Battery cell and battery

Abstract

The utility model provides a battery cell and battery, including: first pole piece, diaphragm and second pole piece, first pole piece, diaphragm and second pole piece are laminated in proper order and wound into the battery cell, the battery cell includes bending area and straight area, first pole piece, diaphragm and second pole piece have bending radian in the bending area, and the straight area has bending radian in the straight area. The first pole piece, the diaphragm and the second pole piece are straightly arranged in the straight area; the first pole piece comprises a first current collector, an inner side first active material layer and an outer side first active material layer, the inner side first active material layer is arranged on one side, facing the interior of the battery cell, of the first current collector, and the outer side first active material layer is arranged on one side, facing the exterior of the battery cell, of the first current collector; the inner side first active material layer is provided with a first hole opening area, the first hole opening area is located in the bending area, and a plurality of grooves are formed in the first hole opening area. According to the battery cell provided by the utility model, the charging and discharging capability of the battery cell can be effectively improved.

Description

Technical Field

[0001] This utility model relates to the field of new energy technology, and in particular to a battery cell and battery. Background Technology

[0002] Lithium-ion batteries, characterized by their high energy density, are widely used in digital and power battery fields. As digital products demand increasingly higher fast-charging rates, the areal density and compaction density of battery cells are becoming increasingly higher. This leads to greater pressure on the corners of the cell. During cycling, the compression at these corners causes electrolyte to be squeezed out. As the electrolyte gradually diminishes, it can lead to electrolyte breakage at the corners. With improved fast-charging performance, high-rate charge and discharge typically cause lithium plating on the anode electrode, initially appearing at the corners and gradually worsening with each cycle until it spreads throughout the entire electrode. This is especially true at the convex anode surface, where the winding structure results in a smaller CB (concave-to-convex) and a thicker cathode surface, making the cell more prone to lithium plating and reducing its charging capacity. Conversely, the concave anode surface, corresponding to the convex cathode surface, has a larger CB, making lithium plating less likely. However, the thicker concave anode surface hinders lithium ion transport within the inner layers, resulting in poorer discharge performance. Therefore, a battery cell with better charge and discharge performance is needed. Utility Model Content

[0003] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a battery cell that can effectively improve the charging and discharging capabilities of the battery cell.

[0004] This utility model also proposes a battery.

[0005] A battery cell according to a first aspect of the present invention includes: a first electrode, a separator, and a second electrode. The first electrode, the separator, and the second electrode are sequentially stacked and wound to form the battery cell. The battery cell includes a bending region and a straight region. The first electrode, the separator, and the second electrode have a bending arc in the bending region, and the first electrode, the separator, and the second electrode are straight in the straight region. The first electrode includes a first current collector, an inner first active material layer, and an outer first active material layer. The inner first active material layer is disposed on the side of the first current collector facing the inside of the battery cell, and the outer first active material layer is disposed on the side of the first current collector facing the outside of the battery cell. A first opening region is provided on the inner first active material layer. The first opening region is located in the bending region, and a plurality of grooves are formed in the first opening region.

[0006] The battery cell according to the first aspect of this utility model has at least the following beneficial effects: by providing a groove in the first opening area, the active material in the inner first active material layer is reduced, thereby giving the first opening area better liquid retention capacity, allowing the electrolyte to more fully wet the first electrode. When the first electrode is a cathode, the groove not only improves the charging capacity of the battery cell, allowing lithium ions to be embedded in the cathode more quickly, but also effectively avoids lithium plating. When the first electrode is an anode, it avoids the difficulty of lithium ion transport caused by the large thickness of the anode, thereby improving the discharge capacity of the battery cell.

[0007] According to some embodiments of the present invention, the second electrode includes a second electrode current collector, an inner second electrode active material layer, and an outer second electrode active material layer. The inner second electrode active material layer is disposed on the side of the second electrode current collector facing the inside of the battery cell, and the outer second electrode active material layer is disposed on the side of the second electrode current collector facing the outside of the battery cell. A second opening area is provided on the inner second electrode active material layer, and the second opening area is located within the bending area. Multiple grooves are formed within the second opening area.

