A battery cell, a method of manufacturing the same, a secondary battery, and an electric device

Abstract

The application relates to a battery monomer and a preparation method thereof, a secondary battery and an electric equipment, and belongs to the technical field of battery devices. The width of the welding mark layer of the inner tab in the direction from the inner surface to the outer surface of the bending position of the bending section is gradually increased, that is, the welding strength between the conductive foil and the sub-tab of the inner tab located on the outer side of the bending is gradually increased, so that the welding strength between the conductive foil and the sub-tab can be matched with the corresponding bending stress, and the problems such as the peeling and falling of the welding mark layer to cause virtual welding and the soaring of the internal resistance can be reduced. Meanwhile, the width of the welding mark layer of the inner tab located on the inner side of the bending is small, the influence on the welding of the conductive foil and the outer tab is reduced, the occupation of the space is reduced, and then the welding strength of the electrode tab and the volume energy density of the battery can be considered.

Description

Technical Field

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

[0002] To improve the battery's nail penetration and impact resistance, the current collector is usually changed from metal foil to composite current collector, which includes a support layer (insulating layer) and metal layers (conductive layers) located on the upper and lower sides of the support layer.

[0003] In practical applications, since the upper and lower metal layers of the composite current collector cannot be directly connected, a conductive foil is usually welded to each of the upper and lower metal layers of the composite current collector (hereinafter referred to as the adapter weld) to connect with the outer electrode tab. At the same time, in order to reduce space occupation and increase the volumetric energy density of the battery, a bending welding process is usually adopted. Summary of the Invention

[0004] During bending and forming, the tensile stress on the outer side of the bend is significantly greater than that on the inner side. Furthermore, because the weld stamp of the transition weld is located on the bending side, the high tensile stress on the outer side easily leads to the weld stamp peeling and falling off, causing problems such as poor soldering and a surge in internal resistance. If methods such as widening the weld stamp are used to enhance welding strength, it will affect the welding of the conductive foil and the outer electrode tabs, and it will also encroach on space, impacting the volumetric energy density of the battery. Therefore, under the above circumstances, it is difficult for a single battery cell to simultaneously achieve both the welding strength of the electrode tabs and the volumetric energy density of the battery.

[0005] The purpose of this application is to provide a battery cell and its preparation method, a secondary battery, and an electrical device that can balance the welding strength of the electrode tabs and the volumetric energy density of the battery.

[0006] In a first aspect, embodiments of this application provide a battery cell, which includes: a housing and an electrode assembly. The electrode assembly is housed within the housing. The electrode assembly includes an assembly body and electrode tabs. The assembly body includes stacked electrode sheets. The electrode tabs include inner tabs and outer tabs. The inner tab has a bent section and includes a sub-tab and a conductive foil. The sub-tab and the electrode sheets are connected by a current collector. The current collector is a composite current collector. The conductive foil and the sub-tab are welded together, and a solder layer is present between the conductive foil and the sub-tab. The outer tab is connected to the conductive foil and extends out of the housing. Multiple inner tabs are stacked to form a tab bundle. The tab bundle includes a first tab bundle and a second tab bundle. Along the direction X from the inner surface to the outer surface of the bent section, the first tab bundle and the second tab bundle are arranged sequentially, and the width of the solder layer of the inner tabs in the second tab bundle increases progressively.

[0007] In the technical solution of this application embodiment, by controlling the width of the solder layer of the inner tab in the second tab bundle in the direction from the inner surface to the outer surface of the bending section to gradually increase, that is, the welding strength between the conductive foil and the sub-tab of the inner tab located on the outer side of the bend gradually increases, so that the welding strength between the conductive foil and the sub-tab can match the magnitude of the corresponding bending stress, which can reduce the occurrence of problems such as solder layer peeling and falling off, which can lead to poor soldering and a surge in internal resistance. At the same time, the width of the solder layer of the inner tab located on the inner side of the bend is smaller, which reduces the impact on the welding of the conductive foil and the outer tab, and also reduces the encroachment on space, thereby balancing the welding strength of the electrode tabs and the volumetric energy density of the battery.

