Glyme-based electrolytes for lithium metal batteries using insertion electrodes: An electrochemical study

We report an electrochemical study of end-capped glymes dissolving lithium salts as electrolyte solutions for lithium metal batteries. Various electrolyte formulations including triethylene and diethylene glycol dimethyl ethers as solvents and lithium salts employing bis(fluorosulfonyl)imide (FSI−), bis(trifluoromethanesulfonyl)imide (TFSI−), and bis(pentafluoroethanesulfonyl)imide (BETI−) anions are explored. The ion transport properties, the lithium/electrolyte interphase characteristics and the electrochemical stability window are investigated by means of chronoamperometry, electrochemical impedance spectroscopy, galvanostatic cycling, and voltammetry measurements. The comparative study suggests electrochemical properties well suitable for lithium battery application which enable long cycling. The electrolyte solutions are studied in cells using an insertion cathode material, i.e., lithium iron phosphate (LiFePO4), and the high-energy lithium metal anode. The results reveal that the electrolyte composition has a remarkable effect on the cell performances, and indicate the solutions of LiTFSI salt in either glymes as the most adequate formulations for possible applications among the ones herein investigated.