Cap assembly and cylindrical lithium ion battery

Abstract

The utility model relates to a cap assembly and a cylindrical lithium ion battery. Relates to the technical field of new energy batteries. The explosion-proof device specifically comprises an explosion-proof piece and a top cover plate, the top cover plate comprises a welding protrusion extending upwards and sealing parts arranged on the two sides of the welding protrusion, the sealing parts are stacked on the top of the explosion-proof piece, and a pressure relief area is formed between the bottom of the welding protrusion and the top of the explosion-proof piece; in the vertical direction, the thickness T1 of the sealing part ranges from 0.3 mm to 0.5 mm, and the ratio T2 / T1 of the thickness T2 of the anti-explosion piece to the thickness T1 of the sealing part ranges from 80% to 100%. According to the cylindrical lithium ion battery, the thickness T1 of the sealing part ranges from 0.3 mm to 0.5 mm, and the ratio T2 / T1 of the thickness T2 of the anti-explosion sheet to the thickness T1 of the sealing part ranges from 80% to 100%, so that the sealing performance of the cylindrical lithium ion battery can be guaranteed, the safety performance of the cylindrical lithium ion battery is improved, the anti-explosion performance of the cylindrical lithium ion battery can be guaranteed, and the service life of the cylindrical lithium ion battery is prolonged. And the service life of the cylindrical lithium ion battery is prolonged.

Description

TECHNICAL FIELD

[0001] The utility model relates to new energy battery technical field especially is related to a cap subassembly and cylindrical lithium ion battery. BACKGROUND

[0002] Cylindrical lithium ion batteries are widely used in various fields, including mobile devices, electric vehicles, energy storage systems, consumer electronics, and others, due to their high energy density, good heat dissipation performance, good mechanical strength, ease of manufacture, and wide range of applications. The cap subassembly, as an important component of the cylindrical lithium ion battery, plays a sealing, conducting, and safety protection role in the cylindrical lithium ion battery. Therefore, the optimization of the cap subassembly is particularly important in the design of the cylindrical lithium ion battery.

[0003] The cap subassembly of the cylindrical lithium ion battery typically includes a top cover plate and a burst disc. The top cover plate is arranged on the top of the burst disc and is used for welding with other cylindrical lithium ion batteries during the battery assembly process. The burst disc is used to provide safety protection for the cylindrical lithium ion battery. The existing design of the cap subassembly of the cylindrical lithium ion battery is not entirely reasonable, especially the thickness design of the top cover plate and the burst disc.

[0004] When the cap subassembly is installed in the battery shell, the edge of the battery shell is usually folded inward and then crimped on the top cover plate to complete the sealing of the battery shell. Some cap subassemblies design the thickness of the top cover plate and the burst disc to be too large, resulting in a total height of the top cover plate stacked on the burst disc being too high. When the edge of the battery shell is folded inward and crimped on the top cover plate, the amount of edge covering decreases, which leads to a decrease in sealing ability and causes the cylindrical lithium ion battery to have poor air tightness and leakage.

[0005] Some cap subassemblies design the thickness of the top cover plate and the burst disc to be too small. When the edge of the battery shell is folded inward and crimped on the sealing part, the amount of edge covering is too large, which causes interference between the edge of the battery shell and the welding protrusion on the top cover plate, affecting the sealing of the battery shell. This further causes the cylindrical lithium ion battery to have poor sealing and a risk of leakage. Meanwhile, the small thickness of the burst disc results in poor structural strength of the burst disc. When a large amount of gas is generated in the battery shell, the burst disc cannot withstand the gas pressure within the safety range, which causes the valve to open prematurely and reduces the service life of the cylindrical lithium ion battery. SUMMARY

[0006] The utility model aims at the deficiency of prior art, provides a cap subassembly and cylindrical lithium ion battery, can guarantee the sealing of cylindrical lithium ion battery, improves the safety performance of cylindrical lithium ion battery, can guarantee the burst performance of cylindrical lithium ion battery, prolongs the service life of cylindrical lithium ion battery.

