Li-ion batteries with poly[poly(ethylene glycol) methyl ether methacrylate]-grafted oxidized starch solid and gel polymer electrolytes

Abstract

Polymer electrolytes are considered in lithium-ion batteries because of their high safety and properties such as flexibility, easy moldability, etc. Starch is one of these polymers from renewable resources. Considering the semi-crystal structure of starch and ion conduction in amorphous phase, herein starch is oxidized and then modified with poly[poly(ethylene glycol) methyl ether methacrylate]. Solid polymer electrolytes (SPEs) are prepared by dissolution of lithium salt within polymer while gel polymer electrolytes (GPEs) as crosslinked structures are swollen in lithium salt solution. After validation of successful syntheses, all SPEs and GPEs with different oxidation state and various PEGMA/oxidized starch are evaluated in Li-ion battery performance. The synthesized GPEs and SPEs show the highest ionic conductivity of 5.5 × 10⁻³ and 2.19 × 10⁻⁴ S cm⁻¹, respectively at room temperature. Lithium ion transfer number (t⁺) of 0.6–0.9 and electrochemical stability window of 4.4–4.9 V are obtained for SPEs and GPEs. The discharge capacity is ∼180 mAh g⁻¹ at 0.2 C with capacity retention of 75 % after 100 cycles.