The present disclosure relates to a composite material of formula (I): (LPS)a(OIPC)b wherein each of a and b is a mass % value from 1% to 99% such that a+b is 100%; (LPS) is a material selected from the group consisting of Li3PS4, Li7P3S11, Li10GeP2S11, and a material of formula (II): xLi2S.yP2S5.(100−x−y)LiX; wherein X is I, Cl or Br, each of x and y is a mass % value of from 33.3% to 50% such that x+y is from 75% to 100% and the total mass % of Li2S, P2S5 and LiX is 100%; and (OIPC) is a salt of a cation and a closo-borane cluster anion.