Evaporation Of Electrolyte Research Articles

A hybrid gel-solid-state polymer electrolyte for long-life lithium oxygen batteries.

A hybrid gel-solid-state polymer electrolyte has been used as the separator and an electrolyte for lithium oxygen batteries. It can not only avoid electrolyte evaporation but also protect the lithium metal anode during reactions over long-term cycling. Due to its high ionic conductivity and low activation energy, excellent cycling performance is demonstrated, in which the terminal voltage is higher than 2.2 V after 140 cycles at 0.4 mA cm(-2), with a capacity of 1000 mA h g(composite)(-1).

Correlating Electrolyte Inventory and Lifetime of HT-PEFC by Accelerated Stress Testing

Phosphoric acid electrolyte evaporation in a polybenzimidazole based high temperature polymer electrolyte fuel cell is analyzed as a function of reactant gas stoichiometry and temperature. Based on these results a phosphoric acid vapor pressure curve is derived to predict the fuel cell liftetime with respect to electrolyte inventory. The predicted fuel cell life was validated by means of an accelerated stress test. Additionally, the correlation between electrolyte inventory and fuel cell performance was investigated by recording H2/air and H2/O2 polarization curves during the course of the stress test to gain insight into the relation between acid inventory and the different degradation modes.

Accelerated Life Testing of Double‐Layer Capacitors: Reliability and Safety under Excess Voltage and Temperature

AbstractCommercial 50 F double‐layer capacitors from leading international manufactures were tested with respect to fire protection regulations and general safety hazards in technical pulse–power applications at temperatures of up to 120 °C and voltages up to 4 V. Diagnostic criteria were gathered during a decade of lifetime testing concerning the destruction of the electrode materials and the evaporation of electrolyte. The aging behavior of supercapacitors is quantified on the basis of capacitance loss, parasitic side reactions, and the chemical analysis of decomposition products. Amines, amides, and oligomers of acetonitrile are formed in the electrolyte. The carbon composite electrodes are destroyed by continual stress at high temperatures and operating voltages.

Comparison of Aluminum Electrolytic Capacitor Lifetimes Using Accelerated Life Testing

This research compared the lifetime of similar aluminum electrolytic capacitors from different manufacturers using an accelerated life test, which consisted of critical weight loss testing and rate of weight loss testing. In critical weight loss testing, capacitors are perforated to speed up electrolyte evaporation and the equivalent series resistance (ESR) and weight are measured periodically to determine their relationship. In rate of weight loss testing, capacitors are subjected to final operating conditions (i.e. voltage and ripple current are applied) and the weight is periodically measured over the course of 500 hours. After test completion the relationship between ESR and weight loss is used to calculate the critical weight loss that occurs at datasheet-defined failure, which is typically a 200% increase in ESR. The rate of weight loss is extrapolated to the critical weight to estimate a time to failure that can be compared to other capacitors tested using the same accelerated approach. In this research, testing compared 450 V, 68 μF capacitors from Manufacturer A and Manufacturer B, and results indicated Manufacturer A had a significantly longer lifetime. Therefore, capacitors from Manufacturer A are more reliable than capacitors from Manufacturer B.

Modelling and Fabrication of Micro-SOFC Membrane Structure

Fabrication process of micro-SOFC membrane structure using the bulk micromachining of silicon technique with SiO2 and Si3N4 sacrificial layers is presented in this study. The process involves back side photolithography, magnetron sputtering of platinum thin films, thermal evaporation of YSZ electrolyte, deep reactive ion etching of silicon, and, finally, release of free-standing membrane using CF4/O2 plasma etching.X-ray analysis shows the cubic phase of YSZ electrolyte and platinum electrodes. Modelling of normal stress distribution in the micro-SOFC structure with the Si3N4 sacrificial layer shows that at high temperatures the substrate expands less than the coating, causing tensile stresses in the substrate area next to the coating and compressive stresses in the coating, as the substrate material has a lower coefficient of thermal expansion than the layered Pt/YSZ/Pt coating. DOI: http://dx.doi.org/10.5755/j01.ms.20.2.5585

Pore-filling of Spiro-OMeTAD determined by Rutherford backscattering spectrometry in templated TiO2 photoelectrodes

