A Cathode Interface Coating Process for All-Solid-State Batteries

Abstract

The present invention provides a positive electrode interface coating process for all-solid-state batteries, belonging to the technical field of solid-state batteries. The coating process includes the following steps: S1. Mix 80-85 parts by weight of lithium cobaltate, 5-7 parts of conductive agent, 9-11 parts of binder, 48-52 parts of solvent, 4-6 parts of silanized polyethylene glycol grafted modified nanoparticles, and 4-5 parts of electrolyte powder to obtain a coating slurry; S2. Roll-coat the coating slurry obtained in S1 onto an aluminum foil sheet and dry it to obtain a positive electrode for all-solid-state batteries, with a areal loading of 5.5-6.5 mg / cm 2 ; The electrolyte powder is Li x La3Zr2O 12 , where 5.5 ≤ x ≤ 6. The present invention can significantly improve the cycle stability and service life of the prepared batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and particularly relates to a positive electrode interface coating process for all-solid-state batteries. Background Art

[0002] All-solid-state battery is a battery technology that uses solid electrolytes instead of traditional liquid electrolytes. Compared with traditional lithium-ion batteries, all-solid-state batteries show significant advantages in terms of safety, energy density, etc. The energy density of all-solid-state batteries is several times that of traditional lithium-ion batteries, which means that more energy can be stored in the same volume. Since solid electrolytes are not flammable, non-corrosive, and non-volatile, the safety performance of all-solid-state batteries is greatly enhanced. All-solid-state batteries have a longer cycle life.

[0003] When using aluminum foil as the positive electrode material in all-solid-state batteries, on the one hand, aluminum foil is prone to oxidation reaction in a high-voltage environment to form an aluminum oxide layer, which may lead to a decline in battery performance; on the other hand, the interfacial impedance between aluminum foil and solid electrolyte is large, which will affect the charge-discharge efficiency and cycle life of the battery. Therefore, in order to improve the electrochemical stability of aluminum foil and reduce the interfacial impedance, a slurry / material with good conductivity and good compatibility with the electrolyte can be coated on the surface of the aluminum foil to form a protective layer.

[0004] Existing coating slurries for positive electrodes generally contain components such as active substances (such as lithium cobaltate), conductive agents (such as carbon nanotubes), binders, and solvents. Poor combination of these components will increase the internal resistance of the battery, which will not only reduce the charge-discharge efficiency of the battery, but also accelerate the battery aging process and shorten its service life. Summary of the Invention

[0005] To solve the problems in the background art, the present invention provides a positive electrode interface coating process for all-solid-state batteries, which can significantly improve the cycle stability and service life of the prepared batteries.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A positive electrode interface coating process for all-solid-state batteries includes the following steps:

[0008] S1. By weight, mix 80-85 parts of lithium cobaltate, 5-7 parts of conductive agent, 9-11 parts of binder, 48-52 parts of solvent, 4-6 parts of silanized polyethylene glycol grafted modified nanoparticles, and 4-5 parts of electrolyte powder to obtain a coating slurry;

[0009] S2. Roll coat the coating slurry obtained in S1 onto an aluminum foil sheet and dry it to obtain a positive electrode for all-solid-state batteries with a surface loading of 5.5-6.5 mg / cm 2 ;

[0010] The electrolyte powder is Li x La 3 Zr 2 O 12 , where 5.5 ≤ x ≤ 6.

[0011] Furthermore, the preparation method of the silanized polyethylene glycol grafted modified nanoparticles is as follows:

[0012] A1. Immerse the nanoparticles in a chromic acid solution for 2 h, then wash them successively with deionized water and absolute ethanol, filter and dry them, and then put them into a plasma reaction chamber. Evacuate to a vacuum degree of 7.3×10 -3 Pa, hold for 5 min, then introduce argon gas with a pressure of 40 Pa. The frequency of the microwave plasma device used is 2.45 GHz and the power is 250 W. Hold for 8 - 10 min to obtain pretreated nanoparticles;

[0013] A2. Dissolve the silanized polyethylene glycol in absolute ethanol, adjust the pH to 2 ± 0.2 with hydrochloric acid, keep it in a reflux state, immerse the pretreated nanoparticles obtained in A1 in it for 2.5 - 3 h, then take them out and dry them, and wash them successively with toluene, acetone and deionized water, and then put them into a vacuum drying oven and dry them under reduced pressure at room temperature to obtain the silanized polyethylene glycol grafted modified nanoparticles.

