Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery comprises a shell which comprises an end wall and a side wall arranged around the end wall, and the end wall and the side wall define a containing cavity; the electrode assembly is located in the containing cavity and comprises a winding structure formed by stacking and winding a positive plate, a diaphragm and a negative plate, and the winding structure comprises a first end provided with a positive tab and a second end provided with a negative tab in the height direction; a part of the first insulating film is arranged on the periphery of the first end of the winding structure in a surrounding manner; under the conditions that the first test temperature is 200 DEG C and the test time is 30 minutes, the transverse thermal shrinkage rate of the first insulating film is less than or equal to 1%, and the longitudinal thermal shrinkage rate of the first insulating film is less than or equal to 3%, so that adverse effects on the battery cell are avoided, and the safety of the battery is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to secondary battery field, especially a kind of secondary battery, battery pack and electronic device. BACKGROUND

[0002] In recent years, with the rapid development of electric vehicles, consumer electronics, new energy storage systems, for electric vehicles, battery technology is an important factor for its development.

[0003] In the development of battery technology, how to improve the safety of battery is an urgent technical problem in battery technology. UTILITY MODEL CONTENT

[0004] The utility model solves the technical problems that the prior art is to overcome the above-mentioned technical problems, provide a kind of secondary battery, battery pack and electronic device.

[0005] The utility model is to solve the above-mentioned technical problems by the following technical solutions:

[0006] A kind of secondary battery, it is characterized in that, it includes:

[0007] Shell, including end wall and the side wall being arranged around the end wall, the end wall and the side wall are surrounded and form the containing cavity;

[0008] Electrode assembly, in the containing cavity, the electrode assembly includes positive sheet, diaphragm and negative sheet and is stacked and is wound and forms winding structure, the winding structure includes the first end being provided with positive pole lug and the second end being provided with negative pole lug along height direction;

[0009] First insulating film, part of the first insulating film is surrounded in the outer periphery of the first end of the winding structure;

[0010] Under the condition that the first test temperature is 200 DEG C, test time is 30 minutes, the transverse thermal shrinkage of the first insulating film is less than or equal to 1%, and the longitudinal thermal shrinkage of the first insulating film is less than or equal to 3%.

[0011] In the technical solution, under the condition that the first test temperature is 200 DEG C, test time is 30 minutes, the transverse thermal shrinkage of the first insulating film is less than or equal to 1%, and the longitudinal thermal shrinkage of the first insulating film is less than or equal to 3%, the transverse and longitudinal thermal shrinkage of the first insulating film at high temperature can be effectively controlled, thereby avoiding the adverse effects on the battery cell and improving the safety of the battery.

[0012] Preferably, the peel strength of the first insulating film is 2N / cm-7N / cm;And / or,

[0013] The first insulating film comprises a first base material, a side of the first base material facing the winding structure comprises an area not covered by a first adhesive layer and an area covered by the first adhesive layer; a ratio of a thickness of the first base material to a thickness of the first adhesive layer is 2-6.

[0014] Preferably, the secondary battery further comprises a second insulating film, the second insulating film surrounds an outer periphery of the winding structure, and is located between the first end and the second end along a height direction of the winding structure.

[0015] Under the same test conditions, a transverse heat shrinkage rate of the first insulating film is greater than a transverse heat shrinkage rate of the second insulating film, and / or a longitudinal heat shrinkage rate of the first insulating film is greater than a longitudinal heat shrinkage rate of the second insulating film.

[0016] Preferably, under the condition that a second test temperature is 140℃ and a test time is 30 minutes, a transverse heat shrinkage rate of the second insulating film is less than or equal to 1%, and a longitudinal heat shrinkage rate of the second insulating film is less than or equal to 3%; and / or,

[0017] The second insulating film comprises a second base material, a side of the second base material facing the winding structure comprises an area not covered by a second adhesive layer and an area covered by the second adhesive layer; a ratio of a thickness of the second base material to a thickness of the second adhesive layer is 1.5-2.5.

[0018] Preferably, a peeling strength of the first insulating film is greater than a peeling strength of the second insulating film; and / or,

[0019] The peeling strength of the second insulating film is 1N / cm-4N / cm.

[0020] Preferably, the peeling strength of the first insulating film is 2-7 times the peeling strength of the second insulating film; and / or,

[0021] The peeling strength of the second insulating film is greater than or equal to 1.8N / cm.

