Solid-state lithium ion electrolytes of lithium potassium element oxide based compounds are provided which contain an anionic framework capable of conducting lithium ions. The element atoms are Ir, Sb, I Nb and W. An activation energy of the lithium potassium element oxide compounds is from 0.15 to 0.50 eV and conductivities are from 10−3 to 22 mS/cm at 300K. Compounds of specific formulae are provided and methods to alter the materials with inclusion of aliovalent ions shown. Lithium batteries containing the composite lithium ion electrolytes are also provided. Electrodes containing the lithium potassium element oxide based materials and batteries with such electrodes are also provided.