[0014] Furthermore, the nanoparticles are nano-aluminum oxide powder.

[0015] Furthermore, the preparation method of the silanized polyethylene glycol:

[0016] B1. First weigh 50 g of polyethylene glycol, heat and dissolve it in 500 mL of tetrahydrofuran, cool it after reflux, add 22 g of toluene diisocyanate and 10 g of dibutyltin dilaurate, and react for 24 h at room temperature under nitrogen protection to obtain a pre-product solution;

[0017] B2. Add n-hexane to the pre-product solution obtained in B1 to completely precipitate the pre-product, and place the pre-product in a vacuum drying oven and dry it at 50 °C to obtain a dried pre-product;

[0018] B3. Dissolve the dried pre-product obtained in B2 in tetrahydrofuran, add 1 g of dibutyltin dilaurate and 10 mL of 3-aminopropyltriethoxysilane, and react for 16 h at room temperature under nitrogen protection to obtain a final-product solution;

[0019] B4. Add n-hexane to the final-product solution obtained in B3 to completely precipitate the final-product, and place the final-product in a vacuum drying oven and dry it at 50 °C to obtain the silanized polyethylene glycol.

[0020] Furthermore, the conductive agent is acid-washed carbon nanotubes.

[0021] Furthermore, the preparation method of the pickled carbon nanotubes is as follows: Mix the carbon nanotubes and the concentrated acid solution at a mass ratio of 1:(2 - 3), react at 60°C for 10 - 12 hours under magnetic stirring, then cool to room temperature, perform centrifugal separation, wash with deionized water multiple times, and dry in vacuum to obtain the pickled carbon nanotubes.

[0022] Furthermore, the concentrated acid solution is a mixed solution of concentrated nitric acid and concentrated sulfuric acid, and the volume ratio of concentrated nitric acid to concentrated sulfuric acid is 3:1.

[0023] Furthermore, the preparation method of the electrolyte powder is as follows:

[0024] C1. Weigh LiNO 3 , La(NO 3 ) 3 ·6H 2 O and Zr(NO 3 ) 4 ·5H 2 O according to the stoichiometric ratio, dissolve them in deionized water to obtain a nitrate solution;

[0025] C2. Add citric acid to the nitrate solution obtained in C1, stir in a water bath at 55 - 60°C until it becomes a transparent sol state, age at room temperature for 20 h, and then perform drying treatment to obtain a dry gel;

[0026] C3. Calcinate the dry gel obtained in C2 at 700 - 750°C for 4.5 - 5.5 h to obtain the electrolyte powder.

[0027] Furthermore, the binder includes any one of polyvinyl alcohol, acrylamide, or carboxymethyl cellulose.

[0028] Furthermore, the solvent is water.

[0029] This application has the following beneficial effects:

[0030] 1. For the battery prepared with the positive electrode made by using the coating process of the present invention, the capacity retention rate after 50 cycles is as high as over 95.5%, and the capacity retention rate after 100 cycles is as high as over 89.6%; moreover, the difference in the capacity decline rate between two consecutive 50 - cycle periods is as low as below 1.6%; this shows that the battery prepared by the present invention has a long service life and a stable capacity attenuation rate, that is, it has good cycle stability and a long expected service life.

[0031] 2. The acid-washed carbon nanotubes of the present invention are treated by surface acid washing, and both the binding active sites and the surface roughness are increased; the silanized polyethylene glycol graft-modified nanoparticles (silanized polyethylene glycol graft-modified aluminum trioxide) can not only chemically react with the cathode material / electrolyte through the silane groups on their surfaces to form stable chemical bonds, thereby enhancing the interfacial stability, reducing the interfacial impedance, and improving the cycling performance of the battery; but also generate van der Waals forces and other interactions between the polyethylene glycol segments and the rough surface of the acid-washed carbon nanotubes, thus forming a tight bond. This tight bond helps to firmly fix the acid-washed carbon nanotubes in the electrode, preventing their displacement or detachment during the charge and discharge process, thereby improving the cycling stability and cycling service life of the prepared battery; there is a synergistic effect between the silanized polyethylene glycol graft-modified nanoparticles and the acid-washed carbon nanotubes of the present invention, which can synergistically improve the cycling stability and service life of the prepared battery. Description of the Drawings

