A method of solid electrolyte interface modification

Abstract

The application provides a method for modifying a solid electrolyte interface, and the method for modifying the solid electrolyte interface by soaking ITO after polishing the solid electrolyte can obviously improve the interface performance of the solid electrolyte, greatly improves the critical current density, increases the ability of inhibiting lithium dendrites, and is beneficial to the improvement of the cycle life of a full solid-state battery.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte interface modification, and particularly to a method for solid electrolyte interface modification. Background Technology

[0002] With continuous technological advancements, there is a growing demand for higher energy densities in lithium-ion batteries. Lithium metal, as an anode, possesses enormous capacity potential, but the growth of lithium dendrites prevents its direct use in traditional liquid lithium-ion batteries. Solid-state electrolytes, due to their high shear modulus, have a significant potential to inhibit lithium dendrite formation. Among various types of solid-state electrolytes, garnet-type solid-state electrolyte LLZO stands out due to its high ionic conductivity (~10⁻⁶). -3 The excellent chemical and electrochemical stability of LLZO-based solid-state batteries (S / cm) and Li metal have attracted extensive research. However, at relatively high current densities, dendrite-induced short circuits still occur, which hinders the practical application of solid-state batteries.

[0003] LLZO solid-state electrolytes are sensitive to water and carbon dioxide in the air, spontaneously reacting to form lithium carbonate, which is lithium-repellent and hinders the contact between the solid-state electrolyte and metallic lithium. Furthermore, the surface of the solid-state electrolyte contains numerous pores and defects, resulting in a loose bond with metallic lithium. These defects also serve as preferential growth sites for lithium dendrites, which can cause short circuits and pose safety hazards. To address this problem, a widely adopted solution is interface modification, introducing an interface layer between the solid-state electrolyte and metallic lithium. The addition of this interface layer improves the contact between the solid-state electrolyte and metallic lithium, while also uniformly distributing the local current and suppressing the formation of lithium dendrites.

[0004] Existing methods for introducing interface layers, such as magnetron sputtering, pulsed laser deposition, and electrochemical deposition, have limited deposition areas, require specific environmental conditions (such as vacuum and moisture), and are expensive, thus they have not been effectively applied in solid-state battery production.

[0005] Currently, there is an urgent need for a method for interface modification of solid electrolytes that is simple to prepare, low in cost, and suitable for industrial production. The interface modification method proposed in this invention, which involves directly immersing an ITO dispersion to introduce an ITO protective layer onto the surface of the solid electrolyte, effectively solves the aforementioned problems. Furthermore, the process is simple, low-cost, suitable for mass production, and possesses excellent market potential. Summary of the Invention

[0006] Therefore, this invention proposes a method for modifying the interface of solid electrolytes to solve the above problems.

[0007] A method for modifying the interface of a solid electrolyte includes the following steps:

[0008] (1) Heat the solvent in a water bath, add indium salt and tin salt and stir to prepare an organic ITO dispersion;

[0009] (2) Polish and grind the solid electrolyte sheet, put the ground solid electrolyte sheet into a sample bottle containing ethanol and sonicate it, and dry the sonicated solid electrolyte sheet to obtain the polished solid electrolyte sheet.

[0010] (3) The polished solid electrolyte sheet is immersed in an organic ITO dispersion, and the immersed solid electrolyte sheet is dried to obtain an ITO-attached solid electrolyte sheet.

[0011] (4) The solid electrolyte sheet with ITO attached is placed in a muffle furnace for sintering to obtain the finished product.

[0012] Furthermore, in step (1), the indium salt is at least one of indium oxide, indium hydroxide, and indium trichloride.

[0013] Furthermore, in step (1), the tin salt is at least one of tin trioxide, tin dioxide, and tin dichloride.

[0014] Furthermore, in step (1), the solvent is at least one of ethanol solution, ethylene glycol, N,N-dimethylformamide and isopropanol.

[0015] Furthermore, in step (1), the stoichiometric ratio of the indium salt, tin salt, and solvent is 9:1 to 7:1.

[0016] Furthermore, in step (1), the solvent is heated in a water bath at a temperature of 35-45°C and a rotation speed of 450-550 r / min, and the stirring time is 25-35 min.

