Redox Targeting Insights and Applications for High-Energy-Density Redox Flow Batteries

Abstract

Decarbonizing the grid has been gaining momentum with the shift away from fossil fuels to renewable energy. The addition of energy storage systems will only accelerate this transition and the rapid phase out of conventional power plants. Aqueous redox flow batteries are a potential solution, providing a low-cost storage solution for long-duration energy storage. However, the main barrier to adoption is the low energy density, which require rather large installations to meet energy storage demands. Redox targeting is a solution that breaks the energy density pinning based on the electrolyte solubility limits. This redox chemistry combines the high-energy-density of solid-state media with the low-cost and scalable redox flow battery architecture. Chapter 1 describes the technological developments of redox flow batteries and the current challenges for wide-scale technology adoption. Chapter 2 employs a sodium superionic conductor with aqueous organic redox mediators. Through high surface area macrostructures and solution potential tuning, high material utilization and the largest volumetric capacity enhancement is demonstrated in aqueous anolytes. Chapter 3 describes a new spectrochemical method to probe the ionic diffusion kinetics in Prussian blue/ferricyanide redox targeting systems. The intercalant identity dramatically affects Prussian blue charge-discharge kinetics. The differences reflect the charge-compensation mechanisms and their impact on charge-discharge rates.