Solid-state electrolyte interface modification method and all-solid-state sodium battery

Abstract

The present invention relates to a method for modifying a solid electrolyte interface and a all-solid-state sodium battery. First, an inorganic layer is coated on the surface of a sodium-ion solid electrolyte by means of surface coating with an inorganic dispersion liquid, and then reacted with molten metallic sodium to in-situ generate a dense and uniform interface layer on the surface of the solid electrolyte, which can effectively improve the interfacial contact between the sodium-ion solid electrolyte and metallic sodium, improve the cycle stability of the all-solid-state sodium battery, thereby effectively reducing the interfacial impedance between the solid electrolyte and the metallic sodium negative electrode, inhibiting the growth of sodium dendrites, and the assembled symmetric sodium battery and all-solid-state sodium battery have low interfacial impedance and high cycle stability. The interface modification method proposed by the present invention has easily available raw materials, simple operation, low preparation cost, is conducive to large-scale industrial production, can promote the commercial development of the next-generation all-solid-state sodium battery, and has broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of alkali metal solid-state batteries, and particularly relates to a method for modifying a solid electrolyte interface and an all-solid-state sodium battery. Background Art

[0002] Due to the similar physical and chemical properties of sodium and lithium elements and the rich reserve sources, sodium-ion batteries are considered to have great application prospects in the fields of electric motorcycles, low-speed electric vehicles, and large-scale energy storage. However, the safety hazards brought by the flammability and liquid leakage of traditional liquid electrolytes limit the development of sodium-ion batteries. The all-solid-state sodium battery using non-flammable solid electrolytes is considered a feasible method to solve the safety hazards of sodium-ion batteries and achieve higher energy density. Currently, the sodium-ion solid electrolytes studied mainly include inorganic solid electrolytes ( β β-alumina, sodium superionic conductor, sulfide, complex hydride, etc.), polymer solid electrolytes, and composite solid electrolytes (polymer-inorganic solid electrolyte composite, polymer-polymer composite, inorganic solid electrolyte-amorphous glassy electrolyte composite). Among them, inorganic solid electrolytes have been widely developed due to their high ionic conductivity, high mechanical strength, and high stability. However, the poor interface contact between inorganic solid electrolytes and the sodium metal anode leads to high interface impedance, resulting in non-uniform deposition and stripping of sodium at the interface, which in turn induces the growth of sodium dendrites and ultimately leads to battery short circuit.

[0003] Researchers have taken a series of measures to solve the interface problem between inorganic solid electrolytes and sodium metal, especially using modification techniques such as atomic layer deposition (ALD) and magnetron sputtering for surface and interface improvement. Using these techniques can introduce an intermediate layer between sodium metal and inorganic solid electrolytes, changing the sodiumophobicity of the inorganic solid electrolyte surface to sodiophilicity, thereby improving the poor contact between interfaces and reducing the interface impedance. Researchers found that depositing a TiO2 interface layer on the surface of the Na3Zr2Si2PO 12 solid electrolyte by ALD technology can significantly improve the interface contact between sodium metal and the solid electrolyte, and the interface impedance decreases from 1402 Ω cm 2 to 101 Ω cm 2 (J. Mater. Chem. A, 2020, 8, 7828-7835). In addition, researchers also used magnetron sputtering technology to construct Sn on the surface of Na3Zr2Si2PO 12 surface xThe O / Sn interfacial layer also effectively reduces the interfacial impedance, and the assembled symmetric sodium batteries and all-solid-state sodium batteries both achieve high cycling stability (Small Methods, 2021, 5, 2100339). Although the above methods can effectively improve the interfacial contact between metallic sodium and solid electrolytes, the harsh experimental conditions and complex construction processes limit their practical applications. Therefore, it is imperative to explore a simple and efficient interfacial modification method to construct a stable interface between solid electrolytes and metallic sodium anodes, which can not only contribute to further understanding and clarifying the interfacial reaction and interfacial ion conduction mechanisms but also lay a solid technical foundation for the practical development of all-solid-state sodium batteries.

