Electrochemical decomposition of Li4SiO4 and Li2TiO3 in solid-state thermal cells

Abstract

Cells of the type Au|Li₄SiO₄|Au and Au|Li₂TiO₃|Au behave as secondary cells at high temperatures, ≳ 400 °C. The cell reactants are created in situ by charging the cells in air at e.g. 1.5 V. Electrochemical decomposition of the solid electrolytes occurs giving, as solid products, Li₂CO₃ at the negative electrode and Li₂SiO₃ and TiO₂, respectively, at the positive electrode. Under different charging conditions other products may be obtained with the Li₂TiO₃-containing cell. The products of charging form as a layer on the surfaces of the pellet and the gold electrodes appear to take no part in the reactions. The charged cells have open-circuit voltages in the range 0.4–0.5 V at ca. 500 °C and give discharge currents of e.g. 10–100 µA through a 10⁴Ω load resistance for several days.