Aerogel slurry, preparation method and application thereof

Abstract

The present invention discloses an aerogel slurry, its preparation method, and application. The aerogel slurry comprises the following components, measured by weight: 20-50 parts aerogel powder, 3-6 parts dispersant, 8-12 parts defoaming agent, 120-200 parts film-forming material, and 250-350 parts water. When the aerogel slurry is used in battery separators, under the same coating thickness, the weight gain of the separator coated with aerogel powder is smaller, thereby improving the mass energy density of the subsequent battery cell. While maintaining battery performance, the battery separator is reduced in weight. The separator's thermal insulation properties are significantly improved, providing better protection for heat-sensitive separators, thereby enhancing the safety of the battery cell.

Description

Technical Field

[0001] The present invention relates to the technical field of aerogels, and in particular to an aerogel slurry, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-ion battery separators are a key component of lithium-ion batteries, and their performance directly impacts battery capacity, cycle performance, and safety. The separator substrate is prone to shrinkage when exposed to heat, causing battery short circuits. Therefore, in actual use, a layer of slurry is applied to the separator substrate to improve its thermal stability and safety.

[0003] Currently, the coating slurry used for separator substrates is mostly made from ceramic powder and boehmite. The resulting separators are heavy, making the battery heavy and difficult to transport, and also have poor thermal insulation performance. Therefore, a lightweight, thermally insulating coating material is urgently needed to address these issues.

[0004] Aerogel is a lightweight, three-dimensional porous material with advantages such as low density, low hardness, and low thermal conductivity. It is widely used in technical fields such as thermal insulation. CN109244328A discloses a lithium-ion battery separator and its preparation method, comprising a polyolefin microporous membrane and a coating slurry, which is applied to the polyolefin microporous membrane. The coating slurry is composed of the following components: 3-6 parts chitosan, 5-10 parts nano-zinc oxide, 8-16 parts nano-carbon black, 4-8 parts nano-zirconium oxide, 8-16 parts silica aerogel, 0.6-5 parts amphoteric dispersant, 2-8 parts amphoteric adhesive, 10-20 parts aqueous acrylic emulsion, and 40-60 parts deionized water. Although the coating slurry used in this technical solution contains aerogel powder as a raw material, which can reduce the slurry's weight to a certain extent, its composition is too complex, resulting in poor weight reduction for the battery separator and poor thermal insulation performance. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide an aerogel slurry to solve the problem that the composition of the existing aerogel slurry is too complex, and when used for battery separators, it has poor weight reduction effect on the battery separator and poor thermal insulation performance.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] An aerogel slurry comprises the following components, calculated by mass: 20 to 50 parts of aerogel powder, 3 to 6 parts of a dispersant, 8 to 12 parts of a defoamer, 120 to 200 parts of a film-forming substance and 250 to 350 parts of water.

[0008] Furthermore, the aerogel powder includes silicon-based aerogel powder, alumina aerogel powder or titanium dioxide aerogel powder.

[0009] Furthermore, the particle size of the aerogel powder is 5 to 50 μm. The present invention controls the particle size of the aerogel powder to be 5 to 50 μm because, on the one hand, aerogel powder particles that are too large are not conducive to coating, and on the other hand, aerogel powder particles that are too small may destroy the microstructure of the aerogel powder and affect the thermal insulation performance of the aerogel slurry.

[0010] Furthermore, the thermal conductivity of the aerogel powder is less than 0.016 W / (m·k). The present invention controls the thermal conductivity of the aerogel powder to be less than 0.016 W / (m·k) because the smaller the thermal conductivity, the better the thermal insulation performance of the produced coated diaphragm and the higher the safety of the battery cell.

[0011] Furthermore, the specific surface area of ​​the aerogel powder is ≥600m 2 / g. The present invention controls the specific surface area of ​​aerogel powder to be ≥600m 2 / g, because the larger the specific surface area, the more microporous structures of the powder, the better the intrinsic performance, and the better the porous adsorption performance of the subsequent coating, which is conducive to the adsorption of oxygen and hydrogen and avoids short circuit of the battery.

