Current collector with fireproof coating and preparation method thereof, electrode sheet and lithium ion battery prepared therefrom

Abstract

The present invention discloses a current collector with a fireproof coating, a preparation method thereof, an electrode sheet and a lithium ion battery prepared therefrom. The fireproof coating material includes an acid source, a carbon source, a gas source, a conductive agent, a binder, an antioxidant and a dispersant. The fireproof coating material is mixed evenly with a solvent to form a dispersed solution, which is coated on the surface of the current collector, and a fireproof coating is formed after heat treatment. A slurry containing positive and negative active substances is further coated on the current collector with the fireproof coating to form positive and negative electrode sheets. Then, the positive and negative electrode sheets are made into batteries. The fireproof coating has good chemical stability and has little effect on the charge and discharge performance of the battery. When the battery is in thermal runaway, the fireproof coating rapidly expands to form a porous heat-insulating carbonaceous protective layer and separates the active substance from the current collector, reducing the exchange of ions and electrons during the thermal runaway process, blocking heat transfer, and thus effectively improving the safety of the battery.

Description

Technical Field

[0001] The present invention relates to the field of lithium ion battery safety protection technology, and in particular to a current collector with a fireproof coating, a preparation method thereof, an electrode sheet and a lithium ion battery obtained therefrom. Background Art

[0002] Lithium-ion batteries have been widely used in many fields such as electric vehicles, portable electronic devices, and energy storage power stations, greatly changing people's lives and production methods. In the field of electric vehicles, lithium-ion batteries are the power core of vehicles, promoting the vigorous development of the new energy vehicle industry; in portable electronic devices, their high energy density characteristics make the equipment lighter and more durable; energy storage power stations use lithium-ion batteries to effectively regulate the supply and demand of electricity and ensure the stability of the power grid.

[0003] However, lithium-ion batteries have serious safety risks during use, and thermal runaway is one of the most critical issues. Various factors can cause thermal runaway. For example, electric vehicle collisions may damage the internal structure of the battery and cause a short circuit. Overcharging (such as using inferior chargers or charging system failures) is more common in portable electronic devices. The aging and failure of batteries in energy storage power stations over a long period of time will also increase the risk of thermal runaway.

[0004] Once thermal runaway occurs, it will trigger a series of chain reactions. The temperature inside the battery rises rapidly, causing the electrolyte to decompose and produce flammable gases. At the same time, the properties of the active materials on the pole pieces change under high temperatures, reacting violently with the electrolyte decomposition products, releasing a large amount of heat. This heat accumulation forms a positive feedback, causing the temperature to continue to rise, which may eventually lead to fire or explosion.

[0005] Currently, a variety of measures have been taken for the safety of lithium-ion batteries. The battery management system (BMS) controls the charging and discharging of the battery by monitoring parameters such as voltage, current, and temperature, but it may not respond in time to problems caused by internal physical damage. The thermal management system (liquid cooling, air cooling, etc.) can control the normal operating temperature, but in the extreme case of thermal runaway, the heat dissipation capacity is limited. Although the use of fireproof materials in the battery casing can delay the spread of fire, it cannot solve the problem of fire at the pole piece from the root. As the core component of the battery, the pole piece urgently needs effective fire protection technology to cope with the dangerous conditions in the early stage of thermal runaway and ensure the safe use of lithium-ion batteries. Summary of the invention

[0006] In view of the deficiencies of the prior art, the object of the present invention is to provide a current collector with a fireproof coating, a preparation method thereof, and an electrode sheet and a lithium-ion battery prepared therefrom.

[0007] To solve the above problems, the technical solution adopted by the present invention is: a current collector with a fire-retardant coating, comprising a current collector body and an intumescent fire-retardant coating coated on the current collector body, the intumescent fire-retardant coating comprising the following components according to the percentage of the total weight of the intumescent fire-retardant coating: 10% to 40% acid source, 8% to 25% carbon source, 10% to 32% gas source, 2% to 8% conductive agent, 12% to 36% binder, 2% to 7% antioxidant, and 1% to 5% dispersant.

