Secondary battery

Abstract

The utility model discloses a secondary battery, which comprises an electrode assembly, a first lead and a second lead, the top cover assembly comprises a top cover plate and a pole, the pole comprises a bottom plate arranged on the side, facing the electrode assembly, of the top cover plate, and the first tab is directly connected to the bottom plate. The technical scheme at least can improve the energy density of the battery and save the manufacturing cost.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, and more particularly to a secondary battery. Background Art

[0002] With the development of science and technology, secondary batteries have been widely used in portable electronic devices such as mobile phones, digital cameras, and laptop computers, and have broad application prospects in large and medium-sized electric devices such as electric vehicles, electric bicycles, and energy storage facilities, becoming an important technical means to solve problems such as energy crisis and environmental pollution.

[0003] With the development of secondary battery technology, higher energy density of battery cells is required. Summary of the Utility Model

[0004] In view of the problems in the related art, the present utility model provides a secondary battery, which can at least improve the energy density of the battery and save manufacturing costs.

[0005] The technical solution of the present utility model is realized as follows:

[0006] According to one aspect of the present utility model, there is provided a secondary battery, comprising: an electrode assembly having a first tab; a top cover assembly including a top cover plate and a terminal post, the terminal post including a bottom plate disposed on a side of the top cover plate facing the electrode assembly, wherein the first tab is directly connected to the bottom plate.

[0007] In some embodiments, the first tab further includes an upper metal portion, and the upper metal portion passes through an opening in the top cover plate from a side of the top cover plate facing away from the electrode assembly and is connected to the bottom plate.

[0008] In some embodiments, the first tab is directly connected to the bottom plate by ultrasonic welding.

[0009] In some embodiments, the first tab is directly connected to the bottom plate by torque welding.

[0010] In some embodiments, the first tab and the bottom plate are directly connected at a connection position, wherein the length direction of the connection position is parallel to the length direction of the top cover assembly.

[0011] In some embodiments, the material of the first tab is aluminum.

[0012] In some embodiments, the top cover assembly further includes an insulating and sealing assembly, and the insulating and sealing assembly passes through the opening and isolates the bottom plate and the upper metal portion from the top cover plate.

[0013] In some embodiments, the pole post is the first pole post, the top cover assembly further includes a second pole post, the electrode assembly further has a second tab, and the second tab and the first tab are located at the same end face of the electrode assembly. Wherein, the second pole post includes a bottom plate disposed on the side of the top cover plate facing the electrode assembly, and the second tab is directly connected to the bottom plate of the second pole post.

[0014] In some embodiments, the electrode assembly is the first electrode assembly, and the secondary battery further includes: a second electrode assembly having a first tab and a second tab; wherein, the first tab and the second tab of the second electrode assembly are directly connected to the bottom plate of the first pole post and the bottom plate of the second pole post, respectively.

[0015] In some embodiments, the secondary battery is a square shell battery.

[0016] In the embodiments of the present utility model, by directly connecting the tab to the bottom plate of the pole post, the use of the existing connecting piece is cancelled, so the weight of the battery can be reduced; and because the use of the connecting piece is cancelled, the height of the electrode assembly occupied by the thickness direction of the connecting piece can be released, and the space inside the shell can be utilized more maximally. The saved space inside the shell can be used to increase the size of the electrode assembly to improve the energy density; at the same time, because the connecting piece is cancelled, a process of welding the electrode assembly and the connecting piece can be saved, thus saving the manufacturing cost. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0018] Figure 1 is a top view schematic diagram of the top cover assembly and the electrode assembly in the secondary battery according to the embodiment of the present utility model.

[0019] Figure 2 is a cross-sectional schematic diagram of the pole post in the top cover assembly according to the embodiment of the present utility model.

[0020] Figure 3A is a schematic diagram of the shape of the welding head and welding seat of the ultrasonic welding machine that can be used to weld the tab according to the embodiment of the present utility model.

[0021] Figure 3B is a schematic diagram of the shape of the torque welding needle that can be used to weld the tab according to the embodiment of the present utility model. Detailed Embodiments

[0022] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model fall within the protection scope of the present utility model.

[0023] Currently, most secondary batteries (such as square aluminum shell batteries) use connecting pieces as the bridge and intermediary for connecting the electrode assembly (also known as the bare battery cell) to the top cover or the housing. It is necessary to connect the electrode assembly to the top cover or the housing through the connecting piece. However, the connecting piece itself has a certain thickness, so it will occupy the size of the electrode assembly inside the secondary battery, restricting the improvement of the battery energy density. The thickness of the connecting pieces widely used in the current market is usually 0.5 - 3 mm. If the thickness of the connecting piece is 1 mm and the height of the battery housing is 100 mm, the energy density will be reduced by 1%.

