Battery cell and battery pack

Abstract

The utility model relates to the technical field of batteries, and discloses a battery cell and a battery pack. Wherein the battery cell comprises a shell, two ends of the shell are provided with an opening and a cover plate for sealing the opening, and the cover plate is provided with a pole mounting hole; each pole comprises a main body part and an annular part located on one side of the main body part, axial through holes are formed in the main body parts and the annular parts, and the annular parts are arranged in the pole mounting holes in a penetrating mode; the pole group is arranged in the shell, and tabs are arranged at two ends of the pole group; the pair of connecting sheets are arranged in the shell and are respectively arranged at the two ends of the pole group, positioning columns matched with the axial through holes are formed on the connecting sheets, and the connecting sheets and the pole columns are fixedly connected by inserting the positioning columns into the axial through holes; and the pole columns are connected with the corresponding tabs through the connecting sheets. And the positioning columns matched with the axial through holes are arranged on the connecting sheets, so that the assembling efficiency between the pole columns and the connecting sheets can be improved, the contact area between the connecting sheets and the pole columns can be increased, and the overcurrent capability of the battery cell is improved.

Description

Technical Field

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

[0002] The connecting piece in the battery cell is a metal piece used to connect the pole column of the battery cell and the pole ear of the pole group. It ensures the smooth flow of current between the pole column and the pole ear, and realizes the storage and release of electric energy of the battery cell. However, currently, directly connecting the connecting piece to the pole column makes it difficult to install the two accurately in a short time, and it is bound to extend the assembly time of the battery cell and reduce the production efficiency of the battery cell during the process of adjusting their positioning. Summary of the Utility Model

[0003] In view of this, the utility model provides a battery cell and a battery pack to solve the problems in the related art that it is difficult to accurately position the connecting piece and the pole column, and the long assembly time affects the production efficiency of the battery cell.

[0004] In a first aspect, the utility model provides a battery cell, including:

[0005] A housing with openings at both ends and a cover plate for sealing the openings, and the cover plate is provided with pole column mounting holes;

[0006] A pair of pole columns, each including a main body portion and an annular portion located on one side of the main body portion. An axial through hole is provided in the main body portion and the annular portion, and the annular portion passes through the pole column mounting hole;

[0007] A pole group arranged in the housing and having pole ears at both ends;

[0008] A pair of connecting pieces arranged in the housing and respectively arranged at both ends of the pole group. The connecting piece is formed with a positioning column adapted to the axial through hole, and the connecting piece and the pole column are fixedly connected by inserting the positioning column into the axial through hole; the pole column is connected to the corresponding pole ear through the connecting piece.

[0009] Beneficial effects: By providing an opening on the housing that communicates with its cavity, the present utility model facilitates the operator to assemble structures such as the electrode group into the housing, improving the convenience of assembly. Further, using a cover plate to seal the opening ensures the sealing of the battery cell, reducing the possibility of external moisture, dust and other impurities entering the interior of the battery cell, ensuring the cleanliness and stability of the internal environment of the battery cell, and thus being beneficial to extending the service life of the battery cell. Secondly, axial through holes are formed in the main body portion and the annular portion, which can ensure the smooth flow of current between the pole column and the connecting piece while reducing the self-weight of the pole column, making the battery cell meet the requirements of lightweight. In addition, positioning posts are provided on the connecting piece to cooperate with the axial through holes, which can not only enable the operator to accurately position the pole column and the connecting piece in a short time, improving the assembly efficiency, but also increase the contact area between the connecting piece and the pole column, improving the overcurrent capacity of the battery cell.

[0010] In an alternative embodiment, the annular portion extends axially along the main body portion, and the diameter of the annular portion is smaller than the diameter of the main body portion.

[0011] Beneficial effects: In the present utility model, the annular portion extends axially along the main body portion. On the one hand, it can reduce the complexity of the production process of the pole column and improve the production efficiency; on the other hand, it can also reduce the assembly difficulty between the pole column and the cover plate and improve the assembly efficiency. Secondly, making the diameter of the annular portion smaller than the diameter of the main body portion allows the annular portion to play a role in positioning and guiding during the assembly process, shortening the time consumed for the pole column to be installed and positioned in the pole column mounting hole. In addition, compared with the case where the diameter of the annular portion is adapted to the diameter of the main body portion, the diameter of the annular portion being smaller than the diameter of the main body portion reduces the amount of pole column material used and optimizes the self-weight of the pole column.

