Battery

Abstract

The utility model provides a battery which comprises a battery cell, the battery cell comprises a first pole piece, the first pole piece comprises at least one first straight part and a first bending part connected with the first straight part, and the first bending part is positioned on at least one side of the battery cell in a second direction; the first pole piece comprises a first active material layer, the first active material layer comprises a main body area and an open pore area with concave parts distributed on the surface, the open pore area comprises a first open pore area and a second open pore area, the first open pore area is arranged on the edge of at least one side of the first active material layer in the first direction, and the second open pore area is arranged on the edge of at least one side of the first active material layer in the second direction. The second opening area is arranged on the first bending portion, and the first direction intersects with the second direction. According to the utility model, the heat dissipation performance of the battery can be improved, and meanwhile, higher energy density of the battery is kept.

Description

Technical Field

[0001] The utility model relates to the field of electrochemical energy storage devices, in particular to a battery. Background Art

[0002] Batteries are common electrochemical energy storage devices with a wide range of applications. For example, lithium-ion batteries have advantages such as high energy density and are widely used in electronic products and electric vehicles. However, existing batteries have poor heat dissipation performance. During use, heat is easily accumulated inside the battery, resulting in a low furnace temperature passing rate for the battery, and fire and other safety issues are in urgent need of resolution. Utility Model Content

[0003] The utility model provides a battery, which at least solves the problems existing in the prior art, such as poor heat dissipation performance of the battery, easy heat accumulation during use, and thus low furnace temperature passing rate of the battery.

[0004] The utility model provides a battery, comprising a battery cell, wherein the battery cell comprises a first pole piece, the first pole piece comprises at least one first straight portion, and a first bent portion connected to the first straight portion, the first bent portion is located on at least one side of the battery cell in a second direction; the first pole piece comprises a first active material layer, the first active material layer comprises a main body area, and an opening area with recesses distributed on the surface, the opening area comprises a first opening area and a second opening area, the first opening area is arranged at an edge of at least one side of the first active material layer in the first direction, the second opening area is arranged at the first bent portion, and the first direction intersects with the second direction.

[0005] According to an embodiment of the present invention, the thickness H of the first pole piece corresponding to the main body region is 0 , the thickness H of the first pole piece corresponding to the first opening area 121 , the thickness H of the first pole piece corresponding to the second opening area 122 Satisfy 0.6≤H 0 / (H 121 +H 122 )≤0.9; preferably, the H 0 is 30 to 200 μm; preferably, the H 121 is 20 to 200 μm; preferably, the H 122 20~200μm.

[0006] According to one embodiment of the present invention, the first active material layer is provided with the first opening area on both sides of the edges on the first direction; preferably, the spacing L between the first opening areas on the edges on the two sides is 3 Satisfy 0<L 3≤200mm; and / or, the first active material layer comprises at least two second opening areas; preferably, the distance L between two adjacent second opening areas 4 Satisfy 0<L 4 ≤100mm.

[0007] According to an embodiment of the present invention, the total area of ​​the open areas accounts for 10% to 50% of the total area of ​​the first active material layer.

[0008] According to one embodiment of the present invention, the first opening area is connected to the second opening area; preferably, the area S of the overlapping area of ​​the first opening area and the second opening area 123 The area S of the first opening area 121 Satisfy 0<S 123 / S 121 ≤40%.

[0009] According to one embodiment of the utility model, the width of the first opening area is 1 to 20 mm; and / or, the depth of the recess in the first opening area is less than the thickness of the opening area; and / or, in the opening area, the depth of the recess is 2 to 30 μm, the pore size is 10 to 150 μm, and the spacing between adjacent recesses is 20 to 3000 μm; and / or, the width of the second opening area is 2 mm-20 mm; and / or, the depth of the recess in the second opening area is less than the thickness of the opening area; and / or, in the second opening area, the depth of the recess is 2 to 30 μm, the pore size is 10 to 150 μm, and the spacing between adjacent recesses is 20 to 3000 μm.

[0010] According to one embodiment of the present invention, the porosity of the main area is smaller than the porosity of the open area; preferably, the ratio of the porosity of the main area to the porosity of the first open area is greater than or equal to 0.1, preferably greater than or equal to 0.2, more preferably 0.2-0.8; preferably, the ratio of the porosity of the main area to the porosity of the second open area is greater than or equal to 0.1, preferably greater than or equal to 0.2, preferably 0.2-0.8.

[0011] According to one embodiment of the utility model, the first electrode sheet is a positive electrode sheet; preferably, the battery further comprises a negative electrode sheet, the negative electrode sheet comprises a negative electrode active material layer, and the recessed portion is not distributed on the surface of the negative electrode active material layer.

[0012] According to one embodiment of the utility model, the battery further comprises a second pole piece having a polarity opposite to that of the first pole piece, and a diaphragm located between the first pole piece and the second pole piece, the diaphragm being bonded to the first pole piece and the second pole piece respectively; preferably, the diaphragm comprises a first adhesive layer, a ceramic layer, a substrate layer and a second adhesive layer stacked in sequence, the first adhesive layer being bonded to the first pole piece, and the second adhesive layer being bonded to the second pole piece; preferably, the aperture D of the concave portion of the first opening area is 1 and the thickness H of the ceramic layer of the diaphragm 34 Satisfy 1.2≤D 1 / H 34 ≤160, preferably 2≤D 1 / H 34 ≤150; Preferably, the aperture D of the recess of the second opening area 2 and the thickness H of the ceramic layer of the diaphragm 34 Satisfy 1.2≤D 2 / H 34 ≤160, preferably 2≤D 2 / H 34 ≤150; Preferably, the aperture D of the recess of the first opening area 1 and the thickness H of the first adhesive layer of the diaphragm 31 Satisfy 2.5≤D 1 / H 31 ≤320, preferably 2.5≤D 1 / H 31 ≤300; Preferably, the aperture D of the recess of the second opening area 2 and the thickness H of the first adhesive layer of the diaphragm 31 Satisfy 2.5≤D 2 / H 31 ≤320, preferably 2.5≤D 2 / H 31 ≤300; preferably, the thickness of the substrate layer is 2-20 μm; preferably, the thickness of the ceramic layer is 1-5 μm; preferably, the thickness of the first adhesive layer is 0.5-4 μm; preferably, the thickness of the second adhesive layer is 0.5-4 μm.

[0013] According to an embodiment of the present invention, the first opening area exists in edge areas of the battery cell on two opposite sides in the first direction, and the second opening area exists in edge areas of the battery cell on two opposite sides in the second direction.

[0014] In the battery provided by the utility model, an opening area with recesses distributed on the surface is provided in the first pole piece, and the opening area includes a first opening area provided at the edge of the first active material layer in the first direction, and a second opening area provided at the first bending portion, so that the heat dissipation effect of the battery cell can be improved, thereby improving the heat dissipation performance of the battery, avoiding heat accumulation during the use of the battery, and the resulting safety problems such as low battery furnace temperature passing rate and easy fire, thereby improving the thermal safety performance of the battery. Among them, the heat dissipation effect of the battery cell is improved, and its internal temperature is reduced, which can reduce the side reactions between the active material and other materials in the first pole piece and the components such as the electrolyte, and inhibit the problems such as the gas production and continuous temperature increase of the battery caused by the reaction, thereby improving the thermal stability and thermal safety of the battery, while taking into account the maintenance of the battery's high energy density and capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the planar structure of the first pole piece of an embodiment of the utility model;

[0016] Figure 2 It is a schematic diagram of the stacked structure of the first pole piece, the diaphragm and the second pole piece in one embodiment of the utility model;

[0017] Figure 3 This is a schematic structural diagram of a wound battery cell according to an embodiment of the utility model;

[0018] Figure 4 It is a schematic projection diagram of a battery cell along its thickness direction according to an embodiment of the utility model;

[0019] Figure 5 The figure is a schematic diagram of a battery structure according to an embodiment of the present utility model.

[0020] Explanation of reference numerals: 1: first pole piece; 11: main body area; 12: opening area; 121: first opening area; 122: second opening area; 123: overlapping area; 13: first pole ear; 100: recessed portion; 101: first straight portion; 102: first bent portion; 110: first current collector; 120: first active material layer; 2: second pole piece; 23: second pole ear; 201: second straight portion; 202: second bent portion; 210: second current collector; 220: second active material layer ; 3 diaphragm; 31: first adhesive layer; 34: ceramic layer; 33: substrate layer; 32: second adhesive layer; 4: battery cell; 41: first side; 42: second side; 43: third side; 44: fourth side; 5: package body; 50: cavity; 51: first side; 511: first main body; 512: first connecting part; 52: second side; 521: second main body; 522: second connecting part; 6: ear glue; x: first direction; y: second direction; z: third direction; A: arrow; w 1 : Width of the first opening area; w2 : The width of the second opening area. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the scheme of the utility model, the utility model is further described in detail below. The specific implementation methods listed below are only for describing the principles and features of the utility model. The examples are only used to explain the utility model and do not limit the scope of the utility model. Based on the embodiments of the utility model, all other implementation methods obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model.

[0022] In the related art, the heat dissipation performance of the battery is poor. During use, heat is easily accumulated inside the battery, which may lead to safety problems such as battery fire.

[0023] Specifically, the electrode sheet is an important component of the battery. The electrode sheet contains electrode active materials. During the use of the battery, the heat dissipation effect of the electrode sheet is poor, especially for the electrode sheet with a bent structure. Due to factors such as the greater stress in the bent part (arc area), the arc area is subjected to greater force, and the heat generated here is more difficult to dissipate. The poor heat dissipation effect of the electrode sheet can easily lead to heat accumulation inside the battery cell, which will in turn aggravate the side reactions between the electrode active materials of the electrode sheet and components such as the electrolyte, leading to gas production and further increase in the temperature inside the battery cell, affecting the safety and cycle life of the battery.

[0024] According to the inventors' long-term research, by making holes on the electrode active material layer of the electrode sheet, the heat dissipation effect of the electrode sheet can be improved to a certain extent, thereby improving the heat dissipation performance of the battery. However, if the area of ​​the hole-making region is too large, it will affect the battery's energy density and other performance (for example, when holes are made on the entire surface of the electrode active material layer, the battery energy density is severely lost). Therefore, it is difficult to take into account both the heat dissipation performance and energy density of the battery.

