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Carbon materials have become a focal point in supercapacitors (SCs) due to their perfect charge–discharge behavior, relatively low cost, and excellent electrochemical stability, but the limited electrochemical activity restricts their further development. MXenes (Ti3C2Tx) combine high electrical conductivity, hydrophilicity, and abundance surface functional groups, which contribute to high energy density when compounded with carbon materials. In this work, carbon material derived from mineral water bottles is modified with cetyltrimethylammonium bromide (CTAB) that spontaneously forms into porous heterogeneous structures with Ti3C2Tx under electrostatic interactions. The carbon material hinders the reaggregation of Ti3C2Tx, while Ti3C2Tx increases the electrochemical activity on the surface of the carbon material. A hierarchical porous carbon with a large specific surface area of 1754.3 m2 g−1, promoting the electrolyte migration kinetics and high specific capacitance in 6 m KOH electrolyte (404.1 F g−1 at 1 A g−1). The symmetric SC made as‐prepared carbon electrode shows an extended voltage window (1.8 V), an optimal energy density (31.19 Wh kg−1 at a power density of 450 W kg−1) and a low capacitance decay (1% after 15 000 cycles) in 1.5 m Na2SO4. The preparation of electrode material with a unique structure provides a practical and innovative strategy for the value‐added utilization of waste plastics. [ABSTRACT FROM AUTHOR]

Preparing electrode material integrated with high gravimetric/volumetric capacitance and fast electron/ion transfer is crucial for the practical application. Owing to the structural contradiction, it is a big challenge to construct electrode material with high packing density, sufficient ion transport channels, and fast electronic transfer pathways. Herein, MnO 2 porous carbon composite with abundant porous structure and 3D carbon skeleton was facilely fabricated from Linum usitatissimum. L stems via NaOH activation and MnO 2 introduction. The in-situ introduced MnO 2 not only increases the packing density and the electrical conductivity of the porous carbon but also provides more active sites for oxidation reactions. These unique characteristics endow the resultant MnO 2 porous carbon composite with remarkable gravimetric capacitance of 549 F g−1, volumetric capacitance of 378 F cm−3, and capacitance retention of 54.9 %. Giving the simple process and low cost, this work might offer a new approach for structural design and the practical application of high-performance electrode materials. [ABSTRACT FROM AUTHOR]

Achieving high rate capability of porous carbon at high mass loading is important for developing advanced supercapacitors. But it still remains a big challenge because thick electrode causes severely reduced electric conductivity and blocked ion migration channels. Herein, we develop a micelle-induced assembly method to prepare conductive porous carbon through puzzling flexible graphene quantum dots (GQDs). The unique sp2 hybridized GQDs ensure the product with a two times higher electric conductivity than the commercial activated carbon. The interconnected mesoporous structure promotes robust ion transport kinetics especially at high mass loadings. As supercapacitor electrode, it shows high capacitances of 315 and 170 F g−1 at 1 and 100 A g−1, respectively. Importantly, at a very high mass loading of 20 mg cm−2, it shows a remarkably high areal capacitances of 2.8 F cm−2 at 10 A g−1, which is much better than other reported carbon materials. The symmetric supercapacitors show maximum energy densities of 9.21 and 6.45 Wh kg−1 at the mass loadings of 2 mg cm−2 and 20 mg cm−2, respectively, revealing the structural advantage of GQD-puzzled porous carbon for practical applications. Conductive porous carbon prepared by micelle-induced assembly of graphene quantum dots shows high capacitive and rate performance at high mass loadings due to sufficient ion and electron transport paths. Image 1 • Porous carbon with high conductivity was prepared using the sp2 hybridized GQDs. • Sufficient electron/ion transport paths enable robust electrochemical kinetics. • The sample shows remarkable rate performance especially at high mass loadings. [ABSTRACT FROM AUTHOR]

Zinc ion hybrid capacitors (ZHCs) as a new type of energy storage device, possess high power density, low cost, and safety. However, the unsatisfactory energy density of ZHCs caused by low output voltage and small specific capacitance restricts its practical application. Herein, a novel multiple heteroatoms doping carbon sphere is achieved from the mixture precursors of glucosamine hydrochloride and sodium lignosulfonate via chemical activation strategy. High specific surface area, rich O/N/S-containing functional groups, and good electric conductivity endow the resultant carbon sphere with a superior specific capacity of 233 mAh g−1 at 1 A g−1 and outstanding capacity retention of 83 mAh g−1 at 50 A g−1. Remarkably, as-assembled ZHC exhibits a conspicuous energy density of 209.7 Wh kg−1 at 900 W kg−1, and its energy density still maintains 74.7 Wh kg−1 at 45,000 W kg−1. Furthermore, after 10,000 cycles, the resultant carbon sphere achieves 100% capacitance retention. This work offers a feasible strategy for carbon cathode materials with enhancing energy density and rate capability, and concurrently reasonable cycling stability. [Display omitted] • Carbon sphere is prepared by sodium lignosulfonate and glucosamine hydrochloride. • Multiple heteroatoms doping improve the electrochemical performance. • The assembled Zn-ion hybrid capacitors has excellent electrochemical performance. • This work provides a feasible strategy for carbon cathode materials. [ABSTRACT FROM AUTHOR]