Liquid-state dye-sensitized solar cells can suffer from electrolyte evaporation and leakage. Therefore solid-state hole transporting materials are investigated as alternative electrolyte materials. However, in solid-state dye-sensitized solar cells, optimal TiO2 films thickness is limited to a few microns allowing the adsorption of only a low quantity of photoactive dye and thus leading to poor light harvesting and low conversion efficiency. In order to overcome this limitation, high surface area templated films are investigated as alternative to nanocrystalline films prepared by doctor-blade or screen-printing. Moreover, templating is expected to improve the pore accessibility what would promote the solid electrolyte penetration inside the porous network, making possible efficient charge transfers. In this study, films prepared from different structuring agents are discussed in terms of microstructural properties (porosity, crystallinity) as well as impact on the dye loading and Spiro-OMeTAD (2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenylamine)9,9′-spirobifluorene) solid electrolyte filling. We first report Rutherford backscattering spectrometry as an innovative non-destructive tool to characterize the hole transporting materials infiltration. Templated films show dye loading more than two times higher than nanocrystalline films prepared by doctor-blade or screen-printing and solid electrolyte infiltration up to 88%.

Development of quasi‐solid‐state dye‐sensitized solar cell based on an electrospun polyvinylidene fluoride–polyacrylonitrile membrane electrolyte

ABSTRACTDye sensitized solar cell (DSSC) has been magnetizing more awareness in current research due to more efficiency. The foremost drawback of the solar cell is the evaporation of organic electrolyte. In order to address this problem, the polyvinylidene fluoride–polyacrylonitrile–Electrospinning Fibrous Membranes were prepared by electrospinning method and the photovoltaic performances were evaluated. The polyvinylidene fluoride and polyacrylonitrile were mixed in N,N′‐dimethylformamide and acetone at an applied potential of 15 kV. The surface morphology of membrane is interconnected with network structure and a large number of voids were observed from Field Emission Scanning Electron Microscopy images. The electrolyte uptakes up to 310% were observed and it shows an increase in the ionic conductivity up to 6.12 × 10−2 S cm−1 at 25°C. The fabricated DSSCs show open circuit voltage (Voc) of 0.74 V, fill factor (FF) of 0.65 and short circuit current (Jsc) of 6.20 mA cm−2 at an incident light intensity of 100 mW cm−2. The photovoltaic efficiency also reached up to 3.09%. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 40022.

Graphene nanosheet supported bifunctional catalyst for high cycle life Li-air batteries

Rechargeable lithium-air batteries offer great promise for transportation and stationary applications due to their high specific energy and energy density. Although their theoretical discharge capacity is extremely high, the practical capacity is much lower and is always cathode limited. A key for rechargeable systems is the development of an air electrode with a bifunctional catalyst on an electrochemically stable carbon matrix. The use of graphene as a catalyst matrix for the air cathode has been studied in this work. A Li-air cell using an air cathode consisting of nano-Pt on graphene nanosheets (GNS) has shown promising performance at 80% energy efficiency with an average capacity of 1200 mAh g−1 and more than 20 cycles without significant loss of total energy efficiency. Replacement of Pt with a bifunctional catalyst resulted in more than 100 cycles with an average capacity of 1200 mAh g−1 and total energy efficiency of about 70%. Electrochemical impedance spectroscopy data revealed increasing solution and charge transfer resistance during cycling, which hindered the cycle life. The increased solution resistance can be attributed to the evaporation and decomposition of electrolyte especially at high charge voltages. Further investigation on ionic liquid based electrolytes in Li-air systems is being conducted.

Polyaniline membranes as waterproof barriers for lithium air batteries

Highly conductive polyaniline (PANI) membranes synthesized by a proton doping method are used as waterproof barriers for lithium air batteries. When the membrane is attached to the air cathode, it promotes lithium ion transport into the electrode and blocks the moisture entrance, which can protect the lithium anode from erosion. Electrolyte evaporation from the battery is also greatly reduced. Electrochemical tests show that lithium air cells with this design deliver a much higher specific capacity, 3241mAhg−1 (referring to carbon), under high relative humidity (RH>20%) conditions; the cells also have an excellent rate capability.

