A battery

Abstract

The application provides a battery, comprising a battery cell, the battery cell comprising a first pole piece, the first pole piece comprising at least one first straight part and a first bending part connected with the first straight part, the first bending part being located on at least one side of the battery cell in a second direction; the first pole piece comprising a first active material layer; the first active material layer comprising a main body region and an open hole region with concave parts distributed on the surface, the open hole region comprising a first open hole region provided on an edge of at least one side of the first active material layer in a first direction and a second open hole region provided on the first bending part, the first direction intersecting the second direction; the resistivity R0 of the main body region, the resistivity R1 of the first open hole region and the resistivity R2 of the second open hole region satisfy 0.5<=R0 / (R1+R2)<=20. The application can improve the heat dissipation performance of the battery while maintaining a high energy density of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemical energy storage devices, in particular to a battery. BACKGROUND

[0002] Battery is a common electrochemical energy storage device, widely used, for example, lithium ion battery has the advantages of high energy density, etc. Widely used in electronic products and electric vehicles and other fields. However, the existing battery has poor heat dissipation performance, and heat accumulation is easy to occur in the battery during use, which reduces the battery oven temperature test pass rate and easily causes safety problems such as fire, which needs to be solved urgently. SUMMARY

[0003] The present application provides a battery to at least solve the problem of poor heat dissipation performance of the existing battery, easy to occur heat accumulation during use, and further cause low battery oven temperature test pass rate.

[0004] The present application provides a battery, comprising a cell, the cell comprising a first pole piece, the first pole piece comprising at least one first straight part and a first bending part connected with the first straight part, the first bending part being located on at least one side of the cell in a second direction; the first pole piece comprises a first active material layer, the first active material layer comprising a main body region and an open hole region with recesses distributed on the surface, the open hole region comprising a first open hole region provided on at least one side of the edge of the first active material layer in a first direction, and a second open hole region provided on the first bending part, the first direction intersecting the second direction; the resistivity of the main body region R0, the resistivity of the first open hole region R1, and the resistivity of the second open hole region R2 satisfy 0.5≤R0 / (R1+R2)≤20.

[0005] According to an embodiment of the present application, the ratio of the resistivity of the first open hole region to the resistivity of the main body region is greater than or equal to 0.2 and less than 1, preferably 0.2~0.7; and / or, the ratio of the resistivity of the second open hole region to the resistivity of the main body region is greater than or equal to 0.2 and less than 1, preferably 0.2~0.7; and / or, 0.54≤R0 / (R1+R2)≤18, preferably 0.55≤R0 / (R1+R2)≤3; and / or, the resistivity R0 of the main body region is 120~250 KΩ·cm; and / or, the resistivity R1 of the first open hole region is 40~150 KΩ·cm; and / or, the resistivity R2 of the second open hole region is 40~150 KΩ·cm.

[0006] According to an embodiment of the present application, the porosity of the main body region is less than the porosity of the open hole region; preferably, the porosity of the main body region , the porosity of the first open hole region , the porosity of the second open-cell region satisfies ; preferably, the ratio of the porosity of the bulk region and the porosity of the first open-cell region is greater than or equal to 0.1, preferably 0.2-1; preferably, the ratio of the porosity of the bulk region and the porosity of the second open-cell region is greater than or equal to 0.1, preferably 0.2-1; preferably, the porosity of the bulk region is 12%-30%; preferably, the porosity of the first open-cell region is 15%-30%; preferably, the porosity of the second open-cell region is 15%-30%.

[0007] According to an embodiment of the present application, the area density p0 of the bulk region, the area density p1 of the first open-cell region, the area density p2 of the second open-cell region satisfy 0.5≤p0 / (p1+p2)≤1.5, preferably 0.51≤p0 / (p1+p2)≤0.61; and / or, the ratio of the area density of the first open-cell region and the area density of the bulk region is greater than or equal to 0.5 and less than 1, preferably 0.6-0.93; and / or, the ratio of the area density of the second open-cell region and the area density of the bulk region is greater than or equal to 0.5 and less than 1, preferably 0.6-0.93; and / or, the area density of the bulk region is between 0.01-0.03 g / cm 2 ; and / or, the area density of the first open-cell region is between 0.01-0.03 g / cm 2 ; and / or, the area density of the second open-cell region is between 0.01-0.03 g / cm 2 .

[0008] According to an embodiment of the present application, the first electrode tab is a positive electrode tab; preferably, the battery further comprises a negative electrode tab, the negative electrode tab comprising a second active material layer, the second active material layer comprising a first region corresponding to the main region, and a first sub-region corresponding to the first aperture region, and a second sub-region corresponding to the second aperture region; wherein the ratio of the surface capacity of the first region to the surface capacity of the main region N / P0, and the ratio of the surface capacity of the first sub-region to the surface capacity of the first aperture region N / P1 satisfy 0.02≤N / P1-N / P0≤2, preferably 0.05≤N / P1-N / P0≤0.5; and / or, the ratio of the surface capacity of the first region to the surface capacity of the main region N / P0, and the ratio of the surface capacity of the second sub-region to the surface capacity of the second aperture region N / P2 satisfy 0.02≤N / P2-N / P0≤2, preferably 0.05≤N / P2-N / P0≤0.5; and / or, the surface capacity of the main region is 1.5~4mAh / cm 2 ; and / or, the surface capacity of the aperture region is 1.0~3.5mAh / cm 2 .

[0009] According to an embodiment of the present application, the battery further comprises a second electrode tab opposite in polarity to the first electrode tab, and a separator between the first electrode tab and the second electrode tab, the separator being bonded to the first electrode tab and the second electrode tab respectively; preferably, the separator comprises a first adhesive layer, a ceramic layer, a substrate layer and a second adhesive layer which are sequentially stacked, the first adhesive layer being bonded to the first electrode tab, and the second adhesive layer being bonded to the second electrode tab; preferably, the thickness of the substrate layer is 2~20μm; preferably, the thickness of the ceramic layer is 1~5μm; preferably, the thickness of the first adhesive layer is 0.5~4μm; preferably, the thickness of the second adhesive layer is 0.5~4μm; preferably, the pore size D1 of the recess of the first aperture region and the thickness H 34 of the ceramic layer of the separator satisfy 1.2≤D1 / H 34 ≤160, preferably 2≤D1 / H 34 ≤150; preferably, the pore size D2 of the recess of the second aperture region and the thickness H 34 of the ceramic layer of the separator satisfy 1.2≤D2 / H 34 ≤160, preferably 2≤D2 / H 34 ≤150; preferably, the pore size D1 of the recess of the first aperture region and the thickness H 31 of the first adhesive layer of the separator satisfy 2.5≤D1 / H 31 ≤320, preferably 2.5≤D1 / H 31≤300; preferably, the hole diameter D2 of the recess of the second aperture region and the thickness H of the first adhesive layer of the separator satisfy 2.5≤D2 / H 31 satisfy 2.5≤D2 / H 31 ≤320, preferably 2.5≤D2 / H 31 ≤300; preferably, the peeling force F0 of the separator from the main body region, the peeling force F1 of the separator from the first aperture region, and the peeling force F2 of the separator from the second aperture region satisfy F0>F1+F2.

[0010] According to an embodiment of the present application, the first active material layer is provided with the first aperture region on both sides in the first direction; and / or, the width of the first aperture region is 1-9 mm; and / or, in the first aperture region, the depth of the recess is 2-30 μm, the hole diameter of the recess is 10-150 μm, and the distance between adjacent recesses is 20-3000 μm, preferably 20-300 μm; the depth of the recess in the first aperture region is less than the thickness of the first aperture region; and / or, the width of the second aperture region is 2-20 mm; and / or, in the second aperture region, the depth of the recess is 2-30 μm, the hole diameter of the recess is 10-150 μm, and the distance between adjacent recesses is 20-3000 μm, preferably 20-300 μm; and / or, the depth of the recess in the second aperture region is less than the thickness of the second aperture region.

[0011] According to an embodiment of the present application, the first electrode tab includes a plurality of the first bent portions, part of the first bent portions are located at the third side of the battery cell, and the other part of the first bent portions are located at the fourth side of the battery cell, at least one of the first bent portions located at the third side of the battery cell is provided with the second aperture region, and at least one of the first bent portions located at the fourth side of the battery cell is provided with the second aperture region; preferably, each of the first bent portions located at the third side of the battery cell and having the first active material layer is provided with the second aperture region; and / or, each of the first bent portions located at the fourth side of the battery cell and having the first active material layer is provided with the second aperture region.

[0012] According to an embodiment of the present application, the first electrode tab is a positive electrode tab, and the battery cell further includes a negative electrode tab, the negative electrode tab includes a negative active material layer, the negative active material layer includes a silicon-based material, and the mass content of the silicon-based material in the negative active material layer is 0.5-30%.

[0013] According to one embodiment of the present invention, the battery satisfies 1 < V2 / V1 ≤ 2, where V1 is the volume of the battery, V2 is the volume of the battery after being kept at a temperature of T0 for a time t in a fully charged state, 130℃ ≤ T0 ≤ 150℃, 55min ≤ t ≤ 65min; and / or, the battery satisfies 0.5 ≤ (T max -T0) / C≤5, where C is the capacity of the battery in Ah, T max The maximum temperature reached by the battery in a fully charged state during the process of maintaining it in an environment at temperature T0, where 130℃≤T0≤150℃, and T max The unit is ℃.

[0014] In the battery provided by this invention, the cell has openings distributed along its side edges in different directions, satisfying 0.5 ≤ R0 / (R1+R2) ≤ 20. This improves the cell's heat dissipation, thereby enhancing the battery's overall heat dissipation performance and preventing heat accumulation during use. This also mitigates safety issues such as low furnace temperature throughput and increased susceptibility to fire, thus improving the battery's thermal safety. Furthermore, the improved heat dissipation of the cell lowers its internal temperature, reducing side reactions between active materials in the first electrode and electrolyte components, and suppressing gas generation and continuous temperature increases. This enhances the battery's thermal stability and safety while maintaining high energy density and capacity. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the planar structure of the first electrode sheet according to an embodiment of the present invention;

[0016] Figure 2 This is a schematic diagram of the stacked structure of the first electrode, the diaphragm, and the second electrode in one embodiment of the present invention;

[0017] Figure 3 This is a schematic diagram of the structure of a wound battery cell according to an embodiment of the present invention;

[0018] Figure 4 This is a schematic projection of a battery cell along its thickness direction according to an embodiment of the present invention.

[0019] Figure 5 This is a schematic diagram of a battery structure according to an embodiment of the present invention.

[0020] Explanation of reference signs: 1: first tab; 11: main body area; 12: opening area; 121: first opening area; 122: second opening area; 13: first tab; 100: recess; 101: first straight part; 102: first bending part; 110: first current collector; 120: first active material layer; 2: second tab; 23: second tab; 201: second straight part; 202: second bending part; 210: second current collector; 220: second active material layer; 3: separator; 31: first adhesive layer; 34: ceramic layer; 33: base material layer; 32: second adhesive layer; 4: battery cell; 41: first side; 42: second side; 43: third side; 44: fourth side; 5: package; 50: cavity; 51: first side part; 511: first main body part; 512: first connecting part; 52: second side part; 521: second main body part; 522: second connecting part; 6: tab adhesive; x: first direction; y: second direction; z: third direction; A: arrow. DETAILED DESCRIPTION

[0021] In order for those skilled in the art to better understand the solutions of the present application, the present application is further described in detail below. The specific embodiments listed below are only to describe the principles and characteristics of the present application, and the examples are only to explain the present application, and not to limit the scope of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0022] In the related art, the heat dissipation performance of the battery is poor, and heat accumulation is prone to occur inside the battery during use, which may cause safety problems such as fire of the battery.

