The Research On Preparation Of Sodium Beta Alumina In Sodium-Sulfur Batteries

The sodium-sulfur battery had been investigated in those years when invented by Ford Company in 1967. The quality of soudium beta alumina (SBA) which is the solid conductor of sodium ion has important influence on sodium-sulfur battery. The conventional synthesis of solid conductor which includes synthesis and sintering in order to obtain dense bodies for use as a solid electrolyte usually requires high temperatures (1873K) and long times (30h). A substantial amount of Na2O may be lost during such high temperature heat treatment, the consequence of which may be deleterious when the electrolyte is used for device application. To overcome this problem, the use of microwave as heating source for the processing of SBA was attempted in the present process.The synthesis of microwave technology is the original method in the present. It has the advantage of heating fast and volume heating, which means that the way of gas escaping was the same with temperature grads. The high density of ceramic material can be obtained. The sodium beta alumina was prepared by the microwave assisting Sol-gel method. The influence of pretreatment temperature, microwave times and the existence of the second heating source of SiC on the components of powder was investigated.The main components of sample were Na₂O·xAl₂O₃ and MgAl₂O₄ when the gel was decomposed at the range of 1073K to 1273K. The phase of Na₂O·xAl₂O₃ is a good microwave absorber whereas the phase MgAl2O4 does not absorb microwave at all. The main components of sample were almost the complex ofβ- Al₂O₃andβ″- Al₂O₃when the gel was decomposed at 1373K. It was calculated that the proportion ofβ″comparing withβphase was 62.9%. The XRD result showed that it was almost MgO stabilizedβ′′- Al₂O₃ when the sample was exposed to microwave oven for 60min. The proportion ofβ″comparing withβwas almost constant as the decomposing temperature developing to 1673K. The grain grew up intensively as the temperature reach up to 1673K. So it was improper to develop temperature at this time. The holding times in microwave oven had intense influence on the component of sample. The proportion ofβ″comparing withβincreases as the holding times prolonged. The existence of the second heating source SiC could shorten the microwave response time for the reason that SiC can absorb microwave intensively.The ionic conductivity of solid electrolyte was tested by electrochemical impedance spectroscopy. The ionic conductivity reaches up to 37.38Ω·cm when the sample was exposed to microwave oven for 60min. The ionic conductivity was higher than the reference for the reason that the microwave distribution of domestic microwave oven was asymmetrical. It was improper to dispose pellets with domestic microwave oven.