Surface modification boosting amorphous vanadium oxides anode toward stable and rapid sodium ion storage

Abstract

Sodium-ion batteries (SIBs) are receiving increasing attention for their flexibility and low cost, showing potential to replace the well-studied lithium-ion batteries (LIBs). Compared to lithium ion, sodium ion possesses larger radius, leading to the volume expansion during insertion/extraction. Therefore, amorphous anode materials with low volume expansion and fast ion diffusion are more suitable for the SIBs. Among them, vanadium-based oxides are regarded as promising alternatives according to their advantages of high theoretical capacity, abundance, and low cost. However, the shortcomings such as poor conductivity, aggregation, and pulverization restrict their development as the anode of SIBs. Herein, the vanadium oxide is modified by graphene sheets, and a VOx/rGO-5 % composite is reported as the anode material for SIBs, which has promising electrochemical performance. The VOx/rGO-5 % anode remains a discharge specific capacity of 185 mAh g−1 over 400 cycles under 0.5 A g−1. Meanwhile, VOx/rGO-5 % anode also exhibits a rate capability of 189 mAh g−1 at 2 A g−1. Moreover, the sodium ion storage kinetics in VOx/rGO-5 % is investigated. This work affirms the possibility of vanadium-based oxides being the anode materials of SIBs.