Porous flame-retardant coating containing fire extinguishing agent in holes, preparation method of porous flame-retardant coating and battery pack

Abstract

The invention provides a porous flame-retardant coating containing a fire extinguishing agent in pores, a preparation method of the porous flame-retardant coating and a battery pack, and relates to the field of batteries. The invention discloses a porous flame-retardant coating containing a fire extinguishing agent. The porous flame-retardant coating comprises a bonding transition layer, a porous flame-retardant layer and a wear-resistant protective layer which are sequentially stacked, the bonding transition layer comprises the following raw materials in parts by mass: 85-95 parts of bonding resin, 2-5 parts of a cross-linking agent and 3-10 parts of a tackifier; the porous flame-retardant layer comprises a three-dimensional communicated porous structure and a fire extinguishing agent arranged in the porous structure; the porous flame-retardant layer comprises the following raw materials in parts by mass: 40-60 parts of flame-retardant resin, 20-40 parts of a fire extinguishing agent and 1-5 parts of a first auxiliary agent; the wear-resistant protective layer comprises the following raw materials in parts by mass: 80-90 parts of modified epoxy resin, 5-10 parts of a curing agent and 1-5 parts of a second aid. The coating loads a fire extinguishing agent through a porous structure, a fire extinguishing medium can be actively released when a fire occurs, and the defect that a traditional coating only can insulate heat passively is overcome.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to a porous flame-retardant coating containing fire extinguishing agent in pores and a preparation method thereof and a battery pack. BACKGROUND

[0002] As the core link of battery pack safety protection, the performance boundary of flame-retardant technology is facing unprecedented challenges, and the limitations of existing protection means are becoming increasingly prominent. At present, the mainstream battery pack flame-retardant protection scheme in the industry mainly falls into three categories: first, physical compartments are set inside the battery pack to block the spread of fire by fireproof materials (such as mica plate, ceramic fiber, fireproof felt, etc.), but this type of way can only delay the spread of fire, and cannot actively suppress the generated fire or flammable gas; second, a spray fire extinguishing system or gas fire extinguishing device is used, which can achieve active fire extinguishing function by releasing fire extinguishing medium, but it needs to be equipped with nozzles, pipelines, liquid tanks, etc., the overall structure is complex, occupies a large space, and has high requirements for the sealing of the battery pack, which is difficult to adapt to the miniaturization and integration of the battery design; third, a flame-retardant coating is coated on the surface of the battery monomer or inside the battery pack shell, such as epoxy resin-based flame-retardant coating, ammonium polyphosphate-based intumescent flame-retardant coating, etc. This type of coating mainly blocks heat and oxygen by forming an expanded carbon layer, which expands to 20-30 times the original coating after being heated, but the monomers inside the battery pack are densely arranged and the space is narrow, which cannot provide enough space for the expansion of the coating, resulting in incomplete formation of the carbon layer and easy breakage, which greatly reduces the fireproof effect, and this type of coating lacks the ability to actively release fire extinguishing medium, and the fire extinguishing efficiency is low.

[0003] Therefore, the current industry urgently needs a coating technology with simple structure, strong adaptability, which can actively release fire extinguishing medium when the battery pack catches fire, and achieve rapid fire extinguishing and sustained flame-retardant effect, to solve the problems of insufficient active fire extinguishing ability, complex structure, and insufficient flame-retardant effect of existing protection means. SUMMARY

[0004] The purpose of the present application is to provide a porous flame-retardant coating containing fire extinguishing agent in pores and a preparation method thereof and a battery pack to solve the above problems.

[0005] To achieve the above purpose, the first aspect of the present application provides a porous flame-retardant coating containing fire extinguishing agent in pores, which comprises a bonding transition layer, a porous flame-retardant layer and a wear-resistant protective layer which are sequentially stacked; The raw materials of the bonding transition layer include, by mass fraction: 85-95 parts of bonding resin, 2-5 parts of crosslinking agent and 3-10 parts of tackifier; The porous flame-retardant layer comprises a three-dimensional interconnected porous structure and fire extinguishing agent arranged in the porous structure; the raw materials of the porous flame-retardant layer include, by mass fraction: 40-60 parts of flame-retardant resin, 20-40 parts of fire extinguishing agent and 1-5 parts of first additive; The raw material of the wear-resistant protective layer comprises, by mass fraction, modified epoxy resin 80-90 parts, curing agent 5-10 parts, and second additive 1-5 parts.

[0006] Optionally, the porous fire-retardant coating layer with fire extinguishing agent in the pores satisfies at least one of the following conditions: (1) the thickness of the porous fire-retardant coating layer with fire extinguishing agent in the pores is 50-1000 μm; (2) the thickness of the adhesive transition layer is 10-100 μm, and the adhesive strength is ≥5 MPa; (3) the thickness of the porous fire-retardant layer is 30-700 μm; (4) the thickness of the wear-resistant protective layer is 10-200 μm.

[0007] Optionally, the thickness of the porous fire-retardant coating layer with fire extinguishing agent in the pores is 500-800 μm.

[0008] Optionally, the porous fire-retardant coating layer with fire extinguishing agent in the pores satisfies at least one of the following conditions: (1) the adhesive resin comprises ethylene-vinyl acetate copolymer and / or polyurethane modified acrylate; (2) the crosslinking agent comprises isocyanate crosslinking agent; (3) the tackifier comprises rosin resin and / or terpene resin; (4) the fire-retardant resin comprises modified phenolic resin modified by ammonium polyphosphate; the phosphorus content in the modified phenolic resin is ≥15%, and the oxygen index is ≥35%; (5) the fire extinguishing agent comprises liquid fire extinguishing agent and / or solid fire extinguishing agent; (6) the raw material of the first additive comprises, by mass fraction, dispersing agent 0.5-2 parts, defoaming agent 0.2-1 part, and antioxidant 0.3-2 parts; (7) the raw material of the modified epoxy resin comprises bisphenol A type epoxy resin and nano silicon dioxide; the mass of the nano silicon dioxide accounts for 1%-3% of the mass of the raw material of the modified epoxy resin; (8) the curing agent comprises fatty amine curing agent; (9) the raw material of the second additive comprises, by mass fraction, leveling agent 0.5-2 parts and wear-resistant agent 0.5-3 parts.