[0004] Chinese Patent CN 111430660 B discloses that SnO2 layers are coated on the Na 3 .4 Zr2Si 2 .4 P 0 .6 O 12 solid electrolyte powder by means of calcination, and then the SnO2-coated Na 3 .4 Zr2Si 2 .4 P 0 .6 O 12 solid electrolyte powder reacts with metallic sodium at 250 °C to prepare a composite sodium anode, and a fast ion conduction network is constructed inside the sodium anode. However, this technology does not involve the interfacial modification method of sodium ion solid electrolytes. Among them, the Na 3 .4 Zr2Si 2 .4 P 0 .6 O 12 composite sodium anode prepared by the reaction of solid electrolyte and molten sodium shows good cycling stability in liquid batteries and does not involve all-solid-state sodium batteries. Summary of the Invention

[0005] The object of the present invention is to provide a method for modifying the interface of solid electrolytes and an all-solid-state sodium battery, which can overcome the defects in the prior art, that is, harsh experimental conditions and complex construction processes must be applied for interface modification to improve the problem of poor contact between sodium ion solid electrolytes and metallic sodium anodes. The present invention first covers an inorganic coating on the surface of inorganic sodium ion solid electrolytes by means of dispersion coating. The coated sodium ion solid electrolytes react with molten metallic sodium to generate a uniform and dense interfacial layer, which can effectively improve the contact between metallic sodium and solid electrolytes. The symmetric sodium batteries and all-solid-state sodium batteries assembled based on this method in the present invention both exhibit low interfacial impedance and high cycling stability.

[0006] The method for modifying the interface of solid electrolytes provided by the present invention includes the following steps:

[0007] 1) Prepare an inorganic sodium-ion solid electrolyte by a high-temperature solid-state or sol-gel method.

[0008] 2) Prepare an inorganic dispersion by ultrasonic and stirring methods. The ultrasonic dispersion time is 5 - 120 min, the magnetic stirrer stirring time is 2 - 6 h, and the mass fraction of the inorganic substance in the dispersion is 100 mg / mL - 500 mg / mL.

[0009] 3) Measure 10 - 100 μL of the inorganic dispersion, and uniformly coat the inorganic substance on the surface of the inorganic sodium-ion solid electrolyte by a dropping method, and dry it at a temperature of 50 - 100 °C for 30 min - 2 h.

[0010] 4) The inorganic sodium-ion solid electrolyte coated with an inorganic substance coating reacts with molten metallic sodium to form a uniform and dense interfacial layer. The reaction temperature is 250 - 300 °C, and the reaction time is 5 - 60 min.

[0011] The sodium-ion solid electrolyte described above is a sodium superionic conductor (NASICON)-type solid electrolyte Na3Zr2Si2PO 12 oxide β -Al2O3 solid electrolyte, or a sulfide Na3PS4 solid electrolyte.

[0012] The inorganic substance is one or a combination of metal fluorides, metal oxides, and metal sulfides. Preferably, SnF2, SnO, or SnS, etc.; the thickness of the coating layer is 10 - 20 μm; optionally, the thickness of the coating layer is 15 μm.

[0013] The dispersion solvent is one or a combination of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, acetone, isopropanol, ethanol, and methanol.

[0014] The coating method includes one or a combination of drop coating and spin coating; the synthesis method of the sodium superionic conductor (NASICON)-type solid electrolyte Na3Zr2Si2PO 12 is specifically as follows: Weigh anhydrous sodium carbonate, calcium oxide, zirconium dioxide, silicon dioxide, and ammonium dihydrogen phosphate according to a stoichiometric ratio of 3.3 : 0.1 : 1.9 : 2 : 1.1, put them into a ball milling tank and mix and ball mill for 6 - 8 h, calcine in a muffle furnace at 1100 °C (in air) for 8 - 10 h, cool naturally and then continue to put it into the ball milling tank and ball mill for 6 - 8 h, and finally press the powder material at a pressure of 20 MPa and sinter at 1200 °C for 8 h. After cooling, the NCZSP solid electrolyte is obtained.

[0015] The present invention provides an interface-modified sodium-ion solid electrolyte obtained by the above modification method, and a symmetrical sodium battery and an all-solid-state sodium battery assembled therefrom.

[0016] The present invention provides a symmetrical sodium battery including: a sodium-ion solid electrolyte with an interfacial layer modification, metallic sodium, a current collector, and a battery case; the all-solid-state sodium battery includes: a sodium-ion solid electrolyte with an interfacial layer modification, metallic sodium, a cathode material, a current collector, and a battery case.

