Secondary battery and electronic device

Abstract

The invention relates to the technical field of batteries, and discloses a secondary battery and electronic equipment, a shell of the secondary battery comprises an accommodating cavity and a first side wall, and the first side wall is provided with a first through hole. The pressure relief assembly is arranged on the first side wall and covers the first through hole, the pressure relief assembly comprises a metal deformation piece and a sealing piece, the metal deformation piece comprises an active deformation layer, a polymer layer and a passive deformation layer, the polymer layer is connected with the active deformation layer and the passive deformation layer, and the sealing piece is connected with the active deformation layer and the first side wall; or the sealing piece is connected with the passive deformation layer and the first side wall; the thermal expansion coefficient of the active deformation layer is larger than that of the passive deformation layer. According to the secondary battery, the metal deformation piece is arranged as a pressure relief structure, the pressure relief efficiency can be improved, the polymer layer isolates the active deformation layer from the passive deformation layer, the probability of electrochemical corrosion caused by direct contact of the active deformation layer and the passive deformation layer can be reduced, stress relief is facilitated, and the service life of the battery is prolonged. And stable deformation performance and reset performance of the active deformation layer and the passive deformation layer are ensured.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of batteries, and in particular, to a secondary battery and an electronic device. Background Art

[0002] With the rapid development of new energy technologies, batteries have been widely used in fields such as mobile phones, laptop computers, and electric vehicles, and the quality and safety requirements for batteries are getting higher and higher. However, when the battery is in a high-temperature environment or short-circuited, it is easy to cause the battery to undergo thermal runaway, and the internal air pressure of the battery gradually increases, which easily leads to the battery catching fire or even exploding, posing a safety risk. Summary of the Invention

[0003] The embodiments of the present application provide a secondary battery and an electronic device, which can effectively solve the problem of thermal runaway of the secondary battery, and are beneficial to reducing the probability of chemical corrosion of the pressure relief component and improving the service life of the pressure relief component.

[0004] The embodiments of the present application provide a secondary battery, including a housing and a pressure relief component. The housing is provided with a receiving cavity, and the housing includes a first side wall, and a through first through hole is provided along the thickness direction of the first side wall. The pressure relief component is disposed on the first side wall and covers the first through hole. The pressure relief component includes a metal deformation member and a sealing member. The metal deformation member includes an active deformation layer, a polymer layer, and a passive deformation layer. The polymer layer is respectively connected to the active deformation layer and the passive deformation layer. The sealing member is connected to the active deformation layer and the first side wall, and the passive deformation layer is disposed on the side of the active deformation layer away from the first side wall; or, the sealing member is connected to the passive deformation layer and the first side wall, and the active deformation layer is disposed on the side of the passive deformation layer away from the first side wall. The coefficient of thermal expansion G1 of the active deformation layer is greater than the coefficient of thermal expansion G2 of the passive deformation layer.

[0005] In the secondary battery of the embodiments of the present application, by providing a metal deformation member as a pressure relief structure, due to the different coefficients of thermal expansion of the active deformation layer and the passive deformation layer, when the temperature changes, the deformation of the active deformation layer is greater than that of the passive layer, so that the entire metal deformation member will bend toward the side of the passive deformation layer. The coefficient of thermal expansion G1 of the active deformation layer is greater than the coefficient of thermal expansion G2 of the passive deformation layer. The characteristics of metal thermal expansion are effectively utilized, which can increase the action response speed of the pressure relief component to improve the pressure relief efficiency. And by providing a polymer layer between the active deformation layer and the passive deformation layer, on the one hand, the polymer layer isolates the active deformation layer and the passive deformation layer, thereby reducing the probability of electrochemical corrosion caused by the direct contact between the active deformation layer and the passive deformation layer. On the other hand, the polymer layer bonds the active deformation layer and the passive deformation layer respectively, which helps to eliminate stress, ensure the stable deformation performance and reset performance of the active deformation layer and the passive deformation layer, and extend the service life of the active deformation layer and the passive deformation layer.

[0006] In some embodiments, the melting point T1 of the polymer layer and the melting point T2 of the seal satisfy: T1-T2≥15°C. Controlling the difference between the melting point T1 of the polymer layer and the melting point T2 of the seal to 15°C or above can effectively ensure that when the seal is heated and melted, the polymer layer can still maintain its shape, and the active deformation layer and the passive deformation layer will not be separated, and the normal operation of the active deformation layer and the passive deformation layer will not be affected.

[0007] In some embodiments, the melting point T1 of the polymer layer and the operating temperature T3 of the active deformation layer satisfy: T1-T3≥10°C, and / or, the melting point T1 of the polymer layer and the operating temperature T4 of the passive deformation layer satisfy: T1-T4≥10°C. By controlling the difference between the melting point T1 of the polymer layer and the operating temperature T3 of the active deformation layer and / or the operating temperature T4 of the passive deformation layer to 10°C or more, the probability of the polymer layer melting and failing when the active deformation layer and the passive deformation layer are deformed can be reduced.

[0008] In some embodiments, along the thickness direction of the first side wall, the first side wall has a first surface and a second surface, the first surface defines a local boundary of the receiving cavity, the second surface is away from the receiving cavity, and the first through hole penetrates the first surface and the second surface. The metal deformable member is located in the receiving cavity, and the seal is respectively connected to the first surface and the active deformation layer, or the seal is respectively connected to the first surface and the passive deformation layer; or, the metal deformable member is located outside the receiving cavity, and the seal is respectively connected to the second surface and the active deformation layer, or the seal is respectively connected to the second surface and the passive deformation layer. The pressure relief component is arranged in the receiving cavity, and the space between the head of the battery cell assembly and the first side wall can be effectively utilized without affecting the pressure relief effect, and the probability of the pressure relief component located in the receiving cavity being damaged by the outside is reduced. The pressure relief component is arranged outside the receiving cavity, and it is easier to connect the pressure relief component to the housing on the outside of the housing. When the secondary battery is thermally runaway, the metal deformable member bends away from the receiving cavity, which is consistent with the direction in which the gas in the receiving cavity is discharged outward, reducing the obstruction of the metal deformable member to the gas flow and increasing the pressure relief speed. Specifically, when the passive deformation layer is closer to the receiving cavity, the middle of the metal deformation piece bulges outward to open the first through hole, and when the active deformation layer is closer to the receiving cavity, the edge of the metal deformation piece warps outward to open the first through hole.

