Self-Healing Double-Cross-Linked Supramolecular Binders of a Polyacrylamide-Grafted Soy Protein Isolate for Li–S Batteries
Hui Wang, Yinyan Wang, Peitao Zheng, Yu Yang, Yukun Chen, Yuliang Cao, Yonghong Deng, Chaoyang Wang
Abstract
With extremely high theoretical energy density, lithium–sulfur (Li–S) batteries have attracted abundant interest as a promising next-generation energy storage device. Polymer binders as an ingredient of cathodes are of great significance in pursuit of stabilized electrochemistry. Herein, we fabricate a self-healing, water-based, and double-cross-linked soy protein isolate (SPI)-polyacrylamide (PAM) binder for the sulfur cathode, which is facilely synthesized by copolymerization of methacrylated SPI and acrylamide. It was demonstrated that methacrylated SPI acted as a macro-cross-linker, combining with dynamic hydrogen bonding cross-linking from PAM, endowing the SPI-PAM polymer binder satisfactory bonding strength and excellent self-healing ability. Moreover, the SPI-PAM exhibits superior lithium polysulfide anchoring capability to impede the dissolution and diffusion of lithium polysulfides in an electrolyte. Li–S batteries with such a robust SPI-PAM binder can stabilize the charge and discharge for 400 cycles at a high rate of 6 C; the average specific capacity loss per cycle is only 0.0545%, and even at an ultrahigh current density of 20 C, the specific capacity still remains at 148.2 mA h g–1. With a sulfur loading of 2.3 mg cm–2, the SPI-PAM-based sulfur cathodes demonstrate remarkable cycling performances at 0.5 C for 200 cycles, and the capacity remains at 707.7 mA h g–1. The kind of green binders from bioresources modified with PAM have a good application in high-energy density Li–S batteries.