Cesium-doped graphene grown in situ with ultra-small TiO2 nanoparticles for high-performance lithium-ion batteries

Abstract

For applications of lithium-ion batteries (LIBs), to improve the electronic conductivity and the electrochemical kinetics of the electrode material, a novel composite of ultra-small TiO₂ nanoparticles grown in situ on cesium-doped reduced graphene oxide was prepared. The ultra-small TiO₂ nanoparticles (∼7 nm), which were obtained by refluxing in anhydrous ethanol, were evenly distributed on the graphene surface, endowing high reactivity with Li⁺. In particular, doping of graphene with Cs was proposed and was performed in the electrode material of LIBs by a facile method. The electron-doping effect of graphene was proved to increase the electronic conductivity of the composite. Benefiting from these properties, a Cs-doped rGO/TiO₂ (CsGT) electrode displayed good cyclability and particularly outstanding rate capability. The CsGT electrode exhibited a capacity of 163 mA h g⁻¹ at 0.4C after 100 cycles, as well as a capacity of 109 mA h g⁻¹ with a retention of 55.4% when the current density was increased to 20C, which was much better than the performance of control samples. At a current density of 40C, the CsGT electrode exhibited a highly reversible capacity of 70 mA h g⁻¹ after 1000 cycles. The superiority of doping with Cs in comparison with calcination under a reducing atmosphere is carefully discussed via detailed characterization and electrochemical impedance spectroscopy (EIS) analysis.