Loading...

Influences of Magnetic Nanoparticles and Magnetic Field on the Performance of the Redox Flow Batteries

Rahimi, Mohammad | 2021

432 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53907 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Molaei Dehkordi, Asghar; Gharibi, Hossein
  7. Abstract:
  8. The novel concept of using magnetic nanofluidic electrolyte for redox flow batteries (RFBs) is demonstrated for the first time. In this regard, the stable magnetic nanofluidic electrolytes are prepared by dispersing magnetic modified multiwalled carbon nanotubes (MMWCNTs) in the positive electrolyte of a polysulfide-iodide redox flow battery at mass concentrations of less than 0.3 g L−1. The electrochemical behavior of magnetic nanofluidic electrolyte was examined using cyclic voltammetry at different mass concentrations of MMWCNTs with a carbon felt electrode. Higher and stable peak current densities were observed at larger mass concentrations of MMWCNTs. A polysulfide-iodide redox flow battery was employed to evaluate the influence of magnetic nanofluidic electrolyte on the battery performance for various mass concentrations, velocities of flowing electrolyte, and current densities using electrochemical impedance spectroscopy, polarization, and galvanostatic charge-discharge experiments. A decrease in ohmic resistance as well as reductions in the charge-transfer and mass-transfer resistances were observed for the magnetic nanofluidic electrolyte compared to those obtained in the absence of MMWCNTs. Adding MMWCNTs to the positive electrolyte at the mass concentration of 0.3 g L−1 results in enhanced performance of the polysulfide-iodide redox flow battery, whereby the peak power density increases by 45% and an energy efficiency of 79.91% was obtained at a current density of 20 mA cm−2. Moreover, high coulombic efficiency close to 100% and stable cycling performance over 200 cycles were achieved using magnetic nanofluidic electrolyte. After 50 cycles, at a current density of 30 mA cm−2, the energy efficiency of the battery operated with magnetic nanofluidic electrolyte remains 10% greater than that obtained in the absence of MMWCNTs. Besides improving the battery performance, MMWCNTs can be separated and recovered using magnetic decantation during electrolyte replacement for redox flow batteries involving high capacity fade and precipitation, which preserves system cost-benefits. The magnetic nanofluidic electrolyte could be applied for different redox solutions using appropriate magnetic nanoscale conductors. This innovative concept opens up a new opportunity to develop the next generation of high-performance and low-cost flow batteries. Moreover, a novel approach named a magnetic flowable electrode (MFE) is proposed for the first time to enable enhancement of RFBs performance. This approach enables the formation of a high active surface area electrode from magnetic nanomaterials, without the need to fabricate a self-supporting threedimensional electrode structure. To form a simple MFE, magnetic modified carbon nanotubes are dispersed in the electrolyte, and permanent magnets are embedded behind the current feeder to apply a magnetic field across the flow cell channels. With circulating electrolyte, magnetic carbon nanotubes are aggregated on the graphite bipolar plate to form a well-structured nanoscale percolating network and chains serving as an electrode. The superior electrochemical activity and stability of the MFE approach is demonstrated successfully relative to a conventional stationary carbon felt electrode using the positive electrode of a polysulfide-iodide RFB. The MFE provides high electrochemical active surface area and porosity, which result in lower cell impedances and pump losses, and higher battery efficiencies. The polysulfide-iodide RFB using an MFE gives stable cycling performance over 200 cycles (with replacement of the electrolyte after 100 cycles) and delivers a high energy efficiency of 79.3% at a current density of 20 mA cm−2, which is larger than all previous reports for this RFB system. The MFE design opens new opportunities to develop the next-generation RFB systems and can be applied in various flow battery chemistries
  9. Keywords:
  10. Nanofluid ; Carbon Nanotubes ; Redox Flow Batteries (RFB) ; Magnetic Nanodot ; Magnetic Flowable Electrode ; Polysulfide-Iodide

 Digital Object List

 Bookmark

No TOC