A method for reducing grain boundary resistance of an inorganic oxide solid electrolyte, a film obtained therefrom and its application

Abstract

The present invention belongs to the technical field of all-solid-state lithium batteries, and in particular relates to a method for reducing the grain boundary resistance of an oxide inorganic solid electrolyte. First, a dispersion of two-dimensional nanosheets of an oxide inorganic solid electrolyte is prepared; then, the two-dimensional nanosheets of the oxide inorganic solid electrolyte in the dispersion are stacked on a base film to form a layered framework; then, a precursor solution of g-C3N4 is introduced into the layered framework; finally, a calcination treatment is performed under an inert atmosphere to obtain a layered oxide inorganic solid electrolyte membrane with an in-situ grown g-C3N4 modified layer. The present invention provides a method for reducing the grain boundary resistance of an oxide inorganic solid electrolyte, wherein the g-C3N4 grain boundary modification used does not require high-temperature sintering, and after the grain boundary is modified, the obtained thin layered inorganic solid electrolyte has good room temperature ionic conductivity and high mechanical strength, and can well inhibit the growth of lithium dendrites. The battery assembled with the electrolyte has excellent cycle life and high safety, reduces battery capacity decay, and increases battery life.

Description

Technical Field

[0001] The present invention belongs to the technical field of all-solid-state lithium batteries, and particularly relates to a method for reducing the grain boundary resistance of an oxide inorganic solid electrolyte, a prepared film and applications thereof. Background Art

[0002] Nowadays, all-solid-state lithium batteries are considered to be the most promising new generation energy storage devices due to their high safety and high energy density. The ionic conductivity of the solid electrolyte determines the performance of the battery. Oxide inorganic solid electrolytes, including perovskite-type Li 0.34 La 0.56 TiO3(LLTO), garnet-type Li7La3Zr2O 12 (LLZO), NASICON type Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and Li 1+x Al x Ge 2-x (PO4)3, has a high ionic conductivity at room temperature (10 -3 S cm -1 -10 -2 S cm -1 ) and low migration energy barriers (0.2-0.3 eV) have been widely studied (Nat. Commun. 2017, 8, 15893). However, conventional oxide inorganic solid electrolyte membranes, primarily prepared from hot- or cold-pressed oxide inorganic solid electrolyte particles, typically exhibit ionic conductivity 2 to 3 orders of magnitude lower than that of the bulk oxide inorganic solid electrolyte. This is primarily due to the presence of numerous grain boundaries within the oxide inorganic solid electrolyte membrane, which hinder lithium ion transport.

[0003] To solve this problem, scholars have conducted extensive research on eliminating grain boundaries. The solutions currently proposed can be divided into two categories: fusing grain boundaries through high-temperature sintering and adding grain boundary modification layers. By increasing the sintering temperature to fuse the grain boundaries, the size of the ceramic particles can be increased and the number of grain boundaries can be reduced. For example, LLTO films have been prepared by tape casting and then sintered at 1260°C for 12 hours. The high-temperature sintering process promotes the growth of LLTO particles and reduces the number of LLTO grain boundaries (Adv. Mater. 2020, 32, 1906221). However, this process requires a long time of sintering at high temperatures (>1000°C). Adding a grain boundary modification layer is a simple and effective method. The grain boundary modification layer can fill the gaps between ceramic particles, acting as a binder and bridge, allowing lithium ions to transfer quickly at the grain boundaries. At present, some scholars have used the ball milling method to coat LiBH4 on the surface of LLZTO particles, and then prepared an oxide inorganic solid electrolyte membrane by cold pressing. The effective lithium ion transfer channel of the grain boundary modification layer LiBH4 at the grain boundary of LLZTO particles significantly enhances the ion conductivity of the oxide inorganic solid electrolyte membrane (Adv.Funct.Mater.2021,31,2009692). Although great progress has been made, the uneven shape of ceramic particles always leads to uneven distribution of grain boundary modifiers. Due to the complex grain boundary structure, it is difficult to explore the lithium ion transfer process within the grain boundary, and it is also difficult to determine the selection principle of the grain boundary modification layer. This is not conducive to the development of the grain boundary modification layer. At the same time, the thickness of the oxide inorganic solid electrolyte membrane currently prepared is generally thicker (200-1000μm), and there are more grain boundaries between the particles. Therefore, it is urgent to develop an oxide inorganic solid electrolyte membrane with a regular structure and a thinner thickness. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for reducing the grain boundary resistance of an oxide inorganic solid electrolyte, which can more effectively reduce the grain boundary resistance of an oxide inorganic solid electrolyte two-dimensional nanosheet, so that the oxide inorganic solid electrolyte can be better applied in the field of all-solid-state lithium batteries.

