Effect of preconditioning on cycling performance of aqueous Zn-ion batteries

Abstract

In this study, we provide valuable insights into the preconditioning effects on optimization of a zinc ion (Zn–MnO₂) battery with lower current rates. While other academic papers aim to provide fundamental insights and highly engineered approaches, this paper aims to provide a commercially relevant study that improves the performance of a full system that can be applied at scale. We demonstrate that fast C-rate preconditioning effectively improves the performance of Zn–MnO₂ full cells when used in synergy with an aqueous electrolyte with 1 vol% acetonitrile additive and optimized ZnSO₄ and MnSO₄ salt concentrations. Three cycles of preconditioning protocols using C/3 rate and 1C rate led to a remarkable specific discharge capacity of over 500 mAh g⁻¹ for low loading cathodes of ∼2 mg cm⁻² after 25 cycles at C/10 rate. Discharge capacity ∼350 mAh g⁻¹ and high coulombic efficiency of 99% can be maintained even after increasing electrode loadings to commercially relevant levels of ∼6 mg cm⁻². These results demonstrate that preconditioning could activate internal restructuring of the electrolytic MnO₂ cathode during fast-rate cycling and can lead to the creation of more efficient pathways for both electrons and ions, improving the overall conductivity and Zn²⁺ transport. It highlights electrochemical preconditioning as a simple yet powerful strategy to achieve high specific discharge capacities in commercial aqueous zinc-ion batteries.