[0009] In some embodiments, the pressure relief assembly includes a connector, the connector is fixed to the first side wall, the connector is provided with a second through hole, the second through hole is connected to the first through hole, the sealing member is connected to the connector, the connector is connected to the active deformation layer, or the connector is connected to the passive deformation layer, and the metal deformation member covers the second through hole. Adding a connector to connect the sealing member and the first side wall can facilitate the connection and fixation of the sealing member and the housing, and also help to improve the sealing between the sealing member and the housing.

[0010] In some embodiments, the connecting member is a metal ring, and the metal ring is welded to the first side wall. The connecting member is arranged in a ring sheet shape. On the one hand, it is convenient for the connecting member to be welded to the housing. On the other hand, the force in the circumferential direction of the connecting member is uniform, reducing stress concentration. On the other hand, the pressure relief hole can be made smaller by controlling the inner diameter of the ring sheet, so as to improve the sealing performance of the secondary battery under normal working conditions.

[0011] In some embodiments, the outer diameter D2 of the connecting member and the diameter D1 of the first through hole satisfy: D2 > D1. And / or, the outer diameter D3 of the active deformation layer and the outer diameter D2 of the connecting member satisfy: D3 ≤ D2, and the outer diameter D3 of the active deformation layer and the diameter D4 of the second through hole of the connecting member satisfy: D3 > D4. Setting the outer diameter of the connecting member to be larger than the diameter of the first through hole enables the connecting member to be fixedly connected to the first side wall. Setting the outer diameter of the active deformation layer to be smaller than or equal to the outer diameter of the connecting member can reduce the difficulty of laser welding the connecting member to the housing. Setting the outer diameter of the active deformation layer to be larger than the diameter of the second through hole can ensure that the active deformation layer can completely cover the second through hole to seal the second through hole under normal working conditions.

[0012] In some embodiments, the diameter D1 of the first through hole satisfies: 0.5 mm ≤ D1 ≤ 5.5 mm; and / or, the outer diameter D2 of the connecting member satisfies: 1 mm ≤ D2 ≤ 6 mm; and / or, the outer diameter D3 of the active deformation layer satisfies: 0.1 mm ≤ D3 ≤ 6 mm; and / or, the diameter D4 of the second through hole satisfies: 0.1 mm ≤ D4 ≤ 4 mm. On the basis of ensuring that the exhaust rate of the first through hole is greater than or equal to the gas generation rate during the thermal runaway of the battery cell assembly, the smaller the diameter of the first through hole, the less water vapor, oxygen, etc. outside the secondary battery enter the accommodation cavity through the first through hole, thereby reducing the side reaction rate of the battery cell assembly caused by water vapor and oxygen, and reducing the risk of explosion and fire of the battery cell assembly.

[0013] In some embodiments, the outer diameter D3 of the active deformation layer, the outer diameter D5 of the polymer layer, and the outer diameter D6 of the passive deformation layer are equal. The metal deformation part is directly obtained by processes such as integral stamping and cutting. In this way, the outer diameters of the three are equal, which is beneficial to improving production efficiency. Or, the outer diameter D5 of the polymer layer is larger than the outer diameter of at least one of the active deformation layer and the passive deformation layer, so that the polymer layer can effectively isolate the active deformation layer and the passive deformation layer, reducing the probability of electrochemical corrosion when they come into contact.

[0014] In some embodiments, the material of the active deformation layer includes at least one of Inconel alloy, nickel, copper, copper-tin-zinc alloy, copper-zinc alloy, or alloy steel; the material of the passive deformation layer includes at least one of nickel-iron alloy, invar alloy, Inconel, or manganin. The above materials are highly sensitive to temperature, which is beneficial to the thermal deformation of the active deformation layer and the passive deformation layer. The material of the connecting member includes at least one of aluminum, nickel, and stainless steel, which is beneficial to the welding of the connecting member to the housing and reduces the probability of corrosion and rust of the connecting member.

[0015] In some embodiments, the material of the polymer layer includes at least one of polypropylene, polyimide, polyethylene terephthalate, polyamide, polycarbonate, polyphenylene sulfide, polyvinylidene fluoride, polytetrafluoroethylene, polyether ether ketone, liquid crystal polymer, polyaryletherketone, polyurethane plastic, polystyrene, and polyvinyl chloride. The above materials all have good chemical stability, enabling the polymer layer to resist chemical corrosion to a certain extent, effectively isolating the active deformation layer and the passive deformation layer, and facilitating the extension of the service life of both.

[0016] In some embodiments, the secondary battery includes a battery cell assembly and a terminal assembly. The battery cell assembly is disposed in the receiving cavity. The battery cell assembly has a head, and the head is opposite to and spaced from the first side wall; the terminal assembly is disposed through the first side wall, and the terminal assembly is electrically connected to the head of the battery cell assembly. By disposing the pressure relief component and the terminal component on the same side wall of the housing, the space between the battery cell assembly and the first side wall can be effectively utilized, and when thermal runaway occurs, the gas accumulated between the battery cell assembly and the first side wall is more likely to push open the pressure relief component for pressure relief.

[0017] Another technical solution adopted in the embodiments of the present application is: to provide an electronic device including the secondary battery, and the secondary battery is used to provide electrical energy.

[0018] The beneficial effects of the embodiments of the present application are: In the secondary battery of the embodiments of the present application, by setting a metal deformation member as the pressure relief structure, the characteristic of metal thermal expansion is effectively utilized, which can increase the action response speed of the metal deformation member to improve the pressure relief efficiency. And by setting a polymer layer between the active deformation layer and the passive deformation layer, on the one hand, the polymer layer isolates the active deformation layer and the passive deformation layer, thereby reducing the probability of electrochemical corrosion caused by the direct contact between the active deformation layer and the passive deformation layer; on the other hand, the polymer layer bonds the active deformation layer and the passive deformation layer respectively, which helps to eliminate stress, ensure the stable deformation performance and reset performance of the active deformation layer and the passive deformation layer, and extend the service life of the active deformation layer and the passive deformation layer. Description of the Drawings

[0019] To more clearly illustrate the technical solutions in the specific embodiments of the present application, the following will briefly introduce the drawings required for use in the description of the specific embodiments. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to actual scale.

