Cylindrical battery and preparation method therefor, and electronic device

Abstract

A cylindrical battery and a preparation method therefor, and an electronic device. In a winding direction, a first adhesive layer comprises a first portion and a third portion connected to each other, the third portion being bonded to a first surface, and the first portion extending out of a first starting end. In the winding direction, a second adhesive layer comprises a second portion and a fourth portion connected to each other, the fourth portion being bonded to a second surface, the second portion extending out of the first starting end, and the second portion being bonded to the first portion. The diameter of the outermost ring of an electrode assembly is R1, the diameter of the innermost ring of the electrode assembly is R2, the diameter of a casing is R3, and the diameter of the secondary inner ring of the electrode assembly is R4. In the winding direction, the length of the first portion is L1, the length of the third portion is L3, the length of the second portion is L2, and the length of the fourth portion is L4. The following relationship is satisfied: L1≥π(R3-R1+R4-R2)+1 / (4×L3), and / or L2≥π(R3-R1+R4-R2)+1 / (4×L4). A first electrode sheet can be prevented from being exposed from the first adhesive layer and the second adhesive layer in the winding direction due to slippage, thereby preventing burrs at the first starting end from piercing a separator, thus reducing the occurrence of a short circuit.

Description

Cylindrical battery, preparation method thereof and electronic device TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a cylindrical battery, a preparation method thereof and an electronic device. BACKGROUND

[0002] With the rapid development of modern science and technology, the demand for high-performance energy storage devices in the field of portable electronic devices, electric vehicles and the like is increasing. As an efficient and environmentally friendly energy storage device, lithium ion batteries have been widely used in many fields due to their high energy density, long cycle life, low self-discharge rate and other advantages. In the continuous development process of lithium ion batteries, the safety performance of the battery is increasingly required.

[0003] SUMMARY

[0004] The present application aims to provide a cylindrical battery, a preparation method thereof and an electronic device, and aims to improve the safety performance of the battery.

[0005] The technical scheme adopted by the embodiments of the present application is as follows:

[0006] In a first aspect, a cylindrical battery includes a shell and an electrode assembly disposed in the shell. The electrode assembly includes a first electrode tab, a separator film, and a second electrode tab stacked and wound. In the winding direction, the first electrode tab includes a first starting end, and the first starting end is located at a next innermost electrode tab of the electrode assembly. The cylindrical battery further includes a first adhesive layer and a second adhesive layer. The first electrode tab includes a first surface facing away from a winding center and a second surface facing the winding center. In the winding direction, the first adhesive layer includes a first portion and a third portion connected to each other, the third portion is bonded to the first surface, and the first portion extends beyond the first starting end. In the winding direction, the second adhesive layer includes a second portion and a fourth portion connected to each other, the fourth portion is bonded to the second surface, the second portion extends beyond the first starting end, and the second portion is bonded to the first portion. The outermost diameter of the electrode assembly is R1, the innermost diameter of the electrode assembly is R2, the diameter of the shell is R3, the diameter of the next innermost electrode tab is R4, the length of the first portion in the winding direction is L1, the length of the third portion in the winding direction is L3, the length of the second portion in the winding direction is L2, and the length of the fourth portion in the winding direction is L4. The following conditions are met: L1≥π(R3-R1+R4-R2)+1 / (4×L3), and / or L2≥π(R3-R1+R4-R2)+1 / (4×L4).

[0007] In the above technical scheme, the first starting end can be prevented from being exposed along the winding direction from the first adhesive layer and the second adhesive layer due to the expansion of the electrode tab during long-term charge and discharge cycles, thereby reducing the risk of the burr on the first surface of the first starting end piercing the separator film and reducing the risk of short circuit, and thus improving the safety performance of the cylindrical battery.

[0008] In some embodiments, 1.5mm≤L1≤5mm, which can reduce the impact of the first adhesive layer on the energy density of the cylindrical battery while covering the burr, facilitating the winding of the first tab. In some other embodiments, 1.5mm≤L2≤5mm, which can reduce the impact of the second adhesive layer on the energy density of the cylindrical battery while covering the burr, facilitating the winding of the first tab.

[0009] In some embodiments, 1.5mm≤L1≤4mm, which further reduces the impact on the energy density while reducing the short circuit caused by the tab slip. In some other embodiments, 1.5mm≤L2≤4mm, which further reduces the impact on the energy density while reducing the short circuit caused by the tab slip.

[0010] In some embodiments, 0.6mm≤L3≤10mm, which can reduce the exposure of the first starting end from the first adhesive layer. In some other embodiments, 0.6mm≤L4≤10mm, which can reduce the exposure of the first starting end from the second adhesive layer.

[0011] In some embodiments, the second tab includes a second starting end, the second starting end is located at the innermost circle tab of the electrode assembly, and the second starting end is beyond the first starting end in the winding direction.

[0012] In some embodiments, the housing includes a first wall portion and a second wall portion arranged oppositely in the axial direction of the cylindrical battery. The cylindrical battery further includes a first tab ear, one end of the first tab ear is connected to the outermost circle of the first tab, and the other end of the first tab ear is connected to the first wall portion. The first tab ear is arranged at the outermost circle of the first tab, and the inner circle is more prone to slip in the winding direction. Defining L1≥π(R3-R1+R4-R2)+1 / (4×L3) and / or L2≥π(R3-R1+R4-R2)+1 / (4×L4) can reduce the occurrence of short circuit.

[0013] In some embodiments, the housing includes a first wall portion and a second wall portion arranged oppositely in the axial direction of the cylindrical battery. The outermost circle of the first tab is connected to the first wall portion, and the outermost circle of the second tab is connected to the second wall portion. Then the inner circle is more prone to slip in the winding direction. Defining L1≥π(R3-R1+R4-R2)+1 / (4×L3) and / or L2≥π(R3-R1+R4-R2)+1 / (4×L4) can reduce the occurrence of short circuit.

[0014] In some embodiments, the first tab further comprises a first tail end in the winding direction, the first tail end is located at the next outer circle tab of the electrode assembly. The cylindrical battery further comprises a third adhesive layer and a fourth adhesive layer, the third adhesive layer comprises a ninth portion and an eleventh portion connected in the winding direction, the ninth portion is bonded to the first surface, and the eleventh portion extends out of the first tail end. The second adhesive layer comprises a tenth portion and a twelfth portion connected in the winding direction, the tenth portion is bonded to the second surface, and the twelfth portion extends out of the first tail end. The length of the ninth portion is L 11 , the length of the eleventh portion is L 10 , the length of the tenth portion is L 12 , and the length of the twelfth portion is L 11 . It satisfies: L 12 ≥ π(R3-R1+R4-R2)+1 / (4×L 10 ). The first tail end can be reduced to slip out of the third adhesive layer and the fourth adhesive layer in the winding direction due to the expansion of the tab during long-term charge and discharge cycles, the burr of the first tail end can be reduced to pierce the separator, and the short circuit can be reduced.

[0015] In some embodiments, 1.5mm≤L 11 ≤5mm, the third adhesive layer can cover the burr while reducing the impact on the energy density of the cylindrical battery. In other embodiments, 1.5mm≤L 12 ≤5mm, the fourth adhesive layer can cover the burr while reducing the impact on the energy density of the cylindrical battery, which is beneficial to the winding of the first tab.

[0016] In some embodiments, 1.5mm≤L 11 ≤4mm, further reducing the impact on the energy density while reducing the short circuit caused by the tab slip. In other embodiments, 1.5mm≤L 12 ≤4mm, further reducing the impact on the energy density while reducing the short circuit caused by the tab slip.

[0017] In some embodiments, the first tab is a positive electrode tab, and the second tab is a negative electrode tab. The third portion further includes a fifth portion and a seventh portion, which are portions of the third portion that extend beyond the edges of the first tab in the width direction of the first tab. The first tab includes first and second edges that are oppositely disposed in the width direction of the first tab, and the fifth portion extends beyond the first edge and the seventh portion extends beyond the second edge. The second tab includes first and second regions, which extend beyond the first and second edges, respectively, on opposite sides of the first tab in the width direction of the second tab. The separation film includes third and fourth regions, which extend beyond the first and second regions, respectively, on opposite sides of the second tab in the width direction of the second tab. In the width direction of the second tab, the first region has a width W1 and the second region has a width W2; in the width direction of the separation film, the third region has a width W3 and the fourth region has a width W4; and in the width direction of the first tab, the fifth portion has a width W5 and the seventh portion has a width W7. The following conditions are satisfied: W1≤W5≤W1+W3, and / or W2≤W7≤W2+W4.