[0009] Optionally, the porous fire-retardant coating layer with fire extinguishing agent in the pores satisfies at least one of the following conditions: (1) the isocyanate crosslinking agent comprises diisocyanate and / or hexamethylene diisocyanate; (2) the liquid fire extinguishing agent comprises water-based fire retardant and / or phosphate ester fire-retardant liquid; (3) the solid fire extinguishing agent comprises one or more of ultra-fine aluminum hydroxide, ultra-fine magnesium hydroxide and melamine cyanurate; (4) the dispersing agent comprises a polycarboxylate compound; (5) the defoaming agent comprises an organic silicon defoaming agent; (6) the antioxidant comprises a hindered phenol compound; (7) the fatty amine curing agent comprises ethylenediamine and / or diethylenetriamine; (8) the leveling agent comprises an acrylate leveling agent; (9) the wear-resistant agent comprises aluminum nitride.

[0010] Optionally, the porous fire-retardant coating layer with fire extinguishing agent in the pores satisfies at least one of the following conditions: (1) the pore diameter of the porous fire-retardant layer is 1-50 μm, and the porosity is 30%-60%; (2) the mass of the fire extinguishing agent is 20%-40% of the mass of the porous fire-retardant coating layer with fire extinguishing agent in the pores; (3) the thickness of the porous fire-retardant layer is ≥2 times the average pore diameter in the porous structure.

[0011] The second aspect of the present application provides a preparation method of the porous fire-retardant coating layer with fire extinguishing agent in the pores, comprising: mixing and first dispersing raw materials of the porous fire-retardant layer and a pore-forming agent to obtain a porous fire-retardant slurry; mixing and second dispersing raw materials of the bonding transition layer and the wear-resistant protective layer respectively to obtain a bonding transition slurry and a wear-resistant protective slurry respectively; arranging the bonding transition slurry on the surface of the battery pack substrate and performing first solidification to obtain a bonding transition layer; arranging the bonding transition slurry on the surface of the bonding transition layer and performing second solidification to obtain a porous fire-retardant layer; arranging the wear-resistant protective slurry on the surface of the porous fire-retardant layer and performing third solidification to obtain the porous fire-retardant coating layer with fire extinguishing agent in the pores.

[0012] Optionally, the porous fire-retardant coating layer with fire extinguishing agent in the pores satisfies at least one of the following conditions: (1) the pore-forming agent comprises a thermal decomposition compound and / or a soluble salt compound; (2) the rotation speed of the first dispersion is 1000-1500 r / min, the temperature is 50-60°C, and the time is 30-60 min; (3) the rotation speed of the second dispersion is 800-1200 r / min, and the time is 20-40 min; (4) the temperature of the first solidification is 80-100℃, and the time is 15-30min; (5) the temperature of the third solidification is 150-180℃, and the time is 30-60min.

[0013] Optionally, the porous flame-retardant coating containing fire extinguishing agent in the pores satisfies at least one of the following conditions: (1) the thermal decomposition compound includes ammonium bicarbonate and / or azodicarbonamide; (2) the soluble salt compound includes one or more of sodium chloride, sodium bicarbonate, potassium chloride, sodium nitrate and sodium sulfate; (3) when the pore-forming agent includes the thermal decomposition compound, the temperature of the second solidification is 120-150℃, and the time is 20-40min; (4) when the pore-forming agent includes the soluble salt compound, the second solidification includes: placing the wear-resistant protective slurry arranged on the surface of the adhesive transition layer at room temperature for 10-20min, then soaking in water for 5-10min, and then drying, the drying temperature is 60-80℃, and the time is 10-15min.

[0014] The third aspect of the present application provides a battery pack, comprising a base body and the porous flame-retardant coating containing fire extinguishing agent in the pores arranged on the surface of the base body; The adhesive transition layer in the porous flame-retardant coating containing fire extinguishing agent in the pores is adjacent to the base body.

[0015] Compared with the prior art, the beneficial effects of the present application include: The fire-retardant coating provided by the application is porous and contains fire extinguishing agents in the pores. The fire extinguishing agents are loaded by the porous structure, and the fire extinguishing medium can be actively released when a fire occurs, rapidly cooling and oxygen isolation, solving the defect that the traditional coating can only passively isolate heat. At the same time, the carbon layer formed by carbonization of the resin matrix can realize sustained fire retardation, greatly improving the protection duration. More importantly, the raw materials of each layer form a significant synergistic effect: the bonding resin, crosslinking agent and tackifier of the bonding transition layer synergistically strengthen the interlayer bonding; the fire-retardant resin, fire extinguishing agent and first additive of the porous fire-retardant layer synergistically optimize the fire extinguishing efficiency and long-term fire retardation; the modified epoxy resin, curing agent and second additive of the wear-resistant protective layer synergistically improve the protection performance and interlayer compatibility; and the strong bonding between layers is achieved through hydrogen bonding, chemical bonding and mechanical anchoring, avoiding interface failure and forming an integrated protection system of "intra-layer synergistic effect-interlayer stable bonding". The coating also has the advantages of simple structure, strong adaptability, safety and environmental protection, and good stability. The coating is a composite layered structure, which is suitable for battery packs of various sizes and types, has high compatibility, and the selected fire extinguishing agents (such as aluminum hydroxide and phosphate esters) are all halogen-free and low-toxicity substances, which will not release harmful gases during the fire extinguishing process. The coating is stable in performance at room temperature and normal use temperature (≤150℃), and the fire extinguishing agent does not leak, which does not affect the electrical performance of the battery pack. The coating has good bonding strength (≥5MPa) and wear resistance, and can withstand slight impact and friction during the assembly and use of the battery pack. At the same time, the design of the porous structure reduces the overall density of the coating (density ≤1.2g / cm 3 ), which does not significantly increase the weight of the battery pack, meeting the design requirements of lightweight battery pack.

