Winding battery cell and secondary battery

Abstract

The invention provides a wound battery cell and a secondary battery, the wound battery cell comprises a wound battery cell base body and gummed paper, the wound battery cell base body is formed by stacking a positive pole piece, a diaphragm and a negative pole piece and winding along the winding direction, the wound battery cell base body comprises N bending areas, a bending area where the positive pole piece, the diaphragm and the negative pole piece are simultaneously bent along the same direction for the first time is a first bending area; n > = 5; the gummed paper comprises a porous base material layer and a coating layer arranged on at least one side surface of the porous base material layer; the porous base material layer comprises a plurality of fibers, the plurality of fibers are crossed and / or laminated to form pores, and the coating layer is partially embedded into the pores; wherein the gummed paper comprises first gummed paper which is at least partially positioned in the first bending area, and the first gummed paper covers at least part of the surface of at least one of the positive pole piece, the diaphragm and the negative pole piece. The wound battery cell provided by the invention has excellent energy density and cycle performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary batteries, and particularly relates to a wound battery cell and a secondary battery. Background Art

[0002] Lithium-ion batteries are widely used in fields such as mobile phones, laptop computers, and electric vehicles. With the gradual expansion of the application market demand, new requirements are constantly being put forward for the energy density of lithium-ion batteries. Using thick electrode sheets and increasing the compaction density to improve the energy density of lithium-ion batteries is a commonly used method at present. However, when the areal density of the positive and negative electrode sheets is relatively high or the compaction density is relatively large, the flexibility of the positive and negative electrode sheets will significantly deteriorate, resulting in powder shedding or fracture at the inner bending part of the electrode sheet during the winding process of the battery cell, affecting the energy density and cycle life of the wound battery cell, and even causing safety risks such as internal short circuits.

[0003] In order to reduce the above-mentioned stress and improve the powder shedding or fracture problem, at present, when preparing a wound battery cell, adhesive tape is pasted on the electrode sheet, and by increasing the radius of curvature of the arc, the powder shedding or fracture phenomenon of the electrode sheet is improved. However, the effect of the above method in improving the energy density and cycle performance of the wound battery cell is not significant. Summary of the Invention

[0004] The present invention provides a wound battery cell, which has excellent energy density and cycle life.

[0005] The present invention further provides a secondary battery, including the above-mentioned wound battery cell, so that the secondary battery has excellent energy density and cycle life.

[0006] In a first aspect of the present invention, a wound battery cell is provided, including a wound battery cell body and adhesive tape. The wound battery cell body is formed by laminating a positive electrode sheet, a separator, and a negative electrode sheet and winding them along the winding direction. The wound battery cell body includes N bending regions, and the bending region where the positive electrode sheet, the separator, and the negative electrode sheet are bent in the same direction for the first time is the first bending region; N≥5;

[0007] The adhesive tape includes a porous base material layer and a coating layer provided on at least one surface of the porous base material layer; the porous base material layer includes a plurality of fibers, and pores are formed by crossing and / or laminating between the plurality of fibers, and part of the coating layer is embedded in the pores;

[0008] Wherein, the adhesive tape includes a first adhesive tape at least partially located in the first bending region, and the first adhesive tape covers at least part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet.

[0009] The wound battery cell as described above, wherein, in the direction away from the first bending region in sequence, the bending regions are the second bending region, the third bending region, and the fourth bending region respectively; the adhesive tape further includes a second adhesive tape at least partially located in the second bending region, and the second adhesive tape covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet;

[0010] And / or, the adhesive tape further includes a third adhesive tape at least partially located in the third bending region, and the third adhesive tape covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet;

[0011] And / or, the adhesive tape further includes a fourth adhesive tape at least partially located in the fourth bending region, and the fourth adhesive tape covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet.

[0012] The wound battery cell as described above, wherein, in the bending region where the adhesive tape is provided, the adhesive tape covers at least the inner surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet, and the inner surface is close to the winding center.

[0013] The wound battery cell as described above, wherein, in the bending region where the adhesive tape is provided, the adhesive tape also covers at least the outer surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet, and the outer surface is away from the winding center;

[0014] Preferably, in the same bending region, the adhesive force of the adhesive tape located on the inner surface is less than or equal to the adhesive force of the adhesive tape located on the outer surface.

[0015] The wound battery cell as described above, wherein the wound battery cell substrate further includes a first straight region and a second straight region connected to both sides of each bending region; the adhesive tape includes a bending section and a first straight section and a second straight section connected to both ends of the bending section. In the bending region where the adhesive tape is provided, the bending section is located in the bending region and covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet, the first straight section is located in the first straight region and covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet, and the second straight section is located in the second straight region and covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet;

[0016] In the winding direction of the wound core substrate, the lengths of the first straight section and the second straight section are different.

[0017] The wound battery cell as described above, the second adhesive tape covers at least a part of the surface of the positive electrode sheet, and at least one of the two ends of the second adhesive tape exceeds the junction of the negative active layers on both sides of the negative electrode sheet; and / or,

[0018] The fourth adhesive tape covers at least a part of the surface of the positive electrode sheet, and at least one of the two ends of the fourth adhesive tape extends beyond the junction of the negative active layers on both sides of the negative electrode sheet.

[0019] The wound battery cell as described above, wherein the coating layer includes a part embedded in the pores and a part located on the surface of the porous substrate layer, and the thickness of the part on the surface does not exceed three times the sum of the diameters of two of the fibers;

[0020] And / or, the diameter of the fiber is 2 μm to 20 μm; and / or, the pore diameter of the pores is 0.1 μm to 50 μm; and / or, the thickness of the porous substrate layer is 5 μm to 20 μm; and / or, the thickness of the coating layer is 2 μm to 15 μm.

[0021] The wound battery cell as described above, wherein the bending stiffness of the adhesive tape is ≤ 15 mN.

[0022] The wound battery cell as described above, wherein the coating layer includes filler particles and an adhesive; wherein, the mass ratio of the adhesive to the filler particles is (25 to 70):(30 to 75);

[0023] Preferably, the adhesive includes at least one of polyisobutylene, styrene-isoprene copolymer, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber;

[0024] Preferably, the filler particles include at least one of alumina, boehmite, Li7La3Zr2O 12 、Li3xLa (2 / 3-x) / 3 TiO3、Li1+xAl x Ti 2-x (PO4)3, magnesium oxide, titanium oxide, hafnium dioxide, tin dioxide, cerium dioxide, nickel oxide, zirconium oxide, zinc oxide, calcium oxide, magnesium hydroxide, aluminum hydroxide, barium hydroxide, barium sulfate, calcium silicate, titanium dioxide.

