Secondary battery and electronic device

Abstract

The present application discloses a secondary battery and an electronic device. The secondary battery comprises a housing and an electrode assembly; the electrode assembly is arranged in the housing; and in a first direction, the housing comprises a first wall portion and a second wall portion arranged opposite to each other. The secondary battery further includes a first cushioning member, and the first cushioning member is disposed between the first wall portion and the electrode assembly. The first cushioning member comprises a first end portion, a first position, and a second end portion; and in a second direction, the first end portion and the second end portion are arranged opposite to each other, and the first end portion and the second end portion both extend out of the electrode assembly. The center of the electrode assembly in the second direction is a first center, and in the first direction, the projection of the first center on the first cushioning member is located at the first position. In the first direction, the thickness of the first cushioning member at the first position is H1, the thickness of the first end portion is H11, and the thickness of the second end portion is H12; H1<H11, and H1<H12. The problems such as housing deformation and damage to the electrode assembly can be reduced, thereby improving the safety of the secondary battery.

Description

Secondary batteries and electronic devices Technical Field

[0001] This application relates to the field of battery technology, and in particular to a secondary battery and electronic device. Background Technology

[0002] With the rapid development of modern technology, the demand for high-performance energy storage devices is increasing in fields such as portable electronic devices and electric vehicles. Lithium-ion batteries, as a highly efficient and environmentally friendly energy storage device, have been widely used in many fields. However, during long-term charge-discharge cycles, the electrode components of lithium-ion batteries are prone to expansion, which can lead to irregular deformation of the casing. Summary of the Invention

[0003] This application aims to provide a secondary battery and electronic device that reduces the technical problem of irregular deformation of the secondary battery casing.

[0004] In a first aspect, this application proposes a secondary battery, including a housing and an electrode assembly. The electrode assembly is disposed within the housing. Along a first direction, the housing includes a first wall and a second wall disposed opposite to each other. The secondary battery also includes a first buffer member disposed between the first wall and the electrode assembly. The first buffer member includes a first end, a first position, and a second end. Along a second direction, the first end and the second end are disposed opposite to each other, and both the first end and the second end extend out of the electrode assembly. The center of the electrode assembly along the second direction is a first center, and along the first direction, the projection of the first center onto the first buffer member is located at the first position. Along the first direction, the thickness of the first buffer member at the first position is H1, and the thickness of the first end is H. 11 The thickness of the second end is H. 12 H1 <H 11 H1 <H 12 The first direction is the thickness direction of the secondary battery, and the second direction is perpendicular to the first direction.

[0005] In the above technical solution, the first buffer can buffer the expansion of the electrode assembly, reducing direct pressure from the electrode assembly on the first wall, thereby reducing shell deformation and damage to the electrode assembly. Furthermore, the first and second ends of the first buffer are thicker, enabling it to transfer some of the pressure generated by the electrode assembly's expansion to the stronger first corner (the area where the first part connects to the first wall), utilizing the stronger load-bearing capacity of the first corner to disperse the pressure. The thinner thickness at the first position allows for some expansion space in the middle of the electrode assembly. When the middle of the electrode assembly contacts the first buffer, the first buffer also buffers the electrode assembly, reducing direct contact and pressure between the electrode assembly and the shell, effectively protecting both the electrode assembly and the shell. This reduces shell deformation and electrode assembly damage, improving the safety of the secondary battery.

[0006] In some embodiments, 0.1×H 11 ≤H1≤0.9×H 11 This design effectively buffers the expansion of the electrode assembly and makes efficient use of the space between the electrode assembly and the first wall. The thicker first end provides sufficient support and cushioning at the first corner, while the appropriate thinning at the first position avoids excessively occupying the space needed for the bulge in the middle of the electrode assembly, thus optimizing space utilization and contributing to the compactness of the overall secondary battery structure. Based on the same inventive concept, 0.1×H 12 ≤H1≤0.9×H 12 0.1×H 12 ≤H1≤0.9×H 12 .

[0007] In some embodiments, a thickness of 0.1mm ≤ H1 ≤ 0.9mm allows the first buffer to withstand and disperse the pressure generated by the expansion of the electrode assembly, reducing the possibility that it is too thin to provide basic cushioning, thereby reducing direct pressure from the electrode assembly on the first wall. It also reduces the first buffer from excessively occupying the space between the electrode assembly and the first wall, which helps maintain the overall compactness of the battery. Preferably, the thickness is 0.3mm ≤ H1 ≤ 0.7mm.

[0008] In some embodiments, 0.5mm≤H 11 With a thickness ≤1mm, the first end can be easily supported between the first wall and the electrode assembly, thereby effectively transmitting pressure to the first corner and reducing premature deformation or damage of the first buffer at the first corner due to insufficient thickness. This also reduces the impact on the energy density of the secondary battery. Based on the same inventive concept, 0.5mm≤H 12 ≤1mm.

[0009] In some embodiments, the distance between the first wall portion and the electrode assembly along the thickness direction of the secondary battery is H3, where 0.5 × H3 ≤ H11 The thickness ≤ H3 ensures that the first end has sufficient thickness to support the electrode assembly and the first wall, thus providing a buffering effect. Based on the same inventive concept, 0.5 × H3 ≤ H 12 ≤H3.

[0010] In some embodiments, the thickness of the first buffer gradually increases from the first position to the first end. This allows the buffer to absorb and disperse pressure more effectively at different positions, reducing local over- or under-buffering and achieving a more uniform buffering effect, thus protecting the first wall and the electrode assembly. Based on the same inventive concept, the thickness of the first buffer gradually increases from the first position to the second end.

[0011] In some embodiments, the first buffer member is recessed in the direction away from the electrode assembly, so that a first buffer space is formed on the side of the first buffer member facing the electrode assembly. The presence of the first buffer space provides additional expandable space for the expansion of the electrode assembly during charging and discharging. When the electrode assembly expands, part of its volume can fill the first buffer space. Through its own elastic deformation and the containing effect of the first buffer space, the first buffer member can more effectively absorb the pressure generated by the expansion of the electrode assembly, further relieving the pressure on the first wall and reducing the risk of deformation or damage to the housing.

