Single battery

Abstract

The utility model provides a single battery. The single battery comprises a shell; the cover plate assembly is arranged on the shell in a covering manner, an accommodating cavity is defined by the cover plate assembly and the shell together, and the cover plate assembly comprises a cover plate body and a pole column penetrating through the cover plate body in the height direction of the single battery; the at least one electrode assembly is accommodated in the accommodating cavity, and a tab of the electrode assembly is directly and electrically connected with one side, facing the electrode assembly, of the pole; a welding groove is formed in the side, away from the electrode assembly, of the pole, and the tab is welded to the surface of the side, facing the electrode assembly, of the pole. The projection of a welding mark formed by welding in the height direction is located at the bottom of the welding groove. By arranging the specific structure, the size of the electrode assembly can be effectively and relatively increased, so that the energy density of the battery is effectively improved; moreover, by arranging the welding groove for the laser to pass through, the pole is directly connected to the tab in a laser penetration welding manner, so that the influence on peripheral components caused by excessive heat is avoided.

Description

Technical Field

[0001] The utility model relates to a single cell. Background Art

[0002] With the development of lithium battery technology, higher energy density of battery cells is required. At present, square batteries mostly use adapter plates as the bridge for connecting the electrode assembly and the terminal post. The electrode assembly and the terminal post need to be connected together through the adapter plate. The adapter plate itself has a certain thickness, which will occupy the size of the electrode assembly inside the battery and limit the improvement of the energy density of the battery cell.

[0003] In the prior art, there is a method without an adapter plate for the terminal post. A bottom plate is formed on the bottom surface of the terminal post. The originally loose tab ears of the electrode assembly are welded into a whole by using ultrasonic welding technology, and then the tab ears are welded to the bottom plate by using laser welding technology. However, in the process of welding the tab ears to the bottom plate by using laser welding technology, since the laser welding is carried out from the side of the tab ear away from the terminal post, and the laser welding will form a molten pool after the welding part reaches the melting point. The positive tab ear uses aluminum, and the expansion coefficient of aluminum is relatively large. During the process of melting and solidifying of the molten pool, the volume change will cause the foil to break; and because the heat generated by laser welding is relatively large, it will cause the insulating parts for insulation in the top cover and the sealing parts for sealing inside the terminal post to melt, affecting the insulation and sealing effects. Summary of the Utility Model

[0004] The technical problem to be solved by the utility model is to overcome the defect that the method of using an adapter plate to connect the electrode assembly and the terminal post in the prior art restricts the energy density of the battery cell, while the method of connecting the electrode assembly and the terminal post without an adapter plate will cause the foil to break and affect the insulation and sealing effects during laser welding, and to provide a single cell.

[0005] The utility model solves the above technical problem by the following technical solutions:

[0006] A single cell, characterized in that it comprises:

[0007] A housing;

[0008] A cover plate assembly, covering the housing and jointly defining a receiving cavity with the housing. The cover plate assembly includes a cover plate body and a terminal post penetrating the cover plate body along the height direction of the single cell;

[0009] At least one electrode assembly, received in the receiving cavity, and the tab ear of the electrode assembly is directly electrically connected to the side of the terminal post facing the electrode assembly;

[0010] Wherein, a welding groove is formed on one side of the pole column away from the electrode assembly, and the tab is welded to the surface of the pole column facing the electrode assembly; the projection of the weld mark formed by welding in the height direction of the single cell is located at the bottom of the welding groove.

[0011] In this technical solution, by directly welding the tab to the surface of the pole column facing the electrode assembly, the use of a transfer piece in the prior art is avoided. Within the specified size range of the single cell, the size of the electrode assembly can be effectively increased relatively, thereby effectively improving the battery energy density. Moreover, by forming a welding groove on one side of the pole column away from the electrode assembly, and the projection of the weld mark formed by welding in the height direction of the single cell is located at the bottom of the welding groove, that is to say, the laser passes through the welding groove to connect the pole column and the tab together, so that the pole column is directly connected to the tab by laser penetration welding, avoiding excessive heat generation and affecting the surrounding components.

[0012] Preferably, the electrode assembly further includes an electrode body, and the electrode body includes multiple layers of electrodes stacked along the thickness direction of the single cell, and at least part of the layers of electrodes extend out of the tab; among the multiple layers of electrodes, the electrode close to the housing along the thickness direction is the outermost layer electrode, and the electrode far from the housing is the innermost layer electrode;

[0013] The multiple layers of tabs of each electrode assembly are bent in the same direction, and the bent part of the tab in the outermost layer is stacked on the surface close to the cover plate assembly of the bent part of the tab in the innermost layer along the height direction.

