The impact of flow on electrolyte resistance in single-flow batteries

Developing large-scale storage of intermittent renewable energy to meet growing energy demands is a pressing current need. Multiphase single flow batteries are a promising solution for such grid-scale energy storage, demonstrating an affordable redox flow battery design that reduces both cell and balance of plant costs. However, their major limitation is the considerable variance in electrolyte conductivity under different battery flow conditions and electrolyte properties, with no current predictive model to comprehensively understand and optimize it. Here, we develop an analytical model for such emulsion electrolytes with a continuous aqueous-based phase and dispersed reactant-rich phase, which enables electrolyte resistance prediction. We show that a key mechanism affecting electrolyte conductivity is the formation of a sedimented layer along the flow channel, revealing the critical effect of non-aqueous phase sedimentation. Experimental validation using a zinc-bromine single flow battery demonstrates excellent agreement with theoretical results during both transient and steady operations, allowing extraction of challenging-to-measure parameters, such as the in-situ size of dispersed phase droplets. This foundational model is essential in minimizing power losses, improving electrolyte and cell designs, and holds broad applicability across diverse chemistries for single-flow batteries. [Display omitted] •Electrolyte resistance limits the performance of single flow batteries.•Sedimentation greatly affects electrolyte resistance, reducing power output.•A model is provided for the electrolyte separation in a multiphase flow battery.•Adjusting conditions reduces sedimentation thickness and electrolyte resistance.•Experiments validate theory for both transient and steady operations.