Secondary battery and electronic device

Abstract

The invention provides a secondary battery and an electronic device, the secondary battery comprises a winding type electrode assembly, the electrode assembly comprises a first pole piece, each circle of the first pole piece comprises two straight areas, and the width of the straight areas is Lmm along the width direction of the electrode assembly. A plurality of through holes are formed in the first area and the second area of at least one circle of first pole piece, and the plurality of through holes in the second area are symmetrical to the plurality of through holes in the first area along the center line. A first through hole is formed in the position close to the first edge, N through holes are formed in the first area in the direction from the first edge to the center, N is larger than or equal to 5 and smaller than or equal to 20, and N is a positive integer; the diameter of the maximum circumcircle of the outer contour of the first through hole is D1 mm, D1 = A * L, 1.5% < = A < = 6%, the diameter of the maximum circumcircle of the outer contour of the nth through hole is Dnmm, Dn = Bn-1 * D1, 2 < = n < = N, and 0.6 < = B < = 0.9. Through the arrangement, the cycle performance of the secondary battery is improved.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a secondary battery and an electronic device. Background Art

[0002] Secondary batteries have the advantages of good rate performance, light weight, long cycle life, no memory effect and good stability. They are widely used energy storage and power products under current technical conditions.

[0003] With the demand for high-capacity applications, the volume of secondary batteries has gradually increased, and the length and width of the pole pieces in the secondary batteries have also increased accordingly, making the pole pieces susceptible to black spots due to insufficient electrolyte infiltration, thereby reducing the cycle performance of the secondary batteries. Summary of the invention

[0004] The purpose of the present application is to provide a secondary battery and an electronic device to improve the wetting of the electrolyte on the pole piece, especially the middle part of the pole piece, thereby improving the cycle performance of the secondary battery while taking into account the strength of the pole piece.

[0005] It should be noted that in the invention content of this application, lithium-ion batteries are used as an example of secondary batteries to explain this application, but the secondary batteries of this application are not limited to lithium-ion batteries. The specific technical solutions are as follows:

[0006] The first aspect of the present application provides a secondary battery, comprising a wound electrode assembly, the electrode assembly comprising a first electrode sheet, each circle of the first electrode sheet comprising two straight areas and two bending areas connected to the two straight areas, the two bending areas being arranged oppositely along the width direction of the electrode assembly; along the width direction of the electrode assembly, any straight area has a first edge and a second edge opposite to each other, the width of a single straight area is L mm, the position at L / 2 from the first edge or the second edge is the center of the straight area, the straight line passing through the center and perpendicular to the width direction of the electrode assembly is the center line of the straight area, the area from the first edge to the center line is the first area of ​​the straight area, and the area from the center line to the second edge is the second area of ​​the straight area. A plurality of through holes are arranged on the first area and the second area of ​​at least one circle of the first electrode sheet, the plurality of through holes in the second area are symmetrical with the plurality of through holes arranged on the first area along the center line; the first through hole is arranged near the first edge, and N through holes are arranged in sequence on the first area along the direction from the first edge to the center line, 5≤N≤20 and N is a positive integer. The diameter of the maximum circumscribed circle of the outer contour of the first through hole on the surface of the first electrode is D 1 mm, D 1 =A×L, 1.5%≤A≤6%, optionally, 1.8%≤A≤3.75%. The diameter of the maximum circumscribed circle of the outer contour of the nth through hole on the surface of the first pole piece is D n mm, D n =Bn-1 ×D 1 , 2≤n≤N, 0.6≤B≤0.9. By setting the through holes and adjusting the values ​​of N, A and B within the above range, while taking into account the strength of the electrode sheet of the secondary battery, it is beneficial to shorten the flow path of the electrolyte in the width direction of the first electrode sheet in the wound state, and improve the penetration efficiency of the electrolyte in the width direction of the first electrode sheet in the wound state. In addition, the through holes set on the first electrode sheet absorb and store the electrolyte, and an electrolyte potential difference is formed at the position of the middle part of the electrode assembly where the electrolyte is easily consumed, thereby improving the replenishment efficiency of the electrolyte during the cycle of the secondary battery, strengthening the infiltration effect of the electrolyte on the electrode assembly, and thus improving the cycle performance of the secondary battery.

[0007] In one or more embodiments, the first pole piece includes a first current collector and a first material layer located on at least one surface of the first current collector. Based on the surface area of ​​the straight area, the sum of the areas of the outer contours of the through holes on the first material layer in any straight area accounts for S, 0.5%≤S≤18%. By adjusting the sum of the areas of the outer contours of the plurality of through holes to account for within the above range, while taking into account the strength of the first pole piece, it is beneficial to shorten the flow path of the electrolyte in the width direction of the first pole piece in the wound state, improve the penetration efficiency of the electrolyte in the width direction of the first pole piece in the wound state, and reduce the risk of black spots or lithium precipitation in the middle of the electrode assembly due to insufficient electrolyte infiltration in the middle of the wound electrode assembly in the late cycle of the secondary battery due to insufficient electrolyte, shorten the flow path of the electrolyte in the width direction of the first pole piece in the wound state, thereby improving the cycle performance of the secondary battery and taking into account the safety performance of the secondary battery.

[0008] In one or more embodiments, along the width direction of the electrode assembly, the spacing between two adjacent through holes located on the first region is 5 mm to 22 mm. By adjusting the spacing between two adjacent through holes located on the first region within the above range, the distance between the two adjacent through holes is moderate, which is conducive to improving the wetting effect of the electrolyte on the electrode sheet, especially the middle part of the electrode sheet, while reducing the actual production and processing difficulty, as well as the risk of local collapse of the first electrode sheet during the processing process, improving the electrolyte infiltration efficiency and wetting performance of the electrode assembly, thereby improving the cycle performance of the secondary battery.

[0009] In one or more embodiments, the thickness of the electrode assembly is T mm, and along the width direction of the electrode assembly, the distance between the first through hole and the first edge is L 1 mm, T / 2≤L 1 ≤L / 4, 20≤T≤70. By adjusting L 1The values ​​of and T being within the above ranges are conducive to reducing the risk of insufficient infiltration of the electrolyte into the electrode sheet, and at the same time are conducive to reducing the risk of local collapse of the flat area of ​​the through hole to the first electrode sheet, thereby improving the wetting efficiency and wetting performance of the electrolyte on the electrode sheet, and improving the wetting effect of the electrolyte on the electrode assembly, thereby improving the cycle performance of the secondary battery while taking into account the safety performance of the secondary battery.

[0010] In one or more embodiments, the first electrode sheet includes a first current collector and a first material layer located on at least one surface of the first current collector. Along the length direction of the electrode assembly, the first material layer in the straight region has a third edge and a fourth edge opposite to each other, and the shortest distance between a single through hole and the third edge or the fourth edge is L. 2 mm, 5≤L 2 ≤10. By adjusting L 2 The value of is within the above range, which reduces the risk of the through hole being set too close to the edge of the material layer, resulting in bending of the edge of the first electrode or powdering of the material layer, and is beneficial to reducing the risk of insufficient infiltration of the electrode by the electrolyte, and is also beneficial to reducing the influence of the setting of the through hole on the strength of the first electrode, thereby improving the wetting efficiency and wetting performance of the electrolyte on the electrode, improving the wetting effect of the electrolyte on the electrode, and improving the cycle performance of the secondary battery, while taking into account the safety performance of the secondary battery.

[0011] In one or more embodiments, the first pole piece includes a first current collector and a first material layer located on at least one surface of the first current collector, and the thickness of the first material layer on a single surface of the first current collector is H. 1 μm, 120≤H 1 ≤600. By adjusting the thickness H of the first material layer 1 Within the above range, the safety risk caused by the poor strength of the electrode due to the thin material layer is reduced, which is conducive to reducing the actual processing difficulty, improving the diffusion efficiency of the electrolyte, improving the wetting effect of the electrolyte on the electrode, and improving the cycle performance of the secondary battery.

[0012] In one or more embodiments, the thickness of the first current collector is H 2 μm, 5≤H 2 ≤20. By adjusting the thickness H of the first current collector 2 Within the above range, it is beneficial to reduce the processing difficulty of the first pole piece, while taking into account the cycle performance of the secondary battery, and improving the strength of the first pole piece.

[0013] In one or more embodiments, 80≤L≤600. By adjusting the width L of a single straight region within the above range, it is beneficial to reduce the processing difficulty while taking into account the strength and cycle performance of the first pole piece.

[0014] In one or more embodiments, the first electrode sheet is a positive electrode sheet and / or a negative electrode sheet. By providing a through hole on the straight area of ​​the positive electrode sheet and / or the negative electrode sheet, it is beneficial to improve the wetting efficiency and wetting performance of the electrolyte on the electrode sheet, especially the middle part of the electrode sheet, and improve the wetting effect of the electrolyte on the electrode sheet, thereby improving the cycle performance of the secondary battery while taking into account the strength of the electrode sheet.

