Secondary battery and electric device

Abstract

The invention discloses a secondary battery and electric equipment. The secondary battery comprises an electrode assembly and a packaging bag for accommodating the electrode assembly. The packaging bag comprises a packaging bag body and side sealing folded edges, and the electrode assembly is arranged in the packaging bag body. The packaging bag body comprises a side wall, and the side sealing folded edge is connected with the side wall in the extending direction of the side sealing folded edge and fixed to the side, away from the containing cavity, of the side wall. The side sealing folding edge comprises a sealing area and an unsealed area. The unsealed area is communicated with the containing cavity, when the electrode assembly expands, at least one part of the side sealing folding edge can be expanded, and therefore stress distribution at the first end of the side sealing folding edge is improved, and the capacity of the packaging bag for bearing expansion of the electrode assembly is improved. The sealing area is connected with the non-sealing area, and the sealing area can seal the containing cavity and meanwhile can reduce the possibility that the side sealing folded edges are excessively opened. Therefore, after the electrode assembly is expanded, the integrity of the packaging bag can be improved, so that the safety performance of the secondary battery can be improved.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to a secondary battery and electrical equipment. Background Art

[0002] Soft-pack batteries are widely used in electronic devices in various industries due to their advantages such as light weight, low mold cost and high safety. Soft-pack batteries usually include electrode components and packaging bags. The packaging bags usually need to be provided with pits to accommodate the electrode components. Currently, packaging bags often adopt a single-pit design or a double-pit design. Summary of the invention

[0003] For secondary batteries in the prior art, the inventors found that no matter the packaging bag adopts a single-hole design or a double-hole design, after multiple charge and discharge cycles, the electrode assembly of the secondary battery will inevitably expand to a certain extent, causing the packaging bag to bulge under force. Since the packaging bag is subjected to greater stress at the side seal fold, the packaging bag is easily damaged at the side seal fold, causing the secondary battery to fail.

[0004] In view of the above situation, it is necessary to provide a secondary battery that can reduce the possibility of damage to the packaging bag, thereby helping to reduce the risk of secondary battery failure.

[0005] The first aspect of the present application provides a secondary battery, including an electrode assembly and a packaging bag for accommodating the electrode assembly. The packaging bag includes a packaging bag body and a side seal fold, the packaging bag body is provided with a receiving cavity, and the electrode assembly is arranged in the receiving cavity. The packaging bag body includes a side wall, and along the extension direction of the side seal fold, the side seal fold is connected to the side wall and fixed to the side of the side wall away from the receiving cavity. The side seal fold includes a sealed area and an unsealed area, the unsealed area is connected to the receiving cavity, and the sealed area is connected to the unsealed area.

[0006] Along the extension direction of the side seal fold, the side seal fold is connected to the side wall of the packaging bag body and fixed to the side of the side wall of the packaging bag body away from the receiving cavity, and the side seal fold includes an unsealed area connected to the receiving cavity. When the electrode assembly expands, at least a portion of the side seal fold can be stretched open, thereby improving the stress distribution at the first end of the side seal fold and improving the ability of the packaging bag to withstand the expansion of the electrode assembly. The side seal fold also includes a sealing area connected to the unsealed area. The sealing area can reduce the possibility of the side seal fold being excessively stretched while sealing the receiving cavity. In this way, after the electrode assembly expands, it is beneficial to improve the integrity of the packaging bag, thereby improving the safety performance of the secondary battery.

[0007] In one or more of the above embodiments, the packaging bag body includes a first shell and a second shell, the first shell is connected to the second shell, the first shell is provided with a first pit, the second shell is provided with a second pit, and the first pit and the second pit together form a receiving cavity. For a secondary battery with a double pit structure design, when the electrode assembly is cyclically expanded, stress concentration is more likely to occur at the side seal fold. By providing an unsealed area and a sealed area at the side seal fold, the problem of damage to the packaging bag at the side seal fold caused by the cyclic expansion of the electrode assembly can be effectively alleviated, thereby improving the safety performance of the secondary battery.

[0008] In one or more of the above embodiments, the packaging bag body includes a first shell and a second shell, and the side wall includes a first side wall and a second side wall, the first side wall is located in the first shell, and the second side wall is located in the second shell. The side seal fold includes a first side seal fold and a second side seal fold, and along the extension direction of the side seal fold, the side seal fold has a first end and a second end, at the first end, the first side seal fold is connected to the first side wall, and the second side seal fold is connected to the second side wall, and at the second end, the first side seal fold is connected to the second side seal fold, and is fixed to the first side wall or the second side wall. When the electrode assembly expands and causes the packaging bag body to bulge under force, since the first side seal fold is connected to the first side wall and the second side seal fold is connected to the second side wall, the first side seal fold can be easily driven by the first side wall, and the second side seal fold can be easily driven by the second side wall, which is conducive to improving the convenience of opening the side seal fold, thereby facilitating improving the convenience of alleviating the bulging of the packaging bag body under force.

