Round lithium battery and associated manufacturing process

Abstract

A round lithium battery comprising a housing, a battery cell, a positive terminal battery cover plate assembly, and a negative terminal battery cover plate assembly, wherein the housing is a metallic round tube, the battery cell being located inside the housing and comprising a positive terminal foil, a negative terminal foil, and a separating membrane, wherein the positive terminal foil and the negative terminal foil are separated from each other by the separating membrane and then rolled into a cylinder, characterized in that At the upper end of the positive terminal foil, several positive terminal tabs are provided spaced apart from one another; wherein at the lower end of the battery cell, the positive terminal foil, the separating membrane and the negative terminal foil, whose lengths are in ascending order, do not meet flush, wherein an extension part of the negative terminal foil covers the lower end of the battery in such a way that it is pressed against it and is separated from the positive terminal foil by the separating membrane; the positive terminal battery cover plate assembly comprises a disc-shaped positive terminal battery cover plate and a seal, wherein the seal is ring-shaped, arranged around the circumference of the positive terminal battery cover plate and firmly connected to the positive terminal battery cover plate, wherein a safety valve is provided on the positive terminal battery cover plate, and wherein the positive terminal tabs are electrically connected to the positive terminal battery cover plate; The negative terminal battery cover plate assembly comprises a current collector, a negative terminal battery cover plate, and a current collector holder, wherein the current collector holder is an annular element having a recess on one side, wherein the current collector has a current collector body and a current collector connection section, wherein the current collector body is rigidly connected to the upper region of the current collector holder, wherein the current collector connection section is located on the recessed side of the annular element and is rigidly connected to the cover plate, wherein the current collector connection section has a flexible curved structure such that the cover plate is located below the current collector holder in the assembled state, and wherein the current collector body is electrically connected to the extension part of the negative terminal foil.

Description

TECHNICAL AREA

[0001] The present invention relates to a lithium-ion battery, specifically a cylindrical lithium-ion battery and an associated manufacturing method, in particular a round lithium battery designed for use as a traction battery. STATE OF THE ART

[0002] With the ongoing development of the new energy sector, lithium-ion batteries are finding application in various electric vehicles. Due to the high discharge current of a traction battery, the generation of gas by the internal electrolyte during use leads to increased internal pressure, which in turn increases susceptibility to safety risks. To reduce heat generation during battery operation, a flat-plate electrode termination was developed. In this design, a positive and a negative electrode plate extend from the top and bottom of a battery cell, respectively, forming a flat plate. This plate is then flattened and welded onto a current collector plate to reduce electrical resistance and heat generation at the termination point.However, such a design makes electrolyte filling more difficult and impairs the electrolyte filling and battery formation.

[0003] Chinese invention application CN110600795A discloses a cylindrical lithium-ion battery. It comprises a battery cell, a housing, and a current collector disc. The height of the battery cell is less than that of the housing. The housing is cylindrical, and the battery cell is located inside it. A tab is provided at each of the two ends of the battery cell. One end is designated as a positive terminal tab, and the other as a negative terminal tab. The end surface of the battery cell tab is designed as an annular stepped surface. An annular groove is provided on the current collector disc for both the positive and negative terminals, serving as a welding area. The annular stepped surface on the tab and the annular groove on the current collector disc are welded together, with a defined distance maintained between the beginning and end of the weld path.In the above design, the electrode is routed via the current collector disc. However, providing a positive-terminal current collector disc impairs the electrolyte filling and the battery's structure. While the annular groove on the current collector disc allows for a fit with the tab of the annular stepped surface, this creates a small weld area on the inner and outer rings and impairs the current flow from some of the wound layers. Furthermore, a large gap exists between the current collector disc and the casing, and vibration or pressure can easily loosen the weld or cause other problems, thus affecting the battery's normal use. Additionally, this design fails to address the safety issue caused by gas generation within the battery.

