Electrode tab, battery, and electric device

Abstract

The application provides an electrode tab, a battery and an electric device. The electrode tab comprises a current collector and an active material layer arranged on at least one side surface of the current collector. The active material layer comprises a first active material layer and a second active material layer arranged in the same layer and connected with the first active material layer. In the direction from the first active material layer to the second active material layer, the thickness of the second active material layer gradually decreases. The first active material layer comprises a first active material, and the second active material layer comprises a second active material. The mass content of the first active material in the first active material layer is less than the mass content of the second active material in the second active material layer. The electrode tab provided by the application is not prone to lithium precipitation reaction, has high volume energy density and mass energy density, low preparation cost, and is beneficial to improving the capacity and service life of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to an electrode tab, a battery and an electric device. BACKGROUND

[0002] At present, in order to improve the production capacity of the electrode tab, the electrode tab is prepared by adopting multi-coating, the relative area capacity in the electrode tab is not matched, which leads to the decrease of the ratio of the negative electrode capacity to the positive electrode capacity, and the lithium precipitation phenomenon is easy to occur, which is not conducive to improving the cycle stability of the battery. In the related technology, the ratio of the negative electrode capacity to the positive electrode capacity is improved by increasing the area density of the electrode tab to reduce the probability of occurrence of the lithium precipitation phenomenon, but this method will lead to the decrease of the volume energy density and the weight energy density of the electrode tab, the increase of the preparation cost, and is not conducive to improving the wide application of the electrode tab. Therefore, an electrode tab which is not easy to occur the lithium precipitation phenomenon, has high volume energy density and weight energy density, and low preparation cost is needed. SUMMARY

[0003] In view of this, the present application provides an electrode tab, a battery and an electric device, which is not easy to occur the lithium precipitation phenomenon, has high volume energy density and weight energy density, and low preparation cost, and is conducive to improving the electrochemical performance and industrial application of the battery.

[0004] In a first aspect, the present application provides an electrode tab, which comprises a current collector and an active material layer arranged on at least one side surface of the current collector, the active material layer comprises a first active material layer and a second active material layer arranged in the same layer and connected with the first active material layer, the thickness of the second active material layer gradually decreases in the direction from the first active material layer to the second active material layer, the first active material layer comprises a first active material, the second active material layer comprises a second active material, and the mass content of the first active material in the first active material layer is less than the mass content of the second active material in the second active material layer.

[0005] Optionally, the second active material layer is arranged on one side of the first active material layer, or the second active material layer is arranged on opposite sides of the first active material layer.

[0006] Optionally, in the first active material layer, the mass content of the first active material is 93%-97.2%.

[0007] Optionally, in the second active material layer, the mass content of the second active material is 96.2%-98.5%.

[0008] Optionally, the primary particle size D50 of the first active material is less than the primary particle size D50 of the second active material.

[0009] Optionally, the mass content of the carbon coating layer of the first active material is greater than the mass content of the carbon coating layer of the second active material.

[0010] Optionally, the primary particle size D50 of the first active material is 0.3 μm-9 μm.

[0011] Optionally, the primary particle size D50 of the second active material is 0.7 μm-15 μm.

[0012] Optionally, the mass content of the carbon coating layer of the first active material is 0.5%-2%.

[0013] Optionally, the mass content of the carbon coating layer of the second active material is less than or equal to 0.5%.

[0014] Optionally, the first active material layer further comprises a first conductive agent and a first binder, and the second active material layer further comprises a second conductive agent and a second binder.

[0015] Optionally, the mass content of the first conductive agent in the first active material layer is greater than the mass content of the second conductive agent in the second active material layer.

[0016] Optionally, the mass content of the first binder in the first active material layer is greater than the mass content of the second binder in the second active material layer.

[0017] Optionally, in the first active material layer, the mass content of the first conductive agent is 0.5%-2%, and the mass content of the first binder is 1%-3%.

[0018] Optionally, in the second active material layer, the mass content of the second conductive agent is less than or equal to 1%, and the mass content of the second binder is 0.5%-2%.

[0019] Optionally, the thickness of the first active material layer is 92 μm-300 μm, and the maximum thickness of the second active material layer is 92 μm-300 μm.

[0020] Optionally, the size of the first active material layer in the direction from the second active material layer to the first active material layer is 80 mm-1000 mm.

[0021] Optionally, the size of the second active material layer in the direction from the first active material layer to the second active material layer is 10 mm-30 mm.

[0022] Optionally, the areal density of the electrode tab is 150 g / m 2 -600 g / m 2.

[0023] The electrode pole piece provided by the application has a low probability of lithium precipitation, high volume energy density and mass energy density, improved cycle stability of the electrode pole piece, and is beneficial to improving the service life of the battery.

[0024] In a second aspect, the application provides a battery, which comprises a positive pole piece and a negative pole piece, and a separator arranged between the positive pole piece and the negative pole piece, wherein the negative pole piece comprises the electrode pole piece of the first aspect.

[0025] Optionally, the positive pole piece comprises the electrode pole piece of the first aspect.

[0026] The battery provided by the application has excellent electrochemical performance, a long service life, and strong product competitiveness.

[0027] In a third aspect, the application provides a power consumption device, which comprises the battery of the second aspect.

[0028] The power consumption device provided by the application has excellent comprehensive performance, high safety performance, and strong market competitiveness. DETAILED DESCRIPTION

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. The specific embodiments described herein are only used to explain the application, and are not used to limit the application.

[0030] Figure 1 A cross-sectional schematic view of the electrode pole piece provided by an embodiment of the application.

[0031] Figure 2 A cross-sectional schematic view of the electrode pole piece provided by another embodiment of the application.

[0032] Figure 3 A cross-sectional schematic view of the electrode pole piece provided by still another embodiment of the application.

[0033] Legend of reference signs: 100-electrode pole piece; 10-current collector; 20-active material layer; 21-first active material layer; 22-second active material layer; 11-tab. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0035] Referring to Figure 1 , the cross-sectional schematic diagram of the electrode tab provided in an embodiment of the present application, the electrode tab 100 includes a current collector 10 and an active material layer 20 arranged on at least one side surface of the current collector 10, the active material layer 20 includes a first active material layer 21 and a second active material layer 22 arranged in the same layer and connected with the first active material layer 21, the thickness of the second active material layer 22 gradually decreases in the direction from the first active material layer 21 to the second active material layer 22, the first active material layer 21 includes a first active material, and the second active material layer 22 includes a second active material, the mass content of the first active material in the first active material layer 21 is less than the mass content of the second active material in the second active material layer 22. The electrode tab provided in the present application controls the relationship between the mass content of the first active material in the first active material layer and the mass content of the second active material in the second active material layer, so that the number of ion intercalation sites in the second active material layer increases, the capacity of the second active material layer is improved, and the capacity, volume energy density and weight energy density of the electrode tab are improved, the probability of lithium precipitation phenomenon of the electrode tab in the use process is reduced, and the capacity, cycle stability and service life of the battery are improved.

