Single battery, battery pack and electric equipment

Abstract

The utility model discloses a single battery, a battery pack and electric equipment, and belongs to the technical field of batteries. According to the single battery, a first nick is formed in the middle of a base body, and the first nick is small in rigidity, large in pressure and easier to burst; when the air pressure exceeds the preset pressure, the base body explodes along the first nick, the base body exploding from the middle to the periphery pierces the explosion-proof valve patch and extrudes the explosion-proof valve patch, rapid discharge of gas in the battery cell is achieved, meanwhile, the first nick bends and extends from the first end to the second end, so that the extension path of the first nick is lengthened, and the gas in the battery cell is discharged rapidly. And the area when the base body is exploded can be enlarged, and the gas exhaust speed is increased.

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and specifically relates to a single cell, a battery pack and an electrical device. Background Art

[0002] Batteries are usually equipped with explosion-proof valves to release high-temperature gas in time when the battery thermally runs away. The thickness of the explosion-proof valve is usually smaller than that of the battery shell. There are also notches on the explosion-proof valve. When the battery cell thermally runs away, the high-pressure gas will cause the explosion-proof valve to crack at the notch, and the valve will be opened in time to release pressure, thereby preventing the battery from exploding due to high pressure.

[0003] The existing explosion-proof valve opens from the side, and a layer of explosion-proof valve patch is adhered to the outside of the explosion-proof valve. When the thermal runaway pressure is relatively small, the explosion-proof valve patch will increase the resistance to opening the explosion-proof valve, which will affect the timely discharge of gas inside the battery cell to a certain extent. Utility Model Content

[0004] Purpose of the utility model: The embodiment of the present application provides a single cell battery, aiming to overcome the technical problem that the current explosion-proof valve opens from the side and affects the timely discharge of gas inside the battery cell.

[0005] Technical solution: The single cell described in the embodiment of the present application comprises: an explosion-proof valve having a first direction and a second direction, the explosion-proof valve comprising a base and a connecting portion surrounding and connected to the outer periphery of the base;

[0006] The base is provided with a first notch, the first notch has a first end and a second end opposite to each other along a first direction, the base has a geometric center I, the geometric center I is located between the first end and the second end, and the first notch extends in a curved manner from the first end to the second end;

[0007] The connecting portion includes a first section, a second section, a third section and a fourth section connected end to end, the first section and the third section are respectively arranged on both sides of the first notch in the first direction, the second section and the fourth section are respectively arranged on both sides of the first notch in the second direction, and the first direction and the second direction intersect;

[0008] In the second direction, the first notch and the second segment have a minimum first dimension L1 mm, and the first notch and the fourth segment have a minimum second dimension L2 mm, satisfying: 0.14≤L1 / L2≤6.9.

[0009] In some embodiments, a third dimension L3 mm exists between the first notch and the first segment, and a fourth dimension L4 mm exists between the first notch and the third segment, satisfying: 0.07≤L3 / L4≤13.3.

[0010] In some embodiments, the first notch includes a plurality of notch units arranged in a first direction. Adjacent two notch units are connected end to end. Each notch unit extends along an arc track, and the convex directions of adjacent two notch units are opposite.

[0011] In some embodiments, the radius of the notch unit is D mm, satisfying: 3.17 ≤ D ≤ 6.33.

[0012] In some embodiments, a second notch is further provided. The second notch is disposed on the base body. The second notch is located between the connecting portion and the first notch and surrounds at least a part of the first notch.

[0013] In some embodiments, the second notch is communicated with the first notch.

[0014] In some embodiments, the explosion-proof valve is provided with a plurality of the second notches, and the plurality of second notches are arranged at intervals around the first notch.

[0015] In some embodiments, the second notch is arc-shaped. The first end is communicated with one second notch, and the second end is communicated with another second notch.

[0016] Correspondingly, a battery pack according to an embodiment of the present application includes the above-mentioned single cell.

[0017] Correspondingly, an electrical device according to an embodiment of the present application includes the above-mentioned single cell, or the above-mentioned battery pack.

[0018] Beneficial effects: The geometric center I is located between the first end and the second end of the first notch, which limits the overall shape or distribution trend of the first notch in the first direction. The ratio range of L1 and L2 limits the relative position of the first notch in the second direction with respect to the geometric center I, so that the first notch is close to the geometric center I. When the air pressure generated inside the single cell continues to be discharged outwards, the base body will burst along the first notch. The base body that bursts from the middle to the surrounding will pierce the explosion-proof valve patch and push it open, realizing the rapid discharge of the gas inside the battery core and reducing the impact force on other parts above the explosion-proof valve when the gas is discharged.

