Wound battery cell and battery

Abstract

The present invention relates to the technical field of batteries, and discloses a wound battery cell and a battery. The wound battery cell includes a pole piece; a separator disposed between adjacent positive and negative pole pieces; the wound battery cell is formed by sequentially laminating and winding a positive pole piece, a separator, and a negative pole piece; a bent portion is formed after the pole piece is wound; the pole piece includes a base layer and an active material layer coated on at least one side of the base layer, the thickness of the active material layer is T1, and the thickness of the base layer is T2; the wound battery cell further includes: a strengthening layer attached to the active material layer of the positive pole piece and / or the negative pole piece, and the strengthening layer covers at least one bent portion and at least covers a part of the surface of the bent portion; in the unfolded state of the wound battery cell, the length of the strengthening layer along the length direction of the pole piece is L1, satisfying: 0.026 mm ≤ (T2 / T1)·L1 ≤ 33.3 mm. The wound battery cell provided by the present invention enables the strengthening layer to have a better stretching effect on the pole piece and prevents the pole piece from being stretched at the microscopic level.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a wound battery cell and a battery. Background Art

[0002] In the battery field, winding cells is one of the mainstream battery forming methods. It is usually made by stacking the positive electrode sheet, separator and negative electrode sheet in sequence, and then winding them in a certain order using a fixed winding needle.

[0003] During the preparation of the electrode, a wet active material layer is usually coated on the base layer, and then dried to form the electrode for use. When the active material layer of the electrode of the wound battery cell is coated thickly, the electrode located in the inner several turns of the battery cell is prone to falling off due to the large folding angle and the dry and brittle active material layer after winding, and the base layer is prone to fracture, resulting in the electrode breaking. Figure 9 As shown, the battery performance is affected. By sticking tape on the surface of the active material layer, the occurrence of material dropout can be reduced, but the sticky tape layer will lead to poor heat dissipation inside the battery. Summary of the invention

[0004] In view of this, the present invention provides a wound battery cell and a battery to solve the problem of how to balance the easy breakage of the electrode sheets located in several turns inside the battery cell roll and the poor heat dissipation effect when the active material layer of the electrode sheets of the wound battery cell is coated thickly.

[0005] In a first aspect, the present invention provides a wound battery cell, comprising:

[0006] Electrode, including positive electrode and negative electrode;

[0007] A diaphragm is disposed between adjacent positive and negative electrode sheets;

[0008] The wound battery cell includes a positive electrode sheet, a separator and a negative electrode sheet; a bending portion is formed after the electrode sheet is wound;

[0009] The pole piece includes a base layer and an active material layer coated on at least one side of the base layer, the thickness of the active material layer is T1, in micrometers; the thickness of the base layer is T2, in micrometers;

[0010] The wound battery cell further includes: a reinforcement layer, which is attached to the active material layer of the positive electrode sheet and / or the negative electrode sheet, and the reinforcement layer covers at least one bent portion and at least a portion of the surface of the bent portion;

[0011] When the wound battery cell is unfolded, the length of the reinforcement layer along the length direction of the pole piece is L1, in millimeters; and satisfies: 0.026 mm ≤ (T2 / T1)·L1 ≤ 33.3 mm.

[0012] Beneficial effects: In this embodiment, by limiting the ratio of T2 / T1, the proportional relationship between the thickness T2 of the base layer and the thickness T1 of the active material layer is defined. When the ratio is smaller, it indicates that the proportion of the thickness T1 of the active material layer relative to the thickness T2 of the base layer is larger, that is, the thickness T1 of the active material layer is thicker. At this time, it is necessary to increase the length L1 of the reinforcing layer along the length direction of the electrode sheet to ensure the stretching effect of the reinforcing layer on the electrode sheet and reduce the occurrence of electrode sheet breakage. When the ratio is larger, it indicates that the proportion of the thickness T1 of the active material layer relative to the thickness T2 of the base layer is smaller, that is, the thickness T1 of the active material layer is thinner. At this time, the length L1 of the reinforcing layer along the length direction of the electrode sheet can be appropriately reduced, which can not only ensure the stretching effect of the reinforcing layer on the electrode sheet, but also ensure that the wound battery cell has good heat dissipation performance and avoid the situation of excessive temperature. When the thickness T1 of the active material layer is larger, the risk of electrode sheet fracture is greater. Correspondingly, in order to reduce the phenomenon of the electrode sheet being stretched at the microscopic level, on the premise of meeting the heat dissipation performance requirements, the length of the reinforcing layer is appropriately increased, so that the stretching effect of the reinforcing layer on the electrode sheet is better, and the phenomenon of the electrode sheet being stretched at the microscopic level is more effectively prevented, thereby preventing the situation of the active material layer falling off and reducing the occurrence of electrode sheet breakage.

[0013] In a second aspect, the present invention also provides a battery, including: a battery case, and the wound battery cell as described above disposed in the battery case.

