Battery pole piece, secondary battery and electric equipment

Abstract

The utility model discloses a battery pole piece, a secondary battery and electric equipment. The battery pole piece comprises a current collector, a priming coat arranged on the surface of at least one side of the current collector, and an active layer arranged on the surface of one side, far away from the current collector, of the priming coat, the bottom coating comprises a first conducting layer and a second conducting layer which are arranged in parallel along the length direction of the battery pole piece, the active layer at least partially covers the surface of one side, far away from the current collector, of the first conducting layer, and the surface of one side, far away from the current collector, of the second conducting layer is at least partially not covered by the active layer; the conductivity of the first conductive layer is greater than that of the second conductive layer. The bottom coating is arranged on the current collector of the battery pole piece, and the bottom coating can enable the current collector, which is not covered by the active layer, of the second conductive layer to be locally short-circuited in advance when the battery pole piece is mechanically abused, so that the safety performance of the battery is improved, and the battery pole piece has relatively good conductivity and can improve the charging capability and the energy density of the battery.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to a battery electrode sheet, a secondary battery and an electrical equipment. Background Art

[0002] With the increasingly wide application of lithium secondary batteries in passenger cars and mobile electronic devices, the market and consumers have higher and higher requirements for the performance of lithium secondary batteries. To improve the safety performance of lithium secondary batteries, by coating a bottom layer on the surface of the current collector of the battery electrode sheet, it is possible to prevent the burrs on the current collector after slitting from piercing the separator, avoid the short - circuit phenomenon of the battery, and thus improve the battery safety. However, most of the components of the bottom layer used in the existing battery electrode sheets are insulating materials, and the ability of insulating materials to conduct lithium ions is poor, which will greatly increase the impedance of lithium - ion batteries, reduce the energy density of the batteries, and affect the cycle performance of the batteries. Summary of the Utility Model

[0003] In view of this, the embodiments of the present utility model provide a battery electrode sheet, a secondary battery and an electrical equipment. A bottom layer is provided on the current collector of the battery electrode sheet. When the battery electrode sheet is mechanically abused, the bottom layer can cause the current collector at the place where the second conductive layer is not covered by the active layer to have a local short - circuit in advance, improving the safety performance of the battery, and also has good conductivity, which can improve the energy density and cycle performance of the battery.

[0004] In the first aspect, the embodiments of the present utility model provide a battery electrode sheet, which includes a current collector, a bottom layer provided on at least one surface of the current collector, and an active layer provided on the surface of the bottom layer away from the current collector; the bottom layer includes a first conductive layer and a second conductive layer arranged in parallel along the length direction of the battery electrode sheet, at least part of the active layer covers the surface of the first conductive layer away from the current collector, and at least part of the surface of the second conductive layer away from the current collector is not covered by the active layer; and the conductivity of the first conductive layer is greater than that of the second conductive layer.

[0005] In the embodiment of the present utility model, 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.

[0006] In some embodiments of the present utility model, the conductivity of the first conductive layer at 25 °C is 0.5 S / m - 10 S / m, and the conductivity of the second conductive layer at 25 °C is 0.1 S / m - 5 S / cm.

[0007] In the embodiment of the present utility model, 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.

[0008] In an embodiment of the present utility model, the positive projection of the first conductive layer in the thickness direction of the battery electrode sheet covers at least more than 70% of the active layer.

[0009] In an embodiment of the present utility model, the elongation rate of the first conductive layer is 0.02%-2%.

[0010] In an embodiment of the present utility model, the thickness of the first conductive layer is 0.2 μm-15 μm; the thickness of the second conductive layer is 0.2 μm-15 μm; the thickness of the active layer is 0.005 mm-1.00 mm.

[0011] In an embodiment of the present utility model, the thickness of the first conductive layer is 1 μm-10 μm; the thickness of the second conductive layer is 1 μm-10 μm; the thickness of the active layer is 0.02 mm-0.2 mm.

[0012] In an embodiment of the present utility model, 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).

[0013] In an embodiment of the present utility model, 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).

[0014] In an embodiment of the present utility model, the first conductive layer and the second conductive layer have the same thickness.

[0015] In an embodiment of the present utility model, the size of the first conductive layer in the length direction of the battery electrode sheet is larger than the size of the second conductive layer in the length direction of the battery electrode sheet.

