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A three-dimentional(3D) long-range networking Li3V2(PO4)3/C fiber membrane was fabricated by a modified electrospinning method and a hot-press calcination process. The combined use of polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP) promotes the growth of Li3V2(PO4)3 crystals on the surface of the conductive carbon fibers. The adopted hot-press process is favorable to achieve a flexible 3D long-range networks. The Li3V2(PO4)3/C fiber membrane calcined at 800°C for 20h with a high specific surface area of 186.4m2/g and a wide pore size distribution can be used as self-standing, binder-free cathodes and exhibits excellent electrochemical performances. The discharge capacity is up to 196.8, 150.4 and 145.2 mAh/g at the current density of 0.1C, 5C and 10C, respectively. After the rate tests, the Li3V2(PO4)3/C fiber membrane cathode still exhibits an excellent cycle stability at 5C with a discharge capacity of 143.4 mAh/g after 850 cycles. These high performances are ascribed to the enhanced electronic and ionic conductivities owing to the 3D long-range conductive networks, well-crystallized Li3V2(PO4)3 particles in-situ grown on the surface of carbon fibers and the novel binder-free, self-standing structural characterics.
One of the fundamental requirements of a power system, especially in a small isolated power system (SIPS), is secure and reliable energy supply. In this paper, a novel Energy-Based System Well-being Analysis framework (EBSWBA) is presented to assess the reliability of systems containing renewable energy sources (RES), fossil-fueled sources and electricity storage. The framework combines the advantages of the well-known System Well-being Analysis (SWBA) and Expected Energy Not-Served (EENS) approaches, thus overcoming the weaknesses of the SWBA by considering all key factors that influence the system adequacy. Furthermore, two techniques are proposed for calculation of the EBSWBA indices: the Monte-Carlo Simulation (MCS) adopted for the EBSWBA framework, and the Contingency Enumeration for Small Isolated Power Systems (CESIPS) technique, which is derived from the Contingency Enumeration (CE) methodology. These techniques enable formation of probability distributions of the indices. The comparison of the results of classical SWBA and EBSWBA when applied to different SIPS architectures, operating schemes and load profiles demonstrates the superiority of EBSWBA over SWBA in terms of rendered information about the system state as well as in terms of computational efficiency, especially when the CESIPS technique is used for calculation of the EBSWBA indices.
Passivation of zinc electrodes caused by formation of oxy-products with low electrical conductivity is one of the most important phenomena which limits the current density during discharge and contributes to the poor cyclability of zinc-based batteries. The present review critically discusses the existing experimental findings related to passivation of zinc in alkaline electrolyte as well as the state of the mathematical modelling of this process. Despite numerous investigations over several decades, no general consensus about the underlying mechanisms and the strategies to prevent passivation could be achieved. Main reason for this uncertainty is that different processes can lead to passivation. On the one hand, precipitation of so-called type 1 films occurs above a critical zincate concentration while on the other hand the direct oxidation of the zinc surface takes place below a certain potential, leading to type 2 passive films. As long as formed films remain porous, passivation does not necessarily lead to complete breakdown of the electrode activity. It is therefore recommended to conduct further measurements employing a combination of techniques in which both the potential and the concentration of zincates at the electrode surface can be precisely controlled. It is also proposed to carry out systematic studies on the influence of temperature, electrolyte flow, and electrolyte composition – including additives – on the passivation time and the structure of the passive film. Finally, the purity and the structure of the zinc electrode may also have an influence on the passivation processes and should be considered during future studies.
