Enhancement of the stability window of PEO for high voltage all-solid-state lithium batteries

Abstract

Polyethylene oxide (PEO), one of the leading polymer electrolytes recommended against the safety concerns of liquid electrolytes, is unsuitable for high potential positive electrodes (e.g. LiNixMnyCozO2) needed to meet the increasing energy demand. Herein PEO main chain has been stabilized by modifying its (-OH) reactive terminal group. Modification of the reactive (-OH) group with (-OCH3) and (- C---N) terminal groups exhibit a remarkable increase in the ionic conductivity at ambient temperature (4.52 symbolscript 10-4 S cm-1). In addition, electrochemical stability window (ESW) has been expanded (>4.18 V). The modified gel polymer electrolyte (GPE) has exhibited 150 mAh g-1 discharge capacity and has retained 92% of its capacity for 50 cycles in charge-discharge tests. Instead of increasing the ESW with inorganic additives, modification of PEO's (-OH) reactive terminal groups and making the PEO main chain a stable matrix can be a more permanent solution/strategy in the first instance. Moreover, developed solid electrolyte promise stability, safety and flexibility, making their utilization possible even with complex geometry batteries with high energy density.