[0009] In one or more of the above embodiments, the secondary battery further includes a first pole ear and a second pole ear, the first pole ear is electrically connected to the positive electrode of the electrode assembly, the second pole ear is electrically connected to the negative electrode of the electrode assembly, and the first pole ear and the second pole ear extend out of the packaging bag along the first direction. Observed along the first direction, the dimension of the first side wall along its own extension direction is C1, and the dimension of the second side wall along its own extension direction is C2, C1 ≥ C2. At the second end, the side seal fold is fixed to the first side wall. In this case, by fixing the side seal fold to the larger of the first side wall and the second side wall, the dimension of the side seal fold along its own extension direction can be longer, so that the side seal fold has more space to set the unsealed area, which is conducive to increasing the degree to which the side seal fold can be stretched, and better optimizing the stress distribution at the side seal fold, thereby alleviating the problem of damage to the packaging bag at the side seal fold caused by the cyclic expansion of the electrode assembly.

[0010] In one or more of the above embodiments, the first side seal fold edge includes a first bonding layer, the second side seal fold edge includes a second bonding layer, and the first bonding layer and the second bonding layer are welded to form a sealing area. Along the extension direction of the side seal fold edge, the length of the unsealed area is A, the length of the sealed area is B, and A ≥ 0.3B. The first bonding layer and the second bonding layer are welded to form a sealing area, which can make the connection between the first side seal fold edge and the second side seal fold edge more stable, which is beneficial to improve the stability of the sealed receiving cavity in the sealing area. In addition, A ≥ 0.3B helps the unsealed area to be opened in time when the electrode assembly expands cyclically.

[0011] In one or more of the above embodiments, 4.5 mm ≤ B ≤ 7.5 mm.

[0012] In one or more of the above embodiments, along the extension direction of the side seal fold, the side seal fold includes a first bending section, a connecting section and a second bending section, the connecting section connects the first bending section and the second bending section, the first end is located at the first bending section, and the second end is located at the second bending section. At the second end, the second side seal fold is fixed to the first side wall. The length of the first bending section is M, the length of the second bending section is N, A+B<2C1, N<M<C1. On the premise that the side seal fold does not exceed the first side wall of the packaging bag as much as possible, the size of the side seal fold along its own extension direction can be longer, which can make the side seal fold have more space to set the unsealed area, which is conducive to increasing the degree to which the side seal fold can be stretched and better optimizing the stress distribution at the side seal fold. It can make the sealing area have sufficient size, which is conducive to improving the sealing of the sealing area to the receiving cavity. In addition, when the length A of the unsealed area exceeds the size C1 of the first side wall, it is conducive to keeping the size of the secondary battery in the thickness direction unchanged.

[0013] In one or more of the above embodiments, at the second end, the first side seal fold is fixed to the first side wall. Along the extension direction of the side seal fold, the length of the seal area is B, A+B<C1. In this case, the size of the side seal fold along its own extension direction is smaller than the size of the first side wall along its own extension direction, which is conducive to keeping the size of the secondary battery in the thickness direction unchanged.

[0014] In one or more of the above embodiments, A≤0.4C1. In this way, while the unsealed area of ​​the side seal fold can be stretched in time to optimize the stress distribution of the packaging bag, the length of the unsealed area is not too long, and thus the length of the side seal fold is not too long, which is conducive to improving the convenience of manufacturing the side seal fold of the packaging bag when producing secondary batteries.

[0015] In one or more of the above embodiments, 6mm≤C1≤10mm.

[0016] In one or more of the above embodiments, the secondary battery includes a fixing member, which is disposed in the receiving cavity. The electrode assembly is fixedly connected to the packaging bag through the fixing member. In this case, the electrode assembly can be relatively stable relative to the packaging bag, thereby helping the unsealed area to function better and improving the overall stability of the secondary battery.

[0017] The second aspect of the present application provides an electrical device, comprising the secondary battery of the first aspect of the present application. The packaging bag of the secondary battery is not easily damaged, and the electrolyte is not easily leaked, which is conducive to extending the service life of the electrical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A front view of a secondary battery provided in accordance with an embodiment of the present application.

[0019] Figure 2 For the first embodiment of this application Figure 1 Cross-sectional view along the median section line II-II.

[0020] Figure 3 for Figure 2 Enlarged view of area III.

[0021] Figure 4 The second embodiment of this application is Figure 1 Cross-sectional view along the median section line II-II.

[0022] Figure 5 for Figure 4 Enlarged view of area V.

[0023] Figure 6 A schematic diagram of the partial structure of the side seal fold provided in one embodiment of the present application.

