Cylindrical battery, preparation method thereof and electronic equipment

Abstract

According to the cylindrical battery, the preparation method thereof and the electronic equipment, in the winding direction, a first adhesive layer comprises a first part and a third part which are connected, the third part is bonded with a first surface, and the first part extends out of a first starting end; in the winding direction, the second adhesive layer comprises a second part and a fourth part which are connected, the fourth part is bonded with the second surface, the second part extends out of the first starting end, and the second part is bonded with the first part. The diameter of the outermost ring of the electrode assembly is R < 1 >, the diameter of the innermost ring of the electrode assembly is R < 2 >, the diameter of the shell is R < 3 >, the diameter of the secondary inner ring of the electrode assembly is R < 4 >, and in the winding direction, the length of the first part is L < 1 >, the length of the third part is L < 3 >, the length of the second part is L < 2 >, and the length of the fourth part is L < 4 >. L < 1 > is greater than or equal to pi (R < 3-R > 1 + R < 4-R > 2) + 1 / (4 * L < 3 >), and / or L < 2 > is greater than or equal to pi (R < 3-R > 1 + R < 4-R > 2) + 1 / (4 * L < 4 >). The first pole piece can be prevented from being exposed out of the first adhesive layer and the second adhesive layer along the winding direction due to slippage, so that burrs at the first starting end are prevented from puncturing an isolating membrane, and short circuit is reduced.

Description

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. SUMMARY

[0003] 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.

[0004] The technical scheme adopted by the embodiments of the present application is as follows:

[0005] 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 the 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. It is satisfied that L1≥π(R3-R1+R4-R2)+1 / (4×L3), and / or L2≥π(R3-R1+R4-R2)+1 / (4×L4).

[0006] 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 thereby improving the safety performance of the cylindrical battery.

[0007] 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.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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.

[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 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.

[0013] 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, thereby reducing the short circuit.

[0014] In some embodiments, 1.5mm≤L 11 ≤5mm, which can cover the burr while reducing the impact of the third adhesive layer on the energy density of the cylindrical battery. In other embodiments, 1.5mm≤L 12 ≤5mm, which can cover the burr while reducing the impact of the fourth adhesive layer on the energy density of the cylindrical battery, which is conducive to the winding of the first tab.

[0015] In some embodiments, 1.5mm≤L 11 ≤4mm, which further reduces the impact on the energy density while reducing the short circuit caused by the tab slip. In other embodiments, 1.5mm≤L 12 ≤4mm, which further reduces the impact on the energy density while reducing the short circuit caused by the tab slip.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] In a second aspect, the present application provides a preparation method of a cylindrical battery, comprising:

[0021] 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 for 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.

[0022] 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).

[0023] In some embodiments, the method further comprises: along the length direction of the current collector, the bonding length between the second integral adhesive layer and the first section is L4, and the bonding length between the second integral adhesive layer and the second section 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 ).

[0024] 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.

[0025] 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

[0026] 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, and in which like reference numbers designate similar elements unless otherwise specified. The drawings in which:

[0027] Figure 1 Structure diagram of the cylindrical battery of some embodiments of the present application;

[0028] Figure 2 Structure diagram of the cylindrical battery of some embodiments of the present application;

[0029] Figure 3 Structure diagram of the electrode assembly of some embodiments of the present application;

[0030] Figure 4 Structure diagram of the first electrode sheet of some embodiments of the present application;

[0031] Figure 5 Structure diagram of the first electrode sheet of some embodiments of the present application; Figure 1 D-D cross-sectional view of the first electrode sheet of some embodiments of the present application;

[0032] Figure 6 Structure diagram of the first electrode sheet of some embodiments of the present application (after adhesive application);

[0033] Figure 7 Structure diagram of the first electrode sheet of some embodiments of the present application (after adhesive application);

[0034] Figure 8 Structure diagram of the first electrode sheet of some embodiments of the present application; Figure 6part A-A cross-sectional view in FIG. 1;

[0035] Figure 9 part A-A cross-sectional view in FIG. 1; Figure 1 part B-B cross-sectional view in FIG. 1;

[0036] Figure 10 part A-A cross-sectional view in FIG. 1; Figure 6 part A-A cross-sectional view in FIG. 1;

[0037] Figure 11 part A-A cross-sectional view in FIG. 1; Figure 5 enlarged view of part A in FIG. 1;

[0038] Figure 12 schematic diagram of the bonding structure of the first adhesive layer and the second adhesive layer for some embodiments of the present application;

[0039] Figure 13 schematic diagram of the bonding structure of the first adhesive layer and the second adhesive layer for some embodiments of the present application;

[0040] Figure 14 schematic diagram of the cutting of the current collector for some embodiments of the present application;

[0041] Figure 15 schematic diagram of the cutting of the current collector for some embodiments of the present application;

[0042] Figure 16 schematic diagram of the bonding of the first and second integral adhesive layers to the cutting position for some embodiments of the present application;

[0043] Figure 17 schematic diagram of the cutting of the first and second integral adhesive layers for some embodiments of the present application.

