Secondary battery, battery pack, and electronic device

Abstract

Some embodiments of the utility model provide a secondary battery. The secondary battery comprises an electrode assembly formed by laminating and winding a first diaphragm, a positive pole piece, a second diaphragm and a negative pole piece, the first diaphragm comprises a first base film, the first base film is in direct contact with the positive pole piece, or a heat-resistant layer in direct contact with the positive pole piece is arranged on the surface, facing the positive pole piece, of the first diaphragm, and the second diaphragm comprises a second base film and an adhesive layer located on the side, facing the positive pole piece, of the second base film. According to the secondary battery provided by the utility model, the infiltration of the secondary battery can be improved at least under the condition of maintaining relatively high energy density. Other embodiments of the utility model also provide a battery pack and an electronic device.

Description

Technical Field

[0001] The present application relates to the field of batteries, and more particularly, provides a secondary battery, a battery pack, and an electronic device. Background Art

[0002] At present, the application of electrochemical devices is becoming more and more extensive, such as the application of secondary batteries (such as lithium-ion batteries) to electronic devices such as cars, energy storage, mobile phones, tablet computers, wearable devices, mobile power supplies, electronic cigarettes, digital products, power tools, power devices, energy storage devices, etc., and it is particularly important in the field of new energy. With the further development of fields such as electric vehicles, people’s demand for energy density is also getting higher and higher. At present, in order to pursue higher group margins to obtain higher energy density, the winding tension of the electrode sheets and diaphragms of the electrode assemblies in existing secondary batteries is relatively large, resulting in a smaller inter-layer spacing between the positive and negative electrode sheets, thereby exacerbating the difficulty of electrolyte infiltration. Correspondingly, the poor infiltration of secondary batteries will affect the safety performance and electrochemical performance of the battery. Therefore, while maintaining a higher energy density, improving the infiltration of secondary batteries is one of the difficulties that secondary batteries currently need to overcome. Utility Model Content

[0003] In response to the above problems existing in the prior art, the present application provides a secondary battery, a battery pack and an electronic device, which can at least improve the wetting of the secondary battery while maintaining a relatively high energy density.

[0004] According to one aspect of the present application, a secondary battery is provided, comprising: an electrode assembly formed by stacking and winding a first diaphragm, a positive electrode sheet, a second diaphragm, and a negative electrode sheet; the first diaphragm comprises a first base film, the first base film is in direct contact with the positive electrode sheet, or the surface of the first diaphragm facing the positive electrode sheet is provided with a heat-resistant layer in direct contact with the positive electrode sheet, and the second diaphragm comprises a second base film and a glue layer located on the side of the second base film facing the positive electrode sheet.

[0005] In some embodiments, the positive electrode sheet includes a concave surface and a convex surface on opposite sides, and the second separator faces the concave surface of the positive electrode sheet.

[0006] In some embodiments, the second diaphragm further includes a heat-resistant layer located between the second base film and the glue layer.

[0007] In some embodiments, the adhesive layer is a polyvinylidene fluoride layer.

[0008] In some embodiments, the first separator further includes a heat-resistant layer on a side of the first base film facing away from the positive electrode sheet.

[0009] In some embodiments, the second separator further includes a heat-resistant layer on a side of the second base film facing away from the positive electrode sheet.

[0010] In some embodiments, the heat-resistant layer on the side of the first base film facing away from the positive electrode tab and the heat-resistant layer on the side of the second base film facing away from the positive electrode tab directly contact the negative electrode tab.

[0011] In some embodiments, the secondary battery is a cylindrical battery.

[0012] An embodiment of the present application further provides a battery pack comprising any one of the above-mentioned secondary batteries.

[0013] An embodiment of the present application further provides an electronic device comprising at least one of the secondary battery and the battery pack described above.

