Some Thoughts on Transport in and Design of Li-Ion Cathodes
Professor Alan West, Columbia Electrochemical Energy Center, Department of Chemical Engineering, Columbia University
Batteries are complex, with important phenomena arising from multiple length scales. Advances thus require multiscale experimental inquiries, and mathematical models, including multiscale models, may be employed to design, analyze and integrate studies. In early-stage research efforts, close collaboration with experimental efforts may result both in dramatically improved model fidelity and in more optimal utilization of experimental resources. We present approaches to augment physics-based models of Li-ion cathodes with statistical methodologies. Several examples are illustrated.
Alan West received his PhD in Chemical Engineering from the University of California and his BS from Case Western Reserve University. He is the co-director of the Columbia Electrochemical Energy Center and is the Samuel Ruben-Peter G. Viele Professor of Electrochemistry, with appointments in the Department of Chemical Engineering and the Department of Earth and Environmental Engineering. His research interests include batteries, electrochemical synthesis, and fuel cells.
Enabling Energy Dense Lithium Battery Anodes with Thin Film Electrolytes
Professor Wyatt Tenhaeff, Department of Chemical Engineering, University of Rochester
Lithium ion batteries (LIBs) are essential to modern daily life, powering smartphones, laptop/tablet computers, and increasingly electric vehicles. In the nearly 30 years since their commercial introduction, the graphite anode of LIBs has not substantially changed. Graphite reversibly hosts Li+ through intercalation/deintercalation and forms a stable solid-electrolyte interface through electrochemical reduction of the liquid electrolyte – critical to the reversible cycling of LIBs. However, graphite anodes possess a relatively low specific capacity (372 mAh g-1). Next-generation Si and Li metal anodes offer an order-of-magnitude enhancement in specific capacity but suffer from several fundamental challenges.
This presentation demonstrates how solid electrolyte thin films can be employed to address these challenges in Li metal and Si anodes, enabling next generation energy-dense batteries. For Li metal anodes, a solid electrolyte interfacial layer consisting of a lithium phosphorous oxynitride (Lipon) thin film electrolyte coupled to a gold-alloying interlayer was developed and shown to promote the electrodeposition of smooth, homogeneous, mirror-like Li metal morphologies. The effectiveness and integrity of the Lipon protective layer was assessed using in operando impedance spectroscopy and ex situ SEM/EDS characterization. Strategies to incorporate ultrathin layers of Lipon (~50 nm thick) into conventional lithium ion battery cell designs will also be discussed. A significant challenge with Si anodes is the >300% volume expansion, resulting in unstable passivation of the electrode surface. Conformal nanoscale polymer films were synthesized as artificial solid electrolyte interface (SEI) layers for Si using initiated chemical vapor deposition (iCVD). Ultrathin films on the order of 25 nm thick were shown to improve specific capacity retention, coulombic efficiency, and rate capability, which is attributed to a mediation of the electrolyte reduction processes. This presentation discusses the progress to date on these two critical anode materials and highlights outstanding questions and engineering challenges for the future.
Wyatt E. Tenhaeff is an Associate Professor in the Department of Chemical Engineering at the University of Rochester. He received a B.S. in Chemical Engineering from Oregon State University in 2004 and Ph.D. in Chemical Engineering from the Massachusetts Institute of Technology in 2009, specializing in vapor deposition of polymer thin films. Following his Ph.D., Dr. Tenhaeff received a Weinberg Fellowship at Oak Ridge National Laboratory, joining the thin film battery group. Following the fellowship, he transitioned to a Staff Scientist position. Then in 2013, he began his academic career at the University of Rochester. His current research interests are energy storage, solid state lithium metal batteries, and thin film deposition technologies. He has received several recognitions including an R&D 100 award for his work on safe impact resistant electrolytes for lithium ion batteries, the Curtis Award for Nontenured Faculty Teaching at the University of Rochester, and the NSF CAREER award.
The Wright Way to Get to Zero Emissions in the Aviation Industry
Jeff Engler, Founder & CEO, Wright Electric
Wright Electric is a leader in the future of sustainable, lower emissions air travel; building electric planes that lower fuel cost, noise, emissions, and runway takeoff time. Wright's flagship airplane under development is the Wright 1, a 186-seat airliner with 800 mile range, targeting entry into service in 2030. Wright has engineering contracts with NASA and the US Department of Energy and partners with airlines such as easyJet, the third largest short-haul airline in the world. Wright is funded by Y Combinator, venture funds, and family offices.
Jeff Engler is the Founder and CEO of Wright Electric. He has led the idea from YCombinator to successful testing of a belt-driven drivetrain for a hybrid-electric crop duster. He previously co-founded Podimetrics, a regulated medical device company.
