Enhancement of charge transport in interconnected lignin-derived carbon fibrous network for flexible battery-supercapacitor hybrid device

Abstract Self-supporting and flexible carbon fibrous mats are promising electrode materials for wearable devices. The contact resistance between adjacent fibers is still a limit for further improvement of energy storage performance. Herein, an activated interconnected lignin-derived carbon fibrous network (AILCFN) is fabricated by electrospinning followed by heat treatment. The unique interconnected structure between fibers in AILCFN is designed by controlling the ratio of soft Kraft lignin fractions with different thermal mobility. While the interconnected fibers are benefited for the electron transport and conductive property of the carbon networks, the high specific surface area is synergistically conduced to the direct channels for the fast ion transfer. The as-prepared AILCFN-3 exhibits an excellent specific capacitance and a high rate capability (69% from the current density from 1 to 20 mA cm−2). Further, AILCFN-3 can act as the scaffold to support the electrodeposited Ni-Co-S nanosheets. The AILCFN/Ni-Co-S composite electrode displays a high specific capacity of 1140.0 C g−1 at a current density of 10 A g−1. The assembled AILCFN/Ni-Co-S//AILCFN-3 BSH exhibits a high energy density of 30.8 Wh kg−1 with a power density of 0.8 kW kg−1 and demonstrates both excellent cyclability and flexibility, attributed to the high effective specific surface area and advantageous interconnected structure. The self-powered system assembled onto a lab coat can continuously power for the electronic watch under sunlight illumination and dark environment, demonstrating the promising potential of AILCFN in future wearable electronics. This work represents a “waste into wealth” direction of conversion strategy from biomass waste lignin to value-added energy storage materials, which conversely turns different thermal property of lignin fractions to good account, and breaks through the application limits caused by the heterogeneity.