Metal carbonates: alternative to metal oxides for supercapacitor applications? A case study of MnCO3 vs MnO2

Abstract

We report here the potential competency of MnCO 3 versus MnO 2 for supercapacitor applications. MnCO 3 was synthesized by a hydrothermal method using KMnO 4 as a manganese source and either sugar or pyrrole as carbon source. MnCO 3 synthesized using sugar and pyrrole as carbon source is referred hereafter as MnCO 3 (s) and MnCO 3 (p), respectively. The synthesized products were characterized by powder X-ray diffraction, scanning electron microscopic and transmission electron microscopic studies. Microscopic studies revealed that MnO 2 possesses micro-flower-like morphology constructed by self-assembled nano-petals. While the morphology of MnCO 3 (s) is sub-micron size particles of different shape, the morphology of MnCO 3 (p) is crystalline particles of 10-20 nm dia. The capacitive characteristics of MnO 2 , MnCO 3 (s) and MnCO 3 (p) were evaluated in aqueous 0.1 M Mg(ClO 4 ) 2 electrolyte between 0 and 1 V using cyclic voltammetry and galvanostatic charge/discharge cycling. Specific capacitance (SC) values of 216 and 296 F g −1 obtained for MnCO 3 (s) and MnCO 3 (p) are 35 and 85 % higher than SC value of 160 F g −1 obtained for MnO 2 , respectively. Besides better capacitive storage characteristics, MnCO 3 (s) and MnCO 3 (p) have also exhibited better rate capability and cycle life than MnO 2 .

A high energy density asymmetric supercapacitor utilizing a nickel phosphate/graphene foam composite as the cathode and carbonized iron cations adsorbed onto polyaniline as the anode

“…Moreover, for Ni 3 (PO 4 ) 2 /60 mg GF composite the current response is found to be further improved compared to Ni 3 (PO 4 ) 2 /30 mg GF. A Ni 3 (PO 4 ) 2 /90 mg GF composite shows the highest current response suggesting a high specic capacity according to eqn (1), and this could be attributed to the presence of an appropriate amount of GF which effectively synergise with Ni 3 (PO 4 ) 2 and improves its electrical conductivity owing to the outstanding electrical conductivity of graphene. A Ni 3 (PO 4 ) 2 / 120 mg GF composite shows a drop in current response compared to Ni 3 (PO 4 ) 2 /90 mg GF composite and that could be due to the high content of GF relative to the Ni 3 (PO 4 ) 2 material in the composite which negatively affects the synergy between the Ni 3 (PO 4 ) 2 and the GF, as mentioned earlier.…”

“…Clearly, the CD curves are nonlinear which further conrm the faradic property of the electrode material. The specic capacity of Ni 3 (PO 4 ) 2 /90 mg GF composite was calculated using eqn (1) and the values are 48, 41, 37, 29 and 25 mA h g À1 for current densities of 0.5, 1.0, 2.0, 5.0 and 10.0 A g À1 respectively, as shown in Fig. 6(b).…”

“…Over the past years, supercapacitors have attracted much attention, because of their long cycle life, short charging time, high power density, etc., and they are used in a variety of domestic, commercial and industrial applications such as portable electronic devices, micro-electromechanical systems, and hybrid electric/plug-in-hybrid vehicles. [1][2][3][4] Nowadays, amongst other energy storage systems, supercapacitors have become the main focus for renewable and sustainable energy sources. [5][6][7][8][9] Therefore, for future energy storage systems, effort is focussed on developing new materials with high electrochemical performance.…”

Electrodeposited MnCO3 as a High Performance Electrode Material for Supercapacitor

“…The electrodeposited MnCO 3 exhibits high cycling stability over 10,000 cycles with retention of 92% of its initial specific capacitance value and 100% coulombic efficiency (Figure a). In general, poor cycling stability with a gradual decrease in the specific capacitance value during extended cycling is reported for MnCO 3 ,. To understand the high cycling stability of electrodeposited MnCO 3 , electrochemical impedance spectra were recorded before cycling and after 10,000 cycles and are presented in Figure b.…”

“…In addition, it also exhibits electrochromism . Besides these applications, MnCO 3 is also studied extensively as an anode material in lithium‐ion batteries and as an electroactive material in supercapacitors …”