[0023] Specifically, the electrode sheet is an important component of the battery, and contains electrode active material. During use of the battery, the heat dissipation effect of the electrode sheet is poor, especially for the electrode sheet with a bending structure, the bending part of the electrode sheet has a large stress and other factors, making it difficult to dissipate heat from the bending part of the electrode sheet. The poor heat dissipation effect of the electrode sheet may cause heat accumulation inside the battery cell, which may further intensify the side reaction between the electrode active material of the electrode sheet and the electrolyte and other components, resulting in problems such as gas generation, further temperature rise inside the battery cell, and affecting the safety and cycle life of the battery.

[0024] According to the long-term research of the inventor, by making pores on the electrode active material layer of the electrode sheet, the heat dissipation effect of the electrode sheet can be improved to some extent, and the heat dissipation performance of the battery is improved. However, if the area ratio of the pore-making area is too large, the energy density and other performances of the battery will be affected (for example, when making pores on the entire surface of the electrode active material layer, the energy density of the battery is severely lost), therefore, it is difficult to balance the heat dissipation performance and energy density of the battery.

[0025] Therefore, the embodiment of the present application provides a battery, such as Figures 1 to 5 As shown in the figure, the battery comprises a battery cell 4, the battery cell 4 comprises a first pole piece 1, the first pole piece 1 comprises at least one first straight part 101 and a first bending part (circular arc area) 102 connected with the first straight part 101, the first bending part 102 is located on at least one side of the battery cell in a second direction y; the first pole piece 1 comprises a first active material layer 120; the first active material layer 120 comprises a main body area 11 and an open hole area 12 with concave parts 100 distributed on the surface, the open hole area 12 comprises a first open hole area 121 provided on the edge of at least one side of the first active material layer 120 in a first direction x and a second open hole area 122 provided on the first bending part, the first direction x and the second direction y intersect; the resistivity R0 of the main body area 11, the resistivity R1 of the first open hole area 121 and the resistivity R2 of the second open hole area 122 satisfy 0.5≤R0 / (R1+R2)≤20.

[0026] In this way, by providing the first open hole area 121 on at least one side edge of the first pole piece 1 in the first direction x, and at the same time providing the second open hole area 122 on the first bending part 102, and controlling 0.5≤R0 / (R1+R2)≤20, it is beneficial to improve the heat dissipation performance of the battery, while taking into account maintaining a relatively high energy density of the battery.

[0027] Specifically, the first open hole area 121 is provided on at least one side of the first active material layer 120 in the first direction x, so that the first open hole area 12 exists on at least one side edge area of the battery cell 4 in the first direction x, and at the same time, the second open hole area 122 is provided on the first bending part 102, so that the second open hole area 122 exists on at least one side edge area of the battery cell 4 in the second direction y, so that the open hole area 12 exists on the side edge in different directions of the battery cell 4, which is beneficial to release the heat inside the battery cell 4 from different directions, improve the heat dissipation effect of the battery cell 4, and further improve the heat dissipation performance of the battery, avoid the heat accumulation inside the battery, and the thermal safety problems caused thereby, such as the fire of the battery. Wherein, the heat dissipation effect of the battery cell 4 is improved, the internal temperature is reduced, the side reaction between the active material and other materials in the first pole piece 1 and the electrolyte and other components is reduced, and the problems caused thereby, such as the continuous temperature rise and gas production of the battery, are inhibited, thereby the thermal stability and thermal safety performance of the battery can be improved. At the same time, the first active material layer 120 of the first pole piece 1 comprises the main body area 11, and 0.5≤R0 / (R1+R2)≤20 is controlled, which is beneficial to improve the heat dissipation performance of the battery while maintaining a relatively high energy density of the first pole piece 1, and improve the energy density and capacity performance of the battery.

[0028] According to the research of the inventor, the resistivity of the opening region 12 is less than the resistivity R0 of the main body region 11, that is, the resistivity R1 of the first opening region 121 and the resistivity R2 of the second opening region 122 are respectively less than the resistivity R0 of the main body region 11 (R1 < R0, R2 < R0), and the resistivity is positively correlated with the heat dissipation performance and negatively correlated with the energy density, that is, the smaller the resistivity, the better the heat dissipation performance, and the greater the resistivity, the greater the loss of energy density. By synergistically regulating the resistivity R0 of the main body region 11, the resistivity R1 of the first opening region 121, and the resistivity R2 of the second opening region 122, it can meet 0.5 ≤ R0 / (R1+R2) ≤ 20, which can improve the heat dissipation performance of the battery cell 4 through the opening region 12. At the same time, the energy density loss is compensated by the main body region 11, so that the battery cell 4 maintains a high energy density, thereby achieving a balance between the heat dissipation performance and capacity of the battery. Wherein, if R0 / (R1+R2) < 0.5, the heat dissipation performance of the battery is poor, and if R0 / (R1+R2) > 20, the energy density loss of the battery is serious.

[0029] Wherein, the resistivity R1 of the first opening region 121 can be greater than, equal to, or less than the resistivity R2 of the second opening region 122.

[0030] Exemplarily, R0 / (R1+R2) can be 0.5, 0.54, 0.55, 0.6, 0.65, 0.9, 0.92, 1, 1.2, 1.22, 1.5, 2, 2.5, 3, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or a range formed by any two of them, preferably 0.54 ≤ R0 / (R1+R2) ≤ 18, further preferably 0.54 ≤ R0 / (R1+R2) ≤ 5, further preferably 0.55 ≤ R0 / (R1+R2) ≤ 3, for example 0.55 ≤ R0 / (R1+R2) ≤ 1.2.

[0031] Specifically, the ratio of the resistivity of the opening region 12 to the resistivity R0 of the main body region 11 (R1 / R0, R2 / R0) is less than 1, which can be greater than or equal to 0.1, further can be greater than or equal to 0.2, specifically can be 0.2-0.7, for example 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 or a range formed by any two of them. Wherein, R1 / R0 can be greater than, equal to, or less than R2 / R0.

[0032] In some embodiments, the bulk region 11 can have a resistivity R0 of 120-250 KΩ·cm, for example 120 KΩ·cm, 150 KΩ·cm, 180 KΩ·cm, 200 KΩ·cm, 210 KΩ·cm, 215 KΩ·cm, 220 KΩ·cm, 225 KΩ·cm, 230 KΩ·cm, 240 KΩ·cm, 250 KΩ·cm, or a range defined by any two of them.

[0033] In some embodiments, the first open region 121 can have a resistivity R1 of 5-250 KΩ·cm, preferably 40-150 KΩ·cm, and the second open region 122 can have a resistivity R2 of 5-250 KΩ·cm, preferably 40-150 KΩ·cm.

[0034] For example, the resistivity (R1, R2) of the open region 12 described above can be 5 KΩ·cm, 10 KΩ·cm, 20 KΩ·cm, 30 KΩ·cm, 40 KΩ·cm, 50 KΩ·cm, 60 KΩ·cm, 70 KΩ·cm, 80 KΩ·cm, 90 KΩ·cm, 100 KΩ·cm, 110 KΩ·cm, 120 KΩ·cm, 130 KΩ·cm, 140 KΩ·cm, 150 KΩ·cm, 180 KΩ·cm, 210 KΩ·cm, 240 KΩ·cm, 250 KΩ·cm, or a range defined by any two of them.

[0035] Continuing to refer to Figures 1 to 5 The battery further includes a package 5 encapsulating the cell 4, the cell 4 being located in a cavity 50 enclosed by the package 5, the cell 4 further including a second tab 2 opposite in polarity to the first tab 1, a first lug 13 connected to the first tab 1, a second lug 23 connected to the second tab 2, and a separator 3 located between the first tab 1 and the second tab 2, the separator 3 being spaced between the first tab 1 and the second tab 2 to prevent short circuiting of the positive and negative electrodes.

[0036] Specifically, the first tab 1 includes a first current collector 110, and a first active material layer 120 located on a surface of the first current collector 110. The first active material layer 120 can be provided on one surface of the first current collector 110, or on both surfaces of the first current collector 110.

[0037] Specifically, the first active material layer 120 can include the first active material, the first conductive agent and the first binder, and in the first active material layer 120, the mass content of the first active material layer 120 can be 70% to 99%, the mass content of the first conductive agent can be 0.5% to 15%, and the mass content of the first binder can be 0.5% to 15%.

[0038] Specifically, the first tab 13 is connected with the first current collector 110, the first tab 13 can be welded on the first current collector 110, or the first tab 13 can be formed by the first current collector 110 extending outward (for example, the first tab 13 is formed by the first current collector 110 extending outward in a direction away from the first active material layer 120 in the width direction or the length direction of the first tab 1), and the first tab 13 can be arranged at the end of the first tab 1 in the length direction, or arranged at one side or opposite sides of the first tab 1 in the width direction, and the number of the first tab 13 on the first tab 1 can be one or more, which is not particularly limited.

[0039] In some embodiments, as shown in Figure 1 , the first tab 13 on the first tab 1 can be a middle tab structure, that is, the first tab 13 is arranged at the middle of at least one side of the first tab 1 in the first direction x, and the extension direction of the first tab 13 can be substantially parallel to the first direction x, which is beneficial to improve the heat dissipation performance of the battery cell 4 and the like.

[0040] As shown in Figure 4 and Figure 5 , the first tab 13 extends out of the package 5, and specifically, the first tab 13 can extend out of the package 5 from one side of the battery in the first direction x, that is, the first tab 13 is connected with one side of the first tab 12 in the first direction x and extends out of the package 5 from the side.

[0041] In addition, the second tab 2 includes the second current collector 210 and the second active material layer 220 on the surface of the second current collector 210, and the second active material layer 220 can be arranged on one surface of the second current collector 210, or the second active material layer 220 can be arranged on both the front and back surfaces of the second current collector 210.

[0042] Specifically, the second active material layer 220 can include the second active material, the second conductive agent and the second binder, and in the second active material layer 220, the mass content of the second active material layer 220 can be 70% to 99%, the mass content of the second conductive agent can be 0.5% to 15%, and the mass content of the second binder can be 0.5% to 15%.

[0043] Specifically, the second tab 23 is connected with the second current collector 210, the second tab 23 can be welded on the second current collector 210, or extends outwardly from the second current collector 210 (for example, the second tab 23 extends outwardly from the second current collector 210 in a direction away from the second active material layer 220 in the width direction or the length direction of the second tab 2), and the second tab 23 can be specifically arranged at the end in the length direction of the second tab 2, or arranged at one side or opposite sides in the width direction of the second tab 2, and the number of the second tab 23 on the second tab 2 can be one or more, which is not particularly limited.

[0044] In some embodiments, the second tab 23 on the second tab 2 can be a middle tab structure, that is, the second tab 23 is arranged at the middle of at least one side of the second tab 2 in the first direction x, and the extension direction of the second tab 23 can be substantially parallel to the first direction x, which is beneficial to improve the heat dissipation performance of the battery cell 4 and the like.

[0045] As shown in Figure 4 and Figure 5 , the second tab 23 extends out of the package 5, and specifically can extend out of the package 5 from one side of the battery in the first direction x, that is, the second tab 23 is connected with one side of the second tab 2 in the first direction x and extends out of the package 5 from the side.