[0014] The above-mentioned technical solution of the present application makes the side of the second diaphragm facing the positive electrode sheet include a glue layer sheet located on the second base film, so that the glue layer can be distributed in an island shape similar to a sponge to increase the distance between the positive electrode sheet and the second base film, thereby at least improving the infiltration of the electrolyte into the positive electrode sheet. In addition, because the glue layer is not provided on the side of the first base film facing the positive electrode sheet, the distance between the first base film and the positive electrode sheet can be smaller, so that the secondary battery can maintain a higher energy density. In addition, by arranging the first diaphragm and the second diaphragm differently, the first diaphragm and the second diaphragm can be arranged more flexibly by more comprehensively considering factors such as the energy density of the secondary battery. In addition, since the glue layer increases the distance between the positive electrode sheet and the second base film, this increase in distance can also alleviate the stress concentration caused by the expansion of the electrode sheet during the charge and discharge cycle of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without inventive work. It is worth noting that, according to standard industry practices, the various components are not drawn to scale and are for illustrative purposes only. In fact, for the clarity of discussion, the sizes of the various components can be arbitrarily increased or decreased.

[0016] Figure 1 A schematic diagram of a vehicle according to an embodiment of the present application is shown.

[0017] Figure 2 A cross-sectional view of a secondary battery according to an embodiment of the present application is shown.

[0018] Figure 3 A schematic top view of an electrode assembly according to an embodiment of the present application is shown.

[0019] Figure 4 The embodiment according to the present application is shown Figure 3An enlarged schematic diagram of the first separator region of the electrode assembly.

[0020] Figure 5 The embodiment according to the present application is shown Figure 3 An enlarged schematic diagram of the second separator region of the electrode assembly.

[0021] Figure 6 A schematic cross-sectional view of an electrode assembly according to an embodiment of the present application is shown.

[0022] Figure 7 Another embodiment of the present application is shown Figure 3 An enlarged schematic diagram of the first separator region of the electrode assembly.

[0023] Figure 8 Another embodiment of the present application is shown Figure 3 An enlarged schematic diagram of the second separator region of the electrode assembly.

[0024] Figure 9 Another embodiment of the present application is shown Figure 3 An enlarged schematic diagram of the first separator region of the electrode assembly.

[0025] Figure 10 A schematic perspective view of a secondary battery according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0026] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of this application.

[0027] The following disclosure provides many different embodiments or examples for implementing the different features of the provided subject matter. Specific examples of components and arrangements will be described below to simplify the present invention. Of course, these are merely examples and are not intended to limit the present invention. For example, in the following description, forming a first component above or on a second component may include an embodiment in which the first component and the second component are in direct contact, and may also include an embodiment in which an additional component is formed between the first component and the second component so that the first component and the second component may not be in direct contact. Moreover, the present invention may repeatedly refer to numbers and / or letters in various examples. This repetition is merely for simplicity and clarity and does not in itself represent a relationship between the various embodiments and / or configurations discussed.

[0028] In addition, the embodiments and features in the embodiments of the present application may be combined with each other unless they conflict. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments. It should be understood that the specific structures shown in the drawings are merely for ease of explanation and are not intended to limit the present application. When describing a specific figure, other structures not described in the drawings may be provided according to actual needs and are not intended to limit the present application.

[0029] As fossil resources become increasingly scarce, lithium-ion batteries have become the primary power source for new energy vehicles due to their environmental friendliness. New energy vehicles are gradually replacing fuel-powered vehicles. Currently, cylindrical batteries are widely used in new energy vehicles due to their high assembly efficiency and low production costs.

