Battery cell, battery pack and electric equipment

Abstract

The utility model relates to a battery cell, a battery pack and electric equipment. The battery cell comprises a positive plate, a negative plate and a diaphragm; the positive plate, the negative plate and the diaphragm are laminated and wound to form a winding structure; in the width direction of the battery cell, the battery cell comprises a straight area and bending areas positioned at the two ends of the straight area; in the bending area, at least part of the structure of the negative plate is provided with a porous area; a plurality of through holes penetrating through the pole piece in the thickness direction of the pole piece are formed in the porous area at intervals, the through holes form first orifices in the side, away from the winding center, of the negative pole piece and form second orifices in the side, close to the winding center, of the negative pole piece, and the aperture of the first orifices is larger than that of the second orifices; the negative plate comprises a negative current collector and a negative active layer arranged on the surface of the negative current collector; and along the winding direction of the battery cell, the size of the porous area is W1, the tensile strength of the negative current collector is G, W1 / G is more than or equal to 0.005 mm / MPa and less than or equal to 0.06 mm / MPa, and G is more than or equal to 300 MPa and less than or equal to 800 MPa.

Description

Technical Field

[0001] This utility model relates to the field of lithium-ion battery technology, specifically to a battery cell, battery pack, and electrical equipment. Background Technology

[0002] With the rapid development of lithium-ion battery technology, wound batteries are widely used in electric vehicles, energy storage systems, and other fields due to their high energy density and good electrochemical performance. However, wound batteries still face many challenges in practical applications. The electrolyte wetting effect in the middle area of ​​the core is poor, especially under high compaction conditions, where the wetting problem becomes more pronounced. As the number of cycles increases, the electrolyte is continuously consumed, leading to uneven electrolyte distribution inside the battery, which in turn causes problems such as lithium plating in the bending area. Especially in silicon-doped anode batteries, the anode sheet undergoes significant anisotropic expansion during lithiation, exacerbating the compression of the middle part of the core and further worsening the wetting effect. Utility Model Content

[0003] The purpose of this invention is to solve the problems of poor electrolyte wetting effect, slow reflux speed, and easy lithium deposition in the bending area of ​​wound batteries, thereby providing a battery cell, battery pack, and electrical equipment.

[0004] In a first aspect, this utility model provides a battery cell, comprising a positive electrode, a negative electrode, and a separator, wherein the separator is disposed between the positive and negative electrode, and the positive electrode, negative electrode, and separator are stacked and wound to form a wound structure; along the width direction of the battery cell, the battery cell includes a flat region and bent regions located at both ends of the flat region; in the bent regions, at least a portion of the negative electrode has a porous region; the porous region is provided with a plurality of through holes that penetrate the electrode along the thickness direction of the electrode, the through holes being located on the negative electrode away from the winding center. A first aperture is formed on one side of the negative electrode sheet, and a second aperture is formed on the side of the negative electrode sheet near the winding center. The diameter of the first aperture is larger than that of the second aperture. The negative electrode sheet includes a negative current collector and a negative active layer disposed on the surface of the negative current collector. Along the winding direction of the cell, the size of the porous region is W1, and the tensile strength of the negative current collector is G. W1 and G satisfy: 0.005mm / MPa≤W1 / G≤0.06mm / MPa, and 300MPa≤G≤800MPa.

[0005] In one optional embodiment, the battery cell includes a positive electrode tab and a negative electrode tab. The positive electrode sheet includes a positive current collector and a positive active layer disposed on the surface of the positive current collector. The positive electrode tab is connected to the positive current collector, and the negative electrode tab is connected to the negative current collector. Along the winding direction of the battery cell, the negative electrode sheet includes a first segment, a second segment, and a third segment connected in sequence. The starting end of the first segment is the winding starting end of the negative electrode sheet. Along the thickness direction of the battery cell, the ending end of the first segment is located on the side of the positive electrode tab near the winding center, and the ending end of the first segment is adjacent to the positive electrode tab. Along the winding direction of the battery cell, the second segment is located between the ending end of the first segment and the negative electrode tab, and the third segment is located between the negative electrode tab and the winding end of the negative electrode sheet. The second segment has a porous region on at least a portion of its structure in the bending region.

[0006] In one alternative embodiment, the first segment has a porous region on at least a portion of the structure of the bending region; and / or, the third segment has a porous region on at least a portion of the structure of the bending region.

[0007] In one optional embodiment, along the winding direction of the battery cell and from the start end to the end end of the first segment, the first segment includes a connected single-sided coating area and a double-sided coating area; in the single-sided coating area, a negative electrode active layer is provided on one of the surfaces of the negative electrode current collector along the thickness direction; in the double-sided coating area, a negative electrode active layer is provided on both opposite surfaces of the negative electrode current collector along the thickness direction; the porous region is located in the double-sided coating area.

[0008] In one optional embodiment, the negative electrode sheet includes a plurality of bent portions located in the bending region, the bent portions including a first bent portion and a second bent portion; along the winding direction of the battery cell, the first fold formed by the double-sided coating region in the bending region is the first bent portion, and the double-sided coating region forms a straight portion in the straight region; along the width direction of the battery cell, the first bent portion and the second bent portion are respectively connected to the two ends of the straight portion; the first bent portion is the starting fold for setting the porous region; or, the second bent portion is the starting fold for setting the porous region.

[0009] In one optional embodiment, the negative electrode sheet includes a plurality of bent portions located in the bending region; in any one of the bent portions provided with a porous region, the area of ​​one side of the bent portion in the thickness direction of the negative electrode sheet is S1; in the porous region, the sum of the areas of the first openings of all through holes is S2, and 0 < S2 / S1 ≤ 30%.

[0010] In one optional embodiment, in the porous region, the spacing between adjacent through holes is D1, 120μm≤D1≤2000μm; and / or, the diameter of the first orifice is D2, 20μm≤D2≤200μm; and / or, the diameter of the second orifice is D4, 1μm≤D4≤50μm; and / or, the size W1 of the porous region satisfies: 4mm≤W1≤20mm.

[0011] In one optional embodiment, both ends of the porous region are provided with non-porous regions along the width direction of the negative electrode sheet; the size of the non-porous region is D3 in the width direction of the negative electrode sheet, 0.5mm≤D3≤20mm; the width direction of the negative electrode sheet is perpendicular to the thickness direction of the battery cell, the width direction of the battery cell, and the winding direction of the battery cell.

[0012] Secondly, this utility model also provides a battery pack, including the battery cells as described above.

[0013] Thirdly, this utility model also provides an electrical device, including the battery cell as described above, or the battery pack as described above.

