Pole piece, laminated battery cell and electric equipment

Abstract

The invention provides a pole piece, a laminated battery cell and electric equipment. The pole piece comprises a current collector, an active substance layer and a supporting layer, the current collector comprises a single-sided region, and the active material layer is arranged on one side of the single-sided region in the thickness direction of the current collector; the supporting layer is arranged on the side, away from the active material layer, of the single-face area so as to weaken the stress difference of the two sides of the single-face area in the thickness direction. The supporting layer is arranged on the side, deviating from the active material layer, of the single-face area of the current collector, the supporting layer can enhance the strength of the pole piece, reduce the stress difference caused by the fact that the active material layer is arranged on the single side of the current collector, and reduce the risk that the pole piece is curled, so that the quality of a battery cell with the pole piece is improved, and under the condition that the warping rate of the pole piece is the same, the reliability of the battery cell is improved. Compared with the scheme that the warping rate of the pole piece is reduced by increasing the thickness of the current collector, the battery cell manufactured by the pole piece in the scheme has higher energy density.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a pole piece, a laminated battery cell and an electrical device. Background Art

[0002] With the rapid development of new energy technologies, battery cells have been widely used in electronic equipment, electric vehicles, electric two-wheeled vehicles, power tools, etc. As the application of battery cells becomes more and more extensive, higher requirements are placed on the quality of battery cells. Summary of the invention

[0003] The embodiments of the present application provide a pole piece, a laminated battery cell and an electrical device to improve the quality of the battery cell.

[0004] In a first aspect, an embodiment of the present application provides a pole piece, comprising a current collector, an active material layer and a support layer; the current collector comprises a single-sided region, and along the thickness direction of the current collector, the active material layer is arranged on one side of the single-sided region; the support layer is arranged on the side of the single-sided region away from the active material layer to weaken the stress difference on both sides of the single-sided region along the thickness direction.

[0005] In one or more of the above optional embodiments, the single-sided region of the current collector is provided with an active material layer only on one side along its thickness direction. By providing a support layer on the side of the single-sided region of the current collector away from the active material layer, the support layer can enhance the strength of the pole piece, reduce the stress difference between the two sides caused by the current collector only having the active material layer on one side, reduce the risk of the pole piece curling, and thus improve the quality of the battery cell with the pole piece. In addition, when the warpage of the pole piece is the same, the battery cell formed by the pole piece manufacturing of this scheme has a higher energy density than the scheme of increasing the thickness of the current collector to reduce the warpage of the pole piece.

[0006] In some embodiments of the first aspect of the present application, when observed along the thickness direction of the current collector, a projection of the active material layer and a projection of the support layer at least partially overlap.

[0007] In one or more of the above optional embodiments, when observed along the thickness direction of the current collector, the projection of the active material layer and the projection of the support layer at least partially overlap, so that the support layer can weaken the stress difference caused by the unilateral arrangement of the active material layer on the current collector in the area corresponding to the active material layer, reduce the risk of curling of the electrode sheet, and thus improve the quality of the battery cell equipped with the electrode sheet.

[0008] In some embodiments of the first aspect of the present application, when observed along the thickness direction of the current collector, the ratio of the area of ​​the projection of the support layer covering the projection of the active material layer to the area of ​​the active material layer in the single-sided area is greater than or equal to 0.75 and less than or equal to 1.

[0009] In one or more of the above optional embodiments, when observed along the thickness direction of the current collector, the ratio of the area of ​​the projection of the active material layer covered by the projection of the support layer to the area of ​​the active material layer in the single-sided area is greater than or equal to 0.75, and the area of ​​the active material layer covered by the support layer is large enough, which is beneficial for the support layer to reduce the stress difference caused by the single-sided arrangement of the active material layer in the area corresponding to the active material layer, reduce the risk of curling of the pole piece, and thus improve the quality of the battery cell. When observed along the thickness direction of the current collector, the ratio of the area of ​​the projection of the active material layer covered by the projection of the support layer to the area of ​​the active material layer in the single-sided area is less than or equal to 1, which can reduce material waste.

[0010] In some embodiments of the first aspect of the present application, when observed along the thickness direction of the current collector, the ratio of the area of ​​the projection of the support layer covering the projection of the active material layer to the area of ​​the active material layer in the single-sided area is greater than or equal to 0.95.

[0011] In one or more of the above optional embodiments, when observed along the thickness direction of the current collector, the ratio of the area of ​​the projection of the support layer covering the projection of the active material layer to the area of ​​the active material layer in the single-sided area is greater than or equal to 0.95. The support layer covers a larger area of ​​the active material layer, which is beneficial for the support layer to reduce the stress difference caused by the single-side arrangement of the active material layer in the area corresponding to the active material layer, further reduce the risk of curling of the electrode, and thus further improve the quality of the battery cell.

[0012] In some embodiments of the first aspect of the present application, when observed along the thickness direction of the current collector, the projection of the support layer completely covers the projection of the active material layer in the single-sided area.

[0013] In one or more of the above optional embodiments, when observed in the thickness direction of the current collector, the projection of the support layer completely covers the projection of the active material layer in the single-sided area, so that the support layer can minimize the stress difference on both sides of the single-sided area along the thickness direction, reduce the risk of curling of the pole piece, and thus improve the quality of the battery cell equipped with the pole piece.

[0014] In some embodiments of the first aspect of the present application, the Mohs hardness of the support layer is greater than the Mohs hardness of the active material layer.

[0015] In one or more of the above optional embodiments, the Mohs hardness of the supporting layer is greater than the Mohs hardness of the active material layer, so that the supporting layer has better mechanical properties, so that the supporting layer can weaken the stress difference caused by the unilateral arrangement of the active material layer on the current collector in the area corresponding to the active material layer, reduce the risk of curling of the pole piece, and thus improve the quality of the battery cell having the pole piece.

[0016] In some embodiments of the first aspect of the present application, the Mohs hardness of the support layer is greater than 6.5.

[0017] In one or more of the above optional embodiments, the Mohs hardness of the support layer is greater than 6.5, so that the support layer has better mechanical properties, so that the support layer can weaken the stress difference caused by the unilateral arrangement of the active material layer on the current collector in the area corresponding to the active material layer, reduce the risk of curling of the electrode sheet, and thus improve the quality of the battery cell having the electrode sheet.

[0018] In some embodiments of the first aspect of the present application, the material of the support layer is an insulating material.

[0019] In one or more of the above optional embodiments, the support layer is made of insulating material, which reduces the risk of short circuit in the area of ​​the current collector not coated with the active material layer, thereby improving the safety performance of the battery cell with the pole piece.

[0020] In some embodiments of the first aspect of the present application, the support layer comprises ceramic.

[0021] In one or more of the above optional embodiments, the support layer includes ceramics, which have good strength and insulation properties.

[0022] In some embodiments of the first aspect of the present application, the material of the support layer also includes an adhesive, the weight percentage of the ceramic is greater than 90%, and the weight percentage of the adhesive is greater than 0.5% and less than 5%.

[0023] In one or more of the above optional embodiments, the weight percentage of the ceramic in the support layer is greater than 90%, and the weight percentage of the adhesive in the support layer is greater than 0% and less than 5%, so that the support layer has better hardness and strength, which can better reduce the stress difference caused by the unilateral setting of the active material layer on the current collector and reduce the risk of curling of the pole piece.

[0024] In some embodiments of the first aspect of the present application, the adhesive includes a polyacrylate adhesive.

[0025] In one or more of the above optional embodiments, the adhesive includes a polyacrylate adhesive, which has the advantages of being environmentally friendly, multifunctional, high bonding, and high shear strength.

[0026] In some embodiments of the first aspect of the present application, the material of the support layer also includes a non-white dye.

[0027] In one or more of the above optional embodiments, the material of the support layer also includes a non-white dye to facilitate the distinction between the pole piece and the isolation membrane.

[0028] In some embodiments of the first aspect of the present application, the weight percentage of the coloring agent is greater than 0% and less than 5%.

[0029] In one or more of the above optional embodiments, the weight percentage of the dye is greater than 0% and less than 5%, so that the weight proportion of the dye is relatively small, thereby reducing the influence of the dye on the strength of the support layer.

[0030] In some embodiments of the first aspect of the present application, the thickness of the support layer is 2 μm to 20 μm.

[0031] In one or more of the above optional embodiments, the thickness of the support layer is greater than or equal to 2 μm, so that the support layer has good strength, can better reduce the stress difference caused by the active material layer being arranged on one side of the current collector, and reduce the risk of curling of the pole piece. The thickness of the support layer is less than or equal to 20 μm to avoid the energy density of the battery cell being reduced due to excessive thickness of the support layer.

[0032] In some embodiments of the first aspect of the present application, the current collector includes an insulating layer and two conductive layers. Along the thickness direction of the current collector, the two conductive layers are respectively arranged on both sides of the insulating layer, the active material layer is arranged on a side of one of the two conductive layers away from the insulating layer, and the support layer is arranged on a side of the other of the two conductive layers away from the insulating layer.

