Secondary battery and battery pack

Abstract

The utility model relates to the technical field of secondary batteries, in particular to a secondary battery and a battery pack. The battery comprises a shell, a top cover, a battery cell and a connecting piece, the battery cell is contained in a containing cavity defined by the shell and the top cover, the connecting piece comprises a tab connecting part connected with a tab of the battery cell in a welded mode and a pole connecting part connected with a pole on the top cover in a welded mode, and the tab connecting part and the pole connecting part are connected through a transition part. And the distance F between the first surface, facing the battery cell, of the tab connecting part and the second surface, facing the battery cell, of the pole connecting part is greater than 0 and less than or equal to 0.5 mm after the tab connecting part is shifted. Therefore, the potential difference formed by the pole connecting part and the tab connecting part on one side facing the top cover is utilized to avoid the part, extending towards the battery cell, of the pole on the top cover, the bent tab height of the battery cell is fully utilized under the condition of ensuring normal assembly of the secondary battery, the space utilization rate in the secondary battery is improved, and the energy density of the secondary battery is improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a secondary battery and battery pack. Background Technology

[0002] In secondary batteries, connecting tabs are typically used to connect the battery cell's tabs to the terminals on the battery's top cover. These connecting tabs are flat and are usually stacked and welded together with the terminals and tabs along the height direction, occupying a significant amount of internal space within the battery cell. Looking at the secondary battery's height, the structural layers are, in order: top cover, lower plastic layer, lower terminal height, connecting tab thickness, and space for accommodating the bent tabs. The space for accommodating the bent tabs and the height of the terminals occupy a large proportion of the total space. However, due to the requirements for connection strength and welding quality reliability, the height of the terminals cannot be reduced accordingly. Therefore, it is necessary to develop an irregularly shaped connecting tab to improve the internal space utilization of the secondary battery by making reasonable use of the height space, thereby increasing the energy density of the secondary battery. Utility Model Content

[0003] The purpose of this invention is to provide a secondary battery and battery pack, so as to improve the utilization rate of the internal space of the secondary battery and increase the energy density of the secondary battery to a certain extent.

[0004] This utility model provides a secondary battery, including a casing, a top cover, a battery cell, and a connecting piece;

[0005] The battery cell is housed within a cavity formed by the housing and the top cover;

[0006] The connecting piece includes a connected tab connecting part and a pole connecting part;

[0007] The connecting piece is disposed between the battery cell and the top cover. The battery cell includes a tab. The tab connecting part is welded to the tab. The top cover is provided with a post. The post connecting part is welded to the post.

[0008] The electrode post connection is connected to the electrode tab connection through a transition portion, so that the electrode post connection is offset by a predetermined distance relative to the electrode tab connection towards the battery cell. The side surface of the electrode tab connection facing the battery cell is the first surface, and the side surface of the electrode post connection facing the battery cell is the second surface. The first surface and the second surface are spaced apart by a distance F along the thickness direction of the connecting piece, and the distance F satisfies: 0 < F ≤ 0.5 mm.

[0009] Furthermore, a predetermined distance G is spaced between the top cover and the pole connection portion, wherein G and F satisfy: 0.5mm≤GF<1.0mm.

[0010] Furthermore, G satisfies: 0.8mm≤G≤1.5mm.

[0011] Furthermore, the secondary battery includes a plurality of cells, and the tabs of the plurality of cells all include first tabs of the same polarity;

[0012] The tab connection portion is located on the same side of the width direction of the pole post connection portion, and the tab connection portion is provided with at least one welding area, and each welding area is provided with at least one first tab.

[0013] Furthermore, the secondary battery includes a plurality of cells, and the tabs of the plurality of cells all include first tabs of the same polarity;

[0014] The electrode connection portion is provided on both sides of the electrode post connection portion, and each electrode connection portion is provided with at least one welding area, and at least one first electrode tab can be stacked on each welding area.

[0015] Furthermore, the pole connection includes a body and a boss connected to the side of the body facing the pole. The pole has a first groove, and the boss is adapted to be inserted into the first groove. The outer wall of the boss is connected to the inner wall of the first groove.

