Kevin G. Gallagher
Argonne National Laboratory
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Featured researches published by Kevin G. Gallagher.
Energy and Environmental Science | 2014
Kevin G. Gallagher; Steven G. Goebel; Thomas Greszler; Mark Mathias; Wolfgang Oelerich; Damla Eroglu; Venkat Srinivasan
Researchers worldwide view the high theoretical specific energy of the lithium–air or lithium–oxygen battery as a promising path to a transformational energy-storage system for electric vehicles. Here, we present a self-consistent material-to-system analysis of the best-case mass, volume, and cost values for the nonaqueous lithium–oxygen battery and compare them with current and advanced lithium-based batteries using metal-oxide positive electrodes. Surprisingly, despite their high theoretical specific energy, lithium–oxygen systems were projected to achieve parity with other candidate chemistries as a result of the requirement to deliver and purify or to enclose the gaseous oxygen reactant. The theoretical specific energy, which leads to predictions of an order of magnitude improvement over a traditional lithium-ion battery, is shown to be an inadequate predictor of systems-level cost, volume, and mass. This analysis reveals the importance of system-level considerations and identifies the reversible lithium-metal negative electrode as a common, critical high-risk technology needed for batteries to reach long-term automotive objectives. Additionally, advanced lithium-ion technology was found to be a moderate risk pathway to achieve the majority of volume and cost reductions.
Energy and Environmental Science | 2015
Jennifer B. Dunn; Linda Gaines; Jarod C. Kelly; Christine James; Kevin G. Gallagher
Three key questions have driven recent discussions of the energy and environmental impacts of automotive lithium-ion batteries. We address each of them, beginning with whether the energy intensity of producing all materials used in batteries or that of battery assembly is greater. Notably, battery assembly energy intensity depends on assembly facility throughput because energy consumption of equipment, especially the dry room, is mainly throughput-independent. Low-throughput facilities therefore will have higher energy intensities than near-capacity facilities. In our analysis, adopting an assembly energy intensity reflective of a low-throughput plant caused the assembly stage to dominate cradle-to-gate battery energy and environmental impact results. Results generated with an at-capacity assembly plant energy intensity, however, indicated cathode material production and aluminium use as a structural material were the drivers. Estimates of cradle-to-gate battery energy and environmental impacts must therefore be interpreted in light of assumptions made about assembly facility throughput. The second key question is whether battery recycling is worthwhile if battery assembly dominates battery cradle-to-gate impacts. In this case, even if recycled cathode materials are less energy and emissions intensive than virgin cathode materials, little energy and environmental benefit is obtained from their use because the energy consumed in assembly is so high. We reviewed the local impacts of metals recovery for cathode materials and concluded that avoiding or reducing these impacts, including SOx emissions and water contamination, is a key motivator of battery recycling regardless of the energy intensity of assembly. Finally, we address whether electric vehicles (EV) offer improved energy and environmental performance compared to internal combustion-engine vehicles (ICV). This analysis illustrated that, even if a battery assembly energy reflective of a low-throughput facility is adopted, EVs consume less petroleum and emit fewer greenhouse gases (GHG) than an ICV on a life-cycle basis. The only scenario in which an EV emitted more GHGs than an ICV was when it used solely coal-derived electricity as a fuel source. SOx emissions, however, were up to four times greater for EVs than ICVs. These emissions could be reduced through battery recycling.
Accounts of Chemical Research | 2015
Jason R. Croy; Mahalingam Balasubramanian; Kevin G. Gallagher; Anthony K. Burrell
The commercial introduction of the lithium-ion (Li-ion) battery nearly 25 years ago marked a technological turning point. Portable electronics, dependent on energy storage devices, have permeated our world and profoundly affected our daily lives in a way that cannot be understated. Now, at a time when societies and governments alike are acutely aware of the need for advanced energy solutions, the Li-ion battery may again change the way we do business. With roughly two-thirds of daily oil consumption in the United States allotted for transportation, the possibility of efficient and affordable electric vehicles suggests a way to substantially alleviate the Countrys dependence on oil and mitigate the rise of greenhouse gases. Although commercialized Li-ion batteries do not currently meet the stringent demands of a would-be, economically competitive, electrified vehicle fleet, significant efforts are being focused on promising new materials for the next generation of Li-ion batteries. The leading class of materials most suitable for the challenge is the Li- and manganese-rich class of oxides. Denoted as LMR-NMC (Li-manganese-rich, nickel, manganese, cobalt), these materials could significantly improve energy densities, cost, and safety, relative to state-of-the-art Ni- and Co-rich Li-ion cells, if successfully developed.1 The success or failure of such a development relies heavily on understanding two defining characteristics of LMR-NMC cathodes. The first is a mechanism whereby the average voltage of cells continuously decreases with each successive charge and discharge cycle. This phenomenon, known as voltage fade, decreases the energy output of cells to unacceptable levels too early in cycling. The second characteristic is a pronounced hysteresis, or voltage difference, between charge and discharge cycles. The hysteresis represents not only an energy inefficiency (i.e., energy in vs energy out) but may also complicate the state of charge/depth of discharge management of larger systems, especially when accompanied by voltage fade. In 2012, the United States Department of Energys Office of Vehicle Technologies, well aware of the inherent potential of LMR-NMC materials for improving the energy density of automotive energy storage systems, tasked a team of scientists across the National Laboratory Complex to investigate the phenomenon of voltage fade. Unique studies using synchrotron X-ray absorption (XAS) and high-resolution diffraction (HR-XRD) were coupled with nuclear magnetic resonance spectroscopy (NMR), neutron diffraction, high-resolution transmission electron microscopy (HR-TEM), first-principles calculations, molecular dynamics simulations, and detailed electrochemical analyses. These studies demonstrated for the first time the atomic-scale, structure-property relationships that exist between nanoscale inhomogeneities and defects, and the macroscale, electrochemical performance of these layered oxides. These inhomogeneities and defects have been directly correlated with voltage fade and hysteresis, and a model describing these mechanisms has been proposed. This Account gives a brief summary of the findings of this recently concluded, approximately three-year investigation. The interested reader is directed to the extensive body of work cited in the given references for a more comprehensive review of the subject.