[0033] In one or more of the above optional embodiments, the current collector includes an insulating layer and two conductive layers. The insulating layer is used as a mechanical support skeleton of the current collector, thereby reducing metal burrs caused by mechanical damage to the battery cell equipped with the pole piece, which is beneficial to improving the safety performance of the battery cell equipped with the pole piece.

[0034] In some embodiments of the first aspect of the present application, along the thickness direction of the current collector, the size of the insulating layer is W1, 3.4 μm≤W1≤12 μm.

[0035] In one or more of the above optional embodiments, the size of the insulating layer along the thickness direction of the current collector is greater than or equal to 3.4 μm, which can play a good mechanical support role, thereby reducing the metal burrs caused by mechanical damage to the battery cell with the pole piece, thereby helping to improve the safety performance of the battery cell with the pole piece. The size of the insulating layer along the thickness direction of the current collector is less than or equal to 12 μm, which is conducive to the light weight of the current collector.

[0036] In some embodiments of the first aspect of the present application, along the thickness direction of the current collector, the size of the conductive layer is W2, 0.5 μm≤W2≤3 μm.

[0037] In one or more of the above optional embodiments, along the thickness direction of the current collector, the size of the conductive layer is greater than or equal to 0.5 μm, which is conducive to the current collector having better conductivity. Along the thickness direction of the current collector, the size of the conductive layer is less than or equal to 3 μm, which can reduce the metal burrs caused by mechanical damage to the battery cell with the pole piece, thereby helping to improve the safety performance of the battery cell with the pole piece. Since the thinner the conductive layer in the current collector, the greater the problem of curling, because the design of the present application can make the metal layer thinner, W2 can be limited to less than or equal to 3 μm.

[0038] In some embodiments of the first aspect of the present application, the current collector is a metal layer.

[0039] In one or more of the above optional embodiments, the current collector is a metal layer, so that the current collector has better strength and current flow capacity.

[0040] In some embodiments of the first aspect of the present application, along the thickness direction of the current collector, the thickness of the current collector is W3, 8μm≤W3≤20μm.

[0041] In one or more of the above optional embodiments, the size of the current collector along the thickness direction of the current collector is greater than or equal to 8 μm, which is conducive to the current collector having good conductivity. The size of the current collector along the thickness direction of the current collector is less than or equal to 20 μm, which can reduce the metal burrs caused by mechanical damage to the battery cell with the pole piece, thereby helping to improve the safety performance of the battery cell with the pole piece.

[0042] In a second aspect, an embodiment of the present application provides a laminated battery cell, comprising a plurality of inner pole sheets and an outermost pole sheet, wherein the plurality of inner pole sheets and the outermost pole sheet are stacked, and along the stacking direction, the outermost pole sheet is the pole sheet described in any one of the first aspects.

[0043] In one or more of the above optional embodiments, the outermost electrode sheet of the stacked battery cell is the electrode sheet provided by any embodiment of the first aspect, and the outermost electrode sheet is provided with a support layer on the side of the current collector away from the active material layer. The support layer can enhance the strength of the electrode sheet, weaken the stress difference caused by the active material layer being provided on one side of the current collector, and reduce the risk of curling of the electrode sheet, thereby improving the quality of the stacked battery cell.

[0044] In the second aspect, the application embodiment provides an electrical device, including the laminated battery cell provided in the embodiment of the second aspect.

[0045] In one or more of the above optional embodiments, the laminated battery core provided in the second aspect embodiment has good quality, which is beneficial to improving the power reliability and power safety of electrical equipment powered by the laminated battery core. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope.

[0047] Figure 1 A schematic diagram of the structure of a battery cell provided in some embodiments of the present application;

[0048] Figure 2 for Figure 1 A1-A1 sectional view;

[0049] Figure 3 A schematic diagram of the structure of a battery cell provided in some other embodiments of the present application;

[0050] Figure 4 for Figure 3 A2-A2 sectional view;

[0051] Figure 5 A cross-sectional view of a battery cell provided in some further embodiments of the present application;

[0052] Figure 6 A cross-sectional view of a battery cell provided in some other embodiments of the present application;

[0053] Figure 7 A schematic diagram of the structure of a pole piece provided in some embodiments of the present application;

[0054] Figure 8 A schematic diagram of the structure of a pole piece provided in some other embodiments of the present application;

[0055] Fig. 9 A schematic diagram of the structure of a pole piece provided in some further embodiments of the present application;

[0056] Fig.10 A schematic diagram of the structure of pole pieces provided in other embodiments of the present application;

[0057] Fig.11 This is a schematic diagram of the structure of pole pieces provided in some further embodiments of the present application.

[0058] Icon: 100-battery cell; 10-housing; 20-electrode assembly; 21-pole piece; 21a-positive electrode piece; 21b-negative electrode piece; 211-current collector; 2111-insulating layer; 2112-conductive layer; 212-active material layer; 213-support layer; 211a-empty foil area; 22-inner electrode piece; 23-outermost electrode piece; 24-separating film; 25-positive electrode ear; 26-negative electrode ear; 27-insulating part; X-thickness direction of current collector; Y-length direction of current collector; Z-width direction of current collector; A-single-sided area. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0060] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0061] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0062] In the description of the embodiments of the present application, it should be noted that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the application is usually placed when in use, or the orientation or positional relationship commonly understood by those skilled in the art, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0063] In the description of the embodiments of the present application, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0064] At present, judging from the development of the market situation, the application of battery cells is becoming more and more extensive. Battery cells are widely used in electric vehicles such as electric bicycles, electric motorcycles, electric vehicles, as well as electric tools, drones, energy storage equipment and other fields. With the continuous expansion of the application field of battery cells, the market demand is also constantly expanding.

[0065] The battery cells include wound battery cells and laminated battery cells. The electrode assembly of the laminated battery cell includes a plurality of pole pieces with opposite polarities alternately stacked, thereby forming a plurality of inner pole pieces and two outermost pole pieces in the stacking direction. The current collector of the outermost pole piece is provided with an active material side layer only on one side in the thickness direction, that is, the outermost pole piece is a single-sided coating structure. Since the active material layer is provided on one side of the outermost pole piece, there is a stress difference on both sides of the outermost pole piece, which is prone to severe curling, especially when the current collector is a composite current collector. Because the thickness of the composite current collector is thin, the curling of the outermost pole piece is more serious, thereby reducing the quality of the battery cell.

[0066] Based on the above considerations, in order to alleviate the problem of curling of the outermost electrode of the stacked battery cell, an embodiment of the present application provides a electrode, which includes a current collector, an active material layer and a support layer; the current collector includes a single-sided area, and along the thickness direction of the current collector, the active material layer is arranged on one side of the single-sided area; the support layer is arranged on the side of the single-sided area away from the active material layer.

[0067] The single-sided area of ​​the current collector is provided with an active material layer only on one side along the thickness direction. By providing a support layer on the side of the single-sided area of ​​the current collector away from the active material layer, the support layer can enhance the strength of the electrode piece, weaken the stress difference on both sides of the single-sided area along the thickness direction, reduce the risk of curling of the electrode piece, and thus improve the quality of the battery cell equipped with the electrode piece.

[0068] The battery cell with the pole piece disclosed in the embodiment of the present application can be used in, but not limited to, electric two-wheeled vehicles, electric tools, drones, energy storage devices and other electrical equipment. The battery cell manufactured with the pole piece having the working conditions of the present application can also be used as the power supply system of the electrical equipment, which is conducive to improving the safety performance of the battery cell.

[0069] The present application provides an electric device using a battery cell as a power source, and the electric device may be, but is not limited to, electronic equipment, electric tools, electric vehicles, drones, and energy storage devices. Among them, electronic equipment may include mobile phones, tablets, laptops, etc., electric tools may include electric drills, electric saws, etc., and electric vehicles may include electric cars, electric motorcycles, electric bicycles, etc.

[0070] like Figure 1-Figure 4As shown, an embodiment of the present application provides a battery cell 100, and the battery cell 100 may be a laminated battery cell. The battery cell 100 includes a housing 10 and an electrode assembly 20. The electrode assembly 20 is accommodated in the housing 10, and the electrode assembly 20 may be a laminated electrode assembly. The electrode assembly 20 includes a plurality of stacked pole pieces 21, and along the stacking direction of the pole pieces 21, two adjacent pole pieces 21 have opposite polarities, that is, in the stacking direction, one of the two adjacent pole pieces 21 is a positive pole piece 21a, and the other is a negative pole piece 21b. An isolation film 24 is provided between two adjacent pole pieces 21 of opposite polarity, and the isolation film 24 insulates and separates the two pole pieces 21 of opposite polarity, thereby reducing the risk of short circuit of the battery cell 100. The material of the isolation film 24 may include PP (polypropylene) or PE (polyethylene), etc.

[0071] The shell 10 may be a hard shell, for example, the shell 10 is a steel shell or an aluminum shell, forming a steel shell battery or an aluminum shell battery.

