Battery cell, energy storage device and electric device

Abstract

This application provides a battery cell, an energy storage device, and an electrical appliance. The battery cell includes a negative electrode, a separator, and a positive electrode. The negative electrode, separator, and positive electrode are sequentially stacked and wound to form multiple turns. In each turn, the negative electrode and / or the positive electrode have a flat area and a corner area with varying thickness of the active material layer along its length, the corner area corresponding to the corner portion after the battery cell is wound. The thickness of the active material layer changes from the thickness T0 in the flat area, and returns to T0 after passing through the corner portion. The corner area includes a corner preparation area, a corner core area, and a transition recovery area sequentially arranged. In the corner preparation area, the thickness of the active material layer changes from T0 to Kn*T0; in the corner core area, the thickness of the active material layer remains at Kn*T0; in the transition recovery area, the thickness of the active material layer returns from Kn*T0 to the thickness T0, where Kn is the thickness variation coefficient of the active material layer on the nth turn of the electrode, 0 < Kn ≤ 3, n ≥ 1.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a battery cell, an energy storage device, and an electrical device. Background Technology

[0002] In the manufacturing of energy storage devices, such as batteries, the electrodes of wound cells need to be bent significantly at the corners, resulting in a small radius of curvature in that area. During the subsequent hot-pressing process, this leads to severe stress concentration. On one hand, it easily causes the active material layer (coating) to peel off, i.e., "powder shedding," and the falling particles can cause internal short circuits within the cell, posing a safety risk. On the other hand, the hardened active material layer of the bent electrode can puncture the separator, also posing a safety risk.

[0003] Currently, methods to address this issue typically include increasing the amount of binder, thinning the electrode as a whole, or optimizing hot-pressing parameters. However, these methods have inherent drawbacks such as reducing energy density and sacrificing battery capacity, and cannot fundamentally solve the stress concentration problem at corners.

[0004] Therefore, there is an urgent need in this field for a new solution that can effectively prevent powder shedding at the corners of the battery cells without affecting the core performance of the energy storage device. Summary of the Invention

[0005] In view of the above problems, this application provides a battery cell, an energy storage device, and an electrical appliance.

[0006] In a first aspect, this application provides a battery cell. The battery cell includes a negative electrode, a separator, and a positive electrode. The negative electrode, the separator, and the positive electrode are sequentially stacked and wound to form multiple turns. In each turn, the negative electrode and / or the positive electrode have a flat area and a corner area with varying thickness of the active material layer along its length, the corner area corresponding to the corner portion after the battery cell is wound. The thickness of the corner area during the thickness variation process is Kn*T0, where T0 is the thickness of the active material layer in the flat area, Kn is the thickness variation coefficient of the active material layer on the nth turn of the electrode, 0≤Kn≤3, n≥1.

[0007] The aforementioned technical solution for the battery cell establishes a corner region for the active material layer at the corresponding winding corner of the electrode sheet. The thickness of this corner region during its change is Kn*T0. On one hand, this allows the electrode sheet to adapt more smoothly to bending deformation and release stress during winding and hot pressing through self-adjustment of its thickness. This avoids the breakage and shedding of the active material layer (i.e., "powder shedding") caused by insufficient stress release due to an excessively small bending radius in traditional designs, thus improving the manufacturing yield and structural reliability of the battery cell. On the other hand, it also prevents the active material layer from puncturing the separator in the inner ring. Furthermore, this technical solution solves the "powder shedding" problem without requiring increased binder usage, overall electrode thinning, or optimized hot pressing parameters. While effectively solving the corner powder shedding problem, it maintains the high active material load in the flat area of ​​the battery cell, thereby ensuring that the core performance of the energy storage device—high energy density and high capacity—remains unaffected.

[0008] As an optional technical solution of this application, the thickness of the active material layer changes from the thickness T0 of the flat area and returns to the thickness T0 after passing the corner. The corner area includes a corner preparation area, a corner core area, and a transition recovery area arranged sequentially. In the corner preparation area, the thickness of the active material layer changes from T0 to Kn*T0. In the corner core area, the thickness of the active material layer remains at Kn*T0. In the transition recovery area, the thickness of the active material layer returns from Kn*T0 to the thickness T0 of the flat area.

[0009] In the aforementioned technical solution, the corner area is further divided into a corner preparation area, a corner core area, and a transition recovery area. The thickness of the corner preparation area and the transition recovery area vary, achieving a smooth and gradual deformation of the electrode sheet as it enters and leaves the corner. This design results in a more uniform stress distribution, avoiding secondary stress concentration that may be caused by abrupt changes in thickness. This further reduces the risk of the active material layer peeling off or breaking due to stress concentration in the corner preparation and transition recovery areas, thus improving the structural integrity and reliability of the battery cell.

[0010] As an optional technical solution of this application, the negative electrode and the positive electrode are wound to form multiple layers, and the battery cell satisfies the following relationship:

[0011]

[0012] Where x = 1, 2, ..., N, and N ≥ 2, x is the number of electrode layers, and the value of x increases from the inner ring to the outer ring. y(x) is the thickness of the active material layer on the x-th electrode layer, N is the total number of electrode layers in the cell, and Y is the total thickness of the active material layer on all N electrode layers. The thickness of the active material layer on each electrode layer is greater than or equal to 0.1Y and less than or equal to 0.5Y.

[0013] In the above technical solution, the battery cell satisfies the above relationship, ensuring that the thickness of the active material layer increases from the inner ring to the outer ring. This thickness distribution can compensate for the uneven stress caused by the difference in circumference between the inner and outer rings during the winding process, reduce stress concentration, thereby reducing the risk of deformation of the battery cell during cyclic use and improving mechanical stability and cycle life.

[0014] As an optional technical solution of this application, the corner preparation area and the transition recovery area have the same size in the cell length direction and are smaller than the size of the corner core area in the cell length direction.

[0015] In the above technical solution, the length of the corner preparation area and the transition recovery area are the same and shorter than the length of the corner core area. There is enough length in the main corner stress area (corner core area) to maintain stable mechanical support. At the same time, the deformation adjustment process when entering and exiting the corner is more symmetrical and efficient, realizing precise stress buffering and protection of the corner core area.

[0016] As an optional technical solution of this application, the overall thickness of the battery cell corresponding to the flat area is the same as the overall thickness of the corner area. In the above technical solution, the overall thickness of the battery cell corresponding to the flat area is the same as the overall thickness of the corner area, which makes the thickness of the active material layer in the inner corner area smaller than the thickness of the active material layer in the outer corner area. That is, the active material layer in the inner circle is less, but the overall thickness of the active material layer is kept constant by the active material layer in the outer circle, thereby ensuring the energy density of the battery cell. At the same time, the smaller thickness of the active material layer in the corner area of ​​the inner circle can prevent the active material layer from puncturing the separator in the inner circle, ensuring the safety of the battery cell. As an optional technical solution of this application, the thickness variation coefficient Kn changes with the number of winding turns n of the battery cell, and the value of Kn gradually increases as n increases.