[0030] The electrode assembly of the cylindrical battery is large in size, and in order to ensure a high electrode assembly group margin (the diameter of the electrode assembly divided by the inner diameter of the shell, the current group margin can be greater than 97%) to obtain a higher energy density, the winding stress of the electrode and the diaphragm is usually large, which will lead to a smaller layer spacing of the positive and negative electrode sheets, thereby exacerbating the difficulty of electrolyte infiltration, thereby increasing the process difficulty and affecting the processing efficiency. In addition, the battery cell with poor infiltration is very easy to deposit lithium, posing a great safety hazard. Furthermore, in the radial direction of the cylindrical battery, the stress will be relatively small at the position closer to the center and the outer surface, while the stress will be relatively large at the position far away from the center and the outer surface. The layer spacing of the positive and negative electrode sheets is relatively small, so the electrolyte infiltration is relatively poor, and the distribution of the electrolyte in the radial direction is uneven. In addition, due to the effect of gravity, the electrolyte is mainly concentrated at the bottom of the cylindrical battery, so the distribution of the electrolyte in the upper and lower directions is also uneven. This uneven distribution of the electrolyte will also affect the electrical performance and safety performance of the cylindrical battery. Existing methods for improving battery wetting mainly include adding wetting agents to the pole pieces or improving the injection process. However, adding wetting agents to the pole pieces usually deteriorates the electrochemical performance of the battery, while improving the injection process may prolong the injection time, thereby affecting processing efficiency. However, in the prior art, battery wetting is rarely improved from the perspective of the diaphragm. In addition, the two diaphragms in cylindrical batteries in the prior art are generally the same, but this is disadvantageous for the battery configuration. For example, both diaphragms include a glue layer, which increases the battery cost, and the thickness of both diaphragms is relatively large, which wastes the energy density of the battery.

[0031] The inventors of this application have discovered that by providing the second separator 110 with a glue layer 114 located on the first surface 112s1 of the second base film 112 facing the positive electrode tab 128, with the glue layer 114 directly facing the positive electrode tab, the glue layer 114 can be distributed in a sponge-like, island-like pattern on the first surface 112s1 of the second base film 112 to increase the distance between the positive electrode tab 128 and the second base film 112, thereby at least improving the electrolyte's infiltration of the positive electrode tab 128. Furthermore, by not providing the glue layer on the side of the first base film 106 facing the positive electrode tab 128, the distance between the first base film 106 and the positive electrode tab 128 can be reduced, thereby enabling the secondary battery 100 to maintain a high energy density. Furthermore, by providing the first separator 104 and the second separator 110 differently, the first separator 104 and the second separator 110 can be more flexibly configured, taking into account factors such as the energy density of the secondary battery 100 in a more comprehensive manner. In addition, the adhesive layer 114 increases the distance between the positive electrode plate 128 and the second base film 112 . This increase in distance can also alleviate stress concentration caused by expansion of the plate during charge and discharge cycles of the secondary battery 100 .

[0032] According to one aspect of the present application, an electronic device is provided. For ease of illustration, the following description uses a vehicle as an example of the electronic device. It is readily understood that the electronic device provided herein is not limited to vehicles; the electronic device may include a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, and the like. Figure 1 FIG2 shows a schematic diagram of a vehicle 1000 according to an embodiment of the present application. Figure 1 The vehicle 1000 is provided with a battery pack 1002 inside. The battery pack 1002 can be provided at the bottom, head, or tail of the vehicle body 1001. The battery pack 1002 can be used to power the vehicle 1000. For example, the battery pack 1002 can serve as an operating power source for the vehicle 1000.

[0033] Furthermore, the vehicle 1000 may also include a controller and a motor, and the controller is used to control the battery pack 1002 to power the motor, for example, for starting, navigating, and driving the vehicle 1000. The battery pack 1002 mentioned in the embodiment of the present application may include one or more secondary batteries described below to provide higher voltage and capacity. When there are multiple secondary batteries, the multiple batteries are connected in series, in parallel, or in mixed connection through a busbar component. The secondary batteries in the battery pack 1002 can be cylindrical batteries, square batteries, etc., which are not limited in the embodiment of the present application.

