Preparation of Novel Lithium-Ion Conductors Composed of LiSCN-AlCl3 and Silica Particles.

Development of solid-state lithium-ion conducting materials is strongly desired for many kinds of electrochemical applications, such as electrolytes for solid-state lithium batteries, because of the high safety and reliability against inflammability or leakage of electrolytes. A number of performances are required for the lithium-ion solid electrolytes: high ionic conductivity, wide electrochemical window, stability and compatibility against electrodes, high transport number of lithium ions, and so on. For solid-state lithium-ion conductors, a variety of materials, such as polymers, gels, glasses, and crystals, have been widely studied. Solid-state lithium-ion conductor composites consisting of a low-temperature molten salt in the system LiSCN-AlCl{sub 3} and monodispersed silica particles derived from a sol-gel process were prepared. The appearance of the composites changed from viscous liquid to fine powder with the addition of 70 mass % silica particles to the molten salt. The crystallization of the molten salt causing a decrease of conductivity was prevented in a wide temperature range by the addition of silica particles. In spite of the significant change of appearance with the addition of the particles, conductivity of the composites with 70 mass % silica particles was higher than 1 x 10{sup {minus}4}S cm{sup {minus}1}. the conductivity value of the composites wasmore » as high as that of pure molten salt. The ion-transport number of the composites was higher than 0.9999. The value obtained by dividing the dc conductivity using nonblocking electrodes by the ac conductivity was 0.58, indicating that main conducting species was lithium ions.« less