锂金属参比电极稳定性研究

锂离子电池商业化应用已有30多年,但目前的电池性能仍不能满足社会发展的需求。为此,须不断开发高性能的电池材料。电化学测量是电池材料开发不可或缺的关键技术。锂金属电极是锂离子电池电化学测量中最常用的参比电极,其电位稳定性将影响电化学测量结果的准确性。报道一种能提高锂金属参比电极电位稳定性的锂金属表面处理方法。将有机锌盐和氟代碳酸酯的混合溶液滴加在锂金属表面,通过锂金属与溶液组分的反应,在锂金属表面形成一层含锌锂合金和氟化锂的混合界面膜,可降低锂溶解/沉积过电位。处理得到的锂金属电极在Li//Li对称电池中用1 mA/cm2的电流及1 mA·h/cm2的容量恒电流连续充放电,该对称电池的电压稳定时间是未处理电池的2倍以上。这种锂金属电极表面处理方法可提高电极材料电化学性能测量的稳定性,有利于锂离子电池新材料的开发。     

Progress in industrial demonstration of advanced unipolar electrolysis

Continuing development of industrial unipolar electrolysers has led to two generations of advanced designs. The Generation I design is based on modifications to proved commercial equipment, with use of electrode activation techniques to achieve significant reductions in operating voltages at increased current levels. The Generation II design incorporates changes in cell geometry which significantly reduce the ohmic resistance and allow economic operation at current densities above 5 kA m^?2. Construction has recently been completed of a 1.2-MW experimental plant which is being used for evaluation of full-scale commercial modules of the new electrolyser designs. This facility is described, and initial performance results from the first 600-kW phase of Generation I cells are reported. This report is supported by data from 12 000 h of operation of 20-kW prototype cells, and from testing of electrode activation systems in 2-kW pilot electrolysers.     

Experimental measurement and analysis of Raman/infrared methods for lithium batteries

拉曼光谱和傅里叶变换红外光谱是重要的物理表征方法，在电化学领域尤其是锂电池领域具有广泛的应用，常用于分析分子价键、官能团振动和转动能级跃迁状态、物相结构变化、稳定性、表面现象以及反应机理，相关谱学数据又可以计算化学键的键能、键长、键角等。本文介绍了拉曼和红外光谱的基本原理、测试方法、测试注意事项、常用测试设备及测试流程，并结合实际案例，具体分析了拉曼和红外光谱在锂电池电极材料、电解质、黏结剂等组分分析方面，及其在充放电循环中的生成产物对电化学稳定性的影响方面的应用研究。     

发动机快速热试台架研究

发动机热磨合试验系统采用模块化设计,所有的组件都可以快速方便地替换和升级,能很好地满足柔性化生产的需要,同时基于网络化设计的思想,热试系统中的每台台架PLC和工控机均通过网络彼此相连,从而可以实现整个热试过程的自动数据采集和控制,提高了试验稳定性和生产效率。     

Considerations for the selection of an applicable energy efficiency test procedure for electric motors in Malaysia: Lessons for other developing countries

Electric motors are a major energy-consuming appliance in the industrial sector. According to a survey, electric motors account for more than 70% of the total growth from 1991 to 2004 in electricity consumption in this sector in Malaysia. To reduce electricity consumption, Malaysia should consider resetting the minimum energy efficiency standards for electric motors sometime in the coming year. The first step towards adopting energy efficiency standards is the creation of a procedure for testing and rating equipment. An energy test procedure is the technical foundation for all energy efficiency standards, energy labels and other related programs. The test conditions in the test procedure must represent the conditions of the country. This paper presents the process for the selection of an energy test procedure for electric motors in Malaysia based on the country's conditions and requirements. The adoption of test procedures for electric motors internationally by several countries is also discussed in this paper. Even though the paper only discusses the test procedure for electric motors in Malaysia, the methods can be directly applied in other countries without major modifications.     

Applications of carbon nanotubes in the lithium-ion batteries

碳纳米管因具有优异的电导率、热导率、力学性能以及独特的结构形貌,被用于改进锂离子电池性能。该文总结了近年来碳纳米管作为锂离子电池的添加剂、电极材料复合基体以及集流体的最新研究进展,重点介绍了最新的碳纳米管作为电极材料添加剂的使用方法、碳纳米管与电极材料的不同复合方法及其对锂离子电池容量性能、倍率性能以及循环寿命的影响。同时指出了碳纳米管在锂离子电池中大规模应用时需要克服的问题,如降低碳纳米管的制备成本、开发适用于工业生产的复合技术、改善碳纳米管的分散性能等。     

