Tuning Local Structures for Advanced Single-Crystalline Li-Rich Cathodes

Abstract

Single-crystalline Li-rich layered oxides cathodes (SC-LLOs) have been extensively explored as promising cathodes for advanced lithium-ion batteries due to their prominent mechanical and electrochemical properties. However, the undesirable reactivity and sluggish kinetics of anionic redox chemistry have impeded the realization of long cycle life with high capacity and reversibility. Herein, a local structure regulation strategy is skillfully developed to tune domain distribution and stacking faults of Co-free single-crystalline Li1.2Mn0.6Ni0.2O2 via adjusting the Li incorporation during synthesis, thereby manipulating the oxygen coordination environment and anionic redox behavior. The dispersed Li2MnO3 domains distribution together with mild stacking faults tailor unstable Li-O-Li configuration by promoting their transformation into Li-O-TM configuration, generating interfacial oxygen and decreasing bond angle, contributing to exploit anionic redox activity and reversibility. Additionally, theoretic calculations specifically unveil that local structure adjustment lowers the O 2p band center and increases oxygen vacancy formation energy, effectively suppressing oxygen release. Moreover, the narrowed bandgap and reduced Li+ migration barrier enhance anionic redox kinetics through improved electronic conductivity and ionic diffusivity. Consequently, structurally optimized SC-LLOs outperforms the upgrading discharging capacity, extending cyclic stability and excellent rate performance. This work provides a strategy for designing ultra-stable and high-performance SC-LLOs via through controlled crystallographic defects and domain structure engineering.

Keywords: Single crystalline, Li-rich, domain distribution, anionic redox activity, stacking faults