Graphite–graphite oxide composite electrode for vanadium redox flow battery

A graphite/graphite oxide (GO) composite electrode for vanadium redox battery (VRB) was prepared successfully in this paper. The materials were characterized with X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. The specific surface area was measured by the Brunauer–Emmett–Teller method. The redox reactions of [VO₂]⁺/[VO]²⁺ and V³⁺/V²⁺ were studied with cyclic voltammetry and electrochemical impedance spectroscopy. The results indicated that the electrochemical performances of the electrode were improved greatly when 3 wt% GO was added into graphite electrode. The redox peak currents of [VO₂]⁺/[VO]²⁺ and V³⁺/V²⁺ couples on the composite electrode were increased nearly twice as large as that on the graphite electrode, and the charge transfer resistances of the redox pairs on the composite electrode are also reduced. The enhanced electrochemical activity could be ascribed to the presence of plentiful oxygen functional groups on the basal planes and sheet edges of the GO and large specific surface areas introduced by the GO.     

羟基自由基对全钒液流电池石墨毡电极的性能影响

采用H2SO4和H2O2的分解产物羟基自由基,对石墨毡电极进行表面处理。循环伏安法和交流阻抗测试显示,处理后石墨毡的阴阳极峰电流分别提高160.96%和120.24%,极化反应电阻从74.95 Ω·cm2显著降低至18.92 Ω·cm2。红外光谱测试表明石墨毡处理后表面含有大量含氧亲水基团,拉曼光谱测试结果显示处理后石墨毡的石墨化度降低,进一步证明了石墨毡电极表面受到了不同程度的氧化。X射线光电子能谱测试显示石墨毡处理后的含氧量提高0.58%,定量地证明了红外光谱和拉曼光谱的测试结果。采用自制静态单电池对石墨毡电极进行测试,处理后石墨毡的充放电容量分别提高37.04%和22.22%,表明该方法处理石墨毡电极能够显著提高全钒液流电池性能。     

Investigation of Ir-modified carbon felt as the positive electrode of an all-vanadium redox flow battery

Porous graphite felts have been used as electrode materials for all-vanadium redox flow batteries due to their wide operating potential range, stability as both an anode and a cathode, and availability in high surface area. In this paper, the carbon felt was modified by pyrolysis of Ir reduced from H₂IrCl₆. ac impedance and steady-state polarization measurements showed that the Ir-modified materials have improved activity and lowered overpotential of the desired V(IV)/V(V) redox process. Ir-modification of carbon felt enhanced the electro-conductivity of electrode materials. The Ir-material, when coated on the graphite felt electrode surface, lowered the cell internal resistance. A test cell was assembled with the Ir-modified carbon felt as the activation layer of the positive electrode, the unmodified raw felt as the activation layer of the negative electrode. At an operating current density of 20 mA cm⁻², a voltage efficiency of 87.5% was achieved. The resistance of the cell using Ir-modified felt decreased 25% compared to the cell using non-modified felt.     

全钒液流电池关键材料研究进展

全钒液流电池是一种新型高效电能转化与储存装置。由于其电池输出功率与储能容量彼此独立,适用于风能、太阳能等可再生能源发电过程和电网调峰过程作为规模化储能装置使用。本文在介绍全钒液流电池原理基础上,重点围绕电池过程的关键材料展开讨论,包括电极材料的种类、各自特点与电极改性方法;电池隔膜材料的筛选结果、材料改性方法等国内外研究进展。     

全钒氧化还原液流电池的发展现状

简要介绍了全钒氧化还原液流电池的工作原理,并对钒电池的组成及其电解液的制备方法和钒电池的分类及市场前景进行了简明叙述。列举了钒电池在国外的商业化情况,并简要分析了国内外钒电池的发展过程和研究现状。中国风能、太阳能等可再生资源储量丰富,对环境友好的大容量存储电池需求迫切,因此认为近几年中国全钒氧化还原液流电池具有良好的发展前景,这将会极大促进中国钒资源的开发。     

Synthesis of sulfonated poly(fluorenyl ether thioether ketone)s with bulky-block structure and its application in vanadium redox flow battery

High-molecular-weight bulky-block poly(fluorenyl ether thioether ketone)s were successfully synthesized by a two steps one-pot protocol using N,N′-dimethy-S-carbamate masked dithiols for vanadium redox flow battery (VRB) application. The followed sulfonation procedure gave birth to novel sulfonated block poly(fluorenyl ether thioether ketone)s (SPFETKs) with controlled ionic exchange capacities (IEC). Membranes with proton conductivities higher than (IEC > 1.66 mequiv. g⁻¹) or comparable to (IEC < 1.66 mequiv. g⁻¹) that of Nafion117 membrane were achieved. The VO²⁺ permeabilities of SPFETKs membranes were much lower than that of Nafion117 membrane. The thermal properties, mechanical properties, oxidative stability, water uptake, proton conductivity, VO²⁺ permeability and cell performance were investigated in detail.     

