Ultra-fast transfer and high storage of Li + /Na + in MnO quantum dots@carbon hetero-nanotubes: Appropriate quantum dots to improve the rate

Carbon materials play indispensable roles in energy-related systems, and constructing fast chargeable carbon anodes is still one of the most interesting and meaningful topics in energy storage and conversion fields. Selection of an appropriate structure and quantity of quantum dots can improve the rate performances. Here we report a unique molecular beam template approach to inlay MnO quantum dots (MnOQD) into walls of carbon hetero-nanotubes to form a brand-new composite (MnOQD@CHNTs) and investigate the influences of the inlaid quantum dots on the structures and the fast charging properties of carbon hetero-nanotubes. Plenty of tiny inlaid MnOQD in the walls of carbon nanotubes are proved to be capable of expanding the carbon layer spacing, decreasing the degree of order, forming heterojunctions with carbon, and altering the local electronic cloud density of carbon. Therefore, the capability of MnOQD@CHNTs for Li+/Na+ transfer and storage is greatly improved due to the quantum dot effect of MnO. As a result, the MnOQD@CHNTs exhibit excellent cycling and rate performances as both lithium-ion battery (LIB) and sodium-ion battery (SIB) anodes, e.g. fully charged in 28.3 s with a capacity of 392.8 mA h g-1 (~ 125.6 C) in LIB (the best ever reported).