Preparation And Properties Of ?''-Al₂O₃ Solid Electrolyte Materials

The?"-Al₂O₃ solid electrolyte is used in sodium-sulfur batteries and gas sensors due to its high ionic conductivity,stability and safety.Acting as a dual function of electrolytes and membranes,it has a unique market prospect in energy storage system technology and new energy electric vehicles.However,due to the interface contact problem of the solid electrolyte and the immaturity of the preparation process,its industrial application is limited.In this paper,?-Al₂O₃,??+??-Al₂O₃ and?-AlOOH were used as the aluminum source to synthesize magnesium-stabilized?"-Al₂O₃ powder.The?"-Al₂O₃ solid electrolyte was prepared by hot pressing sintering with a higher content of?"phase and a more uniform microstructure of powder.To study the effects of hot pressing sintering temperature,pressure and different content of WO₃ doping on the performance of magnesium-stabilized?"-Al₂O₃solid electrolyte,by X-ray diffraction?XRD?,field emission electron scanning electron microscopy?SEM?,density tester,thermogravimetric differential thermal analysis?TG-DSC?,and electrochemical impedance spectroscopy?EIS?were used to characterize the phase content,relative density,microstructure and ionic conductivity of magnesium-stabilized?"-Al₂O₃ solid electrolyte.This article contains the following three sections:?1?Preparation of magnesium-stable?"-Al₂O₃ powder by solid phase synthesis using different aluminum sources??-Al₂O₃,??+??-Al₂O₃,?-AlOOH?,sodium carbonate and magnesium oxide as raw materials,respectively.The temperature?1100?-1700??was calcined for 2h.Through the calculation of phase content,microstructure,particle size distribution and thermogravimetric analysis,the optimal solid phase method was used to prepare the aluminum source and synthesis temperature of magnesium stabilized?"-A₂O₃powder,whichprovided reference for the industrialproduction of?"-Al₂O₃powder.Experiments show that boehmite??-AlOOH?prepared by hydrothermal treatment of aluminum nitrate nonahydrate and urea at 200? is a good aluminum source,and high-purity?"-Al₂O₃ can be obtained at a lower temperature?1150??.The powder has a?"phase content of 98.2%.Between 1150? and 1600?,the?"phase remains relatively stable,and no?"decomposition occurs.According to the distribution of phase purity and microscopic particle size,it is known that 1200?-1300? is a better synthesis temperature for preparing magnesium stabilized?"-Al₂O₃ powder.?2?Using the?"-A₂O₃ powder with the highest?"phase content and relatively uniform microstructure obtained in the first part?1?,the magnesium stabilized?"-A₂O₃ solid electrolyte was prepared by hot pressing sintering using the powder as a fixed raw material.The effects of sintering temperature?1300?-1500??and pressure?25MPa-45MPa?onthepropertiesofmagnesiumstabilized?"-Al₂O₃solidelectrolytewere investigated.Through the calculation of phase content,bulk density test,microstructure and ionic conductivity,a suitable hot-press sintering process for preparing magnesium-stabilized?"-Al₂O₃ solid electrolyte was obtained.Experiments show that the electrochemical performance of?"-Al₂O₃ solid electrolyte is determined by the combination of phase purity and densification.The temperature sintering is 1400?,and the pressure is 40MPa,which is a good hot pressing sintering parameter.The?"phase content is 98.7%,the relative density is98.0%,the room temperature ionic conductivity is 2.5×10^-4S/cm,and the microscopic particle size is about 1um.?3?By means of the optimal hot pressing sintering process obtained by the optimal?"-Al₂O₃powder obtained in the first part?1?and the second part?2?.Study on the effect of doping amount of WO₃?0.0%-2.0%?on the performance of magnesium stabilized?"-Al₂O₃ solid electrolyte.The optimum doping amount of WO₃ was obtained by calculation of phase content,bulk density test,microstructure and ionic conductivity.Experiments show that the phase content and ionic conductivity of?"-Al₂O₃ solid electrolyte increase first and then decrease with the increase of WO₃ doping amount.The optimal doping amount of WO₃ is1.0%,the?"phase content is 99.0%,the relative density is 98.3%,and the ionic conductivity is 3.7×10^-4S/cm.