Extending Electrochemical Stability Window As a Result of Carbonate-Ketone Side Chain Modified Polyethylene Glycol Electrolytes for Lithium Batteries

Abstract

Solid state batteries are of wide interest owing to their high energy density and safety. Their stability with high voltage cathodes is not new to the researchers and are advantageous in various terms. Although ethylene oxide side chains being one of the most studied system also suffers from serious setback with its prime backbone. Here in our work, we studied the effect of terminal group of linear and tri-arm polyethylene glycol (PEG-OH) by converting it to carbonate-ketone (Carb-ket) from hydroxyl. We synthesized the polyethylene carb-ket (TPEG-carb-ket) terminal by ring opening reaction. The carb-ket functionality at the chain end not only increase the electrochemical stability window > 4.47 V but also limits the parasitic reactions with lithium metal stabilising SEI at the interface. The latter demonstrated the superior galvanostatic charge-discharge of LiFePO4 using as synthesized electrolyte loaded with LiTFSI salts as compare to similar chain length PEG-OH. This make the vast impact on controlling the undesired decomposed products at the interface to facilitate the high coulombic efficiency and capacity retention The TPEG-carb-ket also hinted at stable interface with lithium as a result of stripping and plating for more than 1200 h. These experiment results provide important insights backed by AIMD simulations in comparison with hydroxyl terminal system. Our study would aide with the major step on improving the higher voltage cathode with superior performance in the lithium batteries.