[0024] Embodiments of the present application provide a secondary battery. Refer to Figure 1 As shown, the secondary battery 100 may include a first electrode assembly 110. The first electrode assembly 110 may include a main body portion 111, a first tab 112, and a second tab 114. The main body portion 111 may be formed by stacking and winding a first electrode plate (such as a positive electrode plate), a second electrode plate (such as a negative electrode plate), and a separator located between the first electrode plate and the second electrode plate. The separator serves as an insulator between the first electrode plate and the second electrode plate. The first tab 112 and the second tab 114 may be formed by the uncoated active material foils (also known as current collectors) of the first electrode plate and the second electrode plate. In some embodiments, the first tab 112 and the second tab 114 each include multiple layers of foils.

[0025] In this embodiment, the secondary battery 100 is a square shell battery. The main body portion 111 is an overall flat rectangular structure. The main body portion 111 may have an axial direction D1, and the main body portion 111 may be formed by winding the first electrode plate, the second electrode plate, and the separator around the axial direction D1. The axial direction D1 of the main body portion 111 may be its height direction. The main body portion 111 has two opposite end faces along the axial direction D1. The second tab 114 and the first tab 112 are both located at the same end face of the first electrode assembly 110. The secondary battery 100 may further include a second electrode assembly 130. Similar to the first electrode assembly 110, the second electrode assembly 130 has a main body portion 131, a first tab 132, and a second tab 134 located at the same end face of the main body portion 131. In this embodiment, for example, the first tabs 112 and 132 of the first electrode assembly 110 and the second electrode assembly 130 are used as the positive electrode tabs, and the second tabs 114 and 134 of the first electrode assembly 110 and the second electrode assembly 130 are used as the negative electrode tabs for illustration.

[0026] In addition, the secondary battery 100 may further include a top cover assembly 150, and the top cover assembly 150 may include a top cover plate 151, a first pole column 152, and a second pole column 154. The first tab 112 and the second tab 114 of the first electrode assembly 110 are located at an end face of the first electrode assembly 110 adjacent to the top cover assembly 150. The first tab 132 and the second tab 134 of the second electrode assembly 130 are located at an end face of the second electrode assembly 130 adjacent to the top cover assembly 150. It should be understood that the first electrode assembly 110 and the second electrode assembly 130 may be accommodated in a housing (not shown), and the top cover assembly 150 can be used to seal an opening of the housing.

[0027] In some embodiments, at least one tab of at least one electrode assembly is connected to a corresponding pole column in the manner described in this application. In Figure 1 embodiments, the first tab 112 and the second tab 114 of the first electrode assembly 110, and the first tab 132 and the second tab 134 of the second electrode assembly 130 may all be connected to the corresponding first pole column 152 and second pole column 154 in the manner described in this application. The structures of the first pole column 152 and the second pole column 154 may be similar or the same. Hereinafter, the structure of the first pole column 152 and the connection between the first tab 112 of the first electrode assembly 110 and the first pole column 152 will be mainly used to illustrate the embodiments of this application.

[0028] Figure 2 is a cross-sectional schematic view of the first pole column 152 in the top cover assembly 150 according to an embodiment of this application. Figure 1 and Figure 2 The directions X, Y, and Z in are perpendicular to each other. Refer to Figure 2 As shown, the top cover assembly 150 may include a top cover plate 151 and a first pole column 152. The first pole column 152 may include a bottom plate 152A disposed on a side of the top cover plate 151 facing the first electrode assembly 110 (see Figure 1 ).

[0029] Combined with Figure 1 and Figure 2As shown, the first tab 112 of the first electrode assembly 110 can be directly connected to the bottom plate 152A of the first terminal 152. By directly connecting the first tab 112 to the bottom plate 152A of the first terminal 152, the use of the existing connecting piece is cancelled, so the battery weight can be reduced; and because the use of the connecting piece is cancelled, the height of the electrode assembly occupied by the thickness direction of the connecting piece can be released, making better use of the space inside the housing. The saved space inside the housing can be used to increase the size of the electrode assembly to improve the energy density; at the same time, because the connecting piece is cancelled, a process of welding the electrode assembly to the connecting piece can be saved, saving the manufacturing cost. The thickness of the connecting piece widely used in the current market is usually 0.5 - 3 mm. If the thickness of the connecting piece is 1 mm and the height of the electrode assembly is 100 mm, by cancelling the connecting piece, the energy density of the electrode assembly can be increased by 1%.

