Polymer Ni–MH battery based on PEO–PVA–KOH polymer electrolyte

An alkaline polymer electrolyte film has been prepared by a solvent-casting method. Poly(vinyl alcohol), PVA is added to improve the ionic conductivity of the electrolyte. The ionic conductivity increases from 10⁻⁷ to 10⁻² S cm⁻¹ at room temperature when the weight percent ratio of poly(ethylene oxide), PEO to PVA is increased from 10:0 to 5:5. The activation energy of the ionic conductivity for the PEO–PVA–KOH polymer electrolyte is 3–8 kJ mol⁻¹. The properties of the electrolyte film are characterized by a wide variety of techniques and it is found that the film exhibits good mechanical stability and high ionic conductivity at room temperature. The application of such electrolyte films to nickel–metal-hydride (Ni–MH) batteries is examined and the electrochemical characteristics of a polymer Ni–MH battery are obtained.     

Ambient lithium–air battery enabled by a versatile oxygen electrode based on boron carbide supported ruthenium

Li-air batteries (LABs) operated in ambient air containing moisture and CO₂ highly desire the oxygen electrodes to have capability of Li₂CO₃ and LiOH decomposition and electrochemical stability. Here we report the application of a stable non-carbon based oxygen electrode based on boron carbide supported ruthenium (Ru/B₄C) for ambient LABs. LABs using Ru/B₄C deliver a discharge capacity of 2689 mA h g⁻¹ and voltage plateaus of 2.7 V and 3.8 V for discharge and charge process, respectively at 0.1 mA cm⁻², which are comparable to those for Ru/B₄C-based Li–O₂ battery (2796 mA h g⁻¹, 2.8 V and 3.7 V, respectively). Under limited capacity of 300 mA h g⁻¹, LAB exhibits 45 stable cycles, close to the 50 cycles for its Li–O₂ battery counterpart. The typical product for the first discharge for LAB is the mixture of Li₂CO₃ and Li₂O₂ with relative content ratio of 62:38, which cannot be detected after the first charge. The non-carbon based Ru/B₄C oxygen electrode provides a promising approach for the stable operation of LABs in ambient air.     

Fabrication and characteristics of a composite cathode of sulfonated polyaniline and Ramsdellite–MnO2 for a new rechargeable lithium polymer battery

The ionic conductivity of a polyacrylonitrile (PAN)-based solid polymer electrolyte is 1.4×10⁻³ S cm⁻¹, which is sufficient for the electrolyte to be used in a rechargeable lithium polymer battery. The anodic stability of the solid polymer electrolyte is over 4.6 V (vs. Li/Li⁺). A reduced, highly sulfonated form of polyaniline (SPAn) and Ramsdellite–MnO₂ (R-MnO₂) are synthesized and used as a cathodic material for a rechargeable lithium polymer battery. Three kinds of cathodes are prepared from SPAn, R-MnO₂, and a mixture of SPAn and R-MnO₂. The electrochemical properties and diffusion coefficient of lithium ions in each cathode, and the interface between the solid polymer electrolyte and each cathode are investigated by cyclic voltammetry and impedance spectroscopy. The redox processes of the SPAn cathode are two-step reactions. The cathodic and anodic peak currents increase as the cycle number increases. In the redox processes of the R-MnO₂ cathode, the cathodic peak current on the second cycle is 62% of that on the first cycle. The Li/R-MnO₂ battery has a very high initial discharge capacity, but very poor cycleability. For the composite cathode, the cathodic peak current on the second cycle is 72% of that on the first cycle, i.e., higher than that for the R-MnO₂ cathode. The diffusion coefficient of the composite cathode during the discharge process is close to the sum of each variation in the SPAn and R-MnO₂ cathodes. The instability of the R-MnO₂ cathode at x=0.3 and x=0.2 during the charge process is not observed with the composite cathode. The discharge–charge performance of three types of battery are investigated. The initial discharge capacity of the Li/composite cathode battery is 97.0 m Ah g⁻¹. This battery has higher discharge capacity than the Li/SPAn battery (66.8 m Ah g⁻¹), and better cycleability than the Li/R-MnO₂ battery.     

