Pole piece, battery and electric device

Abstract

This invention provides an electrode, a battery, and an electrical device, comprising: a current collector, a first active material layer, and a second active material layer; the current collector has a first surface and a second surface facing away from each other along a first direction, the first active material layer is disposed on the first surface, and the second active material layer is disposed on the second surface, the first direction being the thickness direction of the current collector; along the second direction, the current collector has a first end and a second end, the first active material layer and the second active material layer at the first end are flush, and the first active material layer and the second active material layer at the second end are offset, the second direction being the length direction of the current collector, in which the tail end of the first active material layer is located between the tail end of the second active material layer and the second end of the current collector; a groove is formed on the first active material layer, and the projection of the tail end of the second active material layer along the first direction falls within the groove. For the electrode of this invention, damage to the electrode can be effectively prevented during rolling.

Description

Technical Field

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

[0002] Currently, with the increasing market demand for consumer batteries, especially the increasing requirements for ED (volume energy density), the foil materials (aluminum and copper foil substrates) used in cell design are becoming thinner and thinner. In wound cell design, there are significant thickness changes at the junction of the single and double sides of the electrode, leading to excessive foil stretching at the junction during the rolling process. Existing electrode structures suffer from excessive foil stretching at the single and double-sided junctions, which easily leads to problems such as strip breakage during rolling, winding, FCT (Final Turning Test), and post-cycle cell breakage. Therefore, a new electrode design is needed to effectively prevent damage during the rolling process. 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 an electrode sheet that can effectively prevent damage to the electrode sheet during rolling.

[0004] This utility model also proposes a battery.

[0005] This utility model also proposes an electrical device.

[0006] An electrode sheet according to a first aspect of the present invention includes: a current collector, a first active material layer, and a second active material layer; the current collector has a first surface and a second surface disposed opposite to each other along a first direction, the first active material layer is disposed on the first surface, and the second active material layer is disposed on the second surface, the first direction being the thickness direction of the current collector, and along a second direction, the current collector has a first end and a second end, the first active material layer and the second active material layer located at the first end are flush, and the first active material layer and the second active material layer located at the second end are offset, the second direction being the length direction of the current collector, and in the second direction, the tail end of the first active material layer is located between the tail end of the second active material layer and the second end of the current collector; a groove is formed on the first active material layer, and the projection of the tail end of the second active material layer along the first direction is within the groove.

[0007] The electrode sheet according to the first aspect of the present invention has at least the following beneficial effects: by providing a groove on the first active material layer on the first surface, the thickness variation of the electrode sheet at the tail end of the second surface is reduced, thereby reducing the unidirectional impact force on the electrode sheet when it is rolled, thus effectively reducing the damage to the electrode sheet and preventing the electrode sheet from breaking and being damaged during subsequent use.

[0008] According to some embodiments of the present invention, the groove includes a bottom surface and a first transition region and a second transition region disposed adjacent to each other on both sides of the bottom surface along the second direction. The thickness of the first active material layer in the first transition region gradually decreases along the direction close to the bottom surface, and the thickness of the second active material layer in the second transition region gradually decreases along the direction close to the bottom surface.

[0009] According to some embodiments of the present invention, the distance between the bottom surface and the first surface is H, and the thickness of the first active material layer is D, where 0.3D≤H≤0.7D.

[0010] According to some embodiments of the present invention, the tail end of the second active material layer is no more than 0.1 mm away from the midpoint of the bottom surface in the second direction.

[0011] According to some embodiments of the present invention, multiple steps are provided in the first transition zone along the second direction, the distance between two adjacent steps in the first direction is A, 8um≤A≤12um, and the length of the step in the second direction is B, 0.1mm≤B≤1mm.

[0012] According to some embodiments of the present invention, a thinning surface is provided at the tail end of the second active material layer, and the distance between the thinning surface and the second surface of the current collector gradually decreases in the direction toward the second end of the current collector.