[0014] By utilizing the technical solution of this utility model, a porous region is formed in at least a portion of the structure of the negative electrode located in the bending area. The through holes in the porous region allow electrolyte to pass through, improving the electrolyte's reflux capacity during circulation and the wetting effect of the electrolyte in the bending area, effectively alleviating the lithium plating problem of the battery cell. Specifically, the diameter of the first orifice of the through hole is larger than the diameter of the second orifice. The first orifice is located on the side of the negative electrode away from the winding center and has a larger diameter, which reduces flow resistance. The second orifice is located on the side of the negative electrode closer to the winding center and has a smaller diameter, which generates capillary action. During the electrolyte injection stage, the electrolyte enters the through hole through the first orifice and flows out through the second orifice, gradually permeating towards the winding center side. Because the first orifice has a larger diameter, it reduces the flow resistance of the electrolyte during injection, accelerating the entry of the electrolyte from the second orifice into the interlayer gap. The second orifice has a smaller diameter, which, through capillary action, promotes the gradual penetration of the electrolyte into the electrode interlayer closer to the winding center, forming a gradient flow and improving the overall wetting effect. During the charge-discharge cycle of the battery cell, the negative electrode sheet is subjected to expansion and compression in the bending area. The smaller diameter of the second orifice, through capillary action, effectively reduces the excessive compression of electrolyte from the side closer to the winding center to the side farther away from the winding center during expansion. The larger diameter of the first orifice makes it easier to guide the free electrolyte from the side farther away from the winding center to the side closer to the winding center, replenishing the consumed electrolyte in a timely manner and enhancing the electrolyte reflux capacity. Meanwhile, since setting through holes on the negative electrode sheet will reduce the tensile strength of the negative electrode sheet, this application ensures that the width of the porous region is reasonable to achieve slow lithium dissolution, while reasonably setting the ratio of the width of the porous region to the tensile strength of the negative electrode current collector. This ensures that the negative electrode current collector can still maintain good mechanical properties during winding and negative electrode cyclic expansion, reduce strip breakage, and avoid short circuits caused by negative electrode sheet breakage during cycling, thereby preventing safety issues. Attached Figure Description

[0015] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the overall structure of a battery cell according to an embodiment of the present utility model;

[0017] Figure 2 A schematic diagram of the structure of a through hole in a porous region according to an embodiment of this utility model;

[0018] Figure 3 This is a schematic diagram of the structure of a negative electrode sheet in its unfolded state according to an embodiment of the present invention;

[0019] Figure 4 This is a schematic diagram of the three-dimensional structure of a battery cell.

[0020] Explanation of reference numerals in the attached figures:

[0021] 1. Positive electrode sheet; 11. Positive current collector; 12. Positive active layer; 2. Negative electrode sheet; 21. Negative current collector; 22. Negative active layer; 23. First section; 23a. Starting end; 23b. Ending end; 231. Single-sided coating area; 232. Double-sided coating area; 233. Junction of single and double-sided coatings; 24. Second section; 25. Third section; 26. Bending section; 261. First bending section; 262. Second bending section; 27. Porous area; 271. Through hole; 2711-First orifice; 2712. Second orifice; 28. Non-porous area; 3. Separator; 4. Positive electrode tab; 5. Negative electrode tab; 6. Bending area; 7. Straight area; R. Winding direction of the cell; X. Thickness direction of the cell; Y. Width direction of the cell; Z. Width direction of the negative electrode sheet; T. Thickness direction of the negative electrode sheet. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0023] The following is combined Figures 1 to 4 The following describes embodiments of the present invention.

[0024] According to embodiments of the present invention, in one aspect, a battery cell is provided, such as... Figure 1 As shown, the battery cell includes a positive electrode 1, a negative electrode 2, and a separator 3. The separator 3 is disposed between the positive electrode 1 and the negative electrode 2. The positive electrode 1, the negative electrode 2, and the separator 3 are stacked and wound to form a wound structure. Along the width direction Y of the battery cell, the battery cell includes a flat region 7 and bending regions 6 located at both ends of the flat region 7. In the bending region 6, at least a portion of the structure of the negative electrode 2 is provided with a porous region 27. A plurality of through holes 271 penetrating the electrode along the thickness direction of the electrode are provided at intervals on the porous region 27. It can be understood that the porous region 27 is disposed on the negative electrode 2, and the through holes 271 penetrating the electrode along the thickness direction of the electrode specifically means penetrating the negative electrode 2 along the thickness direction T of the negative electrode. A through-hole 271 is formed on the side of the negative electrode 2 away from the winding center, forming a first aperture 2711, and on the side of the negative electrode 2 closer to the winding center, forming a second aperture 2712. The diameter of the first aperture 2711 is larger than the diameter of the second aperture 2712. The negative electrode 2 includes a negative current collector 21 and a negative active layer 22 disposed on the surface of the negative current collector 21. Along the winding direction R of the battery cell, the size of the porous region 27 is W1, and the tensile strength of the negative current collector 21 is G. W1 and G satisfy: 0.005mm / MPa≤W1 / G≤0.06mm / MPa, and 300MPa≤G≤800MPa.

[0025] For example, W1 / G can be 0.005mm / MPa, 0.01mm / MPa, 0.015mm / MPa, 0.02mm / MPa, 0.025mm / MPa, 0.03mm / MPa, 0.035mm / MPa, 0.04mm / MPa, 0.05mm / MPa, 0.055mm / MPa, 0.06mm / MPa, etc.

[0026] For example, G can be 300MPa, 350MPa, 400MPa, 450MPa, 500MPa, 550MPa, 600MPa, 650MPa, 700MPa, 750MPa, 800MPa, etc.

[0027] It should be noted that the reference Figure 1 and Figure 4The battery cell forming the wound structure has a width direction (Y), a length direction, a thickness direction (X), and a winding direction (R). In some cases, the width direction (Y), length direction, and thickness direction (X) are perpendicular to each other, and the length direction is perpendicular to the winding direction (R). Taking the negative electrode 2 as an example, the negative electrode 2 has a width direction (Z) and a length direction. During the winding process, it is usually wound along the length direction of the negative electrode 2. After winding, the length direction of the negative electrode 2 extends along the winding direction (R) of the battery cell, and the width direction (Z) of the negative electrode 2 is also the length direction of the battery cell.

