Electrolyte Science for Divalent Metal Batteries

Abstract

Multivalent cation-based electrochemical energy storage concepts provide great promise and great challenges as beyond Li-ion technologies. Such systems based on Mg2+, Zn2+, or Ca2+ cations challenge current understanding of solvation and resultant properties in non-aqueous electrolytes, where the doubly-charged cation introduces new liquid solvation behavior compared to the more established alkali-metal (Li+, Na+) systems. In this presentation, we drive toward a more unified framework for understanding of solvation phenomena through a systematic comparison of solvation structure and dynamics in organic divalent electrolytes. Connecting these solvation trends to critical ensemble electrolyte properties such as ion transport and electrochemical stability will be the focus of this work. Specifically, we will highlight lessons learned from ethereal solvent systems (cylic ethers and glymes), which are the solvents most commonly employed in beyond Li-ion chemistries at large. We will discuss how the competition between anion and solvent coordination with the divalent cation regulates the observed electrochemical behavior and connect these themes to the principles of electrolyte design.