[0014] In this technical solution, by setting the multiple layers of tabs of each electrode assembly to be bent in the same direction, and the bent part of the tab in the outermost layer is stacked on the surface close to the cover plate assembly of the bent part of the tab in the innermost layer along the height direction, the size of the electrode assembly can be further effectively increased relatively, thereby effectively improving the battery energy density.

[0015] Preferably, in each electrode assembly, at least part of the bent parts of the multiple layers of tabs are located within the orthographic projection of the weld mark along the height direction.

[0016] In this technical solution, by setting that in each electrode assembly, at least part of the bent parts of the multiple layers of tabs are located within the orthographic projection of the weld mark along the height direction, the electrical connection between each electrode assembly and the pole column is realized.

[0017] Preferably, in each electrode assembly, the electrode in the outermost layer extends out of the tab, and at least part of the bent part of the tab is located within the orthographic projection of the weld mark along the height direction.

[0018] In this technical solution, by arranging the electrode located in the outermost layer to extend out the tab, and at least a part of the bent portion of the tab in the height direction is located within the orthographic projection of the welding mark, the electrical connection between the electrode in the outermost layer and the pole column is realized.

[0019] Preferably, when the number of the electrode assemblies is one, the bent portions of the multiple tabs of the electrode assembly are located within the orthographic projection of the electrode body of the electrode assembly in the height direction;

[0020] When the number of the electrode assemblies is multiple, the multiple electrode assemblies are stacked in sequence in the thickness direction, and the bent portions of the multiple tabs of each electrode assembly are located within the orthographic projection of the electrode bodies of the multiple electrode assemblies in the height direction.

[0021] In this technical solution, through the above arrangement, the bent portion of the tab will not protrude beyond the outer contour of the electrode bodies of all the electrode assemblies in the thickness direction, avoiding affecting the assembly of the electrode assembly and the housing.

[0022] Preferably, when the number of the electrode assemblies is one, the dimension of the bent portion of the tab in the outermost layer in the thickness direction is less than the thickness of the electrode body and greater than or equal to 50% of the thickness of the electrode body;

[0023] When the number of the electrode assemblies is multiple, the multiple electrode assemblies are stacked in sequence in the thickness direction, and the dimension of the bent portion of the tab in the outermost layer in the thickness direction is less than the total thickness of the electrode bodies of the multiple electrode assemblies and greater than or equal to 50% of the thickness of the electrode body of the electrode assembly where it is located.

[0024] In this technical solution, by setting the value range of the dimension of the bent portion of the tab in the outermost layer in the thickness direction, it is ensured that the bent portion of the tab in the outermost layer will not protrude beyond the electrode bodies of all the electrode assemblies in the thickness direction, thus affecting the assembly of the electrode assembly and the housing; at the same time, it can be ensured that the bent portion of the tab in the outermost layer can overlap with the welding mark at the middle position in the thickness direction, thereby realizing the electrical connection between the electrode in the outermost layer and the pole column.

[0025] Preferably, in each electrode assembly, the number of layers of the electrode having the tab is greater than 50% of the total number of layers of all the electrodes.

[0026] In this technical solution, by setting that in each electrode assembly, the number of layers of the electrode having the tab is greater than 50% of the total number of layers of all the electrodes, the process stability can be ensured. This is because a part of the tabs needs to be designed more than 50% of the number of layers to avoid welding through the tabs during laser welding.

[0027] Preferably, in each of the electrode assemblies, the number of layers of the electrode having the tab is 60%-90% of the total number of layers of all the electrodes.

[0028] In this technical solution, by setting the number of layers of the electrode having the tab to be 60%-90% of the total number of layers of all the electrodes in each electrode assembly, on the one hand, it is to avoid the problem that when the number of layers is too small, the tab is easily penetrated during laser welding; on the other hand, it is to avoid the problem that when the number of tab layers is too large, the stacked tabs will occupy a part of the internal space of the battery cell.

[0029] Preferably, the area of the welding mark is greater than or equal to 80 mm 2 。

[0030] In this technical solution, by setting the area of the welding mark to be greater than or equal to 80 mm 2 , it is used to ensure the current passing area and connection strength at this position.

[0031] Preferably, the welding groove is opened in the pole column on the side away from the electrode assembly along the height direction, the height of the pole column is greater than the depth of the welding groove, and the difference between the height of the pole column and the depth of the welding groove is greater than or equal to 0.7 mm.

