battery

Abstract

This invention relates to the field of secondary battery technology and discloses a battery including a membrane housing and an electrode assembly. The membrane housing includes a first end face and a top sealing edge. The first end face has a convex surface and a concave surface, with the concave surface located on one side of the convex surface. The top sealing edge includes a first sealing edge corresponding to the convex surface and a second sealing edge corresponding to the concave surface. The electrode assembly includes a cell body and tabs. The tabs include multiple layers of tab sheets stacked together to form a tab cluster and connected to lead-out tabs, which extend from the second sealing edge to the outside of the membrane housing. The first sealing edge has a first bend, which bends along one side of the thickness direction. The second sealing edge has a second bend, which bends along one side of the thickness direction. Along a first direction, the maximum gap between the second bend and the concave surface is G, which ranges from 0.3 mm to 2 mm. This invention can reduce the risk of warping and tearing of the top sealing edge during bending, as well as the risk of breakage of the multiple layers of tab sheets inside the battery.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, and more specifically to batteries. Background Technology

[0002] As the demand for battery energy density increases, the top sealing edge of pouch batteries is usually bent and fitted to the battery end face to improve the space utilization of the battery compartment, thereby increasing the battery energy density.

[0003] However, problems such as warping, incomplete bending, and film tearing can easily occur when bending the top seal edge, affecting the reliability of the encapsulation. At the same time, after the top seal edge is bent and attached to the battery end face, it can easily compress the soft multi-layered electrode tabs inside the cell. During long-term use of the battery, the electrode tabs are at risk of breakage, affecting the battery reliability. Summary of the Invention

[0004] This invention provides a battery that improves upon the problems of the top sealing edge of the battery casing easily warping and tearing when bent, and the multi-layered electrode tabs inside the battery easily breaking.

[0005] The battery of the present invention includes a membrane housing and an electrode assembly disposed within the membrane housing; the membrane housing includes a first end face and a top sealing edge protruding from the first end face along a first direction, the first end face having a convex surface and a concave surface, the concave surface being located on one side of the convex surface along a second direction, the second direction, the first direction, and the thickness direction of the battery being mutually perpendicular; the sealing edge includes a first sealing edge corresponding to the convex surface and a second sealing edge corresponding to the concave surface, the edge of the second sealing edge being lower than the edge of the first sealing edge along the first direction; the electrode assembly includes a cell body and a tab extending from the side of the cell body near the first end face, and so on. The electrode tab includes multiple layers of electrode tab sheets, which are stacked together to form an electrode tab cluster and extend from the second sealing edge to the outside of the membrane shell; the first sealing edge has a first bend portion, which bends along one side of the thickness direction, and the projection of the first bend portion at least partially overlaps with the convex surface along the first direction; the second sealing edge has a second bend portion, which bends along one side of the thickness direction, and the projection of the second bend portion at least partially overlaps with the concave surface along the first direction; along the first direction, there is a gap G between the second bend portion and the concave surface, where G ranges from 0.3 mm to 2 mm.

[0006] Beneficial effects: The first end face forms a convex surface and a concave surface. The top sealing edge includes a first sealing edge and a second sealing edge corresponding to the convex and concave surfaces, and the edge of the second sealing edge is lower than the edge of the first sealing edge. The first sealing edge and the second sealing edge form a stepped height difference, so that when the first sealing edge is bent, the first bent part bends along the area where the convex surface is located, and when the second sealing edge is bent, the second bent part bends along the area where the concave surface is located. Since the first sealing edge and the second sealing edge bend at two different heights corresponding to the convex and concave surfaces, the bending span of a single top sealing edge (first sealing edge or second sealing edge) is reduced compared to the bending span of the entire top sealing edge in the past. The bending stress is dispersed and significantly reduced, making it less likely for the second sealing edge to be pulled when the first sealing edge is bent, or vice versa. This reduces the risk of the entire top sealing edge lifting, reduces the risk of membrane shell tearing, and improves the sealing reliability of the membrane shell.

[0007] Because the bending stress at the bends of the first and second sealing edges is significantly reduced, there is no need to excessively compress the top sealing edge when bending the top sealing edge as before, which effectively improves the risk of multi-layer electrode tab breakage. At the same time, there is a gap between the second bend and the concave surface. When the first end face of the battery is subjected to external impact, the gap can absorb the impact force and avoid direct impact on the multi-layer electrode tab, thus reducing the risk of multi-layer electrode tab breakage. Attached Figure Description

[0008] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0009] Figure 1 This is a perspective view of a battery according to an embodiment of the present invention; Figure 2 This is a front view of a battery with both the first and second sealing edges in an unfolded state, according to an embodiment of the present invention. Figure 3 This is a front view of a battery with the first seal in a bent state and the second seal in an unfolded state, according to an embodiment of the present invention. Figure 4 This is a front view of a battery with both the first and second sealing edges in a bent state, according to an embodiment of the present invention. Figure 5 This is a schematic diagram of the first cross-section of a battery according to an embodiment of the present invention; Figure 6 This is a front view of the battery according to an embodiment of the present invention; Figure 7 This is a front view of the protective plate according to an embodiment of the present invention; Figure 8This is a schematic diagram of the second cross-section of the battery according to an embodiment of the present invention.

[0010] Explanation of reference numerals in the attached figures: 10-Membrane shell; 11-First end face; 111-Convex surface; 112-Concave surface; 112a-First concave surface; 112b-Second concave surface; 12-Top sealing edge; 121-First sealing edge; 121a-First bend; 122-Second sealing edge; 122a-Second bend; 123-First inclined surface; 124-Second inclined surface; 20-Electrode assembly; 21-Cell body; 22-Multilayer electrode tabs; 23-Leading electrode tabs; 30 - Protection board; 31 - Functional board; 32 - Flexible board; 321 - First part; 322 - Second part; 323 - Third part; 324 - Electrical connector; X - First direction; Y - Second direction; Z - Thickness direction. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0012] The top sealing edge of the battery casing is prone to warping, incomplete bending, and tearing after bending, affecting the reliability of the encapsulation. At the same time, during the process of bending the top sealing edge to fit the battery end face, it is easy to compress the soft multi-layered electrode tabs inside the cell. During long-term use of the battery, the electrode tabs are at risk of breakage, affecting battery safety.