[0019] The battery pack of the embodiment of the present application includes the above-mentioned single cell, so it can have all the technical features and beneficial effects of the above-mentioned single cell.

[0020] The electrical device of the embodiment of the present application includes the above-mentioned single cell or the above-mentioned battery pack, so it can have all the technical features and technical effects of the above-mentioned single cell or battery pack. Description of the Drawings

[0021] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those skilled in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0022] Figure 1 Schematic diagram of the three-dimensional structure of the single cell provided by the embodiment of the present application;

[0023] Figure 2 Explosion diagram of the single cell provided by the embodiment of the present application;

[0024] Figure 3 Schematic diagram of the structure of the housing provided by the embodiment of the present application;

[0025] Figure 4 Front view of the explosion-proof valve provided by the embodiment of the present application;

[0026] Figure 5 Schematic diagram of the structure of the first notch provided by the embodiment of the present application;

[0027] Figure 6 Schematic diagram of the structure of the notch unit provided by the embodiment of the present application;

[0028] Figure 7 Schematic diagram of the center line provided by the embodiment of the present application;

[0029] Figure 8 Schematic diagram of the combined structure of the first notch and the second notch provided by the embodiment of the present application;

[0030] Figure 9 Schematic diagram of the combined structure of the first notch and multiple second notches provided by the embodiment of the present application.

[0031] Reference numerals: 1, housing; 11, accommodation cavity; 12, open end; 2, top cover assembly; 21, pressure relief hole; 22, terminal post; 3, explosion-proof valve; 31, base body; 311, first notch; 3110, notch unit; 3111, first end; 3112, second end; 3113, first arc segment; 3114, second straight segment; 3115, third arc segment; 3116, fourth straight segment; 3117, first side line; 3118, second side line; 312, second notch; 32, connecting portion; 321, first segment; 322, second segment; 323, third segment; 324, fourth segment; 4, winding core. Detailed implementation manners

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. 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 skilled in the art without creative efforts belong to the scope of protection of the present application.

[0033] In the description of the present application, "a plurality of" means two or more, and at least one means one, two or more, unless otherwise specifically defined. Isometric scaling means changing the size of an object according to the same scale factor and keeping its shape and ratio unchanged. It maintains the relative relationship between them by scaling the width and height of the object simultaneously.

[0034] For example, assume that the width of a rectangle is 10 cm and the height is 5 cm. If isometric scaling is performed with a scale factor of 2, both the width and height of the rectangle will be multiplied by 2, becoming 20 cm wide and 10 cm high. The shape and ratio of the rectangle remain unchanged before and after scaling.

[0035] The geometric center describes the most central position of an object with a certain symmetry. These objects may include circles, spheres, parallelograms, etc. For example, in a circle, the geometric center is the center of the circle; in a sphere, the geometric center is the center of the sphere; in a parallelogram, the geometric center usually refers to the intersection of the two diagonals.

[0036] It should also be noted that in the accompanying drawings of the embodiments of the present application, the arrow marked with x represents the first direction x of the explosion-proof valve, and the arrow marked with y represents the second direction y of the explosion-proof valve. The introduction of the first direction x and the second direction y is to more clearly describe the structure and relative position relationship of each component in the explosion-proof valve. In actual applications, the first direction x and the second direction y may change according to the different placement methods of the explosion-proof valve.

[0037] In the related art, an explosion-proof valve protection patch is attached to the side of the explosion-proof valve facing away from the battery cell, and a sealed space is formed between the explosion-proof valve and the explosion-proof valve protection patch, thereby preventing the residual electrolyte on the top cover assembly from flowing into the upper surface of the explosion-proof film during liquid injection, and at the same time preventing foreign objects from piercing the explosion-proof film.

[0038] The single battery in the embodiments of the present application can be a square shell battery or a cylindrical battery.

[0039] Please also combine Figure 1 、 Figure 2 and Figure 3, the single cell of the embodiment of the present application includes a housing 1, a wound core 4, a top cover assembly 2 and an explosion-proof valve 3. The housing 1 has a receiving cavity 11 and an opening 12 communicating with the receiving cavity 11; the wound core 4 is formed by laminating or winding electrode sheets and separators, and the wound core 4 is accommodated in the receiving cavity 11; the top cover assembly 2 is connected to the housing 1 and seals the opening 12 to close the opening 12; two pole columns 22 are provided on the top cover assembly 2, one end of each pole column 22 is connected to the wound core 4, and the other end is used for connecting to an external circuit.

