Roll core, preparation method of roll core and battery

Abstract

The invention discloses a winding core which is in a prism shape, the winding core comprises a composite layer, and the composite layer is wound in the winding direction to form the prism shape; the composite layer includes: a separator wound in a winding direction; the pole pieces are attached to the diaphragm and are distributed at intervals along the winding direction; wherein the pole pieces are located on the side face of the prism shape, and the interval between every two adjacent pole pieces in the winding direction is located on the side edge of the prism shape. By adopting the technical scheme, while the space utilization rate and the energy density of the roll core are improved, the direct bending of the pole piece in the winding process is avoided, the easy breakage of the pole piece caused by the stress concentration of the continuously wound pole piece at the side edge of the prism shape is avoided, and the stability and the safety of the roll core structure are ensured. The invention further provides a preparation method of the roll core. The preparation method is used for preparing the roll core. The direct bending stress concentration of the continuously rolled pole piece at the side edge of the prism shape can be avoided. The invention also discloses a battery which comprises the roll core.

Description

Technical Field

[0001] The present invention belongs to the field of batteries and relates to a winding core, a method for preparing the winding core, and a battery. Background Art

[0002] With the rapid development of electric vehicles and energy storage systems, lithium-ion batteries, as key energy storage devices, have become a focus of industry attention regarding their energy density and space utilization. Currently, in the field of power lithium-ion batteries, the main core structures are cylindrical and square. When traditional cylindrical cores are arranged in a battery pack, the gaps between the circular cross-sections result in low space utilization, making it difficult to meet the requirements of high-energy-density applications.

[0003] Patent document CN116454414A describes a winding core and battery comprising a positive electrode sheet, a first separator, a negative electrode sheet, a second separator, and a central composite tube. The core is wound around a corresponding winding section, preventing active material from falling out. While the patent document focuses on the stability of the winding core's internal structure, the cylindrical core does not adequately address improving battery pack space utilization.

[0004] Patent document CN221201341U discloses a battery comprising a housing comprising a regular prismatic outer shell and a cylindrical inner shell, with a cylindrical winding core inserted through and secured to the inner shell. The patent document utilizes a prismatic outer shell and cylindrical winding core, leaving a large gap between the winding core and the outer shell, resulting in low space utilization.

[0005] The existing core structure has the following major issues: First, the traditional cylindrical core has low space utilization within the battery pack, limiting overall energy density. Second, when a cylindrical core is packaged in a square or hexagonal shell, a large gap between the core and the shell is created, also reducing space utilization. While low energy density and space utilization can be addressed by winding the core into a prismatic shape, this also introduces the risk of stress concentration and fracture at the electrode edges due to bending. Summary of the Invention

[0006] The purpose of the present invention is to solve the problem of how to improve the space utilization and energy density of the winding core and prevent the pole piece from being broken due to stress concentration at the side edges of the prism shape.

[0007] In a first aspect, the present invention provides a winding core having a prism shape, the winding core comprising a composite layer, the composite layer being formed into a prism shape by rolling along a winding direction;

[0008] The composite layer includes:

[0009] The diaphragm is rolled along the winding direction;

[0010] Pole pieces, attached to the diaphragm and spaced apart along the winding direction;

[0011] The pole pieces are located on the side of the prism shape, and the interval between two adjacent pole pieces along the winding direction is located at the side edge of the prism shape.

[0012] The above technical solution is adopted. By winding the core into a prismatic shape instead of putting a prismatic shell on the outside of the cylindrical core, when the cores are stacked, the gap between the cores is reduced to improve the space utilization of the cores. By winding to form multiple layers of prismatic shapes, the effective area of the pole pieces in the core is increased under the same volume, thereby improving the energy density of the core. The pole pieces are attached to the diaphragm and spaced along the winding direction, so that the pole pieces are located on the side of the prismatic shape, avoiding direct bending of the pole pieces during the winding process. The gap between two adjacent pole pieces along the winding direction is located at the side edge of the prismatic shape, so that the gap between the pole pieces is set at the side edge where stress concentration is easy to concentrate and bend, avoiding the problem of continuous winding of pole pieces directly bending at the side edge of the prismatic shape and stress concentration, which causes the pole pieces to break easily, thereby ensuring the stability and safety of the core structure.

[0013] According to another embodiment of the present invention, the diaphragm includes an inner diaphragm and an outer diaphragm, the inner diaphragm and the outer diaphragm are arranged opposite to each other along a first direction, and the first direction is perpendicular to the axial direction of the prism shape;

[0014] The pole piece includes a first pole piece and a second pole piece, the second pole piece and the first pole piece have opposite polarities, and the second pole piece and the first pole piece are correspondingly arranged along a first direction;

[0015] The first pole piece is located between the inner diaphragm and the outer diaphragm along the first direction, the second pole piece is arranged on the inner side of the inner diaphragm or the outer side of the outer diaphragm, or part of the second pole piece is located on the inner side of the inner diaphragm and the other part is located on the outer side of the outer diaphragm.

[0016] According to another specific embodiment of the present invention, the winding core is in the shape of a hexagonal prism.

[0017] According to another embodiment of the present invention, the composite layer is rolled along the winding direction to form a multi-layered prism shape.

[0018] The side lengths of the pole pieces in each layer are equal, and the side lengths of the pole pieces in each layer increase from the inside to the outside along the first direction. The side length of the pole piece is the length of the projection of the pole piece on a plane perpendicular to the axial direction of the prism shape.

[0019] In a second aspect, the present invention further provides a method for preparing a roll core, which is used to prepare the above-mentioned roll core, comprising the following steps:

[0020] Preparation of composite layer: conveying the diaphragm, cutting the electrode pieces, attaching the electrode pieces to the diaphragm so that the electrode pieces are spaced apart along the winding direction to form a composite layer;

[0021] Rolling the composite layer: Rolling the composite layer into a prism shape along the winding direction so that the pole pieces are located on the side of the prism shape and the interval between two adjacent pole pieces along the winding direction is located at the side edge of the prism shape.

[0022] By adopting the above technical solution, the composite layer is rolled into a prismatic shape. Compared with a cylindrical core, the gap between the stacked cores is reduced, thereby improving space utilization. By rolling the composite layer into a prismatic shape, the effective area of the electrode within the same volume is increased, thereby improving the energy density of the core. By cutting the electrode and attaching the electrode to the diaphragm, the electrode is spaced along the winding direction to form a composite layer. The electrode is located on the side of the prismatic shape, thereby avoiding direct bending of the electrode during the winding process. The gap between two adjacent electrode pieces along the winding direction is located at the side edge of the prismatic shape, so that the gap between two adjacent electrode pieces is set at the side edge that is prone to stress concentration and bending, thereby avoiding the problem of continuous rolled electrode pieces being directly bent at the side edge of the prismatic shape, resulting in stress concentration and easy breakage of the electrode pieces, thereby ensuring the stability and safety of the core structure.

