Explosion-proof valve and battery cell

Abstract

The invention relates to the technical field of batteries, and discloses an explosion-proof valve and a battery cell. The explosion-proof valve comprises a valve body; the number of the nicks is n, the nicks are arranged on the valve body, the nicks are located on any side of the valve body in the thickness direction of the valve body, the residual thicknesses of the nicks are sequentially decreased from the first nick to the nth nick, and n is larger than or equal to 2. According to the explosion-proof valve, the plurality of nicks are arranged on the valve body, and the residual thicknesses of different nicks are different, so that positions corresponding to different nicks can be broken under different pressures, the explosion-proof valve can be opened from different positions under different pressures, a multi-stage exhaust passage is formed, effective exhaust and pressure relief during thermal runaway of a battery cell are facilitated, and the explosion-proof effect is improved. The problem that the explosion-proof valve cannot be opened due to deformation of the battery cell or unstable gas production rate in the traditional design form of a single nick is avoided, effective exhaust and pressure relief when the safety of the battery cell fails are facilitated, and the safety of the battery cell is improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to explosion-proof valves and battery cells. Background Technology

[0002] Battery cells are susceptible to thermal runaway during use. To enhance safety, explosion-proof valves are installed on the cell's cover or casing. These valves open when the internal pressure reaches a certain level, releasing the high-temperature, high-pressure fumes generated by thermal runaway and preventing explosions due to excessive internal pressure. The explosion-proof valves have grooves that break when the internal pressure reaches a certain threshold, opening the area enclosed by the grooves to create an exhaust channel. Current explosion-proof valves typically employ a single-opening design. However, this design suffers from delayed or ineffective opening, leading to safety failure and potentially causing cell explosions, thus compromising battery safety. Summary of the Invention

[0003] In view of this, the present invention provides an explosion-proof valve and a battery cell to solve the problem of explosion-proof valves not opening in a timely manner or not opening effectively.

[0004] In a first aspect, the present invention provides an explosion-proof valve, comprising: a valve body; and a groove, wherein the number of grooves is n, the grooves are disposed on the valve body, and the grooves are located on any side of the valve body along the thickness direction of the valve body, and the residual thickness of the grooves decreases sequentially from the first groove to the nth groove, wherein n≥2.

[0005] Beneficial effects: By setting multiple grooves on the valve body, with different residual thicknesses for each groove, the corresponding locations can break under different pressures. This allows the explosion-proof valve to open from different positions under different pressures, forming a multi-stage exhaust channel. This facilitates effective exhaust and pressure relief in the event of thermal runaway of the battery cell, avoiding the problem of the explosion-proof valve failing to open due to battery cell deformation or unstable gas production rate in the traditional single-groove design. It also facilitates effective exhaust and pressure relief in the event of battery cell safety failure, thus improving battery cell safety.

[0006] In one optional embodiment, the first to the nth grooves are sequentially provided along the direction from the edge of the valve body to the center of the valve body, where the value of n is in the range of 2≤n≤5.

[0007] Beneficial effects: From the edge to the center of the valve body, the residual thickness of multiple grooves decreases sequentially, so the opening pressure value at multiple grooves decreases from the outside to the inside. This allows the explosion-proof valve to gradually form an exhaust channel from the outside to the inside during the opening process. This conforms to the actual situation that the required exhaust capacity increases as the internal air pressure of the battery cell gradually increases. This helps the battery cell to exhaust and depressurize more effectively during thermal runaway. At the same time, controlling the number of grooves to between 2 and 5 ensures the multi-stage opening function of the explosion-proof valve while avoiding the processing complexity and cost increase caused by too many grooves.

[0008] In one optional embodiment, the residual thickness of the groove along the thickness direction of the valve body is M, and the residual thickness of the nth groove and the residual thickness of the (n-1)th groove satisfy the following relationship: M n =M n-1 -F, where 0.02 mm < F ≤ 0.15 mm.

[0009] Beneficial effects: It ensures that the opening pressure corresponding to two adjacent notches has a reasonable pressure gradient, forming an effective multi-stage exhaust channel, ensuring the effective opening of the explosion-proof valve, thereby improving the safety performance of the battery cell.

[0010] In one optional embodiment, the value of M is in the range of 0.05 mm ≤ M ≤ 0.25 mm; and / or, the opening pressure corresponding to the notch is P, wherein the value of P is in the range of 0.6 MPa ≤ P ≤ 1.5 MPa, and the opening pressure corresponding to the notch decreases sequentially from the first notch to the nth notch.

[0011] Beneficial effects: By limiting M to a value between 0.05 mm and 0.25 mm, premature opening of the explosion-proof valve can be avoided, as well as failure to open the explosion-proof valve, ensuring that the explosion-proof valve opens within a suitable pressure range and improving the safety performance of the battery cell; and / or, by limiting P to a value between 0.6 MPa and 1.5 MPa, the explosion-proof valve can be ensured to open within a suitable pressure range, neither too early nor too late, thereby improving the safety performance of the battery cell.

[0012] In one alternative implementation, the shape of the n grooves includes at least a portion that is annular and / or I-shaped.

[0013] Beneficial effects: Both the ring and I-shaped shapes are relatively simple and easy to process. They also ensure that the explosion-proof valve can form a sufficiently effective venting area when it opens from the groove, which is conducive to the smooth venting of the explosion-proof valve in the event of thermal runaway of the battery cell and improves the safety of the battery cell.

