Improved Na-beta ''-Al2O3 solid electrolyte, preparation method and application

Abstract

The invention provides an improved Na-beta ''-Al2O3 solid electrolyte, and a preparation method and application thereof, and belongs to the technical field of solid sodium batteries. The invention aims to solve the problem of poor interface contact between sodium anodes of the traditional Na-beta ''-Al2O3 material. The key point of the invention is that a specific element doping strategy is adopted, the doping element is at least one of Mg, Sn, Ga, In, Ti, Pb and Zn, and in-situ alloying is carried out at the interface of the electrolyte and the sodium metal electrode. The alloying process does not need an additional coating or a middle layer, spontaneous formation is achieved in the assembling process, and the interface stability is greatly improved. Results show that the method not only improves the overall performance of the electrolyte, but also ensures the cycling stability and rate capability of the all-solid-state sodium metal battery. The strategy realizes a remarkable progress in the aspect of interface engineering, and provides reliable technical support and theoretical guidance for developing a high-performance sodium ion solid-state battery.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state sodium batteries, and in particular to an improved Na-β″-Al 2 O 3 Solid electrolytes, preparation methods and applications. Background Art

[0002] In the solid electrolyte of solid-state sodium batteries, Na-β″-Al 2 O 3 Due to its wide electrochemical stability window and excellent stability to metallic sodium, it is suitable for high energy density and high voltage applications. However, its practical application still faces significant interfacial contact problems. Na-β″-Al 2 O 3 The poor wettability to sodium makes it difficult to form a stable electrode-electrolyte contact. During the charge-discharge cycle, the interface with the sodium anode is prone to degradation, resulting in an increase in the interface impedance, affecting the overall performance of the battery. In addition, the unstable interface can easily lead to the formation of sodium dendrites, which not only pierce the electrolyte layer and cause a short circuit, but also accelerate the aging of the interface and shorten the battery life.

[0003] Introducing additional coatings or intermediate layers, enhancing interfacial bonding through high temperature treatment, and applying higher mechanical pressure to improve interfacial contact. Although these methods can improve interface stability to a certain extent, they also have obvious limitations. For example, the introduction of additional coatings or intermediate layers increases manufacturing complexity and cost, and may introduce new chemical reaction risks; high temperature treatment limits the choice of materials and increases process difficulty and cost; applying higher mechanical pressure requires higher packaging accuracy and structural strength, limiting its wide application. Therefore, existing interface modification technologies have failed to fundamentally solve the problem, especially in terms of keeping low costs and simplifying processes.

[0004] Therefore, there is an urgent need for a low-cost interface modification technology that can achieve a stable interface under low stacking pressure to solve the above problems. Summary of the invention

[0005] The object of the present invention is to provide an improved Na-β″-Al 2 O 3 Solid electrolyte, preparation method and application, using element doping combined with in-situ alloying technology can significantly improve Na-β″-Al 2 O 3 Interfacial stability between solid electrolyte and sodium anode.

[0006] To achieve the above object, the present invention provides an improved Na-β″-Al 2 O 3Application of solid electrolytes, before assembling the battery, to the improved Na-β″-Al 2 O 3 The solid electrolyte surface is pretreated and then in-situ alloyed by heating and ultrasonic welding;

[0007] Select sodium ferrovanadium phosphate, sodium vanadium phosphate or layered TM oxide (Na x TMO 2 , TM=Fe, Mn, Ni, Co, Cr, Ti, V and their combinations) as the positive electrode, add 5-10 μL electrolyte (NaClO 4 or NaPF 6 Sodium salt and EC / PC / DMC / PC solvent combination) were dropped on the modified Na-β″-Al 2 O 3 On the other side of the solid electrolyte, a solid-state sodium battery is assembled using nickel mesh or shrapnel.

[0008] Preferably, the pretreatment is pickling or heat treatment;

[0009] The acid solution used for pickling is a mixture of one or more of diluted hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid. The acid solution is applied to the improved Na-β″-Al 2 O 3 Solid electrolyte surface 10s-1min;

[0010] The heat treatment temperature is 500-900° C., and the heat treatment time is 1-4 hours.

[0011] Preferably, the heating temperature is 50-80°C.