[0014] Since the battery includes a wound battery cell and has the same effects as the wound battery cell, it will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0016] Figure 1 It is a cross-sectional view of the wound battery cell of the present invention;

[0017] Figure 2 is Figure 1 a partial enlarged view of;

[0018] Figure 3 is a partial enlarged view of another wound battery cell;

[0019] Figure 4 is a partial enlarged view of still another wound battery cell;

[0020] Figure 5 It is a partial schematic view of the wound battery cell of the present invention in an unfolded state;

[0021] Figure 6 This is a cross-sectional view of a pole piece of the present invention;

[0022] Figure 7 This is a cross-sectional view of another pole piece of the present invention;

[0023] Figure 8 This is a schematic diagram of the winding battery cell area division of the present invention;

[0024] Figure 9 This is a schematic diagram of a break occurring at the bent part of the pole piece.

[0025] Explanation of reference numerals:

[0026] 1. Arc area; 11. Bent part; 2. Straight area;

[0027] 10. Diaphragm; 20. Pole piece; 21. Positive pole piece; 22. Negative pole piece; 30. Reinforcing layer;

[0028] 201. Base layer; 202. Active material layer. Detailed implementation manners

[0029] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present invention.

[0030] In the description of the present invention, it should be noted that the orientation or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] In the battery field, winding cells is one of the mainstream battery forming methods. It is usually made by stacking the positive electrode sheet, separator and negative electrode sheet in sequence, and then winding them in a certain order using a fixed winding needle.

[0034] During the preparation of the electrode, a moist active material layer is usually coated on the base layer, and then dried to form the electrode for use. When the active material layer of the electrode of the wound battery cell is coated thickly, the electrode located in the arc area, on which the thicker active material layer is coated, will be stretched at the microscopic level. In particular, the electrode located in the inner several turns of the wound battery cell will be stretched more obviously at the microscopic level due to the larger bending angle of the arc area, which will make the dry and brittle active material layer easy to fall off after winding, and the base layer will be easy to break, resulting in the electrode breaking, such as Figure 9 As shown, thus affecting the battery performance.

[0035] It should be noted that the base layer is also the current collector layer, which is used to realize the current transmission function of the positive and negative electrode sheets. The material of the base layer may include copper foil, aluminum foil, copper-aluminum composite, nickel, etc.

[0036] It should be noted that the active material layer includes positive and negative electrode materials that can realize battery ion transmission, where the ions include lithium ions, sodium ions, etc. Commonly used lithium-ion battery positive electrode materials include: lithium cobalt oxide (LiCoO2), lithium iron phosphate (LiFePO4), lithium manganese oxide (LiMn2O4), nickel cobalt manganese oxide (NCM), nickel cobalt aluminum oxide (NCA): lithium-rich manganese-based materials, lithium manganese iron phosphate (LMFP), lithium nickel oxide (LiNiO2). Commonly used lithium-ion battery negative electrode materials include: carbon materials (such as natural graphite, artificial graphite, soft carbon, hard carbon, carbon nanotubes and graphene, etc.), silicon-based materials, tin-based materials, lithium titanate, etc.

[0037] In the winding battery cell provided by the embodiment of the present invention, by attaching the reinforcing layer 30 to the active material layer 202 of the positive electrode sheet 21 and / or the negative electrode sheet 22, and the reinforcing layer 30 covers at least one bending part 11 and at least a part of the surface of the bending part 11, the bonding effect of the reinforcing layer 30 can be utilized to prevent the pasted electrode sheet 20 from being stretched at the microscopic level, thereby reducing the occurrence of electrode sheet breakage, and the pasted reinforcing layer 30 can prevent the active material layer from falling off, thereby ensuring the continuity of the electrode sheet and avoiding affecting the battery performance.

[0038] The following will describe the embodiments of the present invention in conjunction with Figures 1 to 8 ,

[0039] According to an embodiment of the present invention, on the one hand, a winding battery cell is provided, including:

[0040] An electrode sheet 20, including a positive electrode sheet 21 and a negative electrode sheet 22;

[0041] A separator 10, disposed between adjacent positive electrode sheets 21 and negative electrode sheets 22;

[0042] The winding battery cell includes a positive electrode sheet 21, a separator 10, and a negative electrode sheet 22; after the electrode sheet 20 is wound, a bending part 11 is formed;

[0043] The electrode sheet 20 includes a base layer 201 and an active material layer 202 coated on at least one side of the base layer 201. The thickness of the active material layer 202 is T1, in micrometers; the thickness of the base layer 201 is T2, in micrometers;

[0044] The winding battery cell further includes: a reinforcing layer 30, attached to the active material layer 202 of the positive electrode sheet 21 and / or the negative electrode sheet 22, and the reinforcing layer 30 covers at least one bending part 11 and at least a part of the surface of the bending part 11;

[0045] In the unfolded state of the winding battery cell, the length of the reinforcing layer 30 in the length direction of the electrode sheet is L1, in millimeters; satisfying: 0.026 mm ≤ (T2 / T1)·L1 ≤ 33.3 mm.

