Battery and method for manufacturing battery

Abstract

A battery (200) and a method for manufacturing the battery (200). The battery (200) comprises a housing (201) and a battery cell (100), wherein the battery cell (100) is arranged inside the housing (201); and the battery cell (100) comprises a separator (103), a plurality of first electrode sheets (101) and a plurality of second electrode sheets (102), which are stacked on each other, the separator (103) comprising a plurality of separation bodies, and each separation body comprising a body portion (104), a transition portion (105) and a shrunk portion (106). The shrunk portions (106) of the separator (103) are formed by means of heat-shrinking the edges of the separator (103). Because the separator (103) is heat-shrunk, the size of the separator (103) is reduced, reducing the risk of the separator (103) protruding relative to the housing (201) after the battery cell (100) is placed in the housing (201), thereby reducing the probability of pseudo welding caused by the protruding separator (103) during welding of a housing cover. In addition, the heating enables some adjacent shrunk portions (106) to fuse together, and an adhesive force generated between the fused shrunk portions (106) can also restrain the separator (103) to reduce the probability of a short circuit inside the battery cell (100) caused by the shrinking of the separator (103) during a subsequent heating test or use, thereby improving the product yield.

Description

Battery and battery manufacturing method TECHNICAL FIELD

[0001] The present application relates to the field of battery processing, in particular to a battery and a battery manufacturing method. BACKGROUND

[0002] The laminated cell is a common cell, which is formed by stacking the cathode sheet, the isolation film and the anode sheet in sequence. The battery using this type of cell is packaged by placing the cell into a shell. After the cell is placed into the shell, the isolation film will be folded. The folded part of the isolation film is exposed to the opening of the cell. This part of the isolation film will affect the final packaging of the shell, that is, the welding process of the opening with the shell cover, resulting in a virtual weld of the shell cover. The isolation film also has the phenomenon of internal short circuit of the cell caused by the contact of the positive and negative electrode sheets due to shrinkage in the subsequent test or use, which reduces the product yield.

[0003] SUMMARY

[0004] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a battery which can reduce the influence of the isolation film on the welding of the shell and reduce the risk of internal short circuit of the cell, thereby improving the yield of the product. The present application also provides a battery manufacturing method.

[0005] According to the battery of the first aspect of the present application, the battery comprises a shell and a cell, the cell is arranged in the interior of the shell, the cell comprises an isolation film, a plurality of first electrode sheets and a plurality of second electrode sheets which are stacked with each other, the isolation film comprises a plurality of separation bodies, and each separation body comprises a body portion, a transition portion and a shrinkage portion. One body portion is arranged between one first electrode sheet and one second electrode sheet, the transition portion is connected to the edge of the body portion, in the stacking direction of the first electrode sheet and the second electrode sheet, two adjacent transition portions jointly wrap at least one side edge of the second electrode sheet, and the shrinkage portion is connected to the side edge of the transition portion away from the body portion, in the stacking direction of the first electrode sheet and the second electrode sheet, at least two adjacent shrinkage portions are connected to each other.

[0006] According to the battery of the present application, the shrinkage portion of the isolation film is formed by heating and shrinking the edge of the isolation film. Since the isolation film is heated and shrunk, the size of the isolation film is smaller than that of the isolation film without heating and pretreatment. The risk of the isolation film extending out of the shell after the cell is placed into the shell is reduced, thereby reducing the probability of virtual welding caused by the extended isolation film during welding of the shell cover. In addition, the adjacent shrinkage portions are fused due to heating, and the adhesive force between the fused shrinkage portions can also restrain the isolation film to reduce the probability of internal short circuit of the cell caused by shrinkage during subsequent heating test or use, thereby improving the yield of the product.

[0007] According to some embodiments of the present application, the bonding force F between the two connected shrinkage portions satisfies: 0<F<10 N / mm.

[0008] According to some embodiments of the present application, the inner end of the shrinkage portion for connecting one end of the transition portion is the inner end of the shrinkage portion, the included angle between the tangent line of the inner end of the shrinkage portion and the plane where the second pole piece is located is the wrapping angle, and 0°<the wrapping angle<90°; preferably, 20°≤the wrapping angle≤65°.

[0009] According to some embodiments of the present application, the battery further comprises a first tab connected to the first pole piece, the body portion comprises opposite first and second edges and opposite third and fourth edges, the first tab protrudes relative to the fourth edge, and all regions of the first, second, and third edges are provided with the shrinkage portion, and at least part of the region of the fourth edge is provided with the shrinkage portion.

