Surface Al-doping for compromise between facilitating oxygen redox and enhancing structural stability of Li-rich layered oxide

• Surface aluminum (Al) doping is proposed to facilitate the oxygen redox and stabilize the structure of the Li-rich layered oxide. • The covalent Al-O bond improves the reversibility of the oxygen redox and lower the oxygen oxidation potential. • The doped Al 3+ ions inhibit the migration of the transition metal and enhance the structural stability. The Li-rich Mn-based (LMR) layered oxides are regarded as the most promising cathode materials for the next generation high energy-density Li-ion batteries, but suffer from severe capacity decay, sustaining voltage dropping and voltage hysteresis during cycling. Herein surface Al-doping was applied to lower the oxygen oxidation potential and have the surface oxygen reversibly participate in the charge compensation. The doped Al 3+ ions in the Li and/or the transition metal (TM) layer(s) close to the surface of the oxide form covalent Al-O bonds and enhance the structural stability of LMR. Density functional theory calculations demonstrate that surface Al-doping lowers the potential of oxygen oxidation and inhibits the TM migration and the resultant structural degradation. The structural stability and reversible electrochemical reactions of Al-doped LMR were demonstrated by the Raman and XAS spectroscopic studies. The doped oxide delivers a capacity of 305 mAh g − 1 at 0.1C and a coulombic efficiency as high as 91% in the first cycle. Its capacity retention reaches 87% while the average discharge potential decays only 312 mV at 1C in 100 cycles. These findings provide the revelation for utilizing the Al-ions to enhance the reversibility of the oxygen redox and to construct the stable structure for the Li-rich layered cathode materials.