[0016] In an embodiment of the present utility model, the ratio of the size of the first conductive layer in the length direction of the battery electrode sheet to the size of the second conductive layer in the length direction of the battery electrode sheet is (10-1000):1.

[0017] In an embodiment of the present utility model, the battery electrode sheet includes a current collector, bottom coatings provided on opposite two side surfaces of the current collector, and an active layer provided on a surface of the bottom coating away from the current collector.

[0018] In the embodiment of the present utility model, the bottom coating and the active layer are disposed on both opposite surfaces of the current collector. The dimension difference of the first conductive layers on both opposite sides of the current collector in the length direction of the battery electrode sheet is less than or equal to 500 mm; the dimension difference of the second conductive layers on both opposite sides of the current collector in the length direction of the battery electrode sheet is less than or equal to 500 mm; the dimension difference of the active layers on both opposite sides of the current collector in the length direction of the battery electrode sheet is less than or equal to 500 mm.

[0019] In the embodiment of the present utility model, 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 1 μm - 50 μm; the active layer is selected from a positive active layer or a negative active layer.

[0020] The current collector of the battery electrode sheet provided by the present utility model is provided with a bottom coating, which has good electrochemical stability and thermal stability and can be stably used in various positive and negative electrode material systems. When the battery electrode sheet is mechanically abused, it can cause a local short circuit of the current collector at the part where the second conductive layer is not covered by the active layer in advance, improving the safety performance of the battery, and has good conductivity, which can improve the charging ability and energy density of the battery.

[0021] In a second aspect, the present utility model further provides a secondary battery, which includes a positive electrode sheet, a negative electrode sheet, and an insulating member located between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet and / or the negative electrode sheet includes the battery electrode sheet described in the first aspect.

[0022] The secondary battery provided by the present embodiment contains a battery electrode sheet, which has both good safety performance and energy density, and is beneficial to improving the safety and energy density of the secondary battery.

[0023] In a third aspect, the present utility model further provides an electrical device, which includes the secondary battery described in the second aspect.

[0024] The electrical device provided by the present embodiment contains a secondary battery, which has both good safety performance and energy density, and is beneficial to improving the safety and power performance of the electrical device and enhancing the market competitiveness of the electrical device. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings required for use in the embodiments of the present utility model will be described below.

[0026] Figure 1 It is a schematic cross-sectional structure view of a battery electrode sheet provided by an embodiment of the present utility model along its own thickness direction.

[0027] Description of the Reference Numerals in the Drawings

[0028] 10 - Battery electrode; 11 - Current collector; 12 - Bottom coating; 13 - Active layer; 1 - First conductive layer; 2 - Second conductive layer. Detailed implementation manners

[0029] The following are the preferred implementation manners of the embodiments of the present utility model. It should be noted that for those of ordinary skill in the art in the technical field, without departing from the principle of the embodiments of the present utility model, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the embodiments of the present utility model.

[0030] See Figure 1 , Figure 1 is a schematic cross-sectional structure diagram of the battery electrode 10 provided by an embodiment of the present utility model along its own thickness direction. The battery electrode 10 includes a current collector 11, a bottom coating 12 provided on at least one surface of the current collector 11, and an active layer 13 provided on the surface of the bottom coating 12 away from the current collector; the bottom coating 12 includes a first conductive layer 1 and a second conductive layer 2 arranged in parallel along the length direction of the battery electrode, at least part of the active layer 13 covers the surface of the first conductive layer 1 away from the current collector 11, and at least part of the surface of the second conductive layer 2 away from the current collector 11 is not covered by the active layer 13; and the conductivity of the first conductive layer 1 is greater than that of the second conductive layer 2.

[0031] A bottom coating 12 is provided on the current collector 11 of the battery electrode 10 provided by the embodiment of the present utility model. The bottom coating 12 includes a first conductive layer 1 and a second conductive layer 2 arranged in parallel. Among them, the first conductive layer 1 has good conductivity, which can not only improve the battery cycle performance, but also improve the charging ability and energy density of the battery. The second conductive layer 2 can cause a local short circuit of the current collector at the place where the second conductive layer 2 is not covered by the active layer in case of mechanical abuse (bending and unfolding or puncturing), thereby improving the safety performance of the battery. Both the first conductive layer 1 and the second conductive layer 2 can effectively avoid the battery short circuit phenomenon caused by the burrs on the current collector piercing the diaphragm after slitting, and improve the safety performance of the battery. In addition, the conductivity of the first conductive layer 1 is greater than that of the second conductive layer 2. A greater conductivity of the first conductive layer 1 is beneficial to ensuring the battery cycle performance, thereby improving the durability of the battery, and a smaller conductivity of the second conductive layer 2 is beneficial to improving the safety performance of the battery.