[0010] According to some embodiments of the present application, the protruding size of the isolation film relative to the first pole piece along the length direction of the battery cell is L1, and 0.1 mm≤L1<3 mm.

[0011] According to some embodiments of the present application, the protruding size of the isolation film relative to the first pole piece along the width direction of the battery cell is L2, and 0.1 mm≤L2<1 mm.

[0012] According to some embodiments of the present application, the corners of the isolation film and the first pole piece are all rounded corners, the rounded corner radius of the isolation film is R1, the rounded corner radius of the first pole piece is R2, and R1≤R2+L2.

[0013] According to some embodiments of the present application, along the width direction of the battery cell, the distance between the inner wall of the shell and the outer edge of the isolation film corresponding thereto is L3, and L3≥0.

[0014] According to some embodiments of the present application, along the width direction of the battery cell, the distance between the inner wall of the shell and the outer edge of the isolation film corresponding thereto is L3, and the distance between the inner wall of the shell and the outer edge of the first pole piece corresponding thereto is L4, and 0 mm≤L3<(L4-0.1) mm.

[0015] The battery manufacturing method according to the second aspect of the embodiments of the present application comprises the following steps: stacking the first pole piece, the second pole piece, and the isolation film relative to each other, the stacked isolation film comprises a plurality of separation bodies, the separation body comprises a body portion arranged between adjacent first and second pole pieces, a transition portion connected to the edge of the body portion, and a shrinkage portion connected to the side edge of the transition portion away from the body portion; heating the shrinkage portion to make the shrinkage portion shrink and at least two adjacent shrinkage portions connected to each other; obtaining a battery cell; and packaging the battery cell into a shell.

[0016] According to the battery manufacturing method of the embodiments of the present application, at least the following beneficial effects are achieved: the shrinkage portions of the isolation film are formed by shrinking the edges of the isolation film through heating, and because the isolation film is heated and shrunk, the size of the isolation film is smaller than that of the isolation film without the heating pretreatment, thereby reducing the risk of the isolation film extending out of the shell after the battery cell is placed into the shell, thereby reducing the probability of a false weld caused by the extended isolation film when the shell cover is welded, and because the heating causes the adjacent shrinkage portions to be fused with each other, the adhesion force generated between the shrinkage portions after the fusion can also restrain the isolation film to reduce the probability of a short circuit in the battery cell caused by the shrinkage of the isolation film during the subsequent heating test or use, thereby improving the yield of the product.

[0017] According to some embodiments of the present application, the heat shrinkage temperature of the isolation film is T1, the heating temperature of the isolation film is T2, and the heating temperature T2 in the step of heating the shrinkage portions is set to satisfy the following relationship: 5℃ < T2-T1 < 100℃.

[0018] According to some embodiments of the present application, the base material of the isolation film includes at least one of polyethylene and polypropylene, and 140℃ ≤ T2 ≤ 170℃.

[0019] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0020] The present application will be further described below in conjunction with the accompanying drawings and embodiments, in which:

[0021] FIG. 1 is a front view of a battery cell in a first embodiment of the present application;

[0022] FIG. 2 is a front view of a battery in an embodiment of the present application;

[0023] FIG. 3 is a top view of a battery cell in an embodiment of the present application;

[0024] FIG. 4 is a front view of a battery cell in a first embodiment of the prior art;

[0025] FIG. 5 is a front view of a battery in the prior art;

[0026] FIG. 6 is a top view of a battery cell in the prior art;

[0027] FIG. 7 is a top view of a battery cell placed in a shell in an embodiment of the present application;

[0028] FIG. 8 is a top view of a special-shaped battery cell in the prior art;

[0029] FIG. 9 is a front view of a battery cell in a second embodiment of the prior art;

[0030] FIG. 10 is a front view of an electric core in a second embodiment of the present application.

[0031] Reference signs: electric core 100, first pole piece 101, second pole piece 102, separator 103, body part 104, transition part 105, shrinkage part 106, single-sided sheet 107, double-sided sheet 108, adhesive 109, first side 110, second side 111, wrapping angle 112, battery 200, case 201, storage cavity 202, first tab 301, second tab 302, first edge 303, second edge 304, third edge 305, fourth edge 306. DETAILED DESCRIPTION

[0032] Embodiments of the present application are described in detail below with reference to the attached drawings, which are examples of embodiments of the present application. The embodiments described below are examples for explaining the present application and should not be construed as limiting the present application.