[0023] According to another specific embodiment of the present invention, attaching the electrode to the diaphragm includes:

[0024] Coat the surface of the diaphragm with adhesive, preheat the diaphragm and / or the pole piece, place the pole piece on the diaphragm, and composite the pole piece and the diaphragm by rolling.

[0025] According to another specific embodiment of the present invention, the electrode includes a first electrode and a second electrode, the second electrode has opposite polarity to the first electrode, and a core preparation system is used to prepare the core, and the core preparation system includes:

[0026] A first oven, used for preheating the first pole piece;

[0027] A first rolling unit, used for compounding the first pole piece and the diaphragm;

[0028] A second oven, used for preheating the second pole piece;

[0029] A second rolling unit is used to composite the first pole piece, the diaphragm and the second pole piece;

[0030] A first pole piece shearing unit, located between the first oven and the first rolling unit, for shearing the first pole piece;

[0031] The second pole piece shearing unit is located between the second oven and the second rolling unit and is used to shear the second pole piece. Shearing the pole piece includes:

[0032] The first pole pieces are alternately sheared by two or more first pole piece shearing units and / or the second pole pieces are alternately sheared by two or more second pole piece shearing units.

[0033] According to another specific embodiment of the present invention, the electrode includes a first electrode and a second electrode, the second electrode and the first electrode have opposite polarities, the diaphragm includes an inner diaphragm and an outer diaphragm, the inner diaphragm and the outer diaphragm are arranged relative to each other along a first direction, the first direction is perpendicular to the axial direction of the prism shape, and preparing the composite layer includes:

[0034] The first pole piece is attached between the inner diaphragm and the outer diaphragm, a part of the second pole piece is attached to the inner side of the inner diaphragm and the other part is attached to the outer side of the outer diaphragm, and the second pole piece is set at a position corresponding to the first pole piece along the first direction.

[0035] According to another specific embodiment of the present invention, the side length of the pole piece is a preset length, and the side length of the pole piece is the length of the projection of the pole piece on a plane perpendicular to the axial direction of the prism shape. The method for preparing the winding core further includes:

[0036] During the composite layer rolling process, the side length of the current electrode and the bottom side length of the winding core of the layer where the current electrode is located are detected;

[0037] Calculate the actual ratio of the side length of the current electrode to the bottom side length of the winding core of the layer where the current electrode is located;

[0038] Determine whether the actual ratio falls within the preset ratio range. If so, cut the electrode according to the preset length. If not, modify the preset length of the electrode so that the actual ratio of the side length of the electrode and the bottom side length of the winding core of the layer where the electrode is located falls within the preset ratio range.

[0039] According to another specific embodiment of the present invention, the preset length of the modified pole piece is determined according to the following method:

[0040] Get the bottom side length of the winding core of the layer where the current electrode is located, modify the preset length of the electrode according to the bottom side length and the preset ratio range, and cut the electrode according to the modified preset length.

[0041] According to another specific embodiment of the present invention, the method for preparing the core includes:

[0042] Detect the side length of the electrode on the first side of each layer and the side length of the bottom side of the winding core where the electrode is located. The first side is the side of the winding core where the electrode is first attached in each layer along the winding direction.

[0043] Calculate the actual ratio between the side length of the pole piece and the side length of the bottom surface of the winding core where the pole piece is located;

[0044] Determine whether the actual ratio falls within the preset ratio range. If so, cut the remaining pole pieces of the layer where the pole piece is located according to the preset length. If not, modify the preset length of the remaining pole pieces of the layer where the pole piece is located so that the actual ratio of the side length of the remaining pole pieces of the layer where the pole piece is located and the bottom side length of the winding core of the layer where the pole piece is located falls within the preset ratio range.

[0045] In a third aspect, the present invention further provides a battery comprising the aforementioned winding core.

[0046] The battery adopts the above technical solution, including the above-mentioned core. By winding the core into a prismatic shape instead of enclosing a cylindrical core with a prismatic shell, when the cores are stacked, the gap between the cores is reduced, thereby improving the space utilization of the core. By winding to form multiple layers of prismatic shapes, the effective area of the electrode in the core is increased under the same volume, thereby improving the energy density of the core. The electrode is attached to the diaphragm and spaced along the winding direction, so that the electrode is located on the side of the prismatic shape, avoiding direct bending of the electrode during the winding process. The gap between two adjacent electrode sheets along the winding direction is located at the side edge of the prismatic shape, so that the gap between the electrode sheets is set at the side edge where stress concentration is easy to concentrate and bend, avoiding the problem of continuous winding of electrode sheets directly bending at the side edge of the prismatic shape and stress concentration, which leads to easy breakage of the electrode sheets, thereby ensuring the stability and safety of the core structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A schematic structural diagram of a winding core is shown;

[0048] Figure 2 Schematic diagram showing the structure of the composite layer before rolling in an embodiment of the present invention Figure 1 ;

[0049] Figure 3 A schematic structural diagram of a winding core formed into a prism shape in an embodiment of the present invention is shown;

[0050] Figure 4 Schematic diagram showing the spatial position of the electrode and the diaphragm before the electrode is attached in the embodiment of the present invention Figure 1 ;

[0051] Figure 5 Schematic diagram showing the spatial position of the electrode and the diaphragm before the electrode is attached in the embodiment of the present invention Figure 2 ;

[0052] Figure 6 Schematic diagram showing the spatial position of the electrode and the diaphragm before the electrode is attached in the embodiment of the present invention Figure 3 ;

[0053] Figure 7 Schematic diagram of the stacking structure of the core in the embodiment of the present invention Figure 1 ;

[0054] Figure 8 The process of preparing the core in the embodiment of the present invention is shown Figure 1 ;

[0055] Figure 9 The structure of the core preparation system in the embodiment of the present invention is shown as follows Figure 1 ;

[0056] Figure 10 The structure of the core preparation system in the embodiment of the present invention is shown as follows Figure 2 ;

[0057] Figure 11 The structure of the core preparation system in the embodiment of the present invention is shown as follows Figure 3 ;

[0058] Figure 12 The structure of the core preparation system in the embodiment of the present invention is shown as follows Figure 4 ;

[0059] Figure 13 The process of preparing the core in the embodiment of the present invention is shown Figure 2 ;

