Battery cell and battery

Abstract

The utility model provides an electric core and battery, first active material layer coats in the one side of first current collector's direction anode piece, second active material layer coats in the one side of first current collector's back anode piece, third active material layer coats in the one side of second current collector's direction cathode piece, fourth active material layer coats in the one side of second current collector's back cathode piece, first recess is set up in the one side of third active material layer's back second current collector, the projection of pole lug in first direction is in the projection of first recess in first direction, second recess is set up in the one side of fourth active material layer's back second current collector, the projection of pole lug in first direction is in the projection of second recess in first direction, first direction is the laminated direction of cathode piece, diaphragm and anode piece, for the electric core of the utility model, can improve the energy density of electric core under the premise of guaranteeing the safety performance of electric core.

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] With continuous technological advancements and innovation, the demand for various smart devices, especially smartphones and computers, is growing daily. The widespread adoption of these devices has led to higher requirements for the performance and safety of smart products. Among numerous performance indicators, energy density has become the focus of attention for both consumers and manufacturers. High-energy-density battery cells exhibit a significant volume effect during charging and discharging, resulting in greater anode expansion. This expansion can cause copper foil fatigue after cycling, ultimately leading to foil breakage. Specifically, at the anode position corresponding to the cathode tab, the cathode tab's thickness is greater than the anode tab's. The protruding cathode tab relative to the electrode thickness direction results in a larger diameter of the wound core at the cathode tab location, subjecting this position to greater stress during charging and discharging, thus causing anode electrode breakage. This phenomenon significantly degrades cell performance, increases internal resistance and leads to uneven charging and discharging processes, generating overheating and short-circuit risks, shortening battery life, and potentially causing safety accidents. Therefore, ensuring that electrode breakage does not occur during battery cell production and use is crucial for guaranteeing cell safety and reliability. Thus, a battery cell that can effectively reduce electrode breakage 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 prevent electrode breakage during use.

[0004] This utility model also proposes a battery.

[0005] A battery cell according to a first aspect of the present invention includes: a tab, a cathode plate, a separator, and an anode plate, wherein the cathode plate, the separator, and the anode plate are sequentially stacked and wound into a core; the cathode plate includes a first current collector, a first active material layer, and a second active material layer, wherein the first active material layer is coated on the side of the first current collector facing the anode plate, and the second active material layer is coated on the side of the first current collector facing away from the anode plate; the tab is disposed on the first current collector and protrudes from the side of the first active material layer facing the anode plate; the anode plate includes a second current collector, a third active material layer, and a fourth active material layer, wherein the third active material layer is coated on the side of the first current collector facing away from the anode plate. The second current collector faces the cathode sheet, and the fourth active material layer is coated on the side of the second current collector facing away from the cathode sheet. A first groove and a second groove are present. The first groove is formed on the side of the third active material layer facing away from the second current collector, and the depth of the first groove is not greater than the thickness of the third active material layer. The projection of the electrode tab in a first direction falls within the projection of the first groove in the first direction. The second groove is formed on the side of the fourth active material layer facing away from the second current collector, and the projection of the electrode tab in the first direction falls within the projection of the second groove in the first direction. The first direction is the stacking direction of the cathode sheet, the diaphragm, and the anode sheet.

[0006] The battery cell according to the first aspect of this utility model has at least the following beneficial effects: by providing a first groove to accommodate the tab, the degree of bending and protrusion of the anode plate caused by the tab is reduced. Simultaneously, by providing a second groove, the second current collector is accommodated after protruding outwards, further preventing the anode plate from protruding outwards. The accommodation of the protruding tab by the first and second grooves effectively reduces unevenness in the battery cell at the tab location, thereby effectively optimizing the stress distribution in the battery cell, making the stress distribution in the battery cell more uniform, and thus greatly reducing the risk of anode plate breakage.

[0007] According to some embodiments of the present invention, the depth of the second groove is not greater than the thickness of the fourth active material layer.

[0008] According to some embodiments of the present invention, the sum of the depth of the first groove and the depth of the second groove is not less than the height of the tab protruding from the cathode plate.

[0009] According to some embodiments of the present invention, the material of the second current collector is copper foil.

[0010] According to some embodiments of the present invention, a plurality of tabs are provided on the first current collector, and the interval between adjacent tabs in a second direction is not less than 5 mm, wherein the second direction is the extending direction of the cathode sheet.

[0011] According to some embodiments of the present invention, the distance between the edge of the projection of the tab in the first direction and the edge of the projection of the first groove in the first direction is not less than 1 mm and not more than 2 mm.

[0012] According to some embodiments of the present invention, the edge of the projection of the first groove in the first direction is located between the edge of the projection of the tab in the first direction and the edge of the projection of the first groove in the first direction.

[0013] According to some embodiments of the present invention, the electrode tab is disposed on the side of the first current collector facing away from the center of the winding core.