[0025] The second aspect of the present invention provides a secondary battery, including the wound battery cell as described above.

[0026] The wound cell provided by the present invention has a first adhesive tape arranged in the first bending area of ​​the wound cell substrate. By arranging the first adhesive tape in the first bending area, the curvature radius of the bending of the pole piece in the first bending area is increased, the bending stress is reduced, and the problem of powder loss or breakage caused by the bending of the pole piece is improved. In addition, the adhesive tape can further prevent the protruding or loose particles on the surface of the active layer from piercing the diaphragm to avoid short circuit; at the same time, the first adhesive tape includes a porous substrate layer and a coating layer, and the porous substrate layer and the coating layer both have pores. When the first adhesive tape is attached to the wound cell substrate through the coating layer, the pores of the porous substrate layer and the coating layer are used to provide channels for lithium ion insertion and extraction, so that the adhesive tape has ion conductivity. Therefore, the wound cell has excellent energy density and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0028] Figure 1 This is a schematic diagram of the structure of a wound battery cell in Example 1 of the present invention;

[0029] Figure 2 Schematic diagram of the structure of the wound battery cell in Example 10 of the present invention;

[0030] Figure 3 This is a schematic diagram of the adhesive tape structure in Example 1 of the present invention;

[0031] Figure 4 This is a SEM image of the side of the adhesive tape containing the coating layer in Example 1 of the present invention;

[0032] Figure 5 This is a SEM image of the side of the adhesive tape in Example 1 of the present invention without the coating layer.

[0033] Reference numerals:

[0034] 1-coating layer; 2-porous substrate layer; 3-first adhesive tape; 4-positive electrode current collector; 5-diaphragm; 6-positive electrode active material coating; 7-negative electrode current collector; 8-negative electrode active material coating; 9-first bend; 10-second bend; 11-third bend; 12-fourth bend.

[0035] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the present invention more clear, the following will, in conjunction with the embodiments of the present invention, clearly and completely describe the technical solutions in the embodiments of the present invention. Apparently, the described embodiments are some, rather than all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0037] When improving the energy density of a lithium-ion battery in the prior art, thick electrode sheets and increased compaction density are adopted. The problems brought about thereby are: the flexibility of the electrode sheet will significantly deteriorate, resulting in the phenomenon of powder dropping or fracture of the electrode sheet during the winding process of the battery cell, thereby affecting the performance of the lithium-ion battery.

[0038] To solve this problem, those skilled in the art paste adhesive tape at the bending part of the inner circle of the electrode sheet to increase the arc curvature radius and reduce stress, thereby improving the problem of powder dropping or fracture; however, the effect is not ideal and will lead to a decrease in the energy density of the battery.

[0039] Through creative efforts, the inventor found that the reason for the unsatisfactory above effect lies in: on the one hand, when setting the adhesive tape in the wound battery cell matrix, the setting position of the adhesive tape directly affects the improvement effect of the powder dropping or fracture problem; on the other hand, the existing adhesive tape for lithium-ion batteries cannot conduct ions, and the capacity will be lost after pasting, resulting in a decrease in the energy density of the battery. Therefore, reducing the bending stress of the electrode sheet in the wound battery cell matrix and improving the ion-conducting characteristics of the adhesive tape can be used as improvement points to improve the powder dropping or fracture problem of the electrode sheet and the ion-conducting performance of the adhesive tape, thereby improving the energy density and cycle life of the wound battery cell, and further realizing the improvement of the energy density and cycle life of the battery.

[0040] Based on this, in the first aspect of the present invention, a wound battery cell is provided. Please refer to Figure 1 、 Figure 2 and Figure 3 simultaneously. The wound battery cell includes a wound battery cell matrix and an adhesive tape. The wound battery cell matrix is formed by laminating a positive electrode sheet, a separator, and a negative electrode sheet and winding them along the winding direction. The wound battery cell matrix includes N bending regions. The bending region where the positive electrode sheet, the separator, and the negative electrode sheet are bent in the same direction for the first time is the first bending region 9; N≥5;

[0041] The adhesive tape includes a porous base material layer 2 and a coating layer 1 provided on at least one surface of the porous base material layer 2; the porous base material layer 2 contains a plurality of fibers, and pores are formed by crossing and / or laminating between the plurality of fibers; part of the coating layer 1 is embedded in the pores;

[0042] Among them, the adhesive tape includes a first adhesive tape 3 at least partially located in the first bending region 9, and the first adhesive tape 3 covers at least part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet.

[0043] The adhesive tape of the present invention includes a porous substrate layer and a coating layer. Herein, the material of the porous substrate layer is not limited in the present invention. For example, it can be a commonly used polymer fiber in the art. Pores can be formed by crossing among several polymer fibers forming the porous substrate layer, can be formed by laminating, or there can be pores formed by crossing and pores formed by laminating at the same time.

[0044] The wound battery cell substrate of the present invention includes N bending regions. Each bending region includes a positive electrode tab, a negative electrode tab, and a separator located between the two. The first bending region 9 is the bending region where the positive electrode tab, the separator, and the negative electrode tab are bent in the same direction for the first time. And, a first adhesive tape 3 having the above composition is provided in the first bending region 9.

[0045] It should be noted that the first adhesive tape 3 can be provided on the surface of one of the positive electrode tab, the separator, and the negative electrode tab in the first bending region 9; it can also be provided on the surfaces of two of the positive electrode tab, the separator, and the negative electrode tab in the first bending region 9; it can also be provided on the surfaces of the positive electrode tab, the separator, and the negative electrode tab in the first bending region 9. When specifically setting, the coating layer of the first adhesive tape is adhered to the surface of at least one of the positive electrode tab, the separator, and the negative electrode tab.