[0033] In the description of the present application, it should be understood that the orientation description, such as the orientation or position relationship indicated by up, down, front, back, left, right, etc. is based on the orientation or position relationship shown in the drawings, and is only for the purpose of describing the present application and simplifying the description, and therefore cannot be understood as limiting the present application. The device or element indicated must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application.

[0034] In the description of the present application, if the meaning of several is more than one, the meaning of multiple is more than two, greater than, less than, more than, etc. are understood as not including the number, above, below, etc. are understood as including the number. If it is described as first, second, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the order of indicated technical features.

[0035] In the description of the present application, unless otherwise explicitly limited, the words such as setting, installing, connecting, etc. should be broadly understood, and the person skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical solution.

[0036] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples.

[0037] Referring to FIG. 1 and FIG. 2, the battery 200 according to the first embodiment of the present application includes a shell 201 and a cell 100, the cell 100 is arranged inside the shell 201, the cell 100 includes a plurality of first pole pieces 101, a plurality of second pole pieces 102 and a separator film 103 which are stacked with each other, the separator film 103 includes a plurality of partitions, the partition includes a body part 104, a transition part 105 and a shrink part 106. One body part 104 is arranged between one first pole piece 101 and one second pole piece 102, the transition part 105 is connected to the edge of the body part 104, in the stacking direction of the first pole piece 101 and the second pole piece 102, two adjacent transition parts 105 collectively wrap at least one side edge of the second pole piece 102, the shrink part 106 is connected to the side edge of the transition part 105 away from the body part 104, in the stacking direction of the first pole piece 101 and the second pole piece 102, at least two adjacent shrink parts 106 are connected to each other. Referring to FIG. 4 to FIG. 6, FIG. 4 is a structural schematic diagram of a prior art jelly-roll cell 100, in which the separator film 103 is relatively flat, in order to avoid the short circuit caused by the contact between the first pole piece 101 and the second pole piece 102, so the distance of the extension is also relatively long, therefore, as shown in FIG. 5 and FIG. 6, after the cell 100 is placed in the shell 201, the separator film 103 will extend out more relative to the shell 201, this part of the separator film 103 will interfere with the welding position of the opening on the shell 201, causing the shell 201 to perform a false welding during the packaging welding, and after the edge of the separator film 103 in the cell 100 in the embodiment of the present application is heat treated to form the shrink part 106, as shown in FIG. 3, the size of the extension relative to the first pole piece 101 is smaller, and the cell 100 is placed in the shell 201, which is less likely to extend out compared with the separator film 103 without treatment, reducing the probability of false welding caused by the extension of the separator film 103, and due to the heating, part of the adjacent shrink parts 106 are fused to each other, the adhesion force generated between the shrink parts 106 after the fusion can also restrain the separator film 103 to reduce the probability of short circuit in the cell 100 caused by shrinkage during the subsequent heating test or use, and improve the yield of the product.

[0038] It should be noted that, with reference to FIG. 8, in some embodiments of the present application, the isolation film 103 of the special-shaped battery cell 100 shown in FIG. 8 can also be processed to reduce the probability of causing virtual welding and leading to internal short circuit of the battery cell 100. It should be noted that there are various ways of stacking the isolation film in the battery cell 100, in addition to the bag-making type stacking shown in FIGS. 1 and 4, Z-shaped stacking (as shown in FIGS. 9 and 10) and alternating stacking of multiple isolation films can also be used, and the battery cell 100 of the embodiments of the present application is applicable to the above-mentioned various ways of stacking the isolation film.

[0039] It should be noted that, with reference to FIGS. 1 and 2, in some embodiments of the present application, the shrinkage portion 106 of the isolation film 103 is formed by heating and shrinking the edge of the isolation film 103. Due to the shrinkage portion 106, the shrinkage range of the isolation film 103 that has been shrunk once at high temperature during the hot box test is smaller than that of the isolation film 103 without preheating, which can effectively avoid the contact between the positive plate and the negative plate caused by the shrinkage of the isolation film 103 during the hot box test, thereby improving the pass rate of the battery 200 through the hot box test.

[0040] It should be noted that, with reference to FIG. 1, in some embodiments of the present application, the first plate 101 is the anode plate, the second plate 102 is the cathode plate, and the first plate 101 protrudes relative to the second plate 102. Charge is mainly released by the anode, so the anode plate is longer and wider than the cathode plate to accommodate more ions and maintain good electrochemical performance.

