A single cell battery and a method for preparing the same

Abstract

The present invention relates to a single cell battery, including a battery shell, an upper and lower end cover, a first and second electrodes, and a first and second busbars. A hollow pin hole is provided in the center of the lower end cover, a connecting cylindrical pin is fixed in the hollow pin hole, the connecting cylindrical pin is fixed to the center hole of the first busbar, the first busbar is fixed to the first electrode, and the lower end cover is fixed to the first busbar and the first electrode through the hollow pin hole to form an integral structure; the upper end cover is buckled with the upper open end of the battery shell, the upper end cover is fixed to the second busbar and the second electrode to form an upper end cover integral structure, and the two ends of the battery cell in the battery shell are the first electrode and the second electrode respectively. Preparation method: winding electrode group; laser welding and sealing of the hollow pin hole and the connecting cylindrical pin; laser welding of the first busbar and the first electrode; laser welding of the upper end cover, the second busbar and the second electrode; liquid injection and sealing. Beneficial effects: The present invention not only reduces the welding process and the use of structural parts, but also can detect and evaluate the laser welding effect.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries, and in particular relates to a single cell and a preparation method thereof. Background Art

[0002] Lithium-ion battery cells generally include battery shells and various structural components. The structural components connect the battery components into an integrated structure through various connection methods. The connection between the busbar and the end cover includes a soft connection method through a metal sheet or a hard connection method through laser penetration welding. The soft connection method is that the two ends of the soft metal sheet are fixed to the busbar and the end cover by laser welding to form an integral structure. This process has many welding steps. The use of soft metal sheets not only increases the material cost, but also increases the occupancy rate of the overall battery space; the hard connection method of laser penetration welding: although it can reduce the cost of welding step materials and improve the utilization rate of space, during the laser penetration welding process, welding slag can easily cause self-discharge of the battery. The laser beam passes through the hollow pin hole / end cover and acts on the busbar. The high-power laser can easily damage the structural components of the hollow pin hole, and the insulation of the hollow pin hole is destroyed, causing the battery to short-circuit. More importantly, the welding effect of laser penetration welding cannot be directly detected in the production. For this reason, the accuracy of the cell size in the process is high, which makes the processing technology of the overall battery process difficult.

[0003] Therefore, how to more reasonably connect the assembly structure of the busbar and the end cover is an urgent problem to be solved in battery technology. Summary of the invention

[0004] The present invention aims to overcome the deficiencies in the prior art and provides a single cell battery, which adopts a fixing method in which a first busbar is inserted into a hollow pin hole of a lower end cover through a connecting cylindrical pin and then directly welded to a first electrode. This not only removes the structural parts of soft metal sheets, but also improves the space utilization rate and energy density of the battery, and can also timely detect and evaluate the laser welding effect.

[0005] To achieve the above-mentioned purpose, the present invention is implemented through the following technical scheme: a single cell, comprising a battery shell, an upper and lower end covers, a first and a second electrode, and a first and a second busbar, wherein: the bottom of the battery shell is buckled and fixedly connected with the lower end cover to form an integral structure, a hollow pin hole is provided at the center of the lower end cover, a connecting cylindrical pin is fixedly connected in the hollow pin hole, the connecting cylindrical pin is fixedly connected to the center hole of the first busbar, the first busbar is fixedly connected to the first electrode, the lower end cover is fixedly connected to the first busbar and the first electrode through the hollow pin hole to form an integral structure, the hollow pin hole of the lower end cover is connected to a sealing insulating component; the upper end cover is buckled with the upper open end of the battery shell, the upper end cover is fixedly connected to the second busbar and the second electrode from the outside to the inside in sequence to form the upper end cover integral structure, the battery shell has a hollow battery cell built in, and the two ends of the battery cell are the first electrode and the second electrode respectively.

[0006] Furthermore, the sealing insulation assembly includes a hollow rivet, a hollow inner insulation sheet, a hollow sealing ring, a hollow outer insulation pad and a rivet pad which are sequentially connected from the inside to the outside, and are inserted into the hollow pin hole of the lower end cover one by one and riveted to form a hollow pin hole with an integral structure.

