Electrochemical Performance and Mechanism of Calcium Metal‒Organic Battery

Abundance of Ca, its low redox potential and high specific capacity make Ca metal batteries an attractive energy storage system for the future. Recent demonstration of room temperature calcium plating/stripping opened new avenue of development, but performance of cathode materials is still lagging behind. Due to nature of divalent cations, conversion and coordination electrochemical reactions show better performance compared to insertion. Herein we demonstrate use of anthraquinone based polymer as cathode material for Ca metal‒organic battery. Electrochemical mechanism investigation confirms reversible reduction of carbonyl bond and coordination with Ca 2+ cations in the discharged state opening a pathway toward high energy density battery. Continued performance of 2‐electrode cell is strongly hampered by overpotential increase connected with Ca stripping process on Ca metal anode stating need for further development of Ca electrolytes. Ca metal‒organic battery promise to achieve cells with gravimetric energy density on the practical level compared to state‐of‐the‐art Li‐ion batteries.