[0008] As an optional implementation, along the direction X from the inner surface to the outer surface of the bending section, the length of the inner ear in the first ear bundle gradually decreases, and the length of the inner ear in the second ear bundle gradually increases, and the length of the inner ear in the second ear bundle closer to the first ear bundle is less than the length of the inner ear in the first ear bundle closer to the second ear bundle.

[0009] In the above implementation process, the electrode bundle is divided into a first electrode bundle and a second electrode bundle by using the shortest inner electrode bundle as the boundary, and the width of the solder layer of the inner electrode bundle is the narrowest in the second electrode bundle. Under the premise of meeting the welding strength, the impact on the welding of the conductive foil and the outer electrode bundle and the encroachment on the space are better reduced, which is beneficial to the volumetric energy density of the battery.

[0010] As an optional implementation, the width of the solder paste layer is 1mm to 10mm.

[0011] In the above implementation process, by controlling the width of the solder layer to be 1mm~10mm, within this width range, the welding strength between the conductive foil and the sub-tab can meet the resistance to the bending stress of the inner tab at each location, reducing the occurrence of problems such as solder layer peeling and detachment leading to poor soldering and a surge in internal resistance. At the same time, it can also reduce the impact on the welding of the conductive foil and the outer tab, and reduce the encroachment on space, thus balancing the welding strength of the electrode tabs and the volumetric energy density of the battery.

[0012] As an optional implementation, the thickness of the component body is not less than 10 mm, measured in the stacking direction of the component body.

[0013] In the above implementation process, the problems caused by the bending stress of the inner tab are more significant for component bodies with a thickness of not less than 10mm. The aforementioned solution can effectively improve the problems caused by solder layer peeling and falling off, which leads to poor soldering and a surge in internal resistance.

[0014] As an optional implementation, the number of inner electrodes in the electrode bundle is not less than 5 layers.

[0015] In the above implementation process, the number of inner tabs is no less than 5 layers of tab bundle. The more significant the problem caused by the bending stress of the inner tabs, the better the solution can be to improve the problem of solder layer peeling and falling off, which leads to poor soldering and a surge in internal resistance.

[0016] As an optional implementation, in the second tab bundle, the solder layer width of a single inner tab is gradually changing, and is counted sequentially along the direction X from the inner surface to the outer surface of the bending section. The maximum value of the solder layer width of an inner tab is equal to the minimum value of the solder layer width of the next adjacent inner tab.

[0017] In the above implementation process, by making the width of the solder layer of a single inner tab in the second tab bundle gradually change, and making the maximum value of the solder layer width of an inner tab equal to the minimum value of the solder layer width of the next adjacent inner tab, the manufacturing difficulty and cost of inner tabs with different solder layer widths can be effectively reduced, which is conducive to the industrial production of battery cells.

[0018] As an alternative implementation, in multiple inner tabs, the end of the solder layer closest to the sub-tab is located on the same plane in a flattened state.

[0019] In the above implementation process, by having the end of the solder layer near the sub-tab be on the same plane in the flattened state, the difficulty and cost of preparing inner tabs with different solder layer widths can be effectively reduced, which is conducive to the industrial production of battery cells.

[0020] As an optional implementation, the electrode assembly is a stacked electrode assembly.

[0021] As an optional implementation, the housing is a soft housing.

[0022] Secondly, embodiments of this application provide a method for preparing a battery cell, the method comprising: An electrode precursor is obtained, which includes a current collector precursor and a sub-electrode precursor. A welding roller is used to weld the conductive foil precursor and the sub-electrode precursor, and then die-cut them to obtain multiple electrode sheets; the surface of the welding roller has a welding working area with a first width and a second width, the first width being greater than the second width; Multiple electrode plates are stacked to obtain an electrode assembly; The electrode assembly is placed inside the housing to obtain a battery cell, which is the battery cell provided by the first aspect.

[0023] In the technical solution of this application embodiment, by using a specific welding roller for welding, inner tabs with different solder layer widths can be easily manufactured and stacked sequentially. By controlling the width of the solder layer of the inner tabs in the second tab bundle to increase sequentially from the inner surface to the outer surface of the bending section, the welding strength between the conductive foil and the sub-tab of the inner tab located on the outer side of the bend increases sequentially. This allows the welding strength between the conductive foil and the sub-tab to match the corresponding bending stress, reducing the occurrence of problems such as solder layer peeling and detachment leading to poor soldering and a surge in internal resistance. At the same time, the width of the solder layer of the inner tab located on the inner side of the bend is smaller, reducing the impact on the welding of the conductive foil and the outer tab, and also reducing the encroachment on space. Thus, it is possible to balance the welding strength of the electrode tabs and the volumetric energy density of the battery.

