Ultra-stable Mn1-xNixCO3 nano/sub-microspheres positive electrodes for high-performance solid-state asymmetric supercapacitors

Long-term cycling performance of electrodes for application in supercapcitor has received large research interest in recent years. Ultra-stable Mn1-xNixCO3 (x-0, 0.20, 0.25 and 0.30) nano/sub-microspheres were synthesized via simple co-precipitation method and the Mn1-xNixCO3 was confirmed by XRD, FT-IR, XPS and their morphology was studied by SEM and TEM analysis. Among the various Mn1-xNixCO3 electrodes, the Mn0.75Ni0.25CO3 electrode exhibited the higher specific capacitance (364 F g(-1) at 1 A g(-1)) with capacity retention of 96% after 7500 cycles at 5 A g(-1). Moreover, the assembled solid-state asymmetric supercapacitor based on Mn0.75Ni0.25CO3//graphene nanosheets performed a high specific capacity of 46 F g(-1) and energy density of 25 Wh kg(-1) at a power density of 499 W kg(-1) along with high capacity retention of 87.7% after 7500 cycles. The improved electrochemical performances are mainly owing to the intrinsic conductivity and electrochemical activity of MnCO3 after Mn1-xNixCO3 (x-0.20, 0.25 and 0.30) with appropriate Ni concentration. This study highlights the potentiality of the Mn0.75Ni0.25CO3//GNS asymmetric supercapacitor device for promising energy storage applications.