[0012] Preferably, the frequency of the ultrasonic welding is 40-50 KHz, and the welding time is 30 s-2 min.

[0013] The present invention also provides an improved Na-β″-Al 2 O 3 The method for preparing a solid electrolyte comprises the following steps:

[0014] Step S1: Select Na-β″-Al 2 O 3 Precursor materials, including sodium carbonate, sodium hydroxide, aluminum oxide, aluminum hydroxide;

[0015] Selecting doping materials, including one or a combination of oxides, carbonates or hydroxides of Mg, Sn, Ga, In, Ti, Pb and Zn;

[0016] According to the target molecular formula Na 1+y M x Al 10+z O17 Weigh the corresponding raw materials and mix with Na-β″-Al 2 O 3 Precursor materials are mixed and the materials are uniformly mixed using a ball mill, wherein M is a doping raw material, x is 0-0.67, y is 0-1, and z is 0-1;

[0017] Step S2, preliminarily sintering the mixed powder at a temperature range of 1200-1500° C. for 2-4 hours to obtain a preliminary solid electrolyte precursor;

[0018] Step S3, the powder obtained by ball-milling and drying the preliminary solid electrolyte precursor is pressed to obtain a ceramic green body, and the ceramic green body is placed in a high-temperature furnace for sintering. After the sintering is completed, it is cooled naturally or the cooling rate is controlled according to a predetermined program (2-5°C / min).

[0019] Preferably, for Ga element doping, Na-β″-Al 2 O 3 (Na 1.77 Al 11 O 17 ) and Na-β″-Ga 2 O 3 (Na 1.98 Ga 10.67 O 17 ) preliminary solid electrolyte precursor powder, and then the two are mixed according to Na 1.77 Al (11-n) Ga n O 17 The mixture is ball-milled and pressed into a shape in a ratio of (n=0-1) to obtain a ceramic green body.

[0020] Preferably, in step S1, the rotation speed of the ball mill is 300-1200 r / min, and the ball milling time is 1-12 h.

[0021] Preferably, in step S3, the pressure during the pressing process is 200-300 MPa, and the pressing time is 5-30 min.

[0022] Preferably, in step S3, the sintering temperature is 1400-1600°C.

[0023] The present invention also provides an improved Na-β″-Al 2 O 3 Improved Na-β″-Al prepared by solid electrolyte preparation method 2 O 3 Solid electrolyte.

[0024] Therefore, the present invention adopts the above-mentioned improved Na-β″-Al 2O 3 Solid electrolyte, preparation method and application, the beneficial technical effects are as follows:

[0025] During the battery assembly process, a stable alloy layer is spontaneously formed between the sodium anode and the electrolyte, without the need for additional coatings or intermediate layers, simplifying the manufacturing process and reducing costs. The formed alloy layer significantly enhances the wettability of the electrolyte to sodium, ensures good electrode-electrolyte contact, and reduces interface resistance. At the same time, the stable alloy interface effectively inhibits the formation of sodium dendrites, improving the safety and cycle life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the Na under different sintering conditions in Example 1 1.67 Mg 0.67 Al 10.33 O 17 Solid electrolyte ceramic sheet density;

[0027] Figure 2 The Na in Example 2 was sintered at 1550°C for 2 hours. 1.77 Al 10 GaO 17 SEM and EDS results of solid electrolyte ceramic sheets; among them, Figure 2 (a) in the equation is Na 1.77 Al 10 GaO 17 SEM image of solid electrolyte ceramic sheet; Figure 2 (b) in the equation is Na 1.77 Al 10 GaO 17 EDS results of the corresponding surface distribution of Al element in solid electrolyte ceramics; Figure 2 (c) in the equation is Na 1.77 Al 10 GaO 17 EDS results of the corresponding surface distribution of Na element in solid electrolyte ceramics; Figure 2 (d) in the equation is Na 1.77 Al 10 GaO 17 EDS results of the corresponding surface distribution of Ga element in solid electrolyte ceramics; Figure 2 (e) in the equation is Na 1.77 Al 10 GaO 17 EDS results of the corresponding surface distribution of O element in solid electrolyte ceramics;

[0028] Figure 3 is the Na under different sintering conditions in Example 3 1.67 Mg 0.67 Al 9.33 GaO17 Solid electrolyte ceramic sheet density;

