Engineering nanoscale Ni3Se4/CoSe2/NC heterostructures with rigid construction for sodium ion storage

Engineering transition bimetallic selenide heterostructures could effectively accelerate charge transfer and promote reaction kinetics for the anode materials in sodium ion batteries. Especially, the nanoscale heterointerfaces with abundant grain boundaries could provide tremendous active sizes with enhanced capacity. However, constructing homogeneous nanoscale heterostructures with rigid framework upon cycling remains a huge challenge because of the severe cracking and aggregation of the nanoscale heterostructures during cycling. In this regard, nanoscale Ni3Se4/CoSe2 heterostructures within the nitrogen doped carbon networks (denoted as Ni3Se4/CoSe2/NC) is rationally designed in this work. The nitrogen doped carbon greatly boosts the electronic conductivity and effectively mitigates the agglomeration and volumetric alteration of Ni3Se4/CoSe2, thereafter guaranteeing the structural stability of heterostructured Ni3Se4/CoSe2 nanoparticles. As a proof-of-concept, the electrochemical behavior of the Ni3Se4/CoSe2/NC is largely improved, when compared with bare Ni3Se4/CoSe2 and carbon-encapsulated Ni3Se4/CoSe2 (Ni3Se4/CoSe2@NC). DFT calculations confirms the built-in electric field in the interface of Ni3Se4/CoSe2 which enhances charge carrier transport and promoting reaction kinetics. As expected, the Ni3Se4/CoSe2/NC exhibits the most excellent performance in SIBs, providing a high reversible capacity of 605.7 mA h g−1 at 0.1 A g−1 and 205 mA h g−1 at 5 A g−1.