[0008] The acid source includes one or more of ammonium polyphosphate, melamine phosphate, aminotrimethylene phosphonic acid, and high-purity aluminum phosphate; the carbon source includes one or more of pentaerythritol, dipentaerythritol, and phenolic resin; the gas source includes one or more of melamine, dicyandiamide, and guanidine carbonate; the conductive agent includes one or more of conductive carbon black, single-walled carbon nanotubes, and multi-walled carbon nanotubes; the binder includes one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyurethane; the antioxidant is one or more of hindered phenol antioxidants, phosphite antioxidants, and metal passivator benzotriazole; the dispersant is one or more of sodium hexametaphosphate, polyvinyl pyrrolidone, and polycarboxylic acid ammonium salt.

[0009] The current collector body is aluminum foil, copper foil, composite aluminum foil, or composite copper foil; the thickness of the current collector body is 3um to 20um, and the thickness of the intumescent fireproof coating is 2um to 8um.

[0010] The method for preparing the current collector having the fire retardant coating comprises the following steps:

[0011] 1) Ingredients: Accurately weigh the acid source, carbon source, gas source, binder, conductive agent, antioxidant and dispersant according to the proportion;

[0012] 2) Mixing: Place the weighed acid source, carbon source, gas source, conductive agent, binder, antioxidant and dispersant in a high-speed mixer, and stir at a low speed of 300-800 rpm for 5-30 minutes to preliminarily mix the components and form a loose mixture;

[0013] 3) Dispersion treatment: slowly add an appropriate amount of solvent into the mixer, increase the stirring speed to 1000-1500 rpm, and stir for 10-15 minutes to fully disperse the components in the solvent to form a uniform dispersion;

[0014] 4) Grinding and refinement: The dispersion is transferred to a sand mill or a ball mill for grinding. The grinding time is determined to be 0.5 to 3 hours according to the required fineness, so that the particle size reaches the micron level or even the nanometer level to improve the uniformity and flatness of the coating.

[0015] 5) Degassing treatment: placing the ground dispersion in a vacuum degassing device, degassing for 10-20 minutes under a vacuum degree of -0.05 MPa to -0.09 MPa, removing bubbles in the dispersion to obtain a dispersion of an intumescent fire retardant coating material that can be used to coat lithium ion battery pole pieces;

[0016] 6) applying a fire retardant coating, applying the dispersion of the intumescent fire retardant coating material obtained in step 5) onto the current collector body by dipping or spraying;

[0017] 7) Heat treatment of fire-retardant coating: Place the current collector coated with the fire-retardant coating in an environment with a temperature of 30-50°C and a relative humidity of 1%-10% and dry it for 0.5h-2h to evaporate the solvent and initially solidify the coating; then place the current collector containing the fire-retardant coating at 60°C for 0.5h-2h to further enhance the bonding strength between the coating and the current collector body and the stability of the coating, thereby obtaining a current collector with a fire-retardant coating.

[0018] The solvent in step 3) is one or both of N-methylpyrrolidone and acetone. The amount of solvent added is controlled according to the concentration requirement of the final coating material. The solid content of the coating material is between 30% and 70%.

[0019] Step 4) After grinding and refining, the particle size of the coating material particles is 200nm~2um to improve the uniformity and flatness of the coating.

[0020] Step 6) The dip coating is to immerse the current collector body in the dispersion of the intumescent fire retardant coating material for 1-10s and a pulling speed of 0.5-8cm / s. The spray coating is pressure spraying, the distance between the spray gun and the electrode is maintained at 0.1-10mm, and the spray gun moves at a speed of 0.5-8cm / s.

[0021] An electrode sheet of a lithium ion battery comprises the above-mentioned current collector with a fireproof coating or the current collector with a fireproof coating prepared by the above-mentioned preparation method and an active material layer arranged on the surface of the expansion type fireproof coating.

[0022] The active material layer includes active materials, conductive agents, and binders, and the active materials include positive electrode active materials and negative electrode active materials; the positive electrode active material is one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, nickel cobalt manganese ternary material and nickel cobalt aluminum ternary material; the negative electrode active material includes one or more of graphite, hard carbon, soft carbon, silicon dioxide, and lithium titanate; the conductive agent includes one or more of conductive carbon black, acetylene black, carbon fiber, and carbon nanotubes; the binder includes one or more of polyvinylidene fluoride, styrene-butadiene rubber, and sodium carboxymethyl cellulose.

