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 positioned in the accommodating cavity and comprises a winding structure formed by laminating and winding a positive plate, a diaphragm and a negative plate; the first 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 of the winding structure in the height direction of the winding structure; if the thickness of the first insulating film is w and the diameter of the electrode assembly is D, w / D is 0.00086-0.00185. By setting the ratio of the thickness of the first insulating film to the diameter of the electrode assembly to be 0.00086-0.00185, the safety of the battery can be improved, and meanwhile, the normal exertion of the capacity of the battery core can be ensured.

Description

Technical Field

[0001] This utility model relates to the field of secondary batteries, and in particular to a secondary battery, a battery pack, and an electronic device. Background Technology

[0002] In recent years, with the rapid development of electric vehicles, consumer electronics, and new energy storage systems, battery technology has become an important factor in the development of electric vehicles.

[0003] In the development of battery technology, how to improve battery safety while ensuring the maximum utilization of cell capacity is a technical problem that urgently needs to be solved. Utility Model Content

[0004] The technical problem to be solved by this utility model is to overcome the above-mentioned technical problems of the prior art and provide a secondary battery, a battery pack and an electronic device.

[0005] The present invention solves the above-mentioned technical problems through the following technical solution:

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

[0007] The housing includes an end wall and a side wall surrounding the end wall, the end wall and the side wall forming a receiving cavity;

[0008] An electrode assembly is located within the receiving cavity. The electrode assembly includes a positive electrode sheet, a separator, and a negative electrode sheet stacked and wound together to form a wound structure. The wound structure includes a first end with a positive electrode tab and a second end with a negative electrode tab along the height direction.

[0009] A first insulating film is disposed around the outer periphery of the winding structure and is located between the first end and the second end along the height direction of the winding structure.

[0010] Let the thickness of the first insulating film be w, and the diameter of the electrode assembly be D, then w / D is 0.00086-0.00185.

[0011] In this technical solution, by setting the ratio of the thickness of the first insulating film to the diameter of the electrode assembly to 0.00086-0.00185, the safety of the battery can be improved while ensuring the normal operation of the cell capacity. Specifically, by setting the ratio of the thickness of the first insulating film to the diameter of the electrode assembly within a certain range, on the one hand, it avoids the first insulating film being too thin, which would form wrinkles that can store electrolyte. Electrolyte in these wrinkles would then seep into the casing and corrode it, thus improving battery safety. On the other hand, it avoids the first insulating film being too thick, which would affect the overall size of the electrode assembly, thereby affecting the normal operation of the cell capacity and the energy density of the battery.

[0012] Preferably, the thickness of the first insulating film is 40 μm-70 μm; and / or,

[0013] The first insulating film includes a first substrate, the side of the first substrate facing the winding structure including a region not covered by the first adhesive layer and a region covered by the first adhesive layer; the ratio of the thickness of the first substrate to the thickness of the first adhesive layer is 1.5-12, and / or the thickness of the first substrate is 30μm-60μm.

[0014] Preferably, the secondary battery further includes a second insulating film, a portion of which surrounds the outer periphery of the first end of the winding structure;

[0015] The peel strength of the second insulating film is greater than that of the first insulating film.

[0016] Preferably, the thickness ratio of the first insulating film to the second insulating film is 0.8-1.1; and / or,

[0017] Along the radial direction of the winding structure, the second insulating film does not overlap with the first insulating film; the second insulating film is continuously arranged along the circumferential direction of the winding structure and does not overlap, forming an uncovered area of ​​the winding structure that is not covered by the second insulating film on the outer periphery of the winding structure, and the orthogonal projection of the overlapping portion of the first insulating film along the circumferential direction of the winding structure at least partially falls on the uncovered area of ​​the winding structure along the height direction.

[0018] And / or,

[0019] The second insulating film includes a first portion and a second portion connected together. The first portion surrounds the outer periphery of the first end of the winding structure and extends along the height direction. The second portion is bent toward the central hole of the winding structure and covers the side of the positive electrode tab connection portion of the first current collector connected to the positive electrode tab that is away from the electrode assembly.

