A Minireview on Polyurethane-Based Flexible Electrodes for Wearable Supercapacitors: Strategies, Syntheses and Electrochemical Performance Evaluations

Advancements in the field of wearable gadgets necessitate flexible and safe energy storage devices to power them. Rechargeable batteries are the best choices for long-run applications, but their safety is a major constraint. Supercapacitors evolved as an alternate solution whereby the safety, flexibility, and high-rate performances are assured. A crucial step involved in the manufacturing of a wearable supercapacitor is the preparation of highly flexible and bendable electrodes. The electrode-active materials possessing exceptional electrochemical performances, combined with highly flexible polymers, are used to prepare flexible electrodes for supercapacitors. The performance of a supercapacitor mainly depends on the electrochemical activity of the electrode-active material; hence, their incorporation in the polymer network requires proper attention to retain the performance. In this review article, we discuss the salient features of polyurethane (PU)-based flexible electrodes, particularly for application in wearable supercapacitors where PU is used as both an electrolyte additive/filler and an electrode-active material. The salient features of PU include low cost, easy synthesis, light weight, high flexibility and bendability, good resilience, etc., hence, their application has attracted attention in the preparation of flexible supercapacitor electrodes. The various advanced strategies adopted to prepare the PU-based flexible supercapacitor electrodes are explained in detail, and the electrochemical performances of the PU-based supercapacitor by emphasizing their flexibility features are unravelled.