Structural and electrochemical features of (Li2S)x(SiS2)100–x superionic glasses

Abstract

Silicon is easily available and thus its use in solid electrolytes in all-solid-state lithium-ion batteries can reduce the cost of the system. Thus, significant research attention is focused on (Li2S)x(SiS2)100−x glasses as solid electrolytes because they exhibit the highest ionic conductivities among Li ion conducting glasses. However, there is a paucity of details on how Li ions actually travel through an operating device. In the present work, four-probe AC impedance measurements, synchrotron X-ray diffraction experiments, and time-of-flight neutron diffraction experiments were performed using 7Li-enriched (7Li2S)x(SiS2)100−x glasses (x = 40, 50, and 60). We demonstrated the three-dimensional atomic configurations and conduction pathways of Li ions for (7Li2S)x(SiS2)100−x glasses via reverse Monte Carlo (RMC) modeling and bond valence sum (BVS) imaging. Specifically, BVS imaging indicated that the frameworks of the (Li2S)x(SiS2)100−x glasses facilitate high mobility of the conducting Li ions when compared with those of (Li2S)x(GeS2)100−x glasses and (Li2S)x(P2S5)100−x glasses.