Battery monomer, battery and electric equipment

Abstract

The utility model provides a battery monomer, a battery and electric equipment. The battery monomer comprises a shell; the shell comprises a first wall part, the first wall part is provided with a first groove, the first groove is sunken from a first surface in the thickness direction of the first wall part to a direction close to a second surface, the first groove defines at least one preset pressure relief area, and the first wall part is configured to be capable of cracking along at least part of the first groove when the battery monomer is subjected to pressure relief; wherein the sum S1 of the areas of all the preset pressure relief areas is 0.03-0.3 time of the area S2 of the first surface, so that the risks of burst, explosion, fire and the like of the shell of the battery monomer caused by untimely pressure relief of the first wall part can be reduced; and the risk of liquid leakage caused by phenomena such as advanced actuation or fatigue cracking of the first wall part after the battery monomer is used for a long time is reduced, so that the service life of the battery monomer is prolonged, and the use reliability of the battery monomer is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell, a battery and an electrical device. Background Art

[0002] Batteries are widely used in new energy vehicles, electronic equipment and other fields. As the demand for batteries increases, higher requirements are placed on battery reliability.

[0003] In battery technology, the pressure relief component of a battery cell is one of the important factors affecting the reliability of the battery cell. The pressure relief component is used to release the pressure inside the battery cell. The pressure relief component can release the pressure inside the battery cell when the pressure or temperature inside the battery cell reaches a threshold. However, after multiple cycles and long-term use of the battery cell, the pressure relief component is prone to premature pressure relief or fatigue cracking, which reduces the reliability of the battery cell. Summary of the invention

[0004] The embodiments of the present application provide a battery cell, a battery, and an electrical device to improve the reliability of the battery cell.

[0005] In a first aspect, an embodiment of the present application provides a battery cell, comprising a shell; the shell comprising a first wall portion, wherein the first wall portion has a first surface and a second surface arranged opposite to each other in a thickness direction of the first wall portion; the first wall portion is provided with a first groove, the first groove is recessed from the first surface toward a direction close to the second surface, the first groove defines at least one predetermined pressure relief area, and the first wall portion is configured to be able to split along at least part of the first groove when the battery cell is depressurized; wherein the sum S1 of the areas of all the predetermined pressure relief areas is 0.03 to 0.3 times the area S2 of the first surface.

[0006] In the above technical solution, the first wall portion of the shell is provided with a first groove, and the bottom wall of the first groove forms a first weak portion, thereby forming a pressure relief component on the first wall portion. The first weak portion can be cracked when the battery cell is depressurized to release the pressure inside the battery cell, so as to reduce the occurrence of explosion, fire and other problems caused by excessive internal pressure of the battery cell. By setting the sum of the areas S1 of all the predetermined pressure relief zones to 0.03 to 0.3 times the area S2 of the first surface provided with the first groove, that is, the ratio of the sum of the areas S1 of all the predetermined pressure relief zones to the area S2 of the first surface provided with the first groove is set to 0.03 to 0.3, the relative sizes of the sum of the areas S1 of all the predetermined pressure relief zones and the area S2 of the first surface provided with the first groove are set more reasonably, and setting the ratio to be greater than or equal to 0.03 can alleviate the problem of insufficient area of ​​the predetermined pressure relief zones, so as to alleviate the phenomenon that the bursting pressure required by the first wall portion when the battery cell is depressurized is too large due to the excessive pressure bearing capacity of the bottom wall of the first groove, thereby reducing the risk of bursting, explosion, fire, etc. of the battery cell shell caused by untimely pressure relief of the first wall portion, thereby effectively improving the reliability of the battery cell. The expansion force generated by the expansion of the battery cell during use will cause the first wall portion to deform. Setting the ratio to less than or equal to 0.3 can alleviate the problem that the strength and rigidity of the first wall portion are reduced and it is easy to deform greatly due to the fact that the area of ​​the predetermined pressure relief area is too large relative to the area of ​​the first surface. It can also reduce the concentration of stress on the bottom wall of the first groove when the expansion force generated by the expansion during the use of the battery cell acts on the first wall portion, and enable the predetermined pressure relief area to absorb a part of the expansion force, thereby effectively alleviating the phenomenon of tensile deformation of the bottom wall of the first groove of the first wall portion, so as to reduce the strain and strain amplitude of the bottom wall of the first groove of the first wall portion, that is, it can reduce the deformation of the bottom wall of the first groove, and further alleviate the phenomenon that the structural strength of the bottom wall of the first groove of the first wall portion is reduced due to excessive strain and strain amplitude, thereby reducing the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion in the corresponding area of ​​the first groove after long-term use of the battery cell, so as to improve the stability of the battery cell, which is conducive to improving the service life and reliability of the battery cell.

[0007] In some embodiments of the first aspect of the present application, 500 mm 2 ≤S1≤1300mm 2 .

[0008] In the above technical solution, the sum of the areas of all the predetermined pressure relief zones S1 is limited to 500mm 2 Up to 1300mm 2 , the sum of the areas of all the predetermined pressure relief zones S1 is set to be greater than or equal to 500mm 2, which can alleviate the problem of insufficient area of ​​the predetermined pressure relief area, so as to alleviate the phenomenon that the pressure bearing capacity of the bottom wall of the first groove is too large, which causes the first wall to have too large a bursting pressure when the battery cell is depressurized, thereby reducing the risk of bursting, explosion, fire, etc. of the battery cell shell due to untimely pressure relief of the first wall, and further effectively improve the reliability of the battery cell. The sum of the areas of all predetermined pressure relief areas is set to be less than or equal to 1300mm 2 , which can alleviate the problem that the strength of the first wall portion is reduced and a large deformation is easily caused due to the large area of ​​the predetermined pressure relief area. It can also reduce the concentration of stress on the bottom wall of the first groove when the expansion force generated by expansion during the use of the battery cell acts on the first wall portion, and enable the predetermined pressure relief area to absorb a part of the expansion force, thereby effectively alleviating the phenomenon of tensile deformation of the bottom wall of the first groove of the first wall portion, so as to reduce the strain and strain amplitude of the bottom wall of the first groove of the first wall portion, that is, it can reduce the deformation of the bottom wall of the first groove, and further alleviate the phenomenon that the structural strength of the bottom wall of the first groove of the first wall portion is reduced due to excessive strain and strain amplitude, thereby reducing the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion in the corresponding area of ​​the first groove after long-term use of the battery cell, so as to improve the stability of the battery cell, which is conducive to improving the service life and reliability of the battery cell.

[0009] In some embodiments of the first aspect of the present application, 5000 mm 2 ≤S2≤8500mm 2 .

[0010] In the above technical solution, by setting the area S2 of the first surface where the first groove is set to 6000mm 2 Up to 8500mm 2 , the area of ​​the first surface is set to be greater than or equal to 6000mm 2, can alleviate the problem that the first wall strength is reduced and large deformation occurs easily due to the small area of ​​the first surface, and can also reduce the concentration of stress on the bottom wall of the first groove when the expansion force generated by the expansion during the use of the battery cell acts on the first wall, and make the predetermined pressure relief area absorb part of the expansion force, so as to effectively alleviate the phenomenon of tensile deformation of the bottom wall of the first groove of the first wall, so as to reduce the strain and strain amplitude of the bottom wall of the first groove of the first wall, that is, it can reduce the deformation of the bottom wall of the first groove, and then alleviate the phenomenon of structural strength reduction of the bottom wall of the first groove of the first wall due to excessive strain and strain amplitude, and then reduce the risk of leakage caused by premature actuation or fatigue cracking of the first wall in the corresponding area of ​​the first groove after long-term use of the battery cell, so as to improve the use stability of the battery cell, which is conducive to improving the service life and reliability of the battery cell. The area of ​​the first surface is set to be less than or equal to 8500mm 2 , which can alleviate the problem that the first surface area is too small, resulting in the first wall portion having greater strength and rigidity and being able to withstand greater pressure and being difficult to deform, and alleviate the problem that the pressure bearing capacity of the bottom wall of the first groove is too large, resulting in the first wall portion having an excessively large bursting pressure when the battery cell is depressurized, thereby reducing the risk of bursting, explosion, fire, etc. of the battery cell shell due to untimely pressure relief at the first wall portion, and further effectively improving the reliability of the battery cell.

[0011] In some embodiments of the first aspect of the present application, the first wall portion is a rectangular wall portion; along the width direction of the first wall portion, the size of the first surface is c; along the length direction of the first wall portion, the size of the first surface is d, S2=c*d; wherein, 55mm≤c≤85mm, 100mm≤d≤260mm.

[0012] In the above technical solution, the first wall portion is a rectangular wall portion, which is convenient for manufacturing and molding, and also convenient for measuring the area of ​​the first surface.

[0013] In some embodiments of the first aspect of the present application, the first wall portion is a rectangular wall portion; along the length direction of the first wall portion, the first wall portion is formed with at least one predetermined pressure relief area, and the sum of the sizes a of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is 0.1 to 0.5 times the size d of the first surface along the length direction of the first wall portion.

[0014] In the above technical solution, the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is 0.1 to 0.5 times the size d of the first surface along the length direction of the first wall portion, that is, the ratio of the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion to the size d of the first surface in the length direction of the first wall portion is limited to 0.1 to 0.5, wherein the ratio of the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion to the size d of the first surface in the length direction of the first wall portion is greater than or equal to 0.1, which can alleviate the phenomenon that the pressure bearing capacity of the bottom wall of the first groove is too large, resulting in excessive bursting pressure required by the first wall portion when the battery cell is depressurized, thereby reducing the risk of bursting, explosion, fire, etc. of the battery cell shell caused by untimely pressure relief of the first wall portion, and further effectively improving the reliability of the battery cell. The ratio of the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion to the size d of the first surface in the length direction of the first wall portion is less than or equal to 0.5, which can reduce the deformation of the bottom wall of the first groove when the expansion force generated by expansion during the use of the battery cell acts on the first wall portion, thereby reducing the phenomenon that the bottom wall of the first groove of the first wall portion is reduced in structural strength due to excessive deformation, and further reduces the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion at the corresponding position of the first groove after long-term use of the battery cell, thereby improving the stability of the use of the battery cell. Qualitative analysis can improve the service life and reliability of the battery cell. Therefore, the sum of the sizes a of all predetermined pressure relief areas arranged along the length direction of the first wall portion is 0.1 to 0.5 times the size d of the first surface along the length direction of the first wall portion. This can reduce the risks of bursting, explosion, fire, etc. of the battery cell shell due to untimely pressure relief of the first wall portion, and reduce the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion at the corresponding position of the first groove of the battery cell after long-term use, so as to improve the stability of the battery cell and improve the service life and reliability of the battery cell.

[0015] In some embodiments of the first aspect of the present application, the first wall portion is a rectangular wall portion; along the width direction of the first wall portion, the first groove defines at least one predetermined pressure relief area, and the sum of the sizes b of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is 0.3 to 0.7 times the size c of the first surface along the width direction of the first wall portion.

[0016] In the above technical solution, the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is 0.3 to 0.7 times the size c of the first surface along the width direction of the first wall portion, that is, the ratio of the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion to the size of the first surface in the curl direction of the first wall portion is limited to 0.3 to 0.7, wherein, by making the ratio of the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion to the size of the first surface in the curl direction of the first wall portion greater than or equal to 0.3, the phenomenon that the pressure bearing capacity of the bottom wall of the first groove is too large, resulting in excessive bursting pressure required by the first wall portion when the battery cell is depressurized, can be alleviated, thereby reducing the risk of bursting, explosion, fire, etc. of the battery cell shell caused by untimely pressure relief of the first wall portion, and further effectively improving the reliability of the battery cell. By making the ratio of the sum of the sizes b of all predetermined pressure relief areas arranged along the width direction of the first wall portion to the size of the first surface in the curl direction of the first wall portion less than or equal to 0.7, the degree of material stacking in the width direction of the first wall portion during the manufacturing process of the first groove can be reduced, thereby alleviating the problem of poor flatness of the surface of the battery cell in the width direction of the first wall portion due to the formation of the first groove.

[0017] In some embodiments of the first aspect of the present application, the first wall portion is a rectangular wall portion; along the length direction of the first wall portion, the first wall portion forms at least one predetermined pressure relief zone, and the sum of the sizes of all the predetermined pressure relief zones arranged along the length direction of the first wall portion is a, 26mm≤a≤50mm.

[0018] In the above technical solution, the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is greater than or equal to 26 mm, which not only facilitates the processing and forming of the first groove and defines the predetermined pressure relief area, but also helps to increase the area of ​​the predetermined pressure relief area, thereby alleviating the phenomenon that the pressure bearing capacity of the bottom wall of the first groove is too large, resulting in excessive bursting pressure required by the first wall portion when the battery cell is depressurized, thereby reducing the risk of bursting, explosion, fire, etc. of the battery cell shell due to untimely pressure relief of the first wall portion, and further effectively improving the reliability of the battery cell. The sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is less than or equal to 50 mm, which can reduce the deformation of the bottom wall of the first groove when the expansion force generated by expansion during the use of the battery cell acts on the first wall portion, thereby reducing the structural strength of the bottom wall of the first groove of the first wall portion due to excessive deformation, and further reduce the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion at the corresponding position of the first groove after long-term use of the battery cell, thereby improving the use stability of the battery cell and improving the service life and reliability of the battery cell.

[0019] In some embodiments of the first aspect of the present application, the first wall portion is a rectangular wall portion; along the width direction of the first wall portion, the first groove defines at least one predetermined pressure relief area, and the sum of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is b, where 18 mm ≤ b ≤ 62 mm.

[0020] In the above technical solution, the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is greater than or equal to 18 mm, which not only facilitates the processing and forming of the first groove and defines the predetermined pressure relief area, but also helps to increase the area of the predetermined pressure relief area, relieve the excessive pressure-bearing capacity of the bottom wall of the first groove, and avoid the phenomenon that the bursting pressure required for the first wall portion during the pressure relief of the battery cell is too large. Thus, the risks such as bursting, explosion, and fire of the outer shell of the battery cell caused by untimely pressure relief of the first wall portion can be reduced, and further the use reliability of the battery cell can be effectively improved. The sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is less than or equal to 62 mm, which can reduce the degree of material accumulation in the width direction of the first wall portion during the manufacturing process of the first groove, thereby relieving the problem of poor flatness of the surface of the battery cell in the width direction of the first wall portion caused by the formation of the first groove.

[0021] In some embodiments of the first aspect of the present application, the first wall portion is a rectangular wall portion; along the length direction of the first wall portion, the first wall portion forms at least one predetermined pressure relief area, and the sum of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is a; along the width direction of the first wall portion, the first groove defines at least one predetermined pressure relief area, and the sum of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is b, and along the width direction of the first wall portion, the size of the first surface is c; when 10 mm ≤ c ≤ 40 mm, the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is 2 to 3 times the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion; when 40 mm < c ≤ 60 mm, the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is 1 to 2 times the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion; when 60 mm < c, the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is 0.4 to 1 times the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion.

[0022] In the above technical solution, when 10 mm ≤ c ≤ 40 mm, the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is 2 to 3 times the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion, that is, the ratio of the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is 2 to 3. The ratio of the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is greater than or equal to 2, and the bursting pressure is more stable, which is beneficial to the timely pressure relief of the first wall portion, so as to reduce the risks such as the bursting, explosion, and fire of the outer shell of the battery cell caused by the untimely pressure relief of the first wall portion, and further effectively improve the use reliability of the battery cell; the ratio of the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is less than or equal to 3, which is beneficial to a larger valve opening angle of the predetermined pressure relief area when the first groove cracks, so that the first wall portion has a larger pressure relief area, which is beneficial to the timely pressure relief of the first wall portion, reduces the risks such as the bursting, explosion, and fire of the outer shell of the battery cell, and improves the reliability of the battery cell. When 40 mm < c ≤ 60 mm, the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is 1 to 2 times the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion, that is, the ratio of the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is 1 to 2. The ratio of the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is greater than or equal to 1, and the bursting pressure is more stable, which is beneficial to the timely pressure relief of the first wall portion, so as to reduce the risks such as the bursting, explosion, and fire of the outer shell of the battery cell caused by the untimely pressure relief of the first wall portion, and further effectively improve the use reliability of the battery cell; the ratio of the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is less than or equal to 2, which is beneficial to a larger valve opening angle of the predetermined pressure relief area when the first groove cracks, so that the first wall portion has a larger pressure relief area, which is beneficial to the timely pressure relief of the first wall portion, reduces the risks such as the bursting, explosion, and fire of the outer shell of the battery cell, and improves the reliability of the battery cell.When 60mm < c, the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is 0.4 times to 1 times the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion, that is, the ratio of the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is 0.4 to 1. The ratio of the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is greater than or equal to 0.4, and the bursting pressure is more stable, which is beneficial to the timely pressure relief of the first wall portion, so as to reduce the risks such as bursting, explosion, and fire of the outer shell of the battery cell caused by the untimely pressure relief of the first wall portion, and further effectively improve the use reliability of the battery cell; the ratio of the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is less than or equal to 1, which is beneficial to a larger opening angle of the predetermined pressure relief area when the first groove cracks, so that the first wall portion has a larger pressure relief area, which is beneficial to the timely pressure relief of the first wall portion, reduces the risks such as bursting, explosion, and fire of the outer shell of the battery cell, and improves the reliability of the battery cell.

[0023] In some embodiments of the first aspect of the present application, the first wall portion further includes a second groove, and the second groove is configured to guide the opening of the predetermined pressure relief area.

[0024] In the above technical solution, since the second groove is provided on the first wall portion, a weak portion is formed in the area corresponding to the second groove on the first wall portion. The weak portion corresponding to the second groove can guide the opening of the predetermined pressure relief area, so as to improve the opening effect of the predetermined pressure relief area of the first wall portion, which is beneficial to increasing the pressure relief area of the battery cell after the predetermined pressure relief area is opened, and further improving the pressure relief rate of the battery cell when thermal runaway occurs, so as to reduce the risks such as fire explosion and connection failure caused by untimely pressure relief of the battery cell, and is beneficial to improving the use reliability of the battery cell. The second groove is provided on the first wall portion, so that a weak portion is formed in the area where the second groove is provided and the bottom surface of the second groove corresponds. The battery cell with this structure is convenient to form a weak portion on the first wall portion, which is beneficial to reducing the difficulty of forming a weak portion on the first wall portion to guide the opening of the predetermined pressure relief area, so as to improve the production efficiency of the battery cell.

[0025] In some embodiments of the first aspect of the present application, the second groove is recessed from the second surface towards the direction close to the first surface.

[0026] In the above technical solution, the second groove is recessed from the second surface toward the direction close to the first surface, and the first groove and the second groove are arranged on opposite sides of the first wall portion along the thickness direction of the first wall portion, so as to facilitate the processing of the first groove and the second groove on both sides of the first wall portion along the thickness direction of the first wall portion respectively, which is beneficial to reduce the mutual influence of the first groove and the second groove during the processing process.

[0027] In some embodiments of the first aspect of the present application, the first surface is a surface of the first wall portion facing away from the interior of the shell, and the second surface is a surface of the first wall portion facing the interior of the shell.

[0028] In the above technical solution, by respectively arranging the first groove and the second groove on the first surface and the second surface of the first wall portion that are opposite to each other along the thickness direction of the first wall portion, it is convenient to process the first groove and the second groove on both sides of the first wall portion along the thickness direction of the first wall portion, which is conducive to reducing the mutual influence of the first groove and the second groove during the processing. And the second groove is arranged on the second surface of the first wall portion facing the inside of the shell, so that the predetermined pressure relief area is opened around the bottom wall of the second groove and turned to the outside of the shell, thereby reducing the interference effect of the groove side of the second groove on the predetermined pressure relief area during the turning process, which is conducive to improving the turning effect of the predetermined pressure relief area.

[0029] In some embodiments of the first aspect of the present application, the first groove and the second groove are not in contact.

[0030] In the above technical solution, by setting the first groove and the second groove as a structure that does not contact each other, on the one hand, the mutual influence between the first groove and the second groove during the processing can be reduced; on the other hand, the phenomenon of the corresponding area of ​​the second groove cracking when the first groove cracks to release pressure can be reduced, and the stress influence between the first groove and the second groove can be reduced.

[0031] In some embodiments of the first aspect of the present application, the first groove includes a first groove segment and a second groove segment, the first groove segment and the second groove segment are connected, and the first groove segment and the second groove segment jointly define at least one predetermined pressure relief area.

[0032] In the above technical solution, the first groove includes a first groove section and a second groove section, and the first groove section and the second groove section are interconnected structures. On the one hand, the pressure relief area of ​​the battery cell can be increased to increase the pressure relief rate of the battery cell. On the other hand, the position where the first groove section and the second groove section are interconnected is weaker, which is easier to crack and open the predetermined pressure relief area to release the internal pressure of the battery cell.

[0033] In some embodiments of the first aspect of the present application, the first groove also includes a third groove segment, the first groove segment and the third groove segment are arranged opposite to each other, the second groove segment connects the first groove segment and the third groove segment, and the first groove segment, the second groove segment and the third groove segment jointly define at least one predetermined pressure relief area.

[0034] In the above technical solution, the first groove is provided with a first groove section and a third groove section which are arranged opposite to each other, and a second groove section connecting the first groove section and the third groove section, so that the first wall portion can be split along the first groove section, the second groove section and the third groove section when the battery cell is depressurized, so as to open the predetermined pressure relief area to release the internal pressure of the battery cell. The first groove with such a structure makes the intersection position of the first groove section and the second groove section and the intersection position of the second groove section and the third groove section weaker, easier to split and open the predetermined pressure relief area for pressure relief, and can further improve the pressure relief area and pressure relief rate of the battery cell.

[0035] In some embodiments of the first aspect of the present application, the position where the second slot segment is connected to the first slot segment deviates from the two ends of the first slot segment, and the position where the second slot segment is connected to the third slot segment deviates from the two ends of the third slot segment.

[0036] In the above technical solution, the position where the second groove section is connected to the first groove section deviates from the two ends of the first groove section, and the connection position of the first groove section and the second groove section is set to be located between the two ends of the first groove section, and the position where the second groove section and the third groove section are connected deviates from the two ends of the third groove section, and the connection position of the third groove section and the second groove section is set to be located between the two ends of the third groove section. The first groove section, the second groove section and the third groove section form a structure similar to an "H" shape, so that both sides of the second groove section of the first groove can form a predetermined pressure relief area, and the two predetermined pressure relief areas can be opened in a split manner for pressure relief when the battery cell is depressurized, which is beneficial to further increase the pressure relief effect of the battery cell and can effectively improve the pressure relief rate of the battery cell.

[0037] In some embodiments of the first aspect of the present application, the first groove defines two predetermined pressure relief areas, and the two predetermined pressure relief areas are respectively located on both sides of the second groove section; the first wall portion also includes a second groove, and the second groove is configured to guide the predetermined pressure relief area to open, and at least one second groove is correspondingly arranged for each predetermined pressure relief area, and the first groove is located between the two second grooves.

