Negative pole piece, battery monomer, battery and electric device

Abstract

The invention discloses a negative pole piece, a battery monomer, a battery and a power utilization device, the negative pole piece comprises a main body area, a thinning area arranged on one side of the main body area and a tab arranged on one side of the thinning area, the compaction value of the thinning area is smaller than that of the main body area, and the thickness of the tab is smaller than that of the main body area. The compaction value of the thinning area close to the tab is reduced corresponding to the main body area, so that the purpose of influencing the transmission resistance of lithium ions in the negative pole piece is achieved, the high temperature rise near the tab of the negative pole piece is improved, and the problems of side reaction increase, negative pole local internal resistance increase, local lithium precipitation and capacity diving caused by the high temperature rise are further avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of power batteries, and in particular to a negative electrode plate, a battery cell, a battery and an electrical device. Background Art

[0002] Power batteries are widely used in different fields due to their high energy density and environmental friendliness. For example, mobile phones, laptops or other daily electronic products. In particular, in order to cope with environmental issues, gasoline price issues, and energy storage issues, the application of power batteries has rapidly expanded to the transportation field. Lithium-ion batteries have also become the first choice for cars with high endurance.

[0003] During the use of lithium batteries, the capacity of aluminum shell batteries is high, and a high temperature rise will occur during fast charging. The temperature rise is even higher in the area near the lug due to the concentration of current. The high temperature rise during the charging process will cause the high-temperature side reaction to intensify, causing the negative electrode impedance in the area near the lug to increase rapidly, and the negative electrode potential to decrease rapidly until it is lower than the lithium deposition potential, thereby causing lithium deposition, resulting in a rapid capacity drop and causing safety issues. In response to this phenomenon, there is currently no other effective method except to reduce the overall current.

[0004] Therefore, it is necessary to design a negative electrode plate, a battery cell, a battery and an electrical device to improve the high temperature rise near the ear of the negative electrode plate, so as to avoid the increase of side reactions caused by the high temperature rise, the increase of the local internal resistance of the negative electrode, the local lithium deposition and the capacity drop. Summary of the invention

[0005] The object of the present invention is to overcome the deficiencies of the prior art and to provide a negative electrode plate, a battery cell, a battery and an electrical device. The negative electrode plate changes the compaction of the thinned area near the pole ear, thereby reducing the temperature rise in the vicinity, reducing the side reactions caused by the high temperature rise and the increase in the local internal resistance of the negative electrode plate, thereby avoiding the problems of local lithium precipitation and cycle water diving.

[0006] According to a first aspect of the present invention, a negative electrode plate is provided, comprising a main body region, a thinning region arranged on one side of the main body region, and a pole ear arranged on one side of the thinning region, wherein the compaction value of the thinning region is smaller than the compaction value of the main body region. This arrangement reduces the compaction of the thinning region, so that the compaction value of this part is smaller than the compaction value of the main body region, thereby achieving the effect of improving battery performance. In particular, this arrangement has a simple structure, is relatively easy to implement in terms of process, and can effectively reduce production costs.

[0007] In one embodiment, the compaction value of the thinned area is A, and the compaction value of the main area is B, wherein A = (0.65-0.9) * B. This setting optimizes the relationship between the compaction value of the thinned area and the compaction value of the main area, which not only ensures that the side reactions caused by the high temperature rise of the negative electrode plate and the increase of the local internal resistance of the negative electrode plate are reduced, thereby avoiding the problems of local lithium deposition and cycle diving, but also compatibility and ensure that the volume ratio of the battery cell meets the requirements.

[0008] In one embodiment, the compaction value of the skived area is positively correlated with the proportion of the width of the skived area in the total width of the main area and the skived area, and the compaction value of the skived area decreases as the proportion of the width of the skived area in the total width of the main area and the skived area decreases. That is, in different batches of products, the compaction value of the skived area varies with the value of the width of the skived area divided by the width of the main area and the skived area, so as to achieve a more optimized setting.

[0009] Preferably, when the percentage of the width of the thinned zone in the total width of the main area and the thinned zone is greater than or equal to 3% and less than 5%, the compaction value A of the thinned zone is (0.65-0.75)*B. When the percentage of the width of the thinned zone in the total width of the main area and the thinned zone is greater than or equal to 5% and less than 10%, the compaction value A of the thinned zone is (0.7-0.8)*B. When the percentage of the width of the thinned zone in the total width of the main area and the thinned zone is greater than or equal to 10% and less than 15%, the compaction value A of the thinned zone is (0.75-0.85)*B. When the percentage of the width of the thinned zone in the total width of the main area and the thinned zone is greater than or equal to 15%, the compaction value A of the thinned zone is (0.8-0.9)*B. This setting can ensure the optimal performance of all aspects of the battery cell.

[0010] According to a second aspect of the present invention, a battery cell is provided, comprising the above-mentioned negative electrode plate.

[0011] According to a third aspect of the present invention, a battery is provided, comprising one or more of the above-mentioned battery cells.