[0032] In the embodiments of the present utility model, 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, 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, 10 S / m.

[0033] In the embodiments of the present utility model, 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, 20:1.

[0034] In the embodiments of the present utility model, the orthographic projection of the first conductive layer 1 in the thickness direction of the battery electrode sheet 10 covers at least more than 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 sheet 10 covers 70%, 75%, 80%, 85%, 90%, 95%, 100% of the active layer 13.

[0035] In the embodiments of the present utility model, the elongation rate of the first conductive layer 1 is 0.02% - 2%. The measurement method of the elongation rate is to stretch the battery electrode sheet sample with a universal mechanical testing machine, measure the total deformation amount ΔL of the gauge section and the original gauge length L, and calculate the percentage of the total deformation amount ΔL of the gauge section to the original gauge length L, which is the elongation rate δ, (δ = ΔL / L × 100%). The high elongation rate of the first conductive layer 1 can enhance the peeling strength between the active layer 13 and the current collector 11, avoid the separation of the active layer 13 and the current collector 11, and improve the battery cycle performance. In some embodiments, the elongation rate 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%, 2%.

[0036] In the embodiments of the present utility model, the thickness of the first conductive layer 1 can be 0.2 μm - 15 μm, which is beneficial to the tight connection between the first conductive layer 1, the active layer 13 and the current collector 11, ensuring the safety performance of the battery, without affecting the energy density of the battery, and also beneficial to cost control. In some embodiments, the thickness of the first conductive layer 1 can be, for example, 0.2 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm or 15 μm. In some embodiments of the present utility model, the thickness of the first conductive layer 1 can be 1 μm - 10 μm. In the embodiments of the present utility model, the thickness of the second conductive layer 2 can be 0.2 μm - 15 μm, which is beneficial to the tight connection between the second conductive layer 2 and the current collector 11, ensuring the safety performance of the battery, without affecting the energy density of the battery, and also beneficial to cost control. 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 the present utility model, the thickness of the second conductive layer 2 can be 1 μm - 10 μm.

[0037] In the embodiments of the present utility model, the thicknesses of the first conductive layer 1 and the second conductive layer 2 can be the same or different.

[0038] In the embodiments of the present utility model, the thickness of the active layer can be 0.01 mm - 1 mm, which can not only ensure the capacity of the battery, but also reduce the heat accumulation inside the battery, reducing the risk of the battery short - circuiting or overheating. In some embodiments, the thickness of the active layer can be, for example, 0.01 mm, 0.02 mm, 0.04 mm, 0.045 mm, 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm. In some embodiments of the present utility model, the thickness of the active layer 13 is 0.02 mm - 0.2 mm.

[0039] In the embodiments of the present utility model, 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, while ensuring the safety performance of the battery core, further improve the energy density of the battery, and improve the cycle performance and service life. In some embodiments, the thickness ratio of the first conductive layer 1 to the active layer 13 can be, for example, 1:(2 - 200).

[0040] In the embodiments of the present utility model, 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 not only ensure the capacity of the battery, but also reduce the heat accumulation inside the battery, thereby reducing the risk of the battery short - circuiting or overheating, and improving the safety performance and service life of the battery. In some embodiments, the thickness ratio of the second conductive layer 2 to the active layer 13 can be, for example, 1:(2 - 200).

[0041] In the embodiments of the present utility model, the size of the first conductive layer 1 in the length direction of the battery electrode sheet 10 is larger than the size of the second conductive layer 2 in the length direction of the battery electrode sheet 10. Controlling the size of the first conductive layer in the length direction of the battery electrode sheet to be larger than that of the second conductive layer can further improve the cycling performance of the battery cell.