[0044] Explanation of Reference Signs:

[0045] 100, cylindrical battery;

[0046] 10, case; 11, first wall portion; 111, first electrode terminal; 12, second wall portion; 13, main body portion; 14, opening;

[0047] 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;

[0048] 30, first adhesive layer; 31, first portion; 33, third portion; 35, fifth portion; 37, seventh portion;

[0049] 40, second adhesive layer; 42, second portion; 44, fourth portion; 46, sixth portion; 48, eighth portion;

[0050] 50, third adhesive layer; 59, ninth portion; 511, eleventh portion;

[0051] 60, fourth adhesive layer; 610, tenth portion; 612, twelfth portion;

[0052] 200, current collector; 201, first segment; 203, first cutting position; 202, second segment; 204, second cutting position;

[0053] 300, cutter;

[0054] 400, first integral adhesive layer;

[0055] 500, second integral adhesive layer;

[0056] X, first direction; Y, second direction; Z, third direction; K, axial direction; S, winding direction. DETAILED DESCRIPTION

[0057] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application.

[0058] In the embodiments of the present application, the phrase “in an embodiment” means that a specific feature, structure or property described in connection with the embodiment can be included in at least one embodiment of the present application. The appearance of this phrase at various places in the specification does not necessarily mean that it refers to the same embodiment, nor is it an independent or alternative embodiment to other embodiments.

[0059] 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 “plurality” is two or more, unless otherwise explicitly and specifically limited.

[0060] In the description of the embodiments of the present application, the term "and / or" is merely an 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 that the front and rear associated objects are in an "or" relationship.

[0061] 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.

[0062] In a first aspect, the present application provides a cylindrical battery 100, please refer to Figure 1 and Figure 2 The cylindrical battery 100 includes a shell 10, and an electrode assembly 20 and an electrolyte (not marked in the figure) accommodated in the shell 10. The electrolyte infiltrates the electrode assembly 20 in the shell 10, so that an electrochemical reaction occurs.

[0063] For the above-mentioned shell 10, please refer to Figure 1 and Figure 2 The shell 10 can adopt a columnar shape, and 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.

[0064] The shell 10 can be made of conductive metal materials such as aluminum, aluminum alloy, steel, stainless steel, nickel, copper, or magnesium alloy, which makes the shell 10 able to lead out a certain polarity of the cylindrical battery 100, for example, the shell 10 itself as the positive electrode or negative electrode of the cylindrical battery 100. In other embodiments, the shell 10 can also be made of soft package materials, such as aluminum plastic film or copper plastic film, etc.

[0065] For the above-mentioned electrode assembly 20, please refer to Figure 2 and Figure 3The outermost diameter of the electrode assembly 20 is smaller than the inner diameter of the housing 10, so that the electrode assembly 20 can be easily placed in the housing 10. The electrode assembly 20 includes a first electrode tab 21, a second electrode tab 22, and a separator 23. The first electrode tab 21, the separator 23, and the second electrode tab 22 are stacked and wound, and the separator 23 is disposed between the first electrode tab 21 and the second electrode tab 22 to insulate and separate them. The innermost portion of the electrode assembly 20 can have a gap space, so that the electrolyte can enter the innermost portion of the electrode assembly 20 and then infiltrate the first electrode tab 21 and the second electrode tab 22 from the inside of the electrode assembly 20. In other embodiments, the gap space can also have a column.

[0066] The first electrode tab 21 and the second electrode tab 22 have opposite polarities. For example, the first electrode tab 21 is a positive electrode tab, and the second electrode tab 22 is a negative electrode tab. Alternatively, the first electrode tab 21 is a negative electrode tab, and the second electrode tab 22 is a positive electrode tab. In some embodiments, the first electrode tab 21 can be electrically connected to the first wall portion 11, so that the first wall portion 11 leads out one polarity of the cylindrical battery 100. The second electrode tab 22 can be electrically connected to the second wall portion 12, so that the second wall portion 12 leads out the other polarity of the cylindrical battery 100. By insulating the first wall portion 11 from the second wall portion 12, the occurrence of short circuits can be reduced.

[0067] For example, referring to Figure 4 and Figure 5 , the first electrode tab 21 includes a first current collector 211 and a first active material layer 212, and the first active material layer 212 can be disposed 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 tab 21 in the width direction can have an empty foil area (not shown in the figure) or a plurality of first electrode tabs 214. By flattening the empty foil area or the plurality of first electrode 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 tab 22 can also be similarly disposed, and the other polarity can be led out through the second wall portion 12.

[0068] It should be noted that the electrode tab is wound along its length direction (first direction X), and after winding, the length direction of the electrode tab is the winding direction S, and the width direction (second direction Y) is the axial direction K of the cylindrical battery 100.

[0069] In other embodiments, referring to Figure 5 , the first electrode tab 21 has a single first electrode tab 214, and the first wall portion 11 leads out one polarity by being electrically connected to the single first electrode tab 214. The second electrode tab 22 can also have a single second electrode tab (not shown in the figure), and the second wall portion 12 leads out the other polarity by being electrically connected to the single second electrode tab. The first wall portion 11 and the second bottom wall 12 can each have a pole column, which can be used to lead out the positive and negative poles.

[0070] During winding, if the starting section of the pole piece is provided with the active material layer, the active material layer of this part may be pressed against the separator 23, which is easy to cause the separator 23 to be damaged, and affects the roundness of the innermost circle of the electrode assembly 20, resulting in poor structural stability of the electrode assembly 20.

[0071] To reduce the above problems, in the embodiments of the present application, please refer to Figure 3 and Figure 4 , along the winding direction S, the first current collector 211 includes a first starting empty foil section 2111, which can reduce the damage of the separator 23 and improve the structural stability of the electrode assembly 20.

[0072] Along the winding direction S described above, the first pole piece 21 includes a first starting end 2113 and a first ending end 2114, and 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 in the next innermost circle pole piece of the electrode assembly 20, wherein the innermost circle pole piece of the electrode assembly 20 is part of the second pole piece 22.

