Preparation method of high-performance composite solid electrolyte membrane and application thereof in all-solid-state lithium battery

Abstract

The application discloses a preparation method of a high-performance composite solid-state electrolyte membrane and application of the high-performance composite solid-state electrolyte membrane in a full solid-state lithium battery. The application first prepares a vermiculite two-dimensional nanosheet dispersion liquid by taking a thermal expansion vermiculite as raw material; then stacks the vermiculite two-dimensional nanosheets in the dispersion liquid on a base film to form a layered framework; and finally introduces a eutectic solvent obtained by mixing N-methylacetamide and lithium bistrifluoromethanesulfonimide into the layered framework to obtain a high-performance solid-liquid mixed composite solid-state electrolyte membrane. The high-performance composite solid-state electrolyte membrane prepared by the application can better inhibit the volatilization problem of liquid electrolyte and inhibit the problem of side reactions of liquid small molecules and positive and negative electrodes, thereby improving the interface stability and showing better lithium lithium long cycle stability than a traditional electrolyte membrane.

Description

I. TECHNICAL FIELD

[0001] The application belongs to the technical field of all-solid-state lithium batteries, and particularly relates to a preparation method of a high-performance composite solid-state electrolyte film for inhibiting volatilization of liquid electrolyte and improving interface stability and application thereof in all-solid-state lithium batteries. II. BACKGROUND

[0002] Lithium batteries have achieved great success in the past few decades as a new type of energy storage device, and the electrolyte as a core component thereof has attracted much attention and directly determines the performance of the battery. Ceramic solid-state electrolytes (SSEs) can provide comparable conductivity to liquid electrolytes at room temperature, but most ceramic particles have poor interface contact with two electrodes and poor mechanical properties. Solid polymer electrolytes (SPEs) have good mechanical properties and are suitable for traditional battery manufacturing. However, the lithium conductivity of SPEs at room temperature is limited, and the battery usually needs to work at a high temperature (> 60℃). Solid-liquid hybrid electrolytes (SLHEs) are very promising electrolytes in lithium metal batteries. However, most components of SLHEs are flammable and volatile, which poses a safety hazard.

[0003] Deep eutectic solvents (DESs) are green liquid media formed by mixing two or three components through hydrogen bonding interactions. DESs have many common characteristics with ionic liquids (ILs), such as low vapor pressure (usually less than 100 Pa at 373 K), good thermal and chemical stability, non-flammability, and good component adjustability. It has been used in the design of solid-state electrolytes for lithium metal batteries, by adjusting the composition, structure and performance of the mixture to achieve efficient transport of lithium ions and stable electrochemical performance. There are also studies combining DESs with other materials, such as porous materials, polymers, etc., to further optimize the performance of solid electrolytes. However, due to the poor compatibility of amide-based DES electrolytes with lithium metal, the reaction of free amide molecules with lithium metal leads to uneven lithium deposition, reducing the long-term cycle stability of the assembled battery. Therefore, improving the interface stability between lithium metal and DESs is the key to realizing its long cycle life. Currently, some scholars have nano-sized the free amide molecules of deep eutectic solvents by using UiO-66-NH2 in a polyoxide (PEO) matrix, achieving excellent symmetric electrochemical cycle performance within 3600 hours. Overall, DESs as a new type of solid electrolyte material have potential application prospects and development space.

[0004] Layered materials have attracted extensive attention in the field of solid-state electrolytes due to their unique structure and properties. In particular, layered materials such as clays and MXenes have interlayer spaces that can be filled with electrolyte solutions or polymers to produce solid-state electrolytes with high ionic conductivity and good mechanical properties. In addition, the high surface area and porosity of layered materials are beneficial to the diffusion of lithium ions, improving the electrochemical performance of batteries. In this case, the development of solid-state electrolytes based on layered materials represents a promising approach to manufacturing next-generation high-performance energy storage devices. III. SUMMARY

[0005] The technical problem to be solved by the present application is: Based on the development status and existing problems of existing lithium battery solid-state electrolytes, the present application provides a preparation method of a high-performance composite solid-state electrolyte film for inhibiting the volatilization of liquid electrolyte and improving interface stability and its application in all-solid-state lithium batteries. The high-performance composite solid-state electrolyte film prepared by the present application can effectively inhibit the volatilization of liquid electrolyte and better improve the interface stability.

