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MnO2–Mn3O4 heterostructure materials are applied in aqueous magnesium ion energy storage for the first time. The heterostructure yields an exceptionally high pseudocapacitance contribution, resulting in a specific capacitance of 313.5 F g−1 at 1 A g−1, which contrasts with that of MnO2 (108.8 F g−1) and Mn3O4 (123.5 F g−1). Additionally, it shows potential for practical applications as a cathode for magnesium ion hybrid supercapacitors (MHS). [ABSTRACT FROM AUTHOR]

Exploring anode materials with an excellent electrochemical performance is of great significance for supercapacitor applications. In this work, a N-doped-carbon-nanofiber (NCNF)-supported Fe3C/Fe2O3 nanoparticle (NCFCO) composite was synthesized via the facile carbonizing and subsequent annealing of electrospinning nanofibers containing an Fe source. In the hybrid structure, the porous carbon nanofibers used as a substrate could provide fast electron and ion transport for the Faradic reactions of Fe3C/Fe2O3 during charge–discharge cycling. The as-obtained NCFCO yields a high specific capacitance of 590.1 F g−1 at 2 A g−1, superior to that of NCNF-supported Fe3C nanoparticles (NCFC, 261.7 F g−1), and NCNFs/Fe2O3 (NCFO, 398.3 F g−1). The asymmetric supercapacitor, which was assembled using the NCFCO anode and activated carbon cathode, delivered a large energy density of 14.2 Wh kg−1 at 800 W kg−1. Additionally, it demonstrated an impressive capacitance retention of 96.7%, even after 10,000 cycles. The superior electrochemical performance can be ascribed to the synergistic contributions of NCNF and Fe3C/Fe2O3. [ABSTRACT FROM AUTHOR]

• Self-healable and redox bromide-ion hydrogel electrolyte was synthesized. • SAM-Zn exhibits excellent self-healing and electrochemical properties. • Assembled supercapacitor displays remarkable energy density and stability. Functional energy storage devices are usually dependent on functional hydrogel electrolytes, due to their high conductivity, flexibility and special functionality. However, the function of hydrogel electrolytes mostly depends on the functional groups of the polymer chain or their interaction with ions. The compatibility of function and electrochemical performance is the key to building a functional hydrogel electrolyte. In this study, a functionally integrated self-healable and redox bromide-ion additive hydrogel electrolyte (SAM-Zn) was synthesized based on a natural polymer backbone (sodium alginate aqueous solution), which exhibits outstanding self-healing ability and excellent mechanical properties. When SAM-Zn is assembled into Zn-ion hybrid supercapacitors (SAM-ZHS), which can achieve 219.4 mA h g−1 at a wider voltage window (0–2.6 V), higher energy density of 210 Wh kg−1 at 1914.6 W kg−1. Besides, the self-healed SAM-ZHS displayed excellent cycling stability after 2,000 cycles with 96.8% capacity retention. This work provides a simple strategy for the combination of self-healing properties and excellent electrochemical properties in hydrogel electrolytes. [ABSTRACT FROM AUTHOR]

High-performance porous carbon materials have always received much interest for supercapacitors due to their excellent cycling stability, superior conductivity, etc. Herein, sulfur, phosphorous and chlorine tri-doped hierarchically porous carbon (SPC) were prepared by simply co-activating using KOH and Na 2 S with wheat bran as precursor. Na 2 S can not only improve the specific surface area (1310.3 m2 g−1 to 1585.5 m2 g−1) and pore volume (0.767 cm3 g−1 to 0.977 cm3 g−1), but also introduce sulfur atoms to contribute extra pseudocapacitance. Benefitting from the heteroatom doping and surface structure optimizing, the as-prepared SPC exhibits a large specific capacitance of 488 F g−1 (at 1 A g−1), superior to the porous carbon that was only activated by KOH (245 F g−1 at 1 A g−1), and still remains 51.6% of the initial specific capacitance at 20 A g−1.The supercapacitor assembled by SPC delivers a high energy density of 12.5 Wh kg−1 (at 250 W kg−1). After charge-discharge for 9000 cycles (at 10 A g−1), the capacitance can still remain 96% of the initial value, showing that SPC is a promising candidate for high-performance supercapacitor. [Display omitted] • S, P, Cl tri-doped porous carbon was successfully prepared via KOH and Na 2 S co-activation. • The co-activation method can improve the specific surface area, pore volume, and S content of the as-obtained carbon. • The as-prepared SPC exhibits considerable pseudocapacitance contribution. • Symmetric supercapacitor constructed by the optimized SPC delivers high energy density and long term cycling stability. [ABSTRACT FROM AUTHOR]

The exploration of new-family flexible carbon architectures is significant with regard to flexible electrochemical capacitors. Herein we show the carbonization of core-shell structured metal-organic frameworks (MOFs) (i.e. , ZIF-8@ZIF-67) on a waste biomass of cosmetic cotton to prepare flexible nitrogen-doped carbon heteroarchitectures (hetero-fNCs) that possess high supercapacitive properties, including a high energy density of 30 Wh kg−1 at 1440 W kg−1 and good capacitance retention of 89.5% after 5000 cycles. Our elaborately designed hetero-fNCs demonstrate multiple advantages: (i) The outer-layer ZIF-67-derived mesoporous carbons show abundant mesopores, providing abundant ion-diffusion pathways for mass transport and rich graphite microstructures, improving electrical conductivity for electron transfer; (ii) the inter-layer ZIF-8-derived microporous carbons possess a mass of micropores for more charge storage; (iii) the inner-layer cosmetic cotton-derived flexible carbons afford good mechanical flexibility, guaranteeing performance stability during use; and (iv) the plentiful nitrogen dopants within all carbon components increase the capacitance through their pseudocapacitive contribution. As a consequence, the flexible supercapacitor based on hetero-fNCs exhibits high energy and power densities, as well as good bending stability, highlighting the significance of MOFs and flexible biomass materials. Image 1 • hetero-fNCs were prepared by carbonizing bilayered MOFs/flexible biomass. • hetero-fNCs exhibited excellent flexibility, hierarchical pores and good electrical conductivity. • hetero-fNCs exhibited excellent supercapacitive properties and good stability. [ABSTRACT FROM AUTHOR]