Dual Cross-Linked Multifunctional Binder for High-Performance Lithium–Sulfur Batteries
Rongnan Guo, Wang Dong, Ding Pan, Yong Chen, Hanyu Zhao
Abstract
Lithium–sulfur batteries suffer from volume variation, insulation of sulfur, and a severe shuttle effect, leading to an inferior cycling performance. Herein, a dual cross-linked binder (CPS), which contains chemical covalent bonds and physical hydrogen bonds, is fabricated for lithium–sulfur batteries through carboxymethyl cellulose conjugated with catechol groups and thiolated branched polyethylenimine. The chemical covalent cross-linked bonds are formed via the Michael addition reaction that avoids consumption of catechol groups. The dynamic hydrogen bonds consume the stress energy and repair the cracks, which are caused by the remarkable volume change of sulfur. Combining the rigid and soft moieties, polar groups, and dual cross-linked structure in the CPS, the CPS prominently tolerates and buffers the huge volume change of active materials, resulting in maintenance of the cathode integrity. Additionally, the CPS effectively immobilizes the lithium polysulfides into the cathodes, remarkably accelerates the reaction kinetics, and significantly facilitates lithium-ion diffusion. As a result, the sulfur cathode with CPS exhibits a high initial capacity of 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.