[0024] Figure 7 An overall schematic diagram of an electrical device provided in one embodiment of the present application.

[0025] Main component symbols 1000, electrical equipment; 100, secondary battery; 10, packaging bag; 101, receiving cavity; 102, unsealed area; 103, sealed area; 104, overflow portion; 11, packaging bag body; 111, first shell; 112, second shell; 113, side wall; 1131, first side wall; 1132, second side wall; 12, side seal fold; 12a, first end; 12b, second end; 1201, first bending section; 1202, connecting section; 1203, second bending section ; 121, first side seal fold; 1211, first bonding layer; 1212, first barrier layer; 1213, first protective layer; 122, second side seal fold; 1221, second bonding layer; 1222, second barrier layer; 1223, second protective layer; 20, electrode assembly; 21, first pole piece; 22, second pole piece; 23, diaphragm; 30, first pole ear; 40, second pole ear; 50, first pole ear glue; 60, second pole ear glue; 70, fixing piece; X, first direction. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0027] It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be a centrally disposed element at the same time. When an element is considered to be "disposed on" another element, it may be directly disposed on the other element or there may be a centrally disposed element at the same time.

[0028] Unless otherwise specified, the term "plurality" as used herein means two or more than two.

[0029] The terms "first", "second", etc. are only used to distinguish different objects and shall not be understood as indicating or implying relative importance or implying the quantity, specific order or primary and secondary relationship of the technical features indicated.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0031] It should be understood that, considering the actual processing tolerance factors, in the technical solution of the present application, when the two elements are arranged parallel / vertically and in the same direction, there may be a certain angle between the two elements, and a tolerance of 0-±10% is allowed between the two elements. A tolerance of 0-±10% is allowed between the two elements greater than, equal to or less than.

[0032] An embodiment of the present application provides a secondary battery, including an electrode assembly and a packaging bag for accommodating the electrode assembly. The packaging bag includes a packaging bag body and a side seal fold, the packaging bag body is provided with a receiving cavity, and the electrode assembly is arranged in the receiving cavity. The packaging bag body includes a side wall, and along the extension direction of the side seal fold, the side seal fold is connected to the side wall and fixed to the side of the side wall away from the receiving cavity. The side seal fold includes a sealed area and an unsealed area, the unsealed area is connected to the receiving cavity, and the sealed area is connected to the unsealed area.

[0033] In the secondary battery of the present application, along the extension direction of the side seal fold, the side seal fold is connected to the side wall of the packaging bag body and fixed to the side of the side wall of the packaging bag body away from the receiving cavity, and the side seal fold includes an unsealed area connected to the receiving cavity. When the electrode assembly expands, at least a portion of the side seal fold can be stretched open, thereby improving the stress distribution at the first end of the side seal fold and improving the ability of the packaging bag to withstand the expansion of the electrode assembly. The side seal fold also includes a sealing area connected to the unsealed area. The sealing area can reduce the possibility of the side seal fold being over-stretched while sealing the receiving cavity. In this way, it helps to improve the integrity of the packaging bag after the electrode assembly expands, which is beneficial to improving the safety performance of the secondary battery.

[0034] Some embodiments of the present application will be described below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0035] See also Figures 1 to 4 An embodiment of the present application provides a secondary battery 100 , including a packaging bag 10 and an electrode assembly 20 , wherein the packaging bag 10 accommodates the electrode assembly 20 .

[0036] See also Figure 2 The packaging bag 10 includes a packaging bag body 11 , and the packaging bag body 11 is provided with a receiving cavity 101 .

[0037] The receiving chamber 101 is filled with an electrolyte, and the electrolyte includes an electrolyte salt. In some embodiments, the electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt. The electrolyte salt includes, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), bistrifluoromethanesulfonyl imide lithium LiN(CF3SO2)2 (LiTFSI), bis(fluorosulfonyl)imide lithium Li(N(SO2F)2) (LiFSI), lithium hexafluorocesium oxide (LiCsF6), lithium perchlorate (LiClO4) or lithium trifluoromethanesulfonate (LiCF3SO3).

[0038] The electrode assembly 20 is disposed in the receiving cavity 101. Figure 2 The electrode assembly 20 includes a negative electrode sheet 21 , a positive electrode sheet 22 and a separator 23 , and the separator 23 separates the negative electrode sheet 21 from the positive electrode sheet 22 .

[0039] In some embodiments, see Figure 2 and Figure 4 , the electrode assembly 20 is a winding structure, a single negative electrode sheet 21 and a single positive electrode sheet 22 are stacked and wound, and the separator 23 is arranged between the negative electrode sheet 21 and the positive electrode sheet 22. In some other embodiments, the electrode assembly 20 is a stacked structure, a plurality of negative electrode sheets 21 and a plurality of positive electrode sheets 22 are alternately stacked, and the separator 23 is arranged between any adjacent negative electrode sheets 21 and positive electrode sheets 22.

