Battery cell and battery

Abstract

The utility model discloses a battery cell and a battery. The battery cell comprises a first pole piece, a first diaphragm, a second pole piece and a second diaphragm which are sequentially stacked and wound; the first diaphragm is provided with a first extension section, a first arc section and a first starting end, the first extension section is positioned between the first pole piece and the second diaphragm, and the first extension section extends towards a first direction from one end connected with the first arc section; the second diaphragm is provided with a second extension section, a second arc section and a second starting end, the second extension section is positioned between the second pole piece and the first diaphragm, and the second extension section extends towards a second direction from one end connected with the second arc section; and in the thickness direction of the battery cell, the projection of the first extension section and the projection of the second extension section are at least partially overlapped. The problems that empty foil exists at the head of the pole piece in the prior art, the energy density of the battery is easily reduced, and the head of the positive electrode and the head of the negative electrode are contacted can be solved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell and a battery. Background Art

[0002] As a new type of secondary battery, lithium-ion battery has the advantages of high energy density and power density, high operating voltage, light weight, small size, long cycle life, good safety, and green environmental protection. It is widely used in various electronic products.

[0003] Existing battery cell structures usually adopt two structures: head-placed pole tabs and center-placed pole tabs. However, both structures have empty foils at the pole head and redundant diaphragms at the pole head, which leads to reduced pole utilization and further reduced battery energy density. Utility Model Content

[0004] The main purpose of the present application is to provide a battery cell and a battery to solve the problem in the prior art that there is empty foil at the head of the pole piece, which easily reduces the energy density of the battery and causes contact between the heads of the positive and negative poles.

[0005] According to one aspect of the present application, a battery cell is provided, comprising a first pole sheet, a first separator, a second pole sheet and a second separator which are sequentially stacked and wound, wherein the first pole sheet and the second pole sheet each comprise a current collector and an active material layer disposed on a surface of the current collector;

[0006] The first diaphragm has a first extension section, a first arc section and a first starting end, the first arc section is connected to an end of the first extension section away from the first starting end, the first extension section is located between the first pole piece and the second diaphragm, and the first extension section extends from an end connected to the first arc section toward a first direction;

[0007] The second diaphragm has a second extension section, a second arc section and a second starting end, the second arc section is connected to an end of the second extension section away from the second starting end, the second extension section is located between the second pole piece and the first diaphragm, and the second extension section extends from an end connected to the second arc section toward a second direction opposite to the first direction;

[0008] Wherein, along the thickness direction of the battery core, the projection of the first extension segment and the projection of the second extension segment at least partially overlap.

[0009] Further, along the first direction, the maximum length between the first starting end and the first arc segment is L1, and the overlapping length of the first extension segment and the second extension segment is L0, wherein L0 and L1 satisfy the relationship: L0≤L1;

[0010] Alternatively, along the first direction, the maximum length between the second starting end and the second arc segment is L2, and the overlapping length of the first extension segment and the second extension segment is L3, wherein L3 and L2 satisfy the relationship: L3≤L2.

[0011] Further, the first pole piece has a first pole piece starting end, a first straight section and a first bent section, the first bent section is connected to an end of the first straight section away from the first pole piece starting end, the first straight section is located between the second extension section and the first diaphragm, and the first straight section extends from an end connected to the first bent section toward the first direction;

[0012] The second pole piece has a second pole piece starting end, a second straight section and a second bent section, the second bent section is connected to an end of the second straight section away from the starting end of the second pole piece, the second straight section is located between the first extension section and the second diaphragm, and the second straight section extends from an end connected to the second bent section toward the second direction.

[0013] Further, the starting end of the first pole piece is aligned with the first starting end; and / or,

[0014] The second pole piece starting end is aligned with the second starting end.

[0015] Further, the first diaphragm further has a first diaphragm end, the first pole piece further has a first pole piece end, and the first diaphragm end is aligned with the first pole piece end; and / or,

[0016] The second diaphragm further has a second diaphragm end, the second pole piece further has a second pole piece end, and the second diaphragm end is aligned with the second pole piece end.

