Battery cell and battery pack comprising same

Abstract

A battery cell and a battery pack comprising same. The battery cell comprises: a casing; a jelly roll comprising a first electrode sheet, a second electrode sheet, and a first separator, the first electrode sheet, the first separator and the second electrode sheet being sequentially stacked and wound to form an inner ring part, and the tail part of the first separator being separately wound to form an outer ring part; and a liquid absorption layer disposed on the outer ring part. The liquid absorption layer is provided in the jelly roll of the battery cell, the liquid absorption layer can quickly absorb an electrolyte and swells, thereby shortening the liquid injection time, and the swelling liquid absorption layer can shape the electrode sheets, thereby avoiding wrinkling of the electrode sheets.

Description

A single cell and a battery pack comprising the same

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Chinese Patent Application No. 202323175417.5 filed on November 22, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to a single cell and a battery pack comprising the same. Background Art

[0004] Lithium battery separators are typically coated with a coating to allow for expansion of the electrode during charging and discharging, preventing wrinkling. The coating also allows for rapid electrolyte absorption during injection. However, the cost of installing a coating is high. Without it, electrolyte absorption takes longer, and the separator and electrode cannot adhere tightly, causing wrinkling.

[0005] Application Contents

[0006] The purpose of this application is to provide a single cell and a battery pack including the same, wherein there is no coating layer on the diaphragm, which can reduce the absorption time of the electrolyte and avoid wrinkling of the electrode.

[0007] In order to achieve the above objectives, the present application provides a single battery, comprising:

[0008] A shell having an accommodating cavity therein;

[0009] A winding core is disposed in the housing, the winding core has a first direction, the winding core includes a first pole piece, a second pole piece, and a first diaphragm, the first pole piece and the second pole piece have opposite polarities, the first diaphragm is disposed between the first pole piece and the second pole piece, the first pole piece, the first diaphragm, and the second pole piece are stacked and wound to form an inner ring portion, the axial direction of the inner ring portion is parallel to the first direction, the tail of the first diaphragm is unwound to form an outer ring portion, and the inner ring portion and the outer ring portion are coaxially disposed;

[0010] The liquid absorbing layer is arranged on the outer ring portion, and the liquid absorbing layer has a porous structure for absorbing electrolyte and is elastic.

[0011] In some embodiments of the present application:

[0012] The winding core has a second direction, the liquid-absorbing layer includes a first mating surface and a second mating surface extending along the second direction, the winding core has a third direction, in which the first mating surface and the second mating surface are arranged opposite to each other, and the second mating surface is connected to the tail of the first diaphragm;

[0013] The first direction, the second direction and the third direction intersect with each other.

[0014] In some embodiments of the present application,

[0015] The second mating surface is bonded to the tail portion of the first diaphragm.

[0016] In some embodiments of the present application:

[0017] The outer ring portion includes straight portions relatively arranged along the third direction, and the liquid absorbing layer is arranged on the straight portions.

[0018] In some embodiments of the present application:

[0019] The outer ring portion has at least one empty winding turn. In the third direction, the liquid-absorbing layer is located between the inner ring portion and the tail portion of the first diaphragm forming the outer ring portion.

[0020] In some embodiments of the present application:

[0021] The first mating surface faces the inner ring portion, and the surface area of ​​the second mating surface is larger than the surface area of ​​the first mating surface;

[0022] In the third direction, the projection of the first mating surface completely falls within the projection outline of the second mating surface.

[0023] In some embodiments of the present application:

[0024] In the third direction, the maximum size of the liquid-absorbing layer is L1 mm, the maximum size of the winding core is L1′ mm, and the following conditions are satisfied: L1 / L1′≤0.1, and / or,

[0025] In the first direction, the maximum size of the liquid-absorbing layer is L3 mm, and the maximum size of the winding core is L3′ mm, satisfying: L3 / L3′≤1.

[0026] In some embodiments of the present application:

[0027] The porosity of the liquid absorbing layer is 20%-60%, and / or the surface density of the liquid absorbing layer is less than or equal to 10 g / mm 2 .

[0028] In some embodiments of the present application:

[0029] The area of ​​the first mating surface is S1mm 2 , the area of ​​the second mating surface is S2mm 2 , satisfying: 0.55<S1 / S2<0.8.