Research progress of cathode materials for lithium-sulfur batteries

锂硫电池作为一种非常有前途的高能化学电源,随着电动汽车和便携式电子设备的发展,因其高理论比容量（1675 mA·h/g）和高理论能量密度（2600 W·h/kg）引起了人们的广泛关注。然而,锂硫电池发展过程中的一些挑战不可避免,包括硫较低的离子和电子导电性,较差的循环性以及生成的多硫化物易溶于有机溶剂等缺点,制约了锂硫电池的发展。本文结合近年来锂硫电池正极材料的研究进展,简要阐述了锂硫电池正极材料的研究现状、问题及面临的挑战。锂硫电池由于其发展中面临技术瓶颈难以突破,导致现在还无法大规模的应用,因而对其性能的改进也就成了当今的研究热点。硫电极材料电导率低、循环性能差,可以通过碳包覆或者掺杂改善材料性能。然而由于成本和技术问题,大部分锂硫电池正极材料目前还主要处于研究试验阶段。因此,在提高材料性能的前提下,通过碳包覆或者掺杂改善工艺,探索一条适合工业化生产的道路是下一阶段研究的重点。     

A critical review on progress of the electrode materials of vanadium redox flow battery

Nowadays, renewable energy sources are taken great attention by the researchers and the investors around the world due to increasing energy demand of today's knowledge societies. Since these sources are non-continuous, the effective storage and re-use of the energy produced from renewable energy sources have great importance. Although classical energy storage systems such as lead acid batteries and Li-ion batteries can be used for this goal, the new generation energy storage system is needed for large-scale energy storage applications. In this point, vanadium redox flow batteries (VRFBs) are shinning like a star for this area. VRFBs consist of electrode, electrolyte, and membrane component. The battery electrodes as positive and negative electrodes play a key role on the performance and cyclic life of the system. In this work, electrode materials used as positive electrode, negative electrode, and both of electrodes in the latest literature were complained and presented. From graphene-coated and heteroatom-doped carbon-based electrodes to metal oxides decorated carbon-based electrodes, a large scale on the modification of carbon-based electrodes is available on the electrode materials of the VRFBs. By the discovering of novel electrode components for the battery system, the using of the VRFBs probably increase in a short time for many industrial and residential applications.     

C,N co-doped Co3O4 hollow spheres prepared via hydrothermal reaction for improved electrochemical activity

Superior electrode materials play a key role on the electrochemical performance for the lithium-ion batteries and supercapacitors. The Co₃O₄-based materials are promising electrode materials due to their high specific capacity and energy density. However, the poor cycle performance limits their applications during the process of the commercialization for the lithium-ion batteries and supercapacitors. Because of the poor cycle stability, C, N co-doped Co₃O₄ hollow spheres are successfully prepared and used as electrode materials for the lithium-ion batteries and supercapacitors. Via the C, N co-doping process, the electronic conductivity is greatly improved. Moreover, the hollow structure could ensure the structural stability during the electrochemical process. As a result, the cycle performance and specific capacity are greatly improved when the C, N co-doped Co₃O₄ composites are used as electrode materials for the lithium-ion batteries and supercapacitors.     

Energy efficiency criteria in uninterruptible power supply selection

With the generalized use of microelectronic devices, server computers and other susceptible equipment, the subject related to power quality (PQ) and its relationship to vulnerability of high performance plants are becoming an increasing concern to the industry. This paper addresses how uninterruptible power supply (UPS), particularly when configured in distributed DC mode, can become an energy efficient (EE) solution in high-tech buildings, especially when integrated with complimentary PQ measures. The paper is based on PQ audits conducted at different high-tech industries over the last years. It was found that the main problems for the equipment installed were voltage sags (or dips). Among all categories of electrical disturbances, voltage sags and momentary interruptions are the nemeses of the automated industrial process. The paper analyzes the capabilities of modern electronic power supplies and the convenience of embedded solution. Finally it is addresses the role of the Standards on the protection of electronic equipment and the implications for the final costumer.     

Stress and creep damage analysis for HTR heat exchangers at very high temperatures

The Helium-Cooled High Temperature Reactor (HTR) can supply process heat for methane reforming at temperatures of nearly 1000°C. As is the usual requirement for equipment used in a nuclear plant, the process heat exchangers must operate with a high reliability. This implies both that the exchanger tubes must be made from alloys which are very resistant to high temperatures and that the operational pressures are adjusted so that primary stresses in the tube walls are small. However, secondary stresses—an order of magnitude larger than primary stresses—are produced by the temperature profile through the wall.

With consideration of creep, the time-dependent stress-strain distributions in the tube walls were calculated using the Finite Element Programme ASKA. The creep damage was estimated using Robinson's rule. The results showed that operation was possible for 100 000 h.

