Environmental Molecular Sciences Laboratory Research Articles

One thousand soils for molecular understanding of belowground carbon cycling

While significant progress has been made in understanding global carbon (C) cycling, the mechanisms regulating belowground C fluxes and storage are still uncertain. New molecular technologies have the power to elucidate these processes, yet we have no widespread standardized implementation of molecular techniques. To address this gap, we introduce the Molecular Observation Network (MONet), a decadal vision from the Environmental Molecular Sciences Laboratory (EMSL), to develop a national network for understanding the molecular composition, physical structure, and hydraulic and biological properties of soil and water. These data are essential for advancing the next generation of multiscale Earth systems models. In this paper, we discuss the 1000 Soils Pilot for MONet, including a description of standardized sampling materials and protocols and a use case to highlight the utility of molecular-level and microstructural measurements for assessing the impacts of wildfire on soil. While the 1000 Soils Pilot generated a plethora of data, we focus on assessments of soil organic matter (SOM) chemistry via Fourier-transform ion cyclotron resonance-mass spectrometry and microstructural properties via X-ray computed tomography to highlight the effects of recent fire history in forested ecosystems on belowground C cycling. We observed decreases in soil respiration, microbial biomass, and potential enzyme activity in soils with high frequency burns. Additionally, the nominal oxidation state of carbon in SOM increased with burn frequency in surface soils. This results in a quantifiable shift in the molecular signature of SOM and shows that wildfire may result in oxidation of SOM and structural changes to soil pore networks that persist into deeper soils.

How Halide Sub-Lattice Affects Li Ion Transport in Antiperovskites

Li-based antiperovskites (LiAP, Li3-x OH x X, X = Cl, Br) are an emergent class of Li-ion conductors that are potential candidates for electrolytes in all-solid-state batteries. As a material class, pLiAP shows vast compositional design freedom; however, the resulting properties are susceptible to synthesis and processing methodologies. For example, proton incorporation and halide mixing stabilize the perovskite cubic phase near room temperature, and halides mixtures near the eutectic points drive the solid-state reaction temperature down, allowing for faster synthesis and processing conditions (< 1 h). The mixed halogen compositions, such as Li2OHCl0.37Br0.63, also show a 30-fold improvement in room temperature ionic conductivity of a single halide structure, 1.5 x 10-6 vs. 4.9 x 10-8 S cm-1 (Li2OHCl). Despite the growing interest in these materials, important questions remain about LiAPs on the structure-property correlation upon halide substitution and the correlations between the OH/halide dynamics and the Li-ion transport. We thus attempted to deconvolute how proton dynamics and halide substitution enhance or impede ionic conduction in pLiAP at compositions near the halide salts' eutectic points.We combined infrared spectroscopy and nuclear magnetic resonance (NMR) with first-principles density functional theory (DFT) calculations to deconvolute halide mixing effects from local proton dynamics on Li-ion transport. The NMR results and ab initio molecular dynamics suggest that Li+ transport is more strongly correlated with halide dynamics. While the hydroxide does stabilize the highly conductive cubic structure, it limits correlative ionic transport and thus lowers Li+ conductivity.Experiment design, data analysis, and manuscript preparation (RLS) were supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering. Synthesis (THB and JN) were supported by Asst. Secretary, Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (VTO) through the Advanced Battery Materials Research (BMR) Program. P. J. acknowledges partial support by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-FG02-96ER45579. H. F. was supported from U.S. Department of Energy (Award No. DE-EE0008865). This research used 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. The NMR characterization part of the work is supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, and Basic Energy Sciences. The NMR work was performed at the W. R. Wiley Environmental Molecular Sciences Laboratory, a DOE User Facility sponsored by the Office of Biological and Environmental Research, located at Pacific Northwest National Laboratory. Figure 1

WHONDRS-GUI: a web application for global survey of surface water metabolites.

BackgroundThe Worldwide Hydrobiogeochemistry Observation Network for Dynamic River Systems (WHONDRS) is a consortium that aims to understand complex hydrologic, biogeochemical, and microbial connections within river corridors experiencing perturbations such as dam operations, floods, and droughts. For one ongoing WHONDRS sampling campaign, surface water metabolite and microbiome samples are collected through a global survey to generate knowledge across diverse river corridors. Metabolomics analysis and a suite of geochemical analyses have been performed for collected samples through the Environmental Molecular Sciences Laboratory (EMSL). The obtained knowledge and data package inform mechanistic and data-driven models to enhance predictions of outcomes of hydrologic perturbations and watershed function, one of the most critical components in model-data integration. To support efforts of the multi-domain integration and make the ever-growing data package more accessible for researchers across the world, a Shiny/R Graphical User Interface (GUI) called WHONDRS-GUI was created.ResultsThe web application can be run on any modern web browser without any programming or operational system requirements, thus providing an open, well-structured, discoverable dataset for WHONDRS. Together with a context-aware dynamic user interface, the WHONDRS-GUI has functionality for searching, compiling, integrating, visualizing and exporting different data types that can easily be used by the community. The web application and data package are available at https://data.ess-dive.lbl.gov/view/doi:10.15485/1484811, which enables users to simultaneously obtain access to the data and code and to subsequently run the web app locally. The WHONDRS-GUI is also available for online use at Shiny Server (https://xmlin.shinyapps.io/whondrs/).

