Designing a High-Power Sodium-Ion Battery by in Situ Metal Plating

Sodium-ion batteries represent a drop-in technology and a more sustainable alternative to lithium-ion batteries, but higher energies and power levels are required to meet the demands for a greener electrification. Here, the design of an anode-free sodium-ion battery is presented, and the performance of the battery is discussed in terms of reduced mass and high power capabilities. The cell consists of an iron hexacyano­ferrate–reduced graphene oxide composite as cathode material, the synthesis of which is tailored to achieve minimal structural defects (3%) and water content. Its high-potential redox couple Fe_LS(C) is stabilized at high current rates, granting the full cell high discharge voltage and power. As negative substrate, a carbon-coated aluminum foil was adopted for in situ plating/stripping of Na metal, showing very small voltage hysteresis up to an applied current of 2 mA/cm². Overall, this simplified full-cell architecture can deliver 340 Wh/kg and 500 W/kg at nominal 1C (= 150 mA/g), retaining 80% of its capacity over 250 cycles, with the possibility of reaching 9000 W/kg at 20C. Bridging the boundaries between batteries and super­capacitors, this research aims to expand the range of possible applications for Na-ion technology.