[0012] In some embodiments, the housing is a metal housing with high structural strength, which allows the first buffer to form a certain compression between the first wall and the electrode assembly, fully utilizing the function of the first buffer and reducing housing deformation.

[0013] In some embodiments, the first buffer element is made of at least one of ABS plastic, silicone, or nitrile rubber. Each material has good elasticity and flexibility, and can deform when subjected to external impact, absorbing and dispersing pressure, thereby playing a role in cushioning and shock absorption.

[0014] In some embodiments, the electrode assembly includes a first electrode, a separator, and a second electrode. Along a first direction, a plurality of first electrodes and a plurality of second electrodes are alternately stacked, with a separator disposed between adjacent first and second electrodes. By providing a first buffer between the electrode assembly and the first wall portion, and by having larger ends and a smaller thickness in the middle of the first buffer, the deformation of the housing can be reduced even in stacked electrode assemblies. The solution of this application is particularly suitable for stacked electrode assemblies.

[0015] In some embodiments, the second electrode is a negative electrode, which includes a negative electrode active material, including silicon. Adding silicon to the negative electrode can increase the capacity and energy density of the secondary battery, thus meeting the requirements for long-lasting operation. By providing a first buffer between the electrode assembly and the first wall, with the first buffer being larger at both ends and thinner in the middle, it can reduce casing deformation even when applied to silicon-based secondary batteries. The solution of this application is particularly suitable for silicon-based secondary batteries.

[0016] In some embodiments, along a third direction, the first buffer further includes a third end and a fourth end disposed opposite to each other, the third end and the fourth end extending out of the electrode assembly. Along a first direction, the thickness of the third end is H. 13 The thickness of the fourth end is H. 14 H1 <H 13 H1 <H 14 The first, second, and third directions are all perpendicular to each other. This allows the first buffer member to form a structure that is thin in the middle and thick around the edges. The thinner middle section provides some space for the expansion of the electrode assembly, reducing excessive pressure on the middle of the first wall and preventing deformation. The thicker edges correspond to the first corner where the cover connects to the first part, and can withstand and disperse greater pressure. The strong load-bearing capacity of the first corner buffers the force generated by the expansion of the electrode assembly, allowing the first buffer member to distribute the pressure more reasonably and evenly to the first corner where the cover connects to the first part.

[0017] In some embodiments, the secondary battery further includes a second buffer member disposed between the second wall portion and the electrode assembly. The second buffer member includes a fifth end portion, a second position portion, and a sixth end portion. Along a second direction, the fifth end portion and the sixth end portion are disposed opposite each other, and the third end portion and the fourth end portion extend beyond the electrode assembly. Along a first direction, the projection of the first center onto the second buffer member is located at the second position portion. Along the first direction, the thickness of the second buffer member at the second position portion is H2, and the thickness of the fifth end portion is H. 25 The thickness of the sixth end is H. 26 H2 <H 25 H2 <H 26The second buffer can cushion the expansion of the electrode assembly on the other side, reducing direct pressure from the electrode assembly on the second wall, thereby reducing casing deformation and damage to the electrode assembly. Furthermore, the fifth and sixth ends of the second buffer are thicker, allowing some of the pressure generated by the electrode assembly's expansion to the stronger second corner (the area where the second wall connects to the annular sidewall), utilizing the stronger load-bearing capacity of the second corner to disperse the pressure. The thinner thickness at the second position allows for some expansion space in the middle of the electrode assembly. When the middle of the electrode assembly contacts the second buffer, the buffer further cushions the electrode assembly, reducing direct contact and pressure between the electrode assembly and the casing, effectively protecting both the electrode assembly and the casing. This reduces casing deformation and electrode assembly damage, improving the safety of the secondary battery.

[0018] Secondly, this application also proposes an electronic device including a secondary battery as described in any of the embodiments of the first aspect above.

[0019] Additional aspects and advantages of the embodiments of this application will be described, shown, or illustrated in part by way of implementation of the embodiments of this application in the following description. Attached Figure Description

[0020] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, which are not intended to limit the embodiments, and elements having the same reference numerals in the drawings are designated as similar elements.

[0021] Figure 1 is a cross-sectional view of a secondary battery according to some embodiments of this application;

[0022] Figure 2 is a schematic diagram of the stacked structure of the first electrode and the second electrode in some embodiments of this application;

[0023] Figure 3 is a cross-sectional view of a first buffer element according to some embodiments of this application;

[0024] Figure 4 is a schematic diagram of the structure of the first buffer in some embodiments of this application;

[0025] Figure 5 is a schematic diagram of the structure of the first buffer in some embodiments of this application;

[0026] Figure 6 is a cross-sectional view of a secondary battery according to some embodiments of this application.

[0027] Explanation of reference numerals in the attached drawings: 100, secondary battery; 10, casing; 11, first part; 11a, first cavity; 111, second wall; 112, annular sidewall; 12, cover; 121, first wall; 20, electrode assembly; 20a, first center; 21, first electrode; 211, first current collector; 212, first active material layer; 22, second electrode; 221, second current collector; 222, second active material layer; 23, separator; 30, first buffer; 30a, first position; 30b, first buffer space; 31, first end; 32, second end; 33, third end; 34, fourth end; 40, second buffer; 40a, second position; 41, fifth end; 42, sixth end; 50, first corner position; 60, second corner position; X, first direction; Y, second direction; Z, third direction. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0029] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0030] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0031] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0032] The technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0033] In a first aspect, this application proposes a secondary battery 100. Referring to Figure 1, the secondary battery 100 includes a housing 10 and an electrode assembly 20 and an electrolyte (not shown in the figure) housed within the housing 10. The electrolyte wets the electrode assembly 20 within the housing 10, thereby causing an electrochemical reaction.

[0034] The housing 10 described above can be made of metallic materials such as aluminum, aluminum alloy, steel, stainless steel, nickel, copper, or magnesium alloy, giving it a certain structural strength to protect the electrode assembly 20 inside the secondary battery 100. Furthermore, each material of the housing 10 has good thermal conductivity, which helps improve the heat dissipation performance of the secondary battery 100. Simultaneously, each material has good electrical conductivity, allowing the housing 10 to lead out a specific polarity of the secondary battery 100, for example, using the housing 10 itself as the positive or negative electrode of the secondary battery 100. In other embodiments, the housing 10 can also be made of a soft-pack material, such as an aluminum-plastic film or a copper-plastic film.

