Synthesis of open helmet-like carbon skeletons for application in lithium-ion batteries

Abstract

How to optimize the interior space of symmetric (for example, hollow carbon spheres) and asymmetric (for example, hollow carbon bowls) hollow carbon structures is a big challenge for their application in energy storage devices. Here we synthesize open helmet-like carbon skeletons, carbon nanohelmets (CNHs), which preserve all advantages of hollow structures but also fully utilize the inner walls of carbon. As an example, the as-fabricated NiO/CNH anode exhibits high reversible capacity, excellent cycling stability and superior rate properties in lithium-ion batteries. These remarkable performances are attributed to the ingenious helmet-like structures, which provide a large amount of active sites for Li⁺ insertion/extraction from the inner walls of carbon; buffer the large volume change of NiO during charging/discharging effectively with the open structure; and reduce the internal resistance significantly due to excellent contact between NiO nanoparticles and carbon. The facile strategy reported in this work may open an avenue to synthesize open hollow structures for practical applications.