Organic-inorganic hybrid hydrogel electrolytes were prepared by mixing hydrotalcite, cross-linked potassium poly(acrylate) and 6 M KOH solution. The organicinorganic hybrid hydrogel electrolytes had high ionic conductivity (0.456-0.540 S cm −1 ) at 30 °C. Moreover, the mechanical strength of the hydrogel electrolytes was high enough to form a 2-3 mm thick freestanding membrane because of the reinforcement with hydrotalcite.

Organic-inorganic hybrid hydrogel electrolyte with ionic conductivity and electrochemical window comparable to the corresponding electrolyte solution was used for assembling an all solid-state rechargeable Ni-Zn cell. The all solid-state rechargeable Ni-Zn cell was superior in charge-discharge performance to the conventional Ni-Zn cell when the distance between the positive and negative electrodes became shorter. Charge retention at the first cycle of this cell was almost 100% even at 2 C discharge rate, but discharge capacity was decreased with repeating chargedischarge cycle.