Wireless Chemical Charging of a Metal-Ion Battery by Magnetic Particles

The state-of-the-art battery performance is often limited by the cathode, and consequently, expanding the storage metrics often requires a heavy cathode. Since charge is stored within the bulk of the electrodes in most batteries, energy/power trade-off is one of their classical challenges, and alternative cell chemistries that avoid these drawbacks are highly sought after. We demonstrate an ultra-high-capacity metal-ion battery comprising an acidic aqueous electrolyte with suspended magnetite particles and a hexacyanometallate-based insertion cathode. During discharge, the hexacyanometallate is reversibly reduced, and its original redox state is restored during intermittent periods by wirelessly charging with magnetite particles. Recovery involves sacrificial surface redox of the Fe3+/Fe2+ couple in magnetite particles with the formation of water and re-oxidation of hexacyanometallate. The structural flexibility of the magnetite particles with respect to their oxidation states leads to a high cumulative capacity battery, which offers opportunities for fast and remote charging with minimal power losses.