Fabrication of asymmetric supercapacitor device using Mn-doped NiCo2O4 with improved electrochemical performance

• Mn-doped NiCo 2 O 4 synthesized through Co-precipitation method. • Superior specific capacity of 10 % Mn-doped NiCo 2 O 4 sample is observed (∼1070 C g -1 at 2.0 Ag -1 ). • 10 % Mn-doped NiCo 2 O 4 //AC asymmetric supercapacitor device is prepared. • Impressive energy and power densities of 20.58 Wh kg -1 and ∼370 W kg -1 at 2 Ag -1 are obtained. • An array of 51 LEDs with NITK design was illuminated for 5 min. NiCo 2 O 4 is prepared through a facile co-precipitation method followed by calcination without any surfactant with variable amounts of Mn-doping viz. 0 %, 5 %, 10 % and 15 %. The as-prepared samples are named MNC0, MNC5, MNC10,and MNC15 according to the amount of Mn-dopant. Each produced sample exposed a different morphology with the expectation of different electrochemical behavior, which was confirmed through various electrochemical techniques in a three-electrode set-up. The materials with Mn-doping exhibit a notable specific capacity, prolonged discharge times, and minimal charge transfer resistance compared to MNC0. Specifically, at 2.0 Ag -1 , the obtained specific capacity quantities for MNC0, MNC5, MNC10 and MNC15 are 354.0, 726.04, 1070.4 and 981.5 Cg -1 . The Mn-doped NiCo 2 O 4 //AC (activated carbon) asymmetric supercapacitor device, when assembled, demonstrates impressive powerdensity and energy density of 370.37 W kg -1 and 20.58 Wh kg -1 at 2.00 A g -1 respectively, along with retention cycling stability of 81 % and coulombic efficiency of 94 – 98 % after 4000 cycles. The realistic demonstration of powering yellow and green LEDs highlights the practical application of fabricated energy storage devices. This work explores a range of Mn concentrations and their impact on the electrochemical performance of the materials. This study demonstrated significant improvements in capacitance, cycling stability, and charge transfer resistance compared to undoped NiCo 2 O 4 .