Synthesis of 3Li2S-1P2S5-xLil solid electrolytes by liquid-phase shaking method for all-solid-state Li metal batteries

3Li(2)S-1P(2)S(5)-xLiI (x = 0, 0.5, 0.9, 1) solid electrolytes were synthesized by liquid-phase shaking methods using ethyl propionate as a reaction medium. The X-ray diffraction results showed that the main phase at both x = 0.9 and 1.0 was Li4PS4I. The highest ionic conductivity at 25 degrees C was 7.8 x 10(-4) S cm(-1) for 3Li(2)S-1P(2)S(5)-0.9LiI (Li6.9P2S8I0.9), although it was 6.4 x 10(-4) S cm(-1) for 3Li(2)S-1P(2)S(5)-1LiI (Li7P2S8I). Despite the lower ionic conductivity of 3Li(2)S-1P(2)S(5)-1LiI (Li7P2S8I), it exhibited a better stability toward Li metal than 3Li(2)S-1P(2)S(5)-0.9LiI (Li6.9P2S8I0.9), indicating that the amount of LiI strongly affects the stability of the electrolyte against Li metal. In addition, 3Li(2)S-1P(2)S(5)-1LiI (Li7P2S8I) was employed in both the cathode composite and separator in the all-solid-state battery in which LiNbO3 coated-LiNi1/3Mn1/3Co1/3O2 and Li were used as cathode and anode, respectively. The all-solid-state battery showed the reversible capacity of approximately 140 mAh g(-1), indicating that 3Li(2)S-1P(2)S(5)-1LiI (Li7P2S8I) solid electrolyte is suitable for an all-solid-state Li metal battery. [GRAPHICS] .