[0017] Further, the battery cell has a first pole lug and a second pole lug, a first empty foil area is provided on the first pole sheet, and the first pole lug is provided in the first empty foil area; and / or,

[0018] A second empty foil area is provided on the second pole piece, and the second pole tab is located in the second empty foil area.

[0019] Furthermore, the first empty foil area is arranged close to a starting end of the first pole piece, and the second empty foil area is arranged close to a starting end of the second pole piece.

[0020] Further, along the length direction of the first pole piece, the first empty foil area is arranged at the middle position of the first pole piece, and along the length direction of the second pole piece, the second empty foil area is arranged at the middle position of the second pole piece.

[0021] Furthermore, the battery cell also includes adhesive tape, which is arranged on the surface of the second pole piece close to the second arc segment, and along the thickness direction of the battery cell, the projection of the adhesive tape at least partially covers the starting end of the first pole piece.

[0022] On the other hand, the present application also provides a battery, which includes the above-mentioned battery cell and also includes a casing.

[0023] In the present application, compared with the battery cell structure in the prior art, the present application adopts a plug-in structure for the first extension section of the first diaphragm and the second extension section of the second diaphragm, and makes the projection of the first extension section along the thickness direction of the battery cell and the projection of the second extension section along the thickness direction of the battery cell at least partially overlap, which can prevent the battery cell from short-circuiting due to contact between the first pole piece and the second pole piece, thereby extending the service life of the battery. At the same time, the present application provides active material layers on the opposite sides of the first pole piece and the opposite sides of the second pole piece to avoid empty foil at the heads of the first pole piece and the second pole piece, thereby improving the energy density of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0025] Figure 1 This is a schematic structural diagram of a first embodiment of a battery cell disclosed in an embodiment of the present application;

[0026] Figure 2 A schematic structural diagram of a second embodiment of the battery cell disclosed in the examples of the present application;

[0027] Figure 3 A schematic structural diagram of a third embodiment of the battery cell disclosed in the examples of the present application;

[0028] Figure 4 This is a schematic structural diagram of a fourth embodiment of the battery cell disclosed in the examples of this application;

[0029] Figure 5 This is a schematic structural diagram of a fifth embodiment of the battery cell disclosed in the examples of this application;

[0030] Figure 6 The present invention is a flow chart of a method for preparing a battery disclosed in an embodiment of the present application.

[0031] The above drawings include the following reference numerals:

[0032] 10. First pole piece; 11. Starting end of first pole piece; 12. End of first pole piece; 13. First empty foil area; 14. First straight section; 15. First bent section; 20. First diaphragm; 21. First extension section; 211. First starting end; 22. First arc section; 23. End of first diaphragm; 30. Second pole piece; 31. Starting end of second pole piece; 32. End of second pole piece; 33. Second empty foil area; 34. Second straight section; 35. Second bent section; 40. Second diaphragm; 41. Second extension section; 411. Second starting end; 42. Second arc section; 43. End of second diaphragm; 50. Active material layer; 60. First pole ear; 70. Second pole ear; 80. Adhesive tape; 90. Straight section; 100. Curved section. DETAILED DESCRIPTION

[0033] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0034] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0035] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0036] As mentioned in the background technology, in the prior art, the electrode head of the battery structure with the electrode head and the electrode middle structure has empty foil, and there is also redundant diaphragm at the electrode head, which not only reduces the utilization rate of the electrode, but also reduces the energy density of the battery. Therefore, in order to avoid the empty foil at the electrode head and the contact between the positive and negative electrode heads, the inventor of this application has designed a new type of battery cell, which will be described in detail below.

[0037] It should be noted that the first direction in this application is the attached Figure 1 The direction indicated by the letter X in the middle, the second direction is the Figure 1 The direction indicated by the letter Y in the figure is the thickness direction of the battery cell. Figure 1 The direction indicated by the letter Z in the figure is the length direction of the first pole piece and the second pole piece. Figure 1 The direction indicated by the letter A.

[0038] See also Figures 1 to 6 As shown, the present application provides a battery cell, which includes a first pole piece 10 , a first diaphragm 20 , a second pole piece 30 and a second diaphragm 40 .