[0072] The outer shell 10 may also be formed of a relatively soft material, for example, the outer shell 10 is an aluminum-plastic film or a steel-plastic film, forming a soft-pack battery cell.

[0073] The multiple pole pieces 21 of the electrode assembly 20 of the laminated battery cell 100 include an inner pole piece 22 and an outermost pole piece 23. There are two outermost pole pieces 23, and the multiple inner pole pieces 22 are located between the two outermost pole pieces 23. The outermost pole piece 23 can be a single-sided coated pole piece, that is, the current collector 211 of the outermost pole piece 23 is only provided with an active material layer 212 on one side facing the inner pole piece 22. The inner pole piece 22 can be a double-sided coated pole piece, that is, the current collector of the inner pole piece 22 is coated with an active material layer on both surfaces along its thickness direction.

[0074] The battery cell 100 further includes a positive electrode tab 25 and a negative electrode tab 26. The positive electrode tab 25 is connected to the positive electrode sheet 21a and extends out of the housing 10, and the negative electrode tab 26 is connected to the negative electrode sheet 21b and extends out of the housing 10. Figure 1 , Figure 2 As shown, the positive electrode tab 25 and the negative electrode tab 26 may extend from the same end of the housing 10. Figure 3 , Figure 4 It can be seen that the positive electrode tab 25 and the negative electrode tab 26 can also extend from opposite ends of the housing 10 .

[0075] The positive electrode ear 25 and the current collector 211 of the positive electrode sheet 21a can be integrally formed, for example, the positive electrode ear 25 and the current collector 211 of the positive electrode sheet 21a are formed by die-cutting the substrate, thereby realizing the integral forming of the positive electrode ear 25 and the current collector 211 of the positive electrode sheet 21a. The positive electrode ear 25 and the current collector 211 of the positive electrode sheet 21a can be separately set, and then connected into one by welding connection, conductive adhesive connection, riveting connection, etc.

[0076] The negative electrode ear 26 and the current collector of the negative electrode sheet 21b can be integrally formed, for example, the negative electrode ear 26 and the current collector of the negative electrode sheet 21b are formed by die-cutting the substrate, thereby realizing the integral forming of the negative electrode ear 26 and the current collector of the negative electrode sheet 21b. The negative electrode ear 26 and the current collector of the negative electrode sheet 21b can be separately set, and then connected into one by welding connection, conductive adhesive connection, riveting connection, etc.

[0077] The two outermost electrodes 23 of the laminated battery cell can be positive electrodes 21a. Figure 2 , Figure 4 The figure shows the case where the outermost electrode sheets 23 of the laminated battery cell are all positive electrode sheets 21a. The two outermost electrode sheets 23 of the laminated battery cell can also be negative electrode sheets 21b. Figure 5 The figure shows the case where the outermost electrode sheets 23 of the laminated battery cell 100 are all negative electrode sheets 21b. The two outermost electrode sheets 23 of the laminated battery cell 100 can also be one outermost electrode sheet 23 is a positive electrode sheet 21a, and the other outermost electrode sheet 23 is a negative electrode sheet 21b. Figure 6 , it is shown that the two outermost electrode sheets 23 of the laminated battery cell 100 may also be a case where one outermost electrode sheet 23 is a positive electrode sheet 21 a and the other outermost electrode sheet 23 is a negative electrode sheet 21 b .

[0078] The present application embodiment provides a pole piece 21, which can be used as the pole piece 21 of the outermost pole piece 23 of the laminated battery core 100. Figure 7 , Figure 8 As shown, the pole piece 21 includes a current collector 211, an active material layer 212 and a support layer 213; the current collector 211 includes a single-sided area A, and along the thickness direction X of the current collector, the active material layer 212 is arranged on one side of the single-sided area A; the support layer 213 is arranged on the side of the single-sided area A away from the active material layer 212.

[0079] If the electrode sheet 21 is a positive electrode sheet 21a, the current collector 211 is a positive electrode current collector, the active material layer 212 is a positive electrode active material layer, the material of the positive electrode current collector may include aluminum, and the positive electrode active material may be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganese oxide, etc. If the electrode sheet 21 is a negative electrode sheet 21b, the current collector is a negative electrode current collector, the active material layer 212 is a negative electrode active material layer, the material of the negative electrode current collector may include copper, and the negative electrode active material may be carbon or silicon, etc.

[0080] The active material layer 212 is disposed on one side of the current collector 211 along the thickness direction X of the current collector, which means that the active material layer 212 is disposed on only one side of the current collector 211 along the thickness direction X of the current collector. The active material layer 212 is disposed on the surface of the current collector 211 along its thickness direction. The support layer 213 is disposed on the surface of the current collector 211 away from the active material layer 212 along its thickness direction. In other words, along the thickness direction X of the current collector, the active material layer 212 and the support layer 213 are disposed on two opposite surfaces of the current collector 211, respectively. The active material layer 212 is disposed on only one side of the current collector 211 along its thickness direction. By disposing the support layer 213 on the side of the current collector 211 away from the active material layer 212, the support layer 213 can enhance the strength of the pole piece 21, reduce the stress difference between the two sides of the single-sided area A along the thickness direction, reduce the risk of curling of the pole piece 21, and thus improve the quality of the battery cell 100 having the pole piece 21. In addition, when the warpage of the pole piece 21 is the same, compared with the solution of increasing the thickness of the current collector 211 to reduce the warpage of the pole piece 21, the battery cell 100 manufactured by the pole piece 21 of this solution has a higher energy density.

[0081] The stacking direction of the pole pieces of the laminated battery cell is parallel to the thickness direction X of the current collector.

[0082] like Figure 7 As shown, in some embodiments, the current collector 211 is a metal layer.

[0083] When the electrode sheet 21 is a positive electrode sheet 21a, the current collector 211 may be aluminum. When the electrode sheet 21 is a negative electrode sheet 21b, the current collector 211 may be copper. The current collector 211 is a metal layer, so that the current collector 211 has better strength and current carrying capacity.

[0084] like Figure 7 As shown, in the embodiment where the current collector 211 is a metal layer, along the thickness direction X of the current collector, the thickness of the current collector is W3, 8 μm≤W3≤20 μm.

[0085] Exemplarily, W3 may be 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, etc.

[0086] Along the thickness direction X of the current collector, the size of the current collector 211 is greater than or equal to 8 μm, which is conducive to the current collector 211 having good conductivity. Along the thickness direction X of the current collector, the size of the current collector 211 is less than or equal to 20 μm, which can reduce the metal burrs caused by mechanical damage to the battery cell 100 with the pole piece 21, thereby helping to improve the safety performance of the battery cell 100 with the pole piece 21. Since the thinner the metal layer in the current collector, the greater the problem of curling, because the design of the present application can make the metal layer thinner, so W2 can be limited to less than or equal to 20 μm.

[0087] like Figure 8 As shown, in other embodiments, the current collector 211 may be a composite current collector 211. The current collector 211 includes an insulating layer 2111 and two conductive layers 2112. Along the thickness direction X of the current collector, the two conductive layers 2112 are respectively arranged on both sides of the insulating layer 2111, the active material layer 212 is arranged on the side of one of the two conductive layers 2112 away from the insulating layer 2111, and the support layer 213 is arranged on the side of the other of the two conductive layers 2112 away from the insulating layer 2111.

[0088] Along the thickness direction X of the current collector, two conductive layers 2112 are respectively arranged on two opposite surfaces of the insulating layer 2111. The material of the insulating layer 2111 can be a polymer material. The material of the conductive layer 2112 can be a metal. When the pole piece 21 is a positive pole piece 21a, the material of the conductive layer 2112 can be aluminum. When the pole piece 21 is a negative pole piece 21b, the material of the conductive layer 2112 can be copper.

[0089] The current collector 211 includes an insulating layer 2111 and two conductive layers 2112. The insulating layer 2111 is used as a mechanical support skeleton of the current collector 211, thereby reducing metal burrs caused by mechanical damage to the battery cell 100 having the pole piece 21, which is beneficial to improving the safety performance of the battery cell 100 having the pole piece 21.

[0090] Since the support layer 213 is provided on the side of the single-sided region A of the current collector 211 away from the active material layer 212, the support layer 213 can enhance the mechanical properties of the current collector 211 and reduce the risk of curling of the current collector 211. Compared with the current collector without the support layer 213, after the support layer 213 is provided on the side of the single-sided region A of the current collector 211 away from the active material layer 212, the thickness of the current collector 211 itself can be made smaller.

[0091] like Figure 8 As shown, in the embodiment where the current collector 211 is a composite current collector, along the thickness direction X of the current collector, the size of the insulating layer 2111 is W1, and 3.4 μm≤W1≤12 μm.

[0092] By way of example, W1 may be 3.4 μm, 4 μm, 4.5 μm, 5 μm, 6 μm, 7 μm, 8 μm, 8 μm, 10 μm, 11 μm, 12 μm, etc.