Solar energy has experienced phenomenal growth in recent years due to both technological improvements resulting in cost reductions and government policies supportive of renewable energy development and utilization. This study analyzes the technical, economic and policy aspects of solar energy development and deployment. While the cost of solar energy has declined rapidly in the recent past, it still remains much higher than the cost of conventional energy technologies. Like other renewable energy technologies, solar energy benefits from fiscal and regulatory incentives, including tax credits and exemptions, feed-in-tariff, preferential interest rates, renewable portfolio standards and voluntary green power programs in many countries. The emerging carbon credit markets are expected to provide additional incentives to solar energy deployment; however, the scale of incentives provided by the existing carbon market instruments, such as, the Clean Development Mechanism of the Kyoto Protocol is limited. Despite the huge technical potential, the development and large scale deployment of solar energy technologies world-wide still has to overcome a number of technical, financial, regulatory and institutional barriers. The continuation of policy supports might be necessary for several decades to maintain and enhance the growth of solar energy in both developed and developing countries.
Most queries in wireless sensor network (WSN) applications are issued at the point of the base station or gateway node of the network. However, for critical applications of WSNs there is a great need to access the real-time data inside the WSN from the nodes, because the real-time data may no longer be accessed through the base station only. So, the real-time data can be given access directly to the external users (parties) those who are authorized to access data as and when they demand. The user authentication plays a vital role for this purpose. In this paper, we propose a new password-based user authentication scheme in hierarchical wireless sensor networks. Our proposed scheme achieves better security and efficiency as compared to those for other existing password-based approaches. In addition, our scheme has merit to change dynamically the user's password locally without the help of the base station or gateway node. Furthermore, our scheme supports dynamic nodes addition after the initial deployment of nodes in the existing sensor network.
Increasing the available cell voltage for electrochemical double layer capacitors (EDLC) is one route to simultaneously increase energy density and power density of the EDLC. Increased cell voltage may, however, introduce faradaic reactions such as ion insertion and electrolyte decomposition, which potentially limit the lifetime of the device. Using a purpose designed pressure cell, we have, for the first time, measured the pressure increase in capacitor cells based on real EDLC electrode coils in 1M (C2H5)4NBF4/propylene carbonate electrolyte during cycling between 0 and 2.5V and for constant cell voltages up to 3V. During cycling a reversible pressure decrease was observed upon charging. An irreversible pressure increase was monitored during load tests at constant cell voltages above 2.5V. The absolute amount of gases evolved could be determined by means of simultaneous compressibility monitoring.
Lithium metal as an attractive anode material has been widely used in the advanced energy storage technology such as lithium-sulfur and lithium-air batteries. However, suffering from the uncontrollable deposition, growth of lithium dendrite and the serious volume change within cycling process, the commercial application of lithium anode is impeded by the safety hazards and limited span-life. Here, we demonstrate a kind of bamboo-derived 3D hierarchical porous carbon decorated by ZnO quantum dots which can serve as a lithiophilic scaffold for dendrite-free Li metal anode. This carbon scaffold is stable against the serious volumetric change during cycles. In addition, the 3D porous scaffold can reduce the effective local current density. Most importantly, the lithiophilic ZnO quantum dots within the carbon can be used to induce lithium deposition. Notably, lithium metal up to 131 mAh cm−2 can be confined within ZnO@HPC, achieving acceptable volume expansion, considerable reduction in overpotential and effective dendrite suppression. Thus, 3D Li within ZnO@HPC scaffold could exhibit better capability and much lower voltage hysteresis when compared with Li foil in cells paired with LiCoO2. The function of the ZnO decorated 3D hierarchical porous carbon scaffold might provide innovative insights into the design principles for metallic lithium anodes.
Not only sharp competition but also legislation are pushing development of hybrid drive trains. Based on conventional internal combustion engine (ICE) vehicles, these drive trains offer a wide range of benefits from reduced fuel consumption and emission to multifaceted performance improvements. Hybrid electric drive trains may also facilitate the introduction of fuel cells (FC). The battery is the key component for all hybrid drive trains, as it dominates cost and performance issues. The selection of the right battery technology for the specific automotive application is an important task with an impact on costs of development and use. Safety, power, and high cycle life are a must for all hybrid applications. The greatest pressure to reduce cost is in soft hybrids, where lead-acid embedded in a considerate management presents the cheapest solution, with a considerable improvement in performance needed. From mild to full hybridization, an improvement in specific power makes higher costs more acceptable, provided that the battery’s service life is equivalent to the vehicle’s lifetime. Today, this is proven for the nickel–metal hydride system. Lithium ion batteries, which make use of a multiple safety concept, and with some development anticipated, provide even better prospects in terms of performance and costs. Also, their scalability permits their application in battery electric vehicles—the basis for better performance and enhanced user acceptance. Development targets for the batteries are discussed with a focus on system aspects such as electrical and thermal management and safety.
