodiments, the electrode sheet is wound multiple turns along the winding direction. The tabs include multiple tab portions spaced apart along the winding direction, and the multiple tab portions are bent toward the winding center of the electrode sheet to form an end face, to which the electrode lead-out structure is welded.

[0041] Thirdly, embodiments of this application provide a battery comprising a plurality of battery cells according to any of the embodiments of the second aspect.

[0042] Fourthly, embodiments of this application provide an electrical device including a battery cell according to any embodiment of the second aspect, wherein the battery cell is used to provide electrical energy. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0044] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0045] Figure 2 Explosion diagrams of batteries provided for some embodiments of this application;

[0046] Figure 3 for Figure 2 The diagram shows the structure of the battery module.

[0047] Figure 4 This is an exploded schematic diagram of a battery cell provided in some embodiments of this application;

[0048] Figure 5 A partial cross-sectional schematic diagram of a battery cell provided in some embodiments of this application;

[0049] Figure 6 This is a schematic diagram of the structure of the electrode assembly of a battery cell provided in some embodiments of this application;

[0050] Figure 7 This is a schematic diagram of the structure of the electrode provided in some embodiments of this application;

[0051] Figure 8 for Figure 7 The diagram shows a cross-sectional view of the electrode along line AA.

[0052] Figure 9 A cross-sectional schematic diagram of the electrode provided in some embodiments of this application;

[0053] Figure 10 Cross-sectional schematic diagrams of electrode sheets provided for other embodiments of this application;

[0054] Figure 11 A partial structural schematic diagram of a battery cell provided in some embodiments of this application;

[0055] Figure 12 A cross-sectional schematic diagram of an electrode sheet provided for some embodiments of this application;

[0056] Figure 13 A partial structural schematic diagram of a battery cell provided in some embodiments of this application;

[0057] Figure 14 Schematic diagrams of the electrode sheet in its unfolded state provided in some embodiments of this application;

[0058] Figure 15 This is a partial schematic diagram of a battery cell provided in some embodiments of this application.

[0059] The reference numerals in the accompanying drawings for the specific embodiments are as follows:

[0060] 1. Vehicle; 2. Battery; 3. Controller; 4. Motor; 5. Housing; 5a. First housing section; 5b. Second housing section; 5c. Receiving space; 6. Battery module; 7. Battery cell; 10. Electrode assembly; 11. Electrode sheet; 111. Insulating substrate; 112. Conductive layer; 112a. First part; 112b. Second part; 113. Active material layer; 114. Tab; 114a. First tab; 114b. Diode tab; 114c, end face; 114d, tab portion; 115, first weld portion; 116, adhesive layer; 117, insulating layer; 11a, first electrode; 11b, second electrode; 12, separator; 20, outer shell; 21, housing; 22, end cap; 30, electrode lead-out structure; 31, electrode terminal; 32, current collector; 33, connecting portion; V, winding direction; X, first direction; Y, second direction; Z, thickness direction. Detailed Implementation

[0061] 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.

[0062] 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.

[0063] In this application, the reference to "embodiment" means that a particular 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 in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0064] 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.

[0065] 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: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0066] 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.

[0067] In this application, "multiple" means two or more (including two).

[0068] In this application, the term "parallel" includes not only the case of absolute parallelism, but also the case of approximate parallelism as commonly understood in engineering; similarly, "perpendicular" includes not only the case of absolute perpendicularity, but also the case of approximate perpendicularity as commonly understood in engineering.

[0069] In this application, the battery cell may include a lithium-ion secondary battery cell, a lithium-ion primary battery cell, a lithium-sulfur battery cell, a sodium-lithium-ion battery cell, a sodium-ion battery cell, or a magnesium-ion battery cell, etc., and the embodiments of this application are not limited thereto. The battery cell may be cylindrical, flat, cuboid, or other shapes, etc., and the embodiments of this application are not limited thereto.

[0070] The battery mentioned in the embodiments of this application refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity. A battery may also generally include a housing for encapsulating one or more battery cells. The housing prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0071] A battery cell comprises electrode components and an electrolyte. The electrode components include a positive electrode, a negative electrode, and a separator. The battery cell primarily functions by the movement of metal ions between the positive and negative electrodes. The positive electrode includes a positive current collector and a positive active material layer, which is coated on the surface of the positive current collector. Taking a lithium-ion battery as an example, the positive current collector can be made of aluminum, and the positive active material layer includes the positive active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode includes a negative current collector and a negative active material layer, which is coated on the surface of the negative current collector. The negative current collector can be made of copper, and the negative active material layer includes the negative active material, which can be carbon or silicon, etc. The separator can be made of PP (polypropylene) or PE (polyethylene), etc.

[0072] In a battery cell, the current collector (such as the positive electrode current collector or the negative electrode current collector) is an indispensable part. It not only carries the active material, but also collects the electrons generated by the electrochemical reaction and guides them to the external circuit, thereby realizing the process of converting chemical energy into electrical energy.

[0073] In related technologies, current collectors are generally made of metal foil, but metal foil has a large weight, which limits the further improvement of the energy density of battery cells. During the use of a battery cell, when the current collector of the electrode is punctured by an external structure, burrs will be generated at the puncture site. These burrs can easily puncture the separator and cause the positive and negative electrodes to conduct, thereby causing an internal short circuit in the battery cell and posing a risk of fire or explosion.

[0074] To improve safety, the inventors designed an electrode employing a multi-layered current collector. Specifically, the current collector may include an insulating substrate and a conductive layer disposed on the surface of the insulating substrate. The active material layer of the electrode may be coated on the surface of the conductive layer facing away from the insulating substrate. The conductive layer can collect electrons generated by the electrochemical reaction and guide them to the external circuit. With the same thickness, compared to current collectors made of metal foil, the multi-layered current collector including the insulating substrate has a smaller weight, thereby further increasing the energy density of the battery cell. The smaller thickness of the conductive layer results in less burr at the puncture site when the current collector is punctured by an external structure. This reduces the risk of burrs puncturing the separator, thereby reducing the possibility of short circuits and improving the safety of the battery cell.

[0075] The inventors noted that although the current collector with a multi-layer structure reduces the thickness of the conductive layer, the reduction in the thickness of the conductive layer also reduces the current carrying capacity of the conductive layer. If the thickness of the conductive layer is too small, it will cause severe heat generation in the conductive layer, affecting the cycle life of the battery cell.

[0076] In view of this, embodiments of this application provide an electrode sheet that adjusts the thickness of the conductive layer by combining the current carrying capacity of the conductive layer and the size of the electrode sheet, so as to reduce the thickness of the conductive layer while meeting the current carrying capacity requirements of the conductive layer, thereby extending the cycle life of the battery cell and improving the energy density of the battery cell.

[0077] The electrode plates described in the embodiments of this application are applicable to battery cells, batteries, and electrical devices that use batteries.

[0078] Electrical devices 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 devices.

[0079] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device.

[0080] Figure 1 The diagram shows the structural features of a vehicle provided in some embodiments of this application.