[0007] Furthermore, the first busbar is evenly provided with positioning grooves for welding tooling along its outer circular edge, and the first busbar is evenly provided with fan-shaped hollows welded to the first electrode, and the first busbar between the two fan-shaped hollows constitutes a guide plate.

[0008] Furthermore, a stamped raised cylinder is provided at the center of the first busbar, and the raised cylinder is inserted into a hollow pin hole for fixation.

[0009] Furthermore, a liquid injection hole is provided at the center of the upper end cover, a downwardly bent annular reinforcing rib is provided at the upper end cover, and a plurality of explosion-proof scoring lines are provided on the surface of the upper end cover.

[0010] Furthermore, the second busbar is provided with a stopper that is tilted 90° along its outer circular edge, the second busbar is provided with a central circular hole, and a plurality of downward welding protrusions (1002) are provided around the central circular hole, the inner diameter of the stopper is larger than the outer diameter of the annular reinforcement rib of the upper end cover, the stopper of the second busbar is fixedly connected to the annular reinforcement rib of the upper end cover, and the downward welding protrusion of the second busbar is fixedly connected to the second electrode.

[0011] Furthermore, the second busbar is evenly provided with positioning grooves cooperating with the welding tooling along its outer circumferential edge.

[0012] Furthermore, the downward welding protrusion of the second busbar is disposed between the positioning groove and the central circular hole to form a welding area.

[0013] Furthermore, the second busbar is evenly distributed with a plurality of overflow holes.

[0014] A method for preparing a single cell battery, the specific steps are as follows:

[0015] (1) Pre-kneading and flattening the electrode group after winding to obtain an electrode group having a first electrode and a second electrode, wherein the electrode ear height before flattening is 6-10 mm, the electrode ear inclination angle during pre-kneading reaches 30-60°, and the electrode ear height after flattening is 1.5-3 mm;

[0016] (2) A hollow rivet, a hollow inner insulating sheet, a hollow sealing ring, a hollow outer insulating pad and a rivet pad are sequentially mounted on the circular hole of the lower end cover from the inside to the outside, and after riveting, an integral hollow pin hole is formed. A connecting cylindrical pin is inserted into the hollow pin hole. The hollow pin hole and the connecting cylindrical pin are connected in a dynamic fit, and laser welding is performed to seal the weld. The weld depth is 0.1-0.3 mm and the weld width is 0.1-0.2 mm.

[0017] (3) The connecting cylindrical pin passes through the central circular hole of the first busbar and is laser welded. The fan-shaped hollow of the first busbar and the first electrode are laser welded into an integral structure. The welding area is in the shape of an arrow. The number of weld points is 80-120 or the number of weld lines is 6-10. The weld width of the weld points or weld lines is 0.1-0.2 mm and the weld depth is 0.1-0.3 mm.

[0018] (4) Wrap the insulating sheet or insulating tape around the first busbar and the outer side of the first electrode to prevent them from contacting the battery case, and buckle and weld the lower end cover to the battery case;

[0019] (5) The stopper of the second busbar is fitted with the annular reinforcement rib of the upper end cover by laser welding, and the downward welding protrusion of the second busbar is laser welded to the second electrode. The laser welding power is above 100-1000W, the welding area is in the shape of an arrow, the number of welds is 80-120 or the number of weld lines is 6-10, the weld width of the welds or weld lines is 0.1-0.2mm, and the weld depth is 0.1-0.3mm;

[0020] (6) Place the electrode group welded as above into the cylindrical battery casing, connect the cylindrical pins to extend into the hollow pin holes until the end faces are flush, and seal them by laser welding;

[0021] (7) The upper end cover is sealed and welded to the battery shell, and the electrolyte is injected through the injection hole on the upper end surface. After the formation is completed, the PIN is laser welded to seal it. The laser welding power is above 100-1000W to make a single battery.

