Battery electrode sheet, secondary battery and electrical device

Abstract

A battery electrode sheet, the battery electrode sheet comprising a current collector, a bottom coating layer arranged on at least one side surface of the current collector, and an active layer arranged on the side surface of the bottom coating layer away from the current collector. The bottom coating layer comprises a first conductive layer and a second conductive layer arranged side by side in the length direction of the battery electrode sheet. The active layer at least partially covers the side surface of the first conductive layer away from the current collector, and the side surface of the second conductive layer away from the current collector is at least partially uncovered with the active layer, the conductivity of the first conductive layer being greater than the conductivity of the second conductive layer.

Description

Battery electrodes, secondary batteries and electrical equipment

[0001] Priority information

[0002] This application claims priority and benefits to patent application No. 2024214458014, filed with the China National Intellectual Property Administration on June 21, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] 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

[0004] With the increasingly widespread application of lithium-ion batteries in passenger vehicles and mobile electronic devices, the market and consumers are placing higher demands on their performance. To improve the safety performance of lithium-ion batteries, applying a base coating to the current collector surface of the battery electrode 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, which significantly increases the impedance of lithium-ion batteries, reduces energy density, and affects cycle performance. Summary of the Invention

[0005] This application provides a battery electrode, a secondary battery, and an electrical device. The current collector of the battery electrode is provided with a base coating. This base coating can prevent local short circuits in the current collector where the second conductive layer is not covered by the active layer when the battery electrode is subjected to mechanical abuse, 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] In a first aspect, embodiments of this application provide a battery electrode, which includes a current collector, a base coating disposed on at least one surface of the current collector, and an active layer disposed on the surface of the base coating away from the current collector; the base coating includes a first conductive layer and a second conductive layer disposed side-by-side along the length direction of the battery electrode, the active layer at least partially covering the surface of the first conductive layer away from the current collector, and the surface of the second conductive layer away from the current collector is at least partially not covered by the active layer; and the conductivity of the first conductive layer is greater than the conductivity of the second conductive layer.

[0007] In this embodiment of the application, the conductivity of the first conductive layer at 25°C is 0.1 S / m-10 S / m, and the conductivity of the second conductive layer at 25°C is 0.01 S / m-10 S / m.

[0008] In some embodiments of this application, the conductivity of the first conductive layer at 25°C is 0.5S / m-10S / m, and the conductivity of the second conductive layer at 25°C is 0.1S / m-5S / cm.

[0009] In this embodiment of the application, the ratio of the conductivity of the first conductive layer at 25°C to the conductivity of the second conductive layer at 25°C is (1-20):1.

[0010] In this embodiment of the application, the orthogonal projection of the first conductive layer in the thickness direction of the battery electrode covers at least 70% of the active layer.

[0011] In this embodiment of the application, the elongation of the first conductive layer is 0.02%-2%.

[0012] In this embodiment of the application, the thickness of the first conductive layer is 0.2μm-15μm; the thickness of the second conductive layer is 0.2μm-15μm; and the thickness of the active layer is 0.005mm-1.00mm.

[0013] In this embodiment of the application, the thickness of the first conductive layer is 1μm-10μm; the thickness of the second conductive layer is 1μm-10μm; and the thickness of the active layer is 0.02mm-0.2mm.

[0014] In this embodiment of the application, the thickness ratio of the first conductive layer to the active layer is 1:(2-1000); the thickness ratio of the second conductive layer to the active layer is 1:(2-1000).

[0015] In this embodiment of the application, the thickness ratio of the first conductive layer to the active layer is 1:(2-200); the thickness ratio of the second conductive layer to the active layer is 1:(2-200).

[0016] In this embodiment of the application, the first conductive layer and the second conductive layer have the same thickness.

[0017] In this embodiment of the application, the dimension of the first conductive layer in the length direction of the battery electrode is larger than the dimension of the second conductive layer in the length direction of the battery electrode.

[0018] In this embodiment of the application, the ratio of the dimension of the first conductive layer in the length direction of the battery electrode to the dimension of the second conductive layer in the length direction of the battery electrode is (10-1000):1.

