Battery cell and battery pack

Abstract

The application relates to the technical field of batteries, and discloses a battery cell and a battery pack. The battery cell comprises a shell with an open end, the open end of the shell forms a first end face, a cover plate assembly comprises a cover plate body, the cover plate body comprises a body part and a boss, the boss is connected to one side of the body part in the Z direction, the body part is lapped on the first end face, the boss extends into the inner cavity of the shell, and the boss is arranged in a spaced mode with the shell; a guide ring is sleeved on the boss and clamped between the boss and the shell, and the height of the guide ring in the Z direction is greater than the thickness of the boss in the Z direction. By sleeving the guide ring on the outer circumferential side of the boss, the area where the guide ring is in contact with the inner wall of the shell forms a support area, the setting of the guide ring increases the support height of the inner wall of the shell, improves the support stability, reduces the strain of the heat affected zone without increasing the thickness of the cover plate body, avoids the abnormal problem that the welding heat affected zone of the shell is prone to cracking under the action of a large fatigue stress, and improves the safety of the battery cell.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to battery cells and battery packs. Background Technology

[0002] The main structure of a battery cell includes a casing, a cover plate, electrode groups, side plates, and bare cell insulating sheets. The cover plate and casing, after being welded together, form a sealed space with sufficient mechanical strength to protect the electrode groups. The side plates and bare cell insulating sheets, after being welded and fixed, wrap around the outside of the electrode groups. The bare cell insulating sheets are fused and fixed to the plastic parts of the cover plate, thus ensuring the electrode groups are well secured within the casing and preventing short circuits.

[0003] In the prior art, the cover plate and the shell are welded after assembly. The welding of the shell and the cover plate generates a lot of heat. The mechanical properties of the shell area around the center of the weld are reduced after being heated. However, because the cover plate body is thin and the mating section between the cover plate and the shell is short, this heated area (heat-affected zone) does not have sufficient contact support. When the cell is subjected to force, the heat-affected zone of the shell is subjected to a large stress. The heat-affected zone of the shell is prone to fatigue fracture, causing cell leakage and failure, which seriously affects the safety of the cell. Summary of the Invention

[0004] This invention provides a battery cell and battery pack to solve the problem of easy cracking in the heat-affected zone of the weld on the casing.

[0005] In a first aspect, the present invention provides a battery cell, comprising: a housing having an open end, the open end of the housing forming a first end face; a cover plate assembly including a cover plate body, the cover plate body including a body portion and a boss, the boss being connected to one side of the body portion along the Z direction, the body portion overlapping the first end face, the boss extending into the inner cavity of the housing, and the boss being spaced apart from the housing; and a guide ring sleeved on the boss and sandwiched between the boss and the housing, the height of the guide ring along the Z direction being greater than the thickness of the boss along the Z direction.

[0006] Beneficial effects: By setting the cover plate body, including the body part and the boss, the boss extends into the inner cavity of the shell as a guide mating section, which facilitates the assembly of the cover plate assembly with the shell. By setting a guide ring on the outer periphery of the boss, the guide ring abuts between the boss and the inner wall of the shell. The area where the guide ring contacts the inner wall of the shell forms a support area. The height of the guide ring in the Z direction is greater than the height of the boss in the Z direction. Compared with the traditional structure that only relies on the boss to support the inner wall of the shell, the setting of the guide ring increases the height of the support area in the Z direction, that is, increases the support height of the inner wall of the shell, improves the support stability, and avoids the problem of large stress in the heat-affected zone on the shell after the mechanical properties are degraded. It reduces the strain in the heat-affected zone without increasing the thickness of the cover plate body, avoids the abnormal problem that the welded heat-affected zone of the shell is prone to cracking under large fatigue stress, and improves the safety of the battery cell.

[0007] In one optional embodiment, the guide ring has a first surface that abuts against the inner wall of the housing, the first surface having a height of m along the Z direction, and the housing having a wall thickness of n in the XY plane, wherein m and n satisfy the relationship: 5≤m / n≤10.

[0008] Beneficial effects: It can ensure that the heat-affected zone of the weld on the shell does not exceed the lower end of the guide ring, so that the guide ring can effectively play a supporting role and avoid cracking of the heat-affected zone of the shell. It can also avoid excessive weight of the guide ring, which is conducive to improving the energy density of the cell.

[0009] In one optional embodiment, the height m of the first surface along the Z direction is in the range of 2 mm ≤ m ≤ 15 mm. And / or, the wall thickness n of the shell in the XY plane is in the range of 0.25 mm ≤ n ≤ 1.5 mm.

[0010] Beneficial effects: By limiting m to a value within the range of 2 mm to 15 mm, the guide ring has a reasonable effective height, which can ensure that the guide ring can provide effective support for the heat-affected zone on the shell, and avoid excessive weight of the guide ring, thus balancing the safety and energy density of the battery cell. And / or, by limiting n to a value within the range of 0.25 mm to 1.5 mm, it is possible to ensure that the casing itself has sufficient structural strength to avoid casing deformation or cracking, and also to avoid excessive casing weight, which is beneficial to reducing costs and increasing the energy density of the battery cell.

