Battery and electric equipment

Abstract

The invention relates to a battery and electric equipment, the battery comprises a pole piece, the pole piece comprises a current collector, an active substance layer and a tab, the active substance layer is arranged on the current collector, the active substance layer is provided with a groove, the current collector comprises an empty foil area, the groove exposes the empty foil area, the tab is arranged in the groove and is electrically connected with the empty foil area, and the tab comprises a first part and a second part, observed along the thickness direction of the tab, the first part is the overlapped part of the tab and the empty foil region, and the second part is positioned outside the empty foil region; the first part comprises a first surface facing the empty foil area, the first surface comprises a first area and a second area, the first area and the empty foil area are in insulated connection through an insulating layer, and the first part is electrically connected with the empty foil area through the second area; the first region is located on one side of the second region facing the second portion. According to the invention, the insulating layer is arranged in the first region, so that the current density of the region near the groove is adjusted, the accumulation of lithium ions in the active layer region near the groove is relieved, and the problem of lithium precipitation is reduced.

Description

Technical Field

[0001] This application relates to the technical field of lithium batteries, and particularly to a battery and an electrical device using the same. Background Art

[0002] Lithium-ion batteries have advantages such as high energy density and fast charging speed, and have become the most widely used secondary batteries at present.

[0003] The battery electrode plate includes a current collector, an active layer coated on the current collector, and a tab welded to the current collector. The active layer forms a groove on one side surface of the current collector, so that the part of the current collector located in the groove is exposed. The tab is fixed to the current collector in the groove by welding. However, with the introduction of the Si (silicon) system, during the high-energy density and high-rate charging process, lithium ions are likely to accumulate in the active layer area near the groove, resulting in the problem of lithium deposition, which in turn affects the battery performance. Summary of the Invention

[0004] Based on this, a battery and an electrical device using the same are provided, which can reduce the accumulation of lithium ions in the active layer area near the groove during the high-energy density and high-rate charging process, reduce the problem of lithium deposition, and improve the battery performance.

[0005] In one embodiment, this application includes a battery, which includes an electrode plate. The electrode plate includes a current collector, an active material layer, and a tab. The active material layer is disposed on the current collector. The active material layer is provided with a groove. The current collector includes an empty foil area. The groove exposes the empty foil area. The tab is disposed in the groove and is electrically connected to the empty foil area. The tab includes a first part and a second part connected to each other. When observed along the thickness direction of the tab, the first part is the part of the tab that coincides with the empty foil area, and the second part is located outside the empty foil area; the first part includes a first surface facing the empty foil area. The first surface includes a first area and a second area. An insulating layer is provided between the first area and the empty foil area for insulating connection. The second area is the area enclosed by the outer edge of the part where the tab is in conductive contact with the empty foil area; the first area is located on the side of the second area facing the second part; along the extending direction of the tab, the first surface has a first edge and a second edge arranged oppositely. The first edge is located on the side of the second edge facing the second part; there is a contact edge between the first area and the second area. Along the extending direction of the tab, the first area extends from the contact edge to the first edge, and the second area extends from the contact edge to the second edge.

[0006] In one embodiment, the area of the first area is S1, the area of the first surface is S2, and S1 / S2≥0.2.

[0007] In one embodiment, the insulating layer includes an adhesive layer, the adhesive layer is bonded between the first surface and the empty foil area, the first area is insulated and connected to the empty foil area through the adhesive layer, the second area is provided with a protrusion, and the protrusion passes through the adhesive layer and is electrically connected to the current collector.

[0008] In one embodiment, a plurality of protrusions are provided and arranged at intervals along the length and width directions of the second area, and the protrusions are in contact with the empty foil area.

[0009] In one embodiment, the adhesive layer includes at least one of hot melt adhesive, pressure sensitive adhesive and thermosetting adhesive.

[0010] In one embodiment, the material of the adhesive layer includes at least one of epoxy resin, polyolefin, polystyrene, polymethyl methacrylate, phenolic resin or styrene-butadiene rubber.

[0011] In one embodiment, the insulating layer is an insulating coating, and the second area is welded to the empty foil area.

[0012] In one embodiment, the insulating coating includes at least one of ceramic coating and glass fiber coating.

[0013] In one embodiment, the shape of the second area includes any one of a rectangle and a trapezoid.

[0014] In one embodiment, the second area is trapezoidal. Along the extension direction of the first part, the second area includes a long side and a short side arranged oppositely, and the short side is closer to the second part than the long side.

[0015] In one embodiment, 0.3 ≤ area S1 / area S2 ≤ 0.85.

