Battery cell and battery

Abstract

The utility model relates to the technical field of battery energy, in particular to a battery cell and a battery. The battery cell comprises a first pole piece, a second pole piece and a diaphragm positioned between the second pole piece and the first pole piece, the first pole piece comprises a first current collector, a first connecting layer, a first active layer and a first tab, the first tab extends out from the edge of one side of the first current collector, the first connecting layer covers the first current collector, and the first active layer covers one side, deviating from the first current collector, of the first connecting layer; the first connecting layer is provided with a first covering part exceeding the first current collector, the first covering part covers part of the first tab, the first active layer is provided with a second covering part exceeding the first current collector, and the second covering part covers one side, deviating from the first tab, of the first covering part. The second covering part on the first tab increases the local CB value of the battery cell, and the first tab has more lithium embedding sites, so that lithium precipitation caused by high current density on the first tab is reduced, and the safety of the battery is improved.

Description

Technical Field

[0001] This application relates to the technical field of battery energy, and particularly to a battery cell and a battery. Background Art

[0002] Lithium-ion batteries have become the main power source for consumer electronics and electric vehicles due to their many advantages. With the increasing demands of people, lithium-ion batteries are gradually developing towards fast charging, long life, high energy density, and high safety.

[0003] Currently, the battery cell of a battery includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet. The separator isolates the positive electrode sheet and the negative electrode sheet to prevent contact short circuit between the positive electrode sheet and the negative electrode sheet. However, the current density at the tab position of the electrode sheet is relatively large, and lithium deposition is likely to occur at the tab position of the negative electrode sheet in the later stage of battery cycling, affecting the safety of the battery. Utility Model Content

[0004] Based on this, this application provides a battery cell and a battery to solve the problem in the related art that the current density at the tab position of the electrode sheet is relatively large, and lithium deposition is likely to occur at the tab position of the first electrode sheet in the later stage of battery cycling.

[0005] On the one hand, this application provides a battery cell, including a first electrode sheet, a second electrode sheet, and a separator located between the second electrode sheet and the first electrode sheet;

[0006] The first electrode sheet includes a first current collector, a first connection layer, a first active layer, and a first tab. The first tab extends from one side edge of the first current collector. The first connection layer covers the first current collector. The first active layer covers the side of the first connection layer facing away from the first current collector. The first connection layer has a first covering portion that extends beyond the first current collector, and the first covering portion covers part of the first tab. The first active layer has a second covering portion that extends beyond the first current collector, and the second covering portion covers the side of the first covering portion facing away from the first tab.

[0007] In a possible implementation, the width of the first connection layer at the first covering portion is greater than or equal to the width of the first active layer at the second covering portion.

[0008] In a possible implementation, the relationship between the width H1 of the first connection layer at the first covering portion and the width H2 of the first active layer at the second covering portion satisfies: 0mm ≤ H1 - H2 ≤ 3mm; and / or,

[0009] The thickness of the first connection layer is 0.3μm - 2μm; and / or,

[0010] The width H3 of the second covering portion satisfies: 0.1mm ≤ H3 ≤ 1mm; and / or,

[0011] The width H4 of the first covering portion satisfies: 0.1 mm ≤ H4 ≤ 3.1 mm; and / or,

[0012] The ratio of the width of the second covering portion to the width of the first covering portion is 0.4 - 1.

[0013] In a possible implementation, the thickness difference between the second covering portion and the rest of the first active layer is less than or equal to 3 μm.

[0014] In a possible implementation, the second electrode tab includes a second current collector, a second tab, a second active layer, and a safety coating. The end of the second tab is connected to the edge of the second current collector. The safety coating is located on the side of the second active layer facing the second tab in the width direction of the second electrode tab. The safety coating has a third covering portion that extends beyond the second current collector, and the third covering portion covers part of the second tab.

[0015] In a possible implementation, in the thickness direction of the battery cell, the projections of the third covering portion of the safety coating and the first covering portion at least partially overlap.

[0016] In a possible implementation, the end of the first connection layer away from the first active layer extends beyond the end of the safety coating away from the second active layer.

[0017] In a possible implementation, the first active layer and / or the second active layer includes active particles and fibers, and the fibers extend in the first direction.

[0018] In a possible implementation, the ratio of the breaking tensile force of the first electrode tab and / or the second electrode tab in the first direction to the breaking tensile force of the electrode tab in the second direction is (1 - 2):1, preferably, (1.02 - 1.52):1; and / or,

[0019] The ratio range of the length of the fiber to the diameter of the fiber is 10 - 1000; and / or,

[0020] Along the thickness direction of the first electrode tab and / or the second electrode tab, adjacent active particles are connected by fibers.

[0021] In a possible implementation, the fibers form a composite network, and the active particles of the first active layer are dispersed on the composite network.

[0022] In a possible implementation, the fibers include one or more of fibrous PTFE, PVDF, PE, ETEF, FEP, PVP, PEO, CMC, SBR, PAA, and hot melt adhesive; and / or,

[0023] The active particles of the second active layer include at least one of LiCoO2, LiMn2O4, LiMnO2, LiNiO2, LiFePO4, LiMnPO4, LiCoxNi1-xO2 (0≤x≤1) and LiCoxNi1-x-yAlyO2 (0≤x≤1, 0≤y≤1); and / or,

[0024] The active particles of the first active layer include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesophase carbon microspheres, Si, SiOx, Si-C, and SiOx-C. The silicon content of the first active layer is 3%-100%.