[0012] In an alternative embodiment, an annular flange is provided on the circumferential side of the annular portion near one end of the connecting piece, and the annular flange is connected to the upper surface of the connecting piece.

[0013] Beneficial effects: In the present utility model, the main body portion and the annular flange at both ends of the annular portion can form a limiting structure for the pole column through cooperation with the cover plate, preventing the pole column from deviating from the preset position during the assembly or use of the battery cell, and improving the use stability and safety of the battery cell. Secondly, by providing an annular flange at one end of the annular portion close to the connecting piece, the contact area between the pole column and the connecting piece can be increased. In this way, not only can the connection stability between the two be improved, but also the overcurrent capacity of the battery cell can be improved.

[0014] In an alternative embodiment, it further includes a sealing ring, a plastic ring and a plastic plate. The sealing ring is sleeved outside the annular portion and abuts against the wall of the pole post mounting hole. The plastic ring is sleeved outside the main body portion and its lower surface fits against the upper surface of the cover plate. The plastic plate is sleeved outside the annular portion and is located between the cover plate and the annular flange.

[0015] Advantages: By providing the sealing ring, the plastic ring and the plastic plate, the present utility model can seal the gap between the pole post and the pole post mounting hole to prevent the electrolyte inside the battery cell from leaking out through the above-mentioned gap. Secondly, since the material of the cover plate is usually a metal conductive material, the use of the plastic ring can keep the cover plate and the pole post in an insulated and isolated state at all times. Similarly, by using the plastic plate, the cover plate and the connecting piece can be kept in an insulated and isolated state at all times, thus ensuring the safety of use of the battery cell. In addition, since part of the structures of the plastic ring and the plastic plate and the sealing ring are located between the main body portion and the annular flange, the sealing ring, the plastic ring and the plastic plate can be firmly fixed on the cover plate through the limiting cooperation of the main body portion and the annular flange.

[0016] In an alternative embodiment, a welding through-hole is provided on one of the cover plates, and a liquid injection hole and an explosion-proof valve are provided on the other cover plate.

[0017] Advantages: By providing the liquid injection hole and the explosion-proof valve on the cover plate, on the one hand, the self-structure of the cover plate can be made more compact and the structural layout on the cover plate can be optimized; on the other hand, it is convenient to add electrolyte into the battery cell, and at the same time, the pressure inside the battery cell can be prevented from being too high, improving the safety of use of the battery cell. In addition, by providing the welding through-hole on the cover plate, the present utility model can leave an operation space for the operator to quickly connect the pole ear and the connecting piece, improving the convenience of operation.

[0018] In an alternative embodiment, the pole ear is arranged offset from the corresponding pole post. One of the pole ears includes a body connected to the electrode group and a bent portion bent from the end of the body toward one side. The bent portion is arranged corresponding to the welding through-hole. One of the connecting pieces is fixed in the space defined by the body and the bent portion and fits against the lower surface of the bent portion.

[0019] Beneficial effect: The pole and the pole ear of the utility model are staggered, which utilizes the space in other directions inside the shell. Compared with the existing connection piece and the pole ear are arranged along the axial direction of the pole, the connection piece and the pole ear in the shell height direction (the axial direction of the pole) in the connected state The space inside the shell is reduced, and the utilization rate of the internal space of the shell is improved, thereby allowing the battery cell to store more energy in the same volume. Furthermore, the pole ear is connected to the connection piece through the bending portion, which can reduce the difficulty of connecting the pole ear and the connection piece, and can also reduce the occupation of the internal space of the shell by the two in the connected state.

[0020] In an optional implementation, the pole lugs and the corresponding poles are staggered along the length direction of the shell.

[0021] Beneficial effect: The utility model allows the pole and the pole ear to be staggered along the length direction of the shell, and can utilize the space in the length direction of the shell to arrange the connecting piece on the pole group along the length direction of the shell. In this way, compared with the existing connection piece and the pole ear are arranged along the axial direction of the pole, the longitudinal distance between the pole ear and the pole will become relatively small, thereby reducing the occupation of the internal space of the shell.

[0022] In an optional embodiment, the connecting piece includes a pole connecting portion connected to the pole and a pole lug connecting portion connected to the pole lug, and the positioning column is located on the pole connecting portion.

[0023] Beneficial effect: Since the pole lug and pole post in the utility model are staggered, the connecting piece is divided into a pole post connecting part and a pole lug connecting part, so that the connecting piece can be adapted to the position of the pole lug and the pole post, so that the pole lug and the pole post can be connected, realizing smooth flow of current between the pole lug and the pole post.