[0019] In this embodiment of the application, the battery electrode includes a current collector, a base coating disposed on opposite sides of the current collector, and an active layer disposed on the side of the base coating away from the current collector.

[0020] In this embodiment of the application, the base coating layer and the active layer are provided on both opposite sides of the current collector. The difference in size between the first conductive layers on opposite sides of the current collector in the length direction of the battery electrode is less than or equal to 500 mm. The difference in size between the second conductive layers on opposite sides of the current collector in the length direction of the battery electrode is less than or equal to 500 mm. The difference in size between the active layers on opposite sides of the current collector in the length direction of the battery electrode is less than or equal to 500 mm.

[0021] In this embodiment of the application, the current collector is selected from aluminum foil, copper foil, nickel foil, aluminum alloy foil, copper alloy foil, or nickel alloy foil; the thickness of the current collector is 1μm-50μm; and the active layer is selected from the positive electrode active layer or the negative electrode active layer.

[0022] The battery electrode provided in this application has a base coating on the current collector. This base coating has good electrochemical stability and thermal stability, and can be used stably in various positive and negative electrode material systems. It can prevent local short circuits in the current collector where the second conductive layer is not covered by the active layer when the battery electrode is subjected to mechanical abuse, thereby improving the safety performance of the battery. It also has good conductivity, which can improve the charging capacity and energy density of the battery.

[0023] Secondly, this application also 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 includes the battery electrode described in the first aspect.

[0024] The secondary battery provided by this invention contains battery electrodes that have both good safety performance and energy density, which is beneficial to improving the safety and energy density of the secondary battery.

[0025] Thirdly, this application also provides an electrical device, including the secondary battery described in the second aspect.

[0026] The electrical equipment provided by this invention contains a secondary battery, which has both good safety performance and energy density, thus improving the safety and power performance of the electrical equipment and enhancing its market competitiveness. Attached Figure Description

[0027] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, wherein:

[0028] Figure 1 is a schematic cross-sectional view of a battery electrode along its thickness direction according to an embodiment of this application.

[0029] The reference numerals in the attached diagram are as follows: 10-Battery electrode; 11-Current collector; 12-Undercoating layer; 13-Active layer; 1-First conductive layer; 2-Second conductive layer. Detailed Implementation

[0030] The following are preferred embodiments of the present application. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of the embodiments of the present application, and these improvements and modifications are also considered to be within the protection scope of the embodiments of the present application.

[0031] Referring to Figure 1, Figure 1 is a schematic cross-sectional view of a battery electrode 10 along its thickness direction according to an embodiment of this application. The battery electrode 10 includes a current collector 11, a base coating 12 disposed on at least one surface of the current collector 11, and an active layer 13 disposed on the surface of the base coating 12 away from the current collector. The base coating 12 includes a first conductive layer 1 and a second conductive layer 2 disposed side by side along the length direction of the battery electrode. The active layer 13 at least partially covers the surface of the first conductive layer 1 away from the current collector 11, and the surface of the second conductive layer 2 away from the current collector 11 is at least partially not covered by the active layer 13. The conductivity of the first conductive layer 1 is greater than the conductivity of the second conductive layer 2.

[0032] The battery electrode 10 provided in this embodiment has a base coating 12 on its current collector 11. This base coating 12 includes a first conductive layer 1 and a second conductive layer 2 arranged in parallel. The first conductive layer 1 has good conductivity, which improves both battery cycle performance and charging capacity and energy density. The second conductive layer 2 can prevent premature local short circuits in the current collector where it is not covered by the active layer during mechanical abuse (bending, unfolding, or puncture), thus improving battery safety. Both the first conductive layer 1 and the second conductive layer 2 can effectively prevent short circuits caused by burrs on the current collector piercing the separator after cutting, further improving battery safety. Furthermore, the conductivity of the first conductive layer 1 is greater than that of the second conductive layer 2. The higher conductivity of the first conductive layer 1 helps ensure battery cycle performance and improves battery durability, while the lower conductivity of the second conductive layer 2 helps improve battery safety.

