Li ⁺ Solid-State Transport of T-Nb ₂ O ₅ with Nanolayer Al ₂ O ₃

A nanoscale Al2O3 artificial solid electrolyte interface (SEI) was constructed on T-Nb2O5 via a coprecipitation method. By expanding the lattice spacing and optimizing the interfacial structure, the Nb5+/Nb2+ redox reaction was effectively activated, enhancing the lithium storage performance. With an optimal Al2O3 coating (1.5 wt %, ∼1.5 nm thickness), the lattice spacing of the T-Nb2O5 (001) plane increased from 0.39 to 0.42 nm, facilitating smooth Li+ transport. Chemically inert C–Al bonds and dynamically equilibrated Al–F bonds gradually formed on the Al2O3 surface during cycling. These synergistically suppressed further electrolyte decomposition, resulting in a reduced SEI thickness of 6 nm and a decreased interfacial activation energy of 23 kJ mol–1. T-Nb2O5@Al2O3-1.5% delivered a high discharge capacity of 313.2 mAh g–1 after 100 cycles at 0.1 mA cm–2 (0.33C) and 198.1 mAh g–1 after 1000 cycles at 1 mA cm–2, indicating significant improvements in capacity density, rate capability, and cycling stability.