[0020] Preferably, the first insulating film includes a first substrate, the side of the first substrate facing the winding structure including a region not covered by the first adhesive layer and a region covered by the first adhesive layer; the second insulating film includes a second substrate, the side of the second substrate facing the winding structure including a region not covered by the second adhesive layer and a region covered by the second adhesive layer;

[0021] The thickness of the second adhesive layer is greater than or equal to the thickness of the first adhesive layer; and / or,

[0022] The first substrate and the second substrate are made of the same material; and / or,

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

[0024] The first substrate is made of PET or PI, and the second substrate is made of PET or PI; and / or,

[0025] The first adhesive layer contains polyacrylate, the second adhesive layer contains polyacrylate; and / or,

[0026] The thickness of the second substrate is 30μm-60μm; the thickness of the second adhesive layer is 5μm-20μm.

[0027] Preferably, the thickness difference between the second adhesive layer and the first adhesive layer is less than 10 μm.

[0028] Preferably, the thickness difference between the second adhesive layer and the first adhesive layer is less than 5 μm.

[0029] Preferably, the secondary battery further includes:

[0030] The first current collector is located between the positive electrode tab and the end wall of the housing along the height direction;

[0031] The electrode post passes through the end wall and is electrically connected to the positive electrode tab through the first collector plate; the electrode post has a liquid injection through hole along the height direction;

[0032] A first insulating seal is located between the end wall and the first collector plate;

[0033] And / or,

[0034] The housing has an opening at the end of its receiving cavity away from the end wall; the housing also includes a pressing part formed at the end of the side wall near the opening and recessed into the housing.

[0035] The secondary battery also includes:

[0036] Cover plate, installed in the opening;

[0037] A second insulating seal is disposed around the periphery of the cover plate to insulate and seal the cover plate and the housing;

[0038] The second collector is disposed between the electrode assembly and the cover plate and is electrically connected to the housing. The connecting piece of the second collector is located on the side of the crimping part facing the electrode assembly and is welded to the crimping part.

[0039] And / or,

[0040] The secondary battery is a cylindrical battery.

[0041] A battery pack characterized in that it includes a secondary battery as described above.

[0042] An electronic device characterized in that it includes a battery pack as described above.

[0043] The positive and progressive effects of this utility model are as follows:

[0044] This invention improves battery safety while ensuring the normal operation of the cell capacity by setting the ratio of the thickness of the first insulating film to the diameter of the electrode assembly to be 0.00086-0.00185. Specifically, by setting the ratio of the thickness of the first insulating film to the diameter of the electrode assembly within a certain range, on the one hand, it avoids the first insulating film being too thin, which would form wrinkles that can store electrolyte. Electrolyte in these wrinkles would seep into the casing and corrode it, thus improving battery safety. On the other hand, it avoids the first insulating film being too thick, which would affect the overall size of the electrode assembly, thereby affecting the normal operation of the cell capacity and the energy density of the battery. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the structure of a secondary battery according to an embodiment of the present invention.

[0046] Figure 2 This is a cross-sectional structural diagram of a secondary battery according to an embodiment of the present invention.

[0047] Figure 3 for Figure 2 A magnified schematic diagram of part A in the middle.

[0048] Figure 4 for Figure 2 A magnified schematic diagram of part B in the middle section.

[0049] Figure 5 This is a partial cross-sectional view of a secondary battery according to an embodiment of the present invention.

[0050] Figure 6 for Figure 5 A magnified schematic diagram of part C in the middle.

[0051] Figure 7 This is a partial cross-sectional view of a secondary battery according to a preferred embodiment of the present invention.

[0052] Figure 8 This is a three-dimensional structural diagram of the electrode assembly of a secondary battery according to a preferred embodiment of the present invention.

[0053] Figure 9 This is a cross-sectional view of the electrode assembly of a secondary battery according to a preferred embodiment of the present invention.

[0054] Figure 10 This is a partial cross-sectional view of the first insulating film of a secondary battery according to a preferred embodiment of the present invention when unfolded.

[0055] Figure 11 This is a partial cross-sectional view of the second insulating film of a secondary battery according to a preferred embodiment of the present invention when unfolded.

[0056] Figure 12 This is a schematic diagram of the battery pack structure according to a preferred embodiment of the present invention.

