Lithium battery microcapsule fire extinguishing coating and preparation method and application thereof

Abstract

The invention belongs to the technical field of fire extinguishing agents, and particularly relates to a lithium battery microcapsule fire extinguishing coating and a preparation method and application thereof. By means of the microcapsule technology, the heat stability and the response speed of the fire extinguishing agent are improved. And through the core-shell structure design, effective coating and controlled release of the fire extinguishing agent are achieved. The hydroxymethyl cellulose is used as a matrix, so that the adhesive force and the mechanical strength of the coating are enhanced, a uniform fireproof layer is further formed on the surface of the lithium battery, and the thermal safety performance of the battery is improved. Therefore, the microcapsule fire extinguishing coating for the lithium battery disclosed by the invention can quickly release the microcapsule fire extinguishing agent when the battery is subjected to thermal runaway, so as to realize an inhibition effect on thermal runaway propagation.

Description

Technical Field

[0001] The invention belongs to the technical field of fire extinguishing agents, and specifically relates to a lithium battery microcapsule fire extinguishing coating and a preparation method and application thereof. Background Art

[0002] With the rapid development of lithium battery technology, its safety issues are particularly prominent. Lithium batteries are widely used in new energy vehicles and energy storage due to their high energy density and long cycle life. However, lithium batteries may cause thermal runaway due to thermal abuse, overheating, short circuit or extrusion during long-term use, which may cause fire or even explosion, posing a serious threat to people's lives and property.

[0003] In response to the fire problem of lithium batteries, researchers have developed a variety of fire extinguishing agents to improve their safety. For example, CN 116077881A proposed a lithium battery composite coated fire extinguishing agent, which uses microencapsulation technology to make fluorocarbon fire extinguishing materials and water into core-shell structure powder to improve fire extinguishing efficiency and reduce costs. CN 116059574 A discloses a lithium battery composite fire extinguishing agent, which combines fire extinguishing microcapsules and hydrogels to effectively deal with the thermal runaway phenomenon of lithium batteries through synergistic effects.

[0004] Although the above research has made some progress in improving the fire extinguishing efficiency of lithium batteries, the existing technology is still lacking in the research of coatings. Specifically, the existing technology focuses on the chemical composition and fire extinguishing mechanism of fire extinguishing agents, while there is relatively little research on how to effectively integrate fire extinguishing agents into the physical structure of batteries, especially as fire-resistant coatings on the outer layer of batteries. Such coatings can not only respond quickly when a fire occurs, but also have potential advantages in preventing the spread of fire and improving the overall safety of batteries.

[0005] In addition, the fire extinguishing agents in the prior art are mostly in liquid or powder form, which are difficult to distribute evenly, easy to lose, or have adverse effects on battery performance in practical applications. Developing a new type of fire retardant coating that can form an effective protective layer on the surface of lithium batteries is of great significance for improving the safety of lithium batteries. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a new type of lithium battery fire-retardant coating to address the problems existing in the prior art. The coating can not only effectively absorb and block heat to prevent thermal runaway of the lithium battery, but also has the advantages of easy coating, uniform distribution and long-term stability, thereby significantly improving the safety and reliability of the lithium battery.

[0007] In order to achieve the above objectives, the first objective of the present invention is to provide a lithium battery microcapsule fire extinguishing coating, which adopts the following technical scheme:

[0008] A lithium battery microcapsule fire extinguishing coating comprises a coating matrix composed of hydroxymethyl cellulose and a microcapsule fire extinguishing agent embedded in the matrix.

[0009] It is worth noting that the present invention uses hydroxymethyl cellulose as a matrix material to form a uniform coating with good adhesion, and has embedded microcapsule fire extinguishing agent, which can form an effective fire barrier on the surface of the lithium battery. Among them, the microcapsules can realize the precise release of the fire extinguishing agent at a specific temperature in the early stage of thermal runaway of the lithium battery, thereby inhibiting the thermal runaway of the lithium battery and the propagation of thermal runaway, and then realizing the in-situ early inhibition of thermal runaway of the lithium battery. The coating uses a hydroxymethyl cellulose matrix to form a three-dimensional network structure to provide the mechanical strength and thermal stability of the coating, and the hydroxymethyl cellulose can form a gel system through hydrolysis and gelation, and carbonize at high temperature, thereby reducing the degradation rate of the polymer, making the microcapsule fire extinguishing agent more stable and reliable.

[0010] Furthermore, the microcapsule fire extinguishing agent includes a shell material composed of a polymer resin and a core material composed of a fluorine-containing fire extinguishing agent and a refrigerant.

[0011] Furthermore, the polymer resin is urea-formaldehyde resin, and the fluorine-containing fire extinguishing agent and refrigerant include one or a combination of dodecafluoro-2-methylpentane-3-one, hexafluorobutene, 1,1,2,2,3,3,4,4-nonafluoro-4-methoxybutane, trans-1-chloro-3,3,3-trifluoropropene, and 2-bromo-3,3,3-trifluoropropene.

