Research On The Preparation Of Na-?"-Al₂O₃ Solid Electrolytes Using Nano-?-Al₂O₃ Powders

Sodium sulfor battery is one of the most promising candidates for electrochemical energy storage technology,Na-?"-Al2O3 solid electrolyte separates the outer chamber of molten sulphur and the inner of molten sodium chamber and allows Na+ through.Inskie the battery,the current is carried by the through of Na+.Therefore,Na-?"-Al2O3 is the key component of sodium sulfur battery,which largely affect the quality and life of the battery performance.The conventional method for Na-?"-Al2O3 synthesis is using commercial a-Al2O3 as the raw materials.However,commercial ?-Al2O3 performs solid state reaction at high sintering temperature,the Na2O evoaporates at high temperature will seriously affect the conductivity of the electrolyte and consume a lot of energy,which is not conducive to industrial production.In this paper,the Na-?"-Al2O3 solid electrolyte was prepared with high active and small size of nano-?-Al2O3 as raw material.The properties of the precusors and solid electrolytes synthesis by solid-state reaction using nano-?-Al2O3,as well as the influence of stabilizer MgO and Li2CO3 were studied.The results demonstrated that:(1)The size of raw material is nanometer,and the main phase group is 96.9%?-Al2O3.nano-?-Al2O3 transformed to ?-Al2O3 at 849.7?,and transformed to?-Al2O3 at 1084.8?,the transition phase alumina is completely converted to a-Al2O3 at 1200?.(2)The content of ?"-Al2O3 in the precursor powders was the highest,which reach 87.26%and a multilayer rhombohedral Na-?"-Al2O3 emerge at 1200?.(3)The content of ?"-Al2O3 in the precursor powders was the highest with the amount of 1.0 wt%MgO,and it showed a multilayer stacked flake structure.(4)The addition of Li2CO3 is not conducive to the synthesis of precursor powders.After adding Li2CO3,the content of ?"-Al2O3 in the precursor powders decreased,and the crystal morphology changed from the regular sheet structure to the floc structure.(5)Under the test conditions,the relative density of the electrolyte materials prepared by the addition of 1.0 wt%MgO was over 95.23%at 1550?,the apparent porosity reached 2.03%,the content of ?"-Al2O3 in the sample is 98.29%,the bending strength of the sample reached 234.26MPa.The conductivity reaches 0.128 s·cm-1 and the conductance activation energy is 0.26eV at 350?.(6)Under the premise of sintering temperature of 1550? and the addition of 1.0 wt%MgO,the relative density of the samples reached 95.09%with the amount of 0.8 wt%Li2CO3;the content of the ?"-Al2O3 was 96.83%;the bending strength is 220MPa,and the ionic conductivity is 0.049 s·cm-1 at 350?.(7)Under the test conditions,the effect of the stabilizer MgO was better than the stabilizer(MgO+Li2CO3),and the comprehensive performance of the solid electrolyte was best with the amount of 1.0 wt%MgO.