[0073] During cutting, the first current collector 211 will form a cutting burr at the first starting section 2113 and the first ending end 2114, and the burr is easy to pierce the separator, especially in the case of high stress on the inner circle, the risk of the burr piercing the separator is higher.

[0074] In the embodiments of the present application, please refer to Figure 6 to Figure 8 , the cylindrical battery 100 further includes a first adhesive layer 30 and a second adhesive layer 40. After winding, the first pole piece 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.

[0075] 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 burr on the first surface 21a, reduces the cutting burr piercing the separator 23, and further reduces the short circuit.

[0076] 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 to 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 covers part of the cutting burr on the second surface 21b, reduces the cutting burr piercing the separator 23, and further reduces the short circuit.

[0077] The first adhesive layer 30 includes a substrate layer (not shown in the figure) and an adhesive layer (not shown in the figure). The adhesive layer is arranged on the surface of the substrate layer and adheres to the first tab 21. The substrate layer can be made of polyimide (PI) or polyester (PET), and the adhesive layer can be made of polypropylene (PP), polyethylene (PE), polyvinylidene fluoride (PVDF), or acrylic. The adhesive force between the first adhesive layer 30 and the first tab 21 can reach 0.15 N / mm or more, and after being soaked in electrolyte, the adhesive force can reach 0.1 N / mm or more. The second adhesive layer 40 and the third adhesive layer 50 and the fourth adhesive layer 60 described below can also be arranged in a similar manner.

[0078] The present inventors have found that during the charge and discharge cycles of the cylindrical battery 100, the first tab 21 and the second tab 22 can expand, which can cause the first tab 21 and the second tab 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 housing 10 and the inner ring space of the electrode assembly 20. For example, the first starting end 2113 slides towards the inner ring to occupy the inner ring space, and the first ending end 2114 slides towards the outer ring to occupy the gap space between the housing 10. However, the first adhesive layer 30 and the second adhesive layer 40 have a small amount of sliding due to the extrusion of the layers of tabs and the friction between the tabs. The sliding directions of the adjacent two layers of tabs can be opposite, which can 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 can directly exceed the first adhesive layer 30 and the second adhesive layer 40, so that the first starting end 2113 is exposed, which can easily cause the burr of the first starting end 2113 to pierce the separator 23, and there is a risk of short circuit.

[0079] Furthermore, the present inventors have found that the third portion 33, as the portion adhered to the first tab 21, the sliding amount 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 and discharge cycles of the cylindrical battery 100, and the electrode assembly 20 occupies part of the gap space of the innermost ring and part of the gap space between the housing 10, in the extreme case, the sliding direction of the first adhesive layer 30 and the first starting end 2113 is opposite, and the sliding amount of the first adhesive layer is approximately 1 / (4×L3), L3 is the length of the third portion 33 along the winding direction S, that is, the length of the first adhesive layer 30 adhered to the first tab 21.

[0080] In some 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 risk of the first starting end 2113 sliding out of the first adhesive layer 30 along the winding direction S due to the expansion of the electrode tab during long-term charge and discharge cycles, thereby reducing the risk of the burr of the first surface 21a of the first starting end 2113 piercing the separator 23 and reducing the risk of short circuit. Figure 9 The outermost circle diameter of the electrode assembly 20 is R1, the innermost circle diameter 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 electrode tab of the inner circle of the electrode assembly 20 is R4.

[0081] 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 focusing and fine focusing 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 to just surround the edge of the cylindrical battery. During adjustment, the accuracy of the measurement can be ensured by zooming in on the image and fine-tuning the position of the measurement tool. The measurement result is read. The software automatically displays the diameter value of the circular measurement tool. The diameter of the electrode tab of the inner circle of the electrode assembly 20 can also be measured by scanning the electrode assembly 20 using a computer tomography instrument (CT).

[0082] It should be noted that the above-mentioned 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.

[0083] In some embodiments, the second electrode tab 22 includes a second starting end 22a, which is located at the innermost circle of the electrode assembly 20 and protrudes beyond the first starting end 2113 along the winding direction S.

[0084] In some embodiments, the first portion 31 and the second portion 42 are bonded to each other after protruding from 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 electrode tab 21, and reduce the risk of the first starting end 2113 of the first electrode tab 21 being exposed from the first adhesive layer 30 and the second adhesive layer 40.

[0085] The inventors of the present application have found that if the length of the first portion 31 is too small, it can be difficult to effectively isolate the burr of the first starting end 2113 of the first surface 21a, 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 pole piece 21, but also causes the energy density of the cylindrical battery 100 to be lost. In the embodiments of the present application, 1.5mm≤L1≤5mm is limited, which can cover the burr while reducing the influence of the first adhesive layer 30 on the energy density of the cylindrical battery 100, and is conducive to the winding of the first pole piece 21. Preferably, 1.5mm≤L1≤4mm is limited, which further reduces the short circuit while reducing the influence on the energy density.

[0086] Based on the same inventive concept as described above, the second adhesive layer 40 can also be similarly arranged. The slip amount of the second adhesive layer 40 approximately satisfies 1 / (4×L4), and L4 is the length of the fourth portion 44, that is, the bonding length of the second adhesive layer 40 and the first pole piece 21. In the embodiments of the present application, the length of the second portion 42 along the winding direction S is L2, and L2≥π(R3-R1+R4-R2)+1 / (4×L4), which can reduce the situation that the first starting end 2113 slips along the winding direction S and exceeds the second adhesive layer 40 due to the expansion of the pole piece during the long-term charge-discharge cycle of the cylindrical battery 100, and further reduces the situation that the burr of the second surface 21b of the first starting end 2113 pierces the separator 23, thereby reducing the short circuit.

