添加剂对甲基磺酸铅液流电池负极枝晶形态影响的研究

发布时间：2018-11-09 16:20

【摘要】：将具有间歇性和不稳定性特点的风、光可再生能源与储能系统配套使用是优化能源结构、缓解并网压力,改善电力质量的核心手段。甲基磺酸铅液流电池以其结构简单、成本低廉、耐候性强及易再生循环等优点,而被认为是有望成为万次循环的长寿命周期和兆瓦级容量的电站式储能系统。但甲基磺酸铅液流电池充电过程中,因可溶性Pb2+优先以枝晶形态于负极沉积,容易引发电池正负极短路,从而严重影响电池的储电效率和使用寿命。基于此,本文以1.0mol/LH+和0.7mol/LPb2+为电解液,通过向电解液中添加金属离子添加剂(Sn2+)、有机添加剂十烷基三甲基氢氧化铵(HDTAH)来抑制电池负极枝晶生长和改善电池循环性能,利用LAND动力电池测试系统、循环伏安法(CV)、计时电流法(CA)、线性扫描(LSV)等电化学方法并结合扫描电子显微镜(SEM)、X射线衍射(XRD)、X射线光电子能谱(XPS )等表面检测方法系统地探究添加剂对电池负极枝晶的抑制机理及其对储电效率和循环寿命影响的规律,得到以下的研究结果:一、电解液添加剂为金属离子Sn2+,添加浓度为0.8mmol/L～1.Ommol/L时,铅在电池负极沉积较为平整,且铅颗粒团聚体之间紧凑致密,电池的平均放电容量提高。电解液中使用Sn2+添加剂抑制负极枝晶形态的作用机制:1)促进铅的电沉积,提高Pb/Pb2+电对的可逆性及Pb2+在电极表面的扩散系数;2)改变铅的电结晶方式,由“三维瞬时成核”转变为“三维连续成核”,使铅的成核密度提高;3)使铅和锡共沉积生成PbSn固溶体先于铅在(111)面上的生长,从而抑制了负极铅的枝晶形态。电解液中Sn2+的加入使电池的平均库仑效率提高至约90%、平均能量效率提高至86.4%,电池的使用寿命提高216%。Sn2+的最佳添加量为 0.8mmol/L。二、电解液添加剂HDTAH,浓度为1.5mmol/L～2.5mmol/L时,改变电池负极的枝晶形态,使铅在负极沉积更加平整、致密,从而提高放电容量。电解液中添加HDTAH作用:1)吸附在电极表面,提高电池的阴极极化,可达到细化负极铅晶粒的作用;2)可抑制铅在负极表面的电沉积,但Pb/Pb2+电对可逆性有所提高;3) HDTAH吸附在铅晶粒生长点上,改变铅的生长方向;4)使铅在负极上的以“三维瞬时成核”方式沉积,从而提高铅的成核密度,但降低Pb2+在电极表面的扩散系数;(5)使电池的充放电效率提高至89%、平均能量效率约80%、循环寿命较未使用添加剂提高190%。HDTAH添加剂的最佳添加量为2.5mmol/L。
[Abstract]:It is the core means to optimize the energy structure, relieve the grid pressure and improve the power quality by combining the wind with the energy storage system with intermittent and unstable wind. Lead methanesulfonate flow battery is considered to be a power plant energy storage system with long life cycle and megawatt capacity due to its simple structure, low cost, strong weathering resistance and easy regeneration cycle. However, in the charging process of lead methanesulfonate battery, soluble Pb2 is preferentially deposited in the negative electrode in dendritic form, which can lead to the short circuit of the positive and negative electrode of the battery, which seriously affects the storage efficiency and service life of the battery. In this paper, 1.0mol/LH and 0.7mol/LPb2 were used as electrolyte, and metal ion additive (Sn2) was added to the electrolyte. The organic additive decyl trimethyl ammonium hydroxide (HDTAH) was used to inhibit the growth of negative dendrite and improve the cycle performance of the battery. The cyclic voltammetry (CV),) chronoamperometric method (CA),) was used to test the battery with LAND power battery test system. Linear scanning (LSV) and other electrochemical methods combined with scanning electron microscope (SEM), X ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and other surface detection methods are used to study the inhibition mechanism of additives on negative dendrite and its influence on storage efficiency and cycle life. The results are as follows: 1. The electrolyte additive is metal ion Sn2, and when the concentration of 0.8mmol/L~1.Ommol/L is added, the lead deposition in the negative electrode of the battery is relatively smooth, and the lead particles are compact and compact, and the average discharge capacity of the battery is increased. The mechanism of inhibition of negative dendritic morphology by Sn2 additive in electrolyte: 1) promoting the electrodeposition of lead, improving the reversibility of Pb/Pb2 pair and the diffusion coefficient of Pb2 on the electrode surface; 2) changing the electrocrystallization mode of lead from "three dimensional instantaneous nucleation" to "three dimensional continuous nucleation", so as to increase the nucleation density of lead; 3) PbSn solid solution was formed by co-deposition of lead and tin, which inhibited the dendritic morphology of negative lead. The addition of Sn2 in electrolyte increases the average Coulomb efficiency of the battery to about 90 and the average energy efficiency to 86.4. The optimum addition amount of 216%.Sn2 for increasing the life of the battery is 0.8 mmol / L. Secondly, when the concentration of electrolyte additive HDTAH, is 1.5mmol/L~2.5mmol/L, the dendrite morphology of the negative electrode of the battery is changed, which makes the deposition of lead in the negative electrode more smooth and dense, thus increasing the discharge capacity. The effect of adding HDTAH into electrolyte is as follows: 1) adsorbing on the electrode surface to improve cathode polarization of the battery, and 2) inhibiting the electrodeposition of lead on the surface of negative electrode, but improving the reversibility of Pb/Pb2; (3) HDTAH adsorbed on lead grain growth point to change the growth direction of lead, 4) lead was deposited on negative electrode in "three dimensional instantaneous nucleation" mode, thus increasing the nucleation density of lead, but decreasing the diffusion coefficient of Pb2 on the electrode surface; (5) the charge and discharge efficiency of the battery is increased to 89, and the average energy efficiency is about 80. The optimum addition amount of 190%.HDTAH additive is 2.5 mmol / L.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

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