[0024] In an optional embodiment, a gap is left between the tab connection portion and the inner wall of the shell extending along the length direction thereof, and the bending portion is arranged on the upper surface of the tab connection portion through the body, through the gap and the welding through hole.

[0025] Beneficial effect: Since the lower surface of the bent portion needs to fit with the upper surface of the tab connection portion, if the bent portion is to come to the upper surface of the tab connection portion, it is usually necessary to set a passage opening suitable for the body to pass through on the tab connection portion. However, this will make the structure of the tab connection portion relatively complicated and increase the initial production cost. Therefore, in order to solve the above problem, the utility model allows the body to pass through the gap between the tab connection portion and the inner wall extending along the length direction of the shell and the welding through hole on the cover plate, which can simplify the structure of the connecting piece without making complex adjustments to the structure of the connecting piece.

[0026] In a second aspect, the utility model further provides a battery pack, comprising:

[0027] Multiple such battery cells.

[0028] Beneficial effects: Since the connecting piece and the pole column in the above-mentioned battery cell are fixedly connected together through the positioning column and the axial through hole, after the above-mentioned battery cell is adopted in the battery pack of the present invention, the assembly time of the battery pack itself can be shortened, and the production efficiency of the battery pack itself can be improved. In addition, the battery pack of the present invention has all the advantages of the above-mentioned battery cell, which will not be elaborated here. Description of the Drawings

[0029] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 Partial structural schematic diagram of a battery cell according to an embodiment of the present invention;

[0031] Figure 2 Partial structural schematic diagram of another battery cell according to an embodiment of the present invention;

[0032] Figure 3 Connection schematic diagram of a pole column and a connecting piece according to an embodiment of the present invention;

[0033] Figure 4 Partial structural schematic diagram of a connecting piece according to an embodiment of the present invention;

[0034] Figure 5 Cross-sectional schematic diagram of a cover plate according to an embodiment of the present invention;

[0035] Figure 6 Bottom view schematic diagram of a cover plate according to an embodiment of the present invention;

[0036] Figure 7 Structural schematic diagram of another cover plate according to an embodiment of the present invention;

[0037] Figure 8 For Figure 7 Cross-sectional schematic diagram of the shown cover plate;

[0038] Figure 9 For Figure 7 Bottom view schematic diagram of the shown cover plate.

[0039] Explanation of the reference numerals in the drawings:

[0040] 1. Housing; 101. Cover plate; 1011. Welding through-hole; 1012. Liquid injection hole; 1013. Explosion-proof valve; 1014. Sealing plate; 2. Terminal; 201. Main body part; 202. Annular part; 203. Annular flange; 3. Tab; 4. Connecting piece; 401. Positioning post; 402. Terminal connecting part; 403. Tab connecting part; 5. Sealing ring; 6. Plastic ring; 7. Plastic plate. Detailed implementation mode

[0041] To make the objectives, technical solutions and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Apparently, the described embodiments are some but not all of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0042] Aiming at the problems in the related art that it is difficult to accurately position the connecting piece and the terminal, and the assembly time is long, which affects the production efficiency of the battery cell, the present utility model provides a battery cell and a battery pack.

[0043] The following combines Figures 1 to 9 , to describe the embodiments of the present utility model.

[0044] According to the embodiments of the present utility model, on the one hand, as Figures 1 to 4 and Figure 9 shown, a battery cell is provided, including: a housing 1, a pair of terminals 2, a cell assembly and a pair of connecting pieces 4.

[0045] Specifically, both ends of the housing 1 are provided with openings and a cover plate 101 for sealing the openings. The cover plate 101 is provided with terminal mounting holes; a pair of terminals 2 each include a main body part 201 and an annular part 202 located on one side of the main body part 201. An axial through-hole is provided in the main body part 201 and the annular part 202, and the annular part 202 is inserted through the terminal mounting hole; the cell assembly is arranged in the housing 1 and tabs 3 are provided at both ends; a pair of connecting pieces 4 are arranged in the housing 1 and are respectively arranged at both ends of the cell assembly. The connecting piece 4 is formed with a positioning post 401 adapted to the axial through-hole, and the connecting piece 4 and the terminal 2 are fixedly connected by inserting the positioning post 401 into the axial through-hole; the terminal 2 is connected to the corresponding tab 3 through the connecting piece 4.

