Investigating the Impact of Particle Size on the Performance and Internal Resistance of Aqueous Zinc Ion Batteries with a Manganese Sesquioxide Cathode

Abstract

Aqueous zinc ion batteries are considered to be one of the most promising battery types for stationary energy storage applications. Due to their aqueous electrolyte, they are inherently safe concerning flammability and environmentally friendly. In this work, the strong influence of the particle size of manganese sesquioxide on the performance of the battery is investigated. Ball milling was used to decrease the particle diameter. The resulting powders were used as active material for the cathodes, which were assembled in coin cells as full cells together with zinc foil anodes and aqueous electrolyte. It was shown that about one third of the original particle size can nearly triple the initial capacity when charged with constant current and constant end-of-charge voltage. Additionally, smaller particles were found to be responsible for the collapse of capacity at high current densities. By means of electrochemical impedance spectroscopy, it was shown that particle size also has a large impact on the internal resistance. Initially, the internal resistance of the cells with small particles was about half that of those with big particles, but became larger during cycling. This reveals accelerated aging processes when the reactive surface of the active material is increased by smaller particles.