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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.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Investigating the Chemical Reactivity of Lithium Silicate Model SEI Layers

Silicon anodes suffer from an unstable solid electrolyte interphase (SEI) layer that contributes to undesirable capacity fade with cycling. A key part to addressing this unstable SEI formation is to examine how certain components of the SEI react with the electrolyte over time. One SEI component that has not been thoroughly studied in the context of the chemical reactivity against the electrolyte is lithiated silicate. Four model silicate thin films with increasing lithium content were deposited by radio frequency (RF) magnetron sputtering to study how the lithiation of the native oxide on a silicon anode affects the chemical stability of the anode surface. SiO2, Li2Si2O5, Li2SiO3, and Li3SiOx films were exposed to 1.2 M LiPF6 in the 3:7 wt% ethylene carbonate/ethyl methyl carbonate (EC/EMC) electrolyte for periods of time that are representative of the amount of time it takes to undergo cell formations. Soaked samples were rinsed, dried, and characterized by a combination of attenuated total reflectance-infrared spectroscopy (ATR-IR), focused ion beam-secondary electron microscopy (FIB-SEM), and X-ray photoelectron spectroscopy (XPS) depth profiling. It was found that the rate of the decrease in film thickness of the silicates exposed to the electrolyte over time increases as a function of the lithium content in the thin film. This reaction involves HF etching and LiPF6 salt degradation leading to silicate loss and fluorination throughout the bulk. Understanding this chemical instability is critical to determining the overall mechanism of SEI degradation over time.

ADVANCED PROPULSION SYSTEMS,ENERGY STORAGE↗
DOE OSTI2025

Reactivity of Carbonate Solvent Electrolytes on Lithium Silicon Anodes

Silicon (Si) is promising for lithium-ion battery (LIB) anodes due to their high theoretical capacity and low electrochemical potential. However, significant challenges remain, including severe volumetric expansion during cycling and the electrochemical instability of electrolytes, which leads to the formation of a nonuniform solid electrolyte interphase (SEI). To investigate SEI formation mechanisms, computational molecular dynamics simulations offer valuable insights. In this work, we examine the trajectories and charge transfer behavior of lithium hexafluorophosphate (LiPF 6 ) salt with various solvent compositions using density functional theory (DFT) and ab initio molecular dynamics (AIMD). Among the tested electrolyte systems, LiPF 6 with vinylene carbonate (VC) added to ethyl methyl carbonate (EMC) exhibits the lowest reactivity with the Si anode. In contrast, the effects of fluoroethylene carbonate (FEC) and VC depend on whether the primary solvent is EMC alone or a mixture of ethylene carbonate (EC) and EMC. Moreover, we show that electrolyte reactivity varies with the degree of lithiation of the Si anode (LiSi vs Li 15 Si 4 ) and under different charge states. To decouple electrolyte reactivity from surface effects, we analyze the dissociation and formation energies of individual species from solvated configurations. Overall, these first-principles-based findings provide a strategic foundation for electrolyte design to improve cycling stability and extend calendar life in LIBs using Si anodes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on BaLiSi by Materials Project

LiBaSi crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Li is bonded in a trigonal planar geometry to six equivalent Ba and three equivalent Si atoms. All Li–Ba bond lengths are 3.47 Å. All Li–Si bond lengths are 2.87 Å. Ba is bonded to six equivalent Li and six equivalent Si atoms to form a mixture of distorted edge and face-sharing BaLi6Si6 cuboctahedra. All Ba–Si bond lengths are 3.47 Å. Si is bonded in a distorted trigonal planar geometry to three equivalent Li and six equivalent Ba atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li(YSi)2 by Materials Project

Li(YSi)2 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Li is bonded in a distorted square co-planar geometry to four equivalent Si atoms. All Li–Si bond lengths are 2.86 Å. Y is bonded in a 6-coordinate geometry to six equivalent Si atoms. There are two shorter (2.93 Å) and four longer (3.02 Å) Y–Si bond lengths. Si is bonded in a 9-coordinate geometry to two equivalent Li, six equivalent Y, and one Si atom. The Si–Si bond length is 2.39 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li15Si4 by Materials Project