[0046] Specifically, as shown in Figure 4 and Figure 5 , the first tab 13 and the second tab 23 can be located at the same side of the battery cell 4, and the second tab 23 and the first tab 13 extend out of the package 5 from the same side of the battery.

[0047] Generally, the package 5 can include a top sealing edge and side sealing edges, the top sealing edge is located at one side of the battery in the first direction x, and the side sealing edges are located at opposite sides of the battery in the second direction y, and the first tab 13 and the second tab 23 can extend out of the package 5 from the top sealing edge.

[0048] Specifically, as shown in Figure 5 , the package 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, and 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 at 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 a sealing edge (i.e., a top sealing edge and side sealing edges) of the package 5.

[0049] In the sealing edge part where the first tab 13 extends, the first tab 13 is located between the first connecting part 512 and the second connecting part 522, and the first tab 13 can be specifically bonded (i.e., one side of the first tab 13 in the thickness direction is bonded to the first connecting part 512 by the tab adhesive 6, and the other side of the first tab 13 in the thickness direction is bonded to the second connecting part 522 by the tab adhesive 6) to the first connecting part 512 and the second connecting part 522 by the tab adhesive 6 respectively.

[0050] In the sealing edge part where the second tab 23 extends, the second tab 23 is located between the first connecting part 512 and the second connecting part 522, and the second tab 23 can be specifically bonded (i.e., one side of the second tab 23 in the thickness direction is bonded to the first connecting part 512 by the tab adhesive 6, and the other side of the second tab 23 in the thickness direction is bonded to the second connecting part 522 by the tab adhesive 6) to the first connecting part 512 and the second connecting part 522 by the tab adhesive 6 respectively.

[0051] In addition, in the sealing edge part where no tab extends, the first connecting part 512 and the second connecting part 522 are connected, for example, bonded, so that the packaging body 5 surrounds the sealed cavity 50 to achieve the packaging of the battery cell 4.

[0052] In the embodiments of the present application, the tab adhesive 6 can be a conventional tab adhesive material in the art, and no particular limitation is made thereto.

[0053] Generally, the sealing edge part where the tab (the first tab 13, the second tab 23) extends is a relatively weak part on the packaging body 5, which is easily broken by the gas generated inside the battery due to side reactions and other factors when the battery encounters high temperature, so that the gas inside the battery can be discharged from the sealing edge part, and the heat inside the battery is carried out from the battery, avoiding the continuous increase of the temperature inside the battery, and further avoiding the problems such as fire and explosion of the battery.

[0054] Specifically, the edge region of at least one side of the battery cell 4 in the first direction x is provided with a first opening region 121, and the edge region of at least one side of the battery cell 4 in the second direction y is provided with a second opening region 122, when the battery encounters high temperature, the heat inside the battery cell 4 is released to the cavity 50 surrounded by the packaging body 5 along the side edges in different directions of the battery cell 4, when the temperature and gas inside the battery reach a certain degree, the gas inside the battery can break through the sealing edge part where the tab extends, realizing directional pressure relief, and carrying out heat, avoiding the problems such as fire and explosion of the battery.

[0055] Specifically, the first opening region 121 is a region with a width of w1 (w1>0) extending from the outer edge of the first active material layer 120 in the direction toward the main body region 11. That is, a hole is formed in this region to form the first opening region 121. The width w1 of the first opening region 121 refers to the width of the first opening region 121 in the direction along the first opening region 121 to the main body region 11.

[0056] Specifically, the first active material layer 120 may have a first opening region 121 on one side edge in the first direction x, and correspondingly, the battery cell 4 may have a first opening region 121 on one side edge in the first direction; or, the first active material layer 120 may have a first opening region 121 on both sides edge in the first direction x, and correspondingly, the battery cell 4 may have a first opening region 121 on both sides edge in the first direction x.

[0057] Specifically, such as Figure 4 As shown, the battery has a first side 41 and a second side 42 opposite to each other in the first direction x. At least one of the edge regions of the first side 41 and the edge regions of the second side 42 has a first opening region 121. Preferably, both the edge regions of the first side 41 and the edge regions of the second side 42 have opening regions 121 (that is, both edge regions of the opposite sides of the cell 4 in the first direction x have opening regions 121), which is beneficial to further improve the heat dissipation performance of the cell 4.

[0058] Specifically, the width w1 of the first opening area 121 can be greater than or equal to 1mm, which is beneficial to improving the heat dissipation performance of the battery cell 4. It can be further less than or equal to 20mm (1mm≤w1≤20mm), and even further less than or equal to 12mm (1mm≤w1≤12mm), which is beneficial to take into account the high energy density of the battery cell 4.

[0059] In contrast, if the width w1 of the first opening area 121 is too small, the improvement on the heat dissipation effect of the first electrode 1 will be limited. If the width w1 of the first opening area 121 is too large, the first active material in the first electrode 1 will be lost too much, which will affect the energy density and capacity of the battery. Therefore, taking these factors into consideration, the width w1 of the first opening area 121 is preferably 1~9mm, such as 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm or any combination thereof, which is beneficial to improve the heat dissipation performance of the battery while maintaining higher energy density and capacity.

[0060] The width w1 of the first opening region 121 refers to the width of one side of the first opening region 121. For example, when the first active material layer 120 has first opening regions 121 on both sides in the first direction x, the width w1 of the first opening region 121 refers to the width of one side of the first opening region 121, rather than the sum of the widths of the first opening regions 121 on both sides.

[0061] Specifically, the width direction of the first opening region 121, the direction from the first opening region 121 to the main body region 11, the width direction of the first tab 1, and the width direction of the first active material layer 120 are parallel to each other. The length direction of the first opening region 121, the length direction of the first tab 1, and the length direction of the first active material layer 120 are parallel to each other.

[0062] Specifically, the first active material layer 120 includes at least two second opening regions 122, and the first tab includes at least two first bending portions 102. Each second opening region 122 in the first active material layer 120 corresponds to a first bending portion 102. For the corresponding second opening region 122 and first bending portion 102, the second opening region 122 is located in the first bending portion 102, that is, the second opening region 122 is at least partially located in the first bending portion 102 in which the second opening region 122 is located. The projection of the first bending portion 102 in the thickness direction of the first bending portion 102 at least partially overlaps the projection of the second opening region 122 in the thickness direction of the first bending portion 102.

[0063] Specifically, for each first bending portion 102 provided with a second opening region 122, the width w2 of the second opening region 122 thereon can be less than, equal to, or greater than the width w 102 of the first bending portion 102. The width w2 of the second opening region 122 refers to the width of the second opening region 122 in the bending direction of the first bending portion 102 in which the second opening region 122 is located. The width w 102 of the first bending portion 102 refers to the width of the first bending portion 102 in the bending direction of the first bending portion 102. Figure 1 Specifically, before the first tab 1 is wound (as shown in FIG. 1), the width w2 of the second opening region 122 refers to the width of the second opening region 122 in the length direction of the first tab 1. The width w 102 of the first bending portion 102 refers to the width of the first bending portion 102 in the length direction of the first tab 1.

[0064] For example, when the width w2 of the second opening region 122 is greater than the width w 102When the width w2 of the second opening region 122 is greater than the width w of the first bending portion 102, the second opening region 122 covers the first bending portion 102 and extends beyond the first bending portion 102, i.e., the second opening region 122 extends to the first straight portion 101 at opposite ends of the first bending portion 102 in the bending direction of the first bending portion 102. 102 When the width w2 of the second opening region 122 is less than or equal to the width w of the first bending portion 102, the second opening region 122 can be entirely located in the first bending portion 102, i.e., the projection of the first bending portion 102 in the thickness direction of the first bending portion 102 covers the second opening region 122 in 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 width w2 of the second opening region 122 is substantially equal to the width w of the first bending portion 102, the second opening region 122 is substantially overlapped with the first bending portion 102. 102 When the width w2 of the second opening region 122 is less than or equal to the width w of the first bending portion 102, the second opening region 122 can be entirely located in the first bending portion 102, i.e., the projection of the first bending portion 102 in the thickness direction of the first bending portion 102 covers the second opening region 122 in 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 width w2 of the second opening region 122 is substantially equal to the width w of the first bending portion 102, the second opening region 122 is substantially overlapped with the first bending portion 102.

[0065] In some embodiments, the width w2 of the second opening region 122 can be 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 formed by any two of them.

[0066] With reference to Figure 4 , the first bending portion 102 is located at least one side of the battery cell 4 in the second direction y, i.e., at least one side of the battery cell 4 in the second direction y has the first bending portion 102, and the second opening region 122 is arranged in the first bending portion 102, so that the edge region of at least one side of the battery cell 4 in the second direction y has the second opening region 122.

[0067] Specifically, the battery cell 4 has opposite third and fourth sides 43 and 44 in the second direction y, wherein at least one of the edge region of the third side 43 and the edge region of the fourth side 44 has the first bending portion 102, so that at least one of the third and fourth sides 43 and 44 has the second opening region 122.

[0068] Generally, the opposite two sides of the battery cell 4 in the second direction y each have the first bending portion 102 (i.e., the third and fourth sides 43 and 44 of the battery cell each have the first bending portion 102), wherein the first bending portion 102 of the third side 43 and the first bending portion 102 of the fourth side 44 each have the second opening region 122, so that the edge region of the third side 43 and the edge region of the fourth side 44 of the battery cell 4 each have the second opening region 122 (i.e., the edge region of the opposite two sides of the battery cell 4 in the second direction y each has the second opening region 122), which is beneficial to further improve the heat dissipation performance of the battery cell 4.

[0069] In addition, the second tab 2 comprises at least one second straight portion 201 and a second bending portion 202 connected with the second straight portion 201, the second straight portion 201 of the second tab 2 corresponds to the first straight portion 101 of the first tab 1, and both are generally arranged in a stack, and the second bending portion 202 of the second tab 2 corresponds to the first bending portion 102 of the first tab 1.

[0070] In some embodiments, as shown in Figure 3 , the battery cell 4 is a winding type battery cell 4, that is, the first tab 1 and the second tab 2 each have a winding structure, wherein the first tab 1 comprises a plurality of first straight portions 101 and a first bending portion (circular arc region) 102 connected between each two adjacent first straight portions 101, the first tab 1 is bent by the first bending portion 102, thereby forming a winding structure; the second tab 2 comprises a plurality of second straight portions 201 and a second bending portion (circular arc region) 202 connected between each two adjacent second straight portions 201, the second tab 2 is bent by the second bending portion 202, thereby forming a winding structure. Wherein the first straight portions 101 of the first tab 1 and the second straight portions 201 of the second tab 2 are arranged in a stack, and the first straight portions 101 and the second straight portions 201 are arranged alternately, the first straight portions 101 and the second straight portions 201 are separated by the diaphragm 3, and the first bending portion 102 and the second bending portion 202 are separated by the diaphragm 3.

[0071] When the battery cell 4 is a winding type battery cell 4, the stress of the bending portion is large, heat dissipation is difficult, the side reaction of the electrode material and the electrolyte and other components is serious, which can easily lead to problems such as gas production and continuous heating inside the battery, and further can easily lead to the battery catching fire. In the embodiment of the present application, the first opening region 121 is arranged at the edge of the first tab 1, and the second opening region 122 is arranged at the first bending portion 102, a step is formed in these regions, which is beneficial to heat dissipation of the battery cell 4, and specifically, the gas (heat) generated due to the side reaction of the electrode active material and the electrolyte and other components can be released along the conduction direction (heat flow direction) shown by the arrow A in Figure 4 , that is, the heat is dissipated along the conduction direction shown by the arrow A in Figure 4 .