[0007] The utility model provides a cap assembly, including the anti -explosion piece and the top cover board, the top cover board includes the welding protruding upwards to the both sides of the welding protruding set up the sealing portion, the sealing portion is stacked in the top of the anti -explosion piece, the bottom of the welding protruding and the top of the anti -explosion piece form the pressure relief area, in the vertical direction, the thickness T1 of the sealing portion is 0.3mm~0.5mm, the thickness T2 of the anti -explosion piece, and the ratio T2 / T1 of the thickness T1 of the sealing portion is 80% -100%.

[0008] Further, in the vertical direction, the thickness T2 of the anti -explosion piece is 0.25mm~0.45mm.

[0009] Further, the top of the anti -explosion piece is equipped with the anti -explosion score, in the vertical direction, the thickness T3 of the anti -explosion piece at the anti -explosion score, and the ratio T3 / T2 of the thickness T2 of the anti -explosion piece is 32%~50%.

[0010] Further, the top of the anti -explosion piece is equipped with the reinforcing boss extending upwards, the reinforcing boss is located the outside of the anti -explosion score, and the ratio T2 / T4 of the thickness T2 of the anti -explosion piece and the thickness T4 of the anti -explosion piece at the reinforcing boss is 62%~78%.

[0011] Further, the bottom of the anti -explosion piece is equipped with the welding boss extending downwards, and the ratio T2 / T5 of the thickness T2 of the anti -explosion piece and the thickness T5 of the anti -explosion piece at the welding boss is 60~80% in the vertical direction.

[0012] Further, the transition boss is arranged between the anti -explosion score and the reinforcing boss, and the ratio L1 / L2 of the length L1 of the transition boss and the length L2 of the reinforcing boss is 15%~35% in the horizontal direction.

[0013] Further, the ratio L2 / L3 of the length L2 of the reinforcing boss and the length L3 from the anti -explosion score to the central axis of the anti -explosion piece is 12%~22% in the horizontal direction.

[0014] Further, the length L3 from the anti -explosion score to the central axis of the anti -explosion piece is 3mm~7mm in the horizontal direction.

[0015] Further, the included angle A between the both sides of the welding protruding and the horizontal plane is 90°~140°

[0016] The utility model also provides a cylindrical lithium ion battery, including the cap assembly above.

[0017] The cap assembly and cylindrical lithium ion battery have the following beneficial effects:

[0018] (1) The thickness T1 of the sealing portion is set to be between 0.3mm and 0.5mm, and the ratio T2 / T1 of the thickness T2 of the explosion-proof sheet to the thickness T1 of the sealing portion is set to be between 80% and 100%, so that the sealing property of the cylindrical lithium ion battery is ensured, the safety performance of the cylindrical lithium ion battery is improved, the explosion-proof property of the cylindrical lithium ion battery is ensured, and the service life of the cylindrical lithium ion battery is prolonged.

[0019] (2) The thickness T2 of the explosion-proof sheet is limited to be between 0.25mm and 0.45mm, so that when the value of T1 and the value of T2 / T1 are determined, the value of T2 is also referred to, so that the value of T2 obtained according to the value of T1 and the value of T2 / T1 is within the range, so that the structural strength of the explosion-proof sheet is further ensured, and the service life of the cylindrical lithium ion battery is prolonged.

[0020] (3) The ratio T3 / T2 of the thickness T3 of the explosion-proof sheet at the explosion-proof notch to the thickness T2 of the explosion-proof sheet is set to be between 32% and 50%, so that the valve opening pressure of the explosion-proof valve along the area where the explosion-proof notch is located is within the safety pressure range of the battery shell, and the explosion-proof property of the cylindrical lithium ion battery is ensured, and the service life of the cylindrical lithium ion battery is prolonged.

