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• Synthesis of V 2 O 5 via simple thermal decomposition of ammonium metavanadate and glycine. • More than two fold increase in specific capacitance under light for V 2 O 5 ||AC device. • V 2 O 5 ||V 2 O 5 device was charged under light to 200 mV in 1 h. • Outstanding coulombic efficiency of 98% even after 40,000 cycles at a high current density of 10 and 15 mA cm−2. A photo-assisted energy storage system enables a new pathway to utilize unlimited solar energy. Herein, V 2 O 5 was synthesized using a simple, time-saving thermal decomposition process. The V 2 O 5 samples were characterized thoroughly. The photo-electrochemical performances of the as-prepared V 2 O 5 samples were evaluated using a three-electrode system. The material showed increased specific capacity from 45 C g−1 to 69 C g−1 in the presence of light. The photo-assisted V 2 O 5 ||V 2 O 5 and V 2 O 5 ||AC (activated carbon) ASC (asymetric supercapacitors) FTO devices effectively responded to the light sources. The areal capacity of the V 2 O 5 ||AC ASC FTO photo-assisted charging device was 112 mC cm−2 under the given light intensity, whereas the device tested using the conventional process (without light irradiation) delivered only 45 mC cm−2 at the same current density. Further, the asymmetric FTO device delivered high specific energy and power density of 9.8 Wh kg−1, and 29 W kg−1 respectively, in the presence of light. Notably, the symmetric FTO device was photo charged to 200 mV in 1 h without any external current and was discharged in the dark at 0.01 mA cm−2. On the other hand, V 2 O 5 symmetric coin cell delivered excellent cycle stability over 40,000 cycles at different current rates with an outstanding coulombic efficiency of 98%. These results are a clear indication that the photo charging-based supercapacitor will pave an innovative path in constructing futuristic energy storage devices. [ABSTRACT FROM AUTHOR]

• The power density decreases with increasing cathode diameter for the button cells. • Because the polarization resistances associated with gas diffusion process increases. • The polarization resistance also increases with increasing fuel utilization. • The power density is low for large-scale cells under high fuel utilization. Small-scale planar solid oxide fuel cells (SOFCs) with several centimeters in diameter called "button cells" or "coin cells" are widely used for fundamental research. Although the performance of large-scale cells is inferior to that of button cells, the precise reason is unclear. In the present work, electrochemical impedance spectroscopy (EIS) are performed for button cells with different cathode areas under different fuel utilization, and distribution of relaxation times analysis was conducted to deconvolute the EIS. The power density decreased with increasing cathode diameter for the button cells. The polarization resistances associated with the gas diffusion process at low frequencies increased for a cell with a large cathode area, when the gas flow path is different between the inner and outer electrode areas for the button cells. The polarization resistance related to the gas diffusion process also increases with increasing fuel utilization. As a result of simple simulation considering the Nernst loss, the power density at 0.75 V was estimated to be 0.169 W/cm2 at U f = 0.8 for a large-scall cell with dimensions of 10 × 10 cm2, which is smaller than that for a button cell with a cathode diameter of 6 mm (0.730 W/cm2 at U f = 0.04). [Display omitted] [ABSTRACT FROM AUTHOR]

Layered two-dimensional (2D) materials such as transition metal dichalcogenides (TMDCs) are receiving increased interest for applications in energy storage due to their high specific surface area and versatile electronic structure. In this work, we prepare solvent stabilised dispersions of a variety of few-layer thick TMDC crystals (MoS 2 , MoSe 2 , WS 2 , and TiS 2 ) by ultrasonication. The exfoliated materials were first characterised by a variety of techniques to determine their quality. These dispersions were then used to form supercapacitor electrodes by filtration, without use of any further conductive additives or polymeric binders. These thin layer TMDC electrodes were assembled into symmetrical coin-cell devices for comparative electrochemical testing. It was found that despite being the most widely studied material, MoS 2 suffers from inferior charge storage properties compared to the much higher conductivity and lower density TiS 2 . Impedance spectroscopy was used to investigate the charge storage mechanisms inside the coin cells, which were found to consist of a combination of both rapid, but low magnitude, electric double layer capacitance and much slower, but higher magnitude, ion adsorption pseudocapacitance. [ABSTRACT FROM AUTHOR]

