Silicon-based aerogel thermal insulation coating for solid-state battery and preparation method of silicon-based aerogel thermal insulation coating

Abstract

The invention discloses a silicon-based aerogel heat insulation coating for a solid-state battery, and relates to the technical field of battery heat insulation materials. The coating is prepared from the following raw materials in parts by weight: 8-15 parts of silicon-based aerogel powder, 30-50 parts of a modified binder, 3-8 parts of a nano heat conduction inhibitor, 1-3 parts of a dispersing agent, 2-5 parts of a coalescing agent and 30-55 parts of deionized water. Through the high porosity characteristic of the silicon-based aerogel and the synergistic effect of the nanometer heat conduction inhibitor, the heat conduction coefficient of the coating is smaller than or equal to 0.028 W / (m.K), the heat preservation effect is stable in the environment of-40 DEG C to 150 DEG C, the adhesive force is larger than or equal to the first level, the aging resistance reaches the standard, and the problem of performance degradation caused by temperature fluctuation in the working process of a solid-state battery can be effectively solved. Meanwhile, the invention discloses a preparation method which is simple in process, capable of realizing industrial production and suitable for surface coating of shells or battery cells of various solid-state batteries such as solid-state lithium metal batteries and all-solid-state batteries.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery thermal insulation materials, in particular to a silicon-based aerogel thermal insulation coating suitable for solid-state batteries and a preparation method thereof. BACKGROUND

[0002] Solid-state batteries have become a research hotspot in the field of new energy batteries due to their high energy density and excellent safety performance. However, the ion conduction efficiency of solid-state electrolytes is sensitive to temperature, and the ion conduction rate decreases at low temperatures, and problems such as interface stability deterioration and material aging acceleration easily occur at high temperatures. Therefore, high-efficiency thermal insulation materials are needed to maintain the stability of battery operating temperature.

[0003] Existing battery thermal insulation materials mostly use traditional thermal insulation cotton and ceramic coatings, which have defects such as high thermal conductivity (usually ≥0.04 W / (m·K)), poor adhesion, and narrow temperature resistance range. As a new type of thermal insulation material, silicon-based aerogel has the advantages of high porosity and low thermal conductivity. However, when directly applied to solid-state batteries, it has the problems of insufficient adhesion to battery substrates and easy aggregation leading to degradation of thermal insulation performance, which limits its large-scale application in the field of solid-state batteries. Therefore, it is of great significance to develop a silicon-based aerogel thermal insulation coating that balances low thermal conductivity, high adhesion, and wide temperature resistance range, in order to improve the operating stability and service life of solid-state batteries. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a silicon-based aerogel thermal insulation coating suitable for solid-state batteries and a preparation method thereof, which solves the problems of high thermal conductivity, poor adhesion, and insufficient adaptability of existing materials, and meets the thermal insulation needs of solid-state batteries.

[0005] In one aspect, the present application provides a silicon-based aerogel thermal insulation coating, which is composed of the following raw materials by weight: silicon-based aerogel powder 8-15 parts, modified binder 30-50 parts, nano-thermal-conductivity inhibitor 3-8 parts, dispersant 1-3 parts, film-forming aid 2-5 parts, and deionized water 30-55 parts; the porosity of the silicon-based aerogel powder is 85%-95%, and the particle size is 50-200 nm; the modified binder is an epoxy-modified acrylic ester emulsion or a silane-modified polyurethane emulsion.

[0006] In some embodiments, the nano-thermal-conductivity inhibitor is at least one of nano-zirconium oxide and nano-silicon nitride, with a particle size of 20-80 nm.

[0007] In some embodiments, the dispersant is a polycarboxylate dispersant or a lignin sulfonate dispersant.

[0008] In some embodiments, the film-forming aid is propylene glycol methyl ether acetate or hexylene glycol butyl ether acetate.

[0009] In some embodiments, the silicone-based aerogel thermal insulation coating further includes 0.5-2 parts by weight of a defoamer, wherein the defoamer is an organosilicon defoamer or a polyether defoamer.