[0032] Figure 1 、Trend chart of the comparison of the capacity retention rate test data of the batteries prepared in Examples 1-7 and Comparative Examples 1-3 of the present invention after 50 cycles and 100 cycles;

[0033] Figure 2 、Trend chart of the comparison of the test data of the capacity degradation rate of the batteries prepared in Examples 1-7 and Comparative Examples 1-3 of the present invention after two consecutive 50-cycle cycles and the difference between the two. Detailed Description of the Invention

[0034] The following further describes the present application in detail with reference to the examples.

[0035] The raw materials of the examples and comparative examples of the present application are all commercially available, unless otherwise specified.

[0036] Example 1: (1) Preparation of silanized polyethylene glycol, and its preparation method is as follows:

[0037] B1. First, weigh 50 g of polyethylene glycol, heat and dissolve it in 500 mL of tetrahydrofuran, reflux for 2 h, and the heating temperature is about 65 °C, that is, heat to near the boiling point of the organic solvent tetrahydrofuran to ensure complete dissolution and create good conditions for subsequent chemical reactions. Add 22 g of toluene diisocyanate and 10 g of dibutyltin dilaurate, and stir and react at room temperature under nitrogen protection at 100 r / min for 24 h. React the toluene diisocyanate with the hydroxyl groups of polyethylene glycol to introduce isocyanate groups to obtain a pre-product solution.

[0038] B2. Add n-hexane to the pre-product solution obtained in B1 to completely precipitate the pre-product, and place the pre-product in a vacuum drying oven and dry it at 50 °C to obtain a dried pre-product. The pre-product is purified through the precipitation and drying processes to remove unreacted reagents and solvents.

[0039] B3. Dissolve the dried pre-product obtained in B2 in 400 mL of tetrahydrofuran, add 1 g of dibutyltin dilaurate and 10 mL of 3-aminopropyltriethoxysilane, and react for 16 h at room temperature under nitrogen protection to obtain the final product solution. The silyl group is introduced by the reaction of 3-aminopropyltriethoxysilane with the isocyanate groups in the pre-product.

[0040] B4. Add n-hexane to the final product solution obtained in B3 to completely precipitate the final product. Place the final product in a vacuum drying oven and dry it at 50 °C to obtain the silylated polyethylene glycol. The final product is purified through the precipitation and drying processes to remove unreacted reagents and solvents.

[0041] Among them, polyethylene glycol (PEG2000) was purchased from Xingtai Xinlanxing Technology Co., Ltd. Tetrahydrofuran (high-quality grade) was purchased from Shanghai Denuo Chemical Co., Ltd. Toluene diisocyanate (TDI) was purchased from Guangzhou North Chemical Co., Ltd. Dibutyltin dilaurate (WCAT-WS2, industrial grade) was purchased from Guangzhou Yourun Synthetic Materials Co., Ltd. 3-aminopropyltriethoxysilane (KH-550) was purchased from Guangdong Hualitai Chemical Co., Ltd.

[0042] (2) Prepare silylated polyethylene glycol grafted modified nanoparticles, and the preparation method is as follows:

[0043] A1. Immerse the nano-aluminum oxide powder in the chromic acid solution for 2 h to remove impurities and oxide layers on the surface of the nanoparticles and increase the active sites on its surface. The concentration of the chromic acid solution is 1.2 M, and this concentration is sufficient to effectively clean and activate the surface of the nano-aluminum oxide powder without causing excessive corrosion or damage to the nano-aluminum oxide powder itself. Then wash it successively with deionized water and absolute ethanol to remove the residual acidic solution and impurities. After filtration and drying, put it into the plasma reaction chamber, evacuate to a vacuum degree of 7.3×10 -3 Pa, hold for 5 min, then introduce argon, the air pressure is 40 Pa, the frequency of the used microwave plasma device is 2.45 GHz, the power is 250 W, and then hold for 9 min to obtain the pretreated nanoparticles. The surface of the nanoparticles is further cleaned and activated through plasma treatment to make it more suitable for subsequent grafting reactions.

