<p>Polymer electrolytes are much of interest for the development of flexible Na-based energy storage systems with desirable structure design and safety. However, the low ionic conductivity at ambient temperature, poor mechanical strength and high interfacial resistance of solid polymer electrolytes (SPEs) hinder their wide applications. Novel strategies like cross-linking polymer matrices, binary salt systems and incorporation of additives such as plasticizers, nanomaterials, ionic liquids and inorganic filler paving the way for improvement of electrochemical and mechanical properties of polymer electrolytes. This mini-review provides a comprehensive overview of various types of polymer electrolytes, namely solid, gel and composite developed for sodium-based energy storage systems. The review highlights the key performance aspects, namely ionic conductivity and electrochemical stability and mechanical strength which are essential for improving the efficiency and longevity of these devices. Furthermore, recent advancements in biopolymer-based renewable polymer electrolytes, focusing on their potential applications in flexible sodium-ion batteries and sodium-ion capacitors are discussed.</p> Graphical abstract <p></p>