Selvakumaran Dinesh

This review highlights the recent developments of cathode materials for aqueous zinc-ion batteries, which are cost effective and have good safety.

Three-dimensional (3D) nanostructures are commonly endowed with numerous active sites, large specific surface area and good mechanical strength, which makes them as an efficient candidate for energy storage and conversion. Herein, by considering the advantages of 3D nanostructures we successfully fabricated carbon coated nickel sulfide on nickel foam (C@NS@NF) with a unique 3D tree-like superstructures via a two-step hydrothermal process. In virtue of its hierarchical superstructures, 3D tree-like architecture and carbon shell encapsulation, the as-fabricated carbon coated Ni3S2 can be directly served as binder-free bifunctional electrodes for supercapacitor and hydrogen evolution reaction (HER), where high specific areal capacitances (6.086 F cm-2 at 10 mA cm-2) for supercapacitors and low overpotential (92 mV at 10 mA cm-2) for electrocatalyst have been demonstrated. These inspiring results of this material makes it as a potential candidate for energy storage and conversion.

A honeycomb‐like 3D N/S co‐doped porous carbon‐coated cobalt sulfide (CoS, Co₉S₈, and Co_1–xS) composite (CS@PC) is successfully prepared using polyacrylonitrile (PAN) as the nitrogen‐containing carbon source through a facile solvothermal method and subsequent in situ conversion. As an anode for lithium‐ion batteries (LIBs), the CS@PC composite exhibits excellent electrochemical performance, including high reversible capacity, good rate capability, and cyclic stability. The composite electrode delivers specific capacities of 781.2 and 466.0 mAh g⁻¹ at 0.1 and 5 A g⁻¹, respectively. When cycled at a current density of 1 A g⁻¹, it displays a high reversible capacity of 717.0 mAh g⁻¹ after 500 cycles. The ability to provide this level of performance is attributed to the unique 3D multi‐level porous architecture with large electrode–electrolyte contact area, bicontinuous electron/ion transport pathways, and attractive structure stability. Such micro‐/nanoscale design and engineering strategies may also be used to explore other nanocomposites to boost their energy storage performance.

Flexible hybrid electrodes with high electronic conductivity and porosity have attracted great attention for energy storage and conversion systems. Herein, we report the fabrication of a porous graphitic carbon wrapped MnO/Ni microsphere network (MnO/Ni/CNF) by a combined solvothermal and electrospinning method followed by stabilization and carbonization processes. Carbon nanofibers which link porous MnO/Ni/C microspheres function as both a 3D conductive network and a current collector for the flexible composite electrode. Meanwhile, the porous MnO/Ni microspheres are coated with porous graphene-like carbon layers, further improving the electronic conductivity and facilitating the electrolyte penetration. When directly utilized as an anode material for LIBs, the MnO/Ni/CNF electrode exhibits excellent electrochemical performances, including high reversible capacity, good cycle stability and rate capability. The as-prepared flexible electrode delivers a capacity of 534.5 mA h g⁻¹ at 200 mA g⁻¹ after 100 cycles (based on the whole electrode mass) and possesses a capacity retention of 95.7% even after long-term 600 cycles at 1 A g⁻¹, suggesting its promising applicability in lithium ion batteries as a flexible binder-free anode.

Cubic spinel phase mesoporous Mn₂SnO₄ nanoparticles (NPs) were successfully prepared by a facile hydrothermal method. The formations of Mn₂SnO₄ NPs were characterized by thermo gravimetric/differential thermal (TG/DT) analysis. The understanding of TG/DT analysis prepared NPs were calcinated at different temperature and investigated through x-ray diffraction (XRD) patterns. XRD analysis confirms the Mn₂SnO₄ NPs has spinel cubic phase and evaluated mean crystalline size ~30 nm. The calcinated sample at 850 °C was optimized and chosen for the further investigations. The surface morphology of Mn₂SnO₄ NPs was analyzed by field emission-scanning electron microscope (FE-SEM) and high resolution-transmission electron microscope (HR-TEM) analysis which indicates Mn₂SnO₄ NPs were in nearly spherical shaped. Energy dispersive spectroscopy (EDS) analysis revealed the presence of Mn, Sn and O elements. The stability of the Mn₂SnO₄ NPs analyzed through dynamic light scattering (DLS) measurements which shows good stability. The surface area of the Mn₂SnO₄ NPs ~38.747 m² g⁻¹ measured through Brunauer–Emmett–Teller (BET) method. In the present investigation, cyclic voltammetry (CV) measurements exhibits superior specific capacitance value 540 Fg⁻¹ at a scan rate of 2 mV s⁻¹ from the result, Mn₂SnO₄ NPs could be a potential and novel electrode material for super capacitance applications.