[0032] In this technical solution, by setting the height of the pole column to be greater than the depth of the welding groove, and the difference between the height of the pole column and the depth of the welding groove to be greater than or equal to 0.7 mm, that is, setting the height of the solid structure below the welding groove to be at least 0.7 mm, to ensure the strength of the solid structure of the pole column below the welding groove.

[0033] Preferably, the pole column includes a through portion and a connecting plate, the connecting plate is located on the side of the cover plate body facing the electrode assembly, the through portion includes a first end close to the electrode assembly and a second end far from the electrode assembly, the second end of the through portion penetrates through the cover plate body, and the first end of the through portion is connected to the connecting plate;

[0034] The welding groove is opened in the through portion along the height direction, and the orthographic projection of the welding groove along the height direction is located within the outer edge of the connecting plate, and the thickness of the connecting plate is 0.5 mm - 1 mm.

[0035] In this technical solution, the welding groove is arranged in the through portion in the height direction, and the positive projection of the welding groove in the height direction is located within the outer edge of the connecting plate. That is to say, at least part of the solid structure below the welding groove is the structure of the connecting plate. Further, by setting the thickness range of the connecting plate, it is avoided that the thickness of the connecting plate is too thin, resulting in insufficient strength of the solid structure below the welding groove; while the thickness of the connecting plate is too thick, resulting in a relatively high energy required for laser penetration welding, which has a greater thermal impact on the insulating parts and sealing parts around the connecting plate.

[0036] The positive and progressive effects of the present utility model are as follows:

[0037] In the present utility model, the tab is directly welded to the surface of the pole column on the side facing the electrode assembly, thereby avoiding the use of the adapter plate in the prior art. Within the specified standard size range of the single cell, the size of the electrode assembly can be effectively increased relatively, thereby effectively improving the battery energy density. And, by opening a welding groove on the side of the pole column away from the electrode assembly, and the projection of the weld mark formed by welding in the height direction of the single cell is located at the bottom of the welding groove. That is to say, the laser passes through the welding groove to connect the pole column and the tab together, so that the pole column is directly connected to the tab by means of laser penetration welding, avoiding the generation of excessive heat and affecting the surrounding components. Description of the Drawings

[0038] Figure 1 It is a schematic cross-sectional structure view of the single cell of Embodiment 1 of the present utility model.

[0039] Figure 2 It is a schematic top view structure view of the electrode assembly of the single cell of Embodiment 1 of the present utility model.

[0040] Figure 3 It is a schematic structure view of the laser penetration welding track of the single cell of Embodiment 1 of the present utility model.

[0041] Figure 4 It is a schematic cross-sectional structure view of the single cell of Embodiment 2 of the present utility model.

[0042] Description of the Reference Numerals

[0043] Single cell 1

[0044] Shell 10

[0045] Cover plate assembly 20

[0046] Cover plate body 21

[0047] Pole column 22

[0048] Welding groove 221

[0049] Through portion 222

[0050] Connecting plate 223

[0051] Insulating part 23

[0052] Sealing part 24

[0053] Accommodating cavity 30

[0054] Electrode assembly 40

[0055] Tab 41

[0056] Electrode body 42

[0057] Electrode 421

[0058] Insulating layer 422

[0059] Welding mark A

[0060] Height direction H of the single cell

[0061] Thickness direction T of the single cell

[0062] Thickness t1 of the electrode body

[0063] Dimension t2 of the bent part of the tab along the thickness direction

[0064] Thickness h1 of the connecting plate Specific embodiments

[0065] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, in which the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0066] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "circumferential", "radial", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

[0067] In addition, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present utility model, "a plurality" means two or more, unless otherwise specifically defined.

[0068] Embodiment 1

[0069] As Figure 1 and Figure 2 shown, this embodiment provides a single cell 1. The single cell 1 includes: a housing 10, a cover assembly 20, and an electrode assembly 40. The number of the electrode assemblies 40 is one. However, this is not limited thereto. In other embodiments, the number of the electrode assemblies 40 may also be two, three, four, or other values.

[0070] The cover assembly 20 is disposed on the housing 10 and together with the housing 10 defines an accommodation cavity 30. The cover assembly 20 includes a cover body 21 and a pole column 22 penetrating through the cover body 21 along the height direction H of the single cell 1.

[0071] The electrode assembly 40 is accommodated in the accommodation cavity 30, and the tab 41 of the electrode assembly 40 is directly electrically connected to one side of the pole column 22 facing the electrode assembly 40.