Endurance study of a solid polymer electrolyte direct ethanol fuel cell based on a Pt–Sn anode catalyst

The performance decay of a solid polymer electrolyte direct ethanol fuel cell (DEFC) based on a Pt₃Sn₁/C anode catalyst during an endurance test has been investigated. The effect of different cell shut-down procedures on the cycled behaviour of the DEFC has been studied. To get specific insights into the degradation mechanism, polarization and ac-impedance spectroscopy studies have been carried out. These analyses have been complemented by post-operation transmission electron microscopy and X-ray diffraction studies. The combination of these techniques has allowed to get information on recoverable and unrecoverable losses. This provides a basis for further improvement of DEFC components.     

Discharge–charge characteristics and performance of Li/FeOOH(an) battery with PAN-based polymer electrolyte

The discharge–charge characteristics and performance of a Li/FeOOH(an) solid polymer battery are investigated. The cell uses a cathode of amorphous FeOOH with aniline derivatives (FeOOH(an)) and a polyacrylonitrile-based solid polymer electrolyte. The ionic conductivity of the electrolyte sample used for electrochemical measurements is 1.6×10⁻³ Ω⁻¹ cm⁻¹ at room temperature. Its anodic stability is above 4.5 V. The diffusion coefficient of Li⁺ ions into the cathode is found to be 2.97×10⁻¹¹ cm² s⁻¹ by a.c. impedance spectroscopy. Variations of impedance parameters and the diffusion coefficient are investigated during the first discharge–charge. From the results of these measurements, it is concluded that the structure of FeOOH(an) is deformed by Li⁺ ion insertion/extraction. The electrochemical redox reaction of FeOOH(an) is investigated by cyclic voltammetry. In the potential range 2.0 to ∼4.0 V, the first discharge–charge is irreversible. Thereafter, reversible cycling processes take place. The initial discharge capacity is ∼130 mA h g⁻¹ at a current density of 0.1 mA cm⁻².     

Charge–discharge characteristics of LiCoO2/mesocarbon microbeads battery with poly(vinyl chloride)-based composite polymer electrolyte

Polyvinyl chloride (PVC)-based composite polymer electrolyte films consisting of PVC–LiCF₃SO₃–SiO₂ are prepared by the solution-casting method. The electrical properties of the electrolyte are investigated for ionic conductivity and its dependence on temperature. The electrolyte with the highest ionic conductivity is used to fabricate a LiCoO₂/PVC–LiCF₃SO₃–SiO₂/mesocarbon microbeads (MCMB) battery. The charge–discharge characteristics and performance of the battery at room temperature are evaluated to ascertain the effective viability, of these solid electrolytes in lithium-polymer batteries. Battery performances is also investigated at 313, 323 and 333 K.     

Novel electrospun poly(vinylidene fluoride-co-hexafluoropropylene)–in situ SiO2 composite membrane-based polymer electrolyte for lithium batteries

Composite membranes of poly(vinylidene fluoride-co-hexafluoropropylene) {P(VdF-HFP)} and different composition of silica have been prepared by electrospinning polymer solution containing in situ generated silica. These membranes are made up of fibers of 1–2 μm diameters. These fibers are stacked in layers to produce fully interconnected pores that results in high porosity. Polymer electrolytes were prepared by immobilizing 1 M LiPF₆ in ethylene carbonate (EC)/dimethyl carbonate (DMC) in the membranes. The composite membranes exhibit a high electrolyte uptake of 550–600%. The optimum electrochemical properties have been observed for the polymer electrolyte containing 6% in situ silica to show ionic conductivity of 8.06 mS cm⁻¹ at 20 °C, electrolyte retention ratio of 0.85, anodic stability up to 4.6 V versus Li/Li⁺, and a good compatibility with lithium metal resulting in low interfacial resistance. A first cycle specific capacity of 170 mAh g⁻¹ was obtained when the polymer electrolyte was evaluated in a Li/lithium iron phosphate (LiFePO₄) cell at 0.1 C-rate at 25 °C, corresponding to 100% utilization of the cathode material. The properties of composite membrane prepared with in situ silica were observed to be comparatively better than the one prepared by direct addition of silica.     

