Growing Electrocatalytic Conjugated Microporous Polymers on Self-Standing Carbon Nanotube Films Promotes the Rate Capability of Li-S Batteries.

Abstract

Lithium-sulfur (Li-S) batteries hold great promise for widespread application on account of their high theoretical energy density (2600Wh kg-1 ) and the advantages of sulfur. Practical use, however, is impeded by the shuttle effect of polysulfides along with sluggish cathode kinetics. it is reported that such deleterious issues can be overcome by using a composite film (denoted as V-CMP@MWNT) that consists of a conjugated microporous polymer (CMP) embedded with vanadium single-atom catalysts (V SACs) and a network of multi-walled carbon nanotubes (MWNTs). V-CMP@MWNT films are fabricated by first electropolymerizing a bidentate ligand designed to coordinate to V metals on self-standing MWNT films followed by treating the CMP with a solution containing V ions. Li-S cells containing a V-CMP@MWNT film as interlayer exhibit outstanding performance metrics including a high cycling stability (616mA h g-1 at 0.5 C after 1000 cycles) and rate capability (804mA h g-1 at 10 C). An extraordinary area-specific capacity of 13.2mA h cm-2 is also measured at a high sulfur loading of 12.2mg cm-2 . The underlying mechanism that enables the V SACs to promote cathode kinetics and suppress the shuttle effect is elucidated through a series of electrochemical and spectroscopic techniques.