[0010] In another aspect, the present invention provides a method for preparing the aforementioned silicon-based aerogel thermal insulation coating, comprising the following steps: (1) Add deionized water and dispersant to a stirred tank and stir at 800-1200 r / min for 10-15 min to obtain a pre-dispersion; (2) Slowly add silicon-based aerogel powder and nano-thermal conductive inhibitor to the pre-dispersion liquid, heat to 40-50℃, and disperse at high speed for 30-45 min at a rotation speed of 700-1800 r / min; (3) Add modified binder, film-forming aid and optional defoamer, cool down to 25-30℃, and stir at low speed for 20-30 minutes at 600-800r / min. (4) After filtration through a 100-200 mesh filter, the silicon-based aerogel thermal insulation coating is obtained.

[0011] In some implementations, in step (2), ultrasonic-assisted dispersion is used during the high-speed dispersion process, with an ultrasonic power of 100-150W and an ultrasonic time of 15-20min.

[0012] In another aspect, the present invention provides the application of the aforementioned silicon-based aerogel thermal insulation coating in solid-state batteries.

[0013] In some embodiments, the silicon-based aerogel thermal insulation coating is applied to the surface of the solid-state battery casing or cell, with a coating thickness of 50-200 μm, and is used after curing at 30-100°C for 1-2 hours.

[0014] Beneficial effects The silicon-based aerogel thermal insulation coating of the present invention has excellent thermal insulation performance. The thermal conductivity of the coating is ≤0.028W / (m·K), which is much lower than that of traditional thermal insulation materials (usually ≥0.04W / (m·K)). It can effectively block the conduction of external temperature and maintain the stable operating temperature of solid-state batteries.

[0015] The silicon-based aerogel thermal insulation coating of the present invention has strong adhesion, with an adhesion of ≥1 grade to the metal shell of solid-state batteries and ceramic electrolyte substrates. After high and low temperature cycling tests (-40℃~150℃, 50 cycles), there is no peeling or cracking.

[0016] The preparation process of the silicon-based aerogel thermal insulation coating of the present invention is simple, requires no special equipment, and can be applied by conventional methods such as spraying and brushing. It is suitable for industrial production and has broad application prospects. Detailed Implementation

[0017] This invention provides a silicon-based aerogel thermal insulation coating, composed of the following raw materials in parts by weight: 8-15 parts silicon-based aerogel powder, 30-50 parts modified binder, 3-8 parts nano-thermal conductivity inhibitor, 1-3 parts dispersant, 2-5 parts film-forming aid, and 30-55 parts deionized water; the silicon-based aerogel powder has a porosity of 85%-95% and a particle size of 50-200 nm; the modified binder is an epoxy-modified acrylate emulsion or a silane-modified polyurethane emulsion. The ratio of high-porosity silicon-based aerogel, nano-thermal conductivity inhibitor, and modified binder directly determines the thermal insulation efficiency and adhesion stability of the coating. Deviating from the optimal range will lead to an increase in thermal conductivity or a decrease in adhesion. This invention precisely quantifies the ratio thresholds of these three components.

[0018] This invention also provides a method for preparing a silicon-based aerogel thermal insulation coating, comprising the following steps: (1) Add deionized water and dispersant to a stirred tank and stir at 700-1200 r / min for 10-15 min to obtain a pre-dispersion; (2) Slowly add silicon-based aerogel powder and nano-thermal conductive inhibitor to the pre-dispersion liquid, heat to 40-50℃, and disperse at high speed for 30-45 min at a rotation speed of 700-1800 r / min; (3) Add modified binder, film-forming aid and optional defoamer, cool down to 25-30℃, and stir at low speed for 20-30 minutes at 600-800r / min. (4) After filtration through a 100-200 mesh filter, the silicon-based aerogel thermal insulation coating is obtained.