[0005] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0006] A method for reducing the grain boundary resistance of an oxide inorganic solid electrolyte, the key being an oxide inorganic solid electrolyte membrane prepared by the following method:

[0007] 1) preparing a dispersion of two-dimensional oxide inorganic solid electrolyte nanosheets;

[0008] 2) stacking the oxide inorganic solid electrolyte two-dimensional nanosheets in the dispersion of step 1) on the base film to form a layered framework;

[0009] 3) introducing the g-C3N4 precursor solution into the layered framework obtained in step 2);

[0010] 4) calcining the product of step 3) under an inert atmosphere to obtain a layered oxide inorganic solid electrolyte membrane with an in-situ grown g-C3N4 modified layer.

[0011] In step 1), sucrose is used as a structure-directing agent for sintering to prepare an oxide inorganic solid electrolyte sheet framework, which is then dispersed in acetonitrile or ethanol solvent to obtain an oxide inorganic solid electrolyte two-dimensional nanosheet dispersion.

[0012] Specifically, the oxide inorganic solid electrolyte sheet framework can be prepared by existing conventional methods, and then liquid phase exfoliation is performed to obtain the oxide inorganic solid electrolyte two-dimensional nanosheet dispersion.

[0013] Taking the LLZO sheet framework as an example, the oxide inorganic solid electrolyte sheet framework can be prepared as follows: sucrose, lithium nitrate, lanthanum nitrate hexahydrate, and zirconyl nitrate are magnetically stirred and mixed in deionized water for 6-24 hours to prepare a mixed solution of sucrose and LLZO precursor. Among them, the molar ratio of sucrose, lithium nitrate, lanthanum nitrate hexahydrate, and zirconyl nitrate is 1.45:8.0:3.0:2.0, and the amount of deionized water is 70-150mL. The mixed solution is then sintered at 150-300℃ for 2-5h and 800-1000℃ for 1-4h to obtain the LLZO sheet framework.

[0014] In step 1), the liquid phase exfoliation is to uniformly disperse the oxide inorganic solid electrolyte sheet framework into acetonitrile or ethanol solvent at room temperature, then ultrasonicate the dispersion at 50-100kHz for 10-30min, and then centrifuge at 2000-3000r / min for 20-30min to obtain the oxide inorganic solid electrolyte two-dimensional nanosheet dispersion.

[0015] The oxide inorganic solid electrolyte two-dimensional nanosheet can be selected from Li 0.34 La 0.56 TiO3(LLTO), Li7La3Zr2O 12 (LLZO), Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP) and Li 1.5 Al 0.5 Ge 1.5 At least one of (PO4)3(LAGP) nanosheets, preferably Li7La3Zr2O 12 (LLZO) two-dimensional nanosheets.

[0016] In step 2), the oxide inorganic solid electrolyte two-dimensional nanosheet dispersion is stacked on the base film by suction filtration or spraying to obtain a layered framework, and then dried in an inert atmosphere for 24-48 hours to obtain a layered framework.

[0017] The concentration of the oxide inorganic solid electrolyte two-dimensional nanosheet dispersion is preferably 0.2-0.5 g / L, and the layered framework is preferably stacked by filtration. The layered framework obtained using 200-1000 mL of the dispersion has a thickness of 20-100 μm.

[0018] In the step 3), the precursor of g-C3N4 can be selected from one of cyanamide, urea or melamine, and the amount of g-C3N4 introduced is 8%-12% of the mass of the inorganic solid electrolyte two-dimensional nanosheets in terms of cyanamide. If other precursors are used, the amount can be converted accordingly according to the amount of cyanamide.

