Pole piece and battery

Abstract

The utility model provides a kind of pole piece and battery, comprising: current collector, first active material layer and second active material layer;The current collector is provided with first face and second face along the first direction opposite, the first direction is the thickness direction of the current collector, the first active material layer is coated on the first face, and the second active material layer is coated on the second face;In 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 tail end of current collector, and second direction is the length direction of the current collector;Second face is provided with reinforcing portion, and the projection of the tail end of second active material layer along the first direction is on the reinforcing portion, and the thickness of reinforcing portion in the first direction does not exceed 40% of the thickness of the second active material layer in the first direction.The pole piece of the utility model can effectively prevent the pole piece from being damaged when rolling the pole piece.

Description

Technical Field

[0001] This utility model relates to the field of new energy technology, and in particular to an electrode sheet and a battery. 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 during the rolling process.

[0004] This utility model also proposes a battery.

[0005] 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 direction being the thickness direction of the current collector; the first active material layer is coated on the first surface, and the second active material layer is coated on the second surface; in a 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 tail end of the current collector, the second direction being the length direction of the current collector; a reinforcing portion is disposed on the second surface, the projection of the tail end of the second active material layer along the first direction onto the reinforcing portion, and the thickness of the reinforcing portion in the first direction not exceeding 40% of the thickness of the second active material layer in the first direction.

[0006] The electrode sheet according to the first aspect of the present invention has at least the following beneficial effects: by providing a reinforcing portion on the second surface, the unidirectional impact force generated by the pressure roller during the rolling of the electrode sheet is first applied to the reinforcing portion, thereby reducing the impact force on the current collector at the tail end of the second active material layer. At the same time, the reinforcing portion also shares the bending and tensile forces of the current collector, thereby improving the tensile strength of the electrode sheet and effectively reducing the damage to the electrode sheet during the rolling process, preventing the electrode sheet from breaking and being damaged during subsequent use.

[0007] According to some embodiments of the present invention, the elastic modulus of the reinforcing part in the first direction is greater than the elastic modulus of the current collector.

[0008] According to some embodiments of the present invention, the tensile strength of the reinforcing part in the second direction is greater than the tensile strength of the current collector.

[0009] According to some embodiments of the present invention, the reinforcing part includes a first layer and a second layer, wherein the tensile strength of the first layer is greater than that of the second layer, the elastic modulus of the second layer is greater than that of the first layer, the first layer is disposed on the second surface, and the second layer is disposed on the side of the first layer facing away from the current collector.

[0010] According to some embodiments of the present invention, the second layer extends beyond the edge of the first layer in the second direction, and the portion of the second layer extending beyond the edge of the first layer is fixed to the second surface.

[0011] According to some embodiments of the present invention, the thickness of the first layer in the first direction does not exceed 20% of the thickness of the second active material layer in the first direction.

[0012] According to some embodiments of the present invention, the portion of the second layer extending beyond the edge of the first layer includes a compressed state, wherein the compressed state is a state of being compressed by rollers, and in the compressed state, the thickness of the portion of the second layer extending beyond the edge of the first layer in the first direction does not exceed 10% of the thickness of the second active material layer in the first direction.

[0013] According to some embodiments of the present invention, the tail end of the second active material layer is provided with an inclined surface, and the distance between the inclined surface and the current collector gradually decreases in the direction toward the tail end of the current collector.

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

[0015] The battery according to a second aspect of the present invention includes the electrode sheet described in any 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 A schematic diagram of the structure of the electrode sheet of this utility model with a reinforcing part; Figure 2 This is a schematic diagram of the structure of the reinforcing part of the electrode sheet of this utility model, including a first layer and a second layer; Figure 3 A schematic diagram of the structure of the electrode sheet of this utility model with an inclined surface; Figure 4 This is a schematic diagram of the structure of the electrode sheet of this utility model, in which the second layer extends from the first layer.