[0046] The wound battery cell provided by the present invention has excellent battery energy density and cycle life. The reasons are as follows: On the one hand, in the wound battery cell substrate, the curvature radius of the first bending part is the smallest. When winding, the bending stress on the electrode tab or the separator in the first bending region 9 is the largest, and the probability of generating powder falling or fracture problems is the largest and the most serious. Therefore, the first adhesive tape 3 is provided in the first bending region 9, reducing the bending stress in the first bending region 9, greatly reducing the probability of generating powder falling or fracture problems. In addition, the adhesive tape can further prevent particles from piercing the separator to avoid short circuit, ensuring the normal operation of the wound battery cell, thereby ensuring a relatively high battery energy density and a long cycle life; on the other hand, the pores in the porous substrate layer and the coating layer of the adhesive tape can provide channels for the insertion and extraction of active ions, so as to ensure that more active ions can participate in the charge and discharge of the battery. Therefore, after the adhesive tape is provided in the first bending region 9, by reducing the bending stress of the wound core in the mechanical dimension and isolating the contact between the positive and negative electrodes in the physical space dimension, and at the same time promoting the efficient migration of active ions during the insertion and extraction process of the electrodes in the electrochemical dimension, realizing double synergistic optimization, and further enabling the wound battery cell provided by the present invention to have a relatively high battery energy density and cycle life.

[0047] The wound battery cell of the present invention can be a wound structure formed by laminating a positive electrode sheet, a separator, and a negative electrode sheet as shown in Figure 1 or a wound structure in which the positive electrode sheet and the negative electrode sheet are inserted on both sides of the separator as shown in Figure 2 .

[0048] Except for the first bending region 9, in the direction away from the first bending region in sequence along the length direction of the electrode sheet, the bending regions are the second bending region 10, the third bending region 11, and the fourth bending region 12 respectively. Among them, the second bending region 10 is closest to the first bending region 9. One side of the second bending region 10 away from the first bending region 9 is the third bending region 11, and one side of the third bending region 11 away from the second bending region 10 is the fourth bending region 12. In a specific embodiment, the adhesive tape further includes a second adhesive tape at least partially located in the second bending region 10, and the second adhesive tape covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet. Since the radius of curvature of the second bending region 10 is also small and the bending stress is large, the second adhesive tape is provided in the second bending region 10 to increase the radius of curvature of the second bending region 10, reduce the bending stress, and further reduce the probability of powder falling or fracture; at the same time, the pores of the second adhesive tape can further promote the insertion and extraction of active ions and improve the transport efficiency of active ions.

[0049] As Figure 2 shown, in a specific embodiment, the wound battery cell includes a wound battery cell body and an adhesive tape. The wound battery cell body is formed by laminating a positive electrode sheet, a separator, and a negative electrode sheet. In the winding direction, the first winding starting section of the positive electrode sheet and the second winding starting section of the negative electrode sheet extend in different directions respectively, and the inner side of the first winding starting section in the thickness direction is directly opposite to the inner side of the second winding starting section in the thickness direction, and the winding starting end of the negative electrode corresponds to the first bending region of the positive electrode; in the direction away from the first bending region in sequence along the length direction of the positive electrode sheet, the bending regions are the first bending region 9 and the second bending region 10 respectively, and the first bending region 9 and the second bending region 10 of the positive electrode sheet are provided with the adhesive tape on the inner surface close to the winding center.

[0050] In a specific embodiment, the adhesive tape further includes a third adhesive tape at least partially located in the third bending region 11, and the third adhesive tape covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet. Relatively speaking, although the bending stress received by the third bending region 11 is smaller than that received by the first bending region 9 and the second bending region 10, powder falling or fracture may still occur. Therefore, the third adhesive tape is provided in the third bending region 11 to increase the radius of curvature of the third bending region 11, reduce the bending stress, and further reduce the probability of powder falling or fracture; at the same time, the pores of the third adhesive tape can further promote the insertion and extraction of active ions and improve the transport efficiency of active ions.

[0051] In a specific embodiment, the adhesive tape further includes a fourth adhesive tape at least partially located in the fourth bending region 12, and the fourth adhesive tape covers at least a part of the surface of at least one of the positive electrode plate, the separator, and the negative electrode plate. Relatively speaking, although the bending stress on the fourth bending region 12 is smaller than that on the first bending region 9, the second bending region 10, and the third bending region 11, there may still be powder shedding or fracture phenomena. Therefore, a fourth adhesive tape is provided in the fourth bending region 12 to increase the radius of curvature of the fourth bending region 12, reduce the bending stress, and further reduce the probability of powder shedding or fracture problems; at the same time, the pores of the fourth adhesive tape can further promote the insertion and extraction of active ions and improve the transport efficiency of active ions.

[0052] Further, in the bending region provided with the adhesive tape, the adhesive tape covers at least the inner surface of at least one of the positive electrode plate, the separator, and the negative electrode plate, where the inner surface is close to the winding center.

[0053] As described above, when at least one of the first adhesive tape, the second adhesive tape, the third adhesive tape, and the fourth adhesive tape is provided according to the foregoing limitations, the adhesive tape can be provided on the inner surface of at least one of the positive electrode plate, the separator, and the negative electrode plate in the corresponding bending region. Since the inner surface is close to the winding center, the radius of curvature of the inner surface is smaller and the bending stress is greater. The active coating on the inner circle is more likely to be extruded and shed powder under the action of the extrusion stress. Therefore, providing the adhesive tape on the inner surface can minimize the bending stress to the greatest extent, thereby reducing the probability of powder shedding or fracture problems.

[0054] To further increase the radius of curvature, an adhesive tape can also be provided on the outer surface of at least one of the positive electrode plate, the separator, and the negative electrode plate to further reduce the probability of powder shedding or fracture problems. Here, the outer surface refers to the surface on the same bending region as the above inner surface and on the side away from the winding center.

[0055] When both the inner surface and the outer surface exist in the same bending region, the adhesion of the adhesive tape on the inner surface is less than or equal to the adhesion of the adhesive tape on the outer surface. During the winding process, since the outer surface is farther from the winding center, the adhesive tape on the outer surface will wrap the electrode plate; while the inner surface is closer to the winding center, so the adhesive tape on the inner surface will be wrapped by the electrode plate. Therefore, the present invention further limits the adhesion of the adhesive tape on the inner surface to be less than or equal to the adhesion of the adhesive tape on the outer surface, so that the adhesion between the adhesive tape on the outer surface and the electrode plate or the separator is large enough to further ensure the flatness after the adhesive tape is pasted.