New Science with Atom Probe Tomography Enabled via an Environmental Transfer Hub

Journal Article New Science with Atom Probe Tomography Enabled via an Environmental Transfer Hub Get access Mark G Wirth, Mark G Wirth Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA Corresponding authors: mark.wirth@pnnl.gov, daniel.perea@pnnl.gov Search for other works by this author on: Oxford Academic Google Scholar Daniel E Perea Daniel E Perea Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA Corresponding authors: mark.wirth@pnnl.gov, daniel.perea@pnnl.gov Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 25, Issue S2, 1 August 2019, Pages 340–341, https://doi.org/10.1017/S1431927619002435 Published: 01 August 2019

(Invited) Development of Dual-Salts/Carbonate-Solvents Electrolytes for Fast Charging and Stable Cycling Lithium Metal Batteries

Rechargeable lithium (Li) metal batteries have received increasing attentions in recent years because of their high theoretical energy densities from the contribution of Li metal anode that has an ultrahigh theoretical specific capacity (3860 mAh g-1), the lowest redox potential (-3.040 V vs. the standard hydrogen electrode) and a low gravimetric density (0.534 g cm-3). However, significant challenges including Li dendrite growth and low Coulombic efficiency still impede the successful deployment of rechargeable Li metal batteries. A lot of efforts have been made in the past 45 years to address these problems, including the application of polymer electrolytes, solid-state electrolytes, ionic liquids, highly concentrated liquid electrolytes, additives, protecting layers, interlayers between Li and separator, nanoscale design, selective deposition, Li-reduced graphene oxide composites, and so on. Although some progresses have been achieved the challenges still remain. It has been reported that ether-based electrolytes are relatively stable with Li metal anode and can allow Li metal anodes to be cycled at reasonably high charging current densities, but these electrolytes are not stable at voltages above 4 V vs. Li/Li+. The conventional Li-ion battery electrolytes based on LiPF6/carbonate-solvents are stable at least up to 4.3 V but they suffer from the low Coulombic efficiency and poor charging current densities due to the reactivity of Li metal with LiPF6 salt and carbonate solvents. In the talk, we present the development of electrolytes based on LiTFSI-LiBOB dual-salt in carbonate solvent mixtures for rechargeable Li metal batteries with conventional Li-ion battery cathodes. It has been found that the dual-salt electrolytes greatly enhance the performances of Li metal batteries in terms of long-term cycling stability and fast charging capability over the conventional LiPF6/carbonate electrolytes. The dual-salt electrolytes also protect Li metal anodes by suppressing the corrosions of Li metal caused by the reactions of Li metal and electrolytes. Certain additives at a small amount level can even further significantly protect the Li metal anode and improve the battery performances. The possible mechanisms have been proposed based on the comprehensive characterizations. The details of the results will be reported at the meeting. Acknowledgements The research has been supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy (DOE) through the Advanced Battery Materials Research (BMR) Program and the Battery500 Consortium. The microscopy and spectroscopy measurements were performed at the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.

Structural Transformations in High Capacity Li2Cu0.5Ni0.5O2 Cathodes

Cathode chemistries with more than one lithium per transition metal (multi-lithium cathodes) are one approach for increasing the energy density of lithium-ion cells. Examples include lithium-rich NMCs (xLi2MnO3·(1−x)LiMO2 where M=Mn, Ni, Co), anti-fluorite type oxides, and several polyanionic compounds. Many of these cathodes have very high theoretical capacities, but none has proven practical for commercial cells. These materials generally undergo structural transformations, often accompanied by oxygen loss, which limit electrochemical reversibility. In this contribution, we present a thorough investigation of Li2Cu0.5Ni0.5O2, as a model system to understand the larger family of multi-lithium cathodes. Results from XRD, Raman spectroscopy, TEM, XANES, and gas evolution measurements follow the chemical, structural, and morphological changes that occur during electrochemical cycling. Our study broadly demonstrates the challenges associated with multi-lithium transition metal oxides, where there is close interplay between structure, transport, and oxygen loss that limits their use as high capacity cathodes for advanced lithium-ion systems. Acknowledgement Research has been supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy through the Advanced Battery Materials Research (BMR) Program. The authors acknowledge the support of Stanford Synchrotron Radiation Lightsource, a Directorate of SLAC National Accelerator Laboratory and an Office of Science User Facility operated for the U.S. Department of Energy Office of Science by Stanford University. X-ray diffraction was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. The TEM work was conducted in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a DOE User Facility operated by Battelle for the DOE Office of Biological and Environmental Research. Pacific Northwest National Laboratory is operated for the DOE under Contract DE-AC06-76RLO 1830.

21 Tesla Fourier Transform Ion Cyclotron Resonance Mass Spectrometer Greatly Expands Mass Spectrometry Toolbox.

We provide the initial performance evaluation of a 21 Tesla Fourier transform ion cyclotron resonance mass spectrometer operating at the Environmental Molecular Sciences Laboratory at the Pacific Northwest National Laboratory. The spectrometer constructed for the 21T system employs a commercial dual linear ion trap mass spectrometer coupled to a FTICR spectrometer designed and built in-house. Performance gains from moving to higher magnetic field strength are exemplified by the measurement of peptide isotopic fine structure, complex natural organic matter mixtures, and large proteins. Accurate determination of isotopic fine structure was demonstrated for doubly charged Substance P with minimal spectral averaging, and 8158 molecular formulas assigned to Suwannee River Fulvic Acid standard with root-mean-square (RMS) error of 10ppb. We also demonstrated superior performance for intact proteins; namely, broadband isotopic resolution of the entire charge state distribution of apo-transferrin (78kDa) and facile isotopic resolution of monoclonal antibody under a variety of acquisition parameters (e.g., 6s time-domains with absorption mode processing yielded resolution of approximately 1M at m/z = 2700). Graphical Abstract ᅟ.