[0017] In the above technical solution, the thickness variation coefficient Kn gradually increases with the number of winding turns n of the battery cell. This allows regions with high curvature and bending stress in the inner ring to cope with stress to the extreme with a smaller Kn value (or even 0), while regions with low curvature in the outer ring can provide more active material with a larger Kn value. In this way, the mechanical safety of the inner ring of the battery cell and the energy density of the outer ring are optimally balanced overall.

[0018] As an optional technical solution of this application, both the negative electrode and the positive electrode are provided with the corner area. The corner preparation area of ​​the negative electrode and the corner preparation area of ​​the positive electrode are offset from each other in the length direction of the battery cell. The transition recovery area of ​​the negative electrode and the transition recovery area of ​​the positive electrode are offset from each other in the length direction of the battery cell.

[0019] In the above technical solution, the corner preparation areas of the negative electrode and the positive electrode are staggered along the length of the cell, and the transition recovery areas of the negative electrode and the positive electrode are also staggered along the length of the cell. This avoids the mechanical weakness point where two electrode layers simultaneously become extremely thin at the same location within the cell. As a result, the mechanical strength of the cell is more continuously and uniformly distributed along its thickness, preventing potential risks caused by local structural weakening and further improving the overall structural stability of the cell.

[0020] As an optional technical solution of this application, the corner preparation area of ​​the negative electrode is closer to the starting end of the negative electrode than the corner preparation area of ​​the positive electrode, and the transition recovery area of ​​the positive electrode is farther away from the starting end of the negative electrode than the transition recovery area of ​​the negative electrode. In the length direction of the cell, the misalignment interval between the corner preparation area of ​​the negative electrode and the corner preparation area of ​​the positive electrode is the same as the misalignment interval D1 between the transition recovery area of ​​the positive electrode and the transition recovery area of ​​the negative electrode. There is a distance difference D2 between the starting end of the negative electrode and the starting end of the positive electrode. The misalignment interval D1 and the distance difference D2 satisfy: 0≤D1 / D2≤10.

[0021] In the above technical solution, the misalignment interval D1 and the distance difference D2 are designed to satisfy: 0≤D1 / D2≤10. This ensures that the misalignment effect is sufficient to avoid the superposition of mechanical weak points, and that the overall alignment of the electrode and the stability of the winding process are not affected by the excessive misalignment interval. It also ensures that the negative electrode and the positive electrode can form a stable and aligned stacked structure at the beginning of winding. In this way, it can effectively prevent initial manufacturing defects such as electrode folding and separator edge curling caused by improper end alignment, and improve the yield of the winding process.

[0022] As an optional technical solution of this application, in each turn, the thickness variation coefficient Kn of the negative electrode sheet and the thickness variation coefficient Kn of the positive electrode sheet are the same, and the specific capacity ratio of all turns in the cell is the same.

[0023] In the above technical solution, the thickness variation coefficient Kn of the negative electrode and the positive electrode is the same in each turn, which ensures that the negative and positive electrode capacity ratio (N / P ratio) of all turns in the cell remains consistent. This fundamentally guarantees that the negative electrode capacity is always sufficient to receive lithium ions extracted from the positive electrode in any turn or at any corner, thereby effectively preventing the precipitation of lithium dendrites at the corner and improving the cycle life and safety performance of the cell.

[0024] As an optional technical solution of this application, when Kn=0, tape is attached to the exposed area of ​​the current collector in the corner area where the thickness of the active material layer is zero.

[0025] In the above technical solution, when the current collector is exposed at Kn=0, tape is attached to the exposed area. The tape can not only lubricate and prevent burrs during winding, but also provide insulation protection for the exposed current collector inside the cell, preventing it from contacting the opposite electrode and causing an internal short circuit, thus further enhancing the safety of the cell.

[0026] Secondly, this application provides an energy storage device. The energy storage device includes a housing, a top cover assembly, and a battery cell as described in any of the above embodiments. The housing has an opening. The top cover assembly seals the opening of the housing and, together with the housing, forms a receiving cavity. The battery cell is housed within the receiving cavity.

[0027] In the energy storage device described above, the cell incorporates an active material layer with a corner region corresponding to the winding corner of the electrode. The thickness of this corner region during its change is Kn*T0. This allows the electrode to adapt more smoothly to bending deformation and release stress during winding and hot pressing through self-adjustment of its thickness. This avoids the breakage and shedding of the active material layer (i.e., "powder shedding") caused by insufficient stress release due to an excessively small bending radius in traditional designs, thus improving the cell's manufacturing yield and structural reliability. Furthermore, it prevents the active material layer from puncturing the separator in the inner ring. Moreover, this technology solves the "powder shedding" problem without requiring increased binder usage, overall electrode thinning, or optimized hot pressing parameters. While effectively addressing the corner powder shedding problem, it preserves the high active material load in the flat area of ​​the cell, ensuring that the core performance characteristics of the energy storage device—high energy density and high capacity—remain unaffected.

[0028] Thirdly, this application provides an electrical appliance. The electrical appliance includes the energy storage device described in any of the above embodiments.

[0029] In the aforementioned technical solution for electrical equipment, the energy storage cell incorporates an active material layer in the corner region corresponding to the winding corner of the electrode. The thickness of this corner region during its change is Kn*T0. This allows the electrode to adapt more smoothly to bending deformation and release stress during winding and hot pressing through self-adjustment of its thickness. This avoids the breakage and shedding of the active material layer (i.e., "powder shedding") caused by insufficient stress release due to an excessively small bending radius in traditional designs, thus improving the cell's manufacturing yield and structural reliability. Furthermore, it prevents the active material layer from puncturing the separator in the inner ring. Moreover, this technical solution solves the "powder shedding" problem without requiring increased binder usage, overall electrode thinning, or optimized hot pressing parameters. While effectively addressing the corner powder shedding problem, it preserves the high active material load in the flat area of ​​the cell, ensuring that the core performance characteristics of the energy storage device—high energy density and high capacity—remain unaffected.

[0030] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0031] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0032] Figure 1 This is a cross-sectional schematic diagram of a battery cell according to some embodiments of this application;

[0033] Figure 2 This is a cross-sectional schematic diagram of a battery cell according to other embodiments of this application;

[0034] Figure 3 yes Figure 2 The diagram shows the unfolded negative electrode and positive electrode of the battery cell.

[0035] Figure 4 This is a three-dimensional assembly diagram of a battery cell according to some embodiments of this application;

[0036] Figure 5 for Figure 4 The diagram shows a three-dimensional exploded view of a single battery cell;

[0037] Figure 6 This is a three-dimensional structural diagram of a battery pack according to some embodiments of this application;

[0038] Figure 7 This is a schematic diagram of the planar structure of an electrical device according to some embodiments of this application.