[0093] The size of the insulating layer 2111 along the thickness direction X of the current collector is greater than or equal to 3.4 μm, which can play a good mechanical support role, thereby reducing the metal burrs caused by mechanical damage to the battery cell 100 with the pole piece 21, thereby helping to improve the safety performance of the battery cell 100 with the pole piece 21. The size of the insulating layer 2111 along the thickness direction X of the current collector is less than or equal to 12 μm, which is conducive to the light weight of the current collector 211.

[0094] Along the thickness direction X of the current collector, the size of the conductive layer 2112 is W2, 0.5 μm≤W2≤3 μm.

[0095] Illustratively, W2 may be 0.5 μm, 0.7 μm, 1 μm, 1.3 μm, 1.5 μm, 1.7 μm, 2 μm, 2.3 μm, 2.5 μm, 2.7 μm, 3 μm, etc.

[0096] Along the thickness direction X of the current collector, the size of the conductive layer 2112 is greater than or equal to 0.5 μm, which is beneficial for the current collector 211 to have good conductivity. Along the thickness direction X of the current collector, the size of the conductive layer 2112 is less than or equal to 3 μm, which can reduce the metal burrs caused by mechanical damage to the battery cell 100 with the pole piece 21, thereby improving the safety performance of the battery cell 100 with the pole piece 21.

[0097] like Fig. 9 , Fig.10 As shown, the single-sided area A can be the entire area of ​​the current collector 211. It can be understood that the single-sided area A is the current collector 211, and any area of ​​the current collector 211 is provided with an active material layer 212 on only one side in the thickness direction of the current collector and a support layer 213 on the other side.

[0098] In other embodiments, Fig.11As shown, the single-sided area A can be a part of the current collector 211, that is, the current collector 211 is provided with an active material layer 212 on only one side of the single-sided area A along the thickness direction X of the current collector, and the current collector 211 is provided with a support layer 213 on the other side of the single-sided area A along the thickness direction X of the current collector, and the active material layer 212 is provided on both sides of the thickness direction X of the current collector in a part of the area of ​​the current collector 211. Such a pole piece 21 can be used for a wound battery cell or a laminated battery cell. In the case where the pole piece 21 is wound to form a wound battery cell, the area of ​​the current collector 211 provided with the active material layer 212 on both sides of the thickness direction X of the current collector is wound to form the inner circle layer of the wound battery cell, and the single-sided area A is wound to form the outermost circle layer of the wound battery cell. For another example, the area of ​​the current collector 211 provided with the active material layer 212 on both sides of the thickness direction X of the current collector is wound to form the outer circle layer of the wound battery cell, and the single-sided area A is wound to form the innermost circle layer of the wound battery cell.

[0099] In some embodiments, when viewed along the thickness direction X of the current collector, the projection of the active material layer 212 and the projection of the support layer 213 at least partially overlap.

[0100] When observed along the thickness direction X of the current collector, the projection of the active material layer 212 and the projection of the support layer 213 at least partially overlap. It can be understood that in the plane perpendicular to the thickness direction X of the current collector, the orthographic projection of the active material layer 212 and the orthographic projection of the support layer 213 at least partially overlap.

[0101] When observed along the thickness direction X of the current collector, the projection of the active material layer 212 and the projection of the support layer 213 may completely overlap or partially overlap. When observed along the thickness direction X of the current collector, the projection of the active material layer 212 and the projection of the support layer 213 at least partially overlap, so that the support layer 213 can reduce the stress difference on both sides of the region corresponding to the active material layer 212 along the thickness direction, reduce the risk of curling of the pole piece 21, and thus improve the quality of the battery cell 100 having the pole piece 21.

[0102] In some embodiments, when viewed along the thickness direction X of the current collector, the ratio of the area of ​​the projection of the support layer 213 covering the projection of the active material layer 212 to the area of ​​the active material layer 212 in the single-sided area A is greater than or equal to 0.75 and less than or equal to 1.

[0103] When viewed along the thickness direction X of the current collector, the area where the projection of the support layer 213 covers the projection of the active material layer 212 refers to the area of ​​the overlapping region between the projection of the support layer 213 and the projection of the active material layer 212 in the single-sided area A.

[0104] For example, when observed along the thickness direction X of the current collector, the ratio of the projection area of ​​the support layer 213 covering the projection area of ​​the active material layer 212 to the area of ​​the active material layer in the single-sided area A can be 0.75, 0.8, 0.85, 0.9, 0.95, 1, etc.

[0105] When observed along the thickness direction X of the current collector, the ratio of the area of ​​the projection of the active material layer 212 covered by the projection of the support layer 213 to the area of ​​the active material layer 212 in the single-sided area A is greater than or equal to 0.75, and the area of ​​the active material layer 212 covered by the support layer 213 is large enough, which is conducive to the support layer 213 to reduce the stress difference on both sides of the region corresponding to the active material layer 212 along the thickness direction, reduce the risk of curling of the pole piece 21, and thus improve the quality of the battery cell 100. When observed along the thickness direction X of the current collector, the ratio of the area of ​​the projection of the active material layer 212 covered by the projection of the support layer 213 to the area of ​​the active material layer 212 in the single-sided area A is less than or equal to 1, which can reduce material waste.

[0106] In some embodiments, when viewed along the thickness direction X of the current collector, the ratio of the area of ​​the projection of the support layer 213 covering the projection of the active material layer 212 to the area of ​​the active material layer in the single-sided area A is equal to or greater than 0.95.

[0107] When observed along the thickness direction X of the current collector, the ratio of the projection area of ​​the active material layer 212 covered by the projection of the support layer 213 to the area of ​​the active material layer 212 in the single-sided area A is greater than or equal to 0.95. The area of ​​the active material layer 212 covered by the support layer 213 is large enough, which is beneficial for the support layer 213 to weaken the stress difference on both sides of the area corresponding to the active material layer 212 along the thickness direction, further reducing the risk of curling of the pole piece 21, thereby further improving the quality of the battery cell 100.

[0108] In some embodiments, when viewed along the thickness direction X of the current collector, the projection of the support layer 213 completely covers the projection of the active material layer 212 in the single-sided area A.

[0109] Observing along the thickness direction X of the current collector, the support layer 213 completely covers the active material layer 212 in the single-sided area A. It can be understood that in the plane perpendicular to the thickness direction X of the current collector, the orthographic projection of the active material layer 212 in the single-sided area A is located within the orthographic projection of the support layer 213.

[0110] Among them, in the plane perpendicular to the thickness direction X of the current collector, the edge of the orthographic projection of the support layer 213 may exceed the edge of the orthographic projection of the active material layer 212 in the single-sided area A, for example, the orthographic projection of the support layer 213 exceeds the two edges of the active material layer 212 in the single-sided area A in the width direction Z of the current collector, and / or, the orthographic projection of the support layer 213 exceeds the two edges of the active material layer 212 in the single-sided area A in the length direction Y of the current collector.

[0111] In a plane perpendicular to the thickness direction X of the current collector, an edge of the orthographic projection of the support layer 213 may be flush with an edge of the orthographic projection of the active material layer 212 in the single-sided region A.

[0112] The thickness direction X of the current collector, the width direction Z of the current collector and the length direction Y of the current collector are perpendicular to each other.

[0113] Observing in the thickness direction X of the current collector, the projection of the support layer 213 completely covers the projection of the active material layer 212 in the single-sided area A, so that the support layer 213 can weaken the stress difference on both sides of the area corresponding to the active material layer 212 along the thickness direction, reduce the risk of curling of the pole piece 21, and thus improve the quality of the battery cell 100 having the pole piece 21.

[0114] In some embodiments, the Mohs hardness of the support layer 213 is greater than the Mohs hardness of the active material layer 212 .

[0115] The measurement method of Mohs hardness is as follows: Mohs hardness can be measured by scratch method. The hardness value measured by scratch method indicates the ability of the material to resist local surface fracture. During the test, a set of reference materials with different hardness grades are used to compare scratches with the material to be tested, so as to determine the hardness grade of the material to be tested. For the support layer 213, a set of reference support layer 213 materials with different hardness grades are used to compare scratches with the material to be tested, so as to determine the hardness grade of the material to be tested.

[0116] The Mohs hardness of the support layer 213 is greater than the Mohs hardness of the active material layer 212, so that the support layer 213 has better mechanical properties, so that the support layer 213 can weaken the stress difference on both sides of the area corresponding to the active material layer 212 along the thickness direction, reduce the risk of curling of the electrode 21, and thus improve the quality of the battery cell 100 with the electrode 21.

[0117] In some embodiments, the support layer 213 has a Mohs hardness greater than 6.5.

[0118] Illustratively, the Mohs hardness of the support layer 213 may be 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or the like.

[0119] The Mohs hardness of the support layer 213 is greater than 6.5, so that the support layer 213 has better mechanical properties, so that the support layer 213 can weaken the stress difference on both sides of the area corresponding to the active material layer 212 along the thickness direction, reduce the risk of curling of the electrode 21, and thus improve the quality of the battery cell 100 with the electrode 21.