[0040] In some embodiments, the negative electrode sheet 21 includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is disposed on two opposite sides of the negative electrode current collector along the thickness direction. The positive electrode sheet 22 includes a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is disposed on two opposite sides of the positive electrode current collector along the thickness direction.

[0041] In some embodiments, the negative electrode current collector is made of copper foil, and the positive electrode current collector is made of aluminum foil.

[0042] In some embodiments, the material of the negative electrode active material layer includes at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen material, and silicon-carbon material. The material of the positive electrode active material layer includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, or lithium manganese oxide.

[0043] In some embodiments, the diaphragm 23 is an insulating film material such as a polyethylene film, a polypropylene film, a polyester film, or a polyimide film.

[0044] In some embodiments, see Figure 1 The secondary battery 100 further includes a first pole tab 30 and a second pole tab 40, wherein the first pole tab 30 is electrically connected to the positive electrode of the electrode assembly 20, and the second pole tab 40 is electrically connected to the negative electrode of the electrode assembly 20. The first pole tab 30 and the second pole tab 40 extend out of the packaging bag 10 along the first direction X. In some embodiments, the first pole tab 30 is electrically connected to the negative electrode sheet 21, and the second pole tab 40 is electrically connected to the positive electrode sheet 22.

[0045] In some embodiments, see Figure 1The secondary battery 100 further includes a first tab glue 50 and a second tab glue 60. The first tab 30 is insulated and disposed in the packaging bag 10 by the first tab glue 50, and the second tab 40 is insulated and disposed in the packaging bag 10 by the second tab glue 60. This is beneficial to reduce the risk of short circuit of the secondary battery 100.

[0046] See also Figure 2 The packaging bag 10 includes a side seal fold 12, and the side seal fold 12 is connected to the packaging bag body 11. In some embodiments, the packaging bag body 11 includes a side wall 113. Along the extension direction of the side seal fold 12, the side seal fold 12 is connected to the side wall 113 and fixed to the side of the side wall 113 away from the receiving cavity 101. In some embodiments, along the extension direction of the side seal fold 12, the side seal fold 12 has a first end 12a and a second end 12b (see Figure 3 ), the first end 12a is connected to the side wall 113, and the portion between the first end 12a and the second end 12b or the second end 12b is fixed to a side of the side wall 113 away from the receiving cavity 101.

[0047] In some embodiments, see Figure 3 The side sealing fold 12 is provided with an unsealed area 102 and a sealed area 103 , wherein the unsealed area 102 is connected to the receiving cavity 101 , and the sealed area 103 is connected to the unsealed area 102 . The receiving cavity 101 is sealed by the sealed area 103 .

[0048] Along the extension direction of the side seal fold 12, the side seal fold 12 is connected to the side wall 113 of the packaging bag body 11 and fixed to the side of the side wall 113 of the packaging bag body 11 away from the receiving cavity 101, and the side seal fold 12 includes an unsealed area 102 connected to the receiving cavity 101. When the electrode assembly 20 expands, at least a portion of the side seal fold 12 can be stretched open, thereby improving the stress distribution at the first end 12a of the side seal fold 12 and improving the ability of the packaging bag 10 to withstand the expansion of the electrode assembly 20. The side seal fold 12 also includes a sealing area 103 connected to the unsealed area 102. The sealing area 103 can reduce the possibility of the side seal fold 12 being excessively stretched while sealing the receiving cavity 101. In this way, after the electrode assembly 20 expands, it helps to improve the integrity of the packaging bag 10, thereby helping to improve the safety performance of the secondary battery 100.

[0049] In some embodiments, when the material of the negative electrode active material layer includes silicon-based materials such as silicon, silicon-oxygen materials and silicon-carbon materials, the cyclic expansion phenomenon of the electrode assembly 20 is more significant, and the stress at the side seal fold 12 is more concentrated. By providing the side seal fold 12 with an unsealed area 102 and a sealed area 103, the problem of damage of the packaging bag 10 at the side seal fold 12 caused by the cyclic expansion of the electrode assembly 20 can be effectively alleviated, thereby improving the safety performance of the secondary battery 100.

[0050] In some embodiments, see Figure 2 The packaging bag body 11 includes a first shell 111 and a second shell 112, and the first shell 111 is connected to the second shell 112. The first shell 111 is provided with a first pit, and the second shell 112 is provided with a second pit, and the first pit and the second pit together form a receiving cavity 101. For the secondary battery 100 with a double pit structure design, when the electrode assembly 20 is cyclically expanded, stress concentration is more likely to occur at the side seal fold 12. By providing the side seal fold 12 with an unsealed area 102 and a sealed area 103, the packaging bag 10 caused by the cyclic expansion of the electrode assembly 20 at the side seal fold 12 can be effectively alleviated. The problem of damage to the packaging bag 10 at the side seal fold 12 and the like can be improved, thereby improving the safety performance of the secondary battery 100. In some other embodiments, only the first shell 111 may be provided with the first pit, and the second shell 112 may not be provided with the second pit; or only the second shell 112 may be provided with the second pit, and the first shell 111 may not be provided with the first pit.