[0013] Research has revealed that the main reasons for problems such as warping, incomplete bending, and membrane tearing during top sealing edge bending are that, due to the continuous integral structure of the top sealing edge, the entire edge rotates synchronously on the same plane during the overall bending process, resulting in a large bending span and significant stress concentration at the bending point. This stress concentration causes the rebound force of the top sealing edge to detach from the end face to exceed the bending constraint force, making it prone to warping and failing to adhere to the end face. Therefore, the bending force of the top sealing edge is usually increased and pressed against the end face to overcome the rebound stress, thus ensuring the top sealing plate adheres to the end face. However, excessive bending force can easily lead to membrane tearing, resulting in poor sealing reliability. When the top sealing edge is bent and pressed towards the end face, a compressive force is formed on the end face of the battery cell. This compressive force is transmitted from the end face to the multi-layered tabs located between the battery cell body and the end face inside the membrane shell. Because the multi-layered tabs are relatively soft and each layer is relatively weak, they are prone to breakage under the compressive force. Meanwhile, when the battery end face is subjected to external impact, the impact force is directly transmitted through the membrane and top seal to the end face and the multi-layered tabs inside the end face, increasing the risk of the tabs breaking and failing after being subjected to impact.

[0014] This application provides a battery including a membrane housing and an electrode assembly disposed within the membrane housing. The membrane housing includes a first end face and a top sealing edge protruding from the first end face along a first direction. The first end face has a convex surface and a concave surface. Along a second direction, the concave surface is located on one side of the convex surface. The second direction, the first direction, and the thickness direction of the battery are perpendicular to each other. The top sealing edge includes a first sealing edge corresponding to the convex surface and a second sealing edge corresponding to the concave surface. Along the first direction, the edge of the second sealing edge is lower than the edge of the first sealing edge. The electrode assembly includes a cell body and a tab extending from the cell body near the first end face. The tab includes multiple layers of tab sheets stacked together and connected to a lead-out tab. The lead-out tab extends from the second sealing edge to the outside of the membrane housing. The first sealing edge has a first bend, which bends along one side of the thickness direction, and along the first direction, the projection of the first bend at least partially overlaps with the convex surface. The second sealing edge has a second bend, which bends along one side of the thickness direction, and along the first direction, the projection of the second bend at least partially overlaps with the concave surface. Along the first direction, the maximum gap between the second bend and the concave surface is G, and the range of G is 0.3mm to 2mm.

[0015] With this configuration, the first end face forms a convex and a concave surface. The top sealing edge includes a first sealing edge and a second sealing edge corresponding to the convex and concave surfaces, with the edge of the second sealing edge lower than the edge of the first sealing edge, creating a stepped height difference between the first and second sealing edges. When the first sealing edge is bent, the first bent portion bends along the area of ​​the convex surface; when the second sealing edge is bent, the second bent portion bends along the area of ​​the concave surface. Because the first and second sealing edges bend at different heights on the convex and concave surfaces, the bending span of a single top sealing edge (first or second sealing edge) is reduced compared to the bending span of the entire top sealing edge. The bending stress is distributed at the bending points of the first and second sealing edges, significantly reducing the bending stress. This makes it less likely for the first sealing edge to pull the second sealing edge when bending, or vice versa, thereby reducing the risk of the entire top sealing edge lifting, reducing the risk of membrane shell tearing, and improving the sealing reliability of the membrane shell.

[0016] Because the bending stress at the bends of the first and second sealing edges is significantly reduced, there is no need to excessively compress the top sealing edge when bending the top sealing edge as before, which effectively improves the risk of multi-layer electrode tab breakage. At the same time, there is a gap between the second bend and the concave surface. When the first end face of the battery is subjected to external impact, the gap can absorb the impact force and avoid direct impact on the multi-layer electrode tab, thus reducing the risk of multi-layer electrode tab breakage.

[0017] In addition, the concave surface sinks downward relative to the convex surface along the first direction, forming a recessed receiving area along the first direction on the first end face. The protection plate can be arranged in the receiving area to avoid protruding beyond the end face of the cell, thereby improving the space utilization rate on the first end face of the cell. Under the same battery compartment space, the size of the cell active area can be increased, and the overall energy density of the battery is improved.

[0018] The following is combined with Figures 1 to 8 The embodiments of the present invention will be described in detail below.

[0019] An embodiment of this application provides a battery. The battery includes a housing 10 and an electrode assembly 20 disposed within the housing 10. The housing 10 includes a first end face 11 and a top sealing edge 12 protruding from the first end face 11 along a first direction X. The first end face 11 has a convex surface 111 and a concave surface 112. Along a second direction Y, the concave surface 112 is located on one side of the convex surface 111. The second direction Y, the first direction X, and the thickness direction Z of the battery are all perpendicular to each other. The top sealing edge 12 includes a first sealing edge 121 corresponding to the convex surface 111 and a second sealing edge 122 corresponding to the concave surface 112. Along the first direction X, the edge of the second sealing edge 122 is lower than the edge of the first sealing edge 121. The electrode assembly 20 includes a cell body 21 and an electrode tab extending from the cell body 21 near the first end face 11. The electrode tab includes multiple layers of electrode tab sheets 22, which are stacked together to form an electrode tab cluster and connected to a lead-out electrode tab 23. The lead-out electrode tab 23 extends from the second sealing edge 122 to the outside of the membrane housing 10. The first sealing edge 121 has a first bend 121a, which is bent along one side of the thickness direction Z, and along the first direction X, the projection of the first bend 121a at least partially overlaps with the convex surface 111. The second sealing edge 122 has a second bend 122a, which is bent along one side of the thickness direction Z, and along the first direction X, the projection of the second bend 122a at least partially overlaps with the concave surface 112. Along the first direction X, the maximum gap between the second bend 122a and the concave surface 112 is G, which ranges from 0.3 mm to 2 mm.

[0020] The membrane housing 10 is the external encapsulation structure of the battery, used to seal the electrode assembly 20 and provide external protection. The membrane housing 10 can be made of aluminum-plastic composite membrane.