Li15Si4 crystallizes in the cubic I-43d space group. The structure is three-dimensional. there are two inequivalent Li sites. In the first Li site, Li is bonded in a 3-coordinate geometry to two equivalent Li and three equivalent Si atoms. There are one shorter (2.73 Å) and one longer (2.79 Å) Li–Li bond lengths. There are a spread of Li–Si bond distances ranging from 2.61–2.81 Å. In the second Li site, Li is bonded to eight equivalent Li and four equivalent Si atoms to form LiLi8Si4 cuboctahedra that share corners with eight equivalent SiLi12 cuboctahedra, edges with eight equivalent LiLi8Si4 cuboctahedra, and faces with four equivalent SiLi12 cuboctahedra. All Li–Si bond lengths are 2.86 Å. Si is bonded to twelve Li atoms to form distorted SiLi12 cuboctahedra that share corners with six equivalent LiLi8Si4 cuboctahedra, edges with six equivalent SiLi12 cuboctahedra, faces with three equivalent LiLi8Si4 cuboctahedra, and faces with five equivalent SiLi12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiSiIr2 by Materials Project

LiIr2Si is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Li is bonded in a body-centered cubic geometry to eight equivalent Ir and six equivalent Si atoms. All Li–Ir bond lengths are 2.52 Å. All Li–Si bond lengths are 2.91 Å. Ir is bonded in a body-centered cubic geometry to four equivalent Li and four equivalent Si atoms. All Ir–Si bond lengths are 2.52 Å. Si is bonded in a distorted body-centered cubic geometry to six equivalent Li and eight equivalent Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li(NdSi)2 by Materials Project

Li(NdSi)2 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Li is bonded in a distorted square co-planar geometry to four equivalent Si atoms. All Li–Si bond lengths are 3.00 Å. Nd is bonded in a 6-coordinate geometry to six equivalent Si atoms. There are two shorter (3.03 Å) and four longer (3.11 Å) Nd–Si bond lengths. Si is bonded in a 9-coordinate geometry to two equivalent Li, six equivalent Nd, and one Si atom. The Si–Si bond length is 2.41 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr2LiMgSi3 by Materials Project

LiSr2MgSi3 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. Li is bonded in a 4-coordinate geometry to two equivalent Sr, one Mg, and four Si atoms. Both Li–Sr bond lengths are 3.19 Å. The Li–Mg bond length is 2.82 Å. There are a spread of Li–Si bond distances ranging from 2.76–2.86 Å. There are two inequivalent Sr sites. In the first Sr site, Sr is bonded in a 9-coordinate geometry to nine Si atoms. There are a spread of Sr–Si bond distances ranging from 3.23–3.36 Å. In the second Sr site, Sr is bonded in a 12-coordinate geometry to two equivalent Li, three equivalent Mg, and six Si atoms. There are one shorter (3.30 Å) and two longer (3.33 Å) Sr–Mg bond lengths. There are a spread of Sr–Si bond distances ranging from 3.24–3.35 Å. Mg is bonded in a 12-coordinate geometry to one Li, three equivalent Sr, and four Si atoms. There are a spread of Mg–Si bond distances ranging from 2.77–2.86 Å. There are three inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to three equivalent Li, three Sr, and three equivalent Mg atoms. In the second Si site, Si is bonded in a 1-coordinate geometry to six Sr, one Mg, and two equivalent Si atoms. There are one shorter (2.38 Å) and one longer (2.40 Å) Si–Si bond lengths. In the third Si site, Si is bonded in a 1-coordinate geometry to one Li, six Sr, and two equivalent Si atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li2PmSi by Materials Project

Li2PmSi is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Li is bonded in a body-centered cubic geometry to four equivalent Pm and four equivalent Si atoms. All Li–Pm bond lengths are 2.83 Å. All Li–Si bond lengths are 2.83 Å. Pm is bonded in a 8-coordinate geometry to eight equivalent Li and six equivalent Si atoms. All Pm–Si bond lengths are 3.27 Å. Si is bonded in a body-centered cubic geometry to eight equivalent Li and six equivalent Pm atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiSiPd2 by Materials Project