[0039] The reference numerals in the detailed embodiments are as follows:

[0040] Electrical equipment 10000; Energy storage device 1000; Battery cell 1001; Battery pack 1003; Battery box 10031; Box body 10033; Cover 10035; First load 2000; Second load 3000; Conversion device 4000;

[0041] Cell 100; electrode 10, negative electrode 10a, positive electrode 10b, current collector 11, active material layer 13, flat area 131, corner area 133, corner preparation area 1331, corner core area 1333, transition recovery area 1335, separator 30;

[0042] Housing 300; Top cover assembly 500;

[0043] The length direction of the battery cell is X, the length direction of the electrode is R, and the thickness direction is Z. Detailed Implementation

[0044] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0045] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0046] In this document, the term "implementation" means that a specific feature, structure, or characteristic described in connection with an implementation may be included in at least one implementation of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same implementation, nor is it a separate or alternative implementation mutually exclusive with other implementations. It will be explicitly and implicitly understood by those skilled in the art that the implementations described herein can be combined with other implementations.

[0047] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, the simultaneous existence of mounting protrusions and mounting holes, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following associated objects have an "or" relationship.

[0048] In the description of the embodiments of this application, the technical terms "center", "first", "second", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "level", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of 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. Therefore, they should not be construed as limitations on the embodiments of this application.

[0049] In the description of the embodiments of this application, unless otherwise explicitly specified and limited, the technical terms such as "installation", "connection", "linking", and "fixing" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components.

[0050] In the manufacturing of energy storage devices, such as batteries, the electrodes of wound cells need to be significantly bent at the corners, resulting in a small radius of curvature in that area. During the subsequent hot-pressing process, this leads to severe stress concentration, easily causing the active material layer (coating) to peel off, i.e., "powder shedding." The shed particles may puncture the separator, causing a short circuit inside the cell and posing a safety risk. Currently, methods to solve this problem typically include increasing the amount of binder, thinning the electrodes overall, or optimizing hot-pressing parameters. However, these methods have inherent drawbacks such as reducing energy density and sacrificing battery capacity, and cannot fundamentally solve the stress concentration problem at the corners. To address this issue, this application provides a cell 100 ( Figures 1 to 3 As shown), energy storage device ( Figures 4 to 6 (as shown) and electrical equipment ( Figure 7 (As shown).

[0051] Please see Figures 1 to 3 In a first aspect, this application provides a battery cell 100. The battery cell 100 includes a negative electrode 10a, a separator 30, and a positive electrode 10b. The negative electrode 10a, separator 30, and positive electrode 10b are sequentially stacked and wound to form multiple turns. In each turn, the negative electrode 10a and / or the positive electrode 10b have a flat area 131 of an active material layer 13 and a corner area 133 with varying thickness along the length direction R. The corner area 133 corresponds to the corner portion of the battery cell 100 after winding. The thickness of the corner area 133 during the thickness variation process is Kn*T0, where T0 is the thickness of the active material layer in the flat area, Kn is the thickness variation coefficient of the active material layer 13 on the nth turn of the electrode, 0≤Kn≤3, n≥1.

[0052] The negative electrode 10a is an electrode 10 in the battery cell 100 used to load the negative electrode active material. The negative electrode 10a includes an anode current collector and a layer of negative electrode active material coated on at least one surface of the anode current collector. The material of the anode current collector includes, but is not limited to, copper foil, copper alloy foil, or other conductive metal foil suitable for the anode. The material of the negative electrode active material layer includes, but is not limited to, at least one of graphite, silicon-carbon composite material, lithium metal, or lithium titanium oxide. The negative electrode active material layer may also include a conductive agent and a binder.

[0053] The positive electrode 10b is a component in the battery cell 100 used to load the positive electrode active material. The positive electrode 10b includes a positive current collector and a layer of positive electrode active material coated on at least one surface of the positive current collector. The material of the positive current collector includes, but is not limited to, aluminum foil, aluminum alloy foil, or other conductive metal foil suitable for the cathode. The material of the positive electrode active material layer includes, but is not limited to, at least one of lithium cobalt oxide, lithium iron phosphate, ternary materials (such as NCM or NCA), or lithium manganese oxide. The positive electrode active material layer may also include a conductive agent and a binder.

[0054] The separator 30 is an insulating element disposed between the negative electrode 10a and the positive electrode 10b, used to prevent physical contact and short circuit between the negative electrode 10a and the positive electrode 10b while allowing lithium ions to pass through. The materials of the separator 30 include, but are not limited to, polyethylene (PE), polypropylene (PP), or a multilayer composite film formed by both (such as PP / PE / PP). The surface of the separator 30 may also be coated with a ceramic coating or an aramid coating to improve its heat resistance and mechanical strength.

[0055] Winding refers to the process of sequentially stacking the negative electrode 10a, separator 30, and positive electrode 10b, and then winding them around a central axis (such as a winding needle) to form a multi-turn layered structure. In the battery cell 100 of this application, "one turn" refers to a complete annular unit composed of one layer of negative electrode 10a, two layers of separator 30, and one layer of positive electrode 10b. Each turn has two layers of separator 30, located on opposite sides of the negative electrode 10a, to ensure that even when the electrode 10 undergoes a certain deformation, the negative electrode 10a and the positive electrode 10b remain insulated. The battery cell 100 may include several to dozens of turns. From the inner turn to the outer turn, the value of n increases.

[0056] The corner area refers to the arc-shaped bending area formed after the battery cell 100 is wound. Its radius of curvature is small, and it is a concentrated area of ​​mechanical stress. The corner area 133 is preset during the electrode sheet 10 manufacturing stage, so that after winding, the corner area 133 can be precisely aligned with and cover the entire corner area, thereby realizing the stress release function at the corner area.

[0057] The flattened area 131 is a region on the electrode 10 where the active material layer 13 has a uniform thickness and is used to constitute the main capacity of the cell 100. The thickness T0 of the flattened area 131 is determined according to the design capacity of the cell 100. Both the negative electrode 10a and the positive electrode 10b have flattened areas 131 of the active material layer 13 along their length direction R. It should be noted that when the electrode 10 is in a wound state, the length direction of the negative electrode 10a and the length direction of the positive electrode 10b are the winding directions, such as... Figure 1 and Figure 2The R referred to herein is a straight line corresponding to the flat area 131 and a curve corresponding to the corner area 133; when the electrode sheet 10 is in a flat state, the length directions of the negative electrode sheet 10a and the positive electrode sheet 10b are the flattening directions, as Figure 3 referred to by the R herein.

[0058] The corner area 133 refers to an area on the electrode sheet 10 where the thickness of the active material layer 13 changes, which is specifically designed to adapt to the bending deformation at the winding corner. The corner area 133 is formed by controlling the slurry discharge amount using a coating die head with a specific thickness profile during the previous coating process, so as to form a coating of the active material with a thickness gradient in the length direction R of the electrode sheet 10. The corner area 133 corresponds to the arc-shaped corner part of the battery cell 100 after winding. In some embodiments, the negative electrode sheet 10a is provided with a flat area 131 and a corner area 133 of the active material layer 13 in the length direction R. In some other embodiments, the positive electrode sheet 10b is provided with a flat area 131 and a corner area 133 of the active material layer 13 in the length direction R. In still some other embodiments, the negative electrode sheet 10a is provided with a flat area 131 and a corner area 133 of the active material layer 13 in the length direction R, and the positive electrode sheet 10b is provided with a flat area 131 and a corner area 133 of the active material layer 13 in the length direction R, as Figures 1 to 3 shown.