[0044] A2. Dissolve the silylated polyethylene glycol in absolute ethanol, adjust the pH to about 2 with hydrochloric acid, maintain the reflux state to ensure complete dissolution of the silylated polyethylene glycol, and adjust the pH value of the solution to promote the grafting reaction. Immerse the pretreated nanoparticles obtained in A1 in it for 2.8 h to allow the silylated polyethylene glycol to undergo a grafting reaction with the active sites on the surface of the nanoparticles, forming stable chemical bonding. Finally, take it out and dry, wash it successively with toluene, acetone and deionized water, and then put it into a vacuum drying oven for drying under reduced pressure at room temperature to remove the unreacted silylated polyethylene glycol and other impurities, thus obtaining pure silylated polyethylene glycol grafted and modified nanoparticles.

[0045] Among them, nano-aluminum oxide powder (YHL-8891) was purchased from Pengyi Mineral Products Processing Factory, Lingshou County.

[0046] (3) Prepare the conductive agent pickled carbon nanotubes, and its preparation method is as follows:

[0047] Mix the carbon nanotubes and the concentrated acid solution according to a mass ratio of 1:2.5. The concentrated acid solution is a mixed solution of concentrated nitric acid and concentrated sulfuric acid, and the volume ratio of concentrated nitric acid to concentrated sulfuric acid is 3:1. Then, under magnetic stirring at 120 r / min, react at 60 °C for 11 hours. Then cool to room temperature, centrifuge and wash 3 times with deionized water, and dry in vacuum to obtain pickled carbon nanotubes. Through pickling treatment, more defects and active sites are generated on the surface of the carbon nanotubes, and the surface of the carbon nanotubes is damaged to a certain extent, significantly increasing the surface roughness of the carbon nanotubes.

[0048] Among them, the carbon nanotubes (JT-TNMG001) were purchased from Qingdao Jintao Graphite Co., Ltd.

[0049] (4) Prepare the electrolyte powder, which is Li 5.8 La 3 Zr 2 O 12 , and its preparation method is as follows:

[0050] C1. Weigh LiNO 3 , La(NO 3 ) 3 ·6H 2 O and Zr(NO 3 ) 4 ·5H 2 O according to the stoichiometric ratio and dissolve them in deionized water to obtain a nitrate solution.

[0051] C2. Add citric acid to the nitrate solution obtained in C1. The dosage of citric acid is 2 times the total amount of the substances of all nitrates. Then, under the condition of a water bath at 58 °C, stir until it becomes a transparent sol state. After aging at room temperature for 20 h, dry it in a forced-air drying oven at 160 °C for 12 h to obtain a dry gel.

[0052] C3. Use a tubular furnace to calcine the dry gel obtained in C2 at 730 °C for 5 h to obtain the electrolyte powder.

[0053] Among them, lithium nitrate LiNO 3 , purchased from Hubei Kewode Chemical Co., Ltd. Lanthanum nitrate hexahydrate La(NO 3 ) 3 ·6H 2 O, with an active ingredient of 99%, purchased from Shandong New Kinetic Energy Chemical Co., Ltd. Zirconium nitrate pentahydrate Zr(NO 3 ) 4 ·5H 2 O, purchased from Shandong Desheng New Materials Co., Ltd.

[0054] (5) A positive electrode interface coating process for all-solid-state batteries, comprising the following steps:

[0055] S1. By weight, mix 82 parts of lithium cobaltate, 6 parts of pickled carbon nanotubes, 10 parts of binder carboxymethyl cellulose, 50 parts of water, 5 parts of silanized polyethylene glycol graft-modified nanoparticles, and 4.5 parts of electrolyte powder in a disperser, and stir at a speed of 200 r / min for 30 min to achieve a mixing effect and obtain the coating slurry.

[0056] S2. Roll-coat the coating slurry obtained in S1 onto an aluminum foil sheet and dry it to obtain the positive electrode for all-solid-state batteries, with a surface loading of 5.9 mg / cm 2 .

