Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Anode material”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Experimental and Computational Investigation of Lepidocrocite Anodes for Sodium-Ion Batteries

In this work, we investigated several titanates with lepidocrocite-type structures (general formula A x Ti1- y M y O 4 , with A = Na and M = Li or Mg), having potential utility as anode materials for sodium-ion batteries. First-principles calculations were used to determine key battery metrics, including potential profiles, structural changes during sodiation, and sodium diffusion energy barriers for several compositions, and were compared to experimental results. Site limitations were found to be critical determinants of the gravimetric capacities, which are also affected both by the stacking arrangement of the corrugated layers and the identity of M (Li or Mg). To explain the experimentally observed lattice parameter changes observed as a function of the state of charge, it was necessary to assume the participation of water/solvent during the sodium intercalation process. Here, sodium diffusion barriers were also found to vary as a function of state of charge and diffusion direction, with a spread of 0.06-1.3 eV at low sodium contents, narrowing to 0.3-0.5 eV at higher sodium contents. Based on these results, strategies for selecting and improving the performance of these electrode materials are suggested.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Understanding and Controlling Anionic Electrochemical Activity in High-Capacity Oxides for Next Generation Li-Ion Batteries

Rechargeable Li-ion batteries with higher energy density are in urgent demand to address the global challenge of energy storage. In comparison with anode materials, the relatively low capacity of cathode oxides, which exhibit classical cationic redox activity, has become one of the major bottlenecks to reach higher energy density. Recently, anionic activity, such as oxygen redox reaction, has been discovered in the electrochemical processes, providing extra reversible capacity for certain transition-metal oxides. Consequently, a more complete understanding and precise controlling on anionic electrochemical activity in these high-capacity oxides have become a flourishing, yet challenging subject. Here, this perspective highlights (1) key features of the anionic electrochemical activities; (2) computational and experimental tools to characterize and quantify the anionic activity; and (3) design principles that correlate the chemical and structural compositions with high reversible capacity to accelerate the discovery of novel cathode oxides for next generation Li-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2017

Revealing the Conversion Mechanism of Transition Metal Oxide Electrodes during Lithiation from First-Principles

Transition metal oxides such as Co3O4 and NiO are of significant interest as conversion anode materials for lithium-ion batteries (LIBs), due to their remarkably high theoretical capacities and low cost. While many previous experiments have found that the charge/discharge reactions of Co3O4 and NiO can be highly reversible, detailed information about the mechanisms of these reactions, such as the origin of the voltage hysteresis (>1.0 V) between the charge/discharge cycles, is still poorly understood. In this work, we develop and utilize a new computational mechanistic approach that helps elucidate the hysteresis and nonequilibrium reaction pathways associated with these conversion materials. We apply this methodology to investigate a variety of lithiation reaction pathways of Co3O4 and NiO by systematically exploring the energetics of a large number of equilibrium and nonequilibrium LixCo3O4 (0 ≤ x ≤ 8) and LixNiO (0 ≤ x ≤ 2) structural configurations using first-principles calculations. The overall value of the voltages from our nonequilibrium pathway is in much better agreement with experimental lithiation than the calculated equilibrium voltage while the overall value of the latter reasonably agrees with experimental delithiation. Hence, we propose the charge and discharge processes proceed through equilibrium and nonequilibrium reaction paths, respectively, which contribute significantly to the experimentally observed voltage hysteresis in Co3O4 and NiO. Additionally, we find a low-energy, lithiated intermediate phase (Li3Co3O4) with an oxygen framework equal to that of the initial Co3O4 spinel phase. This intermediate phase represents the capacity threshold below which limited volume expansion and better reversibility can be realized and above which reactions lead to structural degradation and huge expansion.

