Positive electrode current collector safety coating with thermal response characteristic

Abstract

The invention discloses a positive electrode current collector safety coating with a thermal response characteristic. The coating comprises safety particles and a binder, the safety particle comprises a matrix; the surface of the base body is coated with an insulating ceramic material layer; the surface, far away from the substrate, of the insulating ceramic material layer is coated with a conductive carbon material layer; the expansion coefficient of the matrix is 1.9-20 * 10 <-5 > / K; the expansion coefficient of the insulating ceramic material layer is 2-8 * 10 <-6 > / K. Under normal temperature, the conductive carbon layer ensures high conductivity of the coating; at high temperature, the difference of thermal expansion coefficients inside and outside the safety particle core shell is large, the inner core expands when being heated, and the first coating structure is made of a ceramic material and has high brittleness, so that the coating structure is embrittled under the stress difference to form a plurality of insulating fragments, the conductivity of the safety coating is greatly reduced, and the service life of the safety coating is prolonged. A current path between the positive active material and the current collector is cut off, and the risk of further thermal runaway is reduced.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a safety coating for a positive electrode current collector with thermal response characteristics. Background Technology

[0002] In lithium-ion battery applications, the current collector is a key component, primarily responsible for carrying electrode materials and conducting electrons. Choosing the right current collector is a prerequisite for the successful operation of a lithium-ion battery. An ideal current collector needs to meet characteristics such as high conductivity, good flexibility, strong stability, light weight and thinness, good compatibility and bonding with battery active materials, and low cost and easy availability.

[0003] With the increase in energy density of lithium-ion batteries, the risk of thermal runaway increases significantly. In existing technologies, conductive coatings are typically used on the positive electrode current collector to enhance interfacial conductivity. However, under high-temperature conditions, these coatings cannot effectively interrupt the current path, leading to exacerbated thermal runaway. Existing technologies generally achieve temperature response by adding thermistor materials (such as barium titanate), but the following problems remain: 1) the thermistor material itself has poor conductivity, affecting the positive electrode's electronic conductivity; 2) the amount of thermistor material added is limited. Therefore, to further improve the thermal response characteristics of the current collector and enhance battery safety, this invention proposes a safety coating for the positive electrode current collector with thermal response characteristics. Summary of the Invention

[0004] This method proposes a safety coating for the positive electrode current collector with thermal response characteristics to improve the thermal response characteristics of the current collector and enhance battery safety. The above objective can be achieved through the following technical solutions: A safety coating for a positive electrode current collector with thermal response characteristics, the coating comprising safety particles and a binder; The safety particle includes a matrix; the surface of the matrix is ​​coated with an insulating ceramic material layer; and the surface of the insulating ceramic material layer away from the matrix is ​​coated with a conductive carbon material layer. The coefficient of thermal expansion of the matrix is ​​1.9~20×10⁻⁶. -5 / K; The coefficient of thermal expansion of the insulating ceramic material layer is 2~8×10⁻⁶. -6 / K.

[0005] Optionally, the matrix is ​​made of a polymer material; Preferably, the polymer material includes at least one of polytetrafluoroethylene, polyethylene, and polyamide; Preferably, the insulating ceramic material layer comprises at least one of burlite, alumina, and silicon dioxide.

[0006] Preferably, the insulating ceramic material layer is an insulating ceramic material layer with a porous structure; The porosity of the insulating ceramic material layer with a porous structure is ≥30%.

[0007] Optionally, the conductive carbon material includes at least one of graphene, carbon black, and graphite; Preferably, the safety particles in the coating have a mass fraction of 60% to 90%.

[0008] Optionally, the matrix particle size is 100~200nm; the thickness of the insulating ceramic material layer is 50~120nm; and the thickness of the conductive carbon material layer is 10~50nm.

[0009] Optionally, the adhesive includes at least one of PVDF, PMMA, and PAA; Preferably, the positive electrode current collector safety coating with thermal response characteristics further includes a conductive agent; Preferably, the conductive agent is at least one selected from graphene, carbon black, and graphite. The positive electrode current collector safety coating with thermal response characteristics comprises the following components in parts by weight: 5-10 portions of safety granules; 0.5 to 1 part of conductive agent; 1-2 parts adhesive.