[0021] The first end face 11 is the end face on the membrane shell 10 that is perpendicular to the large surface of the battery. The first end face 11 faces the outside of the battery, that is, it is an outer end face of the battery.

[0022] The first end face 11 has a convex surface 111 and a concave surface 112. The convex surface 111 is a region on the first end face 11 that protrudes relatively along the first direction X, that is, the region on the convex surface 111 extends away from the main body 21 along the first direction X. The concave surface 112 is a region on the first end face 11 that sinks relatively along the first direction X, that is, the region on the concave surface 112 is recessed towards the main body 21 along the first direction X. A height difference is formed between the concave surface 112 and the convex surface 111.

[0023] Along the second direction Y, the concave surface 112 is located on one side of the convex surface 111, that is, the concave surface 112 and the convex surface 111 are arranged and distributed along the second direction Y. For example, along the second direction Y, the end of the convex surface 111 away from the concave surface 112 extends to one edge of the first end face 11, and the end of the concave surface 112 away from the convex surface 111 extends to the other edge of the first end face 11.

[0024] The first direction X is parallel to the large surface of the battery and perpendicular to the first end face 11. The second direction Y is parallel to the large surface of the battery and perpendicular to the first direction X. The thickness direction Z is perpendicular to the large surface of the battery. The first direction X, the second direction Y, and the thickness direction Z are all perpendicular to each other, forming a mutually orthogonal three-dimensional coordinate system.

[0025] The top seal 12 is a sealing structure that extends outward along the first direction X from the edge of the first end face 11 of the membrane housing 10. The top seal 12 can be formed by a hot-press sealing process and is used to enclose the electrode assembly 20 inside the membrane housing 10.

[0026] The top sealing edge 12 includes a first sealing edge 121 corresponding to the convex surface 111 and a second sealing edge 122 corresponding to the concave surface 112. The first sealing edge 121 can be the portion of the top sealing edge 12 that is directly opposite to the convex surface 111 along the first direction X, and the second sealing edge 122 can be the portion of the top sealing edge 12 that is directly opposite to the concave surface 112 along the first direction X.

[0027] Along the first direction X, the edge of the second sealing edge 122 is lower than the edge of the first sealing edge 121, that is, the first sealing edge 121 and the second sealing edge 122 form a stepped height difference.

[0028] The electrode assembly 20 is the core component for realizing electrochemical energy storage and electrical energy output inside the battery, including the cell body 21 and the tabs. The cell body 21 is the main structure in the electrode assembly 20 that realizes electrochemical reaction and energy storage. The cell body 21 is formed by a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode, forming a wound structure or a stacked structure.

[0029] The tab is a conductive structure extending from the cell body 21, used to conduct the current generated by the cell body 21 to an external circuit. The tab includes multiple layers of tab sheets 22, which are tab clusters formed by stacking the uncoated portions of the current collectors of each electrode sheet in the cell body 21 along the thickness direction Z. The lead-out tab 23 is a conductive component connected to the multiple layers of tab sheets 22 and extending outwards from the battery. The lead-out tab 23 extends from the second sealing edge 122 corresponding to the concave surface 112, that is, the lead-out tab 23 extends out of the membrane shell 10 from the sealing edge area. The lead-out tab 23 can be sealed to the second sealing edge 122 using tab adhesive.

[0030] The first bending portion 121a is a bending area formed by bending the first sealing edge 121 along one side of the thickness direction Z. The bending direction is from the outside of the membrane shell 10 toward the cell body 21 along the thickness direction Z. After bending, the projection of the first bending portion 121a along the first direction X at least partially overlaps with the convex surface 111, that is, after bending, the first bending portion 121a covers or partially covers the area where the convex surface 111 is located.

[0031] The second bending portion 122a is a bending area formed by bending the second sealing edge 122 along one side of the thickness direction Z. The bending direction is from the outside of the membrane shell 10 toward the battery cell body 21 along the thickness direction Z. After bending, the projection of the second bending portion 122a along the first direction X at least partially overlaps with the concave surface 112, that is, after bending, the second bending portion 122a covers or partially covers the area where the concave surface 112 is located.

[0032] Along the first direction X, the maximum gap between the second bent portion 122a and the concave surface 112 is G, where G is the distance along the first direction X between the position of the second bent portion 122a closest to the concave surface 112 after bending and the position of the concave surface 112 furthest from the second bent portion 122a. When the first end face 11 forms one concave surface 112, the gap between the second bent portion 122a and the concave surface 112 is G. When the first end face 11 forms two or more concave surfaces 112, the gap between the second bent portion 122a and the deepest concave surface 112 is G.

[0033] Regarding the measurement of G, after the second sealing edge 122 of the battery is bent, a feeler gauge can be inserted between the second bent portion 122a and the concave surface 112 along the first direction X to measure the gap value. Alternatively, an image measuring instrument can be used to photograph the cross-section of the second bent portion 122a and the concave surface 112 along the first direction X, and the maximum gap can be measured using image processing software.

[0034] If G is too large, the gap between the second bend 122a and the concave surface 112 will be too large, resulting in excessive space waste, increased overall battery length, reduced battery compartment space utilization, and decreased battery volumetric energy density. If G is too small, the gap between the second bend 122a and the concave surface 112 will be too small, causing the second bend 122a to be too close to the concave surface 112 after bending. The compressive force generated during bending will be transmitted through the concave surface 112 to the multi-layer electrode tab 22 stacking connection structure inside the cell body 21, increasing the risk of plastic deformation or even breakage of the electrode tabs under pressure. At the same time, a small gap will result in insufficient clearance space during external impacts, with the impact force directly transmitted to the electrode tabs, increasing the risk of electrode tab breakage. Therefore, by controlling G within the range of 0.3mm to 2mm, sufficient buffer clearance space can be provided for the bending of the second bend 122a and external impacts to reduce the risk of electrode tab breakage under pressure, while maintaining a reasonable gap between the sealing edge and the end face to improve the battery compartment space utilization.