[0036] In an embodiment of the present application, the thickness of the second active material layer gradually decreases in the direction from the first active material layer to the second active material layer (as shown by the direction of the arrow in Figure 1 , the thickness of the second active material layer gradually decreases. The gradual decrease can be linear decrease, or non-linear decrease, such as gradient decrease, parabolic decrease, etc. The region where the thickness of the active material layer of the electrode tab gradually decreases is defined as a thinning region, and the region where the thickness remains unchanged is defined as a non-thinning region. Therefore, the first active material layer is a non-thinning region, and the second active material layer is a thinning region. By increasing the content of the second active material in the thinning region, the capacity of the thinning region in the electrode tab is improved, the capacity of the electrode tab is improved, the lithium precipitation phenomenon is alleviated, and the energy density of the electrode tab is improved.

[0037] In the present application, the current collector converts chemical energy into electrical energy for output, and improves the conductivity of the electrode tab. The current collector is a positive electrode current collector or a negative electrode current collector. When the electrode tab is a positive electrode tab, the current collector is a positive electrode current collector, and when the electrode tab is a negative electrode tab, the current collector is a negative electrode current collector. In an embodiment of the present application, the positive electrode current collector can be, but is not limited to, at least one of copper, aluminum, nickel and stainless steel; and the negative electrode current collector can include, but is not limited to, at least one of copper, aluminum, nickel and stainless steel. In an embodiment of the present application, when the current collector is a positive electrode current collector, the electrode tab is a positive electrode tab, and the current collector can be an aluminum foil. In another embodiment of the present application, when the current collector is a negative electrode current collector, the electrode tab is a negative electrode tab, and the current collector can be a copper foil.

[0038] In one embodiment of the present application, the active material layer completely covers the surface of the current collector; that is, the orthographic projection of the active material layer on the surface of the current collector completely covers the surface of the current collector. Figure 2 , is a cross-sectional schematic diagram of an electrode plate provided in another embodiment of the present application. In the electrode plate 100, there is an area on the surface of the current collector 10 that is not covered by the active material layer 20. The area in the current collector 10 that is not covered by the active material layer 20 serves as the tab 11. One end of the tab 11 is connected to the second active material layer 22 (thinned area), and the other end of the tab 11 can be connected to an external device to perform a charge and discharge cycle. In some embodiments, the second active material layer is disposed on one side of the first active material layer. Specifically, when the electrode plate has a tab, the second active material layer can be disposed between the first active material layer and the tab. In other embodiments, the second active material layer is disposed on opposite sides of the first active material layer. Specifically, when the electrode plate has a tab, the second active material layer can be disposed between the first active material layer and the tab.

[0039] In one embodiment of the present application, Figure 1 As shown, the electrode plate 100 includes a current collector 10 and an active material layer 20 disposed on one side of the current collector 10. The active material layer 20 includes a first active material layer 21 and a second active material layer 22. The first active material layer 21 and the second active material layer 22 are disposed on the same side of the current collector 10. Figure 3 , is a cross-sectional schematic diagram of an electrode plate provided in another embodiment of the present application. The electrode plate 100 includes a current collector 10 and an active material layer 20 provided on opposite sides of the current collector 10. This can further improve the energy density of the electrode plate and reduce the probability of lithium plating in the electrode plate. In the present application, the first active material can be a positive electrode active material or a negative electrode active material. When the electrode plate is a positive electrode plate, the first active material is a positive electrode active material. When the electrode plate is a negative electrode plate, the first active material is a negative electrode active material. In one embodiment of the present application, the positive electrode active material can include but is not limited to at least one of lithium cobalt oxide material, nickel cobalt manganese material, nickel cobalt aluminum material, nickel cobalt manganese aluminum material, lithium iron phosphate material, lithium manganese phosphate material, lithium vanadium phosphate material, lithium manganese oxide material and lithium-rich manganese-based material; the negative electrode active material can include but is not limited to at least one of artificial graphite, natural graphite, hard carbon, soft carbon and graphene. In one embodiment of the present application, when the first active material is a positive electrode active material, the first active material can be a lithium iron phosphate material. In another embodiment of the present application, when the first active material is a negative electrode active material, the first active material may be artificial graphite.

[0040] In the present application, the second active material layer comprises a second active material, which can be a positive active material or a negative active material. When the electrode pole piece is a positive pole piece, the second active material is a positive active material; when the electrode pole piece is a negative pole piece, the second active material is a negative active material, which can improve the conductivity and capacity density of the electrode pole piece. In an embodiment of the present application, the positive active material can include, but is not limited to, at least one of lithium cobaltate material, nickel cobalt manganese material, nickel cobalt aluminum material, nickel cobalt manganese aluminum material, lithium iron phosphate material, lithium manganese phosphate material, lithium vanadium phosphate material, lithium manganate material and lithium-rich manganese-based material; the negative active material can include, but is not limited to, at least one of artificial graphite, natural graphite, hard carbon, soft carbon and graphene. In an embodiment of the present application, when the second active material is a positive active material, the second active material can be a lithium iron phosphate material. In another embodiment of the present application, when the second active material is a negative active material, the second active material can be artificial graphite.

[0041] In an embodiment of the present application, the mass content of the first active material in the first active material layer is 93%-97.2%, which can improve the energy density and conductivity of the electrode pole piece. Specifically, the mass content of the first active material in the first active material layer can be, but is not limited to, 93%, 94%, 95%, 96%, 9.65% or 97.2%, etc. In an embodiment of the present application, when the first active material is a negative active material, the mass content of the first active material in the first active material layer can be 93%-97%, which can improve the energy density of the negative pole piece. In another embodiment of the present application, when the first active material is a positive active material, the mass content of the first active material in the first active material layer can be 95%-97.2%, which can improve the energy density of the positive pole piece.

[0042] In an embodiment of the present application, the mass content of the second active material in the second active material layer is 96.2%-98.5%, which can improve the energy density and conductivity of the electrode pole piece. Specifically, the mass content of the second active material in the second active material layer can be, but is not limited to, 96.2%, 96.5%, 96.8%, 97%, 9.75% or 98.5%, etc. In an embodiment of the present application, when the second active material is a negative active material, the mass content of the second active material in the second active material layer can be 96.2%-98.5%, which can improve the energy density of the negative pole piece. In another embodiment of the present application, when the second active material is a positive active material, the mass content of the second active material in the second active material layer can be 97%-98.5%, which can improve the energy density of the positive pole piece.

[0043] The particle size D50 in the present application is the particle size corresponding to the cumulative volume distribution percentage of 50%. In an embodiment of the present application, the primary particle size D50 of the first active material is smaller than the primary particle size D50 of the second active material. With the same mass of active material, the smaller the primary particle size D50 of the active material, the greater the specific surface area, the more ion deintercalation sites, and the shorter the lithium ion diffusion distance, which is conducive to improving the conductivity and specific capacity of the active material. Since the second active material layer is close to the tab area, the temperature rises during charging and discharging, and a large-particle-size active material can be used to take advantage of the improved kinetic performance of the active material at high temperatures to improve the conductivity of the second active material layer, which is conducive to improving the high-temperature resistance and service life of the electrode sheet, reducing the preparation cost of the electrode sheet, and avoiding lithium precipitation during use of the electrode sheet.