[0020] Figure 1 It is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0021] Figure 2 It is an exploded view of a secondary battery according to an embodiment of the present application.

[0022] Figure 3 It is a partial cross-sectional view of a secondary battery according to an embodiment of the present application when the pressure relief component is located in the accommodation cavity and in a sealed state.

[0023] Figure 4 It is a partial cross-sectional view of a secondary battery according to an embodiment of the present application when the pressure relief component is located in the accommodation cavity and in a pressure relief state.

[0024] Figure 5 It is a partial cross-sectional view of a secondary battery according to another embodiment of the present application when the pressure relief component is located in the accommodation cavity and in a pressure relief state.

[0025] Figure 6 It is a partial cross-sectional view of a secondary battery according to an embodiment of the present application when the pressure relief component is located outside the housing and in a sealed state.

[0026] Figure 7 It is a partial cross-sectional view of a secondary battery according to an embodiment of the present application when the pressure relief component is located outside the housing and in a pressure relief state.

[0027] Figure 8 It is a partial cross-sectional view of a secondary battery according to another embodiment of the present application when the pressure relief component is located outside the housing and in a pressure relief state.

[0028] Figure 9 It is an exploded view of a secondary battery according to another embodiment of the present application.

[0029] Figure 10 It is a partial cross-sectional view of a secondary battery according to another embodiment of the present application when the pressure relief component is located outside the housing and in a sealed state.

[0030] Figure 11 It is a dimension marking diagram of a pressure relief component of a secondary battery according to another embodiment of the present application.

[0031] The reference numerals in the specific embodiments are as follows:

[0032] 100. Secondary battery; 10. Housing; 11. Receiving cavity; 12. First side wall; 121. First through hole; 122. First surface; 123. Second surface; 20. Pressure relief component; 21. Metal deformation member; 211. Active deformation layer; 212. Polymer layer; 213. Passive deformation layer; 22. Seal; 23. Connecting member; 231. Second through hole; 30. Battery cell assembly; 31. Head; 30a. Spacing; 40. Terminal assembly; X. Thickness direction. Detailed implementation manners

[0033] For the convenience of understanding the present application, the present application will be described in more detail below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is expressed as "fixed to" another element, it can be directly on the other element, or there can be one or more intermediate elements therebetween. When an element is expressed as "connected to" another element, it can be directly connected to the other element, or there can be one or more intermediate elements therebetween. The terms "upper", "lower", "inner", "outer", "vertical", "horizontal", etc. used in this specification indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0034] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not used to limit this application. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0035] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0036] The diameter of the metal sheet in the present application means that when observed along the thickness direction of the metal sheet, the outer contour of the entire metal sheet can be observed, and the diameter of the outer contour itself or the diameter of the circumscribed circle where it is located is the diameter of the metal sheet.

[0037] The inner diameter and outer diameter are the same in principle, and both refer to the diameter of the structure itself or the diameter of the circumscribed circle of the contour.

[0038] Please refer to Figure 1 and Figure 2, this application provides a secondary battery 100, which includes a housing 10, a pressure relief component 20, an electrode core component 30, and a terminal component 40. The pressure relief component 20 is disposed on the housing 10 to achieve pressure relief when the secondary battery 100 undergoes thermal runaway. The electrode core component 30 is disposed inside the housing 10, and the terminal component 40 is disposed on the housing 10. The terminal component 40 is electrically connected to the electrode core component 30 to form the positive terminal or negative terminal of the secondary battery 100. Of course, there is also electrolyte inside the housing 10, and the electrolyte infiltrates the electrode core component 30 so that the electrode core component 30 can normally undergo an electrochemical reaction.

[0039] In some embodiments, the housing 10 is a square rigid steel shell. The housing 10 is provided with a receiving cavity 11 for accommodating the electrode core component 30. The housing 10 includes a first side wall 12, and a through first through hole 121 is provided along the thickness direction X of the first side wall 12. The first through hole 121 communicates with the outside and the receiving cavity 11. The pressure relief component 20 is disposed on the first side wall 12 of the housing 10 and covers the first through hole 121. Under normal operating conditions, the pressure relief component 20 covers and seals the first through hole 121 so that the receiving cavity 11 remains in a sealed state. When the electrode core component 30 undergoes thermal runaway, the pressure relief component 20 can open at least part of the first through hole 121 to quickly discharge the high-pressure gas inside the receiving cavity 11, achieve pressure relief of the secondary battery 100, and reduce the probability of its explosion and fire.

[0040] The pressure relief component 20 includes a metal deformation member 21 and a sealing member 22. The metal deformation member 21 includes an active deformation layer 211, a polymer layer 212, and a passive deformation layer 213. The polymer layer 212 is disposed between the active deformation layer 211 and the passive deformation layer 213 and is respectively connected to the active deformation layer 211 and the passive deformation layer 213. When the active deformation layer 211 is closer to the first side wall 12 than the passive deformation layer 213, the sealing member 22 connects the active deformation layer 211 and the first side wall 12 of the housing 10, or when the passive deformation layer 213 is closer to the first side wall 12 than the active deformation layer 211, the sealing member 22 connects the passive deformation layer 213 and the first side wall 12 of the housing 10, so that the entire metal deformation member 21 is fixed on the first side wall 12. Among them, the thermal expansion coefficient G1 of the active deformation layer 211 is greater than the thermal expansion coefficient G2 of the passive deformation layer 213.

