Battery cell structure and lithium ion battery

Abstract

This utility model discloses a cell structure and a lithium-ion battery, including a positive electrode, a negative electrode, and a separator. The positive electrode has a positive tab, and the negative electrode has a negative tab. The starting ends of the positive and negative electrode are stacked and wound together to form a core. The separator is disposed between adjacent positive and negative electrode sheets. The core includes a first bending region, a first extension region, a second bending region, and a second extension region sequentially along the winding direction. Each turn of the positive electrode in the first extension region has a positive tab, and each turn of the negative electrode in the first extension region has a negative tab. The second extension region includes an inner ring region and an outer ring region. The positive electrode in the inner ring region has a positive tab, and the negative electrode in the inner ring region has a negative tab. This utility model effectively solves the problem of lithium deposition at the inner ring corner of the core by adding tabs to the inner ring region, which is beneficial for large-scale application.

Description

Technical Field

[0001] This utility model belongs to the field of battery manufacturing technology, and relates to a cell structure, and more particularly to a cell structure and a lithium-ion battery. Background Technology

[0002] Currently, with the rapid development of the energy storage lithium battery industry, the continuous improvement of battery energy density has become a core pursuit, directly driving the continuous increase in the thickness of energy storage lithium battery cores. To adapt to this change, the core tabs typically adopt a single-sided tab design for A / B cores.

[0003] However, as the core size increases further, the adverse effects of the large curvature at the apex of the inner core on battery performance become increasingly prominent. From the microscopic mechanism of battery operation, the large curvature in this region causes many problems: (1) The large curvature at the apex changes the normal electric field distribution, making the current density at the corner much higher than that in the flat area. This uneven current distribution easily leads to excessively intense local electrochemical reactions; (2) The sharp corner structure prolongs the diffusion path of lithium ions inside the electrode, easily causing a significant increase in the local lithium ion concentration gradient; (3) The diffusion conditions in the large curvature region itself are poor, and the diffusion speed is slow. At the end of charging, the region is prone to the phenomenon of "local lithium depletion".

[0004] The aforementioned problems caused by high curvature combine to result in lithium plating easily occurring at the inner apex of the wound cell, while this does not occur at the outer apex and other parts of the cell due to their lower curvature. Lithium plating not only reduces battery performance, shortens cycle life, and limits fast-charging capacity, but also poses serious safety hazards such as combustion and explosion.

[0005] Therefore, how to provide a battery cell that improves lithium plating at corners and effectively solves the problem of lithium plating at the corners of the inner ring of the core has become a technical challenge that urgently needs to be overcome by those skilled in the art. Utility Model Content

[0006] To address the shortcomings of existing technologies, the purpose of this utility model is to provide a cell structure and a lithium-ion battery, which effectively solves the problem of lithium deposition at the corners of the inner ring of the core by adding tabs to the inner ring area of ​​the core.

[0007] To achieve the objective of this utility model, the following technical solution is adopted:

[0008] In a first aspect, this utility model provides a battery cell structure, including a positive electrode sheet, a negative electrode sheet, and a separator. A positive electrode tab is disposed on the positive electrode sheet, and a negative electrode tab is disposed on the negative electrode sheet. The starting ends of the positive and negative electrode sheets are stacked and wound together to form a core. The separator is disposed between adjacent positive and negative electrode sheets. The core includes, along the winding direction, a first bending region, a first extension region, a second bending region, and a second extension region, sequentially connected. Each turn of the positive electrode sheet in the first extension region is provided with a positive electrode tab, and each turn of the negative electrode sheet in the first extension region is provided with a negative electrode tab. The second extension region includes an inner ring region and an outer ring region. The positive electrode sheet in the inner ring region is provided with a positive electrode tab, and the negative electrode sheet in the inner ring region is provided with a negative electrode tab.

[0009] For winding cores with large curvature at corners, this invention adds tabs to the inner ring area of ​​the winding core to reduce the current density at the corner apex during charging and discharging, and increase the lithium ion diffusion rate in the bending area, thereby effectively avoiding lithium plating. The structure is simple and the effect is obvious, ultimately improving battery performance, extending cycle life, providing effective protection for fast charging of batteries, and preventing safety problems such as combustion and explosion caused by lithium plating.