[0017] The cathode material described above is prepared from an active material, a conductive carbon material, a binder, and a dispersing solvent, and the mass ratio of the active material in the electrode is 70-90%; the active material of the cathode material is Na3V2(PO4)3, Na3V2(PO4)2F3, NaCrO2, Na[Ni 0.5 Mn 0.5 O2, Na 2 / 3 MnO2; the conductive carbon material includes one or a mixture of two or more of Ketjen black, acetylene black, superconducting carbon black, carbon fiber, and carbon nanotube in any proportion; the binder is a mixture of one or two or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and styrene-butadiene resin (SBR) in any proportion; the dispersing solvent is one or a combination of N-methylpyrrolidone, N,N-dimethylformamide, ethanol, and methanol.

[0018] The assembly of the all-solid-state sodium battery provided by the present invention includes the following steps:

[0019] 1) Weigh and add an active material (such as Na3V2(PO4)3), a conductive carbon material (such as Ketjen black), and a binder (such as PVDF) into a dispersing solvent (such as N-methylpyrrolidone), and grind for 30 min to obtain a uniformly mixed slurry.

[0020] 2) Uniformly coat the above slurry onto an aluminum foil and dry it in vacuum at 100 °C for 12 h to make a cathode electrode sheet.

[0021] 3) Assemble a metallic sodium sheet, an inorganic sodium-ion solid electrolyte, the cathode electrode sheet, and the battery case into an all-solid-state sodium battery.

[0022] The present invention provides a simple and efficient method for modifying the interface of a sodium-ion solid electrolyte, which effectively improves the problem of poor contact between the sodium-ion solid electrolyte and the metallic sodium anode. The assembled symmetrical sodium battery and all-solid-state sodium battery both exhibit low interfacial impedance and high cycle stability. The interfacial impedance of the symmetrical sodium battery assembled from an unmodified sodium-ion solid electrolyte is as high as 1625 Ω cm 2 , at 0.3 mA cm –2The short - circuit occurred after only 70 h of cycling at a current density of [current density value], and the all - solid - state battery also showed poor cycling stability. However, the interfacial impedance of the symmetric sodium battery assembled with the solid electrolyte modified by SnF2 was reduced to 8 Ω cm 2 , and it could stably cycle for 1000 h at a current density of 0.3 mA cm –2 without short - circuit occurring, and the all - solid - state sodium battery also showed excellent cycling stability.

[0023] The reasons for the excellent electrochemical performance of the solid electrolyte modified by the interface modification (SnF2) in the present invention can be summarized as follows:

[0024] (1) In the present invention, a dense inorganic coating can be constructed on the surface of the sodium - ion solid electrolyte by a simple drop - coating method.

[0025] (2) By reacting the inorganic layer with molten sodium metal, a dense and uniform interfacial layer is constructed between the sodium - ion solid electrolyte and sodium metal, thereby effectively reducing the interfacial impedance, inhibiting the growth of sodium dendrites, and improving the cycling stability of the all - solid - state sodium battery.

[0026] Different from the present invention, CN 111430660 B prepares a composite sodium anode. Among them, the method for modifying the interface of the sodium - ion solid electrolyte is not involved. The Na 3 .4 Zr2Si 2 .4 P 0 .6 O 12 solid electrolyte reacts with molten sodium to prepare a composite sodium anode, which shows good cycling stability in liquid batteries and does not involve all - solid - state sodium batteries. In the present invention, an inorganic coating is directly constructed on the surface of the sodium - ion solid electrolyte and then reacts with molten sodium metal to in - situ generate an interfacial layer on the surface of the solid electrolyte, thereby increasing the interfacial contact between sodium metal and the sodium - ion solid electrolyte, reducing the interfacial impedance, and increasing the cycling stability of the symmetric sodium battery and the all - solid - state sodium battery.

[0027] In summary, the outstanding substantive features of the present invention are as follows:

[0028] (1) The method is simple and efficient, with the prospect of large - scale application. The coating method in CN 111430660 B requires dispersing the solid electrolyte powder in the precursor solution first, and then coating the target substance on the surface of the solid electrolyte through a high - temperature calcination reaction; in the present invention, the target substance is directly coated on the surface of the sodium - ion solid electrolyte by a drop - coating method without an additional calcination process.

[0029] (2) The inorganic-coated sodium solid electrolyte prepared by the present invention reacts with molten metallic sodium, and can form a uniform and dense interfacial layer on the surface of the solid electrolyte. This interfacial layer can effectively improve the interfacial contact between metallic sodium and the sodium solid electrolyte, reduce the interfacial impedance, inhibit the growth of sodium dendrites, and improve the cycle stability of symmetric sodium batteries and all-solid-state sodium batteries.