[0072] Wherein, a welding groove 221 is formed on one side of the pole column 22 away from the electrode assembly 40, and the tab 41 is welded to the surface of the pole column 22 on the side facing the electrode assembly 40; the projection of the weld mark formed by welding in the height direction H of the single cell 1 is located at the bottom 1 of the welding groove 221.

[0073] In this way, by directly welding the tab 41 to the surface of the pole column 22 on the side facing the electrode assembly 40, the use of a jumper in the prior art is avoided, and within the specified size range of the single cell 1, the size of the electrode assembly 40 can be effectively increased relatively, thereby effectively improving the battery energy density; and by forming a welding groove 221 on one side of the pole column 22 away from the electrode assembly 40 and the projection of the weld mark formed by welding in the height direction H of the single cell 1 being located at the bottom of the welding groove 221, that is, the laser passes through the welding groove 221 to connect the pole column 22 and the tab 41 together, so that the pole column 22 is directly connected to the tab 41 by laser penetration welding, avoiding excessive heat generation and affecting the surrounding components.

[0074] Preferably, the electrode assembly 40 further includes an electrode body 42. The electrode body 42 includes multiple layers of electrodes 421 stacked along the thickness direction T of the single cell 1, and at least part of the layers of electrodes 421 extend out of the tab 41. Among the multiple layers of electrodes 421, the electrode 421 closer to the housing 10 along the thickness direction T is the outer-layer electrode 421, and the electrode 421 farther from the housing 10 is the inner-layer electrode 421. The multiple tabs 41 of the electrode assembly 40 are bent in the same direction, and the bent part of the tab 41 in the outer layer is stacked on the surface close to the cover plate assembly 20 of the bent part of the tab 41 in the inner layer along the height direction H. In this way, by setting the multiple tabs 41 of each electrode assembly 40 to be bent in the same direction, and the bent part of the tab 41 in the outer layer is stacked on the surface close to the cover plate assembly 20 of the bent part of the tab 41 in the inner layer along the height direction H, the size of the electrode assembly 40 can be effectively increased relatively, thereby effectively improving the battery energy density. This is because in the prior art, it is usually necessary to weld all the originally loose tabs of the electrode assembly 40 into a whole, and then bend them and perform the next welding process with the adapter plate. This results in the need to leave space for bending the whole tabs. At least about 2-3 mm of height for bending the whole tabs needs to be left to prevent the tabs from being inserted inside. This part of the space for bending the whole tabs will occupy the height of the electrode assembly itself. In this embodiment, the multiple tabs 41 of the electrode assembly 40 are directly bent in the same direction, and the bent part of the tab 41 in the outer layer is stacked on the surface close to the cover plate assembly 20 of the bent part of the tab 41 in the inner layer along the height direction H, thereby avoiding the need to reserve space for bending the whole tab 41, and achieving the beneficial technical effect of further effectively increasing the size of the electrode assembly 40 relatively, thereby effectively improving the battery energy density. At the same time, it can also prevent internal short circuit caused by the insertion of the tab 41.

[0075] It should be noted that the electrode body 42 includes multiple layers of electrodes 421 stacked along the thickness direction T of the single cell 1. The method of stacking the multiple layers of electrodes 421 includes two methods: winding and laminating. Specifically, the electrode body 42 in this embodiment is formed by the winding method, and an insulating layer 422 is provided between adjacent layers of electrodes 421. The multiple layers of electrodes 421 include multiple layers of first electrodes and multiple layers of second electrodes. The first electrode is the positive electrode, and the second electrode is the negative electrode; or the first electrode is the negative electrode, and the second electrode is the positive electrode. However, it is not limited to this. In other embodiments, the electrode body 42 can also be formed by the lamination method.

[0076] In the electrode assembly 40, at least part of the bent parts of the multiple tabs 41 are located within the orthographic projection of the welding mark A along the height direction H to achieve the electrical connection between each electrode assembly 40 and the pole post 22.

[0077] In the electrode assembly 40, the outermost electrode 421 extends out the tab 41, and at least a part of the bent portion of the tab 41 in the height direction H is within the orthographic projection of the welding mark A, so as to realize the electrical connection between the outermost electrode 421 and the terminal post 22.

