Heterogeneous interface designing of bimetallic selenides nanocubes for superior sodium storage

Abstract

In a variety of anode materials for sodium ion batteries (SIBs), high theoretical capacity, low cost and abundant transition metal chalcogenides (TMCs) stand out from them. However, critical challenges of SIBs originated from inferior conductivity and severe volume expansion during sodiation/desodiation are still the main obstacles to promote the application of TMCs materials. Thus, the designed bimetallic nanocubes NiSe2/Fe2NiSe4@C with the heterogeneous interface and core-shell structure are prepared by a simple co-precipitation method followed by simultaneous carbonization and selenization. The carbon shell layer not only produces excellent electrical conductivity, but also effectively protects the active material in the core. Meanwhile, the design of nanometer size and reserved space can greatly alleviate the stress and strain caused by the volume expansion. Moreover, the heterogeneous interface with the synergistic effect of bimetal can promote the adsorption of sodium ions and accelerate the conduction of electrons and ions. Bringing these advantages together, the hetero-bimetallic NSe/FNSe@C composite electrode for SIBs exhibits superior rate performance and outstanding cycle stability, which can deliver a high specific capacity of 312 mA h g−1 at 2 A g−1 and the capacity remains more than 95% after 1200 cycles with negligible capacity attenuation of only 0.007% per cycle.