Battery cell with bipolar electrode groups

Abstract

The application discloses a battery cell with bipolar polar group and belongs to the technical field of battery cells. The battery cell comprises a winding core, a first current collector, a second current collector and an insulation layer. The winding core is provided with positive and negative poles at two axial ends, and a symmetrical conductive structure is formed by cooperating with the center poles at the two ends. The insulation layer adopts a composite structure of an insulation sheet and a flexible high-temperature-resistant adhesive tape, precisely limits the lap joint size of the adhesive tape, fully covers and coats key insulation areas of the battery cell, is suitable for the deformation of the battery cell and high and low temperature working conditions, and has strong insulation stability. The negative current collector is designed as a racetrack-shaped special-shaped structure, and the distribution of the welding marks of the current collector and the size matching of the pole welding are optimized. The battery cell disclosed by the application has the advantages of high safety, long service life and low cost.

Description

Technical Field

[0001] This invention relates to a battery cell, and more particularly to a battery cell having a bipolar electrode group. Background Technology

[0002] Lithium-ion batteries are widely used in the new energy vehicle field due to their advantages such as high specific energy, long cycle life, and no memory effect. As the requirements of terminal devices for battery fast charging capability, high-rate discharge performance, and safety and reliability continue to increase, the electrode current collection structure, current conduction path, and insulation protection system inside the cell have become the core factors restricting the rate performance, internal resistance consistency, and thermal safety performance of the cell.

[0003] Currently, commercially available cylindrical cells generally adopt a single-pole current collector structure: the current from the tab is collected at one end of the core through the current collector plate and then led out from the center pole as the positive terminal, while the current at the other end is conducted through the current collector plate to the metal casing, which is used as the negative terminal for output. Taking the negative terminal as an example, its current conduction path is: tab - current collector plate - current collector plate edge - casing, that is, the negative current must be converted and output through the overlapping area between the current collector plate edge and the casing, and the current collector plate edge carries a large current for a long time. The existing single-pole structure has the following defects: (1) great safety hazards. The negative current of the single-pole structure is conducted through the edge of the current collector and the shell. The edge of the current collector carries a large current for a long time, which is prone to local current concentration, polarization intensification and Joule heat accumulation. Moreover, the edge area is close to the insulation structure. If there are minor process defects in the insulation layer, or long-term thermal expansion and contraction leads to insulation aging and damage, it is very easy to cause partial discharge and insulation breakdown, which will eventually lead to short circuit and thermal runaway of the battery cell. (2) Conventional negative current collectors mostly adopt a round structure, which uses a large amount of copper material and has low material utilization, which greatly increases the production cost of the battery cell. (3) Existing battery cells mostly use a single rigid insulating pad or ordinary tape to cover the battery. The adaptability is poor and it cannot adapt to the expansion, contraction and high and low temperature alternating working conditions during the charging and discharging process of the battery cell. After long-term use, the insulation layer is prone to cracking, falling off and overlapping failure, and the reliability of insulation protection is insufficient.

[0004] In conclusion, improvements are needed to the existing cylindrical batteries. Summary of the Invention

[0005] In order to overcome the shortcomings of the existing technology, the present invention provides a battery cell with a bipolar electrode group.

[0006] To achieve the above objectives, the present invention discloses a battery cell having a bipolar electrode group, comprising, The core has a first end and a second end opposite to each other in the axial direction, the first end is connected to an electrode to form a positive terminal, and the second end is connected to an electrode to form a negative terminal; The first collector is connected to the positive terminal, and a positive terminal post is formed or connected at the center of the first collector. The second collector is connected to the negative terminal, and a negative terminal post is formed or connected at the center of the second collector. An insulating layer is provided to electrically isolate the core, the first current collector, and the second current collector from the housing.

[0007] Preferably, the insulating layer includes a first insulating sheet and a second insulating sheet, the first insulating sheet being attached to the side of the first collector plate opposite to the winding core, and the second insulating sheet being attached to the side of the second collector plate opposite to the winding core.

[0008] Preferably, the insulating layer further includes a flexible high-temperature resistant tape, which includes a first section, a second section, and a third section. The second section covers the outer surface of the core, and the two ends of the core form blank areas not covered by the second section. The first section extends from the end face of the core to overlap with the second section, and the first section covers the edge of the first collector and one of the blank areas. The third section extends from the end face of the core to overlap with the second section, and the third section covers the edge of the second collector and another blank area.

