Pole piece, secondary battery and electric device

Abstract

The invention discloses a pole piece, a secondary battery and an electric device, and belongs to the technical field of batteries, the pole piece comprises a current collector, an active material layer and a carbon material layer, the active material layer and the carbon material layer are sequentially arranged on at least one surface of the current collector, b / a is controlled to be greater than or equal to 2 and less than or equal to 20, and the carbon material layer forms a conductive network on the surface of the active material layer, so that the internal resistance is effectively reduced; the preparation method has the advantages of improving the electron transmission efficiency, effectively improving the rapid heat dissipation performance of the pole piece, effectively inhibiting the volume expansion of the active material in the charging and discharging process, protecting the current collector and the active material layer to a certain extent, improving the ion diffusion rate, shortening the ion diffusion path and improving the service life. And the safety, the cycling stability and the first effect of the pole piece are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to an electrode sheet, a secondary battery, and an electrical device. Background Art

[0002] In recent years, due to advantages such as strong fast charging ability and high energy density, secondary batteries have received attention in both 3C products, and fields such as electric vehicles and energy storage. As the market share of secondary batteries becomes higher and higher, the safety problems they face need to be solved urgently.

[0003] The safety problems of secondary batteries are mainly caused by battery thermal runaway. That is, heat is released due to some abnormal reaction inside the secondary battery, and due to insufficient heat dissipation capacity inside the secondary battery, the internal temperature continues to rise, further accumulating heat, and then triggering more heat-generating side reactions, resulting in the secondary battery catching fire or even exploding, thus seriously threatening the life and property safety of users.

[0004] In view of this, the present application is proposed. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide an electrode sheet, a secondary battery, and an electrical device, and the electrode sheet has excellent safety, cycle stability, and first efficiency.

[0006] To achieve the above purpose, in the first aspect of the present invention, the present invention provides an electrode sheet, including a current collector and an active material layer and a carbon material layer sequentially arranged on at least one surface of the current collector, the carbon material layer including a carbon material and a metal; the metal includes at least one of gallium, cobalt, palladium, ruthenium, platinum, and copper; the single-layer thickness of the carbon material is a, and the thickness of the carbon material layer is b, satisfying: 2 ≤ b / a ≤ 20.

[0007] As an embodiment of the present application, at least one of the following (Ⅰ) to (Ⅱ) is satisfied:

[0008] (Ⅰ) 0.7 nm ≤ a ≤ 1 nm;

[0009] (Ⅱ) 1 nm ≤ b ≤ 15 nm.

[0010] As an embodiment of the present application, the mass percentage content of the metal in the carbon material layer ≤ 0.2%.

[0011] As an embodiment of the present application, the carbon material includes at least one of graphene and carbon nanotubes.

[0012] As an embodiment of the present application, the porosity of the carbon material layer is 0.1 to 35%, preferably 0.1 to 1.5%, more preferably 0.5 to 1%.

[0013] As an embodiment of the present application, the interlayer spacing of the carbon material is 0.34 to 0.36 nm.

[0014] As an embodiment of the present application, the current collector includes a substrate layer and a carbon-coated layer located on at least one surface of the substrate layer; the carbon-coated layer includes the following components in parts by weight: 50 to 70% of a conductive agent and 30 to 50% of a binder.

[0015] As an embodiment of the present application, at least one of the following (Ⅲ) to (Ⅴ) is satisfied:

[0016] (Ⅲ) The thickness of the substrate layer is 6 to 15 μm;

[0017] (Ⅳ) The thickness of the carbon-coated layer is 1 to 15 μm;

[0018] (Ⅴ) The substrate layer includes one of aluminum, copper, silver, nickel, zinc, magnesium, zirconium, cobalt, titanium, and tantalum.

[0019] In the second aspect of the present invention, the present invention provides a method for preparing a pole piece, including the following steps:

[0020] Coat an active slurry on at least one surface of the current collector to form an active material layer;

[0021] Place the catalyst in a CVD reaction chamber, introduce an inert gas, heat-treat the catalyst, then introduce a hydrocarbon carbon source gas for reaction, cool down, and keep warm to grow a carbon material on the surface of the active material layer, and perform secondary rolling to form a carbon material layer.

[0022] As an embodiment of the present application, at least one of the following (Ⅵ) to (Ⅺ) is satisfied:

[0023] (Ⅵ) The flow rate of the inert gas introduced is 100 to 300 sccm;

[0024] (Ⅶ) The temperature of the heat treatment is 700 to 1200 °C, and the heat treatment time is 4 to 10 min;

[0025] (Ⅷ) The flow rate of the hydrocarbon carbon source gas introduced is 100 to 300 sccm;

[0026] (Ⅸ) The reaction temperature time is 5 to 10 min;

[0027] (Ⅹ) The heat preservation temperature is 50 to 200 °C, and the heat preservation time is 4 to 10 min;

[0028] (Ⅺ) The growth time is 5 to 10 min;

[0029] (Ⅻ) The purity of the hydrocarbon carbon source gas is ≥99.99%.

