Battery electrode sheet, secondary battery, and electric device

Abstract

A battery electrode sheet (10), a secondary battery and an electric device. The battery electrode sheet (10) comprises a current collector (11), a priming coat (12) and an active material layer (13), wherein the priming coat (12) comprises a first coating (1) and a second coating (2); and the active material layer (13) at least partially covers the surface of the side, away from the current collector (11), of the first coating (1), and at least part of the surface of the side, away from the current collector (11), of the second coating (2) is not covered with the active material layer (13). Each of the first coating (1) and the second coating (2) comprises an inorganic solid compound, and the mass percentage content of the inorganic solid compound in the second coating (2) is greater than that of the inorganic solid compound in the first coating (1). By means of the special structural design of the priming coat (12) on the current collector (11) of the battery electrode sheet (10), the battery electrode sheet (10) has excellent safety performance and electrochemical performance.

Description

Battery electrodes, secondary batteries and electrical equipment

[0001] This application claims priority to Chinese Patent Application No. 202410814498.9, filed on June 21, 2024, entitled "Battery Electrode, Secondary Battery and Electrical Equipment", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, and in particular to a battery electrode, a secondary battery, and an electrical device. Background Technology

[0003] With the increasingly widespread application of lithium-ion batteries in passenger vehicles and mobile electronic devices, improving their safety performance while ensuring energy density, fast charging capability, and cycle life has become a pressing issue. To enhance battery safety, applying a base coating to the current collector surface of the battery electrodes can prevent burrs on the current collector from puncturing the separator after cutting, thus avoiding short circuits and improving battery safety. However, the base coatings used in existing battery electrodes are mostly composed of insulating materials. Insulating materials have poor lithium-ion conductivity, significantly increasing the impedance of the lithium-ion battery, reducing its energy density, and affecting its cycle performance.

[0004] Application content

[0005] This application provides a battery electrode, a secondary battery, and an electrical device. The battery electrode has a special structural design for the distribution of the bottom coating and active material layer on the current collector, which enables the battery electrode to have both excellent safety performance and electrochemical performance. It can prevent the outer current collector from short-circuiting in advance during mechanical abuse (bending, unfolding, or puncture), thereby improving the safety performance of the battery. It also has good conductivity, which can improve the energy density and cycle performance of the battery.

[0006] A first aspect of this application provides a battery electrode, the battery electrode comprising a current collector, a base coating disposed on at least one surface of the current collector, and an active material layer disposed on the surface of the base coating away from the current collector; the base coating comprises a first coating and a second coating disposed side-by-side along the length direction of the battery electrode, the active material layer at least partially covering the surface of the first coating away from the current collector, and the surface of the second coating away from the current collector at least partially not covered by the active material layer; both the first coating and the second coating comprise inorganic solid compounds, and the mass percentage of inorganic solid compounds in the second coating is greater than the mass percentage of inorganic solid compounds in the first coating.

[0007] In this embodiment of the application, the elongation of the first coating is 0.02%-2%.

[0008] In this embodiment of the application, the first coating and the second coating further include a conductive agent, wherein 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; 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%-20%.

[0009] In this embodiment of the application, the conductivity of the first coating at 25°C is 0.1 S / m-10 S / m, the conductivity of the second coating at 25°C is 0.02 S / m-10 S / m, and the conductivity of the first coating is greater than that of the second coating.

[0010] In this application, the inorganic solid compound includes one or more of zirconium oxide, magnesium oxide, silicon oxide, silicon suboxide, aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, boehmite, gibbsite, barium sulfate, calcium sulfate, and calcium silicate.

[0011] In this embodiment of the application, the inorganic solid compound in the first coating has a mass percentage content of 70%-98%, and the conductive agent has a mass percentage content of 0.1%-20%; the inorganic solid compound in the second coating has a mass percentage content of 70%-98%, and the conductive agent has a mass percentage content of 0.1%-20%.

[0012] In this embodiment of the application, the particle size D50 of the inorganic solid compound is 0.05μm-50μm.

[0013] In this embodiment of the application, the thickness of the first coating is 0.2μm-15μm, the thickness of the second coating is 0.2μm-15μm, and the thickness of the active material layer is 0.01mm-1mm.

[0014] In this embodiment of the application, the thickness of the first coating is 1μm-10μm, the thickness of the second coating is 1μm-10μm, and the thickness of the active material layer is 0.02mm-0.2mm.

[0015] In this embodiment of the application, the thickness ratio of the first coating to the active material layer is 1:(2-1000); the thickness ratio of the second coating to the active material layer is 1:(2-1000).

[0016] In this embodiment of the application, the thickness ratio of the first coating to the active material layer is 1:(2-200); the thickness ratio of the second coating to the active material layer is 1:(2-200).

[0017] In this embodiment of the application, the ratio of the coating area of ​​the second coating to that of the active material layer is 1:(2-5000); the ratio of the size of the second coating in the length direction of the battery electrode to that of the active material layer in the length direction of the battery electrode is 1:(2-5000).

[0018] In this embodiment of the application, the ratio of the coating area of ​​the second coating to that of the active material layer is 1:(2-500); the ratio of the size of the second coating in the length direction of the battery electrode to that of the active material layer in the length direction of the battery electrode is 1:(2-1000).

[0019] In this application embodiment, the conductive agent includes one or more of graphite-based conductive agents, carbon fibers, carbon nanotubes, graphene, conductive carbon black, and conductive polymers.

[0020] The adhesive includes one or more of the following: polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, carboxymethyl cellulose, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl alcohol, polytetrafluoroethylene, polyolefins, fluorinated rubber, polyacrylamide, polymethyl methacrylate-butyl acrylate, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene oxide, water-soluble acrylic adhesives, styrene-butadiene latex, polyvinyl acetate, polyurethane, lithium cellulose acetate, lithium cellulose butyrate acetate, lithium cellulose propionate acetate, cyanoethyl amylopectin lithium, cyanoethyl polyvinyl alcohol lithium, cyanoethyl cellulose lithium, cyanoethyl sucrose lithium, and lithium carboxymethyl cellulose.

[0021] The current collector includes aluminum foil, copper foil, nickel foil, aluminum alloy foil, copper alloy foil, or nickel alloy foil.