The effect of temperature and solid concentration on dynamic viscosity of MWCNT/MgO (20–80)–SAE50 hybrid nano-lubricant and proposing a new correlation: An experimental study

The main objective of the present paper is to investigate the dynamic viscosity of MWCNT/MgO (20–80)–SAE50 hybrid nano-lubricant. The experiments carried out in solid concentrations ranging from 0.25% to 2% and temperatures ranging from 25 °C to 50 °C. The results revealed that the nano-lubricant shows Newtonian behavior in all the studied temperatures and solid concentrations. Furthermore, the experimental results showed that the dynamic viscosity decreased as the temperature increased. It is also revealed that increasing the solid concentration leads to increasing the dynamic viscosity of the nano-lubricant in all the temperatures. The maximum increase in dynamic viscosity took place at the solid concentration of 2% and temperature of 40 °C by 65% while the minimum increase was at the solid concentration of 0.25% and temperature of 25 °C by 14.4%. Finally, applying curve fitting method on the experimental data, a new model to predict the dynamic viscosity of the studied nano-lubricant in terms of temperature and solid concentration has been proposed.     

A paste type negative electrode using a MmNi5 based hydrogen storage alloy for a nickel–metal hydride (Ni–MH) battery

Different conducting materials (nickel, copper, cobalt, graphite) were mixed with a MmNi₅ type hydrogen storage alloy, and negative electrodes for a nickel–metal hydride(Ni–MH) rechargeable battery were prepared and examined with respect to the discharge capacity of the electrodes. The change in the discharge capacity of the electrodes with different conducting materials was measured as a function of the number of electrochemical charge and discharge cycles. From the measurements, the electrodes with cobalt and graphite were found to yield much higher discharge capacities than those with nickel or cobalt. From a comparative discharge measurements for an electrode composed of only cobalt powder without the alloy and an electrode with a mixture of cobalt and the alloy, an appreciable contribution of the cobalt surface to the enhancement of charge and discharge capacities was found.     

An experimental study on energy generation with a photovoltaic (PV)–solar thermal hybrid system

A hybrid system, composed of a photovoltaic (PV) module and a solar thermal collector is constructed and tested for energy collection at a geographic location of Cyprus. Normally, it is required to install a PV system occupying an area of about 10 m² in order to produce electrical energy; 7 kWh/day, required by a typical household. In this experimental study, we used only two PV modules of area approximately 0.6 m² (i.e., 1.3×0.47 m²) each. PV modules absorb a considerable amount of solar radiation that generate undesirable heat. This thermal energy, however, may be utilized in water pre-heating applications. The proposed hybrid system produces about 2.8 kWh thermal energy daily. Various attachments that are placed over the hybrid modules lead to a total of 11.5% loss in electrical energy generation. This loss, however, represents only 1% of the 7 kWh energy that is consumed by a typical household in northern Cyprus. The pay-back period for the modification is less than 2 years. The low investment cost and the relatively short pay-back period make this hybrid system economically attractive.     

A hybrid power plant (Solar–Wind–Hydrogen) model based in artificial intelligence for a remote-housing application in Mexico

World fossil fuel reserve is expected to be exhausted in coming few decades. Therefore, the decentralization of energy production requires the design and integration of different energy sources and conversion technologies to meet the power demand for single remote housing applications in a sustainable way under various weather conditions. This work focuses on the integration of photovoltaic (PV) system, micro-wind turbine (WT), Polymeric Exchange Membrane Fuel Cell (PEM-FC) stack and PEM water electrolyzer (PEM-WE), for a sustained power generation system (2.5 kW). The main contribution of this work is the hybridization of alternate energy sources with the hydrogen conversion systems using mid-term and short-term storage models based in artificial intelligence techniques built from experimental data (measurements obtained from the site of interest), this models allow to obtain better accuracy in performance prediction (PV_MSE = 8.4%, PEM-FC_MSE = 2.4%, PEM-WE_MSE = 1.96%, GSR_MSE = 7.9%, WT_MSE = 14%) with a practical design and dynamic under intelligent control strategies to build an autonomous system.     