[0030] In some embodiments, the first tab 112 and the bottom plate 152A of the first terminal 152 are directly connected at the connection position 190. The bottom plate 152A of the first terminal 152 can overlap and be directly connected to the first tab 112 in the area of the connection position 190. The connection position 190 can have a rectangular top view shape. The length direction (Y direction) of the connection position 190 is parallel to the length direction of the top cover assembly 150.

[0031] Specifically, the first terminal 152 may further include an upper metal part 152B, and the upper metal part 152B is located on the side of the top cover plate 151 facing away from the first electrode assembly 110 (see Figure 1 ), passes through the opening 151v in the top cover plate 151 and is connected to the bottom plate 152A. In the vertical direction Z passing through the opening 151v, the projection of the bottom plate 152A can completely cover the opening 151v, that is to say, the size of the bottom plate 152A is larger than the size of the opening 151v.

[0032] The upper metal part 152B may include a first metal part 1521 and a second metal part 1522 connected between the first metal part 1521 and the bottom plate 152A. The size of the first metal part 1521 is also larger than the size of the opening 151v, and the size of the second metal part 1522 is smaller than the opening 151v, and the second metal part 1522 passes through the opening 151v, so that the upper metal part 152B can have a T-shaped cross-sectional structure. In some embodiments, the material of the bottom plate 152A of the first terminal 152 can be pure aluminum, pure copper, nickel-plated copper, alloy, etc. The thickness of the bottom plate 152A can be in the range of 0.5 mm - 3 mm. In some embodiments, the upper metal part 152B and the bottom plate 152A can be connected into a whole by riveting, stamping, machining, friction stir welding, etc., and pass through the opening 151v of the top cover plate 151 to achieve the effect of internal and external electrical connection.

[0033] In addition, the top cover assembly 150 may further include an insulating and sealing assembly 160. The insulating and sealing assembly 160 passes through the opening 151v and isolates the bottom plate 152A and the upper metal part 152B from the top cover plate 151. Specifically, the insulating and sealing assembly 160 may include an insulating component 162 and a sealing ring 164 on the insulating component 162. The insulating component 162 may be, for example, insulating plastic.

[0034] To achieve the direct connection between the first tab 112 and the bottom plate 152A, welding can be used. One prior art method is to use ultrasonic welding to weld the originally loose tab foils of the electrode assembly into a whole, and then use laser welding to weld the tab to the top cover or the housing. However, if the existing laser welding process is used to weld the tab to the top cover or the housing, since laser welding will cause the tab at the welding part to reach the melting point and melt, the foil will break due to the thermal expansion and contraction of the material when the tab undergoes the liquid-solid state change.

[0035] According to some embodiments of the present application, the first tab 112 can be directly connected to the bottom plate 152A by ultrasonic welding. In some embodiments, the power range of the ultrasonic welder used can be 3000W - 9000W. In some embodiments, the parameters of the ultrasonic welding used can be: energy 200 - 800J, amplitude 20% - 70%, air pressure 0.1 - 0.6MPa, welding time 0.2 - 0.7s. The shape of the welding head and welding seat 200 of the ultrasonic welder that can be used can be spherical (as shown in Figure 3A ). In some embodiments, the shape of the welding head and welding seat 200 of the ultrasonic welder can also be diamond-shaped (for example, as shown in Figure 3B , shown as a square in Figure 3B ). It should be understood that the above power range, parameters, and the shape of the welding head and welding seat of the ultrasonic welding are only exemplary.

[0036] According to some other embodiments of the present application, the first tab 112 can be directly connected to the bottom plate 152A by torque welding. In some embodiments, the power range of the torque welder used is 1200W - 9000W. In some embodiments, the parameters of the torque welding used are: energy 200 - 800J, torque 20% - 70%, air pressure 0.1 - 0.6MPa, welding time 0.2 - 0.7s. The shape of the torque welding needle 300 of the torque welder that can be used can be spherical (as shown in Figure 3A ). In some embodiments, the shape of the torque welding needle 300 can also be diamond-shaped (for example, as shown in Figure 3B , shown as a square in Figure 3B ). It should be understood that the above power range, parameters, and the shape of the welding head and welding seat of the torque welding are only exemplary.