[0004] Chinese invention application CN109088037A discloses a current collector disc weld structure for a cylindrical battery. An aluminum pole plate comprises a current collector disc section and a connecting section. A copper pole plate and a positive terminal cover plate are arranged one above the other on the connecting section from top to bottom and attached to the connecting section. A disc sleeve is slid onto the outer circumference of the current collector disc section and attached to it. The disc sleeve is made of an insulating material. The inclusion of the disc sleeve ensures the stability of the current collector disc and thus allows for an increased welding diameter of the current collector disc.However, applying such a structure to a negative-terminal battery cover plate presents the following problem: The disc sleeve and the current collector disc are positioned relative to each other using several positioning rods. This results in several fan-shaped areas of the current collector disc and the battery cell being separated by the disc sleeve, and the current collector disc can only be welded to a tab via several welding grooves. Despite the increased welding area in the radial direction, the circumferential welding area is reduced, thus impairing the current conduction. Furthermore, the design, in which the disc sleeve is pushed onto the current collector disc, makes welding more difficult.

[0005] Chinese patent application CN106025112A discloses a positive-terminal lithium battery cover plate. It comprises a cover plate body, a positive-terminal screw holder, a positive-terminal rod, a rivet, a positive-terminal connection plate, and an explosion-proof valve. The cover plate body is circular. The positive-terminal screw holder is located in the center of the front surface of the cover plate body. The positive-terminal rod is located in the center of the positive-terminal screw holder and is positioned 6 mm higher than the positive-terminal screw holder. The rivet is located on the positive-terminal screw holder and is situated at the left and right ends of the positive-terminal rod. The positive-terminal connection plate is firmly connected to the rear surface of the cover plate body via the rivet. The explosion-proof valve is located at the top of the positive-terminal screw holder. One end of the positive-terminal connection plate is semicircular.In this technical design, the positive terminal rod is positioned in the center of the cover plate, and an explosion-proof valve and an electrolyte filling port are provided on two sides. A connection plate is used to establish a connection with a positive terminal plate of the battery.Although the inclusion of the explosion-proof valve improves the battery's safety performance, the overall design has the following disadvantages: (1) The explosion-proof valve and the electrolyte filling port are located on two sides of the cover plate, resulting in multiple sealing points on the cover plate and thus requiring more complex manufacturing and assembly techniques; (2) The terminal assembly in the round battery uses a vertically wound structure with a through-hole in its center, and the electrolyte filling port is located on a side edge of the cover plate, which impairs the electrolyte filling rate.

[0006] Therefore, a problem to be solved in the design of the structure of a lithium battery is to consider the electrolyte filling, the battery formation, the discharge capability and the safety protection of a round lithium battery. CONTENT OF THE PRESENT INVENTION

[0007] The present invention is based on the objective of providing a round lithium battery. Through structural design, while ensuring the discharge capability of the lithium battery, the electrolyte filling and battery formation efficiency as well as the structural safety performance are simultaneously improved. Another objective of the invention is to provide a manufacturing process for a round lithium battery.

[0008] According to the invention, the problem is solved by the following technical embodiment: A round lithium battery comprises a housing, a battery cell, a positive terminal battery cover plate assembly and a negative terminal battery cover plate assembly, wherein the housing is a metallic round tube, wherein the battery cell is located inside the housing and comprises a positive terminal foil, a negative terminal foil and a separating membrane, wherein the positive terminal foil and the negative terminal foil are separated from each other by the separating membrane and then rolled into a cylinder, wherein At the upper end of the positive terminal foil, several positive terminal tabs are provided spaced apart from one another; wherein at the lower end of the battery cell, the positive terminal foil, the separating membrane and the negative terminal foil, whose lengths are in ascending order, do not meet flush, wherein an extension part of the negative terminal foil covers the lower end of the battery in such a way that it is pressed against it and is separated from the positive terminal foil by the separating membrane; the positive terminal battery cover plate assembly comprises a disc-shaped positive terminal battery cover plate and a seal, wherein the seal is ring-shaped, arranged around the circumference of the positive terminal battery cover plate and firmly connected to the positive terminal battery cover plate, wherein a safety valve is provided on the positive terminal battery cover plate, and wherein the positive terminal tabs are electrically connected to the positive terminal battery cover plate; The negative terminal battery cover plate assembly comprises a current collector, a negative terminal battery cover plate, and a current collector holder, wherein the current collector holder is an annular element having a recess on one side, wherein the current collector has a current collector body and a current collector connection section, wherein the current collector body is rigidly connected to the upper region of the current collector holder, wherein the current collector connection section is located on the recessed side of the annular element and is rigidly connected to the cover plate, wherein the current collector connection section has a flexible curved structure such that the cover plate is located below the current collector holder in the assembled state, and wherein the current collector body is electrically connected to the extension part of the negative terminal foil.

