| Sodium sulfur battery is a closely watched electrochemical energy storage technology with its superior performance. It gradually attracts the attention of scientists around the world as its system energy conversion efficiency is up to80%, high security and low cost. As a new member of electrochemical energy family, sodium-sulfur battery’s product, on one hand, makes up the crisis triggered by the lack of energy, on the other hand it is a real sense of environmentally as it does not emit any harmful substances, nor will cause the secondary pollution by after using or scrapping. Sodium sulfur battery for energy storage has unique advantages, mainly in the large reserves of raw materials, high energy and power density, long life, subject to site constraints and easy maintenance, etc.Sodium-sulfur battery is different from common battery, which is made of solid electrolyte to separate the two liquid electrode:a central tube made by β"-alumina solid electrolyte separate the inner chamber of molten sodium(melting point is98℃) and the outer chamber of molten sulfur(melting point is119℃), and allow Na+through. Inside the battery, the current is carried by the through of Na+. Therefore,β"-alumina ceramic tube is the critical component of sodium-sulfur battery, which largely affect the quality and life of the battery performance. It must have a high ionic conductivity, long life of ion migration, good fiber structure, mechanical properties and the exact size of the deviation. All these applications ask for high level ceramic tube preparation method. At present, the problems for making ceramic tube are powder synthesis and tube molding.This paper mainly studies the problems exist on the preparation of ceramic powders and powder preparation wafers. Different methods and different raw materials are used to prepare β"-alumina and then find out the most suitable preparation method. Calculate the β"-alumina content with formula by changing the molar ratio of raw materials and calcining temperatures to find out the best conditions to prepare β"-alumina powders. Chemical reactions during calcining process are studied by thermodynamics and DSC curve. Compared the different phenomena of two kinds of powders in preparing P"-alumina ceramic wafers made by pressing and sintering. The results show:1) Using a-alumina and sodium carbonate to produce (3"-alumina powders by solid-state synthesis method is the most suitable method.2) When the calcination temperature is1250℃and the molar ratio of raw materials is about5:1, after calcination the content of β"-alumina is about95%and the impurity only contains β-alumina. Therefore, this the optimum condition for preparing β"-alumina3) The reactions of α-alumina and sodium carbonate occur at1170℃to produce β"-and β-alumina, and β"-alumina is easier to produce than β-alumina; α-alumina is produced again at1360℃mainly due to the volatilize of sodium oxide while makes the decomposition of β"-and β-alumina more easily, and as the content of β"-alumina is much more than that of β-alumina, therefore, the produce of α-alumina is mainly on the decomposition of β"-alumina; β"-alumina transforms into β-alumina at1530℃while sodium aluminate produces as well.4) The calcining process can effectively reduce powder particle size and aggregation; Pressing density of calcined powders is lower than that of non-calcined powders; The density of ceramic wafers prepared by calcined powder has a higher density than the other; The sintering process can reduce of element of Na evaporated from the alumina ceramic during the sintering process. |
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