[0018] Icon labels: 1. Current collector; 11. First surface; 12. Second surface; 2. First active material layer; 3. Second active material layer; 31. Inclined surface; 4. Reinforcing part; 41. First layer; 42. Second layer. Detailed Implementation

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] During battery manufacturing, rolling enhances the adhesion between the active material and the foil, preventing peeling during electrolyte immersion and battery use. However, rolling the electrodes can easily damage them. Especially when long and short film surfaces are formed on the electrode, the thickness variation results in significant impact force during rolling, causing damage. After multiple charge-discharge cycles, particularly in wound pouch lithium-ion batteries, repeated volume expansion and contraction can lead to accumulated mechanical stress and eventual electrode breakage. Active material layers are coated on both sides of the current collector. Due to the cell's design, one side has a longer active material layer (long film, first side), while the other side has a shorter layer (short film, second side). This difference in thickness at the boundary between the long and short film surfaces creates a variation in electrode thickness.

[0024] Electrode breakage increases the battery's internal resistance, reducing its charging and discharging efficiency. Furthermore, broken electrodes cannot effectively participate in electrochemical reactions, leading to a decrease in usable capacity and causing capacity decay. Electrode breakage also affects battery safety and lifespan. For example, a broken electrode may puncture the battery separator, causing an internal short circuit and generating significant heat, potentially leading to thermal runaway or even an explosion. Breakage can also cause battery leakage, corroding and contaminating the surrounding structure and internal battery pack. Additionally, electrode breakage accelerates the battery's aging process, shortening its lifespan.

[0025] Reference Figure 1 , Figure 2 , Figure 3 and Figure 4The electrode sheet 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, where the first direction is the thickness direction of the current collector 1. 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 a 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 tail end of the current collector 1, where the second direction is the length direction of the current collector 1. That is, the tail end of the first active material layer 2 extends further, exceeding the tail end of the second active material layer 3. At the end of the coating of the second active material layer 3, i.e., at the tail end of the second active material layer 3, the thickness of the electrode sheet suddenly decreases due to the disappearance of the thickness of the second active material layer 3. When the broken electrode sheet is rolled, the pressure roller applies a certain pressure to the electrode sheet in the first direction. Therefore, when the roller presses to the tail end of the second active material layer 3, it will exert an impact force on the current collector 1, and at the same time, it will change the pressure direction, causing the current collector 1 to undergo tensile or bending deformation. This can easily damage 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.

[0026] In this embodiment of the invention, a reinforcing portion 4 is provided on the second surface 12 of the electrode. The projection of the tail end of the second active material layer 3 along the first direction is on the reinforcing portion 4. The reinforcing portion 4 is fixedly disposed on the current collector 1, and the second active material layer 3 covers and is fixed on the reinforcing portion 4. The thickness of the reinforcing portion 4 in the first direction does not exceed 40% of the thickness of the second active material layer 3 in the first direction. The reinforcing portion 4 can make the electrode have greater tensile strength at the location of the reinforcing portion 4, thereby better preventing the electrode from breaking. At the same time, the reinforcing portion 4 can also buffer the impact force, thereby reducing the impact force on the current collector 1. In some embodiments, a material with higher hardness can also be selected as the reinforcing portion 4, which can not only better resist the bending of the current collector 1 during rolling, but also better disperse the impact force of the pressure roller on the current collector 1, further reducing the possibility of electrode breakage.

[0027] According to some embodiments of the present invention, the elastic modulus of the reinforcing part 4 in the first direction is greater than that of the current collector 1. The reinforcing part 4 has a larger elastic modulus in the first direction, which allows for better buffering of impact forces, thereby providing better protection for the current collector 1.

[0028] According to some embodiments of this utility model, the tensile strength of the reinforcing part 4 in the second direction is greater than the tensile strength of the current collector 1. By using the greater tensile strength of the reinforcing part 4, excessive elongation of the current collector 1 during the rolling process is avoided, thereby preventing damage caused by excessive elongation of the current collector 1.

[0029] According to some embodiments of the present invention, the reinforcing part 4 includes a first layer 41 and a second layer 42, wherein the first layer 41 is fixed to the current collector 1, and the second layer 42 is fixed to the first layer 41. The tensile strength of the first layer 41 is greater than that of the second layer 42, and the elastic modulus of the second layer 42 is greater than that of the first layer 41. The first layer 41 is disposed on the second surface 12, and the second layer 42 is disposed on the side of the first layer 41 facing away from the current collector 1. The first layer 41 and the second layer 42 enable the reinforcing part 4 to have a larger elastic modulus in the first direction and a larger tensile strength in the second direction, thereby reinforcing the current collector 1 from both the first and second directions.