[0025] In view of this, the present invention provides a battery, such as Figures 1 to 5 As shown, the battery includes a battery cell 4, the battery cell 4 includes a first pole piece 1, the first pole piece 1 includes at least one first straight portion 101, and a first bent portion 102 connected to the first straight portion 101, the first bent portion 102 is located on at least one side of the battery cell 4 in the second direction y; the first pole piece 1 includes a first active material layer 120, the first active material layer 120 includes a main body area 11, and an opening area 12 with recesses 100 distributed on the surface, the opening area 12 includes a first opening area 121 and a second opening area 122, the first opening area 121 is arranged at the edge of at least one side of the first active material layer 120 in the first direction x, the second opening area 122 is arranged at the first bent portion 102, and the first direction x and the second direction y intersect.

[0026] In the embodiment of the utility model, a first opening area 121 is provided at least on one side edge of the first active material layer in the first direction x, and a second opening area 122 is provided at the first bending portion 102, which is conducive to forming a continuous heat dissipation channel at the edge of the battery cell 4 in the first direction x and the second direction y, dissipating the heat generated in the battery cell 4, avoiding heat accumulation in a local area, causing local overheating, and causing thermal safety problems. Among them, the second opening area 122 is provided in the first bending portion (arc area) 102, so that the arc area forms a heat dissipation channel, which is conducive to dissipating the heat in the arc area of ​​the battery cell 4, solving the problem of poor heat dissipation effect in the arc area.

[0027] Therefore, in the embodiment of the utility model, there are opening areas 12 on the side edges of the battery cell 4 in different directions (the opening area 12 on the edge in the first direction is the first opening area 121, and the opening area 12 on the edge in the second direction is the second opening area 122 provided in the first bending portion 102), which is conducive to the release of heat inside the battery cell 4 from different directions, improving the heat dissipation effect of the battery cell 4, thereby improving the heat dissipation performance of the battery, avoiding the accumulation of heat inside the battery, and the resulting battery fire. Among them, the heat dissipation effect of the battery cell 4 is improved, and its internal temperature is reduced, which can reduce the side reactions between the active material and other materials in the first pole piece 1 and the components such as the electrolyte, and inhibit the resulting battery gas production and temperature continuous increase, thereby improving the thermal stability and thermal safety of the battery. At the same time, the first active material layer 120 of the first pole piece 1 includes the main body area 11, which is conducive to maintaining a higher energy density of the first pole piece 1 while improving the heat dissipation performance of the battery, and improving the energy density and capacity of the battery.

[0028] Continue to refer Figures 1 to 5 The battery also includes a packaging body 5 for packaging a battery cell 4, the battery cell 4 is located in a cavity 50 surrounded by the packaging body 5, the battery cell 4 also includes a second pole piece 2 with a polarity opposite to that of the first pole piece 1, a first pole ear 13 connected to the first pole piece 1, a second pole ear 23 connected to the second pole piece 2, and a diaphragm 3 located between the first pole piece 1 and the second pole piece 2, the diaphragm 3 is spaced between the first pole piece 1 and the second pole piece 2 to prevent short circuit between the positive and negative poles.

[0029] Specifically, the first electrode 1 includes a first current collector 110 and a first active material layer 120 located on the surface of the first current collector 110 . The first active material layer 120 can be arranged on one surface of the first current collector 110 , or on both the front and back surfaces of the first current collector 110 .

[0030] Specifically, the first active material layer 120 may include a first active material, a first conductive agent and a first binder. In the first active material layer 120, the mass content of the first active material layer 120 may be 70% to 99%, the mass content of the first conductive agent may be 0.5% to 15%, and the mass content of the first binder may be 0.5% to 15%.

[0031] Specifically, the first pole ear 13 is connected to the first current collector 110. The first pole ear 13 can be welded on the first current collector 110, or extended outward from the first current collector 110 (for example, the first pole ear 13 is formed by the first current collector 110 extending outward in the width direction or length direction of the first pole sheet 1 in a direction away from the first active material layer 120). The first pole ear 13 can be specifically arranged at the end of the length direction of the first pole sheet 1, or on one side or two opposite sides in the width direction of the first pole sheet 1. The number of the first pole ears 13 on the first pole sheet 1 can be one or more, and there is no special restriction on this.

[0032] In some embodiments, Figure 1 As shown, the first pole ear 13 on the first pole piece 1 can be a pole ear center structure, that is, the first pole ear 13 is arranged in the middle of at least one side of the first pole piece 1 in the first direction x, and the extension direction of the first pole ear 13 can be basically parallel to the first direction x, which is beneficial to improve the heat dissipation and other performance of the battery cell 4.

[0033] like Figure 4 and Figure 5 As shown, the first pole ear 13 extends out of the package 5, specifically, it can extend out of the package 5 from one side of the battery in the first direction x, that is, the first pole ear 13 is connected to one side of the first pole piece 12 in the first direction x and extends out of the package 5 from this side.

[0034] In addition, the second pole piece 2 includes a second current collector 210 and a second active material layer 220 located on the surface of the second current collector 210 . The second active material layer 220 can be set on one surface of the second current collector 210 , or on both the front and back surfaces of the second current collector 210 .

[0035] Specifically, the second active material layer 220 may include a second active material, a second conductive agent and a second binder. In the second active material layer 220, the mass content of the second active material layer 220 may be 70% to 99%, the mass content of the second conductive agent may be 0.5% to 15%, and the mass content of the second binder may be 0.5% to 15%.

[0036] Specifically, the second pole ear 23 is connected to the second current collector 210. The second pole ear 23 can be welded on the second current collector 210, or extended outward from the second current collector (for example, the second pole ear 23 is formed by the second current collector 210 extending outward in the width direction or length direction of the second pole sheet 2 in a direction away from the second active material layer 220). The second pole ear 23 can be specifically arranged at the end of the second pole sheet 2 in the length direction, or on one side or two opposite sides in the width direction of the second pole sheet 2. The number of second pole ears 23 on the second pole sheet 2 can be one or more, and there is no special limitation on this.

[0037] In some embodiments, the second pole ear 23 on the second pole piece 2 can be a pole ear center structure, that is, the second pole ear 23 is arranged in the middle of at least one side of the second pole piece 2 in the first direction x, and the extension direction of the second pole ear 23 can be basically parallel to the first direction x, which is beneficial to improve the heat dissipation and other performance of the battery cell 4.

[0038] like Figure 4 and Figure 5 As shown, the second pole ear 23 extends out of the package 5, specifically, it can extend out of the package 5 from one side of the battery in the first direction x, that is, the second pole ear 23 is connected to one side of the second pole piece 2 in the first direction x and extends out of the package 5 from this side.

[0039] Specifically, Figure 4 and Figure 5 As shown, the first pole tab 13 and the second pole tab 23 may be located on the same side of the battery cell 4 , and the second pole tab 23 and the first pole tab 13 extend out of the package 5 from the same side of the battery.

[0040] Generally, the package body 5 may include a top seal and a side seal. The top seal is located on one side of the battery in the first direction x, and the side seals are located on opposite sides of the battery in the second direction y. The first pole ear 13 and the second pole ear 23 may extend out of the package body 5 from the top seal.

[0041] Specifically, if Figure 5 As shown, the package body 5 includes a first side portion 51 and a second side portion 52, the first side portion 51 includes a first main body portion 511 and a first connecting portion 512, the second side portion 52 includes a second main body portion 521 and a second connecting portion 522, the first main body portion 511 and the second main body portion 521 are respectively located on opposite sides of the battery cell 4 in the third direction z, and the first connecting portion 512 and the second connecting portion 522 are connected to form the edge sealing of the package body 5 (i.e., the top edge sealing and the side edge sealing).

[0042] Among them, in the edge sealing portion where the first pole ear 13 extends out, the first pole ear 13 is located between the first connecting portion 512 and the second connecting portion 522, and the first pole ear 13 can be specifically bonded to the first connecting portion 512 and the second connecting portion 522 respectively through the pole ear glue 6 (that is, one side of the first pole ear 13 in the thickness direction is bonded to the first connecting portion 512 through the pole ear glue 6, and the other side of the first pole ear 13 in the thickness direction is bonded to the second connecting portion 522 through the pole ear glue 6).

[0043] Among them, in the edge sealing portion where the second pole ear 23 extends out, the second pole ear 23 is located between the first connecting portion 512 and the second connecting portion 522, and the second pole ear 23 can be specifically bonded to the first connecting portion 512 and the second connecting portion 522 respectively through the pole ear glue 6 (that is, one side of the second pole ear 23 in the thickness direction is bonded to the first connecting portion 512 through the pole ear glue 6, and the other side of the second pole ear 23 in the thickness direction is bonded to the second connecting portion 522 through the pole ear glue 6).

[0044] In addition, at the edge sealing portion where no tabs extend out, the first connection portion 512 and the second connection portion 522 are connected, for example, bonded, so that the packaging body 5 is surrounded to form a closed cavity 50 , thereby encapsulating the battery cell 4 .

[0045] In the embodiment of the utility model, the tab glue 6 can be any conventional tab glue material in the art, and there is no particular limitation on this.

[0046] Generally, the edge sealing portion where the pole ears (the first pole ear 13 and the second pole ear 23) extend is a relatively weak portion on the package body 5. When the battery encounters high temperature, the edge sealing portion is easily broken by the gas generated by side reactions inside the battery, so that the gas inside the battery can be leaked from the edge sealing portion. At the same time, the heat inside the battery is carried by the gas and released from the inside of the battery, thereby preventing the internal temperature of the battery from continuing to rise, thereby preventing the battery from catching fire, exploding, and other problems.

[0047] Specifically, Figures 1 to 4 As shown, the edge area of ​​at least one side of the battery cell 4 in the first direction x is provided with a first opening area 121, and at the same time, the edge area of ​​at least one side of the battery cell 4 in the second direction y is provided with a second opening area 122. When the battery encounters high temperature, the heat inside the battery cell 4 is released along the sides of the battery cell 4 in different directions into the cavity 50 surrounded by the packaging body 5. When the temperature and gas inside the battery reach a certain level, the gas inside the battery can break through the edge sealing part where the pole ear protrudes, realize directional pressure relief, and carry away heat at the same time, so as to avoid problems such as fire and explosion of the battery.

[0048] Specifically, the first opening area 121 extends from the outer edge of the first active material layer 120 toward the main body area 11 with a width of w 1 (w1 >0), that is, holes are made in this area to form a first opening area 121, and the width w of the first opening area 121 is 1 It refers to the width of the first opening area 121 in the direction from the first opening area 121 to the main body area 11.

[0049] Specifically, the first active material layer 120 may be provided with a first opening area 121 on one side edge in the first direction x, and accordingly, the battery cell 4 may have a first opening area 121 on one side edge in the first direction; or, the first active material layer 120 may be provided with first opening areas 121 on both sides of the edges on opposite sides in the first direction x, and accordingly, the battery cell 4 may have first opening areas 121 on both sides of the edges on opposite sides in the first direction x.

