Ultrafine TiO2 and Nb2O5 Nanoparticles on Reduced Graphene Oxide As Anode Materials for Lithium and Sodium Ion Batteries

Abstract

The potential practical application of electric vehicles and large-scale energy storage system, have prompted extensive research in the development of electrode materials with high performance and high rate capability. Ultrafine TiO2 and Nb2O5 nanocrystals/reduced graphene oxide (TiO2/rGO and Nb2O5/rGO) were prepared by controllable hydrolysis and followed by thermal treatment. First, hydrolysis of titanium or niobium precursor formed amorphous hydroxide thin layer on graphene oxide (GO). After annealing at 450 °C under forming gas, amorphous hydroxide layer converted to TiO2 or Nb2O5 nanocrystals with particle size of around 5 nm or 3 nm, respectively, and GO reduced to rGO with enhanced conductivity. TiO2/rGO and Nb2O5/rGO were demonstrated as promising anode materials for high performance lithium ion batteries and sodium ion batteries. The architecture of ultrafine TiO2 or Nb2O5 nanocrystals anchored on highly conductive rGO network and can not only enhance charge transfer and buffer the volume change during lithiation/delithiation or sodiation/desodiation processes, but also provide more active surface area for lithium or sodium ion storage, resulting in superior rate and cycle performance. Ex situ XPS analysis revealed that the sodium ion storage mechanism in Nb2O5 could be accompanied with Nb5+/Nb4+ redox reaction and the ultrafine Nb2O5 NCs provide more surface area to accomplish the redox reaction.