Enhancing the process of CO2 reduction reaction by using CTAB to construct contact ion pair in Li-CO2 battery

Aprotic Li-CO₂ batteries have attracted growing interest due to their high theoretical energy density and its ability to use green house gas CO₂ for energy storage. However, the poor ability of activating CO₂ in organic electrolyte often leads to the premature termination of CO₂ reduction reaction (CO₂RR) directly. Here in this work, cetyl trimethyl ammonium bromide (CTAB) was introduced into a dimethyl sulfoxide (DMSO) based Li-CO₂ battery for the first time to enhance the CO₂RR. Significantly improved electrochemical performances, including reduced discharge over-potential and increased discharge capacity, can be achieved with the addition of CTAB. Ab initio molecular dynamics (AIMD) simulations show that quaternary ammonium group CTA⁺ can accelerate CO₂ reduction process by forming more stable contact ion pair (CIP) with CO₂^–, reducing the energy barrier for CO₂RR, thus improving the CO₂ reduction process. In addition, adding CTA⁺ is also favorable for the solution-phase growth of discharge products because of the improved migration ability of stable CTA⁺-CO₂^– CIP in the electrolyte, which is beneficial for improving the utilization ratio of cathode. This work could facilitate the development of CO₂RR by providing a novel understanding of CO₂RR mechanism in organic system.