[0016] In one embodiment, 0.4 ≤ area S1 / area S2 ≤ 0.6.

[0017] In one embodiment, the active material layer includes a first active layer and a second active layer located on opposite sides of the current collector, and the groove is located in the first active layer or the second active layer.

[0018] In a second aspect, an embodiment of the present application provides an electrical device, including the battery according to any one of claims 1-11.

[0019] According to the battery and electrical equipment provided by the embodiments of the present application, the battery includes a pole piece. The pole piece includes a current collector, an active material layer, and a tab. The active material layer is disposed on the current collector. The active material layer is provided with a groove. The current collector includes an empty foil area. The groove exposes the empty foil area. The tab is disposed in the groove and electrically connected to the empty foil area. The tab includes a first part and a second part connected to each other. When observed along the thickness direction of the tab, the first part is the part of the tab that coincides with the empty foil area, and the second part is located outside the empty foil area; the first part includes a first surface facing the empty foil area. The first surface includes a first area and a second area. An insulating layer is disposed between the first area and the empty foil area for insulating connection. The second area is the area enclosed by the outer edge of the part where the tab is in conductive contact with the empty foil area; the first area is located on the side of the second area facing the second part; along the extending direction of the tab, the first surface has a first edge and a second edge disposed opposite to each other. The first edge is located on the side of the second edge facing the second part; there is a contact edge between the first area and the second area. Along the extending direction of the tab, the first area extends from the contact edge to the first edge, and the second area extends from the contact edge to the second edge. The insulating connection between the first area and the empty foil area through the insulating layer can optimize the electrical connection area between the tab and the empty foil area in the groove, thereby reducing the maximum value of the current density in the area near the groove, improving the current distribution state in this area, making the current distribution more uniform, thus alleviating the accumulation of lithium ions in the active material layer area near the groove, alleviating the problem of lithium deposition, and further improving the battery performance. Description of the Drawings

[0020] Figure 1 Schematic diagram showing the structure of a pole piece provided by an embodiment of the present application Figure 1 ;

[0021] Figure 2 Schematic diagram showing the structure of a pole piece provided by an embodiment of the present application Figure 2 ;

[0022] Figure 3 Schematic diagram showing the structure of a pole piece provided by an embodiment of the present application Figure 3 ;

[0023] Figure 4 Schematic diagram showing the structure of a pole piece provided by an embodiment of the present application Figure 4 ;

[0024] Figure 5 Schematic diagram showing the structure of a tab provided by an embodiment of the present application Figure 1 ;

[0025] Figure 6 Schematic diagram showing the structure of a tab provided by an embodiment of the present application Figure 2 。

[0026] Description of the Reference Numerals:

[0027] 1. Current collector; 11. Empty foil area; 2. Active material layer; 21. Groove; 22. First active layer; 23. Second active layer; 3. Tab; 31. First part; 311. First surface; 3111. First area; 3112. Second area; 3121. Protrusion; 32. Second part; 4. Insulating layer. Detailed implementation mode

[0028] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0029] It should be noted that the illustrations provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the drawings, rather than being drawn according to the number, shape and size of the components in actual implementation. The type, quantity and proportion of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0030] The structures, proportions, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those who are familiar with this technology to understand and read, and are not used to limit the limiting conditions under which the present invention can be implemented. Therefore, they do not have technical substance significance. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the efficacy that the present invention can produce and the purpose that can be achieved, should still fall within the scope that the technical content disclosed by the present invention can cover.

[0031] The orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "middle", "longitudinal", "transverse", "horizontal", "inner", "outer", "radial", "circumferential", etc. cited in this specification is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0032] The active layer is provided with grooves on one side surface of the current collector, so that the part of the current collector located in the grooves is exposed. The tab is fixed on the current collector in the grooves by welding. During the charging process, the current density in the area near the cell slot is too high, and lithium ions are likely to accumulate in the active layer area near the grooves, resulting in the problem of lithium deposition, which in turn affects the battery performance.

[0033] To solve the above problems, refer to Figures 1 - 3 , Figure 1Schematic diagram of the structure of a pole piece provided by an embodiment of the present application Figure 1 (Observed along the thickness direction of the tab) Figure 2 Schematic diagram of the structure of a pole piece provided by an embodiment of the present application Figure 2 , Figure 3 Schematic diagram of the structure of a pole piece provided by an embodiment of the present application Figure 3 .