[0059] The thickness change coefficient Kn is a dimensionless coefficient, which is used to characterize the change degree of the thickness of the active material layer 13 in the corner area 133 of the nth turn of the electrode sheet 10 relative to the thickness T0 of the flat area 131. The value range of Kn is from 0 to 3. When Kn = 1, it means that the thickness of the active material layer 13 at this point is the same as the thickness T0 of the flat area 131; when 0 ≤ Kn < 1, it means that the thickness of the active material layer 13 at this point is thinned. For example, when Kn = 0.5, it means that the thickness of the active material layer 13 is halved, and when Kn = 0, it means that there is no active material layer 13 at this point, only the current collector 11; when 1 < Kn ≤ 3, it means that the thickness of the active material layer 13 at this point is thickened. For example, when Kn = 2, it means that the thickness of the active material layer 13 is doubled. By setting different Kn values for different turns n of the battery cell 100 in this application, fine control of the stress distribution and capacity distribution of the entire battery cell 100 can be achieved.

[0060] The battery cell 100 described above incorporates a corner region 133 of the active material layer 13 at the corresponding winding corner of the electrode 10. The thickness of the corner region 133 during its change is Kn*T0. This allows the electrode 10 to more smoothly adapt to bending deformation and release stress during winding and hot pressing through adaptive thickness adjustment. This avoids the breakage and shedding of the active material layer (i.e., "powder shedding") caused by excessively small bending radius and lack of stress release in traditional designs, thus improving the manufacturing yield and structural reliability of the battery cell 100. Furthermore, it prevents the active material layer from puncturing the separator in the inner ring. On the other hand, the battery cell 100 of this technical solution can solve the "powder shedding" problem without increasing the amount of binder, thinning the electrode sheet 10 as a whole, or optimizing the hot pressing parameters. While effectively solving the problem of powder shedding at the corner, it preserves the high active material load of the battery cell 100 in the flat area 131, thereby ensuring that the core performance of the energy storage device 1000 - high energy density and high capacity - is not affected.

[0061] Please see Figures 1 to 3 As an optional technical solution of this application, the thickness of the active material layer 13 changes from the thickness T0 of the flat area 131 and returns to the thickness T0 after passing the corner. The corner area 133 includes a corner preparation area 1331, a corner core area 1333, and a transition recovery area 1335 arranged sequentially. In the corner preparation area 1331, the thickness of the active material layer 13 changes from T0 to Kn*T0. In the corner core area 1333, the thickness of the active material layer 13 remains at Kn*T0. In the transition recovery area 1335, the thickness of the active material layer 13 returns from Kn*T0 to the thickness T0 of the flat area 131.

[0062] The corner preparation region 1331 is the initial transition region where the thickness of the active material layer 13 in the corner region 133 begins to change. The corner preparation region 1331 is located between the flattening region 131 and the corner core region 1333. Within the corner preparation region 1331, the thickness of the active material layer 13 starts from the thickness T0 of the flattening region 131 and decreases or increases along the length direction R of the electrode 10 until it reaches the designed thickness Kn*T0 of the corner core region 1333. This design variation allows the stiffness and bending resistance of the electrode 10 to transition smoothly before entering the corner core region 1333, avoiding new stress concentration points caused by abrupt changes in thickness.

[0063] The corner core region 1333 is the core area within the corner region 133 corresponding to the largest curvature and the most concentrated stress at the corner. Within the corner core region 1333, the thickness of the active material layer 13 remains constant at Kn*T0. The corner core region 1333 directly bears and disperses the maximum bending stress with a stable and optimized thickness (typically less than T0). Maintaining a constant thickness ensures the consistency of the mechanical properties of the corner core region 1333, providing uniform stress support for the corner.

[0064] The transition recovery zone 1335 is the final transition area where the thickness of the active material layer 13 in the corner region 133 recovers from the corner core region 1333 to the flattening region 131. The transition recovery zone 1335 is located between the corner core region 1333 and the next flattening region 131. Within the transition recovery zone 1335, the thickness of the active material layer 13 starts from Kn*T0, gradually changes along the length direction R of the electrode 10, and recovers to the thickness T0 of the flattening region 131. The transition recovery zone 1335 corresponds to the corner preparation region 1331, ensuring that the structural stiffness of the electrode 10 can smoothly recover to its normal state when leaving the corner, avoiding peel stress caused by abrupt stiffness changes at the thickness recovery interface.

[0065] In the above technical solution, the corner region 133 is further divided into a corner preparation region 1331, a corner core region 1333, and a transition recovery region 1335. The thickness of the corner preparation region 1331 and the thickness of the transition recovery region 1335 gradually change, achieving smooth and gradual deformation of the electrode 10 when entering and leaving the corner. This design makes the stress distribution more uniform, avoids secondary stress concentration that may be caused by abrupt changes in thickness, thereby reducing the risk of the active material layer 13 peeling off or breaking due to stress concentration in the corner preparation region 1331 and the transition recovery region 1335, and improving the structural integrity and reliability of the cell 100.

[0066] Please see Figure 1 and Figure 2 As an optional technical solution of this application, the negative electrode 10a and the positive electrode 10b are wound to form multiple layers, and the cell 100 satisfies the following relationship:

[0067]

[0068] Where x = 1, 2, ..., N, and N ≥ 2, x is the number of layers of electrode 10, and the value of x increases from the inner circle to the outer circle. y(x) is the thickness of the active material layer 13 on the x-th electrode 10, N is the total number of electrode 10 layers in the cell 100, and Y is the total thickness of the active material layer 13 on all N electrode layers 10. The thickness of the active material layer 13 on each electrode layer 10 is greater than or equal to 0.1Y and less than or equal to 0.5Y.

[0069] The battery cell 100 satisfies the above relationship, which ensures that the thickness of the active material layer 13 increases from the inner ring to the outer ring. This thickness distribution can compensate for the uneven stress caused by the difference in circumference between the inner and outer rings during the winding process, reduce stress concentration, thereby reducing the risk of deformation of the battery cell 100 during cyclic use and improving mechanical stability and cycle life.

[0070] The parameter m is automatically adjusted based on the total number of layers N, ensuring that the thickness of the active material layer 13 on each electrode 10 always meets the requirements. The constraints ensure that, regardless of the number of layers in the electrode 10, the innermost layer will never be too thin to avoid insufficient active material, and the outermost layer will never be too thick to avoid overcrowding. This makes the structure of the cell 100 more balanced and improves the consistency of the utilization rate of active material.

[0071] Please see Figure 1 and Figure 2 As an optional technical solution of this application, the corner preparation area 1331 and the transition recovery area 1335 have the same size in the length direction X of the cell 100, and are smaller than the size of the corner core area 1333 in the length direction X of the cell 100.

[0072] The length of the corner preparation area 1331 is its dimension along the length direction X of the cell 100. The length of the transition recovery area 1335 is its dimension along the length direction X of the cell 100. In this design, the lengths of the corner preparation area 1331 and the transition recovery area 1335 are the same. This symmetrical design ensures that the deformation process of the electrode 10 when entering and leaving the corner is symmetrical, which is beneficial for the symmetrical release and absorption of stress.