[0034] Figure 2 A cross-sectional view of a secondary battery 100 according to an embodiment of the present application is shown. Figure 2The secondary battery 100 is shown as a cylindrical battery, but it is easy to understand that the secondary battery 100 of the embodiment of the present application is not limited to a cylindrical battery. Figure 3 1 shows a schematic top view of the electrode assembly 102 according to an embodiment of the present application. Figure 4 and Figure 5 1 and 150 of the first and second diaphragms 104 and 110 of the electrode assembly 102 according to an embodiment of the present application are shown in FIG. Figures 2 to 5 As shown, in some embodiments, the secondary battery 100 includes an electrode assembly 102, which is formed by stacking and winding a first separator 104, a positive electrode sheet 128, a second separator 110, and a negative electrode sheet 130. The first separator 104 includes a first base film 106, which is in direct contact with the positive electrode sheet 128, or a heat-resistant layer 115 is provided on the surface of the first separator 104 facing the positive electrode sheet 128, which is in direct contact with the positive electrode sheet 128. The second separator 110 includes a second base film 112 and a glue layer 114 located on the side of the second base film 112 facing the positive electrode sheet 128. In some embodiments, the glue layer 114 directly faces the positive electrode sheet 128. Accordingly, the glue layer 114 serves as the outermost layer of the second separator 110 facing the positive electrode sheet 128, and there is no glue layer between the first separator 104 and the positive electrode sheet 128. Furthermore, it is readily understood that the two opposing surfaces of the first base film 106 are a first surface 106s1 facing the positive electrode tab 128 and a second surface 106s2 opposite the first surface 106s1. In the secondary battery 100 of the embodiment of the present application, the second base film 112 of the second separator 110 has an adhesive layer 114 on its first surface 112s1 facing the positive electrode tab 128. By having the adhesive layer 114 directly facing the positive electrode tab 128, the adhesive layer 114 is distributed in a sponge-like island pattern on the first surface 112s1 of the second base film 112. This increases the distance between the positive electrode tab 128 and the second base film 112. Furthermore, this island pattern allows for more electrolyte storage, thereby at least improving the electrolyte's infiltration of the positive electrode tab 128. Furthermore, by not providing a glue layer on the side of the first base film 106 facing the positive electrode tab 128, the distance between the first base film 106 and the positive electrode tab 128 can be reduced, thereby maintaining a high energy density for the secondary battery 100. Furthermore, by providing different configurations for the first and second separators 104, 110, factors such as the energy density of the secondary battery 100 can be more comprehensively considered, allowing for more flexible configurations of the first and second separators 104, 110. In some embodiments, the glue layer 114 can be a polyvinylidene fluoride layer.

[0035] To further explain the glue layer 114 facing the positive electrode 128, Figure 6 FIG2 shows a cross-sectional schematic diagram of an electrode assembly 102 according to an embodiment of the present application. Figure 2、 Figure 3 and Figure 6 As shown, the positive electrode sheet 128 of the electrode assembly 102 includes a positive electrode current collector 1211 and a positive electrode active material layer coated on the positive electrode current collector 1211, and a first coating area 1212 coated with the positive electrode active material layer and a first uncoated area 1213 not coated with the positive electrode active material layer are formed on the positive electrode current collector 1211. The first coating area 1212 and the first uncoated area 1213 are arranged axially along the electrode assembly 102 (that is, arranged in the vertical direction), and the first uncoated area 1213 extends to one end in the height direction of the secondary battery 100 to the outside of the first diaphragm 104 and the second diaphragm 110, and is bent toward the axis of the electrode assembly 102 (that is, toward the middle of the electrode assembly 102) to form a stacked positive electrode tab 125. The negative electrode sheet 130 includes a negative electrode current collector 1231 and a negative electrode active material layer coated on the negative electrode current collector 1231. A second coating area 1232 coated with the negative electrode active material layer and a second uncoated area 1233 not coated with the negative electrode active material layer are formed on the negative electrode current collector 1231. The second coating area 1232 and the second uncoated area 1233 are arranged axially along the electrode assembly 102. The second uncoated area 1233 extends to the other end of the secondary battery 100 in the height direction to the outside of the first diaphragm 104 and the second diaphragm 110, and is bent toward the axis of the electrode assembly 102 to form a stacked negative electrode tab 124; the first diaphragm 104 and the second diaphragm 110 are arranged between the positive electrode sheet 128 and the negative electrode sheet 130 to isolate the positive electrode active material layer and the negative electrode active material layer. Taking the lithium-ion secondary battery 100 as an example, the positive electrode current collector 1211 can be made of aluminum, and the positive electrode active material layer includes a positive electrode active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. The negative electrode current collector 1231 can be made of copper, and the negative electrode active material layer includes a negative electrode active material, which can be carbon or silicon.