[0025] On the other hand, the present application also provides a battery, comprising a shell and the above-mentioned battery cell, wherein the battery cell is located inside the shell.

[0026] The present application provides a cell and a battery, the cell comprising a first pole piece, a second pole piece and a diaphragm between the second pole piece and the first pole piece, wherein the first pole piece comprises a first current collector, a first connecting layer, a first active layer and a first pole ear, the first pole ear extending from one side edge of the first current collector, and the first connecting layer is located between the first current collector and the first active layer in the thickness direction of the first pole piece. The first connecting layer ensures the conductivity between the first active layer and the first current collector and the first pole ear respectively, and the first active layer is composited on the first current collector through the first connecting layer. The first connecting layer has a first covering portion extending beyond the first current collector, the first active layer has a second covering portion extending beyond the first current collector, the first covering portion covers a portion of the first pole ear, and the second covering portion covers the side of the first covering portion away from the first pole ear. By arranging the second covering portion on the first pole ear, the first pole ear has a negative electrode active material, the local CB value of the cell is increased, the first pole ear has more lithium insertion sites, the lithium plating due to the high current density on the first pole ear is reduced, and the safety of the battery is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction 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.

[0028] Figure 1 A partial cross-sectional view of a battery cell provided in an embodiment of the present application;

[0029] Figure 2 A cross-sectional view of a first pole piece provided in an embodiment of the present application;

[0030] Figure 3Top view of the first electrode provided by the embodiment of the present application;

[0031] Figure 4 Cross-sectional view of the second electrode provided by the embodiment of the present application;

[0032] Figure 5 Top view of the second electrode provided by the embodiment of the present application.

[0033] Explanation of reference numerals:

[0034] 100 - Second electrode; 110 - Second current collector; 120 - Second tab; 130 - Second active layer; 140 - Safety coating;

[0035] 200 - First electrode; 210 - First current collector; 220 - First connection layer; 221 - First covering part; 230 - First active layer; 231 - Second covering part; 240 - First tab;

[0036] 300 - Separator. Detailed implementation manners

[0037] To make the objectives, technical solutions, and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below with reference to the accompanying drawings in the preferred embodiments of the present application. In the drawings, the same or similar reference numerals denote the same or similar components or components with the same or similar functions throughout. The described embodiments are some, but not all, of the embodiments of the present application. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application and should not be construed as limiting the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application. The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0038] In the description of the present application, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it may be a fixed connection, or an indirect connection through an intermediate medium, or the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0039] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0040] The terms "first", "second", "third" (if any) in the description and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence.

[0041] In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or display comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or displays.

[0042] In the prior art, the battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet. The separator isolates the positive electrode sheet and the negative electrode sheet to prevent contact short circuit between the positive electrode sheet and the negative electrode sheet. Among them, the positive electrode sheet is provided with a positive electrode tab, and the negative electrode sheet is provided with a negative electrode tab, and the external power connection of the battery cell is realized through the positive electrode tab and the negative electrode tab. However, the current density at the position of the electrode tab of the electrode sheet is relatively large, and lithium deposition is likely to occur on the negative electrode tab of the negative electrode sheet in the later stage of battery cycling.

[0043] After repeated thinking and verification, the inventor found that if the active layer of the negative electrode sheet can partially extend to the negative electrode tab, the active layer of the negative electrode sheet is compounded on the negative electrode current collector and the negative electrode tab through a bottom coating. The part of the negative electrode active layer located on the negative electrode tab provides more lithium intercalation sites, increases the local CB value of the battery cell, and reduces lithium deposition on the negative electrode tab due to the large current density.

[0044] In view of this, the inventor designed a battery cell and a battery. The first electrode sheet of the battery cell includes a first current collector, a first connection layer, a first active layer, and a first electrode tab. The first connection layer covers a part of the first current collector and the first electrode tab, the first active layer covers the first connection layer, and a part of the first active layer is located on the first electrode tab. The part of the first active layer located on the first electrode tab can provide more lithium intercalation sites and reduce lithium deposition on the first electrode tab due to the large current density.

[0045] The technical solutions of the battery cell and the battery provided in the embodiments of the present application will be described in detail below with reference to the drawings.

[0046] Refer toFigures 1 to 3 As shown, the battery cell provided by the embodiment of the present application includes a first electrode tab 200, a second electrode tab 100, and a separator 300 located between the second electrode tab 100 and the first electrode tab 200. The first electrode tab 200 includes a first current collector 210, a first connection layer 220, a first active layer 230, and a first tab 240. The first tab 240 extends from one side edge of the first current collector 210. The first connection layer 220 covers the first current collector 210, and the first active layer 230 covers the side of the first connection layer 220 facing away from the first current collector 210. The first connection layer 220 has a first covering portion 221 that extends beyond the first current collector 210, and the first covering portion 221 covers a part of the first tab 240. The first active layer 230 has a second covering portion 231 that extends beyond the first current collector 210, and the second covering portion 231 covers the side of the first covering portion 221 facing away from the first tab 240.