[0022] Beneficial effects: This patent adopts the method of passing the pole through the hollow pin hole and directly welding the busbar and the end cover to reduce the welding process and the use of structural parts, improve the space utilization rate of the battery, and improve the energy density of the battery. It can also detect and evaluate the laser welding effect. The error range of the battery cell size is relatively large -3.0-2.0mm. When the penetration welding technology is used, the error range of the battery cell size is about ±1.0mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the structural explosion diagram of the battery cell;

[0024] Figure 2 is a cross-sectional view of a battery cell;

[0025] Figure 3 yes Figure 2 A partial enlarged view of the middle A part;

[0026] Figure 4 It is a combined structural diagram of the first busbar and the connecting cylindrical pin;

[0027] Figure 5 It is a mechanical stamping integrated structure diagram of the first busbar and the connecting cylindrical pin;

[0028] Figure 6 yes Figure 5 A cross-sectional view of a stamped integrated structure;

[0029] Figure 7 yes Figure 2 A partial enlarged view of the middle B part;

[0030] Figure 8 is a schematic diagram of the structure of the second busbar; ;

[0031] Fig. 9 It is a schematic diagram of the structure of the upper end cover;

[0032] Fig.10 It is a schematic diagram of the welding structure between the annular reinforcement rib of the upper end cover and the stopper of the second busbar;

[0033] Fig.11 It is a schematic diagram of the overall structure of a single battery.

[0034] In the figure: battery housing 1; lower end cover 2; hollow pin hole 3; aluminum rivet 301; inner insulating sheet 302; sealing ring 303; outer insulating pad 304; aluminum rivet pad 305; pin hole 306; insulating tape or insulating sheet 4; connecting cylindrical pin 5; first busbar 6; first busbar welding tool positioning area 601; first busbar and connecting cylindrical pin integrated central forming area 602; T-shaped guide area 603; peach-shaped cutting area 604; first busbar and first electrode welding area 60 5; battery cell 7; first electrode 8; second electrode 9; second busbar 10; second busbar welding tool positioning area 1001; second busbar and second electrode welding area 1002; second busbar edge raised area 1003; overflow hole 1004; upper end cover 11; inwardly protruding reinforcing rib 1101 of the upper end cover; score line structure 1102; injection hole 1103; second busbar edge raised area and inwardly protruding reinforcing rib welding area 1003-1101 of the upper end cover, PIN 12; DETAILED DESCRIPTION

[0035] In order to be able to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other. In the following description, many specific details are set forth in order to fully understand the present invention, and the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the art without making creative work are within the scope of protection of the present invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0036] In the various embodiments of the present invention, for the convenience of description and not to limit the present invention, the term "connection" used in the patent application specification and claims of the present invention is not limited to physical or mechanical connection, but may include electrical connection, whether direct or indirect. "Up", "down", "below", "left", "right", etc. are only used to indicate relative position relationship. When the absolute position of the described object changes, the relative position relationship also changes accordingly.

[0037] See the attached drawings for details. The present invention provides a single cell battery, comprising a battery shell, an upper and lower end cover, a first and a second electrode, and a first and a second busbar. The bottom of the battery shell is buckled and fixedly connected with the lower end cover to form an integral structure. A hollow pin hole is provided in the center of the lower end cover, and a connecting cylindrical pin is fixedly connected in the hollow pin hole. The connecting cylindrical pin is fixedly connected to the center hole of the first busbar, and the first busbar is fixedly connected to the first electrode. The lower end cover is fixedly connected to the first busbar and the first electrode through the hollow pin hole to form an integral structure. The hollow pin hole of the lower end cover is connected to a sealing insulating component; the upper end cover is buckled with the upper open end of the battery shell, and the upper end cover is fixedly connected to the second busbar and the second electrode from the outside to the inside in sequence to form an upper end cover integral structure. A hollow battery cell is built in the battery shell, and the two ends of the battery cell are the first electrode and the second electrode respectively.

[0038] Furthermore, the sealing insulation assembly includes a hollow rivet, a hollow inner insulation sheet, a hollow sealing ring, a hollow outer insulation pad and a rivet pad which are sequentially connected from the inside to the outside, and are inserted into the hollow pin hole of the lower end cover one by one and riveted to form a hollow pin hole with an integral structure.

[0039] Furthermore, the first busbar is evenly provided with positioning grooves for welding tooling along its outer circular edge, and the first busbar is evenly provided with fan-shaped hollows welded to the first electrode, and the first busbar between the two fan-shaped hollows constitutes a guide plate.

[0040] Furthermore, a stamped raised cylinder is provided at the center of the first busbar, and the raised cylinder is inserted into a hollow pin hole for fixation.