[0030] In some embodiments of the present application:

[0031] The winding core further includes a second diaphragm, the second diaphragm, the first pole piece, the first diaphragm and the second pole piece are stacked and wound to form the inner ring portion, and the tail portion of the first diaphragm and the tail portion of the second diaphragm are unwound to form the outer ring portion;

[0032] The liquid absorbing layer is connected to the tail of the second diaphragm.

[0033] The present application also provides a battery pack, comprising:

[0034] Box;

[0035] Several single cells as described in any of the above paragraphs are arranged inside the box and electrically connected to each other.

[0036] The present application provides a battery pack and a single battery thereof, which have the following advantages compared with the prior art:

[0037] In the single battery cell of this application, the first electrode sheet, the first separator, and the second electrode sheet are stacked and wound to form an inner coil. The tail of the first separator is left unwound to form an outer coil. A porous and elastic liquid-absorbing layer is provided on the outer coil. The liquid-absorbing layer rapidly absorbs electrolyte and swells, shortening the injection time. Furthermore, the swollen liquid-absorbing layer can shape the coil core, preventing wrinkles in the electrode sheet.

[0038] The battery pack of the present application, including the above-mentioned single battery, can reduce the absorption time of the electrolyte and avoid the wrinkling of the electrode, thereby improving the overall product quality of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG1 is a perspective schematic diagram of a single cell according to an embodiment of the present application.

[0040] FIG2 is a schematic diagram of a roll core and a liquid-absorbing layer according to an embodiment of the present application.

[0041] FIG3 is an enlarged schematic diagram of point A in FIG2 .

[0042] FIG4 is a schematic structural diagram of the liquid absorbing layer according to an embodiment of the present application.

[0043] FIG5 is a schematic structural diagram of the liquid-absorbing layer according to an embodiment of the present application from another angle.

[0044] FIG6 is a schematic diagram of the winding core and the liquid-absorbing layer from another angle according to an embodiment of the present application.

[0045] FIG7 is a schematic diagram of the expansion of the first pole piece according to an embodiment of the present application.

[0046] FIG8 is a schematic diagram of the expansion of the second pole piece according to an embodiment of the present application.

[0047] In the figure, 1, winding core; 2, liquid absorption layer; 3, shell;

[0048] 11. First pole piece; 12. Second pole piece; 13. First diaphragm; 14. Second diaphragm; 15. Inner ring; 16. Outer ring; 21. First mating surface; 22. Second mating surface; 161. Straight portion; 31. Accommodating cavity; X, second direction; Y, third direction; Z, first direction. DETAILED DESCRIPTION

[0049] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0050] In the description of this application, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended only to facilitate the description of this application and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be construed as limiting this application. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0051] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0052] Furthermore, in the description of the present application, unless otherwise specified, “plurality” means two or more.

[0053] For those skilled in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0054] 1 to 3 , a single battery according to a preferred embodiment of the present application includes a housing 3 , a winding core 1 , and a liquid absorbing layer 2 .

[0055] The housing 3 has an accommodating chamber 31 therein.

[0056] The accommodating cavity 31 is used for placing the winding core 1 . An opening communicating with the accommodating cavity 31 is provided on the top surface of the shell 3 . The opening is used for allowing the winding core 1 to pass through and be placed in the accommodating cavity 31 .

[0057] The winding core 1 is arranged in the accommodating cavity 31, and includes a first pole piece 11, a second pole piece 12, and a first diaphragm 13. The polarities of the first pole piece 11 and the second pole piece 12 are opposite. The first diaphragm 13 is arranged between the first pole piece 11 and the second pole piece 12. The first pole piece 11, the first diaphragm 13 and the second pole piece 12 are stacked and wound to form an inner ring portion 15. The axial direction of the inner ring portion 15 is parallel to the first direction Z. The tail of the first diaphragm 13 forms an outer ring portion 16, and the inner ring portion 15 and the outer ring portion 16 are coaxially arranged.

[0058] In this embodiment, the first electrode 11 and the second electrode 12 are respectively the positive electrode and the negative electrode. Figures 7 and 8 schematically illustrate the first electrode 11 and the second electrode 12, which are unfolded and not wound. The first electrode 11 and the second electrode 12 are shorter than the first diaphragm 13. After the first electrode 11, the first diaphragm 13, and the second electrode 12 are wound to form the inner coil 15, the first electrode 11 and the second electrode 12 are wound completely, and the longer first diaphragm 13 continues to be wound, that is, it is wound by itself without the first electrode 11 and the second electrode 12, i.e., it is wound empty, and the outer coil 16 is formed.

