Polycyclic Quinone and Its Dithiin Derivative As Cathode Materials for Sustainable Aqueous Zn-Organic Secondary Batteries

Abstract

Aqueous Zinc-ion (Zn-ion) batteries are considered as attractive energy storage devices for large scale applications owing to their intrinsic safety, low cost and robustness1. However, their implementation is held back by sluggish diffusion kinetics of Zn2+ into inorganic host materials. Therefore, the focus is on redox active organic materials particularly quinone derivatives. These materials show moderate coulombic repulsions to the Zn2+ diffusion by having big tunnels in the crystal lattice2. Yet, very few organic materials have been reported for aqueous Zn-ion batteries. In the contextual importance of exploring new organic materials that can reversibly host Zn2+. Herein, we have explored highly conjugated pentacene-5,7,12,14-tetraone (PT) as cathode material for aqueous ZIBs for the first time. The versatile features such as strong π-stacking, high theoretical capacity (i.e. 317 mAh g-1 for 4e- transfer), structural diversity, inherent insolubility and non-defamation upon electrochemical process unlike simple quinones make PT a promising candidate to study. Moreover, we used filter paper as a separator instead of nafion membrane and ZnSO4 as supporting electrolyte salt which makes this battery more environmentally friendly and cost effective. In order to improve the rate capability and cycling stability, PT was incorporated in the mesoporous nanonetwork of CMK-3 carbon. In addition, the discharge voltage of the cell was enhanced by introducing sulfur atoms in the PT skeleton. Figure 1