Selenium-impregnated hollow carbon microspheres as efficient cathode materials for lithium-selenium batteries

Se-impregnated hollow carbon (C-Se) microspheres were studied as cathode materials for Li-Se batteries. Hollow carbon microspheres containing micro- and mesopores were prepared by SnO₂ leaching in the core-shell-structured SnO₂@C composite microspheres prepared by one-pot spray pyrolysis. The mean size of the empty cores and the mean shell thickness of the hollow carbon microspheres were 490 and 90 nm, respectively. Metallic Se was impregnated into the hollow carbon microspheres by vapor inclusion. The Se content in the C-Se microspheres was measured by thermogravimetric analysis (TGA) to be 59.5 wt%. The discharge capacities of the C-Se microspheres in the 2nd and 1,000^th cycles at a constant current density of 0.5 A g⁻¹ were 603 and 525 mA h g⁻¹, respectively, and the capacity retention measured from the 2nd cycle was 87%. The capacity retention of the C-Se microspheres measured from the 10th cycle was almost 100%. The structural stability of the C-Se composite microspheres during repeated Li-insertion and desertion process resulted in excellent Li-ion storage performance.