[0041] It should be noted that, with reference to FIG. 1, in some embodiments of the present application, the first plate 101 includes a single-sided plate 107 and a double-sided plate 108. The single-sided plate 107 has an active material layer only on the side facing the second plate 102, and the double-sided plate 108 has an active material layer on both sides. In this way, the energy density and energy utilization rate can be improved.

[0042] Referring to FIG. 1, in some embodiments of the present application, the bonding force F between the two shrinkage portions 106 connected to each other satisfies: 0 < F < 10 N / mm. Such a design can bond the isolation films 103 of different layers to each other, and the bonding force generated therebetween can on the one hand allow the battery cell 100 to have mutual restraint force between the isolation films 103 during the heat box test, so that the isolation films 103 are not prone to shrinkage in high temperature, thereby further improving the passing rate of the heat box test; on the other hand, as shown in FIG. 1, the bending generated when the shrinkage portion 106 shrinks and bonds further reduces the extension length of the first tab 101 relative to the first tab 101, thereby avoiding the situation that the isolation film 103 extends relative to the shell 201 after the battery cell 100 is placed into the shell 201 during the manufacturing process of the battery 200, and improving the quality of the battery 200. It should be noted that the bonding force generated between the isolation films 103 is preferably generated by heat treating the shrinkage portion 106, so that the isolation film 103 shrinks while being melted to a certain extent, and the melting and bonding of the adjacent isolation film 103 after being heated, melted, cooled and then cooled generates the bonding force between each other, so that one process achieves two purposes, thereby improving the processing efficiency. The bonding force can also be generated by adding an adhesive or other chemical material between the isolation films 103. However, the bonding force F is controlled to be 0-10 N / mm because if the bonding force is greater than 10 N / mm, a long time of heat treatment or the addition of an adhesive between the isolation films 103 is required, and such a process is complicated and a long time of heat treatment can cause the isolation film 103 to shrink too much, thereby causing the first tab 101 and the second tab 102 to contact and cause short circuit.

[0043] It should be noted that in some embodiments of the present application, the isolation film 103 during the lamination process of the battery cell 100 can be stacked in a multi-piece manner as shown in FIG. 4, or can be stacked in a Z-shaped staggered manner (as shown in FIGS. 9 and 10), and the first tab 101 and the second tab 102 are alternately placed therein to form the battery cell 100. The battery cell 100 formed in the two manners can be finally formed in the state shown in FIG. 1 by heat treating the edges of the isolation film 103.

[0044] Referring to FIG. 1, in some embodiments of the present application, the inner end of the shrinkage portion 106 connected to the transition portion 105 is the inner end of the shrinkage portion 106, and the included angle between the tangent line of the inner end of the shrinkage portion 106 and the plane where the second tab 102 is located is the cladding angle 112, and 0° < cladding angle 112 < 90°; preferably, 20° ≤ cladding angle 112 ≤ 65°. Making the shrinkage portion 106 have a certain degree of bending can reduce the length of the isolation film 103 finally extending relative to the first tab 101, and reduce the probability that the isolation film 103 interferes with the opening of the shell 201 after the battery cell 100 is placed into the shell 201, thereby affecting the welding packaging.

[0045] Referring to FIG. 3, in some embodiments of the present application, the battery 200 further comprises a first tab 301 connected to the first tab 101, the body part 104 comprises opposite first and second edges 303 and 304, and opposite third and fourth edges 305 and 306, the first tab 301 protrudes relative to the fourth edge 306, all areas of the first, second and third edges 303, 304 and 305 are provided with the shrinkage part 106, and at least part of the area of the fourth edge 306 is provided with the shrinkage part 106. The tab serves as a connecting bridge for the internal and external circuits of the battery 200, and its conductive performance directly affects the charging and discharging efficiency of the battery 200, and good connection between the tab and the tab can ensure that the electrical energy inside the battery 200 is smoothly transmitted to the external circuit or input from the external circuit to the battery 200, thereby improving the charging and discharging efficiency of the battery 200, so in addition to the first tab 301 connected to the first tab 101, the second tab 302 is also connected to the second tab 102. In some embodiments of the present application, at least part of the area of the fourth edge 306 is provided with the shrinkage part 106, which refers to the two sides of the first tab 301 and the second tab 302 in FIG. 3. Since the first tab 301 and the second tab 302 themselves have a certain size, and also need to be welded with the shell 201, a larger space will be reserved between the tab end and the shell 201, so the isolation film 103 in the middle part of the first tab 301 and the second tab 302 can not be shrunk, and this part will not exceed the shell 201 after the battery cell 100 is placed in the shell 201. Specifically, in some embodiments of the present application, the distance between the fourth edge 306 and the inner wall edge of the shell 201 is reserved to be more than 2mm, so there is enough space to place the isolation film 103. However, it should be noted that the part between the first tab 301 and the second tab 302 can also be heat treated to shrink, which is a derivative embodiment of the present application and has the same technical effect. As for the two sides of the first tab 301 and the second tab 302 being processed with part of the shrinkage part 106, it is to make the structure of the corner part of the battery cell 100 more compact, to prevent the corner part from simultaneously existing the processed isolation film 103 and the unprocessed isolation film 103 and interfering with each other, and at the same time, the shrinkage part 106 processing of the fourth edge 306 will not increase the processing difficulty, and the left side of the first edge 303 and the fourth edge 306 can be processed together, and the right side of the second edge 304 and the fourth edge 306 can be processed together.