[0087] Similarly 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 influence of the first adhesive layer 30 on the energy density of the cylindrical battery 100, and is conducive to the winding of the first pole piece 21. Preferably, 1.5mm≤L2≤4mm is limited, which further reduces the short circuit while reducing the influence on the energy density.

[0088] In some embodiments, the slip amount of the first adhesive layer 30 can be greater than the slip amount of the first pole piece 21, causing the first pole piece 21 to be separated from the first adhesive layer 30 on the side away from the first portion 31 of the third portion 33. To reduce this problem, in the present application, L3≥1 / (4×L3) is limited, which reduces the situation that the first adhesive layer 30 exceeds the first starting end 2113, and further reduces the short circuit. Based on the same inventive concept, L4≥1 / (4×L4) is limited, which reduces the situation that the second adhesive layer 40 exceeds the first starting end, and further reduces the short circuit.

[0089] 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 influence 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 influence on the energy density.

[0090] In some embodiments, along the axial direction K of the cylindrical battery 100, the shell 10 comprises a first wall portion 11 and a second wall portion 12 arranged oppositely. The first tab 214 is connected to the outermost circle of the first electrode tab 21 at one end, and connected to the first wall portion 11 at the other end. The first tab 214 is arranged at the outermost circle of the first electrode tab 21, and the inner circle is more prone to slip in the winding direction S. By limiting L1≥π(R3-R1+R4-R2)+1 / (4×L3) and L2≥π(R3-R1+R4-R2)+1 / (4×L4), the occurrence of short circuit can be reduced.

[0091] In some embodiments, along the axial direction K of the cylindrical battery 100, the shell 10 comprises a first wall portion 11 and a second wall portion 12 arranged oppositely. The first tab 214 is connected to the outermost circle of the first electrode tab 21 at one end, and connected to the first wall portion 11 at the other end. The first tab 214 is arranged at the outermost circle of the first electrode tab 21, and the inner circle is more prone to slip in the winding direction S. By limiting L1≥π(R3-R1+R4-R2)+1 / (4×L3) and L2≥π(R3-R1+R4-R2)+1 / (4×L4), the occurrence of short circuit can be reduced.

[0092] For the burr of the first end 2114 described above, the present inventors have found that when the first end 2114 is located at the outermost circle of the electrode assembly 20, the burr of the first end 2114 may also slip due to the presence of the electrode tab of opposite polarity on both sides of the thickness direction of the innermost circle electrode tab and the smaller limiting force of the outermost circle electrode tab, thereby increasing the risk of the burr of the first end 2114 piercing the separator 23, and further leading to the short circuit between the first electrode tab 21 and the second electrode tab 22.

[0093] To reduce the risk of the first end 2114 piercing the separator 23, please refer to Figure 3 and Figure 4 , along the winding direction S, the first electrode tab 21 further comprises a first end empty foil segment 2112, the first end 2114 is one end of the first end empty foil segment 2112 away from the first start end 2113, and the first end 2114 is located at the outermost circle of the electrode assembly 20. In the embodiments of the present application, please refer to Figure 6 , Figure 7 and Figure 10 , the cylindrical battery 100 further comprises a third adhesive layer 50 and a fourth adhesive layer 60.

[0094] The third adhesive layer 50 can be arranged on the first surface 21a of the first tailing 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 with each other, the ninth portion 59 is bonded with the first surface 21a, and the eleventh portion 511 extends out of the first tailing end 2114, so that the third adhesive layer 50 covers part of the cutting burrs on the first surface 21a, reduces the cutting burrs from piercing the separator 23, and further reduces the short circuit.

[0095] 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 with each other, the tenth portion 610 is bonded with the second surface 21b, and the twelfth portion 612 extends out of the first tailing end 2114, so that the fourth adhesive layer 60 covers part of the cutting burrs on the second surface 21b, reduces the cutting burrs from piercing the separator 23, and further reduces the short circuit.

[0096] The eleventh portion 511 and the twelfth portion 612 are bonded with each other after extending out of the first tailing end 2114, which can improve the overall connection strength of the third adhesive layer 50, the fourth adhesive layer 60 and the first pole piece 21, reduce the exposure of the first tailing end 2114 from the third adhesive layer 50 and the fourth adhesive layer 60, and further reduce the piercing of the cutting burrs of the first tailing end 2113 on the separator 23.

[0097] Similarly to the first starting end 2113, along the winding direction S, the length of the ninth portion 59 is L9, the length of the eleventh portion 511 is L 11 , and L 11 ≥π(R3-R1+R4-R2)+1 / (4×L9), which can reduce the first tailing end 2114 from sliding along the winding direction S and exceeding the third adhesive layer 50 due to the expansion of the pole piece during the long-term charge and discharge cycle of the cylindrical battery 100, and further reduce the piercing of the cutting burrs of the first tailing end 2114 on the separator 23, and reduce the short circuit.

