Dual-functional urea induced interface reaction enables the improved cycling stability of cation-disordered Li_1.2Ti_0.4Mn_0.4O₂ cathode

Cation-disordered rocksalt (DRX) oxides show promise as lithium-ion battery cathodes due to their high theoretical capacity derived from anionic redox. However, the challenges of poor anionic redox reversibility, causing oxygen loss and voltage hysteresis, lead to rapid capacity decay. This study employs a dual-functional urea treatment on Li_1.2Ti_0.4Mn_0.4O₂ DRX cathodes, generating oxygen vacancies in the subsurface and a protective carbon nitride layer on the surface through interface reactions. Characterization via X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy confirms these alterations. The presence of oxygen vacancies reduces the average Mn valence, increasing the capacity contributed by Mn and enhancing the reversibility of anionic oxygen redox, thus curbing oxygen loss. Additionally, the carbon nitride layer curtails the parasitic reaction between active oxygen species and the electrolyte. Urea-treated Li_1.2Ti_0.4Mn_0.4O₂ exhibits enhanced electrochemical performance, retaining a higher capacity (151 mAh⋅g⁻¹, 80.3% of capacity retention) after 50 cycles compared to neat Li_1.2Ti_0.4Mn_0.4O₂ (117 mAh⋅g⁻¹, 64.6% retention). Furthermore, the treatment improves lithium-ion diffusion and rate capability. This dual-functional urea approach presents a promising strategy for enhancing DRX cathode materials and advancing high-performance lithium-ion batteries.