Discharge/charge process of classical lithium sulphur battery proceeds through intermediate polysulphides which are soluble in classical electrolyte systems. Due to concentration gradient soluble polysulphides easily diffuse/migrate out from cathode composite forming non-uniform distribution of the sulphur within cathode. Eventually polysulphides can be completely reduced on the metallic lithium anode. In this work we compare the sorption properties of manganese modified zeolite silicalite-1 (MnS-1) with a cathode composite containing SBA-15 additive and a cathode composite without additive. Careful analysis using XPS and FIB microscopy equipped with EDX show improved retention of polysulphide species within cathode composite in the case of MnS-1 zeolite as an additive. Interestingly, the amount of sulphur species detected by XPS on the metallic lithium is very similar regardless on cathode composite we use. Finally, similar cycling behaviour can be observed if MnS-1 zeolite is used as an interlayer between composite cathode and separator.
Temperature monitoring is important for improving the safety and performance of Lithium Ion Batteries (LIB). This paper presents the feasibility study to insert flexible polymer embedded thin film thermocouples (TFTCs) in a lithium ion battery pouch cell for in-situ temperature monitoring. A technique to fabricate polyimide embedded TFTC sensors on glass substrates and later transfer it onto thin copper foils is presented. The sensor transfer process can be easily integrated into the assembly process of a pouch cell, thus holding promise in implementing in Battery Management Systems (BMS). Internal temperature of the LIB pouch cell was measured in-situ when the sensor embedded battery was operated at high rate charge–discharge cycles. The polyimide embedded TFTCs survived the battery assembly process and the battery electrolyte environment. It is observed that the heat generation inside the battery is dominant during the high-rate of discharges. The developed technique can serve to improve the battery safety and performance when implemented in battery management systems and enhance the understanding of heat generation and its effects.
The average increase in the rate of the energy density of secondary batteries has been about 3% in the past 60 years. Obviously, a great breakthrough is needed in order to increase the energy density from the current 210 Wh kg−1 of Li-ion batteries to the ambitious target of 500–700 Wh kg−1 to satisfy application in electrical vehicles. A thermodynamic calculation on the theoretical energy densities of 1172 systems is performed and energy storage mechanisms are discussed, aiming to determine the theoretical and practical limits of storing chemical energy and to screen possible systems. Among all calculated systems, the Li/F2 battery processes the highest energy density and the Li/O2 battery ranks as the second highest, theoretically about ten times higher than current Li-ion batteries. In this paper, energy densities of Li-ion batteries and a comparison of Li, Na, Mg, Al, Zn-based batteries, Li-storage capacities of the electrode materials and conversion reactions for energy storage, in addition to resource and environmental concerns, are analyzed.
This paper will report on the electrochemical and material characterization of a potential planar anode stack for all-solid-state 3D-integrated batteries. The first element of the stack is the silicon substrate. On top of silicon, a Li diffusion barrier layer material is deposited in order to effectively shield the substrate from the battery stack. Several materials are investigated with conventional electrochemical techniques. The best candidates, sputtered and atomic layer deposited (ALD) TiN, are studied in more detail with ex situ X-ray diffraction (XRD) and the reaction mechanism of these materials with Li is discussed. The third element of the stack is the active anode material. Thin films of poly-Si are studied towards their thermodynamic and kinetic properties. Moreover, the growth of SEI layers on top of poly-Si anodes cycled in two liquid electrolytes has been investigated by means of ex situ SEM. Strikingly, when poly-Si is covered with a solid-state electrolyte, prolonged lifetime is found, enabling future 3D-integrated all-solid-state batteries.