[0006] To solve the above problems, the technical scheme adopted by the present application is:

[0007] The present application provides a preparation method of a high-performance composite solid-state electrolyte film for inhibiting the volatilization of liquid electrolyte and improving interface stability, which comprises the following steps:

[0008] 1) Preparation of vermiculite two-dimensional nanosheet dispersion liquid:

[0009] a. Add raw material heat-expanded vermiculite to saturated NaCl solution and heat stir, then wash with deionized water to obtain sodium ion intercalated expanded vermiculite;

[0010] b. Add the obtained sodium ion intercalated expanded vermiculite to LiCl solution for reflux reaction, then filter, and wash with deionized water and anhydrous ethanol in turn after filtration until no Cl - is detected in the filtrate, to obtain lithium ion intercalated expanded vermiculite;

[0011] c. Add the lithium ion intercalated expanded vermiculite obtained in step b to deionized water and stir, then perform ultrasonic treatment after stirring; centrifuge after treatment to remove unpeeled vermiculite sheets to obtain vermiculite nanosheet dispersion liquid (the concentration of the vermiculite nanosheet dispersion liquid is calibrated by drying and weighing method);

[0012] 2) Dilute the vermiculite nanosheet dispersion liquid obtained in step c with deionized water or anhydrous ethanol, the dilution ratio is 15-20 times, then perform low-pressure vacuum suction filtration and drying after dilution to obtain vermiculite two-dimensional nanosheet layered film;

[0013] 3) Preparation of the deep eutectic solvent: N-methylacetamide is mixed with lithium bistrifluoromethanesulfonimide, and then placed in a glove box for stirring at room temperature under an argon atmosphere for 4-6 h. The deep eutectic solvent is obtained after the reaction.

[0014] 4) The obtained deep eutectic solvent is vacuum filtered into the layered film of the exfoliated vermiculite two-dimensional nanosheet obtained in step 2) for processing to obtain a high-performance composite solid electrolyte film.

[0015] According to the preparation method of the high-performance composite solid electrolyte film for inhibiting the volatilization of the liquid electrolyte and improving the interface stability, the mass ratio between the heat-expanded vermiculite and sodium chloride in the saturated NaCl solution in step a is 0.8-1.2:20 (the saturated sodium chloride solution is prepared by adding 40 g of sodium chloride to 100 mL of water).

[0016] The heating temperature is controlled to be 120-130°C, and the stirring time is 48 h.

[0017] According to the preparation method of the high-performance composite solid electrolyte film for inhibiting the volatilization of the liquid electrolyte and improving the interface stability, the concentration of the LiCl solution in step b is 2-2.5 mol / L, the oil bath temperature is 120-130°C during the reflux reaction, and the time is 24-48 h.

[0018] The mass-to-volume ratio between the sodium ion intercalated expanded vermiculite and the LiCl solution is 1 g:45-60 mL.

[0019] According to the preparation method of the high-performance composite solid electrolyte film for inhibiting the volatilization of the liquid electrolyte and improving the interface stability, the mass-to-volume ratio added between the lithium ion intercalated expanded vermiculite and the deionized water in step c is 1 g:350-500 mL; the magnetic stirring speed is 600-800 rpm, the magnetic stirring time is 30-60 min; the ultrasonic treatment time is 30-60 min; the centrifugation speed is 6000-8000 rpm, and the centrifugation time is 10-15 min.

[0020] According to the preparation method of the high-performance composite solid electrolyte film for inhibiting the volatilization of the liquid electrolyte and improving the interface stability, the concentration of the vermiculite nanosheet dispersion liquid obtained in step c is 0.7-1 g / L.

[0021] According to the preparation method of the high-performance composite solid electrolyte film for inhibiting the volatilization of the liquid electrolyte and improving the interface stability, the pressure is controlled to be -0.05-0 MPa during the low-pressure vacuum filtration in step 2); and the drying temperature is controlled to be 50-60°C, and the drying time is 40-50 h.