[0073] It should be noted that the length direction X of the cell 100 is consistent with the length direction R of the electrode 10 when it is flattened, and also with the length direction R of the corresponding flat area 131 of the electrode 10. The length of the corner core area 1333 is the dimension of the corner core area 1333 in the length direction X of the cell 100.

[0074] In the above technical solution, the corner preparation area 1331 and the transition recovery area 1335 have the same length but are shorter than the corner core area 1333. In the main corner stress area (corner core area 1333), there is enough length to ensure that the stress is evenly borne, that is, there is enough length to maintain stable mechanical support. At the same time, the deformation adjustment process when entering and exiting the corner is more symmetrical and efficient, thus achieving precise stress buffering and protection of the corner core area 1333.

[0075] Please see Figures 1 to 3 As an optional technical solution of this application, the overall thickness of the flat area 131 of the battery cell 100 is the same as the overall thickness of the corner area 133.

[0076] In the above technical solution, the overall thickness of the flat area 131 of the battery cell 100 is the same as the overall thickness of the corner area 133. This allows the thickness of the active material layer in the corner area 133 of the inner ring to be less than the thickness of the active material layer in the corner area of ​​the outer ring. In other words, the active material layer in the inner ring is less, but the overall thickness of the active material layer is kept constant by the active material layer in the outer ring, thereby ensuring the energy density of the battery cell 100. At the same time, the smaller thickness of the active material layer in the corner area 133 of the inner ring can prevent the active material layer from puncturing the separator in the inner ring, thus ensuring the safety of the battery cell 100 in use.

[0077] Please see Figures 1 to 3 As an optional technical solution of this application, the thickness variation coefficient Kn varies with the number of turns n of the battery cell 100, and the value of Kn gradually increases as n increases.

[0078] When cell 100 is wound, the inner ring (with a smaller n) has a smaller radius of curvature, resulting in more severe bending and greater stress. The outer ring (with a larger n) has a larger radius of curvature, resulting in gentler bending and less stress.

[0079] Based on this, the thickness variation coefficient Kn in this technical solution is dynamically designed to be a function of the number of rings n, i.e., Kn=f(n), and the function is an increasing function. Specifically, for the innermost ring (e.g., n=1), due to the extremely high curvature, a smaller Kn value (e.g., 0≤K1≤0.8) can be used to maximize stress release and ensure safety by significantly thinning or even eliminating the active material layer 13. As the number of rings n increases, the curvature decreases, and the Kn value can be gradually increased (e.g., K2>K1, K3>K2, etc.). For the outermost ring, a Kn value close to or even greater than 1 can be used (e.g., 1.2≤Kn≤2), because the stress is already relatively small thereafter. Increasing the thickness of the active material layer 13 is beneficial to improving the capacity of the corner region 133 (specifically, the corner preparation region 1331 and / or the transition recovery region 1335), balancing the total capacity loss caused by the thinning of the inner ring.

[0080] In the above technical solution, the thickness variation coefficient Kn gradually increases with the number of winding turns n of the battery cell 100. This allows regions with high curvature and bending stress in the inner ring to cope with stress using a smaller Kn value (or even 0), while regions with low curvature in the outer ring can provide more active material using a larger Kn value. In this way, the mechanical safety of the inner ring of the battery cell 100 and the energy density of the outer ring are balanced overall.

[0081] Please see Figure 2As an optional technical solution of this application, both the negative electrode 10a and the positive electrode 10b are provided with corner areas 133. The corner preparation area 1331 of the negative electrode 10a and the corner preparation area 1331 of the positive electrode 10b are offset in the length direction X of the cell 100. The transition recovery area 1335 of the negative electrode 10a and the transition recovery area 1335 of the positive electrode 10b are offset in the length direction X of the cell 100.

[0082] The misalignment setting refers to the fact that, along the length X direction of the cell 100, the starting point (or center point) of the corner preparation area 1331 of the negative electrode 10a does not coincide with the starting point (or center point) of the corner preparation area 1331 of the positive electrode 10b, and there is an axial distance between them. Similarly, the transition recovery area 1335 of the negative electrode 10a and the transition recovery area 1335 of the positive electrode 10b are misaligned along the length X direction of the cell 100, and their ending points (or center points) along the length X direction of the cell 100 also do not coincide.

[0083] This avoids the simultaneous entry or exit of the transition phase with drastic thickness changes for the negative electrode 10a and the positive electrode 10b after winding into the cell 100. The corner preparation region 1331 and the transition recovery region 1335 are areas of thickness change, containing a continuous stiffness gradient from the normal thickness T0 to the optimized thickness Kn*T0 (or vice versa). If these regions of the two electrodes 10 are aligned in the thickness direction Z, then at a certain cross-section of the cell 100, a situation may arise where, for example, the negative electrode 10a is located at a position where the thickness of the active material layer 13 is 0.3T0, and the positive electrode 10b is also located at a position where the thickness of the active material layer 13 is 0.3T0. This would create a superimposed weak point in stiffness.

[0084] In this technical solution, the corner preparation area 1331 of the negative electrode 10a and the corner preparation area 1331 of the positive electrode 10b are staggered in the length direction X of the cell 100. Similarly, the transition recovery area 1335 of the negative electrode 10a and the transition recovery area 1335 of the positive electrode 10b are staggered in the length direction X of the cell 100. This ensures that on any cross-section of the cell 100, when one electrode 10 is in the transition zone where stiffness changes most drastically (where the thickness of the active material layer 13 is 0.3T0), the other electrode 10 is in a position with relatively stable stiffness (where the thickness of the active material layer 13 is 0.6T0). This design staggers the "troughs" of the mechanical strength of the two electrodes 10 in the thickness direction Z, making the overall compression and expansion resistance of the cell 100 more continuous and gradual in the thickness direction Z, eliminating concentrated areas of strength failure risk.

[0085] The above technical solution, in which the corner preparation area 1331 of the negative electrode 10a and the corner preparation area 1331 of the positive electrode 10b are staggered in the length direction X of the cell 100, and the transition recovery area 1335 of the negative electrode 10a and the transition recovery area 1335 of the positive electrode 10b are staggered in the length direction X of the cell 100, can effectively avoid the superposition of the stiffness gradient change areas of the two electrodes in the thickness direction Z, and disperse the possible mechanical weak points in the thickness direction Z, thereby improving the structural consistency and overall reliability of the wound cell 100 in the thickness direction Z.

[0086] Please see Figure 2 and Figure 3 As an optional technical solution of this application, the corner preparation area 1331 of the negative electrode 10a is closer to the starting end of the negative electrode 10a than the corner preparation area 1331 of the positive electrode 10b, and the transition recovery area 1335 of the positive electrode 10b is farther away from the starting end of the negative electrode 10a than the transition recovery area 1335 of the negative electrode 10a. In the length direction X of the cell 100, the misalignment interval between the corner preparation area 1331 of the negative electrode 10a and the corner preparation area 1331 of the positive electrode 10b is the same as the misalignment interval D1 between the transition recovery area 1335 of the positive electrode 10b and the transition recovery area 1335 of the negative electrode 10a. There is a distance difference D2 between the starting end of the negative electrode 10a and the starting end of the positive electrode 10b. The misalignment interval D1 and the distance difference D2 satisfy: 0≤D1 / D2≤10.

