Battery cell and battery

Abstract

The utility model provides a battery cell and a battery, and relates to the technical field of batteries. The battery cell provided by the utility model comprises a pole piece, tabs and a diaphragm, the pole piece comprises a positive pole piece and a negative pole piece, the diaphragm is arranged between the positive pole piece and the negative pole piece, and the tabs can comprise a positive tab and a negative tab which are positioned on the same side of the pole piece; the positive plate comprises a composite current collector, and the tab comprises at least two metal sheets; the at least two metal sheets are connected to the edges of the two sides of the composite current collector respectively; at least partial areas of the at least two metal sheets are mutually welded to form a welding area, so that the contact area between the pole piece and the tab is increased, the overcurrent capability between the pole piece and the tab is improved, the poor comprehensive performance of the battery cell is improved, the temperature rise at the tab is prevented from being too high during charging and discharging, and the tab is prevented from being easily fused and the battery is prevented from being on fire.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell and a battery. Background Art

[0002] Rechargeable batteries, also known as secondary batteries, refer to electrochemical energy devices that can be charged and discharged in cycles, such as lithium-ion batteries, which are widely used in electronic products such as mobile phones, electric vehicles, tablets, and wearable devices.

[0003] In the related art, the battery cell includes a positive electrode sheet, a negative electrode sheet and a separator, the separator is arranged between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet and the negative electrode sheet are respectively connected with a positive electrode ear and a negative electrode ear. In order to improve the energy density of the battery cell, the current collector of the electrode sheet in the battery cell can adopt a composite current collector, that is, the current collector is a multi-layer composite structure.

[0004] However, the current use of composite current collectors in batteries will lead to a weakening of the current flow capacity between the pole piece and the pole ear, poor overall performance of the battery cell, and excessive temperature rise at the pole ear during charging and discharging, causing the pole ear to easily melt and even cause the battery to catch fire. Utility Model Content

[0005] In view of the above problems, the embodiments of the present application provide a battery cell and a battery to solve the technical problems that when the current battery electrode adopts a composite current collector, the current flow capacity between the electrode and the pole ear is weakened, the overall performance of the battery cell is poor, and the temperature rise at the pole ear is too high during charging and discharging.

[0006] In order to achieve the above-mentioned purpose, the present application provides a battery cell, which includes a pole piece, a pole ear and a diaphragm, the pole piece includes a positive pole piece and a negative pole piece, the diaphragm is arranged between the positive pole piece and the negative pole piece, the pole ear may include a positive pole ear and a negative pole ear located on the same side of the pole piece; the positive pole piece includes a composite current collector, and the positive pole ear includes at least two metal sheets; at least two metal sheets are respectively connected to the edges of both sides of the composite current collector; at least part of the area of ​​at least two metal sheets is welded to each other to form a positive electrode welding area. On the side of the composite current collector connected to the pole ear, the distance between the edge of the diaphragm and the edge of the composite current collector is H3, and the height of the welding area is H, wherein H<H3, and / or, H3≥2.0mm.

[0007] The battery provided in the embodiment of the present application improves the design of the battery structure and uses a pole piece with a composite current collector. The pole lug connected to each pole piece is connected and welded together using at least two metal sheets, thereby increasing the contact area between the pole piece and the pole lug, improving the current flow capacity between the pole piece and the pole lug, improving the poor overall performance of the battery cell, avoiding excessive temperature rise at the pole lug during charging and discharging, thereby preventing the pole lug from easily melting and the battery from catching fire.

[0008] As an optional implementation, at least one of the at least two metal sheets has a pole ear portion, and the pole ear portion is located outside the welding area; the width of at least a portion of the welding area is greater than the width of the pole ear.

[0009] As an optional embodiment, the positive electrode welding area includes a first welding area and a second welding area, the first welding area is connected to the composite current collector, and the second welding area is connected to the side of the first welding area away from the composite current collector; the pole ear is located on the side of the second welding area away from the first welding area.

[0010] As an optional implementation, the width of the first welding area is D1, and the width of the second welding area is D2, wherein D1×0.5≥D2≥D1×0.2.

[0011] As an optional implementation, the height of the first welding area is H1, and the height of the second welding area is H2, wherein 0.05≤(D2×H2) / (D1×H1)≤0.6.

[0012] As an optional implementation, the projections of the positive electrode sheet and the negative electrode sheet perpendicular to the surface of the diaphragm are within the coverage of the diaphragm; the projection of the positive electrode welding area perpendicular to the surface of the diaphragm is within the coverage of the diaphragm.

[0013] At the same time, by optimizing the coverage between the separator and the pole piece in the battery, the proportion of poor coverage during the production process is reduced, the process yield and efficiency of the battery cell are improved, the quality of the battery cell is improved, and the overall performance of the battery is improved.

[0014] As an optional implementation, on the side of the composite current collector connected to the pole ear, the distance between the edge of the separator and the edge of the composite current collector is H3; the height of the welding area is H, wherein H<H3, and / or H3≥2.0mm.