[0013] According to some embodiments of the present invention, the thinning surface is an inclined plane, an arc-shaped surface, or a stepped surface.

[0014] According to some embodiments of the present invention, the angle between the direction of the inclined plane toward the first end and the second surface does not exceed 45°.

[0015] According to some embodiments of the present invention, the second transition zone is disposed on the side close to the second end of the current collector, and a thinning surface is disposed at the tail end of the second active material layer, wherein the projection of the thinning surface in the first direction coincides with the projection of the second transition zone in the first direction.

[0016] According to some embodiments of the present invention, in the second transition zone, the thickness of the electrode in the second direction is M, and in the bottom surface, the thickness of the electrode in the second direction is N, where 0.8N≤M≤0.9N.

[0017] The battery according to a second aspect of the present invention includes the electrode sheet described in any of the above embodiments.

[0018] The electrical device according to a third aspect of the present invention includes the battery described in the above embodiments.

[0019] 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

[0020] Figure 1 A schematic diagram of the structure for setting grooves in the electrode sheet of this utility model;

[0021] Figure 2 A schematic diagram of the structure of the electrode sheet of this utility model with steps;

[0022] Figure 3 A schematic diagram of the structure of the electrode sheet of this utility model with an inclined plane;

[0023] Figure 4 This is a schematic diagram of the structure in which the inclined plane of the electrode plate coincides with the second transition zone of this utility model;

[0024] Figure 5 This is a schematic diagram of the structure of the electrode sheet in Embodiment 2 of this utility model;

[0025] Figure 6 This is a schematic diagram of the structure of the electrode sheet in Embodiment 4 of this utility model;

[0026] Figure 7 This is a schematic diagram of the structure of the electrode sheet in Embodiment 5 of this utility model;

[0027] Figure 8 This is a schematic diagram of the structure of the electrode sheet in Embodiment Six of this utility model;

[0028] Figure 9 This is a schematic diagram of the structure of the electrode control group of this utility model.

[0029] Icon labels:

[0030] 1. Current collector; 11. First surface; 12. Second surface; 2. First active material layer; 21. First tail end; 22. Groove; 23. Bottom surface; 24. First transition zone; 25. Second transition zone; 26. Step; 3. Second active material layer; 31. Second tail end; 32. Thinned surface. Detailed Implementation

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] In electrochemical devices, the placement of a first and second surface on the positive and negative electrodes is primarily driven by several considerations: adapting to the cell's structure and performance requirements, improving battery safety and stability, and optimizing manufacturing processes and costs. Electrochemical devices, such as lithium-ion batteries, have complex cell structures and demanding performance. The placement of the first and second surfaces allows for better adaptation to the specific structural and performance requirements of the cell. For example, in some cell designs, adjusting the film length on the electrode surface is necessary to optimize electrolyte wetting and lithium-ion transport paths. The first surface may be more conducive to uniform electrolyte distribution and rapid lithium-ion transport, while the second surface may reduce unnecessary electrolyte consumption and side reactions in specific areas. The placement of the first and second surfaces also improves battery safety and stability. By precisely controlling the length and distribution of the film, the internal electric field and current distribution of the battery can be optimized, reducing potential safety hazards such as localized overheating and lithium dendrite growth. Furthermore, the first surface may contribute to the formation of a more stable solid electrolyte interphase (SEI) film, thereby protecting the negative electrode material from electrolyte corrosion and improving the battery's cycle life and high-temperature storage performance. In battery manufacturing, the placement of the first and second electrodes can optimize production processes and reduce costs. By adjusting process parameters such as coating and drying, it's easier to control the length of specific film layers, thereby improving production efficiency and product quality. Simultaneously, a well-designed film layer length can reduce unnecessary material waste and energy consumption, lowering production costs. In summary, the placement of the first and second electrodes on the positive and negative plates is based on considerations such as adapting to cell structure and performance requirements, improving battery safety and stability, and optimizing production processes and costs. These designs contribute to enhancing the overall performance and market competitiveness of the battery.