[0057] Figure 13 This is a schematic diagram of the structure of an electronic device according to a preferred embodiment of the present invention.

[0058] Explanation of reference numerals in the attached figures

[0059] Electronic devices 1000

[0060] Battery pack 100

[0061] Work Department 300

[0062] Box 310

[0063] Box lid 320

[0064] Secondary battery 1

[0065] Casing 10

[0066] end wall 11

[0067] Side wall 12

[0068] Receiving cavity 13

[0069] Opening 14

[0070] crimping part 15

[0071] Electrode assembly 20

[0072] 201 winding structure

[0073] Positive electrode 21

[0074] Positive electrode 211

[0075] Positive electrode starting end 217

[0076] Positive electrode end 218

[0077] Diaphragm 22

[0078] Diaphragm initiation end 221

[0079] Diaphragm end 222

[0080] Negative electrode 23

[0081] negative electrode starting end 237

[0082] negative electrode end 238

[0083] First collection disk 31

[0084] pole post connection part 311

[0085] Positive electrode tab connection part 312

[0086] Second collection disk 32

[0087] First insulating film 40

[0088] First substrate 41

[0089] First adhesive layer 42

[0090] First insulating seal 50

[0091] Second insulating film 60

[0092] Second substrate 61

[0093] Second adhesive layer 62

[0094] Part 1, 63

[0095] Part 2, 64

[0096] 70 pole

[0097] Injection port 71

[0098] Cover plate 80

[0099] Second insulating seal 90

[0100] Height direction H of the winding structure

[0101] Radial R of the wound structure

[0102] Circumferential P of the wound structure

[0103] Preset direction Q

[0104] The thickness w of the first insulating film

[0105] The thickness w1 of the first substrate

[0106] The thickness of the first adhesive layer is w2

[0107] The thickness a of the second insulating film

[0108] The thickness a1 of the second substrate

[0109] The thickness of the second adhesive layer is a2 Detailed Implementation

[0110] The present invention will be described more clearly and completely below with reference to the accompanying drawings, using a preferred embodiment.

[0111] like Figures 1 to 7 As 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.

[0112] 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.

[0113] 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.

[0114] The first insulating film 40 is disposed around the outer periphery of the winding structure 201 and is located between the first end and the second end along the height direction H of the winding structure 201. The first insulating film 40 is a structure that fixes the tail end of the diaphragm 22.

[0115] Let the thickness of the first insulating film 40 be w, and the diameter of the electrode assembly 20 be D, then w / D is 0.00086-0.00185.

[0116] In this way, by setting the ratio of the thickness w of the first insulating film 40 to the diameter D of the electrode assembly 20 to 0.00086-0.00185, the safety of the battery can be improved while ensuring the normal operation of the cell capacity. Specifically, by setting the ratio of the thickness w of the first insulating film 40 to the diameter D of the electrode assembly within a certain range, on the one hand, it avoids the first insulating film 40 being too thin, which would form wrinkles that can store electrolyte. The electrolyte in the wrinkles would then seep into the casing 10 and cause corrosion to the casing 10, thereby improving the safety of the battery. On the other hand, it avoids the first insulating film 40 being too thick, which would affect the overall size of the electrode assembly 20, thereby affecting the normal operation of the cell capacity and the energy density of the battery.

[0117] Preferably, the thickness w of the first insulating film 40 is 40μm-70μm. By setting a specific range for the thickness w of the first insulating film 40, on the one hand, it avoids the first insulating film 40 being too thin, which would form wrinkles that can store electrolyte. Electrolyte in the wrinkles would then seep into the casing 10 and corrode the casing 10, thereby improving battery safety. On the other hand, it avoids the first insulating film 40 being too thick, which would affect the overall size of the electrode assembly 20, thereby affecting the normal performance of the cell capacity and the energy density of the battery.

[0118] Specifically, the first insulating film 40 includes a first substrate 41, the side of the first substrate 41 facing the winding structure 201 including 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 (polyethylene terephthalate) or PI (polyimide). The first adhesive layer 42 contains polyacrylate.

