Inorganic solid-state electrolyte surface modification method and solid-state lithium metal symmetric battery

Abstract

The invention discloses an inorganic solid-state electrolyte surface modification method and a solid-state lithium metal symmetric battery, and belongs to the technical field of solid-state batteries. The method comprises the following steps: in an inert atmosphere, coating the surface of an inorganic solid electrolyte sheet with a fluorine-containing compound through a chemical vapor deposition method to obtain the inorganic solid electrolyte sheet with the surface modified with the fluorine-containing compound; the fluorine-containing compound is selected from one or more of acrylic acid 2, 2, 3, 3, 3-pentafluoropropyl ester, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 8-tridecafluorooctyl acrylate, 2-(perfluorooctyl) ethyl methacrylate and perfluoro (4-methyl-3, 6-dioxa-7-octylene) sulfonyl fluoride. According to the method, the interface compatibility and stability of the inorganic solid-state electrolyte and the lithium metal negative electrode are improved, and the long cycle performance of the solid-state lithium metal symmetric battery under high current density is realized. In addition, the method is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and in particular to a method for surface modification of an inorganic solid-state electrolyte and a solid-state lithium metal symmetrical battery. Background Art

[0002] As the next generation of energy storage technology, all-solid-state lithium metal batteries are expected to address the safety issues of commercial lithium-ion batteries and further improve their energy density. As the core of solid-state batteries, solid electrolytes must not only have excellent electrochemical properties but also have a certain degree of interfacial stability with the lithium metal cathode.

[0003] Although existing inorganic solid electrolytes have high ionic conductivity, inorganic solid electrolytes composed of central high-valent metal ions are easily reduced to metal elements when in contact with lithium metal, and the interface will continue to deteriorate. To solve this problem, sulfide solid electrolytes such as Li6PS5Cl or Li / Li6PS5Cl are often introduced between the halide solid electrolyte and lithium metal, thereby forming a stable ion-conductive solid electrolyte interface layer at the interface. Therefore, sulfide solid electrolytes are often used as separator electrolytes to separate lithium metal and inorganic solid electrolytes. However, the double-layer electrolyte configuration complicates the battery manufacturing process and also significantly restricts the energy density. Therefore, although the existing interface protection layer strategy alleviates the side reactions between the lithium metal negative electrode and the electrolyte, its application is greatly limited due to the above-mentioned shortcomings.

[0004] Therefore, it is of great significance to study and develop a new, cheap, fast and easy-to-scalable method for surface modification of inorganic solid electrolytes to better improve their interface problems with lithium metal negative electrodes. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a method for surface modification of an inorganic solid electrolyte and a solid-state lithium metal symmetrical battery. The inorganic solid electrolyte sheet with a surface modification containing a fluorine-containing compound prepared by the method can be used in a solid-state lithium metal symmetrical battery to achieve long-term cycling stability at high current density.

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

[0007] The present invention provides a method for surface modification of an inorganic solid electrolyte sheet, comprising the following steps:

[0008] In an inert atmosphere, a fluorine-containing compound is coated on the surface of an inorganic solid electrolyte sheet by a chemical vapor deposition method to obtain an inorganic solid electrolyte sheet with a surface modified with the fluorine-containing compound;

[0009] The fluorine-containing compound is selected from one or more of 2,2,3,3,3-pentafluoropropyl acrylate, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate, 2-(perfluorooctyl)ethyl methacrylate, and perfluoro(4-methyl-3,6-dioxa-7-octene)sulfonyl fluoride; more preferably, the fluorine-containing compound is selected from 2,2,3,3,3-pentafluoropropyl acrylate, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate or 2-(perfluorooctyl)ethyl methacrylate.

[0010] The above method achieves isolation of the inorganic solid electrolyte sheet and the lithium metal negative electrode by surface modification of the inorganic solid electrolyte sheet, thereby alleviating interfacial side reactions.