Smart Electrochemical Oxygen Sensor for Personal Protective Equipment

Self contained closed circuit rebreathers are life supporting breathing systems, where the exhaled gas is recycled by filtering CO2 and replacing metabolized O2. For the O2 injection control galvanic O2 sensors are used to measure the partial pressure of O2. A malfunction of the sensors can lead to a gas mixture beyond life supporting limits which is life threatening. Galvanic O2 sensors are often used in anaesthetic machines in hospitals. Also in this case, a malfunction of the sensors can cause severe injury to a person. It is obvious that such sensors are key elements in life supporting equipment and as such must be designed in order to achieve high functional safety. However these sensors are consuming sensors, and with that, will fail at a certain time. Failure modes include current limitation, non linearity, electrolyte evaporation or leakage, etc. Within this paper a novel low cost read out electronic circuit for galvanic O2 sensors is presented, which allows not only digital readout, digital temperature compensation, on board storage of calibration and manufacturing data, but also can be used for performing voltammetry cycles to test the Pb anode for exhaustion. First measurements are presented and compared to data from a Solartron SI 1287 impedance analyzer, which is state-of-the-art in electrochemical sensor characterization.

Quasi-gel-state ionic liquid electrolyte with alkyl-pyrazolium iodide for dye-sensitized solar cells

Abstract A series of non-volatile viscous ionic liquid, 1-alkyl-2-methylpyrazolium iodides (RPyI: R = C 3 –C 7 ), were synthesized for the electrolyte of dye-sensitized solar cells (DSSC). Most of RPyI revealed extremely viscous quasi-gel-state electrolytes potentially preventing leakage and evaporation of electrolytes of the solar cells. A DSSC using the electrolyte composed of 1-hexyl-2-methylpyrazolium iodide (C 6 PyI) with iodine exhibiting higher conversion efficiency of 3.8% (under 1 Sun) for 10% larger short-circuit photocurrent, J SC , than that with a conventional ionic liquid, 1-hexyl-3-methyllimidazolium iodide (C 6 ImI) with iodine, in spite of less favorable viscosity (2013 mPa s (C 6 PyI/I 2 ) vs. 1439 mPa s (C 6 ImI/I 2 )) for the physical diffusion of charge carriers in the electrolyte. Furthermore, the quasi-gel-state electrolytes composed of a series of RPyI ionic liquids surprisingly exhibiting comparable J SC to that with much less viscous C 6 ImI/I 2 . We discuss the results of quasi-gel-state RPyI ionic liquid electrolyte for DSSC based on the Grotthus-like electron exchange mechanism of iodide redox species in the highly viscous RPyI ionic liquid evaluated qualitatively by Raman spectroscopic observation of poly-iodide species.

The Dye Sensitized Solar Cell Stability and Performance Study Using Different Electrolytes

ABSTRACTThe overarching goal of Dye Sensitized Solar Cells (DSSCs) is to improve photovoltaic performance and their long-term stability for use in practical applications because of their simple fabrication technology at a reasonable cost. The focus of this paper is to achieve cell stability and also to improve solar energy conversion efficiency experimenting with different electrolytes. The electrolyte’s role is critical to sustain the DSS cell performance over time to instill cell stability. Four different electrolytes, Iodolyte R-150, AN-50, PN-50 and MPN-100, are experimented in this work for fabricating the dye-sensitized solar cells for studying both the stability and efficiency of the DSSCs.The electrolyte selection was made using the following key electrolyte parameters; lower viscosity for easier injection into the cell, lower vapor pressure and higher boiling point to minimize electrolyte evaporation, wide redox window to generate sufficient donating electrons to the dye, lower cost and non-toxicity. Electrolytes with higher concentration of Iodolyte were chosen for this study to widen redox potential window. These are Iodide based redox electrolytes and are made with 100 mM of tri-iodide in 3-methoxypropionitrile. The results of this investigation revealed that the cell with Iodolyte R-150 electrolyte achieved improved performance having an efficiency of 10.2% when compared to the reference cell efficiency of 8.4% with Iodolyte R-50. These cells were stabilized over a time of 4 weeks. The fill factor of the cell changed about 10% and the internal resistance decreased from 6.7 to 4.3 Ω. The results of this experiment demonstrated reduced internal resistance, and improved fill factor contributed to higher cell efficiency and stability. The results of the work presented in this paper support the argument that electrolytes with higher Iodolyte concentration can enhance the cell efficiency and stability along with scaling down of the cell size.

