Cylindrical lithium battery

Abstract

The utility model provides a cylindrical lithium battery. The cylindrical lithium battery comprises a shell, a cap, a positive collector plate, a roll core and a negative collector plate, the positive electrode of the roll core is connected with the cap through the positive collector plate, and the negative electrode of the roll core is connected with the shell through the negative collector plate; wherein the cap is provided with an anti-explosion valve plate, and the anti-explosion valve plate is provided with a first nick and a second nick which are intersected; the positive collector plate comprises a plate body part and a tail part, the tail part comprises a bending part, a weakening part and a connecting part which are arranged in sequence, the weakening part is provided with at least one groove, the cross sectional area of the tail part at the deepest position of the groove is Sn, the cross sectional area of the tail part at the connecting part is Sc, and Sn / Sc is 45%-65%. By reasonably setting the cross sectional area of the groove, the positive collector plate can have enough mechanical strength and a relatively good short-circuit protection function. By arranging the first nick and the second nick which are intersected, the effect that the explosion-proof valve plate quickly responds to realize quick pressure relief in the battery is achieved.

Description

Technical Field

[0001] This application relates to the technical field of lithium batteries, and in particular to a cylindrical lithium battery. Background Art

[0002] Cylindrical batteries are usually encapsulated with a cylindrical steel shell. The bare battery core is made by a winding process to form a cylindrical winding core. The cap is located at the top of the battery and is connected to the positive electrode in the winding core through a positive current collector plate. In related technologies, a cylindrical lithium battery with a full tab structure includes components such as a metal shell, a winding core, and a cap. Among them, the winding core is cylindrical. After the tabs of its positive and negative electrodes are flattened, circular end faces with a flat cross-section are formed at both ends. Therefore, a positive current collector plate and a negative current collector plate can also be added to the positive and negative electrodes respectively. The full tab structure and the addition of the positive current collector plate and the negative current collector plate enable electrons to be transmitted longitudinally from the current collector to the current collector plate, and by increasing the current conduction area and shortening the current conduction distance, the charge and discharge performance of the cylindrical lithium battery can be effectively improved.

[0003] The existing positive current collector plate for cylindrical lithium batteries consists of a plate body part and a tail part. The plate body part is used to connect with the winding core, and the tail part is bent and connected to the cap. Since the battery core of a cylindrical lithium battery is prone to catching fire and exploding in case of a short circuit, and the tail of the existing positive current collector plate of the cylindrical lithium battery generally has a relatively wide width for better current guiding performance and convenient connection with the cap, lacking a short-circuit protection function. In order to have a better short-circuit protection function, a fusing area can be set at the tail of the positive current collector plate. However, if the size of the fusing area is not designed reasonably, on the one hand, it will reduce the mechanical strength of the tail of the current collector plate, increasing the risk of the tail breaking during the production process; on the other hand, there may also be adverse effects such as uncontrollable fusing current and uncontrollable fusing position in the fusing area, which is not conducive to the rapid passage of electrons, increasing the internal resistance of the battery and affecting the normal use of the battery. Therefore, for the positive current collector plate, how to ensure that the positive current collector plate has sufficient mechanical strength while also achieving a better short-circuit protection function; is an urgent problem to be solved at present.

[0004] In addition, cylindrical lithium batteries have good safety due to uniform stress and good heat dissipation performance. However, in actual use, due to improper use, internal defects, manufacturing processes, and other reasons, cylindrical lithium batteries may still have the safety risk of internal pressure imbalance. To avoid battery deformation, bulging, or even combustion or explosion, it is necessary to relieve the pressure inside the battery in a timely manner. For cylindrical batteries, the causes and locations of the internal gas generation are relatively complex. Therefore, the pressure distribution inside the battery is usually irregular. For example, in some cases, the gas pressure in the middle region of the battery rises rapidly and reaches the limit value, while in other cases, the gas pressure in the edge region inside the battery rises rapidly and reaches the limit value. Therefore, it can be understood that although the explosion-proof groove located at the periphery of the explosion-proof valve body can meet the requirement of bursting when the gas pressure in the edge region inside the battery rises and reaches the limit value, for the case where the gas pressure in the middle region inside the battery rises and reaches the limit value, the explosion-proof groove cannot immediately respond and break. As the gas continues to be generated inside the battery and the gas pressure in the edge region also reaches the limit value, the explosion-proof groove will break and the battery will relieve the pressure. Therefore, this kind of explosion-proof valve structure has certain potential safety hazards. Utility Model Content

[0005] The embodiments of the present application provide a cylindrical lithium battery to at least achieve the balance between the mechanical strength and short-circuit protection of the positive current collector plate in the cylindrical lithium battery, and the rapid response of the explosion-proof valve sheet to achieve rapid pressure relief inside the battery.

[0006] A cylindrical lithium battery provided by the embodiments of the present application includes: a housing, a cap, a positive current collector plate, a wound core, and a negative current collector plate. The positive electrode of the wound core is connected to the cap through the positive current collector plate, and the negative electrode of the wound core is connected to the housing through the negative current collector plate; wherein:

[0007] The cap includes an explosion-proof valve sheet and a terminal plate arranged in a stacked manner. Among them, the explosion-proof valve sheet is provided with a scoring component, and the scoring component includes a first score and a second score. The first score is a closed circle with its head and tail connected, and the second score is in the shape of a line segment. The first score intersects with the second score;

[0008] The positive current collector plate includes a plate body part and a tail. The tail includes a bent part, a weakened part, and a connecting part arranged in sequence. The bent part is connected to the plate body part, the plate body part is connected to the wound core, and the connecting part is connected to the terminal plate. At least one groove is provided in the weakened part. The cross-sectional area of the tail at the deepest position of the groove is Sn, and the cross-sectional area of the tail at the connecting part is Sc. Sn / Sc is 45%-65%.