[0018] The first starting end can be reduced to slide along the axial direction of the cylindrical battery to extend beyond the fifth portion and / or the seventh portion, thereby reducing short circuit occurrence and improving the impact resistance of the cylindrical battery. The fifth portion and / or the seventh portion can also be reduced to occupy excessive space, thereby reducing the impact on the energy density and the impact on the packaging strength of the cylindrical battery.

[0019] In some embodiments, the fourth portion further includes a sixth portion and an eighth portion, which are portions of the fourth portion that extend beyond the edges of the first tab in the width direction of the first tab. In the width direction of the first tab, the sixth portion has a width W6 and the eighth portion has a width W8. The following conditions are satisfied: W1≤W6≤W1+W3, and / or W2≤W8≤W2+W4. The first starting end can be reduced to slide along the axial direction to extend beyond the sixth portion and / or the eighth portion, thereby reducing short circuit occurrence and improving the impact resistance of the cylindrical battery. The sixth portion and / or the eighth portion can also be reduced to occupy excessive space, thereby reducing the impact on the energy density and the impact on the packaging strength of the cylindrical battery.

[0020] In some embodiments, the projection of the partial first adhesive layer is located outside the projection of the second adhesive layer along the thickness direction of the first tab, so that the first adhesive layer bonds the partial separator. In some other embodiments, the projection of the partial second adhesive layer is located outside the projection of the first adhesive layer, so that the second adhesive layer bonds the partial separator. Such a structure can improve the overall bonding strength of the electrode assembly, reduce the tab loosening, and further reduce the first starting end slippage. Moreover, the first tab is bonded to the separator by the first adhesive layer and / or the second adhesive layer, so that the first tab is tightly combined with the separator, the bonding force between the first tab and the separator can be enhanced, the first tab and the separator are less likely to separate during the charging and discharging process, and thus the safety problems such as internal short circuit are reduced.

[0021] In a second aspect, the present application provides a preparation method of a cylindrical battery, comprising:

[0022] The current collector is provided, and the current collector is cut to obtain a first segment and a second segment. The first segment includes a first cutting position, and the second segment includes a second cutting position. The current collector includes a first surface and a second surface arranged oppositely along the thickness direction of the current collector. The first segment is separated from the second segment by a predetermined distance. A first integral adhesive layer is provided, one end of the first integral adhesive layer is bonded to the first surface of the first segment, and the other end of the first integral adhesive layer is bonded to the first surface of the second segment. The bonding length of the first integral adhesive layer to the first segment along the length direction of the current collector is L3. A second integral adhesive layer is provided, one end of the second integral adhesive layer is bonded to the second surface of the first segment, and the other end of the second integral adhesive layer is bonded to the second surface of the second segment. The first integral adhesive layer and the second integral adhesive layer are bonded between the first cutting position and the second cutting position. The first cutting position and the second cutting position include a first position, and the length between the first position and the first cutting position along the length direction of the current collector is L1. The first integral adhesive layer and the second integral adhesive layer are cut along the first position. The current collector is cut several times to obtain a first current collector. The first cutting position forms a first starting end of the first current collector, and the second cutting position forms a first ending end of the first current collector along the length direction of the first current collector. A first tab is prepared based on the first current collector. A second tab is provided, and a wound electrode assembly is prepared. The first starting end of the first tab is located in a secondary innermost tab of the electrode assembly, and the first ending end is located in a secondary outermost tab of the electrode assembly. The diameter of the outermost tab of the electrode assembly is R1, the diameter of the innermost tab of the electrode assembly is R2, and the diameter of the secondary innermost tab of the electrode assembly is R4. A shell is provided, and the electrode assembly is arranged in the shell. The diameter of the shell is R3. L1≥π(R3-R1+R4-R2)+1 / (4×L3) is satisfied.

[0023] In some embodiments, the above method further comprises: the bonding length of the first integral adhesive layer to the second segment along the length direction of the current collector is L9, the length between the first position and the second cutting position along the length direction of the current collector is L 11 . L 11≥ π (R3- R1+ R4- R2) + 1 / (4 x L9).

[0024] In some embodiments, the method further comprises: the bonding length of the second integral adhesive layer to the first segment is L4, and the bonding length of the second integral adhesive layer to the second segment is L 10 . The following conditions are met: L1≥ π (R3- R1+ R4- R2) + 1 / (4 x L4) ; and / or, L 11 ≥ π (R3- R1+ R4- R2) + 1 / (4 x L 10 ).

[0025] In a third aspect, the present application further provides an electronic device comprising the cylindrical battery according to any one of the embodiments of the first aspect and the second aspect.

[0026] Additional aspects and advantages of the embodiments of the present application will be described in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following description and accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0027] One or more embodiments are illustrated by way of example in the accompanying drawings, which are not necessarily drawn to scale, and which, if any, are further applicable to the generic functional description set forth herein maintained in cooperation therewith. The drawings in which like reference numerals refer to similar elements include the following figures:

[0028] FIG. 1 is a schematic structural diagram of a cylindrical battery according to some embodiments of the present application;

[0029] FIG. 2 is a schematic exploded diagram of a cylindrical battery according to some embodiments of the present application;

[0030] FIG. 3 is a schematic diagram of a winding structure of an electrode assembly according to some embodiments of the present application;

[0031] FIG. 4 is a schematic structural diagram of a first electrode sheet according to some embodiments of the present application;

[0032] FIG. 5 is a D-D cross-sectional view of FIG. 1 according to some embodiments of the present application;

[0033] FIG. 6 is a schematic structural diagram of a first electrode sheet after being pasted with an adhesive according to some embodiments of the present application;

[0034] FIG. 7 is a schematic structural diagram of a first electrode sheet after being pasted with an adhesive according to some embodiments of the present application;

[0035] FIG. 8 is a partial A-A cross-sectional view of FIG. 6 according to some embodiments of the present application;

[0036] FIG. 9 is a B-B cross-sectional view of FIG. 1 according to some embodiments of the present application;

[0037] FIG. 10 is a partial A-A cross-sectional view of FIG. 6 according to some embodiments of the present application;

[0038] FIG. 11 is a partial enlarged view of A in FIG. 5 according to some embodiments of the present application;

[0039] FIG. 12 is a schematic view of the bonding structure of the first adhesive layer and the second adhesive layer according to some embodiments of the present application;

[0040] FIG. 13 is a schematic view of the bonding structure of the first adhesive layer and the second adhesive layer according to some embodiments of the present application;

[0041] FIG. 14 is a schematic view of the cutting of the current collector according to some embodiments of the present application;

[0042] FIG. 15 is a schematic view of the cutting of the current collector according to some embodiments of the present application;

[0043] FIG. 16 is a schematic view of the bonding of the first integral adhesive layer and the second integral adhesive layer to the cutting position according to some embodiments of the present application;

[0044] FIG. 17 is a schematic view of the cutting of the first integral adhesive layer and the second integral adhesive layer according to some embodiments of the present application.

[0045] BRIEF DESCRIPTION OF DRAWINGS 100, cylindrical battery; 10, housing; 11, first wall portion; 111, first electrode terminal; 12, second wall portion; 13, main body portion; 14, opening; 20, electrode assembly; 21, first tab; 21a, first surface; 21b, second surface; 21c, first edge; 21d, second edge; 211, first current collector; 212, first active material layer; 2111, first initial empty foil segment; 2112, first final empty foil segment; 2113, first initial end; 2114, first final end; 214, first tab; 22, second tab; 22a, second initial end; 221, first region; 222, second region; 23, separator; 233, third region; 234, fourth region; 30, first adhesive layer; 31, first portion; 33, third portion; 35, fifth portion; 37, seventh portion; 40, second adhesive layer; 42, second portion; 44, fourth portion; 46, sixth portion; 48, eighth portion; 50, third adhesive layer; 59, ninth portion; 511, eleventh portion; 60, fourth adhesive layer; 610, tenth portion; 612, twelfth portion; 200, current collector; 201, first segment; 203, first cutting position; 202, second segment; 204, second cutting position; 300, cutter; 400, first integral adhesive layer; 500, second integral adhesive layer; X, first direction; Y, second direction; Z, third direction; K, axial direction; S, winding direction. DETAILED DESCRIPTION

[0046] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings for the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application.

[0047] In the embodiments of the present application, the phrase "embodiments" means that the specific features, structures or properties described in combination with the embodiments can be included in at least one embodiment of the present application. The phrase appears at various places in the specification does not necessarily all refer to the same embodiments, nor are they necessarily mutually exclusive or alternative embodiments to other embodiments.

[0048] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise explicitly and specifically limited.

