Highly efficient β-Bi2O3/Bi battery electrodes by reactive annealing from sol-gel precursors

Abstract

The need of achieving low-impact and low-cost functional materials through sustainable and efficient methodologies is one of the goals of the current research in the field of materials science and energy storage. In this study, a new facile route for obtaining battery-like electrode Bi-based films is presented. Specifically, ∼1.3 μm-thick β-Bi₂O₃ films were prepared from oxynitrate via a simple sol-gel/elution process upon titanium foils, followed by annealing in forming gas at 350°C. A multi-technique approach, involving Raman, X-ray Photoelectron Spectroscopy, X-ray Diffraction, Scanning Electron Microscopy and optical characterization, demonstrates the formation of a nanocrystalline porous bismuth oxide (20–30 nm in size) consisting of β-Bi₂O₃ phase with the crucial presence of Bi⁰. Annealing at 350°C in different environments (i.e. air and N₂), do not produce crystalline phases. The reported method improves the synthesis of β-Bi₂O₃ phase through a ∼1.3 μm-thick film realization and a controlled phase production by reactive annealing at moderate temperatures. Cyclic Voltammetry and Galvanostatic Charge Discharge analyses reveal a double-redox behaviour for the β-Bi₂O₃ /Bi⁰ battery electrode with a specific capacity (capacitance) of 195 mA*h/g (350 F/g) at 0.5 A/g. The data highlight the promising usage of sol-gel/elution for the realization of ∼1.3 μm-thick film for energy storage applications.