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This work reports an electro‐analytical study of NaCoO2 as cathode material synthesized by a low‐temperature combustion method for aqueous sodium‐ion batteries. The synthesized cathode material was electrochemically characterized in 2 M NaOH aqueous electrolyte. The obtained material‘s physical characteristics are investigated by X‐Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X‐ray analysis (EDX), Thermo‐Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) to evaluate its crystal structure, crystal size, composition, and surface morphology. From SEM images, the crystal size of the synthesized NaCoO2 is found to be varying between 50–100 nm with good crystallinity. From TGA studies, the material shows thermal stability up to around 300 °C with maximum weight loss at about 375 °C. Electrochemical behaviour of NaCoO2 in 2 M aqueous sodium electrolytes are evaluated using cyclic voltammetry and galvanostatic charge‐discharge techniques. The cell, NaTi2(PO4)3/2 M NaOH/NaCoO2 constructed in aqueous 2 M NaOH is found to deliver a discharge capacity of 89 mAh g−1 at C/10 rate. It retains its initial capacity over 55 cycles and at a high Crate of 1 C a discharge capacity of 34 mAh g−1 was obtained which can be compared with that obtained for NaCoO2 in non‐aqueous battery systems.

Metamaterials are the major type of artificially engineered materials which exhibit naturally unobtainable properties according to how their microarchitectures are engineered. Owing to their unique and controllable effective properties, including electric permittivity and magnetic permeability, the metamaterials play a vital role in the development of meta-devices. Therefore, the recent research has mainly focused on shifting towards achieving tunable, switchable, nonlinear, and sensing functionalities. In this review, we summarize the recent progress in terahertz, microwave electromagnetic, and photonic metamaterials, and their applications. The review also encompasses the role of metamaterials in the advancement of microwave sensors, photonic devices, antennas, energy harvesting, and superconducting quantum interference devices (SQUIDs).

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