[0049] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents a "or" relationship between the front and rear associated objects.

[0050] The technical features involved in the different embodiments of the present application described below can be combined with each other as long as there is no conflict between them.

[0051] In a first aspect, the present application provides a cylindrical battery 100, please refer to FIG. 1 and FIG. 2, the cylindrical battery 100 includes a shell 10 and an electrode assembly 20 and an electrolyte (not marked in the figure) received in the shell 10. The electrolyte infiltrates the electrode assembly 20 in the shell 10, so that an electrochemical reaction occurs.

[0052] For the above-mentioned shell 10, please refer to FIG. 1 and FIG. 2, the shell 10 can adopt a columnar shape, the shell 10 includes a first wall part 11, a second wall part 12 and a main body part 13. Along the axial direction K of the cylindrical battery 100, the first wall part 11 and the second wall part 12 can be connected to the two ends of the main body part 13 respectively. The second wall part 12 can be integrally provided with the main body part 13 or separately provided, and the end of the main body part 13 opposite to the second wall part 12 is provided with an opening 14. The electrode assembly 20 can be placed in the shell 10 through the opening 14, and the shell 10 can be sealed by covering the opening 14 with the first wall part 11.

[0053] The shell 10 can be made of an electrically conductive metal material such as aluminum, aluminum alloy, steel, stainless steel, nickel, copper, or magnesium alloy, which allows the shell 10 to lead out a certain polarity of the cylindrical battery 100, for example, the shell 10 itself as the positive or negative electrode of the cylindrical battery 100. In other embodiments, the shell 10 can also be made of a soft package material, for example, an aluminum-plastic film or a copper-plastic film.

[0054] For the above-mentioned electrode assembly 20, please refer to FIGS. 2 and 3. The outermost circle diameter of the electrode assembly 20 is smaller than the inner circle diameter of the shell 10, which facilitates the placement of the electrode assembly 20 in the shell 10. The electrode assembly 20 includes a first electrode sheet 21, a second electrode sheet 22, and a separator 23. The first electrode sheet 21, the separator 23, and the second electrode sheet 22 are stacked and wound, and the separator 23 is arranged between the first electrode sheet 21 and the second electrode sheet 22 to insulate and separate them. The innermost circle of the electrode assembly 20 can be provided with a gap space, which facilitates the entry of the electrolyte into the innermost circle of the electrode assembly 20, and then the first electrode sheet 21 and the second electrode sheet 22 are infiltrated from the inside of the electrode assembly 20. In other embodiments, the gap space can also be provided with a column.

[0055] The first electrode sheet 21 and the second electrode sheet 22 have opposite polarities, for example, the first electrode sheet 21 is a positive electrode sheet, and the second electrode sheet 22 is a negative electrode sheet. Or the first electrode sheet 21 is a negative electrode sheet, and the second electrode sheet 22 is a positive electrode sheet. In some embodiments, the first electrode sheet 21 can be electrically connected to the first wall portion 11, which allows the first wall portion 11 to lead out one polarity of the cylindrical battery 100, and the second electrode sheet 22 can be electrically connected to the second wall portion 12, which allows the second wall portion 12 to lead out another polarity of the cylindrical battery 100. By insulating the first wall portion 11 from the second wall portion 12, the occurrence of short circuit can be reduced.

[0056] For example, please further refer to FIGS. 4 and 5. The first electrode sheet 21 includes a first current collector 211 and a first active material layer 212, and the first active material layer 212 can be arranged on at least one surface of the first current collector 211 in the thickness direction (third direction Z) of the first current collector 211. One side of the first electrode sheet 21 in the width direction can be provided with a blank foil area (not labeled in the figure) or a plurality of first tabs 214. By flattening the blank foil area or the plurality of first tabs 214 to form a flattened surface, and electrically connecting the flattened surface to the first wall portion 11, one polarity can be led out. The second electrode sheet 22 can also be similarly arranged, and the other polarity can be led out through the second wall portion 12.

[0057] It should be noted that the electrode sheet is wound along its length direction (first direction X), and after winding, the length direction of the electrode sheet is the winding direction S, and the width direction (second direction Y) is the axial direction K of the cylindrical battery 100.

[0058] In some other embodiments, referring to FIG. 5, the first tab 21 has a single first lug 214, which is electrically connected to the first wall 11 to make the first wall 11 lead out one polarity. The second tab 22 can also have a single second lug (not shown in the figure), which is electrically connected to the second wall 12 to make the second wall 12 lead out another polarity. The first wall 11 and the second wall 12 can each have a pole, which can be used to lead out the positive and negative poles.

[0059] During winding, if the starting section of the winding is provided with the active material layer, the active material layer in this part can be pressed against the separator 23, which can easily cause the separator 23 to be damaged and affect the roundness of the innermost circle of the electrode assembly 20, resulting in poor structural stability of the electrode assembly 20.

[0060] To reduce the above problems, in the embodiments of the present application, referring to FIGS. 3 and 4, along the winding direction S, the first current collector 211 includes a first starting empty foil section 2111, which can reduce the damage to the separator 23 and improve the structural stability of the electrode assembly 20.

[0061] Along the winding direction S, the first tab 21 includes a first starting end 2113 and a first ending end 2114. The first starting end 2113 is one end of the first starting empty foil section 2111 away from the first ending end 2114. In the embodiments of the present application, the first starting end 2113 is located at the second innermost circle tab of the electrode assembly 20, wherein the innermost circle tab of the electrode assembly 20 is part of the second tab 22.

[0062] During cutting, the first current collector 211 can form cutting burrs at the first starting section 2113 and the first ending end 2114. The burrs can easily pierce the separator, especially in the case of high stress on the inner circle, the risk of the burrs piercing the separator is higher.

[0063] In the embodiments of the present application, referring to FIGS. 6 to 8, the cylindrical battery 100 further includes a first adhesive layer 30 and a second adhesive layer 40. After winding, the first tab 21 includes a first surface 21a facing away from the winding center and a second surface 21b facing the winding center. The first adhesive layer 30 is arranged on the first surface 21a of the first starting empty foil section 2111.

[0064] For example, along the winding direction S, the first adhesive layer 30 includes a first portion 31 and a third portion 33 connected to each other. The third portion 33 is bonded to the first surface 21a, and the first portion 31 extends out of the first starting end 2113, so that the first adhesive layer 30 covers part of the cutting burrs on the first surface 21a, reduces the risk of the cutting burrs piercing the separator 23, and further reduces the risk of short circuit.

[0065] The second adhesive layer 40 can also be arranged similarly to the first adhesive layer 30, for example, along the winding direction S, the second adhesive layer 40 includes a second portion 42 and a fourth portion 44 connected with each other, the fourth portion 44 is bonded to the second surface 21b, and the second portion 42 extends out of the first starting end 2113, so that the second adhesive layer 40 can cover part of the cutting burr on the second surface 21b, reduce the cutting burr piercing the separator 23, and further reduce the short circuit.

[0066] The first adhesive layer 30 includes a substrate layer (not shown in the figure) and a bonding layer (not shown in the figure), and the bonding layer is arranged on the surface of the substrate layer and bonded to the first electrode sheet 21. The substrate layer can be made of polyimide (PI) or polyester (PET) material, and the bonding layer can be made of polypropylene (PP), polyethylene (PE), polyvinylidene fluoride (PVDF) or acrylic material, so that the bonding force between the first adhesive layer 30 and the first electrode sheet 21 can reach 0.15 N / mm or more, and after being soaked by the electrolyte, the bonding force can reach 0.1 N / mm or more. The second adhesive layer 40 and the following third adhesive layer 50 and fourth adhesive layer 60 can also be arranged similarly.

[0067] The inventors of the present application have found that during the charge and discharge cycle of the cylindrical battery 100, the first electrode sheet 21 and the second electrode sheet 22 will swell, which may cause the first electrode sheet 21 and the second electrode sheet 22 to slide towards the inner ring and the outer ring along the winding direction S, and even cause the electrode assembly 20 to occupy the gap space between the shell 10 and the inner ring space of the electrode assembly 20. For example, the first starting end 2113 slides towards the inner ring and occupies the inner ring space, and the first ending end 2114 slides towards the outer ring and occupies the gap space between the shell 10. However, the first adhesive layer 30 and the second adhesive layer 40 have small sliding amounts due to the extrusion of the layers of electrode sheets and the friction between the layers of electrode sheets, and the sliding directions of the adjacent two layers of electrode sheets may be opposite, which may cause the first adhesive layer 30 and the second adhesive layer 40 to slide in the opposite direction of the first starting end 2113. During the sliding process, the first starting end 2113 may directly exceed the first adhesive layer 30 and the second adhesive layer 40, so that the first starting end 2113 is exposed, which is easy to cause the cutting burr of the first starting end 2113 to pierce the separator 23, and there is a risk of short circuit.