[0022] Preferably, a ratio of a thickness of the second insulating film to a thickness of the first insulating film is 0.8-1.1; and / or,

[0023] Along a radial direction of the winding structure, the first insulating film and the second insulating film do not overlap; the second insulating film is continuously arranged along a circumferential direction of the winding structure and does not overlap, forming a winding structure uncovered area not covered by the second insulating film at an outer periphery of the winding structure, and a projection of an overlapping part of the first insulating film along the circumferential direction of the winding structure in the height direction at least partially falls in the winding structure uncovered area; and / or,

[0024] The first insulating film includes a first portion and a second portion connected to each other, the first portion surrounds the outer periphery of the first end of the winding structure and extends in the height direction, and the second portion is bent toward the center hole of the winding structure and covers the side of the positive tab connecting portion of the first current collecting plate connected to the positive tab away from the electrode assembly.

[0025] Preferably, the secondary battery further includes:

[0026] A first current collecting plate located between the positive tab and the end wall of the housing in the height direction;

[0027] A pole penetrating the end wall and electrically connected to the positive tab through the first current collecting plate;

[0028] A first insulating seal located between the end wall and the first current collecting plate;

[0029] And / or,

[0030] The accommodating cavity of the housing is provided with an opening at one end away from the end wall, and the housing further includes a crimping portion formed at one end of the side wall close to the opening and recessed toward the inside of the housing;

[0031] The secondary battery further includes:

[0032] A cover plate installed at the opening;

[0033] A second insulating seal surrounding the periphery of the cover plate to insulate and seal the cover plate and the housing;

[0034] A second current collecting plate arranged between the electrode assembly and the cover plate and electrically connected to the housing, a connecting piece of the second current collecting plate being located at one side of the crimping portion facing the electrode assembly and welded to the crimping portion;

[0035] And / or,

[0036] The secondary battery is a cylindrical battery.

[0037] A battery pack including the secondary battery.

[0038] An electronic device including the battery pack.

[0039] The positive progress effect of the utility model lies in:

[0040] Since the first insulating film is arranged at the position of the first end of the electrode assembly, which is the position of the welding of the end wall and the external busbar (the busbar is generally used for the series connection between two adjacent battery cells), a high temperature is generated during welding, and the first insulating film will generate a large transverse and longitudinal thermal shrinkage rate at high temperature, which will adversely affect the battery cell and thus affect the safety of the battery.

[0041] In the utility model, the transverse thermal shrinkage rate of the first insulating film is less than or equal to 1% and the longitudinal thermal shrinkage rate of the first insulating film is less than or equal to 3% under the condition that the first test temperature is 200 DEG C and the test time is 30 minutes, the transverse and longitudinal thermal shrinkage rates of the first insulating film at high temperature can be effectively controlled, thus the adverse effect on the battery cell is avoided, and the safety of the battery is improved. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 It is a structure schematic view of the secondary battery of an embodiment of the utility model.

[0043] Figure 2 It is a sectional structure schematic view of the secondary battery of an embodiment of the utility model.

[0044] Figure 3 It is Figure 2 It is a local amplification structure schematic view of part A.

[0045] Figure 4 It is Figure 2 It is a local amplification structure schematic view of part B.

[0046] Figure 5 It is a local sectional structure schematic view of the secondary battery of an embodiment of the utility model.

[0047] Figure 6 It is Figure 5 It is a local amplification structure schematic view of part C.

[0048] Figure 7 It is a local sectional structure schematic view of the secondary battery of another angle of a preferred embodiment of the utility model.

[0049] Figure 8 It is a three-dimensional structure schematic view of the electrode assembly of the secondary battery of a preferred embodiment of the utility model.

[0050] Figure 9 It is a sectional structure schematic view of the electrode assembly of the secondary battery of a preferred embodiment of the utility model.

[0051] Figure 10 It is a local sectional structure schematic view of the first insulating film of the secondary battery of a preferred embodiment of the utility model when unfolded.

[0052] Figure 11 It is the local section view structure schematic drawing of the second insulating film of the secondary battery of a preferred embodiment of the utility model.

[0053] Figure 12 It is the structure schematic drawing of the battery pack of a preferred embodiment of the utility model.

[0054] Figure 13 It is the structure schematic drawing of the electronic device of a preferred embodiment of the utility model.