[0036] During battery use, the electrodes are prone to breakage under the following conditions: charge-discharge cycles, drying processes, and improper use or maintenance, especially damage caused by rolling during electrode pressing. After multiple charge-discharge cycles, especially for wound soft-pack lithium-ion batteries, the electrodes may experience mechanical stress accumulation due to repeated volume expansion and contraction under pressure, eventually leading to breakage. This breakage usually occurs at the first bend of the innermost layer of the negative electrode, as this area is stress-concentrated and easily affected by external pressure. During the drying and film formation process of lithium-ion battery electrodes, the evaporation of the coating solvent causes volume shrinkage, while the rigid substrate restricts the tensile stress within the coating. When these tensile stresses exceed the bonding force between coating particles, the electrode will crack. The cracking is affected by various factors such as the selection of coating materials, coating thickness, current collector materials, and the temperature and humidity of the drying environment. Under improper use conditions such as overcharging, over-discharging, high-current charging and discharging, or high-temperature discharging, the active materials on the electrodes react intensely, easily causing uneven electrochemical reactions, leading to electrode bending and breakage. Furthermore, storing batteries without recharging after use will accelerate grid corrosion and may also cause plate breakage. In summary, the risk of battery plate breakage during use is affected by various factors, including the number of charge-discharge cycles, drying conditions, and usage and maintenance methods. To ensure battery performance and lifespan, these adverse factors should be avoided as much as possible, and appropriate protective measures should be taken.

[0037] Battery electrode breakage can cause several problems, including: decreased battery performance, capacity decay, safety hazards, and reduced battery life. Electrode breakage increases internal resistance, reducing charge and discharge efficiency. This is because a broken electrode increases internal resistance, hindering current flow. Electrode breakage can also lead to capacity decay. A broken electrode cannot effectively participate in electrochemical reactions, reducing usable capacity. Over time, capacity decay becomes increasingly noticeable until it no longer meets usage requirements. Electrode breakage can also pose safety hazards. A broken electrode may puncture the battery separator, causing an internal short circuit. This short circuit generates significant heat, potentially leading to thermal runaway or even an explosion. Furthermore, broken electrodes can cause leakage, corroding and polluting the battery pack and surrounding environment. Electrode breakage accelerates the aging process, shortening battery life. This is because broken electrodes can no longer withstand the mechanical stress and electrochemical corrosion during charge and discharge, leading to a gradual decline in battery performance. In conclusion, electrode breakage in batteries can severely impact battery performance, capacity, safety, and lifespan. Therefore, during battery production and use, strict control over electrode quality and process parameters is crucial to prevent electrode breakage. Furthermore, batteries exhibiting electrode breakage should be promptly replaced or repaired to ensure normal operation and safety.

[0038] In battery manufacturing, electrode rolling is a crucial step that significantly improves battery performance, safety, and stability. It enhances the adhesion between the active material and the current collector foil: After coating and drying, the peel strength between the active material and the current collector foil is very low. Rolling strengthens this adhesion, preventing peeling during electrolyte immersion and battery use. It also increases battery energy density: Rolling compresses the cell volume, reducing porosity between the active material, conductive agent, and binder within the electrode, thus increasing energy density. Furthermore, it ensures a smooth and flat electrode surface: Rolled electrodes have a smooth and flat surface, preventing burrs on the coating surface from piercing the separator and causing short circuits, improving battery safety. Finally, rolling increases electronic conductivity: Rolling brings the active material and conductive agent particles into closer contact, improving electronic conductivity and enhancing battery performance. Finally, it affects the battery's electrochemical performance: The compaction density of the electrodes significantly impacts the battery's electrochemical performance. Within a certain range, as compaction density increases, the interparticle spacing of active materials decreases, the contact area increases, and the number of pathways and bridges facilitating ion conduction increases, resulting in a decrease in the battery's internal resistance. Appropriate compaction density can increase the battery's discharge capacity, reduce internal resistance, reduce polarization losses, and extend the battery's cycle life.

