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; the second insulating film is arranged on the periphery of the winding structure in a surrounding mode and located between the first end and the second end in the height direction of the winding structure. Wherein the peel strength of the first insulating film is greater than the peel strength of the second insulating film. The peeling strength of the first insulating film is set to be greater than that of the second insulating film, so that the normal development of the capacity of the battery cell is ensured.

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 concerning its development.

[0003] In the development of battery technology, how to ensure that the maximum extent of the capacity of battery cell, is a battery technology in an urgent need to solve the technical problem. UTILITY MODEL CONTENTS

[0004] The utility model solves the technical problems in the prior art, and provides a secondary battery, a battery pack and an electronic device.

[0005] The utility model solves the above technical problems by the following technical solutions:

[0006] A secondary battery, characterized in that it comprises:

[0007] A housing comprising an end wall and a side wall arranged around the end wall, the end wall and the side wall forming a receiving cavity;

[0008] An electrode assembly located in the receiving cavity, the electrode assembly comprising a positive electrode sheet, a separator and a negative electrode sheet stacked 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;

[0009] A first insulating film, part of the first insulating film surrounding the outer periphery of the first end of the wound structure;

[0010] 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;

[0011] Wherein, the peeling strength of the first insulating film is greater than the peeling strength of the second insulating film.

[0012] In the technical solution, the winding structure expands and shrinks during the charging and discharging process. If the adhesion of the second insulating film is too high, the expansion of the winding structure will be restricted, which is not conducive to the capacity of the battery cell. On the other hand, if the adhesion of the second insulating film is too low, the winding structure will be loose. For the first insulating film, it needs to fix the winding structure and the positive tab at the same time, and needs a larger adhesion to ensure that the winding structure and the positive tab will not be loose, which is conducive to the first end of the winding structure entering the shell. Moreover, if the adhesion of the first insulating film is too low, it will fall off and cause insulation failure, which may cause the positive tab to contact the shell and short circuit. Therefore, in the technical solution, the peeling strength of the first insulating film is greater than the peeling strength of the second insulating film, which can ensure the normal capacity of the battery cell.

[0013] Preferably, the peeling strength of the first insulating film is 2-7 times the peeling strength of the second insulating film; and / or,

[0014] The peeling strength of the first insulating film is 2-7 N / cm; and / or,

[0015] The peeling strength of the second insulating film is 1-4 N / cm.

[0016] Preferably, the peeling strength of the first insulating film is greater than or equal to 2.4 N / cm; and / or,

[0017] The peeling strength of the second insulating film is greater than or equal to 1.8 N / cm.

[0018] Preferably, 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,

[0019] Along the 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 the circumferential direction of the winding structure and does not overlap, forming a winding structure uncovered area on the outer periphery of the winding structure which is not covered by the second insulating film, and the overlapping part of the first insulating film along the circumferential direction of the winding structure falls at least partially on the winding structure uncovered area in the height direction.

[0020] Preferably, the first insulating film surrounds at least one circle of the outer periphery of the winding structure close to the first end.

[0021] Preferably, the first insulating film comprises a first substrate, one side of the first substrate towards the winding structure comprises an area not covered by a first adhesive layer and an area covered by the first adhesive layer; the second insulating film comprises a second substrate, one side of the second substrate towards the winding structure comprises an area not covered by a second adhesive layer and an area covered by the second adhesive layer;

[0022] The thickness of the first adhesive layer is greater than the thickness of the second adhesive layer; and / or,

[0023] The first substrate and the second substrate are made of the same material; and / or,

[0024] The first adhesive layer and the second adhesive layer are made of the same material; and / or,

[0025] The first substrate is made of PET or PI, and the second substrate is made of PET or PI; and / or,

[0026] The first adhesive layer contains polyacrylate, and the second adhesive layer contains polyacrylate.

[0027] Preferably, 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 along 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 connection part of the first current collector plate away from the electrode assembly.

