Pathways to next-generation redox flow batteries

electrochemistry;nitrobenzene;crossover;Redox flow battery (RFB);NAqRFB;AqRFB;NAqRFBs;Techno economic model

Dmello, Rylan Doyle ; Smith ; Kyle C.

关键词: electrochemistry;    nitrobenzene;    crossover;    Redox flow battery (RFB);    NAqRFB;    AqRFB;    NAqRFBs;    Techno economic model;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/90840/DMELLO-THESIS-2016.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Redox flow batteries (RFBs) provide a promising pathway towards grid-scale energy storage but are inhibited from widespread implementation due to high costs. RFBs are divided into aqueous (Aq) and nonaqueous (NAq) redox flow batteries, both of which show distinct challenges to build low-cost RFBs with battery prices less than 100 per kWh-1. Overcoming these cost challenges requires a detailed electrolyte techno-economic (TE) model, which explicitly quantifies RFB redox active material, salt, and solvent costs. TE model results identify active species concentration and cell voltage as critical cost-constraining parameters for nonaqueous and aqueous RFBs respectively. Active species concentration targets for NAqRFBs are decreased by increasing cell voltage, and by decreasing area-specific resistance, redox active material molecular weight, and salt molecular weight and concentration. Similarly, cell voltage targets for AqRFBs are decreased by decreasing area-specific resistance and redox active material cost per unit mass and molecular weight. Alternative design pathways for nonaqueous and aqueous RFBs are proposed which decrease NAqRFB redox active material molality targets to 1.1 mol kg-1 and AqRFB cell voltage targets to 0.6 V, and which could potentially decrease RFB battery price to 90 per kWh-1. This TE model is used to analyze a group of experimentally tested nitrobenzene derivatives to find optimal redox active material potential, molecular weight, and salt molecular weight for next-generation nonaqueous RFBs. Nitrobenzene derivatives are found to have a battery price of 260 per kWh-1 when used with TBAPF6 salt, but on switching to TMABF4 salt with lower molecular weight, the battery price can be reduced further to 160 per kWh-1 albeit with higher active material molality targets. Finally, an analytical model of redox active species crossover in nonaqueous RFBs is developed and implemented in order to reduce coulombic inefficiencies in RFBs by selecting optimal operating parameters. The degree of crossover is found to be highly sensitive to current density and separator permeability, and can be decreased by an order of magnitude using thicker separators and higher current densities.