[0033] In this embodiment, the conductivity of the first conductive layer 1 at 25°C is 0.1 S / m-10 S / m, and the conductivity of the second conductive layer 2 at 25°C is 0.01 S / m-10 S / m. In some embodiments, the conductivity of the first conductive layer 1 at 25°C is 0.5 S / m-10 S / m, and the conductivity of the second conductive layer 2 at 25°C is 0.1 S / m-5 S / m. In some specific embodiments, the conductivity of the first conductive layer 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 conductivity of the second conductive layer 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.

[0034] In this embodiment, the ratio of the conductivity of the first conductive layer 1 at 25°C to the conductivity of the second conductive layer 2 at 25°C is (1-20):1. In some specific embodiments, the ratio of the conductivity of the first conductive layer 1 at 25°C to the conductivity of the second conductive layer 2 at 25°C can be, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 8:1, 10:1, 15:1, or 20:1.

[0035] In this embodiment, the orthographic projection of the first conductive layer 1 in the thickness direction of the battery electrode 10 covers at least 70% of the active layer 13. In some specific embodiments, the orthographic projection of the first conductive layer 1 in the thickness direction of the battery electrode 10 covers 70%, 75%, 80%, 85%, 90%, 95%, and 100% of the active layer 13.

[0036] In this embodiment, the elongation of the first conductive layer 1 is 0.02%-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%). A high elongation of the first conductive layer 1 enhances the peel strength between the active layer 13 and the current collector 11, preventing separation of the active layer 13 and the current collector 11 and improving battery cycle performance. In some embodiments, the elongation of the first conductive layer 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%.

[0037] In this embodiment, the thickness of the first conductive layer 1 can be 0.2μm-15μm, which facilitates a tight connection between the first conductive layer 1 and the active layer 13 and the current collector 11, ensuring battery safety performance, without affecting the battery's energy density, and also helps control costs. In some embodiments, the thickness of the first conductive layer 1 can be, for example, 0.2μm, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 12μm, or 15μm. In some embodiments of this application, the thickness of the first conductive layer 1 can be 1μm-10μm. In this embodiment, the thickness of the second conductive layer 2 can be 0.2μm-15μm, which facilitates a tight connection between the second conductive layer 2 and the current collector 11, ensuring battery safety performance, without affecting the battery's energy density, and also helps control costs. In some embodiments, the thickness of the second conductive 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. In some embodiments of this application, the thickness of the second conductive layer 2 can be 1 μm-10 μm.

[0038] In this embodiment of the application, the thicknesses of the first conductive layer 1 and the second conductive layer 2 may be the same or different.

[0039] In this embodiment, the thickness of the active layer can be 0.01mm-1mm, which ensures battery capacity while reducing heat accumulation inside the battery, thus lowering the risk of short circuits or overheating. In some embodiments, the thickness of the active layer 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. In some embodiments of this application, the thickness of the active layer 13 is 0.02mm-0.2mm.

[0040] In this embodiment, the thickness ratio of the first conductive layer 1 to the active layer 13 can be 1:(2-1000). Setting the thickness ratio of the first conductive layer to the active layer within a suitable range can further improve the energy density of the battery, enhance cycle performance, and extend its service life while ensuring the safety performance of the battery cell. In some embodiments, the thickness ratio of the first conductive layer 1 to the active layer 13 can be, for example, 1:(2-200).

[0041] In this embodiment, the thickness ratio of the second conductive layer 2 to the active layer 13 can be 1:(2-1000). Controlling the thickness ratio of the second conductive layer to the active layer within a suitable range can ensure the battery capacity while reducing heat accumulation inside the battery, thereby reducing the risk of short circuits or overheating and improving the battery's safety performance and service life. In some embodiments, the thickness ratio of the second conductive layer 2 to the active layer 13 can be, for example, 1:(2-200).

[0042] In this embodiment, the size of the first conductive layer 1 in the length direction of the battery electrode 10 is larger than the size of the second conductive layer 2 in the length direction of the battery electrode 10. Controlling the size of the first conductive layer in the length direction of the battery electrode to be larger than the size of the second conductive layer can further improve the cycle performance of the battery cell.

