This invention concerns an improved PEM for fuel cell applications such that the membrane is more robust. Specifically, this invention provides PEM in MEA systems that have nano-particles carrying proton conducting groups, and improved dimensional stability relative to conductivity. This invention provides a composition of matter for a high proton conductance, solid polymer electrolyte membrane, said membrane comprising: A) a nano-additive carrying proton conducting groups having a size from about 1 nm to about 1,000 run; B) a carrier polymer for the nano-additive of Part A; and C) a proton exchange membrane (PEM) or membrane electrode assembly (MEA) formed by mixing the components of Part A and Part B above. These proton conducting groups are contributed by POSS-based nano-additives or cyclic phosphazene-based nano-additives or small molecules carrying sulfonic acid groups in fuel cells or batteries.