[0029] Figure 4 The Na in Example 3 after sintering at 1550°C for 2h 1.67 Mg 0.67 Al 9.33 GaO 17 SEM and EDS results of solid electrolyte ceramic sheets; among them, Figure 4 (a) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 SEM image of solid electrolyte ceramic sheet; Figure 4 (b) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 EDS results of the corresponding surface distribution of Al element in solid electrolyte ceramics; Figure 4 (c) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 EDS results of the corresponding surface distribution of O element in solid electrolyte ceramics; Figure 4 (d) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 EDS results of the corresponding surface distribution of Ga element in solid electrolyte ceramics; Figure 4 (e) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 EDS results of the corresponding surface distribution of Na element in solid electrolyte ceramics; Figure 4 (f) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 EDS results of the corresponding surface distribution of Mg element in solid electrolyte ceramics;

[0030] Figure 5 The Na in Example 3 after sintering at 1550℃ for different time periods 1.67 Mg 0.67 Al 9.33 GaO 17 Variable temperature ionic conductivity of solid electrolyte ceramic sheets;

[0031] Figure 6 is Na under different sintering conditions in Example 4 1.67 Zn 0.67 Al10.33 O 17 Solid electrolyte ceramic sheet density;

[0032] Figure 7 is Na under different sintering conditions in Example 5 1.67 Pb 0.67 Al 10.33 O 17 Solid electrolyte ceramic sheet density;

[0033] Figure 8 is Na under different sintering conditions in Example 6 1.67 Sn 0.33 Al 10.33 O 17 Solid electrolyte ceramic sheet density;

[0034] Fig. 9 The original Na in Example 7 1.67 Mg 0.67 Al 9.33 GaO 17 Ceramic electrolyte sheet and comparison of C1s, Na 1s after acid treatment and vacuum heat treatment, and comparison of single C1s and Na 1s spectra; Fig. 9 (a) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 Changes in C1s spectra of original, acid-treated, and vacuum-heat-treated; Fig. 9 (b) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 Original C1s spectrum; Fig. 9 (c) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 C1s spectrum after acid treatment; Fig. 9 (d) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 C1s spectrum after heat treatment; Fig. 9 (e) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 Changes in Na 1s spectra of original, acid-treated, and vacuum-heat-treated samples; Fig. 9 (f) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17Original Na 1s spectrum; Fig. 9 (g) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 Na 1s spectrum after acid treatment; Fig. 9 (h) in is Na 1.67 Mg 0.67 Al 9.33 GaO 17 C1s spectrum after heat treatment;

[0035] Fig.10 For the use of Na in Example 8 1.67 Mg 0.67 Al 10.33 O 17 STEM and EDS images of the interface of the button cell assembled with ceramic sheets after cycling; Fig.10 (a) in the equation is Na 1.67 Mg 0.67 Al 10.33 O 17 STEM image of the interface between the ceramic sheet and sodium metal; Fig.10 (b) in the equation is Na 1.67 Mg 0.67 Al 10.33 O 17 EDS results of the corresponding surface distribution of Na element at the interface between ceramic sheet and sodium metal; Fig.10 (c) in the equation is Na 1.67 Mg 0.67 Al 10.33 O 17 EDS results of the corresponding surface distribution of Mg element at the interface between ceramic sheet and sodium metal; Fig.10 (d) in the equation is Na 1.67 Mg 0.67 Al 10.33 O 17 EDS results of the corresponding surface distribution of Al element at the interface between ceramic sheet and sodium metal; Fig.10 (e) in the equation is Na 1.67 Mg 0.67 Al 10.33 O 17 EDS results of the corresponding surface distribution of O element at the interface between ceramic sheet and sodium metal;

[0036] Fig.11 is Na after ultrasonic welding in Example 9 1.67 Mg 0.67 Al 9.33 GaO 17 SEM and line EDS images of the Na interface of the ceramic sheet; Fig.11 (a) is the Na after ultrasonic welding1.67 Mg 0.67 Al 9.33 GaO 17 SEM image of the Na interface of the ceramic sheet; Fig.11 (b) is the Na after ultrasonic welding 1.67 Mg 0.67 Al 9.33 GaO 17 Line EDS image of the Na interface of the ceramic sheet;

