Rechargeable lithium-ion batteries of today operate by an electrochemical process that involves intercalation reactions that warrants the use of electrode materials having very specific structures and properties. Further, they are limited to the insertion of one Li per 3D metal. One way to circumvent this intrinsic limitation and achieve higher capacities would be the use of electrode materials in which the metal-redox oxidation state could reversibly change by more than one unit. Through the discovery of conversion or displacement reactions, it is possible to reversibly change by more than one unit. Further, the need for materials with open structures or good electronic ionic conductivity is eliminated, thus leading to a new area in materials for lithium ion battery. In this paper, we present a review enlightens new reaction schemes and their potential impact on applications.

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ZnCo 2 O 4 nanomaterial was prepared by coprecipitation method and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), and galvanostatic charge-discharge tests at various current densities. It is shown that the crystal structure and surface morphology play an important role in the enhancement of the specific capacitance. The TEM results clearly indicate that the prepared material shows aggregated particles. The particle size powder was about 50 nm, and SEM pictures indicate a porous morphology. The electrochemical behavior of ZnCo 2 O 4 was characterized by mixing equal proportion of carbon nanofoam (CNF). From CV, it is concluded that the combination of redox and pseudocapacitance increases the specific capacitance up to 77 F g −1 at 5 mV s −1 scan rate. The ZnCo 2 O 4 -based supercapacitor cell has good cyclic stability and high coulombic efficiency.

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