An alternative composite polymer electrolyte for high performances lithium battery

Abstract

A composite electrolyte consisting of polyethylene-glycol dimethyl-ether (MW 2000 g mol−1), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) conducting salt, lithium nitrate (LiNO3) film-forming additive, and nanometric silica (SiO2) filler, is herein obtained by a scalable solvent casting pathway and thoroughly investigated for application in lithium metal polymer battery. Structure and morphology of the electrolyte are investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively, while its electrochemical features are revealed by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), chronoamperometry, and galvanostatic cycling tests in lithium cell. The room-temperature structure of the composite electrolyte reflects the combination into a complex of the membrane components, while its morphology appears smooth with uniform distribution of salts and ceramic. The electrolyte shows an ionic conductivity over 10−4 S cm−1 above 40 °C promoted by repeated heating and cooling, lithium transference number ranging from 0.22 at 45 °C to 0.27 at 70 °C, low interphase resistance and polarization in lithium cell, and an electrochemical stability window extending above 4.4 V. These optimal features allow the membrane to operate in a lithium cell with LiFePO4 cathode at 50 °C, with specific capacity exceeding 150 mAh g−1 and coulombic efficiency approaching 100% over prolonged cycling.