[0046] Referring to FIG. 3, in some embodiments of the present application, the protruding size of the isolation film 103 along the length direction of the battery cell 100 relative to the first pole piece 101 is L1, 0.1mm≤L1<3mm, and specifically, L1 can be 0.1mm, 1.5mm, 2.7mm, etc. It should be noted that the protruding above refers to the size of the head of the isolation film 103 protruding relative to the head of the first pole piece 101, or the size of the tail of the isolation film 103 protruding relative to the tail of the first pole piece 101. The isolation film 103 in FIG. 3 is the isolation film 103 after the edge is heat treated. This size range well balances the safety and the double advantages of avoiding virtual welding after being installed in the shell 201. The following are specific embodiments. When L1 is 0.05mm, the size of the isolation film 103 protruding is too small. Although the isolation film 103 does not interfere with the shell 201 and does not affect the welding process, the isolation film 103 further shrinks during the subsequent heat box test, causing the first pole piece 101 and the second pole piece 102 to contact and cause short circuit, which has safety hazards. When L1 is 1.5mm, the isolation film 103 does not interfere with the shell 201, and also does not cause short circuit after shrinking during the heat box test. When L1 is 3mm, the isolation film 103 still protrudes a relatively long distance. During the test, there is no short circuit in the battery cell 100. However, after the battery cell 100 is installed in the shell 201, the isolation film 103 protrudes out of the shell 201, affecting the step of packaging and welding the shell 201.

[0047] It should be noted that referring to FIG. 6, the protruding size of the isolation film 103 along the length direction of the battery cell 100 relative to the first pole piece 101 in the prior art is L5.

[0048] It should be noted that referring to FIG. 3, in some embodiments of the present application, the length direction of the battery cell 100 is the distribution direction of the head and the tail shown in the figure, and the width direction of the battery cell 100 is the distribution direction of the left and right shown in the figure.

[0049] According to some embodiments of the present application, the protruding size of the isolation film 103 along the width direction of the battery cell 100 relative to the first pole piece 101 is L2, 0.1mm≤L2<1mm, and specifically, L2 can be 0.1mm, 0.3mm, 0.7mm, etc. It should be noted that the protruding above refers to the size of the left side of the isolation film 103 protruding relative to the left side of the first pole piece 101, or the size of the right side of the isolation film 103 protruding relative to the right side of the first pole piece 101. The isolation film 103 in FIG. 3 is the isolation film 103 after the edge is heat treated. This size range well balances the safety and the double advantages of avoiding virtual welding after being installed in the shell 201. The following are specific embodiments. When L2 is 0.05mm, the protruding size of the isolation film 103 is too small. Although the isolation film 103 does not interfere with the shell 201 and does not affect the welding process, the isolation film 103 further shrinks during the subsequent heat chamber test, causing the first pole piece 101 and the second pole piece 102 to contact and cause short circuit, which has safety hazards. When L2 is 0.1mm, the isolation film 103 does not interfere with the shell 201, and after shrinking during the heat chamber test, it also does not cause short circuit. When L2 is 1mm, the isolation film 103 still protrudes a relatively long distance. During the test, it does not cause short circuit in the battery cell 100, but after the battery cell 100 is installed in the shell 201, the isolation film 103 protrudes out of the shell 201, affecting the step of packaging and welding the shell 201.

[0050] It should be noted that with reference to FIG. 6, the protruding size of the isolation film 103 along the width direction of the battery cell 100 relative to the first pole piece 101 is L6.

