(6dy) Electrolyte Design and Fundamental Studies of Battery Systems for Better Energy Storage Media

My research group will be at the interface of chemical engineering and chemistry. Using experimental and computational tools, we will design and synthesize new electrolytes, study ionic transport processes, and probe the kinetics of electrochemical reactions in multiple battery systems.

Motivation

Increased use of portable electronics, and the need to move from fossil fuels to intermittent renewable energy technologies have generated intense interest in energy storage media such as batteries. Lithium-ion (Li-ion) batteries are the most energy-dense batteries commercially available. They have dominated the portable electronic market, helped spur the growth (and expected boom) in electric vehicles, and are envisioned as an integral part of the future grid that is dependent on solar and wind. However, current Li-ion batteries have reached their capacity limitations, are expensive, and are dangerous.

Batteries can be broken down into roughly three components: cathode, electrolyte, and anode. Current Li-ion battery cathodes use transition metal oxides with limited capacities (e.g., LiCoO₂ with 145 mAh/g) and whose cost scales with the cobalt content. Secondly, electrolytes currently use carbonate-based solvents that are volatile and flammable; responsible for high fire risks of these batteries. In addition to cost and safety concerns, the choice of anode (graphite) and the heavy intercalation cathodes limit the energy densities that can be obtained. Therefore, researchers have focused on shifting from a graphite anode (372 mAh/g) to lithium metal (3860 mAh/g); designing electrolytes that are safer and with a wider electrochemical stability window; and cathodes that do not depend on intercalation chemistry but conversion reactions (oxygen and sulfur reduction).

Research interests

1. Design new small molecule and polymer electrolytes

All rechargeable battery systems (lithium-ion, lithium-metal, lithium sulfur etc.) need better electrolytes. Higher energy densities can be obtained in these battery chemistries if the electrolytes were stable across a wider electrochemical range, had higher ionic conductivities, were more selective (preferential solubility of lithium salt compared to the electrochemically active specie such as sulfur), and safer. My research interest involves the design, synthesis, and characterization of new electrolytes (small molecules and polymers). Furthermore, density functional theory (DFT) and molecular dynamics (MD) tools will be used to obtain structure-property relationships, better understand transport properties in these systems, and study the functionalities responsible for ionic conduction.

2. Develop new lithium and multivalent-ion battery chemistries

My lab will study lithium-based battery chemistries such as lithium metal and lithium-sulfur, and perform fundamental electrochemical studies on multivalent ion chemistries such as magnesium to better understand magnesium deposition and stripping in non-Grignard-based electrolytes.

3. Design in situ tools to better study batteries during operation in real world settings

Current battery management systems depend on simple measurements of temperature and pressure to develop their models to predict the state of health and lifetime of battery cells. We will design sensors that can be inserted into batteries to better monitor the state and health of batteries during real world use.

Doctoral research (PI: Paula Hammond, MIT)

My PhD work focused on a new class of batteries – lithium-air – with theoretical energy densities at least three times that of Li-ion (1–6). Conventional lithium-air batteries use lithium metal as the anode, an ether based electrolyte, and oxygen as the active specie in the cathode. Despite the high energy density promise, Li-air batteries have poor battery capacity retention, and pose a greater safety hazard compared to Li-ion because of the presence of oxygen. Hence, my work explored nonflammable polymer electrolytes that can be used for lithium-air batteries. I studied polymer stability in the presence of highly reactive reduced oxygen species (such as Li₂O₂), and developed selection rules for designing stable polymers for lithium-air use (3). Using these rules, we fabricated gel polymer electrolytes that controlled the oxygen reduction process, and yielded a previously unreported 1 mol e⁻/mol O₂ process; showing that careful selection of the gel polymer electrolyte can finely tune the battery chemistry (4).

Postdoctoral research (PI: Zhenan Bao, Stanford)

During my PhD, I obtained skills in electrochemistry, electrolyte design, spectroscopic characterization, battery fabrication among others. However, my postdoctoral work has delved more into the synthesis and characterization of new electrolyte compounds. Furthermore, my work incorporates MD/DFT-based tools to study the molecular properties, lithium-ion transport, and kinetics of sulfur reduction in these new electrolytes.

Teaching Interests:

Teaching interests

I love to teach and mentor, and have actively sought these opportunities. I am interested in teaching chemical engineering reaction kinetics, thermodynamics, fundamentals of polymer science, and elective graduate courses (e.g., electrochemistry). During my graduate career, I was an instructor for an MIT undergraduate course “Polymer Science Laboratory” where I taught polymer synthesis, characterization, theory and applications. I have also tutored math and chemistry classes at a local high school, and have mentored multiple undergraduates pursuing research under my guidance. On behalf of MIT, I attended multiple conferences and events to recruit minority engineers to pursue graduate studies.

Selected publications

1. Chibueze V. Amanchukwu, Hao-Hsun Chang, and Paula T. Hammond. “Influence of Ammonium Salts on Discharge and Charge of Li–O₂” J. Phys. Chem. C. 2017, 121, 17671-17681.
2. Michal Tulodziecki, Graham M. Leverick, Chibueze V. Amanchukwu, Yu Katayama, David G. Kwabi, Fanny Barde, Paula T. Hammond, and Yang Shao-Horn. “The Role of Iodide on the Formation of Lithium Hydroxide in Lithium-Oxygen Batteries.” Energy Environ. Sci. 2017, 10, 1828-1842.
3. Chibueze V. Amanchukwu, Jonathon R. Harding, Yang Shao-Horn, and Paula T. Hammond. “Understanding the chemical stability of polymers for lithium-air batteries.” Mater. 2015, 27, 550-561
4. Chibueze V. Amanchukwu, Hao-Hsun Chang, Magali Gauthier, Shuting Feng, Thomas P. Batcho, and Paula T. Hammond. “One electron process in a gel polymer electrolyte Li-O₂” Chem. Mater. 2016, 28, 7167-7177.
5. Chibueze V. Amanchukwu, Magali Gauthier, Thomas P. Batcho, Chanez Symister, Yang Shao-Horn, Julio D’Arcy, and Paula T. Hammond. “Evaluation and stability of PEDOT electroactive polymer electrodes for Li-O₂” J. Phys. Chem. Lett. 2016, 7, 3770-3775
6. Jonathon R. Harding, Chibueze V. Amanchukwu, Paula T. Hammond, and Yang Shao-Horn. “Instability of Polyethylene Oxide upon oxidation in Lithium-Air Batteries.” J. Phys. Chem. C. 2015, 119, 6947-6955.