[0055] Explanation of reference signs

[0056] Electronic device 1000

[0057] Battery pack 100

[0058] Working part 300

[0059] Box body 310

[0060] Box cover 320

[0061] Secondary battery 1

[0062] Shell 10

[0063] End wall 11

[0064] Side wall 12

[0065] Accommodating cavity 13

[0066] Opening 14

[0067] Pressing joint 15

[0068] Electrode assembly 20

[0069] Winding structure 201

[0070] Positive plate 21

[0071] Positive tab 211

[0072] Positive plate starting end 217

[0073] Positive plate end 218

[0074] Separator 22

[0075] Separator starting end 221

[0076] Separator end 222

[0077] Negative plate 23

[0078] Negative plate starting end 237

[0079] Negative electrode tab end 238

[0080] First current collecting disc 31

[0081] Pole connecting part 311

[0082] Positive electrode tab connecting part 312

[0083] Second current collecting disc 32

[0084] First insulating film 40

[0085] First base material 41

[0086] First adhesive layer 42

[0087] First part 43

[0088] Second part 44

[0089] First insulating seal 50

[0090] Second insulating film 60

[0091] Second base material 61

[0092] Second adhesive layer 62

[0093] Pole 70

[0094] Cover plate 80

[0095] Second insulating seal 90

[0096] Height direction H of winding structure

[0097] Radial direction R of winding structure

[0098] Circumferential direction P of winding structure

[0099] Thickness a of first insulating film

[0100] Thickness a1 of first base material

[0101] Thickness a2 of first adhesive layer

[0102] Thickness b of second insulating film

[0103] Thickness b1 of second base material

[0104] Thickness b2 of second adhesive layer DETAILED DESCRIPTION

[0105] The utility model will be described in more detail below with reference to the preferred embodiments and drawings.

[0106] As Figures 1 to 7As shown, this embodiment provides a secondary battery 1. The secondary battery 1 includes: a casing 10, an electrode assembly 20, and a first insulating film 40.

[0107] The housing 10 includes an end wall 11 and a side wall 12 surrounding the end wall 11. The end wall 11 and the side wall 12 form a receiving cavity 13 for accommodating the electrode assembly 20, electrolyte, and other necessary battery components. The connection between the end wall 11 and the side wall 12 can be achieved in various ways, such as integral stamping, integral casting, or separate welding.

[0108] like Figure 8 and Figure 9 As shown, the electrode assembly 20 is located in the receiving cavity 13. The electrode assembly 20 includes a winding structure 201 formed by stacking and winding a positive electrode 21, a diaphragm 22 and a negative electrode 23. The winding structure 201 includes a first end with a positive electrode tab 211 and a second end with a negative electrode tab along the height direction H.

[0109] A portion of the first insulating film 40 is disposed around the outer periphery of the first end of the winding structure 201. The first insulating film 40 simultaneously fixes the winding structure 201 and the positive electrode tab 211.

[0110] Under the conditions of a first test temperature of 200℃ and a test time of 30 minutes, the transverse thermal shrinkage rate of the first insulating film 40 is less than or equal to 1%, and the longitudinal thermal shrinkage rate of the first insulating film 40 is less than or equal to 3%.

[0111] Since the first insulating film 40 is located at the first end of the electrode assembly 20, which is the welding position between the end wall 11 and the external adapter (the adapter is generally a busbar, used for series connection between two adjacent cells), a high temperature will be generated during welding. If the first insulating film 40 generates a large lateral and longitudinal thermal shrinkage rate at high temperature, it will have an adverse effect on the cell, thereby affecting the safety of the battery.

[0112] In this embodiment, by setting the first test temperature to 200°C and the test time to 30 minutes, the lateral thermal shrinkage rate of the first insulating film 40 is less than or equal to 1%, and the longitudinal thermal shrinkage rate of the first insulating film 40 is less than or equal to 3%. This effectively controls the lateral and longitudinal thermal shrinkage rates of the first insulating film 40 at high temperatures, thereby avoiding adverse effects on the battery cell and improving battery safety.

[0113] It should be noted that the high temperature resistance test of the insulation film is as follows: the insulation film to be tested is attached to a steel plate or aluminum foil, and a 2 kg pressure roller is rolled back and forth twice; the oven is set to the temperature, and the sample is placed in the oven after the preset temperature is reached; the power of the oven is turned off after the test is completed, and the sample is taken out and naturally cooled for one hour before testing. The test parameters are as follows: the sample size of the insulation film is 25mm*100mm (determined according to the experimental requirements, not a fixed value), which can be the actual size of the insulation film directly detached from the battery; the test temperature is 200 degrees (determined according to the experimental requirements, not a fixed value); the test time is 30 minutes (determined according to the experimental requirements, not a fixed value). The judgment standard is the shrinkage size of the second test, and whether there is residual glue after tearing off.

[0114] Before the battery is made, that is, the first insulation film 40 is not fixed to the outer periphery of the electrode assembly 20, the test can be carried out in the unfolded state of the first insulation film 40; or if it is a battery, that is, the first insulation film 40 has been fixed to the outer periphery of the electrode assembly 20, the first insulation film 40 can be peeled off from the outer periphery of the electrode assembly 20 and then tested.