[0009] Preferably, the overlap length between the first segment and the second segment is defined as X, and the overlap length between the third segment and the second segment is defined as Y, where X = 3~8mm and Y = 3~8mm.

[0010] Preferably, the overlap length between the first section and the first collector plate is defined as M, and the overlap length between the third section and the second collector plate is defined as N, where M = 5~10mm and N = 5~10mm.

[0011] Preferably, the main body of the second collector plate is in the shape of a racetrack, which includes two oppositely arranged arc segments and two parallel straight edges connecting the two arc segments.

[0012] Preferably, the outer diameter of the core is defined as D, the diameter of the arc segment in the second collector plate is defined as D2, and the distance between the two parallel straight edges is defined as h, where D2 = (0.8~0.95)D and h = (0.6~0.8)D.

[0013] Preferably, the first collector has 4 to 8 solder marks, and the included angle between two adjacent solder marks is 45° to 90°; the second collector has 4 to 8 solder marks symmetrically distributed, and the included angle between two adjacent solder marks is 60° to 80°.

[0014] Preferably, the diameter of the positive terminal is defined as D3, the welding area of ​​the positive terminal is defined as D4, the diameter of the negative terminal is defined as D5, and the welding area of ​​the negative terminal is defined as D6; wherein, D3 = (0.2~0.4)D4, D5 = (0.2~0.4)D6.

[0015] The present invention has the following technical effects: 1. This invention adopts a double-ended central pole structure. After the current is introduced into the current collector by the core electrode and the tab, it is directly concentrated and output to the central pole along the shortest radial path. The edge of the current collector is only used as a welding and fixing structure and does not carry the current conduction function at all. This completely avoids the safety hazards of the traditional structure of "large current at the edge - Joule heat accumulation - insulation layer stress damage - breakdown short circuit - thermal runaway", and realizes the upgrade of cell safety protection from passive protection to active avoidance.

[0016] 2. The positive and negative terminals are respectively arranged at the central axis positions at both ends of the core to achieve bidirectional symmetrical current output, which greatly reduces the current path difference between the inner and outer rings of the core, improves the uniformity of current density distribution across the entire area, reduces the potential difference of the electrode and Joule heat loss, effectively improves the high-rate charge and discharge capability of the cell, and extends the cycle life.

[0017] 3. The negative electrode second current collector adopts a racetrack-shaped irregular structure, which significantly reduces the amount of copper material used while ensuring sufficient welding of the outer electrode plates and stable current conduction. This solves the problems of material redundancy and high cost of traditional circular current collectors, and reduces the production cost of the battery cell without degrading electrical performance.

[0018] 4. A three-layer fully enclosed insulation structure is adopted, consisting of "flexible tape wrapping around the outer periphery of the core, insulating sheet covering the end face of the current collector, and flexible tape sealing of the overlapping area." Only the conductive area of ​​the central electrode is exposed, while the rest of the structure is completely insulated. The flexible insulation structure can adapt to the expansion of the battery cell during charging and discharging, as well as alternating high and low temperature conditions, avoiding the defects of rigid insulation structures that are prone to cracking and falling off. The insulation stability, temperature resistance, and resistance to electrolyte corrosion are greatly improved.

[0019] 5. By limiting the number of positive and negative current collector solder pads, the angle ratio, and the size ratio of the electrode post to the welding area, we ensure that the electrode tabs and current collectors are welded evenly and in sufficient contact, and that the current conduction is uniform without concentrated dead angles, thereby further reducing the contact internal resistance and improving the overall consistency of the battery cell. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure at the second end of the core in this invention; Figure 2 This is a schematic diagram of the structure at the first end of the core in this invention; Figure 3 for Figure 1 Exploded view of the structure; Figure 4 for Figure 2 Exploded view of the structure; Figure 5 This is an exploded view of the structure of the present invention; Figure 6 This is a schematic diagram of the structure of the second collector disk in this invention; Figure 7 This is a schematic diagram of the structure of the first collector disk in this invention; Figure 8 This is a cross-sectional view of the flexible high-temperature resistant tape in this invention.