[0009] In the above technical design, a structure with multiple tabs is used for the positive terminal exit structure, while a solid tab structure is used for the negative terminal exit structure, in contrast to the prior art design in which the same structure is used for both the positive and negative terminal exit structures. This eliminates any influence of the positive terminal exit structure on the electrolyte charge and the battery's formation. Simultaneously, the solid tab structure of the negative terminal improves the battery's overcurrent capability and reduces its cooling requirements.Since a current collector structure is used for the negative terminal and a connection is made for the positive terminal via several tabs, the negative terminal assembly can first be attached by welding and mounted to the housing, and finally the positive terminal battery cover plate can be mounted, thus simplifying the assembly process.

[0010] In the above technical embodiment, a through-hole is provided in the center of the positive terminal battery cover plate, which has a stepped structure around its circumference, the through-hole forming an electrolyte filling bore, the through-hole and the stepped structure together forming a safety valve mounting position around its circumference, the safety valve being attached to the safety valve mounting position in the delivered battery state, the thickness of the positive terminal battery cover plate being less than the total thickness of the cover plate around its circumference, thus forming a seal fixing section, the seal being placed around the seal fixing section, and one end of the battery housing being rolled onto the seal, thus forming a tight and secure connection with the positive terminal battery cover plate.

[0011] In a further technical embodiment, the safety valve consists of a safety valve body and a safety valve cap, wherein the stepped structure on the circumference of the through-bore is deeper in the middle and flatter on the circumference and comprises, from the inside out, a through-bore, a deeper first stage and a flatter second stage, wherein the circumference of the safety valve body is attached to the first stage and the safety valve cap is attached to the second stage.

[0012] In the above technical design, various structures in the prior art designed for attachment to the through-hole, such as a bursting diaphragm structure, a needle structure, etc., can be used as the safety valve body.

[0013] In the above technical embodiment, the current collector body is essentially disc-shaped and has a downward-curved structure around its circumference. This annular element is an injection-molded plastic component that encloses the downward-curved structure, so that the current collector body and the annular element form a single unit. The current collector body is rigidly connected to the upper part of the current collector holder. This prevents the current collector body and the battery cell from being obscured by the current collector holder, ensuring a large weld area between the current collector body and the extension of the negative terminal of the battery cell. This guarantees current uniformity and the electrode's overcurrent protection.

[0014] Furthermore, the provision of the current collector holder provides a positioning reference, which facilitates the assembly of the negative pole cover plate assembly.

[0015] In the above technical design, it is provided that several radially arranged reinforcing grooves are provided on the current collector body and that a negative pole weld connection section is formed between fan-shaped sections of adjacent reinforcing grooves.

[0016] In a preferred technical embodiment, it is provided that the reinforcing grooves are provided in a number of four and that the individual reinforcing grooves are arranged uniformly spaced 90° apart from each other on a round disk, wherein the recess is located between two of the reinforcing grooves, and wherein the arc length of the recess in the circumferential direction is 60° to 90°.

[0017] In the above technical design, it is provided that the part of the negative terminal foil projecting beyond the battery cell has such a length that, in the pressed state, adjacent layers are connected to each other in the overlapping joint and thus form a one-piece negative terminal exit section.