[0039] The battery cell includes a first electrode sheet 10, a first diaphragm 20, a second electrode sheet 30 and a second diaphragm 40 which are stacked and wound in sequence. The first electrode sheet 10 and the second electrode sheet 30 both include a current collector and an active material layer 50 arranged on the surface of the current collector. The first diaphragm 20 has a first extension section 21, a first arc section 22 and a first starting end 211. The first arc section 22 is connected to an end of the first extension section 21 away from the first starting end 211. The first extension section 21 is located between the first electrode sheet 10 and the second diaphragm 40, and the first extension section 21 extends from the first electrode sheet 10 to the second diaphragm 40. One end connected to the arc segment 22 extends toward the first direction; the second diaphragm 40 has a second extension segment 41, a second arc segment 42 and a second starting end 411, the second arc segment 42 is connected to the end of the second extension segment 41 away from the second starting end 411, the second extension segment 41 is located between the second electrode 30 and the first diaphragm 20, and the second extension segment 41 extends from the end connected to the second arc segment 42 toward a second direction opposite to the first direction; along the thickness direction of the battery cell, the projection of the first extension segment 21 at least partially overlaps with the projection of the second extension segment 41.

[0040] In this embodiment, the first diaphragm 20 has a first extension section 21, and the second diaphragm 40 has a second extension section 41. When the battery cell is actually processed, the first electrode sheet 10, the first diaphragm 20, the second electrode sheet 30 and the second diaphragm 40 can be stacked together in sequence, and then a winding process is used to form a winding core. After the processing is completed, the first extension section 21 and the second extension section 41 are located at the innermost circle of the battery cell, and the first extension section 21 and the second extension section 41 are in opposite directions, so that Figure 1Taking the direction shown as an example, the first extension section 21 extends toward the first direction, and the second extension section 41 extends toward the second direction, wherein the first direction and the second direction are opposite, and at the same time, the starting end of the winding of the first pole piece 10 faces the first direction, and the starting end of the winding of the second pole piece 30 faces the second direction, so that a plug-in type diaphragm winding core structure can be formed. At this time, the projection of the first extension section 21 along the thickness direction of the battery cell and the projection of the second extension section 41 along the thickness direction of the battery cell at least partially overlap, effectively avoiding the contact between the head of the first pole piece 10 and the head of the second pole piece 30, thereby preventing the battery cell from short-circuiting, thereby avoiding the battery cell from generating too much heat and causing serious damage to the battery life, and extending the battery life to a certain extent. In addition, in this embodiment, an active material layer 50 is provided on the opposite sides of the first pole piece 10 and the opposite sides of the second pole piece 30, and the active material layer 50 is coated from the head of the first pole piece 10 and the head of the second pole piece 30, so that the head of the first pole piece 10 and the second pole piece 30 can be avoided from having empty foil, which not only improves the utilization rate of the pole piece, but also improves the energy density of the battery.

[0041] That is to say, compared with the battery cell structure in the prior art, in this embodiment, the first extension segment 21 of the first diaphragm 20 and the second extension segment 41 of the second diaphragm 40 adopt a plug-in structure, and the projection of the first extension segment 21 along the thickness direction of the battery cell and the projection of the second extension segment 41 along the thickness direction of the battery cell at least partially overlap each other, which can prevent the battery cell from short-circuiting due to contact between the first electrode sheet 10 and the second electrode sheet 30, thereby extending the service life of the battery. At the same time, in this embodiment, active material layers 50 are provided on the opposite sides of the first electrode sheet 10 and the opposite sides of the second electrode sheet 30 to avoid the appearance of empty foil at the heads of the first electrode sheet 10 and the second electrode sheet 30, thereby improving the energy density of the battery.

[0042] Specifically, the polarities of the first pole piece 10 and the second pole piece 30 in this embodiment are opposite, wherein the first pole piece 10 is a negative pole piece and the second pole piece 30 is a positive pole piece.