[0036] Combined with reference Figure 3 and Figure 6 As shown, generally speaking, for energy density considerations, active material layers are coated on opposite sides of the positive electrode sheet 128 and the negative electrode sheet 130. At the same time, the capacity of the positive electrode sheet 128 is set to be smaller than that of the negative electrode sheet 130 to prevent lithium from precipitating in the negative electrode sheet 130. Therefore, it is necessary to ensure that the ratio of the capacity of the positive electrode sheet 128 to the capacity of the negative electrode sheet 130 (hereinafter referred to as CB) is greater than 1. For ease of description, see Figure 3As shown, the positive electrode sheet 128 includes a concave surface and a convex surface on opposite sides. The surface of the positive electrode sheet 128 facing the negative electrode sheet 130 (i.e., along the radial direction, toward the middle of the electrode assembly 102) is referred to as the concave surface, and the surface of the positive electrode sheet 128 away from the negative electrode sheet 130 (i.e., along the radial direction, away from the middle of the electrode assembly 102) is referred to as the convex surface. The second separator 110 faces the concave surface of the positive electrode sheet 128. Since the positive electrode sheet 128 surrounds the negative electrode sheet 130, the area of ​​the positive electrode sheet 128 is larger than that of the negative electrode sheet 130. Therefore, the positive active material layer on the concave surface of the positive electrode sheet 128 facing the negative electrode sheet 130 needs to be coated relatively thinly (i.e., the surface density is low) to meet the CB requirement (CB describes the negative electrode discharge capacity / positive electrode discharge capacity). Therefore, the surface density of the positive active material layer on the concave surface of the positive electrode sheet 128 is generally less than the surface density of the positive active material layer on the convex surface of the positive electrode sheet 128. Accordingly, after winding, the gap between the positive electrode sheet 128 and the second separator 110 is smaller, so it is more difficult for the electrolyte to infiltrate the concave surface of the positive electrode sheet. Therefore, in the embodiment of the present application, making the glue layer 114 directly face the positive electrode sheet 128 can increase the distance between the second separator 110 and the positive electrode sheet 128 to improve the infiltration of the positive electrode sheet 128, while at the same time, there is no glue layer between the first base film 106 of the first separator 104 and the positive electrode sheet 128 to reduce the distance between the first base film 106 and the positive electrode sheet 128, thereby making the secondary battery 100 have a relatively high energy density.

[0037] Return Reference Figure 4As shown, in some embodiments, the first separator 104 further includes a heat-resistant layer 115 located on the first surface 106s1 of the first base film 106. Generally speaking, in the prior art, separators are usually very thin PP (polypropylene) or PE (polyethylene). The heat generated during battery cycling or when the battery is abnormal may cause the separator to shrink due to heat, thereby causing the positive electrode and the negative electrode to contact and cause the risk of short circuit. In the embodiment of the present application, by making the first separator 104 include a heat-resistant layer 115 located on the first surface 106s1 of the first base film 106 facing the positive electrode 128, the inorganic particles in the heat-resistant layer 115 have good heat resistance, which can improve the heat resistance of the first separator 104, thereby reducing the risk of short circuit between the positive electrode 128 and the negative electrode 130. In some embodiments, the heat-resistant layer 115 is in direct contact with the first base film 106. In some embodiments, the heat-resistant layer 115 may include at least one of aluminum oxide, boehmite, titanium oxide, etc. However, the heat-resistant layer 115 is optional. In other embodiments, the first separator 104 may not include the heat-resistant layer 115 on the first surface 106s1 of the first base film 106. In this embodiment, the first base film 106 is in direct contact with the positive electrode plate 128.