[0008] According to some embodiments of the present invention, the thickness of the inner first active material layer in the first direction is H, the depth of the groove in the first direction is not less than 0.1H and not greater than 0.9H, and the first direction is the thickness direction of the first electrode sheet.

[0009] According to some embodiments of the present invention, the inner first active material layer has an upper edge and a lower edge along a second direction, and a center line is provided on the inner first active material layer. The center line is arranged along the second direction, which is the winding direction of the first electrode sheet. The distance from the center line to the upper edge along a third direction is equal to the distance from the center line to the lower edge. The third direction is the width direction of the first electrode sheet. The depth of the groove away from the center line along the third direction decreases sequentially.

[0010] According to some embodiments of the present invention, the width of the first opening area in the third direction is equal to the width of the inner first active material layer in the third direction. The first opening area is provided with multiple partitions along the third direction. The width of the multiple partitions in the third direction is equal. The depth difference between the grooves in the same partition does not exceed 0.1H. The depth difference between the grooves in adjacent partitions is not less than 0.09H and not greater than 0.11H.

[0011] According to some embodiments of the present invention, the first opening area is provided with seven partitions along the third direction, the partition located on the center line is the center partition, and the depth of the groove in the center partition is not less than 0.89H and not greater than 0.91H.

[0012] According to some embodiments of the present invention, the length of the first opening area on the first electrode of the first layer of the battery cell winding in the second direction is L, the second direction is the winding direction of the first electrode, the thickness of the first electrode is A, the thickness of the second electrode is B, the thickness of the separator is C, and the length of the first opening area on the first electrode of the Nth layer of the battery cell winding in the third direction is S, where S=L+π*[(N-1)*(A+B+2C)] / 2.

[0013] According to some embodiments of this utility model, the groove is a circular hole, and the diameter of the groove is not less than 20 μm and not greater than 90 μm.

[0014] According to some embodiments of the present invention, the grooves are arranged in an array within the first opening area, and the spacing between the grooves is not less than 1 mm and not more than 3 mm.

[0015] The battery according to a second aspect of the present invention includes the battery cell described in any one of the above embodiments.

[0016] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the winding structure of a battery cell according to the present invention;

[0018] Figure 2 This is a schematic diagram of the unfolded structure of the first electrode of a battery cell according to the present invention;

[0019] Figure 3 This is a schematic diagram of the structure of the first opening area of ​​a battery cell according to the present invention;

[0020] Figure 4 This is a schematic cross-sectional view of the first opening area of ​​the adhesive tape of a battery cell according to the present invention.

[0021] Icon labels:

[0022] 1. First electrode; 11. First current collector; 12. Inner first active material layer; 13. Outer first active material layer; 14. First opening area; 2. Second electrode; 3. Diaphragm; 4. Groove; 5. Bending area; 6. Straight area; 7. Center line. Detailed Implementation

[0023] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0024] In the description of this utility model, it should be understood that the orientation descriptions, such as up and down, are 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.

[0025] In the description of this utility model, "multiple" refers to two or more. The use of "first" and "second" is for distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features or their sequential relationship.

[0026] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0027] Insufficient electrolyte wetting can hinder ion transport, limiting the battery's discharge or charge rate within a short period and thus affecting its charge / discharge rate. Simultaneously, inadequate electrolyte wetting of the electrode surface can lead to the formation of "dead zones," restricting lithium-ion transport and consequently impacting the battery's cycle performance. Furthermore, uneven wetting can result in uneven current density distribution, affecting the battery's energy density and cycle life.

[0028] When the electrolyte is insufficiently wetted, lithium ions at the positive and negative electrodes are prone to meet inside the cell, generating exothermic and gas-releasing phenomena. This can cause the electrolyte to be squeezed out, resulting in lithium plating. Lithium plating not only affects cell performance and lifespan but can also pose safety hazards. Furthermore, insufficient electrolyte wetting leads to increased internal battery temperature, raising the risk of thermal runaway or explosion.

[0029] Incomplete wetting can lead to problems such as active material stripping and lithium dendrite growth, which can increase the cell's internal resistance and reduce its capacity, accelerating the cell's aging process. More seriously, it can cause localized overheating during charging and discharging, leading to thermal runaway and safety issues such as fires and explosions.