[0030] According to some embodiments of the present invention, the second layer 42 extends beyond the edge of the first layer 41 in the second direction, and the portion of the second layer 42 extending beyond the edge of the first layer 41 is fixed to the second surface 12. By extending a portion of the structure of the second layer 42 beyond the edge of the first layer 41, the second layer 42 can continue to buffer the impact force when rolled against the edge of the first layer 41, thereby better protecting the current collector 1.

[0031] According to some embodiments of the present invention, the thickness of the first layer 41 in the first direction does not exceed 20% of the thickness of the second active material layer 3 in the first direction. When the thickness of the first layer 41 is large, it will damage the current collector 1 when it is rolled to the edge of the first layer 41. Setting the first layer 41 with a smaller thickness can protect the current collector 1 to a greater extent.

[0032] According to some embodiments of the present invention, the portion of the second layer 42 extending beyond the edge of the first layer 41 includes a compressed state, which is a state of being compressed by rollers. In the compressed state, the thickness of the portion of the second layer 42 extending beyond the edge of the first layer 41 in the first direction does not exceed 10% of the thickness of the second active material layer 3 in the first direction. The thinner the thickness of the portion of the second layer 42 extending beyond the edge of the first layer 41 after compression, the better the impact force on the current collector 1 can be reduced, and the better the current collector 1 can be protected.

[0033] According to some embodiments of this utility model, the tail end of the second active material layer 3 is provided with an inclined surface 31, and the distance between the inclined surface 31 and the current collector 1 gradually decreases in the direction towards the tail end of the current collector 1. The inclined surface 31 can effectively reduce the impact force on the current collector 1 during rolling, thereby better protecting the current collector 1.

[0034] According to some embodiments of this utility model, the angle between the inclined surface 31 and the first surface 11 does not exceed 45°. When the angle between the inclined surface 31 and the current collector 1 is too large, the impact force on the current collector 1 is large. Therefore, the inclination angle of the inclined surface 31 relative to the first surface 11 is limited.

[0035] The battery according to a second aspect of the present invention includes the electrode sheet described in any of the above embodiments.

[0036] Experiments were conducted on multiple sets of batteries with reinforcement sections 4 of varying sizes. The test method involved performing 100 charge-discharge cycles to check for electrode breakage. Batteries that broke after 100 cycles were considered unqualified. Batteries that did not break after 100 cycles were considered qualified.

[0037] In Example 1, the total thickness of the electrode at the reinforcing part 4 is 18.5 μm. The area of ​​the overlapping region between the reinforcing part 4 and the second active material layer 3 on the second surface 12 in the thickness direction is 100% of the area of ​​the reinforcing part 4. The thickness of the second active material layer 3 is 7.4 μm. The tensile strength of the reinforcing part 4 is 278 MPa, and the elastic modulus of the reinforcing part 4 is 210 GPa. The results after cyclic testing are qualified.

[0038] In Example 2, the total thickness of the electrode at the reinforcing part 4 is 18.5 μm. The area of ​​the overlapping region between the reinforcing part 4 and the second active material layer 3 on the second surface 12 in the thickness direction is 100% of the area of ​​the reinforcing part 4. The thickness of the second active material layer 3 is 5.55 μm. The tensile strength of the reinforcing part 4 is 262 MPa, and the elastic modulus of the reinforcing part 4 is 206 GPa. The results after cyclic testing are qualified.

[0039] In Example 3, the total thickness of the electrode at the reinforcing part 4 is 18.5 μm. The area of ​​the overlapping region between the reinforcing part 4 and the second active material layer 3 on the second surface 12 in the thickness direction is 100% of the area of ​​the reinforcing part 4. The thickness of the second active material layer 3 is 3.7 μm. The tensile strength of the reinforcing part 4 is 255 MPa, and the elastic modulus of the reinforcing part 4 is 203 GPa. The results after cyclic testing are qualified.

[0040] In Example 4, the total thickness of the electrode at the reinforcing part 4 is 18.5 μm. The area of ​​the overlapping region between the reinforcing part 4 and the second active material layer 3 on the second surface 12 in the thickness direction is 100% of the area of ​​the reinforcing part 4. The thickness of the second active material layer 3 is 9.25 μm. The tensile strength of the reinforcing part 4 is 245 MPa, and the elastic modulus of the reinforcing part 4 is 194 GPa. The result after cyclic testing was unqualified.

