Sucrose-assisted one step hydrothermal synthesis of MnCO3/Mn3O4 hybrid materials for electrochemical energy storage

Abstract

Multicomponent hybrid materials are signified as promising electrode materials for energy storage application due to synergistic effect of existing components. In this work, MnCO3/ Mn3O4 hybrid materials are synthesized by simple one-step sucrose-assisted hydrothermal method with KMnO4 as the only starting raw source. The presence of sucrose, reaction time, and temperature are found to be crucial for the final composition/ structure of the obtained products. After 12 h hydrothermal treatment at 180 °C, the synthesized hybrid material (MS-12) possesses relatively homogeneous nanooctahedron morphology and good crystallinity. Among all the tested electrode materials as pseudocapacitor, MS-12 exhibits better specific capacitance (capacity) of 191.0 Fg−1 (229.2 Cg−1) in comparison to other hybrid materials synthesized during 6 h (MS-6; 105.8/ 127.0 Fg−1/ Cg−1), 24 h (MS-24; 98.3/ 118.0 Fg−1/ Cg−1), and bare δ-MnO2 obtained without sucrose (M-24; 73.7/ 88.4 Fg−1/ Cg−1) at a specific current of 1.0 Ag−1. Moreover, MS-12 shows excellent cyclic stability with 97.8% capacitive retention from its initial value even after 3000 continuous cycles at 1.5 Ag−1. The better electrochemical performance of MS-12 hybrid material may be originated due to the relatively more bulk/ electrochemical active surface area, favorable pore size, as well as synergistic impact of both MnCO3 and mixed valance oxide (Mn3O4). Based on three-electrode configuration performances, MS-12//AC asymmetric supercapacitor (ASC) device is also assembled using MS-12 hybrid material as the positive and active carbon as the negative electrode. The fabricated ASC shows appreciable specific capacitance (capacity) of 73.5 Fg−1 (147.0 Cg−1) at a specific current of 1.0 Ag−1 and a specific energy of 40.8 Whkg−1 at a specific power of 1000 Wkg−1. In terms of long term cyclic stability, the device represents 81.4% capacitive retention after 2000 charging-discharging cycles at a specific current of 1.0 Ag−1.