[0081] like Figure 1 As shown, a battery 2 is installed inside the vehicle 1. The battery 2 can be located at the bottom, front, or rear of the vehicle 1. The battery 2 can be used to power the vehicle 1; for example, the battery 2 can serve as the operating power source for the vehicle 1.

[0082] Vehicle 1 may also include controller 3 and motor 4. Controller 3 is used to control battery 2 to supply power to motor 4, for example, for the power needs of vehicle 1 during start-up, navigation and driving.

[0083] In some embodiments of this application, the battery 2 can not only serve as the operating power source for the vehicle 1, but also as the driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0084] Figure 2This is an exploded schematic diagram of a battery provided for some embodiments of this application.

[0085] like Figure 2 As shown, battery 2 includes a housing 5 and battery cells ( Figure 2 (Not shown), the battery cells are housed inside the casing 5.

[0086] The housing 5 is used to house individual battery cells, and the housing 5 can have various structures. In some embodiments, the housing 5 may include a first housing portion 5a and a second housing portion 5b, which overlap each other, and together define a housing space 5c for housing the individual battery cells. The second housing portion 5b may be a hollow structure with one end open, and the first housing portion 5a may be a plate-like structure, with the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c; alternatively, both the first housing portion 5a and the second housing portion 5b may be hollow structures with one side open, with the open side of the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c. Of course, the first housing portion 5a and the second housing portion 5b can have various shapes, such as cylinders, cuboids, etc.

[0087] To improve the sealing performance after the first housing part 5a and the second housing part 5b are connected, a sealing element, such as sealant or sealing ring, can also be provided between the first housing part 5a and the second housing part 5b.

[0088] Assuming that the first box section 5a covers the top of the second box section 5b, the first box section 5a can also be called the upper box cover, and the second box section 5b can also be called the lower box.

[0089] In battery 2, there can be one or more individual battery cells. If there are multiple individual battery cells, they can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple individual battery cells are connected in both series and parallel configurations. Multiple individual battery cells can be directly connected in series, parallel, or in a mixed configuration and then housed within housing 5. Alternatively, multiple individual battery cells can first be connected in series, parallel, or in a mixed configuration to form battery module 6, and then multiple battery modules 6 can be connected in series, parallel, or in a mixed configuration to form a whole and housed within housing 5.

[0090] Figure 3 for Figure 2 The diagram shows the structure of the battery module.

[0091] like Figure 3 As shown, in some embodiments, there are multiple battery cells 7, which are first connected in series, parallel, or mixed to form a battery module 6. The multiple battery modules 6 are then connected in series, parallel, or mixed to form a whole and housed in a casing.

[0092] Multiple battery cells 7 in battery module 6 can be electrically connected through a busbar component to achieve parallel, series, or mixed connection of multiple battery cells 7 in battery module 6.

[0093] The battery cell 7 can be a cylindrical battery cell, a square battery cell, or a battery cell of other shapes.

[0094] Figure 4 This is an exploded schematic diagram of a battery cell provided in some embodiments of this application; Figure 5 A partial cross-sectional schematic diagram of a battery cell provided in some embodiments of this application; Figure 6 This is a schematic diagram of the structure of the electrode assembly of a battery cell provided in some embodiments of this application.

[0095] like Figures 4 to 6 As shown, the battery cell 7 in this embodiment includes a housing 20 and an electrode assembly 10, with the electrode assembly 10 housed within the housing 20.

[0096] The outer shell 20 is a hollow structure, with an internal cavity for accommodating the electrode assembly 10 and the electrolyte. The shape of the outer shell 20 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is cylindrical, a cylindrical outer shell can be used; if the electrode assembly 10 is cuboid, a cuboid outer shell can be used. Optionally, both the electrode assembly 10 and the outer shell 20 are cylindrical.

[0097] In some embodiments, the housing 20 includes a housing 21 and an end cap 22, the housing 21 having an opening and the end cap 22 being connected to the housing 21 and used to close the opening.

[0098] End cap 22 is sealed to housing 21 to form a sealed space for accommodating electrode assembly 10 and electrolyte. In some examples, housing 21 has an opening at one end, and end cap 22 is configured as one that covers the opening of housing 21. In other examples, housing 21 has openings at both opposite ends, and end cap 22 is configured as two, with each end cap 22 covering one of the two openings of housing 21.

[0099] In some embodiments, the electrode assembly 10 includes electrodes and a spacer 12. Exemplarily, multiple electrodes are provided, including a first electrode 11a and a second electrode 11b with opposite polarities, and the spacer 12 is used to insulate the first electrode 11a and the second electrode 11b. The electrode assembly 10 operates primarily by the movement of metal ions between the first electrode 11a and the second electrode 11b.

[0100] One of the first electrode 11a and the second electrode 11b is the positive electrode, and the other of the first electrode 11a and the second electrode 11b is the negative electrode.

[0101] In some embodiments, the first electrode 11a, the second electrode 11b, and the spacer 12 are all strip structures, and the first electrode 11a, the second electrode 11b, and the spacer 12 are wound together around a central axis to form a wound structure. The wound structure can be a cylindrical structure, a flat structure, or other shapes.

[0102] In some embodiments, the battery cell 7 further includes an electrode lead-out structure 30 disposed on the housing 20 and used for electrical connection with the electrode assembly 10 to discharge the electrical energy generated by the electrode assembly 10.

[0103] In some embodiments, the electrode lead-out structure 30 includes an electrode terminal 31, at least a portion of which is exposed to the outside of the housing 20 to enable electrical connection with other structures (e.g., busbar components).

[0104] In some embodiments, at least a portion of the electrode terminal 31 is housed within the housing 20 and directly connected to the electrode sheet; exemplarily, the electrode terminal 31 is welded to the electrode sheet.

[0105] In other embodiments, the electrode lead-out structure 30 further includes a current collector 32 for connecting the electrode sheet and the electrode terminal 31. Exemplarily, during assembly, the first electrode sheet 11a can be welded to the current collector 32 first, and then the current collector 32 can be welded to the electrode terminal 31.

[0106] In some other embodiments, the electrode lead-out structure 30 may be integrally formed with the housing 20. For example, the electrode lead-out structure 30 may be integrally formed with the end cap 22, and the first electrode 11a may be directly welded to the end cap 22.

[0107] Figure 7 This is a schematic diagram of the structure of the electrode provided in some embodiments of this application; Figure 8 for Figure 7 The diagram shows a cross-sectional view of the electrode along line AA.

[0108] like Figure 7 and Figure 8As shown, the electrode 11 in this embodiment includes an insulating substrate 111, a conductive layer 112, and an active material layer 113. The conductive layer 112 is disposed on the surface of the insulating substrate 111. The active material layer 113 is coated on the surface of the conductive layer 112 facing away from the insulating substrate 111. The conductive layer 112 includes a first portion 112a coated with the active material layer 113 and a second portion 112b uncoated with the active material layer 113. The first portion 112a and the second portion 112b are arranged along a first direction X. The resistivity of the conductive layer 112 is ρ1, the specific heat capacity of the conductive layer 112 is C, the density of the conductive layer 112 is ρ2, and the constant K = ρ1 / (C·ρ2). The thickness of the conductive layer 112 is d1, the dimension of the first portion 112a along the first direction X is W, and d1, W, and K satisfy: 0.001 J / (Ω·mm). 4 ·℃)≤d1 / (K·W)≤0.0075J / (Ω·mm 4 ·℃).