[0047] Here, the length direction of the first electrode tab 200 is defined as Figure 3 the direction indicated by the X-axis in Figures 1 - 3 and the width direction of the first electrode tab 200 is the direction indicated by the Y-axis in Figure 1 and Figure 2 the thickness direction of the first electrode tab 200 is the direction indicated by the Z-axis in

[0048] Among them, the battery cell provided by the embodiment of the present application can be a wound core or a stacked core. When the battery cell is a wound core, the first connection layer 220 and the first active layer 230 are both provided on both opposite sides of the first current collector 210; when the battery cell is a stacked core, the first connection layer 220 and the first active layer 230 can be provided only on one side of the first current collector 210, or can be provided on both opposite sides of the first current collector 210. In this embodiment, the first electrode tab 200 is the negative electrode tab of the battery cell, and the second electrode tab 100 is the positive electrode tab of the battery cell.

[0049] Optionally, as Figure 1 shown, the separator 300 extends beyond the first active layer 230 on both sides in the width direction of the first electrode tab 200. On one side of the first electrode tab 200, the width of the part where the separator 300 extends beyond the first active layer 230 is between 0.5 mm and 3 mm. The above setting enables the separator 300 to effectively isolate the second electrode tab 100 from contacting the first electrode tab 200 while also avoiding the excessive width of the battery cell, which is beneficial to ensuring the energy density of the battery.

[0050] In one embodiment, the first electrode tab 200 provided in the present application is prepared by a dry process, that is, the active material, the binder, and the conductive agent are dry-mixed without using a solvent to form a composite material with a substantially 100% solid component concentration. Dry mixing refers to the following method: the positive electrode active material and the binder material are mixed without using a solvent in a state where the solid component concentration is substantially 100%. When performing dry mixing, a conductive material or the like other than the positive electrode active material and the binder material may also be added. In the case of adding a material other than the positive electrode active material and the binder material, the solid component concentration in the dry mixing is also substantially 100%. First, the first active layer 230 is formed into a film, the first connection layer 220 is placed between the first current collector 210 and the first active layer 230, and the first connection layer 220 is softened by hot roll pressing to fix the first current collector 210 on the first active layer 230. The first connection layer 220 can reliably fix the first active layer 230 on the first current collector 210 and the first electrode tab 240, and the first active layer 230 is not likely to have powder falling off or peeling from the first current collector 210 / the first electrode tab 240.

[0051] It can be understood that the first current collector 210 and the first electrode tab 240 are an integral part. For example, a copper foil can be die-cut to form the first current collector 210 and the first electrode tab 240. In a possible implementation manner, the width of the portion of the first active layer 230 located on the first current collector 210 may be the same as the width of the first current collector 210, and the width of the portion of the first connection layer 220 located on the first current collector 210 may be the same as the width of the first current collector 210.

[0052] Here, the end of the first electrode tab 240 connected to the first current collector 210 is defined as the root of the first electrode tab 240, the end of the first electrode tab 240 away from the first current collector 210 is defined as the head of the first electrode tab 240, the end of the first current collector 210 connected to the first electrode tab 240 is defined as the first end of the first current collector 210, and the end of the first current collector 210 away from the first electrode tab 240 is defined as the second end of the first current collector 210. It can be understood that the first active layer 230 and the first connection layer 220 extend beyond the first end of the first current collector 210 and cover the root of the first electrode tab 240. Optionally, the size of the first covering portion 221 in the length direction of the first electrode tab 200, the size of the second covering portion 231 in the length direction of the first electrode tab 200, and the size of the first electrode tab 240 in the length direction of the first electrode tab 200 are the same.

[0053] Schematically, the first connection layer 220 includes a conductive agent and a binder. The binder can be conventional PVDF and / or SBR, or it can be a hot melt adhesive, including EVA, TPR, polyolefin, polyamide (PA), polyester (PES), polyethylene (LOPE and HDPE), and polyester amide (PEA), etc. The conductive agent can be one or a mixture of conductive carbon black, carbon fiber, conductive graphite, graphene, carbon nanotubes, acetylene black, Ketjen black, copper, nickel, aluminum, silver, and gold, etc. Preferred conductive agents with a relatively large specific surface area such as conductive carbon black, carbon nanotubes, or graphene can make the roughness of the first connection layer 220 greater through the relatively large specific surface area of the conductive agent, which is beneficial to improving the adhesion and peel strength between the first active layer 230 and the first connection layer 220.

[0054] For the battery cell provided in this embodiment, its first electrode 200 includes a first current collector 210, a first connection layer 220, a first active layer 230, and a first tab 240. In the thickness direction of the first electrode 200, the first connection layer 220 is located between the first current collector 210 and the first active layer 230. The first connection layer 220 ensures the electrical conductivity between the first active layer 230 and the first current collector 210 and the first tab 240 respectively, and the first active layer 230 is laminated on the first current collector 210 through the first connection layer 220. The first connection layer 220 has a first covering portion 221 that extends beyond the first current collector 210, and the first active layer 230 has a second covering portion 231 that extends beyond the first current collector 210. The first covering portion 221 covers the first tab 240, and the second covering portion 231 covers the side of the first covering portion 221 facing away from the first tab 240. By providing the second covering portion 231 on the first tab 240, the first tab 240 has negative active material, increasing the local CB value (the ratio of the areal capacity of the first electrode 200 to that of the second electrode 100) of the battery cell. The first tab 240 has more lithium insertion sites, reducing lithium deposition on the first tab 240 due to high current density and improving the safety of the battery.

