Winding battery cell, battery and battery module

Abstract

The invention relates to a winding battery cell, a battery and a battery module. The wound battery cell comprises a battery cell body 1 formed by laminating and winding a positive pole piece 10, a negative pole piece 11 and a diaphragm 12, the straight sections 11A and the bent sections 11B are alternately arranged in the winding direction; at least one surface of the negative electrode current collector 110 of the straight section 11A is coated with a negative electrode active material layer 111, and the surface of the negative electrode current collector 110 of the bent section 11B is not coated with the negative electrode active material layer 111; a plurality of positive pole pieces 10 are arranged, and the projections of the positive pole pieces 10 in the thickness direction of the battery cell body 1 fall into the straight section 11A; the battery cell body 1 meets the condition that Ln / [pi * n-1 * Ta + 2 * n * Ts + n * Tc / 2] is larger than or equal to 1.0 and smaller than or equal to 1.5, and Ts is the thickness of the diaphragm; tc is the thickness of the positive pole piece; ta is the thickness of the negative pole piece; n is a positive integer and represents the number of winding turns of the battery cell body 1; and Ln represents the width of the nth circle of bending section 11B. According to the scheme provided by the invention, the energy density, the safety performance and the cycle performance of the battery can be improved while the production efficiency is improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to wound cells, batteries and battery modules. Background Technology

[0002] In the manufacturing process of lithium-ion batteries, winding and stacking are two common cell forming methods, which have a direct impact on the energy density and production efficiency of the battery.

[0003] Currently widely used wound battery cells suffer from insufficient space utilization at the winding arc, preventing the active materials in that area from fully utilizing their potential. This results in a loss of energy density and negatively impacts battery safety and cycle performance. While stacked battery cells eliminate the wasted space at the arc through a flat stacking method, theoretically increasing energy density, their complex and slower manufacturing process leads to significantly lower overall production efficiency compared to the winding process.

[0004] Therefore, how to improve battery energy density, safety performance, and cycle performance while increasing production efficiency is an urgent problem to be solved. Summary of the Invention

[0005] To address or partially address the problems existing in related technologies, this application provides a wound cell, battery, and battery module that can improve battery energy density, safety performance, and cycle performance while increasing production efficiency.

[0006] This application provides a wound battery cell, comprising a battery cell body formed by stacking and winding a positive electrode sheet, a negative electrode sheet, and a separator; the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on at least one side of the negative electrode current collector; it includes alternately arranged straight sections and curved sections along the winding direction; at least one surface of the negative electrode current collector in the straight section is coated with the negative electrode active material layer, and the surface of the negative electrode current collector in the curved section is not coated with the negative electrode active material layer; the positive electrode sheet is provided in multiple forms, and each of the straight sections of the negative electrode sheet and the multiple positive electrode sheets are alternately stacked in the thickness direction of the battery cell body, and the projection of the positive electrode sheet in the thickness direction of the battery cell body falls within the straight section; and the battery cell body satisfies: 1.0≤Ln / [π××Ta+2×n×Ts+n×Tc) / 2]≤1.5 Wherein, Ts is the thickness of the separator; Tc is the thickness of the positive electrode sheet; Ta is the thickness of the negative electrode sheet; n is a positive integer representing the number of turns of the battery cell body; Ln represents the width of the nth bend. As an optional embodiment, the positive electrode sheet includes a positive current collector and a positive active material layer coated on at least one side of the positive current collector. The projected width of the positive active material layer in the thickness direction of the battery cell body is W1, and the width of the negative active material layer on the straight section is W2, where W2 > W1.

[0007] As an optional embodiment, 6mm < W2-W1 < 20mm; and / or, Ln <W1。

[0008] As an optional embodiment, along the width direction of the cell body, the negative electrode active material layer extends beyond the positive electrode active material layer on both sides of the positive electrode active material layer.

[0009] As an optional embodiment, along the width direction of the cell body, the negative electrode active material layer extends 3mm to 10mm beyond the positive electrode active material layer on both sides of the positive electrode active material layer.