[0046] In some embodiments, the winding battery cell includes a straight area 2 and arc areas 1 located on both sides of the straight area 2 in the first direction, and the bending part 11 is located in the arc area 1. In conjunction with Figure 8As shown, since the wound battery cell is formed by winding, the electrode plates located in the straight region 2 are in a straight state, and the active material layer 202 coated on the electrode plate 20 in this region does not show the phenomenon of being stretched at the microscopic level. At the winding corner, an arc region 1 will be formed. Due to the bending of the electrode plate 20 in this region, a bending portion 11 will be formed, and there are multiple bending portions 11 in the arc region 1, and the multiple bending portions 11 are arranged in a stacked state; and the active material layer 202 coated on the electrode plate 20 in the arc region 1 shows the phenomenon of being stretched at the microscopic level.

[0047] In this embodiment, the wound battery cell can be wound in the order of separator 10, positive electrode plate 21, separator 10, negative electrode plate 22, separator 10; or it can be wound in the order of separator 10, negative electrode plate 22, separator 10, positive electrode plate 21, separator 10.

[0048] In this embodiment, the electrode plates of the wound battery cell are continuous.

[0049] In this embodiment, the reinforcing layer 30 is attached to the active material layer 202 to prevent the active material layer 202 from losing material. The reinforcing layer 30 can be an insulating tape with an adhesive backing, or a plastic film material adsorbed on the surface; for example: PET (polyester film), PI (polyimide film), BOPP (biaxially oriented polypropylene film), Nomex (meta-aramid paper). By attaching the reinforcing layer 30 to the active material layer 202 of the positive electrode plate 21 and / or the negative electrode plate 22, and the reinforcing layer 30 covers at least one bending portion 11 and at least a partial surface of the bending portion 11, a constraining effect is exerted on the active material layer 202 coated on the surface of the electrode plate 20.

[0050] In this embodiment, the reinforcing layer 30 is at least located in the arc region 1. Since the active material layer coated on the electrode plate in the arc region 1 is stretched at the microscopic level, the pasting effect of the reinforcing layer 30 is utilized to exert a constraining effect on the active material layer 202 coated on the surface of the electrode plate 20, reducing the situation where the active material layer is stretched at the microscopic level, preventing the active material layer from losing material and falling off, and thus reducing the occurrence of electrode plate breakage. In addition, by controlling the reinforcing layer 30 within the region of the arc region 1, it can not only prevent the active material layer from losing material and falling off, but also avoid the situation where the too large covering area of the pasted reinforcing layer 30 leads to poor heat dissipation effect inside the battery.

[0051] As a variation, the reinforcing layer 30 can also be further extended to the straight region 2, so as to make the stretching effect of the reinforcing layer 30 on the electrode plate 20 better by increasing the pasting area, more effectively preventing the phenomenon that the electrode plate is stretched at the microscopic level, and further preventing the situation where the active material layer loses material and falls off.

[0052] The wound battery cell is formed by sequentially laminating and winding a positive electrode sheet 21, a separator 10, and a negative electrode sheet 22. Both the positive electrode sheet 21 and the negative electrode sheet 22 are coated with an active material layer 202. In this embodiment, the reinforcing layer 30 can be attached to at least one surface of the positive electrode sheet 21, or to at least one surface of the negative electrode sheet 22, or the reinforcing layer 30 can be attached to at least one surface of both the positive electrode sheet 21 and the negative electrode sheet 22.

[0053] The electrode sheet 20 includes a base layer 201 and an active material layer 202 coated on at least one side of the base layer 201. Figure 6 As shown, the active material layer 202 can be coated on both sides of the base layer 201 in the thickness direction. Wherein, the thickness of the base layer 201 is T2, and the thicknesses of the active material layers 202 on both sides of the base layer 201 in the thickness direction are T11 and T12 respectively. In this embodiment, the thickness T1 of the active material layer 202 can specifically be T1 = T11 + T12.

[0054] Additionally, as shown Figure 7 the active material layer 202 is coated on one side of the base layer 201 in the thickness direction. Wherein, the thickness of the base layer 201 is T2, and the thickness of the active material layer 202 on one side of the base layer 201 in the thickness direction is T1.

[0055] When the thickness T1 of the active material layer 202 is relatively large, the risk of electrode sheet fracture is relatively high. Correspondingly, in order to reduce the occurrence of the phenomenon that the electrode sheet is stretched at the microscopic level, on the premise of meeting the heat dissipation performance requirements, the length of the reinforcing layer 30 is appropriately increased, so that the stretching effect of the reinforcing layer 30 on the electrode sheet 20 is better, more effectively preventing the phenomenon that the electrode sheet is stretched at the microscopic level, and thus preventing the situation of the active material layer falling off and reducing the occurrence of electrode sheet breakage.