[0015] In one or more embodiments, the shape of the outer contour of a single through hole includes one of a circle, an ellipse or a polygon. By adjusting the shape of the outer contour of the through hole within the above range, the actual processing difficulty is reduced, the wetting performance of the electrode assembly is taken into account, and the production efficiency is improved.

[0016] In one or more embodiments, the secondary battery is a soft pack secondary battery or a square secondary battery.

[0017] The second aspect of the present application provides an electronic device, which includes the secondary battery in any of the above embodiments. The secondary battery of the present application has good cycle performance, so the electronic device of the present application has a long service life.

[0018] Beneficial effects of the embodiments of the present application:

[0019] The embodiments of the present application provide a secondary battery and an electronic device. By setting through holes of different sizes on each circle of the first electrode sheet along the width direction of the electrode assembly, it is beneficial to improve the infiltration of the electrolyte into the electrode sheet, shorten the transmission path of the electrolyte on the electrode sheet, and take into account the strength of the electrode sheet, so that the secondary battery has both safety performance and good cycle performance.

[0020] Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and a person skilled in the art can also obtain other embodiments based on these drawings.

[0022] Figure 1 A schematic diagram of a winding structure formed by an electrode assembly in one embodiment of the present application;

[0023] Figure 2 for Figure 1 A schematic diagram of a first straight region of a first pole piece in one circle of a winding structure formed by an electrode assembly;

[0024] Figure 3 for Figure 1A schematic diagram of a part of the structure of a first straight region of a first electrode sheet in a winding structure formed by an electrode assembly along the width direction and the length direction of the electrode assembly;

[0025] Figure 4 This is a partial structural schematic diagram of a first electrode sheet located in a first straight region along the thickness direction of an electrode assembly in one embodiment of the present application;

[0026] Figure 5 A schematic diagram of a winding structure formed by an electrode assembly in another embodiment of the present application;

[0027] Figure 6 Schematic diagram of the diffusion of electrolyte on part of the first pole piece during the wettability test of the first pole piece.

[0028] Figure numerals: electrode assembly 001; first pole piece 10; straight area 101; first straight area 1011; bending area 102; through hole 20; first through hole 21; first edge 31; second edge 32; center 33 of the straight area; center line 34; third edge 35; fourth edge 36; first current collector 41; first material layer 42. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present application and the accompanying drawings to clearly and completely describe the technical solutions in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0030] As the volume of the secondary battery increases, the length and width of the pole piece in the secondary battery also increase, which easily leads to the problem of insufficient electrolyte infiltration in the middle of the pole piece. In the later stage of the secondary battery cycle, the pole piece, especially the middle of the pole piece, is prone to black spots or lithium precipitation, resulting in a decrease in the cycle performance of the secondary battery. Based on this, the present application provides a secondary battery, which has a good infiltration effect on the pole piece due to the shortened transmission path of the electrolyte on the pole piece, and the secondary battery has good cycle performance.

[0031] It should be noted that in the specific implementation of the present application, lithium-ion batteries are used as an example of secondary batteries to explain the present application, but the secondary batteries of the present application are not limited to lithium-ion batteries. The specific technical solutions are as follows:

[0032] The first aspect of the present application provides a secondary battery, comprising a wound electrode assembly, the electrode assembly comprising a first electrode sheet, each circle of the first electrode sheet comprising two straight areas and two bending areas connected to the two straight areas, the two bending areas being arranged oppositely along the width direction of the wound electrode assembly; along the width direction of the electrode assembly, any straight area has a first edge and a second edge opposite to each other, the width of a single straight area is L mm, the position at L / 2 from the first edge or the second edge is the center of the straight area, the straight line passing through the center and perpendicular to the width direction of the electrode assembly is the center line of the straight area, the area from the first edge to the center line is the first area of ​​the straight area, and the area from the center line to the second edge is the second area of ​​the straight area. A plurality of through holes are arranged on the first area and the second area of ​​at least one circle of the first electrode sheet, the plurality of through holes in the second area are symmetrical with the plurality of through holes arranged on the first area along the center line; the first through hole is arranged near the first edge, and N through holes are arranged in sequence on the first area along the direction from the first edge to the center line, 5≤N≤20, and N is a positive integer. For example, the value of N may be any one of 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20. The diameter of the maximum circumscribed circle of the outer contour of the first through hole on the surface of the first electrode piece is D 1 mm, D 1 =A×L, 1.5%≤A≤6%, optionally, 1.8%≤A≤3.75%. For example, the value of A can be any one of 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.2%, 2.5%, 2.8%, 3%, 3.25%, 3.5%, 3.75%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5.0%, 5.2%, 5.5%, 5.8%, 6%. The diameter of the maximum circumscribed circle of the outer contour of the nth through hole on the surface of the first pole piece is D n mm, D n =B n-1 ×D 1 , 2≤n≤N, 0.6≤B≤0.9, for example, when N is 20, 2≤n≤20, the value of n can be any one of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20; the value of B can be any one of 0.6, 0.64, 0.68, 0.71, 0.75, 0.79, 0.83, 0.87, 0.9. In the present application, it can be understood that "multiple" means two or more, and "through hole" means a hole that passes through the material layer and the current collector of the first pole piece, and the thickness of the through hole is the sum of the thickness of the first current collector and the first material layer in the first pole piece.

[0033] In the present application, the first electrode sheet can be a positive electrode sheet and / or a negative electrode sheet. For ease of understanding, the electrode assembly is defined as having its own width direction as the X direction, its own thickness direction as the Y direction, and its own length direction as the Z direction in a wound state. It is understandable that the positive electrode sheet, the positive electrode material layer, the positive electrode collector, the negative electrode sheet, the negative electrode material layer, the negative electrode collector, and the separator are in the same length direction, width direction, and thickness direction as the electrode assembly in a wound state. For example, Figure 1 to Figure 2 As shown, the electrode assembly 001 is formed by stacking and winding a separator, a positive electrode sheet, a separator, and a negative electrode sheet. The positive electrode sheet includes a positive electrode collector and a positive electrode material layer arranged on both surfaces of the positive electrode collector. The negative electrode sheet includes a negative electrode collector and a negative electrode material layer arranged on both surfaces of the negative electrode collector. The first electrode sheet 10 is a negative electrode sheet. In the wound state, the electrode assembly 001 includes multiple turns of the first electrode sheet 10. Each turn of the first electrode sheet 10 includes two straight areas 101 and two bending areas 102 arranged oppositely along the width direction (X direction) of the electrode assembly 001. Along the width direction (X direction) of the electrode assembly 001 (i.e., the length direction after the first electrode sheet 10 is unfolded), any straight area 101 has a first edge 31 and a second edge 32 opposite to each other. Among them, the first straight area 1011 includes a first edge 31 and a second edge 32. The straight line passing through the center 33 of the first straight area 1011 and perpendicular to the width direction (X direction) of the electrode assembly 001 (that is, the length direction of the first electrode piece 10 after unfolding) is the center line 34 of the first straight area 1011. The area from the first edge 31 to the center line 34 of the first straight area 1011 is the first area of ​​the first straight area 1011. The area from the center line 34 of the first straight area 1011 to the second edge 32 is the second area of ​​the first straight area 1011. The first area and the second area are symmetrical about the center line 34.

[0034] Along the width direction (X direction) of the electrode assembly (i.e., the length direction of the first electrode sheet 10 after unfolding), through holes 20 are provided on both the first area and the second area of ​​the first straight area 1011. The through holes 20 provided on the second area are symmetrical with the through holes 20 provided on the first area along the center line 34, and thus the through holes 20 in the first area are symmetrical with the through holes 20 in the second area along the center line 34. The first through hole 21 is provided near the first edge 31, and five through holes are provided in sequence on the first area along the direction from the first edge 31 to the center line 34. It should be noted that the number, size, and spacing of the through holes in the figure are only for exemplary purposes.

