Stabilization effects of Al doping for enhanced cycling performances of Li-rich layered oxides

Despite the promising high energy density, Li-rich layered oxides still suffer from capacity fade and voltage decay during prolonged cycling. Doping could be effective in addressing such problems, but current studies pay less attention on rhombohedral phases. To this end, Al incorporated Li-1.14(Ni0.136Co0.10Al0.03Mn0.544)O-2 oxides are investigated. Rietveld refined X-ray diffraction and transmission electron microscope results, along with electrochemical analyses, prove the substitution of Al for Co as well as its influence mainly on rhombohedral components. With slight capacity decreases, Al doped cathodes attain superior cycling performances, presenting a capacity retention up to 94.7% as compared to 81.7% for the pristine ones after 100 cycles. Most importantly, the fatal voltage decay, is alleviated as well through the obstructed formation of spinel-like phases, which are confirmed by the ex-situ XRD and further estimated by Raman spectra. Additionally, interfaces of Al doped electrodes are also somewhat enhanced as indicated by the electrochemical impedance study. These results suggest a notable stabilization effects on host framework in Li-rich layered oxides through manipulations on rhombohedral phases.