[0034] The present application provides a battery. The battery includes a pole piece. The pole piece includes a current collector 1, an active material layer 2, and a tab 3. The active material layer 2 is disposed on the current collector 1. The active material layer 2 is provided with a groove 21. The current collector 1 includes a bare foil area 11. The groove 21 exposes the bare foil area 11. The tab 3 is disposed in the groove 21 and is electrically connected to the bare foil area 11. The tab 3 includes a first part 31 and a second part 32 connected to each other. Observed along the thickness direction of the tab 3, the first part 31 is the part of the tab 3 that coincides with the bare foil area 11, and the second part 32 is located outside the bare foil area 11; the first part 31 includes a first surface 311 facing the bare foil area 11. The first surface 311 includes a first area 3111 and a second area 3112. An insulating layer 4 is disposed between the first area 3111 and the bare foil area 11 for insulating connection. The second area 3112 is an area formed by surrounding the outer edge of the part where the tab 3 is in conductive contact with the bare foil area 11; the first area 3111 is located on the side of the second area 3112 facing the second part 32; along the extending direction of the tab 3, the first surface 311 has a first edge and a second edge disposed opposite to each other. The first edge is located on the side of the second edge facing the second part; there is a contact edge between the first area 3111 and the second area 3112. Along the extending direction of the tab 3, the first area 3111 extends from the contact edge to the first edge, and the second area 3112 extends from the contact edge to the second edge.

[0035] It should be understood that the battery includes a pole piece. The pole piece is an important component of a secondary battery. The pole piece is usually divided into two types: a cathode and an anode. Their functions are to carry ions during charging and discharging respectively, and convert chemical energy into electrical energy. The pole piece in the battery of the present application can represent either a cathode or an anode, or can represent both types of pole pieces in the battery at the same time. The present application does not make any restrictions. In one example, the pole piece of the present application is selected as the anode.

[0036] The electrode includes a current collector 1. The current collector 1 serves as the conductive substrate of the electrode and can be an aluminum foil or a copper foil with an overall flat and strip-like structure. For example, when the current collector 1 is a positive current collector, an aluminum foil can be used; when the current collector 1 is a negative current collector, a copper foil can be used. Aluminum foils and copper foils have high electrical conductivity, which can effectively reduce the internal resistance of the secondary battery and facilitate the improvement of the energy density and power density of the secondary battery. In addition, aluminum foils and copper foils also have good mechanical strength and can withstand the expansion and contraction of the secondary battery during charge and discharge, ensuring the stability and safety of the secondary battery.

[0037] The electrode includes an active material layer 2. The active material layer 2 includes an active material, a conductive agent, an adhesive, etc. After mixing and stirring the above-mentioned material components evenly, they are coated on the surface of the current collector 1 to obtain the active material layer 2. When the electrode is a positive electrode, the active material can be selected from one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium manganese iron phosphate, and cobalt-free materials. When the electrode is a negative electrode, the active material can be selected from one or more of graphite, soft carbon, hard carbon, carbon fiber, elemental silicon, silicon oxide, and silicon alloy.

[0038] A groove 21 can be provided in the active material layer 2 to expose the empty foil area 11 of the current collector 1 for facilitating connection with the tab 3 of the electrode. Among them, the active material layer 2 includes a first active layer 22 and a second active layer 23 located on opposite sides of the current collector 1. One groove 21 can be provided, and one groove 21 can be provided in the first active layer 22 or the second active layer 23 to form a single-sided groove; two grooves 21 can also be provided, and the two grooves 21 are simultaneously provided at the corresponding positions of the first active layer 22 and the second active layer 23 to form a double-sided groove; this application does not make any restrictions. In one example, the groove 21 is provided in the first active layer 22 or the second active layer 23 to form a single-sided groove. Compared with the setting of the double-sided groove, the setting of the single-sided groove can make full use of the internal space of the battery and improve the energy density of the battery.

[0039] The electrode also includes a tab 3. The tab 3 is the bridge for connecting the battery to the external circuit and can conduct the current flowing through the current collector 1 to the external circuit. The tab 3 includes a first part 31 and a second part 32 connected to each other. The first part 31 and the second part 32 are made of the same material and are integrally formed. When observing along the thickness direction of the tab 3, the first part 31 is the part where the tab 3 coincides with the empty foil area 11, that is, the first part 31 is located in the groove 21, and the second part 32 is located outside the empty foil area 11, that is, the second part 32 is located outside the groove 21.

