【作者】 乔永莲；

【导师】 张懿； 翟玉春； 许茜；

【作者基本信息】 东北大学 ， 冶金物理化学， 2009， 博士

【摘要】 钒电池是近年来开发出的一种新型储能电池,因其能量效率高,使用寿命长,对环境友好以及价格便宜,操作和维护费用低等诸多特点,得到了迅速发展。但目前钒电池还存在一些问题,影响钒电池性能的因素有很多,其中电极材料性能、正负极电极反应是重要因素。本论文针对钒电池电极材料进行了改性研究,计算了不同工作电极反应的动力学参数。分析了电池充放电过程中电池性能的变化及其电池失效的原因。主要研究内容和取得的成果如下：1.在胶中添加不同的导电填料,研究导电胶的导电性和电化学性能,测试结果表明,40%膨胀石墨导电胶的电阻率较低,40%石墨毡导电胶的电阻率高,以碳黑为导电填料,掺杂膨胀石墨和微粒石墨,导电胶的导电性能得到改善。电化学性能测试表明,40%石墨毡导电胶的析氧电位较高,不容易发生析氧腐蚀。2.采用循环伏安法和线性极化法研究了硫酸氧钒溶液中V5+/V4+电对在不同工作电极上的氧化还原反应。结果表明,在石墨电极上表现出较好的可逆性；导电塑料电极在硫酸氧钒溶液中有较宽的水稳定区；而在铂电极上硫酸氧钒更易析氢。Ⅴ(Ⅳ)电化学还原成Ⅴ(Ⅳ)的速率常数远小于Ⅴ(Ⅳ)电化学氧化成Ⅴ(Ⅴ)的速率常数。因此,使用硫酸氧钒溶液进行CV测试经常不出现V4+/V3+的还原峰。计算了V5+/V4+在石墨、铂片和导电塑料板电极上氧化反应的动力学参数,交换电流密度分别为石墨电极1.60×10-3A·cm-2,铂电极2.541×10-4A·cm-2,导电塑料电极3.814×10-A·cm-2,而在导电塑料板电极上,V4+/V3+交换电流密度为3.235×10-6A·cm-2。3.利用循环伏安法和计时电流法对1.0-2.5 mo1·L-1 H2S04+0.1-1.0 mo1·L-1VOS04电解液中Ⅴ(Ⅳ)的扩散系数进行了估算。Ⅴ(Ⅳ)的扩散系数随Ⅴ(Ⅳ)浓度的增加有明显的减小,从1.58×10-3降至2.03×10-4cm·S-1；而溶液的硫酸浓度对Ⅴ(Ⅳ)的扩散系数影响较小。V5+/V4+电对的氧化还原反应是受扩散控制的不可逆反应过程,提高电解液中Ⅴ(Ⅳ)的浓度可以加速氧化反应速度；电解液中的硫酸浓度对Ⅴ(Ⅳ)的氧化反应影响不明显。4.采用高锰酸钾溶液对石墨毡进行氧化处理,考察了溶液的浓度、温度对石墨毡性能的影响,结果表明,经过不同高锰酸钾溶液处理的石墨毡表面有更多的表面活性基团,其亲水性得到改善。石墨毡表面在经过高锰酸钾溶液氧化过程中沉积上高锰酸钾时,不利于Ⅴ(Ⅳ)在其上面进行反应。经过90℃水浴下饱和高锰酸钾溶液处理的石墨毡电极出现了三对钒离子的氧化还原峰,电化学性能得到改善。5.采用化学沉积法和物理吸附法在石墨毡表面沉积SnO2是可行的。采用物理吸附法沉积SnO2时,SnO2沉积量较少,且只是依浮在石墨毡表面；而采用化学沉积法沉积SnO2时,可以得到均匀且与石墨毡表面结合紧密的SnO2薄膜。石墨毡表面沉积SnO2后,V3+/V2+电对、V4+/V3+电对、V5+/V4+电对的氧化反应峰电流均提高,氧化反应峰出峰持续时间提高,说明Sn02对钒离子在电极表面的反应具有一定的催化作用。且包覆Sn02后电极的电化学窗口变宽,延缓了电极的析氢和析氧反应。6.对钒电池反复充放电,研究失效的钒电池的性能。结果表明,失效钒电池正极一侧的导电塑料集流板和石墨毡都存在有氧腐蚀,碳流失造成集流板电阻升高；石墨毡中的碳纤维坑蚀现象明显；钒电池充电过程中正极析出的氧原子具有强氧化性,与碳的反应活性相似于500℃以上空气中的氧；本研究对正极在充电过程中存在的阳极析氧过程做了初步的探讨,找到极板腐蚀的原因。钒电池负极在充电过程中存在析氢过程,在石墨毡上生成-CH2官能团。7.在聚乙烯中掺杂碳黑的导电塑料板上可以实施电化学镀镍,得到具有一定厚度且与导电塑料基体之间结合力大于2.3 MPa的镍镀层。在导电塑料板上的镍电镀层可以保留镀件基体的表面特征,基体表面的平整度高,镍镀层表面更光亮。光镍镀层在NaCl水溶液中的腐蚀电位高于哑光镍镀层的腐蚀电位,且在相同的极化电压下光镍镀层的阳极溶解速度远小于哑光镍的溶解速度。更多还原

