Preserving the reversibility of oxygen redox to stabilize Li-rich cathodes for long-life and high-energy lithium-ion batteries

A surficial oxygen-regulation strategy is developed for Li-rich cathodes. • A high-entropy perovskite buffer layer stabilizes anionic redox chemistry. • The perovskite layer suppresses irreversible oxygen release. • It mitigates transition metal migration via stable oxygen vacancies. • Modified cathode shows 87% capacity retention after 150 cycles at 0.5C. Li-rich Mn-based layered oxides, of much interest due to ultrahigh specific capacity (over 300 mAh g −1 ) and low cost, have become a promising cathode of Li-ion batteries to fulfil the long-mileage demand of electric vehicles. However, they are still haunted by a critical challenge of severe oxygen release and irreversible phase transition, which consequently results in rapid voltage fade and even triggering the parasitic thermal runaway. Coating on the surface of cathode particles could partially alleviate these issues, while generally falls short in handling oxygen activity and the chemo-physical mobility of the highly reactive oxygen species. Herein, we report a direct regulation strategy of anionic redox chemistry by constructing a high-entropy perovskite buffer layer (Li 0.37 Sr 0.05 La 0.567 ZrO 2.875 F 0.125 ), which was introduced to the surface of Li-rich cathodes to restrain the release of activated surficial lattice oxygen ions by its stable oxygen vacancies and effectively improves the safety performance. Moreover, our results also demonstrates that the cycle life of modified cathodes is prolonged and the voltage fade is slowed compared to the pristine sample. This work demonstrates that stabilizing the highly active surficial oxygenates provides new design principle for high-safe and long-term cycling lithium-ion batteries.