[0010] As an optional embodiment, the positive electrode sheet is provided on the outer side of the straight section of the outermost ring of the negative current collector. On the outermost layer of the cell body, the positive current collector is coated with the positive active material layer on the side facing the inside of the cell body, and a safety coating is coated on the side facing the outside.

[0011] As an optional embodiment, the safety coating includes at least one of a ceramic coating or a high-temperature resistant polymer coating.

[0012] As an optional embodiment, the diaphragm is pre-attached to both sides of the negative electrode sheet to form an integral structure before being wound with the positive electrode sheet.

[0013] A second aspect of this application provides a battery comprising the aforementioned wound cell.

[0014] A third aspect of this application provides a battery module, including the aforementioned battery.

[0015] The technical solution provided in this application may include the following beneficial results: The positive electrode in this application is a single sheet, ensuring that its projection in the thickness direction falls entirely within the straight section of the negative electrode, thus avoiding the winding arc area. Secondly, the curved section of the negative current collector is not coated with any active material. These two measures fundamentally free up the extremely underutilized corner space in traditional wound cells, making the internal structure of the cell more compact and maximizing energy density. Furthermore, it solves the risk of "corner lithium deposition" in wound cells. Because there is no active material in the negative current collector at the corner, lithium ions cannot deposit in this area to form lithium dendrites, greatly improving the battery's fast-charging performance and cycle life safety. Simultaneously, it avoids problems such as powder shedding and cracking caused by stress concentration at the winding corners, ensuring the integrity of the cell structure and production yield. In this application, if Ln / [π×((n-1)×Ta+2×n×Ts+n×Tc) / 2]<1, it indicates that the width of the empty foil area is too small. During the winding process, the coating area of ​​the negative electrode sheet may partially bend, forming a bent section. The negative electrode active material layer in the bent section may be at risk of lithium plating, affecting the performance of the cell. If Ln / [π×((n-1)×Ta+2×n×Ts+n×Tc) / 2]>1.5, it indicates that the foil material in the empty foil area will be redundant, the width of the bent section will increase, and energy density will be lost. In addition, during the winding process, if the width of the empty foil area is too large, the negative electrode sheet corresponding to the positive electrode active material layer may be an empty foil, which poses a safety risk. Therefore, by setting 1.0≤Ln / [π×((n-1)×Ta+2×n×Ts+n×Tc) / 2]≤1.5, this application can reduce the width of the curved section and maximize the width of the straight section. This not only continues the advantages of high production efficiency and fast pace of the winding process, but also improves the energy density, safety performance and cycle performance of the winding structure.

[0016] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0017] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments thereof in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments thereof.

[0018] Figure 1 This is a schematic diagram of the structure of a wound battery cell shown in an embodiment of this application; Figure 2 This is a schematic diagram showing the result of the negative electrode sheet before winding, as illustrated in the embodiments of this application; Figure 3 This is a schematic diagram of the pre-composite structure of the negative electrode sheet and the separator shown in the embodiments of this application.

[0019] Figure label: In the diagram: 1. Cell body; 10. Positive electrode sheet; 100. Positive current collector; 101. Positive active material layer; 102. Safety coating; 11. Negative electrode sheet; 110. Negative current collector; 111. Negative active material layer; 11A. Straight section; 11B. Bending section; 12. Separator. Detailed Implementation

[0020] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While embodiments of this application are shown in the drawings, it should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0021] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0022] In the description of this application, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0023] Unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0024] Currently widely used wound battery cells suffer from insufficient space utilization at the winding arc, preventing the active materials in that area from fully utilizing their potential. This results in a loss of energy density and negatively impacts battery safety and cycle performance. While stacked battery cells eliminate this wasted space at the arc through a flat stacking method, theoretically increasing energy density, their complex and slower manufacturing process leads to significantly lower overall production efficiency compared to wound cells. Therefore, improving battery energy density while simultaneously increasing production efficiency is a pressing issue that needs to be addressed.