[0030] In a third aspect of the present invention, the present invention provides a secondary battery, including the electrode sheet described above.

[0031] In a fourth aspect of the present invention, the present invention provides an electrical device, including the secondary battery described above.

[0032] The beneficial effects of the present invention are as follows: The electrode sheet of the present application includes a current collector and an active material layer and a carbon material layer sequentially arranged on at least one surface of the current collector. By controlling 2 ≤ b / a ≤ 20, the carbon material layer forms a conductive network on the surface of the active material layer, effectively reducing the internal resistance, improving the electron transfer efficiency, effectively improving the rapid heat dissipation performance of the electrode sheet, effectively suppressing the volume expansion of the active material (such as the positive electrode active material and the negative electrode active material) during charge and discharge, and at the same time having a certain protective effect on the current collector and the active material layer, improving the ion diffusion rate, shortening the ion diffusion path, and effectively improving the safety, cycle stability and initial efficiency of the electrode sheet. Detailed Embodiments

[0033] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0034] In the present application, among the technically characterized described in an open-ended manner, it includes a closed technical solution composed of the listed features, and also includes an open technical solution containing the listed features.

[0035] In the present application, regarding the numerical range, unless otherwise specified, the above numerical range is considered continuous, and includes the minimum value and the maximum value of the range, as well as each value between such minimum value and maximum value. Further, when the range refers to an integer, it includes each integer between the minimum value and the maximum value of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0036] In the present application, there is no particular limitation on the specific dispersion and stirring treatment methods.

[0037] Unless otherwise specified, the component raw materials or instruments used in each embodiment and comparative example of the present invention are all commercially available raw materials or instruments, and the component raw materials used in each parallel experiment are the same.

[0038] In order to improve the thermal runaway problem of lithium-ion batteries, the prior art modifies the main materials with graphene before batching to reduce the heat generation of the battery and improve the safety performance of the battery. However, in actual production, graphene is prone to agglomeration during batching, and its size and structure are easily damaged during rapid dispersion, resulting in graphene being unable to effectively exert its effects, and its heat dissipation and conductivity are far less than expected. The prior art improves from the level of the electrode sheet, and performs a safety coating treatment on the surface of the active material of the positive and negative electrode sheets to prepare a safety-coated electrode sheet. This safety coating uses insulating particles, which is not conducive to fast charging and high-rate discharging of the battery. The prior art sets a heat insulation layer between the electrode sheet and the current collector, which effectively prevents heat from diffusing from the current collector to the positive or negative electrode active material layer. However, the conductivity of this heat insulation layer is not ideal. The prior art directly obtains a graphene layer on the surface of the positive electrode active material layer by chemical vapor deposition. The temperature for forming the graphene layer is 600-900°C, and at the same time, it requires ultraviolet light irradiation, which will damage the structure of the positive electrode active material layer, thereby resulting in a decline in electrochemical performance.

[0039] Therefore, based on the above problems, an electrode sheet provided by an embodiment of the present application includes a current collector and an active material layer and a carbon material layer sequentially provided on at least one surface of the current collector. The carbon material layer includes a carbon material and a metal. The metal includes at least one of gallium, cobalt, palladium, ruthenium, platinum, and copper. The single-layer thickness of the carbon material is a, and the thickness of the carbon material layer is b, satisfying: 2≤b / a≤20. For example, it can be a range composed of any two values among 2, 4, 5, 6, 8, 10, 12, 14, 15, 16, 18, and 20.

[0040] The electrode sheet of the present application includes a current collector and an active material layer and a carbon material layer sequentially provided on at least one surface of the current collector. By controlling 2≤b / a≤20, the carbon material layer forms a conductive network on the surface of the active material layer, effectively reducing the internal resistance, improving the electron transfer efficiency, effectively improving the fast heat dissipation performance of the electrode sheet, effectively suppressing the volume expansion of the active material (such as the positive electrode active material and the negative electrode active material) during charge and discharge, and at the same time having a certain protective effect on the current collector and the active material layer, improving the ion diffusion rate, shortening the ion diffusion path, and effectively improving the safety, cycle stability, and initial efficiency of the electrode sheet.

[0041] In one embodiment, 4≤b / a≤16. For example, it can be a range composed of any two values among 4, 5, 6, 8, 10, 12, 14, 15, and 16.

[0042] In one embodiment, 0.7 nm ≤ a ≤ 1 nm. For example, it can be 0.7 nm, 0.75 nm, 0.8 nm, 0.85 nm, 0.9 nm, 0.95 nm, 1 nm, or a range composed of any two of these values. By controlling a within this range, the conductivity of the carbon material layer can be further improved, a more dense conductive network structure can be formed, and the safety, cycle stability, and initial efficiency of the electrode sheet can be further improved.

[0043] In one embodiment, 1 nm ≤ b ≤ 15 nm. For example, it can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, or a range composed of any two of these values. By controlling b within this range, the ion diffusion rate can be increased, the ion diffusion path can be shortened, the structural stability of the carbon material layer can be improved, a better protective effect can be achieved, and the safety, cycle stability, and initial efficiency of the electrode sheet can be further improved.