[0041] Furthermore, a liquid injection hole is provided at the center of the upper end cover, a downwardly bent annular reinforcing rib is provided at the upper end cover, and a plurality of explosion-proof scoring lines are provided on the surface of the upper end cover.

[0042] Furthermore, the second busbar is provided with a stopper that is tilted 90° along its outer circular edge, the second busbar is provided with a central circular hole, and a plurality of downward welding protrusions (1002) are provided around the central circular hole, the inner diameter of the stopper is larger than the outer diameter of the annular reinforcement rib of the upper end cover, the stopper of the second busbar is fixedly connected to the annular reinforcement rib of the upper end cover, and the downward welding protrusion of the second busbar is fixedly connected to the second electrode.

[0043] Furthermore, the second busbar is evenly provided with positioning grooves cooperating with the welding tooling along its outer circumferential edge.

[0044] Furthermore, the downward welding protrusion of the second busbar is disposed between the positioning groove and the central circular hole to form a welding area.

[0045] Furthermore, the second busbar is evenly distributed with a plurality of overflow holes.

[0046] A method for preparing a single cell battery, the specific steps are as follows:

[0047] (1) Pre-kneading and flattening the electrode group after winding to obtain an electrode group having a first electrode and a second electrode, wherein the electrode ear height before flattening is 6-10 mm, the electrode ear inclination angle during pre-kneading reaches 30-60°, and the electrode ear height after flattening is 1.5-3 mm;

[0048] (2) A hollow rivet, a hollow inner insulating sheet, a hollow sealing ring, a hollow outer insulating pad and a rivet pad are sequentially mounted on the circular hole of the lower end cover from the inside to the outside, and after riveting, an integral hollow pin hole is formed. A connecting cylindrical pin is inserted into the hollow pin hole. The hollow pin hole and the connecting cylindrical pin are connected in a dynamic fit, and laser welding is performed to seal the weld. The weld depth is 0.1-0.3 mm and the weld width is 0.1-0.2 mm.

[0049] (3) The connecting cylindrical pin passes through the central circular hole of the first busbar and is laser welded. The fan-shaped hollow of the first busbar and the first electrode are laser welded into an integral structure. The welding area is in the shape of an arrow. The number of weld points is 80-120 or the number of weld lines is 6-10. The weld width of the weld points or weld lines is 0.1-0.2 mm and the weld depth is 0.1-0.3 mm.

[0050] (4) Wrap the insulating sheet or insulating tape around the first busbar and the outer side of the first electrode to prevent them from contacting the battery case, and buckle and weld the lower end cover to the battery case;

[0051] (5) The stopper of the second busbar is fitted with the annular reinforcement rib of the upper end cover by laser welding, and the downward welding protrusion of the second busbar is laser welded to the second electrode. The laser welding power is above 100-1000W, the welding area is in the shape of an arrow, the number of welds is 80-120 or the number of weld lines is 6-10, the weld width of the welds or weld lines is 0.1-0.2mm, and the weld depth is 0.1-0.3mm;

[0052] (6) Place the electrode group welded as above into the cylindrical battery casing, connect the cylindrical pins to extend into the hollow pin holes until the end faces are flush, and seal them by laser welding;

[0053] (7) The upper end cover is sealed and welded to the battery shell, and the electrolyte is injected through the injection hole on the upper end surface. After the formation is completed, the PIN is laser welded to seal it. The laser welding power is above 100-1000W to make a single battery.

[0054] The above-mentioned single cell battery can be applied to electrical equipment such as plug-in hybrid vehicles, electric vehicles, and energy storage batteries.

[0055] The structure and preparation method of the single cell of the embodiment are further described below with reference to the accompanying drawings Example

[0056] Note: The expression "first, second..." (e.g., first busbar) in this embodiment refers to the description of some technical features in sequence from bottom to top of the battery housing.

