Wound cell and electrochemical device

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a winding type battery cell and an electrochemical device.The winding type battery cell comprises an electrolyte and a positive plate, a diaphragm and a negative plate which are sequentially stacked and wound, and the winding type battery cell comprises a straight area and an arc area; the positive plate comprises a first area and a second area, the first area is located in an arc area, the second area is located in a straight area, the first area is provided with a first surface and a second surface which are oppositely arranged in the first direction, the first surface is provided with a first protrusion and / or the second surface is provided with a second protrusion, the height of the first protrusion is h1 [mu] m, and the height of the second protrusion is h2 [mu] m; the negative plate comprises a negative active layer, the percentage content of silicon in the negative active layer is x, and the thickness of the negative plate is t [mu] m; h1, h2, x and t meet the following relation: (h1 + h2) / (t * x0.3) = 0.2-0.5. The winding type battery cell can solve the problems of lithium precipitation and interface failure.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion batteries, and in particular to a wound battery cell and an electrochemical device. Background Art

[0002] Lithium-ion batteries are the most widely used batteries in portable electronics, electric vehicles, power tools and various power grid applications due to their high power and energy density, low cost and long life cycle. In order to meet the rapidly growing endurance requirements of the electronics and electric vehicle industries, researchers usually choose to add silicon negative electrodes with higher specific capacity and compress the electrode rolling thickness to the extreme in order to produce lithium-ion batteries with high volume energy density.

[0003] The silicon negative electrode material itself has a large volume expansion, especially at the arc part, the pole piece is constrained by the membrane shell space after expansion, and the pole piece at the arc part will be subject to greater stress. In addition, due to the large volume change during the lithium insertion and de-lithiation process of silicon materials, the pole piece has an expansion-contraction "breathing" effect, and is subject to greater stress after lithium insertion and expansion, which makes the bonding force between the negative electrode active material and the diaphragm greater. After de-lithiation and shrinkage, part of the negative electrode material will be bonded to the diaphragm, causing the active material and the current collector to debond, resulting in interface failure. The negative electrode material at the debonding position cannot receive positive electrode lithium ions, causing lithium ions to be embedded or precipitated at other locations on the current collector where they remain bonded, causing lithium precipitation and internal short circuits, which can cause safety problems in severe cases. Summary of the invention

[0004] In view of this, the present invention provides a wound battery cell and an electrochemical device to solve the problem of interface failure of debonding between active material and current collector and lithium deposition caused by stress concentration in the arc area.

[0005] In a first aspect, the present invention provides a wound battery cell, the wound battery cell comprising an electrolyte and a positive electrode sheet, a separator and a negative electrode sheet stacked and wound in sequence, the wound battery cell comprising a straight area and arc areas located at both ends of the straight area, the positive electrode sheet comprising a first area and a second area, the first area being located in the arc area, the second area being located in the straight area, the first area having a first surface and a second surface arranged opposite to each other along a first direction, the first surface being provided with a first protrusion, and / or the second surface being provided with a second protrusion, the height of the first protrusion being h1 μm, and the height of the second protrusion being h2 μm; the negative electrode sheet comprising a negative electrode current collector and a negative electrode active layer located on the negative electrode current collector, the negative electrode active layer comprising a silicon-carbon composite material and / or a silicon-oxygen composite material, the percentage of silicon element in the negative electrode active layer being x, and the thickness of the negative electrode sheet being t μm; wherein the relationship among h1, h2, x and t satisfies: (h1+h2) / (t*x 0.3)=0.2~0.5, 0%<x≤50%, 25≤t≤100, at least one of h1 and h2 is greater than 0, and h1+h2≤25.

[0006] The wound battery cell of the present invention reserves expansion space for the negative electrode sheet by arranging a protruding structure in the arc area of ​​the positive electrode sheet. A larger reserved space will affect the performance such as energy density. When the reserved space is smaller, it will be subjected to greater stress after lithium insertion and expansion, so that the bonding force between the negative electrode active material and the diaphragm at this location is greater. After lithium removal and shrinkage, part of the negative electrode active material will be bonded to the diaphragm, resulting in debonding of the active material and the current collector. Lithium ions are embedded or precipitated at other places on the negative electrode sheet where bonding is maintained, causing lithium precipitation and internal short circuit. Therefore, by comprehensively controlling the relationship between the thickness and silicon content of the negative electrode sheet and the height of the first protrusion and the second protrusion, the relationship between h1, h2, x and t satisfies: (h1+h2) / (t*x 0.3 )=0.2~0.5; It can ensure that a suitable expansion space can be reserved for the negative electrode sheet to avoid the debonding of the active material on the negative electrode sheet and the current collector; The mechanism of achieving the above effect through the above relationship is as follows:

[0007] h1+h2 is the total space reserved for the expansion of the negative electrode sheet; the higher the percentage of silicon element x, the greater the expansion of the negative electrode sheet, but the expansion of the negative electrode sheet and the product of the thickness t of the negative electrode sheet are not in a linear positive correlation. This paper fits the percentage of silicon element x and matches it with the product of the thickness t of the negative electrode sheet to make it satisfy a linear positive correlation with the expansion size. Therefore, the space size can be adapted by controlling the ratio of the space reserved between the protruding structures to the expansion size of the negative electrode within the range of 0.2 to 0.5, thereby avoiding the debonding of the active material and the current collector on the negative electrode sheet due to excessive expansion size, reducing lithium plating, and effectively improving the cycle performance and safety performance.

[0008] In a second aspect, the present invention further provides an optimized electrolyte composition for use with a wound battery cell, wherein the electrolyte includes a film-forming additive, preferably fluoroethylene carbonate (FEC), and the mass proportion of the film-forming additive in the electrolyte is 15%-25%.