[0068] Furthermore, the inventors of the present application have found that, as the portion 33 bonded to the first tab 21, the slippage of the first adhesive layer 30 along the winding direction S is related to the length of the third portion 33. After long-term charge-discharge cycles of the cylindrical battery 100 and occupation of the gap space of the partial innermost circle of the electrode assembly 20 and occupation of the gap space between the electrode assembly 20 and the shell 10, in the extreme case, the slippage direction of the first adhesive layer 30 is opposite to the first starting end 2113, and the slippage amount of the first adhesive layer approximately satisfies 1 / (4*L3), L3 being the length of the third portion 33 along the winding direction S, that is, the bonding length of the first adhesive layer 30 and the first tab 21.

[0069] In the embodiments of the present application, the length of the first portion 31 along the winding direction S satisfies L1≥π(R3-R1+R4-R2)+1 / (4*L3), which can reduce the first starting end 2113 slipping along the winding direction S due to the expansion of the tab during the long-term charge-discharge cycles of the cylindrical battery 100, thereby reducing the burr of the first surface 21a of the first starting end 2113 piercing the separator 23 and reducing the occurrence of short circuits. Referring to FIG. 9, the diameter of the outermost circle of the electrode assembly 20 is R1, the diameter of the innermost circle of the electrode assembly 20 is R2, the diameter of the shell 10 (the inner circle of the shell 10) is R3, and the diameter of the tab of the innermost circle of the electrode assembly 20 is R4.

[0070] For the measurement of R1, R2, R3, and R4, the measurement can be performed by using a Keyence microscope. For example, after disassembling the battery sample, the sample is fixed on the sample stage of the microscope, the power of the Keyence microscope is turned on, and the microscope software is started. The coarse focus and fine focus knobs of the microscope are used to focus the sample clearly. During focusing, the real-time image in the microscope software can be observed to ensure that the edge and details of the sample are clearly visible. In the Keyence microscope software, the circular measurement tool is selected for diameter measurement. The center of the circular measurement tool is aligned with the center of the cylindrical battery, and then the size of the measurement tool is adjusted so that it just surrounds the edge of the cylindrical battery. During adjustment, the image can be zoomed in and the position of the measurement tool can be finely adjusted to ensure the accuracy of the measurement. The measurement result is read. The software automatically displays the diameter value of the circular measurement tool. The diameter of the tab of the innermost circle of the electrode assembly 20 can also be measured by using a computer tomography instrument (CT) to scan the electrode assembly 20.

[0071] It should be noted that the above diameter R1 can be the diameter of the outermost circle of the electrode assembly 20 itself or the diameter of the fitting circle where the outermost circle of the electrode assembly 20 is located, and R2, R3, and the following R4 and R5 are similar.

[0072] In some embodiments, the second tab 22 comprises a second starting end 22a, the second starting end 22a is located at the innermost ring of the electrode assembly 20, and the second starting end 22a exceeds the first starting end 2113 in the winding direction S.

[0073] In some embodiments, the first portion 31 and the second portion 42 are bonded to each other after extending the first starting end 2113, which can improve the overall connection strength of the first adhesive layer 30, the second adhesive layer 40, and the first tab 21, and reduce the risk of the first starting end 2113 of the first tab 21 being exposed from the first adhesive layer 30 and the second adhesive layer 40.

[0074] The inventors of the present application have found that if the length of the first portion 31 is too small, it may be difficult to effectively isolate the burr of the first surface 21a of the first starting end 2113, and if the length of the first portion 31 is too large, it occupies a large space, which not only affects the winding of the first tab 21, but also causes the loss of energy density of the cylindrical battery 100. In the embodiments of the present application, 1.5mm≤L1≤5mm is limited, which can cover the burr while reducing the impact of the first adhesive layer 30 on the energy density of the cylindrical battery 100, and is conducive to the winding of the first tab 21. Preferably, 1.5mm≤L1≤4mm, which further reduces the short circuit while reducing the impact on the energy density.

[0075] Based on the same inventive concept described above, the second adhesive layer 40 can also be similarly arranged, and the slip amount of the second adhesive layer 40 approximately satisfies 1 / (4×L4), L4 being the length of the fourth portion 44, i.e., the bonding length of the second adhesive layer 40 and the first tab 21. In the embodiments of the present application, the length of the second portion 42 is L2 in the winding direction S, and L2≥π(R3-R1+R4-R2)+1 / (4×L4), which can reduce the first starting end 2113 slipping along the winding direction S due to the expansion of the tab during the long-term charge-discharge cycle of the cylindrical battery 100, and further reduce the burr of the second surface 21b of the first starting end 2113 piercing the separator 23, thereby reducing the short circuit.

[0076] Similar to the first adhesive layer 30 described above, in the embodiments of the present application, 1.5mm≤L2≤5mm is limited, which can cover the burr while reducing the impact of the first adhesive layer 30 on the energy density of the cylindrical battery 100, and is conducive to the winding of the first tab 21. Preferably, 1.5mm≤L2≤4mm, which further reduces the short circuit while reducing the impact on the energy density.

[0077] In some embodiments, the slippage amount of the first adhesive layer 30 can be greater than the slippage amount of the first tab 21, causing the first tab 21 to separate from the first adhesive layer 30 away from the side of the first portion 31 to the third portion 33. To reduce this problem, in the present application, L3≥1 / (4×L3) is defined to reduce the first adhesive layer 30 beyond the first starting end 2113, thereby reducing the occurrence of short circuit. Based on the same inventive concept, L4≥1 / (4×L4) is defined to reduce the second adhesive layer 40 beyond the first starting end 2113, thereby reducing the occurrence of short circuit.

[0078] For the length of the third portion 33, in some embodiments, 0.6mm≤L3≤10mm can reduce the exposure of the first starting end 2113 from the first adhesive layer and reduce the impact on the energy density. For the length of the fourth portion 44, 0.6mm≤L4≤10mm can reduce the exposure of the first starting end 2113 from the second adhesive layer and reduce the impact on the energy density.

[0079] In some embodiments, along the axial direction K of the cylindrical battery 100, the shell 10 includes oppositely arranged first and second wall portions 11 and 12. The cylindrical battery 100 includes a first tab 214, one end of which is connected to the outermost circle of the first tab 21, and the other end of which is connected to the first wall portion 11. The first tab 214 is arranged at the outermost circle of the first tab 21, and the inner circle is more prone to slippage in the winding direction S. Defining L1≥π(R3-R1+R4-R2)+1 / (4×L3) and L2≥π(R3-R1+R4-R2)+1 / (4×L4) can reduce the occurrence of short circuit.

[0080] In some embodiments, along the axial direction K of the cylindrical battery 100, the shell 10 includes oppositely arranged first and second wall portions 11 and 12. The outermost circle of the first tab 21 is connected to the first wall portion 11, and the outermost circle of the second tab 22 is connected to the second wall portion 12. Then the inner circle is more prone to slippage in the winding direction S. Defining L1≥π(R3-R1+R4-R2)+1 / (4×L3) and L2≥π(R3-R1+R4-R2)+1 / (4×L4) can reduce the occurrence of short circuit.

[0081] For the burr of the above-mentioned first ending end 2114, the present inventors have found that when the first ending end 2114 is located at the next outer circle tab of the electrode assembly 20, the first ending end 2114 can also slip because there are heteropolarity tabs on both sides of the next inner circle tab in the thickness direction of the next inner circle tab, and the restraining force of the next outer circle tab is small, thereby increasing the risk of the burr of the first starting end 2113 piercing the separator 23, and further causing the first tab 21 to contact the second tab 22 and short circuit.

[0082] To reduce the risk of the first end 2114 piercing the separator 23, please refer to FIG. 3 and FIG. 4, along the winding direction S, the first tab 21 further comprises a first tail empty foil segment 2112, the first end 2114 is one end of the first tail empty foil segment 2112 away from the first starting end 2113, and the first end 2114 is located at the secondary outer ring tab of the electrode assembly 20. In the embodiments of the present application, please refer to FIG. 6, FIG. 7 and FIG. 10, the cylindrical battery 100 further comprises a third adhesive layer 50 and a fourth adhesive layer 60.