[0057] The battery cell provided in this embodiment is a cylindrical battery, including a battery housing 1, a lower end cover 2, a hollow pin hole 3, a pin hole 306, a connecting cylindrical pin 5, a first busbar 6, a first electrode 8, a second electrode 9, a second busbar 10, a liquid injection hole 1103, an upper end cover 11, an overflow hole 1004 and other structural parts;

[0058] See attached for details Figure 1 , battery housing 1, the battery housing is a U-shaped shell, one end is an open end, the other end is a closed end, and a hollow pin hole is provided at the closed end, which is used as a first electrode lead-out terminal for connecting an external structural member;

[0059] The lower end cover 2 is at the closed end of the U-shaped shell, and is an integrated structure with the side wall of the shell, and has a hollow pin hole 3 thereon; the hollow pin hole is located at the closed end of the U-shaped shell, and is firstly cut by mechanical cutting to form a center circle with the center of the lower end cover as the center diameter of 18 mm, and the rivet 301, the inner insulating sheet 302, the sealing ring 303, the lower end cover, the outer insulating pad 304, and the rivet pad 305 are assembled from the inside to the outside at the center circle to form the hollow pin hole 3, and the depth of the hollow pin hole is 4.1 mm and the width is 11.8 mm. The pin hole 306 of the hollow pin hole 3 is matched with the connecting cylindrical pin 5 and is laser welded, and the matching clearance between the pin hole and the connecting cylindrical pin is 20-30 μm;

[0060] Among them, the hollow pin hole 3 has the characteristic of being insulated from the end cover; optionally, the inner insulating sheet, the sealing ring and the outer insulating pad are made into an integrated structure.

[0061] The connecting cylindrical pin 5 is an intermediate structural component connecting the first busbar 6 and the hollow pin hole 3;

[0062] The connecting cylindrical pin 5 is welded to the first busbar 6. The connecting cylindrical pin can be designed to be solid or hollow;

[0063] See attached for details Figure 5-6 The cylindrical pin and the first busbar can be connected by a stamping integrated structure or a riveting integrated structure.

[0064] See attached for details Figure 4 The diameter of the first busbar 6 is Φ40.1mm. The first busbar includes a first busbar welding tooling positioning groove 601, a connecting cylindrical pin center forming area 602, a T-shaped guide area 603, a peach-shaped cutting area 604, and a first busbar and a first electrode welding area composition 605. The first busbar is welded to the first electrode. The laser welding power is 300W, the number of welding lines is 10, the weld width of the welding line is 0.15mm, and the weld depth is 0.2mm.

[0065] Optionally, by adjusting the laser welding parameters to 100-650W, the first busbar and the first electrode welding area can be welded into a shape such as a line, an arrow, an arc, or an S shape;

[0066] Optionally, the laser welding of the first busbar and the first electrode may be performed by pulsed laser spot welding, continuous laser line welding, or laser dot matrix welding.

[0067] The first electrode and the second electrode are two electrically different tab ends formed by winding the positive and negative electrode sheets, respectively, wherein the tab height before flattening is 6 mm, and then pre-flattening is performed, at which time the tab angle is inclined by 35°, and then a flattening step is performed, and finally the tab height after flattening reaches about 1.5 mm, that is, the first and second electrode surfaces with different electrical properties are prepared.

[0068] The diameter of the second busbar 10 is Φ43.7 mm. The second busbar includes a second busbar welding tool positioning groove 1001, a second busbar and second electrode welding area 1002, a second busbar edge raised area 1003, and an overflow hole 1004. The laser welding power is 650 W, the number of welding lines is 12, the weld width of the welding line is 0.2 mm, and the weld depth is 0.3 mm.

[0069] Optionally, by adjusting the laser welding parameters to 100-650W, the first busbar and the first electrode welding area can be welded into a shape such as a line, an arrow, an arc, or an S shape;

[0070] Optionally, the laser welding of the first busbar and the first electrode may be performed by pulsed laser spot welding, continuous laser line welding, or laser dot matrix welding.

[0071] Structural details of the second busbar: The raised areas on the edge of the second busbar are intermittently distributed, with 6 discontinuous 90° raised arcs of equal length and equal spacing. The outer diameter of the raised arc is slightly smaller than the diameter of the second electrode. The inner diameter of the raised arc of the second busbar is larger than the outer diameter of the inwardly raised reinforcement rib of the upper end cover. The injection holes are respectively distributed in the six sector-shaped areas separated by the welding area and the central area of ​​the second busbar. The injection holes in the central area, the center hole of the battery cell and the center line of the hollow pin hole coincide with each other.