[0016] The preparation method of the fire-retardant coating provided by the application is provided, and the coating is a composite layered structure, and the preparation process is mature and the raw materials are easy to obtain.

[0017] The battery pack provided by the application has excellent fireproof performance. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as limiting the scope of the application.

[0019] Figure 1 The structure schematic diagram of the fire-retardant coating provided for example 1 is provided.

[0020] Main element symbol explanation: 100-bonding transition layer; 200-porous fire-retardant layer; 300-wear-resistant protective layer. DETAILED DESCRIPTION

[0021] Firstly, the scheme provided by the application is explained in more detail, as follows: The application provides a porous flame-retardant coating containing fire extinguishing agent in the pores, comprising a bonding transition layer, a porous flame-retardant layer and a wear-resistant protective layer which are sequentially stacked; The raw materials of the bonding transition layer include, by mass fraction, 85-95 parts of bonding resin, 2-5 parts of crosslinking agent and 3-10 parts of tackifier; Optionally, the raw materials of the bonding transition layer include, by mass fraction, 85 parts of bonding resin, 2 parts of crosslinking agent and 3 parts of tackifier, or any value between 85 and 95 parts of bonding resin, between 2 and 5 parts of crosslinking agent, and between 3 and 10 parts of tackifier; It should be noted that the bonding resin serves as a matrix to provide interlayer basic adhesion, realize firm combination of the matrix and the porous flame-retardant layer, and guarantee the overall structural stability of the coating; the crosslinking agent induces resin crosslinking and curing to improve the mechanical strength of the layer and prevent interlayer peeling; the thickening agent optimizes the interface wetting performance, enhances the interface action between the resin matrix and the porous flame-retardant layer, and supplements the adhesion strength; the polar groups of the tackifier form hydrogen bond action with the bonding resin and the flame-retardant resin of the porous flame-retardant layer, and the crosslinking agent can strengthen the interlayer chemical bonding to significantly improve the interface bonding force between the bonding layer transition layer and the porous flame-retardant layer, avoiding interlayer peeling; The porous flame-retardant layer includes a three-dimensionally connected porous structure and fire extinguishing agent arranged in the porous structure; the raw materials of the porous flame-retardant layer include, by mass fraction, 40-60 parts of flame-retardant resin, 20-40 parts of fire extinguishing agent and 1-5 parts of first additive; Optionally, the raw materials of the porous flame-retardant layer include, by mass fraction, 40 parts of flame-retardant resin, 20 parts of fire extinguishing agent and 1 part of first additive, or any value between 40 and 60 parts of flame-retardant resin, between 20 and 40 parts of fire extinguishing agent, and between 1 and 5 parts of first additive; It should be noted that the flame-retardant resin as the matrix skeleton of the porous flame-retardant layer constructs a three-dimensional interconnected porous structure, provides basic flame-retardant performance and structural support, carries and fixes the fire extinguishing agent, and guarantees the stability of the layer shape and the compatibility of adjacent layers; the fire extinguishing agent is the core flame-retardant functional component, filled in the porous structure, which efficiently inhibits the spread of fire by heat absorption, suppression of combustion chain reaction, etc., and strengthens the flame-retardant effect of the coating; the first additive promotes the uniform dispersion of the fire extinguishing agent, improves the formability of the coating, and at the same time improves the interfacial compatibility between the layer and other layers, so as to guarantee the synergistic effect of the flame-retardant function and the structural performance; the coordination between the surface active groups of the flame-retardant resin and the fire extinguishing agent, and the dispersant in the first additive can optimize the dispersibility of the fire extinguishing agent, and the three components together ensure that the fire extinguishing agent is efficiently loaded in the porous structure without blocking the pore channels, so as to realize the dual effect of rapid release of the fire extinguishing medium and carbonization of the resin for flame retardation. The raw materials of the wear-resistant protective layer include, by mass fraction: modified epoxy resin 80-90 parts, curing agent 5-10 parts, and second additive 1-5 parts. Optionally, the modified epoxy resin can be 80 parts, 85 parts, 90 parts, or any value between 80 and 90 parts, the curing agent can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, or any value between 5 and 10 parts, and the second additive can be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, or any value between 1 and 5 parts.

[0022] It should be noted that the modified epoxy resin is the matrix of the wear-resistant protective layer, which provides excellent mechanical wear resistance, constructs the outermost protective barrier of the coating, and at the same time guarantees the interfacial compatibility with the underlying porous flame-retardant layer, resists external friction, impact, etc., and prolongs the service life of the coating; the curing agent and the modified epoxy resin undergo crosslinking and curing reaction to form a dense and stable three-dimensional network structure, which improves the hardness and adhesion of the protective layer, and ensures the long-term effect of the wear-resistant and protective functions; the second additive optimizes the film-forming property and surface flatness of the coating, improves the anti-aging and anti-ultraviolet performance of the layer, coordinates the compatibility of the matrix and the curing agent, and further strengthens the synergistic effect of wear resistance and protection.

[0023] It should also be noted that the flame-retardant coating with porous structure and fire extinguishing agent in the pores has a special porous structure design, which loads high-efficiency fire extinguishing agent in the pores. When the battery pack triggers abnormal temperature rise due to thermal runaway or initial fire, the pore structure of the coating is broken or the internal fire extinguishing medium is released rapidly, which directly acts on the fire source and the combustible gas release source, forming a dual protection mechanism of "physical barrier + active fire extinguishing", thereby greatly shortening the fire response time, improving the fire extinguishing efficiency, and significantly enhancing the safety and fireproof performance of the battery pack in the thermal runaway scenario.

[0024] It should be noted that the polar groups of the tackifier form hydrogen bonding with the adhesive resin, the flame-retardant resin of the porous flame-retardant layer, and the crosslinking agent can strengthen the interlayer chemical bonding; the flame-retardant resin forms coordination bonding with the surface active groups of the fire extinguishing agent, and the dispersant in the first additive can optimize the dispersibility of the fire extinguishing agent; the modified component of the modified epoxy resin can penetrate into the surface pores of the porous flame-retardant layer to form mechanical anchoring, and the curing agent reacts with the surface hydroxyl groups of the flame-retardant resin; the modified component in the modified epoxy resin can penetrate into the surface pores of the porous flame-retardant layer to form mechanical anchoring, and the curing agent reacts with the surface hydroxyl groups of the flame-retardant resin, thereby synergistically improving the bonding strength of the wear-resistant protective layer and the porous flame-retardant layer, while ensuring the overall wear resistance and high temperature resistance of the coating.