[0035] For example, G can be 0.3mm, 0.35mm, 0.42mm, 0.51mm, 0.65mm, 0.8mm, 1mm, 1.2mm, 1.38mm, 1.55mm, 1.7mm, 1.85mm, 1.95mm, 2mm, etc., or a value within the range of any two of the above values.

[0036] In the above scheme, a convex surface 111 and a concave surface 112 are formed by the first end face 11. The top sealing edge 12 includes a first sealing edge 121 corresponding to the convex surface 111 and a second sealing edge 122 corresponding to the concave surface 112. The edge of the second sealing edge 122 is lower than the edge of the first sealing edge 121. The first sealing edge 121 and the second sealing edge 122 form a stepped height difference, so that when the first sealing edge 121 is bent, the first bent part 121a bends along the area where the convex surface 111 is located, and when the second sealing edge 122 is bent, the second bent part 122a bends along the area where the concave surface 112 is located. Since the first sealing edge 121 and the second sealing edge 122 are bent at different heights on the convex surface 111 and the concave surface 112 respectively, the bending span of a single top sealing edge 12 is reduced compared to the bending span of the entire top sealing edge 12. The bending stress is distributed at the bending points of the first sealing edge 121 and the second sealing edge 122, and the bending stress is greatly reduced. This makes it less likely for the first sealing edge 121 to pull the second sealing edge 122 when it is bent, or for the second sealing edge 122 to pull the first sealing edge 121 when it is bent. As a result, the risk of the entire top sealing edge 12 lifting is reduced, the risk of the membrane shell 10 tearing is reduced, and the sealing reliability of the membrane shell 10 is improved.

[0037] Because the bending stress at the bends of the first sealing edge 121 and the second sealing edge 122 is significantly reduced, the top sealing edge 12 is no longer subject to excessive compression during the previous overall bending process. This improves the risk of breakage of the multilayer tabs 22 inside the membrane housing 10 caused by the top sealing edge 12 compressing the first end face 11. Simultaneously, a gap exists between the second bend 122a and the concave surface 112. When the first end face 11 of the battery is subjected to external impact, the gap can absorb the impact force, preventing direct impact on the multilayer tabs 22 and further reducing the risk of breakage.

[0038] In addition, the concave surface 112 sinks down relative to the convex surface 111 along the first direction X, forming a recessed receiving area along the first direction X on the first end face 11. The protection plate 30 can be arranged in this receiving area to avoid protruding beyond the end face of the cell, thereby improving the space utilization rate on the first end face 11 of the cell. Under the same battery compartment space, the size of the active area of ​​the cell can be increased, and the overall energy density of the battery is improved.

[0039] Furthermore, the second sealing edge 122 corresponding to the concave surface 112 has a longer sealing edge width along the second direction Y compared to the first sealing edge 121 corresponding to the convex surface 111. The lead-out tab 23 is led out from the second sealing edge 122 corresponding to the concave surface 112, so that the sealing width of the lead-out tab 23 and the tab adhesive is guaranteed, and the sealing reliability is improved.

[0040] In some embodiments, the concave surface 112 includes a first concave surface 112a and a second concave surface 112b. Along the second direction Y, the first concave surface 112a is located between the convex surface 111 and the second concave surface 112b. Along the first direction X, the second concave surface 112b is lower than the first concave surface 112a, and the lead-out tab 23 extends from the portion of the second sealing edge 122 corresponding to the second concave surface 112b. Along the first direction X, the distance between the second bend 122a and the second concave surface 112b is G.

[0041] The first concave surface 112a is a sub-region of the concave surface 112 that is close to the convex surface 111. The first concave surface 112a sinks relative to the convex surface 111 along the first direction X, but the sinking depth is less than that of the second concave surface 112b.

[0042] The second concave surface 112b is a sub-region of the concave surface 112 that is far away from the convex surface 111. The second concave surface 112b sinks further relative to the first concave surface 112a along the first direction X, that is, the second concave surface 112b is closer to the interior of the cell body 21 along the first direction X.

[0043] Along the second direction Y, the first concave surface 112a is located between the convex surface 111 and the second concave surface 112b, forming a three-level stepped structure from the convex surface 111 to the first concave surface 112a and then to the second concave surface 112b.

[0044] The lead-out tab 23 is led out from the part of the second edge 122 corresponding to the second concave surface 112b, that is, the lead-out tab 23 extends out of the membrane shell 10 from the edge position corresponding to the deepest second concave surface 112b region.

[0045] Along the first direction X, the distance between the second bent portion 122a and the second concave surface 112b is G, that is, the gap G is formed between the second bent portion 122a and the deepest second concave surface 112b.

[0046] The first concave surface 112a and the second concave surface 112b form a double-layered recessed structure. The second concave surface 112b further recesses along the first direction X, providing a deeper accommodating space for the lead-out tab 23 and the subsequently arranged flexible plate 32. A gap G is maintained between the second bent portion 122a and the second concave surface 112b. The gap G provides buffer protection for the tab connection structure in the deep region. External impact forces require a greater buffer depth to reach the tab, further reducing the risk of tab breakage.

[0047] In some embodiments, in the unfolded state of the second edge sealing 122, the dimension W3 between the edge of the second edge sealing 122 and the second concave surface 112b along the first direction X ranges from 1.5mm to 5mm.

[0048] And / or, in the unfolded state of the second sealing edge 122, the dimension W2 between the edge of the second sealing edge 122 and the first concave surface 112a along the first direction X ranges from 1.2mm to 5mm.

[0049] And / or, in the unfolded state of the first sealing edge 121, the dimension W1 between the edge of the first sealing edge 121 and the convex surface 111 along the first direction X ranges from 1.2mm to 5mm.

[0050] W3 is the dimension between the edge of the second sealing edge 122 and the second concave surface 112b in the first direction X when the second sealing edge 122 is unfolded, that is, the sealing edge width of the second sealing edge 122 in the region of the second concave surface 112b.

[0051] W2 is the dimension between the edge of the second sealing edge 122 and the first concave surface 112a when the second sealing edge 122 is unfolded, that is, the sealing edge width of the second sealing edge 122 in the region of the first concave surface 112a.

[0052] W1 is the dimension between the edge of the first sealing edge 121 and the convex surface 111 when the first sealing edge 121 is unfolded, that is, the sealing edge width of the first sealing edge 121 in the area of ​​the convex surface 111.