[0119] The ratio of the thickness w1 of the first substrate 41 to the thickness w2 of the first adhesive layer 42 is 1.5-12. By setting the range of the ratio of the thickness w1 of the first substrate 41 to the thickness w2 of the first adhesive layer 42, the proportions of the thickness w1 of the first substrate 41 and the thickness w2 of the first adhesive layer 42 in the second insulating film 60 are balanced, so that the first insulating film 40 can both fix the end of the diaphragm 22 and have corresponding support strength.

[0120] Preferably, the thickness w1 of the first substrate is 30μm-60μm. By setting the range of the thickness w1 of the first substrate 41, on the one hand, it avoids the thickness w1 of the first substrate 41 being too small, thus lacking the required support strength; on the other hand, it avoids the thickness w1 of the first substrate 41 being too large, thus affecting the diameter of the electrode assembly 20 and consequently affecting the energy density.

[0121] The secondary battery 1 also includes a second insulating film 60, a portion of which surrounds the outer periphery of the first end of the winding structure 201. The second insulating film 60 simultaneously fixes the winding structure 201 and the positive electrode tab 211.

[0122] Preferably, the peel strength of the second insulating film 60 is greater than that of the first insulating film 40. Since the winding structure 201 expands and contracts during charging and discharging, if the adhesive force of the first insulating film 40, which serves as the end structure for fixing the separator 22, is too high, it will restrict the expansion of the winding structure 201, hindering the cell's capacity utilization. On the other hand, if the adhesive force of the first insulating film 40 is too low, it will be unable to fix the winding structure 201, causing it to loosen. As for the second insulating film 60, as described above, it needs greater adhesive force to simultaneously fix the winding structure 201 and the positive electrode tab 211, ensuring that they do not loosen and facilitating the insertion of the first end of the winding structure 201 into the casing. Furthermore, if the adhesive force of the second insulating film 60 is too low and it falls off, it will cause insulation failure, posing a risk of the positive electrode tab 211 contacting the casing 10 and causing a short circuit. Therefore, in this embodiment, by setting the peel strength of the second insulating film 60 to be greater than that of the first insulating film 40, the normal performance of the cell capacity can be guaranteed.

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

[0124] The peel strength test adopts Method 1 of GB / T 2792-2014: Test method for 180° peel strength of adhesive tape to stainless steel, unit N / cm. If the insulating film has been made into a battery, the test can be performed according to the appropriate length of the insulating film in the battery, based on the corresponding GB / T 2792-2014 standard, and is not limited to the actual length of the insulating film defined in GB.

[0125] Preferably, the peel strength of the second insulating film 60 is 2 to 7 times that of the first insulating film 40, for example, it can be 2, 3.5, 4.5, 5.8, or 7 times, that is, the peel strength of the second insulating film 60 is greater than that of the first insulating film 40. By setting the peel strength of the second insulating film 60 to be greater than that of the first insulating film 40, excessively high peel strength of the second insulating film 60 is avoided, which would lead to wasted manufacturing costs.

[0126] Specifically, the peel strength of the second insulating film 60 is 2 N / cm-7 N / cm; the peel strength of the first insulating film 40 is 1 N / cm-4 N / cm. By setting the peel strength range of the second insulating film 60, on the one hand, it avoids the peel strength of the second insulating film 60 being too small, i.e., the adhesive force of the second insulating film 60 being too weak, thus failing to simultaneously fix the winding structure 201 and the positive electrode tab 211; on the other hand, it avoids the peel strength of the second insulating film 60 being too large, i.e., the adhesive force of the second insulating film 60 being too strong, resulting in wasted manufacturing costs. By setting the peel strength range of the first insulating film 40, on the one hand, it avoids the peel strength of the first insulating film 40 being too small, i.e., the adhesive force of the first insulating film 40 being too weak, thus failing to fix the winding structure 201; on the other hand, it avoids the peel strength of the first insulating film 40 being too large, restricting the expansion of the winding structure 201, which is not conducive to the utilization of the cell capacity, and also results in wasted manufacturing costs.

[0127] Preferably, the peel strength of the second insulating film 60 is greater than or equal to 2.4 N / cm; and the peel strength of the first insulating film 40 is greater than or equal to 1.8 N / cm.

