Mechano-chemical Synthesis of Lithium Ion Conducting Materials in the System Li₂O-Li₂S-P₂S₅

Abstract

Amorphous solid electrolytes were prepared in the compositions 75 {(1-x)Li₂O⋅xLi₂S}⋅5P₂S₅ (mol%) by using a high-energy ball-milling process. The amorphous materials showed lithium ion conductivities higher than 10^-3 Sm^-1 at room temperature. The amorphous 7.5Li₂O⋅67.5Li₂S⋅5P₂S₅ (mol%) sample showed the highest lithium ion conductivity σ_298K=2.7×10^-2 Sm^-1 at room temperature among the obtained samples. An all-solid-state battery was assembled by using the amorphous 7.5Li₂O⋅67.5Li₂S⋅5P₂S₅ sample as solid electrolytes. In the battery, TiS₂ and Li_4.4Si were employed as positive and negative electrode materials, respectively. The discharge-charge cycling test of the battery was carried out at room temperature under a constant current density of 64μAcm^-2 with the discharge-charge criteria of voltages 1.1 and 2.6 V. The battery showed successive reversibility with a large specific capacity; the specific capacity calculated on the base of the weight of the TiS₂ positive electrode materials was about 170 mAhg^-1.