[0056] As Figure 1As shown, in a specific embodiment, the wound cell substrate further includes a first flat region and a second flat region connected to both sides of each bending region; the adhesive tape includes a bending section and a first flat section and a second flat section connected to both ends of the bending section. In the bending region where the adhesive tape is provided, the bending section is located in the bending region and covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet. The first flat section is located in the first flat region and covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet. The second flat section is located in the second flat region and covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet; in the width direction of the wound core substrate, the lengths of the first flat section and the second flat section are different.

[0057] Except for the bending regions, the wound cell substrate further includes a first flat region and a second flat region connected to both sides of each bending region. The adhesive tape of the present invention can also be provided in the first flat region and the second flat region. Taking the first adhesive tape as an example, the first adhesive tape includes three parts, namely a bending section, a first flat section, and a second flat section, wherein the first flat section is located at one end of the bending section, and the second flat section is located at the other end of the bending section. Specifically, the bending section is provided in the bending region, the first flat section is provided in the first flat region, and the second flat section is provided in the second flat region.

[0058] Taking the case where the adhesive tape is provided on the positive electrode sheet as an example, the end of the first flat section far from the bending section forms a first intersection with the positive electrode sheet, and the end of the second flat section far from the bending section forms a second intersection with the positive electrode sheet. When the lengths of the first flat section and the second flat section are different, the projections of the first intersection and the second intersection in the width direction of the wound core substrate are misaligned, reducing the thickness difference generated when the first flat region and the second flat region are covered with the adhesive tape at the same time, and alleviating the problem of uneven force during formation.

[0059] In a specific embodiment, the second adhesive tape covers at least a part of the surface of the positive electrode sheet, and at least one of the two ends of the second adhesive tape exceeds the junction of the negative active layers on both sides of the negative electrode sheet.

[0060] In order to further improve the toughness of the positive electrode sheet, it is preferably to cover at least a part of the surface of the positive electrode sheet with the adhesive tape.

[0061] When the positive electrode tab in the second bending area 10 covers the second adhesive tape, the second adhesive tape includes a bent section, a first straight section, and a second straight section; wherein, the bent section is located in the second bending area 10, the first straight section is located in the first straight area connected to the second bending area 10, and the second straight section is located in the second straight area connected to the second bending area 10. At this time, the two ends of the second adhesive tape are respectively one end of the first straight section far from the bent section and one end of the second straight section far from the bent section. Since the lengths of the negative active layers on both sides of the negative electrode tab are different, the end of the negative active layer with a shorter length forms a single-sided and double-sided junction with the negative active layer with a longer length, resulting in a certain thickness difference in the negative electrode tab itself. When at least one of the above two ends exceeds the single-sided and double-sided junction of the negative active layers on both sides of the negative electrode tab in the second bending area 10, the thickness difference can be further reduced, and the interface problem can be improved.

[0062] In a specific embodiment, the fourth adhesive tape covers at least part of the surface of the positive electrode tab, and at least one of the two ends of the fourth adhesive tape exceeds the junction of the negative active layers on both sides of the negative electrode tab. When the positive electrode tab in the fourth bending area 12 covers the fourth adhesive tape, the fourth adhesive tape includes a bent section, a first straight section, and a second straight section; wherein, the bent section is located in the fourth bending area 12, the first straight section is located in the first straight area connected to the fourth bending area 12, and the second straight section is located in the second straight area connected to the fourth bending area 12. At this time, the two ends of the fourth adhesive tape are respectively one end of the first straight section far from the bent section and one end of the second straight section far from the bent section. Since the lengths of the negative active layers on both sides of the negative electrode tab are different, the end of the negative active layer with a shorter length forms a single-sided and double-sided junction with the negative active layer with a longer length, resulting in a certain thickness difference in the negative electrode tab itself. When at least one of the above two ends exceeds the single-sided and double-sided junction of the negative active layers on both sides of the negative electrode tab, the thickness difference can be further reduced, the stress in the arc area can be further reduced, and the interface problem can be improved.

[0063] In a specific embodiment, the coating layer includes a part embedded in the pores and a part located on the surface of the porous substrate layer, and the thickness of the surface part does not exceed three times the sum of the diameters of two fibers. Within this range, the hardness and softness of the adhesive tape can be ensured to be moderate, so that it can maintain good flexibility, further reduce the bending stress, and improve the problem of powder falling or fracture caused by the bending of the tab.

[0064] Exemplarily, the thickness of the coating layer 1 is 0.5 times, 1 time, 1.5 times, 2 times, 2.5 times or three times the sum of the diameters of any two fibers, or a range composed of any two of these values.

[0065] Exemplarily, the porous substrate layer of the present invention includes at least one of polyethylene terephthalate fiber, polyethylene fiber, polypropylene fiber, polyimide fiber, polyvinyl chloride fiber, and composite fibers of polyethylene fiber and polypropylene fiber. It should be noted that when the porous substrate layer is a mixture of the above substances, the present invention does not specifically limit the proportion of each specific substance in the mixture.

[0066] The present invention does not specifically limit the sources of the substances in the porous substrate layer, and commercially available products or products prepared by conventional preparation methods well-known to those skilled in the art can be used.

[0067] In a specific embodiment, the diameter of the fiber is 2 μm to 20 μm. When the fiber diameter is within this range, the flexibility of the adhesive tape is better, which can better reduce the bending stress of the positive electrode sheet, separator or negative electrode sheet, and can make the substrate layer of the adhesive tape have appropriate pores, ensuring good ion conductivity of the adhesive tape.

[0068] Exemplarily, the diameter of the fiber is 2 μm, 3 μm, 6 μm, 8 μm, 10 μm, 13 μm, 15 μm, 17 μm, 18 μm or 20 μm, or a range composed of any two of these values; preferably, the diameter of the fiber is 3 μm to 6 μm.

[0069] In a specific embodiment, the pore diameter of the pores is 0.1 μm to 50 μm. Within this range, the softness, ion conductivity and mechanical strength of the adhesive tape are all good, while reducing the bending stress of the positive electrode sheet, separator or negative electrode sheet, further improving the transmission efficiency of active ions.

[0070] Exemplarily, the pore diameter of the pores is 0.1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm, or a range composed of any two of these values; preferably, the pore diameter of the pores is 0.5 μm to 10 μm.

