High-Performance Li-CO₂ Batteries from Free-Standing, Binder-Free, Bifunctional Three-Dimensional Carbon Catalysts

A free-standing, binder-free, N-doped double-layered three-dimensional (3D) CNT/G cathode consisting of a structure with vertically aligned N-doped CNTs sandwiched between two N-doped graphene layers of a seamless junction at the CNT/G interfaces (3D NCNT/G) was developed for Li-CO2 batteries. It was found that the N-doped 3D CNT/G architecture could not only facilitate CO2 gas and electrolyte diffusion through the vertically aligned open channels and electron transport via the 3D carbon network but also provide a large surface area to support numerous triphase active sites for efficient charge and discharge. As a result, the resultant Li-CO2 batteries showed a large specific capacity of 17534.1 mAh g–1 with high Coulombic efficiency of 98.3% and low overpotential (1.13 V) and good cycling stability (up to 180 discharge–charge cycles with a cutoff capacity of 1000 mAh g–1 at 100 mA g–1). This work represents a new approach to efficient energy storage with affordable, metal-free, binder-free, and porous carbon-based catalytic electrodes.