(Battery Division Postdoctoral Associate Research Award Address, sponsored by MTI Corporation and the Jiang Family Foundation) The Solvation Structure of Active Cations in Next-Generation Battery Electrolytes

Abstract

Next-generation batteries offer the promise of higher performance using materials that are less expensive and more abundant than those in convention Li-ion cells. From a fundamental point-of-view, the new chemistries involved in these also systems allow for exploration of the unknown and generation of new, fundamental knowledge. To that end, this talk will explore the local structure of the active cations in electrolyte solutions for Li-S and Mg batteries and the effect of this structure on the charge storage reactions and ultimately on the battery metrics. The first part of the talk will discuss the emerging solvate electrolytes as possible electrolyte solutions for Li-S batteries. The solvate electrolytes are characterized by extremely high quantities of salt resulting in interesting electrochemistry at the S cathode. Because the behavior of the electrolyte solution is governed by the complexes in the solution, we will explore the local solvation structure of the active cation, Li+, and how it is affected by the addition of what are commonly thought to be innocuous cosolvents. The addition of the cosolvents to the solvate electrolyte results in subtle but important changes in the Li+ solvation structure that affect the kinetics of the S reduction.The second part of the talk will focus on electrolytes for Mg batteries. We will explore the local structure of Mg2+ in the seemingly simple MgCl2 + AlCl3 in THF electrolyte known as the magnesium aluminum chloride complex (MACC) electrolyte. The importance of Mg speciation in active electrolytes and the effect these complexes have on the charge transfer processes at the electrode-electrolyte interface will be addressed. We will also explore the role of chloride in facilitating the electrodeposition of divalent Mg2+ and the implications of using halogenated electrolytes in full cells. Figure 1