Provided is a
solid state
electrolyte for a rechargeable
lithium battery, comprising a
lithium ion-conducting
polymer matrix or binder and a
lithium ion-conducting inorganic species dispersed in or chemically bonded by the
polymer matrix or binder, wherein the lithium
ion-conducting inorganic species is selected from a mixture of a
sodium-conducting species or
sodium salt and a lithium-conducting species or lithium salt selected from Li2CO3, Li2O, Li2C2O4, LiOH, LiX, ROCO2Li, HCOLi, ROLi, (ROCO2Li)2, (CH2OCO2Li)2, Li2S, LixSOy, or a combination thereof, wherein X=F, Cl, I, or Br, R=a
hydrocarbon group, x=0-1, y=1-4; and wherein the
polymer matrix or binder is in an amount from 1% to 99% by volume of the
electrolyte composition. Also provided are a process for producing this
solid state
electrolyte and a lithium secondary battery containing such a
solid state electrolyte.