[0083] The third adhesive layer 50 can be arranged on the first surface 21a of the first tail empty foil segment 2112, for example, along the winding direction S, the third adhesive layer 50 comprises a ninth portion 59 and an eleventh portion 511 connected to each other, the ninth portion 59 is bonded to the first surface 21a, and the eleventh portion 511 extends out of the first end 2114. This can make the third adhesive layer 50 cover part of the cutting burr on the first surface 21a, reduce the cutting burr piercing the separator 23, and further reduce the occurrence of short circuit.

[0084] The fourth adhesive layer 60 can also be arranged similarly to the third adhesive layer 50, for example, along the winding direction S, the second adhesive layer 40 comprises a tenth portion 610 and a twelfth portion 612 connected to each other, the tenth portion 610 is bonded to the second surface 21b, and the twelfth portion 612 extends out of the first end 2114. This can make the fourth adhesive layer 60 cover part of the cutting burr on the second surface 21b, reduce the cutting burr piercing the separator 23, and further reduce the occurrence of short circuit.

[0085] The eleventh portion 511 and the twelfth portion 612 are bonded to each other after extending out of the first end 2114, which can improve the overall connection strength of the third adhesive layer 50, the fourth adhesive layer 60 and the first tab 21, reduce the exposure of the first end 2114 from the third adhesive layer 50 and the fourth adhesive layer 60, and further reduce the piercing of the cutting burr on the first end 2113 to the separator 23.

[0086] Similar to the first starting end 2113 described above, along the winding direction S, the length of the ninth portion 59 is L9, and the length of the eleventh portion 511 is L 11 , which satisfies L 11 ≥ π(R3-R1+R4-R2) + 1 / (4×L9). This can reduce the occurrence of the first end 2114 sliding along the winding direction S and exceeding the third adhesive layer 50 due to the expansion of the tab during the long-term charge and discharge cycle of the cylindrical battery 100, and further reduce the piercing of the cutting burr on the first surface 21a of the first end 2114 to the separator 23 and the occurrence of short circuit.

[0087] Based on the same inventive concept described above, the fourth adhesive layer 60 can also be arranged similarly. In the embodiments of the present application, along the winding direction S, the length of the tenth portion 610 is L 10 , and the length of the twelfth portion 612 is L12 , satisfy L 12 ≥ π(R3-R1+R4-R2)+1 / (4×L 10 ), the first end 2114 of the cylindrical battery 100 can be prevented from sliding out of the fourth adhesive layer 60 in the winding direction S due to the expansion of the electrode tab during long-term charge and discharge cycles, thereby reducing the risk of short circuit caused by the burr on the second surface 21b of the first end 2114 piercing the separator 23.

[0088] In some embodiments of the present application, 1.5mm≤L 11 ≤5mm, which can cover the burr while reducing the impact of the third adhesive layer 50 on the energy density of the cylindrical battery 100. In other embodiments, 1.5mm≤L 12 ≤5mm, which can cover the burr while reducing the impact of the fourth adhesive layer 60 on the energy density of the cylindrical battery 100.

[0089] Based on the same inventive concept, in some embodiments, 1.5mm≤L 11 ≤4mm, which can further reduce the impact on the energy density while reducing the risk of short circuit caused by the expansion of the electrode tab. In other embodiments, 1.5mm≤L 12 ≤4mm, which can further reduce the impact on the energy density while reducing the risk of short circuit caused by the expansion of the electrode tab.

[0090] In some embodiments, please refer to FIGS. 6 and 7, the third portion 33 further includes a fifth portion 35 and a seventh portion 37, which are two portions of the third portion 33 extending beyond the edge of the first electrode tab 21 in the width direction (second direction Y) of the first electrode tab 21. The first electrode tab 21 includes a first edge 21c and a second edge 21d arranged opposite to each other in the width direction (second direction Y) of the first electrode tab 21, the fifth portion 35 extends beyond the first edge 21c so as to cover part of the burr on the first edge 21c, and the seventh portion 37 extends beyond the second edge 21d so as to cover part of the burr on the second edge 21d.

[0091] In some embodiments, please further refer to FIG. 5 and FIG. 11, taking the first tab 21 as the positive electrode tab and the second tab 22 as the negative electrode tab as an example. The second tab 22 includes a first region 221 and a second region 222. Along the width direction (second direction Y) of the second tab 22, the first region 221 is beyond the first edge 21c on one side of the first tab 21, and the second region 222 is beyond the second edge 21d on the other side of the first tab 21. For example, along the width direction (second direction Y) of the second tab 22, the width of the first region 221 is W1, and the width of the second region 222 is W2. In the embodiments of the present application, it is limited that 0.1mm≤W1≤0.6mm and 0.1mm≤W2≤0.6mm, which can make the second tab 22 have enough excess to embed the first tab 21 and escape from lithium ions, so as to reduce the occurrence of lithium precipitation.

[0092] The isolation film 23 includes a third region 233 and a fourth region 234. Along the width direction (second direction Y) of the second tab 22, the third region 233 is beyond the first region 221 on one side of the second tab 22, and the fourth region 234 is beyond the second region 222 on the other side of the second tab 22. For example, along the width direction (second direction Y) of the isolation film 23, the width of the third region 233 is W3, and the width of the fourth region 234 is W4. In the embodiments of the present application, it is limited that 0.4mm≤W3≤1.2mm and / or 0.4mm≤W4≤1.2mm, which can make the isolation film 23 insulate the first tab 21 from the second tab 22 and reduce the occurrence of short circuit.

[0093] In some embodiments, along the width direction (second direction Y) of the first tab 21, the width of the fifth part 35 is W5, and the width of the seventh part 37 is W7. In the embodiments of the present application, it is satisfied that W1≤W5≤W1+W3, which can reduce the first starting end 2113 from sliding along the axial direction K to beyond the fifth part 35, thereby reducing the occurrence of short circuit, improving the anti-collision performance of the cylindrical battery 100, and reducing the impact on the energy density and the packaging strength. Based on the same inventive concept, W2≤W7≤W2+W4, which can reduce the first starting end 2113 from sliding along the axial direction K to beyond the seventh part 37, thereby reducing the occurrence of short circuit, improving the anti-collision performance of the cylindrical battery 100, and reducing the impact on the energy density and the packaging strength.

[0094] The second adhesive layer 40 can also be arranged similarly to the first adhesive layer 30. The fourth portion 44 further includes a sixth portion 46 and an eighth portion 48. Along the width direction (second direction Y) of the first tab 21, the sixth portion 46 and the eighth portion 48 are portions of the fourth portion 44 that extend beyond the edge of the first tab 21. The width of the sixth portion 46 along the width direction (second direction Y) of the first tab 21 is W6, and the second width of the eighth portion 48 is W8. In embodiments of the present application, W1≤W6≤W1+W3, which can reduce the first starting end 2113 from sliding along the axial direction K to extend beyond the sixth portion 46, thereby reducing the occurrence of short circuits. Based on the same inventive concept, W2≤W8≤W2+W4, which can reduce the first starting end 2113 from sliding along the axial direction K to extend beyond the eighth portion 48, thereby reducing the occurrence of short circuits.

[0095] In some embodiments, referring to FIGS. 12 and 13, the projection of the portion of the first adhesive layer 30 along the thickness direction (third direction Z) of the first tab 21 is located outside the projection of the second adhesive layer 40. In other embodiments, the projection of the second adhesive layer 40 is located outside the projection of the first adhesive layer 30, which can enable the second adhesive layer 40 to bond the portion of the separator 23. For example, the fifth portion 35 and the sixth portion 46 have a non-overlapping region, and this portion can extend beyond the sixth portion 46 along the width direction (second direction Y) of the first tab 21 or the winding direction S, which can enable the fifth portion 35 to bond the portion of the separator 23. Similarly, the sixth portion 46 can also bond the portion of the separator 23. This can improve the overall bonding strength of the electrode assembly 20, reduce the loosening of the tabs, and thereby reduce the sliding of the first starting end 2113. Furthermore, the close bonding of the first tab 21 and the separator 23 can enhance the bonding force between the first tab 21 and the separator 23, reduce the separation of the first tab 21 and the separator 23 during charging and discharging, and thereby reduce safety issues such as internal short circuits.

[0096] In other embodiments, the seventh portion 37 and the eighth portion 48 can also be arranged to be non-overlapping, and the separator 23 can be bonded by the seventh portion 37 and the eighth portion 48. Alternatively, the first portion 31 and the second portion 42 can be arranged to be non-overlapping, and the separator 23 can be bonded by the first portion 31 and the second portion 42.