[0041] When the battery cell assembly 30 undergoes thermal runaway, the heat inside the accommodation cavity 11 is transferred to the metal deformation member 21. Since the coefficient of thermal expansion G1 of the active deformation layer 211 is greater than the coefficient of thermal expansion G2 of the passive deformation layer 213, the amount of deformation of the active deformation layer 211 is greater than that of the passive deformation layer 213. The active deformation layer 211 bends towards the passive deformation layer 213, and the first through hole 121 is opened. The gas inside the accommodation cavity 11 can be discharged to the outside through the first through hole 121 to achieve pressure relief. When the temperature inside the accommodation cavity 11 drops, the active deformation layer 211 and the passive deformation layer 213 gradually return to their initial states to cover the first through hole 121, thereby sealing the accommodation cavity 11.

[0042] For the measurement of the coefficients of thermal expansion of the active deformation layer 211 and the passive deformation layer 213, a dilatometer can be used for measurement. Specifically: First, prepare a rectangular sample to ensure that the surface of the sample is smooth and defect-free. Use a dilatometer, calibrate the equipment to ensure the accuracy of the measurement. Place the sample in the dilatometer and conduct tests in a controlled temperature environment. Slowly and uniformly change the temperature, and measure the dimensional changes of the sample. During the temperature change process, the dilatometer will record the length changes of the sample and record the length change data at different temperatures. Use the formula to calculate the linear coefficient of thermal expansion G = ΔL / (L0×ΔT), where ΔL is the length change, L0 is the initial length, and ΔT is the temperature change.

[0043] Compared with the prior art that uses a pressure relief valve body as the pressure relief structure of the secondary battery 100, the pressure relief principle of the pressure relief valve body is that the high-temperature and high-pressure gas inside the accommodation cavity 11 directly breaks through the pressure relief valve for pressure relief. In the embodiment of the present application, the secondary battery 100 sets the metal deformation member 21 as the pressure relief structure. On the one hand, it effectively utilizes the characteristic of metal expanding when heated, which can increase the action response speed of the metal deformation member 21 to improve the pressure relief efficiency. On the other hand, the metal deformation member 21 can return to its initial state after the temperature drops and can be reused, reducing costs.

[0044] In the secondary battery 100 of the embodiment of the present application, the metal deformation member 21 is provided with a polymer layer 212 between the active deformation layer 211 and the passive deformation layer 213. On the first hand, the polymer layer 212 isolates the active deformation layer 211 and the passive deformation layer 213, thereby reducing the probability of electrochemical corrosion caused by the direct contact between the active deformation layer 211 and the passive deformation layer 213. On the second hand, the polymer layer 212 bonds the active deformation layer 211 and the passive deformation layer 213 respectively, which helps to eliminate stress, ensure the stable deformation performance and reset performance of the active deformation layer 211 and the passive deformation layer 213, and extend the service life of the active deformation layer 211 and the passive deformation layer 213.

[0045] In some embodiments, the material of the active deformation layer 211 includes at least one of Inconel alloy, nickel, copper, copper-tin-zinc alloy, copper-zinc alloy or alloy steel. The material of the passive deformation layer 213 includes at least one of nickel-iron alloy, invar alloy, Inconel or manganin. The above materials are highly sensitive to temperature, which is beneficial to the thermal deformation of the active deformation layer 211 and the passive deformation layer 213.

[0046] The material of the polymer layer 212 includes at least one of polypropylene, polyimide, polyethylene terephthalate, polyamide, polycarbonate, polyphenylene sulfide, polyvinylidene fluoride, polytetrafluoroethylene, polyether ether ketone, liquid crystal polymer, polyaryletherketone, polyurethane plastic, polystyrene, polyvinyl chloride. Each of the above materials has a certain strength and toughness, can withstand a certain external force, and has a better protective effect on the active deformation layer 211 and the passive deformation layer 213. Moreover, the above materials all have good chemical stability, enabling the polymer layer to resist chemical corrosion to a certain extent, effectively isolating the active deformation layer 211 and the passive deformation layer 213, which is beneficial to extending the service life of the two.

[0047] In some embodiments, the melting point T1 of the polymer layer 212 is greater than the melting point T2 of the seal 22. Under the normal working conditions of the secondary battery 100, the seal 22 fixes the active deformation layer 211 on the first side wall 12 of the housing 10, and the seal 22 is solid to ensure the sealing effect. When the cell assembly 30 undergoes thermal runaway, the seal 22 is heated and at least partially becomes in a molten state, and the bonding effect of the seal 22 on the active deformation layer 211 is reduced, enabling the active deformation layer 211 to bend smoothly towards the passive deformation layer 213 to open the first through hole 121 for pressure relief. Setting the melting point T1 of the polymer layer 212 to be greater than the melting point T2 of the seal 22 can enable the polymer layer 212 to maintain its shape to bond the active deformation layer 211 and the passive deformation layer 213 when the seal 22 is heated and melted, reducing the bending stress. When the active deformation layer 211 and the passive deformation layer 213 return to their original shapes, the polymer layer 212 can effectively separate the active deformation layer 211 and the passive deformation layer 213. In some embodiments, the melting point T1 of the polymer layer 212 and the melting point T2 of the seal 22 satisfy: T1 - T2 ≥ 15°C. Controlling the difference between the melting point T1 of the polymer layer 212 and the melting point T2 of the seal 22 at 15°C and above can effectively ensure that the polymer layer 212 can still maintain its shape when the seal 22 is heated and melted, without affecting the normal operation of the active deformation layer 211 and the passive deformation layer 213.

[0048] For easy understanding, the following is illustrated by experiments:

[0049] In this experiment, several embodiments were set up. The number of secondary batteries in each embodiment was 20, and they had the same structure and the same other parameters. The difference was the different melting points T1 of the polymer layer 212 and the melting point T2 of the seal 22. The experimental data is shown in Table 1 below.

[0050] Table 1

[0051] Melting point T1 / °C of the polymer layer Melting point T2 / °C of the seal Success rate of pressure relief Example 1 115 125 14 / 20 Example 2 120 125 15 / 20 Example 3 125 125 18 / 20 Example 4 130 125 19 / 20 Example 5 135 125 19 / 20 Example 6 140 125 20 / 20 Example 7 145 125 20 / 20

[0052] Among them, the test method for the pressure relief success rate is as follows: Use a hot box to uniformly heat 20 secondary batteries, measure the temperature of the secondary batteries through a temperature measuring instrument (any temperature measuring instrument in any existing technology can be used). When the temperature of the secondary battery reaches 125 °C and is maintained for 30 min, then judge whether the pressure relief is successful. The judgment criterion is that the secondary battery does not explode, does not smoke, and does not catch fire. The number of secondary batteries for which the pressure relief component successfully relieves pressure is N, and the ratio of N to the total number 20 is the pressure relief success rate of the secondary batteries in this embodiment.