[0010] A positive current collector with thermal response characteristics, wherein the positive current collector with thermal response characteristics comprises the aforementioned positive current collector safety coating with thermal response characteristics.

[0011] A method for preparing a positive electrode current collector with thermal response characteristics includes the following steps: Step 1) The matrix is ​​added to an aluminum salt or silicate solution and subjected to a hydrothermal reaction to form an insulating ceramic material layer on the surface of the matrix, thereby obtaining microparticles with a first coating layer; Step 2) Deposit a conductive carbon material layer on the surface of the microparticles with the first coating layer to obtain safe microparticles; Step 3) Coat the surface of the positive current collector with a slurry containing safety particles and binder, and after drying, obtain the positive current collector with thermal response characteristics.

[0012] Optionally, the temperature of the hydrothermal reaction in step one) is 110~140℃ and the time is 10~16h; Preferably, in step one), the matrix is ​​added to an 8-12 mol / L aluminum salt solution to carry out a hydrothermal reaction, forming a boehmite layer on the surface of the matrix; then, it is heated at 400-600°C for 10-16 hours to transform the boehmite layer into a porous alumina layer; thus obtaining microparticles with a first coating layer.

[0013] Optionally, a conductive carbon material layer is deposited on the surface of the microparticles having the first coating layer using a vapor phase deposition method; Preferably, the slurry also contains a conductive agent.

[0014] The present invention also proposes the application of the aforementioned positive electrode current collector with thermal response characteristics in the preparation of batteries.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention proposes a safety coating for a positive electrode current collector with thermal response characteristics. The coating comprises safety particles and a binder. The safety particles include a substrate, the surface of which is coated with an insulating ceramic material layer. Furthermore, the surface of the insulating ceramic material layer away from the substrate is coated with a conductive carbon material layer. The coefficient of thermal expansion of the substrate is 1.9~20×10⁻⁶. -5 / K; The coefficient of thermal expansion of the insulating ceramic material layer is 2~8×10. -6 / K. At normal temperatures, the conductive carbon layer ensures high conductivity of the coating, improving the conductivity between the positive electrode active material and the current collector. However, at high temperatures, the difference in thermal expansion coefficients between the core and shell of the safety particle is significant. The core expands when heated, resulting in a large stress difference between the inside and outside. Furthermore, since the first coating structure is made of ceramic material, it is relatively brittle. Under this stress difference, the coating structure will crack, forming multiple insulating fragments. This greatly reduces the conductivity of the safety coating, cuts off the current path between the positive electrode active material and the current collector, and reduces the risk of further thermal runaway.

[0016] The insulating ceramic material layer in this invention preferably adopts a porous structure, which can improve the dispersion of the broken porous ceramic fragments and enhance the insulation. In addition, the porous structure has strong adsorption properties, which can absorb the electrolyte in the positive electrode active material layer and the battery, inhibit the oxygen release reaction between the positive electrode active material and the electrolyte, and reduce the risk of fire. Detailed Implementation

[0017] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0018] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0019] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0020] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0021] The present invention also proposes a positive electrode current collector safety coating with thermal response characteristics, wherein the coating contains safety particles and a binder; The safety particle includes a matrix; the surface of the matrix is ​​coated with an insulating ceramic material layer; and the surface of the insulating ceramic material layer away from the matrix is ​​coated with a conductive carbon material layer. The coefficient of thermal expansion of the matrix is ​​1.9~20×10⁻⁶. -5 / K; The coefficient of thermal expansion of the insulating ceramic material layer is 2~8×10⁻⁶. -6 / K.

[0022] During use, the thermal expansion coefficients of the inner and outer shells of the safety particles differ significantly. When the core is heated, it expands, resulting in a large stress difference between the inner and outer shells. Furthermore, since the first coating structure is made of ceramic material, which is brittle, this stress difference can cause the coating structure to crack, forming multiple insulating fragments. This significantly reduces the conductivity of the safety coating, cuts off the current path between the positive electrode active material and the current collector, and reduces the risk of further thermal runaway.

[0023] Optionally, the matrix is ​​made of a polymer material; Preferably, the polymer material includes at least one of polytetrafluoroethylene, polyethylene, and polyamide; Preferably, the insulating ceramic material layer comprises at least one of burlite, alumina, and silicon dioxide.