[0043] Further, see Figure 1 As shown, along the first direction, the maximum length between the first starting end 211 and the first arc segment 22 in this embodiment is L1, and the overlapping length of the first extension segment 21 and the second extension segment 41 is L0, wherein L0 and L1 satisfy the relationship: L0≤L1; or, see Figure 2 As shown, along the first direction, the maximum length between the second starting end 411 and the second arc segment 42 in this embodiment is L2, and the overlapping length of the first extension segment 21 and the second extension segment 41 is L3, wherein L3 and L2 satisfy the relationship: L3≤L2.

[0044] Specifically, the present application defines the length between the first starting end 211 and the highest point of the arc line of the first arc segment 22 as the maximum length L1 between the first starting end 211 and the first arc segment 22, and defines the length between the second starting end 411 and the highest point of the arc line of the second arc segment 42 as the maximum length L2 between the second starting end 411 and the second arc segment 42.

[0045] It can be understood that when L0≤L1 or L3≤L2, the projection of the first extension segment 21 along the thickness direction of the battery cell and the projection of the second extension segment 41 along the thickness direction of the battery cell can at least partially overlap with each other, effectively avoiding contact between the head of the first pole piece 10 and the head of the second pole piece 30, thereby preventing the battery cell from short circuiting, and further avoiding the battery cell from generating excessive heat which would cause serious damage to the battery life, thereby extending the battery life to a certain extent.

[0046] Specifically, see Figure 1 As shown, in an embodiment shown in the present application, along the first direction, the maximum length between the first starting end 211 and the first arc segment 22 is L1, and the overlapping length of the first extension segment 21 and the second extension segment 41 is L0, wherein L0 and L1 satisfy the relationship: L0<L1, so that the battery cell can be prevented from short-circuiting due to the contact between the first pole piece 10 and the second pole piece 30, thereby extending the service life of the battery; or, see Figure 2 As shown, in another embodiment shown in the present application, along the first direction, the maximum length between the second starting end 411 and the second arc segment 42 is L2, and the overlapping length of the first extension segment 21 and the second extension segment 41 is L3, wherein L3 and L2 satisfy the relationship: L3<L2, so that the battery cell can be prevented from short circuiting due to the contact between the first electrode 10 and the second electrode 30, thereby extending the service life of the battery.

[0047] That is to say, Figure 1 The embodiment shows that the first starting end 211 of the first diaphragm 20 is aligned with the first pole piece starting end 11, while the second starting end 411 of the second diaphragm 40 is not aligned with the second pole piece starting end 31; Figure 2 The embodiment shows that the first starting end 211 of the first diaphragm 20 is not aligned with the first pole piece starting end 11 , while the second starting end 411 of the second diaphragm 40 is aligned with the second pole piece starting end 31 .

[0048] Further, see Figure 1 to Figure 2As shown, the first pole piece 10 in this embodiment has a first pole piece starting end 11, a first straight section 14 and a first bent section 15, the first bent section 15 is connected to the end of the first straight section 14 away from the first pole piece starting end 11, the first straight section 14 is located between the second extension section 41 and the first diaphragm 20, and the first straight section 14 extends from the end connected to the first bent section 15 toward the first direction; the second pole piece 30 has a second pole piece starting end 31, a second straight section 34 and a second bent section 35, the second bent section 35 is connected to the end of the second straight section 34 away from the second pole piece starting end 31, the second straight section 34 is located between the first extension section 21 and the second diaphragm 40, and the second straight section 34 extends from the end connected to the second bent section 35 toward the second direction.

[0049] That is to say, the first straight section 14 of the first pole piece 10 and the second straight section 34 of the second pole piece 30, as well as the first extension section 21 of the first diaphragm 20 and the second extension section 41 of the second diaphragm 40 in this embodiment all adopt a plug-in structure. The existence of the first extension section 21 and the second extension section 41 can prevent the first straight section 14 and the second straight section 34 from making contact, thereby avoiding a short circuit in the battery cell, thereby extending the service life of the battery to a certain extent.