Mitigation of solvent evaporation in dye‐sensitized solar cells based on liquid electrolyte by introducing regular‐fencing‐patterned polymer films

Leakage and evaporation of electrolytes (organic solvent) are important reliability concerns for the commercialization of dye‐sensitized solar cells (DSSCs) employing liquid electrolytes. To mitigate the leakage/evaporation of organic solvent in liquid electrolytes, a regular‐fencing‐patterned polymer film has been introduced in between the two electrodes of DSSCs. The polymer film can prevent organic solvent leakage and decrease its evaporation rate because it has a fence pattern which can seal the liquid electrolyte within the gaps of the fence. By changing the gap width and film thickness, various patterns of polymer films have been fabricated and the performance of DSSCs employing the patterned polymer films has been examined. The best energy conversion efficiency was measured to be 2.71%.

Electrochemical properties and cycle performance of electrospun poly(vinylidene fluoride)-based fibrous membrane electrolytes for Li-ion polymer battery

Prototype cells were prepared by hot pressing of the cathode and the anode coated with poly(vinylidenefluoride-hexafluoropropylene) P(VdF-HFP) and poly(vinylidene fluoride) PVdF-based fibrous membranes, respectively. Electrochemical properties and cycle performance of them before and after hot pressing were investigated. Pressing of the fibrous membrane resulted in decrease of the apparent porosity and electrolyte uptake. The prototype cell using hot-pressed membrane electrolyte showed continuous fading of the capacity while that using non-pressing fibrous membrane almost retained the initial capacity after 100 cycles at room temperature (0.5 C rate). In the case of cycle test at 80 °C, however, the capacity was slightly decreased after the initial capacity fading of about 6.5% during the first 10 cycles due to the evaporation of liquid electrolytes. Rate performance exhibited about 97% and 72% of the full capacity at the 1 C rate and 2 C rate, respectively. The capacities at 5 C rate and 10 C rate were about 27–28% of the full capacity similarly because of the reduction of the entrapped liquid phase due to the swell of the fibrous structure.

New design for a safe lithium-ion gel polymer battery

We present a new design of a lithium-ion gel polymer battery which is fabricated using a semi-interpenetrating network (semi-IPN) type gel polymer and LiCoO 2, covered by an ion conductive polyurethane. A 7 wt.% solution of a semi-IPN gel polymer, composed of a fully cyanoethylated cellulose derivative and multifunctional poly(oxyethylene)methacrylate has an ionic conductivity of 2.7 × 10 −3 S cm −1 at 25 °C, and has a higher degree of control of liquid electrolyte evaporation when compared with conventional fluoride polymer gels. Another ion conductive polymer, a caprolactone segmented polyurethane, arranged on the surface of the cathode active material in order to increase the start temperature of the thermal runaway reaction worked as planned, raising the exothermic decomposition temperature by 50 °C. A large (2500 mAh) cell showed good discharge performance and improved safety characteristics as judged by a nail penetration test. Furthermore, this battery system exhibited a unique phenomenon, that of preventing overcharging. The new design of this lithium-ion gel polymer battery could be promising for large batteries that must be inherently safe, such as batteries for mobile applications.

The removal of nickel from copper electrorefining bleed-off electrolyte

When high nickel-containing copper concentrates from South Africa started to comprise part of the feed to a Zambian copper smelter at Mufulira, the level of Ni in the copper anodes produced increased. The high nickel, copper anodes started to pose a problem at the electrorefining stage as they led to a progressive increase in the Ni tenor of the electrolyte. In order to produce high quality copper cathodes with less than 1 ppm Ni, it became necessary to bleed-off large volumes of foul electrolyte contaminated with nickel. The study reported in this paper was part of the effort aimed at devising a less costly method for the removal of nickel in the electrolyte. The investigation was carried out on a laboratory scale using contaminated electrolyte collected from the refinery. In the first of two methods considered, it was established that aqueous ammonia is able to precipitate nickel from copper electrorefining bleed-off electrolyte, forming precipitates with 10–13% Ni. A major drawback of this method, however, was found to be the cost of ammonia solution used for Ni precipitation relative to the value of acid retained in the electrolyte. The other method considered, involved partial electrolyte evaporation with a view of crystallizing nickel sulphate from samples of bleed-off electrolyte issuing from a liberator circuit. It has been demonstrated that evaporative crystallisation of nickel sulphate could be a very effective means of controlling nickel in the Mufulira tankhouse. At 66.5% and 80% electrolyte evaporation, 81% and 100% of the nickel was crystallized from foul electrolyte, respectively. Over 95% of the sulphuric acid in initial samples was retained in the purified electrolyte at a concentration of over 1000 g/l. Initial estimates have indicated that the cost of evaporative crystallisation of nickel sulphate would be quite low compared to the value of sulphuric acid that would be present in the purified electrolye.

