Exploring the possibilities of aqueous Magnesium-ion batteries

Aqueous magnesium-ion batteries (AMiBs) hold promise as a safe, sustainable, and high-energy alternative to lithium-ion batteries (LiBs). However, their development is hampered by the limited electrochemical stability window of aqueous electrolytes and the lack of suitable electrode materials. This study investigates the feasibility of MgMn2O4 spinel as a cathode material for AMiBs, focusing on optimising its synthesis, and cell setup, and understanding its charge storage mechanism. We systematically studied the effect of synthesis conditions on MgMn2O4 properties, followed by comprehensive electrochemical testing in a carefully designed cell setup. This setup minimises interference from parasitic processes, such as current collector corrosion, by employing rigorously selected current collectors. The detrimental impact of oxygen on current collector stability was also investigated. Our findings reveal an initial activation process in MgMn2O4, linked to the dissolution of Mn from the surface. This dissolution stabilises after the 10th cycle, leading to improved performance. Combining on-line ICP and XANES analysis confirms that while Mn redox activity continues, dissolution significantly diminishes, suggesting the formation of a favourable cathode-electrolyte interphase (CEI) during cycling. This research contributes to the development of high-performance AMiBs by providing insights into the crucial factors influencing their performance and stability.