[0115] In addition, the transverse and longitudinal directions of the first insulation film 40 refer to the transverse direction of the first insulation film 40 itself (the length direction of the first insulation film 40 itself or the circumferential direction P of the winding structure 201) and the longitudinal direction (the width direction of the first insulation film 40 itself).

[0116] Further, the peeling strength of the first insulation film 40 is 2N / cm-7N / cm. By setting the value range of the peeling strength of the first insulation film 40, on the one hand, the peeling strength of the first insulation film 40 is too small, that is, the adhesion of the first insulation film 40 is too small, so that it cannot play the role of fixing the winding structure 201 and the positive tab 211 at the same time; on the other hand, the peeling strength of the first insulation film 40 is too large, that is, the adhesion of the first insulation film 40 is too large, which causes waste of manufacturing cost. Preferably, the peeling strength of the first insulation film 40 is greater than or equal to 2.4N / cm.

[0117] Preferably, the first insulation film 40 is arranged at least one circle around the outer periphery of the winding structure 201 close to the first end. Because the positive tab 211 is a full tab design, by arranging the first insulation film 40 at least one circle around the outer periphery of the winding structure 201 close to the first end, the insulation of the positive tab 211 and the shell 10 can be effectively guaranteed.

[0118] In the embodiment, the secondary battery 1 further comprises a second insulation film 60, which surrounds the outer periphery of the winding structure 201 and is located between the first end and the second end in the height direction H of the winding structure 201. The second insulation film 60 is a structure for fixing the end of the separator 22.

[0119] Under the same test conditions, the lateral thermal shrinkage rate of the first insulating film 40 is greater than the lateral thermal shrinkage rate of the second insulating film 60, and the longitudinal thermal shrinkage rate of the first insulating film 40 is greater than the longitudinal thermal shrinkage rate of the second insulating film 60. Since the second insulating film 60 is located between the first end and the second end of the winding structure 201 along the height direction H, the position where the second insulating film 60 is located is less affected by the high temperature when the terminal wall 11 is welded with the external adapter tab than the position of the first end, so the second insulating film 60 does not need to have a better thermal shrinkage rate. By setting the lateral thermal shrinkage rate of the first insulating film 40 to be greater than the lateral thermal shrinkage rate of the second insulating film 60, and the longitudinal thermal shrinkage rate of the first insulating film 40 to be greater than the longitudinal thermal shrinkage rate of the second insulating film 60, the normal function of the second insulating film 60 in fixing the end of the separator 22 can be ensured, and the waste of manufacturing cost can be avoided.

[0120] Preferably, under the condition that the second test temperature is 140°C and the test time is 30 minutes, the lateral thermal shrinkage rate of the second insulating film 60 is less than or equal to 1%, and the longitudinal thermal shrinkage rate of the second insulating film 60 is less than or equal to 3%, so that the normal function of the second insulating film 60 in fixing the end of the separator 22 can be ensured, and the waste of manufacturing cost can be avoided.

[0121] The peeling strength of the first insulating film 40 is greater than the peeling strength of the second insulating film 60.

[0122] Since the winding structure 201 will expand and contract during the charging and discharging process, if the adhesion of the second insulating film 60, which is a structure for fixing the end of the separator 22, is too high, it will restrict the expansion of the winding structure 201, which is not conducive to the capacity of the battery cell. On the other hand, if the adhesion of the second insulating film 60 is too low, it will not be able to fix the winding structure 201, and the winding structure 201 will be loose. As for the first insulating film 40, as mentioned above, it needs to fix the winding structure 201 and the positive tab 211 at the same time, and needs greater adhesion to ensure that the winding structure 201 and the positive tab 211 will not be loose, which is conducive to the first end of the winding structure 201 entering the shell. Moreover, if the adhesion of the first insulating film 40 is too low, it will fall off and cause insulation failure, which will cause the positive tab 211 to contact the shell 10 and risk short circuit. Therefore, in this embodiment, by setting the peeling strength of the first insulating film 40 to be greater than the peeling strength of the second insulating film 60, the normal capacity of the battery cell can be ensured.

[0123] It should be noted that the peeling strength of the first insulating film 40 and the peeling strength of the second insulating film 60 are tested by the test method for adhesive tape peeling strength in the national standard GBT2792-2014.

