Engineering the architecture and oxygen deficiency of T-Nb2O5-carbon-graphene composite for high-rate lithium-ion batteries

Developing advanced architectures using a cost-effective synthesis strategy is still a challenge for wide-spread commercial application of Nb2O5 in high-power rechargeable lithium-ion batteries (LIBs). Here we report a new two-dimensional (2D) architecture composed of oxygen-vacancy-rich T-Nb2O5 on reduced graphene oxide nanosheet and carbon (2D Nb2O5-C-rGO), which is synthesized via a one-pot hydrolysis route followed by a heat treatment. As an anode for LIBs, the 2D Nb2O5-C-rGO architecture shows excellent rate capability (achieving a capacity of 114 mAh g(-1) at 100 C or 20 A g(-1)) and cycling stability (maintaining a capacity of 147 mAh g(-1) at 5 C for 1,500 cycles and 107 mAh g(-1) at 50 C for 5,000 cycles). Experimental investigations and density functional theory (DFT)-based calculations reveal that the outstanding Li+ storage performance of the 2D Nb2O5-C-rGO electrode is attributed to the enhanced electronic conductivity facilitated by the C-rGO electronic network and fast Li+ migration within small Nb2O5 grains enhanced by in-situ formed lattice oxygen vacancies, which alter the Nb d band structure and Li+ interaction. This work results in an anode with advanced architecture for fast Li+ storage and provides more insight into the energy storage mechanism in the Nb2O5-based carbonaceous composite electrodes.