[0023] A lithium ion battery adopts the electrode sheet mentioned above.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: the intumescent fire-retardant coating of the present invention has good thermal stability and chemical stability, and its thickness is 2 to 8 um. During the normal charge and discharge process of lithium-ion batteries, it has little effect on the performance indicators such as the internal resistance and capacity of the battery. When the battery has thermal runaway, the acid source in the coating begins to decompose to produce acidic substances, catalyzing the dehydration of the carbon source into carbon, and at the same time the gas source decomposes to produce a large amount of gas, causing the coating to expand rapidly. As the coating expands, the active material on the battery pole piece gradually separates from the current collector, reducing the exchange of ions and electrons during thermal runaway. After expansion, the thickness of the coating can reach 5 to 10 times the original thickness, forming a porous and heat-insulating carbonaceous protective layer. This protective layer can effectively block heat transfer, reduce the contact between the active material on the pole piece and oxygen, and inhibit the release of combustible gas, thereby improving the fire safety of lithium-ion batteries. DETAILED DESCRIPTION

[0025] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0026] The current collector with a fireproof coating of the present invention comprises a current collector body and an intumescent fireproof coating coated on the current collector body. The intumescent fireproof coating comprises the following components according to the percentage of the total weight of the intumescent fireproof coating: 10% to 40% of an acid source, 8% to 25% of a carbon source, 10% to 32% of a gas source, 2% to 8% of a conductive agent, 12% to 36% of a binder, 2% to 7% of an antioxidant, and 1% to 5% of a dispersant.

[0027] The acid source includes one or more of ammonium polyphosphate, melamine phosphate, aminotrimethylene phosphonic acid, and high-purity aluminum phosphate; the carbon source includes one or more of pentaerythritol, dipentaerythritol, and phenolic resin; the gas source includes one or more of melamine, dicyandiamide, and guanidine carbonate; the conductive agent includes one or more of conductive carbon black, single-walled carbon nanotubes, and multi-walled carbon nanotubes; the binder includes one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyurethane; the antioxidant is one or more of hindered phenol antioxidants, phosphite antioxidants, and metal passivator benzotriazole; the dispersant is one or more of sodium hexametaphosphate, polyvinyl pyrrolidone, and polycarboxylic acid ammonium salt.

[0028] The current collector body is aluminum foil, copper foil, composite aluminum foil, or composite copper foil; the thickness of the current collector body is 3um to 20um, and the thickness of the intumescent fireproof coating is 2um to 8um.

[0029] The method for preparing the current collector having the fire retardant coating comprises the following steps:

[0030] 1) Ingredients: Accurately weigh the acid source, carbon source, gas source, binder, conductive agent, antioxidant and dispersant according to the proportion;

[0031] 2) Mixing: Place the weighed acid source, carbon source, gas source, conductive agent, binder, antioxidant and dispersant in a high-speed mixer, and stir at a low speed of 300-800 rpm for 5-30 minutes to preliminarily mix the components and form a loose mixture;

[0032] 3) Dispersion treatment: slowly add an appropriate amount of solvent into the mixer, increase the stirring speed to 1000-1500 rpm, and stir for 10-15 minutes to fully disperse the components in the solvent to form a uniform dispersion;

[0033] 4) Grinding and refinement: The dispersion is transferred to a sand mill or a ball mill for grinding. The grinding time is determined to be 0.5 to 3 hours according to the required fineness, so that the particle size reaches the micron level or even the nanometer level to improve the uniformity and flatness of the coating.