[0098] Based on the same inventive concept, the fourth adhesive layer 60 can also be arranged similarly, and in the embodiments of the present application, along the winding direction S, the length of the tenth portion 610 is L 10 , the length of the twelfth portion 612 is L 12 , and L 12 ≥π(R3-R1+R4-R2)+1 / (4×L 10 ), which can reduce the first tailing end 2114 from sliding along the winding direction S and exceeding the fourth adhesive layer 60 due to the expansion of the pole piece during the long-term charge and discharge cycle of the cylindrical battery 100, and further reduce the piercing of the cutting burrs of the first tailing end 2114 on the separator 23, and reduce the short circuit.

[0099] In some embodiments, 1.5mm≤L 11 ≤5mm, which can cover the burrs while reducing the impact of the third adhesive layer 50 on the energy density of the cylindrical battery 100. In some other embodiments, 1.5mm≤L 12 ≤5mm, which can cover the burrs while reducing the impact of the fourth adhesive layer 60 on the energy density of the cylindrical battery 100.

[0100] Based on the same inventive concept, in some embodiments, 1.5mm≤L 11 ≤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≤L 12 ≤4mm, which further reduces the impact on the energy density while reducing the short circuit caused by the tab slip.

[0101] In some embodiments, please refer to Figure 6 and Figure 7 The third part 33 further includes a fifth part 35 and a seventh part 37, which are two parts of the third part 33 beyond the edge of the first tab 21 along the width direction (second direction Y) of the first tab 21. The first tab 21 includes oppositely arranged first and second edges 21c and 21d along the width direction (second direction Y) of the first tab 21, the fifth part 35 extends beyond the first edge 21c, so that the fifth part 35 covers part of the burrs of the first edge 21c, and the seventh part 37 extends beyond the second edge 21d, so that the seventh part 37 covers part of the burrs of the second edge 21d.

[0102] In some embodiments, please further refer to Figure 5 and Figure 11 Take the first tab 21 as a positive electrode tab and the second tab 22 as a negative electrode tab as an example. The second tab 22 includes a first region 221 and a second region 222, which are beyond the first edge 21c on one side of the first tab 21 and beyond the second edge 21d on the other side of the first tab 21 along the width direction (second direction Y) of the second tab 22. For example, the width of the first region 221 is W1 and the width of the second region 222 is W2 along the width direction (second direction Y) of the second tab 22, and in some embodiments of the present application, 0.1mm≤W1≤0.6mm and 0.1mm≤W2≤0.6mm, which can make the second tab 22 have sufficient excess to embed the lithium ion and reduce the occurrence of lithium precipitation.

[0103] The isolation film 23 includes a third region 233 and a fourth region 234, 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 along the width direction (the second direction Y) of the isolation film 23. For example, the width of the third region 233 is W3, and the width of the fourth region 234 is W4 along the width direction (the second direction Y) of the isolation film 23, and in the embodiments of the present application, 0.4mm≤W3≤1.2mm and / or 0.4mm≤W4≤1.2mm are defined, which can make the isolation film 23 isolate the first tab 21 from the second tab 22 and reduce short circuit.

[0104] In some embodiments, the width of the fifth portion 35 is W5, and the width of the seventh portion 37 is W7 along the width direction (the second direction Y) of the first tab 21. In the embodiments of the present application, W1≤W5≤W1+W3 are met, which can reduce the first starting end 2113 from sliding along the axial direction K to beyond the fifth portion 35, thereby reducing short circuit and improving the anti-impact 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 are met, which can reduce the first starting end 2113 from sliding along the axial direction K to beyond the seventh portion 37, thereby reducing short circuit and improving the anti-impact performance of the cylindrical battery 100 and reducing the impact on the energy density and the packaging strength.

[0105] The second adhesive layer 40 can also be arranged similarly to the first adhesive layer 30, and the fourth portion 44 further includes a sixth portion 46 and an eighth portion 48, the sixth portion 46 and the eighth portion 48 are portions of the fourth portion 44 beyond the edge of the first tab 21 along the width direction (the second direction Y) of the first tab 21. The width of the sixth portion 46 is W6, and the second width of the eighth portion 48 is W8 along the width direction (the second direction Y) of the first tab 21. In the embodiments of the present application, W1≤W6≤W1+W3 are met, which can reduce the first starting end 2113 from sliding along the axial direction K to beyond the sixth portion 46, thereby reducing short circuit. Based on the same inventive concept, W2≤W8≤W2+W4 are met, which can reduce the first starting end 2113 from sliding along the axial direction K to beyond the eighth portion 48, thereby reducing short circuit.

[0106] In some embodiments, please refer to Figure 12 and Figure 13In some embodiments, the projection of the partial first adhesive layer 30 is located outside the projection of the second adhesive layer 40 along the thickness direction (third direction Z) of the first tab 21. 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 partial separator 23. For example, the fifth portion 35 and the sixth portion 46 have a non-overlapping area, and the fifth portion 35 can be located 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 partial separator 23. Similarly, the sixth portion 46 can also bond the partial separator 23. The overall bonding strength of the electrode assembly 20 can be improved, the tab looseness can be reduced, and thus the first starting end 2113 can be prevented from slipping. In addition, 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 the charging and discharging process, and thus reduce the safety problems such as internal short circuit.

[0107] In other embodiments, the seventh portion 37 and the eighth portion 48 can 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 non-overlapping, and the separator 23 can be bonded by the first portion 31 and the second portion 42.

[0108] In a second aspect, the application further provides a method for manufacturing a cylindrical battery 100, which includes the following steps:

[0109] The current collector 200 (current collector roll) is provided, and the current collector 200 is cut to obtain a first section 201 and a second section 202. For example, refer to Figure 14 and Figure 15 The current collector 200 can be cut into the first section 201 and the second section 202 by the cutter 300, and the first cutting position 203 is located at the first section 201, and the second cutting position 204 is located at the second section 202. The current collector 200 includes the first surface 21a and the second surface 21b arranged oppositely along the thickness direction (third direction Z) of the current collector 200.