[0012] Furthermore, the mass moisture absorption rate of the aerogel powder is ≤5.0%. The present invention controls the mass moisture absorption rate of the aerogel powder to ≤5.0% because the use of hydrophobic aerogel powder can make the aerogel powder more stable in the slurry and will not cause changes in the physical and chemical properties of the powder due to fluctuations in moisture.

[0013] Furthermore, the viscosity of the aerogel slurry is 6000 to 12000 mPa·s.

[0014] Furthermore, the film-forming substance includes pure acrylic emulsion or styrene acrylic emulsion.

[0015] The method for preparing the aerogel slurry comprises the following steps:

[0016] (1) Add the film-forming material to water and stir at a speed of 700-1000 r / min for 10-20 minutes;

[0017] (2) Add dispersant and stir for 5 to 8 minutes;

[0018] (3) adding a portion of the defoamer to the mixed solution obtained in step (2) and stirring for 5 to 8 minutes;

[0019] (4) adding aerogel powder in small amounts and multiple times to the mixed solution obtained in step (3), adding the remaining defoaming agent, and continuously stirring at a speed of 1000-1800 r / min for 2-3 hours;

[0020] (5) The slurry prepared in step (4) is vacuum degassed for 30 to 50 minutes to obtain an aerogel slurry.

[0021] Furthermore, the present invention provides application of the aerogel slurry in battery separators.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The aerogel slurry of the present invention is prepared with aerogel powder as a base material, water as a solvent, an aqueous surfactant as a dispersant, and supplemented with a defoaming agent and a film-forming substance. The obtained aerogel slurry has simple ingredients, low cost, and is easy to prepare. And because the aerogel powder in the aerogel slurry of the present invention has a large specific gravity, with the assistance of other additives, the aerogel slurry of the present invention, when used for battery separators, perfectly retains the characteristics of low density and excellent thermal insulation performance of the aerogel powder. When used for battery separators, under the coating conditions of the same thickness, the weight gain of the coated separator is smaller, and the mass energy density of the subsequent battery cell is improved; while ensuring the battery performance, the weight reduction of the battery separator is achieved; and compared with traditional coating materials, the aerogel slurry of the present invention also significantly improves the thermal insulation performance of the separator, better protects the heat-sensitive separator, and thus improves the safety of the battery cell.

[0024] 2. The inventors of the present invention have found that due to the large porosity of aerogel powder, when trace amounts of oxygen and hydrogen are generated during the initial failure of the positive and negative electrodes of the battery cell, the oxygen and hydrogen will be adsorbed by the aerogel powder, thereby preventing the battery from short-circuiting.

[0025] 3. The aerogel slurry of the present invention produces virtually no powdering after coating the battery separator. Due to the low hardness of the aerogel powder, it does not damage the roller during the roll-coating process. Furthermore, since the aerogel oxide contains fewer impurities, it also has fewer side effects on the battery cell system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a scanning electron microscope image (SEM image) of the silica aerogel powder used in Example 1;

[0027] Figure 2 This is a picture of a PP diaphragm manually coated with the slurry obtained in Example 1. DETAILED DESCRIPTION

[0028] The specific implementation methods of the present invention are further described in detail below with reference to specific examples.

[0029] The numerical ranges herein are understood to specifically disclose every intervening value between the upper and lower limits of the range. Each smaller range between any stated value or intervening value in a stated range and any other stated value or intervening value in that stated range is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0030] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art. Although the present invention has only described preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail. As used herein, "comprising", "including", "having", "containing", etc. are all open-ended terms, meaning including but not limited to.

[0031] Unless otherwise specified, the experimental methods used in the present invention are all conventional methods.

[0032] Unless otherwise specified, the materials, reagents, etc. used in the present invention can be purchased or synthesized by known methods.

[0033] The quantitative tests in the present invention were repeated three times and the results were averaged.