[0022] In this embodiment, the active material layer comprises an active material, a binder, and a conductive agent; the active material accounts for 70%-99.5% of the total mass of the active material layer, and the conductive agent accounts for 0.1%-20% of the total mass of the active material layer; the active material comprises a positive electrode active material and a negative electrode active material, wherein the positive electrode active material comprises one or more of lithium cobalt oxide, lithium iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadium oxide phosphate, sodium vanadium oxide phosphate, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, lithium titanate, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium-rich manganese-based positive electrode material, and sulfur; and the negative electrode active material comprises one or more of graphite, hard carbon, silicon-based negative electrode, lithium metal, lithium alloy negative electrode, and lithium titanate.

[0023] The battery electrode provided in this application has a special design for the base coating and active material layer, which makes the battery electrode have both excellent safety performance and electrochemical performance. It can prevent the outer current collector from short-circuiting in advance during mechanical abuse (bending, unfolding or puncturing), thus improving the safety performance of the battery. It also has good conductivity, which can improve the cycle performance and energy density of the battery.

[0024] A second aspect of this application provides a secondary battery, the secondary battery including a positive electrode, a negative electrode, and an insulating member located between the positive electrode and the negative electrode, wherein the positive electrode and / or the negative electrode are as provided in the first aspect of this application.

[0025] A third aspect of this application provides an electrical device comprising a secondary battery as provided in the second aspect of this application. Attached Figure Description

[0026] Figure 1 is a schematic cross-sectional view of a battery electrode sheet along its thickness direction according to an embodiment of this application;

[0027] Figure 2 is a schematic cross-sectional view of the battery electrode along its thickness direction according to another embodiment of this application;

[0028] Figure 3 is a schematic cross-sectional view of the battery electrode along its thickness direction according to another embodiment of this application;

[0029] Figure 4 is a schematic cross-sectional view of the battery electrode sheet provided in Comparative Example 1 of this application along its own thickness direction.

[0030] Figure 5 is a schematic cross-sectional view of the battery electrode sheet provided in Comparative Example 2 of this application along its own thickness direction.

[0031] Figure 6 is a schematic cross-sectional view of the battery electrode sheet provided in Comparative Example 3 of this application along its own thickness direction.

[0032] The reference numerals in the attached diagram are as follows: 10 - Battery electrode; 11 - Current collector; 12 - Base coating; 13 - Active material layer; 1 - First coating; 2 - Second coating. Detailed Implementation

[0033] The present application will be further described in detail below with reference to preferred embodiments, but the scope of protection of the present application is not limited to the following specific embodiments.

[0034] In this application, all technical terms have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this application.

[0035] The widespread application of lithium-ion batteries in various fields has placed higher demands on their performance. While ensuring energy density, fast charging capability, and cycle life, further improving the safety performance of lithium-ion batteries has become an urgent problem to solve. Many methods to improve lithium-ion battery safety come at the cost of sacrificing the battery's electrochemical performance. To improve the safety of rechargeable batteries, coating the current collector surface of the battery electrode with a base coating can prevent burrs on the current collector from piercing the separator after cutting, thus avoiding short circuits and improving battery safety. However, the base coatings used in existing battery electrodes are mostly composed of insulating materials. Insulating materials have poor lithium-ion conductivity, which significantly increases the impedance of the lithium-ion battery, reduces its energy density, and affects its cycle performance.

[0036] To address the aforementioned issues, this application provides a battery electrode. This battery electrode employs a special structural design for the distribution of the undercoating layer and the active material layer on the current collector, enabling it to possess both excellent safety and electrochemical performance. It can prevent premature local short circuits in the outer current collector during mechanical abuse (bending, unfolding, or puncture), thereby improving battery safety, while also exhibiting good conductivity, thus enhancing battery cycle performance and energy density.

[0037] This application provides a battery electrode 10, which includes a current collector 11, a base coating 12 disposed on at least one surface of the current collector 11, and an active material layer 13 disposed on the surface of the base coating 12 away from the current collector 11. The base coating 12 includes a first coating 1 and a second coating 2 disposed side-by-side along the length of the battery electrode. The active material layer 13 at least partially covers the surface of the first coating 1 away from the current collector 11, and the surface of the second coating 2 away from the current collector 11 is at least partially not covered by the active material layer 13. That is, the second coating 2 is disposed on the current collector 11 and covers part of the surface of the current collector 11, and the first coating 1 and the active material layer 13 are sequentially stacked on the current collector 11, with the active material layer 13 covering part of the surface of the current collector 11. In this application embodiment, the second coating 2 and the active material layer 13 may completely cover the surface of the current collector 11 or partially cover the surface of the current collector 11. In this embodiment, the active material layer 13 can completely cover the surface of the first coating 1 away from the current collector 11, or it can partially cover the surface of the first coating 1 away from the current collector 11. In this embodiment, the first coating 1 comprises an inorganic solid compound; the second coating 2 comprises an inorganic solid compound; and the mass percentage of the inorganic solid compound in the second coating is greater than the mass percentage of the inorganic solid compound in the first coating. By placing the first coating 1 between the current collector 11 and the active material layer 13, this application ensures that it has a large resistance, improving the short-circuit resistance of the battery under abnormal conditions and enhancing battery safety. By controlling the content of the inorganic solid compound in the second coating 2 to be greater than that in the first coating, this application allows the partially or completely exposed second coating 2 to have good mechanical properties, improving battery safety and lifespan. Furthermore, it allows the first coating 1 to better connect the current collector and the active material layer, providing a good ion transport channel, thereby improving battery cycle performance and resulting in a battery electrode with both good safety and cycle performance.

[0038] In some embodiments of this application, the orthographic projection of the first coating 1 in the thickness direction of the battery electrode 10 covers at least 70% of the active material layer 13. In some embodiments of this application, the orthographic projection of the first coating 1 in the thickness direction of the battery electrode 10 covers 70%, 75%, 80%, 85%, 90%, 95%, and 100% of the active material layer 13. In some embodiments of this application, the active material layer 13 completely overlaps with the orthographic projection of the first coating 1 in the thickness direction of the battery electrode 10.