[0055] In addition, the first connection layer 220 can ensure the electrical conductivity between the first active layer 230 and the first current collector 210 and the first tab 240 respectively, and at the same time reliably fix the first active layer 230 on the first current collector 210 and the first tab 240. The first active layer 230 is not likely to have powder falling off or peeling from the first current collector 210 / the first tab 240. The first covering portion 221 and the second covering portion 231 do not completely cover the first tab 240, which is beneficial to improving the energy density of the battery.

[0056] In one embodiment, as Figures 1 - 3 shown, the width H1 of the first connection layer 220 at the first covering portion 221 is greater than or equal to the width H2 of the first active layer 230 at the second covering portion 231.

[0057] Among them, the projection of the first connection layer 220 in the thickness direction of the first electrode tab 200 covers the projection of the first active layer 230 in the thickness direction of the first electrode tab 200. During the preparation of the first electrode tab 200, the first connection layer 220 is first covered on the first current collector 210, the first active layer 230 is covered on the side of the first connection layer 220 facing away from the first current collector 210, hot roll pressing is performed, and finally die cutting is performed to form the first electrode tab 200. Figures 1 - 3 It is shown that the width of the portion of the first connection layer 220 located on the first current collector 210 is the same as the width of the portion of the first active layer 230 located on the first current collector 210. When the first active layer 230 covers the first connection layer 220, the edge of the first active layer 230 does not extend beyond the first connection layer 220.

[0058] The above settings enable the first active layer 230 to be reliably fixed on the first current collector 210, while ensuring the conductivity between each region of the first active layer 230 and the first current collector 210 and the first electrode tab 240 respectively.

[0059] In a specific embodiment, as Figures 1 - 3 shown, the width H1 of the first connection layer 220 at the first covering portion 221 and the width H2 of the first active layer 230 at the second covering portion 231 satisfy: 0 mm ≤ H1 - H2 ≤ 3 mm.

[0060] Exemplarily, the difference between H1 and H2 can be 0 mm, 1 mm, 2 mm or 3 mm, etc., and is not uniquely limited here. When H1 - H2 > 3 mm, the width of the portion of the first connection layer 220 exceeding the first active layer 230 is relatively large. The portion of the first connection layer 220 exceeding the first active layer 230 located on the first electrode tab 240 will affect the bending of the first electrode tab 240, resulting in poor welding of the first electrode tab 240.

[0061] This structure ensures the connection reliability between the first active layer 230, the first current collector 210 and the first electrode tab 240. At the same time, it ensures the conductivity between each region of the first active layer 230 and the first current collector 210 and the first electrode tab 240, and can also ensure the welding performance of the first electrode tab 240.

[0062] Schematically, the thickness of the first connection layer 220 is 0.3 μm - 2 μm.

[0063] Among them, the thickness of the first connection layer 220 can be 0.3 μm, 1 μm, 2 μm, etc., and there is no unique limitation here. When the thickness of the first connection layer 220 is less than 0.3 μm, the first active layer 230 cannot be reliably fixed on the first current collector 210 and the first tab 240; when the thickness of the first connection layer 220 is greater than 2 μm, the thickness of the first electrode sheet 200 is relatively large, resulting in a decrease in the energy density of the battery.

[0064] The above settings can ensure the reliable fixation of the first active layer 230 on the first current collector 210 and the first tab 240 while also ensuring the energy density of the battery.

[0065] In one embodiment, as Figures 1 - 3 shown, the width H3 of the second covering portion 231 satisfies: 0.1 mm ≤ H3 ≤ 1 mm.

[0066] Exemplarily, the width H3 of the second covering portion 231 can be 0.1 mm, 0.5 mm, 1 mm, etc., and there is no unique limitation here. When the width H3 of the second covering portion 231 is less than 0.1 mm, there is less negative active material on the first tab 240, and the improvement effect on lithium deposition on the first tab 240 is small. At the same time, the thinning area of the first active layer 230 may be located at the edge of the first current collector 210 facing the first tab 240, and lithium deposition may occur at the edge of the first electrode sheet 200 facing the first tab 240; when the width H3 of the second covering portion 231 is greater than 1 mm, there is more negative active material on the first tab 240, reducing the energy density of the battery and affecting the bending of the first tab 240.

[0067] That is to say, the above settings can ensure the improvement effect on lithium deposition on the first tab 240, avoid lithium deposition at the edge of the first electrode sheet 200 facing the first tab 240, and ensure the energy density of the battery and the bending performance of the first tab 240.

[0068] Schematically, the width H4 of the first covering portion 221 satisfies: 0.1 mm ≤ H4 ≤ 3.1 mm.

