An Alternative Charge-Storage Mechanism for High-Performance Sodium-Ion and Potassium-Ion Anodes

The development of suitable electrode materials remains a great challenge for alternative battery technologies such as sodium-ion and potassium-ion batteries; especially with regard to the negative electrode. Herein, Fe-doped CeO 2 (Ce 0.9 Fe 0.1 O 2−δ ), which has very recently been introduced as a new anode material for lithium-ion batteries, is investigated as an insertion-type active material for the negative electrode of these alternative battery technologies, offering high specific capacity and very good rate capability in half-cells and full-cells. The complementary combination of experimental and computational methods allows directly relating the great capacity increase (by about 100%) to the off-centered Fe position and a selective reduction process, thus enabling substantially more sodium and potassium cations to be reversibly de-/inserted.