[0034] 5) Degassing treatment: placing the ground dispersion in a vacuum degassing device, degassing for 10-20 minutes under a vacuum degree of -0.05 MPa to -0.09 MPa, removing bubbles in the dispersion to obtain a dispersion of an intumescent fire retardant coating material that can be used to coat lithium ion battery pole pieces;

[0035] 6) applying a fire retardant coating, applying the dispersion of the intumescent fire retardant coating material obtained in step 5) onto the current collector body by dipping or spraying;

[0036] 7) Heat treatment of fire-retardant coating: Place the current collector coated with the fire-retardant coating in an environment with a temperature of 30-50°C and a relative humidity of 1%-10% and dry it for 0.5h-2h to evaporate the solvent and initially solidify the coating; then place the current collector containing the fire-retardant coating at 60°C for 0.5h-2h to further enhance the bonding strength between the coating and the current collector body and the stability of the coating, thereby obtaining a current collector with a fire-retardant coating.

[0037] The solvent in step 3) is one or both of N-methylpyrrolidone and acetone. The amount of solvent added is controlled according to the concentration requirement of the final coating material. The solid content of the coating material is between 30% and 70%.

[0038] Step 4) After grinding and refining, the particle size of the coating material particles is 200nm~2um to improve the uniformity and flatness of the coating.

[0039] Step 6) The dip coating is to immerse the current collector body in the dispersion of the intumescent fire retardant coating material for 1-10s and a pulling speed of 0.5-8cm / s. The spray coating is pressure spraying, the distance between the spray gun and the electrode is maintained at 0.1-10mm, and the spray gun moves at a speed of 0.5-8cm / s.

[0040] An electrode sheet of a lithium ion battery comprises the above-mentioned current collector with a fireproof coating or the current collector with a fireproof coating prepared by the above-mentioned preparation method and an active material layer arranged on the surface of the expansion type fireproof coating.

[0041] The active material layer includes active materials, conductive agents, and binders, and the active materials include positive electrode active materials and negative electrode active materials; the positive electrode active material is one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, nickel cobalt manganese ternary material and nickel cobalt aluminum ternary material; the negative electrode active material includes one or more of graphite, hard carbon, soft carbon, silicon dioxide, and lithium titanate; the conductive agent includes one or more of conductive carbon black, acetylene black, carbon fiber, and carbon nanotubes; the binder includes one or more of polyvinylidene fluoride, styrene-butadiene rubber, and sodium carboxymethyl cellulose.

[0042] The present invention also discloses a lithium-ion battery; the lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet and a separator between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet and the negative electrode sheet are the positive electrode sheet and the negative electrode sheet mentioned above. The separator adopts at least one of a polyolefin-based double-sided ceramic coating separator or a polyolefin-based single-sided ceramic coating separator; the polypropylene-based double-sided ceramic coating separator and the polyolefin-based single-sided ceramic coating separator have a thickness of 6 to 30 μm.

[0043] Take the positive electrode sheet and negative electrode sheet prepared above, weld conductive tabs on the positive electrode sheet and negative electrode sheet respectively, place the separator between the positive electrode sheet and the negative electrode sheet, wind or stack the positive electrode sheet, separator and negative electrode sheet to form a bare battery cell, and wrap it in an aluminum-plastic film; inject an electrolyte with a concentration of 1 mol / L; encapsulate, form, and age to obtain a soft-package battery.

[0044] Example 1

[0045] The first step is to prepare an intumescent fireproof coating material. Ammonium polyphosphate, pentaerythritol, melamine, conductive carbon black, polyvinylidene fluoride, hindered phenol antioxidant, and sodium hexametaphosphate are accurately weighed in order according to weight percentages of 30%, 21%, 25%, 5%, 12%, 5%, and 2%.

[0046] The second step is mixing. The weighed materials are placed in a high-speed mixer and stirred at a low speed of 300 rpm for 10 minutes to mix the components evenly to form a dispersed mixture.

[0047] The third step is dispersion treatment. Slowly add an appropriate amount of N-methylpyrrolidone solvent into the mixer, increase the stirring speed to 1000 rpm, and stir for 10 minutes to fully disperse the components in the solvent to form a uniform dispersion with a solid content of 60%;

[0048] The fourth step is grinding and refinement: the dispersion is transferred to a ball mill for grinding for 3 hours, so that the particle size reaches 500nm, improving the uniformity and flatness of the coating.