[0046] In this embodiment, an opening communicating with the cavity is provided on the housing 1, which facilitates the operator to assemble relevant structures such as the electrode group into the housing 1 and improves the assembly convenience. Further, the cover plate 101 is used to seal the opening, ensuring the sealing of the battery cell, reducing the possibility of external moisture, dust and other impurities entering the interior of the battery cell, ensuring the cleanliness and stability of the internal environment of the battery cell, and thus being beneficial to extending the service life of the battery cell. Secondly, axial through holes are formed in the main body portion 201 and the annular portion 202, which can ensure the smooth flow of current between the pole column 2 and the connecting piece 4 while reducing the self-weight of the pole column 2, making the battery cell meet the requirements of lightweight. In addition, positioning posts 401 matching with the axial through holes are provided on the connecting piece 4, which can not only enable the operator to accurately position the pole column 2 and the connecting piece 4 in a short time, improving the assembly efficiency, but also increase the contact area between the connecting piece 4 and the pole column 2, improving the over-current capacity of the battery cell.

[0047] According to an embodiment of the present invention, as Figure 3 shown, the annular portion 202 extends along the axial direction of the main body portion 201, and the diameter of the annular portion 202 is smaller than that of the main body portion 201. In this embodiment, the annular portion 202 extends along the axial direction of the main body portion 201. On the one hand, it can reduce the complexity of the production process of the pole column 2 and improve the production efficiency; on the other hand, it can also reduce the assembly difficulty between the pole column 2 and the cover plate 101 and improve the assembly efficiency. Secondly, making the diameter of the annular portion 202 smaller than that of the main body portion 201 can enable the annular portion 202 to play a role of positioning and guiding during the assembly process, shortening the time consumed for the pole column 2 to be installed and positioned in the pole column mounting hole. In addition, compared with the case where the diameter of the annular portion 202 is adapted to that of the main body portion 201, the diameter of the annular portion 202 being smaller than that of the main body portion 201 reduces the material usage of the pole column 2 and optimizes the self-weight of the pole column 2.

[0048] According to an embodiment of the present invention, as Figure 3 shown, an annular flange 203 is provided on the circumferential side of the annular portion 202 near one end of the connecting piece 4, and the annular flange 203 is connected to the upper surface of the connecting piece 4. In this embodiment, the main body portion 201 and the annular flange 203 at both ends of the annular portion 202 can form a limiting structure of the pole column 2 through cooperation with the cover plate 101, avoiding the pole column 2 from deviating from the preset position during the assembly or use of the battery cell, and improving the use stability and safety of the battery cell. Secondly, by providing the annular flange 203 at one end of the annular portion 202 near the connecting piece 4, the contact area between the pole column 2 and the connecting piece 4 can be increased. In this way, not only the connection stability between the two can be improved, but also the over-current capacity of the battery cell can be improved.

[0049] It should be noted that the upper surface of the connecting piece 4 in this embodiment refers to the side of the connecting piece 4 away from the electrode group.

[0050] According to an embodiment of the present utility model, as Figure 3 shown, it further includes a sealing ring 5, a plastic ring 6 and a plastic plate 7. The sealing ring 5 is sleeved outside the annular portion 202 and abuts against the wall of the pole post mounting hole. The plastic ring 6 is sleeved outside the main body portion 201 and its lower surface is attached to the upper surface of the cover plate 101. The plastic plate 7 is sleeved outside the annular portion 202 and is located between the cover plate 101 and the annular flange 203. In this embodiment, by providing the sealing ring 5, the plastic ring 6 and the plastic plate 7, the gap between the pole post 2 and the pole post mounting hole can be sealed to prevent the electrolyte inside the battery cell from overflowing from the above-mentioned gap. Secondly, since the material of the cover plate 101 is usually a metal conductive material, the use of the plastic ring 6 can keep the cover plate 101 and the pole post 2 in an insulated and isolated state all the time. Similarly, by using the plastic plate 7, the cover plate 101 and the connecting piece 4 can be kept in an insulated and isolated state all the time, thus ensuring the use safety of the battery cell. In addition, since part of the structures of the plastic ring 6 and the plastic plate 7 and the sealing ring 5 are located between the main body portion 201 and the annular flange 203, the sealing ring 5, the plastic ring 6 and the plastic plate 7 can be firmly fixed on the cover plate 101 through the limiting cooperation of the main body portion 201 and the annular flange 203.