[0109] In this embodiment, the conductive layer 112 can be disposed on one side surface of the insulating substrate 111, or on opposite side surfaces of the insulating substrate 111. In this embodiment, the thickness d1 refers to the thickness of the conductive layer 112 disposed on one side surface of the insulating substrate 111. Exemplarily, conductive layers 112 are disposed on both side surfaces of the insulating substrate 111, and the thickness of the conductive layer 112 on both side surfaces is d1.

[0110] In this embodiment, the electrode 11 can be either the positive electrode or the negative electrode in the electrode assembly 10.

[0111] For example, conductive layers 112 are provided on both sides of the insulating substrate 111, and an active material layer 113 is coated on the surface of each conductive layer 112.

[0112] The surface of the first part 112a facing away from the insulating substrate 111 is covered by an active material layer 113, while the surface of the second part 112b facing away from the insulating substrate 111 is not covered by the active material layer 113. The surface of the second part 112b facing away from the insulating substrate 111 may be exposed or coated with other coatings that do not contain active materials.

[0113] The active material layer 113 is used to generate an electric current by electrochemically interacting with the electrolyte. The first part 112a can collect the generated current and guide it to the external circuit through the second part 112b.

[0114] For example, the size of the active material layer 113 along the first direction X is the same as the size of the first portion 112a along the first direction X.

[0115] The current-carrying capacity of the conductive layer 112 is related to its resistivity ρ1, specific heat capacity C, and density ρ2. Specifically, the smaller the K value, the higher the current-carrying capacity of the conductive layer 112; the larger the K value, the weaker the current-carrying capacity of the conductive layer 112.

[0116] The smaller the value of d1, the greater the resistance of the conductive layer 112, and the higher the heat generated when current passes through it; the larger the value of K, the weaker the current carrying capacity of the conductive layer 112.

[0117] During charging and discharging, the first part 112a collects the current generated by the active material layer 113 and conducts it to the second part 112b. The current collected in the region of the first part 112a far from the second part 112b needs to flow through the region of the first part 112a close to the second part 112b to reach the second part 112b. Therefore, during charging and discharging, the current flowing through the region of the first part 112a close to the second part 112b is larger, and the heat generated in this region is greater. The larger the value of W, the larger the capacity of the active material layer 113, the greater the current generated by the active material layer 113 during charging and discharging, and the higher the heat generated in the region of the first part 112a close to the second part 112b.

[0118] In summary, the smaller the value of d1 / (K·W), the more heat is generated by the conductive layer 112 during charging and discharging, the higher the temperature, the faster the active material layer 113 coated on the conductive layer 112 ages, and the faster the capacity of the battery cell 7 decreases. If the value of d1 / (K·W) is too small, the temperature of the electrode 11 will be too high under high-rate charging and discharging conditions, causing the active material layer 113 to age faster, the battery cell 7 will not meet the lifespan requirements, and may even cause safety problems.

[0119] Through research and experimentation, the inventors limited the value of d1 / (K·W) to greater than or equal to 0.001J / (Ω·mm²). 4 The temperature of the battery cell 7 is reduced by ℃ to reduce the heat generated by the electrode 11 during the charging and discharging process, thereby lowering the temperature of the battery cell 7 and enabling the battery cell 7 to be used under high-rate charging and discharging conditions, ensuring the cycle life of the battery cell 7 and reducing safety risks.

[0120] The larger the value of d1, the larger the volume and weight of the conductive layer 112, and the lower the energy density of the battery cell 7. The smaller the value of K, the higher the current carrying capacity of the conductive layer 112, and the less the electrode 11 needs the thickness of the conductive layer 112. The smaller the value of W, the smaller the current on the conductive layer 112, and the less the electrode 11 needs the thickness of the conductive layer 112.

[0121] If d1 / (K·W) is too large, the thickness d1 of the conductive layer 112 will be too large, resulting in a low energy density of the battery cell 7.

[0122] Through research and experimentation, the inventors limited the value of d1 / (K·W) to less than or equal to 0.0075 J / (Ω·mm²). 4 The thickness of the conductive layer 112 is reduced to increase the energy density of the battery cell 7 and extend the cycle life of the battery cell 7 when the current carrying capacity and heat generation of the conductive layer 112 meet the requirements.

[0123] In some embodiments, the conductive layer 112 may be copper foil, aluminum foil, or nickel foil. For example, the K value of the copper foil is 0.0050 Ω·mm. 4 ·℃ / J, the K value of the aluminum foil is 0.0120Ω·mm. 4 ·℃ / J, the K value of the nickel foil is 0.0167Ω·mm. 4 ·℃ / J.

[0124] In some embodiments, the value of d1 / (K·W) is 0.001J / (Ω·mm²). 4 ·℃), 0.002J / (Ω·mm 4 ·℃), 0.003J / (Ω·mm 4 ·℃), 0.005J / (Ω·mm 4 ·℃), 0.007J / (Ω·mm 4 ·℃) or 0.0075J / (Ω·mm 4 ·℃).

[0125] In some embodiments, d1, W, and K satisfy: 0.002 J / (Ω·mm 4 ·℃)≤d1 / (K·W)≤0.003J / (Ω·mm 4 ·℃).

[0126] In some embodiments, d1 is 0.5 μm-5 μm. Optionally, d1 is 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm.

[0127] In some embodiments, the electrode 11 further includes a tab 114, which is welded to the second portion 112b to form a first weld portion 115. In the first direction X, one end of the tab 114 opposite to the active material layer 113 protrudes from the second portion 112b.

[0128] In the thickness direction Z of the electrode sheet 11, a portion of the tab 114 overlaps with the second portion 112b; the portion of the tab 114 that overlaps with the second portion 112b is welded to the second portion 112b and forms a first welded portion 115.

[0129] The tab 114 can be used to draw out the current on the second part 112b.

[0130] The portion of tab 114 that protrudes from the second part 112b in the first direction X can be used to connect to the electrode lead-out structure.

[0131] In some embodiments, the thickness of the tab 114 is d2, where d2 is greater than d1. The thickness of the tab 114 is greater than the thickness of the conductive layer 112 to improve the current carrying capacity of the tab 114.

[0132] In some embodiments, d2 is 1μm-100μm.

[0133] The smaller d2 is, the smaller the current-carrying area of ​​the tab 114, and the weaker its current-carrying capacity. The larger d2 is, the larger the volume and weight of the tab 114, the more heat is generated during the welding of the tab 114 and the conductive layer 112, and the more prone the tab 114 and the conductive layer 112 are to welding defects. The inventors limited the value of d2 to 1μm-100μm to ensure that the tab 114 meets the current-carrying requirements and to reduce the heat generated by the tab 114 during the welding process.