[0024] As an alternative implementation, the welding work area is continuous along the circumferential direction of the welding roller.

[0025] In the above implementation process, by making the welding working area continuous, it is beneficial to improve the welding strength between the conductive foil of the inner electrode and the sub-electrode, and also to realize die cutting of any size to match the needs of different battery sizes.

[0026] As an alternative implementation, the width of the welding working area is gradually varied along the circumferential direction of the welding roller.

[0027] In the above implementation process, by making the width of the welding working area gradually change, it is beneficial to quickly produce inner tabs with different solder layer widths, and it is also beneficial to realize die cutting of any size to match the needs of different battery sizes.

[0028] As an alternative implementation, the edges of the welding work area are smooth.

[0029] In the above implementation process, by making the edges of the welding work area smooth, it is beneficial to achieve die-cutting of any size to match the needs of different battery sizes.

[0030] As an optional implementation method, the welding speed is 1m / min to 100m / min.

[0031] As an optional implementation method, the welding pressure is 0.1MPa~1MPa.

[0032] Thirdly, this application provides a secondary battery, which includes the battery cell provided in the first aspect.

[0033] Fourthly, this application provides an electrical device, which includes a battery cell provided in the first aspect or a secondary battery provided in the third aspect. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the structure of a single battery cell provided in an embodiment of this application; Figure 2 This is a schematic diagram of the structure of the electrode assembly provided in the embodiments of this application; Figure 3 This is a schematic diagram of the inner electrode tab provided in an embodiment of this application; Figure 4 A flowchart illustrating the method provided in the embodiments of this application; Figure 5 This is a schematic diagram showing the surface development of the roll-welded roller provided in an embodiment of this application.

[0036] Reference numerals: 1000-cell battery; 100-casing; 200-electrode assembly; 10-assembly body; 11-electrode plate; 11a-current collector; 11b-active material layer; 20-electrode tab; 21-inner tab; 21a-sub-tab; 21b-conductive foil; 21c-soldering layer; 22-outer tab; 23-tab bundle; 23a-first tab bundle; 23b-second tab bundle; 2000-roll welding roller; 2000a-welding work area. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0038] In the description of this application, it should be noted that the terms "inner" and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0039] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "setup" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0040] Composite current collectors have good nail penetration and impact resistance. Since the upper and lower metal layers of the composite current collector cannot be directly connected, a conductive foil is usually welded to each of the upper and lower metal layers of the composite current collector (hereinafter referred to as the adapter weld) to connect with the outer electrode. At the same time, in order to reduce space occupation and increase the volumetric energy density of the battery, a bending welding process is usually adopted.

[0041] During bending and forming, the tensile stress on the outer side of the bend is significantly greater than that on the inner side. Furthermore, because the weld stamp of the transition weld is located on the bending side, the high tensile stress on the outer side easily leads to the weld stamp peeling and falling off, causing problems such as poor soldering and a surge in internal resistance. If methods such as widening the weld stamp are used to enhance welding strength, it will affect the welding of the conductive foil and the outer electrode tabs, and it will also encroach on space, impacting the volumetric energy density of the battery. Therefore, under the above circumstances, it is difficult for a single battery cell to simultaneously achieve both the welding strength of the electrode tabs and the volumetric energy density of the battery.

[0042] Therefore, this application intends to provide a battery cell and its preparation method, a secondary battery, and an electrical device that can balance the welding strength of the electrode tabs and the volumetric energy density of the battery.