[0057] Among them, lithium cobaltate (model HPC05, content 99%) is purchased from Shenzhen Zhongyue Chemical Co., Ltd. Carboxymethyl cellulose (HB-3520) is purchased from Chongqing Xiangyu Chemical Co., Ltd.

[0058] According to the battery assembly process, assemble the negative electrode, solid electrolyte, and positive electrode into a battery. Among them, the negative electrode material uses a lithium metal sheet. Preparation of the solid electrolyte: Weigh 0.6 g of electrolyte powder (Li 5.8 La 3 Zr 2 O 12 ) in an agate mortar and grind it for 10 min to obtain a powder with uniform particles. Then, put the powder into a mold with a diameter of 13 mm and use a tablet press to press it into a green body; after the obtained green body disc is pressed into a dense green body under 250 MPa, place it in an alumina crucible covered with a layer of mother powder of the same composition, and cover the dense green body with another layer of mother powder to form a lithium-rich sintering atmosphere, and sinter it at 1060 °C for 10 h; after sintering, scrape off the mother powder and polish it with 1000# sandpaper until the surface is flat to obtain it. The positive electrode material uses the positive electrode for all-solid-state batteries prepared by the above coating process.

[0059] Example 2: The difference between this example and Example 1 is: (3) Preparation of the conductive agent, pickled carbon nanotubes, and the preparation method is as follows:

[0060] Mix carbon nanotubes and concentrated acid solution at a mass ratio of 1:2, then react at 60 °C for 10 hours under magnetic stirring at 120 r / min. Then cool to room temperature, centrifuge, wash 3 times with deionized water, and dry in vacuum to obtain pickled carbon nanotubes.

[0061] Example 3: The difference between this example and Example 1 is: (3) Preparation of the conductive agent, pickled carbon nanotubes, and the preparation method is as follows:

[0062] Mix carbon nanotubes and concentrated acid solution at a mass ratio of 1:3, then react at 60 °C for 12 hours under magnetic stirring at 120 r / min. Then cool to room temperature, centrifuge, wash 3 times with deionized water, and dry in vacuum to obtain pickled carbon nanotubes.

[0063] Example 4: The difference between this example and Example 1 is: (4) Preparation of the electrolyte powder, which is Li 5.5 La 3 Zr 2 O 12 , and the preparation method is as follows:

[0064] C1. Weigh LiNO 3 , La(NO 3 ) 3 ·6H 2 O and Zr(NO 3 ) 4 ·5H 2 O according to the stoichiometric ratio, dissolve them in deionized water to obtain a nitrate solution.

[0065] C2. Add citric acid to the nitrate solution obtained in C1. The amount of citric acid used is 2 times the total amount of nitrate substances. Then, under the condition of a 55 °C water bath, stir until it becomes a transparent sol state. After aging at room temperature for 20 h, dry in a forced-air drying oven at 160 °C for 12 h to obtain a dry gel.

[0066] C3. Use a tube furnace to calcine the dry gel obtained in C2 at 700 °C for 4.5 h to obtain the electrolyte powder.

[0067] Example 5: The difference between this example and Example 1 is: (4) Preparation of the electrolyte powder, which is Li 6 La 3 Zr 2 O 12 , and the preparation method is as follows:

[0068] C1. Weigh LiNO 3, La(NO 3 ) 3 ·6H 2 O and Zr(NO 3 ) 4 ·5H 2 O were dissolved in deionized water to obtain a nitrate solution.

[0069] C2. Citric acid was added to the nitrate solution obtained in C1. The amount of citric acid used was 2 times the total amount of nitrate substances. Then, under the condition of a 60°C water bath, it was stirred until it became a transparent sol state. After aging at room temperature for 20 h, it was dried in a forced-air drying oven at 160°C for 12 h to obtain a dry gel.

[0070] C3. Using a tube furnace, the dry gel obtained in C2 was calcined at 750°C for 5.5 h to obtain the electrolyte powder.