[0022] According to the preparation method of the high-performance composite solid-state electrolyte film for inhibiting the volatilization of liquid electrolyte and improving the interface stability, the mixing molar ratio between the N-methylacetamide and lithium bistrifluoromethanesulfonimide in the step 3) is 3.5-5:1.

[0023] According to the preparation method of the high-performance composite solid-state electrolyte film for inhibiting the volatilization of liquid electrolyte and improving the interface stability, the pressure during the suction filtration in the step 4) is-0.05-0 MPa.

[0024] According to the preparation method of the high-performance composite solid-state electrolyte film for inhibiting the volatilization of liquid electrolyte and improving the interface stability, the thickness of the obtained high-performance composite solid-state electrolyte film is 14-20 μm.

[0025] The application of the high-performance composite solid-state electrolyte film prepared by the above method in a full solid-state lithium battery.

[0026] The high-performance composite solid-state electrolyte film prepared by the application effectively inhibits the volatilization of liquid electrolyte and better improves the interface stability. The high ionic conductivity of the eutectic solvent and the fast ion transfer path provided by the vermiculite framework realize the preparation of the high-performance composite solid-state electrolyte film. The vermiculite has high mechanical strength and can effectively inhibit the growth of lithium dendrites. The framework structure of the vermiculite reduces the contact between the liquid small molecules and the positive and negative electrodes, reduces the occurrence of side reactions, and provides the cycle stability of the battery. The electrolyte film applied in the full solid-state lithium battery can realize excellent electrochemical performance and safety performance.

[0027] The principle adopted by the technical scheme of the application is as follows:

[0028] 1) The high-performance composite solid-state electrolyte film is prepared by drawing the eutectic solvent into the interlayer of the vermiculite, wherein the vermiculite framework provides a fast ion transfer channel and the eutectic solvent provides high ion transfer performance.

[0029] 2) Compared with the liquid electrolyte, the composite solid-state electrolyte can well inhibit the volatilization problem of the liquid electrolyte, solve the interface contact problem, and greatly improve the long cycle stability of the battery.

[0030] 3) After introducing the eutectic solvent into the vermiculite layer framework, the poor interface contact is improved, and the problem of side reactions between the liquid small molecules and the positive and negative electrodes is also improved, so that the composite solid-state electrolyte film shows more excellent lithium lithium pair charging performance than the liquid electrolyte.

[0031] In summary, the application draws the eutectic solvent into the vermiculite framework, which not only provides high battery performance for the composite solid electrolyte film, but also provides a solution to the problem of reducing the volatilization of the liquid electrolyte and the problem of reaction with the lithium negative electrode. From the preparation idea, the vermiculite nanosheet is prepared by intercalation method, then is drawn into a vermiculite layered film framework, and finally the eutectic solvent is drawn into the interlayer of the vermiculite framework to obtain a high-performance composite solid electrolyte film.

[0032] The positive beneficial effects of the application are as follows:

[0033] 1. The eutectic solvent used in the technical solution of the application has the advantages of high ionic conductivity, good stability, non-flammability and adjustable composition. After the eutectic solvent is drawn into the vermiculite framework, the composite solid electrolyte film obtained can effectively inhibit the growth of lithium dendrites, and the lithium iron phosphate / lithium battery assembled by the electrolyte has excellent cycle life and high safety, which reduces the capacity attenuation of the battery (60℃, 0.5C, the capacity is 144.4mAh g -1 after 200 cycles, and the capacity retention rate is 93.3%), and increases the service life of the battery.

[0034] 2. The draw filtration method used in the technical solution of the application is easy to implement, easy to scale up production, and has high production efficiency.

[0035] 3. The solid-liquid mixed composite solid electrolyte film prepared by the application can better inhibit the volatilization problem of the liquid electrolyte and the problem of side reactions of the liquid small molecules with the positive and negative electrodes, thereby improving the interface stability; the lithium-lithium symmetric battery assembled can be cycled for 700h without short circuit phenomenon. IV. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The scanning electron microscope image of the vermiculite nanosheet obtained in step 1) of Example 1 of the application;

[0037] The scanning electron microscope image of the vermiculite nanosheet obtained in step 1) of Example 1 of the application; Figure 1 It can be seen that the vermiculite nanosheet has a typical two-dimensional structure, and the size of the nanosheet is 1-2μm.