Under accident conditions, load-controlled stresses in the tube walls may be an order of magnitude larger than under normal operation conditions. Here the stress distribution near the tube closure was investigated and it was found that lower stresses occurred in the transition and closure region than in the undisturbed tube area. In this way it could be shown that the closure is not seriously put at risk.     

Testing aqueous caustic electrolyzers at high temperatures

Increasing the electrochemical cell operating temperature allows a general improvement of the operating energetics of hydrogen production via alkaline solution water electrolysis. Considerations of operation of these advanced cells above 100°C leads to a reexamination of all of the basic materials stabilities. One previous controversy has been with respect to the upper temperature value for a stable asbestos electrochemical cell separator. In addition to testing alternative materials for the cell separator, one must examine which of the structural polymers can be used as a cell frame, reexamine the stability of the selected anode electrocatalyst and finally, determine if the plumbing and piping selected will introduce corrosion products which could affect the cathode electrocatalyst. This paper describes the work performed at Teledyne Energy Systems on the studies of alkaline electrolyzers and materials for operation at temperatures up to 150°C. This program, under contract to the Brookhaven National Laboratory, has proceeded through the design and construction of an applied research sized test system. The materials testing and preliminary test results obtained with the system are described.     

A novel peak load shaving algorithm via real‐time battery scheduling for residential distributed energy storage systems

As population grows and energy consumption increases, generation, transmission, and energy distribution costs also increase. Sudden and unpredicted demand increase at peak periods might lead to failure and even damage the power grid. This is a challenge for stability and reliability of the grid. Peak load shaving is considered as an effective approach while transition from peak load periods. In this paper, peak load shaving is modeled mathematically through storing energy on demand side and solved using optimization method. Using the results obtained from solving the optimization problem, a simple effective algorithm is proposed for peak load shaving via real‐time scheduling of distributed battery storage systems without complicated calculations. All characteristics required for systemic design of peak load shaving for residential, commercial, and industrial loads are presented. This method can be used in the presence of photovoltaic arrays or other renewable or nonrenewable distributed energy resources simultaneously, and it can be adapted to different conditions and demands. Here, real measured data of a residential state, an office building with photovoltaics, a hotel, and a small office are used for simulation, and GAMS is used for analysis.     

Comparison of degradation behaviors for open-ended and closed proton exchange membrane fuel cells during startup and shutdown cycles

As catalyst support materials, the oxidation of carbon materials is considered one of the major factors for performance decay during the startup and shutdown process of proton exchange membrane fuel cells, which must be mitigated to achieve acceptable durability. In this paper, the effect of cathode exhaust conditions on the degradation behaviors of fuel cells is investigated using two single cells named the open-ended and closed cells. The cathode inlet pressure during the introduction of the dummy load is an important factor in analyzing the performance decay of membrane electrode assemblies under different conditions. Electrochemical techniques, including the measurement of polarization curves, cyclic and linear sweep voltammetry, and cross-sectional scanning electron microscopy of tested membrane electrode assemblies, are employed to evaluate the performance decay of fuel cells. The results show that a closed cathode exhaust valve during the introduction of the dummy load would significantly alleviate both the performance decay and the decrease in the electrochemically active surface area, resulting in an improvement in fuel cell durability. No significant deterioration of the membranes is observed for both the open-ended and the closed cells during frequent startup and shutdown processes.     

Initial approaches in benchmarking and round robin testing for proton exchange membrane water electrolyzers

As ever-increasing amounts of renewable electricity enter the energy supply mix on a regional, national and international basis, greater emphasis is being placed on energy conversion and storage technologies to deal with the oscillations, excess and lack of electricity. Hydrogen generation via proton exchange membrane water electrolysis (PEMWE) is one technology that offers a pathway to store large amounts of electricity in the form of hydrogen. The challenges to widespread adoption of PEM water electrolyzers lie in their high capital and operating costs which both need to be reduced through R&D. An evaluation of reported PEMWE performance data in the literature reveals that there are excessive variations of in situ performance results that make it difficult to draw conclusions on the pathway forward to performance optimization and future R&D directions. To enable the meaningful comparison of in situ performance evaluation across laboratories there is an obvious need for standardization of materials and testing protocols. Herein, we address this need by reporting the results of a round robin test effort conducted at the laboratories of five contributors to the IEA Electrolysis Annex 30. For this effort a method and equipment framework were first developed and then verified with respect to its feasibility for measuring water electrolysis performance accurately across the various laboratories. The effort utilized identical sets of test articles, materials, and test cells, and employed a set of shared test protocols. It further defined a minimum skeleton of requirements for the test station equipment. The maximum observed deviation between laboratories at 1 A cm⁻² at cell temperatures of 60 °C and 80 °C was 27 and 20 mV, respectively. The deviation of the results from laboratory to laboratory was 2–3 times higher than the lowest deviation observed at one single lab and test station. However, the highest deviations observed were one-tenth of those extracted by a literature survey on similar material sets. The work endorses the urgent need to identify one or more reference sets of materials in addition to the method and equipment framework introduced here, to enable accurate comparison of results across the entire community. The results further imply that cell temperature control appears to be the most significant source of deviation between results, and that care must be taken with respect to break-in conditions and cell electrical connections for meaningful performance data.     