[0028] In this embodiment, by providing a porous region 27 on at least a portion of the structure of the negative electrode 2 located in the bending region 6, the through holes 271 on the porous region 27 allow the electrolyte to pass through, improving the electrolyte's reflux capacity during circulation and the electrolyte's wetting effect in the bending region 6, effectively alleviating the lithium plating problem of the battery cell. Specifically, the diameter of the first orifice 2711 of the through hole 271 is larger than the diameter of the second orifice 2712. The first orifice 2711 is located on the side of the negative electrode 2 away from the winding center, i.e., the outer side, and its larger diameter reduces flow resistance. The second orifice 2712 is located on the side of the negative electrode 2 closer to the winding center, i.e., the inner side, and its smaller diameter generates capillary action.

[0029] During the electrolyte injection stage, the electrolyte enters through the first orifice 2711 into the through-hole 271 and flows out through the second orifice 2712, gradually permeating towards the winding center. Because the first orifice 2711 has a larger diameter, it reduces the electrolyte flow resistance during injection, accelerating the electrolyte's entry into the interlayer gap from the second orifice 2712. The second orifice 2712 has a smaller diameter, which, through capillary action, promotes the gradual permeation of the electrolyte into the electrode interlayer closer to the winding center, forming a gradient flow and improving the overall wetting effect. In the bending zone 6, due to the high interlayer pressure and compact structure inside the winding structure, the electrolyte is prone to uneven distribution. If the first orifice 2711 is located on the side of the negative electrode 2 closer to the winding center, although it can replenish the internal electrolyte, the smaller diameter of the second orifice 2712 on the side of the negative electrode 2 furthest from the winding center limits the electrolyte's entry speed, resulting in insufficient outer layer wetting.

[0030] During the charge-discharge cycle of the battery cell, the negative electrode 2 is subjected to expansion and compression in the bending area 6. The smaller diameter of the second orifice 2712 effectively reduces the excess electrolyte being squeezed away from the winding center during expansion through capillary action. Meanwhile, the larger diameter of the first orifice 2711 facilitates the diversion of free electrolyte from the winding center to the side closer to it, replenishing electrolyte consumption and enhancing electrolyte reflux capacity.

[0031] Furthermore, the presence of through holes 271 on the negative electrode sheet 2 in the bending region 6 reduces the tensile strength of the negative electrode current collector 21. In this embodiment, while ensuring a reasonable width of the porous region 27 to achieve slow lithium dissolution, by reasonably setting the ratio of the width of the porous region 27 to the tensile strength of the negative electrode current collector 21, it is possible to ensure that the negative electrode current collector 21 maintains good mechanical properties during winding and negative electrode cyclic expansion, reducing strip breakage and avoiding short circuits caused by the breakage of the negative electrode sheet 2 during cycling, thereby preventing safety issues.

[0032] The multiple through holes 271 in the porous region 27 can be arranged in an array, such as a rectangular arrangement, a circular arrangement, etc., or they can be arranged randomly or in a gradient arrangement, as long as they can allow the electrolyte to pass through. For example, such as Figure 3 As shown, in each porous region 27, multiple through holes 271 are arranged in a rectangular pattern, that is, at least two rows are spaced apart in the winding direction R of the battery cell, and multiple columns are spaced apart in the width direction Z of the negative electrode sheet. For example, as shown... Figure 2 As shown, the through hole 271 can be tapered, with the larger diameter end of the tapered shape forming the first orifice 2711 and the smaller diameter end forming the second orifice 2712. Understandably, Figure 2 and Figure 3 The diagram shown is only for illustrating the arrangement and shape of the through holes 271. The number of rows of through holes 271 on each porous area 27 in the winding direction R of the battery cell can be two, three, four or other, as long as the porous area 27 can be filled.

[0033] Furthermore, in some embodiments, the negative electrode 2 includes a plurality of bends 26 located in the bending region 6. In any bend 26 provided with a porous region 27, the sum of the areas on one side of the bend 26 in the thickness direction T of the negative electrode is S1. In the porous region 27, the sum of the areas of the first openings 2711 of all through holes 271 is S2, where 0 < S2 / S1 ≤ 30%.

[0034] It is understandable that the area S1 of one side of the aforementioned bent portion 26 can be the surface area near the winding center or the surface area away from the winding center. For example... Figure 3 As shown, Figure 3 This diagram shows the structure of the negative electrode 2 in its flattened state. The thickness direction T of the negative electrode is also shown. Figure 3 The direction of the bend towards the inside of the paper. Essentially, the bend 26 is formed by bending a portion of the negative electrode 2 within the bending region 6. Therefore, after bending, the surface area of ​​the bend 26 near the winding center is equal to the surface area of ​​the side away from the winding center. Specifically, the single-sided area S1 of the aforementioned bend 26 can be understood as the area under the condition that the negative electrode 2 is in its flattened state (i.e.,...). Figure 3 In the state shown, the area of ​​the projected portion 26 on the thickness direction T of the negative electrode sheet is S2. Correspondingly, the sum of the areas of the first openings 2711 of all through holes 271 in the porous region 27 can be understood as the sum of the areas of the projected portions 271 of all through holes 271 in the porous region 27 on the thickness direction T of the negative electrode sheet in the flattened state of the negative electrode sheet 2.

[0035] This configuration ensures electrolyte reflux capability while further preventing electrode breakage due to excessive or overly dense vias 271. Furthermore, if the perforation area of ​​vias 271 is too large, it can lead to excessively low local cell balance (CB) values, resulting in lithium plating. In this embodiment, by reasonably controlling the ratio of S2 to S1, excessively large perforation areas can be avoided, thus preventing lithium plating. It should be noted that the cell balance (CB) value refers to the margin by which the capacity of the negative electrode exceeds the capacity of the positive electrode under the same conditions and at the same stage.

[0036] For example, the value of S2 / S1 can be 0.1%, 0.3%, 0.5%, 1%, 1.5%, 2%, 3%, 5%, 7%, 10%, 12%, 15%, 17%, 20%, 23%, 25%, 27%, 30%, etc.

[0037] In some embodiments, along the winding direction R of the battery cell, the size W1 of the porous region 27 satisfies: 4mm ≤ W1 ≤ 20mm. By reasonably controlling the setting size of W1, the electrolyte wetting effect and the reflux capacity during the cycling process can be reasonably regulated, thereby effectively mitigating the lithium desorption problem.

[0038] For example, W1 can be 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, etc.

[0039] Furthermore, along the winding direction R of the battery cell, the size of any bend 26 with a porous region 27 is W2, and the size of the porous region 27 on it is W1, where W1 ≥ W2. This arrangement ensures that the through holes 271 are fully distributed across the bend 26, guaranteeing the electrolyte wetting effect of the bend 26 and the electrode liquid reflux capability during circulation, thereby effectively mitigating the lithium desorption problem.

