Electrolyte optimization for enhanced electrode performance in aqueous Zn//WO3 mixed-ion battery

Aqueous electrochemical energy storage has emerged as a low-cost and sustainable technology. Among the diverse array of electrode materials, tungsten trioxide (WO₃) holds promise due to its unique electrochemical properties and environmental compatibility. In this study, we investigate the potential of WO₃ for aqueous energy storage applications, focusing on its performance in different electrolytes, namely, 0.5 M Na₂SO₄, 1.0 M ZnSO₄, and 0.5 M Al₂(SO₄)₃. Electrochemical measurements and density functional theory (DFT) calculations indicate that the charge density of electrolyte cation influences the WO₃ electrode performance. A superior performance is observed in the Al₂(SO₄)₃ electrolyte due to the high charge density of Al³⁺ ions. We further investigate WO₃ as a cathode in the full-cell configuration using Zn metal as an anode and a mixed solution of 1.0 M ZnSO₄ and 0.5 M Al₂(SO₄)₃ as an electrolyte. The mixed-ion Zn//WO₃ battery exhibits high specific energy and good cycling stability, highlighting the feasibility of WO₃ as an electrode for practical aqueous energy storage. Overall, this study provides insights into the electrochemical behavior of WO₃ in aqueous environments and underscores its potential for advancing sustainable energy solutions