A heat-insulating flame-retardant heat-absorbing composite material for high-density energy storage devices and a preparation method and application thereof

Abstract

The present application relates to a kind of high-density energy storage device heat-insulating flame-retardant heat-absorbing composite material and its preparation method and application, and the composite material includes: basic magnesium sulfate whisker 10~15 parts;Basic magnesium carbonate 0~5 parts;Calcium sulfate 0~5 parts;Calcium silicate 0~5 parts;Salt 0~2 parts;Water 14~21 parts;Auxiliary agent 1 part.Compared with prior art, the present application provides a kind of high-density energy storage device heat-insulating flame-retardant heat-absorbing composite material and its preparation method, with low temperature heat-absorbing, effectively delay the curve rate of temperature rise section, high temperature section has good heat-insulating flame-retardant, prevent fire spread rapidly.In low temperature heat-absorbing, high temperature heat-insulating flame-retardant, it plays the effect of double protection to high-density energy storage device.

Description

Technical Field

[0001] This invention belongs to the field of material compounding and modification technology, and relates to a heat-insulating, flame-retardant, and heat-absorbing composite material for high-density energy storage devices, its preparation method, and its application. Background Technology

[0002] With the continuous development of high-density energy storage technology, its application scenarios in various fields are becoming increasingly widespread, and the corresponding safety issues are receiving more and more attention. Taking high-power new energy transportation vehicles as an example, the high-density energy storage devices equipped with them operate under complex conditions for a long time, including continuous vibration, mechanical collisions, and stress from thermal cycles, which can easily lead to wear or puncture of the internal diaphragm, thereby triggering a violent chemical reaction between lithium and sulfur.

[0003] Industry testing data shows that after a high-density energy storage device is damaged and triggers a chemical exothermic reaction, its thermal runaway process exhibits phased characteristics: when the temperature is below 90℃, the separator begins to dissolve, and the temperature rise is relatively slow; as the temperature rises to the range of 90℃ to 130℃, the rate of temperature rise gradually accelerates; once the temperature exceeds 130℃, the rate of temperature rise increases dramatically, accompanied by open flame combustion. In high-density battery systems, such flames can trigger a chain reaction of thermal diffusion within a confined space. Without effective suppression measures, this can lead to a chain reaction of thermal runaway, causing significant casualties and property damage.

[0004] Currently, common protective measures often involve covering high-density energy storage units with flame-retardant and heat-insulating materials such as aerogel and high-silica cotton. For example, CN116891595A discloses a polyimide-based composite aerogel material, which is made of polyimide, hydroxyapatite, and ammonium polyphosphate through freeze-drying and high-temperature calcination to form a porous aerogel structure framework with high-temperature resistance and flame-retardant properties. Silica aerogel with superior heat-insulating function is introduced into the framework pores to prepare this material. It can be used to prepare heat-insulating and flame-retardant plates for lithium-ion battery packs, effectively blocking the propagation of battery thermal runaway and ensuring that the internal materials of batteries that have not experienced thermal runaway do not suffer significant damage. However, while this type of material has good heat insulation and fire resistance, it can create a closed, high-pressure environment when the energy storage device experiences thermal runaway, thus exacerbating the danger. Furthermore, its function is limited to physical heat insulation and cannot effectively intervene in the critical initial stage of thermal runaway, making it difficult to effectively delay the accident process and buy valuable time for personnel evacuation and property transfer. Summary of the Invention

[0005] The purpose of this invention is to provide a heat-insulating, flame-retardant, and heat-absorbing composite material for high-density energy storage devices and its preparation method. This material combines heat absorption at medium and low temperatures, effectively slowing down the rate of temperature rise, with good heat insulation and flame retardancy at high temperatures, preventing rapid fire spread. By absorbing heat at medium and low temperatures and providing heat insulation and flame retardancy at high temperatures, it offers dual protection for high-density energy storage devices.

[0006] The objective of this invention can be achieved through the following technical solutions: The first aspect of the present invention provides a heat-insulating, flame-retardant, and heat-absorbing composite material, comprising the following components and their weight percentages: 10-15 parts of basic magnesium sulfate whiskers; 0-5 parts of basic magnesium carbonate; 0-5 parts of calcium sulfate; 0-5 parts of calcium silicate; 0-2 parts salt; 14-21 parts water; One part of the auxiliary agent.

[0007] In some specific embodiments, the composite material includes the following components and their weight percentages: 10 parts of basic magnesium sulfate whiskers; 5 parts calcium silicate; 19 parts water; One part of the auxiliary agent.

