Dual Cross-Linked Multifunctional Binder for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur batteries suffer from volume variation,insulationof sulfur, and a severe shuttle effect, leading to an inferior cyclingperformance. Herein, a dual cross-linked binder (CPS), which containschemical covalent bonds and physical hydrogen bonds, is fabricatedfor lithium-sulfur batteries through carboxymethyl celluloseconjugated with catechol groups and thiolated branched polyethylenimine.The chemical covalent cross-linked bonds are formed via the Michaeladdition reaction that avoids consumption of catechol groups. Thedynamic hydrogen bonds consume the stress energy and repair the cracks,which are caused by the remarkable volume change of sulfur. Combiningthe rigid and soft moieties, polar groups, and dual cross-linked structurein the CPS, the CPS prominently tolerates and buffers the huge volumechange of active materials, resulting in maintenance of the cathodeintegrity. Additionally, the CPS effectively immobilizes the lithiumpolysulfides into the cathodes, remarkably accelerates the reactionkinetics, and significantly facilitates lithium-ion diffusion. Asa result, the sulfur cathode with CPS exhibits a high initial capacityof 1380 mAh g(-1). At a mass loading of 8.5 mg cm(-2) and an electrolyte/sulfur ratio of 5 & mu;L mg(-1), the sulfur cathode with CPS retains 627 mAh g(-1) after 100 cycles at a rate of 0.5 C.

Automated summary

A dual cross-linked binder (CPS) consisting of chemical covalent bonds and physical hydrogen bonds is developed to improve the cycling performance of lithium-sulfur batteries. The CPS effectively tolerates and buffers the volume change of active materials, maintains the cathode integrity, and immobilizes the lithium polysulfides. This results in accelerated reaction kinetics, enhanced lithium-ion diffusion, and high initial capacity and cycle stability.