[0078] The bent portions of the multi-layer tabs 41 of the electrode assembly 40 are within the orthographic projection of the electrode body 42 of the electrode assembly 40 in the height direction H, so that the bent portions of the tabs 41 do not protrude beyond the outer contour of the electrode body 42 in the thickness direction T, avoiding affecting the assembly of the electrode assembly 40 and the housing 10.

[0079] In this embodiment, the dimension t2 of the bent portion of the outermost tab 41 in the thickness direction T is less than the thickness t1 of the electrode body 42 and greater than or equal to 50% of the thickness t1 of the electrode body 42, so as to ensure that the bent portion of the outermost tab 41 does not protrude beyond the electrode body 42 in the thickness direction T, thus affecting the assembly of the electrode assembly 40 and the housing 10; at the same time, it can ensure that the bent portion of the outermost tab 41 can overlap with the welding mark A at the middle position in the thickness direction T, so as to realize the electrical connection between the outermost electrode 421 and the terminal post 22.

[0080] In the electrode assembly 40, the number of layers of the electrodes 421 with tabs 41 is greater than 50% of the total number of layers of all the electrodes 421 to ensure process stability. This is because, a part more than 50% of the number of layers is designed for the tabs 41 to avoid welding through the tabs 41 during laser welding. During actual use, the number of layers of the tabs 41 is 20 - 100 layers, and the single-layer thickness is 10 - 15 μm / layer for aluminum foil and 4 - 8 μm / layer for copper foil; the actual welding parameters of the tabs 41 are generally controlled within 30% - 90% of the designed number of layers (for example, if the designed number of layers of the tabs 41 is 50 layers, then it is necessary to ensure that the number of welded connection layers is 15 - 45 layers).

[0081] Preferably, the number of layers of the electrodes 421 with tabs 41 in the electrode assembly 40 is 60% - 90% of the total number of layers of all the electrodes 421. In this way, by setting the number of layers of the electrodes 421 with tabs 41 in the electrode assembly 40 to be 60% - 90% of the total number of layers of all the electrodes 421, on the one hand, it is to avoid the problem that it is easy to weld through the tabs 41 during laser welding due to too few layers; on the other hand, it is to avoid the problem that the stacked tabs 41 will occupy a part of the internal space of the battery cell due to too many layers of the tabs 41.

[0082] Preferably, the area of the welding mark A is greater than or equal to 80 mm 2 , to ensure the current passing area and connection strength at this position. The trajectory of the laser penetration welding is as Figure 3 shown, and it can be circular, square, linear, etc.

[0083] Preferably, the welding groove 221 is formed in the pole column 22 on the side away from the electrode assembly 40 along the height direction H. The height of the pole column 22 is greater than the depth of the welding groove 221, and the difference between the height of the pole column 22 and the depth of the welding groove 221 is greater than or equal to 0.7 mm. That is, the height of the solid structure located below the welding groove 221 is at least 0.7 mm to ensure the strength of the solid structure of the pole column below the welding groove. The height of the pole column 22 is the dimension of the pole column 22 along the height direction H; the depth of the welding groove 221 is the dimension of the welding groove 221 along the height direction H.

[0084] In this embodiment, specifically, the pole column 22 includes a through portion 222 and a connecting plate 223. The connecting plate 223 is located on the side of the cover body 21 facing the electrode assembly 40. The through portion 222 includes a first end close to the electrode assembly 40 and a second end away from the electrode assembly 40. The second end of the through portion 222 penetrates through the cover body 21, and the first end of the through portion 222 is connected to the connecting plate 223.

[0085] The material of the connecting plate 223 can be pure aluminum, pure copper, nickel-plated copper, alloy, etc. The through portion 222 and the connecting plate 223 are connected into a whole by means of riveting, stamping, machining, friction stir welding, etc., so as to achieve the effect of internal and external electrical connection.

