Let It Catch: A Short-Branched Protein for Efficiently Capturing Polysulfides in Lithium-Sulfur Batteries

Uncovering the key contributions of molecular details to capture polysulfides is important for applying suitable materials that can effectively restrain the shuttle effect in advanced lithium-sulfur batteries. This is particularly true for natural biomolecules with substantial structural and compositional diversities strongly impacting their functions. Here, natural gelatin and zein proteins are first denatured and then adopted for fabrication of nanocomposite interlayers via functionalization of carbon nanofibers. From the results of experiment and molecular dynamic simulations, it is found that the lengths of the sidechains on the two proteins play critical roles. The short-branched gelatin shows significantly stronger adsorption of polysulfides, as compared with zein comprising many long-chain residues. The gelatin-based interlayer, along with its good porous structures/electrical conductivity, greatly suppresses the shuttle effect and yields exceptional electrochemical performance. Furthermore, the implementation of proteins as functional binder additives further supports the finding that gelatin enables stronger polysulfide-trapping. As a result, high-loading sulfur cathodes (9.4 mg cm(-2)) are realized, which deliver a high average areal capacity of 8.2 mAh cm(-2) over 100 cycles at 0.1 A g(-1). This work demonstrates the importance of sidechain length in capturing polysulfides and provides a new insight in selecting and design of desired polysulfide-binding molecules.