Battery electrode, secondary battery, and electric device

Abstract

The application provides a battery pole piece, a secondary battery and an electric device. The battery pole piece comprises a current collector, a bottom coating layer arranged on at least one side surface of the current collector, and an active layer arranged on a side surface of the bottom coating layer away from the current collector. The bottom coating layer comprises a first coating layer and a second coating layer arranged side by side along the length direction of the battery pole piece. The active layer at least partially covers a side surface of the first coating layer away from the current collector, and a side surface of the second coating layer away from the current collector is at least partially uncovered by the active layer. The first coating layer and the second coating layer both comprise inorganic solid compounds, and the mass percentage content of the inorganic solid compounds in the second coating layer is greater than that in the first coating layer. The battery pole piece has excellent safety performance and electrochemical performance through special structural design of the coating layer on the current collector.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the technical field of battery, in particular to a battery pole piece, a secondary battery and an electric equipment. BACKGROUND

[0002] With the more and more wide application of lithium secondary batteries to passenger cars and mobile electronic devices, under the premise of ensuring energy density, fast charging ability and cycle life, how to further improve the safety performance of lithium ion batteries has become a problem to be solved. In order to improve the safety performance of the secondary battery, by coating a primer layer on the surface of the current collector of the battery pole piece, the burr on the current collector after slitting can be avoided to pierce the separator, the short circuit phenomenon of the battery can be avoided, and the safety of the battery can be improved. However, the composition of the primer layer used in the existing battery pole piece is mostly insulating material, and the insulating material has poor ability to conduct lithium ions, which can greatly increase the impedance of the lithium ion battery and reduce the energy density of the battery, and affect the cycle performance of the battery. SUMMARY

[0003] In view of this, the present application provides a battery pole piece, a secondary battery and an electric equipment, which has excellent safety performance and electrochemical performance by special structural design of the distribution of the primer layer and the active material layer on the current collector, can cause local short circuit of the outer current collector in advance when mechanically abused (bending and unfolding or needle puncture), improve the safety performance of the battery, and has good conductivity, which can improve the energy density and cycle performance of the battery.

[0004] The first aspect of the present application provides a battery pole piece, which comprises a current collector, a primer layer arranged on at least one side surface of the current collector, and an active material layer arranged on the side surface of the primer layer away from the current collector; the primer layer comprises a first coating layer and a second coating layer arranged side by side along the length direction of the battery pole piece, the active material layer at least partially covers the side surface of the first coating layer away from the current collector, and the side surface of the second coating layer away from the current collector is at least partially uncovered by the active material layer; the first coating layer and the second coating layer both comprise inorganic solid compounds, and the mass percentage content of inorganic solid compounds in the second coating layer is greater than that in the first coating layer.

[0005] In the embodiment of the present application, the elongation rate of the first coating layer is 0.02%-2%.

[0006] In the embodiments of the present application, the first coating and the second coating further comprise a conductive agent, the mass ratio of the inorganic solid compound to the conductive agent in the second coating is greater than the mass ratio of the inorganic solid compound to the conductive agent in the first coating; and the difference between the mass percentage of the inorganic solid compound in the second coating and the mass percentage of the inorganic solid compound in the first coating is 0.1% to 20%.

[0007] In the embodiments of the present application, the electrical conductivity of the first coating at 25℃ is 0.1 S / m to 10 S / m, the electrical conductivity of the second coating at 25℃ is 0.02 S / m to 10 S / m, and the electrical conductivity of the first coating is greater than the electrical conductivity of the second coating.

[0008] In the embodiments of the present application, the inorganic solid compound comprises one or more of zirconium oxide, magnesium oxide, silicon oxide, silicon monoxide, aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, boehmite, diaspore, barium sulfate, calcium sulfate, and calcium silicate.

[0009] In the embodiments of the present application, in the first coating, the mass percentage of the inorganic solid compound is 70% to 98%, and the mass percentage of the conductive agent is 0.1% to 20%; and in the second coating, the mass percentage of the inorganic solid compound is 70% to 98%, and the mass percentage of the conductive agent is 0.1% to 20%.

[0010] In the embodiments of the present application, the particle size D50 of the inorganic solid compound is 0.05 μm to 50 μm.

[0011] In the embodiments of the present application, the thickness of the first coating is 0.2 μm to 15 μm, the thickness of the second coating is 0.2 μm to 15 μm, and the thickness of the active material layer is 0.01 mm to 1 mm.

[0012] In the embodiments of the present application, the thickness of the first coating is 1 μm to 10 μm, the thickness of the second coating is 1 μm to 10 μm, and the thickness of the active material layer is 0.02 mm to 0.2 mm.

[0013] In the embodiments of the present application, the ratio of the thickness of the first coating to the thickness of the active material layer is 1:(2-1000), and the ratio of the thickness of the second coating to the thickness of the active material layer is 1:(2-1000).

[0014] In the embodiments of the present application, the ratio of the thickness of the first coating to the thickness of the active material layer is 1:(2-200), and the ratio of the thickness of the second coating to the thickness of the active material layer is 1:(2-200).

[0015] In the embodiments of the present application, the ratio of the coating area of the second coating layer to the active material layer is 1:(2-5000); the ratio of the size of the second coating layer in the length direction of the battery pole piece to the size of the active material layer in the length direction of the battery pole piece is 1:(2-5000).

[0016] In the embodiments of the present application, the ratio of the coating area of the second coating layer to the active material layer is 1:(2-500); the ratio of the size of the second coating layer in the length direction of the battery pole piece to the size of the active material layer in the length direction of the battery pole piece is 1:(2-1000).

[0017] In the embodiments of the present application, the conductive agent includes one or more of graphite-based conductive agent, carbon fiber, carbon nanotube, graphene, conductive carbon black, and conductive polymer.

[0018] The binder includes one or more of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, carboxymethyl cellulose, sodium carboxymethyl cellulose, styrene butadiene rubber, polyvinyl alcohol, polytetrafluoroethylene, polyolefin, fluorinated rubber, polyacrylamide, polymethyl methacrylate-butyl acrylate, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene oxide, acrylic water-soluble glue, styrene butadiene latex, polyvinyl acetate, polyurethane, cellulose lithium acetate, cellulose lithium acetate butyrate, cellulose lithium acetate propionate, lithium carboxymethyl cellulose, lithium carboxymethyl cellulose, lithium carboxymethyl cellulose, lithium carboxymethyl cellulose, and lithium carboxymethyl cellulose.

[0019] The current collector includes aluminum foil, copper foil, nickel foil, aluminum alloy foil, copper alloy foil, or nickel alloy foil.