[0071] In a specific embodiment, the thickness of the porous substrate layer is 5 μm to 20 μm. Within this range, the softness, ion conductivity and mechanical strength of the adhesive tape are all good, while reducing the bending stress of the positive electrode sheet, separator or negative electrode sheet, further improving the transmission efficiency of active ions.

[0072] Exemplarily, the thickness of the porous substrate layer is 5 μm, 7 μm, 9 μm, 10 μm, 12 μm, 14 μm, 15 μm, 17 μm, 19 μm or 20 μm, or a range composed of any two of these values.

[0073] In a specific embodiment, the thickness of the coating layer is 2 μm to 15 μm. When the thickness of the coating layer 1 is within this range, the flexibility of the adhesive tape is better, and it can better reduce the bending stress of the positive electrode sheet, the separator or the negative electrode sheet.

[0074] Exemplarily, the thickness of the coating layer 1 is 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm or 15 μm, or a range composed of any two of these values.

[0075] In a specific embodiment, the bending stiffness of the adhesive tape ≤ 15 mN. The bending stiffness refers to the ability of a material to resist deformation during the bending process and is usually used to evaluate the flexibility and bending resistance of the material.

[0076] When factors such as the diameter of the fiber, the thickness of the coating layer, the porosity of the porous substrate layer, the thickness of the porous substrate layer, and the pore diameter of the porous substrate layer are further defined and adjusted, the bending stiffness of the adhesive tape meets the above range. At this time, the flexibility of the adhesive tape in the wound state can be relatively high, and the problems of powder falling or fracture at the position where the electrode sheet or the separator is attached to the adhesive tape due to winding or bending stress can be improved.

[0077] Exemplarily, the bending stiffness of the adhesive tape is 2 mN, 4 mN, 6 mN, 8 mN, 10 mN, 12 mN, 14 mN or 15 mN, or a range composed of any two of these values.

[0078] In a specific embodiment, the coating layer includes filler particles and a binder, and the mass ratio of the binder to the filler particles is (25 - 70):(30 - 75). The pores formed between the filler particles can provide channels for active ions, further enhancing the ion conductivity of the bonding layer; at the same time, the filler particles themselves can adsorb the electrolyte, further facilitating the transport of active ions. The binder is used to paste the adhesive tape in the desired position. Within the above mass ratio range, the coating layer 1 can improve the ion conductivity of the adhesive tape while ensuring long-term bonding performance, and further enhance the flexibility of the adhesive tape.

[0079] Exemplarily, the mass ratio of the filler particles to the binder is 25:75, 35:65, 40:60, 50:50, 52:48, 55:45, 57:43, 60:40, 62:38, 64:36, 66:34, 68:32 or 70:30, or a range composed of any two of these values.

[0080] The present invention does not specifically limit the type of the adhesive. Preferably, the adhesive includes at least one of polyisobutene, styrene-isoprene copolymer, copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber.

[0081] It should be noted that when the adhesive includes multiple (two or more) of the above substances at the same time, the present invention does not specifically limit the proportion of each substance.

[0082] The present invention does not specifically limit the type of the filler particles. Preferably, the filler particles include at least one of alumina, boehmite, Li7La3Zr2O 12 、Li3xLa (2 / 3-x) / 3 TiO3, Li1+xAl x Ti 2-x (PO4)3, magnesium oxide, titanium oxide, hafnium dioxide, tin dioxide, cerium dioxide, nickel oxide, zirconium oxide, zinc oxide, calcium oxide, magnesium hydroxide, aluminum hydroxide, barium hydroxide, barium sulfate, calcium silicate, and titanium dioxide.

[0083] It should be noted that when the filler particles include multiple (two or more) of the above substances at the same time, the present invention does not specifically limit the proportion of each substance.

[0084] Furthermore, in order to better coat the filler particles on the porous substrate layer, the Dv50 of the filler particles is controlled.

[0085] In one embodiment, the Dv50 of the filler particles is 150 nm to 2 μm. Within this range, the thickness of the coating layer can be better regulated and the distribution of the filler particles is more uniform, so that the content of the electrolyte adsorbed by the adhesive tape is appropriate and uniform, which is convenient for balancing and reducing the transport impedance of the electrolyte, thereby realizing the efficient conduction of active ions.

[0086] Exemplarily, the Dv50 of the filler particles is 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, 1 μm, 1.5 μm or 2 μm, or the range composed of any two of these values.

[0087] Dv50 is a parameter used to describe the size distribution of particles or droplets, indicating that in the volume distribution, 50% of the particles or droplets have a diameter smaller than this value. It is commonly used to evaluate the uniformity of sprays, emulsions, or suspensions. The smaller the value, the finer the particles or droplets.

[0088] The present invention does not limit the composition of the positive electrode active material, binder, conductive agent, and current collector in the positive electrode sheet, and they can be common materials in the art.

[0089] For example, the positive electrode sheet of the present invention includes a positive electrode current collector and a positive electrode active material coating applied on at least one surface of the positive electrode current collector; the positive electrode active material coating includes a positive electrode active material, a conductive agent, and a binder.

[0090] The present invention does not specifically limit the type of the positive electrode active material, and it can be a conventional material in the art. For example, the positive electrode active material includes at least one of lithium cobaltate, lithium cobaltate (LCO), nickel cobalt manganese ternary material (NCM), nickel cobalt aluminum ternary material (NCA), nickel cobalt manganese aluminum quaternary material (NCMA), lithium iron phosphate (LFP), lithium manganese phosphate (LMP), lithium vanadium phosphate (LVP), lithium manganate (LMO), lithium-rich manganese-based, sulfur, NaxMO2 (M is a transition metal element such as Fe, Co, Ni, Mn, Cr, Ti, etc.), sodium iron sulfate, sodium fluorophosphate vanadate, and sodium vanadate phosphate.

[0091] The present invention does not specifically limit the material of the positive electrode current collector, and it can be a conventional material in the art. For example, the material of the positive electrode current collector can be any one of aluminum foil and nickel foil.

[0092] The present invention does not specifically limit the type of the conductive agent, and it can be a conventional material in the art. For example, the conductive agent can be selected from at least one of carbon black, acetylene black, graphene, Ketjen black, carbon fiber, carbon nanotube, and conductive graphite.