[0021] (4) The ratio T2 / T4 of the thickness T2 of the explosion-proof sheet to the thickness T4 of the explosion-proof sheet at the reinforcing boss is set to be between 62% and 78%, so that the reinforcing effect of the reinforcing boss on the joint of the explosion-proof sheet and the explosion-proof notch is ensured, the explosion-proof property of the cylindrical lithium ion battery is improved, the operation of extruding the material at the position of the explosion-proof notch to form the reinforcing boss outside the explosion-proof notch is simple and convenient, the production efficiency of the cylindrical lithium ion battery is improved, and the production cost of the cylindrical lithium ion battery is reduced.

[0022] (5) The ratio T2 / T5 of the thickness T2 of the explosion-proof sheet to the thickness T5 of the explosion-proof sheet at the welding boss is set to be between 60% and 80%, so that the structural strength of the explosion-proof sheet is ensured, the service life of the cylindrical lithium ion battery is prolonged, the phenomenon of welding through of the welding boss and the bottom cover plate during welding is prevented, the risk of liquid leakage of the cylindrical lithium ion battery is reduced, and the safety performance of the cylindrical lithium ion battery is improved.

[0023] (6) the cap assembly sets the ratio L1 / L2 of the length L1 of the transition boss and the length L2 of the reinforcing boss between 15% and 35%, which not only ensures that the material at the position of the explosion-proof notch is extruded to the reinforcing boss through the transition boss in the forming process of the explosion-proof disc, facilitates the operation and is easy to implement, improves the production efficiency of the cylindrical lithium ion battery and reduces the production cost of the cylindrical lithium ion battery, but also ensures the reinforcing effect of the reinforcing boss on the junction of the explosion-proof disc and the explosion-proof notch, and improves the safety performance of the cylindrical lithium ion battery;

[0024] (7) the cap assembly sets the ratio L2 / L3 of the length L2 of the reinforcing boss and the length L3 of the explosion-proof notch to the central axis of the explosion-proof disc between 12% and 22%, which not only ensures the effective valve area of the explosion-proof disc and enhances the pressure relief capacity of the explosion-proof disc, but also ensures the reinforcing effect of the reinforcing boss on the junction of the explosion-proof disc and the explosion-proof notch, and further improves the safety performance of the cylindrical lithium ion battery;

[0025] (8) the length L3 of the explosion-proof notch to the central axis of the explosion-proof disc of the cap assembly ranges from 3mm to 7mm, in actual implementation, the value of L3 is determined first, then the value of L2 is determined according to L2 / L3, and then the value of L1 is determined according to L1 / L2. BRIEF DESCRIPTION OF DRAWINGS

[0026] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application. In these drawings, like reference numerals are used to represent similar elements.

[0027] Figure 1 is a structural schematic view of a cap assembly of an embodiment of the present application;

[0028] Figure 2 is a structural schematic view of a top cover plate of a cap assembly of an embodiment of the present application;

[0029] Figure 3 is Figure 1 is an enlarged schematic view of position B in FIG. 2.

[0030] In the figure: 1, top cover plate; 11, welding protrusion; 12, sealing portion; 2, explosion-proof disc; 21, explosion-proof notch; 22, reinforcing boss; 23, welding boss; 24, transition boss; 3, pressure relief area. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the utility model embodiment clearer, the technical scheme in the utility model embodiment will be clearly and completely described below in combination with the drawings in the utility model embodiment. Based on the embodiments in the utility model, all other embodiments obtained by the ordinary skilled in the art without creative labor belong to the protection scope of the utility model.

[0032] Please refer to Figures 1 to 3 The cap assembly of the utility model embodiment comprises an explosion-proof sheet 2 and a top cover plate 1, the top cover plate 1 is arranged at the top of the explosion-proof sheet 2 and is used for leading out the positive electrode of the cylindrical lithium ion battery. The top cover plate 1 comprises a welding protrusion 11 located at the middle part and sealing parts 12 located at both sides of the welding protrusion 11, and the sealing parts 12 are stacked at the top of the explosion-proof sheet 2. Since the welding protrusion 11 extends upwards, a pressure relief area 3 is formed between the bottom of the welding protrusion 11 and the top of the explosion-proof sheet 2, thereby relieving pressure through the explosion-proof sheet 2 and realizing explosion-proof protection of the cylindrical lithium ion battery.