[0014] In one optional embodiment, the groove is an annular portion, and a connecting segment is further included within the annular area where the groove is located. The connecting segment is connected end to end to the groove. Along the thickness direction of the valve body, the thickness of the connecting segment is greater than the residual thickness of the groove to which it is connected, and the difference between the two is 0.03 mm to 0.15 mm.

[0015] Beneficial effects: If the structural strength of the connecting section is greater than that of the etched section connected to it, then when the explosion-proof valve breaks at the etched section, the connecting section will not break. This allows the opening area of ​​the explosion-proof valve, enclosed by the etched section, to flip up around the connecting section towards the outside of the housing. This ensures the smooth formation of an exhaust channel and prevents the opening area from flying out directly and causing further damage to surrounding personnel or equipment. At the same time, the thickness difference between the connecting section and the etched section is controlled between 0.03 mm and 0.15 mm. This ensures that the connecting section has sufficient strength to prevent it from breaking when the explosion-proof valve is opened, and also avoids difficulties in opening the explosion-proof valve or obstruction of the exhaust channel due to excessive thickness difference. This ensures effective exhaust of the explosion-proof valve while further improving safety and reliability.

[0016] In one alternative implementation, along the circumference of the notch, the circumference of the ring containing the notch is C, and the length of the connecting segment is L, where L < 1 / 2 × C.

[0017] Beneficial effects: By designing a connecting segment locally on the ring where the etched part is located, and limiting the length of the connecting segment to less than half the circumference of the ring, the connecting segment occupies a reasonable proportion within the ring area where the etched part is connected to it. This ensures the structural strength of the connecting segment and allows the opening area enclosed by the etched part to open smoothly when the explosion-proof valve is opened, forming an effective exhaust channel to release gas in a timely manner and ensure the safety of the battery cell.

[0018] In one optional embodiment, the inner ring of the first groove has a dimension A along the width direction of the valve body, and the spacing between the inner rings of two adjacent grooves along the width direction of the valve body is B; wherein, B and A satisfy the following relationship: 0.1 < B / A ≤ 0.35; and / or, the value range of A is: 7.5 mm < A ≤ 80 mm; and / or, the value range of B is: 1 mm ≤ B ≤ 28 mm.

[0019] Beneficial effects: By limiting the ratio of B to A to between 0.1 and 0.35, the markings are reasonably distributed on the valve body, which facilitates processing and ensures the multi-stage opening function of the explosion-proof valve, improving the safety performance of the battery cell; and / or, by limiting the value of A to between 7.5 mm and 80 mm, the markings are reasonably distributed, facilitating processing and manufacturing, and ensuring that the explosion-proof valve has sufficient structural strength. This allows for the formation of an effective multi-stage venting channel during thermal runaway of the battery cell, ensuring timely discharge of internal gas and preventing explosions due to excessive gas pressure. Simultaneously, a reasonable inner ring size allows the explosion-proof valve to form a sufficiently large venting area when open, improving venting efficiency and further enhancing the safety performance of the battery cell; and / or, by limiting the value of B to between 1 mm and 28 mm, the markings are reasonably distributed on the valve body, facilitating processing and ensuring structural strength. This also allows the explosion-proof valve to form a stable and effective multi-stage venting channel during thermal runaway of the battery cell, timely discharge of internal gas, preventing explosion risks, and improving the overall safety performance of the battery cell.

[0020] In one optional embodiment, the n grooves are arranged on the same side or opposite sides of the valve body along the thickness direction of the valve body; and / or, the explosion-proof valve further includes a welded part, which is connected around the circumferential edge of the valve body. Along the thickness direction of the valve body, the thickness of the welded part is h1, and the thickness of the valve body is h0, wherein h1 is greater than h0, and 0.2 mm ≤ h1 - h0 ≤ 0.6 mm; and / or, the valve body is further provided with reinforcing ribs.

[0021] Beneficial effects: The n notches can be arranged on the same side or different sides of the valve body, offering flexibility and ease of processing; and / or, by setting a welded part at the circumferential edge of the valve body, the explosion-proof valve can be easily welded to the cover plate body or shell through the welded part, and the thickness of the welded part is greater than the thickness of the valve body, ensuring welding strength while avoiding affecting the opening of the valve body. At the same time, by limiting the difference between the thickness of the welded part and the thickness of the valve body to between 0.2 mm and 0.6 mm, it can be ensured that the welded part has sufficient strength to withstand the thermal and mechanical stress during the welding process, preventing cracking or detachment during welding or use, and avoiding increased weight and cost due to excessively thick welded parts. This saves costs while ensuring the safety of the battery cell and is conducive to improving the energy density of the battery cell; and / or, by setting reinforcing ribs on the valve body, the structural strength of the valve body itself is further ensured, preventing the valve body from opening prematurely and affecting the normal opening and venting effect of the explosion-proof valve.