[0039] In this embodiment, the elongation of the first coating 1 is 0.02%-2%. In some specific embodiments, the elongation of the first coating 1 can be, 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 determined by stretching the battery electrode sample using a universal testing machine, measuring the total deformation ΔL of the gauge length segment relative to the original gauge length L, and calculating the percentage of the total deformation ΔL to the original gauge length L, which is the elongation δ (δ = ΔL / L × 100%). The first coating 1 has both good elongation and conductivity, which can enhance the bonding force between the active material layer 13 and the current collector 11, prevent the active material layer 13 from separating from the current collector 11, ensure a good bonding interface for the battery electrode inside the cell, and improve the battery's charging capacity and energy density. The second coating 2 is applied to the blank surface of the current collector 11 and is not covered by the active material layer 13. That is, one side of the second coating 2 is in direct contact with the current collector, and the other side is exposed on the outer surface of the battery electrode 10. When the battery electrode is subjected to mechanical abuse such as bending, unfolding, or puncture, a local short circuit can occur in advance, which can significantly reduce the heat generated at the short circuit location of the current collector, avoid the cell temperature from getting too high, reduce the probability of fire and other dangers, and improve the safety performance of the battery electrode. In some embodiments of this application, the battery electrode 10 is a positive electrode. The first coating 1 and the second coating 2, which have a certain thickness, together serve as the base coating of the current collector 11 and are in direct contact with the current collector. This can prevent burrs on the current collector after cutting from piercing the separator, thereby preventing short circuits between the negative electrode and the positive electrode and improving the safety performance of the battery. In addition, both the first coating 1 and the second coating 2 contain 3 inorganic solid compounds, which can balance the safety performance and electrochemical performance of the first coating 1 and the second coating 2. While the inorganic solid compounds improve the safety performance of the base coating, the conductive agent can make the first coating 1 and the second coating 2 have a certain conductivity, thereby avoiding the phenomenon that the insulation of the base coating leads to a significant decrease in the electrochemical performance of the battery.

[0040] In this embodiment, the mass ratio of inorganic solid compound to conductive agent in the second coating 2 is greater than that in the first coating 1. In this embodiment, the difference between the percentage of inorganic solid compound in the second coating 2 and the percentage of inorganic solid compound in the first coating 1 is 0.1%-20%. In some specific embodiments, the difference can be, for example, 0.1%, 0.5%, 1%, 2%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, or 20%. By controlling the content of inorganic solid compound in the second coating 2 to be greater than that in the first coating, this application can ensure that the partially or completely exposed second coating 2 has good mechanical properties, improving battery safety and lifespan. Furthermore, it allows the first coating 1 to better connect the current collector and the active material layer, providing a good ion transport channel, thereby improving battery cycle performance and resulting in a battery electrode with both good safety and cycle performance.

[0041] In this embodiment, the first coating 1 and the second coating 2 further include a conductive agent. In some embodiments, the total content of inorganic solid compounds and conductive agents in the first and second coatings is the same, and the mass ratio of inorganic solid compounds to conductive agents in the second coating 2 is greater than the mass ratio of inorganic solid compounds to conductive agents in the first coating. In this embodiment, the conductivity of the first coating 1 at 25°C is 0.1 S / m-10 S / m, and the conductivity of the second coating 2 at 25°C is 0.01 S / m-10 S / m, and the conductivity of the first coating 1 at 25°C is greater than the conductivity of the second coating 2 at 25°C. In some specific embodiments of this application, the electrical conductivity of the first coating 1 at 25°C can be, 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, and the electrical conductivity of the second coating 2 at 25°C can be, 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. This application controls the conductivity within a suitable range by maintaining the mass ratio of inorganic solid compounds and conductive agents in the first coating 1 and the second coating 2 within an appropriate range. This allows the first coating 1 and the second coating 2 to serve as the base coatings for the current collector 11, possessing both good safety and conductivity properties. Furthermore, by controlling the conductivity of the first coating 1 to be greater than that of the second coating 2, this application ensures that the first coating 1, located between the current collector 11 and the active material layer 13, has better conductivity, further improving the electron conduction of the battery electrode in the thickness direction, thereby enhancing the electrochemical performance of the battery. Simultaneously, it results in the second coating 2, exposed on the surface, having greater resistance, further enhancing its contribution to the safety performance of the battery electrode. In this embodiment, the conductivity of the base coating 12 is greater than that of the active material layer 13. A higher conductivity in the active material layer provides higher energy density for the battery, while a slightly lower conductivity in the base coating enhances the safety performance of the battery electrode.

[0042] In this application, the inorganic solid compounds include one or more of zirconium oxide, magnesium oxide, silicon oxide, silicon suboxide, aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, boehmite, gibbsite, barium sulfate, calcium sulfate, and calcium silicate. These inorganic solid compounds possess good chemical and thermal stability. Adding them to the first coating 1 and the second coating 2 can effectively improve the safety performance of the battery electrode 10, enabling its stable use in various positive and negative electrode material systems. Even if it comes into direct contact with the active material during needle puncture or mechanical abuse, it will not cause a short circuit. In this application, the inorganic solid compounds are selected according to the conductivity requirements of the actual base coating. The conductivity of inorganic solid compounds is affected by factors such as their particle size distribution and specific surface area. Generally, the smaller the particle size and the larger the specific surface area of ​​the inorganic solid compound, the higher the conductivity. The second coating may not have an active material layer covering it; only high safety, i.e., low conductivity, needs to be considered. Therefore, the conductivity of the second coating is low. In this application, the first coating is in contact with the active material layer, and it is necessary to improve safety performance while also ensuring the performance of the active material layer. The second coating is partially or completely exposed, primarily for its role in improving safety performance. Therefore, it is necessary to select a suitable inorganic solid compound so that the conductivity of the first coating 1 is greater than that of the second coating 2. In some embodiments of this application, the inorganic solid compound includes one or more of alumina, lithium iron phosphate, boehmite, and gibbsite.

[0043] In this application, the particle size D50 of the inorganic solid compound is 0.05 μm-50 μm. In some specific embodiments of this 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 also be further controlled. In this application, the particle size D50 refers to the particle size corresponding to a particle size distribution percentage of 50%. In this application, the particle size distribution is tested using a laser particle size analyzer. Specifically, the test optical parameters are first set according to the refractive index of the material. Before adding the test sample, the dispersion medium is added to the test cell, the background value is adjusted to ensure that the sample is dispersed in the dispersion medium within a suitable range, and then the test is performed.

