(2ak) Resisting Dendrites in Lithium Batteries, One Pinhole at a Time

For humanity to successfully transition from fossil fuels, the mismatch in the demand and supply of renewable energy must be addressed by reliable, high energy storage systems. One promising energy storage system is the lithium metal battery (LMB), owing to the high gravimetric capacity of lithium (3860 mAh/g). The potential gain in volumetric and gravimetric energy density offered by LMBs could usurp today’s lithium-ion battery technology and revolutionize energy storage. However, the lifetime of LMBs is hindered by morphological instabilities experienced during the electrodeposition of lithium.

Modifications of the solid electrolyte interphase (SEI) and electrolyte are the most common strategies for improving lithium metal morphology. However, electrolyte and SEI engineering are often tedious, based on trial and error, and insufficient for enhancing lithium electrodeposition. My thesis work is focused on developing SEI and electrolyte-independent battery architectures for understanding and controlling the electrodeposition of lithium metal. Specifically, by using atomic layer deposition (ALD) to grow thin films on the copper current collector of lithium metal batteries, I have transformed conventional wisdom by showing that the electrodeposition of lithium metal occurs atop, rather than beneath ALD-grown films. Based on this new lithium deposition architecture, I have discovered and demonstrated the efficacy of three new principles that impact lithium deposition and improve lithium metal batteries, namely:

1. I have demonstrated that metal oxides with lithium reaction potentials above Li/Li⁺ redox potential can alloy with Li⁺ ions to form electrodeposition surfaces that favor the coalescence of low surface area Li particles.
2. Second, I have introduced a new method for controlling the solid electrolyte interphase (SEI) in lithium metal batteries by demonstrating that anions adsorb preferentially atop Lewis acidic current collectors, resulting in the preferential decomposition of anions in battery electrolytes.
3. Third, I have revealed that electrical resistance of thin film metal oxides can promote lateral growth of Li particles by inducing preferential Li nucleation at pinhole sites and promoting radial diffusion-dominated growth of Li.

My meet the faculty poster presentation at AiChE will cover all the aforementioned with emphasis on the third discovery - the control of lithium morphology using electrical resistance. By modifying the current collector with atomic layer deposited (ALD) thin films of ZnO, SnO₂, and Al₂O₃, we show that lithium deposits atop, rather than beneath, the thin films, resulting in changes in lithium morphology and battery performance that are strongly dependent on the electrical resistance of the ALD films. The results show that low resistance copper modification films like SnO₂ and ZnO provide numerous sites for lithium nucleation and promote the formation of high surface area (fast electrolyte consuming) lithium deposits, while the highly resistive Al₂O₃-modified copper reduces the available sites for lithium nucleation and promotes the formation of low surface area (slow electrolyte consuming) clusters of lithium deposits.

We propose and demonstrate the first recorded mechanism for the connection between electrical resistance and lithium growth - we propose that, in resistive substrates, lithium metal nucleates atop only pinhole sites, then grows laterally by the radial diffusion of lithium ions from the electrolyte. We prove this mechanism analytically, using diffusion controlled current equations, and experimentally by introducing patterned pinholes into a resistive, pinhole-free substrate. We generalize the concept of resistance-controlled morphology and demonstrate high battery performance in three distinct classes of electrolytes, culminating in anode-free pouch cells that retain 60% of their initial discharge capacity after 100 cycles. This work presents a new approach for understanding the electrodeposition of lithium and tuning the performance of lithium metal batteries.

My faculty research work will be based on the combination of surface science and data science for solving energy-related challenges. More specifically, my group will work on using the electrodeposition platform that I developed during my PhD to understand the nucleation, coalescence, and growth of reactive metals in promising battery chemistries. In addition, my group will leverage existing, and design new data science algorithms for accelerating the discovery of new thin films that control the growth of reactive metals and new electrolytes that enable promising battery chemistries.

Teaching interests

When I was much younger, I was fortunate to have teachers that believed in me, and spurred by their vote of confidence, I strongly believed that I could surmount any academic challenge. I have come to understand that academic learning, like most things, entails the management of conceptual chunks of information and the psychological wiring to approach problems with enthusiasm. Equipped with these experiences, I help my students make connections between theory and practice by breaking down concepts into manageable pieces and encouraging them to believe in themselves.

To teach effectively, I have found that it is essential to find multiple ways to help students engage with the class material some of which include using visual aids to improve retention, using analogies to strengthen understanding, and solving concrete problems to build intuition. In addition to helping students understand the material, I also invest a lot of time in knowing how students misunderstand the material; there are more ways to misunderstand than there are to understand, so I always find it helpful to think of ways that concepts can be misconstrued and how problems can be approached incorrectly. By understanding these misconceptions quickly when talking to students, I have observed that they feel supported by knowing that their thought process can be fixed with small tweaks. Finally, I find ways to reference the work of Psychology Professor, Carole Dweck, by encouraging students to adopt a growth mindset especially when learning challenging concepts – I remind them that the intuition for problem solving is built by repeated and careful practice. Using these techniques, I have taught classes like kinetics and reactor design, process control and dynamics, and process optimization, in which I felt immense joy from seeing the glow in a student’s eyes when they understood something, figured out the solution to a problem, and even explained concepts to their classmates. I have also been fortunate to receive kind feedback from my student in the form of positive evaluations and nominations for teaching awards. Outside of the classroom, I also find ways to teach and mentor students across all cadres of life, from prospective graduate students who I guide in areas of graduate school applications personally and through two of my nonprofit organizations (WOKE foundation and Association of Nigerian Scholars in America), to current graduate students within and outside my PhD group who I teach concepts of surface science, electrochemistry, and data science.

All my scholarly experiences have equipped me to teach any chemical engineering classes in an undergraduate curriculum and graduate classes such as applied mathematics in chemical engineering processes, advanced spectroscopy in chemical engineering, advanced chemical and reaction kinetics, statistical thermodynamics, and advanced heat and mass transfer. In addition, drawing from my expertise outside of chemical engineering, I would be honored to develop new curriculum in exciting and scientifically crucial areas such as the structure and reactivity of solid surfaces, introduction to machine learning for chemical engineers, new methods in thin film synthesis, and the electrochemical principles of battery operation. I feel fortunate to be in a position to groom the next generation of scientists and I look forward to mentoring and teaching tomorrow’s leaders.