[0042] In the embodiments of the present utility model, the ratio of the size of the first conductive layer 1 in the length direction of the battery electrode sheet to the size of the second conductive layer 2 in the length direction of the battery electrode sheet can be (10 - 1000):1. In some embodiments, the ratio of the size of the first conductive layer 1 in the length direction of the battery electrode sheet to the size of the second conductive layer 2 in the length direction of the battery electrode sheet 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, 1000:1. In the embodiments of the present utility model, the area overlap degree of the orthographic projection of the first conductive layer 1 and the active layer 13 in the thickness direction of the battery electrode sheet 10 is greater than or equal to 70%. The first conductive layer 1 has high conductivity and elongation, which is beneficial to better balance the safety and charging efficiency of the battery electrode sheet 10.

[0043] In the embodiments of the present utility model, the first conductive layer 1 is a first inorganic solid compound layer. The 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 zirconia, magnesia, lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, boehmite, silicon oxide, silicon suboxide, diaspore, alumina, barium sulfate, calcium sulfate, and calcium silicate. The above - mentioned first inorganic solid compounds have strong chemical stability and thermal stability, and can be stably used in various positive and negative electrode material systems. Even when punctured by a needle or mechanically abused, they will not short - circuit when in 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.

[0044] 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 can not only ensure the safety performance of the battery, but also ensure the conductivity of the first conductive layer, improving the energy density and charging ability. 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.

[0045] In the embodiments of the present utility model, the preparation method of the first conductive layer 1 includes but is not limited to coating or spraying, and includes but is not limited to the following steps: adding the first inorganic solid compound, the first binder and the first conductive agent into a solvent, and stirring and dispersing to obtain a first mixed slurry, and coating or spraying the first mixed slurry on at least one side of the current collector 11 by a coater, a spraying machine or an infiltration device. Among them, the solvent can be water, ethanol, N-methylpyrrolidone (NMP), acetone, N,N-dimethylformamide (DMF), phenyl solvent, ethylene glycol or furan.

[0046] In the embodiments of the present utility model, the second conductive layer 2 is a second inorganic solid compound layer, and the 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 zirconia, magnesia, lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, boehmite, silicon oxide, silicon suboxide, diaspore, alumina, barium sulfate, calcium sulfate and calcium silicate. The above-mentioned second inorganic solid compounds have strong chemical stability and thermal stability and can be stably used in various positive and negative electrode material systems. Even when punctured by a needle or mechanically abused, they will not short-circuit when directly contacting the negative electrode material. 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.

[0047] 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 can not only ensure the safety performance of the battery, but also ensure the conductivity of the second conductive layer, making the current distribution of the whole battery more uniform. 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.

[0048] In the embodiments of the present utility model, the preparation method of the second conductive layer 2 includes but is not limited to coating or spraying, and includes but is not limited to the following steps: adding the second inorganic solid compound, the second binder and the second conductive agent into a solvent, and stirring and dispersing to obtain a second mixed slurry, and coating or spraying the second mixed slurry on at least one side of the current collector 11 by a coater, a spraying machine or an infiltration device.

[0049] In the embodiments of the present utility model, the active layer is selected from a positive electrode active layer or a 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 cobaltate, lithium iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadium oxyphosphate, sodium vanadium oxyphosphate, lithium nickelate, lithium manganate, lithium nickel cobalt aluminate, lithium titanate, lithium manganate, lithium nickelate, and lithium nickel cobalt manganate, and may also be one or more of the improved materials based on the above 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, and may also be one or more of the improved materials based on the above negative electrode active materials.

[0050] In the embodiments of the present utility model, 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 to achieving the appropriate capacity of the battery. 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.

[0051] In the embodiments of the present utility model, the preparation method of the positive electrode active layer includes, but is not limited to, coating or spraying, and includes, but is not limited to, the following steps: adding the positive electrode active material, the third binder, and the third conductive agent into a solvent, and stirring and dispersing to obtain a third mixed slurry, and coating or spraying the third mixed slurry on the surface of the bottom coating 12 away from the current collector 11 by a coater, a spraying machine or an infiltration device.

[0052] In the embodiments of the present utility model, 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 to achieving the appropriate capacity of the battery. 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.

[0053] In the embodiments of the present utility model, the preparation method of the negative electrode active layer includes, but is not limited to, coating or spraying, and includes, but is not limited to, the following steps: adding the negative electrode active material, the fourth binder, and the fourth conductive agent into a solvent, and stirring and dispersing to obtain a fourth mixed slurry, and coating or spraying the fourth mixed slurry on the surface of the bottom coating 12 away from the current collector 11 by a coater, a spraying machine or an infiltration device.

