Development of Stabilized Organic Cathodes Via Grafting Redox-Active Molecules to Carbon in Aqueous Zinc-Ion Batteries for Energy Storage Systems

Abstract

Despite being in the early stages of development, aqueous zinc-ion batteries (ZIBs) show much promise for grid scale energy storage with their safe, simple design, and high theoretical volumetric energy density. One of the major bottlenecks of ZIB performance is their limited practical cathode specific capacity. Organic redox-active molecules are gaining attraction as alternative cathode active materials to the more standard metal oxides. The limited capacity of cathodes using organic compounds as active materials can be addressed by the versatile nature of redox capable organic cathode design. However, these cathodes are often plagued by capacity fade. We developed aqueous ZIB cathodes with organic molecules grafted to carbon substrate via a facile synthesis technique. Electrochemical and material analysis confirmed the presence of covalent grafting. This tunable grafting method anchored and stabilized the redox active molecules which could easily be incorporated into a ZIB cathode. By fixing the molecules, capacity fade was mitigated as the cells were charged and discharged. Additionally, using this flexible synthesis methodology the cathode composition and structure was translated from work done on lithium-ion batteries and optimized for ZIB performance. In this work, the tunable organic cathode synthesis methods employ the use of simple chemical modifications that avoids the utilization and waste of expensive and hazardous compounds. This methodology has the flexibility to apply inexpensive and sustainable precursors to improve ZIB sustainability not only for lab scale use but also for pilot scale production. This approach highlights the promise of grafted organic materials for next generation ZIB cathodes.