[0009] The cylindrical lithium battery according to the embodiments of the present application has at least the following beneficial effects:

[0010] By reasonably setting the cross-sectional area of the groove, the positive current collector plate can have sufficient mechanical strength and a good short-circuit protection function. The explosion-proof valve plate is provided with intersecting first and second notches. The positions of the first notch and the second notch are different. When abnormal conditions such as overheating and short-circuit occur inside the battery, resulting in a sharp rise in the internal air pressure, when the air pressure at the position inside the battery corresponding to the first notch reaches the preset value first, the first notch breaks first. Since the first notch and the second notch intersect, the breakage of the first notch will drive the breakage of the second notch, thereby expanding the opening area of the explosion-proof valve plate and increasing the pressure relief speed. Since the first notch drives the second notch to break after the air pressure corresponding to the first notch reaches the preset value, it can be opened before the air pressure at the position corresponding to the second notch reaches the preset air pressure, expanding the pressure relief area and achieving rapid pressure relief. Similarly, when the air pressure inside the battery corresponding to the second notch reaches the preset value, the breakage of the second notch will also drive the breakage of the first notch, achieving the effect of rapid pressure relief. Since the positive current collector plate has requirements for mechanical strength, an explosion-proof valve plate is needed to reinforce it in terms of short-circuit protection. If the positive current collector plate has high mechanical strength, it may not fuse for a long time under the condition of high internal air pressure in the battery. At this time, if the positive current collector plate remains in a conducting state continuously, the internal pressure of the battery will continue to rise. Therefore, it is necessary to discharge the gas as soon as possible. At this time, the explosion-proof valve plate can achieve rapid pressure relief to ensure the safety of the cylindrical lithium battery.

[0011] In some alternative embodiments, the shape of the disk body part is a closed axisymmetric figure formed by sequentially connecting the first side, the arc, the second side, and the third side end to end. Both the first side and the second side are connected to one end of the tail. A first opening is provided at the center of the arc of the disk body part, and a second opening area is provided in the area of the disk body part other than the first opening. The second opening area is provided with at least two second openings. The area of the first opening is S1, and the opening area of the second opening area is S2. S2 / S1 is 0.9 - 1.5. The notch assembly is located on the side end face of the explosion-proof valve plate away from the positive current collector plate, and the explosion-proof valve plate is provided with a thinning part extending radially along the explosion-proof valve plate. The first opening and the second opening area of the disk body part provide a penetration channel for the electrolyte, improving the infiltration efficiency of the electrolyte. By reasonably controlling the areas of the first opening and the second opening area, it is ensured that the disk body part has sufficient weldable area with the core. Setting the notch assembly on the side end face facing away from the positive current collector plate helps to relieve pressure promptly and quickly. Setting a thinning part on the explosion-proof valve plate is beneficial to achieving rapid pressure relief inside the battery.

[0012] In some alternative embodiments, the length of the fourth side of the tail on the positive current collector plate, which is far from the disc body portion, from the third side is L1, the distance from the center position of the groove to the third side is L2, and L2 / L1 is 60%-80%; the first notch is provided within the range of the thinning portion, the depth of the first notch is D1, the thickness of the thinning portion is D2, and 30%≤D1 / D2≤60%. By setting the position of the groove on the tail, the fusing position can be predicted, improving the safety of the battery. If D1 / D2 is small, the depth of the first notch is shallow, while the remaining thickness of the thinning portion is deep. In this way, a relatively large pressure inside the battery is required for the first notch to break, that is, the pressure value for the explosion-proof valve piece to open is high, and the gas inside the battery cannot be released in time, increasing the safety risk; conversely, if D1 / D2 is large, the depth of the first notch is deep, while the remaining thickness of the thinning portion is thin. In this way, the pressure value for the explosion-proof valve piece to open is low, easily causing the explosion-proof valve piece to open accidentally. By controlling the ratio of D1 / D2, the threshold value of the pressure released inside the battery can be controlled, ensuring and improving the safety of the battery during use.

[0013] In some alternative embodiments, the tail includes a fifth side and a sixth side along the length direction of the tail. The two ends of the fifth side are respectively connected to the fourth side and the first side, the two ends of the sixth side are respectively connected to the fourth side and the second side, the included angle θ1 between the fifth side and the first side is 45-90°, and the included angle θ2 between the sixth side and the second side is 45-90°; chamfered portions are provided at the bottoms of the first notch and the second notch. The reasonable angle ranges between the fifth side and the first side, and between the sixth side and the second side help to balance the mechanical properties of the positive current collector plate and the size of the weldable area of the disc body portion. By providing chamfered portions at the bottoms of the first notch and the second notch, the stress concentration at the bottoms of the first notch and the second notch can be reduced, and the risk of the explosion-proof piece opening accidentally when the pressure value does not reach the preset value can be lowered.

[0014] In some alternative embodiments, the diameter of the first opening is D3, the diameter of the second opening is D4, and D4 / D3 is 50%-70%; the diameter of the arc is D5, the diameter of the core is D6, and D5 / D6 is 80%-95%; chamfered portions with the same radius R are provided at the bottoms of the first notch and the second notch. By reasonably setting the diameter parameter of the second opening, on the one hand, the weldable area is retained, and on the other hand, the infiltration effect of the electrolyte is improved. By reasonably setting the diameter sizes of the disc body portion and the core, the welding performance is helped to be improved. The radii of the chamfered portions of the first notch and the second notch are the same, which can reduce the design and manufacturing costs.

[0015] In some alternative embodiments, the area of the second opening is S3, and S3 / S1 is 0.3 - 0.5; the distance between the center of the first opening and the center of the second opening is L3, the diameter of the arc is D5, and L3 / D5 is 25% - 35%. In some embodiments, the range of L3 is 4.5 - 7 mm. Chamfered portions are provided at the bottoms of the first notch and the second notch, and the radius of the chamfered portion is R, and the length of R is 0.05 - 0.15 mm. By further defining the area relationship between the first opening and the second opening, it is ensured that both the first opening and the second opening can exert corresponding effects of improving penetration, while retaining a larger weldable area. Through the design of the spacing between the first opening and the second opening, firstly, the efficiency of electrolyte infiltration is improved, and secondly, the blockage of the second opening caused by the subsequent encapsulation process is avoided. If the radius of the chamfered portion is too small, the stress concentration at the bottoms of the first notch and the second notch cannot be effectively reduced; conversely, if the radius of the chamfered portion is too large, the processing difficulty of the mold will be too great, increasing the cost. By controlling the radius of the chamfered portion, the problems of mold processing difficulty and notch stress concentration can be balanced.

