Dual Cross-Linked\nMultifunctional Binder for High-Performance\nLithium–Sulfur Batteries

Abstract

Lithium–sulfur batteries suffer from volume variation,\ninsulation\nof sulfur, and a severe shuttle effect, leading to an inferior cycling\nperformance. Herein, a dual cross-linked binder (CPS), which contains\nchemical covalent bonds and physical hydrogen bonds, is fabricated\nfor lithium–sulfur batteries through carboxymethyl cellulose\nconjugated with catechol groups and thiolated branched polyethylenimine.\nThe chemical covalent cross-linked bonds are formed via the Michael\naddition reaction that avoids consumption of catechol groups. The\ndynamic hydrogen bonds consume the stress energy and repair the cracks,\nwhich are caused by the remarkable volume change of sulfur. Combining\nthe rigid and soft moieties, polar groups, and dual cross-linked structure\nin the CPS, the CPS prominently tolerates and buffers the huge volume\nchange of active materials, resulting in maintenance of the cathode\nintegrity. Additionally, the CPS effectively immobilizes the lithium\npolysulfides into the cathodes, remarkably accelerates the reaction\nkinetics, and significantly facilitates lithium-ion diffusion. As\na result, the sulfur cathode with CPS exhibits a high initial capacity\nof 1380 mAh g^–1. At a mass loading of 8.5 mg cm^–2 and an electrolyte/sulfur ratio of 5 μL mg^–1, the sulfur cathode with CPS retains 627 mAh g^–1 after 100 cycles at a rate of 0.5 C.