大功率全钒液流电池流场结构的构效关系及调控机制研究

Vanadium flow battery (VFB) is one of the preferred techniques for efficient large-scale energy storage applications. To meet the requirement of popularization of renewable energies, the development of hundred-megawatt-class VFB energy storage systems is urgently needed. Cost reduction is the key for the commercialization of the VFB systems, which can be achieved by developing high power vanadium flow battery stacks with high power densities. One of the effective strategies for high power density stacks is the decreasing of the polarization by optimizing the flow field structure and hence improving the suitability of the coupling microfields inside the stacks. In regard to this, a simplified and reliable three-dimensional mechanism model, which contains the flow field geometry, has been established in this project for high power vanadium flow battery stacks via sensitivity analysis and model updating optimization. The accuracy and reliability of the model have been verified by polarization curve measurements and charge-discharge performance tests. By combining numerical simulation and experimental verification, the effect of the flow field stucture on the characteristics of the microfields, along with their coupling mechanism inside a high power vanadium flow battery stack, has been explored. Based on the above results, the key structure parameters have been verified and an effective regulatory and optimization strategy for the flow field structure design has been developed to achieve a most suitable adaption of the multi-microfields coupling process. The strategy can provide helpful theoretical and technical guidance for optimization designs and engineering applications of high power vanadium flow battery stacks (eg, kW class stack) with high power densities.

为满足可再生能源普及应用对百兆瓦以上级大规模全钒液流电池系统的需要和商业化对其降低成本的要求，研发高功率密度的大功率全钒液流电池电堆极为重要。优化流场结构，提高电堆内部各微观场间耦合作用的适配性，降低极化是提高电堆功率密度的有效途径。本项目首先在现有的小尺度全电池模型基础上，结合灵敏度分析和模型参数修正，构建合理简化、考虑流场结构在内的kW级大功率电堆三维模型，以极化特性和充放电性能实验验证并优化模型的准确性和可行性；将数值模拟和实验验证相结合，系统分析流场结构，重点是电解液进口导流流道、进口分配流道、出口集液流道、出口导流流道和多孔电极结构对电堆内部浓度场、质量场、温度场、反应场等微观场特性及各场间耦合作用适配性的影响机制，解明影响电池性能的关键流场结构参数，建立多场协同作用下电堆流场结构的优化调控策略，搭建出kW级高功率密度液流电池电堆，实现高功率密度、大功率电堆的工程放大应用。

为满足可再生能源普及应用对百兆瓦以上级大规模全钒液流电池系统的需要和商业化对其降低成本的要求，研发高功率密度的大功率全钒液流电池电堆极为重要。优化流场结构，提高电堆内部各微观场间耦合作用的适配性，降低极化是提高电堆功率密度的有效途径。本项目首先在现有的小尺度全电池模型基础上，考虑离子互串的影响，并引入极化模型，构建出合理简化、考虑流场结构在内的kW级大功率电堆三维瞬态模型，以极化特性和充放电性能实验验证并优化模型的准确性和可行性；将数值模拟和实验验证相结合，系统分析了矩型平推流和梯形平推流流场结构，主要包括电解液进口导流流道、进口分配流道、出口集液流道、出口导流流道和多孔电极结构对电堆内部浓度场、质量场、温度场、反应场等微观场特性及各场间耦合作用适配性的影响机制，明确了影响电池性能的关键流场结构参数，建立了多场协同作用下电堆流场结构的优化调控策略。以所建的梯形平推流结构设计优化策略为指导，开发出kW级高功率密度梯形液流电池电堆，电堆在160mA/cm2时，能量效率为81.5%，电解液利用率为72.3%；将短流程矩型平推流结构成功应用于2 kW、30 kW级及研究部第2代15kW级高功率密度全钒液流电池电堆。其中2 kW级电堆在保持能量效率不低于80%的条件下，工作电流密度由80mA/cm2提高至160mA/cm2，电堆的功率密度提高了一倍，在电流密度为120 mA/cm2下电解液利用率提高了24%；30 kW级电堆的额定工作电流密度由80 mA/cm2提高到120 mA/cm2，电堆的功率密度提高了50%；第二代15kW高功率密度全钒液流电池电堆输出功率达18kW，在电流密度207mA/cm2下能量效率超过80%，相比第一代15kW电堆功率密度提高了25%。本项目研究成果为高功率密度、大功率电堆的工程放大应用提供了强有力的技术支撑。大幅度缩短了高性能电堆开发周期，促进了液流电池产业化进程。项目执行期间，发表 SCI 论文3 篇，申报发明专利7件，获授权发明专利7件，制定国际标准1项，行业标准2项。