[0011] In one optional embodiment, the guide ring includes an overlapping section and an extension section. The overlapping section coincides with the boss along the Z direction, and the extension section is connected to one end of the overlapping section that is away from the body portion along the Z direction. The guide ring has a first surface that abuts against the inner wall of the housing. The height of the first surface along the Z direction is m, and the height of the area of ​​the extension section that abuts against the inner wall of the housing along the Z direction is m1. The relationship between m1 and m is: 0.5 ≤ m1 / m ≤ 0.8.

[0012] Beneficial effects: It can ensure that the guide ring has sufficient support height for the shell, reduce the stress and strain in the welding heat-affected zone, avoid fatigue cracking of the shell, control the weight of the battery cell, save costs, and ensure smooth assembly of the guide ring and the cover plate body, thereby improving production efficiency.

[0013] In one optional implementation, the height of the overlapping segment along the Z direction is m2, wherein the value of m2 is in the range of 1 mm ≤ m2 ≤ 3 mm. And / or, the height of the overlapping segment along the Z direction is m2, and the thickness of the body part along the Z direction is h, wherein h and m2 satisfy the relationship: 1≤m2 / h≤2.

[0014] Beneficial effects: By limiting m2 to a value within the range of 1 mm to 3 mm, it is possible to ensure that there is sufficient mating height between the guide ring and the cover plate body, ensuring smooth assembly of the guide ring onto the cover plate body, thereby ensuring assembly yield. It is also possible to avoid excessive thickness and weight of the cover plate body, reducing the molding difficulty of the cover plate body, thereby ensuring molding yield, saving costs, and improving the energy density of the battery cell. And / or, by limiting m2 / h to a value within the range of 1 to 2, the cover plate body has a reasonable structural shape, which can ensure the smooth assembly of the guide ring with the cover plate body and the shell, thereby ensuring the assembly yield, and can also avoid the cover plate body being too thick and heavy, ensuring the smooth forming of the cover plate body, ensuring the forming yield, saving costs, and improving the energy density of the battery cell.

[0015] In one optional embodiment, the end of the guide ring away from the body in the Z direction is chamfered, and the height of the chamfer in the Z direction is C, wherein the value of C is in the range of 0.15 mm ≤ C ≤ 0.45 mm.

[0016] Beneficial effects: The chamfer provides guidance when assembling the guide ring and the housing, facilitating the smooth insertion of the cover plate body and the guide ring into the housing and ensuring a smooth assembly process. By limiting C to a value within the range of 0.15 mm to 0.45 mm, it is possible to ensure that the chamfer provides an effective guiding function, ensuring that the guide ring and the cover plate body can be smoothly assembled with the housing, while also avoiding excessive total height of the guide ring, thereby reducing weight and cost. Furthermore, it ensures that the guide ring has sufficient effective height to provide effective support for the heat-affected zone of the housing and prevent the housing from cracking.

[0017] In one optional embodiment, the guide ring has a wall thickness of t in the XY plane, and the housing has a wall thickness of n in the XY plane, wherein t and n satisfy the relationship: 3≤t / n≤5.

[0018] Beneficial effects: It can ensure that the guide ring has sufficient strength, thereby ensuring that the guide ring effectively supports the heat-affected zone on the shell and avoids cracking due to excessive stress on the shell. It can also avoid excessive weight of the guide ring, thereby saving costs.

[0019] In one optional embodiment, the wall thickness t of the guide ring in the XY plane is in the range of 0.8 mm ≤ t ≤ 3 mm.

[0020] Beneficial effects: It can ensure that the guide ring has sufficient strength, thereby ensuring that the guide ring effectively supports the heat-affected zone on the shell and avoids cracking due to excessive stress on the shell. It can also avoid excessive weight of the guide ring, thereby saving costs and helping to improve the energy density of the battery cell.

[0021] In one alternative implementation, the guide ring is made of metal.

[0022] Beneficial effects: Metals have high structural strength and hardness, which can stably support the inner side of the shell, improve the support stability of the guide ring on the heat-affected zone of the shell welding, reduce the stress generated in the heat-affected zone of the shell after being subjected to force, thereby reducing the fatigue strength of the shell, reducing the possibility of fatigue fracture, and improving the safety of the battery cell.

[0023] Secondly, the present invention also provides a battery pack, comprising: a housing; and the aforementioned battery cell, wherein the battery cell is disposed within the housing. Since the battery pack includes the battery cell and has the same effects as the battery cell, further details are omitted here. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the structure of a battery cell before the improvement. Figure 2 for Figure 1 A partially enlarged schematic diagram of the cross-sectional view of the battery cell shown; Figure 3 This is a front view of a battery cell according to an embodiment of the present invention; Figure 4 for Figure 3 The side view of the battery cell shown; Figure 5 for Figure 4 A schematic diagram of the assembly structure of the shell, cover plate assembly and guide ring in the cross-sectional view along the AA direction; Figure 6 for Figure 5 A magnified view of part B in the diagram; Figure 7 This is a top view of an assembly structure of a cover plate assembly and a guide ring according to an embodiment of the present invention; Figure 8 for Figure 7 A cross-sectional view along the DD direction; Figure 9 for Figure 7 Cross-sectional view along the EE direction; Figure 10 for Figure 7 An exploded view of the assembly structure of the cover plate assembly and the guide ring shown. Figure 11 for Figure 10 A schematic diagram of the structure after the guide ring and the cover plate body are assembled.