[0093] The present invention does not specifically limit the type of the binder, and it can be a conventional material in the art. For example, the binder can be selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polymers containing ethylene oxide, polyvinylpyrrolidone, and polyurethane.

[0094] The present invention does not specifically limit the preparation method of the positive electrode sheet. In one embodiment, the positive electrode can be prepared by a method including the following steps:

[0095] Disperse the positive electrode active material, conductive agent, and binder in an N-methylpyrrolidone (NMP) solvent, and fully stir and mix to form a uniform positive electrode slurry; uniformly coat the positive electrode slurry on the positive electrode current collector, and obtain the positive electrode sheet after drying, rolling, and slitting.

[0096] The present invention does not impose any specific restrictions on the amounts of the positive electrode active material, the conductive agent and the adhesive, and these amounts can be adjusted according to actual conditions.

[0097] The present invention does not limit the composition of the negative electrode active material, binder, conductive agent and current collector in the negative electrode plate, and they may be materials commonly used in the art.

[0098] The negative electrode sheet of the present invention comprises a negative electrode current collector and a negative electrode active material coating coated on at least one surface of the negative electrode current collector; the negative electrode active material coating comprises a negative electrode active material, a binder and a conductive agent.

[0099] The present invention does not specifically limit the material of the negative electrode current collector, which can be any conventional material in the art. For example, the negative electrode current collector can be any one of copper foil, nickel foam, and copper foam.

[0100] The present invention does not specifically limit the type of negative electrode active material, and it can be any negative electrode active material commonly used in current batteries. For example, the negative electrode active material can be selected from at least one of graphite, hard carbon, soft carbon, mesophase carbon microspheres, silicon-based negative electrode materials (mainly including silicon oxide, silicon-carbon negative electrode), tin-based negative electrode materials (mainly including tin, tin alloy), lithium titanate and lithium metal.

[0101] The present invention does not specifically limit the type of the binder, and it can be a binder commonly used in the negative electrode of the current battery. For example, the binder can be selected from at least one of carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate.

[0102] The present invention does not specifically limit the type of the conductive agent, and it can be a conductive agent commonly used in the negative electrode of the current battery. For example, the conductive agent can be selected from at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, graphene, carbon nanotubes, and conductive graphite.

[0103] The present invention does not specifically limit the method for preparing the negative electrode sheet. In one embodiment, the negative electrode sheet can be prepared by a method comprising the following steps:

[0104] The negative electrode active material, the conductive agent and the binder are dispersed in deionized water, and fully stirred and mixed to form a uniform negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode collector, and the negative electrode sheet is obtained after drying, rolling and cutting.

[0105] The present invention does not impose any specific restrictions on the amounts of the negative electrode active material, the conductive agent, and the adhesive, which can be adjusted according to actual conditions.

[0106] The material of the separator in the present invention is not limited and can be a common material in the art.

[0107] For example, the separator can be selected from any one of a polypropylene separator (PP), a polyethylene separator (PE), a polypropylene / polyethylene double-layer composite film (PP / PE), a polyimide electrospun separator (PI), a polypropylene / polyethylene / polypropylene three-layer composite film (PP / PE / PP), a cellulose non-woven separator, and a separator with a ceramic coating.

[0108] The fourth aspect of the present invention provides a secondary battery including the above-mentioned wound battery cell. Therefore, this secondary battery has a high energy density and cycle life.

[0109] The secondary battery of the present invention can be a lithium-ion battery or a sodium-ion battery.

[0110] In addition to the above-mentioned positive electrode, negative electrode, and separator, the secondary battery of the present invention further includes an electrolyte.

[0111] The present invention does not specifically limit the composition of the electrolyte, which may include one or more of the solvents commonly used in current battery electrolytes, as well as the electrolyte lithium salts commonly used in current battery electrolytes. For example, the solvent may include at least one of ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), diethyl carbonate (DEC), difluoroethylene carbonate (DFEC), dipropyl carbonate, ethyl methyl carbonate (EMC), ethyl acetate, ethyl propionate, propyl acetate, propyl propionate, sulfolane, and γ-butyrolactone; the lithium salt may include at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

[0112] The present invention does not have special requirements for the method of manufacturing the secondary battery, and a conventional manufacturing method in the art can be used.

[0113] In one embodiment, the above battery cell is subjected to liquid injection, aging, formation, vacuum sealing, and sorting to obtain a secondary battery. This secondary battery is made from the above battery cell, so it has a high energy density and cycle life.

[0114] Example 1 (Sticking adhesive tape at the first bending point of the positive electrode tab)

[0115] The adhesive tape in this example includes a porous substrate layer and a coating layer. The porous substrate layer is polyethylene terephthalate, and the adhesive layer includes polyethylene terephthalate and alumina.

[0116] Among them, the diameter of the fibers in the porous substrate layer is 3 μm, and the thickness of the coating layer is 6 μm; the thickness of the porous substrate layer is 10 μm, and the pore diameter of the pores is 20 μm.

[0117] The mass ratio of the binder to the filler particles in the coating layer is 60:40; among them, the Dv50 of the filler particles is 800 nm.

[0118] Figure 4 The SEM image of one side of the adhesive tape prepared in this example containing the coating layer Figure 5 The SEM image of the side of the adhesive tape in Example 1 of the present invention without the coating layer.

[0119] Paste the adhesive tape prepared in this example on the positive electrode tab, and prepare a secondary battery. The specific steps include:

[0120] (1) Preparation of the positive electrode tab

[0121] Disperse the positive electrode active material lithium cobaltate, the binder PVDF, and the conductive carbon black in N-methylpyrrolidone to obtain a uniform positive electrode active material slurry; in the positive electrode active material layer slurry, the solid components include 97 wt% of lithium cobaltate, 2 wt% of the binder PVDF, and 1 wt% of the conductive agent. Coat the positive electrode slurry evenly on both sides of the aluminum foil. The thickness of the aluminum foil used is 8 μm. The coated electrode tab is dried and rolled to obtain a rolled electrode tab. The thickness of the rolled electrode tab is 130 μm; then it is slit and welded with the positive electrode tab to obtain the positive electrode tab. By testing the position of the first bending area of the electrode tab, paste the above adhesive tape on the first bending area to obtain the positive electrode tab to be wound.