[0028] Preferably, the secondary battery further includes:

[0029] A first current collector plate located between the positive tab and the end wall of the shell along the height direction;

[0030] A pole passing through the end wall and electrically connected to the positive tab through the first current collector plate, the pole being provided with a liquid injection through hole along the height direction;

[0031] A first insulating seal located between the end wall and the first current collector plate;

[0032] And / or,

[0033] The accommodating cavity of the shell is provided with an opening at one end away from the end wall, and the shell further includes a crimping part formed at one end of the side wall close to the opening and recessed toward the inside of the shell;

[0034] The secondary battery further includes:

[0035] A cover plate installed at the opening;

[0036] A second insulating seal surrounding the periphery of the cover plate to insulate and seal the cover plate and the shell;

[0037] A second current collector plate arranged between the electrode assembly and the cover plate and electrically connected to the shell, the connecting piece of the second current collector plate being located at the side of the crimping part facing the electrode assembly and being welded to the crimping part.

[0038] and / or,

[0039] The secondary battery is a cylindrical battery.

[0040] A battery pack characterized by comprising the secondary battery described above.

[0041] An electronic device characterized by comprising the battery pack described above.

[0042] The positive progress effect of the utility model lies in:

[0043] Because the winding structure will expand and shrink in the charging and discharging process, if the adhesive force of the second insulating film is too high, the expansion of the winding structure will be restricted, which is not conducive to the capacity of the battery cell; on the other hand, if the adhesive force of the second insulating film is too low, the winding structure will not be fixed, and the winding structure will be loose. As for the first insulating film, it needs to fix the winding structure and the positive electrode lug at the same time, and needs a greater adhesive force to ensure that the winding structure and the positive electrode lug will not be loose, which is conducive to the first end of the winding structure entering the shell; in addition, if the adhesive force of the first insulating film is too small and falls off, it will cause insulation failure and the risk of short circuit caused by the contact between the positive electrode lug and the shell. Therefore, in the utility model, by setting the peeling strength of the first insulating film to be greater than that of the second insulating film, the normal capacity of the battery cell can be ensured. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 It is a structure schematic view of a secondary battery of an embodiment of the utility model.

[0045] Figure 2 It is a sectional structure schematic view of a secondary battery of an embodiment of the utility model.

[0046] Figure 3 It is Figure 2 It is a local enlarged structure schematic view of part A.

[0047] Figure 4 It is Figure 2 It is a local enlarged structure schematic view of part B.

[0048] Figure 5 It is a local sectional structure schematic view of a secondary battery of an embodiment of the utility model.

[0049] Figure 6 It is Figure 5 It is a local enlarged structure schematic view of part C.

[0050] Figure 7 It is a local sectional structure schematic view of a secondary battery of another angle of a preferred embodiment of the utility model.

[0051] Figure 8The utility model discloses a preferable embodiment's second battery's electrode subassembly's three-dimensional structure schematic diagram.

[0052] Figure 9 The utility model discloses a preferable embodiment's second battery's electrode subassembly's sectional structure schematic diagram.

[0053] Figure 10 The utility model discloses a preferable embodiment's second battery's first insulating film's local sectional structure schematic diagram when unfolding.

[0054] Figure 11 The utility model discloses a preferable embodiment's second battery's second insulating film's local sectional structure schematic diagram when unfolding.

[0055] Figure 12 The utility model discloses a preferable embodiment's battery pack's structure schematic diagram.

[0056] Figure 13 The utility model discloses a preferable embodiment's electronic device's structure schematic diagram.