[0039] Reference Figure 1 , Figure 2 and Figure 3 The electrode in the first embodiment of this utility model includes: a current collector 1, a first active material layer 2, and a second active material layer 3. The current collector 1 has a first surface 11 and a second surface 12 arranged opposite to each other along a first direction, which is the thickness direction of the current collector 1. Along a second direction, the current collector 1 has a first end and a second end. The first active material layer 2 and the second active material layer 3 at the first end are flush, while the first active material layer 2 and the second active material layer 3 at the second end are staggered. The first active material layer 2 is coated on the first surface 11, and the second active material layer 3 is coated on the second surface 12. In the second direction, the tail end of the first active material layer 2 is located between the tail end of the second active material layer 3 and the second end of the current collector 1. The second direction is the length direction of the current collector 1. Specifically, the tail end of the first active material layer 2 is a first tail end 21, and the tail end of the second active material layer 3 is a second tail end 31. That is, the tail end of the first active material layer 2 extends further than the tail end of the second active material layer 3. At the point where the coating of the second active material layer 3 ends, i.e., at the tail end of the second active material layer 3, the thickness of the electrode suddenly decreases due to the disappearance of the thickness of the second active material layer 3. During the rolling process, the pressure roller applies pressure to the electrode in the first direction. Therefore, when rolling to the tail end of the second active material layer 3, an impact force is applied to the current collector 1, and the pressure direction changes, causing the current collector 1 to stretch, deform, or bend. This easily damages the position on the current collector 1 corresponding to the tail end of the second active material layer 3. During subsequent battery use, when the battery electrodes expand and contract, breakage is likely to occur at the tail end of the second active material layer 3.

[0040] A groove 22 is formed on the first surface 11, and the projection of the tail end of the second active material layer 3 along the first direction falls within the groove 22. By setting the groove 22, the change in the force direction during the rolling of the electrode is smaller, that is, the amount of stretching caused to the current collector 1 when rolling the second active material layer 3 is reduced, thereby reducing damage to the current collector 1 and effectively reducing the phenomenon of breakage of the current collector 1. If the thickness of the current collector 1 decreases on one side, the thinner side of the current collector 1 will bend during the rolling process, causing the current collector 1 to be unbalanced in force at that position. The greater the change in thickness, the greater the bending. Therefore, the groove 22 is set so that the thickness difference between the second active material layer 3 and the first active material layer 2 at the tail end of the second active material layer 3 is smaller, thereby effectively protecting the current collector 1.

[0041] According to some embodiments of this utility model, refer to Figure 2The distance between the bottom surface 23 and the first surface 11 is H, and the thickness of the first active material layer 2 is D, where 0.3D ≤ H ≤ 0.7D. When the groove 22 is deeper, i.e., the distance between the bottom surface 23 and the first surface 11 is smaller, the current collector 1 is more easily damaged at the point where the roller presses onto the groove 22. When the groove 22 is shallower, i.e., the distance between the bottom surface 23 and the first surface 11 is larger, it cannot adequately protect the current collector 1 at the tail end of the second active material layer 3. Therefore, limiting the depth of the groove 22, i.e., the distance between the bottom surface 23 and the first surface 11, more effectively protects the current collector 1.

[0042] According to some embodiments of this utility model, the tail end of the second active material layer 3 is no more than 0.1 mm from the midpoint of the bottom surface 23 in the second direction. The groove 22 will also cause some impact and deformation to the current collector 1 on both sides along the second direction. The closer the tail end of the second active material layer 3 is to the midpoint of the bottom surface 23, the farther apart the affected points on the current collector 1 will be, thus avoiding mutual interference between the rolling effects on the current collector 1 at the three points: the point entering the groove 22, the tail end of the second active material layer 3, and the point exiting the groove 22. If these three points are close together, they will affect each other, causing significant damage to the current collector 1.

