Center For Functional Nanomaterials Research Articles

(Invited) Fluorinated Linear Carbonate Electrolyte for Lithium-Ion Batteries with Fast-Charging, High Voltage, and Wide Operating Temperatures

Lithium-ion batteries (LIBs) are key solutions to clean energy. Their high energy densities have led to the dominance of LIBs in mobile devices and electric vehicles. However, traditional electrolyte limits their operation at high voltage and extreme environmental temperatures. Here, we designed a new multifunctional electrolyte, in which lithium bis(fluorosulfonyl)imide (LiFSI) is used as salt and fluorinated diethyl carbonate (DFDEC) is used as the major solvent. With this optimized electrolyte, the graphite||LiNi0.8Mn0.1Co0.1O2 (NMC811) full cells are capable of fast-charging and can deliver long-term cycling with a cutoff voltage as high as 4.5V. Specifically, the battery shows the capacity retention of 84.3% after 500 cycles with an average coulombic efficiency (CE) as high as 99.93%. Synchrotron-based characterization suggests the formation of anion derived, LiF-rich interphases on the surfaces of both graphite anode and NMC811 cathode. Thanks to the fast ion transport and stable interphase, the cell in the optimized electrolyte demonstrates stable cycling behavior within a wide operating temperature. At high temperature (60 ºC), the full cell delivers 88.8% of its initial capacity after 130 cycles at a high current density of 1C. At low temperature (-20 ºC), the optimized electrolyte enables a capacity retention of 90.9% after 100 cycles when charging and discharging at 0.2C.Acknowledgment: The work done at Brookhaven National Laboratory was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technology Office of the U.S. DOE through Applied Battery Research for Transportation (ABRT) program under contract no. DE-SC0012704. The electrodes used in this study were produced at the U.S. Department of Energy’s (DOE) CAMP (Cell Analysis, Modeling and Prototyping) Facility, Argonne National Laboratory. The CAMP Facility is fully supported by the DOE Vehicle Technologies Office (VTO). This research used beamline 7-ID-2 (SST-2) of the National Synchrotron Light Source II, U.S. DOE Office of Science User Facilities, operated for the DOE Office of Science by Brookhaven National Laboratory under contract number DE-SC0012704. SEM measurements for this manuscript were performed at Center for Functional Nanomaterials, a U.S. DOE office of Science User Facility, at Brookhaven National Laboratory under the contract number DE-SC0012704.

Isoxazole-Based Electrolytes for Lithium Metal Protection and Lithium-Sulfurized Polyacrylonitrile (SPAN) Battery Operating at Low Temperature

A new electrolyte system using isoxazole as the salt dissolving solvent has been developed and studied for lithium metal batteries. By using fluoroethylene carbonate (FEC) as an additive and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) as a diluent for localized high concentration electrolyte (LHCE), isoxazole-based electrolytes were successfully implemented in lithium metal batteries, demonstrating excellent lithium metal protection capability. Utilizing several advanced characterization techniques (including synchrotron-based X-ray absorption spectroscopy and photoelectron spectroscopy), the solid electrolyte interphase (SEI) formed on the Li-metal anode in cells using these electrolytes was thoroughly investigated. The high ionic conductivity of isoxazole at low temperature and the low impedance of SEI formed in LHCE significantly improved the low-temperature performance of Li-sulfurized polyacrylonitrile (SPAN) batteries, delivering 273.8 mAh g-1 capacity at -30°C with 99.85% capacity retention after 50 cycles.Acknowledgment: The work done at Brookhaven National Laboratory was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technology Office of the US Department of Energy (DOE) through the Advanced Battery Materials Research (BMR) Program, including Battery500 Consortium under contract number DE-SC0012704. This research used beamline 8-BM (TES) and 7-ID-2 (SST-2) of the National Synchrotron Light Source II, U.S. DOE Office of Science User Facilities, operated for the DOE Office of Science by Brookhaven National Laboratory under contract number DE-SC0012704. SEM measurements for this manuscript were performed at Center for Functional Nanomaterials, a U.S. DOE office of Science User Facility, at Brookhaven National Laboratory under the contract number DE-SC0012704.

Use of Multi-Modal Synchrotron Analytical Techniques Combined with Electrochemical Analysis to Understand Anomalous Localized and General Corrosion Behavior of Additively Manufactured 316L Stainless Steel