[0050] Further, see Figure 3 As shown, the first pole piece starting end 11 of this embodiment is aligned with the first starting end 211; and / or, the second pole piece starting end 31 of this embodiment is aligned with the second starting end 411. Specifically, Figure 3 The illustrated embodiments and Figure 1 as well as Figure 2 The difference between the embodiment shown in the figure is that the first starting end 211 of the first diaphragm 20 is aligned with the first pole piece starting end 11, and the second starting end 411 of the second diaphragm 40 is aligned with the second pole piece starting end 31. Since the diaphragm and the pole piece are aligned, the diaphragm and the pole piece can be cut at the same time during the production process of the battery cell, which is beneficial to the subsequent winding of the diaphragm and the pole piece, and improves the winding efficiency of the winding process to a certain extent.

[0051] In this embodiment, the first pole piece 10, the first diaphragm 20, the second pole piece 30 and the second diaphragm 40 are stacked together in sequence, and a winding process is adopted to form a winding core, wherein the winding core is wound with the first pole piece starting end 11, the first starting end 211, the second pole piece starting end 31 and the second starting end 411 as the winding head ends, so that the first pole piece starting end 11, the first starting end 211, the second pole piece starting end 31 and the second starting end 411 are located in the innermost circle of the battery cell, and then the first straight section 14, the first extension section 21, the second straight section 34 and the second extension section 41 are located in the innermost circle of the battery cell.

[0052] Further, see Figure 4 As shown, the first diaphragm 20 in this embodiment further has a first diaphragm end 23, the first pole piece 10 further has a first pole piece end 12, and the first diaphragm end 23 is aligned with the first pole piece end 12; and / or, the second diaphragm 40 in this embodiment further has a second diaphragm end 43, the second pole piece 30 further has a second pole piece end 32, and the second diaphragm end 43 is aligned with the second pole piece end 32. Specifically, Figure 4 The illustrated embodiments and Figure 1 as well as Figure 2 The difference between the illustrated embodiment is that the first diaphragm end 23 is aligned with the first pole piece end 12, and the second diaphragm end 43 is aligned with the second pole piece end 32. Since the diaphragm and the pole piece are aligned, the diaphragm and the pole piece can be cut at the same time during the production process of the battery cell, which is beneficial to the subsequent winding of the diaphragm and the pole piece, and improves the winding efficiency of the winding process to a certain extent.

[0053] In this embodiment, the first pole piece 10, the first diaphragm 20, the second pole piece 30 and the second diaphragm 40 are stacked together in sequence and formed into a winding core by a winding process. The first pole piece end 12, the first diaphragm end 23, the second pole piece end 32 and the second diaphragm end 43 are located at the outermost circle of the battery cell.

[0054] Further, the battery cell in this embodiment has a first pole tab 60 and a second pole tab 70, a first empty foil area 13 is provided on the first pole piece 10, the first empty foil area 13 separates the active material layer 50 on the first pole piece 10, and the first pole tab 60 is arranged in the first empty foil area 13; and / or, a second empty foil area 33 is provided on the second pole piece 30 in this embodiment, the second empty foil area 33 separates the active material layer 50 on the second pole piece 30, and the second pole tab 70 is located in the second empty foil area 33. Specifically, the first pole piece 10 and the second pole piece 30 in this embodiment are both provided with an empty foil area, and the pole tabs can be installed in the empty foil area to realize the charging and discharging process of the battery. In addition, when the first pole piece 10 and the second pole piece 30 are wound using a winding process, the presence of the first empty foil area 13 can prevent bulging from occurring at the location of the first pole ear 60 on the first pole piece 10, and the presence of the second empty foil area 33 can prevent bulging from occurring at the location of the second pole ear 70 on the second pole piece 30, thereby extending the service life of the battery to a certain extent.

[0055] It can be understood that, since the first pole piece 10 in this embodiment is a negative pole piece and the second pole piece 30 is a positive pole piece, the first pole tab 60 is a negative pole tab and the second pole tab 70 is a positive pole tab.

[0056] Further, see Figures 1 to 4As shown, in this embodiment, the first empty foil area 13 is arranged near the first pole piece starting end 11, and the second empty foil area 33 is arranged near the second pole piece starting end 31. That is, Figures 1 to 4 The embodiment in FIG. 1 shows the structure of the tab head arrangement.

