Effect of the Complexing Agent on the Synthesis of WO3 Nanostructures for Energy Storage Applications

Abstract

Nowadays, energy problems have become one of our society’s biggest challenges and have drawn worldwide attention. Rechargeable lithium-ion batteries (LIBs) are a good option to solve these problems thanks to their high energy density and good cycle stability. However, much effort has recently been devoted to find alternative anode materials and replace graphite in LIBs, like tungsten oxide (WO3) which has attracted much interest as an anode due to its excellent properties. In this work, a simple method is used to synthesize crystalline WO3 nanostructures, with well-defined morphology using an electrochemical procedure known as electrochemical anodization. This method presents several advantages such as being a simple procedure and easy to control its parameters. During the anodization, two different complexing agents (oxygen peroxide and citric acid) were used. The effect of each complexing agent on the anode behaviour of nanostructures in lithium-ion batteries has been evaluated. On the one hand, Field Emission Scanning Electron Microscopy (FE-SEM) has been used to study the morphology of the samples, Raman Spectroscopy technique has been employed to verify the composition and crystallinity of the nanostructures and Electrochemical Impedance Spectroscopy (EIS) was performed to study their electrochemical properties. Finally, the different samples were applied as an anode for energy storage in Li-ion batteries and their specific capacity was evaluated by Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and Charge-Discharge curves. The nanostructures that presented better electrochemical properties and superior behaviour as anode in lithium-ion batteries were those synthesized with H2O2 as a complexing agent. This sample presents lower resistance to charge transfer and better behaviour during the cycling process, their specific capacity values during discharge and charge 318 mAh·g-1 and 310 mAh·g-1, respectively.