Electrode and Conductive Additive Compatibility Yielding Excellent Rate Capability and Long Cycle Life for Sustainable Organic Aqueous Zn-Ion Batteries

Abstract

Aqueous Zn-ion batteries have tremendous potential to penetrate the energy storage market, as an alternative to Li-ion batteries, given the high volumetric capacity of Zn (5853 mAh cm–3), cost-effectiveness, earth abundance, and enhanced safety arising from using the aqueous electrolyte. However, its performance is stunted due to the poor rate capability and low cycle life originating from the degradation of cathode materials upon Zn2+ insertion/deinsertion. Thanks to the stability of aromatic organic cathode materials with the required intermolecular spacing, pentacene-5,7,12,14-tetraone (PT) is encapsulated into mesoporous conductive carbon (CMK-3) additive, which ensures the electrode performs charge–discharge at rates as high as 20 A gPT–1 (63C) with ∼ 46% capacity retention. Such rates are common for supercapacitors; therefore, this work is of significance because an excellent faradic behavior is obtained due to the chemical robustness of the cell. Further, the PT/CMK-3 composite electrode exhibited outstanding cycling stability up to 5000 cycles with more than 95% capacity retention at 2.5 A gPT–1. To enhance the potential and thereby cell voltage and energy density, sulfur (S) was introduced to the PT skeleton to obtain dibenzo[b,i]thianthrene-5,7,12,14-tetraone (SPT).