[0097] In a second aspect, the present application also provides a method for manufacturing a cylindrical battery 100, including the following steps:

[0098] The current application provides a current collector 200 (current collector roll), the current collector 200 is cut to obtain a first section 201 and a second section 202. For example, referring to FIG. 14 and FIG. 15, the current collector 200 can be cut by a cutter 300 into the first section 201 and the second section 202, a first cutting position 203 is located at the first section 201, and a second cutting position 204 is located at the second section 202. The current collector 200 includes a first surface 21a and a second surface 21b oppositely arranged along a thickness direction (third direction Z) of the current collector 200.

[0099] The first section 201 and the second section 202 are pulled apart by a predetermined distance, so that a gap space is formed between the first cutting position 203 and the second cutting position 204.

[0100] A first whole adhesive layer 400 is provided, referring to FIG. 16 and FIG. 17, one end of the first whole adhesive layer 400 is bonded to the first surface 21a of the first section 201, and the other end of the first whole adhesive layer 400 is bonded to the first surface 21a of the second section 202. The bonding length of the first whole adhesive layer 400 to the first section 201 along a length direction (first direction X) of the current collector 200 is L3.

[0101] A second whole adhesive layer 500 is provided, one end of the second whole adhesive layer 500 is bonded to the second surface 21b of the first section 201, the other end of the second whole adhesive layer 500 is bonded to the second surface 21b of the second section 202, and the first whole adhesive layer 400 and the second whole adhesive layer 500 are bonded between the first cutting position 203 and the second cutting position 204.

[0102] The first cutting position 203 and the second cutting position 204 include a first position C, and the length between the first position C and the first cutting position 203 along the length direction (first direction X) of the current collector 200 is L1.

[0103] The first whole adhesive layer 400 and the second whole adhesive layer 500 are cut along the first position C, so that the first whole adhesive layer 400 is divided into a first adhesive layer 30 bonded to the first surface 21a of the first section 201 and a third adhesive layer 50 bonded to the first surface 21a of the second section 202, and the second whole adhesive layer 500 is divided into a second adhesive layer 40 bonded to the second surface 21b of the first section 201 and a fourth adhesive layer 60 bonded to the second surface 21b of the second section 202.

[0104] The current collector 200 is cut several times to obtain a first current collector, the first cutting position 203 forms a first starting end 2113 of the first current collector, and the second cutting position 204 forms a first ending end 2114 of the first current collector along the length direction (first direction X) of the first current collector.

[0105] The first tab 21 is prepared based on the first current collector, the second tab 22 is provided, and the winding-shaped electrode assembly 20 is prepared. The first starting end 2113 of the first tab 21 is located at the next inner circle tab of the electrode assembly 20, the first ending end 2114 is located at the next outer circle tab of the electrode assembly 20, the outermost circle diameter of the electrode assembly 20 is R1, and the innermost circle diameter of the electrode assembly 20 is R2.

[0106] The shell 10 is provided, and the electrode assembly 20 is arranged in the shell 10. The diameter of the shell 10 is R3, and the diameter of the next inner circle tab of the electrode assembly 20 is R4. L1 is greater than or equal to π(R3-R1+R4-R2)+1 / (4×L3).

[0107] It can be understood that the length between the first position C and the first cutting position 203 is L1, that is, the length of the first part 31 is L1, and the bonding length of the first integral adhesive layer 400 and the first section 201 is L3. That is, the length of the third part 33 is L3. L1 is greater than or equal to π(R3-R1+R4-R2)+1 / (4×L3), which can reduce the first starting end 2113 of the first tab 21 beyond the first adhesive layer 30 in the winding direction S, thereby reducing the burr of the first surface 21a of the first starting end 2113 from piercing the isolation film 23 and reducing short circuit.

[0108] In some embodiments, the above method further includes that the length of the first current collector is L, and the first tab 214 is connected at a position of the first current collector, which is N away from the first ending end 2114. The bonding length of the first integral adhesive layer 400 and the second section 202 is L9, and the length between the first position C and the second cutting position 204 is L 11 In the embodiments of the present application, L 11 is greater than or equal to π(R3-R1+R4-R2)+1 / (4×L9).

[0109] The bonding length of the first integral adhesive layer 400 and the second section 202 is L9, that is, the length of the ninth part 59 is L9, and the length between the first position C and the second section 202 is L 11 , that is, the length of the eleventh part 511 is L 11 In the embodiments of the present application, L 11 is greater than or equal to π(R3-R1+R4-R2)+1 / (4×L9), which can reduce the first ending end 2114 beyond the third adhesive layer 50 in the winding direction S, thereby reducing the burr of the first surface 21a of the first ending end 2114 from piercing the isolation film 23 and reducing short circuit.

[0110] In some embodiments, the method further comprises: along the length direction (the first direction X) of the current collector 200, the bonding length of the second integral adhesive layer 500 and the first section 201 is L4, the bonding length of the second integral adhesive layer 500 and the second section 202 is L 10 . L1≥π(R3-R1+R4-R2)+1 / (4×L4) is satisfied; and / or, L 11 ≥π(R3-R1+R4-R2)+1 / (4×L 10 ).

[0111] In the embodiments of the present application, the bonding length of the second integral adhesive layer 500 and the first section 201 is L4, that is, the length of the fourth portion 44 is L4, and according to the above cutting method, the length L2 of the second portion 42 can be obtained as L1≥π(R3-R1+R4-R2)+1 / (4×L4). The first starting end 2113 of the first pole piece 21 can be reduced to protrude beyond the second adhesive layer 40 in the winding direction S, thereby reducing the burr of the first surface 21b of the first starting end 2113 to pierce the isolation film 23 and reducing the short circuit.

[0112] In the embodiments of the present application, the bonding length of the second integral adhesive layer 500 and the second section 202 is L 10 , that is, the length of the tenth portion 610 is L 10 , and according to the above cutting method, the length L 12 ≥π(R3-R1+R4-R2)+1 / (4×L 10 ) of the twelfth portion 612 can be obtained. The first ending end 2114 of the first pole piece 21 can be reduced to protrude beyond the fourth adhesive layer 60 in the winding direction S, thereby reducing the burr of the first surface 21b of the first ending end 2114 to pierce the isolation film 23 and reducing the short circuit.

[0113] In a third aspect, the present application further provides an electronic device comprising the cylindrical battery 100 according to any one of the embodiments of the second aspect. The electronic device of the embodiments of the present application is not particularly limited and can be any electronic device known in the prior art. For example, the electronic device includes but is not limited to a Bluetooth headset, a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric vehicle, an electric car, a ship, a spacecraft, etc. The electric toy can include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric plane toy, etc. The spacecraft can include an airplane, a rocket, a space shuttle, a spacecraft, etc.

[0114] Experiment 1: Charge-discharge cycle test of lithium ion battery

[0115] Embodiment A1:

[0116] <Preparation of positive pole piece>

[0117] The positive electrode active material lithium cobaltate, the positive electrode conductive agent acetylene black, and the positive electrode binder polyvinylidene fluoride (PVDF, weight average molecular weight 5 x 10 5 ) were mixed in a mass ratio of 94:3:3, N-methyl pyrrolidone (NMP) was added as a solvent, a positive electrode slurry with a solid content of 75 wt% was prepared, and the positive electrode slurry was stirred uniformly in a vacuum stirrer. An aluminum foil current collector roll with a thickness of 12 um was cut, and a first integral adhesive layer and a second integral adhesive layer were attached to both cutting positions. The two integral adhesive layers were cut, and a first adhesive layer and a second adhesive layer were formed on both sides of the cutting position in the thickness direction, respectively, and a third adhesive layer and a fourth adhesive layer were formed on both sides of the other cutting position in the thickness direction, respectively. The positive electrode current collector roll was cut into a positive electrode current collector with a length of 380 mm, and the above-mentioned adhesive cutting operation was repeated. The adhesive length of the first adhesive layer to the positive electrode current collector (third part) L3 = 2.5 mm, and the first part L1 = 1 mm of the positive electrode current collector extends out. The adhesive length of the second adhesive layer to the positive electrode current collector (L4) L4 = 2.5 mm, and the second part L2 = 1 mm of the positive electrode current collector extends out. The positive electrode slurry was uniformly coated on one surface of the positive electrode current collector aluminum foil, and the aluminum foil was left with an empty foil area without positive electrode slurry at both ends, and the aluminum foil was dried at 110°C to obtain a positive electrode tab with a single-sided positive electrode active material layer. Then, the above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode tab with a double-sided positive electrode active material layer. The coating weight of the positive electrode tab was 25 mg / cm 2 .