[0009] When the silicon negative electrode material expands or contracts in the present invention, (h1+h2) / (t*x 0.3) relationship, although it can alleviate the shedding of the negative electrode active layer, the stress in the arc area of ​​the battery is still greater than that in the straight area. At the junction between the position with high stress and the position with low stress, the SEI film is not stable, and continuous rupture and repair will occur, affecting the cycle life; the present invention can stabilize the structure of the SEI film by adding a film-forming additive FEC with a mass ratio of 15% to 25%, better adapt to the volume change of the silicon negative electrode during the process of lithium removal and lithium insertion, and avoid the problem of local lithium precipitation caused by the obstruction of lithium ion transmission in the unstable area of ​​the SEI film, which is consistent with (h1+h2) / (t*x 0.3 ) relationship, effectively avoiding lithium plating and improving cycle performance.

[0010] In some optional embodiments, 0

[0011] In some optional embodiments, the second surface is provided with a first groove, and the first groove is arranged corresponding to the first protrusion; and / or the first surface is provided with a second groove, and the second groove is arranged corresponding to the second protrusion.

[0012] In some optional embodiments, a projection of the first groove in the first direction is adjacent to a projection of the second protrusion in the first direction, and / or a projection of the second groove in the first direction is adjacent to a projection of the first protrusion in the first direction.

[0013] In some optional embodiments, the first area has a plurality of first protrusion rows and a plurality of second protrusion rows, the first protrusion row has a plurality of first protrusions distributed along the second direction, the second protrusion row has a plurality of second protrusions distributed along the second direction, the first protrusion rows and the second protrusion rows are alternately arranged along a third direction, and the first direction, the second direction and the third direction are arranged perpendicularly in pairs.

[0014] In some optional embodiments, along the fifth direction, the first protrusions and the second grooves are alternately arranged, and the fifth direction and the third direction have a first preset angle; and / or, along the sixth direction, the first protrusions and the second grooves are alternately arranged, and the sixth direction and the third direction have a second preset angle, and the deflection directions of the fifth direction and the sixth direction are opposite.

[0015] In some optional embodiments, the first preset angle ranges from 15° to 75°; and / or the second preset angle ranges from 15° to 75°.

[0016] ​In some optional embodiments, the first protrusion has a first projection along the first direction, and the center distance between two adjacent first projections in the second direction is d1 mm, and d1 satisfies: 0.5≤d1≤15; and / or, the second protrusion has a second projection along the first direction, and the center distance between two adjacent second projections in the second direction is d2 mm, and d2 satisfies: 0.5≤d2≤15.

[0017] In some optional embodiments, in two adjacent rows of first protrusions, the center distance between the first projections of the two nearest first protrusions is d3 mm, and d3 satisfies: 0.5≤d3≤15; and / or, in two adjacent rows of second protrusions, the center distance between the second projections of the two nearest second protrusions is d4 mm, and d4 satisfies: 0.5≤d4≤15.

[0018] In some optional embodiments, d1=d2, d3=d4.

[0019] In some optional embodiments, the diameter of the first projection is r1 mm, the diameter of the second projection is r2 mm, and in adjacent rows of the first protrusions and the second protrusions, the center distance between the first projection of the first protrusion and the second projection of the second protrusion that is closest to each other is d5 mm, and the relationship among d5, r1, and r2 satisfies: d5 / (r1+r2)≥4.

[0020] In some optional embodiments, r1 satisfies: 0.5≤r1≤3, and / or, r2 satisfies: 0.5≤r2≤3, and / or, d5 satisfies: 4≤d5≤10.

[0021] In some optional embodiments, the elongation at break of the positive electrode sheet is γ%, where γ satisfies: 1.5≤γ≤5.

[0022] In some optional embodiments, the relationship among r1, h1 and γ satisfies: The relationship among r2, h2 and γ satisfies:

[0023] In some optional embodiments, along the horizontal axis of the inner center of the wound battery cell, the straight area includes an upper straight area and a lower straight area, the thickness of the arc area is R, the thickness of the upper straight area is T, the units of R and T are the same, and the relationship between R and T satisfies: R / T=0.98~1.3.

[0024] In a third aspect, the present invention further provides an electrochemical device, comprising the wound battery cell described in the first aspect and a shell, wherein the wound battery cell is accommodated in the shell.

[0025] The present invention comprehensively controls the relationship between the height of the first protrusion and the second protrusion and the thickness and silicon content of the negative electrode sheet so that the relationship between h1, h2, x and t satisfies: (h1+h2) / (t*x 0.3 )=0.2~0.5, which can ensure that a suitable expansion space can be reserved for the negative electrode sheet, avoid the debonding of the active material on the negative electrode sheet and the current collector, reduce lithium plating, and effectively improve the cycle performance and safety performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 This is one of the structural schematic diagrams of a wound battery cell according to an embodiment of the present invention;

[0028] Figure 2 This is a second structural schematic diagram of a wound battery cell according to an embodiment of the present invention;

[0029] Figure 3 This is one of the structural schematic diagrams of the positive electrode sheet of the wound battery cell according to an embodiment of the present invention;

[0030] Figure 4 This is the second structural schematic diagram of the positive electrode sheet of the wound battery cell according to an embodiment of the present invention.

[0031] Description of reference numerals:

