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Aqueous zinc‐ion batteries (AZIBs) are promising candidates for grid‐scale energy‐storage systems, which are essential for maintaining and distributing energy generated from various sources. In contrast to current commercial lithium‐ion batteries (LIBs), AZIBs offer advantages such as, but not limited to, high safety, low cost, and fast kinetics. Zn intercalation material serves as the key element for the suitability of Zn‐ion batteries (ZIBs) for grid and stationary applications. Different materials are tested as cathode materials for ZIBs, including manganese oxides and vanadium oxides. MnO2‐ and V2O5‐based cathodes, in particular, seem compatible with ZIBs, with the potential to perform better than existing batteries in the market. Due to the fast and facile (de)intercalation‐type storage mechanism of Zn2+ ions, layered electrode materials generally have a more stable structure during battery charge and discharge cycles. Materials with large interlayer spacing are expected to exhibit good electrochemical performance, thereby favoring hydrated and cation‐intercalated materials in the development of AZIBs cathodes. Herein, an overview is provided on the synthesis, morphology, and electrochemical performance of various MnO2‐ and V2O5‐based cathode materials in AZIB, as well as the challenges that must be overcome to reach the commercialization of AZIBs.

The potential application of rechargeable multivalent ion batteries in portable devices and renewable energy grid integration have gained substantial research interest in aqueous Zn-ion batteries (ZIBs). Compared to Li-based batteries, ZIBs offer lower costs, higher energy density, and safety that make them more attractive for energy storage in grid integration applications. Currently, more research is required to find a suitable cathode material for ZIBs with high capacity and structural stability during charge/discharge cycling. Vanadium phosphate (VOP) compounds as cathode material for ZIBs have been of particular interest, owing to vanadium’s diverse oxidation states. In this present work, two VOP compounds, [H0.6(VO)3(PO4)3(H2O)3].4H2O and VOPO4.2H2O, were synthesized from phosphoric acid and different sources of vanadium via a simple hydrothermal method. Various characterization techniques were carried out, revealing the layered structure of both products and high purity of [H0.6(VO)3(PO4)3(H2O)3].4H2O. Zn/VOP batteries were prepared using Zn metal as counter and reference electrode and 3 M ZnSO4.7H2O as electrolyte. Electrochemical tests were conducted to evaluate the cycling performance of VOPs as cathode material for aqueous Zn-ion batteries. Based on the results, both compounds have shown highly reversible Zn-ion intercalation and deintercalation. VOPO4.2H2O achieved a higher specific capacity of up to 85 mAh/g during discharging, as opposed to 65 mAh/g for the hydrated VOP complex. However, [H0.6(VO)3(PO4)3(H2O)3].4H2O is more stable with higher reproducibility than VOPO4.2H2O during cycling. Nevertheless, more research is still required to enhance the specific capacity and improve the cycling performance of VOP-based cathodes for their prospective use in aqueous ZIBs.

Carbon materials play an integral role in our everyday lives. Extensive research has been carried out on the applications of carbon materials in its various morphologies and properties. The addition of dopants in carbon materials, whether in situ or post‐treatment, has gained significant interest and has driven researchers to explore its benefits and address existing issues. Nitrogen doping, in particular, has been shown to be a highly effective strategy in creating advanced materials for various applications, such as CO2 capture, energy conversion, and energy storage. However, the key factors that contribute to the properties and performance of the material, such as method of synthesis, starting materials, level of doping, and porosity, should be considered and studied at great depths. In this review, the synthesis methods of N‐doped carbon materials and their recent progress in CO2 adsorption, energy conversion, and energy storage applications is discussed. These applications represent some of the most important and promising solutions to burgeoning issues in environmental and energy fields. In addition, the remaining issues with N‐doped carbon materials and the possible strategies to overcome them will be discussed.

A generation of lithium-ion batteries that can deliver high energy and fast charging rates without compromising safety is in high demand. Despite extensive research efforts, the current Li-ion technology cannot match the requirements for large-scale electrochemical energy storage applications. Niobium-based oxides have been of particular interest lately due to their fast charging capabilities, moderately high capacity, long cycle life, and high working voltage, which prevents lithium plating and dendrite formation. However, the synthesis of niobate compounds typically involves high temperatures exceeding 1100 °C or complex chemical synthesis. In this work, a nickel niobate compound (NiNb2O6) has been synthesized through a facile and scalable method based on solid-state reaction between nickel and niobium precursors. The synthesis was assisted by mechanical techniques to enhance the reaction rate and drive the reaction to completion prior to a heat treatment at 900 °C. Findings from X-ray diffraction confirmed the formation of pure orthorhombic NiNb2O6. The as-prepared anode material was assembled in a half-cell vs Li/Li+ and delivered a maximum specific charge capacity of about 240 mAh g–1 at a rate of 0.1 A g–1 (0.42 C) with 100% Coulombic efficiency. Orthorhombic NiNb2O6 exhibited a stable cyclability (145 mAh g–1 for 0.8 A g–1 (3.4 C)), high capacity retention (90% after 1000 cycles at 3.4 C), and robust rate performance. Electrochemical tests and post-mortem analysis results confirm an intercalation-type mechanism during lithiation with high reversibility and pseudocapacitive behavior.