Relevant Features of a Triethylene Glycol Dimethyl Ether-Based Electrolyte for Application in Lithium Battery

Abstract

Triethylene glycol dimethyl ether (TREGDME) dissolving lithium trifluoromethanesulfonate (LiCF₃SO₃) is studied as a suitable electrolyte medium for lithium battery. Thermal and rheological characteristics, transport properties of the dissolved species, and the electrochemical behavior in lithium cell represent the most relevant investigated properties of the new electrolyte. The self-diffusion coefficients, the lithium transference numbers, the ionic conductivity, and the ion association degree of the solution are determined by pulse field gradient nuclear magnetic resonance and electrochemical impedance spectroscopy. The study sheds light on the determinant role of the lithium nitrate (LiNO₃) addition for allowing cell operation by improving the electrode/electrolyte interfaces and widening the voltage stability window. Accordingly, an electrochemical activation procedure of the Li/LiFePO₄ cell using the upgraded electrolyte leads to the formation of stable interfaces at the electrodes surface as clearly evidenced by cyclic voltammetry, impedance spectroscopy, and ex situ scanning electron microscopy. Therefore, the lithium battery employing the TREGDME-LiCF₃SO₃-LiNO₃ solution shows a stable galvanostatic cycling, a high efficiency, and a notable rate capability upon the electrochemical conditions adopted herein.