Power to the Plasma
Putting theory into practice to unlock the secrets of ionic liquids
Room-temperature ionic liquids (RTILs) have the potential to revolutionize a wide range of industrial applications—including the design of ultrafast rechargeable batteries—thanks to their safety and stability at relatively high voltages. These mixtures of charged molecules—“effectively condensed plasma”—are efficient solvents and excellent conductors of electricity. But despite recent breakthroughs in aluminum-ion batteries and other applications, these “designer solvents” remain woefully misunderstood.
Dr. Martin Z. Bazant, professor of chemical engineering and mathematics at MIT, has harbored a passion for electrochemical systems throughout his career. He remains frustrated, however, by the insufficiency of current models to adequately encompass RTILs. With the support of a Bose Research Grant, Dr. Bazant seeks to develop the first microscopic theories of ion transport and reaction kinetics in ionic liquids using a three-pronged approach that combines theory, simulation, and experimentation. Gaining a more thorough understanding of the properties and behavior of these unique mixtures will ultimately have wide-ranging impact beyond metal batteries.
Explaining the inexplicable
In many respects, RTILs are an enigmatic topic of research. In an ionic liquid, the ions themselves form the liquid, rather than being dissolved in water or another solvent. They have a low volatility, meaning that there is less risk of contamination in the event the liquid is released; for this reason, many RTILs have been developed as “green” alternatives to toxic organic solvents used in synthetic chemistry. But they also exhibit slow diffusion and reaction kinetics, which have thus far limited their use in batteries.
In an effort to better conceive of how RTILs work, Dr. Bazant’s research plan combines molecular simulation, theory, and experimentation under one roof—the first such comprehensive undertaking of its kind. This three-part approach could have a transformative impact on our understanding of RTILs through the development of design principles to guide the choice of ions and additives for RTILs, and the creation of new mathematical models that encapsulate the mixtures’ complicated electrostatic properties.
To go beyond existing modeling paradigms, I have long felt that a combined theoretical, computational, and experimental approach is needed, and this is what the Bose Research Grant could enable.”
The battery of the future
Dr. Bazant’s research is largely theoretical in its focus, making his project unlikely to receive funding from traditional sources—but ideally suited for a Bose Research Grant. Through a brute force process of trial and error, a traditional research center could potentially develop and commercialize a faster, more efficient rechargeable battery. But with a more patient, systematic approach, Dr. Bazant’s findings can lay the groundwork for a more complex model of RTILs, have major ramifications across a variety of applications, and contribute significantly to the field of electrochemistry as a whole.
Dr. Bazant cites Professor Bose’s pioneering research on the simulation of sound in buildings—which ultimately achieved unprecedented and unexpected success—as an inspiration for his own research. If successful, his work could effect substantial advancements not only in batteries, but also supercapacitors, actuators, and green synthetic chemistry.
New understanding yields a larger design space
Through molecular simulation, Dr. Bazant and his team are now investigating the effects of the structures forming in RTILs, which is revealing more complex patterns of charges occurring within the solvent species. “We’re breaking new ground, learning that these structures have an outsize impact on the viscosity, transport capability, and general stability of the ions,” says Dr. Bazant. “There’s still a long way to go, but this knowledge will help us to one day create batteries with high electrical stability that maintain a high transport rate.”
Initially, his team didn’t have much experience conducting molecular simulations, and they had to build their capability to do so relatively quickly. Reflecting on this challenge, Dr. Bazant expresses that overcoming such obstacles feel emblematic of his academic journey. “I received my Ph.D. in physics, and taught mathematics at MIT before joining the Department of Chemical Engineering. I’ve always tried to integrate different methods and skills to achieve a more unified approach to science,” he says. “This project takes that even journey further for me and my team, and is now leading to new understanding and opportunities that were unexpected at the onset of this Fellowship.”