[0043] In this embodiment, the ratio of the dimension of the first conductive layer 1 along the length of the battery electrode to the dimension of the second conductive layer 2 along the length of the battery electrode can be (10-1000):1. In some embodiments, the ratio of the dimension of the first conductive layer 1 along the length of the battery electrode to the dimension of the second conductive layer 2 along the length of the battery electrode can be, for example, 10:1, 15:1, 18:1, 20:1, 22:1, 25:1, 30:1, 50:1, 100:1, 200:1, 300:1, 500:1, 800:1, or 1000:1. In this embodiment, the overlap of the areas of the first conductive layer 1 and the active layer 13 projected onto the battery electrode 10 along its thickness direction is greater than or equal to 70%. The first conductive layer 1 has high conductivity and elongation, which is beneficial for better balancing the safety and charging efficiency of the battery electrode 10.

[0044] In this embodiment, the first conductive layer 1 is a first inorganic solid compound layer. This first inorganic solid compound layer is a material layer containing a first inorganic solid compound, a first binder, and a first conductive agent. Specifically, the first inorganic solid compound includes, but is not limited to, one or more of zirconium oxide, magnesium oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, boehmite, silicon oxide, silicon suboxide, gibbsite, aluminum oxide, barium sulfate, calcium sulfate, and calcium silicate. The aforementioned first inorganic solid compound possesses strong chemical and thermal stability and can be stably used in various positive and negative electrode material systems. Even when punctured or subjected to mechanical abuse, it will not short-circuit upon direct contact with the negative electrode material. The first inorganic solid compound can be a composite of one or more of spherical particles, irregular particles, porous particles, filamentous, and fibrous inorganic solid compounds.

[0045] In some embodiments, the mass of the first inorganic solid compound can be 70%-98% of the mass of the first conductive layer 1, which ensures both the safety performance of the battery and the conductivity of the first conductive layer, thereby improving energy density and charging capability. In some embodiments, the mass of the first inorganic solid compound can be, for example, 70%, 75%, 80%, 85%, 90%, 95%, or 98% of the mass of the first conductive layer 1.

[0046] In this embodiment, the preparation method of the first conductive layer 1 includes, but is not limited to, coating or spraying, including, but not limited to, the following steps: adding a first inorganic solid compound, a first binder, and a first conductive agent to a solvent, and stirring to disperse them to obtain a first mixed slurry; 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. The solvent may be water, ethanol, N-methylpyrrolidone (NMP), acetone, N,N-dimethylformamide (DMF), phenyl solvent, ethylene glycol, or furan.

[0047] In this embodiment, the second conductive layer 2 is a second inorganic solid compound layer. This second inorganic solid compound layer is a material layer containing a second inorganic solid compound, a second binder, and a second conductive agent. Specifically, the second inorganic solid compound includes, but is not limited to, one or more of zirconium oxide, magnesium oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, boehmite, silicon oxide, silicon suboxide, gibbsite, aluminum oxide, barium sulfate, calcium sulfate, and calcium silicate. The aforementioned second inorganic solid compounds possess strong chemical and thermal stability, allowing for stable use in various positive and negative electrode material systems. Even when punctured or subjected to mechanical abuse, direct contact with the negative electrode material will not cause a short circuit. The second inorganic solid compound can be a composite of one or more of spherical particles, irregular particles, porous particles, filamentous, and fibrous inorganic solid compounds.

[0048] In some embodiments, the mass of the second inorganic solid compound can be 70%-98% of the mass of the second conductive layer 2, which ensures both the safety performance of the battery and the conductivity of the second conductive layer, resulting in a more uniform current distribution throughout the battery. In some embodiments, the mass of the second inorganic solid compound can be, for example, 70%, 75%, 80%, 85%, 90%, 95%, or 98% of the mass of the second conductive layer 2.

[0049] In this application embodiment, the preparation method of the second conductive layer 2 includes, but is not limited to, coating or spraying, including, but not limited to, the following steps: adding the second inorganic solid compound, the second binder and the second 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.

[0050] In this embodiment, the active layer is selected from either the positive electrode active layer or the negative electrode active layer. The positive electrode active layer is a material layer containing a positive electrode active material, a third binder, and a third conductive agent; the negative electrode active layer is a material layer containing a negative electrode active material, a fourth binder, and a fourth conductive agent. Specifically, the positive electrode 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, and lithium nickel cobalt manganese oxide, or one or more improved materials based on the above-mentioned positive electrode active materials; the negative electrode active material includes, but is not limited to, one or more of graphite, hard carbon, silicon-based negative electrode materials, lithium metal, lithium alloy negative electrode materials, and lithium titanate, or one or more improved materials based on the above-mentioned negative electrode active materials.

