Cesium-doped layered Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathodes with enhanced electrochemical performance

Lithium-rich layered cathode materials recently arouse highly attention for the high discharge capacities over conventional cathode materials, but trapped for severe voltage decay, poor cycling stability and inferior rate performance upon cycling. In this work, introducing Cs ions into the Li layer is employed to prepare Cs⁺-doped cathode material Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ via a simple sol-gel method and a subsequent calcination process. The Cs⁺ − doped sample exhibits much enhanced electrochemical performances in comparison with that of pristine sample, especially the rate capability (171.1 mAh g⁻¹ compared to 150.2 mAh g⁻¹ at 5C). Meanwhile, the Cs-doped one reaches an initial discharge capacity of 247.4 mAh g⁻¹ with improved initial Coulombic efficiency of 86.0% at 0.2C rate and outruns for 177.9 mAh g⁻¹ of discharge capacity after 100 cycles at 0.5C. Additionally, it is observed that the Cs⁺- doped sample has a well-defined layered structure and an expanded Li slab space caused by the Cs⁺ accommodation, which provides facile Li⁺ diffusion paths and reduces the energy barrier of the Li⁺ insertion/extraction in the crystal lattice. More importantly, the Cs doping is in favor of stabilizing the crystal structure and meanwhile restraining the decrease of discharge voltage by alleviating the phase transition of layered to spinel structure upon cycling, thus greatly contributing to the better electrochemical performances.