(Invited) CsPF6 and Propylene Carbonate in Conventional LiPF6/Carbonate Electrolytes for Enhanced Lithium-Ion Battery Performances in Wide Temperature Range

Lithium-ion batteries (LIBs) have achieved great successes in portable electronic devices and have now started to enter the large-scale energy storage applications in transportations (such as pure electric vehicles and plug-in hybrid electric vehicles) and smart grid. Graphite is widely used as the anode material in the state-of-the-art LIBs. However, the graphite anode is usually only compatible with an ethylene carbonate (EC)-based electrolyte. In a propylene carbonate (PC)-containing electrolyte, which is advantageous over the EC-based counterpart due to its wider temperature range and lower cost, the graphite anode experiences significant exfoliation problem by the PC intercalation during the Li+ intercalation at charging steps. Thus a PC-containing electrolyte cannot be used in LIBs with graphite anode unless some solid electrolyte interphase (SEI) film-formation additives are included in the electrolytes. Such SEI formation additives normally contain unsaturated bonds or are unstable cyclic compounds, e.g. vinylene carbonate (VC), fluoroethylene carbonate (FEC), and lithium bis(oxalato)borate (LiBOB). They play an important role in the protection of the graphite structure from destruction by PC intercalation. However, these additives usually result in a thick SEI layer, which greatly reduces rate capability, limits low-temperature performance and hampers cycling stability at elevated temperatures through additional impedance and poor thermal stability.Recently, we have demonstrated that cesium cation (Cs+) as a novel electrolyte additive can direct the formation of a uniform, ultrathin and compact SEI layer on graphite electrode surface in EC-PC-containing electrolytes.[1] This SEI can not only significantly improve the compatibility between graphite anode and PC-containing electrolyte, but also lead to superior rate capability, enhanced low-temperature discharge performance, and excellent cycling stability at elevated temperatures.We also foundthat PC content in the electrolytes has great effect on the performances of graphite anode in half cells and full cells, and an optimal PC content of 20% by weight in solvent mixtures is identified.[2] The synergistic effects of Cs+ additive and appropriate amount of PC enable the formation of a robust, ultrathin and compact SEI layer on the surface of graphite electrode, which is only permeable for de-solvated Li+ ions and allows fast Li+ transport through it. In the continuation study, we further optimized the electrolyte formulations with CsPF6 additive by adjusting the EC and PC contents in electrolytes and evaluated the performances of graphite||LiNi0.80Co0.15Al0.05O2 full cells in terms of cycling at room temperature and elevated temperature, rate capacity and low-temperature discharge. One optimized electrolyte formulation is found to give about 70% discharge capacity retention at -40°C when compared to the room temperature discharge of the full cells, and simultaneously maintains other excellent performances. It is indicated that the optimal electrolyte consisting of CsPF6 and PC in conventional LiPF6/EC-based electrolyte is of great potential use in the state-of-the-art LIBs. The details of the results will be reported at the meeting. Acknowledgements This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, the Advanced Battery Materials Research Programs of the U.S. Department of Energy (DOE), and the Laboratory Directed Research and Development (LDRD) Project under the Technology Investment Program at Pacific Northwest National Laboratory (PNNL). The microscopy and spectroscopy measurements were performed at the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at PNNL.

The Effects of Synthesis Conditions on the Performances of Ni-Rich LiNixMnyCozO2 Cathode Materials for Lithium-Ion Batteries

