Power Sources For Portable Devices Research Articles

Evaluation of a copper based gel polymer electrolyte and its performance in a primary cell

Portable electronic device industry is vastly developing over the last few years. As electrochemical batteries are suitable power sources for portable devices, demand for reliable and efficient batteries have also been increased. Since liquid electrolytes can cause several safety hazards due to leaking of the electrolyte, studies on gel polymer electrolytes have been able to attract many researchers. In this research work, a gel polymer electrolyte based primary cell was fabricated and discharge characteristics were studied. To prepare the gel polymer electrolyte, Polymethylmethacrylate (PMMA), Ethylene Carbonate (EC), Propylene Carbonate (PC) and Copper trifluoromethanesulfonate (Cu(CF 3 SO 3 ) 2 - CuTf) were used. Gel polymer electrolyte sample which contained 22.5% PMMA: 30% EC: 30% PC: 17.5% CuTf showed a conductivity of 2.34 10 -3 S cm -1 at room temperature with an appreciable mechanical stability. Primary cell with Cu and Mg electrodes showed 1.73 V open circuit potential, 131 µA h capacity and 1.13 mA short circuit current. DOI: http://dx.doi.org/10.4038/sljp.v15i0.6686 Sri Lankan Journal of Physics, Vol. 15 (2014) 45-51

Nanowire Electrodes for Advanced Lithium Batteries

Since the commercialization of lithium ion batteries (LIBs) in the past two decades, rechargeable LIBs have become widespread power sources for portable devices used in daily life. However, current demands require higher energy density and power density of batteries. The electrochemical energy storage performance of LIBs could be improved by applying nanomaterial electrodes, but their fast capacity fading is still one of the key limitations and the mechanism needs to be clearly understood. Single nanowire electrode devices are considered as a versatile platform for in situ probing the direct relationship between electrical transport, structure change, and other properties of the single nanowire electrode along with the charge/discharge process. The results indicate the conductivity decrease of the nanowire electrode and the structural disorder/destruction during electrochemical reactions which limit the cycling performance of LIBs. Based on the in situ observations, some feasible structure architecture strategies, including prelithiation, coaxial structure, nanowire arrays and hierarchical structure architecture, are proposed and utilized to restrain the conductivity decrease and structural disorder/destruction. Further, the applications of nanowire electrodes in some “beyond Li-ion” batteries, such as Li-S and Li-air battery, are also described.

Introduction and Foreword to Focus Issue on Intercalation Compounds for Rechargeable Batteries

This issue is a first for the Journal of The Electrochemical Society; an issue devoted to a single topic, in this case Battery Intercalation Electrodes. Many of these papers were presented at the 222nd meeting of The Electrochemical Society in Honolulu, Hawaii, in October 2012. This issue is very timely, as 2013 represents 40 years of research on intercalation compounds for battery electrodes. Some of the precursor research that generated interest in solid-state electrochemistry, mixed conductors, “insertion” compounds, and rechargeable batteries came out of the research group of Prof. Bob Huggins at Stanford University. We are very pleased that Bob has contributed to this issue. Out of Bob’s lab in 1972 came a very predictive article “Beta Alumina, Prelude to a Revolution in Solid State Electrochemistry,”1 and several future pioneers in the field. Without the resulting breakthroughs leading to today’s lithium-ion batteries, the portable electronics revolution would not have been enabled.2 In 1972, both Exxon and Bell Laboratories mounted major, but fairly quiet, efforts on lithium battery research. These studies resulted in the discovery of the key role of intercalation reactions3 and the first commercial lithium batteries, and recently showed the longevity of such cells. Figure 1 shows a solar-recharged Li/TiS2 cell clock, built in the mid-1970s and still operating today. Ongoing testing of such cells at Rutgers University have shown that they still retain the majority of their capacity,4 demonstrating the remarkable lifetime of lithium cells. Around 1991, a second breakthrough occurred when SONY embarked on the very successful commercialization of the Li-ion battery5 based on a carbon anode and a LiCoO2 cathode.6 This cell configuration led to lithium-ion batteries becoming the dominant power source for portable devices, driving out NiMH. However, the high cost of cobalt, which is driven by its use in batteries, has resulted in that material being partially replaced by a combination of nickel and manganese, leading to the NMC class of materials such as LiNi0.6Mn0.4Co0.2O2. In addition to lower costs, these compounds are also more thermally stable. Another breakthrough occurred in 1997 with the discovery of the electrochemical activity of the olivine LiFePO4. This discovery enabled the construction of safer large batteries, with a minimal risk of oxygen evolution on charging. Such batteries have found application in all-electric drive HEV buses, where an 11 kWh battery system is used, and over 25 million miles have been driven in the United States. Olivine batteries are also in use in 8 – 32 MW size grid systems; one such system is used in West Virginia for smoothing and load leveling (Fig. 2). Spinel LiM2O4 intercalation compounds remain one of the key players in both positive and negative electrodes of lithium ion batteries since LiMn2O4 was found to be electrochemically active in 1983.8 Today, 4V Spinel is used in electric vehicles such as the Nissan Leaf, and major research efforts are being carried out on both the high