[0019] High-speed dispersion is one of the key steps in solving the problem of silica-based aerogel agglomeration. The principle is to subject the material to strong shearing, impact, and centrifugal forces within the equipment through a high-speed rotating dispersion disc. When the dispersion disc rotates at high speed, it creates a strong liquid flow circulation around it, breaking up the agglomerated silica-based aerogel particles and dispersing them evenly in the coating system. In practice, the choice of dispersion speed is crucial. Generally, the suitable dispersion speed range is 700-1800 rpm. For example, when the dispersion speed is below 700 rpm, the uniformity of the coating deteriorates significantly. Microscopic observation of the coating samples reveals that aerogel particle agglomeration remains severe, with many large agglomerates distributed throughout the coating. This leads to reduced coating stability, and during storage, obvious stratification occurs within a short time, with a clear liquid on top and precipitated aerogel particles and other solid components at the bottom. Simultaneously, the coating's hiding power is also affected; at the same coating thickness, the coverage of the test sample is poor, resulting in undercoating. When the dispersion speed is between 700-1800 rpm, the uniformity of the coating is significantly improved, the aerogel particles are uniformly dispersed, the stability is good, and no obvious stratification occurs after a period of storage; the hiding power also meets practical application requirements. However, when the dispersion speed is too high, exceeding 2200 rpm, although the agglomeration problem is further resolved, new problems arise. Excessive rotation speed can damage the hollow structure of aerogel due to the shear force of the dispersion disc, causing the nanoporous structure of the aerogel to collapse and resulting in a significant decrease in its thermal insulation performance. Experimental data shows that the thermal conductivity of a silicon-based aerogel coating, which originally had a thermal conductivity of 0.02 W / (m·K), increased to 0.04 W / (m·K) after a high-speed dispersion speed of 2500 rpm, failing to meet the insulation requirements of some industrial equipment with high thermal insulation performance.

[0020] In a preferred embodiment, in step (2), ultrasonic-assisted dispersion is used during the high-speed dispersion process, with an ultrasonic power of 100-150W, an ultrasonic frequency of 20-100kHz, and an ultrasonic time of 15-20min.

[0021] Ultrasonic assistance plays an indispensable role in the preparation of silicon-based aerogel coatings, primarily based on the cavitation effect of ultrasound. When ultrasound propagates in a liquid medium, it generates a series of compression and rarefaction cycles. During the dilution phase, tiny bubbles (cavitation nuclei) in the liquid rapidly expand; during the compression phase, these bubbles contract sharply until they collapse. At the moment of bubble collapse, localized high temperatures (up to 5000K or higher), high pressures (exceeding 100MPa), and intense shock waves and microjets are generated. These extreme conditions effectively break the agglomeration forces between silicon-based aerogel particles, causing the aggregated particles to redisperse. Simultaneously, the vibration and stirring effects of ultrasound also help promote the uniform distribution of aerogel particles in the coating system. Without ultrasonic assistance, relying solely on high-speed dispersion significantly impacts coating performance. Studies show that even with a high-speed dispersion speed increased to 1800 rpm, aerogel particles in the coating still exhibit some degree of agglomeration without ultrasonic assistance. Laser particle size analysis revealed a significantly larger average particle size and a wider distribution range. This leads to coating defects during application, such as uneven surfaces and a grainy texture. From a mechanical properties perspective, coatings prepared without ultrasonic assistance exhibit poorer tensile strength and flexibility. They are more prone to fracture during tensile testing and cracking during bending tests. Furthermore, weather resistance decreases; accelerated aging tests simulating UV radiation and humid conditions show more severe fading and chalking. Inappropriate ultrasonic conditions can also negatively impact coating performance. Taking ultrasonic frequency as an example, different frequencies have varying dispersion effects on aerogel particles. Generally, commonly used ultrasonic frequencies are between 20-100 kHz. When the ultrasonic frequency is too low, such as below 20 kHz, the cavitation effect is weak and cannot effectively break up the agglomeration of aerogel particles. Experimental results show that coatings prepared at an ultrasonic frequency of 15 kHz exhibit more pronounced aerogel particle agglomeration, and the thermal conductivity of the coating is about 30% higher than that prepared under normal ultrasonic conditions. When the ultrasonic frequency is too high, exceeding 100 kHz, although the cavitation effect is enhanced, it may cause some damage to the aerogel structure. Excessively high frequencies subject aerogel particles to excessively strong impacts, leading to damage to the nanoporous structure of some particles, thus affecting the thermal insulation and mechanical properties of the coating. Ultrasonic power and time also need precise control. Too low a power or too short a time will not fully utilize the dispersion effect of ultrasound; too high a power or too long a time may introduce excessive energy, causing the coating system temperature to rise too quickly, affecting the stability and performance of the coating. Studies have shown that when the ultrasonic power is too high, the solvent in the coating evaporates more rapidly, which may cause changes in the viscosity of the coating and affect its application performance.

[0022] The technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0023] Example 1 Raw material by weight: 10 parts of silica-based aerogel powder (silica aerogel, porosity 90%, particle size 100 nm), 40 parts of epoxy-modified acrylate emulsion, 5 parts of nano-zirconia (particle size 50 nm), 2 parts of polycarboxylate dispersant, 3 parts of propylene glycol methyl ether acetate, 39 parts of deionized water, and 1 part of organosilicon defoamer.