[0030] (3) The raw materials of the interfacial modification method proposed by the present invention are easily available, the operation is simple, and the preparation cost is low, which is conducive to large-scale industrial production. It can be seen from this that the present invention can promote the commercial development of the next-generation all-solid-state sodium batteries and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 for Na 3.2 Ca 0.1 Zr 1.9 Si2PO 12 XRD pattern of the (NCZSP) solid electrolyte.

[0032] Figure 2 Electrochemical impedance spectrum of the NCZSP solid electrolyte.

[0033] Figure 3 SEM and EDS diagrams of the coating layer formed after NCZSP is coated with SnF2.

[0034] Figure 4 EIS diagrams of the Na / SnF2-NCZSP / Na and Na / NCZSP / Na symmetric sodium batteries.

[0035] Figure 5 for Na / SnF2-NCZSP / Na and Na / NCZSP / Na symmetric sodium batteries at 0.3 mA cm –2 Cyclic performance diagrams at a current density.

[0036] Figure 6 Cyclic performance diagrams of the Na3V2(PO4)3 / SnF2-NCZSP / Na and Na3V2(PO4)3 / NCZSP / Na all-solid-state sodium batteries at a current density of 0.2 C.

[0037] The present invention will be further described in detail below in conjunction with embodiments, but the implementation manners of the present invention are not limited thereto.

[0038] Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0039] Example 1:

[0040] A surface modification method for generating an interfacial layer between NASICON-type solid electrolyte Na 3.2 Ca 0.1 Zr 1.9 Si2PO 12 (NCZSP) and molten sodium metal after coating with SnF2, which improves the poor contact between the solid electrolyte and the sodium metal anode, and assembles a symmetric sodium battery and an all-solid-state sodium battery with high cycle stability performance. The specific operation steps are as follows:

[0041] 1) Prepare the NCZSP solid electrolyte by the high-temperature solid-state synthesis method. Specifically: Weigh anhydrous sodium carbonate (99.99%), calcium oxide (99.90%), zirconium dioxide (99.90%), silicon dioxide (99.90%), and ammonium dihydrogen phosphate (99.99%) according to the stoichiometric ratio of 3.3 : 0.1 : 1.9 : 2 : 1.1. Put the above materials into a ball milling tank and mix and ball mill for 6 h. Calcinate in a muffle furnace at 1100 °C (in air) for 10 h. After natural cooling, continue to put it into the ball milling tank and ball mill for 6 h. Finally, press the powder material at a pressure of 20 MPa and sinter at 1200 °C for 8 h. After cooling, the NCZSP solid electrolyte is obtained. The preparation of such solid electrolytes is not limited to this method. The characterization of the prepared solid electrolyte is as Figure 1 , and the obtained NCZSP is orthorhombic; the electrochemical impedance spectrum of the solid electrolyte is as Figure 2 shown, and its ionic conductivity is 1.46 mS cm –1 .

[0042] 2) Weigh 1 g of SnF2 powder and add it to 5 mL of isopropyl alcohol organic solvent. After ultrasonic dispersion at room temperature for 1 h, stir magnetically for 2 h to prepare a SnF2 isopropyl alcohol dispersion; Use a pipette to measure 50 μL of the SnF2 dispersion, and evenly coat SnF2 on the surface of NCZSP by the dropping method, and dry at 80 °C for 2 h to obtain a SnF2-coated NCZSP solid electrolyte. The SEM image and EDS image of the SnF2-coated solid electrolyte are as Figure 2 shown, and the thickness of the SnF2 coating layer is about 15 μm.

[0043] 3) React 50 mg of molten sodium metal with the SnF2-coated NCZSP solid electrolyte at 230 °C for 5 min, and a uniform and dense interfacial layer (SnF2-NCZSP) is formed on the surface of the NCZSP solid electrolyte.