[0020] In the embodiments of the present application, the active material layer includes active material, binder, and conductive agent; the mass of the active material accounts for 70%-99.5% of the total mass of the active material layer, and the mass of the conductive agent accounts for 0.1%-20% of the total mass of the active material layer; the active material includes one or more of positive electrode active material and negative electrode active material, the positive electrode active material includes one or more of lithium cobaltate, lithium iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadium oxyphosphate, sodium vanadium oxyphosphate, lithium nickelate, lithium manganate, lithium nickel cobalt aluminum, lithium titanate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium-rich manganese-based positive electrode material, and sulfur, and the negative electrode active material includes one or more of graphite, hard carbon, silicon-based negative electrode, lithium metal, lithium alloy negative electrode, and lithium titanate.

[0021] The battery pole piece provided in the application has excellent safety performance and electrochemical performance by special design of the undercoat layer and the active material layer, which can cause local short circuit of the outer current collector in advance when mechanical abuse (bending, unfolding or needle puncture) occurs, thereby improving the safety performance of the battery, and has good conductivity, which can improve the cycle performance and energy density of the battery.

[0022] The second aspect of the application provides a secondary battery, which comprises a positive pole piece, a negative pole piece and an insulating piece between the positive pole piece and the negative pole piece, wherein the positive pole piece and / or the negative pole piece is the battery pole piece provided in the first aspect of the application.

[0023] The third aspect of the application provides a power consumption device comprising the secondary battery provided in the second aspect of the application. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The cross-sectional structure of the battery pole piece provided in an embodiment of the application along the thickness direction of the battery pole piece is shown in the figure;

[0025] Figure 2 The cross-sectional structure of the battery pole piece provided in another embodiment of the application along the thickness direction of the battery pole piece is shown in the figure;

[0026] Figure 3 The cross-sectional structure of the battery pole piece provided in another embodiment of the application along the thickness direction of the battery pole piece is shown in the figure;

[0027] Figure 4 The cross-sectional structure of the battery pole piece provided in the comparative example 1 of the application along the thickness direction of the battery pole piece is shown in the figure;

[0028] Figure 5 The cross-sectional structure of the battery pole piece provided in the comparative example 2 of the application along the thickness direction of the battery pole piece is shown in the figure;

[0029] Figure 6 The cross-sectional structure of the battery pole piece provided in the comparative example 3 of the application along the thickness direction of the battery pole piece is shown in the figure.

[0030] EXPLANATION OF DRAWINGS

[0031] 10-battery pole piece; 11-current collector; 12-undercoat layer; 13-active material layer; 1-first coating layer; 2-second coating layer. DETAILED DESCRIPTION

[0032] The application will be further described in detail below in combination with preferred embodiments, but the protection scope of the application is not limited to the following specific embodiments.

[0033] In the present application, all the professional terms have the same meaning as generally understood by those skilled in the art, and the professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present application.

[0034] The wide application of lithium ion batteries in various fields puts forward higher requirements for the performance of lithium ion batteries. Under the premise of ensuring energy density, fast charging ability and cycle life, how to further improve the safety performance of lithium ion batteries has become a problem to be solved. Many methods to improve the safety of lithium ion batteries are at the expense of the electrochemical performance of lithium ion batteries. In order to improve the safety performance of secondary batteries, by coating a primer layer on the surface of the current collector of the battery electrode sheet, the burr on the current collector after slitting can be avoided to pierce the separator, the short circuit phenomenon of the battery can be avoided, and the safety of the battery can be improved. However, the composition of the primer layer used in the existing battery electrode sheet is mostly insulating material, and the ability of the insulating material to conduct lithium ions is poor, which will greatly increase the impedance of the lithium ion battery and reduce the energy density of the battery, affecting the cycle performance of the battery.

[0035] In view of the above problems, the present application provides a battery electrode sheet, which has excellent safety performance and electrochemical performance by special structural design of the distribution of the primer layer and the active material layer on the current collector. The battery electrode sheet can cause local short circuit of the outer current collector in advance when mechanically abused (bending and unfolding or needle puncture), thereby improving the safety performance of the battery, and has good conductivity, which can improve the cycle performance and energy density of the battery.

[0036] The application provides a battery pole piece 10, which comprises a current collector 11, a primer layer 12 arranged on at least one side surface of the current collector 11, and an active material layer 13 arranged on the side surface of the primer layer 12 away from the current collector 11; the primer layer 12 comprises a first coating layer 1 and a second coating layer 2 arranged side by side along the length direction of the battery pole piece, the active material layer 13 at least partially covers the side surface of the first coating layer 1 away from the current collector 11, and the side surface of the second coating layer 2 away from the current collector 11 is at least partially uncovered by the active material layer 13. That is, the second coating layer 2 is arranged on the current collector 11 and covers part of the surface of the current collector 11, and the first coating layer 1 and the active material layer 13 are sequentially arranged on the current collector 11 and the active material layer 13 covers part of the surface of the current collector 11. In the application, the second coating layer 2 and the active material layer 13 can completely cover the surface of the current collector 11 or partially cover the surface of the current collector 11. In the application, the active material layer 13 can completely cover the side surface of the first coating layer 1 away from the current collector 11 or partially cover the side surface of the first coating layer 1 away from the current collector 11. In the application, the first coating layer 1 comprises an inorganic solid compound; the second coating layer 2 comprises an inorganic solid compound; and the mass percentage of the inorganic solid compound in the second coating layer is greater than the mass percentage of the inorganic solid compound in the first coating layer. The application arranges the first coating layer 1 between the current collector 11 and the active material layer 13, which can ensure that the first coating layer 1 has a large resistance, improve the short-circuit resistance of the battery in the case of short circuit under abnormal conditions, and improve the safety performance of the battery. The application controls the content of the inorganic solid compound in the second coating layer 2 to be greater than the content of the inorganic solid compound in the first coating layer, so that part or all of the exposed second coating layer 2 has good mechanical properties, improves the safety performance and service life of the battery, and makes the first coating layer 1 better connect the current collector and the active material layer, provide a good ion transmission channel, and thus improve the cycle performance of the battery, so as to obtain a battery pole piece with good safety performance and cycle performance.

[0037] In some embodiments of the application, the orthographic projection of the first coating layer 1 in the thickness direction of the battery pole piece 10 covers more than 70% of the active material layer 13. In some embodiments of the application, the orthographic projection of the first coating layer 1 in the thickness direction of the battery pole piece 10 covers 70%, 75%, 80%, 85%, 90%, 95%, or 100% of the active material layer 13. In some embodiments of the application, the orthographic projection of the active material layer 13 and the first coating layer 1 in the thickness direction of the battery pole piece 10 completely coincides.