木质素磺酸钠作为全钒液流电池添加剂的研究

摘要〖HTSS〗：采用电化学方法分析了不同含量木质素磺酸钠对钒电池正极电解液的影响。交流阻抗、紫外可见光谱和单电池充放电实验验证了木质素磺酸钠添加后的效果。分析结果表明：添加量为0.1% 时,电荷传递电阻由5.446Ω·cm2 减小到1.002Ω·cm2 ,双电层电容由4.16×10-4F·cm-2 减小到1.298×10-4F·cm-2 ,添加不同含量的木质素磺酸钠并没有显著影响激发态波长和吸光度,但是充放电性能显著提高,这表明木质素磺酸钠具有很强的化学及电化学稳定性,有利于提高钒离子的传导和电能的储存。     

全钒液流电池VO2+离子跨膜渗透行为

采用静止型全钒氧化还原液流电池,利用紫外分光光度法,研究电解液钒离子跨膜渗透行为,讨论浓度、温度、荷电状态(SOC)、电场以及渗透压等对VO²⁺离子跨膜传质的影响,关联相应的钒离子渗透系数。研究结果表明,提高钒电解液浓度可以有效减缓钒离子跨膜传递速率,提高能量效率;适当降低体系温度,可以抑制钒离子的跨膜渗透,减小电池化学短路的发生;VO²⁺离子渗透系数随SOC值增加而迅速减小;正向电场存在会促进VO²⁺离子透膜扩散,加剧电池自放电;隔膜两侧液面渗透压的作用会加速钒离子跨膜渗透,造成电池容量衰减。     

全钒液流电池模拟与仿真研究进展

全钒液流电池(VRB)的模拟和仿真是电池系统设计、放大、控制和优化的基础。根据VRB模型的复杂程度,本文详细介绍了VRB经验和半经验模型的研究内容,重点分析了近年来发展迅速的机理模型研究,对比分析了每个模型的优缺点,指出了VRB模拟和仿真未来的研究方向主要是建立接近真实的模型以及与实际运行控制系统联合,同时模拟仿真的实体也应从单电池向电堆、模块和电池系统发展。     

暂态边界电压法在线测试全钒液流电池阻抗

国内首次采用暂态边界电压法在线研究了全钒液流电池（VRB）的特性,建立了由电压源、电阻以及一个电阻与电容并联的3部分串联而成的等效电路模型;研究了电流密度和荷电状态（SOC）对等效电路元件的影响。实验结果表明,极化阻抗随电流密度的增加有轻微下降,在充电初期和放电末期达到最大值。与极化阻抗相比,充、放电过程中的欧姆阻抗最大,是导致电压损失的主要因素,分别为1.905Ω?cm2和 2.139 Ω?cm2,暂态边界电压法是一种简单且有效的表征全钒液流电池性能的新方法。     

A simple model for the vanadium redox battery

A two-dimensional stationary model, based on the universal conservation laws and coupled with electrochemical reactions, is applied to describe a single all-vanadium redox flow cell. Emphasis is placed on studying the effects of applied current density, electrode porosity and local mass transfer coefficient on the cell performance. The model results indicate that bulk reaction rate depends on the applied current density. The transfer current density and over-potential increase almost twice as the applied current density doubled. A decrease in electrode porosity leads to a more rapid depletion of the reactant concentration, a higher integral average value of the transfer current density and a more uniform distribution of the over-potential. The local mass transfer coefficient only affects the value of the over-potential.     