[0134] In some embodiments, two conductive layers 112 are provided, with the two conductive layers 112 respectively disposed on both sides of the insulating substrate 111. The tabs 114 include a first tab 114a and a second tab 114b, which are respectively welded to the second portions 112b of the two conductive layers 112. The first tab 114a and the second tab 114b are respectively used to draw out the current from the two conductive layers 112.

[0135] The aforementioned d2 refers to the thickness of a single tab 114. For example, the thickness of both the first tab 114a and the second tab 114b is d2.

[0136] In the first direction X, the dimensions of the first tab 114a and the second tab 114b may be the same or different. In some examples, the end of the first tab 114a facing away from the active material layer 113 is flush with the end of the second tab 114b facing away from the active material layer 113. In other examples, the end of the first tab 114a facing away from the active material layer 113 extends beyond the second tab 114b, and the second tab 114b is bent toward and connected to the first tab 114a.

[0137] In some embodiments, the first tab 114a is welded to the corresponding conductive layer 112 to form a first welding sub-part, and the second tab 114b is welded to the corresponding conductive layer 112 to form a second welding sub-part. The first welding part 115 includes the first welding sub-part and the second welding sub-part.

[0138] In some examples, the insulating substrate 111 separates the first weld sub-part and the second weld sub-part. In other examples, a portion of the insulating substrate 111 is soldered through, and the first weld sub-part and the second weld sub-part are directly joined together.

[0139] Figure 9 This is a cross-sectional schematic diagram of an electrode sheet provided in some embodiments of this application.

[0140] like Figure 9 As shown, in some embodiments, the electrode 11 further includes an adhesive layer 116, which is connected to the tab 114 and covers at least a portion of the first weld portion 115.

[0141] The adhesive layer 116 may cover a portion of the first welded portion 115 or the entire first welded portion 115.

[0142] The adhesive layer 116 can be applied only to the tab 114, or it can be applied to both the conductive layer 112 and the tab 114.

[0143] Some particles may remain on the first weld portion 115. When the battery cell 7 is subjected to external impact, these particles may fall into the interior of the electrode assembly, causing a short circuit risk. The adhesive layer 116 of this embodiment can fix at least some of the particles on the first weld portion 115, reducing the risk of particles falling into the electrode assembly and improving safety.

[0144] In some embodiments, the adhesive layer 116 is formed by curing a colloid. Exemplarily, the colloid includes an adhesive, which may include at least one of epoxy resin, acrylate, and styrene-butadiene rubber.

[0145] In some embodiments, the colloid comprises ceramic particles, which may include at least one of boehmite, silica, and zirconium oxide. The ceramic particles can enhance the puncture strength and insulation of the adhesive layer 116.

[0146] In some embodiments, the colloid includes a color recognition agent, such as charcoal, Prussian blue, etc.

[0147] In some embodiments, the viscosity of the colloid is 1000 MPa·s. The colloid has good flowability during coating, which can cover the uneven areas of the first weld portion 115 and reduce the risk of missed coating.

[0148] In some embodiments, the thickness of the adhesive layer 116 is 0.01 mm to 0.1 mm. The adhesive layer 116 has good toughness and strength, and it is not easy to fall off during the winding and molding process of the electrode assembly 10.

[0149] In some embodiments, a portion of the adhesive layer 116 is located between the active material layer 113 and the tab 114 in the first direction X, coated on the second portion 112b and connected to the active material layer 113.

[0150] During the forming process of electrode 11, the active material layer 113 generally needs to be rolled to increase its compaction density. During rolling, the first part 112a is stressed while the second part 112b is not. This can easily lead to stress concentration at the connection between the first part 112a and the second part 112b, increasing the risk of cracking at the connection.

[0151] The adhesive layer 116 is connected to the active material layer 113 and can cover the connection between the first part 112a and the second part 112b, reducing the risk of cracking of the conductive layer 112 and ensuring the current carrying capacity of the conductive layer 112. The adhesive layer 116 can also connect the tab 114 to the conductive layer 112 and the active material layer 113, thereby reducing the risk of the tab 114 falling off.

[0152] In some embodiments, the electrode 11 further includes an insulating layer 117, at least a portion of which is located on the side of the adhesive layer 116 opposite to the first weld portion 115 and is connected to the adhesive layer 116.

[0153] The insulating layer 117 protects the adhesive layer 116, reducing the risk of short circuits caused by the weld puncturing the adhesive layer 116 and improving safety. The insulating layer 117 also improves the insulation of the electrode 11, reducing the risk of short circuits caused by the positive and negative electrodes colliding. The adhesive layer 116 also connects the insulating layer 117 to the tab 114, reducing the risk of the insulating layer 117 detaching.

[0154] In some embodiments, the insulating layer 117 completely covers the adhesive layer 116 to reduce the exposed area of ​​the adhesive layer 116 and reduce the risk of the adhesive layer 116 separating from the first weld portion 115 during immersion in the electrolyte.

[0155] In this embodiment, "covering" refers to covering in the thickness direction Z, that is, the insulating layer 117 completely covers the adhesive layer 116 in the thickness direction Z of the electrode 11.

[0156] In some embodiments, both the insulating layer 117 and the adhesive layer 116 include an adhesive, the weight ratio of the adhesive in the insulating layer 117 to the insulating layer 117 is N1, and the weight ratio of the adhesive in the adhesive layer 116 to the adhesive layer 116 is N2, where N1 is less than N2.

[0157] The adhesive layer 116 has a higher adhesive content, which allows it to adhere better to the first welded portion 115 and reduces the risk of separation between the adhesive layer 116 and the first welded portion 115. The insulating layer 117 does not need to be connected to the first welded portion 115 and can contain less adhesive. In this way, the insulating layer 117 can be made of more high-strength material to improve the overall strength of the insulating layer 117.

[0158] In some embodiments, the insulating layer 117 is formed by curing an insulating slurry. The insulating slurry may include ceramic particles and an adhesive. The ceramic particles may include at least one of alumina, silicon oxide, and zirconium oxide, and the adhesive may include at least one of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

[0159] In some embodiments, the viscosity of the insulating slurry is 3000 MPa·s-10000 MPa·s.

[0160] In some embodiments, the viscosity of the insulating slurry used to prepare the insulating layer 117 is greater than the viscosity of the colloid used to prepare the adhesive layer 116. The low-viscosity colloid has better flowability during coating and molding to cover the uneven areas of the first weld portion 115 and reduce the risk of incomplete coating; the high-viscosity insulating slurry can have higher strength after molding to reduce the risk of the insulating layer 117 being punctured.

[0161] In some embodiments, the thickness of the insulating layer 117 is 0.005 mm to 0.5 mm.

[0162] In some embodiments, the insulating layer 117 further includes a dispersant, such as sodium carboxymethyl cellulose.

[0163] In some embodiments, in the first direction X, the portion of the tab 114 extending beyond the conductive layer 112 is not coated with the insulating layer 117.