Micro-Tubular Solid Oxide Fuel Cell with Graded Anode and Cobalt-Free SrFe<sub>0.9</sub>Sb<sub>0.1</sub>O <sub>3−δ</sub> Perovskite Cathode

Micro-tubular solid oxide fuel cell (SOFC) has been fabricated with NiO-YSZ hollow fiber as anode support and SrFe0.9Sb0.1O3−δ-Sm0.2Ce0.8O1.9(SFSb-SDC) composite cathode. The NiO-YSZ hollow fiber anode was prepared by the immersion-induced phase inversion technique and shows a special asymmetrical structure with long and large finger-like porous structure near the lumen side of the hollow fiber. A thin and dense electrolyte membrane (about 12μm) was deposited on the anode by a vacuum-assisted dip-coating process. The performance of the as-prepared micro-tubular SOFC was tested at 600-800°C with humidified H2 as fuel and ambient air as the oxidant. The peak power densities of 462.8, 336.6 and 201.4 mWcm-2can be obtained at 800, 700 and 600°C, respectively. The experimental results indicate that the cobalt-free SFSb was a promising cathode material and the prepared YSZ-based micro-tubular SOFC has potential applications as power sources for portable devices.

Micro-Tubular Solid Oxide Fuel Cell with Asymmetric Structure Anode and La<sub>0.6</sub>Sr<sub>0.4</sub>Co<sub>0.8</sub>Cu<sub>0.2</sub>O<sub>3−δ</sub> Perovskite Cathode

Micro-tubular solid oxide fuel cell (SOFC) has been fabricated with NiO-YSZ hollow fiber as anode support and La0.6Sr0.4Co0.8Cu0.2O3−δ-Sm0.2Ce0.8O1.9 (LSCCu-SDC) composite cathode. The NiO-YSZ hollow fiber anode was prepared by the immersion-induced phase inversion technique and shows a special asymmetrical structure with porous sponge-like structure in the middle and finger-like structure on the inner and outer side of the hollow fiber. A thin and dense electrolyte membrane (about 12μm) was deposited on the anode by a vacuum-assisted dip-coating process. The performance of the as-prepared hollow fiber SOFC (HF-SOFC) was tested at 600-800°C with humidified H2 as fuel and ambient air as the oxidant. The peak power densities of 531.1, 362.5 and 214.6mWcm-2 can be obtained at 800, 700 and 600°C, respectively. The good performance at intermediate temperature (IT) indicates promising applications as power sources for portable devices for the prepared YSZ-based micro-tubular SOFCs with LSCCu-SDC composite cathode.

