From Mechanisms to Commercialization: CuO Positive Electrodes for Rechargeable Alkaline Zinc Batteries.

Cupric oxide (CuO) is a promising positive electrode material for rechargeable alkaline Zn batteries, offering earth-abundant composition, high theoretical capacity (674 mAh/g), and compatibility with safe aqueous electrolytes. Despite early commercial success as a primary battery dating to the Lalande-Chaperon cell (1883), rechargeability has only recently been demonstrated with Bi2O3 additives and carbon coatings, which help suppress resistive Cu2O accumulation and limit active material dissolution. Significant barriers remain, including poorly understood failure mechanisms at high depth of discharge and limited cathode utilization. This review summarizes the electrochemical mechanisms of Cu and CuO in alkaline electrolyte, critically examines recent advances in Bi2O3-modified and carbon-coated electrodes, including uncertainty about charge products and the mechanistic role of Bi, and identifies priority directions for future research. A cell-level energy density and cost analysis demonstrates that cathode areal capacity and Zn anode utilization are the dominant cost drivers, with areal capacities exceeding 40 mAh/cm2 required to reach storage costs below 100 USD/kWh, a target achievable with existing materials if electrode engineering challenges are resolved.