[0128] Preferably, the second insulating film 60 is disposed around the outer periphery of the winding structure 201 near the first end for at least one turn. Because the positive electrode tab 211 is a full-tab design, by providing the second insulating film 60 around the outer periphery of the winding structure 201 near the first end for at least one turn, the insulation between the positive electrode tab 211 and the housing 10 can be effectively guaranteed.

[0129] Along the radial direction R of the winding structure 201, the second insulating film 60 does not overlap with the first insulating film 40. That is, along the height direction H of the winding structure 201, a portion of the winding structure 201 covers the first insulating film 40, and the first insulating film 40 and the second insulating film 60 are staggered to avoid the electrode assembly 20 from overlapping along the radial direction R, which would affect the diameter of the electrode assembly 20 and thus improve the energy density. In addition, the first insulating film 40 also serves to fix the outer ring diaphragm 22 and prevent the diaphragm 22 from loosening.

[0130] Please refer to the following: Figure 9 The positive electrode 21 includes a positive electrode start end 217 and a positive electrode end 218; the negative electrode 23 includes a negative electrode start end 237 and a negative electrode end 238. The separator 22 includes a separator start end 221 and a separator end 222. The first insulating film 40 includes, but is not limited to, a finishing tape for fixing the separator end 222. That is, the first insulating film 40 can be a finishing tape or other insulating structures, such as a Mylar film. Regardless of the structure of the first insulating film 40, its radial direction R along the winding structure 201 and its orthographic projection onto the second insulating film 60 do not overlap.

[0131] The first insulating film 40 is continuously disposed along the circumferential direction P of the winding structure 201 without overlapping, forming an uncovered area of ​​the winding structure 201 that is not covered by the first insulating film 40 on the outer periphery. The orthographic projection of the overlapping portion of the second insulating film 60 along the circumferential direction P of the winding structure 201 in the height direction H at least partially falls on the uncovered area of ​​the winding structure. By ensuring that the orthographic projection of the overlapping portion of the second insulating film 60 along the circumferential direction P of the winding structure 201 in the height direction H at least partially falls on the uncovered area of ​​the winding structure, the overlapping portion of the second insulating film 60 along the circumferential direction P of the winding structure 201 and the first insulating film 40 are not overlapped in the radial direction R, which would affect the diameter of the cell and thus improve the energy density. Furthermore, the second insulating film 60 can provide support for the uncovered area of ​​the winding structure, preventing a large difference in stress between the uncovered area and the covered area covered by the first insulating film 40 during battery use, which could lead to lithium plating after battery expansion.

[0132] Specifically, the second insulating film 60 includes a second substrate 61, the side of the second substrate 61 facing the winding structure 201 including a region not covered by the second adhesive layer 62 and a region covered by the second adhesive layer 62. The material of the second substrate 61 is PET or PI. The adhesive layer of the second insulating film 60 contains polyacrylate.

[0133] Preferably, the ratio of the thickness w of the first insulating film 40 to the thickness a of the second insulating film 60 is 0.8-1.1, for example, it can be 0.8, 0.85, 0.95, 1.0, or 1.1. By setting the range of the ratio of the thicknesses of the first insulating film 40 and the second insulating film 60, the diameters of the electrode assembly 20 can be made more consistent, improving the energy density of the battery and making the assembly more precise.

[0134] The second substrate 61 is made of the same material as the first substrate 41; the second adhesive layer 62 is made of the same material as the first adhesive layer 42, so as to facilitate the integration of the first insulating film 40 and the second insulating film 60 into a single structure, thereby improving production efficiency and reducing the diameter of the battery cell, thus ensuring the energy density of the battery. However, this is not a limitation. In other embodiments, the materials of the second substrate 61 and the first substrate 41 may be different, and similarly, the materials of the second adhesive layer 62 and the first adhesive layer 42 may also be different.

[0135] Preferably, the thickness a2 of the second adhesive layer 62 is greater than the thickness w2 of the first adhesive layer 42, so that the peel strength of the second insulating film 60 is greater than that of the first insulating film 40. In the battery, the second adhesive layer 62 will directly contact the positive electrode tab 211 or the current collector, and will face the metal. The first adhesive layer 42 is on the outer periphery of the separator 22, so the second adhesive layer 62 needs to be thicker to contact the unevenness of the metal surface, and it needs to prevent short circuit caused by contact between the metal and the casing 10. Therefore, the second adhesive layer 62 is thicker.