[0040] A pressure relief hole 21 communicating with the receiving cavity 11 is provided on the top cover assembly 2. The explosion-proof valve 3 is connected to the top cover assembly 2 and seals the pressure relief hole 21. When the air pressure generated inside the battery cell exceeds the preset pressure, the explosion-proof valve 3 breaks open, and the gas inside the battery cell is discharged from the pressure relief hole 21 to achieve pressure relief.

[0041] Please refer to Figure 4 , in some embodiments, the explosion-proof valve 3 has a first direction and a second direction, and the first direction and the second direction intersect. The explosion-proof valve 3 includes a base body 31 and a connecting portion 32 connected around the outer periphery of the base body 31. The base body 31 has a geometric center I. A first notch 311 is provided on the base body 31. The opening of the first notch 311 faces away from the receiving cavity 11. The first notch 311 has a first end 3111 and a second end 3112 opposite to each other in the first direction, and the geometric center I is located between the first end 3111 and the second end 3112. The first notch 311 extends curvedly from the first end 3111 to the second end 3112.

[0042] Please refer to Figure 2 and Figure 4 , the connecting portion 32 is connected to the side of the top cover assembly 2 facing the wound core 4 and is arranged around the pressure relief hole 21 to form an annular structure. The connecting portion 32 blocks at least a part of the pressure relief hole 21, and the connecting portion 32 and the base body 31 jointly seal the pressure relief hole 21.

[0043] Please refer to Figure 4 , the connecting portion 32 includes a first section 321, a second section 322, a third section 323 and a fourth section 324 connected end to end. The first section 321 and the third section 323 are respectively arranged on both sides of the first notch 311 in the first direction, and the second section 322 and the fourth section 324 are respectively arranged on both sides of the first notch 311 in the second direction.

[0044] In the second direction, the minimum first dimension between the first notch 311 and the second section 322 is L1mm, and the minimum second dimension between the first notch 311 and the fourth section 324 is L2mm, satisfying: 0.14 ≤ L1 / L2 ≤ 6.9.

[0045] Please refer to Figure 4 and Figure 5, the outer periphery of the base body 31 has a first arc segment 3113, a second straight segment 3114, a third arc segment 3115, and a fourth straight segment 3116 that are connected end to end. The first arc segment 3113 and the third arc segment 3115 are spaced apart along the first direction. The second straight segment 3114 and the fourth straight segment 3116 are arranged at intervals along the second direction and both extend along the first direction. The inner diameters of the first arc segment 3113 and the third arc segment 3115 are equal, and the lengths of the second straight segment 3114 and the fourth straight segment 3116 are equal. The midpoint of the connection line between the centers of the first arc segment 3113 and the third arc segment 3115 is the geometric center of the base body 31, marked as I in the attached drawing.

[0046] The first end 3111 and the second end 3112 of the first notch 311 are distributed on both sides of the geometric center I, that is, the geometric center I is located inside the first notch 311, or the bending extension path of the first notch 311 passes through the geometric center I, so that the position of the first notch 311 is close to the geometric center I for rapid bursting during pressure relief.

[0047] The ratio of L1 / L2 can be any value among 0.14, 0.56, 1, 4, 6.9 or the range value between any two values. In the range of 0.14 to 1, the smaller the ratio of L1 / L2, the more the first notch 311 gradually shifts towards the second segment 322; in the range of 1 to 6.9, the larger the ratio of L1 / L2, the more the first notch 311 gradually shifts towards the fourth segment 324. The ratio of L1 / L2 defines the distributable interval of the first notch 311 in the second direction, increasing the setting range of the first notch 311 on the basis of ensuring the bursting effect of the first notch 311.

[0048] The minimum first dimension L1mm is the minimum distance between the first notch 311 and the second segment 322, and the minimum second dimension L2mm is the minimum distance between the first notch 311 and the fourth segment 324. Since the first notch 311 bends and extends, the minimum distance means measuring the distances between the second segment 322 and the fourth segment 324 and the parts with the largest fluctuation amplitude of the first notch 311 respectively, avoiding the situation where the first notch 311 extends beyond the base body 31.