[0025] In addition, the resin matrix is a general term for the resins of the wear-resistant layer, the porous flame-retardant layer, and the adhesive layer, and the resin is the matrix material. Carbonization is a process in which H, O, and other elements of the resin matrix are decomposed when exposed to fire, leaving behind carbon elements to form a solid hard shell.

[0026] In some embodiments, the porous flame-retardant coating with fire extinguishing agent in the pores satisfies at least one of the following conditions: (1) The thickness of the porous flame-retardant coating with fire extinguishing agent in the pores is 50-1000 μm; Optionally, the thickness of the porous flame-retardant coating with fire extinguishing agent in the pores can be 50 μm, 100 μm, 200 μm, 400 μm, 600 μm, 800 μm, 1000 μm, or any value between 50-1000 μm; (2) The thickness of the adhesive transition layer is 10-100 μm, and the adhesive strength is ≥5 MPa; Optionally, the thickness of the adhesive transition layer can be 10 μm, 50 μm, 100 μm, or any value between 10-100 μm, and the adhesive strength can be 5 Mpa, 10 Mpa, 20 Mpa, 50 Mpa, or any value ≥5 Mpa; It should be noted that the core function of the adhesive transition layer is to improve the interfacial adhesive strength of the coating and the battery pack substrate (such as an aluminum alloy shell or a battery separator); (3) The thickness of the porous flame-retardant layer is 30-700 μm; Optionally, the thickness of the porous flame-retardant layer can be 30 μm, 100 μm, 300 μm, 700 μm, or any value between 30-700 μm; It should be noted that the porous flame-retardant layer is the core functional layer of the coating that realizes the active fire extinguishing and passive flame-retardant functions, and its interior not only contains the above-mentioned three-dimensional interconnected porous structure, but also has the pores of the porous structure filled with fire extinguishing agent; (4) The thickness of the wear-resistant protective layer is 10-200 μm.

[0027] Optionally, the thickness of the wear-resistant protective layer can be any value between 10μm, 50μm, 100μm, 150μm, 200μm or 10-200μm.

[0028] It should be noted that the wear-resistant protective layer serves to prevent scratches, block external dust and moisture, and also has a certain degree of high-temperature resistance.

[0029] In some embodiments, the thickness of the porous flame-retardant coating containing extinguishing agent within its pores is 500-800 μm.

[0030] Optionally, the thickness of the porous flame-retardant coating containing extinguishing agent can be any value between 500 and 800 μm, ranging from 500 μm, 600 μm, 700 μm, to 800 μm.

[0031] In some embodiments, the porous flame-retardant coating containing extinguishing agent within its pores satisfies at least one of the following conditions: (1) The adhesive resin includes ethylene-vinyl acetate copolymer and / or polyurethane modified acrylate; (2) The crosslinking agent includes isocyanate crosslinking agents; (3) The tackifier includes rosin resin and / or terpene resin; (4) The flame-retardant resin includes a modified phenolic resin modified with ammonium polyphosphate; the modified phenolic resin has a phosphorus content ≥15% and an oxygen index ≥35%; Optionally, the phosphorus content in the modified phenolic resin can be any value between 15%, 20%, 30% or ≥15%, and the oxygen index can be any value between 35%, 40%, 45%, 50% or ≥35%. It should be noted that ammonium polyphosphate modification can enhance the compatibility between flame-retardant resin and fire extinguishing agent. The polyphosphoric acid produced by its decomposition synergistically promotes the formation of carbon layer with the fire extinguishing agent, thereby improving the long-lasting flame retardancy. (5) The extinguishing agent includes liquid extinguishing agent and / or solid extinguishing agent; (6) The raw materials of the first auxiliary agent, by weight, include: 0.5-2 parts of dispersant, 0.2-1 parts of defoamer, and 0.3-2 parts of antioxidant; Optionally, the raw materials of the first auxiliary agent, by weight, include dispersant in any value between 0.5 parts, 1 part, 2 parts or 0.5-2 parts, defoamer in any value between 0.2 parts, 0.5 parts, 1 part or 0.2-1 parts, and antioxidant in any value between 0.3 parts, 1 part, 1.5 parts, 2 parts or 0.3-2 parts; (7) The raw materials of the modified epoxy resin include bisphenol A type epoxy resin and nano silica; the mass of the nano silica accounts for 1%-3% of the mass of the raw materials of the modified epoxy resin; Optionally, the mass of nano-silica can be any value between 1%, 2%, 3% or 1-3% of the mass of the modified epoxy resin raw material. It should be noted that the synergistic optimization of coating viscosity and hardness by nano-silica and epoxy resin not only facilitates interlayer penetration and bonding but also enhances the protective performance of the wear-resistant protective layer. (8) The curing agent includes aliphatic amine curing agents; (9) The raw materials of the second additive, by mass, include: 0.5-2 parts of leveling agent and 0.5-3 parts of wear-resistant agent.

[0032] Optionally, the raw materials of the second auxiliary agent, by weight, may be any value between 0.5 parts, 1 part, 1.5 parts, 2 parts or 0.5-2 parts for leveling agent and any value between 0.5 parts, 1 part, 2 parts, 3 parts or 0.5-3 parts for abrasion resistant agent.

[0033] In some embodiments, the porous flame-retardant coating containing extinguishing agent within its pores satisfies at least one of the following conditions: (1) The isocyanate crosslinking agent includes diisocyanate and / or hexamethylene diisocyanate; (2) The liquid extinguishing agent includes water-based flame retardants and / or phosphate ester flame retardants; (3) The solid extinguishing agent includes one or more of ultrafine aluminum hydroxide, ultrafine magnesium hydroxide and melamine cyanurate; (4) The dispersant includes polycarboxylate compounds; (5) The defoamer includes silicone defoamers; (6) The antioxidants include hindered phenolic compounds; (7) The fatty amine curing agent includes ethylenediamine and / or diethylenetriamine; (8) The leveling agent includes acrylate leveling agents; (9) The wear-resistant agent includes aluminum nitride.

