钒氧化还原液流储能电池

介绍了钒氧化还原液流储能电池(VRB)的原理及特点,并与其他储能电池体系进行了比较;论述了VRB的国内外研发现状。由于VRB具有循环寿命长、能量效率高、深度放电性能好、运行费用少及环境危害小等优点,使VRB非常适合用于风力发电场及太阳能光伏发电站以及电网调峰等的储能,其开发及在储能领域应用具有十分重要意义。     

Towards understanding the poor thermal stability of V electrolyte solution in Vanadium Redox Flow Batteries

The V⁵⁺ electrolyte solution from Vanadium Redox Flow Batteries was studied by variable temperature ¹⁷O and ⁵¹V Nuclear Magnetic Resonance (NMR) spectroscopy and density functional theory (DFT) based computational modeling. It was found that the V⁵⁺ species exist as hydrated penta co-ordinated vanadate ion, i.e. [VO₂(H₂O)₃]¹⁺. This hydrated structure is not stable at elevated temperature and change into neutral H₃VO₄ molecule via a deprotonation process and subsequently leading to the observed V₂O₅ precipitation in V⁵⁺ electrolyte solutions.     

全钒液流电池储能在配电网中优化配置策略

再生能源的大量接入对配电网造成许多不利影响,应用全钒液流电池（VRB）储能技术可有效促进可再生能源消纳,减少可再生能源并网造成的不利影响。分析了VRB储能的充放电特性,并在此基础上建立了电池模型,充分考虑配电网中风电、光伏发电、负荷需求的不确定性和VRB储能电池的经济性,提出了一种VRB储能优化配置策略,利用遗传算法进行求解,在IEEE33节点电网模型中进行仿真分析,验证了这种策略可有效提高可再生能源消纳,减少大电网中传统燃料能源输入电量。     

Modeling of a Vanadium Redox Flow Battery for power system dynamic studies

Vanadium Redox Flow Battery (VRB) is an electrochemical energy storage system based on a reversible chemical reaction within a sealed electrolyte. Several models have been developed which now offer a good understanding of the VRB operating principles; this knowledge is important to evaluate its performance when applied in power systems. However, these models depend on parameters that are difficult to obtain experimentally or in data sheets. In this regard, this article presents a new VRB model based on the stack efficiency curves, usually determined by the manufacturer. This model is especially useful for computing intensive applications, such as power system dynamic studies, in order to maintain a low run-time. Finally, the simulation results obtained through the proposed model are compared with laboratory results of an experimental VRB system, showing a striking resemblance with only a little relative error arising from them.     

基于两级全钒液流电池的风电储能系统的功率优化分配控制

为更好地利用储能系统平抑风电功率波动,采用了两级全钒液流电池(VRB)储能的功率优化分配及控制策略。基于直驱型永磁同步风电系统的工作原理及系统变流器的控制策略,建立了全钒液流电池等效电路模型,采用基于VRB组荷电状态(SOC)的双模式切换的双闭环控制策略,通过比较每级电池组荷电状态值确定优选目标,以VRB组最大充放电功率为电池组安全充放电的约束条件,提出两级VRB组的功率优化分配控制策略,利用Matlab/Simulink仿真平台,在变风速条件下对不同荷电状态的两级VRB储能系统平抑风电功率波动进行仿真,并与功率平均分配策略作对比。结果表明,两级VRB储能系统功率优化分配控制策略能有效平抑风电机组功率波动,同时,还确保了电池组工作于安全运行区域,有效地减少了VRB组的充放电次数,延长了电池组的寿命。     

甲基磺酸和硫酸作为钒电池负极混合支持电解质

本文研究了甲基磺酸和硫酸混酸作为负极电解液混合支持电解质对V(III)电解液的电化学性能、稳定性、运动粘度和电池性能的影响。结果表明：以甲基磺酸和硫酸为混合支持电解质能提高V(II)/V(III)电对反应的可逆性,延迟电解液在低温下出现结晶的时间,降低电解液的运动粘度。但对电池性能有不良的影响,降低了电池库伦效率,加速了负极电解液中的钒离子向正极迁移,加快了电池容量和能量的衰减。     

金属有机骨架及其衍生结构在锂硫电池中的应用

Li-S电池由于其高放电比容量(1 675 mAh/g)已被视为理想的储能系统之一.锂硫电池的巨大挑战是硫的利用率和锂金属枝晶等问题.金属有机骨架(MOFs)由于其具有可控的结构、高比表面积在锂硫电池中备受关注.主要论述了近几年国内外MOFs及其衍生结构材料在锂硫电池正极和隔膜中应用的研究进展,对合成方法、结构以及电化学性能等方面进行了相应的总结,并对目前存在的问题以及下一步的工作方向做出分析与展望.     