[0059] In this embodiment, the height direction of the winding core 1 is the first direction Z. There are also a second direction X and a third direction Y. The length direction of the winding core 1 is the second direction X, and the width direction of the winding core 1 is the third direction Y. The first direction Z, the second direction X, and the third direction Y are perpendicular to each other. Perpendicular refers to an angle of 85° to 95°.

[0060] In this embodiment, the first diaphragm 13 can be a PE diaphragm or a PP diaphragm without a coating layer. There is no need to set a coating layer on the diaphragm, which can save the coating process of the diaphragm 13, improve the production efficiency of the single cell, and reduce the manufacturing cost of the single cell.

[0061] The liquid absorbing layer 2 is disposed on the outer ring portion 16 . The liquid absorbing layer 2 has a porous structure for absorbing electrolyte and is elastic.

[0062] The liquid-absorbing layer 2 is made of aerogel particles, an active agent and an adhesive to form a porous structure that can quickly absorb electrolyte. After absorbing the electrolyte, the liquid-absorbing layer 2 will swell and the overall size of the liquid-absorbing layer 2 will expand.

[0063] In this embodiment, the liquid absorbing layer 2 can be made of any material such as carbon aerogel, silicon aerogel, silicon-based aerogel, foam, etc.

[0064] The single cell battery of this embodiment is capable of rapidly absorbing electrolyte and swelling by providing a liquid absorbing layer 2, thereby shortening the injection time. Moreover, the swollen liquid absorbing layer 2 expands as a whole, thereby maintaining a tight fit between the diaphragm 13 and the first electrode piece 11 and the second electrode piece 12, and shaping the winding core 1 to avoid wrinkling of the electrode pieces.

[0065] In some embodiments, referring to Figures 4 and 5, the liquid-absorbing layer 2 includes a first mating surface 21 and a second mating surface 22 extending along the second direction X. In the third direction Y, the first mating surface 21 and the second mating surface 22 are arranged opposite to each other, and the second mating surface 22 is connected to the tail of the first diaphragm 13.

[0066] The setting of the first matching surface 21 and the second matching surface 22 enables the liquid absorbing layer 2 to adapt to the shape of the winding core 1. After the liquid absorbing layer 2 expands after absorbing the electrolyte, it is better pressed on the winding core 1, thereby ensuring the shaping effect of the winding core 1 and further ensuring that the electrode is not wrinkled.

[0067] In some embodiments, the single cell further includes an adhesive layer disposed along the third direction Y between the second mating surface 22 and the rear end of the first diaphragm 13. The second mating surface 22 is bonded to the rear end of the first diaphragm 13 via the adhesive layer. In other embodiments, the second mating surface 22 and the rear end of the first diaphragm 13 may be connected via other connection methods. The adhesive layer of this embodiment is easy to implement in the single cell manufacturing process.

[0068] In some embodiments, the outer ring portion 16 includes straight portions 161 arranged relatively along the third direction Y, and the liquid-absorbing layer 2 is disposed on the straight portions 161 .

[0069] The outer ring portion 16 has two parallel straight portions 161, and a bent portion is provided to connect the two straight portions 161. Both the straight portion 161 and the bent portion are formed after the core 1 is hot-pressed, and essentially distinguish different parts of the outer ring portion 16.

[0070] The liquid absorbing layer 2 is arranged on the straight portion 161 , which can better adapt to the shape of the winding core 1 after hot pressing, ensure the shaping effect of the winding core 1 , and further ensure that the electrode is not wrinkled.

[0071] In some embodiments, the outer ring portion 16 has at least one empty coil. In the third direction Y, the liquid-absorbing layer 2 is located between the inner ring portion 15 and the tail of the first diaphragm 13 forming the outer ring portion 16 .

[0072] The number of empty coils is at least 1, which means that the empty coils exceed 1, and the excess part may not be a full circle.

[0073] The position of the liquid absorbing layer 2 is determined according to the manufacturing process of the battery cell. In other embodiments, the liquid absorbing layer 2 may also be set at other positions of the outer ring portion 16 .

[0074] In some embodiments, the first mating surface 21 faces the inner ring portion 15 , and the area of ​​the second mating surface 22 is larger than that of the first mating surface 21 ; in the third direction Y, the projection of the first mating surface 21 completely falls into the projection outline of the second mating surface 22 .