[0021] 100. Core; 101. First end; 102. Second end; 103. Electrode; 200. First Collector Disk; 300. Second collector disk; 301. Circular arc segment; 302. Parallel straight edge; 400. Insulation layer; 401. First insulating sheet; 402. Second insulating sheet; 403. Flexible high-temperature resistant tape; 404. First section; 405. Second section; 406. Third section; 407. Blank area. Detailed Implementation

[0022] The principles and features of the present invention are described below with reference to embodiments; the examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0023] A battery cell with bipolar electrode groups has a core structure including a wound core 100, a first current collector 200, a second current collector 300, and an insulating layer 400. This battery cell is installed in a battery casing to form a battery. The wound core 100 is a cylindrical wound structure, with its axial ends defined as a first end 101 and a second end 102. The first end 101 forms the positive terminal through a connecting electrode 103, and the second end 102 forms the negative terminal through a connecting electrode 103, achieving independent arrangement of the positive and negative electrodes.

[0024] The first current collector 200 is connected to the positive terminal of the core 100, and the positive terminal is integrally formed or welded to its center; the second current collector 300 is connected to the negative terminal of the core 100, and the negative terminal is integrally formed or welded to its center. Both terminals are arranged in a coaxial manner to achieve bidirectional symmetrical axial current output.

[0025] The insulation layer 400 adopts a multi-layer composite flexible insulation structure, including a first insulating sheet 401, a second insulating sheet 402, and a flexible high-temperature resistant tape 403. The first insulating sheet 401 is attached to and covers the outer end face of the first collector plate 200, and the second insulating sheet 402 is attached to and covers the outer end face of the second collector plate 300, thereby achieving basic insulation isolation on the outside of the collector plate.

[0026] The flexible high-temperature resistant tape 403 is divided into a first section 404, a second section 405, and a third section 406 along the axial direction of the core 100. The second section 405 completely covers the outer circular sidewall of the core 100, leaving blank areas 407 at both ends of the core 100 along the axial direction for welding and assembling the manifold. The first section 404 extends from the first end face of the core and overlaps with the end of the second section 405, completely covering the edge of the first manifold 200 and the corresponding blank area 407. The third section 406 extends from the second end face of the core and overlaps with the end of the second section 405, completely covering the edge of the second manifold 300 and the corresponding blank area 407.

[0027] Section 404 extends outward along the end face of core 100, wrapping around the edge of first collector 200 and the corresponding blank area 407 of core 100. Section 404 and first collector 200 maintain an overlap of length M to ensure reliable adhesion and insulation between the tape and the edge of collector 200. Section 404 also extends inward to form an overlap of length X with section 405 to ensure the bonding strength of the tape itself. Similarly, section 406 extends outward along the other end face of core 100, wrapping around the edge of second collector 300 and the blank area 407 on the other side of core 100. Section 406 and second collector 300 maintain an overlap of length N. Section 406 extends inward to form an overlap of length Y with section 405.

[0028] The overlap length between section 404 and the first current collector 200 is defined as M, and the overlap length between section 406 and the second current collector 300 is defined as N; where M = 5-10 mm and N = 5-10 mm. Preferably, the overlap length between section 404 and section 405 is defined as X, and the overlap length between section 406 and section 405 is defined as Y; where X = 3-8 mm and Y = 3-8 mm. The overlap area widths X and Y are controlled within 3-8 mm, and the overlap widths M and N between the flexible tape and the current collector are controlled within 5-10 mm to ensure a tight, gapless overlap and eliminate insulation dead angles. By limiting the above overlap length range, the insulation reliability at the core end and current collector edge can be guaranteed, while avoiding excessive tape occupation of the internal space of the battery cell and controlling the amount of tape material used.

[0029] The second current collector 300 adopts a racetrack-shaped structure, formed by two symmetrical arc segments 301 and two parallel straight edges 302. Compared with the existing disc-shaped second current collector, the racetrack-shaped structure reduces material usage and achieves weight reduction while simplifying the overall structure, all while meeting the requirements for conductive connection. Based on the outer diameter D of the core, the diameter D2 of the arc segment 301 is 0.8~0.95D, and the distance h between the two parallel straight edges 302 is 0.6~0.8D. This dimensional ratio minimizes copper consumption and reduces production costs while fully covering the outer ring electrode of the core and ensuring welding area and conductivity.

[0030] In terms of welding structure design, the first current collector 200 is equipped with 4 to 8 evenly distributed welding marks, with the angle between adjacent welding marks being 45° to 90°, to achieve 360° all-round uniform welding; the second current collector 300 is equipped with 4 to 8 symmetrically distributed welding marks, with the angle between adjacent welding marks being 60° to 80°, to ensure that the welding force of the negative current collector is uniform and the current conduction is consistent.