Effect of organic additives on positive electrolyte for vanadium redox battery

Fructose, mannitol, glucose, d-sorbitol are explored as additives in electrolyte for vanadium redox battery (VRB), respectively. The effects of additives on electrolyte are studied by cyclic voltammetry (CV), charge–discharge technique, electrochemical impedance spectroscopy (EIS) and Raman spectroscopy. The results indicate that the vanadium redox cell using the electrolyte with the additive of d-sorbitol exhibits the best electrochemical performance (the energy efficiency 81.8%). The EIS results indicate that the electrochemical activity of the electrolyte is improved by adding d-sorbitol, which can be interpreted as the increase of available (–OH) groups providing active sites for electron transfer. The Raman spectra show that VO²⁺ ions take part in forming a complex with the d-sorbitol, which not only improve solubility of V(V) electrolyte, but also provide more activity sites for the V(IV)/V(V) redox reaction.     

多硫化钠/溴液流电池研究进展

介绍了多硫化钠/溴液流电池(PSB)的原理与特点及其正负极电极材料的制备、离子交换膜改性及电池组等方面的国内外技术发展现状,指出PSB目前急待解决的问题是高性能低成本的离子交换膜、高稳定性的电极材料的研制及电池组结构优化设计。     

全钒液流电池石墨毡电极的Ga2O3修饰

为提高全钒液流电池石墨毡电极的电化学性能, 采用热分解法将纳米Ga₂O₃沉积在全钒液流电池石墨毡电极表面。通过循环伏安测试、动电位极化曲线测试、扫描电镜测试(SEM)、X射线光电子能谱分析(XPS)和充放电实验考察了Ga₂O₃对石墨毡电化学性能和表面形貌的影响。研究结果表明:Ga₂O₃对电极反应具有显著的催化作用, 当用Ga₂O₃电极修饰石墨毡时, 电池正负极反应活性较未处理前分别提高13%和18%, 同时也导致全钒液流电池的容量更大, 电流效率和能量效率更高。     

离子液体BMIMBF4对全钒液流电池正极电解液的影响

为提高全钒液流电池的能量密度和正极电解液稳定性,采用循环伏安、交流阻抗等方法,研究了1-丁基-3-甲基咪唑四氟硼酸盐（BMIMBF₄）作为正极电解液添加剂对溶液稳定性和电化学反应活性的影响,并对其机理进行了初步探讨。实验结果表明,添加BMIMBF₄后,正极电解液中五价钒离子的稳定性显著提高,电解液的电化学反应活性也有所提升。当添加量为1%时,电池的单位体积电容量比有所增加,并且能量效率有所提升。     

钒液流电池变电流快速充电方法

  基于电池快速充电基本原理,采用了变电流间歇恒压充电方法,并结合正交试验方法,对自制单片钒液流电池进行了一系列的充放电测试,获得了最佳充电参数。结果表明：采用变电流间歇恒压充电方法,充电时间相比恒流恒压充电方法缩短近50%;且获得了大致相同的放电容量,放电比率为100%;多次充放电循环后,放电容量未见衰减,取得了良好充电效果。     

Sulfonated polyimide/chitosan composite membrane for vanadium redox flow battery: Membrane preparation,characterization, and single cell performance

A novel sulfonated polyimide/chitosan (SPI/CS) composite membrane was prepared from self‐made SPI (50% of sulfonation degree) through an immersion and self‐assembly method, which was successfully applied in vanadium redox flow battery (VRB). The proton conductivity of SPI/CS composite membrane is effectively improved compared to the plain SPI membrane. The VO²⁺ permeability coefficient across SPI/CS composite membrane is 1.12 × 10^?7 cm² min^?1, which is only one tenth of that of Nafion® 117 membrane. Meanwhile, the proton selectivity of SPI/CS composite membrane is about eight times higher than that of Nafion® 117 membrane. In addition, the oxidative stability SPI/CS composite membrane is superior to that of pristine SPI membrane. The VRB single cell using SPI/CS composite membrane showed higher energy efficiency (88.6%) than that using Nafion® 117 membrane, indicating that SPI/CS composite membrane is a promising proton conductive membrane for VRB application. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

大规模蓄电储能全钒液流电池研究进展

全钒液流电池是一种新型蓄电储能设备,不仅可以用作太阳能、风能发电过程配套的储能装置,还可以用于电网调峰,提高电网稳定性,保障电网安全。本文综述全钒液流电池的国内外技术发展状况,包括研究开发历史、电池关键材料和典型工艺过程;展望大规模蓄电储能的电池技术未来发展趋势。