[0034] The dispersants used in the present invention are all water-based surfactants, including HL-FS-01 (manufacturer: Hualu (Tianjin) New Materials Technology Co., Ltd.) or SN5040 (manufacturer: Shenzhen Jitian Chemical Co., Ltd.). The defoamers used in the present invention include BYK-025 (manufacturer: BYK Chemical Co., Ltd., Germany) or 681-F (manufacturer: Linyi Kaiao Chemical Co., Ltd.).

[0035] Example 1

[0036] A method for preparing an aerogel slurry comprises the following steps:

[0037] (1) Add 150 g of styrene-acrylic emulsion to 300 g of desalted water and stir at 800 r / min for 15 min;

[0038] (2) Add 3 g of SN5040 and stir for 6 min;

[0039] (3) Add 4 g of defoamer (BYK-025) to the mixed solution obtained in step (2) and stir for 6 min;

[0040] (4) Silica aerogel powder (particle size 25 μm, thermal conductivity 0.015 W / (m·k), specific surface area 600 m2) was added to the mixed solution obtained in step (3) three times. 2 / g, mass moisture absorption rate 5.0%), add 10g each time, then add 6g of defoamer (BYK-025), and continue stirring at a speed of 1400r / min for 2.5h;

[0041] Figure 1 This is a scanning electron microscope image (SEM image) of silica aerogel powder. Figure 1 It can be seen that the powder used in the experiment of this embodiment has a regular spherical morphology and good quality, and can be used for the subsequent preparation of aerogel slurry.

[0042] (5) The slurry prepared in step (4) was vacuum degassed for 30 minutes to obtain an aerogel slurry.

[0043] Viscosity test: The obtained slurry was subjected to a viscosity test, and the viscosity was 8600 mPa·s.

[0044] Preparation of diaphragm: The aerogel slurry obtained in this example was evenly coated on the PP diaphragm with a scraper of 100 μm thickness, and after standing for 4 hours at 25°C, it was placed in a vacuum drying oven at 60°C and dried for 2 hours to obtain the finished battery diaphragm (such as Figure 2 As shown). Figure 2 It can be seen that the surface of the diaphragm coated with the slurry of the present invention has no abnormality, no flow, no accumulation, and is overall flat and uniform, and the slurry coating effect is good.

[0045] Example 2

[0046] A method for preparing an aerogel slurry comprises the following steps:

[0047] (1) Add 120 g of pure acrylic acid emulsion to 250 ml of desalted water and stir at 700 r / min for 20 min;

[0048] (2) Add 5 g of HL-FS-01 and stir for 5 min;

[0049] (3) Add 6 g of defoamer (681-F) to the mixed solution obtained in step (2) and stir for 5 min;

[0050] (4) Alumina aerogel powder (particle size 5 μm, thermal conductivity 0.015 W / (m·k), specific surface area 700 m2) was added to the mixed solution obtained in step (3) three times. 2 / g, mass moisture absorption rate 4.0%), add 15 g each time, then add 4 g of defoamer (681-F), and continue stirring at a speed of 1200 r / min for 3 h;

[0051] (5) The slurry prepared in step (4) was vacuum degassed for 40 minutes to obtain an aerogel slurry.

[0052] Viscosity test: The obtained slurry was subjected to a viscosity test, and the viscosity was 6500 mPa·s.

[0053] Preparation of diaphragm: The aerogel slurry obtained in this example was evenly coated on the PP diaphragm using a scraper with a thickness of 100 μm. The slurry was allowed to stand at 40°C for 2 hours and then dried in a vacuum drying oven at 60°C for 2 hours to obtain a finished battery diaphragm.

[0054] Example 3

[0055] A method for preparing an aerogel slurry comprises the following steps:

[0056] (1) Add 200 g of styrene-acrylic emulsion to 350 g of desalted water and stir at a speed of 1000 r / min for 10 min;

[0057] (2) Add 6 g of SN5040 and stir for 8 minutes;

[0058] (3) Add 5 g of defoamer (BYK-025) to the mixed solution obtained in step (2) and stir for 8 min;

[0059] (4) Titanium dioxide aerogel powder (particle size 50 μm, thermal conductivity 0.015 W / (m·k), specific surface area 600 m2) was added to the mixed solution obtained in step (3) three times. 2 / g, mass moisture absorption rate 5.0%), add 8g each time, then add 7g of defoamer (BYK-025), and continue stirring at a speed of 1800r / min for 2h;

[0060] (5) The slurry obtained in step (4) was vacuum degassed for 50 minutes to obtain an aerogel slurry.

