新規リチウムイオン伝導性個体電解質の開発

抄録

Lithium-ion Conductive Solid Electrolytes have attracted the particular interest for possible applications as solid electrolyte of lithium ion secondary batteries and many studies for them have been carried out. In recent years, the crystal structures, the ionic conductivity and the dynamics of component ions for a series of compounds MBr-m' Br₃ (M=Li, Cu, Ag ; M'=Al, Ga, In) was investigated and it was found that Li₃InBr₆ is a good lithium ion conductor with high ionic conductivity, α～10^-3 Scm^-1, at 330 K. Because this solid electrolyte, Li₃InBr₆ shows such high conductivity only at high temperature phase, I tried to dope this compound with another element to improve its ionic conductivity in this study. In Li₃InBr₆ doped with divalent cations (M=Mg, Ca, and Ba), the conductivity decreased with x unfortunately, accompanied by a broadening of the ¹¹⁵In NMR spectra. In Li_3-2xSr_xInBr₆(x ≤ 0.7), the conductivity of high temperature phase also decreased with an increase of x but LiSrInBr₆ show almost the same conductivity to Li₃InBr₆. The conductivity of the low temperature phase in Li_3-2xMg_xInBr₆(x ≤ 0.4) increased with x. On the other hand, in the case of the compounds doped with CI ion, Li₃InBr_6-xCl_x, phase transition temperature lowered in the compound of x = 3 and the high ionic conduction phase is stable under the room temperature. Furthermore, the value of the ionic conductivity of the Li₃InBr₃Cl₃ was almost equal to the original Li₃InBr₆.