[0040] In some embodiments, the spacing between adjacent through holes 271 in the porous region 27 is D1, where 120μm≤D1≤2000μm, preferably 200μm≤D1≤1500μm. In this embodiment, by reasonably controlling the spacing D1 between adjacent through holes 271, it is possible to avoid the through holes 271 on the porous region 27 being too dense or too sparse. If they are too dense, it is easy to reduce the tensile strength of the negative electrode current collector 21, thereby reducing the mechanical properties of the negative electrode sheet 2 and making it difficult to ensure the safety performance of the battery cell; if they are too sparse, it is easy to reduce the reflux capacity and wetting effect of the electrolyte, making it difficult to effectively mitigate the lithium desorption problem.

[0041] For example, D1 can be 120μm, 150μm, 200μm, 300μm, 400μm, 500μm, 600μm, 700μm, 800μm, 900μm, 1000μm, 1100μm, 1200μm, 1300μm, 1400μm, 1500μm, 1800μm, 2000μm, etc.

[0042] Understandably, the depth of the through hole 271 is the same as the thickness of the electrode sheet, which will not be described in detail here.

[0043] In some embodiments, the pore size of the first orifice 2711 is D2, where 20μm≤D2≤200μm, preferably 50μm≤D2≤150μm. The pore size of the second orifice 2712 only needs to be smaller than the pore size D2 of the first orifice 2711. In this embodiment, by reasonably controlling the pore size of the first orifice 2711, the requirements for electrolyte reflux and wetting can be met while avoiding problems such as strip breakage due to excessively large pore size affecting the tensile strength of the negative electrode current collector 21, thus ensuring the safety performance of the battery cell. Simultaneously, it avoids problems such as lithium plating caused by excessively large pore size of the first orifice 2711 leading to excessively small local CB values ​​in the negative electrode sheet 2.

[0044] For example, D2 can be 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, etc.

[0045] In some embodiments, the aperture of the second orifice 2712 is D4, where 1μm≤D4≤50μm. In this embodiment, by reasonably controlling the aperture of the first orifice 2711, sufficient capillary force can be ensured to promote the flow of electrolyte towards the winding center during the electrolyte injection stage, thereby improving the electrolyte wetting effect. During the charge-discharge cycle of the battery cell, it effectively reduces the excessive squeezing of electrolyte from the side near the winding center to the side away from the winding center during the expansion process, effectively slowing down lithium release.

[0046] For example, D4 ​​can be 1μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, etc.

[0047] In some embodiments, such as Figure 3 As shown, along the width direction Z of the negative electrode sheet, which is also the length direction of the battery cell, both ends of the porous region 27 are provided with non-porous regions 28. It can be understood that the non-porous region 28 specifically refers to the area where the aforementioned through holes 271 are not provided. It may include the empty foil areas at both ends of the width direction of the negative electrode sheet 2, or it may include areas where the negative electrode active layer 22 is partially provided. In the width direction Z of the negative electrode sheet, the size of the non-porous region 28 is D3, 0.5mm≤D3≤20mm. Because the electrolyte reflux capacity is strong at both ends of the battery cell along its length, the consumed electrolyte can be replenished in a timely manner, but the electrolyte in the middle of the battery cell cannot quickly complete the reflux. In this embodiment, by setting the porous region 27 between the non-porous regions 28 at both ends and reasonably controlling the size of the non-porous regions 28, the reflux effect of the electrolyte in the middle of the battery cell can be guaranteed, while the overall size of the porous region 27 can be reduced, ensuring the mechanical properties of the negative electrode sheet 2, thereby ensuring the safety performance of the battery cell.

[0048] For example, D3 can be 0.5mm, 1mm, 1.5mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, etc.

[0049] Furthermore, the battery cell includes a positive electrode tab 4 and a negative electrode tab 5. The positive electrode 1 includes a positive current collector 11 and a positive active layer 12 disposed on the surface of the positive current collector 11. The positive electrode tab 4 is connected to the positive current collector 11, and the negative electrode tab 5 is connected to the negative current collector 21. Typically, the current density in the electrode region (interlayer) between the positive electrode tab 4 and the negative electrode tab 5 is relatively high, which accelerates the consumption of electrolyte during charging and discharging. Therefore, the electrolyte return rate in this region is slow, and insufficient electrolyte is prone to occur after cycling, resulting in lithium plating.

[0050] To address the issue of lithium plating easily in the electrode region between the positive electrode tab 4 and the negative electrode tab 5, in some embodiments, such as... Figure 1As shown, along the winding direction R of the battery cell, the negative electrode 2 includes a first segment 23, a second segment 24, and a third segment 25 connected in sequence. The starting end 23a of the first segment 23 is the starting end of the winding of the negative electrode 2. Along the thickness direction X of the battery cell, the ending end 23b of the first segment 23 is located on the side of the positive electrode tab 4 near the winding center, and the ending end 23b of the first segment 23 is adjacent to the positive electrode tab 4. That is, along the thickness direction X of the battery cell, there is no other interlayer structure of positive electrode 1 or negative electrode 2 between the ending end 23b of the first segment 23 and the positive electrode tab 4; and along the thickness direction X of the battery cell, at least a portion of the projection of the positive electrode tab 4 falls on the ending end 23b of the first segment 23.

[0051] Furthermore, along the winding direction R of the battery cell, the second segment 24 is located between the termination end 23b of the first segment 23 and the negative electrode tab 5, and the third segment 25 is located between the negative electrode tab 5 and the winding end of the negative electrode sheet 2. The second segment 24 of the negative electrode sheet 2 has the aforementioned porous region 27 in at least a portion of the structure of the bending region 6. In this embodiment, by perforating at least a portion of the structure of the bending region 6 on the second segment 24, the electrolyte reflux rate in the electrode area between the positive electrode tab 4 and the negative electrode tab 5 can be increased, thereby replenishing the electrolyte in a timely manner and mitigating the lithium desorption problem.

[0052] Specifically, the aforementioned bending portion 26 includes multiple third bending portions, which are formed by bending within the bending region 6 of the second segment 24. In some embodiments, the multiple third bending portions on the second segment 24 are provided with the aforementioned porous region 27. That is, along the winding direction R of the battery cell, and from the winding center towards the winding end, the bending portions 26 of the negative electrode 2 between the number of turns where the negative electrode tab 5 and the number of turns where the positive electrode tab 4 are located are all provided with porous regions 27. This arrangement can sufficiently ensure the electrolyte reflux rate in the electrode area between the positive electrode tab 4 and the negative electrode tab 5, replenishing the electrolyte in a timely manner and preventing lithium plating.

