A Flexible and Self-Healable Gelled Polymer Electrolyte Based on a Dynamically Cross-Linked PVA Ionogel for High-Performance Supercapacitors

Abstract

Ionogels combine the virtues of polymers and ionic liquids (ILs) and have greater potential for supercapacitors (SCs) than hydrogels and organic gels. Undoubtedly, the self-healing ability of ionogels dramatically improves the reliability of related SCs. Herein, we reported a dynamic diol-borate ester-cross-linked polyvinyl alcohol (PVA) ionogel electrolyte for smart double-layer capacitors. The results indicated that 1-ethyl-3-methylimidazolium chloride (EmimCl) could form a strong interaction with the hydroxy groups on PVA, thereby depressing the crystallization efficiently. The resultant ionogel exhibited an amorphous nature with excellent ionic conductivity up to 2.43 × 10–3 S/cm, high flexibility, and 95% healing efficiency when the IL content was 90 vol %. It could be inferred from the fact that EmimCl acted not only as an ion provider to improve the ionic conductivity but also as a plasticizer to enhance the chain mobility and self-healing efficiency. Based on the unique properties of PVA-boric acid/EmimCl ionogels, a flexible and self-healable SC was assembled. The as-prepared SC delivered a specific capacitance of 90 F/g at 0.1 A/g and retained 98% capacitance after 3000 charge–discharge cycles at a current density of 2 A/g. More interestingly, it could tolerate physical bending and healing without significant performance deterioration. The present study provides a novel strategy to prepare self-healable ionogel electrolytes that can be applied to smart energy storage devices.