Additive manufacturing (AM) of alloys such as stainless steels has the potential to be a disruptive technology for design of complex structures which eliminates the potentially damaging effects of mechanical failure and localized corrosion associated with interfaces between separate parts (which can now be printed as part of a single assembly). In addition, increasingly complex geometries can be manufactured with nearly as much ease as simple ones, and new mechanisms for optimization and generative design can allow manufacturers to achieve significant material and weight savings. However, challenges remain, in particular due to the potential for material variability both between parts made with the same nominal build parameters and even within a single build, as the consistency in properties inherent in the commercial-scale forging of alloys to be machined into components is exchanged for the considerable advantages of on-site, distributed custom parts production. Our studies and related work by other groups indicates that this is clearly true in the case of corrosion susceptibility in AM alloys. By studying the relationship between build parameters and electrochemical properties, we propose that it will be possible to tailor alloys for enhanced corrosion properties.AM processes produce materials with hierarchical microstructures containing fusion boundaries at the macroscale, irregular grains and grain boundaries at the microscale, and subgrain dislocation structures at the nanoscale. In laser powder bed fusion (LPBF) formed 316L stainless steel structures, corrosion performance has been discussed in the context of chemical heterogeneities formed in the presence of these hierarchical microstructures. Furthermore, localized corrosion (pitting) is closely related to microstructural defects including dislocation structures, inclusions, and localized elemental segregation which has been found to occur during the very rapid heating and cooling which occurs during laser fusion AM processes.In this presentation, we explore multi-modal synchrotron X-ray techniques for quantifying hierarchical microstructures and their connection to the underlying chemical distribution in 316L stainless steel, as well as localized heterogeneities in the passive film structure. Our results show that the dislocation density depends on the printing conditions with implications for the chemical distribution at the nanoscale, which in turn may play a key role in inconsistent corrosion behavior. Furthermore, we discuss the correlation between this print-formed alloy surface microstructure (dislocation structures, Mn inclusions, and elemental segregation), and local heterogeneities in the passive film formed on LPDF 316L in Cl-containing media. These heterogeneities observed in the passive layer may in turn impact repassivation and other processes critical in localized cession phenomena.Samples formed at varying speeds using pulsed and continuous laser deposition are compared via cyclic polarization in 3.5% NaCl and 0.1M HCl solutions, as well as using Mott-Schottky analysis of passive layers formed in 0.1M HCl. Surface corrosion layers are characterized using laboratory-based X-ray photoelectron spectroscopy to determine the impact on passivity of the aforementioned microsegregation associated with process-induced microstructures. Corrosion rates and pit densities are then discussed to build a connection between printing conditions and corrosion performance vis-à-vis microstructural and chemical information from synchrotron measurements performed at Brookhaven National Laboratory (BNL), including high energy X-ray diffraction using the X-ray Powder Diffraction (XPD) beamline at the National Synchrotron Light Source-II (NSLS-II) which provided data on minor precipitate population(s), atomic structure and dislocation microstructures critical to corrosion behavior. In addition, heterogeneities in elemental composition data is provided by 2D X-ray fluorescence (XRF) and 2D X-ray Absorption Spectroscopy (XAS) nanometer resolution-mapping obtained at the Hard X-ray Nanoprobe (HXN) beamline at the NSLS-II and correlated with process-induced hierarchal structures via use of the microscopy facilities at the Center for Functional Nanomaterials (CFN). X-ray photoemission microspectroscopy/low energy electron microscopy (XPEEM/LEEM) conducted at the Electron Spectro-Microscopy beamline at the NSLS-II provides evidence that the passive layer itself contains inhomogeneities, including areas enriched in oxidized Cr and Mn, as well as microstructural boundaries, reflecting the inhomogeneities in the microstructure of the alloy surface beneath. Mott-Schottky analysis of the passive layer provides further evidence that these inhomogeneities, correlated with alloy microstructure, impact the semiconducting character (and hence protective properties) of the passive layer.By employing a combination of multi-modal synchrotron characterization techniques, electron microscopy, and baseline testing protocol combined with electrochemical polarization experiments, we are able to study the role of microstructure across multiple length scales on electrochemical properties and corrosion performance. Understanding the impact of microstructure and chemical heterogeneities on the susceptibility to pitting and intergranular attack will enable microstructurally-informed process optimization and materials design for enhancing the corrosion resistance of LPBF 316L stainless steel, with implications for AM and subsequent durability of alloys in general.

Finalizing Construction of a New Data Center at BNL

Computational science, data management and analysis have been key factors in the success of Brookhaven National Laboratory’s scientific programs at the Relativistic Heavy Ion Collider (RHIC), the National Synchrotron Light Source II (NSLS-II), the Center for Functional Nanomaterials (CFN), and in biological, atmospheric, and energy systems science, Lattice Quantum Chromodynamics (LQCD) and Materials Science, as well as our participation in international research collaborations, such as the ATLAS experiment at Europe’s Large Hadron Collider (LHC) at CERN (Switzerland) and the Belle II experiment at KEK (Japan). The construction of a new data center is an acknowledgement of the increasing demand for computing and storage services at BNL in the near term and enable the Lab to address the needs of the future experiments at the High-Luminosity LHC at CERN and the Electron-Ion Collider (EIC) at BNL in the long term.