[0030] Reference Figure 1 , Figure 2 , Figure 3 and Figure 4 The battery cell in the first embodiment of this utility model includes: a first electrode 1, a separator 3, and a second electrode 2. The first electrode 1, the separator 3, and the second electrode 2 are stacked and wound in sequence to form the battery cell. The battery cell includes a bending region 5 and a straight region 6. The first electrode 1, the separator 3, and the second electrode 2 have a bending arc in the bending region 5, and the first electrode 1, the separator 3, and the second electrode 2 are straight in the straight region 6. The first electrode 1 includes a first current collector 11, an inner first active material layer 12, and an outer first active material layer 13. The inner first active material layer 12 is disposed on the side of the first current collector 11 facing the inside of the battery cell, and the outer first active material layer 13 is disposed on the side of the first current collector 11 facing the outside of the battery cell. A first opening region 14 is provided on the inner first active material layer 12. The first opening region 14 is located within the bending region 5, and a plurality of grooves 4 are formed in the first opening region 14. In a wound battery cell, the bending deformation of the bending region 5 increases the compressive force between the electrodes, preventing the electrolyte in the bending region 5 from fully wetting the electrodes. Therefore, a groove 4 is provided in the first opening region 14 on the first electrode 1. The groove 4 can hold more electrolyte, thus ensuring more electrolyte in the bending region 5 of the battery cell and preventing lithium plating due to insufficient electrolyte. It also increases the contact area between the active material and the electrolyte in the first opening region 14, improving the ability of lithium ions to insert or extract.

[0031] When the first electrode 1 is a cathode, the anode sheet at the convex surface of the bending region 5, i.e., the side where the current collector of the anode sheet faces outwards from the cell, is affected by the winding structure. The convex surface of the anode corresponds to the concave surface of the cathode, i.e., the side where the first current collector 11 faces inwards from the cell. This results in a smaller CB value and a larger thickness of the concave cathode surface, making the cell prone to lithium plating and weakening its charging capacity. Therefore, a groove 4 is formed in the first opening region 14, thereby reducing the mass of active material on the cathode sheet within the first opening region 14, increasing the CB value, effectively preventing lithium plating, and simultaneously increasing the electrolyte content and contact area of ​​the active material layer within the first opening region 14. This allows the outer first active material layer 13 to have more sufficient contact with the electrolyte, thereby improving the cell's charging capacity. When the first electrode 1 is an anode, the cell's discharge capacity can be improved.

[0032] According to some embodiments of this utility model, the second electrode 2 includes a second electrode 2 current collector, an inner second electrode 2 active material layer, and an outer second electrode 2 active material layer. The inner second electrode 2 active material layer is disposed on the side of the second electrode 2 current collector facing the inside of the battery cell, and the outer second electrode 2 active material layer is disposed on the side of the second electrode 2 current collector facing the outside of the battery cell. A second opening area is provided on the inner second electrode 2 active material layer, which is located within the bending area 5. Multiple grooves 4 are formed within the second opening area. When the first electrode 1 is an anode, the second electrode 2 is a cathode. When the first electrode 1 is a cathode, the second electrode 2 is an anode. When both the first electrode 1 and the second electrode 2 have grooves 4 in the bending area 5, that is, grooves 4 are provided in both the first opening area 14 and the second opening area, lithium plating in the battery cell can be effectively avoided, and the charge and discharge performance of the battery cell can be improved.

[0033] According to some embodiments of this utility model, the thickness of the inner first active material layer 12 in the first direction is H, and the depth of the groove 4 in the first direction is not less than 0.1H and not greater than 0.9H, where the first direction is the thickness direction of the first electrode 1. If the depth of the groove 4 is too large, the first current collector 11 will be exposed; if the depth of the groove 4 is too small, sufficient electrolyte cannot be retained. Therefore, the depth of the groove 4 is limited to ensure sufficient electrolyte while preventing the first current collector 11 from being exposed.

