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Baggetto, Loic

Publications and source records attributed to Baggetto, Loic.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Amorphous alumina thin films deposited on titanium: Interfacial chemistry and thermal oxidation barrier properties

Ti/Al 2 O 3 bilayer stacks are used as model systems to investigate the role of atomic layer deposition (ALD) and chemical vapor deposition (CVD) to prepare 30-180 nm thick amorphous alumina films as protective barriers for the medium temperature oxidation (500-600⁰C) of titanium, which is employed in aeronautic applications. X-ray diffraction (XRD), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) results show that the films produced from the direct liquid injection (DLI) CVD of aluminum tri-isopropoxide (ATI) are poor oxygen barriers. The films processed using the ALD of trimethylaluminum (TMA) show good barrier properties but an extensive intermixing with Ti which subsequently oxidizes. In contrast, the films prepared from dimethyl aluminum isopropoxide (DMAI) by CVD are excellent oxygen barriers and show little intermixing with Ti. Overall, these measurements correlate the effect of the alumina coating thickness, morphology, and stoichiometry resulting from the preparation method to the oxidation barrier properties, and show that compact and stoichiometric amorphous alumina films offer superior barrier properties.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Probing Battery Chemistry with Liquid Cell Electron Energy Loss Spectroscopy

We demonstrate the ability to apply electron energy loss spectroscopy (EELS) to follow the chemistry and oxidation states of LiMn 2 O 4 and Li 4 Ti 5 O1 2 battery electrodes within a battery solvent. The use and importance of in situ electrochemical cells coupled with a scanning/transmission electron microscope (S/TEM) has expanded and been applied to follow changes in battery chemistry during electrochemical cycling. Furthermore, we discuss experimental parameters that influence measurement sensitivity and provide a framework to apply this important analytical method to future in situ electrochemical studies.

25 ENERGY STORAGE↗
DOE OSTI2015

Preparation and CO 2 adsorption properties of soft-templated mesoporous carbons derived from chestnut tannin precursors

This paper presents a soft templating approach for mesoporous carbon using the polyphenolic heterogeneous biomass, chestnut tannin, as the carbon precursor. By varying synthesis parameters such as tannin:surfactant ratio, cross-linker, reaction time and acid catalyst, the pore structure could be controllably modulated from lamellar to a more ordered hexagonal array. Carbonization at 600 °C under nitrogen produced a bimodal micro-mesoporous carbonaceous material exhibiting enhanced hydrogen bonding with the soft template, similar to that shown by soft-templating of phenolic-formaldehyde resins, allowing for a tailorable pore size. By utilizing the acidic nature of chestnut tannin (i.e. gallic and ellagic acid), hexagonal-type mesostructures were formed without the use of an acid catalyst. The porous carbon materials were activated with ammonia to increase the available surface area and incorporate nitrogen-containing functionality which led to a maximum CO 2 adsorption capacity at 1 bar of 3.44 mmol/g and 2.27 mmol/g at 0 °C and 25 °C, respectively. The ammonia-activated carbon exhibited multiple peaks in the adsorption energy distribution which indicates heterogeneity of adsorption sites for CO 2 capture.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Understanding the role of NH 4 F and Al 2 O 3 surface co-modification on lithium-excess layered oxide Li 1.2 Ni 0.2 Mn 0.6 O 2

In this work we prepared Li 1.2 Ni 0.2 Mn 0.6 O 2 (LNMO) using a hydroxide co-precipitation method and investigated the effect of co-modification with NH 4 F and Al 2 O 3 . After surface co-modification, the first cycle Coulombic efficiency of Li 1.2 Ni 0.2 Mn 0.6 O 2 improved from 82.7% to 87.5%, and the reversible discharge capacity improved from 253 to 287 mAh g –1 at C/20. Moreover, the rate capability also increased significantly. A combination of neutron diffraction (ND), high-resolution transmission electron microscopy (HRTEM), aberration-corrected scanning transmission electron microscopy (a-STEM)/electron energy loss spectroscopy (EELS), and X-ray photoelectron spectroscopy (XPS) revealed the changes of surface structure and chemistry after NH 4 F and Al 2 O 3 surface co-modification while the bulk properties showed relatively no changes. These complex changes on the material s surface include the formation of an amorphous Al 2 O 3 coating, the transformation of layered material to a spinel-like phase on the surface, the formation of nanoislands of active material, and the partial chemical reduction of surface Mn 4+ . Such enhanced discharge capacity of the modified material can be primarily assigned to three aspects: decreased irreversible oxygen loss, the activation of cathode material facilitated with preactivated Mn 3+ on the surface, and stabilization of the Ni-redox pair. In conclusion, these insights will provide guidance for the surface modification in high-voltage-cathode battery materials of the future.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Type I clathrates as novel silicon anodes: An electrochemical and structural investigation