[0017] Furthermore, in step (2), the surface of the solid electrolyte sheet is polished sequentially with 400-mesh, 800-mesh, 1200-mesh, and 1500-mesh sandpaper, placed in a sample bottle containing ethanol, ultrasonically dispersed for 2-4 minutes, and dried in an oven at 100-140℃ for 13-17 minutes to obtain the polished solid electrolyte sheet.

[0018] Furthermore, in step (2), the solid electrolyte sheet is a garnet-type solid electrolyte LLZO.

[0019] Furthermore, in step (3), the polished solid electrolyte sheet is immersed in an organic ITO dispersion for 25-35 seconds, and the drying is performed at 100-140°C for 10-20 minutes.

[0020] Furthermore, in step (4), the solid electrolyte sheet with ITO attached is placed in a muffle furnace for sintering, heated to 550-600℃ at a heating rate of 2.5-3.5℃ / min, held for 2-3 hours, and then naturally cooled to room temperature to obtain the finished product.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention modifies the electrolyte sheet by immersing it in an ITO dispersion after grinding and polishing. This significantly improves the interfacial performance of the solid electrolyte, greatly increases the critical current density, enhances the ability to suppress lithium dendrites, and is beneficial to improving the cycle life of all-solid-state batteries. The solid electrolyte interface modification method of this invention has a simple process flow, low cost, and is suitable for widespread application. Attached Figure Description

[0023] Figure 1 Example 1: XRD test images of solid electrolyte sheet after interface modification

[0024] Figure 2 Example 1: SEM image of solid electrolyte sheet after interface modification

[0025] Figure 3 Example 1: SEM image of cross-section of solid electrolyte sheet after interface modification

[0026] Figure 4 Comparative Example 3: SEM image of the cross-section of a solid electrolyte sheet after interface modification.

[0027] Figure 5 Example 1: AC impedance diagrams of solid electrolyte sheet before and after interface modification

[0028] Figure 6 AC impedance diagrams of solid electrolyte sheets after interface modification in Examples 1-2

[0029] Figure 7 Example 1: Critical current density test before and after interface modification of solid electrolyte sheet (25℃) Detailed Implementation

[0030] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

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

[0032] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0033] Example 1: A method for modifying the interface of a solid electrolyte

[0034] (1) Isopropanol was heated in a water bath at 40°C and 500 r / min for 30 min. Indium oxide (In2O3) and tin trioxide (Sn2O3) were added and stirred. The stoichiometric ratio of indium oxide, tin trioxide and isopropanol was 9:5:1 to prepare an organic ITO dispersion.

[0035] (2) Garnet-type solid electrolyte sheet LLZO(Li 6.25 Ga 0.25 La3Zr2O 12 The surface was polished sequentially with 400-grit, 800-grit, 1200-grit, and 1500-grit sandpaper, then placed in a sample bottle containing ethanol and ultrasonically dispersed for 3 minutes. Finally, it was dried in an oven at 120°C for 15 minutes to obtain the polished solid electrolyte sheet.

[0036] (3) The polished solid electrolyte sheet was immersed in an organic ITO dispersion for 30 seconds, and the immersed solid electrolyte sheet was dried at 120°C for 15 minutes to obtain an ITO-attached solid electrolyte sheet.

[0037] (4) The solid electrolyte sheet with ITO attached is placed in a muffle furnace for sintering. The temperature is raised to 550°C at a heating rate of 3°C / min and held for 2 hours. The product is then naturally cooled to room temperature.

[0038] Example 2: A method for modifying the interface of a solid electrolyte

[0039] (1) Isopropanol is heated in a water bath at 35°C and 450 r / min for 25-35 min. Indium hydroxide (In(OH)3) and tin trioxide (Sn2O3) are added and stirred. The stoichiometric ratio of indium hydroxide, tin trioxide and isopropanol is 9:5:1 to prepare an organic ITO dispersion.

[0040] (2) Garnet-type solid electrolyte sheet LLZO(Li 6.25 Ga 0.25 La3Zr2O 12 The surface was polished sequentially with 400-grit, 800-grit, 1200-grit, and 1500-grit sandpaper, then placed in a sample bottle containing ethanol for ultrasonic dispersion for 3 minutes, and dried in an oven at 120°C for 13 minutes to obtain the polished solid electrolyte sheet.

[0041] (3) The polished solid electrolyte sheet was immersed in an organic ITO dispersion for 30 seconds, and the immersed solid electrolyte sheet was dried at 120°C for 15 minutes to obtain an ITO-attached solid electrolyte sheet.