[0038] In the above technical solution, the second groove can guide the corresponding predetermined pressure relief area to open, and at least one second groove is arranged corresponding to each predetermined pressure relief area, so as to improve the opening effect of each predetermined pressure relief area of ​​the first wall portion, which is beneficial to increase the pressure relief area of ​​the battery cell after the predetermined pressure relief area is opened, and then can improve the pressure relief rate of the battery cell when thermal runaway occurs, so as to reduce the risk of fire, explosion, connection failure, etc. caused by untimely pressure relief of the battery cell, which is beneficial to improve the reliability of the battery cell.

[0039] In some embodiments of the first aspect of the present application, the second slot segment and the second groove are arranged opposite to each other along a first direction, and along the first direction, the first slot segment and the third slot segment are both arranged at intervals from the second groove.

[0040] In the above technical solution, the second groove section and the second groove are arranged opposite to each other along the first direction, and the first groove section and the third groove section are arranged at intervals from the second groove along the first direction, then the first groove section, the second groove section and the third groove section are not in contact with the second groove, which can reduce the mutual influence between the first groove and the second groove during the processing, and reduce the phenomenon that the area corresponding to the second groove is cracked when the first groove is cracked and the pressure is released, and can reduce the stress influence between the first groove and the second groove. The second groove section and the second groove are arranged opposite to each other along the first direction, and the first groove section and the third groove section are arranged at intervals from the second groove along the first direction, then the second groove is located between the edge of the first wall portion along the first direction and the first notch, and the second groove can play a buffering role between the first groove and the edge of the first wall portion located in the first direction, reduce the risk of the first groove being cracked due to external force, and improve the reliability of the battery cell.

[0041] In some embodiments of the first aspect of the present application, the first wall portion is a rectangular wall portion, and the first direction is parallel to a width direction of the first wall portion.

[0042] In the above technical solution, the first direction is parallel to the width direction of the first wall portion, and the second groove section is arranged opposite to the second groove along the width direction of the first wall portion. The first groove section and the third groove section are arranged at intervals from the second groove along the width direction of the first wall portion, and the first groove section, the second groove section and the third groove section are not in contact with the second groove in the width direction of the first wall portion, which can reduce the mutual influence between the first groove and the second groove during the processing, and reduce the phenomenon that the area corresponding to the first groove causes the area corresponding to the second groove to crack when the area corresponding to the first groove cracks and releases pressure, and can reduce the stress influence between the first groove and the second groove. The second groove section is arranged opposite to the second groove along the width direction of the first wall portion, and the first groove section and the third groove section are arranged at intervals from the second groove along the width direction of the first wall portion, and the second groove is located between the edge of the first wall portion along the width direction of the first wall portion and the first notch, and the second groove can play a buffering role between the first groove and the edge of the first wall portion located in the first direction, reduce the risk of the first groove cracking due to external force, and improve the reliability of the battery cell.

[0043] In some embodiments of the first aspect of the present application, the first groove is a multi-level notch groove, which is a multi-level notch groove arranged in sequence along the direction from the first surface to the second surface, and in two adjacent levels of the notch grooves, the first-level notch groove away from the first surface is arranged on the groove bottom surface of the first-level notch groove close to the first surface.

[0044] In the above technical scheme, by setting the first groove as a stepped groove structure arranged along the thickness direction of the wall portion, so that the first groove is a groove formed by multiple processing, when such a structure is used to form grooves of equal depth on the first wall portion, on the one hand, the depth of a single processing of the notched groove can be reduced, which is beneficial to reducing the manufacturing difficulty and demand for manufacturing equipment for forming grooves of equal depth, so as to reduce manufacturing costs, and can reduce the forming force exerted on the first wall portion during a single processing during the formation of the first groove, which is beneficial to reducing the risk of cracks in the first wall portion, so as to improve the production quality of the battery cell, and on the other hand, can improve the flow shape of the bottom wall of the first groove during the formation process, which is beneficial to the flow of the material generated when forming the bottom wall of the first groove, so as to improve the consistency of the structure of the multi-stage notched groove.

[0045] In some embodiments of the first aspect of the present application, the first groove is a three-level notch groove, and the three-level notch grooves are arranged in sequence from the first surface to the second surface.

[0046] In the above technical scheme, the first groove is a three-level notch groove. When forming grooves of the same depth, it can reduce the depth of the notch groove in a single processing, which is beneficial to reduce the manufacturing difficulty and demand for manufacturing equipment for forming grooves of the same thickness, so as to reduce manufacturing costs. It can also reduce the forming force that the first wall portion is subjected to in a single processing during the formation of the bottom wall of the first groove, which is beneficial to reduce the risk of cracks in the first wall portion, so as to improve the production quality of the battery cell. On the other hand, it can improve the flow shape of the bottom wall of the first groove during the formation process, which is beneficial to the flow of materials generated when forming the first groove, so as to improve the structural consistency of the multi-level notch grooves; it also alleviates the problem of increased processing time due to multiple processing required for the formation of the first groove.

[0047] In some embodiments of the first aspect of the present application, the battery cell includes an electrode assembly, the electrode assembly is accommodated in the housing, and the first wall portion supports the electrode assembly.

[0048] In the above technical solution, the first wall portion supports the electrode assembly, and the first wall portion is arranged on the second wall portion, which can reduce the risk of the discharged substance acting on other electrical connection structures when the battery cell is depressurized, thereby reducing the risk of causing other reliability problems.

[0049] In some embodiments of the first aspect of the present application, the battery cell includes an electrode terminal, and the electrode terminal is disposed on other wall portions of the housing except the first wall portion.

[0050] In the above technical solution, the electrode terminals are arranged on other walls of the shell except the first wall portion, so the risk of the substances released from the battery cell when the pressure is released acts on the electrode terminals is low, which can reduce the risk of the battery cell short circuiting due to the electrical connection formed between the substances released from the battery cell when the pressure is released and the electrode terminals, causing thermal runaway of the battery cell again.

[0051] In some embodiments of the first aspect of the present application, the electrode terminal is disposed on a wall of the housing opposite to the first wall portion.

[0052] In the above technical solution, the electrode terminal is arranged on the wall portion of the shell opposite to the first wall portion, so that the distance between the electrode terminal and the first wall portion is farther, which can further reduce the risk of the discharged substance acting on the electrode terminal when the battery cell is depressurized, and further reduce the risk of the battery cell short circuiting due to the electrical connection formed by the discharged substance and the electrode terminal when the battery cell is depressurized, causing the battery cell to thermal runaway again.

[0053] In some embodiments of the first aspect of the present application, the outer shell includes a shell and an end cover; the shell has at least one opening; the end cover corresponds to the opening one by one, and the end cover is connected to the shell and closes the opening; wherein at least one of the end covers is the first wall portion, or the shell includes the first wall portion.

[0054] In the above technical solution, by setting the first wall of the shell as an end cap for closing the opening of the shell, the battery cell with this structure is convenient to set the first wall on the end cap, which is conducive to reducing the manufacturing difficulty of the battery cell, so as to improve the production efficiency of the battery cell. By setting the first wall of the shell as a wall of the shell, the battery cell with this structure can make the area of ​​the shell where the first wall is set away from the end cap, so as to effectively alleviate the phenomenon that the stress generated by the connection between the end cap and the shell acts on the first wall, so as to reduce the impact on the predetermined pressure relief area of ​​the first wall and the corresponding area of ​​the first groove, thereby helping to reduce the risk of cracking or structural strength reduction of the first wall under the pulling effect of stress, so as to improve the service life and reliability of the battery cell.

[0055] In some embodiments of the first aspect of the present application, the shell has two openings arranged opposite to each other; the outer shell includes two end covers, each end cover is connected to the shell and closes one of the openings, and the shell includes the first wall portion.

[0056] In the above technical solution, the shell of the outer shell has two openings arranged opposite to each other, and the two end covers respectively close the two openings. The battery cell using this structure is convenient for assembling the battery cell from both ends of the shell, which is conducive to reducing the manufacturing and assembly difficulties of the battery cell. The shell includes a first wall portion, which is not provided on the end cover, and can reduce the risk of the substance released when the battery cell is depressurized to act on other structures of the battery, thereby further reducing the risk of the battery cell short circuiting again and causing thermal runaway of the battery cell due to the electrical connection between the substance released when the battery cell is depressurized and the electrode terminal.

[0057] In some embodiments of the first aspect of the present application, the shell has an opening, and a wall portion of the shell arranged opposite to the opening is the first wall portion.

[0058] In the above technical solution, the wall portion of the shell that is arranged opposite to the opening is the first wall portion, which can reduce the risk of the substance released when the battery cell is depressurized acting on other structures of the battery, thereby further reducing the risk of the battery cell short circuiting due to the electrical connection formed between the substance released when the battery cell is depressurized and the electrode terminals, which may cause thermal runaway of the battery cell again.

[0059] In some embodiments of the first aspect of the present application, the material of the first wall portion includes steel.

[0060] In the above technical solution, the material of the first wall portion includes steel. Steel has the characteristic of high strength. The first wall portion made of steel has better strength. When the bursting pressure of the battery cell is constant, the first wall portion can be made thinner to reduce the volume of the first wall portion.

[0061] In some embodiments of the first aspect of the present application, the steel material is carbon steel or stainless steel.

[0062] In some embodiments of the first aspect of the present application, the material of the first wall portion includes aluminum alloy.

[0063] In the above technical solution, the aluminum alloy has the characteristics of light weight and good ductility, and it is easier to process the first groove on the first wall portion.

[0064] In some embodiments of the first aspect of the present application, the aluminum alloy includes the following components in mass percentage: aluminum ≥ 99.6%, copper ≤ 0.05%, iron ≤ 0.35%, magnesium ≤ 0.03%, manganese ≤ 0.03%, silicon ≤ 0.25%, titanium ≤ 0.03%, vanadium ≤ 0.05%, zinc ≤ 0.05%, and other single elements ≤ 0.03%.

[0065] In the above technical solution, the aluminum alloy has lower hardness and better forming ability, which reduces the difficulty of processing the first groove, is conducive to improving the processing accuracy of the first groove, and improves the pressure relief consistency of the first wall.

[0066] In some embodiments of the first aspect of the present application, the aluminum alloy includes the following components in mass percentage: aluminum ≥ 96.7%, 0.05% ≤ copper ≤ 0.2%, iron ≤ 0.7%, manganese ≤ 1.5%, silicon ≤ 0.6%, zinc ≤ 0.1%, other single element components ≤ 0.05%, and the total composition of other elements ≤ 0.15%.

[0067] In the above technical solution, the first wall portion made of the aluminum alloy has higher hardness, greater strength and good anti-destruction ability.

[0068] In a second aspect, an embodiment of the present application further provides a battery, comprising the above-mentioned battery cell.

[0069] In a third aspect, an embodiment of the present application further provides an electrical device, comprising the above-mentioned battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0071] Figure 1 A schematic diagram of the structure of a vehicle provided in some embodiments of the present application;

[0072] Figure 2 An exploded view of a battery provided for some embodiments of the present application;

[0073] Figure 3 A schematic diagram of the structure of a battery cell provided in some embodiments of the present application;

[0074] Figure 4 An exploded view of a battery cell provided for some embodiments of the present application;

[0075] Figure 5 A bottom view of a housing provided for some embodiments of the present application;

[0076] Figure 6 A cross-sectional view of a first wall portion provided for some embodiments of the present application;

[0077] Figure 7 for Figure 6 The enlarged view of B1 in the middle;

[0078] Figure 8 A bottom view of a housing provided for some other embodiments of the present application;

[0079] Fig. 9 A bottom view of a housing provided for some further embodiments of the present application;

[0080] Fig.10 A bottom view of a housing provided for some other embodiments of the present application;

[0081] Fig.11 A bottom view of a housing provided for yet some other embodiments of the present application;

[0082] Fig.12 is a schematic diagram of the first wall portion observed along the length direction after the first groove is cracked;

[0083] Fig.13 A bottom view of a housing provided for yet some embodiments of the present application;

[0084] Fig.14 A bottom view of a housing provided for yet other embodiments of the present application;

[0085] Fig.15 A bottom view of a housing provided for some other embodiments of the present application;

[0086] Fig.16 A bottom view of a housing provided for yet other embodiments of the present application;

[0087] Fig.17 A bottom view of a housing provided for some other embodiments of the present application;

[0088] Fig.18 for Fig.17 Cross-sectional view along the Q1-Q1 direction;

[0089] Fig.19 for Fig.18 The enlarged view of B2 in the middle;

[0090] Fig. 20 for Fig.18 The enlarged view of B3 in the middle;

[0091] Fig.21 A bottom view of a housing provided for some further embodiments of the present application;

[0092] Fig. 22 A bottom view of a housing provided in some other embodiments of the present application;

[0093] Fig.23 for Fig. 22 Sectional view along Q2-Q2 direction;

[0094] Fig.24 for Fig.23 The enlarged view of B4 in the middle;

[0095] Fig.25 for Fig. 22 Sectional view along Q3-Q3 direction;

[0096] Fig.26 for Fig.23 The enlarged view of B5 in the middle;

[0097] Fig. 27 for Fig.23 Enlarged view of B6 in the middle.

[0098] Icon: 1000-vehicle; 100-battery; 10-box; 11-first box body; 12-second box body; 20-battery cell; 21-housing; 211-first wall; 2111-first surface; 2112-second surface; 212-housing; 2121-opening; 2122-second wall; 2123-third wall; 2124-fourth wall; 2125-fifth wall; 2126-first chamfered surface; 2127-second chamfered surface; 2128-third chamfered surface; 2129-fourth chamfered surface; 213-end cover; 22-pressure relief component; 221-first groove; 2211-first weak part; 2211a-first weak section; 2212-first groove section; 2213-second groove section ;2214-third groove section;2215-fourth groove section;222-second groove;2221-second weak part;221a-first sub-groove;221a1-first section;221a2-second section;221a3-third section;221b-second sub-groove;221b1-fourth section;221b2-fifth section;221b3-sixth section;221c-third sub-groove;221c1-seventh section;221c2-eighth section;221c3-ninth section;23-electrode assembly;231-ear;24-electrode terminal;25-current collecting member;200-controller;300-motor;X-thickness direction of the first wall;Y-width direction of the first wall;Z-length direction of the first wall;P-predetermined pressure relief area. DETAILED DESCRIPTION

[0099] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0100] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0101] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0102] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0103] In the description of the embodiments of the present application, it should be noted that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the application is usually placed when in use, or the orientation or positional relationship commonly understood by those skilled in the art, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0104] The term "and / or" in this application is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this application generally indicates that the associated objects before and after are in an "or" relationship.

[0105] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0106] The term "plurality" used in the present application refers to two or more (including two).

[0107] In the embodiment of the present application, the battery cell may be a secondary battery. A secondary battery refers to a battery cell that can be continuously used by activating active materials by charging after the battery cell is discharged.

[0108] The battery cell can be a lithium ion battery, a sodium ion battery, a sodium lithium ion battery, a lithium metal battery, a sodium metal battery, a lithium sulfur battery, a magnesium ion battery, a nickel hydrogen battery, a nickel cadmium battery, a lead storage battery, etc., which is not limited in the embodiments of the present application.

[0109] A battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charge and discharge process of the battery cell, active ions (such as lithium ions) are embedded and removed between the positive electrode and the negative electrode. The separator is set between the positive electrode and the negative electrode to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through.

[0110] In some embodiments, the positive electrode may be a positive electrode sheet, and the positive electrode sheet may include a positive electrode current collector and a positive electrode active material disposed on at least one surface of the positive electrode current collector.

[0111] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0112] As an example, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium, etc. may be used. The composite current collector may include a polymer material base and a metal layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0113] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds, etc.

[0114] In some embodiments, the positive electrode may be a foamed metal. The foamed metal may be a nickel foam, a copper foam, an aluminum foam, an alloy foam, etc. When the foamed metal is used as the positive electrode, the positive electrode active material may not be provided on the surface of the foamed metal, but of course, the positive electrode active material may also be provided. As an example, a lithium source material, potassium metal or sodium metal may also be filled or / and deposited in the foamed metal, and the lithium source material is lithium metal and / or a lithium-rich material.

[0115] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative electrode current collector.

[0116] As an example, the negative electrode current collector may be a metal foil, a foamed metal or a composite current collector. For example, as the metal foil, aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrode, nickel or titanium with a silver surface treatment may be used. The foamed metal may be a nickel foam, a copper foam, an aluminum foam, an alloy foam, etc. The composite current collector may include a polymer material base and a metal layer. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0117] As an example, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.

[0118] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0119] As an example, the negative electrode active material may adopt the negative electrode active material for the battery cell 20 known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0120] In some embodiments, the material of the positive electrode current collector may be aluminum, and the material of the negative electrode current collector may be copper.

[0121] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode and the negative electrode.

[0122] In some embodiments, the separator is a separator membrane. There may be many types of separator membranes, and any known porous separator membrane with good chemical stability and mechanical stability may be selected.

[0123] As an example, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different. The separator may be a separate component located between the positive and negative electrodes, or may be attached to the surface of the positive and negative electrodes.

[0124] In some embodiments, the separator is a solid electrolyte, which is disposed between the positive electrode and the negative electrode and serves to transmit ions and isolate the positive and negative electrodes.

[0125] In some embodiments, the battery cell further includes an electrolyte, which plays a role in conducting ions between the positive and negative electrodes. The electrolyte can be liquid, gel or solid. Among them, the liquid electrolyte includes an electrolyte salt and a solvent.

[0126] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0127] In some embodiments, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone. The solvent may also be an ether solvent. The ether solvent may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether and crown ether.

[0128] Among them, the gel electrolyte includes a skeleton network with a polymer as the electrolyte, combined with an ionic liquid-lithium salt.

[0129] Among them, solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0130] As an example, the polymer solid electrolyte may be polyether (polyethylene oxide), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, a single ion polymer, polyionic liquid-lithium salt, cellulose, and the like.

[0131] As an example, the inorganic solid electrolyte may include an oxide solid electrolyte (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON film), a sulfide solid electrolyte (crystalline lithium superion conductor (lithium germanium phosphosulfide, silver germanium sulfide), amorphous sulfide) and one or more of a halide solid electrolyte, a nitride solid electrolyte and a hydride solid electrolyte.

[0132] As an example, the composite solid electrolyte is formed by adding an inorganic solid electrolyte filler to a polymer solid electrolyte.

[0133] In some embodiments, the electrode assembly is a wound structure, wherein the positive electrode sheet and the negative electrode sheet are wound into the wound structure.

[0134] In some embodiments, the electrode assembly is a laminate structure.

[0135] As an example, a plurality of positive electrode sheets and a plurality of negative electrode sheets may be provided respectively, and the plurality of positive electrode sheets and the plurality of negative electrode sheets may be alternately stacked.

[0136] As an example, a plurality of positive electrode sheets may be provided, and the negative electrode sheet may be folded to form a plurality of stacked folded segments, with a positive electrode sheet being sandwiched between adjacent folded segments.

[0137] As an example, both the positive electrode sheet and the negative electrode sheet are folded to form a plurality of folded sections that are stacked.

[0138] As an example, a plurality of separators may be provided, each of which is provided between any adjacent positive electrode sheets or negative electrode sheets.

[0139] As an example, the separator may be disposed continuously, and may be disposed between any adjacent positive electrode sheets or negative electrode sheets by folding or winding.

[0140] In some embodiments, the shape of the electrode assembly can be cylindrical, flat, or polygonal.

[0141] In some embodiments, the electrode assembly is provided with tabs, which can lead current out of the electrode assembly. The tabs include a positive tab and a negative tab.

[0142] In some embodiments, the battery cell may include a housing. The housing is used to encapsulate components such as the electrode assembly and the electrolyte. The housing may be a steel housing, an aluminum housing, a plastic housing (such as polypropylene), a composite metal housing (such as a copper-aluminum composite housing), or an aluminum-plastic film.

[0143] As an example, the battery cell may be a cylindrical battery cell, a prismatic battery cell, a soft-pack battery cell or a battery cell of other shapes. The prismatic battery cell includes but is not limited to a square-shell battery cell, a blade-shaped battery cell, a polygonal battery, such as a hexagonal battery, etc.

[0144] The battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity.

[0145] In some embodiments, the battery may be a battery module. When there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0146] In some embodiments, the battery may be a battery pack, which includes a case and battery cells, wherein the battery cells or battery modules are accommodated in the case.

[0147] In some embodiments, the box body can be used as a part of the chassis structure of the vehicle. For example, part of the box body can become at least a part of the floor of the vehicle, or part of the box body 10 can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0148] In some embodiments, the battery may be an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

[0149] Batteries have outstanding advantages such as high energy density, low environmental pollution, high power density, long service life, wide adaptability, and low self-discharge coefficient. They are an important part of the development of new energy today. The development of battery technology must consider many design factors at the same time, such as performance parameters such as energy density, cycle life, discharge capacity, and charge and discharge rate. In addition, the reliability of the battery must also be considered.

[0150] In battery technology, for general battery cells, in order to reduce the risk of explosion, fire and other problems in the battery cells, a first wall portion can be set on the battery cell to release the internal pressure of the battery cell through the first wall portion, thereby reducing the risk of explosion, fire and other problems in the battery cell and improving the reliability of the battery cell. In the related art, the first wall portion is usually formed on the shell by an integrated molding process, that is, integrated on the shell of the battery cell, or connected to the wall portion of the shell by welding, clamping, etc., so that when the internal pressure or temperature of the battery cell reaches a threshold, the first wall portion can be actuated and opened to release the internal pressure of the battery cell. However, the battery cell is prone to expansion during use or charging and discharging, and the expansion force generated by the battery cell will act on the first wall portion, so that the first wall portion is very likely to be stretched and deformed, and the first wall portion will be strained and have a large strain amplitude, thereby reducing the structural strength of the first wall portion of the battery cell, resulting in poor stability in use of the first wall portion, and easily causing the first wall portion to be actuated early to release pressure or fatigue cracking during use, which is not conducive to improving the service life and reliability of the battery cell.

[0151] Based on the above considerations, in order to alleviate the problem of premature actuation of pressure relief or fatigue cracking of the first wall portion of the battery cell during use, an embodiment of the present application provides a battery cell, the battery cell includes a shell; the shell includes a first wall portion, in the thickness direction of the first wall portion, the first wall portion has a first surface and a second surface arranged opposite to each other; the first wall portion is provided with a first groove, the first groove is recessed from the first surface toward the direction close to the second surface, the first groove defines at least one predetermined pressure relief area, and the first wall portion is configured to be able to crack along at least part of the first groove when the battery cell is depressurized; wherein the sum of the areas S1 of all the predetermined pressure relief areas is 0.03 times to 0.3 times the area S2 of the first surface.