[0038] In some embodiments, the first coating layer 1 has an elongation of 0.02% to 2%. In some embodiments, the first coating layer 1 has an elongation of, for example, 0.02%, 0.05%, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, or 2%. The elongation is measured by stretching the battery electrode sheet sample using a universal mechanical testing machine, measuring the total deformation ΔL of the gauge section and the original gauge length L, and calculating the percentage of the total deformation ΔL of the gauge section and the original gauge length L, i.e., the elongation δ, (δ = ΔL / L x 100%). The first coating layer 1 has good elongation and conductivity, which can enhance the bonding force between the active material layer 13 and the current collector 11, avoid separation of the active material layer 13 and the current collector 11, ensure good adhesion interface of the battery electrode sheet in the battery cell, and improve the charging capacity and energy density of the battery. The second coating layer 2 is arranged on the blank surface of the current collector 11 and is not covered by the active material layer 13, i.e., one side of the second coating layer 2 directly contacts the current collector, and the other side is exposed on the outer surface of the battery electrode sheet 10. When the battery electrode sheet is mechanically abused, such as bending and unfolding, and needle piercing, local short circuit occurs in advance, which greatly reduces the heat generated at the short circuit position of the current collector, avoids high temperature of the battery cell, reduces the probability of fire and other dangers, and improves the safety performance of the battery electrode sheet. In some embodiments of the present application, the battery electrode sheet 10 is a positive electrode sheet, and the first coating layer 1 and the second coating layer 2 with a certain thickness together act as the bottom coating layer of the current collector 11 and directly contact the current collector, which can avoid the spurs on the current collector after slitting from piercing the separator, thereby avoiding the short circuit phenomenon between the negative electrode sheet and the positive electrode sheet, and improving the safety performance of the battery. In addition, the first coating layer 1 and the second coating layer 2 both contain 3 inorganic solid compounds, which can balance the safety performance and electrochemical performance of the first coating layer 1 and the second coating layer 2. The inorganic solid compounds improve the safety performance of the bottom coating layer, while the conductive agent enables the first coating layer 1 and the second coating layer 2 to have certain conductivity, thereby avoiding the phenomenon that the insulation of the bottom coating layer greatly reduces the electrochemical performance of the battery.

[0039] In the embodiments of the present application, the mass ratio of the inorganic solid compound to the conductive agent in the second coating layer 2 is greater than the mass ratio of the inorganic solid compound to the conductive agent in the first coating layer 1. In the embodiments of the present application, the difference between the proportion of the mass of the inorganic solid compound in the total mass of the second coating layer 2 and the proportion of the mass of the inorganic solid compound in the total mass of the first coating layer 1 is 0.1%-20%, and in some specific embodiments, the difference may, for example, be 0.1%, 0.5%, 1%, 2%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, or 20%. By controlling the content of the inorganic solid compound in the second coating layer 2 to be greater than the content of the inorganic solid compound in the first coating layer, the present application can make part or all of the exposed second coating layer 2 have good mechanical properties, improve the safety performance and service life of the battery, and make the first coating layer 1 better connect the current collector and the active material layer, provide a good ion transmission channel, and thus improve the cycle performance of the battery, thereby obtaining a battery pole piece with good safety performance and cycle performance.

[0040] In some embodiments, the first coating and the second coating have the same total content of inorganic solid compound and conductive agent, and the mass ratio of inorganic solid compound to conductive agent in the second coating 2 is greater than the mass ratio of inorganic solid compound to conductive agent in the first coating. In some embodiments, the first coating 1 has an electrical conductivity of 0.1 S / m to 10 S / m at 25°C, and the second coating 2 has an electrical conductivity of 0.01 S / m to 10 S / m at 25°C, and the electrical conductivity of the first coating 1 at 25°C is greater than the electrical conductivity of the second coating 2 at 25°C. In some embodiments, the first coating 1 has an electrical conductivity of, for example, 0.1 S / m, 0.2 S / m, 0.3 S / m, 0.4 S / m, 0.5 S / m, 0.8 S / m, 1 S / m, 2 S / m, 3 S / m, 4 S / m, 5 S / m, 6 S / m, 8 S / m, or 10 S / m at 25°C, and the second coating 2 has an electrical conductivity of, for example, 0.01 S / m, 0.02 S / m, 0.05 S / m, 0.1 S / m, 0.2 S / m, 0.5 S / m, 1 S / m, 2 S / m, 4 S / m, 5 S / m, 6 S / m, 8 S / m, or 10 S / m at 25°C. By controlling the mass ratio of inorganic solid compound to conductive agent in the first coating 1 and the second coating 2 within a suitable range, and thereby controlling the electrical conductivity within a suitable range, the first coating 1 and the second coating 2 can have both good safety performance and good electrical conductivity as the undercoat of the current collector 11. In addition, by controlling the electrical conductivity of the first coating 1 to be greater than the electrical conductivity of the second coating 2, the first coating 1 between the current collector 11 and the active material layer 13 can have better electrical conductivity, further improving the electronic conduction of the battery pole piece in the thickness direction, thereby improving the electrochemical performance of the battery, while the second coating 2 exposed on the surface has greater resistance, further improving its contribution to the safety performance of the battery pole piece. In some embodiments, the electrical conductivity of the undercoat 12 is greater than the electrical conductivity of the active material layer 13. The active material layer has better electrical conductivity, which can provide higher energy density for the battery, and the electrical conductivity of the undercoat is slightly lower than that of the active material layer, which can improve the safety performance of the battery pole piece.

[0041] In the embodiments of the present application, the inorganic solid compound includes one or more of zirconium oxide, magnesium oxide, silicon oxide, silicon monoxide, aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, boehmite, diaspore, barium sulfate, calcium sulfate, and calcium silicate. These inorganic solid compounds have good chemical stability and thermal stability. Adding them to the first coating layer 1 and the second coating layer 2 can effectively improve the safety performance of the battery pole piece 10, allowing it to be stably used in various positive and negative electrode material systems, and not causing short circuit even when directly contacting the active material after being pierced by a needle or being mechanically abused. In the present application, the inorganic solid compound is selected according to the actual conductivity requirement of the base coating layer. The conductivity of the inorganic solid compound is affected by factors such as its particle size distribution and specific surface area. Generally speaking, the smaller the particle size of the inorganic solid compound, the larger the specific surface area, and the higher the conductivity. The second coating layer can be free of an active material layer covering it, and only high safety, i.e., low conductivity, can be considered. Therefore, the second coating layer has low conductivity. In the present application, the first coating layer is in contact with the active material layer, and it is necessary to improve the safety performance while taking into account the performance of the active material layer. The second coating layer is partially or entirely exposed, and it is mainly considered to improve the safety performance. Therefore, it is necessary to select a suitable inorganic solid compound to make the conductivity of the first coating layer 1 greater than that of the second coating layer 2. In some embodiments of the present application, the inorganic solid compound includes one or more of aluminum oxide, lithium iron phosphate, boehmite, and diaspore.