[0035] Referring to Figure 1, the housing 10 includes a first part 11 and a cover 12. The first part 11 has a first cavity 11a, and the electrode assembly 20 can be disposed in the first cavity 11a. The cover 12 does not have a cavity, or the cover 12 has a second cavity (not shown in the figure). By covering the first cavity 11a with the cover 12 and connecting the cover 12 to the first part 11, the first part 11 and the cover 12 together form a complete housing 10. The connection method between the cover 12 and the first part 11 includes, but is not limited to, welding or bonding.

[0036] The electrode assembly 20 includes a first electrode 21, a second electrode 22, and a separator 23. The first electrode 21 and the second electrode 22 have opposite polarities; for example, the first electrode 21 is a positive electrode and the second electrode 22 is a negative electrode. Alternatively, the first electrode 21 is a negative electrode and the second electrode 22 is a positive electrode. The separator 23 is disposed between the first electrode 21 and the second electrode 22 to insulatingly separate them.

[0037] Referring to Figures 1 and 2, the first electrode 21 includes a first current collector 211 and a first active material layer 212. The first current collector 211 serves as the conductive substrate of the first electrode 21 and can be an integrally flat aluminum foil. Aluminum foil has high conductivity and low resistance, which can improve the charge / discharge rate of the secondary battery 100. The first active material layer 212 can be stacked on at least one surface of the first current collector 211 in the thickness direction. Taking the first electrode 21 as a positive electrode as an example, the first active material layer 212 includes a positive electrode active material, a conductive agent, and a binder, etc. These material components are mixed, stirred evenly, and coated onto the first current collector 211 to obtain the first active material layer 212. The positive electrode active material includes one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide, or lithium manganese iron phosphate.

[0038] Referring to Figures 1 and 2, the second electrode 22 includes a second current collector 221 and a second active material layer 222. The second current collector 221 serves as the conductive substrate of the second electrode 22 and can be an integrally flat copper foil. Copper foil has high conductivity and low resistance, which can improve the charge / discharge rate of the secondary battery 100. The second active material layer 222 can be disposed on at least one surface of the second current collector 221 in the thickness direction. Taking the second electrode 22 as a negative electrode as an example, the second active material layer 222 includes a negative electrode active material, a conductive agent, and a binder, etc. These materials are mixed, stirred evenly, and coated onto the second current collector 221 to obtain the second active material layer 222. The negative electrode active material includes one or more of graphite, soft carbon, hard carbon, carbon fiber, elemental silicon, silicon oxide, silicon alloy, etc.

[0039] Referring to Figure 1, along the first direction X (the thickness direction of the secondary battery 100), the housing 10 includes a first wall portion 121 and a second wall portion 111 disposed opposite to each other. When the cover 12 does not have a cavity, the cover 12 itself is the first wall portion 121. In some other embodiments, the first wall portion 121 may also be the bottom wall of the first portion 11.

[0040] During the charge-discharge cycle of the secondary battery 100, lithium ions are extracted and inserted into the positive and negative electrodes of the electrode assembly 20, causing the electrodes to expand and the volume of the electrode assembly 20 to increase. The electrode assembly 20 then exerts an expansion force on the casing 10. The inventors of this application have discovered that the structural characteristics of the casing 10 make the middle part of the cover 12 more prone to bulging under this expansion force, resulting in irregular deformation of the casing 10. The area where the first part 11 connects to the first wall 121 (denoted as the first corner 50) has greater strength and can better resist the expansion force, while the middle part is relatively independent and bears more concentrated pressure, making it prone to bulging in the middle of the first wall 121. This may have a certain impact on the performance and safety of the secondary battery 100. For example, the outer electrode of the electrode assembly 20 may deform and misalign due to compression, leading to a short circuit. In extreme cases, it may even damage the seal of the secondary battery 100, causing leakage and posing a safety hazard.

[0041] To mitigate the aforementioned problems, in the embodiments of this application, referring to Figures 1 and 3, the secondary battery 100 further includes a first buffer member 30, which is disposed between the first wall portion 121 and the electrode assembly 20. The first buffer member 30 includes a first end portion 31, a first position 30a, and a second end portion 32. Along the second direction Y, the first end portion 31 and the second end portion 32 are disposed opposite each other, and both the first end portion 31 and the second end portion 32 extend out of the electrode assembly 20. The center of the electrode assembly 20 along the second direction Y is a first center 20a, and along the first direction X, the projection of the first center 20a onto the first buffer member 30 is located at the first position 30a. Along the first direction X, the thickness of the first buffer member 30 at the first position 30a is H1, and the thickness of the first end portion 31 is H. 11 The thickness of the second end 32 is H. 12 H1 <H 11 H1 <H 12 The second direction Y can be the length or width direction of the secondary battery 100, and the second direction Y is perpendicular to the first direction X.

[0042] In the embodiments of this application, the first buffer 30 can buffer the expansion of the electrode assembly 20, reducing the direct pressure of the electrode assembly 20 on the first wall portion 121, thereby reducing irregular deformation of the housing 10 and reducing pressure damage to the electrode assembly 20. Furthermore, the first end 31 and the second end 32 of the first buffer 30 are thicker, enabling the transfer of some of the pressure generated by the expansion of the electrode assembly 20 to the stronger first corner position 50 (the area where the first portion 11 connects to the first wall portion 121), utilizing the stronger load-bearing capacity of the first corner position 50 to disperse the pressure. The first position 30a is thinner, allowing for a certain expansion space in the middle of the electrode assembly 20. When the middle of the electrode assembly 20 contacts the first buffer 30, the first buffer 30 can also buffer the electrode assembly 20, reducing direct contact and pressure between the electrode assembly 20 and the housing 10, thereby effectively protecting the electrode assembly 20 and the housing 10, reducing problems such as deformation of the housing 10 and damage to the electrode assembly 20, and improving the safety of the secondary battery 100. Furthermore, the thickness difference design of the first buffer 30 can make more reasonable use of the internal space of the secondary battery 100. The thinner center will not excessively occupy the space required for the bulge in the middle of the electrode assembly 20, while the thicker ends can meet the requirements of withstanding greater pressure. It will not waste space due to excessive overall thickness, which helps to improve the compactness of the secondary battery 100 structure.

