Polyethylene glycol-grafted cellulose-based gel polymer electrolyte for long-life Li-ion batteries

A PEG grafted cellulose gel polymer electrolyte was designed by simple UV-induced reaction with superior performances for lithium-ion battery. • The PEG modified cellulose gel polymer electrolyte was successfully synthesized. • The desirable toughness and wettability to liquid electrolyte was obtained. • The assembled LiFePO 4 cells with gel films owned a long-life cycling property. Recently, highly abundant natural materials have been used in the fields of energy storage because of their environmental friendliness and low cost. However, use of some natural materials like cellulose as host matrices of gel polymer electrolytes (GPEs) is challenging owing to the strong intra- and inter-molecular hydrogen bonding. Herein, a green GPE film was prepared by chemically grafting soft chain-polyethylene glycol (PEG) onto the backbone of cellulose. The introduction of PEG significantly improved the toughness of cellulose from 118 × 10 3 to 270 × 10 3 kJ m −3 , as well as raised the wettability in carbonate-based liquid electrolyte solutions from 22.6% to 141.7%. The first cycle coulomb efficiency stayed above 90%. The capacity retention of LiFePO 4 /Li batteries assembled with the as-obtained GPE reached 80.3% after 300 cycles at 0.2 C. In sum, the as-obtained cellulose-based GPEs look promising to replace separators and liquid electrolytes in Li-ion batteries.