[0032] 1. wound battery cell; 11. straight area; 12. arc area; 100. positive electrode sheet; 110. positive current collector; 120. positive active layer; 130. first region; 131. first protrusion; 132. second protrusion; 133. first groove; 134. second groove; 135. first surface; 136. second surface; 137. first protrusion row; 138. second protrusion row; 140. second region; 200. positive electrode tab; 300. negative electrode sheet; 310. negative current collector; 320. negative active layer; 400. negative electrode tab. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0034] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0035] In the description of the present invention, "plurality" means two or more. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0036] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] The inventors of the present invention have found that as the lithium battery cycle progresses, the positive and negative electrodes of the lithium-ion battery continue to expand. In the straight area (unbent area) of the wound lithium battery (i.e., the battery including the wound battery cell), the expansion is not constrained and can expand freely. There is no stress accumulation between the positive and negative electrode sheets and between the separator and the electrode sheets, or the stress accumulation is small and does not affect the cycle performance. However, in the arc area (bent area) of the wound lithium battery, due to the constraint of the aluminum-plastic film and the characteristics of the battery cell itself at the arc, it cannot expand freely in the width direction of the battery cell, which eventually leads to stress accumulation at the arc. In addition, in order to meet the rapidly growing endurance requirements of the electronics and electric vehicle industries, researchers usually choose to add silicon negative electrodes with higher specific capacity. As the silicon content increases and the electrode volume continues to compress, the negative electrode sheet continues to expand during the battery cycle, and the arc area is more prone to stress concentration, resulting in severe compression of the volume of the arc area, making the bonding force between the negative electrode active material and the diaphragm greater. After the lithium de-shrinkage, some of the negative electrode active materials will adhere to the diaphragm, causing the active material to debond from the current collector, and lithium ions will be embedded or precipitated in other places on the negative electrode sheet where they remain bonded, causing lithium precipitation and internal short circuits. That is, conventional lithium batteries containing silicon negative electrodes will obviously experience interface failure and lithium precipitation problems, which seriously affect the cycle life and safety of lithium-ion batteries.

[0038] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0039] like Figure 1-Figure 4 As shown, according to an embodiment of the present invention, on the one hand, a wound battery cell 1 is provided, the wound battery cell 1 includes an electrolyte and a positive electrode sheet 100, a separator and a negative electrode sheet 300 stacked and wound in sequence, the wound battery cell 1 has an unbent straight area 11 and a bent arc area 12, and the arc area 12 is connected to both ends of the straight area 11.

[0040] The positive electrode sheet 100 includes a first region 130 and a second region 140. The first region 130 is located in the arc region 12, and the second region 140 is located in the straight region 11. The first region 130 and the second region 140 may be connected to each other. The first region 130 has a first surface 135 and a second surface 136 arranged opposite to each other along a first direction. The first surface 135 is provided with a first protrusion 131, and the second surface 136 is provided with a second protrusion 132. The height of the first protrusion 131 is h1μm, and the height of the second protrusion 132 is h2μm. The first aspect is the thickness direction of the positive electrode sheet 100, that is, the radial direction of the wound battery cell 1.

[0041] The positive electrode sheet 100 includes a positive electrode current collector 110 and a positive electrode active layer 120 located on the positive electrode current collector 110, and the negative electrode sheet 300 includes a negative electrode current collector 310 and a negative electrode active layer 320 located on the negative electrode current collector 310. The negative electrode active layer 320 includes a silicon-carbon composite material and / or a silicon-oxygen composite material. The percentage of silicon in the negative electrode active layer 320 is x, and the thickness of the negative electrode sheet 300 is tμm. Among them, the relationship between h1, h2, x and t satisfies: (h1+h2) / (t*x 0.3 )=0.2~0.5, 0%<x≤50%, 25≤t≤100, at least one of h1 and h2 is greater than 0, and h1+h2≤25.

[0042] In the wound battery cell 1, a first region 130 and a second region 140 are arranged on the positive electrode sheet 100. By arranging the first protrusion 131 and the second protrusion 132, the thickness of the first region 130 can be increased so that the thickness of the first region 130 is greater than the thickness of the second region 140. Therefore, the first region 130 has a larger compressible volume, and the first region 130 is located in the arc region 12, that is, a larger expansion space is reserved for the arc region 12. The positive electrode sheet 100 can be deformed to absorb the expansion of the silicon volume of the negative electrode sheet 300 during the lithium removal and lithium insertion process, thereby avoiding the debonding of the active material and the current collector on the negative electrode sheet due to excessive expansion size, reducing the lithium precipitation, and effectively improving the cycle performance and safety performance; in addition, the probability of the positive electrode sheet 100 being broken by force can also be reduced, and the infiltration effect of the arc region 12 is good.

[0043] For lithium batteries containing silicon negative electrodes, if the percentage x of silicon element is too low, the energy density will be low; if the percentage x of silicon element is too high, it will cause excessive expansion, affecting battery safety and cycle performance. If the thickness t of the negative electrode sheet is too small, the energy density will be reduced; if the thickness t is too large, it will cause excessive expansion, affecting battery safety and cycle performance.

[0044] If only the heights h1 and h2 of the first protrusion 131 and the second protrusion 132 are adjusted, it is impossible to adapt to the expansion of the negative electrode sheet of the lithium battery containing a silicon negative electrode; specifically, the sum of h1 and h2 may be too much or too little compared to the expansion space of the negative electrode sheet. If it is too much, it will increase the space and reduce the energy density. If it is too little, the expansion space reserved for the negative electrode sheet is too small and the pressure increases. Even if the requirements for electrolyte infiltration are met, the active material on the negative electrode sheet may debond from the current collector, affecting the battery safety and cycle performance.

[0045] The inventors have found that the thickness t of the negative electrode sheet 300 is positively correlated with the expansion degree of the negative electrode sheet 300. The larger the thickness t, the greater the expansion degree. The percentage x of the silicon element in the negative electrode active layer 320 is also positively correlated with the expansion degree of the negative electrode sheet 300. That is, the higher the percentage of the silicon element in the negative electrode active layer 320, the greater the expansion degree of the negative electrode sheet 300. However, after multiplying or summing the thickness t of the negative electrode sheet and the percentage x of the silicon element, the negative electrode sheet has a non-linear positive correlation with the expansion degree of the negative electrode sheet. It is impossible to effectively obtain the space required to pass through the protruding structure based on the thickness t of the negative electrode sheet and the percentage x of the silicon element. In the present invention, the product of the percentage x of the silicon element after fitting and the thickness t of the negative electrode sheet is used to make the expansion size of the negative electrode sheet and the space reserved between the protruding structures meet a linear positive correlation. By controlling (h1+h2) / (t*x 0.3 ) is between 0.2 and 0.5, which can not only prevent the sum of the heights of the first protrusion 131 and the second protrusion 132 from being too large, thereby ensuring the energy density of the wound battery cell 1, but also leave a suitable space for the expansion of the negative electrode sheet in the arc area 12, thereby improving the wetting effect of the arc area 12. At the same time, it can also reduce the pressure caused by the expansion of the active material of the negative electrode sheet after lithium insertion, thereby reducing the bonding force between the active material and the diaphragm, thereby avoiding the interface failure problem caused by the debonding of the active material and the current collector after the lithium desorption shrinkage, and effectively avoiding the lithium plating problem caused by the embedding or precipitation of too many lithium ions in other active material positions on the negative electrode current collector to improve the lithium plating situation in the arc area 12 and enhance the cycle performance of the battery.