[0050] Specifically, if Figure 4 As shown, the battery has a first side 41 and a second side 42 relative to each other in the first direction x, wherein at least one of the edge area of ​​the first side 41 and the edge area of ​​the second side 42 has an opening area 12, and specifically, both the edge area of ​​the first side 41 and the edge area of ​​the second side 42 have opening areas 12 (that is, both the edge areas of the battery cell 4 on the opposite sides in the first direction x have opening areas 12), which is beneficial to further improve the heat dissipation performance of the battery cell 4.

[0051] Among them, the opening area 12 existing in the edge area of ​​the first side 41 of the battery cell 4 is a first opening area 121 arranged on one side edge of the first active material layer 120 in the first direction x, and the opening area 12 existing in the edge area of ​​the second side 42 of the battery cell 4 is a first opening area 121 arranged on the other side edge of the first active material layer 120 in the first direction x.

[0052] Relatively speaking, if the width w of the first opening area 121 is 1 If the width w of the first opening area 121 is too small, the improvement of the heat dissipation effect of the first electrode plate 1 is limited. 1 If the width w of the first opening area 121 is too large, the first active material in the first electrode sheet 1 will be lost too much, which will affect the energy density and capacity of the battery. Therefore, considering these factors comprehensively, the width w of the first opening area 121 is preferably 1 The diameter of the battery is 1 to 20 mm, for example, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 13 mm, 15 mm, 18 mm, 20 mm or any two thereof, which is beneficial for improving the heat dissipation performance of the battery while maintaining higher energy density and capacity of the battery.

[0053] The width w of the first opening area 121 is 1It refers to the width of the first opening area 121 on one side. For example, when the first opening area 121 exists on both sides of the first active material layer 120 in the first direction x, the width w of the first opening area 121 is 1 It refers to the width of the first opening area 121 on one side, rather than the sum of the widths of the first opening areas 121 on both sides.

[0054] Specifically, the width direction of the first opening area 121, the direction along the first opening area 121 to the main area 11, the width direction of the first electrode 1, the width direction of the first active material layer 120, and the first direction x are parallel to each other, and the length direction of the first opening area 121, the length direction of the first electrode 1, and the length direction of the first active material layer 120 are parallel to each other.

[0055] In addition, in some embodiments, the edges of the first active material layer 120 on two opposite sides in the first direction x are provided with first opening areas 121, and the spacing L of the first opening areas provided on the edges of the first active material layer 120 on two opposite sides in the first direction x is 3 Can satisfy 0<L 3 ≤200mm, L 3 For example, it is 0.5mm, 1mm, 5mm, 10mm, 20mm, 40mm, 50mm, 70mm, 90mm, 100mm, 130mm, 150mm, 180mm, 200mm or any two thereof. Relatively speaking, if L 3 Too large (L 3 >200mm), the width of the entire first active material layer 120 is larger, and accordingly, the first electrode sheet 1 is larger, the capacity of the battery cell 4 is large, and the heat generated is large, which is not conducive to the heat dissipation performance of the battery cell 4 (for example, the furnace temperature passing rate of the battery cell 4 is low). Therefore, by controlling 0<L 3 ≤200mm, which is beneficial to further improve the heat dissipation performance.

[0056] The spacing L of the first opening area 121 is 3 It refers to the distance in the first direction x between the first opening area 121 disposed on one side of the first active material layer 120 in the first direction x and the first opening area 121 disposed on the other side of the first active material layer 120 in the first direction x.

[0057] Specifically, the first active material layer 120 includes at least two second opening areas 122, the first electrode plate 1 includes at least two first bending portions 102, each second opening area 122 in the first active material layer 120 corresponds to a first bending portion 102, and for the corresponding second opening area 122 and the first bending portion 102, the second opening area 122 is arranged on the first bending portion 102, that is, the projection of the first bending portion 102 along the thickness direction of the first bending portion 102 and the projection of the second opening area 122 arranged on the first bending portion 102 along the thickness direction of the first bending portion 102 at least partially overlap.

[0058] Specifically, for each first bending portion 102 having a second opening area 122, the width w of the second opening area 122 thereon is 2 It can be less than, equal to, or greater than the width w of the first bending portion 102 102 , the width w of the second opening area 122 2 It refers to the width of the second opening area 122 along the bending direction of the first bending portion 102 where it is located. The width w of the first bending portion 102 102 It refers to the width of the first bending portion 102 along the bending direction of the first bending portion 102. Figure 1 As shown), the width w of the second opening area 122 2 refers to the width of the second region 122 in the length direction of the first electrode 1, and the width w of the first bent portion 102 102 It refers to the width of the first bent portion 102 in the length direction of the first pole piece 1 .

[0059] For example, when the width w of the second opening area 122 is 2 Greater than the width w of the first bending portion 102 102 When the second opening area 122 covers the first bending portion 102 and exceeds the first bending portion 102, that is, the second opening area 122 at both opposite ends in the bending direction of the first bending portion 102 extends to the first straight portion 101 respectively; when the width w of the second opening area 122 is 2 Less than or equal to the width w of the first bending portion 102 102 , the second opening area 122 can be completely located in the first bending portion 102 where it is located, that is, the projection of the first bending portion 102 along the thickness direction of the first bending portion 102 covers the projection of the second opening area 122 thereon along the thickness direction of the first bending portion 102 (the projection is perpendicular to the thickness direction of the first bending portion 102), wherein, when the w of the second opening area 122 2 is substantially equal to the width w of the first bending portion 102 102 When the second opening area 122 is substantially overlapped with the first bending portion 102 .

[0060] In some embodiments, the width w of the second opening area 122 is 2 It may be in the range of 2 mm to 20 mm, for example, 2 mm, 5 mm, 8 mm, 10 mm, 13 mm, 15 mm, 18 mm, 20 mm or a range consisting of any two of them.

[0061] Continue to refer Figure 3 and Figure 4 The first bending portion 102 is located on at least one side of the battery cell 4 in the second direction y, that is, the battery cell 4 has the first bending portion 102 on at least one side in the second direction y, and the second opening area 122 is arranged on the first bending portion 102, so that the second opening area 122 exists in the edge area of ​​at least one side of the battery cell 4 in the second direction.

[0062] Specifically, the battery cell 4 has a third side 43 and a fourth side 44 relative to each other in the second direction y, wherein at least one of the third side 43 and the fourth side 44 of the battery cell 4 has a first bending portion 102, so that at least one of the edge area of ​​the third side 43 and the edge area of ​​the fourth side 44 has a second opening area 122.

[0063] Generally, there are first bending portions 102 on both sides of the battery cell 4 on the second direction y (i.e., both the third side 43 and the fourth side 44 of the battery cell 4 have the first bending portion 102), wherein the first bending portion 102 on the third side 43 and the first bending portion 102 on the fourth side 44 are respectively provided with second opening areas 122, so that the edge areas of the third side 43 and the edge areas of the fourth side 44 of the battery cell 4 respectively have second opening areas 122 (i.e., both the edge areas of the battery cell 4 on the two sides on the second direction y have second opening areas 122), which is beneficial to further improve the heat dissipation performance of the battery cell 4.

[0064] In addition, the second pole piece 2 includes at least one second straight portion 201 and a second bent portion 202 connected to the second straight portion 201. The second straight portion 201 of the second pole piece 2 corresponds to the first straight portion 101 of the first pole piece 1. The two are generally stacked, and the second bent portion 202 of the second pole piece 2 corresponds to the first bent portion 102 of the first pole piece 1.

[0065] Specifically, Figure 3As shown, the battery cell 4 is a wound battery cell 4, that is, the first pole piece 1 and the second pole piece 2 respectively have a wound structure, wherein the first pole piece 1 includes a plurality of first straight portions 101, and a first bending portion (arc area) 102 connected between every two adjacent first straight portions 101, and the first pole piece 1 is bent through the first bending portion 102 to form a wound structure; the second pole piece 2 includes a plurality of second straight portions 201, and a second bending portion (arc area) 202 connected between every two adjacent second straight portions 201, and the second pole piece 2 is bent through the second bending portion 202 to form a wound structure. Among them, the first straight portions 101 of the first pole piece 1 and the second straight portions 201 of the second pole piece 2 are stacked, and the first straight portions 101 and the second straight portions 201 are staggered, the first straight portions 101 and the second straight portions 201 are separated by the diaphragm 3, and the first bent portion 102 and the second bent portion 202 are separated by the diaphragm 3.

[0066] Continue to refer Figure 3 The first pole piece 1 includes a plurality of first bending portions 102, and correspondingly, the second pole piece 2 includes a plurality of second bending portions 202, part of the first bending portions 102 and part of the second bending portions 202 are located on one side of the battery cell 4 in the second direction y (the third side 43), and another part of the first bending portion 102 and another part of the second bending portion 202 are located on the other side of the battery cell 4 in the second direction y (the fourth side 44).

[0067] The second opening area 122 is provided on at least one first bending portion 102 , and preferably, the first active material layer 120 on each first bending portion 102 having the first active material layer 120 in the first electrode sheet 1 is provided with a second opening area 122 .

[0068] Generally, there are multiple first bend portions 102 located on the third side 43 of the battery cell 4, wherein at least one first bend portion 102 located on the third side 43 of the battery cell 4 is provided with a second opening area 122, and preferably each first bend portion 102 with a first active material layer 120 located on the third side 43 of the battery cell 4 is provided with a second opening area 122; there are multiple first bend portions 102 located on the fourth side 44 of the battery cell 4, wherein at least one first bend portion 102 located on the fourth side 44 of the battery cell 4 is provided with a second opening area 122, and preferably each first bend portion 102 with a first active material layer 120 located on the fourth side 44 of the battery cell 4 is provided with a second opening area 122.

[0069] In some specific embodiments, Figure 4As shown, the edge regions of the battery cell 4 on both sides of the first direction x respectively have first opening regions 121 (the edges of the first active material layer 120 on both sides of the first direction x respectively have first opening regions 121), and the edge regions of the battery cell 4 on both sides of the second direction y respectively have second opening regions 122 (the first bending portions 102 on both sides of the battery cell 4 on the second direction y respectively have second opening regions 122). In this way, the edges of the battery cell 4 are surrounded by opening regions 12, which is beneficial to further improve the heat dissipation effect of the battery cell 4. Specifically, as Figure 4 As shown, in the projection of the battery cell 4 along the thickness direction of the battery cell 4 (the projection is perpendicular to the thickness direction of the battery cell 4), there are opening areas 12 on all four edges of the battery cell 4, that is, there are recesses 100 on all four edges of the battery cell 4. The heat flow inside the battery is as follows: Figure 4 As shown by arrow A in the figure, the portion of the package 5 where the pole ear protrudes is relatively weak. When the temperature inside the battery reaches a high temperature, the heat inside the battery (carried by the gas generated by factors such as the side reactions of the electrode material and the electrolyte) will leak out from the portion where the pole ear protrudes, thereby avoiding problems such as battery fire.

