Synthesis of CoSe2 nanoparticles embedded in N-doped carbon with conformal TiO2 shell for sodium-ion batteries

CoSe2 is a potential anode material for sodium-ion batteries in terms of their high sodium storage capacity and tunable properties. However, structural degradation and unstable interphase during the reversible sodiation and de-sodiation lead to fast capacity decay. In this work, we develop a nanocomposite architecture based on CoSe2 nanoparticles embedded in N-doped carbon matrix with conformal TiO2 coating (CoSe2@NC@TiO2) by using a metal-organic framework-assisted strategy. The small CoSe2 nanoparticles and N-doped carbon matrix facilitate charge transport and suppress the structural degradation, while the redox-active TiO2 shell further strengthens the structural and interfacial stability without decreasing the capacity. The as-prepared CoSe2@NC@TiO2 nanocomposite particles deliver a reversible sodium storage capacity of 520 mAh g(-1) at 0.1 A g(-1) with a capacity retention of 78% after 200 cycles, in contrast to the rapid capacity fading after 50 cycles of the pristine CoSe2@NC particles without TiO2 shell.