Vertically Aligned N-doped Carbon Nanotubes Arrays as Efficient Binder-free Catalysts for Flexible Li-CO2 Batteries

The Li-CO2 battery is a newly-emerging energy storage and conversion system, making CO2 renewable utilization and capture in a green way. However, the unsatisfactory electrochemical performances such as high polarization, short cyclic life and poor rate capability caused by the sluggish decomposition the product Li2CO3 and the lacking of mechanical flexibility due to the rigid cathode, greatly hinder its real application, especially for the compliant and wearable devices. Herein, the vertically aligned N-doped carbon nanotube (VA-NCNT) arrays on Ti wire are prepared as freestanding, binder-free cathodes for flexible quasi-solid-state Li-CO2 battery. The VA-NCNT arrays have thousands of vertical CNT with high N-doping percentage, rich defects and void space, which facilitate the CO2 diffusion and electrolyte permeation, provide exposed active sites and more space for the formation and accommodation of Li2CO3 and help the oxidation of Li2CO3 and amorphous carbon in charge process. As a result, the fabricated battery shows ultralong cycle life, small potential gap, outstanding rate capability and high flexibility. Our work provides an alternative option towards CO2 conversion and utilization as high performance energy sources.