Dual Network Electrode Binder toward Practical Lithium–Sulfur Battery Applications

Lithium–sulfur (Li–S) batteries are widely regarded as one of the most promising next-generation energy storage devices due to their high energy density. Nevertheless, fast capacity fade caused by the tremendous volume changes of S-based cathodes and polysulfide shuttling during cycling remains to be effectively tackled prior to practical applications. Inspired by skeletal muscle, here, we develop a responsive network/confinement network blend (RCB) binder to remove the above bottlenecks. The as-developed binder is prepared through simply blending an aqueous hyaluronic acid (HA) solution and an oily solution with a tetrazole group-based copolymer of polyacrylonitrile and poly(ethylene glycol) bisazide. Hydrophobic tetrazole group-containing polymer (denoted as PCP) condenses in the mixture solution forming submicrometer-sized irregular spherical domains as the confinement network similar to myofilament, while water-soluble HA constructs a responsive network mimicking the fascia of skeletal muscle; meanwhile, the formed responsive network can coordinate the force among the confinement network by linking with PCP via ionic bonding. The RCB binder exhibits superior mechanical matching and adhesive properties and thus can effectively accommodate the huge volume change of S-based electrodes. Additionally, abundant polar groups such as carboxylic, amide, cyano, and tetrazole groups allow the RCB binder to effectively capture lithium polysulfide through strong anchoring effect. As a result, Li–S batteries assembled with a limited RCB binder dosage (5 wt % of the whole electrode film weight) exhibit remarkable improvement in both cycling and rate performance, even under high S loadings. Such skeletal muscle-inspired binder design helps boost the advance of S-based cathode binders toward practical battery applications.