Reversible Two-Electron Ni(II/0) Redox Couples for Grid-Scale Battery Storage

In this project, Professor Byron Farnum of the Department of Chemistry and Biochemistry at Auburn University is developing novel molecular approaches for grid-scale electrical energy storage in redox-flow batteries (RFBs). These batteries serve as critical storage devices that balance the production and demand of electrical energy to provide safe and reliable power to the industrial, commercial, and residential consumers. Professor Farnum’s approach is to store two-electrons per molecule, greatly increasing the energy density of the RFB while also reducing cost of materials. Through the course of this research, graduate and undergraduate researchers will receive training and experience in inorganic synthesis, characterization techniques, electrochemical measurements, and in the communication of their scientific results. Furthermore, Professor Farnum is committed to outreach efforts that encourage college freshman to choose STEM majors and provide research opportunities to undergraduate students at small colleges and universities across the Alabama/Georgia region. Maximizing the energy density of RFBs is a uniquely chemical challenge and requires new ideas and understanding of redox storage mechanisms. Two-electron transfer reactions with first-row transition metals are rare in the literature, especially outside the context of catalysis. This is because first-row metals tend to proceed by one-electron transfer reactions. The proposed strategy will be divided into three research aims: (1) Controlling one-electron versus two-electron cycles using nickel bis(diphosphine) coordination complexes, (2) Driving two-electron transfer mechanisms with halide coordination, and (3) Producing highly stable Ni(II/0) redox couple with energy densities exceeding 100 Wh/L. These aims will be achieved by controlling changes in coordination environment between Ni(II) and Ni(0) to result in an unstable Ni(I) intermediate that yields favorable two-electron transfer. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.