[0124] The peeling strength test adopts the method 1 in the national standard GBT2792-2014: test method for 180° peeling strength of adhesive tape and stainless steel, unit N / cm. If the insulation film has been made into a battery, the corresponding GBT2792-2014 standard can be tested according to the appropriate length of the insulation film in the battery, and it is not limited to the actual length of the insulation film defined in GB.

[0125] Preferably, the peeling strength of the first insulation film 40 is 2-7 times the peeling strength of the second insulation film 60, for example, it can be 2 times, 3.5 times, 4.5 times, 5.8 times or 7 times, etc., that is, the peeling strength of the first insulation film 40 is greater than the peeling strength of the second insulation film 60. By setting the range of the peeling strength of the first insulation film 40 greater than the peeling strength of the second insulation film 60, it is avoided to cause waste of manufacturing cost due to too high peeling strength of the first insulation film 40.

[0126] Specifically, the peeling strength of the second insulation film 60 is 1 N / cm-4 N / cm. By setting the value range of the peeling strength of the second insulation film 60, on the one hand, it is avoided that the peeling strength of the second insulation film 60 is too small, that is, the adhesion of the second insulation film 60 is too small, so that it cannot play the role of fixing the winding structure 201; on the other hand, it is avoided that the peeling strength of the second insulation film 60 is too large, which restricts the expansion of the winding structure 201, is not conducive to the capacity of the battery, and causes waste of manufacturing cost. Preferably, the peeling strength of the second insulation film 60 is greater than or equal to 1.8 N / cm.

[0127] The ratio of the thickness b of the second insulation film 60 to the thickness a of the first insulation film 40 is 0.8-1.1, for example, it can be 0.8, 0.85, 0.95, 1.0 or 1.1, etc. By setting the value range of the ratio of the thickness of the second insulation film 60 and the first insulation film 40, the diameter of the electrode assembly 20 can be made more consistent, the energy density of the battery is improved, and the assembly is more accurate.

[0128] Along the radial direction R of the winding structure 201, the first insulation film 40 and the second insulation film 60 do not overlap, that is, along the height direction H of the winding structure 201, the winding structure 201 partially covers the second insulation film 60, and the second insulation film 60 and the first insulation film 40 are staggered to avoid the superposition of the electrode assembly 20 along the radial direction R, which affects the diameter of the electrode assembly 20, thereby improving the energy density; and the second insulation film 60 also plays a role in fixing the outer ring diaphragm 22 to prevent the diaphragm 22 from loosening.

[0129] As Figure 10As shown, the first insulating film 40 includes a first base material 41, and the first base material 41 includes an area not covered by the first adhesive layer 42 and an area covered by the first adhesive layer 42 on the side facing the winding structure 201. The material of the first base material 41 is PET (English full name: Polyethylene terephthalate, Chinese name: polyethylene terephthalate) or PI (English full name: Polyimide, Chinese name: polyimide). The adhesive layer of the first insulating film 40 contains polyacrylate.

[0130] The ratio of the thickness a1 of the first base material 41 to the thickness a2 of the first adhesive layer 42 is 2-6. By setting the value range of the ratio of the thickness a1 of the first base material 41 to the thickness a2 of the first adhesive layer 42, the proportion of the thickness a1 of the first base material 41 and the thickness a2 of the first adhesive layer 42 in the first insulating film 40 is balanced, so that the first insulating film 40 can realize the simultaneous fixation of the winding structure 201 and the positive tab 211, and also has the corresponding support strength.

[0131] As shown, Figure 11 The second insulating film 60 includes a second base material 61, and the second base material 61 includes an area not covered by the second adhesive layer 62 and an area covered by the second adhesive layer 62 on the side facing the winding structure 201. The material of the second base material 61 is PET or PI. The second adhesive layer 62 contains polyacrylate.

[0132] The ratio of the thickness b1 of the second base material 61 to the thickness b2 of the second adhesive layer 62 of the second insulating film 60 is 1.5-2.5. By setting the value range of the ratio of the thickness b1 of the second base material 61 to the thickness b2 of the second adhesive layer 62, the proportion of the thickness b1 of the second base material 61 and the thickness b2 of the second adhesive layer 62 in the first insulating film 40 is balanced, so that the second insulating film 60 can realize the fixation of the separator end 222, and also has the corresponding support strength.

[0133] The materials of the first base material 41 and the second base material 61 are the same; the materials of the first adhesive layer 42 and the second adhesive layer 62 are the same, so as to facilitate the second insulating film 60 and the first insulating film 40 to be an integral structure, to improve the production efficiency, and at the same time, the diameter of the battery cell can be reduced, thereby ensuring the energy density of the battery. But not limited to this, in other embodiments, the materials of the first base material 41 and the second base material 61 can also be different, and similarly, the materials of the first adhesive layer 42 and the second adhesive layer 62 can also be different.