[0070] In some embodiments, in the first active material layer 120, the distance L between two adjacent second opening areas 122 is 4 Can satisfy 0<L 4 ≤100mm, L 4 For example, the range is 0.5 mm, 1 mm, 5 mm, 10 mm, 15 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm or any two thereof.

[0071] Specifically, Figure 1 As shown, the distance L between two adjacent second opening areas 122 4 It refers to the distance between the two adjacent second opening areas 122 in the length direction of the first pole piece 1 before the first pole piece 1 is wound; after the first pole piece 1 forms a wound structure (such as Figure 3 As shown), the distance L between two adjacent second opening areas 122 4 It is the distance between the second opening areas 122 of two adjacent first bending portions 102 in the winding direction (ie, one of the two adjacent first bending portions 102 is located at the third side of the battery cell 4 and the other is located at the fourth side of the battery cell 4 ).

[0072] Specifically, in the first electrode plate 1 , the length of the first opening area 121 is substantially equal to the length of the first active material layer 120 , that is, the first opening area 121 extends continuously from one end of the first active material layer 120 in the length direction to the other end of the first active material layer 120 in the length direction.

[0073] Specifically, the length direction of the second opening area 122 is parallel to the length direction of the first bending portion 102, and the second opening area 122 may not be connected to the first opening area 121, that is, there is a main body area 11 between the two (that is, the second opening area 122 and the first opening area 121 are separated by the main body area 11), or, the second opening area 122 may be connected to the first opening area 121 (directly in contact), that is, there is no main body area 11 between the two whose surface is not distributed with the recessed portion 100. Relatively speaking, when the second opening area 122 is connected to the first opening area 121, a connected heat dissipation channel is formed in the edge area of ​​the first bending portion 102 and the first active material layer 120 in the first direction x, which is more conducive to improving the heat dissipation effect.

[0074] In some embodiments, Figure 1 As shown, when the first active material layer 120 has first opening areas 121 on the edges on both sides of the opposite sides in the first direction x, for any second opening area 122, one end thereof is connected to the first opening area 121 on the edge on one side of the first active material layer 120, and the other end is connected to the first opening area 121 on the edge on the other side of the first active material layer 120.

[0075] Specifically, on the first pole piece 1 , the main area 11 is the other area except the opening area 12 , and the surface of the main area 11 is not pore-formed, that is, the surface of the main area 11 is not provided with the above-mentioned recess 100 , so that the porosity of the main area 11 is smaller than the porosity of the opening area 12 .

[0076] Specifically, the first pole piece 1 may have a main body region 11 (ie, the main body regions 11 on the first pole piece 1 are continuously arranged), or, as Figure 1 As shown, the first pole piece 1 has a plurality of main body regions 11 , and every two main body regions 11 are separated by an opening region 12 .

[0077] Specifically, if Figure 1 As shown, before the first electrode sheet 1 is wound, the main body regions 11 are distributed along the length direction of the first electrode sheet 1, and a second opening region 122 is provided between every two adjacent main body regions 11 (that is, every two adjacent main body regions 11 are separated by the second opening region 122), and each main body region 11 has first opening regions 121 on both sides opposite to each other in the first direction x. At this time, the spacing L of the first opening regions 121 provided on the first active material layer 120 on both sides opposite to each other in the first direction x is 3 is also the width of the main body area 11 in the first direction x. The distance L between the two adjacent second opening areas 122 is 4 It is also the length of the main body region 11 between the two adjacent second opening regions 122 in the length direction of the first pole piece 1 .

[0078] In some embodiments, the first opening area 121 is connected to the second opening area 122, and the area S of the overlapping region 123 of the two is 123 The area S of the first opening area 121 121 Satisfy 0<S 123 / S 121 ≤40%, S 123 / S 121 For example, a range of 0.1%, 0.5%, 1%, 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or any two thereof is beneficial to improving the heat dissipation performance of the battery cell while maintaining a higher energy density of the battery cell.

[0079] Specifically, the first opening area 121 includes a first sub-opening area located at the first straight portion 101, and a second sub-opening area located at the first bending portion 102. The second sub-opening area is connected to the second opening area 122, and the two form an overlapping area 123. The width of the overlapping area 123 in the bending direction of the first bending portion 102 is equal to the width of the second opening area 122 in the bending direction of the first bending portion 102. The width of the overlapping area 123 in the first direction x is equal to the width of the first opening area 121 (second sub-opening area) in the first direction x. The overlapping area 123 can specifically be the second sub-opening area.

[0080] Generally, the total area of ​​the main region 11 in the first active material layer 120 is greater than or equal to the total area of ​​the opening region 12 (the total area of ​​the main region 11 accounts for 50% or more of the total area of ​​the first active material layer 120). In some preferred embodiments, the total area of ​​the opening region 12 accounts for 10% to 50% of the total area of ​​the first active material layer 120, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% or a range composed of any two of them, which is beneficial to improve the heat dissipation performance of the battery cell 4 while maintaining a high energy density of the battery. In this way, it is beneficial to improve the heat dissipation effect while avoiding excessive capacity loss due to excessive perforation area.

[0081] Among them, the total area of ​​the main area 11 refers to the sum of the areas of all the main areas 11 in the first pole piece 1, and the area of ​​each main area 11 refers to the surface area of ​​the main area 11 (the first active material layer 120 without the recess 100) (that is, the projection area of ​​the main area 11 on the surface of the first current collector 110); the total area of ​​the opening area 12 refers to the sum of the areas of all the opening areas 12 in the first pole piece 1, and the area of ​​each opening area 12 refers to the surface area of ​​the opening area 12 (the first active material layer 120 with recesses 100 distributed on the surface) (that is, the projection area of ​​the opening area 12 on the surface of the first current collector 110), and the total area of ​​the first active material layer = the total area of ​​the main area 11 + the total area of ​​the opening area 12.

[0082] Specifically, the battery of the embodiment of the utility model can be a soft-package battery, that is, the package body 5 is a soft-package film, which can be a conventional soft-package material in the art, for example, the package body 5 includes an aluminum-plastic film, but is not limited thereto.

[0083] In the embodiment of the utility model, the first direction x intersects with the second direction y, and the two can be perpendicular to each other. The first direction x, the width direction of the first pole piece 1, and the width direction of the second pole piece 2 are parallel to each other. When forming the wound battery cell 4, the first pole piece 1, the diaphragm 3 and the second pole piece 2 are stacked in sequence to form a laminated structure, and then wound along the length direction of the laminated structure (also the length direction of the first pole piece 1 and the second pole piece 2).

[0084] Exemplarily, the width direction of the battery cell 4 is parallel to the first direction x, and the length direction of the battery cell 4 is parallel to the second direction y; or, the length direction of the battery cell 4 is parallel to the first direction x, and the width direction of the battery cell 4 is parallel to the second direction y.

[0085] For example, Figure 1 : is a schematic diagram of the structure of the first pole piece 1 before winding. Before winding, the width direction of the first pole piece 1 is parallel to the first direction x, and the length direction of the first pole piece 1 is parallel to the second direction y. When winding, the first pole piece 1 is wound along the length direction. After the first pole piece 1 is wound (that is, the first pole piece 1 is formed as shown in FIG. Figure 3 In the wound structure of the wound battery cell 4 shown in the figure, the length direction of the wound battery cell 4, the length direction of the first straight portion 101, the length direction of the second straight portion 201, and the second direction y are parallel to each other, and the width direction of the wound battery cell 4, the width direction of the first straight portion 101, the width direction of the second straight portion 201, and the first direction x are parallel to each other.

[0086] In addition, the second direction y intersects with the third direction z, and the two can be specifically perpendicular to each other; the first direction x intersects with the third direction z, and the two can be specifically perpendicular to each other, and the third direction z, the thickness direction of the battery cell 4, the thickness direction of the battery, the thickness direction of the first pole sheet 1, the thickness direction of the second pole sheet 2, the thickness direction of the first pole ear 13, the thickness direction of the second pole ear 23, the direction along the first main body 511 to the second main body 521, and the direction along the first connecting portion 512 to the second connecting portion 522 are parallel to each other.

[0087] Specifically, the porosity of the open area 12 is greater than the porosity φ of the main area 11. 0 , that is, the porosity φ of the first opening area 121 1 , the porosity φ of the second opening area 122 2 are respectively greater than the porosity φ of the main region 11 0 (φ 1 >φ 0,φ 2 >φ 0 ), which is beneficial to improve the heat dissipation performance of the battery cell while further maintaining the high energy density and capacity of the battery. Among them, the porosity of the first opening area 121 is φ 1 The porosity φ of the second open area 122 may be greater than, equal to, or less than 2 .

[0088] Specifically, the porosity φ of the main region 11 is 0 The ratio of the porosity of the open area 12 (φ 0 / φ 1 ,φ 0 / φ 2 ) may be greater than or equal to 0.1, further may be greater than or equal to 0.2, specifically may be in the range of 0.2 to 0.8, for example, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or any two thereof. 0 / φ 1 Can be greater than, equal to, or less than φ 0 / φ 2 .

[0089] In some embodiments, the porosity of the open area 12 and the porosity of the main area 11 are φ 0 The difference (φ 1 -φ 0 ,φ 2 -φ 0 ) may be greater than or equal to 5%, specifically 5% to 50%, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% or any two thereof. 1 -φ 0 Can be greater than, equal to, or less than φ 2 -φ 0 .

[0090] Specifically, the porosity φ of the main region 11 is 0 , the porosity φ of the first opening area 121 1 , the porosity φ of the second opening area 122 2 Can satisfy 0.1≤φ 0 / (φ 1 +φ 2 )≤0.53, preferably 0.1≤φ 0 / (φ 1 +φ 2 )≤0.48, more preferably 0.2≤φ 0 / (φ 1 +φ 2)≤0.4, thus, the opening area 12 has a larger porosity, which is conducive to timely dissipating the gas and heat generated at the interface between the first pole piece 1 and the electrolyte into the cavity 50 of the package 5, avoiding the local accumulation of heat in the battery cell 4 and causing local overheating, thereby further improving the thermal stability and other performance of the battery while maintaining a larger energy density of the battery.

[0091] For example, φ 0 / (φ 1 +φ 2 ) can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.36, 0.4, 0.45, 0.48, 0.5, 0.52, 0.53 or a range consisting of any two of them.