[0022] Secondly, the present invention also provides a battery cell, comprising: a housing having an open end; a cover plate assembly covering the open end of the housing, the cover plate assembly including a cover plate body; and the aforementioned explosion-proof valve, the explosion-proof valve being disposed on the cover plate body or the housing. Since the battery cell includes an explosion-proof valve and has the same effect as an explosion-proof valve, it will not be described in detail here. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of an explosion-proof valve according to an embodiment of the present invention; Figure 2 for Figure 1 The top view of the explosion-proof valve shown; Figure 3 for Figure 2 A cross-sectional view along the EE direction; Figure 4 for Figure 3 A magnified view of part of F; Figure 5 This is a schematic diagram of the structure of another explosion-proof valve according to an embodiment of the present invention; Figure 6 for Figure 5 Cross-sectional view along the GG direction; Figure 7 for Figure 6 A magnified view of part of J; Figure 8 This is a schematic diagram of the structure of a cover plate assembly according to an embodiment of the present invention; Figure 9 for Figure 8 A cross-sectional view along the KK direction; Figure 10 for Figure 9 A magnified view of a portion of Q; Figure 11 for Figure 8 A cross-sectional view along the NN direction.

[0025] Explanation of reference numerals in the attached figures: 10. Valve body; 20. Score; 201. First score; 202. Second score; 30. Connecting section; 40. Welded part; 50. Reinforcing rib; 61. Cover plate body; 611. Explosion-proof hole; 62. First plastic part; 63. Second plastic part; 64. Pole post; 65. Riveting block; 66. Explosion-proof patch. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Battery cells are susceptible to thermal runaway during use. To improve cell safety, explosion-proof valves are installed on the cell's cover or casing. These valves open when the internal pressure reaches a certain level, releasing the high-temperature, high-pressure fumes generated by thermal runaway and preventing explosions due to excessive internal pressure. The explosion-proof valves have grooves that break when the internal pressure reaches a certain value, opening the area enclosed by the grooves to form an exhaust channel. Existing explosion-proof valves typically employ a single-opening design, meaning they have only one groove. However, cell deformation or unstable gas production rates can affect the valve's opening. This traditional single-opening design means that cell deformation or unstable gas production rates can prevent the valve from opening, leading to safety failure and potentially causing a more dangerous situation such as a cell explosion, thus compromising cell safety.

[0028] The following is combined Figures 1 to 11 The following describes embodiments of the present invention.

[0029] According to embodiments of the present invention, in one aspect, an explosion-proof valve is provided, such as... Figures 1 to 7 As shown, the explosion-proof valve includes a valve body 10 and grooves 20. There are n grooves 20, which are disposed on the valve body 10 and located on any side of the valve body 10 along its thickness direction. The residual thickness of each groove 20 decreases sequentially from the first groove 20 to the nth groove 20, where n ≥ 2. It should be noted that the thickness of the valve body 10 refers to... Figures 3 to 4 , Figures 6 to 7 The direction indicated by the middle arrow "Z"; the residual thickness of the notch 20 refers to the difference between the thickness of the valve body 10 and the recess depth of the notch 20 along the thickness direction of the valve body 10, that is, the thickness of the remaining solid part of the valve body 10 after the notch 20 is made; n is a positive integer.

[0030] The explosion-proof valve of this embodiment has multiple notches 20 on the valve body 10, and the residual thickness of different notches 20 is different. This allows the positions corresponding to different notches 20 to break under different pressures, so that the explosion-proof valve can be opened from different positions under different pressures, forming a multi-stage exhaust channel. This is beneficial for effective exhaust and pressure relief when the battery cell is thermally runaway, avoiding the problem that the explosion-proof valve cannot be opened due to battery cell deformation or unstable gas production rate in the traditional single-notch design. It is beneficial for effective exhaust and pressure relief when the battery cell fails, thus improving the safety of the battery cell.

[0031] Specifically, when the internal pressure of the battery cell gradually increases, the explosion-proof valve will first break at the smallest residual thickness mark 20, forming a first-stage exhaust channel to discharge some high-temperature and high-pressure flue gas and reduce the internal pressure of the battery cell. If the internal pressure of the battery cell continues to rise, the mark 20 with the next smallest residual thickness will break next, forming a second-stage exhaust channel to further discharge flue gas. This process continues until all marks 20 break, forming a complete exhaust channel, ensuring that the internal pressure of the battery cell will not be too high and cause an explosion. This multi-stage opening design allows the explosion-proof valve to flexibly form an appropriately sized exhaust channel according to changes in the internal pressure of the battery cell. Furthermore, even if the mark 20 with a smaller residual thickness fails to break in time due to battery cell deformation or unstable gas production rate, i.e., the first-stage exhaust channel does not open in time, the explosion-proof valve can still break at the mark 20 with a larger residual thickness when the internal pressure of the battery cell rises, i.e., the second-stage exhaust channel opens, to ensure timely exhaust and pressure relief of the battery cell, further improving the safety performance of the battery cell.

[0032] It should be noted that the explosion-proof valve has intersecting X, Y, and Z directions. Preferably, the X, Y, and Z directions are perpendicular to each other, where the Z direction is the thickness direction of the explosion-proof valve. Figures 3 to 4 , Figures 6 to 7 , Figures 9 to 11 The direction indicated by the middle arrow (Z) is as follows: X direction is as follows. Figures 2 to 5 , Figures 8 to 10 The direction indicated by the middle arrow ("X") is as follows: The Y direction is as follows... Figure 2 , Figures 5 to 7 , Figure 11 The direction of the "Y" indicated by the middle arrow.