[0042] In the embodiments of the present application, the particle size D50 of the inorganic solid compound is 0.05 μm-50 μm. In some specific embodiments of the present application, the particle size of the inorganic solid compound can be, for example, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm. By controlling the particle size of the inorganic solid compound within a suitable range, the conductivity of the inorganic solid compound can be further adjusted in the present application. In the embodiments of the present application, the particle size D50 refers to the particle size corresponding to the particle size distribution percentage of 50%. In the embodiments of the present application, the particle size distribution is tested by a laser particle size analyzer. Specifically, first, the test optical parameters are set according to the refractive index of the material. Before adding the test sample, the dispersion medium is added to the test tank, the background value is adjusted to ensure that it is within a suitable range, the sample is dispersed in the dispersion medium, and then the test is performed.

[0043] In the embodiments of the present application, the shape of the inorganic solid compound is not limited, and the inorganic solid compound includes, but is not limited to, one or more of a combination of spherical particles, irregular particles, porous particles, filamentous, and fibrous inorganic solid compounds.

[0044] In the first coating layer 1, the mass percentage of the inorganic solid compound is 70%-98%, and the mass percentage of the conductive agent is 0.1%-20%. In the present application, the mass percentage of the inorganic solid compound in the first coating layer 1 refers to the mass of the inorganic solid compound in the first coating layer 1 accounting for 70%-98% of the total mass of the first coating layer 1; and the mass percentage of the conductive agent in the first coating layer 1 refers to the mass of the conductive agent in the first coating layer 1 accounting for 0.1%-20% of the total mass of the first coating layer 1. In some specific embodiments of the present application, the mass percentage of the inorganic solid compound in the first coating layer 1 may, for example, be 70%, 72.5%, 75%, 77.5%, 80%, 82.5%, 84%, 84.5%, 84.9%, 85%, 90%, or 98%, and the mass percentage of the conductive agent may, for example, be 0.1%, 0.5%, 1%, 2%, 2.5%, 5%, 7.5%, 10%, 12.5%, 15%, or 20%. Controlling the content of the inorganic solid compound and the conductive agent in the first coating layer 1 within a suitable range can not only ensure the safety performance of the battery, but also as much as possible improve the conductivity of the first coating layer and the energy density and charging capacity of the battery.

[0045] In the second coating layer 2, the mass percentage of the inorganic solid compound is 70%-98%, and the mass percentage of the conductive agent is 0.1%-20%. In the present application, the mass percentage of the inorganic solid compound in the second coating layer 2 refers to the mass of the inorganic solid compound in the second coating layer 2 accounting for 70%-98% of the total mass of the second coating layer 2; and the mass percentage of the conductive agent in the second coating layer 2 refers to the mass of the conductive agent in the second coating layer 2 accounting for 0.1%-20% of the total mass of the second coating layer 2. In some specific embodiments of the present application, the mass percentage of the inorganic solid compound in the second coating layer 2 may, for example, be 70%-98%, and the mass percentage of the conductive agent may, for example, be 0.1%-20%. Controlling the content of the inorganic solid compound and the conductive agent in the second coating layer 2 within a suitable range can not only ensure that the second coating layer has a certain conductivity, but also has good safety performance.

[0046] In some embodiments of the present application, the thickness of the first coating layer 1 is 1 μm to 10 μm. In some specific embodiments of the present application, the thickness of the first coating layer 1 can be, for example, 0.2 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, or 15 μm. Controlling the thickness of the first coating layer 1 within an appropriate range is conducive to the close connection between the active material layer 13 and the current collector 11, ensures the safety performance of the battery, does not affect the energy density of the battery, and is also conducive to cost control.

[0047] In some embodiments of the present application, the thickness of the second coating layer 2 is 1 μm to 10 μm. In some specific embodiments of the present application, the thickness of the second coating layer 2 can be, for example, 0.2 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, or 15 μm. Controlling the thickness of the second coating layer 2 within an appropriate range is conducive to the close connection between the second coating layer 2 and the current collector 11, ensures the safety performance of the battery, does not affect the energy density of the battery, and is also conducive to cost control.

[0048] In some embodiments of the present application, the thickness of the first coating layer 1 can be the same as or different from the thickness of the second coating layer 2. In some embodiments of the present application, as shown in FIG. 1, the thickness of the first coating layer 1 is the same as the thickness of the second coating layer 2 in the battery pole piece 10; in other embodiments of the present application, as shown in FIG. 2, the thickness of the first coating layer 1 is different from the thickness of the second coating layer 2 in the battery pole piece 10. Figure 1 Figure 2 In some embodiments of the present application, as shown in FIG. 1, the thickness of the first coating layer 1 is the same as the thickness of the second coating layer 2 in the battery pole piece 10; in other embodiments of the present application, as shown in FIG. 2, the thickness of the first coating layer 1 is different from the thickness of the second coating layer 2 in the battery pole piece 10.

[0049] ​In some embodiments of the present application, the thickness of the active material layer 13 is 0.01 mm to 1 mm. In some embodiments of the present application, the thickness of the active material layer 13 is 0.02 mm to 0.2 mm. In some specific embodiments of the present application, the thickness of the active material layer 13 can be, for example, 0.01 mm, 0.02 mm, 0.04 mm, 0.045 mm, 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1 mm. Controlling the thickness of the active material layer 13 within an appropriate range can ensure the capacity of the battery while reducing the accumulation of heat inside the battery and reducing the risk of short circuit or overheating of the battery.

[0050] In some embodiments of the present application, the ratio of the thickness of the first coating layer 1 to the thickness of the active material layer 13 is 1: (2-1000), and the ratio of the thickness of the second coating layer 2 to the thickness of the active material layer 13 is 1: (2-1000). In some embodiments of the present application, the ratio of the thickness of the first coating layer 1 to the thickness of the active material layer 13 is 1: (2-500), and the ratio of the thickness of the second coating layer 2 to the thickness of the active material layer 13 is 1: (2-500). In some specific embodiments of the present application, the ratio of the thickness of the first coating layer 1 to the thickness of the active material layer 13 is 1: (2-200), and the ratio of the thickness of the second coating layer 2 to the thickness of the active material layer 13 is 1: (2-200). Controlling the ratio of the thickness of the first coating layer and the second coating layer to the thickness of the active material layer within an appropriate range can ensure the capacity of the battery while reducing the accumulation of heat inside the battery and reducing the risk of short circuit or overheating of the battery.

[0051] In some embodiments of the present application, the ratio of the coating area of the second coating layer 2 to the coating area of the active material layer 13 is 1: (2-5000). In some embodiments of the present application, the ratio of the coating area of the second coating layer 2 to the coating area of the active material layer 13 is 1: (2-500). In some embodiments of the present application, the ratio of the size of the second coating layer 2 in the length direction of the battery pole piece 10 to the size of the active material layer 13 in the length direction of the battery pole piece 10 is 1: (2-5000). In some embodiments of the present application, the ratio of the size of the second coating layer 2 in the length direction of the battery pole piece 10 to the size of the active material layer 13 in the length direction of the battery pole piece 10 is 1: (2-1000). Controlling the size ratio of the two within an appropriate range can ensure the safety performance of the battery while not affecting the energy density of the battery and being conducive to controlling the production and preparation cost. In some embodiments of the present application, the second coating layer 2 and the active material layer 13 fully cover the width direction of the battery pole piece 10, and the shape of the first coating layer 1, the second coating layer 2, and the active material layer 13 can be, for example, a rectangle.