Journal of the American Chemical Society | 2015
Fulya Dogan; Brandon R. Long; Jason R. Croy; Kevin G. Gallagher; Hakim Iddir; John T. Russell; Mahalingam Balasubramanian; Baris Key
Direct observations of structure-electrochemical activity relationships continue to be a key challenge in secondary battery research. (6)Li magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy is the only structural probe currently available that can quantitatively characterize local lithium environments on the subnanometer scale that dominates the free energy for site occupation in lithium-ion (Li-ion) intercalation materials. In the present study, we use this local probe to gain new insights into the complex electrochemical behavior of activated 0.5(6)Li2MnO3·0.5(6)LiMn(0.5)Ni(0.5)O2, lithium- and manganese-rich transition-metal (TM) oxide intercalation electrodes. We show direct evidence of path-dependent lithium site occupation, correlated to structural reorganization of the metal oxide and the electrochemical hysteresis, during lithium insertion and extraction. We report new (6)Li resonances centered at ∼1600 ppm that are assigned to LiMn6-TM(tet) sites, specifically, a hyperfine shift related to a small fraction of re-entrant tetrahedral TMs (Mn(tet)), located above or below lithium layers, coordinated to LiMn6 units. The intensity of the TM layer lithium sites correlated with tetrahedral TMs loses intensity after cycling, indicating limited reversibility of TM migrations upon cycling. These findings reveal that defect sites, even in dilute concentrations, can have a profound effect on the overall electrochemical behavior.
Journal of The Electrochemical Society | 2008
Kevin G. Gallagher; David T. Wong; Thomas F. Fuller
The electrochemical oxidation of carbon black catalyst supports is recognized as a durability challenge to the commercialization of low-temperature fuel cells in the transportation sector. An investigation of the effect of the transient potentials experienced in this environment is presented. The exposure of carbon black to square wave potential cycling results in an oxidation process different than the constant potential hold historically used to characterize this corrosion process. The differences are characterized using the liquid half-cell and single fuel cell testing, coupled with electrochemical techniques and online gas analysis. Although cyclic voltammetry and X-ray photoelectron spectroscopy are unable to quantify significant differences in the surface oxide chemistry, online gas analysis measurements demonstrate different corrosion activities.
Journal of The Electrochemical Society | 2008
Kevin G. Gallagher; Robert M. Darling; Timothy W. Patterson; Michael L. Perry
Capillary pressure saturation relations (CPSRs) are presented for Toray TGP-H-060 and Mitsubishi rayon carbon fiber paper which can both be used as gas diffusion layers (GDLs) in proton-exchange membrane fuel cells (PEMFCs). The saturation is measured using water over a range of capillary pressures. Boundary and scanning curves for imbibition and drainage are measured to further understand the hysteresis observed during PEMFC operation. The primary source of hysteresis in CPSRs is attributed to the difference in advancing and receding contact angles. The measured hysteresis is predicted to have a significant effect on mass transport in the GDL and thus performance in PEMFCs.
Journal of The Electrochemical Society | 2010
Kevin G. Gallagher; Gleb Yushin; Thomas F. Fuller
Carbon is ubiquitous in electrochemical energy devices and may exist in varied forms ranging from crystalline or amorphous to novel nanostructures based on a few sheets of graphene. The electrochemical oxidation of carbon results in the performance degradation of the electrochemical device. A study on the structure-reactivity relationship of the electrochemical oxidation of graphene-based carbon materials (carbon black, carbon onions, multiwalled nanotubes, and exfoliated graphite platelets) is presented. High resolution transmission electron microscopy, X-ray diffraction, elemental analysis, and N 2 adsorption were used to characterize the materials tested. Both liquid half-cell tests and proton exchange membrane fuel cell tests with inline carbon dioxide analysis were used to study the electrochemical behavior. The electrochemical oxidation of 10 seemingly disparate carbon materials was separated into two distinct mechanisms. Both mechanisms approach an 80% current efficiency for carbon dioxide formation. Iron and sulfur impurities are insignificant controlling factors. The difference between the two mechanisms is tentatively attributed to the degree of interlayer interaction between graphene sheets.