[0152] The first wall portion of the shell is provided with a first groove, and the bottom wall of the first groove forms a first weak portion, thereby forming a pressure relief component on the first wall portion. The first weak portion can be cracked when the battery cell is depressurized to release the pressure inside the battery cell, so as to reduce the occurrence of explosion, fire and other problems caused by excessive internal pressure of the battery cell. By setting the sum of the areas S1 of all the predetermined pressure relief zones to 0.03 to 0.3 times the area S2 of the first surface provided with the first groove, that is, the ratio of the sum of the areas S1 of all the predetermined pressure relief zones to the area S2 of the first surface provided with the first groove is set to 0.03 to 0.3, the relative sizes of the sum of the areas S1 of all the predetermined pressure relief zones and the area S2 of the first surface provided with the first groove are set more reasonably, and setting the ratio to be greater than or equal to 0.03 can alleviate the problem of insufficient area of ​​the predetermined pressure relief zones, so as to alleviate the phenomenon that the bursting pressure required by the first wall portion when the battery cell is depressurized is too large due to the excessive pressure bearing capacity of the bottom wall of the first groove, thereby reducing the risk of bursting, explosion, fire, etc. of the battery cell shell caused by untimely pressure relief of the first wall portion, thereby effectively improving the reliability of the battery cell. The expansion force generated by the expansion of the battery cell during use will cause the first wall portion to deform. Setting the ratio to less than or equal to 0.3 can alleviate the problem that the strength and rigidity of the first wall portion are reduced and it is easy to deform greatly due to the fact that the area of ​​the predetermined pressure relief area is too large relative to the area of ​​the first surface. It can also reduce the concentration of stress on the bottom wall of the first groove when the expansion force generated by the expansion during the use of the battery cell acts on the first wall portion, and enable the predetermined pressure relief area to absorb a part of the expansion force, thereby effectively alleviating the phenomenon of tensile deformation of the bottom wall of the first groove of the first wall portion, so as to reduce the strain and strain amplitude of the bottom wall of the first groove of the first wall portion, that is, it can reduce the deformation of the bottom wall of the first groove, and further alleviate the phenomenon that the structural strength of the bottom wall of the first groove of the first wall portion is reduced due to excessive strain and strain amplitude, thereby reducing the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion in the corresponding area of ​​the first groove after long-term use of the battery cell, so as to improve the stability of the battery cell, which is conducive to improving the service life and reliability of the battery cell.

[0153] The battery cell disclosed in the embodiment of the present application can be used in, but not limited to, electrical equipment such as vehicles, ships or aircraft. The power supply system of the electrical equipment can be composed of the battery cell, battery, etc. disclosed in the present application, which is helpful to alleviate the problem of premature actuation pressure relief or fatigue cracking of the first wall of the battery cell during use, so as to improve the reliability and service life of the battery cell.

[0154] The embodiment of the present application provides an electric device using a battery as a power source, and the electric device may be, but is not limited to, a mobile phone, a tablet, a laptop, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, etc. Among them, the electric toy may include a fixed or mobile electric toy, for example, a game console, an electric car toy, an electric ship toy, an electric airplane toy, etc., and the spacecraft may include an airplane, a rocket, a space shuttle, a spacecraft, etc.

[0155] For the convenience of description, the following embodiments are described by taking a vehicle as an example of an electrical device in an embodiment of the present application.

[0156] Please refer to Figure 1 , Figure 1 A schematic diagram of the structure of a vehicle 1000 provided for some embodiments of the present application. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 may be provided at the bottom of the vehicle 1000, or at the head of the vehicle 1000, or at the tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000, for example, the battery 100 may be used as an operating power source or a power source for the vehicle 1000, etc. The vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to power the motor 300, for example, for the starting, navigation and working power requirements of the vehicle 1000 during driving.

[0157] In some embodiments of the present application, the battery 100 can not only serve as an operating power source or a use power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0158] Please refer to Figure 2 and Figure 3 , Figure 2 An exploded view of a battery 100 provided in some embodiments of the present application, Figure 3 The schematic diagram of the structure of the battery cell 20 provided in some embodiments of the present application is as follows. The battery 100 comprises a box body 10 and a battery cell 20 , and the battery cell 20 is used to be accommodated in the box body 10 .

[0159] The box body 10 is used to provide an assembly space for the battery cell 20, and the box body 10 can adopt a variety of structures. In some embodiments, the box body 10 may include a first box body 11 and a second box body 12, the first box body 11 and the second box body 12 cover each other, and the first box body 11 and the second box body 12 jointly define an assembly space for accommodating the battery cell 20. The second box body 12 may be a hollow structure with one end open, and the first box body 11 may be a plate-like structure, and the first box body 11 covers the open side of the second box body 12, so that the first box body 11 and the second box body 12 jointly define an assembly space; the first box body 11 and the second box body 12 may also be hollow structures with one side open, and the open side of the first box body 11 covers the open side of the second box body 12.

[0160] Of course, the box body 10 formed by the first box body 11 and the second box body 12 can be in various shapes, such as a cylinder, a cuboid or a cube. Figure 2 In the embodiment, the box body 10 is in the shape of a rectangular parallelepiped.

[0161] In the battery 100, the battery cell 20 disposed in the box 10 may be one or more. When there are more than one battery cell 20 disposed in the box 10, the multiple battery cells 20 may be connected in series, in parallel, or in mixed connection. Mixed connection means that the multiple battery cells 20 are both connected in series and in parallel. The multiple battery cells 20 may be directly connected in series, in parallel, or in mixed connection, and then the whole formed by the multiple battery cells 20 may be accommodated in the box 10; of course, the battery 100 may also be a battery module formed by connecting multiple battery cells 20 in series, in parallel, or in mixed connection, and then the multiple battery modules may be connected in series, in parallel, or in mixed connection to form a whole, and then the whole may be accommodated in the box 10.

[0162] In some embodiments, the battery 100 may further include other structures. For example, the battery 100 may further include a busbar component, which is used to connect the plurality of battery cells 20 to achieve electrical connection between the plurality of battery cells 20 .

[0163] Each battery cell 20 may be a secondary battery or a primary battery; it may also be a lithium-sulfur battery, a sodium-ion battery or a magnesium-ion battery, but is not limited thereto. The battery cell 20 may be in a rectangular parallelepiped, a cylinder, a prism or other shapes. For example, Figure 3 In the figure, the battery cell 20 is a rectangular parallelepiped structure.

[0164] In some embodiments, Figure 3-Figure 7As shown, the battery cell 20 includes a shell 21; the shell 21 includes a first wall portion 211; along the thickness direction X of the first wall portion, the first wall portion 211 has a first surface 2111 and a second surface 2112 that are oppositely arranged, and the first wall portion 211 is provided with a first groove 221, the first groove 221 is recessed from the first surface 2111 to a direction close to the second surface 2112, the first groove 221 defines at least one predetermined pressure relief area P, and the first wall portion 211 is configured to be able to split along at least part of the first groove 221 when the battery cell 20 is depressurized; wherein the sum S1 of the areas of all the predetermined pressure relief areas P is 0.03 times to 0.3 times the area S2 of the first surface 2111.

[0165] Among them, see Figure 4 As shown, the battery cell 20 may further include an electrode assembly 23, which is accommodated in the outer shell 21. The electrode assembly 23 is a component in the battery cell 20 where an electrochemical reaction occurs. The structure of the electrode assembly 23 may be various. For example, the electrode assembly 23 may be a wound structure formed by winding a positive electrode sheet, an isolation member, and a negative electrode sheet, or may be a stacked structure formed by stacking a positive electrode sheet, an isolation member, and a negative electrode sheet.

[0166] Exemplarily, the isolation member is an isolation membrane, and a main material of the isolation membrane may be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0167] The battery cell 20 may include one electrode assembly 23 or multiple electrode assemblies 23. Figure 4 In the embodiment, the battery cell 20 includes two electrode assemblies 23, and the two electrode assemblies 23 are stacked along the thickness direction of the electrode assemblies 23. The stacking direction of the two electrode assemblies 23 may be the thickness direction of the battery cell 20. Of course, in other embodiments, the number of electrode assemblies 23 included in the battery cell 20 may also be three, four, five, etc.

[0168] In some embodiments, the battery cell 20 further includes an electrolyte contained in the housing 21. The electrolyte may be an electrolytic solution.

[0169] In some embodiments, the housing 21 may include a shell 212 and an end cap 213, wherein a receiving cavity is formed inside the shell 212, the receiving cavity is used to receive the electrode assembly 23, and the receiving cavity has at least one opening 2121, that is, the shell 212 is a hollow structure with at least one end opening 2121, and the end cap 213 covers the opening 2121 of the shell 212 and forms a sealed connection to form an enclosed space for receiving the electrode assembly 23 and the electrolyte.

[0170] The first wall portion 211 may be an end cover 213 of the housing 21, or a wall portion of the shell 212 of the housing 21. Figure 3 and Figure 4 In the embodiment, the first wall portion 211 is the end cover 213. Of course, the structure of the battery cell 20 is not limited thereto, and in other embodiments, the first wall portion 211 may also be a wall portion disposed opposite to the shell 212 and the end cover 213, that is, the bottom wall of the shell 212, and the first wall portion 211 may also be a side wall adjacent to and connected to the shell 212 and the end cover 213, and the side wall may be a wall disposed around the end cover 213 and forming the opening 2121.

[0171] When assembling the battery cell 20 , the electrode assembly 23 may be placed in the housing 212 first, and the housing 212 may be filled with electrolyte. The end cap 213 may then be closed on the opening 2121 of the housing 212 to complete the assembly of the battery cell 20 .

[0172] The shell 212 can be in various shapes, such as a cylinder, a cuboid, or a prism structure. The shape of the shell 212 can be determined according to the specific shape of the electrode assembly 23. For example, if the electrode assembly 23 is a cylindrical structure, a shell 212 with a cylindrical structure can be selected; if the electrode assembly 23 is a cuboid structure, a shell 212 with a cuboid structure can be selected. Of course, the structure of the end cap 213 can also be various, such as the end cap 213 being a plate-like structure or a hollow structure with one end open. For example, in Figure 3 , Figure 4 In the embodiment, the shell 212 is a rectangular parallelepiped structure, the length direction Z of the first wall is the length direction of the battery cell 20 , the width direction Y of the first wall is the thickness direction of the battery cell 20 , and the thickness direction X of the first wall is the height direction of the battery cell 20 .

[0173] Of course, it is understandable that the outer shell 21 is not limited to the above structure, and the outer shell 21 may also be other structures. For example, the outer shell 21 may include a shell body 212 and two end caps 213. The shell body 212 is a hollow structure with openings 2121 formed at both opposite ends. One end cap 213 corresponds to an opening 2121 of the shell body 212 and forms a sealed connection to form an enclosed space for accommodating the electrode assembly 23 and the electrolyte. That is, the shell body 212 has openings 2121 on both opposite sides, and the two end caps 213 are respectively covered on both sides of the shell body 212 to close the corresponding openings 2121.

[0174] The shell 21 may be made of various materials, such as copper, iron, aluminum, steel or aluminum alloy.

[0175] In some embodiments, the battery cell 20 further includes an electrode terminal 24 . The electrode terminal 24 may be insulated and mounted on the housing 21 , and the electrode terminal 24 is electrically connected to the electrode assembly 23 to output or input electrical energy of the battery cell 20 .

[0176] It should be noted that the electrode terminal 24 is insulated and mounted on the housing 21 , that is, no electrical connection is formed between the electrode terminal 24 and the housing 21 .

[0177] The battery cell 20 may include one electrode terminal 24 or two electrode terminals 24. Figure 3 , Figure 4 As shown, the battery cell 20 includes two electrode terminals 24, which are arranged at intervals along the length direction Z of the first wall portion. Each electrode assembly 23 has two pole ears 231, which are arranged at intervals along the length direction Y of the wall portion. The two pole ears 231 have opposite polarities, and the two electrode terminals 24 are respectively electrically connected to the two pole ears 231 of the electrode assembly 23 with opposite polarities, so as to realize the input or output of the positive and negative electrodes of the battery cell 20.

[0178] It should be noted that one pole ear 231 of the electrode assembly 23 can be a component formed by mutually stacking and connecting areas on the positive electrode sheet that are not coated with the positive electrode active material layer, forming a positive pole ear 231, and the other pole ear 231 can be a component formed by mutually stacking and connecting areas on the negative electrode sheet that are not coated with the negative electrode active material layer, forming a negative pole ear 231.

[0179] Exemplarily, the electrode terminal 24 may be made of a variety of materials. For example, the electrode terminal 24 may be made of copper, iron, aluminum, steel, or aluminum alloy.

[0180] There are many positions where the electrode terminal 24 is installed on the housing 21. For example, Figure 3 and Figure 4 In the embodiment, the two electrode terminals 24 are both mounted on the end cap 213 of the outer shell 21. Of course, the structure of the battery cell 20 is not limited thereto. In the embodiment where the battery cell 20 includes two electrode terminals 24, the two electrode terminals 24 may also be both mounted on the shell 212 of the outer shell 21. Similarly, the two electrode terminals 24 may also be one electrode terminal 24 mounted on the shell 212 of the outer shell 21, and the other electrode terminal 24 mounted on the end cap 213 of the outer shell 21.

[0181] In some embodiments, see Figure 4As shown, the battery cell 20 may also include two current collecting components 25, both of which are arranged in the outer shell 21 and are spaced apart along the length direction Z of the first wall portion, and each current collecting component 25 is used to connect an electrode terminal 24 and a plurality of electrode lugs 231 with the same polarity in the electrode assemblies 23 to achieve electrical connection between the electrode terminal 24 and the electrode assembly 23, which is beneficial to reduce the difficulty of assembly between the lug 231 and the electrode terminal 24.

[0182] Exemplarily, the material of the current collecting component 25 may be various, for example, the material of the current collecting component 25 may be copper, iron, aluminum, steel or aluminum alloy.

[0183] In the embodiment of the present application, the pressure relief component 22 of the first wall portion 211 plays a role of pressure relief in the battery cell 20, and is used to release the pressure inside the battery cell 20 when the internal pressure or temperature of the battery cell 20 reaches a predetermined value.

[0184] In this embodiment, the first wall portion 211 is an integrally formed structure, that is, the first weak portion 2211 formed on the bottom wall of the first groove 221 and the predetermined pressure relief area P domain are both formed on the first wall portion 211 .

[0185] The first surface 2111 and the second surface 2112 are two surfaces of the first wall portion 211 that are opposite to each other in the thickness direction X. The first groove 221 is recessed from the first surface 2111 to the second surface 2112 . It can be understood that the first groove 221 is disposed on the first surface 2111 .

[0186] The first wall portion 211 forms a first weak portion 2211 at a position corresponding to the first groove 221, that is, the bottom wall of the first groove 221 is the first weak portion 2211. The bottom wall of the first groove 221 is a part of the first wall portion 211. The bottom wall of the first groove 221 is the area of ​​the first wall portion 211 with the smallest thickness in the thickness direction X of the first wall portion. Therefore, the bottom wall of the first groove 221 is more likely to crack due to the increase in air pressure inside the battery cell 20 than other areas of the first wall portion 211. The extension trajectory of the first groove 221 is the cracking trajectory of the first wall portion 211. The first wall portion 211 can open the predetermined pressure relief area P after at least part of the bottom wall of the first groove 221 is cracked, so that the battery cell 20 can release the pressure inside the battery cell 20 from the predetermined pressure relief area P.

[0187] The first groove 221 defines at least one predetermined pressure relief area P, that is, the predetermined pressure relief area P is a part of the first wall portion 211. The first groove 221 can define one predetermined pressure relief area P. The first groove 221 can also define multiple predetermined pressure relief areas P, such as two predetermined pressure relief areas P, three predetermined pressure relief areas P, four predetermined pressure relief areas P, etc.

[0188] Depending on the different structural shapes of the first groove 221, the predetermined pressure relief area P is formed in different ways. For example, in some embodiments, along the extension direction of the first groove 221, the first groove 221 forms a closed structure, and the space surrounded by the first groove 221 is the predetermined pressure relief area P. For example, Figure 3-Figure 5 As described above, the extension track of the first groove 221 is an ellipse, and the first groove 221 defines an ellipse-shaped predetermined pressure relief area P. In this embodiment, the sum S1 of the areas of all the predetermined pressure relief areas P is the area of ​​the area surrounded by the outer contour of the first groove 221. The outer contour of the first groove 221 is the contour of the edge of the first groove 221 closest to the first wall portion 211 in the width direction of the first groove 221.

[0189] In other embodiments, along the extension direction of the first groove 221, the first groove 221 is a non-enclosed structure, and the predetermined pressure relief area P is defined by the first groove 221 and the connecting line of the ends of the first groove 221. It should be noted that the connecting line of the ends of the first groove 221 is a virtual line. Figure 8 As shown, along the extension direction of the first groove 221, the first groove 221 is V-shaped, and the predetermined pressure relief area P is defined by the V-shaped first groove 221 and the connecting line of the two ends of the V-shaped first groove 221. Fig. 9 As shown, along the extension direction of the first groove 221, the first groove 221 is U-shaped, and the predetermined pressure relief area P is defined by the U-shaped first groove 221 and the connecting line of the two ends of the U-shaped first groove 221. In this case, the sum S1 of the areas of all the predetermined pressure relief areas P is the area of ​​the area enclosed by the outer contour of the first groove 221 and the connecting line of the ends of the first groove 221. Figure 8 , Fig. 9 The dotted line shown at the position of the first wall portion 211 is a line connecting the ends of the first groove 221 . Figure 11-Figure 16 The dotted line parallel to the second groove 222 is a line connecting the ends of the first groove section 2212 and the third groove section 2214 of the first groove 221 in the extension direction thereof. The two dotted lines and the first groove 221 together form two predetermined pressure relief areas P. Fig.15 The dotted line in FIG. 2 is a line connecting the ends of the first groove section 2212 and the third groove section 2214 of the first groove 221 in the extension direction thereof. The two dotted lines and the first groove 221 together form two predetermined pressure relief areas P.

[0190] Fig.17 The dotted line parallel to the second groove 222 is a line connecting the ends of the first groove section 2212 and the third groove section 2214 of the first groove 221 in the extension direction thereof. The two dotted lines and the first groove 221 together form two predetermined pressure relief areas P.

[0191] The first groove 221 includes at least one groove section, and the groove bottom wall of each groove section of the first groove 221 forms a first weak section 2211a correspondingly, and the first weak sections 2211a formed by each groove section together form a first weak portion 2211. It should be noted that each groove section of the first groove 221 is a structure extending along a smooth trajectory, such as a structure extending along a straight line or an arc. The groove section of the first groove 221 can be one or more. If the first groove 221 is a straight line structure, an arc structure or an annular structure, the first groove 221 only includes one groove section, and the groove bottom wall of the first groove 221 forms a first weak portion 2211 including one first weak section 2211a. If the first groove 221 is a "V"-shaped structure, a "U"-shaped structure or an "H"-shaped structure, the first groove 221 includes multiple groove sections, and the groove bottom wall of the first groove 221 forms a first weak portion 2211 including multiple first weak sections 2211a. Exemplarily, in Figure 3-Figure 5 In the embodiment, a first groove 221 is disposed on the first wall portion 211, and the first groove 221 is an annular groove, and the first groove 221 includes a groove section, and the groove bottom wall of the first groove 221 forms a first weak portion 2211 including a first weak section 2211a. For another example, Figure 8 As shown, a first groove 221 is provided on the first wall portion 211, and the first groove 221 includes a first groove section 2212 and a second groove section 2213 connected to form a V-shaped first groove 221, and the groove bottom wall of the first groove section 2212 and the groove bottom wall of the second groove section 2213 respectively form a first weak section 2211a, and the first weak portion 2211 formed by the groove bottom wall of the first groove 221 includes two first weak sections 2211a.

[0192] like Fig. 9 As shown, a first groove 221 is provided on the first wall portion 211, and the groove bottom wall of the first groove 221 forms a first weak portion 2211. The first groove 221 includes a first groove section 2212, a second groove section 2213 and a third groove section 2214 connected to form a U-shaped first groove 221. The first groove section 2212 and the third groove section 2214 are arranged opposite to each other, and the second groove section 2213 is connected to the first groove section 2212. The groove bottom wall of the first groove section 2212, the groove bottom wall of the second groove section 2213 and the groove bottom wall of the third groove section 2214 respectively form a first weak section 2211a, and the first groove 221 includes three groove sections. The first weak portion 2211 formed by the groove bottom wall of the first groove 221 includes three first weak sections 2211a.

[0193] For example, in Fig.10In the embodiment, a first groove 221 is provided on the first wall portion 211, and a first weak portion 2211 is formed on the groove bottom wall of the first groove 221. The first groove 221 includes a first groove section 2212, a second groove section 2213, a third groove section 2214 and a fourth groove section 2215. The first groove section 2212 and the third groove section 2214 are arranged opposite to each other, the second groove section 2213 connects the first groove section 2212 and the third groove section 2214, and the fourth groove section 2215 is located at the first groove section 2 212 and the third groove section 2214, and the fourth groove section 2215 is connected to the second groove section 2213, then the groove bottom wall of the first groove section 2212, the groove bottom wall of the second groove section 2213, the groove bottom wall of the third groove section 2214 and the groove bottom wall of the fourth groove section 2215 all form a first weak section 2211a, the first groove 221 includes four groove sections, and the first weak portion 2211 formed by the groove bottom wall of the first groove 221 includes four first weak sections 2211a.

[0194] The sum S1 of the areas of all the predetermined pressure relief zones P is set to 0.03 to 0.3 times the area S2 of the first surface 2111 provided with the first groove 221, that is, the ratio of the sum S1 of the areas of all the predetermined pressure relief zones P to the area S2 of the first surface 2111 provided with the first groove 221 is set to 0.03 to 0.3. Exemplarily, the ratio S1 of the sum S1 of the areas of all the predetermined pressure relief zones P and the area S2 of the first surface 2111, that is, S1 / S2 can be: 0.03, 0.04, 0.05, 0.0588, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, etc.

[0195] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail in conjunction with Examples 1-7 and Comparative Examples 1-4. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0196] Example 1

[0197] 1. Preparation of battery cell 20

[0198] 1) Preparation of positive electrode

[0199] The positive electrode active material LiNi 0.7 Co 0.1 Mn 0.1O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are used to prepare positive electrode slurry in N-methylpyrrolidone (NMP), wherein the solid content in the positive electrode slurry is 50wt%, and the solid content of LiNi 0.7 Co 0.1 Mn 0.1 The mass ratio of O2, Super P and PVDF is 8:1:1. The positive electrode slurry is coated on the upper and lower surfaces of the current collector aluminum foil and dried at 85°C and then cold pressed. Then, it is trimmed, cut and stripped, and then dried at 85°C under vacuum conditions for 4 hours to make the positive electrode sheet.

[0200] 2) Preparation of negative electrode

[0201] Graphite, conductive agent Super P, thickener carboxymethyl cellulose (CMC), and adhesive styrene butadiene rubber (SBR) are mixed evenly in deionized water to prepare a negative electrode slurry, wherein the solid content in the negative electrode slurry is 30wt%, and the mass ratio of graphite, silicon oxide, Super P, CMC and adhesive styrene butadiene rubber (SBR) in the solid component is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C, and then cold pressed, trimmed, cut into pieces, and slit, and then dried at 120°C under vacuum conditions for 12 hours to prepare a negative electrode sheet.

[0202] 3) Preparation of electrolyte

[0203] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), the fully dried electrolyte salt LiPF6 was dissolved in a mixed solvent (the mixed solvent included ethylene carbonate (EC) and diethyl carbonate (DEC), and ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a mass ratio of 50:50), and after mixing evenly, a liquid electrolyte with a concentration of 1 mol / L was obtained.

[0204] 4) Isolation parts

[0205] A 16 μm polyethylene film was used as a separator.