Yao, Zhenpeng↗
DOE OSTI2017

Atomic Layer Deposition of Aluminum Sulfide: Growth Mechanism and Electrochemical Evaluation in Lithium-Ion Batteries

This work describes the synthesis of aluminum sulfide (AlS x ) thin films by atomic layer deposition (ALD) using tris(dimethylamido)aluminum and hydrogen sulfide. We employed a suite of in situ measurement techniques to explore the ALD AlS x growth mechanism, including quartz crystal microbalance, quadrupole mass spectrometry, and Fourier transform infrared spectroscopy. A variety of ex situ characterization techniques were used to determine the growth characteristics, morphology, elemental composition, and crystallinity of the resultant AlS x films. This study revealed that the AlS x growth was self-limiting in the temperature range 100–250 °C, and the growth per cycle decreased linearly with increasing temperature from ~0.45 Å/cycle at 100 °C to ~0.1 Å/cycle at 250 °C. The AlSx films were amorphous in this temperature range. We conducted electrochemical testing to evaluate the ALD AlS x as a potential anode material for lithium-ion batteries (LIBs). Finally, the ALD AlS x exhibited reliable cyclability over 60 discharge–charge cycles with a sustainable discharge capacity of 640 mAh/g at a current density of 100 mA/g in the voltage window of 0.6–3.5 V.

25 ENERGY STORAGE↗
DOE OSTI2025

Low-Temperature Processing of Pyrolysis Bio-Oil for Sustainable Biographite Production

Catalytic graphitization of pyrolysis bio-oil with iron (Fe) can produce an anode material for lithium-ion batteries (LIBs) at a moderate temperature. The key challenge to scaling up the process is foaming, which occurs due to the oxidation of Fe by the organic acids present in bio-oil. This study explored five different pathways to control foaming in bio-oil upon Fe addition, including (i) defoamers use, (ii) use of iron oxide (Fe2O3) as graphitization catalyst, (iii) pH adjustment of bio-oil, (iv) bio-oil coking (300-500 degrees C), and (v) low-temperature pretreatment of bio-oil (150-200 degrees C). The low-temperature pretreatment successfully avoided foaming by removing the volatile acids in bio-oil. The bio-oil was solidified and powdered for even mixing with the Fe catalyst. The biographite catalytically prepared at 1500 degrees C following this pathway demonstrated nearly theoretical specific gravimetric capacity (~370 mAh/g), high initial Coulombic efficiency (90.03%), and minimal capacity fading after 50 cycles in LIB half-cells. The low-temperature pretreatment pathway also addressed the viscosity, swelling, and aging issues associated with bio-oil processing and will make scale-up endeavors more attainable.

09 BIOMASS FUELS↗
DOE OSTI2021

Structure and Reactivity of Pristine and Reduced Spinel CoFe 2 O 4 (001)/(100) Surfaces

Cobalt ferrite, CoFe 2 O 4 (CFO), nanocrystals are efficient and competitive anode materials in the field of electrochemical water splitting. Using density functional theory with on-site Hubbard U corrections (DFT+U), we have investigated the structural, electronic and magnetic properties of CFO (001)/(100) surfaces, as well as their reactivities towards water adsorption. Special attention has been focused on the formation of oxygen vacancies (V O ), due to their key role in the oxidation activity of metal oxides, often based on the Mars-van-Krevelen mechanism. Our results show that vacancy formation is easiest at oxygen sites that are not bound to tetrahedrally-coordinated Fe. Water adsorbs mainly in molecular form on the Co/Fe metal cations, whereas it dissociates at defects. In comparison to other spinels, CFO is similar to NiFe 2 O 4 , exhibiting relatively low energy cost of V O formation and a strong affinity of the vacancies towards water. Furthermore, these findings suggest that CFO may be a more promising oxidation catalyst than NiCo 2 O 4 and Co 3 O 4 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

The Chemistry of Electrolyte Reduction on Silicon Electrodes Revealed by in Situ ATR-FTIR Spectroscopy