[0164] The portion of tab 114 extending beyond conductive layer 112 is used to connect to the electrode lead-out structure. If insulating layer 117 is coated onto the portion of tab 114 extending beyond conductive layer 112, it may interfere with the connection between tab 114 and the current lead-out structure. Therefore, optionally, the portion of tab 114 extending beyond conductive layer 112 is not coated with insulating layer 117.

[0165] In some embodiments, the electrode 11 may be formed according to the following steps: providing an insulating substrate 111 and a conductive layer 112, the conductive layer 112 being disposed on the surface of the insulating substrate 111; coating an active slurry on the surface of the conductive layer 112 away from the insulating substrate 111, the active slurry curing to form an active material layer 113; welding a tab 114 to the portion of the conductive layer 112 not coated with the active material layer 113 to form a first weld portion 115; coating an adhesive on the conductive layer 112 and the tab 114 to cover the first weld portion 115; and coating an insulating slurry on the adhesive.

[0166] After the colloid cures, it forms an adhesive layer 116, and after the insulating slurry cures, it forms an insulating layer 117.

[0167] Figure 10 This is a cross-sectional schematic diagram of an electrode sheet provided for other embodiments of this application.

[0168] like Figure 10 As shown, in some embodiments, the electrode 11 further includes an insulating layer 117, which is connected to the tab 114 and the active material layer 113, and covers at least a portion of the first weld portion 115.

[0169] The insulating layer 117 can fix at least some of the particles on the first weld portion 115, reducing the risk of particles falling into the electrode assembly 10 and improving safety.

[0170] In some embodiments, the electrode 11 may omit the adhesive layer, and the insulating layer 117 may be directly bonded to the first welded portion 115.

[0171] In some embodiments, the insulating layer 117 comprises ceramic particles and an adhesive, wherein the weight ratio of the adhesive to the insulating layer 117 is greater than or equal to 0.1.

[0172] The high adhesive content in the insulating layer 117 allows it to adhere better to the first welded part 115, reducing the risk of separation between the insulating layer 117 and the first welded part 115.

[0173] Figure 11 This is a partial structural diagram of a battery cell provided in some embodiments of this application.

[0174] Please refer to the above as well. Figures 4 to 11 This application also provides a battery cell 7, which includes a housing 20, an electrode assembly 10, and an electrode lead-out structure 30. The electrode assembly 10 is housed within the housing 20. The electrode assembly 10 includes electrode sheets 11 from any of the foregoing embodiments. The electrode lead-out structure 30 is disposed on the housing 20 and connected to a tab 114. The electrode lead-out structure 30 is used to conduct electrical energy generated by the electrode assembly 10.

[0175] In some embodiments, two conductive layers 112 are provided, and the two conductive layers 112 are respectively disposed on both sides of the insulating substrate 111. The tabs 114 include a first tab 114a and a second tab 114b, and the first tab 114a and the second tab 114b are respectively welded to the second portion 112b of the two conductive layers 112.

[0176] The first tab 114a and the second tab 114b are used to draw out the current on the two conductive layers 112, respectively.

[0177] In some embodiments, the electrode lead-out structure 30 has a connecting portion 33. In the first direction X, the connecting portion 33 is located on the side of the first tab 114a away from the active material layer 113. The connecting portion 33 abuts and is welded to the first tab 114a and abuts and is welded to the second tab 114b. The thickness of the connecting portion 33 is t. The first tab 114a, in its flattened state, extends beyond the first welding portion 115 by an dimension h2 in the first direction X. t and h2 satisfy: 2.5 ≤ h2 / t ≤ 10. The second tab 114b, in its flattened state, extends beyond the first welding portion 115 by an dimension h3 in the first direction X. t and h3 satisfy: 2.5 ≤ h3 / t ≤ 10.

[0178] The connecting portion 33 is the part of the electrode lead-out structure 30 that abuts against the first electrode tab 114a and the second electrode tab 114b. Exemplarily, the connecting portion 33 may be a current collector 32, or a part of a current collector 32. Optionally, the connecting portion 33 is a flat plate structure.

[0179] The first tab 114a can be flattened, bent or otherwise processed to form a relatively dense end face 114c, which can be used to abut and weld with the connecting part 33.

[0180] The flattened state of the first electrode tab 114a refers to restoring the first electrode tab 114a to a flat state. For example, the electrode assembly 10 can be disassembled and the electrode plate 11 can be unfolded as a whole. Then, the first electrode tab 114a can be flattened again using a device, and then the value of h2 can be measured.

[0181] Similarly, the flattened state of the second tab 114b refers to restoring the second tab 114b to a flat state. For example, the electrode assembly 10 can be disassembled and the electrode plate 11 can be unfolded as a whole, and then the second tab 114b can be flattened again using a device, and then the value of h3 can be measured.

[0182] The larger h2 is, the larger the portion of the first tab 114a that can be welded to the connection part 33, but the larger the space occupied by the first tab 114a is also. The smaller the value of t is, the less heat is generated during welding, the lower the connection strength between the first tab 114a and the connection part 33, and the smaller the current carrying capacity of the connection part 33. If h2 / t is too large, it will result in the first tab 114a occupying a large space, insufficient energy density of the battery cell 7, and a higher risk of connection failure between the connection part 33 and the first tab 114a.

[0183] The smaller h2 is, the smaller the portion of the first tab 114a that can be welded to the connecting part 33, but the smaller the space occupied by the first tab 114a is also. The larger the value of t is, the more heat is generated during welding, and the more heat is transferred to the first tab 114a and the insulating member 12, and the higher the risk of the tab 114a and the insulating member 12 being burned. If h2 / t is too small, the risk of the first tab 114a and the insulating member 12 being burned is relatively high.

[0184] Therefore, in this embodiment, the value of h2 / t is limited to 2.5-10 to ensure the connection strength between the connecting part 33 and the first electrode 114a, reduce the risk of the first electrode 114a being melted through, and improve the energy density. Optionally, the value of h2 / t is limited to 5-7.5.

[0185] Similarly, in this embodiment, the value of h3 / t is limited to 2.5-10 to ensure the connection strength between the connecting part 33 and the second electrode 114b, reduce the risk of the second electrode 114b being melted through, and improve the energy density. Optionally, the value of h3 / t is limited to 5-7.5.

[0186] In some embodiments, the value of h2 / t can be 2.5, 4, 5, 7.5, 9, or 10. In some embodiments, the value of h3 / t can be 2.5, 4, 5, 7.5, 9, or 10.

[0187] In some embodiments, the connecting portion 33 is welded to the first electrode tab and the second electrode tab to form a second welded portion.

[0188] In some embodiments, the electrode 11 is wound in multiple turns. In the radial direction of the electrode assembly 10, the spacing between two adjacent turns of the electrode 11 is d3, where 0.2 mm ≤ d3 ≤ 0.4 mm.

[0189] d3 is the radial distance between two adjacent rings of the same electrode 11.

[0190] The electrode 11 (e.g., the first electrode 11a) is wound into multiple turns, and correspondingly, the tab 114 is also wound into multiple turns. The larger the value of d3, the larger the distance between two adjacent turns of tab 114, increasing the risk of the laser passing between the tabs 114 during welding of the tabs 114 and the electrode lead-out structure. If the value of d3 is too large, the insulating member 12 of the electrode assembly 10 may be burned by the laser, posing a safety risk. Therefore, in this embodiment, the value of d3 is limited to less than or equal to 0.4 mm to improve safety.

