Battery thermal runaway self-inhibition coating based on heat absorption type reverse thermit reaction as well as preparation method and application of battery thermal runaway self-inhibition coating

Abstract

The invention discloses a battery thermal runaway self-inhibition coating based on a heat absorption type reverse thermit reaction as well as a preparation method and application thereof. The battery thermal runaway self-inhibition coating comprises the following raw materials in percentage by weight: 40-60% of Fe2O3, 15-25% of Al powder, 20-35% of a heat absorption additive, 5-10% of a binder and 0-5% of a trigger regulator, the heat absorption additive is Bi2O3 or SrCO3; the binder is a potassium silicate aqueous solution or high-temperature-resistant polysiloxane resin; the trigger regulator is copper oxide or manganese dioxide. The coating is not a single functional material, but is a'reaction system ', an thermit reaction is converted into an endothermic reaction by introducing an endothermic additive, and a product of the coating can be fused and sintered in situ to generate a compact porous ceramic-metal composite heat insulation layer during the endothermic reaction, so that a battery cell can be isolated in space, and the performance of the battery cell is improved. And heat radiation can be effectively blocked due to low heat conductivity, so that double insurance of heat absorption and isolation is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new energy battery safety technology, more particularly to a battery thermal runaway self-inhibition coating based on endothermic reverse aluminothermic reaction and a preparation method and application thereof. BACKGROUND

[0002] Currently, the thermal safety problem of new energy batteries has become a key bottleneck restricting their development. Once thermal runaway occurs, it will release a huge amount of energy instantaneously, leading to fire and explosion. The existing prevention and control means are mostly of the "after-the-fact remedy" type, which has a fundamental defect: External systems (such as perfluorohexanone injection and water cooling system): there is a delay in response, and the range of action is concentrated outside the battery, making it difficult to quickly penetrate the core area of thermal runaway and prevent the internal chain heat release reaction, resulting in a high rekindling rate.

[0003] Phase change materials (PCM): rely on physical heat absorption, with limited heat of fusion (usually <200 J / g), which is often insufficient in the face of a huge amount of energy in thermal runaway, and cannot play a physical isolation role.

[0004] Traditional fireproof separator: can only delay the spread of heat, but cannot absorb and neutralize heat, and is only a temporary solution.

[0005] Aluminothermic reaction is known for its high heat release, and cannot be directly used in battery fire extinguishing. The present application revolutionarily transforms the high-heat-release aluminothermic reaction into a strong-heat-absorption "reverse aluminothermic reaction" through thermodynamic design, creating a new passive safety solution with built-in, self-triggering, and high efficiency, which eradicates the risk of thermal runaway from two dimensions of energy neutralization and physical isolation. SUMMARY

[0006] In view of the deficiencies of the prior art, one of the purposes of the present application is to provide a battery thermal runaway self-inhibition coating based on endothermic reverse aluminothermic reaction to solve the problems of delayed response, low efficiency, and inability to intervene internally in the prior art.

[0007] To solve the above technical problems, the present application provides the following technical solutions: A battery thermal runaway self-inhibition coating based on endothermic reverse aluminothermic reaction, comprising the following raw materials by weight percentage: Fe2O340-60%, Al powder 15-25%, endothermic additive 20-35%, binder 5-10%, and trigger regulator 0-5%; The Fe2O3 is preferably in a flaky or acicular morphology to increase the reaction contact area and improve the reaction rate; The endothermic additive is bismuth trioxide (Bi2O3) or strontium carbonate (SrCO3); The decomposition reaction of bismuth trioxide (Bi2O3) is: 2Bi2O3→4Bi+3O2 ΔH=+541.4kJ / mol. It is a strongly endothermic reaction. The generated metallic Bi has a low melting point (271.4℃), which helps to form a liquid phase in the reaction zone and promotes the sintering and covering of the product layer. The decomposition reaction of strontium carbonate (SrCO3) is: SrCO3→SrO+CO2 ΔH=+234kJ / mol. It is an endothermic reaction. The CO2 gas produced by decomposition can dilute the concentration of combustible gas and play an auxiliary role in chemical inerting. The binder is an aqueous solution of potassium silicate (K2SiO3) or a high-temperature resistant polysiloxane resin. Its function is not only to bond, but also to form a silicate ceramic phase at high temperatures, which together with the reaction products enhances the density and mechanical strength of the barrier layer. The trigger modifier is copper oxide or manganese dioxide. These substances have a lower initial reaction temperature with Al and can be used to fine-tune the overall trigger response temperature of the coating, making it more accurately match the initial temperature window (~400°C) of battery thermal runaway.