[0044] In an embodiment of the present application, the mass content of the carbon coating layer of the first active material is greater than the mass content of the carbon coating layer of the second active material. The higher the mass content of the carbon coating layer, the thicker the coating layer, which can improve the conductivity of the active material. Since the second active material layer is close to the tab area, the temperature rises during charging and discharging, and a small-mass-content carbon-coated active material can be used to take advantage of the improved kinetic performance of the active material at high temperatures to maintain the high conductivity of the second active material layer, which improves the volume energy density and weight energy density of the electrode sheet, and further improves the thermal stability and safety performance of the battery and reduces the risk of thermal runaway of the battery.

[0045] In an embodiment of the present application, the primary particle size D50 of the first active material is 0.3-9 μm. Specifically, the primary particle size D50 of the first active material can be, but is not limited to, 0.3 μm, 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, or 9 μm, etc. In an embodiment of the present application, when the first active material is a negative active material, the primary particle size D50 of the first active material can be 6-9 μm. In another embodiment of the present application, when the first active material is a positive active material, the primary particle size D50 of the first active material can be 0.3-1.3 μm.

[0046] In an embodiment of the present application, the primary particle size D50 of the second active material is 0.7-15 μm. Specifically, the primary particle size D50 of the second active material can be, but is not limited to, 0.7 μm, 1 μm, 2 μm, 8 μm, 10 μm, 13 μm, or 15 μm, etc. In an embodiment of the present application, when the second active material is a negative active material, the primary particle size D50 of the second active material can be 9-15 μm. In another embodiment of the present application, when the second active material is a positive active material, the primary particle size of the second active material can be 0.7-2 μm.

[0047] In an embodiment of the present application, the mass content of the carbon coating layer of the first active material is 0.5%-2%. The higher the mass content of the carbon coating layer, the more carbon is coated on the surface of the active material, and the thicker the carbon layer. An appropriate mass content of the carbon coating layer is conducive to improving the conductivity of the active material, enhancing the safety performance of the battery, and reducing the risk of thermal runaway of the battery. Specifically, the mass content of the carbon coating layer of the first active material can be, but is not limited to, 0.5%, 1%, 1.2%, 1.6%, 1.8% or 2%, etc.

[0048] In an embodiment of the present application, the mass content of the carbon coating layer of the second active material is less than or equal to 0.5%. Specifically, the mass content of the carbon coating layer of the second active material can be, but is not limited to, less than or equal to 0.5%, less than or equal to 0.4%, less than or equal to 0.3%, less than or equal to 0.2%, or less than or equal to 0.1%, etc. In an embodiment of the present application, when the electrode sheet is a negative electrode sheet, the mass content of the carbon coating layer of the second active material can be less than or equal to 0.5%.

[0049] In an embodiment of the present application, the first active material layer further comprises a first conductive agent and a first binder. The first conductive agent can improve the conductivity of the electrode sheet, and the first binder can improve the binding ability between the components of the first active material layer and between the first active material layer and the current collector, which is conducive to improving the mechanical properties of the electrode sheet.

[0050] The first conductive agent can be a positive electrode conductive agent or a negative electrode conductive agent. When the electrode sheet is a positive electrode sheet, the first conductive agent is a positive electrode conductive agent, and when the electrode sheet is a negative electrode sheet, the first conductive agent is a negative electrode conductive agent, which can improve the conductivity of the electrode sheet. In an embodiment of the present application, the positive electrode conductive agent can include, but is not limited to, at least one of carbon nanotubes, acetylene black, graphene, conductive graphite and carbon black; and the negative electrode conductive agent can include, but is not limited to, at least one of carbon nanotubes, acetylene black, graphene, conductive graphite and carbon black. In an embodiment of the present application, when the first conductive agent is a positive electrode conductive agent, the first conductive agent can be carbon nanotubes. In another embodiment of the present application, when the first conductive agent is a negative electrode conductive agent, the first conductive agent can be carbon black.

[0051] In an embodiment of the present application, the mass content of the first conductive agent in the first active material layer is 0.5%-2%, which can improve the conductivity of the electrode tab. Specifically, the mass content of the first conductive agent in the first active material layer can be, but is not limited to, 0.5%, 0.8%, 1%, 1.5%, 1.8% or 2%, etc. In an embodiment of the present application, when the first conductive agent is a positive electrode conductive agent, the mass content of the first conductive agent in the first active material layer can be 1%-2%. In another embodiment of the present application, when the first conductive agent is a negative electrode conductive agent, the mass content of the first conductive agent in the first active material layer can be 0.5%-2%.

[0052] The first binder can be a positive electrode binder or a negative electrode binder. When the electrode tab is a positive electrode tab, the first binder is a positive electrode binder. When the electrode tab is a negative electrode tab, the first binder is a negative electrode binder, which can improve the mechanical properties of the electrode tab. In an embodiment of the present application, the positive electrode binder can include, but is not limited to, at least one of polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, polybutadiene, acrylic resin, epoxy resin, polyethylene oxide, sodium carboxymethyl cellulose and styrene butadiene rubber; the negative electrode binder can include, but is not limited to, at least one of polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, polybutadiene, acrylic resin, epoxy resin, polyethylene oxide, sodium carboxymethyl cellulose and styrene butadiene rubber. In an embodiment of the present application, when the first binder is a positive electrode binder, the first binder can be polyvinylidene fluoride. In another embodiment of the present application, when the first binder is a negative electrode binder, the first binder can be styrene butadiene rubber.

[0053] In an embodiment of the present application, the mass content of the first binder in the first active material layer is 1%-3%, and the appropriate first binder can improve the mechanical properties of the electrode tab. Specifically, the mass content of the first binder in the first active material layer can be, but is not limited to, 1%, 1.2%, 1.8%, 2%, 2.4%, 2.6%, 2.8% or 3%, etc. In an embodiment of the present application, when the first binder is a positive electrode binder, the mass content of the first binder in the first active material layer can be 1.8%-3%. In another embodiment of the present application, when the first binder is a negative electrode binder, the mass content of the first binder in the first active material layer can be 1%-2%.

[0054] In an embodiment of the present application, the second active material layer further includes a second conductive agent and a second binder. The second conductive agent can improve the conductivity of the electrode tab, and the second binder can improve the binding ability between the components of the second active material layer and between the second active material layer and the current collector, which is conducive to improving the mechanical properties of the electrode tab.

[0055] The second conductive agent can be a positive electrode conductive agent or a negative electrode conductive agent. When the electrode tab is a positive electrode tab, the second conductive agent is a positive electrode conductive agent. When the electrode tab is a negative electrode tab, the second conductive agent is a negative electrode conductive agent. The second conductive agent can improve the conductivity of the electrode tab. In an embodiment of the present application, the positive electrode conductive agent can include, but is not limited to, at least one of carbon nanotubes, acetylene black, graphene, conductive graphite, and carbon black. The negative electrode conductive agent can include, but is not limited to, at least one of carbon nanotubes, acetylene black, graphene, conductive graphite, and carbon black. In an embodiment of the present application, when the second conductive agent is a positive electrode conductive agent, the second conductive agent can be conductive graphite. In another embodiment of the present application, when the second conductive agent is a negative electrode conductive agent, the second conductive agent can be carbon nanotubes.