[0043] According to some embodiments of this utility model, refer to Figure 2 Within the first transition zone 24, multiple steps 26 are arranged along the second direction. The distance between two adjacent steps 26 in the first direction is A, where 8µm ≤ A ≤ 12µm, and the length of the step 26 in the second direction is B, where 0.1mm ≤ B ≤ 1mm. The arrangement of multiple steps 26 along the second direction within the first transition zone 24 helps to disperse the impact and bending effects of the current collector 1, thus providing better protection for it. Furthermore, the same steps 26 as those in the first transition zone 24 can be arranged in the second transition zone 25.

[0044] According to some embodiments of this utility model, a thinning surface 32 is provided at the tail end of the second active material layer 3, and the distance between the thinning surface 32 and the second surface gradually decreases along the direction towards the second end of the current collector 1. By setting it to be inclined, the impact force on the current collector 1 during rolling can be greatly reduced, thereby better protecting the current collector 1. Specifically, the thinning surface can be set as an inclined plane, or it can be set as an arc-shaped surface or a stepped surface. The stepped surface consists of several planes with a gradually decreasing distance from the second surface.

[0045] According to some embodiments of this utility model, refer to Figure 4The angle between the inclined plane and the first surface 11 shall not exceed 45°. If the angle between the inclined plane and the current collector 1 is too large, the impact force on the current collector 1 will be greater. Therefore, the inclination angle of the inclined plane relative to the first surface 11 is limited.

[0046] According to some embodiments of this utility model, the second transition zone 25 is disposed on the side of the bottom surface 23 near the second end of the current collector 1, and the projection of the inclined plane in the first direction coincides with the projection of the second transition zone 25 in the first direction. By coinciding the projection of the inclined plane in the first direction with the projection of the second transition zone 25 in the first direction, the overall thickness variation of the electrode in the inclined plane region is reduced to a greater extent, thereby better protecting the current collector 1.

[0047] According to some embodiments of this utility model, within the second transition region 25, the thickness of the electrode in the second direction is M, and within the bottom surface 23, the thickness of the electrode in the second direction is N, where 0.8N ≤ M ≤ 0.9N. Within the second transition region 25, the thickness of the first active material layer 2 gradually increases in the direction away from the bottom surface 23, while the thickness of the second active material layer 3 gradually decreases in the direction away from the bottom surface 23. Therefore, the thickness variation of the electrode within the second transition region 25 is smaller, resulting in less impact force on the current collector 1 and thus better protection of the current collector 1.

[0048] The battery according to a second aspect of the present invention includes the electrode sheet described in any of the above embodiments.

[0049] The electrical device according to a third aspect of the present invention includes the battery described in the above embodiments.

[0050] In Example 1, refer to Figure 1 The groove depth was set to 20 μm, and the thickness of the first active material layer 2 and the second active material layer 3 were both 38.5 μm. After rolling the electrode, the probability of current collector breakage was 0.18%.

[0051] In the second and third embodiments, refer to Figure 5 and Figure 3In the first and second transition zones, both are configured as stepped surfaces. In the second embodiment, each zone has three stepped surfaces, with each step having a width of 5 μm in the second direction and a height of 5 μm in the first direction. The thickness of the first active material layer 2 and the second active material layer 3 is 38.5 μm. Three stepped surfaces are provided at the tail end of the second active material layer 3, with each step having a width of 5 μm in the second direction and a height of 5 μm in the first direction. The probability of current collector breakage after rolling the electrode is 0.10%. In the third embodiment, both the first and second transition zones have two stepped surfaces, with each step having a width of 5 μm in the second direction and a height of 5 μm in the first direction. The thickness of the first active material layer 2 and the second active material layer 3 is 38.5 μm. An inclined plane with an inclination angle of 45° is provided at the tail end of the second active material layer 3. The probability of current collector breakage after rolling the electrode is 0.15%.

