Cobalt manganese phosphate and sulfide electrode materials for potential applications of battery-supercapacitor hybrid devices

Abstract

Electrode materials with efficient electrochemical properties are always desirable for high storage energy devices. Here, due to the attractive attributes of metal phosphates and sulfides, we present a sonochemically synthesized binary composite of cobalt manganese phosphate (CoMn(PO4)2) and sulfide (CoMnS) for the real-world applications. The surface and structural properties of the synthesized materials are then investigated through X-ray diffraction (XRD) and scanning electron microscopy (SEM). Subsequently, the prepared electrode materials are optimized through electrochemical measurements performed in a three-electrode assembly. The best performing electrode, (CoMnS (S2) yielding a specific capacity (Qs) of 537 C/g at a current density js of 1 A/g) is then amalgamated with a carbonaceous electrode (activated carbon AC) for the fabrication of asymmetric (supercapattery) device. The constructed device (S2//AC) is then subjected to a two-electrode setup, providing an outstanding specific energy (Es) of 73.52 Wh/kg and a maximum specific power (Ps) of 10,200 W/kg. Afterwards, the device is analyzed for a stability test and preserved a maximum capacity retention of 90.03% against 10 A/g for 10,000 charge-discharge cycles. A semi-empirical approach via Dunn's model is next exploited to scrutinize the negative (capacitive) and positive (diffusive) electrode contributions for the device.