HCl＋H2SO4为支持电解质的钒电池正极电解液热力学性质研究

Vanadium battery is an electrochemical energy storage system, due to its fast and large capacity current charge/ discharge, it is an ideal power form of the mass storage for wind energy, solar energy and smart grid. Vanadium electrolyte is the core of energy storage and energy conversion of vanadium battery. Low energy density and poor stability of the electrolyte is the key barrier restricting the application and development of vanadium battery. It has been reported that the supporting electrolyte with mixed (HCl+ H2SO4) can increase concentration of vanadium ions and improve stability of the electrolyte, which is attributed to the generation of [VO2Cl]0 ion pair in the electrolyte. However reports concerning the thermodynamic properties of the electrolyte with mixed supporting electrolyte as well as the [VO2Cl]0 ion pair are little. In this project, basic thermodynamic data of the positive electrolyte with mixed supporting electrolyte is determined by EMF method, density method and calorimetry. The thermodynamic functions, apparent molar volume and apparent molar heat capacity of [VO2Cl]0 for association process is calculated. The thermodynamic properties of electrolyte with mixed supporting electrolyte under different charging and discharging state is estimated using Nernst equation, Debye-Hückel equation and Pitzer theory. The results of the project will provide a theoretical basis for the composition design, performance prediction and the practical application of vanadium electrolyte with new mixed supporting electrolyte.

钒电池作为可大容量、快速充放电液流储能电池，是满足风能、太阳能发电及智能电网大规模储能需求的理想储能技术。电解液是钒电池能量存储转换的核心，目前电解液低能量密度和较差的稳定性在很大程度上制约了钒电池的商业化进展。有研究证实混合（HCl+ H2SO4）作支持电解质可明显提高钒离子浓度和稳定性，其原因可能是[VO2Cl]0离子对的形成，但关于混合电解质钒电解液及离子对的热力学性质研究还未见报道。本项目采用电动势法、密度法和量热法测定混合电解质正极钒电解液的基础热力学数据，计算[VO2Cl]0离子对缔合过程的热力学函数、表观摩尔体积以及摩尔热容等热力学性质，采用Nernst方程和Debye-Hückel公式以及Pitzer电解质溶液理论相结合的方法，估算不同充放电状态下，混合电解质电解液的热力学性质。本项目的研究结果将为新的混合电解质钒溶液体系的组成设计、性能预测及钒电池的实际应用提供理论基础。

钒电池作为容量和功率可独立设计、长寿命 大容量、快速充放电，电化学可逆性好的液流储能电池受到了广泛的关注，被认为是能够在未来取代石油而满足风能、太阳能发电及智能电网大规模储能需求的理想储能技术。电解液是钒电池能量存储转换的核心，目前电解液低能量密度和较差的稳定性在很大程度上制约了钒电池的商业化进展。有研究证实混合（HCl+ H2SO4）作支持电解质可明显提高钒离子浓度和稳定性，其原因可能是[VO2Cl]0离子对的形成，但关于混合电解质钒电解液及离子对的热力学性质研究还未见报道。.本项目采用电动势法、热容法、密度法分别测定（HCl＋H2SO4）混合体系正极电解液的电动势、热容、密度等基础热力学数据，这些物化性质均温度的升高而降低，随浓度的增加而增加。以基础的热力学数据为基础，用Pitzer 理论与离子缔合平衡结合的方法计算（HCl＋H2SO4）混合体系正极电解液的[VO2Cl]0 和[VOSO4]0 离子对缔合过程的热力学函数（缔合常数、缔合Gibss 自由能、缔合焓、缔合熵等）以及[VO2Cl]0和[VOSO4]0 活度系数的Pitzer 参数、各个离子的浓度和活度等热力学参数，研究了其随温度与溶液组成的变化规律。针对原有溶液物化性质预测方程只适用稀浓度和组分单一等问题，本项目提出在确定（HCl＋H2SO4）混合体系正极电解液各热力学性质和Pitzer参数的基础上，采用Nernst 方程和Debye-Hückel 公式以及Pitzer 电解质溶液理论相结合的方法，建立了建立了高浓度、多组分电解液预测方程，预测不同充放电状态下正极电解液的热力学性质，获得其随温度和组成的变化规律。. 本项目的研究结果直接为钒电池技术发展提供科学支撑；同时，也将为钒离子溶液化学与热力学理论或知识体系的发展与完善做出积极贡献，具有较大的学术意义和实用价值。