[0086] The welding groove 221 is formed in the through portion 222 along the height direction H, and the positive projection of the welding groove 221 along the height direction H is located within the outer edge of the connecting plate 223. That is to say, at least part of the solid structure below the welding groove 221 is the structure of the connecting plate 223. Further, the thickness h1 of the connecting plate 223 is 0.5 mm - 1 mm. By setting the thickness range of the connecting plate 223, it is possible to avoid the situation where the thickness h1 of the connecting plate 223 is too thin, resulting in insufficient strength of the solid structure below the welding groove 221; while if the thickness h1 of the connecting plate 223 is too thick, it will lead to a relatively high energy required for laser penetration welding, which has a greater thermal impact on the insulating member 23 and the sealing member 24 around the connecting plate 223. It should be noted that the solid structure located below the welding groove 221 along the height direction H is the bottom of the welding groove 221, and the welding mark A is located within the contour of the bottom of the welding groove 221. The height of the solid structure below the welding groove 221, that is, the thickness of the bottom of the welding groove 221, is variable according to the relationship with the thickness of the connecting plate 223 as required by the design. The thickness of the bottom of the welding groove 221 can be the sum of the height of part of the through portion 222 and the thickness of the connecting plate 223 (corresponding to the state where the welding groove 221 does not penetrate the through portion 222), or it can be equal to the thickness of the connecting plate 223 (corresponding to the state where the welding groove 221 just penetrates the through portion 222), or it can be less than the thickness of the connecting plate 223 (corresponding to the state where the welding groove 221 not only penetrates the through portion 222 but also partially penetrates the connecting plate 223). The thickness h1 of the connecting plate 223 is the dimension of the connecting plate 223 along the height direction H of the single cell 1; the thickness of the bottom of the welding groove 221 is the dimension of the bottom of the welding groove 221 along the height direction H of the single cell 1; the height of the through portion 222 is the dimension of the through portion 222 along the height direction H of the single cell 1.

[0087] During actual use, the thickness of the adapter plate is generally 0.5 mm - 3 mm; taking an adapter plate with a thickness of 1 mm and the thickness of the connecting plate 223 of the pole 22 changed from 1.8 mm to 0.5 mm as an example, generally, the reserved space for preventing the inner insertion of the tab 41, the folded tab 41, is 2 mm - 3 mm, and taking the height of the electrode assembly 40 as 100 mm as an example, by adopting the design scheme of the single cell 1 in this embodiment, a total of 4 - 5 mm of internal space can be saved. Taking 5 mm as an example, the energy density can be increased by 5%.

[0088] The cover plate assembly 20 further includes an insulating member 23 disposed on the side of the cover plate body 21 facing the electrode assembly 40, and the insulating member 23 is disposed between the cover plate body 21 and the connecting plate 223. In this embodiment, the material of the insulating member 23 is plastic, but it is not limited thereto, and other insulating materials can also be used. The through portion 222 of the pole 22 passes through the cover plate body 21 and the insulating member 23 in sequence.

[0089] The cover plate assembly 20 further includes a seal 24, which is clamped between the terminal post 22 and the cover plate body 21. In this embodiment, the seal 24 is an O-ring, and the material of the seal 24 is plastic, but it is not limited thereto, and it can also be other insulating materials.

[0090] In this embodiment, the terminal post 22 and the tab 41 are connected together by laser penetration welding. The lasers used include single-mode, single-mode ring, multi-mode ring, and green lasers. The fiber core diameter range of the single-mode laser includes 14μm - 25μm, and the power range is 1000W - 2000W; the inner core diameter of the single-mode ring is 14μm - 25μm, the outer core diameter is 50μm - 100μm, the outer ring power is 1000W - 2000W, and the inner ring power is 1000W - 2000W; the inner core diameter of the multi-mode ring is 50μm - 100μm, the outer core diameter is 150μm - 600μm, the outer ring power is 1000W - 2000W, and the inner ring power is 2000W - 4000W.

[0091] The terminal post 22 includes a positive terminal post and a negative terminal post. During actual use, the parameter range for welding the positive terminal post and the corresponding tab with a single-mode ring laser is: outer ring power 1000W - 2000W, inner ring power 400W - 800W, defocus -2 - +2, welding speed 300mm / s - 500mm / s; the parameter range for welding the negative terminal post and the corresponding tab is: outer ring power 1000 - 2000W, inner ring power 400W - 800W, defocus -2 - +2, welding speed 300mm / s - 500mm / s.

[0092] In this embodiment, the single cell 1 avoids using the adapter plate in the prior art by welding the tab 41 to the surface of the terminal post 22 on the side facing the electrode assembly 40. Within the specified size range of the single cell 1, the size of the electrode assembly 40 can be effectively increased relatively, thereby effectively improving the battery energy density; at the same time, since the adapter plate is cancelled, the weight can be reduced, and a process of welding the electrode assembly 40 to the adapter plate can be saved, saving the manufacturing cost. And, by opening a welding groove 221 on the side of the terminal post 22 away from the electrode assembly 40, and the projection of the weld mark formed by welding in the height direction H of the single cell 1 is located at the bottom of the welding groove 221, that is, the laser passes through the welding groove 221 to connect the terminal post 22 and the tab 41 together, so that the terminal post 22 is directly connected to the tab 41 by laser penetration welding, avoiding excessive heat generation and affecting the surrounding components.