[0054] In the embodiments of the present utility model, the first conductive agent, the second conductive agent, the third conductive agent, and the fourth conductive agent can independently be selected from one or more of graphite conductive agents, carbon fibers, carbon nanotubes, graphene, conductive carbon blacks, 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 blacks include, but are 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 conductive agent, the second conductive agent, the third conductive agent, and the fourth conductive agent can be selected from the same one or more conductive agents, or can be selected from different one or more conductive agents.

[0055] 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 can not only ensure the conductivity of the first conductive layer but also not affect the short-circuit prevention performance of the first conductive layer 1. 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%, 20% of the mass of the first conductive layer 1.

[0056] 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 not only improve the conductivity of the second conductive layer but also not affect the short-circuit prevention performance of the second conductive layer 2. 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%, 20% of the mass of the second conductive layer 2.

[0057] 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 not only improve the conductivity of the positive electrode active layer and enhance the charge and discharge capacity but also not affect the capacity of the positive electrode active layer. 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%, 20% of the mass of the positive electrode active layer.

[0058] 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 not only improve the conductivity of the negative electrode active layer and enhance the charge and discharge capacity but also not affect the capacity of the negative electrode active layer. 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%, 20% of the mass of the negative electrode active layer.

[0059] In the embodiments of the present utility model, 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.

[0060] In the embodiments of the present utility model, the first binder, the second binder, the third binder, and the fourth binder can independently be selected from one or more of polyvinylidene fluoride (PVDF), polymethyl methacrylate, polyacrylonitrile, carboxymethyl cellulose, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl alcohol, polytetrafluoroethylene, polyolefins, fluororubber, polyacrylamide, polymethyl methacrylate-butyl acrylate, polyvinylpyrrolidone (PVP), polyvinyl alcohol, polyethylene oxide, acrylic water-soluble glue, styrene-butadiene latex, polyvinyl acetate, polyurethane, lithium acetate cellulose, lithium acetate butyrate cellulose, lithium acetate propionate cellulose, lithium cyanoethyl branched starch, lithium cyanoethyl polyvinyl alcohol, lithium cyanoethyl cellulose, lithium cyanoethyl sucrose, and lithium carboxymethyl cellulose. The first binder, the second binder, the third binder, and the fourth binder can be selected from the same one or more binders, or can be selected from different one or more binders.

[0061] In some embodiments, the mass of the first binder can be 0.5%-20% of the mass of the first conductive layer 1, which can not only improve the adhesion of the first conductive layer 1 and enhance the cycling performance of the battery, but also does not affect the conductivity of the first conductive layer. In some embodiments, the mass of the first binder can be 0.5%, 1%, 1.5%, 2%, 5%, 8%, 10%, 15%, 20% of the mass of the first conductive layer 1.

[0062] In some embodiments, the mass of the second binder can be 0.5%-20% of the mass of the second conductive layer 2, which can not only improve the adhesion of the second conductive layer 2 and enhance the cycling performance of the battery, but also does not affect the short-circuit prevention performance of the second conductive layer. In some embodiments, the mass of the second binder can be 0.5%, 1%, 1.5%, 2%, 5%, 8%, 10%, 15%, 20% of the mass of the second conductive layer 2.

[0063] 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 not only improve the adhesion of the positive electrode active layer and enhance the cycling performance of the battery, but also does not affect 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%, 20% of the mass of the positive electrode active layer.

[0064] 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 not only improve the adhesion of the negative electrode active layer and enhance the cycling performance of the battery, but also does not affect the capacity of the negative electrode active layer. In some examples, the mass of the fourth binder can be 0.5%, 1%, 1.5%, 2%, 5%, 8%, 10%, 15%, 20% of the mass of the negative electrode active layer.

[0065] In an embodiment of the present utility model, the battery electrode sheet 10 includes a current collector 11, a bottom coating 12 provided on opposite surfaces of the current collector 11, and an active layer 13 provided on a surface of the bottom coating 12 away from the current collector 11.