[0051] In some embodiments, the side wall 113 includes a first side wall 1131 and a second side wall 1132 , the first side wall 1131 is located in the first shell 111 , and the second side wall 1132 is located in the second shell 112 .

[0052] In some embodiments, the first side wall 1131 and the second side wall 1132 are arc-shaped, such as circular arc and elliptical arc. When the electrode assembly 20 is a winding structure, the first side wall 1131 and the second side wall 1132 can better conform to the electrode assembly 20, which is beneficial to improve the energy density of the secondary battery 100.

[0053] In some embodiments, see Figure 3 , the side seal fold 12 includes a first side seal fold 121 and a second side seal fold 122. At the first end 12a, the first side seal fold 121 is connected to the first side wall 1131, and the second side seal fold 122 is connected to the second side wall 1132. At the second end 12b, the first side seal fold 121 is connected to the second side seal fold 122 and is fixed to the first side wall 1131 or the second side wall 1132. In this case, when the electrode assembly 20 expands and causes the packaging bag body 11 to bulge under force, since the first side seal fold 121 is connected to the first side wall 1131 and the second side seal fold 122 is connected to the second side wall 1132, the first side seal fold 121 can be easily driven by the first side wall 1131, and the second side seal fold 122 can be easily driven by the second side wall 1132, which is conducive to improving the convenience of opening the side seal fold 12, thereby facilitating the convenience of alleviating the bulging of the packaging bag body 11 under force.

[0054] In some embodiments, the side seal fold 12 is a single fold structure, the side seal fold 12 extends toward the first side wall 1131, and the first side seal fold 121 is fixed to the first side wall 1131 (see Figure 3In some other embodiments, the side seal fold 12 is a single-fold structure, the side seal fold 12 extends toward the second side wall 1132, and the second side seal fold 122 is fixed to the second side wall 1132 (not shown).

[0055] In some embodiments, the side seal fold 12 is a double-fold structure, the side seal fold 12 first extends toward the first side wall 1131 and then extends toward the second side wall 1132, and the second side seal fold 122 is fixed to the first side wall 1131 (see Figure 5 In some other embodiments, the side seal fold 12 first extends toward the second side wall 1132 and then extends toward the first side wall 1131 , and the first side seal fold 121 is fixed to the second side wall 1132 (not shown).

[0056] It should be understood that, under the premise of keeping the size of the secondary battery 100 in the thickness direction unchanged, compared with the side seal fold 12 with a single fold structure, the side seal fold 12 with a double fold structure can make the size of the side seal fold 12 itself longer, so that the side seal fold 12 can have more space to set the unsealed area 102.

[0057] In some embodiments, see Figure 2 , observed along the first direction X, the dimension of the first side wall 1131 along its own extension direction is C1, and the dimension of the second side wall 1132 along its own extension direction is C2, C1 ≥ C2. At the second end 12b, the side seal fold 12 is fixed to the first side wall 1131. In this case, by fixing the side seal fold 12 to the larger one of the first side wall 1131 and the second side wall 1132, the dimension of the side seal fold 12 along its own extension direction can be longer, which can allow the side seal fold 12 to have more space for setting the unsealed area 102, thereby facilitating increasing the degree to which the side seal fold 12 can be stretched, and better optimizing the stress distribution at the side seal fold 12, thereby alleviating problems such as damage of the packaging bag 10 at the side seal fold 12 caused by the cyclic expansion of the electrode assembly 20.

[0058] In some embodiments, 6 mm ≤ C1 ≤ 10 mm. For example, C1 is 6 mm, 7 mm, 8 mm, 9 mm, and 10 mm.

[0059] In some embodiments, see Figure 6 The first side sealing fold 121 includes a first bonding layer 1211, the second side sealing fold 122 includes a second bonding layer 1221, and the first bonding layer 1211 and the second bonding layer 1221 are welded to form the sealing area 103. In this case, the connection between the first side sealing fold 121 and the second side sealing fold 122 can be made more stable, which is conducive to improving the stability of the sealing area 103 sealing the receiving cavity 101.

[0060] In some embodiments, the material of the first bonding layer 1211 and the second bonding layer 1221 includes at least one electrolyte-resistant material such as polypropylene, polyethylene, and ethylene acrylic acid copolymer.