[0071] Example 6: The difference between this example and Example 1 lies in: (5) A positive electrode interface coating process for an all-solid-state battery, including the following steps:

[0072] S1. By weight, 80 parts of lithium cobaltate, 5 parts of acid-washed carbon nanotubes, 9 parts of binder carboxymethyl cellulose, 48 parts of water, 4 parts of silanized polyethylene glycol graft-modified nanoparticles, and 4 parts of electrolyte powder were mixed in a disperser and stirred at a speed of 200 r / min for 30 min to achieve a mixing effect, obtaining a coating slurry.

[0073] S2. The coating slurry obtained in S1 was roll-coated onto an aluminum foil sheet and dried to obtain the positive electrode for the all-solid-state battery, with a surface loading of 6.0 mg / cm 2 .

[0074] Example 7: The difference between this example and Example 1 lies in: (5) A positive electrode interface coating process for an all-solid-state battery, including the following steps:

[0075] S1. By weight, 85 parts of lithium cobaltate, 7 parts of acid-washed carbon nanotubes, 11 parts of binder carboxymethyl cellulose, 52 parts of water, 6 parts of silanized polyethylene glycol graft-modified nanoparticles, and 5 parts of electrolyte powder were mixed in a disperser and stirred at a speed of 200 r / min for 30 min to achieve a mixing effect, obtaining a coating slurry.

[0076] S2. The coating slurry obtained in S1 was roll-coated onto an aluminum foil sheet and dried to obtain the positive electrode for the all-solid-state battery, with a surface loading of 5.7 mg / cm 2 .

[0077] Comparative Example 1: The difference between this comparative example and Example 1 lies in: In the preparation of the coating slurry, the acid-washed carbon nanotubes were replaced with carbon nanotubes, and the silanized polyethylene glycol graft-modified nanoparticles were replaced with nano-aluminum oxide powder.

[0078] Specifically, by weight parts, 82 parts of lithium cobaltate, 6 parts of carbon nanotubes, 10 parts of binder carboxymethyl cellulose, 50 parts of water, 5 parts of nano-aluminum trioxide powder, and 4.5 parts of electrolyte powder are mixed in a disperser and stirred at a speed of 200 r / min for 30 min to achieve a uniform mixing effect, obtaining a coating slurry.

[0079] Comparative Example 2: The difference between this comparative example and Example 1 lies in that: in the preparation of the coating slurry, the silanized polyethylene glycol graft-modified nanoparticles are replaced by nano-aluminum trioxide powder.

[0080] Specifically, by weight parts, 82 parts of lithium cobaltate, 6 parts of pickled carbon nanotubes, 10 parts of binder carboxymethyl cellulose, 50 parts of water, 5 parts of nano-aluminum trioxide powder, and 4.5 parts of electrolyte powder are mixed in a disperser and stirred at a speed of 200 r / min for 30 min to achieve a uniform mixing effect, obtaining a coating slurry.

[0081] Comparative Example 3: The difference between this comparative example and Example 1 lies in that: in the preparation of the coating slurry, the pickled carbon nanotubes are replaced by carbon nanotubes.

[0082] Specifically, by weight parts, 82 parts of lithium cobaltate, 6 parts of carbon nanotubes, 10 parts of binder carboxymethyl cellulose, 50 parts of water, 5 parts of silanized polyethylene glycol graft-modified nanoparticles, and 4.5 parts of electrolyte powder are mixed in a disperser and stirred at a speed of 200 r / min for 30 min to achieve a uniform mixing effect, obtaining a coating slurry.

[0083] Test Example: Test objects: The batteries prepared in Examples 1-7 and Comparative Examples 1-5.

[0084] Test content: Under the conditions of 60 °C and 0.2C, the capacity retention rates of each test object are tested for 50 cycles and 100 cycles; and the capacity decline rates of two consecutive 50-cycle cycles (the capacity decline rate of the first 50-cycle cycle and the capacity decline rate of the second 50-cycle cycle) are calculated, as well as the difference between the two (the difference in the capacity decline rates of two consecutive 50-cycle cycles).

[0085] The capacity decline rate of the first 50-cycle cycle = 100% - the capacity retention rate of the 50-cycle cycle;

[0086] The capacity decline rate of the second 50-cycle cycle = 100% - the capacity retention rate of the 100-cycle cycle - the capacity decline rate of the first 50-cycle cycle;

[0087] The difference in the capacity decline rates of two consecutive 50-cycle cycles = the capacity decline rate of the second 50-cycle cycle - the capacity decline rate of the first 50-cycle cycle.