[0034] In some embodiments, the porous flame-retardant coating containing extinguishing agent within its pores satisfies at least one of the following conditions: (1) The pore diameter of the porous flame-retardant layer is 1-50 μm, and the porosity is 30%-60%; Optionally, the pore diameter of the porous flame-retardant layer can be any value between 1μm, 10μm, 25μm, 50μm or 1-50μm, and the porosity can be any value between 30%, 40%, 50%, 60% or 30-60%. (2) The mass of the extinguishing agent is 20%-40% of the mass of the porous flame-retardant coating containing the extinguishing agent within its pores; Optionally, the mass of the extinguishing agent can be any value between 20%, 30%, 40%, or 20-40% of the mass of the porous flame-retardant coating containing the extinguishing agent within its pores. (3) The thickness of the porous flame retardant layer is ≥ twice the average diameter of the pores in the porous structure.

[0035] It is important to note that the thickness design is matched with the raw materials to ensure sufficient extinguishing agent load, while forming a gradient flame-retardant structure to achieve synergy between continuous fire extinguishing and oxygen isolation protection.

[0036] A second aspect of this application provides a method for preparing the porous flame-retardant coating containing a fire extinguishing agent, comprising: The raw materials and pore-forming agent of the porous flame-retardant layer are mixed and first dispersed to obtain a porous flame-retardant slurry; The raw materials for the bonding transition layer and the wear-resistant protective layer are mixed and dispersed separately to obtain the bonding transition slurry and the wear-resistant protective slurry, respectively. The bonding transition slurry is applied to the surface of the battery pack substrate and cured for the first time to obtain the bonding transition layer. The bonding transition slurry is applied to the surface of the bonding transition layer and then cured a second time to obtain a porous flame-retardant layer. Abrasion-resistant protective slurry is applied to the surface of the porous flame-retardant layer and then subjected to a third curing process to obtain a porous flame-retardant coating containing extinguishing agent within the pores.

[0037] In some embodiments, the porous flame-retardant coating containing extinguishing agent within its pores satisfies at least one of the following conditions: (1) The pore-forming agent includes thermally decomposable compounds and / or soluble salt compounds; (2) The first dispersion is carried out at a rotation speed of 1000-1500 r / min, a temperature of 50-60℃, and a time of 30-60 min; Optionally, the rotation speed of the first dispersion can be any value between 1000 r / min, 1250 r / min, and 1500 r / min; the temperature can be any value between 50℃, 55℃, 60℃, or 50-60℃; and the time can be any value between 30min, 40min, 50min, 60min, or 30-60min. (3) The second dispersion rotation speed is 800-1200 r / min, and the time is 20-40 min; Optionally, the rotational speed of the second dispersion can be any value between 800 r / min, 900 r / min, 1000 r / min, 1200 r / min or 800-1200 r / min, and the time can be any value between 20 min, 30 min, 40 min or 20-40 min. (4) The first curing temperature is 80-100℃ and the time is 15-30min; Optionally, the first curing temperature can be any value between 80℃, 90℃, 100℃ or 80-100℃, and the time can be any value between 15min, 20min, 30min or 15-30min; (5) The temperature of the third curing is 150-180℃ and the time is 30-60min.

[0038] Optionally, the third curing temperature can be any value between 150℃, 160℃, 170℃, 180℃ or 150-180℃, and the time can be any value between 30min, 40min, 50min, 60min or 30-60min.

[0039] In some embodiments, the porous flame-retardant coating containing extinguishing agent within its pores satisfies at least one of the following conditions: (1) The thermally decomposable compounds include ammonium bicarbonate and / or azodicarbonamide; (2) The soluble salt compounds include one or more of sodium chloride, sodium bicarbonate, potassium chloride, sodium nitrate, and sodium sulfate; (3) When the pore-forming agent includes a thermally decomposable compound, the second curing temperature is 120-150℃ and the time is 20-40 min; Optionally, the time can be any value between 20 min, 30 min, 40 min, or 20-40 min; (4) When the pore-forming agent includes soluble salt compounds, the second curing includes: placing the wear-resistant protective slurry disposed on the surface of the bonding transition layer at room temperature for 10-20 minutes, then immersing it in water for 5-10 minutes, and then drying it at a temperature of 60-80°C for 10-15 minutes.

[0040] Optionally, the wear-resistant protective slurry on the surface of the bonding transition layer can be left at room temperature for any value between 10 min, 15 min, 20 min, or 10-20 min; the soaking time can be any value between 5 min, 7 min, 9 min, 10 min, or 5-10 min; the drying temperature can be any value between 60℃, 70℃, 80℃, or 60-80℃; and the drying time can be any value between 10 min, 12 min, 14 min, 15 min, or 10-15 min.

[0041] A third aspect of this application provides a battery pack, including a substrate and a porous flame-retardant coating disposed on the surface of the substrate, wherein the pores contain a fire extinguishing agent. The bonding transition layer in the porous flame-retardant coating containing fire extinguishing agent is adjacent to the substrate.

[0042] It should be noted that the porous flame-retardant coating containing fire extinguishing agent has a layered composite structure and can be applied to the inner wall of the battery pack casing, the surface of the battery cells, or the surface of the separator between battery modules.

[0043] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0044] Example 1 This embodiment provides a porous flame-retardant coating containing a fire extinguishing agent within its pores, comprising a bonding transition layer 100, a porous flame-retardant layer 200, and a wear-resistant protective layer 300 stacked sequentially, as shown in the specific structure below. Figure 1 As shown.

