Polymer‐based solid electrolytes (PSEs) have attracted tremendous interests for the next‐generation lithium batteries in terms of high safety and energy density along with good flexibility. Remarkable performances have been demonstrated in PSEs, which endowed PSEs with the potential to replace liquid electrolytes to meet the market demands. In this review, polymer matrices, different polymer architectures, and functional filler materials used in PSEs are discussed to explore the design concepts, methodologies, working mechanisms, and pros and cons of various PSEs. In addition, their recent notable applications in all‐solid‐state lithium ion batteries, lithium–sulfur batteries, suppression of lithium dendrites, and flexible lithium batteries are also introduced. Finally, the challenges and future prospects are sketched to provide strategies to explore novel PSEs for high‐performance all‐solid‐state lithium batteries.

A convenient in-cell electropolymerization method is developed to prepare a conductive polymer, PEDOT, as a cathode binder inside a Li–S cell for the enhancement of the cell performance.