[0052] In some embodiments of the present application, the active material layer 13 includes an active material, a binder, and a conductive agent. In some embodiments of the present application, the active material in the active material layer 13 accounts for 70-99.5% of the total mass of the active material layer 13. In some specific embodiments of the present application, the active material in the active material layer 13 may, for example, account for 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 98%, 99.5% of the total mass of the active material layer 13. Controlling the content of the active material in the active material layer within the above range is conducive to achieving a suitable capacity of the battery.

[0053] In some embodiments of the present application, the battery electrode sheet 10 is a positive electrode sheet, and the active material includes, but is not limited to, one or more of lithium cobaltate, lithium iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadium oxyphosphate, sodium vanadium oxyphosphate, lithium nickelate, lithium manganate, lithium nickel cobalt aluminum phosphate, lithium titanate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium-rich manganese-based positive electrode material, and sulfur. In some other embodiments of the present application, the battery electrode sheet 10 is a negative electrode sheet, and the active material includes, but is not limited to, one or more of graphite, hard carbon, silicon-based negative electrode, lithium metal, lithium alloy negative electrode, and lithium titanate.

[0054] In some embodiments of the present application, the conductive agent in the active material layer 13 accounts for 0.1-20% of the total mass of the active material layer 13. In some specific embodiments of the present application, the conductive agent in the active material layer 13 may, for example, account for 0.1%, 0.5%, 1%, 2%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20% of the total mass of the active material layer 13. Controlling the content of the conductive agent in the active material layer within the above range is conducive to further improving the conductivity of the battery electrode sheet.

[0055] In some embodiments of the present application, the conductive agent includes one or more of graphite-based conductive agent, carbon fiber, carbon nanotube, graphene, conductive carbon black, and conductive polymer. In some embodiments of the present application, the graphite conductive agent includes, but is not limited to, graphite, KS-6, KS-15, SFG-6, and SFG-15, and the conductive carbon black includes, but is not limited to, hard carbon, acetylene black, Ketjen black, Super P, Super S, amorphous carbon, activated carbon, 350G, and BP2000.

[0056] In the embodiments of the present application, the primer layer further comprises a binder, and the binder comprises one or more of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, carboxymethyl cellulose, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl alcohol, polytetrafluoroethylene, polyolefin, fluorinated rubber, polyacrylamide, polymethyl methacrylate-butyl acrylate, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene oxide, acrylic water-soluble glue, styrene-butadiene latex, polyvinyl acetate, polyurethane, lithium cellulose acetate, lithium cellulose acetate butyrate, lithium cellulose acetate propionate, lithium cyanoethyl branched amylose, lithium cyanoethyl polyvinyl alcohol, lithium cyanoethyl cellulose, lithium cyanoethyl sucrose, and lithium carboxymethyl cellulose.

[0057] In the embodiments of the present application, the mass of the binder in the first coating layer 1 accounts for 1%-20% of the total mass of the first coating layer 1; the mass of the binder in the second coating layer 2 accounts for 1%-20% of the total mass of the second coating layer 2; and the mass of the binder in the active material layer 13 accounts for 1%-20% of the total mass of the active material layer 13. Controlling the binder in the first coating layer, the second coating layer, and the active material layer within a suitable range can make the slurries of the first coating layer, the second coating layer, and the active material layer better shaped, facilitate coating during subsequent preparation of the battery pole piece, and also improve the binding force between the various parts of the battery pole piece.

[0058] In the embodiments of the present application, the battery pole piece can be a positive pole piece or a negative pole piece, and the current collector 11 includes but is not limited to an aluminum foil, a copper foil, a nickel foil, an aluminum alloy foil, a copper alloy foil, or a nickel alloy foil. In some specific embodiments of the present application, the battery pole piece is a positive pole piece, and the current collector 11 is an aluminum foil. In other specific embodiments of the present application, the battery pole piece is a negative pole piece, and the current collector 11 is a copper foil.

[0059] In the embodiments of the present application, the thickness of the current collector 11 is 1 μm-50 μm, which can ensure the transmission efficiency of the current and is also conducive to the conduction and dispersion of the heat generated by the battery during the charging and discharging process, thereby improving the safety of the battery. In some embodiments of the present application, the thickness of the current collector 11 can be, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 15 μm, 16 μm, 18 μm, 20 μm, 25 μm, 30 μm, 40 μm, or 50 μm.

[0060] In the embodiments of the present application, the current collector 11 can comprise a hollow foil area, which can be used for tab connection and fixation.

[0061] In the embodiments of the present application, the preparation method of the first coating layer 1 includes but is not limited to coating or spraying, and includes but is not limited to the following steps: adding the inorganic solid compound, the binder and the conductive agent into a solvent, and stirring and dispersing to obtain a first mixed slurry, and using a coating machine, a spraying machine or an infiltration device to coat or spray the first mixed slurry on at least one side of the current collector 11.

[0062] In the embodiments of the present application, the preparation method of the second coating layer 2 includes but is not limited to coating or spraying, and includes but is not limited to the following steps: adding the inorganic solid compound, the binder and the conductive agent into a solvent, and stirring and dispersing to obtain a second mixed slurry, and using a coating machine, a spraying machine or an infiltration device to coat or spray the second mixed slurry on at least one side of the current collector 11.

[0063] In the embodiments of the present application, the solvent can be water, ethanol, N-methyl pyrrolidone (NMP), acetone, N,N-dimethylformamide (DMF), a phenyl solvent, ethylene glycol or furan.

[0064] In the novel embodiments of the present application, the preparation method of the active material layer 13 includes but is not limited to coating or spraying, and includes but is not limited to the following steps: adding the active material, the binder and the conductive agent into a solvent, and stirring and dispersing to obtain an active material mixed slurry, and using a coating machine, a spraying machine or an infiltration device to coat or spray the active material mixed slurry on the surface of the first coating layer 1 away from the current collector 11.

[0065] The battery pole provided by the present application has excellent safety performance and electrochemical performance due to the special design of the undercoat layer and the active material layer, and can not only cause local short circuit of the outer current collector in advance when mechanically abused (bent and unfolded or punctured) to improve the safety performance of the battery, but also has good conductivity to improve the cycle performance and energy density of the battery.

