Intercalation chemistry of the zinc-manganese dioxide (Zn-MnO2) electrochemical cell aiming at the development of aqueous rechargeable batteries is presented. This study includes electrochemical characterization of MnO2 in saturated aqueous lithium hydroxide (LiOH) and potassium hydroxide (KOH) electrolytes. The lithium insertion into MnO2 results in the formation of LixMnO2. The reversible deintercalation process prevails in the presence of LiOH electrolyte. Rather than the usual protonation (H+) which is apparent in the literature while using KOH electrolyte, in this work, K+ ion insertion into MnO2 is observed. However, the K+ ion insertion is found to be irreversible. The intercalation mechanism is confirmed using various techniques to characterize the discharged MnO2 cathode in LiOH and KOH electrolytes. The influence of small amounts of Bi2O3 (bismuth oxide) additive on the discharge behavior of MnO2 is also discussed.