液流电池催化剂原位电沉积过程电化学与物质传输耦合特性研究

The metal catalyst prepared by the in-situ electrodeposition in the porous electrode, with unique advantages including highly catalytic activity, easy regeneration and good stability, is an effective route to develop the high-performance redox flow battery systems. The in-situ electrodeposition process is affected by many factors such as convection, diffusion, electro-migration, reaction kinetics, pore structure evolution, which results in the issues of uneven catalyst distribution and limited battery performance, requiring deep investigations. In order to improve the catalyst distribution and practical catalytic effect, this project will investigate the coupled electrochemical and mass transport characteristics during the in-situ catalyst electrodeposition in the redox flow batteries: unveil the catalyst nucleation kinetics based on the current step control technique and scanning electron microscope technique; illuminate mass transport characteristics in the porous electrode with non-constant pore structure during the electrodeposition process using the polarization tests and thermogravimetric analysis; develop a coupled electrodeposition and mass transport model and a computing program for the in-situ electrodeposition process with the consideration of catalyst nucleation and growth as well as the pore structure evolution, investigate the catalyst distribution mechanism for the in-situ electrodeposition based on the numerical simulation and experimental characterization, and optimize the electrodeposition parameters. The results will contribute to the development of the high-performance and long-lived redox flow batteries, and promote the large-scale storage and reliable employment of intermittent renewable sources.

多孔电极原位电沉积制备金属催化剂，具有催化活性高、易再生、稳定性好等独特优势，是发展高性能液流储能电池系统的有效途径。原位电沉积过程受对流、扩散、电迁移、反应动力学、孔隙结构演化等多种因素综合作用，存在催化剂分布不均、电池性能受限的问题，尚缺乏深入研究。为提升催化剂分布均一度及实际催化效果，本项目拟开展液流电池催化剂原位电沉积过程电化学与物质传输耦合特性研究：基于阶跃电流控制技术及扫描电镜表征技术，探究催化剂成核动力学特性；采用极化测试技术及热重分析方法，探索电沉积过程多孔电极变孔隙结构条件下物质传输机制；综合考虑催化剂成核生长动力学与电极变孔隙特征，发展电沉积与物质传输耦合模型及数值计算程序，并结合数值模拟与实验表征阐明原位电沉积催化剂分布规律，优化电沉积参数，改善催化剂分布。研究成果将有助于发展高性能长寿命液流电池，促进间歇性可再生能源大规模储存与可靠利用。

项目探索了全钒液流电池负极催化剂原位电沉积过程铋离子浓度、电解液流量、电镀运行电流密度、电镀方式、流场结构等关键过程因素对铋催化剂在多孔电极中分布影响规律；并基于实验结果，创新性地提出了间歇电镀的方法，较传统恒流电镀方案，可以使得铋催化剂在多孔电极内实现更均匀的分布，进而提高了全钒液流电池的电压效率。项目系统研究了流场对电解液在电池内运输的影响规律，基于电化学物料传输耦合模型探究了流场结构参数对电池性能的影响，并提出了新型分级叉指型流场。该流道结构在传统单级叉指型流场结构的基础上，进一步构建了分层级的流道结构，克服了流道设计中物质传输与泵功损失的矛盾，能够更高效地把电解液输配到多孔电极中。基于原位电镀催化剂方法，开发出400 cm2瓦高性能全钒液流电池原型机，运行电流密度达到320 mA cm-2，输出功率达到150 W，考虑泵功的能量效率达到75%，这将为未来高性能液流电池电堆开发提供有力指导。