[0087] The misalignment interval D1 is the aforementioned "axial distance". Specifically, D1 / D2 can be any one of 0, 1.0, 2.0, 3.0, 4.0, 4.5, 5.2, 6.3, 7.4, 8.1, 9.2, 10.0 or any value between two adjacent values. The misalignment interval D1 and the distance difference D2 are designed to satisfy: 0≤D1 / D2≤10. This ensures that the misalignment effect is sufficient to avoid the superposition of mechanical weak points, and that the overall alignment of the electrode and the stability of the winding process are not affected by an excessively large misalignment interval D1. It also ensures that the negative electrode 10a and the positive electrode 10b can form a stable and aligned stacked structure at the beginning of winding. In this way, it can effectively prevent initial manufacturing defects such as electrode folding and separator edge curling caused by improper end alignment, and improve the yield of the winding process.

[0088] The misalignment interval D1 satisfies the condition: 0mm < D1 ≤ 30mm. Specifically, the misalignment interval D1 can be any one of 0mm, 1mm, 2mm, 3mm, 4mm, 4.5mm, 5.2mm, 6.3mm, 7.4mm, 8.1mm, 9.2mm, 10.3mm, 11.4mm, 12.5mm, 13.2mm, 14.3mm, 15.4mm, 16.1mm, 17.2mm, 18.3mm, 19.4mm, 20.5mm, 21.2mm, 22.3mm, 23.4mm, 24.5mm, 25.2mm, 26.3mm, 27.4mm, 28.1mm, 29.2mm, and 30.0mm, or any value between two adjacent values. If D1=0mm, then the starting point of the corner preparation area 1331 of the negative electrode 10a is aligned with the starting point of the corner preparation area 1331 of the positive electrode 10b, and the ending point of the transition recovery area 1335 of the negative electrode 10a is aligned with the ending point of the transition recovery area 1335 of the positive electrode 10b without misalignment. Thus, neither the corner preparation area 1331 nor the transition recovery area 1335 can play the role of misalignment in avoiding the superposition of mechanical weak points. If D1 is greater than 30mm, the misalignment distance is too large. An excessively large misalignment distance may result in the corner core region 1333 of one electrode 10 (such as negative electrode 10a) having ended after winding, while the corner core region 1333 of another electrode 10 (such as positive electrode 10b) has just begun. This phase difference may produce unexpected electrochemical or mechanical interactions in local areas, and also places excessively high requirements on the alignment accuracy of the electrode 10 in the initial winding section, which is not conducive to process control.

[0089] In the above technical solution, the misalignment interval D1 is designed to satisfy: 0mm<D1≤30mm, which ensures that the misalignment effect is sufficient to avoid the superposition of mechanical weak points, and that the overall alignment of the electrode 10 and the stability of the winding process will not be affected by the excessive misalignment interval.

[0090] Please see Figures 1 to 3 As an optional technical solution of this application, the distance difference D2 between the starting end of the negative electrode 10a and the starting end of the positive electrode 10b satisfies: 3mm≤D2≤12mm.

[0091] The starting end of the negative electrode 10a refers to the end of the negative electrode 10a that is first fixed by the winding needle at the start of winding. The starting end of the positive electrode 10b refers to the end of the positive electrode 10b that is first fixed by the winding needle at the start of winding. The distance difference D2 refers to the straight-line distance between the starting ends of the negative electrode 10a and the positive electrode 10b, measured along the length direction R of the electrode 10 in the stacked state. In this scheme, the starting end of the negative electrode 10a is further forward than the starting end of the positive electrode 10b. Specifically, D2 can be any one of 3mm, 3.5mm, 4mm, 4.7mm, 5.2mm, 5.5mm, 6.3mm, 6.7mm, 7.0mm, 7.5mm, 8.1mm, 8.6mm, 9.2mm, 9.7mm, 10.3mm, 10.9mm, 11mm, 11.4mm, 11.7mm, and 12.0mm, or any value between two adjacent values. This ensures that the positive and negative electrode sheets and the separator 30 can form a stable sandwich structure at the start of winding. If D2 is less than 3mm, the ends of the positive and negative electrode sheets are almost aligned, and under the initial winding tension, the fragile ends of the electrode sheets 10 (especially the coating edges) are prone to folding or coating damage. If D2 is greater than 12mm, then in the initial stage of winding, there is a small area where only one side of the electrode 10 (such as the negative electrode 10a) and the diaphragm 30 are wound. This asymmetrical layered structure may cause the initial coil of the core to be uneven and loose, or even cause the diaphragm 30 to curl, affecting the structural consistency of the entire core.

[0092] In the above technical solution, the distance difference D2 between the starting end of the negative electrode 10a and the starting end of the positive electrode 10b satisfies 3mm≤D2≤12mm, which ensures that the negative electrode 10a and the positive electrode 10b can form a stable stacked structure at the beginning of winding. In this way, it can effectively prevent initial manufacturing defects such as electrode 10 folding and separator 30 edge curling caused by improper end alignment, and improve the yield of the winding process.

[0093] Please see Figures 1 to 3 As an optional technical solution of this application, in each turn, the thickness variation coefficient Kn of the negative electrode 10a and the thickness variation coefficient Kn of the positive electrode 10b are the same, and the specific capacity ratio of all turns in the cell 100 is the same.

[0094] The specific capacity ratio, also known as the negative / positive electrode capacity ratio (N / P ratio), is a crucial safety parameter in the design of a battery cell. The specific capacity ratio is the ratio of the reversible capacity per unit area of ​​the negative electrode 10a to the reversible capacity per unit area of ​​the positive electrode 10b. To ensure that lithium ions extracted from the positive electrode 10b are completely received (intercalated) by the negative electrode 10a without lithium plating during charging (the positive electrode 10b is the anode, undergoing oxidation and losing electrons; the negative electrode 10a is the cathode, undergoing reduction and gaining electrons), the N / P ratio typically needs to be greater than 1.

[0095] In this technical solution, the Kn values ​​of the negative electrode 10a and the positive electrode 10b are set to the same value in each turn. Since the thickness of the active material layer 13 is directly related to the capacity per unit area, when the Kn values ​​of the negative electrode 10a and the positive electrode 10b change synchronously, their capacity ratio within the same turn remains unchanged. That is, the N / P ratio of all turns in the cell 100 is the same. This ensures that from the inner to the outer turn of the cell 100, at any turn's corner, the negative electrode 10a always has sufficient redundant capacity to receive lithium ions extracted from the positive electrode 10b. If the Kn values ​​of the negative electrode 10a and the positive electrode 10b are not synchronized, the N / P ratio of a certain turn may be too low. During fast charging or low-temperature charging, the negative electrode 10a at the turn of that turn may not be able to embed all lithium ions in time, thus causing lithium metal deposition (lithium plating), resulting in serious safety hazards and rapid capacity decay.