[0016] Furthermore, the cross-sectional area of ​​the boss decreases from the end closest to the pole post connection to the end furthest from the pole post connection.

[0017] Furthermore, a second groove is formed on the side of the boss away from the pole post. The second groove penetrates the side of the boss away from the pole post and the body. Welding embossing is provided on the bottom wall of the second groove.

[0018] Furthermore, the welding embossing is a plurality of dot-shaped grooves arranged in an array; or, the welding embossing is a plurality of strip-shaped grooves arranged in a crisscross pattern; or, the welding embossing is a plurality of annular grooves arranged concentrically.

[0019] This utility model also provides a battery pack, including any of the rechargeable batteries described above.

[0020] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0021] The secondary battery provided by this utility model includes a casing, a top cover, a battery cell, and a connecting piece. The battery cell is housed within a cavity formed by the casing and the top cover. The top cover has terminals, and one end of the battery cell with a tab faces the top cover. The connecting piece is located between the battery cell and the top cover. The connecting piece includes a connected tab connection portion and a terminal connection portion. The connecting piece is welded to the tab of the battery cell via the tab connection portion and to the terminal on the top cover via the terminal connection portion, thereby achieving electrical connection between the tab and the terminal. The connecting piece also includes a transition portion. The terminal connection portion is connected to the tab connection portion via the transition portion. This utilizes the bending height space of the secondary battery's tabs to offset the terminal connection portion towards the battery cell by a predetermined distance relative to the tab connection portion. This utilizes the positional difference between the terminal connection portion and the tab connection portion on the side facing the top cover to avoid the portion of the terminal on the top cover extending towards the battery cell. Furthermore, it fully utilizes the bending height of the battery cell's tabs to effectively improve the internal space utilization of the secondary battery and increase its volumetric energy density.

[0022] Specifically, the surface of the tab connection facing the cell is the first surface, and the surface of the post connection facing the cell is the second surface. The first surface and the second surface are spaced apart by a distance F in the thickness direction of the connecting piece, and 0 < F ≤ 0.5 mm. This ensures the normal assembly of the secondary battery and makes reasonable use of the bending height of the cell tab to improve the volumetric energy density of the secondary battery.

[0023] This utility model also provides a battery pack including the aforementioned secondary battery, thus the battery pack also has the beneficial effects of a secondary battery. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 A schematic diagram of the structure of a connecting piece for a secondary battery provided in an embodiment of this utility model;

[0026] Figure 2 for Figure 1 The diagram shown is an assembly schematic of the connecting piece from a first-view perspective.

[0027] Figure 3 for Figure 1 The diagram shown is an assembly schematic of the connecting piece from a second-view perspective.

[0028] Figure 4A schematic diagram of another connecting piece for a secondary battery provided in an embodiment of this utility model;

[0029] Figure 5 for Figure 4 The diagram shows the assembly of the connecting piece from a first-person perspective.

[0030] Figure 6 This is another structural schematic diagram of the connecting piece for a secondary battery provided in an embodiment of the present utility model;

[0031] Figure 7 for Figure 6 The diagram shown is an assembly schematic of the connecting piece from a first-view perspective.

[0032] Figure 8 for Figure 6 The diagram shown is an assembly schematic of the connecting piece from a second-view perspective.

[0033] Figure 9 This is a schematic diagram of the structure of a secondary battery provided in an embodiment of the present invention.

[0034] Figure label:

[0035] 1-Connecting piece, 11-Electrode connecting part, 111-Welding area, 12-Electrode connecting part, 121-Body, 122-Boss, 123-Second groove, 124-Welding embossing, 13-Transition part;

[0036] 2-cell, 21-tab, 211-first tab;

[0037] 3-Top cover, 4-Pole post, 5-Lower plastic, 51-Main body, 6-Shell, 61-Receiving cavity. Detailed Implementation

[0038] The technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this utility model, but not all embodiments.

