Synthesis and electrochemical characterization of Li2S and Li6−xPS5−xCl1+x−yBry (0 ≤ x ≤ 0.7; 0 ≤ y ≤ 1.7) for all-solid-state lithium-ion batteries

The lithium-phosphorus-thiohalides (LPS X ) with superionic conduction are strong candidates for the new-generation solid electrolytes (SEs) in all-solid-state lithium-ion batteries (ASSLIBs). In this work, Li 6− x PS 5− x Cl 1+ x − y Br y (LPSCB; 0 ≤  x  ≤ 0.7; 0 ≤  y  ≤ 1.7) was synthesized by a solid-state method in which the key raw material of Li 2 S was prepared by an improved carbothermal reduction method without late decarbonization. The lattice flexibility and the degree of structural order are opposite effect and would lead to an optimum of the ionic conductivity at a composition of LPSCB. Li 6 PS 5 Br- and Li 5.5 PS 4.5 Br 1.5 -based ASSLIBs had the best rate capacity and cycle performance in Li 6 PS 5 Cl 1− y Br y - (0 ≤  y  ≤ 1) and Li 5.5 PS 4.5 Cl 1.5− y Br y -based ones (0 ≤  y  ≤ 1.5), respectively. To increase the ionic conductivity of LPSCB-type SEs and capacity/cycle performance of the related ASSLIBs, Br-introduction, mutual substitution and excess- X substitution were extremely effective strategies. Graphical