[0056] In an embodiment of the present application, the mass content of the second conductive agent in the second active material layer is less than or equal to 1%. The appropriate mass of the second conductive agent can slow down the lithium precipitation phenomenon of the electrode tab. Specifically, the mass content of the second conductive agent in the second active material layer can be, but is not limited to, less than or equal to 1%, less than or equal to 0.8%, less than or equal to 0.7%, less than or equal to 0.5%, less than or equal to 0.3%, or less than or equal to 0.1%, etc.

[0057] The second binder can be a positive electrode binder or a negative electrode binder. When the electrode tab is a positive electrode tab, the second binder is a positive electrode binder. When the electrode tab is a negative electrode tab, the second binder is a negative electrode binder. The second binder can improve the mechanical properties of the electrode tab. In an embodiment of the present application, the positive electrode binder can include, but is not limited to, at least one of polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, polybutadiene, acrylic resin, epoxy resin, polyethylene oxide, sodium carboxymethyl cellulose, and styrene butadiene rubber. The negative electrode binder can include, but is not limited to, at least one of polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, polybutadiene, acrylic resin, epoxy resin, polyethylene oxide, sodium carboxymethyl cellulose, and styrene butadiene rubber. In an embodiment of the present application, when the second binder is a positive electrode binder, the second binder can be polyvinylidene fluoride. In another embodiment of the present application, when the second binder is a negative electrode binder, the second binder can be polytetrafluoroethylene.

[0058] In one embodiment of the present application, the mass content of the second binder in the second active material layer is 0.5%-2%. Specifically, the mass content of the second binder in the second active material layer can be, but is not limited to, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8% or 2%. In one embodiment of the present application, when the second binder is a positive electrode binder, the mass content of the second binder in the second active material layer can be 1.5%-2%. In another embodiment of the present application, when the second binder is a negative electrode binder, the mass content of the second binder in the second active material layer can be 0.5%-1.2%.

[0059] In one embodiment of the present application, the mass content of the first conductive agent in the first active material layer is greater than the mass content of the second conductive agent in the second active material layer. Because the second active material layer is located near the tab region, its temperature rises during charge and discharge. This temperature increase improves the kinetic properties of the second active material, maintaining the high conductivity of the second active material layer. This reduces the use of conductive agents and reduces the cost of electrode sheet production.

[0060] In one embodiment of the present application, the mass content of the first binder in the first active material layer is greater than the mass content of the second binder in the second active material layer. Since the content of the second conductive agent in the second active material layer decreases, its solid content is also reduced. This allows the use of a binder with a lower mass content, which not only achieves dispersion of the second active material and the second conductive agent but also maintains the mechanical properties of the electrode sheet, reduces the production cost of the electrode sheet, and facilitates the industrial application of the electrode sheet.

[0061] In one embodiment of the present application, when the electrode plate is a negative electrode plate, the first active material layer also includes a first thickener to promote uniform distribution of the first active material layer. Specifically, the first thickener may include, but is not limited to, sodium carboxymethyl cellulose or lithium carboxymethyl cellulose. In one embodiment of the present application, the first thickener may be sodium carboxymethyl cellulose, and the negative electrode binder may be styrene-butadiene rubber.

[0062] In one embodiment of the present application, the mass content of the first thickener in the first active material layer is 1.5%-3%. Specifically, the mass content of the first thickener in the first active material layer may be, but is not limited to, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.7%, 2.8%, or 3%. In one embodiment of the present application, the mass content of the first thickener in the first active material layer may be 1.5%-2.5%. In another embodiment of the present application, the mass content of the first thickener in the first active material layer may be 2%-3%.

[0063] In an embodiment of the present application, when the electrode tab is a negative electrode tab, the second active material layer further comprises a second thickening agent, which can promote uniform distribution of the second active material layer. Specifically, the second thickening agent can include, but is not limited to, sodium carboxymethyl cellulose or lithium carboxymethyl cellulose, etc. In an embodiment of the present application, the second thickening agent can be sodium carboxymethyl cellulose, and the negative electrode binder can be styrene-butadiene rubber.

[0064] In an embodiment of the present application, the mass content of the second thickening agent in the second active material layer is 1%-1.5%. Specifically, the mass content of the second thickening agent in the second active material layer can be, but is not limited to, 1%, 1.2%, 1.3%, 1.4%, or 1.5%, etc. In an embodiment of the present application, the mass content of the second thickening agent in the second active material layer can be 1%-1.2%. In another embodiment of the present application, the mass content of the second thickening agent in the second active material layer can be 1.2%-1.5%.

[0065] In an embodiment of the present application, the thickness of the first active material layer is 92 μm-300 μm. Specifically, the thickness of the first active material layer can be, but is not limited to, 92 μm, 100 μm, 150 μm, 200 μm, 250 μm, or 300 μm, etc. In an embodiment of the present application, when the electrode tab is a positive electrode tab, the thickness of the first active material layer can be 130 μm-300 μm. In another embodiment of the present application, when the electrode tab is a negative electrode tab, the thickness of the first active material layer can be 100 μm-180 μm.

[0066] In an embodiment of the present application, in the direction from the second active material layer to the first active material layer, the size of the first active material layer is 80 mm-1000 mm. The large size of the first active material layer is conducive to improving the energy density of the electrode tab. Specifically, in the direction from the second active material layer to the first active material layer, the size of the first active material layer can be, but is not limited to, 80 mm, 100 mm, 200 mm, 400 mm, 600 mm, 800 mm, or 1000 mm, etc. In an embodiment of the present application, in the direction from the second active material layer to the first active material layer, the size of the first active material layer can be 80 mm-600 mm. In another embodiment of the present application, in the direction from the second active material layer to the first active material layer, the size of the first active material layer can be 500 mm-1000 mm.

[0067] In an embodiment of the present application, the maximum thickness of the second active material layer is 92 μm-300 μm. Specifically, the maximum thickness of the second active material layer can be, but is not limited to, 92 μm, 100 μm, 120 μm, 150 μm, 180 μm, 220 μm, 250 μm or 300 μm, etc. In an embodiment of the present application, when the electrode tab is a positive electrode tab, the maximum thickness of the second active material layer is 120 μm-270 μm. In another embodiment of the present application, when the electrode tab is a negative electrode tab, the maximum thickness of the second active material layer is 92 μm-165 μm. In some embodiments, the thickness of the second active material layer gradually decreases from 92 μm-300 μm to 0 μm in the direction from the first active material layer to the second active material layer.

[0068] In an embodiment of the present application, the size of the second active material layer in the direction from the first active material layer to the second active material layer is 10 mm-30 mm. The small size of the second active material layer is conducive to reducing the lithium precipitation phenomenon of the electrode tab. Specifically, the size of the second active material layer in the direction from the first active material layer to the second active material layer can be, but is not limited to, 10 mm, 15 mm, 20 mm, 25 mm or 30 mm, etc. In an embodiment of the present application, the size of the second active material layer in the direction from the first active material layer to the second active material layer is 10 mm-20 mm. In another embodiment of the present application, the size of the second active material layer in the direction from the first active material layer to the second active material layer is 15 mm-30 mm.