[0039] The components of the present invention embodiments described and shown in the accompanying drawings can typically be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0040] Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0041] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and 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, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0042] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" 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 mechanical connection or an electrical 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 utility model based on the specific circumstances.

[0043] The following reference Figures 1 to 9 This application describes a secondary battery and battery pack according to some embodiments.

[0044] This application provides a secondary battery, such as Figure 9 As shown, the secondary battery includes a casing 6, a top cover 3, a battery cell 2, and a connecting piece 1. The battery cell 2 is assembled by stacking a positive electrode, a separator, and a negative electrode in sequence through a stacking or winding process to form a positive electrode tab and a negative electrode tab. The battery cell 2 is housed in a cavity 61 formed by the casing 6 and the top cover 3. The top cover 3 is provided with a terminal post 4. One end of the battery cell 2 with a terminal tab 21 faces the top cover 3. The connecting piece 1 is provided between the battery cell 2 and the top cover 3, so that the terminal tab 21 and the terminal post 4 of the same polarity are electrically connected through the connecting piece 1; that is, the positive electrode tab of the battery cell 2 is electrically connected to the positive terminal post on the top cover 3 through a conductive connecting piece 1, and the negative electrode tab of the battery cell 2 is electrically connected to the negative terminal post on the top cover 3 through another conductive connecting piece 1.

[0045] like Figure 1 and Figure 2 As shown, the connecting piece 1 includes a connected tab connecting part 11 and a pole connecting part 12. When the tabs 21 and poles 4 of the same polarity are electrically connected, the connecting piece 1 is welded to the tabs 21 of the battery cell 2 through the tab connecting part 11, so that the connecting piece 1 is electrically connected to the tabs 21. At the same time, the connecting piece 1 is welded to the poles 4 on the top cover 3 through the pole connecting part 12, so that the connecting piece 1 is electrically connected to the poles 4. Thus, the connection between the tabs 21 and the poles 4 is achieved through the connecting piece 1.

[0046] Before being connected to the terminal post 4 using the connecting piece 1, the tab 21 of the battery cell 2 is bent, so that the tab 21 of the battery cell 2 occupies a certain folded tab height in the length direction of the battery cell 2. In this embodiment, the connecting piece 1 also includes a transition portion 13, and the terminal post connecting portion 12 is connected to the tab connecting portion 11 through the transition portion 13. By utilizing the folded tab height, the terminal post connecting portion 12 is offset by a predetermined distance relative to the tab connecting portion 11 towards the battery cell 2. This utilizes the positional difference formed between the terminal post connecting portion 12 and the tab connecting portion 11 on the side facing the top cover 3 to avoid the portion of the terminal post 4 on the top cover 3 that extends towards the battery cell 2. In this way, the folded tab height of the battery cell 2 can be fully utilized to reduce the distance between the battery cell 2 and the top cover 3, thereby effectively improving the space utilization rate inside the secondary battery and increasing the energy density of the secondary battery.

[0047] In this embodiment, the side surface of the tab connection portion 11 facing the cell 2 is the first surface, and the side surface of the pole connection portion 12 facing the cell 2 is the second surface. Both the first and second surfaces are planar structures. The first and second surfaces are spaced apart by a distance F in the thickness direction of the connecting piece 1, and 0 < F ≤ 0.5 mm. This ensures the normal assembly of the secondary battery and effectively utilizes the tab height of the cell 2 to improve the volumetric energy density of the secondary battery.

[0048] In this embodiment, the transition portion 13 is located between the tab connection portion 11 and the pole post connection portion 12. The transition portion 13 has an inclined structure, that is, the transition portion 13 is inclinedly connected to the tab connection portion 11, and the transition portion 13 is also inclinedly connected to the pole post connection portion 12.

[0049] In this embodiment, the F value is measured on the incoming material of the connecting piece 1. That is, when the connecting piece is not welded to the tab 21 and the pole post 4, the offset of the first surface of the tab connection 11 and the second surface of the pole post connection 12 in the thickness direction of the connecting piece 1 is measured to obtain the F value of the connecting piece.