[0049] During measurement, the measuring tool can be used to select the two points on the second segment 322 that are closest to the first notch 311, measure the distance between the two points to obtain L1; select the two points on the fourth segment 324 that are closest to the first notch 311, and measure to obtain L2. The measuring tool can be a vernier caliper, a digital caliper, a ruler, etc.

[0050] The first end 3111 and the second end 3112 are distributed on both sides of the geometric center I, surrounding the geometric center I inside the first notch 311, such that the position of the first notch 311 in the first direction is close to the geometric center I. The first dimension L1 and the second dimension L2 further define the relative position of the first notch 311 in the second direction, such that the first notch 311 is within a certain range of the geometric center I.

[0051] Since the first notch 311 is arranged close to the geometric center I, the pressure it receives is greater than that received at a position deviated from the geometric center I, and it is also more likely to burst. When the internal pressure of the battery cell exceeds the set pressure, the matrix 31 bursts from the middle to the surroundings. Under this bursting form, the acting force of the matrix 31 on the patch is relatively concentrated, and the patch can be quickly pushed open to allow the high-pressure gas to escape, achieving the purpose of protecting the battery safely. At the same time, the first notch 311 bends and extends, making the extension path of the first notch 311 longer, which can expand the area when the matrix 31 bursts and accelerate the gas discharge speed.

[0052] Please refer to Figure 4 , in some embodiments, in the first direction, there is a third dimension L3 mm between the first notch 311 and the first section 321, and a fourth dimension L4 mm between the first notch 311 and the third section 323, satisfying: 0.07 ≤ L3 / L4 ≤ 13.3. The ratio of L3 / L4 defines the distribution interval of the first notch 311 in the first direction, increasing the range of arrangement of the first notch 311 on the matrix 31 while ensuring the bursting effect of the first notch 311.

[0053] When measuring the third dimension L3, select the two closest points between the first end 3111 and the first section 321 for measurement. When measuring the fourth dimension L4, select the two closest points between the second end 3112 and the third section 323 for measurement; the measuring tool can be a vernier caliper, a digital caliper, a ruler, etc.

[0054] The ratio of L3 / L4 can be any value of 0.07, 0.39, 0.84, 1, 1.18, 3.0, 13.3 or a range value between any two values. In the range of 0.07 to 1, the third dimension L3 is less than the fourth dimension L4, and the smaller the ratio of L3 / L4, the more the first notch 311 deviates towards the first section 321; when the ratio of L3 / L4 is 1, the third dimension L3 is equal to the fourth dimension L4, indicating that the first notch 311 is in the central position of the matrix 31 in the first direction; in the range of 1 to 13.30, the third dimension L3 is greater than the fourth dimension L4, and the larger the ratio of L3 / L4, the more the first notch 311 deviates towards the third section 323.

[0055] Next, multiple embodiments and comparative examples are provided to illustrate the effect of the explosion-proof valve 3 of the present application. The influence of the ratio of L1 / L2 and the ratio of L3 / L4 on the opening of the explosion-proof valve 3 can be determined by the bursting pressure. The determination criterion is: when the bursting pressure is between 0.97 MPa and 1.06 MPa, it is qualified; when the bursting pressure is less than 0.97 MPa or greater than 1.06 MPa, it is unqualified. The test method for the bursting pressure of the explosion-proof valve 3 is as follows: Use a battery explosion and flipping integrated machine, design and process corresponding upper and lower explosion-proof dies according to the corresponding cell model of the battery; turn on the "power" button of the device, boot the computer, turn on the "air source" button, and then click to calibrate the pressure for calibration; clamp the upper and lower dies of this model on the device, place the top cover on the lower die, click the "start" button to conduct the test. After the explosion-proof valve on the top cover explodes, the bursting pressure will be displayed on the device. Record the measured data, remove the top cover and the upper and lower dies, and the test is completed. The test results of the embodiments and comparative examples are as follows in the table:

[0056]

[0057] As shown in the above table, according to Embodiments 1 to 12, the ratio of L1 / L2 is within 0.14 to 6.9, and the bursting pressure of the explosion-proof valve 3 is qualified. When the ratio of L1 / L2 is less than 0.14 or greater than 6.9, the bursting pressure of the explosion-proof valve 3 is unqualified; according to Embodiments 6 to 14, based on the ratio of L1 / L2 being 1, that is, the first notch 311 is at the geometric center I in the second direction. If the ratio of L3 / L4 is within 0.07 to 13.3, the bursting pressure of the explosion-proof valve 3 is within the qualified range. If the ratio of L3 / L4 is less than 0.07 or greater than 13.3, the bursting pressure of the explosion-proof valve 3 is unqualified.

