全钒液流电池不对称设计及相关科学问题研究

Vanadium redox flow battery (VRFB) has unique and highly competitive features compared to other secondary battery systems, including the ability to scale-up the battery storage capacity at low capital cost, long cycle life, and flexible design. VRFB can be used in the fields such as large-scale electricity energy storage, peak shaving, and distributed power supply et al. However, low energy density and serious capacity fading are still the technical problems which restrict the commercial application of VRFB. By asymmetrical design, this project can adjust the electrodes (the activation extent and the thickness of the electrode) and electrolyte (vanadium ion concentration and the concentration of sulfuric acid) of the cathode and anode of the VRFB, to achieve: (1) electrode kinetics matches with the electrochemical reaction on cathode and anode, to eliminate the side reaction of hydrogen (oxygen) evolution; (2) reduces the net electrolyte migration rate during the charge-discharge process; (3) increases the coulomb efficiency and energy efficiency of the VRFB, and finally, extends its cycle life. In the meantime, the project is also aimed to reveal the mechanism of electrolyte imbalances and charge capacity fading of the asymmetric VRFB through in-situ monitoring the change of concentration (volume) of the anolyte and catholyte, real-time tracking the change of the concentration of side reaction products in the gas phase of the electrolyte tank, combined with the charge-discharge test and electrochemical impedance spectroscopy measurements. It will provide a scientific basis for further research and development of large scale, long cycle life, and highly efficient VRFB energy storage system based on the asymmetric design.

全钒液流电池（钒电池）具有易规模化、长寿命、选址自由等特点，是最有前景的储能技术之一，可应用于大规模储能、电网调峰、分布式供电等领域。能量密度偏低和蓄电容量衰减较快是制约钒电池实际应用的技术难题和研究热点。本项目拟通过对钒电池正、负极的电极（电极活化程度和厚度的不同）和电解液（钒离子浓度和硫酸浓度的不同）进行不对称设计和调控，实现钒电池正、负极电化学反应的电极过程动力学匹配，减少析氢（氧）副反应，降低钒电池充、放电过程中的电解液净迁移率，提高钒电池的电流效率和能量效率，延长其循环寿命；同时在不对称钒电池长期充放电运行过程中，在线监测正、负极电解液浓度和体积变化，实时跟踪正、负极电解液储罐气相组分中的副反应产物浓度变化，结合电池充放电测试数据和电化学阻抗谱的变化趋势，揭示不对称钒电池的电解液失衡和电池容量衰减机制，为进一步研制基于不对称设计的大功率、长寿命、高效率钒电池储能系统提供科学依据。

全钒液流电池具有容易规模化（兆瓦级）、超长寿命（>10000次循环）、设计灵活（功率和容量独立）、安全性高（水相电解液体系）、回收残值高（电解液几乎可永久性利用）等突出优点，成为目前发展最快、最有前景的大规模（电网级）储能技术之一。.能量密度偏低和蓄电容量衰减较快是制约全钒液流电池实际应用的技术难题和研究热点，对全钒液流电池的关键材料（电极和电解液）进行系统研究和合理使用是解决上述问题的有效手段。本项目的主要研究内容包括全钒液流电池在线监测系统的搭建及优化、电极评价方法学优化、电极在半电池和全电池下的合理电化学评价、正极析氧副反应的在线检测、负极析氢副反应及其抑制、正负极电解液的不对称设计以及酸度对电解液和电池性能的综合影响等方面。通过对全钒液流电池电极和电解液进行不对称设计和调控，有效地抑制了充放电过程中析氢（氧）等副反应、降低了电解液净迁移率、减缓了蓄电容量衰减、提高了能量效率和循环稳定性。结合在线监测系统所获得的正负极电解液体积、各价态钒离子浓度和副反应比例等实时数据，揭示了长周期循环过程中全钒液流电池电解液失衡和电池容量衰减机制。.我们相信，本项目在电极、电解液和在线监测等方面取得的基础/创新研究成果，将为进一步研制基于不对称设计的大功率、长寿命、高效率全钒液流电池储能系统提供科学依据和数据支持。