[0015] As an optional implementation, on the side of the composite current collector facing away from the electrode tab, the distance between the edge of the separator and the edge of the composite current collector is H4; wherein H3>H4≥0.2 mm.

[0016] As an optional embodiment, the negative electrode ear is connected to the negative electrode sheet; the projection of the positive electrode welding area in a direction perpendicular to the surface of the electrode sheet at least partially covers the negative electrode ear. As an optional embodiment, the area where the projection of the diaphragm overlaps with the electrode sheet forms a hot pressing area, and the area where the diaphragm exceeds the projection of the electrode sheet forms an extension area; the surface of the diaphragm is coated with a coating layer;

[0017] The coverage of the adhesive layer in the extended area is 5% to 60%, and / or the coverage of the adhesive layer in the hot pressing area is 10% to 75%.

[0018] As an optional embodiment, the coating layer has glue spots; the height of the glue spots in the extension area is h1 in the direction perpendicular to the diaphragm surface, 1μm≤h1≤10μm; and / or the height of the glue spots in the hot pressing area is h2 in the direction perpendicular to the diaphragm surface, 0.5μm≤h2≤5μm.

[0019] As an optional embodiment, the negative electrode sheet may include a composite current collector, and the negative electrode ear includes at least two metal sheets; the at least two metal sheets of the negative electrode ear are respectively connected to the two side edges of the composite current collector of the negative electrode sheet; at least partial areas of the at least two metal sheets of the negative electrode ear are welded to each other to form a negative electrode welding area.

[0020] As an optional embodiment, the metal sheet includes at least one of an aluminum metal sheet, an aluminum-nickel alloy sheet, and an aluminum-zinc alloy sheet.

[0021] In a second aspect, the present application provides a battery, comprising a shell and a battery cell according to the above technical solution arranged inside the shell.

[0022] The present application provides a battery cell and a battery, wherein the battery cell comprises a pole piece, a pole ear and a diaphragm, the pole piece comprises a positive pole piece and a negative pole piece, the diaphragm is arranged between the positive pole piece and the negative pole piece, the pole ear may include a positive pole ear and a negative pole ear located on the same side of the pole piece; the positive pole piece comprises a composite current collector, and the pole ear comprises at least two metal sheets; the at least two metal sheets are respectively connected to the two side edges of the composite current collector; at least partial areas of the at least two metal sheets are welded to each other to form a positive electrode welding area, thereby increasing the contact area between the pole piece and the pole ear, improving the current flow capacity between the pole piece and the pole ear, improving the poor comprehensive performance of the battery cell, avoiding excessive temperature rise at the pole ear during charging and discharging, thereby avoiding easy melting of the pole ear and battery fire.

[0023] In addition to the technical problems solved by the present application, the technical features that constitute the technical solutions, and the beneficial effects brought about by the technical features of these technical solutions described above, other technical problems that can be solved by the battery cells and batteries provided by the present application, other technical features included in the technical solutions, and the beneficial effects brought about by these technical features will be further described in detail in the specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 A schematic diagram of overlapping projections of the positive electrode tab and the negative electrode tab welding area in a battery cell provided in an embodiment of the present application;

[0026] Figure 2 A cross-sectional view of a battery cell provided in an embodiment of the present application;

[0027] Figure 3 Schematic diagram of the size of the welding area of ​​the battery cell provided in the embodiment of the present application Figure 1 ;

[0028] Figure 4 Schematic diagram of the size of the welding area of ​​the battery cell provided in the embodiment of the present application Figure 2 ;

[0029] Figure 5 A schematic diagram of a hot pressing area and a protruding area of ​​a battery cell provided in an embodiment of the present application;

[0030] Figure 6 A schematic diagram of the size of the diaphragm glue points of the battery cell provided in the embodiment of the present application;

[0031] Figure 7 A schematic diagram of the structure of a battery cell provided in an embodiment of the present application.

[0032] Description of reference numerals:

[0033] 100-pole sheet; 100a-positive electrode sheet; 100b-negative electrode sheet; 110-composite current collector;

[0034] 200-pole ear; 200a-positive pole ear; 200b-negative pole ear; 201-metal sheet; 210-positive electrode welding area; 211-first welding area; 212-second welding area; 220-pole ear portion;

[0035] 300-diaphragm; 301-hot pressing zone; 302-extending zone. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0037] Rechargeable batteries are also called secondary batteries, which refer to electrochemical energy devices that can be used for charge and discharge cycles, such as lithium-ion batteries. With the development of lithium-ion batteries, their application range is becoming more and more extensive, ranging from wearable electronic products such as Bluetooth headsets, electronic watches, mobile phone batteries, etc. to cars, airplanes, etc. Lithium-ion batteries are involved. Currently, a large number of batteries are multi-pole or full-pole type batteries. This type of battery has a large number of soft poles, which makes the battery have better charge and discharge performance. During the charge and discharge process, the current passing through a single soft pole is small, so that the temperature rise at the soft pole becomes smaller, the battery environment will be relatively mild, and the battery's overall performance will be excellent.