Abstract: Three classes of molecules have been shown to be successful for protecting lithium-ion cells during overcharge. These three classes are, the molecule 2,5-di-tert-butyl-1,4-dimethoxybenzene (DDB), molecules based on a phenothiazine core, such as 10-methylphenothiazine (MPT) and molecules based on a 2,2,6,6-tetramethylpiperidinyl-oxide (TEMPO) core, such as TEMPO and 4-cyano-TEMPO. These molecules were examined using Li-ion coin cells, three-electrode cyclic voltammetry and four-electrode cyclic voltammetry. Three-electrode cyclic voltammetry was used to measure the diffusion coefficients and the stability of the shuttle molecules at high and low potentials. The transport of electrons through the solid-electrolyte interface on the negative electrode to the oxidized shuttle molecule was studied using the four-electrode cell for electrolytes containing both LiPF6 and lithium bis(oxalato)borate salts. The rate of charge transfer to the oxidized TEMPO and MPT molecules is significantly reduced on glassy carbon below 1.7V (versus Li/Li+) in electrolytes containing LiBOB, but not in electrolytes containing LiPF6. Charge transfer to oxidized DDB seems facile at all potentials above 0.2V in both LiPF6 and LiBOB electrolytes. [Copyright &y& Elsevier]

• Easily synthesizable low-cost electro-active material of novel quinone derivative. • Optimized values for the electrode are 1.0 V, 1180 F g−1 at 9.5 A g−1, 10000 cycles. • Increased in performance by 6 e− transfer and incorporating high amount of quinone. • Cell having high in rate capability, cycle stability, energy and power density. The development of electrode materials for supercapacitors is a necessary research and development work to address the present-day energy crises. The improvement of productive pseudo-capacitors requires quick and reversible kinetics of redox-molecules. In the development of pseudo-capacitors, quinone/hydroquinone redox couples are one of the promising molecules. Graphite sheet, along with quinone molecules with an increased number of carbonyl groups, is expected to give higher performance hybrid supercapacitors. In this direction, a simple one-step reaction of p-benzoquinone and dopamine hydrochloride to 2,5-bis((3,4-dihydroxyphenethyl)amino)cyclohexa-2,5-diene-1,4-dione molecule (BQ-DP) is carried and confirmed the formation from Fourier-transform infrared, high-resolution mass, proton and carbon nuclear magnetic resonance spectra. This molecule is used as a redox system along with a graphite sheet as active electrode material for supercapacitor, wherein a redox system consists of three quinone groups with six electrons transfer reaction. Cyclic voltammetry and charge-discharge graphs, and two constant phase elements obtained from EIS measurement clearly show the contribution of both electrochemical double layer and pseudo-capacitor components. Both benzoquinone and dopamine groups are involved in the redox reaction. The values of specific capacitance for this electrode are 910 F g−1 at 5 mV s−1 and 1180 F g−1 at 9.5 A g−1, respectively. This cell is subjected to 10,000 charge-discharge cycles, which underwent decay in specific capacitance from 416 to 209 F g−1 up to 1000 cycles and then remains constant up to 7000 cycles. In the case of a negligible contribution of EDLC, the supercapacitor cell could be treated as a battery cell. The battery gives an initial specific capacity of 115–58 mAh g−1 at 1000 cycles. This quinone molecule showed higher electrochemical performance compared to the earlier reports on quinone molecules for supercapacitors. An alternative strategy to increase the performance of the quinone-graphite electrode is made by making holes on graphite sheet and accommodated more amount of electro-active quinone molecule and used as an electrode in symmetric cell configuration in coin cell and subjected for 5000 cycles in the voltage range from 0 to 1 V at 9.5 F g−1. The value of specific capacitance for the symmetric cell obtained from charge-discharge measurement for the electrode (419 F g−1) is found to be higher than that of the electrode without holes (324 F g−1). Redox system of quinone having capability of six electron transfer was synthesized easily as a high-performance electrode for supercapacitor with high energy density, high power density and longer cycle life. Image, graphical abstract [ABSTRACT FROM AUTHOR]