While silicon is the most promising next-generation anode material for lithium-ion batteries (LIBs), silicon electrodes exhibit significant capacity fade with cycling. A common hypothesis is that the capacity loss is due to the solid electrolyte interphase (SEI) forming in the first cycle and becoming destabilized by large cyclic volume changes. A cell for in situ attenuated total reflection-Fourier transform infrared spectroscopy with controllable penetration depth was used to study the chemistry at the electrode–electrolyte interface. The SEI product precursors at the interface were successfully identified and differentiated from free or solvated solvent molecules in the bulk electrolyte. Intriguingly, for the most common electrolyte consisting of ethylene carbonate and diethyl carbonate, ethylene carbonate was found to directly reduce to lithium ethylene dicarbonate on the lithiated silicon surface and diethyl carbonate to selectively reduce to diethyl 2,5-dioxahexane dicarboxylate on the surface of the native silicon-oxide film. In conclusion, understanding this surface dependence of the SEI composition is critical to tuning the silicon electrode surface condition and, ultimately, enhancing the performance of future LIBs.

25 ENERGY STORAGE↗
DOE OSTI2019

H 2 Dissociation on Noble Metal Single Atom Catalysts Adsorbed on and Doped into CeO 2 (111)

In this study, we used density functional theory (DFT) calculations to investigate the dissociation of H 2 on an Ag single atom catalyst adsorbed on the pristine CeO 2 (111) surface (Ag/CeO 2 ), or substituting a surface Ce atom on the reduced (Ag:CeO 2-x ) and partially hydrogenated (Ag:H–CeO 2 ) surfaces. The initial state of the H 2 dissociation reaction in the different investigated models corresponds to distinct oxidation states, +1, +2, or +3, of the Ag atom, thus allowing us to examine the influence of the charge transfers between the noble metal, the oxide, and the hydrogen atoms on the reaction pathway and activation energy. In all investigated models, the computed barrier of H 2 dissociation is lowered by about 0.6 eV in comparison to that on metal-free CeO 2 . On Ag/CeO 2 and Ag:CeO 2-x , also the energy of H 2 dissociative adsorption is smaller than that on metal-free ceria. These results suggest that CeO 2 modified with dispersed Ag atoms is a promising anode material for proton exchange membrane fuel cells. Lastly, further comparison of our results for Ag to analogous calculations for Cu and Au single atom catalysts reveals trends in the computed barriers that can be related to the change of the metal oxidation state in the reaction.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Solid-State Li-Ion Batteries Using Fast, Stable, Glassy Nanocomposite Electrolytes for Good Safety and Long Cycle-Life

The development of safe, stable, and long-life Li-ion batteries is being intensively pursued to enable the electrification of transportation and intelligent grid applications. Here, we report a new solid-state Li-ion battery technology, using a solid nanocomposite electrolyte composed of porous silica matrices with in situ immobilizing Li+ conducting ionic liquid, anode material of MCMB, and cathode material of LiCoO 2 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 , or LiFePO 4 . An injection printing method is used for the electrode/electrolyte preparation. Solid nanocomposite electrolytes exhibit superior performance to the conventional organic electrolytes with regard to safety and cycle-life. They also have a transparent glassy structure with high ionic conductivity and good mechanical strength. Solid-state full cells tested with the various cathodes exhibited high specific capacities, long cycling stability, and excellent high temperature performance. This solid-state battery technology will provide new avenues for the rational engineering of advanced Li-ion batteries and other electrochemical devices.

