Pitch-derived 3D amorphous carbon encapsulated sulfur-rich cathode for aqueous Zn-S batteries

Rechargeable aqueous zinc batteries have attracted much attention due to their high security, plentiful zinc resources, and environmental friendliness. However, it can only offer limited specific capacity and energy density based on ion insertion chemistry cathode. Herein, we design a low-cost and high-energy density aqueous Zn-S battery where the conversion cathode was fabricated by pitch-derived three-dimensional(3D) amorphous carbon encapsulated industrial-grade sulfur powder. The cost of the chemical substances for this aqueous Zn-S battery might be reduced to $9.38 per kW h based on the affordable cost of the raw ingredients. It is found that the PAC/S-60.33% cathode reveals excellent electrochemical performance, including a high reversible capacity(633.5 mAh g^(-1)at 0.5 A g^(-1)), high energy density(297.5 Wh kg^(-1)), an excellent rate capability(204.5 mAh g^(-1) at 5.5 A g^(-1)), as well as good cycling stability(180 mAh g^(-1)after 400 cycles at 5.0 A g^(-1)). Besides, the reaction mechanism of the cathode was investigated using ex-situ X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), and transmission electron microscope(TEM). It was demonstrated that the cathode undergoes a conversion reaction between S and Zn S. Furthermore, the discoveries also offer prospective possibilities to fabricate more secure and inexpensive battery systems.