[0060] Figure 14 The process of preparing the core in the embodiment of the present invention is shown Figure 3 ;

[0061] Figure 15 The process of preparing the core in the embodiment of the present invention is shown Figure 4 ;

[0062] Figure 16 The process of preparing the core in the embodiment of the present invention is shown Figure 5 ;

[0063] Figure 17 Schematic diagram showing the structure of the composite layer before rolling in an embodiment of the present invention Figure 2 ;

[0064] Figure 18 Schematic diagram of the core stacking structure in an embodiment of the present invention Figure 2 ;

[0065] Figure 19 Schematic diagram of the core stacking structure in an embodiment of the present invention Figure 3 . DETAILED DESCRIPTION

[0066] The following specific embodiments illustrate the embodiments of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this invention are limited to this embodiment. On the contrary, the purpose of introducing the invention in conjunction with the embodiment is to cover other options or modifications that may be extended based on the claims of the present invention. In order to provide a deep understanding of the present invention, the following description will contain many specific details. The present invention can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the present invention, some specific details will be omitted in the description. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other unless there is a conflict.

[0067] It should be noted that in this specification, similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0068] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0069] like Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of a winding core. Figure 1 The winding method for the center core solves the problems of low core energy density and low space utilization by winding the pole piece 02 and separator 03 into a prismatic shape. However, the pole piece 02 is continuous at the side edges 04 of the core 01, and the pole piece 02 bends at these edges. This causes stress concentration on the pole piece 02 at these edges, making it prone to breakage and affecting the safety and stability of the core 01.

[0070] In a first aspect, the present invention provides a winding core 1, which is in the shape of a prism. Figure 2 and Figure 3 As shown, Figure 2 Schematic diagram of the structure of the composite layer 2 before rolling in an embodiment of the present invention, Figure 3 The structure diagram of the winding core 1 formed into a prism shape in an embodiment of the present invention is shown in FIG. The winding core 1 includes a composite layer 2, and the composite layer 2 is formed into a prism shape by rolling along the winding direction. The winding direction is Figure 2 and Figure 3 The composite layer 2 includes: a diaphragm 3, which is rolled along the winding direction. A pole piece 4, which is attached to the diaphragm 3 and rolled along the winding direction ( Figure 2 and Figure 3The electrode pieces 4 are spaced apart along the prism-shaped side 5 (in the X-direction). The winding direction is the length of the separator 3. The electrode pieces 4 are located on the side 5 of the prism shape. The spacing between two adjacent electrode pieces 4 along the winding direction is located at the side edge 6 of the prism shape. The composite layer 2 is wound to form a multi-layered prism shape. The separator 3 separates the electrode pieces 4 of each layer, that is, a separator 3 is provided between each layer of electrode pieces 4, and the electrode pieces 4 are attached to the separator 3.

[0071] The pole pieces 4 are spaced apart along the winding direction, and the spacing between two adjacent pole pieces 4 is located at the side edges 6 of the prism shape. This prevents the pole pieces 4 from bending directly during the winding process, reduces the stress concentration of the pole pieces 4 at the side edges 6 of the prism shape, and thus reduces the risk of the pole pieces 4 breaking. The diaphragm 3 not only isolates each layer of pole pieces 4 to prevent short circuits, but also plays a role in attaching the pole pieces 4 during the winding process. The diaphragm 3 can absorb and disperse the mechanical stress at the side edges 6, thereby preventing the pole pieces 4 from bending directly, reducing the deformation and stress of the pole pieces 4 during the winding process, thereby reducing the risk of the pole pieces 4 breaking and improving the stability and safety of the winding core 1.

[0072] By adopting the above technical solution, by winding the core 1 into a prismatic shape rather than enclosing a cylindrical core with a prismatic shell, when the cores 1 are stacked, the gap between the cores 1 is reduced, thereby improving the space utilization of the core 1. The effective area of the electrode in the core 1 is increased at the same volume, thereby improving the energy density of the core 1. The electrode 4 is attached to the diaphragm 3 and spaced along the winding direction, so that the electrode 4 is located on the side 5 of the prismatic shape, avoiding direct bending of the electrode 4 during the winding process. The spacing between two adjacent electrode 4 along the winding direction is located at the side edge 6 of the prismatic shape. The spacing between the electrode 4 is set at the side edge 6 where stress is easily concentrated and bent. This avoids the problem of the continuous winding of the electrode 4 directly bending at the side edge 6 of the prismatic shape and stress concentration, which makes the electrode 4 easy to break, thereby ensuring the stability and safety of the core 1 structure.

[0073] like Figures 4 to 6 As shown, the diaphragm 3 includes an inner diaphragm 31 and an outer diaphragm 32, and the inner diaphragm 31 and the outer diaphragm 32 are arranged relative to each other along a first direction, and the first direction is perpendicular to the axial direction of the prism shape. Figure 4 The winding direction is Figure 4The pole piece 4 includes a first pole piece 41 and a second pole piece 42. The second pole piece 42 has opposite polarity to the first pole piece 41, and the second pole piece 42 is arranged corresponding to the first pole piece 41 along the first direction. The second pole piece 42 is arranged at a position corresponding to the first pole piece 41 along the first direction, which can increase the overlapping area of the first pole piece 41 and the second pole piece 42. It can maximize the utilization of the active materials on the first pole piece 41 and the second pole piece 42 without increasing the volume of the battery, and avoid the waste of active materials in the non-overlapping area of the first pole piece 41 and the second pole piece 42 due to not participating in the electrochemical reaction, thereby optimizing space utilization.

[0074] In some embodiments, as Figure 4 As shown, the first pole piece 41 is located between the inner diaphragm 31 and the outer diaphragm 32 along a first direction, and the second pole piece 42 is disposed on the inner side of the inner diaphragm 31. The structural design of the inner diaphragm 31 and the outer diaphragm 32 positions the first pole piece 41 between the two diaphragm layers, and the second pole piece 42 on the inner side of the inner diaphragm. During the winding process, the second pole piece 42 is clamped between the outer diaphragm 32 of the previous composite layer 2 and the inner diaphragm 31 of the current composite layer 2. This structure can better secure the pole piece 4 and reduce displacement or damage to the pole piece 4 due to vibration or impact during winding and battery use.

[0075] In some embodiments, as Figure 5 As shown, the first pole piece 41 is located between the inner diaphragm 31 and the outer diaphragm 32 along a first direction, and the second pole piece 42 is disposed outside the outer diaphragm 32. By arranging the first pole piece 41 between the inner diaphragm 31 and the outer diaphragm 32 and the second pole piece 42 outside the outer diaphragm 32, the second pole piece 42 is clamped between the outer diaphragm 32 of the current composite layer 2 and the inner diaphragm 31 of the next composite layer 2 during the winding process. This structure can better secure the pole piece and reduce displacement or damage of the pole piece 4 due to vibration or impact during winding and battery use.