[0045] The raw materials for the bonding transition layer, by weight, include: 90 parts of ethylene-vinyl acetate copolymer (EVA resin, purchased from Shanghai Jizhi Biochemical Technology Co., Ltd.), 3 parts of hexamethylene diisocyanate, and 7 parts of rosin resin. The raw materials of the porous flame retardant layer, by weight, include: 53 parts of ammonium polyphosphate modified phenolic resin (phosphorus content 16%, oxygen index 36%), 30 parts of ultrafine aluminum hydroxide (particle size 0.8μm), 1 part of polycarboxylate dispersant (solid content 40%), 0.5 parts of organosilicon defoamer (polysiloxane-polyether copolymer), and 1 part of hindered phenolic antioxidant (hindered phenol 1010); The raw materials for the wear-resistant protective layer, by weight, include: 88 parts of nano-silica (2% addition) modified bisphenol A epoxy resin, 8 parts of ethylenediamine, 1.5 parts of acrylate leveling agent, and 2.5 parts of aluminum nitride (particle size 10-15μm, purity 99.2%).

[0046] The second aspect of this embodiment provides a method for preparing a porous flame-retardant coating containing a fire extinguishing agent within its pores. The specific preparation process is as follows: S1: Add the porous flame retardant layer raw material and 15 parts of ammonium bicarbonate (particle size 10-20μm) into a high-speed disperser and disperse for 45 minutes at a speed of 1200r / min and a temperature of 55℃ to form a uniform slurry; S2: The raw materials for the bonding transition layer and the wear-resistant protective layer are respectively fed into the dispersion equipment and dispersed for 30 minutes at a speed of 1000 r / min and at room temperature to obtain the corresponding slurry; S3: After the inner wall of the aluminum alloy shell is pretreated by sandblasting to remove rust and alcohol degreasing, the bonding transition layer slurry is applied by roller coating process. The wet film thickness is controlled so that the thickness after curing is 50μm. Then, it is baked in an oven at 85℃ for 20 minutes to complete the curing. S4: A porous flame-retardant slurry is applied to the surface of the cured bonding transition layer using an air spraying process. The wet film thickness is controlled to achieve a cured thickness of 400μm. The film is then baked in a 130℃ oven for 30 minutes. During this time, ammonium bicarbonate is decomposed by heat to form pores, resulting in a porous structure with a pore diameter of 5-25μm and a porosity of 45%. Ultrafine aluminum hydroxide is adsorbed inside the pores. S5: An air spraying process is used to coat the surface of the porous flame-retardant layer with a wear-resistant protective layer slurry. The wet film thickness is controlled so that the thickness after curing is 80μm. The coating is then baked in a 160℃ oven for 45 minutes to complete the curing process. After natural cooling, a porous flame-retardant coating containing fire extinguishing agent is obtained.

[0047] Example 2 The first aspect of this embodiment provides a porous flame-retardant coating containing a fire extinguishing agent, comprising an adhesive transition layer, a porous flame-retardant layer, and a wear-resistant protective layer stacked sequentially.

[0048] The raw materials of the bonding transition layer, by weight, include: 85 parts of polyurethane modified acrylate (purchased from Wanhua Chemical, solid content 55%), 5 parts of diisocyanate, and 10 parts of terpene resin. The raw materials of the porous flame retardant layer, by weight, include: 40 parts of silicone resin, 35 parts of phosphate ester flame retardant liquid (resorcinol bis, phosphorus content ≥10%), 2 parts of polycarboxylate (polycarboxylate ammonium salt, solid content 40-50%) dispersant, 1 part of silicone defoamer (polysiloxane-polyether copolymer, oily, solid content 35%), and 2 parts of hindered phenolic antioxidant (hindered phenol 1010). The raw materials for the wear-resistant protective layer, by weight, include: 85 parts of nano-silica (3% addition) modified bisphenol A epoxy resin, 10 parts of diethylenetriamine, 2 parts of acrylate leveling agent, and 3 parts of aluminum nitride (particle size 15-20μm, purity 99.5%).

[0049] The second aspect of this embodiment provides a method for preparing a porous flame-retardant coating containing a fire extinguishing agent within its pores. The specific preparation process is as follows: S1: Add the porous flame retardant layer raw material and 20 parts of sodium chloride (particle size 20-30μm) into a high-speed disperser and disperse for 30 minutes at a speed of 1500r / min and a temperature of 60℃ to form a uniform slurry. Then add 20% of the total mass of deionized water, adjust the speed to 800r / min, and stir at room temperature for 15 minutes until the sodium chloride is completely dissolved to obtain the porous flame retardant layer slurry. S2: The raw materials for the bonding transition layer and the wear-resistant protective layer are respectively fed into a dispersion device and dispersed at 800 r / min and room temperature for 40 min to obtain the corresponding slurry; S3: After plasma cleaning pretreatment of the battery cell surface, the bonding transition layer slurry is applied by air spraying process. The wet film thickness is controlled so that the cured thickness is 100μm. The curing is completed by baking in a 100℃ oven for 15min. S4: A porous flame-retardant slurry is applied to the surface of the cured bonding transition layer using an air spraying process. The wet film thickness is controlled to achieve a cured thickness of 700 μm. The film is left at room temperature for 20 minutes to set, then immersed in deionized water for 10 minutes to wash away sodium chloride. Finally, it is dried in a 70°C oven for 15 minutes to form a porous structure with a pore diameter of 10-35 μm and a porosity of 60%. The phosphate ester flame retardant liquid is retained in the pores through the resin micro-swelling effect. S5: The wear-resistant protective layer slurry is coated on the surface of the porous flame-retardant layer using an air spraying process. The wet film thickness is controlled to achieve a cured thickness of 200μm. The coating is then baked at 180℃ for 30 minutes to complete the curing process and naturally cooled to obtain the finished flame-retardant coating.

[0050] Example 3 The first aspect of this embodiment provides a porous flame-retardant coating containing a fire extinguishing agent, comprising an adhesive transition layer, a porous flame-retardant layer, and a wear-resistant protective layer stacked sequentially.