[0038] In order to further improve the weight energy density of the battery cell, a composite current collector can be used for the electrode of the battery cell. However, the use of a composite current collector will weaken the current flow capacity between the battery electrode and the pole tab, causing a high temperature rise at the pole tab when the battery is charged and discharged, deteriorating the battery use environment, and further causing the overall performance of the battery cell to deteriorate. When the battery is charged and discharged, the temperature at the pole tab may even rise too high, causing accidents such as the pole tab melting and the battery catching fire, affecting the safety performance of the battery.

[0039] The present application provides a battery cell and a battery. By improving the design of the battery structure and using a pole piece with a composite current collector, the pole ear connected to each pole piece is connected and welded together using at least two metal sheets, thereby increasing the contact area between the pole piece and the pole ear, improving the current flow capacity between the pole piece and the pole ear, improving the poor overall performance of the battery cell, avoiding excessive temperature rise at the pole ear during charging and discharging, thereby preventing the pole ear from easily melting and the battery from catching fire.

[0040] The following is a description of the battery cells and batteries of the embodiments of the present application in conjunction with the accompanying drawings. It should be noted that the battery cells provided in the embodiments of the present application are applied to batteries, and the batteries may be lithium batteries, which may be charged and discharged and recycled, and the battery cells and batteries may be used in scenarios including but not limited to electronic products, energy storage devices, transportation vehicles, such as new energy vehicles, charging stations, etc., which are not specifically limited in the embodiments of the present application.

[0041] Figure 1 This is a schematic diagram of overlapping projections of the positive electrode tab and the negative electrode tab welding area in the battery cell provided in an embodiment of the present application. Figure 2 A cross-sectional view of a battery cell provided in an embodiment of the present application.

[0042] Please refer to Figure 1 and Figure 2 An embodiment of the present application provides a battery cell, which includes a pole piece 100 and a pole tab 200. The pole piece 100 may include a positive pole piece 100a and a negative pole piece 100b. The pole tab 200 may include a positive pole tab 200a and a negative pole tab 200b.

[0043] The positive electrode sheet 100a includes a composite current collector 110, and the positive electrode tab 200a includes at least two metal sheets 201. The at least two metal sheets 201 are respectively connected to the two side edges of the composite current collector 110. At least parts of the at least two metal sheets 201 are welded to each other to form a positive electrode welding area 210.

[0044] In the embodiment of the present application, the negative electrode ear 200b is connected to the negative electrode sheet 100b. The positive electrode welding area 210 and the negative electrode sheet may at least partially overlap. In this way, the contact area between the positive electrode sheet 100a and the positive electrode ear 200a can be increased corresponding to the positive electrode sheet 100a using the composite current collector 110, thereby improving the current capacity.

[0045] It is understood that the composite current collector 110 includes a substrate and a metal layer located on the surface of both sides of the substrate, thereby improving the energy storage density of the battery. The metal sheets 201 of the pole tab 200 are respectively connected to the two sides of the composite current collector 110, so that different metal sheets 201 can be electrically connected to the metal layers on both sides of the composite current collector 110. The metal sheets 201 are welded and connected so that the metal sheets 201 connected to both sides of the composite current collector 110 can be electrically connected, which can increase the contact area between the pole sheet 100 and the pole tab 200.

[0046] It should be noted that in the battery provided in the embodiment of the present application, the positive electrode sheet 100a may adopt the composite current collector 110, and the negative electrode sheet 100b may not adopt the composite current collector 110. Alternatively, both the positive electrode sheet 100a and the negative electrode sheet 100b may adopt the composite current collector 110. In this case, the connection structure between the negative electrode ear 200b and the negative electrode sheet 100b may be the same as that between the positive electrode ear 200a and the positive electrode sheet 100a, which will not be repeated here. When the pole ear 200 connected to each pole piece 100 is connected and welded together using at least two metal sheets 201, the contact area between the pole piece 100 and the pole ear 200 can be increased, and the current flow capacity between the pole piece 100 and the pole ear 200 can be improved, the poor overall performance of the battery cell can be improved, and the temperature rise at the pole ear 200 can be avoided during charging and discharging, thereby avoiding the pole ear 200 from easily melting and the battery catching fire.

[0047] The specific structure of connecting the electrode tab 200 and the composite current collector 110 of the electrode sheet 100 is described in detail below.

[0048] Please continue to refer to Figure 1 and Figure 2In a possible implementation, at least one of the at least two metal sheets 201 has a pole ear portion 220, and the pole ear portion 220 is located outside the positive electrode welding area 210. The width of at least a portion of the positive electrode welding area 210 is greater than the width of the pole ear 200. In this way, the pole ear 200 can have a larger contact area when being welded to the pole sheet 100, thereby improving the current carrying capacity.