[0044] In one embodiment, the mass percentage content of the metal in the carbon material layer ≤ 0.2%. The carbon material layer has a low metal impurity content, which can effectively avoid oxidation reactions during charging, effectively improve the structural stability of the electrode sheet, and effectively improve the safety performance, cycle stability, and initial efficiency of the electrode sheet.

[0045] In one embodiment, the carbon material includes at least one of graphene and carbon nanotubes.

[0046] In one embodiment, the porosity of the carbon material layer is 0.1 - 35%. For example, it can be 0.1%, 0.5%, 1%, 1.5%, 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, or a range composed of any two of these values.

[0047] In one embodiment, the porosity of the carbon material layer is 0.1 - 1.5%.

[0048] In one embodiment, the porosity of the carbon material layer is 0.5 - 1%.

[0049] In one embodiment, the interlayer spacing of the carbon material is 0.34 - 0.36 nm.

[0050] Among them, the interlayer spacing of the carbon material, the single-layer thickness of the carbon material, and the thickness of the carbon material layer described in this application are all obtained through projective TEM testing.

[0051] Among them, the porosity of the carbon material layer is imaged on the cross-section or surface of the carbon material layer by a scanning electron microscope (SEM), and the porosity of the carbon material layer can be obtained by analyzing with AVIZO software.

[0052] In one embodiment, the current collector includes a substrate layer and a carbon-coated layer located on at least one surface of the substrate layer; the carbon-coated layer includes the following components in parts by weight: 50-70% conductive agent, 30-50% binder.

[0053] In one embodiment, the thickness of the substrate layer is 6-15 μm, for example, it can be 6 μm, 8 μm, 10 μm, 12 μm, 15 μm or a range composed of any two of these values.

[0054] In one embodiment, the thickness of the carbon-coated layer is 1-15 μm, for example, it can be 1 μm, 2 μm, 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 15 μm or a range composed of any two of these values. In one embodiment, the substrate layer includes one of aluminum, copper, silver, nickel, zinc, magnesium, zirconium, cobalt, titanium, tantalum.

[0055] In one embodiment, the form of the substrate layer is not particularly limited. The form of the substrate layer can be a metal foil, a metal cylinder, a metal strip coil, a metal plate, a metal foil, a metal plate mesh, a stamped metal, a foamed metal, etc.

[0056] In one embodiment, the active material layer includes a positive electrode active material layer or a negative electrode active material.

[0057] In one embodiment, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material can adopt the positive electrode active materials known in the art for secondary batteries. As a non-limiting example, the positive electrode active material can include lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials or substances, and other conventional materials or substances that can be used as positive electrode active materials for secondary batteries can also be used. These positive electrode active substances can be used alone or in combination of two or more. Among them, non-limiting examples of lithium transition metal oxides can include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds, etc.

[0058] In one embodiment, the positive electrode active material layer further includes a conductive agent and a binder.

[0059] In one embodiment, the negative electrode active material layer includes a negative electrode active material, which may be at least one of natural graphite, artificial graphite, mesophase carbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , spinel-structured lithium titanate Li 4 Ti 5 O 12 , Li-Al alloy, metallic lithium, etc.

[0060] In one embodiment, the negative electrode active material layer further includes a conductive agent and a binder.

[0061] In one embodiment, the type of the conductive agent mentioned in the present application is not limited, and known conductive agents can be used.

[0062] In one embodiment, the conductive agent includes at least one of carbon materials such as acetylene black, needle coke, carbon nanotubes, and graphene.

[0063] In one embodiment, the type of the binder mentioned in the present application is not limited, and known binders can be used.

[0064] In one embodiment, the binder includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose, styrene-butadiene rubber, nitrile rubber, fluororubber, isoprene rubber, polybutadiene rubber, ethylene-propylene rubber, polyvinyl acetate, ethylene-vinyl acetate copolymer, propylene-α-olefin copolymer, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene difluoride, and polytetrafluoroethylene-ethylene copolymer.

[0065] One embodiment of the present application provides a method for preparing a pole piece, including the following steps:

[0066] Coating an active slurry on at least one surface of a current collector to form an active material layer;

[0067] Putting a catalyst into a CVD reaction chamber, introducing an inert gas, heat-treating the catalyst, then introducing a hydrocarbon carbon source gas for reaction, cooling down, and keeping warm to grow carbon materials on the surface of the active material layer, and performing secondary rolling to form a carbon material layer.

[0068] The present application creatively grows a carbon material layer in situ on the surface of the active material layer, which can form a more uniform and dense conductive network structure, effectively improve the heat dissipation effect on the surface of the electrode sheet. Compared with directly adding carbon materials during batching, it can effectively avoid the agglomeration of carbon materials and prevent the destruction of the lamellar structure of carbon materials during stirring and dispersion, effectively increase the content of carbon materials in the carbon material layer. Moreover, in the CVD reaction process of the present invention, a catalyst is introduced, which can effectively reduce the reaction temperature, avoid the destruction of the structure of the active material layer, effectively improve the rapid heat dissipation ability of the electrode sheet, and enhance safety and electrochemical performance.