[0008] In some specific embodiments, the basic magnesium sulfate whiskers have a diameter of no more than 2 μm, a length of 5~150 μm, and an aspect ratio of 5~100.

[0009] In some specific embodiments, the chemical formula of the basic magnesium sulfate whiskers is xMgSO4·yMg(OH)2·zH2O, where x=3~6, y=1~6, and z=3~10. The microstructure has flocculent, bundled, fibrous, or needle-like forms, and the diameter cross-section is cylindrical, elliptical, hexagonal, or its approximate regular structure.

[0010] In some specific embodiments, the basic magnesium carbonate is in the form of flocculent, bundled, fibrous or needle-like structures, with a diameter not exceeding 2 μm, a length of 5~150 μm, and an aspect ratio of 5~100.

[0011] In some specific embodiments, the basic magnesium carbonate has the chemical formula xMgCO3·yMg(OH)2·zH2O, where x = 1~5, y = 1~3, and z = 2~10, and is of a heavy or light type. It can be in powder, granular, or have a microstructure that is flocculent, clustered, fibrous, or needle-like, and its crystals can contain entirely continuous or partially hollow structures. Its diameter profile is cylindrical, elliptical, hexagonal, or a similarly regular structure. Preferably, the material can undergo special surface modification treatment, which refers to surface functional group modification to increase its hydrophilic or oleophilic properties.

[0012] In some specific embodiments, the calcium sulfate is in the form of flocculent, bundled, fibrous or needle-like structures, with a diameter not exceeding 2 μm, a length of 5~150 μm, and an aspect ratio of 5~100.

[0013] In some specific embodiments, the calcium sulfate has the chemical formula CaSO4 and its hydrate CaSO4·xH2O. Its microcrystalline structure can be disordered, or it can be flocculent, clustered, fibrous, needle-like, etc. Simultaneously, its crystals can contain entirely continuous or partially hollow structures, with a diameter profile that is cylindrical, elliptical, hexagonal, or its approximately regular shape. In particular, this material can undergo special surface modification treatments, referring to surface functional group modification to increase its hydrophilic or oleophilic properties.

[0014] In some specific embodiments, the calcium silicate is in the form of flocculent, bundled, fibrous or needle-like structures, with a diameter not exceeding 2 μm, a length of 5~150 μm, and an aspect ratio of 5~100.

[0015] In some specific embodiments, the calcium silicate has the chemical formula CaSiO3 and its hydrate xCaO·ySiO2·zH2O, where x=1~6, y=1~6, and z=2~11. Its crystal structure can be disordered, or it can be spherical, hollow spherical, flocculent, bundled, fibrous, or needle-like. Simultaneously, its crystals can contain entirely continuous or partially hollow structures, with a diameter profile that is cylindrical, elliptical, hexagonal, or its approximate regular shape. In particular, this material can undergo special surface modification treatments, referring to surface functional group modification to increase its hydrophilic or oleophilic properties.

[0016] In some specific embodiments, the salt is a magnesium, aluminum, or calcium salt, selected from at least one of sodium carbonate, aluminum sulfate, magnesium sulfate, calcium chloride, or magnesium chloride; alternatively, a corresponding high-hydrate salt may be selected, preferably a magnesium, aluminum, or calcium salt with more than 5 water molecules of crystallization, specifically selected from at least one of sodium carbonate decahydrate, aluminum sulfate octadecahydrate, magnesium sulfate heptahydrate, calcium chloride hexahydrate, or magnesium chloride hexahydrate.

[0017] In some specific embodiments, the additives are selected from polyethylene glycol (PEG), polyvinyl alcohol (PVA), high carbon surfactants, anionic surfactants, sodium lauryl ester, sodium carboxymethyl cellulose (CMCNa), glass fiber, carbon fiber, polyether ether ketone (PEEK) fiber, nylon fiber, cellulose or pulp fiber.

[0018] The high-carbon surfactant is selected from at least one of sodium stearate, sodium oleate, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, hexadecyl sulfonate, or C16-C18 fatty alcohol ether phosphate salts; The anionic surfactant is selected from at least one of sodium dodecyl sulfate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium linear alkylbenzene sulfonate, or sodium dioctyl sulfosuccinate.