[0044] 4) Assemble sodium symmetric batteries using the above-mentioned SnF2-NCZSP with an interfacial layer and the unmodified NCZSP solid electrolyte. Assemble them into the battery mold in the order of nickel mesh, metallic sodium, SnF2-NCZSP or NCZSP, metallic sodium, nickel mesh to form a symmetric sodium battery; Assemble the coin-type all-solid-state sodium battery of R2032 in the order of negative electrode case, metallic sodium, SnF2-NCZSP or NCZSP, Na3V2(PO4)3 electrode sheet, gasket, spring piece, positive electrode case. Conduct electrochemical performance characterization on the assembled batteries, and the results are shown in Figures 3 - 5 。

[0045] Figure 1 is the XRD pattern of the NCZSP solid electrolyte, indicating that the prepared NCZSP is orthorhombic phase.

[0046] Figure 2 is the electrochemical impedance spectrum of the NCZSP solid electrolyte. Analysis shows that the ionic conductivity of the prepared NCZSP is 1.46 mS cm –1 。

[0047] Figure 3 are the SEM image and EDS image of the NCZSP coated with SnF2 to form a coating layer. It can be seen that the coating layer is uniform and dense, with a thickness of about 15 μm.

[0048] Figure 4 are the EIS diagrams of the assembled Na / SnF2-NCZSP / Na and Na / NCZSP / Na symmetric batteries. By comparing the data, it can be seen that the interfacial impedance of the symmetric battery assembled with unmodified NCZSP is as high as 1625 Ω cm 2 ,indicating poor interfacial contact between the solid electrolyte and metallic sodium; while the interfacial impedance of the metallic sodium / SnF2-NCZSP / metallic sodium symmetric battery is 8 Ω cm 2 ,indicating that the dense interfacial layer obtained by the reaction of NCZSP coated with SnF2 and molten sodium can effectively improve the interfacial contact between the solid electrolyte and metallic sodium, and significantly reduce the interfacial impedance.

[0049] Figure 5 are the metallic sodium / SnF2-NCZSP / metallic sodium and metallic sodium / NCZSP / metallic sodium symmetric batteries at 0.3 mA cm –2Cycling performance graph at a current density. Through data comparison, it can be seen that the symmetric battery assembled with unmodified NCZSP has severe voltage fluctuations during the cycling test and short-circuits after 70 h of cycling, indicating that the interface contact between unmodified NCZSP and metallic sodium is poor. During the cycling process of the battery, metallic sodium undergoes non-uniform deposition and stripping on the surface of NCZSP, resulting in the formation of sodium dendrites and ultimately triggering short-circuits. However, the symmetric battery assembled with SnF2-NCZSP exhibits excellent cycling stability. At a current density of 0.3 mA cm –2 −2, the symmetric battery can stably cycle for 1000 h and maintain an overpotential below 35 mV, indicating that the dense interface layer obtained by the reaction of NCZSP coated with SnF2 with molten sodium can improve the interface contact, promote the uniform deposition and stripping of sodium at the interface, and effectively inhibit the growth of sodium dendrites.

[0050] Figure 6 are the cycling performance graphs of all-solid-state sodium batteries of metallic sodium / SnF2-NCZSP / Na3V2(PO4)3 and metallic sodium / NCZSP / Na3V2(PO4)3 at a current density of 0.2 C. The all-solid-state sodium battery assembled with SnF2-NCZSP has a discharge specific capacity of 107 mAh g -1 −1 and still has a capacity retention rate of 84% after 100 cycles, and the Coulombic efficiency remains above 99.8% during the cycling process. However, the all-solid-state sodium battery assembled with unmodified NCZSP has poor cycling stability, and the capacity retention rate of the battery is only 44% after 100 cycles. The above results indicate that the interface layer formed by NCZSP solid electrolyte coated with SnF2 and molten metallic sodium can significantly improve the cycling stability of all-solid-state sodium batteries.

[0051] Example 2:

[0052] A surface modification method for generating an interface layer after coating NASICON-type solid electrolyte Na 3.2 Ca 0.1 Zr 1.9 Si2PO 12 (NCZSP) with SnO and then reacting with molten metallic sodium to improve the poor contact between the solid electrolyte and the metallic sodium negative electrode and assemble symmetric sodium batteries and all-solid-state sodium batteries with high cycling stability. The specific operation steps are as follows:

[0053] 1) The NCZSP solid electrolyte was prepared by a high-temperature solid-state synthesis method, specifically as follows: Anhydrous sodium carbonate (99.99%), calcium oxide (99.90%), zirconium dioxide (99.90%), silicon dioxide (99.90%), and ammonium dihydrogen phosphate (99.99%) were weighed according to a stoichiometric ratio of 3.3 : 0.1 : 1.9 : 2 : 1.1. The above materials were placed in a ball-milling tank and ball-milled for 8 h, calcined in a muffle furnace at 1100 °C (in air) for 8 h, naturally cooled, and then placed back in the ball-milling tank and ball-milled for 8 h. Finally, the powdered material was pressed into tablets under a pressure of 20 MPa and sintered at 1200 °C for 8 h. After cooling, the NCZSP solid electrolyte was obtained.