[0038] Figure 2 The scanning electron microscope image of the vermiculite layered framework prepared in step 2) of Example 1 of the application;

[0039] The scanning electron microscope image of the vermiculite layered framework prepared in step 2) of Example 1 of the application; Figure 2 It can be seen that the vermiculite framework has a stacked structure.

[0040] Figure 3 The physical image of the eutectic solvent prepared in Comparative Example 1 of the application;

[0041] Figure 4A physical map of the composite solid electrolyte film after the eutectic solvent prepared in embodiment 1 is extracted into the layer-shaped framework of vermiculite;

[0042] Figure 5 A cross-section scanning electron microscope image of the composite solid electrolyte film after the eutectic solvent prepared in embodiment 1 is extracted into the layer-shaped framework of vermiculite;

[0043] Figure 6 A surface scanning electron microscope image of the lithium sheet after lithium-lithium pair charging in embodiment 1;

[0044] By Figure 6 It can be seen that the lithium metal surface is smooth and dense without obvious defects, indicating that the interface between the composite solid electrolyte film and the lithium negative electrode is stable.

[0045] Figure 7 A lithium-lithium pair charging long cycle curve of embodiment 1 and comparative example 1;

[0046] By Figure 7 It can be seen that the lithium-lithium pair battery assembled by the composite solid electrolyte film can be cycled for 700h without short circuit phenomenon;

[0047] Figure 8 Rate cycle performance of a lithium iron phosphate / lithium battery assembled by the high-performance composite solid electrolyte film obtained in embodiment 1;

[0048] By Figure 8 It can be seen that at 60℃, 0.5C, the capacity is 144.4mAh g -1 after 200 cycles, and the capacity retention rate is 93.3%. V. DETAILED DESCRIPTION

[0049] The present application is further described below in conjunction with embodiments, but does not limit the scope of protection of the technical solutions of the present application.

[0050] Embodiment 1:

[0051] The preparation method of the high-performance composite solid electrolyte film for inhibiting the volatilization of liquid electrolyte and improving the interface stability is as follows:

[0052] 1) Preparation of vermiculite two-dimensional nanosheet dispersion liquid:

[0053] a. Add 2g of raw material thermal expansion vermiculite to saturated NaCl solution (saturated NaCl solution is prepared by dissolving 40g of sodium chloride in 100mL of water), and magnetically stir at 120℃ for 48h, then wash with deionized water for 5 times, and obtain sodium ion intercalated expanded vermiculite after washing;

[0054] b. The obtained sodium ion intercalated expanded vermiculite was added into 50 mL of a 2 mol / L LiCl solution for reflux reaction for 24 h (oil bath temperature was 120℃), and after reaction, filtration was performed, and after filtration, the obtained filtrate was washed with deionized water for 5 times and anhydrous ethanol for 3 times, and at this time, no Cl - was detected in the filtrate.

[0055] c. 0.5 g of the obtained lithium ion intercalated expanded vermiculite was added into 200 mL of deionized water for magnetic stirring for 30 min, and after stirring, ultrasonic treatment was performed for 30 min; after treatment, centrifugation was performed, and the unexfoliated vermiculite sheets were removed, to obtain a vermiculite nanosheet dispersion (the concentration of the vermiculite nanosheet dispersion was calibrated by a drying and weighing method, and the concentration was about 1 g / L).

[0056] 2) 20 mL of the obtained vermiculite nanosheet dispersion was diluted with 300 mL of deionized water and uniformly dispersed by ultrasonic treatment, and then low-pressure vacuum filtration and drying (drying temperature was 60℃, and drying time was 45 h) were performed under the condition of -0.05-0 MPa, to obtain a vermiculite two-dimensional nanosheet layered film.

[0057] 3) Preparation of a eutectic solvent: N-methylacetamide and lithium bistrifluoromethanesulfonimide were mixed in a molar ratio of 4:1, and then placed in a glove box, and stirred at room temperature for 4 h under an argon atmosphere, to obtain a eutectic solvent.