[0024] Preferably, the insulating ceramic material layer is an insulating ceramic material layer with a porous structure; The porosity of the insulating ceramic material layer with a porous structure is ≥30%.

[0025] The first coating structure preferably adopts a porous structure, which can improve the dispersion of the broken porous ceramic fragments and enhance insulation. Furthermore, the porous structure has strong adsorption properties, which can absorb the electrolyte in the positive electrode active material layer and the battery, inhibiting the oxygen release reaction between the positive electrode active material and the electrolyte, and reducing the risk of fire. Specifically, the porous structure can be prepared by first preparing boehmite, and then converting the boehmite layer into a porous alumina layer through heating.

[0026] Furthermore, the conductive carbon material includes at least one of graphene, carbon black, and graphite; Preferably, the safety particles in the coating have a mass fraction of 60% to 90%.

[0027] Furthermore, the matrix particle size is 100~200nm; the thickness of the insulating ceramic material layer is 50~120nm; and the thickness of the conductive carbon material layer is 10~50nm.

[0028] Furthermore, the adhesive includes at least one of PVDF, PMMA, and PAA; Preferably, the positive electrode current collector safety coating with thermal response characteristics further includes a conductive agent; Preferably, the conductive agent is at least one of graphene, carbon black, and graphite.

[0029] Furthermore, the positive electrode current collector safety coating with thermal response characteristics comprises the following components in parts by weight: 5-10 portions of safety granules; 0.5 to 1 part of conductive agent; 1-2 parts adhesive.

[0030] The present invention also proposes a positive current collector with thermal response characteristics, wherein the positive current collector with thermal response characteristics comprises the aforementioned positive current collector safety coating with thermal response characteristics.

[0031] This invention also proposes a method for preparing a positive current collector with thermal response characteristics, comprising the following steps: Step 1) The matrix is ​​added to an aluminum salt or silicate solution and subjected to a hydrothermal reaction to form an insulating ceramic material layer on the surface of the matrix, thereby obtaining microparticles with a first coating layer; Step 2) Deposit a conductive carbon material layer on the surface of the microparticles with the first coating layer to obtain safe microparticles; Step 3) Coat the surface of the positive current collector with a slurry containing safety particles and binder, and after drying, obtain the positive current collector with thermal response characteristics.

[0032] Furthermore, the temperature of the hydrothermal reaction in step one) is 110~140℃, and the time is 10~16h; In one specific implementation, in step one), the matrix is ​​added to an 8-12 mol / L aluminum salt solution to carry out a hydrothermal reaction, forming a boehmite layer on the surface of the matrix; then, it is heated at 400-600°C for 10-16 hours to transform the boehmite layer into a porous alumina layer; thus obtaining microparticles with a first coating layer.

[0033] Furthermore, in step two), a conductive carbon material layer is deposited on the surface of the microparticles with the first coating layer using a vapor deposition method; Preferably, the slurry also contains a conductive agent.

[0034] The present invention also proposes the application of the above-mentioned positive electrode current collector with thermal response characteristics in the preparation of batteries.

[0035] Example 1 Aluminum nitrate was dissolved in deionized water to obtain an 8 mol / L solution. Ammonia water was added dropwise as a precipitant, causing the solution to gradually become turbid, and a white precipitate was observed to form. Polytetrafluoroethylene (PTFE) particles with a D50 of 150 nm were added to the resulting mixture and placed in a high-pressure reactor for constant-temperature heat treatment at 120 °C for 12 hours. After the reaction was complete, the reaction product was removed, washed, and dried to obtain PTFE microspheres coated with a boehmite layer, with a coating thickness of approximately 80 nm. The microspheres were placed in a plasma vapor deposition apparatus, evacuated to 10 Pa, and methane was introduced with two gas replacements at a flow rate of 100 ml / min. The methane flow rate was adjusted to 1 L / min, and the argon flow rate was 100 ml / min. The temperature was increased to 200 °C at a rate of 3 °C / min. The pulse frequency was set to HF 600 W (high frequency) and LF 300 W (low frequency). The plasma was excited, and vapor deposition began. The reaction time was controlled to be 1 h, allowing the gaseous carbon source to be deposited and covered on the microspheres. The coating layer thickness was 10 nm, forming safe particles with a core-shell structure coated with carbon black.