[0026] Explanation of reference numerals in the attached figures: 1. Housing; 11. First end face; 2. Cover plate assembly; 21. Cover plate body; 211. Body part; 212. Boss; 22. Pole post; 23. First plastic part; 24. Second plastic part; 25. Riveting block; 26. Sealing ring; 3. Guide ring; 301. Chamfer; 302. First surface; 31. Overlapping section; 32. Extension section; 4. Pole group; 5. Side plate; 6. End plate; 7. Bare cell insulation sheet. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] With the increasing maturity of lithium-ion battery technology, lithium-ion batteries are widely used as power batteries in electric vehicles and energy storage, and the requirements for the performance and safety of lithium-ion batteries are becoming increasingly stringent.

[0029] like Figures 1 to 2 As shown, the main structure of the blade battery cell currently includes: a cover plate assembly 2 (the cover plate body 21 integrates the electrode post 22, explosion-proof valve, upper plastic, lower plastic, and liquid injection hole), a housing 1, an end plate 6, a side plate 5, a bare battery cell insulating sheet 7, and an electrode group 4. The cover plate body 21 and the housing 1, after being welded together, form a sealed space with a certain mechanical strength to protect the electrode group 4; the side plate 5 and the bare battery cell insulating sheet 7 are welded and fixed to the outside of the electrode group 4; in addition, the bare battery cell insulating sheet 7 is fused and fixed to the plastic parts of the positive and negative electrode cover plate assembly, thereby ensuring that the electrode group 4 is well fixed inside the housing and preventing short circuits in the electrode group. The shell 1 and the cover plate body 21 are guided and matched. The cover plate body 21 is relatively thin and the shell-cover mating section is relatively short. The welding around the shell cover plate generates a lot of heat. The mechanical properties of the shell area around the center of the weld decrease after being heated. Since this heated area (heat-affected zone) does not have sufficient guiding contact support, the heat-affected zone of the shell is subjected to a lot of stress after the cell is subjected to force. The heat-affected zone of the shell is prone to fatigue fracture, resulting in cell leakage and failure.

[0030] The following is combined with Figures 3 to 11 The following describes embodiments of the present invention.

[0031] According to an embodiment of the present invention, a battery cell is provided, comprising: a housing 1, a cover plate assembly 2, and a guide ring 3. The housing 1 has an open end, the open end of which forms a first end face 11; the cover plate assembly 2 includes a cover plate body 21, the cover plate body 21 including a body portion 211 and a boss 212, the boss 212 being connected to one side of the body portion 211 along the Z direction, the body portion 211 overlapping the first end face 11, the boss 212 extending into the inner cavity of the housing 1, and the boss 212 and the housing 1 being spaced apart in the XY plane; the guide ring 3 is sleeved on the boss 212 and sandwiched between the boss 212 and the housing 1, the height of the guide ring 3 along the Z direction being greater than the thickness of the boss 212 along the Z direction.

[0032] It should be noted that the battery cell has two perpendicular X, Y, and Z directions (e.g., Figures 3 to 6As shown in the diagram, specifically, the X direction is the width direction of the battery cell, the Y direction is the thickness direction of the battery cell, and the Z direction is the length direction of the battery cell. At least one end of the housing 1 along the Z direction is configured as an open end, and the first end face 11 is parallel to the XY plane. A boss 212 is fixedly connected along the Z direction to the side of the body portion 211 facing the inner cavity of the housing 1. Preferably, the boss 212 and the body portion 211 are integrally formed. The outer peripheral contour of the boss 212 is smaller than the outer peripheral contour of the body portion 211. The portion of the body portion 211 outside the outer peripheral contour of the boss 212 forms an overlapping ring, which overlaps the first end face 11. Preferably, the outer peripheral contour of the body portion 211 coincides with the outer peripheral contour of the housing 1 in the XY plane, so as to facilitate welding of the cover plate body 21 to the housing 1.