[0096] In the above technical solution, the thickness variation coefficient Kn of the negative electrode 10a and the positive electrode 10b is the same in each turn, ensuring that the negative and positive electrode capacity ratio (N / P ratio) of all turns in the cell 100 remains consistent. This fundamentally guarantees that in any turn and at any corner, the capacity of the negative electrode 10a is always sufficient to receive the lithium ions released from the positive electrode 10b, thereby effectively preventing the precipitation of lithium dendrites at the corner and improving the cycle life and safety performance of the cell 100.

[0097] Please see Figures 1 to 3 As an optional technical solution of this application, when Kn=0, tape is attached to the exposed area of ​​the current collector in the corner area 133 where the thickness of the active material layer 13 is zero.

[0098] When Kn=0, in a specific section of the corner region 133 of the electrode 10 (e.g., the corner core region 1333), the active material layer 13 is completely uncoated, exposing the current collector 11 underneath, forming an exposed area of ​​the current collector 11. The exposed metal current collector 11 (such as copper foil or aluminum foil) may have microscopic burrs at its edges. During winding and subsequent processes, these burrs pose a risk of piercing the diaphragm 30, causing an internal short circuit.

[0099] The tape is designed to withstand the baking temperature of the electrode 10 (typically exceeding 100°C) and the heat generated during the use of the battery cell 100. The tape's base material is typically polyimide (PI) or PET, and the adhesive is a high-temperature resistant adhesive such as acrylate. In this design, the tape is applied to the exposed area of ​​the current collector 11. On one hand, the tape covers and wraps around the edge of the current collector 11, eliminating the risk of burrs piercing the separator 30; on the other hand, the tape adds a reliable insulating layer between the exposed current collector 11 and the opposing electrode 10, preventing short circuits; furthermore, the smooth surface of the tape provides lubrication during winding, reducing friction.

[0100] In the above technical solution, when the current collector 11 is exposed when Kn=0, tape is attached to the exposed area. The tape can not only lubricate and prevent burrs during winding, but also provide insulation protection for the exposed current collector 11 inside the cell 100, preventing it from contacting the opposing electrode 10 and causing an internal short circuit, thus further enhancing the safety of the cell 100.

[0101] Please see Figures 4 to 6 Secondly, this application provides an energy storage device 1000. The energy storage device 1000 is a device capable of reversibly storing and releasing electrical energy. Specifically, the energy storage device 1000 can be a single battery cell 1001 (… Figure 4 and Figure 5 (As shown), it can also be a battery pack 1003 composed of one or more battery cells 1001 (as shown). Figure 6 (As shown).

[0102] Please see Figure 6 When the energy storage device 1000 is a battery pack 1003 composed of multiple battery cells 1001, the battery pack 1003 includes battery cells 1001 and a battery box 10031. A battery cell 1001 is the smallest unit for storing and releasing electrical energy. The battery pack 1003 can store and release energy by connecting and controlling the battery cells 1001. Multiple battery cells 1001 can be connected in series, parallel, or in a hybrid configuration. A hybrid configuration means that multiple battery cells 1001 are connected in both series and parallel connections. Multiple battery cells 1001 can be directly connected in series, parallel, or in a hybrid configuration, and then the entire assembly of the multiple battery cells 1001 is housed within a carrier (e.g., the battery box 10031). The battery pack 1003 may also include other structures; for example, the battery pack 1003 may also include a busbar (not shown) for electrical connection between multiple battery cells 1001. It is understandable that the number of battery cells 1001 in the battery pack 1003 can be adjusted adaptively according to the application scenario and capacity.

[0103] Please see Figure 4 and Figure 5The battery cell 1001 includes a top cover assembly 500, a housing 300, and a battery cell 100. The housing 300 has an opening, and the top cover assembly 500 is installed in the housing 300 and closes the opening. The battery cell 100 is housed within the housing 300. The housing 300 is a structure for housing the battery cell 100. The cross-section of the housing 300 may be, but is not limited to, circular, elliptical, square, or other polygonal shapes. The material of the housing 300 includes, but is not limited to, metals and non-metals, wherein metals include aluminum, iron, steel, aluminum alloys, or iron alloys, and non-metals include, but are not limited to, plastics. In this application, the cross-section of the housing 300 is square, which facilitates integration into a square battery cell. The material of the housing 300 is aluminum alloy, which, while ensuring rigidity, also makes the battery cell 1001 lighter and easier to transport.

[0104] Cell 100 is the core structure within battery cell 1001 that converts electrical energy into chemical energy through a chemical reaction for charging and discharging. Please refer to... Figure 1 or Figure 2 The battery cell 100 is generally made by winding an electrode assembly onto a mandrel. The electrode assembly mainly includes a negative electrode 10a, a positive electrode 10b, and a separator 30. In one possible design, the negative electrode 10a, separator 30, and positive electrode 10b are sequentially stacked and attached to the mandrel by adhesive or hot-melt methods, and then wound to form the battery cell 100. After the battery cell 100 is formed, it has gaps, through which the electrolyte can enter the battery cell 100. The electrolyte is used to wet the battery cell 100, ensuring that ions can move freely during the charging and discharging process of the battery cell 100. The electrolyte includes, but is not limited to, lithium salt electrolytes, organic solvents, and additives. A separator 30 is provided between adjacent negative electrode 10a and positive electrode 10b to separate the negative electrode 10a and the positive electrode 10b.

[0105] The battery box 10031 is a structure for holding individual battery cells 1001. The cross-section of the battery box 10031 may be, but is not limited to, circular, elliptical, square, or other polygonal shapes. The material of the battery box 10031 includes, but is not limited to, metal or non-metal. Metals include aluminum, iron, steel, aluminum alloys, or iron alloys, while non-metals include, but are not limited to, plastics. In this application, the cross-section of the battery box 10031 is rectangular. The material of the battery box 10031 is aluminum alloy, which, while ensuring strength, also makes the battery pack 1003 lighter and easier to transport.

[0106] The battery box 10031 includes a box body 10033 and a cover 10035. The box body 10033 and the cover 10035 are combined to form a receiving cavity, in which a battery cell 1001 is received. The box body 10033 is the component in the battery box 10031 that loads and supports the battery cell 1001. One end of the box body 10033 is closed, and the other end has an opening for the battery cell 1001 to be inserted into the receiving cavity. The cover 10035 is the component in the battery box 10031 that covers the opening. The connection between the box body 10033 and the cover 10035 can be detachable or non-detachable. Detachable connections include, but are not limited to, screw connections, snap-fit ​​connections, or a combination of screw connections and snap-fit ​​connections. Non-detachable connections include, but are not limited to, glued connections, welded connections, or a combination of glued connections and welded connections. In this application, the box body 10033 and the cover 10035 are detachably connected.