[0036] Safety particles, carbon nanotube conductive agent, and CMC binder are mixed in a mass ratio of 10:1:1 and coated onto the surface of the positive electrode current collector. After drying, a safety coating is formed.

[0037] Example 2 Aluminum nitrate was dissolved in deionized water to obtain an 8 mol / L solution. Ammonia water was added dropwise as a precipitant, causing the solution to gradually become turbid, and a white precipitate was observed to form. Polytetrafluoroethylene (PTFE) particles with a D50 of 150 nm were added to the resulting mixture and placed in a reaction vessel. The mixture was then heat-treated at a constant temperature of 120 °C for 12 hours. The temperature was then increased to 400 °C and maintained for 12 hours, causing the burlite layer deposited on the surface of the resin particles to transform into a porous alumina layer with a porosity of 33% and water. After the reaction, the product was removed, washed, and dried to obtain PTFE microspheres coated with a porous alumina layer, with a coating thickness of approximately 50 nm. The microspheres were placed in a vapor deposition apparatus and protected with argon gas. The temperature was increased to 700°C at a rate of 3°C / min. Methane was then introduced for vapor deposition at a flow rate of 3L / min, and the reaction time was controlled to be 3h. This allowed the gaseous carbon source to be deposited and covered on the microspheres, with a coating thickness of 20nm, forming safe particles with a core-shell structure coated with carbon black.

[0038] Safety particles, carbon nanotube conductive agent, and CMC binder are mixed in a mass ratio of 10:1:1 and coated onto the surface of the positive electrode current collector. After drying, a safety coating is formed.

[0039] Example 3 Aluminum nitrate was dissolved in deionized water to obtain a 12 mol / L solution. Ammonia water was added dropwise as a precipitant, causing the solution to gradually become turbid, and a white precipitate was observed to form. Polyethylene particles with a particle size D50 of 200 nm were added to the resulting mixture and placed in a high-pressure reactor. The mixture was then subjected to constant temperature heat treatment at 120℃ for 12 hours. The temperature was then increased to 400℃ and maintained for 12 hours, causing the boehmite layer deposited on the surface of the resin particles to transform into a porous alumina layer with a porosity of 35% and water. After the reaction, the reaction product was removed, washed, and dried to obtain polyethylene microspheres coated with a porous alumina layer, with a coating thickness of approximately 90 nm. The microspheres were placed in a vapor deposition apparatus and protected with argon gas. The temperature was increased to 700°C at a rate of 3°C / min. Methane was then introduced for vapor deposition at a flow rate of 3L / min, and the reaction time was controlled to be 3h. This allowed the gaseous carbon source to be deposited and covered on the microspheres, with a coating thickness of 20nm, forming safe particles with a core-shell structure coated with carbon black.

[0040] Safety particles, carbon nanotube conductive agent, and CMC binder are mixed in a mass ratio of 10:1:1 and coated onto the surface of the positive electrode current collector. After drying, a safety coating is formed.

[0041] Example 4 Aluminum nitrate was dissolved in deionized water to obtain an 8 mol / L solution. Ammonia water was added dropwise as a precipitant, causing the solution to gradually become turbid, and a white precipitate was observed to form. Polytetrafluoroethylene (PTFE) particles with a D50 of 150 nm were added to the resulting mixture and placed in a high-pressure reactor. The mixture was then subjected to constant-temperature heat treatment at 120 °C for 12 hours. The temperature was then increased to 400 °C and maintained for 12 hours, causing the burlite layer deposited on the surface of the resin particles to transform into a porous alumina layer with a porosity of 34% and water. After the reaction, the reaction product was removed, washed, and dried to obtain PTFE microspheres coated with a porous alumina layer, with a coating thickness of approximately 50 nm. The microspheres were placed in a vapor deposition apparatus and protected with argon gas. The temperature was increased to 700°C at a rate of 3°C / min. Methane was then introduced for vapor deposition at a flow rate of 3L / min, and the reaction time was controlled to be 3h. This allowed the gaseous carbon source to be deposited and covered on the microspheres, with a coating thickness of 20nm, forming safe particles with a core-shell structure coated with carbon black.

