Synthesis of lithium conducting titanium phosphates by the sol-gel process

Abstract

Abstract The synthesis of solid electrolytes based on titanium and lithium phosphates was studied using the sol-gel method. Particular attention was paid to phosphate precursors, which were mixtures of phosphate mono- and di-esters prepared by solvolysis of P4O10 in isopropanol. Reaction of these precursors with titanium and lithium alkoxides yielded homogeneous gels, and after drying and thermal cleavage of the esters at 300°C, amorphous inorganic products. For the composition corresponding to the stoichiometric formula of a stable compound such as LiTi2(PO4)3, the phase crystallized as early as 550°C by nucleation from the amorphous mixture. Ionic conductivity measured at room temperature was of the order of 10-5 S.cm-1 which increased after heat treatment at higher temperatures. If the composition did not correspond to a stable thermodynamic phase, phase separation occurred, and ionic conductivity decreased between 500°C and 700°C.