[0058] 4) The obtained eutectic solvent was vacuum filtered into the vermiculite two-dimensional nanosheet layered film obtained in step 2) under the condition of -0.05-0 MPa, to obtain a high-performance composite solid-state electrolyte film.

[0059] The high-performance composite solid-state electrolyte film obtained in Example 1 was assembled into a full solid-state lithium battery.

[0060] In this example, the positive electrode material of the full solid-state lithium battery was lithium iron phosphate, and specifically, a slurry was obtained by mixing lithium iron phosphate, conductive carbon black and a binder in a mass ratio of 8:1:1, the obtained slurry was coated on an aluminum foil, and then the aluminum foil was vacuum dried at 110℃ for 24 hours to obtain the positive electrode material; then the positive electrode material was cut into a circular sheet with a diameter of 12 mm by a cutter to assemble the full solid-state lithium battery. The negative electrode material of the full solid-state lithium battery was a commercially available lithium sheet with a diameter of 16 mm.

[0061] Performance test was performed on the assembled battery, and the discharge capacity was 144.4 mAh g -1 after 200 cycles at 60℃ and 0.5C.

[0062] Comparative Example 1:

[0063] 1) In a glove box, weigh N-methylacetamide and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) two monomers for mixing, the mixing molar ratio between the two is 4:1, after weighing, put the two into a beaker, mix thoroughly;

[0064] 2) Then add a magnetic stirrer in the beaker, put it on a magnetic stirrer for thorough stirring (stir at room temperature for 4h), until the two monomers in the beaker are fully dissolved, finally obtain a eutectic solvent;

[0065] 3) The obtained eutectic solvent is used as a liquid electrolyte to assemble a lithium-lithium pair charging battery in a glove box, PP is used as a diaphragm, and lithium sheets are used as positive and negative electrodes to assemble a lithium-lithium pair charging battery. Then the battery is tested for related performance, and the physical map and test related performance analysis map are shown in Figure 3 and Figure 7 .

[0066] The high-performance solid-state electrolyte film prepared in Example 1 of the present application is also assembled into the same lithium-lithium pair charging battery as in Comparative Example 1, and the PP film is replaced with a high-performance composite solid-state electrolyte film, and the lithium-lithium pair charging performance of the two is compared.

[0067] As can be seen from the above, the high-performance composite solid-state electrolyte film obtained in Example 1 of the present application better suppresses the problem of liquid electrolyte evaporation, and also suppresses the problem of side reactions between liquid small molecules and positive and negative electrodes, improves the interface stability, and shows better long cycle stability than traditional electrolyte films.

[0068] Comparative Example 2:

[0069] 1) In a glove box, weigh butanedinitrile and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) two monomers for mixing, the mixing molar ratio between the two is 3.3:1, after weighing, put the two into a beaker, mix thoroughly, and heat (80℃);

[0070] 2) Then add a magnetic stirrer in the beaker, put it on a magnetic stirrer for thorough stirring (stir at room temperature for 4h), until the two monomers in the beaker are fully dissolved, finally obtain a eutectic solvent;

[0071] 3) The obtained eutectic solvent is used as a liquid electrolyte to assemble a lithium-lithium pair charging battery in a glove box, PP is used as a diaphragm, and lithium sheets are used as positive and negative electrodes to assemble a lithium-lithium pair charging battery. Then the battery is tested for related performance.

[0072] Comparative Example 3:

[0073] 1) The vermiculite nanosheet dispersion liquid obtained in step c of Example 1 is diluted with 300 mL of deionized water, ultrasonically dispersed, then low-pressure vacuum filtration and drying are performed to obtain a vermiculite two-dimensional nanosheet layered film;

[0074] 2) The eutectic solvent obtained in Comparative Example 2 was vacuum filtered into the layered film of vermiculite two-dimensional nanosheets obtained in step 1) for treatment, to obtain a composite solid-state electrolyte film.

[0075] 3) The composite solid-state electrolyte film prepared in step 2) was assembled into a lithium-lithium pair battery with lithium pieces as the positive and negative electrodes in a glove box. Then, the battery obtained was subjected to relevant performance tests.

