Crosslinked cyanometallate–chitosan nanosheet assembled aerogels as efficient catalysts to boost polysulfide redox kinetics in lithium–sulfur batteries

Abstract

A novel class of crosslinked cyanometallate/chitosan nanosheet-assembled aerogels is fabricated via simple yet effective sol–gel polymerization and subsequent dehydration, and functions as efficient electrocatalysts for boosting the polysulfide redox kinetics in Li–S batteries. Cyanometallate (e.g. Fe(CN)₆³⁻), as a unique crosslinking agent, can induce abundant hydrogen bridges in the chitosan matrix and thus impart the composite with an intriguing aerogel morphology and remarkably increased surface area with mesoporosity. The synergies between two ubiquitous components are beneficial to fully expose and utilize sufficient active sites, enabling the composite aerogel to exhibit remarkably improved activity towards polysulfide adsorption and catalytic conversion. The aerogel catalysts can functionalize the commercial separator and endow Li–S batteries (even with usage of a simple carbon black/sulfur cathode) with a large specific capacity, excellent rate capability and cycling stability, and a large areal capacity. This proposed design idea can be expanded to produce various aerogels based on other cyanometallates such as Co(CN)₆³⁻.