[0033] The battery cell of this embodiment uses a cover plate body 21 including a body portion 211 and a boss 212. The boss 212 extends into the inner cavity of the housing 1 as a guide mating section, facilitating the assembly of the cover plate assembly 2 and the housing 1. A guide ring 3 is sleeved on the outer periphery of the boss 212, and the guide ring 3 abuts against the inner wall of the housing 1. The area where the guide ring 3 contacts the inner wall of the housing 1 forms a support area. The height of the guide ring 3 along the Z direction is greater than the height of the boss 212 along the Z direction. Compared with the traditional structure where the inner wall of the housing 1 is supported only by the boss 212, the setting of the guide ring 3 increases the height of the support area along the Z direction, that is, increases the support height of the inner wall of the housing 1, improves the support stability, and avoids the problem of large stress in the heat-affected zone on the housing 1 after the mechanical properties are degraded. Without increasing the thickness of the cover plate body 21, the strain in the heat-affected zone is reduced, avoiding the abnormal problem that the welded heat-affected zone of the housing 1 is prone to cracking under large fatigue stress, thus improving the safety of the battery cell.

[0034] The inner wall of the shell 1 refers to the wall surface of the shell 1 facing its inner cavity.

[0035] It should be noted that the orthographic projection of the guide ring 3 along the Z direction in the XY plane is annular. The guide ring 3 is a complete ring. Adding the guide ring 3 to the outer periphery of the boss 212 allows for assembly. During assembly, the guide ring 3 is first assembled with the cover plate body 21, and then both are assembled onto the housing 1. The guide ring 3 provides good guidance during assembly and ensures that the entire area of ​​the housing 1 near the opening is supported by the guide ring 3 after assembly, further reducing the stress generated on the housing 1 during welding. The welding method between the housing 1 and the cover plate body 21 is peripheral welding.

[0036] In one embodiment, the guide ring 3 is made of metal. Metal has high structural strength and hardness, and can stably support the inner side of the housing 1, improving the support stability of the guide ring 3 on the welded heat-affected zone of the housing 1, reducing the stress generated in the heat-affected zone of the housing 1 after being subjected to force, thereby improving the fatigue strength of the housing 1, reducing the possibility of fatigue fracture, and improving the safety of the battery cell.

[0037] Optionally, the guide ring 3 can be made of a metal with mechanical properties far greater than aluminum, such as copper, iron, or alloy steel, which can further ensure the stability of the guide ring 3 in supporting the housing 1.

[0038] In one embodiment, further combination Figure 6 , Figures 9 to 10 As shown, the guide ring 3 has a first surface 302 that abuts against the inner wall of the housing 1. The height of the first surface 302 along the Z direction is m, and the wall thickness of the housing 1 in the XY plane is n. The relationship between m and n is: 5 ≤ m / n ≤ 10, where m and n are both in mm. Here, m is the height along the Z direction of the area where the guide ring 3 actually abuts against the inner wall of the housing 1, i.e., the effective height of the guide ring 3. For a guide ring 3 with a chamfer 301 at the end, the effective height is the height of the guide ring 3 minus the height of the chamfered section; for a guide ring 3 without a chamfer 301, the effective height is the height of the entire guide ring 3.

[0039] It should be noted that the shell 1 is composed of multiple side walls, where n is the wall thickness of the side walls. The greater the wall thickness of the shell 1, the greater the welding power when welding the shell 1 to the cover plate body 21, and the larger the range of the peripheral welding heat-affected zone. That is, the width of the peripheral welding heat-affected zone along the Z direction increases with the increase of the shell 1 wall thickness. Therefore, the larger n is, the larger m needs to be. If m / n is less than 5, the effective height of the guide ring 3 is too small relative to the wall thickness of the shell 1, and the boundary of the heat-affected zone may exceed the lower end of the guide ring 3. The guide ring 3 cannot play an effective supporting role, and the heat-affected zone on the shell 1 will still generate large stress under load, making it prone to fatigue cracking. If m / n is greater than 10, the guide ring 3 is redundant in design, too heavy, and the structure is overweight. Here, the lower end of the guide ring 3 refers to the end of the guide ring 3 facing the inner cavity of the shell along the Z direction.

[0040] Therefore, by limiting m / n to a value between 5 and 10, the effective height of the guide ring 3 is linked to the wall thickness of the housing 1. This ensures that the welding heat-affected zone on the housing 1 does not exceed the lower end of the guide ring 3, allowing the guide ring 3 to effectively play a supporting role and preventing cracking of the heat-affected zone of the housing 1. It also avoids excessive weight of the guide ring 3, which is beneficial to improving the energy density of the battery cell.

[0041] Optionally, m / n can take any value from 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or a value between any two values.

[0042] In one embodiment, the height *m* of the first surface 302 along the Z direction ranges from 2 mm to 15 mm. If *m* is less than 2 mm, the height of the first surface 302 along the Z direction is too small, meaning the effective height of the guide ring 3 is too small, resulting in insufficient support for the housing 1. This can easily lead to the heat-affected zone of the housing 1 extending beyond the lower end of the guide ring 3, failing to effectively reduce the stress on the housing 1. If *m* is greater than 15 mm, the height of the first surface 302 along the Z direction is too large, meaning the effective height of the guide ring 3 is too large, resulting in redundant design and excessive weight. Therefore, by limiting *m* to a value between 2 mm and 15 mm, the guide ring 3 has a reasonable effective height, ensuring that it provides effective support for the heat-affected zone on the housing 1 while avoiding excessive weight, thus balancing the safety and energy density of the battery cell.