LiPd2Si is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Li is bonded in a body-centered cubic geometry to eight equivalent Pd and six equivalent Si atoms. All Li–Pd bond lengths are 2.58 Å. All Li–Si bond lengths are 2.98 Å. Pd is bonded in a body-centered cubic geometry to four equivalent Li and four equivalent Si atoms. All Pd–Si bond lengths are 2.58 Å. Si is bonded in a distorted body-centered cubic geometry to six equivalent Li and eight equivalent Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiSiRu2 by Materials Project

LiRu2Si is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Li is bonded in a body-centered cubic geometry to eight equivalent Ru and six equivalent Si atoms. All Li–Ru bond lengths are 2.52 Å. All Li–Si bond lengths are 2.91 Å. Ru is bonded in a body-centered cubic geometry to four equivalent Li and four equivalent Si atoms. All Ru–Si bond lengths are 2.52 Å. Si is bonded in a distorted body-centered cubic geometry to six equivalent Li and eight equivalent Ru atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiSiRh2 by Materials Project

LiRh2Si is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Li is bonded in a body-centered cubic geometry to eight equivalent Rh and six equivalent Si atoms. All Li–Rh bond lengths are 2.51 Å. All Li–Si bond lengths are 2.90 Å. Rh is bonded in a body-centered cubic geometry to four equivalent Li and four equivalent Si atoms. All Rh–Si bond lengths are 2.51 Å. Si is bonded in a distorted body-centered cubic geometry to six equivalent Li and eight equivalent Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Bioinspired mechanically interlocking holey graphene@SiO 2 anode

Mechanically interlocking structures that can enhance adhesion at the interface and regulate the stress distribution have been widely observed in biological systems. Inspired by the biological structures in the wings of beetles, we synthesized a holey graphene@SiO 2 anode with strong mechanical interlocking, characterized it electrochemically, and explained its performance by finite element analysis and density functional calculations. The mechanically interlocking structure enhances lithium-ion (Li + ) storage by transmitting the strain from SiO 2 to the holey graphene and by a mechano-electrochemical coupling effect. The interlocking fit hinders the abscission of SiO 2 and the distinctive structure reduces the stress and strain of SiO 2 during (de)lithiation. The positive mechano-electrochemical coupling effect preserves the amount of electrochemically active phase (Li x Si) during cycles and facilitates Li + diffusion. Therefore, the capacity shows only a slight attenuation after 8000 cycles (cycling stability), and the specific capacity is ~1200 mA h g –1 at 5 A/g (rate-performance). This study furnishes a novel way to design high-performance Li + /Na + /K + /Al 3+ anodes with large volume expansion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Exploration, Prediction, and Experimental Verification of Structure and Optoelectronic Properties in I 2 -Eu-IV-X 4 (I = Li, Cu, Ag; IV = Si, Ge, Sn; X = S, Se) Chalcogenide Semiconductors

Recently, there has been extensive research into photovoltaic, thermoelectric, and nonlinear optical applications of chalcogenide semiconductors within the large set of defect-resistant I 2 -II-IV-X4 (I = Li, Cu, Ag; II = Ba, Sr, Eu, Pb; IV = Si, Ge, Sn; X = S, Se) compounds. Five Eu-including compounds have previously been reported within this family, but a comparative study of possible structures and electronic properties of all 18 Eu-based combinations is still absent. Herein, we use hybrid density functional theory to study rare-earth-including I 2 -II-IV-X 4 semiconductors with Eu on the II site, in order to further understand this family and test the geometric tolerance factor approach (reported in our previous work) as a tool for predicting potential stable structures. We investigate how the exchange mixing parameter of the HSE06 density functional, α, affects the energetic positions of electronic levels, especially of the localized f-electron orbitals near the band edges of the extended semiconductor structures, using literature photoemission and band gap data of EuS for comparison. Lowest-energy quaternary structure candidates, energy band structures, and densities of states are computationally predicted for all 18 materials. Based on its predicted photovoltaics-relevant band gap, the previously unknown compound Cu 2 EuSnSe 4 was selected and synthesized. Furthermore, the experimental structure, lattice parameters, and band gap of Cu 2 EuSnSe 4 are consistent with the computational predictions, confirming a 1.55 eV band gap.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