[0042] Safety particles and CMC binder are mixed at a mass ratio of 12:1 and coated onto the surface of the positive electrode current collector. After drying, a safety coating is formed.

[0043] Comparative Example 1 A mixture of graphite conductive agent, carbon nanotube conductive agent, thermally responsive material barium titanate, and CMC binder in a mass ratio of 10:1:1:1 is applied to the surface of the positive electrode current collector and dried to form a safety coating.

[0044] Comparative Example 2 A mixture of graphite conductive agent, carbon nanotube conductive agent, thermally responsive material barium titanate, and CMC binder in a mass ratio of 5:1:6:1 is applied to the surface of the positive electrode current collector and dried to form a safety coating.

[0045] Comparative Example 3 Graphite conductive agent, carbon nanotube conductive agent and CMC binder are mixed in a mass ratio of 10:1:1 and coated onto the surface of the positive electrode current collector. After drying, a coating is formed.

[0046] Comparative Example 4 The difference from Example 2 is that this comparative example directly selects alumina particles with a particle size D50 of 250 nm, puts them into a vapor deposition device, introduces argon gas for protection, heats up to 700 °C at a heating rate of 3 °C / min, then introduces methane for vapor deposition at a flow rate of 3 L / min, and controls the reaction time to 3 h, so that the gaseous carbon source is deposited and covers the microspheres, with a coating layer thickness of 20 nm, forming microspheres with a core-shell structure coated with carbon black.

[0047] Comparative Example 5 The difference from Example 2 is that there is no vapor deposition process and the safety particles have no second coating layer.

[0048] Comparative Example 6 The difference from Example 2 is that aluminum nitrate was dissolved in deionized water to obtain a 15 mol / L solution; and the solution was heat-treated at a constant temperature in a high-pressure reactor for 24 hours, resulting in an aluminum oxide coating layer thickness of approximately 150 nm.

[0049] Comparative Example 7 The difference from Example 2 is that the vapor deposition reaction time is 6 hours and the carbon black coating thickness is about 100 nm.

[0050] Test case Battery fabrication: Positive electrode: The positive electrode current collectors from the examples and comparative examples were selected, and positive electrode slurry was coated on both sides of their surfaces. The components of the slurry were: 92 parts lithium iron phosphate, 3 parts carbon nanotubes, 2 parts Super P, and 3 parts PVDF. The solvent was NMP, and the solid content was 60%. Negative electrode: Conventional copper foil is used as the negative electrode current collector, and a negative electrode slurry is coated on both sides of its surface. The composition of the slurry is: 95 parts graphite, 1 part Super P, 2 parts SBR, and 2 parts CMC. The solvent is deionized water, and the solid content is 48%. The diaphragm is a ceramic diaphragm with a thickness of 9μm; Electrolyte composition: solvent is EC, content is 88%, solute is LiFP, content is 12%; After the positive and negative electrodes are coated, dried, and die-cut, they are stacked with a separator and injected with electrolyte to form a stacked soft-pack battery.

[0051] Electrode penetration resistance test: The sample was cut into 3*3cm pieces and tested using an electrode resistance meter. The sample was placed in the electrode resistance meter and tested under a pressure of 60MPa. The penetration resistance of the sample was recorded.

[0052] Hot trigger test: 1. Fully charge the sample battery, i.e., charge it at a constant current of 0.5C to 3.65V, and then charge it at a constant voltage of 0.05C to the cutoff point; 2. Set heating points on both sides of the fully charged sample battery and heat the battery at a rate of 3℃ / min. 3. For every 10°C increase in battery temperature, use a multimeter connected to the positive and negative terminals of the battery to test its internal resistance. 4. Set temperature detection points on the positive and negative terminals of the battery and read the temperature change of the battery until the temperature rise rate of the battery terminals is less than 1℃ / h, then stop heating. 5. Observe the changes in battery status during the above heating process, and whether smoke, fire, or explosion occurs.

