Fast and Trap-Minimized Li Transport via Size-Mismatch-Driven Cation-Ordering Control in Li-Excess Disordered Rocksalt Cathodes

Li-excess cation-disordered rocksalt (DRX) is considered a promising cathode for lithium-ion batteries owing to its high-energy densities. However, short-range cation ordering (SRCO) commonly arises in DRX cathodes due to local electrostatic interactions and size similarities among cations, resulting in Li-trapping and sluggish Li-transport. Here, we propose that the SRCO suppression in the DRX system can be achieved without complex high-entropy composition by simultaneously tuning electrostatic interactions and the cationic size effect. The incorporation of Ti 4+ into Li–Nb/Mn DRX, being lower-valent and smaller than Nb 5+, weakens high-valence-driven interactions and increases the ionic size mismatch with Li +, thereby promoting Li/TM mixing and energetically disfavoring the SRCO formation. Thus, a low-entropy DRX, Li 1.2 Nb 0.15 Mn 0.55 Ti 0.1 O 2 (LNM-0.1Ti) exhibits significantly enhanced Li + transport, reduced voltage hysteresis, and improved structural stability compared to Li 1.2 Nb 0.2 Mn 0.6 O 2 (LNM) due to disruption of SRCO. LNM-0.1Ti delivers a high capacity of ∼327 mAh g –1 and an energy density of ∼1026 Wh kg –1, outperforming LNM (∼274 mAh g –1, ∼837 Wh kg –1 ). Notably, the higher-Ti composition, Li 1.2 Nb 0.1 Mn 0.5 Ti 0.2 O 2, exhibits reduced rate capability and energy density compared with LNM-0.1Ti, underscoring the importance of compositional balance in optimizing low-entropy DRX performance. These findings highlight a practical strategy for the development of high-performance DRX cathodes.