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

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.