[0076] In some embodiments, as Figure 3 and Figure 6As shown, the first pole piece 41 is located between the inner diaphragm 31 and the outer diaphragm 32 along the first direction, a portion of the second pole piece 42 is located on the inner side of the inner diaphragm 31, and another portion is located on the outer side of the outer diaphragm 32. A portion of the second pole piece 42 is located on the inner side of the inner diaphragm 31, opposite to the first pole piece 41 along the first direction, while another portion of the second pole piece 42 is located on the outer side of the outer diaphragm 32, opposite to the first pole piece 41 along the first direction. The second pole pieces 42 may be located alternately on the inner side of the inner diaphragm 31 and on the outer side of the outer diaphragm 32, or a plurality of second pole pieces 42 may be located on the inner side of the inner diaphragm 31 and on the outer side of the outer diaphragm 32. The interval between two first pole pieces 41 adjacent along the winding direction is located at the side edge of the prism shape. The two second pole pieces 42 adjacent along the winding direction refer to two second pole pieces 42 corresponding to the two first pole pieces 41 adjacent along the winding direction along the first direction, and the interval between the two second pole pieces 42 adjacent along the winding direction is also located at the side edge of the prism shape.

[0077] refer to Figure 6 and Figure 17 The first pole piece 41 is located between the inner diaphragm 31 and the outer diaphragm 32 along the first direction, a portion of the second pole piece 42 is located on the inner side of the inner diaphragm 31, and the other portion is located on the outer side of the outer diaphragm 32. The first pole piece 41 and the second pole piece 42 are compounded to form a composite layer 2.

[0078] By adopting the above technical solution, a part of the second pole piece 42 is located on the inner side of the inner diaphragm 31, and the other part is located on the outer side of the outer diaphragm 32. The second pole piece 42 can be produced alternately by two production lines. For example, two second pole piece shearing units 152 are used to alternately shear the second pole piece 42, and the second pole piece is respectively attached to the inner side of the inner diaphragm 31 and the outer side of the outer diaphragm 32, thereby improving the preparation speed of the composite layer 2 of the core 1 and thereby improving production efficiency.

[0079] like Figure 7 As shown, the winding core 1 is in the shape of a hexagonal prism. Figure 7 This is a schematic diagram of the bottom surface of multiple stacked cores 1 in an embodiment of the present invention. The cores 1 are hexagonal in shape, allowing adjacent cores 1 to fit tightly together, with minimal gaps between them. Therefore, the hexagonal shape of the cores 1 provides high space utilization and energy density.

[0080] like Figure 18 and Figure 19 As shown, the winding core 1 is in the shape of a hexagonal prism. Figure 18 This is a schematic diagram of the structure of stacking multiple winding cores 1 in an embodiment of the present invention. Figure 18 As shown, the core 1 is a blade battery, and the core 1 is in the shape of a hexagonal prism. The gap between two adjacent cores 1 is small, which has high space utilization and energy density. Figure 19 As shown, Figure 19The diagram is a schematic diagram of a structure in which multiple winding cores 1 are stacked in an embodiment of the present invention. The winding cores 1 are in the shape of a hexagonal prism, and the gap between two adjacent winding cores 1 is small, which has high space utilization and energy density.

[0081] In some embodiments, continue to refer to Figure 3 , the composite layer 2 is rolled along the winding direction to form a multi-layer stacked prism shape. The composite layer 2 is rolled along a polygonal path, and the edges of the composite layer 2 are arranged according to the outline of the polygon to form a multi-layer stacked prism shape. For example, the winding core 1 is in the shape of a hexagonal prism, and the composite layer 2 is rolled along a polygonal path, and the edges of the composite layer 2 are arranged according to the outline of the hexagon, that is, on the bottom surface of the hexagonal prism shape, the edges of the composite layer 2 are rolled to form a hexagon, thereby forming a multi-layer stacked hexagonal prism shape. Among them, the shape of the pole piece 4 is rectangular, and the side lengths of the pole pieces 4 in each layer are equal. The side lengths of the pole pieces 4 of each layer along the first direction increase from the inside to the outside. The side length L of the pole piece 4 is the length of the projection of the pole piece 4 on a plane perpendicular to the axial direction of the prism shape, and the axial direction refers to Figure 3 The Z direction in . Figure 2 As shown, from the perspective of unfolding the composite layer 2, the side length L of the pole piece 4 refers to the length of the pole piece along the winding direction X. The longitudinal direction of the diaphragm 3 is the winding direction, and the diaphragm 3 extends along the longitudinal direction. The side length L of the pole piece is also the dimension of the pole piece 4 in the longitudinal direction of the diaphragm.

[0082] By adopting the above technical solution, by increasing the side length of the electrode 4 from the inside to the outside, the space inside the prism can be more effectively utilized, so that the entire core structure can accommodate more active materials under a certain volume, thereby improving the energy density of the core.

[0083] In some embodiments, the side length of the pole pieces 4 of each layer along the first direction increases from inside to outside. For example, the side length of the pole pieces 4 of each layer along the first direction increases from inside to outside in an arithmetic progression or a geometric progression.

[0084] The above technical solution, by increasing the side length of the electrode sheet 4 in an arithmetic or geometric progression, helps to more effectively fill the internal space of the core, reducing voids, thereby improving the space utilization and energy density of the entire core and the battery pack formed by the core. The design of increasing the side length of the electrode sheet 4 in an arithmetic or geometric progression can make the internal resistance of the battery formed by the core more uniform, thereby reducing the overall internal resistance and improving the charge and discharge efficiency and power output of the battery formed by the core.

[0085] In some embodiments, the pole pieces 4 are spaced apart along the winding direction, and the interval between two adjacent pole pieces 4 is a preset distance. The preset distance can be set according to the shape and size of the winding core. Preferably, the preset distance can be 1 mm to 5 mm, and the preset distance of each layer along the first direction increases from the inside to the outside. Alternatively, the preset distance between each layer of pole pieces can be fixed. The side length of the pole piece 4 can be 10 mm to 200 mm. The length of the diaphragm can be 500 mm to 8000 mm, and the width of the diaphragm can be 35 mm to 600 mm. The thickness of the diaphragm can be 10 μm to 30 μm.