[0012] It is worth noting that the microcapsule fire extinguishing agent material used in the present invention is green and environmentally friendly. The core material uses a fluorine-containing fire extinguishing agent and a refrigerant to comprehensively exert the effects of physical inhibition (evaporation heat absorption) and chemical inhibition (eliminating free radicals to interrupt chain reactions), and synergistically achieves in-situ early inhibition of thermal runaway of lithium batteries. The lithium battery microcapsule fire extinguishing coating disclosed in the present invention uses hydroxymethyl cellulose as a matrix material to form a uniform coating with good adhesion, and has embedded microcapsule fire extinguishing agents, which can quickly release the fire extinguishing agent when thermal runaway occurs in the lithium battery, achieving on-site fire extinguishing and cooling.

[0013] The second object of the present invention is to provide a method for preparing the lithium battery microcapsule fire extinguishing coating as described above.

[0014] A method for preparing a lithium battery microcapsule fire extinguishing coating comprises the following steps: firstly dissolving hydroxymethyl cellulose in a solution to form a polymer matrix, then dispersing a microcapsule fire extinguishing agent in the polymer matrix solution, and coating the solution on the outer surface of a lithium ion battery after drying to obtain a lithium battery microcapsule fire extinguishing coating.

[0015] Furthermore, the specific steps of the preparation method include:

[0016] S1, dissolving hydroxymethyl cellulose with a viscosity of 100,000 in water to form a solution;

[0017] S2, uniformly dispersing the microcapsule fire extinguishing agent in the hydroxymethyl cellulose solution, and adjusting the viscosity of the mixture;

[0018] S3, applying the mixture obtained in step S2 to the outer surface of the lithium-ion battery, and drying to form a fire extinguishing coating.

[0019] It is worth noting that the in-situ polymerization method used in the present invention to synthesize microcapsules can achieve precise control of particle size and shell thickness, high core material embedding rate, enhanced thermal stability of microcapsules, and improved fire extinguishing efficiency.

[0020] Furthermore, the drying method in step S3 is solvent evaporation at ambient temperature.

[0021] The third object of the present invention is to provide an application of the lithium battery microcapsule fire extinguishing coating as described above.

[0022] The invention discloses an application of a lithium battery microcapsule fire extinguishing coating in lithium battery products.

[0023] Furthermore, the lithium battery products include new energy electric vehicles or large energy storage systems.

[0024] During operation, the lithium battery microcapsule fire extinguishing coating is applied to the battery surface. When a fire occurs, the external temperature rise stimulates the fluorine-containing fire extinguishing agent and the refrigerant to absorb heat and vaporize, breaking the polymer shell and releasing the internal fire extinguishing agent, quickly extinguishing the initial fire source and preventing the thermal runaway of the lithium battery from spreading.

[0025] Compared with the prior art, the present invention utilizes microcapsule technology to improve the thermal stability and response speed of the fire extinguishing agent. And through the core-shell structure design, the effective coating and controlled release of the fire extinguishing agent are achieved. The present invention uses hydroxymethyl cellulose as a matrix to enhance the adhesion and mechanical strength of the coating, thereby forming a uniform fireproof layer on the surface of the lithium battery, thereby improving the thermal safety performance of the battery. Therefore, the lithium battery microcapsule fire extinguishing coating disclosed in the present invention can quickly release the microcapsule fire extinguishing agent when the battery has thermal runaway, so as to achieve the effect of inhibiting the spread of thermal runaway. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without creative work.

[0027] Figure 1This is the SEM image of the lithium battery microcapsule fire extinguishing agent prepared by the present invention.

[0028] Figure 2 Optical image and SEM image of the lithium battery microcapsule fire extinguishing coating prepared by the present invention.

[0029] Figure 3 This is a TG-DSC curve representation of the thermal stability of the lithium battery microcapsule fire extinguishing coating prepared in the present invention.

[0030] Figure 4 This is a comparison chart of the fire protection test of the lithium battery microcapsule fire extinguishing coating prepared by the present invention, wherein the left side is without the lithium battery microcapsule fire extinguishing coating, and the right side is with the lithium battery microcapsule fire extinguishing coating.

[0031] Figure 5 The lithium battery microcapsule fire extinguishing coating prepared by the present invention and its thickness measurement. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] The word "embodiment" used here as an "exemplary" does not necessarily mean that any embodiment described is superior to or better than other embodiments. Unless otherwise specified, the performance index tests in the embodiments of this application are performed using conventional test methods in the art. It should be understood that the terms described in this application are only used to describe specific implementation methods and are not used to limit the content disclosed in this application.