[0053] This invention does not specifically limit the number of the third bends; the specific number depends on the number of turns between the number of turns where the negative electrode 5 is located and the number of turns where the positive electrode 4 is located. For example, the number of turns between the number of turns where the negative electrode 5 is located and the number of turns where the positive electrode 4 is located can be 2 to 8 turns, and correspondingly, the number of third bends can be 4 to 16.

[0054] Furthermore, in some embodiments, the first segment 23 has a porous region 27 on at least a portion of the structure of the bending region 6 to further improve the interlayer electrolyte reflux capability of the cell and avoid lithium plating problems. Exemplarily, the bending portion 26 also includes a fourth bending portion, which is formed on the first segment 23 and extends from the winding center towards the winding end. The fourth bending portion is the last bend formed by the first segment 23 in the bending region 6, that is, the fourth bending portion is located close to the second segment 24. The porous region 27 is provided at least on the fourth bending portion of the first segment 23. Since the fourth bending portion is close to the second segment 24, that is, close to the electrode area between the positive tab 4 and the negative tab 5, it can further improve the reflux rate of the electrode area between the positive tab 4 and the negative tab 5, replenish the electrolyte in a timely manner, and avoid lithium plating problems.

[0055] In some embodiments, the third segment 25 may also have a porous region 27 on at least a portion of the structure of the bending region 6 to further improve the electrolyte wetting effect between the cell layers and the reflux rate during the cycle, ensuring sufficient electrolyte and avoiding lithium plating problems.

[0056] Further, in some embodiments, along the winding direction R of the battery cell, and from the starting end 23a to the ending end 23b of the first segment 23, the first segment 23 includes a connected single-sided coating region 231 and a double-sided coating region 232. Alternatively, in some cases, an uncoated region is also provided at the end of the single-sided coating region 231 away from the double-sided coating region 232, which is also the empty foil region located at the winding starting end. In the single-sided coating region 231, a negative electrode active layer 22 is provided on one surface of the negative electrode current collector 21 along the thickness direction; in the double-sided coating region 232, a negative electrode active layer 22 is provided on both opposite surfaces of the negative electrode current collector 21 along the thickness direction. The aforementioned porous regions 27 are all located in the double-sided coating region 232. In this embodiment, the porous region 27 is set in the double-sided coating region 232, that is, the single-sided coating region 231 does not have the porous region 27. This can prevent burrs from being generated on the side of the negative electrode current collector 21 in the single-sided region where the negative electrode active layer 22 is not set, avoid problems such as burrs piercing the diaphragm 3 or powder falling off, and prevent short circuits.

[0057] Understandably, the second section 24 and the third section 25 are usually only provided with double-sided coating area 232, that is, the porous area 27 is also located in the double-sided coating area 232 on the second section 24 and the third section 25.

[0058] Furthermore, in some embodiments, the bending portion 26 further includes a first bending portion 261 and a second bending portion 262, which are formed on the first segment 23. Specifically, along the winding direction R of the battery cell, the first fold formed by the double-sided coating region 232 in the bending region 6 is the first bending portion 261, and the double-sided coating region 232 forms a straight portion in the straight region 7. Along the width direction Y of the battery cell, the first bending portion 261 and the second bending portion 262 are respectively connected to the two ends of the straight portion. The first bending portion 261 can be the starting fold of the porous region 27; or, the second bending portion 262 can be the starting fold of the porous region 27. This arrangement can further expand the perforation range, ensuring the electrolyte wetting effect between battery cell layers and the reflux capacity during cycling, thereby reducing the risk of lithium plating.

[0059] Specifically, a single-sided coating area 231 and a double-sided coating area 232 have a single-sided / double-sided coating boundary 233. Understandably, the first bend 261 is the first fold formed by the double-sided coating area 232 in the bending area 6. In some cases, the first bend 261 is completely formed on the double-sided coating area 232, meaning the single-sided / double-sided coating boundary 233 is located outside the first bend 261. In this case, the first bend 261 can be used as the starting fold for setting the porous area 27. Alternatively, in some cases, the first bend 261 is partially formed on the double-sided coating area 232 and partially formed on the single-sided coating area 231, meaning the single-sided / double-sided coating boundary 233 is located on the first bend 261. At this point, if the first bend 261 is used as the starting bend for setting the porous region 27, some through holes 271 may fall into the single-sided coating area 231, increasing the risk of burrs. Furthermore, if the negative electrode active layer 22 is coated on the negative electrode current collector 21 and there is a coating tail, it will affect the drilling positioning. Therefore, it is preferable to use the second bend 262 as the starting bend for setting the porous region 27. Of course, if the single / double-sided coating junction 233 is located on the first bend 261, the first bend 261 can also be used as the starting bend for setting the porous region 27, in which case the porous region 27 is only set on the portion of the first bend 261 located on the double-sided coating area 232.

[0060] The beneficial effects of the battery cell of this invention will be explained below with reference to the test results of Comparative Example 1 and Examples 1-3.

[0061] Comparative Example 1

[0062] Positive electrode preparation: Lithium cobalt oxide, conductive agent (a mixture of conductive carbon black and carbon nanotubes), and PVDF are placed in NMP (N-methylpyrrolidone) at a mass ratio of 98.20:1:0.8 and stirred evenly to obtain a positive electrode slurry; the positive electrode slurry is uniformly coated on both sides of the positive electrode current collector 11 (aluminum foil), and then dried, rolled and cut in sequence to obtain the positive electrode sheet 1.

[0063] Negative electrode preparation: Artificial graphite (graphite mixed with 17% silicon-carbon), conductive agent, and binder are placed in deionized water at a mass ratio of 96.6:0.9:2.5 and stirred evenly to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated onto the negative electrode current collector 21 (copper foil), and then subjected to drying, rolling, and slitting processes to obtain the negative electrode sheet 2. The elongation strength G of the negative electrode current collector 21 is 500 MPa.

[0064] Battery fabrication: The separator 3 is made of a 7.5μm thick substrate + ceramic + adhesive-coated separator 3. The electrolyte includes lithium salt LiPF6 and solvents, the solvents being ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC), with a molar ratio of DEC:EC:EMC = 1:1:1. The above-slit and prepared positive electrode sheet 1, negative electrode sheet 2, and separator 3 are rolled into a wound cell structure. After the cell undergoes hot pressing, encapsulation, electrolyte injection, formation, and secondary sealing, a lithium-ion battery, i.e., a battery cell, is obtained.