[0066] In an embodiment of the present utility model, first conductive layers 1 are provided on opposite surfaces of the current collector 11, and the difference in dimensions of the first conductive layers 1 on opposite sides of the current collector 11 in the length direction of the battery electrode sheet 10 is less than or equal to 500 mm. In some embodiments, the dimensions of the first conductive layers 1 on opposite sides of the current collector 11 in the length direction of the battery electrode sheet 10 are the same. In some other embodiments, the difference in dimensions of the first conductive layers 1 on opposite sides of the current collector 11 in the length direction of the battery electrode sheet 10 can be 10 mm, 20 mm, 50 mm, 80 mm, 100 mm, 200 mm, 300 mm, 500 mm. In an embodiment of the present utility model, second conductive layers 2 are provided on opposite surfaces of the current collector 11, and the difference in dimensions of the second conductive layers 2 on opposite sides of the current collector 11 in the length direction of the battery electrode sheet 10 is less than or equal to 500 mm. In some embodiments, the dimensions of the second conductive layers 2 on opposite sides of the current collector 11 in the length direction of the battery electrode sheet 10 are the same. In some other embodiments, the difference in dimensions of the second conductive layers 2 on opposite sides of the current collector 11 in the length direction of the battery electrode sheet 10 can be 10 mm, 20 mm, 50 mm, 80 mm, 100 mm, 200 mm, 300 mm, 500 mm. By controlling the difference in dimensions of the first conductive layer and the second conductive layer on opposite sides of the current collector within a certain range in the length direction of the battery electrode sheet, the safety performance of the battery cell can be further improved in this application.

[0067] In the embodiments of the present utility model, active layers 13 are provided on both opposite surfaces of the current collector 11, and the difference in the dimensions of the active layers 13 on both opposite sides of the current collector 11 in the length direction of the battery electrode sheet 10 is less than or equal to 500 mm. In some embodiments, the dimensions of the active layers 13 on both opposite sides of the current collector 11 in the length direction of the battery electrode sheet 10 are the same. In other embodiments, the difference in the dimensions of the active layers 13 on both opposite sides of the current collector 11 in the length direction of the battery electrode sheet 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 the dimensions of the active layers on both opposite sides of the current collector within a certain range in the length direction of the battery electrode sheet, the safety performance of the battery cell can be further improved in this application.

[0068] In the embodiments of the present utility model, 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.

[0069] In the embodiments of the present utility model, the thickness of the current collector can be 1 μm - 50 μm, which can not only ensure the current transmission efficiency but also facilitate the conduction and dispersion of the heat generated during the charge and discharge process of the battery, improving the safety of the battery. In some embodiments, the thickness of the current collector can be, for example, 1 μm, 3 μm, 5 μm, 9 μm, 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm.

[0070] In the embodiments of the present utility model, the current collector 11 can include an empty foil area, which can be used for tab connection and fixation.

[0071] In one embodiment of the present utility model, the preparation of the positive electrode sheet includes: adding a polyvinylidene fluoride (PVDF) binder with a mass fraction of 15%, a Super P conductive agent with a mass fraction of 5%, and a boehmite inorganic solid compound with a mass fraction of 80% into an N-methylpyrrolidone (NMP) solvent to obtain a first mixed slurry; adding a polyvinylidene fluoride (PVDF) binder with a mass fraction of 5%, a Super P conductive agent with a mass fraction of 5%, and a boehmite inorganic solid compound with a mass fraction of 90% into an N-methylpyrrolidone (NMP) solvent to obtain a second mixed slurry; adding a polyvinylidene fluoride (PVDF) binder with a mass fraction of 1%, a Super P conductive agent with a mass fraction of 1%, and a lithium cobaltate positive electrode active material with a mass fraction of 98% into 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 both opposite surfaces of an aluminum foil with a thickness of 9 μm to obtain a first conductive layer 1, a second conductive layer 2, and an active layer 13 (positive electrode active layer), as Figure 1As shown, the active layer 13 (positive electrode active layer) completely covers the surface of the first conductive layer 1 on the side away from the current collector 11 (aluminum foil), and the second conductive layer 2 covers the surfaces of the opposite sides of the aluminum foil not covered by the first conductive layer 1. There is no uncoated blank aluminum foil. After drying, a positive electrode plate is obtained by pressing.