[0053] Optionally, W3 is greater than W2.

[0054] If W3 is too large, the sealing width of the second sealing edge 122 in the area of ​​the second concave surface 112b will be too large, reducing the space utilization of the battery compartment. If W3 is too small, the sealing width of the second sealing edge 122 in the area of ​​the second concave surface 112b will be insufficient, resulting in insufficient sealing dimensions for the lead-out tab 23 and the tab adhesive, increasing the risk of electrolyte leakage. Therefore, by controlling W3 within the range of 1.5mm to 5mm, it is possible to ensure the sealing width of the lead-out tab 23 and the tab adhesive, improving sealing reliability, while also reducing the space occupied at the battery head and improving the space utilization of the battery compartment.

[0055] For example, W3 can be 1.5mm, 1.7mm, 1.9mm, 2.2mm, 2.6mm, 3.1mm, 3.5mm, 3.9mm, 4.3mm, 4.7mm, 5.0mm, or a value within the range of any two of the above values.

[0056] W3 is greater than W2 and / or W1, and the second concave surface 112b region has the largest sealing width, which fully guarantees the sealing width of the lead-out tab 23 and the tab adhesive, thus improving the sealing reliability.

[0057] In some embodiments, when both the first sealing edge 121 and the second sealing edge 122 are unfolded, along the first direction X, the edge of the first sealing edge 121 protrudes beyond the edge of the second sealing edge 122, and the height difference A between the edge of the first sealing edge 121 and the edge of the second sealing edge 122 ranges from 1 mm to 3 mm.

[0058] The height difference A is the distance between the edge of the first sealing edge 121 and the edge of the second sealing edge 122 along the first direction X, that is, the size by which the first sealing edge 121 protrudes from the second sealing edge 122 along the first direction X.

[0059] The first edge seal 121 and the second edge seal 122 form a height difference of 1mm to 3mm. When the first edge seal 121 is bent, it is not easy to pull the second edge seal 122, or when the second edge seal 122 is bent, it is not easy to pull the first edge seal 121. The bending stress is dispersed, the risk of the top edge seal 12 lifting is reduced, and the risk of the film shell 10 tearing is reduced.

[0060] For example, A can be 1.0mm, 1.2mm, 1.4mm, 1.6mm, 1.9mm, 2.2mm, 2.5mm, 2.7mm, 2.9mm, 3.0mm, etc., or a value within the range of any two of the above values.

[0061] In some embodiments, when the first edge 121 is bent and the second edge 122 is unfolded, the height difference B between the side of the first bent portion 121a facing away from the convex surface 111 and the edge of the second edge 122 along the first direction X is greater than 0.

[0062] The height difference B is greater than 0, that is, the side of the first bent part 121a that is away from the convex surface 111 protrudes out of the edge of the second sealing edge 122 in the unfolded state along the first direction X.

[0063] With this configuration, the first bending portion 121a does not compress the second sealing edge 122 after bending. The first sealing edge 121 and the second sealing edge 122 do not interfere with each other during the bending process, reducing the stress generated when the first sealing edge 121 is bent and thus reducing the stress transmission to the second sealing edge 122. The second sealing edge 122 is almost unaffected by the bending of the first sealing edge 121 when it is unfolded. The stress of the second sealing edge 122 during subsequent bending is controllable, the bending stress does not accumulate, the bending quality is improved, the risk of the top sealing edge 12 lifting is reduced, the risk of the film shell 10 tearing is reduced, and the packaging reliability is improved.

[0064] In some embodiments, when both the first edge 121 and the second edge 122 are bent, the height difference E between the side of the first bent portion 121a facing away from the convex surface 111 and the side of the second bent portion 122a facing away from the concave surface 112 along the first direction X is in the range of 1mm to 3mm.

[0065] The side of the first bent portion 121a that faces away from the convex surface 111 is the outer surface of the first bent portion 121a after bending. The side of the second bent portion 122a that faces away from the concave surface 112 is the outer surface of the second bent portion 122a after bending.

[0066] If E is too large, the height difference between the first bend 121a and the second bend 122a will be too large, resulting in excessive space at the battery head corresponding to the concave surface 112 and wasted space. If E is too small, the first bend 121a and the second bend 122a will be almost flush, the accommodating depth of the concave surface 112 area will be insufficient, the arrangement space of the protection plate 30 will be limited, and the effect of improving space utilization will be reduced. Therefore, by controlling E within the range of 1mm to 3mm, sufficient installation depth for the protection plate 30 can be provided while avoiding unnecessary space waste.

[0067] For example, E can be 1.0mm, 1.2mm, 1.4mm, 1.7mm, 2.0mm, 2.3mm, 2.5mm, 2.7mm, 2.9mm, 3.0mm, etc., or a value within the range of any two of the above values.

[0068] In some embodiments, the battery further includes a protection plate 30, which includes a functional plate 31 and a flexible plate 32. The flexible plate 32 is electrically connected to the lead-out tab 23 and the functional plate 31. The flexible plate 32 is at least partially located in the gap between the second bend 122a and the second concave surface 112b. The functional plate 31 is at least partially located on the side of the second bend 122a away from the second concave surface 112b. Along the first direction X, the functional plate 31 has overlapping portions with both the first concave surface 112a and the second concave surface 112b.

[0069] The protection board 30 is a circuit board for the protection and management of the battery, used to realize the overcharge, over-discharge, and overcurrent protection and power management functions of the battery.

[0070] Functional board 31 is the main board area on the protection board 30 where electrical components are arranged. Functional board 31 can have a certain thickness and hardness.

[0071] The flexible plate 32 is an electrical connection board between the functional plate 31 and the lead-out tab 23. The flexible plate 32 can be bent and deformed.

[0072] The functional plate 31 is at least partially located on the side of the second bend 122a away from the second concave surface 112b, that is, the functional plate 31 is located on the outside of the second bend 122a along the first direction X.

[0073] The flexible plate 32 can be bent so that part of it is located in the gap between the second bent portion 122a and the second concave surface 112b, or it can be located entirely in the gap.