[0049] The fifth step is degassing treatment. The ground dispersion is placed in a vacuum degassing device and degassed for 20 minutes at a vacuum degree of -0.05 MPa to remove bubbles in the dispersion and obtain a dispersion of an expandable fire-retardant coating material that can be used to coat lithium-ion battery pole pieces.

[0050] Step 6: Dip coating: dip the 9um aluminum foil current collector into the dispersion of the intumescent fire retardant coating material obtained in step 5. The dipping time is 3s and the pulling speed is 1.5cm / s, so that the dispersion adheres to the aluminum foil current collector.

[0051] The seventh step is heat treatment of the fire-retardant coating. The current collector coated with the fire-retardant coating obtained in the sixth step is placed in an environment with a temperature of 45°C and a relative humidity of 1% and dried for 0.5 hours to enhance the bonding strength between the electrode and the current collector body and the stability of the coating, thereby obtaining a current collector with a fire-retardant coating.

[0052] Example 2

[0053] The first step is to prepare an intumescent fireproof coating material, which comprises 30%, 8%, 32%, 8%, 12%, 7% and 3% by weight respectively, of melamine phosphate, dipentaerythritol, dicyandiamide, single-walled carbon nanotubes, styrene-butadiene rubber, phosphite antioxidant and polycarboxylic acid ammonium salt.

[0054] The second step is mixing. The weighed materials are placed in a high-speed mixer and stirred at a low speed of 500 rpm for 15 minutes to mix the components evenly to form a dispersed mixture.

[0055] The third step is dispersion treatment. Slowly add an appropriate amount of N-methylpyrrolidone solvent into the mixer, increase the stirring speed to 1200 rpm, and stir for 12 minutes to fully disperse the components in the solvent to form a uniform dispersion with a solid content of 30%;

[0056] The fourth step is grinding and refinement: the dispersion is transferred to a ball mill for grinding for 3 hours, so that the particle size reaches 900nm, improving the uniformity and flatness of the coating.

[0057] The fifth step is degassing. The ground dispersion is placed in a vacuum degassing device and degassed for 10 minutes at a vacuum degree of -0.09 MPa to remove bubbles in the dispersion and obtain a dispersion of an expandable fire-retardant coating material that can be used to coat lithium-ion battery pole pieces.

[0058] Step 6: Spray coating: Use pressure spraying to coat the 8um copper foil current collector. Keep the distance between the spray gun and the electrode at 0.1mm and the movement speed of the spray gun at 0.5cm / s. Spray the dispersion onto the copper foil current collector.

[0059] The seventh step is heat treatment of the fire-retardant coating. The current collector coated with the fire-retardant coating obtained in the sixth step is placed in an environment with a temperature of 30°C and a relative humidity of 10% and dried for 2 hours to evaporate the solvent and initially solidify the coating. The current collector containing the fire-retardant coating is then placed at 60°C for 2 hours to further enhance the bonding strength between the electrode and the current collector body and the stability of the coating, thereby obtaining a current collector with a fire-retardant coating.

[0060] Example 3

[0061] The first step is to prepare an intumescent fireproof coating material. The weight percentages are 40%, 25%, 10%, 20%, 2%, 3%, and 3% respectively. Aminotrimethylenephosphonic acid, phenolic resin, guanidine carbonate, multi-walled carbon nanotubes, polyvinylidene fluoride-hexafluoropropylene copolymer, benzotriazole, and polyvinylpyrrolidone.

[0062] The second step is mixing. The weighed materials are placed in a high-speed mixer and stirred at a low speed of 800 rpm for 30 minutes to mix the components evenly to form a dispersed mixture.

[0063] The third step is dispersion treatment. Slowly add an appropriate amount of N-methylpyrrolidone solvent into the mixer, increase the stirring speed to 1500 rpm, and stir for 10 minutes to fully disperse the components in the solvent to form a uniform dispersion with a solid content of 70%;

[0064] The fourth step is grinding and refinement: the dispersion is transferred to a ball mill for grinding for 0.5 hours, so that the particle size reaches 2um, improving the uniformity and flatness of the coating.

