Carbon cloth (CC) is widely used as a freestanding substrate for energy storage devices, due to its high conductivity, special porous network, and good mechanical flexibility. However, it is still challenging to fully utilize the space of CC to achieve a high mass loading of electroactive materials and ultimately fulfill high electrochemical performance. Herein, a new strategy is proposed to fill the gaps and voids in CC with a functionalized graphene hydrogel (FGH) through one-step hydrothermal treatment of oxidized CC submerged in a mixture of graphene oxide and p-phenylenediamine. The as-prepared FGH/functionalized CC is then adopted as a scaffold to load a lignosulfonate/polyaniline (Lig/PANI) hydrogel via in situ polymerization of aniline in the presence of lignosulfonate, and thereby an integrated textile (Lig/PANI/FGH/FCC) is obtained. The symmetric supercapacitor assembled with Lig/PANI/FGH/FCC electrodes and 1 M H₂SO₄ electrolyte shows a superior areal capacitance of 1223 mF cm⁻² and an energy density of 169.9 μW h cm⁻² at 2 mA cm⁻². Moreover, the assembled flexible all-solid-state supercapacitor presents competitive energy density (160.6 μW h cm⁻² at 1000 μW cm⁻²) and excellent flexibility. This design of anchoring a hierarchical porous conductive network in a macroscopic macropore framework paves a new avenue towards high mass loading and low interfacial resistance in macroporous material-based electrodes for high-performance energy storage devices.

Natural nacre built up with a brick-and-mortar architecture, exhibiting extraordinary strength and toughness, provides an inspiration to construct high-performance multifunctional films for flexible energy storage and portable electrical devices. In the present work, a nacre-mimetic graphene-based film (CNT@PANI/rGO/TA) is fabricated following this idea, wherein electroactive biomass tannin (TA) serves as glue, accompanied by the “mortar” polyaniline wrapped carbon nanotubes (CNT@PANI), to stick the reduced graphene oxide (rGO) “bricks” together. Benefiting from the thin layer of PANI on CNTs, the CNT@PANI nanowires intercalate into the rGO interlayers thus interlocking the nanosheets, and resulting in a well-defined porous multilayered structure. The obtained CNT@PANI/rGO/TA film exhibits both high mechanical strength (174.6 MPa) and toughness (9.17 MJ m⁻³). Meanwhile, the all-solid-state flexible supercapacitor assembled with CNT@PANI/rGO/TA demonstrates a high capacitance of 548.6 F cm⁻³ and an outstanding rate performance of 70.5% from 1 A g⁻¹ to 50 A g⁻¹. Even at −40 °C, the specific capacitance of the supercapacitor is up to 454.9 F cm⁻³, approximately 83% of the capacitance delivered at room temperature. The strategy of using electroactive biomass as glue to construct a nacre-mimetic graphene-based film with high strength, toughness and energy storage performance is proved to be straightforward and effective.

Carbon is predominantly used in zinc-ion hybrid capacitors (ZIHCs) as an electrode material. Nitrogen doping and strategic design can enhance its electrochemical properties. Melamine formaldehyde resin, serving as a hard carbon precursor, synthesizes nitrogen-doped porous carbon after annealing. Incorporating transition metal catalysts like Ni, Co, and Fe alters the morphology, pore structure, graphitization degree, and nitrogen doping types/proportions. Electrochemical tests reveal a superior capacitance of 159.5 F g⁻¹ at a scan rate of 1 mV s⁻¹ and rate performance in Fe-catalyzed N-doped porous carbon (Fe-NDPC). Advanced analysis shows Fe-NDPC’s high graphitic nitrogen content and graphitization degree, boosting its electric double-layer capacitance (EDLC) and pseudocapacitance. Its abundant micro- and mesopores increase the surface area fourfold compared to non-catalyzed samples, favoring EDLC and fast electrolyte transport. This study guides catalyst application in carbon materials for supercapacitors, illuminating how catalysts influence nitrogen-doped porous carbon structure and performance.

Tea waste contains various substances with phenolic hydroxyl groups, including lignin, tannins, tea polyphenols, etc., which are rarely utilized. In this study, tea waste was directly dispersed with graphene oxide to prepare tea waste/reduced graphene oxide (TW/rGO) hydrogel through a one-step hydrothermal method. The prepared hydrogel presented a continuous three-dimensional porous structure and exhibited good mechanical properties with a compressive strength of 53.4 ± 4.0 kPa. It also showed excellent electrochemical performance as an electrode material. Its specific capacitance reached 434.7 F g⁻¹ at a current density of 1 A g⁻¹, and its capacitance retention was 55.8% when the current density was increased to 100 A g⁻¹. In addition, an TW/rGO assembled all-solid-state supercapacitor demonstrated a superior specific capacitance of 372.8 F g⁻¹ and a competitive energy density of 12.9 Wh kg⁻¹ at 1 A g⁻¹.