Fast Charge‐Transfer Rates in Li‐CO2 Batteries with a Coupled Cation‐Electron Transfer Process

Abstract Li‐CO 2 batteries with a high theoretical energy density (1876 Wh kg −1 ) have unique benefits for reversible carbon fixation for energy storage systems. However, due to lack of stable and highly active catalysts, the long‐term operation of Li‐CO 2 batteries is limited to low current densities (mainly <0.2 mA cm −2 ) that are far from practical conditions. In this work, it is discovered that, with an ionic liquid‐based electrolyte, highly active and stable transition metal trichalcogenide alloy catalysts of Sb 0.67 Bi 1.33 X 3 (X = S, Te) enable operation of the Li‐CO 2 battery at a very high current rate of 1 mA cm −2 for up to 220 cycles. It is revealed that: i) the type of chalcogenide (Te vs S) significantly affects the electronic and catalytic properties of the catalysts, ii) a coupled cation‐electron charge transfer process facilitates the carbon dioxide reduction reaction (CO 2 RR) occurring during discharge, and iii) the concentration of ionic liquid in the electrolyte controls the number of participating CO 2 molecules in reactions. A combination of these key factors is found to be crucial for a successful operation of the Li‐CO 2 chemistry at high current rates. This work introduces a new class of catalysts with potential to fundamentally solve challenges of this type of batteries.