[0206] 5) Preparation of battery cell 20

[0207] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is in the middle of the positive and negative electrode sheets to isolate the positive and negative electrodes, and the electrode assembly 23 is wound, and the electrode assembly 23 is placed in an aluminum shell 21, and the prepared electrolyte is injected into the dried shell 21, and the battery cell 20 is prepared by packaging, standing, forming, shaping, and capacity testing. The shell 21 of the battery cell 20 is a rectangular parallelepiped structure, and the shell 212 of the shell 21 is a structure with an opening 2121 formed at one end. The wall portion of the shell 212 opposite to the end cover 213 is a first wall portion 211, and the first wall portion 211 is a rectangular wall portion, and the first wall portion 211 is provided on the first wall portion 211 of the shell 21, and the first wall portion 211 and the first wall portion 211 are integrally formed. The first wall portion 211 is provided with a first groove 221, so that the bottom wall of the first groove 221 forms a first weak portion 2211, the first groove 221 is an H-shaped structure, and the first groove 221 is a three-level notch groove, and the first groove 221 is provided on the outer surface of the first wall portion 211. Among them, the sum S1 of the areas of all the predetermined pressure relief areas P of the first wall portion 211 of the battery cell 20 of Example 1 is 420mm 2 , the area S2 of the first surface 2111 is 14000mm 2 .

[0208] The preparation methods of the battery cells 20 of Examples 2-7 and Comparative Examples 1-4 are the same as that of Example 1, except that the sum S1 of the areas of all the predetermined pressure relief areas P and the area S2 of the first surface 2111 are different.

[0209] The number of fatigue cycles of the battery cells 20 during long-term use is obtained by performing fatigue tests on the battery cells 20 in Examples 1-7 and Comparative Examples 1-4, and the breath-holding time of the battery cells 20 during thermal runaway is obtained by performing thermal runaway tests on the battery cells 20, so as to evaluate the reliability of the battery cells 20, as shown in Table 1.

[0210] The fatigue times of the battery cell 20 are measured as follows:

[0211] 1) Prepare a special test fixture. Specifically, the fixture consists of three 10 mm steel plates (a first steel plate, a second steel plate, and a third steel plate). Each steel plate can completely cover the large surface of the battery cell 20 (the large surface of the battery cell 20 refers to the outer surface of the shell 212 that is perpendicular to the width direction Y along the first wall). The first steel plate and the third steel plate are located at both ends of the fixture and are fixed by bolts. The second steel plate is located between the first steel plate and the third steel plate, and the second steel plate is constrained by a guide rail. The second steel plate can only move in a translational direction perpendicular to the plane of the steel plate.

[0212] 2) Install the battery cell 20 between the first steel plate and the second steel plate, and place a support structure between the large surface of one side of the battery cell 20 and the first steel plate, and between the large surface of the other side and the second steel plate. The support structure can be an insulation pad or a water-cooling plate (consistent with the material / structure between two adjacent battery cells 20 in the actual battery 100). The support structure can be compressed to provide expansion space for the battery cell 20 during the charge and discharge cycle aging process; the large surface of the battery cell 20 is in contact with the support structure, the first steel plate is in contact with the corresponding support structure, the second steel plate is in contact with the corresponding support structure, and a pressure sensor is provided between the second steel plate and the third steel plate.

[0213] 3) The position of the second steel plate is adjusted by the bolt preload, and the pressure sensor is observed so that the initial extrusion force on the battery cell 20 is 2000N, and the two electrical connection parts (positive electrode terminal 24 and negative electrode terminal 24) of the battery cell 20 are connected to the charging and discharging equipment.

[0214] 4) Place the battery cell 20 and the fixture in a constant temperature environment of 25±2°C, and start the test after the battery cell 20 reaches temperature equilibrium.

[0215] 5) The test steps are carried out in accordance with Chapter 6.4 "Standard Cycle Life" of "GBT31484-2015 Requirements and Test Methods for Cycle Life of Power Batteries for Electric Vehicles", and the test cycle end condition is changed to "stop the test until the first wall portion 211 is damaged at the first groove 221".

[0216] Specifically, test according to the following steps:

[0217] a) Discharge to 2.8v with 1I1(A) current;

[0218] b) Leave it for no less than 30 minutes;

[0219] c) Charge according to method 6.1.1.3 of GBT31484-2015 Cycle life requirements and test methods for power batteries for electric vehicles;

[0220] d) Leave it for no less than 30 minutes;

[0221] e) Discharge to 2.8v with a current of 1I1(A);

[0222] f) Repeat steps b) to e) until the first groove 221 of the first wall portion 211 is damaged and the test is stopped.

[0223] That is, the test process continuously observes the area where the first wall portion 211 of the battery cell 20 is provided with the first groove 221 until the pressure relief portion is damaged and leaks, and the number of cycles is recorded as the cycle fatigue number of the battery cell 20. Among them, the more cycle fatigue numbers the battery cell 20 has, the lower the probability of the battery cell 20 opening the valve and leaking due to gas production during long-term use, and the longer the service life.

[0224] The thermal runaway test method of battery cell 20 is as follows:

[0225] 1. Select the heating plate according to the size of the battery cell 20. The size of the heating plate should cover as much surface of the battery cell 20 as possible (covering area ≥ 60%);

[0226] 2. Charge the battery cell 20 to 100% SOC before testing and ensure that the temperature of the battery cell 20 is 25±5℃;

[0227] 3. Sensor layout:

[0228] 1) Arrangement of temperature sensing wires: A layer of Teflon is attached to the center areas of the two large surfaces of the battery cell 20, a temperature sensing wire is arranged above the Teflon, and another layer of Teflon is attached;

[0229] 2) Layout of voltage sampling line: A layer of Teflon is attached to the positive electrode terminal, negative electrode terminal and housing 21 of the battery cell 20, a voltage sampling line is arranged above the Teflon, and another layer of Teflon is attached;

[0230] 3) Air pipe arrangement: Drill a hole in the first wall 211 of the housing 21 of the battery cell 20. The drilling position is located at the center of the edge of the first groove 221 and the side of the housing 212 (the outer surface of the wall adjacent to the first wall 211 along the length direction Z of the housing 212). Extend the air pipe into the hole and seal it, and connect the air pipe to the air pressure sensor.

[0231] 4) Connect the temperature sensing wire, voltage sampling wire and air pressure sensor to the data acquisition instrument to collect and analyze data in real time. The collection frequency of the data acquisition instrument is ≤0.1s;

[0232] 4. Assemble the fixture so that the fixture completely covers the large surface of the battery cell 20, with a clamping force of 3000N. Note: The arrangement order of the fixture, heating plate and battery cell 20 is: fixture + heating plate + battery cell 20 + fixture;

[0233] 5. Test, turn on the data acquisition instrument to collect temperature, voltage, and air pressure data, and then turn on the heating plate at a power of 500W to heat the battery cell 20 until the battery cell 20 thermally runs away.

[0234] 6. Obtain the pressure holding time of the battery cell 20, determine the thermal runaway moment and the valve opening moment according to the temperature, voltage and air pressure data collected by the data acquisition instrument, and obtain the pressure holding time of the battery cell 20 according to the pressure holding time = valve opening moment - thermal runaway moment.

[0235] Thermal runaway judgment criteria: a) The trigger object generates a voltage drop, and the voltage drops to more than 25% of the initial voltage; b) The temperature at the detection point reaches the maximum operating temperature specified by the manufacturer; c) The temperature rise rate dT / dt at the detection point is ≥1℃ / s and lasts for more than 3s. When a) and c) or b) and c) occur, it is judged that thermal runaway has occurred and the thermal runaway moment is determined.

[0236] Valve opening time determination: When the air pressure drops by more than 25%, it can be determined that the valve is open (the first groove 221 is cracked), and the moment when the air pressure begins to drop is the valve opening time.

[0237] The number of fatigue cycles of the battery cells 20 during long-term use is obtained by performing fatigue tests on the battery cells 20 in Examples 1-7 and Comparative Examples 1-4, and the breath-holding time of the battery cells 20 during thermal runaway is obtained by performing thermal runaway tests on the battery cells 20, so as to evaluate the reliability of the battery cells 20, as shown in Table 1.

[0238] Table 1:

[0239]

[0240] As can be seen from Table 1, as S1 / S2 gradually increases, the holding time of the battery cell 20 becomes shorter, that is, as S1 / S2 gradually increases, the timely pressure relief performance of the battery cell 20 becomes better, and the probability of explosion and fire in the case of thermal runaway of the battery cell 20 is lower. As S1 / S2 gradually increases, the fatigue times of the battery cell 20 gradually decreases, that is, as S1 / S2 gradually increases, the possibility of fatigue valve opening and leakage of the battery cell 20 during long-term use gradually increases.

[0241] In Table 1, when S1 / S2 is 0.01 and 0.02, the holding time of the battery cell 20 is 4.7s and 3.9s respectively, which are much longer than the holding time when S1 / S2 is 0.03, 0.0588, 0.08, 0.1, 0.15, 0.25, 0.3, 0.4, and 0.5, that is, the holding time of the battery cell 20 in Comparative Example 1 and Comparative Example 2 during thermal runaway is much longer than the holding time of the battery cell 20 in Examples 1 to 7, Comparative Example 3, and Comparative Example 4. Therefore, when S1 / S2≥0.03, the holding time of the battery cell 20 during thermal runaway is shorter, which can increase the possibility of timely pressure relief of the first wall portion 211 of the battery cell 20, and reduce the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall portion 211.

[0242] In Table 1, when S1 / S2 is 0.4 and 0.5, the fatigue times of the battery cell 20 are 873 and 750 respectively, which are much smaller than the fatigue times when S1 / S2 is 0.01, 0.02, 0.03, 0.0588, 0.08, 0.1, 0.15, 0.25 and 0.3, that is, the fatigue times of the battery cells 20 in Comparative Examples 3 and 4 are much smaller than the fatigue times of the battery cells 20 in Examples 1 to 7, Comparative Examples 1 and 2. Therefore, when S1 / S2≤0.3, the fatigue times of the battery cell 20 are large, so that the battery cell 20 has a higher fatigue life, thereby reducing the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion 211 in the corresponding area of ​​the first groove 221 after long-term use of the battery cell 20. Therefore, 0.03≤S1 / S2≤0.3 can take into account both reducing the risk of bursting, explosion, fire, etc. in the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall portion 211, and reducing the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion 211 at the corresponding position of the first groove 221 of the battery cell 20 after long-term use, thereby improving the use stability of the battery cell 20 and improving the service life and reliability of the battery cell 20.

[0243] In summary, by setting the sum S1 of the areas of all the predetermined pressure relief areas P to 0.03 to 0.3 times the area S2 of the first surface 2111 provided with the first groove 221, that is, the ratio of the sum S1 of the areas of all the predetermined pressure relief areas P to the area S2 of the first surface 2111 provided with the first groove 221 is set to 0.03 to 0.3, so that the relative size setting of the sum S1 of the areas of all the predetermined pressure relief areas P and the area S2 of the first surface 2111 provided with the first groove 221 is more reasonably set, and setting the ratio to be greater than or equal to 0.03 can alleviate the problem of insufficient area of ​​the predetermined pressure relief area P, so as to alleviate the phenomenon that the pressure bearing capacity of the bottom wall of the first groove 221 is too large, resulting in excessive bursting pressure required by the first wall portion 211 when the battery cell 20 is depressurized, thereby reducing the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall portion 211, and thus effectively improving the reliability of the battery cell 20. The expansion force generated by the expansion of the battery cell 20 during use will cause the first wall portion 211 to deform. Setting the ratio to be less than or equal to 0.3 can alleviate the problem that the strength and rigidity of the first wall portion 211 are reduced and it is easy to deform greatly due to the area of ​​the predetermined pressure relief area P being too large relative to the area of ​​the first surface 2111. It can also reduce the concentration of stress on the bottom wall of the first groove 221 when the expansion force generated by the expansion of the battery cell 20 during use acts on the first wall portion 211, and enable the predetermined pressure relief area P to absorb a part of the expansion force, thereby effectively alleviating the first groove of the first wall portion 211. The bottom wall of the groove 221 undergoes tensile deformation and the like to reduce the strain and strain amplitude of the bottom wall of the groove of the first groove 221 of the first wall portion 211, that is, the deformation of the bottom wall of the groove of the first groove 221 can be reduced, and thus the phenomenon that the bottom wall of the groove of the first groove 221 of the first wall portion 211 is reduced due to excessive strain and strain amplitude can be alleviated, thereby reducing the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion 211 in the corresponding area of ​​the first groove 221 after long-term use of the battery cell 20, thereby improving the use stability of the battery cell 20, which is beneficial to improving the service life and reliability of the battery cell 20.

[0244] In some embodiments, 500 mm 2 ≤S1≤1300mm 2 .

[0245] For example, S1 may be 500 mm. 2 、600mm 2 、630mm 2 、650mm 2 , 800mm 2 , 900mm 2 , 1000mm 2 、1200mm2 、1250mm 2 、1300mm 2 wait.

[0246] Please continue to refer to Table 1. When S1≥500mm 2 The holding time of the battery cell 20 is 420mm compared to S1. 2 The holding time of the battery cell 20 is shorter, which can increase the possibility of timely pressure relief of the first wall 211 of the battery cell 20 and reduce the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall 211. When S1≤1300mm 2 The fatigue times of the battery cell 20 at S1 is 1500 mm. 2 、1600mm 2 The fatigue times of the battery cell 20 are greater, so that the battery cell 20 has a higher fatigue life, thereby further reducing the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion 211 in the corresponding area of ​​the first groove 221 of the battery cell 20 after long-term use. 2 ≤S1≤1300mm 2 , which can reduce the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall portion 211, and reduce the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion 211 at the corresponding position of the first groove 221 of the battery cell 20 after long-term use, thereby improving the use stability of the battery cell 20 and improving the service life and reliability of the battery cell 20.

[0247] Therefore, by limiting the sum of the areas S1 of all the predetermined pressure relief zones P to 500 mm 2 Up to 1300mm 2 , the sum of the areas of all predetermined pressure relief zones P is set to be greater than or equal to 500mm 2 , which can alleviate the problem of insufficient area of ​​the predetermined pressure relief area P, so as to alleviate the phenomenon that the pressure bearing capacity of the bottom wall of the first groove 221 is too large, resulting in the first wall portion 211 having too large a bursting pressure when the battery cell 20 is depressurized, thereby reducing the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall portion 211, and further effectively improving the reliability of the battery cell 20. The sum of the areas of all predetermined pressure relief areas P is set to be less than or equal to 1300mm 2, which can alleviate the problem that the strength of the first wall portion 211 is reduced and large deformation occurs easily due to the large area of ​​the predetermined pressure relief area P, and can also reduce the concentration of stress on the bottom wall of the first groove 221 when the expansion force generated by expansion during the use of the battery cell 20 acts on the first wall portion 211, and enable the predetermined pressure relief area P to absorb a part of the expansion force, thereby effectively alleviating the phenomenon of tensile deformation and the like of the bottom wall of the first groove 221 of the first wall portion 211, so as to reduce the strain and strain amplitude of the bottom wall of the first groove 221 of the first wall portion 211, that is, it can reduce the deformation of the bottom wall of the first groove 221, and further alleviate the phenomenon that the structural strength of the bottom wall of the first groove 221 of the first wall portion 211 is reduced due to excessive strain and strain amplitude, thereby reducing the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion 211 in the corresponding area of ​​the first groove 221 after long-term use of the battery cell 20, so as to improve the use stability of the battery cell 20, which is conducive to improving the service life and use reliability of the battery cell 20.

[0248] In some embodiments, 5000 mm 2 ≤S2≤8500mm 2 .

[0249] For example, S2 may be 5000 mm. 2 、6000mm 2 、6500mm 2 , 7000mm 2 、7500mm 2 、8500mm 2 wait.

[0250] Please continue to refer to Table 1. When S2 ≥ 5000 mm 2 The fatigue times of the battery cell 20 at S2 is 4300 mm compared to S2. 2 The fatigue times of the battery cell 20 are greater, so that the fatigue life of the battery cell 20 is higher, thereby further reducing the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion 211 in the area corresponding to the first groove 221 of the battery cell 20 after long-term use. 2 The holding time of the battery cell 20 is 14000mm compared to S2. 2 The battery cell 20 has a shorter holding time, which can increase the possibility of timely pressure relief of the first wall 211 of the battery cell 20 and reduce the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall 211. Therefore, 5000mm 2 ≤S2≤8500mm 2, which can reduce the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall portion 211, and reduce the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion 211 at the corresponding position of the first groove 221 of the battery cell 20 after long-term use, thereby improving the use stability of the battery cell 20 and improving the service life and reliability of the battery cell 20.

[0251] Therefore, by setting the area S2 of the first surface 2111 where the first groove 221 is provided to 5000 mm 2 Up to 8500mm 2 The area of ​​the first surface 2111 is set to be greater than or equal to 5000mm 2 , which can alleviate the problem that the strength of the first wall portion 211 is reduced and large deformation occurs easily due to the small area of ​​the first surface 2111, and can also reduce the concentration of stress on the bottom wall of the first groove 221 when the expansion force generated by expansion during the use of the battery cell 20 acts on the first wall portion 211, and enable the predetermined pressure relief area P to absorb a part of the expansion force, thereby effectively alleviating the phenomenon of tensile deformation and the like of the bottom wall of the first groove 221 of the first wall portion 211, so as to reduce the strain and strain amplitude of the bottom wall of the first groove 221 of the first wall portion 211, that is, it can reduce the deformation of the bottom wall of the first groove 221, and further alleviate the phenomenon that the structural strength of the bottom wall of the first groove 221 of the first wall portion 211 is reduced due to excessive strain and strain amplitude, thereby reducing the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion 211 in the corresponding area of ​​the first groove 221 after long-term use of the battery cell 20, so as to improve the use stability of the battery cell 20, which is conducive to improving the service life and use reliability of the battery cell 20. The area of ​​the first surface 2111 is set to be less than or equal to 8500mm 2 , which can alleviate the problem that the first surface 2111 is too small, resulting in the first wall portion 211 having greater strength and rigidity and being able to withstand greater pressure and being difficult to deform, so as to alleviate the problem that the pressure bearing capacity of the bottom wall of the first groove 221 is too large, resulting in the first wall portion 211 having an excessively large bursting pressure when the battery cell 20 is depressurized, thereby reducing the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall portion 211, and further effectively improving the reliability of the battery cell 20.

[0252] In some embodiments, the first wall portion 211 is a rectangular wall portion; along the width direction Y of the first wall portion, the size of the first surface 2111 is c; along the length direction Z of the first wall portion, the size of the first surface 2111 is d, S2=c*d; wherein, 55mm≤c≤85mm, 100mm≤d≤260mm.

[0253] c is the dimension of the first surface 2111 along the width direction Y of the first wall portion. d is the dimension of the first surface 2111 along the length direction Z of the first wall portion.

[0254] Since it is difficult to determine the boundaries of the first wall portion 211 in the length direction and the width direction after the battery cell 20 is assembled, in some embodiments, the distance c between the outer surface of the second wall portion 2122 and the outer surface of the third wall portion 2123 connected at both ends of the first wall portion in the width direction Y can be measured. ， The distance between the outer surface of the second wall portion 2122 and the outer surface of the third wall portion 2123 is equivalent to the dimension c of the first wall portion 211 in the width direction Y of the first wall portion, that is, c ， =c. In some cases, the outer surface of the second wall portion 2122 and the surface of the first wall portion 211 facing away from the interior of the shell 212 (the first surface 2111) are connected by a first chamfered surface 2126, and the outer surface of the third wall portion 2123 and the surface of the first wall portion 211 facing away from the interior of the shell 212 (the first surface 2111) are connected by a second chamfered surface 2127. Along the width direction Y of the first wall portion, the size of the first chamfered surface 2126 is R1, and the size of the second chamfered surface 2127 is R2. Then, the size c of the first surface 2111 is the distance between the outer surface of the second wall portion 2122 and the outer surface of the third wall portion 2123 along the width direction Y of the first wall portion minus the size of the first chamfered surface 2126 in the width direction Y of the first wall and minus the size of the second chamfered surface 2127 in the width direction Y of the first wall, that is, c=c ， -R1-R2. The first chamfered surface 2126 and the second chamfered surface 2127 may be chamfered surfaces or rounded surfaces. In the embodiment where the first chamfered surface 2126 and the second chamfered surface 2127 are rounded surfaces, R1 may be the radius of the first chamfered surface 2126, and R2 may be the radius of the second chamfered surface 2127.

[0255] The distance d between the outer surface of the fourth wall portion 2124 and the outer surface of the fifth wall portion 2125 connected at both ends of the length direction Z of the first wall portion can be measured. ’ The distance between the outer surface of the fourth wall portion 2124 and the outer surface of the fifth wall portion 2125 is equivalent to the dimension d of the first wall portion 211 in the length direction Z of the first wall portion, that is, d=d ’In some cases, the outer surface of the fourth wall portion 2124 and the surface of the first wall portion 211 facing away from the interior of the shell 212 (the first surface 2111) are connected by the third chamfered surface 2128, and the outer surface of the fifth wall portion 2125 and the surface of the first wall portion 211 facing away from the interior of the shell 212 (the first surface 2111) are connected by the fourth chamfered surface 2129. Along the length direction Z of the first wall portion, the size of the third chamfered surface 2128 is R3, and the size of the fourth chamfered surface 2129 is R3. Then, the size d of the first surface 2111 is the distance between the outer surface of the fourth wall portion 2124 and the outer surface of the fifth wall portion 2125 along the length direction Z of the first wall portion minus the size of the third chamfered surface 2128 in the width direction Y of the first wall portion and minus the size of the fourth chamfered surface 2129 in the width direction Y of the first wall portion, that is, d=d ， -R3-R4. The third chamfered surface 2128 and the fourth chamfered surface 2129 may be chamfered surfaces or rounded surfaces. In the embodiment where the third chamfered surface 2128 and the fourth chamfered surface 2129 are rounded surfaces, R3 may be the radius of the first chamfered surface 2126, and R4 may be the radius of the second chamfered surface 2127.

[0256] For example, Figure 3 As shown, the first wall portion 211 is an end cap 213, and the end cap 213 covers the opening 2121 of the housing 212. Along the width direction Y of the first wall portion, the housing 212 has a second wall portion 2122 and a third wall portion 2123 opposite to each other, and one end of the second wall portion 2122 forming the opening 2121 and one end of the third wall portion 2123 forming the opening 2121 are respectively connected to both ends of the end cap 213. Along the length direction Z of the first wall portion, the housing 212 has a fourth wall portion 2124 and a fifth wall portion 2125 opposite to each other, and one end of the fourth wall portion 2124 forming the opening 2121 and one end of the fifth wall portion 2125 forming the opening 2121 are respectively connected to both ends of the end cap 213.

[0257] like Figure 3 As shown, if the end cover 213 and the housing 212 are not easy to disassemble, the dimension c of the first surface 2111 in the width direction Y of the first wall can be obtained by measuring the distance c' between the outer surface of the second wall 2122 and the outer surface of the third wall 2123 in the width direction Y of the first wall, and the dimension d of the first surface 2111 in the length direction Z of the first wall can be obtained by measuring the distance d' between the outer surface of the fourth wall 2124 and the outer surface of the fifth wall 2125 in the length direction Z of the first wall. Figure 4 As shown, if the end cover 213 and the shell 212 are easy to disassemble, the size of the end cover 213 in the length direction Z of the first wall portion and the size of the end cover 213 in the length direction Z of the first wall portion can be directly measured to obtain c and d.