[0110] The first section 201 and the second section 202 are pulled apart by a predetermined distance, so that the gap space is formed between the first cutting position 203 and the second cutting position 204.

[0111] The first integral adhesive layer 400 is provided, refer to Figure 16 and Figure 17 One end of the first integral adhesive layer 400 is bonded to the first surface 21a of the first section 201, and the other end of the first integral adhesive layer 400 is bonded to the first surface 21a of the second section 202. The bonding length of the first integral adhesive layer 400 and the first section 201 along the length direction (first direction X) of the current collector 200 is L3.

[0112] The second integral adhesive layer 500 is provided, one end of the second integral adhesive layer 500 is bonded to the second surface 21b of the first section 201, the other end of the second integral adhesive layer 500 is bonded to the second surface 21b of the second section 202, and the first integral adhesive layer 400 and the second integral adhesive layer 500 are bonded between the first cutting position 203 and the second cutting position 204.

[0113] 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 (the first direction X) of the current collector 200 is L1.

[0114] Cutting the first integral adhesive layer 400 and the second integral adhesive layer 500 along the first position C can divide the first integral adhesive layer 400 into the first adhesive layer 30 bonded to the first surface 21a of the first section 201 and the third adhesive layer 50 bonded to the first surface 21a of the second section 202, and can divide the second integral adhesive layer 500 into the second adhesive layer 40 bonded to the second surface 21b of the first section 201 and the fourth adhesive layer 60 bonded to the second surface 21b of the second section 202.

[0115] Cutting the current collector 200 several times to obtain a first current collector, and 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 (the first direction X) of the first current collector.

[0116] Based on the first current collector, a first pole piece 21 is prepared, a second pole piece 22 is provided, and a wound electrode assembly 20 is prepared. Wherein the first starting end 2113 of the first pole piece 21 is located at the innermost circle pole piece of the electrode assembly 20, the first ending end 2114 is located at the outermost circle pole piece of the electrode assembly 20, the diameter of the outermost circle of the electrode assembly 20 is R1, and the diameter of the innermost circle of the electrode assembly 20 is R2.

[0117] A shell 10 is provided, and the electrode assembly 20 is arranged in the shell 10, wherein the diameter of the shell 10 is R3, and the diameter of the innermost circle pole piece of the electrode assembly 20 is R4. L1≥π(R3-R1+R4-R2)+1 / (4×L3) is satisfied.

[0118] 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. Limiting L1≥π(R3-R1+R4-R2)+1 / (4×L3) can reduce the first starting end 2113 of the first pole piece 21 from the first adhesive layer 30 along 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 the short circuit.

[0119] In some embodiments, the method further comprises 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 end 2114. The bonding length of the first integral adhesive layer 400 and the second section 202 is L9 in the length direction (the first direction X) of the current collector 200, and the length between the first position C and the second cutting position 204 is L 11 In embodiments of the present application, L 11 ≥ π(R3-R1+R4-R2)+1 / (4×L9).

[0120] 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 embodiments of the present application, L 11 ≥ π(R3-R1+R4-R2)+1 / (4×L9), which can reduce the first 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 end 2114 to pierce the isolation film 23 and reducing short circuit.

[0121] In some embodiments, the method further comprises that the bonding length of the second integral adhesive layer 500 and the first section 201 is L4 in the length direction (the first direction X) of the current collector 200, and the bonding length of the second integral adhesive layer 500 and the second section 202 is L 10 ≥ π(R3-R1+R4-R2)+1 / (4×L4); and / or, L 11 ≥ π(R3-R1+R4-R2)+1 / (4×L 10 ).

[0122] In 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 part 44 is L4, and according to the above cutting method, the length L2 of the second part 42 can be obtained as L1≥ L1≥ π(R3-R1+R4-R2)+1 / (4×L4). This can reduce the first tab 21 beyond the second adhesive layer 40 in the winding direction S, thereby reducing the burr of the second surface 21b of the first end 2113 to pierce the isolation film 23 and reducing short circuit.

[0123] In 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 part 610 is L 10 , and according to the above cutting method, the length L of the twelfth part 612 can be obtained as12 ≥ π (R3-R1+ R4-R2) + 1 / (4 x L 10 ). The first end 2114 of the first tab 21 can be reduced to protrude beyond the fourth adhesive layer 60 in the winding direction S, thereby reducing the risk of the second surface 21b of the first end 2114 piercing the separator 23 and reducing the risk of short circuit.

[0124] In a third aspect, the present application also provides an electronic device comprising the cylindrical battery 100 according to any one of the embodiments of the second aspect. The electronic device according to the embodiments of the present application is not particularly limited and can be any electronic device known in the 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. Among them, the electric toy can include a fixed or mobile electric toy, for example, a game console, an electric car toy, an electric ship toy, an electric plane toy, etc., and the spacecraft can include an airplane, a rocket, a space shuttle, a spacecraft, etc.

