Cost-Effective Water-Soluble Poly(vinyl alcohol) as a Functional Binder for High-Sulfur-Loading Cathodes in Lithium-Sulfur Batteries.

Abstract

Binder, as one of the key components, plays a crucial role in improving the capacity and cycling performance of lithium–sulfur (Li–S) batteries. In this work, commercially available, low-cost, water-soluble polyvinyl alcohol (PVA) has been systematically investigated as a functional polymer binder for high-sulfur-loading cathodes, with the aim of enhancing sulfur utilization, reducing capacity decay, and extending cycling life of the cathodes. In comparison with polyvinylidene fluoride as a conventional binder, PVA shows a valuable polysulfide entrapping ability and a much stronger binding strength. Its superior polysulfide entrapping ability has been verified through theoretical density functional theory calculations and an experimental ex situ adsorption study. In electrochemical Li–S battery performance evaluation, at a sulfur loading density of 3.5 mg cm–2, the sulfur cathode assembled with the PVA binder displays at 0.5 C a very slow capacity decay of only 0.010% per cycle over 250 cycles. Additionally, the strong binding strength of PVA allows the fabrication of thick sulfur cathodes with a high sulfur loading density of 10.5 mg cm–2, which shows a high areal capacity of 4.0 mA h cm–2 and a high cycling stability (capacity decay of 0.1% per cycle). In consideration of the superior capacity retention and cycling performance of its enabled cathodes, the cost-effective PVA is a promising candidate for high-sulfur-loading cathodes in practical applications.