[0018] In a preferred technical embodiment, the housing is provided to be a round tube made of stainless steel or stainless iron.

[0019] According to the invention, the other problem is solved by a manufacturing process for the above-mentioned round lithium battery, which comprises the following steps: (1) Laying the positive pole foil and the negative pole foil, separated from each other by the separating membrane, on top of each other and rolling them into a cylinder; (2) Forming and ultrasonic welding of the positive terminal tabs and flattening of the extension part of the negative terminal foil, thereby forming the battery cell; (3) Laser welding of the negative terminal battery cover plate and the current collector connection section to obtain the negative terminal battery cover plate assembly; (4) Welding the current collector body and the extension part of the negative terminal foil at several points, thereby mounting the negative terminal battery cover plate assembly to the battery cell to obtain a negative terminal battery cover plate and battery cell assembly; (5) Installing the negative terminal battery cover plate and battery cell assembly into the battery housing and completely sealing and securing the perimeter of the negative terminal battery cover plate and the battery housing by welding; (6) Welding the positive terminal tabs onto the back of the positive terminal battery cover plate, installing the positive terminal battery cover plate into the housing and sealing and securing the battery housing and the positive terminal battery cover plate by rolling; (7) Extracting gas from the battery through the through-hole in the positive terminal battery cover plate and filling with electrolyte; (8) Welding and fastening the safety valve onto the through-hole, thereby achieving the installation of the lithium battery.

[0020] In a further technical embodiment, it is provided that after the safety valve is attached by welding, the safety valve cap is then fitted and the entire battery is encased with an external insulating film.

[0021] Thanks to the application of the above technical features, the present invention offers the following advantages over the prior art: 1. The present invention overcomes the misconception, based on traditional thinking, that the same structure is used for the positive terminal exit structure and the negative terminal exit structure, and creatively proposes the use of different exit structures, namely a multi-tab structure for the positive terminal exit structure and a full-tab structure for the negative terminal exit structure, which is advantageous for both electrolyte filling and battery formation while ensuring overcurrent resistance of the battery; 2. The present invention modifies the traditional prior art approach of arranging the electrode rod in the center of the battery cover plate. Instead, the electrode is guided out through an annular opening in the center of the circular cover plate, allowing the electrolyte filling port and safety valve to be located in the center. Central electrolyte filling effectively increases the electrolyte filling rate. The electrolyte filling port and safety valve are located at the same point, so that welding the safety valve simultaneously seals the electrolyte filling port, thus eliminating the need for a separate sealing step. 3. In the present invention, the seal forms a one-piece structure together with the battery positive terminal cover plate by casting, which is advantageous for the subsequent fastening of the battery positive terminal cover plate and the battery housing by rolling and increases the good part rate; 4. In the present invention, the reliable mounting of the current collector is ensured by providing a current collector holder that is firmly connected to the current collector, and a larger welding surface is achieved, which provides increased overcurrent resistance of the battery. A plastic element can be used as the current collector holder, and injection molding ensures that the current collector holder encloses and is connected to the current collector body during its molding process, thus forming a single-piece structure and facilitating assembly. 5. In the present invention, the negative terminal battery cover plate assembly is first connected to the battery cell and installed in the housing. The negative terminal battery cover plate assembly is then welded to the housing, followed by the positive terminal tabs being welded to the positive terminal battery cover plate assembly. Finally, the positive terminal battery cover plate is attached to the housing by rolling. This ensures convenient and reliable assembly. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 a schematic structural sectional view of an embodiment of the present invention; Fig. 2 a top view of Fig. 1; Fig. 3 a schematic exploded view of Fig. 1; Fig. 4 a schematic structural view of a battery cell; Fig. 5 an enlarged schematic representation of point B according to Fig. 4; Fig. 6 a top view of a positive terminal cover plate assembly according to an embodiment; Fig. 7 a section view through line AA according to Fig. 6; Fig. 8 a schematic exploded view according to Fig. 7; Fig. 9 a schematic representation of a negative pole cover plate assembly according to an exemplary embodiment in the unfolded state; Fig. 10 a section view through line CC according to Fig. 9; Fig. 11 an enlarged schematic representation of location D according to Fig. 10;