[0043] Regarding the shape of the first buffer 30, the first buffer 30 can be a structure with a small thickness in the middle and a large thickness at both ends in the second direction Y, which can accommodate the expansion of the electrode assembly 20. In some other embodiments, referring to FIG5, along the third direction Z, the first buffer 30 further includes a third end 33 and a fourth end 34 disposed opposite to each other, the third end 33 and the fourth end 34 extending out of the electrode assembly 20. Along the first direction X, the thickness of the third end 33 is H. 13 The thickness of the fourth end 34 is H. 14 H1 <H 13 H1 <H 14 This design allows the first buffer member 30 to have a structure that is thinner in the middle and thicker around the edges. The thinner middle section provides some space for the expansion of the electrode assembly 20, reducing excessive pressure on the middle of the first wall portion 121 and preventing deformation. The thicker edges correspond to the first corner 50 where the cover 12 connects to the first portion 11, and can withstand and disperse greater pressure. The strong load-bearing capacity of the first corner 50 buffers the force generated by the expansion of the electrode assembly 20, allowing the first buffer member 30 to distribute the pressure more reasonably to the first corner 50 where the cover 12 connects to the first portion 11. The first direction X, the second direction Y, and the third direction Z are all perpendicular to each other.

[0044] In some embodiments, the first end 31, the first position 30a, and the second end 32 are all located on a straight line parallel to the second direction Y. In this case, the first end 31 can be considered as a straight line, and the thickness H of the first end 31 is... 11 This refers to the height of the straight line in the first direction X. In some other embodiments, when the first end 31 is a plane (along the second direction Y, the two opposite sides of the first buffer 30), the thickness of the first end 31 is H. 11 It can be the average thickness of the first end 31. For example, along the third direction Z, five points are evenly selected on the first end 31, the thickness of the five points is measured, and the average thickness of the five points is taken as H. 11 The thickness of each end can be determined similarly.

[0045] In some embodiments, please refer to Figure 3, 0.1×H 11 ≤H1≤0.9×H 11 0.1×H can be selected 11 Up to 0.9×H 11 Any value in, for example, choosing 0.1×H 11 0.2×H 11 0.3×H 11 0.4×H 11 0.5×H 11 0.6×H 11 0.7×H 11 0.8×H 11 Or 0.9×H 11 The expansion of the electrode assembly 20 can be effectively buffered, and the space between the electrode assembly 20 and the first wall portion 121 can be effectively utilized. The first end 31 is thicker than the first position 30a, which allows the first end 31 to provide sufficient support and buffering at the first corner 50. The first position 30a is appropriately thinned without excessively occupying the space required for the bulge in the middle of the electrode assembly 20, thus optimizing space utilization and helping to improve the overall compactness of the secondary battery 100. When the electrode assembly expands, the first end 31 and the second end 32 preferentially transmit the pressure generated by the expansion to the first corner 50, which has a stronger resistance to deformation. As the electrode assembly 20 continues to expand and comes into contact with the first position 30a, the pressure can be distributed throughout the first wall portion 121. Since the first position 30a is thinner, the pressure on the part of the first wall portion 121 corresponding to the first position 30a is also smaller. However, the first end 31 and the second end 32 are thicker, resulting in a larger pressure at the first corner 50. This means that the part of the first wall 121 with weaker resistance to deformation is subjected to less pressure, while the part with stronger resistance to deformation is subjected to greater pressure, making the stress on the first wall 121 more reasonable, reducing irregular deformation of the shell 10, and especially reducing the bulge in the middle.

[0046] If the thickness at the first position 30a is large, for example, exceeding 0.9 × H 11 This would occupy a significant amount of space. When the electrode assembly 20 expands, it may increase the pressure on the middle portion of the first wall 121, potentially causing bulging, deformation, or even damage. It may also exert additional compressive force on the electrode assembly 20, affecting its performance and lifespan. If the thickness at the first position 30a is small, for example, less than 0.1 × H... 11 The ability of the buffer electrode assembly 20 to expand will also decrease, making it difficult to fully absorb and disperse pressure, and may cause more pressure to be transmitted to the first end 31 and the second end 32. Although the first corner 50 has strong resistance to deformation, excessive pressure transmitted to the first corner 50 may also cause the first wall 121 to deform.

[0047] Based on the same inventive concept, 0.1×H 12 ≤H1≤0.9×H 12 0.1×H can be selected 12 Up to 0.9×H 12 Any value in H1, for example, H1 is chosen as 0.1 × H. 12 0.2×H 12 0.3×H 12 0.4×H 12 0.5×H 12 0.6×H 12 0.7×H 12 0.8×H 12 Or 0.9×H 12 The second end 32 is thicker than the first position 30a, which allows the second end 32 to provide sufficient support and cushioning at the first corner 50, further optimizing space utilization and helping to improve the overall compactness of the secondary battery 100 structure.

[0048] The thickness at the first position 30a can be specifically selected based on the thickness of the first end 31 and the second end 32. In some embodiments, 0.1mm ≤ H1 ≤ 0.9mm, and any value from 0.1mm to 0.9mm can be selected, such as H1 being 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, or 0.9mm. Setting the lower limit to 0.1mm allows the first buffer 30 to withstand and disperse the pressure generated by the expansion of the electrode assembly 20, reducing the possibility of it being too thin to provide basic buffering, thereby reducing the direct compression of the first wall portion 121 by the electrode assembly 20. Furthermore, setting the upper limit to 0.9mm reduces the first buffer 30 from excessively occupying the space between the electrode assembly 20 and the first wall portion 121, which helps maintain the overall compactness of the battery. Preferably, 0.3mm ≤ H1 ≤ 0.7mm.