In this study, silicon clathrates contain cage-like structures that can encapsulate various guest atoms or molecules. Here we present an electrochemical evaluation of type I silicon clathrates based on Ba 8 Al y Si 46-y for the anode material in lithium-ion batteries. Post-cycling characterization with NMR and XRD show no discernible structural or volume changes even after electrochemical insertion of 44 Li into the clathrate structure. The observed properties are in stark contrast with lithiation of other silicon anodes, which become amorphous and suffer from larger volume changes. The lithiation/delithiation processes are proposed to occur in single phase reactions at approximately 0.2 and 0.4 V vs. Li/Li + , respectively, distinct from other diamond cubic or amorphous silicon anodes. Reversible capacities as high as 499 mAh g -1 at a 5 mA g -1 rate were observed for silicon clathrate with composition Ba 8 Al 8.54 S i37.46 , corresponding to Li:Si of 1.18:1. The results show that silicon clathrates could be promising durable anodes for lithium-ion batteries.

36 MATERIALS SCIENCE↗
DOE OSTI2014

The Local Atomic Structure and Chemical Bonding in Sodium Tin Phases

To understand these electrochemically-derived materials we have reinvestigated the formation of Na-Sn alloys to identify all the phases which form when x ≥ 1 (NaxSn) and characterized the local bonding around the Sn atoms with X-ray diffraction, 119 Sn M ssbauer spectroscopy, and X-ray absorption spectroscopies. The results from the well-defined crystallographic materials were compared to the spectroscopic measurements of the local Sn structures in the electrochemically prepared materials. The reinvestigation of the Na-Sn compounds yields a number of new results: (i) Na 7 Sn 3 is a new thermodynamically-stable phase with a rhombohedral structure and R-3m space group; (ii) orthorhombic Na 9 Sn 4 (Cmcm) has relatively slow formation kinetics suggesting why it does not form at room temperature during the electrochemical reaction; (iii) orthorhombic Na 14.78 Sn 4 (Pnma), better described as Na 16-x Sn 4 , is Na-richer than cubic Na 15 Sn 4 (I-43d). Characterization of electrochemically prepared Na-Sn alloys indicate that, at the exception of Na 7 Sn 3 and Na 15 Sn 4 , different crystal structures than similar Na-Sn compositions prepared via classic solid state reactions are formed. These phases are composed of disordered structures characteristic of kinetic-driven solid-state amorphization reactions. In these structures, Sn coordinates in asymmetric environments, which differ significantly from the environments present in Na-Sn model compounds.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

The reaction mechanism of FeSb 2 as anode for sodium-ion batteries

The electrochemical reaction of FeSb 2 with Na is reported for the first time. The first discharge (sodiation) potential profile of FeSb 2 is characterized by a gentle slope centered at 0.25 V. During charge (Na removal) and the subsequent discharge, the main reaction takes place near 0.7 V and 0.4 V, respectively. The reversible storage capacity amounts to 360 mA h g -1 , which is smaller than the theoretical value of 537 mA h g -1 . The reaction, studied by ex situ and in situ X-ray diffraction, is found to proceed by the consumption of crystalline FeSb 2 to form an amorphous phase. Upon further sodiation, the formation of nanocrystalline Na3Sb domains is evidenced. During desodiation, Na 3 Sb domains convert into an amorphous phase. The chemical environment of Fe, probed by 57 Fe Mo ssbauer spectroscopy, undergoes significant changes during the reaction. During sodiation, the well-resolved doublet of FeSb2 with an isomer shift around 0.45 mm s -1 and a quadrupole splitting of 1.26 mm s -1 is gradually converted into a doublet line centered at about 0.15 mm s1 along with a singlet line around 0 mm s -1 . The former signal results from the formation of a Fe-rich FexSb alloy with an estimated composition of Fe4Sb while the latter signal corresponds to superparamagnetic Fe due to the formation of nanosized pure Fe domains. Interestingly the signal of Fe4Sb remains unaltered during desodiation. This mechanism is substantially different than that observed during the reaction with Li. The irreversible formation of a Fe-rich Fe 4 Sb alloy and the absence of full desodiation of Sb domains explain the lower than theoretical practical storage capacity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Sodium manganese oxide thin films as cathodes for Na-ion batteries

