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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]

Manganese oxides are commonly employed as a cathode for magnesium ion storage in aqueous magnesium ion hybrid supercapacitors (MHS). However, sluggish reaction kinetics still hinders their practical application. Herein, we designed K-birnessite-MnO2 and electrostatically spun mulberry-like carbon composites (K-MnO2/HMCs) via an in situ growth technique. Benefiting from the 3D conductive carbon network substrate, the in situ fabricated K-MnO2 exhibits more active sites and provides more interfacial contact area between the electrode material and the electrolyte. This improvement enhances its conductivity, facilitating the rapid transfer of electrons, diffusion of ions, and redox reactions. As a result, K-MnO2/HMC-based MHS achieves a specific capacity of 168 mA h g−1 at 0.5 A g−1, simultaneously exhibiting a superior energy density of 111.1 W h kg−1 at a power density of 505 W kg−1. Furthermore, it demonstrates excellent high rate performance and a long cycling life for aqueous magnesium ion storage, offering new insights for MHS applications. [ABSTRACT FROM AUTHOR]

Currently, electrospun carbon nanofibers (ECNFs) have attracted much attention due to their flexibility and easy fabrication. However, ECNFs generally show poor electrical conductivity, greatly limiting their practical application. In this work, flexible hierarchically porous carbon polyhedra embedded carbon nanofibers doped with N and S (NSCPCNF) were synthesized by electrospinning a metal–organic framework ZIF-67 and a thiourea incorporated polyacrylonitrile precursor with subsequent carbonization. Due to the enhanced specific surface area, improved charge transfer ability and pseudocapacitive contribution by N, S dual doping, the as-obtained NSCPCNF shows a much higher specific capacitance of 396 F g−1 at a current density of 1 A g−1 in 1 mol L−1 H2SO4 electrolyte (three-electrode mode) than that of ECNFs (192 F g−1). More importantly, a flexible supercapacitor (FSC) assembled using NSCPCNF electrodes achieves a high specific capacitance of 103 F g−1 at a current density of 0.5 A g−1 (two-electrode mode), and a high energy density of 14.3 W h kg−1 at a power density of 250 W kg−1, which outperforms most of the reported ECNF based FSCs, and it also exhibits a high capacitance retention (107% of the initial value after 3000 charge–discharge cycles) and superior bending stability. The strategy proposed in this work provides the feasibility to explore high-performance flexible electrode materials for FSCs. [ABSTRACT FROM AUTHOR]

In this work, porous carbon spheres with hierarchical pores (denoted as hCSs) were fabricated via a sol–gel process using a surfactant-directing assembly strategy and investigated as capacitive deionization (CDI) electrode materials for the first time. By using transmission electron microscopy and N2 adsorption/desorption analyses, a hierarchy of micropores and mesopores was demonstrated to be present in the hCSs. Based on the results of CDI measurements, the hCSs obtained at 800 °C (hCSs-800) displayed the best electrosorption performance of all the hCS samples tested: hCSs-800 exhibited a high electrosorption capacity of 15.8 mg g−1 when the initial NaCl concentration was 500 mg L−1. Furthermore, according to a Kim–Yoon plot analysis, hCSs-800 integrated the merits of both a high electrosorption capacity and fast electrosorption rate, indicating the superiority of these hCSs for CDI applications. [ABSTRACT FROM AUTHOR]

Pursuing active, low-cost, and stable electrode materials with superior rate capability and long-life cycling performances for lithium-ion batteries remains a big challenge. In this study, a carbon-coated shuttle-like Fe 2 O 3 /Fe 1- x S heterostructure is synthesized by simply annealing Fe-based metal-organic frameworks (MIL-88(Fe)) as precursors and sublimed sulfur. Carbon-coated Fe 2 O 3 /Fe 1- x S displays a unique structure with ultrafine Fe 2 O 3 /Fe 1- x S nanoparticles distributed in the hollow and porous carbon matrix, which offers a large specific surface area and fast charge transfer ability, and alleviates the volume change upon cycling. When evaluated as an anode material for lithium-ion batteries, it exhibits an ultra-high specific capacity of 1200 mA h g -1 at 0.1 A g -1 , and superior high rate capability with a capacity of 345 mA h g -1 at a very high current density of 5.0 A g -1 owing to its high electrical conductivity and enhanced pseudocapacitive contribution from surface effects. The current strategy is promising to synthesize the carbon-coated porous structure from metal-organic frameworks for next-generation energy-storage applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)