[0107] When the battery box 10031 includes a box body 10033 and a cover 10035, the battery box 10031 may not be made of a single material. For example, the box body 10033 and the cover 10035 may be made of the same material, aluminum alloy. The battery box 10031 may also have different components made of different materials. For example, the box body 10033 may be made of metal, while the cover 10035 may be made of plastic. Of course, the materials of the box body 10033 and the cover 10035 may also be combinations of other different materials, which will not be listed here.

[0108] Please combine Figures 1 to 3 In the energy storage device 100 of the above-mentioned technical solution, the battery cell 100 has a corner region 133 of the active material layer 13 in the area corresponding to the winding corner of the electrode 10. The thickness of the corner region 133 during the change process is Kn*T0. On the one hand, the electrode 10 can adapt to bending deformation more smoothly to release stress by self-adjusting its own thickness during winding and hot pressing. This avoids the breakage and shedding of the active material layer (i.e., "powder shedding") caused by the small bending radius and lack of stress release in traditional designs, thereby improving the manufacturing yield and structural reliability of the battery cell 100. On the other hand, it also prevents the active material layer from puncturing the separator in the inner ring. On the other hand, the battery cell 100 of this technical solution can solve the "powder shedding" problem without increasing the amount of binder, thinning the electrode sheet 10 as a whole, or optimizing the hot pressing parameters. While effectively solving the problem of powder shedding at the corner, it preserves the high active material load of the battery cell 100 in the flat area 131, thereby ensuring that the core performance of the energy storage device 1000 - high energy density and high capacity - is not affected.

[0109] Please see Figure 7 Thirdly, this application provides an electrical appliance 10000. The electrical appliance 10000 includes the energy storage device 1000 of any of the above embodiments.

[0110] Electrical equipment 10000 can include, but is not limited to, power tools, mobile phones, ships, spacecraft, or residential energy storage systems. Spacecraft can include drones, rockets, and space shuttles. This application uses a residential energy storage system as an example to illustrate the concept.

[0111] The residential energy storage system includes an energy storage device 1000 (taking a battery pack 1003 as an example), a conversion device 4000 (photovoltaic panel), a first load 2000 (streetlight), and a second load 3000 (household appliances). The energy storage device 1000 can be wall-mounted on an outdoor wall. Specifically, the conversion device 4000 can be a photovoltaic conversion device, installed on the roof, used to convert solar energy into electrical energy. The energy storage device 1000 is used to store this electrical energy and supply it to streetlights and household appliances during peak electricity prices, or to supply power when the grid experiences a power outage, or to supply power to the grid after being connected to the grid. It should be noted that the energy storage device 1000 in this application is not limited to residential energy storage scenarios.

[0112] Please combine Figures 1 to 3 In the aforementioned technical solution of the electrical equipment 1000, the battery cell 100 of the energy storage device 100 has a corner region 133 of the active material layer 13 in the region corresponding to the winding corner of the electrode 10, and the thickness of the corner region 133 during the change process is Kn*T0. On the one hand, this allows the electrode 10 to adapt to bending deformation more smoothly to release stress by self-adjusting its own thickness during winding and hot pressing. This avoids the breakage and shedding of the active material layer (i.e., "powder shedding") caused by the small bending radius and lack of stress release in traditional designs, thereby improving the manufacturing yield and structural reliability of the battery cell 100. On the other hand, it also prevents the active material layer from puncturing the separator in the inner ring. On the other hand, the battery cell 100 of this technical solution can solve the "powder shedding" problem without increasing the amount of binder, thinning the electrode sheet 10 as a whole, or optimizing the hot pressing parameters. While effectively solving the problem of powder shedding at the corner, it preserves the high active material load of the battery cell 100 in the flat area 131, thereby ensuring that the core performance of the energy storage device 1000 - high energy density and high capacity - is not affected.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell comprising a negative electrode, a separator, and a positive electrode, wherein the negative electrode, the separator, and the positive electrode are sequentially stacked and wound into multiple turns, characterized in that, In each turn, the negative electrode and / or the positive electrode are provided with a flat area and a corner area with varying thickness of active material layer in their length direction. The corner area corresponds to the corner part after the cell is wound. The thickness of the active material layer changes from the thickness T0 of the flat area and returns to the thickness T0 after passing the corner part. The corner area includes a corner preparation area, a corner core area and a transition recovery area arranged in sequence. In the corner preparation area, the thickness of the active material layer varies from T0 to Kn*T0; In the core area at the corner, the thickness of the active material layer is maintained at Kn*T0; In the transition recovery zone, the thickness of the active material layer recovers from Kn*T0 to the thickness T0 of the flat zone, where T0 is the thickness of the active material layer in the flat zone, and Kn is the thickness variation coefficient of the active material layer on the nth electrode, 0 < Kn ≤ 3, n ≥ 1. The thickness variation coefficient Kn changes with the number of winding turns n of the battery cell, and the value of Kn gradually increases as n increases. The K1 of the innermost ring satisfies: 0 < K1 ≤ 0.8, and the Kn of the outermost ring satisfies: 1.2 ≤ Kn ≤ 2.

2. The battery cell according to claim 1, characterized in that, The corner preparation area and the transition recovery area have the same size in the length direction of the cell, and are smaller than the size of the corner core area in the length direction of the cell.

3. The battery cell according to claim 1, characterized in that, The overall thickness of the battery cell corresponding to the flat area is the same as the overall thickness corresponding to the corner area.

4. The battery cell according to any one of claims 1 to 3, characterized in that, Both the negative electrode and the positive electrode are provided with the corner area. The corner preparation area of ​​the negative electrode and the corner preparation area of ​​the positive electrode are offset from each other in the length direction of the cell. The transition recovery area of ​​the negative electrode and the transition recovery area of ​​the positive electrode are also offset from each other in the length direction of the cell.

5. The battery cell according to claim 4, characterized in that, The corner preparation area of ​​the negative electrode is closer to the starting end of the negative electrode than the corner preparation area of ​​the positive electrode. The transition recovery area of ​​the positive electrode is farther away from the starting end of the negative electrode than the transition recovery area of ​​the negative electrode. In the length direction of the cell, the misalignment interval between the corner preparation areas of the negative electrode and the corner preparation areas of the positive electrode is the same as the misalignment interval D1 between the transition recovery areas of the positive electrode and the transition recovery areas of the negative electrode. There is a distance difference D2 between the starting end of the negative electrode and the starting end of the positive electrode. The misalignment interval D1 and the distance difference D2 satisfy: 0≤D1 / D2≤10.

6. The battery cell according to claim 4, characterized in that, In each turn, the thickness variation coefficient Kn of the negative electrode sheet is the same as that of the positive electrode sheet, and the negative-to-positive electrode capacity ratio is the same for all turns in the cell.

7. The battery cell according to any one of claims 1 to 3, characterized in that, When K1 is zero, tape is applied to the exposed area of ​​the current collector in the corner region where the thickness of the active material layer is zero.

8. An energy storage device, characterized in that, include: The casing has an opening; A top cover assembly that seals the opening of the housing and forms a receiving cavity together with the housing; and The battery cell according to any one of claims 1-7, wherein the battery cell is housed within the accommodating cavity.

9. An electrical appliance, characterized in that, The electrical equipment includes the energy storage device as described in claim 8.

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