Comparative exergy analysis of direct alcohol fuel cells using fuel mixtures

Within the last years there has been increasing interest in direct liquid fuel cells as power sources for portable devices and, in the future, power plants for electric vehicles and other transport media as ships will join those applications. Methanol is considerably more convenient and easy to use than gaseous hydrogen and a considerable work is devoted to the development of direct methanol fuel cells. But ethanol has much lower toxicity and from an ecological viewpoint ethanol is exceptional among all other types of fuel as is the only chemical fuel in renewable supply. The aim of this study is to investigate the possibility of using direct alcohol fuel cells fed with alcohol mixtures. For this purpose, a comparative exergy analysis of a direct alcohol fuel cell fed with alcohol mixtures against the same fuel cell fed with single alcohols is performed. The exergetic efficiency and the exergy loss and destruction are calculated and compared in each case. When alcohol mixtures are fed to the fuel cell, the contribution of each fuel to the fuel cell performance is weighted attending to their relative proportion in the aqueous solution. The optimum alcohol composition for methanol/ethanol mixtures has been determined.

An anode-supported hollow fiber solid oxide fuel cell with (Pr 0.5Nd 0.5) 0.7Sr 0.3MnO 3− δ–YSZ composite cathode

A NiO–YSZ anode-supported hollow fiber solid oxide fuel cell (HF-SOFC) has been fabricated with stable (Pr 0.5Nd 0.5) 0.7Sr 0.3MnO 3− δ –YSZ (PNSM–YSZ) composite cathode. The NiO–YSZ hollow fiber anode was prepared by the immersion-induced phase inversion technique and shows a special asymmetrical structure with long and large finger-like porous structure near the lumen side of the hollow fiber. A thin and dense YSZ electrolyte membrane (about 10 μm) was deposited on the anode by a vacuum-assisted dip-coating process. The performance of the as-prepared HF-SOFC was tested at 600–800 °C with humidified H 2 as fuel and ambient air as the oxidant. The peak power densities of 459, 325 and 172 mW cm −2 can be obtained at 800, 700 and 600 °C, respectively. The good performance at intermediate temperatures indicates promising applications as power sources for portable devices for the prepared YSZ-based micro-tubular SOFCs with PNSM–YSZ composite cathode.

A Franklin Array Antenna for Wireless Charging Applications

A Franklin array antenna is proposed in this work to be used for wireless charging applications. It is a fascinating idea to use radio waves as the power source for portable devices. However, due to the relative long wavelength, the power density of microwave radiation dilutes as it propagates. According to power budget analysis, at a distance of one meter, if transmitting and receiving antennas of moderate gains are used, only a few mW is available with a one watt transmitter. In order to enhance the available power level and increase the remote operation distance, larger antennas, which intercept more radiated power, can be employed. In this work, a rectenna made of a high gain Franklin array and RF-to-DC rectifler was developed. RF-to-DC power conversion e-ciency was evaluated.

Ion‐Exchange Plasma Membranes for Fuel Cells on a Micrometer Scale

AbstractRecent advances in miniaturization technology make polymer electrolyte membrane fuel cells very attractive as power sources for portable devices. Ion‐exchange membranes for microscale fuel cells are synthesized by plasma polymerization (using a precursor containing ion‐exchange groups) and intensively characterized. Ion‐exchange plasma membranes are thin, amorphous, and dense materials with no defects. Spectroscopic analyses reveal a polymer‐type matrix containing a rather high concentration of ion‐exchange groups. Under the best synthesis conditions, membranes show a satisfying ionic conduction level and a high compatibility with other active layers of fuel cells, making them suitable for insertion in such power‐supply devices.

D242 燃料貯蔵型 DMFC におけるメタノール供給方法に関する研究

A direct methanol fuel cell (DMFC) is considered as prospective power sources for portable devices and is studied intensively. Although a fuel-strage-type one seems to be much practical, in many cases, experiments using a fuel-supply pomp are conducted. In this study, effects of fuel feed method on DMFC performance are investigated. It is shown that the output power of fuel-storage-type DMFCs decreases gradually because of development of a concentration boundary layer and so on. Next, a simple method for estimation of fuel concentration at the anode catalysis layer is proposed and its effectiveness is shown. Finally it is shown that by supplying fuel as a vapor, DMFC keeps higher performance than that of a liquid-feed type, but because of dry up of membranes, its performance goes down significantly after a long operation.

携帯機器用パワー源の新展開(第2部 : ITを支える機械工学)

携帯機器用パワー源の新展開(第2部 : ITを支える機械工学)