[0056] In this embodiment, by limiting the ratio of T2 / T1, the proportional relationship between the thickness T2 of the base layer 201 and the thickness T1 of the active material layer 202 is limited. When the ratio is smaller, it indicates that the proportion of the thickness T1 of the active material layer 202 relative to the thickness T2 of the base layer 201 is larger, that is, the thickness T1 of the active material layer 202 is thicker. At this time, it is necessary to increase the length L1 of the reinforcing layer 30 along the length direction of the electrode sheet to ensure the stretching effect of the reinforcing layer 30 on the electrode sheet 20 and reduce the occurrence of electrode sheet breakage. When the ratio is larger, it indicates that the proportion of the thickness T1 of the active material layer 202 relative to the thickness T2 of the base layer 201 is smaller, that is, the thickness T1 of the active material layer 202 is thinner. At this time, the length L1 of the reinforcing layer 30 along the length direction of the electrode sheet can be appropriately reduced, which can not only ensure the stretching effect of the reinforcing layer 30 on the electrode sheet 20, but also ensure that the wound battery cell has good heat dissipation performance and avoid the situation of too high temperature.

[0057] Exemplarily, in this embodiment, the value of (T2 / T1)·L1 can be 0.026 mm, or 0.05 mm, or 0.1 mm, or 0.2 mm, or 0.3 mm, or 0.5 mm, or 0.9 mm, or 1 mm, or 2 mm, or 3 mm, or 5 mm, or 8 mm, or 10 mm, or 12 mm, or 15 mm, or 18 mm, or 20 mm, or 22 mm, or 25 mm, or 28 mm, or 30 mm, or 32 mm, or 33.3 mm, or 33.3 mm, etc., or can also be an interval range formed by any two of the above values.

[0058] In some embodiments, the value range of the thickness T1 of the active material layer 202 is: 30 μm ≤ T1 ≤ 560 μm;

[0059] And / or, the value range of the thickness T2 of the base layer 201 is: 3 μm ≤ T2 ≤ 20 μm;

[0060] And / or, the value range of the length L1 of the reinforcing layer 30 in the length direction of the electrode tab is: 5 mm ≤ L1 ≤ 50 mm.

[0061] Exemplarily, in this embodiment, the value of T1 can be 30 μm, or 50 μm, or 80 μm, or 100 μm, or 130 μm, or 150 μm, or 230 μm, or 300 μm, or 350 μm, or 400 μm, or 450 μm, or 480 μm, or 500 μm, or 530 μm, or 560 μm, etc., or can also be an interval range formed by any two of the above values.

[0062] Exemplarily, in this embodiment, the value of T2 can be 3 μm, or 7 μm, or 10 μm, or 15 μm, or 17 μm, or 20 μm, etc., or can also be an interval range formed by any two of the above values.

[0063] Exemplarily, in this embodiment, the value of L1 can be 5 mm, or 8 mm, or 10 mm, or 15 mm, or 21 mm, or 25 mm, or 28 mm, or 32 mm, or 37 mm, or 40 mm, or 45 mm, or 50 mm, etc., or can also be an interval range formed by any two of the above values.

[0064] In some embodiments, the reinforcing layer 30 is attached to the winding turns within the range of the 1st turn to the 10th turn of the winding starting end of the wound battery cell; the value range of the thickness T1 of the active material layer 202 is: 320 μm ≤ T1 ≤ 560 μm.

[0065] Combined with Figure 8As shown, the wound battery cell is formed in a form of winding layer by layer, where the winding starting end refers to the area of the wound battery cell closer to the winding center. At the bending part 11 of the innermost layer of the wound battery cell, the two layers of electrode foils on both sides of the bending part 11 are substantially in a state of being attached to each other. That is, the bending angle of the bending part 11 of the innermost layer of the wound battery cell is the largest, approaching a 180° bend, and the phenomenon that the active material layer 202 coated on the bending part 11 of the innermost layer of the wound battery cell is stretched most severely at the microscopic level. As the number of winding layers increases, the bending part 11 gradually away from the winding center gradually bends in an arc shape, and the phenomenon that the active material layer 202 coated on the bending part 11 is stretched at the microscopic level gradually alleviates. After repeated tests, the phenomenon that the active material layer 202 coated on the bending part 11 within the range of the 1st to 10th winding turns from the winding starting end of the wound battery cell is stretched at the microscopic level is relatively obvious, and the situation of the active material layer falling off is likely to occur. By attaching the reinforcing layer 30 within the range of the 1st to 10th winding turns from the winding starting end of the wound battery cell, the phenomenon that the active material layer 202 coated on the bending part 11 is stretched at the microscopic level can be better overcome, and at the winding turn position with relatively low risk, the situation of redundant pasting of the reinforcing layer 30 will not occur, avoiding a large reduction in energy density.

