Inspired by plant body frameworks bionics: Fabrication of self-healing polyvinyl alcohol/cellulose nanocrystals composite hydrogels reinforced by polyurethane sponges for flexible supercapacitors.

With the booming development of electronic technology, ultra-toughness and self-healing supercapacitors have drawn substantial attentions. In this work, inspired by plant body frameworks, a novel method was proposed to prepare self-healing conductive hydrogels based on self-healing polyurethane sponge (PUS) network. First, a self-healing PUS based on multiple hydrogen bonding interactions and disulfide bonds was prepared. Subsequently, PUS was combined with polyvinyl alcohol (PVA)/cellulose nanocrystals (CNF) composite hydrogels crosslinked by borate ester bonds and hydrogen bonding interactions to manufacture the sponge network reinforced self-healing conductive hydrogels. Due to the reinforcement of PUS, the composite hydrogels had excellent mechanical properties, with a tensile strength of 1.81 MPa and a compressive strength of 1.96 MPa. After 400 times of charge-discharge cycles under bending deformation, the supercapacitor could maintain 90.1 % of the original specific capacitance value. Furthermore, the hydrogels could be healed at room temperature due to the hydrogen bonds and reversible borate bonds in PVA/CNF matrix, as well as the disulfide bonds and multiple hydrogen bonds in PUS. The healed supercapacitor could maintain 75.2 % of the original specific capacitance value after 400 times of charge-discharge cycles. Therefore, the as-prepared self-healing and tough conductive hydrogels may have promising prospects in electronic devices.