Optimizing SnO_{2- x} /Fe₂ O₃ Hetero-Nanocrystals Toward Rapid and Highly Reversible Lithium Storage

Engineering oxygen vacancy and boosting Li₂ O reversibility on oxides-based electrode are of significance but remains a challenge in high-power lithium-ion batteries. Herein, the heterogenous SnO_{2- x} /Fe₂ O_{3- y} nanocrystals are demonstrated with tailorable x and y values enabled by a glucose-assisted spray combustion technique. Density functional theory calculations unveil the SnO_{2- x} /Fe₂ O₃ with a maximum x value has the optimal electronic structure, the metallic Fe generated from Fe₂ O₃ can markedly reduce the free energy to break Li-O bonds for accelerating subsequent delithiation process of Li₂ O. Consequently, the optimized SnO_{2- x} /Fe₂ O₃ exhibits a remarkably enhanced electrochemical reversibility and reaction kinetics. After stabilized by reduced graphene oxide, the hybrid delivers a high reversible specific capacity of 1113 mAh g^-1 with superior rate performance (474 mAh g^-1 at 20 A g^-1 ) and long cycle life (negligible loss after 500 cycles at 5 A g^-1 ), the oxygen vacancy and microstructure are well-maintained after cycles. This work provides the possibilities for skillfully regulating oxygen vacancy and meantime enhancing Li₂ O reversibility.