Final Defense: William McLeod

About the event

Speaker: William McLeod

Host: Dr. Jeff Bell

Title: MAGNETIC FIELD APPLICATIONS FOR LOW-COST ENERGY STORAGE

Abstract: Demand for electrochemical energy storage (EES) is rising, driven by integration of intermittent renewable energy sources, demand for electric vehicles, and increasing ubiquity of portable electronics. This diverse range of applications requires a diverse body of EES devices; however, the current EES market primarily consists of only a select few technologies. In particular, the battery market is dominated by the lithium-ion battery (LIB), which exhibits excellent electrochemical performance but is expensive, has a poor safety record, relies on materials with limited and ethically questionable sourcing, requires toxic and environmentally hazardous organic electrolytes, and cannot currently be practically recycled. A leading alternative is the aqueous zinc-ion battery (AZIB), which is dramatically cheaper and safer, and utilizes abundant and environmentally benign materials including nontoxic and nonflammable water-based electrolytes. Despite these advantages, the AZIB has yet to achieve commercial success primarily due to poor energy density. This poor energy density is partly a result of the narrow electrochemical stability window of water but also partly a result of inefficient utilization of incorporated active materials, namely the zinc metal anode, only a small fraction of which participates in cycling in the standard configuration. This presentation therefore discusses two main strategies to improve the energy density of AZIBs: increasing the utilization of active material through the anode-free configuration and improving the capacity through novel synthesis of cathode materials. Both strategies utilize magnetic fields, the former through permanent magnets incorporated into the device for operation and the latter via permanent magnets applied during electrochemical synthesis of active material. A fundamental investigation is performed on the effect of magnetic fields on the electroplating/stripping of aqueous zinc electrolytes. The ability of magnetic fields to improve the performance of anode-free AZIBs is demonstrated using current collectors first of copper then of graphene oxide, constituting the first ever carbon-based anode-free AZIB. The effect of a magnetic field on the electropolymerization of aniline is investigated for applications in supercapacitors and AZIBs, including the copolymerization of aniline and metanilic acid. Finally, magnetic fields were utilized for the electrodeposition of MnO2 for binder-free cathodes with improved areal capacity and capacity retention. These strategies demonstrate multiple ways that magnetic fields can be utilized to improve the performance of low-cost energy storage devices.