[0008] The battery thermal runaway self-inhibition coating of the present invention is not a single-function material, but a "reaction system". By introducing endothermic additives (Bi2O3 or SrCO3), the aluminothermic reaction is transformed into an endothermic reaction. While it is endothermic, its products (Al2O3, Fe, Bi, etc.) can be melted and sintered in situ to form a dense porous ceramic-metal composite insulation layer, which can isolate the battery cell in space. Moreover, its low thermal conductivity can effectively block thermal radiation, achieving a double insurance of "heat absorption" and "isolation".

[0009] Preferably, the particle size of the Fe2O3 is 100-500 nm.

[0010] Preferably, the Al powder has a particle size of 1-5 μm. The Al powder has high activity and a fast reaction start-up. The particle size needs to be larger than the nanometer scale to ensure storage stability and avoid premature reaction.

[0011] The second objective of this invention is to provide a method for preparing the above-mentioned battery thermal runaway self-inhibition coating based on endothermic reverse aluminothermic reaction, comprising the following steps: (1) Powder pretreatment: The powder components in the raw materials are placed in a vacuum drying oven for drying. (2) Dry premixing: The dried powder is put into a three-dimensional motion mixer according to the formula ratio and run at a speed of 15-20 rpm for 4-6 hours under inert gas protection; (3) Slurry preparation: Mix the uniformly mixed dry powder with the binder (such as potassium silicate solution diluted with deionized water to a solid content of 40%) at a weight ratio of 3:1. Use a planetary mixer to stir at 500 rpm for 5 minutes and then at 1500 rpm for 30 minutes to obtain a uniform and stable slurry with a viscosity of 3000-5000 cP. (4) Coating: Use a spray gun to spray the slurry obtained in step (3) onto the workpiece, spraying multiple thin layers, and leveling at 80°C for 5 minutes after each layer is sprayed. (5) Curing: After coating, the workpiece is transferred to a forced-air drying oven for curing. The temperature program is set to rise from room temperature to 100℃ at 2℃ / min and hold for 1h, then rise to 180℃ at 1℃ / min and hold for 2h. This process allows the adhesive to fully cross-link and cure, forming a dense and firm coating, thus obtaining a battery thermal runaway self-inhibiting coating with a film thickness of 100-200μm.

[0012] Furthermore, in step (1), the drying temperature is 105±5℃ and the drying time is more than 4 hours to ensure the removal of moisture and prevent clumping or adverse reaction with the binder during subsequent processing.

[0013] Furthermore, in step (2), the inert gas is argon.

[0014] Furthermore, in step (4), the workpiece needs to be pre-blasted to increase surface roughness before coating, and then cleaned with acetone to remove oil.

[0015] Further, in step (4), the nozzle diameter of the spray gun is 1.0-1.3mm, the spraying pressure is 0.4-0.6MPa, and the distance between the spray gun and the workpiece is 20-30cm.

[0016] The third objective of this invention is to provide the application of the aforementioned battery thermal runaway self-inhibiting coating in the inner wall of the battery casing or in the fireproof partition of the battery module.

[0017] Furthermore, the battery includes a lithium-ion battery, a sodium-ion battery, or a solid-state battery.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. The battery thermal runaway self-inhibition coating of the present invention is not a single-function material, but a "reaction system". By introducing endothermic additives (Bi2O3 or SrCO3), the aluminothermic reaction is transformed into an endothermic reaction. While it is endothermic, its products (Al2O3, Fe, Bi, etc.) can be melted and sintered in situ to form a dense porous ceramic-metal composite insulation layer, which can isolate the battery cell in space. Moreover, its low thermal conductivity can effectively block thermal radiation, achieving a double insurance of "heat absorption" and "isolation".

[0019] 2. This invention is the first to propose and realize the application of "reverse aluminothermic reaction" in battery safety, which completely subverts the inherent property of "high exothermic" in the traditional aluminothermic reaction. Through precise thermodynamic design, endothermic additives (Bi2O3 or SrCO3) are introduced to transform it into a net endothermic chemical reaction, which neutralizes the energy basis of thermal runaway from the root. This is a fundamental breakthrough in principle.

