Improving Cycle Stability and Kinetics of Rechargeable Al/CO2 Batteries By Functional Cathode Materials

Abstract

Metal-CO2 batteries have emerged as a promising solution for advancing energy storage technology and sequestering carbon dioxide from ambient air. Aluminum (Al) is an appealing anode material for electrochemical CO2 capture and conversion due to its lower cost and reactivity in comparison to lithium and sodium anode materials, making it safer and more accessible for manufacturing. Its abundance across various regions of the world further adds to Al’s attractiveness. Additionally, Aluminum boasts a high specific energy of 2980A·hour/kg, suggesting that its electrochemical conversion with CO2 can produce large amounts of electrical energy. Previous study shows that Aluminum/CO2 batteries possess a remarkable discharge capability with the introduction of a small amount of oxygen, however, these batteries are not rechargeable.By utilizing a homogeneous iodine-based redox mediator, our group demonstrated that the Al-CO2 battery can achieve reversible discharge and charge with minimal overpotential of 0.05V, reducing stripping/plating overpotentials by 40% across various current rates compared to an unmodified imidazolium-based ionic liquid electrolyte. This is achieved by replacing oxygen gas with aluminum iodide in the electrolyte, which maintains high discharge capacity and enables the battery to be recharged for up to 12 cycles at a 20 mA/gcarbon rate.Examining the discharge and charge rates of different cathode materials was necessary to demonstrate the improvement in cycle stability. By utilizing functional carbon-based materials with increased surface area, heteroatom doping and unique pore structure as the cathode, we demonstrate that the rechargeable Al-CO2 battery can enhance CO2 reduction during the discharge processes, thereby improving reaction kinetics.Higher surface area and porous materials facilitate faster electron transfer during the electrochemical reactions while allowing better CO2 diffusion into the cathode, improving reaction rates.