[0053] According to the data of Embodiment 1 to Embodiment 3 in Table 1 above, when the melting point T1 of the polymer layer in the pressure relief component is less than or equal to the melting point T2 of the seal, during the process of the temperature rise of some secondary batteries, the bonding force of the polymer layer decreases earlier than that of the seal, and the active deformation layer and the passive deformation layer cannot effectively maintain the bonding form, and even the two separate and fall off, and normal bending deformation cannot be achieved. And the pressure relief structure of the present application is that due to the different thermal expansion coefficients of the bimetal layer, the stress generated by the deformation of the bimetal layer enables the pressure relief component to be detached as a whole. Therefore, the active deformation layer and the passive deformation layer in the pressure relief component cannot maintain the bonding form, which will cause pressure relief lag. According to the data of Embodiment 4 to Embodiment 7, when the melting point T1 of the polymer layer in the pressure relief component is greater than the melting point T2 of the seal, and the difference between the two is less than 15 °C, the metal deformation parts in most secondary batteries can deform normally to relieve pressure, and the pressure relief success rate is significantly improved; however, when the melting points of the two are close or the difference is small, there may still be a situation where the metal deformation parts cannot deform and relieve pressure normally. When the difference between the melting points of the two is 15 °C or more, it can effectively ensure that the metal deformation parts can deform normally to relieve pressure.

[0054] In some embodiments, the melting point T1 of the polymer layer 212 is greater than the operating temperature T3 of the active deformation layer 211, and / or the melting point T1 of the polymer layer 212 is greater than the operating temperature T4 of the passive deformation layer 213. By setting the melting point of the polymer layer 212 to be greater than the operating temperature of the active deformation layer 211 and / or the passive deformation layer 213, during the process of the active deformation layer 211 and the passive deformation layer 213 expanding and deforming when heated, the polymer layer 212 can maintain the bonding of the active deformation layer 211 and the passive deformation layer 213, effectively spacing the two, and reducing the stress during their deformation.

[0055] In some embodiments, the melting point T1 of the polymer layer 212 and the operating temperature T3 of the active deformation layer 211 satisfy: T1 - T3 ≥ 10°C, and / or, the melting point T1 of the polymer layer 212 and the operating temperature T4 of the passive deformation layer 213 satisfy: T1 - T4 ≥ 10°C. Controlling the difference between the melting point T1 of the polymer layer 212 and the operating temperature T3 of the active deformation layer 211 and / or the operating temperature T4 of the passive deformation layer 213 at 10°C or more can reduce the probability of the polymer layer 212 melting and failing when the active deformation layer 211 and the passive deformation layer 213 deform.

[0056] The principles and methods for measuring the operating temperature T3 of the active deformation layer 211 or the operating temperature T4 of the passive deformation layer 213 are as follows:

[0057] [Measurement principle] A bimetallic strip is composed of two metal layers with different thermal expansion coefficients (a1 and a2, a1 > a2) laminated together. When the temperature changes, the two metal layers expand to different extents, causing the bimetallic strip to bend towards the side with a lower expansion coefficient. The bimetallic strip is heated, and the temperature at which the bimetallic strip begins to deform is the operating temperature.

[0058] [Measurement method]

[0059] 1. Sample fixation: Fix one end of the bimetallic strip, and leave the other end free or connect it to a contact / displacement sensor to ensure that the deformation is unobstructed.

[0060] 2. Temperature control device: Use a thermostatic bath, temperature control box, or heating platform, equipped with a high-precision temperature sensor (such as PT100, thermocouple), and place it near the bimetallic strip after calibration.

[0061] 3. Action detection system: (a) Electrical contact method: Connect a circuit (such as an LED or ammeter), and record the temperature when the bimetallic strip triggers the contact to open / close. (b) Displacement measurement method: Use a laser displacement meter or micrometer to monitor the deformation amount in real time, and record the temperature when the preset value is reached.

[0062] 4. Heating and recording: Heat at a slow and constant rate (such as 0.5°C / min) to avoid thermal hysteresis; synchronously record the temperature and the change in deformation / electrical signal to capture the temperature at the moment of action.

[0063] 5. Repeatability test: Conduct multiple heating and cooling cycles (3 - 5 times), calculate the average value and deviation of the operating temperature, and evaluate the stability.

[0064] 6. Error control: Ensure uniform heating (such as oil bath or forced convection), calibrate the temperature sensor, control the environmental temperature fluctuation, and use a low heating rate to reduce the influence of hysteresis.

[0065] In some embodiments, please refer to Figure 10 and Figure 11 , the outer diameter D3 of the active deformation layer 211, the outer diameter D5 of the polymer layer 212, and the outer diameter D6 of the passive deformation layer 213 are equal. During the production process, the polymer layer 212 can be first disposed between the active deformation layer 211 and the passive deformation layer 213 so that the three form an integral body, and then the metal deformation part 21 can be directly obtained through processes such as integral stamping and cutting. In this way, the outer diameters of the three are equal, which is beneficial to improving production efficiency. In other embodiments, the outer diameter D5 of the polymer layer 212 is greater than at least one of the outer diameter D3 of the active deformation layer 211 and the outer diameter D6 of the passive deformation layer 213. In the production process of this embodiment, the active deformation layer 211, the passive deformation layer 213, and the polymer layer 212 can be separately manufactured independently, and then the three are stacked separately. Among them, the outer diameter of the polymer layer 212 is the largest among the three, so that the polymer layer 212 can effectively isolate the active deformation layer 211 and the passive deformation layer 213, reducing the probability of electrochemical corrosion occurring when they come into contact.