[0019] In some specific embodiments, the additive has a flocculent, bundled, fibrous, or needle-like structure with a cylindrical, elliptical, hexagonal, triangular, or approximately regular cross-section. Each individual fiber has a diameter of less than 10 μm, a length of 50–500 μm, and an aspect ratio between 5 and 100. Preferably, the material can undergo special surface modification treatment, specifically surface functional group modification, to increase its hydrophilic or oleophilic properties.

[0020] A second aspect of the present invention provides a method for preparing the heat-insulating, flame-retardant, and heat-absorbing composite material as described above, comprising: mixing basic magnesium sulfate whiskers, basic magnesium carbonate, calcium sulfate, calcium silicate, salt, water, and additives to obtain the composite material.

[0021] In some specific embodiments, the basic magnesium sulfate whiskers, basic magnesium carbonate, calcium sulfate, and calcium silicate are treated with a coupling agent before being mixed; the coupling agent treatment includes: immersing the basic magnesium sulfate whiskers, basic magnesium carbonate, calcium sulfate, and calcium silicate in a coupling agent aqueous solution with pH=4~6 to obtain the mixture. The coupling agent is selected from KH550 coupling agent; The impregnation process involves an impregnation temperature of 30-40°C and an impregnation time of 50-60 minutes.

[0022] In some specific embodiments, before the basic magnesium sulfate whiskers, basic magnesium carbonate, calcium sulfate, and calcium silicate are mixed, they are first subjected to PEG grafting superhydrophilic modification; the modification method includes: treating the basic magnesium sulfate whiskers, basic magnesium carbonate, calcium sulfate, and calcium silicate with a coupling agent, preparing a 2-5 wt% toluene solution of PEG-silane, and heating it under reflux in a nitrogen atmosphere to obtain the final product; The coupling agent treatment includes: immersing basic magnesium sulfate whiskers, basic magnesium carbonate, calcium sulfate, and calcium silicate in a coupling agent aqueous solution with a pH of 4-6 to obtain the desired product. The coupling agent is selected from KH550 coupling agent; During the impregnation process, the impregnation temperature is 30~40℃ and the impregnation time is 50~60 min; In the heating and reflux process, the reflux temperature is 30~40℃ and the reflux time is 50~60 min.

[0023] A third aspect of the present invention provides an application of the heat-insulating, flame-retardant, and heat-absorbing composite material as described above, including using the heat-insulating, flame-retardant, and heat-absorbing composite material to prepare the heat-insulating and flame-retardant structure of a high-density energy storage device.

[0024] In some specific embodiments, the preparation method of the heat-insulating and flame-retardant structure includes: pressing the heat-insulating and flame-retardant heat-absorbing composite material into shape and then sealing it; the pressing pressure is 1~8 MPa.

[0025] Compared with the prior art, the present invention has the following beneficial effects: This invention increases the enthalpy of the low-temperature heat absorption phase transition by using water and employs needle-like whisker hydrophilic materials to effectively absorb heat and slow down the rate of temperature rise. It also has good thermal insulation properties at high temperatures, preventing the rapid spread of fire and providing dual protection. It is expected to be applied in high-density energy storage, new energy batteries and other equipment. Detailed Implementation

[0026] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0027] The following are more detailed implementation examples, which further illustrate the technical solution of the present invention and the technical effects that can be obtained.

[0028] In the following embodiments, unless otherwise specified, the raw materials, reagents, or processing techniques are all conventional commercial products or conventional processing techniques in the art, including processing at room temperature, processing at atmospheric pressure, and processing in air atmosphere.

[0029] In the following examples, the basic magnesium sulfate used has the chemical formula MgSO4·5Mg(OH)2·3H2O, an aspect ratio of 8~70, and a whisker structure with a length of 4~120 μm; the basic magnesium carbonate has the chemical formula 3MgCO3·Mg(OH)2·3H2O, is heavy magnesium carbonate, granular, with a particle size of 20~150 μm; the calcium sulfate has the chemical formula CaSO4·2H2O, an aspect ratio of 8~70, and a whisker structure with a length of 4~120 μm; and the calcium silicate has the chemical formula Ca5Si6O. 16 (OH)·4H2O, with an aspect ratio of 8~70 and a length of 4~120 μm whisker structure; Examples 1-6: A heat-insulating, flame-retardant, and heat-absorbing composite material for high-density energy storage devices has the following formulation as shown in Table 1, in g.

[0030] Table 1 The preparation method includes: placing the materials of each embodiment into a high-speed mixer according to Table 1 and mixing them thoroughly. The powder is then transferred into a rigid film chamber and pressed and held at a pressure of 3 MPa per unit area for 30 seconds to form a sheet with a thickness of 2 mm. The sheet is then removed, transferred into an aluminum-plastic bag, and vacuum heat-sealed to produce the product.