[0016] In some alternative embodiments, at the non-grooved position of the tail, the length of the cross-section of the tail along the width direction of the tail is L4, and at the grooved position of the tail, the length of the cross-section of the tail along the width direction of the tail is L5, 3L4 / 8 ≤ L5 ≤ 3L4 / 4; the first notch is circular in shape, both ends of the second notch are connected to the first notch, and the diameter of the first notch is equal to the length of the second notch. By reasonably designing the width of the tail at the groove, both ends of the second notch are connected to the first notch to balance the mechanical properties of the tail and the safety performance of the battery, reduce the risk of tail breakage, and improve the yield rate. Since the first notch is circular in shape, the second notch is in the shape of a line segment, both ends of the second notch are connected to the first notch, and the length of the second notch is the same as the diameter of the first notch, the second notch passes through the center of the first notch and bisects the first notch, which is convenient for processing.

[0017] In some alternative embodiments, the core includes a central shaft hole that communicates with both ends of the core along the central axis direction of the core. The diameter of the central shaft hole is D8. A first opening is provided at the center of the arc of the disk portion, and the diameter of the first opening is D3. The range of D3 / D8 is 1.4 - 1.8. The length of the at least one groove along the length direction of the tail is L6. At the non-groove position of the tail, the length of the cross-section of the tail along the width direction of the tail is L4, and 0 < L6 ≤ L4. The explosion-proof valve sheet is provided with a thinning portion extending radially along the explosion-proof valve sheet, and the thickness of the thinning portion is D2. The depth of the second notch is D7, and D2 < D7. If the diameter of the first opening is too small, it is not conducive to the infiltration of the liquid injection. If the diameter of the first opening is too large, the weldable area will be correspondingly reduced, restricting the welding process between the disk portion and the core. The size L6 of the groove along the length direction of the tail within a reasonable range helps to improve the safety of the battery. If L6 is too large, it is difficult to determine the fusing position of the tail, thereby increasing the safety risk of the battery. On the contrary, if L6 is too small, the fusing sensitivity of the tail increases, and there is a possibility of fusing under the safety current. By increasing the depth of the second notch, the influence of the increased thickness of the explosion-proof valve sheet body in the middle region on the second notch can be reduced to ensure that the explosion-proof valve sheet opens smoothly at the second notch.

[0018] In some alternative embodiments, the diameter of the arc is D5, and D3 / D5 is 25 - 35%. The shape of the disk portion is a closed axisymmetric figure formed by sequentially connecting a first side, an arc, a second side, and a third side end to end. Both the first side and the second side are connected to one end of the tail. The length of the fourth side of the tail on the positive current collector disk away from the disk portion from the third side is L1, and L1 / D5 is 85 - 95%. The depth of the middle part of the second notch is greater than the depth of the two ends of the second notch. A reasonable diameter range of the first opening first ensures a sufficient weldable area of the disk portion, while also improving the liquid injection efficiency and reducing potential risks during the production process. By reasonably designing the length of the tail, it helps to balance the production efficiency and safety performance of the battery. By setting the depth of the second notch such that the depth in the middle is greater than that at the two ends, that is, the depth of the second notch is deeper in the middle and shallower at the two ends, the influence of the stepped change in the thickness of the explosion-proof valve sheet body in the middle region can be reduced to ensure that the explosion-proof valve sheet opens smoothly at the second notch.

[0019] In some alternative embodiments, the line connecting the intersection point of the first side and the tail to the center of the arc is H1, the line connecting the intersection point of the second side and the tail to the center of the arc is H2, and the angle between H1 and H2 is θ3, where 40° ≤ θ3 ≤ 60°; on the weakening part, a first groove and a second groove are respectively provided at both ends along the same width direction of the tail. The line connecting the endpoint of the first groove close to the disc body to the center of the arc is H3, and the line connecting the endpoint of the second groove close to the disc body to the center of the arc is H4. The connection line of H3 and H4 forms an angle θ4. At the non-groove position of the tail, the length of the cross-section of the tail along the width direction of the tail is L4, and the diameter of the arc is D5, where 20° ≤ θ4 ≤ 40°, and L4 = D5 * sin. The angle design of θ3 ensures that the disc body still has a weldable area of more than 75% after the opening. The angle design of θ4 and the length design of L4 first ensure that the tail has sufficient mechanical strength to prevent breakage during the production process, while facilitating the rapid passage of electrons, reducing the internal resistance of the battery, and maximizing the retention of the weldable area on the disc body. Description of the Drawings

[0020] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments of the present application. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 is an overall structural schematic diagram of a cylindrical lithium battery provided by an embodiment of the present application;

[0022] Figure 2 is an exploded view of the cap, the positive current collector disc and the wound core provided by an embodiment of the present application;

[0023] Figure 3 is a cross-sectional schematic diagram of the cap provided by an embodiment of the present application;

[0024] Figure 4 is a top view schematic diagram of the explosion-proof valve sheet provided by an embodiment of the present application;

[0025] Figure 5 is a structural schematic diagram of the positive current collector disc provided by an embodiment of the present application;

[0026] Figure 6 is Figure 5 a sectional view along A - A' at the groove position of the tail in

[0027] Figure 7 is Figure 5Cross-sectional view along B-B' at the connection part position at the tail;

[0028] Figure 8 is Figure 5 Cross-sectional view along C-C' of the positive current collector plate in;

[0029] Figure 9 Is a bottom view schematic diagram of the positive current collector plate provided by the embodiment of the present application;

[0030] Figure 10 Is a structural schematic diagram of the positive current collector plate after being unfolded provided by the embodiment of the present application;

[0031] Figure 11 Is a structural schematic diagram of the positive current collector plate after being unfolded provided by the embodiment of the present application;

[0032] Figure 12 Is a top view schematic diagram of the core and the positive current collector plate provided by the embodiment of the present application;

[0033] Figure 13 Is a cross-sectional schematic diagram of the explosion-proof valve piece provided by the embodiment of the present application;

[0034] Figure 14 is Figure 13 Local schematic diagram at A in;

[0035] Figure 15 is Figure 13 Local schematic diagram at B in.