[0014] The battery according to a second aspect of the present invention is characterized in that it comprises the battery cell described in any one of the above embodiments.

[0015] 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

[0016] Figure 1 This is an exploded structural diagram of a battery cell according to the present invention;

[0017] Figure 2 This is a schematic diagram of the structure of a battery cell during its retraction according to this utility model;

[0018] Figure 3 This is a schematic diagram of the structure of a battery cell during expansion according to the present invention;

[0019] Figure 4 This is a schematic diagram of the structure of the anode plate of a battery cell according to the present invention;

[0020] Figure 5 This is a cross-sectional schematic diagram of the anode plate of a battery cell according to the present invention.

[0021] Icon labels:

[0022] 1. Cathode plate; 11. First current collector; 12. First active material layer; 13. Second active material layer; 2. Anode plate; 21. Second current collector; 22. Third active material layer; 23. Fourth active material layer; 24. First groove; 25. Second groove; 3. Diaphragm; 4. Tab. 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] The manufacturing process of a wound battery cell mainly includes the following steps: electrode sheet preparation, separator preparation, cell winding, electrolyte filling, and sealing. The electrode sheet is the core component of the battery cell, typically composed of foil and active material. Both the positive and negative electrode sheets require coating with active material and drying processes to ensure the active material is uniformly distributed on the foil surface and cured. The separator is the key material for separating the positive and negative electrodes, usually a thin film made of polymer materials. The separator's preparation needs to ensure good insulation properties and mechanical strength to prevent short circuits between the positive and negative electrodes. Cell winding is the core step in the manufacturing process. The positive and negative electrode sheets and the separator are stacked in a specific order (e.g., negative electrode, separator, positive electrode, separator), and then wound into a cylindrical structure using a winding machine. During winding, parameters such as tension, speed, and the number of winding layers need to be strictly controlled to ensure the uniformity and consistency of the battery cell. After winding, the electrolyte needs to be filled into the cell through impregnation or coating. The electrolyte is the medium for ion transport in the battery and has a significant impact on battery performance. The battery cell is sealed, and a sealant is added to the seal to ensure that the electrolyte does not leak. The cell is then placed in an aluminum-plastic composite film bag and heat-sealed. Finally, the cell is packaged into its final form using a compression or hot-pressing process.

[0028] Battery cells exhibit significant volume effects during charging and discharging. Firstly, complex electrochemical reactions occur internally during charging and discharging. Taking lithium-ion batteries as an example, during charging, lithium ions are extracted from the positive electrode material, move through the electrolyte to the negative electrode material, and release electrons in the process. During discharging, the reverse occurs: lithium ions are extracted from the negative electrode material, move to the positive electrode material, and absorb electrons in the process. This insertion and extraction of lithium ions leads to changes in the structure of the positive and negative electrode materials, causing volume expansion or contraction. Secondly, gases may be generated inside the cell during charging and discharging. These gases mainly originate from electrolyte decomposition and side reactions of active materials. Gas generation increases the internal pressure of the cell, causing changes in cell volume. Especially under overcharge or over-discharge conditions, the internal reactions may become uncontrolled, generating large amounts of gas and leading to significant changes in cell volume. Furthermore, the expansion coefficients of the positive and negative electrode materials and the electrolyte itself also affect the cell's volume change. Different materials have different coefficients of thermal expansion. During charging and discharging, the volume of the positive and negative electrode materials changes due to the insertion and extraction of lithium ions, while the volume of the electrolyte may also change due to factors such as temperature and pressure. These changes collectively affect the battery cell, resulting in a significant volume effect. Finally, temperature is also a crucial factor influencing cell volume changes. Under high-temperature conditions, the chemical reactions inside the cell are more active, leading to more pronounced battery volume changes. High temperatures can also cause electrolyte expansion, further impacting battery volume. Furthermore, mechanical pressure can also cause changes in cell volume. Under high-pressure environments, increased internal pressure can cause deformation of the battery casing, thus affecting battery volume.

[0029] Reference Figure 1 , Figure 2 and Figure 3The battery cell in the first embodiment of this utility model includes: tabs 4, a cathode plate 1, a separator 3, and an anode plate 2. The cathode plate 1, the separator 3, and the anode plate 2 are stacked and wound into a core in sequence. The cathode plate 1 includes a first current collector 11, a first active material layer 12, and a second active material layer 13. The first active material layer 12 is coated on the side of the first current collector 11 facing the anode plate 2, and the second active material layer 13 is coated on the side of the first current collector 11 facing away from the anode plate 2. Tabs 4 are disposed on the first current collector 11 and protrude from the side of the first active material layer 12 facing the anode plate 2. Due to limitations in materials, some tabs 4 need to be made thicker. When the thickness of the tab 4 is greater than the thickness of the first active material layer 12, the tab 4 will protrude from the side of the first active material layer 12 facing the anode plate 2. When the cathode plate 1, diaphragm 3, and anode plate 2 are stacked sequentially, the protruding electrode plates will push up the anode plate 2, resulting in greater deformation of the anode plate 2 at that position. This also causes the entire cell to expand, concentrating stress on the anode plate 2 at the position corresponding to the tab 4. This makes the position of the anode plate 2 corresponding to the tab 4 prone to breakage. To effectively avoid this situation, a first groove 24 and a second groove 25 are provided on the anode plate 2.

