Fundamental electrochemistry of batteries 'beyond Li-ion', with a specific focus on metal-air chemistries
The lithium-ion battery is a truly remarkable technology; one which has found commercial application in numerous devices requiring portable energy storage. However, through decades of development, Li-ion batteries are now reaching physical limits in terms of the amount of energy they can store per unit volume. Our research will broadly focus on new battery chemistries that have promise to improve upon the energy density of Li-ion batteries. Among the many alternatives being explored, metal-air batteries possess very high theoretical energy densities, but suffer from poor rechargeability and Coulombic efficiency. Our laboratory’s specific focus will be to assess, and then address, the shortcomings of metal-air batteries through a systematic approach involving state-of-the-art electrochemical and spectroscopic characterization. Current projects include novel electrolyte development for Li-air batteries, fundamental characterization of Na-air batteries, corrosion suppression of Mg metal anodes in aqueous electrolytes, and outgassing of high voltage Li-excess Li-ion battery electrodes.
High Li ion transference number polymer electrolytes to enable high energy Li-ion batteries
In typical liquid electrolytes, most of the ionic current is initially carried by the anion, with a lithium ion transference number (t) ranging from 0.1-0.4 (i.e., only 10-40% of the ionic current is carried by Li ions). As a result of this low t, and in combination with the consumption/formation of the electroactive Li ions at the battery cathode/anode, salt concentration gradients are established within the battery in order to maintain electroneutrality, deleteriously affecting the battery performance. Specifically, as a battery discharge proceeds, the ionic concentration within the porous battery cathode, where Li ions are consumed, continuously decreases until it reaches zero at some shallow depth within the electrode, limiting the ultimate electrode thickness. High t electrolytes could significantly reduce, or perhaps eliminate, concentration polarization at high discharge rates, enabling thicker electrodes to be used, which would increase the ratio of electrochemically active battery components to passive cell components (such as the electrolytes), thereby increasing the energy density of the cell, particularly at high current rates desirable for electric vehicles. Our group works to understand the effect of various polymer properties, both chemical and physical, on the electrode/electrolyte interfaces and the polymer conductivity, thereby allowing us to optimize electrolyte composition to impart low impedance and enhanced Li-ion battery performance.
The stability and performance of Li-ion cathode materials
The traditional cathode in a lithium-ion battery is a layered lithium transition metal oxide. This stoichiometric oxide delivers reversible capacity by utilizing the redox capability of the transition metal. The achievable reversible capacity of these oxides, however, is much lower than the theoretical capacity, and despite the breadth of research in this field, the nature of this limitation is still highly debated. Our focus is to understand this limitation by decoupling the linked roles of electrolyte and oxide degradation by using a combination of spectroscopic and in-situ techniques. Our lab is also interested in several new classes of cathode materials that depart from the traditional layered stoichiometric oxides. These new classes of materials promise much higher theoretical capacities than the traditional oxides, but suffer from poorly understood limitations in stability and cyclability. Our lab wishes to understand how the identity of the transition metal, the extent of lithium content, and the crystal structure, as well as the electrolyte, all play a role in the stability and reversible capacities of these new cathode materials.
Electrocatalysis, with a focus on photocatalytic CO2 reduction
Using inputs of only sunlight, electricity, carbon dioxide, and water, photocatalytic CO2 reduction imitates nature by producing fuels directly from the sun. These solar fuels lead to greater independence from fossil fuels and mitigate the effects of climate change by consuming CO2 that would otherwise be released into the atmosphere. Our research specifically targets a strategy to improve efficiency and selectivity of CO2 electrochemical reduction, both of which currently hinder the practicality of CO2-to-hydrocarbon conversion. Plasmon-assisted photocatalytic CO2 reduction leads to greater selectivity and lower overpotentials by unlocking unique mechanistic pathways. The electron dynamics in an irradiated plasmonic nanoparticle can alter the electronic coupling with surface adsorbed CO2 and reaction intermediates, thereby changing the binding energy of these species and the catalytic properties of the plasmonic metals. The wide tunability of the plasmon resonance frequency with shape, size, and material confers fine control over these catalytic mechanisms, allowing for optimization of the photocatalytic performance. Our laboratory is exploring novel composite electrodes of nanostructured materials that exhibit strong plasmonic and electrocatalytic behavior, leading to enhanced CO2 reduction.