[0022] Reference numerals: 1. Safety valve cap; 2. Safety valve body; 3. Positive terminal battery cover plate; 4. Seal; 5. Insulating washer; 6. Positive terminal tab; 7. Housing; 8. Battery cell; 9. Current collector; 10. Negative terminal battery cover plate; 11. Positive terminal foil; 12. Negative terminal foil; 13. Separating membrane; 14. Through hole; 15. First stage; 16. Second stage; 17. Seal fixing section; 18. Current collector holder; 19. Recess; 20. Current collector body; 21. Current collector connection section; 22. Bent section; 23. Reinforcing groove; 24. Negative terminal weld connection section. DETAILED DESCRIPTION

[0023] The present invention will now be discussed in more detail with reference to the exemplary embodiments and the accompanying drawings.

[0024] First embodiment: It is applied to Fig. 1 to 3 are indicated. A round lithium battery comprises a housing 7, a battery cell 8, a positive terminal battery cover plate assembly, and a negative terminal battery cover plate assembly. The housing 7 is a round metallic tube. The battery cell 8 is located inside the housing 7.

[0025] It will be on Fig. 4 and Fig. 5. The battery cell 8 comprises a positive terminal foil 11, a negative terminal foil 12, and a separating membrane 13. The positive terminal foil 11 and the negative terminal foil 12 are separated from each other by the separating membrane 13 and then rolled into a cylinder. Several positive terminal tabs 6 are spaced apart at the upper end of the positive terminal foil 11. An insulating washer 5 is provided between the battery cell 8 and the positive terminal battery cover plate assembly. At the lower end of the battery cell, the positive terminal foil 11, the separating membrane 13, and the negative terminal foil 12, whose lengths are in ascending order, do not meet flush. An extension of the negative terminal foil 12 covers the lower end of the battery in such a way that, after flattening, it is pressed against it and is separated from the positive terminal foil 11 by the separating membrane 13.

[0026] It will be on Fig. 6 to 8. The positive terminal battery cover plate assembly comprises a round-shaped positive terminal battery cover plate 3 and a seal 4. The seal 4 is ring-shaped, arranged around the circumference of the positive terminal battery cover plate 3, and firmly connected to the positive terminal battery cover plate 3. A safety valve is provided on the positive terminal battery cover plate 3. The positive terminal lugs 6 are electrically connected to the positive terminal battery cover plate 3.

[0027] A through-hole 14 is provided in the center of the positive terminal battery cover plate 3, which has a two-layer stepped structure around its circumference, namely a deeper first step 15 and a shallower second step 16. A safety valve body 2 is attached to the first step 15. A safety valve cap 1 is attached to the second step 16.

[0028] The seal 4 is ring-shaped. To accommodate the installation of the seal 4, the thickness of the positive terminal battery cover plate 3 is less around its circumference than the overall thickness of the cover plate, thus forming a seal fixing section 17. The seal 4 is cast onto the sealing fixing section 17, completely enclosing it. To increase the contact area and thus ensure that the seal and the battery cover plate are a single piece, the sealing fixing section 17 has a step.

[0029] It will be on Fig. Reference is made to figures 9 to 11. The negative terminal battery cover plate assembly comprises a current collector 9, a negative terminal battery cover plate 10, and a current collector holder 18. The current collector holder 18 is an annular element with a recess 19 on one side. The current collector 9 can be a stamped metal plate and, functionally, comprises two parts: a current collector body 20 and a current collector connection section 21. The current collector body 20 is essentially disc-shaped and has a downwardly curved section 22 on its circumference, as can be seen from Fig. 10 and Fig. This results in 11. The annular current collector holder 18 is formed by injection molding and encloses the curved section 22, so that the current collector body and the annular element form a single-piece structure. The current collector body 20 is located on the current collector holder 18.

