High-Performance Biomass-Based Flexible Solid-State Supercapacitor Constructed of Pressure-Sensitive Lignin-Based and Cellulose Hydrogels

Employing renewable, earth-abundant, environmentally friendly, low-cost natural materials to design flexible supercapacitors (FSCs) as energy storage devices in wearable/portable electronics represents the global perspective to build sustainable and green society. Chemically stable and flexible cellulose and electroactive lignin have been employed to construct a biomass-based FSC for the first time. The FSC was assembled using lignosulfonate/single-walled carbon nanotube_HNO₃ (Lig/SWCNT_HNO₃) pressure-sensitive hydrogels as electrodes and cellulose hydrogels as an electrolyte separator. The assembled biomass-based FSC shows high specific capacitance (292 F g^–1 at a current density of 0.5 A g^–1), excellent rate capability, and an outstanding energy density of 17.1 W h kg^–1 at a power density of 324 W kg^–1. Remarkably, the FSC presents outstanding electrochemical stability even suffering 1000 bending cycles. Such excellent flexibility, stability, and electrochemical performance enable the designed biomass-based FSCs as prominent candidates in applications of wearable electronic devices

Metal–Organic Coordination Polymer to Prepare Density Controllable and High Nitrogen-Doped Content Carbon/Graphene for High Performance Supercapacitors

Design and preparation of carbon-based electrode material with high nitrogen-doping ratio and appropriate density attract much interest for supercapacitors in practical application. Herein, three porous carbon/graphene (NCG_Cu, NCG_Fe, and NCG_Zn) with high doping ratio of nitrogen have been prepared via directly pyrolysis of graphene oxide (GO)/metal–organic coordination polymer (MOCP) composites, which were formed by reacting 4,4′-bipyridine (BPD) with CuCl₂, FeCl₃, and ZnCl₂, respectively. As-prepared NCG_Cu, NCG_Fe and NCG_Zn showed high nitrogen doping ratio of 10.68, 12.99, and 11.21 at. %; and high density of 1.52, 0.84, and 1.15 g cm^–3, respectively. When as-prepared samples were used as supercapacitor electrodes, NCG_Cu, NCG_Fe and NCG_Zn exhibited high gravimetric specific capacitances of 369, 298.5, 309.5 F g^–1, corresponding to high volumetric specific capacitances of 560.9, 250.7, 355.9 F cm^–3 at a current density of 0.5 A g^–1, as well as good cycling stability, nearly 100% of the capacitance retained after 1000 cycles even at a large current density of 10 A g^–1. It is expected that the provided novel strategy can be used to develop electrode materials in high performance energy conversion/storage devices