Superb high voltage performance of LiCoO2 with structure and surface highly stabilized by co-doping trace Mg and F during one-pot solid-state synthesis

Abstract

Superior high voltage performance of LiCoO2 (LCO) is rarely achieved due to severe structure destruction and side reactions at high voltage. Here, a facile solid-state-reaction strategy via co-doping trace Mg and F ions using MgO and LiF sources is proposed. Trace Mg and F co-doped LCO (LCO-MF) achieves superb rate capability and long-term cycling stability both in half and full cells, such as a capacity of 124 mAh/g at 20 C (1 C = 280 mA/g), a capacity retention of 80.8% after 500 cycles at 4.6 V (1 C) in half cell, and a capacity retention of 92.3% after 2200 cycles at 4.5 V (1 C) in full cell. Mg predominantly pillars and stabilizes the Li channels to promote Li+ transport and phase transitions effectively, especially at high voltages, and F weakens the oxygen repulsion to improve electronic conduction and suppresses the release of oxygen and thus stabilizes the surface, which synergistically stabilizes structure and surface effectively. The strategy of simultaneously enhancing structure reversibility and stabilizing surface for performance improvement of LCO via co-doping and optimizing trace dual cations and anions during one-pot solid-state synthesis is suitable for mass production.