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

Abstract

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.

Protein‐Engineered Functional Materials for Bioelectronics

“…To investigate the effects of the spatial molecular structure of proteins on polysulfide‐trapping, gelatin and zein protein with different amino acid compositions were adopted for the fabrication of conductive interlayers. [ 138 ] As can be seen in Figure 13e, zein contained more long chain amino acids such as Glu, Leu and Phe, while gelatin mainly consisted of short chain amino acids (Gly, Pro, Ala, etc.) The different amino acid compositions led to different side chain structures of the two proteins.…”

“…Influence of molecule structure to polysulfide‐trapping capability (Reproduced with permission. [ 138 ] Copyright 2020, Wiley‐VCH): e) Weight percentage of primary amino acids of zein and gelatin; f) Simulation results of the number of trapped Li 2 S 4 by proteins verses time; g) Cycle stability and Coulombic efficiency batteries with gelatin/carbon nanofiber (CNF) and zein/CNF interlayers.…”

Environmentally Friendly Binders for Lithium‐Sulfur Batteries

“…Through the strong affinity of carbonyl groups towards Li 2 S x , SAA delivered 576 mA h g −1 at 0.5 C after 100 cycles, corresponding 152 mA h g −1 more than unmodified gelatin based sulfur cathode. Chen et al . destroyed the secondary and higher level structures of two proteins (gelatin and zein) and obtained two random polypeptide chains, which were dominated by short sidechains (denatured gelatin) or long sidechains (denatured zein).…”

Bio‐Derived Materials Achieving High Performance in Alkali Metal–Chalcogen Batteries

“…employed a short‐branched protein as a functional binder additive to adsorb PSs and obtained high sulfur loading. [ 80 ] The binding sites could be opened up by the short‐branched residues derived from gelatin, entrapping the PSs in a “molecular cage,” while only a small amount of PSs was absorbed by the long‐branched residues derived from zein ( Figure a,b). Owing to the high PS‐capturing ability, the short‐branched gelatin could be used as a functional binder additive for the cathodes to achieve high sulfur loading (Figure 2c).…”

“…Reproduced with permission. [ 80 ] Copyright 2020, Wiley‐VCH GmbH. Electrochemical performances of high‐loading sulfur cathodes with proteins as the functional additives.…”