[0052] In the fourth embodiment, reference is made to... Figure 6 Two stepped surfaces are provided in the first transition zone. The width and height of each step in the second direction are both 5 μm. An inclined plane with an inclination angle of 45° is provided in the second transition zone. An inclined plane with an inclination angle of 45° is provided at the tail end of the second active material layer 3. The probability of current collector breakage after the electrode is rolled is 0.15%.

[0053] In the fifth and sixth embodiments, refer to Figure 7 and Figure 8 In both the first and second transition zones, an inclined plane with a tilt angle of 45° is provided. In the fifth embodiment, the tail end of the second active material layer 3 is also an inclined plane with a tilt angle of 45°. The probability of current collector breakage after rolling the electrode is 0.15%. In the sixth embodiment, the tail end of the second active material layer 3 is provided with three stepped surfaces, each step having a width of 5µm in the second direction and a height of 5µm in the first direction. The probability of current collector breakage after rolling the electrode is 0.10%.

[0054] It should be noted that in the above embodiments, the thickness of the first active material layer 2 and the thickness of the second active material layer 3 are both 38.5 μm. A control group was also set up, with reference to... Figure 9 Without grooves, and with the tail end of the second active material layer 3 being a vertical plane with the normal direction of the second direction, after processing in the same rolling method, the probability of the current collector breaking is 0.30%.

[0055] 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. An electrode sheet, characterized in that, include: Current collector, first active material layer, and second active material layer; The current collector has a first surface and a second surface facing away from each other along a first direction. The first active material layer is disposed on the first surface, and the second active material layer is disposed on the second surface. The first direction is the thickness direction of the current collector. Along the second direction, the current collector has a first end and a second end. The first active material layer and the second active material layer at the first end are disposed flush, and the first active material layer and the second active material layer at the second end are disposed offset. The second direction is the length direction of the current collector. In the second direction, the tail end of the first active material layer is located between the tail end of the second active material layer and the second end of the current collector. The first active material layer has a groove, and the projection of the tail end of the second active material layer along the first direction is within the groove.

2. The electrode sheet according to claim 1, characterized in that, The groove includes a bottom surface and a first transition zone and a second transition zone disposed adjacent to each other on both sides of the bottom surface along the second direction. The thickness of the first active material layer in the first transition zone gradually decreases along the direction close to the bottom surface, and the thickness of the second active material layer in the second transition zone gradually decreases along the direction close to the bottom surface.

3. The electrode sheet according to claim 2, characterized in that, The distance between the bottom surface and the first surface is H, and the thickness of the first active material layer is D, where 0.3D≤H≤0.7D.

4. The electrode sheet according to claim 2, characterized in that, The tail end of the second active material layer is no more than 0.1 mm from the midpoint of the bottom surface in the second direction.

5. The electrode sheet according to claim 2, characterized in that, The first transition zone has multiple steps arranged along the second direction. The distance between two adjacent steps in the first direction is A, where 8um ≤ A ≤ 12um. The length of the step in the second direction is B, where 0.1mm ≤ B ≤ 1mm.

6. The electrode sheet according to any one of claims 1-5, characterized in that, The tail end of the second active material layer is provided with a thinning surface, and the distance between the thinning surface and the second surface of the current collector gradually decreases in the direction toward the second end of the current collector.

7. The electrode sheet according to claim 6, characterized in that, The thinning surface is an inclined plane, an arc surface, or a stepped surface.

8. The electrode sheet according to claim 7, characterized in that, The angle between the direction of the inclined plane toward the first end and the second surface does not exceed 45°.

9. The electrode sheet according to claim 2, characterized in that, The second transition zone is located on the side near the second end of the current collector, and a thinning surface is provided at the tail end of the second active material layer. The projection of the thinning surface in the first direction coincides with the projection of the second transition zone in the first direction.

10. The electrode sheet according to claim 9, characterized in that, Within the second transition zone, the thickness of the electrode in the second direction is M, and within the bottom surface, the thickness of the electrode in the second direction is N, where 0.8N≤M≤0.9N.

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

12. An electrical appliance, characterized in that, Includes the battery described in claim 11.

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