[0030] The current collector body 20 has four radially arranged reinforcing grooves 23, spaced evenly apart at 90° intervals on a circular disc. A negative pole weld connection section 24 is formed between the fan-shaped sections of adjacent reinforcing grooves 23. The recess 19 is located between two of the reinforcing grooves. A circular through-hole is provided in the center of the current collector body.

[0031] The current collector connection section 21 is located on the recessed side of the annular element, and its outer end is welded to the negative terminal battery cover plate 10. The current collector connection section 21 has a flexible, curved structure, such that the negative terminal battery cover plate 10 is located below the current collector holder when assembled.

[0032] The current collector body is rigidly connected to the upper part of the current collector holder. This prevents the current collector body and battery cell from being obscured by the current collector holder, ensuring a large welding area between the current collector body and the extension of the negative terminal of the battery cell. This guarantees current uniformity and electrode overcurrent protection. Furthermore, the current collector holder provides a positioning reference, simplifying the assembly of the negative terminal cover plate assembly.

[0033] The manufacturing process of the present embodiment comprises the following steps: (1) Laying the positive pole foil and the negative pole foil, separated from each other by the separating membrane, on top of each other and rolling them into a cylinder; (2) Forming and ultrasonic welding of the positive terminal tabs and flattening of the extension part of the negative terminal foil, thereby forming the battery cell; (3) Laser welding of the negative terminal battery cover plate and the current collector connection section to obtain the negative terminal battery cover plate assembly; (4) Welding the current collector body and the extension part of the negative terminal foil at several points, thereby mounting the negative terminal battery cover plate assembly to the battery cell to obtain a negative terminal battery cover plate and battery cell assembly; (5) Installing the negative terminal battery cover plate and battery cell assembly into the battery housing and completely sealing and securing the perimeter of the negative terminal battery cover plate and the battery housing by welding; (6) Welding the positive terminal tabs onto the back of the positive terminal battery cover plate, installing the positive terminal battery cover plate into the housing and sealing and securing the battery housing and the positive terminal battery cover plate by rolling; (7) Extracting gas from the battery through the through-hole in the positive terminal battery cover plate and filling with electrolyte; (8) Welding and fastening the safety valve onto the through-hole; (9) Attaching the safety valve cap; (10) Wrapping the entire battery with an external insulating film, thus completing the battery assembly.