Within the development of ‘soft solution processing’ (SSP) which aims to fabricate ceramics from solutions without a firing step, as a more environmentally friendly technique, we propose a method of ‘direct patterning’ which makes patterned ceramic films in a solution without a firing step. In the present paper, we show for the first time ‘electrochemically activated (liquid∣liquid) interfacial reactions’ for the direct patterning of LiCoO2 as a progression of the hydrothermal-electrochemical deposition method, which is a typical SSP technique.
Cryogenic-electron microscopy is rapidly transforming battery research. Now, this powerful technique has been used to identify lithium hydride as a surprising culprit behind Li-ion battery failure.
Rechargeable aqueous zinc ion batteries are considered as a good substitute for large-scale energy storage due to their cost-effectiveness, materials abundance and safety. However, suitable cathode materials with high capacity and long cycling stability are still rare. Herein, we propose the first use of ZnMn2O4/N-doped graphene nanocomposite as cathode material, which exhibits a maximum discharge capacity of 221 mAh g−1 at 100 mA g−1, and ultralong cycle life with 97.4% capacity retention after 2500 cycles at 1000 mA g−1. The outstanding performance is attributed to the synergistic effect of superfine ZnMn2O4 nanoparticles (21 nm) that provide rapid surface capacitive reaction and short electronic/ion transport path lengths, as well as the highly conductive N-doped graphene medium that could facilities the fast electronic transport and stabilizes the composite structure to tolerate volume expansion during charge/discharge process. Significant insight into the zinc ion storage mechanism is confirmed by galvanostatic intermittent titration technique, ex-situ X-ray diffraction, and X-ray photoelectron spectroscopy characterizations. The long-term stability, high specific capacity together with the facile preparation method propose the ZnMn2O4/N-doped graphene hybrid a new class of competitive cathode material for zinc ion battery.
Aftab Ansari and his colleagues show that antibody-mediated masking of α4β7 integrin impedes intravaginal transmission of simian immunodeficiency virus in macaques.
A preliminary screening test of some organo-titanium compounds was conducted. The aim was to find their chemical stability in the electrolyte used for manganese dioxide production. Titanium doped electrolytic manganese dioxide (Ti-EMD) samples were prepared using suitable organo-titanium compounds and a special fine-grained titanium dioxide. The Ti-EMD samples were characterised by conducting physical, chemical and electrochemical tests on them. Physical tests included: X-ray diffraction analysis and BET surface area determination. Chemical test conducted was the determination of titanium content of samples. The electrochemical characterisation involved: cyclic voltammetry, galvanostatic discharge and application of sample in real cell situations. Doped samples performed well in comparison with TOSOH-Hellas GH-S (commercial battery grade electrolytic manganese dioxide).
Magnesium thermal reduction of the silica aggregation following with HF etching is used to obtain mesoporous nano-Silicon. The product shows an 1844 mAh g−1 discharge capacity in the first cycle with 400 mA g−1 current density and it still delivers a 1444 mAh g−1 capacity after 100 cycles. Additionally, it presents a good rate capability. The mesoporous morphology and the ultra-fine particle are the reasons of the good electrochemical property.
Publisher Summary This chapter focuses on the designs of non-isolated converters. There are many design variables for power supply designs. All of the designs use current mode pulse width modulation (PWM) control because of its inherent advantages in loop stability and current control. One of the problems with current mode control is subharmonic oscillation at duty cycles greater than 50%. Older integrated circuits (ICs) required external means to provide slope compensation to eliminate subharmonic oscillations. The modern ICs such as buck converter, boost converter, inverting controller, buck/boost converter, and charge pump all contain internal slope compensation. The chapter also presents layout considerations. There are two issues that one has to consider. The first is to design the layout of the power supply circuit so it does not interfere with its own operation. The second is to consider how the voltages and potentially huge current densities can interfere with the rest of the system if the power supply is placed too close to sensitive circuits.