磺酸型聚乙烯亚胺单离子导体聚合物电解质的制备及其电化学性能研究

通过胺基与双键官能团的迈克尔加成反应将2-丙烯酰胺基-2-甲基丙磺酸锂(AMPSLi)接枝到聚乙烯亚胺(PEI)链上,对PEI进行功能化改性制备磺酸型单离子导体PEI-AMPSLi,再与聚丙烯腈(PAN)通过静电纺丝制备纳米纤维膜.纳米纤维膜吸收电解液后得到单离子导体聚合物电解质,经热交联处理的聚合物电解质具有10.6...     

Transport Phenomena Within the Cathode for a Polymer Electrolyte Fuel Cell

A one-dimensional two-phase steady model is developed to analyze the coupled phenomena of cathode flooding and mass-transport limitation for a polymer electrolyte fuel cell. In the model, the liquid water transport in the porous electrode is driven by the capillary force based on Darcy's law, while the gas transport is driven by the concentration gradient based on Fick's law. Furthermore, the catalyst layer is treated as a separate computational domain. The capillary pressure continuity is imposed on the interface between the catalyst layer and the gas diffusion layer. Additionally, through Tafel kinetics, the mass transport and the electrochemical reaction are coupled together. The saturation jump at the interface between the gas diffusion layer and the catalyst layer is captured in the results. Meanwhile, the results further indicate that the flooding situation in the catalyst layer is much more serious than that in the gas diffusion layer. Moreover, the saturation level inside the cathode is largely related to the physical, material, and operating parameters. In order to effectively prevent flooding, one should first remove the liquid water residing inside the catalyst layer and keep the boundary value of the liquid water saturation as low as possible.     

Redox behavior of nanohybrid material with defined morphology: Vanadium oxide nanotubes intercalated with polyaniline

Vanadium oxide/polyaniline nanotubes were produced by cationic exchange between hexadecylamine and polyaniline after the synthesis of vanadium oxide nanotubes by sol–gel method followed by hydrothermal treatment. The local structure of this hybrid material was studied by high-resolution transmission electron microscopy, infrared and Raman spectroscopy and small angle X-ray diffraction technique. The results show that polyaniline is intercalated in the interlamellar space of the vanadium oxide nanotube forming a hybrid material with defined morphology. Electrochemical impedance spectroscopy experiments have shown that the apparent diffusion coefficient for nanotubes with template was approximately 1 × 10⁻⁹ cm² s⁻¹. Nanotubes with polyaniline presented an apparent diffusion coefficient at least one order in magnitude higher than the parent material “with template”, comparable with other vanadium oxide described in the literature, revealing a promising material for utilization as cathode for ion-Li batteries.     

Performance and water transport behaviour in Polymer Electrolyte Membrane fuel cells

Water management in fuel cells is important for avoiding the phenomenon of flooding or dehydration in the stack and for maintaining good fuel cell performance and durability. This study focuses on the evaluation of the dynamic performance and behaviour (purge cycle) of the commercial Polymer Electrolyte Membrane (PEM) fuel cell stack towards water transport (water balance) at different operating conditions. The stack was operated at different current loads (0–10 A) and operating temperature (ambient to 50 °C). The results indicated that the measured water accumulation in the stack increased with the increase in current load. The optimal current load was 4 A, with calculated efficiency of 62.8%. The optimal operating temperature was 40 °C, resulting in calculated efficiency of 52.3%. At higher temperature, the fuel cell performance decreased, and the measured water balance was not properly distributed, which could be due to the dehydration and low conductivity of the electrolyte membrane. It can be concluded that the behaviour and performance of the stack, as well as the water balance in the stack, were influenced by the operating conditions. Moreover, this study improves the understanding of fuel cell performance and behaviour based on evaluation of the water balance.     

High-performance anode for Polymer Electrolyte Membrane Fuel Cells by multiple-layer Pt sputter deposition

We investigate the sputtering deposition as a tool for preparing Polymer Electrolyte Membrane Fuel Cell (PEMFC) electrodes with improved performance and catalyst utilization. Anodes of PEMFC with ultra-low loading of Pt (0.05 mg cm⁻²) are developed by alternate sputtering of Pt and painting layers of carbon nanotube ink with Nafion directly on the gas diffusion layer. Sputter depositing alternate layers of Pt on carbon-Nafion layer (CNL) has increased the anode activity over single-layer Pt deposited anode due to improved porosity and the presence of Pt nanoparticles in the inner CNL. Also, we investigated the influence of Nafion content in the CNL. The optimal Nafion content giving less resistance and better performance in an anode is 29 wt.%. This is significantly lower than for standard MEA anodes, indicating sufficient interfacial contact between each CNL. We studied the anodes prepared with 50 wt.% Nafion, which revealed larger ohmic resistance and also, blocks the CNL pores reducing gas permeability. Excellent mass transfer and performance is obtained with three-layer Pt sputter deposited anode with CNL containing 29 wt.% of Nafion.     

