Hierarchically Nitrogen-Doped Carbon Wrapped Ni0.6Fe0.4Se2 Binary-Metal Selenide Nanocubes with Extraordinary Rate Performance and High Pseudocapacitive Contribution for Sodium-Ion Anodes
Because of the considerable theoretical capacity and intrinsic conductivity, transition metal selenides have been considered as advanced electrode materials for sodium-ion batteries (SIBs). However, fast capacity fade and inferior rate performance still impede their large-scale applications. Herein, a hierarchically nitrogen-doped carbon (NC) wrapped binary transition metal selenide (Ni0.6Fe0.4Se2@NC, termed as NFS@NC) nanomaterial derived from polydopamine coated Prussian blue analogs (Ni3[Fe(CN)6]2, Ni-Fe-PBA) was synthesized through low-energy selenization and carbonization process. The Excellent morphology, large surface area, intimate contact of nanoparticles with carbon matrix and better combination of binary metal selenides can achieve outstanding sodium storage performance through their synergy. Notably, the nitrogen-containing organisms are efficiently converted to nitrogen-doped carbon with functional Fe-N-C bonds, facilitating the faster transfer of Na+. As a result, the as-obtained NFS@NC shown superior rate performance (449.3 mA h g−1 at 0.2 A g−1 and 289.5 mA h g−1 at 10 A g−1 ) and stable long-term cyclability (372.4 mA h g−1 after 2000 cycles at 5 A g−1) as anode material for SIBs. Kinetic analysis exhibited that the excellent Na-storage performance of the NFS@NC anode was mainly due to the large pseudocapacitive contribution resulted from the unique nano-multilevel composite structure.