Claims

1. A method for preparing a high-performance composite solid electrolyte membrane that suppresses the volatilization of a liquid electrolyte and improves the stability of an interface, characterized by comprising the steps of: (1) preparing a porous polymer film; (2) impregnating the porous polymer film with a liquid electrolyte; and (3) coating the porous polymer film with a solid electrolyte. The preparation method comprises the following steps: 1) Preparation of vermiculite two-dimensional nanosheet dispersion liquid: a. Add raw material heat-expanded vermiculite into saturated NaCl solution for heating and stirring, then wash with deionized water, and obtain sodium ion intercalated expanded vermiculite after washing; b. The obtained sodium ion intercalated expanded vermiculite is added into a LiCl solution for reflux reaction. After reaction, filtration is performed. After filtration, deionized water and anhydrous ethanol are used for washing in sequence. The washing is performed until no Cl - is detected in the filtrate. The lithium ion intercalated expanded vermiculite is obtained. c. Add the lithium ion intercalated expanded vermiculite obtained in step b into deionized water for stirring, then perform ultrasonic treatment after stirring; perform centrifugation after treatment, remove the unpeeled vermiculite sheets, and obtain vermiculite nanosheet dispersion liquid; 2) Dilute the vermiculite nanosheet dispersion liquid obtained in step c with deionized water or anhydrous ethanol, the dilution multiple is 15-20, perform low-pressure vacuum filtration and drying after dilution, and obtain vermiculite two-dimensional nanosheet layered film; 3) Preparation of eutectic solvent: mix N-methylacetamide and lithium bistrifluoromethanesulfonimide, then place in a glove box, and perform normal temperature stirring reaction for 4-6 h under argon atmosphere, and obtain eutectic solvent after reaction; 4) Perform treatment on the eutectic solvent obtained in step 2) by vacuum filtration to the vermiculite two-dimensional nanosheet layered film, and obtain high-performance composite solid electrolyte film.

2. The method of claim 1, wherein the method is characterized by: The mass ratio between the heat-expanded vermiculite and sodium chloride in the saturated NaCl solution in step a is 0.8-1.2:20; The heating temperature is controlled to be 120-130 DEG C and the stirring time is 48 h during the heating and stirring.

3. The method of claim 1, wherein the method is characterized by: The concentration of the LiCl solution in step b is 2-2.5 mol / L, the oil bath temperature is 120-130 DEG C during the reflux reaction, and the time is 24-48 h; The mass-volume ratio between the sodium ion intercalated expanded vermiculite and the LiCl solution is 1 g:45-60 mL.

4. The method of claim 1, wherein the method is characterized by: The mass-volume ratio between the lithium ion intercalated expanded vermiculite and deionized water added in step c is 1 g:350-500 mL; the stirring speed is 600-800 rpm and the stirring time is 30-60 min; the ultrasonic treatment time is 30-60 min; the centrifugation speed is 6000-8000 rpm and the centrifugation time is 10-15 min.

5. The method of claim 1, wherein the method is characterized by: The concentration of the vermiculite nanosheet dispersion liquid obtained in step c is 0.7-1 g / L.

6. The method of claim 1, wherein the method is characterized by: The pressure is controlled to be-0.05-0 MPa during the low-pressure vacuum filtration in step 2); and the drying temperature is controlled to be 50-60 DEG C and the drying time is 40-50 h during the drying.

7. The method of claim 1, wherein the method is characterized by: The mixing molar ratio between N-methylacetamide and lithium bistrifluoromethanesulfonimide in step 3) is 3.5-5:

1.

8. The method for preparing a high-performance composite solid electrolyte membrane for inhibiting liquid electrolyte volatilization and improving interfacial stability according to claim 1, characterized in that: The pressure is-0.05-0 MPa during the filtration in step 4).

9. The method for preparing a high-performance composite solid electrolyte membrane for inhibiting liquid electrolyte volatilization and improving interfacial stability according to claim 1, characterized in that: The thickness of the high-performance composite solid electrolyte film obtained in step 4) is 14-20 μm.

10. Application of the high-performance composite solid electrolyte film prepared in claim 1 in a full solid-state lithium battery.

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