[0069] In one embodiment, the flow rate of the inert gas introduced is 100 - 300 sccm, for example, it can be 100 sccm, 120 sccm, 150 sccm, 180 sccm, 200 sccm, 220 sccm, 250 sccm, 280 sccm, 300 sccm or the range composed of any two of these values. Among them, representative inert gases include nitrogen, argon and the mixed gas composed of them.

[0070] In one embodiment, the temperature of the heat treatment is 700 - 1200 °C, for example, it can be 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, 950 °C, 1000 °C, 1050 °C, 1100 °C, 1200 °C or the range composed of any two of these values.

[0071] In one embodiment, the heat treatment time is 4 - 10 min, for example, it can be 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min or the range composed of any two of these values.

[0072] In one embodiment, the flow rate of the hydrocarbon carbon source gas introduced is 100 - 300 sccm, for example, 100 sccm, 120 sccm, 150 sccm, 180 sccm, 200 sccm, 220 sccm, 250 sccm, 280 sccm, 300 sccm or the range composed of any two of these values.

[0073] In one embodiment, the hydrocarbon carbon source gas includes at least one of methane, ethane, propane, ethylene, acetylene.

[0074] In one embodiment, the purity of the hydrocarbon carbon source gas ≥ 99.99%.

[0075] In one embodiment, the reaction temperature time is 5 - 10 min, for example, it can be 5 min, 6 min, 7 min, 8 min, 9 min, 10 min or the range composed of any two of these values.

[0076] In one embodiment, the heat preservation temperature is 50 to 200 °C, for example, it can be 50 °C, 60 °C, 80 °C, 100 °C, 120 °C, 150 °C, 180 °C, 200 °C or the range composed of any two of these values.

[0077] In one embodiment, the heat preservation time is 4 to 10 min, for example, it can be 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min or the range composed of any two of these values.

[0078] In one embodiment, the growth time is 5 to 10 min, for example, it can be 5 min, 6 min, 7 min, 8 min, 9 min, 10 min or the range composed of any two of these values.

[0079] In one embodiment, for the secondary rolling, the first rolling is to 75 to 85% of the designed thickness of the electrode sheet, and the second rolling is to the designed thickness of the electrode sheet. The present invention adopts secondary rolling to avoid the destruction of the structure of the carbon material layer.

[0080] In one embodiment, the purity of the hydrocarbon carbon source gas ≥ 99.99%.

[0081] More specifically, the method for preparing the electrode sheet includes the following steps:

[0082] Coating an active slurry on at least one surface of the current collector to form an active material layer;

[0083] The CVD reaction chamber is provided with three layers, namely a catalytic layer (catalyst placement area), a zero lower layer (quenching and cooling), and a growth layer (the current collector is placed in this layer), so as to facilitate the setting of the temperature gradient. First, the catalyst is placed in the catalytic layer, an inert gas is introduced, the catalytic layer is heat-treated, then the hydrocarbon carbon source gas is introduced for reaction. After the reaction, the catalyst enters the zero lower layer for quenching and cooling, and then enters the growth layer for heat preservation. A mixed gas of nitrogen and carbon source gas is purged from the upper end of the catalyst, and carbon materials are grown on the surface of the active material layer, and then secondary rolling is carried out to form a carbon material layer.

[0084] One embodiment of the present application provides a secondary battery including the above-mentioned electrode sheet.

[0085] It should be noted that when the active material layer includes a positive electrode active material layer, the electrode sheet is a positive electrode sheet; the positive electrode sheet can be paired with a conventional negative electrode sheet in the art.

[0086] It should be noted that when the active material layer includes a negative electrode active material layer, the electrode sheet is a negative electrode sheet, and the positive electrode sheet can be paired with a conventional positive electrode sheet in the art, or the negative electrode sheet can be paired with the above-mentioned positive electrode sheet.

[0087] In one embodiment, the secondary battery further includes an electrolyte, and the type of the electrolyte is not particularly limited. Among them, the electrolyte includes an electrolyte salt and an organic solvent, and the specific types of the electrolyte salt and the organic solvent are not particularly limited and can be selected according to actual needs. The electrolyte may further include additives, and the types of the additives are not particularly limited, and may be film-forming additives for the positive electrode and / or the negative electrode, or additives that can improve certain performance of the battery, such as additives for improving the high or low temperature performance of the battery.

[0088] In one embodiment, the secondary battery may include an outer package, and the outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0089] In one embodiment, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, and as plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed, etc.

[0090] The present application does not particularly limit the shape of the secondary battery, and it can be cylindrical, square, or any other shape.

[0091] One embodiment of the present application provides an electrical device, including the above-mentioned secondary battery, and the secondary battery serves as a power supply for the electrical device.

[0092] Exemplarily, the above-mentioned electrical device may include mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto.