[0086] Second, as Figure 8 As shown, the present invention also provides a method for preparing a winding core, which is used to prepare the above-mentioned winding core, comprising the following steps:

[0087] S01: preparing a composite layer: transferring the diaphragm, cutting the pole pieces, and attaching the pole pieces to the diaphragm so that the pole pieces are spaced apart along the winding direction to form a composite layer.

[0088] S02: Rolling the composite layer: Rolling the composite layer into a prism shape along the winding direction, so that the pole pieces are located on the side of the prism shape, and the interval between two adjacent pole pieces along the winding direction is located at the side edge of the prism shape.

[0089] like Figure 2 and Figure 9 As shown, the method for preparing the core includes: preparing a composite layer: transporting the diaphragm through the transport roller 111, transporting the electrode through the transport roller 112, the distance meter 12 detects the side length of the electrode 4 and the distance between the electrode 4 and the electrode 4, cutting the electrode through the electrode cutting unit 15, attaching the electrode 4 to the diaphragm 3, so that the electrode 4 is arranged at intervals along the winding direction, and rolling and compounding through the rolling unit 8 to form a composite layer 2.

[0090] like Figure 2 and Figure 3 As shown, the composite layer is rolled: the composite layer 2 is rolled into a prism shape along the winding direction (X direction), so that the pole piece 4 is located on the side 5 of the prism shape, and the interval between two adjacent pole pieces 4 along the winding direction is located at the side edge 6 of the prism shape.

[0091] By adopting the above technical solution, the pole piece 4 is cut and attached to the diaphragm 3 so that the pole pieces 4 are spaced apart along the winding direction to form a composite layer 2, and the composite layer 2 is rolled into a prism shape so that the pole piece 4 is located on the side 5 of the prism shape, and the interval between two adjacent pole pieces 4 along the winding direction is located at the side edge 6 of the prism shape. The space utilization and energy density of the winding core 1 are improved by rolling to form a prism shape. The position of the interval between the pole piece 4 and the two adjacent pole pieces 4 is used to avoid stress concentration at the side edge 6 of the prism shape of the continuously rolled pole piece 4, which causes the pole piece 4 to break easily, thereby ensuring the stability and safety of the winding core 1 structure.

[0092] In some embodiments, attaching the electrode to the diaphragm includes:

[0093] S011: Coat the surface of the diaphragm with adhesive, preheat the diaphragm and / or pole piece, place the pole piece on the diaphragm, and composite the pole piece and diaphragm by rolling.

[0094] Continue to refer Figure 9 Attaching the electrode to the diaphragm includes: coating an adhesive on the surface of the diaphragm 3, preheating the diaphragm 3 and / or the electrode 4 through an oven 7, placing the electrode 4 on the diaphragm 3, and compounding the electrode 4 and the diaphragm 3 by rolling.

[0095] Specifically, an adhesive is applied to the surface of the diaphragm 3, and the diaphragm 3 or the pole piece 4 is preheated, or the diaphragm 3 and the pole piece 4 are preheated. For example, preheating is performed in the following five situations: preheating the first pole piece 41 using the first oven 71, preheating the second pole piece 42 using the second oven 72, preheating the inner diaphragm 31 using the third oven 73, preheating the outer diaphragm 32 using the fourth oven 74, and preheating the first pole piece 41 and the diaphragm 3 using the fifth oven 75. Alternatively, preheating is performed in any one of the above five situations. Alternatively, preheating is performed in any two of the above five situations. Alternatively, preheating is performed in any three of the above five situations. Alternatively, preheating is performed in any four of the above five situations. Alternatively, preheating is performed in all five of the above situations at the same time. The pole piece 4 is placed on the diaphragm 3, and the pole piece 4 and the diaphragm 3 are compounded by rolling. For example, the first pole piece 41 is placed between the inner diaphragm 31 and the outer diaphragm 32, and the first pole piece, the inner diaphragm 31, and the outer diaphragm 32 are composited by the first rolling unit 81. For example, the second pole piece 42 is placed outside the outer diaphragm 32, and the first pole piece 41, the inner diaphragm 31, the outer diaphragm 32, and the second pole piece 42 are composited by the second rolling unit 82.

[0096] The above technical solution can ensure that the electrode 4 is firmly attached to the diaphragm 3, and the electrode 4 will not move relative to the diaphragm during the production and use of the core, avoiding the short circuit problem caused by the displacement of the electrode 4 and ensuring the safety and stability of the core 1.

[0097] In some embodiments, reference Figures 10 to 12 , the electrode 4 includes a first electrode 41 and a second electrode 42, the second electrode 42 and the first electrode 41 have opposite polarities, and a core preparation system is used to prepare the core, and the core preparation system includes: a first oven 71, for preheating the first electrode 41. A first rolling unit 81, for compounding the first electrode 41 and the diaphragm 3. For example, the first electrode 41 and the inner diaphragm 31 and the outer diaphragm 32 are compounded by the first rolling unit 81. The second oven 72, for preheating the second electrode 42. The second rolling unit 82, for compounding the first electrode 41, the diaphragm 3 and the second electrode 42. For example, the inner diaphragm 31, the first electrode 41, the outer diaphragm 32 and the second electrode 42 are compounded by the second rolling unit 82. The first electrode shearing unit 151, located between the first oven 71 and the first rolling unit 81, is used to shear the first electrode 41. The second pole piece shearing unit 152 is located between the second oven 72 and the second rolling unit 82 and is used to shear the second pole piece 42. Shearing the pole piece includes:

[0098] S012: Alternately shearing the first pole piece by using two or more first pole piece shearing units and / or alternately shearing the second pole piece by using two or more second pole piece shearing units.

[0099] Specifically, if Figure 10 As shown, two second pole piece shearing units 152 are used to alternately shear the second pole piece 42, placing the second pole piece 42 on the inner side of the inner diaphragm 31 or the outer side of the outer diaphragm 32, respectively. This technical solution improves the shearing and transfer speeds of the pole piece 4, thereby increasing the speed of preparing the composite layer and improving production efficiency. Alternating the use of two or more second pole piece shearing units 152 balances the workload of each second pole piece shearing unit 152, extending the service life of each second pole piece shearing unit 152 and reducing wear on each second pole piece shearing unit 152.

[0100] Alternatively, as Figure 11 As shown, two first pole piece shearing units 151 are used to alternately shear the first pole piece 41. This technical solution can increase the shearing and transfer speeds of the pole piece 4, thereby increasing the speed of preparing the composite layer and improving production efficiency. Alternating the use of two or more first pole piece shearing units 151 can balance the workload of each first pole piece shearing unit 151, extend the service life of the first pole piece shearing unit 151, and reduce wear on a single first pole piece shearing unit 151.

