Lithium Deficiencies Engineering in Li-Rich Layered Oxide LiMnNiCoO for High-Stability Cathode.

Li-rich layered oxides have been in focus because of their high specific capacity. However, they usually suffer from poor kinetics, severe voltage decay, and capacity fading. Herein, a long-neglected Li-deficient method is demonstrated to address these problems by simply reducing the lithium content. Appropriate lithium vacancies can improve dynamics features and induce surface spinel coating and nickel doping in the bulk. Therefore, the elaborately designed LiMnNiCoO cathode possesses improved initial Coulombic efficiency, excellent rate capability, largely suppressed voltage decay, and outstanding long-term cycling stability. Specifically, it shows a superior capacity retention of 93.1% after 500 cycles at 1 C (250 mA g) with respect to the initial discharge capacity (193.9 mA h g), and the average voltage still exceeds 3.1 V. In addition, the discharge capacity at 10 C can be as high as 132.9 mA h g. More importantly, a Li-deficient cathode can also serve as a prototype for further performance enhancement, as there are plenty of vacancies.