Molten Salt Assisted Assembly (MASA) of novel mesoporous Ni0.5Mn0.5Co2O4 for high-performance asymmetric supercapacitors

Abstract

Mesoporous transition metal oxides (TMO) are immensely investigated as electrode materials in supercapacitors. The molten salt assisted self-assembly (MASA) process enables a facile route for the synthesis of the mesoporous TMO. In this study, mesoporous nickel manganese cobaltite (Ni_0.5Mn_0.5Co₂O₄) is synthesized for the first time using a MASA process and is evaluated as a novel electrode-active material for asymmetric supercapacitors. The objective of this work is to quantitatively measure the performance improvement in the Ni_0.5Mn_0.5Co₂O₄ electrode based on its composition and reveal the improvement mechanism through electrochemical methods. The electrochemical performance of the NiCo₂O₄ and MnCo₂O₄ prepared by MASA is also investigated, in order to understand the synergistic effect of Ni and Mn elements in the same cobaltite structure. In line with the data obtained from half cells, a full asymmetric cell is prepared by assembling the appropriate amount of Ni_0.5Mn_0.5Co₂O₄ and activated carbon through the charge balance theory. The test results show that the specific capacitance C_A (C_s) values are 2.62F/cm² (92.1F/g) for mesoporous NiCo₂O₄, 0.26F/cm² (9.8F/g) for mesoporous MnCo₂O₄, and 9.53F/cm² (338.5F/g) for mesoporous Ni_0.5Mn_0.5Co₂O₄ under the test conditions of 5 mA/cm². The asymmetric supercapacitor assembled with Ni_0.5Mn_0.5Co₂O₄ and activated carbon demonstrates a superior energy density of 79.52 Wh/kg at 1 mA/cm². The findings of the study highlight the importance of substituting the electrode with Ni_0.5Mn_0.5Co₂O₄ to enhance the C_A (C_s) by achieving proper surface properties and electrochemical activity.