[0066] In some embodiments, please refer to Figure 3 and Figure 6 , along the thickness direction X of the first side wall 12, the first side wall 12 has a first surface 122 and a second surface 123. The first surface 122 defines a partial boundary of the receiving cavity 11, the second surface 123 faces away from the receiving cavity 11, and the first through hole 121 penetrates through the first surface 122 and the second surface 123. The pressure relief component 20 can be disposed on the first surface 122, that is, the pressure relief component 20 is located inside the receiving cavity 11, or the pressure relief component 20 can be disposed on the second surface 123, that is, the pressure relief component 20 is located outside the receiving cavity 11.

[0067] As an example, as Figure 3 and Figure 4 shown, the pressure relief component 20 is disposed inside the receiving cavity 11. The seal 22 is respectively connected to the first surface 122 and the active deformation layer 211. The active deformation layer 211 is closer to the first side wall 12 than the passive deformation layer 213, and the metal deformation part 21 is located inside the receiving cavity 11. When the battery cell assembly 30 undergoes a thermal runaway, the edge regions of the active deformation layer 211 and the passive deformation layer 213 bend towards the battery cell assembly 30, and the region farther away from the center of the metal deformation part 21 has a greater deformation amount, so that at least a part of the first through hole 121 is opened, and the gas inside the receiving cavity 11 is discharged to the outside through the first through hole 121 to achieve pressure relief.

[0068] Or as Figure 5As shown, the seal 22 is respectively connected to the first surface 122 and the passive deformation layer 213. The passive deformation layer 213 is closer to the first side wall 12 than the active deformation layer 211. The metal deformation member 21 is located in the accommodation cavity 11. When the battery cell assembly 30 undergoes thermal runaway, the central regions of the active deformation layer 211 and the passive deformation layer 213 bend towards the battery cell assembly 30, and the region closer to the center of the metal deformation member 21 has a greater deformation amount, so that at least a part of the first through hole 121 is opened.

[0069] The pressure relief assembly 20 is arranged in the accommodation cavity 11. During the normal use of the secondary battery 100, the probability of the pressure relief assembly 20 being damaged can be reduced. When the secondary battery 100 undergoes thermal runaway, since there is a spaced arrangement between the battery cell assembly 30 and the first side wall 12 of the housing 10, the space of this part of the interval can be fully utilized to install the pressure relief assembly 20, without affecting the normal deformation and pressure relief of the metal deformation member 21.

[0070] As another example, as Figure 6 and Figure 7 shown, the pressure relief assembly 20 is arranged outside the accommodation cavity 11. The active deformation layer 211 is closer to the first side wall 12 than the passive deformation layer 213. The seal 22 is respectively connected to the second surface 123 and the active deformation layer 211. The metal deformation member 21 is located outside the accommodation cavity 11. When the battery cell assembly 30 undergoes thermal runaway, the edge regions of the active deformation layer 211 and the passive deformation layer 213 bend towards the side away from the battery cell assembly 30, and the region farther away from the center of the metal deformation member 21 has a greater deformation amount, so that at least a part of the first through hole 121 is opened, and the gas in the accommodation cavity 11 is discharged to the outside through the first through hole 121 to achieve pressure relief.

[0071] Or as Figure 8 shown, the seal 22 is respectively connected to the second surface 123 and the passive deformation layer 213. The passive deformation layer 213 is closer to the first side wall 12 than the active deformation layer 211. The metal deformation member 21 is located outside the accommodation cavity 11. When the battery cell assembly 30 undergoes thermal runaway, the central regions of the active deformation layer 211 and the passive deformation layer 213 bend towards the direction away from the battery cell assembly 30, and the region closer to the center of the metal deformation member 21 has a greater deformation amount, so that at least a part of the first through hole 121 is opened.

[0072] The pressure relief component 20 is arranged outside the accommodation cavity 11. It is easier to install and connect the pressure relief component 20 to the housing 10 on the outside of the housing 10. When the secondary battery 100 undergoes thermal runaway, since the metal deformation part 21 bends away from the accommodation cavity 11, which is consistent with the direction of the gas flowing outwards from the accommodation cavity 11, the blockage of the metal deformation part 21 to the gas flow is reduced, and the pressure relief speed is increased. In addition, when the battery cell assembly 30 generates a large amount of gas and heat in a very short time, the metal deformation part 21 located outside the housing 10 can be directly flushed open by the pressure relief gas to completely open the first through hole 121, enabling timely and fastest pressure relief and reducing the probability of explosion and fire of the secondary battery 100.

[0073] In some embodiments, along the thickness direction X of the pressure relief component 20, the seal 22 can directly abut against the surface of the active deformation layer 211, or the seal 22 can directly abut against the surface of the passive deformation layer 213. In other embodiments, the seal 22 can be connected to the active deformation layer 211 or the passive deformation layer 213 through other components. For example, a composite layer that connects and fixes the active deformation layer 211 and the seal 22 under normal working conditions. When the secondary battery 100 undergoes thermal runaway, the bonding performance of the composite layer decreases, which is beneficial for the thermal deformation of the active deformation layer 211.

[0074] In some embodiments, please refer to Figure 9 and Figure 10 , the pressure relief component 20 further includes a connecting member 23, and the connecting member 23 is fixed to the first surface 122 or the second surface 123 of the first side wall 12. Taking the connecting member 23 being fixed to the second surface 123 of the first side wall 12 as an example, the connecting member 23 is provided with a second through hole 231, and the second through hole 231 communicates with the first through hole 121. The connecting member 23 has a sheet-like structure. One side surface of the connecting member 23 is connected to the second surface 123 of the housing 10, the seal 22 is connected to the other side surface of the connecting member 23, the connecting member 23 is connected to the active deformation layer 211 through the seal 22, and the metal deformation part 21 covers the second through hole 231.

