Bimetallic selenide heterostructure with directional built-in electric-field confined in N-doped carbon nanofibers for superior sodium storage with ultralong lifespan

Constructing heterostructure is considered as an effective strategy to address the sluggish electronic and ionic kinetics of anode materials for sodium ion batteries (SIBs). However, realizing the orientated growth and uniform distribution of the heterostructure is still a great challenge. Herein, the regulated novel CoSe2/NiSe2 heterostructure confined in N-doped carbon nanofibers (CoSe2/NiSe2@N-C) are prepared by using Co/Ni-ZIF template, in which, the CoSe2/NiSe2 heterostructures realize uniform distribution on a micro level. Benefiting from the unique heterostructure and N-doped carbon nanofibers, the CoSe2/NiSe2@N-C deliveries superior rate capability and durable cycle lifespan with a reversible capacity of 400.5 mA h g−1 after 5000 cycles at 2 A g−1. The Na-ion full battery with CoSe2/NiSe2@N-C anode and layered oxide cathode displays a remarkable energy density of 563 W h kg−1 with 241.1 W kg−1 at 0.1 A g−1. The theoretical calculations disclose that the periodic and directional built-in electric-field along with the heterointerfaces of CoSe2/NiSe2@N-C can accelerate electrochemical reaction kinetics. The in (ex) situ experimental measurements reveal the reversible conversion reaction and stable structure of CoSe2/NiSe2@N-C during Na+ insertion/extraction. The study highlights the potential ability of precisely controlled heterostructure to stimulate the electrochemical performances of advanced anode for SIBs.