[0049] In some embodiments, 0.5mm≤H 11 ≤1mm, any value from 0.5mm to 1mm can be selected, for example, H 11 The thickness can be selected from 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, or 1mm. A lower limit of 0.5mm facilitates the support of the first end 31 between the first wall portion 121 and the electrode assembly 20. When the electrode assembly 20 expands, the first end 31 can withstand greater pressure, effectively transferring the pressure to the first corner 50, reducing premature deformation or damage to the first buffer member 30 at the first corner 50 due to insufficient thickness. A higher limit of 1mm reduces the space occupied by the first buffer member 30, thereby reducing the energy density loss of the secondary battery 100.

[0050] Based on the same inventive concept, 0.5mm≤H 12 ≤1mm, any value from 0.5mm to 1mm can be selected, for example, H 12 The thickness can be selected from 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, or 1mm, etc. This can effectively accommodate the expansion of the electrode assembly 20 and reduce the energy density loss of the secondary battery 100.

[0051] In some embodiments, referring to Figures 1 and 3, the distance between the first wall portion 121 and the electrode assembly 20 along the thickness direction (first direction X) of the secondary battery 100 is H3, where 0.5 × H3 ≤ H 11The thickness of the first end 31 is ≤H3, ensuring sufficient thickness for the first end 31 to support the electrode assembly 20 and the first wall 121, thus providing a buffering effect. If the thickness of the first end 31 is small, for example, less than 0.5×H3, it may be more easily compressed to its limit, making it difficult to fully absorb and disperse pressure, and also difficult to effectively transmit force to the first corner 50, resulting in poor buffering effect; it may also cause a large force to be generated directly between the electrode assembly 20 and the first wall 121, which may easily cause deformation and misalignment of the outer electrode sheet and the separator 23 of the electrode assembly 20, posing a safety risk. If the thickness of the first end 31 is large, for example, greater than H3, it may cause the first buffer 30 to be in a compressed state from the beginning, which may result in waste of the material of the first buffer 30, and may cause excessive pressure to be transmitted to the first corner 50, resulting in pressure concentration, and may also cause deformation of the first wall 121; at the same time, it also occupies a large space, causing a loss of energy density of the secondary battery 100.

[0052] Based on the same inventive concept, 0.5 × H³ ≤ H 12 The thickness is ≤H3, which allows the second end 32 to have sufficient thickness to support between the electrode assembly 20 and the first wall portion 121, thereby playing a buffering role and reducing the impact on the energy density of the secondary battery 100.

[0053] In some embodiments, referring to FIG3, the thickness of the first buffer 30 gradually increases from the first position 30a to the first end 31. The pressure generated by the expansion of the electrode assembly 20 is generally relatively large near the first end 31 and relatively small in the center. By gradually changing the thickness, the first buffer 30 can provide a gradually increasing buffering capacity from the center to the end when the electrode assembly 20 expands. This allows the first buffer 30 to absorb and disperse pressure more effectively at different positions, reducing local over- or under-buffering, thereby achieving a more uniform buffering effect and protecting the first wall 121 and the electrode assembly 20. Furthermore, this gradually changing thickness design can make more rational use of the internal space of the secondary battery 100. The thinner center will not excessively occupy the space required for the bulge in the middle of the electrode assembly 20, while the thicker end can meet the requirements of withstanding greater pressure, without wasting space due to excessive overall thickness, which helps to improve the compactness of the secondary battery 100 structure.

[0054] Based on the same inventive concept, the thickness of the first buffer 30 gradually increases from the first position 30a to the second end 32. This allows the first buffer 30 to absorb and disperse pressure more effectively at different positions, reducing local over- or under-buffering, thereby achieving a more uniform buffering effect and protecting the first wall portion 121 and the electrode assembly 20.

[0055] In some embodiments, referring to Figures 1 and 3, the first buffer member 30 is recessed in the direction away from the electrode assembly 20, so that a first buffer space 30b is formed on the side of the first buffer member 30 facing the electrode assembly 20. The presence of the first buffer space 30b provides additional expandable space for the electrode assembly 20 to expand during the charging and discharging process. When the electrode assembly 20 expands, part of its volume can be filled into the first buffer space 30b. Through its own elastic deformation and the containing effect of the first buffer space 30b, the first buffer member 30 can more effectively absorb the pressure generated by the expansion of the electrode assembly 20, further relieving the pressure on the first wall portion 121 and reducing the risk of deformation and damage to the housing 10.

[0056] In some embodiments, the surface of the first buffer member 30 facing away from the electrode assembly 20 is fitted to the first wall portion 121, for example, by directly bonding the first buffer member 30 to the first wall portion 121, which can improve the stability of the connection between the first buffer member 30 and the first wall portion 121. During installation, the first buffer member 30 is simply placed facing the electrode assembly 20, and the cover 12 is connected and fixed to the first portion 11. The fitted arrangement allows for a larger contact area between the first buffer member 30 and the first wall portion 121. The larger contact area allows the pressure generated by the expansion of the electrode assembly 20 to be more evenly distributed to the first wall portion 121 through the first buffer member 30, reducing the risk of deformation, cracking, etc., of the first wall portion 121 due to excessive local stress.

[0057] In some embodiments, the housing 10 is a metal housing 10, for example, the housing 10 is made of metal materials such as steel, stainless steel or nickel. The housing 10 has high structural strength, so that the first buffer 30 can form a certain compression between the first wall portion 121 and the electrode assembly 20, giving full play to the role of the first buffer 30 and reducing the deformation of the housing 10.

[0058] The material of the first buffer 30 includes at least one of ABS plastic, silicone, or nitrile rubber. Each material possesses good elasticity and flexibility, enabling it to deform under external impact, absorbing and dispersing pressure, thus providing cushioning and shock absorption. Furthermore, each material exhibits good insulation properties, isolating the electrode assembly 20 from the metal casing 10 and reducing the risk of short circuits due to direct contact between the electrode assembly 20 and the casing 10. For example, when the casing 10 leads out the negative electrode, the positive electrode of the electrode assembly 20 may be exposed due to expansion and compression, potentially causing a short circuit upon contact with the casing 10. The first buffer 30 effectively reduces the occurrence of such situations. Simultaneously, each material possesses excellent corrosion resistance, adapting to the electrolyte environment inside the secondary battery 100, thereby extending the service life of the secondary battery 100.