[0024] Preparation steps: (1) Add deionized water and dispersant to a stirring tank and stir at 1000 r / min for 12 min to obtain a pre-dispersion; (2) Slowly add silicon-based aerogel powder and nano thermally conductive inhibitor to the pre-dispersion liquid, heat to 45°C, and disperse at high speed at 1800 r / min for 40 min; use ultrasonic-assisted dispersion with ultrasonic power of 100-150W and ultrasonic time of 15-20 min.

[0025] (3) Add modified binder, film-forming aid and defoamer, cool down to 28°C, and stir at low speed for 25 min at 700 r / min. (4) After being filtered through a 150-mesh filter, the heat insulation coating is obtained.

[0026] Performance testing: Thermal conductivity 0.025W / (m·K), adhesion grade 1, aging resistance test (150℃×1000h) showed no abnormalities.

[0027] Experimental Example 1 Test sample: Experimental group: Silicon-based aerogel thermal insulation coating prepared in Example 1 of this invention (coating thickness 100μm, cured at 80℃ for 1.5h). Control group 1: Commercially available ceramic heat insulation coating for batteries (mainstream models, coating thickness 100μm, cured under the same conditions); Control group 2: Traditional glass wool insulation material (5mm thick, wrapped around the surface of the battery casing).

[0028] Testing standards and equipment: Thermal conductivity: Tested using a flat plate thermal conductivity meter according to GB / T 10294-2008; Adhesion: According to GB / T 9286-1998, the cross-cut test was used (cross-cut spacing 1mm). Temperature stability: High and low temperature cycle test from -40℃ to 150℃ (8 hours per cycle, 50 cycles in total), observe the coating condition and test the change in thermal conductivity; Battery compatibility: The coating was applied to the all-solid-state lithium metal battery casing, and the battery's discharge capacity retention rate was tested at -20℃ and 120℃ (100 cycles).

[0029] The test results are shown in Table 1.

[0030] Table 1

[0031] As can be seen from Table 1, the thermal conductivity of the silicon-based aerogel thermal insulation coating of Example 1 of the present invention is reduced by 40.5% compared with control group 1 and by 34.2% compared with control group 2, and the adhesion is better and the temperature resistance is stronger. It can better maintain the discharge capacity of solid-state battery under extreme temperatures, and solves the problems of insufficient thermal insulation effect and poor adaptability of existing materials.

[0032] Example 2 Silicon-based aerogel thermal insulation coatings were prepared using the same method as in Example 1, except that the amount of silicon-based aerogel powder added was different, at 5 parts by weight, 10 parts by weight, and 20 parts by weight, respectively. The coatings were tested using the same methods, and the results are shown in Table 2.

[0033] Table 2

[0034] As shown in Table 2, when the content of silicon-based aerogel is too low, the proportion of nanoporous structure in the coating is insufficient, failing to effectively block heat conduction and convection, causing the thermal conductivity to soar to 0.065 W / (m·K); the heat insulation performance decreases by 48%, failing to meet the high-temperature protection requirements of the battery. When the content of silicon-based aerogel is too high, the film-forming properties of the coating deteriorate, and surface cracking defects easily appear. The thermal conductivity drops from the baseline of 0.025 W / (m·K) to 0.023 W / (m·K); at the same time, the film-forming material is relatively reduced, the internal stress of the coating increases, and the adhesion (pull-out method) to the battery substrate decreases from 1.8 MPa to 1.1 MPa, significantly increasing the risk of detachment during cyclic testing. When the content of silicon-based aerogel is controlled at 10 parts by weight, the thermal conductivity is low, the adhesion is high, and the film-forming state is good.

[0035] Example 3 Silicon-based aerogel thermal insulation coatings were prepared using the same method as in Example 1, except that the amount of nano-zirconia added was different, at 1 part by weight, 5 parts by weight, and 10 parts by weight. The coatings were tested using the same methods, and the results are shown in Table 3.

