A self-responsive molecular flame-retardant smart microcapsule and preparation method thereof

Abstract

The embodiment of the present invention discloses an autonomously responsive molecular flame-retardant smart microcapsule and a preparation method thereof. The autonomously responsive molecular flame-retardant smart microcapsule includes a liquid-gas phase change flame retardant and a polymer shell; wherein the liquid-gas phase change flame retardant is disposed in the polymer shell. Furthermore, a shell modification structure is disposed on the outer surface of the polymer shell. The autonomously responsive molecular flame-retardant smart microcapsule of the embodiment of the present invention can achieve autonomous flame retardancy of lithium batteries with a small amount of addition; at the same time, microencapsulation avoids the influence of flame retardants on the electrochemical properties of the battery, and the surface modification of the microcapsule improves the lithium ion conductivity. Thereby, the safety performance of the lithium battery can be significantly improved without affecting its electrochemical performance, and the problems of lithium batteries being prone to fire and combustion under extreme conditions such as puncture and thermal runaway can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field related to lithium ion batteries, and in particular to an autonomously responsive molecular flame-retardant smart microcapsule and a preparation method thereof. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, long cycle life, and low self-discharge, and are widely used in portable electronic devices, electric vehicles and other fields. However, lithium-ion batteries are prone to safety problems such as fire and explosion under extreme conditions such as overcharging, over-discharging, extrusion, puncture and thermal runaway during long-term service. Among them, highly flammable organic electrolytes are one of the main factors that cause thermal runaway, fire and even explosion of lithium-ion batteries under the above conditions. Therefore, it is crucial to develop material technology with good flame retardant properties.

[0003] The flame retardants that have been used are mainly divided into halogen flame retardants and halogen-free flame retardants. Among them, phosphorus flame retardants are a type of flame retardant with many types, wide applications, and much attention among halogen-free flame retardants. However, most phosphorus flame retardants have disadvantages such as easy moisture absorption, poor thermal stability, and poor compatibility with the matrix. In particular, adding existing flame retardants directly to the electrolyte is likely to inhibit ion transmission and reduce the material transmission rate, which is not conducive to improving the electrochemical performance of the battery.

[0004] In order to overcome the above shortcomings, flame retardant modification can be performed, including ultrafine treatment, silane surface modification, etc. Among them, microencapsulation, which forms flame retardant microcapsules by encapsulating flame retardants in shell materials, is an effective method to improve the stability and compatibility of flame retardants.

[0005] However, the existing flame-retardant microcapsules respond passively to high temperatures, that is, the flame retardant can only be released after the capsule wall melts and ruptures under high temperature conditions, thereby achieving the purpose of flame retardancy.

[0006] In addition, the core material content of existing flame-retardant microcapsules is low, and a large number of microcapsules need to be added to achieve flame retardancy of the electrolyte, which will reduce the energy density of the battery. Summary of the invention

[0007] In order to solve at least one of the technical problems of the above-mentioned prior art, one aspect of the present invention discloses an autonomously responsive molecular flame-retardant smart microcapsule.

[0008] The autonomously responsive molecular flame-retardant smart microcapsule comprises a liquid-gas phase-change flame retardant and a high molecular polymer shell; wherein the liquid-gas phase-change flame retardant is arranged in the high molecular polymer shell.

[0009] According to a preferred embodiment of the present invention, the autonomously responsive molecular flame-retardant smart microcapsule further comprises a shell modification structure; the shell modification structure is arranged on the outer surface of the high molecular polymer shell.

[0010] According to a preferred embodiment of the present invention, the shell modification structure is ceramic nanoparticles arranged on the outer surface of the high molecular polymer shell.

[0011] According to a preferred embodiment of the present invention, the ceramic nanoparticles are lithium lanthanum titanium oxide nanoparticles, lithium lanthanum zirconium oxide nanoparticles or lithium aluminum titanium phosphorus nanoparticles.

[0012] According to a preferred embodiment of the present invention, the liquid-gas phase change flame retardant is perfluorohexanone.