[0101] Alternatively, as Figure 12As shown, two first pole piece cutting units 151 are used to alternately cut the first pole piece 41, and two second pole piece cutting units 152 are used to alternately cut the second pole piece 42. The above technical solution can significantly improve the efficiency of pole piece cutting, thereby improving the efficiency of core preparation, while reducing the workload of the pole piece cutting units 15, extending the service life of the pole piece cutting units 15, and reducing the wear of each pole piece cutting unit 15.

[0102] In some embodiments, reference Figure 6 The electrode 4 includes a first electrode 41 and a second electrode 42, wherein the second electrode 42 and the first electrode 41 have opposite polarities. The diaphragm 3 includes an inner diaphragm 31 and an outer diaphragm 32, wherein the inner diaphragm 31 and the outer diaphragm 32 are arranged relative to each other along a first direction, wherein the first direction (the Y direction in the figure) is perpendicular to the axial direction of the prism shape. S01: Preparing a composite layer includes:

[0103] S013: Attach the first pole piece between the inner diaphragm and the outer diaphragm, attach a portion of the second pole piece to the inner side of the inner diaphragm and the other portion to the outer side of the outer diaphragm, and set the second pole piece at a position corresponding to the first pole piece along the first direction.

[0104] By adopting the above technical solution, a part of the second pole piece 42 is located on the inner side of the inner diaphragm 31, and the other part is located on the outer side of the outer diaphragm 32. The second pole piece 42 can be produced alternately by two production lines. For example, two second pole piece shearing units 152 are used to alternately shear the second pole piece 42, and the second pole piece is respectively attached to the inner side of the inner diaphragm 31 and the outer side of the outer diaphragm 32, thereby improving the preparation speed of the composite layer 2 of the core 1 and thereby improving production efficiency.

[0105] In some embodiments, the side length of the pole piece 4 is a preset length, and the side length of the pole piece 4 is the length of the projection of the pole piece 4 on a plane perpendicular to the axial direction of the prism shape. Figure 13 The preparation method of the core further comprises:

[0106] S03: During the process of rolling the composite layer, the side length of the current pole piece and the side length of the bottom surface of the winding core of the layer where the current pole piece is located are detected.

[0107] S04: Calculate the actual ratio of the side length of the current electrode piece to the side length of the bottom surface of the winding core of the layer where the current electrode piece is located.

[0108] S05: Determine whether the actual ratio falls within a preset ratio range. If so, execute S06-1: Cut the electrode according to the preset length. If not, execute S06-2: Modify the preset length of the electrode so that the actual ratio of the side length of the electrode and the bottom side length of the winding core in the layer where the electrode is located falls within the preset ratio range.

[0109] Specifically, refer to Figures 9 to 12The diaphragm is transported by the transport roller 111, and the electrode is transported by the transport roller 112. The distance meter 12 detects the side length of the electrode 4 and the distance between the electrode 4. The electrode is transported by the transport platform 13, and the electrode is sheared by the electrode shearing unit 15. The electrode 4 is attached to the diaphragm 3 so that the electrode 4 is spaced apart along the winding direction. The electrode is rolled and compounded by the rolling unit 8 to form a composite layer 2. Figure 2-Figure 3 , rolling the composite layer: roll the composite layer 2 into a prism shape along the winding direction (X direction), and roll it through the hexagonal winding needle 14 so that the pole piece 4 is located on the side 5 of the prism shape, and the interval between two adjacent pole pieces 4 along the winding direction is located at the side edge 6 of the prism shape.

[0110] Continue to refer Figure 3 as well as Figures 9 to 12 In the process of rolling the composite layer, the detection unit 9 is used to detect the side length L of the current pole piece 4 and the side length C of the bottom surface of the winding core of the layer where the current pole piece 4 is located. The detection unit 9 transmits the detection results of the side length L of the current pole piece 4 and the side length C of the bottom surface of the winding core of the layer where the current pole piece 4 is located to the controller 10, and the controller 10 calculates the actual ratio of the side length L of the current pole piece and the side length C of the bottom surface of the winding core 1 of the layer where the current pole piece is located. Determine whether the actual ratio falls within the preset ratio range. If so, the controller 10 transmits a control signal to the rangefinder 12 and the pole piece cutting unit 15 to cut the pole piece according to the preset length. If not, modify the preset length of the pole piece 4 so that the actual ratio of the side length L of the pole piece 4 and the side length C of the bottom surface of the winding core of the layer where the pole piece is located falls within the preset ratio range.

[0111] The preset ratio range is, for example, a ratio of the side length L of the current electrode 4 to the side length C of the bottom surface of the winding core of the layer where the current electrode 4 is located, which is 0.9-1.

[0112] Specifically, for example, the current pole piece refers to the first side of the winding core that is currently rolled up. The first side is the side of the winding core to which the pole piece is first attached in each layer along the winding direction. The originally planned preset length of the pole piece 4 is M, and the preset length M is, for example, 92mm. However, due to factors such as errors in the rolling process and errors in the thickness of the composite layer, the actual side length L of the pole piece 4 is not equal to the preset length M. If the actual side length L is 75mm, the actual bottom side length of the layer where the current pole piece is located is 90mm. When the preset ratio range is, for example, 0.9-1. The actual ratio of the side length L of the current pole piece and the bottom side length C of the winding core of the layer where the current pole piece is located will not fall within the preset ratio range. If the pole piece 4 is cut according to the preset length of 92mm, the pole piece may bend at the side edge, resulting in stress concentration and easy breakage. At this time, it is necessary to modify the preset length of the pole piece 4, and modify the preset length M of the pole piece 4 to between 81mm-90mm, so that the actual ratio of the side length L of the pole piece 4 and the bottom side length C of the winding core of the layer where the pole piece is located falls within the preset ratio range.

[0113] If the actual ratio of the side length L of the current electrode to the bottom side length C of the winding core 1 in the layer where the current electrode is located is less than the preset ratio range, it means that the side length L of the electrode 4 is too short, the distance between two adjacent electrode sheets 4 along the winding direction is too large, the actual ratio of the electrode sheets in the formed composite layer is too small, and the energy density and space utilization of the winding core are too low. The preset length of the electrode 4 should be modified, that is, the preset length of the electrode 4 should be increased so that the actual ratio of the side length L of the electrode 4 to the bottom side length C of the winding core in the layer where the electrode is located falls within the preset ratio range.

