Novel SeS2 doped Li2S-P2S5 solid electrolyte with high ionic conductivity for all-solid-state lithium sulfur batteries

Li2S-P2S5 (LPS) based glass-ceramic electrolytes doped with SeS2 are prepared by a facile high-energy ball milling combined annealing way. The structures, ionic conductivities and electrochemical stabilities of the 70Li2S·(30 − x)P2S5·xSeS2 (x = 0, 0.3, 0.5, 1, 3, 5) glass-ceramic electrolytes are investigated. By combining X-ray powder diffraction (XRD) analysis-refinement and first-principle calculations, it is confirmed that a little amount of SeS2 (x ≤ 1) can be successfully doped into the framework of LPS composite, and as such, the ionic conductivity can be greatly enhanced by the substitution of a part of P2S5 with SeS2. In particular, the 70Li2S·29P2S5·1SeS2 glass-ceramic exhibits the highest conductivity of 5.28 × 10−3 S·cm−1 at 20 °C with a low activation energy of 24.7 kJ·mol−1, and higher electrochemical stability than the original 70Li2S·30P2S5 glass-ceramic. Furthermore, all-solid-state battery assembled based on 70Li2S·29P2S5·1SeS2 electrolyte and sulfur-reduced graphene oxide (S-rGO) composite electrode shows excellent rate capability and cycling stability at low temperatures. Furthermore, electrochemical impedance spectroscopy (EIS) analyses and the cross-section observe by scanning electron microscope (SEM) of all-solid-state lithium-ion batteries reveal that addition of SeS2 into the Li2S-P2S5 electrolyte substrate can decrease the interfacial resistance between the electrodes and solid electrolyte and reduce the production of lithium dendrites. These results indicate that 70Li2S·29P2S5·1SeS2 electrolyte can be served as an effective solid electrolyte for the construction of high performance all-solid-state batteries.