[0092] In some embodiments, the porosity φ of the main region 11 is 0 It may be in the range of 12% to 30%, for example, 12%, 15%, 18%, 20%, 23%, 25%, 28%, 30% or any two thereof.

[0093] In some embodiments, the porosity of the first open area 121 is 1 It can be 14% to 50%, preferably 15% to 30%. The porosity of the second opening area 122 is φ 2 It may be 14% to 50%, preferably 15% to 30%.

[0094] For example, the porosity (φ 1 ,φ 2 ) can be 14%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 35%, 40%, 45%, 50% or a range consisting of any two thereof.

[0095] In the embodiment of the utility model, the diaphragm 3 can be bonded to the first pole piece 1 and the second pole piece 2 respectively, that is, one side of the diaphragm 3 is bonded to the first pole piece 1 and the other side is bonded to the second pole piece 2. This is beneficial to shorten the interface distance between the positive and negative electrodes, shorten the path of ions (such as lithium ions of lithium-ion batteries) when they are embedded and de-embedded between the positive and negative electrodes, thereby improving the charging and discharging performance of the battery. At the same time, it is also beneficial for the diaphragm 3 to be more stably spaced between the positive and negative electrodes, improving the structural stability of the battery cell 4, and further avoiding the risk of short circuit between the positive and negative electrodes.

[0096] Generally, in the first pole piece 1, the opening area 12 is distributed with recesses 100, and the adhesion force (peeling force) between the diaphragm 3 and the opening area 12 is smaller than the adhesion force (peeling force) between the diaphragm 3 and the main area 11. In the wound battery cell 4, the adhesion force between the diaphragm 3 and the first opening area 121 and the adhesion force between the diaphragm 3 and the second opening area 122 are both smaller than the adhesion force between the diaphragm 3 and the main area 11.

[0097] In the embodiment of the utility model, the peeling force may specifically be a 180° peeling force measured by a 180° peeling force test.

[0098] Specifically, the diaphragm 3 may include a substrate layer 33, a first adhesive layer 31 located on one side of the substrate layer 33, and a second adhesive layer 32 located on the other side of the substrate layer 33, the first adhesive layer 31 is bonded to the first pole piece 1, and the second adhesive layer 32 is bonded to the second pole piece 2, that is, the first adhesive layer 31 and the second adhesive layer 32 are respectively the surface layers on the opposite sides of the diaphragm 3, and the diaphragm 3 is bonded to the first pole piece 1 through the first adhesive layer 31 (that is, the first adhesive layer 31 is bonded to the first pole piece 1), and is bonded to the second pole piece 2 through the second adhesive layer 32 (that is, the second adhesive layer 32 is bonded to the second pole piece 2).

[0099] In addition, the diaphragm 3 may further include a ceramic layer 34, which may be located between the first adhesive layer 31 and the substrate layer 33, that is, the diaphragm 3 includes a first adhesive layer 31, a ceramic layer 34, a substrate layer 33 and a second adhesive layer 32 stacked in sequence. By introducing the ceramic layer 34, the heat shrinkage resistance of the diaphragm 3 can be improved, thereby avoiding the diaphragm 3 from shrinking due to heat and the resulting short circuit of the positive and negative electrodes.

[0100] Among them, the substrate layer 33 can be a conventional membrane 3 material in the field, for example, the substrate layer 33 includes one of a polypropylene membrane 3 (PP), a polyethylene membrane 3 (PE), a polypropylene / polyethylene (PP / PE) double-layer composite film, a polyimide electrospinning membrane 3 (PI), a polypropylene / polyethylene / polypropylene (PP / PE / PP) three-layer composite film, and a cellulose non-woven fabric membrane 3.

[0101] In addition, the ceramic layer 34 may include aluminum oxide and / or boehmite. Further, the ceramic layer 34 may include an aluminum oxide layer and / or a boehmite layer.

[0102] In addition, the first adhesive layer 31 may include a PVDF layer, that is, the material of the first adhesive layer 31 is PVDF, and it is mainly formed of PVDF.

[0103] In addition, the second adhesive layer 32 may include a PVDF layer, that is, the material of the second adhesive layer 32 is PVDF, and it is mainly formed of PVDF.

[0104] In some embodiments, the aperture D of the concave portion 100 of the first opening area 121 is 1 and the thickness H of the ceramic layer 34 of the diaphragm 3 34 Can satisfy 1≤D 1 / H 34 ≤162, preferably 1.2≤D 1 / H 34 ≤160, more preferably 2≤D1 / H 34 ≤150.

[0105] In addition, the aperture D of the concave portion 100 of the second opening area 122 is 2 and the thickness H of the ceramic layer 34 of the diaphragm 3 34 Can satisfy 1≤D 2 / H 34 ≤162, preferably 1.2≤D 2 / H 34 ≤160, more preferably 2≤D 2 / H 34 ≤150.

[0106] Among them, D 1 / H 34 Can be greater than, equal to, or less than D 2 / H 34 .

[0107] For example, D 1 / H 34 , D 2 / H 34 Each independently may be 2, 5, 10, 20, 30, 40, 50, 70, 90, 100, 120, 130, 150 or a range consisting of any two thereof.

[0108] In addition, the aperture D of the concave portion 100 of the first opening area 121 is 1 and the thickness H of the first adhesive layer 31 of the diaphragm 3 11 Can satisfy 2.5≤D 1 / H 31 ≤320, preferably 2.5≤D 1 / H 31 ≤300.

[0109] In addition, the aperture D of the concave portion 100 of the second opening area 122 is 2 and the thickness H of the first adhesive layer 31 of the diaphragm 3 31 Can satisfy 2.5≤D 2 / H 31 ≤320, preferably 2.5≤D 2 / H 31 ≤300.

[0110] Among them, D 1 / H 31 Can be greater than, equal to, or less than D 2 / H 31 .

[0111] For example, D 1 / H 31 , D 2 / H 31 Each independently may be 2, 2.5, 5, 10, 30, 50, 80, 100, 130, 150, 180, 200, 230, 250, 280, 300, 320 or a range consisting of any two of them.

[0112] In a high temperature environment such as a furnace temperature test, gas and heat will be generated at the interface between the diaphragm 3 and the first pole piece 1. By setting the opening area 12 in the first pole piece 1 and controlling the aperture of the concave portion 100 of the opening area 12 and the thickness ratio of the first adhesive layer 31 and the ceramic layer 34 within the above range, the opening area 12 of the first pole piece 1 and the diaphragm 3 have a relatively small adhesion force, thereby facilitating the gas to be discharged to the outside of the battery cell 4. At the same time, the heat generated by factors such as side reactions between the electrode material and the electrolyte and other components inside the battery is carried and discharged by the gas, thereby avoiding heat accumulation inside the battery and thermal safety problems such as fire caused thereby, thereby improving the thermal safety of the battery; in addition, if D / H 34 and / or D / H 31 If the aperture D is too large, the active material of the first electrode 1 will be lost more, resulting in a greater loss of capacity, affecting the energy density of the battery. 34 and / or D / H 31 If the diameter of the concave portion 100 on the surface of the first pole piece 1 is too small, the improvement of the heat dissipation effect of the battery cell 4 is limited. Therefore, by controlling the aperture of the concave portion 100 in the opening area 12 and the thickness ratio of the first glue layer 31 and the ceramic layer 34 within the above range, it is beneficial to achieve a balance between battery thermal safety and energy density.

[0113] Specifically, the thickness of the base material layer 33 may be 2 to 20 μm, for example, 2 μm, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm or a range consisting of any two thereof.

[0114] Specifically, the thickness of the first adhesive layer 31 is 0.5-4 μm, for example, 0.5 μm, 1 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or any two thereof.

[0115] Specifically, the thickness of the second adhesive layer 32 is 0.5-4 μm, for example, 0.5 μm, 1 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or any two thereof.

[0116] Specifically, the thickness of the ceramic layer 34 is 1 to 5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or a range consisting of any two thereof.

[0117] In some embodiments, the first electrode sheet 1 is a positive electrode sheet, the second electrode sheet 2 is a negative electrode sheet, and accordingly, the first active material layer 120 is a positive electrode active material layer, the first active material is a positive electrode active material, the first current collector 110 is a positive electrode current collector, the second active material layer 220 is a negative electrode active material layer, the second active material is a negative electrode active material, and the second current collector 210 is a negative electrode current collector.

[0118] In other embodiments, the first electrode sheet 1 is a negative electrode sheet, and the second electrode sheet 2 is a positive electrode sheet. Accordingly, the first active material layer 120 is a negative electrode active material layer, the first active material is a negative electrode active material, the first current collector 110 is a negative electrode current collector, the second active material layer 220 is a positive electrode active material layer, the second active material is a positive electrode active material, and the second current collector 210 is a positive electrode current collector.

[0119] After further research, it is preferred that the first electrode sheet 1 is a positive electrode sheet. In this way, while improving the heat dissipation performance of the battery, it can also have at least the following advantages: (1) According to the inventor's research, the temperature at which the positive electrode material and the electrolyte undergo side reactions is usually lower than the temperature at which the negative electrode material and the electrolyte undergo side reactions. Therefore, by providing an opening area 12 in the positive electrode active material layer, the heat dissipation performance of the positive electrode sheet is improved, the risk of side reactions between the positive electrode material such as the positive electrode active material and the electrolyte can be reduced, and the safety and thermal stability of the battery can be further improved; (2) By providing an opening area 12 on the positive electrode sheet, the N / P (ratio of the negative electrode surface capacity N to the positive electrode surface capacity P) corresponding to the opening area 12 in the battery cell 4 can be reduced, thereby suppressing the problem of negative electrode lithium plating and further improving the safety and other performance of the battery; (3) Compared with the negative electrode sheet, the bonding force between the positive electrode sheet and the diaphragm 3 is lower. Providing an opening area 12 on the positive electrode sheet is more conducive to improving the heat dissipation performance of the battery cell 4.

[0120] Specifically, the surface of the negative electrode active material layer has no recesses 100, that is, the negative electrode active material layer has not been perforated, that is, the negative electrode active material layer has no opening area with recesses 100 distributed on the surface. If the negative electrode sheet is perforated, the electrical contact area between the electrolyte and the negative electrode will be larger, and more heat will be generated in a high temperature environment (such as a furnace temperature test process), making failure more likely to occur.

[0121] Specifically, the recess 100 may be a hole or a groove (a continuous linear groove), for example, a circular hole, but is not limited thereto.