[0050] In this embodiment, preferably, the side surface of the pole connection portion 12 facing the top cover 3 is spaced apart from the top cover 3 by a predetermined distance G, 0.8mm≤G≤1.5mm.

[0051] The electrode post 4 is inserted through the top cover 3, and the electrode post 4 and the top cover 3 are separated by the lower plastic 5 to achieve insulation; here, the lower plastic 5 includes a main body 51, which is laid on the side of the top cover 3 facing the cell 2, and the surface of the main body 51 facing the cell 2 is defined as the lower surface of the top cover 3.

[0052] After the battery cell 2 and the connecting piece 1 are assembled, the battery cell 2 needs to be installed into the housing 6, and then the top cover 3 is assembled onto the housing 6, and the pole post 4 on the top cover 3 is attached to and welded to the pole post connecting part 12 of the connecting piece 1; when the pole post connecting part 12 is attached to the pole post 4, the distance between the pole post connecting part 12 and the lower surface of the top cover is G.

[0053] G satisfies 0.8mm≤G≤1.5mm and G is greater than F, so that when the terminal connection 12 is in contact with the terminal 4, the tab connection 11 can form a gap of GF between it and the lower surface of the top cover 3. When the welding area of ​​the tab connection 11 and the tab 21 deforms, causing the welding area of ​​the tab connection 11 to protrude towards the top cover 3, the gap of GF can avoid the deformation of the tab connection 11, so that the deformed area of ​​the tab connection 11 will not interfere with the top cover 3, thereby not affecting the assembly of the top cover 3 and the shell 6, and not affecting the assembly of the terminal 4 and the terminal connection 12, so that the secondary battery can be assembled smoothly.

[0054] Here, the gap GF refers to the distance between the undeformed planar area of ​​the tab connection 11 and the lower surface of the top cover 3. The value of GF is the maximum allowable deformation of the welding area of ​​the tab connection 11. If the deformation of the tab connection 11 exceeds the value of GF, the deformed area of ​​the tab connection 11 will abut against the lower surface of the top cover 3 during assembly, preventing the top cover 3 from being properly assembled on the housing 6. This also prevents the pole post 4 from contacting the pole post connection 12 for subsequent welding assembly. More preferably, G and F satisfy: 0.5mm ≤ GF < 1.0mm.

[0055] In this embodiment, since the lower surface of the pole post 4 is in contact with the pole post connecting part 12, and the distance between the lower surface of the pole post 4 and the lower surface of the top cover 3 is also G, the value of G can be obtained by measuring the distance between the lower surface of the pole post 4 and the lower surface of the top cover 3 on the incoming material of the top cover 3, and then the value of GF can be calculated.

[0056] Next, using several example connectors shown in Table 1, we will illustrate the assembly compatibility of the connectors and their impact on the volumetric energy density of the secondary battery when different G and F values ​​are selected.

[0057] Table 1

[0058]

[0059]

[0060] In Example 1, the connecting piece has F=0, meaning it is a flat connecting piece as in the prior art, and the tab connecting part and the pole connecting part of the connecting piece are located in the same plane; in Examples 2 to 9, the connecting piece has F≠0, and the tab connecting part and the pole connecting part of the connecting piece are located in different planes.

[0061] The following will explain the impact of the connecting pieces on the assembly of the secondary battery in each example, and with Example 1 as a reference, explain the impact of using the connecting pieces in Examples 2 to 9 on the volumetric energy density of the battery. The volumetric energy density of the battery refers to the ratio of the battery's energy to its volume.

[0062] Example 1:

[0063] F=0, the connecting piece is a flat connecting piece as in the prior art, G=1mm, GF=1mm, and there is a 1mm gap between the top cover and the tab connection to absorb welding deformation of the tab connection, that is, the maximum allowable deformation of the tab connection is 1.0mm. Usually, the deformation generated when the tab connection is welded to the tab will not exceed 1.0mm, and under good welding process control, the welding deformation will not exceed 0.5mm; therefore, the connecting piece of the prior art in Example 1 can still meet the assembly requirements of the secondary battery even when the tab connection has a large amount of deformation, but it does not make reasonable use of the tab space of the cell, resulting in a lower volumetric energy density of the cell.