[0020] 3. This invention integrates a battery thermal runaway self-suppression coating as a passive safety element into the battery casing or module. The coating's triggering relies entirely on the heat generated by the thermal runaway itself, without the need for any external power supply, sensor, or control logic. This greatly improves the reliability and simplicity of the safety system and achieves the highest level of safety redundancy.

[0021] 4. This invention opens up a new path for "in-situ intervention" for internal thermal runaway of batteries, and integrates safety functions from the outside of the battery system (module and pack level) to the cell level, realizing a paradigm shift from "external remedy" to "internal eradication". The coating of this invention is located at the closest position to the thermal runaway initiation point, which can achieve the fastest response and the most effective intervention, and is particularly suitable for next-generation high energy density solid-state batteries. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the square aluminum-cased battery coated with a self-inhibiting coating according to Embodiment 2 of the present invention; Figure 2 This is a comparison curve of the needle penetration test between the control group and the coated group in Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of the structure of the lithium iron phosphate energy storage battery coated with a self-inhibiting coating according to Embodiment 3 of the present invention; Figure 4 A comparison of the heat absorption efficiency per unit mass of traditional PCM and the self-inhibiting coating prepared in this invention.

[0023] Explanation of the labels in the diagram: 1. Battery casing; 2. Self-inhibiting coating; 3. Battery module; 4. Battery cell; 5. Fireproof partition. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available. For any specific techniques or conditions not specified in the examples, they can be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions.

[0026] Example 1 This embodiment provides a method for preparing a battery thermal runaway self-inhibition coating based on an endothermic reverse aluminothermic reaction. The self-inhibition coating comprises the following raw materials by weight percentage: 40-60% Fe2O3 (particle size 100-500nm), 15-25% Al powder (particle size 1-5μm), 20-35% endothermic additive, 5-10% binder, and 0-5% trigger regulator; wherein, the endothermic additive is bismuth trioxide (Bi2O3) or strontium carbonate (SrCO3), and the binder is an aqueous solution of potassium silicate (K2SiO3) or a high-temperature resistant polysiloxane resin. The preparation process is as follows: (1) Powder pretreatment: Place all powder raw materials (Fe2O3, Al, Bi2O3) in a vacuum drying oven and dry at 105±5℃ for more than 4 hours to ensure the removal of moisture and prevent clumping or adverse reaction with binder in subsequent processing; (2) Dry premixing: The dried powder is put into a three-dimensional motion mixer according to the formula ratio. Under the protection of inert gas (such as argon), it is run at a low speed of 15-20 rpm for 4-6 hours. High-energy ball milling is strictly prohibited to avoid frictional heat or mechanical sparks that may cause accidental ignition or change the morphology of the powder. (3) Slurry preparation: Mix the uniformly mixed dry powder with the binder (such as potassium silicate solution diluted with deionized water to a solid content of 40%) at a weight ratio of 3:1. Use a planetary mixer to stir at 500 rpm for 5 minutes and then at 1500 rpm for 30 minutes to obtain a uniform and stable slurry with a viscosity of 3000-5000 cP. (4) Coating: Sandblast the workpiece to increase the surface roughness, and clean it with acetone to remove oil. Use a spray gun to spray the slurry prepared in step (3) onto the workpiece. Spray multiple thin layers. After each layer is sprayed, allow it to level at 80°C for 5 minutes. The nozzle diameter of the spray gun is 1.0-1.3 mm, the spraying pressure is 0.4-0.6 MPa, and the distance between the spray gun and the workpiece is 20-30 cm. (5) Curing: After coating, the workpiece is transferred to a forced-air drying oven for curing. The temperature program is set to rise from room temperature to 100℃ at 2℃ / min, hold for 1h, then rise to 180℃ at 1℃ / min, hold for 2h, and a self-inhibiting coating with a film thickness of 100-200μm can be obtained.

[0027] Working mechanism of self-inhibiting coating: Latency period: When the battery is working normally, the coating is a stable solid coating that is compatible with electrolyte vapor and has no measurable effect on the battery's impedance, capacity, or cycle life.

[0028] Trigger: When thermal runaway occurs inside the battery, heat is transferred to the coating. Once the local temperature of the coating reaches its trigger temperature (T_trigger, which is adjusted between 450-600℃ by the formulation), the reaction is activated.