[0074] Along the first direction X, the functional plate 31 has overlapping portions with the first concave surface 112a and the second concave surface 112b. That is, the projection of the functional plate 31 along the first direction X covers the area where the first concave surface 112a and the second concave surface 112b are located. It can completely cover or cover part of the first concave surface 112a and part of the second concave surface 112b.

[0075] The flexible plate 32 is located in the gap G, which provides a channel and buffer space for its arrangement. The flexible plate 32 does not occupy additional battery compartment space, making the battery head space layout more compact. The functional plate 31 is located outside the second bend 122a and overlaps with both the first concave surface 112a and the second concave surface 112b. The projection range of the functional plate 31 along the first direction X covers the area of ​​the concave surface 112. The functional plate 31 makes full use of the accommodating area formed by the concave surface 112 for its arrangement, improving the space utilization rate of the battery head.

[0076] In some embodiments, the flexible plate 32 includes a first portion 321, a second portion 322, and a third portion 323. The first portion 321 is at least partially located on the side of the functional plate 31 away from the second concave surface 112b. The second portion 322 is connected to the end of the first portion 321 away from the convex surface 111 along the second direction Y. The second portion 322 is located in the gap between the second bend 122a and the second concave surface 112b. The third portion 323 extends from the first portion 321 on one side of the first direction X. The third portion 323 is provided with an electrical connector 324. Along the first direction X, the second portion 322, the functional plate 31, the lead-out tab 23, the first portion 321, the second bend 122a, and the second concave surface 112b at least partially overlap.

[0077] The first part 321 is the main section of the flexible plate 32 that is electrically connected to the functional plate 31. The first part 321 is at least partially located on the side of the functional plate 31 away from the second concave surface 112b. The first part 321 can be attached to the outer surface of the functional plate 31.

[0078] The second part 322 is a transition section in the flexible plate 32 that connects to the first part 321 and extends in the direction of the second concave surface 112b. The second part 322 is connected to the end of the first part 321 away from the convex surface 111 along the second direction Y. That is, the second part 322 extends from the far end of the first part 321 along the second direction Y and bends into the gap G.

[0079] The third part 323 is a connection section extending from the first part 321 along the first direction X in the flexible board 32. The third part 323 is provided with an electrical connector 324, which is used to connect to an external circuit.

[0080] Along the first direction X, the second part 322, the functional plate 31, the lead-out tab 23, the first part 321, the second bent part 122a, and the second concave surface 112b overlap at least partially, that is, the above-mentioned components form a stacked arrangement structure along the first direction X.

[0081] With this configuration, the dimensions of the battery head along the first direction X are further controlled, and the space utilization rate is further improved.

[0082] In some embodiments, along the second direction Y, the dimension D of the second concave surface 112b ranges from 16 mm to 40 mm. And / or, along the second direction Y, the dimension C of the second bend 122a is greater than the dimension of the functional plate 31.

[0083] D is the dimension of the second concave surface 112b along the second direction Y, that is, the length of the second concave surface 112b in the second direction Y. C is the dimension of the second bent portion 122a along the second direction Y, that is, the length of the second bent portion 122a in the second direction Y.

[0084] If D is too large, the second concave surface 112b will be too long along the second direction Y, occupying too much space on the first end face 11 along the second direction Y, and compressing the convex surface 111 along the second direction Y, thus reducing battery capacity. If D is too small, the second concave surface 112b will be too short along the second direction Y, resulting in insufficient dimensions for the lead-out tab 23 and the tab adhesive sealant, reducing sealing reliability. Therefore, by controlling D within the range of 16mm to 40mm, both the dimensions of the lead-out tab 23 and the tab adhesive sealant can be ensured, while also increasing battery capacity.

[0085] For example, D can be 16mm, 17mm, 19mm, 21mm, 24mm, 27mm, 30mm, 33mm, 36mm, 38mm, 40mm, etc., or a value within the range of any two of the above values.

[0086] In some embodiments, the first edge banding 121 and the second edge banding 122 are connected by a first bevel 123.

[0087] And / or, the convex surface 111 and the concave surface 112 are connected by a second inclined surface 124.

[0088] And / or, the tabs include a positive tab and a negative tab, the positive tab includes multiple positive tabs, the negative tab includes multiple negative tabs, the multiple positive tabs and the multiple negative tabs are spaced apart along the second direction Y, and the multiple positive tabs and the multiple negative tabs extend from the second sealing edge 122 corresponding to the concave surface 112 to the outside of the membrane shell 10 through the lead-out tabs 23.

[0089] The first slope 123 is a sloped structure that transitions between the first edge seal 121 and the second edge seal 122 along the first direction X. The first slope 123 connects the edges of the first edge seal 121 and the second edge seal 122, so that the top edge seal 12 forms a sloped transition from the first edge seal 121 to the second edge seal 122.

[0090] The second inclined surface 124 is an inclined structure that transitions between the convex surface 111 and the concave surface 112 along the first direction X. The second inclined surface 124 connects the convex surface 111 and the concave surface 112, so that the first end face 11 forms a slope transition from the convex surface 111 to the concave surface 112.

[0091] The first sealing edge 121 and the second sealing edge 122 are connected by a first inclined surface 123. The height change of the top sealing edge 12 from the first sealing edge 121 to the second sealing edge 122 is smoothly transitioned along the inclined surface, which avoids stress concentration and sudden change in the transition area of ​​the top sealing edge 12 when bending, reduces the risk of tearing of the membrane shell 10, and improves the bending reliability of the top sealing edge 12.

[0092] The convex surface 111 and the concave surface 112 are connected by a second inclined surface 124. The height change of the first end face 11 from the convex surface 111 to the concave surface 112 is smoothly transitioned along the inclined surface, avoiding interference between the sharp corner and the first and second sealing edges 121 and 122 after bending. This provides clearance space for the bending of the first and second sealing edges 121 and 122, and improves the reliability of bending.

[0093] The multi-layer positive electrode tabs and multi-layer negative electrode tabs extend from the second sealing edge 122 corresponding to the concave surface 112 to the outside of the membrane shell 10 through the lead-out tabs 23, which reduces the risk of breakage of both the positive and negative electrode tabs, and the sealing size of each tab adhesive is sufficient, thus improving the sealing reliability.

