(Energy Technology Division Supramaniam Srinivasan Young Investigator Award Address) Towards Deterministic Electrode Design: Elucidating the Role of Surface Chemistry and Microstructure on Flow Battery Performance

Abstract

Redox flow batteries (RFBs) are promising for energy-intensive grid storage applications, but further improvements are needed for universal adoption.1,2 While research efforts have primarily focused on molecular engineering of redox couples as a means of reducing system cost, advances in other critical systems components also hold significant cost reduction potential. Of particular importance are the porous electrodes which are responsible for multiple critical functions in the flow cell related to thermodynamics, kinetics, and transport including providing surfaces for electrochemical reactions, enabling uniform liquid electrolyte distribution with low hydraulic resistance, as well as conducting electrons and heat. However, there is limited knowledge on how to systematically design and implement these materials in emerging RFB applications, forcing the repurposing of available materials that are not tailored for this electrochemical system. Moreover, current generation materials, which are typically developed via empirical approaches, lack control of surface chemistry (e.g., compositional heterogeneity) and morphology (e.g., broad pore size distribution). This fundamentally limits the performance, durability and, consequently, the cost of resultant systems. In this talk, I will discuss methods for disaggregating and quantifying resistive losses in various porous electrodes using model redox couples, diagnostic flow cells, and electrochemical modeling.3,4 When applied in combination with suitable spectroscopy and microscopy techniques, structure-performance relations can be elucidated5,6 which may eventually lead to design rules that enable the fabrication of chemistry-specific electrodes based solely on the knowledge of the physical and electrochemical properties of the redox active electrolyte.