[0093] Embodiment 2

[0094] As Figure 4As shown, the overall structure of the single cell 1 in this embodiment is basically the same as that in Embodiment 1. The difference is that the number of electrode assemblies 40 is two. The two electrode assemblies 40 are stacked in sequence along the thickness direction T of the single cell 1.

[0095] For each of the two electrode assemblies 40, the multi-layer tabs 41 of each electrode assembly 40 are bent in the same direction, and the bent portion of the tab 41 located on the outer layer is stacked on the surface close to the cover plate assembly 20 of the bent portion of the tab 41 located on the inner layer along the height direction H. In this way, by setting the multi-layer tabs 41 of each electrode assembly 40 to be bent in the same direction, and the bent portion of the tab 41 located on the outer layer is stacked on the surface close to the cover plate assembly 20 of the bent portion of the tab 41 located on the inner layer along the height direction H, the size of the electrode assembly 40 can be effectively increased relatively, thereby effectively improving the battery energy density.

[0096] In each of the two electrode assemblies 40, at least a part of the bent portion of the multi-layer tabs 41 is within the orthographic projection of the welding mark A along the height direction H to achieve the electrical connection between each electrode assembly 40 and the terminal 22. That is to say, the bending direction of the multi-layer tabs 41 of each electrode assembly 40 needs to be able to achieve its electrical connection with the terminal 22. Specifically, in this embodiment, the multi-layer tabs 41 of the electrode assembly 40 located Figure 4 on the left side are bent to the right, while the multi-layer tabs 41 of the electrode assembly 40 located on the right side are bent to the right, so as to overlap with the welding mark A located at the middle position in the thickness direction T in the height direction H, so as to realize the connection of the tabs 41 of the electrode assemblies 40 located on both sides with the terminal 22.

[0097] The bent portion of the multi-layer tabs 41 of each electrode assembly 40 in the two electrode assemblies 40 is within the orthographic projection of the electrode body 42 of the two electrode assemblies 40 along the height direction H, so that the bent portion of the tab 41 will not protrude from the outer contour of the electrode body 42 of all electrode assemblies 40 along the thickness direction T, avoiding affecting the assembly of the electrode assembly 40 and the housing 10.

[0098] In the two electrode assemblies 40, the size t2 of the bent portion of the tab 41 located on the outermost layer along the thickness direction T is less than the total thickness of the electrode bodies 42 of the two electrode assemblies 40 (that is, the sum of the thicknesses t1 of the two electrode bodies), and greater than or equal to 50% of the thickness t1 of the electrode body 42 of the electrode assembly 40 where it is located, so as to ensure that the bent portion of the tab 41 located on the outermost layer will not protrude from the electrode bodies 42 of all electrode assemblies 40 along the thickness direction T, thereby affecting the assembly of the electrode assembly 40 and the housing 10; at the same time, it can ensure that the bent portion of the tab 41 located on the outermost layer can overlap with the welding mark A located at the middle position in the thickness direction T, thereby realizing the electrical connection between the outermost electrode 421 and the terminal 22.

[0099] In each of the two electrode assemblies 40, the number of layers of the electrode 421 having the tab 41 is greater than 50% of the total number of layers of all the electrodes 421 to ensure process stability.

[0100] Preferably, in each of the two electrode assemblies 40, the number of layers of the electrode 421 having the tab 41 is 60%-90% of the total number of layers of all the electrodes 421. In this way, by setting the number of layers of the electrode 421 having the tab 41 in each electrode assembly 40 to be 60%-90% of the total number of layers of all the electrodes 421, on the one hand, in order to avoid the problem that when the number of layers is too small, the tab 41 is easily penetrated during laser welding; on the other hand, in order to avoid the problem that when the number of layers of the tab 41 is too large, the stacked tabs 41 will occupy a part of the internal space of the battery cell.

[0101] It should be noted that in other embodiments, the number of the electrode assemblies 40 may also be three, four or other numbers. When the number of the electrode assemblies 40 is multiple, the setting method of the electrode assemblies 40 is basically the same as that of the two electrode assemblies 40, and will not be repeated here. Only the bending direction of the tab 41 of each of the multiple electrode assemblies 40 can be adjusted accordingly according to the design requirements. For example, when the number of the electrode assemblies 40 is three, the tab 41 of the electrode assembly 40 located in the middle and one of its adjacent electrode assemblies 40 can be bent towards the middle position (the position where the welding mark A is located), while the tab 41 of the remaining another electrode assembly 40 is bent towards the middle position (the position where the welding mark A is located). However, it is not limited thereto, and other bending methods may also be used, as long as at least part of the bent portion of the tab 41 of each electrode assembly 40 can be electrically connected to the terminal 22.