[0118] <Preparation of a negative electrode tab>

[0119] The negative electrode active material graphite powder, silicon powder, conductive agent conductive carbon black (Super P), and binder styrene-butadiene rubber (SBR) were mixed in a weight ratio of 87.5:10:1:1.5, and then deionized water was added as a solvent to prepare a negative electrode slurry with a solid content of 50 wt% and stir uniformly. A copper foil with a thickness of 5 um and a length of 410 mm was selected as a negative electrode current collector, the negative electrode slurry was uniformly coated on one surface of the negative electrode current collector copper foil, and the copper foil was left with an empty foil area without negative electrode slurry at both ends, and the copper foil was dried at 90°C to obtain a single-sided negative electrode tab. After the above steps were completed, the single-sided coating of the negative electrode tab was completed. Then, the above steps were repeated on the other surface of the negative electrode tab to obtain a double-sided negative electrode tab with a negative electrode active material layer. The coating weight of the negative electrode tab was 6.5 mg / cm 2 .

[0120] <Preparation of a separator>

[0121] A polyethylene (PE) with a thickness of 7 um and a 2 um aluminum oxide (Al2O3) coated porous film were used as a separator.

[0122] <Preparation of electrolyte>

[0123] In a dry argon atmosphere, ethylene carbonate, methyl ethyl carbonate and diethyl carbonate were mixed in a mass ratio of 30:50:20 to obtain an organic solution, then lithium salt lithium hexafluorophosphate was dissolved and uniformly mixed in the organic solvent to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0124] <Preparation of lithium ion battery>

[0125] An aluminum sheet with a width of 3 mm was used as the positive tab, and the positive tab was welded to the empty foil area of the tail section of the positive electrode sheet. A nickel sheet with a width of 3 mm was used as the negative tab, and the negative tab was welded to the empty foil area of the tail section of the negative electrode sheet. The above-prepared separator, positive electrode sheet, separator, negative electrode sheet were stacked in order, and wound to obtain an electrode assembly, wherein the outermost circle diameter of the electrode assembly was R1 = 10.35 mm, the innermost circle diameter of the electrode assembly was R2 = 2.3 mm, the inner circle diameter of the shell was R3 = 10.5 mm, and the electrode assembly next to the inner circle was R4 = 2.5 mm. The electrode assembly was subjected to hot pressing (pressure 5 MPa, temperature 65℃, pressure holding time 10s). The electrode assembly was placed in a cylindrical shell, and the positive tab was welded to the top wall of the shell, and the negative tab was welded to the bottom wall of the shell. After removing the water at 80℃, the electrolyte was injected, and after packaging, injection, formation, capacity test, voltage resistance test and other processes, a secondary battery was prepared.

[0126] Charge-discharge cycle test: the above-prepared lithium ion battery was placed in a test temperature of 25℃ environment for 30min, and the secondary battery was placed in a test temperature of 25℃ environment for 30min. The following charging steps were performed to charge to 4.45V:

[0127] (1) 2.5C constant current charging to 4.15V, constant voltage charging to 1.5C;

[0128] (2) 1.5C constant current charging to 4.18V, constant voltage charging to 0.5C;

[0129] (3) 0.5C constant current charging to 4.45V, constant voltage charging to 0.02C;

[0130] After standing for 10min, the following steps were performed for discharging:

[0131] 1C constant current discharging to 3V, which was one cycle.

[0132] After 1000 cycles of charge-discharge, the lithium ion battery was disassembled, and whether the first starting end of the electrode sheet exceeded the adhesive layer was observed. If it exceeded, it was considered invalid. Each group of tests 50 samples, the number of failures is N, and the failure rate is N / 50.

[0133] The relevant parameters in Examples A2 to A26 and Comparative Examples A1 to A3 are shown in Table 1 below, and the remaining parameters are consistent with those in Example A1.

[0134] Table 1

[0135] According to Table 1 above, in combination with Examples A1 to A26, it can be seen that when L1≥π(R3-R1+R4-R2)+1 / (4×L3) and L2≥π(R3-R1+R4-R2)+1 / (4×L4), the cycle failure rate of the lithium ion battery can be effectively reduced. Therefore, in the embodiments of the present application, L1≥π(R3-R1+R4-R2)+1 / (4×L3) and L2≥π(R3-R1+R4-R2)+1 / (4×L4) are limited, which can reduce the first starting end slip of the pole piece due to the expansion of the pole piece during long-term charge and discharge cycles, and thus reduce the burr of the first surface of the first starting end piercing the separator, and reduce the short circuit.

[0136] In Examples A10 and A11, the drop failure rate is similar, and in Example A10, the lengths of the first and second parts are smaller, and the impact on the energy density of the cylindrical battery is smaller. Therefore, in the present application, 1.5mm≤L1≤5mm and 1.5mm≤L2≤5mm can be selected. In Examples A2 to A8, the drop failure rate is further reduced, and in the embodiments of the present application, 1.5mm≤L1≤4mm and 1.5mm≤L2≤4mm are preferred, which further reduces the short circuit caused by the slip of the pole piece while reducing the impact on the energy density.

[0137] In combination with Examples A13 to A26, in Examples A14 to A26, the cycle failure rate is reduced, and in Example A25, the third part is too long and occupies a large space, which will cause a loss of energy density. In the present application, 0.6mm≤L3≤10mm and 0.6mm≤L4≤10mm can be selected, which can reduce the short circuit while reducing the impact on the energy density of the cylindrical battery.

[0138] Experiment Two: Drop Test of Lithium Ion Battery

[0139] Drop test method: lithium ion battery is placed in 25℃ environment for 30 minutes, and then charged in the following steps: constant current charging to 4.53V at 0.5C, constant voltage charging to 0.05C, standing for 60min, then testing the voltage of lithium ion battery before drop test; the lithium ion battery is loaded into the clamp, and the drop equipment is used to drop freely from a distance of 1.75m from the marble ground, and randomly drop 60 times. After the drop test, it is placed at room temperature for 24h, and the voltage of the lithium ion battery is measured and recorded. The appearance of the lithium ion battery is checked before and after the test and photographed. The pass criteria of drop test: voltage drop <30mV, 50 lithium ion batteries are tested, the number of lithium ion batteries that fail the test is X, and the test failure rate is X / 50.

[0140] Different from example A3, the relevant parameters in examples B1 to B7 are shown in Table 2, and the remaining parameters are consistent with example A3. Different from example A3, in example B1, the first adhesive layer further comprises a fifth part and a seventh part, the fifth part extends out of the positive electrode sheet along the width direction of the positive electrode sheet, the width W5 of the fifth part is 0.3mm; the seventh part extends out of the positive electrode sheet on the other side, the width W7 of the seventh part is 0.3mm. The negative electrode sheet comprises a first region and a second region, the first region extends beyond the positive electrode sheet along the width direction of the negative electrode sheet, and the second region extends beyond the positive electrode sheet on the other side. The width W1 of the first region is 0.3mm, and the width W2 of the second region is 0.3mm. The separator film comprises a third region and a fourth region, the third region extends beyond the first region along the width direction of the second electrode sheet, and the fourth region extends beyond the second region. The width W3 of the third region is 0.5mm, and the width W4 of the fourth region is 0.5mm. The remaining examples are similar.

[0141] Table 2

[0142] According to Table 2, in combination with Embodiment A3 and Embodiments B1-B7, in Embodiments B3-B7, the drop failure rate is less than that of Embodiments B1, B2 and A3, Embodiments B3-B7 can reduce the first starting end from sliding along the axial direction of the cylindrical battery to exceed the fifth portion and / or the seventh portion, thereby reducing the occurrence of short circuit and improving the impact resistance of the cylindrical battery. In Embodiment B7, the drop failure rate is similar to that of Embodiments B5 and B6, but in Embodiments B5 and B6, the occupied space is smaller and the impact on energy density is smaller. Therefore, in the embodiments of the present application, W1≤W5≤W1+W3 and W2≤W7≤W2+W4 can be selected to improve the impact resistance of the cylindrical battery and reduce the excessive space occupied by the fifth portion and the seventh portion, thereby reducing the impact on the energy density. Similarly, W1≤W6≤W1+W3 and W2≤W8≤W2+W4 can be selected. The first starting end can be reduced from sliding along the axial direction to exceed the sixth portion and the eighth portion, thereby reducing the occurrence of short circuit, improving the impact resistance of the cylindrical battery, and reducing the excessive space occupied by the sixth portion and / or the eighth portion, thereby reducing the impact on the energy density.