Phase transformations in high-capacity anodes for K-ion batteries: a solid-state NMR study
Drew Ells, Columbia Chemical Engineering PhD Student
K-ion batteries have recently attracted interest due to their potential to offer a cheaper, high-rate alternative to Li-ion batteries. However, the larger atomic size of K compared to Li requires detailed evaluation of possible electrode materials that allow reversible potassiation/depotassiation. Tin phosphide anodes offer high capacities for use in K-ion batteries and may partially mitigate the volume expansion associated with alloying reactions by forming ternary intermediates and/or undergoing phase separation. Using solid-state nuclear magnetic resonance (SSNMR) techniques, we conducted a detailed characterization of tin phosphide (de)potassiation and suggest possible failure mechanisms.
Use physics-based modeling to understand the transport inside Li-ion batteries and to guide the cell optimization
Zeyu Hui, Columbia Chemical Engineering PhD Student
Battery electrodes are complex multiscale, multifunctional materials. The length scale at which the dominant impedance arises may be difficult to determine even with the most advanced experimental characterization efforts, and thus modeling can play an important role in analysis. Discharge and voltage relaxation curves, interrogated with theory, are used to distinguish between transport impedance that arise on the scale of the active crystal and on the scale of agglomerates (secondary particles) comprised of nanoscale crystals. Model-selection algorithms are applied to determine that the agglomerate scale is dominant in the Li(Ni0.33Mn0.33Co0.33)O2 electrode studied here.
Then physics-based models are optimized by varying porosity and mass loading to achieve maximum energy density. Although transport losses occur on both the electrode and particle scales, the electrode-scale optimal design is independent of the smaller scale properties. Electrode-scale properties such as tortuosity, electrolyte concentration, and Li-ion diffusion coefficient all impact optimal design. Optimal material loadings and porosity can be readily correlated to account for these physical and architectural properties, as demonstrated for four distinct electrode materials. Correlations are also in agreement with prior optimization results in the literature. The results presented here show that with a re-scaling of the current rate, the optimal results follow a general design rule that is captured in a convenient correlation.
Understanding Li+ Transport in Polymer Electrolytes at the Kuhn Scale with Coarse-Grained Molecular Dynamics and Broadband Dielectric Spectroscopy
Marshall Tekell, Columbia Chemical Engineering PhD Candidate
In order to study the length (~102 nm) and time (~102 ns) scales corresponding to Li+ diffusion in nanostructured solid polymer electrolytes, new coarse-grained models that (1) capture local electrostatic interactions between Li+ and the polymer chain (r ~ 2-5 Å) and (2) nanocomposite structural features on the polymer chain length scale (〈𝑅𝑔〉 ~101−2 Å) are required. In this work, we report the structure and dynamics of coarse-grained molecular dynamics (CG-MD) simulation of a Stockmayer polymer electrolyte, an adaptation of the Kremer-Grest bead-spring polymer at the Kuhn scale, wherein ideal dipoles are embedded in each bead. In agreement with previous work, we find that the ionic conductivity of the electrolyte is maximized at intermediate Stockmayer polymer polarity, 𝜇, and the Li+-PEO Lennard-Jones length, 𝜎𝐿𝑖−𝑃𝐸𝑂, due to the convolution of electrolyte coordination structure and the short (< 1 ns) and long (> 1 ns) dynamics of all three electrolyte components. We then compare the ionic conductivity and segmental dynamics of the polymer electrolyte simulation to the PEO:LiTFSI (EO:Li = 10:1) experimental system. Using broadband dielectric spectroscopy (BDS) and equivalent circuit modeling, we show that the conductivity and 𝛼-relaxation are linked via the Nernst-Einstein equation at the Kuhn scale. These results indicate that the structure and dynamics of fully atomistic electrolyte models are well-approximated in this coarse-grained model that should be useful to study the effect of ceramic surfaces and nanoconfinement.
Concentration Gradients and Hot-Spots Induced by Flow of Current in Polymer Electrolytes
Professor Nitash P. Balsara, Chemical and Biomolecular Engineering Department University of California, Berkeley and Materials Sciences Division Lawrence Berkeley National Laboratory
The need for creating safe electrolytes for lithium batteries is significant given the continued safety problems associated with current lithium-ion batteries. Nonflammable polymer electrolytes offer a possible solution but the rate of lithium-ion transport is too low for practical applications. In this talk, I will discuss some of the fundamental factors that limit ion transport in polymers. In all electrolytes, the current generated at steady state is governed by the applied potential. This relationship, which one might call a modified Ohm’s Law, depends on Stefan-Maxwell diffusion coefficients. In the first part of my talk, we show experimental results indicating that these diffusion coefficients are negative over a substantial salt concentration range in polymer electrolytes. We use these diffusion coefficients to analyze and predict battery performance. A crucial ingredient in the analysis is a “condition” that my PhD student Danielle Pesko arrived at; I call this the Pesko condition. In the second part of my talk, I examine the passage of current through a nanostructured block copolymer. Salt concentration gradients caused by the passage of current cause order-order and order-disorder phase transitions that are taken as indicators of the local salt concentration in the cell. It enables the detection of salt concentration hot spots, regions where the local salt concentration is much higher than that in the surrounding regions. We discuss the implications of this phenomenon in the context of transport limitations that may arise generally when current flows through heterogeneous media.