In poly(ethylene oxide) (PEO) based solid polymer electrolytes, the interaction between cations and the ether oxygen plays a major role in ion conductivity. Measurements with differential scanning calorimetry (DSC) illustrated clearly the modification of the PEO crystalline structure with increasing content of magnesium salt. FTIR spectral studies suggest interaction of Mg2+ cations with the ether oxygen of PEO, where a 1100cm−1 broad band corresponds to COC stretching and severe deformation occurs. A spectral band at ∼623cm−1 corresponds to the ClO4 − anion and shows the growth of a shoulder at a higher wave number with increasing salt content. The apparent new envelope at ∼634.5cm−1 clearly indicates ClO4 −–Mg2+ ion pairing. Ionic conductivity increases with salt content, and is optimized at 15wt.% Mg salt (O:Mg ratio 28:1). The decrease in ion conductivity at higher salt contents is due to ion–ion association, which leads to ion pair formation (i.e. aggregation of ionic salt) and retards the motion of ions.
The aim of this study is to compare cognitive functioning between treatment-seeking individuals with obesity and healthy-weight adults.
Pristine and MnO2-coated LiNi0.2Li0.2Mn0.6O2 powders have been synthesized in this paper. The effect of MnO2 coating on the physical and electrochemical properties is discussed through the characterizations of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electrochemical impedance spectroscopy (EIS), discharge, cyclic and rate performance tests. The materials show layered structure before and after coating. The MnO2-coated LiNi0.2Li0.2Mn0.6O2 electrodes show better discharge capacity, first coulomb efficiency, cyclic performance and rate capacity compared with pristine LiNi0.2Li0.2Mn0.6O2. And the LiNi0.2Li0.2Mn0.6O2 coated with MnO2 decomposing from manganese carbonate has the best performance. The first coulomb efficiency is 82.7%. The discharge capacities at 0.1 and 10 C are 253 and 99 mAh g−1, respectively, and it presents no obvious capacity loss after 50 cycles. The discharge and cyclic voltammetry (CV) curves show that the coated MnO2 reacts with Li+ during the charge and discharge cycle, which is responsible for higher discharge capacity after coating. Electrochemical impedance spectroscopy (EIS) results show that the R ct of LiNi0.2Li0.2Mn0.6O2 electrode decreases after coating, which is due to the suppression of the solid electrolyte interfacial (SEI) layer development and is responsible for the better cyclic and rate performance.
PVdF-based separators are very promising materials in electrochemical energy storage systems but they suffer from fairly poor mechanical properties. To overcome this drawback, composite PVdF separators were fabricated and characterized in electrolytes of Li-ion batteries and supercapacitors. Macroporous PVdF composite separators were prepared by phase inversion method using PA and PET, and non-woven cellulose as support layers. Ionic conductivity and thermomechanical analyses were performed using electrolytes of Li-ion batteries and supercapacitors. The composite approach allowed a tremendous increase of the mechanical performances of the separator (between 340 and 750MPa) compared to the unreinforced PVdF separator (56MPa), without compromising the ionic conductivities (up to 15.6mScm−1).
Zinc electrode with polyvinyl alcohol(PVA)/poly(diallyldimethylammonium chloride) (PDDA) film coated ZnO was prepared by a chemical cross-linking method. The PVA/PDDA polymer film has an interpenetrating network structure where PVA works as polymer matrix and PDDA as anion charge carriers. Fourier transform infrared spectra (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies reveal that a polymer film with well-connected three dimensional network structure is formed around ZnO nanoparticles. Linear sweep voltammetry, cyclic voltammetry (CV) and charge/discharge cycling tests were carried out on the ZnO/PVA/PDDA composite electrode, which exhibits higher electrochemical activity and dramatically superior cycle stability than the bare ZnO electrode without polymer films. The ZnO/PVA/PDDA electrode showed remarkably lower solubility during cycling.