[0011] The fluorine-containing compound is deposited and adsorbed on the surface of the inorganic solid electrolyte sheet by chemical vapor deposition to form a flexible protective layer. The flexible protective layer can closely adhere to the lithium metal and the rigid inorganic solid electrolyte sheet, isolating the direct contact between the lithium metal and the electrolyte, thereby effectively inhibiting side reactions, improving the interface compatibility between the inorganic solid electrolyte and the lithium metal negative electrode material, and enhancing the stability of the interface between the inorganic solid electrolyte and the lithium metal negative electrode, thereby achieving long-cycle performance of solid-state lithium metal symmetrical batteries at high current density. The flexible protective layer can improve the uniformity of lithium ion deposition and deposition stress, and in situ generate lithium fluoride with the lithium metal negative electrode during the electrochemical cycle, which is beneficial to the lithium metal interface.

[0012] The flexible protective layer will not undergo significant chemical reactions with the inorganic solid electrolyte sheet, ensuring that when used as a surface modification layer material, it has little effect on the inorganic solid electrolyte structure and battery energy density and other properties. It can effectively block the side reactions between the inorganic solid electrolyte and the lithium metal negative electrode, improve the stability of the interface between the inorganic solid electrolyte and lithium, and thus ensure the stable operation of the electrochemical system.

[0013] Moreover, due to the presence of fluorine-containing compounds, lithium fluoride with low electronic conductivity, high interfacial energy and strong lithium dendrite inhibition ability can be formed during the electrochemical cycle, thereby further inhibiting the side reactions between the lithium metal negative electrode and the inorganic solid electrolyte, reducing unnecessary energy loss and performance degradation, and further significantly improving the overall reliability of the electrochemical system.

[0014] In addition, the present invention improves the mechanical properties of the inorganic solid electrolyte and reduces its rigidity by introducing the fluorine-containing compound, thereby alleviating the stress caused by the volume change of the lithium metal negative electrode during the charge and discharge process, and enhancing the mechanical stability and cycle life of the inorganic solid electrolyte.

[0015] In the above-mentioned method for surface modification of an inorganic solid electrolyte sheet, the preparation of the inorganic solid electrolyte sheet comprises the following steps:

[0016] The inorganic solid electrolyte powder is placed in a mold, and the mold is demoulded after cold pressing to prepare the inorganic solid electrolyte sheet.

[0017] The cold pressing pressure is preferably 300-500 MPa, more preferably 300 MPa.

[0018] The diameter of the mold is preferably 8-12 mm; more preferably 10 mm.

[0019] In the above-mentioned method for surface modification of inorganic solid electrolyte sheets, by controlling the modification amount of the fluorine-containing compound, the structural integrity and certain flexibility of the inorganic solid electrolyte can be maintained. If the modification amount of the fluorine-containing compound is too much, it will hinder the migration path of ions, resulting in a decrease in the ionic conductivity of the inorganic solid electrolyte. It will also cause the mechanical strength of the inorganic solid electrolyte to decrease, making it difficult to inhibit the growth of lithium dendrites. If the modification amount of the fluorine-containing compound is too little, it will not be possible to achieve complete and uniform adsorption on the surface of the inorganic solid electrolyte, and the surface modification effect of the inorganic solid electrolyte cannot be achieved.

[0020] Preferably, the ratio of the fluorine-containing compound to the inorganic solid electrolyte sheet is (0.1-5) μL:120 mg.

[0021] In the method for surface modification of inorganic solid electrolyte sheets of the present invention, the temperature and time of the chemical vapor deposition method need to be controlled to better ensure the sufficient volatilization of the liquid fluorine-containing compound while avoiding overheating or structural damage of the material that may be caused by excessive temperature.

[0022] Preferably, the temperature of the chemical vapor deposition method is 50°C-120°C, more preferably 50°C-90°C, and preferably 50°C, 70°C or 80°C in some specific embodiments of the present invention.

[0023] Preferably, the chemical vapor deposition process is performed for 24-36 hours; in some specific embodiments of the present invention, the chemical vapor deposition process is preferably performed for 24 hours, 28 hours or 32 hours.

[0024] The chemical vapor deposition method of the present invention is carried out under an inert atmosphere in order to prevent chemical reactions such as oxidation of the inorganic solid electrolyte sheet.