[0031] Examples 7-9: A heat-insulating, flame-retardant, and heat-absorbing composite material for high-density energy storage devices has a formulation shown in Table 2, with units of g.

[0032] Table 2 Preparation methods include: Surface treatment of inorganic powder: According to the formula in Table 2, basic magnesium sulfate, basic magnesium carbonate, calcium sulfate and calcium silicate powders are placed in a mixed solution with pH=5.5 (water and alcohol v:v=1:1), and then KH550 coupling agent (2% of the total mass of basic magnesium sulfate, basic magnesium carbonate, calcium sulfate and calcium silicate powders) is added. The mixture is thoroughly mixed at 30℃ for 50 min, and then washed and dried to obtain surface-modified inorganic powder. According to the formula in Table 2, inorganic powder, salt, water and additives are put into a high-speed mixer and mixed thoroughly. The resulting powder is transferred into a rigid film cavity and pressed and held at a pressure of 5 MPa per unit area for 30 seconds to form a sheet with a thickness of 2 mm. After the sheet is removed, it is transferred into an aluminum-plastic bag and vacuum heat-sealed to produce the product.

[0033] Performance testing The properties of the heat-insulating, flame-retardant, and heat-absorbing composite materials prepared in Examples 1-9 were characterized. The characterized properties and the characterization methods included: 1) DSC testing GB / T 19466.3-2025, 2) Thermal insulation test: Place the sheet to be tested on a heating platform at 675℃, place K-type thermocouples on both sides of the sheet, apply a pressure of 2 MPa to the sheet, maintain for 20 min, and compare the temperature difference between the two ends of the sheet. 3) Water retention test: Place the product in a room temperature air environment and let it lose water naturally until it reaches constant weight.

[0034] The characterization results are shown in Table 3.

[0035] Table 3 As shown in Table 3, using Example 1 as the standard sample, Examples 2 and 3 respectively replaced the calcium sulfate in Example 1 with an equal amount of basic magnesium carbonate and calcium silicate. The results were a decrease in water content and a decrease in enthalpy value.

[0036] Compared with Example 1, Example 4 added magnesium chloride, which slightly decreased the water content and enthalpy value, but slightly increased the water retention performance.

[0037] Compared with Example 6, Example 6' had an additional small amount of magnesium chloride. The water retention test showed that after 12 hours, the water loss rate of Example 6' was 37%, while that of Example 6 was 45%. This shows that the addition of a small amount of magnesium chloride can significantly improve the water retention of the product.

[0038] Compared with Example 1, Example 5 used basic magnesium sulfate by weight, which reduced the water content by about 17%. Compared with Example 1, Example 6 used basic magnesium carbonate by weight, which reduced the water content by about 44% and had poorer processability.

[0039] Compared with Examples 2-6, Example 1 uses a compound system of basic magnesium sulfate and calcium sulfate, which has good water retention and moldability. Meanwhile, Example 7 is based on Example 1 and undergoes coupling modification, which further improves water retention and moldability.

[0040] This invention utilizes a highly heat-resistant hydrate, which, under fixed pressure, can be molded while retaining more bound water. Simultaneously, at the microscopic level, the whisker structure of the material is used to construct an aerogel-like porous structure, which helps to improve the thermal insulation effect. The resulting product can achieve a DSC of 850~1100 J / g, which is significantly better than conventional existing materials such as aerogels with thermal insulation values ​​of only 350~450℃, DSC values ​​of only 150~300 J / g, and no heat absorption function, as well as high-silica cotton.

[0041] Furthermore, this invention, through modification with a coupling agent, endows the material with high hydrophilicity, enabling it to adsorb and stabilize a large amount of free water while preventing droplet formation. This improves the product's DSC (Digital Saxometry) while ensuring molding stability. For a detailed comparison, see Tables 2 and 1. Example 9, using powder compounding and coupling modification, allows for the addition of 52 wt% water, the highest water content among all products, while also exhibiting the optimal DSC and insulation values. A higher DSC value represents a higher endothermic enthalpy, enabling the absorption of more heat in the early stages of a fire, thus reducing the temperature curve. Simultaneously, the high water content, after volatilization at high temperatures, creates numerous microporous structures within the material, further enhancing its insulation performance and increasing its flame retardancy.

