(4ew) Solving the Next Generation of Transport Challenges in Electrochemically Mediated Processes

The vision for my future research program is to enable the next generation of electrochemically mediated processes by developing a set of tools and methods to understand and solve transport challenges inherent to these new systems. Electrochemical systems subsist of many complex transport processes that must be balanced to achieve high efficiency and good performance. Within the electrolyte, the motion of charged species is crucial to achieving high current, while novel systems that incorporate gas, such as carbon capture, depend on the transport of that gas to the active species or site. My interest in research thus far has been motivated by a desire to understand, demonstrate, and explain fundamental transport concepts in complicated electrochemical systems in an accessible manner to enable improved efficiency, safety, and overall performance. As the global availability of inexpensive renewable electricity enables the reinvention of many processes with electrochemistry, exciting transport questions involving these new electrochemical systems will arise. My group will be well positioned to tackle these new areas.

Emerging challenges that we will begin to address include understanding how novel cell designs and nonaqueous or polymeric electrolytes can overcome transport issues in electrochemically mediated carbon capture. Simultaneously, using related characterization methods, we will study ion transport in nonaqueous oligomeric polyelectrolyte solutions to gain further fundamental understanding in this largely unexplored area, and to examine their use in batteries and other electrochemical devices. My combined background in batteries, electrochemistry, polymers, and carbon capture will provide a unique angle to tackle these problems.

Postdoctoral Research: Electrochemically Mediated Carbon Capture

Massachusetts Institute of Technology with Professor T. Alan Hatton

In my postdoctoral work, I have sought to address a variety of transport challenges in electrochemically mediated carbon capture, a process that relies on high volume gas - liquid contact on top of salt transport and electrochemical reactions. Working closely with colleagues in the Hatton Lab, we demonstrated the potential of novel liquid redox molecules to avoid substantial water or gas distribution requirements that are inherent to other electrochemically mediated techniques. Further, making use of fundamental chemical engineering principles, we built a nondimensional model of large area gas contacting processes for direct air capture of CO₂ that could be tied to electrochemical regeneration methods. In a final, ongoing project combining finite element modeling with electrochemical and analytical techniques, we have examined cell geometries that would enable much higher surface area for gas – liquid contact inside of the electrochemical cell through use of hollow fibers and novel sorbent formulations.

Graduate Research: High Transference Number Polymer – Based Electrolytes

University of California, Berkeley with Professor Bryan McCloskey

My graduate work focused on the synthesis and characterization of polymer – based high transference number electrolytes that limit the formation of concentration gradients in lithium batteries. In a lithium-ion battery under high-rate conditions (fast charge or discharge), concentration gradients within the electrolyte can be exacerbated to the point that the active species in solution, lithium ions, are depleted within porous electrodes. By modulating the relative motion of the lithium and counterions (characterized by the transference number), the magnitude of these gradients can be attenuated. Leveraging a variety of electrochemical and analytical techniques at UC Berkeley and Lawrence Berkeley National Lab, my project examined ion transport behavior in our synthesized dry polymer electrolytes and nonaqueous polyelectrolyte solutions. Within the field of dry, solid polymer electrolytes, I illuminated a fundamental trade-off between polymer segmental motion and ion solubility, and the unexpected manifestation of this trade-off in a common analytical approach. The rich physics involved in the motion of counterions around solvated polyelectrolytes, and particularly short-chain polyelectrolytes, are relatively unexplored in nonaqueous solutions. During my project, I demonstrated that the solvent dielectric constant was a poor predictor of solution performance, despite frequent use in traditional polyelectrolyte theory. In a later work, I found that enhanced solvation of the polymer backbone could lead to reduced lithium-ion motion in concentrated oligomeric polyelectrolyte solutions. Finally, seeking to translate our fundamental investigations to practice, I established that the addition of crown ethers could promote ion dissociation and enable battery operation with a simple sulfonated polymer in traditional battery solvents.