[0035] When the value of N, A, and / or; B is too small, that is, less than the lower limit of the present application, the number of through holes set on the first area of ​​the first straight area of ​​the first pole piece is insufficient, and / or; each through hole is too small, the electrolyte has few flow paths in the width direction of the first pole piece in the wound state (i.e., the length direction of the first pole piece after unfolding), and the electrolyte is insufficiently infiltrated in the thickness direction of the electrode assembly, and the middle part of the wound electrode assembly is insufficiently infiltrated. In the late cycle of the secondary battery, the middle part of the electrode assembly is prone to black spots or lithium precipitation due to insufficient electrolyte, thereby failing to effectively improve the cycle performance of the secondary battery. When the value of N, A, and / or; B is too large, that is, greater than the upper limit of the present application, due to the excessive number of through holes set on the first pole piece, and / or; each through hole is too large, resulting in a decrease in the strength of the straight area of ​​the first pole piece, and the strength of the first pole piece is reduced accordingly, thereby affecting the safety performance of the secondary battery. Moreover, in the actual production process, a large number of through holes is not conducive to the processing and large-scale production of electrode assemblies. The present application provides through holes and adjusts the values ​​of N, A and B within the above ranges, which is beneficial to shortening the flow path of the electrolyte in the width direction of the electrode assembly in the wound state (i.e., the length direction after the first electrode sheet is unfolded) while taking into account the safety performance of the secondary battery, and improving the penetration efficiency of the electrolyte in the width direction of the electrode assembly in the wound state (i.e., the length direction after the first electrode sheet is unfolded). In addition, the through holes provided on the first electrode sheet absorb and store the electrolyte, and form an electrolyte potential difference at the position of the middle part of the electrode assembly where the electrolyte is easily consumed, thereby improving the replenishment efficiency of the electrolyte during the cycle of the secondary battery, enhancing the infiltration effect of the electrolyte on the electrode assembly, and thus improving the cycle performance of the secondary battery. In the present application, the above-mentioned "a plurality of through holes are provided on both the first area and the second area of ​​at least one circle of the first electrode sheet" means that a plurality of through holes are provided on the first area and the second area of ​​a circle of the first electrode sheet, or a plurality of through holes are provided on the first area and the second area of ​​multiple circles of the first electrode sheet.

[0036] In one or more embodiments, 80≤L≤600. For example, the value of L may be any one of 80, 140, 180, 220, 260, 290, 320, 340, 380, 420, 460, 500, 550, and 600. By adjusting the value of L within the above range, it is beneficial to shorten the flow path of the electrolyte in the width direction of the electrode assembly in the wound state (i.e., the length direction after the first electrode sheet is unfolded), and the effect of improving the penetration efficiency of the electrolyte in the width direction of the electrode assembly in the wound state (i.e., the length direction after the first electrode sheet is unfolded) is more obvious. While taking into account the safety performance of the secondary battery, the cycle performance of the secondary battery is further improved, while taking into account the actual production needs and reducing the processing difficulty.

[0037] In one or more embodiments, the first pole piece includes a first current collector and a first material layer located on at least one surface of the first current collector, and based on the surface area of ​​the straight region, the sum of the areas of the outer contours of the through holes on the first material layer of any straight region accounts for S, 0.5%≤S≤18%. For example, the value of S can be any one of 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, and 18%. By regulating the value of S within the above range, while taking into account the strength of the first electrode sheet, it is beneficial to shorten the flow path of the electrolyte in the width direction of the electrode assembly in the wound state (i.e., the length direction after the first electrode sheet is unfolded), and improve the penetration efficiency of the electrolyte in the width direction of the electrode assembly in the wound state (i.e., the length direction after the first electrode sheet is unfolded). It is beneficial to reduce the risk of black spots or lithium precipitation in the middle of the electrode assembly due to insufficient electrolyte infiltration into the middle of the wound electrode assembly in the late cycle of the secondary battery, shorten the flow path of the electrolyte in the width direction of the electrode assembly in the wound state (i.e., the length direction after the first electrode sheet is unfolded), thereby improving the cycle performance of the secondary battery and taking into account the safety performance of the secondary battery.

[0038] In one or more embodiments, along the width direction of the electrode assembly, the distance L between two adjacent through holes located in the first region is 3 5mm to 22mm. For example, L 3 The value of can be any one of 5, 6, 8, 10, 12, 14, 15, 18, 20, 22. Figure 2 As shown, along the width direction (X direction) of the electrode assembly 001 (i.e., the length direction of the first electrode sheet after unfolding), the distance between two adjacent through holes 20 located in the first area is L 3 mm. In this application, the spacing between two adjacent through holes refers to the shortest distance between the through hole edge of any through hole and the through hole edge of the adjacent through hole along the width direction of the electrode assembly (i.e., the length direction of the first electrode sheet after unfolding). 3 The value of is within the above range, so that the distance between two adjacent through holes is moderate, which is beneficial to improving the wetting effect of the electrolyte on the electrode sheet, especially the middle part of the electrode sheet, while reducing the difficulty of actual production and processing, as well as the risk of local collapse of the first electrode sheet during processing, and improving the wetting efficiency and wetting performance of the electrolyte on the electrode assembly, thereby improving the cycle performance of the secondary battery.

[0039] In one or more embodiments, the thickness of the electrode assembly is T mm, and along the width direction of the electrode assembly, the distance between the first through hole and the first edge is L 1 mm, T / 2≤L 1≤L / 4, 20≤T≤70. For example, the value of T can be any one of 20, 25, 30, 40, 45, 50, 55, 60, 65, 70. Figure 2 As shown, along the width direction (X direction) of the electrode assembly 001 (i.e., the length direction of the first electrode sheet after unfolding), the distance between the first through hole 21 and the first edge 31 is L 1 mm. In this application, the distance between the first through hole and the first edge along the width direction of the electrode assembly refers to the shortest distance between the through hole edge of the first through hole and the first edge along the width direction of the electrode assembly (i.e., the length direction of the first electrode after unfolding). In addition, the first through hole is the through hole closest to the first edge, and the distances between other through holes and the first edge are not less than the distance between the first through hole and the first edge. By adjusting L 1 The values ​​of and T being within the above ranges are beneficial to reducing the risk of insufficient infiltration of the electrolyte into the electrode sheet, and at the same time are beneficial to reducing the risk of local collapse of the through hole on the straight area of ​​the first electrode sheet, thereby improving the wetting efficiency and wetting performance of the electrolyte on the electrode sheet, and improving the wetting effect of the electrolyte on the electrode assembly, thereby improving the cycle performance of the secondary battery, while taking into account the safety performance and processing performance of the secondary battery.

[0040] In one or more embodiments, 10≤L 1 ≤150, for example, L 1 The value of can be any one of 10, 25, 45, 65, 80, 90, 100, 110, 130, 150. By adjusting L 1 The value of is within the above range, which is beneficial to reducing the risk of insufficient infiltration of the electrolyte into the electrode sheet, and at the same time is beneficial to reducing the risk of local collapse of the straight area of ​​the through hole to the first electrode sheet, thereby improving the wetting efficiency and wetting performance of the electrolyte on the electrode sheet, and improving the wetting effect of the electrolyte on the electrode assembly, thereby improving the cycle performance of the secondary battery, while taking into account the safety performance and processing performance of the secondary battery.

[0041] In one or more embodiments, 10≤L 1 ≤40, for example, L 1 The value of can be any one of 10, 15, 20, 25, 27, 30, 34, 38, 40. By adjusting L 1 The value of is within the above range, which is beneficial to reducing the risk of insufficient infiltration of the electrolyte into the electrode sheet, and at the same time is beneficial to reducing the risk of local collapse of the straight area of ​​the through hole to the first electrode sheet, thereby improving the wetting efficiency and wetting performance of the electrolyte on the electrode sheet, and improving the wetting effect of the electrolyte on the electrode assembly, thereby improving the cycle performance of the secondary battery, while taking into account the safety performance and processing performance of the secondary battery.

[0042] In one or more embodiments, the first electrode sheet includes a first current collector and a first material layer located on at least one surface of the first current collector. Along the length direction of the electrode assembly, the first material layer in the straight region has a third edge and a fourth edge opposite to each other, and the shortest distance between a single through hole and the third edge or the fourth edge is L. 2 mm, 5≤L 2 ≤10. For example, L 2 The value of can be any one of 5, 6, 7, 7.5, 8, 9, and 10. Figure 3 As shown, along the length direction (Z direction) of the electrode assembly 001 (i.e., the width direction of the first electrode sheet after unfolding), the first material layer of the straight region 101 has a third edge 35 and a fourth edge 36 opposite to each other, the first through hole 21 is close to the third edge 35, and the shortest distance between the first through hole 21 and the third edge 35 is L 2 mm. In the present application, the shortest distance between a through hole and the third edge or the fourth edge along the length direction of the electrode assembly refers to the shortest distance between the through hole edge of any through hole and the third edge or the fourth edge along the length direction of the electrode assembly (i.e. the width direction after the first electrode piece is unfolded). Moreover, along the length direction of the electrode assembly (i.e. the width direction after the first electrode piece is unfolded), the distance between any through hole and the third edge or the fourth edge is not less than the above shortest distance. By adjusting L 2 When the value is within the above range, the risk of the through hole being set too close to the edge of the material layer, resulting in bending of the edge of the first electrode or powdering of the material layer, is reduced, and the risk of insufficient infiltration of the electrolyte into the electrode is reduced. At the same time, it is beneficial to reduce the impact of the setting of the through hole on the safety performance of the first electrode, improves the wetting efficiency and wetting performance of the electrolyte on the electrode, improves the wetting effect of the electrolyte on the electrode, improves the cycle performance of the secondary battery, and takes into account the safety performance of the secondary battery.