[0042] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A heat-insulating, flame-retardant, and heat-absorbing composite material, characterized in that, Includes the following components and their weight percentages: 10-15 parts of basic magnesium sulfate whiskers; 0-5 parts of basic magnesium carbonate; 0-5 parts of calcium sulfate; 0-5 parts of calcium silicate; 0-2 parts salt; 14-21 parts water; One part of the auxiliary agent.

2. The heat-insulating, flame-retardant, and heat-absorbing composite material according to claim 1, characterized in that, The basic magnesium sulfate whiskers have a diameter not exceeding 2 μm, a length of 5~150 μm, and an aspect ratio of 5~100. The basic magnesium carbonate is in the form of flocculent, bundled, fibrous or needle-like structures, with a diameter not exceeding 2 μm, a length of 5~150 μm, and an aspect ratio of 5~100.

3. The heat-insulating, flame-retardant, and heat-absorbing composite material according to claim 1, characterized in that, The calcium sulfate is in the form of flocculent, bundled, fibrous or needle-like structures, with a diameter not exceeding 2 μm, a length of 5~150 μm, and an aspect ratio of 5~100.

4. The heat-insulating, flame-retardant, and heat-absorbing composite material according to claim 1, characterized in that, The calcium silicate is in the form of flocculent, bundled, fibrous or needle-like structures, with a diameter not exceeding 2 μm, a length of 5~150 μm, and an aspect ratio of 5~100. The salt is selected from at least one of sodium carbonate, aluminum sulfate, magnesium sulfate, calcium chloride, or magnesium chloride; preferably, the corresponding hydrate, including at least one of sodium carbonate decahydrate, aluminum sulfate octadecahydrate, magnesium sulfate heptahydrate, calcium chloride hexahydrate, or magnesium chloride hexahydrate.

5. The heat-insulating, flame-retardant, and heat-absorbing composite material according to claim 1, characterized in that, The additives are selected from polyethylene glycol, polyvinyl alcohol, high carbon surfactants, anionic surfactants, sodium lauryl ester, sodium carboxymethyl cellulose, glass fiber, carbon fiber, polyetheretherketone fiber, nylon fiber, cellulose or pulp fiber.

6. A method for preparing a heat-insulating, flame-retardant, and heat-absorbing composite material as described in any one of claims 1 to 5, characterized in that, include: The following mixture is prepared by mixing basic magnesium sulfate whiskers, basic magnesium carbonate, calcium sulfate, calcium silicate, salt, water, and additives.

7. The method for preparing the heat-insulating, flame-retardant, and heat-absorbing composite material according to claim 6, characterized in that, Before mixing, a coupling agent treatment is performed; the coupling agent treatment includes: impregnating basic magnesium sulfate whiskers, basic magnesium carbonate, calcium sulfate, and calcium silicate in a coupling agent aqueous solution with pH=4~6 to obtain the product. The coupling agent is selected from KH550 coupling agent; The impregnation process involves an impregnation temperature of 30-40°C and an impregnation time of 50-60 minutes.

8. The method for preparing the heat-insulating, flame-retardant, and heat-absorbing composite material according to claim 6, characterized in that, Before mixing, PEG grafting superhydrophilic modification is performed. The modification method includes: treating basic magnesium sulfate whiskers, basic magnesium carbonate, calcium sulfate, and calcium silicate coupling agent, preparing a 2-5 wt% PEG-silane toluene solution, and heating under nitrogen atmosphere and reflux to obtain the final product. The coupling agent treatment includes: immersing basic magnesium sulfate whiskers, basic magnesium carbonate, calcium sulfate, and calcium silicate in a coupling agent aqueous solution with a pH of 4-6 to obtain the desired product. The coupling agent is selected from KH550 coupling agent; During the impregnation process, the impregnation temperature is 30~40℃ and the impregnation time is 50~60 min; In the heating and reflux process, the reflux temperature is 30~40 ℃ and the reflux time is 50~60 min.

9. The application of a heat-insulating, flame-retardant, and heat-absorbing composite material as described in any one of claims 1 to 5, characterized in that, The heat-insulating, flame-retardant, and heat-absorbing composite material is used to prepare the heat-insulating and flame-retardant structure of high-density energy storage devices.

10. The method for preparing the high-density energy storage device heat-insulating, flame-retardant, and heat-absorbing composite material according to claim 9, characterized in that, The method for preparing the heat-insulating and flame-retardant structure includes: pressing a heat-insulating and flame-retardant heat-absorbing composite material into a mold and then encapsulating it. The pressure for compression molding is 1~8 MPa.

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