[0046] That is to say, by limiting the sum of the heights of the first protrusion 131 and the second protrusion 132, the thickness of the negative electrode sheet 300 and the product of the fitted silicon doping amount to satisfy the above relationship, the space reserved by the positive electrode sheet 100 in the arc area 12 can be more adapted to the expansion of the negative electrode sheet, reserving a suitable expansion space for the negative electrode sheet in the arc area 12, avoiding the problem of debonding of the active material and the current collector caused by excessive stress in the arc area 12 during subsequent expansion, effectively improving the problems of lithium deposition and interface failure in the arc area 12, extending the cycle life of the wound battery cell 1, and improving the safety of the wound battery cell 1.

[0047] As an example, x can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%. t can be 25, 30, 40, 50, 60, 70, 80, 90, 100. In h1+h2, h1 can be 0, 1, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19 or 20, h2 can be 0, 0.1, 0.5, 1, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19 or 20, and at least one of h1 and h2 is not 0. h1+h2 can be 1, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 or 25. (h1+h2) / (t*x 0.3 ) can be 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49 or 0.5.

[0048] In an optional embodiment, the electrolyte includes a film-forming additive, and the film-forming additive is preferably fluoroethylene carbonate. The percentage of the fluoroethylene carbonate in the electrolyte is 15% to 25%.

[0049] When the silicon negative electrode material expands or contracts in the present invention, (h1+h2) / (t*x 0.3 ) relationship, although it can ensure that the negative electrode active layer will not fall off, the stress in the arc area of ​​the battery is still greater than that in the straight area. At the junction between the position with high stress and the position with low stress, the SEI film is not stable, and continuous rupture and repair will occur, affecting the cycle life; the present invention can stabilize the structure of the SEI film by adding a film-forming additive FEC with a mass proportion of 15% to 25% in the electrolyte, better adapt to the volume change of the silicon negative electrode during the process of lithium removal and lithium insertion, and avoid the problem of local lithium precipitation caused by the obstruction of lithium ion transmission in the unstable area of ​​the SEI film, which is consistent with (h1+h2) / (t*x 0.3 ) relationship, effectively avoiding lithium plating and improving cycle performance.

[0050] As an example, the mass proportion of FEC in the electrolyte may be 15%, 18%, 20%, 23% or 25%.

[0051] In an optional embodiment, 0

[0052] like Figure 2-Figure 4 As shown, in some embodiments, the second surface 136 is provided with a first groove 133, and the first groove 133 is arranged corresponding to the first protrusion 131; and / or, the first surface 135 is provided with a second groove 134, and the second groove 134 is arranged corresponding to the second protrusion 132. This arrangement can make the processing of the positive electrode sheet 100 more convenient, and the molding of the first protrusion 131, the second protrusion 132, the first groove 133 and the second groove 134 is simpler. The embossing process can be directly used to make the height h1 of the first protrusion 131 and the depth h3 of the first groove 133 equal, and the height h2 of the second protrusion 132 and the depth h4 of the second groove 134 equal. No additional material is added to the first protrusion 131 and the second protrusion 132, thereby avoiding material costs. The formed concave-convex structure can help improve the force uniformity of each area of ​​the positive electrode sheet 100, increase the structural strength of the positive electrode sheet 100, further reduce the probability of the positive electrode sheet 100 breaking due to uneven force when the arc area 12 expands, and extend the service life of the positive electrode sheet 100.

[0053] Further, the projection of the first groove 133 in the first direction is adjacent to the projection of the second protrusion 132 in the first direction, and / or the projection of the second groove 134 in the first direction is adjacent to the projection of the first protrusion 131 in the first direction. The first region 130 has a plurality of first protrusion rows 137 and a plurality of second protrusion rows 138, the first protrusion row 137 has a plurality of first protrusions 131 distributed along the second direction, the second protrusion row 138 has a plurality of second protrusions 132 distributed along the second direction, the first protrusion row 137 and the second protrusion row 138 are alternately arranged along the third direction, and the first direction, the second direction and the third direction are arranged perpendicularly in pairs. This arrangement can avoid relative interference between the first protrusion 131 and the second protrusion 132 during the manufacturing process, which is conducive to ensuring the structural integrity of the first protrusion 131 and the second protrusion 132, thereby avoiding the positive electrode sheet 100 from breaking, and ensuring the wetting effect of the arc area 12, and ensuring the lithium precipitation effect of the arc area 12.

[0054] It should be noted that the second direction may be the length direction of the positive electrode sheet 100 , that is, the winding direction of the wound battery cell 1 ; and the third direction may be the width direction of the positive electrode sheet 100 .

[0055] ​Along the fifth direction, the first protrusions 131 and the second grooves 134 are arranged alternately, and the fifth direction and the third direction have a first preset angle; and / or, along the sixth direction, the first protrusions 131 and the second grooves 134 are arranged alternately, and the sixth direction and the third direction have a second preset angle, and the deflection directions of the fifth direction and the sixth direction are opposite.

[0056] In this way, the first protrusion 131 and the second protrusion 132 (corresponding to the second groove 134) can be staggered to avoid mutual interference between the first protrusion 131 and the second protrusion 132. In addition, the number of the first protrusion 131 and the second protrusion 132 is increased, and more space is left between the positive electrode sheet 100 and the negative electrode sheet 300 for storing electrolyte, which further improves the wettability of the arc area 12, and reserves more buffer space for the expansion of the negative electrode sheet 300, further reduces the lithium precipitation problem, and improves the cycle performance of the battery. At the same time, the space of the first surface 135 and the second surface 136 can be fully utilized, so that the wettability can be improved and the lithium precipitation problem can be further reduced.