[0025] Preferably, the inert atmosphere is selected from argon with a purity of ≥99.999%, wherein the contents of oxygen and water are both below 0.1 ppm.

[0026] In the above method, the chemical vapor deposition method specifically includes the following steps: transferring the inorganic solid electrolyte sheet to a glass bottle in a temperature control device, dripping the fluorine-containing compound (liquid) into the glass bottle along the wall of the glass bottle, and then sealing the glass bottle with a sealing film. After 12-18 hours, the bottle cap is opened and the inorganic solid electrolyte sheet is turned over, and the sealing is continued for 12-18 hours. After chemical vapor deposition, an inorganic solid electrolyte sheet with a surface modified with a fluorine-containing compound is prepared.

[0027] The above-mentioned flipping is to avoid excessive / insufficient modification on one side, thereby improving the uniformity of the surface modification of the electrolyte sheet and improving the efficiency of the entire deposition process.

[0028] In the method for modifying the surface of an inorganic solid electrolyte sheet of the present invention, pretreatment is also included before chemical vapor deposition.

[0029] The pre-processing is specifically as follows:

[0030] Place glass bottles and other containers needed in a vacuum (0.01-0.05MPa) oven at 60℃-80℃ for 6-24 hours to ensure that all trace moisture is removed.

[0031] The above method has a wide range of applications and can be effectively applied to various types of inorganic solid electrolytes, further improving the interfacial stability of inorganic solid electrolytes to lithium metal negative electrodes.

[0032] Preferably, the inorganic solid electrolyte sheet is composed of Li 0.388 Ta 0.238 La 0.475 Cl3、Li 0.9 NbO 0.9 Cl 4.1 , Li3InC16, Li3YC16, Li3ScC16, Li3ErCl6, Li3HoC16, Li2ZrC16, Li 1.75 ZrCl 4.75 O 0.5 , Li2HfC16, LiTaCl6, LiTaOCl4, LiAlCl 2.5 O 0.75 、Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 、Li 9.54 Si 0.6 Ge 0.4 P 1.44 S 11.1 Br 0.3 O 0.6 、Li7P3S11 , lithium phosphosulfur chloride, lithium germanium phosphosulfide, lithium lanthanum titanium oxide, lithium lanthanum zirconium oxide or NASICON type oxide; more preferably Li 0.388 Ta 0.238 La 0.475 Cl3.

[0033] The present invention also provides an inorganic solid electrolyte sheet with a surface modified with a fluorine-containing compound, which is prepared by the above method.

[0034] Preferably, the surface Young's modulus of the inorganic solid electrolyte sheet modified with a fluorine-containing compound is 2-6 GPa;

[0035] The ionic conductivity of the inorganic solid electrolyte sheet with the surface modified with a fluorine-containing compound is 0.1-1 mS / cm.

[0036] The present invention also provides a solid-state lithium metal symmetrical battery, comprising the above-mentioned inorganic solid electrolyte sheet with a surface modified with a fluorine-containing compound and a lithium metal negative electrode.

[0037] Preferably, the solid-state lithium metal symmetrical battery has a surface current density of 1 mA cm -2 Under the test conditions, 5mAh cm -2 The surface capacity achieved a stable cycle of 1100 hours.

[0038] The preparation method of the solid-state lithium metal symmetrical battery comprises the following steps:

[0039] First, adhere two thin lithium metal foils to the middle parts of two stainless steel gaskets respectively, place the positive electrode shell (concave side facing up) on the operating table, place one of the stainless steel gaskets in the positive electrode shell with the lithium metal side facing up, then put in the electrolyte sheet, and place the other gasket on top with the lithium metal side facing down, cover it with the negative electrode shell (convex side facing down), and finally seal it with a small hydraulic button battery sealing machine.

