Inducing CO 2 Partial Reduction Enables Operation of Li‐CO 2 Battery Cathode Longer than One Year

ABSTRACT When CO 2 undergoes a two‐electron partial reduction during the discharging process of Li‐CO 2 batteries, it produces thermodynamically active Li 2 C 2 O 4 , which readily decomposes during subsequent charging. This offers a promising opportunity to mitigate the large charging overpotential and enhance the battery's cycling stability. However, as an intermediate, Li 2 C 2 O 4 tends to transform to the inert Li 2 CO 3 readily. In this work, we report a high‐performance cathode catalyst featuring ultrasmall RuO 2 and BiOCl uniformly co‐decorated on an MXene substrate (RuO 2 ‐BiOCl). It effectively stabilizes Li 2 C 2 O 4 during discharge, facilitating the two‐electron partial reduction of CO 2 ; meanwhile, it can also modulate the morphology of discharge products, resulting in an intimate and extensive solid–solid interface between the insulating discharging product and the electrocatalyst. This together avoids accumulation of bulky, highly inertial and insulating Li 2 CO 3 in the cathode during cycling, which decreases the charging polarization and prolongs the Li‐CO 2 battery life span. The optimal Li‐CO 2 battery delivers a high discharge capacity of 10.33 mAh cm −2 during the first full cycle, and extraordinary durability, sustaining over 10 000 h of operation with a fixed areal capacity of 0.10 mAh cm −2 at 0.02 mA cm −2 . By tuning the CO 2 reduction path, this work offers a novel approach for building high‐performance, practically workable Li‐CO 2 batteries.