[0057] Further, see Figure 5 As shown, along the length direction of the first pole piece 10, the first empty foil area 13 in this embodiment is arranged at the middle position of the first pole piece 10, and along the length direction of the second pole piece 30, the second empty foil area 33 in this embodiment is arranged at the middle position of the second pole piece 30. That is, Figure 5 The embodiment in the figure shows a structure in which the pole ear is placed in the middle.

[0058] Specifically, the middle position of the first pole piece 10 is the middle position away from the opposite ends of the first pole piece 10 when the first pole piece 10 is unfolded; the middle position of the second pole piece 30 is the middle position away from the opposite ends of the second pole piece 30 when the second pole piece 30 is unfolded.

[0059] It can be understood that, no matter the structure of the pole ear head placement or the structure of the pole ear middle placement, the first diaphragm 20 and the second diaphragm 40 in this embodiment adopt the diaphragm insertion method, which effectively ensures that the head of the first pole piece 10 and the head of the second pole piece 30 do not come into contact. At the same time, in this embodiment, active material layers 50 are arranged on the opposite sides of the head of the first pole piece 10 and the opposite sides of the head of the second pole piece 30, which can not only prevent the head of the first pole piece 10 and the head of the second pole piece 30 from having an empty foil area, improve the utilization rate of the pole piece to a certain extent, and improve the energy density of the battery, but also prevent the head of the first pole piece 10 and the head of the second pole piece 30 from having a single-sided area, effectively ensuring the consistency of the force on the opposite sides of the first pole piece 10 and the opposite sides of the second pole piece 30, thereby avoiding wrinkles in the pole piece during the winding process.

[0060] It should be noted that after the pole piece or diaphragm is made into a winding core through a winding process, a straight segment 90 and a curved segment 100 will be formed due to the winding. Each time the pole piece or diaphragm is wound one circle, the pole piece or diaphragm will form two straight segments 90 and two curved segments 100, wherein the two straight segments 90 in one circle are connected by the curved segments 100 at both ends. After the pole piece or diaphragm is wound into a winding core, the first straight segment 90, the first curved segment 100, the second straight segment 90, the second curved segment 100, the third straight segment 90, the third curved segment 100, etc. will be formed from the inner circle of the winding core in sequence, and so on. In this embodiment, the first extension segment 21 and the second extension segment 41, as well as the first straight segment 14 and the second straight segment 34 all belong to the above-mentioned straight segment 90, and the first arc segment 22 and the second arc segment 42, as well as the first bend segment 15 and the second bend segment 35 all belong to the above-mentioned bend segment 100.

[0061] Specifically, in this embodiment Figures 1 to 5 The diagram shows a situation where the first pole piece 10 includes five straight segments 90 and four curved segments 100, and the second pole piece 30 includes six straight segments 90 and six curved segments 100, and an active material layer 50 is provided on opposite sides of the first pole piece 10, on opposite sides of the first to fourth straight segments 90 of the second pole piece 30, and on a single side of the fourth to sixth straight segments 90 of the second pole piece 30.

[0062] Optionally, the first straight segment 90 of the first pole piece 10 is consistent with the extension direction of the first extension segment 21 of the first diaphragm 20, and the first straight segment 90 of the second pole piece 30 is consistent with the extension direction of the second extension segment 41 of the second diaphragm 40. Such an arrangement can ensure that the head of the first pole piece 10 is aligned with the first starting end 211 of the first diaphragm 20, and the head of the second pole piece 30 is aligned with the second starting end 411 of the second diaphragm 40, effectively preventing the presence of excess diaphragm at the head of the first pole piece 10 and the head of the second pole piece 30, thereby improving the energy density of the battery.