[0066] In this embodiment, the value range of the thickness T1 of the active material layer 202 can be further preferably: 320 μm ≤ T1 ≤ 560 μm; and the value of (T2 / T1)·L1 can be further preferably 0.046 mm ≤ (T2 / T1)·L1 ≤ 3.12 mm.

[0067] Exemplarily, in this embodiment, the value of T1 can be 320 μm or 350 μm or 400 μm or 450 μm or 480 μm or 500 μm or 530 μm or 560 μm, etc., or it can also be an interval range formed by any two of the above numerical values.

[0068] Exemplarily, in this embodiment, the value of (T2 / T1)·L1 can be 0.046 mm or 0.05 mm or 0.1 mm or 0.2 mm or 0.3 mm or 0.5 mm or 0.9 mm or 1 mm or 1.2 mm or 1.5 mm or 1.8 mm or 1.9 mm or 2 mm or 2.3 mm or 2.5 mm or 2.8 mm or 3 mm or 3.1 mm or 3.12 mm, etc., or it can also be an interval range formed by any two of the above numerical values.

[0069] In some embodiments, the thickness of the reinforcing layer 30 is greater than the thickness of the separator 10.

[0070] In some embodiments, the hardness of the reinforcing layer 30 is greater than the hardness of the separator 10. Thereby improving the structural strength of the separator 10 and preventing the separator 10 from being torn.

[0071] In some embodiments, along the width direction of the electrode tab, both ends of the reinforcing layer 30 do not extend beyond the electrode tab 20. By making both ends of the reinforcing layer 30 not extend beyond the electrode tab 20, it is possible to avoid an overlapping area between the reinforcing layer 30 and the separator 10, so that the reinforcing layer 30 will not interfere with the folding and hemming of the separator 10, and avoid the occurrence of wrinkling of the separator 10.

[0072] Specifically, along the width direction of the electrode tab, both ends of the reinforcing layer 30 do not extend beyond the base layer 201 of the electrode tab 20. That is, along the width direction of the electrode tab, both ends of the reinforcing layer 30 can be located between the base layer 201 and the active material layer 202 of the electrode tab 20, so that the reinforcing layer 30 can better cover the active material layer 202, while avoiding an overlapping area between the reinforcing layer 30 and the separator 10.

[0073] As a variation, as shown in Figure 5 Along the width direction of the electrode tab, both ends of the reinforcing layer 30 extend beyond the electrode tab 20. By extending both ends of the reinforcing layer 30 beyond the electrode tab 20, it is possible to better constrain the active material layer 202 coated on the surface of the electrode tab 20, and prevent the occurrence of the situation where the active material layer falls off.

[0074] In some embodiments, as shown in Figure 5 When the wound battery cell is in the unfolded state, the axis of symmetry of the reinforcing layer 30 parallel to the width direction of the electrode tab is R2; the central symmetry line of the arc region 1 parallel to the width direction of the electrode tab is R1, where the deviation distance between R1 and R2 is D, satisfying: 0 mm ≤ D ≤ 10 mm.

[0075] It should be noted that the central symmetry line R1 of the arc region 1 specifically refers to: as shown in Figure 1 When the wound battery cell is in the wound state, along the second direction, the intersection position of the arc region 1 and one of the flat regions 2 is defined as the first boundary line, and the intersection position of the arc region 1 and the other flat region 2 is defined as the second boundary line. Further, as shown in Figure 5 When the wound battery cell is in the unfolded state, the central symmetry line of the first boundary line and the second boundary line of the arc region 1 is R1.

[0076] By controlling the upper limit of the deviation distance D between R1 and R2, it is possible to avoid the situation where the reinforcing layer 30 adheres more on one side of the arc region 1 and less on the other side, and ensure that when the reinforcing layer 30 covers the electrode tab at the arc region 1, it can be evenly strengthened on both sides of the central symmetry line R1 of the arc region 1, thereby effectively ensuring the strengthening effect.

[0077] Exemplarily, in this embodiment, the value of D can be 0 mm or 1 mm or 2 mm or 3 mm or 5 mm or 7 mm or 8 mm or 10 mm, etc., or it can also be an interval range formed by any two of the above numerical values.

[0078] In some embodiments, one side of the base layer 201 is coated with an active material layer 202, satisfying: 0.053 mm ≤ (T2 / T1)·L1 ≤ 20 mm.

[0079] That is, the base layer 201 is coated with the active material layer 202 only on one side. When coated on one side, the overall thickness of the active material layer 202 coated on the electrode sheet 20 is relatively small. The phenomenon that the active material layer 202 coated on the electrode sheet 20 in the arc region 1 is stretched at the microscopic level is relatively light, and the upper limit of the overall parameter (T2 / T1)·L1 can be appropriately smaller.

