A self-healable and highly flexible supercapacitor integrated by dynamically cross-linked electro-conductive hydrogels based on nanocellulose-templated carbon nanotubes embedded in a viscoelastic polymer network

Recent development of flexible and self-healable electro-conductive hydrogels (ECHs) are considered as promising soft materials towards intelligent applications. Nonetheless, realizing the integrated features of high electro-conductivity, viscoelasticity and mechanical toughness, as well as inherent mouldability, fast self-healing ability, and ideal electrochemical properties is still challenging. Herein, we report a kind of multifunctional ECHs based on a polyvinyl alcohol-borax (PVAB) hydrogel and carbon nanotubecellulose nanofiber (CNT-CNF) nanohybrids that combines the conductivity of CNTs and template function of CNFs. CNFs serve as dispersant to uniformly stabilize CNTs in suspension. As-prepared CNT-CNF nanohybrids are uniformly dispersed into PVAB to construct freeze-standing CNT-CNF/PVAB composite hydrogels. Owing to a conductive and reinforcing dual-network structure, the compression stress (similar to 93 kPa) and storage modulus (similar to 7.12 kPa) of CNT-CNF/PVAB are 2.7 and 1.9-fold larger than those of CNF/PVAB. CNT-CNF/PVAB also exhibits low density (similar to 1.1 g cm(-3)), high water content (similar to 95%), pH sensitivity, intrinsic mouldability and 20s self-healing capability. The solid-state supercapacitor assembled by PVAB-based hydrogels has a specific capacitance of 117.1 F g(-1) and a capacitance retention of 96.4% after 1000 cycles. The self-healable and flexible supercapacitor demonstrates an ideal capacitance retention (similar to 98.2%) after ten damaging/self-healing cycles and a capacitance retention (similar to 95%) after 1000 cycles under various deformation. (C) 2019 Elsevier Ltd. All rights reserved.