[0019] Specifically, the precursor of g-C3N4 can be dispersed in acetonitrile under magnetic stirring to obtain a uniformly dispersed solution.

[0020] The precursor is then introduced into the layered framework of step 2) by vacuum filtering the uniformly dispersed acetonitrile solution, with a filtration pressure of 1-5 MPa.

[0021] In step 4), a thin layered inorganic solid electrolyte membrane with an in-situ grown g-C3N4 modified layer is obtained by sintering at 520°C for 3-5h under a nitrogen atmosphere.

[0022] The gas flow rate of nitrogen is 10-30 mL / min, preferably controlled to 20 mL / min.

[0023] The present invention provides a method for reducing the grain boundary resistance of two-dimensional oxide inorganic solid electrolyte nanosheets. By modifying the surface of the oxide inorganic solid electrolyte nanosheets with g-C3N4, the grain boundary resistance can be effectively reduced, thereby achieving the purpose of preparing a highly conductive oxide inorganic solid electrolyte membrane. The g-C3N4 acts as a binder and bridging agent at the grain boundaries, providing a lithium ion transfer path. The resulting g-C3N4 / oxide inorganic solid electrolyte membrane has high ionic conductivity and mechanical strength, effectively inhibiting the growth of lithium dendrites. Application of this electrolyte membrane in all-solid-state lithium batteries can achieve excellent electrochemical and safety performance.

[0024] The obtained thin layered inorganic solid electrolyte membrane with in-situ grown g-C3N4 modified layer has a thickness of 30-100 μm.

[0025] The principles of the present invention are as follows:

[0026] 1) The oxide inorganic solid electrolyte two-dimensional nanosheets in the present invention are preferably two-dimensional nanosheets with good chemical stability to the lithium negative electrode; compared with the oxide inorganic solid electrolyte particles, the two-dimensional nanosheets themselves have less grain boundary resistance, and because the two-dimensional nanosheets are relatively regular, good contact between the modified layer and the oxide inorganic solid electrolyte two-dimensional nanosheets can be achieved;

[0027] 2) Compared with oxide inorganic solid electrolyte particle tablets, the layered framework can greatly reduce the thickness of the electrolyte membrane, provide a shorter transfer path for lithium ion transfer, and greatly improve the lithium ion transfer capacity;

[0028] 3) The introduction of g-C3N4 soft phase within the layered framework can effectively bridge the oxide inorganic solid electrolyte two-dimensional nanosheets, provide a fast lithium ion transfer path at the grain boundary, and increase the mechanical properties of the membrane.

[0029] Generally speaking, the present invention replaces oxide inorganic solid electrolyte particles with two-dimensional nanosheets of oxide inorganic solid electrolyte, and uses a soft phase such as g-C3N4 as a grain boundary modification to modify the two-dimensional nanosheets, thereby reducing the grain boundary resistance of the oxide inorganic solid electrolyte. From the preparation process, the obtained two-dimensional nanosheets are first self-assembled into a layered framework under vacuum filtration, and then a precursor of g-C3N4, such as monocyanamide (CH2N2), is dissolved in acetonitrile and filtered to the interlayer of the layered framework. Finally, sintering is carried out under an N2 atmosphere, and g-C3N4 is in situ grown between the layers of the layered framework to obtain a thin layered inorganic solid electrolyte membrane with an in-situ grown g-C3N4 modified layer.