[0041] In Example 5, the total thickness of the electrode at the reinforcing part 4 is 18.5 μm. The area of ​​the overlapping region between the reinforcing part 4 and the second active material layer 3 on the second surface 12 in the thickness direction is 90% of the area of ​​the reinforcing part 4. The thickness of the second active material layer 3 is 7.4 μm. The tensile strength of the reinforcing part 4 is 279 MPa, and the elastic modulus of the reinforcing part 4 is 208 GPa. The results after cyclic testing are qualified.

[0042] In Example 6, the total thickness of the electrode at the reinforcing part 4 is 18.5 μm. The area of ​​the overlapping region between the reinforcing part 4 and the second active material layer 3 on the second surface 12 in the thickness direction is 80% of the area of ​​the reinforcing part 4. The thickness of the second active material layer 3 is 7.4 μm. The tensile strength of the reinforcing part 4 is 264 MPa, and the elastic modulus of the reinforcing part 4 is 204 GPa. The results after cyclic testing are qualified.

[0043] In Example 7, the total thickness of the electrode at the reinforcing part 4 is 18.5 μm. The area of ​​the overlapping region between the reinforcing part 4 and the second active material layer 3 on the second surface 12 in the thickness direction is 70% of the area of ​​the reinforcing part 4. The thickness of the second active material layer 3 is 7.4 μm. The tensile strength of the reinforcing part 4 is 256 MPa, and the elastic modulus of the reinforcing part 4 is 203 GPa. The results after cyclic testing are qualified.

[0044] In Example 8, the total thickness of the electrode at the reinforcing part 4 is 18.5 μm. The area of ​​the overlapping region between the reinforcing part 4 and the second active material layer 3 on the second surface 12 in the thickness direction is 60% of the area of ​​the reinforcing part 4. The thickness of the second active material layer 3 is 7.4 μm. The tensile strength of the reinforcing part 4 is 247 MPa, and the elastic modulus of the reinforcing part 4 is 196 GPa. The result after cyclic testing is unqualified.

[0045] The comparison of the above experimental data shows that setting sufficient elastic film and tensile strength in the reinforcing part 4 can effectively prevent the electrode from breaking after multiple cycles of charging and discharging.

[0046] 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 direction being the thickness direction of the current collector, the first active material layer being coated on the first surface, and the second active material layer being coated on the second surface. 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 tail end of the current collector, and the second direction is the length direction of the current collector; A reinforcing portion is provided on the second surface, and the projection of the tail end of the second active material layer along the first direction onto the reinforcing portion. The thickness of the reinforcing portion in the first direction does not exceed 40% of the thickness of the second active material layer in the first direction.

2. The electrode sheet according to claim 1, characterized in that, The elastic modulus of the reinforcing part in the first direction is greater than the elastic modulus of the current collector.

3. The electrode sheet according to claim 1, characterized in that, The tensile strength of the reinforcing part in the second direction is greater than the tensile strength of the current collector.

4. The electrode sheet according to claim 1, characterized in that, The reinforcing part includes a first layer and a second layer. The tensile strength of the first layer is greater than that of the second layer, and the elastic modulus of the second layer is greater than that of the first layer. The first layer is disposed on the second surface, and the second layer is disposed on the side of the first layer that is away from the current collector.

5. The electrode sheet according to claim 4, characterized in that, The second layer extends beyond the edge of the first layer in the second direction, and the portion of the second layer extending beyond the edge of the first layer is fixed to the second surface.

6. The electrode sheet according to claim 5, characterized in that, The thickness of the first layer in the first direction does not exceed 20% of the thickness of the second active material layer in the first direction.

7. The electrode sheet according to claim 6, characterized in that, The portion of the second layer extending beyond the edge of the first layer includes a compressed state, which is a state of being compressed by rolling. In the compressed state, the thickness of the portion of the second layer extending beyond the edge of the first layer in the first direction does not exceed 10% of the thickness of the second active material layer in the first direction.

8. The electrode sheet according to claim 1, characterized in that, The tail end of the second active material layer is provided with an inclined surface, and the distance between the inclined surface and the current collector gradually decreases in the direction toward the tail end of the current collector.

9. The electrode sheet according to claim 8, characterized in that, The angle between the inclined surface and the first surface does not exceed 45°.

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

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