[0040] The first part 31 includes a first surface 311 facing the empty foil area 11. The first surface 311 includes a mutually connected first area 3111 and a second area 3112. The first area 3111 is a continuous surface. An insulating connection is provided between the first area 3111 and the empty foil area 11 through an insulating layer 4, so that the tab 3 is insulated from the current collector 1 at the first area 3111. The second area 3112 is an area enclosed by the outer edge of the part where the tab 3 is in conductive contact with the empty foil area 11; the first area 3111 is located on the side of the second area 3112 facing the second part 32; along the extension direction of the tab 3, the first surface 311 has a relatively arranged first edge and second edge, and the first edge is located on the side of the second edge facing the second part 32; there is a contact edge between the first area 3111 and the second area 3112. Along the extension direction of the tab 3, the first area 3111 extends from the contact edge to the first edge, and the second area 3112 extends from the contact edge to the second edge. The present application does not limit the shapes of the first area 3111 and the second area 3112.

[0041] Among them, the first surface 311 only includes one first area 3111 and one second area 3112.

[0042] In some optional embodiments, the area of the first area 3111 is area S1, and the area of the first surface 311 is area S2. When S1 / S2≥0.2, the insulating layer 4 can be provided to optimize the current distribution effect and reduce the risk of lithium deposition.

[0043] Among them, the first part 31 is electrically connected to the empty foil area 11 through the second area 3112. The connection method can be welding, gluing or other methods, which are not limited in the present application, so that the current flowing through the current collector 1 is led to the external circuit. An insulating connection is provided between the first area 3111 and the empty foil area 11 through an insulating layer 4. The present application does not limit the insulating layer 4. The insulating layer 4 can be an insulating coating, an adhesive layer or other material layers. The setting of the first area 3111 can optimize the electrical connection area between the tab 3 and the empty foil area 11 in the groove 21, thereby reducing the maximum value of the current density in the area near the groove 21, improving the current distribution state in this area, making the current distribution more uniform, thus alleviating the accumulation of lithium ions in the active material layer area near the groove 21, alleviating the lithium deposition problem, and further improving the battery performance.

[0044] In some alternative embodiments, the insulating layer 4 includes an adhesive layer, which is bonded between the first surface 311 and the empty foil area 11. The first area 3111 is insulated and connected to the empty foil area 11 through the adhesive layer. The second area 3112 is provided with a protrusion 3121, and the protrusion 3121 passes through the adhesive layer and is electrically connected to the current collector 1. The adhesive layer fixedly connects the tab 3 to the empty foil area 11. The arrangement of the adhesive layer does not require a welding seat and a welding head. Therefore, in this application, a groove 21 can be provided only on one side of the current collector 1, and the active material layer can be retained on the back of the groove 21, thereby making full use of the internal space of the battery and improving the energy density of the battery. Moreover, by using the adhesive layer, the first part 31 of the tab 3 can be entirely bonded to the current collector 1, resulting in a larger connection area and higher connection strength.

[0045] A plurality of protrusions 3121 are protrudingly provided in the second area 3112. The material of the protrusions 3121 is the same as that of the tab 3 and is integrally formed. It should be understood that the area surrounded by the outer edge of the part of the tab 3 in conductive contact with the empty foil area 11 refers to the area surrounded by the outermost protrusions 3121. Along the thickness direction of the tab 3, the protrusions 3121 protrude from the second area 3112, that is, the protrusions 3121 protrude relative to the tab 3 in the thickness direction. The protrusions 3121 can be formed on the tab 3 by methods such as laser treatment or extrusion forming. When the insulating layer 4 (adhesive layer) is bonded between the tab 3 and the empty foil area 11, the protrusions 3121 are embedded in the adhesive layer. The arrangement of the protrusions 3121 can increase the bonding area between the adhesive layer and the tab 3, making the bonding between the adhesive layer and the tab 3 more firm and improving the connection strength between the tab 3 and the current collector 1. Moreover, the arrangement of the protrusions 3121 enables the tab 3 to be electrically connected to the current collector through the protrusions 3121. Compared with the traditional tab connection mode, it can reduce a certain electrical connection area, have a certain optimization effect on the current density near the groove 21, and be more convenient for adapting to the high-rate charge and discharge of secondary batteries. At the same time, the protrusions 3121 play a role similar to that of a reinforcing rib, which can improve the strength of the tab 3, reduce the risk of the tab 3 being torn, and improve the anti-collision performance of the secondary battery.

[0046] In this application, no setting is made on the shape of the protrusions 3121. The protrusions 3121 can be strip-shaped, spherical, hemispherical or any other shape. The protrusions 3121 pass through the adhesive layer and contact the current collector 1, so that the protrusions 3121 are electrically connected to the current collector 1, enabling the tab 3 to be electrically connected to the current collector 1 through the second area 3112.