(Invited) Stabilizing High-Nickel Content Layered Cathode Materials through Introducing Hierarchical Valence Gradient

Stabilizing high-nickel content layered cathode materials through introducing hierarchical valence gradient Ruoqian Lin1, Seongmin Bak1, Huolin L. Xin2, Xiao-Qing. Yang1,* 1 Chemistry Division, Brookhaven National Laboratory 2 Department of Physics and Astronomy, University of California, IrvineHigh Ni-content layered oxide as cathode materials for lithium-ion batteries have attracted great research interest recently. Taking advantage of two-electron transfer per Ni by the Ni2+/Ni4+ redox, high-Ni-content cathode materials can potentially provide much higher capacity than traditional layered cathode materials such as LiCoO2 or Li Ni1/3Mn1/3Co1/3O2 (NMC333). However, the structure and surface instability of this type of materials renders poor capacity retention and thermal stability, which need to be addressed for this material to be used as lithium-ion battery cathode material for electric vehicles. To overcome all these challenges, we investigated a new type of secondary particle engineering that has a uniform Ni:Mn:Co 811 chemical composition throughout the particle but with the nickel oxidation state spatially changing from Ni2+ to Ni3+ along the radial direction of the particle from the surface to the center. The goal of this study is to understand how this new gradient structure slows down the performance deterioration and structural degradation of high-Ni-content materials. Also, this study will differentiate the effect of Ni valence gradience from the concentration gradience, which has been widely utilized to improve the surface and structural stability of high-Ni-content cathode materials. By combining in-situ/ex-situ multi-scale multi-probe characterization tool, including electron and synchrotron X-ray imaging and spectroscopy, the LiNi0.8Mn0.1Co0.1O2 with Ni valence gradience is investigated at multiple length scales. We found that nanopores and micro cracks are more favored to be formed in the center of the secondary particles rather than on the surfaces, which indicates that degradation could initiate from the center bulk rather than particle surfaces. It is also found that Ni valence gradience along the radial direction across the secondary particle is well retained during electrochemical cycling, which implies that lower valence state Ni on the surfaces can stabilize the material surfaces and mitigate the internal structure degradation. Time-resolved in-situ thermal stability studies show that, compared with regular LiNi0.8Mn0.1Co0.1O2 materials, introducing Ni valence gradience greatly enhances the thermal stability and prohibits oxygen release related thermal runaway. It is also found that calcination atmosphere is one of the key factors that can tune the chemical hierarchical structure of high-Ni-content cathode materials, which provides valuable guidance for future material design and scaling up synthesis. Acknowledgement The work done at Brookhaven National Laboratory was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technology Office of the U.S. DOE through the Advanced Battery Materials Research (BMR) Program, including Battery500 Consortium under contract No. DE-SC0012704. This research used the National Synchrotron Light Source II and the Center for Functional Nano-materials (CFN), U.S. DOE Office of Science User Facilities operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. Thework done by UCI was supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Award Number: DE-EE0008444. Dr. Y. Shin was supported by the Office of Vehicle Technologies of the U.S. Department of Energy under contract number DE-AC02-06CH11357.

Use of Multi-Modal Synchrotron Analytical Techniques to Understand Anomalous Localized and General Corrosion Behavior of Additively Manufactured 316L Stainless Steel

Additive manufacturing (AM) of alloys such as stainless steels has the potential to be a disruptive technology for design of complex structures which eliminates the potentially damaging effects of mechanical failure and localized corrosion associated with interfaces between separate parts (which can now be printed as part of a single assembly). In addition, increasingly complex geometries can be manufactured with nearly as much ease as simple ones, and new mechanisms for optimization and generative design can allow manufacturers to achieve significant material and weight savings. However, challenges remain, in particular due to the potential for material variabilities both between parts made with the same nominal build parameters and even within a single build, as the consistency in properties inherent in the commercial-scale forging of alloys to be machined into components is exchanged for the considerable advantages of on-site, distributed custom parts production. Our studies and related work by other groups indicates that this is clearly true in the case of corrosion susceptibility in AM alloys. By studying the relationship between build parameters and electrochemical properties, we propose that it will be possible to tailor alloys for enhanced corrosion properties.AM processes produce materials with hierarchical microstructures containing fusion boundaries at the macroscale, irregular grains and grain boundaries at the microscale, and subgrain dislocation structures at the nanoscale. In laser powder bed fusion (LPBF) formed 316L stainless steel structures, corrosion performance has been discussed in the context of chemical heterogeneities formed in the presence of these hierarchical microstructures. However, the large variability in reported measurements underscores the need for statistically significant microstructural data, which is often difficult to access via electron microscopy alone. In this presentation, we explore multi-modal synchrotron X-ray techniques for quantifying hierarchical microstructures and their connection to the underlying chemical distribution in 316L stainless steel. Our results show that the dislocation density depends on the printing conditions with implications for the chemical distribution at the nanoscale, which in turn may play a key role in inconsistent corrosion behavior.LPDF 316L samples formed at varying speeds using pulsed and continuous laser deposition are compared via cyclic polarization in 3.5% NaCl and 0.1M HCl solutions, as well as using standard methods for characterizing sensitization. Surface corrosion layers are characterized using laboratory-based X-ray photoelectron spectroscopy to determine the impact on passivity of the aforementioned microsegregation associated with process-induced microstructures. Corrosion rates and pit densities are then discussed to build a connection between printing conditions and corrosion performance vis-à-vis microstructural and chemical information from synchrotron measurements performed at Brookhaven National Laboratory (BNL), including high energy X-ray diffraction using the X-ray Powder Diffraction (XPD) beamline at the National Synchrotron Light Source-II (NSLS-II) which provided data on minor precipitate population(s), atomic structure and dislocation microstructures critical to corrosion behavior. In addition, heterogeneities in elemental composition data is provided by 2D X-ray fluorescence (XRF) and 2D X-ray Absorption Spectroscopy (XAS) nanometer resolution-mapping obtained at the Hard X-ray Nanoprobe (HXN) beamline at the NSLS-II and correlated with process-induced hierarchal structures via use of the microscopy facilities at the Center for Functional Nanomaterials (CFN).By employing a combination of multi-modal synchrotron characterization techniques, electron microscopy, and baseline testing protocol combined with electrochemical polarization experiments, we are able to study the the role of microstructure across multiple length scales on electrochemical properties and corrosion performance. Understanding the impact of microstructure and chemical heterogeneities on the susceptibility to pitting and intergranular attack will enable microstructurally-informed process optimization and materials design for enhancing the corrosion resistance of LPBF 316L stainless steel, with implications for AM and subsequent durability of alloys in general.