Numerical study of liquid-gas and liquid-liquid Taylor flows using a two-phase flow model based on Arbitrary-Lagrangian–Eulerian (ALE) formulation

The liquid-gas and liquid-liquid Taylor flows in circular capillary tubes are numerically studied using a mathematical model developed in the frame of Arbitrary-Lagrangian–Eulerian (ALE), where the interface is tracked so that the important interfacial curvature and forces for Taylor flow can be accurately estimated. It is found that for liquid-gas Taylor flow, thin film thickness predicted by the present numerical model agrees very well with the benchmark experimental data both in visco-capillary and visco-inertia flow regimes. Thin film thicknesses decreases first and then increases as Reynolds number (Re) increases at relatively large capillary numbers (Ca). With the increase of Ca, classical pressure drop correlations become inaccurate, because of strong internal circulation inside liquid slug, the appearance of waves at rear meniscus, as well as the deviation from semi-spherical shape of head meniscus. For liquid-liquid flow, when Ca is small, thin film thickness correlations for liquid-gas flow can be used since the disperse phase has negligible effects, while when Ca is relatively large, the viscosity ratio and density ratio of continuous phase to disperse phase become two additional influencing factors. The larger are the viscosity ratio and the density ratio, the thicker is the film thickness. Different from stagnant thin film in liquid-gas flow, the flow in thin film of liquid-liquid flow is not stagnant and has a large contribution to pressure drop. The numerical model developed in this study is shown to be a powerful and accurate tool to study both the liquid-gas and liquid-liquid Taylor flows.     

Studies on Li–Mn–O spinel system (obtained from melt-impregnation method) as a cathode for 4 V lithium batteries: Part V. Enhancement of the elevated temperature performance of Li/LiMn2O4 cells

Stoichiometric LiMn₂O₄, metal-ion doped (Li⁺ and Co³⁺) spinels, Li_1+xMn_2−x−yM_yO₄, and fluorine substituted spinel, Li_1+xMn₂O_4−zF_z, are examined as cathodes in Li/organic electrolyte/Li_xMn₂O₄ cells containing various electrolytes at both room temperature and 50°C. The elevated temperature performance is improved with the metal-ion doped and fluorine substituted spinels in LiBF₄ base electrolyte solution.     

Pt–Ru nanoparticles anchored on poly(brilliant cresyl blue) as a new polymeric support: Application as an efficient electrocatalyst in methanol oxidation reaction

The glassy carbon electrode is modified by poly(brilliant cresyl blue) (PBCB) to be applied as a new green and efficient platform for Pt and Pt–Ru alloy nanoparticles deposition. Surface composition, morphology and catalytic activity of these modified electrodes towards methanol oxidation are assessed by applying X-ray diffraction, field emission scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy techniques. The X-ray diffraction patterns reveal that the highly crystalline Pt and Pt–Ru alloy and RuO₂ nanoparticles with low crystallinity are deposited on the PBCB modified glassy carbon electrodes. The microscopic images indicate smaller size and better distribution of deposited nanoparticles on the surface of PBCB modified electrodes. Cyclic voltammetry and electrochemical impedance spectroscopy results reveal that PBCB supported Pt and Pt–Ru nanoparticles have better electrocatalytic performance and durability towards methanol oxidation rather than the unsupported nanoparticles. From the obtained results it can be concluded that the presence of PBCB not only improves the stability of nanoparticles on the surface, but also leads to the formation of smaller size and more uniform distribution of nanoparticles on the surface, which, in turn, cause the nanoparticles to provide a higher accessible surface area and more active centers for the oxidation of methanol. The results will be valuable in extending the applications of this polymer in surface modification steps and in developing promising catalyst supports to be applied in direct methanol fuel cells.     