[0047] In some alternative embodiments, a plurality of protrusions 3121 are provided and are evenly spaced along the length and width directions of the second area 312. The arrangement of the plurality of protrusions 3121 can improve the connection strength between the tab 3 and the current collector 1.

[0048] Furthermore, the cross-sectional area of ​​the protrusion 3121 gradually decreases in the direction toward the empty foil area 11 , so that the end of the protrusion 3121 away from the electrode tab 3 is set as a pointed end, so as to improve the smoothness of the protrusion 3121 passing through the glue layer.

[0049] The present application fixes the electrode tab 3 to the current collector 1 through the adhesive layer, and the first region 3111 is insulated and connected to the current collector 1 through the adhesive layer, and the second region 3112 is electrically connected to the current collector 1 through the protrusion 3121, thereby improving the convenience and stability of the connection.

[0050] In some optional embodiments, the adhesive layer includes at least one of a hot melt adhesive, a pressure sensitive adhesive, and a thermosetting adhesive. For example, the adhesive layer may be a hot melt adhesive, and the adhesive layer may be first bonded to the empty foil area 11, and then the tab 3 may be bonded to the adhesive layer by hot pressing, and the hot pressing adhesive layer may be melted and embedded in the embedding groove 21, and the tab 3 may be fixed to the current collector 1 after the adhesive layer is cured. The adhesive layer may also be a thermosetting adhesive, and after the adhesive layer is bonded to the empty foil area 11, it may be cured by hot pressing to fix the tab 3 to the current collector 1.

[0051] In some optional embodiments, the material of the glue layer includes at least one of epoxy resin, polyolefin, polystyrene, polymethyl methacrylate, phenolic resin or styrene-butadiene rubber. In one example, the glue layer includes epoxy resin, which has excellent bonding properties and chemical corrosion resistance, strong bonding properties and small swelling after soaking, and can adapt to various electrochemical reactions inside the battery, and the epoxy resin can be cured by heating or reacting with a curing agent to form a solid glue layer. The glue layer can also be made of a mixture of two or more of epoxy resin, polyolefin, polystyrene, polymethyl methacrylate, phenolic resin or styrene-butadiene rubber, which is determined according to actual conditions and is not limited by this application.

[0052] In some optional embodiments, the second region 3112 is bonded to the empty foil region 11 through a conductive adhesive layer having conductivity, and the first region 3111 is bonded to the empty foil region 11 through an insulating adhesive layer. In this way, the electrical connection between the tab 3 and the current collector 1 can be achieved by bonding the second region 3112 through the conductive adhesive layer. For example, the conductive adhesive layer includes conductive metal fillers such as silver, copper, and nickel, so that the adhesive layer has conductivity.

[0053] Reference Figure 4 , showing a schematic diagram of the structure of a pole piece provided in an embodiment of the present application Figure 4, in some alternative embodiments, the insulating layer 4 is an insulating coating, and the second region 3112 is welded to the empty foil region 11. It should be understood that, at this time, the region formed by enclosing the outer edge of the portion where the tab 3 is in conductive contact with the empty foil region 11 refers to the region where the tab 3 is directly in contact with the empty foil region 11 and no insulating coating is provided. During manufacturing, the insulating coating can be first applied to the first region 3111 to ensure insulation between the first region 3111 and the current collector 1, and then the second region 3112 is welded to the empty foil region 11.

[0054] In some alternative embodiments, the insulating coating includes at least one of a ceramic coating and a glass fiber coating. The ceramic coating and the glass fiber coating have good thermal stability. When the current collector 1 is welded to the tab 3, the insulating coating is less affected by the welding when using the ceramic coating and the glass fiber coating, and at the same time, the insulating property can be maintained.

[0055] Referring to Figure 5 and Figure 6 , Figure 5 shows a schematic structure of a tab provided by an embodiment of the present application Figure 1 , Figure 6 shows a schematic structure of a tab provided by an embodiment of the present application Figure 2 . In some alternative embodiments, the shape of the second region 3112 includes any one of a rectangle and a trapezoid. The shape of the second region 3112 is not limited in the present application. However, when the area is certain, when the shape of the second region 3112 is a rectangle or a trapezoid, it can have a better effect of optimizing the current distribution in the region around the groove 21, thereby further reducing the risk of lithium plating. As Figure 6 shown, when the second region 3112 is trapezoidal, along the extending direction of the first portion 31, the second region 3112 includes a long side and a short side that are oppositely arranged, and the short side is closer to the second portion 32 than the long side.