[0043] In one or more embodiments, the first pole piece includes a first current collector and a first material layer located on at least one surface of the first current collector, and the thickness of the first material layer on a single surface of the first current collector is H. 1 μm, 120≤H 1 ≤600. For example, H 1 The value of can be any one of 120, 160, 200, 260, 320, 360, 420, 480, 520, 580, 600. Figure 4 As shown, the first pole piece 10 includes a first current collector 41 and a first material layer 42 located on two surfaces of the first current collector 41. The thickness of the first material layer 42 on one side of the first current collector is H. 1 μm. By regulating H 1The value of is within the above range, which reduces the safety risk caused by the poor strength of the electrode due to the thin material layer, is conducive to reducing the actual processing difficulty, improving the diffusion efficiency of the electrolyte, improving the infiltration effect of the electrolyte on the electrode, and improving the cycle performance of the secondary battery. In this application, the thickness of the first material layer H 1 It can be regulated by means known to those skilled in the art. For example, when the slurry is coated on the surface of the first current collector, the amount of coating per unit area is increased to increase the thickness of the first material layer on the basis of other conditions remaining unchanged and the solid content of the slurry being constant. The present application does not impose any particular limitation as long as the purpose of the present application can be achieved.

[0044] In one or more embodiments, the thickness of the first current collector is H 2 μm, 5≤H 2 ≤20. For example, H 2 The value of can be any one of 5, 6, 8, 10, 12.5, 15, 17, and 20. Figure 4 As shown, the thickness of the first current collector 41 of the first pole piece 10 is H 2 μm. By regulating H 2 The value of is within the above range, which is conducive to reducing the difficulty of processing the first pole piece, taking into account the cycle performance of the secondary battery, and improving the strength of the first pole piece. 2 There is no particular limitation on the regulation method, as long as the purpose of this application can be achieved. For example, commercially available current collectors with different thicknesses can be selected, and combined with the "N, A, B, S, L" in this application. 1 , L 2 , L 3 , H 1 , H 2 The thickness of the current collector of the first pole piece is determined by the "test" test method, and then the current collector of the first pole piece with the required thickness is selected.

[0045] In one or more embodiments, each circle of the first electrode plate includes a first straight area and a second straight area, and along the thickness direction of the electrode assembly, there is at least a partial overlap area between the projections of the multiple corresponding through holes in the multiple first straight areas.

[0046] In one or more embodiments, each circle of the first electrode sheet includes a first straight region and a second straight region, and along the thickness direction of the electrode assembly, there is at least a partial overlap between the projections of the multiple corresponding through holes in the multiple second straight regions.

[0047] In one or more embodiments, each circle of the first electrode plate includes a first straight area and a second straight area, and multiple first straight areas in the electrode assembly are provided with multiple through holes, and along the thickness direction of the electrode assembly, there is at least a partial overlap between the projections of the multiple through holes corresponding to each other in the multiple first straight areas, and, multiple second straight areas in the electrode assembly are provided with multiple through holes, and along the thickness direction of the electrode assembly, there is at least a partial overlap between the projections of the multiple through holes corresponding to each other in the multiple second straight areas.

[0048] In the present application, through holes are provided on the first straight areas and / or second straight areas of multiple turns of first pole pieces, and there is at least a partial overlapping area between the projections of the multiple through holes corresponding to each other in the multiple first straight areas and / or multiple second straight areas along the thickness direction of the electrode assembly. Along the thickness direction of the electrode assembly, the multiple through holes corresponding to each other in the multiple first straight areas and / or multiple second straight areas shorten and increase the flow path of the electrolyte. When the electrode assembly is injected with liquid, the electrolyte flows through the flow path formed by the multiple through holes corresponding to each other in the multiple first straight areas and / or multiple second straight areas, and infiltrates into each turn of the first pole piece where the through holes are located, thereby shortening the infiltration path of the electrolyte, improving the infiltration speed, and thereby improving the cycle performance of the electrode assembly.

[0049] In one or more embodiments, along the length direction of the electrode assembly (i.e., the width direction of the first pole piece after it is unfolded), the through holes arranged on any straight area of ​​the first pole piece are distributed in a matrix. In the present application, along the width direction of the first pole piece after it is unfolded, multiple rows of through holes are arranged in any straight area, and the spacing between the corresponding through holes in each row is equal. The present application does not have any special restrictions on the number of rows of through holes. Those skilled in the art can set them according to the actual specifications of the first pole piece, as long as the purpose of the present application can be achieved. For example, the number of rows of through holes arranged on the first straight area of ​​the first pole piece can be 1 to 20 rows.

[0050] In one or more embodiments, the shape of the outer contour of a single through hole includes one of a circle, an ellipse or a polygon. In the present application, there is no particular limitation on the shape of the polygon, as long as the purpose of the present application can be achieved. For example, the shape of the outer contour of a single through hole can be independently selected from one of a triangle, a rectangle, a trapezoid, a square, a pentagon or a hexagon. By adjusting the shape of the outer contour of the through hole, the actual processing difficulty is reduced and the actual production efficiency is improved.

[0051] In one or more embodiments, the first electrode sheet is a negative electrode sheet. By providing a plurality of through holes on the straight area of ​​at least one circle of the negative electrode sheet, it is beneficial to further improve the wetting efficiency and wetting performance of the electrolyte on the negative electrode sheet, especially the middle part of the negative electrode sheet, better improve the wetting effect of the electrolyte on the negative electrode sheet, and improve the cycle performance of the secondary battery.

[0052] In one or more embodiments, the first electrode sheet is a positive electrode sheet. By providing a plurality of through holes on the straight area of ​​at least one circle of the positive electrode sheet, it is beneficial to further improve the wetting efficiency and wetting performance of the electrolyte on the positive electrode sheet, especially the middle part of the positive electrode sheet, better improve the wetting effect of the electrolyte on the positive electrode sheet, and improve the cycle performance of the secondary battery.

[0053] When the first electrode sheet is a positive electrode sheet or a negative electrode sheet, the electrode assembly further includes a second electrode sheet. For example, when the first electrode sheet is a negative electrode sheet, the second electrode sheet is a positive electrode sheet; when the first electrode sheet is a positive electrode sheet, the second electrode sheet is a negative electrode sheet.

[0054] In one or more embodiments, the first electrode sheet is a positive electrode sheet and a negative electrode sheet. Figure 5 As shown, along the width direction (X direction) of the electrode assembly 001 (i.e., the length direction of the first electrode sheet 10 after it is unfolded), the first electrode sheet 10 is a positive electrode sheet and a negative electrode sheet, and five through holes 20 are arranged on the first area of ​​each straight area of ​​each circle of positive electrode sheets and negative electrode sheets. By arranging a plurality of through holes on the straight areas of at least one circle of positive electrode sheets and at least one circle of negative electrode sheets, it is beneficial to improve the wetting efficiency and wetting performance of the electrolyte on the electrode sheets, especially the middle part of the electrode sheets, and improve the wetting effect of the electrolyte on the electrode sheets, thereby improving the cycle performance of the secondary battery.

[0055] In the present application, when the first electrode sheet is a positive electrode sheet, “the first electrode sheet includes a first current collector and a first material layer located on at least one surface of the first current collector” means that the positive electrode sheet includes a positive current collector and a positive electrode material layer located on at least one surface of the positive current collector. The above-mentioned “positive electrode material layer located on at least one surface of the positive electrode current collector” means that the positive electrode material layer can be arranged on one surface of the positive electrode current collector along its own thickness direction, or can be arranged on two surfaces of the positive electrode current collector along its own thickness direction. It should be noted that the “surface” here refers to the coating area of ​​the positive electrode current collector where the positive electrode material layer is arranged. The present application has no special restrictions on the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, the positive electrode current collector may include aluminum foil, aluminum alloy foil or a composite current collector (such as an aluminum-carbon composite current collector). The positive electrode material layer of the present application includes a positive electrode active material. The present application has no special restrictions on the type of positive electrode active material, as long as the purpose of the present application can be achieved. For example, the positive electrode active material may include lithium nickel cobalt manganese oxide (LiNi 0.90 Co 0.05 Mn 0.05 O 2 (NCM955), NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO 2), lithium manganate, lithium iron manganese phosphate or lithium titanate, etc. In the present application, the positive electrode active material may also contain non-metallic elements, for example, the non-metallic elements include at least one of fluorine, phosphorus, boron, chlorine, silicon or sulfur. In the present application, the positive electrode material layer may also include a positive electrode binder and a conductive agent. The present application does not particularly limit the type of positive electrode binder in the positive electrode material layer, as long as the purpose of the present application can be achieved. For example, the positive electrode binder may include but is not limited to polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acid salt, polyvinyl pyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene. The present application does not particularly limit the type of conductive agent in the positive electrode material layer, as long as the purpose of the present application can be achieved. For example, the conductive agent may include but is not limited to at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, Ketjen black, graphene, metal materials or conductive polymers. The above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers may include but are not limited to vapor grown carbon fibers (VGCF) and / or nano carbon fibers. The above-mentioned metal materials may include but are not limited to metal powders and / or metal fibers. Specifically, the metal may include but is not limited to at least one of copper, nickel, aluminum or silver. The above-mentioned conductive polymers may include but are not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole. The present application does not particularly limit the mass ratio of the positive electrode active material, the conductive agent, and the positive electrode binder in the positive electrode material layer. Those skilled in the art can choose according to actual needs as long as the purpose of the present application can be achieved.