[0072] Continuing to refer to Figure 3 , the first tab 1 comprises a plurality of first bending portions 102, and correspondingly, the second tab 2 comprises a plurality of second bending portions 202, part of the first bending portions 102 and part of the second bending portions 202 are located at the edge region of one side (the third side 43) of the battery cell 4 in the second direction y, and another part of the first bending portions 102 and another part of the second bending portions 202 are located at the edge region of the other side (the fourth side 44) of the battery cell 4 in the second direction y.

[0073] At least one of the first bending portions 102 is provided with the second opening area 122, and preferably each of the first bending portions 102 with the first active material layer 120 is provided with the second opening area 122.

[0074] Generally, the number of the first bending portions 102 on the third side 43 of the battery cell 4 is multiple, and at least one of the first bending portions 102 on the third side 43 of the battery cell 4 is provided with the second opening area 122, and preferably each of the first bending portions 102 with the first active material layer 120 on the third side 43 of the battery cell 4 is provided with the second opening area 122. The number of the first bending portions 102 on the fourth side 44 of the battery cell 4 is multiple, and at least one of the first bending portions 102 on the fourth side 44 of the battery cell 4 is provided with the second opening area 122, and preferably each of the first bending portions 102 with the first active material layer 120 on the fourth side 44 of the battery cell 4 is provided with the second opening area 122. In this way, the second opening area 122 exists on the edge area of the opposite sides of the battery cell 4 in the second direction y, which is beneficial to further improve the heat dissipation effect of the battery cell 4.

[0075] In some embodiments, as shown in FIG. 1, the edge area of the opposite sides of the battery cell 4 in the first direction x respectively exists the first opening area 121, and the edge area of the opposite sides of the battery cell 4 in the second direction y respectively exists the second opening area 122. In this way, the opening area 12 exists on the four edges of the battery cell 4, which is beneficial to further improve the heat dissipation effect of the battery cell 4. Figure 4 Figure 4 Figure 4

[0076] Specifically, in the first tab 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 is continuously extended from one end of the length direction of the first active material layer 120 to the other end of the length direction of the first active material layer 120.

[0077] ​​​Specifically, the length direction of the second opening region 122 is parallel to the length direction (bending direction) of the first bending part 102, and the second opening region 122 can be not connected with the first opening region 121, that is, there is the body region 11 between the two (that is, the second opening region 122 and the first opening region 121 are spaced apart by the body region 11), or the second opening region 122 is connected with the first opening region 121, that is, there is no body region 11 of the surface of which the recess 100 is not distributed between the two. In comparison, when the second opening region 122 is connected with the first opening region 121, the edge region of the first bending part 102 and the first active material layer 120 in the first direction x forms a continuous heat dissipation channel, which is more conducive to improving the heat dissipation effect.

[0078] In some embodiments, as shown in FIG. 1, when the first active material layer 120 is provided with the first opening region 121 on each of the opposite sides in the first direction x, for any second opening region 122, one end of the second opening region 122 is connected with the first opening region 121 provided on one side of the first active material layer 120, and the other end of the second opening region 122 is connected with the first opening region 121 provided on the other side of the first active material layer 120. Figure 1

[0079] Specifically, on the first pole piece 1, the body region 11 is the region other than the opening region 12, and the surface of the body region 11 is not subjected to pore-forming, that is, the surface of the body region 11 is not provided with the recess 100.

[0080] Specifically, the first pole piece 1 can have one body region 11 (that is, the body region 11 on the first pole piece 1 is continuously provided), or the first pole piece 1 has a plurality of body regions 11, and each two body regions 11 are spaced apart by the opening region 12.

[0081] For example, as shown in FIG. 1, the first pole piece 1 has a plurality of body regions 11, and before the first pole piece 1 is wound, the body regions 11 are distributed along the length direction of the first pole piece 1, and each two adjacent body regions 11 are provided with the second opening region 122 (that is, each two adjacent body regions 11 are spaced apart by the second opening region 122), and each body region 11 has the first opening region 121 on each of the opposite sides in the first direction x. Figure 1

[0082] ​​Generally, the total area of the body regions 11 in the first active material layer 120 is greater than the total area of the opening regions 12 (the total area of the body regions 11 accounts for more than 50% of the total area of the first active material layer 120), the total area of the body regions 11 refers to the sum of the areas of all the body regions 11 in the first tab 1, the area of each body region 11 refers to the surface area of the body region 11 (i.e. the projection area of the body region 11 on the surface of the first current collector 110) of the first active material layer 120 without the recess 100; the total area of the opening regions 12 refers to the sum of the areas of all the opening regions 12 in the first tab 1, the area of each opening region 12 refers to the surface area of the opening region 12 (i.e. the projection area of the opening region 12 on the surface of the first current collector 110) of the first active material layer 120 with the surface distribution of the recess 100, the total area of the first active material layer = the total area of the body regions 11 + the total area of the opening regions 12.

[0083] Specifically, the battery of the embodiment of the present application can be a soft package battery, i.e. the packaging body 5 is a soft package film, which can be a conventional soft package material in the art, for example, the packaging body 5 comprises an aluminum plastic film, but is not limited thereto.

[0084] In the embodiment of the present application, the first direction x intersects with the second direction y, and the two directions can be perpendicular to each other, the first direction x, the width direction of the first tab 1 and the width direction of the second tab 2 are parallel to each other, and when forming the wound type battery cell 4, the first tab 1, the diaphragm 3 and the second tab 2 are sequentially stacked to form a laminated structure, and then winding is performed along the length direction of the laminated structure (also the length direction of the first tab 1 and the second tab 2).

[0085] For example, 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.

[0086] For example, Figure 1 The first tab 1 before winding is shown in the structure schematic view, before winding, the width direction of the first tab 1 is parallel to the first direction x, and the length direction of the first tab 1 is parallel to the second direction y, when winding, winding is performed along the length direction of the first tab 1, after winding of the first tab 1 (i.e. the first tab 1 forms the winding structure in the wound type battery cell 4 as shown in Figure 3 The length direction of the wound type battery cell 4, the length direction of the first straight part 101, the length direction of the second straight part 201, the second direction y are parallel to each other, and the width direction of the wound type battery cell 4, the width direction of the first straight part 101, the width direction of the second straight part 201, the first direction x are parallel to each other.

[0087] In addition, the second direction y intersects with the third direction z, and the two directions can be perpendicular to each other in particular; the first direction x intersects with the third direction z, and the two directions can be perpendicular to each other in particular, 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 piece 1, the thickness direction of the second pole piece 2, the thickness direction of the first tab 13, the thickness direction of the second tab 23, the direction along the first main body part 511 to the second main body part 521, and the direction along the first connecting part 512 to the second connecting part 522 are parallel to each other.

[0088] Specifically, the porosity of the main body area 11 is less than the porosity of the open area 12, the porosity of the first open area 121 , and the porosity of the second open area 122 are all greater than the porosity of the main body area 11 ( > , > ), which is conducive to improving the heat dissipation performance of the battery cell while further taking into account maintaining the high energy density and capacity of the battery. Among them, the porosity of the first open area 121 may be greater than, equal to, or less than the porosity of the second open area 122 .

[0089] Specifically, the ratio of the porosity of the main body area 11 to the porosity of the open area 12 / , / may be greater than or equal to 0.1, and further can be greater than or equal to 0.2, and specifically can be 0.2-1, such as 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or a range composed of any two of them. Among them, / may be greater than, equal to, or less than / .

[0090] In some embodiments, the difference between the porosity of the open area 12 and the porosity of the main body area 11 ( - , - ) can be greater than or equal to 5%, and specifically can be 5%-50%, such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or a range composed of any two of them. Among them, - may be greater than, equal to, or less than - .

[0091] Specifically, the porosity of the main body region 11 , the porosity of the first open region 121 , the porosity of the second open region 122 may satisfy .

[0092] Further research shows that preferably , further preferably , in this way, the open region 12 has a larger porosity, which is conducive to the timely dissipation of the gas and heat generated at the interface between the first pole piece 1 and the electrolyte into the cavity 50 of the packaging body 5, avoiding the local accumulation of heat in the electric core 4 and causing local overheating, thereby further improving the thermal stability and other properties of the battery, while maintaining a larger energy density of the battery.

[0093] Exemplarily, may 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.

[0094] In some embodiments, the porosity of the main body region 11 may be 12% to 30%, for example, 12%, 15%, 18%, 20%, 23%, 25%, 28%, 30% or a range consisting of any two of them.

[0095] In some embodiments, the porosity of the first open region 121 may be 14% to 50%, preferably 15% to 30%, and the porosity of the second open region 122 may be 14% to 50%, preferably 15% to 30%.

[0096] Exemplarily, the porosity of the above open region 12 , may be 14%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 35%, 40%, 45%, 50% or a range consisting of any two of them.

[0097] In the embodiment of the present application, the diaphragm 3 can be bonded with the first and second pole pieces 1 and 2 respectively, that is, one side of the diaphragm 3 is bonded with the first pole piece 1 and the other side is bonded with the second pole piece 2, which is conducive to shortening the interface distance between the positive and negative electrodes, shortening the path of ions (such as lithium ions in lithium ion batteries) during deintercalation between the positive and negative electrodes, thereby improving the charge and discharge performance of the battery. At the same time, it is also conducive to more stably spacing the diaphragm 3 between the positive and negative electrodes, improving the structural stability of the battery cell 4, and further avoiding the risk of positive and negative electrode contact short circuit.

[0098] Generally, in the first pole piece 1, the opening area 12 is distributed with a recess 100, and the bonding force (peeling force) of the diaphragm 3 with the opening area 12 is less than the bonding force (peeling force) of the diaphragm 3 with the main body area 11. The bonding force of the diaphragm 3 with the first opening area 121 and the bonding force of the diaphragm 3 with the second opening area 122 are both less than the bonding force of the diaphragm 3 with the main body area 11.

[0099] In some embodiments, the peeling force F0 of the diaphragm 3 with the main body area 11, the peeling force F1 of the diaphragm 3 with the first opening area 121, and the peeling force F2 of the diaphragm 3 with the second opening area 122 satisfy F0>F1+F2, which is conducive to further improving the heat dissipation performance of the battery.

[0100] In the embodiment of the present application, the peeling force can be specifically the 180° peeling force measured by 180° peeling force test.

[0101] Specifically, the diaphragm 3 can include a substrate layer 33, a first adhesive layer 31 on one side of the substrate layer 33, and a second adhesive layer 32 on the other side of the substrate layer 33. The first adhesive layer 31 is bonded with the first pole piece 1, and the second adhesive layer 32 is bonded with the second pole piece 2. That is, the first and second adhesive layers 31 and 32 are respectively the surface layers on opposite sides of the diaphragm 3. The diaphragm 3 is bonded with the first pole piece 1 through the first adhesive layer 31 and bonded with the second pole piece 2 through the second adhesive layer 32.

[0102] In addition, the diaphragm 3 can also include a ceramic layer 34, which can be located between the first adhesive layer 31 and the substrate layer 33, that is, the diaphragm 3 includes the first adhesive layer 31, the ceramic layer 34, the substrate layer 33 and the second adhesive layer 32 which are sequentially stacked. By introducing the ceramic layer 34, the heat shrinkage resistance of the diaphragm 3 can be improved, and problems such as heat shrinkage of the diaphragm 3 and resulting positive and negative electrode contact short circuit can be avoided.

