From Copper to Basic Copper Carbonate: A Reversible Conversion Cathode in Aqueous Anion Batteries.

Dual-ion batteries that use anions and cations as charge carriers represent a promising energy-storage technology. However, an uncharted area is to explore transition metals as electrodes to host carbonate in conversion reactions. Here we report the reversible conversion reaction from copper to Cu 2 CO 3 (OH) 2 , where the copper electrode comprising K 2 CO 3 and KOH solid is self-sufficient with anion-charge carriers. This electrode dissociates and associates K + ions during battery charge and discharge. The copper active mass and the anion-bearing cathode exhibit a reversible capacity of 664 mAh g -1 and 299 mAh g -1 , respectively, and relatively stable cycling in a saturated mixture electrolyte of K 2 CO 3 and KOH. The results open an avenue to use carbonate as a charge carrier for batteries to serve for the consumption and storage of CO 2 .