Construction of high sulfur loading electrode with functional binder of polyacrylic acid polymer grafted with polyethylene glycol for lithium/sulfur batteries

Abstract

Construction of high sulfur loading is crucial for the development of high energy density lithium/sulfur batteries. The binder is indispensable for constructing high active material loading electrode. Here, cross-linked polymeric network of polyacrylic acid polymer grafted polyethylene glycol (PAA-g-PEG) as functional binder has been developed for constructing high sulfur loading electrode in lithium/sulfur batteries. The cross-linked structure of PAA-g-PEG polymer binder has enhanced the active material adhesion, mechanical properties, which decreased overpotential polarization, improved the lithium ions diffusion coefficient, and reduced the self-discharge. More importantly, the PAA-g-PEG functional binder could alleviate the expansion of high sulfur loading electrode. Due to the above advantages, the carbon nanotubes modified sulfur electrode (CNTs@S; sulfur content: 84.3%) with PAA-g-PEG binder obtains the first discharge specific capacity of 795 mAh g−1 at 2.56 mA cm−2 (0.3 C) under a sulfur loading of 5.1 mg cm−2, with a decay rate of 0.07% per cycle over 200 cycles. Even with the high sulfur loading of 9.6 mg cm−2, the CNTs@S electrode exhibits an initial area capacity of 9.5 mAh cm−2 at a current density of 1.61 mA cm−2, and the capacity retention of 97.5% over 50 cycles.