(577e) High Power Symmetric Zinc Iodine Redox Flow Batteries with Functionalized Carbon Electrodes
AIChE Annual Meeting
2022
2022 Annual Meeting
Transport and Energy Processes
Advanced Electrochemical Energy Storage Technologies II
Wednesday, November 16, 2022 - 5:00pm to 5:20pm
Redox flow batteries (RFBs) have emerged as promising candidates for low cost energy storage to support renewable energy generation. Vanadium redox flow batteries (VRFB) are the most widely commercialized RFB but are restricted by expense due to the high cost and limited availability of vanadium and corrosion due to the highly acidic electrolyte. The zinc iodine (ZnI2) redox flow battery has great potential as an alternative to VRFB because it consists of low cost, environmentally friendly and widely available materials. Additionally, it is a symmetric battery which has a highly electroactive electrolyte on both sides of the battery which minimizes electrolyte crossover. Previously we showed that carbon electrodes modified with redox-active iron nanoparticles yield increased rates of charge transfer, improved voltage efficiencies at elevated current densities and higher power densities in coin cells using iron based redox electrolytes. Here we show that using iron modified carbon electrodes in a zinc iodine redox flow battery increases the charge transfer kinetics and power capabilities. The economic value and enhanced electrochemical performance can rival the vanadium chemistry and makes the ZnI2 RFB a viable option for large scale electrochemical energy storage applications.
In this work, we studied how carbon electrodes functionalized with redox active iron particles affect the performance of zinc iodine redox flow batteries. Small scale ZnI2 RFBs were assembled with pure carbon nanotube electrodes and then with carbon nanotubes containing iron particles electrodes. The electrodes were conditioned and then tested over a range of currents, flowrates, and electrolyte concentrations. Cyclic voltammetry and electrochemical impedance spectroscopy were also conducted to evaluate the performance of the redox electrolyte paired with the electrodes. Our ZnI2 RFB with carbon electrodes containing redox-active iron particles exhibited lower charge transfer resistances, higher discharge voltages and were able to sustain currents of up to 700mA, which is a 28% increase relative to the system with pure carbon electrodes. Polarization analysis showed that iron electrodes demonstrated less effect of electrolyte flowrate on electrochemical performance and an approximately 50% increase (89mW/cm2 to 44mW/cm2) in power density at 110mA/cm2 relative to pure carbon electrodes. The results indicate that iron modified electrodes improve the kinetics at the electrode-electrolyte interface and electrolyte utilization and thus can be employed in other RFB chemistries to reduce material costs and improve efficiency. The adaptation of functionalized carbon electrodes in low cost RFBs like the zinc iodine provides cost effective electrochemical energy storage for expansion of intermittent energy sources such as wind and solar to off grid applications.
In this work, we studied how carbon electrodes functionalized with redox active iron particles affect the performance of zinc iodine redox flow batteries. Small scale ZnI2 RFBs were assembled with pure carbon nanotube electrodes and then with carbon nanotubes containing iron particles electrodes. The electrodes were conditioned and then tested over a range of currents, flowrates, and electrolyte concentrations. Cyclic voltammetry and electrochemical impedance spectroscopy were also conducted to evaluate the performance of the redox electrolyte paired with the electrodes. Our ZnI2 RFB with carbon electrodes containing redox-active iron particles exhibited lower charge transfer resistances, higher discharge voltages and were able to sustain currents of up to 700mA, which is a 28% increase relative to the system with pure carbon electrodes. Polarization analysis showed that iron electrodes demonstrated less effect of electrolyte flowrate on electrochemical performance and an approximately 50% increase (89mW/cm2 to 44mW/cm2) in power density at 110mA/cm2 relative to pure carbon electrodes. The results indicate that iron modified electrodes improve the kinetics at the electrode-electrolyte interface and electrolyte utilization and thus can be employed in other RFB chemistries to reduce material costs and improve efficiency. The adaptation of functionalized carbon electrodes in low cost RFBs like the zinc iodine provides cost effective electrochemical energy storage for expansion of intermittent energy sources such as wind and solar to off grid applications.