[0034] According to some embodiments of this utility model, the inner first active material layer 12 has an upper edge and a lower edge along a second direction, and a center line 7 is provided on the inner first active material layer 12. The center line 7 is arranged along the second direction, which is the winding direction of the first electrode 1. The distance from the center line 7 to the upper edge along a third direction is equal to the distance from the center line 7 to the lower edge. The third direction is the width direction of the first electrode 1. The depth of the groove 4 away from the center line 7 decreases sequentially along the third direction. Electrolyte is more likely to be lacking at the center of the inner first active material layer 12, so the depth of the groove 4 is set deeper near the center line 7 to accommodate more electrolyte. The groove 4 is closer to the upper or lower edge away from the center line 7, and electrolyte is easier to penetrate. Therefore, the groove 4 is set shallower to obtain sufficient electrolyte.

[0035] According to some embodiments of this utility model, the width of the first opening region 14 in the third direction is equal to the width of the inner first active material layer 12 in the third direction. The first opening region 14 is provided with multiple partitions along the third direction, and the widths of these partitions in the third direction are equal. The depth difference between the grooves 4 within the same partition does not exceed 0.1H, and the depth difference between the grooves 4 in adjacent partitions is not less than 0.09H and not greater than 0.11H. Specifically, the first opening region 14 is provided with seven partitions along the third direction, with the partition located on the center line 7 being the central partition. The depth of the grooves 4 within the central partition is not less than 0.89H and not greater than 0.91H. Further partitioning the first opening region to limit the depth of the grooves 4 results in more uniform electrolyte containment.

[0036] According to some embodiments of this utility model, the length of the first opening region 14 on the first electrode 1 of the first layer of the battery cell winding is L in the second direction, where the second direction is the winding direction of the first electrode 1. The thickness of the first electrode 1 is A, the thickness of the second electrode 2 is B, and the thickness of the separator 3 is C. The length of the first opening region 14 on the first electrode 1 of the Nth layer of the battery cell winding in the third direction is S, where S = L + π * [(N-1) * (A + B + 2C)] / 2. During battery cell winding, a semi-circular shape is formed in the bending region 5. Within the bending region 5, the length of the first electrode 1 gradually increases from the inside to the outside of the winding layers, i.e., the winding radius increases, and the winding length also increases. Therefore, the length L of the first opening region 14 also needs to be increased. This allows the grooves 4 to be distributed more fully and evenly within the winding region.

[0037] According to some embodiments of this utility model, the groove 4 is a circular hole, and the diameter of the groove 4 is not less than 20 μm and not more than 90 μm. The groove 4 can be set as a strip or polygon, but setting the groove 4 as a circular hole makes the groove 4 easier to set and also makes the groove 4 easier to contain electrolyte. If the diameter of the groove 4 is too small, it cannot contain enough electrolyte. If the space of the groove 4 is too large, it is easy to form a broken bridge in the groove 4, thereby causing lithium plating.

[0038] According to some embodiments of this utility model, the grooves 4 are arranged in an array within the first opening region 14, and the spacing between the grooves 4 is not less than 1 mm and not more than 3 mm. If the spacing between the grooves 4 is too small, it may cause damage to the structure of the active material within the first opening region 14; if the spacing between the grooves 4 is too large, it will reduce the amount of electrolyte that can be contained.

[0039] The battery according to the second aspect of the present invention includes the battery cell of any of the above embodiments.

[0040] Lithium plating in batteries refers to the uneven deposition of lithium ions on the surface of the secondary electrode during battery charging, eventually forming lithium metal dendrites. The appearance of these dendrites poses a significant threat to battery health. First, from a safety perspective, lithium dendrite growth is a double-edged sword. It can not only pierce the battery's internal separator, causing direct contact between the positive and negative electrodes, but this contact often has catastrophic consequences. Once a short circuit occurs, the internal temperature of the battery will rise sharply, triggering a series of chain reactions, potentially leading to overheating, expansion, or even fire and explosion, posing a significant safety hazard to users. Second, battery life is also significantly reduced due to lithium dendrite formation. The continuous growth of lithium dendrites consumes the battery's precious lithium-ion resources. As lithium ions decrease, the number of rechargeable cycles and capacity of the battery gradually decline. Users will find that a battery that could have lasted for several years may experience significant performance degradation in a very short time. Furthermore, the battery's charging and discharging efficiency is also severely affected. The formation of lithium dendrites increases the internal resistance of the battery, making the flow of electrons within the battery less smooth. This increased resistance not only reduces charging speed but also affects power output during discharge, thus lowering the overall battery performance. Finally, the stability of battery performance is also affected by the uneven growth of lithium dendrites. The growth of lithium dendrites can lead to voltage instability during battery use. These voltage fluctuations directly affect the devices powered by the battery, causing them to operate unstably or even shut down unexpectedly. Therefore, lithium plating is a phenomenon that must be strictly controlled and avoided in the design and use of lithium-ion batteries. Battery manufacturers and researchers have been working to reduce or eliminate lithium dendrite formation by improving battery materials, optimizing battery structure, and optimizing charging strategies to ensure battery safety, extend its lifespan, and maintain its performance stability and reliability.