[0043] Figure 1 For a schematic diagram of the structure of a single battery cell provided in the embodiments of this application, please refer to [link / reference]. Figure 1 This application provides a battery cell 1000, which includes a housing 100 and an electrode assembly 200, wherein the electrode assembly 200 is housed within the housing 100. Figure 2 For a schematic diagram of the electrode assembly 200 provided in the embodiments of this application, please refer to [link / reference]. Figure 2 The electrode assembly 200 includes an assembly body 10 and electrode tabs 20. The assembly body 10 includes stacked electrode plates 11, and the electrode tabs 20 include inner tabs 21 and outer tabs 22. Figure 3 For a schematic diagram of the inner electrode tab 21 provided in the embodiments of this application, please refer to [link / reference]. Figure 3The inner electrode 21 has a bent section and includes a sub-electrode 21a and a conductive foil 21b. The sub-electrode 21a is connected to the current collector 11a of the electrode plate 11. The current collector 11a is a composite current collector 11a. The conductive foil 21b and the sub-electrode 21a are welded together, and there is a solder layer 21c between the conductive foil 21b and the sub-electrode 21a. The outer electrode 22 is connected to the conductive foil 21b and extends out of the shell 100. Multiple inner electrodes 21 are stacked to form an electrode bundle 23. The electrode bundle 23 includes a first electrode bundle 23a and a second electrode bundle 23b. Along the direction X from the inner surface to the outer surface of the bent section, the first electrode bundle 23a and the second electrode bundle 23b are arranged sequentially, and the width of the solder layer 21c of the inner electrode 21 in the second electrode bundle 23b increases gradually.

[0044] The component body 10 includes electrode plates 11 and a separator membrane disposed between two electrode plates 11. Each electrode plate 11 includes a current collector and a membrane layer. The membrane layer is coated on the surface of the current collector, and the current collector without the membrane layer protrudes beyond the current collector with the membrane layer, serving as a sub-electrode tab. The membrane layer includes an active material layer 11b. The electrode plate 11 can be a positive electrode plate or a negative electrode plate. The component body 10 can be a wound electrode assembly 200 or a stacked electrode assembly 200; the embodiments of this application are not limited to these. At least a portion of the component body 10 is in contact with the electrolyte, which can mean that a portion of the component body 10 is immersed in the electrolyte, or that the component body 10 is completely immersed in the electrolyte.

[0045] The inner electrode 21 having a bent section means that the sub-electrode 21a and the conductive foil 21b are made by bending and welding process, resulting in at least one bending of the entire inner electrode 21, forming a bent section.

[0046] Sub-tab 21a usually refers to the current collector 11a of the electrode plate 11 which is die-cut, that is, the sub-tab 21a and the current collector 11a of the electrode plate 11 are an integral structure.

[0047] The composite current collector 11a may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector 11a may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0048] The welding connection between conductive foil 21b and sub-electrode 21a refers to the welding connection between conductive foil 21b and sub-electrode 21a using a bending welding process. After welding, a solder mark is formed between conductive foil 21b and sub-electrode 21a, which is the solder mark layer 21c.

[0049] The outer electrode tab 22 and the conductive foil 21b are also usually connected by welding.

[0050] The width of solder layer 21c refers to the size of solder layer 21c along the extension direction of sub-tab 21a.

[0051] The battery cell 1000 controls the width of the solder layer 21c of the inner tab 21 in the second tab bundle 23b to gradually increase from the inner surface to the outer surface of the bending section. This means the welding strength between the conductive foil 21b and the sub-tab 21a of the inner tab 21 located on the outer side of the bend increases progressively. This ensures the welding strength between the conductive foil 21b and the sub-tab 21a matches the corresponding bending stress, reducing the risk of solder layer 21c peeling and detachment leading to poor soldering and increased internal resistance. Simultaneously, the solder layer 21c of the inner tab 21 located on the inner side of the bend is smaller, reducing its impact on the welding of the conductive foil 21b and the outer tab 22, and also reducing space encroachment. This balances the welding strength of the electrode tabs 20 with the volumetric energy density of the battery.

[0052] Those skilled in the art will understand that, since the tensile stress on the inner tab 21 (i.e., the inner tab 21 belonging to the first tab bundle 23a) is not large, and its position does not correspond to the outer tab 22, it hardly constitutes an encroachment on space. Therefore, the width of the solder layer 21c between the conductive foil 21b and the sub-tab 21a in the inner tab 21 of the first tab bundle 23a only needs to meet the connection strength requirements, that is, a smaller solder layer 21c width can be used. Of course, a larger solder layer 21c width can also be used between the conductive foil 21b and the sub-tab 21a in the inner tab 21 of the first tab bundle 23a.

