A preparation method of a composite aerogel dehumidification material and a composite aerogel dehumidification material prepared by the method

Abstract

The application relates to the technical field of dehumidification materials, and provides a preparation method of a composite aerogel dehumidification material and the composite aerogel dehumidification material prepared by the method. The preparation method comprises the following steps: preparing an aerogel material from wood nanocellulose, a polyamide acid salt solution and deionized water; and then compounding the aerogel with a hygroscopic salt solution. The obtained composite aerogel dehumidification material has a hygroscopic effect higher than that of existing molecular sieves and silica gel.

Description

Technical Field

[0001] This invention relates to the field of dehumidification materials technology, and in particular to a novel dehumidification material composed of a gel matrix and salts. Specifically, it relates to a method for preparing a composite aerogel dehumidification material and the composite aerogel dehumidification material prepared by the method. Background Technology

[0002] In recent years, the power lithium battery industry has entered a stage of orderly development, with the main focus of power lithium battery planning being breakthroughs in key technologies for high-safety power batteries for new energy vehicles. Lithium battery production has strict requirements for humidity control, as excessive humidity can adversely affect electrolytes, battery performance, capacity, and internal resistance, and even lead to safety issues. Therefore, efficient dehumidification technology has become an indispensable part of lithium battery production.

[0003] Aerogels possess high porosity and low density, which provides a foundation for their application in lithium battery dehumidification. High porosity means that aerogels can hold more moisture, while low density helps reduce weight. With continuous technological advancements, the demand for efficient and environmentally friendly dehumidification materials is increasing. Dehumidification materials composed of gel matrices and salts, as a novel material, have broad application prospects.

[0004] Therefore, we propose a method for preparing composite aerogel dehumidifying materials and the composite aerogel dehumidifying materials prepared by this method. Summary of the Invention

[0005] (a) Technical problems to be solved This invention provides a method for preparing a composite aerogel dehumidifying material and the composite aerogel dehumidifying material prepared by the method, which effectively improves the moisture absorption effect of the material.

[0006] Technical solution

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a composite aerogel dehumidifying material is characterized by first preparing an aerogel material from lignocellulose nanofibers, polyamic acid salt (PAAS) solution and deionized water; then combining the aerogel with a hygroscopic salt solution to obtain the composite aerogel dehumidifying material.

[0008] Furthermore, the mass ratio of lignocellulose nanoparticles, polyamic acid salt (PAAS) solution, and deionized water is 1-1.6:1:0.2-6.

[0009] Furthermore, the mass ratio of lignocellulose nanoparticles, polyamic acid salt (PAAS) solution, and deionized water is 1:1:0.5.

[0010] Furthermore, the preparation method of aerogel materials is as follows: S1. Mix lignocellulose nanoparticles, polyamic acid salt (PAAS) solution and deionized water in a mass ratio of 1:1:0.5 and freeze dry. S2. The freeze-dried material obtained in step S1 is first cured and then carbonized. The curing temperature is 300℃, the heating rate is 3℃ / min, and the holding time is 2h; the carbonization temperature is 600℃, the heating rate is 3℃ / min, and the holding time is 1h, to obtain the aerogel material.

[0011] Furthermore, the aerogel material is immersed in a hygroscopic salt solution, placed in a vacuum drying oven to combine the aerogel material with the hygroscopic salt lithium chloride, and then dried at 100°C for 1 hour to obtain a composite aerogel dehumidifying material.

[0012] Furthermore, the hygroscopic salt solution is a lithium chloride solution.

[0013] Furthermore, the concentration of the lithium chloride solution is 10-20 wt%.

[0014] Furthermore, the concentration of the lithium chloride solution is 15 wt%.