[0075] Through such a structure, the absorbent layer 2 can avoid the bent parts at both ends of the winding core 1, and the absorbent layer 2 can be better connected to the winding core 1. In addition, the absorbent layer 2 and the winding core 1 are relatively flat, which is conducive to the absorbent layer 2 to realize its own function.

[0076] In some embodiments, in the third direction Y, the maximum dimension of the absorbent layer 2 is L1 mm, and the maximum dimension of the winding core 1 is L1′ mm, satisfying: L1 / L1′≤0.1, and / or, in the first direction Z, the maximum dimension of the absorbent layer 2 is L3 mm, and the maximum dimension of the winding core 1 is L3′ mm, satisfying: L3 / L3′≤1.

[0077] The term "and / or" means that L1 / L1′≤0.1 and L3 / L3′≤1 can be satisfied at the same time, or either L1 / L1′≤0.1 or L3 / L3′≤1 can be satisfied.

[0078] The ratio L1 / L1′ ≤ 0.1 limits the size of the liquid-absorbing layer 2 in the third direction Y. Both the liquid-absorbing layer 2 and the winding core 1 are located within the accommodating cavity 31 and are subject to the spatial constraints of the accommodating cavity 31. If the L1 / L1′ ratio is greater than 0.1, the liquid-absorbing layer 2 will occupy an excessive amount of the housing 3's internal thickness, squeezing out the space that should be used for the winding core 1 and affecting the cell's energy density.

[0079] When measuring the dimensions L1 and L1′, a common length measuring tool such as a ruler or a tape measure may be used.

[0080] When measuring L1, a single cell is taken in which the liquid-absorbing layer 2 is swollen after electrolyte injection. One edge of the liquid-absorbing layer 2 in the third direction Y is used as a reference edge. The distance between the reference edge and the other edge along the third direction Y is measured using a length measuring tool. Multiple measurements are taken and the average value is taken. The maximum dimension of the liquid-absorbing layer 2 along the third direction Y is obtained as L1 mm.

[0081] When measuring L1′, take a single battery cell in which the core 1 has expanded after electrolyte injection. Use one edge of the core 1 in the third direction Y as the reference edge. Use a length measuring tool to measure the distance between the reference edge and the other edge along the third direction Y. Measure multiple times and take the average value. The maximum dimension of the core 1 along the third direction Y is L1′ mm.

[0082] Figure 6 shows the core and absorbent layer from another angle. L3 / L3′ ≤ 1 limits the size of the absorbent layer 2 in the first direction Z, as shown in Figures 4 and 6. If the ratio L3 / L3′ is greater than 1, the absorbent layer 2 will be taller than the core 1, resulting in the absorbent layer 2 occupying an excessive amount of space. This means that the internal height of the housing 3 is excessively occupied by the absorbent layer 2, leaving excess free space within the accommodating cavity 31, affecting the energy density of the battery cell.

[0083] When measuring the dimensions L3 and L3′, a common length measuring tool such as a ruler or a tape measure may be used.

[0084] When measuring L3, a single cell with the liquid-absorbing layer 2 swollen after electrolyte injection is taken. One edge of the liquid-absorbing layer 2 in the first direction Z is used as a reference edge. The distance between the reference edge and the other edge is measured along the first direction Z using a length measuring tool. Multiple measurements are taken and the average value is taken. The maximum dimension of the liquid-absorbing layer 2 along the first direction Z is L3 mm.

[0085] When measuring L3′, take a single battery cell in which the core 1 has expanded after electrolyte injection. Use one edge of the core 1 in the first direction Z as the reference edge. Use a length measuring tool to measure the distance between the reference edge and the other edge along the first direction Z. Measure multiple times and take the average value. The maximum dimension of the core 1 along the first direction Z is L3′ mm.

[0086] In some embodiments, the porosity of the liquid-absorbing layer 2 is 20%-60%, and / or the surface density of the liquid-absorbing layer 2 is less than or equal to 10 g / mm 2 .

[0087] And / or means that the porosity can be 20%-60% and the surface density is less than or equal to 10g / mm 2 , or either of the two can be satisfied.