[0065] The fifth step is degassing. The ground dispersion is placed in a vacuum degassing device and degassed for 15 minutes at a vacuum degree of -0.09 MPa to remove bubbles in the dispersion and obtain a dispersion of an expandable fire retardant coating material that can be used to coat lithium-ion battery pole pieces.

[0066] Step 6: Spray coating: Use pressure spraying to coat the 12um aluminum foil current collector. Keep the distance between the spray gun and the electrode at 0.1mm and the movement speed of the spray gun at 0.5cm / s. Spray the dispersion onto the copper foil current collector.

[0067] The seventh step is heat treatment of the fire-retardant coating. The current collector coated with the fire-retardant coating obtained in the sixth step is placed in an environment with a temperature of 30°C and a relative humidity of 10% and dried for 2 hours to evaporate the solvent and initially solidify the coating. The current collector containing the fire-retardant coating is then placed at 60°C for 2 hours to further enhance the bonding strength between the electrode and the current collector body and the stability of the coating, thereby obtaining a current collector with a fire-retardant coating.

[0068] Example 4

[0069] Preparation of positive and negative electrodes and batteries for lithium-ion batteries. The positive and negative electrode slurries are prepared using NMP as a solvent. The positive electrode components include a positive electrode active material, which is a ternary material of nickel-cobalt-manganese (NCM811), a carbon black conductive agent, and a polyvinylidene fluoride binder, preferably in a weight ratio of 94%, 3%, and 3%. The negative electrode components include graphite, a single-walled carbon nanotube conductive agent, and a polyvinylidene fluoride binder, preferably in a weight ratio of 95%, 2.5%, and 2.5%. The prepared positive and negative electrode slurries are respectively applied to the collectors with fire-retardant coatings in the above-mentioned embodiments 1-3 to form positive and negative electrode sheets. The positive and negative electrode sheets are assembled into lithium-ion battery dry cells through processes such as die-cutting and assembly, and liquid electrolyte is injected, and lithium-ion batteries are prepared using traditional lithium-ion battery production processes.

[0070] Furthermore, the same type of lithium ion batteries prepared using the fire retardant coating current collectors of Examples 1-3 and conventional current collectors without fire retardant coating were subjected to short circuit and needle puncture safety tests according to GJB4477-2002, and the results are shown in Table 1. By comparison, it is found that the battery safety of the current collector with fire retardant coating is significantly higher than that of the conventional current collector.

[0071] Table 1 Performance of lithium-ion batteries prepared using current collectors with fireproof coatings of the embodiments and conventional current collectors

[0072] Current collector type Battery Model-Capacity Short Circuit acupuncture Conventional current collector 100310-50Ah Fire, failed Fire, failed Example 1 100310-50Ah pass pass Example 2 100310-50Ah pass pass Example 3 100310-50Ah pass pass

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A current collector having a fire retardant coating, characterized in that: The invention comprises a current collector body and an intumescent fire-retardant coating coated on the current collector body. The intumescent fire-retardant coating comprises the following components according to the percentage of the total weight of the intumescent fire-retardant coating: 10% to 40% of an acid source, 8% to 25% of a carbon source, 10% to 32% of a gas source, 2% to 8% of a conductive agent, 12% to 36% of a binder, 2% to 7% of an antioxidant, and 1% to 5% of a dispersant.

2. The current collector with a fire retardant coating according to claim 1, characterized in that: The acid source includes one or more of ammonium polyphosphate, melamine phosphate, aminotrimethylene phosphonic acid, and high-purity aluminum phosphate; the carbon source includes one or more of pentaerythritol, dipentaerythritol, and phenolic resin; the gas source includes one or more of melamine, dicyandiamide, and guanidine carbonate; the conductive agent includes one or more of conductive carbon black, single-walled carbon nanotubes, and multi-walled carbon nanotubes; the binder includes one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyurethane; the antioxidant is one or more of hindered phenol antioxidants, phosphite antioxidants, and metal passivator benzotriazole; the dispersant is one or more of sodium hexametaphosphate, polyvinyl pyrrolidone, and polycarboxylic acid ammonium salt.