[0102] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that this is only an example, and the protection scope of the present invention is defined by the appended claims. Without departing from the principle and essence of the present invention, those skilled in the art can make various changes or modifications to these embodiments, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A single cell, characterized in that, It includes: A housing; A cover plate assembly, which is disposed on the housing and jointly defines a receiving cavity with the housing. The cover plate assembly includes a cover plate body and a pole column penetrating through the cover plate body along the height direction of the single cell; At least one electrode assembly, which is received in the receiving cavity, and the tab of the electrode assembly is directly electrically connected to the side of the pole column facing the electrode assembly; Wherein, a welding groove is formed on the side of the pole column away from the electrode assembly, and the tab is welded to the surface of the pole column facing the electrode assembly; the projection of the weld mark formed by welding in the height direction of the single cell is located at the bottom of the welding groove.

2. The single cell according to claim 1, characterized in that, The electrode assembly further includes an electrode body, and the electrode body includes multiple layers of electrodes stacked along the thickness direction of the single cell, and at least part of the layers of the electrodes extend out of the tab; among the multiple layers of electrodes, the electrode close to the housing along the thickness direction is the electrode located on the outer layer, and the electrode away from the housing is the electrode located on the inner layer; The tabs of the multiple layers of each electrode assembly are bent in the same direction, and the bent part of the tab located on the outer layer is stacked on the surface of the bent part of the tab located on the inner layer close to the cover plate assembly along the height direction.

3. The single cell according to claim 2, wherein In each electrode assembly, at least part of the bent parts of the multiple layers of tabs along the height direction are within the orthographic projection of the weld mark.

4. The single cell according to claim 2, characterized in that, In each electrode assembly, the electrode located on the outermost layer extends out of the tab, and at least part of the bent part of the tab along the height direction is within the orthographic projection of the weld mark.

5. The single cell according to claim 2, wherein When the number of the electrode assemblies is one, the bent parts of the tabs of the multiple layers of the electrode assembly are within the orthographic projection of the electrode body of the electrode assembly along the height direction; When the number of the electrode assemblies is multiple, the multiple electrode assemblies are stacked in sequence along the thickness direction, and the bent parts of the tabs of the multiple layers of each electrode assembly are within the orthographic projection of the electrode bodies of the multiple electrode assemblies along the height direction.

6. The single cell according to claim 2, wherein When the number of the electrode assemblies is one, the dimension of the bent part of the tab located on the outermost layer along the thickness direction is smaller than the thickness of the electrode body, and is greater than or equal to 50% of the thickness of the electrode body; When the number of the electrode assemblies is multiple, the multiple electrode assemblies are stacked in sequence along the thickness direction, and the dimension of the bent part of the tab located on the outermost layer along the thickness direction is smaller than the total thickness of the electrode bodies of the multiple electrode assemblies, and is greater than or equal to 50% of the thickness of the electrode body of the electrode assembly where it is located.

7. The single cell according to claim 2, wherein In each electrode assembly, the number of layers of the electrode having the tab is greater than 50% of the total number of layers of all the electrodes.

8. The single cell according to claim 7, characterized in that, In each electrode assembly, the number of layers of the electrode having the tab is 60%-90% of the total number of layers of all the electrodes.

9. The single cell according to claim 1, wherein The area of the welding mark is greater than or equal to 80 mm 2 .

10. The single cell according to any one of claims 1-9, characterized in that, The welding groove is formed on the side of the pole column away from the electrode assembly along the height direction. The height of the pole column is greater than the depth of the welding groove, and the difference between the height of the pole column and the depth of the welding groove is greater than or equal to 0.7 mm.

11. The single battery according to any one of claims 1-9, characterized in that, The pole column includes a through portion and a connecting plate. The connecting plate is located on the side of the cover plate body facing the electrode assembly. The through portion includes a first end close to the electrode assembly and a second end away from the electrode assembly. The second end of the through portion penetrates through the cover plate body, and the first end of the through portion is connected to the connecting plate. The welding groove is formed on the through portion along the height direction, and the orthographic projection of the welding groove along the height direction is located within the outer edge of the connecting plate. The thickness of the connecting plate is 0.5 mm - 1 mm.

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