[0030] The electrolyte prepared by the present invention has low grain boundary resistance and a thin electrolyte membrane, shortening the lithium ion transfer path and enhancing lithium ion conductivity. The prepared electrolyte has high mechanical strength, effectively inhibiting lithium dendrite growth and enhancing the battery's cycle performance.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention provides a method for reducing the grain boundary resistance of an oxide inorganic solid electrolyte. Compared with currently commonly used methods, the g-C3N4 grain boundary modification used in the present invention does not require high-temperature sintering, saving time and labor. After the grain boundary is modified, the obtained thin layered inorganic solid electrolyte has good room temperature ionic conductivity and high mechanical strength, and can effectively inhibit the growth of lithium dendrites. The battery assembled with the electrolyte has an excellent cycle life and high safety, reduces the capacity decay of the battery, and increases the life of the battery. In addition, the non-high-temperature sintering method used in the present invention is easy to implement, easy to scale up production, and has high production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a scanning electron microscope image of the LLZO nanosheets in step 1) of Example 1 of the present invention;

[0034] Figure 2 This is a scanning electron microscope image of the LLZO layered framework prepared in step 2) of Example 1 of the present invention;

[0035] Figure 3 The cross-sectional scanning electron microscope image and the corresponding physical image of the g-C3N4 modified thin layered inorganic solid electrolyte membrane prepared in Example 1 of the present invention;

[0036] Figure 4 The electrochemical impedance spectroscopy diagrams of Example 1, Comparative Example 1, and Comparative Example 2 are shown;

[0037] Figure 5 The temperature-conductivity diagrams of Example 1, Comparative Example 1, and Comparative Example 2 are shown;

[0038] Figure 6 Nanoindentation curves of Example 1 and Comparative Example 2;

[0039] Figure 7 The 0.5C long cycle performance of the lithium iron phosphate / lithium battery assembled with the g-C3N4 modified thin layered inorganic solid electrolyte membrane obtained in Example 1;

[0040] Figure 8 The rate cycling performance of the lithium iron phosphate / lithium battery assembled with the g-C3N4 modified thin layered inorganic solid electrolyte membrane obtained in Example 1. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto:

[0042] Example 1

[0043] A method for reducing the grain boundary resistance of an oxide inorganic solid electrolyte comprises the following steps:

[0044] 1) Lithium nitrate (0.583 g), lanthanum nitrate hexahydrate (1.300 g), zirconyl nitrate (0.462 g), sucrose (0.500 g), and deionized water (70 mL) were stirred at room temperature for 12 h to obtain a mixed solution. The solution was then sintered at 250°C for 4 h and then at 950°C for 4 h to obtain LLZO sheet frameworks. Finally, the obtained LLZO sheet frameworks were dispersed in acetonitrile solution (50 mL), magnetically stirred for 10 h, ultrasonicated at 50 kHz for 30 min, and then centrifuged at 2000 r / min for 30 min to obtain a dispersion of LLZO two-dimensional nanosheets with a concentration of 0.2 g / L.

[0045] 2) taking the LLZO two-dimensional nanosheet dispersion (200 mL) from step 1) into a vacuum filtration apparatus and filtering at a filtration pressure of 0.02 MPa to allow the LLZO two-dimensional nanosheets to stack on the nylon base membrane to form an LLZO layered framework;

[0046] 3) Dissolve cyanamide (0.01 g) in acetonitrile (1.0 mL) and stir magnetically for 4 h to obtain a g-C3N4 precursor solution with a concentration of 0.01 g / mL. Take 0.4 mL of this precursor solution and add it to a vacuum filtration device. Under a filtration pressure of 1.0 MPa, filter it into the interlayers of the LLZO layered framework to obtain an LLZO layered framework with the interlayers filled with g-C3N4 precursor. Finally, place it in an argon-filled glove box and dry it for 24 h.

[0047] 4) The resulting precursor-filled layered framework was sintered in a muffle furnace at 520°C for 4 hours under a nitrogen atmosphere at a nitrogen flow rate of 20 mL / min. This yielded a thin, 30 μm-thick layered inorganic solid electrolyte membrane with an in-situ g-C₃N₄ modified layer.

[0048] The electrolyte membrane is assembled into an all-solid-state lithium battery.

[0049] In this embodiment, the positive electrode material for the all-solid-state lithium battery is lithium iron phosphate. Specifically, a slurry with a mass ratio of lithium iron phosphate: conductive carbon black: binder = 8:1:1 is applied to aluminum foil and then vacuum-dried at 120°C for 24 hours to obtain the positive electrode material. The positive electrode material is then cut into 12mm diameter discs with a cutter to form the all-solid-state lithium battery. The negative electrode material for the all-solid-state lithium battery is a commercially available 16mm diameter lithium sheet.