[0072] In an embodiment of the present utility model, the preparation of the negative electrode plate includes: adding a polyvinylidene fluoride (PVDF) binder with a mass fraction of 15%, a Super P conductive agent with a mass fraction of 5%, and an alumina inorganic solid compound with a mass fraction of 80% into an N-methylpyrrolidone (NMP) solvent to obtain a first mixed slurry; adding a polyvinylidene fluoride (PVDF) binder with a mass fraction of 5%, a Super P conductive agent with a mass fraction of 5%, and an alumina inorganic solid compound with a mass fraction of 90% into an N-methylpyrrolidone (NMP) solvent to obtain a second mixed slurry; mixing natural graphite, conductive carbon Super P, sodium carboxymethyl cellulose, and styrene-butadiene rubber in a mass ratio of 100:0.5:1:1 in deionized water and stirring to obtain a third mixed slurry. The first mixed slurry, the second mixed slurry, and the third mixed slurry are respectively coated on specific positions on the surfaces of the opposite sides of a 9-μm-thick copper foil to obtain the first conductive layer 1, the second conductive layer 2, and the active layer 13 (negative electrode active layer), as Figure 1 As shown, the active layer 13 (negative electrode active layer) completely covers the surface of the first conductive layer 1 on the side away from the current collector 11 (copper foil), and the second conductive layer 2 covers the surfaces of the opposite sides of the copper foil not covered by the first conductive layer 1. There is no uncoated blank copper foil. After drying, a negative electrode plate is obtained by pressing.

[0073] The present utility model also provides a secondary battery, including a positive electrode plate, a negative electrode plate, a separator and an electrolyte located between the positive electrode plate and the negative electrode plate. The positive electrode plate and / or the negative electrode plate includes the battery electrode plate in any of the above embodiments.

[0074] The secondary battery provided by the present embodiment contains a battery electrode plate, which has both good safety performance and energy density, and is beneficial to improving the safety and energy density of the secondary battery.

[0075] In the embodiment of the present utility model, the separator includes, but is not limited to, one or more of a polyethylene (PE) separator, a polypropylene (PP) separator, a polyimide separator, a polyvinylidene fluoride separator, a vinylidene fluoride-hexafluoropropylene separator, a polyacrylonitrile separator, and a polymethyl methacrylate separator.

[0076] In the embodiments of the present utility model, the thickness of the separator can be 1 μm - 50 μm, which can not only avoid direct contact between the positive and negative electrodes and prevent the risk of short circuit inside the battery, but also ensure the charge conduction and ion transport efficiency between the positive and negative electrodes. In some embodiments, the thickness of the separator can be, for example, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm.

[0077] In the embodiments of the present utility model, the electrolyte includes, but is not limited to, any one of traditional liquid electrolytes, ionic liquid electrolytes, gelled electrolytes, water-in-lithium-salt electrolytes and solid electrolytes.

[0078] In the embodiments of the present utility model, 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 perfluorobutanesulfonate, lithium chloroaluminate, lithium fluorosulfonimide, lithium perfluoroalkyltrifluoroborate, lithium perfluoroalkylpentafluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(fluorosulfonyl)imide (LiFSI), lithium chloride and lithium nitrate; the ionic liquid can be one or more of imidazole-based ionic liquids, pyrrole-based ionic liquids, piperidine-based ionic liquids, quaternary ammonium-based ionic liquids, quaternary phosphonium-based ionic liquids and sulfonylimide-based ionic liquids (TFS).

[0079] In the embodiments of the present utility model, the traditional liquid electrolyte includes a lithium salt and an electrolyte solvent. Specifically, the electrolyte solvent can be one or more of deionized water, ethyl methyl 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.

[0080] In the embodiments of the present utility model, the secondary battery further includes a battery case for encapsulating the positive electrode sheet, the negative electrode sheet, the electrolyte and the separator. In some embodiments, the battery case includes, but is not limited to, a steel case, an aluminum case, an aluminum-plastic film case, an aluminum alloy case or a steel alloy case.

[0081] In the embodiments of the present utility model, the preparation of the secondary battery may be to form an electrode assembly by winding or laminating a positive electrode sheet, a separator, and a negative electrode sheet, then place the electrode assembly in a battery case, and add a conventional liquid electrolyte, an ionic liquid electrolyte, a gelled electrolyte, or a lithium salt-in-water electrolyte after drying, and obtain the secondary battery through processes such as encapsulation, aging, and formation. The preparation of the secondary battery may also be to coat a solid electrolyte on the positive electrode sheet and the negative electrode sheet, form an electrode assembly by winding or laminating, then place the electrode assembly in a battery case, and obtain the secondary battery through processes such as encapsulation, aging, and formation after drying.