[0012] According to a fourth aspect of the present invention, there is provided an electric device, comprising the above-mentioned battery, the battery being used to provide electric energy. The negative electrode sheet of the present application is used to make the battery have good performance and to increase the service life of the electric device.

[0013] The above technical solution has the following beneficial effects: the temperature near the tab of the negative electrode plate increases, the compaction value of the thinned area adjacent to the tab is reduced, the porosity of the area with reduced compaction value is high, the lithium ion diffusion performance can be improved, the corresponding internal resistance of the negative electrode plate can be reduced, and thus the local temperature rise can be reduced, solving the problem of cyclic lithium deposition and water diving caused by local high-temperature side reactions. Especially during long-cycle use, this arrangement can improve the use stability of the corresponding battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The disclosure of the present invention will become more easily understood with reference to the accompanying drawings. It should be understood that these drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In the drawings:

[0015] Figure 1 A negative electrode sheet according to an embodiment of the present invention is shown.

[0016] The drawings are not drawn to scale. DETAILED DESCRIPTION

[0017] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0018] One embodiment of the present invention provides a negative electrode plate. Figure 1 As shown, the negative electrode plate 1 includes a tab 2, a main area 3 and a thinning area 4. Among them, the thinning area 4 is arranged on one side of the main area 3. The tab 2 is arranged on one side of the thinning area 4. According to the present application, the compaction value of the thinning area 4 is lower than the compaction value of the main area 3. This setting reduces the compaction of the thinning area 4, so that the compaction value of this part is smaller than the compaction value of the main area 3. Since the tab 2 is relatively close to the thinning area 4, the transmission resistance of lithium ions inside the negative electrode plate is affected, thereby achieving the purpose of affecting the internal resistance of the battery and subsequent lithium deposition and cycle diving. In particular, this setting treats the thinning area 4 as a whole and changes its compaction value, which is relatively easy to implement in terms of process and can effectively reduce production costs.

[0019] Assume that the compaction value of the thinned area 4 is A, and the compaction value of the main area 3 is B. According to the present application, A = (0.65-0.9) * B. This setting optimizes the relationship between the compaction value of the thinned area 4 and the compaction value of the main area 3, which not only ensures that the side reactions caused by the high temperature rise of the negative electrode plate and the increase of the local internal resistance of the negative electrode plate are reduced, thereby avoiding the problems of local lithium precipitation and cycle diving, but also ensures the volume ratio and capacity of the battery cell with compatibility.

[0020] In one embodiment, the compaction value of the thinning zone 4 varies with the size of the width of the thinning zone 4 as a percentage of the sum of the widths of the thinning zone 4 and the main zone 3. Specifically, the compaction value of the thinning zone 4 is positively correlated with the size of the width of the thinning zone 4 as a percentage of the total width of the main zone 3 and the thinning zone 4, and the compaction value of the thinning zone 4 decreases as the size of the width of the thinning zone 4 as a percentage of the total width of the main zone 3 and the thinning zone 4 decreases. When the value obtained by the width of the thinning zone 4 as a percentage of the sum of the widths of the thinning zone 4 and the main zone 3 decreases, the compaction value of the thinning zone 4 also decreases. That is to say, in different batches of products, the compaction value of the thinning zone 4 varies with the size of the width of the thinning zone 4 as a percentage of the sum of the widths of the thinning zone 4 and the main zone 3. It should be noted that the width here refers to Figure 1 Dimensions in the upper-middle area.

[0021] More specifically, when the percentage of the width of the thinned zone 4 in the total width of the main body zone 3 and the thinned zone 4 is greater than or equal to 3% and less than 5%, the compaction value A of the thinned zone 4 is (0.65-0.75)*B. When the percentage of the width of the thinned zone 4 in the total width of the main body zone 3 and the thinned zone 4 is greater than or equal to 5% and less than 10%, the compaction value A of the thinned zone 4 is (0.7-0.8)*B. When the percentage of the width of the thinned zone 4 in the total width of the main body zone 3 and the thinned zone 4 is greater than or equal to 10% and less than 15%, the compaction value A of the thinned zone 4 is (0.75-0.85)*B. When the percentage of the width of the skived area 4 in the total width of the main area 3 and the skived area 4 is greater than or equal to 15%, the compaction value A of the skived area 4 = (0.8-0.9)*B, and the compaction value A of the skived area 4 = (0.8-0.9)*B. This setting can ensure the optimal performance of the battery cell in all aspects. This setting further optimizes the relationship between the compaction value of the skived area 4 and the compaction value of the main area 3. It should be noted that this setting can also be further adjusted according to actual application conditions.

[0022] Several practical examples are given below to further illustrate and explain this application. For 190Ah square shell batteries, a temperature sensing line is embedded to detect the highest temperature of the thinned area near the tab during 4CCC-CV (first charging at 4C constant current to 4.25V, then gradually reducing the current to 0.05C at a constant voltage of 4.25V before ending the charging process), and the battery cell is disassembled after 1000 cycles to observe whether there is lithium deposition on the interface.