[0059] The electrode assembly 20 can be wound, for example, by stacking and winding a first electrode 21, a separator 23, and a second electrode 22 to form a wound electrode assembly 20. The electrode assembly 20 can also be stacked, for example, by alternately stacking several first electrode 21s and several second electrode 22s, with a separator 23 between adjacent first electrode 21s and second electrode 22s. Regardless of whether the electrode assembly 20 is stacked or wound, the expansion in its middle is greater than that at its ends. By placing a first buffer 30 between the electrode assembly 20 and the first wall portion 121, the expansion force of the electrode assembly 20 can be effectively absorbed, reducing direct pressure on the first wall portion 121. The inventors of this application have discovered that the stacked electrode assembly 20 does not have a winding binding force, and its middle part expands to a greater extent. In the embodiments of this application, by providing a first buffer 30 between the electrode assembly 20 and the first wall portion 121, and the first buffer 30 having larger ends and a smaller middle thickness, it can reduce the deformation of the housing 10 even in the stacked electrode assembly 20. The solution of this application is particularly suitable for the stacked electrode assembly 20.

[0060] In the embodiments of this application, the second electrode 22 is a negative electrode, which includes a negative electrode active material, including silicon. Silicon has a theoretical specific capacity of up to 4200 mAh / g, while the theoretical specific capacity of traditional graphite negative electrode active materials is only 372 mAh / g. Adding silicon to the negative electrode can increase the capacity and energy density of the secondary battery 100, thus meeting the requirements for long-lasting battery life.

[0061] However, the inventors of this application have discovered that during the charge-discharge cycle of the secondary battery 100, the insertion and extraction of lithium ions cause significant changes in the volume of silicon. During charging, a large number of lithium ions are inserted into the silicon material, leading to an increase in the thickness of the negative electrode sheet; during discharging, lithium ions are extracted, causing the volume of the silicon material to shrink. However, due to the irreversible structural changes that occur during repeated volume changes, the negative electrode sheet is difficult to fully recover to its initial thickness after multiple cycles, resulting in increased expansion of the electrode sheet and consequently, increased expansion force of the electrode assembly 20 on the first wall portion 121. In this application, by providing a first buffer member 30 between the electrode assembly 20 and the first wall portion 121, and by having larger ends and a smaller thickness in the middle of the first buffer member 30, even when applied to a silicon-based secondary battery 100, it can effectively reduce the deformation of the casing 10. The solution of this application is particularly suitable for silicon-based secondary batteries 100.

[0062] Referring to Figure 6, in an embodiment of this application, the secondary battery 100 further includes a second buffer 40. The second buffer 40 can be similarly configured to the first buffer 30, and is disposed between the second wall portion 111 and the electrode assembly 20. For example, the first portion 11 includes the second wall portion 111 and an annular sidewall 112 connected to the second wall portion 111. The annular sidewall 112 surrounds and connects to the second wall portion 111, thereby enclosing and forming a first cavity 11a. The second buffer 40 includes a fifth end portion 41, a second position 40a, and a sixth end portion 42. Along the second direction Y, the fifth end portion 41 and the sixth end portion 42 are disposed opposite to each other, and the fifth end portion 41 and the sixth end portion 42 extend out of the electrode assembly 20. Along the first direction X, the projection of the first center 20a onto the second buffer 40 is located at the second position 40a. Along the first direction X, the thickness of the second buffer 40 at the second position 40a is H2, and the thickness of the fifth end portion 41 is H. 25 The thickness of the sixth end 42 is H. 26 H2 <H 25 H2 <H 26 .

[0063] The second buffer 40 can buffer the expansion of the electrode assembly 20 from the other side, reducing the direct pressure of the electrode assembly 20 on the second wall portion 111, thereby reducing the deformation of the housing 10 and the damage caused by the pressure on the electrode assembly 20. Furthermore, the fifth end 41 and the sixth end 42 of the second buffer 40 are thicker, enabling it to transfer some of the pressure generated by the expansion of the electrode assembly 20 to the stronger second corner position 60 (the area where the second wall portion 111 connects to the annular sidewall 112), utilizing the stronger load-bearing capacity of the second corner position 60 to disperse the pressure. The second position 40a is thinner, allowing for a certain expansion space in the middle of the electrode assembly 20. When the middle of the electrode assembly 20 contacts the second buffer 40, the second buffer 40 can also buffer the electrode assembly 20, reducing direct contact and pressure between the electrode assembly 20 and the housing 10, thus effectively protecting the electrode assembly 20 and the housing 10, reducing deformation of the housing 10 and damage to the electrode assembly 20, and improving the safety of the secondary battery 100.

[0064] Secondly, this application also proposes an electronic device, including a secondary battery 100 as described in any embodiment of the first aspect above. The electronic device in this application is not particularly limited and can be any electronic device known in the prior art. For example, electronic devices include, but are not limited to, Bluetooth headsets, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., while spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0065] Example 1:

[0066] <Preparation of the positive electrode>

[0067] The positive electrode active material is lithium cobalt oxide, the positive electrode conductive agent is acetylene black, and the positive electrode binder is polyvinylidene fluoride (PVDF, with a weight average molecular weight of 5×10⁻⁶). 5 The materials were mixed at a mass ratio of 94:3:3, with N-methylpyrrolidone (NMP) added as a solvent to prepare a positive electrode slurry with a solid content of 75 wt%, and stirred evenly under vacuum. An aluminum foil with a thickness of 10 μm, a length of 338.5 mm, and a width of 3.5 mm was used as the positive electrode current collector. The positive electrode slurry was uniformly coated onto one surface of the aluminum foil and dried at 110°C to obtain a positive electrode sheet with a single-sided coating of positive active material. The above steps were then repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of positive active material. The coated electrode sheet was then cold-pressed to obtain a cold-pressed positive electrode sheet with a double-sided coating of positive active material. The single-sided coating weight of the positive electrode sheet was 21 mg / cm³. 2 The thickness of single-sided cold pressing is 62.25 μm, and the thickness of double-sided cold pressing is 112.5 μm.