[0075] The seal 22 and the housing 10 are connected by adding a connecting member 23. On the one hand, it can reduce the probability of the seal 22 aging and failing, resulting in a decrease in the sealing performance at the first through hole 121. On the other hand, it can reduce the difficulty of fixing the seal 22 and the housing 10. Specifically, since the volume of the housing 10 is much larger than the volumes of the seal 22 and the metal deformation member 21, due to the material of the seal 22, it is difficult to directly connect the seal 22 and the housing 10. By adding the connecting member 23 as an intermediate connecting body, the volume of the connecting member 23 can be comparable to the volume of the seal 22, and the material of the connecting member 23 can be various, which increases the connection methods between the connecting member 23 and the housing 10 and reduces the installation difficulty. For example, during the installation process, the seal 22 is activated by high-temperature pressing, so that the seal 22 is fixedly connected to the metal deformation member 21 and the connecting member 23 respectively to form a whole, and then the connecting member 23 and the housing 10 are connected in various ways such as hot pressing, glue bonding, welding, snap connection, and snap-fastening connection.

[0076] In some embodiments, the connecting member 23 is a metal ring, and the interior of the metal ring has a second through hole 231. The metal ring is connected to the first side wall 12 of the housing 10 by laser welding. Setting the connecting member 23 into a ring shape has several advantages. On the one hand, it is convenient for welding the connecting member 23 and the housing 10. On the other hand, it makes the force on the circumferential direction of the connecting member 23 uniform and reduces stress concentration. Moreover, the pressure relief hole can be made smaller by controlling the inner diameter of the ring. For example, if the inner diameter of the ring is smaller than the diameter of the first through hole 121, the pressure can be relieved through the inner diameter of the connecting member 23 at this time. The material of the connecting member 23 is preferably at least one of aluminum, nickel, stainless steel, etc., which is beneficial to welding the connecting member 23 and the housing 10 and reduces the probability of the connecting member 23 corroding and rusting. In other embodiments, the connecting member 23 can also be in other shapes, such as rectangular, oval, or irregular shapes, etc.

[0077] In some embodiments, such as Figure 11As shown, the outer diameter D2 of the connecting member 23 and the diameter D1 of the first through hole 121 satisfy: D2 > D1; and / or, the outer diameter D3 of the active deformation layer 211 and the outer diameter D2 of the connecting member 23 satisfy: D3 ≤ D2, and the outer diameter D3 of the active deformation layer 211 and the diameter D4 of the second through hole 231 of the connecting member 23 satisfy: D3 > D4. Setting the outer diameter of the connecting member 23 to be greater than the diameter of the first through hole 121 enables the connecting member 23 to be fixedly connected to the first side wall 12. Setting the outer diameter of the active deformation layer 211 to be less than or equal to the outer diameter of the connecting member 23 can reduce the difficulty of laser welding the connecting member 23 to the housing 10. Especially when the outer diameter of the active deformation layer 211 is less than the outer diameter of the connecting member 23, the connecting member 23 protrudes radially from the active deformation layer 211, enabling there to be a sufficient welding area for welding to the housing 10. Setting the outer diameter of the active deformation layer 211 to be greater than the diameter of the second through hole 231 can ensure that the active deformation layer 211 completely covers the second through hole 231 to seal the second through hole 231 under normal operating conditions.

[0078] In some embodiments, the diameter D1 of the first through hole 121 satisfies: 0.5 mm ≤ D1 ≤ 5.5 mm. The inventors have found that for the currently mainstream-sized secondary battery 100, setting the diameter of the first through hole 121 between 0.5 millimeters and 5.5 millimeters can enable the exhaust rate of the first through hole 121 to be greater than or equal to the gas production rate during thermal runaway of the battery cell assembly 30 when the secondary battery 100 experiences thermal runaway, thereby meeting the requirement for pressure relief. And on the basis of ensuring that the exhaust rate of the first through hole 121 is greater than or equal to the gas production rate during thermal runaway of the battery cell assembly 30, the smaller the diameter of the first through hole 121, the less water vapor, oxygen, etc. outside the secondary battery 100 enter the accommodation cavity 11 through the first through hole 121, thereby reducing the side reaction rate of the battery cell assembly 30 caused by water vapor and oxygen, etc., and reducing the risk of explosion and fire of the battery cell assembly 30. Based on the setting of the diameter of the first through hole 121, the outer diameter D2 of the connecting member 23 satisfies: 1 mm ≤ D2 ≤ 6 mm; and / or, the diameter D4 of the second through hole 231 satisfies: 0.1 mm ≤ D4 ≤ 4 mm; and / or, the outer diameter D3 of the active deformation layer 211 satisfies: 0.1 mm ≤ D3 ≤ 6 mm.

[0079] In some embodiments, please refer to Figure 2, the battery cell assembly 30 is disposed in the accommodation cavity 11. The battery cell assembly 30 has a head 31, and the head 31 is opposite to and spaced from the first side wall 12 of the housing 10 to have a spaced space 30a. The head 31 of the battery cell assembly 30 is the end from which the tab of the battery cell assembly 30 extends. The pole assembly 40 is disposed through the first side wall 12, and the pole assembly 40 is electrically connected to the head 31 of the battery cell assembly 30. More specifically, the pole assembly 40 is electrically connected to the tab in the battery cell assembly 30. In the embodiment of the present application, both the pressure relief assembly 20 and the pole assembly 40 are disposed on the first side wall 12 of the housing 10. On the one hand, the setting of the pole assembly 40 makes the head 31 of the battery cell assembly 30 spaced from the first side wall 12. When the pressure relief assembly 20 is disposed inside the first side wall 12, the spaced space 30a between the battery cell assembly 30 and the first side wall 12 can be fully utilized; or when the pressure relief assembly 20 is welded to the outside of the first side wall 12, the spaced space 30a can reduce the transfer of welding heat to the battery cell assembly 30 and reduce the negative impact of heat on the battery cell assembly 30. On the other hand, during the thermal runaway of the battery cell assembly 30, the released gas accumulates in the spaced space 30a between the battery cell assembly 30 and the first side wall 12, and disposing the pressure relief assembly 20 on the first side wall 12 is beneficial to the rapid pressure relief of the gas. Of course, in other embodiments, a first through hole 121 may be provided on other side walls of the housing 10 to dispose the pressure relief assembly 20 on other side walls of the housing 10, and the first through hole 121 is made to communicate with the outside and the space between the battery cell assembly 30 and the first side wall 12 as much as possible, which is beneficial to the pressure relief of the gas.

[0080] The present application also provides an embodiment of an electronic device. The electronic device includes a secondary battery for providing electrical energy. For the structure and function of the secondary battery, reference may be made to the above embodiments and will not be elaborated here.