[0082] The present utility model 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, an electric vehicle, an electric motorcycle, an electric bicycle, a mobile power supply, a drone, a mobile phone, a computer, a camera, a power tool, a smart home, or a wearable device.

[0083] The electrical device provided by the present embodiment contains a secondary battery, which has both good safety performance and energy density, is beneficial to improving the safety and power performance of the electrical device, and enhancing the market competitiveness of the electrical device.

[0084] The above only expresses several preferred embodiments of the present utility model. However, as described above, it should be understood that the present utility model is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications, and environments, and can be changed within the scope of the inventive concept described herein through the above teachings or the techniques or knowledge in related fields. Any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present utility model shall fall within the protection scope of the appended claims of the present utility model.

Claims

1. A battery pole piece, characterized in that: The battery electrode sheet includes a current collector, a primer layer disposed on at least one side of the current collector, and an active layer disposed on a side of the primer layer away from the current collector; the primer layer includes a first conductive layer and a second conductive layer disposed in parallel along the length direction of the battery electrode sheet, the active layer at least partially covers a side of the first conductive layer away from the current collector, and a side of the second conductive layer away from the current collector is at least partially not covered by the active layer; and the electrical conductivity of the first conductive layer is greater than the electrical conductivity of the second conductive layer.

2. The battery pole piece according to claim 1, characterized in that: The electrical conductivity of the first conductive layer at 25° C. is 0.1 S / m-10 S / m, and the electrical conductivity of the second conductive layer at 25° C. is 0.01 S / m-10 S / m.

3. The battery pole piece according to claim 1, characterized in that: The ratio of the electrical conductivity of the first conductive layer at 25° C. to the electrical conductivity of the second conductive layer at 25° C. is (1-20):

1.

4. The battery pole piece according to claim 1, characterized in that: The orthographic projection of the first conductive layer in the thickness direction of the battery electrode sheet covers at least 70% of the active layer.

5. The battery pole piece according to claim 1, characterized in that: The elongation of the first conductive layer is 0.02%-2%.

6. The battery pole piece according to claim 1, characterized in that: The thickness of the first conductive layer is 0.2 μm-15 μm; the thickness of the second conductive layer is 0.2 μm-15 μm; and the thickness of the active layer is 0.01 mm-1 mm.

7. The battery pole piece according to claim 1, characterized in that: The thickness of the first conductive layer is 1 μm-10 μm; the thickness of the second conductive layer is 1 μm-10 μm; and the thickness of the active layer is 0.02 mm-0.2 mm.

8. The battery pole piece according to claim 1, characterized in that: 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 pole piece according to claim 1, characterized in that: 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 pole piece according to any one of claims 8 or 9, characterized in that: The first conductive layer and the second conductive layer have the same thickness.

11. The battery pole piece according to claim 1, characterized in that: The dimension of the first conductive layer in the length direction of the battery electrode sheet is greater than the dimension of the second conductive layer in the length direction of the battery electrode sheet.

12. The battery pole piece according to claim 11, characterized in that: The ratio of the size of the first conductive layer in the length direction of the battery electrode sheet to the size of the second conductive layer in the length direction of the battery electrode sheet is (10-1000):

1.

13. The battery pole piece according to claim 1, characterized in that: The battery pole piece comprises a current collector, a base coating layer arranged on two opposite sides of the current collector, and an active layer arranged on a side of the base coating layer away from the current collector.

14. The battery pole piece according to claim 13, characterized in that: The base coating and the active layer are provided on the opposite side surfaces of the current collector, the difference in size between the first conductive layers on the opposite sides of the current collector in the length direction of the battery electrode sheet is less than or equal to 500 mm; the difference in size between the second conductive layers on the opposite sides of the current collector in the length direction of the battery electrode sheet is less than or equal to 500 mm; the difference in size between the active layers on the opposite sides of the current collector in the length direction of the battery electrode sheet is less than or equal to 500 mm.

15. The battery pole piece according to claim 1, characterized in that: 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 1 μm-50 μm; and the active layer is selected from a positive electrode active layer or a negative electrode active layer.

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

17. An electrical equipment, characterized in that: Includes the secondary battery as claimed in claim 16.

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