[0044] In the embodiments of this application, the shape of the inorganic solid compound is not limited. The inorganic solid compound includes, but is not limited to, one or more of the following: spherical particles, irregular particles, porous particles, filamentous and fibrous inorganic solid compounds.

[0045] In this embodiment of the application, the inorganic solid compound in the first coating 1 has a mass percentage content of 70%-98%, and the conductive agent has a mass percentage content of 0.1%-20%. In this application, the mass percentage content of the inorganic solid compound in the first coating 1 being 70%-98% means that the inorganic solid compound accounts for 70%-98% of the total mass of the first coating 1; the mass percentage content of the conductive agent in the first coating 1 being 0.1%-20% means that the conductive agent accounts for 0.1%-20% of the total mass of the first coating 1. In some specific embodiments of this application, the mass percentage of the inorganic solid compound in the first coating 1 can be, for example, 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 can be, for example, 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 1 within a suitable range ensures the safety performance of the battery while maximizing the conductivity of the first coating, thereby improving the energy density and charging capacity of the battery.

[0046] In this embodiment of the application, the inorganic solid compound in the second coating 2 has a mass percentage content of 70%-98%, and the conductive agent has a mass percentage content of 0.1%-20%. In this application, the mass percentage content of the inorganic solid compound in the second coating 2 of 70%-98% means that the inorganic solid compound accounts for 70%-98% of the total mass of the second coating 2; the mass percentage content of the conductive agent in the second coating 2 of 0.1%-20% means that the conductive agent accounts for 0.1%-20% of the total mass of the second coating 2. In some specific embodiments of this application, the mass percentage content of the inorganic solid compound in the second coating 2 may, for example, be 70%-98%, and the mass percentage content of the conductive agent may, for example, be 0.1%-20%. By controlling the content of the inorganic solid compound and the conductive agent in the second coating 2 within a suitable range, it is possible to ensure that the second coating has a certain conductivity while also providing good safety performance.

[0047] In this application, the thickness of the first coating 1 is 0.2 μm-15 μm. In some embodiments of this application, the thickness of the first coating 1 is 1 μm-10 μm. In some specific embodiments of this application, the thickness of the first coating 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 1 within a suitable range is beneficial for a tight connection between the active material layer 13 and the current collector 11, ensuring the safety performance of the battery, without affecting the energy density of the battery, and also helps to control costs.

[0048] In this application, the thickness of the second coating 2 is 0.2 μm-15 μm. In some embodiments of this application, the thickness of the second coating 2 is 1 μm-10 μm. In some specific embodiments of this application, the thickness of the second coating 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 2 within a suitable range is beneficial for a tight connection between the second coating 2 and the current collector 11, ensuring the safety performance of the battery, without affecting the energy density of the battery, and also helps to control costs.

[0049] In this application, the thickness of the first coating 1 and the thickness of the second coating 2 can be the same or different. In some embodiments of this application, as shown in FIG1, the thickness of the first coating 1 and the thickness of the second coating 2 in the battery electrode 10 are the same; in other embodiments of this application, as shown in FIG2, the thickness of the first coating 1 and the thickness of the second coating 2 in the battery electrode 10 are different. When the thickness of the first coating 1 and the thickness of the second coating 2 are different, the thickness of the second coating 2 can be greater than or less than the first coating 1. In this application, the thickness ratio of the first coating 1 to the second coating 2 is 1:(0.1-10).

[0050] In this application, the thickness of the active material layer 13 is 0.01mm-1mm. In some embodiments of this application, the thickness of the active material layer 13 is 0.02mm-0.2mm. In some specific embodiments of this application, the thickness of the active material layer 13 can be, for example, 0.01mm, 0.02mm, 0.04mm, 0.045mm, 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.1mm, 0.15mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, or 1mm. Controlling the thickness of the active material layer 13 within a suitable range can ensure the battery capacity while reducing heat accumulation inside the battery, thus lowering the risk of short circuits or overheating.

[0051] In this application embodiment, the thickness ratio of the first coating 1 to the active material layer 13 is 1:(2-1000); the thickness ratio of the second coating 2 to the active material layer 13 is 1:(2-1000). In some embodiments of this application, the thickness ratio of the first coating 1 to the active material layer 13 is 1:(2-500); the thickness ratio of the second coating 2 to the active material layer 13 is 1:(2-500). In some specific embodiments of this application, the thickness ratio of the first coating 1 to the active material layer 13 is 1:(2-200); the thickness ratio of the second coating 2 to the active material layer 13 is 1:(2-200). Controlling the thickness ratio of the first coating and the second coating to the active material layer within a suitable range can ensure the battery capacity while reducing heat accumulation inside the battery, thus reducing the risk of short circuits or overheating.

[0052] In some embodiments of this application, the ratio of the coating area of ​​the second coating 2 to the coating area of ​​the active material layer 13 is 1:(2-5000). In some embodiments of this application, the ratio of the coating area of ​​the second coating 2 to the coating area of ​​the active material layer 13 is 1:(2-500). In some embodiments of this application, the ratio of the dimension of the second coating 2 along the length of the battery electrode 10 to the dimension of the active material layer 13 along the length of the battery electrode 10 is 1:(2-5000). In some embodiments of this application, the ratio of the dimension of the second coating 2 along the length of the battery electrode 10 to the dimension of the active material layer 13 along the length of the battery electrode 10 is 1:(2-1000). Controlling the size ratio of the two within a suitable range can ensure the safety performance of the battery without affecting the energy density of the battery and is beneficial to controlling the production cost. In some embodiments of this application, the second coating 2 and the active material layer 13 cover the width of the battery electrode 10, and the shapes of the first coating 1, the second coating 2, and the active material layer 13 can be, for example, rectangular.

[0053] In this embodiment, the active material layer 13 includes an active material, a binder, and a conductive agent. In this embodiment, the active material in the active material layer 13 comprises 70%-99.5% of its total mass. In some specific embodiments, the active material in the active material layer 13 may, for example, comprise 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 98%, or 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 beneficial for achieving appropriate battery capacity.

