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

Abstract

Developing advanced architectures using a cost-effective synthesis strategy is still a challenge for wide-spread commercial application of Nb 2 O 5 in high-power rechargeable lithium-ion batteries (LIBs). Here we report a new two-dimensional (2D) architecture composed of oxygen-vacancy-rich T -Nb 2 O 5 on reduced graphene oxide nanosheet and carbon (2D Nb 2 O 5 -C-rGO), which is synthesized via a one-pot hydrolysis route followed by a heat-treatment. As an anode for LIBs, the 2D Nb 2 O 5 -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 Nb 2 O 5 -C-rGO electrode is attributed to the enhanced electronic conductivity facilitated by the C-rGO electronic network and fast Li + migration within small Nb 2 O 5 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 Nb 2 O 5 -based carbonaceous composite electrodes. • A 2D T -Nb 2 O 5 -C-rGO composite anode was synthesized via a cost-effective route. • The architecture and oxygen deficiency were co-engineered by the synthesis route. • High electronic and ionic conductivities were achieved. • The anode delivered a superior rate-capability and stability for Li + storage.