[0051] The raw materials of the bonding transition layer, by weight, include: 85 parts of polyurethane modified acrylate (purchased from Wanhua Chemical, hydroxyl-terminated polyurethane prepolymer grafted acrylate copolymer), 5 parts of hexamethylene diisocyanate, and 10 parts of rosin resin. The raw materials for the porous flame retardant layer, by weight, include: 60 parts of ammonium polyphosphate modified phenolic resin (phosphorus content 15%, oxygen index 38%), 20 parts of melamine cyanurate, 1.5 parts of polycarboxylate dispersant (solid content 40-50%), 0.2 parts of organosilicon defoamer (polysiloxane-polyether copolymer), and 0.3 parts of hindered phenolic antioxidant (hindered phenol 1010); The raw materials for the wear-resistant protective layer, by weight, include: 90 parts of nano-silica (1% addition) modified bisphenol A epoxy resin, 5 parts of ethylenediamine, 2.5 parts of acrylate leveling agent, and 2.5 parts of aluminum nitride (particle size 12-18μm, purity 99.3%).

[0052] The second aspect of this embodiment provides a method for preparing a porous flame-retardant coating containing a fire extinguishing agent within its pores. The specific preparation process is as follows: S1: The porous flame retardant layer raw material and 18 parts of azodicarbonamide (particle size 1-5μm) are put into a high-speed disperser and dispersed for 40 minutes at a speed of 1300r / min and a temperature of 58℃ to form a porous flame retardant layer slurry. S2: The raw materials for the bonding transition layer and the wear-resistant protective layer are respectively fed into a dispersion device and dispersed for 35 minutes at a speed of 900 r / min and at room temperature to obtain the corresponding slurry. S3: After sandblasting and acetone degreasing pretreatment of the battery module separator surface, the bonding transition layer slurry is applied by roller coating process. The wet film thickness is controlled so that the thickness after curing is 10μm. The curing is completed by baking in a 90℃ oven for 18 minutes. S4: A porous flame-retardant slurry is coated onto the surface of the cured bonding transition layer using a roller coating process. The wet film thickness is controlled so that the cured thickness is 30μm. The film is then baked in an oven at 210℃ for 35min. The azodicarbonamide decomposes under heat to form pores, resulting in a porous structure with a pore diameter of 8-15μm and a porosity of 50%. The melamine cyanurate flame retardant is adsorbed into the pores. S5: A wear-resistant protective layer slurry is coated on the surface of the porous flame-retardant layer using a roller coating process. The wet film thickness is controlled so that the thickness after curing is 10μm. The coating is then baked in an oven at 170℃ for 40 minutes to complete the curing process and allowed to cool naturally to obtain the finished flame-retardant coating.

[0053] Comparative Example 1 The difference from Example 1 is that the flame retardant layer has no porous structure, that is, no pore-forming agent is added during preparation.

[0054] The comparative coating has no internal pores, and the ultrafine aluminum hydroxide (fire extinguishing agent) is directly dispersed in the ammonium polyphosphate modified phenolic resin matrix.

[0055] Comparative Example 2 The difference from Example 2 is that no phosphate ester flame retardant liquid (fire extinguishing agent) is added to the porous flame retardant layer, while the other raw material ratios and preparation processes are the same as in Example 2; the coating has a porous structure inside, but no fire extinguishing agent is filled in the pores.

[0056] Comparative Example 3 The difference from Example 3 is that the bonding transition layer and wear-resistant protective layer are removed, and the porous flame-retardant slurry is directly coated on the surface of the battery module separator. The remaining raw material ratios and preparation processes are the same as in Example 3.

[0057] The flame-retardant coatings prepared in the above embodiments and comparative examples were subjected to relevant performance tests, and the test results are shown in Table 1. The total thickness of the flame-retardant coating was tested according to the magnetic method in GB / T13452.2; the adhesive strength of the coating was tested according to the method in GB / T 5210; and the flame-retardant rating of the coating was tested and evaluated according to the method in GB / T 2408. A simulated battery thermal runaway environment (800℃ thermal radiation, radiation intensity 50kW / m2) was used, and a high-speed camera recorded the time from heating to releasing the extinguishing agent. A battery module simulation device was built, and a thermal runaway triggering test was conducted according to GB / T 36276 to calculate the percentage of the non-spreading area after thermal runaway to the total area of ​​the module. The mass loss of the coating after 1000 revolutions under a 500g load was tested according to GB / T 1768.

[0058] Table 1 Performance Tests

[0059] analyze: The results show that Examples 1-3 all have excellent comprehensive performance; the bonding strength exceeds 5MPa, ensuring a strong bond with the substrate; the flame retardant rating reaches V-0, meeting the high flame retardant requirements; the response speed is less than 3.5s, which can quickly respond to thermal runaway; the thermal runaway propagation inhibition rate is ≥88%, which can effectively prevent the spread of fire; the wear amount is ≤6mg / 1000 rpm, which has good wear resistance.

[0060] Compared with Example 1, Comparative Example 1 lacks a porous structure, so the extinguishing agent cannot be released quickly, resulting in a response time of 8.0s and a thermal runaway propagation inhibition rate of 55%, proving that a porous structure is the key to improving the response efficiency of the coating. Compared with Example 2, Comparative Example 2 has no active fire extinguishing function because there is no fire extinguishing agent filling the pores, and the thermal runaway propagation inhibition rate is only 40%, indicating that the fire extinguishing agent is the core element to achieve active flame retardancy.

[0061] Compared with Example 3, Comparative Example 3, due to the lack of an adhesive transition layer and a wear-resistant protective layer, had a bonding strength reduced to 2.3 MPa and a wear rate increased to 20 mg / 1000 rpm, indicating that the multilayer structure can significantly improve the bonding strength and wear resistance of the coating.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0063] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A porous flame-retardant coating containing a fire extinguishing agent within its pores, characterized in that, It includes an adhesive transition layer, a porous flame-retardant layer, and a wear-resistant protective layer that are stacked in sequence; The raw materials of the bonding transition layer, by weight, include: 85-95 parts of bonding resin, 2-5 parts of crosslinking agent, and 3-10 parts of tackifier; The porous flame-retardant layer includes a three-dimensional interconnected porous structure and a fire extinguishing agent disposed in the porous structure; the raw materials of the porous flame-retardant layer, by mass, include: 40-60 parts of flame-retardant resin, 20-40 parts of fire extinguishing agent and 1-5 parts of first additive. The raw materials of the wear-resistant protective layer, by weight, include: 80-90 parts of modified epoxy resin, 5-10 parts of curing agent, and 1-5 parts of second auxiliary agent.

