Multifunctional Chitosan–Covalent Bonded Multi‐Walled Carbon Nanotubes Composite Binder for Enhanced Electrochemical Performances of Lithium–Sulfur Batteries

Abstract Lithium–sulfur batteries (LSBs) are considered as one of the most promising next‐generation energy‐storage devices because of their high energy density. However, the long‐term use of LSBs is mainly limited by polysulfide shuttling and cathode structural degradation caused by volume changes during charging and discharging. To address these issues, a multifunctional, high‐performance aqueous binder is developed by modifying a natural polysaccharide with multi‐walled carbon nanotubes (MWCNTs). Specifically, the catechol‐conjugated chitosan (CCS) acts as the binder, showing strong polysulfide adsorption, while the MWCNTs covalently bonded to CCS enhance the mechanical toughness and electronic conductivity. The resulting CCS‐MWCNTs composite binder exhibits a tensile strength of 40 MPa and a strain at break of 300%, which are higher than those of CCS. As a binder for sulfur cathodes, the CCS‐MWCNTs binder demonstrates superior cyclic stability and rate capability. At a sulfur loading of 2.0 mg cm⁻ 2 , it delivers an initial capacity of 1016 mAh g⁻¹ at 0.2 C and retains 690 mAh g⁻¹ after 100 cycles, significantly outperforming commercial polyvinylidene difluoride (PVDF), sodium carboxymethylcellulose/styrene butadiene rubber (CMC/SBR), and CCS binders. This study demonstrates the potential applications of polysaccharide binders in metal‐sulfur batteries by innovatively incorporating carbon nanotubes into the biopolymer binder, providing a promising alternative for environmentally friendly energy storage.