[0064] Example 2:

[0065] F = 0.5mm, G = 1mm, GF = 0.5mm. There is a 0.5mm gap between the top cover and the electrode tab connection to absorb welding deformation of the electrode tab connection. The connecting piece is suitable for cases with small welding deformation. The maximum allowable deformation of the electrode tab connection is 0.5mm.

[0066] Therefore, when the welding deformation at the tab connection does not exceed 0.5mm, the assembly of the top cover will not interfere with the connecting piece, and the secondary battery can be assembled smoothly. Furthermore, compared to Example 1, the total height of the secondary battery using the connecting piece of Example 2 is reduced by 0.5mm, resulting in an increase in the battery's volumetric energy density of 0.5mm / X. Here, X represents the total height of the secondary battery using Example 1.

[0067] Example 3:

[0068] F = 0.3mm, G = 1mm, GF = 0.7mm. The connecting piece is suitable for situations where the welding deformation is moderate. The maximum allowable deformation of the electrode lug connection is 0.7mm.

[0069] Therefore, when the welding deformation of the tab connection does not exceed 0.7mm, the assembly of the top cover will not interfere with the connecting piece, and the secondary battery can be assembled smoothly. Furthermore, compared with Example 1, the total height of the secondary battery using the connecting piece of Example 3 is reduced by 0.3mm, which increases the battery energy density by 0.3mm / X.

[0070] Example 4:

[0071] F = 0.1mm, G = 1mm, GF = 0.9mm. The connecting piece is suitable for situations with large welding deformation. The maximum allowable deformation of the electrode lug connection is 0.9mm.

[0072] Therefore, when the welding deformation of the tab connection does not exceed 0.9mm, the assembly of the top cover will not interfere with the connecting piece, and the secondary battery can be assembled smoothly. Furthermore, compared with Example 1, the total height of the secondary battery using the connecting piece of Example 4 is reduced by 0.1mm, which increases the battery energy density by 0.1mm / X.

[0073] Example 5:

[0074] F = 0.6mm, G = 0.8mm, GF = 0.2mm. Because the value of F is too large, the value of GF is too small. In the actual welding process, it is difficult to control the welding deformation of the electrode connection part to below 0.2mm. This causes the top cover to interfere with the electrode connection part during assembly, the top cover cannot be assembled properly, and the electrode post and the electrode post connection part cannot be attached, that is, the secondary battery cannot be assembled.

[0075] In cases where secondary batteries cannot be assembled, volumetric energy density will no longer be compared with Example 1.

[0076] Example 6:

[0077] With F = 0.3 mm, G = 1.5 mm, and GF = 1.2 mm, although the values ​​of these three values ​​make the value of GF large enough to meet the assembly requirements of the secondary battery when the connecting piece has a large amount of welding deformation, the value of G is large, which makes the total height of the secondary battery in Example 6 increase by 0.2 mm compared with Example 1, and the volumetric energy density of the battery decreases.

[0078] Example 7:

[0079] F = 0.5mm, G = 1.5mm, GF = 1.0mm. The values ​​of these three values ​​can meet the assembly requirements of the secondary battery when the connecting piece has a large amount of welding deformation. However, the value of G is too large, so the total height of the secondary battery in Example 7 remains unchanged compared to Example 1, and the volumetric energy density of the battery is not improved.

[0080] Example 8:

[0081] F = 0.1mm, G = 0.5mm, GF = 0.4mm. Due to the small value of GF, it is difficult to control the welding deformation of the electrode connection part to below 0.4mm during the actual welding process. This causes interference between the top cover and the electrode connection part during assembly, preventing the top cover from being assembled properly and the electrode post and electrode post connection part from touching, thus preventing the secondary battery from being assembled.

[0082] In cases where secondary batteries cannot be assembled, volumetric energy density will no longer be compared with Example 1.