[0065] Comparative Example 2

[0066] The difference between Comparative Example 2 and Comparative Example 1 is that, in the negative electrode preparation step, holes are drilled in the bent portion 26 of the negative electrode sheet 2 between the positive and negative electrode tabs 5 to form a porous region 27. In the porous region 27, the diameter D2 of the first aperture 2711 of each through-hole 271 is 20 μm, the diameter D4 of the second aperture 2712 is 100 μm, and the spacing D1 between adjacent through-holes is 500 μm. Along the winding direction R of the battery cell, the size W1 of the porous region 27 is 4 mm, the elongation strength G of the negative electrode current collector 21 is 500 MPa, and W1 / G is 0.008. The remaining steps are the same as in Comparative Example 1.

[0067] Comparative Example 3

[0068] The difference between Comparative Example 3 and Comparative Example 1 is that, in the negative electrode preparation step, holes are drilled in the bent portion 26 of the negative electrode sheet 2 between the positive and negative electrode tabs 5 to form a porous region 27. In the porous region 27, the diameter D2 of the first aperture 2711 of each through-hole 271 is 100 μm, the diameter D4 of the second aperture 2712 is 20 μm, and the spacing D1 between adjacent through-holes is 500 μm. Along the winding direction R of the battery cell, the size W1 of the porous region 27 is 2 mm, the elongation strength G of the negative electrode current collector 21 is 500 MPa, and W1 / G is 0.004. The remaining steps are the same as in Comparative Example 1.

[0069] Comparative Example 4

[0070] The difference between Comparative Example 4 and Comparative Example 1 is that, in the negative electrode preparation step, holes are drilled in the bent portion 26 of the negative electrode sheet 2 between the positive and negative electrode tabs 5 to form a porous region 27. In the porous region 27, the diameter D2 of the first aperture 2711 of each through-hole 271 is 100 μm, the diameter D4 of the second aperture 2712 is 20 μm, and the spacing D1 between adjacent through-holes is 500 μm. Along the winding direction R of the battery cell, the size W1 of the porous region 27 is 35 mm, the elongation G of the negative electrode current collector 21 is 500 MPa, and W1 / G is 0.07. The remaining steps are the same as in Comparative Example 1.

[0071] Example 1

[0072] The difference between this embodiment and Comparative Example 1 is that, in the negative electrode preparation step, holes are drilled in the bent portion 26 of the negative electrode sheet 2 between the positive and negative electrode tabs 5 to form a porous region 27. In the porous region 27, the diameter D2 of the first aperture 2711 of each through-hole 271 is 100 μm, the diameter D4 of the second aperture 2712 is 20 μm, and the spacing D1 between adjacent through-holes is 500 μm. Along the winding direction R of the battery cell, the size W1 of the porous region 27 is 4 mm, the elongation strength G of the negative electrode current collector 21 is 500 MPa, and W1 / G is 0.008. The remaining steps are the same as in Comparative Example 1.

[0073] Example 2

[0074] The difference between this embodiment and Comparative Example 1 is that, in the negative electrode preparation step, holes are drilled in the bent portion 26 of the negative electrode sheet 2 between the positive and negative electrode tabs 5 to form a porous region 27. In the porous region 27, the diameter D2 of the first aperture 2711 of each through-hole 271 is 50 μm, the diameter D4 of the second aperture 2712 is 10 μm, and the spacing D1 between adjacent through-holes is 500 μm. Along the winding direction R of the battery cell, the size W1 of the porous region 27 is 4 mm, the elongation strength G of the negative electrode current collector 21 is 500 MPa, and W1 / G is 0.008. The remaining steps are the same as in Comparative Example 1.

[0075] Example 3

[0076] The difference between this embodiment and Comparative Example 1 is that, in the negative electrode preparation step, holes are drilled in the bent portion 26 of the negative electrode sheet 2 between the positive and negative electrode tabs 5 to form a porous region 27. In the porous region 27, the diameter D2 of the first aperture 2711 of each through-hole 271 is 150 μm, the diameter D4 of the second aperture 2712 is 50 μm, and the spacing D1 between adjacent through-holes is 500 μm. Along the winding direction R of the battery cell, the size W1 of the porous region 27 is 4 mm, the elongation strength G of the negative electrode current collector 21 is 500 MPa, and W1 / G is 0.008. The remaining steps are the same as in Comparative Example 1.

[0077] Example 4

[0078] The difference between this embodiment and Comparative Example 1 is that, in the negative electrode preparation step, holes are drilled in the bent portion 26 of the negative electrode sheet 2 between the positive and negative electrode tabs 5 to form a porous region 27. In the porous region 27, the diameter D2 of the first aperture 2711 of each through-hole 271 is 150 μm, the diameter D4 of the second aperture 2712 is 50 μm, and the spacing D1 between adjacent through-holes is 500 μm. Along the winding direction R of the battery cell, the size W1 of the porous region 27 is 4 mm, the elongation strength G of the negative electrode current collector 21 is 800 MPa, and W1 / G is 0.005. The remaining steps are the same as in Comparative Example 1.

[0079] Example 5

[0080] The difference between this embodiment and Comparative Example 1 is that, in the negative electrode preparation step, holes are drilled in the bent portion 26 of the negative electrode sheet 2 between the positive and negative electrode tabs 5 to form a porous region 27. In the porous region 27, the diameter D2 of the first aperture 2711 of each through-hole 271 is 100 μm, the diameter D4 of the second aperture 2712 is 20 μm, and the spacing D1 between adjacent through-holes is 500 μm. Along the winding direction R of the battery cell, the size W1 of the porous region 27 is 8 mm, the elongation strength G of the negative electrode current collector 21 is 500 MPa, and W1 / G is 0.016. The remaining steps are the same as in Comparative Example 1.

[0081] Example 6

[0082] The difference between this embodiment and Comparative Example 1 is that, in the negative electrode preparation step, holes are drilled in the bent portion 26 of the negative electrode sheet 2 between the positive and negative electrode tabs 5 to form a porous region 27. In the porous region 27, the diameter D2 of the first aperture 2711 of each through-hole 271 is 100 μm, the diameter D4 of the second aperture 2712 is 20 μm, and the spacing D1 between adjacent through-holes is 500 μm. Along the winding direction R of the battery cell, the size W1 of the porous region 27 is 10 mm, the elongation strength G of the negative electrode current collector 21 is 500 MPa, and W1 / G is 0.02. The remaining steps are the same as in Comparative Example 1.

