Chemical vs Electrochemical Formation of Li 2 CO 3 as a Discharge Product in Li–O 2 /CO 2 Batteries by Controlling the Superoxide Intermediate

The Li–O 2 /CO 2 battery with high capacity has recently been proposed as a new protocol to convert CO 2 . However, the fundamental mechanism for the reaction still remains hazy. Here, we investigated the discharge processes of Li–O 2 /CO 2 (70%/30%) batteries in two solvents, dimethyl sulfoxide (DMSO) and 1,2-dimethoxyethane (DME). During discharge, both solvents initially show the reduction of oxygen. However, afterward, the solvent affects the reaction pathways of superoxide species by solvating Li + with different strength, depending on the so-called donor number. More precisely, the initial formation of CO 4 •– is favored in DMSO at the expense of lithium superoxide formation that we observed in DME. Despite the different intermediate processes, X-ray diffraction showed that Li 2 CO 3 was the final discharge product in both solvents. Moreover, we observed that CO 2 cannot be reduced within the electrochemical stability window of DMSO and DME.