Rechargeable lithium-ion batteries (LIBs) have become the dominant power sources not only for the consumer electronic devices but also for the pure electric vehicles (EVs) and plug-in electric vehicles (PHEVs) because of their high energy density, light weight and long cycle life. The increasing need on minimizing global warming and environmental pollution have accelerated the development of EVs. With the state of the art LIBs used in automobile industry, the driving range of EVs is still far behind those of conventional vehicles using internal combustion engines. Therefore, there is an urgent need to further improve both energy density and power capability of LIBs, to improve the driving range and decrease the recharging time. To meet these requirements, a lot of effort has been made in the search of high energy density electrode materials, especially the cathode materials. Recently, Ni-rich layered cathode materials LiNixMnyCozO2 (x ≥ 0.6) have received great attention as a potential cathode alternative due to their high achievable discharge capacity (200~220 mAh g-1),1 representing a significant improvement in energy density (~780 Wh kg-1) as compared to LiCoO2 (~570 Wh kg-1) and spinel LiMn2O4 (~440 Wh kg-1). Ni-rich cathode materials also show much higher lithium ion diffusion coefficients, signifying a superior power density as compared to other LiNixMnyCozO2 cathodes with lower Ni contents.2 The other advantage of Ni-rich cathode materials is the reduction of production cost owing to the reduced Co content. However, there are still some technical challenges hindering the mass applications of Ni-rich cathode materials, including (i) Li/Ni cation mixing due to the difficulty in maintaining all the Ni in 3+ valence state, (ii) micro strain and micro crack formation due to the significant volume variation during charge/discharge processes, (iii) safety issue because of the aggressive thermal reactions between the delithiated Ni-rich materials and the electrolyte. Much effort has been devoted to improving the electrochemical performance of the Ni-rich cathode materials.3 Representative approaches include lattice doping, surface treatment/modification, tuning the material compositions, and a smart design of core-shell or concentration gradient structures. Other than these useful treatment and design, the synthetic conditions, such as co-precipitation pH value, particle size, lithium content, calcination temperature, calcination atmosphere (O2, air etc.), heating/cooling rates, also play an important role in manipulating the material structural properties and thus influencing the electrochemical performances of prepared Ni-rich cathode materials. Herein, we systematically investigated the effects of calcination temperature on the primary particle size, cation mixing and the electrochemical performances of Ni-rich cathode materials. It is found that higher calcination temperature leads to considerable increase of primary particle size, which is supposed to largely reduce the side reactions between cathode material and the electrolytes. However, the materials prepared at high temperatures exhibited much poorer long-term cycling stability both at room temperature and high temperature of 60oC, in addition to their inferior rate performance. Therefore, the fundamental reasons behind this phenomenon are investigated in detail, which will be presented and discussed during the meeting. Acknowledgements This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, the Advanced Battery Materials Research Programs of the U.S. Department of Energy (DOE). The microscopy and spectroscopy measurements were performed at the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. References 1) A. Manthiram, J.C. Knight, S-T, Myung, S-M Oh, Y-K Sun, Adv. Energy Mater., 1501010 (2015). 2) Y. Wei, J. Zheng, S. Cui, X. Song, Y. Su, W. Deng, Z. Wu, X. Wang, W. Wang, M. Rao, Y. Lin, C. Wang, K. Amine, F. Pang, J. Am. Chem. Soc., 137, 8364 (2015). 3) W. Liu, P. Oh, X. Liu, M-J Lee, W. Cho, S. Chae, Y. Kim, J. Cho, Angew. Chem. Int. Ed., 54, 4440 (2015).

A Stable Carbon-Free Cathode for Rechargeable Lithium-Oxygen Battery with Long Cycle Performance

Lithium-oxygen (Li-O2) batteries have extremely high theoretical specific capacities and energy densities than Li-ion batteries. It is estimated that a practical Li-O2 battery could provide 3-5 times gravimetric energy density of conventional Li-ion batteries. The cathode active material (oxygen) is not stored in the Li-O2 battery and can be obtained from the environment outside the batteries. However, the cycle performances of these Li-O2 batteries are still limited by the stability of the air electrode and the electrolyte. Carbon-based electrodes are believed to decompose during charge and promote electrolyte decomposition as well. The fabrication of a stable and highly active carbon-free cathode for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) becomes a great challenge at present for the development of rechargeable Li-O2battery. Recently, some carbon-free cathode materials have been reported, including noble metals,1 oxides,2 and carbides.3 Metal oxides have low conductivities and are mainly utilized at low current densities. Noble metals show outstanding performance but may not be applicable due to the high cost and high density. Carbides can achieve good bi-functional activities for ORR and OER and be with low cost. However, only TiC was reported to achieve high cycle performance as a carbon-free cathode for Li-O2 batteries so far. Here we report the application of a novel material for the carbon-free cathode of Li-O2 batteries. The battery can be stably operated for more than 200 cycles with a stable voltage profile under the capacity-limited condition. With the aid of structure and composition characterizations, the mechanism of discharge and charge process is also investigated. This novel material is very promising for the use as an alternative carbon-free cathode, as well as for studying and exploring the stable electrolyte in rechargeable Li-O2batteries. Acknowledgements This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, the Advanced Battery Materials Research Programs of the U.S. Department of Energy (DOE). The microscopy and spectroscopy measurements were performed at the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. References Z. Peng, S. A. Freunberger, Y. Chen, P. G. Bruce, A Reversible and Higher-Rate Li-O2 Battery, Science., 337, 563 (2012). M. M. O. Thotiyl, S. A. Freunberger, Z. Peng, Y. Chen, Z. Liu, P. G. Bruce, A stable cathode for the aprotic Li-O2 battery, Nature Materials, 12, 1050 (2013). F. Li, D.M. Tang, Y. Chen, D. Golberg, H. Kitaura, T. Zhang, A. Yamada, H. Zhou, Ru/ITO: A Carbon-Free Cathode for Nonaqueous Li-O2 Battery, Nano Lett., 13, 4702 (2013).