[0120] The support layer 213 may be made of various materials. In some embodiments, the support layer 213 is made of insulating material.

[0121] The support layer 213 is made of an insulating material, which reduces the risk of short circuit caused by the region of the current collector 211 not coated with the active material layer 212 , thereby improving the safety performance of the battery cell 100 having the electrode sheet 21 .

[0122] In the embodiment where the support layer 213 is made of insulating material, the support layer 213 may be a ceramic layer. The ceramic layer has good strength and insulation properties, so that the support layer 213 can reduce the stress difference on both sides of the region corresponding to the active material layer 212 along the thickness direction, reduce the risk of curling of the pole piece 21, and thus improve the quality of the battery cell 100 having the pole piece 21.

[0123] The support layer 213 includes ceramics. The support layer 213 is a ceramic layer. The ceramics may be hard ceramics, which have good strength and insulation properties.

[0124] The hardness of ceramics can be measured by the indentation method. The hardness value measured by the indentation method indicates the ability of the material to resist surface plastic deformation. During the test, a certain shape of indenter is pressed into the material surface under static load, and the hardness is calculated by measuring the area or depth of the indentation. For the support layer 213, during the test, a certain shape of indenter is pressed into the surface of the support layer 213 material under static load, and the hardness is calculated by measuring the area or depth of the indentation.

[0125] In some embodiments, the material of the support layer 213 may include an adhesive. The hard ceramic and the adhesive are mixed to form a slurry, which is then coated on the surface of the current collector 211 to form the support layer 213 .

[0126] The materials of hard ceramics include but are not limited to zirconium oxide, silicon dioxide, aluminum oxide, boehmite, silicon nitride and the like.

[0127] The materials of the adhesive include but are not limited to styrene-butadiene latex SBR, styrene-acrylate SAR, polyacrylic acid PPA, sodium carboxymethyl cellulose CMC-Na, polyvinylidene fluoride PVDF, hydrogenated nitrile rubber HNBR, polyvinyl alcohol PVA, and polyurethane.

[0128] In some embodiments, the adhesive comprises a polyacrylate adhesive.

[0129] The adhesive includes polyacrylate adhesive, which has the advantages of environmental protection, multi-function, high adhesion, high shear strength, etc.

[0130] In some embodiments, the weight percentage of ceramic is greater than 90%. The weight percentage of ceramic refers to the mass proportion of hard ceramic in the support layer 213. The weight percentage of hard ceramic in the support layer 213 is greater than 90%, so that the support layer 213 has good hardness and strength, and can better reduce the stress difference on both sides of the single-sided area A along the thickness direction, and reduce the risk of curling of the pole piece 21.

[0131] In some embodiments, the weight percentage of the adhesive in the support layer 213 is less than 5%. The weight percentage of the adhesive refers to the mass proportion of the adhesive in the support layer 213. The weight percentage of the adhesive in the support layer 213 is greater than 0% and less than 5%, so that the support layer 213 has better hardness and strength, can better reduce the stress difference on both sides of the single-sided area A along the thickness direction, and reduce the risk of curling of the pole piece 21.

[0132] The test method for the weight percentage of the adhesive is as follows: bake the ceramic layer (support layer 213) at a high temperature of 300°C until the weight of the ceramic layer (support layer 213) no longer changes, and calculate the weight reduction value divided by the original mass of the ceramic layer (support layer 213) without the adhesive content.

[0133] In some embodiments, the material of the support layer 213 further includes a non-white dye. The material of the support layer 213 includes a non-white dye to facilitate the distinction between the pole piece 21 and the isolation film 24 .

[0134] Exemplarily, the dye included in the material of the support layer 213 may be red dye, green dye, blue dye, orange dye, etc. The material of the dye includes but is not limited to carbon powder, kaolin, feldspar, quartz, clay, etc.

[0135] In some embodiments, the weight percentage of the dye is greater than 0% and less than 5%. The weight percentage of the dye refers to the mass proportion of the dye in the ceramic layer (support layer 213). The weight percentage of the dye in the support layer 213 is less than 5%, which makes the weight proportion of the dye smaller, reduces the effect of the dye on the strength of the support layer 213, and can also make the hard ceramic in the ceramic layer have a higher weight proportion, so that the support layer 213 has better hardness and strength, can better reduce the stress difference on both sides of the single-sided area A along the thickness direction, and reduce the risk of curling of the pole piece 21.

[0136] In some embodiments, the thickness of the support layer 213 is 2 μm to 20 μm.

[0137] The thickness of the support layer 213 is the distance between the surface of the support layer 213 facing the current collector 211 and the surface away from the current collector 211 along the thickness direction X of the current collector. Figure 8 As shown, the thickness of the support layer 213 is H, 2μm≤H≤20μm. For example, the thickness H of the support layer 213 can be 2μm, 3μm, 5μm, 7μm, 9μm, 11μm, 13μm, 15μm, 17μm, 19μm, 20μm, etc.

[0138] The thickness of the support layer 213 is greater than or equal to 2 μm, so that the support layer 213 has good strength, can better reduce the stress difference on both sides of the single-sided area A along the thickness direction, and reduce the risk of curling of the pole piece 21. The thickness of the support layer 213 is less than or equal to 20 μm to avoid the support layer 213 being too thick and causing the energy density of the battery cell 100 to decrease.

[0139] like Fig. 9 , Fig.10 As shown, in some embodiments, the pole piece 21 is further provided with an insulating member 27, the surface of the current collector 211 provided with the active material layer 212 includes an empty foil area 211a extending beyond the active material layer 212, and the insulating member 27 is arranged in the empty foil area 211a to reduce the risk of internal short circuit of the battery cell 100.

[0140] The following method is used to test the warpage of the pole piece 21:

[0141] Take the cold-pressed electrode 21 and cut it into multiple rectangular samples, for example, cut it into a rectangular sample with a length of 100 mm and a width of 50 mm; spread the sample on a marble platform with the coating active material layer 212 facing upward, and measure the dimensions L1 and L2 of the sample along the length direction Y and the width direction of the current collector in a naturally stretched state; use a steel ruler or a glass plate to flatten the sample and measure the dimensions L3 and L4 of the sample along the length direction Y and the width direction of the current collector; the warpage of the sample along the length direction Y of the current collector = (L3-L1) / L3*100%; the warpage of the sample along the width direction Z of the current collector = (L4-L2) / L4*100%.

[0142] The data in Table 1 are obtained by the above-mentioned pole piece 21 warpage test method:

[0143] It should be noted that the embodiments in Table 1 where the current collector 211 is aluminum foil or copper foil are cases where the current collector 211 is a metal layer. The embodiments where the current collector 211 is a composite aluminum foil or composite copper foil are cases where the current collector 211 includes an insulating layer 2111 and two conductive layers 2112, that is, the current collector 211 is a composite current collector 211.

[0144] Table 1

[0145]

[0146]

[0147]

[0148] In Table 1, when the electrode sheet 21 is a positive electrode sheet 21a, the active material layer 212 is lithium cobalt oxide:

[0149] (1) If the current collector 211 of the positive electrode sheet 21a is a metal layer, that is, the current collector 211 of the positive electrode sheet 21a is an aluminum foil, it can be seen from the comparative example 3 and the examples 1 to 10 that when the thickness of the current collector 211 is the same, the examples 1 to 10 are provided with a support layer 213 relative to the comparative example 3, and the warpage of the electrode sheet 21 in the examples 1 to 10 is significantly reduced relative to the warpage of the electrode sheet 21 in the comparative example 1, and the quality rate of the laminated battery cell is significantly increased. And as the thickness of the support layer 213 increases, the warpage of the electrode sheet 21 tends to gradually decrease, and the quality rate of the laminated battery cell 100 tends to gradually increase.

[0150] It can be seen from Comparative Example 1 and Example 3, and Comparative Example 2 and Example 2 that, when the pole piece warpage is the same, the thickness of the current collector 211 in Comparative Example 1 is greater than the sum of the thicknesses of the current collector 211 and the support layer 213 in Example 3, the thickness of the current collector 211 in Comparative Example 2 is greater than the sum of the thicknesses of the current collector 211 and the support layer 213 in Example 2, the energy density of the laminated cell in Comparative Example 1 is less than the energy density of the laminated cell in Example 3, and the energy density of the laminated cell in Comparative Example 2 is less than the energy density of the laminated cell in Example 2. Therefore, when the warpage of the pole piece is the same, the battery cell 100 manufactured by the pole piece 21 of this scheme has a higher energy density than the scheme in which the thickness of the current collector 211 is increased to reduce the warpage of the pole piece 21.