[0069] Specifically, the width H4 of the first covering portion 221 can be set according to the width H3 of the second covering portion 231. The width H4 of the first covering portion 221 can be 0.1 mm, 1.5 mm, 3.1 mm, etc., and is not uniquely limited herein. When the width H4 of the first covering portion 221 is less than 0.1 mm, the edge of the second covering portion 231 will protrude from the first covering portion 221, affecting the reliability of the connection between the second covering portion 231 and the first tab 240, and at the same time affecting the electrical conductivity between the second covering portion 231 and the first tab 240. When the width H4 of the first covering portion 221 is greater than 3.1 mm, the first connection layer 220 on the first tab 240 is relatively wide, affecting the energy density of the battery and the bending performance of the first tab 240.

[0070] By setting the width H4 of the first covering portion 221, the reliability of the connection between the second covering portion 231 and the first tab 240 is ensured, the powder falling off the first covering portion 221 on the first tab 240 is reduced, the risk of short circuit between the second electrode sheet 100 and the first electrode sheet 200 is reduced, the electrical conductivity between the second covering portion 231 and the first tab 240 is ensured, and at the same time the energy density of the battery and the bending performance of the first tab 240 are ensured.

[0071] In a possible implementation manner, the thickness difference between the second covering portion 231 and the rest of the first active layer 230 is less than or equal to 3 μm.

[0072] It is worth mentioning that due to the ductility of the first active layer 230 and the first connection layer 220, the thickness of the second covering portion 231 changes. Since the first electrode sheet 200 provided in this application is prepared by a dry process, compared with the first electrode sheet 200 prepared by wet coating, the width of the region where the thickness of the first active layer 230 changes is narrower, that is, the width of the region where the thickness of the first active layer 230 changes does not exceed 3 mm. Schematically, the region occupied by the second covering portion 231 is the thinning region of the first active layer 230, and the thickness of the second covering portion 231 is specifically the average thickness of the second covering portion 231. The thickness difference between the second covering portion 231 and the rest of the first active layer 230 being less than or equal to 3 μm can ensure the thickness of the second covering portion 231, and thus the second covering portion 231 can provide more lithium insertion sites, making it not easy for lithium to deposit on the edge of the first electrode sheet 200.

[0073] Such as Figure 1 、 Figure 4 and Figure 5As shown, the second electrode sheet 100 includes a second current collector 110, a second tab 120, a second active layer 130, and a safety coating 140. The end of the second tab 120 is connected to the edge of the second current collector 110. The safety coating 140 is located on the side of the second active layer 130 facing the second tab 120 in the width direction of the second electrode sheet 100. The safety coating 140 has a third covering portion that extends beyond the second current collector 110, and the third covering portion covers a part of the second tab 120.

[0074] Herein, the length direction of the second electrode sheet 100 is defined as Figure 5 the direction indicated by the X-axis in Figure 1 , Figure 4 and Figure 5 the direction indicated by the Y-axis in Figure 1 and Figure 4 the direction indicated by the Z-axis in.

[0075] Exemplarily, the second current collector 110 and the second tab 120 can be an integral part, and the second current collector 110 and the second tab 120 can be formed by die-cutting a copper foil. Among them, the second active layer 130 and the safety coating 140 can be provided only on one side of the second current collector 110, or the second active layer 130 and the safety coating 140 can be provided on both sides of the second current collector 110 respectively. Schematically, the second active layer 130 and the safety coating 140 are arranged side by side in the width direction of the second electrode sheet 100.

[0076] Optionally, there is an overlapping area between the safety coating 140 and the second active layer 130, that is, part of the safety coating 140 can cover one end of the second active layer 130 facing the second tab 120. The width of the overlapping area can be 0 mm - 1 mm.

[0077] Exemplarily, the safety coating 140 includes a binder and a solid insulating material. The binder can be conventional PVDF and / or SBR, or can be a hot melt adhesive, including EVA-based, TPR-based, polyolefin-based, polyamide (PA), polyester (PES), polyethylene (LOPE and HDPE), and polyester amide (PEA), etc. The solid insulating material is an inorganic solid insulating material and / or an organic solid insulating material. It can be at least one of BaSO4, CaSiO3, Al2O3, γ-AlOOH, CaSiO4, polypropylene, polyethylene, polytetrafluoroethylene, and polyvinylidene fluoride.

[0078] In a possible implementation manner, a second connection layer can be provided between the second active layer 130 and the second current collector 110, and the projection of the second connection layer in the thickness direction of the second electrode sheet 100 covers the projection of the second active layer 130 in the thickness direction of the second electrode sheet 100.

[0079] As shown Figure 5 in the figure, the third covering portion covers one end where the second tab 120 is connected to the second current collector 110, and the width of the third covering portion may be the same as the width of the corresponding second tab 120.

[0080] It should be noted that when die-cutting the second electrode sheet 100, burrs will be generated on the side edges of the end where the second tab 120 is connected to the second current collector 110. When laser cleaning the second electrode sheet 100, molten beads will be generated on the side edges of the end where the second tab 120 is connected to the second current collector 110. By providing the safety coating 140 on the second electrode sheet 100 and covering a part of the second tab 120 with the third covering portion of the safety coating 140, the burrs and / or molten beads can be covered by the safety coating 140, thereby avoiding the burrs and / or molten beads piercing the separator 300 and causing the battery to short-circuit.