[0080] Exemplarily, in this embodiment, the value of (T2 / T1)·L1 can be 0.053 mm or 0.1 mm or 0.2 mm or 0.3 mm or 0.5 mm or 0.9 mm or 1 mm or 2 mm or 3 mm or 5 mm or 8 mm or 10 mm or 12 mm or 15 mm or 18 mm or 20 mm, etc., or can also be an interval range formed by any two of the above numerical values.

[0081] In some embodiments, both sides of the base layer 201 are coated with the active material layer 202. The thickness of the active material layer 202 on one side of the base layer 201 is T11, and the thickness of the active material layer 202 on the other side of the base layer 201 is T12, satisfying: 0.08 mm ≤ (T2 / T1)·L1 ≤ 16.7 mm, where T1 = T11 + T12.

[0082] That is, the base layer 201 is coated with the active material layer 202 on both sides in the thickness direction. When coated on both sides, the overall thickness of the active material layer 202 coated on the electrode sheet 20 is relatively large. The phenomenon that the active material layer 202 coated on the electrode sheet 20 in the arc region 1 is stretched at the microscopic level is relatively heavy, and the upper limit of the overall parameter (T2 / T1)·L1 can be appropriately larger.

[0083] Exemplarily, in this embodiment, the value of (T2 / T1)·L1 can be 0.08 mm or 0.1 mm or 0.2 mm or 0.3 mm or 0.5 mm or 0.9 mm or 1 mm or 2 mm or 3 mm or 5 mm or 8 mm or 10 mm or 12 mm or 15 mm or 16.7 mm, etc., or can also be an interval range formed by any two of the above numerical values.

[0084] In some embodiments, the reinforcing layer 30 is attached to the surface of the positive electrode sheet 21 or the negative electrode sheet 22 on the side coated with the active material layer 202, satisfying: 0.14 mm ≤ (T2 / T1)·L1 ≤ 20 mm.

[0085] That is, the reinforcing layer 30 is only attached to the pole piece 20 of one of the polarities, and specifically attached to the surface of the pole piece 20 on the side coated with the active material layer 202. At this time, the constraint effect of the reinforcing layer 30 on the active material layer 202 is better, and the upper limit of the overall parameter of (T2 / T1)·L1 can be appropriately smaller.

[0086] Exemplarily, in this embodiment, the value of (T2 / T1)·L1 can be 0.14 mm or 0.2 mm or 0.3 mm or 0.5 mm or 0.9 mm or 1 mm or 2 mm or 3 mm or 5 mm or 8 mm or 10 mm or 12 mm or 15 mm or 16 mm or 18 mm or 20 mm, etc., and can also be the range formed by any two of the above values.

[0087] In some embodiments, the reinforcing layer 30 is attached to the surface of one side of the base layer 201 of the positive pole piece 21 or the negative pole piece 22, satisfying: 0.053 mm ≤ (T2 / T1)·L1 ≤ 10 mm.

[0088] That is, the reinforcing layer 30 is only attached to the pole piece 20 of one of the polarities, and specifically attached to the surface of the pole piece 20 on the side forming the base layer 201. At this time, the constraint effect of the reinforcing layer 30 on the active material layer 202 is poor, and the upper limit of the overall parameter of (T2 / T1)·L1 can be appropriately larger.

[0089] Exemplarily, in this embodiment, the value of (T2 / T1)·L1 can be 0.053 mm or 0.1 mm or 0.2 mm or 0.3 mm or 0.5 mm or 0.9 mm or 1 mm or 2 mm or 3 mm or 5 mm or 8 mm or 10 mm, etc., and can also be the range formed by any two of the above values.

[0090] Since there is a difference in the thickness of the active material layer 202 coated on the positive pole piece 21 and the thickness of the active material layer 202 coated on the negative pole piece 22, in this embodiment, the thickness of the active material layer 202 coated on the positive pole piece 21 can be greater than the thickness of the active material layer 202 coated on the negative pole piece 22.

[0091] In some embodiments, as shown in Figure 4 The reinforcing layer 30 is attached to the surface of the positive pole piece 21 facing the winding center, satisfying: 0.21 mm ≤ (T2 / T1)·L1 ≤ 16.7 mm.

[0092] In some embodiments, as shown in Figure 3 The reinforcing layer 30 is attached to the surface of the negative pole piece 22 facing the winding center, satisfying: 0.08 mm ≤ (T2 / T1)·L1 ≤ 9 mm.

[0093] In some embodiments, as shown in Figure 2As shown, the reinforcing layer 30 is attached to the surface of the positive electrode sheet 21 on the side facing the winding center, and the reinforcing layer 30 is also attached to the surface of the negative electrode sheet 22 on the side facing the winding center, satisfying: 0.08 mm ≤ (T2 / T1)·L1 ≤ 16.7 mm.

[0094] As a variation, it can also be that the thickness of the active material layer 202 coated on the positive electrode sheet 21 is less than the thickness of the active material layer 202 coated on the negative electrode sheet 22. As another variation, it can also be that the thickness of the active material layer 202 coated on the positive electrode sheet 21 is equal to the thickness of the active material layer 202 coated on the negative electrode sheet 22.