[0033] In one embodiment, from the edge of the valve body 10 to the center, the first to the nth notches 20 are sequentially arranged, where n ranges from 2 to 5. By designating the notch 20 closest to the edge of the valve body 10 as the first notch and the notch 20 closest to the center of the valve body 10 as the last notch, the residual thickness of the multiple notches 20 decreases sequentially from the edge to the center of the valve body 10. This results in a decrease in the opening pressure value at each notch 20 from the outside in, allowing the explosion-proof valve to gradually form an exhaust channel from the outside in during opening. This aligns with the actual situation where the required exhaust capacity increases as the internal gas pressure of the battery cell gradually rises, facilitating more effective exhaust and pressure relief during thermal runaway. Furthermore, controlling the number of notches to between 2 and 5 ensures the multi-stage opening function of the explosion-proof valve while avoiding the increased processing complexity and cost associated with excessive notches. The "from the outside in" refers to the distance from the edge of the valve body 10 to its center.

[0034] In one embodiment, along the thickness direction of the valve body 10, the residual thickness of the notch 20 is M, and the residual thickness of the nth notch 20 and the residual thickness of the (n-1)th notch 20 satisfy the following relationship: M n =M n-1 -F, where 0.02 mm < F ≤ 0.15 mm, n is the number of explosion-proof valves, 2 ≤ n ≤ 5, and n is a positive integer. It should be noted that the residual thickness of the first notch 20 is M1, the residual thickness of the second notch 20 is M2, and so on, the residual thickness of the (n-1)th notch 20 is M... n-1 The residual thickness of the nth notch 20 is M. n F represents the difference in residual thickness between two adjacent notches 20. If F is less than or equal to 0.02 mm, the difference is too small, making it difficult for the opening pressure of adjacent notches 20 to form a significant pressure gradient during the opening process of the explosion-proof valve, thus affecting the multi-stage opening effect. If F is greater than 0.15 mm, the difference is too large, causing excessive pressure jumps during the opening of the explosion-proof valve, which is not conducive to the smooth release of internal gas pressure and may even prevent the explosion-proof valve from opening in time, potentially leading to the risk of the battery cell exploding due to excessive internal gas pressure. Therefore, by limiting the difference in residual thickness between two adjacent notches 20 to be greater than 0.02 mm and less than or equal to 0.15 mm, a reasonable pressure gradient is ensured for the opening pressure corresponding to the two adjacent notches 20, forming an effective multi-stage exhaust channel, guaranteeing the effective opening of the explosion-proof valve, and thus improving the safety performance of the battery cell.

[0035] Optionally, the value of F is any one of 0.022 mm, 0.025 mm, 0.05 mm, 0.08 mm, 0.10 mm, 0.12 mm, 0.14 mm, 0.15 mm, or a value between any two of these values.

[0036] Let's take n=2 as an example for further explanation. Figures 3 to 4 As shown, the groove 20 includes a first groove 201 and a second groove 202. Along the direction from the edge of the valve body 10 to its center, the first groove is the first groove 201 and the second groove is the second groove 202. The residual thickness of the first groove 201 is M1 and the residual thickness of the second groove 202 is M2. Then M2 = M1 - F. The difference between the residual thickness of the first groove 201 and the residual thickness of the second groove 202 is F.

[0037] In one embodiment, the value of M ranges from 0.05 mm to 0.25 mm. It should be noted that M represents the residual thickness of any single notch 20. If M is less than 0.05 mm, the residual thickness of notch 20 is too small, which may cause the explosion-proof valve to open prematurely before reaching the expected pressure, affecting the normal use of the battery cell. If M is greater than 0.25 mm, the residual thickness of notch 20 is too large, and the explosion-proof valve may not be able to open in time when the internal pressure of the battery cell rises to a dangerous level, thus failing to effectively vent and depressurize, increasing the risk of battery cell explosion. Therefore, by limiting the value of M to between 0.05 mm and 0.25 mm, premature opening of the explosion-proof valve can be avoided, as well as failure to open the explosion-proof valve, ensuring that the explosion-proof valve opens within a suitable pressure range and improving the safety performance of the battery cell.

[0038] Optionally, the value of M is any one of 0.05 mm, 0.08 mm, 0.10 mm, 0.12 mm, 0.15 mm, 0.18 mm, 0.20 mm, 0.23 mm, 0.25 mm, or a value between any two of these values.

[0039] In one embodiment, the opening pressure corresponding to the notch 20 is P, where the value of P ranges from 0.6 MPa ≤ P ≤ 1.5 MPa, and the opening pressure corresponding to the notch 20 decreases sequentially from the first notch 20 to the nth notch 20. It should be noted that P represents the opening pressure at any of the notches 20. When the gas pressure inside the battery cell reaches a preset pressure value, the explosion-proof valve breaks at the notch 20 corresponding to that preset pressure value. From the first notch 20 to the nth notch 20, the residual thickness of the notch 20 decreases sequentially, and correspondingly, the opening pressure of the notch 20 decreases sequentially. If P is less than 0.6 MPa, the opening pressure at the notch 20 is too low, which may cause the explosion-proof valve to open prematurely when the battery cell is working normally or when there are slight gas pressure fluctuations, affecting the stability and service life of the battery cell. If P is greater than 1.5 MPa, the opening pressure at the notch 20 is too high, and the explosion-proof valve may not be able to open in time when the gas pressure inside the battery cell rises to a dangerous level, thus failing to effectively vent and depressurize, increasing the risk of battery cell explosion. Therefore, by limiting P to a value between 0.6 MPa and 1.5 MPa, it can be ensured that the explosion-proof valve opens within a suitable pressure range, neither too early nor too late, thereby improving the safety performance of the battery cell.