[0057] Mark explanation

[0058] Electronic device 1000

[0059] Battery pack 100

[0060] Work department 300

[0061] Box 310

[0062] Box cover 320

[0063] Second battery 1

[0064] Shell 10

[0065] End wall 11

[0066] Side wall 12

[0067] Accommodate cavity 13

[0068] Opening 14

[0069] Pressure joint part 15

[0070] Electrode subassembly 20

[0071] Winding structure 201

[0072] Positive plate 21

[0073] Positive pole lug 211

[0074] Positive plate starting end 217

[0075] Positive plate end 218

[0076] septum 22

[0077] septum start end 221

[0078] septum end end 222

[0079] negative electrode sheet 23

[0080] negative electrode sheet start end 237

[0081] negative electrode sheet end end 238

[0082] first current collector disc 31

[0083] pole connecting portion 311

[0084] positive electrode tab connecting portion 312

[0085] second current collector disc 32

[0086] first insulating film 40

[0087] first base material 41

[0088] first adhesive layer 42

[0089] first part 43

[0090] second part 44

[0091] first insulating seal 50

[0092] second insulating film 60

[0093] second base material 61

[0094] second adhesive layer 62

[0095] pole 70

[0096] liquid injection through hole 71

[0097] cover plate 80

[0098] second insulating seal 90

[0099] height direction H of winding structure

[0100] radial direction R of winding structure

[0101] circumferential direction P of winding structure

[0102] thickness a of first insulating film

[0103] thickness a1 of first base material

[0104] thickness a2 of first adhesive layer

[0105] thickness b of second insulating film

[0106] The thickness b1 of the second substrate

[0107] The thickness b2 of the second adhesive layer DETAILED DESCRIPTION

[0108] A preferred embodiment is described below in conjunction with the accompanying drawings.

[0109] As Figures 1 to 7 shown, the embodiment provides a secondary battery 1. The secondary battery 1 includes a housing 10, an electrode assembly 20, a first insulating film 40, and a second insulating film 60.

[0110] The housing 10 includes an end wall 11 and a side wall 12 arranged around the end wall 11, and the end wall 11 and the side wall 12 are arranged to form a receiving cavity 13 for accommodating the electrode assembly 20, electrolyte, and other necessary components of the battery. The connection between the end wall 11 and the side wall 12 can be achieved in various ways, such as one-piece stamping, one-piece casting, or separate welding.

[0111] As Figure 8 and Figure 9 shown, the electrode assembly 20 is located in the receiving cavity 13, and the electrode assembly 20 includes a positive electrode sheet 21, a separator 22, and a negative electrode sheet 23 stacked and wound to form a wound structure 201, the wound structure 201 including a first end provided with a positive electrode tab 211 and a second end provided with a negative electrode tab in the height direction H.

[0112] Part of the first insulating film 40 is arranged around the outer periphery of the first end of the wound structure 201. The first insulating film 40 simultaneously fixes the wound structure 201 and the positive electrode tab 211.

[0113] The second insulating film 60 is arranged around the outer periphery of the wound structure 201, and is located between the first end and the second end in the height direction H of the wound structure 201. The second insulating film 60 is a structure for fixing the end of the separator 22.

[0114] The peeling strength of the first insulating film 40 is greater than the peeling strength of the second insulating film 60.

[0115] Since the winding structure 201 will expand and shrink during the charging and discharging process, if the adhesive force of the second insulating film 60, which is the structure fixing the end of the diaphragm 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 adhesive force 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 described above, it needs to fix the winding structure 201 and the positive tab 211 at the same time, and needs a greater adhesive force 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 adhesive force of the first insulating film 40 is too small and falls off, it will cause insulation failure and there is a risk of the positive tab 211 contacting the shell 10 and short-circuiting. Therefore, in the present embodiment, by setting the peel strength of the first insulating film 40 to be greater than the peel strength of the second insulating film 60, the normal capacity of the battery cell can be ensured.

[0116] It should be noted that the peel strength of the first insulating film 40 and the peel strength of the second insulating film 60 are tested by the test method for adhesive tape peel strength in the national standard GBT2792-2014.

[0117] The peel strength test uses Method 1 in the national standard GBT2792-2014: Test method for 180° peel strength of adhesive tape and stainless steel, unit N / cm. If the insulating film has been made into a battery, the corresponding GBT2792-2014 standard can be tested according to the appropriate length of the insulating film in the battery, and is not limited to the actual length of the insulating film defined in GB.

