Effect of binders on the microstructural and electrochemical performance of high‐sulphur‐loading electrodes in lithium‐sulphur batteries

Abstract

Construction of a high-sulphur-loading electrode is an effective approach for achieving a high-specific energy density in lithium-sulphur batteries. The polymer binder has an important influence on the microstructural and electrochemical behaviours of high-sulphur-loading electrodes. In the study, three commonly used binders, namely polyvinylidene fluoride (PVDF), polyacrylonitrile (LA133), and polyacrylic acid (PAA), were used with high-sulphur-loading electrodes, and their electrochemical performance characteristics were investigated. The water-soluble binders LA133 and PAA showed significantly better performance than PVDF. The PAA binder effectively decreased the overpotential polarisation and resistance, increasing the lithium-ion diffusion coefficient and accelerating the redox reaction of polysulphides. The CNTs@S electrode with PAA as the binder showed the first discharge specific capacity of 703 mAh g−1 at a sulphur loading of 5.1 mg cm−2 at 0.3 C, with a decay rate of 0.1% over 150 cycles. Even with a higher sulphur loading of 7.1 mg cm−2, the electrode exhibited an initial capacity of 6.3 mAh cm−2 at a current density of 1.19 mA cm−2 and capacity retention of 98.4% over 50 cycles. In addition, the electrode with the PAA binder showed significantly increased volume energy density. The aqueous PAA binder is more suitable for the fabrication of high-sulphur-loading electrodes for lithium-sulphur batteries.