[0053] In some embodiments, along the direction X from the inner surface to the outer surface of the bending section, the length of the inner pole ear 21 in the first pole ear bundle 23a gradually decreases, and the length of the inner pole ear 21 in the second pole ear bundle 23b gradually increases, and the length of the inner pole ear 21 in the second pole ear bundle 23b near the first pole ear bundle 23a is less than the length of the inner pole ear 21 in the first pole ear bundle 23a near the second pole ear bundle 23b.

[0054] The length of the inner electrode 21 refers to its size along the direction in which the inner electrode 21 extends.

[0055] By dividing the tab bundle 23 into a first tab bundle 23a and a second tab bundle 23b with the shortest inner tab 21 as the boundary, and making the width of the solder layer 21c of the inner tab 21 the narrowest in the second tab bundle 23b, the impact on the welding of the conductive foil 21b and the outer tab 22 and the encroachment on space are better reduced while meeting the welding strength requirements, which is beneficial to the volumetric energy density of the battery.

[0056] In some embodiments, the width of the solder layer 21c is 1mm to 10mm. By controlling the width of the solder layer 21c to be 1mm to 10mm, within this width range, the welding strength between the conductive foil 21b and the sub-tab 21a can meet the resistance to bending stress of the inner tab 21 at each location, reducing the occurrence of problems such as solder layer 21c peeling and falling off, which can lead to poor soldering and a surge in internal resistance. At the same time, it can also reduce the impact on the welding of the conductive foil 21b and the outer tab 22, and reduce the encroachment on space, thereby balancing the welding strength of the electrode tab 20 and the volumetric energy density of the battery.

[0057] For example, the width of the solder layer 21c can be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, etc., or it can be any value in the range of 1 mm to 10 mm.

[0058] In some embodiments, the thickness of the component body 10 is not less than 10 mm in the stacking direction of the component body 10. The component body 10 with a thickness of not less than 10 mm is more prone to problems caused by bending stress of the inner tab 21. The aforementioned solution can better improve problems such as the peeling and falling off of the solder layer 21c, which leads to poor soldering and a surge in internal resistance.

[0059] For example, the thickness of the component body 10 can be 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 22 mm, 24 mm, 26 mm, 28 mm, 30 mm, etc., depending on the stacking direction of the component body 10, and it can also be any value within the range of not less than 10 mm.

[0060] In some embodiments, the number of inner tabs 21 in the tab bundle 23 is not less than 5 layers. The more the number of inner tabs 21 in the tab bundle 23 is not less than 5 layers, the more significant the problem caused by the bending stress of the inner tabs 21 will be. However, by adopting the aforementioned solution, the problems such as the peeling and falling off of the solder layer 21c leading to poor soldering and a surge in internal resistance can be better improved.

[0061] For example, taking into account the stacking direction of the component body 10, the number of inner tabs 21 in the tab bundle 23 can be 5, 10, 15, 20, 40, 60 or 80 layers, etc., or it can be any value within the range of not less than 5 layers.

[0062] In some embodiments, in the second tab bundle 23b, the width of the solder layer 21c of a single inner tab 21 is gradually changing, and is counted sequentially along the direction X from the inner surface to the outer surface of the bending position of the bending segment. The maximum value of the solder layer 21c width of an inner tab 21 is equal to the minimum value of the solder width of the next adjacent inner tab 21.

[0063] The term "gradually changing width of solder layer 21c of a single inner tab 21" means that the width of solder layer 21c of a single inner tab 21 gradually increases or gradually decreases.

[0064] By making the width of the solder layer 21c of a single inner tab 21 in the second tab bundle 23b gradually change, and making the maximum value of the solder layer 21c width of an inner tab 21 equal to the minimum value of the solder layer width of the next adjacent inner tab 21, the manufacturing difficulty and cost of inner tabs 21 with different solder layer 21c widths can be effectively reduced, which is beneficial to the industrial production of battery cells 1000.

[0065] In some embodiments, among the plurality of inner tabs 21, the end of the solder layer 21c near the sub-tab 21a is located on the same plane in a flattened state.

[0066] The flattened state refers to the state when the sub-electrode 21a and the current collector 11a are divided by the same plane.