[0050] The performance test of the assembled battery showed that the thin layered inorganic solid electrolyte membrane modified with g-C3N4 had a small grain boundary resistance at room temperature and an ionic conductivity of 2.5×10 -4 S cm -1 The compressive strength is 2.6 GPa. The discharge capacity is 147.7 mAh g after 150 cycles at 60°C and 0.5C. -1 , the attenuation per turn is 0.05%.

[0051] Figure 1 Shown is a scanning electron microscope image of the LLZO nanosheets in step 1) of this embodiment; Figure 1 It can be seen that LLZO nanosheets have a typical two-dimensional structure, and the size of the nanosheets is 1-2 μm.

[0052] Figure 2 The cross-sectional SEM image of the LLZO layered framework in step 2) of this embodiment is shown; Figure 2It can be seen that the LLZO framework has a layer-by-layer stacking structure with a film thickness of 27 μm.

[0053] Figure 3 The cross-sectional SEM image and the physical image of the g-C3N4 modified thin layered inorganic solid electrolyte membrane prepared in this embodiment are shown; Figure 3 It can be seen that after the in situ growth of g-C3N4, the LLZO layered framework becomes dense, g-C3N4 fills the interlayer, and the film thickness is 30μm.

[0054] Example 2

[0055] A method for reducing the grain boundary resistance of an oxide inorganic solid electrolyte comprises the following steps:

[0056] 1) The preparation method of LLZO two-dimensional nanosheet solution is the same as that in Example 1;

[0057] 2) taking the LLZO two-dimensional nanosheet dispersion (300 mL) from step 1) into a vacuum filtration apparatus and filtering at a filtration pressure of 0.02 MPa to allow the LLZO two-dimensional nanosheets to stack on the nylon base membrane to form an LLZO layered framework;

[0058] 3) Dissolve cyanamide (0.01 g) in acetonitrile (1.0 mL) and stir magnetically for 4 h to obtain a g-C3N4 precursor solution with a concentration of 0.01 g / mL. Take 0.6 mL of this precursor solution and add it to a vacuum filtration device. Under a filtration pressure of 2.0 MPa, filter it into the interlayers of the LLZO layered framework to obtain an LLZO layered framework with the interlayers filled with g-C3N4 precursor. Finally, place it in an argon-filled glove box and dry it for 10 h.

[0059] 4) The resulting precursor-filled layered framework was sintered in a muffle furnace at 520°C for 4 hours under a nitrogen atmosphere at a nitrogen flow rate of 20 mL / min. This yielded a thin, 45 μm-thick layered inorganic solid electrolyte membrane with an in-situ g-C₃N₄ modified layer.

[0060] Example 3

[0061] A method for reducing the grain boundary resistance of an oxide inorganic solid electrolyte comprises the following steps:

[0062] 1) The preparation method of LLZO two-dimensional nanosheet solution is the same as that in Example 1;

[0063] 2) taking the LLZO two-dimensional nanosheet dispersion (500 mL) from step 1) into a vacuum filtration apparatus and filtering at a filtration pressure of 0.02 MPa to allow the LLZO two-dimensional nanosheets to stack on the nylon base membrane to form an LLZO layered framework;

[0064] 3) Dissolve cyanamide (0.01 g) in acetonitrile (1.0 mL) and stir magnetically for 4 h to obtain a g-C3N4 precursor solution with a concentration of 0.01 g / mL. This precursor solution is then added to a vacuum filtration device and filtered into the interlayers of the LLZO layered framework at a filtration pressure of 3.0 MPa to obtain an LLZO layered framework filled with g-C3N4 precursor. Finally, place the solution in an argon-filled glove box and dry it for 10 h.

[0065] 4) The resulting precursor-filled layered framework was sintered in a muffle furnace at 520°C for 4 hours under a nitrogen atmosphere at a nitrogen flow rate of 20 mL / min. This yielded a thin layered inorganic solid electrolyte membrane with an in-situ g-C₃N₄ modified layer, 80 μm thick.