[0010] In addition, this utility model only adds electrode tabs to the inner ring area of ​​the core. Compared with the traditional single-sided electrode tab structure design of the core, the number of additional electrode tabs is very limited and does not affect the process parameters of electrode tab welding power, thus ensuring the smooth progress of subsequent process procedures.

[0011] Preferably, the number of turns in the inner ring area accounts for 0.1%-45% of the total number of turns in the core.

[0012] Preferably, the total number of turns of the core is ≥10 turns.

[0013] Preferably, the positive electrode tab is disposed on the side of the first extension region near the first bending region; the negative electrode tab is disposed on the side of the first extension region near the second bending region.

[0014] Alternatively, the positive electrode tab may be disposed on the side of the first extension region away from the first bending region; and the negative electrode tab may be disposed on the side of the first extension region away from the second bending region.

[0015] Preferably, the positive electrode tab is disposed on the inner ring area near the first bending area; the negative electrode tab is disposed on the inner ring area near the second bending area.

[0016] Alternatively, the positive electrode tab may be disposed on the inner ring area away from the first bending area; the negative electrode tab may be disposed on the inner ring area away from the second bending area.

[0017] Preferably, the positive electrode tab in the first extension region corresponds to the position of the positive electrode tab in the inner ring region.

[0018] Preferably, the negative electrode tab in the first extension region corresponds to the position of the negative electrode tab in the inner ring region.

[0019] Preferably, the first extension region and the second extension region are symmetrically arranged.

[0020] Preferably, the first bending area and the second extension area are symmetrically arranged.

[0021] Preferably, after the core is flattened, the spacing between the positive electrode tabs is 200mm-350mm.

[0022] Preferably, after the core is flattened, the spacing between the negative electrode tabs is 200mm-350mm.

[0023] Preferably, after the core is flattened, the spacing between the positive electrode tabs forms an arithmetic sequence.

[0024] Preferably, after the core is flattened, the spacing between the negative electrode tabs forms an arithmetic sequence.

[0025] Secondly, this utility model provides a lithium-ion battery, which at least includes the cell structure described in the first aspect.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) For winding cores with large curvature at corners, this utility model adds tabs to the inner ring area of ​​the winding core to reduce the current density at the corner apex during charging and discharging, and increases the lithium ion diffusion rate in the bending area, thereby effectively avoiding lithium plating. The structure is simple and the effect is obvious, which ultimately improves battery performance, extends cycle life, provides effective protection for fast charging of batteries, and prevents safety problems such as combustion and explosion caused by lithium plating of batteries.

[0028] (2) This utility model only adds electrode tabs to the inner ring area of ​​the core. Compared with the traditional single-sided electrode tab structure design of the core, the number of additional electrode tabs is very limited and does not affect the process parameters of electrode tab welding power, thus ensuring the smooth progress of subsequent process. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the battery cell structure provided in Example 1;

[0030] Figure 2 It is a battery pack composed of the cells provided in Example 1;

[0031] Figure 3This is a schematic diagram of the battery cell structure provided in Comparative Example 1;

[0032] Figure 4 It is a battery pack composed of cells provided in Comparative Example 1.

[0033] Wherein: 1-First bending zone; 2-First extension zone; 3-Second bending zone; 4-Second extension zone; 5-Positive electrode tab; 6-Negative electrode tab. Detailed Implementation

[0034] It should be understood that in the description of this utility model, the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0035] It should be noted that, in the description of this utility model, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0036] An embodiment of this utility model provides a battery cell structure, including a positive electrode sheet, a negative electrode sheet, and a separator. A positive electrode tab is disposed on the positive electrode sheet, and a negative electrode tab is disposed on the negative electrode sheet. The starting ends of the positive and negative electrode sheets are stacked and wound together to form a core. The separator is disposed between adjacent positive and negative electrode sheets. The core includes, along the winding direction, a first bending region, a first extension region, a second bending region, and a second extension region, sequentially connected. Each turn of the positive electrode sheet in the first extension region has a positive electrode tab, and each turn of the negative electrode sheet in the first extension region has a negative electrode tab. The second extension region includes an inner ring region and an outer ring region. The positive electrode sheet in the inner ring region has a positive electrode tab, and the negative electrode sheet in the inner ring region has a negative electrode tab.

