In pursuit of high-energy and safe batteries, researchers are working to replace the common liquid electrolytes with solid ion conductors. Solid polymer electrolytes are promising candidates but often have limited ionic conductivities of < 10-5 S/cm. This conductivity dilemma has persisted since the solid polymer electrolyte concept was proposed in 1978. The team at the University of Maryland overcame this challenge by inventing a disruptive super ion conductor using expanded cellulose derived from tree wood. This super ion conductor yields a record-high ionic conductivity of 1.5×10−3 S/cm (10–100x- improvement), which is a significant step toward bringing solid-state battery technology to the mass market. This expanded cellulose concept could be a paradigm shifting advance for next-generation batteries. The molecular-expanding strategy also allows for a wide range of applications, such as fuel cells.