[0054] In some embodiments of this application, the battery electrode 10 is a positive electrode, and the active material includes, but is not limited to, one or more of lithium cobalt oxide, lithium iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadium oxide phosphate, sodium vanadium oxide phosphate, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, lithium titanate, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium-rich manganese-based positive electrode materials, and sulfur. In other embodiments of this application, the battery electrode 10 is a negative electrode, 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.

[0055] In this embodiment, the mass of 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 this application, the mass of the conductive agent in the active material layer 13 can, for example, account for 0.1%, 0.5%, 1%, 2%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, or 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 beneficial to further improve the conductivity of the battery electrode.

[0056] In this application, the conductive agent includes one or more of graphite-based conductive agents, carbon fibers, carbon nanotubes, graphene, conductive carbon black, and conductive polymers. In some embodiments of this 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.

[0057] In this embodiment of the application, the primer layer further includes an adhesive, which includes one or more of the following: polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, carboxymethyl cellulose, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl alcohol, polytetrafluoroethylene, polyolefins, fluorinated rubber, polyacrylamide, polymethyl methacrylate-butyl acrylate, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene oxide, water-soluble acrylic adhesives, styrene-butadiene latex, polyvinyl acetate, polyurethane, lithium cellulose acetate, lithium cellulose butyrate acetate, lithium cellulose propionate acetate, lithium cyanoethyl branched starch, lithium cyanoethyl polyvinyl alcohol, lithium cyanoethyl cellulose, lithium cyanoethyl sucrose, and lithium carboxymethyl cellulose.

[0058] In this embodiment, the binder in the first coating 1 accounts for 1%-20% of the total mass of the first coating 1; the binder in the second coating 2 accounts for 1%-20% of the total mass of the second coating 2; and 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, second coating, and active material layer within a suitable range allows for better forming of the slurry of the first coating, second coating, and active material layer, facilitating coating during subsequent battery electrode fabrication, and also improving the bonding strength between different parts of the battery electrode.

[0059] In this application, the battery electrode can be either a positive or negative electrode, and the current collector 11 includes, but is not limited to, aluminum foil, copper foil, nickel foil, aluminum alloy foil, copper alloy foil, or nickel alloy foil. In some specific embodiments of this application, the battery electrode is a positive electrode, and the current collector 11 is aluminum foil. In other specific embodiments of this application, the battery electrode is a negative electrode, and the current collector 11 is copper foil.

[0060] In this embodiment, the thickness of the current collector 11 is 1μm-50μm, which ensures both current transmission efficiency and facilitates the conduction and dissipation of heat generated during battery charging and discharging, thereby improving battery safety. In some embodiments of this application, the thickness of the current collector 11 can be, for example, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 15μm, 16μm, 18μm, 20μm, 25μm, 30μm, 40μm, or 50μm.

[0061] In this embodiment of the application, the current collector 11 may include an empty foil area, which can be used for electrode connection and fixation.

[0062] In the embodiments of this application, the preparation method of the first coating 1 includes, but is not limited to, coating or spraying, including, but not limited to, the following steps: adding an inorganic solid compound, a binder and a conductive agent to a solvent and stirring to disperse them to obtain a first mixed slurry, and coating or spraying the first mixed slurry onto at least one side of the current collector 11 using a coating machine, a spraying machine or a wetting device.

[0063] In this application embodiment, the preparation method of the second coating 2 includes, but is not limited to, coating or spraying, including, but not limited to, the following steps: adding an inorganic solid compound, a binder and a conductive agent to a solvent and stirring to disperse them to obtain a second mixed slurry, and coating or spraying the second mixed slurry onto at least one side of the current collector 11 using a coating machine, a spraying machine or a wetting device.

[0064] In the embodiments of this application, the solvent may be water, ethanol, N-methylpyrrolidone (NMP), acetone, N,N-dimethylformamide (DMF), phenyl solvent, ethylene glycol or furan.

[0065] In the novel embodiments of this application, the preparation method of the active material layer 13 includes, but is not limited to, coating or spraying, including, but not limited to, the following steps: adding active material, binder and conductive agent to solvent and stirring to disperse to obtain active material mixed slurry, and coating or spraying the active material mixed slurry onto the surface of the first coating layer 1 away from the current collector 11 using a coating machine, spraying machine or wetting device.

[0066] The battery electrode provided in this application has a special design for the base coating and active material layer, which makes the battery electrode have both excellent safety performance and electrochemical performance. It can prevent the outer current collector from short-circuiting in advance during mechanical abuse (bending, unfolding or puncturing), thus improving the safety performance of the battery. It also has good conductivity, which can improve the cycle performance and energy density of the battery.

[0067] This application also provides a secondary battery, including a positive electrode, a negative electrode, and a separator and electrolyte located between the positive electrode and the negative electrode. The positive electrode includes the battery electrode in any of the above embodiments, and / or the negative electrode includes the battery electrode in any of the above embodiments.

[0068] The secondary battery provided in this application contains battery electrodes, which have both good safety performance and energy density, thus contributing to a comprehensive improvement in the safety performance and energy density of the secondary battery.

[0069] In the novel embodiments of this application, the diaphragm includes, but is not limited to, one or more of the following: polyethylene (PE) diaphragm, polypropylene (PP) diaphragm, polyimide diaphragm, polyvinylidene fluoride diaphragm, vinylidene fluoride-hexafluoropropylene diaphragm, polyacrylonitrile diaphragm, and polymethyl methacrylate diaphragm.

[0070] In this application, the thickness of the separator can be 1μm-50μm, which can avoid direct contact between the positive and negative electrodes, preventing the risk of short circuits inside the battery, while ensuring the efficiency of charge conduction and ion transport between the positive and negative electrodes. In some specific embodiments of this application, the thickness of the separator can be, for example, 1μm, 3μm, 5μm, 8μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, and 50μm.

[0071] In the embodiments of this application, the electrolyte includes, but is not limited to, any one of the following: traditional liquid electrolyte, ionic liquid electrolyte, gelled electrolyte, lithium salt water-in-water electrolyte, and solid electrolyte.

