Building a Rechargeable Voltaic Battery via Reversible Oxide Anion Insertion in Copper Electrodes

Voltaic pile, the very first battery built by humanity in 1800, plays a seminal role in battery development history. However, the premature design leads to the inevitable copper ion dissolution issue, which dictates its primary battery nature. To address this issue, solid-state electrolytes, ion exchange membranes, and/or sophisticated electrolytes are widely utilized, leading to high costs and complicated cell configuration. Herein, we build a rechargeable zinc-copper voltaic battery from simple and cheap electrolyte/separator materials, thus eliminating the need to use the above components. Notably, our battery leverages the Zn₄SO₄(OH)₆·xH₂O precipitation in ZnSO₄ electrolytes, a common side reaction in zinc batteries, to provide a "locally alkaline" environment for copper electrodes. Consequently, oxide (O^2-) anion insertion takes place and readily transforms copper to copper(I) oxide (Cu₂O) without any copper ion dissolution issue. Therefore, this battery realizes a high capacity of ∼370 mA h g^-1 and a long cycling of ∼500 cycles. Our work provides an innovative approach to stabilize anion insertion in metal electrodes for energy storage.