[0151] It can be seen from Examples 1 to 10 that although the pole piece curvature of Examples 9 and 10 is lower than that of Examples 1 to 8 and the laminated core superiority rate is greater than that of Examples 1 to 8, the energy density of the core in Examples 9 and 10 is lower than that of the laminated core in Examples 1 to 8. Therefore, when the thickness of the support layer 213 is less than or equal to 20 μm, the pole piece curvature is lower, the superiority rate of the laminated core is higher, and the energy density of the laminated core is higher. Compared with Examples 2 to 10, Example 1 has a higher pole piece curvature and a lower superiority rate of the laminated core. When the thickness of the support layer 213 is greater than or equal to 2 μm, the pole piece curvature is lower, the superiority rate of the laminated core is higher, and the energy density of the laminated core is higher. In summary, when the thickness of the support layer 213 is greater than or equal to 2 μm and less than or equal to 20 μm, the pole piece curvature is lower, the superiority rate of the laminated core is higher, and the energy density of the laminated core is higher.

[0152] (2) If the current collector 211 of the positive electrode sheet 21a is a composite current collector, that is, the current collector 211 of the positive electrode sheet 21a is a composite aluminum foil, referring to Comparative Example 6 and Examples 11 to 20, it can be seen that when the thickness of the current collector 211 is the same, Examples 11 to 20 are provided with a support layer 213 relative to Comparative Example 6, and the warpage of the electrode sheet 21 in Examples 11 to 20 is significantly reduced relative to the warpage of the electrode sheet 21 in Comparative Example 2, and the superiority rate of the laminated battery cell 100 is significantly increased. And as the thickness of the support layer 213 increases, the warpage of the electrode sheet 21 tends to gradually decrease, and the superiority rate of the laminated battery cell 100 tends to gradually increase.

[0153] It can be seen from Comparative Example 4 and Example 12, and Comparative Example 5 and Example 13 that, when the pole piece warpage is the same, the thickness of the current collector 211 in Comparative Example 4 is greater than the sum of the thicknesses of the current collector 211 and the support layer 213 in Example 12, the thickness of the current collector 211 in Comparative Example 5 is greater than the sum of the thicknesses of the current collector 211 and the support layer 213 in Example 13, the energy density of the laminated cell in Comparative Example 4 is less than the energy density of the laminated cell in Example 12, and the energy density of the laminated cell in Comparative Example 5 is less than the energy density of the laminated cell in Example 13. Therefore, when the pole piece warpage is the same, the battery cell 100 manufactured by the pole piece 21 of this scheme has a higher energy density than the scheme in which the thickness of the current collector 211 is increased to reduce the warpage of the pole piece 21.

[0154] It can be seen from Examples 11 to 20 that although the pole piece warping rates of Examples 19 and 20 are lower than those of Examples 11 to 18 and the excellence rate of the stacked cells is greater than that of Examples 11 to 18, the energy density of the cells in Examples 19 and 20 is lower than that of the stacked cells in Examples 11 to 18. Therefore, when the thickness of the support layer 213 is less than or equal to 20 μm, the pole piece warping rate is lower, the excellence rate of the stacked cells is higher, and the energy density of the stacked cells is higher. Example 11 has a higher pole piece warping rate and a lower quality rate of the laminated battery cell than Examples 12 to 20. When the thickness of the support layer 213 is greater than or equal to 2 μm, the pole piece warping rate is lower, the quality rate of the laminated battery cell is higher, and the energy density of the laminated battery cell is higher. In summary, when the thickness of the support layer 213 is greater than or equal to 2 μm and less than or equal to 20 μm, the pole piece warping rate is lower, the quality rate of the laminated battery cell is higher, and the energy density of the laminated battery cell is higher.

[0155] When the electrode sheet 21 is a negative electrode sheet 21b, the active material layer 212 is graphite:

[0156] (1) If the current collector 211 of the negative electrode sheet 21b is a metal layer, that is, the current collector 211 of the negative electrode sheet 21b is a copper foil, referring to Comparative Example 9 and Examples 21 to 30, it can be seen that when the thickness of the current collector 211 is the same, Examples 21 to 30 are provided with a support layer 213 relative to Comparative Example 9, and the warpage of the electrode sheet 21 in Examples 21 to 30 is significantly reduced relative to the warpage of the electrode sheet 21 in Comparative Example 3, and the superiority rate of the laminated battery cell 100 is significantly increased. And as the thickness of the support layer 213 increases, the warpage of the electrode sheet 21 tends to gradually decrease, and the superiority rate of the laminated battery cell 100 tends to gradually increase.

[0157] It can be seen from Comparative Example 7 and Example 22, and Comparative Example 8 and Example 23 that, when the pole piece warpage is the same, the thickness of the current collector 211 in Comparative Example 7 is greater than the sum of the thicknesses of the current collector 211 and the support layer 213 in Example 22, the thickness of the current collector 211 in Comparative Example 8 is greater than the sum of the thicknesses of the current collector 211 and the support layer 213 in Example 23, the energy density of the stacked cell in Comparative Example 7 is less than the energy density of the stacked cell in Example 22, and the energy density of the stacked cell in Comparative Example 8 is less than the energy density of the stacked cell in Example 23. Therefore, when the pole piece warpage is the same, the battery cell 100 manufactured by the pole piece 21 of this scheme has a higher energy density than the scheme in which the thickness of the current collector 211 is increased to reduce the warpage of the pole piece 21.

[0158] It can be seen from Examples 21 to 30 that although the pole piece warping rates of Examples 29 and 30 are lower than those of Examples 21 to 28 and the excellence rate of the laminated cells is greater than that of Examples 21 to 28, the energy density of the cells in Examples 29 and 30 is lower than that of the laminated cells in Examples 21 to 28. Therefore, when the thickness of the support layer 213 is less than or equal to 20 μm, the pole piece warping rate is lower, the excellence rate of the laminated cells is higher, and the energy density of the laminated cells is higher. Example 21 has a higher pole piece warping rate and a lower quality rate of the laminated battery cell than Examples 22 to 30. When the thickness of the support layer 213 is greater than or equal to 2 μm, the pole piece warping rate is lower, the quality rate of the laminated battery cell is higher, and the energy density of the laminated battery cell is higher. In summary, when the thickness of the support layer 213 is greater than or equal to 2 μm and less than or equal to 20 μm, the pole piece warping rate is lower, the quality rate of the laminated battery cell is higher, and the energy density of the laminated battery cell is higher.

[0159] (2) If the current collector 211 of the negative electrode sheet 21b is a composite current collector 211, that is, the current collector 211 of the negative electrode sheet 21b is a composite copper foil, referring to Comparative Example 12 and Examples 31 to 40, it can be seen that when the thickness of the current collector 211 is the same, Examples 31 to 40 are provided with a support layer 213 relative to Comparative Example 12, and the warpage of the electrode sheet 21 in Examples 31 to 40 is significantly reduced relative to the warpage of the electrode sheet 21 in Comparative Example 12, and the superiority rate of the laminated battery cell 100 is significantly increased. And as the thickness of the support layer 213 increases, the warpage of the electrode sheet 21 tends to gradually decrease, and the superiority rate of the laminated battery cell 100 tends to gradually increase.

[0160] It can be seen from Comparative Example 10 and Example 32, and Comparative Example 11 and Example 33 that, when the pole piece warpage is the same, the thickness of the current collector 211 in Comparative Example 10 is greater than the sum of the thicknesses of the current collector 211 and the support layer 213 in Example 32, the thickness of the current collector 211 in Comparative Example 11 is greater than the sum of the thicknesses of the current collector 211 and the support layer 213 in Example 33, the energy density of the stacked cell in Comparative Example 10 is less than the energy density of the stacked cell in Example 32, and the energy density of the stacked cell in Comparative Example 11 is less than the energy density of the stacked cell in Example 33. Therefore, when the warpage of the pole piece is the same, the battery cell 100 manufactured by the pole piece 21 of this scheme has a higher energy density than the scheme in which the thickness of the current collector 211 is increased to reduce the warpage of the pole piece 21.

[0161] It can be seen from Examples 31 to 10 that although the pole piece warping rates of Examples 39 and 40 are lower than those of Examples 31 to 38 and the excellence rate of the laminated cells is greater than that of Examples 31 to 38, the energy density of the cells in Examples 39 and 40 is lower than the energy density of the laminated cells in Examples 31 to 39. Therefore, when the thickness of the support layer 213 is less than or equal to 20 μm, the pole piece warping rate is lower, the excellence rate of the laminated cells is higher, and the energy density of the laminated cells is higher. Example 31 has a higher pole piece warping rate and a lower quality rate of the laminated battery cell than Examples 32 to 40. When the thickness of the support layer 213 is greater than or equal to 2 μm, the pole piece warping rate is lower, the quality rate of the laminated battery cell is higher, and the energy density of the laminated battery cell is higher. In summary, when the thickness of the support layer 213 is greater than or equal to 2 μm and less than or equal to 20 μm, the pole piece warping rate is lower, the quality rate of the laminated battery cell is higher, and the energy density of the laminated battery cell is higher.

[0162] In summary, by providing a support layer 213 on the side of the single-sided region A of the current collector 211 away from the active material layer 212, the support layer 213 can reduce the stress difference on both sides of the active single-sided region A along the thickness direction, reduce the risk of curling of the pole piece 21, and thus improve the quality of the battery cell 100 with the pole piece 21. Under the condition that the warpage of the pole piece 21 is the same, compared with the solution of increasing the thickness of the current collector 211 to reduce the warpage of the pole piece 21, the battery cell 100 manufactured by providing the pole piece 21 with the support layer 213 in the single-sided region A has a higher energy density.

