No abstract

Lithium-rich layered oxides always suffer from low initial Coulombic efficiency, poor rate capability and rapid voltage fading. Herein, engineering oxygen vacancies in hierarchically Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 porous microspheres (L@S) is carried out to suppress the formation of irreversible Li 2 O during the initial discharge process and improve the Li + diffusion kinetics and structural stability of the cathode mateiral. As a result, the prepared L@S cathode delivers high initial Coulombic efficiency of 92.3% and large specific capacity of 292.6 mA h g −1 at 0.1 C. More importantly, a large reversible capacity of 222 mA h g −1 with a capacity retention of 95.7% can be obtained after 100 cycles at 10 C. Even cycled at ultrahigh rate of 20 C, the L@S cathode can deliver stable reversible capacity of 153 mA h g −1 after 100 cycles. Moreover, the full cell using L@S as cathode and Li 4 Ti 5 O 12 as anode exhibits a relatively high reversible capacity of 141 mA h g −1 with an outstanding voltage retention of 97% after 400 cycles at a large current density of 3 C. These results may shed light on the improvement of electrochemical performances of lithiumrich layered oxides via the multiscale coordinated design based on atomic defects, microstructure and composition.