In the past decade, due to the demands of the electrochemical energy storage sector, there has been a quest for novel supercapacitor electrode materials that offer champion storage characteristics. Recently, transition metal oxynitrides (TMONs) have gained a lot of attention as electrode materials for supercapacitor (SC) applications due to their unique properties such as high electronic conductivity, wettability, corrosion resistance and chemical robustness. Nanostructuring strategies of TMONs opens fresh avenues for energy storage. Though various transition metal oxides (TMO) and metal nitrides (TMN) have been explored as electrode materials for SC applications, they have limitations associated with poor cyclability and rate capabilities. Hence, there is a value to exploring intermediate transition oxynitride compounds (TMONs) in place of pure TMOs and TMNs. So, here we propose that the synthesis of TMONs with desired morphology and high surface are to be carried out to achieve the high cyclic stabile, rate capable and high energy density supercapacitors.

In this context, we have carried out the systematic study of the nanostructured nano-spherical CrOXNY nanoparticle as an electrode material for SC applications. The electrochemical performance of the CrOXNY electrode is tested in both the three and two electrode assembly. The CrOXNY electrode shows capacitance of 146 F g-1 at 10 m V s-1 in the three electrode configuration. The symmetric coin cell (CR2032) is fabricated and tested up to 10,000 cycles at 2 A g-1 and it shows excellent capacity retention up to 98 %. The energy and power densities of the symmetric device are ~ 8 W h kg-1 and 28.8 kW kg-1 respectively. As a proof of concept, a red light-emitting diode (LED) is lit by serially connecting two symmetric coin cells (2 V). These attributes of CrOXNY, such as excellent capacitance retention, long cyclic stability, and high rate capability, indicates that it can be used as a durable electrode material for SC technology. So, here we propose that the synthesis of TMONs with desired morphology and high surface is to be carried out to achieve the high cycle stable, rate capable and high energy density supercapacitors. Towards this end of thesis, the following four activities will be carried out: i). synthesis of TMONs and their composites for high energy density supercapacitors, ii) fabrication of both symmetric and asymmetric SCs device configuration based on TMONs electrode materials to expand voltage window (up to 2V by using aqueous electrolyte and 4V for ionic liquids), iii) use of organic electrolyte to further improve the performance of SC device, and iv) testing of as fabricated SC device under extreme conditions such as high humidity (30% to 99% RH) and freezing temperature (-70 oC) to validate real time applications.