[0025] To address the aforementioned issues, this application provides a wound battery cell that can improve battery energy density, safety performance, and cycle performance while increasing production efficiency.

[0026] The technical solutions of the embodiments of this application are described in detail below with reference to the accompanying drawings.

[0027] Figure 1 This is a schematic diagram of the structure of a wound battery cell shown in an embodiment of this application.

[0028] See Figure 1 and Figure 2 This application provides a wound battery cell, including a battery cell body 1 formed by stacking and winding a positive electrode 10, a negative electrode 11, and a separator 12; the negative electrode 11 includes a negative current collector 110 and a negative active material layer 111 coated on at least one side of the negative current collector 110; it includes alternating straight sections 11A and curved sections 11B along the winding direction; at least one surface of the negative current collector 110 in the straight section 11A is coated with the negative active material layer 111, while the surface of the negative current collector 110 in the curved section 11B is not coated with the negative active material layer 111; there are multiple positive electrode 10s, and each straight section 11A of the negative electrode 11 and the multiple positive electrode 10s are alternately stacked in the thickness direction of the battery cell body 1, and the projection of the positive electrode 10 in the thickness direction of the battery cell body 1 falls into the straight section 11A; and the battery cell body 1 satisfies: 1.0≤Ln / [π×((n-1)×Ta+2×n×Ts+n×Tc) / 2]≤1.5 Where Ts is the thickness of the separator; Tc is the thickness of the positive electrode; Ta is the thickness of the negative electrode; n is a positive integer representing the number of turns of the cell body 1; Ln represents the width of the nth bend segment 11B.

[0029] In this application, the thickness direction of the cell body 1 is parallel to... Figure 1 The top and bottom directions are consistent.

[0030] In this embodiment, the negative electrode 11 is divided into two functional regions along the winding direction: a straight section 11A and a bent section 11B. The straight section 11A performs the main electrochemical reaction function, and its surface is coated with a negative electrode active material layer 111, which is the main active region for lithium-ion insertion / extraction. The bent section 11B performs current conduction and mechanical shaping functions. This region is not coated with the negative electrode active material layer 111, retaining only the more flexible current collector itself. This allows the negative electrode 11 to bend more smoothly when wound to a rounded corner, preventing the coating from cracking or peeling off due to stress. See also... Figure 2 The negative electrode 11 is intermittently coated to form alternating coated and empty foil areas. During winding, the coated areas are arranged flat to form a straight section 11A, while the empty foil areas are bent to form a bent section 11B. Furthermore, from the starting point to the ending point (the head and tail of the negative electrode 11), the width Ln of the empty foil area gradually increases, excluding the tail of the negative electrode 11. See also... Figure 1 For example, the curved segment 11B marked with a red circle represents the first curved segment 11B with a width of L1, and the curved segment 11B marked with a green circle represents the second curved segment 11B with a width of L2.

[0031] The positive electrode 10 is a single piece (i.e., its length matches the straight section 11A in the winding direction), rather than a continuous electrode covering the entire winding length. The projection of the positive electrode 10 onto the thickness of the cell body 1 falls entirely within the area of ​​the straight section 11A. This ensures that the positive electrode will never directly face the "blank" curved section of the negative electrode at any position, thus eliminating the risk of lithium plating at corners due to local overcharging or inability to intercalate lithium.

[0032] In a conventional wound battery cell, the positive and negative electrodes and the separator are wound together, resulting in large corners in the arc region and significant energy density loss. In this embodiment, the positive electrode 10 is a single sheet, ensuring its projection in the thickness direction falls entirely within the straight section of the negative electrode 11, thus avoiding the winding arc region. Furthermore, the curved section 11B of the negative current collector 110 is not coated with any active material. These two measures fundamentally free up the extremely underutilized corner space in traditional wound batteries, making the internal structure of the battery core more compact and maximizing energy density. They also eliminate the risk of "corner lithium deposition" in wound batteries. Since the negative current collector 110 at the corner lacks active material, lithium ions cannot deposit in this area to form lithium dendrites, greatly improving the battery's fast-charging performance and cycle life safety. Simultaneously, it avoids problems such as powder shedding and cracking caused by stress concentration at the winding corners, ensuring the integrity of the battery structure and production yield.