[0013] According to a preferred embodiment of the present invention, the high molecular polymer shell is a polymethyl methacrylate shell or a polystyrene shell.

[0014] According to a preferred embodiment of the present invention, the particle size of the autonomously responsive molecular flame-retardant smart microcapsule is 300nm-5um; the content of the liquid-gas phase change flame retardant in the autonomously responsive molecular flame-retardant smart microcapsule is 60wt%-90wt%.

[0015] Another aspect of the present invention discloses a method for preparing autonomously responsive molecular flame-retardant smart microcapsules.

[0016] The preparation method of the autonomous responsive molecular flame retardant smart microcapsule is as follows: an aqueous solution containing an active agent is used as a continuous phase, and a liquid-gas phase change flame retardant solution and an organic solvent in which a high molecular weight polymer is dissolved are used as inner and outer dispersed phases for preparation.

[0017] According to a preferred embodiment of the present invention, the method for preparing the autonomously responsive molecular flame-retardant smart microcapsules comprises the following steps:

[0018] Step 1, configuration of three-phase solution:

[0019] An inner phase fluid, an intermediate fluid and an outer phase fluid are configured; wherein the inner phase fluid is an organic solution containing a liquid-gas phase change flame retardant, the intermediate fluid is an organic solvent containing a high molecular polymer, and the outer phase fluid is an aqueous solution containing an active agent;

[0020] Step 2, emulsion preparation:

[0021] In a microfluidic device, the inner phase fluid, the intermediate fluid and the outer phase fluid configured in step 1 are respectively injected into the microfluidic chip by a microfluidic pump to form a stable water-in-oil-in-oil emulsion;

[0022] Step 3: Shell curing:

[0023] In the aqueous phase solution containing the oil-in-water-in-oil emulsion formed in step 2, the volatilization of the organic solvent is accelerated by increasing the temperature, inducing the continuous entanglement and crosslinking of the polymer chains, and finally solidifying into a shell, thereby obtaining microcapsules.

[0024] According to a preferred embodiment of the present invention, the method for preparing the autonomously responsive molecular flame-retardant smart microcapsules further comprises:

[0025] Step 4: Shell surface modification:

[0026] Under stirring, ceramic nanoparticles are added to the solution of the microcapsules obtained in step 3, stirred for a period of time, and then washed with water / ethanol at least once, thereby obtaining the autonomously responsive molecular flame-retardant smart microcapsules.

[0027] Compared with the prior art, the autonomously responsive molecular flame-retardant smart microcapsules and the preparation method thereof according to the embodiment of the present invention have the following beneficial effects:

[0028] The autonomously responsive molecular flame-retardant smart microcapsules of the embodiments of the present invention use liquid-gas phase-change flame-retardant microcapsules as autonomous response sites. When the temperature of the lithium battery rises sharply and exceeds the response threshold, the liquid-gas phase-change molecules in the microcapsules absorb heat and vaporize and actively explode the shell layer, automatically releasing the flame retardant, and realizing the autonomous response of the flame-retardant microcapsules to high temperatures; through the synergistic effect of the chemical flame retardancy and physical asphyxiation of the carbonate solvent in the electrolyte to produce hydrogen free radicals by the thermal decomposition of the fluorine element flame-retardant molecular groups in the liquid-gas phase-change flame retardant, the lithium battery can be quickly blocked from burning at high temperatures or even after a fire. Furthermore, the shell of the molecular flame-retardant smart microcapsule is modified with ceramic nanoparticles to induce the oriented arrangement of the shell polymer segments, and the anions of the lithium salt in the electrolyte are fixed by the shell modification, ultimately improving the ionic conductivity of the electrolyte.

[0029] As a result, the autonomously responsive molecular flame-retardant smart microcapsules of the embodiment of the present invention can achieve autonomous flame retardancy of lithium batteries with a small amount of addition; at the same time, microencapsulation avoids the influence of flame retardants on the electrochemical properties of batteries, and surface modification of microcapsules improves lithium ion conductivity.