[0042] (4) The solid electrolyte sheet with ITO attached is placed in a muffle furnace for sintering. The temperature is raised to 550°C at a heating rate of 3°C / min and held for 2 hours. The product is then naturally cooled to room temperature.

[0043] Example 3: A method for modifying the interface of a solid electrolyte.

[0044] (1) Isopropanol is heated in a water bath at 35°C and 450 r / min for 25-35 min. Indium oxide (In2O3) and tin trioxide (Sn2O3) are added and stirred. The indium oxide, tin trioxide and isopropanol are in a stoichiometric ratio of 9:1:1 to obtain an organic ITO dispersion.

[0045] (2) Garnet-type solid electrolyte sheet LLZO(Li 6.25 Ga 0.25 La3Zr2O 12 The surface was polished sequentially with 400-grit, 800-grit, 1200-grit, and 1500-grit sandpaper, then placed in a sample bottle containing ethanol for ultrasonic dispersion for 2 minutes, and dried in a 100°C oven for 13 minutes to obtain the polished solid electrolyte sheet.

[0046] (3) The polished solid electrolyte sheet was immersed in an organic ITO dispersion for 30 seconds, and the immersed solid electrolyte sheet was dried at 120°C for 15 minutes to obtain an ITO-attached solid electrolyte sheet.

[0047] (4) The solid electrolyte sheet with ITO attached is placed in a muffle furnace for sintering. The temperature is raised to 600°C at a heating rate of 3°C / min and held for 2 hours. The product is then naturally cooled to room temperature.

[0048] Example 4: A method for modifying the interface of a solid electrolyte

[0049] (1) Isopropanol was heated in a water bath at 45°C and 550 r / min for 35 min. Indium oxide (In2O3) and tin trioxide (Sn2O3) were added and stirred. The stoichiometric ratio of indium oxide, tin trioxide and isopropanol was 9:7:1 to prepare an organic ITO dispersion.

[0050] (2) Garnet-type solid electrolyte sheet LLZO(Li 6.25 Ga 0.25 La3Zr2O 12 The surface was polished sequentially with 400-grit, 800-grit, 1200-grit, and 1500-grit sandpaper, then placed in a sample bottle containing ethanol and ultrasonically dispersed for 4 minutes. Finally, it was dried in an oven at 140°C for 17 minutes to obtain the polished solid electrolyte sheet.

[0051] (3) The polished solid electrolyte sheet was immersed in an organic ITO dispersion for 30 seconds, and the immersed solid electrolyte sheet was dried at 120°C for 15 minutes to obtain an ITO-attached solid electrolyte sheet.

[0052] (4) The solid electrolyte sheet with ITO attached is placed in a muffle furnace for sintering. The temperature is raised to 550°C at a heating rate of 3°C / min and held for 3 hours. The sheet is then naturally cooled to room temperature to obtain the finished product.

[0053] Comparative Example 1

[0054] (1) Isopropanol was heated in a water bath at 40°C and 500 r / min for 30 min. Indium oxide (In2O3) and tin trioxide (Sn2O3) were added and stirred. The stoichiometric ratio of indium oxide, tin trioxide and isopropanol was 9:5:1 to prepare an organic ITO dispersion.

[0055] (2) Garnet-type solid electrolyte sheet LLZO(Li 6.25 Ga 0.25 La3Zr2O 12 The surface was polished sequentially with 400-grit, 800-grit, 1200-grit, and 1500-grit sandpaper, then placed in a sample bottle containing ethanol and ultrasonically dispersed for 3 minutes. Finally, it was dried in an oven at 120°C for 15 minutes to obtain the polished solid electrolyte sheet.

[0056] (3) The polished solid electrolyte sheet was immersed in an organic ITO dispersion for 30 seconds, and the immersed solid electrolyte sheet was dried at 120°C for 15 minutes to obtain an ITO-attached solid electrolyte sheet.

[0057] (4) The solid electrolyte sheet with ITO attached is placed in a muffle furnace for sintering. The temperature is raised to 550°C at a heating rate of 5°C / min and held for 2 hours. The product is then naturally cooled to room temperature.

[0058] The difference between Comparative Example 1 and Example 1 is that the heating rate of the muffle furnace in step (4) is different, which leads to poor bonding between the ITO layer and the garnet-type solid electrolyte, resulting in a decrease in the performance of the prepared solid electrolyte.

