High-valence Sb doping stabilizes lithium-rich layered oxides and facilitates lithium-ion transport

High-valence Sb 5+ doping mitigates oxygen loss and transition-metal migration. • Enlarged Li-layer spacing and reduced cation mixing favor Li + migration. • 3.Sb 5+ helps preserve the Li 2 MnO 3 -like superlattice during cycling. The pursuit of higher-energy lithium-ion batteries has brought lithium-rich manganese-based layered oxides to the forefront owing to their high theoretical capacities. However, the practical application is impeded by structural instability, transition metal (TM) migration, and sluggish Li⁺ diffusion kinetics during high-voltage cycling. To address these issues, a lattice-level strategy based on pentavalent antimony (Sb⁵⁺) doping is employed. Sb⁵⁺ incorporation helps stabilize the layered framework by enhancing the local Sb-O/TM-O bonding environment and mitigates oxygen-related structural degradation. Concurrently, the expanded Li-layer spacing and reduced cation mixing provide more favorable pathways for Li⁺ transport, as supported by GITT analysis. Experimental results demonstrate that the optimized Sb-doped material (denoted S3-LLO) retains 91.9 % of its initial capacity over 100 cycles at 1C and delivers a discharge capacity of 169.7 mAh g⁻¹ at 5C. This work provides insight into mitigating structural degradation and enhancing kinetic properties of Li-rich Mn-based cathodes via high-valence cation doping.