Leo W. Gordon

Materials Research Laboratory, Room 3115, UCSB

+1 (917) 742-7804

I am a postdoctoral scholar in the Clément group at UC Santa Barbara where I investigate ion transport processes in polymeric materials using NMR methodologies such as pulsed-field gradient and electrophoretic NMR. I recently completed my Ph.D. research at The City College of New York (CCNY) working in the field of energy storage materials where I was advised by Prof. Robert J. Messinger.

The primary focus of my Ph.D. was using NMR characterisation techniques to determine charge storage mechanisms and to understand electrolyte speciation. Solid-state NMR is my main tool for investigating charge storage, which I apply to understand ionic and electronic charge storage mechanisms in organic electrodes for rechargeable aluminium batteries. I also have expertise in liquid NMR, which I have demonstrated through my work on lithium metal battery electrolytes, along with molten salt electrolytes for aluminum batteries. I have further interests in metal anode surface chemistries, lithium cathode recycling, and the nuances of charge storage with different molten salt electrolyte speciations. My central PhD work has culminated in publications including articles in the Journal of Physical Chemistry C, ACS Applied Materials & Interfaces, and the Journal of Magnetic Resonance.

Before joining the Chemical Engineering department at CCNY, I attained an integrated Masters degree in Chemistry (MChem) from the University of Edinburgh, Scotland. During my thesis research I worked to develop and understand novel designs for multi-microelectrode arrays for electrochemical sensing applications. Also during the bachelors portion of my degree, I briefly investigated dye-sensitised solar cells (DSSCs) using plant derived dyes, targeting low-cost and minimally corrosive materials.

In my free time I enjoy bouldering to keep fit, and to make time-saving GUI programs to process data - many of which can be found on my GitHub profile!

News

Mar 24, 2023	Today I sucessfully defended my PhD thesis “Molecular Elucidation of Reaction Mechanisms in Aluminum and Lithium Metal Batteries by Solid-State NMR Spectroscopy and Electrochemical Methods”. My PhD journey has been a greatly enjoyable 5 years and I have far too many people to thank for getting me to this point. However, I must acknowledge my committee members, Prof. Alex Couzis, Prof. Ruth Stark, Prof. George John, Prof. Elizabeth Biddinger, and my advisor Prof. Robert Messinger for their great support today. Special thanks to Rob for all the hard work we put in together!
Feb 27, 2023	The latest work from our group “Reversible Zinc Electrodeposition at −60 °C Using a Deep Eutectic Electrolyte for Low-Temperature Zinc Metal Batteries” was published today. In this work we demonstrate an electrolyte with a deep-eutectic point to enable reversible zinc electrodeposition down to temperatures of -60 °C. We make 0.1 M Zn(TFSI)₂ electrolytes in different ratios of [EMIm]TFSI with gamma-butyrolactone (GBL) which are probed electrochemically to determine their macroscopic properties, and further analysed at the molecular level via NMR spectroscopy and molecular dynamics (MD) simulations to explain the differences in performance from an atomistic approach.
Jan 25, 2023	Our new study of aluminium-organic batteries, entitled “Revealing Impacts of Electrolyte Speciation on Ionic Charge Storage in Aluminum-Quinone Batteries by NMR Spectroscopy”, is now out in the Journal of Magnetic Resonance. This is a detailed analysis of the ionic charge storage mechanisms in aluminium-quinone batteries where we begin by detailing the speciation of three different Lewis acidic ionic liquid/ionic liquid analogue electrolytes by liquid-state NMR, we then use solid-state NMR to determine the nature of the complexed ions upon electrochemical discharge in each electrolyte. We further use DFT calculations to both determine the most favorable electroactive cation generation pathways and to link the experimentally derived NMR quadrupolar parameters to a physical basis of ion interaction with different quinone structures. Finally, we also validate our hypothesised mechanisms with targeted experiments, proving the function of various ionic species.
Sep 28, 2022	The 4th battery and energy storage conference, taking place this year in CUNY’s very own Advanced Science and Research Center building, was a fast-paced and highly engaging few days. Great talks from many people with a variety of topics - from space applications, to cutting edge recycling techniques.
Sep 13, 2022	ECS 2022 was a nice conference with lots of engaging talks, including from Nobel Laureate Prof. Stan Whittingham, who even stopped by the student mixer to mingle with the student members of ECS. It was great to meet a lot of new people, especially finally being able to meet people in person.

