FeS2@CNT composite with synergistic battery/capacitor builds outstanding sodium-ion storage

Pyrite (FeS2) as one of the most promising anode material candidates for sodium ion batteries suffers from sluggish electrochemical kinetics and large volume expansion, leading to rapid capacity decline and poor rate performance. In this work, ultra-fine FeS2 nanoparticles anchored on carbon nanotube conductive network (FeS2@CNT) were synthesized by one-step pyrolysis combined with solid vulcanization method. On the one hand, the conductive network of CNT not only provides necessary expansion space for FeS2 during the sodiation/desodiation process, but also improves the conductivity of the composites. On the other hand, ultra-fine FeS2 nanoparticle (54 nm) shortens the diffusion paths of Na-ions and triggers the outstanding pseudocapacitance effect. Owing to the synergic effect of battery/capacitor hybrid energy storage, the obtained FeS2@CNT composites exhibit excellent sodium ion storage performance.