[0033] In this embodiment of the application, if Ln / [π×((n-1)×Ta+2×n×Ts+n×Tc) / 2]<1, it indicates that the width of the empty foil area is too small. During the winding process, the coating area of ​​the negative electrode sheet 11 may be partially bent to form a bent section 11B. The negative electrode active material layer 111 of the bent section 11B may have the risk of lithium plating, which will affect the performance of the battery cell.

[0034] If Ln / [π×((n-1)×Ta+2×n×Ts+n×Tc) / 2]>1.5, it indicates that the foil material in the empty foil region will be redundant, the width of the bent section 11B will increase, and the energy density will be lost. In addition, during the winding process, due to the large width of the empty foil region, the negative electrode sheet 11 corresponding to the positive electrode active material layer may be empty foil, which poses a safety risk.

[0035] Therefore, by setting 1.0≤Ln / [π×((n-1)×Ta+2×n×Ts+n×Tc) / 2]≤1.5, the width of the curved section 11B can be reduced, thereby maximizing the width of the straight section 11A. This not only continues the advantages of high production efficiency and fast pace of the winding process, but also improves the energy density, safety performance and cycle performance of the winding structure.

[0036] As an optional embodiment, the positive electrode 10 includes a positive current collector 100 and a positive active material layer 101 coated on at least one side of the positive current collector 100. The projected width of the positive active material layer 101 in the thickness direction of the cell body 1 is W1, and the width of the negative active material layer 111 coated on the straight section 11A is W2, where W2 > W1.

[0037] During charging and discharging, lithium ions escape from the positive electrode and need to find an active material at the negative electrode to intercalate. If lithium ions at the edge of the positive electrode face an area without negative electrode material (such as a separator or blank current collector), they will precipitate as metallic lithium on the surface of the negative electrode (especially on copper foil), forming lithium dendrites, which poses a serious safety risk. By designing W2 > W1, it is ensured that lithium ions escaping from any position on the positive electrode always have sufficient active material at the negative electrode to "receive" them along their path, fundamentally eliminating the risk of edge lithium deposition caused by the mismatch between the size of the positive and negative electrodes.

[0038] In a preferred embodiment, 6mm < W2 - W1 < 20mm.

[0039] If W2 - W1 is too small (e.g., < 3 mm), during winding or under the minor deformations during long-term cycling, the wrapping may fail due to alignment deviation, resulting in insufficient safety margin. If W2 - W1 is too large (e.g., > 10 mm), it means there is an excessive amount of negative electrode active material that does not participate in the reaction, which will reduce the mass energy density and volume energy density of the battery cell. In the embodiments of the present application, by setting 6 mm < W2 - W1 < 20 mm, a balance between safety and energy can be achieved.

[0040] As a preferred embodiment, Ln < W1.

[0041] In the embodiments of the present application, L1 < L2 <... < Ln. During the winding process, as the number of winding turns increases, the radian of the bending section 11B becomes larger, so the corresponding Ln becomes larger.

[0042] Setting the width of the bending section 11B with the maximum number of winding turns to be less than W1 ensures the safety redundancy of the bending section 11B and prevents the situation where the negative electrode tab 11 corresponding to the positive electrode active material layer is an empty foil.

[0043] As a preferred embodiment, along the width direction of the battery cell body 1, the negative electrode active material layer 111 extends beyond the positive electrode active material layer 101 on both opposite sides of the positive electrode active material layer 101. In the present application, the width direction of the battery cell body 1 is Figure 1 consistent with the left - right direction above.

[0044] In the present application, the width direction of the battery cell body 1 is Figure 1 consistent with the left - right direction above.