[0093] The following further elaborates the present application with specific examples:

[0094] Example 1

[0095] A method for preparing a secondary battery includes the following steps:

[0096] (1) Preparation of the positive electrode sheet

[0097] Using carbon-coated aluminum foil as the current collector, the carbon-coated aluminum foil includes an aluminum foil and carbon coating layers located on both surfaces of the aluminum foil. The thickness of the aluminum foil is 8 μm, the thickness of the carbon coating layer on one side is 1.5 μm, and the thickness of the entire carbon-coated aluminum foil current collector is 11 μm. The carbon coating layer includes conductive carbon black and PVDF with a mass ratio of 60:40.

[0098] The cathode active material nickel cobalt manganese (NCM811), conductive agent Super-P, and binder PVDF are uniformly dispersed in the solvent NMP according to a mass ratio of 97:2:1 to prepare a cathode active material slurry. The cathode active material slurry is uniformly coated on both sides of the carbon-coated aluminum foil and dried to form a cathode active material layer with a single-sided areal density of 290 g / 1540.25 cm 2 , and the tap density of the cathode active material layer is 3.8 g / cm 3 ;

[0099] The CVD reaction chamber is set up in three layers, namely the catalytic layer (catalyst placement area), the zero lower layer (quenching and cooling), and the growth layer (current collector placed in this layer). First, the molten metal gallium catalyst is placed in the catalytic layer, nitrogen is introduced at 200 sccm, and the catalytic layer is heat-treated at 900 °C for 5 min. Then, high-purity 99.99% ethane carbon source gas is introduced at 200 sccm for reaction. The reacted catalyst enters the zero lower layer for quenching and cooling to 150 °C, and then enters the growth layer for heat preservation. A mixed gas of nitrogen and carbon source gas is purged from the upper end of the catalyst, and carbon materials are grown on the surface of the active material layer for 5 min. Double roll pressing (the thickness of the first roll pressing is four-fifths of the designed thickness of the electrode sheet, and the second roll pressing reduces the thickness to the designed thickness of the electrode sheet (the designed thickness is the thickness in Table 1). Both roll pressings are cold pressings) is performed to form a graphene layer.

[0100] (2) Preparation of the anode electrode sheet: Graphite, conductive agent SP, binder SBR, and CMC are mixed evenly with deionized water according to a mass ratio of 96:1:2:1 to obtain an anode active material slurry. The anode active material slurry is coated on an 8-μm copper foil to make an anode electrode sheet, and the tap density of the anode active material layer is 1.55 g / cm 3 .

[0101] (3) The electrolyte is 1 mol / L LiPF 6 in EC / DMC / DEC with a volume ratio of v:v:v = 1:1:1.

[0102] (4) The separator is a 5-μm PE + 1-μm single-sided ceramic membrane.

[0103] (5) Assembly of the secondary battery: The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet. After winding, hot pressing and shaping, and tab welding, a bare battery cell is obtained. The bare battery cell is placed in an outer packaging aluminum-plastic film and baked in an oven at 85 ± 10 °C for 24 h. The electrolyte prepared above is injected into the dried battery, and after standing, forming, and grading, the preparation of the secondary battery is completed.

[0104] Among them, the parameters of Example 1 are shown in Table 1.

[0105] Example 2

[0106] The difference between Example 2 and Example 1 lies in the different preparation methods of the positive electrode sheet.

[0107] In the preparation method of the positive electrode sheet of this example, the hydrocarbon carbon source gas introduced is ethylene with a purity of 99.99%.

[0108] Example 3

[0109] The difference between Example 3 and Example 1 lies in the different preparation methods of the positive electrode sheet.

[0110] In the preparation method of the positive electrode sheet of this example, the hydrocarbon carbon source gas introduced is acetylene with a purity of 99.99%.

[0111] Example 4

[0112] The difference between Example 4 and Example 1 lies in the different preparation methods of the positive electrode sheet.

[0113] The preparation method of the positive electrode sheet of this example includes the following steps: The CVD reaction chamber is set with three layers, namely the catalytic layer (catalyst placement area), the zero lower layer (quenching and cooling), and the growth layer (current collector placed in this layer). First, the molten metal Co catalyst is placed in the catalytic layer, nitrogen is introduced at 200 sccm, and the catalytic layer is heat-treated at 1100 °C for 5 min. Then, high-purity ethane carbon source gas with a purity of 99.99% is introduced at 200 sccm for reaction. After the reaction, the catalyst enters the zero lower layer for quenching and cooling to 150 °C. The reacted catalyst then enters the growth layer, keeps warm, and a mixed gas of nitrogen and carbon source gas is purged from the upper end of the catalyst, and carbon materials are grown on the surface of the active material layer. The growth time is 5 min, and then roll pressing is carried out to form a graphene layer.

[0114] Example 5

[0115] The difference between Example 5 and Example 1 lies in the different preparation methods of the positive electrode sheet.