Construction of a New Data Center at BNL

Computational science, data management and analysis have been key factors in the success of Brookhaven National Laboratory’s scientific programs at the Relativistic Heavy Ion Collider (RHIC), the National Synchrotron Light Source II (NSLS-II), the Center for Functional Nanomaterials (CFN), and in biological, atmospheric, and energy systems science, Lattice Quantum Chromodynamics (LQCD) and Materials Science, as well as our participation in international research collaborations, such as the ATLAS experiment at Europe’s Large Hadron Collider (LHC) and the Belle II experiment at KEK (Japan). The construction of a new data center is an acknowledgement of the increasing demand for computing and storage services at BNL.

Electrospray deposition tool: Creating compositionally gradient libraries of nanomaterials.

Electrospray deposition (ESD) enables the growth of solution deposited thin films in a precise and continuous manner by the delivery of submicron droplets of dilute solutions to a heated substrate. By combining ESD with programmable motor control and gradient solution pumping in a first-of-its-kind user tool at the Center for Functional Nanomaterials at Brookhaven National Laboratory, we show the ability to create one or two dimensional compositional gradient nanoscale films via ESD. These capabilities make it possible to construct thin film multicomponent "libraries" on a single substrate to rapidly and systematically characterize composition-dependent properties in a variety of material systems such as thin films involving homopolymer and block copolymer blends. We report the design, construction, and validation of a gradient ESD tool that allows users to carefully control the jet stability, flow composition, spray position, and substrate temperature. Calibrated thin films range in thickness from tens to hundreds of nanometers. We demonstrate gradient thin films using a ternary dye triangle as well as a gradual blending of polystyrene homopolymer with poly(styrene-block-methyl methacrylate) on a single substrate. Paired with the rapid measurement capabilities of synchrotron small angle X-ray scattering, this tool forms an integral part of a new platform for high-throughput, autonomous characterization and design of nanomaterial thin films and soft materials more generally.

Author Correction: Continuous production of pure liquid fuel solutions via electrocatalytic CO2 reduction using solid-electrolyte devices

This work was supported by Rice University. This research used the 8-ID (ISS) beamline of the National Synchrotron Light Source II and the Center for Functional Nanomaterials, US Department of Energy Office of Science User Facilities operated for the DOE Office of Science by Brookhaven National Laboratory under contract no. DE-SC0012704. Q.J. and H.N.A. acknowledge the support from King Abdullah University of Science and Technology (KAUST).

In Situ Transmission Electron Microscopy for Energy Applications

Jing Li obtained her BSc from Shandong University, China in 2012 and her PhD from Stony Brook University in 2018, both in Material Science. She was awarded the Presidential Scholar Award twice (2014 and 2015) from the Microscopy Society of America. Her PhD research is on probing reaction dynamics of battery electrode materials in real time using in situ transmission electron microscopy. She is currently working in the semiconductor industry in Silicon Valley, USA. Grayson Johnson obtained his BSc in Chemistry with a specialization in chemical physics at the University of Virginia (2016). Currently, he is a PhD candidate at the University of Virginia with Prof. Sen Zhang. His research interests are primarily in both theoretical and experimental surface chemistry of nanomaterials for oxygen electrocatalysis and CO2-to-fuel conversion. Sen Zhang is an assistant professor of Chemistry at the University of Virginia. He obtained his BSc in polymer chemistry from the University of Science and Technology of China (2008) and his PhD degree in Chemistry from Brown University (2014). He was a NatureNet Postdoc Fellow at the University of Pennsylvania from 2014 to 2016. His current research interests include controlled synthesis, assembly, and characterization of nanosized electrocatalysis for energy or environmental applications. Dong Su is a staff scientist at Center for Functional Nanomaterials in Brookhaven National Laboratory and an adjunct professor in the Materials Science and Chemical Engineering Department of Stony Brook University. He obtained his BSc (1998) and PhD (2003) in condensed matter physics from Nanjing University, China. Before joining Brookhaven Lab in 2008, he performed postdoctoral work at EPFL in Switzerland, at University of Illinois in Urbana Champaign, and at Arizona State University. His current research focuses on developing advanced electron micrscopy techniques for in situ characterization of energy-related materials.