[0054] 2) 1 g of SnO powder was weighed and added to 5 mL of N-methylpyrrolidone organic solvent. After ultrasonic dispersion at room temperature for 30 min, it was magnetically stirred for 2 h to prepare a N-methylpyrrolidone dispersion of SnO. 50 μL of the SnO dispersion was measured with a pipette and uniformly coated onto the surface of NCZSP by the dropping method, and then dried at 80 °C for 2 h to obtain a NCZSP solid electrolyte with SnO coated on its surface. The thickness of the coating layer was about 10 μm.

[0055] 3) 50 mg of molten sodium metal was reacted with the NCZSP solid electrolyte coated with SnO at 230 °C for 10 min, and a uniform and dense interfacial layer (SnO-NCZSP) was formed on the surface of the NCZSP solid electrolyte.

[0056] 4) A sodium symmetric battery was assembled using the above SnO-NCZSP with an interfacial layer and the unmodified NCZSP solid electrolyte. It was assembled into a battery mold in the order of nickel mesh, sodium metal, SnO-NCZSP or NCZSP, sodium metal, nickel mesh to form a symmetric sodium battery; a button-type all-solid-state sodium battery of R2032 was assembled in the order of negative electrode shell, sodium metal, SnO-NCZSP or NCZSP, Na3V2(PO4)3 electrode sheet, gasket, spring piece, and positive electrode shell.

[0057] Example 3:

[0058] A surface modification method for generating an interfacial layer after coating SnS on a NASICON-type solid electrolyte Na 3.2 Ca 0.1 Zr 1.9 Si2PO 12 (NCZSP) and molten sodium metal to improve the poor contact between the solid electrolyte and the sodium metal negative electrode, and assemble a symmetric sodium battery and an all-solid-state sodium battery with high cycle stability performance. The specific operation steps are as follows:

[0059] 1) The NCZSP solid electrolyte was prepared by a high-temperature solid-state synthesis method. Specifically, anhydrous sodium carbonate (99.99%), calcium oxide (99.90%), zirconium dioxide (99.90%), silicon dioxide (99.90%), and ammonium dihydrogen phosphate (99.99%) were weighed according to a stoichiometric ratio of 3.3 : 0.1 : 1.9 : 2 : 1.1. The above materials were put into a ball-milling jar and ball-milled for 8 h, calcined in a muffle furnace at 1100 °C (air) for 8 h, naturally cooled, and then put back into the ball-milling jar for ball-milling for 8 h. Finally, the powder material was pressed into tablets under a pressure of 20 MPa and sintered at 1200 °C for 8 h. After cooling, the NCZSP solid electrolyte was obtained.

[0060] 2) 1 g of SnS powder was weighed and added to 5 mL of N,N-dimethylformamide organic solvent. After ultrasonic dispersion at room temperature for 30 min, it was magnetically stirred for 2 h to prepare a N,N-dimethylformamide dispersion of SnS. 50 μL of the SnS dispersion was measured with a pipette, and SnO was evenly coated on the surface of NCZSP by a dropping method, and then dried at 70 °C for 4 h to obtain a NCZSP solid electrolyte with SnS coated on the surface. The thickness of the coating layer was about 20 μm.

[0061] 3) 50 mg of molten sodium metal was reacted with the NCZSP solid electrolyte coated with SnS at 230 °C for 15 min, and a uniform and dense interfacial layer (SnS-NCZSP) was formed on the surface of the NCZSP solid electrolyte.

[0062] 4) A sodium symmetric battery was assembled using the above SnS-NCZSP with an interfacial layer and the unmodified NCZSP solid electrolyte. It was assembled into a battery mold in the order of nickel mesh, sodium metal, SnS-NCZSP or NCZSP, sodium metal, nickel mesh to form a symmetric sodium battery. A button-type all-solid-state sodium battery of R2032 was assembled in the order of negative electrode shell, sodium metal, SnS-NCZSP or NCZSP, Na3V2(PO4)2F3 electrode sheet, gasket, spring sheet, and positive electrode shell.