[0038] refer to Figure 5 As shown, in some embodiments, the second diaphragm 110 further includes a heat-resistant layer 116 located between the second base film 112 and the adhesive layer 114. By making the second diaphragm 110 include the heat-resistant layer 116 located between the second base film 112 and the second adhesive layer 114, the heat resistance of the second diaphragm 110 can be improved. Figure 5In the embodiment shown, the heat-resistant layer 116 may be in direct contact with the adhesive layer 114. Generally speaking, the inorganic particles in the heat-resistant layer 116 have poor adhesion. By setting the adhesive layer 114 in direct contact with the heat-resistant layer 116, the heat-resistant layer 116 can be prevented from falling off. In some embodiments, the heat-resistant layer 116 is in direct contact with the second base film 112. In addition, the heat-resistant layer 116 may include the same material and thickness as the heat-resistant layer 115, or may include a material and thickness different from the heat-resistant layer 115. In some embodiments, the heat-resistant layer 116 may also include at least one of aluminum oxide, boehmite, titanium oxide, etc. In other embodiments, the second diaphragm 110 may not include the heat-resistant layer 116, and accordingly, the second base film 112 is in direct contact with the adhesive layer 114. In some embodiments, the first base film 106 and the second base film 112 can be the same or different. The first base film 106 and the second base film 112 can both be made of a PE base film or a PP base film, preferably a PE base film. By making the first base film 106 and the second base film 112 the same, the first base film 106 and the second base film 112 have consistent base film properties, thereby improving the performance of the secondary battery 100. In some embodiments, the material of the first base film 106 and the second base film 112 can be at least one of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, and polypropylene.

[0039] Figure 7 and Figure 8 1 and 12 are enlarged schematic views of the first separator 104 and the second separator 110 of the electrode assembly 102 according to another embodiment of the present application. Figure 7 As shown, in some embodiments, the first base film 106 further includes a second surface 106s2 opposite to the first surface 106s1 of the first base film 106. It is not difficult to understand that the second surface 106s2 faces the negative electrode sheet 130. The first separator 104 may further include a heat-resistant layer 117 located on the second surface 106s2 of the first base film 106. In the embodiment where the first separator 104 includes the heat-resistant layer 115 and the heat-resistant layer 117, the heat-resistant layer 115 and the heat-resistant layer 117 directly face the positive electrode sheet 128 and the negative electrode sheet 130, respectively. Accordingly, the heat-resistant layer 115 and the heat-resistant layer 117 respectively constitute the outermost layers on opposite sides of the first separator 104, or the first separator 104 further includes a glue layer located on the heat-resistant layer 117. The presence of the heat-resistant layer 117 will further improve the heat resistance of the first separator 104. The heat-resistant layer 117 may have the same material and thickness as the heat-resistant layer 115 (or the heat-resistant layer 116 ), or may have a different material and thickness than the heat-resistant layer 115 (or the heat-resistant layer 116 ). In some embodiments, the heat-resistant layer 117 is in direct contact with the first base film 104 .

[0040] refer to Figure 8As shown, in some embodiments, the second base film 112 further includes a second surface 112s2 opposite to the first surface 112s1 of the second base film 112. It is not difficult to understand that the second surface 112s2 faces the negative electrode sheet 130. The second separator 110 may further include a heat-resistant layer 119 located on the second surface 112s2 of the second base film 112. In a further embodiment, the second separator 110 may further include a glue layer 120 located on the heat-resistant layer 119. The glue layer 120 may have the same material and thickness as the glue layer 114. The heat-resistant layer 119 may have the same material and thickness as the heat-resistant layer 115 (or the heat-resistant layer 116), and the heat-resistant layer 119 may also include a material and thickness different from the heat-resistant layer 115 (or the heat-resistant layer 116). In this case, the glue layer 114 and the glue layer 120 directly face the positive electrode tab 128 and the negative electrode tab 130, respectively. Accordingly, the glue layer 114 and the glue layer 120 constitute the outermost layers on opposite sides of the second separator 110. In other embodiments, for energy density and cost considerations, the second separator 110 may not include the glue layer 120. In this embodiment, the heat-resistant layer 119 directly faces the negative electrode tab 130.