Journal of The Electrochemical Society | 2009
Kevin G. Gallagher; Bryan S. Pivovar; Thomas F. Fuller
Water uptake and electro-osmosis are investigated to improve the understanding and aid the modeling of water transport in proton-exchange membrane fuel cells (PEMFCs) below 0 C. Measurements of water sorption isotherms show a significant reduction in the water capacity of polymer electrolytes below 0 C. This reduced water content is attributed to the lower vapor pressure of ice compared to supercooled liquid water. At -25 C, 1100 equivalent weight Nafion in equilibrium with vapor over ice has 8 moles of water per sulfonic acid group. Measurements of the electro-osmotic drag coefficient for Nafion and both random and multiblock copolymer sulfonated poly(arylene ether sulfone) (BPSH) chemistries are reported for vapor equilibrated samples below 0 C. The electro-osmotic drag coefficient of BPSH chemistries is found to be {approx}0.4, and that of Nafion is {approx}1. No significant temperature effect on the drag coefficient is found. The implication of an electro-osmotic drag coefficient less than unity is discussed in terms of proton conduction mechanisms. Simulations of the ohmically limited current below 0 C show that a reduced water uptake below 0 C results in a significant decrease in PEMFC performance.
ACS central science | 2017
Chang Wook Lee; Quan Pang; Seungbum Ha; Lei Cheng; Sang Don Han; Kevin R. Zavadil; Kevin G. Gallagher; Linda F. Nazar; Mahalingam Balasubramanian
The lithium–sulfur battery has long been seen as a potential next generation battery chemistry for electric vehicles owing to the high theoretical specific energy and low cost of sulfur. However, even state-of-the-art lithium–sulfur batteries suffer from short lifetimes due to the migration of highly soluble polysulfide intermediates and exhibit less than desired energy density due to the required excess electrolyte. The use of sparingly solvating electrolytes in lithium–sulfur batteries is a promising approach to decouple electrolyte quantity from reaction mechanism, thus creating a pathway toward high energy density that deviates from the current catholyte approach. Herein, we demonstrate that sparingly solvating electrolytes based on compact, polar molecules with a 2:1 ratio of a functional group to lithium salt can fundamentally redirect the lithium–sulfur reaction pathway by inhibiting the traditional mechanism that is based on fully solvated intermediates. In contrast to the standard catholyte sulfur electrochemistry, sparingly solvating electrolytes promote intermediate- and short-chain polysulfide formation during the first third of discharge, before disproportionation results in crystalline lithium sulfide and a restricted fraction of soluble polysulfides which are further reduced during the remaining discharge. Moreover, operation at intermediate temperatures ca. 50 °C allows for minimal overpotentials and high utilization of sulfur at practical rates. This discovery opens the door to a new wave of scientific inquiry based on modifying the electrolyte local structure to tune and control the reaction pathway of many precipitation–dissolution chemistries, lithium–sulfur and beyond.
Physical Chemistry Chemical Physics | 2015
Jason R. Croy; Hakim Iddir; Kevin G. Gallagher; Christopher S. Johnson; R. Benedek; Mahalingam Balasubramanian
Li- and Mn-rich layered oxides with composition xLi2MnO3·(1 -x)LiMO2 enable high capacity and energy density Li-ion batteries, but suffer from degradation with cycling. Evidence of atomic instabilities during the first charge are addressed in this work with X-ray absorption spectroscopy, first principles simulation at the GGA+U level, and existing literature. The pristine material of composition xLi2MnO3·(1 -x)LiMn0.5Ni0.5O2 is assumed in the simulations to have the form of LiMn2 stripes, alternating with NiMn stripes, in the metal layers. The charged state is simulated by removing Li from the Li layer, relaxing the resultant system by steepest descents, then allowing the structure to evolve by molecular dynamics at 1000 K, and finally relaxing the evolved system by steepest descents. The simulations show that about ¼ of the oxygen ions in the Li2MnO3 domains are displaced from their original lattice sites, and form oxygen-oxygen bonds, which significantly lowers the energy, relative to that of the starting structure in which the oxygen sublattice is intact. An important consequence of the displacement of the oxygen is that it enables about ⅓ of the (Li2MnO3 domain) Mn ions to migrate to the delithiated Li layers. The decrease in the coordination of the Mn ions is about twice that of the Ni ions. The approximate agreement of simulated coordination number deficits for Mn and Ni following the first charge with analysis of EXAFS measurements on 0.3Li2MnO3·0.7LiMn0.5Ni0.5O2 suggests that the simulation captures significant features of the real material.