[0191] Between two adjacent turns of an electrode 11, another electrode 11 of opposite polarity and a spacer 12 are required; for example, between two adjacent turns of the first electrode 11a, a second electrode 11b and two layers of spacers 12 are required. If the value of d3 is too small, it will restrict the other electrode 11 and the spacer 12. Therefore, in this embodiment, the value of d3 is limited to be greater than or equal to 0.2 mm to provide space for the spacer and other structures.

[0192] In some embodiments, d3 is 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, or 0.4 mm.

[0193] In some embodiments, the electrode lead-out structure 30 has a connecting portion 33. In the first direction X, the connecting portion 33 is located on the side of the tab 114 opposite to the active material layer 113, and the connecting portion 33 abuts against and is welded to the tab 114. The electrode assembly 10 also includes a spacer 12, which is stacked and wound with the electrode sheet 11. In the first direction X, the minimum distance between the surface of the connecting portion 33 that abuts against the first tab 114a and the spacer 12 is S1, and the thickness of the connecting portion 33 is t, where S1 ≥ 0.75t.

[0194] The larger the value of t, the greater the heat generated between the welded connection 33 and the first tab 114a; the smaller the value of S1, the shorter the heat conduction path between the insulating member 12 and the connection 33, the more heat is conducted to the insulating member 12, and the higher the risk of the insulating member 12 being burned. In this embodiment, S1 is limited to greater than or equal to 0.75t to reduce the heat conducted to the insulating member 12 and reduce the risk of the insulating member 12 being burned.

[0195] In some embodiments, S1 ≥ 1.5t.

[0196] In some embodiments, the tab 114 is wound into multiple turns along the winding direction V, and one end of the multiple turns of the tab 114 away from the active material layer 113 is flattened to form an end face 114c, and the electrode lead-out structure 30 is welded to the end face 114c.

[0197] In this embodiment, the tab 114 can be flattened so that the end region of the tab 114 away from the active material layer 113 is gathered together. The flattening process forms a dense end face 114c at the end of the tab 114 away from the active material layer 113, reducing gaps and facilitating the connection between the tab 114 and the electrode lead-out structure 30.

[0198] In some embodiments, the electrode assembly 10 is generally cylindrical.

[0199] Figure 12 A cross-sectional schematic diagram of an electrode sheet provided for some embodiments of this application; Figure 13 This is a partial structural diagram of a battery cell provided in some embodiments of this application.

[0200] like Figure 12 and Figure 13 As shown, in some embodiments, in the first direction X, one end of the first tab 114a facing away from the active material layer 113 extends beyond the second tab 114b, and the second tab 114b is bent toward the first tab 114a and connected to the first tab 114a. The electrode lead-out structure 30 has a connecting portion 33, which is located on the side of the first tab 114a facing away from the active material layer 113 in the first direction X. The connecting portion 33 abuts against and is welded to the first tab 114a. The thickness of the connecting portion 33 is t, and the dimension by which the first tab 114a extends beyond the first welding portion 115 in the first direction X in the flattened state is h2. t and h2 satisfy: 5 ≤ h2 / t ≤ 20.

[0201] The larger h2 is, the larger the portion of the first tab 114a that can be welded to the connection part 33, but the larger the space occupied by the first tab 114a is also. The smaller the value of t is, the less heat is generated during welding, the lower the connection strength between the first tab 114a and the connection part 33, and the smaller the current carrying capacity of the connection part 33. If h2 / t is too large, it will result in the first tab 114a occupying a large space, insufficient energy density of the battery cell 7, and a higher risk of connection failure between the connection part 33 and the first tab 114a.

[0202] The smaller h2 is, the smaller the portion of the first tab 114a that can be welded to the connecting part 33, but the smaller the space occupied by the first tab 114a is also. The larger the value of t is, the more heat is generated during welding, and the more heat is transferred to the first tab 114a and the insulating member 12, and the higher the risk of the tab 114a and the insulating member 12 being burned. If h2 / t is too small, the risk of the first tab 114a and the insulating member 12 being burned is relatively high.

[0203] In this embodiment, the second tab 114b is not welded to the connecting portion 33. Therefore, the value of h2 / t is limited to 5-20 to ensure the connection strength between the connecting portion 33 and the first tab 114a, reduce the risk of the first tab 114a being melted through, and improve the energy density. Optionally, the value of h2 / t is 10-15.

[0204] Compared to the scheme in which the first tab 114a and the second tab 114b are simultaneously welded to the connecting part 33, the scheme in which only the first tab 114a is welded to the connecting part 33 requires the first tab 114a to have a larger h2.

[0205] Figure 14 This is a schematic diagram of the structure of the electrode in the unfolded state provided in some embodiments of this application; Figure 15 This is a partial schematic diagram of a battery cell 7 provided in some embodiments of this application.

[0206] like Figure 14 and Figure 15 As shown, in some embodiments, the tab 114 includes a plurality of tab portions 114d spaced apart along a second direction Y, which is perpendicular to the first direction X and the thickness direction Z of the electrode 11. In the first direction X, the tab portions 114d protrude from the second portion 112b.

[0207] For example, the first electrode 114a includes a plurality of electrode portions 114d, and the second electrode 114b includes a plurality of electrode portions 114d.

[0208] In this embodiment, the tab 114 is divided into multiple separate tab portions 114d, which makes it easier for the tab portions 114d to be bent after the electrode sheet 11 is wound.

[0209] In some embodiments, the electrode 11 is wound multiple turns along the winding direction V. The tab 114 includes a plurality of tab portions 114d spaced apart along the winding direction V. The plurality of tab portions 114d are bent toward the winding center of the electrode 11 to form an end face 114c, and the electrode lead-out structure 30 is welded to the end face 114c.

[0210] With the electrode sheet 11 in a flattened state, multiple electrode tabs 114d are arranged along the second direction Y. After the electrode sheet 11 is wound, the multiple electrode tabs 114d are arranged along the winding direction V.

[0211] The tab 114d is bent toward the winding center of the electrode 11 to block the gap between two adjacent turns of the electrode 11 and form a dense end face 114c, which facilitates welding with the electrode lead-out structure 30 and reduces the risk of laser leakage.

[0212] According to some embodiments of this application, this application also provides a battery comprising a plurality of battery cells described in any of the above embodiments.

[0213] According to some embodiments of this application, this application also provides an electrical device, including a battery cell as described in any of the above embodiments, and the battery cell is used to provide electrical energy to the electrical device.

[0214] According to some embodiments of this application, refer to Figures 6 to 9 This application provides an electrode 11, which includes an insulating substrate 111, a conductive layer 112, an active material layer 113, and a tab 114. Two conductive layers 112 are disposed on two surfaces of the insulating substrate 111. The active material layer 113 is coated on the surface of the conductive layer 112 facing away from the insulating substrate 111. The conductive layer 112 includes a first portion 112a coated with the active material layer 113 and a second portion 112b uncoated with the active material layer 113. The first portion 112a and the second portion 112b are arranged along a first direction X.