[0015] The method specifically includes the following steps: (a) The polyamic acid solution was reacted with deionized water, and a yellow precipitate was collected. The yellow precipitate was washed with water and dried to obtain a hydrolyzed yellow powder (PAA). (ii) Triethylamine, the hydrolyzed yellow polyamic acid powder prepared in step (i) and water are mixed and stirred to obtain polyamic acid salt, wherein the mass of the hydrolyzed yellow polyamic acid powder is 1g, the mass ratio of triethylamine to the hydrolyzed yellow polyamic acid powder is 1:0.48, and water is added to make up to 10g. (iii) Mix the lignocellulose nanoparticles, the PAAS solution prepared in step (ii), and deionized water at a mass ratio of 1:1:0.5 and freeze-dry. (iv) The freeze-dried material obtained in step (iii) is first solidified and then carbonized. The solidification temperature is 300℃, the heating rate is 3℃ / min, and the holding time is 2h; the carbonization temperature is 600℃, the heating rate is 3℃ / min, and the holding time is 1h, to obtain the aerogel material. (v) Immerse the aerogel material in a 15wt% lithium chloride solution, place it in a vacuum drying oven to combine the aerogel material with the hygroscopic lithium chloride salt, and then dry it at 100℃ for 1h to obtain the composite aerogel dehumidifying material.

[0016] A composite aerogel dehumidifying material is prepared by the above method.

[0017] (III) Beneficial Effects The composite aerogel dehumidifying material of the present invention has the following beneficial effects: 1. The introduction of polyimide, a polymer material, yielded the following excellent properties: (1) Polyimide has excellent mechanical properties and stability, which can enhance the overall structure of composite materials. At the same time, the absorption of moisture during use will not affect the strength of the material. (2) Polyimide has good flame retardant properties. Adding polyimide to the gel skeleton can significantly improve the flame retardant performance of the gel material. The high temperature resistance of polyimide can effectively improve the heat resistance of the gel and prevent it from burning or decomposing at high temperatures. At the same time, the self-extinguishing properties and low smoke generation rate of polyimide can also effectively reduce the smoke and toxic gases generated by the gel during combustion and improve safety.

[0018] 2. LiCl itself has extremely strong hygroscopic properties, but if used alone (such as by direct spreading or forming blocks), it suffers from problems such as leaching and loss, film formation hindering moisture absorption, and short service life. The wood-based gel matrix itself has good hydrophilicity and hygroscopic capacity. The aerogel structure adsorbs some moisture, while also promoting further water absorption by LiCl in the aerogel channels, forming a superimposed effect of capillary adsorption + solution adsorption.

[0019] 3. By optimizing the process, the specific surface area of ​​the gel skeleton is increased, providing more active sites and pore structures, which is conducive to the full contact between water and the material surface, thereby significantly improving the adsorption capacity and rate of the material. Attached Figure Description

[0020] Figure 1 This is a photograph of the sample after thermal imidization in Example 1 of the present invention.

[0021] Figure 2 This is an electron microscope image of the sample after thermal imidization in Example 1 of the present invention.

[0022] Figure 3 This is a photograph of the carbonized sample from Example 1 of the present invention.

[0023] Figure 4 This is an electron microscope image of the carbonized sample from Example 1 of the present invention.

[0024] Figure 5 This is an electron microscope image of the final product, the composite aerogel dehumidifying material, from Example 1 of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0026] A composite aerogel dehumidifying material is prepared by the following method: (i) Apply the polyamic acid solution (Wuhan Kemike Biotechnology Pharmaceutical Co., Ltd.) to the inner wall of a beaker using a sample spoon. Fill the beaker with deionized water to allow it to react fully, generating a yellow precipitate. Collect the precipitate in the beaker, pulverize it with a grinder, and then wash it repeatedly with deionized water. Place the precipitate in a drying oven at 50°C for 24 hours, and then pulverize it again to obtain the hydrolyzed yellow powder (PAA).

[0027] (ii) The catalyst triethylamine, the hydrolyzed polyamic acid yellow powder prepared in step (i) and water are mixed and stirred to obtain polyamic acid salt. The mass of the hydrolyzed polyamic acid yellow powder is 1g, the mass ratio of triethylamine to hydrolyzed polyamic acid yellow powder is 1:0.48, and water is added to make up to 10g.