[0068] <Preparation of Negative Electrode Sheets>

[0069] A mixture of graphite powder (negative electrode active material), silicon powder, conductive carbon black (Super P) as a conductive agent, and styrene-butadiene rubber (SBR) as a binder was prepared in a weight ratio of 87.5:10:1:1.5. Deionized water was then added as a solvent to prepare a negative electrode slurry with a solid content of 50 wt%, and the mixture was stirred thoroughly. A copper foil with a thickness of 8 μm, a length of 374 mm, and a width of 4.1 mm was selected as the negative electrode current collector. The negative electrode slurry was uniformly coated onto one surface of the copper foil and dried at 90°C to obtain a single-sided negative electrode sheet. This completes the single-sided coating of the negative electrode sheet. The above steps were then repeated on the other surface of the negative electrode sheet to obtain a double-sided coated negative electrode sheet. The coated electrode sheet was then cold-pressed to obtain a cold-pressed negative electrode sheet with a double-sided negative electrode active material layer. The single-sided coating weight of the negative electrode sheet was 8.6 mg / cm³. 2 The thickness of single-sided cold pressing is 61.4 μm, and the thickness of double-sided cold pressing is 112.8 μm.

[0070] <Preparation of the separating membrane>

[0071] A porous polyethylene film with a thickness of 7 μm was used as the separator.

[0072] <Electrolyte Preparation>

[0073] In a dry argon atmosphere, ethylene carbonate, methyl ethyl carbonate and diethyl carbonate were mixed in a mass ratio of 30:50:20 to obtain an organic solution. Then, lithium hexafluorophosphate was added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0074] <Preparation of Lithium-ion Batteries>

[0075] Several positive and negative electrode sheets prepared above are alternately stacked, with a separator film placed between adjacent positive and negative electrode sheets to obtain an electrode assembly. The electrode assembly is placed in the first cavity of the first part, and the first cavity is covered by a cover. A first buffer material made of silicone is placed between the cover (the cover does not have a cavity; the cover itself is the first wall portion, hereinafter referred to as the first wall portion) and the electrode assembly. The thickness H1 of the first buffer material at the first position is 0.05 mm, the first position corresponds to the center of the electrode assembly, and the thickness H at the first end is... 11 The thickness H at the second end is 1mm. 12 The thickness H at the third end is 1mm. 13 The thickness H at the fourth end is 1mm. 14The thickness is 1mm. After the positive and negative electrode tabs are welded together, the moisture is removed at 80℃, and then electrolyte is injected. The lithium-ion secondary battery undergoes formation, capacity testing, voltage and internal resistance testing, and other processes to obtain the battery. The distance H3 between the first wall and the electrode assembly is 1mm. The secondary battery is 20mm long, 15mm wide, and 5mm thick, with the thickness S of each wall of the casing being 0.1mm.

[0076] Unlike Example 1, the relevant parameters in Examples 2 to 18 and Comparative Examples 1 to 3 are shown in Table 1 below. In Comparative Example 1, no first buffer was provided.

[0077] Test method for battery swelling:

[0078] A: Place the battery under test on the test platform and ensure that the battery surface makes good contact with the movable plate of the capacitance sensor.

[0079] B: Initial measurement: Record the battery's capacitance value in its initial state as a reference value.

[0080] C: Charge and discharge process: At 25℃, the secondary battery, which has reached a constant temperature, is charged at a constant current of 0.2C until the voltage is the cutoff voltage. Then, it is charged at a constant voltage of the cutoff voltage until the current is 0.02C, and discharged at 0.2C until the voltage is 3.0V. One charge and discharge cycle is one cycle. Record the change in capacitance value after 1000 cycles.

[0081] D: Data Recording and Analysis: Record the changes in capacitance during charging and discharging, and convert the capacitance value into changes in battery thickness through calculation.

[0082] The following benchmarks were used for evaluation: after 1000 charge-discharge cycles at 25°C, the thickness increase should not exceed 10%; that is, for the selected battery, the thickness limit is 5.5mm. Exceeding the limit is considered a failure. Each group of 20 batteries was tested, the number of failures was N, and the failure rate was N / 20.

[0083] Table 1

[0084] According to Table 1 above, and in conjunction with Examples 1 to 12 and Comparative Examples 1 to 3, it can be seen that when H1 is used... <H 11 and H1 <H 12This design effectively reduces the test failure rate. The first buffer can cushion the expansion of the electrode assembly, reducing direct pressure from the electrode assembly on the first wall, thereby reducing deformation of the housing and damage to the electrode assembly. Furthermore, the thicker first and second ends of the first buffer allow some of the pressure generated by the electrode assembly's expansion to the stronger first corner (the area where the first part connects to the first wall), utilizing the stronger load-bearing capacity of the first corner to disperse the pressure. The thinner thickness at the first position allows for some expansion space in the middle of the electrode assembly. When the middle of the electrode assembly contacts the first buffer, the first buffer also cushions the electrode assembly, reducing direct pressure between the electrode assembly and the housing, thus effectively protecting both the electrode assembly and the housing and reducing the risk of bulging in the middle of the first wall.

[0085] In Examples 1 and 2, the thickness at the first location is relatively small, both less than 0.1 × H. 11 The ability of the buffer electrode assembly to expand will also decrease, making it difficult to fully absorb and disperse pressure. This may lead to more pressure being transmitted to the first and second ends. Although the first corner has strong resistance to deformation, excessive pressure transmission to the first corner may also cause irregular deformation of the first wall. In Example 12, the thickness at the first position is relatively large, exceeding 0.9 × H. 11 This would occupy a significant amount of space, and when the electrode assembly expands, it could increase the pressure on the middle portion of the first wall, potentially causing bulging, deformation, or even damage. Therefore, in the embodiments of this application, in conjunction with embodiments 3 to 11, 0.1×H can be selected. 11 ≤H1≤0.9×H 11 For example, a value of 0.1 mm ≤ H1 ≤ 0.9 mm can be selected. In Examples 5 to 9, the failure rate is further reduced. In the embodiments of this application, 0.3 × H1 is preferred. 11 ≤H1≤0.7×H 11 For example, choose 0.3mm ≤ H1 ≤ 0.7mm. Similarly, for the second end, 0.1 × H can be chosen. 12 ≤H1≤0.9×H 12 And preferably 0.3×H 12 ≤H1≤0.7×H 12 For the third end, 0.1 × H can be selected. 13 ≤H1≤0.9×H 13 And preferably 0.3×H 13 ≤H1≤0.7×H 13 For the fourth end, 0.1 × H can be selected. 14 ≤H1≤0.9×H 14 And preferably 0.3×H 14 ≤H1≤0.7×H 14.