Long-term stability of low-power dye-sensitised solar cells prepared by industrial methods

Encapsulated dye-sensitised solar modules designed for low-power indoor applications have been prepared using industrial methods and equipment that can be applied to mass production. The modules have been tested for long-term stability. Especially, the influences of different illumination conditions, humidity, and operation conditions (e.g. short-circuit and open-circuit) have been evaluated. It is shown that the use of an inexpensive UV filter in combination with a novel preparation technique and adequate module encapsulation can provide dye-photovoltaic (dye PV) devices that are stable enough for utilisation in various low-power consumer applications.     

Advances in the development of titanates for anodes in SOFC

Solid oxide fuel cells (SOFCs) are highly efficient energy conversion devices with the advantage that a wide variety of hydrocarbon fuels can be used directly. Recently, the field of research on anodic materials of SOFC has advanced rapidly, with special emphasis on the development of materials with resistance to H₂S as well as to the formation of coke. Therefore, it is crucial to design new anodic materials with higher catalytic activity, stability, tolerance to coke deposition and to sulfur poisoning. Due to their stability in redox conditions, the titanates are among the most studied perovskites. Strontium titanate (SrTiO₃) is a good electronic conductor at low partial pressures of oxygen and during redox cycles and presents excellent dimensional and chemical stabilities as well as sulfur tolerance. However, for application as the anode in a SOFC, it must be doped to improve important properties such as the conductivity and power density. This article describes the progress in the knowledge of titanates with perovskite structure with potential application as anodes for SOFC.     

Polyacene capacitors

We fabricated two types of polyacene capacitor with extremely stable polyacenic semiconductor (PAS) as the positive and negative electrodes. The first one is a coin-type PAS capacitor (six different sizes), which possesses large capacity with high reliability. Its capacity is much larger than that of the conventional electric double-layer capacitor which uses activated carbon as electrode. PAS capacitor can maintain more than 70% of the initial capacity even after 100 000 cycles. Moreover, this capacitor can be charged and discharged in a few minutes as well as at low rate. The second one is a cylinder-type PAS capacitor (diameter: 18 mm, height: 65 mm) which shows high capacity of 100 F and can discharge at the extremely high rate of 80 C. The coin-type PAS capacitor is currently used for memory back-up of electrical and communication equipment, and the cylinder-type is considered to be useful as power back-up for starting drive parts of electric equipment which needs high power density.     

Hydrothermal synthesis of nano-sized MnO2 supported on attapulgite electrode materials for supercapacitors

Among the electrode materials of supercapacitors, transition metal oxides have been widely used because of their low price, high theoretical capacitance and good cycle stability, and MnO₂ is one of the typical representative materials. However, the actual specific capacitance of MnO₂ is low because of its poor conductivity, easy agglomeration in the preparation process and large volume change in the process of repeated charge and discharge. Attapulgite can not only provide a large specific surface area for transition metal oxide materials, but also provide a skeleton on which nano-sized materials can be grown or dispersed. Therefore, the electrochemical performance of electrode materials can be improved by designing nanostructures and compounding a variety of materials with different properties. Herein, a new type of composites electrode material is prepared by simple one-step hydrothermal method. As an electrode material, the ATP-MnO₂ composites exhibited a high specific capacitance of 138.2 F/g at a current density of 0.5 A/g, which was 13.4% higher than that of pure MnO₂ nanoflowers. Under the current density of 3 A/g, the capacitance retention of ATP-MnO₂ composites was 89.4% after 5000 cycles.     

Experimental study of micro-porous layers for PEMFC with gradient hydrophobicity under various humidity conditions

The effect of micro-porous layer (MPL) with hydrophobic gradient design on fuel cell performance and stability is investigated under various relative humidity (RH) conditions. Experimental results show that when such MPL is used between catalyst layer and gas diffusion layer, the membrane may retain more water and stay well humidified, and cell performance is increased at low RH conditions. On the other hand, at high RH conditions, the gradient MPL is able to efficiently remove water from the electrode, achieving maximum performance under these conditions. It is found that the design of hydrophobic gradient must take into consideration factors including gas permeability, electronic resistance and hydrophobic characteristics, because excessive hydrophobicity gradient in the MPL may result into high mass transfer resistance, which causes performance degradation.