Oxygen Reduction on Gold Nanocrystal Surfaces in Alkaline Electrolyte: Effects of Surface Proton Transfer

The surface atomic structures of metal catalysts play critical roles in determining the kinetics and mechanisms of catalytic reactions. Intrinsic correlations between surface structures and catalytic performances have been extensively studied for the bulk single-crystal surfaces. In oxygen reduction reaction (ORR), an essential reaction in energy conversion devices such as alkaline fuel cells, a complete four-electron (4e) ORR is preferred because energy conversion is twice as efficient compared with the partial two-electron (2e) ORR pathway. Adzic and co-workers pioneered the study of structural sensitivity of the ORR pathway on gold (Au) surfaces. They found that the ORR in alkaline electrolytes proceeds via a 2e reduction to hydroperoxide ions (O2H−) on the majority of facets including Au(111)[ 1 ], while the complete 4e reduction to hydroxide ions (OH−) occurs only in a limited potential region on Au(100)[ 2 ] and on the high-index Au(910) and Au(11,1,1) single crystal surfaces with a large fraction of the {100} sub-facet[ 3 ]. However, the reasons for such ORR behaviors on Au surfaces remain unclear. In this study, we synthesized three monofacet Au nanocrystals with well-defined shapes[ 4 ], including octahedra, cubes and truncated ditetragonal prisms (TDPs), which are enclosed by {111}, {100}, and {310} surfaces, respectively. The surface cleanness and high crystallinity of Au nanocrystals are confirmed by several structural characterization techniques, and by electrochemical characterizations including cyclic voltammetry (CV) and thallium underpotential deposition (Tl UPD). The Au octahedral and cubic nanocrystals demonstrate good resemblance of the ORR behaviors to those on their bulk single-crystal counterparts. Intriguingly, the TDP particles enclosed with twelve {310} facets catalyze the 4e ORR over the full potential range that has not been seen. Density functional theory (DFT) calculations were carried out for the ORR on the three Au surfaces without and with co-adsorbed water. The DFT-calculated free energy diagrams, in combination with experimental electrochemical results, elucidate how the surface proton transfers activate the facet- and potential-dependent 4e ORR on Au {100} and {310}. The new insight helps mechanism studies of facet-sensitive catalytic reactions, and provides guidance for designing nanocatalysts with optimal surface structures for various reactions. Acknowledgment The research was carried out at the Center for Functional Nanomaterials and the Chemistry Division of Brookhaven National Laboratory, supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-SC0012704. We acknowledge the computational resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Stand-alone polarization-modulation infrared reflection absorption spectroscopy instrument optimized for the study of catalytic processes at elevated pressures.

This paper describes the design and construction of a compact, "user-friendly" polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS) instrument at the Center for Functional Nanomaterials (CFN) of Brookhaven National Laboratory, which allows studying surfaces at pressures ranging from ultra-high vacuum to 100 Torr. Surface infrared spectroscopy is ideally suited for studying these processes as the vibrational frequencies of the IR chromophores are sensitive to the nature of the bonding environment on the surface. Relying on the surface selection rules, by modulating the polarization of incident light, it is possible to separate the contributions from the isotropic gas or solution phase, from the surface bound species. A spectral frequency range between 1000 cm-1 and 4000 cm-1 can be acquired. While typical spectra with a good signal to noise ratio can be obtained at elevated pressures of gases in ∼2 min at 4 cm-1 resolution, we have also acquired higher resolution spectra at 0.25 cm-1 with longer acquisition times. By way of verification, CO uptake on a heavily oxidized Ru(0001) sample was studied. As part of this test study, the presence of CO adsorbed on Ru bridge sites was confirmed, in agreement with previous ambient pressure X ray photoelectron spectroscopy studies. In terms of instrument performance, it was also determined that the gas phase contribution from CO could be completely removed even up to pressures close to 100 Torr. A second test study demonstrated the use of the technique for studying morphological properties of a spin coated polymer on a conductive surface. Note that this is a novel application of this technique. In this experiment, the polarization of incident light was modulated manually (vs. through a photoelastic modulator). It was demonstrated, in good agreement with the literature, that the polymer chains preferentially lie parallel with the surface. This PM-IRRAS system is small, modular, and easily reconfigurable. It also features a "vacuum suitcase" that allows for the integration of the PM-IRRAS system with the rest of the suite of instrumentation at our laboratory available to external users through the CFN user proposal system.