[0118] Preferably, the peel strength of the first insulating film 40 is 2-7 times the peel strength of the second insulating 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 peel strength of the first insulating film 40 is greater than the peel strength of the second insulating film 60. By setting the peel strength of the first insulating film 40 to be greater than the peel strength of the second insulating film 60, it avoids the waste of manufacturing cost caused by the peel strength of the first insulating film 40 being too high.

[0119] Specifically, the peeling strength of the first insulating film 40 is 2 N / cm-7 N / cm; the peeling strength of the second insulating film 60 is 1 N / cm-4 N / cm. By setting the value range of the peeling strength of the first insulating film 40, on the one hand, it avoids that the peeling strength of the first insulating film 40 is too small, that is, the adhesive force of the first insulating 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, it avoids that the peeling strength of the first insulating film 40 is too large, that is, the adhesive force of the first insulating film 40 is too large, which causes waste of manufacturing cost. By setting the value range of the peeling strength of the second insulating film 60, on the one hand, it avoids that the peeling strength of the second insulating film 60 is too small, that is, the adhesive force of the second insulating film 60 is too small, so that it cannot play the role of fixing the winding structure 201; on the other hand, it avoids that the peeling strength of the second insulating film 60 is too large, which restricts the expansion of the winding structure 201, is not conducive to the capacity of the battery cell, and causes waste of manufacturing cost.

[0120] Preferably, the peeling strength of the first insulating film 40 is greater than or equal to 2.4 N / cm; the peeling strength of the second insulating film 60 is greater than or equal to 1.8 N / cm.

[0121] Preferably, the first insulating 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 insulating 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.

[0122] Along the radial direction R of the winding structure 201, the first insulating film 40 and the second insulating 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 insulating film 60, and the second insulating film 60 and the first insulating film 40 are arranged 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 insulating film 60 also plays the role of fixing the outer ring diaphragm 22 to prevent the diaphragm 22 from loosening.

[0123] Please refer to Figure 9 , the positive sheet 21 includes a positive sheet starting end 217 and a positive sheet ending end 218; the negative sheet 23 includes a negative sheet starting end 237 and a negative sheet ending end 238. The diaphragm 22 includes a diaphragm starting end 221 and a diaphragm ending end 222. The second insulating film 60 includes, but is not limited to, an ending tape for fixing the diaphragm ending end 222. That is, the second insulating film 60 can be an ending tape, or it can be other insulating structures, such as a mylar film. No matter what structure the second insulating film 60 is, its orthographic projection along the radial direction R of the winding structure 201 and the first insulating film 40 does not overlap.

[0124] The second insulating film 60 is continuously arranged along the circumferential direction P of the winding structure 201 without overlapping, and a winding structure uncovered area not covered by the second insulating film 60 is formed at the outer periphery of the winding structure 201. The orthographic projection of the overlapping portion of the first insulating film 40 along the circumferential direction P of the winding structure 201 in the height direction H at least partially falls on the winding structure uncovered area. By arranging the orthographic projection of the overlapping portion of the first insulating film 40 along the circumferential direction P of the winding structure 201 in the height direction H at least partially falls on the winding structure uncovered area, the overlapping 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 is avoided, the diameter of the battery cell is affected, and the energy density is improved. In addition, the first insulating film 40 can support the winding structure uncovered area, and in the use of the battery, the difference between the winding structure uncovered area and the winding structure covered area covered by the second insulating film 60 is large, which can cause the battery to swell and lithium to be separated.

[0125] As shown in Figure 10 , the first insulating film 40 includes a first substrate 41, and the side of the first substrate 41 facing the winding structure 201 includes an area not covered by the first adhesive layer 42 and an area covered by the first adhesive layer 42. The material of the first substrate 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.

[0126] As shown in Figure 11 , the second insulating film 60 includes a second substrate 61, and the side of the second substrate 61 facing the winding structure 201 includes an area not covered by the second adhesive layer 62 and an area covered by the second adhesive layer 62. The material of the second substrate 61 is PET or PI. The second adhesive layer 62 contains polyacrylate.