This paper presents the fabrication and characterization of sodium manganese oxide cathode thin films for rechargeable Na-ion batteries. Layered oxide compounds of nominal compositions Na0.6MnO2 and Na1.0MnO2 have been prepared by radio frequency magnetron sputtering and post-annealing at high temperatures under various conditions. The Na0.6MnO2 thin films possess either a hexagonal or orthorhombic structure while the Na1.0MnO2 films crystallize in a monoclinic structure, as shown by X-ray diffraction and X-ray absorption spectroscopy results. The potential profiles of the film cathodes are characterized by features similar to those measured for the powders and exhibit reversible storage capacities in the range of 50-60 Ah cm-2 m-1, which correspond to about 120-140 mAh g-1, and are maintained over 80 cycles.

Baggetto, Loic↗
DOE OSTI2014

The electrochemical reactions of pure In with Li and Na: anomalous electrolyte decomposition, benefits of FEC additive, phase transitions and electrode performance

Indium thin films are evaluated as an anode material for Li-ion and Na-ion batteries (theoretical capacities of 1012 mAh g-1 for Li and 467 mAh g-1 for Na). The native surface oxides are responsible for the anomalous electrolyte decomposition during the first cycle while oxidized In species are found to be responsible for the electrolyte decomposition during the subsequent cycles. The presence of 5wt% FEC electrolyte additive suppresses the occurrence of the anomalous electrolyte decomposition during the first cycle but is not sufficient to prevent the decomposition upon further cycling from 0 to 2 V. Prevention of the anomalous decomposition can be achieved by restricting the charge cut-off, for instance at 1.1 V, or by using larger amounts of FEC. The In films show moderately good capacity retention with storage capacities when cycled with Li (950 mAh g-1) but significantly less when cycled with Na (125 mAh g-1). XRD data reveal that several known Li-In phases (i.e LiIn, Li3In2, LiIn2 and Li13In3) form during the electrochemical reaction. In contrast, the reaction with Na is severely limited. The largest amount of inserted Na is evidenced for cells short-circuited 40 hrs at 65C, for which the XRD data show the coexistence of NaIn, In, and an unknown phase. During cycling, mechanical degradation due to repeated expansion/shrinkage, evidenced by SEM, coupled with SEI formation is the primary source of the capacity fade. Finally, we show that the In thin films exhibit very high rate capability for both Li (100 C) and Na (30 C).

Hawks, Samantha A↗
DOE OSTI2014

Synthesis and Characterization of Lithium Bis(fluoromalonato)borate (LiBFMB) for Lithium Ion Battery Applications

A new orthochelated salt, lithium bis(monofluoromalonato)borate (LiBFMB), has been synthesized and purified for the first time for application in lithium ion batteries. The presence of fluorine in the borate anion of LiBFMB increases its oxidation potential and also facilitates ion dissociation, as reflected by the ratio of ionic conductivity measured by electrochemical impedance spectroscopy ( exp) and that by ion diffusivity coefficients obtained using pulsed field gradient nuclear magnetic resonance (PFG-NMR) technique ( NMR). Half-cell tests using 5.0 V lithium nickel manganese oxide (LiNi0.5Mn1.5O4) as a cathode and EC/DMC/DEC as a solvent reveals that the impedance of the LiBFMB cell is much larger than those of LiPF6 and LiBOB based cells, which results in lower capacity and poor cycling performance of the former. XPS spectra of the cycled cathode electrode suggest that because of the stability of the LiBFMB salt, the solid electrolyte interphase (SEI) formed on the cathode surface is significantly different from those of LiPF6 and LiBOB based electrolytes, resulting in more solvent decomposition and thicker SEI layer. Initial results also indicate that using high dielectric constant solvent PC alters the surface chemistry, reduces the interfacial impedance, and enhances the performance of LiBFMB based 5.0V cell.