[0049] It can be understood that the pole ear portion 220 is the portion of the pole ear 200 extending relative to the edge of the pole piece 100. When applied to a battery, the pole ear portion 220 can be electrically connected to components such as a converter in the battery to achieve charging and discharging of the battery cell.

[0050] Exemplarily, each positive electrode tab 200a may include two metal sheets 201, and the parts of the two metal sheets 201 connected to the electrode sheet 100 and welded to each other form a positive electrode welding area 210, so that the two metal sheets 201 form a whole when current is input and output. The two metal sheets 201 may be a structure of one long and one short. For example, one of the two metal sheets 201 has a tab portion 220 for electrically connecting the positive electrode tab 200a to the outside, and the other of the two metal sheets 201 has a shorter length extending outside the positive electrode welding area 210, that is, it is only necessary to ensure that the two metal sheets 201 can be welded together to form a tab portion 220 connected to the outside.

[0051] In some embodiments, the positive electrode welding region 210 includes a first welding region 211 and a second welding region 212, wherein the first welding region 211 is connected to the composite current collector 110, and the second welding region 212 is connected to a side of the first welding region 211 away from the composite current collector 110. The pole ear portion 220 is located on a side of the second welding region 212 away from the first welding region 211.

[0052] The metal sheet 201 is welded to the edge of the composite current collector 110 via the second welding region 212 , and the metal sheets 201 on both sides of the composite current collector 110 are directly contacted and welded via the second welding region 212 .

[0053] It can be understood that a first step structure is formed between the first welding area 211 and the edge of the electrode piece 100, and a second step structure is formed between the second welding area 212 and the first welding area 211. This ensures that the electrode tab 200 and the electrode piece 100 have good welding performance, increases the contact area between the electrode tab 200 and the electrode piece 100, and improves the current carrying capacity of the electrode tab 200.

[0054] Figure 3 Schematic diagram of the size of the welding area of ​​the battery cell provided in the embodiment of the present application Figure 1 , Figure 4 Schematic diagram of the size of the welding area of ​​the battery cell provided in the embodiment of the present application Figure 2 .

[0055] Please refer to Figures 1 to 4 In some embodiments, the width of the first welding area 211 is D1, and the width of the second welding area 212 is D2, wherein D1×0.5≥D2≥D1×0.2.

[0056] It is understandable that the width of the first welding area 211 is greater than the width of the second welding area 212, thereby increasing the contact area between the pole tab 200 and the pole piece 100. In the embodiment of the present application, the ratio of the first welding area 211 to the second welding area 212 is controlled within a reasonable range, thereby ensuring that the pole tab 200 has good current flow capacity.

[0057] In some embodiments, the height of the first welding region 211 is H1, and the height of the second welding region 212 is H2, wherein 0.05≤(D2×H2) / (D1×H1)≤0.6.

[0058] It can be understood that the first welding area 211 has a larger area than the second welding area 212, thereby ensuring a larger contact area between the pole tab 200 and the pole piece 100, improving the current flow capacity between the pole piece 100 and the pole tab 200, alleviating the temperature rise during the charging and discharging process, and improving the safety performance of the battery.

[0059] In a possible implementation, the electrode sheet 100 may include a positive electrode sheet 100a and a negative electrode sheet 100b, and the battery further includes a separator 300, which is disposed between the positive electrode sheet 100a and the negative electrode sheet 100b. The projections of the positive electrode sheet 100a and the negative electrode sheet 100b perpendicular to the surface of the separator 300 are within the coverage of the separator 300. The projection of the positive electrode welding area 210 perpendicular to the surface of the separator 300 is within the coverage of the separator 300.

[0060] It is understandable that the diaphragm 300 is used to isolate the positive electrode sheet 100a and the negative electrode sheet 100b to prevent the positive electrode sheet 100a and the negative electrode sheet 100b from contacting each other and causing a short circuit. The positive electrode welding area 210 is set within the coverage range of the diaphragm 300, which optimizes the coverage area between the diaphragm 300 and the electrode sheet 100, reduces the proportion of poor coverage of the diaphragm 300 during the battery production process, and improves the process yield and efficiency of the battery cell. In addition, the quality of the battery cell is improved, and the overall performance of the battery is improved.

[0061] In some embodiments, on the side of the composite current collector 110 connected to the tab 200, the distance between the edge of the separator 300 and the edge of the composite current collector 110 is H3; the height of the positive electrode welding area 210 is H, where H<H3. The height of the positive electrode welding area 210 is less than the height of the separator 300 from the edge of the composite current collector 110 on this side.

[0062] In some embodiments, H3 ≥ 2.0 mm, that is, the specific value of the distance H3 between the edge of the separator 300 and the edge of the composite current collector 110 may be greater than or equal to 2.0 mm.

