A Secondary Al-CO₂ Battery Enabled by Aluminum Iodide as a Homogeneous Redox Mediator

As an emerging energy storage concept, Al-CO₂ batteries have not yet been demonstrated as a rechargeable system that can deliver a high discharge voltage and a high capacity. In this work, we present a homogeneous redox mediator to access a rechargeable Al-CO₂ battery with an ultralow overpotential of 0.05 V. In addition, the resulting rechargeable Al-CO₂ cell can maintain a high discharge voltage of 1.12 V and delivers a high capacity of 9394 mAh/g_carbon. Nuclear magnetic resonance (NMR) analysis indicates that the discharge product is aluminum oxalate which can facilitate the reversible operation of Al-CO₂ batteries. The rechargeable Al-CO₂ battery system demonstrated here holds great promise as a low-cost and high-energy alternative for future grid energy storage applications. Meanwhile, the Al-CO₂ battery system could facilitate capture and concentration of atmospheric CO₂, ultimately benefiting both the energy and environmental sectors of society.