[0033] During the battery grouping process, the welding protrusion 11 is welded with the bus bar, and then the bus bar is connected with the negative electrode of another cylindrical lithium ion battery, thereby conducting the positive and negative electrodes of the adjacent two cylindrical lithium ion batteries, so that a plurality of cylindrical lithium ion batteries are connected in series, and the grouping of the cylindrical lithium ion batteries is realized.

[0034] When the cap assembly is loaded into the battery shell, the edge of the battery shell is folded inward and then is crimped on the sealing part 12, thereby completing the sealing of the battery shell. In the present application, in the vertical direction, the thickness of the sealing part 12 is T1, and the thickness of the explosion-proof sheet 2 is T2.

[0035] If T1 and T2 are set too large, when the edge of the battery shell is folded inward and crimped on the sealing part 12, the amount of edge covering decreases, thereby causing the sealing ability of the battery shell to decrease, and further causing the cylindrical lithium ion battery to easily have poor air tightness and liquid leakage.

[0036] If T1 and T2 are set too small, when the edge of the battery shell is folded inward and crimped on the sealing part 12, since the amount of edge covering is too large, the edge of the battery shell interferes with the welding protrusion 11 on the top cover plate 1, thereby affecting the sealing property of the sealing of the battery shell, and further causing the cylindrical lithium ion battery to have poor sealing property and to have the risk of liquid leakage. Meanwhile, T2 being too small causes the structural strength of the explosion-proof sheet 2 to be poor, and when a large amount of gas is generated in the battery shell, the explosion-proof sheet 2 cannot bear the gas pressure within the safety range, thereby causing the valve to open in advance and reducing the service life of the cylindrical lithium ion battery.

[0037] Therefore, in the present application, the thickness T1 of the sealing portion 12 is set to be between 0.3mm and 0.5mm, and the ratio T2 / T1 of the thickness T2 of the rupture disc 2 to the thickness T1 of the sealing portion 12 is set to be between 80% and 100%. When the cap assembly is installed in the battery shell, the amount of the edge of the battery shell folded inward and crimped on the edge of the sealing portion 12 is prevented from being too large or too small, and the structural strength of the rupture disc 2 is ensured, so that the sealing property of the cylindrical lithium ion battery is ensured, the safety performance of the cylindrical lithium ion battery is improved, the explosion-proof performance of the cylindrical lithium ion battery is ensured, and the service life of the cylindrical lithium ion battery is prolonged.

[0038] In the present embodiment, the numerical range of T1 and the range of T2 / T1 are defined, so that in actual implementation, the value of T1 and the value of T2 / T1 can be determined first, and then the value of T2 is obtained according to the value of T1 and the value of T2 / T1.

[0039] In the present embodiment, the numerical range of T2 of the rupture disc 2 is further limited to be between 0.25mm and 0.45mm, so that when the value of T1 and the value of T2 / T1 are determined, the value range of T2 should also be referred to, so that the value of T2 obtained according to the value of T1 and the value of T2 / T1 is within the range, so as to further ensure the structural strength of the rupture disc 2 and prolong the service life of the cylindrical lithium ion battery. Preferably, in the present application, the thickness T1 of the sealing portion 12 is set to be 0.4mm, and the ratio T2 / T1 of the thickness T2 of the rupture disc 2 to the thickness T1 of the sealing portion 12 is set to be 88%, that is, the thickness T2 of the rupture disc 2 is 0.35mm.

[0040] In the present embodiment, the top of the rupture disc 2 is provided with a rupture notch 21, that is, the side of the rupture disc 2 close to the pressure relief area 3 is provided with a rupture notch 21. When the cylindrical lithium ion battery generates thermal runaway, the pressure in the battery shell increases, and the rupture disc 2 is broken along the area where the rupture notch 21 is located, so as to relieve the pressure of the battery shell, thereby realizing the explosion-proof protection of the cylindrical lithium ion battery.

