全钒液流电池内多物理过程规律与活性离子传输管理及电池优化研究

All vanadium redox flow battery (VRFB) is a typical multi-physical complicated energy system. The overall performance of VRFB is closely related to the coupling physicochemical process of electrolyte flow, active species transport, ions and electron transport and electrochemical reactions occurred inside the cell. In this project, the fundamental research on the coupling phenomena of multi-physical transport process and electrochemistry, mass transport management of active vanadium ions and optimization design of battery structure and operating parameters. A three-dimensional VRFB mathematical model that incorporates mass, charge and momentum transport and conservation as well as electrochemical kinetics will be developed and well validated. Both numerical simulation and experiments will be conducted to reveal the behavior of flow and transport of active species, the distribution of main physical properties (such as concentration, charge potential and local current density etc.) and the main influencing factors. The voltage loss in each electrode due to the mass transport polarization (i.e., concentration loss) and activation polarization caused by electrode reactions will be detailedly explored to ascertain the distribution of voltage loss throughout whole cell and the time-dependent variation of voltage loss on battery state during charge-discharge cycle. Based on the analysis of non-uniformity of species concentration and mass transport loss in convectional cell structure, the studies on local flow field optimization, local mass transport enhancement, and novel high-efficient flow field structure design will be conducted. Based on the analysis of dynamic variation of voltage loss during charge-discharge cycle, novel variable parameters operating strategies will be studied and optimized to improve the overall system performance. Both theoretical and experimental studies on transfer of vanadium ions through membrane and the consequent electrolyte imbalance in a VRFB will be carried out. Emphasis is located on exploring the influence mechanism of asymmetric battery operating parameters on the management of ions transfer trough the membrane, and seek optimal operating strategy to suppress ions crossover and capacity decay. Based on above study, optimal cell structure and operating strategies will be developed which can boost the overall battery performance.

全钒液流是典型的多物理复杂能量系统，材料确定情况下电池性能与其电池复杂结构内电解液流动、物料传输、电荷传输及电化学反应多物理耦合过程密切相关。本项目围绕电池内多物理传输-电化学耦合规律、活性离子传输管理及电池优化设计开展基础研究工作，发展全钒液流电池物料-电荷多物理传输与电池反应耦合数理模型并进行验证，模拟与实验结合，揭示电池内活性物料流动传输特性、物理量场分布规律及其主要影响因素，掌握各电极传输浓差损失和反应活化损失的分布及其随电池状态的动态变化特征。结合电池内物料浓度和传输不均匀性研究，开展局部流场结构优化和传输强化研究，并探索新型流场形式等。结合电池损失动态特性，研究电池动态变工况运行参数（如电解液流量、运行电流等）并优化策略。开展电池膜内活性离子迁移与失衡规律研究，探讨非对称运行参数对离子迁移失衡的调控，优化电池运行策略。通过上述研究提出有效的电池结构和运行策略，提升电池性能。

全钒液流电池是典型的复杂多物理场耦合能量系统，材料确定下电池性能与电池内电解液流动、物料-电荷-热量传输及电化学反应过程密切相关。项目围绕电池内多物理传输-电化学耦合规律、活性离子传输管理及电池优化开展基础研究。建立了液流电池多物理传输-电化学耦合稳态和瞬态数理模型,可实现液流电池内复杂热-电-质传输与电化学反应耦合过程模拟，并研究关键运行与结构参数对电池运行特性的影响规律与机制；从提高电极内部电解液流速和反应物分布均匀性出发，以提高电池净放电功率和系统效率为目标，提出了一种新型回转蛇形流场结构和一种具有局部阻块结构高效传质低流阻新型流场结构，并进行数值验证；通过探究活性离子跨膜迁移机制与规律，从调节钒离子扩散量与对流量的角度出发，以抑制容量衰降为目标，提出了非对称的浓度运行条件策略、非对称压力运行条件策略和非对称电极压缩结构设计方案，为解决离子迁移失衡和容量衰降问题提供新思路；从调节电池内物质传输与电荷传输角度出发，以最小化功率损失和提高电池效率为目标，提出了非对称的电极压缩与非对称的阻块系数结构策略并进行了优化设计；从提高电化学反应活性与提高物质传输的角度出发，以提高电池的综合性能为目标，提出了电沉积铅碳毡电极设计方案，并进行了实验验证；通过探究液流电池关键运行参数等对电池动态运行特性的影响规律，提出了阶跃型变流量与变电池电流的耦合运行调控策略，提升了电池综合性能；开发了蛇形流场全钒液流电池宏观分块网络模型，用于电池性能快速预测；在此基础上，建立了考虑支路电流和电解液分配不均特性的单电池分辨电堆网络模型，提出了非均匀阻力网络设计，实现了电堆一致性和系统效率的协同优化；提出了评价不同规模电堆设计优劣的能量损失分析法，分析了电堆规模放大过程中各项损失占比的演变及其与结构参数的相关性，为不同规模下的电堆设计提供理论指导。