[0037] Fig.12 For the use of Na in Example 9 1.67 Mg 0.67 Al 9.33 GaO 17 STEM and EDS images of the interface of ceramic sheet assembled button battery after cycling; Fig.12 (a) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 STEM image of the interface between the ceramic sheet and sodium metal; Fig.12 (b) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 EDS results of the corresponding surface distribution of Al element at the interface between ceramic sheet and sodium metal; Fig.12 (c) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 EDS results of the corresponding surface distribution of Mg element at the interface between ceramic sheet and sodium metal; Fig.12 (d) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 EDS results of the corresponding surface distribution of Na element at the interface between ceramic sheet and sodium metal; Fig.12 (e) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 EDS results of the corresponding surface distribution of Ga element at the interface between ceramic and sodium metal; Fig.12 (f) in the equation is Na 1.67 Mg 0.67 Al 9.33 GaO 17 EDS results of the corresponding surface distribution of O element at the interface between ceramic sheet and sodium metal;

[0038] Fig.13 For the use of Na in Example 9 1.67 Mg0.67 Al 9.33 GaO 17 Ceramic chip assembled button cell at 0.1mA / cm 2 Na deposition and stripping curves of current density cycling;

[0039] Fig.14 For the use of Na in Example 10 1.67 Mg 0.67 Al 9.33 GaO 17 Rate performance of ceramic button cell at 30°C;

[0040] Fig.15 For the use of Na in Example 11 1.67 Mg 0.67 Al 9.33 GaO 17 And Na 1.67 Mg 0.67 Al 10.33 O 17 1C cycle performance of 2032 button cell assembled with ceramic sheets at 30°C. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0042] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0043] Embodiment 1

[0044] A Na 1.67 Mg 0.67 Al 10.33 O 17 Solid electrolyte, using sodium carbonate, magnesium oxide, γ-alumina as raw materials, according to Na 1.67 Mg 0.67 Al 10.33 O 17 Stoichiometric ratio Weigh about 10g, of which Na 2 CO 3 An excess of 7.5% was placed in a 100ml zirconia ball mill, and zirconia grinding balls with a diameter of 3-5mm were added according to a ball-to-material ratio of 6:1, followed by 40ml of anhydrous ethanol. The mixture was ball milled at 300rpm in a planetary ball mill for 12h. After taking it out, it was transferred to an oven for drying for 12h, and then the powder was transferred to an alumina crucible and sintered at 1200℃ for 2h with a heating rate of 5℃ / min. Then the sintering ball milling was repeated twice to obtain Na 1.67 Mg 0.67 Al 10.33O 17 Precursor powder. Add 1wt% PVA124 binder to the precursor powder, pass through a 100-mesh sieve, and press into shape using a mold with a diameter of 8-15mm, and then perform secondary molding using a cold isostatic press with a molding pressure of 300MPa. After taking it out, bury the surrounding area with loose precursor powder to ensure that the surrounding area of ​​the green blank is evenly heated to prevent deformation and compensate for sodium loss at high temperatures. The heating rate is 2℃ / min, and the optimized sintering temperature is 1450-1550℃.

[0045] Figure 1 is the Na under different sintering conditions 1.67 Mg 0.67 Al 10.33 O 17 Density of solid electrolyte ceramic sheets.

[0046] Embodiment 2

[0047] A Na 1.77 Al 10 GaO 17 Solid electrolyte, using sodium carbonate, magnesium oxide, gallium oxide, γ-alumina as raw materials, according to Na 1.77 Al 10 GaO 17 Stoichiometric ratio Weigh about 10g, of which Na 2 CO 3 An excess of 7.5% was placed in a 100ml zirconia ball mill, and zirconia grinding balls with a diameter of 3-5mm were added according to a ball-to-material ratio of 6:1, followed by 40ml of anhydrous ethanol. The mixture was ball milled at 300rpm in a planetary ball mill for 12h. After taking it out, it was transferred to an oven for drying for 12h, and then the powder was transferred to an alumina crucible and sintered at 1200℃ for 2h with a heating rate of 5℃ / min. Then the sintering ball milling was repeated twice to obtain Na 1.77 Al 10 GaO 17 Precursor powder. Add 1wt% PVA124 binder to the precursor powder, pass through a 100-mesh sieve, and press into shape using a mold with a diameter of 8-15mm. Then, perform secondary molding using a cold isostatic press with a molding pressure of 300MPa. After taking it out, cover the surrounding area with loose precursor powder to heat the surrounding area of ​​the green blank evenly to prevent deformation and compensate for sodium loss at high temperatures. The heating rate is 2℃ / min, and the sintering temperature is 1550℃.