[0116] The preparation method of the positive electrode plate in this embodiment includes the following steps: The CVD reaction chamber is set up in three layers, namely the catalytic layer (catalyst placement area), the zero lower layer (quenching and cooling), and the growth layer (current collector placed in this layer). First, the molten metal Pd catalyst is placed in the catalytic layer, nitrogen is introduced at 200 sccm, the catalytic layer is heat-treated at 1000 °C for 5 min, and then high-purity 99.99% ethane carbon source gas is introduced at 200 sccm for reaction. The reacted catalyst enters the zero lower layer for quenching and cooling to 150 °C, and then enters the growth layer. After heat preservation, the mixed gas of nitrogen and carbon source gas is purged from the upper end of the catalyst, and carbon materials are grown on the surface of the active material layer. The growth time is 5 min, and then rolling is carried out to form a graphene layer.

[0117] Example 6

[0118] The difference between Example 6 and Example 1 lies in the different preparation methods of the positive electrode plate.

[0119] The preparation method of the positive electrode plate in this embodiment includes the following steps: The CVD reaction chamber is set up in three layers, namely the catalytic layer (catalyst placement area), the zero lower layer (quenching and cooling), and the growth layer (current collector placed in this layer). First, the molten metal Ru catalyst is placed in the catalytic layer, nitrogen is introduced at 200 sccm, the catalytic layer is heat-treated at 1200 °C for 5 min, and then high-purity 99.99% ethane carbon source gas is introduced at 200 sccm for reaction. The reacted catalyst enters the zero lower layer for quenching and cooling to 150 °C, and then enters the growth layer. After heat preservation, the mixed gas of nitrogen and carbon source gas is purged from the upper end of the catalyst, and carbon materials are grown on the surface of the active material layer. The growth time is 5 min, and then double rolling (the thickness of the first rolling is four-fifths of the designed thickness of the electrode plate, and the second rolling reduces the thickness to the designed thickness of the electrode plate. Both rollings are cold rollings) is carried out to form a graphene layer.

[0120] Example 7

[0121] The difference between Example 7 and Example 1 lies in the different preparation methods of the positive electrode plate.

[0122] The CVD reaction chamber is set with three layers, namely the catalytic layer (catalyst placement area), the zero lower layer (quenching and cooling), and the growth layer (current collector placed in this layer). First, the molten metal gallium catalyst is placed in the catalytic layer, nitrogen is introduced at 100 sccm, the catalytic layer is heat-treated at 900 °C for 5 min, and then high-purity 99.99% ethane carbon source gas is introduced at 100 sccm for reaction. The reacted catalyst enters the zero lower layer for quenching and cooling to 150 °C, and then enters the growth layer for heat preservation. The mixed gas of nitrogen and carbon source gas is purged from the upper end of the catalyst, and carbon materials are grown on the surface of the active material layer. The growth time is 5 min. Double rolling (the thickness of the first rolling is four-fifths of the designed thickness of the electrode sheet, and the second rolling reduces the thickness to the designed thickness of the electrode sheet. Both rollings are cold rolling) is carried out to form a graphene layer.

[0123] Example 8

[0124] The difference between Example 8 and Example 1 lies in the different preparation methods of the positive electrode sheet.

[0125] The CVD reaction chamber is set with three layers, namely the catalytic layer (catalyst placement area), the zero lower layer (quenching and cooling), and the growth layer (current collector placed in this layer). First, the molten metal gallium catalyst is placed in the catalytic layer, nitrogen is introduced at 300 sccm, the catalytic layer is heat-treated at 900 °C for 5 min, and then high-purity 99.99% ethane carbon source gas is introduced at 300 sccm for reaction. The reacted catalyst enters the zero lower layer for quenching and cooling to 150 °C, and then enters the growth layer for heat preservation. The mixed gas of nitrogen and carbon source gas is purged from the upper end of the catalyst, and carbon materials are grown on the surface of the active material layer. The growth time is 5 min. Double rolling (the thickness of the first rolling is four-fifths of the designed thickness of the electrode sheet, and the second rolling reduces the thickness to the designed thickness of the electrode sheet. Both rollings are cold rolling) is carried out to form a graphene layer.

[0126] Example 9

[0127] The difference between Example 9 and Example 1 lies in the different preparation methods of the positive electrode sheet.

[0128] The CVD reaction chamber is set up in three layers, namely the catalytic layer (catalyst placement area), the zero lower layer (quenching and cooling), and the growth layer (current collector placed in this layer). First, the catalytic layer is filled with molten gallium metal catalyst, nitrogen is introduced at 200 sccm, the catalytic layer is heat-treated at 900 °C for 8 min, and then high-purity 99.99% ethane carbon source gas is introduced at 200 sccm for reaction. The reacted catalyst enters the zero lower layer for quenching and cooling to 150 °C, and then enters the growth layer for heat preservation. The mixed gas of nitrogen and carbon source gas is purged from the upper end of the catalyst, and carbon materials are grown on the surface of the active material layer for 5 min. Then, double rolling (the thickness of the first rolling is four-fifths of the designed thickness of the electrode sheet, and the second rolling reduces the thickness to the designed thickness of the electrode sheet. Both rollings are cold rollings) is carried out to form a graphene layer.

