Hydrofluoric Acid Modified Porous Magnesia Fibers as Immobilizing Agent for Molten Electrolyte in Thermal Battery

In this work porous MgO fibers were prepared by a hydrothermal method and modified by the reaction with different amounts of hydrofluoric acid solution. Their composition, morphology and porosity were characterized. Separators for thermal batteries were prepared by mixing of definite amounts of dry electrolyte powder (LiCl:KCl = 45:55 wt%) with MgO powder, pristine porous MgO fiber or hydrofluoric acid modified porous MgO fiber. The electrolyte leakage of the separator using the modified porous fibers as the immobilizing agent is lower than that of the separator using MgO powder or pristine fiber as the immobilizing agent. Moreover, the model cells using the modified porous MgO fiber as the immobilizing agent show longer discharge time and larger specific capacity compared with the model cells using MgO powder or pristine fiber as the immobilizing agent. It can be concluded that porous magnesia fibers modified by hydrofluoric acid are a promising immobilizing agent for electrolyte in thermal batteries. (C) The Electrochemical Society of Japan, All rights reserved.