[0061] In some embodiments, see Figure 6 The first side sealing edge 121 includes a first barrier layer 1212, which is disposed on the side of the first bonding layer 1211 away from the second side sealing edge 122. The second side sealing edge 122 includes a second barrier layer 1222, which is disposed on the side of the second bonding layer 1221 away from the first side sealing edge 121. The first barrier layer 1212 and the second barrier layer 1222 are conducive to blocking moisture and electrolyte.

[0062] In some embodiments, the material of the first barrier layer 1212 and the second barrier layer 1222 includes aluminum.

[0063] In some embodiments, see Figure 6 The first side seal fold 121 includes a first protective layer 1213, which is disposed on the side of the first barrier layer 1212 away from the second side seal fold 122. The second side seal fold 122 includes a second protective layer 1223, which is disposed on the side of the second barrier layer 1222 away from the first side seal fold 121. The first barrier layer 1212 can be protected by the first protective layer 1213, and the second barrier layer 1222 can be protected by the second protective layer 1223, which is conducive to reducing the risk of damage and failure of the first barrier layer 1212 and the second barrier layer 1222.

[0064] In some embodiments, the material of the first protective layer 1213 and the second protective layer 1223 includes at least one wear-resistant material such as polyester and nylon.

[0065] In some embodiments, when the sealing area 103 is formed by welding the first bonding layer 1211 and the second bonding layer 1221, a portion of the first bonding layer 1211 and the second bonding layer 1221 may overflow to form an overflow portion 104 (see Figure 6 ), since the overflow portion 104 has a certain adhesion effect on the first side seal fold edge 121 and the second side seal fold edge 122, the so-called sealing area 103 at this time includes the overflow portion 104, and the so-called unsealed area 102 has at least part of the first side seal fold edge 121 and the second side seal fold edge 122 that are not adhered by the overflow portion 104.

[0066] In some embodiments, see Figure 3 or Figure 5, along the extension direction of the side seal fold 12, the length of the unsealed area 102 is A, the length of the sealed area 103 is B, and A≥0.3B. In this case, when part of the first bonding layer 1211 and the second bonding layer 1221 overflow to form the overflow portion 104, A≥0.3B can take into account the adhesion effect of the overflow portion 104 on the first side seal fold 121 and the second side seal fold 122, which helps the unsealed area 102 to be opened in time when the electrode assembly 20 expands cyclically.

[0067] In some embodiments, 4.5 mm ≤ B ≤ 7.5 mm. For example, B is 4.5 mm, 6 mm, and 7.5 mm.

[0068] In some other embodiments, the first bonding layer 1211 and the second bonding layer 1221 are directly bonded to form the sealing area 103 , which helps to reduce the possibility of the first bonding layer 1211 and the second bonding layer 1221 overflowing to form the overflow portion 104 .

[0069] In some embodiments, please refer to Figure 2 and Figure 3 , at the second end 12b, the first side seal fold 121 is fixed to the first side wall 1131, A+B<C1. In this case, the size of the side seal fold 12 along its own extension direction is smaller than the size of the first side wall 1131 along its own extension direction, which is conducive to keeping the size of the secondary battery 100 in the thickness direction unchanged.

[0070] In some embodiments, see Figure 5 , along the extension direction of the side seal fold 12, the side seal fold 12 includes a first bending section 1201, a connecting section 1202 and a second bending section 1203, and the connecting section 1202 connects the first bending section 1201 and the second bending section 1203. That is, the side seal fold 12 is a double-fold structure, and the side seal fold 12 first extends toward the first side wall 1131 and then extends toward the second side wall 1132. On the premise that the side seal fold 12 does not exceed the first side wall 1131 of the packaging bag 10 as much as possible, the size of the side seal fold 12 along its own extension direction can be longer, so that the side seal fold 12 has more space to set the unsealed area 102, which is conducive to increasing the degree to which the side seal fold 12 can be stretched, and better optimizing the stress distribution at the side seal fold 12. It can make the sealing area 103 have a sufficient size, which is conducive to improving the sealing performance of the sealing area 103 to the receiving cavity 101.

[0071] In some embodiments, see Figure 5, the first end 12a is located at the first bending section 1201, and the second end 12b is located at the second bending section 1203. At the second end 12b, the second side sealing edge 122 is fixed to the first side wall 1131. Along the extension direction of the side sealing edge 12, the length of the first bending section 1201 is M, the length of the second bending section 1203 is N, A+B<2C1, N<M<C1. When the length A of the unsealed area 102 exceeds the size C1 of the first side wall 1131, it is beneficial to keep the size of the secondary battery 100 in the thickness direction unchanged.

[0072] In some embodiments, 0.3B≤A≤0.4C1. In this way, while the unsealed area 102 of the side seal fold 12 can be stretched in time to optimize the stress distribution of the packaging bag 10, the length of the unsealed area 102 is not too long, so that the length of the side seal fold 12 is not too long, which is conducive to improving the convenience of manufacturing the side seal fold 12 of the packaging bag 10 when the secondary battery 100 is produced.