[0122] Specifically, the opening area 12 is formed by forming holes in a partial area of ​​the first active material layer 120 (such as the edge area and the arc area after the wound battery cell 4 is made), and a plurality of recesses 100 are distributed on its surface. The surface of each opening area 12 (such as each first opening area 121, each second opening area 122, etc.) (that is, the side of the opening area 12 away from the first current collector 110) is distributed with a plurality of recesses 100, and these recesses 100 are basically evenly distributed in the opening area 12 where they are located. The surface (for example, the surface of the opening area 12 is basically arranged in an array (matrix distribution)), these recesses 100 all extend from the surface of the opening area 12 where they are located toward the inside of the opening area 12 where they are located, and the depth direction of the recess 100 is basically parallel to the thickness direction of the opening area 12. The depth of the recess 100 may be less than the thickness of the opening area 12, that is, the recess 100 does not penetrate the opening area 12, that is, there is a first active material layer 120 between the recess 100 and the first current collector 110.

[0123] Specifically, in the first opening area 121 , the depth of the recess 100 is smaller than the thickness of the first opening area 121 ; and in the second opening area 122 , the depth of the recess 100 is smaller than the thickness of the second opening area 122 .

[0124] Generally, the thickness of the opening area 12 is smaller than the thickness of the main body area 11 , and the thickness of the first opening area 121 and the thickness of the second opening area 122 are substantially the same, and are both smaller than the thickness of the main body area 11 .

[0125] Specifically, the thickness H of the first pole piece 1 corresponding to the main region 11 is 0 , the thickness H of the first electrode sheet 1 corresponding to the first opening area 121 121 , the thickness H of the first pole piece 1 corresponding to the second opening area 122 122 Can satisfy 0.6≤H 0 / (H 121 +H 122 )≤0.9,H 0 / (H 121 +H 122 ) for example, is in the range of 0.6, 0.7, 0.8, 0.9 or any two thereof, so that it is beneficial for the main area 11 and the opening area 12 to form a step effect, thereby improving the heat dissipation effect, and at the same time, reducing the battery capacity density loss and maintaining a higher battery capacity.

[0126] In some embodiments, the thickness H of the first pole piece 1 corresponding to the main region 11 is 0 It can be 30 to 140 μm, for example, 30 μm, 50 μm, 70 μm, 90 μm, 100 μm, 120 μm, 140 μm or any two thereof, which is beneficial to improve both the heat dissipation performance and the energy density of the battery.

[0127] In some embodiments, the thickness H of the first electrode plate 1 corresponding to the first opening area 121 is 121 It can be 20 to 130 μm, for example, 20 μm, 40 μm, 50 μm, 60 μm, 70 μm, 90 μm, 100 μm, 120 μm, 130 μm or a range composed of any two of them, which is beneficial to improve both the heat dissipation performance and the energy density of the battery.

[0128] In some embodiments, the thickness H of the first electrode 1 corresponding to the second opening area 122 is 122 It can be 20 to 130 μm, for example, 20 μm, 40 μm, 50 μm, 60 μm, 70 μm, 90 μm, 100 μm, 120 μm, 130 μm or a range composed of any two of them, which is beneficial to improve both the heat dissipation performance and the energy density of the battery.

[0129] In the embodiment of the utility model, the thickness (H) of the first pole piece 1 corresponding to each of the above regions is 0 , H 121 , H 122 ) is substantially equal to the sum of the thickness of the first current collector 110 in the region and the total thickness of the first active material layer 120 located on the first current collector 110, wherein when the first active material layer 120 is provided on both the front and back sides of the first current collector 110, the total thickness of the first active material layer 120 located on the first current collector 110 refers to the sum of the thickness of the first active material layer 120 located on both the front and back sides of the first current collector 110. 0 For example, H 0 =thickness of the first active material layer 120 located on one side of the first current collector 110 +thickness of the first current collector 110 +thickness of the first active material layer 120 located on the other side of the first current collector 110 .

[0130] In some embodiments, the depth of the recess 100 in the opening area 12 (the depth H of the recess 100 in the first opening area 121) is 1 , the depth H of the recess 100 in the second opening area 122 2 ) can be in the range of 2 to 30 μm, for example, 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm or a range consisting of any two of them.

[0131] In addition, in the opening area 12, the aperture D of the recess 100 (the aperture D of the recess 100 in the first opening area 121) 1 , the aperture D of the concave portion 100 in the second opening area 122 2) can be 2 to 330 μm, preferably 10 to 150 μm, for example, 2 μm, 5 μm, 10 μm, 30 μm, 50 μm, 70 μm, 90 μm, 100 μm, 120 μm, 140 μm, 150 μm, 180 μm, 200 μm, 230 μm, 250 μm, 280 μm, 300 μm, 330 μm or a range consisting of any two of them, which is beneficial for improving the heat dissipation performance of the battery cell 4 while maintaining a higher energy density of the battery cell 4.

[0132] In addition, in the opening area 12, the hole spacing of the recesses 100 (the hole spacing L of the recesses 100 in the first opening area 121) is 1 , the hole spacing L of the recessed portion 100 in the second opening area 122 2 ) can be 20 to 3000 μm, for example, 20 μm, 50 μm, 80 μm, 100 μm, 130 μm, 150 μm, 180 μm, 200 μm, 230 μm, 250 μm, 280 μm, 300 μm, 500 μm, 800 μm, 1000 μm, 1300 μm, 1500 μm, 1800 μm, 2000 μm, 2300 μm, 2500 μm, 2800 μm, 3000 μm or the range of any two thereof, preferably 20 to 300 μm.

[0133] In the embodiment of the utility model, the hole spacing (such as L 1 , L 2 ) refers to the distance between the centers of two adjacent recesses 100. For example, if the recess 100 is a circular hole (i.e., the projection of the recess 100 on the surface of the first current collector 110 is a circle), the center of the recess 100 is the center of the recess 100 (also the center of the projection of the recess 100 on the surface of the first current collector 110).

[0134] In an embodiment of the utility model, the positive electrode active material may include a positive electrode lithium-containing active material, which may specifically include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium manganese oxide, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, lithium iron phosphate (LFP), lithium nickel manganese oxide, etc., and the positive electrode current collector may include aluminum foil and other conventional positive electrode current collectors in the field.

[0135] In the embodiment of the utility model, the negative electrode active material may include graphite materials and / or silicon-based materials. Among them, the silicon-based material may include silicon oxide and / or silicon-carbon materials, etc., the graphite material may include graphite and / or graphite-based composite materials, the graphite-based composite materials include graphite, and a coating material present on the surface of graphite, and the coating material may include amorphous carbon (amorphous carbon), for example, the graphite-based material is graphite coated with amorphous carbon (that is, the coating material in the graphite-based composite material is amorphous carbon).

[0136] Specifically, the above-mentioned graphite may include artificial graphite and / or natural graphite.

[0137] In some embodiments, the negative electrode active material includes graphite coated with amorphous carbon, which is beneficial for improving both the fast charging performance and thermal stability of the battery.

[0138] Specifically, the greater the amorphous carbon content in the graphite-based composite material (i.e., the greater the amount of amorphous carbon coating), the more conducive it is to improving the fast charging performance of the battery. However, amorphous carbon is prone to side reactions with the electrolyte. The greater the amount of amorphous carbon coating, the more likely it is to reduce the thermal stability of the graphite-based composite material, which in turn reduces the thermal stability of the battery. Therefore, after the components such as the positive electrode sheet and the negative electrode sheet of the prior art are assembled into a battery, it is often difficult to balance the fast charging performance and thermal stability of the battery. According to the inventor's research, in the embodiment of the utility model, the above-mentioned opening area 12 is provided in the first electrode sheet 1 (such as the positive electrode sheet), which can improve the heat dissipation performance of the battery, improve the thermal stability of the battery, and avoid the risk of battery fire. Therefore, when the amorphous carbon-coated graphite is used as the negative electrode active material, the embodiment of the utility model can improve the fast charging performance of the battery while improving the thermal stability of the battery, that is, the embodiment of the utility model can improve the thermal stability of the fast charging battery, effectively overcoming the defect that the fast charging performance and thermal stability of the battery in the prior art are difficult to balance.

[0139] In some embodiments, the negative electrode active material layer includes a silicon-based material, which is beneficial for improving the thermal stability of the battery while also improving the energy density and capacity of the battery.

[0140] Specifically, the mass content of the silicon-based material in the negative electrode active material layer can be 0.5% to 30%, for example, 0.5%, 1%, 3%, 5%, 8%, 10%, 15%, 20%, 25%, 30% or any two thereof.

[0141] Generally, when a silicon-containing negative electrode (i.e., a negative electrode sheet whose negative electrode active material layer includes a silicon-based material) is used, due to factors such as the presence of a large number of additives with poor thermal stability (such as FEC, etc.) in the electrolyte, it is easy to cause more heat to be generated inside the battery under high temperature environments such as furnace temperature testing, which is not conducive to the thermal stability of the battery. In the embodiment of the utility model, by providing an opening area 12 on the first pole piece 1, it is conducive to dissipating the heat inside the battery cell 4, thereby effectively solving the problem of poor thermal stability of batteries using silicon-containing negative electrodes.

[0142] The conductive agent and the binder in the above-mentioned positive electrode active material layer and the negative electrode active material layer can be conventional materials in the art. For example, the conductive agent includes at least one of conductive carbon black (SP), acetylene black, carbon nanotubes, conductive graphite, and graphene, and the binder includes at least one of polyvinylidene fluoride (PVDF), a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acid salt, carboxymethyl cellulose (CMC), polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene and styrene-butadiene rubber (SBR).

[0143] In the embodiment of the present invention, the positive electrode current collector may be a conventional positive electrode current collector in the art, such as aluminum foil; the negative electrode current collector may be a conventional negative electrode current collector in the art, such as copper foil, such as carbon-coated copper foil.

[0144] In addition, the battery also includes an electrolyte, which includes a solvent, a solute and an additive. The solvent may include an organic solvent, for example, one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), and ethyl propyl carbonate (EPC); the solute may include a lithium salt, and the lithium salt may include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ) lithium hexafluoroarsenate (LiAsF 6 ); the additive may include one or more of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), succinonitrile (SN), adiponitrile (ADN), and 1,3-propane sultone (PS).

[0145] Generally, in order to reduce the instability inside the battery under high voltage electrochemical system, the battery needs to be subjected to a hotbox test to test the thermal stability of the battery. The battery of the present utility model embodiment has good thermal stability, which can specifically meet 1<V 2 / V 1 ≤2, V 1 is the volume of the battery (volume before furnace temperature test), V 2 The battery is fully charged at a temperature of T 0 The volume of the environment after the holding time t (i.e. V 2 is the volume after furnace temperature test), 130℃≤T 0≤150℃, 55min≤t≤65min. Therefore, by arranging the first opening area 121 and the second opening area 122 in the first pole piece 1, a continuous heat dissipation channel is formed at the edges of the battery cell 4 in the first direction x and the second direction y, so that the heat dissipation capacity of the area around the battery cell 4 can be improved, so that the volume growth of the battery cell 4 after the furnace temperature test is significantly reduced, showing good thermal stability.