[0037] Still in combination with Figure 1 andFigure 2 As shown, the first electrode assembly 110 and the bottom plate 152A of the first pole column 152 are welded together by ultrasonic welding or torque welding, which can avoid the process of laser welding, will not reach the melting point of the tab material, will not cause the tab to melt, and will not cause the tab to break due to the transformation between the liquid and solid states. Moreover, the connection strength of ultrasonic welding or torque welding can also be guaranteed to ensure a firm connection between the electrode assembly and the bottom plate 152A of the pole column.

[0038] In the embodiment where the first tab 112 is a positive tab, the material of the first tab 112 can be aluminum. In such an embodiment, the material of the second tab 114, which is a negative tab, can be copper. In some embodiments, the number of foil layers of the positive tab and the negative tab can be 20 - 100 layers respectively, where the thickness of the foil (aluminum foil) of a single-layer positive tab is 10 - 15 μm / layer, and the thickness of the foil (copper foil) of a single-layer negative tab is 4 - 8 μm / layer.

[0039] As described above, if the existing laser welding process is used to weld the tab to the top cover or the housing, the laser welding will cause the welded part to reach the melting point and form a molten pool, and the expansion coefficient of the aluminum used for the positive tab is relatively large. During the process of melting and solidifying of the molten pool, when the aluminum material undergoes liquid-solid state changes, the material expands and contracts thermally, and the volume change will cause the foil to break. By welding the first electrode assembly 110 and the bottom plate 152A of the first pole column 152 together by ultrasonic welding or torque welding, the melting point of the aluminum material will not be reached, the tab will not melt, and the tab will not break due to the transformation between the liquid and solid states.

[0040] In addition, since the top cover assembly 150 also requires the insulation and sealing assembly 160 to isolate the bottom plate 152A and the upper metal part 152B from the top cover plate 151, if the laser welding process is used for welding, due to the relatively large heat generated by laser welding, it will cause the insulation part 162 for insulation in the insulation and sealing assembly 160 and the sealing ring 164 inside the first pole column 152 to melt, which will affect the insulation and sealing effects. By using ultrasonic welding or torque welding to weld the first tab 112 and the bottom plate 152A of the first pole column 152 together, the temperature during the welding process is reduced, which can prevent the insulation part 162 and the sealing ring 164 from melting and prevent the insulation and sealing effects from deteriorating.

[0041] The above are only the preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A secondary battery, characterized in that, Comprising: An electrode assembly having a first tab; A top cover assembly including a top cover plate and a terminal post, the terminal post including a bottom plate disposed on a side of the top cover plate facing the electrode assembly, wherein the first tab is directly connected to the bottom plate.

2. The secondary battery according to claim 1, wherein The first tab further includes an upper metal portion, the upper metal portion passing from a side of the top cover plate facing away from the electrode assembly, through an opening in the top cover plate, and connecting to the bottom plate.

3. The secondary battery according to claim 1, wherein The first tab is directly connected to the bottom plate by ultrasonic welding.

4. The secondary battery according to claim 1, wherein The first tab is directly connected to the bottom plate by torque welding.

5. The secondary battery according to claim 1, wherein The first tab and the bottom plate are directly connected at a connection position, wherein a length direction of the connection position is parallel to a length direction of the top cover assembly.

6. The secondary battery according to claim 1, wherein The material of the first tab is aluminum.

7. The secondary battery according to claim 2, characterized in that, The top cover assembly further includes: An insulating and sealing assembly passing through the opening and isolating the bottom plate and the upper metal portion from the top cover plate.

8. The secondary battery according to claim 1, wherein The terminal post is a first terminal post, the top cover assembly further includes a second terminal post, the electrode assembly further has a second tab, and the second tab and the first tab are located at the same end face of the electrode assembly, wherein the second terminal post includes a bottom plate disposed on a side of the top cover plate facing the electrode assembly, and the second tab is directly connected to the bottom plate of the second terminal post.

9. The secondary battery according to claim 8, characterized in that, The electrode assembly is a first electrode assembly, and the secondary battery further includes: A second electrode assembly having a first tab and a second tab; wherein the first tab and the second tab of the second electrode assembly are respectively directly connected to the bottom plate of the first terminal post and the bottom plate of the second terminal post.

10. The secondary battery according to any one of claims 1-9, characterized in that, The secondary battery is a square shell battery.

Images