25 ENERGY STORAGE↗
DOE OSTI2019

Extended Cycling through Rigid Block Copolymer Electrolytes Enabled by Reducing Impurities in Lithium Metal Electrodes

Successful prevention of lithium dendrite growth would enable the use of lithium metal as an anode material in next-generation rechargeable batteries. Mechanically stiff block copolymer electrolytes have been shown to prolong the life of lithium metal cells by partially suppressing lithium dendrite growth. Yet, impurity particles that are invariably present in the lithium metal nucleate electrodeposition defects that eventually lead to short circuits. Here, we use X-ray tomography to study the morphology of electrodeposited lithium in symmetric cells containing a block copolymer electrolyte. An "electrochemical filtering" treatment was performed on these cells to reduce the concentration of impurity particles near the electrode-electrolyte interface, and cells were cycled to determine the effects of the treatment on lifetime. Depending on the treatment details, the average charge passed before failure was improved by 30-400%. For a cell in which the treatment was most effective, the cycle life was increased by more than an order of magnitude, and the measured number of deposition defects per area was negligible. Other treated cells, however, in which the treated lithium was imperfect, had a higher number of deposition defects per area compared to control cells. A majority of the deposition defects in treated cells were confined within the electrodes. In contrast, most of the deposition defects seen in the control cells were protrusions that invaded the electrolyte phase. The increased lifetime in these imperfectly treated cells was not due to a reduction in the number of deposition defects per area, but rather due to the differences in defect morphology. These findings motivate the development of deposition defect- and impurity-free lithium metal electrodes.

25 ENERGY STORAGE↗
DOE OSTI2015

γ-Fe 2 O 3 Nanocrystalline Microspheres with Hybrid Behavior of Battery-Supercapacitor for Superior Lithium Storage

Maghemite (γ-Fe2O3) nanocrystalline microspheres (MNMs) self-assembled with 52 nm nanocrystals bridged with FeOOH around grain boundaries were formed by solvothermal reaction and thermal oxidation. The unique architecture endows the MNMs with the lithium storage behavior of a hybrid battery-supercapacitor electrode: initial charge capacity of 1060 mAh g–1 at the 100 mA g–1 rate, stable cyclic capacity of 1077.9 mAh g–1 at the same rate after 140 cycles, and rate capability of 538.8 mAh g–1 at 2400 mA g–1. This outstanding performance was attributed to the nanocrystal superiority, which shortens the Li+ diffusion paths. The mechanism of this hybrid anode material was investigated with experimental measurements and structural analysis. The results indicate that at the first discharge, the MNM nanocrystal microsphere, whose structure can buffer the volume change that occurs during lithiation/delithiation, goes through four stages: Li+ insertion in cation vacancies, spinel-to-rocksalt transformation, Li+ intercalation of Li1.75+xFe2O3 nanocrystals, and interfacial Li storage around nanocrystal boundaries. Only the latter two stages were reversible at and after the second charging/discharging cycle, exhibiting the hybrid behavior of a battery-supercapacitor with superior lithium storage.

ferric oxide↗
DOE OSTI2018

Essential Role of Spinel ZnFe 2 O 4 Surfaces during Lithiation

Spinel zinc ferrite (ZnFe 2 O 4 ) is a well-known anode material in lithium ion batteries (LIBs) due to its large theoretical capacity. However, the high potentials observed at the initial stage of lithiation observed cannot be captured using a model of Li + intercalation into the stoichiometric ZnFe 2 O 4 bulk. Here, using density functional theory (DFT) we report for the first time that theZnFe 2 O 4 surfaces are responsible for the measured initial potentials. Among the three identified stable surfaces, ZnFeO 2 -terminated ZnFe 2 O 4 (1 1 0), O-terminated ZnFe 2 O 4 (1 1 1) and Zn-terminated ZnFe 2 O 4 (1 1 1), both (1 1 1) surfaces display higher lithiation potentials than the (1 1 0) surface, and the estimated potentials based on Zn-terminated (1 1 1) fit well with the experimental observations, while using the models based on ZnFe 2 O 4 (1 1 0) and previously ZnFe 2 O 4 bulk, the estimated potentials are much lower. In terms of Li + diffusion, the Zn-terminated ZnFe 2 O 4 (1 1 1) surface is the most active, where the energetically favorable saturation of Li + on the surface is able to facilitate the process. Our results provide a new strategy for the design of LIB materials, via controlling the particle shape and the associated surface characteristics thus enhancing the discharging performance.