Claims

1. A method for modifying a solid electrolyte interface, characterized in that: It includes the following steps: 1) Prepare an inorganic sodium-ion solid electrolyte by a high-temperature solid-phase or sol-gel method; 2) Prepare an inorganic dispersion by ultrasonic and stirring methods. The ultrasonic dispersion time is 5 - 120 min, the magnetic stirring time is 2 - 6 h, and the mass fraction of the inorganic substance in the dispersion is 100 mg / mL - 500 mg / mL; 3) Measure 10 - 100 μL of the inorganic dispersion, and uniformly coat the inorganic substance on the surface of the inorganic sodium-ion solid electrolyte by a dropping method, and dry it at a temperature of 50 - 100 °C for 30 min - 2 h; 4) React the inorganic sodium-ion solid electrolyte coated with an inorganic substance layer with molten metallic sodium to form a uniform and dense interfacial layer. The reaction temperature is 200 - 250 °C, and the reaction time is 5 - 60 min.

2. The method for modifying the solid electrolyte interface according to claim 1, wherein: The solid electrolyte described above is one of sodium superionic conductor (NASICON)-type solid electrolytes, such as Na3Zr2Si2PO 12 , oxides β -Al2O3 solid electrolyte, or sulfide Na3PS4 solid electrolyte 3. The solid electrolyte interface modification method according to claim 1, characterized in that: The inorganic substance is one or a combination of metal fluorides, metal oxides, and metal sulfides.

4. The solid electrolyte interface modification method according to claim 1, wherein: The inorganic substance is SnF2, SnO or SnS; the thickness of the coating layer is 10 - 20 μm.

5. According to the solid electrolyte interface modification method described in claim 1, the solvent of the dispersion is one or a combination of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, acetone, isopropanol, ethanol, and methanol.

6. The solid electrolyte interface modification method according to claim 2, characterized in that: The sodium superionic conductor (NASICON)-type solid electrolyte Na3Zr2Si2PO 12 The synthesis method is as follows: Weigh anhydrous sodium carbonate, calcium oxide, zirconium dioxide, silicon dioxide, and ammonium dihydrogen phosphate according to the stoichiometric ratio of 3.3 : 0.1 : 1.9 : 2 : 1.1, put them into a ball milling tank and mix and ball mill for 6 - 8 h, calcine in a muffle furnace at 1100 °C in an air atmosphere for 8 - 10 h, continue to put it into the ball milling tank for ball milling for 6 - 8 h after natural cooling, finally press the powder material into tablets under a pressure of 20 MPa and sinter at 1200 °C for 8 h, and the NCZSP solid electrolyte can be obtained after cooling.

7. The sodium-ion solid electrolyte with an interface-modified obtained by the modification method described in any one of claims 1 - 6.

8. The fully solid-state sodium battery assembled as claimed in claim 7, comprising: A sodium-ion solid electrolyte with an interfacial layer modification, metallic sodium, a positive electrode material, a current collector, and a battery case.

9. The all-solid-state sodium battery according to claim 8, wherein: The positive electrode material described is prepared from an active material, a conductive carbon material, a binder, and a dispersion solvent. The mass ratio of the active material in the electrode is 70-90%; the active material of the positive electrode material is Na3V2(PO4)3, Na3V2(PO4)2F3, NaCrO2, Na[Ni 0.5 Mn 0.5 O2, Na 2 / 3 MnO2; the conductive carbon material includes one or a mixture of two or more of Ketjen black, acetylene black, super conducting carbon black, carbon fiber, and carbon nanotube in any proportion; the binder is one or a mixture of two or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and styrene-butadiene resin (SBR) in any proportion; the dispersion solvent is one or a combination of N-methylpyrrolidone, N,N-dimethylformamide, ethanol, and methanol.

10. The assembly method of the all-solid-state sodium battery according to claim 9, characterized in that: It includes the following steps: 1) Meter and add an active substance, a conductive carbon material, and a binder into a dispersion solvent and grind for 30 min to obtain a uniformly mixed slurry; 2) Uniformly coat the above slurry on an aluminum foil and vacuum dry it at 100 °C for 12 h to make a positive electrode plate; 3) Assemble a metallic sodium sheet, an inorganic sodium-ion solid electrolyte, the positive electrode plate, and the battery case into an all-solid-state sodium battery.

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