[0040] In one embodiment, the opening pressure corresponding to the first notch 20 is P1, and the opening pressure corresponding to the nth notch 20 is Pn. Pn and P1 satisfy the relationship: Pn = P1 - n × 0.3 MPa. That is, the opening pressure decreases sequentially from the first notch 20 to the nth notch 20. This relationship allows control of the opening pressure of each notch 20, enabling the explosion-proof valve to open sequentially according to a predetermined pressure gradient as the internal pressure of the battery cell gradually increases, forming an effective multi-stage exhaust channel. Specifically, when the internal pressure of the battery cell reaches P1, the first notch 20 will break first, forming the first-stage exhaust channel. If the pressure continues to rise, reaching the opening pressure P2 corresponding to the second notch 20, the second notch 20 will break next, forming the second-stage exhaust channel. This continues until all notches 20 break, forming a complete exhaust channel. This ensures that the battery cell can release pressure and exhaust in a timely and effective manner during thermal runaway, preventing the risk of explosion caused by excessive internal pressure.

[0041] In one embodiment, the shapes of the n notches 20 include at least a portion of annular and / or I-shaped. It should be noted that the shape of the notch 20 refers to the shape of its orthographic projection along the Z direction in the XY plane; the annular shape can be a circular ring, a square ring, or a polygonal ring. The I-shaped notches 20 are preferably arranged closest to the center of the valve body 10. Both annular and I-shaped shapes are relatively simple, easy to manufacture, and ensure that a sufficiently effective venting area is formed when the explosion-proof valve opens from the notch 20, which is beneficial for the explosion-proof valve to smoothly vent during thermal runaway of the battery cell, improving the safety of the battery cell. Of course, the shape of the notch trajectory is not limited to annular, circular, or I-shaped; the shapes of the n notches 20 can also be the same or different.

[0042] It should be noted that the shape of the notch 20 being circular at least partially means that the notch 20 is a complete circle, or it may only be a section of the circle.

[0043] Preferably, the plurality of notches 20 are at least partially racetrack-shaped, and the plurality of notches 20 are concentrically arranged.

[0044] In one embodiment, the groove 20 is an annular portion, and a connecting segment 30 is also included in the annular area where the groove 20 is located. The connecting segment 30 is connected to the groove 20 end to end. Along the thickness direction of the valve body 10, the thickness of the connecting segment 30 is greater than the residual thickness of the groove 20 connected to it, and the difference between the two is 0.03 mm to 0.15 mm. It should be noted that the thickness of the connecting section 30 being greater than the residual thickness of the connected notch 20 means that, for the connecting section 30 and the notch 20 located in the same annular area, the thickness of the connecting section 30 is greater than the residual thickness of the notch 20. This ensures that the structural strength of the connecting section 30 is greater than the structural strength of the connected notch 20. Therefore, when the explosion-proof valve breaks at the notch 20, the connecting section 30 does not break, allowing the opening area of ​​the explosion-proof valve, enclosed by the notch 20, to flip up around the connecting section 30 towards the outside of the housing. This ensures the smooth formation of an exhaust channel and prevents the opening area from flying out directly and causing further damage to surrounding personnel or equipment. At the same time, the thickness difference between the connecting section 30 and the notch 20 is controlled between 0.03 mm and 0.15 mm. This ensures that the connecting section 30 has sufficient strength to prevent it from breaking when the explosion-proof valve opens, and also avoids difficulties in opening the explosion-proof valve or obstruction of the exhaust channel due to an excessive thickness difference. This ensures effective exhaust of the explosion-proof valve while further improving safety and reliability.

[0045] Further integration Figures 6 to 7 As shown, taking the second notch 202 as an example, the residual thickness of the second notch 202 is M2, and the thickness of the connecting segment 30 connected to the second notch 202 is h2. Then the value range of h2-M2 is 0.03 mm to 0.15 mm.

[0046] Optionally, for the connecting segment 30 and the notch 20 located in the same annular region, the difference between the thickness of the connecting segment 30 and the residual thickness of the notch 20 is any one of 0.03 mm, 0.05 mm, 0.07 mm, 0.09 mm, 0.10 mm, 0.12 mm, 0.14 mm, 0.15 mm, or a value between any two of these values.

[0047] Optionally, the thickness of the connecting section 30 is greater than the residual thickness of the notch 20 but less than the thickness of the valve body 10. This means the connecting section 30 undergoes slight processing, retaining sufficient structural strength while facilitating the opening of the explosion-proof valve. It can be understood that, as an alternative implementation, the thickness of the connecting section 30 is equal to the thickness of the valve body 10; that is, the connecting section 30 is not processed and is directly formed from a portion of the valve body 10.

[0048] In one embodiment, along the circumference of the notch 20, the circumference of the ring containing the notch 20 is C, and the length of the connecting segment 30 is L, where L < 1 / 2 × C. It should be noted that the length of the connecting segment 30 refers to its dimension along the circumference of the notch 20. If L is greater than or equal to 1 / 2 × C, the length of the connecting segment 30 is too long, resulting in the notch 20 being too short. This makes it difficult to open the explosion-proof valve, preventing timely gas release and affecting the formation of the gas release channel and the gas release effect of the explosion-proof valve, thus impacting the safety of the battery cell. Therefore, by locally designing the connecting segment 30 on the ring containing the notch 20, and limiting the length of the connecting segment 30 to less than half the circumference of the ring, the connecting segment 30 occupies a reasonable proportion within the ring area containing the notch 20. This ensures the structural strength of the connecting segment 30 and allows the opening area enclosed by the notch 20 to open smoothly when the explosion-proof valve is opened, forming an effective gas release channel to promptly release gas and ensure the safety of the battery cell.