[0103] The substrate layer 33 can be a conventional diaphragm 3 material in the art, for example, the substrate layer 33 includes one of polypropylene diaphragm 3 (PP), polyethylene diaphragm 3 (PE), polypropylene / polyethylene (PP / PE) double-layer composite film, polyimide electrospinning diaphragm 3 (PI), polypropylene / polyethylene / polypropylene (PP / PE / PP) three-layer composite film, and cellulose non-woven diaphragm 3.

[0104] Further, the ceramic layer 34 can comprise alumina and / or boehmite, further, the ceramic layer 34 can comprise an alumina layer and / or a boehmite layer.

[0105] Further, the first adhesive layer 31 can comprise a PVDF layer, i.e. the first adhesive layer 31 is of PVDF, which is mainly formed of PVDF.

[0106] Further, the second adhesive layer 32 can comprise a PVDF layer, i.e. the second adhesive layer 32 is of PVDF, which is mainly formed of PVDF.

[0107] In particular, the hole diameter D1 of the recess 100 of the first open region 121 and the thickness H of the ceramic layer 34 of the membrane 3 34 may satisfy 1≤D1 / H 34 ≤162, preferably 1.2≤D1 / H 34 ≤160, more preferably 2≤D1 / H 34 ≤150.

[0108] In particular, the hole diameter D2 of the recess 100 of the second open region 122 and the thickness H of the ceramic layer 34 of the membrane 3 34 may satisfy 1≤D2 / H 34 ≤162, preferably 1.2≤D2 / H 34 ≤160, more preferably 2≤D2 / H 34 ≤150.

[0109] wherein D1 / H 34 may be greater than, equal to, or less than D2 / H 34 .

[0110] Exemplarily, D1 / H 34 , D2 / H 34 may each independently be 1, 1.2, 2, 5, 10, 20, 30, 40, 50, 70, 90, 100, 120, 130, 150, 155, 160, 162, or a range consisting of any two of them.

[0111] In particular, the hole diameter D1 of the recess 100 of the first open region 121 and the thickness H of the first adhesive layer 31 of the membrane 3 11 may satisfy 2.5≤D1 / H 31 ≤320, preferably 2.5≤D1 / H 31 ≤300.

[0112] In particular, the hole diameter D2 of the recess 100 of the second open region 122 and the thickness H of the first adhesive layer 31 of the membrane 3 31 may satisfy 2.5≤D2 / H 31≤ 320, preferably 2.5 ≤ D2 / H 31 ≤ 300.

[0113] wherein D1 / H 31 may be greater than, equal to, or less than D2 / H 31 .

[0114] Exemplarily, D / H 31 (i.e. D1 / H 31 , D2 / H 31 ) can be in the range of 2, 2.5, 5, 10, 30, 50, 80, 100, 130, 150, 180, 200, 230, 250, 280, 300, 320 or any two thereof.

[0115] In a high-temperature environment such as a furnace temperature test, gas and heat are generated at the interface between the diaphragm 3 and the first tab 1. By providing the opening region 12 in the first tab 1 and controlling the resistivity of the opening region 12 and the main body region 11 to satisfy 0.5 ≤ R0 / (R1+R2) ≤ 20, and the ratio of the pore diameter of the recess 100 of the opening region 12 to the thickness of the first adhesive layer 31 and the ceramic layer 34 being within the above range, it is beneficial for the opening region 12 of the first tab 1 to have a relatively small adhesion with the diaphragm 3, thereby facilitating the discharge of gas to the outside of the battery cell 4, while the heat generated inside the battery due to the side reaction of electrode materials and electrolyte components and other factors is carried away by the gas, avoiding the accumulation of heat inside the battery and the resulting fire and other thermal safety problems, thereby improving the thermal safety of the battery; wherein according to the research and analysis of the inventor, the resistivity of the opening region 12 and other regions is related to the parameters such as the depth of the recess 100 of the opening region 12, and the recess 100 is distributed on the surface of the first active material layer 120, while the diaphragm 3 is bonded to the surface of the first active material layer 120, therefore, by controlling 0.5 ≤ R0 / (R1+R2) ≤ 20, 2.5 ≤ D / H 31 ≤ 300, 2 ≤ D / H 34 ≤ 150, it is more beneficial for the diaphragm 3 to have appropriate adhesion and other properties with the first tab 1, thereby improving the thermal safety and other performance of the battery.

[0116] In addition, if D / H 34 (D1 / H 34 , D2 / H 34 ) and / or D / H 31 (D1 / H 31 , D2 / H 31 ) is too large, the pore diameter D is too large, and the active material of the first tab 1 is lost more, resulting in more capacity loss, affecting the energy density of the battery, and if D / H 34 and / or D / H 31Too small, the recess 100 on the surface of the first tab 1 is too small, and the heat dissipation effect on the battery cell 4 is limited, so by controlling the aperture of the recess 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, it is beneficial to realize the balance of battery thermal safety and energy density.

[0117] Specifically, the thickness of the substrate layer 33 can be 2-20 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 of them.

[0118] 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 a range consisting of any two of them.

[0119] 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 a range consisting of any two of them.

[0120] Specifically, the thickness of the ceramic layer 34 is 1-5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or a range consisting of any two of them.

[0121] In some embodiments, the first tab 1 is a positive tab, the second tab 2 is a negative tab, and correspondingly, the first active material layer 120 is a positive active material layer, the first active material is a positive active material, the first current collector 110 is a positive current collector, the second active material layer 220 is a negative active material layer, the second active material is a negative active material, and the second current collector 210 is a negative current collector.

[0122] In other embodiments, the first tab 1 is a negative tab, the second tab 2 is a positive tab, and correspondingly, the first active material layer 120 is a negative active material layer, the first active material is a negative active material, the first current collector 110 is a negative current collector, the second active material layer 220 is a positive active material layer, the second active material is a positive active material, and the second current collector 210 is a positive current collector.

[0123] Further research shows that the first pole piece 1 is preferably a positive pole piece, so that, while improving the heat dissipation performance of the battery, at least the following advantages can be achieved: (1) According to the research of the inventor, the temperature at which the positive electrode material reacts with the electrolyte is generally lower than the temperature at which the negative electrode material reacts with the electrolyte. Therefore, by providing the opening area 12 in the positive active material layer, the heat dissipation performance of the positive pole piece is improved, and the risk of reaction between the positive electrode material such as positive active material and the electrolyte is reduced, further improving the safety and thermal stability of the battery; (2) By providing the opening area 12 on the positive pole piece, the N / P (ratio of negative electrode surface capacity N and positive electrode surface capacity P) corresponding to the opening area 12 in the battery cell 4 can be reduced, thereby inhibiting the problem of lithium precipitation in the negative electrode and further improving the safety of the battery; (3) Compared with the negative pole piece, the adhesion between the positive pole piece and the separator 3 is lower, and the opening area 12 provided on the positive pole piece is more conducive to improving the heat dissipation performance of the battery cell 4.

[0124] In addition, the second active material layer 220 includes a first region corresponding to the main body region 11 and a second region corresponding to the opening region 12. The first region is the main body region of the second active material layer 220, and the projection of the first region and the main body region 11 in the direction from the first region to the main body region 11 overlaps. The second region is a region of the second active material layer 220 corresponding to the opening region 12 on the first pole piece 1, and the second region corresponds to the opening region 12 one by one, and the projection of the corresponding second region and the opening region 12 in the direction from the second region to the opening region 12 overlaps.

[0125] Specifically, the second region includes a first sub-region corresponding to the first opening region 121 and a second sub-region corresponding to the second opening region 122. The first sub-region is located at the edge of the second active material layer 220, and the projection of the first sub-region and the first opening region 121 in the direction from the first sub-region to the first opening region 121 overlaps. The second sub-region is located at the second bending portion 202, and the projection of the second sub-region and the second opening region 122 in the direction from the second sub-region to the second opening region 122 overlaps.

[0126] Generally, the area density p0 of the main body region 11 is greater than the area density of the opening region 12, the area density of the main body region 11 is greater than the area density p1 of the first opening region 121, the area density of the main body region 11 is greater than the area density p2 of the second opening region 122, and the area density p1 of the first opening region 121 can be greater than, equal to, or less than the area density p2 of the second opening region 122.

[0127] Specifically, the ratio of the areal density of the opening region 12 and the areal density p0 of the main body region 11 (p1 / p0, p2 / p0) is less than 1, which can be greater than or equal to 0.5, further can be greater than or equal to 0.6, specifically can be 0.6-0.93, for example 0.6, 0.7, 0.73, 0.74, 0.8, 0.82, 0.85, 0.88, 0.9, 0.93 or a range consisting of any two of them. Among them, p1 / p0 can be greater than, equal to or less than p2 / p0.

[0128] In some embodiments, the areal density p0 of the main body region 11, the areal density p1 of the first opening region 121, and the areal density p2 of the second opening region 122 can satisfy 0.5≤p0 / (p1+p2)≤1.5, preferably 0.51≤p0 / (p1+p2)≤0.61, so that on the one hand, the main body region 11 has a higher areal density, which is beneficial to compensate for the capacity loss of the opening region 12 through the main body region 11, thereby maintaining a higher energy density of the battery; on the other hand, it is beneficial to increase the height difference between the opening region 12 and the main body region 11, increase the heat dissipation effect, and at the same time, increase the heat dissipation effect at the interface of the first pole piece 1 and the separator 3, thereby improving the heat dissipation performance of the battery cell 4.

[0129] Illustratively, p0 / (p1+p2) can be 0.5, 0.51, 0.53, 0.55, 0.57, 0.6, 0.61, 0.65, 0.7, 0.8, 0.9, 1, 1.3, 1.5 or a range consisting of any two of them, for example 0.53

[0130] Specifically, the areal density p0 of the main body region 11 and the areal density of the opening region 12 can be between 0.01-0.03 g / cm 2 , the areal density p1 of the first opening region 121 and the areal density p2 of the second opening region 122 are between 0.01-0.03 g / cm 2 .

[0131] Illustratively, the areal density p0 of the main body region 11 can be 0.01 g / cm 2 , 0.012 g / cm 2 , 0.015 g / cm 2 , 0.018 g / cm 2 , 0.02 g / cm 2 , 0.023 g / cm 2 , 0.025 g / cm 2 , 0.028 g / cm 2 , 0.03 g / cm 2 or a range consisting of any two of them.

[0132] Exemplarily, the areal density (pi, p2) of the open region 12 can be in the range of 0.01 g / cm 2 , 0.012 g / cm 2 , 0.015 g / cm 2 , 0.018 g / cm 2 , 0.02 g / cm 2 , 0.023 g / cm 2 , 0.025 g / cm 2 , 0.028 g / cm 2 , 0.03 g / cm 2 or a range consisting of any two of them.

[0133] Further, the ratio N / P0 of the areal capacity of the first region to the areal capacity of the main region 11 is greater than the ratio N / P x , i.e. the ratio N / P0 of the areal capacity of the first region to the areal capacity of the main region 11 is greater than the ratio N / P1 of the areal capacity of the first sub-region to the areal capacity of the first open region 121, and the ratio N / P0 of the areal capacity of the first region to the areal capacity of the main region 11 is greater than the ratio N / P2 of the areal capacity of the second sub-region to the areal capacity of the second open region 122.

[0134] In particular, the ratio N / P0 of the areal capacity of the first region to the areal capacity of the main region 11 and the ratio N / P1 of the areal capacity of the first sub-region to the areal capacity of the first open region 121 can satisfy 0.02≤N / P1-N / P0≤2, preferably 0.05≤N / P1-N / P0≤0.2.