[0114] When the actual ratio of the side length L of the current electrode and the bottom side length C of the winding core of the layer where the current electrode is located is greater than the preset ratio range, it means that the side length L of the electrode 4 is too long. During the winding process, the electrode 4 may be located at the side edge of the prism shape. During winding, the electrode may bend at the side edge of the prism shape, causing stress concentration and easy breakage.

[0115] By adopting the above technical solution, through real-time detection and adjustment, the side length L of the pole piece 4 and the bottom side length C of the core are within a preset ratio range, which can maximize the space utilization and the energy density of the battery. By preventing the pole piece 4 from being too long, the risk of bending and breaking of the pole piece 4 at the side edges during the winding process is reduced, thereby improving the reliability and safety of the core 1.

[0116] In some embodiments, reference Figure 14 , S06-2: Modify the preset length of the pole piece according to the following method:

[0117] S0621: Obtain the bottom side length of the winding core of the layer where the current electrode is located, modify the preset length of the electrode according to the bottom side length and the preset ratio range, and cut the electrode according to the modified preset length.

[0118] Specifically, the bottom side length C of the winding core of the layer where the current electrode is located is obtained, the preset length of the electrode 4 is calculated based on the bottom side length C and the preset ratio range, the preset length of the electrode 4 is modified, and the electrode 4 is cut according to the modified preset length.

[0119] Specifically, for example, the originally planned preset length of the pole piece 4 is M, but due to factors such as errors in the rolling process and errors in the thickness of the composite layer, the actual side length L of the pole piece 4 is not equal to the preset length M. The actual ratio of the side length L of the current pole piece and the bottom side length C of the winding core of the layer where the current pole piece is located may not fall within the preset ratio range. In this case, it is necessary to calculate the preset length of the pole piece 4 based on the bottom side length C of the winding core of the layer where the current pole piece is located and the preset ratio range, and modify the preset length of the pole piece 4 so that the actual ratio of the side length L of the pole piece 4 and the bottom side length C of the winding core of the layer where the pole piece is located falls within the preset ratio range.

[0120] By adopting the above technical solution, the preset length of the electrode can be determined according to the real-time bottom side length C and the preset ratio range, and the electrode 4 can be cut according to the preset length, so that the ratio of the side length of the electrode 4 and the bottom side length C of the core is within the preset range. The core produced in this way can meet the requirements of higher energy density without the electrode being located at the bend, resulting in stress concentration and easy breakage.

[0121] In some embodiments, reference Figure 15 , the preparation method of the core comprises:

[0122] S031: Detect the side length of the electrode on the first side of each layer and the side length of the bottom surface of the winding core on which the electrode is located. The first side is the side of the winding core to which the electrode is first attached along the winding direction. Specifically, detect the side length L of the electrode on the side of the winding core to which the electrode is first attached along the winding direction, and detect the side length C of the bottom surface of the winding core on which the electrode is located.

[0123] S041: Calculate the actual ratio of the side length of the electrode to the side length of the bottom surface of the winding core in the layer where the electrode is located. Specifically, calculate the actual ratio of the side length L of the electrode to the side length C of the bottom surface of the winding core in the layer where the electrode is located. The actual ratio reflects the proportion of the electrode to the side surface of the prismatic shape in the layer where the electrode is located.

[0124] S051: Determine whether the actual ratio falls within the preset ratio range. If so, execute S061-1: cut the remaining electrodes of the electrode layer according to the preset length. If not, execute S061-2: modify the preset length of the remaining electrodes of the electrode layer, so that the actual ratio of the side length of the remaining electrodes of the electrode layer and the bottom side length of the winding core of the electrode layer falls within the preset ratio range. Go to the next layer, continue to detect the side length of the electrode on the first side and the bottom side length of the winding core of the electrode layer, calculate the actual ratio of the side length of the electrode and the bottom side length of the winding core of the electrode layer, and determine whether the actual ratio falls within the preset ratio range. If so, cut the remaining electrodes of the electrode layer according to the preset length. If not, modify the preset length of the remaining electrodes of the electrode layer, so that the actual ratio of the side length of the remaining electrodes of the electrode layer and the bottom side length of the winding core of the electrode layer falls within the preset ratio range.

[0125] Specifically, for example, the originally planned preset length of the pole piece 4 is M, but due to factors such as errors in the rolling process and errors in the thickness of the composite layer, the actual side length L of the pole piece 4 is not equal to the preset length M. The actual ratio of the side length L of the current pole piece and the bottom side length C of the winding core of the layer where the current pole piece 4 is located may not fall within the preset ratio range, resulting in the current pole piece 4 being too long or too short. At this time, it is necessary to calculate the preset lengths of the remaining pole pieces 4 in the layer where the pole piece is located based on the bottom side length C of the winding core of the layer where the current pole piece 4 is located and the preset ratio range, and modify the preset lengths of the remaining pole pieces 4 in the layer where the pole piece is located so that the actual ratio of the side lengths L of the remaining pole pieces 4 and the bottom side length C of the winding core of the layer where the pole piece is located falls within the preset ratio range.

[0126] Using this technical solution, for each layer of electrodes, only the side length of the first side of the electrode and the side length of the bottom surface of the winding core on which the electrode is located need to be measured to obtain the preset ratio of the other electrode pieces in the same layer, reducing the workload of detection and calculation and improving production efficiency. At the same time, because only the dimensions of the first side of the electrode need to be measured for each layer, the cumulative error that may be introduced by multiple measurements is reduced, and the accuracy of dimensional control is improved.

[0127] In some embodiments, reference Figure 16 , S061-2: Modify the preset length of the remaining pole pieces in the layer where the pole piece is located, including: S06121: Obtain the bottom side length of the winding core of the layer where the pole piece on the first side of each layer is located, modify the preset length of the remaining pole pieces in the layer where the pole piece is located according to the bottom side length and the preset proportion range, and cut the remaining pole pieces in the layer where the pole piece is located according to the modified preset length.

[0128] The above technical solution can reduce the workload of detection and calculation and improve production efficiency.

[0129] In a third aspect, the present invention further provides a battery comprising the aforementioned winding core.

[0130] The battery adopts the above technical solution, including the above-mentioned core. By winding the core into a prismatic shape instead of enclosing a cylindrical core with a prismatic shell, when the cores are stacked, the gap between the cores is reduced, thereby improving the space utilization of the core. By winding to form multiple layers of prismatic shapes, the effective area of the electrode in the core is increased under the same volume, thereby improving the energy density of the core. The electrode is attached to the diaphragm and spaced along the winding direction, so that the electrode is located on the side of the prismatic shape, avoiding direct bending of the electrode during the winding process. The gap between two adjacent electrode sheets along the winding direction is located at the side edge of the prismatic shape, so that the gap between the electrode sheets is set at the side edge where stress concentration is easy to concentrate and bend, avoiding the problem of continuous winding of electrode sheets directly bending at the side edge of the prismatic shape and stress concentration, which leads to easy breakage of the electrode sheets, thereby ensuring the stability and safety of the core structure.