[0088] If the porosity is too small, the ability of the liquid absorbing layer 2 to absorb the electrolyte is insufficient. If the porosity is too large, the liquid absorbing layer 2 will be soft, the shaping effect of the winding core 1 will be poor, and the ability to prevent the electrode from wrinkling will also be poor.

[0089] If the surface density is too large, there will also be a problem of insufficient ability to absorb electrolyte.

[0090] In some embodiments, the area of ​​the first mating surface 21 is S1 mm 2 The area of ​​the second mating surface 22 is S2mm 2 , satisfying: 0.55<S1 / S2<0.8.

[0091] S1 and S2 are also the two surfaces of the liquid-absorbing layer 2 that are exposed to the core 1. If the ratio S1 / S2 is too large, the adhesion between the liquid-absorbing layer 2 and the first separator 13 will be affected. However, if the ratio S1 / S2 is too small, the liquid-absorbing layer 2 itself is prone to displacement and deformation.

[0092] When calculating dimensions S1 and S2, since both the first mating surface 21 and the second mating surface 22 in this embodiment are rectangular, first use a common length measuring tool, such as a ruler or tape measure, to measure the length of each of the first mating surface 21 and the second mating surface 22 in the second direction X. Then, measure the length of the first mating surface 21 in the first direction Z.

[0093] To calculate S1, in the second direction X, with one edge of the first mating surface 21 as the reference edge, the distance between the other edge and the reference edge is measured multiple times along the second direction X using a length measuring tool. The average value is taken to obtain the length of the first mating surface 21 in the second direction X. Next, in the first direction Z, with one edge of the first mating surface 21 as the reference edge, the distance between the other edge and the reference edge is measured multiple times along the first direction Z using a length measuring tool. The average value is taken to obtain the length of the first mating surface 21 in the first direction Z. The product of these two lengths yields S1.

[0094] When calculating S2, in the second direction X, with one edge of the second mating surface 22 as the reference edge, the distance between the other edge and the reference edge is measured multiple times along the second direction X using a length measuring tool. The average value is taken to obtain the length of the second mating surface 22 in the second direction X. This length is then multiplied by L3 to obtain S2.

[0095] In some embodiments, the winding core 1 further includes a second diaphragm 14, the second diaphragm 14, the first electrode piece 11, the first diaphragm 13 and the second electrode piece 12 are stacked in sequence and wound to form an inner ring 15, and the tail of the first diaphragm 13 and the tail of the second diaphragm 14 are unwound to form an outer ring 16; the liquid absorption layer 2 is connected to the tail of the second diaphragm 14.

[0096] In this case, the liquid absorbing layer 2 is connected to the tail of the second diaphragm 14 in the same manner as the liquid absorbing layer 2 is connected to the tail of the first diaphragm 13 , that is, the liquid absorbing layer 2 is connected to the tail of the second diaphragm 14 by bonding.

[0097] In order to further confirm the effect of the liquid absorbing layer 2, the following test data are provided:

[0098] The core 1 without the liquid-absorbing layer 2 and the core 1 with the liquid-absorbing layer 2 were respectively taken, and the hot pressing and L1′ dimension tests were completed on the same equipment under the same hot pressing parameters. The test results are shown in Table 1.

[0099] The winding core 1 without the liquid absorbing layer 2 and the winding core 1 with the liquid absorbing layer 2 were respectively assembled into single cells in the same assembly method, and liquid filling was completed in the same equipment. Under the same liquid filling volume, the total liquid filling time is shown in Table 1.

[0100] The same cycle conditions were set to perform performance tests on the single cell without the liquid absorption layer 2 and the single cell with the liquid absorption layer 2. The cycle capacity retention rate data of the two are shown in Table 1.

[0101] Table 1

[0102] This shows that after hot pressing, the L1′ dimension of the core 1 with and without the liquid-absorbing layer 2 is not much different. In other words, the thickness of the core 1 after hot pressing is not much different. The single cell with the liquid-absorbing layer 2 has a shorter injection time. The single cell with the liquid-absorbing layer 2 can maintain a rich electrolyte in the core 1, which is beneficial to the circulation of the battery cell.

[0103] This embodiment further provides a battery pack, including a box body and the above-mentioned single cells, wherein the single cells are arranged inside the box body and are electrically connected to each other.

[0104] A plurality of single cells are provided and arranged in several rows. A single cell is electrically connected to adjacent single cells, and all the single cells are electrically connected in series or in parallel.