[0057] The first preset angle ranges from 15° to 75°, and specifically can be 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70° or 75°. And / or, the second preset angle ranges from 15° to 75°, and specifically can be 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70° or 75°.

[0058] like Figure 4 As shown, in some embodiments of the present invention, the first protrusion 131 has a first projection along the first direction, and the center distance between two adjacent first projections in the second direction is d1 mm, and d1 satisfies: 0.5≤d1≤15. Wherein, d1 mm can be 0.5mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm or 15mm.

[0059] The second protrusion 132 has a second projection along the first direction, and the center distance between two adjacent second projections in the second direction is d2 mm, and d2 satisfies: 0.5≤d2≤15. Wherein, d2 mm can be 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm or 15 mm.

[0060] The setting of the range values ​​of d1 and d2 can, on the one hand, avoid the spacing between adjacent first protrusions 131 or second protrusions 132 in the first direction being too close, prevent the first protrusions 131 or second protrusions 132 from interfering with each other in the first direction, and facilitate the processing and manufacturing of the first protrusions 131 or second protrusions 132; on the other hand, the spacing between adjacent first protrusions 131 or second protrusions 132 in the first direction will not be too large, thereby fully utilizing the space of the positive electrode sheet 100, increasing the number of the first protrusions 131 or the second protrusions 132, and increasing the deformable space of the positive electrode sheet 100. The space reserved for the expansion of the arc area 12 is more sufficient, and the porosity of the portion of the positive electrode sheet 100 located in the arc area 12 is higher, further improving the aging wettability.

[0061] Further, in two adjacent first protrusion rows 137, the center distance between the first projections of the two closest first protrusions 131 is d3 mm, and d3 satisfies: 0.5≤d3≤15. Wherein, d3 mm can be 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm or 15 mm.

[0062] In two adjacent second protrusion rows 138, the center distance between the second projections of the two closest second protrusions 132 is d4 mm, and d4 satisfies: 0.5≤d4≤15. Wherein, d4 mm can be 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm or 15 mm.

[0063] The setting of the range values ​​of d3 and d4 can, on the one hand, avoid the spacing between adjacent first protrusions 131 or second protrusions 132 being too close, which is beneficial to processing and manufacturing; on the other hand, it can prevent the spacing between adjacent first protrusions 131 or second protrusions 132 from being too large, thereby fully utilizing the space of the positive electrode sheet 100, increasing the number of first protrusions 131 or second protrusions 132, and increasing the deformable space of the positive electrode sheet 100. More sufficient space is reserved for the expansion of the arc area 12, and the porosity of the portion of the positive electrode sheet 100 located in the arc area 12 is higher, which can improve the aging wettability.

[0064] Specifically, d1 = d3, d2 = d4. In this way, the first protrusion 131 and the second protrusion 132 are distributed most evenly, which increases the buffer space of the arc area 12 while minimizing the damage to the positive electrode sheet 100, thereby reducing the probability of the positive electrode sheet 100 being broken by force.

[0065] like Figure 4As shown, in some embodiments of the present invention, the diameter of the first projection is r1 mm, the diameter of the second projection is r2 mm, and in adjacent first protrusion rows 137 and second protrusion rows 138, the center distance between the first projection of the closest first protrusion 131 and the second projection of the second protrusion 132 is d5 mm, and the relationship between d5, r1, and r2 satisfies: d5 / (r1+r2)≥4.

[0066] The minimum distance between the first protrusion 131 and the second protrusion 132 is greater than 4 times (r1+r2), which can ensure that the distance between the first protrusion 131 and the second protrusion 132 is sufficient, avoid the distance between adjacent first protrusions 131 and second protrusions 132 being too close to affect the structural strength of the positive electrode sheet 100, and help reduce the probability of damage to the positive electrode sheet 100.

[0067] As an example, d5 / (r1+r2) can be 4, 5, 6, 7, 8, 9 or 10.

[0068] In an optional implementation, r1 satisfies: 0.5≤r1≤3, and / or, r2 satisfies: 0.5≤r2≤3, and / or, d5 satisfies: 4≤d5≤10. For example, r1 mm may be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm; r2 mm may be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm; d5 mm may be 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 10 mm.

[0069] Furthermore, the fracture elongation of the positive electrode sheet 100 is γ%, and γ satisfies: 1.5≤γ≤5; if the fracture elongation γ of the positive electrode sheet is too large, it is easy to deform, affecting the cycle performance; if the fracture elongation γ is too small, it is difficult to form the first protrusion and the second protrusion. By adopting a positive electrode sheet 100 with a fracture elongation in the range of 1.5%-5%, better cycle performance can be achieved.

[0070] As an example, the elongation at break γ% may be 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0071] In an optional embodiment, control

[0072] Since the setting of the first protrusion 131 and the second protrusion 132 will stretch the positive electrode sheet 100, the stretching amount of the positive electrode sheet 100 caused by the setting of the first protrusion 131 and the second protrusion 132 needs to be lower than the fracture elongation of the positive electrode sheet 100, so as to avoid the positive electrode sheet 100 from being broken when operating the first protrusion 131 and the second protrusion 132, thereby improving the yield rate of the positive electrode sheet 100.

[0073] like Figure 1 As shown, along the horizontal axis L at the inner center of the wound battery cell 1, the straight area 11 includes an upper straight area and a lower straight area, the thickness of the arc area 12 is R, the thickness of the upper straight area is T, the units of R and T are the same, and the relationship between R and T satisfies: R / T=0.98~1.3.

[0074] The present invention controls the thickness R of the arc region 12 to be substantially equivalent to the thickness of the upper straight region (0.98-1.02) or even higher (1.02-1.3), thereby avoiding stress concentration caused by expansion, reducing the precipitation of lithium dendrites caused by stress concentration, and improving safety performance and cycle performance. That is, the relationship between R and T meets the above requirements, and can ensure that the stress of the arc region 12 will not be significantly transferred outward during the battery cycle, reduce the stress on the outer ring pole piece (i.e., the positive pole piece 100 and the negative pole piece 300 close to the outer arc surface 14 of the arc region 12), suppress the degree of lithium precipitation in the arc region 12, and improve the problem of fracture of the arc region 12.