[0258] In an embodiment where the first wall portion 211 is a wall portion of the housing 212, illustratively, Fig.11 As shown, the first wall portion 211 is the bottom wall of the housing 212 and the end cover 213. Along the width direction Y of the first wall portion, the housing 212 has a second wall portion 2122 and a third wall portion 2123 opposite to each other. The second wall portion 2122 and the third wall portion 2123 are respectively connected to the two ends of the first wall portion 211. Along the length direction Z of the first wall portion, the housing 212 has a fourth wall portion 2124 and a fifth wall portion 2125 opposite to each other. The fourth wall portion 2124 and the fifth wall portion 2125 are respectively connected to the two ends of the first wall portion 211. Along the width direction Y of the first wall portion, the distance between the outer surface of the second wall portion 2122 and the outer surface of the third wall portion 2123 is c'. The second wall portion 2122 is connected between the outer surface of the first wall portion in the width direction Y and the surface of the first wall portion 211 away from the inside of the housing 21 (the first surface 2111) by a first chamfered surface 2126, and the third wall portion 2123 is connected between the outer surface of the first wall portion in the width direction Y and the surface of the first wall portion 211 away from the inside of the housing 21 (the first surface 2111) by a second chamfered surface 2127, and the first chamfered surface 2126 and the second chamfered surface 2127 are both chamfered surfaces, the radius of the first chamfered surface 2126 is R1, and the radius of the second chamfered surface 2127 is R2. c=c'-R1-R2.

[0259] Along the length direction Z of the first wall, the distance between the outer surface of the fourth wall 2124 and the outer surface of the fifth wall 2125 is d'. The outer surface of the fourth wall 2124 in the length direction Z of the first wall and the surface of the first wall 211 facing away from the inside of the housing 21 (the first surface 2111) are connected by a third chamfered surface 2128, and the outer surface of the fifth wall 2125 in the length direction Z of the first wall and the surface of the first wall 211 facing away from the inside of the housing 21 (the first surface 2111) are connected by a fourth chamfered surface 2129. Both the third chamfered surface 2128 and the fourth chamfered surface 2129 are rounded surfaces, the radius of the third chamfered surface 2128 is R3, and the radius of the fourth chamfered surface 2129 is R4. d = d'-R3-R4.

[0260] Exemplarily, c can be 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, 85mm, etc.

[0261] d can be 100mm, 110mm, 120mm, 140mm, 150mm, 160mm, 170mm, 200mm, 230mm, 250mm, 260mm, etc.

[0262] The first wall portion 211 is a rectangular wall portion, which is convenient for manufacturing and molding the battery cell 20 and also convenient for measuring the area of ​​the first surface 2111 .

[0263] In some embodiments, the first wall portion 211 is a rectangular wall portion; along the length direction Z of the first wall portion, the first wall portion 211 is formed with at least one predetermined pressure relief area P, and the sum of the sizes a of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is 0.1 to 0.5 times the size d of the first surface 2111 along the length direction Z of the first wall portion.

[0264] Along the length direction Z of the first wall portion, the first wall portion 211 may form one predetermined pressure relief area P, or may form a plurality of predetermined pressure relief areas P.

[0265] In an embodiment in which a predetermined pressure relief zone P is formed along the length direction Z of the first wall portion 211, the sum a of the sizes of all predetermined pressure relief zones P arranged along the length direction Z of the first wall portion is the size of the predetermined pressure relief zone P along the length direction Z of the first wall portion.

[0266] In an embodiment in which a plurality of predetermined pressure relief zones P are formed on the first wall portion 211 along the length direction Z of the first wall portion, the plurality of predetermined pressure relief zones P are arranged in sequence along the length direction Z of the first wall portion, and two adjacent predetermined pressure relief zones P may share a border. Then, the sum a of the sizes of all predetermined pressure relief zones P arranged along the length direction Z of the first wall portion may be the size between the farthest boundaries of two predetermined pressure relief zones P that are farthest apart from each other among the plurality of predetermined pressure relief zones P.

[0267] The sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is 0.1 to 0.5 times the size d of the first surface 2111 along the length direction Z of the first wall portion, that is, the ratio of the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion to the size d of the first surface 2111 along the length direction Z of the first wall portion is 0.1 to 0.5. Exemplarily, a / d can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.45, 0.5, etc.

[0268] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail in conjunction with Examples 8-13. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0269] The number of fatigue cycles of the battery cell 20 in the long-term use process is obtained by fatigue testing the battery cell 20 in Examples 8-13, and the holding time of the battery cell 20 when thermal runaway is obtained by thermal runaway testing the battery cell 20, so as to evaluate the reliability of the battery cell 20, as shown in Table 2. The test method of the number of fatigue cycles of the battery cell 20 in the use process and the test method of the holding time of the battery cell 20 when thermal runaway are referred to the above method, and the difference between Example 1 and Example 8-Example 13 is that the dimension d of the first surface 2111 along the length direction Z of the first wall portion and the sum a of the dimensions of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion in the length direction Z of the first wall portion are different.

[0270] Table 2:

[0271]

[0272] As can be seen from Table 2, as a / d increases, the holding time of the battery cell 20 becomes shorter, that is, as a / d increases, the timely pressure relief performance of the battery cell 20 becomes better, and the probability of explosion of the battery cell 20 during thermal runaway gradually decreases. As a / d increases, the fatigue times of the battery cell 20 gradually decreases, that is, as a / d increases, the possibility of fatigue valve opening and leakage of the battery cell 20 during long-term use gradually increases, and the reliability of the battery cell 20 gradually decreases.

[0273] In Table 2, when a / d≥0.1, the holding time of the battery cell 20 is shorter, which can increase the possibility of timely pressure relief of the first wall 211 of the battery cell 20, and reduce the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall 211. When a / d≤0.5, the fatigue times of the battery cell 20 are relatively large, so that the battery cell 20 has a higher fatigue life, and further reduces the risk of leakage caused by premature actuation or fatigue cracking of the first wall 211 in the corresponding area of ​​the first groove 221 of the battery cell 20 after long-term use. Therefore, 0.1≤a / d≤0.5 can further reduce the risk of bursting, explosion, fire, etc. in the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall portion 211, and further reduce the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion 211 at the corresponding position of the first groove 221 of the battery cell 20 after long-term use, thereby improving the use stability of the battery cell 20 and improving the service life and reliability of the battery cell 20.

[0274] Therefore, the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is 0.1 to 0.5 times the size d of the first surface 2111 along the length direction Z of the first wall portion, that is, the ratio of the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion to the size d of the first surface 2111 in the length direction Z of the first wall portion is limited to 0.1 to 0.5, wherein the ratio of the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion to the size d of the first surface 2111 in the length direction Z of the first wall portion is greater than or equal to 0.1, which can alleviate the phenomenon that the pressure bearing capacity of the bottom wall of the first groove 221 is too large, resulting in excessive bursting pressure required by the first wall portion 211 when the battery cell 20 is depressurized, thereby reducing the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall portion 211, and further effectively improving the reliability of the battery cell 20. The ratio of the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion to the size d of the first surface 2111 in the length direction Z of the first wall portion is less than or equal to 0.5, which can reduce the deformation of the bottom wall of the first groove 221 when the expansion force generated by the expansion during the use of the battery cell 20 acts on the first wall portion 211, thereby reducing the phenomenon of the structural strength of the bottom wall of the first groove 221 of the first wall portion 211 being reduced due to excessive deformation, and further reducing the occurrence of premature actuation or fatigue cracking of the first wall portion 211 at the corresponding position of the first groove 221 of the battery cell 20 after long-term use. Therefore, 0.05≤a / d≤0.6 can reduce the risk of leakage caused by the phenomenon, so as to improve the use stability of the battery cell 20 and improve the service life and reliability of the battery cell 20. Therefore, 0.05≤a / d≤0.6 can take into account the reduction of the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to the untimely pressure relief of the first wall portion 211, and the reduction of the risk of leakage caused by the phenomenon such as premature actuation or fatigue cracking of the first wall portion 211 at the corresponding position of the first groove 221 of the battery cell 20 after long-term use, so as to improve the use stability of the battery cell 20 and improve the service life and reliability of the battery cell 20.

[0275] Please continue to refer to Table 2. As d decreases, the holding time of the battery cell 20 gradually becomes shorter, and the number of fatigue times of the battery cell 20 gradually decreases. When d≥100mm, the number of fatigue times of the battery cell 20 is large, and the risk of fatigue valve opening and leakage during long-term use of the battery cell 20 is low. When d≤260mm, the holding time of the battery cell 20 during thermal runaway is short, so that the pressure relief of the battery cell 20 is more timely. Therefore, when 100mm≤d≤260mm, the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall 211 of the battery cell 20 is low, and the risk of leakage caused by premature actuation or fatigue cracking of the first wall 211 of the battery cell 20 at the corresponding position of the first groove 221 after long-term use is low, so as to improve the use stability of the battery cell 20 and improve the service life and reliability of the battery cell 20.

[0276] In some embodiments, the first wall portion 211 is a rectangular wall portion; along the width direction Y of the first wall portion, the first groove 221 defines at least one predetermined pressure relief area P, and the sum of the sizes of all predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is b, which is 0.3 to 0.7 times the size c of the first surface 2111 along the width direction Y of the first wall portion.

[0277] The first wall portion 211 may form one predetermined pressure relief area P or a plurality of predetermined pressure relief areas P along the width direction Y of the first wall portion.

[0278] In an embodiment in which a predetermined pressure relief zone P is formed on the first wall portion 211 along the width direction Y of the first wall portion, the sum b of the sizes of all predetermined pressure relief zones P arranged along the width direction Y of the first wall portion is the size of the predetermined pressure relief zone P along the width direction Y of the first wall portion.

[0279] In an embodiment in which a plurality of predetermined pressure relief areas P are formed on the first wall portion 211 along the width direction Y of the first wall portion, the plurality of predetermined pressure relief areas P are arranged in sequence along the width direction Y of the first wall portion, and two adjacent predetermined pressure relief areas P may share a border. Then, the sum b of the sizes of all predetermined pressure relief areas P arranged along the width direction Y of the first wall portion may be the size between the farthest boundaries of two predetermined pressure relief areas P that are farthest apart from each other among the plurality of predetermined pressure relief areas P.

[0280] The sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall is 0.3 to 0.7 times the size c of the first surface 2111 along the width direction Y of the first wall, that is, the ratio of the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall to the size c of the first surface 2111 along the width direction Y of the first wall is 0.3 to 0.7. Exemplarily, b / c may be 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, etc.

[0281] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail in conjunction with Examples 14-20. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0282] The number of fatigue cycles of the battery cell 20 during long-term use is obtained by fatigue testing the battery cell 20 in Examples 14-20, and the reliability of the battery cell 20 is evaluated. The flatness of the surface of the battery cell 20 along the width direction Y of the first wall is evaluated by testing the degree of stacking of the battery cell 20 on any one of the two surfaces of the housing 21 along the width direction Y of the first wall due to the formation of the first groove 221, as shown in Table 3. The method for testing the number of fatigue cycles of the battery cell 20 during use can refer to the above method.

[0283] The method for testing the degree of stacking of the battery cell 20 on any one of the two surfaces of the housing 21 along the width direction Y of the first wall due to the formation of the first groove 221 is as follows:

[0284] For the convenience of description, the two outer surfaces of the shell 21 opposite to each other along the width direction Y of the first wall are defined as the measuring surface. Along the length direction Z of the first wall, four reference points are arranged on each measuring surface, and the four reference points are respectively located on both sides of the first groove 221 along the length direction of the first wall. The plane formed by the four reference points is the reference surface, and the reference surface is parallel to the measuring surface before the first groove 221 is formed. A detection point is obtained in the area corresponding to the measuring surface and the first groove 221, and the distance from the detection point to the reference surface in the width direction Y of the first wall is obtained, so as to obtain the degree of pile-up on the measuring surface caused by the manufacturing of the first groove 221. Among them, the greater the distance from the detection point to the reference surface in the width direction Y of the first wall, the greater the pile-up degree, and the worse the flatness of the surface of the shell 21 in the width direction Y of the first wall. Conversely, the smaller the distance from the detection point to the reference surface in the width direction Y of the first wall, the smaller the pile-up degree, and the better the flatness of the surface of the shell 21 in the width direction Y of the first wall.

[0285] The difference between Example 1 and Example 14 to Example 20 is that the dimension c of the first surface 2111 along the width direction Y of the first wall portion and the sum b of the dimensions of all predetermined pressure relief areas P arranged along the width direction Y of the first wall portion in the length direction Z of the first wall portion are different.

[0286] Table 3:

[0287]

[0288]

[0289] As can be seen from Table 3, as b / c increases, the holding time of the battery cell 20 becomes shorter, that is, as b / c increases, the timely pressure relief performance of the battery cell 20 becomes better, and the probability of explosion of the battery cell 20 during thermal runaway becomes smaller. As b / c increases, in the process of manufacturing the first groove 221, the local material accumulation of the outer shell 21 of the battery cell 20 in the width direction Y of the first wall portion becomes more serious, and the flatness of the two outer surfaces of the outer shell 21 of the battery cell 20 in the width direction Y of the first wall portion becomes worse.

[0290] In Table 3, when b / c≥0.3, the holding time of the battery cell 20 is shorter, which can increase the possibility of timely pressure relief of the first wall 211 of the battery cell 20, and reduce the risk of bursting, explosion, fire, etc. of the shell 21 of the battery cell 20 due to untimely pressure relief of the first wall 211. When b / c≤0.7, the stacking degree of the shell 212 of the battery cell 20 on the two surfaces in the width direction Y of the first wall is small, so that the surface flatness of the shell 21 of the battery cell 20 in the width direction Y of the first wall is better. Therefore, 0.3≤b / c≤0.7 can reduce the risk of bursting, explosion, fire, etc. of the shell 21 of the battery cell 20 due to untimely pressure relief of the first wall 211 and reduce the stacking degree of the shell 212 in the width direction Y of the first wall during the manufacturing process of the first groove 221.

[0291] Therefore, the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is 0.3 to 0.7 times the size c of the first surface 2111 along the width direction Y of the first wall portion, that is, the ratio of the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion to the size of the first surface 2111 in the curling direction of the first wall portion 211 is limited to 0.3 to 0.7, wherein, by making the ratio of the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion to the size of the first surface 2111 in the curling direction of the first wall portion 211 greater than or equal to 0.3, the phenomenon that the pressure bearing capacity of the bottom wall of the first groove 221 is too large, resulting in excessive bursting pressure required by the first wall portion 211 when the battery cell 20 is depressurized, can be alleviated, thereby reducing the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall portion 211, and further effectively improving the reliability of the battery cell 20. By making the ratio of the sum of the sizes b of all predetermined pressure relief areas P arranged along the width direction Y of the first wall portion to the size of the first surface 2111 in the curling direction of the first wall portion 211 less than or equal to 0.7, the degree of material stacking in the width direction Y of the first wall portion during the manufacturing process of the first groove 221 can be reduced, thereby alleviating the problem of poor flatness of the surface of the battery cell 20 in the width direction Y of the first wall portion due to the formation of the first groove 221.

[0292] Please continue to refer to Table 3. As c increases, the holding time of the battery cell 20 gradually becomes shorter, and the degree of protrusion of the two opposite outer surfaces of the shell 21 of the battery cell 20 along the width direction Y of the first wall relative to the reference plane gradually increases. When c≥55mm, the holding time of the battery cell 20 during thermal runaway is shorter, which is conducive to timely pressure relief of the battery cell 20 during thermal runaway, and the probability of explosion of the battery cell 20 during thermal runaway is lower. When c≤85mm, the degree of protrusion of the two opposite outer surfaces of the battery cell 20 along the width direction Y of the first wall relative to the reference plane is smaller, the degree of stacking of the shell 21 in the width direction of the first wall is smaller, and the flatness of the two opposite outer surfaces of the shell 21 along the width direction Y of the first wall is better. Therefore, when 55mm≤c≤85mm, the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to the untimely pressure relief of the first wall 211 is low, so that the reliability of the battery cell 20 is better and the flatness of the two opposite outer surfaces of the outer shell 21 of the battery cell 20 along the width direction Y of the first wall is better.

[0293] In some embodiments, the first wall portion 211 is a rectangular wall portion; along the length direction Z of the first wall portion, the first wall portion 211 is formed with at least one predetermined pressure relief area P, and the sum of the sizes of all predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is a, 26mm≤a≤50mm.

[0294] Along the length direction Z of the first wall portion, the first wall portion 211 may form one predetermined pressure relief area P, or may form a plurality of predetermined pressure relief areas P.

[0295] like Fig. 9 , Fig.10 , Fig.11 , Fig.13 , Fig.14 , Fig.15 , Fig.16 , Fig.17 As shown, in an embodiment in which a predetermined pressure relief zone P is formed on the first wall portion 211 along the length direction Z of the first wall portion, the sum a of the sizes of all predetermined pressure relief zones P arranged along the length direction Z of the first wall portion is the size of the predetermined pressure relief zone P along the length direction Z of the first wall portion.

[0296] like Fig.21 As shown, in the embodiment where the first wall portion 211 forms a plurality of predetermined pressure relief areas P along the length direction Z of the first wall portion, the plurality of predetermined pressure relief areas P are arranged in sequence along the length direction Z of the first wall portion, and two adjacent predetermined pressure relief areas P may share a boundary. Then, the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion may be the size between the farthest boundaries of the two predetermined pressure relief areas P that are farthest apart from each other among the plurality of predetermined pressure relief areas P. Fig.21As shown, the pressure relief does not form two predetermined pressure relief areas P along the length direction Z of the first wall portion, and the two predetermined pressure relief areas P are arranged along the length direction Z of the first wall portion. The two predetermined pressure relief areas P can take the center line of the second groove section 2213 of the first groove in the width direction as the boundary, and the sizes of the two predetermined pressure relief areas P along the length direction Z of the first wall portion are a1 and a2 respectively, then a=a1+a2.

[0297] Illustratively, a can be 26mm, 30mm, 32mm, 40mm, 42mm, 44mm, 46mm, 50mm, etc.

[0298] Please continue to refer to Table 2. When a≥26mm, the holding time of the battery cell 20 is shorter, which can increase the possibility of timely pressure relief of the first wall 211 of the battery cell 20, and reduce the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall 211. When a≤50mm, the fatigue times of the battery cell 20 are large, so that the battery cell 20 has a higher fatigue life, and further reduces the risk of leakage caused by premature actuation or fatigue cracking of the first wall 211 in the corresponding area of ​​the first groove 221 of the battery cell 20 after long-term use. Therefore, 26mm≤a≤50mm can further reduce the risk of bursting, explosion, fire, etc. in the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall portion 211, and further reduce the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion 211 at the corresponding position of the first groove 221 of the battery cell 20 after long-term use, thereby improving the use stability of the battery cell 20 and improving the service life and reliability of the battery cell 20.

[0299] Therefore, the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is greater than or equal to 26 mm, which not only facilitates the processing and forming of the first groove 221 and defines the predetermined pressure relief area P, but also helps to increase the area of ​​the predetermined pressure relief area P, thereby alleviating the phenomenon that the pressure bearing capacity of the bottom wall of the first groove 221 is too large, resulting in excessive bursting pressure required by the first wall portion 211 when the battery cell 20 is depressurized, thereby reducing the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to untimely pressure relief of the first wall portion 211, and further effectively improving the reliability of the battery cell 20. The sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is less than or equal to 50 mm, which can reduce the deformation of the bottom wall of the first groove 221 when the expansion force generated by expansion during the use of the battery cell 20 acts on the first wall portion 211, thereby reducing the phenomenon that the bottom wall of the first groove 221 of the first wall portion 211 is reduced in structural strength due to excessive deformation, and further reduces the risk of leakage caused by premature actuation or fatigue cracking of the first wall portion 211 at the corresponding position of the first groove 221 of the battery cell 20 after long-term use, so as to improve the use stability of the battery cell 20 and improve the service life and reliability of the battery cell 20.

[0300] In some embodiments, the first wall portion 211 is a rectangular wall portion; along the width direction Y of the first wall portion, the first groove 221 defines at least one predetermined pressure relief area P, and the sum of the sizes of all predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is b, 18mm≤b≤62mm.

[0301] The first wall portion 211 may form one predetermined pressure relief area P or a plurality of predetermined pressure relief areas P along the width direction Y of the first wall portion.

[0302] like Fig. 9 As shown, in an embodiment in which a predetermined pressure relief area P is formed on the first wall portion 211 along the width direction Y of the first wall portion, the sum b of the sizes of all predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is the size of the predetermined pressure relief area P along the width direction Y of the first wall portion.

[0303] like Fig.10 , Fig.11 , Figure 13-Figure 17 As shown, in an embodiment in which a plurality of predetermined pressure relief areas P are formed on the first wall portion 211 along the width direction Y of the first wall portion, the plurality of predetermined pressure relief areas P are arranged in sequence along the width direction Y of the first wall portion, and two adjacent predetermined pressure relief areas P may share a border. Then, the sum a of the sizes of all predetermined pressure relief areas P arranged along the width direction Y of the first wall portion may be the size between the farthest boundaries of two predetermined pressure relief areas P that are farthest apart among the plurality of predetermined pressure relief areas P. Fig.10 , Fig.11 , Figure 13-Figure 17 2 shows that the first wall portion 211 forms two predetermined pressure relief areas P in the width direction Y of the first wall portion, and the two predetermined pressure relief areas P are arranged along the width direction Y of the first wall portion, and the two predetermined pressure relief areas P are bounded by the center line of the width direction of the second groove section 2213 of the first groove 221. The dimensions of the two predetermined pressure relief areas P along the width direction Y of the first wall portion are b1 and b2 respectively, and b=b1+b2.

[0304] Exemplarily, b can be 18mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 62mm, etc.

[0305] Please continue to refer to Table 3. When b≥18mm, the holding time of the battery cell 20 is shorter, which can increase the possibility of timely pressure relief of the first wall 211 of the battery cell 20, and reduce the risk of bursting, explosion, fire, etc. of the shell 21 of the battery cell 20 due to untimely pressure relief of the first wall 211. When b≤62mm, the stacking degree of the shell 21 of the battery cell 20 on both surfaces in the width direction Y of the first wall is small, so that the surface flatness of the shell 21 of the battery cell 20 in the width direction Y of the first wall is better. Therefore, 18mm≤b≤62mm can reduce the risk of bursting, explosion, fire, etc. of the shell 21 of the battery cell 20 due to untimely pressure relief of the first wall 211, reduce the stacking degree of the shell 21 in the width direction Y of the first wall during the manufacturing process of the first groove 221, and improve the flatness of the two opposite outer surfaces of the shell 21 in the width direction Y of the first wall.

