Supercapacitors: An Alternate Technology for Energy Storage

The supercapattery designed with a binary composite of niobium silver sulfide (NbAg2S) and activated carbon for enhanced electrochemical performance

A supercapattery is a hybrid device that is a combination of a battery and a capacitor. Niobium sulfide (NbS), silver sulfide (Ag₂S), and niobium silver sulfide (NbAg₂S) were synthesized by a simple hydrothermal method. NbAg₂S (50/50 wt% ratio) had a specific capacity of 654 C g^-1, which was higher than the combined specific capacities of NbS (440 C g^-1) and Ag₂S (232 C g^-1), as determined by the electrochemical investigation of a three-cell assembly. Activated carbon and NbAg₂S were combined to develop the asymmetric device (NbAg₂S//AC). A maximum specific capacity of 142 C g^-1 was delivered by the supercapattery (NbAg₂S//AC). The supercapattery (NbAg₂S/AC) provided 43.06 W h kg^-1 energy density while retaining 750 W kg^-1 power density. The stability of the NbAg₂S//AC device was evaluated by subjecting it to 5000 cycles. After 5000 cycles, the (NbAg₂S/AC) device still had 93% of its initial capacity. This research indicates that merging NbS and Ag₂S (50/50 wt% ratio) may be the best choice for future energy storage technologies.

Cobalt-manganese-zinc ternary phosphate for high performance supercapattery devices

State of the art supercapatteries have received considerable attention for their significant electrochemical performance; however, electrode materials with enhanced charge storage capabilities are desired. Here, we report the synthesis of mixed metal phosphate nanomaterials with different concentrations via a sonochemical approach. Initially, binary metal phosphates based on zinc, cobalt, and manganese were synthesized. Then, the composition of zinc and cobalt was optimized in ternary metal phosphates. Scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction techniques were utilized to examine the surface morphology, elemental analysis and crystal structure of as-synthesized nanomaterials. The electrochemical characterizations were performed in a three cell configuration. Zn0.50Co00.50Mn(PO4)2 delivers the optimum performance with a specific capacity of 1022.52 C g-1 (specific capacitance of 1704.21 F g-1) at 1.2 A g-1. This optimized material was further engaged in an asymmetric device (supercapattery) as a positive electrode material to explore the real device performance. The supercapattery device was found to have an impressive specific energy of 45.45 W h kg-1 at 0.5 A g-1 and provide a remarkable specific power of 4250 W kg-1 at 5 A g-1 current density. The device exhibits excellent capacity preservation of 93% examined after 1500 charge discharge cycles. In addition, to scrutinize the supercapattery performance in terms of capacitive and diffusion controlled processes, a simulation approach was adopted. The real device comprises a capacitive contribution of 8.42% at 3 mV s-1 and 66.56% at 100 mV s-1. This novel progress in ternary metal phosphates results in a fine electrode material for high performance supercapattery applications.

in Situ X-ray Photoelectron Spectroscopic and Electrochemical Studies of the Bromide Anions Dissolved in 1-Ethyl-3-Methyl Imidazolium Tetrafluoroborate

Influence of electrode potential on the electrochemical behavior of a 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF₄) solution containing 5 wt % 1-ethyl-3-methylimidazolium bromide (EMImBr) has been investigated using electrochemical and synchrotron-initiated high-resolution in situ X-ray photoelectron spectroscopy (XPS) methods. Observation of the Br 3d_5/2 in situ XPS signal, collected in a 5 wt % EMImBr solution at an EMImBF₄–vacuum interface, enabled the detection of the start of the electrooxidation process of the Br⁻ anion to Br₃⁻ anion and thereafter to the Br₂ at the micro-mesoporous carbon electrode, polarized continuously at the high fixed positive potentials. A new photoelectron peak, corresponding to B–O bond formation in the B 1s in situ XPS spectra at E ≤ −1.17 V, parallel to the start of the electroreduction of the residual water at the micro-mesoporous carbon electrode, was observed and is discussed. The electroreduction of the residual water caused a reduction in the absolute value of binding energy vs. potential plot slope twice to ca. dBE dE⁻¹ = −0.5 eV V⁻¹ at E ≤ −1.17 V for C 1s, N 1s, B 1s, F 1s, and Br 3d_5/2 photoelectrons.

Hollow nanostructures of metal oxides as next generation electrode materials for supercapacitors

Hollow nanostructures of copper oxides help to stabilize appreciably higher electrochemical characteristics than their solid counter parts of various morphologies. The specific capacitance values, calculated using cyclic voltammetry (CV) and charge-discharge (CD) studies, are found to be much higher than the values reported in literature for copper oxide particles showing  intriguing morphologies or even composites with trendy systems like CNTs, rGO, graphene, etc. The proposed cost-effective synthesis route makes these materials industrially viable for application in alternative energy storage devices. The improved electrochemical response can be attributed to effective access to the higher number of redox sites that become available on the surface, as well as in the cavity of the hollow particles. The ion transport channels also facilitate efficient de-intercalation, which results in the enhancement of cyclability and Coulombic efficiency. The charge storage mechanism in copper oxide structures is also proposed in the paper.