[0075] Among them, the ratio of R to T can be 0.98, 0.99, 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.2, 1.21, 1.22, 1.23, 1.24, 1.25, 1.26, 1.27, 1.28, 1.29, and 1.3.

[0076] On the other hand, the present invention also provides an electrochemical device, which includes the above-mentioned wound battery cell 1 and a shell, wherein the wound battery cell 1 is accommodated in the shell. There is no limitation on the type of the shell, for example, it can be an aluminum-plastic film or other similar or dissimilar materials.

[0077] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0078] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0079] The present invention is described in detail below in conjunction with specific embodiments, which are used to understand but not to limit the present invention.

[0080] Example 1

[0081] The lithium-ion battery of this embodiment is prepared according to the following method.

[0082] (1) Preparation of positive electrode sheet 100:

[0083] LiCoO2: conductive carbon black: PVDF were mixed in a mass ratio of 9.8:0.1:0.1, N-methylpyrrolidone (NMP) was used as a solvent, and then stirred in a planetary mixer for 12 hours to obtain a positive electrode active material slurry; the positive electrode active material slurry was evenly coated on an aluminum foil with a diameter of 8 μm, placed in an oven at 60°C and dried for 24 hours, and then embossed to obtain a positive electrode sheet 100 with a first protrusion 131 having a height h1 of 4 μm and a second protrusion 132 having a height h2 of 4 μm.

[0084] In the positive electrode sheet 100 , the diameter r1 of the first projection of the first protrusion 131 is 1 mm, the diameter r2 of the second projection of the second protrusion 132 is 1 mm, and the corresponding distances of d1 , d2 , d3 , and d4 are adjusted so that d5 reaches 8 mm, wherein d1 = d2 and d3 = d4.

[0085] (2) Preparation of negative electrode sheet 300:

[0086] The negative electrode active material, styrene-butadiene rubber (SBR), lithium polyacrylate, conductive carbon black (SP) and carbon nanotubes (CNTs) are mixed uniformly in a mass ratio of 96.5:1.5:0.5:1.0:0.5, and then an appropriate amount of deionized water is added step by step to obtain a negative electrode slurry under the action of a vacuum mixer; the negative electrode active slurry is uniformly coated on both surfaces of a copper foil by a coating machine; the coated copper foil is dried, and then rolled and slit to obtain a negative electrode sheet 300 with a thickness t of 45 μm. In the prepared negative electrode sheet 300, the negative electrode active material is composed of artificial graphite and silicon carbon, and the percentage x of silicon element in the negative electrode active layer is 10%.

[0087] (3) Preparation of electrolyte:

[0088] LiPF6 is dissolved in an EC / FEC mixed organic solvent to obtain an electrolyte with a lithium salt concentration of 1M, and the percentage content y of FEC in the electrolyte is 15%.

[0089] (4) The diaphragm is a polyethylene (PE) film.

[0090] (5) Preparation of batteries:

[0091] The positive electrode sheet 100, the negative electrode sheet 300 and the separator are wound to form a core roll of R=6mm, T=6mm, which is then wrapped with aluminum-plastic film. After baking to remove moisture, the electrolyte is injected, and the lithium battery is obtained after vacuum packaging, aging, formation, shaping, and sorting.

[0092] Examples 2-9 and Comparative Examples 1-6

[0093] The lithium-ion batteries of Examples 2-9 and Comparative Examples 1-6 are prepared by referring to the method of the lithium-ion battery of Example 1, except that: the height of the first protrusion 131 is h1 μm, the height of the second protrusion 132 is h2 μm, the percentage of silicon in the negative electrode active layer 320 is x, and the thickness of the negative electrode sheet 300 is t μm. The specific settings are shown in Table 1.

[0094] Table 1

[0095]

[0096]

[0097] The other parameter conditions in Examples 2-9 and Comparative Examples 1-6 are the same as those in Example 1.

[0098] Examples 10-14

[0099] The lithium ion batteries of Examples 10-14 were prepared by referring to the method of the lithium ion battery of Example 1, except that the value of the percentage content y of the fluoroethylene carbonate in the electrolyte was adjusted, as shown in Table 2 below.

[0100] Table 2

[0101] y Example 10 20％ Embodiment 11 25％ Example 12 30％ Embodiment 13 10％ Embodiment 14 0％

[0102] The other parameter conditions in Examples 10-14 are the same as those in Example 1.

[0103] Examples 15-22

[0104] The lithium ion batteries of Examples 15-22 are all prepared by referring to the method of the lithium ion battery of Example 1, except that the distances corresponding to d1, d2, d3, and d4 are adjusted so that d5 (mm) reaches the value shown in Table 3, and the values ​​of r1 (mm) and r2 (mm) are adjusted at the same time, as shown in Table 3 below.

[0105] Table 3

[0106] d5(mm) r1(mm) r2(mm) d5 / (r1+r2) Embodiment 15 8.0 0.7 0.7 5.7 Example 16 4.0 0.5 0.5 4.0 Embodiment 17 6.0 0.6 0.6 5.0 Embodiment 18 8.8 0.8 0.8 5.5 Embodiment 19 9.0 1.0 1.0 4.5 Embodiment 20 10.0 2.0 0.5 4.0 Embodiment 21 15.0 3.0 0.1 4.8 Embodiment 22 10.0 2.0 2.0 2.5

[0107] Among them, other parameter conditions in Examples 15-22 are the same as those in Example 1.

[0108] Examples 23-28

[0109] The lithium ion batteries of Examples 23-28 were all prepared by referring to the method of the lithium ion battery of Example 1, except that: the thickness R of the arc area 12 and the thickness T of the upper straight area are shown in Table 4 below.