[0045] This can provide a uniform lithium intercalation environment, help slow down the local aging and failure of the active material, make the attenuation of the entire battery cell more consistent, and thus extend the overall cycle life.

[0046] As a preferred embodiment, along the width direction of the battery cell body 1, the negative electrode active material layer 111 extends beyond the positive electrode active material layer 101 on both opposite sides of the positive electrode active material layer 101 by a width of 3 mm to 10 mm. [[ID=२६]]

[0047] In the embodiments of the present application, setting the width of the negative electrode active material layer 111 extending beyond the positive electrode active material layer 101 on both opposite sides of the positive electrode active material layer 101 to be 3 mm to 10 mm takes into account the possible errors during the actual production of electrode tab cutting and winding alignment, provides sufficient buffer space for process fluctuations, and ensures the yield and consistency in mass production.

[0048] As a preferred embodiment, on the outermost layer of the battery cell body 1, the side surface of the positive electrode current collector 100 facing the inside of the battery cell body 1 is coated with a positive electrode active material layer 101, and the side surface facing the outside is coated with a safety coating 102.

[0049] After the battery cell is wound, if the outermost positive current collector 100 has a positive active material layer 101 coated on the side facing inwards of the battery cell body 1, while the side facing outwards is not coated with a positive active material layer 101, a large internal stress difference will exist between the two sides of the outermost positive current collector. This asymmetrical stress will cause the electrode sheet itself to tend to curl towards the coating layer. At the outermost layer, this curling force has nowhere to be offset, easily causing overall deformation of the battery cell, folding of the outermost electrode sheet, or even puncture of the separator. Therefore, in this embodiment, the outermost positive current collector 100 has a positive active material layer 101 coated on the side facing inwards of the battery cell body 1, and a safety coating 102 coated on the side facing outwards, forming a symmetrical coating. This offsets the internal stress generated by the single-sided active material layer, achieving mechanical balance. This ensures that the wound battery cell has a regular shape and a compact structure, avoiding manufacturing and safety defects caused by curling and folding.

[0050] As a preferred embodiment, the safety coating 102 includes at least one of a ceramic coating or a high-temperature resistant polymer coating.

[0051] The outermost layer of the battery cell is its weakest point, susceptible to external impacts or punctures. Safety coatings (such as ceramic or high-temperature polymer coatings) possess extremely high mechanical strength, effectively preventing internal short circuits caused by foreign object punctures. In the event of thermal runaway, the high-temperature polymer or ceramic coating acts as an effective thermal barrier, delaying heat transfer to the outside of the cell and improving battery safety. Furthermore, even if the cell casing deforms and comes into contact with the outermost electrode, it prevents direct conductivity between the positive current collector 100 and the casing, thus preventing external short circuits.

[0052] As an optional embodiment, see Figure 3 The diaphragm 12 is pre-attached to both sides of the negative electrode 11 to form an integrated structure before being wound with the positive electrode 10.

[0053] In traditional winding, the loose diaphragm is prone to wrinkling at corners due to stress concentration. These wrinkles become weak points during long-term cycling, and are repeatedly stretched by the expansion and contraction of the negative electrode, eventually leading to localized thinning or even rupture of the diaphragm, causing internal short circuits. The pre-composite + hot-pressing process creates an "integrated substrate" for the diaphragm 12 and the negative electrode sheet 11, greatly suppressing relative displacement and fundamentally eliminating the risk of internal short circuits caused by wrinkling or displacement of the diaphragm 12.

[0054] Furthermore, during long-term cycling, the negative electrode active material layer 111 inevitably undergoes volume expansion. In traditional loose structures, this expansion is uneven, easily leading to significant inward stress in localized areas (especially at corners), causing excessive compression of the separator 12, decreased porosity, and obstruction of ion transport channels. The difficulty in localized lithium ion insertion results in lithium dendrite deposition. The pre-composite structure provides strong and uniform in-plane support, more effectively dispersing the expansion force evenly in all directions and avoiding localized stress concentration. This not only maintains the long-term stability of the separator pores, ensuring smooth ion transport, but also maintains the flatness of the negative electrode surface, thereby significantly suppressing lithium deposition caused by stress unevenness and ion blockage.