(Invited) Visualizing Electrochemical Reactions at the Nanoscale By in-Situ TEM

Over the past five years, we have witnessed a rapid growth in liquid and gas flow holders for TEM and X-ray microscopes. These holders have enabled direct imaging of material transformations in liquid and gaseous environments with submicron-scale to atomic-scale spatial resolution. In particular, research regarding electrode materials in lithium ion batteries and nanocatalysts in heterogeneous catalysis has greatly benefited from the emergence of these capabilities. Despite their initial success in in-situ battery studies, similar class of problems in electrocatalysis has been rarely addressed using existing liquid electrochemical holders. In this talk, I will showcase the capability of direct nanoscale visualization of electrochemical formation and degradation of electrocatalysts utilizing an operando TEM liquid holder and I will also discuss existing challenges that the in-situ EM field need to address. Acknowledgement The research used resources of the National Synchrotron Light Source II and the Center for Functional Nanomaterials, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. The electron microscopy experiment was performed at the Center for Functional Nanomaterials. This research is also partially supported by Laboratory Directed Research and Development (LDRD15-037) program at the Brookhaven National Laboratory.

Ab Initio Studies of Ultrathin Ionic Liquid Films on Au (111) Surface

Room-temperature ionic liquids (RTILs) as alternative electrolytes are of great interest to electrochemical energy storage devices, such as supercapacitors. A key to understanding the performance of these systems is to know the ion arrangement near the electrode surface and the ion-electrode interaction. In this work, we will present our ab initio studies of a few layers of 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide (EMMIM TFSI) ionic liquid on gold (111) surface, a system that was recently studied in a novel experiment using low-energy electron and photoemission electron microscopy (LEEM/PEEM). [1] Our work probes different ion arrangements on Au (111) and the corresponding work function change. We further investigate the most stable ion arrangement at different electrode charge densities and identify their out-of-plane layering structure. The dynamics of the ions with reordering and drifting under electric field can be inferred as well. We then use our findings to explain the observed changes in electron reflectivity/photoemission yield in LEEM/PEEM. Together, our results provide important understanding towards the structures and responses of ionic liquids on an electrified metal surface. This research was carried out at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under contract DE-SC0012704. [1] Wattaka Sitaputra, Dario Stacchiola, James F. Wishart, Feng Wang, and Jerzy T. Sadowsk, In situ Probing of Ion Ordering at Electrified Ionic Liquid/Au Interface, Adv. Mater. DOI:10.1002/adma.201606357

DFT investigation of the effect of spin-orbit coupling on the NMR shifts in paramagnetic solids

RP acknowledges financial support from the People Programme (Marie Curie Ac- tions) of the European Union’s Seventh Framework Pro- gramme (FP7/2007-2013) under REA grant agreement n◦ 317127. Via our membership of the U.K.’s HPC Materials Chemistry Consortium, which is funded by EPSRC (n ◦ EP/L000202), this work made use of the facilities of ARCHER, the U.K.’s national high-performance computing service, which is funded by the Office of Science and Technology through EPSRC’s High End Computing Programme. Research was also carried out at the Center for Functional Nanomaterials, Brookhaven National Lab- oratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract n◦ DE-AC02-98CH10886.

Molybdenum-Based Nanomaterials As High Efficient Electrocatalysts for HER

a, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P.R. China b, Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, USA * Email: wangdl81125@hust.edu.cn Electrochemical hydrogen evolution reaction (HER) as an efficient and eco-environmental approach to produce hydrogen has attracted tremendous attention1. Currently, the most efficient catalysts for HER are platinum group metals (e.g. Pt). However, the scarcity and high cost of precious metals limit their large-scale applications2. Therefore, it is of great importance to explore highly active catalysts for HER based on earth-abundant materials for the large scale hydrogen generation in both acid and alkaline media3. Here, carbon supported different molybdenum-based materials (MoP, MoS2, Mo2C) have been systematically synthesized via a simple solvothermal-high temperature treatment method. Different morphologies were obtained such as few layers and nanoparticles structures (Figure 1a and b). Electrochemical tests reveal that the prepared molybdenum- based electrocatalysts exhibit excellent HER performance in both acid and alkaline electrolytes (Figure 1c and d). This could be attributed to the excellent conductivity and the exposed substantial active sites for the nano-structure. In acid medium, carbon supported MoP exhibits the best catalytic activity for HER with an overpotential of 136 mV at a current density of 10 mA cm-2. While Mo2C-C possess the most predominant catalytic performance in alkaline medium compared with MoP and MoS2 with an overpotential of 149 mV. Unexpectedly, in the present work, carbon supported MoS2 possess outstanding catalytic activity in both acid and basic electrolytes which is not common for molybdenum chalcogenides reported. This probably due to the low conductivity and strongly layer numbers dependent on the the active sites. Based on the facile preparation method and excellent electrocatalytic activities, this work will open a novelty avenue to prepare earth abundant based catalysts for energy conversion and storage. Figure 1. TEM images of MoS2-C (a) and Mo2C-C (b). LSVs of molybdenum compounds in 0.5 M H2SO4(c) and 1 M KOH (d). Acknowledgements This work was supported by the National Natural Science Foundation (21306060, 21573083), the Program for New Century Excellent Talents in Universities of China (NCET-13-0237), the Doctoral Fund of Ministry of Education of China (20130142120039).