[0306] Therefore, the sum of the sizes b of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall is greater than or equal to 18 mm, which not only facilitates the processing and forming of the first groove 221 and defines the predetermined pressure relief area P, but also helps to increase the area of ​​the predetermined pressure relief area P, and alleviates the phenomenon that the pressure bearing capacity of the bottom wall of the first groove 221 is too large, which causes the first wall 211 to have too large a bursting pressure when the battery cell 20 is depressurized, thereby reducing the risk of bursting, explosion, fire, etc. of the outer shell 21 of the battery cell 20 due to the untimely pressure relief of the first wall 211, and further effectively improves the reliability of the battery cell 20. The sum of the sizes b of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall is less than or equal to 62 mm, which can reduce the degree of material stacking in the width direction Y of the first wall during the manufacturing process of the first groove 221, thereby alleviating the problem of poor flatness of the surface of the battery cell 20 in the width direction Y of the first wall due to the formation of the first groove 221.

[0307] In some embodiments, the first wall portion 211 is a rectangular wall portion; along the length direction Z of the first wall portion, the first wall portion 211 is formed with at least one predetermined pressure relief area P, and the sum of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is a; along the width direction Y of the first wall portion, the first groove 221 defines at least one predetermined pressure relief area P, and the sum of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is b, and the size of the first surface 2111 is c;

[0308] When 10mm≤c≤40mm, the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is 2 to 3 times the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion.

[0309] The sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is 2 to 3 times the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion, that is, the ratio of the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is 2 to 3. Exemplarily, a / b can be 2, 2.1, 2.2, 2.25, 2.4, 2.5, 2.6, 2.7, 2.8, 3, etc.

[0310] The battery cell 20 satisfying 10 mm ≤ c ≤ 40 mm may also be referred to as a narrow battery cell. Fig.13 The case where c=39 mm and a / b=2 is shown in FIG.

[0311] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail in conjunction with Examples 21-40. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0312] When 10mm≤c≤40mm, the explosion pressure and valve opening angle of the battery cell 20 during thermal runaway and the explosion are obtained for the battery cell 20 in Examples 21 to 40 to evaluate the reliability of the battery cell 20, as shown in Table 4.

[0313] The difference between Example 1 and Example 21-Example 40 lies in that the dimension c of the first surface 2111 along the width direction Y of the first wall portion, the sum of the dimensions a of all predetermined pressure relief areas P arranged along the length direction Z of the first wall portion in the length direction Z of the first wall portion, and the sum of the dimensions b of all predetermined pressure relief areas P arranged along the width direction Y of the first wall portion in the width direction Y of the first wall portion are different.

[0314] Taking the battery cell 20 of model 39203 as an example, the preset standard bursting pressure of the first groove 221 is 1MPa. If the actual bursting pressure of the battery cell 20 during thermal runaway satisfies 1.0±0.2MPa, the bursting pressure of the battery cell 20 is considered stable. The bursting pressure stability is determined by multiple groups of bursting pressure standard deviations. The actual bursting pressure is represented by σ. If the fluctuation value (σ-1) of the actual bursting pressure of the battery cell 20 relative to the standard bursting pressure of the battery cell 20 is less than 0.2MPa, the bursting pressure is considered stable. The actual bursting pressure is the pressure when the first groove 221 begins to crack.

[0315] The actual burst pressure test method is as follows:

[0316] 1) Use two steel plates or aluminum plates as clamps to clamp the two large surfaces of the battery cell 20, with a clamping force of 3000N;

[0317] 2) Use a 3mm drill bit to drill a hole at the position corresponding to the injection hole on the battery cell 20, connect the inflation device to the hole drilled by the drill bit through the air pipe, and inflate the battery cell 20 with the inflation device. The inflation rate of the inflation device into the battery cell 20 is 0.03MPa / s. A pressure gauge is installed on the air pipe to monitor the pressure inside the battery cell 20. The inflation device inflates the battery cell 20;

[0318] 3) The pressure inside the battery cell 20 monitored by the pressure gauge until the first groove ruptures and releases air is the actual bursting pressure of the battery cell 20 .

[0319] The valve opening state of the battery cell 20 is measured by the valve opening angle when the first groove 221 starts to release pressure. Fig.12 As shown, the angle between the plane where the predetermined pressure relief area P of the first groove 221 is located and the plane where the predetermined pressure relief area P is located before the first groove 221 is broken. The valve opening angle is represented by β, and if β>45°, it is qualified; the larger the valve opening angle β, the larger the pressure relief area. The test results of battery cells 20 of various size ratios are as follows.

[0320] Table 4:

[0321]

[0322] Please refer to Table 4. When c = 10 mm, 20 mm, 30 mm, and 40 mm, as a / b gradually increases, the valve opening angle gradually decreases. That is, as a / b gradually increases, the pressure relief area becomes smaller, and the pressure relief effect and efficiency become worse; as a / b gradually increases, the fluctuations of the bursting pressure of each battery cell 20 relative to the standard bursting pressure gradually decrease, and the bursting pressure becomes more stable.

[0323] In Table 4, when c = 10 mm, 20 mm, 30 mm, and 40 mm, when a / b ≥ 2, the fluctuations of the bursting pressure of each battery cell 20 relative to the standard bursting pressure are small, and the bursting pressure is more stable, which is beneficial to the timely pressure relief of the battery cell 20 and the reliability of the battery cell 20; when a / b ≤ 3, when the first groove 221 of the battery cell 20 cracks, the valve opening angle is greater than 45°. When the first groove 221 of the battery cell 20 cracks, the valve opening angle is large, resulting in a large pressure relief area and good pressure relief effect and efficiency.

[0324] Therefore, when 10 mm ≤ c ≤ 40 mm, the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is 2 to 3 times the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion. That is, the ratio of the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction Z of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is 2 to 3. The ratio of the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is greater than or equal to 2, and the bursting pressure is more stable, which is beneficial to the timely pressure relief of the first wall portion 211, thereby being able to reduce the risks such as bursting, explosion, and fire of the outer shell 21 of the battery cell 20 caused by untimely pressure relief of the first wall portion 211, and further being able to effectively improve the reliability of use of the battery cell 20; the ratio of the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is less than or equal to 3, which is beneficial to a larger valve opening angle of the predetermined pressure relief area P when the first groove 221 cracks, so that the first wall portion 211 has a larger pressure relief area, thereby being beneficial to the timely pressure relief of the first wall portion 211 and reducing the risks such as bursting, explosion, and fire of the outer shell 21 of the battery cell 20, and improving the reliability of the battery cell 20.

[0325] In an embodiment, when 40 mm < c ≤ 60 mm, the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is 1 to 2 times the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion.

[0326] The sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is 1 to 2 times the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion, that is, the ratio of the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is 1 to 2. Exemplarily, a / b can be 1, 1.2, 1.4, 1.5, 1.6, 1.7, 1.8, 2, etc.

[0327] The battery cell 20 satisfying 40mm < c ≤ 60mm can also be called a medium-thick battery core. Fig.14 As shown in, the case where c = 50mm and a / b = 1.0.

[0328] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail in combination with Embodiments 41-55. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present application.

[0329] When 40mm < c ≤ 60mm, by obtaining the bursting pressure and the opening valve angle at the time of thermal runaway of the battery cell 20 in Embodiments 73-96, the reliability of the battery cell 20 is evaluated. The specific situation is shown in Table 5. The test methods for the bursting pressure and the opening valve angle at the time of bursting are as above. The model of the test object adopted in Embodiments 41-55 is 54203.

[0330] The differences between Embodiment 1 and Embodiments 41-55 lie in that the size c of the first surface 2111 along the width direction Y of the first wall portion, the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion in the length direction Z of the first wall portion, and the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion in the width direction Y of the first wall portion are different.

[0331] Table 5:

[0332]

[0333] As can be seen from Table 5, when c = 50mm, 55mm, 60mm, as a / b gradually increases, the opening valve angle gradually decreases, that is, as a / b gradually increases, the pressure relief area becomes smaller, and the pressure relief effect and pressure relief efficiency become worse; as a / b gradually increases, the fluctuation of the bursting pressure of each battery cell 20 relative to the standard bursting pressure gradually decreases, and the bursting pressure becomes more and more stable.

[0334] In Table 5, when c = 50 mm, 55 mm, or 60 mm, when a / b ≥ 1, the bursting pressure of each battery cell 20 fluctuates less relative to the standard bursting pressure, and the bursting pressure is more stable, which is beneficial to the timely pressure relief of the battery cell 20 and the reliability of the battery cell 20; when a / b ≤ 2, the valve opening angle is greater than 45° when the first groove 221 of the battery cell 20 cracks, and the valve opening angle is relatively large when the first groove 221 of the battery cell 20 cracks, resulting in a relatively large pressure relief area and good pressure relief effect and efficiency.

[0335] Therefore, when 40 mm < c ≤ 60 mm, the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is 1 to 2 times the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion, that is, the ratio of the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is 1 to 2, and the ratio of the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is greater than or equal to 1, the bursting pressure is more stable, which is beneficial to the timely pressure relief of the first wall portion 211, thereby being able to reduce the risks such as bursting, explosion, and fire of the outer shell 21 of the battery cell 20 caused by untimely pressure relief of the first wall portion 211, and further being able to effectively improve the use reliability of the battery cell 20; the ratio of the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is less than or equal to 2, which is beneficial to a larger valve opening angle of the predetermined pressure relief area P when the first groove 221 cracks, so that the first wall portion 211 has a larger pressure relief area, thereby being beneficial to the timely pressure relief of the first wall portion 211 and reducing the risks such as bursting, explosion, and fire of the outer shell 21 of the battery cell 20 and improving the reliability of the battery cell 20.

[0336] In some embodiments, when 60 mm < c, the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is 0.4 to 1 times the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion.

[0337] The sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is 0.4 to 1 times the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion, that is, the ratio of the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is 0.4 to 1. Exemplarily, a / b can be 0.4, 0.5, 0.6, 0.7, 0.8, 1, etc.

[0338] The battery cell 20 with 60 mm < c can also be called a thick battery core. Fig.15 It shows the case where c = 71 mm and a / b = 0.6. Fig.16 It shows the case where c = 87 mm and a / b = 0.5.

[0339] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail in combination with Embodiments 56 - 73. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0340] When 60 mm < c, by obtaining the bursting pressure and the opening valve angle during thermal runaway of the battery cell 20 in Embodiments 56 - 73 for the battery cell 20, the reliability of the battery cell 20 is evaluated. The specific situation is shown in Table 6. The test methods for the bursting pressure and the opening valve angle during bursting are as above. The model of the test object used in Embodiments 56 - 73 is 87203.

[0341] The differences between Embodiment 1 and Embodiments 56 - 73 lie in that the dimension c of the first surface 2111 along the width direction Y of the first wall portion, the sum a of the dimensions of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion in the length direction Z of the first wall portion, and the sum b of the dimensions of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion in the width direction Y of the first wall portion are different.

[0342] Table 6

[0343]

[0344] It can be seen from Table 6 that when c = 70 mm, 80 mm, 90 mm, as a / b gradually increases, the opening valve angle gradually decreases, that is, as a / b gradually increases, the pressure relief area becomes smaller, and the pressure relief effect and pressure relief efficiency become worse; as a / b gradually increases, the fluctuation of the bursting pressure of each battery cell 20 relative to the standard bursting pressure gradually decreases, and the bursting pressure becomes more stable.

[0345] In Table 6, when c = 70 mm, 80 mm, and 90 mm, when a / b ≥ 0.4, the bursting pressure of each battery cell 20 fluctuates less relative to the standard bursting pressure. The bursting pressure of each battery cell 20 fluctuates less relative to the standard bursting pressure, and the bursting pressure is more stable, which is beneficial for the battery cell 20 to relieve pressure in time and improve the reliability of the battery cell 20; when a / b ≤ 1, the opening valve angle is greater than 45° when the first groove 221 of the battery cell 20 cracks. The opening valve angle is relatively large when the first groove 221 of the battery cell 20 cracks, so that the pressure relief area is relatively large, and the pressure relief effect and efficiency are relatively good.

[0346] Therefore, when 60 mm < c, the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion is 0.4 to 1 times the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion, that is, the ratio of the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is 0.4 to 1. The ratio of the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is greater than or equal to 0.4, and the bursting pressure is more stable, which is beneficial for the first wall portion 211 to relieve pressure in time, thereby reducing the risks such as bursting, explosion, and fire of the outer shell 21 of the battery cell 20 caused by untimely pressure relief of the first wall portion 211, and further effectively improving the use reliability of the battery cell 20; the ratio of the sum a of the sizes of all the predetermined pressure relief areas P arranged along the length direction Z of the first wall portion to the sum b of the sizes of all the predetermined pressure relief areas P arranged along the width direction Y of the first wall portion is less than or equal to 1, which is beneficial for a larger opening valve angle of the predetermined pressure relief area P when the first groove 221 cracks, so that the first wall portion 211 has a larger pressure relief area, thereby being beneficial for the first wall portion 211 to relieve pressure in time, reducing the risks such as bursting, explosion, and fire of the outer shell 21 of the battery cell 20, and improving the reliability of the battery cell 20.

[0347] As Fig.17 shown, in some embodiments, the first wall portion 211 further includes a second groove 222, and the second groove 222 is configured to guide the opening of the predetermined pressure relief area P.

[0348] The bottom wall of the second groove 222 forms a second weak portion 2221, that is, the portion of the first wall portion 211 where the second groove 222 is provided and corresponding to the bottom wall of the second groove 222 is the second weak portion 2221.

[0349] Along the thickness direction X of the first wall portion, the thickness of the second weak portion 2221 is greater than the thickness of the first weak portion 2211 formed by the bottom wall of the first groove 221. The second weak portion 2221 is configured to guide the predetermined pressure relief area P to flip when the first weak portion 2211 is cracked to release the internal pressure of the battery cell 20, thereby achieving the second groove 222 guiding the predetermined pressure relief area P to open.

[0350] Among them, the second weak portion 2221 is configured to guide the predetermined pressure relief area P to flip when the bottom wall of the first groove 221 is cracked, that is, the predetermined pressure relief area P can flip with the second weak portion 2221 as the axis after the bottom wall of the first groove 221 of the first wall portion 211 is cracked, so that after the predetermined pressure relief area P is flipped, the inside of the shell 21 and the outside of the shell 21 are connected to each other for pressure relief.

[0351] Of course, in other embodiments, the second weak portion 2221 may also be other structures. For example, the second weak portion 2221 is formed by heat treating a part of the first wall portion 211 to weaken the strength of the area.

[0352] The first wall portion 211 is provided with a second groove 222, and the first wall portion 211 forms a weak portion in the area corresponding to the second groove 222. The weak portion corresponding to the second groove 222 can guide the predetermined pressure relief area P to open, thereby improving the opening effect of the predetermined pressure relief area P of the first wall portion 211, which is conducive to increasing the pressure relief area of ​​the battery cell 20 after the predetermined pressure relief area P is opened, and further improving the pressure relief rate of the battery cell 20 when thermal runaway occurs, so as to reduce the risk of fire, explosion, connection failure, etc. caused by untimely pressure relief of the battery cell 20, which is conducive to improving the reliability of the battery cell 20. The first wall portion 211 is provided with a second groove 222, so that the first wall portion 211 forms a weak portion in the area corresponding to the groove bottom surface of the second groove 222 where the second groove 222 is provided. The battery cell 20 with such a structure is easy to form a weak portion on the first wall portion 211, which is conducive to reducing the difficulty of forming a weak portion on the first wall portion 211 to guide the predetermined pressure relief area P to open, so as to improve the production efficiency of the battery cell 20.

[0353] In some embodiments, the second groove 222 is recessed from the second surface 2112 toward the first surface 2111 .

[0354] The first groove 221 is disposed on the first surface 2111, and the second groove 222 is disposed on the second surface 2112. The first surface 2111 and the second surface 2112 are surfaces on opposite sides of the first wall portion 211 in the thickness direction X of the first wall portion. Along the thickness direction X of the first wall portion, the first groove 221 and the second groove 222 are disposed on both sides of the first wall portion 211, respectively.

[0355] Exemplarily, the first groove 221 is arranged on the surface of the first wall portion 211 facing away from the interior of the shell 21, and the second groove 222 is arranged on the surface of the first wall portion 211 facing the interior of the shell 21, so that the first groove 221 and the second groove 222 are respectively arranged on both sides of the first wall portion 211.

[0356] The second groove 222 is recessed from the second surface 2112 toward the direction close to the first surface 2111, and the first groove 221 and the second groove 222 are arranged on opposite sides of the first wall portion 211 along the thickness direction X of the first wall portion, so as to facilitate the processing of the first groove 221 and the second groove 222 on both sides of the first wall portion 211 along the thickness direction X of the first wall portion, respectively, which is beneficial to reduce the mutual influence of the first groove 221 and the second groove 222 during the processing.

[0357] like Fig.17 , Fig.18 , Fig.19 , Fig. 20 As shown, in some embodiments, the first surface 2111 is the surface of the first wall portion 211 facing away from the interior of the housing 21 , and the second surface 2112 is the surface of the first wall portion 211 facing the interior of the housing 21 .

[0358] That is, the first groove 221 is disposed on the surface of the first wall portion 211 away from the interior of the housing 21, and the first groove 221 is recessed from the first surface 2111 to the direction close to the second surface 2112. The second groove 222 is disposed on the surface of the first wall portion 211 facing the interior of the housing 21, and the second groove 222 is recessed from the second surface 2112 to the direction close to the first surface 2111.

[0359] By arranging the first groove 221 and the second groove 222 on the first surface 2111 and the second surface 2112 of the first wall portion 211 respectively, which are opposite to each other along the thickness direction X of the first wall portion, it is convenient to process the first groove 221 and the second groove 222 on both sides of the first wall portion 211 along the thickness direction X of the first wall portion, which is conducive to reducing the mutual influence of the first groove 221 and the second groove 222 during the processing. And the second groove 222 is arranged on the second surface 2112 of the first wall portion 211 facing the inside of the shell 21, so that the predetermined pressure relief area P is opened around the bottom wall of the second groove 222 and turned to the outside of the shell 21, so as to reduce the interference effect of the groove side surface of the second groove 222 on the predetermined pressure relief area P during the turning process, which is conducive to improving the turning effect of the predetermined pressure relief area P.

[0360] like Fig.17 As shown, in some embodiments, the first groove 221 and the second groove 222 are not in contact.

[0361] By setting the first groove 221 and the second groove 222 to a structure that does not contact each other, on the one hand, the mutual influence between the first groove 221 and the second groove 222 during the processing can be reduced; on the other hand, the phenomenon of the corresponding area of ​​the second groove 222 cracking when the first groove 221 cracks to release pressure can be reduced, and the stress influence between the first groove 221 and the second groove 222 can be reduced.

[0362] Of course, in other embodiments, such as Fig.11 As shown, the first wall portion 211 may not be provided with the second groove 222 .

[0363] In an embodiment where the first groove 221 includes a plurality of groove segments, for example, Fig.17 As shown, the first groove 221 includes a first groove section 2212 and a second groove section 2213 , the first groove section 2212 and the second groove section 2213 are connected, and the first groove section 2212 and the second groove section 2213 jointly define at least one predetermined pressure relief area P.

[0364] The first groove section 2212 may extend in a straight line. The second groove section 2213 may extend in a straight line. The first groove section 2212 and the second groove section 2213 together define at least one predetermined pressure relief area P, which is configured to be opened when the first wall portion 211 is cracked along at least a portion of the groove bottom wall of the first groove 221 to release the pressure inside the battery cell 20.

[0365] The first slot section 2212 may also extend along a curve, for example, the first slot section 2212 is an arc section. The second slot section 2213 may also extend along a curve, for example, the second slot section 2213 is an arc section.

[0366] The first slot section 2212 and the second slot section 2213 each form a first weak section 2211a, and the first weak portion 2211 may include two first weak sections 2211a. Since the first slot section 2212 and the second slot section 2213 are connected, the first weak section 2211a formed in the first slot section 2212 region and the first weak section 2211a formed in the second slot section 2213 region are connected, forming a first weak portion 2211 including two connected first weak sections 2211a. When one of the first weak sections 2211a begins to crack, it can drive the other first weak section 2211a to crack.

[0367] The first groove section 2212 and the second groove section 2213 jointly define a predetermined pressure relief area P, that is, the first groove section 2212 and the second groove section 2213 are structures arranged along the edge of the predetermined pressure relief area P, so that the setting trajectory of the first groove 221 is arranged along the edge of the predetermined pressure relief area P.

[0368] The predetermined pressure relief area P is configured to be able to be opened when the first weak portion 2211 formed along the bottom wall of at least part of the first groove 221 of the first wall portion 211 is cracked, that is, when the battery cell 20 undergoes thermal runaway and releases internal pressure, the areas of the first groove section 2212 and the second groove section 2213 of the first wall portion 211 can be cracked, so that the predetermined pressure relief area P can be opened and the internal pressure of the battery cell 20 can be released.

[0369] The first slot segment 2212 and the second slot segment 2213 can be connected in various forms, for example, the first slot segment 2212 and the second slot segment 2213 are connected to form a "T" shape, the first slot segment 2212 and the second slot segment 2213 are connected to form a "V" shape, the first slot segment 2212 and the second slot segment 2213 are connected to form an "L" shape, the first slot segment 2212 and the second slot segment 2213 are connected to form an "X" shape, etc.

[0370] The first groove 221 includes a first groove section 2212 and a second groove section 2213, and the first groove section 2212 and the second groove section 2213 are interconnected structures. On the one hand, they can increase the pressure relief area of ​​the battery cell 20 to increase the pressure relief rate of the battery cell 20. On the other hand, the position where the first groove section 2212 and the second groove section 2213 are interconnected is weaker and easier to crack and open the predetermined pressure relief area P to release the internal pressure of the battery cell 20.

[0371] In some embodiments, the first groove 221 also includes a third groove section 2214, the first groove section 2212 and the third groove section 2214 are arranged opposite to each other, the second groove section 2213 connects the first groove section 2212 and the third groove section 2214, and the first groove section 2212, the second groove section 2213 and the third groove section 2214 jointly define at least one predetermined pressure relief area P.

[0372] The third groove section 2214 may extend in a straight line. The first groove section 2212, the second groove section 2213 and the third groove section 2214 together define a predetermined pressure relief area P, which is configured to be opened when the first wall portion 211 is formed along at least a portion of the groove bottom wall of the first groove 221 without cracking, so as to release the internal pressure of the battery cell 20.

[0373] The extension direction of the first slot segment 2212 is parallel to the extension direction of the third slot segment 2214, the extension direction of the first slot segment 2212 is perpendicular to the extension direction of the second slot segment 2213, and the extension direction of the third slot segment 2214 is perpendicular to the extension direction of the second slot segment 2213. In other words, the first slot segment 2212 and the third slot segment 2214 are perpendicular to the second slot segment 2213, respectively.

[0374] The first slot segment 2212, the second slot segment 2213 and the third slot segment 2214 can be connected in various forms, for example, the first slot segment 2212, the second slot segment 2213 and the third slot segment 2214 are connected to form an "H" shape, or the first slot segment 2212, the second slot segment 2213 and the third slot segment 2214 are connected to form a "U" shape.

[0375] In other embodiments, the third slot segment 2214 may also extend along a curve, for example, the third slot segment 2214 is an arc segment.

[0376] Among them, the bottom wall of the first groove section 2212, the bottom wall of the second groove section 2213 and the bottom wall of the third groove section 2214 all form a first weak section 2211a, that is, the first weak portion 2211 includes three first weak sections 2211a, and the three first weak sections 2211a are respectively the bottom wall of the first groove section 2212, the bottom wall of the second groove section 2213 and the bottom wall of the third groove section 2214, and the three first weak sections 2211a constitute the first weak portion 2211.