[0040] Compared with the prior art, the method for surface modification of an inorganic solid electrolyte sheet provided by the present invention comprises the following steps: in an inert atmosphere, a fluorine-containing compound is coated on the surface of the inorganic solid electrolyte sheet by chemical vapor deposition to obtain an inorganic solid electrolyte sheet with a surface modified fluorine-containing compound; the fluorine-containing compound is selected from one or more of 2,2,3,3,3-pentafluoropropyl acrylate, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate, 2-(perfluorooctyl)ethyl methacrylate, and perfluoro(4-methyl-3,6-dioxa-7-octene)sulfonyl fluoride. The modification method forms a flexible protective layer on the surface of the inorganic solid electrolyte sheet by chemical vapor deposition, thereby improving the interface compatibility between the inorganic solid electrolyte and the lithium metal negative electrode material, enhancing the stability of the interface between the inorganic solid electrolyte and the lithium metal negative electrode, and achieving the long cycle performance of the solid-state lithium metal symmetrical battery at high current density. Furthermore, the method is simple to operate, has good repeatability, low energy consumption, low cost, little environmental pollution, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Atomic force microscope images of the modified inorganic solid electrolyte sheets prepared in Example 1 (right) and Comparative Example 1 (left);

[0042] Figure 2 The infrared attenuated total reflection test results of the modified inorganic solid electrolyte sheet and 2,2,3,3,3-pentafluoropropyl acrylate prepared in Example 1 and Comparative Example 1 are shown;

[0043] Figure 3 is the electrochemical impedance spectroscopy of the modified inorganic solid electrolyte sheet prepared in Example 1;

[0044] Figure 4 is the electrochemical impedance spectroscopy of the modified inorganic solid electrolyte sheet prepared in Example 2;

[0045] Figure 5 is the electrochemical impedance spectroscopy of the modified inorganic solid electrolyte sheet prepared in Example 3;

[0046] Figure 6 This is the electrochemical impedance spectroscopy of the modified inorganic solid electrolyte sheet prepared in Comparative Example 1;

[0047] Figure 7 This is a step current test diagram of the modified inorganic solid-state lithium metal symmetrical battery prepared in Comparative Example 2;

[0048] Figure 8 This is a step current test diagram of the modified inorganic solid-state lithium metal symmetrical battery prepared in Example 4;

[0049] Figure 9 This is a constant current long cycle charge and discharge test chart of the modified inorganic solid-state lithium metal symmetrical battery prepared in Example 4;

[0050] Figure 10 This is the XPS test of the modified inorganic solid electrolyte sheet prepared in Example 1 (upper figure) and the electrolyte after long-term constant current cycling of the solid-state lithium metal symmetric battery prepared in Example 4 (lower figure). DETAILED DESCRIPTION

[0051] To further illustrate the present invention, the method for surface modification of an inorganic solid electrolyte and a solid-state lithium metal symmetrical battery provided by the present invention are described in detail below with reference to the examples.

[0052] The following LLTC can be a common commercial product or homemade.

[0053] The raw materials of the homemade LLCC include: lithium chloride (LiCl, Shanghai Aladdin Biochemical Technology Co., Ltd., anhydrous grade, purity 99.9%), lanthanum chloride (LaCl3, Shanghai Aladdin Biochemical Technology Co., Ltd., anhydrous grade, purity 99.9%), tantalum chloride (TaCl5, Shanghai Aladdin Biochemical Technology Co., Ltd., anhydrous grade, purity 99.9%), etc.

[0054] The sources of the following fluorinated compounds are as follows:

[0055] 2,2,3,3,3-pentafluoropropyl acrylate (containing stabilizer TBC, purity 98%, Shanghai Maclean Biochemical Technology Co., Ltd.), 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate (containing stabilizer MEHQ, 97%, Shanghai Maclean Biochemical Technology Co., Ltd.), 2-(perfluorooctyl)ethyl methacrylate (98%, Shanghai Maclean Biochemical Technology Co., Ltd.).