[0083] Example 7

[0084] The difference between this embodiment and Comparative Example 1 is that, in the negative electrode preparation step, holes are drilled in the bent portion 26 of the negative electrode sheet 2 between the positive and negative electrode tabs 5 to form a porous region 27. In the porous region 27, the diameter D2 of the first aperture 2711 of each through-hole 271 is 100 μm, the diameter D4 of the second aperture 2712 is 20 μm, and the spacing D1 between adjacent through-holes is 500 μm. Along the winding direction R of the battery cell, the size W1 of the porous region 27 is 18 mm, the elongation strength G of the negative electrode current collector 21 is 300 MPa, and W1 / G is 0.06. The remaining steps are the same as in Comparative Example 1.

[0085] Example 8

[0086] The difference between this embodiment and Comparative Example 1 is that, in the negative electrode preparation step, holes are drilled in the bent portion 26 of the negative electrode sheet 2 between the positive and negative electrode tabs 5 to form a porous region 27. In the porous region 27, the diameter D2 of the first aperture 2711 of each through-hole 271 is 100 μm, the diameter D4 of the second aperture 2712 is 20 μm, and the spacing D1 between adjacent through-holes is 1000 μm. Along the winding direction R of the battery cell, the size W1 of the porous region 27 is 8 mm, the elongation strength G of the negative electrode current collector 21 is 500 MPa, and W1 / G is 0.016. The remaining steps are the same as in Comparative Example 1.

[0087] The parameters for Comparative Examples 1-4 and Examples 1-8 are shown in Table 1:

[0088]

[0089] Table 1

[0090] The test results for Comparative Examples 1-4 and Examples 1-8 are shown in Table 2:

[0091]

[0092]

[0093] Table 2

[0094] As shown in Table 1, the negative electrode 2 of Comparative Example 1 does not have a porous region 27. The negative electrode 2 of Comparative Example 2 has a porous region 27, but the diameter D2 of the first orifice 2711 in Comparative Example 2 is smaller than the diameter D4 of the second orifice 2712. The negative electrode 2 of Comparative Example 3 has a porous region 27, and the diameter D2 of the first orifice 2711 is larger than the diameter D4 of the second orifice 2712, but the ratio of the size of the porous region 27, W1, to the tensile strength G of the negative electrode current collector 21 is less than 0.005 mm / MPa. The negative electrode 2 of Comparative Example 4 has a porous region 27, and the diameter D2 of the first orifice 2711 is larger than the diameter D4 of the second orifice 2712, but the ratio of the size of the porous region 27, W1, to the tensile strength G of the negative electrode current collector 21 is greater than 0.06 mm / MPa. In Examples 1-8, a porous region 27 is provided on the negative electrode sheet 2, and the aperture D2 of the first aperture 2711 is greater than the aperture D4 of the second aperture 2712. The size of the porous region 27 is such that the ratio of W1 to the tensile strength G of the negative electrode current collector 21 satisfies 0.005mm / MPa≤W1 / G≤0.06mm / MPa.

[0095] During the test, the cell capacity, cycle performance, lithium plating at circular arcs, and fracture conditions of the cells obtained from Comparative Examples 1-4 and Examples 1-8 were tested. The test results are shown in Table 2.

[0096] As shown in Table 2, compared with Comparative Example 1, Examples 1-8 showed no loss in cell capacity, significant improvement in lithium plating during cycling, increased cycle capacity retention, and marked improvement in cycle expansion, with no breakage of the negative electrode 2. This demonstrates that providing a porous region 27 on the bent portion 26 of the negative electrode 2 can improve the electrolyte wetting effect and increase the electrolyte storage capacity, thereby improving the lithium plating problem, increasing the battery capacity retention rate, and mitigating cycle expansion.

[0097] Compared with Comparative Example 2, Examples 1-3 showed no loss of cell capacity, significant improvement in lithium plating during cycling, increased cycle capacity retention, and marked improvement in cycle expansion. Furthermore, no breakage was observed in the negative electrode sheets 2. This demonstrates that in the porous region 27, setting the diameter of the first aperture 2711 on the side furthest from the winding center to be larger than the diameter of the second aperture 2712 on the side closer to the winding center can further improve the electrolyte wetting effect and increase the electrolyte storage capacity, thereby improving the lithium plating problem, increasing the battery capacity retention rate, and mitigating cycle expansion.

[0098] Compared with Comparative Example 3, Examples 1 and 5-7 showed no loss of cell capacity, significant improvement in lithium plating during cycling, increased cycle capacity retention, and significant improvement in cycle expansion. Furthermore, no breakage was observed in the negative electrode sheet 2. This demonstrates that when the diameter of the first aperture 2711 on the side furthest from the winding center in the porous region 27 is set to be larger than the diameter of the second aperture 2712 on the side closer to the winding center, the ratio of the size W1 of the porous region 27 to the tensile strength G of the negative electrode current collector 21 satisfies W1 / G ≥ 0.005 mm / MPa. This improves the electrolyte wetting effect and increases the electrolyte storage capacity, thereby mitigating the lithium plating problem, increasing the battery capacity retention, and improving the cycle expansion issue.

[0099] Compared with Comparative Example 4, Examples 1 and 5-7 showed no loss of cell capacity, significant improvement in cycle lithium plating, increased cycle capacity retention, and significant improvement in cycle expansion. Furthermore, Examples 1 and 5-7 showed no electrode breakage, while Comparative Example 4 showed electrode breakage. This demonstrates that setting the ratio of the size of the porous region 27 (W1) to the tensile strength G of the negative electrode current collector 21 to W1 / G ≤ 0.06 mm / MPa ensures that the negative electrode current collector 21 maintains good mechanical properties during winding and negative electrode cycle expansion, reducing breakage and preventing short circuits caused by negative electrode breakage during cycling, thus avoiding safety issues. The method for determining the lithium plating situation of the 400T battery in Table 2 is explained below:

[0100] Determination of non-lithium deposition: The surface of the fully charged negative electrode in the arc area is golden yellow, and when wiped with a lint-free paper, there is no gray metallic lithium powder on the paper.

[0101] Determination of slight lithium plating: The surface of the fully charged negative electrode in the arc area is dark yellow. When wiped with lint-free paper, gray metallic lithium powder is found on the paper.

[0102] Determination of lithium plating: The surface of the fully charged negative electrode in the arc area is locally gray, with no golden yellow color showing through.

[0103] Determination of severe lithium plating: The entire surface of the fully charged negative electrode in the arc area is gray, with no golden yellow showing through.