[0088] The larger the measured data values of the capacity retention rate of the 50-cycle cycle and the capacity retention rate of the 100-cycle cycle, the longer the service life of the battery.

[0089] The smaller the difference in the capacity decline rate between two consecutive 50 - cycle periods, the more stable the capacity attenuation rate of the battery, indicating that the battery has better cycle stability and a longer expected service life, which is an important advantage for the long - term use and reliability of the battery.

[0090] Test results: See Table 1.

[0091] Table 1. Test data of test examples

[0092]

[0093]

[0094] Result analysis: Analyze Examples 1 - 7 and combine with the data in Table 1 and Figure 1-2 It can be seen that the capacity retention rate of the battery prepared by the present invention is as high as over 95.5% after 50 cycles and over 89.6% after 100 cycles; moreover, the difference in the capacity decline rate between two consecutive 50 - cycle periods is as low as below 1.6%; this shows that the battery prepared by the present invention has a long service life and a stable capacity attenuation rate, that is, it has good cycle stability and a long expected service life.

[0095] Analyze Comparative Example 1 and Comparative Example 2 and combine with the data in Table 1 and Figure 1-2 It can be seen that compared with Comparative Example 1 (using ordinary nano - aluminum oxide powder and carbon nanotubes), in Comparative Example 2, the carbon nanotubes were made into the pickled carbon nanotubes of the present invention for use, and as a result, the capacity retention rates of the prepared battery after 50 cycles and 100 cycles both decreased, while the difference in the capacity decline rate between two consecutive 50 - cycle periods remained basically unchanged. This shows that when using ordinary nano - aluminum oxide powder, pickling the carbon nanotubes will instead lead to a shortened service life of the prepared battery.

[0096] This is because, on the one hand, the binding ability between the pickled carbon nanotubes and ordinary nano - aluminum oxide powder is insufficient, and the synergistic effect of the two cannot be fully exerted, so the improvement effect on the battery service life is limited; on the other hand, the pickling treatment overly erodes the surface of the carbon nanotubes, destroys their original structural integrity, and introduces new defects / impurities on the surface of the carbon nanotubes. These defects / impurities act as obstacles to electron / ion transport, resulting in a decrease in the battery service life; with this ebb and flow, it will lead to the situation that when using ordinary nano - aluminum oxide powder and pickling the carbon nanotubes, not only will the battery service life not be improved, but instead the battery service life will decrease.

[0097] Analyze Comparative Example 1 and Comparative Example 3 and combine with the data in Table 1 and Figure 1-2It can be seen that, compared with Comparative Example 1 (using ordinary nano-aluminum oxide powder and carbon nanotubes), in Comparative Example 3, the nano-aluminum oxide powder was made into the silanized polyethylene glycol grafted modified nanoparticles of the present invention for use, and as a result, the capacity retention rates of the battery after 50 and 100 cycles were both increased, and the difference in the capacity decline rate for two consecutive 50-cycle periods remained basically unchanged. This shows that making the nano-aluminum oxide powder into the silanized polyethylene glycol grafted modified nanoparticles of the present invention can improve the service life of the battery obtained.

[0098] Analyze Example 1 and Comparative Examples 1-3 and combine the data in Table 1 and Figure 1-2 It can be seen that, compared with Comparative Example 3, while retaining the use of the silanized polyethylene glycol grafted modified nanoparticles of the present invention, in Example 1, the carbon nanotubes were made into the pickled carbon nanotubes of the present invention for use, and as a result, the capacity retention rates of the battery after 50 and 100 cycles were further increased, and moreover, the difference in the capacity decline rate for two consecutive 50-cycle periods was significantly reduced. This shows that there is a synergistic effect between the silanized polyethylene glycol grafted modified nanoparticles of the present invention and the pickled carbon nanotubes, which can synergistically improve the cycle stability and service life of the battery obtained.

[0099] In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, without conflict, they can be combined in any suitable manner. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0100] In addition, any combination can be made between various different embodiments of the present invention, as long as it does not violate the idea of the present invention, it should also be regarded as the content disclosed by the present invention.