[0122] (2) Preparation of the negative electrode tab

[0123] Mix and disperse graphite, the binder styrene-butadiene rubber, the thickener sodium carboxymethyl cellulose, and the conductive agent conductive carbon black in deionized water to obtain a negative electrode slurry; in the negative electrode slurry, the solid components include 97 wt% of graphite, 1.5 wt% of sodium carboxymethyl cellulose, 0.5 wt% of conductive carbon black, and 1 wt% of styrene-butadiene rubber. Coat the negative electrode slurry evenly on both sides of the copper foil. The thickness of the copper foil used is 6 μm. The coated electrode tab is dried and rolled to obtain a rolled electrode tab. The thickness of the rolled electrode tab is 165 μm; the electrode tab is then slit and welded with the negative electrode tab to obtain the negative electrode tab. By testing the position of the first bending area of the electrode tab, the negative electrode tab to be wound is obtained.

[0124] (3) According to the settings of the examples and comparative examples, paste the adhesive tape on the first bending area of the corresponding cell components respectively.

[0125] (4) Preparation of the secondary battery:

[0126] The positive electrode sheet, separator, and negative electrode sheet in (3) are stacked in sequence and then wound to form a core, which is encapsulated with an aluminum-plastic film. After baking for 24 h in a vacuum state to remove moisture, a commercially available electrolyte is injected (the electrolyte includes an organic solvent and a lithium salt, the organic solvent is a mixture of diethyl carbonate, dimethyl carbonate, and ethylene carbonate, the volume ratio of the three solvents is 1:1:1, the lithium salt is LiPF6, and the concentration is 1 mol / L). Then, the battery is formed, aged, vacuum sealed, and sorted to obtain a secondary battery.

[0127] Example 2

[0128] This example is basically the same as Example 1, except that:

[0129] In the adhesive tape, the porous substrate layer is polyethylene terephthalate, and the adhesive layer includes a styrene-isoprene copolymer and boehmite.

[0130] Among them, the diameter of the fibers in the porous substrate layer is 2 μm, and the thickness of the coating layer is 2 μm; the thickness of the porous substrate layer is 10 μm, and the pore diameter of the pores is 0.2 μm.

[0131] In the coating layer, the mass ratio of the adhesive to the filler particles is 70:30; among them, the Dv50 of the filler particles is 2 μm.

[0132] The position of the second bending area of the positive electrode sheet is located by a test paper, and the above-mentioned adhesive tape is pasted on the second bending area.

[0133] Example 3

[0134] This example is basically the same as Example 1, except that:

[0135] In the adhesive tape, the porous substrate layer is polyethylene terephthalate, and the adhesive layer includes a styrene-isoprene copolymer and boehmite.

[0136] Among them, the diameter of the fibers in the porous substrate layer is 15 μm, and the thickness of the coating layer is 15 μm; the thickness of the porous substrate layer is 20 μm, and the pore diameter of the pores is 50 μm.

[0137] In the coating layer, the mass ratio of the adhesive to the filler particles is 25:75; among them, the Dv50 of the filler particles is 2 μm.

[0138] The position of the second bending area of the positive electrode sheet is located by a test paper, and the above-mentioned adhesive tape is pasted on the second bending area.

[0139] Example 4

[0140] This example is basically the same as Example 1, except that:

[0141] Locate the position of the fourth bending area of the positive electrode tab through the test paper, and paste the above-mentioned adhesive tape on the fourth bending area.

[0142] Example 5

[0143] This example is basically the same as Example 1, except that:

[0144] Locate the positions of the first and second bending areas of the positive electrode tab through the test paper, and paste the above-mentioned adhesive tape on the first and second bending areas.

[0145] Example 6

[0146] This example is basically the same as Example 1, except that:

[0147] Locate the position of the second bending area of the negative electrode tab through the test paper, and paste the above-mentioned adhesive tape on the second bending area.

[0148] Example 7

[0149] This example is basically the same as Example 1, except that:

[0150] Locate the position of the second bending area of the negative electrode tab through the test paper, and paste the above-mentioned adhesive tape on the second bending area.

[0151] Example 8

[0152] This example is basically the same as Example 1, except that:

[0153] Locate the positions of the first and second bending areas of the negative electrode tab through the test paper, and paste the above-mentioned adhesive tape on the first and second bending areas.

[0154] Example 9

[0155] This example is basically the same as Example 1, except that:

[0156] Locate the position of the first bending area of the separator through the test paper, and paste the above-mentioned adhesive tape on the first bending area.

[0157] Example 10

[0158] This example is basically the same as Example 1, except that:

[0159] Locate the positions of the first and second bending areas of the separator through the test paper, and paste the above-mentioned adhesive tape on the first and second bending areas, as shown in Figure 2 .

[0160] Example 11

[0161] This example is basically the same as Example 1, except that:

[0162] The thickness of the coating layer is 20 μm.

[0163] Example 12

[0164] This example is basically the same as Example 1, except that:

[0165] The diameter of the fibers in the porous substrate layer is 25 μm, and the thickness of the porous substrate is 70 μm.

[0166] Example 13

[0167] This example is basically the same as Example 1, except that:

[0168] The diameter of the fibers in the porous substrate layer is 1.5 μm, and the thickness of the porous substrate is 4.5 μm.

[0169] Example 14

[0170] This example is basically the same as Example 1, except that:

[0171] The thickness of the coating layer is 1.5 μm.

[0172] Comparative Example 1

[0173] This comparative example is basically the same as Example 1, except that:

[0174] No adhesive tape is provided at the first bending position of the positive electrode tab.

[0175] Comparative Example 2

[0176] This comparative example is basically the same as Example 1, except that:

[0177] An adhesive tape that does not conduct ions conventionally is provided at the first bending position of the positive electrode tab.

[0178] Test Example

[0179] 1. Perform a bending stiffness test on the adhesive tapes of the above examples and comparative examples.

[0180] Test according to the national standard GB / T22364-2018 using a stiffness tester, with a bending angle of 15° and a bending length of 10 mm. The test results are shown in Table 1.

[0181] 2. Perform a cycle life and energy density test on the secondary batteries prepared from the above examples and comparative examples.