[0056] The instruments and equipment used in the synthesis of the following inorganic solid electrolyte and the surface modification method of the fluorine-containing compound include:

[0057] YXQM-0.4L planetary ball mill from Changsha Miqi Instrument Equipment Co., Ltd.;

[0058] The following instruments and equipment are used in the testing and assembly of solid electrolyte ionic conductivity and solid-state lithium metal symmetric batteries:

[0059] The equipment includes an MJP-Y ordinary cylindrical mold (Φ10mm) from Shanghai Xinnuo Instrument Co., Ltd., a YLJ-15T-LD manual tablet press and MSK-110 small hydraulic button cell sealer from Hefei Kejing Material Technology Co., Ltd., an SD-900M magnetron sputtering instrument from Beijing Boyuan Micro-Nano Technology Co., Ltd., a DH7001D electrochemical workstation from Jiangsu Donghua Analytical Instrument Co., Ltd., a CT-4008T-5V 20mA-164 battery testing system from Shenzhen Xinweier Electronics Co., Ltd., a DHG-9030A electric heated blast drying oven from Shanghai Jinghong Experimental Equipment Co., Ltd., and a 2032 battery case (positive / negative electrode case, gasket, and spring leaf) from Kelude Laboratory Consumables. The assembly process of the solid-state lithium metal symmetrical battery was carried out in a dry, high-purity argon glove box (argon purity ≥99.999%), with oxygen and water contents below 0.1ppm.

[0060] Example 1

[0061] Li was purified by 2,2,3,3,3-pentafluoropropyl acrylate (containing stabilizer TBC, purity 98%). 0.388 Ta 0.238 La 0.475 Surface modification was performed with Cl3(LLTC).

[0062] In a dry, argon-filled glove box, 120 mg of ball-milled LLTC solid electrolyte powder was weighed and added to an MJP-Y-type conventional cylindrical mold (Ø10 mm). Using a YLJ-15T-LD manual tablet press, a pressure of 300-400 MPa was applied to the mold. After cold pressing for 4-6 minutes, the mold was removed to produce a 10 mm diameter LLTC solid electrolyte tablet.

[0063] In a dry argon-filled glove box, a LLTC solid electrolyte sheet with a diameter of 10 mm was transferred to a dry 100 ml glass bottle. A pipette was used to transfer 0.5 μL of 2,2,3,3,3-pentafluoropropyl acrylate liquid and dripped it into the glass bottle along the wall. The glass bottle was then sealed with a sealing film and placed in an electric blast drying oven (DHG-9030A) at 50 degrees Celsius. After 12 hours, the bottle cap was opened and the electrolyte sheet was carefully turned over. The seal was continued for 12 hours to obtain an electrolyte sheet modified with fluorine-containing organic molecules. After 24 hours, Lithium ion modified with 2,2,3,3,3-pentafluoropropyl acrylate was obtained. 0.388 Ta 0.238 La 0.475 The Cl3 solid electrolyte sheet G1 was stored in a dry argon-filled glove box.

[0064] Example 2

[0065] 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate (stabilized by MEHQ, 97%) was used to 0.388 Ta 0.238 La 0.475 Surface modification was performed with Cl3(LLTC).

[0066] In a dry, argon-filled glove box, 120 mg of ball-milled LLTC solid electrolyte powder was weighed and added to an MJP-Y-type conventional cylindrical mold (Ø10 mm). Using a YLJ-15T-LD manual tablet press, a pressure of 300-400 MPa was applied to the mold. After cold pressing for 4-6 minutes, the mold was removed to produce a 10 mm diameter LLTC solid electrolyte tablet.

[0067] In a dry argon-filled glove box, a 10 mm diameter LLTC solid electrolyte sheet was transferred to a dry 100 ml glass bottle. A pipette was used to transfer 0.5 μl of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate liquid along the wall of the glass bottle and then added to the glass bottle. The glass bottle was then sealed with a sealing film and placed in an electric blast drying oven (DHG-9030A) at 70 degrees Celsius. After 14 hours, the bottle cap was opened and the electrolyte sheet was carefully turned over. The seal was continued for 14 hours to obtain an electrolyte sheet modified with a fluorinated organic molecule. After 28 hours, Lithium ion modified with 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate was obtained. 0.388 Ta 0.238 La 0.475 The Cl3 solid electrolyte sheet G2 was stored in a dry argon-filled glove box.