[0056] In the present application, when the first electrode sheet is a negative electrode sheet, the statement "the first electrode sheet includes a first current collector and a first material layer located on at least one surface of the first current collector" means that the negative electrode sheet includes a negative current collector and a negative electrode material layer located on at least one surface of the negative current collector. The above-mentioned "negative electrode material layer located on at least one surface of the negative current collector" means that the negative electrode material layer can be disposed on one surface of the negative current collector along its thickness direction, or can be disposed on both surfaces of the negative current collector along its thickness direction. It should be noted that the "surface" here refers to the coating area of the negative current collector where the negative electrode material layer is provided. The present application places no particular limitation on the negative current collector, as long as the purpose of the present application can be achieved. For example, the negative current collector can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a composite current collector (such as a lithium-copper composite current collector, a carbon-copper composite current collector, a nickel-copper composite current collector, a titanium-copper composite current collector, etc.). The negative electrode material layer of the present application contains a negative electrode active material. The present application places no particular limitation on the type of the negative electrode active material, as long as the purpose of the present application can be achieved. For example, the negative electrode active material can include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0 < x < 2), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , lithium titanate Li with a spinel structure 4 Ti 5 O 12 , Li-Al alloy, or at least one of metallic lithium. Optionally, the negative electrode material layer may further include a conductive agent and a negative electrode binder. The present application places no particular limitation on the type of the conductive agent in the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the conductive agent can be of the same type as the conductive agent in the above-mentioned positive electrode material layer. The present application places no particular limitation on the type of the negative electrode binder in the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the negative electrode binder can be of the same type as the positive electrode binder in the above-mentioned positive electrode material layer. In the present application, the negative electrode material layer further includes a thickening agent. The present application places no particular limitation on the type of the thickening agent, as long as the purpose of the present application can be achieved. For example, the thickening agent can include at least one of carboxymethyl cellulose or sodium carboxymethyl cellulose. The present application places no particular limitation on the mass ratio of the negative electrode active material, conductive agent, negative electrode binder, and thickening agent in the negative electrode material layer, as long as the purpose of the present application can be achieved.

[0057] The present application has no particular restrictions on the preparation method of the first electrode sheet, as long as the purpose of the present application can be achieved. For example, the preparation method of the first electrode sheet includes but is not limited to the following steps: (1) preparing slurry; (2) coating the slurry on one surface of the first current collector, and drying to obtain the first electrode sheet with a material layer on one side; (3) coating the slurry on the other surface of the current collector, and drying to obtain the first electrode sheet with a material layer on both sides; (4) after cold pressing and stripping, pre-winding the first electrode sheet, determining two straight areas of each circle of the first electrode sheet and two bending areas connected to the two straight areas, the two bending areas are arranged oppositely along the width direction of the electrode assembly, and corresponding through holes are arranged on the straight areas of the first electrode sheet, and along the direction from the edge of each straight area to the center line of the straight area, the diameter of the maximum circumscribed circle of the outer contour of the through hole arranged on the surface of the first electrode sheet gradually decreases, so as to obtain the first electrode sheet.

[0058] The present application has no special restrictions on the solid content of the above-mentioned slurry, as long as the purpose of the present application can be achieved. The present application has no special restrictions on the temperature and time of the above-mentioned drying, as long as the purpose of the present application can be achieved. The present application has no special restrictions on the process parameters of the above-mentioned cold pressing and slitting, as long as the purpose of the present application can be achieved. The present application has no special restrictions on the above-mentioned way of setting the through holes, as long as the purpose of the present application can be achieved. For example, the through holes can be set by punching with a circular cutter, and the diameter of the maximum circumscribed circle of the outer contour of each through hole on the surface of the first pole piece is adjusted by adjusting the power and cutting depth of the circular cutter; the proportion S of the sum of the areas of the outer contours of multiple through holes is adjusted by adjusting the surface area of ​​the straight area, the number of through holes, the shape of the through holes, the power of the circular cutter, the cutting depth, the spacing between the circular cutters or the cutting frequency; the spacing L between two adjacent through holes 3 The control is performed by adjusting the spacing between the circular cutters or the cutting frequency; along the width direction of the electrode assembly (i.e., the length direction of the first electrode sheet after unfolding), the distance L between the first through hole and the first edge is 1 The control is performed by adjusting the spacing between the circular cutters or the cutting frequency; along the length direction of the electrode assembly (i.e. the width direction after the first electrode sheet is unfolded), the shortest distance L between a single through hole and the third edge or the fourth edge 2 It can be controlled by adjusting the spacing between circular cutters or cutting frequency.

[0059] In other embodiments, through holes can also be set by pulse laser drilling, and the diameter of the maximum circumscribed circle of the outer contour of each through hole on the surface of the first pole piece is regulated by adjusting the power and defocus of the pulse laser emitter; the proportion S of the sum of the areas of the outer contours of multiple through holes is regulated by adjusting the surface area of ​​the straight area, the number of through holes, the power of the pulse laser emitter, the defocus, the spacing between the pulse laser emitters or the laser emission frequency; the spacing L between two adjacent through holes is regulated by adjusting the surface area of ​​the straight area, the number of through holes, the power of the pulse laser emitter, the defocus, the spacing between the pulse laser emitters or the laser emission frequency; 3The control is performed by adjusting the spacing between the pulse laser emitters or the laser emission frequency; along the width direction of the electrode assembly (i.e., the length direction of the first electrode sheet after unfolding), the distance L between the first through hole and the first edge 1 The control is performed by adjusting the spacing between the pulse laser emitters or the laser emission frequency of the pulse laser emitters; along the length direction of the electrode assembly (i.e., the width direction after the first pole piece is unfolded), the shortest distance L between a single through hole and the third edge or the fourth edge 2 It can be controlled by adjusting the spacing between pulsed laser emitters or the laser emission frequency.

[0060] In the present application, it can be understood by those skilled in the art that when a through hole is provided on the first pole piece by circular cutting knife punching or pulsed laser punching, the thickness of the through hole is the sum of the thickness of the pole piece material layer and the thickness of the current collector.

[0061] The secondary battery in the present application includes an electrolyte, and the electrolyte includes a lithium salt and a non-aqueous solvent. The lithium salt may include LiPF 6 、LiNO 3 , LiBF 4 、LiClO 4 、LiB(C 6 H 5 ) 4 、LiCH 3 SO 3 、LiCF 3 SO 3 、LiN(SO 2 CF 3 ) 2 、LiC(SO 2 CF 3 ) 3 , Li 2 SiF 6, lithium bis(oxalatoborate) (LiBOB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium difluoroborate. The present application does not limit the content of lithium salt in the electrolyte, as long as the purpose of the present application can be achieved. The present application has no special restrictions on non-aqueous solvents, as long as the purpose of the present application can be achieved. For example, the non-aqueous solvent may include but is not limited to at least one of carbonate compounds, carboxylate compounds, ether compounds or other organic solvents. The above-mentioned carbonate compounds may include but are not limited to at least one of chain carbonate compounds, cyclic carbonate compounds or fluorocarbonate compounds. The above-mentioned chain carbonate compounds may include but are not limited to at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate or methyl ethyl carbonate. The above-mentioned cyclic carbonate may include but is not limited to at least one of ethylene carbonate, propylene carbonate (PC), butylene carbonate or vinyl ethylene carbonate. The fluorinated carbonate compound may include, but is not limited to, at least one of fluorinated ethylene carbonate, 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The above-mentioned carboxylate compound may include, but is not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decalactone, valerolactone, or caprolactone. The above-mentioned ether compound may include but is not limited to at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran. The above-mentioned other organic solvents may include but are not limited to at least one of dimethyl sulfoxide, 1,2-dioxolane, cyclopentane, methyl cyclopentane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate or trioctyl phosphate.

[0062] The present application has no particular restrictions on the diaphragm, as long as the purpose of the present application can be achieved. For example, the material of the diaphragm may include but is not limited to polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid. The type of diaphragm may include at least one of a woven membrane, a non-woven membrane, a microporous membrane, a composite membrane, a rolled membrane or a spun membrane. The diaphragm of the present application may have a porous structure, and the present application has no particular restrictions on the size of the pore size of the porous structure of the diaphragm, as long as the purpose of the present application can be achieved. For example, the size of the pore size can be 0.01 μm to 1 μm. The present application has no particular restrictions on the thickness of the diaphragm, as long as the purpose of the present application can be achieved. For example, the thickness of the diaphragm can be 5 μm to 40 μm.

[0063] In one or more embodiments, the secondary battery is a soft-pack secondary battery or a square secondary battery. By providing through holes of different sizes on each circle of the first pole piece along the width direction of the electrode assembly, it is beneficial to improve the infiltration of the electrolyte into the pole piece, shorten the transmission path of the electrolyte on the pole piece, and take into account the strength of the pole piece, so that the secondary battery has good cycle performance while taking into account safety performance.