[0051] In this embodiment, the mass of the positive electrode active material can be 70%-99.5% of the mass of the positive electrode active layer, which is beneficial for achieving a suitable battery capacity. In some embodiments, the mass of the positive electrode active material can be 70%, 75%, 80%, 85%, 90%, 93%, 98%, 99%, or 99.5% of the mass of the positive electrode active layer.

[0052] In this application embodiment, the preparation method of the positive electrode active layer includes, but is not limited to, coating or spraying, including, but not limited to, the following steps: adding the positive electrode active material, the third binder and the third conductive agent into a solvent, stirring and dispersing to obtain a third mixed slurry, and coating or spraying the third mixed slurry onto the surface of the base layer 12 away from the current collector 11 using a coating machine, spraying machine or wetting device.

[0053] In this embodiment, the mass of the negative electrode active material can be 70%-99.5% of the mass of the negative electrode active layer, which is beneficial for achieving appropriate battery capacity. In some embodiments, the mass of the negative electrode active material can be 70%, 80%, 85%, 90%, 93%, 98%, 99%, or 99.5% of the mass of the negative electrode active layer.

[0054] In the embodiments of this application, the preparation method of the negative electrode active layer includes, but is not limited to, coating or spraying, including, but not limited to, the following steps: adding the negative electrode active material, the fourth binder and the fourth conductive agent into a solvent, stirring and dispersing to obtain a fourth mixed slurry, and coating or spraying the fourth mixed slurry onto the surface of the base layer 12 away from the current collector 11 using a coating machine, spraying machine or wetting device.

[0055] In this application, the first, second, third, and fourth conductive agents can be independently selected from one or more of graphite conductive agents, carbon fibers, carbon nanotubes, graphene, conductive carbon black, and conductive polymers. Specifically, the graphite conductive agents include, but are not limited to, one or more of graphite, KS-6 type conductive graphite, KS-15 type conductive graphite, SFG-6 type conductive graphite, and SFG-15 type conductive graphite; the conductive carbon black includes, but is not limited to, one or more of hard carbon, acetylene black, Ketjen black, conductive carbon black Super P, conductive carbon black Super S, amorphous carbon, activated carbon, conductive carbon black 350G, and conductive carbon black BP2000. The first, second, third, and fourth conductive agents can be selected from the same or different conductive agents.

[0056] In some embodiments, the mass of the first conductive agent can be 0.1%-20% of the mass of the first conductive layer 1, which ensures the conductivity of the first conductive layer without affecting its short-circuit protection performance. In some embodiments, the mass of the first conductive agent can be, for example, 0.1%, 0.5%, 1%, 2.5%, 7.5%, 10%, 12.5%, 15%, 17.5%, or 20% of the mass of the first conductive layer 1.

[0057] In some embodiments, the mass of the second conductive agent can be 0.1%-20% of the mass of the second conductive layer 2, which can improve the conductivity of the second conductive layer without affecting its short-circuit protection performance. In some embodiments, the mass of the second conductive agent can be, for example, 0.1%, 0.5%, 1%, 2.5%, 7.5%, 10%, 12.5%, 15%, 17.5%, or 20% of the mass of the second conductive layer 2.

[0058] In some embodiments, the mass of the third conductive agent can be 0.1%-20% of the mass of the positive electrode active layer, which can improve the conductivity of the positive electrode active layer and enhance its charge-discharge capability without affecting its capacity. In some embodiments, the mass of the third conductive agent can be, for example, 0.1%, 0.5%, 1%, 2.5%, 7.5%, 10%, 12.5%, 15%, 17.5%, or 20% of the mass of the positive electrode active layer.