[0073] In some embodiments, see Figure 2 and Figure 4 The secondary battery 100 includes a fixing member 70, which is disposed in the receiving cavity 101. The electrode assembly 20 is fixedly connected to the packaging bag 10 through the fixing member 70. In this case, the electrode assembly 20 can be relatively stable relative to the packaging bag 10, thereby helping the unsealed area 102 to play a better role and improving the overall stability of the secondary battery 100.

[0074] In some embodiments, the fixing member 70 is adhesive, and one side of the fixing member 70 is bonded to the packaging bag 10 , and the other side of the fixing member 70 is bonded to the electrode assembly 20 .

[0075] In some embodiments, the fixing member 70 is hot melt adhesive.

[0076] See also Figure 7 One embodiment of the present application provides an electric device 1000, comprising the secondary battery 100 as described above. The packaging bag 10 of the secondary battery 100 is not easily damaged, and the electrolyte is not easily leaked, which is conducive to extending the service life of the electric device 1000. The electric device 1000 includes but is not limited to electronic devices such as mobile phones, tablet computers, and laptop computers.

[0077] In order to verify the effect of the length A of the unsealed area 102 of the present application on improving the damage of the packaging bag 10, the inventor of the present application conducted the following experiment on the secondary battery 100, which includes 3 groups of comparative examples and 18 groups of embodiments, each group of comparative examples and each group of embodiments including 100 secondary batteries 100. It should be noted that the secondary batteries 100 in the comparative examples and embodiments are all designed with double punching holes; the side seal folds 12 are all double-fold structures and fixed to the side of the first side wall 1131 away from the receiving cavity 101, wherein the first bonding layer 1211 of the first side seal fold 121 and the second bonding layer 1221 of the second side seal fold 122 are welded to form a sealing area 103, and the sealing area 103 includes an overflow portion 104; the electrode assemblies 20 of the secondary batteries 100 are all winding structures, and the materials of the negative active material layer of the negative electrode sheet 21 in the electrode assembly 20 all include silicon system materials.

[0078] All the secondary batteries 100 in the comparative examples and the embodiments were subjected to a long cycle test. After the test, the experimental results were recorded in Tables 1 and 2. The specific process of the test is as follows: 1) Maintain the test temperature at 25°C; 2) The secondary battery 100 was left to stand for 30 min; 3) 5C constant current charging to 4.25V, then constant voltage charging to 3C; 4) 3C constant current charging to 4.35V, then constant voltage charging to 1.5C; 5) 1.5C constant current charge to 4.45V, then constant voltage charge to 0.05C; 6) Let stand for 5 minutes; 7) 0.7C constant current discharge to 3V; 8) Let stand for 5 minutes; 9) Repeat steps 3 to 8 800 times; 10) The secondary battery 100 is disassembled and the damage of the packaging bag 10 is observed.

[0079] Table 1 According to Comparative Examples 1 to 3 and Examples 1 to 9, it can be seen that although the length B of the sealed area 103 is increasing, since the side seal fold 12 of the secondary battery 100 in Comparative Examples 1 to 3 is not provided with an unsealed area 102, the breakage rate of the packaging bag 10 in Comparative Examples 1 to 3 after the long cycle test is significantly higher than the breakage rate of the packaging bag 10 in Examples 1 to 9. In other words, the unsealed area 102 is provided on the side seal fold 12, which is conducive to reducing the possibility of the packaging bag 10 being damaged.

[0080] According to Examples 1 to 9, it can be seen that when A / B<0.3 (i.e., A<0.3B) is compared with A / B≥0.3 (i.e., A≥0.3B), the breakage rate of the packaging bag 10 in Example 1 is higher than that in Examples 2 and 3, the breakage rate of the packaging bag 10 in Example 4 is higher than that in Examples 5 and 6, and the breakage rate of the packaging bag 10 in Example 7 is higher than that in Examples 8 and 9. This is because the first bonding layer 1211 and the second bonding layer 1221 overflow when being welded to form an overflow portion 104, and the overflow portion 104 adheres to the first side seal fold 121 and the second side seal fold 122, resulting in poor effect of the side seal fold 12 being stretched open, thereby improving the effect of stress distribution at the side seal fold 12. In other words, by setting A≥0.3B, it is helpful to further reduce the possibility of damage to the packaging bag 10.