[0067] By having the end of the solder layer 21c close to the tab 21a lie on the same plane in a flattened state, the manufacturing difficulty and cost of inner tabs 21 with different solder layer 21c widths can be effectively reduced, which is beneficial to the industrial production of battery cells 1000.

[0068] In some embodiments, the electrode assembly 200 is a stacked electrode assembly 200.

[0069] In some embodiments, the housing 100 is a soft-pack housing 100. Specifically, the soft-pack housing 100 may be selected from aluminum-plastic film.

[0070] Figure 4 For a flowchart illustrating the method provided in the embodiments of this application, please refer to [link / reference]. Figure 4 This application provides a method for preparing a single battery cell, the method comprising: S100. Obtain the electrode electrode 11 precursor, which includes the current collector 11a precursor and the current collector 11a precursor includes the sub-electrode tab 21a precursor. The electrode precursor 11 refers to the state before the electrode precursor 11 is die-cut. Multiple electrode precursors 11 can be obtained after die-cutting one electrode precursor 11.

[0071] S200. The conductive foil 21b precursor and the sub-electrode tab 21a precursor are welded using a welding roller 2000 and then die-cut to obtain multiple electrode plates 11. Figure 5 This is a schematic diagram showing the surface development of the welding roller 2000 provided in the embodiments of this application (the left and right ends of the figure are the connecting parts). Please refer to [link / reference]. Figure 5The surface of the welding roller 2000 has a welding working area 2000a, which has a first width and a second width, the first width being greater than the second width. As will be understood by those skilled in the art, the welding roller 2000 consists of a roller base and a welding head. The roller base has a wheel-shaped structure, and the welding head is laid flat on the roller base to form a welding working area 2000a. The welding head is decorated with textures, which can be diamond mesh or arc toothed structures, with a texture depth of 0.05mm to 0.5mm.

[0072] During welding, the two conductive foils 21b precursors are placed on the two surfaces of the sub-tab 21a precursor for welding. The welding process can be as follows: the two conductive foils 21b precursors and the sub-tab 21a precursors stacked together are welded through the gap provided by two welding rollers 2000 in pairs. The width of the corresponding welding working area 2000a of the two welding rollers 2000 is the same.

[0073] S300. Multiple electrode plates 11 are stacked to obtain electrode assembly 200; S400. Place the electrode assembly 200 inside the housing 100 to obtain a battery cell 1000, which is the battery cell 1000 provided above.

[0074] This method utilizes a specific welding roller 2000 for welding, which facilitates the fabrication of inner tabs 21 with varying solder layer 21c widths. These inner tabs are then stacked sequentially. By controlling the direction from the inner to the outer surface of the bending section, the width of the solder layer 21c of the inner tabs 21 in the second tab bundle 23b gradually increases. This means that the welding strength between the conductive foil 21b and the sub-tab 21a of the inner tabs 21 located on the outer side of the bend gradually increases. This ensures that the welding strength between the conductive foil 21b and the sub-tab 21a matches the corresponding bending stress, reducing the risk of solder layer 21c peeling and detachment, which can lead to poor soldering and a surge in internal resistance. Simultaneously, the solder layer 21c of the inner tabs 21 located on the inner side of the bend is smaller, reducing the impact on the welding of the conductive foil 21b and the outer tab 22, and also reducing space encroachment. This balances the welding strength of the electrode tabs 20 with the volumetric energy density of the battery.

[0075] In some embodiments, the welding working area 2000a is continuous along the circumferential direction of the welding roller 2000. Making the welding working area 2000a continuous is beneficial for improving the welding strength between the conductive foil 21b of the inner tab 21 and the sub-tab 21a, and also facilitates die-cutting of any size to match the needs of different battery sizes. In other embodiments, the welding working area 2000a may also be discontinuous along the circumferential direction of the welding roller 2000; this application does not limit this.

[0076] In some embodiments, the width of the welding working area 2000a is gradually varied along the circumferential direction of the welding roller 2000. By making the width of the welding working area 2000a gradually varied, it is advantageous to quickly produce inner tabs 21 with different widths of solder layers 21c, and it also facilitates die-cutting of arbitrary sizes to meet the needs of different battery sizes. In other embodiments, the width of the welding working area 2000a may also be equal along the circumferential direction of the welding roller 2000; this application does not limit this.

