Integrated Surface-to-Bulk Engineering of Li-Rich Mn-Based Cathodes for Reversible Oxygen Redox and Enhanced Interfacial Stability Under Broad-Temperature Conditions.

The pursuit of high-energy-density lithium-ion batteries has established lithium-rich manganese-based layered oxides (LRMs) as compelling cathode candidates. However, their practical application is hindered by irreversible oxygen loss, interfacial degradation, and sluggish reaction kinetics. Notably, kinetic limitations are exacerbated at low temperatures, yet the electrochemical behavior of LRMs under such conditions remains underexplored. Herein, a hierarchical surface-to-bulk engineering strategy integrating an in situ-constructed spinel Li4Ti5O12 interfacial layer, near-surface Ti4+ lattice substitution, and anionic F-doping is developed to simultaneously regulate the surface, near-surface, and bulk regions. The Li4Ti5O12 layer protects the cathode surface against HF corrosion while facilitating Li+ transport; meanwhile, Ti4+ reinforces the oxygen framework through robust Ti─O bonding, and fluorine suppresses transition-metal migration via strong TM─F bonding. As a result, LTO2 achieves a high capacity of 300.85 mAh g-1 at 0.1 C and superior capacity retention of 81.20% after 350 cycles at 1.0 C. The strategy addresses low-temperature kinetic limitations by expanding the lattice parameter, reducing interfacial impedance, and enabling efficient Li+ transport. Consequently, at -20°C, LTO2 delivers 136.70 mAh g-1 and retains 91.80% capacity after 200 cycles at 0.1 C. This work establishes an integrated surface-to-bulk engineering strategy for high-energy-density LRMs under ambient and low-temperature conditions.