[0036] Reference numerals:

[0037] 110 - Housing;

[0038] 120 - Cap, 121 - Terminal board, 122 - Explosion-proof valve piece, 1221 - Scoring component, 1221a - First score, 1221b - Second score, 1222 - Thinning part;

[0039] 130 - Positive current collector plate, 131 - Plate body part, 1311 - First side, 1312 - Arc, 1313 - Second side, 1314 - Third side, 1315 - First opening, 1316 - Second opening, 132 - Tail, 1321 - Bending part, 1322 - Weakening part, 1322a - First groove, 1322b - Second groove, 1323 - Connection part, 1324 - Fourth side, 1325 - Fifth side, 1326 - Sixth side;

[0040] 140 - Core, 141 - Central axis hole;

[0041] 150 - Negative current collector plate. Detailed implementation manners

[0042] The embodiments of the present embodiment will be described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present embodiment, and should not be construed as a limitation to the present embodiment.

[0043] In the description of the present embodiment, it should be understood that with respect to the orientation description, such as the orientation or positional relationship indicated by up, down, front, back, left, right, etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present embodiment and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present embodiment.

[0044] In the description of the present embodiment, the meaning of several is one or more, the meaning of multiple is two or more. Understandings such as greater than, less than, exceeding, etc. do not include the present number, and understandings such as above, below, within, etc. include the present number. If there is a description of first and second, it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0045] In the description of the present embodiment, unless otherwise clearly defined, words such as setting, installing, connecting, etc. should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above words in the present embodiment in combination with the specific content of the technical solution.

[0046] The following will be combined with Figures 1 to 7 to describe in detail the cylindrical lithium battery provided by the embodiments of the present application. Figure 1 is a schematic diagram of the overall structure of a cylindrical lithium battery provided by the embodiments of the present application, Figure 2 is an exploded view of the cap 120, the positive current collector plate and the wound core 140 provided by the embodiments of the present application, Figure 3 is a schematic cross-sectional view of the cap provided by the embodiments of the present application, Figure 4 is a top view schematic diagram of the explosion-proof valve sheet provided by the embodiments of the present application, Figure 5 is a schematic diagram of the structure of the positive current collector plate provided by the embodiments of the present application, Figure 6 is Figure 5 a cross-sectional view along A-A' at the groove position of the tail 132 in Figure 7 is Figure 5 a cross-sectional view along B-B' at the connection position of the tail 132 in Figure 8 is Figure 5 a cross-sectional view along C-C' of the positive current collector plate in

[0047] The cylindrical lithium battery provided by the embodiment of the present application includes a housing 110, a cap 120, a positive current collector plate 130, a wound core 140, and a negative current collector plate 150. The positive electrode of the wound core 140 is connected to the cap 120 through the positive current collector plate 130, and the negative electrode of the wound core 140 is connected to the housing 110 through the negative current collector plate 150, for example, electrically connected.

[0048] The cap 120 includes an explosion-proof valve plate 122 and a terminal plate 121 arranged in a stacked manner. Among them, the explosion-proof valve plate 122 is provided with a scoring component 1221, and the scoring component 1221 includes a first score 1221a and a second score 1221b. The first score 1221a is a closed figure with its head and tail connected, and the first score 1221a is preferably a closed circle. The second score 1221b is in the shape of a line segment, and the first score 1221a intersects the second score 1221b.

[0049] The positive current collector plate 130 includes a plate body part 131 and a tail part 132. The tail part 132 includes a bent part 1321, a weakened part 1322, and a connecting part 1323 arranged in sequence. The bent part 1321 is connected to the plate body part 131, the plate body part 131 is connected to the wound core 140, and the connecting part 1323 is connected to the terminal plate 121. At least one groove 1322a is provided in the weakened part 1322. The cross-sectional area of the tail part 132 at the deepest position of the groove 1322a is Sn, and the cross-sectional area of the tail part 132 at the connecting part 1323 is Sc. Sn / Sc is 45%-65%. In some embodiments, Sn / Sc is specifically 45%, 50%, 55%, 60%, 65%, etc., without limitation.

[0050] By reasonably setting the cross-sectional area of the groove, the positive current collector plate 130 can have sufficient mechanical strength and a good short-circuit protection function. The first notch 1221a and the second notch 1221b are provided on the explosion-proof valve plate 122, and the positions of the first notch 1221a and the second notch 1221b are different. When abnormal conditions such as overheating and short-circuit occur inside the battery, resulting in a sharp rise in the internal air pressure, when the air pressure at the position inside the battery corresponding to the first notch 1221a reaches the preset value first, the first notch 1221a breaks first. Since the first notch 1221a and the second notch 1221b intersect, the breakage of the first notch 1221a will drive the breakage of the second notch 1221b, thereby expanding the opening area of the explosion-proof valve plate 122 and increasing the pressure relief speed. Since the breakage of the first notch 1221a drives the breakage of the second notch 1221b after the air pressure corresponding to the first notch 1221a reaches the preset value, it can be opened before the air pressure corresponding to the second notch 1221b reaches the preset pressure, expanding the pressure relief area and achieving rapid pressure relief. Similarly, when the air pressure inside the battery corresponding to the second notch 1221b reaches the preset value, the breakage of the second notch 1221b will also drive the breakage of the first notch 1221a, achieving the effect of rapid pressure relief. Since the positive current collector plate has requirements for mechanical strength, an explosion-proof valve plate is needed to reinforce the short-circuit protection. If the positive current collector plate has high mechanical strength, it may not fuse for a long time when the internal air pressure of the battery is high. At this time, if the positive current collector plate remains in a conductive state continuously, the internal pressure of the battery will continue to rise. Therefore, it is necessary to discharge the gas as soon as possible. At this time, the explosion-proof valve plate can achieve rapid pressure relief and ensure the safety of the cylindrical lithium battery during use.