[0081] Table 2 According to Examples 10 to 18, it can be seen that when A / C1>0.4 (i.e., A>0.4C1) is compared with A / C1≤0.4 (i.e., A≤0.4C1), the breakage rates of the packaging bags 10 in Examples 11 and 12 are very close to and slightly lower than the breakage rate of the packaging bag 10 in Example 10, the breakage rates of the packaging bags 10 in Examples 14 and 15 are very close to and slightly lower than the breakage rate of the packaging bag 10 in Example 13, and the breakage rates of the packaging bags 10 in Examples 17 and 18 are very close to and slightly lower than the breakage rate of the packaging bag 10 in Example 16. Continuing to increase the length A of the unsealed area 102 will increase the overall length of the side seal fold 12 and the improvement in safety performance is not obvious. That is, when A>0.4C1, further increasing the length A of the unsealed area 102 has little effect on improving the breakage rate of the packaging bag 10, and will increase the overall length of the side seal fold 12, which is not conducive to manufacturing the side seal fold 12 of the packaging bag 10 when the secondary battery 100 is produced. Therefore, by setting A≤0.4C1, it is helpful to improve the convenience of manufacturing the side seal fold 12 of the packaging bag 10.

[0082] According to Table 1 and Table 2, by setting 0.3B≤A≤0.4C1, the possibility of damage to the packaging bag 10 can be further reduced, which is conducive to improving the convenience of manufacturing the side seal fold 12 of the packaging bag 10.

[0083] In addition, those skilled in the art should recognize that the above embodiments are only used to illustrate the present application, and are not intended to limit the present application. As long as they are within the essential scope of the present application, appropriate changes and modifications to the above embodiments are within the scope disclosed in the present application.

Claims

1. A secondary battery, comprising an electrode assembly and a packaging bag for accommodating the electrode assembly, characterized in that: The packaging bag includes a packaging bag body and a side seal fold, the packaging bag body is provided with a receiving cavity, and the electrode assembly is arranged in the receiving cavity; the packaging bag body includes a side wall, along the extension direction of the side seal fold, the side seal fold is connected to the side wall and fixed to the side of the side wall away from the receiving cavity; the side seal fold is provided with an unsealed area and a sealed area, the unsealed area is connected to the receiving cavity, and the sealed area is connected to the unsealed area.

2. The secondary battery according to claim 1, characterized in that: The packaging bag body includes a first shell and a second shell, the first shell is connected to the second shell, the first shell is provided with a first pit, the second shell is provided with a second pit, and the first pit and the second pit together form the receiving cavity.

3. The secondary battery according to claim 1, characterized in that: The packaging bag body includes a first shell and a second shell, the side wall includes a first side wall and a second side wall, the first side wall is located in the first shell, and the second side wall is located in the second shell; the side seal fold includes a first side seal fold and a second side seal fold, along the extension direction of the side seal fold, the side seal fold has a first end and a second end, at the first end, the first side seal fold is connected to the first side wall, and the second side seal fold is connected to the second side wall, at the second end, the first side seal fold is connected to the second side seal fold, and is fixed to the first side wall or the second side wall.

4. The secondary battery according to claim 3, characterized in that: The secondary battery also includes a first pole tab and a second pole tab, the first pole tab is electrically connected to the positive electrode of the electrode assembly, the second pole tab is electrically connected to the negative electrode of the electrode assembly, and the first pole tab and the second pole tab extend out of the packaging bag along a first direction; observed along the first direction, the size of the first side wall along its own extension direction is C1, and the size of the second side wall along its own extension direction is C2, C1≥C2; at the second end, the side seal fold is fixed to the first side wall.

5. The secondary battery according to claim 4, characterized in that: The first side seal fold includes a first bonding layer, the second side seal fold includes a second bonding layer, and the first bonding layer and the second bonding layer are welded to form the sealing area; along the extension direction of the side seal fold, the length of the unsealed area is A, the length of the sealing area is B, and A≥0.3B.

6. The secondary battery according to claim 5, characterized in that: 4.5mm≤B≤7.5mm.

7. The secondary battery according to claim 5, characterized in that: Along the extension direction of the side seal folding edge, the side seal folding edge includes a first bending section, a connecting section and a second bending section, the connecting section connects the first bending section and the second bending section, the first end is located at the first bending section, and the second end is located at the second bending section; at the second end, the second side seal folding edge is fixed to the first side wall; the length of the first bending section is M, the length of the second bending section is N, A+B<2C1, N<M<C1.

8. The secondary battery according to claim 5, characterized in that: At the second end, the first side seal fold is fixed to the first side wall; along the extension direction of the side seal fold, the length of the sealing area is B, A+B<C1.

9. The secondary battery according to any one of claims 5 to 8, characterized in that: A≤0.4C1.

10. The secondary battery according to claim 9, characterized in that: 6mm≤C1≤10mm.

11. The secondary battery according to claim 1, characterized in that: The secondary battery comprises a fixing member, and the fixing member is arranged in the receiving cavity; the electrode assembly is fixedly connected to the packaging bag through the fixing member.

12. An electrical equipment, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 11.

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