Partially Oxidized Cellulose grafted with Polyethylene Glycol mono-Methyl Ether (m-PEG) as Electrolyte Material for Lithium Polymer Battery

Herein, a novel cellulose derivative has been synthesized and investigated as a nature-derived solid polymer electrolyte for lithium batteries. Cellulose is oxidized in a two-step process to dicarboxylic acid cellulose to allow for grafting low molecular weight poly(ethylene glycol) monomethyl ether (550 g mol-1) via Fischer–Speier esterification at the thus obtained carboxyl groups. The chemical structure of the synthesized materials is confirmed by Fourier-transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy as well as X-ray diffraction. Incorporating lithium bis(trifluoromethane-sulfonyl)imide (LiTFSI) as conducting salt and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI) ionic liquid as plasticizer results in the realization of an amorphous and solvent-free solid polymer electrolyte. These electrolyte membranes are characterized by high thermal and electrochemical stability and ionic conductivities of about 1×10−5 S cm−1 at 20 °C and 2.5×10−4 S cm−1 at 80 °C, which enables very stable lithium stripping and plating for more than 800 h.