[0136] Specific testing method: The total thickness of the insulating film is measured using a micrometer. Specifically, select the insulating film to be tested and measure its total thickness at three arbitrarily equidistant locations. The average of these three measurements is then taken as the total thickness of the insulating film. Next, immerse the insulating film in a toluene solution for a certain period (generally 5 minutes or longer). Afterward, remove it and wipe it with a lint-free cloth to obtain the substrate. Then, measure the thickness of the substrate at three arbitrarily equidistant locations and take the average of these three measurements as the substrate thickness. Subtracting the substrate thickness from the total thickness of the insulating film gives the thickness of the adhesive layer.

[0137] Furthermore, the ratio of the thickness a2 of the second adhesive layer 62 to the thickness w2 of the first adhesive layer 42 is 0.8-1.1, for example, it can be 0.8, 0.85, 0.95, 1.0, or 1.1. By setting the range of values ​​for the ratio of the thickness a2 of the second adhesive layer 62 to the thickness w2 of the first adhesive layer 42, the diameters of the electrode assembly 20 can be made more consistent, improving the energy density of the battery and making the assembly more precise.

[0138] Specifically, the thickness a1 of the second substrate 61 is 30μm-60μm. By setting the range of the thickness a1 of the second substrate 61, on the one hand, it avoids the thickness a1 of the second substrate 61 being too small, thus lacking the required support strength; on the other hand, it avoids the thickness a1 of the second substrate 61 being too large, thus affecting the diameter of the electrode assembly 20 and consequently affecting the energy density.

[0139] The thickness a2 of the second adhesive layer 62 is 5μm-20μm. By setting the range of the thickness a1 of the second substrate 61, on the one hand, it avoids the second adhesive layer 62 being too thin and having too weak an adhesive force, thus failing to simultaneously fix the winding structure 201 and the positive electrode tab 211; on the other hand, it avoids the second substrate 61 being too thick and having too strong an adhesive force, which would restrict the expansion of the winding structure 201 and be detrimental to the cell capacity. At the same time, if the thickness a1 of the second substrate 61 is too large, it will affect the diameter of the electrode assembly 20, thereby affecting the energy density.

[0140] Preferably, the thickness difference between the second adhesive layer 62 and the first adhesive layer 42 is less than 10 μm, so that the diameters of the electrode assembly 20 are more consistent, improving the energy density of the battery and making the assembly more precise. More preferably, the thickness difference between the second adhesive layer and the first adhesive layer is less than 5 μm.

[0141] The secondary battery 1 also includes a first current collector 31, which is located along the height direction H between the positive electrode tab 211 and the end wall 11 of the housing 10. The first current collector 31 includes a terminal post 70 connecting part 311 and a positive electrode tab connecting part 312 connected to each other. The positive electrode tab connecting part 312 is electrically connected to the positive electrode tab 211, and the terminal post 70 connecting part 311 is electrically connected to the terminal post 70.

[0142] Preferably, the second insulating film 60 includes a first portion 63 and a second portion 64 connected to each other. The first portion 63 surrounds the outer periphery of the first end of the winding structure 201 and extends along the height direction H. The second portion 64 is bent toward the central hole of the winding structure 201 and covers the side of the positive electrode tab connection portion 312 of the first current collector 31 connected to the positive electrode tab 211 that is away from the electrode assembly 20.

[0143] In this embodiment, the secondary battery 1 is a cylindrical battery. Cylindrical batteries have advantages such as high energy density, long cycle life, and good safety performance. Furthermore, when the secondary battery 1 is a cylindrical battery, because cylindrical batteries have a full tab design, the second insulating film 60 surrounds at least one turn around the outer periphery of the wound structure 201 near the first end, which can insulate the positive electrode tab 211 from the casing 10. However, this is not a limitation; in other embodiments, the secondary battery 1 can also be a prismatic battery or other battery shapes.

[0144] Applying the setting of the thickness w of the first insulating film 40 to the diameter D of the electrode assembly 20 in this embodiment, which is 0.00086-0.00185, to cylindrical batteries can ensure the normal performance of the cell capacity.