[0041] In the present application, in the vertical direction, the thickness of the rupture disc 2 at the rupture notch 21 is T3. In actual use, if the ratio T3 / T2 of T3 to T2 is too large, that is, T3 is too large, the opening pressure of the rupture disc 22 will be too large, and the rupture disc 22 can only be broken along the area where the rupture notch 2121 is located when the pressure in the battery shell exceeds the safe range, thereby affecting the explosion-proof performance of the cylindrical lithium ion battery.

[0042] If the ratio T3 / T2 of T3 to T2 is too small, i.e. T3 is too small, the burst pressure of the burst disc 22 will be too small, i.e. the burst disc 22 will be burst along the area where the burst score 2121 is located before the pressure in the battery case reaches the safety range, thus reducing the service life of the cylindrical lithium ion battery.

[0043] Therefore, in the present application, the ratio T3 / T2 of T3 to T2 is set to 32% to 50%, so that the burst pressure of the burst disc along the area where the burst score 21 is located is within the safety pressure range of the battery case, thus ensuring the burst performance of the cylindrical lithium ion battery and prolonging the service life of the cylindrical lithium ion battery.

[0044] Specifically, in actual implementation, the value of T2 has been determined in the foregoing embodiments, thus the value of T3 can be determined according to the range of T3 / T2 defined in the present embodiment, and the value of T3 can be obtained. Preferably, in the present application, T3 / T2 can be set to 43%.

[0045] In the present embodiment, the top of the burst disc 2 is further provided with a reinforcing boss 22, and the reinforcing boss 22 is arranged outside the burst score 21. In the present application, the burst disc 2 is formed by extruding the material at the position of the burst score 21, so that the reinforcing boss 22 is formed outside the burst score 21, thus the thickness of the burst disc 2 at the burst score 21 is smaller than the thickness of the burst disc 2, and the thickness of the burst disc 2 at the reinforcing boss 22 is greater than the thickness of the burst disc 2.

[0046] In the vertical direction, the thickness of the burst disc 2 at the reinforcing boss 22 is T4, i.e. T3 is smaller than T2, and T4 is greater than T2, the structural strength of the junction of the burst disc 2 and the burst score 21 is reinforced by the reinforcing boss 22, so that the burst disc 2 is preferentially burst along the burst score 21 under the internal pressure of the battery case, thus providing burst protection for the cylindrical lithium ion battery.

[0047] In actual use, if the ratio of T2 to T4 is too large, i.e. the extension height of the reinforcing boss 22 on the top of the burst disc 2 is small, the reinforcing effect of the reinforcing boss 22 on the junction of the burst disc 2 and the burst score 21 will be weakened, thus the burst pressure of the burst disc 2 along the area where the burst score 2121 is located is unstable, which affects the burst performance of the cylindrical lithium ion battery.

[0048] Since the burst disc 2 is formed by extruding the material at the position of the burst score 21, so that the reinforcing boss 22 is formed outside the burst score 21, if the ratio of T2 to T4 is too small, i.e. the extension height of the reinforcing boss 22 on the top of the burst disc 2 is large, it will be difficult to form the burst disc 2, thus increasing the production cost of the cylindrical lithium ion battery and reducing the production efficiency of the cylindrical lithium ion battery.

[0049] Therefore, in the present application, the ratio T2 / T4 of T2 to T4 is set to 62% to 78%, which not only ensures the reinforcing effect of the reinforcing boss 22 on the joint of the explosion-proof sheet 2 and the explosion-proof notch 21, thereby improving the explosion-proof performance of the cylindrical lithium ion battery, but also ensures that the material at the position of the explosion-proof notch 21 is extruded in the forming process of the explosion-proof sheet 2, thereby making the operation of forming the reinforcing boss 22 outside the explosion-proof notch 21 simple and convenient, easy to implement, improving the production efficiency of the cylindrical lithium ion battery, and reducing the production cost of the cylindrical lithium ion battery.

[0050] Specifically, in actual implementation, the value of T2 has been determined in the previous embodiments, so the value of T4 can be obtained by determining the value of T2 / T4 according to the range of T2 / T4 defined in the present embodiment. Preferably, in the present application, T2 / T4 can be set to 70%.