[0083] Example 9:

[0084] With F = 0.5mm, G = 2.0mm, and GF = 1.5mm, although the value of GF can meet the assembly requirements of the secondary battery, the excessively large value of G causes the total height of the secondary battery in Example 9 to increase by 0.5mm compared to Example 1, resulting in a decrease in the volumetric energy density of the battery.

[0085] In one embodiment of this application, preferably, the secondary battery includes multiple battery cells 2, each battery cell 2 including a positive electrode tab and a negative electrode tab, and the positive electrode tabs of the multiple battery cells are electrically connected to the positive terminal on the top cover 3 through a connecting piece 1, and the negative electrode tabs of the multiple battery cells are connected to the negative terminal on the top cover 3 through another connecting piece 1. For ease of description, the first electrode tab 211 is used to refer to the electrode tabs of the same polarity among the multiple battery cells 2, that is, when the connecting piece 1 is used to connect the positive electrode tabs and the positive terminal of the multiple battery cells 2, the first electrode tab 211 refers to the positive electrode tab, and when the connecting piece 1 is used to connect the negative electrode tabs and the negative terminal of the multiple battery cells 2, the first electrode tab 211 refers to the negative electrode tab.

[0086] Regarding one form of the connecting piece 1, the tab connecting portion 11 is located on the same side in the width direction of the pole connecting portion 12, that is, the pole connecting portion 12 has a tab connecting portion 11 on only one side. The tab connecting portion 11 has at least one welding area 111, and at least one first tab 211 can be stacked and welded together at each welding area 111.

[0087] For example, such as Figure 3 As shown, a welding area 111 is provided on the electrode connection part 11, and the first electrodes 211 of multiple battery cells are stacked on the first welding area 111 and welded to each other.

[0088] For example, the electrode connecting part 11 is provided with multiple (two or more) welding areas 111 at intervals. When the number of welding areas 111 is the same as the number of first electrodes 211, the multiple first electrodes 211 are stacked one-to-one at the multiple welding areas 111 and welded together; for example, in Figure 4 and 5In this design, there are two welding areas 111 and two first tabs 211. The two first tabs 211 are stacked one-to-one on the two welding areas 111 and welded together. When the number of welding areas 111 is less than the number of first tabs 211, some of the first tabs 211 can be stacked on the same welding area 111 according to the actual situation.

[0089] Regarding another form of connecting piece 1, such as Figures 6 to 8 As shown, the pole post connecting part 12 is provided with pole tab connecting parts 11 on both opposite sides. Each pole tab connecting part 11 is provided with at least one welding area 111. At least one first pole tab 211 can be stacked and welded together at each welding area 111.

[0090] For example, such as Figure 8 As shown, each of the two electrode connection portions 11 has a welding area 111. The battery cell 2 includes two first electrodes 211, which are stacked one-to-one on the two welding areas 111 and welded together.

[0091] Of course, as the number of first tabs 211 increases, multiple welding areas 111 can be provided on the tab connection part 11 on any side, or multiple first tabs 211 can be stacked at any welding area 111.

[0092] In one embodiment of this application, preferably, as Figure 1 and Figure 2 As shown, the pole connector 12 includes a body 121 and a boss 122. The boss 122 is connected to the side of the body 121 facing the pole 4. The pole 4 has a first groove. When assembling the pole connector 12 and the pole 4, the boss 122 is fitted into the first groove so that the outer wall of the boss 122 is attached to and welded to the inner wall of the first groove, thereby realizing the assembly and positioning of the pole connector 12 and the pole 4 and making them electrically connected.

[0093] In this embodiment, preferably, the boss 122 has a cross-section perpendicular to its own axis, and the area of ​​the cross-section of the boss 122 decreases from one end near the pole post connection 12 to the other end, so as to facilitate the insertion of the boss 122 into the first groove and realize the positioning and assembly of the two. At the same time, it can also increase the contact area between the outer wall of the boss 122 and the inner wall of the first groove to a certain extent, and improve the stability of the electrical connection between the pole post connection 12 and the pole post 4.

