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

CoSe 2 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 CoSe 2 nanoparticles embedded in N-doped carbon matrix with conformal TiO 2 coating (CoSe 2 @NC@TiO 2 ) by using a metal-organic framework-assisted strategy. The small CoSe 2 nanoparticles and N-doped carbon matrix facilitate charge transport and suppress the structural degradation, while the redox-active TiO 2 shell further strengthens the structural and interfacial stability without decreasing the capacity. The as-prepared CoSe 2 @NC@TiO 2 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 CoSe 2 @NC particles without TiO 2 shell.