[0041] Figure 9 FIG1 shows an enlarged schematic diagram of a region 140 of the first separator 106 of the electrode assembly 102 according to another embodiment of the present application. According to another aspect of the present application, another secondary battery 100 is provided, Figure 3 、 Figure 8 and Figure 9 As shown, the secondary battery 100 includes an electrode assembly 102, and the electrode assembly 102 is formed by stacking and winding a first separator 104, a positive electrode sheet 128, a second separator 110, and a negative electrode sheet 130. The first separator 104 includes a first base film 106, and a first layer directly bonded to the second surface 106s2 of the first base film 106 facing away from the positive electrode sheet 128, and there is no glue layer on the first surface 106s1 of the first base film 106 facing the positive electrode sheet 128. The second separator 110 includes a second base film 112, and a second layer directly bonded to the first surface 112s1 of the second base film 112 facing the positive electrode sheet 128. The first layer is one of a single layer and a composite layer, and the second layer is the other of the single layer and the composite layer. The single layer is a glue layer, and the composite layer is a glue layer and a heat-resistant layer stacked in sequence. It is not difficult to understand that when the first layer is a single layer, the second layer is a composite layer; when the first layer is a composite layer, the second layer is a single layer. As Figure 8 and Figure 9 As shown, when the first layer on the second surface 106s2 of the first base film 106 facing away from the positive electrode sheet 128 is a single layer, the single layer is the glue layer 118 (ie, the first diaphragm 104 does not include Figure 8The heat-resistant layer 117 shown in the figure is a heat-resistant layer 117, and the second layer directly bonded to the first surface 112s1 of the second base film 112 facing the positive electrode sheet 128 is a composite layer, which is the heat-resistant layer 119 and the glue layer 120 located on the heat-resistant layer 119. In addition, when the first layer is a composite layer, the composite layer can be the heat-resistant layer 117 and the glue layer 118 located on the heat-resistant layer 117, and the second layer is a single layer, which is the glue layer 120 (that is, in this case, the second diaphragm 110 does not include the adhesive layer 120). Figure 8 Heat-resistant layer 119 shown). In the secondary battery 100 of the embodiment of the present application, the second separator 110 includes a second layer directly bonded to the first surface 112s1 of the second base film 112 facing the positive electrode tab 128. The second layer may be a glue layer 120 or a composite layer of the heat-resistant layer 119 and the glue layer 120. Since the glue layer 114 is distributed in a sponge-like island shape on the first surface 112s1 of the second base film 112, the distance between the positive electrode tab 128 and the second base film 112 is increased, and this island-like distribution can also store more electrolyte, thereby at least improving the infiltration of the electrolyte into the positive electrode tab 128. In addition, by eliminating the glue layer on the first surface 106s1 of the first base film 106 facing the positive electrode tab 128, the distance between the first base film 106 and the positive electrode tab 128 can be smaller, thereby enabling the secondary battery 100 to maintain a higher energy density. In addition, by making the first layer one of a single layer and a composite layer and the second layer the other of a single layer and a composite layer, that is, setting the first diaphragm 104 and the second diaphragm 110 differently, the first diaphragm 104 and the second diaphragm 110 can be set more flexibly by more comprehensively considering factors such as the energy density of the secondary battery 100.

[0042] In the embodiment of the present application, the thickness of each adhesive layer is in the range of 2-6 μm, and the thickness of each heat-resistant layer is in the range of 1-5 μm.