[0094] In this embodiment, preferably, a second groove 123 is formed on the side of the boss 122 away from the pole post 4, and the second groove 123 penetrates the side of the boss 122 away from the pole post 4 and the body 121; as Figure 4As shown, the inner wall of the second groove 123 is provided with welding embossing 124 to avoid high reflection when laser welding the pole connection 12 and the pole 4.

[0095] Preferably, the welding embossing 124 is a plurality of dot-shaped grooves arranged in an array; or, the welding embossing 124 is a plurality of strip-shaped grooves arranged in a crisscross pattern; or, the welding embossing 124 is a plurality of annular grooves arranged concentrically.

[0096] This application also provides a battery pack including the secondary battery of any of the above embodiments.

[0097] In this embodiment, the battery pack includes a secondary battery, and therefore the battery pack has all the beneficial effects of a secondary battery, which will not be described in detail here.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A secondary battery, characterized in that, It includes a housing (6), a top cover (3), a battery cell (2), and a connecting piece (1); The battery cell (2) is housed within a cavity (61) formed by the housing (6) and the top cover (3); The connecting piece (1) includes a connected tab connecting part (11) and a pole connecting part (12); The connecting piece (1) is disposed between the battery cell (2) and the top cover (3). The battery cell (2) includes a tab (21). The tab connecting part (11) is welded to the tab (21). The top cover (3) is provided with a pole post (4). The pole post connecting part (12) is welded to the pole post (4). The pole post connection (12) is connected to the tab connection (11) through the transition part (13), so that the pole post connection (12) is offset by a predetermined distance relative to the tab connection (11) towards the battery cell (2). The side surface of the tab connection (11) facing the battery cell (2) is the first surface, and the side surface of the pole post connection (12) facing the battery cell (2) is the second surface. The first surface and the second surface are spaced apart by a distance F along the thickness direction of the connecting piece (1), and the distance F satisfies: 0 < F ≤ 0.5 mm.

2. The secondary battery according to claim 1, characterized in that, The top cover (3) and the pole connection part (12) are spaced by a predetermined distance G, wherein G and F satisfy: 0.5mm≤GF<1.0mm.

3. The secondary battery according to claim 2, characterized in that, The value of G satisfies: 0.8mm≤G≤1.5mm.

4. The secondary battery according to claim 1, characterized in that, The secondary battery includes a plurality of cells (2), and the tabs (21) of the plurality of cells (2) all include a first tab (211) with the same polarity; The tab connection portion (11) is located on the same side of the width direction of the pole connection portion (12). The tab connection portion (11) is provided with at least one welding area (111), and each welding area (111) is provided with at least one first tab (211).

5. The secondary battery according to claim 1, characterized in that, The secondary battery includes a plurality of cells (2), and the tabs (21) of the plurality of cells (2) all include a first tab (211) with the same polarity; The pole post connecting part (12) is provided with pole tab connecting parts (11) on both sides. Each pole tab connecting part (11) is provided with at least one welding area (111). At least one first pole tab (211) can be stacked on each welding area (111).

6. The secondary battery according to claim 1, characterized in that, The pole post connection part (12) includes a body (121) and a boss (122) connected to the side of the body (121) facing the pole post (4). The pole post (4) has a first groove, and the boss (122) is adapted to be inserted into the first groove. The outer wall of the boss (122) is connected to the inner wall of the first groove.

7. The secondary battery according to claim 6, characterized in that, The cross-sectional area of ​​the boss (122) decreases from the end closest to the pole post connector (12) to the end furthest from the pole post connector (12).

8. The secondary battery according to claim 6, characterized in that, The boss (122) forms a second groove (123) on the side away from the pole post (4). The second groove (123) penetrates the side of the boss (122) away from the pole post (4) and the body (121). The bottom wall of the second groove (123) is provided with welding embossing (124).

9. The secondary battery according to claim 8, characterized in that, The welding embossing (124) is a plurality of dot-shaped grooves arranged in an array; or, the welding embossing (124) is a plurality of strip-shaped grooves arranged in a crisscross pattern; or, the welding embossing (124) is a plurality of annular grooves arranged concentrically.

10. A battery pack, characterized in that, The secondary battery includes any one of claims 1 to 9.

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