Role of precursors mixing sequence on the properties of CoMn2O4 cathode materials and their application in pseudocapacitor

Abstract

In this study, the effect of oxygen vacancy in the CoMn2O4 on pseudocapacitive characteristics was examined, and two tetragonal CoMn2O4 spinel compounds with different oxygen vacancy concentrations and morphologies were synthesized by controlling the mixing sequence of the Co and Mn precursors. The mixing sequence was changed; thus, morphologies were changed from spherical nanoparticles to nanoflakes and oxygen vacancies were increased. Electrochemical studies have revealed that tetragonal CoMn2O4 spinels with a higher number of oxygen vacancies exhibit a higher specific capacitance of 1709 F g−1 than those with a lower number of oxygen vacancies, which have a higher specific capacitance of 990 F g−1. Oxygen vacancies create an active site for oxygen ion intercalation. Therefore, oxidation–reduction reactions occur because of the diffusion of oxygen ions at octahedral/tetrahedral crystal edges. The solid-state asymmetric pseudocapacitor exhibits a maximum energy density of 32 Wh-kg−1 and an excellent cyclic stability of nearly 100%.

Ion accumulation-induced capacitance elevation in a microporous graphene-based supercapacitor

“…3a, d and S6, S7†) of the electrode are well in agreement with each other, although the calculated specific capacitances differ due to the different measurement techniques. 58 The total capacitances are the combination of the rate-independent (EDL) capacitance contribution, m 1 , and faradaic contribution, m 2 , as given by the following equation: 8 where C represents the total capacitance in (F g −1 ) and γ represents the scan rate (V s −1 ).…”

Mononuclear Transition Metal Cymantrenecarboxylates as Precursors for Spinel-Type Manganites

“…Transition metal manganites of spinel type are valuable functional materials. In particular, they are of interest as magnetic materials [ 46 , 47 , 48 ], catalysts [ 49 , 50 ], photovoltaic materials [ 51 ], electrode materials [ 52 , 53 ], and materials for negative temperature coefficient thermistors [ 54 ]. Therefore, we carried out the solid-state thermolysis of the obtained compounds 1 – 8 in the air flow in the temperature range of 25–950 °C.…”

KOH mediated hydrothermally synthesized hexagonal‐CoMn 2 O 4 for energy storage supercapacitor applications

“…The following reactions are used to describe the electrochemical redox reaction mechanism for CoMn 2 O 4 in alkaline electrolyte, 50 …”

“…At higher frequency with a semicircle. Whereas, the intersection point of the semicircle on the x ‐axis at a higher frequency region denotes R s , the electrode's equivalent series resistance, and the diameter of the semicircle denotes R ct , the charge‐transfer resistance of the electrode/electrolyte interface 50 . In the present study, the R s value for the synthesized CoMn 2 O 4 electrode material is 2.2 Ω implying that higher electrical conductivity (very small charge transfer resistance) with excellent ion response in the higher frequency region.…”