PVdF-HFP Quasi-solid-state Electrolyte for Application in Dye-sensitized Solar Cells

A quasi-solid-state polymer electrolyte is prepared by incorporating poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) in a propylene carbonate (PC) / 1,2-dimethoxyethane (DME) / 1-methyl-3-propylimidazolium iodide (MPII) liquid electrolyte. The amount of PVdF-HFP in the liquid electrolyte is varied from 0.1 to 0.4 g. Incorporation of 0.1 g of PVdF-HFP decreases the conductivity of the DME/PC/MPII liquid electrolyte from 1.3×10-2 to 5.6×10-3 S cm-1. Conductivity decreases gradually with increasing PVdF-HFP. No-flow “jelly-like” electrolyte samples are obtained for PVdF-HFP ? 0.2 g. The decrease in conductivity is the result of the decrease in ion mobility. Ion mobility was calculated by impedance spectroscopy. The PVdF-HFP quasi-solid-state electrolytes were assembled into dye sensitized solar cells (DSSCs). The performance of the DSSCs was measured under illumination of a 100 mW cm-2 Xenon light source. The DSSC without PVdF-HFP polymer shows an efficiency of 4.88% with short-circuit current density, Jsc of 11.24 mA cm-2, fill factor, FF of 70% and open circuit voltage, Voc of 619 mV. The presence of PVdF-HFP deteriorates the performance of DSSCs, but problems such as electrolyte leakage and volatilization are eliminated. The performance of DSSCs was found to be correlated to the conductivity behaviour of the electrolyte

Development of pma/pvac-tpai-bmii solid polymer electrolytes for application in dye sensitized solar cell

Electrolyte film of poly(methyl acrylate) (PMA) and poly(vinyl acetate) (PVAc) with composition of 90:10 and 20 wt.% of tetrapropyl ammonium iodide (TPAI) at different of 1-butyl-3- methyl imidazoliumiodide (BMII) concentration were prepared by solution casting technique. Highest conductivities achieve at 5wt.% of BMII is 1.2 x 10-11 S cm-1. Effects of temperature of this sample on the dielectric properties was studied by impedance spectroscopy. The dielectric constant, εr and dielectric loss, εi increased with increasing temperature. Charge carrier relaxation time was extracted from the electrical modulus spectra. It was found that the relaxation time decreased with temperature. The ac conductivity was observed to obey the Jonscher’s Universal Power Law. The correlated barrier hopping model (CBH) was used to interpret the conduction mechanism of the present electrolyte system. Electrolyte films were sandwiched between titanium dioxide photoanode and platinum counter electrode for dye-sensitized solar cells (DSSCs) assembly. The solar cell with 5wt.% showed highest efficiency of 4.62% with maximum short circuit current density(Jsc) of 10.04 mAcm-2, open circuit voltage (Voc) 0.70 V and fill factor, ff of 66.04%

Long-run performance of dye-sensitized solar cell using natural dye extracted from Costus woodsonii leaves

Current work explores the extract from Costus woodsonii leaves as a natural dye sensitizer for DSSC. The effect of solvent on pigment extraction is reported. The acetone is the optimal solvent to extract chlorophyll from C. woodsonii leaves. The presence of chlorophyll is evidenced from the FTIR and UV–Vis studies. The adherence of chlorophyll pigment to the TiO2 surface is supported by the XRD and FESEM. The performance of chlorophyll DSSC with gel-like PVdF-HFP based electrolyte has been investigated from the aspect of the thickness of the TiO2 mesoporous layer and extraction medium. The highest efficiency achieved is 0.65% with a short circuit current density of 2.25 mA cm⁻². The long-run performance of chlorophyll DSSC is monitored. The findings are discussed from the aspect of electron movement at the TiO2/dye interface

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

High-performance porous 3D graphene-based supercapacitors are one of the most promising and challenging directions for future energy technologies. Microporous graphene has been synthesized by the pyrolysis method. The fabricated lightweight graphene with a few layers (FLG) has an ultra-high surface area of 2266 m2 g−1 along with various-sized micropores. The defect-induced morphology and pore size distribution of the fabricated graphene are examined, and the results show that the micropores vary from 0.85 to 1.9 nm and the 1.02 nm pores contribute 30% of the total surface area. The electrochemical behaviour of the electrode fabricated using this graphene has been studied with various concentrations of the KOH electrolyte. The highest specific capacitance of the graphene electrode of 540 F g−1 (close to the theoretical value, ∼550 F g−1) can be achieved by using the 1 M KOH electrolyte. This high specific capacitance contribution involves the counter ion adsorption, co-ion desorption, and ion permutation mechanisms. The formation of a Helmholtz layer, as well as the diffusion of the electrolyte ions, confirms this phenomenon. The symmetrical solid-state supercapacitor fabricated with the graphene electrodes and PVA–KOH gel as the electrolyte exhibits excellent energy and power densities of 18 W h kg−1 and 10.2 kW kg−1, respectively. This supercapacitor also shows a superior 100% coulombic efficiency after 6000 cycles

Ni-rich lithium nickel manganese cobalt oxide cathode materials: A review on the synthesis methods and their electrochemical performances

The demand for lithium-ion batteries (LIBs) has skyrocketed due to the fast-growing global electric vehicle (EV) market. The Ni-rich cathode materials are considered the most relevant next-generation positive-electrode materials for LIBs as they offer low cost and high energy density materials. However, by increasing Ni content in the cathode materials, the materials suffer from poor cycle ability, rate capability and thermal stability. Therefore, this review article focuses on recent advances in the controlled synthesis of lithium nickel manganese cobalt oxide (NMC). This work highlights the advantages and challenges associated with each synthesis method that has been used to produce Ni-rich materials. The crystallography and morphology obtained are discussed, as the performance of LIBs is highly dependent on these properties. To address the drawbacks of Ni-rich cathode materials, certain modifications such as ion doping, and surface coating have been pursued. The correlation between the synthesized and modified NMC materials with their electrochemical performances is summarized. Several gaps, challenges and guidelines are elucidated here in order to provide insights for facilitating research in high-performance cathode for lithium-ion batteries. Factors that govern the formation of nickel-rich layered cathode such as pH, reaction and calcination temperatures have been outlined and discussed

Thermomechanical Analysis of Isora Nanofibril Incorporated Polyethylene Nanocomposites

International audienceThe research on cellulose fiber-reinforced nanocomposites has increased by an unprecedented magnitude over the past few years due to its wide application range and low production cost. However, the incompatibility between cellulose and most thermoplastics has raised significant challenges in composite fabrication. This paper addresses the behavior of plasma-modified polyethylene (PE) reinforced with cellulose nanofibers extracted from isora plants (i.e., isora nanofibrils (INFs)). The crystallization kinetics of PE–INF composites were explained using the Avrami model. The effect of cellulose nanofillers on tuning the physiochemical properties of the nanocomposite was also explored in this work. The increase in mechanical properties was due to the uniform dispersion of fillers in the PE. The investigation on viscoelastic properties confirmed good filler–matrix interactions, facilitating the stress transfer