[0064] The secondary battery of the present application is not particularly limited, and may include any device that generates an electrochemical reaction. In one or more embodiments of the present application, the secondary battery may include, but is not limited to, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0065] The present application has no particular restrictions on the preparation method of the secondary battery, and any preparation method known in the art may be selected as long as the purpose of the present application can be achieved. For example, the preparation method of the secondary battery includes but is not limited to the following steps: stacking the diaphragm, the first pole piece, the diaphragm and the second pole piece in sequence, and winding and folding them as needed to obtain an electrode assembly with a winding structure, placing the electrode assembly in a housing, injecting an electrolyte into the housing and sealing it to obtain a secondary battery.

[0066] The second aspect of the present application provides an electronic device, which includes the secondary battery in any of the above embodiments. The secondary battery of the present application has good cycle performance, so the electronic device of the present application has a long service life.

[0067] The electronic device of the present application is not particularly limited, and it can be used for any electronic device known in the prior art. For example, the electronic device can include but is not limited to a laptop computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0068] Example

[0069] Hereinafter, the embodiments of the present application will be described in more detail with reference to Examples and Comparative Examples. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are by mass.

[0070] Test methods and equipment:

[0071] N, A, B, S, L 1 , L 2 , L 3 , H 1 , H 2 The test:

[0072] At an ambient temperature of 25°C, the lithium-ion battery was disassembled to obtain an electrode assembly, and an electron scanning microscope was used to observe the electrode assembly along the width direction to obtain the number of through holes in the first area on each straight area of ​​the first pole piece provided with through holes, which is the number of through holes N. Then, the pole piece provided with through holes was taken out, i.e., the first pole piece, and soaked in dimethyl carbonate (DMC) for 20 minutes, and then the first pole piece was placed in an oven and dried at 80°C for 12 hours to obtain a test sample of the first pole piece.

[0073] The first pole piece is pre-wound, and the length L of the straight area of ​​the first pole piece and the diameter D of the maximum circumscribed circle of the outer contour of the first through hole on the surface of the first pole piece are measured by an electron scanning microscope. 1 , and calculate the diameter D 1 The ratio of the length L is A; at the same time, the diameter D of the maximum circumscribed circle of the outer contour of the second through hole on the surface of the first pole piece is measured by an electron scanning microscope. 2 , and bring it into D n =B n-1 ×D 1Calculate the value B. Then, use an electron scanning microscope to measure the length and width of the straight area of ​​the first region and the area of ​​the outer contour of the through hole on the first pole piece, and calculate the ratio of the sum of the areas of the outer contours of the plurality of through holes to the area of ​​the straight area, which is the ratio S of the sum of the areas of the outer contours of the plurality of through holes.

[0074] The distance L between two adjacent through holes on the first electrode sheet along the width direction of the electrode assembly is measured using an electron scanning microscope. 3 ; The distance L between the first through hole and the first edge on the first pole piece is measured using an electron scanning microscope 1 ; and using an electron scanning microscope to measure the shortest distance L between a single through hole on the first electrode sheet and the third edge or the fourth edge along the length direction of the electrode assembly 2 .

[0075] Cycle performance test:

[0076] The lithium-ion batteries in the embodiments and comparative examples were subjected to a charge-discharge cycle test in a 25°C constant temperature box. The lithium-ion batteries were charged to 4.2V at a constant current of 2C, and then charged to 0.05V at a constant voltage of 4.2V. After standing for 5 minutes, they were discharged to 2.5V at a constant current of 6C. This was the first cycle, and the first cycle discharge capacity C was recorded. 1 After 600 cycles according to the above cycle process, the discharge capacity C of the lithium-ion battery is recorded. 600 , the cycle capacity retention rate of the 600th cycle is calculated as an indicator for evaluating the wetting effect of the electrolyte on the first pole piece and the cycle performance of the lithium-ion battery, and the formula is shown in formula (I). When the 600-cycle (cls) capacity retention rate is lower, it indicates that the wetting effect of the electrolyte on the first pole piece in the lithium-ion battery is worse, and the cycle performance of the lithium-ion battery is worse; when the 600cls capacity retention rate is higher, it indicates that the wetting effect of the electrolyte on the first pole piece in the lithium-ion battery is better, and the cycle performance of the lithium-ion battery is better.

[0077] 600cls capacity retention rate (%) = C 600 / C 1 ×100%. (I)

[0078] Pole wettability test:

[0079] The diffusion distance of the electrolyte on the surface of the first electrode piece is used to characterize the wettability of the electrolyte on the first electrode piece. The specific operation steps are as follows:

[0080] At an ambient temperature of 25°C, the lithium-ion battery was discharged at 0.5C to 2.5V and then disassembled. The first electrode with a through hole was taken out, and the electrolyte and the side reaction products on the surface were removed by washing with dimethyl carbonate (DMC) for 10 minutes. Then, the first electrode was placed in a 25°C environment for 2 hours to obtain a dry first electrode. The electrolyte was inhaled using a 5mL medical syringe, and the air at the head of the medical syringe was discharged. The unfolded dry first electrode was placed on a horizontal table, and the medical syringe was located directly above the first electrode and perpendicular to the first electrode. The vertical distance between the needle of the medical syringe and the first electrode was 3cm. 1mL of electrolyte was dripped vertically and fell on the first electrode. After 1 minute, the diffusion distance of the electrolyte was measured. A soft ruler with an accuracy of 0.5mm was used for measurement to measure the distance between the two points where the electrolyte diffused the farthest on the first electrode, such as Figure 6 As shown, Figure 6 The value of d in the figure is measured 5 times and the average value is taken to obtain the diffusion distance d of the electrolyte in the first electrode 10. The electrolyte is the same as the electrolyte in Example 1. Figure 6 It is only a schematic diagram of the structure of a portion of the first pole piece in the middle along the length direction (X direction) after the first pole piece is unfolded, and is only for exemplary description.

[0081] When the first electrode sheet is a positive electrode sheet and a negative electrode sheet, the diffusion distance of the electrolyte in the negative electrode sheet obtained by measuring 5 times and the diffusion distance of the electrolyte in the positive electrode sheet obtained by measuring 5 times are averaged to obtain the diffusion distance d of the electrolyte in the first electrode sheet.

[0082] Shock Test:

[0083] After charging the lithium-ion battery to 4.2V at a constant current of 2C, charge it to 0.05C at a constant voltage to reach a fully charged state. Place the fully charged lithium-ion battery on the test bench, and place a round bar with a diameter of 15.8mm and a length of at least 6cm at the center of the wide surface of the lithium-ion battery. Wait for the longitudinal axis of the lithium-ion battery to be parallel to the surface of the test bench and perpendicular to the longitudinal axis of the round bar. Use a 9.1kg heavy hammer to drop it vertically from a height of 610mm and let it fall at the intersection of the round bar and the lithium-ion battery.

[0084] Test pass criteria: pass if no fire or explosion occurs.

[0085] 100 lithium-ion batteries are tested in each embodiment or comparative example, and the impact passing rate of the lithium-ion battery = the number of passed batteries / 100. The greater the impact passing rate of the lithium-ion battery, that is, the greater the number of passed batteries, the better the safety performance of the lithium-ion battery.

[0086] Example 1

[0087] <Preparation of negative electrode sheet>

[0088] The first electrode is the negative electrode. The negative electrode active material artificial graphite, sodium carboxymethyl cellulose (CMC-Na) and styrene-butadiene rubber (SBR) are mixed in a mass ratio of 97.3:1.7:1.0, and then deionized water is added as a solvent, and the mixture is stirred to obtain a negative electrode slurry with a solid content of 50wt%. The negative electrode slurry is evenly coated on a thickness of H 2 On one surface of the negative electrode current collector copper foil with a thickness of 12.5 μm, it was dried at 105°C to obtain a negative electrode sheet coated with a negative electrode material layer on one side. After that, the above steps were repeated on the other surface of the negative electrode current collector copper foil to obtain a negative electrode sheet coated with a negative electrode material layer on both sides. Then, after cold pressing and stripping, the coating area and empty foil area of ​​the negative electrode current collector with a negative electrode material layer were determined along the length direction of the unfolded negative electrode sheet. The coating weight of the negative electrode material layer was 14.6 mg / cm 2 , the thickness of the negative electrode material layer on one side of the negative electrode current collector after cold pressing H 1 is 360μm.

[0089] The negative electrode sheet is pre-wound, and one surface of the negative electrode sheet is selected to determine two straight areas of each circle of the negative electrode sheet and two bending areas connected to the two straight areas, wherein the width of the straight area is set to 325 mm and the length of the straight area is set to 418 mm. The first edge, the second edge and the center line of each straight area are determined, and 15 rows of through holes are respectively set in the first area from the first edge to the center line of each straight area and the second area from the second edge to the center line of each straight area, with 12 through holes in each row. Along the direction from the first edge to the center line, the maximum circumscribed circle of the outer contour of the through holes set in the first area on the surface of the electrode sheet gradually decreases, and the multiple through holes set in the second area are symmetrical with the multiple through holes set in the first area along the center line of the straight area.