[0031] In terms of electrode structure ratio, the diameter D3 of the positive electrode is 0.2 to 0.4 times that of the positive electrode welding area D4, and the diameter D5 of the negative electrode is 0.2 to 0.4 times that of the negative electrode welding area D6. This size ratio can balance the current carrying capacity of the electrode and the welding stability, avoid the electrode being too thin and having insufficient current carrying capacity, or too thick and occupying space and wasting materials, and adapt to the needs of high-rate charging and discharging conditions.

[0032] The working principle of this invention is as follows: During the charging and discharging process of the battery cell, the current generated by the inner and outer ring electrode plates of the core is evenly introduced into the first current collector 200 and the second current collector 300 through the electrode tabs. The current is concentrated and output to the central electrode post along the shortest radial path of the current collector. No current flows through the edge of the current collector, which only serves as a basic function for assembly, fixation, and auxiliary insulation. Combined with a multi-layer flexible fully enclosed insulation structure, the electrical contact between the current collector, the core, and the battery cell shell is completely isolated. At the same time, the symmetrical double-end current collector structure optimizes the current distribution, reduces internal resistance and heat accumulation, and ultimately achieves a comprehensive performance improvement of high safety, low internal resistance, long life, and low cost for the battery cell.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A battery cell having a bipolar electrode group, characterized in that, include, The core (100) has a first end (101) and a second end (102) opposite each other along the axial direction. The first end (101) is connected to a pole piece (103) to form a positive end, and the second end (102) is connected to a pole piece (103) to form a negative end. The first collector (200) is connected to the positive terminal, and the first collector (200) is formed or connected to a positive terminal post; The second collector (300) is connected to the negative terminal, and the second collector (300) is formed or connected to a negative terminal post; An insulating layer (400) is provided to electrically isolate the core (100), the first collector (200), and the second collector (300) from the housing.

2. The battery cell with a bipolar electrode group according to claim 1, characterized in that, The insulating layer (400) includes a first insulating sheet (401) and a second insulating sheet (402). The first insulating sheet (401) is attached to the side of the first collector (200) away from the core (100), and the second insulating sheet (402) is attached to the side of the second collector (300) away from the core (100).

3. The battery cell with a bipolar electrode group according to claim 2, characterized in that, The insulating layer (400) further includes a flexible high-temperature resistant tape (403), which includes a first section (404), a second section (405), and a third section (406). The second section (405) covers the outer surface of the core (100), and the two ends of the core (100) form blank areas (407) not covered by the second section (405). The first section (404) extends from the end face of the core (100) to overlap with the second section (405), and the first section (404) covers the edge of the first collector (200) and one of the blank areas (407). The three-section section (406) extends from the end face side of the core (100) to overlap with the two-section section (405), and the three-section section (406) covers the edge of the second collector plate (300) and another blank area (407).

4. The battery cell with a bipolar electrode group according to claim 1, characterized in that, The overlap length between the first section (404) and the second section (405) is defined as X, and the overlap length between the third section (406) and the second section (405) is defined as Y, where X = 3~8mm and Y = 3~8mm.

5. The battery cell with a bipolar electrode group according to claim 1, characterized in that, The overlap length between section 1 (404) and the first collector plate (200) is defined as M, and the overlap length between section 3 (406) and the second collector plate (300) is defined as N, where M = 5~10mm and Y = 5~10mm.

6. The battery cell with a bipolar electrode group according to claim 1, characterized in that, The main body of the second collector plate (300) is in the shape of a racetrack, which includes two oppositely arranged arc segments (301) and two parallel straight edges (302) connecting the two arc segments (301).

7. The battery cell with a bipolar electrode group according to claim 6, characterized in that, Define the outer diameter of the core (100) as D, define the diameter of the arc segment (301) in the second collector (300) as D2, and define the distance between the two parallel straight edges as h, where D2 = (0.8~0.95)D and h = (0.6~0.8)D.

8. The battery cell with a bipolar electrode group according to claim 1, characterized in that, The first collector plate (200) has 4 to 8 solder marks, and the included angle between two adjacent solder marks is 45° to 90°; the second collector plate (300) has 4 to 8 solder marks that are symmetrically distributed, and the included angle between two adjacent solder marks is 60° to 80°.

9. The battery cell with a bipolar electrode group according to claim 1, characterized in that, The diameter of the positive terminal is defined as D3, the welding area of ​​the positive terminal is defined as D4, the diameter of the negative terminal is defined as D5, and the welding area of ​​the negative terminal is defined as D6; wherein, D3 = (0.2~0.4)D4, D5 = (0.2~0.4)D6.

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