Liao, Chen↗
DOE OSTI2014

Fabrication and characterization of high energy density lithium-rich nickel manganese cobalt oxide cathode thin films

This paper reports a method to prepare Li-rich NMC (Li1.2Mn0.55Ni0.15Co0.1O2) thin film cathodes for Li-ion batteries using magnetron sputtering and post-annealing in O2. The use of thin films with no binder and conductive additives enables to study in detail the surface reaction chemistry upon cycling as well as the microstructural changes in the bulk. We show that it is essential to control the deposition pressure to obtain the expected layered(R-3m)-layered(C2/m) structure, thus providing large reversible capacities up to 270 mAh g-1 and voltage profiles close to those expected. This is substantiated by TEM/SAED results showing that the films consist of a layered structure with trigonal symmetry in which Li/TM ordering is achieved. The study of various XPS core levels determines that the surface is comprised of Mn4+, Co3+ and Ni2+ cations inside an O2- framework. The losses mechanisms are studied during long cycling. After 184 cycles, the microstructure does not reveal the presence of Li/TM ordering, which supports that Li2MnO3 conversion is irreversible. In addition, we characterize that the surface chemistry evolves significantly upon cycling. The surface of cycled discharged electrodes is mostly made of inorganic species (LiF, Lix POy Fz , LixPFy), along with small amounts of organic species with C-O and O-C=O groups such as PEO, LiOR and LiCO2R. Moreover, the results support that Ni and Co migrate into the bulk whereas Mn is enriched at the surface. In the case of Mn, the reduction of Mn4+ into Mn3+ is clearly evidenced, as expected from the activation of Li2MnO3 domains.

Baggetto, Loic↗
DOE OSTI2014

In situ determination of lithium ion cathode/electrolyte thickness and composition as a function of charge

In this work we report the first experimental in situ determination of the thickness and estimated composition of a condensed electrode/electrolyte interface at various states of charge for the high voltage Li-ion cathode LiMn1.5Ni0.5O4 by exploiting the power of neutron reflectometry.1 Understanding the electrode/electrolyte interface is critical to developing an understanding of interfacial reactions needed to model transport phenomena and predict more stable electrolytes for electrochemical cells.2,3 However, developing the ability to control interfacial reactions in electrochemical cells is arguably one of the most critical challenges confronting researchers focused on energy storage and conversion reactions as well as liquid phase reactions such as photocatalysts and biomass conversion.2 For example, in electrochemical energy storage systems, such as batteries, the reactions between a solid electrode and a liquid electrolyte can lead to the formation of the solid electrolyte interphase (SEI), which directly mediates the stability, durability and safety of the cell. Controlling these interfacial reactions is essential to developing new, durable, and higher energy storage systems needed in the future.

Neutron Reflectometry↗
DOE OSTI2013

An Artificial SEI Enables the Use of A LiNi0.5Mn1.5O4 5 V Cathode with Conventional Electrolytes

LiNi0.5Mn1.5O4 spinel is considered one of the most promising cathodes for advanced lithium ion batteries. However, the operation potential of LiNi0.5Mn1.5O4, ~4.75 V, is beyond the high voltage limit of the state-of-art electrolyte, ~4.3 V. Here, using thin films of LiNi0.5Mn1.5O4 as a model material, we show evidence that an artificial solid electrolyte interphase (SEI) enables the use of this 5 V cathode with conventional carbonate electrolytes. A thin coating of Lipon (lithium phosphorus oxynitride) as an artificial SEI on LiNi0.5Mn1.5O4 could remedy the decomposition of the electrolyte. The thickness of the Lipon artificial SEI is optimized by balancing the protection and additional resistance. The strategy of artificial SEI on cathodes is expected to enable the wide application of other high voltage cathodes for lithium ion batteries.

artificial SEI↗
DOE OSTI2013

Cu2Sb thin films as anode for Na-ion batteries

Cu2Sb thin films prepared by magnetron sputtering are evaluated as an anode material for Na-ion batteries. The starting material is composed of nanocrystallites with the desired tetragonal P4/nmm structure. The study of the reaction mechanism reveals the formation of an amorphous/nanocrystalline phase of composition close to Na3Sb as the final reaction product. The solid electrolyte interphase (SEI) material is mostly composed of carbonates (Na2CO3, NaCO3R). The Cu2Sb anode possesses moderate capacity retention with a reversible storage capacity (250 mAh/g) close to the theoretical value (323 mAh/g), an average reaction potential of around 0.55 V vs. Na/Na+, and a high rate performance (10 C-rate).

Baggetto, Loic↗