[0145] The secondary battery 1 also includes an electrode post 70, which passes through the end wall 11 and is electrically connected to the positive electrode tab 211 via a first current collector 31. The electrode post 70 has a liquid injection hole 71 along its height direction H. The liquid injection hole 71 corresponds to the first end of the electrode assembly 20, and electrolyte flows into the housing 10 through the liquid injection hole 71. By providing a specific structure for the second insulating film 60 at the first end, the electrolyte injected through the liquid injection hole 71 can be effectively prevented from entering between the second insulating film 60 and the housing 10, thereby improving the electrolyte wetting efficiency during positive electrode liquid injection.

[0146] The housing 10 has an opening 14 at the end of the receiving cavity 13 away from the end wall 11. The housing 10 also includes a crimping portion 15, which is formed on the side wall 12 near the opening 14 and recessed into the housing 10. The secondary battery 1 also includes 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 surrounds the periphery of the cover plate 80 to insulate and seal the cover plate 80 and the housing 10. The second current collector 32 is disposed between the electrode assembly 20 and the cover plate 80 and is electrically connected to the housing 10. The connecting piece of the second current collector 32 is located on the side of the crimping portion 15 facing the electrode assembly 20 and is welded to the crimping portion 15. In this way, by setting the connecting piece of the second current collector 32 to be located on the side of the crimping part 15 facing the electrode assembly 20 and welded to the crimping part 15, that is, the welding area of ​​the second current collector 32 with the negative electrode tab is located closer to the electrode assembly 20 than the crimping part 15, the influence of the crimping part 15 on the welding area between the tab and the second current collector 32 can be prevented, thereby improving the welding strength between the negative electrode tab and the second current collector 32.

[0147] In this embodiment, the welding sequence of the first current collector 31 and the second current collector 32 of the secondary battery 1 to the electrode assembly 20 is as follows: First, place the first current collector 31; then, press the electrode assembly 20 together on both the positive and negative sides (the pressing process can increase the contact between the current collector and the electrode assembly 20 and avoid poor welding); weld the first current collector 31 using line welding instead of spot welding. This is because the negative electrode tab is relatively soft, and after two pressings, the distance between the second current collector 32 and the electrode assembly 20 will be closer. Spot welding would cause the diaphragm 22 to be burned due to concentrated heat. Wire welding uses less heat and can avoid burning the diaphragm 22, thus avoiding short circuit between the positive and negative electrodes; next, place the second current collector 32; press the electrode assembly 20 together on both the positive and negative sides again; finally, weld the second current collector 32.

[0148] like Figure 12 As shown, this utility model also provides a battery pack 100, which includes the aforementioned secondary battery 1. In one embodiment of the battery pack 100, the battery pack 100 includes a housing 310, a cover 320, and multiple secondary batteries 1. The multiple secondary batteries 1 are placed in the housing 310 and connected in series or parallel, or a combination of series and parallel connections. The cover 320 seals the housing 310 to protect the multiple secondary batteries 1. It should be noted that, in addition to the secondary battery 1 of this utility model, the battery pack 100 may also include a battery pack thermal management system, circuit board, etc. The battery pack 100 can be a battery module, a battery pack, an energy storage cabinet, etc.; these will not be described in detail here.

[0149] like Figure 13As shown, this utility model also provides an electronic device 1000, which includes the aforementioned battery pack 100. A working part 300 is electrically connected to the battery pack 100 to obtain electrical power. As an example, the electronic device 1000 is a vehicle, which can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, but are not limited thereto. The working part 300 is the vehicle body, and the battery pack 100 is located at the bottom of the vehicle body, providing electrical power for the vehicle's operation or the operation of its internal electrical components. However, in other embodiments, the electronic device 1000 can also be a mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, and power tool, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; the working part 300 can be a unit component capable of obtaining electrical power from the battery pack 100 and performing corresponding work, such as a fan blade rotation unit or a vacuum cleaner suction unit. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the aforementioned electronic device 1000.

[0150] While specific embodiments of this utility model have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this 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 this utility model, but all such changes and modifications fall within the scope of protection of this utility model.

