Smart functional binders empowering lithium–sulfur cathodes with enhanced atmospheric stability and catalytic kinetics

Abstract

Although lithium–sulfur (Li–S) batteries have attracted considerable research attention, several critical barriers must be overcome to bridge the gap between laboratory-scale achievements and practical commercial applications. For example, the notorious polysulfide shuttle effect, severe electrode volume changes, and challenging solid–liquid–solid conversion reactions. In this study, we have developed a multifunctional binder by incorporating cobalt(II) phthalocyanine (CoPc) into conventional poly(vinylidene fluoride) (PVDF) at a relatively lower processing temperature, which induces the phase transformation of α-PVDF to β-PVDF, thereby constructing an enhanced localized electric field with three advantages: (1) superior adsorption capabilities and catalytic activity, (2) robust mechanical properties that accommodate substantial volume fluctuations during cycling, and (3) excellent hydrophobic properties allowing for long-term storage in air. As a result, the batteries composed of an optimized PC-10 binder (CoPc added at 10%) maintain a specific capacity of 706 mA h g⁻¹ after 500 cycles at 0.5C, 399 mA h g⁻¹ at 2C after 1000 cycles with a decay rate of only 0.049% per cycle, and 80.5% capacity retention even under high sulfur loading (5 mg cm⁻²). Moreover, the batteries maintained excellent discharge capacity with 1024 and 845 mA h g⁻¹ discharge specific capacities at 0.5C and 1C, respectively, even when the cathode with the PC-10 binder has been exposed to air for 20 days. This strategy has successfully established a multifunctional binder through a simple and feasible approach, offering new insights into addressing the inherent challenges of Li–S batteries.