Optimizing CO2 reduction and evolution reaction mediated by o-phenylenediamine toward high performance Li-CO2 battery

Abstract

Li-CO2 batteries have attracted widespread attention due to their high energy density and environmental friendliness. However, problems such as the activation of CO2 and the decomposition of discharge products (Li2CO3 and C) are the key to restrict its development. Herein, an amine-based o-phenylenediamine (OPD) as a bifunctional liquid catalyst is introduced into Li-CO2 battery, which realizes a great improvement of electrochemical performances by optimizing CO2 reduction and evolution reaction process. Experiments coupled with theoretical calculations verify that the introduced OPD accelerates the migration of the discharge intermediates and makes the discharge products grow through the solution phase pathway, which greatly eliminates the passivation of the cathode as well as releases the battery capacity. Moreover, OPD, as a liquid redox mediator, can effectively promote the decomposition of discharge products, greatly reduce the charging potential and improve round-trip efficiency. Additionally, thanks to the increased activity of CO2 reduction reaction (CDRR) and CO2 evolution reaction (CDER) catalyzed by OPD, the cycling performance of Li-CO2 battery has also been improved.