[0028] (III) Lignocellulose nanofiber (LCNF, SNAST Technology), PAAS solution, and deionized water were mixed at a ratio of 1:1:0.5 and sonicated for 30 min, followed by magnetic stirring for 4 h. Deionized water was used as the solvent and dispersion medium to ensure thorough mixing of LCNF and PAAS to form a uniform gel precursor. After stirring, the solution was injected into a 5 mm diameter spherical mold using a syringe, and then pre-frozen in a refrigerator for 24 h. After pre-freezing, the sample was transferred to a freeze-drying oven, and the freeze-drying time was maintained for 24 h. During the freeze-drying process, once the sample temperature returned to room temperature, the freeze dryer continued to operate for 3 h before the freeze-drying process was completed, and the sample was removed for use.

[0029] (iv) The freeze-dried material was first cured and then carbonized in a tube furnace under a nitrogen atmosphere. The curing temperature was 300℃, the heating rate was 3℃ / min, and the holding time was 2h. Under high-temperature heating conditions, polyamic acid (PAAS) formed an imide ring structure through intramolecular dehydration cyclization reaction, that is, it can be converted into polyimide (PI) after thermal imidization. PI has good thermal stability, mechanical strength, and flame retardancy, and plays a reinforcing and protective role in aerogels, which can enhance the mechanical properties of materials. The carbonization temperature was 600℃, the heating rate was 3℃ / min, and the holding time was 1h. The resulting aerogel material was named C-600. The gas cylinder was turned off after the temperature dropped. For the physical images and scanning electron microscope images of the thermally imidized and carbonized samples, please refer to the appendix. Figure 1-4 .

[0030] A nitrogen atmosphere prevents the oxidation of lignocellulose, which typically leads to material defects such as surface roughness, increased brittleness, and decreased mechanical properties. Nitrogen protection allows the material to maintain better density, mechanical properties, or functional characteristics after heat treatment. A slower heating rate allows the material to gradually release gases and decompose over a longer period, usually resulting in a more ordered and stable carbon structure; while a faster heating rate may cause the material to decompose rapidly, forming more amorphous carbon.

[0031] (V) Completely immerse C-600 in the prepared 15wt% lithium chloride solution (the volume ratio of C-600 to the 15wt% lithium chloride solution can be 1:5 or 1:10, but to reduce the subsequent drying time, the amount of lithium chloride solution can be reduced, and immersion is sufficient). To ensure that C-600 can fully combine with the lithium chloride solution, place it in a vacuum drying oven for vacuum treatment for 1 hour, and then dry it at 100°C for 1 hour to obtain nanocellulose hygroscopic gel, which is the composite aerogel dehumidifying material of the present invention. Its scanning electron microscope image is shown in the attached figure. Figure 5 .

[0032] Lithium chloride is a highly effective hygroscopic agent, capable of rapidly absorbing large amounts of moisture even at very low relative humidity (10%-20% RH). Loading LiCl into the cellulose skeleton significantly improves the overall moisture absorption rate and capacity of the material. However, LiCl is strongly hydrophilic, and excessive amounts can lead to precipitation during moisture absorption, and it may even be washed away in high humidity or liquid water, resulting in poor material durability. Low loading limits the overall moisture absorption capacity, especially in low-humidity environments (<30% RH), where the moisture absorption effect is slow, failing to fully realize the advantages of the composite material.

[0033] The aerogel dehumidifier material prepared in this embodiment was tested and found to be: When the ambient temperature is 8℃ and the humidity is 22%RH, the moisture absorption of the material reaches 0.5g / g after 1400 minutes at a dew point temperature of approximately -11℃. The moisture absorption properties of nanocellulose-based aerogel, 13X molecular sieve, and silica gel were compared under ambient conditions of 2℃ and 16%RH (corresponding to a dew point of approximately -20℃). The results showed that after 1300 minutes of moisture absorption, the nanocellulose-based aerogel achieved a moisture absorption capacity of 0.22 g / g, significantly higher than that of 13X molecular sieve (0.06 g / g) and silica gel (0.04 g / g), representing increases of approximately 267% and 450%, respectively. This material exhibits excellent moisture absorption performance under low-temperature and low-humidity conditions, demonstrating its great potential in deep dehumidification applications.