[0051] In actual implementation, the cover plate assembly is usually provided with a bottom cover plate welded at the bottom of the explosion-proof sheet 2, and the current collector plate is welded at one end of the cover plate assembly and the positive electrode pole of the battery cell at the other end, so that the cover plate assembly leads out the positive electrode of the battery cell. Therefore, in the present embodiment, the explosion-proof sheet 2 is provided with a welding boss 23 at the bottom, which extends downward at the bottom of the explosion-proof sheet 2 and is used for welding with the bottom cover plate.

[0052] In the present application, in the vertical direction, the thickness of the explosion-proof sheet 2 at the welding boss 23 is T5. In actual use, if the ratio T2 / T5 of T2 to T5 is too small, i.e., T2 is too small and T5 is too large, the structural strength of the explosion-proof sheet 2 will be poor, and when a large amount of gas is generated in the battery shell, the explosion-proof sheet 2 cannot withstand the gas pressure within the safety range, thereby opening the valve in advance and reducing the service life of the cylindrical lithium ion battery.

[0053] If the ratio T2 / T5 of T2 to T5 is too large, i.e., T2 is too large and T5 is too small, when the bottom plane of the welding boss 23 is welded with the bottom cover plate, the phenomenon of welding through will easily occur, thereby increasing the risk of liquid leakage of the cylindrical lithium ion battery and reducing the safety performance of the cylindrical lithium ion battery.

[0054] Therefore, in the present application, the ratio T2 / T5 of T2 to T5 is set to 60% to 80%, which not only ensures the structural strength of the explosion-proof sheet 2, thereby prolonging the service life of the cylindrical lithium ion battery, but also prevents the phenomenon of welding through when the welding boss 23 is welded with the bottom cover plate, thereby reducing the risk of liquid leakage of the cylindrical lithium ion battery and improving the safety performance of the cylindrical lithium ion battery.

[0055] Specifically, in actual implementation, the value of T2 has been determined in the foregoing embodiment, and thus the value of T5 can be determined according to the range of T2 / T5 defined in the present embodiment.

[0056] In the foregoing embodiment, it is mentioned that the forming of the rupture disc 2 is achieved by extruding the material at the position of the rupture score 21 to form the reinforcing boss 22 outside the rupture score 21. Therefore, in the present embodiment, the top of the rupture disc 2 is further provided with a transition boss 24, which is arranged between the rupture score 21 and the reinforcing boss 22 and serves to link the rupture score 21 and the reinforcing boss 22.

[0057] In the forming process of the rupture disc 2, the material at the position of the rupture score 21 is extruded to the position of the reinforcing boss 22 through the transition boss 24, so that the thickness T3 of the rupture disc 2 at the position of the rupture score 21 is less than the thickness T2 of the rupture disc 2, and the thickness T4 of the rupture disc 2 at the position of the reinforcing boss 22 is greater than the thickness T2 of the rupture disc 2. The reinforcing boss 22 strengthens the structural strength of the junction of the rupture disc 2 and the rupture score 21, so that the rupture disc 2 is preferentially burst along the rupture score 21 under the internal pressure of the battery shell, thereby protecting the cylindrical lithium ion battery from explosion.

[0058] In the present application, in the horizontal direction, the length of the transition boss 24 is L1, and the length of the reinforcing boss 22 is L2. If the ratio L1 / L2 of L1 to L2 is too small, i.e., L1 is too small and L2 is too large, it is difficult to control the flow of the material when the material at the position of the rupture score 21 is extruded to the reinforcing boss 22 through the transition boss 24 in the forming process of the rupture disc 2, thereby resulting in that the overall flatness of the rupture disc cannot be controlled, and further increasing the production cost of the cylindrical lithium ion battery and reducing the production efficiency of the cylindrical lithium ion battery.

[0059] If the ratio L1 / L2 of L1 to L2 is too large, i.e., L1 is too large and L2 is too small, the reinforcing boss 22 will affect the reinforcing effect on the junction of the rupture disc 2 and the rupture score 21, thereby resulting in that the opening pressure of the rupture disc 2 along the area where the rupture score 21 is located is unstable, and affecting the safety performance of the cylindrical lithium ion battery.