[0055] In this embodiment, the separator 12 can be pre-attached to both sides of the negative electrode 11 by a hot-pressing composite process. The hot-pressing composite process can enhance the connection between the negative electrode 11 and the separator 12, which is beneficial for thickness expansion during long cycles and for improving lithium plating.

[0056] Corresponding to the aforementioned application function implementation device embodiments, this application also provides a battery, a battery module, and corresponding embodiments.

[0057] This application also provides a battery, including the aforementioned wound cell.

[0058] The specific structure of the wound cell is as described in the above embodiments. Since this battery adopts all the technical solutions of all the above embodiments, it has at least all the technical effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0059] In some embodiments, the battery may include an outer packaging that can be used to encapsulate the aforementioned wound cell.

[0060] In some implementations, the battery's outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The battery's outer packaging can also be a soft pack, such as a pouch. The soft pack can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0061] This application does not impose any particular restrictions on the shape of the battery; it can be cylindrical, square, or any other arbitrary shape.

[0062] As an optional embodiment, the positive electrode active material layer 101 includes a positive electrode active material, which includes a transition metal lithium oxide with the chemical formula Li. （1+x） Ni y Co z M （1-y-z）O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; where M is selected from one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0063] In this application, the type of positive electrode current collector 100 is not particularly limited, and it can be any known material suitable for use as the positive electrode current collector 100. In one embodiment, the positive electrode current collector 100 includes metallic materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, as well as carbon materials such as carbon cloth and carbon paper. In one embodiment, the positive electrode current collector 100 is a metallic material.

[0064] In some embodiments, the positive electrode active material also includes a positive electrode conductive agent, a positive electrode binder, and a solvent.

[0065] In some embodiments, the type of positive conductive agent mentioned in the present application is not limited, and any known conductive agent can be used.

[0066] In some embodiments, the positive electrode conductive agent mentioned in the embodiments of this application includes at least one of carbon materials such as natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene.

[0067] In one embodiment, there is no limitation on the type of positive electrode binder mentioned in the embodiments of this application, and any known positive electrode binder can be used.

[0068] In some embodiments, the positive electrode binder includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose.

[0069] As an optional embodiment, the negative electrode active material layer 111 includes a negative electrode active material, which includes artificial graphite and / or silicon-carbon composite materials.

[0070] In the embodiments of this application, there are no particular limitations on the negative electrode current collector 110, as long as it can achieve the purpose of this application, such as copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper or composite current collector, etc.

[0071] In some preferred embodiments, the negative current collector 110 comprises copper foil.

[0072] In some embodiments, the negative electrode active material may also include a negative electrode conductive agent, a negative electrode binder, a thickener, and a solvent.

[0073] The negative electrode conductive agent includes at least one of the following carbon materials: natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene. The negative electrode binder includes styrene-butadiene latex, and the thickener includes CMC. The solvent includes deionized water.

[0074] In some embodiments, there are no particular restrictions on the material and shape of the diaphragm, as long as it does not significantly impair the effectiveness of this application.

[0075] In some embodiments, the diaphragm includes a porous sheet-like or non-woven material with excellent liquid retention properties. The diaphragm includes resin or glass fiber diaphragm materials, including but not limited to polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc.

[0076] This application also provides a battery module, including the aforementioned battery.

[0077] The specific structure of the battery is as described in the above embodiments. Since this battery module adopts all the technical solutions of all the above embodiments, it has at least all the technical effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0078] To further understand the embodiments of this application, the following description is based on the embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of this application.