[0104] According to an embodiment of the present invention, another aspect provides a battery pack including the battery cell as described above. The battery pack of the present invention may include at least one of the aforementioned battery cells, each including a positive electrode 1 and a negative electrode 2. By providing the aforementioned porous region 27 on at least a portion of the structure located in the bending region 6 of the negative electrode 2, and by reasonably controlling the ratio of the size W1 of the porous region 27 to the tensile strength G of the negative electrode current collector 21, the electrolyte wetting effect and reflux capacity during cycling are improved, mitigating lithium desorption issues, while ensuring the mechanical strength of the electrode sheet and avoiding problems such as strip breakage. This prevents the negative electrode 2 from breaking during cycling, thus ensuring the safety performance of the battery cell.

[0105] According to an embodiment of this utility model, in another aspect, an electrical device is also provided, including the battery cell as described above, or including the battery pack as described above. Since the electrical device of this utility model includes the battery cell as described above or the battery pack using the battery cell as described above, it has the same technical effects as the battery cell of this utility model, and will not be described again here. The electrical device of this utility model includes, but is not limited to, portable electronic devices such as mobile phones, laptops, and tablets; household appliances such as headphones and vacuum cleaners; vehicles such as electric cars, electric bicycles, and electric motorcycles; and other devices such as drones and power banks.

[0106] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An electric cell, characterized by, It includes a positive electrode (1), a negative electrode (2) and a separator (3), wherein the separator (3) is disposed between the positive electrode (1) and the negative electrode (2), and the positive electrode (1), the negative electrode (2) and the separator (3) are stacked and wound to form a wound structure; Along the width direction (Y) of the battery cell, the battery cell includes a flat region (7) and a bent region (6) located at both ends of the flat region (7); in the bent region (6), at least a portion of the structure of the negative electrode (2) is provided with a porous region (27); a plurality of through holes (271) are provided at intervals on the porous region (27) that penetrate the electrode along the thickness direction of the electrode, the through holes (271) forming a first aperture (2711) on the side of the negative electrode (2) away from the winding center, and forming a second aperture (2712) on the side of the negative electrode (2) close to the winding center, the aperture of the first aperture (2711) being larger than the aperture of the second aperture (2712); The negative electrode sheet (2) includes a negative electrode current collector (21) and a negative electrode active layer (22) disposed on the surface of the negative electrode current collector (21); along the winding direction (R) of the battery cell, the size of the porous region (27) is W1, the tensile strength of the negative electrode current collector (21) is G, and W1 and G satisfy: 0.005mm / MPa≤W1 / G≤0.06mm / MPa, and 300MPa≤G≤800MPa.

2. The electric cell of claim 1, wherein, The battery cell includes a positive electrode tab (4) and a negative electrode tab (5). The positive electrode plate (1) includes a positive current collector (11) and a positive active layer (12) disposed on the surface of the positive current collector (11). The positive electrode tab (4) is connected to the positive current collector (11), and the negative electrode tab (5) is connected to the negative current collector (21). Along the winding direction (R) of the battery cell, the negative electrode (2) includes a first segment (23), a second segment (24), and a third segment (25) connected in sequence; the starting end (23a) of the first segment (23) is the winding starting end of the negative electrode (2); along the thickness direction (X) of the battery cell, the ending end (23b) of the first segment (23) is located on the side of the positive electrode tab (4) near the winding center, and the ending end (23b) of the first segment (23) is adjacent to the positive electrode tab (4); along the winding direction (R) of the battery cell, the second segment (24) is located between the ending end (23b) of the first segment (23) and the negative electrode tab (5), and the third segment (25) is located between the negative electrode tab (5) and the winding end of the negative electrode (2); The second segment (24) has the porous region (27) provided on at least a portion of the structure of the bending region (6).

3. The electric cell of claim 2, wherein, The first segment (23) has the porous region (27) provided on at least a portion of the structure of the bending region (6); and / or, The third segment (25) has the porous region (27) provided on at least a portion of the structure of the bending region (6).

4. The electric cell of claim 2, wherein, Along the winding direction (R) of the battery cell, and from the starting end (23a) to the ending end (23b) of the first segment (23), the first segment (23) includes a single-sided coating area (231) and a double-sided coating area (232) connected to each other; in the single-sided coating area (231), the negative electrode current collector (21) is provided with the negative electrode active layer (22) on one of its surfaces along the thickness direction; in the double-sided coating area (232), the negative electrode current collector (21) is provided with the negative electrode active layer (22) on both of its opposite surfaces along the thickness direction; The porous region (27) is located in the double-sided coating region (232).

5. The electric cell of claim 4, wherein, The negative electrode sheet (2) includes a plurality of bent portions (26) located in the bending region (6), the bent portions (26) including a first bent portion (261) and a second bent portion (262); along the winding direction (R) of the battery cell, the first bend formed by the double-sided coating region (232) in the bending region (6) is the first bent portion (261), and the double-sided coating region (232) forms a straight portion in the straight region (7); along the width direction (Y) of the battery cell, the first bent portion (261) and the second bent portion (262) are respectively connected to the two ends of the straight portion; The first bend (261) is the starting bend for setting the porous region (27); or, the second bend (262) is the starting bend for setting the porous region (27).

6. The electric cell of any one of claims 1-5, wherein, The negative electrode (2) includes a plurality of bends (26) located in the bending region (6); In any of the bent portions (26) provided with the porous region (27), the area of ​​one side of the bent portion (26) in the thickness direction (T) of the negative electrode sheet is S1; in the porous region (27), the sum of the areas of the first openings (2711) of all the through holes (271) is S2, 0 < S2 / S1 ≤ 30%.

7. The electric cell of any one of claims 1-5, wherein, In the porous region (27), the spacing between adjacent through holes (271) is D1, 120μm≤D1≤2000μm; and / or, The aperture of the first orifice (2711) is D2, 20μm≤D2≤200μm; and / or, The aperture of the second orifice (2712) is D4, 1μm≤D4≤50μm; and / or, The size W1 of the porous region (27) satisfies: 4mm≤W1≤20mm.

8. The electric cell of claim 7, wherein, Along the width direction (Z) of the negative electrode sheet, both ends of the porous region (27) are provided with non-porous regions (28); in the width direction (Z) of the negative electrode sheet, the size of the non-porous region (28) is D3, 0.5mm≤D3≤20mm; The width direction (Z) of the negative electrode sheet is perpendicular to the thickness direction (X), the width direction (Y), and the winding direction (R) of the battery cell.

9. A battery pack, characterized by, include: The battery cell obtained as described in any one of claims 1-8.

10. An electric device, characterized by It includes the battery cell as described in any one of claims 1-8, or the battery pack as described in claim 9.

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