[0094] Example 1: Battery preparation: Step 1: Preparation of the positive electrode sheet Lithium cobalt oxide (LiCoO2), polyvinylidene fluoride (PVDF), carbon black (super P), and carbon nanotubes (CNT) doped with aluminum were mixed in a mass ratio of 95:2.5:1.5:1. N-methylpyrrolidone (NMP) was added as a solvent, and the mixture was stirred at 300 r / min for 4 h in a vacuum mixer until a uniform positive electrode active slurry with good flowability was formed. The positive electrode active slurry was simultaneously coated on both surfaces of an aluminum foil. The coated positive electrode sheet was pre-baked in an oven at 80℃ for 2 h, and then dried in an oven at 120℃ for 12 h. After that, it was rolled to a preset areal density by a roller press and then cut into preset sizes by a slitting machine to obtain the positive electrode sheet.

[0095] Step 2: Preparation of the negative electrode Artificial graphite, silicon-carbon composite material, sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), and conductive carbon black (SP) were mixed in a mass ratio of 73:20:2:2:1:2, with deionized water added as a solvent. The mixture was stirred in a vacuum mixer at 400 r / min for 6 h to obtain a uniform negative electrode active slurry. The negative electrode active slurry was uniformly coated onto both surfaces of a copper foil to form a negative electrode sheet. The coated negative electrode sheet was air-dried at room temperature for 1 h, then transferred to a 90℃ oven for 8 h of drying. It was then cold-pressed to a preset compaction density using a roller press. After slitting, cleaning, and sheet forming, a negative electrode sheet suitable for the positive electrode sheet was obtained.

[0096] Step 3: Preparation of electrolyte In a glove box filled with high-purity argon (moisture content <1ppm, oxygen content <1ppm), 10wt% fluoroethylene carbonate, 12wt% lithium hexafluorophosphate (LiPF6), and 1wt% adiponitrile were added to the electrolyte. The remainder was a mixed solvent consisting of ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) in a mass ratio of 3:4:3. The mixture was stirred thoroughly until LiPF6 was completely dissolved. After testing, the desired electrolyte was obtained with moisture content <20ppm and free acid content <50ppm.

[0097] Step 4: Preparation of lithium-ion batteries The above-prepared positive electrode sheet, negative electrode sheet, and commercially available polyethylene (PE) separator (13 μm thick) are stacked sequentially in the order of positive electrode sheet, separator, and negative electrode sheet. The stacking process is used to form a stacked electrode assembly 20 with protrusions and depressions. Finally, it is placed in an aluminum-plastic film for encapsulation and formation to obtain a battery.

[0098] The preparation methods of Examples 2-9 and Comparative Examples 1-2 are basically the same as those of Example 1. The differences are shown in Table 1.

[0099] Table 1

[0100] Volumetric energy density testing method: In the respective embodiments and comparative examples, the battery is charged at a current of 0.2C to the charging limit voltage, then charged at a constant voltage until the current drops to 0.02C, and then discharged at a current of 0.2C until it reaches 2.8V. The energy of the discharge is denoted as E. The thickness, width, and length of the battery are measured, and their product is calculated to obtain the battery volume, denoted as V. The formula for calculating the volumetric energy density is VED = E / V.

[0101] Method for testing the fracture rate of the ear flap after head impact: In each embodiment and comparative example, 10 batteries from the same batch were used as test samples. A falling ball impact tester was used, with a steel ball of mass 500g dropped freely from a height of 300mm, and the impact point was located at the center of the first end face 11 of the battery. After the impact, the battery was disassembled in a dry environment, and the electrode assembly 20 was removed. The multilayer tabs 22 were observed under a stereomicroscope (10~40x) to see if there were any breaks or cracks. The number of batteries with broken tabs n out of 10 batteries was recorded, and the tab breakage rate was recorded as n / 10×100%.

[0102] Test method for the occurrence rate of curling of the second edge banding: In each embodiment and comparative example, 10 finished batteries from the same batch with the top sealing edge 12 bent were used as test samples. An image measuring instrument was used to measure the gap G between the second bend 122a and the concave surface 112 of each battery after the second sealing edge 122 was bent. The batteries were left to stand at room temperature (25℃±2℃) for 48 hours to allow the rebound stress to fully release. After standing, the image measuring instrument was used again to measure the gap G0 between the second bend 122a and the concave surface 112 of each battery. The difference between G0 and G (i.e., the rebound amount) was calculated. If the difference exceeded 0.2mm, the second sealing edge 122 was determined to be raised; if the difference was less than or equal to 0.2mm, the second sealing edge 122 was determined not to be raised. The number n of batteries with raised second sealing edge 122 out of 10 batteries was recorded, and the occurrence rate of raised second sealing edge 122 was recorded as n / 10×100%.

[0103] Method for testing the leakage rate at the second sealing edge 122 corresponding to the lead-out tab 23: In each embodiment and comparative example, 10 finished batteries from the same batch that had been packaged were used. An electrolyte tracer was coated on the outer surface of the seal corresponding to the lead-out tab 23 on the second seal edge 122 of the battery. The initial state was observed and recorded under a stereomicroscope. The batteries were then placed in a high-temperature and high-humidity test chamber and stored at 60°C and 90%RH for 72 hours. After storage, the batteries were removed, and the lead-out tab 23 on the second seal edge 122 was observed again under a stereomicroscope. If new tracer penetration marks or electrolyte leakage marks appeared after storage, it was determined to be leakage; if no new marks appeared before or after storage, it was determined to be non-leakage. The number of batteries with leakage, n, was recorded, and the leakage rate at the lead-out tab 23 on the second seal edge 122 was recorded as n / 10 × 100%.