[0081] Schematically, as shown Figure 1 、 Figure 4 and Figure 5 in the figure, the width A of the safety coating 140 satisfies: 1 mm ≤ A ≤ 2.5 mm.

[0082] Exemplarily, the width A of the safety coating 140 may be 1 mm, 1.7 mm, 2.5 mm, etc., and is not uniquely limited herein. When the width A of the safety coating 140 is less than 1 mm, the width of the safety coating 140 is relatively narrow, and some burrs and / or molten beads on the second electrode sheet 100 may be located outside the safety coating 140, and there may still be a risk of short circuit caused by the burrs and / or molten beads piercing the separator 300 in the battery; when the width A of the safety coating 140 is greater than 2.5 mm, the width of the safety coating 140 is relatively wide, resulting in a relatively narrow width of the second active layer 130, and the energy density of the battery is relatively low.

[0083] The above setting reliably avoids the short circuit of the battery while ensuring the energy density of the battery.

[0084] In a possible implementation manner, as shown Figure 1 、 Figure 4 and Figure 5 in the figure, the width A1 of the part of the safety coating 140 located on the second current collector 110 satisfies: 0 mm < A1 ≤ 1.5 mm.

[0085] Among them, the width A1 of the part of the safety coating 140 located on the second current collector 110 may be 0.5 mm, 1 mm, 1.5 mm, etc., and is not uniquely limited herein. The width of the part of the safety coating 140 located on the second current collector 110 does not exceed 1.5 mm, which is beneficial to controlling the area ratio of the non-active material on the second current collector 110 and ensuring the energy density of the battery.

[0086] In a possible implementation manner, as shownFigure 1 , Figure 4 and Figure 5 As shown in Figure 5 , the width A2 of the third covering portion satisfies: 0 < A2 ≤ 1 mm.

[0087] Among them, the width A2 of the third covering portion can be 0.3 mm, 0.5 mm, 1 mm, etc., and is not uniquely limited here. A2 > 0 can ensure that there is a third covering portion on the second tab 120, avoiding burrs and / or molten beads on the second electrode sheet 100 from piercing the separator 300 and causing a short circuit in the battery. When A2 > 1 mm, the width of the third covering portion is relatively wide, affecting the energy density of the battery and the bending performance of the second tab 120.

[0088] That is to say, the above settings can effectively avoid the occurrence of a short circuit in the battery while ensuring the bending performance of the second tab 120.

[0089] As Figure 1 , Figure 3 and Figure 5 shown in Figure 5 , the width B1 of the first active layer 230 on the first current collector 210, the width B2 of the second active layer 130, and the width A1 of the safety coating 140 on the upper part of the second current collector 110 satisfy: B1 > B2, and B1 ≤ A1 + B2.

[0090] Among them, the width B1 of the first active layer 230 on the first current collector 210 being greater than the width B2 of the second active layer 130 can ensure that the CB value of the battery cell is greater than 1, enabling the first electrode sheet 200 to have sufficient lithium insertion sites, and it is not easy for lithium to deposit on the edge of the first electrode sheet 200. When B1 > B2 and B1 ≤ A1 + B2, the position of the first active layer 230 on the first current collector 210 facing the first tab 240 is opposite to the position of the safety coating 140 of the second electrode sheet 100. The battery will not short-circuit due to poor covering dimensions of the second electrode sheet 100 and the first electrode sheet 200 during charge and discharge, causing the battery to catch fire and explode. At the same time, the above settings can ensure that the first electrode sheet 200 has sufficient lithium insertion sites while avoiding the part of the first active layer 230 on the first current collector 210 that exceeds the second active layer 130 from being too wide, ensuring the energy density of the battery. In addition, burrs and / or molten beads on the second electrode sheet 100 will not pierce the separator 300 and cause a short circuit in the battery.

[0091] Schematically, as Figure 1 shown in Figure 1 , in the thickness direction of the battery cell, the projections of the third covering portion and the first covering portion 221 of the safety coating 140 at least partially overlap.

[0092] Among them, the third covering portion covers one end where the second tab 120 is connected to the second current collector 110, and the first covering portion 221 covers one end where the first tab 240 is connected to the first current collector 210. In the thickness direction of the battery cell, the projection of the third covering portion and the projection of the first covering portion 221 at least partially overlap, indicating that the projection of the first tab 240 in the thickness direction of the battery cell and the projection of the second tab 120 in the thickness direction of the battery cell at least partially overlap. The above setting can reduce the width of the battery cell occupied by the first tab 240 and the second tab 120, and thus is beneficial to reducing the width of the battery cell.

[0093] Optionally, as Figure 1 shown, in the direction indicated by the X-axis, the distance between the right end of the first active layer 230 on the first current collector 210 and the left end of the safety coating 140 is not less than 0.2 mm. That is, the width of the portion of the first active layer 230 on the first current collector 210 that extends beyond the positive active material layer is not less than 0.2 mm. During the assembly process of the battery cell, the second active layer 130 and the first active layer 230 will not come into direct contact due to assembly tolerances, causing a short circuit. At the same time, it ensures that the first electrode sheet 200 has sufficient lithium insertion sites, making it not easy for lithium to deposit on the edge of the first electrode sheet 200.