[0143] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; under the idea of the present application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the present application as described above, which are not provided in detail for simplicity; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A cylindrical battery comprising a case and an electrode assembly disposed in the case, the electrode assembly comprising a first electrode tab, a separator, and a second electrode tab which are stacked and wound, the first electrode tab comprising a first starting end which is located at an innermost coil electrode tab of the electrode assembly in a winding direction, characterized in that, The cylindrical battery further comprises a first adhesive layer and a second adhesive layer; The first electrode tab comprises a first surface facing away from a winding center and a second surface facing the winding center; In the winding direction, the first adhesive layer comprises a first portion and a third portion connected with each other, the third portion is bonded with the first surface, and the first portion extends out of the first starting end; In the winding direction, the second adhesive layer comprises a second portion and a fourth portion connected with each other, the fourth portion is bonded with the second surface, the second portion extends out of the first starting end, and the second portion is bonded with the first portion; The outermost circle diameter of the electrode assembly is R1, the innermost circle diameter of the electrode assembly is R2, the diameter of the shell is R3, the diameter of the next innermost circle electrode tab of the electrode assembly is R4, the length of the first portion is L1, the length of the third portion is L3, the length of the second portion is L2, and the length of the fourth portion is L4 in the winding direction; L1≥π(R3-R1+R4-R2)+1 / (4×L3), and / or, L2≥π(R3-R1+R4-R2)+1 / (4×L4).

2. The cylindrical battery according to claim 1, characterized by 1.5mm≤L1≤5mm; and / or, 1.5mm≤L2≤5mm.

3. The cylindrical battery according to claim 1 or 2, characterized by 1.5mm≤L1≤4mm; and / or, 1.5mm≤L2≤4mm.

4. The cylindrical battery according to any one of claims 1 to 3, characterized by, L3≥1 / (4×L3), and L4≥1 / (4×L4).

5. The cylindrical battery of claim 4, wherein, 0.6mm≤L3≤10mm and / or, 0.6mm≤L4≤10mm.

6. The cylindrical battery of claim 1, wherein, The second electrode tab comprises a second starting end, the second starting end is located at the innermost circle electrode tab of the electrode assembly, and the second starting end exceeds the first starting end in the winding direction.

7. The cylindrical battery according to any one of claims 1 to 6, characterized by, In the axial direction of the cylindrical battery, the shell comprises a first wall portion and a second wall portion arranged oppositely; The cylindrical battery further comprises a first tab, a portion of the first tab is connected with the outermost circle of the first electrode tab, and another portion of the first tab is connected with the first wall portion.

8. The cylindrical battery according to any one of claims 1 to 6, characterized by, In the axial direction of the cylindrical battery, the shell comprises a first wall portion and a second wall portion arranged oppositely; The outermost circle of the first electrode tab is connected with the first wall portion, and the outermost circle of the second electrode tab is connected with the second wall portion.

9. The cylindrical battery according to any one of claims 1 to 6, characterized by, In the winding direction, the first electrode tab further comprises a first ending end, and the first ending end is located at the next outermost circle electrode tab of the electrode assembly; The cylindrical battery further comprises a third adhesive layer and a fourth adhesive layer, in the winding direction, the third adhesive layer comprises a ninth portion and an eleventh portion connected with each other, the ninth portion is bonded with the first surface, and the eleventh portion extends out of the first ending end; In the winding direction, the second adhesive layer comprises a tenth portion and a twelfth portion connected with each other, the tenth portion is bonded with the second surface, and the twelfth portion extends out of the first ending end; In the winding direction, the length of the ninth portion is L9, the length of the eleventh portion is L 11 , the length of the tenth portion is L 10 , and the length of the twelfth portion is L 12 ; Satisfies: L 11 ≥ π(R3-R1+R4-R2) + 1 / (4 x L9), and / or, L 12 ≥ π(R3-R1+R4-R2) + 1 / (4 x L 10 ).

10. The cylindrical battery of claim 9, wherein, 1.5 mm < L 11 ≤ 5 mm; and / or, 1.5 mm < L 12 ≤ 5 mm.

11. The cylindrical battery of claim 10, wherein, 1.5 mm < L 11 ≤ 4 mm; and / or, 1.5 mm < L 12 ≤ 4 mm.

12. The cylindrical battery according to any one of claims 1 to 11, characterized by, The first electrode tab is a positive electrode tab, and the second electrode tab is a negative electrode tab. The third portion further comprises a fifth portion and a seventh portion, the fifth portion and the seventh portion being portions of the third portion beyond edges of the first tab in a width direction of the first tab; The first tab comprises a first edge and a second edge arranged oppositely in the width direction of the first tab, the fifth portion extends beyond the first edge, and the seventh portion extends beyond the second edge; The second tab comprises a first region and a second region, the first region is beyond the first edge on one side of the first tab in a width direction of the second tab, and the second region is beyond the second edge on another side of the first tab in the width direction of the second tab; The separation film comprises a third region and a fourth region, the third region is beyond the first region on one side of the second tab in a width direction of the separation film, and the fourth region is beyond the second region on another side of the second tab in the width direction of the separation film; The first region has a width W1 in the width direction of the second tab, and the second region has a width W2 in the width direction of the second tab; the third region has a width W3 in the width direction of the separation film, and the fourth region has a width W4 in the width direction of the separation film; the fifth portion has a width W5 in the width direction of the first tab, and the seventh portion has a width W7 in the width direction of the first tab; W1≤W5≤W1+W3 and / or W2≤W7≤W2+W4 are satisfied.

13. The cylindrical battery of claim 12, wherein, The fourth portion further comprises a sixth portion and an eighth portion, the sixth portion and the eighth portion being portions of the fourth portion beyond edges of the first tab in a width direction of the first tab; The sixth portion has a width W6 in the width direction of the first tab, and the eighth portion has a width W8 in the width direction of the first tab; W1≤W6≤W1+W3 and / or W2≤W8≤W2+W4 are satisfied.

14. The cylindrical battery according to any one of claims 1 to 13, characterized by, In a thickness direction of the first tab, a projection of part of the first adhesive layer is located outside a projection of the second adhesive layer, and / or a projection of part of the second adhesive layer is located outside a projection of the first adhesive layer.

15. A method of making a cylindrical battery, characterized by, Comprising: A current collector is provided, and the current collector is cut to obtain a first segment and a second segment, the first segment comprises a first cutting position, and the second segment comprises a second cutting position; wherein, in a thickness direction of the current collector, the current collector comprises a first surface and a second surface arranged oppositely; The first segment and the second segment are pulled apart by a predetermined distance; A first integral adhesive layer is provided, one end of the first integral adhesive layer is bonded to the first surface of the first segment, and the other end of the first integral adhesive layer is bonded to the first surface of the second segment; wherein, in a length direction of the current collector, a bonding length of the first integral adhesive layer to the first segment is L3; A second integral adhesive layer is provided, one end of the second integral adhesive layer is bonded to the second surface of the first segment, the other end of the second integral adhesive layer is bonded to the second surface of the second segment, and the first integral adhesive layer and the second integral adhesive layer are bonded between the first cutting position and the second cutting position. The first cutting position and the second cutting position include a first position, and a length between the first position and the first cutting position along a length direction of the current collector is L1; cutting the first integral adhesive layer and the second integral adhesive layer along the first position; cutting the current collector several times to obtain a first current collector, and the first cutting position forms a first starting end of the first current collector, and the second cutting position forms a first ending end of the first current collector along a length direction of the first current collector; based on the first current collector, a first pole piece is prepared, a second pole piece is provided, and a winding-shaped electrode assembly is prepared; wherein the first starting end of the first pole piece is located at a next innermost circle pole piece of the electrode assembly, the first ending end is located at a next outermost circle pole piece of the electrode assembly, a diameter of an outermost circle of the electrode assembly is R1, a diameter of an innermost circle of the electrode assembly is R2, and a diameter of the next innermost circle pole piece of the electrode assembly is R4; a shell is provided, and the electrode assembly is arranged in the shell, wherein a diameter of the shell is R3; and L1≥π(R3-R1+R4-R2)+1 / (4×L3) is satisfied.

16. The method of claim 15, wherein, The method further comprises: The length of the bonding between the first integral adhesive layer and the second section along the length direction of the current collector is L9, and the length between the first position and the second cutting position is L 11 ; Satisfies: L 11 ≥ π(R3 - R1 + R4 - R2) + 1 / (4 x L9).

17. The method according to claim 15 or 16, characterized in that, The method further comprises: The length of the second integral adhesive layer adhered to the first section is L4, and the length of the second integral adhesive layer adhered to the second section is L 10 ; satisfies: L1≥π(R3-R1+R4-R2)+1 / (4×L4); and / or, L 11 ≥π(R3-R1+R4-R2)+1 / (4×L 10 ).

18. An electronic device, comprising: The cylindrical battery comprises any one of claims 1 to 17. The cylindrical battery comprises any one of claims 1 to 17.

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