[0051] It can be understood that if the first notch 1221a and the second notch 1221b are not connected, they may only break separately and form a gap for pressure relief, and the pressure relief effect is not good, and the purpose of quickly and effectively relieving the pressure of the battery proposed in this application cannot be achieved. Therefore, in the embodiments of the present application, the first notch 1221a and the second notch 1221b that constitute the notch assembly 1221 are set to be connected, that is, they intersect. Therefore, after any one of them breaks, it can extend to the other, causing the other to break. Therefore, the opening area of the explosion-proof valve plate 122 can be expanded, thereby quickly relieving the pressure of the battery.

[0052] In some embodiments, please refer to Figure 9 and Figure 10 , Figure 9 is a bottom view schematic diagram of the positive current collector plate 130, Figure 10It is a schematic structural diagram after the positive current collector disk is unfolded. The shape of the disk body part 131 is a closed axisymmetric figure formed by sequentially connecting the first side 1311, the arc 1312, the second side 1313, and the third side 1314 end to end. Both the first side 1311 and the second side 1313 are connected to one end of the tail part 132. It should be noted that the third side 1314 is for the convenience of describing the disk body part 131, and there is no such side in the actual product. Therefore, Figure 10 It is marked with a dotted line for distinction.

[0053] A first opening 1315 is provided at the center of the arc 1312 of the disk body part 131. The center of the first opening 1315 coincides with the center of the arc 1312. A second opening area is provided in the area of the disk body part 131 other than the first opening 1315. At least two second openings 1316 are provided in the second opening area. The multiple second openings 1316 in the second opening area are an axisymmetric figure as a whole, and the distance from the center of each second opening 1316 to the center of the arc 1312 is equal.

[0054] The area of the first opening 1315 is S1, and the opening area of the second opening area is S2, that is, S2 is the sum of the areas of multiple second openings 1316, only the sum of the opening areas is considered, and the area of the disk body part 131 in the second opening area is not counted. S2 / S1 is 0.9 - 1.5. The first opening 1315 and the second opening area of the disk body part 131 provide a penetration channel for the electrolyte, improving the infiltration efficiency of the electrolyte. By reasonably controlling the areas of the first opening 1315 and the multiple openings in the second opening area, it is ensured that the disk body part 131 has sufficient weldable areas with the winding core 140. In some embodiments, S2 / S1 can be 0.9, 1.1, 1.3, 1.5, etc., and there is no specific limitation.

[0055] In some embodiments, the scoring component 1221 is located on the end face of the explosion-proof valve sheet 122 away from the positive current collector disk 130. Setting the scoring component 1221 on the end face facing away from the positive current collector disk 130 helps to relieve pressure quickly and promptly. Please refer to Figure 13 , Figure 13 It is a cross-sectional schematic diagram of the explosion-proof valve sheet 122. The explosion-proof valve sheet 122 is provided with a thinning part 1222 extending radially along the explosion-proof valve sheet 122. It can be understood that the explosion-proof valve sheet 122 also needs to be designed with a certain thickness to meet the strength requirements for connection and assembly. If the thickness of the explosion-proof valve sheet 122 is too large, it is not conducive to the opening of the explosion-proof valve sheet 122. Therefore, a thinning part 1222 is provided on the explosion-proof valve sheet 122 to facilitate the rapid opening of the explosion-proof valve sheet 122 and realize rapid pressure relief inside the battery.

[0056] In some embodiments, please refer to Figure 10 and Figure 11 , Figure 10and Figure 11 are both structural schematic diagrams after the positive current collector plate 130 is unfolded. On the positive current collector plate 130, the length of the fourth side 1324 of the tail 132 away from the plate body 131 is L1, and the distance from the center position of the groove to the third side 1314 is L2, and L2 / L1 is 60%-80%. In some embodiments, the range of L2 is 8-18 mm. It can be understood that the length of L1, after the positive current collector plate 130 is unfolded, is as shown in Figure 10 , and is the length along the tail 132. After the positive current collector plate 130 is assembled into the battery, the positive current collector plate 130 is bent at the bending part 1321. The length of L1 does not refer to the straight-line distance from the fourth side 1324 to the third side 1314, but is measured along the solid part of the tail 132 in the bending manner. That is, L1 is the distance from the fourth side 1324 to the third side 1314 after the positive current collector plate 130 assembled into the cylindrical lithium battery is disassembled and unfolded. Please refer to Figure 14 , Figure 14 is Figure 13 a partial schematic diagram of the A position in

[0057] In some embodiments, the tail 132 includes a fifth side 1325 and a sixth side 1326 along the length direction of the tail 132. The two ends of the fifth side 1325 are respectively connected to the fourth side 1324 and the first side 1311, and the two ends of the sixth side 1326 are respectively connected to the fourth side 1324 and the second side 1313. The included angle θ1 between the fifth side 1325 and the first side 1311 is 45-90°, and the included angle θ2 between the sixth side 1326 and the second side 1313 is 45-90°. Please refer to Figure 15 , Figure 15 isFigure 13 Partial schematic diagram at B in the figure. Chamfered portions are provided at the bottoms of the first notch 1221a and the second notch 1221b. The reasonable angular ranges between the fifth side 1325 and the first side 1311, and between the sixth side 1326 and the second side 1313 contribute to balancing the mechanical properties of the positive current collector plate 130 and the area size of the weldable region of the plate body 131. By providing chamfered portions at the bottoms of the first notch 1221a and the second notch 1221b, stress concentration at the bottoms of the first notch 1221a and the second notch 1221b can be reduced, and the risk of accidental opening of the explosion-proof film when the pressure value does not reach the preset value can be lowered.

