Temperature and Stability Study of All Oxynitride-Based Asymmetric Supercapacitor

Abstract

Supercapacitors (SCs) or electrochemical capacitors are of substantial utility due to their high-power density, moderate energy density, fast charge-discharge rates, long cycle life (~105 cycles), and environmental friendliness. 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 much 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 open up fresh avenues for energy storage. Various transition metal oxides (TMO) and metal nitrides (TMN) have been explored as electrode materials for SC applications. TMOs and TMNs are prone to poor cyclability and rate capabilities. Hence, there is a value of exploring intermediate transition oxynitride compounds (TMONs) in place of pure TMOs and TMNs.In this work, a simple and scalable soft urea method is used to synthesize chromium oxynitride (CrOxNy) and cerium oxynitride (CeOxNy) nanoparticles in the place of the conventional ammonothermal method. These nanoparticles are used to fabricate asymmetric coin cell devices, where CeOxNy is used as a positive electrode and CrOxNy is used as negative electrode material. The fabricated asymmetric device is subjected to electrochemical characterization techniques such as cyclic voltammetry, galvanostatic charge-discharge (GCD), leakage current analysis, and electrochemical impedance spectroscopy (EIS). From GCD measurement, It reveals that the device exhibits an areal capacitance of 21.48 mF cm-2 at 0.3 mA cm-2, cycled up to 105 cycles at room temperature (25 oC). Further, an asymmetric device is tested at different temperatures (-5 oC, 0 oC, 25 oC, and 50 oC) using an environmental climate chamber to validate the real-time application. The areal capacitance of the device at different temperature is compared and it shows that 11.28 mF cm-2, 12.67 mF cm-2 , 21.48 mF cm-2 , and 8.96 mF cm-2 at -5 oC, 0 oC, 25 oC, and 50 oC respectively. The device retains 41.8% of its areal capacitance even at high temperature (50 oC) when compared with room temperature (25 oC). The temperature-based study provides the promising nature of the fabricated device, and the performance has attributed to the stability of both oxynitride electrode material even at extremely low (-5 oC) and high temperature (50 oC). Figure 1