[0129] Example 10

[0130] The difference between Example 10 and Example 1 lies in the different preparation methods of the positive electrode sheet.

[0131] In the preparation method of the positive electrode sheet in this example, the heat treatment time of the catalytic layer is 10 min.

[0132] Example 11

[0133] The difference between Example 11 and Example 1 lies in the different preparation methods of the positive electrode sheet.

[0134] In the preparation method of the positive electrode sheet in this example, the growth time in the growth layer is 4 min.

[0135] Example 12

[0136] The difference between Example 12 and Example 1 lies in the different preparation methods of the positive electrode sheet.

[0137] In the preparation method of the positive electrode sheet in this example, the growth time in the growth layer is 6 min.

[0138] Example 13

[0139] The difference between Example 13 and Example 1 lies in the different preparation methods of the positive electrode sheet.

[0140] In the preparation method of the positive electrode sheet in this example, the growth time in the growth layer is 8 min.

[0141] Example 14

[0142] The difference between Example 14 and Example 1 lies in the different preparation methods of the positive electrode sheet.

[0143] In the preparation method of the positive electrode sheet in this example, the growth time in the growth layer is 10 min.

[0144] Example 15

[0145] Example 15 is different from Example 1 in that the preparation method of the positive electrode plate is different.

[0146] In the preparation method of the positive electrode plate of this example, after growing graphene, it is not rolled.

[0147] Example 16

[0148] Example 16 is different from Example 1 in that the preparation method of the positive electrode plate is different.

[0149] The preparation method of the positive electrode plate of this example includes the following steps: using pure aluminum foil with a thickness of 8 μm.

[0150] Comparative Example 1

[0151] Comparative Example 1 is different from Example 1 in that the preparation method of the positive electrode plate is different.

[0152] In the preparation method of the positive electrode plate of this example, the purity of the ethane carbon source gas introduced is 98%.

[0153] Comparative Example 2

[0154] Comparative Example 2 is different from Example 1 in that the preparation method of the positive electrode plate is different, and no graphene layer is grown in this example.

[0155] The preparation method of the positive electrode plate of this example includes the following steps:

[0156] Using carbon-coated aluminum foil as the current collector, the carbon-coated aluminum foil includes aluminum foil and carbon coating layers with a thickness of 1.5 μm on both surfaces of the aluminum foil. The thickness of the aluminum foil is 8 μm, the thickness of the carbon coating layer on one side is 1.5 μm, and the thickness of the entire carbon-coated aluminum foil current collector is 11 μm. The carbon coating layer includes conductive carbon black and PVDF with a mass ratio of 60:40.

[0157] The positive electrode active material nickel cobalt manganese (NCM811), conductive agent Super-P, and binder PVDF are uniformly dispersed in the solvent NMP in a mass ratio of 97:2:1 to form a positive electrode active material slurry. The positive electrode active material slurry is uniformly coated on both sides of the carbon-coated aluminum foil and dried to form a positive electrode active material layer with a single-sided areal density of 290 g / 1540.25 cm 2 , and the tap density of the positive electrode active material layer is 3.8 g / cm 3 .

[0158] Comparative Example 3

[0159] Comparative Example 3 is different from Example 1 in that no catalyst is added.

[0160] Comparative Example 4

[0161] Comparative Example 4 formed a graphene layer on the surface of the positive electrode active material layer by coating a graphene slurry.

[0162] (1) Preparation of the positive electrode sheet

[0163] Using carbon-coated aluminum foil as the current collector, the carbon-coated aluminum foil includes aluminum foil and carbon-coated layers with a thickness of 1.5 μm on both surfaces of the aluminum foil. The thickness of the aluminum foil is 8 μm, and the total thickness of the carbon-coated aluminum foil current collector is 11 μm. The mass ratio of the carbon-coated layer is 60:40 conductive carbon black and PVDF.

[0164] The positive electrode active material nickel cobalt manganese, conductive agent Super-P, and binder PVDF were uniformly dispersed in the solvent NMP according to a mass ratio of 97:2:1 to prepare a positive electrode active material slurry. The positive electrode active material slurry was uniformly coated on both sides of the carbon-coated aluminum foil and dried to form a positive electrode active material layer with a thickness of;

[0165] Graphene, dispersant, and binder were mixed evenly according to a mass ratio of 50:10:40, and water was added to prepare a slurry with a solid content of 15%. Then it was coated on the surface of the negative electrode active material layer and dried to form a graphene layer with a coating thickness of 1 μm (it is difficult to achieve a nanometer-level thickness during conventional coating).

[0166] Comparative Example 5

[0167] The difference between Comparative Example 5 and Example 1 is that the preparation method of the positive electrode sheet is different.

[0168] In the preparation method of the positive electrode sheet of this example, the growth layer grew for 2 min..

[0169] Comparative Example 6

[0170] The difference between Comparative Example 6 and Example 1 is that the preparation method of the positive electrode sheet is different.

[0171] In the preparation method of the positive electrode sheet of this example, the growth layer grew for 10 min, and high-purity 99.99% butyne gas was introduced as the carbon source.

