Voltammogram of 3 M ZnSO4 + H2SO4 (pH = 1) exhibited peaks at different positions in comparison to either 3 M ZnSO4 or H2SO4 (pH = 1), indicating the possibility of Zn 2+ and H + co-insertion (Figure , blue). CV of 0.1 M ZnSO4 + H2SO4 (pH = 1) electrolyte with an approximately equal concentration of Zn 2+ and H + ions showed almost identical features to the CV of H2SO4 (pH = 1) suggesting that the insertion of H + ions into the OTQC is preferential if it is present in sufficient concentration (Figure ). Galvanostatic cycling in 1 M Zn(TFSI)2 in the G2 electrolyte was used to determine the possibility of Zn 2+ insertion without the interference of H + ions. Despite substantially decreased capacity in comparison with 3 M ZnSO4 in H2O, galvanostatic cycling in the aprotic electrolyte proved the possibility of reversible Zn 2+ insertion into the OTQC (Figure , black). OTQC experienced significant capacity fading during galvanostatic cycling in the Zn battery using 3 M ZnSO4 electrolyte.