Evidence of anisotropic structures of free-standing porous silicon films

Optical and secondary electron beam images of free-standing porous silicon films reveal a pronounced layered structure. Films tend to split into sheets parallel to the 〈111〉 plane of the initial substrate and form steps and terraces at the broken edge of the film. We have investigated these layers by scanning and transmission electron as well as optical microscopy. We have not observed any significant differences in the microstructure of each layer. Film layering in the cross-section view, caused by these terraces, has a periodicity of about 1 μm. The origin of this effect is discussed and could arise from the electrochemical etching regime used, vertical inhomogeneities in the starting material or mechanical stress-related effect arising from electrolyte evaporation. © 1997 Elsevier Science S.A.

Measurement of phenols on a loop-supported liquid film by micellar electrokinetic chromatography and direct UV detection

This paper describes a direct measurement of phenolic substances in the gas phase at levels relevant to occupational health by micellar electrokinetic chromatography (MEKC) using direct ultraviolet detection. A small circular loop (2 mm O.D.) is formed with 100 mm Pt-wire at the sampling end of a fused-silica capillary. The capillary tip of the sampling end is present at the center of the loop and in the same plane. A thin film of 0.50 m M NaOH is formed on the loop by immersion and withdrawal. The film is in fluid communication with the capillary and acts as an absorber for gaseous phenols. Gas sampling is performed by transferring the film-bearing loop into a chamber through which air is aspirated for a preset time at a preselected flow-rate (typically 1 min at 100 cm 3/min). A part of the film content is then introduced into the capillary by gravity injection and then MEKC is performed. A total of twelve chloro- and nitrophenols were selected for this study. Under the above sampling conditions, limits of detection (LODs) for various phenols range from high-single-digit to low-double-digit ppbv levels. The effect of several critical parameters, such as the composition of the liquid film and the MEKC running electrolyte, sampling period and film evaporation on the collection efficiency, separation efficiency and calibration behaviour are described.

An electrochemical study of the atmospheric corrosion of mild steel-I. Experimental method

A conventional three-electrode measurement system using a Luggin capillary was successfully developed to study the corrosion of metals under thin films of electrolyte. The experimental arrangement also permitted condensation and evaporation of electrolyte directly on to the metal surface from a gas ambient of controlled composition and relative humidity. This arrangement was intended to allow conditions similar to those of atmospheric corrosion. Automatic resistive compensation in the electrolyte was carried out using a current interrupting potentiostat. Using this apparatus, good potentiodynamic data could be obtained with an electrolyte film thickness of 300 μm using an electrolyte of 0.2 M Na 2SO 4. Under these conditions, the cathodic kinetics were clearly controlled by the ambient O 2 concentration. The oxygen reduction rate was found to increase significantly during evaporation of an electrolyte film which is consistent with increased oxygen transport across the reducing film thickness. However, measurement of the electrolyte film resistance showed a rising resistance with decreasing film thickness. This is consistent with ion transport in the plane of the electrolyte film parallel to the metal substrate.

A solid‐state electrochromic device based on polyaniline, prussian blue and an elastomeric electrolyte

Advantages of solid‐state electrochemical devices are the ease of production, no possibility of leakage, and no electrolyte evaporation. One result of the search for such a device is the electrochromic display sketched in the Figure, which uses polyaniline and Prussian Blue as the active electrochromic materials and an elastomer containing Li‐ClO4 as the solid‐state electrolyte. magnified image