[0059] Comparative Example 2

[0060] (1) Isopropanol was heated in a water bath at 40°C and 500 r / min for 30 min. Indium oxide (In2O3) and tin trioxide (Sn2O3) were added and stirred. The stoichiometric ratio of indium oxide, tin trioxide and isopropanol was 9:5:1 to prepare an organic ITO dispersion.

[0061] (2) Garnet-type solid electrolyte sheet LLZO(Li 6.25 Ga 0.25 La3Zr2O 12 The surface was polished sequentially with 400-grit, 800-grit, 1200-grit, and 1500-grit sandpaper, then placed in a sample bottle containing ethanol and ultrasonically dispersed for 3 minutes. Finally, it was dried in an oven at 120°C for 15 minutes to obtain the polished solid electrolyte sheet.

[0062] (3) The polished solid electrolyte sheet was immersed in an organic ITO dispersion for 30 seconds, and the immersed solid electrolyte sheet was dried at 120°C for 15 minutes to obtain an ITO-attached solid electrolyte sheet.

[0063] (4) The solid electrolyte sheet with ITO attached is placed in a muffle furnace for sintering. The temperature is increased to 800°C at a heating rate of 3°C / min, and the holding time is 2h. The sheet is then naturally cooled to room temperature to obtain the finished product.

[0064] The difference between Comparative Example 2 and Example 1 is that the sintering temperature of Comparative Example 2 is 800°C. Microscopic characterization and performance testing of the obtained components revealed that excessively high sintering temperatures can cause ITO segregation, resulting in an uneven ITO layer and a decrease in the performance of the solid electrolyte.

[0065] Comparative Example 3

[0066] (1) Isopropanol was heated in a water bath at 40°C and 500 r / min for 30 min. Indium oxide (In2O3) and tin trioxide (Sn2O3) were added and stirred. The stoichiometric ratio of indium oxide, tin trioxide and isopropanol was 9:5:1 to prepare an organic ITO dispersion.

[0067] (2) Garnet-type solid electrolyte sheet LLZO(Li 6.25 Ga 0.25 La3Zr2O 12 The surface was polished sequentially with 400-grit, 800-grit, 1200-grit, and 1500-grit sandpaper, then placed in a sample bottle containing ethanol and ultrasonically dispersed for 3 minutes. Finally, it was dried in an oven at 120°C for 15 minutes to obtain the polished solid electrolyte sheet.

[0068] (3) The polished solid electrolyte sheet was immersed in an organic ITO dispersion for 30 seconds, and the immersed solid electrolyte sheet was dried at 120°C for 15 minutes to obtain an ITO-attached solid electrolyte sheet.

[0069] (4) The solid electrolyte sheet with ITO attached is placed in a muffle furnace for sintering. The temperature is raised to 450°C at a heating rate of 3°C / min and held for 2 hours. The product is then naturally cooled to room temperature.

[0070] Experimental Example 1

[0071] The product obtained by this invention was tested for phase composition, microstructure, interfacial impedance, and dendrite resistance, as detailed below:

[0072] Test methods

[0073] (1) XRD test

[0074] XRD testing collects corresponding characteristic peaks, which are compared with standard PDF cards in a database to determine the phase composition of the material. This can be used to determine the ITO interface layer in this invention.

[0075] This test used the D2-PHASER instrument from Solartron Analytical GmbH, Germany, with a Cu target X-ray source at 40 kV and a scanning range of 10° to 80°.

[0076] (2) Scanning electron microscopy test

[0077] Scanning electron microscopes can provide a direct view of the surface morphology of materials and can be used to observe the ITO interface layer on the surface of solid electrolytes.

[0078] This test used a Phenom Prox scanning electron microscope from Phenom Scientific Instruments (Shanghai) Co., Ltd.

[0079] (3) AC impedance test

[0080] Electrochemical impedance spectroscopy (EIS) is a common testing method for studying the electrochemical behavior of different systems. Its core idea is to apply an alternating current signal to the system, observe the resulting electrochemical behavior, and summarize the changes in electrochemical behavior based on the frequency of the alternating current signal. It can be used to test the change in interfacial impedance before and after interface modification to determine the improvement of interfacial performance by the invention. The lower the interfacial impedance, the better the contact between the solid electrolyte sheet and lithium metal, and the better the resistance to dendrite formation and cycle performance. This test uses a Li|LLZO|Li symmetric battery.