[0056] In some alternative embodiments, 0.3 ≤ area S1 / area S2 ≤ 0.85. When area S1 / area S2 ≥ 0.3, the effect of optimizing the current distribution by setting the insulating layer will not be too weak, which is beneficial to reducing the risk of lithium plating; when S1 / area S2 ≤ 0.85, the risk of excessively high local temperature caused by local overcurrent can be reduced, and at the same time, the connection strength between the tab 3 and the current collector 1 will not be too small, which is beneficial to the tab 3 having appropriate tensile strength; when 0.3 ≤ area S1 / area S2 ≤ 0.85, the current distribution can be optimized, the maximum value of the current density can be reduced, the tensile strength of the tab 3 can be improved, and the risk of the tab 3 being torn can be reduced.

[0057] Further, 0.4 ≤ area S1 / area S2 ≤ 0.6, which further optimizes the current distribution, reduces the maximum value of the current density, further improves the tensile strength of the tab 3, and reduces the risk of the tab 3 being torn.

[0058] Regarding the thickness of the insulating layer 4, if the thickness of the insulating layer 4 is too large, it will affect the energy density of the battery; if the thickness of the insulating layer 4 is too small, the insulation performance of the insulating layer 4 is likely to be unstable. In the embodiments of the present application, along the thickness direction of the current collector 10, the maximum thickness of the insulating layer 4 is T1, and 2 μm ≤ T1 ≤ 50 μm, which can reduce the influence of the insulating layer 4 on the energy density of the secondary battery while maintaining good stability.

[0059] The present application will be further described below through specific embodiments.

[0060] The preparation process of the battery in Embodiment 1 includes the following steps:

[0061] Preparation of the positive electrode sheet: The positive electrode active material lithium cobaltate, the conductive agent conductive carbon black, and the binder polyvinylidene fluoride (PVDF) are dissolved in an N-methylpyrrolidone (NMP) solution in a weight ratio of 97.5:1:1.5 to form a positive electrode slurry. Aluminum foil is used as the positive electrode current collector, and the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing, and slitting, a positive electrode sheet is obtained.

[0062] Preparation of the negative electrode sheet: The negative electrode active material artificial graphite, silicon oxide, the thickener carboxymethyl cellulose sodium (CMC), and the binder styrene-butadiene rubber (SBR) are mixed in a weight ratio of 86:10:1.5:2.5, deionized water is added, and the mixture is stirred evenly under the action of a vacuum mixer to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil; dried, and then after cold pressing, slicing, and slitting, a negative electrode sheet is obtained.

[0063] Preparation of the separator: The base layer of the separator is polyethylene (PE), alumina ceramic layers are coated on both sides of the base layer 231 of the separator, and then polyvinylidene fluoride (PVDF) is coated on both sides of the coated ceramic layers, and dried.

[0064] Preparation of the electrolyte: In a dry argon atmosphere glove box, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:5:2, and the lithium salt LiPF6 is added. After mixing evenly, an electrolyte is obtained, wherein the mass percentage concentration of LiPF6 is 12.5%.

[0065] After the electrode sheet is cut, a laser can be used to form a groove 21 in the first active layer 22, and the first empty foil area 11 is exposed. An epoxy resin adhesive layer is bonded on the first empty foil area 11 as the insulating layer 4. A protruding portion 3121 is formed on the tab 3 by mechanical crimping. The protruding portions 3121 enclose a second area 3112. The second area 3112 is set as a rectangle, and the tab 3 and the empty foil area 11 with the adhesive layer are fixed by hot pressing. The protruding portion 3121 of the tab 3 faces the adhesive layer. During hot pressing and fixing, the protruding portion 3121 is embedded in the adhesive layer and contacts the empty foil area 11.

[0066] Preparation of the battery: Stack the separator, the positive electrode sheet, the separator, and the negative electrode sheet obtained above in sequence, wind them to obtain an electrode assembly, and perform hot pressing on the electrode assembly at a pressure of 5 MPa, a temperature of 65 °C, and a pressure holding time of 10 s. Put the electrode assembly into a packaging bag made of aluminum-plastic film, and both the positive tab and the negative tab extend from the top sealing edge of the packaging bag. After removing moisture at 80 °C, inject the electrolyte and seal it.