[0063] For example, the specific value of the distance H3 between the edge of the separator 300 and the edge of the composite current collector 110 can be 2.0 mm, 2.1 mm, 2.5 mm, 3 mm, 4 mm, 5 mm, etc., which is not specifically limited in the embodiments of the present application.

[0064] In the embodiment of the present application, the height dimension of the diaphragm 300 exceeding the edge of the pole piece 100 is increased, which can effectively block the positive electrode welding area 210 from contacting the battery casing and prevent the sharp welding point of the positive electrode welding area 210 from scratching the battery casing or the adjacent pole ear 200, thereby avoiding the breakage of the pole ear 200 and poor performance of the battery cell. In addition, the process yield and efficiency of the battery cell can be improved, thereby improving the quality of the battery cell.

[0065] In addition, the diaphragm 300 in the embodiment of the present application has excellent storage performance for the electrolyte in the battery. Since the height dimension of the diaphragm 300 is increased beyond the edge of the pole piece 100, the usage amount of the diaphragm 300 in the battery cell is increased, and the absorption amount of the electrolyte by the battery cell can be increased, thereby achieving the effect of improving the cycle performance.

[0066] It should be noted that the height H of the positive electrode welding area 210 is the sum of the heights of the first welding area 211 and the second welding area 212, that is, H=H1+H2. It is sufficient that the total height of the positive electrode welding area 210 is less than the height from the edge of the side diaphragm 300 to the edge of the composite current collector 110 to ensure that the positive electrode welding area 210 is within the coverage of the diaphragm 300. The embodiment of the present application does not limit the specific height value of the positive electrode welding area 210.

[0067] In some embodiments, on the side of the composite current collector 110 away from the tab 200, the distance between the edge of the separator 300 and the edge of the composite current collector 110 is H4. Wherein, H3>H4≥0.2mm. In this way, on the side where the tab 200 is not provided, the distance between the edge of the separator 300 and the edge of the composite current collector 110 is shorter than that on the side where the tab 200 is provided, which can improve the energy density of the battery.

[0068] For example, on the side of the composite current collector 110 facing away from the pole tab 200, the distance between the edge of the diaphragm 300 and the edge of the composite current collector 110 is H4, and the specific value may include but is not limited to 0.2mm, 0.3mm, 0.5mm, 1mm, 1.5mm, 2mm, 3mm, etc., and only needs to be smaller than the distance between the edge of the diaphragm 300 on the side of the pole tab 200 and the composite current collector 110. The embodiments of the present application do not make specific limitations on this.

[0069] Figure 7 A schematic diagram of the structure of a battery cell provided in an embodiment of the present application.

[0070] Please refer to Figure 7 , and combined with Figures 1 to 4 In a possible implementation, the tab 200 may include a positive tab 200a and a negative tab 200b, the positive tab 200a is welded to the positive electrode sheet 100a, and the negative tab 200b is welded to the negative electrode sheet 100b. The positive electrode welding area 210 of the positive tab 200a overlaps at least partially with the negative electrode welding area of ​​the negative tab 200b. Due to the separation of the separator 300 in between, the positive electrode welding area 210 of the positive tab 200a and the negative electrode welding area of ​​the negative tab 200b will not directly contact.

[0071] For example, the negative electrode sheet 100b may include a composite current collector, and the negative electrode ear 200b includes at least two metal sheets; the at least two metal sheets of the negative electrode ear 200b are respectively connected to the edges of both sides of the composite current collector of the negative electrode sheet 100b; at least part of the at least two metal sheets of the negative electrode ear 200b are welded to each other to form a negative electrode welding area. In this way, when the negative electrode sheet 100b uses a composite current collector, the contact area between the negative electrode sheet 100b and the negative electrode ear 200b can be increased, and the current flow capacity between the negative electrode sheet 100b and the negative electrode ear 200b can be improved.

[0072] It should be noted that at least one of the positive electrode tab 200a and the negative electrode tab 200b can adopt the structure of the above-mentioned multiple metal sheets 201, and when the positive electrode tab 100a and the negative electrode tab 100b both adopt the composite current collector 110, the positive electrode tab 200a and the negative electrode tab 200b both adopt a structure in which multiple metal sheets 201 are welded to each other. While ensuring that the battery has a high energy density, the current capacity of the positive electrode tab 200a and the negative electrode tab 200b can be improved.

[0073] Figure 5 A schematic diagram of the hot pressing area and the extension area of ​​the battery cell provided in an embodiment of the present application, Figure 6 A schematic diagram of the size of the diaphragm glue points of the battery cell provided in an embodiment of the present application.

[0074] Please refer to Figures 1 to 6 In some embodiments, the area where the projection of the diaphragm 300 overlaps with the projection of the pole piece 100 forms a hot pressing area 301, and the area where the diaphragm 300 exceeds the projection of the pole piece 100 forms an extension area 302. The surface of the diaphragm 300 is coated with a glue layer.