Selected Publications

Revealing impacts of electrolyte speciation on ionic charge storage in aluminum-quinone batteries by NMR spectroscopy

Leo W Gordon, Jonah Wang, and Robert J Messinger

Journal of Magnetic Resonance
Mar 2023

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Rechargeable aluminum-organic batteries are composed of earth-abundant, sustainable electrode materials while the molecular structures of the organic materials can be controlled to tune their electrochemical properties. Aluminum metal batteries typically use electrolytes based on chloroaluminate ionic liquids or deep eutectic solvents that are comprised of polyatomic aluminum-containing ions. Quinone-based organic electrodes store charge when chloroaluminous cations (AlCl2+) charge compensate their electrochemically reduced carbonyl groups, even when such cations are not natively present in the electrolyte. However, how ion speciation in the electrolyte affects the ion charge storage mechanism, and resultant battery performance, is not well understood. Here, we couple solid-state NMR spectroscopy with electrochemical and computational methods to show for the first time that electrolyte-dependent ion speciation significantly alters the molecular-level environments of the charge-compensating cations, which in turn influences battery properties. Using 1,5-dichloroanthraquinone (DCQ) for the first time as an organic electrode material, we utilize dipolar-mediated solid-state NMR experiments to elucidate distinct aluminum coordination environments upon discharge that depend significantly on electrolyte speciation. We relate DFT-calculated NMR parameters to experimentally determined quantities, revealing insights into their origins. The results establish that electrolyte ion speciation impacts the local environments of charge-compensating chloroaluminous cations and is a crucial design parameter for rechargeable aluminum-organic batteries.
Molecular-Scale Elucidation of Ionic Charge Storage Mechanisms in Rechargeable Aluminum–Quinone Batteries

Leo W. Gordon, Ankur L. Jadhav, Mikhail Miroshnikov, Theresa Schoetz, George John, and Robert J. Messinger

The Journal of Physical Chemistry C
Aug 2022

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Rechargeable aluminum–organic batteries are of great interest as a next-generation energy storage technology because of the earth abundance, high theoretical capacity, and inherent safety of aluminum metal, coupled with the sustainability, availability, and tunabilty of organic molecules. However, the ionic charge storage mechanisms occurring in aluminum–organic batteries are currently not well understood, in part because of the diversity of possible charge-balancing cations, coupled with a wide array of possible binding modes. For the first time, we use multidimensional solid-state NMR spectroscopy in conjunction with electrochemical methods to elucidate experimentally the ionic and electronic charge storage mechanism in an aluminum–organic battery up from the atomic length scale. In doing so, we present indanthrone quinone (INDQ) as a positive electrode material for rechargeable aluminum batteries, capable of reversibly achieving specific capacities of ca. 200 mAh g^–1 at 0.12 A g^–1 and 100 mAh g^–1 at 2.4 A g^–1 . We demonstrate that INDQ stores charge via reversible electrochemical enolization reactions, which are charge compensated in chloroaluminate ionic liquid electrolytes by cationic chloroaluminous (AlCl₂⁺ ) species in tetrahedral geometries. The results are generalizable to the charge storage mechanisms underpinning anthraquinone-based aluminum batteries. Lastly, the solid-state dipolar-mediated NMR experiments used here establish molecular-level interactions between electroactive ions and organic frameworks while filtering mobile electrolyte species, a methodology applicable to many multiphase host–guest systems.
Performance Leap of Lithium Metal Batteries in LiPF₆ Carbonate Electrolyte by a Phosphorus Pentoxide Acid Scavenger

Jian Zhang, Jiayan Shi, Leo W. Gordon, Nastaran Shojarazavi, Xiaoyu Wen, Yifan Zhao, Jianjun Chen, Chi-Cheung Su, Robert J. Messinger, and Juchen Guo