[0072] In this embodiment, the ionic liquid electrolyte includes 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 trifluoromethanesulfonate, lithium perfluorobutylsulfonate, lithium chloroaluminate, lithium fluorosulfonylimide, lithium perfluoroalkyl trifluoroborate, lithium perfluoroalkyl pentafluorophosphate, lithium bis(fluorosulfonyl)imide (LiFSI), lithium chloride, and lithium nitrate. The ionic liquid can be one or more of imidazole ionic liquids, pyrrole ionic liquids, piperidine ionic liquids, quaternary ammonium ionic liquids, quaternary phosphorus ionic liquids, and sulfonylimide ionic liquids (TFS).

[0073] In the embodiments of this application, the conventional liquid electrolyte includes lithium salt and electrolyte solvent. Specifically, the electrolyte solvent can be one or more of the following: deionized water, methyl ethyl carbonate, methyl propyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl propionate, acid anhydride, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, acetonitrile, N,N-dimethylformamide, sulfolane, dimethyl sulfoxide, and dimethyl sulfite.

[0074] In this application embodiment, the secondary battery further includes a battery casing, which is used to encapsulate the positive electrode, negative electrode, electrolyte, and separator. In some embodiments of this application, the battery casing includes, but is not limited to, a steel casing, an aluminum casing, an aluminum-plastic film casing, an aluminum alloy casing, or an alloy steel casing.

[0075] In this embodiment, the secondary battery can be prepared by winding or stacking a positive electrode, a separator, and a negative electrode to form a battery cell, then placing the battery cell in a battery casing, drying it, adding a traditional liquid electrolyte, ionic liquid electrolyte, gelled electrolyte, or lithium salt-in-water electrolyte, and then performing encapsulation, aging, and formation processes to obtain the secondary battery. Alternatively, the secondary battery can be prepared by coating a solid electrolyte onto the positive and negative electrode plates, winding or stacking them to form a battery cell, placing the battery cell in a battery casing, drying it, and then performing encapsulation, aging, and formation processes to obtain the secondary battery.

[0076] In some embodiments of this application, the secondary battery can be a wound battery, and the coating distribution on both sides of the battery electrode current collector is shown in Figure 1, with the coating distribution on both sides being asymmetrical; in other embodiments of this application, the secondary battery can be a stacked battery, and the coating distribution on both sides of the battery electrode current collector is shown in Figure 3, with the coating distribution on both sides being symmetrical.

[0077] This application also provides an electrical device including the secondary battery described in any of the above embodiments. Specifically, the electrical device includes, but is not limited to, electric vehicles, electric motorcycles, electric bicycles, power banks, drones, mobile phones, computers, cameras, power tools, smart home devices, or wearable devices. The electrical device provided in this application contains a secondary battery that combines good safety performance and energy density, which is beneficial for improving the safety and power performance of the electrical device and enhancing its market competitiveness.

[0078] The technical solution of this application will be further described below through specific embodiments and comparative examples.

[0079] Example 1

[0080] Preparation of the positive electrode: A first mixed slurry is obtained by adding 15% (by mass) of polyvinylidene fluoride (PVDF) binder, 5% of Super P conductive agent, and 80% of boehmite inorganic solid compound to N-methylpyrrolidone (NMP); a second mixed slurry is obtained by adding 5% (by mass) of PVDF binder, 5% of Super P conductive agent, and 90% of boehmite inorganic solid compound to NMP; a third mixed slurry is obtained by adding 1% (by mass) of PVDF binder, 1% of Super P conductive agent, and 80% of boehmite inorganic solid compound to NMP. P-conductive agent and 98% lithium cobalt oxide are added to N-methylpyrrolidone (NMP) to obtain a third mixed slurry. The first mixed slurry, the second mixed slurry, and the active material mixed slurry are coated on specific positions on opposite sides of a 9μm thick aluminum foil to obtain a first coating, a second coating, and a positive electrode active material layer, as shown in Figure 1. The first coating is located between the positive electrode active material layer and the current collector, and the orthogonal projection of the active material layer and the first coating in the thickness direction of the battery electrode completely coincides. The second coating covers all areas of the current collector surface not covered by the positive electrode active material layer. The coating thickness of both the first and second coatings is 3μm, and the coating thickness of the positive electrode active material layer is 0.045mm. After drying, the positive electrode sheet is obtained by coating and pressing.

[0081] Preparation of negative electrode sheet: 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 and stirred to obtain negative electrode slurry, which is then coated and pressed to form negative electrode sheet;

[0082] Preparation of electrolyte: LiPF6 was prepared with ethylene carbonate (EC), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), and ethyl propionate (EP) to form a LiPF6 concentration of 1.2 mol / L. The mass ratio of EC:DEC:FEC:EP was 65:20:10:5, and the electrolyte was obtained.

[0083] Battery preparation: The above-mentioned positive electrode sheet, separator and negative electrode sheet are wound to form a battery cell. The battery cell is then placed in an aluminum-plastic film battery case, dried and then the above-mentioned electrolyte is added. After encapsulation, aging and formation processes, the battery is obtained.

[0084] Example 2

[0085] The difference from Example 1 is that the second mixed slurry includes: 10% by mass of polyvinylidene fluoride (PVDF) binder, 5% of Super P conductive agent and 85% of boehmite inorganic solid compound.

[0086] Example 3

[0087] The difference from Example 1 is that the second mixed slurry includes: 2.5% by mass of polyvinylidene fluoride (PVDF) binder, 2.5% of Super P conductive agent and 95% of boehmite inorganic solid compound.

[0088] Example 4

[0089] The difference from Example 1 is that the inorganic solid compound in the first coating of the positive electrode is aluminum oxide.

[0090] Example 5

[0091] The difference from Example 1 is that the inorganic solid compound in the first coating of the positive electrode is lithium iron phosphate.

[0092] Example 6

[0093] The difference from Example 1 is that the inorganic solid compounds in the first coating of the positive electrode are lithium iron phosphate and borosilicate, and the mass ratio of lithium iron phosphate to borosilicate is 1:1.

[0094] Example 7

[0095] The difference from Example 1 is that the mass percentage of the conductive agent in the first coating 1 of the positive electrode is 0.1%, and the mass percentage of the boehmite inorganic solid compound is 84.9%.

