Regulating Solvation Chemistries via Electric-Field-Induced Locally Concentrated Suspension Electrolytes for Lithium Metal Batteries.

Lithium-ion batteries, as sustainable alternatives to fossil fuels, are in great demand for powering modern society. Their energy density can further be significantly improved by using Li metal anodes; however, Li metal suffers from the critical challenges of unstable solid-electrolyte interphase (SEI) along with uncontrollable dendritic Li growth. Here, a universal electrolyte design principle is proposed and demonstrated by using suspension electrolytes with charged additives. The solvation structure of Li ions can be regulated, as negatively charged additives show strong electrostatic interaction with Li ions, leaving them weakly solvated in the electrolyte. Moreover, negatively charged additives carrying Li ions can be locally concentrated at the surface of the Li metal, enhancing their ability to regulate solvation and improve interfacial mobility, beneficial for the formation of inorganic-rich SEIs and compact Li deposition. Accordingly, Li||Li symmetric cell demonstrates >500 h stable cycling at 2 mA cm and 2 mA h cm and Li||LiFePO cell shows 97% capacity retention after 400 cycles in 1C. The universality of this design is further demonstrated in various negatively charged suspension electrolyte systems. Such an electrolyte design rationale can shed light on the development of advanced electrolyte systems for realizing high-energy-density and long-duration metal battery systems.