[0058] In some embodiments, the diameter of the first opening 1315 is D3, the diameter of the second opening 1316 is D4, and D4 / D3 is 50%-70%. In some embodiments, the range of D4 is 2-4.8 mm. The diameter of the arc 1312 is D5, and the diameter of the core 140 is D6, and D5 / D6 is 80%-95%. Chamfered portions with the same radius R are provided at the bottoms of both the first notch 1221a and the second notch 1221b. By reasonably setting the diameter parameter of the second opening 1316, on the one hand, the area of the weldable region is retained, and on the other hand, the wetting effect of the electrolyte is improved. By reasonably setting the diameter sizes of the plate body 131 and the core 140, the welding performance is helped to be improved. The same radius of the chamfered portions of the first notch 1221a and the second notch 1221b can reduce the design and manufacturing costs.

[0059] In some embodiments, the arc 1312 is 3 / 5-9 / 10 of a full circle, the diameter D5 of the arc 1312 is equal to the diameter of the plate body 131, and the size of the diameter D5 of the arc 1312 is, for example, 15-23 mm. The arc 1312 within the preferred diameter range ensures a large contact area between the plate body 131 and the core 140, an increase in the weldable region, and an expansion of the adaptation range of the wire bonding length and shape.

[0060] In some embodiments, the area of the second opening 1316 is S3, and S3 / S1 is 0.3 - 0.5; the distance between the center of the first opening 1315 and the center of the second opening 1316 is L3, the diameter of the arc 1312 is D5, and L3 / D5 is 25% - 35%; chamfered portions are provided at the bottoms of the first notch 1221a and the second notch 1221b, the radius of the chamfered portion is R, and the length of R is 0.05 - 0.15 mm. More preferably, the length of R is 0.05 mm - 0.1 mm. By further defining the area relationship between the first opening 1315 and the second opening 1316, it is ensured that both the first opening 1315 and the second opening 1316 can exert corresponding effects on improving penetration, while retaining a larger weldable area. Through the design of the spacing between the first opening 1315 and the second opening 1316, firstly, the efficiency of electrolyte infiltration is improved, and secondly, the subsequent encapsulation process is prevented from blocking the second opening 1316. If the radius of the chamfered portion is too small, the stress concentration at the bottoms of the first notch 1221a and the second notch 1221b cannot be effectively reduced; conversely, if the radius of the chamfered portion is too large, the processing difficulty of the mold will be too great, increasing the cost. By controlling the radius of the chamfered portion, the problems of mold processing difficulty and notch stress concentration can be balanced.

[0061] In some embodiments, at the non-groove position of the tail 132, the length of the cross-section of the tail 132 in the width direction of the tail 132 is L4, and at the groove position of the tail 132, the length of the cross-section of the tail 132 in the width direction of the tail 132 is L5, and 3L4 / 8 ≤ L5 ≤ 3L4 / 4; the first notch 1221a is circular in shape, both ends of the second notch 1221b are connected to the first notch 1221a, and the diameter of the first notch 1221a is equal to the length of the second notch 1221b. By reasonably designing the width of the tail 132 at the groove, both ends of the second notch 1221b are connected to the first notch 1221a to balance the mechanical properties of the tail 132 and the safety performance of the battery, reduce the risk of breakage of the tail 132, and improve the yield rate. Since the first notch 1221a is circular in shape and the second notch 1221b is in a line segment shape, both ends of the second notch 1221b are connected to the first notch 1221a, and the length of the second notch 1221b is the same as the diameter of the first notch 1221a, the second notch 1221b passes through the center of the first notch 1221a and bisects the first notch 1221a, which is convenient for processing.

[0062] It can be understood that the shape of the notch assembly 1221 formed by the first notch 1221a and the second notch 1221b is generally similar to the letter "θ". Thus, 2 D-shaped bursting surfaces and 1 O-shaped bursting surface are formed on the explosion-proof sheet body 100.

[0063] In some embodiments, the centers of the first notch 1221a and the explosion-proof valve piece 122 coincide. After such an arrangement, it can be understood that the position of the first notch 1221a is relative to the second notch 1221b. The first notch 1221a is located on the periphery of the explosion-proof valve piece 122 and is circular in shape, while the second notch 1221b is located on the inner periphery of the explosion-proof valve piece 122. Such a position design can better handle the problem that the pressure on the inner and outer perimeters of the battery is too high and cannot be relieved in time.

[0064] In some embodiments, the cross-sectional shapes of the first notch 1221a and the second notch 1221b are trapezoidal in reverse, rectangular, or V-shaped, which is convenient for processing and forming and has a low cost.

[0065] In some embodiments, the cross-sectional shapes of the first notch 1221a and the second notch 1221b are the same, so as to ensure that the fracture patterns of the first notch 1221a and the second notch 1221b are consistent and can be smoothly opened when the pressure reaches the preset value.