High-performance all-solid-state Li–S batteries enabled by an all-electrochem-active prelithiated Si anode

The development of all-solid-state Li–S batteries has been greatly impeded by dendrite growth and dendrite penetration, which are both related to the Li metal anode. As a compromised alternative, we report lithium silicide (Li x Si) as a dendrite-free and high-capacity anode with Li source. Here, the as-synthesized Li x Si is relatively soft, highly electronically conductive, and with a high Li diffusivity. These distinctive properties make Li x Si anode viable as an “all-electrochem-active” electrode (consisted of 100 wt.% Li x Si). Compared with the typical composite electrode, the all-electrochem-active electrode not merely maximizes the electrode-level energy density but also minimizes the electrolyte-related interfacial degradation. Li x Si symmetric cell demonstrates a reversible cycling at 4 mA cm –2 for over 320 h. Stress change and morphological evolution of the Li x Si electrode are investigated upon dealloying/alloying. When paired with a S cathode (active mass loading of 3 mg cm –2 ), Li x Si–S full cell shows a good cycling behavior over 500 cycles and rate performance (69% capacity retained at 1.2C) even at 25 °C.

25 ENERGY STORAGE↗
DOE OSTI2021

Stress-Dependent Chemo-Mechanical Performance of Amorphous Si Anodes for Li-Ion Batteries upon Lithiation

Alloying-type anodes are significantly governed by their chemo-mechanical performance during the electrochemical cycling. The reaction-induced huge volumetric change of these anodes may cause material degradation and failure under mechanical constraints. Here, we investigate the stress-dependent lithiation behavior of amorphous Si (a-Si) anodes using molecular dynamics simulations. It is indicated that a-Si anodes can sustain higher hydrostatic stress than biaxial/uniaxial ones without the occurrence of mechanical failure. Thermodynamic and electrochemical calculations demonstrate that although the lithiation procedure also affects the thermodynamic stability of a-Si anodes, it is mainly dominated by the external mean stresses. Compressive stress is confirmed to destabilize a-Si anodes and further trigger their capacity fading. Compared with our atomistic simulations, previous continuum models underestimate the open-cell potentials of a-Si anodes, due to their ignored large volumetric deformation at higher stresses and Li concentrations. Finally, this computational study provides the intensive atomic-level understanding of the stress-dependent lithiation behavior of a-Si anodes.

25 ENERGY STORAGE↗
DOE OSTI2020

Techno-Economic Assessment of Destabilized Li Hydride Systems for High Temperature Thermal Energy Storage

A comprehensive techno-economic analysis of destabilized Li hydrides, used as thermal energy storage systems in concentrating solar power plants, is presented and discussed. Two systems, operating at temperatures on the order of 550–650 °C, are selected as thermal energy storage units for steam power plants, namely the Si-destabilized Li hydride (LiSi) and the Al-destabilized Li hydride (LiAl). Two thermal energy storage systems, operating at temperatures on the order of 700–750 °C, are selected for integration in supercritical CO2 power plants, namely the Si-destabilized Li hydride (LiSi) and the Sn-destabilized Li hydride (LiSn). Each storage system demonstrates excellent volumetric capacity, achieving values between 100 and 250 kWhth/m3. The LiSi-based thermal energy storage systems can be integrated with steam and supercritical CO2 plants at a specific cost between 107 US$/kWhth and 109 US$/kWhth, with potential to achieve costs on the order of 74 US$/kWhth under enhanced configurations and scenarios. The LiAl-based storage system has the highest potential for large scale applications. The specific cost of the LiAl system, integrated in solar steam power plants, is equal to approximately 74 US$/kWhth, with potential to reach values on the order of 51 US$/kWhth under enhanced performance configurations and scenarios.

Corgnale, Claudio↗