[0068] Example 3

[0069] 2-(Perfluorooctyl)ethyl methacrylate (98%, Shanghai MacLean Biochemical Technology Co., Ltd. manage ). 0.388 Ta 0.238 La 0.475 Surface modification was performed with Cl3(LLTC).

[0070] In a dry, argon-filled glove box, 120 mg of ball-milled LLTC solid electrolyte powder was weighed and added to an MJP-Y-type conventional cylindrical mold (Ø10 mm). Using a YLJ-15T-LD manual tablet press, a pressure of 300-400 MPa was applied to the mold. After cold pressing for 4-6 minutes, the mold was removed to produce a 10 mm diameter LLTC solid electrolyte tablet.

[0071] In a dry argon-filled glove box, a LLTC solid electrolyte sheet with a diameter of 10 mm was transferred to a dry 100 ml glass bottle, and 0.5 microliters of 2-(perfluorooctyl) ethyl methacrylate was transferred using a pipette. The liquid was dripped into the glass bottle along the wall of the glass bottle, and then the glass bottle was sealed with a sealing film and placed in an electric blast drying oven (DHG-9030A) at 80 degrees Celsius. After 16 hours, the bottle cap was opened and the electrolyte sheet was carefully turned over, and the seal was continued for 16 hours to obtain an electrolyte sheet modified with fluorine-containing organic molecules. After 32 hours, Lithium ion battery surface modified with 2-(perfluorooctyl) ethyl methacrylate was obtained. 0.388 Ta 0.238 La 0.475 The Cl3 solid electrolyte sheet G3 was stored in a dry argon-filled glove box.

[0072] Comparative Example 1

[0073] Comparative Example 1 is Li ion which was used directly without surface modification. 0.388 Ta 0.238 La 0.475 Cl3(LLTC) solid electrolyte sheet D-G1.

[0074] In a dry, argon-filled glove box, 120 mg of LLTC solid electrolyte powder, prepared by ball milling, was weighed and added to an MJP-Y-type conventional cylindrical mold (Ø10 mm). Using a YLJ-15T-LD manual tablet press, a pressure of 300–400 MPa was applied to the mold. After cold pressing for 4–6 minutes, the mold was removed to obtain LLTC solid electrolyte sheet D-G1 with a diameter of 10 mm.

[0075] Figure 1 These are atomic force microscope images of the modified inorganic solid electrolyte sheets prepared in Example 1 of the present invention (right figure) and Comparative Example 1 (left figure).

[0076] pass Figure 1 The force-displacement curve data recorded when the nanoprobe is pressed into the sample is combined with the Hertz contact mechanics model to perform numerical analysis on the data, and the elastic modulus of the material can be calculated. Figure 1 (Left) The surface modulus of the electrolyte in comparative example 1 is 5.190 GPa. After vapor deposition modification Figure 1 (Right figure) The surface modulus of the electrolyte in Example 1 is reduced to 2.119 GPa, indicating that the organic layer of 2,2,3,3,3-pentafluoropropyl acrylate weakens the rigidity of the electrolyte surface. The good deformability and wettability of this flexible interface layer reduce the poor contact between the lithium metal negative electrode and the electrolyte interface due to excessive rigidity.

[0077] Figure 2These are the infrared attenuated total reflection test results of the modified inorganic solid electrolyte sheets and 2,2,3,3,3-pentafluoropropyl acrylate prepared in Example 1 and Comparative Example 1 of the present invention.

[0078] The stretching vibration of the C—F bond in the 2,2,3,3,3-pentafluoropropyl acrylate molecule causes a 1200 cm -1 The solid electrolyte sheet of Comparative Example 1 does not have an absorption peak at 1200 cm -1 The absorption peak of CF appeared in the solid electrolyte sheet of Example 1, which proved that a small amount of 2,2,3,3,3-pentafluoropropyl acrylate molecules were adsorbed on the surface of the LLTC electrolyte sheet.