[0029] Endothermic reaction: The inverse aluminothermic reaction occurs as shown in the following equation (taking Bi2O3 as an example): 6Fe₂O₃ + 4Al + 4Bi₂O₃ → 4Fe + 4Al₂O₃ + 8FeO + 8Bi ΔH ≈ +600 kJ (estimated value) This process absorbs heat rapidly within milliseconds to seconds, acting like a highly efficient "chemical heat sink," quickly consuming the heat energy of the surrounding environment and causing a sudden drop in temperature.

[0030] Barrier formation: The reaction products Fe, Al2O3, FeO and Bi melt, eutecticize and sinter at high temperature to form a porous, hard and heat-insulating ceramic-metal composite barrier layer in situ. Its thermal conductivity is extremely low (<1W / m・K), which can effectively block heat radiation, flame propagation and material exchange, and completely isolate the runaway battery cell.

[0031] Example 2 like Figure 1 As shown, in this embodiment, the self-inhibiting coating 2 prepared in Example 1 is coated on the inner wall of the square ternary lithium battery casing 1 to achieve thermal runaway protection of the battery. The test parameters are as follows: Test subjects: Commercial 50Ah NCM811 / graphite square aluminum-cased batteries; control group: uncoated square ternary lithium batteries.

[0032] The raw material composition of the self-inhibiting coating 2 (by weight percentage) is: Fe2O3 (50%), Al powder (20%), Bi2O3 (25%), and K2SiO3 (5%).

[0033] Process: Following the process described in Example 1, a self-inhibiting coating 2 is sprayed onto the inner wall of the battery casing 1 (excluding the top cover pole area), and the dry film thickness is controlled to be 150 μm.

[0034] Test method: Charge the battery to 100% SOC and perform a needle penetration test (φ3mm steel needle, speed 80mm / s).

[0035] Effect: such as Figure 2As shown, after acupuncture, the battery temperature of the control group suddenly rose to >800 °C within 3 seconds and burned violently. When the battery temperature of the coated group rose to 520 °C, the reaction was triggered, and the highest temperature was recorded as 565 °C. After disassembly after the reaction, a dense gray-black sintered body was formed inside the battery, successfully suppressing the thermal runaway within a single cell, and the adjacent cells remained intact. It was calculated that the effective heat absorption of this coating was about 850 J / g, far exceeding that of traditional PCM materials (<200 J / g).

[0036] Example 3 As Figure 3 shown, in this example, the self-inhibiting coating 2 prepared in Example 1 was coated on the metal fireproof partition 5 of the energy storage battery module 3 to achieve thermal runaway protection of the battery. The test parameters are as follows: Test object: Aluminum alloy partition of a 280 Ah lithium iron phosphate energy storage module.

[0037] Raw material composition of the self-inhibiting coating 2 (by weight percentage): Fe2O3 (55%), Al powder (18%), SrCO3 (22%), high-temperature resistant polysiloxane resin (5%).

[0038] Process: According to the process described in Example 1, the self-inhibiting coating 2 was scrape-coated on both sides of the fireproof partition 5, with a dry film thickness of 200 μm, and cured under the specified conditions.

[0039] Test method: Simulate the thermal runaway of a single cell 4 in the module, and use a heating plate to heat the cell 4 until thermal runaway occurs.

[0040] Effect: When the flame and high temperature spread to the partition, the coating was triggered. The measurement by the heat flux meter showed that the temperature rise rate on the back side of the partition decreased significantly. The coating reaction delayed the time for heat to spread to the adjacent cell 4 from <2 minutes in the control group to >15 minutes, winning crucial time for the fire warning and linkage of the entire energy storage system. At the same time, the CO2 gas released by the decomposition of SrCO3 played an auxiliary inerting role within the module.

[0041] Compared with the prior art, the technical solution of the present invention has the following significant and measurable beneficial effects, as shown in the following table:

[0042] As shown in the results of the table, it can be shown that the technical solution of the present invention has the following advantages: 1. Fundamental high performance: By absorbing heat through chemical reactions, the heat absorption per unit mass (>600 J / g) is more than 3 to 4 times that of physical phase change materials, and it can directly neutralize the early heat release of thermal runaway from the energy level, with extremely significant temperature reduction effects.

[0043] 2. Built-in active isolation: The in-situ ceramic barrier generated by the reaction is a unique advantage that cannot be achieved by existing technologies. It not only isolates the battery cell in space, but its low thermal conductivity can also effectively block heat radiation, achieving a double guarantee of "heat absorption" and "isolation".