[0048] Figure 2 is Na after sintering at 1550℃ for 2h 1.77 Al 10 GaO 17 SEM and EDS results of solid electrolyte ceramic wafer.

[0049] Embodiment 3

[0050] A Na 1.67 Mg 0.67 Al 9.33 GaO 17 Solid electrolyte, using sodium carbonate, gallium oxide, and magnesium oxide as raw materials, according to Na 1.67 Mg 0.67 Ga 10.33 O 17 Stoichiometric ratio Weigh about 10g, of which Na 2 CO 3 The excess was 7.5%, ball milling and sintering were carried out at a temperature of 1280°C for 2h, and the heating rate was 5°C / min. Then the sintering and ball milling were repeated twice to obtain Na 1.67 Mg 0.67 Ga 10.33 O 17 Precursor powder. The precursor powder is mixed with Na 1.67 Mg 0.67 Al 10.33 O 17 The precursor powder is Na 1.67 Mg 0.67 Al 9.33 GaO 17 Mix by ball milling in a metering ratio. Use a mold with a diameter of 8-15mm to press and then use a cold isostatic press for secondary molding at a molding pressure of 300MPa. After taking it out, bury the surrounding area with loose precursor powder to make the surrounding area of ​​the green body evenly heated to prevent deformation and compensate for sodium loss at high temperature. The heating rate is 2℃ / min, and the optimized sintering temperature is 1450-1550℃.

[0051] Figure 3 is the Na under different sintering conditions 1.67 Mg 0.67 Al 9.33 GaO 17 Density of solid electrolyte ceramic sheets.

[0052] Figure 4 is Na after sintering at 1550℃ for 2h 1.67 Mg 0.67 Al 9.33 GaO 17 SEM and EDS results of solid electrolyte ceramic wafer.

[0053] Figure 5 is the Na after sintering at 1550℃ for different time 1.67 Mg 0.67 Al 9.33 GaO 17Variable temperature ionic conductivity of solid electrolyte ceramic sheets.

[0054] Embodiment 4

[0055] A Na 1.67 Zn 0.67 Al 10.33 O 17 Solid electrolyte, using sodium carbonate, zinc oxide, γ-alumina as raw materials, according to Na 1.67 Zn 0.67 Al 10.33 O 17 Stoichiometric ratio Weigh about 10g, of which Na 2 CO 3 An excess of 7.5% was placed in a 100ml zirconia ball mill, and zirconia grinding balls with a diameter of 3-5mm were added according to a ball-to-material ratio of 6:1, followed by 40ml of anhydrous ethanol. The mixture was ball milled at 300rpm in a planetary ball mill for 12h. After taking it out, it was transferred to an oven for drying for 12h, and then the powder was transferred to an alumina crucible and sintered at 1200℃ for 2h with a heating rate of 5℃ / min. Then the sintering ball milling was repeated twice to obtain Na 1.67 Zn 0.67 Al 10.33 O 17 Precursor powder. Add 1wt% PVA124 binder to the precursor powder, pass through a 100-mesh sieve, and press into shape using a mold with a diameter of 8-15mm, and then perform secondary molding using a cold isostatic press with a molding pressure of 300MPa. After taking it out, bury the surrounding area with loose precursor powder to ensure that the surrounding area of ​​the green blank is evenly heated to prevent deformation and compensate for sodium loss at high temperatures. The heating rate is 2℃ / min, and the optimized sintering temperature is 1450-1550℃.

[0056] Figure 6 is the Na under different sintering conditions 1.67 Zn 0.67 Al 10.33 O 17 Density of solid electrolyte ceramic sheets.