News and Notes
Sophia was awarded an NSF Graduate Research Fellowship to fund her future graduate studies. Congratulations, Sophia!
Joe published an article about PVDF binder degradation in Li-O2 batteries. Read it here.
Hilda published an article on nonaqueous polyelectrolyte solutions as liquid electrolytes for batteries. Read it here.
Jessica published an article concerning sudden death in Na–O2 batteries. Read it here.
Bryan published an article regarding redox mediation in Li–O2 batteries. Read it here.
Sophia won first place in her division in the AIChE Undergraduate Student Poster Competition. Well done, Sophia!
Pete passed his qualifying exam. Way to go, Pete!
Kyle passed his qualifying exam. Nice work, Kyle!
Hilda presented at the Department of Chemical Engineering colloquium. Great job, Hilda!
Erin passed her qualifying exam. Congratulations, Erin!
We've been behind the times on updating publications in the news and notes section, so please check the publication tab for all articles published by the lab, which have now been fully updated!
Colin published an article regarding iodide redox mediation in Li–O2 batteries. Read it here.
Eddy passed his qualifying exam. Way to go, Eddy!
Jessica and Kyle won each of our department's Dow Outstanding Graduate Student Instructor Awards, given to the best GSIs in our department as voted by their students. Pete and Eddy received Outstanding Graduate Student Instructor Awards. Excellent work by all four!
Hilda, Colin, Jessica, Kyle, and Elizabeth had their abstracts accepted at the AIChE conference in November. Come see their presentations and posters in SF!
Erin, Hyo Won, and Kristian had their abstracts accepted to present at the ECS PRiME conference in October. We'll see you there!
Howie Nguyen joins the lab as an Amgen Scholar for the summer. Welcome, Howie!
Chris graduated and began working at an energy storage start-up. Congratulations, Chris!
Colin was selected for a NASA Space Technology Research Fellowship. Congratulations, Colin!
Jakob Asenbauer joins the lab as a visiting student from U. of Regensberg. Welcome Jakob!
Bryan published an article describing important metrics for battery using solid separator-protected Li metal anodes. Read it here.
Youngsang Kim joins the lab as a postdoctoral researcher, coming from the University of Michigan. Welcome, Youngsang!
Hilda and Bryan are co-authors on a recent publication on hybrid gas separation membranes from Jeff Urban's laboratory. Read it here.
Joe Papp and Elizabeth Corson join the laboratory. Welcome, Joe and Elizabeth!
Burkhard Ohs is visiting the laboratory for 3 months from Prof. Mathias Wessling's group at RTWH Aachen. Welcome, Burkhard!
Colin won the Dow Outstanding Graduate Student Instructor Award and Jessica received the Outstanding Graduate Student Instructor Award. Outstanding work by both!
Erin Creel, Sophia Chan, and Keren Zhang have joined the laboratory. Welcome Erin, Sophia, and Keren!
Colin and Bryan are co-authors on a recently published article in PNAS that elucidates the importance of the electrolyte anion on Li-O2 battery performance. Read it here!
Colin, Sara, Jessica, and Bryan published a review article in ChemComm on challenges facing Li-O2 battery cathodes. Read it here!
Charles Wan is visiting the laboratory for 2 months as an Amgen Scholar. Welcome, Charles!
Kristian Knudsen is visiting the laboratory from the Technological University of Denmark and will be around for the next 3 months. Welcome, Kristian!
Hyo Won Kim has joined the laboratory as a post doc. Welcome, Hyo Won!
Bryan is a co-author on an article that describes electrochemical impedance analysis of discharge and charge processes in Li-O2 batteries. Read it here!
Bryan's work is highlighted in a J. Phys. Chem. Lett. editorial. Read it here!
Bryan is a co-author on a recently published article in Nature Chemistry that describes solubility-induced enhancement of Li-O2 battery capacity. Read it here!
Kyle Diederichsen joins the McCloskey Laboratory. Welcome, Kyle!
Bryan is a co-author on a recently published Li-air battery review in Chemical Reviews. Read it here!
Bryan is a co-author on a recently published article in Science that describes two new polymer-forming reactions. Read it here. Congratulations to Bryan's collaborators at IBM Almaden Research Center and KACST, in particular Jamie Garcia and Jim Hedrick, for this fantastic achievement!
Bryan is a co-author of a chapter in the recently published book, The Lithium-Air Battery: Fundamentals. Read it here!