[0134] Preferably, the thickness a2 of the first adhesive layer 42 is greater than the thickness b2 of the second adhesive layer 62, so that the peeling strength of the first insulating film 40 is greater than that of the second insulating film 60, and the first adhesive layer 42 directly contacts the positive tab 211 or the current collector plate in the battery, facing the metal; the second adhesive layer 62 is on the outer periphery of the separator 22, so the first adhesive layer 42 needs more thickness to contact the unevenness of the metal surface, and needs to prevent the contact between the metal and the shell 10 from causing short circuit, so the first adhesive layer 42 is thicker.

[0135] Specific test method: the total thickness of the insulating film is measured by a micrometer, specifically, select the insulating film to be tested, and measure the total thickness of the insulating film at three equidistant positions, then take the average of the three positions as the total thickness of the insulating film; then, put the insulating film into toluene solution for a period of time (usually 5 minutes or more), then take it out and wipe it with a dust-free cloth to obtain the substrate. At this time, measure the thickness of the substrate at three equidistant positions, then take the average of the three positions as the thickness of the substrate. The thickness of the adhesive layer is obtained by subtracting the thickness of the substrate from the total thickness of the insulating film.

[0136] Please refer to Figure 9 , the positive plate 21 includes a positive plate starting end 217 and a positive plate ending end 218; the negative plate 23 includes a negative plate starting end 237 and a negative plate ending end 238. The separator 22 includes a separator starting end 221 and a separator ending end 222. The second insulating film 60 includes, but is not limited to, an ending adhesive tape for fixing the separator ending end 222. That is, the second insulating film 60 can be an ending adhesive tape, or other insulating structure, such as a mylar film. Regardless of the structure of the second insulating film 60, its radial projection R along the winding structure 201 and the first insulating film 40 do not overlap.

[0137] The second insulating film 60 is continuously arranged along the circumferential direction P of the winding structure 201 and does not overlap, forming a winding structure uncovered area on the outer periphery of the winding structure 201 which is not covered by the second insulating film 60. The radial projection H of the overlapping part of the first insulating film 40 along the circumferential direction P of the winding structure 201 falls at least partially on the winding structure uncovered area. By arranging the radial projection H of the overlapping part of the first insulating film 40 along the circumferential direction P of the winding structure 201 to fall at least partially on the winding structure uncovered area, the overlapping part of the first insulating film 40 along the circumferential direction P of the winding structure 201 and the second insulating film 60 in the radial direction R are avoided, which affects the diameter of the battery, thereby improving the energy density; and the first insulating film 40 can support the winding structure uncovered area, avoiding the difference between the winding structure uncovered area and the winding structure covered area covered by the second insulating film 60 in the battery use, causing the battery to swell and lithium precipitation.

[0138] The secondary battery 1 further includes a first current collecting plate 31 located between the positive tab 211 and the end wall 11 of the case 10 along the height direction H, the first current collecting plate 31 including a connected positive post 70 connecting portion 311 and a positive tab connecting portion 312, the positive tab connecting portion 312 being electrically connected with the positive tab 211, and the positive post 70 connecting portion 311 being electrically connected with the positive post 70.

[0139] Preferably, the first insulating film 40 includes a first portion 43 and a second portion 44 connected with each other, the first portion 43 surrounding the outer periphery of the first end of the wound structure 201 and extending along the height direction H, and the second portion 44 being bent towards the center hole of the wound structure 201 and covering the side of the positive tab connecting portion 312 of the first current collecting plate 31 connected with the positive tab 211 away from the electrode assembly 20.

[0140] In the present embodiment, the secondary battery 1 is a cylindrical battery. The cylindrical battery has the advantages of high energy density, long cycle life, good safety performance, etc. Moreover, when the secondary battery 1 is a cylindrical battery, because the cylindrical battery is a full tab design, the first insulating film 40 surrounds the outer periphery of the wound structure 201 near the first end at least one turn, which can insulate the positive tab 211 and the case 10. However, the present application is not limited thereto, and in other embodiments, the secondary battery 1 can also be a square battery or other shaped battery.

[0141] The setting mode of the present embodiment that the transverse thermal shrinkage rate of the first insulating film 40 is less than or equal to 1% and the longitudinal thermal shrinkage rate of the first insulating film 40 is less than or equal to 3% under the condition of a first test temperature of 200℃ and a test time of 30 minutes is applied to the cylindrical battery, which can effectively control the transverse and longitudinal thermal shrinkage rates of the first insulating film 40 at high temperature, thereby avoiding adverse effects on the battery cell and improving the safety of the battery.