[0096] Example 8

[0097] The only difference from Example 1 is that the mass percentage of the conductive agent in the first coating 1 of the positive electrode is 7.5%, and the mass percentage of the boehmite inorganic solid compound is 77.5%.

[0098] Example 9

[0099] The only difference from Example 1 is that the mass percentage of the conductive agent in the second coating of the positive electrode is 1%.

[0100] Example 10

[0101] The only difference from Example 1 is that the coating thickness of both the first and second coatings is 10 μm, and the coating thickness of the positive electrode active material layer is 0.045 mm.

[0102] Example 11

[0103] The only difference from Example 1 is that the first coating thickness is 10 μm, the second coating thickness is 5 μm, and the positive electrode active material layer thickness is 0.045 mm.

[0104] Example 12

[0105] The only difference from Example 1 is that the coating thickness of the first coating is 5 μm, the coating thickness of the second coating is 10 μm, and the coating thickness of the positive electrode active material layer is 0.045 mm.

[0106] Example 13

[0107] Preparation of positive electrode sheet: 1% by mass of polyvinylidene fluoride (PVDF) binder, 1% of Super P conductive agent and 98% of lithium cobalt oxide are added to N-methylpyrrolidone (NMP) to obtain positive electrode mixed slurry. The positive electrode mixed slurry is coated on specific positions on opposite sides of a 9μm thick aluminum foil to obtain positive electrode active material layer 13. The positive electrode sheet does not have a first coating and a second coating.

[0108] Preparation of the negative electrode: 15% by mass of polyvinylidene fluoride (PVDF) binder, 5% by mass of Super P conductive agent, and 80% by mass of boehmite inorganic solid compound were added to N-methylpyrrolidone (NMP) to obtain a first mixed slurry; 5% by mass of polyvinylidene fluoride (PVDF) binder, 5% by mass of Super P conductive agent, and 90% by mass of boehmite inorganic solid compound were added to N-methylpyrrolidone (NMP) to obtain a second mixed slurry; natural graphite and conductive carbon Super P were then added to the mixture. P, sodium carboxymethyl cellulose, and styrene-butadiene rubber were added to deionized water at 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 were respectively coated on specific positions on opposite sides of a 9μm thick copper foil to obtain a first coating 1, a second coating 2, and a negative electrode active material layer 13, as shown in Figure 1. The negative electrode active material layer 13 completely covers the surface of the first coating 1 away from the current collector 11 (copper foil), and the second coating 2 covers the opposite sides of the copper foil not covered by the first coating 1. There are no uncoated blank copper foils. The coating thickness of the first coating 1 and the second coating 2 is 3μm, and the single-sided coating thickness of the negative electrode active material layer 13 is 0.06mm. After drying, the negative electrode sheet is obtained by coating and pressing.

[0109] Electrolyte preparation: Same as in Example 1;

[0110] Battery preparation: Same as in Example 1.

[0111] Example 14

[0112] Preparation of the positive electrode: Same as in Example 1;

[0113] Preparation of the negative electrode: Same as in Example 13;

[0114] Electrolyte preparation: Same as in Example 1;

[0115] Battery preparation: Same as in Example 1.

[0116] Comparative Example 1

[0117] As shown in Figure 4, the only difference from Example 1 is that the positive electrode does not have a first coating 1.

[0118] Comparative Example 2

[0119] As shown in Figure 5, the only difference from Example 1 is that the positive electrode does not have a second coating 2.

[0120] Comparative Example 3

[0121] As shown in Figure 6, the difference from Example 1 is that the positive electrode active material layer 13 completely covers the surface of the first coating 1 and the second coating 2 away from the current collector 11 (aluminum foil), and there is no uncoated blank aluminum foil.

[0122] Comparative Example 4

[0123] The only difference from Example 1 is that the components of the second mixed slurry are the same as those of the first mixed slurry.

[0124] Performance testing

[0125] The following tests were performed on the batteries of Examples 1-14 and Comparative Examples 1-4:

[0126] (1) Conductivity test:

[0127] The conductivity of the substrates prepared in the examples and comparative examples was tested using an electrode resistance meter at 25°C, with a test area of ​​153.94 mm². 2 The test pressure was 10 MPa.

[0128] (2) Bending and unfolding test and needle puncture test

[0129] Bending and unfolding test method: Using a general bending and unfolding equipment and fixture, the batteries prepared in the examples and comparative examples were fully charged and placed on the bending fixture for fixation. The batteries were pressed down to the target deformation amount. After bending, the flat fixture was replaced and the test product cells were placed on the flat fixture. The pressure plate was pressed down to the target deformation amount to flatten the cells. The bending and unfolding pass rate was obtained. The results are shown in Table 1.

[0130] Needle penetration test method: Using a general needle penetration device and fixture, after the batteries prepared in the examples and comparative examples are fully charged, a conical steel needle is used to penetrate the central part of the battery cell at a certain speed until it is completely penetrated. After that, the needle is withdrawn to obtain a 100% SOC needle penetration pass rate. The results are shown in Table 1.

[0131] (3) Cyclic performance test

[0132] The batteries prepared in the examples and comparative examples were tested in a 23°C constant temperature chamber using a Blue Electric test cabinet. The capacity retention rate after 1000 cycles was calculated as the discharge capacity on the 1000th cycle divided by the discharge capacity on the first cycle. The test steps were as follows:

[0133] 1. Charge at 1.3C to 4.16V, then at 1C to 4.28V, stop at 0.8C, and finally charge at 0.8C to 4.47V, stop at 0.1C, and let stand for 10 minutes;

[0134] 2. Discharge at 0.5C to 3.2V, then let stand for 10 minutes;

[0135] 3. Repeat steps 1 and 2 above for 1000 cycles.

[0136] Table 1 Performance Test Results

[0137] As shown in Table 1, compared with Comparative Examples 1-4, the battery electrode of this application has a higher needle penetration rate and bending unfolding pass rate while ensuring the conductivity and cycle performance of the first and second coatings. This indicates that by making special designs on the battery electrode, this application can significantly improve its safety performance while ensuring that its conductivity and cycle performance remain basically unchanged.

[0138] The preferred embodiments have been described in detail above, but this application is not limited to the specific implementation methods described above. Those skilled in the art can make various specific modifications under the guidance of this application without departing from the protection scope of this application, and these modifications all fall within the protection scope of this application.