Shock-induced nonlocal coupled thermoelasticity analysis (with energy dissipation) in a MEMS/NEMS beam resonator based on Green–Naghdi theory: A meshless implementation considering small-scale effects

In this article, a meshless method based on the generalized finite difference (GFD) method is developed for coupled thermoelsaticity analysis (with energy dissipation) considering small-scale effects in a micro-electromechanical-systems/nano-electromechanical-systems beam resonator. The Green–Naghdi theory of the generalized coupled thermoelasticity and nonlocal Rayleigh beam theory are utilized for dynamic analysis of a micro/nanobeam resonator subjected to thermal shock loading. The small-scale effects and energy dissipation are considered to derive the governing equations for both displacement and temperature fields. The governing equations are discretized in the Laplace domain using GFD method. To find the dynamic and transient behaviors of fields’ variables in time domain, an inversion Laplace technique is utilized, which is called the Talbot method. The effects of some parameters such as small-scale parameter and height of the micro/nanobeam on the dynamic behaviors of temperature and lateral deflection are discussed in detail.     

Nuclear fuel rod cladding oxidation and hydrogen production model based on diffusion theory in a multiphase environment of ZrO2, α-Zr(O), and β-Zr at high temperatures (1273 K–1800 K)

This paper proposes a mathematical model for the oxidation process of zirconium under the theory of oxygen diffusion in Zircaloy. The model considers ZrO₂, α-Zr(O), and β-Zr phases at high temperatures (1273 K–1800 K) in an equivalent fuel rod. The model also considers the heat transfer phenomenon, the decay heat after shutdown, the heat released by the oxidation reaction, the loss of coolant water in the core and the heat transported by the steam produced. A computer program was coded in the C++ environment. The accident scenario of a BWR short term station blackout was simulated with this model. The results are compared with the ones obtained using MELCOR and RELAP/SCDAP codes. The comparison yielded an approximate result for total hydrogen production at the end of the simulation, with a difference of ?2.7% compared with RELAP/SCDAP, and a difference of ?1.11% with MELCOR. With the present model it is possible to calculate the growth of ZrO₂, α-Zr(O), and β-Zr phases through the cladding.     

Inorganic–organic membranes based on Nafion, [(ZrO2)·(HfO2)0.25] and [(SiO2)·(HfO2)0.28]. Part I: Synthesis,thermal stability and performance in a single PEMFC

This work reports the preparation, characterization and test in a single fuel cell of two families of hybrid inorganic-organic proton-conducting membranes, each based on Nafion and a different “core-shell” nanofiller. Nanofillers, based on either a ZrO₂ “core” covered with a HfO₂ “shell” (ZrHf) or a HfO₂ “core” solvated by a “shell” of SiO₂ nanoparticles (SiHf), are considered. The two families of membranes are labelled [Nafion/(ZrHf)_x] and [Nafion/(SiHf)_x], respectively. The morphology of the nanofillers is investigated with high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDX) and electron diffraction (ED) measurements. The mass fractions of nanofiller x used for both families are 0.05, 0.10 or 0.15. The proton exchange capacity (PEC) and the water uptake (WU) of the hybrid membranes are determined. The thermal stability is investigated by high-resolution thermogravimetric measurements (TGA). Each membrane is used in the fabrication of a membrane-electrode assembly (MEA) that is tested in single-cell configuration under operating conditions. The polarization curves are determined by varying the activity of the water vapour (a_H2O) and the back pressure of the reagent streams. A coherent model is proposed to correlate the water uptake and proton conduction of the hybrid membranes with the microscopic interactions between the Nafion host polymer and the particles of the different “core–shell” nanofillers.