[0104] As can be seen from Table 1: In Examples 1-9, when G is in the range of 0.3mm to 2mm, the battery volumetric energy density is high and the breakage rate of the tabs after head impact is low; in Comparative Example 1, G exceeds the lower limit, which is 0.15mm, and the gap between the second bend 122a and the concave surface 112 is too small, resulting in a high breakage rate of the tabs after head impact; in Comparative Example 1, G exceeds the upper limit, which is 2.5mm, resulting in a low battery volumetric energy density. Therefore, it can be seen that when G is in the range of 0.3mm to 2mm, it can provide sufficient buffer space for external impact of the second bend to reduce the risk of tab breakage under pressure, and can also maintain a reasonable gap between the sealing edge and the end face to improve the battery volumetric energy density.

[0105] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A battery, characterized in that, include: Membrane housing (10) and electrode assembly (20) disposed within the membrane housing (10). The membrane shell (10) includes a first end face (11) and a top sealing edge (12) protruding from the first end face (11) along a first direction (X). The first end face (11) is formed with a convex surface (111) and a concave surface (112). Along a second direction (Y), the concave surface (112) is located on one side of the convex surface (111). The second direction (Y), the first direction (X), and the thickness direction (Z) of the battery are perpendicular to each other. The top sealing edge (12) includes a first sealing edge (121) corresponding to the convex surface (111) and a second sealing edge (122) corresponding to the concave surface (112). Along the first direction (X), the edge of the second sealing edge (122) is lower than the edge of the first sealing edge (121). The electrode assembly (20) includes a cell body (21) and a tab extending from the cell body (21) near the first end face (11). The tab includes multiple tab sheets (22), which are stacked together to form a tab cluster and connected to a lead-out tab (23). The lead-out tab (23) extends from the second sealing edge (122) to the outside of the membrane shell (10). The first edge seal (121) has a first bend (121a) that bends along one side of the thickness direction (Z) and along the first direction (X), the projection of the first bend (121a) at least partially overlaps with the convex surface (111); the second edge seal (122) has a second bend (122a) that bends along one side of the thickness direction (Z) and along the first direction (X), the projection of the second bend (122a) at least partially overlaps with the concave surface (112); Along the first direction (X), the maximum gap between the second bend (122a) and the concave surface (112) is G, and the range of G is 0.3mm to 2mm.

2. The battery according to claim 1, characterized in that, The concave surface (112) includes a first concave surface (112a) and a second concave surface (112b). Along the second direction (Y), the first concave surface (112a) is located between the convex surface (111) and the second concave surface (112b). Along the first direction (X), the second concave surface (112b) is lower than the first concave surface (112a). The lead-out tab (23) extends from the portion of the second sealing edge (122) corresponding to the second concave surface (112b) to the outside of the membrane shell (10). Along the first direction (X), the distance between the second bent portion (122a) and the second concave surface (112b) is G.

3. The battery according to claim 2, characterized in that, With the second edge seal (122) in the unfolded state, along the first direction (X), the dimension W3 between the edge of the second edge seal (122) and the second concave surface (112b) ranges from 1.5mm to 5mm. And / or, in the unfolded state of the second sealing edge (122), along the first direction (X), the dimension W2 between the edge of the second sealing edge (122) and the first concave surface (112a) ranges from 1.2 mm to 5 mm; And / or, in the unfolded state of the first sealing edge (121), along the first direction (X), the dimension W1 between the edge of the first sealing edge (121) and the convex surface (111) ranges from 1.2 mm to 5 mm.

4. The battery according to claim 1, characterized in that, With both the first sealing edge (121) and the second sealing edge (122) unfolded, along the first direction (X), the edge of the first sealing edge (121) protrudes from the edge of the second sealing edge (122), and the height difference A between the edge of the first sealing edge (121) and the edge of the second sealing edge (122) ranges from 1 mm to 3 mm.

5. The battery according to claim 4, characterized in that, When the first edge seal (121) is bent and the second edge seal (122) is unfolded, along the first direction (X), the height difference B between the side of the first bent portion (121a) facing away from the convex surface (111) and the edge of the second edge seal (122) is greater than 0.

6. The battery according to claim 4, characterized in that, With both the first edge seal (121) and the second edge seal (122) bent, along the first direction (X), the height difference E between the side of the first bent portion (121a) facing away from the convex surface (111) and the side of the second bent portion (122a) facing away from the concave surface (112) ranges from 1 mm to 3 mm.

7. The battery according to claim 2, characterized in that, The battery also includes a protection plate (30), which includes a functional plate (31) and a flexible plate (32). The flexible plate (32) is electrically connected to the lead-out tab (23) and the functional plate (31). The flexible plate (32) is at least partially located in the gap between the second bend (122a) and the second concave surface (112b). The functional plate (31) is at least partially located on the side of the second bend (122a) away from the second concave surface (112b). Along the first direction, the functional plate (31) has overlapping portions with both the first concave surface (112a) and the second concave surface (112b).

8. The battery according to claim 7, characterized in that, The flexible plate (32) includes a first part (321), a second part (322) and a third part (323). The first part (321) is at least partially located on the side of the functional plate (31) away from the second concave surface (112b). The second part (322) is connected to one end of the first part (321) away from the convex surface (111) along the second direction (Y). The second part (322) is located in the gap between the second bend (122a) and the second concave surface (112b). The third part (323) extends from the first part (321) along the first direction (X) and is provided with an electrical connector (324). Along the first direction (X), the second part (322), the functional plate (31), the lead-out tab (23), the first part (321), the second bend (122a) and the second concave surface (112b) at least partially overlap.

9. The battery according to claim 7, characterized in that, Along the second direction (Y), the dimension D of the second concave surface (112b) ranges from 16mm to 40mm; And / or, along the second direction (Y), the dimension C of the second bend (122a) is greater than the dimension of the functional plate (31).

10. The battery according to claim 1, characterized in that, The first edge banding (121) and the second edge banding (122) are connected by a first bevel (123); And / or, the convex surface (111) and the concave surface (112) are connected by a second inclined surface (124); And / or, the tabs include a positive tab and a negative tab, the positive tab includes multiple positive tabs stacked to form a positive tab cluster, the negative tab includes multiple negative tabs stacked to form a negative tab cluster, the multiple positive tabs and the multiple negative tabs are spaced apart along the second direction (Y), and the multiple positive tabs and the multiple negative tabs extend from the second sealing edge corresponding to the concave surface (112) to the outside of the membrane shell through their respective lead-out tabs.

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