[0043] Optionally, m can take any value from 2 mm, 4 mm, 5 mm, 8 mm, 10 mm, 12 mm, 14 mm, 15 mm, or a value between any two of these values.

[0044] In one embodiment, the wall thickness n of the housing 1 in the XY plane ranges from 0.25 mm to 1.5 mm. It should be noted that for a sidewall parallel to the XZ plane, n refers to the wall thickness along the Y direction; for a sidewall parallel to the YZ plane, n refers to the wall thickness along the X direction. If n is less than 0.25 mm, the wall thickness of the housing 1 is too small, resulting in insufficient structural strength and susceptibility to deformation under external forces. Furthermore, the mechanical properties of the heat-affected zone after welding are poor, making it prone to fracture and reducing reliability, which is detrimental to ensuring the safety of the battery cell. If n is greater than 1.5 mm, the wall thickness of the housing 1 is too large, leading to excessive weight and hindering the improvement of the battery cell's energy density and weight reduction. Therefore, by limiting n to the range of 0.25 mm to 1.5 mm, sufficient structural strength of the housing 1 can be ensured, preventing deformation or cracking, while also avoiding excessive weight, which helps reduce costs and improve the energy density of the battery cell.

[0045] Optionally, n can take any value from 0.25 mm, 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, or a value between any two values.

[0046] In one embodiment, further combination Figure 6As shown, the guide ring 3 includes an overlapping section 31 and an extension section 32. The overlapping section 31 coincides with the boss 212 along the Z direction, and the extension section 32 is connected to the end of the overlapping section 31 that is away from the main body 211 along the Z direction. The guide ring 3 has a first surface 302 that abuts against the inner wall of the housing 1. The height of the first surface 302 along the Z direction is m, and the height of the area of ​​the extension section 32 that abuts against the inner wall of the housing 1 along the Z direction is m1. The relationship between m1 and m is: 0.5 ≤ m1 / m ≤ 0.8, where both m1 and m are in mm. It should be noted that the overlapping section 31 and the extension section 32 are two segments of the guide ring 3 that are fixedly connected along the Z direction, and the dividing line between them is as shown in the figure. Figure 6 As shown by the dashed lines, the guide ring 3 is actually integrally formed. The overlapping section 31 abuts between the outer peripheral surface of the boss 212 and the inner wall of the housing 1, and the extension section 32 extends downward out of the boss 212; m1 is the height of the area where the extension section 32 actually abuts against the inner wall of the housing 1 along the Z direction, that is, the effective height of the extension section 32. For the guide ring 3 with a chamfer 301 at the end, m1 is the height of the remaining part of the extension section 32 after subtracting the chamfered section; for the guide ring 3 without a chamfer 301, m1 is the height of the extension section 32.

[0047] It should be noted that the effective height m of the guide ring 3 is equal to the sum of the effective height m1 of the extension section 32 and the height m2 of the overlapping section 31 along the Z direction. If m1 / m is less than 0.5, the effective height of the extension section 32 is too small relative to the effective height of the guide ring 3. When the thickness of the boss 212 along the Z direction is constant, the total height of the guide ring 3 along the Z direction is too small, resulting in less support for the shell 1 by the guide ring 3, which can easily lead to stress concentration and fatigue cracking of the shell. Alternatively, when the effective height m of the guide ring 3 is constant, the dimensions of the overlapping section 31 and the boss 212 along the Z direction are too large, resulting in an excessively large total thickness and weight of the cover plate body 21, which wastes costs. If m1 / m is greater than 0.8, the proportion of the height of the overlapping section 31 along the Z direction to the effective height of the guide ring 3 is too small, that is, the overlapping area of ​​the guide ring 3 and the cover plate body 21 is small, making it difficult to assemble the guide ring 3 onto the cover plate body 21.

[0048] Therefore, by limiting the value of m1 / m to the range of 0.5 to 0.8, it is possible to ensure that the guide ring 3 has sufficient support height for the shell 1, reduce the stress and strain in the welding heat-affected zone, avoid fatigue cracking of the shell 1, control the weight of the battery cell, save costs, and ensure the smooth assembly of the guide ring 3 and the cover plate body 21, thereby improving production efficiency.

[0049] Optionally, m1 / m can take any value from 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, or a value between any two values.

[0050] In one embodiment, further combination Figure 6 As shown, the height of the overlapping segment 31 along the Z direction is m2, where the value of m2 is in the range of 1 mm ≤ m2 ≤ 3 mm. It should be noted that one end of the overlapping segment 31 along the Z direction abuts against the main body 211, and the other end is flush with the surface of the boss 212 on the side away from the main body 211. That is, the height m2 of the overlapping segment 31 along the Z direction is equal to the thickness of the boss 212 along the Z direction. If m2 is less than 1 mm, the height of the overlapping section 31 is too small, and correspondingly, the thickness of the boss 212 is too small. The guide ring 3 is assembled with the cover plate body 21 by being fitted onto the boss 212. If m2 is too small, the fit height between the guide ring 3 and the cover plate body 21 will be too small, resulting in poor fit between the two, making assembly difficult, low assembly yield, and poor stability after assembly. If m2 is greater than 3 mm, the height of the overlapping section 31 is too large, and correspondingly, the thickness of the boss 212 will be too large. It will be difficult to stamp the cover plate body 21, resulting in a low forming yield. Even if it can be formed, the weight of the formed cover plate body 21 will be too large, the cost will be high, and it will occupy too much space inside the housing 1, compressing the space for the electrode group 4, which is not conducive to improving the energy density of the cell.