[0051] It should be noted that with reference to FIGS. 1 and 3, in some embodiments of the present application, the battery 200 further comprises an adhesive 109, the battery cell 100 comprises a first side 110 and a second side 111 distributed along the thickness direction, one end of the adhesive 109 is adhered to the first side 110, and the other end of the adhesive 109 is adhered to the second side 111. The adhesive 109 can make the connection inside the battery cell 100 more compact and improve the structural stability of the battery cell 100. It should be noted that with reference to FIG. 1, in some embodiments of the present application, the adhesive 109 can be a C-shaped adhesive as shown in FIG. 1, or can continue to extend to the right on the second side 111 and wrap upwards from the right side until the right end of the first side 110 to form a wrap-around type adhesive (not shown in the figure), in addition, as shown in FIG. 3, the adhesive 109 can be provided in multiple, and the multiple adhesives 109 are adhered to the four sides of the battery cell 100, which further improves the structural stability of the battery cell 100; the adhesive 109 can also be longer in the length direction, or the adhesives 109 on the same side in FIG. 3 can be made into one large whole, which can stabilize the structure of the battery cell 100, and in some embodiments of the present application, the adhesive 109 is a single-sided adhesive, and other adhesive materials can also be used.

[0052] With reference to FIG. 7, in some embodiments of the present application, the corners of the isolation film 103 and the first tab 101 are rounded, the radius of the rounded corner of the isolation film 103 is R1, the radius of the rounded corner of the first tab 101 is R2, R1≤R2+L2, along the width direction of the battery cell 100, the distance between the inner wall of the shell 201 and the outer edge of the isolation film 103 corresponding thereto is L3, and L3≥0. With reference to FIGS. 3 and 6, the corners of the unprocessed isolation film 103 in the prior art are right angles, which are relatively sharp, and burrs are more likely to be generated after installation, while the corners of the isolation film 103 in the present solution are rounded, which are more easily placed in the shell 201 and are not easy to scratch other components, and the above limitation on the radius of the rounded corner of each part is to ensure that the isolation film 103 also extends a certain distance at the corner relative to the first tab 101, and meanwhile does not interfere with the inner wall of the shell 201 after entering the shell, thereby ensuring the safety performance of the battery cell 100.

[0053] With reference to FIG. 7, in some embodiments of the present application, along the width direction of the battery cell 100, the distance between the inner wall of the shell 201 and the outer edge of the isolation film 103 corresponding thereto is L3, the distance between the inner wall of the shell 201 and the outer edge of the first tab 101 corresponding thereto is L4, and 0mm≤L3<(L4-0.1)mm. Such a design is to prevent the battery cell 100 from shaking and falling after being installed in the shell 201, and therefore it is preferred that the isolation film 103 is made to fit the inner wall of the shell 201, and when L3≥(L4-0.1)mm, the edge between the isolation film 103 and the inner wall of the shell 201 is too large, which is easy to cause the battery cell 100 to shake and fall.

[0054] The battery manufacturing method according to the second aspect of the present application comprises the following steps:

[0055] The first pole piece 101, the second pole piece 102 and the isolation film 103 are stacked with each other, the stacked isolation film 103 comprises a plurality of layers of separators, each separator comprises a body portion 104 arranged between adjacent first pole piece 101 and second pole piece 102, a transition portion 105 connected to the edge of the body portion 104, and a shrinkage portion 106 connected to the edge of the transition portion 105 away from the body portion 104; the shrinkage portion 106 is heated so that the shrinkage portion 106 shrinks and at least two adjacent shrinkage portions 106 are connected to each other; the battery cell 100 is prepared; and the battery cell 100 is packaged into the shell 201.

[0056] Referring to FIGS. 4-6, FIG. 4 is a structural schematic diagram of a stacked battery cell 100 in the prior art, in which the isolation film 103 is relatively flat. In order to avoid the first pole piece 101 and the second pole piece 102 from contacting each other to cause short circuit, the protruding distance is also relatively long. Therefore, as shown in FIGS. 5 and 6, after the battery cell 100 is placed into the shell 201, the isolation film 103 will protrude out of the shell 201 more, and this part of the isolation film 103 will interfere with the welding position of the opening of the shell 201, causing the shell 201 to be false-welded during packaging welding. In the battery cell 100 in the embodiments of the present application, after the edge of the isolation film 103 is heat-treated to form the shrinkage portion 106, as shown in FIG. 3, the size of the protrusion of the first pole piece 101 is relatively small, and the isolation film 103 is less likely to protrude out when placed in the shell 201 compared with the untreated isolation film 103, reducing the probability of false welding caused by the protrusion of the isolation film 103. In addition, due to the heating, some adjacent shrinkage portions 106 are fused to each other. The adhesion between the shrinkage portions 106 after fusion can also constrain the isolation film 103 to reduce the probability of short circuit in the battery cell 100 caused by shrinkage during subsequent heating tests or use, thereby improving the yield of the product.