[0079] I. Battery Manufacturing Example 1 The structure of the wound battery cell satisfies the following: (a) a battery cell body 1 is formed by stacking and winding a positive electrode 10, a negative electrode 11, and a separator 12; the negative electrode 11 includes a negative current collector 110 and a negative active material layer 111 coated on at least one side of the negative current collector 110; it includes alternating straight sections 11A and curved sections 11B along the winding direction; (b) at least one surface of the negative current collector 110 in the straight section 11A is coated with the negative active material layer 111, and the surface of the negative current collector 110 in the curved section 11B is not coated with the negative active material layer 111; (c) there are multiple positive electrode 10s, and each straight section 11A of the negative electrode 11 and multiple positive electrode 10s are alternately stacked in the thickness direction of the battery cell body 1, and the projection of the positive electrode 10 in the thickness direction of the battery cell body 1 falls into the straight section 11A; and the battery cell body 1 satisfies the relationship (1): 1.0≤Ln / [π×n-1×Ta+2×n×Ts+n×Tc / 2]≤1.5 Where Ts is the thickness of the separator; Tc is the thickness of the positive electrode; Ta is the thickness of the negative electrode; n is a positive integer representing the number of turns of the cell body 1; Ln represents the width of the nth bend segment 11B.

[0080] Examples 2 to 10, and Comparative Examples 1 to 3 The basic content is the same as in Example 1, and the differences are shown in Table 1.

[0081] II. Performance Testing 1. Energy density Place the battery cell in a 25°C room for 2 hours; discharge it at a rate of 0.5C to the lower limit voltage (3.0V), let it stand for 10 minutes; charge it at a constant current and constant voltage rate of 0.5C to the upper limit voltage (4.4V), and cut off the constant voltage step with a current of 0.05C; let it stand for 10 minutes; discharge it at a rate of 0.5C to the lower limit voltage (3.0V), and record the discharge capacity C and energy E.

[0082] This embodiment uses model 486579 as the model. That is, the thickness T of the battery cell is 4.8mm, the width W is 65mm, and the height H is 79mm.

[0083] The energy density of the battery cell is calculated as follows: ED = E / (T * W * H); 2. Safety performance Room temperature 2C lithium plating interface test: Charge at 25℃ with 2C constant current and constant voltage to the upper limit voltage, cut-off current 0.05C, stand for 10 minutes, discharge at 0.5C to 3.0V, repeat for 500 cycles, and finally fully charge in the disassembly room, disassemble the interface, and test whether lithium plating occurs.

[0084] 3. Cyclic performance ① Place the battery cells in a 25℃ room for 2 hours; ② Discharge at a 1C rate to the lower limit voltage (3.0V) and let stand for 10 minutes; ③ Charge at a constant current and constant voltage rate of 1C to the upper limit voltage (4.4V), and cut off the constant voltage step with a current of 0.05C; ④ Cycle steps ② and ③ for 500 cycles. Cycling performance is evaluated based on capacity retention after 500 cycles.

[0085] Performance tests were conducted on the above embodiments and comparative examples, and the test results are shown in Table 1.

[0086] Table 1. Formulation and Test Results

[0087] Note: The structure column shows that the battery cell structure meets the requirements of (a), (b), and (c) above.

[0088] According to Table 1, by comparing Example 1 and Comparative Examples 1 to 3, it can be seen that when the wound cell structure satisfies the contents of (a), (b), and (c) above, and the cell body 1 satisfies the relation (1), the energy density, safety performance and cycle performance of the battery can be improved.

[0089] It can be seen by comparing Example 1 and Example 2 that when further satisfying W2 > W1, the energy density, safety performance, and cycle performance of the battery can be further improved. Further, by comparing Example 2, Example 9, and Example 10, it can be seen that when satisfying W2 > W1 and 6 mm < W2 - W1 < 20 mm, the energy density, safety performance, and cycle performance of the battery can be further improved.

[0090] It can be seen by comparing Example 1 and Example 3 that when further satisfying Ln < W1, the energy density, safety performance, and cycle performance of the battery can be further improved.

[0091] It can be seen by comparing Example 1 and Example 4 that when the diaphragm 12 is pre-attached to both sides of the negative electrode plate 11 through a hot pressing composite process to form an integral structure and then wound with the positive electrode plate 10, the energy density, safety performance, and cycle performance of the battery can be further improved. The solutions of the present application have been described in detail above with reference to the accompanying drawings.