[0069] In an embodiment of the present application, the areal density of the electrode tab is 150 g / m 2 -600 g / m 2 The appropriate areal density of the electrode tab can improve the energy density of the electrode tab, thereby improving the capacity of the battery and reducing the internal resistance of the battery. In the existing preparation process, the negative electrode tab has a thinned area, and the corresponding positive electrode tab is a normally coated area, which reduces the capacity ratio of the thinned area of the negative electrode tab to the positive electrode tab and causes serious lithium precipitation phenomenon, thereby shortening the service life of the battery. In the related art, the capacity of the negative electrode tab is improved by increasing the overall areal density of the negative electrode tab, but the preparation cost of the negative electrode tab is increased, and the volume energy density and the mass energy density of the negative electrode tab are reduced. The electrode tab provided in the present application has an areal density similar to that of the electrode tab in the related art. Without changing the areal density of the electrode tab, the capacity of the second active material layer (thinned area) is improved by controlling the relationship between the first active material in the first active material layer and the second active material in the second active material layer, thereby improving the capacity of the electrode tab, improving the lithium precipitation phenomenon, maintaining a high volume energy density and mass energy density of the electrode tab, and reducing the preparation cost of the electrode tab. Specifically, the areal density of the electrode tab can be, but is not limited to, 150 g / m 2, 200 g / m 2 , 250 g / m 2 , 300 g / m 2 , 350 g / m 2 , 400 g / m 2 , 450 g / m 2 , 500 g / m 2 , 550 g / m 2 or 600 g / m 2 In an embodiment of the present application, when the electrode tab is a positive electrode tab, the areal density of the positive electrode tab can be 300 g / m 2 - 600 g / m 2 , wherein the areal density of the first active material layer can be 300 g / m 2 - 600 g / m 2 , the areal density of the second active material layer is 276 g / m 2 - 599 g / m 2 , and the areal density of the second active material layer gradually decreases in the direction from the first active material layer to the second active material layer. In another embodiment of the present application, when the electrode tab is a negative electrode tab, the areal density of the negative electrode tab can be 150 g / m 2 - 300 g / m 2 , wherein the areal density of the first active material layer can be 150 g / m 2 - 300 g / m 2 , the areal density of the second active material layer is 142 g / m 2 - 299 g / m 2 , and the areal density of the second active material layer gradually decreases in the direction from the first active material layer to the second active material layer.

[0070] An embodiment of the present application provides a method for preparing an electrode tab, comprising:

[0071] coating a first slurry and a second slurry on the surface of the current collector, the first slurry comprising a first active material and the second slurry comprising a second active material; and drying to obtain the electrode tab. The preparation method provided by the present application is novel, simple in preparation process, and low in preparation cost, and can prepare an electrode tab with high volumetric energy density and gravimetric energy density and less prone to lithium precipitation reaction. The electrode tab provided by any one of the above embodiments can be prepared by the preparation method.

[0072] In an embodiment of the present application, the first slurry further comprises a first conductive agent and a first binder, and the mass ratio of the first active material, the first conductive agent and the first binder is (93-97.2):(0.5-2):(1-3). The suitable first slurry ratio can alleviate the lithium precipitation phenomenon of the electrode sheet and improve the energy density of the electrode sheet. Specifically, the mass ratio of the first active material, the first conductive agent and the first binder can be, but is not limited to, 93:0.5:1, 93.5:0.8:1.5, 94:1:1.8, 94.5:1.2:1.8, 95:1.5:2, 96:1.8:2.2, 96.5:1.8:2.5, 97:2:2.8 or 97.2:2:3, etc. In an embodiment of the present application, the mass ratio of the first active material, the first conductive agent and the first binder can be (93-96):(0.5-1.5):(1-2.2). In another embodiment of the present application, the mass ratio of the first active material, the first conductive agent and the first binder can be (95-97.2):(1-2):(2-3).

[0073] In an embodiment of the present application, when the electrode sheet is a negative electrode sheet, the first slurry further comprises a thickening agent, and the mass ratio of the first active material, the first conductive agent, the first binder and the first thickening agent is (93-97.2):(0.5-2):(1-3):(1.5-3). The viscosity of the first slurry can be improved, and the coating capacity of the first slurry can be promoted. Specifically, the mass ratio of the first active material, the first conductive agent, the first binder and the first thickening agent can be, but is not limited to, 93:0.5:1:1.5, 93.5:0.8:1.5:1.8, 94:1:1.8:1.9, 94.5:1.2:1.8:2, 95:1.5:2:2.2, 96:1.8:2.2:2.5, 96.5:1.8:2.5:2.8, 97:2:2.8:2.9 or 97.2:2:3:3, etc. In an embodiment of the present application, the mass ratio of the first active material, the first conductive agent, the first binder and the first thickening agent can be (93-96):(0.5-1):(1-1.8):(1.5-2.5). In another embodiment of the present application, the mass ratio of the first active material, the first conductive agent, the first binder and the first thickening agent can be (95-97.2):(1-2):(1.5-3):(2-3).

[0074] In an embodiment of the present application, the first slurry further comprises a first solvent, and the mass content of the first solvent in the first slurry is 20%-50%. The first solvent can improve the coating capacity of the first slurry and promote the uniform distribution of the first active material in the first active material layer. Specifically, the first solvent can be, but is not limited to, N-methyl pyrrolidone, etc.; and the mass content of the first solvent can be, but is not limited to, 20%, 25%, 30%, 35%, 40%, 45% or 50%, etc. In an embodiment of the present application, the first solvent can be N-methyl pyrrolidone, and the mass content of the first solvent in the first slurry can be 20%-35%.

[0075] In an embodiment of the present application, the second slurry further comprises a second conductive agent and a second binder, and the mass ratio of the second active material, the second conductive agent and the second binder is (96.2-98.5):(0-1):(0.5-2), which can reduce the probability of lithium precipitation of the electrode sheet and improve the energy density of the electrode sheet. Specifically, the mass ratio of the second active material, the second conductive agent and the second binder can be, but is not limited to, 96.2:0:0.5, 96.5:0.1:0.7, 96.8:0.3:0.8, 97:0.5:1, 97.5:0.7:1, 97.8:0.8:1.5, 98:0.8:1.8 or 98.5:1:2, etc. In an embodiment of the present application, the mass ratio of the second active material, the second conductive agent and the second binder can be (96.2-97.5):(0-0.6):(0.5-1.5). In another embodiment of the present application, the mass ratio of the second active material, the second conductive agent and the second binder can be (97-98.5):(0.4-1):(1-2).