[0135] Further, the ratio N / P0 of the areal capacity of the first region to the areal capacity of the main region 11 and the ratio N / P2 of the areal capacity of the second sub-region to the areal capacity of the second open region 122 can satisfy 0.02≤N / P2-N / P0≤2, preferably 0.05≤N / P2-N / P0≤0.2.

[0136] Wherein, N / P1-N / P0 can be greater than, equal to or less than N / P2-N / P0.

[0137] Exemplarily, the above N / P x -N / P0 (i.e. N / P1-N / P0, N / P2-N / P0) can be 0.02, 0.05, 0.08, 0.1, 0.13, 0.15, 0.18, 0.2, 0.5, 0.8, 1, 1.3, 1.5, 1.8, 2 or a range consisting of any two of them, for example 0.05≤N / P1-N / P0≤0.18, 0.05≤N / P2-N / P0≤0.18.

[0138] Therefore, the N / P (N / P1, N / P2) corresponding to the opening region 12 is greater than the N / P (N / P0) corresponding to the main body region 11. On the one hand, the main body region 11 has a larger capacity, and the capacity lost by the opening region due to the pore-forming can be compensated by the main body region 11, thereby maintaining a high energy density of the battery; on the other hand, it is beneficial to increase the height difference between the opening region 12 and the main body region 11, increase the heat dissipation effect, and at the same time, increase the heat dissipation effect at the interface of the first pole piece 1 and the diaphragm 3, thereby improving the heat dissipation performance of the battery cell 4.

[0139] In addition, when the first pole piece 1 is a positive pole piece and the second pole piece 2 is a negative pole piece, the main body region 11 of the first pole piece 1 has a larger area density, and the corresponding N / P (N / P0) is smaller, which means that the negative material (first region) corresponding to the main body region 11 is more fully utilized, and the negative potential is lower. Under the condition that the overall voltage remains unchanged, the positive potential is lowered, the corresponding positive oxidation is reduced, the stability is improved (the more delithiated the positive electrode is, the more unstable it is), thereby improving the thermal safety performance of the battery cell 4.

[0140] In some embodiments, the surface capacity of the main body region 11 can be 1.5-4 mAh / cm 2 , for example, 1.5 mAh / cm 2 , 2 mAh / cm 2 , 2.5 mAh / cm 2 , 3 mAh / cm 2 , 3.5 mAh / cm 2 , 4 mAh / cm 2 , or a range formed by any two of them. Relatively speaking, if the surface capacity of the main body region 11 is too small (<1.5 mAh / cm 2 ), the energy density of the battery is affected, and if the surface capacity of the main body region is too large (>4 mAh / cm 2 ), the heat dissipation performance of the battery is affected. Therefore, by controlling the surface capacity of the main body region 11 within the above range, it is beneficial to further consider improving the energy density and heat dissipation performance of the battery.

[0141] In some embodiments, the surface capacity of the opening region 12 is 1.0-3.5 mAh / cm 2 , i.e., the surface capacity of the first opening region 121 can be 1.0-3.5 mAh / cm 2 , and the surface capacity of the second opening region 122 can be 1.0-3.5 mAh / cm 2 .

[0142] For example, the surface capacity of the opening region 12 (the first opening region 121 and the second opening region 122) described above can be 1 mAh / cm 21.5 mAh / cm 2 2 mAh / cm 2 2.5 mAh / cm 2 3 mAh / cm 2 3.5 mAh / cm 2 or any two of them.

[0143] Specifically, the surface capacity = capacity / area, which can be measured by conventional methods in the art, for example, after assembling into a button cell to test its capacity. Taking the first tab 1 as an example, the surface capacity test process can include: (1) disassemble the battery, take out the first tab 1; (2) cut the tab sample of the measured area from the first tab 1 (when testing the surface capacity of the main body area 11, the tab sample of the measured area is the part of the first tab 1 where the main body area 11 is located, when testing the surface capacity of the opening area 12, the tab sample of the measured area is the part of the first tab 1 where the corresponding opening area 12 is located), and record the surface area (i.e. the projection area of the first active material layer 120 on the first current collector 110 in the tab sample) S of the tab sample; (3) assemble the tab sample of the measured area, the separator 3, the lithium sheet, and the electrolyte into a button cell; (4) charge and discharge the button cell (in the charging process, charge to the charge limit voltage; in the discharging process, discharge to the discharge limit voltage), get the capacity C, and calculate the surface capacity according to the surface capacity = C / S.

[0144] Specifically, the above-mentioned recess 100 can be a hole or a groove (a continuous linear groove), for example, a circular hole, but is not limited thereto.

[0145] Specifically, the opening area 12 is formed by perforating part of the first active material layer 120 (such as the edge area and the circular arc area after being made into a wound cell 4), and has a plurality of recesses (such as holes) 100 distributed on the surface. The surface (i.e. the side of the opening area 12 away from the first current collector 110) of each opening area 12 (such as each first opening area 121, each second opening area 122, etc.) is distributed with a plurality of recesses 100, which are substantially uniformly distributed on the surface of the opening area 12 (for example, substantially arrayed (matrix distributed) on the surface of the opening area 12), and each recess 100 extends from the surface of the opening area 12 to the inside of the opening area 12. The depth direction of the recess 100 is substantially parallel to the thickness direction of the opening area 12, and the depth of the recess 100 can be less than the thickness of the opening area 12, i.e. the recess 100 does not penetrate the opening area 12, i.e. there is a first active material layer 120 between the recess 100 and the first current collector 110.

[0146] Specifically, the depth of the recess 100 in the first open area 121 is less than the thickness of the first open area 121, and the depth of the recess 100 in the second open area 122 is less than the thickness of the second open area 122.

[0147] In some embodiments, the depth of the recess 100 in the open area 12 (the depth H1 of the recess 100 in the first open area 121, the depth H2 of the recess 100 in the second open area 122) can be 2-30 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.

[0148] In addition, the hole diameter D of the hole 100 in the open area 12 (the hole diameter D1 of the hole 100 in the first open area 121, the hole diameter D2 of the hole 100 in the second open area 122) can be 2-330 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.

[0149] Generally, it is preferred that the hole diameter D1 of the recess 100 in the first open area 121 is 10-150 μm, and the hole diameter D2 of the recess 100 in the second open area 122 is 10-150 μm, which is beneficial to improve the heat dissipation performance of the battery cell 4 while maintaining a relatively high energy density of the battery cell 4.

[0150] In addition, in the first open area 121, the hole spacing L1 of the recess 100 can be 20-3000 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 a range consisting of any two of them, preferably 20-300 μm.

[0151] In addition, in the second opening region 122, the hole spacing L2 of the recess 100 can be 20-3000 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 a range between any two of them, preferably 20-300 μm.

[0152] In the embodiments of the present application, the hole spacing (such as L1, L2) refers to the distance between the centers of two adjacent recesses 100. For example, 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 circular), and the center of the recess 100 is the center of the circle of the recess 100 (also the center of the projection of the recess 100 on the surface of the first current collector 110).

[0153] In the embodiments of the present application, the positive active material can include a lithium-containing positive active material, and specifically can include one or more of lithium cobaltate, lithium nickelate, lithium manganate, lithium manganate, nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material, lithium iron phosphate (LFP), lithium nickel manganate, etc. The positive current collector can include an aluminum foil or other conventional positive current collector in the art.

[0154] In the embodiments of the present application, the negative active material can include a graphite-based material and / or a silicon-based material. The silicon-based material can include silicon monoxide and / or silicon-carbon material, etc. The graphite-based material can include graphite and / or graphite-based composite material, which includes graphite and a coating material present on the surface of the graphite. The coating material can include amorphous carbon (non-crystalline carbon), for example, the graphite-based material is non-crystalline carbon-coated graphite (i.e., the coating material in the graphite-based composite material is non-crystalline carbon).

[0155] Specifically, the above-mentioned graphite can include artificial graphite and / or natural graphite.

[0156] In some embodiments, the negative active material includes non-crystalline carbon-coated graphite, which is conducive to improving the fast charging performance and thermal stability of the battery.

[0157] Specifically, the greater the amorphous carbon content (i.e., the greater the amorphous carbon coating amount) in the graphite-based composite material, the more conducive it is to improving the fast-charging performance of the battery. However, amorphous carbon is prone to side reactions with electrolyte, and the greater the amorphous carbon coating amount, the more likely it is to cause the thermal stability of the graphite-based composite material to decrease, and in turn, the thermal stability of the battery to decrease. Therefore, after assembling the components such as the positive electrode sheet and the negative electrode sheet according to the prior art into a battery, the fast-charging performance and the thermal stability of the battery are often difficult to balance. According to the research of the inventor, in the present embodiment, the opening region 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, etc. Therefore, when amorphous carbon-coated graphite is used as the negative active material in the present embodiment, the fast-charging performance of the battery can be improved while the thermal stability of the battery is also improved, that is, the thermal stability of the fast-charging battery can be improved, and the defect that the fast-charging performance and the thermal stability of the battery are difficult to balance in the prior art can be effectively overcome.

[0158] In some embodiments, the negative active material layer includes a silicon-based material, which is conducive to improving the thermal stability of the battery while balancing the improvement of the energy density and capacity of the battery, etc.

[0159] Specifically, the mass content of the silicon-based material in the negative active material layer can be 0.5% to 30%, for example, 0.5%, 1%, 3%, 5%, 8%, 10%, 15%, 20%, 25%, 30%, or a range formed by any two of them.

[0160] Generally, when a silicon-containing negative electrode (i.e., a negative electrode sheet including a silicon-based material in the negative active material layer) is used, due to the presence of a large amount of additives with poor thermal stability (such as FEC, etc.) in the electrolyte, etc., a large amount of heat is easily generated inside the battery in a high-temperature environment such as furnace temperature testing, which is not conducive to the thermal stability of the battery. In the present embodiment, by providing the opening region 12 on the first electrode sheet 1, the heat inside the battery cell 4 can be dissipated, thus effectively solving the problem of poor thermal stability of the battery using a silicon-containing negative electrode.

[0161] The conductive agent and the binder in the above-mentioned positive active material layer and negative 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-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, carboxymethyl cellulose (CMC), polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber (SBR).

[0162] In the embodiments of the present application, the positive current collector can be a conventional positive current collector in the art, for example, including an aluminum foil; and the negative current collector can be a conventional negative current collector in the art, for example, including a copper foil, such as a carbon-coated copper foil, etc.

[0163] In addition, the battery further includes an electrolyte, the electrolyte including a solvent, a solute and an additive, the solvent can include an organic solvent, for example, including one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), and ethyl propyl carbonate (EPC); the solute can include a lithium salt, the lithium salt can include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), and lithium hexafluoroarsenate (LiAsF6); and the additive can 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).

[0164] Generally, in order to reduce the unstable phenomenon in the battery under a 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 embodiments of the present application has good thermal stability, and specifically can satisfy 1

[0165] Exemplarily, V2 / V1 is, for example, 1.005, 1.006, 1.008, 1.01, 1.1, 1.3, 1.5, 1.8, 2, or a range formed by any two of them.

[0166] In some embodiments, V2 / V1≤1.01, for example, 1.005≤V2 / V1≤1.01.

[0167] In addition, the battery can further satisfy 0.5≤(T max -T0) / C≤5, C is the capacity of the battery, in Ah, T maxT0 is the maximum temperature reached by the battery during the process of keeping the battery in the full state of charge in an environment with a temperature of T0, 130℃≤T0≤150℃, T max The unit is ℃.

