Nickel-manganese phosphate: An efficient battery-grade electrode for supercapattery devices

This study investigates the charge storage mechanism in binary metal phosphates of NiMn(PO 4 ) 2 synthesized through sono-chemical method. We studied the surface morphology and elemental analysis through SEM and EDX analysis. From electrochemical measurements, the NiMn(PO 4 ) 2 demonstrates a high Q s of 678 Cg -1 at 0.4 Ag -1 . The supercapattery device is fabricated by considering NiMn(PO 4 ) 2 as a positive and AC as a negative electrode. Also, we noticed effective cyclic stability of 99.2% after 5000 GCD cycles revealing a high specific energy of 63.8 Whkg −1 and a maximum specific power of 11892 Wkg -1 . Furthermore, the impact of capacitive and diffusive contributions to the total capacity of the device is studied by employing Dunn's model. Moreover, power law is employed to calculate the b values for the device; the trend of b value ranges from 0.723 to 0.785 confirming the hybrid nature for the device. The contribution of electrostatic (capacitive) and Faradaic (diffusive) charge storage mechanism amplify the overall energy storage performance of the device. Such features of NiMn(PO 4 ) 2 can offer a unique platform to further investigate new electrode materials for energy storage devices.