[0076] In an embodiment of the present application, when the electrode tab is a negative electrode tab, the second slurry further comprises a thickening agent, and the mass ratio of the second active material, the second conductive agent, the second binder and the second thickening agent is (96.2-98.5):(0-1):(0.5-2):(1-1.5), which can improve the viscosity of the second slurry and promote the coating ability of the second slurry. Specifically, the mass ratio of the second active material, the second conductive agent, the second binder and the second thickening agent can be, but is not limited to, 96.2:0:0.5:1, 96.5:0.1:0.7:1.1, 96.8:0.3:0.8:1.2, 97:0.5:1:1.3, 97.5:0.7:1:1.3, 97.8:0.8:1.5:1.4, 98:0.8:1.8:1.4 or 98.5:1:2:1.5, etc. In an embodiment of the present application, the mass ratio of the second active material, the second conductive agent, the second binder and the second thickening agent can be (96.2-97.5):(0-0.6):(0.5-1.5):(1-1.3). In another embodiment of the present application, the mass ratio of the second active material, the second conductive agent, the second binder and the second thickening agent can be (97-98.5):(0.5-1):(1-2):(1.2-1.5).

[0077] In an embodiment of the present application, the second slurry further comprises a second solvent, and the mass content of the second solvent in the second slurry is 20%-50%, which can improve the coating ability of the second slurry and promote the uniform distribution of the second active material in the second active material layer. Specifically, the second solvent can be, but is not limited to, N-methyl pyrrolidone, etc., and the mass content of the second solvent in the second slurry can be, but is not limited to, 20%, 25%, 30%, 35%, 40%, 45% or 50%, etc. In an embodiment of the present application, the second solvent can be N-methyl pyrrolidone, and the mass content of the second solvent in the second slurry can be 20%-35%.

[0078] The present application also provides a battery comprising a positive electrode tab and a negative electrode tab, and a separator arranged between the positive electrode tab and the negative electrode tab, wherein the negative electrode tab comprises the electrode tab prepared by the preparation method described in any one of the embodiments of the present application. The negative electrode tab provided by the present application improves the capacity of the thinned area of the negative electrode tab, improves the capacity ratio of the negative electrode tab to the positive electrode tab in the battery, reduces the risk of lithium precipitation of the electrode tab, is conducive to improving the electrochemical performance and service life of the electrode tab, and is conducive to the industrial application of the battery.

[0079] In an embodiment of the present application, the positive electrode tab comprises the electrode tab of any one of the above embodiments or the electrode tab prepared by the preparation method of any one of the above embodiments. That is, the positive electrode tab and the negative electrode tab are both the electrode tab provided by the present application. The negative electrode tab comprises a negative current collector and a negative active material layer arranged on the surface of the negative current collector. The negative active material layer comprises a first negative active material layer and a second negative active material layer. In the direction from the first negative active material layer to the second negative active material layer, the thickness of the second negative active material layer gradually decreases. The mass content of the first negative active material in the first negative active material layer is less than that of the second negative active material in the second negative active material layer. The positive electrode tab comprises a positive current collector and a positive active material layer arranged on the surface of the positive current collector. The positive active material layer comprises a first positive active material layer and a second positive active material layer. In the direction from the first positive active material layer to the second positive active material layer, the thickness of the second positive active material layer gradually decreases. The mass content of the first positive active material in the first positive active material layer is less than that of the second positive active material in the second positive active material layer. The positive electrode tab and the negative electrode tab are oppositely arranged. Specifically, the first positive active material layer of the positive electrode tab is oppositely arranged with the second negative active material layer of the negative electrode tab, and the second positive active material layer of the positive electrode tab is oppositely arranged with the first negative active material layer of the negative electrode tab. This is conducive to further relieving the lithium precipitation phenomenon of the battery and improving the capacity and cycle stability of the battery.

[0080] In an embodiment of the present application, the separator can be ion-exchanged to form a complete ion conduction path. Specifically, the separator can be, but is not limited to, a woven membrane, a non-woven fabric, a microporous membrane, a composite membrane, a calendered membrane, or a separator paper, etc. In an embodiment of the present application, the battery further comprises an electrolyte. At least part of the positive electrode tab and at least part of the negative electrode tab are soaked in the electrolyte. The electrolyte of the present application is not particularly limited and can be, but is not limited to, a substance capable of being used as a battery electrolyte in the art.

[0081] The present application also provides a power-consuming device comprising the battery of any one of the above embodiments. The power-consuming device provided by the present application has high energy density and high safety performance, and has strong market competitiveness. The power-consuming device can be a mobile phone, a tablet, a watch, a VR glasses, a vehicle, etc. In an embodiment of the present application, the battery can be used in a vehicle to improve the safety and charging rate of the vehicle and promote the wide application of new energy vehicles, which is conducive to the construction of a green and environmentally friendly environment. In another embodiment of the present application, the battery can also be applied to a mobile phone to reduce the preparation cost of the battery and improve the service life and safety of the battery. The power-consuming device of the present application can be a vehicle, an electronic device, an energy storage system, etc. The above battery can be arranged in the power-consuming device in the form of a single battery, a battery module, a battery pack, a capacitor, etc.

[0082] The effects of the technical solutions of the present application are further described below through specific examples.

[0083] Embodiment 1

[0084] (1) Preparation of the positive electrode tab: the first positive electrode active material (lithium iron phosphate, primary particle size D50 of 0.4 μm), the first positive electrode conductive agent (carbon black), and the first positive electrode binder (polyvinylidene fluoride) are mixed with the first solvent (N-methyl pyrrolidone) to obtain the first positive electrode slurry, and the mass content of the first positive electrode active material in the solid components of the first positive electrode slurry is 96.5%, the mass content of the first positive electrode conductive agent is 1%, and the mass content of the first positive electrode binder is 2.5%;

[0085] The second positive electrode active material (lithium iron phosphate, primary particle size D50 of 0.8 μm), the second positive electrode conductive agent (carbon black), and the second positive electrode binder (polyvinylidene fluoride) are mixed with the second solvent (N-methyl pyrrolidone) to obtain the second positive electrode slurry, and the mass content of the second positive electrode active material in the solid components of the second positive electrode slurry is 97.7%, the mass content of the second positive electrode conductive agent is 0.5%, and the mass content of the second positive electrode binder is 1.8%;

[0086] The first positive electrode slurry and the second positive electrode slurry are respectively coated on the positive electrode current collector, and after drying, the positive electrode tab is obtained; the first positive electrode slurry forms the first positive electrode active material layer (non-thinning area), the thickness of the first positive electrode active material layer is 250 μm, and the area density of the first positive electrode active material layer is 450 g / m 2 The second positive electrode slurry forms the second positive electrode active material layer (thinning area), and the thickness of the second positive electrode active material layer gradually decreases in the direction from the first positive electrode active material layer to the second positive electrode active material layer, the thickness of the second positive electrode active material layer gradually decreases from 250 μm to 230 μm, and the area density of the second positive electrode active material layer is 420 g / m 2 .