[0125] Experiment 1: Charge-discharge cycle test of lithium ion battery

[0126] Example A1:

[0127] <Preparation of the positive electrode tab>

[0128] 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) mixed in a mass ratio of 94:3:3, N-methyl pyrrolidone (NMP) was added as a solvent, and an anode slurry with a solid content of 75 wt% was prepared and uniformly stirred 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 sites. 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 site in the thickness direction, respectively, and a third adhesive layer and a fourth adhesive layer were formed on both sides of the other cutting site in the thickness direction, respectively. The anode current collector roll was cut into an anode current collector with a length of 380 mm, and the above-mentioned adhesive cutting operation was repeated. Among them, the bonding length of the first adhesive layer and the anode current collector (the third part) L3 = 2.5 mm, and it extends out of the anode current collector (the first part) L1 = 1 mm. The bonding length of the second adhesive layer and the anode current collector (L4) L4 = 2.5 mm, and it extends out of the anode current collector (the second part) L2 = 1 mm. The anode slurry was uniformly coated on one surface of the anode current collector aluminum foil, and the aluminum foil was reserved with no anode slurry coated on the two sections at the head and tail, and then dried at 110°C to obtain an anode electrode sheet with a single-sided coated anode active material layer. Then, the above steps were repeated on the other surface of the aluminum foil to obtain an anode electrode sheet with a double-sided coated anode active material layer. The coating weight of the anode electrode sheet was 25 mg / cm 2 .

[0129] <Preparation of a negative electrode sheet>

[0130] The negative 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 uniformly stirred. 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 reserved with no negative electrode slurry coated on the two sections at the head and tail, and then dried at 90°C to obtain a single-sided negative electrode sheet. After the above steps were completed, the single-sided coating of the negative electrode sheet was completed. Then, the above steps were repeated on the other surface of the negative electrode sheet to obtain a double-sided coated negative electrode active material layer negative electrode sheet. The coating weight of the negative electrode sheet was 6.5 mg / cm 2 .

[0131] <Preparation of a separator>

[0132] A polyethylene (PE) with a thickness of 7 um and a 2 um aluminum oxide (Al2O3) coated porous film were used as a separator.

[0133] <Preparation of an electrolyte>

[0134] 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.

[0135] <Preparation of lithium ion battery>

[0136] 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, and 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 sheet diameter R4 = 2.5 mm. The electrode assembly was subjected to hot pressing (pressure 5 MPa, temperature 65℃, 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 the processes of packaging, liquid injection, formation, capacity test, voltage resistance test, etc., a secondary battery was prepared.

[0137] 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 subjected to the following charging steps to charge to 4.45V:

[0138] (1) 2.5C constant current charging to 4.15V, constant voltage charging to 1.5C;

[0139] (2) 1.5C constant current charging to 4.18V, constant voltage charging to 0.5C;

[0140] (3) 0.5C constant current charging to 4.45V, constant voltage charging to 0.02C;

[0141] After standing for 10min, the following steps were carried out for discharging:

[0142] 1C constant current discharging to 3V, which was one cycle.

[0143] 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 to be invalid. Each group of tests 50 samples, the number of failures is N, and the failure rate is N / 50.

[0144] 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.

[0145] Table 1

[0146]

[0147]

[0148] 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.

[0149] 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.

[0150] 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.

[0151] Experiment Two: Drop Test of Lithium Ion Battery

[0152] 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.

[0153] 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 includes 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 includes a first area and a second area, the first area extends beyond the positive electrode sheet along the width direction of the negative electrode sheet, and the second area extends beyond the positive electrode sheet on the other side. The width W1 of the first area is 0.3mm, and the width W2 of the second area is 0.3mm. The separator includes a third area and a fourth area, the third area extends beyond the first area along the width direction of the second sheet, and the fourth area extends beyond the second area. The width W3 of the third area is 0.5mm, and the width W4 of the fourth area is 0.5mm. The remaining examples are similar.

[0154] Table 2

[0155]

[0156] 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.

[0157] 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 housing and an electrode assembly disposed within the housing, the electrode assembly comprising a first electrode, a separator, and a second electrode stacked and wound together, wherein, along the winding direction, the first electrode includes a first starting end located at the second innermost electrode of the electrode assembly, characterized in that, The cylindrical battery also includes a first adhesive layer and a second adhesive layer; The first electrode includes a first surface facing away from the winding center and a second surface facing the winding center; Along the winding direction, the first adhesive layer includes a first part and a third part connected together, the third part being bonded to the first surface, and the first part extending out of the first starting end; Along the winding direction, the second adhesive layer includes a second portion and a fourth portion connected together, the fourth portion being bonded to the second surface, the second portion extending out of the first starting end, and the second portion being 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 housing is R3, the diameter of the second innermost electrode plate of the electrode assembly is R4, and along the winding direction, the length of the first part is L1, the length of the third part is L3, the length of the second part is L2, and the length of the fourth part is L4. The following conditions must be met: 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 in that, 1.5mm≤L1≤5mm; and / or, 1.5mm≤L2≤5mm.

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

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

5. The cylindrical battery according to claim 4, characterized in that, 0.6mm≤L3≤10mm and / or 0.6mm≤L4≤10mm.

6. The cylindrical battery according to claim 1, characterized in that, The second electrode includes a second starting end located at the innermost electrode of the electrode assembly, extending beyond the first starting end along the winding direction.

7. The cylindrical battery according to any one of claims 1 to 6, characterized in that, Along the axial direction of the cylindrical battery, the housing includes a first wall portion and a second wall portion disposed opposite to each other; The cylindrical battery also includes a first tab, a portion of which is connected to the outermost ring of the first electrode, and another portion of which is connected to the first wall portion.