[0059] In some embodiments, the mass of the fourth conductive agent can be 0.1%-20% of the mass of the negative electrode active layer, which can improve the conductivity of the negative electrode active layer and enhance its charge-discharge capability without affecting its capacity. In some embodiments, the mass of the fourth conductive agent can be, for example, 0.1%, 0.5%, 1%, 2.5%, 7.5%, 10%, 12.5%, 15%, 17.5%, or 20% of the mass of the negative electrode active layer.

[0060] In this embodiment, the conductivity of the first conductive layer is greater than that of the second conductive layer. In some embodiments, the conductivity of the first conductive layer is greater than that of the active layer, and the conductivity of the second conductive layer is greater than that of the active layer.

[0061] In this application embodiment, the first adhesive, second adhesive, third adhesive, and fourth adhesive may be independently selected from one or more of the following: polyvinylidene fluoride (PVDF), polymethyl methacrylate, polyacrylonitrile, carboxymethyl cellulose, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl alcohol, polytetrafluoroethylene, polyolefins, fluorinated rubber, polyacrylamide, polymethyl methacrylate-butyl acrylate, polyvinylpyrrolidone (PVP), 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 first adhesive, second adhesive, third adhesive, and fourth adhesive may be selected from the same or different adhesives.

[0062] In some embodiments, the mass of the first adhesive can be 0.5%-20% of the mass of the first conductive layer 1, which can improve the adhesion of the first conductive layer 1 and enhance the cycle performance of the battery without affecting the conductivity of the first conductive layer. In some embodiments, the mass of the first adhesive can be 0.5%, 1%, 1.5%, 2%, 5%, 8%, 10%, 15%, or 20% of the mass of the first conductive layer 1.

[0063] In some embodiments, the mass of the second adhesive can be 0.5%-20% of the mass of the second conductive layer 2, which can improve the adhesion of the second conductive layer 2 and enhance the cycle performance of the battery without affecting the short-circuit protection performance of the second conductive layer. In some embodiments, the mass of the second adhesive can be 0.5%, 1%, 1.5%, 2%, 5%, 8%, 10%, 15%, or 20% of the mass of the second conductive layer 2.

[0064] In some embodiments, the mass of the third binder can be 0.5%-20% of the mass of the positive electrode active layer, which can improve the adhesion of the positive electrode active layer and enhance the cycle performance of the battery without affecting the capacity of the positive electrode active layer. In some embodiments, the mass of the third binder can be 0.5%, 1%, 1.5%, 2%, 5%, 8%, 10%, 15%, or 20% of the mass of the positive electrode active layer.

[0065] In some embodiments, the mass of the fourth binder can be 0.5%-20% of the mass of the negative electrode active layer, which can improve the adhesion of the negative electrode active layer and enhance the cycle performance of the battery without affecting the capacity of the negative electrode active layer. In some embodiments, the mass of the fourth binder can be 0.5%, 1%, 1.5%, 2%, 5%, 8%, 10%, 15%, or 20% of the mass of the negative electrode active layer.

[0066] In this embodiment of the application, the battery electrode 10 includes a current collector 11, a base coating 12 disposed on opposite sides of the current collector 11, and an active layer 13 disposed on the side of the base coating 12 away from the current collector 11.

[0067] In this embodiment, a first conductive layer 1 is provided on both opposite surfaces of the current collector 11, and the difference in size of the first conductive layer 1 on both opposite sides of the current collector 11 along the length of the battery electrode 10 is less than or equal to 500 mm. In some embodiments, the dimensions of the first conductive layer 1 on both opposite sides of the current collector 11 along the length of the battery electrode 10 are the same. In other embodiments, the difference in size of the first conductive layer 1 on both opposite sides of the current collector 11 along the length of the battery electrode 10 can be 10 mm, 20 mm, 50 mm, 80 mm, 100 mm, 200 mm, 300 mm, or 500 mm. In this embodiment, a second conductive layer 2 is provided on both opposite surfaces of the current collector 11, and the difference in size of the second conductive layer 2 on both opposite sides of the current collector 11 along the length of the battery electrode 10 is less than or equal to 500 mm. In some embodiments, the dimensions of the second conductive layer 2 on both opposite sides of the current collector 11 along the length of the battery electrode 10 are the same. In other embodiments, the dimensional difference between the second conductive layers 2 on opposite sides of the current collector 11 along the length of the battery electrode 10 can be 10mm, 20mm, 50mm, 80mm, 100mm, 200mm, 300mm, or 500mm. This application further improves the safety performance of the battery cell by controlling the dimensional difference between the first and second conductive layers on opposite sides of the current collector along the length of the battery electrode within a certain range.

