Electrochemical Performance and Mechanism of Calcium Metal‐Organic Battery

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