[0034] Comparative Example 1 The difference between Comparative Example 1 and Example 1 lies in the difference of step (iv) above. Step (iv) of Comparative Example 1 is as follows: Vacuum drying oven thermal imidization: The sample is placed in a vacuum drying oven and the temperature is gradually increased to 100℃×1h, 150℃×1h, 200℃×0.5h, and 230℃×0.5h to induce thermal imidization reaction and obtain aerogel.

[0035] The material obtained in Example 1 had a specific surface area of ​​268 m². 2 The specific surface area is increased by more than 100 times compared to the control ratio. The increased specific surface area provides more active sites and pore structures, which is conducive to the full contact between water and the material surface, thereby significantly improving the adsorption capacity and rate of the material.

[0036] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention 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 of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a composite aerogel dehumidifying material, characterized in that: First, an aerogel material is prepared from lignocellulose nanoparticles, polyamic acid salt solution, and deionized water; then, the aerogel is compounded with a hygroscopic salt solution to obtain a composite aerogel dehumidifying material. The mass ratio of lignocellulose nanoparticles, polyamic acid salt solution, and deionized water is 1:1:0.

5. The preparation method of aerogel materials is as follows: S1. Mix the lignocellulose nanoparticles, polyamic acid salt solution and deionized water in a mass ratio of 1:1:0.5 and freeze-dry. S2. The freeze-dried material obtained in step S1 is first cured and then carbonized. The curing temperature is 300℃, the heating rate is 3℃ / min, and the holding time is 2h; the carbonization temperature is 600℃, the heating rate is 3℃ / min, and the holding time is 1h, to obtain the aerogel material.

2. The preparation method of the composite aerogel dehumidifying material as described in claim 1, characterized in that: The aerogel material was immersed in a hygroscopic salt solution, placed in a vacuum drying oven to combine the aerogel material with the hygroscopic salt, and dried at 100°C for 1 hour to obtain a composite aerogel dehumidifying material.

3. The preparation method of the composite aerogel dehumidifying material as described in claim 2, characterized in that: The hygroscopic salt solution is a lithium chloride solution.

4. The preparation method of the composite aerogel dehumidifying material as described in claim 3, characterized in that: The concentration of the lithium chloride solution is 10-20 wt%.

5. The preparation method of the composite aerogel dehumidifying material as described in claim 4, characterized in that: The concentration of the lithium chloride solution is 15 wt%.

6. The preparation method of the composite aerogel dehumidifying material as described in claim 1, characterized in that: The method specifically includes the following steps: (a) The polyamic acid solution was reacted with deionized water, and a yellow precipitate was collected. The yellow precipitate was washed with water and dried to obtain the hydrolyzed polyamic acid yellow powder. (ii) Triethylamine, the hydrolyzed yellow polyamic acid powder prepared in step (i) and water are mixed and stirred to obtain polyamic acid salt, wherein the mass of the hydrolyzed yellow polyamic acid powder is 1g, the mass ratio of triethylamine to the hydrolyzed yellow polyamic acid powder is 1:0.48, and water is added to make up to 10g. (iii) Mix the lignocellulose nanoparticles, the polyamic acid salt solution prepared in step (ii), and deionized water at a mass ratio of 1:1:0.5 and freeze-dry. (iv) The freeze-dried material obtained in step (iii) is first solidified and then carbonized. The solidification temperature is 300℃, the heating rate is 3℃ / min, and the holding time is 2h; the carbonization temperature is 600℃, the heating rate is 3℃ / min, and the holding time is 1h, to obtain the aerogel material. (v) Immerse the aerogel material in a 15wt% lithium chloride solution, place it in a vacuum drying oven to combine the aerogel material with the hygroscopic salt lithium chloride, and dry it at 100℃ for 1h to obtain the composite aerogel dehumidifying material.

7. A composite aerogel dehumidifying material, which is prepared by any one of the methods described in claims 1-6.

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