The performance of sodium-based energy storage devices can be improved according to methods and devices based on surface-driven reactions between sodium ions and functional groups attached to surfaces of the cathode. The cathode substrate, which includes a conductive material, can provide high electron conductivity while the surface functional groups can provide reaction sites to store sodium ions. During discharge cycles, sodium ions will bind to the surface functional groups. During charge cycles, the sodium ions will be released from the surface functional groups. The surface-driven reactions are preferred compared to intercalation reactions.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made with Government support under Contract DE-AC0576RLO1830 awarded by the U.S. Department of Energy. The Government has certain rights in the invention.