Highly Efficient Nitrogen and Sulfur Co-Doped Three-Dimensional Graphene-Based Nanocatalysts for the ORR

a, Key Laboratory of Material Chemistry for Energy Conversion and Storage (Huazhong University of Science and Technology), Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P.R. China. *Email: wangdl81125@hust.edu.cnb, Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, USA Graphene, a single-atom-thick hexagonally arrayed sp2 carbon atoms bonded sheet, has attracted tremendous interest in renewable energy conversion and storage devices due to its extraordinary properties, especially ultrahigh specific surface area and predominant electron conductivity1. However, graphene based two-dimensional catalysts suffer from an irreversible re-stacking of the nanosheets due to the strong π-interaction during thermal annealing process and electrochemical measurements which would result in a lower surface area, limiting the mass transfer rate and even decreasing the catalytic activity as well as electrochemical stability. Figure 1 (a) TEM image of NSGCB; (b) ORR activity of NSGCB and the corresponding comparative catalysts; (c) TEM image of NSCNT-3; (d) ORR activity of NSCNT-3 and the corresponding comparative catalysts. Herein, we report two strategies for the synthesis of nitrogen and sulfur co-doped three-dimensional graphene intercalated structure nanomaterials as electro-catalysts for ORR in alkaline medium. One is the insertion of Vulcan XC-72 carbon spheres into the graphene layer, forming a graphene-Vulcan XC-72- grapheme “sandwich-like” structure2. The other way is partially unzipping of multi-walled carbon nanotubes to form a graphene nanoribbon-carbon nanotube-graphene nanoribbon structure. Both of the prepared three-dimensional structured nanocomposites were experienced to nitrogen and sulfur co-doping process, and moreover, the resulting doped electro-catalysts exhibited outstanding ORR performance. AcknowledgementsThis work was supported by the National Natural Science Foundation (21306060, 21573083), the Program for New Century Excellent Talents in Universities of China (NCET-13-0237), the Doctoral Fund of Ministry of Education of China (20130142120039). References (1) Li, Y., Zhao, Y., Cheng, H., Hu, Y., Shi, G., Dai, L., & Qu, L. Nitrogen-doped graphene quantum dots with oxygen-rich functional groups. Journal of the American Chemical Society, 2011, 134, 15-18. (2) Wu, M., Wang, J., Wu, Z., Xin, H. L., & Wang, D. Synergistic enhancement of nitrogen and sulfur co-doped graphene with carbon nanosphere insertion for the electrocatalytic oxygen reduction reaction. Journal of Materials Chemistry A, 2015, 3, 7727-7731. Figure 1

Revealing Corrosion Chemistry in Lithium Ion Battery and Beyond--a Tale of Two "Cities"

Tailoring the surface chemistry to enhance corrosion resistance lies at the heart of materials processing for corrosion control of structural materials. This conventional wisdom, however, can fail miserably when the underlying materials’ function(s) involves chemical reactions. In this talk, I will introduce the concepts of surface passivation and passivity breakdown. I will show that, by tuning the surface composition, passivation can lead to successful optimization of intercalation cathode materials in lithium ion batteries (LIBs).[1,2] On the other hand, self-passivation in anode materials can significantly alter the rate performance of LIBs.[3,4] I will show that the rate capacity of a large family of phase conversion anode materials, i.e. transition metal oxides, is dependent on the stochastic process of passivity breakdown which can be described by a Poisson model.[5] This model can answer the long standing question—why transition metal oxides conversion materials perform much more poorly in sodium ion batteries than in LIBs, even though sodium ions can diffuse equally fast as lithium does in these materials.[6] Reference [1] Metal segregation in hierarchically structured cathode materials for high-energy lithium batteries, Feng Lin, et al, Yijin Liu*, H L Xin*, M Doeff*, Nature Energy, 1, 15004 (2016) [2] Surface reconstruction and chemical evolution of stoichiometric layered cathode materials for lithium-ion batteries, Feng Lin, Isaac Markus, Dennis Nordlund, Tsu-Chien Weng, Mark Asta, H. L. Xin*, M. M. Doeff, Nature Communications, 5, 3529 [3] Phase Evolution for Conversion Reaction Electrodes in Lithium-ion Batteries, Feng Lin, Dennis Nordlund, Tsu-Chien Weng, Ye Zhu, Chunmei Ban, Ryan Richards, and H L Xin*, Nature Communications, 5, 3356 [4] Three-dimensional hollow-structured binary oxide particles as an advanced anode material for high-rate and long cycle life lithium-ion batteries, Deli Wang, et al, H L Xin*, Nano Energy, 20, 212 (2016) [5] Transitions from Near-Surface to Interior Redox upon Lithiation in Conversion Electrode Materials, Kai He et al, Nano Letters, 15, 1437 (2015) [6] Sodiation Kinetics of Metal Oxide Conversion Electrodes: a Comparative Study with Lithiation, Kai He, et al H L Xin*, Dong Su*, Nano Letters, 15, 5755 Acknowledgement HLX acknowledges contributions from all coauthors, to name a few, Feng Lin, Kai He, Dong Su, Marca Doeff, Yijin Liu, Eric Stach, Ryan Richards, Xiqian Yu, Xiao-Qing Yang, Dennis Nordlund, and Deli Wang. This research is supported in part by the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704, and by Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. This research made use of resources of Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, which is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515.