[0146] For example, V 2 / V 1 For example, the range is 1.005, 1.006, 1.008, 1.01, 1.1, 1.3, 1.5, 1.8, 2 or any two thereof.

[0147] In some embodiments, V 2 / V 1 ≤1.01, for example 1.005≤V 2 / V 1 ≤1.01.

[0148] In addition, the battery can also meet 0.5≤(T max -T 0 ) / C≤5, C is the capacity of the battery in Ah, T max The battery is fully charged at a temperature of T 0 The maximum temperature reached during the heat preservation process in the environment is 130℃≤T 0 ≤150℃,T max The unit is ℃.

[0149] For example, (T max -T 0 ) / C can be 0.5, 0.8, 1, 1.18, 1.2, 1.3, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or any two thereof, for example, 0.5≤(T max -T 0 ) / C≤1.

[0150] In specific implementation, the battery volume V can be tested first. 1 Then, the battery is placed in a heating device such as an oven and gradually heated from room temperature to the target temperature T 0 , then at the target temperature T 0 Keep warm for t, then measure the battery volume V 2 ; Wherein, the temperature in the heating device reaches T 0 After that, the battery will usually continue to heat up. The battery temperature can usually be tested by the temperature sensing line of the heating device to obtain the maximum temperature T reached by the battery during the insulation process. max .

[0151] In the embodiment of the utility model, the fully charged state of the battery is the state in which the battery is fully charged. In specific implementation, the battery can be charged to the upper limit voltage to complete the full charge of the battery (that is, the battery reaches the fully charged state), and then the furnace temperature test is performed.

[0152] In the embodiment of the utility model, the positive electrode sheet and the negative electrode sheet can be prepared by conventional methods in the field such as coating method. For example, taking the preparation process of the positive electrode sheet as an example, materials such as the positive electrode active material, the conductive agent and the binder can be placed in a solvent to form a positive electrode slurry. The solvent used includes, for example, N-methylpyrrolidone (NMP). The positive electrode slurry is then applied to the surface of the positive electrode collector. After drying, rolling and other processes, a positive electrode active material layer is formed on the surface of the collector to obtain a positive electrode sheet precursor. Then, a preset area on the surface of the positive electrode sheet precursor is punched to form an opening area 12 to obtain a positive electrode sheet.

[0153] In the embodiment of the utility model, the preset area on the surface of the positive electrode sheet precursor can be punched by conventional methods in the art, for example, laser drilling can be performed using a conventional laser punching machine in the art.

[0154] The battery of the embodiment of the utility model can be prepared by conventional methods in the art, for example, the positive electrode sheet and the negative electrode sheet are cut into pieces according to a preset shape and size; then, the positive electrode sheet, the separator 3 and the negative electrode sheet are stacked in sequence (the stacked structure formed is as shown in FIG. Figure 2 As shown), wound into a wound battery cell 4 (as shown Figure 3 The lithium-ion battery is obtained by packaging, baking, liquid injection (i.e., injecting electrolyte), forming, secondary sealing, sorting, and OCV (open circuit voltage test) the core. These steps / processes are conventional operations in the art and are not particularly limited thereto.

[0155] The present invention is further described below through specific embodiments.

[0156] Example 1

[0157] 1. Preparation of positive electrode

[0158] Adding conductive carbon black and carbon nanotubes to PVDF glue, stirring evenly, adding lithium cobalt oxide thereto, adding NMP thereto, stirring evenly, to obtain a positive electrode slurry;

[0159] The positive electrode slurry is coated on the front and back surfaces of the aluminum foil, and after baking and rolling, a positive electrode active material layer is formed on the front and back surfaces of the aluminum foil to obtain a positive electrode sheet precursor; wherein, in the positive electrode active material layer, the mass content of lithium cobalt oxide is 97.6%, the mass content of PVDF is 1.05%, and the sum of the mass content of conductive carbon black and carbon nanotubes is 1.35% (the mass ratio of conductive carbon black to carbon nanotubes is 1:1);

[0160] Laser drilling is performed on a preset area on the surface of the positive electrode precursor (the formed concave portion (hole) 100 does not penetrate the positive electrode active material layer) to form an opening area 12, thereby obtaining a positive electrode sheet (the structure of the positive electrode sheet is as follows Figure 1 shown).

[0161] 2. Preparation of negative electrode sheet

[0162] Graphite, conductive carbon black, SBR and CMC were mixed evenly in a mass ratio of 97.3:0.5:1.3:0.9, deionized water was added thereto, and after being evenly dispersed, a negative electrode slurry was prepared;

[0163] The negative electrode slurry is coated on the front and back surfaces of the carbon-coated copper foil, and after baking and rolling, a negative electrode active material layer is formed on the front and back surfaces of the carbon-coated copper foil to obtain a negative electrode sheet.

[0164] 3. Battery assembly

[0165] Cutting the positive electrode sheet and the negative electrode sheet into predetermined shapes and sizes;

[0166] Then, the positive electrode sheet, the separator 3 and the negative electrode sheet are stacked in sequence and wound into a wound battery cell 4 (winding core); the winding core is packaged with an aluminum-plastic film, and the lithium-ion battery is obtained after the processes of baking, liquid injection (i.e., injecting electrolyte), formation, secondary sealing, sorting and OCV.

[0167] The preparation process of the electrolyte is as follows: in parts by weight, in a glove box filled with argon (H 2 O<0.1ppm,O 2 <0.1ppm), 40 parts of EC, 40 parts of DEC, and 5 parts of FEC were evenly mixed, and then 10 parts of fully dried lithium hexafluorophosphate were quickly added thereto, and after dissolving, PS and VC (5 parts in total of PS and VC, the mass ratio of PS to VC is 1:1) were added to obtain an electrolyte.

[0168] like Figure 2 As shown, the diaphragm 3 is composed of a first adhesive layer 31, a ceramic layer 34, a substrate layer 33 and a second adhesive layer 32 which are stacked in sequence. The first adhesive layer 31 is bonded to the positive electrode sheet, and the second adhesive layer 32 is bonded to the negative electrode sheet. The first adhesive layer 31 is a PVDF layer with a thickness of 1 μm. The ceramic layer 34 is an aluminum oxide layer with a thickness of 2 μm. The substrate layer 33 is a PP / PE double-layer composite film with a thickness of 5 μm. The second adhesive layer 32 is a PVDF layer with a thickness of 1 μm.

[0169] like Figures 3 to 5As shown, a positive electrode tab (first tab 13) is provided on the positive electrode sheet, and a negative electrode tab (second tab 23) is provided on the negative electrode sheet. The positive electrode tab and the negative electrode tab extend out of the aluminum-plastic film from the same side of the battery in the first direction x (the width direction of the positive electrode sheet and the negative electrode sheet), and at the portion where the tabs extend out, the positive electrode tab and the negative electrode tab are respectively bonded to the aluminum-plastic film by tab glue 6.

[0170] Core structure Figure 3 As shown, the positive electrode sheet includes a plurality of first straight portions 101 and a first bent portion 102 connected between every two adjacent first straight portions 101. The width w of the first bent portion 102 is 102 It is about 10 mm; accordingly, the negative electrode sheet includes a plurality of second straight portions 201 and a second bent portion 202 connected between every two adjacent second straight portions 201 .

[0171] The structure of the positive electrode is as follows Figure 1 As shown, there are first opening areas 121 on both sides of the edges of the positive electrode active material layer in the width direction, and the length of the first opening area 121 is equal to the length of the positive electrode active material layer, so that there are first opening areas 121 on both sides of the battery cell 4 in the first direction x; a second opening area 122 is provided on each first bending portion 102 with the positive electrode active material layer, so that there are second opening areas 122 on both sides of the battery cell 4 in the second direction y, and the opposite ends of each second opening area 122 in the first direction x are respectively connected to the first opening area 121, that is, overlapping areas 123 are formed on both sides of the positive electrode active material layer in the first direction x.

[0172] Embodiment 2 to Embodiment 28: The difference from Embodiment 1 is that the width of each opening area 12, the diameter of the hole 100, the hole depth, the hole spacing and other parameters are different, see Table 1 and Table 2 for details. Except for the differences shown in Table 1 and Table 2, the other conditions are the same. Among them, unless otherwise specified, in each embodiment (such as Embodiment 1, Embodiment 4, Embodiment 22 to Embodiment 28, etc.), the length and / or width of the positive electrode sheet can be adjusted to adjust S 1 / S 121 .

[0173] Comparative Example 1: The difference from Example 1 is that the surface of the positive electrode active material layer is not perforated (ie, the opening area 12 is not provided), and the other conditions are the same as those of Example 1.

[0174] Comparative Example 2: The difference from Example 1 is that the opening area 12 is arranged in the middle area of ​​the first straight portion 101, and the first bent portion 102 and the edges on the opposite sides in the width direction of the positive electrode active material layer are not perforated (i.e., the opening area 12 is not arranged). That is, it is equivalent to translating the first opening area 121 of Example 1 to the first middle position of the positive electrode sheet in the width direction (first direction x) of the positive electrode sheet (in Tables 1 and 2, w 1 , D 1 , L 1 , H 1 The parameters are related parameters of the first opening area 121 translated to the first middle position), and the second opening area 122 of Example 1 is translated to the second middle position of the first straight portion 101 in the second direction y (in Tables 1 and 2, w 2 , D 2 , L 2 , H 2 Parameters such as are related parameters of the second opening area 122 translated to the second middle position); the other conditions are the same as those in Example 1.

[0175] Comparative Example 3: The difference from Example 1 is that only the first opening area 121 is provided on the first electrode sheet 1, and the second opening area 122 is not provided (that is, the positive electrode active material layer on the first bending portion 102 is not punched, and the second opening area 122 is not provided on the first bending portion 102), and the other conditions are the same as Example 1.

[0176] Comparative Example 4: The difference from Example 1 is that only the second opening area 122 is provided on the first electrode sheet 1, but the first opening area 121 is not provided (that is, no holes are punched on the opposite side edges in the width direction of the positive electrode active material layer, and the first opening area 121 does not exist on the opposite side edges in the width direction of the positive electrode active material layer), and the other conditions are the same as those in Example 1.