[0057] Embodiment 5

[0058] A Na 1.67 Pb 0.67 Al 10.33 O 17 Solid electrolyte, using sodium carbonate, lead oxide, γ-alumina as raw materials, according to Na 1.67 Pb 0.67 Al 10.33 O 17 Stoichiometric ratio Weigh about 10g, of which Na 2 CO 3An excess of 7.5% was placed in a 100ml zirconia ball mill, and zirconia grinding balls with a diameter of 3-5mm were added according to a ball-to-material ratio of 6:1, followed by 40ml of anhydrous ethanol. The mixture was ball milled at 300rpm in a planetary ball mill for 12h. After taking it out, it was transferred to an oven for drying for 12h, and then the powder was transferred to an alumina crucible and sintered at 1200℃ for 2h with a heating rate of 5℃ / min. Then the sintering ball milling was repeated twice to obtain Na 1.67 Pb 0.67 Al 10.33 O 17 Precursor powder. Add 1wt% PVA124 binder to the precursor powder, pass through a 100-mesh sieve, and press into shape using a mold with a diameter of 8-15mm, and then perform secondary molding using a cold isostatic press with a molding pressure of 300MPa. After taking it out, bury the surrounding area with loose precursor powder to ensure that the surrounding area of ​​the green blank is evenly heated to prevent deformation and compensate for sodium loss at high temperatures. The heating rate is 2℃ / min, and the optimized sintering temperature is 1450-1550℃.

[0059] Figure 7 is the Na under different sintering conditions 1.67 Pb 0.67 Al 10.33 O 17 Density of solid electrolyte ceramic sheets.

[0060] Embodiment 6

[0061] A Na 1.67 Sn 0.33 Al 10.33 O 17 Solid electrolyte, using sodium carbonate, magnesium oxide, γ-alumina as raw materials, according to Na 1.67 Sn 0.33 Al 10.33 O 17 Stoichiometric ratio Weigh about 10g, of which Na 2 CO 3 An excess of 7.5% was placed in a 100ml zirconia ball mill, and zirconia grinding balls with a diameter of 3-5mm were added according to a ball-to-material ratio of 6:1, followed by 40ml of anhydrous ethanol. The mixture was ball milled at 300rpm in a planetary ball mill for 12h. After taking it out, it was transferred to an oven for drying for 12h, and then the powder was transferred to an alumina crucible and sintered at 1200℃ for 2h with a heating rate of 5℃ / min. Then the sintering ball milling was repeated twice to obtain Na 1.67 Sn 0.33 Al 10.33 O 17Precursor powder. Add 1wt% PVA124 binder to the precursor powder, pass through a 100-mesh sieve, and press into shape using a mold with a diameter of 8-15mm, and then perform secondary molding using a cold isostatic press with a molding pressure of 300MPa. After taking it out, bury the surrounding area with loose precursor powder to ensure that the surrounding area of ​​the green blank is evenly heated to prevent deformation and compensate for sodium loss at high temperatures. The heating rate is 2℃ / min, and the optimized sintering temperature is 1450-1550℃.

[0062] Figure 8 is the Na under different sintering conditions 1.67 Sn 0.33 Al 10.33 O 17 Density of solid electrolyte ceramic sheets.

[0063] Embodiment 7

[0064] A solid electrolyte surface cleaning treatment method, Na 1.67 Mg 0.67 Al 9.33 GaO 17 After grinding, the ceramic sheet was ultrasonically treated with acetone to remove the grinding residue remaining on the surface. Next, the ceramic sheet was immersed in 0.0001 mol / L hydrochloric acid for 1 min. After that, the surface of the ceramic sheet was wiped dry and heat treated at 900 °C in vacuum for 1 h before being transferred to a glove box.

[0065] Fig. 9 For untreated Na 1.67 Mg 0.67 Al 9.33 GaO 17 Comparison of N1s spectra of ceramic electrolyte sheets after acid treatment and vacuum heat treatment, as well as comparison of individual N1s, Na 1s and Na 1s spectra.

[0066] Embodiment 8

[0067] A method for in-situ alloying of sodium metal with a solid electrolyte. Two identical fresh Na disks with a diameter of 10 mm were manually pressed onto the Na 1.67 Mg 0.67 Al 10.33 O 17 The two sides of the ceramic sheet were then placed on a heating table, set at 50°C, and the Na disk on one side of the ceramic was ultrasonically welded for 2 minutes using a handheld ultrasonic machine. Then nickel foam was placed on both sides as a current collector. Finally, the whole was encapsulated in a 2032 button battery.

