Zinc-manganese (Zn/MnO₂) batteries with outstanding advantages of high operation safety, high environmental benignity and high cost performance, is suitable for the application of large-scale energy storage battery. However, the uncontrolled growth of zinc dendrites on the metal zinc anode during charge-discharge cycling causes serious problems such as quick capacity decrease and short circuit failure. In this study, the aqueous electrolyte was converted into a composite quasi-gel electrolyte by adding hydrophilic nano-silica (SiO₂) and sodium alginate (SA), which effectively inhibits the dendrite growth of the surface of the zinc negative electrode and the capacity degradation of the Zn-MnO₂ battery. Galvanostatic charge-discharge tests showed that the Zn/MnO₂ battery with composite gel electrolyte achieves a capacity retention of 78% after 1800 cycles, while the capacity of Zn/MnO₂ battery using ordinary electrolyte almost fails after 1000 cycles. The three-dimensional network structure of the gel electrolyte can improve the distribution uniformity of zinc ion in electrolyte, reduce the capacity decay rate and failure risk of the batteries.