8. The cylindrical battery according to any one of claims 1 to 6, characterized in that, Along the axial direction of the cylindrical battery, the housing includes a first wall portion and a second wall portion disposed opposite to each other; The outermost ring of the first electrode is connected to the first wall portion, and the outermost ring of the second electrode is connected to the second wall portion.

9. The cylindrical battery according to any one of claims 1 to 6, characterized in that, Along the winding direction, the first electrode further includes a first terminal end, which is located on the second outermost electrode of the electrode assembly. The cylindrical battery further includes a third adhesive layer and a fourth adhesive layer. Along the winding direction, the third adhesive layer includes a ninth part and an eleventh part connected to each other. The ninth part is bonded to the first surface, and the eleventh part extends out of the first end. Along the winding direction, the second adhesive layer includes a tenth portion and a twelfth portion connected together, the tenth portion being bonded to the second surface, and the twelfth portion extending beyond the first end; Along the winding direction, the length of the ninth portion is L9, and the length of the eleventh portion is L. 11 The length of the tenth part is L. 10 The length of the twelfth part is L. 12 ; Satisfy: L 11 ≥π(R3-R1+R4-R2)+1 / (4×L9), and / or, L 12 ≥π(R3-R1+R4-R2)+1 / (4×L 10 ).

10. The cylindrical battery according to claim 9, characterized in that, 1.5mm≤L 11 ≤5mm; and / or, 1.5mm≤L 12 ≤5mm.

11. The cylindrical battery according to claim 10, characterized in that, 1.5mm≤L 11 ≤4mm; and / or, 1.5mm≤L 12 ≤4mm.

12. The cylindrical battery according to any one of claims 1 to 11, characterized in that, The first electrode is a positive electrode, and the second electrode is a negative electrode; The third part further includes a fifth part and a seventh part, which are portions of the third part that extend beyond the edge of the first electrode along the width direction of the first electrode. Along the width direction of the first electrode, the first electrode includes a first edge and a second edge disposed opposite to each other, the fifth portion extends out of the first edge, and the seventh portion extends out of the second edge; The second electrode includes a first region and a second region. Along the width direction of the second electrode, the first region extends beyond the first edge on one side of the first electrode, and the second region extends beyond the second edge on the other side of the first electrode. The separator includes a third region and a fourth region. Along the width direction of the second electrode, the third region extends beyond the first region on one side of the second electrode, and the fourth region extends beyond the second region on the other side of the second electrode. Along the width direction of the second electrode, the width of the first region is W1, and the width of the second region is W2; along the width direction of the separator, the width of the third region is W3, and the width of the fourth region is W4; along the width direction of the first electrode, the width of the fifth portion is W5, and the width of the seventh portion is W7. Satisfying: W1≤W5≤W1+W3, and / or, W2≤W7≤W2+W4.

13. The cylindrical battery according to claim 12, characterized in that, The fourth part further includes a sixth part and an eighth part, which are the portions of the fourth part that extend beyond the edge of the first electrode along the width direction of the first electrode. Along the width direction of the first electrode, the width of the sixth portion is W6, and the second width of the eighth portion is W8; Satisfying: W1≤W6≤W1+W3, and / or, W2≤W8≤W2+W4.

14. The cylindrical battery according to any one of claims 1 to 13, characterized in that, Along the thickness direction of the first electrode, a portion of the projection of the first adhesive layer lies outside the projection of the second adhesive layer; and / or, a portion of the projection of the second adhesive layer lies outside the projection of the first adhesive layer.

15. A method for preparing a cylindrical battery, characterized in that, include: A 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 disposed opposite to each other along the thickness direction of the current collector. The first segment and the second segment are spaced at a predetermined distance; A first integral adhesive layer is provided, one end of which is bonded to the first surface of the first segment, and the other end of which is bonded to the first surface of the second segment; wherein, along the length direction of the current collector, the bonding length between the first integral adhesive layer and the first segment is L3. A second integral adhesive layer is provided, one end of which is bonded to the second surface of the first segment, and the other end of which 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 cut position and the second cut position; The first cutting position and the second cutting position are separated by 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; Cut the first integral adhesive layer and the second integral adhesive layer along the first position; The current collector is cut several times to obtain a first current collector. Along the length direction of the first current collector, the first cutting position forms the first starting end of the first current collector, and the second cutting position forms the first ending end of the first current collector. A first electrode is fabricated based on the first current collector, a second electrode is provided, and a wound electrode assembly is fabricated; wherein, the first starting end of the first electrode is located in the second inner circle electrode of the electrode assembly, the first ending end is located in the second outer circle electrode of the electrode assembly, the outermost circle diameter of the electrode assembly is R1, the innermost circle diameter of the electrode assembly is R2, and the second inner circle electrode diameter of the electrode assembly is R4. A housing is provided, and the electrode assembly is disposed within the housing, wherein the diameter of the housing is R3; satisfying: L1≥π(R3-R1+R4-R2)+1 / (4×L3).

16. The method according to claim 15, characterized in that, The method further includes: Along the length of the current collector, the bonding length between the first integral adhesive layer and the second segment is L9, and the length between the first position and the second cut position is L. 11 ; Satisfy: L 11 ≥π(R3-R1+R4-R2)+1 / (4×L9).

17. The method according to claim 15 or 16, characterized in that, The method further includes: Along the length of the current collector, the bonding length between the second integral adhesive layer and the first segment is L4, and the bonding length between the second integral adhesive layer and the second segment is L. 10 ; Satisfying: 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, characterized in that, Including the cylindrical battery as described in any one of claims 1 to 17.

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