ACS Applied Materials & Interfaces
Aug 2022

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Phosphorus pentoxide (P₂O₅) is investigated as an acid scavenger to remove the acidic impurities in a commercial lithium hexafluorophosphate (LiPF₆) carbonate electrolyte to improve the electrochemical properties of Li metal batteries. Nuclear magnetic resonance (NMR) measurements reveal the detailed reaction mechanisms of P₂O₅ with the LiPF₆ electrolyte and its impurities, which removes hydrogen fluoride (HF) and difluorophosphoric acid (HPO₂F₂) and produces phosphorus oxyfluoride (POF₃), OF₂P–O–PF₅– anions, and ethyl difluorophosphate (C₂H₅OPOF₂) as new electrolyte species. The P₂O₅-modified LiPF₆ electrolyte is chemically compatible with a Li metal anode and LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622) cathode, generating a PO_xF_y-rich solid electrolyte interphase (SEI) that leads to highly reversible Li electrodeposition, while eliminating transition metal dissolution and cathode particle cracking. The excellent electrochemical properties of the P₂O₅-modified LiPF₆ electrolytes are demonstrated on Li||NMC622 pouch cells with 0.4 Ah capacity, 50 μm Li anode, 3 mAh cm^–2 NMC622 cathode, and 3 g Ah^–1 electrolyte/capacity ratio. The pouch cells can be galvanostatically cycled at C/3 for 230 cycles with 87.7% retention.
Soluble Electrolyte-Coordinated Sulfide Species Revealed in Al–S Batteries by Nuclear Magnetic Resonance Spectroscopy

Rahul Jay, Ankur L. Jadhav, Leo W. Gordon, and Robert J. Messinger

Chemistry of Materials
May 2022

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Rechargeable aluminum-sulfur (Al-S) batteries have recently garnered significant interest to the low cost, earth abundance, safety, and high theoretical capacity of the electrode materials. However, Al-S batteries exhibit many challenges that plague other metal-sulfur battery systems, including significant capacity fade of the sulfur electrode due to the formation of electrolyte-soluble reaction intermediates. Here, Al-S cells using chloroaluminate-containing ionic liquid electrolytes were investigated up from the molecular level using multidimensional solid-state 27Al MAS NMR spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electrochemical measurements. Solid-state 27Al single-pulse NMR measurements acquired on cycled sulfur electrodes containing electrolyte-soaked separator revealed multiple discharge products, which were distinguished into liquid- and solid-phase products based on 27Al chemical exchange and nutation NMR experiments. During discharge, electrolyte-soluble sulfide species form that coordinate with the AlCl4- chloroaluminate anions, resulting in (SxAlCl4)y- electrolyte complexes. These electrolyte-coordinated sulfide species persist upon charge, resulting in the loss of active mass that explains the significant capacity fade observed upon galvanostatic cycling. XPS, XRD, and solid-state 27Al NMR measurements reveal that solid amorphous Al2S3 forms reversibly upon discharge. The results highlight the technological importance of understanding how electrolyte-soluble sulfide species coordinate with the complex electroactive species used in multivalent metal-sulfur batteries, which can affect their reversibility and electrochemical properties.
Disentangling Faradaic, Pseudocapacitive, and Capacitive Charge Storage: A Tutorial for the Characterization of Batteries, Supercapacitors, and Hybrid Systems

T. Schoetz, L.W. Gordon, S. Ivanov, A. Bund, D. Mandler, and R.J. Messinger

Electrochimica Acta
Apr 2022

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Today’s electrochemical energy storage technologies aim to combine high specific energy and power, as well as long cycle life, into one system to meet increasing demands in performance. These properties, however, are often characteristic of either batteries (high specific energy) or capacitors (high specific power and cyclability). To merge battery- and capacitor-like properties in a hybrid energy storage system, researchers must understand and control the co-existence of multiple charge storage mechanisms. Charge storage mechanisms can be classified as faradaic, capacitive, or pseudocapacitive, where their relative contributions determine the operating principles and electrochemical performance of the system. Hybrid electrochemical energy storage systems can be better understood and analyzed if the primary charge storage mechanism is identified correctly. This tutorial review first defines faradaic and capacitive charge storage mechanisms and then clarifies the definition of pseudocapacitance using a physically intuitive framework. Then, we discuss strategies that enable these charge storage mechanisms to be quantitatively disentangled using common electrochemical techniques. Finally, we outline representative hybrid energy storage systems that combine the electrochemical characteristics of batteries, capacitors and pseudocapacitors. Modern examples are analyzed while step-by-step guides are provided for all mentioned experimental methods in the Supplementary Information.