[0095] Combined with Table 1 below, through several examples and comparative examples, after the winding core of the present application is attached with the reinforcing layer 30, the material dropping situation and heat dissipation effect of the battery bending part 11 under different parameter conditions are summarized.

[0096] The specific test method is as follows: Select a plurality of winding cores with different coating thicknesses and foil thicknesses, and attach insulating tapes to several turns of the winding cores close to the winding center; after assembling into a battery, without injecting electrolyte, put the battery into a heating box for heating, the heating temperature is 105 °C, heat for 10 min, and then put the battery into an environment of 25 °C and let it stand and cool for 30 min, and measure the temperature of the pole column. Because the pole column is welded to the tab, the internal basic temperature of the battery can be transmitted to the pole column through the tab, and the internal heat dissipation effect of the battery can be indirectly measured. And set the pole column temperature less than or equal to 45 °C as the standard range, at this time the internal heat dissipation of the winding core is better; if it is greater than 45 °C, it indicates that the internal heat dissipation of the winding core is poor.

[0097] Subsequently, after injecting electrolyte and forming the battery, disassemble it respectively, and observe the material dropping situation in the corresponding battery bending area. If there is material dropping, it is judged as NG (unqualified), and if there is no material dropping, it is judged as OK (qualified).

[0098] Among them, the battery assembly, electrolyte injection and formation all adopt the conventional processes in battery production, which will not be elaborated here.

[0099] Table 1

[0100]

[0101] Combined with Table 1 above, in Examples 1 to 52, the value range of (T2 / T1)·L1 all satisfies 0.026 mm ≤ (T2 / T1)·L1 ≤ 33.3 mm, and the value of the thickness T1 of the active material layer 202 is in the range of 30 μm ≤ T1 ≤ 560 μm; the value of the thickness T2 of the base layer 201 is in the range of 3 μm ≤ T2 ≤ 20 μm; the value of the length L1 of the reinforcing layer 30 along the length direction of the electrode is in the range of 5 mm ≤ L1 ≤ 50 mm. After testing, the pole column temperature is all less than or equal to 45°C, indicating that the heat dissipation inside the battery cell is good. And by observing the material dropping situation in the bending area of the corresponding battery, no material dropping occurs, meeting the usage requirements.

[0102] In addition, in Examples 53 to 56, although the value of the thickness T1 of the active material layer 202 is not in the range of 30 μm ≤ T1 ≤ 560 μm; the value of the thickness T2 of the base layer 201 is not in the range of 3 μm ≤ T2 ≤ 20 μm; the value of the length L1 of the reinforcing layer 30 along the length direction of the electrode is not in the range of 5 mm ≤ L1 ≤ 50 mm, but the value range of (T2 / T1)·L1 all satisfies 0.026 mm ≤ (T2 / T1)·L1 ≤ 33.3 mm. After testing, the pole column temperature is all less than or equal to 45°C, indicating that the heat dissipation inside the battery cell is good. And by observing the material dropping situation in the bending area of the corresponding battery, no material dropping occurs, meeting the usage requirements.

[0103] In Comparative Examples 1 to 14, the values of (T2 / T1)·L1 all exceed the upper limit of the range of 0.026 mm ≤ (T2 / T1)·L1 ≤ 33.3 mm. After disassembly, no material dropping situation is found, but after testing, the pole column temperature is all greater than 45°C, indicating that the battery has poor heat dissipation and cannot meet the heat dissipation requirements.

[0104] In Comparative Examples 15 to 21, the values of (T2 / T1)·L1 all exceed the lower limit of the range of 0.026 mm ≤ (T2 / T1)·L1 ≤ 33.3 mm. After testing, the pole column temperature is all less than or equal to 45°C, indicating that the heat dissipation inside the battery cell is good and the temperature meets the conditions; but after disassembly and observing the material dropping situation in the bending area of the corresponding battery, material dropping occurs in all cases, and it cannot play a good role in preventing the active material layer from dropping off, and cannot meet the usage requirements.

[0105] According to an embodiment of the present invention, on the other hand, a battery is further provided, including:

[0106] A battery case, and a wound battery cell as described above disposed inside the battery case.

[0107] Obviously, the above embodiments are merely examples for clear illustration and not limitations on the implementation manners. Although the 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 present invention.