[0142] The secondary battery 1 further includes a positive post 70 penetrating the end wall 11 and being electrically connected with the positive tab 211 through the first current collecting plate 31.

[0143] The accommodating cavity 13 of the shell 10 is provided with an opening 14 away from one end of the end wall 11; the shell 10 further comprises a crimping portion 15 which is formed at one end of the side wall 12 close to the opening 14 and is recessed towards the inside of the shell 10. The secondary battery 1 further comprises a cover plate 80, a second insulating seal 90 and a second current collector 32. The cover plate 80 is installed at the opening 14. The second insulating seal 90 is arranged around the periphery of the cover plate 80 to insulate and seal the cover plate 80 and the shell 10. The second current collector 32 is arranged between the electrode assembly 20 and the cover plate 80 and is electrically connected with the shell 10, and the connecting piece of the second current collector 32 is located at the side of the crimping portion 15 facing the electrode assembly 20 and is welded with the crimping portion 15. In this way, by arranging the connecting piece of the second current collector 32 at the side of the crimping portion 15 facing the electrode assembly 20 and welded with the crimping portion 15, that is, the welding area of the second current collector 32 with the negative electrode tab is located at a position closer to the electrode assembly 20 than the crimping portion 15, so that the influence of the crimping portion 15 on the welding area of the negative electrode tab and the second current collector 32 can be prevented, and the welding strength of the tab and the second current collector 32 can be improved.

[0144] The welding sequence of the first current collector 31 and the second current collector 32 of the secondary battery 1 in the embodiment is as follows: first, the first current collector 31 is placed; then, the electrode assembly 20 is pressed on both sides of the positive electrode and the negative electrode (the pressing process can increase the contact between the current collector and the electrode assembly 20 and avoid false welding); the first current collector 31 is welded by adopting linear welding instead of spot welding, because the negative electrode tab is soft, and after being pressed twice, the second current collector 32 is close to the electrode assembly 20, and spot welding causes scalding of the separator 22 due to heat concentration, and linear welding can avoid scalding of the separator 22 and cause short circuit between the positive electrode and the negative electrode; subsequently, the second current collector 32 is placed again; the electrode assembly 20 is pressed on both sides of the positive electrode and the negative electrode again; finally, the second current collector 32 is welded.

[0145] As shown in Figure 12 The utility model also provides a battery pack 100, battery pack 100 includes above -mentioned secondary battery 1, in the embodiment of the utility model battery pack 100, battery pack 100 includes box 310, box lid 320 and multiple secondary batteries 1, multiple secondary batteries 1 are placed in box 310, and are connected in series or parallel with each other, or series and parallel hybrid, and box lid 320 is sealed on box 310 to protect multiple secondary batteries 1. It needs to be explained that battery pack 100 can also include battery pack 100 thermal management system, circuit board etc. part in addition to the secondary battery 1 of the utility model, and battery pack 100 can be battery module also can be battery pack, energy storage electric cabinet etc.; here will not be expanded to explain one by one.

[0146] As shown in Figure 13As shown, the utility model further provides an electronic device 1000, electronic device 1000 includes battery pack 100 described above. Working part 300 is electrically connected with battery pack 100 to obtain electric energy support. As an example, electronic device 1000 is vehicle, and vehicle can be fuel automobile, gas automobile or new energy automobile, and new energy automobile can be pure electric vehicle, hybrid vehicle or extended range vehicle, but is not limited. Working part 300 is vehicle body, and battery pack 100 is arranged at the bottom of vehicle body and provides electric energy support for the running of vehicle or the operation of electrical element in vehicle. However, in some other embodiments, electronic device 1000 can also be mobile phone, portable device, notebook computer, ship, spacecraft, electric toy and electric tool and the like. Spacecraft includes airplane, rocket, space shuttle and spacecraft and the like, and working part 300 can be unit component that can obtain the electric energy of battery pack 100 and make corresponding work, for example, fan blade rotating unit of fan, dust absorption working unit of dust collector and the like. Electric toy includes fixed or mobile electric toy, for example, game machine, electric car toy, electric ship toy and electric plane toy and the like, and electric tool includes metal cutting electric tool, grinding electric tool, assembly electric tool and railway electric tool, for example, electric drill, electric grinder, electric wrench, electric screwdriver, electric hammer, impact drill, concrete vibrator and electric planer and the like. The embodiment of the application does not specially limit the above-mentioned electronic device 1000.

