High Electrochemical Performance of a Nanostructured Electrode Material Based on a Cobalt-Manganese Layered Double Hydroxide

Abstract

In this work, alpha-cobalt hydroxide (Co(OH)₂) and cobalt/manganese layered double hydroxide (CoMn-75-LDH) were synthesized using the Tower method. The alpha phase was confirmed for Co(OH)₂ through XRD analysis. Furthermore, the TEM images showed that the materials are formed by nanoparticles with an average size of ~5 nm. Cyclic voltammetry and galvanostatic charge/discharge measurements were carried out and the CoMn-75-LDH presented a superior electrochemical behavior to Co(OH)₂. The presence of Mn^2+/3+ ions in the crystal structure of CoMn-75-LDH, verified by XPS analysis, enhanced the electrical conductivity of the material, providing more electroactive sites, as a result, the electrochemical performance of the material was improved. Electrochemical studies showed that CoMn-75-LDH has a specific capacitance of 677 F g^-1 at current density of 0.5 A g^-1 compared to Co(OH)₂, whose specific capacitance value was 268.7 F g^-1 at the same current density. In addition, the electrochemical signature of Co(OH)₂ revealed that the electrode material exhibits an extrinsic pseudocapacitive behavior instead of the typical behavior of battery-type materials due to its nanostructured morphology. Also, electrochemical studies showed that the charge storage mechanism for CoMn-75-LDH is controlled by both the capacitive and diffusion process.