[0068] In this embodiment, active layers 13 are provided on both opposite surfaces of the current collector 11, and the difference in size between the active layers 13 on opposite sides of the current collector 11 along the length of the battery electrode 10 is less than or equal to 500 mm. In some embodiments, the sizes of the active layers 13 on opposite sides of the current collector 11 along the length of the battery electrode 10 are consistent. In other embodiments, the difference in size between the active layers 13 on opposite sides of the current collector 11 along the length of the battery electrode 10 can be 10 mm, 20 mm, 50 mm, 80 mm, 100 mm, 200 mm, 300 mm, or 500 mm. By controlling the difference in size between the active layers on opposite sides of the current collector along the length of the battery electrode within a certain range, this application can further improve the safety performance of the battery cell.

[0069] In this embodiment, the current collector 11 is selected from aluminum foil, copper foil, nickel foil, aluminum alloy foil, copper alloy foil, or nickel alloy foil. In some embodiments, the current collector 11 is aluminum foil, and the active layer 13 is a positive electrode active layer. In other embodiments, the current collector 11 is copper foil, and the active layer 13 is a negative electrode active layer.

[0070] In this embodiment, the thickness of the current collector can be 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, the thickness of the current collector can be, for example, 1μm, 3μm, 5μm, 9μm, 10μm, 20μm, 30μm, 40μm, or 50μm.

[0071] 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.

[0072] In one embodiment of this application, the preparation of the positive electrode sheet includes: adding 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 to N-methylpyrrolidone (NMP) solvent to obtain a first mixed slurry; adding 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 to N-methylpyrrolidone (NMP) solvent to obtain a second mixed slurry; and adding 1% by mass of polyvinylidene fluoride (PVDF) binder, 1% by mass of Super P conductive agent, and 80% by mass of Super P conductive agent to NMP solvent to obtain a second mixed slurry. P conductive agent and 98% lithium cobalt oxide positive electrode active material are added to N-methylpyrrolidone (NMP) 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 opposite sides of a 9μm thick aluminum foil to obtain a first conductive layer 1, a second conductive layer 2 and an active layer 13 (positive electrode active layer), as shown in Figure 1. The active layer 13 (positive electrode active layer) completely covers the surface of the first conductive layer 1 away from the current collector 11 (aluminum foil), and the second conductive layer 2 covers the opposite sides of the aluminum foil not covered by the first conductive layer 1. There are no uncoated blank aluminum foils. After drying, the positive electrode sheet is obtained by pressing.

[0073] In one embodiment of this application, the preparation of the negative electrode sheet includes: adding 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 to N-methylpyrrolidone (NMP) solvent to obtain a first mixed slurry; adding 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 to N-methylpyrrolidone (NMP) solvent to obtain a second mixed slurry; and adding natural graphite, conductive carbon Super P... 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, second, and third mixed slurries were then coated onto specific positions on opposite sides of a 9μm thick copper foil to obtain a first conductive layer 1, a second conductive layer 2, and an active layer 13 (negative electrode active layer), as shown in Figure 1. The active layer 13 (negative electrode active layer) completely covers the surface of the first conductive layer 1 away from the current collector 11 (copper foil), and the second conductive layer 2 covers the opposite sides of the copper foil not covered by the first conductive layer 1. There are no uncoated blank copper foils. After drying, the negative electrode sheet is obtained by pressing.

[0074] 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, wherein the positive electrode and / or the negative electrode includes the battery electrode in any of the above embodiments.

[0075] The secondary battery provided by this invention contains battery electrodes that have both good safety performance and energy density, which is beneficial to improving the safety and energy density of the secondary battery.

[0076] In the 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.

[0077] In this embodiment, the thickness of the separator can be 1μm-50μm, which avoids 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 embodiments, the thickness of the separator can be, for example, 1μm, 3μm, 5μm, 8μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, or 50μm.

[0078] 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.

