Water soluble polymer binder with good mechanical property and ionic conductivity for high performance lithium sulfur battery

Abstract

Binder as one of the important components in lithium sulfur (Li–S) battery determinates the stability of the active electrode. However, the volume expansion, poor ionic conductivity and the dissolution of polysulfides in sulfur cathode with traditional binders still restrict the application of Li–S battery. Herein, a water-soluble functional binder (HMM/PAA) is elaborately designed to realize the strong interaction with polysulfide and the good mechanical property via a condensation reaction between polyacrylic acid (PAA) and hexamethylolmelamine (HMM). The abundant polar groups in HMM/PAA could anchor polysulfide and impede their migration. The electron-rich oxygen-containing groups would promote the ion transfer for rapid kinetic reaction by coupling with lithium ion. Moreover, the cross-linked network endues the HMM/PAA binder with the good mechanical properties, contributing to the electrode integrity and avoiding the electrode cracks. Therefore, the HMM/PAA-based battery delivers the excellent rate performance and good capacity retention of 838.2 mAh g−1 at 0.2 C even with the sulfur loading of 5.7 mg cm−2. This work provides an economical and effective strategy for water-soluble binder in high-performance Li–S battery.