Claims

1. A battery electrode (10), characterized in that, The battery electrode (10) includes a current collector (11), a base coating (12) disposed on at least one side surface of the current collector (11), and an active material layer (13) disposed on the side surface of the base coating (12) away from the current collector (11); the base coating (12) includes a first coating (1) and a second coating (2) disposed side by side along the length direction of the battery electrode (10), the active material layer (13) at least partially covers the side surface of the first coating (1) away from the current collector (11), and the side surface of the second coating (2) away from the current collector (11) is at least partially not covered by the active material layer (13); both the first coating (1) and the second coating (2) include inorganic solid compounds, and the mass percentage of inorganic solid compounds in the second coating (2) is greater than the mass percentage of inorganic solid compounds in the first coating (1).

2. The battery electrode (10) as described in claim 1, characterized in that, The elongation of the first coating (1) is 0.02%-2%.

3. The battery electrode (10) as described in any one of claims 1 or 2, characterized in that, The first coating (1) and the second coating (2) further include a conductive agent, wherein the mass ratio of the inorganic solid compound to the conductive agent in the second coating (2) is greater than the mass ratio of the inorganic solid compound to the conductive agent in the first coating (1); The difference between the mass percentage of the inorganic solid compound in the second coating (2) and the mass percentage of the inorganic solid compound in the first coating (1) is 0.1%-20%.

4. The battery electrode (10) as described in any one of claims 1-3, characterized in that, The first coating (1) has a conductivity of 0.1 S / m-10 S / m at 25°C, and the second coating (2) has a conductivity of 0.01 S / m-10 S / m at 25°C. The conductivity of the first coating (1) at 25°C is greater than that of the second coating (2) at 25°C.

5. The battery electrode (10) as described in any one of claims 1-4, characterized in that, The inorganic solid compounds include one or more of zirconium oxide, magnesium oxide, silicon oxide, silicon suboxide, aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, boehmite, gibbsite, barium sulfate, calcium sulfate, and calcium silicate.

6. The battery electrode (10) as described in any one of claims 3-5, characterized in that, In the first coating (1), the inorganic solid compound has a mass percentage content of 70%-98%, and the conductive agent has a mass percentage content of 0.1%-20%; in the second coating (2), the inorganic solid compound has a mass percentage content of 70%-98%, and the conductive agent has a mass percentage content of 0.1%-20%.

7. The battery electrode (10) as described in any one of claims 1-6, characterized in that, The particle size D50 of the inorganic solid compound is 0.05 μm-50 μm.

8. The battery electrode (10) as described in any one of claims 1-7, characterized in that, The thickness of the first coating (1) is 0.2μm-15μm, the thickness of the second coating (2) is 0.2μm-15μm, and the thickness of the active material layer (13) is 0.01mm-1mm.

9. The battery electrode (10) as described in any one of claims 1-8, characterized in that, The thickness of the first coating (1) is 1μm-10μm, the thickness of the second coating (2) is 1μm-10μm, and the thickness of the active material layer (13) is 0.02mm-0.2mm.

10. The battery electrode (10) as described in any one of claims 1-9, characterized in that, The thickness ratio of the first coating (1) to the active material layer (13) is 1:(2-1000); the thickness ratio of the second coating (2) to the active material layer (13) is 1:(2-1000).

11. The battery electrode (10) according to any one of claims 1-10, characterized in that, The thickness ratio of the first coating (1) to the active material layer (13) is 1:(2-200); the thickness ratio of the second coating (2) to the active material layer (13) is 1:(2-200).

12. The battery electrode (10) as described in any one of claims 1-11, characterized in that, The ratio of the coating area of ​​the second coating (2) to that of the active material layer (13) is 1:(2-5000); the ratio of the size of the second coating (2) in the length direction of the battery electrode (10) to the size of the active material layer (13) in the length direction of the battery electrode (10) is 1:(2-5000).

13. The battery electrode (10) as described in any one of claims 1-12, characterized in that, The ratio of the coating area of ​​the second coating (2) to that of the active material layer (13) is 1:(2-500); the ratio of the size of the second coating (2) in the length direction of the battery electrode (10) to that of the active material layer (13) in the length direction of the battery electrode (10) is 1:(2-1000).

14. The battery electrode (10) as described in any one of claims 3-13, characterized in that, The conductive agent includes one or more of the following: graphite-based conductive agents, carbon fibers, carbon nanotubes, graphene, conductive carbon black, and conductive polymers. The battery electrode (10) further includes an adhesive, which includes one or more of the following: polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, carboxymethyl cellulose, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl alcohol, polytetrafluoroethylene, polyolefins, fluorinated rubber, polyacrylamide, polymethyl methacrylate-butyl acrylate, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene oxide, water-soluble acrylic adhesives, styrene-butadiene latex, polyvinyl acetate, polyurethane, lithium cellulose acetate, lithium cellulose butyrate acetate, lithium cellulose propionate acetate, lithium cyanoethyl branched starch, lithium cyanoethyl polyvinyl alcohol, lithium cyanoethyl cellulose, lithium cyanoethyl sucrose, and lithium carboxymethyl cellulose. The current collector (11) includes aluminum foil, copper foil, nickel foil, aluminum alloy foil, copper alloy foil, or nickel alloy foil.

15. The battery electrode (10) as described in any one of claims 1-14, characterized in that, The active material layer (13) includes an active material, a binder, and a conductive agent; the active material accounts for 70%-99.5% of the total mass of the active material layer (13), and the conductive agent accounts for 0.1%-20% of the total mass of the active material layer (13); the active material includes a positive electrode active material and a negative electrode active material, the positive electrode active material includes one or more of lithium cobalt oxide, lithium iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadium oxide phosphate, sodium vanadium oxide phosphate, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, lithium titanate, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, 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.

16. A secondary battery, characterized in that, The secondary battery includes a positive electrode, a negative electrode, and an insulating element located between the positive electrode and the negative electrode, wherein the positive electrode and / or the negative electrode includes a battery electrode (10) as described in any one of claims 1-15.

17. An electrical appliance, characterized in that, The electrical equipment includes the secondary battery as described in claim 16.

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