[0163] The ratio of the area of ​​the projection of the support layer 213 covering the projection of the active material layer 212 to the area of ​​the active material layer 212 in the single-sided area A when observed along the thickness direction X of the current collector is defined as Q. As shown in Table 2:

[0164] Table 2

[0165]

[0166]

[0167]

[0168] In Table 2, when the electrode sheet 21 is a positive electrode sheet 21a, the active material layer 212 is lithium cobalt oxide:

[0169] (1) If the current collector 211 of the positive electrode sheet 21a is a metal layer, that is, the current collector 211 of the positive electrode sheet 21a is an aluminum foil, it can be seen from Examples 41 to 49 that when the thickness of the current collector 211 is the same, the warpage of the electrode sheet 21 in Examples 43 to 49 is smaller than that in Examples 41 and 42, and the laminated battery cell has a higher quality rate. Therefore, when Q ≥ 0.75, the electrode sheet 21 has a lower warpage and a higher quality rate of the laminated battery cell. In Examples 43 to 47, as Q increases, the warpage of the electrode sheet 21 gradually decreases, and the quality rate of the laminated battery cell 100 shows a gradually increasing trend. When Q is greater than or equal to 0.95, the electrode sheet warpage is less than 3%, and the laminated battery cell quality rate is greater than 90%. Therefore, when Q is greater than or equal to 0.95, the risk of electrode sheet warpage is lower and the battery cell quality rate is higher. It can be seen from Example 47, Example 48 and Example 49 that after Q is greater than 1, the warping rate of the pole piece 21 and the quality rate of the laminated battery cell have no obvious change relative to the case where Q is equal to 1. Therefore, when 0.75≤Q≤1, the warping rate of the pole piece 21 is lower, and the laminated battery cell has a higher quality rate. When 0.95≤Q≤1, the warping rate of the pole piece 21 is even lower, and the laminated battery cell has a higher quality rate.

[0170] (2) If the current collector 211 of the positive electrode sheet 21a is a composite current collector, that is, the current collector 211 of the positive electrode sheet 21a is a composite aluminum foil, it can be seen from Examples 50 to 58 that when the thickness of the current collector 211 is the same, the warpage of the electrode sheet 21 in Examples 53 to 58 is smaller than that in Examples 51 and 52, and the laminated battery cell has a higher quality rate. Therefore, when Q ≥ 0.75, the electrode sheet 21 has a lower warpage and a higher quality rate of the laminated battery cell. In Examples 52 to 56, as Q increases, the warpage of the electrode sheet 21 gradually decreases, and the quality rate of the laminated battery cell 100 shows a gradually increasing trend. When Q is greater than or equal to 0.95, the electrode sheet warpage is less than 3%, and the laminated battery cell quality rate is greater than 90%. Therefore, when Q is greater than or equal to 0.95, the risk of electrode sheet warpage is lower and the battery cell quality rate is higher. It can be seen from Example 56, Example 57 and Example 58 that after Q is greater than 1, the warping rate of the pole piece 21 and the quality rate of the laminated battery cell have no obvious change relative to the case where Q is equal to 1. Therefore, when 0.75≤Q≤1, the warping rate of the pole piece 21 is lower, and the laminated battery cell has a higher quality rate. When 0.95≤Q≤1, the warping rate of the pole piece 21 is even lower, and the laminated battery cell has a higher quality rate.

[0171] When the electrode sheet 21 is a negative electrode sheet 21b, the active material layer 212 is graphite:

[0172] (1) If the current collector 211 of the negative electrode sheet 21b is a metal layer, that is, the current collector 211 of the negative electrode sheet 21b is a copper foil, it can be seen from Examples 59 to 67 that when the thickness of the current collector 211 is the same, the warpage of the electrode sheet 21 in Examples 61 to 67 is smaller than that in Examples 59 and 60, and the laminated cell has a higher quality rate. Therefore, when Q ≥ 0.75, the electrode sheet 21 has a lower warpage and a higher quality rate of the laminated cell. In Examples 61 to 67, as Q increases, the warpage of the electrode sheet 21 gradually decreases, and the quality rate of the laminated cell 100 shows a gradually increasing trend. When Q is greater than or equal to 0.95, the electrode sheet warpage is less than 3%, and the laminated cell quality rate is greater than 90%. Therefore, when Q is greater than or equal to 0.95, the risk of electrode sheet warpage is lower and the cell quality rate is higher. It can be seen from Example 65, Example 66 and Example 67 that after Q is greater than 1, the warping rate of the pole piece 21 and the quality rate of the laminated battery cell have no obvious change relative to the case where Q is equal to 1. Therefore, when 0.75≤Q≤1, the warping rate of the pole piece 21 is lower, and the laminated battery cell has a higher quality rate. When 0.95≤Q≤1, the warping rate of the pole piece 21 is even lower, and the laminated battery cell has a higher quality rate.

[0173] (2) If the current collector 211 of the negative electrode sheet 21b is a composite current collector 211, that is, the current collector 211 of the negative electrode sheet 21b is a composite copper foil, it can be seen from Examples 68 to 76 that when the thickness of the current collector 211 is the same, the warpage of the electrode sheet 21 in Examples 70 to 76 is smaller than that in Examples 68 and 69, and the laminated battery cell has a higher quality rate. Therefore, when Q ≥ 0.75, the electrode sheet 21 has a lower warpage and a higher quality rate of the laminated battery cell. In Examples 70 to 74, as Q increases, the warpage of the electrode sheet 21 gradually decreases, and the quality rate of the laminated battery cell 100 shows a gradually increasing trend. When Q is greater than or equal to 0.95, the electrode sheet warpage is less than 3%, and the laminated battery cell quality rate is greater than 90%. Therefore, when Q is greater than or equal to 0.95, the risk of electrode sheet warpage is lower and the battery cell quality rate is higher. It can be seen from Example 74, Example 75 and Example 76 that after Q is greater than 1, the warping rate of the pole piece 21 and the quality rate of the laminated battery cell have no obvious change relative to the case where Q is equal to 1. Therefore, when 0.75≤Q≤1, the warping rate of the pole piece 21 is lower, and the laminated battery cell has a higher quality rate. When 0.95≤Q≤1, the warping rate of the pole piece 21 is even lower, and the laminated battery cell has a higher quality rate.

[0174] In summary, when observing along the thickness direction X of the current collector, the ratio of the area of ​​the projection of the active material layer 212 covered by the projection of the support layer 213 to the area of ​​the active material layer 212 in the single-sided area A is greater than or equal to 0.75 and less than or equal to 1. The area of ​​the active material layer 212 covered by the support layer 213 is large enough, which is beneficial for the support layer 213 to weaken the stress difference on both sides of the active single-sided area A along the thickness direction, reduce the risk of curling of the pole piece 21, thereby improving the quality of the battery cell 100, and can also reduce material waste. When observing along the thickness direction X of the current collector, the ratio of the area of ​​the projection of the active material layer 212 covered by the projection of the support layer 213 to the area of ​​the active material layer 212 in the single-sided area A is greater than or equal to 0.95 and less than or equal to 1, and the warpage rate of the pole piece 21 is lower.

[0175] Table 3

[0176]

[0177]

[0178]

[0179] In Table 3, when the electrode sheet 21 is a positive electrode sheet 21a, the active material layer 212 is lithium cobalt oxide:

[0180] (1) If the current collector 211 of the positive electrode sheet 21a is a metal layer, that is, the current collector 211 of the positive electrode sheet 21a is an aluminum foil, it can be seen from Examples 79 and 80 that the Mohs hardness of the support layer 213 in Example 80 is greater than the Mohs hardness of the active material layer 212, and the Mohs hardness of the active material layer 212 in Example 79 is greater than the Mohs hardness of the support layer 213. The electrode sheet warpage of Example 80 is lower than that of Example 79, and the laminated cell quality rate of Example 80 is higher than that of Example 79. It can be seen from Examples 77, 78, 80 to 85 that, when the Mohs hardness of the active material layer 212 is the same, as the Mohs hardness of the supporting layer 213 increases, the warping rate of the pole piece 21 gradually decreases, and the excellence rate of the stacked battery cell gradually increases. The Mohs hardness of the supporting layer 213 in Examples 80 to 85 is greater than the Mohs hardness of the supporting layer 213 in Examples 77 and 78. When the Mohs hardness of the supporting layer 213 is greater than 6.5, the pole piece warping rate is less than 20%, and the excellence rate of the stacked battery cell is greater than 70%. Therefore, when the Mohs hardness of the supporting layer 213 is greater than 6.5, the pole piece warping rate is lower, and the excellence rate of the stacked battery cell is higher.