Stable Operation of Lithium Metal Batteries by the Formation of Transient High Concentration Electrolyte Layer during Fast Discharge

Lithium (Li) metal anode has an ultrahigh theoretical capacity of 3860 mAh/g and the lowest electrochemical potential at -3.040 V vs. standard hydrogen electrode, which makes the rechargeable Li metal batteries as the “holy grail” of energy storage systems.1 However, the development and application of rechargeable Li metal batteries has been hindered in the past decades mainly due to two major problems¾the Li dendrite growth on Li anode during repeated charge/discharge processes and the low Coulombic efficiency. Although several approaches have been reported to suppress Li dendrite growth on Li metal, including forming Li alloys, adding electrolyte additives, using blocking electrolyte membranes, and to improve Coulombic efficiency, the enhancement on Li protection so far is not satisfactory. Recently, highly concentrated ether-based electrolyte has been reported to be more compatible with Li metal anode because high concentration of Li+ ions in these electrolytes facilities the fast Li deposition/stripping even at high current density conditions.2,3 However, ether-based electrolytes may not be suitable for use at charge cutoff voltage higher than ~4.0 V due to their poor stability against oxidation. In this work, we report for the first time the significantly improved performances of Li metal batteries using a LiNi1/3Mn1/3Co1/3O2 (NMC) cathode and a conventional carbonate solvent-based electrolyte by an appropriate cycling protocol to generate a transient, highly concentrated Li+ ion solution layer in the vicinity of Li metal surface. The highly concentrated electrolyte formed in the vicinity of Li anode surface facilitates the formation of an SEI layer with considerably enhanced stability. It is demonstrated that a high capacity retention >80% after 500 cycles can be achieved for the moderately high areal-capacity Li metal batteries at an optimized charging/discharging process. Based on the results of morphology observation and the composition characterization of the cycled Li metal anodes, a more profound understanding of the underlying mechanism behind the improved performances has been obtained. The fundamental findings of this work provide new insights for the further development of high energy density and long cycle life Li metal batteries. Details of the investigations will be reported and discussed in the presentation. Acknowledgements This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, the Advanced Battery Materials Research Programs of the U.S. Department of Energy (DOE). The microscopy and spectroscopy measurements were performed at the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. References A. Zhanmu, G. Chen, C. Liu, D. Neff, Q. Fang, Z. Yu, W. Xiong, Y. Wang, X. Wang, and B. Z. Jang, Energy Environ. Sci., 5, 5701 (2012). L. Suo, Y.-S. Hu, H. Li, M. Armand, and L. Chen, Nat. Commun., 4, 1481 (2013). J. Qian, W. A. Henderson, W. Xu, P. Bhattacharya, M. Engelhard, O. Borodin, and J.-G. Zhang, Nat. Commun., 6, 6362 (2015).

Behind the Stability of Graphite Anode in PC-Containing Electrolytes with a New Additive

Lithium-ion battery (LIB) is one of the most promising power sources for electronic devices and electric vehicles because of their high energy densities and relatively long lifetime. Graphite is widely used as the anode electrode material in the state-of-the-art LIBs. However, a graphite anode is usually only compatible with an ethylene carbonate (EC)-based electrolyte. In a propylene carbonate (PC)-containing electrolyte, which is advantageous over the EC-based counterpart due to its wider temperature range and higher low-temperature conductivity, the graphite anode experiences significant exfoliation problem during the initial lithium intercalation step. Thus a PC-containing electrolyte cannot be used in LIBs with graphite as the anode unless some solid electrolyte interphase (SEI) film-formation additives are included in the electrolytes. Usually these additives are electrochemically reduced predominantly on the graphite anode surface before PC is intercalated and reduced. Such additives normally contain unsaturated bonds or are unstable cyclic compounds, for instance, vinylene carbonate (VC) and fluoroethylene carbonate (FEC). They play an important role in the protection of the graphitic anode structure from destruction by PC reduction. However, these additives also have certain shortcomings. Usually these additives result in a thick SEI layer, which significantly reduces the rate capability and limits low-temperature performance and cycling stability at elevated temperatures through additional impedance and poor thermal stability. Recently, we developed a novel electrolyte additive that can suppress the PC reductive decomposition on the graphite anode without forming a thick and resistant SEI film. As shown in Figure 1, this additive can not only significantly improve the compatibility between graphite anode and PC-containing electrolyte, but also exhibit superior rate capability and excellent cycling stability at elevated temperatures.This new electrolyte additive can be applied to LIBs and other electrochemical systems using PC-containing electrolytes and graphite anodes. In this work, we systematically investigated the mechanism of the SEI formation by this additive and the protection of graphite anode in PC-containing electrolytes. Several techniques, including computational calculations and simulations, 17O nuclear magnetic resonance (NMR), “soft” electrospray ionization mass spectrometry (ESI-MS), time of flight second ion mass spectrometry (ToF-SIMS), etc. have been used to reveal the reasons behind the compatibility and stability of graphite anode in PC-containing electrolytes with this new additive. The details of the results will be reported at the meeting. Acknowledgements This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technology of the U.S. Department of Energy (DOE). The 17O NMR and ToF-SIMS measurements were performed at the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at PNNL. Figure 1

SEI-Film-Suppression Additive for Enhancing Compatibility and Electrochemical Stability of Graphite Anode in PC-Based Electrolytes

