The present invention relates to a solid-state rechargeable zinc-air battery featuring a novel bifunctional electrocatalyst, a dual-crosslinked polyacrylic acid hydrogel  electrolyte, and a stannate-based additive for in situ zinc anode modification. The cathode comprises a gas diffusion layer coated with ruthenium-ruthenium oxide core- shell nanoparticles supported on nitrogen-doped graphene, providing enhanced bifunctional catalytic activity and stability. The anode consists of zinc metal modified in  situ by a stannate-based additive to form a solid electrolyte interphase layer, effectively suppressing dendrite formation. The electrolyte membrane is a polyacrylic acid  hydrogel, covalently and ionically cross-linked, and soaked in an aqueous solution containing potassium hydroxide, zinc acetate, and a stannate-based additive,  resulting in improved mechanical strength, ionic conductivity, and battery safety. The integrated system delivers high power density, specific capacity, and robust  cycling stability, offering a significant advancement in the field of solid-state zinc-air batteries.