[0181] (2) If the current collector 211 of the positive electrode sheet 21a is a composite current collector, that is, the current collector 211 of the positive electrode sheet 21a is a composite aluminum foil, it can be seen from Examples 88 and 89 that the Mohs hardness of the active material layer 212 in Example 88 is greater than the Mohs hardness of the support layer 213, relative to the Mohs hardness of the support layer 213 in Example 89 being greater than the Mohs hardness of the active material layer 212, the electrode sheet warpage of Example 89 is lower than that of Example 88, and the laminated cell quality rate of Example 89 is higher than that of Example 88. It can be seen from Examples 86, 87, 89 to 94 that, when the Mohs hardness of the active material layer 212 is the same, as the Mohs hardness of the supporting layer 213 increases, the pole piece warping rate gradually decreases, and the excellence rate of the stacked battery cell gradually increases. The Mohs hardness of the supporting layer 213 in Examples 89 to 94 is greater than the Mohs hardness of the supporting layer 213 in Examples 86 and 87. When the Mohs hardness of the supporting layer 213 is greater than 6.5, the pole piece warping rate is less than 20%, and the excellence rate of the stacked battery cell is greater than 70%. Therefore, when the Mohs hardness of the supporting layer 213 is greater than 6.5, the pole piece warping rate is lower, and the excellence rate of the stacked battery cell is higher.

[0182] When the electrode sheet 21 is a negative electrode sheet 21b, the active material layer 212 is graphite:

[0183] (1) If the current collector 211 of the negative electrode sheet 21b is a metal layer, that is, the current collector 211 of the negative electrode sheet 21b is a copper foil, it can be seen from Examples 97 and 98 that the Mohs hardness of the active material layer 212 in Example 97 is greater than the Mohs hardness of the support layer 213, and the Mohs hardness of the support layer 213 in Example 98 is greater than the Mohs hardness of the active material layer 212. The warpage of the electrode sheet in Example 98 is lower than that in Example 97, and the quality rate of the laminated battery cell in Example 98 is higher than that of the laminated battery cell in Example 97. It can be seen from Examples 95, 96, 98 to 103 that, when the Mohs hardness of the active material layer 212 is the same, as the Mohs hardness of the supporting layer 213 increases, the warping rate of the pole piece 21 gradually decreases, and the excellence rate of the stacked battery cell gradually increases. The Mohs hardness of the supporting layer 213 in Examples 98 to 103 is greater than the Mohs hardness of the supporting layer 213 in Examples 95 and 96. When the Mohs hardness of the supporting layer 213 is greater than 6.5, the pole piece warping rate is less than 20%, and the excellence rate of the stacked battery cell is greater than 70%. Therefore, when the Mohs hardness of the supporting layer 213 is greater than 6.5, the pole piece warping rate is lower, and the excellence rate of the stacked battery cell is higher.

[0184] (2) If the current collector 211 of the negative electrode sheet 21b is a composite current collector 211, that is, the current collector 211 of the negative electrode sheet 21b is a composite copper foil, it can be seen from Examples 106 and 107 that the Mohs hardness of the active material layer 212 in Example 106 is greater than the Mohs hardness of the support layer 213, and the Mohs hardness of the support layer 213 in Example 107 is greater than the Mohs hardness of the active material layer 212. The warpage of the electrode sheet in Example 107 is lower than that of the electrode sheet in Example 106, and the quality rate of the laminated battery cell in Example 107 is higher than that of the laminated battery cell in Example 106. It can be seen from Examples 104, 105, and 107 to 112 that, when the Mohs hardness of the active material layer 212 is the same, as the Mohs hardness of the support layer 213 increases, the pole piece warpage gradually decreases, and the excellence rate of the stacked battery cell gradually increases. The Mohs hardness of the support layer 213 in Examples 106 to 112 is greater than the Mohs hardness of the support layer 213 in Examples 104 and 105. When the Mohs hardness of the support layer 213 is greater than 6.5, the pole piece warpage is less than 20%, and the excellence rate of the stacked battery cell is greater than 70%. Therefore, when the Mohs hardness of the support layer 213 is greater than 6.5, the pole piece warpage is lower, and the excellence rate of the stacked battery cell is higher.

[0185] In summary, the Mohs hardness of the support layer 213 is greater than the Mohs hardness of the active material layer 212, which can make the warpage of the pole piece 21 lower and the quality rate of the battery cell 100 higher. The Mohs hardness of the support layer 213 is greater than 6.5, the warpage of the pole piece 21 is lower, and the quality rate of the battery cell 100 is higher.

[0186] An embodiment of the present application also provides a laminated battery cell 100, comprising a plurality of inner pole pieces 22 and an outermost pole piece 23, wherein the plurality of inner pole pieces 22 and the outermost pole piece 23 are stacked, and along the stacking direction of the plurality of pole pieces 21, the outermost pole piece 23 is the pole piece 21 provided in any of the above embodiments.

[0187] The outermost electrode sheet 21 of the stacked battery cell 100 is the electrode sheet 21 provided by any of the above-mentioned embodiments. The outermost electrode sheet 23 is provided with a support layer 213 on the side of the current collector 211 away from the active material layer 212. The support layer 213 can enhance the strength of the electrode sheet 21, weaken the stress difference on both sides of the single-sided area A along the thickness direction, and reduce the risk of curling of the electrode sheet 21, thereby improving the quality of the stacked battery cell 100.

[0188] An embodiment of the present application further provides an electrical device, and the electrical device includes the laminated battery core 100 provided in any of the above embodiments.

[0189] The laminated battery core 100 provided in the above embodiment has good quality, which is beneficial to improving the power reliability and power safety of the electrical equipment powered by the laminated battery core 100 .

[0190] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A pole piece, characterized in that: include: a current collector, the current collector comprising a single-sided region; An active material layer, along the thickness direction of the current collector, the active material layer is arranged on one side of the single-sided area; The support layer is arranged on a side of the single-sided area away from the active material layer to reduce the stress difference between the two sides of the single-sided area along the thickness direction.

2. The pole piece according to claim 1, characterized in that: When viewed along the thickness direction of the current collector, a projection of the active material layer and a projection of the support layer at least partially overlap.

3. The pole piece according to claim 2, characterized in that: Observed along the thickness direction of the current collector, a ratio of an area where a projection of the support layer covers a projection of the active material layer to an area of ​​the active material layer in the single-sided region is greater than or equal to 0.75 and less than or equal to 1.

4. The pole piece according to claim 3, characterized in that: When observed along the thickness direction of the current collector, a ratio of an area where a projection of the support layer covers a projection of the active material layer to an area of ​​the active material layer in the single-sided area is greater than or equal to 0.

95.

5. The pole piece according to claim 3, characterized in that: When observed along the thickness direction of the current collector, the projection of the support layer completely covers the projection of the active material layer in the single-sided area.

6. The pole piece according to claim 1, characterized in that: The Mohs hardness of the support layer is greater than the Mohs hardness of the active material layer.

7. The pole piece according to claim 1, characterized in that: The Mohs hardness of the support layer is greater than 6.

5.

8. The pole piece according to claim 1, characterized in that: The support layer is made of insulating material.

9. The pole piece according to claim 8, characterized in that: The support layer includes ceramic.

10. The pole piece according to claim 9, characterized in that: The support layer also includes an adhesive, the weight percentage of the ceramic is greater than 90%, and the weight percentage of the adhesive is greater than 0.5% and less than 5%.

11. The pole piece according to claim 10, characterized in that: The adhesive includes a polyacrylate adhesive.

12. The pole piece according to claim 10, characterized in that: The support layer also includes a non-white colorant.

13. The pole piece according to claim 12, characterized in that: The weight percentage of the dye is greater than 0% and less than 5%.

14. The pole piece according to any one of claims 1 to 13, characterized in that: The thickness of the support layer is 2 μm to 20 μm.

15. The pole piece according to any one of claims 1 to 13, characterized in that: The current collector includes an insulating layer and two conductive layers. Along the thickness direction of the current collector, the two conductive layers are respectively arranged on both sides of the insulating layer, the active material layer is arranged on the side of one of the two conductive layers away from the insulating layer, and the support layer is arranged on the side of the other of the two conductive layers away from the insulating layer.

16. The pole piece according to claim 15, characterized in that: Along the thickness direction of the current collector, the size of the insulating layer is W1, 3.4 μm≤W1≤12 μm.

17. The pole piece according to claim 15, characterized in that: Along the thickness direction of the current collector, the size of the conductive layer is W2, 0.5 μm≤W2≤3 μm.

18. The pole piece according to any one of claims 1 to 14, characterized in that: The current collector is a metal layer.

19. The pole piece according to claim 18, characterized in that: Along the thickness direction of the current collector, the thickness of the current collector is W3, 8μm≤W3≤20μm.

20. A laminated battery cell, characterized in that: It comprises a plurality of inner pole pieces and an outermost pole piece, wherein the plurality of inner pole pieces and the outermost pole piece are stacked, and along the stacking direction, the outermost pole piece is a pole piece according to any one of claims 1 to 19.

21. An electrical equipment, characterized in that: Comprising the laminated battery core according to claim 20.

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