[0127] The materials of the first substrate 41 and the second substrate 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 to reduce the diameter of the battery cell, thereby ensuring the energy density of the battery. However, it is not limited thereto, and in other embodiments, the materials of the first substrate 41 and the second substrate 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.

[0128] Preferably, the thickness a2 of the first adhesive layer 42 is greater than the thickness b2 of the second adhesive layer 62, so as to achieve that the peeling strength of the first insulating film 40 is greater than the peeling strength of the second insulating film 60, and the first adhesive layer 42 is directly in contact with 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 diaphragm 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.

[0129] Specific test method: the total thickness of the insulating film is measured by using a micrometer, specifically, select the insulating film to be tested, and measure the total thickness of the insulating film at three equidistant positions, and then take the average of the three positions as the total thickness of the insulating film; then, put the insulating film into a toluene solution for a period of time (generally 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, and 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.

[0130] Preferably, the ratio of the thickness b of the second insulating film 60 to the thickness a of the first insulating 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 insulating film 60 to the thickness of the first insulating film 40, the diameters of the electrode assemblies 20 can be made more consistent, the energy density of the battery is improved, and the assembly is more accurate.

[0131] Further, the ratio of the thickness a2 of the first adhesive layer 42 to the thickness b2 of the second adhesive layer 62 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 a2 of the first adhesive layer 42 to the thickness b2 of the second adhesive layer 62, the diameters of the electrode assemblies 20 can be made more consistent, the energy density of the battery is improved, and the assembly is more accurate.

[0132] Preferably, the ratio of the thickness a1 of the first substrate 41 of the first insulating film 40 to the thickness a2 of the first adhesive layer 42 is greater than the ratio of the thickness b1 of the second substrate 61 of the second insulating film 60 to the thickness b2 of the second adhesive layer 62, that is, the proportion of the thickness a1 of the first substrate 41 to the thickness a of the first insulating film 40 is greater than the proportion of the thickness b1 of the second substrate 61 to the thickness b of the second insulating film 60, so that the first substrate 41 has better support strength, and can achieve the effect of fixing the winding structure 201 and the positive tab 211 at the same time.

[0133] Specifically, the ratio of the thickness a1 of the first substrate 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 substrate 41 to the thickness a2 of the first adhesive layer 42, the proportion of the thickness a1 of the first substrate 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.

[0134] The ratio of the thickness b1 of the second substrate 61 of the second insulating film 60 to the thickness b2 of the second adhesive layer 62 is 2-6. By setting the value range of the ratio of the thickness b1 of the second substrate 61 to the thickness b2 of the second adhesive layer 62, the proportion of the thickness b1 of the second substrate 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. Preferably, the ratio of the thickness b1 of the second substrate 61 of the second insulating film 60 to the thickness b2 of the second adhesive layer 62 is 2-3, which has realized the requirement of fixing the separator end 222 and saved the cost.

[0135] The thickness a1 of the first substrate 41 is 20-60 μm. By setting the value range of the thickness a1 of the first substrate 41, on the one hand, the thickness a1 of the first substrate 41 is avoided to be too small and not to have the required support strength, and on the other hand, the thickness a1 of the first substrate 41 is avoided to be too large and affect the diameter of the electrode assembly 20, thereby affecting the energy density.

[0136] The thickness b1 of the second substrate 61 is 20-60 μm. By setting the value range of the thickness b1 of the second substrate 61, on the one hand, the thickness b1 of the second substrate 61 is avoided to be too small and not to have the required support strength, and on the other hand, the thickness b1 of the second substrate 61 is avoided to be too large and affect the diameter of the electrode assembly 20, thereby affecting the energy density.

[0137] The secondary battery 1 further comprises a first current collector 31, the first current collector 31 is located between the positive tab 211 and the end wall 11 of the shell 10 along the height direction H, the first current collector 31 comprises a connected pole 70 connecting portion 311 and a positive tab connecting portion 312, the positive tab connecting portion 312 is electrically connected with the positive tab 211, and the pole 70 connecting portion 311 is electrically connected with the pole 70.