[0030] In summary, the autonomously responsive molecular flame-retardant smart microcapsules of the embodiments of the present invention can significantly improve the safety performance of lithium batteries without affecting their electrochemical performance, and solve the problems of lithium batteries being prone to fire and combustion under extreme working conditions such as puncture and thermal runaway.

[0031] Some additional features of the present invention may be explained in the following description. Some additional features of the present invention will be apparent to those skilled in the art by inspection of the following description and corresponding drawings or by understanding the production or operation of the embodiments. The features disclosed in the present invention may be realized and achieved by practice or use of the various methods, means and combinations of the specific embodiments described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute a limitation of the present invention. In each figure, the same reference numerals represent the same components.

[0033] Figure 1 is a schematic diagram of the preparation process of the molecular flame-retardant smart microcapsules with autonomous response according to some embodiments of the present invention;

[0034] Figure 2 Schematic diagram of the flame retardant process of the autonomously responsive molecular flame retardant smart microcapsule according to some embodiments of the present invention. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0036] It should be noted that if the terms "first", "second", etc. are involved in the specification and claims of the present invention and the above-mentioned drawings, they are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so as to describe the embodiments of the present invention described herein. In addition, if the terms "including" and "having" and any of their variations are involved, it is intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0037] In the present invention, if the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inside", "outside", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like are involved, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings. These terms are mainly used to better describe the present invention and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0038] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those skilled in the art, the specific meanings of these terms in the present invention can be understood according to specific circumstances.

[0039] In addition, in the present invention, the terms "installed", "set", "provided with", "connected", "connected", "socketed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0041] One aspect of an embodiment of the present invention discloses an autonomously responsive molecular flame-retardant smart microcapsule.

[0042] like Figure 1 As shown, the autonomous responsive molecular flame retardant smart microcapsule comprises a liquid-gas phase change flame retardant 1 and a high molecular polymer shell 2. The liquid-gas phase change flame retardant 1 is arranged in the high molecular polymer shell 2.

[0043] For example, the liquid-gas phase change flame retardant 1 may be perfluorohexanone.

[0044] For example, the polymer shell 2 can be made of one or more polymers such as polymethyl methacrylate, polystyrene, etc. For example, the polymer shell can be a polymethyl methacrylate shell or a polystyrene shell.

[0045] The autonomous response molecular flame retardant smart microcapsule of the present embodiment uses liquid-gas phase change flame retardant microcapsule as the autonomous response site. When the temperature of the lithium battery rises sharply and exceeds the response threshold, the liquid-gas phase change molecules in the microcapsule absorb heat and vaporize and actively explode the shell layer, automatically releasing the flame retardant, thereby realizing the autonomous response of the flame retardant microcapsule to high temperature; through the synergistic effect of the chemical flame retardant and physical asphyxiation of the carbonate solvent in the electrolyte to generate hydrogen free radicals by the thermal decomposition of the fluorine element flame retardant molecular group in the liquid-gas phase change flame retardant, the lithium battery can be quickly blocked from burning at high temperature or even after a fire. Figure 2 shown.

[0046] Furthermore, in some embodiments, the autonomous responsive molecular flame-retardant smart microcapsule may further include a shell modification structure 3. The shell modification structure 3 is arranged on the outer surface of the high molecular polymer shell.

[0047] Exemplarily, the shell modification structure is ceramic nanoparticles disposed on the outer surface of the polymer shell, wherein the ceramic nanoparticles can be lithium lanthanum titanium oxide (LLTO) nanoparticles, lithium lanthanum zirconium oxide (LLZO) nanoparticles or lithium aluminum titanium phosphide (LATP) nanoparticles.

[0048] By forming a shell modification structure of ceramic nanoparticles on the outer surface of the polymer shell, the shell polymer segments can be induced to be oriented, and the anions of lithium salts in the electrolyte can be fixed by shell modification, ultimately improving the ionic conductivity of the electrolyte.

