Fig. 1 Optical photographs of different electrolytes (a-c) and SEM images of freeze-dried additives from their aqueous dispersions (d-f)

Fig. 2 FT-IR spectra (a) and TGA curves (b) of different electrolytes

Fig. 3 Galvanostatic charge/discharge curves of Zn-Zn symmetric cells in different electrolytes (a-b), and SEM images of Zn electrodes after 50 cycles at 1 mA?cm-2 (c-f)

Fig. 4 CV (a) and galvanostatic charge/discharge curves (b) of Zn-MnO2 batteries with different electrolytes

Fig. 5 Cycling performance of Zn-MnO2 batteries using different electrolytes at 0.5 (a) and 1 A?g-1 (b); Cross sectional SEM images of zinc electrodes after 100 cycles at 1 A?g-1 (c-f)

Fig. 6 Rate performance of Zn-MnO2 batteries with different electrolytes

Fig. 7 EIS plots of Zn-MnO2 battery with different electrolytes (a) and XRD patterns of Zn anode after 100 cycles (b)

Fig. 8 Schematic illustration showing the Zn dendrite depressing mechanism of the SA/SiO2 quasi-gel electrolyte

Fig. S1 Optical image of sodium alginate powder pressed between two pieces of nickel foams before and after cyclic voltammetry test

Fig. S2 Cyclic voltammetry curves of SiO2 and SA electrodes

Fig. S3 SEM images of zinc electrodes for Zn-MnO2 batteries after 100 charge/discharge cycles in different electrolytes

Fig. S4 Capacity evolution of Zn-MnO2 batteries with a filter paper or glass fiber separator

Fig. S5 Charge and discharge curves of Zn-MnO2 batteries with different electrolytes

Fig. S6 Overpotential measurement of electrodeposited zinc in different electrolytes