Stable Zn anodes enabled by high-modulus agarose gel electrolyte with confined water molecule mobility

•A high-modulus agarose gel electrolyte (AGE) with confined H2O mobility is proposed.•The hydration effect of Zn2+ions is significantly suppressed in AGEs.•AGE can serve as a single Zn2+ conductor with a cation transference number of 0.87.•SO42− are firmly immobilized to prevent the formation of Zn4(OH)6SO4·5H2O byproduct.•AGE-based Zn symmetric batteries show exceptional reversibility and rate capability.