[0172] Table 1 Parameter Table

[0173]

[0174] Performance test:

[0175] Thermal shock passing rate: Tested in accordance with GB 8897.4-2019.

[0176] Normal temperature cycle test: At 25°C, tested in accordance with GB / T 36276-2023.

[0177] 4C charge and discharge temperature rise: Tested in accordance with GB 31241-2022.

[0178] Table 2 Performance test table

[0179] Normal temperature cycle 700cls retention rate / % 4C charge and discharge temperature rise / °C Thermal shock passing rate / % Example 1 90 20 96 Example 2 89 23 90 Example 3 89 24 90 Example 4 87 23 91 Example 5 88 25 90 Example 6 86 25 90 Example 7 85 28 85 Example 8 87 26 88 Example 9 87 25 88 Example 10 88 28 86 Example 11 88 26 89 Example 12 89 27 88 Example 13 88 26 89 Example 14 86 28 86 Example 15 83 30 86 Example 16 82 30 84 Comparative Example 1 78 32 80 Comparative Example 2 72 35 70 Comparative Example 3 76 30 84 Comparative Example 4 80 28 84 Comparative Example 5 77 28 87 Comparative Example 6 76 28 86

[0180] As can be seen from Table 1, the electrode sheet of the present invention includes a current collector and an active material layer and a carbon material layer sequentially arranged on at least one surface of the current collector. By controlling 2 ≤ b / a ≤ 20, the carbon material layer forms a conductive network on the surface of the active material layer, effectively reducing the internal resistance, improving the electron transfer efficiency, effectively improving the rapid heat dissipation performance of the electrode sheet, effectively suppressing the volume expansion of the active material (such as the positive electrode active material and the negative electrode active material) during the charge and discharge process, and at the same time having a certain protective effect on the current collector and the active material layer, improving the ion diffusion rate, shortening the ion diffusion path, and effectively improving the safety, cycle stability and initial efficiency of the electrode sheet.

[0181] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A pole piece, characterized in that: It includes a current collector and an active material layer and a carbon material layer arranged in sequence on at least one surface of the current collector, wherein the carbon material layer includes a carbon material and a metal; the metal includes at least one of gallium, cobalt, palladium, ruthenium, platinum, and copper; the single layer thickness of the carbon material is a, and the thickness of the carbon material layer is b, satisfying: 2≤b / a≤20.

2. The pole piece according to claim 1, characterized in that: Satisfy at least one of the following (I) to (II): (Ⅰ) 0.7nm≤a≤1nm; (Ⅱ)1nm≤b≤15nm.

3. The pole piece according to claim 1, characterized in that: The mass percentage of the metal in the carbon material layer is ≤0.2%; and / or The carbon material includes at least one of graphene and carbon nanotubes.

4. The pole piece according to claim 1, characterized in that: The porosity of the carbon material layer is 0.1 to 35%, preferably 0.1 to 1.5%, more preferably 0.5 to 1%; and / or The interlayer distance of the carbon material is 0.34-0.36 nm.

5. The pole piece according to claim 1, characterized in that: The current collector comprises a base layer and a carbon coating layer located on at least one surface of the base layer; the carbon coating layer comprises the following components in parts by weight: 50-70% of a conductive agent and 30-50% of a binder.

6. The pole piece according to claim 1, characterized in that: Satisfy at least one of the following (III) to (V): (III) the thickness of the substrate layer is 6 to 15 μm; (IV) The thickness of the carbon coating layer is 1 to 15 μm; (V) The base layer includes one of aluminum, copper, silver, nickel, zinc, magnesium, zirconium, cobalt, titanium and tantalum.

7. The method for preparing a pole piece according to any one of claims 1 to 6, characterized in that: The following steps are involved: Coating an active slurry on at least one surface of the current collector to form an active material layer; The catalyst is placed in a CVD reaction chamber, an inert gas is introduced, the catalyst is heat treated, a hydrocarbon carbon source gas is introduced for reaction, the temperature is lowered, the temperature is kept high, a carbon material is grown on the surface of the active material layer, and a second rolling process is performed to form a carbon material layer.

8. The method for preparing a pole piece according to claim 7, characterized in that: Satisfy at least one of the following (VI) to (XI): (VI) the inert gas flow rate is 100 to 300 sccm; (VII) the heat treatment temperature is 700 to 1200° C., and the heat treatment time is 4 to 10 minutes; (VIII) the hydrocarbon carbon source gas has an inlet flow rate of 100 to 300 sccm; (IX) the reaction temperature and time is 5 to 10 minutes; (Ⅹ) the insulation temperature is 50 to 200° C. and the insulation time is 4 to 10 minutes; (Ⅺ) the growth time is 5 to 10 minutes; (XII) The purity of the hydrocarbon carbon source gas is ≥ 99.99%.

9. A secondary battery, characterized in that: The invention comprises a pole piece as described in any one of claims 1 to 6.

10. An electrical device, characterized in that: A secondary battery comprising the secondary battery according to claim 9.

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