[0377] A first weak section 2211a is formed in the area corresponding to the third slot section 2214, and the first weak portion 2211 includes three first weak sections 2211a. The second slot section 2213 connects the first slot section 2212 and the third slot section 2214, and the first weak section 2211a formed in the area corresponding to the second slot section 2213 connects the first weak section 2211a formed in the area corresponding to the first slot section 2212 and the first weak section 2211a formed in the area corresponding to the third slot section 2214. When one of the first weak sections 2211a begins to crack, it can drive another first weak section 2211a to crack, which is conducive to the rapid cracking of the first weak portion 2211 to open the predetermined pressure relief area P and achieve rapid pressure relief.

[0378] The first slot section 2212 and the third slot section 2214 are arranged opposite to each other, that is, the first slot section 2212 and the third slot section 2214 are arranged at intervals. Fig.17 In the embodiment, the first slot segment 2212 and the third slot segment 2214 are arranged at intervals along the length direction Z of the first wall portion, and both the first slot segment 2212 and the third slot segment 2214 extend along the width direction Y of the first wall portion.

[0379] The second slot section 2213 connects the first slot section 2212 and the third slot section 2214. That is, the second slot section 2213 is located between the first slot section 2212 and the third slot section 2214, and the two ends of the second slot section 2213 are respectively connected to the first slot section 2212 and the third slot section 2214. For example, Fig.15In the embodiment, the second slot section 2213 extends along the length direction Y of the wall. Of course, in other embodiments, the second slot section 2213 may also extend the first slot section 2212 and the third slot section 2214 at both ends of the second slot section 2213 in the length direction Y of the wall, respectively.

[0380] The first groove 221 is provided with a first groove section 2212 and a third groove section 2214 which are arranged opposite to each other, and a second groove section 2213 connecting the first groove section 2212 and the third groove section 2214, so that the first wall portion 211 can be split along the first groove section 2212, the second groove section 2213 and the third groove section 2214 when the battery cell 20 is depressurized, so as to open the predetermined pressure relief area P to release the internal pressure of the battery cell 20. The first groove 221 with such a structure makes the intersection position of the first groove section 2212 and the second groove section 2213 and the intersection position of the second groove section 2213 and the third groove section 2214 weaker, and is easier to split and open the predetermined pressure relief area P for pressure relief, and can further increase the pressure relief area and pressure relief rate of the battery cell 20.

[0381] like Fig.17 As shown, in some embodiments, the position where the second slot segment 2213 is connected to the first slot segment 2212 deviates from the two ends of the first slot segment 2212 , and the position where the second slot segment 2213 is connected to the third slot segment 2214 deviates from the two ends of the third slot segment 2214 .

[0382] The position where the second slot segment 2213 is connected to the first slot segment 2212 deviates from the two ends of the extending direction of the first slot segment 2212. The position where the second slot segment 2213 is connected to the third slot segment 2214 deviates from the two ends of the extending direction of the third slot segment 2214.

[0383] Among them, the connection position of the first slot section 2212 and the second slot section 2213 deviates from the two ends of the first slot section 2212, that is, the second slot section 2213 is connected between the two ends of the first slot section 2212. Similarly, the connection position of the third slot section 2214 and the second slot section 2213 deviates from the two ends of the third slot section 2214, that is, the second slot section 2213 is connected between the two ends of the third slot section 2214, so that the shape of the first groove 221 formed by the first slot section 2212, the second slot section 2213 and the third slot section 2214 is an approximately "H"-shaped structure, and predetermined pressure relief areas P are formed on both sides of the second slot section 2213. Of course, the areas of the two predetermined pressure relief areas P may be the same or different.

[0384] Exemplarily, the second slot segment 2213 is a straight structure extending along the length direction Z of the first wall portion, the first slot segment 2212 and the third slot segment 2214 are both straight structures extending along the width direction Y of the first wall portion, and the second slot segment 2213 is located between the first slot segment 2212 and the third slot segment 2214 along the length direction Z of the first wall portion.

[0385] By setting the first slot section 2212, the second slot section 2213 and the third slot section 2214 to extend along a straight trajectory, and setting the first slot section 2212 and the third slot section 2214 to be perpendicular to the second slot section 2213, so that the extension direction of the second slot section 2213 is the arrangement direction of the first slot section 2212 and the third slot section 2214, on the one hand, the regularity of the shape of the first groove 221 can be improved, which is conducive to reducing the processing difficulty of the first groove 221, so as to reduce the manufacturing cost of the battery cell 20; on the other hand, the two predetermined pressure relief areas P located on both sides of the second slot section 2213 relieve pressure in opposite directions when the battery cell 20 is relieved.

[0386] The position where the second groove section 2213 is connected to the first groove section 2212 deviates from the two ends of the first groove section 2212, and the connection position between the first groove section 2212 and the second groove section 2213 is set to be located between the two ends of the first groove section 2212. The position where the second groove section 2213 is connected to the third groove section 2214 deviates from the two ends of the third groove section 2214, and the connection position between the third groove section 2214 and the second groove section 2213 is set to be located between the two ends of the third groove section 2214. The first groove section 2212, the second groove section 2213 and the third groove section 2214 form a structure similar to an "H" shape, so that both sides of the second groove section 2213 of the first groove 221 can form a predetermined pressure relief area P, and the two predetermined pressure relief areas P can be opened in a split manner for pressure relief when the battery cell 20 is pressure-relieved, which is beneficial to further increase the pressure relief effect of the battery cell 20 and can effectively improve the pressure relief rate of the battery cell 20.

[0387] The first groove 221 may also be other structures, see Fig. 9 The shape of the first groove 221 formed by the first groove section 2212, the second groove section 2213 and the third groove section 2214 can be a "U"-shaped structure, that is, one end of the second groove section 2213 is connected to one end of the first groove section 2212, and the other end is connected to one end of the third groove section 2214, so as to form a predetermined pressure relief area P on the first wall portion 211.

[0388] In some embodiments, the first groove 221 further includes a fourth groove section 2215, which is disposed between the first groove section 2212 and the third groove section 2214. The first four groove sections are connected to the third groove section 2214, and a first weak section 2211a is formed in the corresponding area of ​​the first four groove sections.

[0389] For example, Fig.17As shown, the fourth slot section 2215 intersects the second slot section 2213 perpendicularly. The fourth slot section 2215 extends along the width direction Y of the first wall portion. Along the width direction Y of the first wall portion, the length of the fourth slot section 2215 is less than the length of the first slot section 2212, and the length of the fourth slot section 2215 is less than the length of the third slot section 2214.

[0390] The bottom wall of the first four groove sections forms a first weak section 2211a. The bottom wall of the first groove section 2212, the bottom wall of the second groove section 2213, the bottom wall of the third groove section 2214 and the bottom wall of the first four groove sections together form a first weak portion 2211 including four first weak sections 2211a.

[0391] The provision of the fourth slot segment 2215 facilitates the first wall portion 211 to split from the intersection of the second slot segment 2213 and the fourth slot segment 2215, so that two predetermined pressure relief areas P located on both sides of the second slot segment 2213 can be opened synchronously, thereby increasing the pressure relief rate.

[0392] Please continue to refer to Fig.17 In some embodiments, the first groove 221 defines two predetermined pressure relief areas P, and the two predetermined pressure relief areas P are respectively located on both sides of the second groove section 2213; the first wall portion 211 also includes a second groove 222, and the second groove 222 is configured to guide the predetermined pressure relief area P to open, and at least one second groove 222 is correspondingly arranged for each predetermined pressure relief area P, and the first groove 221 is located between the two second grooves 222.

[0393] One second groove 222 may be provided corresponding to each predetermined pressure relief area P, or a plurality of second grooves 222 may be provided correspondingly.

[0394] Each second groove 222 is configured to guide the corresponding predetermined pressure relief area P to flip when the groove bottom wall of the first groove 221 is broken, thereby guiding the predetermined pressure relief area P to open.

[0395] The extension direction of the second groove 222 is parallel to the extension direction of the second groove section 2213 of the first groove 221. The two second grooves 222 are arranged at intervals along the extension direction of the first groove section 2212 of the first groove 221. The first groove section 2212 and the third groove section 2214 of the first groove 221 are located between the two second grooves 222, and the second groove section 2213 is located between the two second grooves 222, so that the first groove 221 is located between the two second grooves 222.

[0396] Each first groove 221 is located between the edge of the first wall 211 and the first groove 221 along the width direction Y of the first wall. The two first grooves 221 separate the edge of the first wall 211 from the first groove 221 at both sides of the first groove 221 along the width direction Y of the first wall.

[0397] The second groove 222 can guide the corresponding predetermined pressure relief area P to open. At least one second groove 222 is correspondingly arranged for each predetermined pressure relief area P, thereby improving the opening effect of each predetermined pressure relief area P of the first wall portion 211, which is beneficial to increasing the pressure relief area of ​​the battery cell 20 after the predetermined pressure relief area P is opened, and further improving the pressure relief rate of the battery cell 20 when thermal runaway occurs, so as to reduce the risk of fire, explosion, connection failure, etc. caused by untimely pressure relief of the battery cell 20, which is beneficial to improving the reliability of the battery cell 20.

[0398] like Fig.17 As shown, in some embodiments, the second slot segment 2213 and the second groove 222 are arranged opposite to each other along the first direction, and along the first direction, the first slot segment 2212 and the third slot segment 2214 are arranged spaced apart from the second groove 222 .

[0399] The second groove section 2213 and the second groove 222 are arranged opposite to each other along the first direction, and along the first direction, the first groove section 2212 and the third groove section 2214 are arranged at intervals from the second groove 222, so the first groove section 2212, the second groove section 2213 and the third groove section 2214 are not in contact with the second groove 222, which can reduce the mutual influence between the first groove 221 and the second groove 222 during the processing, and reduce the phenomenon that the area corresponding to the second groove 222 is cracked when the first groove 221 is cracked and the pressure is released, and can reduce the stress influence between the first groove 221 and the second groove 222. The second groove section 2213 is arranged opposite to the second groove 222 along the first direction, and along the first direction, the first groove section 2212 and the third groove section 2214 are both spaced apart from the second groove 222, so that the second groove 222 is located between the edge of the first wall portion 211 along the first direction and the first notch, and the second groove 222 can play a buffering role between the first groove 221 and the edge of the first wall portion 211 in the first direction, thereby reducing the risk of the first groove 221 cracking due to external force and improving the reliability of the battery cell 20.

[0400] The first direction may be different depending on the structure of the battery cell 20 . For example, in an embodiment where the first wall portion 211 is a rectangular wall portion, the first direction may be a length direction Z of the first wall portion or a width direction Y of the first wall portion.

[0401] In some embodiments, the first wall portion 211 is a rectangular wall portion, and the first direction is parallel to the width direction Y of the first wall portion.

[0402] That is, the first slot section 2212 and the third slot section 2214 extend along the width direction Y of the first wall, and the second groove 222 and the second slot section 2213 extend along the length direction Z of the first wall. The second groove 222 and the second slot section 2213 are arranged opposite to each other along the width direction Y of the first wall.

[0403] The first direction is parallel to the width direction Y of the first wall portion, and the second groove section 2213 and the second groove 222 are arranged opposite to each other along the width direction Y of the first wall portion. Along the width direction Y of the first wall portion, the first groove section 2212 and the third groove section 2214 are spaced apart from the second groove 222. The first groove section 2212, the second groove section 2213 and the third groove section 2214 are not in contact with the second groove 222 in the width direction Y of the first wall portion, which can reduce the mutual influence between the first groove 221 and the second groove 222 during the processing, and reduce the phenomenon that the corresponding area of ​​the first groove 221 causes the corresponding area of ​​the second groove 222 to crack when the pressure is released, and can reduce the stress influence between the first groove 221 and the second groove 222. The second groove section 2213 and the second groove 222 are arranged opposite to each other along the width direction Y of the first wall portion, and the first groove section 2212 and the third groove section 2214 are both arranged to be spaced apart from the second groove 222 along the width direction Y of the first wall portion. Then, the second groove 222 is located between the edge of the first wall portion 211 along the width direction Y of the first wall portion and the first notch. The second groove 222 can play a buffering role between the first groove 221 and the edge of the first wall portion 211 in the first direction, thereby reducing the risk of the first groove 221 cracking due to external force and improving the reliability of the battery cell 20.

[0404] like Fig.21 As shown, in other embodiments, the first slot section 2212 and the third slot section 2214 can also be arranged along the width direction Y of the first wall portion, and the first slot section 2212 and the third slot section 2214 both extend along the length direction Z of the first wall portion, and the second slot section 2213 extends along the width direction Y of the first wall portion and connects the first slot section 2212 and the third slot section 2214. The first groove 221 defines two predetermined pressure relief areas P, and the two predetermined pressure relief areas P are respectively located on both sides of the second slot section 2213 along the length direction Z of the first wall portion. In this way, the first groove 221 defines two predetermined pressure relief areas P arranged side by side in the length direction Z of the first wall portion, and the sizes of the two predetermined pressure relief areas P in the length direction Z of the first wall portion are a1 and a2 respectively, and a=a1+a2. Among them, along the length direction Z of the first wall portion, the dividing line of the two predetermined pressure relief areas P can be the center line of the width direction of the second slot section 2213.

[0405] In some embodiments, Fig.23 , Fig.24 As shown, along the thickness direction X of the first wall portion, the maximum groove depth of the first groove 221 is H1, the thickness of the first wall portion 211 is D, and 0.16≤H1 / D<1.

[0406] H1 / D can take any point value among 0.16, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, 0.42, 0.45, 0.48, 0.5, 0.62, 0.65, 0.68, 0.7, 0.72, 0.75, 0.78, 0.8, 0.82, 0.85, 0.88, 0.9, 0.92, 0.95, 0.98, 0.99, etc., or a range of values ​​between any two of them.

[0407] The thickness of the first wall portion 211 may be a distance between the first surface 2111 and the second surface 2112 along the thickness direction X of the first wall portion.

[0408] In this embodiment, 0.16≤H1 / D<1, so that the maximum depth of the first groove 221 accounts for a small proportion of the thickness of the first wall portion 211, and the bursting pressure of the battery cell 20 is not too high, which is beneficial to improving the timeliness of the pressure release of the battery cell 20.

[0409] In some embodiments, 0.4 mm ≤ H1 ≤ 2 mm, 0.8 mm ≤ D ≤ 2.5 mm.

[0410] H1 can be any point value among 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.75mm, 0.8mm, 0.85mm, 0.9mm, 0.95mm, 1mm, 1.05mm, 1.1mm, 1.15mm, 1.2mm, 1.25mm, 1.3mm, 1.35mm, 1.4mm, 1.45mm, 1.5mm, 1.55mm, 1.6mm, 1.65mm, 1.7mm, 1.75mm, 1.8mm, 1.85mm, 1.9mm, 1.95mm, 2mm, etc., or any range value between any two of them.

[0411] D can be any point value among 0.8mm, 0.85mm, 0.9mm, 0.95mm, 1mm, 1.05mm, 1.1mm, 1.15mm, 1.2mm, 1.25mm, 1.3mm, 1.35mm, 1.4mm, 1.45mm, 1.5mm, 1.55mm, 1.6mm, 1.65mm, 1.7mm, 1.75mm, 1.8mm, 1.85mm, 1.9mm, 1.95mm, 2mm, 2.05mm, 2.1mm, 2.15mm, 2.2mm, 2.25mm, 2.3mm, 2.35mm, 2.4mm, 2.45mm, 2.5mm, etc., or a range value between any two of them.

[0412] In this embodiment, 0.4mm≤H1≤2mm, 0.8mm≤D≤2.5mm, so that the maximum depth of the first groove 221 and the thickness of the first wall 211 are within a reasonable range, which has better economy. The thickness of the first wall 211 is 0.8mm-2.5mm, and the thickness of the first wall 211 is greater than or equal to 0.8mm, so that the first wall 211 has sufficient strength, and the thickness of the first wall 211 is less than or equal to 2mm, so that the thickness of the first wall 211 is not too thick. When the volume of the shell 21 is constant, the internal space of the shell 21 can be increased to make more space for the electrode assembly 23. When the thickness of the first wall 211 is controlled within the range of 0.8mm-2.5mm, the maximum groove depth of the first groove 221 is controlled within the range of 0.4mm-2mm, so that the maximum groove depth of the first groove 221 is more matched with the thickness of the first wall 211, so that the first wall 211 has good pressure relief capacity.

[0413] The first groove 221 may be a primary notch groove.

[0414] In some embodiments, the first groove 221 is a multi-level notch groove, which is a multi-level notch groove arranged in sequence from the first surface 2111 to the second surface 2112. In two adjacent notch grooves, the first-level notch groove away from the first surface 2111 is arranged on the bottom surface of the first-level notch groove close to the first surface 2111.

[0415] That is to say, the first groove 221 is a multi-level stepped groove structure arranged along the thickness direction X of the first wall portion, that is, the first groove 221 is a stepped groove structure formed by multiple stamping processes.

[0416] For example, in Figure 22-Figure 27 In the embodiment, the first groove 221 is a three-step groove structure. Of course, in other embodiments, the first groove 221 can also be a two-step groove, a four-step groove, a five-step groove or a six-step groove.

[0417] It should be noted that in the embodiment where the first groove 221 includes a plurality of groove segments, each groove segment is a multi-step groove structure. Figure 22-Figure 27 In the embodiment, the first groove 221 includes a first groove section 2212, a second groove section 2213 and a third groove section 2214, and the corresponding first groove section 2212, the second groove section 2213 and the third groove section 2214 are all multi-step groove structures. Of course, when the first groove 221 is a curve, a loop or a straight line extending along a smooth trajectory, the first groove 221 is a multi-step groove structure. For example, see Figure 3 , Figure 4 As shown, the first groove 221 is an annular structure, and correspondingly, the first groove 221 as a whole is a multi-step groove structure.

[0418] By setting the first groove 221 as a stepped groove structure arranged along the thickness direction of the wall portion, so that the first groove 221 is a groove formed by multiple processing, when adopting this structure to form grooves of the same depth on the first wall portion 211, on the one hand, the depth of the single processing of the notched groove can be reduced, which is beneficial to reducing the manufacturing difficulty and the demand for manufacturing equipment to form grooves of the same depth, so as to reduce the manufacturing cost; and the forming force exerted on the first wall portion 211 during the single processing during the formation of the first groove 221 can be reduced, which is beneficial to reducing the risk of cracks in the first wall portion 211, so as to improve the production quality of the battery cell 20; on the other hand, the flow shape of the bottom wall of the first groove 221 during the formation process can be improved, which is beneficial to the flow of the material generated when the bottom wall of the first groove 221 is formed, so as to improve the consistency of the structure of the multi-stage notched groove.

[0419] In some embodiments, the first groove 221 is a three-level notch groove, and the three-level notch grooves are arranged in sequence from the first surface 2111 to the second surface 2112.

[0420] The three-level notch grooves defining the first groove 221 are respectively the first sub-groove 221a, the second sub-groove 221b and the third sub-groove 221c, which are arranged in sequence from the first surface 2111 to the second surface 2112, the second sub-groove 221b is arranged at the bottom surface of the first sub-groove 221a, and the third sub-groove 221c is arranged at the bottom surface of the second sub-groove 221b.

[0421] For example, Figure 22-Figure 27As shown, in an embodiment where the first groove 221 includes a first groove segment 2212, a second groove segment 2213 and a third groove segment 2214, the first sub-groove 221a includes a first segment 221a1, a second segment 221a2 and a third segment 221a3, the second sub-groove 221b includes a fourth segment 221b1, a fifth segment 221b2 and a sixth segment 221b3, and the third sub-groove 221c includes a seventh segment 221c1, an eighth segment 221c2 and a ninth segment 221c3. The fourth section 221b1 is arranged on the bottom surface of the groove of the first section 221a1, the seventh section 221c1 is arranged on the bottom surface of the groove of the fourth section 221b1, and the first section 221a1, the fourth section 221b1 and the seventh section 221c1 jointly form the first groove section 2212; the fifth section 221b2 is arranged on the bottom surface of the groove of the second section 221a2, the eighth section 221c2 is arranged on the bottom surface of the groove of the fifth section 221b2, the second section 221a2, the fifth section 221b2 and the eighth section 221c2 jointly form the second groove section 2213; the sixth section 221b3 is arranged on the bottom surface of the groove of the third section 221a3, the ninth section 221c3 is arranged on the bottom surface of the groove of the sixth section 221b3, and the third section 221a3, the sixth section 221b3 and the ninth section 221c3 jointly form the third groove section 2214.

[0422] The first groove 221 is a three-level notch groove. When forming grooves of the same depth, it can reduce the depth of the notch groove in a single processing, which is beneficial to reducing the manufacturing difficulty and demand for manufacturing equipment for forming grooves of the same thickness, so as to reduce manufacturing costs. It can also reduce the forming force that the first wall portion 211 is subjected to in a single processing during the formation of the groove bottom wall of the first groove 221, which is beneficial to reducing the risk of cracks in the first wall portion 211, so as to improve the production quality of the battery cell 20. On the other hand, it can improve the flow shape of the groove bottom wall of the first groove 221 during the formation process, which is beneficial to the flow of materials generated when forming the first groove 221, so as to improve the consistency of the structure of the multi-level notch grooves; it also alleviates the problem of increased processing time due to multiple processing required for the formation of the first groove 221.

[0423] In some embodiments, the first wall portion 211 is an integrally formed structure, and the first wall portion 211 and the first weak portion 2211 are formed by an integrally formed process.

[0424] For example, in Fig.10 In the embodiment, the first wall portion 211 is the bottom wall of the housing 212 disposed opposite to the end cap 213 in the thickness direction X of the first wall portion, and the first wall portion 211 is the bottom wall, and the first groove 221 is disposed on the bottom wall. If the first wall portion 211 is the end cap 213, the first wall portion 211 is the end cap 213, so that the first wall portion 211 can close the opening 2121 of the housing 212, and the two electrode terminals 24 are both mounted on the first wall portion 211.

[0425] By configuring the first wall portion 211 as an integrally formed structure, the battery cell 20 adopting such a structure can improve the structural strength of the pressure relief component 22 provided on the first wall portion 211 and can reduce the risk of liquid leakage generated by the first wall portion 211 .

[0426] In some embodiments, the material of the first wall portion 211 includes aluminum alloy.

[0427] It is understandable that in the embodiment where the first wall portion 211 is integrally formed with the first wall portion 211, the material of the first wall portion 211 includes aluminum alloy. If the first wall portion 211 is an end cover 213, the end cover 213 can be made of aluminum alloy; if the first wall portion 211 is a wall portion in the housing 212, the housing 212 can be made of aluminum alloy.

[0428] Aluminum alloy has the characteristics of light weight and good ductility, so it is easier to process the first groove 221 on the first wall portion 211 , which can effectively reduce the difficulty of forming the first wall portion 211 .

[0429] In some embodiments, the aluminum alloy includes the following components in mass percentage: aluminum ≥ 99.6%, copper ≤ 0.05%, iron ≤ 0.35%, magnesium ≤ 0.03%, manganese ≤ 0.03%, silicon ≤ 0.25%, titanium ≤ 0.03%, vanadium ≤ 0.05%, zinc ≤ 0.05%, and other single elements ≤ 0.03%.