[0049] In one embodiment, further combination Figure 2 As shown, the inner ring of the first notch 20 has a dimension A along the width direction of the valve body 10, and the distance between the inner rings of two adjacent notches 20 along the width direction of the valve body 10 is B. B and A satisfy the relationship: 0.1 < B / A ≤ 0.35, where both B and A are in mm. It should be noted that the explosion-proof valve is racetrack-shaped, and the width direction of the valve body 10 refers to... Figure 2The direction indicated by the middle arrow "Y" and the direction indicated by the arrow "X" represent the length direction of the valve body 10. The first notch 20 is the one closest to the edge of the valve body 10 among all notches 20. The size of its inner ring is the maximum value among the inner ring sizes of all notches 20. If B / A is less than or equal to 0.1, the distance between the inner rings of two adjacent notches 20 is too small relative to the width dimension of the inner ring of the first notch 20, resulting in an overly dense distribution of notches 20, increasing the processing difficulty, and adjacent notches 20 will affect each other, affecting the overall structural strength of the explosion-proof valve. If B / A is greater than 0.35, the distance between the inner rings of two adjacent notches 20 is too large relative to the width dimension of the inner ring of the first notch 20, resulting in an overly sparse distribution of notches 20, making the gradient between the residual thicknesses of multiple notches 20 too large, affecting the formation effect of the multi-stage exhaust channel. Therefore, by limiting the ratio of B to A to between 0.1 and 0.35, the notches 20 are reasonably distributed on the valve body 10, which facilitates processing, ensures the multi-stage opening function of the explosion-proof valve, and improves the safety performance of the battery cell.

[0050] Optionally, the value of B / A is any one of 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 or a value between any two values.

[0051] In one embodiment, the value of A is in the range of 7.5 mm < A ≤ 80 mm. If A is less than 7.5 mm, the inner ring of the first notch 20 is too small along the width of the valve body 10, which will result in the overall distribution of all notches 20 being too compact, increasing the difficulty of processing, and resulting in poor structural strength of the explosion-proof valve. Furthermore, during the opening process of the explosion-proof valve, adjacent notches 20 may affect each other, affecting the step-by-step opening of the explosion-proof valve. At the same time, the maximum opening area of ​​the explosion-proof valve is too small, affecting the exhaust effect of the explosion-proof valve. If A is greater than 80 mm, the inner ring of the first notch 20 is too large, resulting in an oversized explosion-proof valve and poor structural strength. Therefore, by limiting the value of A to between 7.5mm and 80mm, it is possible to ensure a reasonable distribution of the markings, which facilitates processing and manufacturing, and also to ensure that the explosion-proof valve has sufficient structural strength. In the event of thermal runaway of the battery cell, it can form an effective multi-stage exhaust channel, ensuring that the gas inside the battery cell is discharged in time and preventing an explosion caused by excessive gas pressure. At the same time, the reasonable inner ring size can also enable the explosion-proof valve to form a sufficiently large exhaust area when it is opened, thereby improving the exhaust efficiency and further enhancing the safety performance of the battery cell.

[0052] Optionally, the value of A is any one of 8mm, 10mm, 15mm, 20mm, 25mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, or a value between any two of them.

[0053] In one embodiment, the value of B is in the range of 1 mm ≤ B ≤ 28 mm. If B is less than 1 mm, the spacing between the inner rings of two adjacent notches 20 along the width direction of the valve body 10 is too small, which will also lead to the notches 20 being distributed too densely. This not only increases the processing difficulty but may also cause adjacent notches 20 to interfere with each other during the opening of the explosion-proof valve, affecting the stability of the step-by-step opening and the venting effect. If B is greater than 28 mm, the spacing between the inner rings of two adjacent notches 20 along the width direction of the valve body 10 is too large, and the notches 20 are distributed too sparsely, which will lead to an unreasonable gradient of the multi-stage venting channels and reduce the venting efficiency of the explosion-proof valve. Therefore, by limiting the value of B to between 1 mm and 28 mm, it is possible to ensure a reasonable distribution of notches 20 on the valve body 10, which is convenient for processing and ensures structural strength. At the same time, it is possible to enable the explosion-proof valve to form a stable and effective multi-stage venting channel when the battery cell experiences thermal runaway, so as to timely discharge internal gas, prevent the risk of explosion, and improve the overall safety performance of the battery cell.

[0054] Optionally, the value of B is any one of 1 mm, 3 mm, 5 mm, 8 mm, 10 mm, 15 mm, 20 mm, 25 mm, 28 mm, or a value between any two of these values.

[0055] In one embodiment, n notches 20 are disposed on the same side or opposite sides of the valve body 10 along the thickness direction of the valve body 10. The n notches 20 can be arranged on the same side or different sides of the valve body 10, offering flexibility and ease of processing. It should be noted that regardless of whether the n notches 20 are distributed on the same side or opposite sides of the valve body 10, the notches 20 can be opened under their corresponding pressure, ensuring the smooth discharge of gas inside the battery cell.