[0058] Please also combine Figure 6 and Figure 7 , in some embodiments, the first notch 311 includes a plurality of notch units 3110 arranged along the first direction. Each notch unit 3110 extends along an arc trajectory. Adjacent notch units 3110 are connected end to end, and the convex directions of adjacent notch units 3110 in the second direction are opposite. For example, among adjacent notch units 3110, one protrudes in the direction where the second straight segment 3114 is located, while the other protrudes in the direction where the fourth straight segment 3116 is located. This makes the trajectories of adjacent notch units 3110 transition smoothly. During the thermal runaway process, when the air pressure generated inside the single battery breaks through the notch of the explosion-proof valve, it is conducive to quickly cracking along the direction of the notch to effectively exhaust gas.

[0059] Compared with the straight notch, the arc-shaped first notch 311 is relatively smooth, which is conducive to reducing stress concentration, can disperse the external force on the material around the first notch 311, and reduce the possibility of cracks occurring in the first notch 311.

[0060] In some other embodiments, the first notch 311 may also be S-shaped or wavy. Whether it is arc-shaped, S-shaped or wavy, the main point is to reflect that the first notch 311 is continuous and curvedly extended.

[0061] Please also combine Figure 6 and Figure 7 , in some embodiments, the radius of the notch unit 3110 is D mm, satisfying: 3.17 ≤ D ≤ 6.33.

[0062] The first notch 311 includes a first side line 3117 and a second side line 3118 that are oppositely arranged in the second direction. The first side line 3117 and the second side line 3118 have the same shape. The first notch 311 is formed by connecting a plurality of notch units 3110. Therefore, the first side line 3117 or the second side line 3118 can be divided into multiple segments corresponding to the notch units 3110. Each segment of the first side line 3117 or the second side line 3118 forms a center line at equal intervals, that is, the distance between the center line and the first side line 3117 and the second side line 3118 is the same, and the center line is arc-shaped, which is represented by M in the drawings.

[0063] When the size of the base body 31 remains unchanged and the first notch 311 undergoes equi-ratio scaling, the diameter D mm of the center line M will also change synchronously. Therefore, the change in the diameter when the first notch 311 undergoes equi-ratio scaling is represented by the diameter of the center line M.

[0064] The value of D can be any value of 3.17, 4.25, 5.30, 6.33 or the range value between any two values. When the diameter of the center line is larger, the coverage area of the first notch 311 on the base body 31 increases correspondingly, which can increase the bursting area of the base body 31. On the contrary, the bursting area of the base body 31 decreases correspondingly.

[0065] Please refer to Figure 8 , in some embodiments, the explosion-proof valve 3 is further provided with a second notch 312. The second notch 312 is arranged on the base body 31. The second notch 312 is located between the connecting portion 32 and the first notch 311 and is arranged around at least part of the outer periphery of the first notch 311. The opening of the second notch 312 faces away from the accommodation cavity 11 and has the same orientation as the opening of the first notch 311, which is beneficial for blasting.

[0066] The second notch 312 increases the number of notches on the explosion-proof valve 3, so that after the valve is opened, the area where the base body 31 can burst increases, which is beneficial for accelerating the pressure relief speed. The second notch 312 is arranged around the first notch 311. Compared with extending in a single direction, the surrounding arrangement will extend the path of the second notch 312 and make the second notch 312 relatively smooth, which is beneficial for reducing stress concentration and expanding the bursting area of the base body 31.

[0067] Please refer to Figure 8 , in some embodiments, the second notch 312 communicates with the first notch 311. After being connected, the first notch 311 and the second notch 312 can transmit the received pressure, accelerating the bursting speed; since the first notch 311 is located at the geometric center I, the pressure it receives is greater and it is easier to burst. The bursting first notch 311 will quickly spread to the second notch 312, accelerating the pressure relief speed.

[0068] Please refer to Figure 9 , in some embodiments, the explosion-proof valve 3 is provided with a plurality of second notches 312. The plurality of second notches 312 are arranged at intervals around the first notch 311, and each second notch 312 communicates with the first notch 311.