[0215] The tab 114 includes a first tab 114a and a second tab 114b, which are respectively welded to the second portion 112b of the two conductive layers 112. The first tab 114a and the second tab 114b are used to draw out the current on the two conductive layers 112. The first tab 114a is welded to the corresponding conductive layer 112 to form a first welding sub-part, and the second tab 114b is welded to the corresponding conductive layer 112 to form a second welding sub-part. The first welding portion 115 includes the first welding sub-part and the second welding sub-part.

[0216] The electrode 11 also includes an adhesive layer 116 and an insulating layer 117. The adhesive layer 116 is connected to the tab 114 and covers at least a portion of the first weld portion 115. At least a portion of the insulating layer 117 is located on the side of the adhesive layer 116 opposite to the first weld portion 115 and is connected to the adhesive layer 116.

[0217] The resistivity of conductive layer 112 is ρ1, the specific heat capacity of conductive layer 112 is C, the density of conductive layer 112 is ρ2, and the constant K = ρ1 / (C·ρ2). The thickness of conductive layer 112 is d1, and the dimension of the first part 112a along the first direction X is W. d1, W, and K satisfy: 0.001 J / (Ω·mm) 4 ·℃)≤d1 / (K·W)≤0.0075J / (Ω·mm 4 ·℃).

[0218] The present application is further illustrated below with reference to the embodiments.

[0219] To make the inventive purpose, technical solution, and beneficial technical effects of this application clearer, the following describes this application in further detail with reference to embodiments. However, it should be understood that the embodiments of this application are merely for explaining this application and are not intended to limit this application, and the embodiments of this application are not limited to the embodiments given in the specification. Unless otherwise specified, specific experimental or operating conditions in the embodiments are prepared under conventional conditions or according to the conditions recommended by the material supplier.

[0220] Example 1 can be prepared according to the following steps:

[0221] (i) The positive electrode active material NCM523, the conductive agent acetylene black, and the binder PVDF are mixed at a mass ratio of 96:2:2. NMP solvent is added, and the mixture is stirred under vacuum until the system is homogeneous to obtain the positive electrode slurry. The positive electrode slurry is uniformly coated onto the first current collector, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing, slitting, and cutting, the first electrode sheet is obtained. The positive electrode slurry solidifies to form an active material layer.

[0222] (ii) The negative electrode active material graphite or a mixture of graphite and other active materials in different mass ratios, the conductive agent acetylene black, the thickener CMC, and the binder SBR are mixed in a mass ratio of 96.4:1:1.2:1.4. Deionized water is added as a solvent, and the mixture is stirred in a vacuum mixer until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on the second current collector, dried at room temperature, and then transferred to an oven for further drying. The second electrode sheet is then obtained by cold pressing, slitting, and cutting.

[0223] (iii) Ethyl carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0224] (iv) Use a 12μm thick polypropylene film as a separator.

[0225] (v) The first electrode, the separator and the second electrode are stacked together and wound into a cylindrical shape.

[0226] (VI) The electrode assembly is installed into the cylindrical shell, and then the battery cell is obtained through processes such as liquid injection, settling, formation and shaping.

[0227] In step (i), refer to Figure 8 The first current collector includes an insulating substrate 111 and a conductive layer 112 disposed on the surface of the insulating adhesive. The conductive layer 112 is an aluminum foil with a K value of 0.0120 Ω·mm. 4 ·℃ / J, the thickness of the aluminum foil is 0.001mm, and the width W of the area of ​​the aluminum foil coated with the positive electrode paste is 68.5mm.

[0228] In step (VI), the battery cell is cylindrical with a diameter of 46 mm and a height of 95 mm.

[0229] The energy density, temperature and cycle performance of the battery cells prepared in Example 1 were tested.

[0230] Energy density detection: In a 25°C environment, the battery cell starts from the upper limit voltage and discharges at a rate of 0.33C until it reaches the lower limit voltage. The capacity exerted is the capacity of the battery cell. The energy density G of the battery cell is obtained by dividing the capacity of the battery cell by the weight of the battery cell.

[0231] Temperature detection: During fast charging of a single battery cell, the highest temperature Q of the active material layer of the first electrode is detected. Fast charging refers to charging a single battery cell from 0% to 80% within 25 minutes. During the manufacturing of the battery cell, a temperature sensor can be built into the cell, with an opening in the casing to allow the sensor's leads to be routed out. The temperature sensor can detect the temperature of the active material layer in real time.

[0232] Cyclic performance testing: Under normal temperature conditions, the battery cells are charged and discharged at a 1C rate, and a full charge-discharge cycle test is performed until the capacity of the battery cells decays to 80% of the initial capacity. The number of cycles for each battery cell is recorded.

[0233] Example 2: The preparation and testing methods of the battery cell in Example 2 are the same as those in Example 1, except that d1 is 0.0008 mm.

[0234] Example 3: The preparation and testing methods of the battery cell in Example 3 are the same as those in Example 1, except that d1 is 0.0015 mm.

[0235] Example 4: The preparation and testing methods of the battery cell in Example 4 are the same as those in Example 1, except that d1 is 0.002 mm.

[0236] Example 5: The preparation and testing methods of the battery cell in Example 5 are the same as those in Example 1, except that d1 is 0.0025 mm.

[0237] Example 6: The preparation and testing methods of the battery cell in Example 6 are the same as those in Example 1, except that d1 is 0.003 mm.

[0238] Example 7: The preparation and testing methods of the battery cell in Example 7 are the same as those in Example 1, except that d1 is 0.0035 mm.

[0239] Example 8: The preparation and testing methods of the battery cell in Example 8 are the same as those in Example 1, except that d1 is 0.004 mm.

[0240] Example 9: The preparation and testing methods of the battery cell in Example 9 are the same as those in Example 1, except that d1 is 0.0045 mm.

[0241] Example 10: The preparation and testing methods of the battery cell in Example 10 are the same as those in Example 1, except that d1 is 0.005 mm.

[0242] Example 11: The preparation and testing methods of the battery cell in Example 11 are the same as those in Example 1, except that d1 is 0.0062 mm.

[0243] Comparative Example 1: The preparation and testing methods of the battery cell in Comparative Example 1 are the same as those in Example 1, except that d1 is 0.0007 mm.

[0244] Comparative Example 2: The preparation and testing methods of the battery cells in Comparative Example 1 are the same as in Example 1, except that d1 is 0.0065 mm.

[0245] Comparative Example 3: The preparation and testing methods of the battery cells in Comparative Example 3 are the same as those in Example 1, except that d1 is 0.0074 mm.

[0246] The evaluation results of Examples 1-11 and Comparative Examples 1-3 are shown in Table 1.