3. The current collector with a fire retardant coating according to claim 1, characterized in that: The current collector body is aluminum foil, copper foil, composite aluminum foil, or composite copper foil; the thickness of the current collector body is 3um to 20um, and the thickness of the intumescent fireproof coating is 2um to 8um.

4. The method for preparing a current collector having a fire retardant coating according to any one of claims 1 to 3, characterized in that: The following steps are involved: 1) Ingredients: Accurately weigh the acid source, carbon source, gas source, binder, conductive agent, antioxidant and dispersant according to the proportion; 2) Mixing: Place the weighed acid source, carbon source, gas source, conductive agent, binder, antioxidant and dispersant in a high-speed mixer, and stir at a low speed of 300-800 rpm for 5-30 minutes to preliminarily mix the components and form a loose mixture; 3) Dispersion treatment: slowly add an appropriate amount of solvent into the mixer, increase the stirring speed to 1000-1500 rpm, and stir for 10-15 minutes to fully disperse the components in the solvent to form a uniform dispersion; 4) Grinding and refinement: The dispersion is transferred to a sand mill or a ball mill for grinding. The grinding time is determined to be 0.5 to 3 hours according to the required fineness, so that the particle size reaches the micron level or even the nanometer level to improve the uniformity and flatness of the coating. 5) Degassing treatment: placing the ground dispersion in a vacuum degassing device, degassing for 10-20 minutes under a vacuum degree of -0.05 MPa to -0.09 MPa, removing bubbles in the dispersion to obtain a dispersion of an intumescent fire retardant coating material that can be used to coat lithium ion battery pole pieces; 6) applying a fire retardant coating, applying the dispersion of the intumescent fire retardant coating material obtained in step 5) onto the current collector body by dipping or spraying; 7) Heat treatment of fire-retardant coating: Place the current collector coated with the fire-retardant coating in an environment with a temperature of 30-50°C and a relative humidity of 1%-10% and dry it for 0.5h-2h to evaporate the solvent and initially solidify the coating; then place the current collector containing the fire-retardant coating at 60°C for 0.5h-2h to further enhance the bonding strength between the coating and the current collector body and the stability of the coating, thereby obtaining a current collector with a fire-retardant coating.

5. The method for preparing a current collector having a fire retardant coating according to claim 4, characterized in that: The solvent in step 3) is one or both of N-methylpyrrolidone and acetone. The amount of solvent added is controlled according to the concentration requirement of the final coating material. The solid content of the coating material is between 30% and 70%.

6. The method for preparing a current collector having a fire retardant coating according to claim 4, characterized in that: Step 4) After grinding and refining, the particle size of the coating material particles is 200nm~2um to improve the uniformity and flatness of the coating.

7. The method for preparing a current collector having a fire retardant coating according to claim 4, characterized in that: Step 6) The dip coating is to immerse the current collector body in the dispersion of the intumescent fire retardant coating material, the immersion time is 1-10s, the pulling speed is 0.5-8cm / s, the spray coating is pressure spraying, the distance between the spray gun and the electrode is maintained at 0.1-10mm, and the spray gun movement speed is 0.5-8cm / s.

8. An electrode sheet for a lithium ion battery, characterized in that: It comprises a current collector with a fire retardant coating as described in any one of claims 1 to 3 or a current collector with a fire retardant coating prepared by the preparation method as described in any one of claims 4 to 7 and an active material layer arranged on the surface of the intumescent fire retardant coating.

9. The electrode sheet of a lithium-ion battery according to claim 8, characterized in that: The active material layer includes active materials, conductive agents, and binders, and the active materials include positive electrode active materials and negative electrode active materials; the positive electrode active material is one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium cobalt oxide, lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, nickel cobalt manganese ternary material and nickel cobalt aluminum ternary material; the negative electrode active material includes one or more of graphite, hard carbon, soft carbon, silicon dioxide, and lithium titanate; the conductive agent includes one or more of conductive carbon black, acetylene black, carbon fiber, and carbon nanotubes; the binder includes one or more of polyvinylidene fluoride, styrene-butadiene rubber, and sodium carboxymethyl cellulose.

10. A lithium ion battery, characterized in that: The electrode sheet according to claim 8 or 9 is used.