[0041] The embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present utility model.

Claims

1. A battery cell, characterized in that, include: A first electrode, a separator, and a second electrode are sequentially stacked and wound to form a battery cell. The battery cell includes a bent region and a straight region. The first electrode, the separator, and the second electrode have a bending arc in the bent region, and the first electrode, the separator, and the second electrode are straight in the straight region. The first electrode includes a first current collector, an inner first active material layer, and an outer first active material layer. The inner first active material layer is disposed on the side of the first current collector facing the inside of the battery cell, and the outer first active material layer is disposed on the side of the first current collector facing the outside of the battery cell. A first opening area is provided on the inner first active material layer, and the first opening area is located in the bending area. Multiple grooves are formed in the first opening area.

2. The battery cell according to claim 1, characterized in that, The second electrode includes a second electrode current collector, an inner second electrode active material layer, and an outer second electrode active material layer. The inner second electrode active material layer is disposed on the side of the second electrode current collector facing the inside of the battery cell, and the outer second electrode active material layer is disposed on the side of the second electrode current collector facing the outside of the battery cell. A second opening area is provided on the inner second electrode active material layer, and the second opening area is located within the bending area. Multiple grooves are formed within the second opening area.

3. The battery cell according to claim 1, characterized in that, The thickness of the inner first active material layer in the first direction is H, and the depth of the groove in the first direction is not less than 0.1H and not greater than 0.9H, where the first direction is the thickness direction of the first electrode.

4. The battery cell according to claim 3, characterized in that, The inner first active material layer has an upper edge and a lower edge along a second direction. The inner first active material layer has a center line, which is set along the second direction, which is the winding direction of the first electrode. The distance from the center line to the upper edge along the third direction is equal to the distance from the center line to the lower edge. The third direction is the width direction of the first electrode. The depth of the groove away from the center line along the third direction decreases sequentially.

5. The battery cell according to claim 4, characterized in that, The width of the first opening area in the third direction is equal to the width of the inner first active material layer in the third direction. The first opening area is provided with multiple partitions along the third direction. The width of the multiple partitions in the third direction is equal. The depth difference between the grooves in the same partition does not exceed 0.1H. The depth difference between the grooves in adjacent partitions is not less than 0.09H and not greater than 0.11H.

6. The battery cell according to claim 5, characterized in that, The first opening area is provided with seven partitions along the third direction, and the partition located on the center line is the center partition. The depth of the groove in the center partition is not less than 0.89H and not greater than 0.91H.

7. The battery cell according to claim 1, characterized in that, The length of the first opening area on the first electrode of the first layer of the battery cell is L in the second direction, where the second direction is the winding direction of the first electrode. The thickness of the first electrode is A, the thickness of the second electrode is B, and the thickness of the separator is C. The length of the first opening area on the first electrode of the Nth layer of the battery cell in the third direction is S, where S = L + π * [(N-1) * (A + B + 2C)] / 2.

8. The battery cell according to claim 1, characterized in that, The groove is a circular hole, and the diameter of the groove is not less than 20 μm and not more than 90 μm.

9. The battery cell according to claim 1, characterized in that, The grooves are arranged in an array within the first opening area, and the spacing between the grooves is not less than 1 mm and not more than 3 mm.

10. A battery, characterized in that, The battery cell includes any one of claims 1-9.

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