[0061] Viscosity test: The obtained slurry was subjected to a viscosity test, and the viscosity was 11000 mPa·s.

[0062] Preparation of diaphragm: The aerogel slurry obtained in this example was evenly coated on the PP diaphragm using a scraper with a thickness of 100 μm. The slurry was allowed to stand at 60°C for 30 minutes and then dried in a vacuum drying oven at 60°C for 2 hours to obtain a finished battery diaphragm.

[0063] A comparison table of the weight and thermal conductivity of the battery separator obtained by the present invention, the existing battery separator, the base film (PP separator) and the viscosity of the obtained aerogel slurry is shown in Table 1.

[0064] Table 1 Comparison of density and thermal conductivity of finished battery separator and base film as well as viscosity of obtained aerogel slurry

[0065]

[0066] As shown in Table 1, compared with existing ceramic powder oil slurries and aluminum oxide aqueous slurries, the use of the aerogel slurry of the present invention to coat the substrate separator has a lower density gain after coating, effectively achieving a weight reduction for the battery separator, thereby achieving a weight reduction for the battery. Furthermore, the thermal conductivity of the separator coated with the aerogel slurry of the present invention is effectively reduced, providing good protection for heat-sensitive separators, thereby improving the safety of the battery cell. Furthermore, the viscosity of the resulting aerogel slurry fluctuates between 6000 and 12000 mPa·s, with a relatively small fluctuation range. This indicates that the aerogel slurry obtained by the present invention is uniformly dispersed, avoiding uneven subsequent slurry coating, which can cause the battery cell to fail the HIPOT test.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the technical solutions. Those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present invention that do not depart from the purpose and scope of the technical solutions of the present invention should be included in the scope of the claims of the present invention.

Claims

1. An aerogel slurry for preparing a battery separator, characterized in that: The composition comprises the following components by weight: 20 to 50 parts of aerogel powder, 3 to 6 parts of dispersant, 8 to 12 parts of defoaming agent, 120 to 200 parts of film-forming substance and 250 to 350 parts of water; The particle size of the aerogel powder is 5-50 μm; the specific surface area of ​​the aerogel powder is ≥600 m 2 / g.

2. The aerogel slurry according to claim 1, characterized in that: The aerogel powder includes silicon-based aerogel powder, aluminum oxide aerogel powder or titanium dioxide aerogel powder.

3. The aerogel slurry according to claim 1, characterized in that: The thermal conductivity of the aerogel powder is less than 0.016 W / (m·K).

4. The aerogel slurry according to claim 1, characterized in that: The mass moisture absorption rate of the aerogel powder is ≤5.0%.

5. The aerogel slurry according to claim 1, characterized in that: The viscosity of the aerogel slurry is 6000-12000 mPa·s.

6. The aerogel slurry according to claim 1, characterized in that: The film-forming substance includes pure acrylic emulsion or styrene acrylic emulsion.

7. The method for preparing the aerogel slurry according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Add the film-forming material to water and stir at a speed of 700-1000 r / min for 10-20 minutes; (2) Add dispersant and stir for 5-8 minutes; (3) Add part of the defoaming agent to the mixed solution obtained in step (2) and stir for 5 to 8 minutes; (4) After adding aerogel powder in small amounts to the mixed solution obtained in step (3) several times, add the remaining defoaming agent, and continue stirring at a speed of 1000-1800 r / min for 2-3 h; (5) The slurry prepared in step (4) is vacuum degassed for 30 to 50 minutes to obtain an aerogel slurry.

8. Use of the aerogel slurry according to any one of claims 1 to 6 in a battery separator.

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