[0051] Therefore, by limiting m2 to a value within the range of 1 mm to 3 mm, it is possible to ensure that there is sufficient fitting height between the guide ring 3 and the cover plate body 21, ensuring smooth assembly of the guide ring 3 onto the cover plate body 21, thereby ensuring assembly yield. At the same time, it is possible to avoid excessive thickness and weight of the cover plate body 21, reducing the molding difficulty of the cover plate body 21, thereby ensuring molding yield, saving costs, and improving the energy density of the battery cell.

[0052] Optionally, m2 can be any value among 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, and 3 mm, or a value between any two of these values.

[0053] In one embodiment, the height of the overlapping segment 31 along the Z direction is m2, and the thickness of the body portion 211 along the Z direction is h, wherein h and m2 satisfy the relationship: 1≤m2 / h≤2. It should be noted that m2 / h represents the ratio of the height of the overlapping segment 31 to the thickness of the body portion 211, that is, the ratio of the thickness of the boss 212 to the thickness of the body portion 211. If m2 / h is less than 1, the thickness of the boss 212 is too small relative to the thickness of the body portion 211, resulting in insufficient thickness of the boss 212 and poor fit between the boss 212 and the guide ring 3. Consequently, the fit between the housing 1 and the guide ring 3 is poor, leading to low cell assembly yield and difficulty in installation. If m2 / h is greater than 2, the thickness of the boss 212 is too large relative to the thickness of the body portion 211, making it difficult to stamp the cover body 21, resulting in low forming yield, high cost, and hindering the improvement of the cell's energy density.

[0054] Therefore, by limiting m2 / h to a value within the range of 1 to 2, the cover plate body 21 has a reasonable structural shape, which can ensure the smooth assembly of the guide ring 3 with the cover plate body 21 and the shell 1, thereby ensuring the assembly yield. It can also avoid the cover plate body 21 being too thick and heavy, ensuring the smooth forming of the cover plate body 21, ensuring the forming yield, saving costs, and improving the energy density of the battery cell.

[0055] Optionally, m2 / h can take any value from 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or a value between any two values.

[0056] In one embodiment, further combination Figure 6 As shown, the end of the guide ring 3 furthest from the main body 211 along the Z direction is chamfered 301, and the height of the chamfer 301 along the Z direction is C, where the value of C ranges from 0.15 mm to C and from 0.45 mm to 0.15 mm. It should be noted that the chamfer 301 is located on the outer edge of the guide ring 3, that is, the outer edge of the end of the guide ring 3 furthest from the main body 211 along the Z direction is chamfered 301. The chamfer 301 provides guidance when the guide ring 3 is assembled with the housing 1, facilitating the smooth insertion of the cover plate body 21 and the guide ring 3 into the housing 1, ensuring a smooth assembly process, and improving assembly yield and efficiency.

[0057] Where C is the height dimension of chamfer 301 along the Z direction. If C is less than 0.15 mm, chamfer 301 is too small and cannot play a good guiding role. The total height of guide ring 3 along the Z direction is equal to the sum of its effective height m and the height of chamfer 301 along the Z direction. If C is greater than 0.45 mm, chamfer 301 is too large. Under the premise of ensuring that guide ring 3 has sufficient effective height m, it will lead to the total height of guide ring 3 along the Z direction being too large, resulting in design redundancy, waste of materials and costs. Moreover, chamfer 301 removes too much part of guide ring 3, which is not conducive to ensuring the structural stability of guide ring 3. Alternatively, if the total height of guide ring 3 is not too large, the effective height m of guide ring 3 will be insufficient, and it will not be able to provide sufficient support for shell 1. The problem of excessive stress and cracking in the weld heat-affected zone of shell 1 will still exist. Therefore, by limiting C to a value between 0.15 mm and 0.45 mm, it is possible to ensure that the chamfer 301 can provide an effective guiding function, ensuring that the guide ring 3 and the cover plate body 21 can be smoothly assembled with the housing 1, while also avoiding excessive total height of the guide ring 3, thereby reducing weight and cost, and ensuring that the guide ring 3 has sufficient effective height to provide effective support for the heat-affected zone of the housing 1 and prevent the housing 1 from cracking.

[0058] Optionally, C can be any value among 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, and 0.45 mm, or a value between any two of these values.