[0067] The specific process of lithium plating test is as follows:

[0068] (1) Maintain the test temperature at 25 °C;

[0069] (2) Let the battery stand for 30 min;

[0070] (3) Charge at a constant current of 1.3C to 4.1V, and then charge at a constant voltage to 1C;

[0071] (4) Charge at a constant current of 1C to 4.2V, and then charge at a constant voltage to 0.7C;

[0072] (5) Charge at a constant current of 0.7C to 4.3V, and then charge at a constant voltage to 0.025C;

[0073] (6) Let it stand for 5 min;

[0074] (7) Discharge at a constant current of 0.7C to 3V;

[0075] (8) Let it stand for 5 min;

[0076] (9) Repeat steps 3 to 8 for 800 times;

[0077] (10) Disassemble the battery, observe whether lithium plating occurs on the negative electrode sheet. Test 100 batteries, count the number of batteries in each group where lithium plating occurs on the negative electrode sheet. Let the number of batteries with lithium plating on the negative electrode sheet in this group of experiments be N, then the lithium plating incidence rate of the batteries in this group of experiments is N / 100×100%.

[0078] Tensile strength test method:

[0079] Disassemble the battery to obtain the positive electrode sheet and the negative electrode sheet. Taking the negative electrode sheet as an example, use a high-speed tensile testing machine to fix the tab at the lower end of the tensile testing machine, and fix the current collector at the upper end of the high-speed tensile testing machine, keeping both ends on the same vertical plane. Set the speed of the tensile testing machine to 50 mm / min, pull the tab and the current collector, and record the tensile force F (unit: N) when the tab and the current collector are separated. The test results are shown in Table 1.

[0080] Comparative Example 1: The difference from the Example is that the first region is not set. It should be noted that other parameters of Comparative Example 1 are the same as those of Example 1.

[0081] Other parameters of Examples 2-11 are the same as those of Example 1 except for the parameters involved in Table 1.

[0082] Table 1:

[0083] Note: In Table 1, "\ " means that the parameter is not included.

[0084] As shown in the above table, from Comparative Example 1 and Examples 1-6, it can be seen that when the first region is provided on the first surface of the tab and the area S1 / area S2≥0.85, the tab is insulated from the current collector through the first region, which can reduce the maximum value of the current density in the area near the groove, improve the current distribution state in this area, and is beneficial to reducing the risk of lithium deposition.

[0085] From Examples 1-7, it can be seen that when controlling the shape of the second region to be unchanged, by limiting 0.3≤area S1 / area S2≤0.85, the risk of lithium deposition can be reduced, and at the same time, the tab has appropriate tensile strength. When the area S1 / area S2 is greater than or equal to 0.85, the benefit of anti-lithium deposition obtained by continuously increasing S1 gradually decreases. By limiting 0.4≤area S1 / area S2≤0.6, the risk of lithium deposition in the battery can be further reduced and the tensile strength of the tab can be further improved, reducing the risk of tab tearing.

[0086] From Examples 8-10, it can be seen that when other conditions remain unchanged, controlling the shape of the second region to be rectangular or trapezoidal is beneficial to further reducing the risk of lithium deposition and further improving the tensile strength of the tab.

[0087] From Examples 4 and 11, it can be seen that when other conditions remain unchanged, different tab connection methods have the same anti-lithium deposition effect, and using the adhesive tab connection method can further improve the tensile strength of the tab.

[0088] Refer to Figures 1 - 5, this application also includes an electrical device, including the battery described in any of the above. The battery includes electrode plates, and the electrode plates include a current collector 1, an active material layer 2, and an electrode tab 3. The active material layer 2 is disposed on the current collector 1. The active material layer 2 is provided with a groove 21. The current collector 1 includes an empty foil area 11. The groove 21 exposes the empty foil area 11. The electrode tab 3 is disposed in the groove 21 and is electrically connected to the empty foil area 11. The electrode tab 3 includes a first part 31 and a second part 32 connected to each other. When observed along the thickness direction of the electrode tab 3, the first part 31 is the part of the electrode tab 3 that coincides with the empty foil area 11, and the second part 32 is located outside the empty foil area 11; the first part 31 includes a first surface facing the empty foil area 11. The first surface includes a first area 3111 and a second area 3112. An insulating connection is provided between the first area 3111 and the empty foil area 11 through an insulating layer 4. The first part 31 is electrically connected to the empty foil area 11 through the second area 3112; the first area 3111 is located on the side of the second area 3112 facing the second part 32.