[0081] The test was conducted using a Solartron Analytical 1470E electrochemical workstation from the UK, with a vibration amplitude of 10 MV and a frequency range of 1 MHz to 0.1 Hz.

[0082] (4) Critical current density test

[0083] The current density at which lithium dendrites penetrate a solid electrolyte is commonly referred to as the critical current density (CCD). A higher critical current density indicates a stronger resistance to dendrite formation in the material. This test used a Li|LLZO|Li symmetric cell.

[0084] This test used a high-performance battery testing system from Shenzhen Neware.

[0085] See Figure 1 The finished product obtained in Example 1 was tested by XRD, and the results showed that a layer of ITO was successfully introduced into the LLZO surface.

[0086] See Figure 2 The surface of the finished product obtained in Example 1 was successfully modified by immersion in ITO dispersion to introduce an ITO layer on the surface of the solid electrolyte.

[0087] See Figure 3-4 , Figure 3 This is the cross-section of the finished product in Example 1. Figure 4 The cross-section of the finished product in Comparative Example 3 is shown. The finished product obtained in Comparative Example 1 is denser than that obtained in Comparative Example 3, while the ITO layer of the finished product obtained in Comparative Example 3 has obvious gaps between it and the electrolyte surface.

[0088] See Figure 5 , Figure 5 The figures show the AC impedance diagrams of the solid electrolyte sheet in Example 1 before and after interface modification. After interface modification, the interface impedance of the sample decreased from 22560Ω to 90Ω. The reduction in interface impedance indicates that the ITO modification layer successfully enhanced the contact effect between the solid electrolyte and the lithium metal anode, improved the interface performance, and effectively improved the ability of the solid battery to suppress dendrites.

[0089] See Figure 6 , Figure 6 The figures show the AC impedance diagrams of the finished products obtained in Examples 1-2. This demonstrates that using the raw materials of this invention to modify the interface of the solid electrolyte achieves the effect of reducing interface impedance.

[0090] See Figure 7 , Figure 7 For Example 1, the critical current density of the solid electrolyte sheet before and after interface modification was tested (25°C). After interface modification, the critical current density of the solid electrolyte reached 0.668 mA / cm². 2 The unmodified sample, however, showed improvement at a low current density of 0.064 mA / cm². 2 It exhibits significant polarization at 0.096 mA / cm. 2At certain current densities, short circuits occur due to the growth of lithium dendrites. Critical current density test results show that interface modification through ITO immersion significantly improves the interface performance of the solid-state electrolyte, substantially increases the critical current density, enhances the ability to suppress lithium dendrites, and is beneficial for improving the cycle life of all-solid-state batteries.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for modifying the interface of a solid electrolyte, characterized in that, Includes the following steps: The solvent is heated to 35-45℃ in a water bath, and indium salt and tin salt are added and stirred at a speed of 450-550 r / min for 25-35 min to obtain an organic ITO dispersion; the stoichiometric ratio of indium salt, tin salt and solvent is 9:(1~7):1; The surface of the garnet-type solid electrolyte sheet LLZO was polished sequentially with 400-grit, 800-grit, 1200-grit, and 1500-grit sandpaper. The polished solid electrolyte sheet was placed in a sample bottle containing ethanol and ultrasonically dispersed for 2-4 minutes. It was then dried in an oven at 100-140℃ for 13-17 minutes to obtain the polished solid electrolyte sheet. The polished solid electrolyte sheet is immersed in an organic ITO dispersion for 25-35 seconds, and then dried at 100-140℃ for 10-20 minutes to obtain an ITO-attached solid electrolyte sheet. The solid electrolyte sheet with ITO attached is placed in a muffle furnace for sintering. The temperature is increased to 550-600℃ at a heating rate of 2.5-3.5℃ / min, and held for 2-3 hours. The sheet is then naturally cooled to room temperature to obtain the finished product.

2. The method for modifying the interface of a solid electrolyte as described in claim 1, characterized in that, In step (1), the indium salt is at least one of indium oxide, indium hydroxide, and indium trichloride.

3. The method for modifying the interface of a solid electrolyte as described in claim 1, characterized in that, In step (1), the tin salt is at least one of tin trioxide, tin dioxide and tin dichloride.

4. The method for modifying the interface of a solid electrolyte as described in claim 1, characterized in that, In step (1), the solvent is at least one of ethanol solution, ethylene glycol, N,N-dimethylformamide and isopropanol.

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