[0094] Optionally, as Figure 1 shown, in the direction indicated by the X-axis, the distance between the right end of the first active layer 230 on the first current collector 210 and the right end of the safety coating 140 on the second current collector 110 is greater than or equal to 0 and less than or equal to 0.7 mm. It can be understood that the projection of the edge of the second current collector 110 facing the second tab 120 in the thickness direction of the second electrode sheet 100 is located outside the first active layer 230 on the first current collector 210, ensuring that the burrs and / or molten beads on the second electrode sheet 100 do not come into contact with the first active layer. The distance between the right end of the first active layer 230 on the first current collector 210 and the right end of the safety coating 140 on the second current collector 110 does not exceed 0.7 mm, which can ensure that the first electrode sheet 200 has sufficient lithium insertion sites, making it not easy for lithium to deposit on the edge of the first electrode sheet 200. In addition, the above setting ensures that during the assembly process of the battery cell, the second active layer 130 and the first active layer 230 will not come into direct contact due to assembly tolerances, causing a short circuit.

[0095] In one embodiment, the end of the first connection layer 220 away from the first active layer 230 extends beyond the end of the safety coating 140 away from the second active layer 130.

[0096] Among them, the edge of the first active layer 230 extends beyond the edge of the second active layer 130. The width of the part where the first connection layer 220 extends beyond the first active layer 230 is 0 - 3 mm. Exemplarily, the width of the part where the first connection layer 220 extends beyond the first active layer 230 can be 2.8 mm. One end of the safety coating 140 away from the second active layer 130 extends beyond the edge of the first active layer 230, and the width of the part where the safety coating 140 extends beyond the first active layer 230 is not greater than 0.7 mm. The above settings make one end of the first connection layer 220 away from the first active layer 230 extend beyond one end of the safety coating 140 away from the second active layer 130.

[0097] Through the above settings, the edge of the first active layer 230 extends beyond the edge of the second active layer 130, making it not easy for the edge of the first active layer 230 to undergo lithium plating.

[0098] In one embodiment, the first active layer 230 and / or the second active layer 130 includes active particles and fibers, and the fibers extend along the first direction.

[0099] Among them, the first direction is the length direction of the electrode sheet. Fibers refer to continuous or discontinuous filaments. In some embodiments, the fibers are filamentous structures formed by fibrillation or electrostatic spraying of a binder. The present application does not limit the specific material of the fibers, and it can be a binder. It can be understood that the fibers can play a role in binding and fixing the active particles.

[0100] It can be understood that the first active layer 230 and the second active layer 130 further include a conductive agent, and the conductive agent can be one or a mixture of conductive carbon black, carbon fiber, conductive graphite, graphene, carbon nanotube, acetylene black, Ketjen black, copper, nickel, aluminum, silver, gold, etc.

[0101] In this embodiment, the fibers in the first active layer 230 extend along the first direction, which improves the breaking tensile strength of the electrode sheet, reduces the risk of tape breakage, enhances the cycle performance of the battery, and reduces the thickness expansion rate.

[0102] In a specific embodiment, the ratio of the breaking tensile strength of the first electrode sheet 200 and / or the second electrode sheet 100 in the first direction to the breaking tensile strength of the electrode sheet in the second direction is (1 - 2):1.

[0103] Among them, the second direction is the width direction of the electrode sheet. By defining the ratio of the breaking tensile strengths of the electrode sheet in the first direction and the second direction, the expansion of the electrode sheet in the first direction and the second direction during charge and discharge can be effectively alleviated, especially the expansion of the electrode sheet in the first direction.

[0104] Preferably, the ratio of the breaking tensile strength of the first electrode sheet 200 and / or the second electrode sheet 100 in the first direction to the breaking tensile strength of the electrode sheet in the second direction is (1.02 to 1.52):1. The above setting can reduce the internal resistance and interfacial reaction of the electrode sheet, improve the electrochemical performance of the battery, and also improve the mechanical stability of the battery and extend the service life of the battery.

[0105] In a possible implementation, the ratio range of the length of the fiber to the diameter of the fiber is 10 - 1000.

[0106] Exemplarily, the ratio of the length of the fiber to the diameter of the fiber can be 10, 100, 500, 800, 1000, etc., and is not uniquely limited herein. When the ratio of the length of the fiber to the diameter of the fiber is less than 10, it indicates that the degree of fibrillation of the first binder is insufficient, and the first binder is not easy to bond other components of the active layer, making it difficult for the active layer to form; when the ratio of the length of the fiber to the diameter of the fiber is greater than 1000, it indicates that the degree of fibrillation of the first binder is too high, and the stability of the bonding interface formed by the first binder is poor, easily leading to uneven distribution of the components of the active layer. That is to say, the above setting can not only ensure that the active layer is easy to form, but also ensure that the components of the active layer are evenly distributed.

[0107] In a possible implementation, along the thickness direction of the first electrode sheet 200 and / or the second electrode sheet 100, adjacent active particles are connected by fibers. The fibers make the active particles connect more tightly with each other. This further ensures that the fibers play a role in bonding and fixing the active particles, thereby reducing the cyclic expansion rate.

[0108] In one embodiment, the fibers form a composite network, and the active particles of the first active layer 230 are dispersed on the composite network.