[0063] Further, see Figures 1 to 5 As shown, the battery cell in this embodiment further includes adhesive tape 80, which is disposed on the surface of the second pole piece 30 close to the second arc segment 42, and along the thickness direction of the battery cell, the projection of the adhesive tape 80 at least partially covers the starting end 11 of the first pole piece. In this embodiment, the adhesive tape 80 is first arranged on the second pole piece 30, and then the first pole piece 10, the first diaphragm 20, the second pole piece 30 and the second diaphragm 40 are stacked together in sequence, and then a winding core is formed by a winding process. In this process, the second pole piece 30 includes six straight segments 90 and six curved segments 100, and the adhesive tape 80 is located on the inner surface of the first curved segment 100 of the second pole piece 30 (the side of the pole piece close to the center of the battery cell is defined as the inner side, and the side of the pole piece away from the center of the battery cell is defined as the outer side), and since the inner surface of the first curved segment 100 of the second pole piece 30 is also provided with an active material layer 50, the adhesive tape 80 will cover the active material layer 50 here, and the projection of the adhesive tape 80 along the thickness direction of the battery cell at least partially covers the starting end 11 of the first pole piece. Such an arrangement can prevent the first pole piece 10 from shrinking its head, and the adhesive tape 80 cannot cover the head of the first pole piece 10 well, resulting in lithium deposition of the second pole piece 30.

[0064] Optionally, the length of the projection of the adhesive tape 80 covering the starting end 11 of the first pole piece along the thickness direction of the battery cell should not be too long, which may easily affect the energy density of the battery.

[0065] On the other hand, the embodiment of the present application further provides a battery, which includes the above-mentioned battery cell, and thus the battery includes all the technical effects of the above-mentioned battery cell. Since the technical effects of the battery cell have been described in detail above, they will not be repeated here.

[0066] Furthermore, the battery cell in this embodiment also includes a shell. Specifically, the types of shells include aluminum-plastic film or metal shell. The aluminum-plastic film is mainly composed of nylon, aluminum and polypropylene (PP), wherein nylon is located in the outermost layer, aluminum is located in the middle layer, and polypropylene is located in the inner layer. The aluminum-plastic film has extremely high barrier properties, good cold stamping formability, puncture resistance, electrolyte stability, high temperature resistance, insulation, etc.; the metal shell includes an aluminum metal shell or a steel metal shell, etc.

[0067] On the other hand, an embodiment of the present application further provides a method for preparing a battery, hereinafter referred to as the preparation method, which includes all the technical effects of the above-mentioned battery cell.

[0068] Further, see Figure 6 As shown, the preparation method of the battery in this embodiment includes:

[0069] Step S1: preparing a first pole piece 10 and a second pole piece 30, and coating an active material layer 50 on the surfaces of the first pole piece 10 and the second pole piece 30;

[0070] Step S2: bonding the first electrode sheet 10 and the first diaphragm 20 together to form a continuous first composite electrode sheet;

[0071] Step S3: bonding the second electrode sheet 30 and the second diaphragm 40 together to form a continuous second composite electrode sheet;

[0072] Step S4: Winding the first composite electrode sheet and the second composite electrode sheet through a winding process to prepare a battery.

[0073] Specifically, the first pole piece 10, the first diaphragm 20, the second pole piece 30 and the second diaphragm 40 are stacked in sequence so that the first diaphragm 20 and the second diaphragm 40 isolate the first pole piece 10 and the second pole piece 30. When winding, ensure that the first pole piece and the second pole piece wound in the innermost circle have a double-sided active material layer 50, and a first empty foil area 13 is arranged near the head of the first pole piece 10 or in the middle, and a second empty foil area 33 is arranged near the head of the second pole piece 30 or in the middle, wherein the first empty foil area 13 is used for welding the first pole ear 60, and the second empty foil area 33 is used for welding the second pole ear 70.

[0074] Optionally, the first pole piece 10 and the first diaphragm 20 , and the second pole piece 30 and the second diaphragm 40 may be bonded together by hot pressing or using an adhesive.