[0044] 3. Absolute reliability: As a passive safety technology, its triggering does not depend on any external power source, sensor or control system, but is activated only by the energy of thermal runaway itself, avoiding the failure risk that may exist in active systems, and has extremely high reliability.

[0045] 4. Excellent economic efficiency: The main raw materials (Fe2O3, Al, Bi2O3) are all bulk industrial products, resulting in low costs. The coating process is compatible with existing battery manufacturing processes, requires no complex equipment, is easy to scale up, and offers extremely high cost-effectiveness.

[0046] 5. Wide applicability: Since its mechanism of action does not depend on the chemical system of the battery, it can be widely applied to various scenarios such as lithium-ion batteries, sodium-ion batteries, and solid-state batteries, and has broad application prospects.

[0047] The embodiments disclosed in this invention are preferred embodiments, but are not limited thereto. Those skilled in the art can easily understand the spirit of this invention based on the above embodiments and make different extensions and variations, but as long as they do not depart from the spirit of this invention, they are all within the protection scope of this invention.

Claims

1. A battery thermal runaway self-suppression coating based on an endothermic reverse aluminothermic reaction, characterized in that, The raw materials include the following weight percentages: Fe2O3 40-60%, Al powder 15-25%, heat-absorbing additives 20-35%, binder 5-10%, and triggering modifier 0-5%; The heat-absorbing additive is bismuth trioxide or strontium carbonate; The adhesive is an aqueous solution of potassium silicate or a high-temperature resistant polysiloxane resin. The triggering modifier is copper oxide or manganese dioxide.

2. The battery thermal runaway self-suppression coating based on endothermic reverse aluminothermic reaction according to claim 1, characterized in that: The Fe2O3 has a particle size of 100-500 nm.

3. The battery thermal runaway self-suppression coating based on endothermic reverse aluminothermic reaction according to claim 1, characterized in that: The particle size of the Al powder is 1-5 μm.

4. A method for preparing a battery thermal runaway self-inhibition coating based on an endothermic reverse aluminothermic reaction as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Powder pretreatment: The powder components in the raw materials are placed in a vacuum drying oven for drying. (2) Dry premixing: The dried powder is put into a three-dimensional motion mixer according to the formula ratio and run at a speed of 15-20 rpm for 4-6 hours under inert gas protection; (3) Slurry preparation: Mix the uniformly mixed dry powder and binder at a weight ratio of 3:

1. Use a planetary mixer to stir at 500 rpm for 5 minutes and then at 1500 rpm for 30 minutes to obtain a uniform and stable slurry with a viscosity of 3000-5000 cP. (4) Coating: Use a spray gun to spray the slurry obtained in step (3) onto the workpiece, spraying multiple thin layers, and leveling at 80°C for 5 minutes after each layer is sprayed. (5) Curing: After coating, the workpiece is transferred to a forced-air drying oven for curing. The temperature program is set to increase from room temperature to 100℃ at 2℃ / min, hold for 1h, then increase to 180℃ at 1℃ / min, hold for 2h, and a battery thermal runaway self-inhibiting coating with a film thickness of 100-200μm can be obtained.

5. The method for preparing a battery thermal runaway self-inhibition coating based on an endothermic reverse aluminothermic reaction according to claim 4, characterized in that: In step (1), the drying temperature is 105±5℃ and the drying time is more than 4 hours.

6. The method for preparing a battery thermal runaway self-inhibition coating based on an endothermic reverse aluminothermic reaction according to claim 4, characterized in that: In step (2), the inert gas is argon.

7. The method for preparing a battery thermal runaway self-inhibition coating based on an endothermic reverse aluminothermic reaction according to claim 4, characterized in that: In step (4), the workpiece needs to be sandblasted before coating to increase surface roughness and cleaned with acetone to remove oil.

8. The method for preparing a battery thermal runaway self-inhibition coating based on an endothermic reverse aluminothermic reaction according to claim 4, characterized in that: In step (4), the nozzle diameter of the spray gun is 1.0-1.3mm, the spraying pressure is 0.4-0.6MPa, and the distance between the spray gun and the workpiece is 20-30cm.

9. The application of the battery thermal runaway self-inhibiting coating as described in any one of claims 1-3 or the battery thermal runaway self-inhibiting coating prepared by the preparation method described in any one of claims 4-8 in the inner wall of the battery casing or the fireproof partition of the battery module.

10. The application according to claim 9, characterized in that: The battery includes lithium-ion batteries, sodium-ion batteries, or solid-state batteries.

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