[0168] Exemplarily, (T max -T0) / 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 a range composed of any two of them, for example, 0.5≤(T max -T0) / C≤1.

[0169] In specific implementation, the volume V1 of the battery can be tested first, and then the battery is placed in a heating device such as an oven, gradually heated from room temperature to the target temperature T0, and then kept at the target temperature T0 for a time t, and then the volume V2 of the battery is measured; after the temperature in the heating device reaches T0, the battery will continue to heat up, and the temperature of the battery can be tested by a temperature sensing line of the heating device to obtain the maximum temperature T max .

[0170] In the embodiment of the application, the full state of charge of the battery is the state of charging the battery to full capacity, and in specific implementation, the battery can be charged to the upper limit voltage to complete the full charging of the battery (i.e., the battery reaches the full state of charge), and then the furnace temperature test is performed.

[0171] In the embodiment of the application, the positive electrode sheet and the negative electrode sheet can be prepared by conventional methods in the art, for example, in the preparation process of the positive electrode sheet, the positive electrode active material, the conductive agent and the binder and other materials can be placed in a solvent to form a positive electrode slurry, and the solvent used includes N-methyl pyrrolidone (NMP), for example, and then the positive electrode slurry is coated on the surface of the positive electrode current collector, and after drying, rolling and other processes, a positive electrode active material layer is formed on the surface of the current collector to prepare a positive electrode sheet precursor; then, the preset region on the surface of the positive electrode sheet precursor is punched to form an open hole region 12 to prepare the positive electrode sheet.

[0172] In the embodiment of the application, the preset region on the surface of the positive electrode sheet precursor can be punched by conventional methods in the art, for example, laser punching can be performed by using a conventional laser puncher in the art.

[0173] The battery of the embodiment of the application can be prepared by conventional methods in the art, for example, the positive electrode sheet and the negative electrode sheet are cut according to the preset shape and size; then, the positive electrode sheet, the separator 3 and the negative electrode sheet are placed in sequence (the stacked structure is shown in Figure 2 ). Figure 3After the core is encapsulated, baked, injected with electrolyte (i.e. injection of electrolyte), formed, double-sealed, sorted and OCV (open circuit voltage test) and other processes, the lithium ion battery is prepared. These steps / processes are conventional operations in the art and are not particularly limited.

[0174] The application is further described below through specific examples.

[0175] Example 1

[0176] 1. Preparation of the positive electrode sheet

[0177] The conductive carbon black and carbon nanotubes are added to the PVDF glue solution, stirred uniformly, then lithium cobaltate is added, and NMP is added and stirred uniformly to obtain a positive electrode slurry;

[0178] The positive electrode slurry is coated on the positive and negative surfaces of the aluminum foil, and after baking and rolling, the positive electrode active material layer is formed on the positive and negative surfaces of the aluminum foil to obtain a positive electrode sheet precursor. In the positive electrode active material layer, the mass content of lithium cobaltate is 97.6%, the mass content of PVDF is 1.05%, and 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);

[0179] Laser drilling is performed on the surface of the positive electrode sheet precursor in the pre-set area to form a concave part (hole) 100 that does not penetrate the positive electrode active material layer, to form an open hole area 12, and obtain a positive electrode sheet (the structure of the positive electrode sheet is shown in Figure 1 ).

[0180] 2. Preparation of the negative electrode sheet

[0181] The graphite, conductive carbon black, SBR and CMC are mixed uniformly according to a mass ratio of 97.3:0.5:1.3:0.9, deionized water is added, and after being dispersed uniformly, a negative electrode slurry is prepared.

[0182] The negative electrode slurry is coated on the positive and negative surfaces of the carbon-coated copper foil, and after baking and rolling, the negative electrode active material layer is formed on the positive and negative surfaces of the carbon-coated copper foil to obtain a negative electrode sheet.

[0183] 3. Assembly of the battery

[0184] The positive electrode sheet and the negative electrode sheet are cut according to the pre-set shape and size;

[0185] Then, the positive electrode sheet, the separator 3 and the negative electrode sheet are sequentially stacked and placed to form a wound core 4 (core); the core is encapsulated with an aluminum plastic film, and after being sequentially baked, injected with electrolyte (i.e. injection of electrolyte), formed, double-sealed, sorted and OCV, a lithium ion battery is prepared.

[0186] The preparation process of the electrolyte is as follows: in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), 40 parts of EC, 40 parts of DEC, and 5 parts of FEC were uniformly mixed, and then 10 parts of fully dried lithium hexafluorophosphate was rapidly added, after dissolution, 5 parts of PS and VC (the mass ratio of PS to VC was 1:1) were added, to obtain the electrolyte.

[0187] As shown in Figure 2 , the separator 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 sequentially stacked, the first adhesive layer 31 is bonded to the positive electrode sheet, the second adhesive layer 32 is bonded to the negative electrode sheet, the first adhesive layer 31 is a PVDF layer, the thickness of the first adhesive layer 31 is 1 μm, the ceramic layer 34 is an aluminum oxide layer, the thickness of the ceramic layer 34 is 2 μm, the substrate layer 33 is a PP / PE double-layer composite film, the thickness of the substrate layer 33 is 5 μm, and the second adhesive layer 32 is a PVDF layer, the thickness of the second adhesive layer 32 is 1 μm.

[0188] The peeling force F0 of the separator 3 from the main area 11, the peeling force F1 of the separator 3 from the first opening area 121, and the peeling force F2 of the separator 3 from the second opening area 122 satisfy F0 > F1 + F2.

[0189] As shown in Figures 3 to 5 , the positive electrode sheet is provided with a positive electrode tab (first tab 13), and the negative electrode sheet is provided with a negative electrode tab (second tab 23), 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 the positive electrode tab and the negative electrode tab are respectively bonded to the aluminum plastic film through the tab adhesive 6 at the position where the tabs extend out.

[0190] The core structure is as shown in Figure 3 , the positive electrode sheet includes a plurality of first straight sections 101 and a first bending section 102 connected between each two adjacent first straight sections 101, the width w 102 of the first bending section 102 is about 10 mm or so; correspondingly, the negative electrode sheet includes a plurality of second straight sections 201 and a second bending section 202 connected between each two adjacent second straight sections 201.

[0191] The structure of the positive electrode sheet is as shown in Figure 1As shown, the first open hole area 121 exists on each of the opposite edges of the positive active material layer in the width direction, and the length of the first open hole area 121 is equal to the length of the positive active material layer, so that the first open hole area 121 exists on each of the opposite sides of the battery cell 4 in the first direction x; the second open hole area 122 is arranged on each of the first bending portions 102 having the positive active material layer, so that the second open hole area 122 exists on each of the opposite sides of the battery cell 4 in the second direction y; and the total area of the main body area 11 of the positive active material layer is greater than the total area of the open hole area 12.

[0192] Examples 2 to 23: Different from Example 1, the width of each open hole area 12, the hole diameter of the hole 100, the hole depth, the hole spacing, and the parameters such as the resistivity, the area density, and the area capacity of each area are different, and specific parameters are shown in Tables 1 to 3. Except for the differences shown in Tables 1 to 3, the remaining conditions are the same.

[0193] Comparative Example 1: Different from Example 1, the surface of the positive active material layer is not punched (i.e., no open hole area 12 is arranged), and the remaining conditions are the same as those of Example 1.

[0194] Comparative Example 2: Different from Example 1, the open hole area 12 is arranged in the middle area of the first straight portion 101, and the first bending portion 102 and the edges on the opposite sides of the positive active material layer in the width direction are not punched (i.e., no open hole area 12 is arranged). That is, the first open hole area 121 of Example 1 is translated to the first middle position of the positive plate in the width direction (the first direction x) of the positive plate (in Tables 1 to 3, w1, D1, L1, H1, and the like are the related parameters of the first open hole area 121 translated to the first middle position), and the second open hole 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 to 3, w2, D2, L2, H2, and the like are the related parameters of the second open hole area 122 translated to the second middle position). The remaining conditions are the same as those of Example 1.

[0195] Comparative Example 3: Different from Example 1, only the first open hole area 121 is arranged on the first plate 1, and the second open hole area 122 is not arranged (i.e., the positive active material layer on the first bending portion 102 is not punched, and the second open hole area 122 is not arranged on the first bending portion 102). The remaining conditions are the same as those of Example 1.

[0196] Comparative Example 4: The difference from Example 1 is that only the second opening area 122 is provided on the first electrode 1, and the first opening area 121 is not provided (that is, no holes are made on the opposite sides of the width direction of the positive electrode active material layer, and the first opening area 121 does not exist on the opposite sides of the width direction of the positive electrode active material layer). The other conditions are the same as in Example 1.

[0197] In the various embodiments and comparative examples, the width w1 of the first opening region 121, the aperture D1 of the hole in the first opening region 121, the hole spacing L1 of the hole in the first opening region 121, the depth H1 of the hole in the first opening region 121, and the porosity of the first opening region 121 are specified. The resistivity R1 of the first opening region 121, the areal density ρ1 of the first opening region 121, the areal capacity C1 of the first opening region 121, the ratio N / P1 of the areal capacity of the first sub-region of the negative electrode to the areal capacity of the first opening region 121 of the positive electrode, the pore diameter D1 of the first opening region 121 and the thickness H of the first adhesive layer 31 of the separator 3. 31 The ratio (D1 / H) 31 The aperture D1 of the hole in the first opening region 121 and the thickness H of the ceramic layer 34 of the diaphragm 3 are... 34 The ratio (D1 / H) 34 The results are summarized in Table 1.

[0198] In the various embodiments and comparative examples, the width w2 of the second opening region 122, the aperture D2 of the hole in the second opening region 122, the hole spacing L2 of the hole in the second opening region 122, the depth H2 of the hole in the second opening region 122, and the porosity of the second opening region 122 are specified. The resistivity R2 of the second opening region 122, the areal density ρ2 of the second opening region 122, the areal capacity C2 of the second opening region 122, the ratio N / P2 of the areal capacity of the second sub-region of the negative electrode to the areal capacity of the second opening region 122 of the positive electrode, and the pore diameter D2 of the second opening region 122 and the thickness H of the first adhesive layer 31 of the separator 3. 31 The ratio (D2 / H) 31 The aperture D2 of the second opening region 122 and the thickness H of the ceramic layer 34 of the diaphragm 3 are related. 34 The ratio (D2 / H) 34 The results are summarized in Table 2.

[0199] In the various embodiments and comparative examples, R0 / (R1+R2), ρ0 / (ρ1+ρ2), N / P1-N / P0, and N / P2-N / P0 are summarized in Table 3.

[0200] In addition, the V2 / V1 satisfied by the battery in each embodiment and comparative example is shown in Table 3, V1 is the volume of the battery before the 130°C oven temperature test, and V2 is the volume of the battery after being kept at a temperature of 130°C for 60 minutes in a full state (i.e., V2 is the volume of the battery after the 130°C oven temperature test), i.e., T0 = 130°C, t = 60 minutes.

[0201] In addition, the (T max -T0) / C satisfied by the battery in each embodiment and comparative example is shown in Table 3, C is the discharge capacity (5 Ah) of the battery, T max is the maximum temperature reached by the battery during the process of being kept at a temperature of T0 (130°C) in a full state. The test process of the discharge capacity C of the battery is as follows: the battery is charged at a rate of 0.2C to 4.5V, then charged at a constant voltage to 0.025C, and the full charge of the battery is completed; then, the battery is discharged at a rate of 0.2C until the voltage of the battery decreases to 3V, and the capacity discharged during the discharging process is recorded as C.