[0030] The anode plate 2 includes a second current collector 21, a third active material layer 22, and a fourth active material layer 23. The third active material layer 22 is coated on the side of the second current collector 21 facing the cathode plate 1, and the fourth active material layer 23 is coated on the side of the second current collector 21 facing away from the cathode plate 1. A first groove 24 is formed on the side of the third active material layer 22 facing away from the second current collector 21. The depth of the first groove 24 is not greater than the thickness of the third active material layer 22. The projection of the tab 4 in the first direction is within the projection of the first groove 24 in the first direction. A second groove 25 is formed on the side of the fourth active material layer 23 facing away from the second current collector 21. The projection of the tab 4 in the first direction is within the projection of the second groove 25 in the first direction. The first direction is the stacking direction of the cathode plate 1, the diaphragm 3, and the anode plate 2. When the first groove 24 is provided, if the depth of the first groove 24 is set to be large, the thickness of the third active material layer 22 at the bottom of the first groove 24 will be small, or even the second current collector 21 will be directly exposed at the bottom of the first groove 24. When the entire battery cell is squeezed or expands, the tab 4 is at great risk of puncturing the diaphragm 3, thus directly contacting the second current collector 21 and causing an internal short circuit. Therefore, sufficient thickness must be maintained at the bottom of the first groove 24 to ensure the safety of the battery cell, meaning the depth of the first groove 24 cannot be too large, preventing it from fully accommodating the protruding part of the tab 4. After setting the first groove 24, it can accommodate part of the protruding tab 4, but it will still lift the second current collector 21, causing it to deform. Therefore, a second groove 25 is provided to allow space for the deformation of the second current collector 21, effectively preventing the anode plate 2 from bulging out entirely. If the anode plate 2 bulges out entirely, the bulges will accumulate during winding, causing greater deformation of the anode plate 2 located on the outside of the winding core, increasing the likelihood of breakage. Therefore, a second groove 25 is needed to accommodate the deformation of the second current collector 21, thus preventing the anode plate 2 from bulging out.

[0031] According to some embodiments of this utility model, the depth of the second groove 25 is no greater than the thickness of the fourth active material layer 23. This avoids the second current collector 21 being directly exposed in the second groove 25, effectively preventing short circuits inside the battery cell, thus making the battery cell safer.

[0032] According to some embodiments of this utility model, the sum of the depth of the first groove 24 and the depth of the second groove 25 is not less than the height of the tab 4 protruding from the cathode plate 1. At this time, the depth of the first groove 24 and the depth of the second groove 25 are sufficient to accommodate the protruding part of the tab 4, which can better prevent the anode plate 2 from bulging, thereby making the cathode plate 1, the diaphragm 3 and the anode plate 2 stacked together more evenly.

[0033] The cathode sheet is typically made of aluminum foil. To ensure the electrical performance of the battery cell, the tabs 4 on the first current collector 11 are also made of aluminum. Using aluminum for the tabs 4 requires a larger thickness. Therefore, the first groove 24 and the second groove 25 are provided to better accommodate the tabs 4 on the cathode sheet.

[0034] According to some embodiments of this utility model, the material of the second current collector 21 is copper foil. Copper foil has good ductility and is less prone to breakage, therefore it is used as the second current collector 21, making it less prone to breakage under the influence of the tab 4.

[0035] According to some embodiments of this utility model, a plurality of tabs 4 are provided on the first current collector 11, and the spacing between adjacent tabs 4 in a second direction is not less than 5 mm, the second direction being the extension direction of the cathode sheet 1. This avoids the tabs 4 being too close together, thus preventing them from interfering with each other. It also avoids the first groove 24 or the second groove 25 being too close together, thereby preventing the third active material layer 22 or the third material layer from collapsing during compression.

[0036] According to some embodiments of this utility model, the distance between the edge of the projection of the tab 4 in the first direction and the edge of the projection of the first groove 24 in the first direction is not less than 1 mm and not more than 2 mm. If the distance between the edge of the projection of the tab 4 in the first direction and the edge of the projection of the first groove 24 in the first direction is too large, a large gap will be formed, reducing the energy density of the battery cell. If the distance between the edge of the projection of the tab 4 in the first direction and the edge of the projection of the first groove 24 in the first direction is too small, the tab 4 is more likely to collide with the edge of the first groove 24 during the stacking of the cathode sheet 1 and the anode sheet 2, resulting in damage to the third active material layer 22. Therefore, the distance between the edge of the projection of the tab 4 in the first direction and the edge of the projection of the first groove 24 in the first direction is limited to between 1 and 2 mm.