Lithium-ion batteries (LIBs) are one of the most promising power sources for electric vehicles because of their high energy density and long lifetime. Graphite is widely used as anode electrode material in the state-of-the-art LIBs. However, a graphite anode is usually only compatible with an ethylene carbonate (EC)-based electrolyte. When contacting with a propylene carbonate (PC)-based electrolyte, which is advantageous over the EC-based one for its wider temperature range and higher low-temperature conductivity, the graphite anode may suffer from substantial exfoliation problem during the initial lithium intercalation step. Consequently, a PC-based electrolyte cannot be used in LIBs with graphite as the anode unless some solid electrolyte interphase (SEI) film-formation additives are introduced into the electrolytes. Usually this type of additives is reduced predominantly on the graphite electrode surface before PC is intercalated and reduced. These additives mainly contain some functional groups such as vinylene or cyclic unsaturated compounds. For example, vinylene carbonate (VC) and fluoroethylene carbonate (FEC) have been widely studied and used as additives for PC-based electrolytes. They play an important role in the protection of the structure of the graphitic anode from destruction by PC, but they also have some shortcomings. Usually these additives result in a thick SEI protective layer, which could significantly reduce the rate capability and limit low-temperature performance and cycling stability at elevated temperatures because of its additional impedance and poor thermal stability. Recently, we developed a novel electrolyte additive that can suppress the PC reductive decomposition on the graphite anode without a thick and resistant SEI film. The additive may provide a novel protective mechanism for the graphite anode in the PC-containing electrolytes without or with suppressed SEI film formation. The SEI-film-suppression additive can not only significantly improve the compatibility between graphite anode and PC-containing electrolyte, but also exhibit superior rate capability and excellent cycling stability at elevated temperatures.We believe that this new electrolyte additive can be applied to LIBs and other electrochemical systems using PC-containing electrolytes and graphite anodes. The details of the results will be reported. Acknowledgements This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technology of the U.S. Department of Energy (DOE). The electron microscopy and XRD measurements were performed at the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at PNNL.

N-Doping Effect for Polysulfide Reservoir within Mesoscale Electrodes for Practical Application of Lithium Sulfur Batteries

Lithium sulfur batteries have become one of the most promising energy storage technologies, potentially meeting the needs for vehicle electrification and stationary applications, because of its lower costs, environmental friendly property and much higher energy density (cathode theoretical energy: 3500 Wh/kg, or 2800 Wh/L) than that of state-of-art Li-ion batteries. However, many challenges exist for the broad deployment of Li/S system. The main challenge is the low Columbic efficiency and fast capacity decay due to the shuttle reactions caused by the soluble intermediate polysulfide Nitrogen-doped porous carbon (NPC) and multi-wall carbon nanotube (MWCNT) have been frequently studied to immobilize sulfur in lithium-sulfur (Li-S) batteries. However, neither NPC nor MWCNT itself can effectively confine the soluble polysufides if cathode thickness e.g. sulfur loading is increased. In this work, NPC was combined with MWCNT to construct an integrated host structure to immobilize sulfur at a relevant scale. The function of doped nitrogen atoms was revisited and found to effectively attract sulfur radicals generated during the electrochemical process. The addition of MWCNT facilitated the uniform coating of sulfur nanocomposites to a practically usable thickness and homogenized the distribution of sulfur particles in the pristine electrodes, while NPC provided sufficient pore volume to trap dissolved species. More importantly, the wetting issue, the critical challenge for thick sulfur cathodes, is also mitigated after the adoption of MWCNT, leading to a high areal capacity of ca. 2.5 mAh/cm2 with capacity retention of 81.6% over 100 cycles. This work provides clues on the fundamental mechanism of N-doping and the strategies to practically develop nano-structured materials for battery applications. Acknowledgment This work was supported by the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. The EPR, XPS, and SEM analyses were performed in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the U.S. Department of Energy’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL).

Invited Talk: Development of Nonaqueous Redox Flow Battery Technologies

Nonaqueous redox flow batteries are generally considered to have higher energy densities than their aqueous counterparts because of their wider voltage windows. However, their performance has lagged far behind their inherent capability due to the combined limitations of redox chemistry, solubility of redox species, and cell design. Here we report a high-performance nonaqueous lithium–organic redox flow battery with a structure-modified ferrocene cathode. The ionic-liquid derivatization of ferrocene increases the solubility by more than 20 times in the supporting electrolyte (0.85 M as opposed to 0.04 M for pristine ferrocene). This improvement is confirmed by solvation chemistry studies through nuclear magnetic resonance analysis and density functional theory calculation. When coupled with a lithium-graphite hybrid anode, the flow battery exhibits a cell voltage of 3.49 V and energy efficiency over 75% (Figure 1). The method of material modification proved to be a viable way to prepare high-performance electrolyte for nonaqueous redox flow batteries.Development on the total-organic redox flow battery will also be presented. Acknowledgements The authors would like to acknowledge financial support primarily from the U.S. Department of Energy’s (DOE’s) Office of Electricity Delivery and Energy Reliability (OE) (under Contract No. 57558) and the support from Laboratory-Directed Research and Development Program (LDRD) of the Pacific Northwest National Laboratory (PNNL). The NMR characterization was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, and was conducted in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at PNNL. PNNL is a multi-program national laboratory operated by Battelle for DOE under Contract DE-AC05-76RL01830.