[0147] Although the specific embodiments of the utility model are described above, those skilled in the art should understand that this is only an example, and the protection scope of the utility model is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the utility model, and these changes and modifications all fall within the protection scope of the utility model.

Claims

1. A secondary battery characterized by comprising: It comprises: a housing comprising an end wall and a side wall arranged around the end wall, the end wall and the side wall surrounding a containing cavity; an electrode assembly located in the containing cavity, the electrode assembly comprising a positive electrode sheet, a separator, and a negative electrode sheet laminated and wound to form a wound structure, the wound structure comprising a first end provided with a positive electrode tab and a second end provided with a negative electrode tab in the height direction; a first insulating film, part of the first insulating film surrounding the outer periphery of the first end of the wound structure; under the condition that the first test temperature is 200℃ and the test time is 30 minutes, the transverse thermal shrinkage rate of the first insulating film is less than or equal to 1%, and the longitudinal thermal shrinkage rate of the first insulating film is less than or equal to 3%.

2. The secondary battery according to claim 1, wherein the peeling strength of the first insulating film is 2N / cm-7N / cm; and / or the first insulating film comprises a first base material, one side of the first base material towards the wound structure comprising an area not covered with a first adhesive layer and an area covered with the first adhesive layer; the ratio of the thickness of the first base material to the thickness of the first adhesive layer is 2-6.

3. The secondary battery according to claim 1, wherein The secondary battery further comprises a second insulating film, the second insulating film surrounding the outer periphery of the wound structure and located between the first end and the second end in the height direction of the wound structure; under the same test conditions, the transverse thermal shrinkage rate of the first insulating film is greater than that of the second insulating film, and / or the longitudinal thermal shrinkage rate of the first insulating film is greater than that of the second insulating film.

4. The secondary battery according to claim 3, wherein under the condition that the second test temperature is 140℃ and the test time is 30 minutes, the transverse thermal shrinkage rate of the second insulating film is less than or equal to 1%, and the longitudinal thermal shrinkage rate of the second insulating film is less than or equal to 3%; and / or the second insulating film comprises a second base material, one side of the second base material towards the wound structure comprising an area not covered with a second adhesive layer and an area covered with the second adhesive layer; the ratio of the thickness of the second base material to the thickness of the second adhesive layer is 1.5-2.

5.

5. The secondary battery according to claim 3, wherein the peeling strength of the first insulating film is greater than that of the second insulating film; and / or the peeling strength of the second insulating film is 1N / cm-4N / cm.

6. The secondary battery according to claim 5, wherein the peeling strength of the first insulating film is 2-7 times the peeling strength of the second insulating film; and / or the peeling strength of the second insulating film is greater than or equal to 1.8N / cm.

7. The secondary battery according to claim 3, wherein the positive electrode active material layer is formed on the surface of the positive electrode current collector. the ratio of the thickness of the second insulating film to the thickness of the first insulating film is 0.8-1.1; and / or in the radial direction of the wound structure, the first insulating film and the second insulating film do not overlap; the second insulating film is arranged continuously along the circumferential direction of the wound structure and does not overlap, forming a wound structure uncovered area not covered by the second insulating film in the outer periphery of the wound structure, and the overlapping part of the first insulating film along the circumferential direction of the wound structure at least partially falls within the wound structure uncovered area in the height direction; and / or The first insulating film includes a first portion and a second portion connected to each other, the first portion surrounds an outer periphery of the first end of the winding structure and extends in the height direction, and the second portion is bent toward the center hole of the winding structure and covers a side of the positive tab connecting portion of the first current collector plate, which is away from the electrode assembly.

8. The secondary battery according to any one of claims 1 to 7, wherein The secondary battery further includes: a first current collector plate located between the positive tab and an end wall of the case in the height direction; a post passing through the end wall and electrically connected to the positive tab through the first current collector plate; a first insulating seal located between the end wall and the first current collector plate; and / or, an opening is provided at an end of the accommodation cavity of the case, which is away from the end wall, and the case further includes a crimping portion formed at an end of the side wall close to the opening and recessed toward the inside of the case; The secondary battery further includes: a cover plate installed at the opening; a second insulating seal surrounding a periphery of the cover plate to insulate and seal the cover plate and the case; a second current collector plate arranged between the electrode assembly and the cover plate and electrically connected to the case, a connecting tab of the second current collector plate being located at a side of the crimping portion facing the electrode assembly and welded to the crimping portion; and / or, the secondary battery is a cylindrical battery.

9. A battery pack characterized by comprising: The secondary battery includes any one of claims 1-8.

10. An electronic device, comprising: The battery pack includes claim 9. The battery pack includes claim 9.

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