[0066] The embodiments of the present application also provide a secondary battery, which includes a positive pole, a negative pole, and a separator and an electrolyte between the positive pole and the negative pole, the positive pole includes the battery pole in any of the above embodiments, and / or the negative pole includes the battery pole in any of the above embodiments.

[0067] The secondary battery provided by the present application contains the battery pole, which has good safety performance and energy density, and is beneficial to comprehensively improving the safety performance and energy density of the secondary battery.

[0068] In the novel embodiments of the present application, the separator includes but is not limited to one or more of a polyethylene (PE) separator, a polypropylene (PP) separator, a polyimide separator, a polyvinylidene fluoride separator, a polyvinylidene fluoride-hexafluoropropylene separator, a polyacrylonitrile separator and a polymethyl methacrylate separator.

[0069] In some embodiments of the present application, the thickness of the separator can be 1-50 μm, which can avoid direct contact between the positive and negative electrodes, prevent the risk of short circuit inside the battery, and ensure the efficiency of charge conduction and ion transmission between the positive and negative electrodes. In some embodiments of the present application, the thickness of the separator can be, for example, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm.

[0070] In some embodiments of the present application, the electrolyte can include, but is not limited to, any one of a conventional liquid electrolyte, an ionic liquid electrolyte, a gelled electrolyte, a lithium salt water-containing electrolyte, and a solid-state electrolyte.

[0071] In some embodiments of the present application, the ionic liquid electrolyte can include a lithium salt and an ionic liquid. Specifically, the lithium salt can be at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethylsulfonate, lithium perfluorobutylsulfonate, lithium chloroaluminate, lithium fluorosulfonylimide, lithium perfluoroalkyl trifluoroborate, lithium perfluoroalkyl pentafluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide (LiFSI), lithium chloride, and lithium nitrate. The ionic liquid can be one or more of an imidazole-based ionic liquid, a pyrrole-based ionic liquid, a piperidine-based ionic liquid, a quaternary ammonium-based ionic liquid, a quaternary phosphonium-based ionic liquid, and a sulfonimide-based ionic liquid (TFS).

[0072] In some embodiments of the present application, the conventional liquid electrolyte can include a lithium salt and an electrolyte solvent. Specifically, the electrolyte solvent can be one or more of deionized water, methyl ethyl carbonate, methyl propyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl propionate, anhydride, N-methyl pyrrolidone, N-methyl formamide, N-methyl acetamide, acetonitrile, N,N-dimethyl formamide, sulfolane, dimethyl sulfoxide, and dimethyl sulfite.

[0073] In some embodiments of the present application, the secondary battery further includes a battery shell for packaging the positive electrode sheet, the negative electrode sheet, the electrolyte, and the separator. In some embodiments of the present application, the battery shell can include, but is not limited to, a steel shell, an aluminum shell, an aluminum-plastic film shell, an aluminum alloy shell, or an alloy steel shell.

[0074] In the embodiments of the present application, the preparation of the secondary battery can be that the positive electrode sheet, the separator and the negative electrode sheet are made into an electric core by winding or stacking, then the electric core is placed in a battery shell, and after drying, a traditional liquid electrolyte, an ionic liquid electrolyte, a gelled electrolyte or a lithium salt water-containing electrolyte is added, and the secondary battery is obtained through processes such as packaging, aging and formation. The preparation of the secondary battery can also be that the solid-state electrolyte is coated on the positive electrode sheet and the negative electrode sheet, and then the electric core is made by winding or stacking, and then the electric core is placed in a battery shell, and after drying, the secondary battery is obtained through processes such as packaging, aging and formation.

[0075] In some embodiments of the present application, the secondary battery can be a winding battery, and the coating distribution on both sides of the battery electrode sheet current collector is asymmetric as shown in Figure 1 In some embodiments of the present application, the secondary battery can be a winding battery, and the coating distribution on both sides of the battery electrode sheet current collector is asymmetric as shown in Figure 3 In some embodiments of the present application, the secondary battery can be a winding battery, and the coating distribution on both sides of the battery electrode sheet current collector is asymmetric as shown in

[0076] The present application also provides a power-consuming device comprising the secondary battery of any of the above embodiments. Specifically, the power-consuming device includes but is not limited to an electric vehicle, an electric motorcycle, an electric bicycle, a mobile power source, a drone, a mobile phone, a computer, a camera, an electric tool, a smart home or a wearable device. The power-consuming device provided by the present application contains the secondary battery, which has good safety performance and energy density, and is beneficial to improving the safety performance and power performance of the power-consuming device and improving the market competitiveness of the power-consuming device.

[0077] The technical solutions of the present application are further described below through specific examples and comparative examples.

[0078] Example 1

[0079] Preparation of the positive electrode sheet: 15% by mass of polyvinylidene fluoride (PVDF) binder, 5% of Super P conductive agent and 80% of bumbu inorganic solid compound were added into N-methyl pyrrolidone (NMP) to obtain a first mixed slurry; 5% by mass of polyvinylidene fluoride (PVDF) binder, 5% of Super P conductive agent and 90% of bumbu inorganic solid compound were added into N-methyl pyrrolidone (NMP) to obtain a second mixed slurry; 1% by mass of polyvinylidene fluoride (PVDF) binder, 1% of Super P conductive agent and 98% of lithium cobaltate were added into N-methyl pyrrolidone (NMP) to obtain a third mixed slurry, and the first mixed slurry, the second mixed slurry and the active material mixed slurry were coated on the specific positions of the surfaces of the two sides of the 9 μm thick aluminum foil, respectively, to obtain a first coating layer, a second coating layer and a positive electrode active material layer, as shown in Figure 1As shown, the first coating layer is located between the positive active material layer and the current collector, and the positive projection of the active material layer and the first coating layer in the thickness direction of the battery pole piece completely coincides, the second coating layer covers all the areas on the surface of the current collector which are not covered by the positive active material layer, the coating thickness of the first coating layer and the second coating layer is 3 μm, the coating thickness of the positive active material layer is 0.045 mm, and the positive pole piece is obtained after coating and pressing after drying;

[0080] Preparation of the negative pole piece: natural graphite, conductive carbon Super P, sodium carboxymethyl cellulose, and butadiene rubber were added into deionized water in a mass ratio of 100:0.5:1:1, mixed and stirred to obtain a negative electrode slurry, and then coated and pressed to prepare a negative electrode pole piece;

[0081] Preparation of the electrolyte: LiPF6, ethylene carbonate (EC), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), and ethyl propionate (EP) were configured to form a solution with a LiPF6 concentration of 1.2 mol / L, and the mass ratio of EC:DEC:FEC:EP was 65:20:10:5, to obtain an electrolyte;

[0082] Preparation of the battery: the above-mentioned positive pole piece, the separator, and the negative pole piece were wound to form an electric core, and then the electric core was placed in an aluminum plastic film battery shell, dried, and then the above-mentioned electrolyte was added, and the battery was obtained after packaging, aging, and formation processes.