Claims

1. A wound battery cell, characterized in that, Comprising: Pole pieces (20), including a positive pole piece (21) and a negative pole piece (22); A separator (10) disposed between the adjacent positive pole piece (21) and negative pole piece (22); The wound battery cell comprises the positive pole piece (21), the separator (10) and the negative pole piece (22); after the pole pieces (20) are wound, a bent portion (11) is formed; The pole piece (20) comprises a base layer (201) and an active material layer (202) coated on at least one side of the base layer (201), the thickness of the active material layer (202) is T1, in micrometers; the thickness of the base layer (201) is T2, in micrometers; The wound battery cell further comprises: a reinforcing layer (30) attached to the active material layer (202) of the positive pole piece (21) and / or the negative pole piece (22), and the reinforcing layer (30) covers at least one bent portion (11) and at least covers a partial surface of the bent portion (11); In the unfolded state of the wound battery cell, the length of the reinforcing layer (30) in the length direction of the pole piece is L1, in millimeters; Satisfying: 0.026 mm ≤ (T2 / T1)·L1 ≤ 33.3 mm.

2. The wound cell according to claim 1, wherein The value range of the thickness T1 of the active material layer (202) is: 30 μm ≤ T1 ≤ 560 μm; And / or, the value range of the thickness T2 of the base layer (201) is: 3 μm ≤ T2 ≤ 20 μm; And / or, the value range of the length L1 of the reinforcing layer (30) in the length direction of the pole piece is: 5 mm ≤ L1 ≤ 50 mm.

3. The wound battery cell according to claim 1, wherein, The reinforcing layer (30) is attached to the wound battery cell within the range of the 1st to 10th winding turns starting from the winding starting end.

4. The wound battery cell according to claim 3, characterized in that, The value range of the thickness T1 of the active material layer (202) is: 320 μm ≤ T1 ≤ 560 μm; and 0.046 mm ≤ (T2 / T1)·L1 ≤ 3.12 mm.

5. The wound cell according to claim 1, characterized in that, The thickness of the reinforcing layer (30) is greater than the thickness of the separator (10).

6. The wound battery cell according to claim 1, wherein, The hardness of the reinforcing layer (30) is greater than the hardness of the separator (10).

7. The wound cell according to claim 1, wherein Along the width direction of the pole piece, both ends of the reinforcing layer (30) do not extend beyond the pole piece (20).

8. The wound battery cell according to claim 7, wherein Along the width direction of the pole piece, both ends of the reinforcing layer (30) do not extend beyond the base layer (201) of the pole piece (20).

9. The wound battery cell according to claim 1, wherein, Along the width direction of the pole piece, both ends of the reinforcing layer (30) extend beyond the pole piece (20).

10. The wound battery cell according to claim 1, characterized in that, The wound battery cell comprises a flat region (2) and arc regions (1) located on both sides of the flat region (2) along a first direction, and the bent portion (11) is located in the arc region (1).

11. The wound cell according to claim 10, wherein, In the unfolded state of the wound battery cell, the axis of symmetry of the reinforcing layer (30) parallel to the width direction of the pole piece is R2; the central symmetry line of the arc region (1) parallel to the width direction of the pole piece is R1, wherein the deviation distance between R1 and R2 is D, satisfying: 0 mm ≤ D ≤ 10 mm.

12. The wound cell according to claim 1, characterized in that, The active material layer (202) is coated on one side of the base layer (201), satisfying: 0.053 mm ≤ (T2 / T1)·L1 ≤ 20 mm.

13. The wound battery cell according to claim 12, wherein, The reinforcing layer (30) is attached to the surface of the positive electrode sheet (21) or the negative electrode sheet (22) on the side coated with the active material layer (202), satisfying: 0.14 mm ≤ (T2 / T1)·L1 ≤ 20 mm.

14. The wound cell according to claim 12, wherein, The reinforcing layer (30) is attached to the surface of the positive electrode sheet (21) or the negative electrode sheet (22) on the side of the base layer (201), satisfying: 0.053 mm ≤ (T2 / T1)·L1 ≤ 10 mm.

15. The wound cell according to claim 1, characterized in that, Both sides of the base layer (201) are coated with the active material layer (202), and the thickness of the active material layer (202) on one side of the base layer (201) is T11, and the thickness of the active material layer (202) on the other side of the base layer (201) is T12, satisfying: 0.08 mm ≤ (T2 / T1)·L1 ≤ 16.7 mm, where T1 = T11 + T12.

16. The wound battery cell according to claim 15, characterized in that, The reinforcing layer (30) is attached to the surface of the positive electrode sheet (21) facing the winding center, satisfying: 0.21 mm ≤ (T2 / T1)·L1 ≤ 16.7 mm.

17. The wound cell according to claim 15, wherein, The reinforcing layer (30) is attached to the surface of the negative electrode sheet (22) facing the winding center, satisfying: 0.08 mm ≤ (T2 / T1)·L1 ≤ 9 mm.

18. The wound cell according to claim 15, characterized in that, The reinforcing layer (30) is attached to the surface of the positive electrode sheet (21) facing the winding center, and the reinforcing layer (30) is also attached to the surface of the negative electrode sheet (22) facing the winding center, satisfying: 0.08 mm ≤ (T2 / T1)·L1 ≤ 16.7 mm.

19. A battery, characterized in that, It includes a battery case and a wound battery cell as described in any one of claims 1 to 18 provided in the battery case.

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