[0202] In addition, the volume energy density (ED) loss rate of the battery is measured and shown in Table 4. ED = discharge capacity C x voltage platform / volume of battery 4, and the voltage platform of the 4.5V system is about 3.9V; in each embodiment and comparative example, the ED loss rate (energy density loss rate) represents the difference between the ED of the battery of the embodiment or comparative example and the ED of the battery of Comparative Example 1, expressed as a percentage of the ED of the battery of Comparative Example 1, i.e., 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.

[0203] In addition, the oven temperature test pass rate of the battery at different temperatures is shown in Table 4, and the oven temperature test process is as follows: the battery is kept at a temperature of T1 for 1 hour (T1 is 130°C, 132°C, 135°C, and 140°C, respectively, as shown in Table 4), and whether the battery catches fire is observed; if not, it passes, if it catches fire, it does not pass, and the oven temperature test pass rate = number of batteries that pass / total number of batteries subjected to the oven temperature test.

[0204] In addition, the battery was directly charged at different rates (such as 3C direct charging, 4C direct charging and 5C direct charging in Table 4) respectively, and the lithium precipitation of the negative plate was observed. The lithium precipitation of the battery after direct charging at different rates is shown in Table 4. Among them, (1) the battery direct charging process means that the battery constant current process has only one charging current. 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 convert to constant voltage charging to the cut-off current; (2) "slight lithium precipitation" means that after the battery is disassembled, there is a small area of lithium precipitation on the surface of the negative plate, for example, the edge area (i.e. top edge and bottom edge) of the negative plate in the width direction, the crease or single-sided area and other easy lithium precipitation areas; "serious lithium precipitation" means that after the battery is disassembled, there is a large amount of lithium precipitation on the surface of the negative plate, which is reflected in the performance, that is, the capacity of the battery is greatly reduced.

[0205] Table 1

[0206]

[0207] Table 2

[0208]

[0209] Table 3

[0210]

[0211] Table 4

[0212]

[0213] From Tables 1-4, it can be seen that, compared with Comparative Examples 1-4, in Examples 1-23, the first opening area 121 is arranged at the edge in the width direction of the positive plate, and the second opening area 122 is arranged at the first bending part 102 of the positive plate, so that the opening area 12 exists on each side of the battery cell 4 in different directions, and the control is 0.5≤R0 / (R1+R2)≤20, which can significantly improve the thermal safety of the battery, while maintaining a high energy density of the battery, and also can alleviate the lithium precipitation problem of the negative plate.

[0214] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery, characterized in that, The battery cell includes a first electrode, the first electrode including at least one first straight portion and a first bent portion connected to the first straight portion, the first bent portion being located on at least one side of the battery cell in a second direction; The first electrode includes a first active material layer, which includes a main body region and an opening region with recesses distributed on its surface. The opening region includes a first opening region located at at least one edge of the first active material layer in a first direction and a second opening region located at the first bend. The first direction intersects with the second direction. The resistivity R0 of the main body region, the resistivity R1 of the first opening region, and the resistivity R2 of the second opening region satisfy 0.5≤R0 / (R1+R2)≤20; The resistivity R0 of the main region is 120~250 KΩ·cm; The resistivity R1 of the first opening region is 40~150 KΩ·cm; The resistivity R2 of the second opening region is 40~150 KΩ·cm.

2. The battery according to claim 1, characterized in that, The ratio of the resistivity of the first opening region to the resistivity of the main body region is greater than or equal to 0.2 and less than 1; And / or, the ratio of the resistivity of the second opening region to the resistivity of the main body region is greater than or equal to 0.2 and less than 1; And / or, 0.54≤R0 / (R1+R2)≤18.

3. The battery according to claim 2, characterized in that, The ratio of the resistivity of the first opening region to the resistivity of the main body region is 0.2 to 0.7; And / or, the ratio of the resistivity of the second opening region to the resistivity of the main body region is 0.2 to 0.7; And / or, 0.55≤R0 / (R1+R2)≤3.

4. The battery according to claim 1, characterized in that, The porosity of the main body region is less than that of the open area.

5. The battery according to claim 1 or 4, characterized in that, Porosity of the main region Porosity of the first opening region Porosity of the second opening region satisfy ; And / or, the ratio of the porosity of the main body region to the porosity of the first open region is greater than or equal to 0.1; And / or, the ratio of the porosity of the main body region to the porosity of the second open region is greater than or equal to 0.1; And / or, the porosity of the main region It ranges from 12% to 30%; And / or, the porosity of the first opening region It ranges from 15% to 30%; And / or, the porosity of the second opening region It ranges from 15% to 30%.

6. The battery according to claim 5, characterized in that, The ratio of the porosity of the main body region to the porosity of the first open region is 0.2 to 1; And / or, the ratio of the porosity of the main body region to the porosity of the second open region is 0.2 to 1.

7. The battery according to claim 1, characterized in that, The areal density ρ0 of the main body region, the areal density ρ1 of the first opening region, and the areal density ρ2 of the second opening region satisfy 0.5≤ρ0 / (ρ1+ρ2)≤1.5; And / or, the ratio of the areal density of the first opening region to the areal density of the main body region is greater than or equal to 0.5 and less than 1; And / or, the ratio of the areal density of the second opening region to the areal density of the main body region is greater than or equal to 0.5 and less than 1; And / or, the areal density of the main region is between 0.01 and 0.03 g / cm³. 2 between; And / or, the areal density of the first opening region is between 0.01 and 0.03 g / cm³. 2 between; And / or, the areal density of the second opening region is between 0.01 and 0.03 g / cm³. 2 between.

8. The battery according to claim 7, characterized in that, The surface density ρ0 of the main body region, the surface density ρ1 of the first opening region, and the surface density ρ2 of the second opening region satisfy 0.51≤ρ0 / (ρ1+ρ2)≤0.61; And / or, the ratio of the areal density of the first opening region to the areal density of the main body region is 0.6 to 0.93; And / or, the ratio of the areal density of the second opening region to the areal density of the main body region is 0.6 to 0.

93.

9. The battery according to any one of claims 1-4, characterized in that, The first electrode is a positive electrode.

10. The battery according to claim 9, characterized in that, The battery further includes a negative electrode sheet, which comprises a second active material layer. The second active material layer includes a first region corresponding to the main region, a first sub-region corresponding to the first opening region, and a second sub-region corresponding to the second opening region. The ratio of the surface area of ​​the first region to the surface area of ​​the main region, N / P0, and the ratio of the surface area of ​​the first sub-region to the surface area of ​​the first opening region, N / P1, satisfy 0.02≤N / P1-N / P0≤2; And / or, the ratio of the surface area of ​​the first region to the surface area of ​​the main region, N / P0, and the ratio of the surface area of ​​the second sub-region to the surface area of ​​the second opening region, N / P2, satisfy 0.02≤N / P2-N / P0≤2; And / or, the areal capacity of the main body region is 1.5~4mAh / cm². 2 ; And / or, the areal capacity of the opening region is 1.0~3.5mAh / cm². 2 .

11. The battery according to claim 10, characterized in that, 0.05≤N / P1-N / P0≤0.5; And / or, 0.05≤N / P2-N / P0≤0.

5.

12. The battery according to any one of claims 1-4, characterized in that, The battery also includes a second electrode with the opposite polarity to the first electrode and a separator located between the first electrode and the second electrode, the separator being bonded to the first electrode and the second electrode respectively.

13. The battery according to claim 12, characterized in that, The diaphragm includes a first adhesive layer, a ceramic layer, a substrate layer and a second adhesive layer stacked in sequence. The first adhesive layer is bonded to the first electrode and the second adhesive layer is bonded to the second electrode. And / or, the aperture D1 of the recess in the first opening region and the thickness H of the ceramic layer of the diaphragm. 34 Satisfying 1.2≤D1 / H 34 ≤160; And / or, the aperture D2 of the recess in the second opening region and the thickness H of the ceramic layer of the diaphragm. 34 Satisfying 1.2≤D² / H 34 ≤160; And / or, the aperture D1 of the recess in the first opening region and the thickness H of the first adhesive layer of the diaphragm. 31 Satisfying 2.5≤D1 / H 31 ≤320; And / or, the aperture D2 of the recess in the second opening region and the thickness H of the first adhesive layer of the diaphragm. 31 Satisfying 2.5≤D² / H 31 ≤320; And / or, the peel force F0 between the diaphragm and the main body region, the peel force F1 between the diaphragm and the first opening region, and the peel force F2 between the diaphragm and the second opening region satisfy F0 > F1 + F2.

14. The battery according to claim 13, characterized in that, 2≤D1 / H 34 ≤150; And / or, 2≤D² / H 34 ≤150; And / or, 2.5≤D1 / H 31 ≤300; And / or, 2.5 ≤ D² / H 31 ≤300.

15. The battery according to claim 13 or 14, characterized in that, The thickness of the substrate layer is 2~20μm; And / or, the thickness of the ceramic layer is 1~5μm; And / or, the thickness of the first adhesive layer is 0.5~4μm; And / or, the thickness of the second adhesive layer is 0.5~4μm.

16. The battery according to any one of claims 1-4, characterized in that, The first active material layer has the first opening area on both sides of its opposite edges in the first direction; And / or, the width of the first opening area is 1~9mm; And / or, in the first opening region, the depth of the recess is 2~30μm, the diameter of the recess is 10~150μm, and the distance between adjacent recesses is 20~3000μm; The depth of the recess in the first opening region is less than the thickness of the first opening region; And / or, the width of the second opening area is 2mm-20mm; And / or, in the second opening region, the depth of the recess is 2-30 μm, the diameter of the recess is 10-150 μm, and the distance between adjacent recesses is 20-3000 μm; And / or, the depth of the recess in the second opening region is less than the thickness of the second opening region.

17. The battery according to claim 16, characterized in that, In the first opening region, the distance between adjacent recesses is 20~300μm; And / or, in the second opening region, the distance between adjacent recesses is 20~300μm.

18. The battery according to any one of claims 1-4, characterized in that, The battery cell has a third side and a fourth side opposite to each other in the second direction. The first electrode includes a plurality of first bends, some of which are located on the third side of the battery cell and others are located on the fourth side of the battery cell. At least one of the first bends located on the third side of the battery cell is provided with a second opening area, and at least one of the first bends located on the fourth side of the battery cell is provided with a second opening area.

19. The battery according to claim 18, characterized in that, Each of the first bends with the first active material layer on the third side of the battery cell is provided with a second opening area; And / or, each of the first bends with the first active material layer located on the fourth side of the battery cell is provided with the second opening area.

20. The battery according to any one of claims 1-4, characterized in that, The first electrode is a positive electrode, and the cell also includes a negative electrode. The negative electrode includes a negative electrode active material layer, which includes a silicon-based material. The mass content of the silicon-based material in the negative electrode active material layer is 0.5-30%.

21. The battery according to any one of claims 1-4, characterized in that, The battery satisfies 1 < V2 / V1 ≤ 2, where V1 is the volume of the battery, V2 is the volume of the battery after being kept at a temperature of T0 for a time t when fully charged, 130℃ ≤ T0 ≤ 150℃, and 55min ≤ t ≤ 65min. And / or, the battery satisfies 0.5 ≤ (T max -T0) / C≤5, where C is the capacity of the battery in Ah, T max The maximum temperature reached by the battery in a fully charged state during the process of maintaining it in an environment at temperature T0, where 130℃≤T0≤150℃, and T max The unit is ℃.

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