25 ENERGY STORAGE↗
DOE OSTI2019

In Situ Focused Ion Beam Scanning Electron Microscope Study of Microstructural Evolution of Single Tin Particle Anode for Li-Ion Batteries

Tin (Sn) is a potential anode material for high-energy density Li-ion batteries because of its high capacity, safety, abundance and low cost. However, Sn suffers from large volume change during cycling, leading to fast degradation of the electrode. For the first time, the microstructural evolution of micrometer-sized single Sn particle was monitored by focused-ion beam (FIB) polishing and scanning electron microscopy (SEM) imaging during electrochemical cycling by in situ FIB-SEM. Our results show the formation and evolution of cracks during lithiation, evolution of porous structure during delithiation and volume expansion/contraction during cycling. The electrochemical performance and the microstructural evolution of the Sn microparticle during cycling are directly correlated, which provides insights for understanding Sn-based electrode materials.

25 ENERGY STORAGE↗
DOE OSTI2018

Morphology-Controlled Discharge Profile and Reversible Cu Extrusion and Dissolution in Biomimetic CuS

Metal sulfides, such as CuS, SnS2, Co9S8, MoS2, are high capacity anode materials for Li-ion batteries. However, these materials go through a conversion reaction with Li+, which is accompanied by the phase transformation and inevitably results in a huge volume expansions, therefore causing performance degradation. Here, we report nanoscale engineering route to efficiently control the overall volume expansion for enhanced performance. We engineered CuS with nanoplate assembly on a nanostring, leading to a nanostructure of mimicking the crassula baby necklace (CBN) in the natural plant. Using in-situ transmission electron microscopy (in-situ TEM), we probed the lithiation kinetics and dynamic structural transformations. Due to the linkage of the central nanostring, the CuS CBN exhibited fast Li+ diffusion along the axial direction and high mechanical stability during lithiation. The volume expansion was minimal for the CuS CBN due to the pre-engineered gap between these plates. The CuS followed a two-step lithiation process with Cu2S and Li2S formation as the first step and Cu extrusion from Cu2S in the later stage. Interestingly, during the Cu2S to Cu conversion, there was a incubation period before the metallic Cu extrusion, which is featured by the formation of an amorphous structure due to the large lattice strain and distortion associated with the displacement of Cu by Li ions. In the final stage, the lithiated amorphous phase recrystallized to a composite of Cu nanocrystals dispersed in a polycrystalline Li2S matrix. Associate with the nanoscale size, the Cu nanocrystals can reversibly dissolve into the matrix upon delithiation. The present work demonstrates tailoring of desired functionality through nanoscale engineering of using bionic methods.

Han, Shaobo↗
DOE OSTI2019

Isothermal Microcalorimetry: Insight into the Impact of Crystallite Size and Agglomeration on the Lithiation of Magnetite, Fe 3 O 4

Magnetite, Fe 3 O 4 , holds significant interest as a Li-ion anode material because of its high theoretical capacity (926 mAh/g) associated with multiple electron transfers per cation center. Notably, both crystallite size and agglomeration influence ion transport. This report probes the effects of crystallite size (12 and 29 nm) and agglomeration on the reactions involved with the formation of the surface electrolyte interphase on Fe 3 O 4 . Isothermal microcalorimetry (IMC) was used here to determine the parasitic heat evolved during lithiation by considering the total heat measured, cell polarization, and entropic contributions. Interestingly, the 29 nm Fe 3 O 4 -based electrodes produced more parasitic heat than the 12 nm samples (1346 vs 1155 J/g). This observation was explored using scanning electron microscopy (SEM) and X-ray fluorescence (XRF) mapping in conjunction with spatially resolved X-ray absorption spectroscopy (XAS). SEM imaging of the electrodes revealed more agglomerates for the 12 nm material, affirmed by XRF maps. Further, XAS results suggest that Li + transport is more restricted for the smaller crystallite size (12 nm) material, attributed to its greater degree of agglomeration. These results rationalize the IMC data, where agglomerates of the 12 nm material limit solid electrolyte interphase formation and parasitic heat generation during lithiation of Fe 3 O 4 .