[0034] Unless otherwise specified, the technical and scientific terms used in this document have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs; other experimental methods and technical means not specifically specified in this application refer to experimental methods and technical means commonly used by ordinary technicians in this field.

[0035] In order to better illustrate the content of the present application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that the present application can also be implemented without certain specific details. In the embodiments, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of the present application.

[0036] Under the premise of no conflict, the technical features disclosed in the embodiments of the present application can be combined arbitrarily, and the resulting technical solutions belong to the contents disclosed in the embodiments of the present application.

[0037] The present invention discloses a lithium battery microcapsule fire extinguishing coating and a preparation method and application thereof, belonging to the technical field of fire extinguishing agents. The present invention utilizes microcapsule technology to improve the thermal stability and response speed of the fire extinguishing agent. And through the core-shell structure design, the effective coating and controlled release of the fire extinguishing agent are achieved. The present invention adopts hydroxymethyl cellulose as a matrix to enhance the adhesion and mechanical strength of the coating, thereby forming a uniform fireproof layer on the surface of the lithium battery, thereby improving the thermal safety performance of the battery. Therefore, the lithium battery microcapsule fire extinguishing coating disclosed by the present invention can quickly release the microcapsule fire extinguishing agent when the battery has thermal runaway, so as to achieve the effect of inhibiting the spread of thermal runaway.

[0038] In order to better understand the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as a limitation of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above invention content are also considered to fall within the protection scope of the present invention.

[0039] Example 1

[0040] (I) Synthesis of prepolymer

[0041] First, accurately weigh 11.65g of melamine and 11.10g of urea into a clean three-necked flask as the main monomers for the prepolymer reaction. Then add 45g of formaldehyde as a crosslinking agent to the flask, and 45g of deionized water to adjust the concentration of the reaction medium. Use anhydrous sodium carbonate to carefully adjust the pH value of the mixture to 8.5-9.0, and use a precision pH meter to ensure accurate control of the pH value.

[0042] The flask was then placed in an oil bath, stirred at 300 rpm, and heated to 70°C. This temperature was maintained for one hour to allow the reaction to proceed fully. After the reaction was completed, the flask was quickly removed from the oil bath and placed in an ice water bath to achieve rapid cooling to room temperature. After cooling, the reaction mixture was diluted with 187.5 g of deionized water to form a 10 wt% prepolymer solution, which provided raw materials for the next step of microcapsule synthesis.

[0043] (II) Synthesis of microcapsules

[0044] Accurately measure dodecafluoro-2-methylpentane-3-one (C6F 12O), hexafluorobutene, 1,1,2,2,3,3,4,4-nonafluoro-4-methoxybutane (C5H3F9O), trans-1-chloro-3,3,3-trifluoropropene, 2-bromo-3,3,3-trifluoropropene, one or more thereof, totaling 10 mL, as the core material of the microcapsule, is injected into a mixing container. 50 mL of prepolymer solution is added to the container containing the core material to form a mixture of the core material and the prepolymer. 0.3 g of potassium heptadecafluorooctanesulfonate and 0.3 g of 1-octanol are added to the mixture as stabilizers and surfactants to improve the microcapsule formation process. 0.3 g of polyvinyl alcohol is continued to be added to increase the viscosity, and 1 g of citric acid is further adjusted to a pH value of about 5. A magnetic stirrer is used to stir the mixture at a speed of 500 rpm for 6 hours to ensure sufficient emulsification and prepolymer coating. After stirring, the mixture is allowed to stand for 6-12 hours to allow for the sedimentation and agglomeration of the microcapsules. Then, depending on the precipitation of the microcapsules, it is selected whether to perform a centrifugation step to collect the microcapsule solids. The collected microcapsules are dried, and drying or freeze-drying technology can be used to remove residual water to obtain dry microcapsule solids (SEM images are shown in FIG. Figure 1 shown).

[0045] (III) Lithium battery microcapsule fire extinguishing coating

[0046] Accurately weigh 0.2g of hydroxymethyl cellulose (HMC) as the base material of the coating to enhance the adhesion and mechanical strength of the coating. Add 0.2g of BYK-1785 defoamer to HMC to eliminate microbubbles that may be generated during stirring. Add 3g of deionized water to the mixture containing HMC and BYK-1785 to fully dissolve HMC and form a uniform solution. Add 7g of microcapsule solid to the HMC solution and stir it thoroughly with a magnetic stirrer until the microcapsules are evenly dispersed. During stirring, monitor the pH value and viscosity of the solution to ensure the stability and applicability of the coating. Use a wet coating process, such as blade coating, to evenly coat the microcapsule coating on the surface of the 18650 battery substrate. Place the coated 18650 battery in an environment with a temperature of 20-40°C and a relative humidity of 40-60% to gradually cure the coating (optical images and SEM images are shown in Figure 2). Figure 2 shown).