Claims

1. A positive electrode interface coating process for an all-solid-state battery, characterized in that: The steps include: S1. By weight, 80-85 parts of lithium cobalt oxide, 5-7 parts of conductive agent, 9-11 parts of binder, 48-52 parts of solvent, 4-6 parts of silanized polyethylene glycol grafted modified nanoparticles and 4-5 parts of electrolyte powder are mixed to obtain a coating slurry; S2. Roll the coating slurry obtained in S1 onto an aluminum foil and dry it to obtain a positive electrode for an all-solid-state battery with a surface loading of 5.5-6.5 mg / cm 2 ; The electrolyte powder is Li x La3Zr2O 12 , where 5.5≤x≤6; The preparation method of the silanized polyethylene glycol grafted modified nanoparticles is as follows: A1, soaking the nanoparticles in a chromic acid solution for 2 hours, washing, filtering, drying, and then performing microwave plasma surface treatment to obtain pretreated nanoparticles; A2, dissolving silylated polyethylene glycol in anhydrous ethanol, adjusting the pH to 2±0.2, maintaining the reflux state, soaking the pretreated nanoparticles obtained in A1 therein for 2.5-3h, taking out, drying, washing, and drying again, to obtain silylated polyethylene glycol grafted modified nanoparticles; The conductive agent is acid-washed carbon nanotubes; the preparation method of the acid-washed carbon nanotubes is: carbon nanotubes and concentrated acid solution are mixed in a mass ratio of 1: (2-3), stirred and reacted at 60°C for 10-12h, cooled to room temperature, centrifuged, washed with deionized water for multiple times, and vacuum dried to obtain acid-washed carbon nanotubes.

2. The positive electrode interface coating process for all-solid-state batteries according to claim 1, characterized in that: The nanoparticles are nano aluminum oxide powder.

3. The positive electrode interface coating process for all-solid-state batteries according to claim 1, characterized in that: The preparation method of the silylated polyethylene glycol: B1. Weigh 50 g of polyethylene glycol, heat and dissolve it in 500 mL of tetrahydrofuran, reflux and then cool, add 22 g of toluene diisocyanate and 10 g of dibutyltin dilaurate, and react at room temperature under nitrogen protection for 24 h to obtain a pre-product solution; B2, adding n-hexane to the pre-product solution obtained in B1 to completely precipitate the pre-product, and placing the pre-product in a vacuum drying oven at 50° C. to obtain a dry pre-product; B3, dissolving the dried pre-product obtained in B2 in tetrahydrofuran, adding 1 g of dibutyltin disilicate and 10 mL of 3-aminopropyltriethoxysilane, and reacting for 16 h at room temperature under nitrogen protection to obtain a final product solution; B4. Add n-hexane to the final product solution obtained in B3 to completely precipitate the final product. Place the final product in a vacuum drying oven and dry it at 50° C. to obtain silylated polyethylene glycol.

4. The positive electrode interface coating process for all-solid-state batteries according to claim 3, characterized in that: The concentrated acid solution is a mixed solution of concentrated nitric acid and concentrated sulfuric acid, and the volume ratio of the concentrated nitric acid to the concentrated sulfuric acid is 3:

1.

5. The positive electrode interface coating process for all-solid-state batteries according to claim 1, characterized in that: The preparation method of the electrolyte powder is as follows: C1. Weigh LiNO3, La(NO3)3·6H2O and Zr(NO3)4·5H2O in stoichiometric ratio and dissolve them in deionized water to obtain a nitrate solution; C2, add citric acid to the nitrate solution obtained in C1, stir in a water bath at 55-60°C until it becomes a transparent sol, age at room temperature for 20 hours, and then dry to obtain a xerogel; C3. Calcine the dry gel obtained in C2 at 700-750°C for 4.5-5.5h to obtain electrolyte powder.

6. The positive electrode interface coating process for all-solid-state batteries according to claim 1, characterized in that: The binder includes any one of polyvinyl alcohol, acrylamide or carboxymethyl cellulose.

7. The positive electrode interface coating process for all-solid-state batteries according to claim 1, characterized in that: The solvent is water.

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