[0089] Among them, the first part 31 is electrically connected to the empty foil area 11 through the second area 3112. The connection method can be welding or gluing or other methods, which are not limited in this application, so that the current flowing through the current collector 1 is led to the external circuit. An insulating connection is provided between the first area 3111 and the empty foil area 11 through the insulating layer 4. This application does not limit the insulating layer 4. The insulating layer 4 can be a coating or an adhesive layer or other material layers. The setting of the insulating layer 4 can optimize the electrical connection area between the electrode tab 3 and the empty foil area 11 in the groove 21, thereby reducing the maximum value of the current density in the area near the groove 21, improving the current distribution state in this area, making the current distribution more uniform, thus alleviating the accumulation of lithium ions in the active material layer area near the groove 21, alleviating the problem of lithium analysis, and further improving the battery performance.

[0090] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0091] The above-described embodiments only represent several implementation manners of this application. The description is relatively specific and detailed, but it cannot be understood as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several deformations and improvements can still be made, and these all belong to the protection scope of this application. Therefore, the protection scope of the patent of this application should be subject to the appended claims.

Claims

1. A battery, comprising a pole piece, the pole piece comprising a current collector (1), an active material layer (2) and a pole lug (3), the active material layer (2) being arranged on the current collector (1), the active material layer (2) being provided with a groove (21), the current collector (1) comprising a hollow foil area (11), the groove (21) exposing the hollow foil area (11), the pole lug (3) being arranged in the groove (21) and being electrically connected to the hollow foil area (11), characterized in that: The pole lug (3) comprises a first part (31) and a second part (32) which are connected to each other. When observed along the thickness direction of the pole lug (3), the first part (31) is the part where the pole lug (3) overlaps with the empty foil area (11), and the second part (32) is located outside the empty foil area (11); the first part (31) comprises a first surface (311) facing the empty foil area (11), the first surface (311) comprises a first area (3111) and a second area (3112), an insulating connection is arranged between the first area (3111) and the empty foil area (11) through an insulating layer (4), and the second area (3112) is the part where the pole lug (3) overlaps with the empty foil area (11). The first region (3111) is located on the side of the second region (3112) facing the second portion (32); along the extension direction of the pole lug (3), the first surface (311) has a first edge and a second edge that are arranged opposite to each other, and the first edge is located on the side of the second edge facing the second portion (32); there is a contact edge between the first region (3111) and the second region (3112), and along the extension direction of the pole lug (3), the first region (3111) extends from the contact edge to the first edge, and the second region (3112) extends from the contact edge to the second edge.

2. The battery according to claim 1, characterized in that The area of ​​the first region (3111) is S1, the area of ​​the first surface (311) is S2, and S1 / S2≥0.

2.

3. The battery according to claim 1, characterized in that The insulating layer (4) comprises an adhesive layer, the adhesive layer is bonded between the first surface (311) and the empty foil area (11), the first area (3111) is insulated and connected to the empty foil area (11) through the adhesive layer, and the second area (3112) is provided with a protrusion (3121), and the protrusion (3121) passes through the adhesive layer to be electrically connected to the current collector (1).

4. The battery according to claim 3, characterized in that The protrusions (3121) are provided in plurality and are spaced apart along the length and width directions of the second region (3112), and the protrusions (3121) are in contact with the empty foil region (11).

5. The battery according to claim 3, characterized in that The adhesive layer includes at least one of hot melt adhesive, pressure sensitive adhesive and thermosetting adhesive.

6. The battery according to claim 5, characterized in that The material of the adhesive layer includes at least one of epoxy resin, polyolefin, polystyrene, polymethyl methacrylate, phenolic resin or styrene-butadiene rubber.

7. The battery according to claim 1, characterized in that The insulating layer (4) is an insulating coating, and the second region (3112) is welded to the empty foil region (11).

8. The battery according to claim 7, characterized in that The insulating coating includes at least one of a ceramic coating and a glass fiber coating.

9. The battery according to claim 1, characterized in that The shape of the second area (3112) includes either a rectangle or a trapezoid.

10. The battery according to claim 9, characterized in that The second region (3112) is trapezoidal, and along the extension direction of the first portion (31), the second region (3112) includes a long side and a short side that are relatively arranged, and the short side is closer to the second portion (32) than the long side.

11. The battery according to claim 2, characterized in that 0.3≤Area S1 / Area S2≤0.

85.

12. The battery according to claim 10, characterized in that 0.4≤Area S1 / Area S2≤0.

6.

13. The battery according to claim 10, characterized in that The active material layer (2) comprises a first active layer (22) and a second active layer (23) located on opposite sides of the current collector (1), and the groove (21) is located in the first active layer (22) or the second active layer (23).

14. An electrical device, characterized in that: Comprising a battery as claimed in any one of claims 1 to 13.

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