[0069] The plurality of second notches 312 further increase the number of notches on the explosion-proof valve 3, increasing the valve opening area of the base body 31, which is beneficial to reducing the time required for pressure relief.

[0070] In the above embodiments, the second notch 312 is arc-shaped and the number is two. The first end 3111 of the first notch 311 communicates with one second notch 312, and the second end 3112 communicates with the other second notch 312.

[0071] When the explosion-proof valve 3 opens, the first notch 311 cracks and spreads to the second notches 312 on both sides, causing the base body 31 to burst from the middle to the periphery. The bursting base body 31 stabs the patch and pushes the patch outwards, realizing the discharge of the gas inside the housing 1.

[0072] In some other embodiments, two second notches 312 are provided and are spaced apart along the first direction. The first notch 311 is located between the two second notches 312, and the first notch 311 and the second notch 312 are independent of each other, forming a structural design of multiple independent notches. When the first notch 311 or the second notch 312 cracks or is damaged, the other notch can still maintain the integrity of the explosion-proof valve 3, which is beneficial to improving the reliability and safety of the explosion-proof valve 3.

[0073] Correspondingly, a battery pack provided by an embodiment of the present application includes the single battery of the above embodiment. Therefore, this battery pack can have all the technical features and beneficial effects of the above single battery, which will not be elaborated here.

[0074] Correspondingly, an electrical device provided by an embodiment of the present application can be various types of devices such as new energy vehicles, computers, energy storage power supply devices, etc. It can be understood that this electrical device includes the single battery of the above embodiment, or includes the battery pack of the above embodiment, and thus can have all the technical features and technical effects of the above single battery or battery pack, which will not be elaborated here.

[0075] The description of the above embodiments is only used to help understand the technical solutions and their core ideas of the present application. Those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A single cell battery, characterized in that: include: An explosion-proof valve (3) having a first direction and a second direction, the explosion-proof valve (3) comprising a base (31) and a connecting portion (32) connected to the outer periphery of the base (31); The base (31) is provided with a first notch (311), the first notch (311) having a first end (3111) and a second end (3112) opposite to each other along a first direction, the base (31) having a geometric center I, the geometric center I being located between the first end (3111) and the second end (3112), and the first notch (311) extending in a curved manner from the first end (3111) to the second end (3112); The connecting portion (32) comprises a first section (321), a second section (322), a third section (323) and a fourth section (324) connected end to end, the first section (321) and the third section (323) are respectively arranged on both sides of the first notch (311) in the first direction, the second section (322) and the fourth section (324) are respectively arranged on both sides of the first notch (311) in the second direction, and the first direction and the second direction intersect; In the second direction, the first notch (311) and the second section (322) have a minimum first dimension L1 mm, and the first notch (311) and the fourth section (324) have a minimum second dimension L2 mm, satisfying: 0.14≤L1 / L2≤6.

9.

2. The single cell according to claim 1, characterized in that: In the first direction, a third dimension L3 mm exists between the first notch (311) and the first section (321), and a fourth dimension L4 mm exists between the first notch (311) and the third section (323), satisfying: 0.07≤L3 / L4≤13.

3.

3. The single cell according to claim 1, characterized in that: The first notch (311) comprises a plurality of notch units (3110) arranged along a first direction, two adjacent notch units (3110) are connected end to end, each notch unit (3110) extends along an arc track, and the convex directions of two adjacent notch units (3110) are opposite.

4. The single cell according to claim 3, characterized in that: The radius of the notch unit (3110) is D mm, satisfying: 3.17≤D≤6.

33.

5. The single cell according to claim 1, characterized in that: A second notch (312) is also provided. The second notch (312) is arranged on the base (31). The second notch (312) is located between the connecting portion (32) and the first notch (311), and is arranged around at least a portion of the first notch (311).

6. The single cell according to claim 5, characterized in that: The second notch (312) is connected to the first notch (311).

7. The single cell according to claim 5 or 6, characterized in that: The explosion-proof valve (3) is provided with a plurality of the second notches (312), and the plurality of the second notches (312) are arranged at intervals around the first notch (311).

8. The single cell according to claim 7, characterized in that: The second notch (312) is arc-shaped, the first end (3111) is connected to one of the second notches (312), and the second end (3112) is connected to another of the second notches (312).

9. A battery pack, characterized in that: A single cell comprising the single cell according to any one of claims 1 to 8.

10. An electrical device, characterized in that: A single cell comprising any one of claims 1 to 8, or a battery pack comprising claim 9.

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