[0109] In this embodiment, the fibers form a composite network, which plays a bonding role. The composite network increases the contact area between the fibers and the active particles, realizes a tighter connection between the fibers and the active particles, is beneficial to improving the flexibility of the electrode sheet, and prevents cracking and powder falling.

[0110] In one embodiment, the fibers include one or more of fibrous PTFE, PVDF, PE, ETEF, FEP, PVP, PEO, CMC, SBR, PAA, and hot melt adhesives. The above fibers can enable the first active layer 230 and / or the second active layer 130 to form a film. Among them, fibrous PTFE is more likely to enable the first active layer 230 and / or the second active layer 130 to form a film, and PVDF and PE have less ductility and are easier to control the sizes of the second active layer 130 and the first active layer 230.

[0111] In a possible implementation, the active particles of the second active layer 130 include at least one of LiCoO2, LiMn2O4, LiMnO2, LiNiO2, LiFePO4, LiMnPO4, LiCoxNi1-xO2 (0 ≤ x ≤ 1), and LiCoxNi1-x-yAlyO2 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1). During the charging process of the battery, the above-mentioned active particles are more likely to release lithium ions; during the discharging process of the battery, the above-mentioned active particles are more likely to intercalate lithium ions.

[0112] In a possible implementation, the active particles of the first active layer 230 include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesocarbon microbeads, Si, SiOx, Si-C, and SiOx-C, and the silicon content of the first active layer 230 is 3% - 100%. Among them, during the charging process of the battery, the above-mentioned active particles are more likely to intercalate lithium ions; during the discharging process of the battery, the above-mentioned active particles are more likely to release lithium ions. The silicon content of the first active layer 230 being 3% - 100% can make the capacity of the first active layer 230 larger, that is, the first active layer 230 can intercalate more lithium ions during the charging process of the battery.

[0113] The present application also provides a battery, including a housing and the above-mentioned battery cell, and the battery cell is located inside the housing.

[0114] For the battery provided by the present application, due to the adoption of the above-mentioned battery cell, there are more lithium intercalation sites on the first ear 240, reducing the lithium deposition on the first ear 240 due to the large current density, and the safety and cycle performance of the battery are higher.

[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 them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some 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 cell, characterized in that: It includes a first pole piece, a second pole piece, and a diaphragm located between the second pole piece and the first pole piece; The first pole piece includes a first current collector, a first connecting layer, a first active layer and a first pole ear, the first pole ear extends from one side edge of the first current collector, the first connecting layer covers the first current collector, the first active layer covers the side of the first connecting layer away from the first current collector, the first connecting layer has a first covering portion extending beyond the first current collector, the first covering portion covers a portion of the first pole ear, the first active layer has a second covering portion extending beyond the first current collector, and the second covering portion covers the side of the first covering portion away from the first pole ear.

2. The battery cell according to claim 1, characterized in that: The width of the first connection layer at the first covering portion is greater than or equal to the width of the first active layer at the second covering portion.

3. The battery cell according to claim 2, characterized in that: The width H1 of the first connection layer at the first covering portion and the width H2 of the first active layer at the second covering portion satisfy: 0 mm ≤ H1 - H2 ≤ 3 mm; and / or, The thickness of the first connecting layer is 0.3 μm-2 μm; and / or, The width H3 of the second covering portion satisfies: 0.1 mm ≤ H3 ≤ 1 mm; and / or, The width H4 of the first covering portion satisfies: 0.1 mm ≤ H4 ≤ 3.1 mm; and / or, The ratio of the width of the second covering portion to the width of the first covering portion is 0.4-1.

4. The battery cell according to claim 1, characterized in that: A thickness difference between the second covering portion and the remaining portion of the first active layer is less than or equal to 3 μm.

5. The battery cell according to claim 1, characterized in that: The second pole sheet includes a second current collector, a second pole ear, a second active layer and a safety coating, wherein the end of the second pole ear is connected to the edge of the second current collector, and the safety coating is located on the side of the second active layer facing the second pole ear in the width direction of the second pole sheet, and the safety coating has a third covering portion extending beyond the second current collector, and the third covering portion covers a portion of the second pole ear.

6. The battery cell according to claim 5, characterized in that: In the thickness direction of the battery core, a projection of the third covering portion of the safety coating and a projection of the first covering portion at least partially overlap.

7. The battery cell according to claim 5, characterized in that: An end of the first connecting layer away from the first active layer exceeds an end of the safety coating away from the second active layer.

8. The battery cell according to claim 5, characterized in that: The first active layer and / or the second active layer comprises active particles and fibers, and the fibers extend along a first direction.

9. The battery cell according to claim 8, characterized in that: The ratio of the breaking tensile force of the first pole piece and / or the second pole piece in the first direction to the breaking tensile force of the pole piece in the second direction is (1-2): 1; and / or, The ratio between the length of the fiber and the diameter of the fiber is in the range of 10-1000; and / or, Along the thickness direction of the first pole sheet and / or the second pole sheet, adjacent active particles are connected by the fibers.

10. The battery cell according to claim 8, characterized in that: The fibers form a composite network, and the active particles of the first active layer are dispersed on the composite network.

11. A battery, characterized in that: The invention comprises a shell and the battery core according to any one of claims 1 to 10, wherein the battery core is located inside the shell.

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