[0086] In conjunction with Embodiments 13 to 18 and Embodiment 5, in Embodiment 13, the thickness of the first end is relatively small, less than 0.5 × H³. This may cause the first end to be more easily compressed to its limit, making it difficult to fully absorb and disperse pressure, and also making it difficult to effectively transfer force to the first corner, resulting in poor buffering effect. It may also cause a large force to be generated directly between the electrode assembly and the first wall, posing a safety risk. In Embodiments 14 to 18 and Embodiment 5, the expansion of the electrode assembly can be effectively buffered, thereby reducing the risk of irregular deformation of the shell. Therefore, in the embodiments of this application, 0.5 × H³ ≤ H can be selected. 11 ≤H3, for example, choose 0.5mm≤H 11 ≤1mm. Similarly, for the second end, 0.5×H3≤H can be selected. 12 ≤H3, for example, choose 0.5mm≤H 12 ≤1mm. For the third end, 0.5×H3≤H can be selected. 13 ≤H3, for example, choose 0.5mm≤H 13 ≤1mm. For the fourth end, 0.5×H3≤H can be selected. 14 ≤H3, for example, choose 0.5mm≤H 14 ≤1mm.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of this application as described above, which are not provided in detail for the sake of brevity; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A secondary battery, comprising a housing and an electrode assembly, the electrode assembly being disposed within the housing along a first direction, the housing comprising a first wall portion and a second wall portion disposed opposite to each other, characterized in that, The secondary battery further includes a first buffer member, which is disposed between the first wall portion and the electrode assembly; The first buffer includes a first end, a first position, and a second end. Along a second direction, the first end and the second end are disposed opposite to each other, and both the first end and the second end extend out of the electrode assembly. The center of the electrode assembly along the second direction is the first center, and the projection of the first center onto the first buffer along the first direction is located at the first position. In the first direction, the first cushioning member has a thickness H1 at the first position, the first end has a thickness H 11 , and the second end has a thickness H 12 ; H1 < H 11 , H1 < H 12 . Wherein, the first direction is the thickness direction of the secondary battery, and the second direction is perpendicular to the first direction.

2. The secondary battery according to claim 1, characterized in that, 0.1 x H 11 ≤ H1≤ 0.9 x H 11 ; and / or, 0.1 x H 12 ≤ H1≤ 0.9 x H 12 .

3. The secondary battery according to claim 2, characterized in that, 0.3 x H 11 ≤ H1≤ 0.7 x H 11 ; and / or, 0.3 x H 12 ≤ H1≤ 0.7 x H 12 .

4. The secondary battery according to claim 1, characterized in that, 0.1mm≤H1≤0.9mm.

5. The secondary battery according to claim 4, characterized in that, 0.3mm≤H1≤0.7mm.

6. The secondary battery according to any one of claims 1 to 5, characterized in that, 0.5mm≤H 11 ≤1mm; and / or, 0.5mm≤H 12 ≤1mm.

7. The secondary battery according to any one of claims 1 to 6, characterized in that, Along the thickness direction of the secondary battery, the distance between the first wall portion and the electrode assembly is H3; 0.5×H3≤H 11 ≤H3, and / or, 0.5×H3≤H 12 ≤H3.

8. The secondary battery according to any one of claims 1 to 7, characterized in that, Along the first position to the first end, the thickness of the first buffer gradually increases; Along the first position to the second end, the thickness of the first buffer gradually increases.

9. The secondary battery according to any one of claims 1 to 8, characterized in that, The first buffer is recessed in a direction away from the electrode assembly, so that a first buffer space is formed on the side of the first buffer facing the electrode assembly.

10. The secondary battery according to any one of claims 1 to 9, characterized in that, The casing is a metal casing.

11. The secondary battery according to any one of claims 1 to 10, characterized in that, The material of the first buffer includes at least one of ABS plastic, silicone or nitrile rubber.

12. The secondary battery according to any one of claims 1 to 11, characterized in that, The electrode assembly includes a first electrode, a separator, and a second electrode. Along the first direction, a plurality of first electrodes and a plurality of second electrodes are alternately stacked, and the separator is disposed between two adjacent first electrodes and second electrodes.

13. The secondary battery according to claim 12, characterized in that, The second electrode is a negative electrode, which includes a negative electrode active material, and the negative electrode active material includes silicon.

14. The secondary battery according to any one of claims 1 to 13, characterized in that, Along a third direction, the first buffer also includes a third end and a fourth end disposed opposite to each other, the third end and the fourth end extending out of the electrode assembly; Along the first direction, the thickness of the third end is H. 13 The thickness of the fourth end is H. 14 H1 <H 13 H1 <H 14 ; Wherein, the first direction, the second direction, and the third direction are all perpendicular to each other.

15. The secondary battery according to any one of claims 1 to 14, characterized in that, The secondary battery also includes a second buffer, which is disposed between the second wall portion and the electrode assembly; The second buffer includes a fifth end, a second position, and a sixth end. Along the second direction, the fifth end and the sixth end are disposed opposite to each other, and the third end and the fourth end extend out of the electrode assembly. Along the first direction, the projection of the first center onto the second buffer is located at the second position; Along the first direction, the thickness of the second buffer at the second position is H2, and the thickness of the fifth end is H. 25 The thickness of the sixth end is H. 26 H2 <H 25 H2 <H 26 .

16. An electronic device, characterized in that, Includes the secondary battery as described in any one of claims 1 to 15.

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