[0077] In some embodiments, the edges of the welding work area 2000a are smooth. Making the edges of the welding work area 2000a smooth facilitates die-cutting of any size to match the needs of different battery sizes. In other embodiments, the edges of the welding work area 2000a may also be non-smooth, such as stepped, and this application is not limited thereto.

[0078] In some embodiments, the welding speed is 1 m / min to 100 m / min. For example, the welding speed can be 1 m / min, 5 m / min, 10 m / min, 15 m / min, 20 m / min, 25 m / min, 30 m / min, 35 m / min, 40 m / min, 45 m / min, 50 m / min, 55 m / min, 60 m / min, 65 m / min, 70 m / min, 75 m / min, 80 m / min, 85 m / min, 90 m / min, 95 m / min, 100 m / min, etc., or any value within the range of 1 m / min to 100 m / min.

[0079] In some embodiments, the welding pressure is 0.1 MPa to 1 MPa. Exemplary examples include welding pressures of 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa, 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa, 0.5 MPa, 0.55 MPa, 0.6 MPa, 0.65 MPa, 0.7 MPa, 0.75 MPa, 0.8 MPa, 0.85 MPa, 0.9 MPa, 0.95 MPa, 1 MPa, etc., or any value within the range of 0.1 MPa to 1 MPa.

[0080] This application embodiment also provides a secondary battery, which includes the battery cell 1000 provided above.

[0081] In this application, a secondary battery can refer to a single battery cell 1000, or it can refer to a single physical module comprising multiple battery cells 1000 to provide higher voltage and capacity, which can be in the form of a battery pack, battery module, etc. A secondary battery may include a housing for encapsulating multiple battery cells 1000, the housing preventing liquids or other foreign matter from affecting the charging or discharging of the battery cells 1000.

[0082] In some embodiments, the secondary battery includes a housing and a battery cell 1000, with the battery cell 1000 housed within the housing.

[0083] The housing provides a space to house the battery cell 1000. In some embodiments, the housing may include a first part and a second part, which overlap each other to define a space for accommodating the battery cell 1000. The connection between the first and second parts can be sealed using a sealant, such as a sealing ring or sealant.

[0084] The first and second parts can have various shapes, such as cuboids or cylinders. The first part can be a hollow structure with an opening on one side to form a cavity for accommodating the battery cells 1000, and the second part can also be a hollow structure with an opening on one side to form a cavity for accommodating the battery cells 1000. The opening side of the second part covers the opening side of the first part, thus forming a box with accommodating space. Alternatively, the first part can be a hollow structure with an opening on one side, and the second part can be a plate-like structure, with the second part covering the opening side of the first part, thus forming a box with accommodating space.

[0085] In a secondary battery, there can be one or more battery cells 1000. If there are multiple battery cells 1000, they can be connected in series, parallel, or a combination thereof. A combination thereof means that multiple battery cells 1000 are connected in both series and parallel. Multiple battery cells 1000 can be directly connected in series, parallel, or a combination thereof, and then the whole assembly of the multiple battery cells 1000 can be housed in a casing. Alternatively, multiple battery cells 1000 can first be connected in series, parallel, or a combination thereof to form a battery module, and then multiple battery modules can be connected in series, parallel, or a combination thereof to form a whole assembly, which is then housed in a casing. The battery cell 1000 can be cylindrical, flat, cuboid, or other shapes.

[0086] In some embodiments, the secondary battery may further include a busbar component, through which multiple battery cells 1000 can be electrically connected to each other to achieve series, parallel, or mixed connection of multiple battery cells 1000.

[0087] The battery cell 1000 or the secondary battery can be used in electrical equipment such as vehicles, ships, or aircraft. A power system for such electrical equipment can be constructed using the battery cell 1000 disclosed in this application.

[0088] The battery cell 1000 or secondary battery can also be used as an energy storage battery, for example, in residential, industrial and commercial energy storage, grid energy storage, mobile energy storage and other fields.

[0089] This application also provides an electrical device that uses a secondary battery as a power source. The electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0090] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device according to an embodiment of this application.

