Understanding the impact of electrolyte composition on the cathode performance of aqueous Zn-MnO2 batteries using operando XAS

Aqueous Zn metal batteries are considered one of the most promising alternatives to lithium-ion for their safety and cost. With a zinc anode offering a high theoretical capacity of 820 mAh g⁻¹ and the added benefit of a nonflammable aqueous electrolyte, these batteries hold significant potential for demanding applications like electric mobility and grid storage. Nowadays the biggest limitation for commercialization is the development of reliable cathodes. Manganese dioxide (MnO2) has been used as one of the most promising cathode materials for aqueous battery already beyond ten decades due to the considerable capacity, decent voltage, low-cost and rich abundance. Despite being a very common, the mechanism at the MnO2 cathode is still debated, with several different mechanisms suggested. In order to understand the relation between the electrolyte composition and pH and the reaction mechanisms we propose to perform a operando XAS experiments at the Mn, Fe and Zn K-edge to access, valuable and quantitative information on the Mn and Zn speciations and concentrations in the cathode and in the electrolyte for different pH, buffer and redox mediator. The proposed experiment will provide critical insights into how electrolyte composition dictates cathode behavior, guiding the development of more efficient and durable Zn-MnO2 batteries.