【Abstract】 All-vanadium redox flow battery is a new energy storage system developed quickly in recent years. It has some special properties such as high storage efficiency, long service life, environmental friendly, low price, and low costs of operation and maintenance. However, there are many factors influenced VRB performance. Among those factors, the performance of electrode materials and anode and cathode reaction plays an important role in VRB performance. In this paper, the electrode materials of VRB were modified, and the kinetic parameters of varies working electrodes reaction were also calculated. Achievements in this paper are listed as follows:1. The conductivity and the electrochemical properties of the conductive pastern doped different conductive fillers were studied. The results showed that the resistivity of 40% dilates graphite were lower compared with 40% graphite felt. The conductivity of conductive pastern doped dilates graphite and particulate graphite was improved. The electrochemical performance test showed that the oxygen evolution was difficult to occur due to the high oxygen evolution potential of 40% graphite felt.2. The redox reaction of V5+/V4+ couple in VOSO4 solution on various electrodes was studied by cyclic voltammetry and linear polarization method. The results showed that the couple had better redox reversibility, the conductive plastic electrode had broad water stable region, and hydrogen was likely to evolve on platinum electrode. The rate constant of V(IV) electrochemical reduction into V(III)was far less than V(IV) electrochemical oxidation into V(V). Therefore, the reduction peak of V4+/V3+ was not located in the cyclic voltammetry test. The kinetic parameters of oxidation reaction of V5+/V4+ couple on graphite, platinum, and conductive plastic plate were also calculated, and the exchange current density of the couple was 1.60×10-3 A·cm-2,2.541×10-5 A·cm-2, and 3.814×10-5 A·cm-2, respectively, and the exchange current density of the V4+/V3+ couple on conductive plastic plate was 3.235×10-6 A·cm-2.3. The diffusion coefficient of V(IV) in 1.0-2.5 mol·L-1 H2SO4+0.1-1.0 mol·L-1 VOSO4 which was obviously decreased from 1.58×10-3 to 2.03×10-4 cm·S-1 with increasing concentration of V(IV) was estimated by the cyclic voltammetry and chronoamperometry. However, the sulfuric acid concentration had little effect on diffusion coefficient of V(IV). The redox reaction of V5+/V4+ couple was an irreversible reaction controlled by diffusion. The oxidization rate can be accelerated by improving the concentration of V(IV), and the sulfuric acid concentration has no obvious effect on the oxidization of V(IV).4. Graphite felt was treated with potassium permanganate solution, and the effect of concentration and bath temperature on graphite felt performance was experimentally investigated. The results showed that the hydrophilicity was improved due to the appearance of surfactant group on the surface of graphite felt. The potassium permanganate deposited on graphite felt was unfavorable to the reaction of vanadium ions, however, the graphite felt treated with saturation potassium permanganate at 90℃bath could completely embody the vanadium ion valence changes, and improve the electrochemical performance of the graphite felt.5. SnO2 thin films on the surface of graphite felt was successfully deposited by chemical deposition and physical adsorption. Compared with chemical deposition, lesser SnO2 grain was adsorbed on the surface of graphite felt by physical adsorption, while uniform and well-knit SnO2 thin film can be obtained by chemical deposition. The results showed that the peak current and the duration time of oxidation of V3+/V2+ couple, V4+/V3+ couple, and V5+/V4+ couple enhanced after depositing SnO2, this indicated that SnO2 performs a catalytic action on the reaction of vanadium ions on the surface of the electrode, and both the hydrogen and the oxygen evolution overvoltage on the SnO2 modified electrode enhanced.6. The performances of inoperative battery after repeated charge-discharge cycles were studied. The results showed that both conductive plastic current collector plate of the anode and the graphite felt were corroded by oxygen corrosion, and the resistance of the plate increased due to the loss of carbon, while pitting corrosion was observed on the surface of carbon fiber. The oxygen atom evolving on cathode during charging process has strong oxidizability, and its reactivity with carbon is similar to the oxygen in 500℃air. The oxygen evolution on anode during the charging process of the cathode was studied and the reason of electrode corrosion was found. Hydrogen was evolved during the charging process of the cathode, and the-CH2 generated on the graphite felt.7. Nickel coating on the carbon-polythene composite plate was prepared by electrodeposition in a nickel sulphate solution, and the adhesion strength between the nickel coating and substrate can be more than 2.3 MPa. The growth of nickel coating could inherit some characteristics of the substrate geometrics, and therefore the coating roughness was strongly depended on the roughness of the composite plate substrate. The corrosion potential of the bright coating in the NaCl aqueous solution was more positive than that of the dull coating, and the anodic dissolving rate of the bright one was also far lower at the same polarization potential compared with the dull one.更多还原