Long‐Range Cation Disorder Enhances Comprehensive Performance in Mn‐Rich Layered Sodium Cathodes

Abstract

AbstractMn‐rich layered oxides (MRLOs) are promising low‐cost cathode materials for sustainable sodium‐ion batteries (SIBs). However, the low Mn4+/Mn3+ redox potential limits their energy densities, and the Jahn‐Teller distortion that occurs surrounding Mn3+ at low voltages destabilizes the structure. Additionally, complex ordered structures inherently present in MRLOs hinder Na+ migration. In this study, new types of cation ordering structures are discovered in common MRLOs. By regulating oxygen vacancy formation, the transition from short‐range to long‐range cation ordering is disrupted, effectively mitigating cooperative Jahn‐Teller distortion and achieving a 95.3% capacity retention over 1 000 cycles at 8 C. The maximum entropy method (MEM) analysis is performed based on neutron diffraction data, which visualizes significantly optimized Na+ diffusion pathways in long‐range disordered cathode with enhanced Na+ diffusion kinetics. Furthermore, the formation of oxygen vacancy elevates the Mn4+/Mn3+ redox potential, resulting in a competitive energy density of 626 Wh kg−1 within 1.5–4.5 V in a half‐cell configuration. This work offers a multiscale approach to precise elucidation of the cathode crystal structure and provides a feasible pathway to optimize sodium‐ion cathodes by disrupting long‐range cation ordering, ultimately facilitating substantial improvements in electrochemical performance.