Galvanostatic charge/discharge curve of Zn||V6O13cell at a current density of 200 mA g−1. The inset is the amplified V-H2O Pourbaix diagram, while the whole diagram is shown in FigureS3, Supporting Information. The red dotted line indicates a pH of 3.5, which is equivalent to the pH of 3mZn(OTf)2. The voltage at this pH is 1.36 V versus Zn/Zn2+and is attributed to a boundary between VO2+and VO2+.