[0066] In some embodiments, please refer to Figure 12 , Figure 12 is a top view schematic diagram of the core 140 and the positive current collector plate 130. The core 140 includes a central shaft hole 141, and the central shaft hole 141 communicates with both ends of the core 140 along the central axis direction of the core 140. The diameter of the central shaft hole 141 is D8. A first opening 1315 is provided at the center of the arc 1312 of the disk body portion 131, and the diameter of the first opening 1315 is D3. The range of D3 / D8 is 1.4 - 1.8. The length of at least one groove 1322a along the length direction of the tail portion 132 is L6. At the non-groove position of the tail portion 132, the length of the cross-section of the tail portion 132 along the width direction of the tail portion 132 is L4, and 0 < L6 ≤ L4; the explosion-proof valve piece 122 is provided with a thinning portion 1222 extending radially along the explosion-proof valve piece 122, the thickness of the thinning portion 1222 is D2, and the depth of the second notch 1221b is D7, and D2 < D7. If the diameter of the first opening 1315 is too small, it is not conducive to the infiltration of the injection liquid; if the diameter of the first opening 1315 is too large, the weldable area is correspondingly reduced, restricting the welding process between the disk body portion 131 and the core 140. The dimension L6 of the groove along the length direction of the tail portion 132 within a reasonable range helps to improve the safety of the battery. If L6 is too large, it is difficult to determine the fusing position of the tail portion 132, thereby increasing the safety risk of the battery; conversely, if L6 is too small, the fusing sensitivity of the tail portion 132 increases, and there is a possibility of fusing under the safety current. By increasing the depth of the second notch 1221b, the influence of the increased thickness of the main body of the explosion-proof valve piece 122 in the middle region on the second notch 1221b can be reduced to ensure that the explosion-proof valve piece 122 is smoothly opened at the second notch 1221b.

[0067] In some embodiments, the diameter D8 of the central shaft hole 141 is 4 - 8 mm. Within this diameter range, the central shaft hole 141 can achieve a balance between the liquid injection efficiency and the weldable area, while ensuring the safety of welding. If the diameter D8 of the central shaft hole 141 is too small, it is not conducive to the infiltration of liquid injection; if the diameter D8 of the central shaft hole 141 is too large, the weldable area will be correspondingly reduced, restricting the welding process between the disk body portion 131 and the core 140.

[0068] In some embodiments, the diameter of the arc 1312 is D5, and D3 / D5 is 25 - 35%; the length of the fourth side 1324 of the tail 132 on the positive current collector disk 130 away from the disk body portion 131 from the third side 1314 is L1, and L1 / D5 is 85 - 95%; the depth of the middle part of the second notch 1221b is greater than the depth of the two ends of the second notch 1221b. In some embodiments, the range of L1 is 12 - 20 mm. The reasonable diameter range of the first opening 1315 first ensures a sufficient weldable area of the disk body portion 131, while also improving the liquid injection efficiency and reducing potential risks during the production process. By reasonably designing the length of the tail 132, it helps to balance the production efficiency and safety performance of the battery. By setting the depth of the second notch 1221b such that the depth of the middle part is greater than the depth of the two ends, that is, the depth of the second notch 1221b is deeper in the middle and shallower at the two ends, the influence of the thickness step change of the explosion-proof valve sheet 122 body in the middle region can be reduced to ensure that the explosion-proof valve sheet 122 opens smoothly at the second notch 1221b.

[0069] In some embodiments, the line connecting the intersection point of the first side 1311 and the tail 132 to the center of the arc 1312 is H1, the line connecting the intersection point of the second side 1313 and the tail 132 to the center of the arc 1312 is H2, and the included angle between H1 and H2 is θ3, where 40° ≤ θ3 ≤ 60°, and more preferably 40° ≤ θ3 ≤ 60; on the weakening portion 1322, a first groove 1322a and a second groove 1322b are respectively provided at both ends along the same width direction of the tail 132. The line connecting the endpoint of the first groove 1322a close to the disk body portion 131 to the center of the arc 1312 is H3, and the line connecting the endpoint of the second groove 1322b close to the disk body portion 131 to the center of the arc 1312 is H4. The connection line of H3 and H4 forms an included angle θ4. At the non-groove position of the tail 132, the length of the cross-section of the tail 132 along the width direction of the tail 132 is L4, and the diameter of the arc 1312 is D5, where 20° ≤ θ4 ≤ 40°, and L4 = D5 * sin4 / 2. The angle design of θ3 ensures that the disk body portion 131 still has a weldable area of more than 75% after the opening. The angle design of θ4 and the length design of L4 first ensure that the tail 132 has sufficient mechanical strength to prevent breakage during the production process, while facilitating the rapid passage of electrons, reducing the internal resistance of the battery, and maximizing the retention of the weldable area on the disk body portion 131.

[0070] In the description of this specification, the descriptions referring to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this implementation. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0071] Although the embodiments of this implementation have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of this implementation. The scope of this implementation is defined by the claims and their equivalents.

Claims

1. A cylindrical lithium battery, characterized in that: The invention comprises a housing (110), a cap (120), a positive electrode current collecting disk (130), a winding core (140), and a negative electrode current collecting disk (150), wherein the positive electrode of the winding core (140) is connected to the housing (110) through the positive electrode current collecting disk (130), and the negative electrode of the winding core (140) is connected to the housing (110) through the negative electrode current collecting disk (150); The cap (120) comprises an explosion-proof valve sheet (122) and a terminal plate (121) which are stacked, wherein the explosion-proof valve sheet (122) is provided with a notch assembly (1221), and the notch assembly (1221) comprises a first notch (1221a) and a second notch (1221b), wherein the first notch (1221a) is a closed circle connected at both ends, and the second notch (1221b) is a line segment, and the first notch (1221a) and the second notch (1221b) intersect; The positive electrode current collecting disk (130) comprises a disk body (131) and a tail (132); the tail (132) comprises a bending portion (1321), a weakened portion (1322) and a connecting portion (1323) which are arranged in sequence; the bending portion (1321) is connected to the disk body (131); the disk body (131) is connected to the winding core (140); the connecting portion (1323) is connected to the terminal plate (121); at least one groove (1322a) is provided in the weakened portion (1322); the cross-sectional area of ​​the tail (132) at the deepest position of the groove (1322a) is Sn; the cross-sectional area of ​​the tail (132) at the connecting portion (1323) is Sc; Sn / Sc is 45%-65%.