[0087] (2) Preparation of the negative electrode tab:

[0088] The first negative electrode active material (artificial graphite, primary particle size D50 of 8 μm), the first negative electrode conductive agent (carbon black), the first negative electrode binder (styrene-butadiene rubber), and the first thickening agent (sodium carboxymethyl cellulose) are mixed with the first solvent (N-methyl pyrrolidone) to obtain the first negative electrode slurry, and the mass content of the first negative electrode active material in the solid components of the first negative electrode slurry is 96.1%, the mass content of the first negative electrode conductive agent is 1%, the mass content of the first negative electrode binder is 1.3%, and the mass content of the first thickening agent is 1.6%;

[0089] The second negative electrode active material (artificial graphite, primary particle size D50 of 13 μm), the second negative electrode binder (styrene-butadiene rubber), and the second thickening agent (sodium carboxymethyl cellulose) are mixed with the second solvent (N-methyl pyrrolidone) to obtain a second negative electrode slurry, the mass content of the second negative electrode active material in the solid components of the second negative electrode slurry being 97.6%, the mass content of the second negative electrode binder being 1.1%, and the mass content of the second thickening agent being 1.3%;

[0090] The first negative electrode slurry and the second negative electrode slurry are respectively coated on the negative electrode current collector, and after drying, a negative electrode sheet is obtained; the first negative electrode slurry forms a first negative electrode active material layer (non-thinning area), the thickness of the first negative electrode active material layer being 135 μm, and the area density of the first negative electrode active material layer being 204 g / m 2 The second negative electrode slurry forms a second negative electrode active material layer (thinning area), the thickness of the second negative electrode active material layer gradually decreasing in the direction from the first negative electrode active material layer to the second negative electrode active material layer, the thickness of the second negative electrode active material layer gradually decreasing from 135 μm to 125 μm, and the area density of the second negative electrode active material layer being 190 g / m 2 .

[0091] Example 2

[0092] The difference from Example 1 is that the first negative electrode slurry includes a first negative electrode active material (artificial graphite), a first negative electrode conductive agent (carbon black), a first negative electrode binder (styrene-butadiene rubber), and a first thickening agent (sodium carboxymethyl cellulose), the mass content of the first negative electrode active material in the solid components of the first negative electrode slurry being 93%, the mass content of the first negative electrode conductive agent being 2%, the mass content of the first negative electrode binder being 2%, and the mass content of the first thickening agent being 3%;

[0093] The second negative electrode slurry includes a second negative electrode active material (artificial graphite), a second negative electrode conductive agent (carbon black), a second negative electrode binder (styrene-butadiene rubber), and a second thickening agent (sodium carboxymethyl cellulose), the mass content of the second negative electrode active material in the solid components of the second negative electrode slurry being 98.5%, the mass content of the second negative electrode conductive agent being 0.1%, the mass content of the second negative electrode binder being 0.4%, and the mass content of the second thickening agent being 1%.

[0094] Example 3

[0095] The difference from Example 1 is that the first positive electrode slurry includes a first positive electrode active material (lithium iron phosphate), a first positive electrode conductive agent (carbon black), and a first positive electrode binder (polyvinylidene fluoride), the mass content of the first positive electrode active material in the solid components of the first positive electrode slurry being 92%, the mass content of the first positive electrode conductive agent being 4%, and the mass content of the first positive electrode binder being 4%;

[0096] The second positive electrode slurry includes a second positive electrode active material (lithium iron phosphate), a second positive electrode conductive agent (carbon black), and a second positive electrode binder (polyvinylidene fluoride), and the mass content of the second positive electrode active material in the solid components of the second positive electrode slurry is 99%, the mass content of the second positive electrode conductive agent is 0.5%, and the mass content of the second positive electrode binder is 0.5%.

[0097] Example 4

[0098] Differently from Example 1, in the negative electrode sheet, the first negative electrode active material is natural graphite.

[0099] Example 5

[0100] Differently from Example 1, in the solid components of the first negative electrode slurry, the mass content of the first negative electrode active material is 96%, the mass content of the first negative electrode conductive agent is 0.6%, the mass content of the first negative electrode binder is 1.8%, and the mass content of the first thickening agent is 1.6%; in the solid components of the second negative electrode slurry, the mass content of the second negative electrode active material is 96.8%, the mass content of the second negative electrode conductive agent is 0.8%, the mass content of the second negative electrode binder is 1.1%, and the mass content of the second thickening agent is 1.3%.

[0101] Example 6

[0102] Differently from Example 1, in the solid components of the first negative electrode slurry, the mass content of the first negative electrode active material is 96.2%, the mass content of the first negative electrode conductive agent is 1%, the mass content of the first negative electrode binder is 1.2%, and the mass content of the first thickening agent is 1.6%; in the solid components of the second negative electrode slurry, the mass content of the second negative electrode active material is 96.3%, the mass content of the second negative electrode conductive agent is 1%, the mass content of the second negative electrode binder is 1.4%, and the mass content of the second thickening agent is 1.3%.

[0103] Example 7

[0104] Differently from Example 1, in the solid components of the first negative electrode slurry, the mass content of the first negative electrode active material is 94%, the mass content of the first negative electrode conductive agent is 3%, the mass content of the first negative electrode binder is 1.3%, and the mass content of the first thickening agent is 1.6%; in the solid components of the second negative electrode slurry, the mass content of the second negative electrode active material is 96.1%, the mass content of the second negative electrode conductive agent is 1.5%, the mass content of the second negative electrode binder is 1.1%, and the mass content of the second thickening agent is 1.3%.

[0105] Example 8

[0106] The difference from Example 1 is that the mass content of the first negative electrode active material in the solid components of the first negative electrode slurry is 93.4%, the mass content of the first negative electrode conductive agent is 1%, the mass content of the first negative electrode binder is 4%, and the mass content of the first thickening agent is 1.6%; the mass content of the second negative electrode active material in the solid components of the second negative electrode slurry is 94.7%, the mass content of the second negative electrode conductive agent is 1%, the mass content of the second negative electrode binder is 3%, and the mass content of the second thickening agent is 1.3%.

[0107] Example 9

[0108] The difference from Example 1 is that the positive electrode sheet is prepared by coating the second positive electrode slurry on the positive electrode current collector, the thickness of the non-thinned area of the positive electrode sheet is 250 μm, and the thickness of the thinned area of the positive electrode sheet gradually decreases from 250 μm to 230 μm.

[0109] Example 10

[0110] The difference from Example 1 is that the negative electrode sheet is prepared by coating the second negative electrode slurry on the negative electrode current collector, the thickness of the non-thinned area of the negative electrode sheet is 135 μm, and the thickness of the thinned area of the negative electrode sheet gradually decreases from 135 μm to 125 μm.

[0111] Comparative Example 1

[0112] The difference from Example 9 is that the negative electrode sheet is prepared by coating the second negative electrode slurry on the negative electrode current collector, the thickness of the non-thinned area of the negative electrode sheet is 135 μm, and the thickness of the thinned area of the negative electrode sheet gradually decreases from 135 μm to 125 μm.

[0113] Comparative Example 2

[0114] The difference from Example 9 is that the negative electrode sheet is prepared by coating the second negative electrode slurry on the negative electrode current collector, the thickness of the non-thinned area of the negative electrode sheet is 135 μm, and the thickness of the thinned area of the negative electrode sheet gradually decreases from 135 μm to 125 μm; and the positive electrode sheet is prepared by coating the first positive electrode slurry on the positive electrode current collector, the thickness of the non-thinned area of the positive electrode sheet is 250 μm, and the thickness of the thinned area of the positive electrode sheet gradually decreases from 250 μm to 230 μm.

