The invention provides an electrolyte composition which is adapted for use in a rechargeable alkaline electrochemical cell, and especially preferably adapted for use in a rechargeable manganese zinc electrochemical cell, which electrolyte composition imparts improved performance characteristics to the rechargeable alkaline electrochemical cell. The electrolyte composition includes an electrolyte composition in which contains a potassium hydroxide and lithium hydroxide in a concentration and a respective molar ratio of about 1 molar potassium hydroxide to 2.5-3.7 (preferably 1:3) molar lithium hydroxide (1 M KOH:2.5-3.7 M LiOH). Also provided are alkaline electrochemical cells and alkaline batteries comprising the electrolyte compositions. The resultant alkaline electrochemical cells and alkaline batteries exhibit improved performance characteristics, as the electrolyte composition significantly inhibits the passivation of Zn, and may also be useful in this role in other battery chemistries.