(Vittorio de Nora Award) Electrolytes: Discovery to Fundamentals, and Fundamentals to Discovery

Abstract

I am humbled to be among the prominent scientist, engineers, and inventors who have been past ECS Vittorio De Nora Awardees. I have met with Professor De Nora on several occasions, and will share some anecdotes of these encounters throughout my presentation and give some historical perspectives. As you can imagine, because of my personal encounters with Professor De Nora and my long-time affiliation with the ECS, this Award is special to me. In this presentation I will talk about three different types of electrolyte systems that we have addressed over the years.One of my earlier projects was researching the performance factors of the all iron flow battery. This approach to energy storage was actually a direct outcome of Professor De Nora’s push to develop a large flow battery at the Diamond Shamrock Corporation. The effort was driven by the need for large-scale energy storage for power plant load leveling. Of course, the motivation of the all iron approach was that it is a simple redox system with the prospective for low cost and sustainable reactants. We published our experimental findings in 1981 in JES1. After a long hiatus of work on this system, it started to become of interest again about a decade ago with labs and companies pursuing this chemistry. We then introduced the concept of a slurry electrode for the all-iron flow battery, and pursued its development. The slurry electrode/electrolyte system facilitated the design to separate power capacity from energy capacity. I will talk about some of the key experimental observations and analysis with the slurry electrode, and the future prospects for an all-iron slurry energy storage system.The second system I will discuss is the proton conducting high temperature polymer membrane of PBI doped with phosphoric acid, which we introduced in the early 1990s2. Similar to the discovery of the DSA electrode invented by Henri Beer (1980 Vittorio De Nora Awardee) which De Nora is credited for commercializing, the PBI/PA system is an example of chance discovery. The PBI/PA discovery motivated several decades of research, and now is a commercial product. I will tell the story about the origin of the concept (with Professor Ernest Yeager, the 1995 Vittorio De Nora Awardee) and its discovery, and then summarize some of the advances made over the years.Finally, I will talk about the most recent research on electrolytes that I am involved in. There has been a long standing need for advancing the fundamental science for the discovery of new electrolytes for electrochemical energy storage systems including redox flow batteries and electrochemical capacitors; and also for electrochemical processes and devices such as energy conversion, metal deposition, separations and sensors. For example, by specifically designing new electrolytes with higher concentrations of electrochemically active species, low flammability and tunable transport properties, substantial improvements could be realized in (i) energy and power density, (ii) safety and reductions in environmental impact, and (iii) performance of energy storage systems. Our current research focus is on developing the fundamental underpinnings of three materials approaches: deep eutectic solvents (DESs), microemulsions, and nanoparticle organic hybrid materials (NOHMS). I will describe these three materials systems which have molecular and messo-scale structure that influence transport and interfacial properties. The goal of our activity is to develop an understanding of (i) structure-property relationships, (ii) transport mechanisms, (iii) interfacial electrode-electrolyte structure and its evolution, (iv) electron and ion transfer reactions in these structured materials systems, and (v) how these structures and properties can be tailored at the atomistic level to advance performance in electrochemical energy storage systems and electrochemical processes. In order to accomplish this goal, we have assembled a research team consisting of key researchers, students, and postdocs from seven academic institutions and one national lab, all having unique and specialized expertise and facilities. This team forms the DOE Emerging Frontier Research Center on Breakthrough Electrolytes for Energy Storage (EFRC-BEES)3. In this talk, I will address a couple of the approaches we are taking and what we learned about these materials systems as electrolytes4.Finally, I would like to thank the many colleagues and friends who have collaborated with and supported me over the past four to five decades, and especially all of my students and postdocs that I had the pleasure to work with.