[0105] Due to the provision of the above-mentioned single cells, each single cell can quickly absorb the electrolyte and swell, shortening the injection time. Moreover, the swollen liquid absorption layer 2 expands as a whole, shaping the winding core 1 to avoid wrinkling of the electrode, thereby improving the product quality of the single cell and further improving the overall product quality of the battery pack.

[0106] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and replacements can be made without departing from the technical principles of the present application. These improvements and replacements should also be regarded as the scope of protection of the present application.

Claims

1. A single cell battery, comprising: A housing (3) having a receiving chamber (31) therein; A winding core (1) is arranged in the accommodating cavity (31), the winding core (1) has a first direction (Z), the winding core (1) comprises a first pole piece (11), a second pole piece (12), and a first diaphragm (13), the first pole piece (11) and the second pole piece (12) have opposite polarities, the first diaphragm (13) is arranged between the first pole piece (11) and the second pole piece (12), the first pole piece (11), the first diaphragm (13) and the second pole piece (12) are stacked and wound to form an inner ring portion (15), the axial direction of the inner ring portion (15) is parallel to the first direction (Z), the tail of the first diaphragm (13) is unwound to form an outer ring portion (16), and the inner ring portion (15) and the outer ring portion (16) are coaxially arranged; The liquid absorbing layer (2) is arranged on the outer ring portion (16); the liquid absorbing layer (2) is a porous structure for absorbing electrolyte; and the liquid absorbing layer (2) is elastic.

2. The single cell according to claim 1, wherein: The winding core (1) has a second direction (X), the liquid-absorbing layer (2) comprises a first mating surface (21) and a second mating surface (22) extending along the second direction (X), the winding core (1) has a third direction (Y), in which the first mating surface (21) and the second mating surface (22) are arranged opposite to each other, and the second mating surface (22) is connected to the tail of the first diaphragm (13); The first direction (Z), the second direction (X) and the third direction (Y) intersect each other.

3. The single cell according to claim 2, wherein: The second mating surface (22) is bonded to the rear portion of the first diaphragm (13).

4. The single cell according to claim 1, wherein: The outer ring portion (16) comprises straight portions (161) arranged relatively along the third direction (Y), and the liquid absorbing layer is arranged on the straight portions (161).

5. The single cell according to claim 4, wherein: The number of empty turns of the outer ring portion (16) is at least 1 turn, and in the third direction (Y), the liquid absorption layer (2) is located between the inner ring portion (15) and the tail of the first diaphragm (13) forming the outer ring portion (16).

6. The single cell according to claim 4, wherein: The first mating surface (21) faces the inner ring portion (15), and the surface area of ​​the second mating surface (22) is greater than the surface area of ​​the first mating surface (21); In the third direction (Y), the projection of the first mating surface (21) completely falls into the projection contour of the second mating surface (22).

7. The single cell according to claim 4, wherein: In the third direction (Y), the maximum size of the liquid-absorbing layer (2) is L1 mm, and the maximum size of the winding core (1) is L1′ mm, satisfying: L1 / L1′≤0.

1.

8. The single cell according to claim 4, wherein: In the first direction (Z), the maximum size of the liquid-absorbing layer (2) is L3 mm, and the maximum size of the winding core (1) is L3′ mm, satisfying: L3 / L3′≤1.

9. The single cell according to claim 1, wherein: The porosity of the liquid absorbing layer (2) is 20%-60%.

10. The single cell according to claim 1, wherein: The surface density of the liquid absorbing layer (2) is less than or equal to 10 g / mm 2 .

11. The single cell according to claim 2, wherein: The area of ​​the first mating surface (21) is S1mm 2 The area of ​​the second mating surface (22) is S2 mm 2 , satisfying: 0.55<S1 / S2<0.

8.

12. The single cell according to claim 1, characterized in that: The winding core (1) also includes a second diaphragm (14), wherein the second diaphragm (14), the first pole piece (11), the first diaphragm (13) and the second pole piece (12) are stacked and wound to form the inner ring portion (15), and the tail portion of the first diaphragm (13) and the tail portion of the second diaphragm (14) are unwound to form the outer ring portion (16); the liquid absorption layer (2) is connected to the tail portion of the second diaphragm (14).

13. A battery pack comprising: Box; A plurality of single cells according to any one of claims 1 to 12 are arranged inside the box and are electrically connected to each other.

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