Facile synthesis of porous Li-rich layered Li[Li_0.2Mn_0.534Ni_0.133Co_0.133]O₂ as high-performance cathode materials for Li-ion batteries

Lithium-rich layered metal oxides have drawn much recent attention due to their high rechargeable capacity of 250-300 mA h g^-1. Herein, we report the synthesis of porous Li[Li_0.2Mn_0.534Ni_0.133Co_0.133]O₂ metal oxide powders using a facile polymer-thermolysis method. X-ray powder diffractometry (XRD) results show that a well-crystallized layered structure was obtained when the calcination temperatures reach 800 °C. Pores in the range of 100-200 nm are observed using scanning electron microscopy (SEM). The porous Li[Li_0.2Mn_0.534Ni_0.133Co_0.133]O₂ synthesized at 850°C shows much superior electrochemical performance to the sample synthesized by the traditional coprecipitation-calcination method, with a high initial coulombic efficiency of 87% and initial discharge capacity of 245.4 mA h g^-1 at 15 mA g^-1 in the voltage window 2-4.6 V. A capacity retention of 81% was obtained after 300 cycles at 300 mA g^-1. The higher capacity and improved rate performance of porous Li[Li_0.2Mn_0.534Ni_0.133Co_0.133]O₂ can be predominantly attributed to enhanced Li⁺ intercalation kinetics resulting from the highly porous structure.