[0090] Determine A to be 3.75%, B to be 0.75, and set the diameter D of the maximum circumscribed circle of the outer contour of the first through hole near the first edge on the surface of the negative electrode sheet along the length direction of the unfolded negative electrode sheet. 1 mm, D 1 =A×L, the diameter of the maximum circumscribed circle of the outer contour of the nth through hole on the surface of the negative electrode is D n mm, D n =B n-1 ×D 1 The sum of the areas of the outer contours of the multiple through holes accounts for 5.94%. Along the length direction of the unfolded negative electrode sheet, the distance L between the first through hole and the first edge is 1 The distance between two adjacent through holes is 40 mm. 3 The shortest distance L between a single through hole and the third edge or the fourth edge of the straight area along the width direction of the unfolded negative electrode sheet is2 According to the above parameters, laser drilling is performed on the flat area of ​​the negative electrode sheet to obtain a negative electrode sheet with a specification of 16226mm×418mm.

[0091] <Preparation of positive electrode sheet>

[0092] The positive electrode active material is lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ), binder polyvinylidene fluoride (PVDF) and conductive carbon black are dispersed in N-methylpyrrolidone (NMP) solvent in a mass ratio of 94.8:2.8:2.4, and stirred and mixed thoroughly to obtain a positive electrode slurry with a solid content of 72wt%. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 12.5μm, and dried at 105°C to obtain a positive electrode sheet coated with a single-sided positive electrode material layer. After that, the above steps are repeated on the other surface of the positive electrode current collector aluminum foil to obtain a positive electrode sheet coated with a double-sided positive electrode material layer. Then, after cold pressing, cutting, and slitting, it is dried under vacuum conditions at 105°C for 4h to obtain a positive electrode sheet with a specification of 15437mm×414.1mm for standby use. Among them, the coating weight of the positive electrode material layer is 16mg / cm 2 After cold pressing, the thickness of the positive electrode material layer on one side of the positive electrode collector is 400 μm.

[0093] <Diaphragm>

[0094] A polypropylene (PP) film with a thickness of 12 μm was used as the separator.

[0095] <Preparation of Electrolyte>

[0096] In a dry argon atmosphere glove box, organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 30:50:20 to obtain a base solvent, and then lithium salt lithium hexafluorophosphate (LiPF 6 ), and then mix thoroughly to obtain the electrolyte. Based on the quality of the electrolyte, LiPF 6 The mass percentage is 12.5%, and the balance is the basic solvent.

[0097] <Preparation of lithium-ion batteries>

[0098] The prepared diaphragm, positive electrode sheet, diaphragm and negative electrode sheet are stacked in order, so that the diaphragm is between the positive electrode and the negative electrode to play an isolating role. The electrode assembly is wound to form a wound electrode assembly, wherein the width of the electrode assembly is 375mm, the length of the electrode assembly is 418mm, and the thickness of the electrode assembly is 20mm. After flattening, current collecting plate welding, shelling, coding, vacuum drying, electrolyte injection, sealing, high-temperature standing, and then forming capacity, a lithium-ion battery can be obtained. Among them, the upper limit voltage of formation is 3.6V, the formation temperature is 45°C, and the formation standing time is 2h.

[0099] Example 2

[0100] Except that 5 through holes are arranged in each row on the first area and the second area of ​​each flat region of the negative electrode material layer, and relevant preparation parameters are adjusted according to Table 1, the rest is the same as Example 1.

[0101] Example 3

[0102] Except that 20 through holes are arranged in each row on the first area and the second area of ​​each flat region of the negative electrode material layer, and relevant preparation parameters are adjusted according to Table 1, the rest is the same as Example 1.

[0103] Example 4 to Example 12

[0104] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1.

[0105] Example 13

[0106] Except for preparing the positive electrode sheet and the negative electrode sheet according to the following steps, the rest is the same as Example 1.

[0107] <Preparation of positive electrode sheet>

[0108] The first electrode is the positive electrode. 0.8 Co 0.1 Mn 0.1 O 2 ), binder polyvinylidene fluoride (PVDF) and conductive carbon black are dispersed in N-methylpyrrolidone (NMP) solvent in a mass ratio of 94.8:2.8:2.4, and stirred and mixed to obtain a positive electrode slurry with a solid content of 72wt%. The positive electrode slurry is evenly coated on a thickness of H 2On one surface of the positive electrode current collector aluminum foil with a thickness of 12.5 μm, it was dried at 105°C to obtain a positive electrode sheet coated with a positive electrode material layer on one side. After that, the above steps were repeated on the other surface of the positive electrode current collector aluminum foil to obtain a positive electrode sheet coated with a positive electrode material layer on both sides. Then, after cold pressing and stripping, the coating area and empty foil area of ​​the positive electrode current collector with a positive electrode material layer were determined along the length direction of the unfolded positive electrode sheet. The coating weight of the positive electrode material layer was 16 mg / cm 2 , the thickness of the positive electrode material layer on one side of the positive electrode current collector after cold pressing H 1 is 400μm.

[0109] The positive electrode sheet is pre-wound, and one surface of the positive electrode sheet is selected to determine two straight areas of each circle of the positive electrode sheet and two bending areas connected to the two straight areas, wherein the width of the straight area is set to 325 mm and the length of the straight area is set to 414.1 mm. The first edge, the second edge and the center line of each straight area are determined, and 15 rows of through holes are respectively set in the first area from the first edge to the center line of each straight area and the second area from the second edge to the center line of each straight area, with 12 through holes in each row. Along the direction from the first edge to the center line, the maximum circumscribed circle of the outer contour of the through holes set in the first area on the surface of the electrode sheet gradually decreases, and the multiple through holes set in the second area are symmetrical with the multiple through holes set in the first area along the center line of the straight area.

[0110] Determine A to be 3.75%, B to be 0.75, and set the diameter D of the maximum circumscribed circle of the outer contour of the first through hole near the first edge on the surface of the positive electrode sheet along the length direction of the unfolded positive electrode sheet. 1 mm, D 1 =A×L, the diameter of the maximum circumscribed circle of the outer contour of the nth through hole on the surface of the positive electrode is D n mm, D n =B n-1 ×D 1 The sum of the areas of the outer contours of the plurality of through holes accounts for 6% S. Along the length direction of the unfolded positive electrode sheet, the distance L between the first through hole and the first edge is 1 The distance between two adjacent through holes is 40 mm. 3 The shortest distance L between a single through hole and the third edge or the fourth edge of the straight area along the width direction of the unfolded positive electrode sheet is 2 According to the above parameters, laser drilling is performed on the straight area of ​​the positive electrode plate to obtain a positive electrode plate with a specification of 15437mm×414.1mm.

[0111] <Preparation of negative electrode sheet>

[0112] The negative electrode active materials artificial graphite, sodium carboxymethyl cellulose (CMC-Na) and styrene-butadiene rubber (SBR) were mixed in a mass ratio of 97.3:1.7:1.0, and then deionized water was added as a solvent, and the mixture was stirred to obtain a negative electrode slurry with a solid content of 50wt%. The negative electrode slurry was evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 12.5μm, and dried at 105°C to obtain a negative electrode sheet with a single-sided negative electrode material layer. After that, the above steps were repeated on the other surface of the negative electrode current collector copper foil to obtain a negative electrode sheet with a double-sided negative electrode material layer. Then, after cold pressing and striping, it was dried under vacuum conditions at 105°C for 4h to obtain a negative electrode sheet with a specification of 16626mm×418mm for standby use. Among them, the coating weight of the negative electrode material layer is 14.6mg / cm 2 After cold pressing, the thickness of the negative electrode material layer on one side of the negative electrode current collector is 360 μm.

[0113] Embodiment 14

[0114] Except that <Preparation of the positive electrode sheet> is the same as Example 13 and the relevant parameters of the positive electrode sheet are shown in Table 1, the rest is the same as Example 1.

[0115] Comparative Example 1

[0116] Except for providing a blind hole in <Preparation of Negative Electrode Sheet>, the rest is the same as Example 1.

[0117] Comparative Example 2

[0118] Except that two through holes are provided in each row in <Preparation of Negative Electrode Sheet>, the value of A is 1, and the value of B is 0.5, the rest is the same as Example 1.

[0119] Comparative Example 3

[0120] Except that 5 through holes are provided in each row, the value of A is 7, and the value of B is 1 in <Preparation of Negative Electrode Sheet>, the rest is the same as Example 1.

[0121] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Table 1.

[0122] Table 1

[0123]

[0124] Note: “ / ” in Table 1 indicates no relevant preparation parameters.