[0066] Comparative Example 1

[0067] The method for forming a g-C3N4 modified LLZO particle tabletted inorganic solid electrolyte membrane comprises the following steps:

[0068] 1) Lithium nitrate (0.583 g), lanthanum nitrate hexahydrate (1.300 g), zirconyl nitrate (0.462 g), and deionized water (70 mL) were stirred at room temperature for 12 hours to obtain a mixed solution. The solution was then sintered at 250°C for 4 hours and then at 950°C for 4 hours to obtain LLZO particles. Finally, the obtained LLZO particles were ball milled at 200 rpm for 10 hours to obtain LLZO nanoparticles.

[0069] 2) The LLZO nanoparticles (0.4 g) prepared in 1) were added to an acetonitrile solution (10 mL) and magnetically stirred for 4 h to obtain a dispersion of LLZO nanoparticles.

[0070] 3) Dissolve cyanamide (0.04 g) in acetonitrile (10 ml) and stir magnetically for 4 hours to obtain a g-C3N4 precursor solution with a concentration of 0.004 g / mL. This precursor solution is then added to the LLZO nanoparticle dispersion prepared in 2) and stirred magnetically for 10 hours. The mixture is then vacuum-dried in a drying oven for 12 hours to remove the acetonitrile solvent, yielding g-C3N4 precursor-coated LLZO nanoparticles.

[0071] 4) The g-C3N4 precursor-coated LLZO nanoparticles were placed in a 19 mm diameter pressing mold and pressed at 400 MPa for 10 min to obtain a g-C3N4 precursor-coated LLZO electrolyte pellet. The electrolyte pellet was then sintered in a muffle furnace at 520°C for 4 h under a nitrogen atmosphere at a nitrogen flow rate of 20 mL / min. An in situ grown g-C3N4-modified LLZO pellet inorganic solid electrolyte membrane with a thickness of 210 μm was obtained.

[0072] The g-C3N4 modified LLZO particle pressed inorganic solid electrolyte membrane was assembled into a battery according to the method of Example 1 and the performance test was carried out. The results showed that the grain boundary resistance at room temperature was 146Ωcm 2 ; The ionic conductivity is 9.39×10 -5 S cm -1 ;

[0073] Comparative Example 2

[0074] The LLZO particle tableting inorganic solid electrolyte membrane includes the following steps:

[0075] 1) Taking 0.4 g of the LLZO nanoparticles obtained in step 1) of Comparative Example 1, and using the pressing method in Comparative Example 1 to obtain an LLZO electrolyte sheet;

[0076] 2) The LLZO electrolyte sheet was sintered in a muffle furnace at 520° C. for 4 h under a nitrogen atmosphere at a nitrogen flow rate of 20 mL / min to obtain an LLZO particle pressed inorganic solid electrolyte membrane having a thickness of 200 μm.

[0077] The LLZO particle pressed inorganic solid electrolyte membrane was assembled into a battery according to the method of Example 1 and the performance test results were as follows: the grain boundary resistance at room temperature was 1608Ωcm 2 ; The ionic conductivity is 1.25×10 -5 Scm -1 ; The compressive strength is 1.3GPa.

[0078] Figure 4 Shown are the electrochemical impedance spectroscopy graphs of Example 1, Comparative Example 1, and Comparative Example 2; Figure 5 Shown are the temperature-conductivity diagrams of Example 1, Comparative Example 1, and Comparative Example 2.

[0079] Compared with g-C3N4-modified LLZO particle pressed inorganic solid electrolyte membranes and LLZO particle pressed inorganic solid electrolyte membranes, the g-C3N4-modified thin layered inorganic solid electrolyte membrane obtained in Example 1 exhibits low grain boundary resistance and high ion conductivity due to the g-C3N4 acting as a bridge between layers, a binder, and a lithium ion conductor. g-C3N4 can achieve excellent grain boundary modification.

[0080] Figure 6 The nanoindentation curves of Example 1 and Comparative Example 2 are shown. It is proved that the thin layered inorganic solid electrolyte membrane modified with g-C3N4 obtained in Example 1 of the present invention has high compressive strength.