Nitash P. Balsara is a chemical engineer with a bachelor's degree from the Indian Institute of Technology in Kanpur, India in 1982. His graduate education began with a master's degree from Clarkson University. This was followed by PhD from RPI. After 2 post-docs at the University of Minnesota and Exxon, he joined the faculty of Department of Chemical Engineering at Polytechnic University in Brooklyn. In 2000 he accepted the job that he currently holds: a joint appointment as professor of Chemical Engineering at the University of California, Berkeley, where is currently the Charles W. Tobias Professor of Electrochemistry, and faculty scientist at Lawrence Berkeley National Laboratory. He has managed to hang on to both jobs. Along with his students and collaborators, he cofounded two battery start-ups, Seeo, Inc., and Blue Current.
Silicon Oxide Encapsulated Ruthenium Oxide as an Improved Electrocatalyst for the Oxygen Evolution Reaction in Acidic Media
Dr. Amanda Baxter, Earth Institute Postdoctoral Fellow, Columbia University
Ruthenium oxide nanoparticles are among the most highly active electrocatalysts for the oxygen evolution reaction (OER) in acidic media. However, they are highly unstable, which limits their practical use. Herein, we report that encapsulation of ruthenium oxide (RuO2) nanoparticles by a silicon oxide (SiOx) overlayer improves the OER performance in 0.5 M H2SO4 compared to bare, uncoated RuO2 electrocatalysts. SiOx encapsulated RuO2 (SiOx|RuO2) exhibits an improved electrochemically active surface area and a 10-fold stability enhancement during chronopotentiometry compared to bare RuO2. X-ray photoelectron spectroscopy and Energy-dispersive X-ray spectroscopy (EDS) confirm the presence of the SiOx overlayer while EDS suggests that the SiOx|RuO2 has a more homogeneous catalyst layer composition compared to bare RuO2.
Amanda grew up in Southern California and Colorado. She graduated from McPherson College with a B.S. in chemistry. Then she completed her Ph.D. in chemistry at the University of Southern California. Her Ph.D. research focused on fluorine chemistry and fuel cells. Now an Earth Institute Postdoctoral Fellow, Amanda is exploring new membrane coated electrocatalysts for electrolysis devices. In her free time Amanda enjoys practicing yoga, running and helping her dog live his best life.
1/18/19: Prof. Byungha Shin, KAIST
1/25/19: Nick Brady/Jack Davis, Ph.D. Student at Columbia
2/15/19: Daniel Esposito, Solar Fuels Engineering Lab at Columbia
3/1/19: Jake Russell/Anna Dorfi, Ph.D. Student at Columbia
3/15/19: Alex Couzis, CCNY/Urban Electric Power
4/26/19: Jon Vardner/Steven Denny, Ph.D. Student at Columbia
5/10/19: Qian Cheng/Brian Tackett, Ph.D. Student at Columbia
9/20/19: Prof. Dan Steingart, Co-Director of CEEC
9/27/19: Aykut Aksit, Ph.D. Student at Columbia
Rebecca Ciez, Princeton postdoctoral fellow
10/11/19: Dr. Nongnuch Artrith, Research Scientist at Columbia
10/25/19: Prof. Lauren Marbella, Dept. of Chemical Engineering
11/1/19: Emily Hsu, Ph.D. Student at Columbia
Dr. Amir Zangiabadi, Director of Electron Microscopy Labs
11/22/19: Prof. Bruce Usher, Director of Tamer Center, Columbia Business School
12/6/19: Dr. Kathy Ayers, VP of R&D at Proton Onsite / Nel Hydrogen
2/7/20: Prof. Yuan Yang, Dept. of Applied Physics and Applied Mathematics
2/14/20: Darren Hammell, Executive VP of Business Development, Princeton Power Systems Visiting Fellow at Princeton
4/17/20: Jianzhou Qu, Ph.D. Student at Columbia
4/24/20: Wesley Chang, Ph.D. Student at Princeton
5/1/20: Karthik Mayilvahanan, Ph.D. Student at Columbia
6/26/20: Rob Mohr, Ph.D. Student at Columbia
Sophie Lee, Ph.D. Student at Drexel
7/10/20: Luis Rebollar, Ph.D. Student at Drexel
Dr. Oliver Harris, Tang group at Drexel
7/17/20: Prof. Scott Moura, UC Berkeley
7/31/20: Peter Godart, Ph.D. Student at MIT
8/7/20: Dr. Aziz Abdellahi, Principal Scientist, A123 Systems LLC
10/9/20: Richard May/Suman Gunasekaran, Columbia PhD students
10/16/20: Xueqi Pang/Neal Biswas, Columbia PhD students