[0059] In one embodiment, the chamfer 301 is a 45° chamfer, that is, the dimension of the chamfer 301 along the Z direction is equal to its dimension in the XY plane, which is convenient for processing and has good stability.

[0060] In one embodiment, further combination Figure 6 As shown, the wall thickness of the guide ring 3 in the XY plane is t, and the wall thickness of the housing 1 in the XY plane is n. The relationship between t and n is: 3 ≤ t / n ≤ 5, where both t and n are in mm. It should be noted that the guide ring 3 is supported between the inner wall of the housing 1 and the outer peripheral surface of the boss 212. The wall thickness t of the guide ring 3 is the gap between the inner wall of the housing 1 and the outer peripheral surface of the boss 212. The greater the wall thickness of the housing 1, the greater the welding power when welding the housing 1 to the cover plate body 21, and the larger the area of ​​the surrounding heat-affected zone. Correspondingly, the guide ring 3 needs to be designed with a greater thickness to provide effective support to the housing 1. If t / n is less than 3, the thickness of the guide ring 3 is too small relative to the thickness of the housing 1, resulting in weak structural strength and insufficient support for the heat-affected zone. If t / n is greater than 5, the thickness of the guide ring 3 is too large relative to the thickness of the housing 1, leading to redundant design, excessive weight, and high cost. Therefore, by limiting t / n to a value between 3 and 5, it is possible to ensure that the guide ring 3 has sufficient strength, thereby ensuring that the guide ring 3 effectively supports the heat-affected zone on the shell 1 and avoids excessive stress on the shell 1 and cracking. At the same time, it is possible to avoid excessive weight of the guide ring 3, thereby saving costs.

[0061] Optionally, t / n can take any value from 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8, 5, or a value between any two values.

[0062] In one embodiment, the wall thickness t of the guide ring 3 in the XY plane ranges from 0.8 mm to 3 mm. If t is less than 0.8 mm, the guide ring 3 is too thin, resulting in weak structural strength and insufficient support for the heat-affected zone; if t is greater than 3 mm, the guide ring 3 is too thick, leading to design redundancy and excessive weight. Therefore, by limiting t to the range of 0.8 mm to 3 mm, the guide ring 3 has a reasonable wall thickness. This ensures that the guide ring 3 has sufficient strength to effectively support the heat-affected zone on the housing 1, preventing excessive stress and cracking of the housing 1. It also avoids excessive weight, thus saving costs and improving the energy density of the battery cell.

[0063] Optionally, t can take any value from 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3 mm, or a value between any two values.

[0064] In one embodiment, the cover plate assembly 2 further includes a pole post 22 and a riveting block 25. The cover plate body 21 has a pole post through hole. The pole post 22 includes a column body and a base plate. The column body passes through the pole post through hole. The riveting block 25 is disposed on the side of the cover plate body 21 away from the base plate and is riveted to the column body.

[0065] In one embodiment, the cover plate assembly 2 further includes a first plastic part 23, a second plastic part 24, and a sealing ring 26. The first plastic part 23 is disposed between the riveting block 25 and the cover plate body 21 to ensure insulation between the riveting block 25 and the cover plate body 21; the second plastic part 24 is disposed on the side of the cover plate body 21 opposite to the first plastic part 23, and is at least partially located between the base plate and the cover plate body 21 to ensure insulation between the base plate of the pole post 22 and the cover plate body 21, and insulation between the cover plate body 21 and the pole group 4; the sealing ring 26 is sleeved on the post to ensure sealing and insulation between the pole post 22 and the cover plate body 21. Specifically, the first plastic part 23 is an upper plastic, and the second plastic part 24 is a lower plastic.

[0066] In one embodiment, the battery cell further includes a pole group 4 disposed within the inner cavity of the housing 1, and electrically connected to the terminal post 22 via a tab. The battery cell also includes a side plate 5 and a bare battery cell insulating sheet 7. The side plate 5 is disposed outside the pole group 4, and the bare battery cell insulating sheet 7 wraps around the pole group 4 and the side plate 5 to ensure insulation between the pole group 4 and the housing 1. The battery cell also includes an end plate 6, which is supported between the pole group 4 and the cover plate assembly 2 to fix the pole group 4.

[0067] In this embodiment, the battery cell optimizes the assembly structure relationship between the cover plate and the housing 1. A guide ring 3 is added around the boss 212, which serves as a guide section, on the cover plate body 21. Without increasing the thickness of the cover plate body 21, the strain of the heat-affected zone on the housing 1 is reduced, avoiding large fatigue stress in the welded area around the housing and causing the housing to crack. This solves the abnormal problem of cracking in the heat-affected zone of the peripheral welded housing and improves the safety of the battery cell.

[0068] According to an embodiment of the present invention, in another aspect, a battery pack is also provided, comprising: a housing and the aforementioned battery cells, wherein the battery cells are disposed within the housing. The battery pack contains a plurality of battery cells, and a busbar is further provided therein. The terminals of the battery cells are electrically connected to the busbar, and the plurality of battery cells are electrically connected to each other via the busbar. Optionally, the battery cells are lithium-ion battery cells.