[0072] See attached for details Fig. 9 , the upper end cover 11 is composed of an inwardly protruding reinforcing rib area 1101, a liquid injection hole 1103, and a scoring line 1102;

[0073] Structural details of the upper end cover: The inwardly protruding reinforcement ribs serve as a pressure relief on the one hand, and on the other hand, the outer edge of the protruding structure is fitted with the inner edge of the protruding arc of the second busbar and connected by laser welding. The overflow hole can evenly disperse the liquid injected from the injection hole into the battery cell.

[0074] The specific steps of the battery monomer preparation method are as follows:

[0075] S1: The electrode group after winding is pre-kneaded and flattened to obtain an electrode group having a first electrode and a second electrode, wherein the height of the pole ear before flattening is 6 mm, the inclination angle of the pole ear during pre-kneading reaches 35°, and the height of the pole ear after flattening is 1.5 mm, and the flattening machine is a conventional equipment for battery production;

[0076] S2: Using laser welding (welding machine name: round non-standard welding machine), the first busbar is mechanically stamped into a stamped integrated structure with a central protrusion, and is connected to the first electrode by laser welding. The welding area is welded into an arrow shape, the number of weld lines is 10, the weld width of the weld line is 0.15 mm, and the weld depth is 0.2 mm;

[0077] S3: Wrapping an insulating sheet or an insulating tape around the outer side of the welded combined or integrated structure to prevent the first busbar and the first electrode surface from contacting the battery housing, thereby providing insulation protection;

[0078] S4: turning over the prepared battery electrode group, connecting the second electrode to the second busbar by laser welding, the welding area is welded into an arrow shape, the number of weld lines is 12, the weld width of the weld line is 0.2 mm, and the weld depth is 0.3 mm;

[0079] S5: The obtained combined pole group, the raised welding area on the edge of the second busbar is fitted with the inward protrusion of the upper end cover, and is connected by laser side wall welding. The laser welding power is above 1000W, the penetration depth of the weld is 0.3mm, and the weld width is 0.2mm;

[0080] S6: placing the electrode group after welding into a cylindrical battery housing, extending the connecting cylindrical pin into the hollow pin hole, wherein the gap between the hollow pin hole and the connecting cylindrical pin is 20-30 μm, and laser welding is performed for sealing, the weld depth is 0.2 mm, and the weld width is 0.18 mm;

[0081] S7: The upper end cover is sealed and welded to the cylindrical battery shell, and the electrolyte is injected through the overflow hole on the second end face. After the formation is completed, the PIN is laser welded for sealing. The laser welding power is above 1000W, the melting depth of the weld is 0.3mm, and the melting width is 0.2mm.

[0082] The first busbar of the present invention is welded into an integral structure by connecting the lower end cover, the first busbar and the first electrode by means of cylindrical pins; and the upper end cover is fixedly connected with the second busbar and the second electrode in sequence from the outside to the inside to form the overall structure of the upper end cover, which not only removes the structural parts of the soft metal sheet, but also improves the space utilization rate and energy density of the battery, and can also timely detect and evaluate the laser welding effect.