电力系统储能及全钒液流电池的应用进展

全钒液流电池因其安全可靠、使用寿命长、环境友好、电池均匀性好、可实时直接监测其充放电状态等特点,已成为规模储能技术领域的首选技术之一。本文对储能技术的研究背景、储能在电力系统中的作用进行了分析,并重点对全钒液流电池储能技术在电力系统中的应用进行了概述。     

CO-tolerant electrodes developed with PhosphoMolybdic Acid for Polymer Electrolyte Fuel Cell (PEFCs) application

Several approaches were used to improve the CO-tolerant electrodes for polymer electrolyte fuel cells (PEFCs) when using processed H₂ as a fuel. The employment of transition metals oxides (WO_x, MoO_x) promotes CO oxidation and, for this reason, heteropolyacids (like PWA, PMoA, SiWA, etc.) containing these oxides were selected in this work, for the development of CO-tolerant electrodes.     

Cross-over and performance modeling of liquid-feed Polymer Electrolyte Membrane Direct Ethanol Fuel Cells

Polymer Electrolyte Membrane Direct Ethanol Fuel Cells (PEM-DEFC) offer the possibility of a carbon-neutral, easily-handled small-scale power source but suffer from disadvantages such as high anode over-potentials and fuel cross-over. In the present work, a comprehensive one-dimensional, single phase, isothermal mathematical model is developed for a liquid-feed PEM-DEFC, taking into account all the necessary mass transport and electrochemical phenomena on both the anode side and the cathode side. Tafel kinetics expressions (with appropriate kinetic data taken from the literature) have been used to describe the electrochemical oxidation of ethanol at the anode and the simultaneous ethanol oxidation and oxygen reduction reaction at the cathode. The model fully accounts for the mixed potential effect caused by ethanol cross-over at the cathode and is validated using the data from the literature. Model predictions over a range of operating conditions show that ethanol cross-over can cause a significant loss of fuel in terms of production of electricity. Under optimized conditions, it is shown that a PEM-DEFC can be operated at a current density of 0.3 A cm⁻² with a power density of 0.1 W cm⁻² with a fuel utilization factor of about 90%.     

Effect of Succinonitrile on Electrical,Structural and Thermal Properties of PVA-Based Polymer Electrolyte for Magnesium Battery

This paper report the synthesis and properties of a series of composite polymer electrolytes formed by dispersion of a non-ionic organic plastic material SN （succinonitrile） into poly（vinyl alcohol） complexed with magnesium acid salt. SEM （scanning electron microscope） images of different SN concentrations of films revealed that large open pore structure were also frequently present, when SN content increase up to 7.5 wt%. The addition of SN greatly enhances ionic conductivities of the electrolytes which is due to the high polarity and diffusivity of SN. The Mg2~ （magnesium ion） ion conduction is confirmed from impedance spectroscopy and transport number measurements. The highest conducting sample in the plasticized system was used to fabricate Mg （magnesium） battery with configuration Mg/SPE/TiO2. The discharge capacity of the fabricated battery was 17.5 mAh/gm.     

A Facile Route for Polymer Electrolyte Membrane Fuel Cell Electrodes with in situ Grown Pt Nanowires

Novel Gas Diffusion Electrodes (GDEs) for Polymer Electrolyte Membrane Fuel Cells (PEMFCs) were prepared by in situ growing Pt nanowires on carbon paper using a facile deposition method at room temperature. Pt nanowires, with a length 100–150 nm, were uniformly coated on the carbon fiber surfaces in carbon paper. This route was much simpler than the traditional method for preparing GDEs because there were no processes needed to make the ink or print the catalysis layer. Membrane Electrode Assemblies (MEAs) were made with the as-prepared GDEs and tested in a 25 cm² PEMFC fed by hydrogen/air. The impedance spectroscopy and polarization curve measurement showed that the as-prepared GDE possessed a lower charge transfer resistance and a higher power density than did the conventional one with ELAT^® GDE LT120EW. The excellent performance obtained and the simple steps made the process a promising technique for preparing GDEs in PEMFCs for commercial applications.     

Characterization of Pt supported on commercial fluorinated carbon as cathode catalysts for Polymer Electrolyte Membrane Fuel Cell

Pt nanoparticles supported on carbon monofluoride (CFx), synthesized from H₂PtCl₆ using NaHB₄ as a reducing agent has been investigated as a cathode electrocatalyst in fuel cells. Surface characterization, performed by transmission electron microscopy (TEM) and powder X-ray diffraction (PXRD), shows a homogeneous distribution and high dispersion of metal particles. Kinetic parameters for the electrocatalyst are also obtained from the steady state measurements using a rotating disk electrode (RDE) in 0.5 M H₂SO₄ solution. Analysis by Koutecky–Levich equation indicates an overall 4 e^? oxygen reduction reaction (ORR). Evaluation of the catalyst in single cell membrane electrode assemblies (MEAs) for proton exchange membrane based Direct Methanol Fuel Cell (DMFC) and H₂ Fuel Cell at different temperatures and flows of O₂ and Air are shown and compared against commercial Pt/C as the cathode electrocatalyst. Evaluation of Pt/CFx in H₂ fed fuel cells shows a comparable performance against a commercial catalyst having a higher platinum loading. However, in direct methanol fuel cell cathodes, an improved performance is observed at low O₂ and air flows showing up to 60–70% increase in the peak power density at very low flows (60 mL min^?1).