Teaching Interests

Throughout my academic career I have always greatly enjoyed teaching, finding motivation and energy by turning to younger students and trainees. As a Professor, I would be particularly interested in teaching and developing courses focused on transport processes, but would happily teach other fundamental chemical engineering subjects or subjects in electrochemistry. Beyond the core subjects and those related to my research, as an undergraduate I greatly benefitted from training in applied statistics, polymer engineering, and introductions to Matlab, Python, and Excel. While not as directly related to my planned research activities, these are courses which I believe are incredibly foundational to young engineers and I would be excited to contribute to them or assist in building them into new courses.

I have experience in most levels of teaching at the college level within chemical engineering. In my undergraduate degree, I served as one of two primary teaching assistants in Thermodynamics, and again in Separations and Mass Transfer. During my graduate career I assisted in teaching the introductory chemical engineering course, the first semester of undergraduate transport processes (comprising momentum and heat transport) and served as graduate student instructor for the graduate transport class. As recognition for my commitment to excellence in teaching, I received both the outstanding graduate student instructor award and the Dow Award for excellence in teaching. I am passionate about trying new methods of instruction, particularly leveraging technology to reach individuals in large classes, and have always dedicated significant time to ensuring my students understood and cared about the material in each class. I strive to create respectful and inclusive environments and look forward to implementing new teaching methods towards empowering the next generation.

Commitment to Leadership and Inclusivity

During my graduate and postdoctoral career, I came to recognize my own privilege in science and society and have continuously strived to dedicate time towards improving the climate for all. As a graduate student I served as co-president of our graduate student organization and as a representative to the campus student government, while as a postdoc I helped to revive and lead the Postdoctoral Association’s Diversity, Equity, and Inclusion committee. I have advocated to improve postdoc hiring practices, dedicated time to MIT Committees like Task Force 2021, and worked to gain official recognition for the postdoc women in research group (POWER), a newly formed Black Postdoc Group (BPG), and the LGBTQ+ postdoc group, qtPhD’s.

I look forward to continuing to serve and advocate during my time as a professor, using my platform and privilege to allow students and others to focus on their interests and find a sense of belonging that leads them to make even stronger contributions to their fields.

Selected Awards

2020, Intelligence Community Postdoctoral Fellowship

2018, Finalist, Excellence in Graduate Polymer Research (AIChE)

2016, DOW Excellence in Teaching Award at UC Berkeley

2016, Outstanding Graduate Student Instructor

2014, Marilyn and Howard L. Anseth Outstanding Undergraduate Research Award

Selected Publications

(1) Diederichsen, K.M.*; Liu, Y.*; Seo, H.; Ozbek, N.; Hatton T.A.; Towards Solvent-Free Continuous-Flow Electrochemically Mediated Carbon Capture with High Concentration Quinone Chemistry. Submitted.

(2) Diederichsen, K. M.; McCloskey, B. D. Electrolyte Additives to Enable Nonaqueous Polyelectrolyte Solutions for Lithium-Ion Batteries. Mol. Syst. Des. Eng. 2020, 5, 91–96.

(3) Diederichsen, K. M.; Terrell, R. C.; McCloskey, B. D. Counterion Transport and Transference Number in Aqueous and Nonaqueous Short-Chain Polyelectrolyte Solutions. J. Phys. Chem. B 2019, 123, 10858–10867.

(4) Diederichsen, K. M.; Fong, K. D.; Terrell, R. C.; Persson, K. A.; McCloskey, B. D. Investigation of Solvent Type and Salt Addition in High Transference Number Nonaqueous Polyelectrolyte Solutions for Lithium-Ion Batteries. Macromolecules. 2018, 51, 8761–8771.

(5) Diederichsen, K. M.; McShane, E. J.; McCloskey, B. D. Promising Routes to a High Li + Transference Number Electrolyte for Lithium-Ion Batteries. ACS Energy Letters. 2017, 2, 2563–2575.

(6) Diederichsen, K. M.; Buss, H. G.; McCloskey, B. D. The Compensation Effect in the Vogel–Tammann–Fulcher (VTF) Equation for Polymer-Based Electrolytes. Macromolecules 2017, 50, 3831–3840.

(7) Diederichsen, K. M.; Brow, R. R.; Stoykovich, M. P. Percolating Transport and the Conductive Scaling Relationship in Lamellar Block Copolymers under Confinement. ACS Nano 2015, 9, 2465–2476.