[0056] In one embodiment, the explosion-proof valve further includes a welded portion 40, which is connected around the circumferential edge of the valve body 10. Along the thickness direction of the valve body 10, the thickness of the welded portion 40 is h1, and the thickness of the valve body 10 is h0, wherein h1 is greater than h0, and 0.2 mm ≤ h1 - h0 ≤ 0.6 mm. By providing a welded part on the circumferential edge of the valve body 10, the explosion-proof valve can be easily welded to the cover plate body 61 or the shell through the welded part 40. The thickness of the welded part 40 is greater than the thickness of the valve body 10, which ensures the welding strength and avoids affecting the opening of the valve body 10. At the same time, by limiting the difference between the thickness of the welded part 40 and the thickness of the valve body 10 to between 0.2 mm and 0.6 mm, it can be ensured that the welded part 40 has sufficient strength to withstand the thermal and mechanical stress during the welding process, preventing cracking or detachment during welding or use. It can also avoid the increase in weight and cost due to excessive thickness of the welded part. This saves costs while ensuring the safety of the battery cell and is conducive to improving the energy density of the battery cell.

[0057] Optionally, the values ​​of h1-h0 are any one of 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, 0.6 mm, or a value between any two of them.

[0058] In one embodiment, such as Figures 1 to 2 As shown, the valve body 10 is also provided with reinforcing ribs 50. By providing reinforcing ribs 50 on the valve body 10, the structural strength of the valve body 10 itself is further guaranteed, and the valve body 10 is prevented from opening prematurely, which would affect the normal opening and exhaust effect of the explosion-proof valve.

[0059] It should be noted that the specific shape, quantity, and position of the reinforcing rib 50 can be designed according to actual needs. Preferably, the reinforcing rib 50 is located on the central plane of the explosion-proof valve. The reinforcing rib 50 consists of two opposing arc-shaped segments that are tangential to each other. The reinforcing rib 50 connects to the innermost notch 20, which can reduce the stress on the notch 20 and prevent premature opening of the explosion-proof valve due to stress concentration, thereby improving safety performance. Of course, the reinforcing rib 50 can also be selected in various forms such as strips or crosses, and its distribution position can be flexibly adjusted according to the stress condition of the valve body 10 to achieve the best structural reinforcement effect, thereby further improving the safety performance of the battery cell.

[0060] The explosion-proof valve in this embodiment adopts a multi-score design, with different residual thicknesses of different scores 20, ensuring that the explosion-proof valve opens under different pressures. This facilitates effective venting and pressure relief when the battery cell fails, preventing the explosion-proof valve from failing to open due to battery cell deformation and unstable gas production rate, thus improving battery cell safety.

[0061] According to an embodiment of the present invention, in another aspect, a battery cell is also provided, comprising: a housing, a cover assembly, and the aforementioned explosion-proof valve. The housing has an open end; the cover assembly covers the open end of the housing, and the cover assembly includes a cover body 61; the explosion-proof valve is disposed on the cover body 61 or on the housing. The battery cell also includes an electrode assembly disposed within the inner cavity of the housing. Optionally, the battery cell is a lithium-ion battery cell.

[0062] Further integration Figures 8 to 11As shown, the cover assembly includes: a cover body 61, on which an explosion-proof hole 611 is formed, and an explosion-proof valve is installed in the explosion-proof hole 611. An explosion-proof patch 66 is affixed to the side of the explosion-proof hole 611 facing the outside of the housing to protect the explosion-proof valve. The cover assembly also includes a first plastic part 62, which is disposed on the side of the cover body 61 facing the inside of the housing to improve the insulation between the cover body 61 and the electrode group. The first plastic part 62 has a vent hole corresponding to the explosion-proof valve to ensure that the gas inside the cell can smoothly reach the explosion-proof valve. The cover assembly also includes an electrode post 64, in which the cover body 61 also has an electrode post hole, and the electrode post 64 is disposed in the electrode post hole and electrically connected to the electrode tab on the electrode group. The cover plate assembly also includes a riveting block 65 and a second plastic part 63. The riveting block 65 is disposed on the side of the cover plate body 61 opposite to the first plastic part 62. The pole post 64 is riveted to the cover plate body 61 through the riveting block 65. The second plastic part 63 is disposed between the riveting block 65 and the cover plate body 61 to ensure the insulation between the riveting block 65 and the cover plate body 61.

[0063] The following examples and comparative examples verify the influence of the parameters of the explosion-proof valve on its performance. The examples and comparative examples are shown in Table 1. When n=2 (that is, the number of notches 20 set on the explosion-proof valve is two), explosion-proof valves are designed with different parameters, and safety tests and related tests are carried out on the battery cells. The corresponding test results are recorded.

[0064] Table 1

[0065] It should be noted that there are two notches on the explosion-proof valve, including a first notch 201 and a second notch 202. The residual thickness of the first notch 201 is M1, and the residual thickness of the second notch 202 is M2. The difference between the residual thicknesses of the first notch 201 and the second notch 202 is F = M1 - M2. The opening pressure corresponding to the first notch 201 is P1, and the opening pressure corresponding to the second notch 202 is P2. The dimension of the inner ring of the first notch 201 along the width direction of the valve body 10 is A, and the distance between the inner rings of the first notch 201 and the second notch 202 along the width direction of the valve body 10 is B.