25 ENERGY STORAGE↗
DOE OSTI2016

Cluster-Inspired Design of High-Capacity Anode for Li-Ion Batteries

One of the greatest challenges in next-generation Li-ion batteries (LIB) is to develop high charge capacity anodes with long cycle life. Inspired by the experimental observation of a magic Ti13C22 cluster and its layer-by-layer growth, we have constructed one-dimensional nanowires using Ti9C13 clusters as well as those based on planar-tetracoordinate carbon-containing (ptC) Ti8C12 metcar and TiC clusters with bulk cubic crystal structure. Using density functional theory and molecular dynamics we studied their energetic and thermal stability as well as their potential for LIB anode. The Ti9C13 nanowire is found to be stable up to 2500 K and has a charge capacity five times larger than that of the graphite anode being used today. Furthermore, unlike silicon nanotube anode materials, the Ti9C13 nanowire does not suffer from volume expansion/contraction during lithiation/delithiation processes.

Zhao, Tianshan↗
DOE OSTI2019

Temperature-Dependent Solubility of Solid Electrolyte Interphase on Silicon Electrodes

The lithium-ion batteries powering mass market electric vehicles must be capable of operating in a wide temperature range. Temperature variation has the possibility to greatly affect the stability of the solid electrolyte interphase (SEI) responsible for mitigating capacity fade due to electrolyte decomposition in the lithium-ion battery. Here, we explore the solubility of the SEI on the silicon (Si) electrode, an alternative anode material to the conventional graphite electrode, at temperatures ranging from -10 to 50 °C. Through use of an electrochemical protocol with a high cathodic cutoff voltage, we measure the evolution of the SEI independently of competing Si mechanical stress. We correlate the electrochemical data with three-dimensional resistivity versus depth profiling as well as atomic force microscopy to show that SEI dissolution occurs at significantly faster rates at higher temperatures.

25 ENERGY STORAGE↗
DOE OSTI2015

Beyond Yolk–Shell Nanoparticles: Fe 3 O 4 @Fe 3 C Core@Shell Nanoparticles as Yolks and Carbon Nanospindles as Shells for Efficient Lithium Ion Storage

In order to well address the problems of large volume change and dissolution of Fe 3 O 4 nanomaterials during Li + intercalation/extraction, herein we demonstrate a one-step in situ nanospace-confined pyrolysis strategy for robust yolk–shell nanospindles with very sufficient internal void space (VSIVS) for high-rate and long-term lithium ion batteries (LIBs), in which an Fe 3 O 4 @Fe 3 C core@shell nanoparticle is well confined in the compartment of a hollow carbon nanospindle. This structure can not only introduce VSIVS to accommodate volume change of Fe 3 O 4 but also afford a dual shell of Fe 3 C and carbon to restrict Fe 3 O 4 dissolution, thus providing dual roles for greatly improving the capacity retention. Consequently, Fe 3 O 4 @Fe 3 C–C yolk–shell nanospindles deliver a high reversible capacity of 1128.3 mAh g –1 at even 500 mA g –1 , excellent high rate capacity (604.8 mAh g –1 at 2000 mA g – 1), and prolonged cycling life (maintaining 1120.2 mAh g –1 at 500 mA g –1 for 100 cycles) for LIBs, which are much better than those of Fe 3 O 4 @C core@shell nanospindles and Fe 3 O 4 nanoparticles. The present Fe 3 O 4 @Fe 3 C–C yolk–shell nanospindles are the most efficient Fe 3 O 4 -based anode materials ever reported for LIBs.

25 ENERGY STORAGE↗