Evaluating the synthesis of Mg[Al(hfip)₄]₂ electrolyte for Mg rechargeable batteries: purity, electrochemical performance and costs

Enhancing the performance of electrolytes stands as one of the key challenges for moving toward practical applications of Mg batteries. Within this work, we investigate different synthesis procedures for the state-of-the-art MgAlhfip electrolyte. The results show that the purity and electrochemical performance of MgAlhfip electrolytes depend on whether they are synthesized from organometallic or inorganic reagents. Additionally, electrolyte properties vary depending on the electrolyte preparation method, either in situ electrolyte formation or salt isolation. To improve electrolyte performance, we explore two approaches: additional salt isolation steps and the use of a scavenging additive. Salt precipitation results in a modest improvement in the coulombic efficiency of Mg plating/stripping, while a scavenging additive significantly reduces overpotentials and enhances coulombic efficiency, especially in electrolytes synthesized from inorganic reagents. Finally, investigated syntheses are evaluated in terms of their practical applicability through procedure complexity and costs of used chemicals. Based on this, we propose a synthesis procedure that strikes a balance between the electrochemical performance of Mg electrolyte and its costs.