Novel Magnetic Flowable Electrode for Redox Flow Batteries: A Polysulfide/Iodide Case Study

Abstract

A novel approach named a magnetic flowable electrode (MFE) is proposed for the first time to enable enhancement of redox flow batteries (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.

Cathode materials for halide-based aqueous redox flow batteries: recent progress and future perspectives

“…Dehkordi et al first proposed the concept of the magnetic flowable electrode (MFE) by using a magnetic nano-fluid electrolyte (MNE) to improve the performance of the PIRFB test system. 87,88 The MFE has a high active surface area, without the need to fabricate a self-supporting three-dimensional structure, and the MNE was effectively dispersed through the battery electrolyte with a low mass concentration that can aggregate on the electrode. MFE strengthens the entanglement of the nanoscale conductors in the conductive networks.…”

External field–assisted batteries toward performance improvement

“…Aside from the abovementioned positive effect of the magnetic field on batteries, which mainly concentrates on Li-and Zn-based systems with liquid electrolytes, the magnetic field has also shown its power in redox flow batteries and all-solid-state batteries. 61,62 For example, in nonaqueous iron-vanadium redox flow batteries, the applied magnetic field can act on paramagnetic Fe and V ions and make them undergo the Lorentz force, which can markedly enhance the mass transfer in the electrolyte. 61 Moreover, the charge and discharge performances of this Fe-V redox flow battery system in terms of cycle number and energy efficiency have been improved.…”

Membrane-Current Collector-Based Flow-Electrode Capacitive Deionization System: A Novel Stack Configuration for Scale-Up Desalination

“…Fourth, one that few researchers have focused on, is the enormous energy consumption for driving flow electrodes. Although the improvement of dispersibility is generally considered to be an effective method to reduce the viscosity of the carbon slurry, excessive high dispersibility of electrode particles will cause a low collision between the electrode particles and the current collectors. , One exciting option is to replace the pressure drive by noncontact driving forces such as gravitational potential energy and magnetic force to drive the electrode particles directly. , …”

“…53,54 ■ ASSOCIATED CONTENT * sı Supporting InformationThe Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.1c03829. Calculation of current density; variation in conductivity as a function of NaCl concentration; dimension of the electrode chamber; schematic of the FCDI configuration; image of activated carbon particles and titanium mesh; desalination performance at SCC and SC mode and at series operation; effects of carbon content on the inlet pressure and thermodynamic energy efficiencies; and comparison of desalination performance of a gradient FCDI system with previous studies (PDF)…”