[0066] For the battery cells of Examples 1 to 5, all parameters of the explosion-proof valve are within the range defined in this application. As the air pressure applied to the explosion-proof valve increases, the second notch 202 and the first notch 201 open step by step, and the battery cell safety test is passed (OK).

[0067] For the battery cell of Comparative Example 1, the difference M1-M2 between the residual thickness of the first notch 201 and the second notch 202 is 0.015 mm, which is less than 0.02 mm and is not within the range defined in this application. During the battery cell safety test, the first notch 201 and the second notch 202 are opened at the same time. The explosion-proof valve cannot be opened in advance from the second notch 202 to release pressure, resulting in insufficient venting capacity. The battery cell safety test fails (NG).

[0068] For the battery cell of Comparative Example 2, the B / A value is 0.09, which is less than 0.1 and is not within the range defined in this application. The cell manufacturing and storage process is prone to cracking and leakage at the explosion-proof valve scoring position. The scoring spacing of the explosion-proof valve is too small, the scoring position has poor strength, and the cell and the whole package vibration test fails.

[0069] For the battery cell of Comparative Example 3, the B / A value is 0.37, which is greater than 0.35 and is not within the range defined in this application. The spacing of the explosion-proof valve scribbles is too large, the second scribbles 202 of the explosion-proof valve open prematurely, the venting and pressure relief capacity is insufficient, and the battery cell fails the safety test.

[0070] For the battery cell of Comparative Example 4, the difference M1-M2 between the residual thickness of the first notch 201 and the second notch 202 is 0.155 mm, which is greater than 0.15 mm and is not within the range defined in this application. During the battery cell safety test, the opening pressure corresponding to the first notch 201 is too high, the explosion-proof valve cannot be opened in time from the first notch 201, and the exhaust capacity of the second notch 202 is insufficient, so the safety test fails.

[0071] In summary, when the parameters of the explosion-proof valve are within the range defined in this application, it can be ensured that as the internal air pressure of the battery cell increases, the explosion-proof valve can be opened step by step in the order from the nth mark to the 1st mark, forming a multi-stage exhaust channel, which is conducive to effective exhaust and pressure relief in the event of thermal runaway of the battery cell and improves the safety performance of the battery cell.

[0072] Unless otherwise stated, the values ​​and test methods of the parameters mentioned in this application can be determined using commonly used test methods in the art. For example, the safety test of the battery cell can be performed by gradually increasing the internal pressure by filling the battery with an inert gas (such as nitrogen) to simulate the pressure increase caused by gas production in the battery, thereby verifying the opening pressure of the explosion-proof valve. Unless otherwise stated, the test temperature for all parameters is 25°C.

[0073] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An explosion relief valve, characterized in that The valve body comprises: n score lines, which are arranged on the valve body and located on either side of the valve body along the thickness direction of the valve body, wherein the residual thickness of the score lines decreases from the first score line to the nth score line, and n≥2. The first score line to the nth score line are arranged in sequence along the direction from the edge of the valve body to the center of the valve body, and n is in the range of 2≤n≤5.

2. The explosion relief valve of claim 1, wherein M is in the range of 0.05 mm≤M≤0.25 mm.

3. The explosion relief valve of claim 2, wherein, The residual thickness of the score is M along the thickness direction of the valve body, and the residual thickness of the nth score and the residual thickness of the n-1th score satisfy the relationship: M n =M n-1 -F, wherein 0.02 mm < F ≤ 0.15 mm.

4. The explosion relief valve of claim 3, wherein The opening pressure corresponding to the score lines is P, wherein P is in the range of 0.6 Mpa≤P≤1.5 Mpa, and the opening pressure corresponding to the score lines decreases from the first score line to the nth score line. The shape of the n score lines comprises at least part of a ring shape and / or an I-shaped profile.

5. The explosion relief valve of claim 1, wherein, The part of the score line in the ring shape further comprises a connecting section connected to the first and last score lines in the ring-shaped area, and the thickness of the connecting section is greater than the residual thickness of the score line connected thereto along the thickness direction of the valve body, and the difference between them is 0.03 mm~0.15 mm.

6. The explosion relief valve of claim 5, wherein, Along the circumferential direction of the score line, the circumference of the ring-shaped area where the score line is located is C, and the length of the connecting section is L, wherein L<1 / 2×C.

7. The explosion relief valve of claim 6, wherein, The inner ring of the first score line has a size A along the width direction of the valve body, and the interval between the inner rings of the adjacent two score lines along the width direction of the valve body is B.

8. The explosion relief valve of claim 6, wherein, Wherein, the relationship between B and A satisfies the formula: 0.1 And / or, A is in the range of 7.5 mm And / or, B is in the range of 1 mm≤B≤28 mm. The n score lines are arranged on the same side or opposite sides of the valve body along the thickness direction of the valve body.

9. Explosion relief valve according to any of claims 1 to 8, characterized in that And / or, the explosion-proof valve further comprises a welding portion, which is connected around the circumferential edge of the valve body, and the thickness of the welding portion along the thickness direction of the valve body is h1, and the thickness of the valve body is h0, wherein h1 is greater than h0, and 0.2 mm≤h1-h0≤0.6 mm. And / or, the valve body is further provided with a reinforcing rib. The shell has an open end; 10. An electric cell characterized by The cover plate assembly comprises a cover plate body; The explosion-proof valve according to any one of claims 1 to 9 is arranged on the cover plate body or the shell. ​ ​

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