2. The cylindrical lithium battery according to claim 1, characterized in that: The disk body (131) is in the shape of a closed axisymmetric figure consisting of a first side (1311), an arc (1312), a second side (1313) and a third side (1314) connected end to end in sequence, wherein the first side (1311) and the second side (1313) are both connected to one end of the tail portion (132); a first opening (1315) is provided at the center of the arc (1312) of the disk body (131), and a portion of the disk body (131) other than the first opening (1315) is provided with a first opening (1315). ) is provided with a second opening area, the second opening area is provided with at least two second openings (1316), the area of ​​the first opening (1315) is S1, the opening area of ​​the second opening area is S2, and S2 / S1 is 0.9-1.5; the notch assembly (1221) is located on a side end surface of the explosion-proof valve plate (122) away from the positive electrode current collecting disk (130), and the explosion-proof valve plate (122) is provided with a thinning portion (1222) extending radially along the explosion-proof valve plate (122).

3. The cylindrical lithium battery according to claim 2, characterized in that: The length of the fourth side (1324) of the tail (132) on the positive electrode current collecting disk (130) away from the disk body (131) from the third side (1314) is L1, the distance between the center position of the groove (1322a) and the third side (1314) is L2, and L2 / L1 is 60%-80%; the first notch (1221a) is arranged within the range of the thinning portion (1222), the depth of the first notch (1221a) is D1, the thickness of the thinning portion (1222) is D2, and 30%≤D1 / D2≤60%.

4. The cylindrical lithium battery according to claim 3, characterized in that: The tail portion (132) comprises a fifth side (1325) and a sixth side (1326) along the length direction of the tail portion (132); two ends of the fifth side (1325) are respectively connected to the fourth side (1324) and the first side (1311); two ends of the sixth side (1326) are respectively connected to the fourth side (1324) and the second side (1313); an angle θ1 between the fifth side (1325) and the first side (1311) is 45-90°; an angle θ2 between the sixth side (1326) and the second side (1313) is 45-90°; and chamfered portions are provided at the bottoms of the first notch (1221a) and the second notch (1221b).

5. The cylindrical lithium battery according to any one of claims 2 to 4, characterized in that: The diameter of the first opening (1315) is D3, the diameter of the second opening (1316) is D4, and D4 / D3 is 50%-70%; the diameter of the arc (1312) is D5, the diameter of the winding core (140) is D6, and D5 / D6 is 80%-95%; the bottoms of the first notch (1221a) and the second notch (1221b) are both provided with chamfered portions, and the radii R of the chamfered portions are the same.

6. The cylindrical lithium battery according to any one of claims 2 to 4, characterized in that: The area of ​​the second opening (1316) is S3, and S3 / S1 is 0.3-0.5; the distance from the center of the first opening (1315) to the center of the second opening (1316) is L3, the diameter of the arc (1312) is D5, and L3 / D5 is 25%-35%; the bottoms of the first notch (1221a) and the second notch (1221b) are both provided with chamfered portions, the radius of the chamfered portions is R, and the length of R is 0.05-0.15 mm.

7. The cylindrical lithium battery according to any one of claims 1 to 4, characterized in that: At the non-groove position of the tail (132), the length of the cross section of the tail (132) along the width direction of the tail (132) is L4, and at the groove position of the tail (132), the length of the cross section of the tail (132) along the width direction of the tail (132) is L5, 3L4 / 8≤L5≤3L4 / 4; the first notch (1221a) is circular, both ends of the second notch (1221b) are connected to the first notch (1221a), and the diameter of the first notch (1221a) is equal to the length of the second notch (1221b).

8. The cylindrical lithium battery according to any one of claims 1 to 4, characterized in that: The winding core (140) comprises a central axis hole (141), wherein the central axis hole (141) connects two ends of the winding core (140) along the central axis direction of the winding core (140), and the diameter of the central axis hole (141) is D8. A first opening (1315) is provided at the center of the circular arc (1312) of the disk body (131), and the diameter of the first opening (1315) is D3, and the range of D3 / D8 is 1.4-1.8; the at least one groove (13 22a) the length of the tail portion (132) along the length direction is L6, and at the non-groove position of the tail portion (132), the length of the cross section of the tail portion (132) along the width direction of the tail portion (132) is L4, 0<L6≤L4; the explosion-proof valve plate (122) is provided with a thinning portion (1222) extending radially along the explosion-proof valve plate (122), the thickness of the thinning portion (1222) is D2, and the depth of the second notch (1221b) is D7, D2<D7.

9. The cylindrical lithium battery according to claim 8, characterized in that: The diameter of the circular arc (1312) is D5, and D3 / D5 is 25-35%; the shape of the disk body (131) is a closed axially symmetrical figure composed of a first side (1311), a circular arc (1312), a second side (1313) and a third side (1314) connected end to end in sequence, the first side (1311) and the second side (1313) are both connected to one end of the tail (132); the length of the fourth side (1324) of the tail (132) on the positive electrode current collecting disk (130) away from the disk body (131) from the third side (1314) is L1, and L1 / D5 is 85-95%; the depth of the middle part of the second notch (1221b) is greater than the depth of the two ends of the second notch (1221b).

10. The cylindrical lithium battery according to any one of claims 2 to 4, characterized in that: A line connecting the intersection of the first side (1311) and the tail (132) and the center of the arc (1312) is H1, a line connecting the intersection of the second side (1313) and the tail (132) and the center of the arc (1312) is H2, an angle between H1 and H2 is θ3, 40°≤θ3≤60°; a first groove (1322a) and a second groove (1322b) are respectively provided at two ends of the weakened portion (1322) along the same width direction of the tail (132), the first groove (1322a) being close to the A line connecting one end point of the disk body (131) and the center point of the circular arc (1312) is H3, a line connecting one end point of the second groove (1322b) close to the disk body (131) and the center point of the circular arc (1312) is H4, and a line connecting H3 and H4 forms an angle θ4. At a non-groove position of the tail (132), a length of a cross section of the tail (132) along the width direction of the tail (132) is L4, and a diameter of the circular arc (1312) is D5, 20°≤θ4≤40°, and L4=D5*sin(θ4 / 2).

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