[0115] Comparative Example 3

[0116] The difference from Example 9 is that in the negative electrode sheet, the first negative electrode slurry forms the second negative electrode active material layer, and the second negative electrode slurry forms the first negative electrode active material layer.

[0117] Performance detection

[0118] The negative electrode tab, the positive electrode tab and the separator prepared in the above Examples 1-10 and Comparative Examples 1-3 were stacked and assembled with an aluminum shell, followed by cover welding, shell welding, baking, liquid injection, aging, formation and other processes to obtain a battery.

[0119] The batteries prepared in the above Examples 1-10 and Comparative Examples 1-3 were subjected to mass energy density testing. The testing process was as follows: the battery was charged at 1C constant current to 3.8V at room temperature 25℃, then charged at constant voltage to the cut-off current 0.05C, after the battery was fully charged, the battery was discharged at 1 / 3C discharge rate, the energy of the battery at 1 / 3C discharge rate was calculated, recorded as the battery energy, marked as W. At the same time, the weight of the battery was measured and recorded, marked as M, the mass energy density (Wh / kg) = W / M. The test results are shown in Table 1.

[0120] The batteries prepared in the above Examples 1-10 and Comparative Examples 1-3 were subjected to volume energy density testing. The testing process was as follows: the battery was charged at 1C constant current to 3.8V at room temperature 25℃, then charged at constant voltage to the cut-off current 0.05C, after the battery was fully charged, the battery was discharged at 1 / 3C discharge rate, the energy of the battery at 1 / 3C discharge rate was calculated, recorded as the battery energy, marked as W. At the same time, the volume of the battery was measured and recorded, marked as V, the volume energy density (Wh / L) = W / V. The test results are shown in Table 1.

[0121] The batteries prepared in the above Examples 1-10 and Comparative Examples 1-3 were subjected to cycle testing. After 100 cycles, the sample after 100 cycles was disassembled and the negative electrode tab interface was observed and recorded by taking pictures. The test results are shown in Table 1.

[0122] The batteries prepared in the above Examples 1-10 and Comparative Examples 1-3 were subjected to fast charging cycle testing. The testing process was as follows: after standing for 30min at room temperature 25℃, the battery was charged at 2.65C constant current to 30% SOC, 2C constant current to 40% SOC, 1.7C constant current to 65% SOC, 1.4C constant current to 70% SOC, 1.1C constant current to 75% SOC, 0.8C constant current to 90% SOC, 0.65C constant current to 95% SOC, 0.3C constant current to 100% SOC, and then stood for 30min. The battery was discharged at 1C discharge rate, and the above steps were repeated until the state of health (SOH) of the battery was 80%, and the fast charging cycle number was recorded. The results are shown in Table 1.

[0123] Table 1 Performance test results

[0124]

[0125]

[0126] According to the embodiments 1-10 and the comparative examples 1-3, it can be seen that the electrode tab provided by the present application reduces the probability of lithium precipitation of the electrode tab in use by controlling the mass content of the first active material in the first active material layer and the mass content of the second active material layer in the second active material layer, without reducing the volume energy density and weight energy density of the electrode tab, which is beneficial to the improvement of the electrochemical performance of the battery. According to the embodiments 1 and 2-8, it can be seen that the suitable content of the active material, the binder and the conductive agent can further improve the energy density of the electrode tab and reduce the probability of lithium precipitation of the electrode tab. According to the embodiments 1 and the comparative examples 1-3, it can be seen that the electrode tab provided by the present application improves the lithium precipitation of the electrode tab by improving the mass relationship of the first active material and the second active material, and the electrode tab has good energy density, which is beneficial to the improvement of the comprehensive performance of the battery.

[0127] The above is the preferred embodiment of the present application, but it cannot be understood as the limitation of the scope of the present application. It should be pointed out that for ordinary skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements are also considered as the protection scope of the present application.

Claims

1. An electrode plate, characterized in that: The electrode plate includes a current collector and an active material layer arranged on at least one side of the current collector, the active material layer includes a first active material layer and a second active material layer arranged in the same layer as and connected to the first active material layer, the thickness of the second active material layer gradually decreases along the direction from the first active material layer to the second active material layer, the first active material layer includes a first active material, the second active material layer includes a second active material, and the mass content of the first active material in the first active material layer is less than the mass content of the second active material layer in the second active material layer.

2. The electrode plate according to claim 1, wherein: The second active material layer is disposed on one side of the first active material layer, or the second active material layers are disposed on opposite sides of the first active material layer.

3. The electrode plate according to claim 1, wherein: In the first active material layer, the mass content of the first active material is 93%-97.2%; In the second active material layer, the mass content of the second active material is 96.2%-98.5%.

4. The electrode plate according to claim 1, wherein: The primary particle size D50 of the first active material is smaller than the primary particle size D50 of the second active material; And / or the mass content of the carbon coating layer of the first active material is greater than the mass content of the carbon coating layer of the second active material.

5. The electrode plate according to claim 4, characterized in that: The primary particle size D50 of the first active material is 0.3 μm-9 μm, and the primary particle size D50 of the second active material is 0.7 μm-15 μm; And / or, the mass content of the carbon coating layer of the first active material is 0.5%-2%, and the mass content of the carbon coating layer of the second active material is less than or equal to 0.5%.

6. The electrode plate according to claim 1, wherein: The first active material layer further includes a first conductive agent and a first binder, and the second active material layer further includes a second conductive agent and a second binder; The mass content of the first conductive agent in the first active material layer is greater than the mass content of the second conductive agent in the second active material layer, and / or the mass content of the first binder in the first active material layer is greater than the mass content of the second binder in the second active material layer.

7. The electrode plate according to claim 6, characterized in that: In the first active material layer, the mass content of the first conductive agent is 0.5%-2%, and the mass content of the first binder is 1%-3%; In the second active material layer, the mass content of the second conductive agent is less than or equal to 1%, and the mass content of the second binder is 0.5%-2%.

8. The electrode plate according to claim 1, wherein: The thickness of the first active material layer is 92 μm-300 μm, and the maximum thickness of the second active material layer is 92 μm-300 μm.

9. The electrode plate according to claim 1, wherein: Along the direction from the second active material layer to the first active material layer, the size of the first active material layer is 80 mm to 1000 mm; Along the direction from the first active material layer to the second active material layer, the size of the second active material layer is 10 mm to 30 mm.

10. The electrode plate according to claim 1, wherein: The surface density of the electrode plate is 150g / m 2 -600g / m 2 .

11. A battery, characterized in that: The battery includes a positive electrode sheet and a negative electrode sheet, and a separator arranged between the positive electrode sheet and the negative electrode sheet, and the negative electrode sheet includes the electrode sheet according to any one of claims 1 to 10.

12. The battery according to claim 11, wherein The positive electrode plate includes the electrode plate according to any one of claims 1 to 10.

13. An electrical device, characterized in that: The electrical device comprises the battery according to any one of claims 11-12.

Images