Faculty of Engineering, Institute for Superconducting & Electronic Materials, University of Wollongong, Wollongong, NSW 2500, Australia.
Department of Chemical and Process Engineering, University of Surrey, Guildford, GU2 7XH, UK.
Angew Chem Int Ed Engl. 2023 Jan 26;62(5):e202213806. doi: 10.1002/anie.202213806. Epub 2022 Dec 22.
The application of Li-rich layered oxides is hindered by their dramatic capacity and voltage decay on cycling. This work comprehensively studies the mechanistic behaviour of cobalt-free Li Ni Mn O and demonstrates the positive impact of two-phase Ru doping. A mechanistic transition from the monoclinic to the hexagonal behaviour is found for the structural evolution of Li Ni Mn O and the improvement mechanism of Ru doping is understood using the combination of in operando and post-mortem synchrotron analyses. The two-phase Ru doping improves the structural reversibility in the first cycle and restrains structural degradation during cycling by stabilizing oxygen (O ) redox and reducing Mn reduction, thus enabling high structural stability, an extraordinarily stable voltage (decay rate <0.45 mV per cycle), and a high capacity-retention rate during long-term cycling. The understanding of the structure-function relationship of Li Ni Mn O sheds light on the selective doping strategy and rational materials design for better-performance Li-rich layered oxides.
富锂层状氧化物的应用受到其在循环过程中容量和电压急剧衰减的阻碍。本工作全面研究了无钴 LiNiMnO 的机理行为，并证明了两相 Ru 掺杂的积极影响。通过原位和事后同步辐射分析的结合，发现 LiNiMnO 的结构演化存在从单斜到六方行为的机理转变，并且理解了 Ru 掺杂的改善机制。两相 Ru 掺杂提高了第一个循环中的结构可逆性，并通过稳定氧（O）氧化还原和减少 Mn 还原来抑制循环过程中的结构降解，从而实现了高结构稳定性、异常稳定的电压（衰减率<0.45 mV/循环）和长期循环中高容量保持率。对 LiNiMnO 结构-功能关系的理解为更好性能的富锂层状氧化物的选择性掺杂策略和合理材料设计提供了思路。