[0053] Table 1. Electrode Penetration Resistance Test Results

[0054] Table 2 Results of thermal triggering test

[0055] The test results are shown in Tables 1 and 2. Under normal temperatures, the conductive carbon layer in each embodiment ensures high conductivity of the coating and improves the conductivity between the positive electrode active material and the current collector. However, at high temperatures, the difference in thermal expansion coefficients between the core and shell of the safety particle is significant. The core expands when heated, resulting in a large stress difference between the inside and outside. Furthermore, since the first coating structure is made of ceramic material, it is relatively brittle. Under this stress difference, the coating structure will crack, forming multiple insulating fragments. This significantly reduces the conductivity of the safety coating and significantly increases the resistance, cutting off the current path between the positive electrode active material and the current collector, thus reducing the risk of further thermal runaway. The resistance improvement effect is even more significant when the insulating ceramic material layer has a porous structure.

[0056] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A safety coating for a positive electrode current collector with thermal response characteristics, characterized in that, The coating contains safety particles and a binder; The safety particle includes a matrix; the surface of the matrix is ​​coated with an insulating ceramic material layer; and the surface of the insulating ceramic material layer away from the matrix is ​​coated with a conductive carbon material layer. The coefficient of thermal expansion of the matrix is ​​1.9~20×10⁻⁶. -5 / K; The coefficient of thermal expansion of the insulating ceramic material layer is 2~8×10⁻⁶. -6 / K.

2. The positive electrode current collector safety coating with thermal response characteristics according to claim 1, characterized in that, The matrix is ​​made of polymer material; Preferably, the polymer material includes at least one of polytetrafluoroethylene, polyethylene, and polyamide; Preferably, the insulating ceramic material layer comprises at least one of burlite, alumina, and silicon dioxide; Preferably, the insulating ceramic material layer is an insulating ceramic material layer with a porous structure; The porosity of the insulating ceramic material layer with a porous structure is ≥30%.

3. The positive electrode current collector safety coating with thermal response characteristics according to claim 1, characterized in that, The conductive carbon material includes at least one of graphene, carbon black, and graphite. Preferably, the safety particles in the coating have a mass fraction of 60% to 90%.

4. The positive electrode current collector safety coating with thermal response characteristics according to claim 1, characterized in that, The matrix particle size is 100~200nm; the thickness of the insulating ceramic material layer is 50~120nm; and the thickness of the conductive carbon material layer is 10~50nm.

5. The positive electrode current collector safety coating with thermal response characteristics according to claim 1, characterized in that, The adhesive includes at least one of PVDF, PMMA, and PAA; Preferably, the positive electrode current collector safety coating with thermal response characteristics further includes a conductive agent; Preferably, the conductive agent is at least one selected from graphene, carbon black, and graphite; The positive electrode current collector safety coating with thermal response characteristics comprises the following components in parts by weight: 5-10 portions of safety granules; 0.5 to 1 part of conductive agent; 1-2 parts adhesive.

6. A positive current collector with thermal response characteristics, characterized in that, The positive current collector with thermal response characteristics comprises a positive current collector safety coating with thermal response characteristics as described in any one of claims 1 to 5.

7. The method for preparing a positive current collector with thermal response characteristics according to claim 6, characterized in that, Includes the following steps: Step 1) The matrix is ​​added to an aluminum salt or silicate solution and subjected to a hydrothermal reaction to form an insulating ceramic material layer on the surface of the matrix, thereby obtaining microparticles with a first coating layer; Step 2) Deposit a conductive carbon material layer on the surface of the microparticles with the first coating layer to obtain safe microparticles; Step 3) Coat the surface of the positive current collector with a slurry containing safety particles and binder, and after drying, obtain the positive current collector with thermal response characteristics.

8. The preparation method according to claim 7, characterized in that, In step one), the hydrothermal reaction temperature is 110~140℃ and the time is 10~16h; Preferably, in step one), the matrix is ​​added to an 8-12 mol / L aluminum salt solution to carry out a hydrothermal reaction, forming a boehmite layer on the surface of the matrix; then, it is heated at 400-600°C for 10-16 hours to transform the boehmite layer into a porous alumina layer; thus obtaining microparticles with a first coating layer.

9. The preparation method according to claim 7, characterized in that, In step two), a conductive carbon material layer is deposited on the surface of microparticles with a first coating layer using a vapor phase deposition method. Preferably, the slurry also contains a conductive agent.

10. The application of the thermally responsive positive electrode current collector safety coating according to claims 1 to 5 and the thermally responsive positive electrode current collector according to claim 6 in the preparation of batteries.

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