[0083] Example 2

[0084] The difference from Example 1 is that the second mixed slurry includes: 10% of polyvinylidene fluoride (PVDF) binder, 5% of Super P conductive agent, and 85% of bumbu inorganic solid compound.

[0085] Example 3

[0086] The difference from Example 1 is that the second mixed slurry includes: 2.5% of polyvinylidene fluoride (PVDF) binder, 2.5% of Super P conductive agent, and 95% of bumbu inorganic solid compound.

[0087] Example 4

[0088] The difference from Example 1 is that the inorganic solid compound in the first coating layer of the positive pole piece is aluminum oxide.

[0089] Example 5

[0090] The difference from Example 1 is that the inorganic solid compound in the first coating layer of the positive pole piece is lithium iron phosphate.

[0091] Example 6

[0092] The difference from Example 1 is that the inorganic solid compound in the first coating layer of the positive electrode sheet is lithium iron phosphate and bormite, and the mass ratio of lithium iron phosphate and bormite is 1:1.

[0093] Example 7

[0094] The difference from Example 1 is that the mass percentage of the conductive agent in the first coating layer 1 of the positive electrode sheet is 0.1%, and the mass percentage of the bormite inorganic solid compound is 84.9%.

[0095] Example 8

[0096] The difference from Example 1 is only that the mass percentage of the conductive agent in the first coating layer 1 of the positive electrode sheet is 7.5%, and the mass percentage of the bormite inorganic solid compound is 77.5%.

[0097] Example 9

[0098] The difference from Example 1 is only that the mass percentage of the conductive agent in the second coating layer of the positive electrode sheet is 1%.

[0099] Example 10

[0100] The difference from Example 1 is only that the coating thickness of the first coating layer and the second coating layer is 10 μm, and the coating thickness of the positive electrode active material layer is 0.045 mm.

[0101] Example 11

[0102] The difference from Example 1 is only that the coating thickness of the first coating layer is 10 μm, the coating thickness of the second coating layer is 5 μm, and the coating thickness of the positive electrode active material layer is 0.045 mm.

[0103] Example 12

[0104] The difference from Example 1 is only that the coating thickness of the first coating layer is 5 μm, the coating thickness of the second coating layer is 10 μm, and the coating thickness of the positive electrode active material layer is 0.045 mm.

[0105] Example 13

[0106] Preparation of the positive electrode sheet: 1% of polyvinylidene fluoride (PVDF) binder, 1% of Super P conductive agent and 98% of lithium cobaltate are added into N-methyl pyrrolidone NMP to obtain a positive electrode mixed slurry, and the positive electrode mixed slurry is coated on the specific position of the surface of the two sides of the 9 μm thick aluminum foil to obtain a positive electrode active material layer 13, and the positive electrode sheet is not provided with a first coating layer and a second coating layer;

[0107] Preparation of the negative electrode sheet: 15% by mass of polyvinylidene fluoride (PVDF) binder, 5% of Super P conductive agent and 80% of boehmite inorganic solid compound are added to N-methylpyrrolidone (NMP) to obtain a first mixed slurry; 5% by mass of polyvinylidene fluoride (PVDF) binder, 5% of Super P conductive agent and 90% of boehmite inorganic solid compound are added to N-methylpyrrolidone (NMP) to obtain a second mixed slurry; natural graphite, conductive carbon Super P, sodium carboxymethyl cellulose and styrene-butadiene rubber are added to deionized water in a mass ratio of 100:0.5:1:1 and mixed to obtain a third mixed slurry. The first mixed slurry, the second mixed slurry and the third mixed slurry are respectively coated on specific positions on the surface of opposite sides of a 9 μm thick copper foil to obtain a first coating 1, a second coating 2 and a negative electrode active material layer 13, as shown in FIG. Figure 1 As shown, the negative electrode active material layer 13 completely covers the surface of the first coating layer 1 on the side away from the current collector 11 (copper foil), and the second coating layer 2 covers the surfaces of the copper foil on the opposite sides not covered by the first coating layer 1. There is no uncoated blank copper foil. The coating thickness of the first coating layer 1 and the second coating layer 2 is 3 μm. The single-side coating thickness of the negative electrode active material layer 13 is 0.06 mm. After drying, the negative electrode sheet is obtained by coating and pressing.

[0108] Preparation of electrolyte: same as in Example 1;

[0109] Preparation of battery: same as in Example 1.

[0110] Example 14

[0111] Preparation of the positive electrode: same as in Example 1;

[0112] Preparation of negative electrode sheet: same as Example 13;

[0113] Preparation of electrolyte: same as in Example 1;

[0114] Preparation of battery: same as in Example 1.

[0115] Comparative Example 1

[0116] like Figure 4 As shown, the only difference from Example 1 is that the positive electrode sheet is not provided with the first coating 1.

[0117] Comparative Example 2

[0118] like Figure 5 As shown, the only difference from Example 1 is that the positive electrode sheet is not provided with the second coating layer 2 .

[0119] Comparative Example 3

[0120] like Figure 6The difference from Example 1 is that the positive active material layer 13 completely covers the surfaces of the first coating layer 1 and the second coating layer 2 away from the current collector 11 (aluminum foil), and there is no uncoated blank aluminum foil.

[0121] Comparative Example 4

[0122] The difference from Example 1 is only that the components of the second mixed slurry are the same as those of the first mixed slurry.

[0123] Performance test

[0124] The batteries of Examples 1-14 and Comparative Examples 1-4 were subjected to the following tests:

[0125] (1) Conductivity test:

[0126] The conductivity of the undercoat sheet prepared in the examples and comparative examples was tested at 25°C using a sheet resistance meter, the test area was 153.94 mm 2 , and the test pressure was 10 MPa.

[0127] (2) Bending and unfolding test and needle puncture test

[0128] Bending and unfolding test method: using a general bending and unfolding device and clamp, the battery prepared in the examples and comparative examples was fully charged and then fixed on the bending special clamp, and the battery was pressed to the target deformation amount; after bending, a flat clamp was replaced, the test product battery was placed on the flat clamp, and the plate was pressed to the target deformation amount to flatten the battery, and the bending and unfolding pass rate was obtained, the results are shown in Table 1;

[0129] Needle puncture test method: using a general needle puncture device and clamp, the battery prepared in the examples and comparative examples was fully charged, a conical steel needle was used to puncture the steel needle into the central part of the battery at a certain speed until it was penetrated, and then the needle was withdrawn, and a 100% SOC needle puncture pass rate was obtained, the results are shown in Table 1.