[0081] In the embodiment of the present application, the secondary battery 100 effectively utilizes the characteristic of metal thermal expansion by providing the metal deformation member 21 as a pressure relief structure, which can increase the action response speed of the pressure relief assembly 20 to improve the pressure relief efficiency. And by disposing the polymer layer 212 between the active deformation layer 211 and the passive deformation layer 213, on the one hand, the polymer layer 212 isolates the active deformation layer 211 and the passive deformation layer 213, thereby reducing the probability of electrochemical corrosion caused by the direct contact between the active deformation layer 211 and the passive deformation layer 213. On the other hand, the polymer layer 212 bonds the active deformation layer 211 and the passive deformation layer 213 respectively, which helps to eliminate stress, ensure the stable deformation performance and reset performance of the active deformation layer 211 and the passive deformation layer 213, and extend the service life of the active deformation layer 211 and the passive deformation layer 213.

[0082] The above are only embodiments of the present application, and do not thereby limit the patent scope of the present application. Any equivalent structural or equivalent process transformations made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, are similarly included within the patent protection scope of the present application.

Claims

1. A secondary battery, characterized in that: include: A housing is provided with a receiving cavity, the housing comprises a first side wall, and the first side wall is provided with a first through hole along the thickness direction thereof; A pressure relief component, disposed on the first side wall and covering the first through hole, the pressure relief component comprising a metal deformation member and a sealing member, the metal deformation member comprising an active deformation layer, a polymer layer and a passive deformation layer, the polymer layer respectively connecting the active deformation layer and the passive deformation layer; The sealing member connects the active deformation layer and the first side wall, and the passive deformation layer is arranged on a side of the active deformation layer away from the first side wall; Or, the sealing member connects the passive deformation layer and the first side wall, and the active deformation layer is arranged on a side of the passive deformation layer away from the first side wall; The thermal expansion coefficient G1 of the active deformation layer is greater than the thermal expansion coefficient G2 of the passive deformation layer.

2. The secondary battery according to claim 1, characterized in that: The melting point T1 of the polymer layer and the melting point T2 of the sealing member satisfy: T1-T2≥15°C.

3. The secondary battery according to claim 2, characterized in that: The melting point T1 of the polymer layer and the operating temperature T3 of the active deformation layer satisfy: T1-T3≥10°C, and / or, The melting point T1 of the polymer layer and the operating temperature T4 of the passive deformation layer satisfy: T1-T4≥10°C.

4. The secondary battery according to any one of claims 1 to 3, characterized in that: Along the thickness direction of the first side wall, the first side wall has a first surface and a second surface, the first surface defines a local boundary of the receiving cavity, the second surface is away from the receiving cavity, and the first through hole passes through the first surface and the second surface; The metal deformation member is located in the receiving cavity, and the sealing member is respectively connected to the first surface and the active deformation layer, or the sealing member is respectively connected to the first surface and the passive deformation layer; or, The metal deformation member is located outside the receiving cavity, and the sealing member is respectively connected to the second surface and the active deformation layer, or the sealing member is respectively connected to the second surface and the passive deformation layer.

5. The secondary battery according to claim 4, characterized in that: The pressure relief assembly includes a connecting piece, which is fixed to the first side wall, and is provided with a second through hole. The second through hole is connected to the first through hole, and the sealing piece is connected to the connecting piece. The connecting piece is connected to the active deformation layer, or the connecting piece is connected to the passive deformation layer, and the metal deformation piece covers the second through hole.

6. The secondary battery according to claim 5, characterized in that: The connecting piece is a metal ring, and the metal ring is welded to the first side wall.

7. The secondary battery according to claim 6, characterized in that: The outer diameter D2 of the connecting member and the diameter D1 of the first through hole satisfy: D2>D1; and / or, The outer diameter D3 of the active deformation layer and the outer diameter D2 of the connecting member satisfy: D3≤D2, and the outer diameter D3 of the active deformation layer and the diameter D4 of the second through hole of the connecting member satisfy: D3>D4.

8. The secondary battery according to claim 7, characterized in that: The diameter D1 of the first through hole satisfies: 0.5 mm ≤ D1 ≤ 5.5 mm; and / or, The outer diameter D2 of the connecting piece satisfies: 1mm≤D2≤6mm; and / or, The outer diameter D3 of the active deformation layer satisfies: 0.1 mm ≤ D3 ≤ 6 mm; and / or, The diameter D4 of the second through hole satisfies: 0.1 mm≤D4≤4 mm.

9. The secondary battery according to claim 7, characterized in that: The outer diameter D3 of the active deformation layer, the outer diameter D5 of the polymer layer and the outer diameter D6 of the passive deformation layer are equal; or, An outer diameter D5 of the polymer layer is greater than an outer diameter of at least one of the active deformation layer and the passive deformation layer.

10. The secondary battery according to claim 5, characterized in that: The material of the active deformation layer includes at least one of nickel-chromium-iron alloy, nickel, copper, copper-tin-zinc alloy, copper-zinc alloy or alloy steel; The material of the passive deformation layer includes at least one of nickel-iron alloy, Invar alloy, nickel-chromium-iron or manganese-copper-nickel; The material of the connecting piece includes at least one of aluminum, nickel and stainless steel.

11. The secondary battery according to claim 1, characterized in that: The material of the polymer layer includes at least one of polypropylene, polyimide, polyethylene terephthalate, polyamide, polycarbonate, polyphenylene sulfide, polyvinylidene fluoride, polytetrafluoroethylene, polyetheretherketone, liquid crystal polymer, polyaryletherketone, polyurethane plastic, polystyrene, and polyvinyl chloride.

12. The secondary battery according to claim 1, characterized in that: The secondary battery includes a cell assembly and a pole assembly. The cell assembly is arranged in the accommodating cavity. The cell assembly has a head, which is opposite to the first side wall and spaced apart. The pole assembly penetrates the first side wall, and the pole assembly is electrically connected to the head of the cell assembly.

13. An electronic device, characterized in that: Comprising the secondary battery as claimed in any one of claims 1 to 12.

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