[0138] Preferably, the first insulating film 40 includes a first portion 43 and a second portion 44 connected to each other, the first portion 43 is arranged around the outer periphery of the first end of the winding structure 201 and extends along the height direction H, and the second portion 44 is bent towards the center hole of the winding structure 201 and covers the side of the positive tab connecting portion 312 of the first current collector 31 connected to the positive tab 211 away from the electrode assembly 20.

[0139] In the 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 is arranged around the outer periphery of the winding structure 201 near the first end at least one turn, so that the positive tab 211 and the shell 10 are insulated. However, the secondary battery 1 can also be a square battery or other shaped battery in other embodiments.

[0140] The setting mode that the peeling strength of the first insulating film 40 is greater than that of the second insulating film 60 in the embodiment is applied to the cylindrical battery, which can ensure the normal play of the cell capacity.

[0141] The secondary battery 1 further includes a pole 70, the pole 70 is arranged through the end wall 11 and is electrically connected to the positive tab 211 through the first current collector 31. The pole 70 is provided with a liquid injection through hole 71 along the height direction H. The liquid injection through hole 71 is arranged corresponding to the first end of the electrode assembly 20, and the electrolyte flows into the shell 10 through the liquid injection through hole 71. Through the specific structure of arranging the first insulating film 40 at the first end, the electrolyte injected through the liquid injection through hole 71 can be effectively prevented from entering between the first insulating film 40 and the shell 10, thereby improving the electrolyte infiltration efficiency when the positive electrode is injected.

[0142] 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 tab and the second current collector 32 can be prevented, and the welding strength of the negative electrode tab and the second current collector 32 can be improved.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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 being arranged to form a receiving cavity; an electrode assembly located in the receiving cavity, the electrode assembly comprising a positive electrode sheet, a separator, and a negative electrode sheet stacked 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 being arranged around the outer periphery of the first end of the wound structure; a second insulating film, the second insulating film being arranged around the outer periphery of the wound structure and being located between the first end and the second end in the height direction of the wound structure; wherein the peeling strength of the first insulating film is greater than the peeling strength of the second insulating film.

2. The secondary battery according to claim 1, 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 first insulating film is 2-7 N / cm; and / or the peeling strength of the second insulating film is 1-4 N / cm.

3. The secondary battery according to claim 2, wherein the peeling strength of the first insulating film is greater than or equal to 2.4 N / cm; and / or the peeling strength of the second insulating film is greater than or equal to 1.8 N / cm.

4. The secondary battery according to claim 1, wherein 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 does not overlap the second insulating film; the second insulating film is continuously arranged in the circumferential direction of the wound structure and does not overlap, forming a wound structure uncovered area in the outer periphery of the wound structure that is not covered by the second insulating film, and the overlapping portion of the first insulating film in the circumferential direction of the wound structure at least partially falls within the wound structure uncovered area in the height direction.

5. The secondary battery according to claim 1, wherein the first insulating film is arranged around the outer periphery of the wound structure near the first end for at least one turn.

6. The secondary battery according to claim 1, wherein the first insulating film comprises a first base material, one side of the first base material facing the wound structure comprising an area not covered by a first adhesive layer and an area covered by the first adhesive layer; the second insulating film comprises a second base material, one side of the second base material facing the wound structure comprising an area not covered by a second adhesive layer and an area covered by the second adhesive layer; the thickness of the first adhesive layer is greater than the thickness of the second adhesive layer; and / or the first base material and the second base material are made of the same material; and / or the first adhesive layer and the second adhesive layer are made of the same material; and / or the first base material is made of PET or PI, and the second base material is made of PET or PI; and / or the first adhesive layer contains polyacrylate, and the second adhesive layer contains polyacrylate.

7. The secondary battery according to claim 1, wherein 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 collector plate 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 the 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, the post being provided with a liquid injection through hole in the height direction; a first insulating seal located between the end wall and the first current collector plate; and / or, an opening is provided at the end of the accommodation cavity of the case away from the end wall, the case further includes a crimping portion formed at the 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 the 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, the connecting piece of the second current collector plate being located at the 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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