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

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. LiNi_xMn_yCo_zO₂) 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 (−CN) terminal groups exhibit a remarkable increase in the ionic conductivity at ambient temperature (4.52 × 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.