[0092] In the above embodiments, the descriptions of each embodiment have their own emphases. For the parts not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments. Those skilled in the art should also know that the actions and modules involved in the specification are not necessarily essential to the present application. In addition, it can be understood that the steps in the method embodiments of the present application can be adjusted, combined, and deleted according to actual needs, and the modules in the device embodiments of the present application can be combined, divided, and deleted according to actual needs.

[0093] The above has described the embodiments of the present application. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of the terms used herein is intended to best explain the principles of the embodiments, the practical application, or the improvement of the technology in the market, or to enable other ordinary skilled persons in the art to understand the disclosed embodiments.

Claims

1. A wound cell core, characterized by, The battery cell body (1) is formed by stacking and winding a positive electrode sheet (10), a negative electrode sheet (11) and a separator (12); the negative electrode sheet (11) comprises a negative electrode current collector (110) and a negative electrode active material layer (111) coated on at least one side of the negative electrode current collector (110); and comprises alternating flat sections (11A) and curved sections (11B) in the winding direction; at least one surface of the negative electrode current collector (110) of the flat section (11A) is coated with the negative electrode active material layer (111), and the surface of the negative electrode current collector (110) of the curved section (11B) is not coated with the negative electrode active material layer (111); the positive electrode sheet (10) is provided in a plurality, and each flat section (11A) of the negative electrode sheet (11) is alternately stacked with a plurality of the positive electrode sheet (10) in the thickness direction of the battery cell body (1), the projection of the positive electrode sheet (10) in the thickness direction of the battery cell body (1) falls within the flat section (11A); and the battery cell body (1) satisfies: 1.0≤Ln / [π×((n-1)×Ta+2×n×Ts+n×Tc) / 2]≤1.5 Wherein, Ts is the thickness of the separator; Tc is the thickness of the positive electrode sheet; Ta is the thickness of the negative electrode sheet; n is a positive integer, representing the winding number of the battery cell body (1); Ln represents the width of the n th curved section (11B).

2. The wound cell according to claim 1, characterized by, The positive electrode sheet (10) comprises a positive electrode current collector (100) and a positive electrode active material layer (101) coated on at least one side of the positive electrode current collector (100), the projection width of the positive electrode active material layer (101) in the thickness direction of the battery cell body (1) is W1, and the width of the negative electrode active material layer (111) on the flat section (11A) is W2, W2>W1.

3. The wound cell according to claim 2, characterized by, 6mm<W2-W1<20mm; and / or, Ln<W1.

4. The wound cell according to claim 2, wherein, Along the width direction of the battery cell body (1), the negative electrode active material layer (111) exceeds the positive electrode active material layer (101) on both sides of the positive electrode active material layer (101).

5. The wound cell according to claim 4, characterized by Along the width direction of the battery cell body (1), the width of the negative electrode active material layer (111) exceeding the positive electrode active material layer (101) on both sides of the positive electrode active material layer (101) is 3mm~10mm.

6. The wound cell according to claim 2, wherein, The outer side of the flat section (11A) of the outermost circle of the negative electrode current collector (110) is provided with the positive electrode sheet (10), and on the outermost layer of the battery cell body (1), the surface of the positive electrode current collector (100) towards the inside of the battery cell body (1) is coated with the positive electrode active material layer (101), and the surface towards the outside is coated with a safety coating layer (102).

7. The wound cell according to claim 6, wherein The safety coating layer (102) comprises at least one of a ceramic coating or a high-temperature resistant polymer coating.

8. The wound cell according to claim 1, wherein, The separator (12) is preattached to both sides of the negative electrode sheet (11) to form an integrated structure, and then wound with the positive electrode sheet (10).

9. A battery, characterized by A wound cell including any one of claims 1 to 8.

10. A battery module, characterized by A battery including a plurality of cells according to claim 9.

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