[0079] 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).

[0080] 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.

[0081] In this 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, 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.

[0082] 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.

[0083] This application also provides an electrical device, including the secondary battery 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.

[0084] The electrical equipment provided by this invention contains a secondary battery, which has both good safety performance and energy density, thus improving the safety and power performance of the electrical equipment and enhancing its market competitiveness.

[0085] The foregoing describes only a few preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the above teachings or the technology or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. A battery electrode, wherein, The battery electrode includes a current collector, a base coating disposed on at least one surface of the current collector, and an active layer disposed on the surface of the base coating away from the current collector; the base coating includes a first conductive layer and a second conductive layer disposed side by side along the length direction of the battery electrode, the active layer at least partially covers the surface of the first conductive layer away from the current collector, and the surface of the second conductive layer away from the current collector is at least partially not covered by the active layer; and the conductivity of the first conductive layer is greater than the conductivity of the second conductive layer.

2. The battery electrode as described in claim 1, wherein, The conductivity of the first conductive layer at 25°C is 0.1 S / m-10 S / m, and the conductivity of the second conductive layer at 25°C is 0.01 S / m-10 S / m.

3. The battery electrode as described in claim 1, wherein, The ratio of the conductivity of the first conductive layer at 25°C to the conductivity of the second conductive layer at 25°C is (1-20):

1.

4. The battery electrode as described in claim 1, wherein, The first conductive layer, when projected onto the battery electrode in the thickness direction, covers at least 70% of the active layer.

5. The battery electrode as described in claim 1, wherein, The elongation of the first conductive layer is 0.02%-2%.

6. The battery electrode as described in claim 1, wherein, The thickness of the first conductive layer is 0.2μm-15μm; the thickness of the second conductive layer is 0.2μm-15μm; and the thickness of the active layer is 0.01mm-1mm.

7. The battery electrode as described in claim 1, wherein, The thickness of the first conductive layer is 1μm-10μm; the thickness of the second conductive layer is 1μm-10μm; and the thickness of the active layer is 0.02mm-0.2mm.

8. The battery electrode as described in claim 1, wherein, The thickness ratio of the first conductive layer to the active layer is 1:(2-1000); the thickness ratio of the second conductive layer to the active layer is 1:(2-1000).

9. The battery electrode as described in claim 1, wherein, The thickness ratio of the first conductive layer to the active layer is 1:(2-200); the thickness ratio of the second conductive layer to the active layer is 1:(2-200).

10. The battery electrode as claimed in any one of claims 8 or 9, wherein, The first conductive layer and the second conductive layer have the same thickness.

11. The battery electrode as claimed in claim 1, wherein, The dimension of the first conductive layer in the length direction of the battery electrode is larger than the dimension of the second conductive layer in the length direction of the battery electrode.

12. The battery electrode as described in claim 11, wherein, The ratio of the dimension of the first conductive layer in the length direction of the battery electrode to the dimension of the second conductive layer in the length direction of the battery electrode is (10-1000):

1.

13. The battery electrode as described in claim 1, wherein, The battery electrode includes a current collector, an undercoating layer disposed on opposite sides of the current collector, and an active layer disposed on the side of the undercoating layer away from the current collector.

14. The battery electrode as described in claim 13, wherein, The current collector has a base coating and an active layer on both opposite sides of its surface. The difference in size between the first conductive layers on opposite sides of the current collector and the length of the battery electrode is less than or equal to 500 mm. The difference in size between the second conductive layers on opposite sides of the current collector and the length of the battery electrode is less than or equal to 500 mm. The difference in size between the active layers on opposite sides of the current collector and the length of the battery electrode is less than or equal to 500 mm.

15. The battery electrode as described in claim 1, wherein, The current collector is selected from aluminum foil, copper foil, nickel foil, aluminum alloy foil, copper alloy foil, or nickel alloy foil; the thickness of the current collector is 1μm-50μm; the active layer is selected from the positive electrode active layer or the negative electrode active layer.

16. A secondary battery, wherein, The secondary battery includes 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 includes a battery electrode as described in any one of claims 1-15.

17. An electrical appliance, wherein, Includes the secondary battery as described in claim 16.

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