[0023] Using the negative electrode sheet in the prior art as a comparative example for the test, it can be understood that the compaction values ​​of the thinning area and the main area of ​​the negative electrode sheet are equal. When the width of the thinning area 4 accounts for 10% of the total width of the thinning area and the main area, the maximum temperature at the center of the thinning area near the pole ear is 70 degrees Celsius, and the capacity retention rate after 1000 cycles is 70%. The results show that there is a more serious lithium precipitation phenomenon. After adopting the negative electrode sheet of the present application, the lithium precipitation phenomenon is greatly reduced or eliminated. When the width of the thinning area 4 accounts for 20% of the total width of the thinning area 4 and the main area 3, the compaction value of the thinning area 4 is A, and the compaction value of the main area 3 is B, and A adopts 0.9*B. The test results show that the maximum temperature at the center of the thinning area 4 near the pole ear 2 is 65 degrees Celsius, and the capacity retention rate after 1000 cycles is 77%. The results show that there is a relatively slight lithium precipitation phenomenon. In the second test, when the width of the thinning zone 4 accounts for 5% of the total width of the thinning zone 4 and the main zone 3, the compaction value of the thinning zone 4 is A, the compaction value of the main zone 3 is B, and A is 0.8*B. The test results show that the highest temperature in the center of the thinning zone 4 near the tab 2 is 62 degrees Celsius, and the capacity retention rate after 1000 cycles is 83%. The results show that there is no lithium precipitation. In the third test, when the width of the thinning zone 4 is 5% of the total width of the thinning zone 4 and the main zone 3, the compaction value of the thinning zone 4 is A, the compaction value of the main zone 3 is B, and A is 0.7*B. The test results show that the highest temperature in the center of the thinning zone 4 near the tab 2 is 55 degrees Celsius, and the capacity retention rate after 1000 cycles is 86%. The results show that there is no lithium precipitation. From this, it can be concluded that by reducing the compaction of the thinning zone 4 relative to the compaction of the main zone 3, the temperature rise of the thinning zone 4 near the pole ear 2 with large local current can be effectively alleviated, the side reaction can be reduced, and the local negative electrode impedance can be reduced to prevent lithium precipitation and cycle diving. In particular, the smaller the compaction value A of the thinning zone 4, the more prominent the effect of alleviating the temperature rise. However, in order to take into account the convenience of production and reduce manufacturing costs, the compaction value A of the thinning zone 4 cannot be reduced all the time. For this reason, the present application uses the size of the total width of the thinning zone 4 and the main zone 3 corresponding to the width of the thinning zone 4 as a parameter, and gives the corresponding relationship between the compaction value A of the thinning zone 4 and the compaction value B of the main zone 3 according to different parameters. Setting the compaction of the thinning zone 4 through this corresponding relationship can effectively ensure the optimal performance of all aspects of the battery cell.

[0024] The present application also relates to a battery cell, including the above-mentioned negative electrode plate. In addition, the present application also relates to a battery, including one or more of the above-mentioned battery cells. In addition, the present application also relates to an electric device, including the above-mentioned battery, and the battery is used to provide electric energy. For example, the electric device can be a new energy vehicle.

[0025] The above are only the principles and preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several other modifications can be made based on the principles of the present invention, which should also be considered as the protection scope of the present invention.

Claims

1. A negative electrode plate, characterized in that: It comprises a main body region, a thinning region arranged on one side of the main body region and a pole ear arranged on one side of the thinning region, wherein the compaction value of the thinning region is smaller than the compaction value of the main body region.

2. The negative electrode sheet according to claim 1, characterized in that: The compaction value of the thinned area is A, and the compaction value of the main area is B, wherein A=(0.65-0.9)*B.

3. The negative electrode sheet according to claim 2, characterized in that: The compression value of the thinned zone is positively correlated with the proportion of the width of the thinned zone in the total width of the main zone and the thinned zone, and the compression value of the thinned zone decreases as the proportion of the width of the thinned zone in the total width of the main zone and the thinned zone decreases.

4. The negative electrode sheet according to claim 3, characterized in that: When the percentage of the width of the thinned area in the total width of the main area and the thinned area is greater than or equal to 3% and less than 5%, the compaction value A of the thinned area=(0.65-0.75)*B.

5. The negative electrode sheet according to claim 3, characterized in that: When the percentage of the width of the thinned area in the total width of the main area and the thinned area is greater than or equal to 5% and less than 10%, the compaction value A of the thinned area=(0.7-0.8)*B.

6. The negative electrode sheet according to claim 3, characterized in that: When the percentage of the width of the thinned area in the total width of the main area and the thinned area is greater than or equal to 10% and less than 15%, the compaction value A of the thinned area=(0.75-0.85)*B.

7. The negative electrode sheet according to claim 3, characterized in that: When the percentage of the width of the thinned area in the total width of the main area and the thinned area is greater than or equal to 15%, the compaction value A of the thinned area=(0.8-0.9)*B.

8. A battery cell, characterized in that: Comprising the negative electrode sheet according to any one of claims 1 to 7.

9. A battery, characterized in that: Comprising one or more battery cells according to claim 8.

10. An electrical device, characterized in that: A battery according to claim 9, for providing electrical energy.

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