[0075] It is understandable that the coating layer on the surface of the diaphragm 300 is a spray coating layer, and the material of the coating layer can be selected from one or more of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyacrylic acid resin, polymethyl acrylate, butyl acrylate-acrylonitrile copolymer, polyacrylonitrile, ethylene-acrylic acid copolymer, polyethyl acrylate or sodium carboxymethyl cellulose, such as butyl acrylate-acrylonitrile copolymer. This embodiment of the present application does not specifically limit this.

[0076] In some embodiments, the coverage of the adhesive layer in the extension area 302 is 5% to 60%. For example, the specific value of the coverage of the adhesive layer in the extension area 302 may include but is not limited to 5%, 6%, 10%, 30%, 50%, 59%, 60%, etc.

[0077] In some embodiments, the coverage of the adhesive layer in the hot pressing area 301 is 10% to 75%. For example, the specific values ​​of the coverage of the adhesive layer in the extension area 302 may include but are not limited to 10%, 11%, 20%, 50%, 70%, 74%, 75%, etc.

[0078] In some embodiments, the glue coating layer has glue dots. The glue dots in the extension area 302 are crater-shaped or cone-shaped as a whole and are distributed on the surface of the diaphragm 300. The height of the glue dots in the extension area 302 in a direction perpendicular to the surface of the diaphragm 300 is h1, 1 μm≤h1≤10 μm.

[0079] For example, the specific value of the height h1 of the glue point of the extension area 302 in the direction perpendicular to the surface of the diaphragm 300 may include but is not limited to 1μm, 1.1μm, 2μm, 5μm, 9μm, 9.9μm, 10μm, etc., and the embodiments of the present application do not make specific limitations on this.

[0080] In some embodiments, the glue spots in the hot pressing zone 301 have a crater or a cone-shaped flattened state. The height of the glue spots in the hot pressing zone 301 in a direction perpendicular to the surface of the diaphragm 300 is h2, and 0.5 μm≤h2≤5 μm.

[0081] For example, the specific value of the height h1 of the glue point of the extension area 302 in the direction perpendicular to the surface of the diaphragm 300 may include but is not limited to 0.5μm, 0.6μm, 1μm, 2μm, 4μm, 4.9μm, 5μm, etc., and the embodiment of the present application does not make any specific limitation on this.

[0082] It should be noted that the ratio of h1 to h2 may be greater than or equal to 0.05 and less than or equal to 20. This embodiment of the present application does not specifically limit this.

[0083] In the embodiment of the present application, the metal sheet 201 includes at least one of an aluminum metal sheet 201, an aluminum-nickel alloy sheet, and an aluminum-zinc alloy sheet, which is not specifically limited in the embodiment of the present application.

[0084] The present application provides a battery, including a shell and a cell in the above technical solution, wherein the cell is arranged inside the shell. The battery includes all the technical solutions and technical effects of the above cell, which will not be described in detail here.

[0085] The battery performance provided in the embodiments of the present application is described below through a battery performance test under specific parameters.

[0086] Preparation of positive electrode sheet 100a:

[0087] The positive electrode active material lithium cobalt oxide (LiCoO2), the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black are mixed in a weight ratio of 96.5:2:1.5, and N-methylpyrrolidone (NMP) is added, and stirred under the action of a vacuum mixer until the mixed system becomes a positive electrode slurry with uniform fluidity; the positive electrode slurry is evenly coated on an aluminum-plated film with a thickness of 9 μm; the coated aluminum foil is baked in an oven with different temperature gradients, and then dried in an oven at 120°C for 8 hours, and then rolled and cut to obtain the required main part of the positive electrode sheet 100a, and then the foil is welded to the main body of the positive electrode sheet 100a by roller welding, and then die-cut to obtain the finished positive electrode sheet 100a.

[0088] By adjusting the sizes of H1 and H2, 8 groups of positive electrode sheets were prepared, which were recorded as groups 1 to 8, and the specific sizes are as follows: H1+H2=4.5mm, D1=150mm, and the control group used conventional tabs, and the widths of the tabs 200 were 45mm and 60mm respectively. The tabs had no step structure and no welding area.

[0089]

[0090] Preparation of negative electrode sheet 100b:

[0091] The negative electrode active material artificial graphite, thickener sodium carboxymethyl cellulose (CMC-Na), binder styrene butadiene rubber, conductive agent acetylene black, and conductive agent single-walled carbon nanotube (SWCNT) were mixed in a weight ratio of 95.9:1:2:1:0.1, and deionized water was added to obtain a negative electrode slurry under the action of a vacuum mixer; the negative electrode slurry was evenly coated on a copper foil with a thickness of 8 μm; and the negative electrode sheet 100b was obtained by drying in an oven at 85°C for 5 hours, rolling and die-cutting.