[0037] For winding cores with large curvature at corners, this invention adds tabs to the inner ring area of ​​the winding core to reduce the current density at the corner apex during charging and discharging, and increase the lithium ion diffusion rate in the bending area, thereby effectively avoiding lithium plating. The structure is simple and the effect is obvious, ultimately improving battery performance, extending cycle life, providing effective protection for fast charging of batteries, and preventing safety problems such as combustion and explosion caused by lithium plating.

[0038] In addition, this utility model only adds electrode tabs to the inner ring area of ​​the core. Compared with the traditional single-sided electrode tab structure design of the core, the number of additional electrode tabs is very limited and does not affect the process parameters of electrode tab welding power, thus ensuring the smooth progress of subsequent process procedures.

[0039] In some embodiments, the number of turns in the inner zone relative to the total number of turns in the core is 0.1%-45%, for example, it can be 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or 45%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0040] This invention specifically limits the proportion of the number of inner rings relative to the total number of core rings, which essentially limits the area where the tabs are added. This not only avoids excessive current density at the corner apex during charging and discharging due to an excessively small tab area, but also prevents changes in subsequent tab welding process parameters due to an excessively large tab area. It effectively balances the improvement of corner lithium plating phenomenon and the smooth progress of subsequent processes.

[0041] In some embodiments, the total number of turns of the core is ≥10 turns, for example, it can be 10 turns, 11 turns, 12 turns, 13 turns, 14 turns, 15 turns, 16 turns, 17 turns, 18 turns, 19 turns or 20 turns, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0042] In some embodiments, the positive electrode tab is disposed on the side of the first extension region near the first bending region; the negative electrode tab is disposed on the side of the first extension region near the second bending region.

[0043] Alternatively, the positive electrode tab may be disposed on the side of the first extension region away from the first bending region; and the negative electrode tab may be disposed on the side of the first extension region away from the second bending region.

[0044] In some embodiments, the positive electrode tab is disposed on the inner ring area near the first bending area; the negative electrode tab is disposed on the inner ring area near the second bending area.

[0045] Alternatively, the positive electrode tab may be disposed on the inner ring area away from the first bending area; the negative electrode tab may be disposed on the inner ring area away from the second bending area.

[0046] In some embodiments, the positive electrode tab of the first extension region corresponds to the position of the positive electrode tab of the inner ring region.

[0047] In some embodiments, the negative electrode tab in the first extension region corresponds to the position of the negative electrode tab in the inner ring region.

[0048] In some embodiments, the first extension region and the second extension region are symmetrically arranged.

[0049] In some embodiments, the first bending region and the second extension region are symmetrically arranged.

[0050] In some embodiments, after the core is flattened, the spacing between the positive electrode tabs is 200mm-350mm, for example, it can be 200mm, 210mm, 220mm, 230mm, 240mm, 250mm, 260mm, 270mm, 280mm, 290mm, 300mm, 310mm, 320mm, 330mm, 340mm or 350mm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0051] In some embodiments, after the core is flattened, the spacing between the negative electrode tabs is 200mm-350mm, for example, it can be 200mm, 210mm, 220mm, 230mm, 240mm, 250mm, 260mm, 270mm, 280mm, 290mm, 300mm, 310mm, 320mm, 330mm, 340mm or 350mm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0052] In some embodiments, after the core is flattened, the spacing between the positive electrode tabs forms an arithmetic sequence.

[0053] In some embodiments, after the core is flattened, the spacing between the negative electrode tabs forms an arithmetic sequence.

[0054] In this invention, the arithmetic sequence specifically refers to adjacent values ​​having essentially the same difference, and the specific difference can be adaptively adjusted based on factors such as the thickness of the electrode sheet and the number of winding turns.

[0055] One embodiment of this utility model also provides a lithium-ion battery, which includes at least the cell structure described in any of the above embodiments.

[0056] The technical solution of this utility model will be further described below with reference to the accompanying drawings and specific embodiments.

[0057] Example 1

[0058] This embodiment provides a battery cell structure, including a positive electrode, a negative electrode, and a separator, such as... Figure 1 As shown, a positive electrode tab 5 is provided on the positive electrode sheet, and a negative electrode tab 6 is provided on the negative electrode sheet. The starting ends of the positive electrode sheet and the negative electrode sheet are stacked on each other and wound together to form a core. The separator is provided between adjacent positive electrode sheets and negative electrode sheets.