Important Roles of Crystallinity in Voltage Fade of Li- and Mn-Rich Cathodes Exemplified By Li2Ru0.5Mn0.5O3 Studies

: Li- and Mn-rich cathode materials have been considered as promising candidates for application of lithium-ion batteries in vehicles due to their high capacity and high energy density (capacity around 250 mAh/g). However, these materials suffer from a serious problem of voltage fade. The average discharge voltage keeps decreasing as the cycling goes on and results in decreased energy output after limited cycles. In order to solve this problem, many efforts have been put in to understand the origin of such phenomenon, mostly from structural and chemical points of view. In this work, the important roles of crystallinity, or the microstructure of the cathode material in voltage fade are studied. The study is carried out on Li2Ru0.5Mn0.5O3 as an example. The material is electrochemically prelithiated to around Li3.2Ru0.5Mn0.5O3 first and then delithiated to Li2Ru0.5Mn0.5O3 . It is shown that even though the crystal structure mostly remains the same, the crystallinity is severely damaged by breaking the sub-micro domains into very fine nano-sized domains. Such loss of crystallinity causes much more significant voltage fade in the following cycling compared with those normally cycled samples. The more severe voltage fade caused by low crystallinity can be attributed to the accelerated oxygen loss due to the increased defects and surface area of the prelithiated sample. These results indicate the great importance of crystallinity of the cathode materials. Acknowledgement The work at Brookhaven National Laboratory was supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies under Contract No. DE-SC0012704. Use of the National Synchrotron Light Source II (NSLS-II) and Center for Functional Nanomaterials at Brookhaven National Laboratory were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contracts No. DE-SC0012704.

Ultra-Low Amount of Pt Decorated Pd-Based Nanoparticles for the Oxygen Reduction Reaction

Ultra-low amount of Pt decorated Pd-based nanoparticles for the oxygen reduction reaction Weiping Xiaoa,Sufen Liua, Huolin L. Xinb, and Deili Wanga,* a, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P.R. China b, Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, USA * Email: wangdl81125@hust.edu.cn Carbon-supported Pt-based catalysts have been considered as an ideal catalyst for the oxygen reduction reaction (ORR)1. In this regard, it is of great essential to enhance the utilization efficiency of Pt to reduce the overall fuel cell system cost. Recently, Pd-based nanomaterials as catalysts for ORR have attracted much attention because of their unique properties, such as the similar properties to Pt, and the relatively low cost compared with Pt2 , 3. Based on this, it is of great significance to design a highly active and stable PdM@Pt core-shell structure nanoparticle with PdM core and ultrathin Pt shell. Here, carbon supported Pd3V@Pt/C core-shell structure nanoparticle has been systematically synthesized via a simple impregnation-reduction method, followed by a spontaneous displacement of Pt. Electrochemical tests reveal that the half-wave potential of Pd3V@Pt/C shifts positively of 80 mV compared with that of Pd/C and the Pt mass activity of Pd3V@Pt/C improves by factors of 10.9 at 0.80 V relative to that of Pt/C. This can be attributed to the strain arising from the mismatch in lattice constant between the Pd3V core and ultrathin Pt shell. Furthermore, the morphology and elemental composition of the Pd3V@Pt/C nanoparticles before and after potential cycling tests are determined using an aberration-corrected Nion scanning transmission electron microscopy (STEM) equipped with an Enfina electron energy loss spectrometer (EELS). After 10 K potential cycling tests, there is no obvious morphology change, because the Pt-rich shell plays an important role in preventing degradation. Acknowledgements This work was supported by the National Natural Science Foundation (21306060, 21573083), the Program for New Century Excellent Talents in Universities of China (NCET-13-0237), the Doctoral Fund of Ministry of Education of China (20130142120039), the Fundamental Research Funds for the Central University (2013TS136, 2014YQ009). References (1) Wang, Y. J.; Zhao, N.; Fang, B.; Li, H.; Bi, X. T.; Wang, H., Chem . rev ., 2015, 115, 3433-3467. (2) Zhao, X.; Chen, S.; Fang, Z.; Ding, J.; Sang, W.; Wang, Y.; Zhao, J.; Peng, Z.; Zeng, J. , J . Am . Chem . Soc ., 2015, 137, 2804-2807. (3) Park, J.; Zhang, L.; Choi, S.-I.; Roling, L. T.; Lu, N.; Herron, J. A.; Xie, S.; Wang, J.; Kim, M. J.; Mavrikakis, M., ACS nano, 2015, 9, 2635-2647.