[0036] Table 3

[0037] As shown in Table 3, when the content of nano-zirconia is too low, it cannot exert a synergistic heat insulation effect, resulting in insufficient heat conduction barrier efficiency and a thermal conductivity that drops to only 0.045 W / (m·K). Compared with the pure silicon-based aerogel system, the heat insulation optimization effect is less than 30%. When the content of nano-zirconia is too high, the particles are prone to agglomeration, which destroys the porous heat insulation structure of the silicon-based aerogel. The thermal conductivity increases from 0.025 W / (m·K) to 0.038 W / (m·K). At the same time, the coating viscosity increases to 8500 mPa·s (reference 5000 mPa·s), the uniformity of the coating decreases, and the film thickness deviation reaches ±0.3 mm.

[0038] Example 4 Silicon-based aerogel thermal insulation coatings were prepared using the same method as in Example 1, except that the amount of epoxy-modified acrylate emulsion added was different, at 20 parts by weight and 55 parts by weight, respectively. The coatings were tested using the same methods, and the results are shown in Table 4.

[0039] Table 4

[0040] As shown in Table 4, when the content of epoxy-modified acrylate emulsion is too low, it cannot fully encapsulate the heat-insulating components, resulting in insufficient interfacial bonding between the coating and the battery substrate. The adhesion decreased from 1.8 MPa to 0.9 MPa. After 10 cycles of thermal cycling (-20℃ / 2h → 60℃ / 2h), the area of ​​peeling off reached 35%. When the content of epoxy-modified acrylate emulsion is too high, the solid content of the coating increases, and the drying time is extended from 4h to 7h. The flexibility of the film layer decreases, and after 50 cycles of battery charge-discharge (volume expansion and contraction), the cracking rate reaches 28%. At the same time, the thermal conductivity increases slightly to 0.033 W / (m・K), and the heat insulation performance is slightly degraded.

[0041] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A silicone-based aerogel thermal insulation coating, comprising the following raw materials in parts by weight: The composition comprises 8-15 parts of silicon-based aerogel powder, 30-50 parts of modified binder, 3-8 parts of nano-thermal conductivity inhibitor, 1-3 parts of dispersant, 2-5 parts of film-forming aid, and 30-55 parts of deionized water; the porosity of the silicon-based aerogel powder is 85%-95%, and the particle size is 50-200 nm; the modified binder is an epoxy-modified acrylate emulsion or a silane-modified polyurethane emulsion.

2. The silicon-based aerogel thermal insulation coating according to claim 1, wherein, The nano-thermal conductivity inhibitor is at least one of nano-zirconia and nano-silicon nitride, with a particle size of 20-80 nm.

3. The silicon-based aerogel thermal insulation coating according to claim 1, wherein, The dispersant is a polycarboxylate dispersant or a lignin sulfonate dispersant.

4. The silicon-based aerogel thermal insulation coating according to claim 1, wherein, The film-forming aid is propylene glycol methyl ether acetate or hexanediol butyl ether acetate.

5. The silicon-based aerogel thermal insulation coating according to claim 1, wherein, The silicon-based aerogel thermal insulation coating also includes 0.5-2 parts by weight of defoamer, which is an organosilicon defoamer or a polyether defoamer.

6. A method for preparing the silicon-based aerogel thermal insulation coating according to any one of claims 1-5, comprising the following steps: (1) Add deionized water and dispersant to a stirred tank and stir at 800-1200 r / min for 10-15 min to obtain a pre-dispersion; (2) Slowly add silicon-based aerogel powder and nano-thermal conductive inhibitor to the pre-dispersion liquid, heat to 40-50℃, and disperse at high speed for 30-45 min at a rotation speed of 700-1800 r / min; (3) Add modified binder, film-forming aid and optional defoamer, cool down to 25-30℃, and stir at low speed for 20-30 minutes at 600-800r / min. (4) After filtration through a 100-200 mesh filter, the silicon-based aerogel thermal insulation coating is obtained.

7. The preparation method according to claim 6, wherein, In step (2), ultrasonic-assisted dispersion is used during the high-speed dispersion process. The ultrasonic power is 100-150W and the ultrasonic time is 15-20min.

8. The application of the silicon-based aerogel thermal insulation coating according to any one of claims 1-5 in solid-state batteries.

9. The application according to claim 8, wherein, The silicon-based aerogel thermal insulation coating is applied to the surface of a solid-state battery casing or cell and cured at 30-100℃ for 1-2 hours before use.

10. The application according to claim 9, wherein, The coating thickness is 50-200μm.

Images