Kinetics of the CO2 reduction reaction in aprotic Li–CO2 batteries: a model study

Abstract

The aprotic Li–CO₂ battery represents a promising technology that can potentially achieve energy conversion and storage and CO₂ recycling simultaneously. However, current Li–CO₂ batteries suffer from the sluggish kinetics of the CO₂ reduction reaction (CO₂RR) which often leads to high discharge overpotential, low energy efficiency, and low power densities. Toward unlocking the energy capabilities of Li–CO₂ batteries, it is crucially important to have a fundamental understanding of the kinetics aspect of the Li–CO₂ electrochemistry. Here we report a brief but comprehensive model to bridge the overall reaction kinetics and the elementary steps of the CO₂RR in Li–CO₂ batteries. A critical kinetics descriptor, i.e., the adsorption energy of the LiCO₂ intermediate on the cathode surface, is proposed to reveal the interplay and competition between two different CO₂RR mechanisms (i.e., the solution- and the surface-mediated pathways) occurring in Li–CO₂ batteries. Our model indicates that tuning the CO₂RR toward the solution-mediated pathway can avoid cathode surface passivation and is favorable for high-capacity and high-rate discharging of Li–CO₂ batteries. The model study reported here sheds light on the kinetics aspect of Li–CO₂ electrochemistry and would be beneficial for the design of better Li–CO₂ batteries.