Synthesis Process of CoSeO Microspheres for Unordinary Li-ion Storage Performances and Mechanism of Their Conversion Reaction with Li ions.

Multicomponent materials with various double cations have been studied as anode materials of lithium-ion batteries (LIBs). Heterostructures formed by coupling different-bandgap nanocrystals enhance the surface reaction kinetics and facilitate charge transport because of the internal electric field at the heterointerface. Accordingly, metal selenites can be considered efficient anode materials of LIBs because they transform into metal selenide and oxide nanocrystals in the first cycle. However, few studies have reported synthesis of uniquely structured metal selenite microspheres. Herein, synthesis of high-porosity CoSeO microspheres is reported. Through one-pot oxidation at 400 °C, CoSe -C microspheres formed by spray pyrolysis transform into CoSeO microspheres showing unordinary cycling and rate performances. The conversion mechanism of CoSeO microspheres for lithium-ion storage is systematically studied by cyclic voltammetry, in situ X-ray diffraction and electrochemical impedance spectroscopy, and transmission electron microscopy. The reversible reaction mechanism of the CoSeO phase from the second cycle onward is evaluated as CoO + xSeO + (1 - x)Se + 4(x + 1)Li + 4( x + 1)e ↔ Co + (2x + 1)Li O + Li Se. The CoSeO microspheres show a high reversible capacity of 709 mA h g for the 1400th cycle at a current density of 3 A g and a high reversible capacity of 526 mA h g even at an extremely high current density of 30 A g .