[0125] From Examples 1 to 14 and Comparative Examples 1 to 3, it can be seen that by setting through holes on the two straight areas of the first pole piece and adjusting the values ​​of N, A and B within the scope of this application, the diffusion distance of the electrolyte in the first pole piece is large, which improves the 600cls capacity retention rate of the lithium-ion battery, indicating that the electrolyte has a good infiltration effect on the first pole piece, the lithium-ion battery has good cycle performance, and the lithium-ion battery has good safety performance. No through holes are set on the straight areas of the positive pole piece and the negative pole piece in Comparative Example 1; the values ​​of N, A and B in Comparative Example 2 are lower than the lower limit of this application; the values ​​of A and B in Comparative Example 3 are higher than the upper limit of this application. The diffusion distance of the electrolyte in Comparative Examples 1 to 2 is small in the first pole piece, and the 600cls capacity retention rate of the obtained lithium-ion battery is low, indicating that the cycle performance of the lithium-ion battery is poor; the through-hole diameter in Comparative Example 3 is large, and the impact test pass rate is low, which affects the safety performance of the lithium-ion battery, and the electrolyte contacts the pole piece too much, resulting in a relatively increased number of side reactions of the lithium-ion battery, and the 600cls capacity retention rate of the obtained lithium-ion battery is low, which reduces the cycle performance of the lithium-ion battery. However, the diffusion distance of the electrolyte in Examples 1 to 14 is large in the first pole piece, and the electrolyte has a better infiltration effect on the pole piece, and the 600cls capacity retention rate of the obtained lithium-ion battery is higher, and the lithium-ion battery has better cycle performance. At the same time, the impact test pass rate is high, taking into account the safety performance of the lithium-ion battery and the actual production requirements.

[0126] The number N of through holes set on the first area of ​​each flat area usually affects the cycle performance and safety performance of the lithium-ion battery. It can be seen from Examples 1 to 3 that when the number of through holes set on the first area of ​​each flat area is within the scope of the present application, the diffusion distance of the electrolyte in the first pole piece is large, and the 600cls capacity retention rate and impact test pass rate of the lithium-ion battery are high, indicating that while taking into account the safety performance, the electrolyte in the lithium-ion battery of the present application has a good infiltration effect on the pole piece, and the lithium-ion battery has good cycle performance.

[0127] The value of A usually affects the cycle performance and safety performance of lithium-ion batteries. It can be seen from Examples 1, 4 to 6 that when the value of A is within the range of this application, the diffusion distance of the electrolyte in the first pole piece is large, and the 600cls capacity retention rate and impact test pass rate of the lithium-ion battery are high, indicating that while taking into account the safety performance, the electrolyte in the lithium-ion battery of this application has a good infiltration effect on the pole piece, and the lithium-ion battery has good cycle performance.

[0128] The value of B usually affects the cycle performance and safety performance of lithium-ion batteries. It can be seen from Examples 1, 7 and 8 that when the value of B is within the range of this application, the diffusion distance of the electrolyte in the first pole piece is large, and the 600cls capacity retention rate and impact test pass rate of the lithium-ion battery are high, indicating that while taking into account the safety performance, the electrolyte in the lithium-ion battery of this application has a good infiltration effect on the pole piece, and the lithium-ion battery has good cycle performance.

[0129] The proportion S of the sum of the areas of the outer contours of the through holes usually affects the cycle performance and safety performance of the lithium-ion battery. It can be seen from Examples 1 to 14 that when the sum of the areas of the outer contours of the through holes accounts for a range within the scope of the present application, the diffusion distance of the electrolyte in the first pole piece is large, and the 600cls capacity retention rate and impact test pass rate of the lithium-ion battery are high, indicating that while taking into account the safety performance, the electrolyte in the lithium-ion battery of the present application has a good infiltration effect on the pole piece, and the lithium-ion battery has good cycle performance.

[0130] Along the length direction of the electrode assembly, the shortest distance L between a single through hole and the third edge or the fourth edge is 2 It usually affects the cycle performance and safety performance of lithium-ion batteries. It can be seen from Examples 1, 9 and 10 that when the shortest distance between a single through hole and the third edge or the fourth edge is within the scope of this application, the diffusion distance of the electrolyte in the first pole piece is large, and the 600cls capacity retention rate and impact test pass rate of the lithium-ion battery are high, indicating that while taking into account the safety performance, the electrolyte in the lithium-ion battery of this application has a good infiltration effect on the pole piece, and the lithium-ion battery has good cycle performance.

[0131] The thickness of the first current collector is H 2 and a thickness H of the first material layer located on at least one surface of the first current collector 1 It usually affects the cycle performance and safety performance of lithium-ion batteries. It can be seen from Examples 1, 11 and 12 that when H 1 With H 2 When the value is within the range of this application, the diffusion distance of the electrolyte in the first electrode is large, and the 600cls capacity retention rate and impact test pass rate of the lithium-ion battery are high, indicating that while taking into account the safety performance, the electrolyte in the lithium-ion battery of this application has a good infiltration effect on the electrode, and the lithium-ion battery has good cycle performance.

[0132] Whether the first pole piece is a positive pole piece and / or a negative pole piece usually affects the cycle performance and safety performance of the lithium-ion battery. It can be seen from Example 1, Example 13 to Example 14 that when the first pole piece is a positive pole piece and / or a negative pole piece, and the parameters of the through hole are set within the scope of this application, the diffusion distance of the electrolyte in the first pole piece is large, and the 600cls capacity retention rate and impact test pass rate of the lithium-ion battery are high, indicating that while taking into account the safety performance, the electrolyte in the lithium-ion battery of this application has a good infiltration effect on the pole piece, and the lithium-ion battery has good cycle performance.

[0133] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method or article including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method or article.

[0134] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0135] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A secondary battery, comprising a wound electrode assembly, the electrode assembly comprising a first electrode sheet, each circle of the first electrode sheet comprising two straight regions and two bending regions connected to the two straight regions, the two bending regions being arranged opposite to each other along the width direction of the electrode assembly; Along the width direction of the electrode assembly, any of the straight regions has a first edge and a second edge opposite to each other, the width of a single straight region is L mm, the area from the first edge to the center line of the straight region is the first area of ​​the straight region, and the area from the center line to the second edge is the second area of ​​the straight region; A plurality of through holes are disposed on the first region and the second region of at least one circle of the first pole piece, and the plurality of through holes in the second region are symmetrical with the plurality of through holes disposed on the first region along the center line; A first through hole is arranged near the first edge, and N through holes are arranged in sequence on the first region along the direction from the first edge to the center line, where 5≤N≤20 and N is a positive integer; in, The diameter of the maximum circumscribed circle of the outer contour of the first through hole on the surface of the first pole piece is D1 mm, D1=A×L, 1.5%≤A≤6%, and the diameter of the maximum circumscribed circle of the outer contour of the nth through hole on the surface of the first pole piece is D n mm, D n =B n-1 ×D1, 2≤n≤N, 0.6≤B≤0.

9.

2. The secondary battery according to claim 1, wherein 1.8%≤A≤3.75%。 3. The secondary battery according to claim 1 or 2, wherein: The first pole piece includes a first current collector and a first material layer located on at least one surface of the first current collector. Based on the surface area of ​​the straight area, the sum of the outer contour areas of the through holes on the first material layer of any straight area accounts for S, 0.5%≤S≤18%.

4. The secondary battery according to any one of claims 1 to 3, wherein Along the width direction of the electrode assembly, a distance between two adjacent through holes located in the first region is 5 mm to 22 mm.

5. The secondary battery according to any one of claims 1 to 4, wherein The thickness of the electrode assembly is T mm, and along the width direction of the electrode assembly, the distance between the first through hole and the first edge is L1 mm, T / 2≤L1≤L / 4, 20≤T≤70.

6. The secondary battery according to any one of claims 1 to 5, wherein The first pole piece includes a first current collector and a first material layer located on at least one surface of the first current collector. Along the length direction of the electrode assembly, the first material layer in the straight area has a third edge and a fourth edge relative to each other. The shortest distance between a single through hole and the third edge or the fourth edge is L2 mm, 5≤L2≤10.

7. The secondary battery according to any one of claims 1 to 6, wherein The first pole piece includes a first current collector and a first material layer located on at least one surface of the first current collector. The thickness of the first material layer is H1 μm, and 120≤H1≤600.

8. The secondary battery according to claim 7, wherein The thickness of the first current collector is H2 μm, 5≤H2≤20.

9. The secondary battery according to any one of claims 1 to 8, wherein 80≤L≤600。 10. The secondary battery according to any one of claims 1 to 9, wherein The first pole piece is a positive pole piece and / or a negative pole piece.

11. The secondary battery according to any one of claims 1 to 10, wherein The outer contour of a single through hole may be in the shape of a circle, an ellipse or a polygon.

12. The secondary battery according to any one of claims 1 to 11, wherein The secondary battery is a soft-pack secondary battery or a square secondary battery. 13 . An electronic device comprising the secondary battery according to claim 1 .

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