2. The porous flame-retardant coating containing a fire extinguishing agent within its pores according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The thickness of the porous flame-retardant coating containing extinguishing agent in the pores is 50-1000 μm; (2) The thickness of the bonding transition layer is 10-100 μm, and the bonding strength is ≥5 MPa; (3) The thickness of the porous flame-retardant layer is 30-700 μm; (4) The thickness of the wear-resistant protective layer is 10-200μm.

3. The porous flame-retardant coating containing a fire extinguishing agent within its pores according to claim 2, characterized in that, The thickness of the porous flame-retardant coating containing fire extinguishing agent is 500-800 μm.

4. The porous flame-retardant coating containing a fire extinguishing agent within its pores according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The adhesive resin includes ethylene-vinyl acetate copolymer and / or polyurethane modified acrylate; (2) The crosslinking agent includes isocyanate crosslinking agents; (3) The tackifier includes rosin resin and / or terpene resin; (4) The flame-retardant resin includes a modified phenolic resin modified with ammonium polyphosphate; the modified phenolic resin has a phosphorus content ≥15% and an oxygen index ≥35%; (5) The extinguishing agent includes liquid extinguishing agent and / or solid extinguishing agent; (6) The raw materials of the first auxiliary agent, by weight, include: 0.5-2 parts of dispersant, 0.2-1 parts of defoamer, and 0.3-2 parts of antioxidant; (7) The raw materials of the modified epoxy resin include bisphenol A type epoxy resin and nano silica; the mass of the nano silica accounts for 1%-3% of the mass of the raw materials of the modified epoxy resin; (8) The curing agent includes aliphatic amine curing agents; (9) The raw materials of the second additive, by mass, include: 0.5-2 parts of leveling agent and 0.5-3 parts of wear-resistant agent.

5. The porous flame-retardant coating containing a fire extinguishing agent within its pores according to claim 4, characterized in that, At least one of the following conditions must be met: (1) The isocyanate crosslinking agent includes diisocyanate and / or hexamethylene diisocyanate; (2) The liquid extinguishing agent includes water-based flame retardants and / or phosphate ester flame retardants; (3) The solid extinguishing agent includes one or more of ultrafine aluminum hydroxide, ultrafine magnesium hydroxide and melamine cyanurate; (4) The dispersant includes polycarboxylate compounds; (5) The defoamer includes silicone defoamers; (6) The antioxidants include hindered phenolic compounds; (7) The fatty amine curing agent includes ethylenediamine and / or diethylenetriamine; (8) The leveling agent includes acrylate leveling agents; (9) The wear-resistant agent includes aluminum nitride.

6. The porous flame-retardant coating containing a fire extinguishing agent within its pores according to any one of claims 1-5, characterized in that, At least one of the following conditions must be met: (1) The pore diameter of the porous flame-retardant layer is 1-50 μm, and the porosity is 30%-60%; (2) The mass of the extinguishing agent is 20%-40% of the mass of the porous flame-retardant coating containing the extinguishing agent within its pores; (3) The thickness of the porous flame retardant layer is ≥ twice the average diameter of the pores in the porous structure.

7. A method for preparing a porous flame-retardant coating containing a fire extinguishing agent within its pores, as described in any one of claims 1-6, characterized in that, include: The raw materials and pore-forming agent of the porous flame-retardant layer are mixed and first dispersed to obtain a porous flame-retardant slurry; The raw materials for the bonding transition layer and the wear-resistant protective layer are mixed and dispersed separately to obtain the bonding transition slurry and the wear-resistant protective slurry, respectively. The bonding transition slurry is applied to the surface of the battery pack substrate and cured for the first time to obtain the bonding transition layer. The bonding transition slurry is applied to the surface of the bonding transition layer and then cured a second time to obtain a porous flame-retardant layer. Abrasion-resistant protective slurry is applied to the surface of the porous flame-retardant layer and then subjected to a third curing process to obtain a porous flame-retardant coating containing extinguishing agent within the pores.

8. The method for preparing a porous flame-retardant coating containing a fire extinguishing agent within its pores according to claim 7, characterized in that, At least one of the following conditions must be met: (1) The pore-forming agent includes thermally decomposable compounds and / or soluble salt compounds; (2) The first dispersion is carried out at a rotation speed of 1000-1500 r / min, a temperature of 50-60℃, and a time of 30-60 min; (3) The second dispersion rotation speed is 800-1200 r / min, and the time is 20-40 min; (4) The first curing temperature is 80-100℃ and the time is 15-30min; (5) The temperature of the third curing is 150-180℃ and the time is 30-60min.

9. The method for preparing a porous flame-retardant coating containing a fire extinguishing agent within its pores according to claim 8, characterized in that, At least one of the following conditions must be met: (1) The thermally decomposable compounds include ammonium bicarbonate and / or azodicarbonamide; (2) The soluble salt compounds include one or more of sodium chloride, sodium bicarbonate, potassium chloride, sodium nitrate, and sodium sulfate; (3) When the pore-forming agent includes a thermally decomposable compound, the second curing temperature is 120-150℃ and the time is 20-40 min; (4) When the pore-forming agent includes soluble salt compounds, the second curing includes: placing the wear-resistant protective slurry disposed on the surface of the bonding transition layer at room temperature for 10-20 minutes, then immersing it in water for 5-10 minutes, and then drying it at a temperature of 60-80°C for 10-15 minutes.

10. A battery pack, characterized in that, The coating includes a substrate and a porous flame-retardant coating disposed on the surface of the substrate, as described in any one of claims 1-6, wherein the pores contain a fire extinguishing agent; The bonding transition layer in the porous flame-retardant coating containing fire extinguishing agent is adjacent to the substrate.

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