[0037] According to some embodiments of this utility model, the edge of the projection of the second groove 25 in the first direction is located between the edge of the projection of the tab 4 in the first direction and the edge of the projection of the first groove 24 in the first direction. This avoids the second groove 25 being too large, which would reduce the energy density of the battery cell, while ensuring sufficient space to accommodate the protruding deformation of the second current collector 21.

[0038] According to some embodiments of this utility model, the tab 4 is disposed on the side of the first current collector 11 opposite to the center of the winding core. When the battery cell expands, the internal stress flows from the inside to the outside. At this time, disposing the tab 4 on the side of the first current collector 11 opposite to the center of the winding core can reduce the influence of the tab 4 on the first current collector 11.

[0039] Several methods can be used to form the first groove 24 and the second groove 25. These include laser methods, masking methods, and coating control methods. In the laser method, a high-power laser beam can directly act on the surface of the anode sheet 2, locally heating the third active material layer 22 and the fourth active material layer 23, causing them to melt or soften, thus achieving a thinner coating. This process utilizes precise laser control to accurately control the coating thickness without affecting the surrounding area. In the masking method, a mask is used to cover the locally thinned area before coating, blocking part of the slurry. After coating, the mask is peeled off, achieving localized thickness control, thereby forming the first groove 24 and the second groove 25.

[0040] The battery according to a second aspect of the present invention is characterized in that it includes a cell comprising any one of the above embodiments.

[0041] In experiments, the battery cell with the second groove exhibited a significant capacity drop after 83 cycles under 0.5C charging and 0.7C discharging conditions, which is insufficient for practical applications. This phenomenon can be attributed to the breakage of the outermost anode electrode. Since this electrode is an externally welded structure, its breakage drastically reduces the effective area of ​​the active material, preventing the cell from effectively storing and releasing energy, thus causing rapid capacity decay. Simultaneously, electrode breakage accelerates cell aging, leading to a shortened cycle life and decreased charge / discharge efficiency. After adding the second groove, the anode structure remained intact. These findings demonstrate that adding the second groove effectively mitigates anode breakage in steel-cased button cell batteries, optimizes the stress distribution of the electrode, and significantly improves the safety and stability of the battery cell.

[0042] 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: The electrode tab, cathode plate, diaphragm, and anode plate are stacked and wound in sequence to form a core; The cathode sheet includes a first current collector, a first active material layer, and a second active material layer. The first active material layer is coated on the side of the first current collector facing the anode sheet, and the second active material layer is coated on the side of the first current collector facing away from the anode sheet. The tab is disposed on the first current collector and protrudes from the side of the first active material layer facing the anode sheet. The anode plate includes a second current collector, a third active material layer, and a fourth active material layer. The third active material layer is coated on the side of the second current collector facing the cathode plate, and the fourth active material layer is coated on the side of the second current collector facing away from the cathode plate. The first groove and the second groove are formed on the side of the third active material layer facing away from the second current collector. The depth of the first groove is not greater than the thickness of the third active material layer. The projection of the electrode tab in the first direction is within the projection of the first groove in the first direction. The second groove is formed on the side of the fourth active material layer facing away from the second current collector. The projection of the electrode tab in the first direction is within the projection of the second groove in the first direction. The first direction is the stacking direction of the cathode sheet, the diaphragm and the anode sheet.

2. The battery cell according to claim 1, characterized in that, The depth of the second groove is not greater than the thickness of the fourth active material layer.

3. The battery cell according to claim 1, characterized in that, The sum of the depth of the first groove and the depth of the second groove is not less than the height of the tab protruding from the cathode plate.

4. The battery cell according to claim 1, characterized in that, The material of the second current collector is copper foil.

5. The battery cell according to claim 1, characterized in that, The first current collector is provided with a plurality of electrodes, and the spacing between adjacent electrodes in a second direction is not less than 5 mm, wherein the second direction is the extension direction of the cathode sheet.

6. The battery cell according to claim 1, characterized in that, The distance between the edge of the projection of the tab in the first direction and the edge of the projection of the first groove in the first direction is not less than 1 mm and not more than 2 mm.

7. The battery cell according to claim 6, characterized in that, The edge of the projection of the second groove in the first direction is located between the edge of the projection of the tab in the first direction and the edge of the projection of the first groove in the first direction.

8. The battery cell according to claim 1, characterized in that, The electrode tab is disposed on the side of the first current collector opposite to the center of the winding core.

9. A battery, characterized in that, Includes the battery cell according to any one of claims 1-8.

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