[0131] Although the present invention has been illustrated and described with reference to certain preferred embodiments thereof, it should be understood by those skilled in the art that the above description is provided as a further detailed description of the present invention in conjunction with specific embodiments thereof, and that the specific implementation of the present invention is not limited to these descriptions. Those skilled in the art may make various changes in form and details, including simple deductions or substitutions, without departing from the spirit and scope of the present invention.

Claims

1. A winding core, characterized in that: The winding core is in a prism shape, and the winding core includes a composite layer, and the composite layer is formed into the prism shape by rolling along a winding direction; The composite layer comprises: a diaphragm, rolled along the winding direction; Pole pieces, attached to the diaphragm and spaced apart along the winding direction; The pole pieces are located on the side surfaces of the prism shape, and the interval between two adjacent pole pieces along the winding direction is located at the side edges of the prism shape.

2. The winding core according to claim 1, wherein: The diaphragm includes an inner diaphragm and an outer diaphragm, the inner diaphragm and the outer diaphragm are arranged opposite to each other along a first direction, and the first direction is perpendicular to the axial direction of the prism shape; The pole piece includes a first pole piece and a second pole piece, the second pole piece and the first pole piece have opposite polarities, and the second pole piece and the first pole piece are correspondingly arranged along the first direction; In which, the first pole piece is located between the inner diaphragm and the outer diaphragm along the first direction, the second pole piece is arranged on the inner side of the inner diaphragm or the outer side of the outer diaphragm, or a part of the second pole piece is located on the inner side of the inner diaphragm and the other part is located on the outer side of the outer diaphragm.

3. The winding core according to claim 1, wherein: The winding core is in the shape of a hexagonal prism.

4. The winding core according to claim 1, wherein: The composite layer is rolled along the winding direction to form the multi-layered prism shape. The side lengths of the pole pieces in each layer are equal, and the side lengths of the pole pieces in each layer increase from the inside to the outside along the first direction. The side lengths of the pole pieces are the lengths of the projections of the pole pieces on a plane perpendicular to the axial direction of the prism shape.

5. A method for preparing a winding core, for preparing the winding core according to any one of claims 1 to 4, characterized in that: The steps include: Preparing a composite layer: conveying the separator, cutting the electrode pieces, and attaching the electrode pieces to the separator so that the electrode pieces are spaced apart along the winding direction to form the composite layer; Rolling the composite layer: rolling the composite layer into a prism shape along the winding direction, so that the pole pieces are located on the side of the prism shape, and the interval between two adjacent pole pieces along the winding direction is located at the side edge of the prism shape.

6. The method for preparing a winding core according to claim 5, wherein: The step of attaching the electrode to the diaphragm includes: An adhesive is applied to the surface of the diaphragm, the diaphragm and / or the pole piece are preheated, the pole piece is placed on the diaphragm, and the pole piece and the diaphragm are compounded by rolling.

7. The method for preparing a winding core according to claim 5, wherein: The pole piece includes a first pole piece and a second pole piece, wherein the second pole piece has opposite polarity to the first pole piece, and the core is prepared by a core preparation system, wherein the core preparation system includes: a first oven, for preheating the first pole piece; a first rolling unit, used for compounding the first pole piece and the diaphragm; a second oven, for preheating the second pole piece; a second rolling unit, configured to composite the first pole piece, the diaphragm, and the second pole piece; a first pole piece shearing unit, located between the first oven and the first rolling unit, for shearing the first pole piece; The second pole piece shearing unit is located between the second oven and the second rolling unit and is used to shear the second pole piece. Shearing the pole piece includes: The first pole piece is alternately cut by two or more first pole piece cutting units and / or the second pole piece is alternately cut by two or more second pole piece cutting units.

8. The method for preparing a winding core according to claim 5, wherein: The electrode piece includes a first electrode piece and a second electrode piece, the second electrode piece and the first electrode piece have opposite polarity, the diaphragm includes an inner diaphragm and an outer diaphragm, the inner diaphragm and the outer diaphragm are arranged relative to each other along a first direction, the first direction is perpendicular to the axial direction of the prism shape, and the preparation of the composite layer includes: The first pole piece is attached between the inner diaphragm and the outer diaphragm, a part of the second pole piece is attached to the inner side of the inner diaphragm and the other part is attached to the outer side of the outer diaphragm, and the second pole piece is set at a position corresponding to the first pole piece along the first direction.

9. The method for preparing a winding core according to claim 5, wherein: The side length of the pole piece is a preset length, and the side length of the pole piece is the length of the projection of the pole piece on a plane perpendicular to the axial direction of the prism shape. The method for preparing the winding core further includes: During the composite layer rolling process, detecting the side length of the current pole piece and the bottom side length of the winding core of the layer where the current pole piece is located; Calculating the actual ratio of the side length of the current electrode piece to the side length of the bottom surface of the winding core of the layer where the current electrode piece is located; Determine whether the actual ratio falls within the preset ratio range. If so, cut the electrode according to the preset length. If not, modify the preset length of the electrode so that the actual ratio of the side length of the electrode and the bottom side length of the winding core of the layer where the electrode is located falls within the preset ratio range.

10. The method for preparing a winding core according to claim 9, wherein: The modification of the preset length of the pole piece is determined according to the following method: The bottom side length of the winding core of the layer where the current electrode is located is obtained, the preset length of the electrode is modified according to the bottom side length and the preset ratio range, and the electrode is cut according to the modified preset length.

11. The method for preparing a winding core according to claim 9, wherein: The preparation method of the winding core comprises: Detecting the side length of the electrode on the first side of each layer and the side length of the bottom side of the winding core of the layer where the electrode is located, wherein the first side is the side of the winding core to which the electrode is first attached in the winding direction; Calculating the actual ratio of the side length of the pole piece to the side length of the bottom surface of the winding core of the layer where the pole piece is located; Determine whether the actual ratio falls within the preset ratio range. If so, cut the remaining pole pieces in the layer where the pole piece is located according to the preset length. If not, modify the preset length of the remaining pole pieces in the layer where the pole piece is located so that the actual ratio of the side length of the remaining pole pieces in the layer where the pole piece is located and the bottom side length of the winding core in the layer where the pole piece is located falls within the preset ratio range.

12. A battery, characterized in that: The invention comprises a winding core as described in any one of claims 1 to 4.

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