Strategies for enhancing ionic conductivity and energy density of gel polymer electrolytes for next-generation flexible energy storage devices

In energy storage devices, gel polymer electrolytes (GPE) are favorable choices of electrolytes due to the absence of leakage, interchangeability with separators and increased safety compared to liquid electrolytes, and their superior ionic conductivity compared to all-solid electrolytes. However, GPEs' scope of application can be restricted by metrics such as ionic conductivity and operating voltage, while the latter is positively correlated to energy density. Herein, different polymer backbones of GPE and the mechanism of ionic conduction are reviewed. Meanwhile, strategies for enhancing ionic conductivity and energy density of GPE are summarized and discussed through selective presentation of pioneering works. Finally, the current challenges and future directions of GPE research for practical application are encapsulated as an attempt to enlighten ensuing endeavors.