Pyrite FeS2@C nanorods as smart cathode for sodium ion battery with ultra-long lifespan and notable rate performance from tunable pseudocapacitance

Sodium ion batteries (SIBs) are a promising replacement for the widely prevalent Li-ion batteries (LIBs) as an efficient energy storage technology. Development of electrode materials with high energy density and high power density is the key to achieving high performance SIBs. Here, we demonstrate a high-capacity and high-rate SIB cathode which is made of one-dimensional FeS 2 nanorods, where an extrinsic pseudocapacitance contribution is found and verified by cyclic voltammetry. The carbon coated FeS 2 nanorods exhibit ultra-long lifespan (9000 cycles), high reversible capacity (506.9 mAh g -1 at 500 mA g -1 ), and outsta nding rate capability (140 mAh g -1 at 20 A g -1 ).