[0049] Among them, the particle size of the autonomously responsive molecular flame-retardant smart microcapsule is 300nm~5um.

[0050] The content of liquid-gas phase change flame retardant in the autonomously responsive molecular flame retardant smart microcapsule is 60wt% to 90wt%.

[0051] Another aspect of the embodiments of the present invention discloses a method for preparing autonomously responsive molecular flame-retardant smart microcapsules.

[0052] The preparation method of the self-responsive molecular flame-retardant smart microcapsules is mainly based on the cross-linking of water-in-oil-in-oil double emulsions prepared by microfluidic technology. That is, the preparation method of the self-responsive molecular flame-retardant smart microcapsules is mainly to use an aqueous solution containing an active agent as a continuous phase, and a liquid-gas phase change flame retardant solution and an organic solvent in which a high molecular weight polymer is dissolved as the inner and outer dispersed phases.

[0053] Exemplarily, the method for preparing the autonomously responsive molecular flame-retardant smart microcapsule comprises the following steps:

[0054] Step 1, configuration of three-phase solution:

[0055] An inner phase fluid, an intermediate fluid and an outer phase fluid are configured, wherein the inner phase fluid is an organic solution containing a liquid-gas phase change flame retardant, the intermediate fluid is an organic solvent containing a high molecular polymer, and the outer phase fluid is an aqueous solution containing an active agent.

[0056] Step 2, emulsion preparation:

[0057] In the microfluidic device, the inner phase fluid, the intermediate fluid and the outer phase fluid configured in step 1 are respectively injected into the microfluidic chip through a microfluidic pump to form a stable water-in-oil-in-oil emulsion.

[0058] Step 3: Shell curing:

[0059] In the aqueous phase solution containing the water-in-oil-in-oil emulsion formed in step 2, the volatilization of the organic solvent is accelerated by increasing the temperature, inducing the continuous entanglement and cross-linking of the polymer chains, and finally solidifying into a shell, thereby obtaining microcapsules.

[0060] Furthermore, the method for preparing the autonomously responsive molecular flame-retardant smart microcapsule may also include:

[0061] Step 4: Shell surface modification:

[0062] Under stirring, ceramic nanoparticles are added to the solution of the microcapsules prepared in step 3, stirred for a period of time, and then washed with water / ethanol at least once, thereby preparing autonomously responsive molecular flame-retardant smart microcapsules.

[0063] The preparation method of the autonomous responsive molecular flame-retardant smart microcapsules of the present invention is further described in detail below through specific examples.

[0064] Example 1

[0065] The method for preparing the autonomously responsive molecular flame-retardant smart microcapsules of this embodiment comprises the following steps:

[0066] Step 1, configuration of three-phase solution:

[0067] The inner phase fluid is a perfluorohexanone solution, the middle phase fluid is a dichloromethane solution containing 5 wt % polystyrene, and the outer phase fluid is an aqueous solution dispersed with 2 wt % F127.

[0068] Step 2, emulsion preparation:

[0069] In the microfluidic device, the inner phase fluid, the middle phase fluid, and the outer phase fluid configured in the above step 1 were injected into the microfluidic chip at a speed of 300uL / min, 500uL / min, and 1200uL / min, respectively, using a microfluidic pump to obtain a stable water-in-oil-in-oil emulsion, which was stored under low temperature conditions.

[0070] Step 3: Shell curing:

[0071] The water-in-oil-in-oil emulsion prepared in step 2 above was placed in a beaker, heated at 30°C for 20 min, and washed with water / ethanol for 3 times to obtain perfluorohexanone microcapsules, such as Figure 1 As shown; wherein, the content of the liquid-gas phase change flame retardant as the core material in the microcapsule is 85%.