[0079] Solid electrolyte sheets G1-G3 and D-G1 prepared in Examples 1-3 and Comparative Example 1 were subjected to gold sputtering on both sides in an SD-900M magnetron sputtering instrument. Ionic conductivity was then measured using a DH7001D electrochemical workstation. The test frequency was 8 MHz to 1 Hz, and the applied bias voltage was 100 mV.

[0080] Figure 3 This is the electrochemical impedance spectroscopy of the modified inorganic solid electrolyte sheet prepared in Example 1.

[0081] Figure 4 This is the electrochemical impedance spectroscopy of the modified inorganic solid electrolyte sheet prepared in Example 2.

[0082] Figure 5 This is the electrochemical impedance spectroscopy of the modified inorganic solid electrolyte sheet prepared in Example 3.

[0083] Figure 6 This is the electrochemical impedance spectroscopy of the modified inorganic solid electrolyte sheet prepared in Comparative Example 1.

[0084] like Figures 3 to 6 As shown in the figure, the abscissa is the real impedance and the ordinate is the imaginary impedance. The results show that the ionic conductivity of the unmodified solid electrolyte sheet can reach 2.23mS / cm. The solid electrolyte sheet after vapor deposition has a certain degree of ion conductivity reduction due to the formation of a fluorine-containing organic layer, which hinders the transmission of lithium ions. However, the ionic conductivity can still be maintained in the range of 0.1 to 1mS / cm.

[0085] Example 4

[0086] A solid-state lithium metal symmetric battery was prepared based on the solid electrolyte sheet G1 in Example 1.

[0087] Two thin lithium metal foils, each 8 mm in diameter, were adhered to the middle of two 304 stainless steel button gaskets (Φ16.1*0.5 mm). The positive electrode shell (concave side up) was placed on a workbench. One of the stainless steel gaskets was placed in the positive electrode shell with the lithium metal side facing up. The electrolyte sheet G1 was then placed on the upper side, and the other gasket was placed on top with the lithium metal side facing down. The negative electrode shell (convex side down) was then covered and sealed with a small hydraulic button cell sealer (MSK-110). This yielded a solid-state lithium metal symmetric battery C1. The above preparation processes were all performed in an argon-filled glove box.

[0088] Comparative Example 2

[0089] A solid-state lithium metal symmetric battery was prepared based on the solid electrolyte sheet D-G1 in Comparative Example 1.

[0090] Two thin lithium metal foils with a diameter of 8 mm were adhered to the middle of two 304 stainless steel button gaskets (Φ16.1*0.5 mm). The positive electrode shell (concave side facing up) was placed on the operating table. One of the stainless steel gaskets was placed in the positive electrode shell with the lithium metal side facing up. The electrolyte sheet D-G1 was then placed on the upper side, and the other gasket was placed on top with the lithium metal side facing down. The negative electrode shell (convex side facing down) was covered and finally sealed with a small hydraulic button cell sealer (MSK-110). A solid-state lithium metal symmetric battery C2 was obtained. The above preparation process was performed in an argon-filled glove box.

[0091] The prepared solid-state lithium metal symmetrical batteries C1 and C2 were electrochemically tested using a CT-4008T-5V 20mA-164 battery testing system. When performing step-galvanostatic tests on C1 and C2, the surface current density was set to 0.51 mA cm -2 , 1.02mA cm -2 、1.53mA cm -2 , 2.04mA cm -2 , 2.55mA cm -2 、3.06mA cm -2 、3.57mA cm -2 and 4.08 mA cm -2 , each current density was cycled 5 times, and each cycle time was 10 hours; when C1 was subjected to a long cycle charge and discharge test at a constant current, the current density was set to 1 mA cm -2 .

[0092] Figure 7 This is a step current test diagram of the modified inorganic solid-state lithium metal symmetrical battery prepared in Comparative Example 2.

[0093] Figure 8This is a step current test diagram of the modified inorganic solid-state lithium metal symmetrical battery prepared in Example 4.

[0094] Figure 9 This is a constant current long cycle charge and discharge test chart of the modified inorganic solid-state lithium metal symmetrical battery prepared in Example 4.