Direct Observation of Electrolyte Degradation Mechanisms in Li-Ion Batteries

Journal Article Direct Observation of Electrolyte Degradation Mechanisms in Li-Ion Batteries Get access B Layla Mehdi, B Layla Mehdi .Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar Patricia Abellan, Patricia Abellan .Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar Lucas R Parent, Lucas R Parent .Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar Meng Gu, Meng Gu .Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar Chiwoo Park, Chiwoo Park .Department of Industrial and Manufacturing Engineering, Florida State University, Tallahassee, FL,USA Search for other works by this author on: Oxford Academic Google Scholar Wu Xu, Wu Xu .Energy and Environmental Directorate, Pacific Northwest National Laboratory, Richland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar Yaohui Zhang, Yaohui Zhang .Energy and Environmental Directorate, Pacific Northwest National Laboratory, Richland, WA, USA.Center for Condensed Matter Science and Technology, Department of Physics, Harbin Institute of Technology, PR China Search for other works by this author on: Oxford Academic Google Scholar Ilke Arslan, Ilke Arslan .Energy and Environmental Directorate, Pacific Northwest National Laboratory, Richland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar Ji-Guang Zhang, Ji-Guang Zhang .Energy and Environmental Directorate, Pacific Northwest National Laboratory, Richland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar Chong-Min Wang, Chong-Min Wang .Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar ... Show more James E Evans, James E Evans .Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar Nigel D Browning Nigel D Browning .Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 20, Issue S3, 1 August 2014, Pages 1624–1625, https://doi.org/10.1017/S1431927614009854 Published: 27 August 2014

A NiII–Bis(diphosphine)–Hydride Complex Containing Proton Relays – Structural Characterization and Electrocatalytic Studies

AbstractThe synthesis of the 1,5‐diphenyl‐3,7‐diisopropyl‐1,5‐diaza‐3,7‐diphosphacyclooctane ligand, PiPr2NPh2, is reported. Two equivalents of the ligand react with [Ni(CH3CN)6](BF4)2 to form the bis(diphosphine)–NiII complex [Ni(PiPr2NPh2)2](BF4)2, which acts as a proton reduction electrocatalyst. In addition to [Ni(PiPr2NPh2)2]2+, we report the synthesis and structural characterization of the Ni0 complex Ni(PiPr2NPh2)2 and the NiII–hydride complex [HNi(PiPr2NPh2)2]BF4. The [HNi(PiPr2NPh2)2]BF4 complex represents the first NiII–hydride in the [Ni(PR2NR′2)2]2+ family of compounds to be structurally characterized. In addition to the experimental data, the mechanism of electrocatalysis facilitated by [Ni(PiPr2NPh2)2]2+ is analyzed by using linear free energy relationships recently established for the [Ni(PR2NR′2)2]2+ family.

Mitigating Voltage Fade in Cathode Materials By Improving Atomic Level Spatial Uniformity of Chemical Species

Lithium- and manganese-rich (LMR) layered-structure cathode materials deliver a much higher energy density than traditional cathode materials such as LiMn2O4 spinel and LiCoO2. However, significant challenges, including voltage fade and limited cycle life in LMR cathodes still remain to be overcome prior to their large-scale market penetration.Here, we report on the direct correlation between voltage fade and atomic level spatial distribution of chemical species among LMR cathode materials (Li[Li0.2Ni0.2M0.6]O2) prepared by several methods, including co-precipitation (CP), sol-gel (SG) and hydrothermal assisted (HA) methods. Quantitative chemical composition analysis was performed on these materials using large-area X-ray energy dispersive spectroscopy (XEDS) mapping. Meanwhile, we used aberration-corrected scanning transmission electron microscopy (STEM) combined with electron energy loss spectroscopy (EELS) to acquire detailed crystallographic data on Li[Li0.2Ni0.2Mn0.6]O2 cathode prepared by different methods. The atomic contrast in high-angle annular dark field (HAADF) STEM imaging identified the details of stacking and ordering in the particles while EELS chemical analysis revealed important chemistry information. We found that the materials prepared by the CP and SG methods exhibit a relatively high propensity for Ni segregation, leading to fast voltage fade and poor cycling stability. However, material prepared by the HA method exhibits very uniform Ni distribution and greatly reduced voltage fade. To the best of our knowledge, this is the first direct atomic-scale evidence to correlate atomic level cation uniformities with the electrochemical performance of cathode materials. More importantly, the voltage fade and energy degradation of LMR cathode materials can be significantly mitigated by improving the uniformity of chemical species in atomic level that are strongly affected by the preparation methods and synthesis conditions. These results also shine the light on the current debate regarding to the average/local structure of LMR cathode materials. LMR cathodes prepared by co-precipitation and sol-gel methods exhibit significant Ni segregation and dominated by LiMO2 R-3m phase, where the preferential segregation of Ni blocks lithium ion diffusion channels, weaken nickel-manganese interactions, lead to easy reduction of the manganese ions and fast voltage/capacity fade. In contrast, LMR cathodes prepared by the hydrothermal assisted method form a solid solution dominated by Li2MO3C2/m monoclinic symmetry with largely suppressed Ni segregation and are more stable against excessive lithium ion removal, enhance Ni-Mn interaction and stabilize crystal structure, leads to greatly reduced voltage fade and excellent cycling stability of LMR cathodes. Therefore, LMR cathodes with uniform distribution of chemical species (minimal Ni segregation) are very promising for use in high-energy Li-ion batteries for large-scale practical applications. The fundamental correlation between the atomic level spatial distribution of the chemical species and the functional stability of the materials found in this work also provides new perspective on the design and development of other functional materials with significantly enhanced stability. Acknowledgements This work is supported by the 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, Subcontract No. 18769, under the Batteries for Advanced Transportation Technologies program. The microscopic study described in this paper is supported by the Laboratory Directed Research and Development Program as part of the Chemical Imaging Initiative at Pacific Northwest National Laboratory (PNNL). The work was conducted in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at PNNL. PNNL is operated by Battelle for the DOE under Contract DE-AC05-76RLO1830. The authors also would like to thank M. M. Thackeray for useful discussions.