[0092] Electrolyte preparation:

[0093] In a glove box filled with argon (water content <10ppm, oxygen content <1ppm), ethylene carbonate (EC), propylene carbonate (PC) and dimethyl carbonate (DEC) are uniformly mixed in a certain mass ratio, and LiPF6 and additives in an amount of 14wt% based on the total mass of the electrolyte are slowly added to the mixed solution, and the electrolyte is obtained by stirring evenly.

[0094] Preparation of diaphragm 300:

[0095] A 7 μm thick polyethylene base film is selected, and a 2 μm thick aluminum oxide coating is coated on one side of the base film. Then, polyvinylidene fluoride resin is sprayed on both sides of the coating film. The film is then dried and cut to obtain a finished diaphragm 300 .

[0096] Preparation of the battery:

[0097] The above 8 groups of positive electrode sheets, separators 300, and negative electrode sheets are stacked to obtain bare cells without liquid injection. The bare cells are welded and packaged to prepare dry cells. Then, after baking, liquid injection, standing, formation, degassing molding, and sorting, the required batteries are obtained, which are named battery 1, battery 2, battery 3, battery 4, battery 5, battery 6, battery 7, and battery 8 respectively.

[0098] Battery Test:

[0099] Rate performance test: Charge the lithium-ion battery to full charge at 0.2C, let it rest for 3 minutes, and discharge it at a discharge current of 2.0C until the cut-off voltage is 3.0V. Measure the maximum temperature of the battery surface and the percentage of discharge capacity during the discharge process. The test results are as follows:

[0100]

[0101] It can be seen from the above data that, for batteries 1 to 4, when D1 and D2 remain unchanged, H1 gradually decreases and the temperature rise at the battery welding point gradually increases, that is, when discharging under the same rate conditions, the area of ​​the first step decreases, and the current density at the welding point increases, resulting in an increase in the temperature rise of the tab 200 at this point, thereby causing an increase in the battery capacity loss. This conclusion is also reflected in batteries 5 to 8.

[0102] Compared with the comparison group 1, the batteries 1 to 4 can effectively reduce the temperature rise of the battery itself during battery discharge and reduce the battery capacity loss by increasing the areas of the first welding area 211 and the second welding area 212.

[0103] By comparing Battery 1 with Battery 5, Battery 2 with Battery 6, Battery 3 with Battery 7, Battery 4 with Battery 8, it can be seen that when H1, H2 and D1 remain unchanged, by increasing D2, the temperature rise at the battery welding point is significantly reduced under the same discharge rate conditions. That is, increasing the size of D2 is equivalent to increasing the area of ​​the second welding area 212. When discharging under the same discharge rate conditions, the area of ​​the first welding area 211 increases, and the current density at the welding point is reduced, so that the temperature rise of the tab 200 at this point is reduced, which is beneficial to reducing the capacity loss of the battery during charging and discharging.

[0104] Cycle test: At room temperature, charge the lithium-ion battery to full charge at 1.0C, with a cut-off current of 0.02C, and leave it at rest for 3 minutes. Discharge it to 3.0V at 1.0C, and leave it at rest for another 3 minutes. The ratio of discharge capacity to initial capacity is calculated as capacity retention rate. Capacity retention rate-cycle number is as follows:

[0105]

[0106] From the above data, it can be seen that from battery 1 to battery 4, when D1 and D2 remain unchanged, H1 gradually decreases, and the capacity retention rate of the battery gradually decreases during the cycle process.

[0107] Compared with the comparative group 1, the battery 1 to the battery 4 can effectively reduce the temperature rise of the battery itself during charging and discharging by increasing the area of ​​the first welding area 211 and the second welding area 212, reduce the battery capacity loss, and improve the capacity retention rate of the battery during the cycle process;

[0108] At the same time, by comparing battery 1 with battery 5, battery 2 with battery 6, battery 3 with battery 7, and battery 4 with battery 8, the above conclusion can also be drawn.

[0109] Therefore, by adjusting the size of the first welding area 211 and the second welding area 212 of the battery tab 200, the current carrying capacity of the tab 200 can be improved, the rate performance of the battery cell can be improved, the current density of the tab 200 during charging and discharging can be reduced, the battery temperature can be reduced, energy loss can be reduced, and the capacity retention rate during the battery cycle can be improved; at the same time, increasing the height of the diaphragm 300 beyond the edge area of ​​the pole piece can increase the absorption of the electrolyte by the battery cell, thereby achieving the effect of improving the cycle performance.

[0110] The present application provides a battery cell and a battery, wherein the battery cell comprises a pole piece and a pole ear 200, the pole piece comprises a positive pole piece and a negative pole piece, and the pole ear comprises a positive pole ear and a negative pole ear; the positive pole piece comprises a composite current collector 110, and the positive pole ear 200 comprises at least two metal sheets 201; the at least two metal sheets 201 are respectively connected to the two side edges of the composite current collector 110; at least partial areas of the at least two metal sheets 201 are welded to each other to form a positive electrode welding area 210, and the negative pole ear is welded to the negative pole piece to form a negative electrode welding area; the positive electrode welding area and the negative electrode welding area at least partially overlap, thereby increasing the contact area between the pole piece and the pole ear 200, improving the current flow capacity between the pole piece and the pole ear 200, improving the poor comprehensive performance of the battery cell, avoiding excessive temperature rise at the pole ear 200 during charging and discharging, thereby avoiding easy melting of the pole ear 200 and battery fire.