[0059] Specifically, the core includes a first bending region 1, a first extension region 2, a second bending region 3, and a second extension region 4 sequentially along the winding direction; each turn of the positive electrode sheet in the first extension region 2 is provided with a positive electrode tab 5, and each turn of the negative electrode sheet in the first extension region 2 is provided with a negative electrode tab 6; the second extension region 4 includes an inner ring region and an outer ring region, the positive electrode sheet in the inner ring region is provided with a positive electrode tab 5, and the negative electrode sheet in the inner ring region is provided with a negative electrode tab 6.

[0060] In this embodiment, the total number of turns of the winding core is 23, and the number of turns in the inner ring area is 10. The positive electrode tab 5 is disposed on the side of the first extension area 2 near the first bending area 1; the negative electrode tab 6 is disposed on the side of the first extension area 2 near the second bending area 3. Simultaneously, the positive electrode tab 5 is disposed on the side of the inner ring area near the first bending area 1; the negative electrode tab 6 is disposed on the side of the inner ring area near the second bending area 3. The positions of the positive electrode tab 5 in the first extension area 2 correspond to the positions of the positive electrode tab 5 in the inner ring area, and the positions of the negative electrode tab 6 in the first extension area 2 correspond to the positions of the negative electrode tab 6 in the inner ring area. The first extension area 2 and the second extension area 4 are symmetrically arranged, and the first bending area 1 and the second extension area 4 are symmetrically arranged. The battery pack assembled using the winding core provided in this embodiment after relative arrangement is shown below. Figure 2 .

[0061] After the core provided in this embodiment is flattened, the spacing between each group of adjacent positive electrode tabs 5 is numbered from the inner circle area to the outer circle area in the manner of D1, D2, D3... The corresponding spacing between positive electrode tabs 5 is shown in Table 1 below.

[0062] Table 1

[0063]

[0064] In this embodiment, the spacing of the positive electrode tab 5 can be adjusted by changing the die-cutting spacing of the electrode sheet. As long as the bipolar tab design of each turn can be achieved, the die-cutting process parameters will not be specifically described here.

[0065] In this embodiment, the spacing arrangement of the negative electrode tab 6 is similar to that of the positive electrode tab 5, so it will not be described in detail here.

[0066] Comparative Example 1

[0067] This comparative example provides a battery cell structure, including a positive electrode, a negative electrode, and a separator, such as... Figure 3 As shown, a positive electrode tab 5 is provided on the positive electrode sheet, and a negative electrode tab 6 is provided on the negative electrode sheet. The starting ends of the positive electrode sheet and the negative electrode sheet are stacked on each other and wound together to form a core. The separator is provided between adjacent positive electrode sheets and negative electrode sheets.

[0068] Specifically, the core includes a first bending region 1, a first extension region 2, a second bending region 3, and a second extension region 4 sequentially along the winding direction; each turn of the positive electrode sheet in the first extension region 2 is provided with a positive electrode tab 5, each turn of the negative electrode sheet in the first extension region 2 is provided with a negative electrode tab 6, and the second extension region 4 is not provided with a positive electrode tab 5 or a negative electrode tab 6.

[0069] In this comparative example, the total number of turns of the winding core is 23; the positive electrode tab 5 is disposed on the side of the first extension region 2 near the first bending region 1; the negative electrode tab 6 is disposed on the side of the first extension region 2 near the second bending region 3. The first extension region 2 and the second extension region 4 are symmetrically arranged, and the first bending region 1 and the second extension region 4 are also symmetrically arranged. The battery cell pack assembled using the winding cores provided in this comparative example with their relative arrangement is shown below. Figure 4 .

[0070] After the core provided in this comparative example is flattened, the spacing between adjacent positive electrode tabs 5 in each group is numbered using the format D1, D2, D3... The corresponding spacing between positive electrode tabs 5 is shown in Table 2 below.

[0071] Table 2

[0072]

[0073] In this comparative example, the spacing of the positive electrode tab 5 can be adjusted by changing the die-cutting spacing of the electrode sheet. As long as the single electrode tab design of each turn can be achieved, the die-cutting process parameters will not be specifically explained here.