[0083] The detailed description of a single cell and its preparation method with reference to the above-mentioned embodiments is illustrative rather than restrictive, and several embodiments can be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A single cell battery, comprising a battery housing, upper and lower end covers, first and second electrodes and first and second busbars, characterized in that: The bottom of the battery case is buckled and fixedly connected with the lower end cover to form an integral structure, a hollow pin hole is provided in the center of the lower end cover, a connecting cylindrical pin is fixedly connected in the hollow pin hole, the connecting cylindrical pin is fixedly connected to the center hole of the first busbar, the first busbar is fixedly connected to the first electrode, the lower end cover is fixedly connected to the first busbar and the first electrode through the hollow pin hole to form an integral structure, and the hollow pin hole of the lower end cover is connected to a sealing insulating component; the upper end cover is buckled with the upper open end of the battery case, and the upper end cover is fixedly connected to the second busbar and the second electrode from the outside to the inside in sequence to form an upper end cover integral structure, and a hollow battery cell is built in the battery case, and the two ends of the battery cell are the first electrode and the second electrode respectively; The sealing insulation assembly comprises a hollow rivet, a hollow inner insulation sheet, a hollow sealing ring, a hollow outer insulation pad and a rivet pad which are sequentially connected from the inside to the outside, and are inserted into the circular hole of the lower end cover one by one and riveted to form a hollow pin hole of the overall structure; The first busbar is evenly provided with positioning grooves for welding tooling along its outer circumferential edge, and the first busbar is evenly provided with fan-shaped hollows welded to the first electrode, and the first busbar between the two fan-shaped hollows constitutes a guide plate; The second busbar is provided with a stopper which is turned up 90° along its outer circle edge, and the second busbar is provided with a central circular hole, and a plurality of downward welding protrusions are provided around the central circular hole, and the inner diameter of the stopper is larger than the outer diameter of the annular reinforcement rib of the upper end cover, the stopper of the second busbar is fixedly connected to the annular reinforcement rib of the upper end cover, and the downward welding protrusion of the second busbar is fixedly connected to the second electrode.

2. The single cell according to claim 1, characterized in that: A stamped raised cylinder is provided at the center of the first busbar, and the raised cylinder is inserted into the hollow pin hole for fixed connection.

3. The single cell according to claim 1, characterized in that: A liquid injection hole is arranged at the center of the upper end cover, a downwardly bent annular reinforcing rib is arranged on the upper end cover, and a plurality of explosion-proof scoring lines are arranged on the surface of the upper end cover.

4. The single cell according to claim 1, characterized in that: The second busbar is evenly provided with positioning grooves matched with the welding tooling along its outer circumferential edge.

5. The single cell according to claim 1, characterized in that: The downward welding protrusion of the second busbar is disposed between the positioning groove and the central circular hole to form a welding area.

6. The single cell according to claim 1, characterized in that: The second busbar is evenly distributed with a plurality of overflow holes.

7. A method for preparing a single cell according to any one of claims 1 to 6, comprising the following steps: (1) Pre-kneading and flattening the electrode group after winding to obtain an electrode group having a first electrode and a second electrode, wherein the electrode ear height before flattening is 6-10 mm, the electrode ear inclination angle during pre-kneading reaches 30-60°, and the electrode ear height after flattening is 1.5-3 mm; (2) A hollow rivet, a hollow inner insulating sheet, a hollow sealing ring, a hollow outer insulating pad and a rivet pad are sequentially mounted on the circular hole of the lower end cover from the inside to the outside, and after riveting, an integral hollow pin hole is formed. A connecting cylindrical pin is inserted into the hollow pin hole. The hollow pin hole and the connecting cylindrical pin are connected in a dynamic fit, and laser welding is performed to seal the weld. The weld depth is 0.1-0.3 mm and the weld width is 0.1-0.2 mm. (3) The connecting cylindrical pin passes through the central circular hole of the first busbar and is laser welded. The fan-shaped hollow of the first busbar and the first electrode are laser welded into an integral structure. The welding area is in the shape of an arrow. The number of weld points is 80-120 or the number of weld lines is 6-10. The weld width of the weld points or weld lines is 0.1-0.2 mm and the weld depth is 0.1-0.3 mm. (4) Wrap the insulating sheet or insulating tape around the first busbar and the outer side of the first electrode to prevent them from contacting the battery case, and buckle and weld the lower end cover to the battery case; (5) The stopper of the second busbar is fitted with the annular reinforcement rib of the upper end cover by laser welding, and the downward welding protrusion of the second busbar is laser welded to the second electrode. The laser welding power is above 100-1000W, the welding area is in the shape of an arrow, the number of welds is 80-120 or the number of weld lines is 6-10, the weld width of the welds or weld lines is 0.1-0.2mm, and the weld depth is 0.1-0.3mm; (6) Place the electrode group welded as above into the cylindrical battery casing, connect the cylindrical pins to extend into the hollow pin holes until the end faces are flush, and seal them by laser welding; (7) The upper end cover is sealed and welded to the battery shell, and the electrolyte is injected through the injection hole on the upper end surface. After the formation is completed, the PIN is laser welded to seal it. The laser welding power is above 100-1000W to make a single battery.

Images