[0072] Step 4: Shell surface modification:

[0073] Under stirring conditions of 300 rpm, 1 wt% of LLTO ceramic nanoparticles were placed into the perfluorohexanone microcapsule solution prepared in the above step 3, stirred for 2 hours, and then washed at least once with water / ethanol to obtain LLTO-modified perfluorohexanone microcapsules; wherein the particle size of the microcapsules was 5 um.

[0074] Furthermore, a gel electrolyte film containing flame retardant microcapsules (such as Figure 2 As shown), the lithium ion conductivity is 5*10 -3 S / cm. After testing, the self-extinguishing time of the electrolyte film is 5s / g.

[0075] Example 2

[0076] The method for preparing the autonomously responsive molecular flame-retardant smart microcapsules of this embodiment comprises the following steps:

[0077] Step 1, configuration of three-phase solution:

[0078] The inner phase fluid is a perfluorohexanone solution, the middle phase fluid is an acetone solution containing 5 wt % polystyrene, and the outer phase fluid is an aqueous solution dispersed with 2 wt % F127.

[0079] Step 2, emulsion preparation:

[0080] In the microfluidic device, the inner phase fluid, middle phase fluid and outer phase fluid configured in the above step 1 were injected into the microfluidic chip at speeds of 300uL / min, 800uL / min and 13200uL / min, respectively, using a microfluidic pump to obtain a stable water-in-oil-in-oil emulsion, which was stored under ice bath conditions.

[0081] Step 3: Shell curing:

[0082] The water-in-oil-in-oil emulsion prepared in the above step 2 is placed in a beaker, heated at 30° C. for 20 minutes, and washed with water / ethanol for 3 times to obtain perfluorohexanone microcapsules; wherein the content of the liquid-gas phase change flame retardant as the core material in the microcapsules is 80%.

[0083] Step 4: Shell surface modification:

[0084] Under stirring conditions of 400 rpm, 1.5 wt% of LLTO ceramic nanoparticles were placed into the perfluorohexanone microcapsule solution prepared in the above step 3, stirred for 2 hours, and then washed several times with water / ethanol to obtain LLTO-modified perfluorohexanone microcapsules; wherein the particle size of the microcapsules was 4.5 um.

[0085] Furthermore, by adding LLTO-modified perfluorohexanone microcapsules into PEO gel polymer at a mass ratio of 5 wt%, a gel electrolyte film containing flame-retardant microcapsules was formed, and the lithium ion conductivity was 8*10 -3 S / cm. After testing, the self-extinguishing time of the electrolyte film is 1g / s.

[0086] The autonomously responsive molecular flame-retardant smart microcapsules of the embodiments of the present invention use liquid-gas phase-change flame-retardant microcapsules as autonomous response sites. When the temperature of the lithium battery rises sharply and exceeds the response threshold, the liquid-gas phase-change molecules in the microcapsules absorb heat and vaporize and actively explode the shell layer, automatically releasing the flame retardant, and realizing the autonomous response of the flame-retardant microcapsules to high temperatures; through the synergistic effect of the chemical flame retardancy and physical asphyxiation of the carbonate solvent in the electrolyte to produce hydrogen free radicals by the thermal decomposition of the fluorine element flame-retardant molecular groups in the liquid-gas phase-change flame retardant, the lithium battery can be quickly blocked from burning at high temperatures or even after a fire. Furthermore, the shell of the molecular flame-retardant smart microcapsule is modified with ceramic nanoparticles to induce the oriented arrangement of the shell polymer segments, and the anions of the lithium salt in the electrolyte are fixed by the shell modification, ultimately improving the ionic conductivity of the electrolyte.

[0087] As a result, the autonomously responsive molecular flame-retardant smart microcapsules of the embodiment of the present invention can achieve autonomous flame retardancy of lithium batteries with a small amount of addition; at the same time, microencapsulation avoids the influence of flame retardants on the electrochemical properties of batteries, and surface modification of microcapsules improves lithium ion conductivity.

[0088] In summary, the autonomously responsive molecular flame-retardant smart microcapsules of the embodiments of the present invention can significantly improve the safety performance of lithium batteries without affecting their electrochemical performance, and solve the problems of lithium batteries being prone to fire and combustion under extreme working conditions such as puncture and thermal runaway.

