Highly stable binary composite of nickel silver sulfide ( NiAg 2 S ) synthesized using the hydrothermal approach for high‐performance supercapattery applications

Abstract

A supercapattery is a device that combines the benefits of supercapacitors' superior power density and cycle stability with the advantages of batteries' higher energy density. We used a simple hydrothermal method to synthesize nickel sulfide (NiS), silver sulfide (Ag2S), and nickel silver sulfide (NiAg2S). The NiS and Ag2S were combined in the best 50/50 weight ratio and found that the specific capacity for NiAg2S is 571.2 C/g which is higher as compared to individual NiS and Ag2S 305.2 C/g and 364 C/g, respectively. Even at 2 A/g, more than 69% of the specific capacity is retained. For asymmetric device fabrication (NiAg2S//AC), the activated carbon was selected as a negative electrode, while NiAg2S was chosen as a positive electrode. A specific capacity of 130.4 C/g was achieved with this device. Energy density for NiAg2S was observed to be 28.97 Wh/kg having a power density of 640 W/kg. To investigate stability, a durability test was performed by subjecting this device to 1000 charging/discharging cycles, which maintain 86% of the initial capacity. Our findings suggest that a mixture of nickel and silver sulfide having a 50/50 weight ratio functioning as an electrode material for supercapattery applications may be more appropriate.