[0111] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, or it can be an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0112] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0113] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of this application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the application described herein can be implemented in an order other than those illustrated or described herein, for example.

[0114] In addition, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements explicitly listed, but may include other steps or elements not explicitly listed or inherent to such process, method, product, or apparatus.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery cell, characterized in that: The invention comprises a pole piece, a pole ear and a diaphragm, wherein the pole piece comprises a positive pole piece and a negative pole piece, and the diaphragm is arranged between the positive pole piece and the negative pole piece; the pole ear comprises a positive pole ear and a negative pole ear located on the same side of the pole piece, the positive pole piece comprises a composite current collector, and the positive pole ear comprises at least two metal sheets; at least two of the metal sheets are respectively connected to the two side edges of the composite current collector; at least parts of the at least two metal sheets are welded to each other to form a positive electrode welding area; On the side of the composite current collector connected to the electrode tab, the distance between the edge of the separator and the edge of the composite current collector is H3, and the height of the welding area is H, wherein H<H3, and / or H3≥2.0 mm.

2. The battery cell according to claim 1, characterized in that: The projections of the positive electrode sheet and the negative electrode sheet perpendicular to the surface of the diaphragm are within the coverage of the diaphragm; the projection of the positive electrode welding area perpendicular to the surface of the diaphragm is within the coverage of the diaphragm.

3. The battery cell according to claim 2, characterized in that: On the side of the composite current collector connected to the electrode tab, the distance between the edge of the separator and the edge of the composite current collector is H3; the height of the welding area is H, wherein H<H3, and / or H3≥2.0 mm.

4. The battery cell according to claim 3, characterized in that: On a side of the composite current collector away from the electrode tab, a distance between an edge of the separator and an edge of the composite current collector is H4; wherein H3>H4≥0.2 mm.

5. The battery cell according to any one of claims 1 to 4, characterized in that: At least one of the at least two metal sheets has a pole ear portion, and the pole ear portion is located outside the welding area; the width of at least a part of the welding area is greater than the width of the pole ear.

6. The battery cell according to claim 5, characterized in that: The positive electrode welding area includes a first welding area and a second welding area, the first welding area is connected to the composite current collector, and the second welding area is connected to a side of the first welding area away from the composite current collector; the pole ear portion is located on a side of the second welding area away from the first welding area.

7. The battery cell according to claim 6, characterized in that: The width of the first welding area is D1, and the width of the second welding area is D2, wherein D1×0.5≥D2≥D1×0.

2.

8. The battery cell according to claim 7, characterized in that: The height of the first welding area is H1, and the height of the second welding area is H2, wherein 0.05≤(D2×H2) / (D1×H1)≤0.

6.

9. The battery cell according to any one of claims 1 to 4, characterized in that: The negative electrode ear is connected to the negative electrode sheet; the projection of the positive electrode welding area in a direction perpendicular to the surface of the electrode sheet at least partially covers the negative electrode ear.

10. The battery cell according to any one of claims 1 to 4, characterized in that: The area where the projection of the diaphragm overlaps with the projection of the pole piece forms a hot pressing area, and the area where the diaphragm exceeds the projection of the pole piece forms a protruding area; the surface of the diaphragm is coated with a rubber coating layer; The coverage rate of the adhesive layer in the extension area is 5% to 60%, and / or the coverage rate of the adhesive layer in the hot pressing area is 10% to 75%.

11. The battery cell according to claim 10, characterized in that: The coating layer has glue spots; the height of the glue spots in the extension area is h1 in the direction perpendicular to the surface of the diaphragm, 1μm≤h1≤10μm; and / or the height of the glue spots in the hot pressing area is h2 in the direction perpendicular to the surface of the diaphragm, 0.5μm≤h2≤5μm.

12. The battery cell according to any one of claims 1 to 4, characterized in that: The negative electrode sheet includes a composite current collector, and the negative electrode ear includes at least two metal sheets; the at least two metal sheets of the negative electrode ear are respectively connected to the two side edges of the composite current collector of the negative electrode sheet; at least partial areas of the at least two metal sheets of the negative electrode ear are welded to each other to form a negative electrode welding area.

13. The battery cell according to any one of claims 1 to 4, characterized in that: The metal sheet includes at least one of an aluminum metal sheet, an aluminum-nickel alloy sheet, and an aluminum-zinc alloy sheet.

14. A battery, characterized in that: It comprises a shell and the battery core according to any one of claims 1 to 13, wherein the battery core is arranged inside the shell.

Images