[0075] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0076] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0077] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A battery cell, characterized in that: It comprises a first pole piece (10), a first diaphragm (20), a second pole piece (30) and a second diaphragm (40) which are stacked and wound in sequence, wherein the first pole piece (10) and the second pole piece (30) both comprise a current collector and an active material layer (50) arranged on the surface of the current collector; The first diaphragm (20) comprises a first extension section (21), a first arc section (22) and a first starting end (211); the first arc section (22) is connected to an end of the first extension section (21) away from the first starting end (211); the first extension section (21) is located between the first pole piece (10) and the second diaphragm (40); and the first extension section (21) extends from an end connected to the first arc section (22) toward a first direction; The second diaphragm (40) comprises a second extension section (41), a second arc section (42) and a second starting end (411), the second arc section (42) is connected to an end of the second extension section (41) away from the second starting end (411), the second extension section (41) is located between the second pole piece (30) and the first diaphragm (20), and the second extension section (41) extends from an end connected to the second arc section (42) towards a second direction opposite to the first direction; Wherein, along the thickness direction of the battery core, the projection of the first extension section (21) and the projection of the second extension section (41) at least partially overlap.

2. The battery cell according to claim 1, characterized in that: Along the first direction, the maximum length between the first starting end (211) and the first arc segment (22) is L1, and the overlapping length of the first extension segment (21) and the second extension segment (41) is L0, wherein L0 and L1 satisfy the relationship: L0≤L1; Alternatively, along the first direction, the maximum length between the second starting end (411) and the second arc segment (42) is L2, and the overlapping length of the first extension segment (21) and the second extension segment (41) is L3, wherein L3 and L2 satisfy the relationship: L3≤L2.

3. The battery cell according to claim 1, characterized in that: The first pole piece (10) comprises a first pole piece starting end (11), a first straight section (14) and a first bent section (15), the first bent section (15) being connected to an end of the first straight section (14) away from the first pole piece starting end (11), the first straight section (14) being located between the second extension section (41) and the first diaphragm (20), and the first straight section (14) extending from an end connected to the first bent section (15) towards the first direction; The second pole piece (30) comprises a second pole piece starting end (31), a second straight section (34) and a second bent section (35); the second bent section (35) is connected to an end of the second straight section (34) away from the second pole piece starting end (31); the second straight section (34) is located between the first extension section (21) and the second diaphragm (40); and the second straight section (34) extends from an end connected to the second bent section (35) toward the second direction.

4. The battery cell according to claim 3, characterized in that: The first pole piece starting end (11) is aligned with the first starting end (211); and / or, The second pole piece starting end (31) is aligned with the second starting end (411).

5. The battery cell according to claim 3, characterized in that: The first diaphragm (20) further comprises a first diaphragm end (23), the first pole piece (10) further comprises a first pole piece end (12), and the first diaphragm end (23) is arranged in alignment with the first pole piece end (12); and / or, The second diaphragm (40) further has a second diaphragm end (43), the second pole piece (30) further has a second pole piece end (32), and the second diaphragm end (43) is arranged in alignment with the second pole piece end (32).

6. The battery cell according to claim 3, characterized in that: The battery cell comprises a first pole lug (60) and a second pole lug (70); a first empty foil area (13) is provided on the first pole sheet (10); and the first pole lug (60) is arranged in the first empty foil area (13); and / or, A second empty foil area (33) is provided on the second pole piece (30), and the second pole tab (70) is located in the second empty foil area (33).

7. The battery cell according to claim 6, characterized in that: The first empty foil area (13) is arranged close to the starting end (11) of the first pole piece, and the second empty foil area (33) is arranged close to the starting end (31) of the second pole piece.

8. The battery cell according to claim 6, characterized in that: The first empty foil area (13) is arranged at a middle position of the first pole piece (10) along the length direction of the first pole piece (10), and the second empty foil area (33) is arranged at a middle position of the second pole piece (30) along the length direction of the second pole piece (30).

9. The battery cell according to claim 3, characterized in that: The battery cell also includes adhesive tape (80), which is arranged on the surface of the second pole piece (30) close to the second arc segment (42), and along the thickness direction of the battery cell, the projection of the adhesive tape (80) at least partially covers the starting end (11) of the first pole piece.

10. A battery, characterized in that: The battery comprises the battery cell according to any one of claims 1 to 9, and further comprises a casing.

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