[0057] It should be noted that, referring to FIG. 1, in some embodiments of the present application, the isolation film 103 is also subjected to a processing procedure of inwardly shrinking and closing. Specifically, a heating device with an arc-shaped slot can be used to wrap the edge of the battery cell 100 therein, so that the shrinkage of the isolation film 103 can only be inwardly shrinking and closing, thereby solving the problem of outward turning of the isolation film 103 and further improving the adhesion between the layers of the isolation film 103.

[0058] In some embodiments of the present application, the heat shrinkage temperature of the isolation film 103 is T1, and the heating temperature of the isolation film 103 is T2. The heating temperature T2 in the step of heating the shrinkage part 106 is set to satisfy the following relationship: 5℃ < T2-T1 < 100℃. It should be noted that the heat shrinkage temperature T1 refers to the temperature at which the isolation film 103 starts to shrink due to the influence of temperature, and the heating temperature T2 refers to the temperature at which the isolation film 103 is heated and hemmed using external equipment. Such design is mainly to ensure that the isolation film 103 can achieve shrinkage effect while not being damaged itself. When T2-T1≤5℃, the difference between the heating temperature and the heat shrinkage temperature is too small, and the shrinkage effect of the isolation film 103 is not obvious. When T2-T1≥100℃, the temperature received by the isolation film 103 is too high, and the isolation film 103 can be damaged or carbonized. The isolation film 103 in the pole region can be closed, which affects the cycle performance of the battery cell 100.

[0059] In some embodiments of the present application, the base material of the isolation film 103 includes at least one of polyethylene and polypropylene, and 140℃≤T2≤170℃. Specifically, the heating temperature can be 140℃, 150℃, 170℃, etc. Polyethylene and polypropylene have stable chemical properties, good porosity and permeability, and can ensure the stable and efficient operation of the battery cell 100. The preferred heating temperature is to balance the safety and the avoidance of false welding after being installed in the shell 201. When the heating temperature is less than 140℃, the heating temperature is too low, the heating effect is not obvious, the shrinkage size of the isolation film 103 is small, and the isolation film 103 still extends a long distance. After the battery cell 100 is installed in the shell 201, the isolation film 103 can still extend out of the shell 201 and affect the step of packaging and welding the shell 201. When the heating temperature is greater than 170℃, the heating temperature is too high, the shrinkage size of the isolation film 103 is too large, and the isolation film 103 can further shrink during the subsequent heat box test, which can cause the first pole piece 101 and the second pole piece 102 to contact and cause short circuit, which has safety hazards.

[0060] It should be noted that in some embodiments of the present application, the base material of the isolation film 103 is further attached with a ceramic coating, and the thickness of the ceramic coating also affects the heat resistance of the isolation film 103. The thicker the ceramic coating, the stronger the heat resistance. Preferably, the thickness of the ceramic coating is controlled to be between 0.5μm and 1μm.

[0061] It should be noted that in some embodiments of the present application, the shrinkage degree of the isolation film 103 is related to multiple factors, in addition to the heating temperature and the size of the isolation film 103 extending from the first pole piece 101 before processing, the heating time, the distance between the heating end face and the isolation film 103 will also affect the shrinkage degree of the isolation film 103. Specifically, the heating time is preferably set to 0.5s-1s, the longer the time, the greater the shrinkage degree of the isolation film 103, the shorter the time, the smaller the shrinkage degree of the isolation film 103; and the heating end face is preferably set to a distance of 0.2mm-0.3mm from the outer circumference of the first pole piece 101, specifically, it can be 0.2mm, 0.25mm, 0.3mm, etc. The closer the distance, the closer the distance between the heating end face and the isolation film 103, the greater the fitting degree between them, the greater the shrinkage degree of the isolation film 103, the farther the distance, the smaller the fitting degree between them, the smaller the shrinkage degree of the isolation film 103. And specifically, the adjustment of these parameters is to observe the state of the isolation film 103 during processing, when the isolation film 103 reaches the ideal state, that is, the size of the extension after shrinkage relative to the first pole piece 101 is within the predetermined range, and each other is also mutually bonded, etc. It means that the processing is completed.

