Nanoengineering of Ultrathin Carbon-Coated T-Nb2O5 Nanosheets for High-Performance Lithium Storage

Niobium pentoxide (Nb2O5) is a promising anode candidate for lithium-ion batteries due to its high theoretical capacity, excellent rate capability, and safe working potential. However, its inherent low conductivity limits its practical application in fast-charging scenarios. In this work, we develop an ultrathin carbon-coated two-dimensional T-Nb2O5 nanosheet composite (T-Nb2O5@UTC) through a facile solvothermal reaction and subsequent CVD acetylene decomposition. This unique design integrates a two-dimensional nanosheet structure with an ultrathin carbon layer, significantly enhancing electronic conductivity, reducing ion diffusion pathways, and preserving structural integrity during cycling. The T-Nb2O5@UTC electrode demonstrates an impressive specific capacity of 214.7 mAh g−1 at a current density of 0.1 A g−1, maintaining 117.9 mAh g−1 at 5 A g−1, much outperforming the bare T-Nb2O5 (179.6 mAh g−1 at 0.1 A g−1 and 62.9 mAh g−1 at 5 A g−1). It exhibits outstanding cyclic stability, retaining a capacity of 87.9% after 200 cycles at 0.1 A g−1 and 83.7% after 1000 cycles at 1 A g−1. In a full-cell configuration, the assembled T-Nb2O5@UTC||LiFePO4 battery exhibits a desirable specific capacity of 186.2 mAh g−1 at 0.1 A g−1 and only a 1.5% capacity decay after 120 cycles. This work underscores a nanostructure engineering strategy for enhancing the electrochemical performance of Nb2O5-based anodes toward high-energy-density and fast-charging applications.