[0068] Fig.10 To utilize Na 1.67 Mg 0.67 Al 10.33 O 17STEM and EDS images of the interface of a button cell assembled with ceramic sheets after cycling. It shows that Mg is precipitated on the Na electrode side.

[0069] Embodiment 9

[0070] A method for in-situ alloying of sodium metal with a solid electrolyte. Two identical fresh Na disks with a diameter of 10 mm were manually pressed onto the Na 1.67 Mg 0.67 Al 9.33 GaO 17 The two sides of the ceramic sheet were then placed on a heating table, set at 50°C, and the Na disk on one side of the ceramic was ultrasonically welded for 2 minutes using a handheld ultrasonic machine. Then nickel foam was placed on both sides as a current collector. Finally, the whole was encapsulated in a 2032 button battery.

[0071] Fig.11 Na after ultrasonic welding 1.67 Mg 0.67 Al 9.33 GaO 17 SEM and line EDS images of the Na interface of the ceramic sheet. It can be seen that part of Ga precipitates from the electrolyte to form Na-Ga alloy in situ.

[0072] Fig.12 To utilize Na 1.67 Mg 0.67 Al 9.33 GaO 17 STEM and EDS images of the interface of the ceramic sheet assembled button cell after cycling. It can be clearly seen that Na-Ga alloy is formed on the Na electrode side.

[0073] Fig.13 To utilize Na 1.67 Mg 0.67 Al 9.33 GaO 17 Ceramic chip assembled button cell at 0.1mA / cm 2 Na deposition-stripping curves with current density cycling.

[0074] Embodiment 10

[0075] A solid-state battery assembly method. The positive electrode uses Na 3 V 2 (PO 4 ) 3 , Super P carbon and polyvinylidene fluoride (PVDF) in a weight ratio of 80:10:10. N-methyl-2-pyrrolidone (NMP) was used as the solvent for the slurry preparation. The slurry was then coated on aluminum foil and heated at 120°C in vacuum for 24h. 3 V 2(PO 4 ) 3 The aluminum foil of the active material is cut into discs with a diameter of 10 mm. The mass loading of the active material in the positive electrode is 1-2 mg. Then, the Na plate with the Na plate welded on the other side is 1.67 Mg 0.67 Al 9.33 GaO 17 5uL of liquid electrolyte [1M NaClO 4 in EC / DMC (1:1) + 5% FEC] to ensure good contact between the electrolyte and the ceramic sheet. Subsequently, the prepared positive electrode sheet was carefully placed on the ceramic sheet, and nickel foam was placed on both sides as current collectors. Finally, the whole was encapsulated in a 2032 button battery.

[0076] Fig.14 It uses Na 1.67 Mg 0.67 Al 9.33 GaO 17 Rate performance of ceramic button cell at 30°C.

[0077] Embodiment 11

[0078] A solid-state battery assembly method. The positive electrode uses Na 3 V 2 (PO 4 ) 3 , Super P carbon and polyvinylidene fluoride (PVDF) in a weight ratio of 80:10:10. N-methyl-2-pyrrolidone (NMP) was used as the solvent for the slurry preparation. The slurry was then coated on aluminum foil and heated at 120°C in vacuum for 24h. 3 V 2 (PO 4 ) 3 Aluminum foil of active material, cut into discs with a diameter of 10 mm, the mass loading of active material in the positive electrode is 2-3 mg / cm 2 Then, the Na plate on the other side has been welded. 1.67 Mg 0.67 Al 9.33 GaO 17 And Na 1.67 Mg 0.67 Al 10.33 O 17 5uL of liquid electrolyte [1M NaClO4 in EC / DMC (1:1) + 5% FEC] was added to the ceramic sheet to ensure good contact between the electrolyte and the ceramic sheet. Subsequently, the prepared positive electrode sheet was carefully placed on the ceramic sheet, and nickel foam was placed on both sides as current collectors. Finally, the whole was encapsulated in a 2032 button battery.