[0060] Therefore, in the present embodiment, the ratio L1 / L2 of L1 to L2 is set to be between 15% and 35%, which not only ensures that the operation of extruding the material at the position of the rupture score 21 to the reinforcing boss 22 through the transition boss 24 in the forming process of the rupture disc 2 is simple, convenient and easy to implement, thereby improving the production efficiency of the cylindrical lithium ion battery and reducing the production cost of the cylindrical lithium ion battery, but also ensures the reinforcing effect of the reinforcing boss 22 on the junction of the rupture disc 2 and the rupture score 21, thereby improving the safety performance of the cylindrical lithium ion battery.

[0061] In the present embodiment, in the horizontal direction, the length of the explosion-proof notch 21 to the axis of the explosion-proof sheet 2 is L3. Since L3 is the radius of the opening valve area of the explosion-proof sheet 2, the size of L3 is positively correlated with the effective opening valve area of the explosion-proof sheet 2. If the ratio of L2 to L3, L2 / L3, is too large, i.e. L2 is too large and L3 is too small, the effective opening valve area of the explosion-proof sheet 2 will be reduced, thereby affecting the pressure relief capacity of the explosion-proof sheet 2.

[0062] If the ratio of L2 to L3, L2 / L3, is too small, i.e. L2 is too small and L3 is too large, the reinforcing effect of the reinforcing boss 22 on the joint of the explosion-proof sheet 2 and the explosion-proof notch 21 will be weakened, thereby making the opening valve pressure unstable when the explosion-proof sheet 2 is punched open along the area where the explosion-proof notch 21 is located, and affecting the safety performance of the cylindrical lithium ion battery.

[0063] Therefore, in the present application, the ratio of L2 to L3, L2 / L3, is set to be between 12% and 22%, thereby ensuring the effective opening valve area of the explosion-proof sheet 2, enhancing the pressure relief capacity of the explosion-proof sheet 2, ensuring the reinforcing effect of the reinforcing boss 22 on the joint of the explosion-proof sheet 2 and the explosion-proof notch 21, and further improving the safety performance of the cylindrical lithium ion battery.

[0064] Specifically, in the present embodiment, in the horizontal direction, the length of the explosion-proof notch 21 to the axis of the explosion-proof sheet 2, L3, is in the range of 3mm to 7mm. Therefore, in actual implementation, the value of L3 can be determined first, and then the value of L2 / L3 can be determined from the value range of L2 / L3 defined in the above embodiment, so as to obtain the value of L2 according to the value of L2 / L3 and the determined value of L3.

[0065] After the value of L2 is determined, the value of L1 / L2 can be determined from the value range of L1 / L2 defined in the above embodiment, so as to obtain the value of L1 according to the value of L1 / L2 and the determined value of L2. Preferably, in the present application, the length of the explosion-proof notch 21 to the axis of the explosion-proof sheet 2, L3, can be set to 5mm, the ratio of L2 to L3, L2 / L3, can be set to 17%, and the ratio of L1 to L2, L1 / L2, can be set to 25%.

[0066] In the present embodiment, the angle between the welding protrusion 11 on both sides and the horizontal plane is A. In the above embodiment, it is mentioned that the welding protrusion 11 extending upward in the middle of the top cover plate 1 is used for welding with the bus bar during the battery grouping process. Specifically, in actual implementation, the welding protrusion 11 is formed on the top cover plate 1 by stamping.

[0067] If the included angle A between the two sides of the welding bump 11 and the horizontal plane is too small, the operation of stamping the welding bump 11 on the top cover plate 1 will be difficult to achieve, thereby increasing the production cost of the cylindrical lithium ion battery and reducing the production efficiency of the cylindrical lithium ion battery; if the included angle A between the two sides of the welding bump 11 and the horizontal plane is too large, the strength of the welding bump 11 will be poor, and in the welding process, the welding bump 11 is prone to deformation or collapse, thereby causing problems such as virtual welding, explosion point, etc. in the welding process, resulting in an increase in the welding failure rate and an increase in the production cost of the cylindrical battery.