[0177] In each embodiment and comparative example, the thickness H of the main body region 11 is 0 , the thickness H of the first opening area 121 121 , the thickness H of the second opening area 122 122 , H 0 / (H 121 +H 122 ), the spacing L between the first opening areas 121 disposed on two opposite sides of the positive electrode active material layer in the first direction x 3 , the distance L between two adjacent second opening areas 122 4 , the total area S of the opening area 12 12 The total area of ​​the positive electrode active material layer S 0 The ratio (S 12 / S 0 ), the area S of the overlapping region 120 123The area S of the first opening area 121 121 Ratio (S 123 / S 121 ), the width w of the first opening area 121 1 , the aperture D of the hole 100 in the first opening area 121 1 , the hole spacing L of the holes 100 in the first opening area 121 1 , the depth H of the hole 100 in the first opening area 121 1 , the porosity φ of the first opening area 121 1 , the width w of the second opening area 122 2 , the aperture D of the hole 100 in the second opening area 122 2 , the hole spacing L of the holes 100 in the second opening area 122 2 , the depth H of the holes 100 in the second opening area 122 2 , the porosity φ of the second opening area 122 2 They are summarized in Tables 1 and 2.

[0178] In addition, in each embodiment and comparative example, the battery satisfies the V 2 / V 1 See Table 4, V 1 is the volume of the battery before the 130°C oven test, V 2 The volume of the battery in a fully charged state after being kept at 130°C for 60 minutes (V 2 is the volume of the battery after being tested at 130°C oven temperature), that is, T 0 =130℃, t=60min.

[0179] In addition, in each embodiment and comparative example, the battery satisfies (T max -T 0 ) / C see Table 4, C is the discharge capacity of the battery, the unit is Ah, T max The battery is fully charged at a temperature of T 0 The maximum temperature reached during the heat preservation process in an environment of (130°C). The test process of the discharge capacity C of the battery is as follows: the battery is charged to 4.5V at a constant current of 0.2C, and then charged to 0.025C at a constant voltage to complete the full charge of the battery; then the battery is discharged at a constant current of 0.2C until the battery voltage drops to 3V, and the capacity discharged during the discharge process is recorded as C.

[0180] In addition, the measured volume energy density (ED) loss rate of the battery is shown in Table 5. Wherein, ED = discharge capacity C × voltage platform / volume of battery cell 4, 4.5V system voltage platform is about 3.9V; in each embodiment and comparative example, ED loss rate (energy density loss rate) represents the percentage of the difference between the ED of the battery of the embodiment or comparative example and the ED of the battery of comparative example 1 to the ED of the battery of comparative example 1, that is, ED loss rate = (ED of the battery of the embodiment or comparative example - ED of the battery of comparative example 1) / ED of the battery of comparative example 1.

[0181] In addition, the pass rate of the furnace temperature test of the battery at different temperatures is shown in Table 5. The furnace temperature test process is as follows: the battery is placed at a temperature of T 1 Keep warm in the environment for 1h (T 1 The furnace temperature test pass rate = the number of batteries that passed / the total number of batteries that underwent furnace temperature test.

[0182] In addition, the lithium deposition on the negative electrode sheet was observed after the battery was directly charged at different rates (such as 3C direct charging, 4C direct charging and 5C direct charging in Table 5). The lithium deposition on the negative electrode sheet was measured after the battery was directly charged at different rates and is shown in Table 5. Among them, (1) the battery direct charging process means that there is only one charging current in the constant current process of the battery. Taking 3C direct charging as an example, the direct charging process is to charge the battery at 3C to the upper limit voltage and then switch to constant voltage charging to the cut-off current; (2) "mild lithium deposition" means that after the battery is disassembled, there is a small area of ​​lithium deposition on the surface of the negative electrode sheet, such as the edge areas on both sides of the negative electrode sheet in the width direction (i.e., the top and bottom edges), folds or single-sided areas, etc.; "severe lithium deposition" means that after the battery is disassembled, there is a large amount of lithium deposition on the surface of the negative electrode sheet, which is reflected in the performance, that is, the battery capacity is greatly attenuated.

[0183] Table 1

[0184]

[0185] Table 2

[0186]

[0187] Table 3

[0188]

[0189] Table 4

[0190]

[0191] It can be seen from Tables 1 to 5 that, relative to Comparative Examples 1 to 4, in Examples 1 to 28, a first opening area 121 is provided at the edge in the width direction of the positive electrode sheet, and a second opening area 122 is provided at the first bending portion 102 of the positive electrode sheet, so that opening areas 12 are respectively present on the sides of the battery cell 4 in different directions, which can significantly improve the thermal safety of the battery while maintaining a high energy density of the battery, and can also alleviate the lithium plating problem of the negative electrode sheet.

[0192] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the utility model.

Claims

1. A battery, characterized in that: A battery cell is provided, wherein the battery cell comprises a first pole piece, wherein the first pole piece comprises at least one first straight portion and a first bent portion connected to the first straight portion, wherein the first bent portion is located on at least one side of the battery cell in a second direction; The first electrode sheet includes a first active material layer, the first active material layer includes a main body area, and an opening area with recesses distributed on the surface, the opening area includes a first opening area and a second opening area, the first opening area is arranged at the edge of at least one side of the first active material layer in a first direction, the second opening area is arranged at the first bending portion, and the first direction intersects with the second direction.

2. The battery according to claim 1, characterized in that The thickness H0 of the first pole piece corresponding to the main body area and the thickness H0 of the first pole piece corresponding to the first opening area 121 , the thickness H of the first pole piece corresponding to the second opening area 122 Satisfy 0.6≤H0 / (H 121 +H 122 )≤0.9; And / or, the thickness H0 of the first pole piece corresponding to the main region is 30-200 μm; And / or, the thickness H of the first pole piece corresponding to the first opening area 121 20~200μm; And / or, the thickness H of the first pole piece corresponding to the second opening area 122 20~200μm.

3. The battery according to claim 1, characterized in that The first opening areas are disposed on edges of the first active material layer on two opposite sides in the first direction.

4. The battery according to claim 3, characterized in that The distance L3 between the first opening areas at the edges of the two opposite sides satisfies 0<L3≤200mm.

5. The battery according to claim 1, characterized in that The first active material layer includes at least two second open areas.

6. The battery according to claim 5, characterized in that The distance L4 between two adjacent second opening areas satisfies 0<L4≤100mm.

7. The battery according to claim 1, characterized in that The total area of ​​the opening region accounts for 10% to 50% of the total area of ​​the first active material layer.

8. The battery according to claim 1, characterized in that The first opening area is connected to the second opening area.

9. The battery according to claim 8, characterized in that The area S of the overlapping region of the first opening area and the second opening area 123 The area S of the first opening area 121 Satisfy 0<S 123 / S 121 ≤40%.

10. The battery according to claim 1, characterized in that The width of the first opening area is 1-20 mm; and / or, the depth of the recess in the first opening area is less than the thickness of the opening area; And / or, in the one opening area, the depth of the concave portion is 2-30 μm, the pore diameter is 10-150 μm, and the spacing between adjacent concave portions is 20-3000 μm; And / or, the width of the second opening area is 2mm-20mm; and / or, the depth of the recess in the second opening area is less than the thickness of the opening area; And / or, in the second opening area, the depth of the recess is 2-30 μm, the pore diameter is 10-150 μm, and the spacing between adjacent recesses is 20-3000 μm.

11. The battery according to claim 1, characterized in that The porosity of the main region is smaller than the porosity of the open pore region.

12. The battery according to claim 11, characterized in that The ratio of the porosity of the main region to the porosity of the first open pore region is greater than or equal to 0.

1.

13. The battery according to claim 12, characterized in that The ratio of the porosity of the main region to the porosity of the first open pore region is greater than or equal to 0.

2.

14. The battery according to claim 13, characterized in that The ratio of the porosity of the main area to the porosity of the first open area is 0.2~0.

8.

15. The battery according to claim 11, characterized in that The ratio of the porosity of the main region to the porosity of the second open pore region is greater than or equal to 0.

1.

16. The battery according to claim 15, characterized in that The ratio of the porosity of the main region to the porosity of the second open pore region is greater than or equal to 0.

2.

17. The battery according to claim 16, characterized in that The ratio of the porosity of the main area to the porosity of the second open area is 0.2~0.

8.

18. The battery according to any one of claims 1 to 17, characterized in that: The first electrode is a positive electrode.

19. The battery according to claim 18, characterized in that The battery further includes a negative electrode sheet, the negative electrode sheet includes a negative electrode active material layer, and the concave portion is not distributed on a surface of the negative electrode active material layer.

20. The battery according to any one of claims 1 to 17, characterized in that: The battery further includes a second pole piece having a polarity opposite to that of the first pole piece, and a diaphragm located between the first pole piece and the second pole piece, wherein the diaphragm is bonded to the first pole piece and the second pole piece respectively.

21. The battery according to claim 20, characterized in that The diaphragm includes a first adhesive layer, a ceramic layer, a substrate layer, and a second adhesive layer which are stacked in sequence. The first adhesive layer is bonded to the first pole piece, and the second adhesive layer is bonded to the second pole piece.

22. The battery according to claim 21, characterized in that The aperture D1 of the concave portion of the first opening area and the thickness H of the ceramic layer of the diaphragm 34 Satisfy 1.2≤D1 / H 34 ≤160.

23. The battery according to claim 22, characterized in that 2≤D1 / H 34 ≤150。 24. The battery according to claim 21, characterized in that The diameter D2 of the concave portion of the second opening area and the thickness H of the ceramic layer of the diaphragm 34 Satisfy 1.2≤D2 / H 34 ≤160.

25. The battery according to claim 24, characterized in that 2≤D2 / H 34 ≤150。 26. The battery according to claim 21, characterized in that The aperture D1 of the concave portion of the first opening area and the thickness H of the first adhesive layer of the diaphragm 31 Satisfy 2.5≤D1 / H 31 ≤320.

27. The battery according to claim 26, characterized in that 2.5≤D1 / H 31 ≤300。 28. The battery according to claim 21, characterized in that The diameter D2 of the concave portion of the second opening area and the thickness H of the first adhesive layer of the diaphragm 31 Satisfy 2.5≤D2 / H 31 ≤320.

29. The battery according to claim 28, characterized in that 2.5≤D2 / H 31 ≤300。 30. The battery according to any one of claims 21 to 29, characterized in that: The thickness of the substrate layer is 2-20 μm; And / or, the thickness of the ceramic layer is 1-5 μm; And / or, the thickness of the first adhesive layer is 0.5-4 μm; And / or, the thickness of the second adhesive layer is 0.5-4 μm.

31. The battery according to any one of claims 1 to 17, characterized in that: The first opening areas exist at edge regions on two opposite sides of the battery cell in the first direction, and the second opening areas exist at edge regions on two opposite sides of the battery cell in the second direction.

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