[0182] 1) Cycle life test

[0183] (1) Under the condition of 25 °C, charge at a constant current of 0.5C to 4.5V, and charge at a constant voltage until it cuts off at 0.05V;

[0184] (2) Discharge at a constant current of 0.5C until it cuts off at 3.0V, and record the first published discharge capacity as the initial capacity Q1;

[0185] (3) Repeat steps 1 - 2, taking the latest discharge capacity as the battery capacity Q2, and calculate the capacity retention rate (%); Capacity retention rate (%) = (Q2 / Q1) × 100%.

[0186] (4) Record the cycle number when the cyclic capacity retention rate drops to 80%, which is denoted as the cycle life.

[0187] The test results are shown in Table 1.

[0188] 2) Energy density test

[0189] Under the condition of 25°C, charge the battery to full at 0.2C and let it stand for 10 min. Discharge the battery at 0.2C to 3.0V to measure the battery capacity.

[0190] Calculation formula:

[0191] Energy density = (battery capacity × average voltage) / battery volume. The test results are shown in Table 1.

[0192] Table 1

[0193]

[0194]

[0195] As can be seen from Table 1, compared with Comparative Examples 1 and 2, the secondary batteries prepared in Examples 1 - 11 of the present invention all have a longer cycle life and a higher energy density. Specifically, the longest cycle life can reach 918 times, and the highest energy density can reach 365 Wh / L; while the secondary batteries in Comparative Example 1 and Comparative Example 2 have a shorter cycle life and a lower energy density. Thus, it can be seen that the wound core of the present invention can significantly improve the cycle life and energy density of the secondary battery.

[0196] Finally, it should be noted that: After considering the specification and practicing the invention disclosed herein, those skilled in the art will easily think of other embodiments of the present invention. The present invention aims to cover any variations, uses, or adaptations of the present invention, which follow the general principles of the present invention and include common general knowledge or conventional technical means in the technical field not disclosed in the present invention. It is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A wound battery cell, characterized in that, It includes a wound battery cell substrate and adhesive tape. The wound battery cell substrate is formed by laminating a positive electrode sheet, a separator, and a negative electrode sheet and winding them in a winding direction. The wound battery cell substrate includes N bending regions. The bending region where the positive electrode sheet, the separator, and the negative electrode sheet are bent in the same direction for the first time is the first bending region; N≥5; The adhesive tape includes a porous base layer and a coating layer provided on at least one surface of the porous base layer; the porous base layer contains a plurality of fibers, and pores are formed by crossing and / or laminating between the plurality of fibers, and the coating layer is partially embedded in the pores; Wherein, the adhesive tape includes a first adhesive tape at least partially located in the first bending region, and the first adhesive tape covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet.

2. The wound battery cell according to claim 1, wherein, In the direction away from the first bending region in sequence, the bending regions are the second bending region, the third bending region, and the fourth bending region respectively; the adhesive tape further includes a second adhesive tape at least partially located in the second bending region, and the second adhesive tape covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet; and / or, the adhesive tape further includes a third adhesive tape at least partially located in the third bending region, and the third adhesive tape covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet; and / or, the adhesive tape further includes a fourth adhesive tape at least partially located in the fourth bending region, and the fourth adhesive tape covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet.

3. The wound battery cell according to claim 1 or 2, characterized in that, In the bending region where the adhesive tape is provided, the adhesive tape covers at least the inner surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet, wherein the inner surface is close to the winding center.

4. The wound cell according to claim 3, wherein In the bending region where the adhesive tape is provided, the adhesive tape also covers at least the outer surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet, and the outer surface is away from the winding center; Preferably, in the same bending region, the adhesion of the adhesive tape located on the inner surface is less than or equal to the adhesion of the adhesive tape located on the outer surface.

5. The wound battery cell according to any one of claims 1-4, characterized in that, The wound battery cell substrate further includes a first flat region and a second flat region connected to both sides of each bending region; the adhesive tape includes a bending section and a first flat section and a second flat section connected to both ends of the bending section. In the bending region where the adhesive tape is provided, the bending section is located in the bending region and covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet, the first flat section is located in the first flat region and covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet, and the second flat section is located in the second flat region and covers at least a part of the surface of at least one of the positive electrode sheet, the separator, and the negative electrode sheet; In the winding direction of the core substrate, the lengths of the first flat section and the second flat section are different.

6. The wound battery cell according to claim 2, wherein, The second adhesive tape covers at least a part of the surface of the positive electrode sheet, and at least one of the two ends of the second adhesive tape exceeds the junction of the negative electrode active layers on both sides of the negative electrode sheet; and / or, The fourth adhesive tape covers at least part of the surface of the positive electrode sheet, and at least one of the two ends of the fourth adhesive tape extends beyond the junction of the negative active layers on both sides of the negative electrode sheet.

7. The wound cell according to any one of claims 1-6, characterized in that, The coating layer includes a part embedded in the pores and a part located on the surface of the porous substrate layer, and the thickness of the part on the surface does not exceed three times the sum of the diameters of two of the fibers; And / or, the diameter of the fiber is 2 μm to 20 μm; and / or, the pore diameter of the pores is 0.1 μm to 50 μm; and / or, the thickness of the porous substrate layer is 5 μm to 20 μm; and / or, the thickness of the coating layer is 2 μm to 15 μm.

8. The wound cell according to any one of claims 1-6, characterized in that, The bending stiffness of the adhesive tape is ≤ 15 mN.

9. The wound battery cell according to any one of claims 1-6, characterized in that, The coating layer includes filler particles and an adhesive, and the mass ratio of the adhesive to the filler particles is (25 - 70):(30 - 75); Preferably, the adhesive includes at least one of polyisobutylene, styrene-isoprene copolymer, copolymer of vinylidene fluoride - hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber; Preferably, the filler particles include at least one of alumina, boehmite, Li7La3Zr2O 12 , Li3xLa (2 / 3-x) / 3 TiO3, Li1+xAl x Ti 2-x (PO4)3, magnesium oxide, titanium oxide, hafnium dioxide, tin dioxide, cerium dioxide, nickel oxide, zirconium oxide, zinc oxide, calcium oxide, magnesium hydroxide, aluminum hydroxide, barium hydroxide, barium sulfate, calcium silicate, titanium dioxide 10. A secondary battery, characterized in that, It includes the wound battery cell according to any one of claims 1 - 9.

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