[0068] Therefore, in the present application, the included angle A between the two sides of the welding bump 11 and the horizontal plane is set to 90°-140°, so that the operation of stamping the welding bump 11 on the top cover plate 1 is simple, convenient and easy to implement, the production efficiency of the cylindrical lithium ion battery is improved, and the structural strength of the welding bump 11 is ensured, thereby reducing the welding failure rate. Preferably, in the present application, the included angle A between the two sides of the welding bump 11 and the horizontal plane can be set to 90°.

[0069] In the embodiments of the present application, a cylindrical lithium ion battery is also provided, which comprises the cap assembly described above.

[0070] The above-described content can be implemented individually or in various combinations, and these variants are within the protection scope of the present application.

[0071] It should be noted that in this paper, relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment containing a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the element defined by the statement "including one" does not exclude the presence of another identical element in the process, method, article or equipment including the element.

[0072] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing embodiments, or make equivalent substitutions for part of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A cap assembly, characterized in that: The device includes an explosion-proof sheet (2) and a top cover plate (1). The top cover plate (1) includes an upwardly extending weld protrusion (11) and sealing portions (12) on both sides of the weld protrusion (11). The sealing portions (12) are stacked on top of the explosion-proof sheet (2). A pressure relief zone (3) is formed between the bottom of the weld protrusion (11) and the top of the explosion-proof sheet (2). In the vertical direction, the thickness T1 of the sealing portion (12) ranges from 0.3 mm to 0.5 mm, and the ratio T2 of the thickness T2 of the explosion-proof sheet (2) to the thickness T1 of the sealing portion (12) is 80%-100%.

2. A cap assembly as described in claim 1, characterized in that: In the vertical direction, the thickness T2 of the explosion-proof sheet (2) ranges from 0.25mm to 0.45mm.

3. A cap assembly as described in claim 1, characterized in that: The explosion-proof sheet (2) has an explosion-proof groove (21) on its top. In the vertical direction, the ratio of the thickness T3 of the explosion-proof sheet (2) at the explosion-proof groove (21) to the thickness T2 of the explosion-proof sheet (2) is 32% to 50%.

4. A cap assembly as described in claim 3, characterized in that: The explosion-proof sheet (2) has an upwardly extending reinforcing boss (22) at its top. The reinforcing boss (22) is located outside the explosion-proof groove (21). The ratio of the thickness T2 of the explosion-proof sheet (2) to the thickness T4 of the explosion-proof sheet (2) at the reinforcing boss (22) is 62% to 78%.

5. A cap assembly as described in claim 1, characterized in that: The bottom of the explosion-proof sheet (2) is provided with a downwardly extending welding boss (23). In the vertical direction, the ratio T2 of the thickness of the explosion-proof sheet (2) to the thickness T5 of the explosion-proof sheet (2) at the welding boss (23) is 60 to 80%.

6. A cap assembly as described in claim 4, characterized in that: A transition boss (24) is provided between the explosion-proof groove (21) and the reinforcing boss (22). In the horizontal direction, the ratio of the length L1 of the transition boss (24) to the length L2 of the reinforcing boss (22) is 15% to 35%.

7. A cap assembly as described in claim 6, characterized in that: In the horizontal direction, the ratio of the length L2 of the reinforcing boss (22) to the length L3 of the explosion-proof groove (21) to the central axis of the explosion-proof sheet (2) is 12% to 22%.

8. A cap assembly as described in claim 7, characterized in that: In the horizontal direction, the length L3 from the explosion-proof notch (21) to the central axis of the explosion-proof sheet (2) ranges from 3mm to 7mm.

9. A cap assembly as described in claim 1, characterized in that: The included angle A between the two sides of the welding protrusion (11) and the horizontal plane is 90° to 140°.

10. A cylindrical lithium-ion battery, characterized in that, Includes the cap assembly as described in any one of claims 1-9.

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