[0051] It should be noted that the upper surface of the cover plate 101 in this embodiment refers to the side of the cover plate 101 away from the electrode group.

[0052] According to an embodiment of the present utility model, as Figure 2 、 Figure 7 and Figure 8 shown, a welding through hole 1011 is provided on one of the cover plates 101, and a liquid injection hole 1012 and an explosion-proof valve 1013 are provided on the other cover plate 101. In this embodiment, by arranging the liquid injection hole 1012 and the explosion-proof valve 1013 on the cover plate 101, on the one hand, the self-structure of the cover plate 101 can be made more compact, and the structural layout on the cover plate 101 can be optimized; on the other hand, it is convenient to add electrolyte into the battery cell, and at the same time, the pressure inside the battery cell can be prevented from being too high, improving the use safety of the battery cell. In addition, in this embodiment, by providing the welding through hole 1011 on the cover plate 101, an operation space for quickly connecting the pole ear 3 and the connecting piece 4 can be left for the operator, improving the operation convenience.

[0053] In order to ensure the sealing performance of the housing 1, in a specific embodiment, as Figure 5 shown, a sealing plate 1014 is provided on the cover plate 101. The sealing plate 1014 is welded to the welding through hole 1011 to seal the welding through hole 1011.

[0054] According to an embodiment of the present utility model, as Figure 1As shown, the tab 3 and the corresponding terminal post 2 are arranged in a dislocation manner. One of the tabs 3 includes a body connected to the electrode group and a bent portion bent from the end of the body toward one side. The bent portion is arranged corresponding to the welding through hole 1011. One of the connecting pieces 4 is fixed in the space defined by the body and the bent portion and is attached to the lower surface of the bent portion. In this embodiment, the terminal post 2 and the tab 3 are arranged in a dislocation manner, making use of the space in other directions inside the housing 1. Compared with the existing connecting piece 4 and tab 3 both arranged along the axial direction of the terminal post 2, the internal space of the housing 1 occupied by the connecting piece 4 and the tab 3 in the height direction (axial direction of the terminal post) of the housing 1 in the connected state is reduced, improving the utilization rate of the internal space of the housing 1. Furthermore, the tab 3 is connected to the connecting piece 4 through the bent portion, which can reduce the operation difficulty of connecting the tab 3 and the connecting piece 4 and also reduce the occupation of the internal space of the housing 1 when they are in the connected state.

[0055] It should be noted that the above-mentioned height direction of the housing 1 is consistent with Figure 1 and Figure 2 the direction shown in. In addition, the lower surface of the bent portion refers to the side of the bent portion facing the upper surface of the connecting piece 4.

[0056] According to an embodiment of the present invention, as Figure 1 shown, the tab 3 and the corresponding terminal post 2 are arranged in a dislocation manner along the length direction of the housing 1. In this embodiment, the terminal post 2 and the tab 3 are arranged in a dislocation manner along the length direction of the housing 1, which can make use of the space in the length direction inside the housing 1 and arrange the connecting piece 4 on the electrode group along the length direction of the housing 1. In this way, compared with the existing connecting piece 4 and tab 3 both arranged along the axial direction of the terminal post 2, the longitudinal distance between the tab 3 and the terminal post 2 will become relatively small, thus reducing the occupation of the internal space of the housing 1.

[0057] It should be noted that the above-mentioned length direction of the housing 1 is consistent with Figure 1 and Figure 2 the direction shown in.

[0058] According to an embodiment of the present invention, as Figure 4 and Figure 6 shown, the connecting piece 4 includes a terminal post connecting portion 402 connected to the terminal post 2 and a tab connecting portion 403 connected to the tab 3. The positioning post 401 is located on the terminal post connecting portion 402. Since the tab 3 and the terminal post 2 in this embodiment are arranged in a dislocation manner, the connecting piece 4 is divided into the terminal post connecting portion 402 and the tab connecting portion 403, which can adapt the position of the connecting piece 4 to the tab 3 and the terminal post 2, so as to connect the tab 3 and the terminal post 2 and realize the smooth flow of current between the tab 3 and the terminal post 2.