[0089] It should be noted that all features disclosed in this specification, or steps in all methods or processes disclosed, except for mutually exclusive features and / or steps, can be combined in any manner.

[0090] In addition, the above specific embodiments are exemplary, and those skilled in the art can come up with various solutions inspired by the disclosure of the present invention, and these solutions also belong to the disclosure scope of the present invention and fall within the protection scope of the present invention. Those skilled in the art should understand that the present invention description and its drawings are illustrative and do not constitute a limitation of the claims. The protection scope of the present invention is defined by the claims and their equivalents.

Claims

1. An autonomously responsive molecular flame-retardant smart microcapsule, characterized in that: The autonomously responsive molecular flame-retardant smart microcapsule comprises a liquid-gas phase-change flame retardant and a high molecular polymer shell; wherein the liquid-gas phase-change flame retardant is arranged in the high molecular polymer shell; the autonomously responsive molecular flame-retardant smart microcapsule also comprises a shell modification structure; The shell modification structure is arranged on the outer surface of the high molecular polymer shell; The shell modification structure is ceramic nanoparticles arranged on the outer surface of the high molecular polymer shell; The ceramic nanoparticles are lithium lanthanum titanium oxide nanoparticles, lithium lanthanum zirconium oxide nanoparticles or lithium aluminum titanium phosphorus nanoparticles.

2. The autonomous responsive molecular flame-retardant smart microcapsule according to claim 1, characterized in that: The liquid-gas phase change flame retardant is perfluorohexanone.

3. The autonomous responsive molecular flame-retardant smart microcapsule according to claim 1, characterized in that: The high molecular polymer shell is a polymethyl methacrylate shell or a polystyrene shell.

4. The autonomous responsive molecular flame-retardant smart microcapsule according to claim 1, characterized in that: The particle size of the autonomously responsive molecular flame-retardant smart microcapsule is 300nm-5um; the content of the liquid-gas phase change flame retardant in the autonomously responsive molecular flame-retardant smart microcapsule is 60wt%-90wt%.

5. A method for preparing the autonomous responsive molecular flame-retardant smart microcapsule according to any one of claims 1 to 4, characterized in that: The preparation method of the autonomous responsive molecular flame-retardant smart microcapsule is: The preparation method is carried out with an aqueous solution containing an active agent as a continuous phase, and a liquid-gas phase change flame retardant solution and an organic solvent in which a high molecular weight polymer is dissolved as an inner and outer dispersed phase.

6. The method for preparing the autonomously responsive molecular flame-retardant smart microcapsules according to claim 5, characterized in that: The method for preparing the autonomously responsive molecular flame-retardant smart microcapsules comprises the following steps: Step 1, configuration of three-phase solution: An inner phase fluid, an intermediate fluid and an outer phase fluid are configured; wherein the inner phase fluid is an organic solution containing a liquid-gas phase change flame retardant, the intermediate fluid is an organic solvent containing a high molecular polymer, and the outer phase fluid is an aqueous solution containing an active agent; Step 2, emulsion preparation: In a microfluidic device, the inner phase fluid, the intermediate fluid and the outer phase fluid configured in step 1 are respectively injected into the microfluidic chip by a microfluidic pump to form a stable water-in-oil-in-oil emulsion; Step 3: Shell curing: In the aqueous phase solution containing the oil-in-water-in-oil emulsion formed in step 2, the volatilization of the organic solvent is accelerated by increasing the temperature, thereby inducing the polymer chains to continuously entangle and crosslink, and finally solidify into a shell, thereby obtaining a microcapsule; Step 4: Shell surface modification: Under stirring, ceramic nanoparticles are added to the solution of the microcapsules obtained in step 3, stirred for a period of time, and then washed with water / ethanol at least once, thereby obtaining the autonomously responsive molecular flame-retardant smart microcapsules.

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