Effect of Heteroatoms doped Nanoporous Carbon for Aqueous Zinc-Bromine Battery: Self-healing mechanism to improve single cell cycle stability

Abstract

As interest in renewable energy increases, the importance of battery-based energy storage system (BESS) that store energy power from renewable development is mainly emphasized. Lithium-ion based secondary batteries, which are most widely used, frequently have ignition problems. One of the next-generation batteries, zinc-bromine based aqueous batteries, are being actively studied based on their high safety and environmental friendliness. However, there is an exorbitant price for flow system due to the use of a membrane, an electrolyte tank, and a pump. In order to eliminate the shortcomings, this research introduced a form of membraneless & flowless battery systems.

This special cell configurations (membraneless & flowless) can accelerate the bromine crossover phenomenon and the self-discharge process. However, the self-discharge process, which interacts with metallic zinc and leads to low Coulombic efficiency, can reduce zinc dendrites and dead zinc. In this study, to improve the reversibility of the bromine redox reactions, nanoporous carbon materials doped with nitrogen and boron heteroatoms was synthesized and coated on graphite felt. Disparate electrochemical performances were observed when carbon was coated with different heteroatoms. These diverse interactions and single cell performances can be explained not only by the effect of various physical properties and computational backgrounds, but also by physicochemical differences in heteroatoms (nitrogen and boron). As one of the electron-donating species, boron can reduce the electron affinity of nitrogen (C–N–B bond) atoms, which can lead to lower reactive activity of oxygen evolution reactions in aqueous electrolytes. In addition, the bromine redox reactions with boron species can be improved by enhancing the reversibility of the bromine chemistry. This enhanced reversibility led to lower overpotentials of single cell test and dramatically increased cycle stability.