High-Voltage-Compatible Dual-Ether Electrolyte for Lithium Metal Batteries

Abstract

To improve the energy density of rechargeable batteries, lithium metal batteries (LMBs) consisting of high-voltage cathodes and metallic lithium anodes have been actively studied. Ether-based organic electrolytes, particularly 1,2-dimethoxyethane (DME), show good performance for LMB anodes, but due to low oxidation stability, they are difficult to apply in conjunction with high-reaction-voltage cathodes such as lithium cobalt oxide (LCO). Here, a dual-solvent system with fluorinated ether with high oxidative stability added as a co-solvent is used to increase the electrolyte oxidation stability. It is found that tetrafluoroethyl tetrafluoropropyl ether (TTE) is most suitable for use as the co-solvent, due to its non-solvation of Li salts and miscibility with DME arising from its non-polar nature. Introduction of a DME/TTE dual solvent with 1.0 M lithium bis­(fluorosulfonyl)­imide (LiFSI) increases the concentration of the salt coordinated by DME to an ultra-high electrolyte concentration of 5.0 M LiFSI. The oxidation stability of the electrolyte is improved by increasing the amount of the DME–Li+ complex. The DME/TTE ratio and the Li salt concentration of the dual-ether electrolyte are optimized through physical and electrochemical analyses. Compared to the conventional carbonated electrolyte, the dual-ether electrolyte shows low resistance and improved cycle performance in LMBs with an LCO cathode.

Enabling uniform Li deposition behavior with dynamic electrostatic shield by the single effect of potassium cation additive for dendrite-free lithium metal batteries

“…Thus far, numerous approaches have been proposed to enable stable plating and a dendrite-free Li metal surface: introducing an artificial surface layer on the surface of Li metal surface, designing three-dimensional Li hosts, optimization of electrolyte composition and more. 1,12,15,[19][20][21][22][23] Among these approaches, electrolyte additives have garnered significant interest as they offer a direct and effective strategy to inhibit Li dendrite growth. The introduction of even small amounts of additives can lead to noticeable improvements, while preserving the conventional manufacturing process.…”