[0110] Table 4

[0111] R / T R(mm) T(mm) Embodiment 23 1.1 6 5.4 Embodiment 24 0.98 5.3 5.4 Embodiment 25 1 5.5 5.5 Embodiment 26 1.3 7.15 5.5 Embodiment 27 0.8 4.32 5.4 Embodiment 28 1.5 8.1 5.4

[0112] The other parameter conditions in Examples 23-28 are the same as those in Example 1.

[0113] The lithium ion batteries prepared by the above-mentioned embodiments and comparative examples were subjected to relevant performance tests, and the test results are recorded in Tables 5 to 8. The test methods are described as follows:

[0114] (1) Cycle life test

[0115] At an ambient temperature of 25°C, the charge and discharge regime is 1.8C constant current constant voltage charging to 4.48V and then 0.05C / 4C discharging to 3.0V for 300 cycles. The capacity retention rate is calculated as follows: Nth discharge capacity / first discharge capacity*100%.

[0116] (2) Battery expansion rate test

[0117] At an ambient temperature of 25°C, the charge and discharge regime is 1.8C constant current constant voltage charging to 4.48V and then 0.05C / 4C discharging to 3.0V for 300 cycles. The expansion rate is calculated as (Nth full charge thickness / first full charge thickness-1)*100%.

[0118] (3) Battery lithium deposition detection and negative electrode interface condition detection

[0119] At 25℃ ambient temperature, the charge and discharge regime is 1.8C constant current constant voltage charging to 4.48V and 0.05C / 4C discharging to 3.0V, for 300 cycles. After the cycle is completed, fully charge the battery and disassemble the battery cell in a dry environment.

[0120] Observe the lithium deposition on the surface of the negative electrode; the degree of lithium deposition is divided into severe lithium deposition > general lithium deposition > slight lithium deposition > no lithium deposition (the degree of lithium deposition decreases in sequence).

[0121] Observe whether the active layer has fallen off and evaluate the interface failure; interface failure detection is divided into severe falling off > general falling off > slight falling off > no falling off (the degree of interface failure decreases in turn).

[0122] Table 5

[0123]

[0124]

[0125] It can be seen from Examples 1-8 and Comparative Examples 5-6 that by controlling the height of the first protrusion and the height of the second protrusion and the thickness and silicon content of the negative electrode sheet, (h1+h2) / (t*x 0.3)=0.2~0.5, the debonding of the active material and the current collector on the negative electrode sheet can be significantly improved, and the lithium precipitation phenomenon can be significantly improved. In addition, the capacity retention rate of the battery is also significantly improved, and the expansion rate is significantly suppressed. This is because the convex structure is set in the arc area, the thickness of the arc area is increased, and a larger expansion space is reserved for the arc area, so that the expansion of the silicon volume of the negative electrode sheet during the lithium removal and lithium insertion process can be absorbed. In addition, it can be seen from Example 9 and Comparative Examples 1-4 that the height of the convexity exceeds 20μm, the height of the first convexity and the second convexity is greater than 25μm, the silicon doping amount is greater than 0.5, or the thickness of the negative electrode sheet does not meet 25≤t≤100, lithium precipitation and interface failure problems will occur.

[0126] Table 6

[0127] Capacity retention rate % Lithium precipitation Expansion rate % Interface Example 10 89.9 No lithium precipitation 9.8 No shedding Embodiment 11 90.8 No lithium precipitation 10.2 No shedding Example 12 86.2 Slight lithium deposition 12.3 Slight shedding Embodiment 13 82.2 General lithium deposition 12.5 Slight shedding Embodiment 14 78.9 Severe lithium deposition 12.8 Slight shedding

[0128] It can be seen from Examples 1 and 14 that the battery of the present invention satisfies (h1+h2) / (t*x 0.3 )=0.2~0.5, by adding fluoroethylene carbonate to the electrolyte, the local lithium precipitation problem caused by the instability of the SEI film can be further improved, and the capacity retention rate of the battery can be significantly improved. It can be seen from Examples 1 and 10-13 that in the battery of the present invention, (h1+h2) / (t*x 0.3 )=0.2~0.5, by controlling the content of fluoroethylene carbonate in the electrolyte within the range of 15-25%, it is possible to ensure that the pole piece does not precipitate lithium and the negative electrode active material does not fall off, effectively reduce the expansion rate and improve the cycle performance. It can be seen from Example 1 and Examples 10-11 that within the content range of fluoroethylene carbonate of the present invention, increasing the content of fluoroethylene carbonate can further improve the cycle performance.

[0129] Table 7

[0130] Capacity retention rate % Lithium precipitation Expansion rate % Interface Embodiment 15 89.4 No lithium precipitation 9.9 No shedding Example 16 90.4 No lithium precipitation 10.8 No shedding Embodiment 17 90.8 No lithium precipitation 10.2 No shedding Embodiment 18 90.9 No lithium precipitation 10.3 No shedding Embodiment 19 89.9 No lithium precipitation 9.8 No shedding Embodiment 20 90 No lithium precipitation 10.2 No shedding Embodiment 21 78.1 Severe lithium deposition 18.8 Severe shedding Embodiment 22 79.8 Severe lithium deposition 19.4 Severe shedding

[0131] It can be seen from Examples 15-20 and Examples 21-22 that by controlling the values ​​of d5, r1, r2 and d5 / (r1+r2) within the optimized range of the present invention, the problems of lithium plating and interface failure in the electrode can be avoided. At the same time, the capacity retention rate of the battery can be above 89% and the expansion rate can be below 11%.

[0132] Table 8

[0133] Capacity retention rate % Lithium precipitation Expansion rate % Interface Embodiment 23 89.4 No lithium precipitation 10.8 No shedding Embodiment 24 90.3 No lithium precipitation 10.4 No shedding Embodiment 25 90.4 No lithium precipitation 10.2 No shedding Embodiment 26 89.9 No lithium precipitation 9.9 No shedding Embodiment 27 79.1 Severe lithium deposition 18.3 Severe shedding Embodiment 28 83.5 General lithium deposition 13.7 General shedding

[0134] From the results of Examples 23-26 and Examples 27-28, it can be seen that controlling the R / T value within the range of 0.98-1.3 can avoid stress concentration caused by expansion, reduce the precipitation of lithium dendrites caused by stress concentration, and improve safety performance and cycle performance.