[0069] The following examples and comparative examples verify the impact of different parameter values ​​on cell performance. The parameter settings and corresponding verification results of the examples and comparative examples are shown in Tables 1 to 3.

[0070] I. The results of the cell impact test and the structural weight under different values ​​of m and m / n for shell wall thickness n=0.35 mm are shown in Table 1.

[0071] Table 1

[0072] 2. The results of the cell impact test and the structural weight under different values ​​of m and m / n for shell wall thickness n=0.5 mm are shown in Table 2.

[0073] Table 2

[0074] III. The results of the cell impact test and the structural weight under different values ​​of m and m / n for shell wall thickness n=0.6 mm are shown in Table 3.

[0075] Table 3

[0076] As can be seen from Tables 1 to 3, in Examples 1-1 to 1-5, Examples 2-1 to 2-5, and Examples 3-1 to 3-5, the values ​​of m / n are all within the range of 5 to 10 defined in this application. After the cell impact test, the heat-affected zone did not crack, and the cell did not exceed the weight limit. However, in Comparative Examples 1-1 to 1-4, Comparative Examples 2-1 to 2-4, and Comparative Examples 3-1 to 3-4, the values ​​of m / n are all less than the lower limit of 5 defined in this application and are not within the range defined in this application. Although the cell did not exceed the weight limit, the heat-affected zone cracked after the cell impact test. In Comparative Examples 1-5 to 1-8, Comparative Examples 2-5 to 2-8, and Comparative Examples 3-5 to 3-8, the values ​​of m / n are all greater than the upper limit of 10 defined in this application and are not within the range defined in this application. Although the heat-affected zone did not crack after the cell impact test, the cell exceeded the weight limit.

[0077] It is evident that when m / n is within the range of 5 to 10 as defined in this application, the cell casing can withstand the impact test without cracking, and the cell weight is also within the range, indicating that the guide ring 3 can effectively play a supporting role, and the guide ring 3 does not have the problem of design redundancy.

[0078] Unless otherwise stated, the values ​​of all parameters and test items mentioned in this application can be determined using test methods commonly used in the art. Unless otherwise stated, the test temperature for all parameters is 25°C.

[0079] Although embodiments of the 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 invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An electric cell, characterized by, include: A housing having an open end, the open end of the housing forming a first end face; A cover plate assembly includes a cover plate body, the cover plate body including a body portion and a boss, the boss being connected to one side of the body portion along the Z direction, the body portion overlapping the first end face, the boss extending into the inner cavity of the housing, and the boss being spaced apart from the housing. A guide ring is fitted onto the boss and sandwiched between the boss and the housing. The height of the guide ring along the Z direction is greater than the thickness of the boss along the Z direction.

2. The electric cell of claim 1, wherein, The guide ring has a first surface that abuts against the inner wall of the housing. The height of the first surface along the Z direction is m, and the wall thickness of the housing in the XY plane is n. The relationship between m and n is: 5≤m / n≤10.

3. The battery cell according to claim 2, characterized in that, The height m of the first surface along the Z direction ranges from 2 mm to 15 mm. And / or, the wall thickness n of the shell in the XY plane is in the range of 0.25 mm ≤ n ≤ 1.5 mm.

4. The battery cell according to claim 1, characterized in that, The guide ring includes an overlapping section and an extension section. The overlapping section coincides with the boss along the Z direction, and the extension section is connected to one end of the overlapping section that is away from the body part along the Z direction. The guide ring has a first surface that abuts against the inner wall of the housing, the first surface having a height of m along the Z direction, and the area of ​​the extension that abuts against the inner wall of the housing having a height of m1 along the Z direction, wherein m1 and m satisfy the relationship: 0.5≤m1 / m≤0.

8.

5. The battery cell according to claim 4, characterized in that, The height of the overlapping segment along the Z direction is m2, where the value of m2 is in the range of 1 mm ≤ m2 ≤ 3 mm. And / or, the height of the overlapping segment along the Z direction is m2, and the thickness of the body part along the Z direction is h, wherein h and m2 satisfy the relationship: 1≤m2 / h≤2.

6. The battery cell according to claim 1, characterized in that, The end of the guide ring away from the main body along the Z direction is chamfered, and the height of the chamfer along the Z direction is C, wherein the value of C is in the range of 0.15 mm ≤ C ≤ 0.45 mm.

7. The battery cell according to claim 1, characterized in that, The guide ring has a wall thickness of t in the XY plane, and the housing has a wall thickness of n in the XY plane, wherein t and n satisfy the relationship: 3≤t / n≤5.

8. The battery cell according to claim 7, characterized in that, The wall thickness t of the guide ring in the XY plane ranges from 0.8 mm to 3 mm.

9. The battery cell according to any one of claims 1 to 8, characterized in that, The guide ring is made of metal.

10. A battery pack, characterized in that, include: Box; The battery cell according to any one of claims 1 to 9, wherein the battery cell is disposed within the housing.

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