[0079] Fig.15 To utilize Na 1.67 Mg 0.67 Al 9.33 GaO 17 And Na 1.67 Mg 0.67 Al 10.33 O 17 The 1C cycle performance of a 2032 button cell assembled with ceramic sheets at 30°C. This indicates that selecting a suitable interface alloying element such as Ga can greatly enhance the cycle performance of the battery.

[0080] It is worth noting that the contents not elaborated in detail in the present invention are all prior art and are well known to those skilled in the art.

[0081] Therefore, the present invention adopts the above-mentioned improved Na-β″-Al 2 O 3 Solid electrolyte, preparation method and application, using element doping combined with in-situ alloying technology can significantly improve Na-β″-Al 2 O 3 Interfacial stability between solid electrolyte and sodium anode.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. Application of improved Na-β″-Al2O3 solid electrolyte, characterized in that: Before assembling the battery, the surface of the improved Na-β″-Al2O3 solid electrolyte was pretreated, and then in-situ alloying was performed by heating and ultrasonic welding. Select sodium ferrovanadium phosphate, sodium vanadium phosphate or layered TM oxide positive electrode, drop the electrolyte on the other side of the improved Na-β″-Al2O3 solid electrolyte, and use nickel mesh or shrapnel to assemble the solid-state sodium battery.

2. The use according to claim 1, characterized in that: The pretreatment is pickling or heat treatment; The acid solution used for pickling is a mixture of one or more of diluted hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, and the acid solution is applied to the surface of the improved Na-β″-Al2O3 solid electrolyte for 10s-1min; The heat treatment temperature is 500-900° C., and the heat treatment time is 1-4 hours.

3. The use according to claim 1, characterized in that: The heating temperature is 50-80°C.

4. The use according to claim 1, characterized in that: The frequency of the ultrasonic welding is 40-50 KHz, and the welding time is 30s-2min.

5. A method for preparing an improved Na-β″-Al2O3 solid electrolyte, characterized in that: The following steps are involved: Step S1, selecting Na-β″-Al2O3 precursor materials, including sodium carbonate, sodium hydroxide, aluminum oxide, and aluminum hydroxide; Selecting doping materials, including one or a combination of oxides, carbonates or hydroxides of Mg, Sn, Ga, In, Ti, Pb and Zn; According to the target molecular formula Na 1+y M x Al 10+z O 17 Weigh the corresponding raw materials, mix them with the Na-β″-Al2O3 precursor material, and use a ball mill to evenly mix the materials, wherein M is the doping raw material, x is 0-0.67, y is 0-1, and z is 0-1; Step S2, preliminarily sintering the mixed powder at a temperature range of 1200-1500° C. for 2-4 hours to obtain a preliminary solid electrolyte precursor; Step S3, the powder obtained by ball-milling and drying the preliminary solid electrolyte precursor is pressed to obtain a ceramic green body, and the ceramic green body is placed in a high-temperature furnace for sintering. After the sintering is completed, it is cooled naturally or the cooling rate is controlled according to a predetermined program.

6. The method for preparing the improved Na-β″-Al2O3 solid electrolyte according to claim 5, characterized in that: For Ga doping, Na-β″-Al2O3(Na 1.77 Al 11 O 17 ) and Na-β″-Ga2O3(Na 1.98 Ga 10.67 O 17 ) preliminary solid electrolyte precursor powder, and then the two are mixed according to Na 1.77 Al (11-n) Ga n O 17 The mixture is ball-milled and pressed into a shape in a ratio of 0.01 to obtain a ceramic green body, wherein n is 0-1.

7. The method for preparing the improved Na-β″-Al2O3 solid electrolyte according to claim 5, characterized in that: In step S1, the rotation speed of the ball mill is 300-1200 r / min, and the ball milling time is 1-12 h.

8. The method for preparing the improved Na-β″-Al2O3 solid electrolyte according to claim 6, characterized in that: In step S3, the pressure during the pressing process is 200-300 MPa, and the pressing time is 5-30 min.

9. The method for preparing the improved Na-β″-Al2O3 solid electrolyte according to claim 7, characterized in that: In step S3, the sintering temperature is 1400-1600°C.

10. An improved Na-β"-Al2O3 solid electrolyte prepared by the method for preparing an improved Na-β"-Al2O3 solid electrolyte according to any one of claims 5 to 9.

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