[0135] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A wound battery cell, characterized in that: It comprises an electrolyte and a positive electrode sheet (100), a separator and a negative electrode sheet (300) which are stacked and wound in sequence; The wound battery core (1) comprises a straight area (11) and arc areas (12) located at two ends of the straight area (11); The positive electrode sheet (100) comprises a first region (130) and a second region (140), the first region (130) being located in the arc region (12), the second region (140) being located in the straight region (11), the first region (130) having a first surface (135) and a second surface (136) being arranged opposite to each other along a first direction, the first surface (135) being provided with a first protrusion (131), and / or the second surface (136) being provided with a second protrusion (132), the first protrusion (131) having a height of h1 μm, and the second protrusion (132) having a height of h2 μm; The negative electrode sheet (300) comprises a negative electrode current collector (310) and a negative electrode active layer (320) located on the negative electrode current collector (310), the negative electrode active layer (320) comprises a silicon-carbon composite material and / or a silicon-oxygen composite material, the percentage content of silicon element in the negative electrode active layer (320) is x, and the thickness of the negative electrode sheet (300) is t μm; Among them, the relationship between h1, h2, x and t satisfies: (h1+h2) / (t*x 0.3 )=0.2~0.5, 0%<x≤50%, 25≤t≤100, at least one of h1 and h2 is greater than 0, and h1+h2≤25.

2. The wound battery cell according to claim 1, characterized in that: The electrolyte includes a film-forming additive, and the film-forming additive includes fluoroethylene carbonate. The percentage content y of the fluoroethylene carbonate in the electrolyte is 15% to 25%.

3. The wound battery cell according to claim 1 or 2, characterized in that: 0<h1≤20, and / or, 0<h2≤20.

4. The wound battery cell according to claim 1, characterized in that: The second surface (136) is provided with a first groove (133), and the first groove (133) is arranged corresponding to the first protrusion (131); and / or, The first surface (135) is provided with a second groove (134), and the second groove (134) is arranged corresponding to the second protrusion (132).

5. The wound battery cell according to claim 4, characterized in that: The projection of the first groove (133) in the first direction is adjacent to the projection of the second protrusion (132) in the first direction, and / or the projection of the second groove (134) in the first direction is adjacent to the projection of the first protrusion (131) in the first direction.

6. The wound battery cell according to claim 4, characterized in that: The first area (130) has a plurality of first protrusion rows (137) and a plurality of second protrusion rows (138); the first protrusion row (137) has a plurality of first protrusions (131) distributed along a second direction; the second protrusion row (138) has a plurality of second protrusions (132) distributed along the second direction; the first protrusion rows (137) and the second protrusion rows (138) are alternately arranged along a third direction; and the first direction, the second direction and the third direction are arranged perpendicularly in pairs.

7. The wound battery cell according to claim 6, characterized in that: Along a fifth direction, the first protrusions (131) and the second grooves (134) are arranged alternately, and the fifth direction and the third direction have a first preset angle; And / or, along a sixth direction, the first protrusions (131) and the second grooves (134) are arranged alternately, the sixth direction and the third direction have a second preset angle, and the fifth direction and the sixth direction have opposite deflection directions.

8. The wound battery cell according to claim 7, characterized in that: The first preset angle ranges from 15° to 75°; and / or, The second preset angle ranges from 15° to 75°.

9. The wound battery cell according to claim 6, characterized in that: The first protrusion (131) has a first projection along the first direction, and the center distance between two adjacent first projections in the second direction is d1 mm, and d1 satisfies: 0.5≤d1≤15; and / or, The second protrusion (132) has a second projection along the first direction, and the center distance between two adjacent second projections in the second direction is d2 mm, and d2 satisfies: 0.5≤d2≤15.

10. The wound battery cell according to claim 9, characterized in that: In two adjacent rows of first protrusions (137), the center distance between the first projections of the two closest first protrusions (131) is d3 mm, and d3 satisfies: 0.5≤d3≤15; and / or, In two adjacent rows of second protrusions (138), the center distance between the second projections of the two closest second protrusions (132) is d4 mm, and d4 satisfies: 0.5≤d4≤15.

11. The wound battery cell according to claim 10, characterized in that: d1=d2, d3=d4.

12. The wound battery cell according to claim 9, characterized in that: The diameter of the first projection is r1 mm, the diameter of the second projection is r2 mm, and in adjacent first protrusion rows (137) and second protrusion rows (138), the center distance between the first projection of the first protrusion (131) closest to the second protrusion (132) is d5 mm, and the relationship between d5, r1, and r2 satisfies: d5 / (r1+r2)≥4.

13. The wound battery cell according to claim 12, characterized in that: r1 satisfies: 0.5≤r1≤3, and / or, r2 satisfies: 0.5≤r2≤3, and / or, d5 satisfies: 4≤d5≤10.

14. The wound battery cell according to claim 13, characterized in that: The fracture elongation of the positive electrode sheet (100) is γ%, and γ satisfies: 1.5≤γ≤5.

15. The wound battery cell according to claim 14, characterized in that: The relationship among r1, h1 and γ satisfies: The relationship among r2, h2 and γ satisfies:

16. The wound battery cell according to any one of claims 1 to 15, characterized in that: Along the horizontal axis at the inner center of the wound battery core, the straight area (11) includes an upper straight area and a lower straight area, the arc area (12) has a thickness of R, the upper straight area has a thickness of T, R and T have the same unit, and the relationship between R and T satisfies: R / T=0.98-1.

3.

17. An electrochemical device, characterized in that: It comprises a wound battery cell (1) as claimed in any one of claims 1 to 16 and a shell, wherein the wound battery cell (1) is accommodated in the shell.

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