Topological Defect-Rich Carbon as a Metal-Free Cathode Catalyst for High-Performance Li-CO2 Batteries

Exploration of the highly efficient bi-functional catalysts toward the reduction of CO2 and decomposition of Li2CO3 at the cathode is the key for high-performance Li-CO2 batteries. Herein, topological defect-rich graphene (TDG) based materials are developed as metal-free cathodes for Li-CO2 batteries, presenting an unprecedented full discharge capacity of over 69 000 mA h g(-1) at the current density of 0.5 A g(-1), a relatively small voltage gap of 1.87 V (Li/Li+) even at an extremely high current density of 2.0 A g(-1), and an excellent long-term stable cycle life of up to 600 cycles at 1.0 A g(-1). The outstanding performance of Li-CO2 batteries with the TDG cathodic electrocatalyst can be attributed to the introduction of topological defects in the carbon skeleton, providing sufficient active sites for CO2 reduction and evolution to facilitate the formation/decomposition of Li2CO3 during the discharging/charging process. The density functional theory calculations reveal the superiority of the negatively charged C atoms in topological defects as the adsorption for CO2 molecules and the activation sites for the decomposition of Li2CO3, and that the heterocyclic pentagon ring (C5) has a relatively low theoretical potential gap (1.01 V) during the charge and discharge processes.