[0430] This aluminum alloy belongs to the third series aluminum, and has lower hardness and better forming ability, which reduces the difficulty of processing the first groove 221 , is conducive to improving the processing accuracy of the first groove 221 , and improves the pressure relief consistency of the first wall portion 211 .

[0431] In some embodiments, the aluminum alloy includes the following components in mass percentage: aluminum ≥ 96.7%, 0.05% ≤ copper ≤ 0.2%, iron ≤ 0.7%, manganese ≤ 1.5%, silicon ≤ 0.6%, zinc ≤ 0.1%, other single element components ≤ 0.05%, and the total composition of other elements ≤ 0.15%.

[0432] This aluminum alloy belongs to the fifth series aluminum. The first wall portion 211 made of this aluminum alloy has higher hardness, greater strength, and good anti-destruction ability.

[0433] In some embodiments, the battery cell 20 includes an electrode assembly 23 , which is accommodated in the housing 21 , and the first wall portion 211 supports the electrode assembly 23 .

[0434] The battery cell 20 may include one or more electrode assemblies 23. In an embodiment where the battery cell 20 includes a plurality of electrode assemblies 23, the plurality of electrode assemblies 23 are stacked in a thickness direction thereof.

[0435] The first wall portion 211 supports the electrode assembly 23 . It can be understood that the first wall portion 211 bears the weight of the electrode assembly 23 .

[0436] The first wall portion 211 supports the electrode assembly 23 . The first wall portion 211 is disposed on the first wall portion 211 , which can reduce the risk of substances released when the battery cell 20 is depressurized acting on other electrical connection structures, thereby reducing the risk of causing other reliability problems.

[0437] In some embodiments, the battery cell 20 includes an electrode terminal 24 , and the electrode terminal 24 is disposed on other walls of the housing 21 except the first wall 211 .

[0438] The electrode terminal 24 is disposed on other walls of the housing 21 except the first wall portion 211 , that is, the electrode terminal 24 and the first wall portion 211 are disposed on different wall portions of the housing 21 .

[0439] The electrode terminal 24 is arranged on other walls of the shell 21 except the first wall portion 211. Therefore, the risk of the substance discharged from the battery cell 20 when the pressure is released acts on the electrode terminal 24 is low, which can reduce the risk of the battery cell 20 short-circuiting due to the substance discharged from the battery cell 20 when the pressure is released and the electrode terminal 24 forming an electrical connection, thereby causing the battery cell 20 to short-circuit and cause thermal runaway of the battery cell 20 again.

[0440] In some embodiments, the electrode terminal 24 is disposed on a wall of the housing 21 opposite to the first wall portion 211 .

[0441] Exemplarily, the shell 212 of the housing 21 has a bottom wall opposite to the opening 2121 , and the end cap 213 covers the opening 2121 , and the end cap 213 is arranged opposite to the bottom wall. The bottom wall is the first wall portion 211 , and the electrode terminal 24 is arranged on the end cap 213 covering the opening 2121 .

[0442] The electrode terminal 24 is arranged on the wall of the shell 21 opposite to the first wall portion 211, so that the distance between the electrode terminal 24 and the first wall portion 211 is farther, which can further reduce the risk of the discharged substance of the battery cell 20 acting on the electrode terminal 24 when the battery cell 20 is depressurized, and further reduce the risk of the battery cell 20 short-circuiting due to the electrical connection formed by the discharged substance and the electrode terminal 24 when the battery cell 20 is depressurized, causing the battery cell 20 to short-circuit again and cause thermal runaway of the battery cell 20.

[0443] In some embodiments, the housing 21 includes a shell 212 and an end cover 213 ; the shell 212 has at least one opening 2121 ; the end cover 213 corresponds to the opening 2121 one by one, the end cover 213 is connected to the shell 212 and closes the opening 2121 ; wherein at least one end cover 213 is a first wall portion 211 .

[0444] The end cover 213 is the first wall portion 211, that is, the first wall portion 211 is disposed on the end cover 213. In the embodiment where the housing 212 has two opposite openings 2121, the housing 21 includes two end covers 213, one of the two end covers 213 may be the first wall, that is, one end cover 213 is provided with the first wall portion 211, or both end covers 213 may be the first wall, that is, both end covers 213 are provided with the first wall portion 211.

[0445] By setting the first wall portion 211 of the shell 21 as the end cover 213 of the shell 21 for closing the opening 2121, the battery cell 20 with this structure is convenient to set the first wall portion 211 on the end cover 213, which is beneficial to reduce the manufacturing difficulty of the battery cell 20 and improve the production efficiency of the battery cell 20.

[0446] It should be noted that the structure of the battery cell 20 is not limited thereto. In some embodiments, the battery cell 20 may also have other structures, for example, Figure 3 and Figure 4 As shown, the housing 21 may include a shell 212 and an end cover 213 . The shell 212 has an interior forming a receiving cavity with an opening 2121 for receiving the electrode assembly 23 . The end cover 213 closes the opening 2121 . The shell 212 includes a first wall portion 211 .

[0447] The shell 212 may include an integrally formed side wall and bottom wall, that is, the shell 212 is manufactured by an integral molding process, such as an integral molding process such as stamping, casting or extrusion molding, that is, the side wall and bottom wall of the shell 212 are an integral structure.

[0448] The housing 212 includes a first wall portion 211, that is, the first wall portion 211 is a wall in the housing 212. Fig.10 In the embodiment, the first wall portion 211 is a bottom wall of the housing 212 disposed opposite to the end cover 213 in the thickness direction X of the first wall portion. Of course, in other embodiments, the first wall portion 211 may also be a side wall of the housing 212.

[0449] By setting the first wall portion 211 of the outer shell 21 as a wall portion of the shell 212, the battery cell 20 adopting this structure can make the area of ​​the outer shell 21 where the first wall portion 211 is set away from the end cover 213, thereby effectively alleviating the stress generated by the connection between the end cover 213 and the shell 212 acting on the first wall portion 211, so as to reduce the impact on the predetermined pressure relief area P of the first wall portion 211 and the corresponding area of ​​the first groove 221, thereby helping to reduce the risk of cracking or reduction in structural strength of the first wall portion 211 under the pulling action of stress, so as to improve the service life and reliability of the battery cell 20.

[0450] It should be noted that the structure of the battery cell 20 can be various. In some embodiments, the shell 212 has two openings 2121 arranged opposite to each other. The outer shell 21 includes two end covers 213, each end cover 213 is connected to the shell 212 and closes an opening 2121. The shell 212 includes a first wall portion 211.

[0451] The housing 212 has an accommodating cavity formed inside, and the two openings 2121 are both connected to the accommodating cavity. The two openings 2121 can be arranged opposite to each other along the thickness direction X of the first wall. In the embodiment where the housing 21 includes two openings 2121 and two end covers 213 , the first wall 211 can also be a wall of the housing 212 .

[0452] The shell 212 of the outer shell 21 has two openings 2121 arranged opposite to each other, and the two end caps 213 respectively close the two openings 2121. The battery cell 20 with such a structure is convenient for assembling the battery cell 20 from both ends of the shell 212, which is conducive to reducing the manufacturing and assembly difficulties of the battery cell 20. The shell 212 includes a first wall portion 211, and the first wall portion 211 is not provided on the end cap 213, which can reduce the risk of the substance released by the battery cell 20 when the pressure is released to act on other structures of the battery 100, thereby further reducing the risk of the battery cell 20 short-circuiting due to the substance released by the battery cell 20 when the pressure is released and the electrode terminal 24 to form an electrical connection, causing the battery cell 20 to short-circuit again and cause thermal runaway of the battery cell 20.

[0453] In the embodiment where the housing 21 includes two openings 2121 and two end covers 213, the two end covers 213 respectively close the two openings 2121, and one of the two end covers 213 is a first wall portion 211. Of course, both end covers 213 may be first wall portions 211, and each first wall portion 211 is provided with a first wall portion 211.

[0454] In some embodiments, the housing 212 has an opening 2121 , and a wall portion of the housing 212 disposed opposite to the opening 2121 is a first wall portion 211 .

[0455] Exemplarily, the wall portion of the shell 212 opposite to the opening 2121 is the bottom wall of the shell 212 , the bottom wall is the first wall portion 211 , the end cover 213 is disposed opposite to the first wall portion 211 , and the electrode terminal 24 is disposed on the end cover 213 .

[0456] The wall portion of the shell 212 that is arranged opposite to the opening 2121 is the first wall portion 211, which can reduce the risk of the substance released from the battery cell 20 when the pressure is released to act on other structures of the battery 100, thereby further reducing the risk of the battery cell 20 short-circuiting due to the substance released from the battery cell 20 when the pressure is released to form an electrical connection with the electrode terminal 24, which may cause the battery cell 20 to short-circuit and cause thermal runaway of the battery cell 20 again.

[0457] In some embodiments, the material of the first wall portion 211 includes steel.

[0458] The steel material can be carbon steel, alloy steel, stainless steel, etc.

[0459] It can be understood that if the first wall portion 211 is an end cover 213 , the end cover 213 may be made of steel; if the first wall portion 211 is a wall portion in the shell 212 , the shell 212 may be made of steel.

[0460] In this embodiment, steel has the characteristic of high strength, and the first wall portion 211 made of steel has better strength. When the bursting pressure of the battery cell 20 is constant, the first wall portion 211 can be made thinner to reduce the volume of the first wall portion 211. The first wall portion 211 is made of steel, and the first wall portion 211 can be made thinner. When the volume of the shell 21 is constant, the volume of the shell 21 can be increased to provide more space for the electrode assembly 23, which is conducive to improving the volume energy density of the battery cell 20.

[0461] In some embodiments, the steel material is carbon steel or stainless steel.

[0462] Carbon steel can be low carbon steel, medium carbon steel or high carbon steel.

[0463] In some embodiments, the material of the first wall portion 211 includes aluminum alloy.

[0464] It can be understood that if the first wall portion 211 is the end cover 213 , the end cover 213 may be made of aluminum alloy; if the first wall portion 211 is the wall portion in the shell 212 , the shell 212 may be made of aluminum alloy.

[0465] Aluminum alloy has the characteristics of light weight and good ductility, and it is easier to process the first groove 221 and the second groove 222 on the first wall portion 211. The first wall portion 211 is made of aluminum alloy, which can effectively reduce the difficulty of forming the first wall portion 211. Since aluminum alloy has good ductility, it is easier to pile materials in the predetermined pressure relief area P when forming the first groove 221.

[0466] In some embodiments, the present application further provides a battery 100 , and the battery 100 includes the battery cell 20 provided in any of the above embodiments.

[0467] Among them, see Figure 2 As shown, the battery 100 may further include a housing 10 , in which the battery cells 20 are accommodated.

[0468] In some embodiments, the box body 10 may include a first box body 11 and a second box body 12 . The first box body 11 and the second box body 12 cover each other, and the first box body 11 and the second box body 12 jointly define an assembly space for accommodating the battery cells 20 .

[0469] Optionally, the second box body 12 can be a hollow structure with one end open, and the first box body 11 can be a plate-like structure. The first box body 11 covers the open side of the second box body 12, so that the first box body 11 and the second box body 12 jointly define an assembly space; the first box body 11 and the second box body 12 can also be hollow structures both with one side open, and the open side of the first box body 11 covers the open side of the second box body 12.

[0470] Of course, the box body 10 formed by the first box body 11 and the second box body 12 can be in various shapes, such as a cylinder or a cuboid. Figure 2 In the embodiment, the box body 10 is a rectangular parallelepiped structure.

[0471] Optionally, the number of battery cells 20 disposed in the box body 10 may be one or more. Figure 2 In the embodiment, a plurality of battery cells 20 are arranged in the box 10 of the battery 100, and the plurality of battery cells 20 can be connected in series, in parallel or in mixed connection. Mixed connection means that the plurality of battery cells 20 are both connected in series and in parallel. The plurality of battery cells 20 can be directly connected in series, in parallel or in mixed connection, and then the whole formed by the plurality of battery cells 20 is accommodated in the box 10; of course, the battery 100 can also be a battery 100 module in the form of a plurality of battery cells 20 connected in series, in parallel or in mixed connection, and then the plurality of battery 100 modules are connected in series, in parallel or in mixed connection to form a whole and accommodated in the box 10.

[0472] The battery 100 may further include other structures. For example, the battery 100 may further include a busbar component, which connects the plurality of battery cells 20 to achieve electrical connection between the plurality of battery cells 20 .

[0473] It should be noted that, in some embodiments, the battery 100 may not be provided with a box 10, and the battery 100 includes a plurality of battery cells 20, and the battery 100 composed of a plurality of battery cells 20 can be directly assembled on an electrical device to provide electrical energy to the electrical device through the plurality of battery cells 20. In other words, the box 10 can be used as a part of the electrical device. Taking the vehicle 1000 as an example of the electrical device, the box 10 can be used as a part of the chassis structure of the vehicle 1000, for example, a part of the box 10 can become at least a part of the floor of the vehicle 1000, or a part of the box 10 can become at least a part of the crossbeam and longitudinal beam of the vehicle 1000.

[0474] In some embodiments, the present application further provides an electrical device, which includes the battery cell 20 provided in any of the above embodiments.

[0475] The battery cell 20 is used to provide electric energy to an electric device, wherein the electric device may be any of the above-mentioned devices or systems using the battery cell 20 .

[0476] The embodiment of the present application provides a battery cell 20, and the battery cell 20 includes the present application provides a battery cell 20, and the battery cell 20 includes a shell 21 and an electrode assembly 23. The shell 21 has a first wall portion 211, and the shell 21 includes a shell 212 and an end cover 213. The shell 212 has an accommodating cavity with an opening 2121 formed inside, and the electrode assembly 23 is accommodated in the accommodating cavity. The end cover 213 closes the opening 2121, and the end cover 213 is the first wall portion 211.

[0477] Along the thickness direction X of the first wall portion, the first wall portion 211 has a first surface 2111 and a second surface 2112 that are arranged opposite to each other. The first surface 2111 is located on the side of the first wall portion 211 that is away from the interior of the housing 21, and the second surface 2112 is located on the side of the first wall portion 211 that faces the interior of the housing 21. The first wall portion 211 is provided with a first groove 221, which is a three-level notch groove that is arranged in sequence from the first surface 2111 to the second surface 2112. The first groove 221 defines two predetermined pressure relief areas P, and the first wall portion 211 is configured to be able to be split along at least a portion of the first groove 221 when the battery cell 20 is depressurized. The second surface 2112 is provided with a second groove 222. Along the thickness direction X of the first wall portion, the thickness of the bottom wall of the second groove 222 is greater than the thickness of the bottom wall of the first groove 221. The second groove 222 is configured to guide the predetermined pressure relief area P to flip when the first groove 221 is cracked to release the internal pressure of the battery cell 20.

[0478] The first groove 221 includes a first groove section 2212, a second groove section 2213, a third groove section 2214 and a fourth groove section 2215. The first groove section 2212, the second groove section 2213, the third groove section 2214 and the fourth groove section 2215 respectively form a first weak section 2211a. Along the length direction Z of the first wall portion, the first groove section 2212 and the third groove section 2214 are arranged relatively spaced apart. The first groove section 2212 and the third groove section 2214 both extend in a straight line along the width direction Y of the first wall portion. The third groove section 2214 extends in a straight line along the length direction Z of the first wall portion. The second groove section 2213 connects the first groove section 2212 and the third groove section 2214. The connection position of the second groove section 2213 and the first groove section 2212 is located between the two ends of the first groove section 2212, and the connection position of the second groove section 2213 and the third groove section 2214 is located between the two ends of the third groove section 2214. The first slot section 2212, the second slot section 2213 and the third slot section 2214 form an H-shaped first groove 221. Along the width direction Y of the first wall portion, two sides of the second slot section 2213 form a predetermined pressure relief area P. The first groove 221 defines two predetermined pressure relief areas P. The fourth slot section 2215 is located between the first slot section 2212 and the third slot section 2214, and the fourth slot section 2215 intersects with the second slot section 2213.

[0479] The sum of the areas S1 of all the predetermined pressure relief zones P is 0.03 to 0.3 times the area S2 of the first surface 2111, 500 mm 2 ≤S1≤1300mm 2 ; 5000mm 2 ≤S2≤8500mm 2 .

[0480] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A battery cell, characterized in that: Comprising: A housing including a first wall portion, in the thickness direction of the first wall portion, the first wall portion having a first surface and a second surface disposed opposite to each other; The first wall portion is provided with a first groove, the first groove recessed from the first surface towards the direction close to the second surface, the first groove defining at least one predetermined pressure relief area, and the first wall portion is configured to be able to crack along at least part of the first groove when the battery cell relieves pressure; Wherein, the sum of the areas S1 of all the predetermined pressure relief areas is 0.03 times to 0.3 times of the area S2 of the first surface.

2. The battery cell according to claim 1, characterized in that: 500mm 2 ≤S1≤1300mm 2 。 3. The battery cell according to claim 1, characterized in that: 5000mm 2 ≤S2≤8500mm 2 。 4. The battery cell according to claim 1, characterized in that: The first wall portion is a rectangular wall portion; Along the width direction of the first wall portion, the size of the first surface is c; along the length direction of the first wall portion, the size of the first surface is d, and S2 = c * d; Wherein, 55mm ≤ c ≤ 85mm; 100mm ≤ d ≤ 260mm.

5. The battery cell according to claim 1, characterized in that: The first wall portion is a rectangular wall portion; Along the length direction of the first wall portion, at least one predetermined pressure relief area is formed on the first wall portion, and the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is 0.1 times to 0.5 times of the size d of the first surface along the length direction of the first wall portion.

6. The battery cell according to claim 1, characterized in that: The first wall portion is a rectangular wall portion; Along the width direction of the first wall portion, the first groove defines at least one predetermined pressure relief area, and the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is 0.3 times to 0.7 times of the size c of the first surface along the width direction of the first wall portion.

7. The battery cell according to claim 1, characterized in that: The first wall portion is a rectangular wall portion; Along the length direction of the first wall portion, at least one predetermined pressure relief area is formed on the first wall portion, and the sum of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is a, and 26mm ≤ a ≤ 50mm.

8. The battery cell according to claim 1, characterized in that: The first wall portion is a rectangular wall portion; Along the width direction of the first wall portion, the first groove defines at least one predetermined pressure relief area, and the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion is 18mm ≤ b ≤ 62mm.

9. The battery cell according to claim 1, characterized in that: The first wall portion is a rectangular wall portion; Along the length direction of the first wall portion, at least one predetermined pressure relief area is formed on the first wall portion, and the sum of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is a; Along the width direction of the first wall portion, the first groove defines at least one predetermined pressure relief area, and the sum of the sizes of all the predetermined pressure relief areas arranged is b, and the size of the first surface is c; When 10mm ≤ c ≤ 40mm, the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is 2 times to 3 times of the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion; When 40mm < c ≤ 60mm, the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is 1 times to 2 times of the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion; When 60 mm < c, the sum a of the sizes of all the predetermined pressure relief areas arranged along the length direction of the first wall portion is 0.4 times to 1 time the sum b of the sizes of all the predetermined pressure relief areas arranged along the width direction of the first wall portion.

10. The battery cell according to claim 1, characterized in that: The first wall portion further includes a second groove configured to guide the opening of the predetermined pressure relief area.

11. The battery cell according to claim 10, characterized in that: The second groove is recessed from the second surface towards the direction close to the first surface.

12. The battery cell according to claim 10, characterized in that: The first surface is the surface of the first wall portion facing away from the interior of the housing, and the second surface is the surface of the first wall portion facing the interior of the housing.

13. The battery cell according to claim 10, characterized in that: The first groove and the second groove do not contact each other.

14. The battery cell according to claim 1, characterized in that: The first groove includes a first groove segment and a second groove segment, the first groove segment and the second groove segment are connected, and the first groove segment and the second groove segment jointly define at least one of the predetermined pressure relief areas.

15. The battery cell according to claim 14, characterized in that: The first groove further includes a third groove segment, the first groove segment and the third groove segment are arranged opposite to each other, the second groove segment connects the first groove segment and the third groove segment, and the first groove segment, the second groove segment and the third groove segment jointly define at least one of the predetermined pressure relief areas.

16. The battery cell according to claim 15, characterized in that: The position where the second groove segment is connected to the first groove segment deviates from both ends of the first groove segment, and the position where the second groove segment is connected to the third groove segment deviates from both ends of the third groove segment.

17. The battery cell according to claim 15, characterized in that: The first groove defines two of the predetermined pressure relief areas, and the two predetermined pressure relief areas are respectively located on both sides of the second groove segment; The first wall portion further includes a second groove configured to guide the opening of the predetermined pressure relief area, at least one of the second grooves is correspondingly arranged for each of the predetermined pressure relief areas, and the first groove is located between the two second grooves.

18. The battery cell according to claim 17, characterized in that: The second groove segment and the second groove are arranged opposite to each other along a first direction, and along the first direction, both the first groove segment and the third groove segment are spaced from the second groove.

19. The battery cell according to claim 18, characterized in that: The first wall portion is a rectangular wall portion, and the first direction is parallel to the width direction of the first wall portion.

20. The battery cell according to claim 1, characterized in that: The first groove is a multi-stage scoring groove, and the multi-stage scoring grooves are sequentially arranged along the direction from the first surface to the second surface. Among two adjacent stages of the scoring grooves, the scoring groove of the stage farther from the first surface is arranged on the groove bottom surface of the scoring groove of the stage closer to the first surface.

21. The battery cell according to claim 20, characterized in that: The first groove is a three-stage scoring groove, and the three-stage scoring grooves are sequentially arranged along the direction from the first surface to the second surface.

22. The battery cell according to any one of claims 1 to 21, characterized in that: The battery cell includes an electrode assembly, the electrode assembly is accommodated in the housing, and the first wall portion supports the electrode assembly.

23. The battery cell according to claim 1, characterized in that: The battery cell includes electrode terminals, and the electrode terminals are arranged on other wall portions of the housing except the first wall portion.

24. The battery cell according to claim 23, characterized in that: The electrode terminals are arranged on the wall of the housing opposite to the first wall portion.

25. The battery cell according to claim 1, characterized in that: The housing includes: A housing body having at least one opening; End caps corresponding to the openings one by one, the end caps are connected to the housing body and close the openings; Wherein, at least one of the end caps is the first wall portion, or the housing body includes the first wall portion.

26. The battery cell according to claim 25, characterized in that: The shell has two openings arranged opposite to each other; the outer shell includes two end covers, each end cover is connected to the shell and closes one opening; the shell includes the first wall portion.

27. The battery cell according to claim 25, characterized in that: The shell has an opening, and a wall portion of the shell disposed opposite to the opening is the first wall portion.

28. The battery cell according to claim 1, characterized in that: The material of the first wall portion includes steel.

29. The battery cell according to claim 28, characterized in that: The steel material is carbon steel or stainless steel.

30. The battery cell according to claim 1, characterized in that The material of the first wall portion includes aluminum alloy.

31. A battery, characterized in that: Comprising a battery cell according to any one of claims 1-30.

32. An electrical equipment, characterized in that: Comprising a battery cell according to any one of claims 1-30.

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