[0047] In order to further demonstrate the beneficial effects of the present invention and to better understand the present invention, the properties and application performance of the lithium battery microcapsule fire extinguishing coating disclosed in the present invention are further illustrated by the following performance tests, but they should not be construed as limitations on the present invention. The properties of the methods obtained by other measurement experiments conducted by technicians in this field based on the above invention content and the applications based on the above properties are also considered to fall within the protection scope of the present invention.

[0048] Coating performance test:

[0049] (1) The thickness of the cured coating was tested and the coating was uniformly 2.4 mm. Figure 5 As shown and meets the design requirements.

[0050] (2) Conduct thermal stability tests to simulate thermal runaway of lithium batteries and evaluate the fire retardant performance of the coating.

[0051] TG and DTG curves are as follows Figure 3 As shown in Figure 2, the mass of the lithium battery microcapsule fire extinguishing coating decreases with increasing temperature, and the mass loss exceeds 40% between 50°C and 400°C. The peak appearing on the DTG curve indicates the temperature interval where a high mass loss rate occurs. This indicates that the core material destroys the polymer shell and is completely released.

[0052] (3) The differential scanning calorimetry (DSC) test results under nitrogen atmosphere are as follows Figure 3 As shown, the lithium battery microcapsule fire extinguishing coating absorbs heat at high temperature and reaches the endothermic peak at 450°C.

[0053] (4) The effectiveness of the coating in real applications is verified through the thermal runaway propagation inhibition test of actual lithium batteries. The experimental device mainly consists of a battery heating system (thermostat and heating rod), a battery, and a temperature recorder. The size of the heating rod is the same as that of an 18650 lithium battery. The heating rod, battery 1, and battery 2 are arranged in sequence. When battery 1 experiences thermal runaway, the microcapsule fire extinguishing coating is verified to inhibit the propagation of thermal runaway.

[0054] like Figure 4 As shown, battery 2 without microcapsule coating will experience thermal runaway due to heat transfer from battery 1, with the maximum temperature reaching 630°C (left). Battery 2 coated with microcapsule coating does not experience thermal runaway (right), and the gas released by the fluorocarbon fire extinguishing material contained in the core effectively extinguishes the combustible gas generated by the fire, and there is no thermal runaway caused by the rapid increase in the temperature of battery 2.

[0055] Therefore, benefiting from the fire extinguishing and heat absorption effect of the lithium battery microcapsule coating, not only can the fire be extinguished in situ at the first time, but the propagation of thermal runaway in the lithium-ion battery module can also be cut off, thus protecting the safety of the entire battery pack.

[0056] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A lithium battery microcapsule fire extinguishing coating, characterized in that: The invention comprises a coating matrix composed of hydroxymethyl cellulose and a microcapsule fire extinguishing agent embedded in the matrix.

2. The lithium battery microcapsule fire extinguishing coating according to claim 1, characterized in that: The microcapsule fire extinguishing agent comprises a shell material composed of a polymer resin and a core material composed of a fluorine-containing fire extinguishing agent and a refrigerant.

3. The lithium battery microcapsule fire extinguishing coating according to claim 2, characterized in that: The polymer resin is urea-formaldehyde resin, and the fluorine-containing fire extinguishing agent and refrigerant include one or a combination of dodecafluoro-2-methylpentane-3-one, hexafluorobutene, 1,1,2,2,3,3,4,4-nonafluoro-4-methoxybutane, trans-1-chloro-3,3,3-trifluoropropene, and 2-bromo-3,3,3-trifluoropropene.

4. A method for preparing a lithium battery microcapsule fire extinguishing coating according to any one of claims 1 to 3, characterized in that: Firstly, hydroxymethyl cellulose is dissolved in a solution to form a polymer matrix, and then a microcapsule fire extinguishing agent is dispersed in the polymer matrix solution, and after drying, the solution is coated on the outer surface of a lithium ion battery to obtain a lithium battery microcapsule fire extinguishing coating.

5. The preparation method according to claim 4, characterized in that: The specific steps include: S1, dissolving hydroxymethyl cellulose with a viscosity of 100,000 in water to form a solution; S2, uniformly dispersing the microcapsule fire extinguishing agent in the hydroxymethyl cellulose solution, and adjusting the viscosity of the mixture; S3, applying the mixture obtained in step S2 to the outer surface of the lithium-ion battery, and drying to form a fire extinguishing coating.

6. The preparation method according to claim 5, characterized in that: The drying method in step S3 is solvent evaporation at ambient temperature.

7. An application of the lithium battery microcapsule fire extinguishing coating according to any one of claims 1 to 3, characterized in that: Application of the lithium battery microcapsule fire extinguishing coating in lithium battery products.

8. The use according to claim 7, characterized in that: The lithium battery products include new energy electric vehicles or large energy storage systems.

Images