Claims

1. A secondary battery, characterized in that, It includes: The housing includes an end wall and a side wall surrounding the end wall, the end wall and the side wall forming a receiving cavity; An electrode assembly is located within the receiving cavity. The electrode assembly includes a positive electrode sheet, a separator, and a negative electrode sheet stacked and wound together to form a wound structure. The wound structure includes a first end with a positive electrode tab and a second end with a negative electrode tab along the height direction. A first insulating film is disposed around the outer periphery of the winding structure and is located between the first end and the second end along the height direction of the winding structure. Let the thickness of the first insulating film be w, and the diameter of the electrode assembly be D, then w / D is 0.00086-0.00185.

2. The secondary battery as described in claim 1, characterized in that, The thickness of the first insulating film is 40 μm-70 μm; and / or, The first insulating film includes a first substrate, the side of the first substrate facing the winding structure including a region not covered by the first adhesive layer and a region covered by the first adhesive layer; the ratio of the thickness of the first substrate to the thickness of the first adhesive layer is 1.5-12, and / or the thickness of the first substrate is 30μm-60μm.

3. The secondary battery as described in claim 1, characterized in that, The secondary battery also includes a second insulating film, a portion of which surrounds the outer periphery of the first end of the winding structure. The peel strength of the second insulating film is greater than that of the first insulating film.

4. The secondary battery as described in claim 3, characterized in that, The thickness ratio of the first insulating film to the second insulating film is 0.8-1.1; and / or, Along the radial direction of the winding structure, the second insulating film does not overlap with the first insulating film; The second insulating film is continuously disposed along the circumferential direction of the winding structure and does not overlap, forming an uncovered area of ​​the winding structure that is not covered by the second insulating film on the outer periphery of the winding structure. The orthogonal projection of the overlapping portion of the first insulating film along the circumferential direction of the winding structure at least partially falls on the uncovered area of ​​the winding structure. And / or, The second insulating film includes a first portion and a second portion connected together. The first portion surrounds the outer periphery of the first end of the winding structure and extends along the height direction. The second portion is bent toward the central hole of the winding structure and covers the side of the positive electrode tab connection portion of the first current collector connected to the positive electrode tab that is away from the electrode assembly.

5. The secondary battery as described in claim 3, characterized in that, The first insulating film includes a first substrate, the side of the first substrate facing the winding structure including a region not covered by the first adhesive layer and a region covered by the first adhesive layer; the second insulating film includes a second substrate, the side of the second substrate facing the winding structure including a region not covered by the second adhesive layer and a region covered by the second adhesive layer; The thickness of the second adhesive layer is greater than or equal to the thickness of the first adhesive layer; and / or, The first substrate and the second substrate 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 substrate is made of PET or PI, and the second substrate is made of PET or PI; and / or, The first adhesive layer contains polyacrylate, the second adhesive layer contains polyacrylate; and / or, The thickness of the second substrate is 30μm-60μm; the thickness of the second adhesive layer is 5μm-20μm.

6. The secondary battery as described in claim 5, characterized in that, The thickness difference between the second adhesive layer and the first adhesive layer is less than 10 μm.

7. The secondary battery as described in claim 6, characterized in that, The thickness difference between the second adhesive layer and the first adhesive layer is less than 5 μm.

8. The secondary battery according to any one of claims 1-7, characterized in that, The secondary battery also includes: The first current collector is located between the positive electrode tab and the end wall of the housing along the height direction; The electrode post passes through the end wall and is electrically connected to the positive electrode tab through the first collector plate; the electrode post has a liquid injection through hole along the height direction; A first insulating seal is located between the end wall and the first collector plate; And / or, The housing has an opening at the end of its receiving cavity away from the end wall; the housing also includes a pressing part formed at the end of the side wall near the opening and recessed into the housing. The secondary battery also includes: Cover plate, installed in the opening; A second insulating seal is disposed around the periphery of the cover plate to insulate and seal the cover plate and the housing; The second collector is disposed between the electrode assembly and the cover plate and is electrically connected to the housing. The connecting piece of the second collector is located on the side of the crimping part facing the electrode assembly and is welded to the crimping part. And / or, The secondary battery is a cylindrical battery.

9. A battery pack, characterized in that, Includes the secondary battery as described in any one of claims 1-8.

10. An electronic device, characterized in that, Includes the battery pack as described in claim 9.

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