Shining a spotlight on intact proteins

Cells react to cues from their environment using various mechanisms that include changes in metabolites, gene expression, protein binding partners, protein localization, and protein posttranslational modifications (PTMs), all of which contribute to altered cellular signatures that enable appropriate cellular responses. Given the seemingly infinite number of mechanisms available to affect protein function and modulate biological processes, the question arises as to how cells manage to interpret protein readouts to accomplish the appropriate cell-type specific response to a particular stimulus.

Reduction Mechanism of Fluoroethylene Carbonate for Stable Solid Electrolyte Interphase Film on Silicon Anode

Silicon (Si) is one of the most promising anode materials for Li-ion batteries because of its very high specific capacity (4212 mAh/g for Li21Si5).1 However, the high specific capacity of silicon is associated with large volume changes (more than 300 percent) when alloyed with lithium. These extreme volume changes can cause severe cracking and disintegration of the electrode and lead to capacity loss. The degradation of the carbonate solvents or the continuous growth of the Solid Electrolyte Interphase (SEI) film during cycling also results in significant irreversible capacity loss because it decreases electrochemical reactivity of electrodes.Fluoroethylene carbonate (FEC) is a well-known electrolyte additive for silicon anodes which can significantly enhance the stability and flexibility of SEI film and improve the stability and Coulombic efficiency of silicon-based anodes.2, 3 Although FEC has demonstrated significant effect on the electrochemical performance of silicon-based anodes, the fundamental mechanisms of this effect are still controversial in the literature. One possible reduction mechanism of FEC on silicon-based anodes is that the FEC first converts into vinylene carbonate (VC) through defluorination and then the resultant VC polymerizes.2, 4, 5 The main products from this mechanism are LiF and poly(vinylene carbonate). Another possible reduction mechanism is that the FEC is reduced through opening the five-member ring to form a (CH2CHFOCO2Li)2 dimer.6 According to these two mechanisms, the FEC reduction products formed in the SEI film should be LiF and poly(vinylene carbonate) or (CH2CHFOCO2Li)2.2, 6 In both cases, the lithium-to-fluorine ratio of the reaction products is close to 1. The majority of the fluorine should exist in either LiF or organic products,4-7but not in both forms. However, our recent analysis found that the ratio of lithium to fluorine is ≥1.5 for the SEI film formed on a silicon-based anode which was cycled in an electrolyte with FEC as additive or pure FEC as solvent (table 1).Our X-ray Photoelectron Spectroscopy (XPS) study also reveals that fluorine exists in both LiF and organic compounds (Figure 1), which cannot be explained by the previous mechanisms proposed in the literature. Therefore, a new mechanism has been proposed (Figure 2) and verified for the reduction and polymerization of FEC and the formation of a stable SEI layer on anode materials. According to this mechanism, FEC is reduced on the anode surface through the opening of the five-member ring, leading to the formation of lithium poly(vinyl carbonate), LiF, and some dimers. Table 1 The percentage of Li, C, O and F in the SEI films in electrolytes (a) 1M LiPF6 in EC/DMC (1:2 in vol), (b) 1M LiPF6 in EC/DMC (1:2 in vol) with 10% FEC and (c) 1M LiClO4in pure FECElements samples%Li%C%O%FLi/F ratioElectrolyte (a), 2 cycles27.723.324.124.91.11Electrolyte (a), 35 cycles22.731.337.68.42.70Electrolyte (b), 2 cycles22.932.532.112.51.83Electrolyte (b), 100 cycles21.033.831.913.31.58Electrolyte (c), 2 cycles21.134.732.212.01.76 Figure 1 XPS spectra of F1s for the SEI film formed in LiClO4/FEC electrolyte Figure 2Proposed possible reduction reaction of FEC Acknowledgment This work was supported by the 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, Subcontract No. 18769 under the Batteries for Advanced Transportation Technologies (BATT) program. A portion of the research was performed in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Reference 1. B. A. Boukamp, G. C. Lesh, and R. A. Huggins, Journal of The Electrochemical Society, 128(4), 725-729 (1981).2. V. Etacheri, O. Haik, Y. Goffer, G. A. Roberts, I. C. Stefan, R. Fasching, and D. Aurbach, Langmuir : the ACS journal of surfaces and colloids, 28(1), 965-976 (2012).3. N.-S. Choi, K. H. Yew, K. Y. Lee, M. Sung, H. Kim, and S.-S. Kim, Journal of Power Sources, 161(2), 1254-1259 (2006).4. D. Aurbach, K. Gamolsky, B. Markovsky, Y. Gofer, M. Schmidt, and U. Heider, Electrochimica Acta, 47(9), 1423-1439 (2002).5. S. S. Zhang, Journal of Power Sources, 162(2), 1379-1394 (2006).6. Z.-C. Wang, J. Xu, W.-H. Yao, Y.-W. Yao, and Y. Yang, ECS Transactions, 41(41), 29-40 (2012).7. H. Wu, G. Chan, J. W. Choi, I. Ryu, Y. Yao, M. T. McDowell, S. W. Lee, A. Jackson, Y. Yang, L. Hu, and Y. Cui, Nat Nano, 7 (5), 310-315 (2012).