[0247] Table 1

[0248]

[0249] Referring to Examples 1-11 and Comparative Examples 1-3, the smaller the value of d1 / (K·W), the more heat is generated by the conductive layer during charging and discharging, the higher the temperature, the faster the active material layer coated on the conductive layer ages, and the faster the capacity of the battery cell decreases. If d1 / (K·W) is larger, the weight of the conductive layer will also be larger, and the energy density of the battery cell will be lower. In this application, d1 / (K·W) is limited to 0.001 J / (Ω·mm²). 4 ·℃)-0.0075J / (Ω·mm 4 •℃) to balance the energy density and cycle performance of individual battery cells.

[0250] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0251] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. An electrode sheet, characterized in that, include: Insulating substrate; A conductive layer is disposed on the surface of the insulating substrate; An active material layer is coated on the surface of the conductive layer away from the insulating substrate. The conductive layer includes a first portion coated with the active material layer and a second portion not coated with the active material layer. The first portion and the second portion are arranged along a first direction. The resistivity of the conductive layer is ρ1, the specific heat capacity of the conductive layer is C, the density of the conductive layer is ρ2, and the constant K = ρ1 / (C·ρ2); The thickness of the conductive layer is d1, and the dimension of the first portion along the first direction is W. d1, W, and K satisfy one of the following conditions: d1=0.001J / (Ω·mm 4 ·℃); d1=0.0061J / (Ω·mm 4 ·℃); d1=0.0075J / (Ω·mm 4 ·℃); 0.0018J / (Ω·mm 4 ℃)≤d1 / (K W)≤0.0024J / (Ω mm 4 ·℃); 0.0030J / (Ω·mm 4 ·℃)≤d1 / (K·W)≤0.0036J / (Ω·mm 4 ·℃); 0.0061J / (Ω·mm 4 ℃)≤d1 / (K W)≤0.0075J / (Ω mm 4 (℃).

2. The electrode sheet according to claim 1, characterized in that, d1 is 0.5μm-5μm.

3. The electrode sheet according to claim 1, characterized in that, It also includes a tab, which is welded to the second part to form a first welded portion; in the first direction, one end of the tab opposite to the active material layer protrudes from the second part.

4. The electrode sheet according to claim 3, characterized in that, The thickness of the electrode tab is d2, which is greater than d1.

5. The electrode sheet according to claim 4, characterized in that, d2 ranges from 1 μm to 100 μm.

6. The electrode sheet according to claim 3, characterized in that, It also includes an adhesive layer that is attached to the tab and covers at least a portion of the first weld.

7. The electrode sheet according to claim 6, characterized in that, A portion of the adhesive layer is located between the active material layer and the tab in the first direction, coated on the second portion, and connected to the active material layer.

8. The electrode sheet according to claim 6, characterized in that, It also includes an insulating layer, at least a portion of which is located on the side of the adhesive layer opposite to the first weld portion and is attached to the adhesive layer.

9. The electrode sheet according to claim 8, characterized in that, Both the insulating layer and the adhesive layer include an adhesive. The weight ratio of the adhesive in the insulating layer to the insulating layer is N1, and the weight ratio of the adhesive in the adhesive layer to the adhesive layer is N2, where N1 is less than N2.

10. The electrode according to claim 8, characterized in that, The insulating layer completely covers the adhesive layer.

11. The electrode sheet according to claim 3, characterized in that, It also includes an insulating layer connected to the tab and the active material layer, and the insulating layer covers at least a portion of the first weld.

12. The electrode sheet according to claim 11, characterized in that, The insulating layer comprises ceramic particles and a binder, wherein the weight ratio of the binder to the insulating layer is greater than or equal to 0.

1.

13. The electrode according to claim 8, characterized in that, In the first direction, the portion of the tab extending beyond the conductive layer is not coated with the insulating layer.

14. The electrode sheet according to any one of claims 3-13, characterized in that, The electrode tab includes a plurality of electrode tab portions spaced apart along a second direction, the second direction being perpendicular to the first direction and the thickness direction of the electrode sheet; In the first direction, the tab protrudes from the second portion.

15. A single battery cell, characterized in that, include: shell; An electrode assembly, housed within the housing, the electrode assembly comprising an electrode sheet according to any one of claims 3-14; as well as An electrode lead-out structure is disposed on the outer shell and connected to the tab of the electrode plate.

16. The battery cell according to claim 15, characterized in that, The conductive layer is configured as two layers, and the two conductive layers are respectively disposed on both sides of the insulating substrate; The electrode includes a first electrode and a second electrode, which are respectively welded to the second portion of the two conductive layers.

17. The battery cell according to claim 16, characterized in that, In the first direction, the end of the first electrode tab that is away from the active material layer extends beyond the second electrode tab, and the second electrode tab bends toward the first electrode tab and is connected to the first electrode tab; The electrode lead-out structure has a connecting part. In the first direction, the connecting part is located on the side of the first electrode tab away from the active material layer. The connecting part abuts against and is welded to the first electrode tab. The thickness of the connecting part is t, and the first electrode tab extends beyond the first welding part by a dimension h2 in the first direction when it is flattened. t and h2 satisfy: 5≤h2 / t≤20.

18. The battery cell according to claim 16, characterized in that, The electrode lead-out structure has a connecting part. In the first direction, the connecting part is located on the side of the first electrode tab away from the active material layer. The connecting part abuts and is welded to the first electrode tab and abuts and is welded to the second electrode tab. The thickness of the connecting part is t, and the first electrode tab extends beyond the first welding part by a dimension h2 in the first direction when it is flattened. t and h2 satisfy: 2.5≤h2 / t≤10; The second electrode tab extends beyond the first welded part by a dimension h3 in the first direction when it is flattened, and t and h3 satisfy: 2.5≤h3 / t≤10.

19. The battery cell according to claim 15, characterized in that, The electrode sheet is wound into multiple turns; In the radial direction of the electrode assembly, the spacing between two adjacent turns of the electrode is d3, where 0.2mm≤d3≤0.4mm.

20. The battery cell according to claim 16, characterized in that, The electrode lead-out structure has a connecting part. In the first direction, the connecting part is located on the side of the electrode tab away from the active material layer. The connecting part abuts against and is welded to the electrode tab. The electrode assembly further includes a spacer, which is stacked and wound with the electrode sheet; In the first direction, the minimum distance between the surface of the connecting part that abuts against the first electrode tab and the insulating member is S1, and the thickness of the connecting part is t, where S1 ≥ 0.75t.

21. The battery cell according to claim 15, characterized in that, The electrode tab is wound into multiple turns along the winding direction. The end of the multiple turns of the electrode tab that is away from the active material layer is flattened and forms an end face. The electrode lead-out structure is welded to the end face.

22. The battery cell according to any one of claims 15 to 21, characterized in that, The electrode sheet is wound into multiple turns along the winding direction; the electrode tab includes multiple electrode tab portions spaced apart along the winding direction, and the multiple electrode tab portions are bent toward the winding center of the electrode sheet to form an end face, and the electrode lead-out structure is welded to the end face.

23. A battery, characterized in that, It includes multiple battery cells according to any one of claims 15-22.

24. An electrical appliance, characterized in that, Includes a battery cell according to any one of claims 15-22, the battery cell being used to provide electrical energy.

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