[0095] like Figures 7-8 The results show that the solid-state lithium metal symmetrical battery prepared in Example 4 is superior to the solid-state lithium metal symmetrical battery prepared in Comparative Example 2 at a higher areal current density of 4.08 mA cm -2 This indicates that the introduction of 2,2,3,3,3-pentafluoropropyl interface protection layer can significantly improve the stability of the electrolyte and lithium metal interface. Figure 9 Shown at 1 mA cm -2 At high current density, the solid-state lithium metal symmetrical battery prepared in Example 4 can ultimately operate stably for more than 1100 hours.

[0096] Figure 10 These are the XPS test results of the F1s orbital of the electrolyte after long-term constant current cycling of the modified inorganic solid electrolyte sheet prepared in Example 1 (upper figure) and the solid-state lithium metal symmetric battery prepared in Example 4 (lower figure). The results show that the fluorine species change after the charge and discharge cycle, and an obvious LiF signal is presented after fitting analysis, which indicates that the improvement of the interface stability between the solid electrolyte and the lithium metal negative electrode is due to the formation of a fluorine-rich halide interface LiF during the charge and discharge cycle.

[0097] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for surface modification of an inorganic solid electrolyte, characterized in that: The following steps are involved: In an inert atmosphere, a fluorine-containing compound is coated on the surface of an inorganic solid electrolyte sheet by a chemical vapor deposition method to obtain an inorganic solid electrolyte sheet with a surface modified with the fluorine-containing compound; The fluorine-containing compound is selected from one or more of 2,2,3,3,3-pentafluoropropyl acrylate, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate, 2-(perfluorooctyl)ethyl methacrylate, and perfluoro(4-methyl-3,6-dioxa-7-octene)sulfonyl fluoride.

2. The method according to claim 1, characterized in that The ratio of the fluorine-containing compound to the inorganic solid electrolyte sheet is (0.1-5) μL:120 mg.

3. The method according to claim 1, characterized in that The temperature of the chemical vapor deposition method is 50°C-120°C.

4. The method according to claim 3, characterized in that The chemical vapor deposition process takes 24-36 hours.

5. The method according to claim 1, wherein The inert atmosphere is selected from argon with a purity of ≥99.999%.

6. The method according to claim 1, characterized in that The inorganic solid electrolyte sheet is composed of Li 0.388 Ta 0.238 La 0.475 Cl3、Li 0.9 NbO 0.9 Cl 4.1 , Li3InC16, Li3YC16, Li3ScC16, Li3ErCl6, Li3HoC16, Li2ZrC16, Li 1.75 ZrCl 4.75 O 0.5 , Li2HfC16, LiTaCl6, LiTaOCl4, LiAlCl 2.5 O 0.75 、Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 、Li 9.54 Si 0.6 Ge 0.4 P 1.44 S 11.1 Br 0.3 O 0.6 、Li7P3S 11 , lithium phosphosulfide chloride, lithium germanium phosphosulfide, lithium lanthanum titanium oxide, lithium lanthanum zirconium oxide or NASICON type oxide.

7. An inorganic solid electrolyte sheet with a surface modified with a fluorine-containing compound, characterized in that: The method is prepared by any one of claims 1 to 5.

8. The surface-modified inorganic solid electrolyte sheet containing a fluorine-containing compound according to claim 7, characterized in that: The surface Young's modulus of the inorganic solid electrolyte sheet modified with a fluorine-containing compound is 2-6 GPa; The ionic conductivity of the inorganic solid electrolyte sheet with the surface modified with a fluorine-containing compound is 0.1-1 mS / cm.

9. A solid-state lithium metal symmetrical battery, characterized in that: The invention comprises an inorganic solid electrolyte sheet with a surface modified with a fluorine-containing compound as claimed in claim 7 and a lithium metal negative electrode.

10. The solid-state lithium metal symmetrical battery according to claim 9, characterized in that: The solid-state lithium metal symmetric battery has a surface current density of 1 mA cm -2 Under the test conditions, 5mAh cm -2 The surface capacity achieved a stable cycle of 1100 hours.

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