Blood-Capillary-Inspired, Free-Standing, Flexible, and Low-Cost Super-Hydrophobic N-CNTs@SS Cathodes for High-Capacity, High-Rate, and Stable Li-Air Batteries

With the rising demand for flexible and wearable electronic devices, flexible power sources with high energy densities are required to provide a sustainable energy supply. Theoretically, rechargeable, flexible Li-O-2/air batteries can provide extremely high specific energy densities; however, the high costs, complex synthetic methods, and inferior mechanical properties of the available flexible cathodes severely limit their practical applications. Herein, inspired by the structure of human blood capillary tissue, this study demonstrates for the first time the in situ growth of interpenetrative hierarchical N-doped carbon nanotubes on the surface of stainless-steel mesh (N-CNTs@SS) for the fabrication of a self-supporting, flexible electrode with excellent physicochemical properties via a facile and scalable one-step strategy. Benefitting from the synergistic effects of the high electronic conductivity and stable 3D interconnected conductive network structure, the Li-O-2 batteries obtained with the N-CNTs@SS cathode exhibit superior electrochemical performance, including a high specific capacity (9299 mA h g(-1) at 500 mA g(-1)), an excellent rate capability, and an exceptional cycle stability (up to 232 cycles). Furthermore, as-fabricated flexible Li-air batteries containing the as-prepared flexible super-hydrophobic cathode show excellent mechanical properties, stable electrochemical performance, and superior H2O resistibility, which enhance their potential to power flexible and wearable electronic devices.