[0081] Figure 7The figure shows the 0.5C cycle performance of the lithium iron phosphate / lithium battery assembled with the g-C3N4 modified thin layered inorganic solid electrolyte membrane obtained in Example 1; Figure 8 The figure shows the rate performance of the lithium iron phosphate / lithium battery assembled with the g-C3N4 modified thin layered inorganic solid electrolyte membrane obtained in Example 1.

[0082] In summary, the thin layered inorganic solid electrolyte membrane modified with g-C3N4 obtained in Example 1 of the present invention has low grain boundary resistance, high room temperature ionic conductivity and mechanical strength due to the grain boundary modification effect of g-C3N4, which enables it to exhibit excellent cycle performance and rate performance in the application of all-solid-state lithium batteries.

Claims

1. A method for reducing the grain boundary resistance of an oxide inorganic solid electrolyte, characterized in that: The oxide inorganic solid electrolyte membrane is prepared by the following method: 1) Preparation of oxide inorganic solid electrolyte two-dimensional nanosheet dispersion; 2) stacking the oxide inorganic solid electrolyte two-dimensional nanosheets in the dispersion in step 1) on the base film to form a layered framework; 3) introducing the precursor solution of g-C3N4 into the layered framework obtained in step 2); 4) calcining the product of step 3) under an inert atmosphere to obtain a layered oxide inorganic solid electrolyte membrane with an in-situ grown g-C3N4 modified layer; In step 1), sucrose is used as a structure-directing agent for sintering to prepare an oxide inorganic solid electrolyte sheet framework, which is then dispersed into acetonitrile or ethanol solvent by ultrasonication, and then centrifuged to obtain an oxide inorganic solid electrolyte two-dimensional nanosheet dispersion; In step 2), the oxide inorganic solid electrolyte two-dimensional nanosheet dispersion is stacked on the base film by filtration or spraying to obtain a layered framework, and then dried under an inert atmosphere for 24-48 hours to obtain a layered framework; In step 3), the uniform dispersion of the g-C3N4 precursor in an organic solvent is vacuum filtered into the layered framework of step 2).

2. The method for reducing the grain boundary resistance of an oxide inorganic solid electrolyte according to claim 1, wherein: In step 3), the precursor of g-C3N4 is one of cyanamide, urea or melamine, and the amount of g-C3N4 introduced is 8%-12% of the mass of the inorganic solid electrolyte two-dimensional nanosheets based on cyanamide.

3. The method for reducing the grain boundary resistance of an oxide inorganic solid electrolyte according to claim 2, wherein: In step 3), the filtration pressure is 1-5 MPa.

4. The method for reducing the grain boundary resistance of an oxide inorganic solid electrolyte according to claim 1, wherein: In step 1), the oxide inorganic solid electrolyte sheet framework is dispersed in acetonitrile or ethanol solvent, ultrasonicated at 50-100 kHz for 10-30 minutes to break the layered framework, and then centrifuged at 2000-3000 r / min for 20-30 minutes to finally obtain an oxide inorganic solid electrolyte two-dimensional nanosheet dispersion.

5. The method for reducing the grain boundary resistance of an oxide inorganic solid electrolyte according to claim 4, wherein: The concentration of the oxide inorganic solid electrolyte two-dimensional nanosheet dispersion is 0.2-0.5 g / L, and the thickness of the layered framework obtained by using 200-1000 mL of the dispersion is 20-100 μm.

6. The method for reducing the grain boundary resistance of an oxide inorganic solid electrolyte according to claim 1, wherein: In step 4), a thin layered inorganic solid electrolyte membrane with an in-situ grown g-C3N4 modified layer is obtained by sintering at 520°C for 3-5 h in a nitrogen atmosphere.

7. The layered inorganic solid electrolyte membrane obtained by the method according to any one of claims 1 to 6, characterized in that The thickness of the film is 30-100 μm.

8. Use of the layered inorganic solid electrolyte membrane according to claim 7 in an all-solid-state lithium battery.

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