[0043] Figure 10 FIG1 shows a perspective schematic diagram of a secondary battery 100 according to an embodiment of the present application. Figure 2 、 Figure 3 and Figure 10As shown, the secondary battery 100 further includes a housing 200, and the electrode assembly 102 is housed within the housing 200. The housing 200 may contain one or more electrode assemblies 102. The housing 200 includes an end wall 202 and a side wall 204 surrounding the end wall 202. As long as a stable seal and electrical connection can be formed, the connection between the end wall 202 and the side wall 204 can be achieved in a variety of ways, such as integral stamping, integral casting, or separate welding. The side wall 204 is not limited to surrounding shapes and can be cylindrical or prismatic, or can be surrounded along any other closed loop contour that matches the end wall 202. In this embodiment, the outer edge of the end wall 202 is circular, and the side wall 204 is cylindrical and surrounds the outer edge of the end wall 202. A circular opening 206 is formed at the end of the side wall 204 facing away from the end wall 202. The housing 200, enclosed by the end wall 202 and the side wall 204, has a housing cavity for accommodating the electrode assembly 102, electrolyte, and other essential battery components. Specifically, the diameter of the housing 200 can be determined based on the specific dimensions of the electrode assembly 102, such as 18 mm, 21 mm, or 46 mm. The housing 200 can be made of a variety of materials, such as copper, iron, aluminum, steel, and aluminum alloys. To prevent rusting of the housing 200 during long-term use, the housing 200 can be coated with a rust-resistant material, such as nickel.

[0044] Further, see Figure 2 As shown, the positive electrode tab 125 of the present invention faces the end wall 202 or the opening 206, and the negative electrode tab 124 faces the other end of the shell 200. Figure 2 In the illustrated embodiment, the positive electrode tab 125 faces the end wall 202 and is electrically connected to the electrode post 208, thereby providing a positive charge to the electrode post 208. The negative electrode tab 124 faces the opening 206, and the housing 200 is electrically connected to the negative electrode tab 124, thereby providing a negative charge. However, in other embodiments, the negative electrode tab 124 may be connected to the electrode post 208, while the positive electrode tab 125 is connected to the housing 200. A cover plate 212 is sealingly mounted on the opening 206; the outer edge shape of the cover plate 212 corresponds to the shape of the opening 206, and the cover plate 212 is connected to the side wall 204 to seal the opening 206. The installation method of the cover plate 212 includes, but is not limited to, mechanical sealing or welding sealing. In this embodiment, the cover plate 212 is sealed to the opening 206 using a mechanical seal.

[0045] It should be understood that the various features of the various embodiments of this application can be replaced or combined. The above description is only a preferred embodiment of this application and is not intended to limit this application. Any combination of the various embodiments within the spirit and principles of this application, as well as any modification, equivalent replacement, and improvement of the embodiments, shall be included in the scope of protection of this application.

Claims

1. A secondary battery, characterized in that: include: An electrode assembly formed by stacking and winding a first separator, a positive electrode sheet, a second separator, and a negative electrode sheet; The first diaphragm includes a first base film, the first base film is in direct contact with the positive electrode sheet, or the surface of the first diaphragm facing the positive electrode sheet is provided with a heat-resistant layer in direct contact with the positive electrode sheet. The second diaphragm includes a second base film and a glue layer located on a side of the second base film facing the positive electrode plate.

2. The secondary battery according to claim 1, wherein The positive electrode plate includes a concave surface and a convex surface on opposite sides, and the second separator faces the concave surface of the positive electrode plate.

3. The secondary battery according to claim 1, wherein The second diaphragm further includes a heat-resistant layer located between the second base film and the glue layer.

4. The secondary battery according to claim 1, wherein The adhesive layer is a polyvinylidene fluoride layer.

5. The secondary battery according to claim 1, wherein The first separator further includes a heat-resistant layer on a side of the first base film facing away from the positive electrode sheet.

6. The secondary battery according to claim 5, characterized in that The second separator further includes a heat-resistant layer on a side of the second base film facing away from the positive electrode sheet.

7. The secondary battery according to claim 6, characterized in that The heat-resistant layer on the side of the first base film facing away from the positive electrode sheet and the heat-resistant layer on the side of the second base film facing away from the positive electrode sheet directly contact the negative electrode sheet.

8. The secondary battery according to claim 1, wherein The secondary battery is a cylindrical battery.

9. A battery pack, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 1 to 8.

10. An electronic device, characterized in that: The invention comprises at least one of the secondary battery according to any one of claims 1 to 8 and the battery pack according to claim 9.

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