[0130] (3) Cycle performance test

[0131] The batteries prepared in the examples and comparative examples were tested in a 23°C constant temperature box, using a Blue King test cabinet, the 1000 cycle capacity retention rate calculation method was the 1000th cycle discharge capacity / first cycle discharge capacity, and the test procedure was:

[0132] 1. Charge to 4.16V at 1.3C, then charge to 4.28V at 1C, cut off at 0.8C, finally charge to 4.47V at 0.8C, cut off at 0.1C, and stand for 10 min;

[0133] 2. Discharge 0.5C to 3.2V, stand for 10 min;

[0134] 3. Repeat the above 1, 2 procedures for 1000 cycles.

[0135] Table 1 Performance test results

[0136]

[0137] From Table 1, compared with Comparative Examples 1-4, the battery pole piece of the application has higher needle penetration rate and bending expansion rate under the premise of ensuring the electrical conductivity and cycle performance of the first coating and the second coating, which shows that the application can significantly improve the safety performance of the battery pole piece by special design, while ensuring that the electrical conductivity and cycle performance of the battery pole piece remain basically unchanged.

[0138] The preferred embodiments are described in detail above, but the application is not limited to the specific embodiments described above. Those skilled in the art can make various specific changes to the application under the inspiration of the application without departing from the scope of the application, and these all belong to the protection scope of the application.

Claims

1. A battery electrode, characterized in that: The battery electrode sheet includes a current collector, a primer layer disposed on at least one side of the current collector, and an active material layer disposed on a side of the primer layer away from the current collector; the primer layer includes a first coating layer and a second coating layer disposed in parallel along the length of the battery electrode sheet, the active material layer at least partially covers a side of the first coating layer away from the current collector, and a side of the second coating layer away from the current collector is at least partially uncovered by the active material layer; The first coating layer and the second coating layer both include an inorganic solid compound and a conductive agent, and the mass percentage of the inorganic solid compound in the second coating layer is greater than the mass percentage of the inorganic solid compound in the first coating layer; the mass ratio of the inorganic solid compound to the conductive agent in the second coating layer is greater than the mass ratio of the inorganic solid compound to the conductive agent in the first coating layer; The difference between the mass percentage of the inorganic solid compound in the second coating layer and the mass percentage of the inorganic solid compound in the first coating layer is 0.1%-20%.

2. The battery electrode according to claim 1, wherein: The elongation of the first coating layer is 0.02%-2%.

3. The battery electrode according to claim 1, wherein: The electrical conductivity of the first coating at 25°C is 0.1S / m-10S / m, the electrical conductivity of the second coating at 25°C is 0.01S / m-10S / m, and the electrical conductivity of the first coating at 25°C is greater than the electrical conductivity of the second coating at 25°C.

4. The battery electrode according to claim 1, wherein: The inorganic solid compound includes one or more of zirconium oxide, magnesium oxide, silicon oxide, silicon monoxide, aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, boehmite, diaspore, barium sulfate, calcium sulfate and calcium silicate.

5. The battery electrode according to claim 1, wherein: In the first coating layer, the mass percentage of the inorganic solid compound is 70%-98%, and the mass percentage of the conductive agent is 0.1%-20%; in the second coating layer, the mass percentage of the inorganic solid compound is 70%-98%, and the mass percentage of the conductive agent is 0.1%-20%.

6. The battery electrode according to claim 1, wherein: The particle size D50 of the inorganic solid compound is 0.05 μm-50 μm.

7. The battery electrode according to claim 1, characterized in that: The thickness of the first coating layer is 0.2 μm-15 μm, the thickness of the second coating layer is 0.2 μm-15 μm, and the thickness of the active material layer is 0.01 mm-1 mm.

8. The battery electrode according to claim 1, wherein: The thickness of the first coating layer is 1 μm-10 μm, the thickness of the second coating layer is 1 μm-10 μm, and the thickness of the active material layer is 0.02 mm-0.2 mm.

9. The battery electrode according to claim 1, wherein: The ratio of the thickness of the first coating layer to the thickness of the active material layer is 1:(2-1000); the ratio of the thickness of the second coating layer to the thickness of the active material layer is 1:(2-1000).

10. The battery electrode according to claim 1, wherein: The ratio of the thickness of the first coating layer to the thickness of the active material layer is 1:(2-200); the ratio of the thickness of the second coating layer to the thickness of the active material layer is 1:(2-200).

11. The battery electrode according to claim 1, wherein: The ratio of the coating area of ​​the second coating layer to the coating area of ​​the active material layer is 1:(2-5000); the ratio of the size of the second coating layer in the length direction of the battery electrode sheet to the size of the active material layer in the length direction of the battery electrode sheet is 1:(2-5000).

12. The battery electrode according to claim 1, wherein: The ratio of the coating area of ​​the second coating layer to the coating area of ​​the active material layer is 1:(2-500); the ratio of the size of the second coating layer in the length direction of the battery electrode sheet to the size of the active material layer in the length direction of the battery electrode sheet is 1:(2-1000).

13. The battery electrode according to claim 1, wherein: The conductive agent includes one or more of graphite conductive agents, carbon fibers, carbon nanotubes, graphene, conductive carbon black, and conductive polymers; The primer layer further includes a binder, which includes one or more of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, carboxymethyl cellulose, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl alcohol, polytetrafluoroethylene, polyolefins, fluorinated rubber, polyacrylamide, polymethyl methacrylate-butyl acrylate, polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene oxide, acrylic acid water-soluble glue, styrene-butadiene latex, polyvinyl acetate, polyurethane, lithium cellulose acetate, lithium cellulose acetate butyrate, lithium cellulose acetate propionate, lithium cyanoethyl pullulan, lithium cyanoethyl polyvinyl alcohol, lithium cyanoethyl cellulose, lithium cyanoethyl sucrose, and lithium carboxymethyl cellulose; The current collector includes aluminum foil, copper foil, nickel foil, aluminum alloy foil, copper alloy foil or nickel alloy foil.

14. The battery electrode according to claim 1, wherein: The active material layer includes active materials, binders and conductive agents; the mass of the active materials accounts for 70%-99.5% of the total mass of the active material layer, and the mass of the conductive agent accounts for 0.1%-20% of the total mass of the active material layer; the active materials include positive electrode active materials and negative electrode active materials, and the positive electrode active materials include lithium cobaltate, lithium iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadium oxyphosphate, sodium vanadium oxyphosphate, lithium nickelate, lithium manganate, lithium nickel cobalt aluminum oxide, lithium titanate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium-rich manganese-based positive electrode materials and sulfur, and the negative electrode active materials include one or more of graphite, hard carbon, silicon-based negative electrode, lithium metal, lithium alloy negative electrode and lithium titanate.

15. A secondary battery, characterized in that: The secondary battery includes a positive electrode sheet, a negative electrode sheet, and an insulating member located between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet and / or the negative electrode sheet include the battery sheet according to any one of claims 1 to 14.

16. An electrical device, characterized in that: The electric device includes the secondary battery according to claim 15 .

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