[0091] The vehicle can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A secondary battery is installed inside the vehicle, which can be located at the bottom, front, or rear of the vehicle. The secondary battery can be used to power the vehicle; for example, it can serve as the vehicle's operating power source. The vehicle may also include a controller and a motor. The controller is used to control the power supply from the secondary battery to the motor, for example, to meet the power needs of starting, navigation, and driving the vehicle.

[0092] In some embodiments of this application, the secondary battery can not only serve as the operating power source for the vehicle, but also as the driving power source for the vehicle, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle.

[0093] It should be noted that, where there is no conflict, the features in the embodiments of this application can be combined with each other.

[0094] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A battery cell, characterized in that, The battery cell includes: case; An electrode assembly is housed within a housing. The electrode assembly includes an assembly body and electrode tabs. The assembly body includes stacked electrode plates. The electrode tabs include an inner tab and an outer tab. The inner tab has a bent section and includes a sub-tab and a conductive foil. The sub-tab and the electrode plates are connected by a current collector. The current collector is a composite current collector. The conductive foil and the sub-tab are welded together, and a solder layer is present between the conductive foil and the sub-tab. The outer tab is connected to the conductive foil and extends out of the housing. Multiple inner tabs are stacked to form a tab bundle, which includes a first tab bundle and a second tab bundle. Along the direction X from the inner surface to the outer surface of the bending section, the first tab bundle and the second tab bundle are arranged sequentially, and the width of the solder layer of the inner tabs in the second tab bundle increases sequentially.

2. The battery cell according to claim 1, characterized in that, Along the direction X from the inner surface to the outer surface of the bending section, the length of the inner electrode ear in the first electrode ear bundle gradually decreases, the length of the inner electrode ear in the second electrode ear bundle gradually increases, and the length of the inner electrode ear in the second electrode ear bundle closer to the first electrode ear bundle is less than the length of the inner electrode ear in the first electrode ear bundle closer to the second electrode ear bundle.

3. The battery cell according to claim 1 or 2, characterized in that, The width of the solder paste layer is 1mm to 10mm.

4. The battery cell according to claim 1 or 2, characterized in that, The thickness of the component body is not less than 10 mm, measured in the stacking direction of the component body.

5. The battery cell according to claim 1 or 2, characterized in that, The number of inner electrodes in the electrode bundle is no less than 5 layers.

6. The battery cell according to claim 1 or 2, characterized in that, In the second tab bundle, the solder layer width of a single inner tab is gradually changing, and is counted sequentially along the direction X from the inner surface to the outer surface of the bending position of the bending segment. The maximum value of the solder layer width of an inner tab is equal to the minimum value of the solder layer width of the next adjacent inner tab.

7. The battery cell according to claim 1 or 2, characterized in that, In the plurality of inner tabs, the end of the solder layer near the sub-tab is located on the same plane in a flattened state.

8. The battery cell according to claim 1 or 2, characterized in that, The electrode assembly is a stacked electrode assembly; and / or The shell is a soft-pack shell.

9. A method for preparing a single battery cell, characterized in that, The method includes: An electrode precursor is obtained, wherein the electrode precursor includes a current collector precursor, and the current collector precursor includes a sub-electrode precursor; A welding roller is used to weld the conductive foil precursor and the sub-electrode precursor together, and then die-cut them to obtain multiple electrode sheets; the surface of the welding roller has a welding working area, which has a first width and a second width, wherein the first width is greater than the second width; Multiple electrode sheets are stacked to obtain an electrode assembly; The electrode assembly is placed inside the housing to obtain a battery cell, wherein the battery cell is a battery cell as described in any one of claims 1 to 8.

10. The method for preparing a battery cell according to claim 9, characterized in that, The welding working area is continuous along the circumferential direction of the welding roller; and / or Along the circumferential direction of the welding roller, the width of the welding working area is gradually changing; and / or The edges of the welding work area are smooth.

11. The method for preparing a battery cell according to claim 9, characterized in that, The welding speed is 1 m / min to 100 m / min; and / or The welding pressure is 0.1 MPa to 1 MPa.

12. A secondary battery, characterized in that, The secondary battery comprises the battery cell according to any one of claims 1 to 8.

13. An electrical appliance, characterized in that, The electrical equipment includes a battery cell as described in any one of claims 1 to 8 or a secondary battery as described in claim 12.

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