[0074] In this comparative example, the spacing arrangement of the negative electrode tab 6 is similar to that of the positive electrode tab 5, so it will not be described in detail here.

[0075] The battery packs composed of the cells provided in Example 1 and Comparative Example 1 were cycled through 100 charge-discharge cycles, and then the batteries were disassembled and compared. The results showed that the cell provided in Example 1 did not exhibit lithium plating at the bends, while the cell provided in Comparative Example 1 showed obvious lithium plating at the bends.

[0076] Therefore, for winding cores with large curvature at corners, this utility model adds tabs to the inner ring area of ​​the winding core to reduce the current density at the corner apex during charging and discharging, and increases the lithium ion diffusion rate in the bending area, thereby effectively avoiding lithium plating. The structure is simple and the effect is obvious, ultimately improving battery performance, extending cycle life, providing effective protection for fast charging of batteries, and preventing safety problems such as combustion and explosion caused by lithium plating.

[0077] In addition, this utility model only adds electrode tabs to the inner ring area of ​​the core. Compared with the traditional single-sided electrode tab structure design of the core, the number of additional electrode tabs is very limited and does not affect the process parameters of electrode tab welding power, thus ensuring the smooth progress of subsequent process procedures.

[0078] The above description is only a specific embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present utility model fall within the protection and disclosure scope of the present utility model.

Claims

1. A battery cell structure comprising a positive electrode plate, a negative electrode plate, and a separator, wherein a positive electrode tab is disposed on the positive electrode plate, a negative electrode tab is disposed on the negative electrode plate, the starting ends of the positive and negative electrode plates are stacked and wound together to form a core, and the separator is disposed between adjacent positive and negative electrode plates, characterized in that, The winding core includes a first bending region, a first extension region, a second bending region, and a second extension region sequentially along the winding direction; each turn of the positive electrode sheet in the first extension region is provided with a positive electrode tab, and each turn of the negative electrode sheet in the first extension region is provided with a negative electrode tab; the second extension region includes an inner ring region and an outer ring region, the positive electrode sheet in the inner ring region is provided with a positive electrode tab, and the negative electrode sheet in the inner ring region is provided with a negative electrode tab.

2. The cell structure according to claim 1, characterized in that, The number of turns in the inner zone accounts for 0.1% to 45% of the total number of turns in the core.

3. The cell structure according to claim 2, characterized in that, The total number of turns of the core is ≥10 turns.

4. The cell structure according to claim 1 or 2, characterized in that, The positive electrode tab is disposed on the first extension area near the first bending area; the negative electrode tab is disposed on the first extension area near the second bending area. Alternatively, the positive electrode tab may be disposed on the side of the first extension region away from the first bending region; and the negative electrode tab may be disposed on the side of the first extension region away from the second bending region.

5. The cell structure according to claim 1 or 2, characterized in that, The positive electrode tab is disposed on the inner ring area near the first bending area; the negative electrode tab is disposed on the inner ring area near the second bending area; Alternatively, the positive electrode tab may be disposed on the inner ring area away from the first bending area; the negative electrode tab may be disposed on the inner ring area away from the second bending area.

6. The cell structure according to claim 1 or 2, characterized in that, The positive electrode tab in the first extended region corresponds to the position of the positive electrode tab in the inner ring region; And / or, the negative electrode tab in the first extension region corresponds to the position of the negative electrode tab in the inner ring region.

7. The cell structure according to claim 1 or 2, characterized in that, The first extension region and the second extension region are symmetrically arranged; And / or, the first bending area and the second extension area are symmetrically arranged.

8. The cell structure according to claim 1 or 2, characterized in that, After the core is flattened, the spacing between the positive electrode tabs is 200mm-350mm; And / or, after the core is flattened, the spacing between the negative electrode tabs is 200mm-350mm.

9. The cell structure according to claim 8, characterized in that, After the core is flattened, the spacing between the positive electrode tabs forms an arithmetic sequence. And / or, after the core is flattened, the spacing between the negative electrode tabs forms an arithmetic sequence.

10. A lithium-ion battery, characterized in that, The lithium-ion battery contains at least the cell structure as described in any one of claims 1-9.

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