Claims

[1] Round lithium battery comprising a housing, a battery cell, a positive terminal battery cover plate assembly and a negative terminal battery cover plate assembly, wherein the housing is a round metallic tube, wherein the battery cell is located inside the housing and comprises a positive terminal foil, a negative terminal foil and a separating membrane, wherein the positive terminal foil and the negative terminal foil are separated from each other by the separating membrane and then rolled into a cylinder, characterized by , that At the upper end of the positive terminal foil, several positive terminal tabs are provided spaced apart from one another; wherein at the lower end of the battery cell, the positive terminal foil, the separating membrane and the negative terminal foil, whose lengths are in ascending order, do not meet flush, wherein an extension part of the negative terminal foil covers the lower end of the battery in such a way that it is pressed against it and is separated from the positive terminal foil by the separating membrane; the positive terminal battery cover plate assembly comprises a disc-shaped positive terminal battery cover plate and a seal, wherein the seal is ring-shaped, arranged around the circumference of the positive terminal battery cover plate and firmly connected to the positive terminal battery cover plate, wherein a safety valve is provided on the positive terminal battery cover plate, and wherein the positive terminal tabs are electrically connected to the positive terminal battery cover plate; The negative terminal battery cover plate assembly comprises a current collector, a negative terminal battery cover plate, and a current collector holder, wherein the current collector holder is an annular element having a recess on one side, wherein the current collector has a current collector body and a current collector connection section, wherein the current collector body is rigidly connected to the upper region of the current collector holder, wherein the current collector connection section is located on the recessed side of the annular element and is rigidly connected to the cover plate, wherein the current collector connection section has a flexible curved structure such that the cover plate is located below the current collector holder in the assembled state, and wherein the current collector body is electrically connected to the extension part of the negative terminal foil. [2] Round lithium battery according to claim 1, characterized bythat a through-hole is provided in the center of the positive terminal battery cover plate, which has a stepped structure on its circumference, wherein the through-hole forms an electrolyte filling hole, wherein the through-hole and the stepped structure together form a safety valve mounting position on its circumference, wherein in the delivered state of the battery the safety valve is attached to the safety valve mounting position, wherein the thickness of the positive terminal battery cover plate on its circumference is less than the total thickness of the cover plate, thus forming a sealing fixing section, wherein the seal is placed on the sealing fixing section enclosing it, and wherein one end of the battery housing is placed on the seal by rolling it on the seal, thus sealing it tightly and firmly connected to the positive terminal battery cover plate. [3] Round lithium battery according to claim 2, characterized by, that the safety valve consists of a safety valve body and a safety valve cap, wherein the stepped structure on the circumference of the through-bore is deeper in the middle and flatter on the circumference and, from the inside out, comprises a through-bore, a deeper first stage and a flatter second stage, wherein the circumference of the safety valve body is attached to the first stage and the safety valve cap is attached to the second stage. [4] Round lithium battery according to claim 1, characterized by , that the current collector body is essentially disc-shaped and has a downwardly curved structure on its circumference, wherein the annular element is an injection-molded plastic element that encloses the downwardly curved structure, so that the current collector body and the annular element form a one-piece structure. [5] Round lithium battery according to claim 4, characterized by, that several radially arranged reinforcing grooves are provided on the current collector body and that a negative pole weld connection section is formed between fan-shaped sections of adjacent reinforcing grooves. [6] Round lithium battery according to claim 5, characterized by , that the reinforcing grooves are provided in a number of four and the individual reinforcing grooves are arranged uniformly spaced 90° apart from each other on a round disk, wherein the recess is located between two of the reinforcing grooves, and wherein the arc length of the recess in the circumferential direction is 60° to 90°. [7] Round lithium battery according to claim 1, characterized by , that the part of the negative terminal foil extending beyond the battery cell has such a length that, in the pressed state, adjacent layers are connected to each other in the overlapping joint and thus form a one-piece negative terminal exit section. [8] Round lithium battery according to claim 1, characterized by that the housing is a round tube made of stainless steel or stainless iron. [9] Manufacturing process for the round lithium battery according to claim 1, characterized by that it includes the following steps: (1) Laying the positive pole foil and the negative pole foil, separated from each other by the separating membrane, on top of each other and rolling them into a cylinder; (2) Forming and ultrasonic welding of the positive terminal tabs and flattening of the extension part of the negative terminal foil, thereby forming the battery cell; (3) Laser welding of the negative terminal battery cover plate and the current collector connection section to obtain the negative terminal battery cover plate assembly; (4) Welding the current collector body and the extension part of the negative terminal foil at several points, thereby mounting the negative terminal battery cover plate assembly to the battery cell to obtain a negative terminal battery cover plate and battery cell assembly; (5) Installing the negative terminal battery cover plate and battery cell assembly into the battery housing and completely sealing and securing the perimeter of the negative terminal battery cover plate and the battery housing by welding; (6) Welding the positive terminal tabs onto the back of the positive terminal battery cover plate, installing the positive terminal battery cover plate into the housing and sealing and securing the battery housing and the positive terminal battery cover plate by rolling; (7) Extracting gas from the battery through the through-hole in the positive terminal battery cover plate and filling with electrolyte; (8) Welding and fastening the safety valve onto the through-hole, thereby achieving the installation of the lithium battery.

10. Manufacturing process for a round lithium battery according to claim 9, characterized by , that after the safety valve is attached by welding, the safety valve cap is then fitted and the entire battery is wrapped with an external insulating film.

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