[0062] In some embodiments of the present application, the complete process of the battery manufacturing method is as follows:

[0063] S1: forming the battery cell 100 by stacking the first pole piece 101, the isolation film 103 and the second pole piece 102 in sequence;

[0064] S2: welding, bonding and bending the first and second pole tabs 301 and 302 at the head of the battery cell 100;

[0065] S3: heating treatment (i.e. edge sealing) of the edge of the isolation film 103;

[0066] S4: bonding the adhesive 109 on the outer circumference of the battery cell 100 to make it stable, and bonding the double-sided adhesive tape on the outer circumference of the battery cell 100 to make the connection with the shell 201 more closely;

[0067] S5: cutting and welding the first and second pole tabs 301 and 302 on the shell 201;

[0068] S6: placing the battery cell 100 into the storage cavity 202 of the shell 201 and welding the shell cover.

[0069] Among them, step S3 is the main process, and the intervals and selection methods of the heating time, the extension distance of the isolation film 103 relative to the first pole piece, the heating temperature and the heating end face relative to the isolation film 103 have been described above.

[0070] The embodiments of the present application are described in detail above with reference to the drawings, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A battery, comprising a shell and a cell, the cell being arranged inside the shell, the cell comprising a separator, a plurality of first electrode sheets and a plurality of second electrode sheets, the separator comprising a plurality of layers of separators, each of the separators comprising: a body portion arranged between adjacent one of the first electrode sheets and one of the second electrode sheets; a transition portion connected to an edge of the body portion; and a shrink portion connected to an edge of the transition portion away from the body portion, at least two adjacent ones of the shrink portions being connected to each other in a stacking direction of the first electrode sheets and the second electrode sheets; wherein an adhesive force F between two of the shrink portions connected to each other satisfies 0 < F < 10 N / mm; wherein an inner end of the shrink portion connected to one end of the transition portion is the shrink portion, and an included angle between a tangent line of the shrink portion at the inner end and a plane in which the second electrode sheet is arranged is a wrapping angle, 0° < the wrapping angle < 90°; and wherein the battery further comprises a first tab connected to the first electrode sheet, the body portion comprises opposite first and second edges and opposite third and fourth edges, the first tab protrudes relative to the fourth edge, all areas of the first, second and third edges are provided with the shrink portion, and at least part of an area of the fourth edge is provided with the shrink portion; wherein a protruding dimension of the separator relative to the first electrode sheet in a length direction of the cell is L1, 0.1 mm < L1 < 3 mm; wherein a protruding dimension of the separator relative to the first electrode sheet in a width direction of the cell is L2, 0.1 mm < L2 < 1 mm; wherein a corner of the separator and a corner of the first electrode sheet are each a rounded corner, a rounded corner radius of the separator is R1, a rounded corner radius of the first electrode sheet is R2, and R1 < R2 + L2; wherein a distance between an inner wall of the shell and an outer edge of the separator corresponding to the inner wall of the shell in the width direction of the cell is L3, L3 ≥ 0; and wherein a distance between the inner wall of the shell and an outer edge of the first electrode sheet corresponding to the inner wall of the shell is L4, 0 mm < L3 < (L4 - 0.1) mm. 10.A method for manufacturing a battery, comprising the following steps: stacking a first electrode sheet, a second electrode sheet and a separator, the separator after being stacked comprising a plurality of layers of separators, each of the separators comprising a body portion arranged between adjacent one of the first electrode sheets and one of the second electrode sheets, a transition portion connected to an edge of the body portion, and a shrink portion connected to an edge of the transition portion away from the body portion; heating the shrink portion so that the shrink portion shrinks and at least two adjacent ones of the shrink portions are connected to each other; obtaining a cell; and packaging the cell into a shell. ​ ​ 2. The battery of claim 1, wherein, ​ 3. The battery of claim 1, wherein, ​ 4. The battery of claim 1, wherein, ​ 5. The battery of claim 1, wherein, ​ 6. The battery of claim 1, wherein, ​ 7. The battery of claim 6, wherein, ​ 8. The battery of claim 1, wherein, ​ 9. The battery of claim 8, wherein, ​ ​ ​ ​ ​ ​ ​ 11. The battery manufacturing method according to claim 10, wherein The heat shrinkage temperature of the separation film is T1, and the heating temperature of the separation film is T2. The heating temperature T2 in the step of heating the shrinkage portion is set to satisfy the following relationship: 5℃ < T2 - T1 < 100℃.

12. The battery manufacturing method according to claim 11, wherein, The base material of the separation film includes at least one of polyethylene and polypropylene, and 140℃ ≤ T2 ≤ 170℃.

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