[0059] According to an embodiment of the present invention, as Figure 6As shown, there is a gap between the tab connection part 403 and the inner wall of the housing 1 extending along its length direction. The bent part is arranged on the upper surface of the tab connection part 403 by passing the body through the gap and the welding through-hole 1011. Since the lower surface of the bent part needs to fit with the upper surface of the tab connection part 403, usually a channel opening suitable for the body to pass through needs to be provided on the tab connection part 403 if we want the bent part to reach the upper surface of the tab connection part 403. However, this will make the self-structure of the tab connection part 403 relatively complex and increase the upfront manufacturing cost. Therefore, to solve the above problems, in this embodiment, the body passes through the gap between the tab connection part 403 and the inner wall of the housing 1 extending along the length direction and the welding through-hole 1011 on the cover plate 101, so that no complex adjustment needs to be made to the structure of the connection piece 4, simplifying the self-structure of the connection piece 4.

[0060] According to an embodiment of the present invention, on the other hand, a battery pack is also provided, including: a plurality of the above-mentioned battery cells. Since the connection piece 4 and the pole column 2 in the above-mentioned battery cells are fixedly connected together by the positioning column 401 and the axial through-hole, after adopting the above-mentioned battery cells, the battery pack of this embodiment can shorten its own assembly time and improve its production efficiency. In addition, the battery pack of the present invention has all the advantages of the above-mentioned battery cells and will not be elaborated here.

[0061] It should be noted that the battery cells in this embodiment include but are not limited to lithium-ion battery cells. A plurality of battery cells can be grouped and electrically connected through a bus bar to form a plurality of battery cell modules, and a plurality of battery cell modules form a battery pack.

[0062] In addition, to achieve the basic functions of the battery pack, the battery pack in this embodiment may also include other necessary modules or components, such as a battery management system, a heat dissipation system, etc. It should be noted that the other necessary modules or components included in the battery pack can be selected from any suitable existing structures. To clearly and briefly illustrate the technical solutions provided in this embodiment, the above parts will not be elaborated here, and the specification drawings have also been simplified accordingly. However, it should be understood that the scope of the present invention is not limited thereby.

[0063] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A battery cell, characterized in that: include: The shell has openings and cover plates sealing the openings at both ends, and the cover plates are provided with pole mounting holes; A pair of poles, each comprising a main body and an annular portion located on one side of the main body, wherein the main body and the annular portion are provided with axial through holes, and the annular portion is inserted into the pole mounting hole; A pole group is arranged in the shell and has pole ears at both ends; A pair of connecting plates are arranged in the shell and respectively arranged at the two ends of the pole group, the connecting plates are formed with positioning columns adapted to the axial through holes, the connecting plates and the poles are fixedly connected by inserting the positioning columns into the axial through holes; the poles are connected to the corresponding pole ears through the connecting plates.

2. The battery cell according to claim 1, characterized in that: The annular portion extends along the axial direction of the main body portion, and a diameter of the annular portion is smaller than a diameter of the main body portion.

3. The battery cell according to claim 2, characterized in that: An annular flange is provided on the circumferential side of the annular portion close to one end of the connecting piece, and the annular flange is connected to the upper surface of the connecting piece.

4. The battery cell according to claim 3, characterized in that: It also includes a sealing ring, a plastic ring and a plastic plate. The sealing ring is sleeved outside the annular portion and abuts against the hole wall of the pole mounting hole; the plastic ring is sleeved outside the main body and the lower surface is in contact with the upper surface of the cover plate; the plastic plate is sleeved outside the annular portion and is located between the cover plate and the annular flange.

5. The battery cell according to any one of claims 1 to 4, characterized in that: One of the cover plates is provided with a welding through hole, and the other cover plate is provided with a liquid injection hole and an explosion-proof valve.

6. The battery cell according to claim 5, characterized in that: The pole ears are staggered with the corresponding pole posts, one of the pole ears comprises a main body connected to the pole group and a bent portion bent from the end of the main body toward one side, the bent portion is arranged corresponding to the welding through hole, and one of the connecting sheets is fixed in the space defined by the main body and the bent portion and fits with the lower surface of the bent portion.

7. The battery cell according to claim 6, characterized in that: The pole lugs and the corresponding poles are staggered along the length direction of the shell.

8. The battery cell according to claim 6, characterized in that: The connecting piece includes a pole connecting portion connected to the pole and a pole lug connecting portion connected to the pole lug, and the positioning column is located on the pole connecting portion.

9. The battery cell according to claim 8, characterized in that: A gap is left between the tab connection portion and the inner wall of the shell extending along the length direction thereof, and the bent portion passes through the body, through the gap and the welding through hole, and is arranged on the upper surface of the tab connection portion.

10. A battery pack, characterized in that: include: A plurality of battery cells according to any one of claims 1 to 9.

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