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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Ultrafine SnO{sub 2} nanocrystals anchored graphene composites as anode material for lithium-ion batteries

Highlights: • Ultrafine SnO{sub 2}@graphene composite is synthesized by a simple hydrothermal method. • SnO{sub 2} nanocrystals with size of ∼5 nm are distributed on the graphene sheets uniformly. • A reversible capacity of 808 mAh g{sup −1} is retained after 100 cycles at 200 mA g{sup −1}. • The capacity recovers to 1290 mAh g{sup −1} after being cycled at various rates for 60 cycles. - Abstract: Ultrafine tin dioxide (SnO{sub 2}) nanocrystals anchored graphene composite is synthesized by a simple hydrothermal method. Well-defined SnO{sub 2} nanocrystals with size of ∼5 nm are uniformly anchored on the graphene sheets. The two-dimensional nanostructure inherits the advantages of graphene, which possesses high electrical conductivity and large surface area. Furthermore, the ultrafine SnO{sub 2} nanocrystals anchoring on graphene sheets facilitate fast ion transportation and prevent aggregation. As a result, the produced nanocomposite exhibits an excellent cycling stability and rate capability for lithium storage (808 mAh g{sup −1} after 100 cycles at 200 mA g{sup −1}, 1290 mAh g{sup −1} at the current of 50 mA g{sup −1} after being cycled at various current densities for 60 cycles)

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Synthesis and lithium insertion properties of ramsdellite Li{sub x}TiO{sub 2} anode materials

Highlights: • Ramsdellite Li{sub x}Ti0{sub 2} with reduced form was prepared as a single phase by a new method. • The capacity was 208 mAh g{sup −1} in the region of 1.0–2.5 V at 0.8 C. • The charge and discharge proceeded in two stages unlike the oxidized form. - Abstract: Ramsdellite Li{sub x}TiO{sub 2} (x = 0.47) with reduced form is successfully prepared as a single phase by heating an amorphous lithium peroxo-polytitanate in 4.8% H{sub 2} at 1100 °C for 0–1 h. The XRD data are well refined with the space group Pnma with a = 0.96076 nm, b = 0.29514 nm and c = 0.50276 nm. The ramsdellite Li{sub x}TiO{sub 2} transforms into a rutile–ramsdellite intergrowth phase by extending the heating time to 1.25–4 h. The capacity of the ramsdellite Li{sub x}TiO{sub 2} in the region of 1.0–2.5 V (vs Li) is 208 mAh g{sup −1} at 0.8 C rate (0.13 mA mg{sup −1}), substantially larger than that of the ramsdellite Li{sub 2}Ti{sub 3}O{sub 7} with oxidized form. The lithium insertion and deinsertion proceeds in two stages: a sloping region at higher potential (1.4–2.3 V) and a plateau region at lower potential (1.3–1.4 V)

36 MATERIALS SCIENCE↗
DOE OSTI2016

Neutron diffraction analysis and electrochemical performance of spinel Ni(Mn{sub 2−x}Co{sub x})O{sub 4} as anode materials for lithium ion battery

Highlights: • The reversible capacity and cyclability of Ni(Mn{sub 2−x}Co{sub x})O{sub 4} first increases and then decreases with increasing Co content. • Neutron diffraction and Rielveld refinements are applied to analyze the site occupancies of Mn, Co, O and Ni. • Excessive Co ions in 8a and 16d sites reduce the structure stability leading to poor electrochemical performance. - Abstract: The effects of Co substitution on the structure and electrochemical performances of spinel Ni(Mn{sub 2−x}Co{sub x})O{sub 4} (x = 0, 0.5, and 1.0) have been investigated. With the increase of Co content the lattice parameters decrease owing to the smaller ion radius of Co than Mn. The reversible capacity and cyclability of Ni(Mn{sub 2−x}Co{sub x})O{sub 4} first increase and then decrease with the increase of Co content and NiMn{sub 1.5}Co{sub 0.5}O{sub 4} shows the best electrochemical performance in compared to the other two samples. Neutron diffraction and Rielveld refinement are further applied to analyze the site occupancies of the elements of Mn, Co, O and Ni. A certain amount of Co ions substitution are favorable to enhance the electrochemical performance, but excessive Co ions in 8a and 16d sites reduce the stability of host structure which leads to the poor electrochemical performance.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Layered Lepidocrocite Type Structure Isolated by Revisiting the Sol–Gel Chemistry of Anatase TiO 2 : A New Anode Material for Batteries

Searches for new electrode materials for batteries must comply on financial and environmental costs to be useful in practical devices. The sol-gel chemistry has been widely used to design and implemented new concepts for the emergence of advanced materials such as hydride organic-inorganic composites. Here, we show that the simple reaction system including titanium alkoxide and water can be used to stabilize a new class of electrode materials. By investigating the crystallization path of anatase TiO2, an X-ray amorphous intermediate phase has been identified whose local structure probed by the pair distribution function, 1 H solid-state NMR and DFT calculations, consists of a layered-type structure as found in the lepido-crocite. This phase presents the following general formula Ti 2-x ⟂ x O 4-4x (OH) 4x .nH 2 O (x ~ 0.5) where the substitution of oxide by hydroxide anions leads to the formation of titanium vacancies (•) and H 2 O molecules are located in interlayers. Solid-state 1H NMR has enabled to characterize three main hydroxide environments that are Ti⟂-OH, Ti 2 ⟂ 2 -OH and Ti3⟂-OH and layered H 2 O molecules. The electrochemical properties of this phase were further investigated versus lithium and is shown to be very promising with reversible capacities of around 200 mAh.g -1 and an operating voltage of 1.55 V. We further showed that the lithium intercalation proceeds via a solid-solution mechanism. 7Li solid-state NMR and DFT calculations allowed to identify lithium host sites that are located at the titanium vacancies and interlayer space with lithium being solvated by structural water molecules. The easy fabrication, the absence of lithium and easier recycling and the encouraging properties makes this class of materials very attractive for competitive electrodes for batteries. We thus demonstrate that the revisit of an “old” chemistry with advanced characterization tools allows discovering new materials of technological relevance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Structural and Electrochemical Characteristics of Ca-Doped “Flower-like” Li 4 Ti 5 O 12 Motifs as High-Rate Anode Materials for Lithium-Ion Batteries

Doped motifs offer an intriguing structural pathway toward improving conductivity for battery applications. Specifically, Ca-doped, three-dimensional “flower-like” Li 4–x Ca x Ti 5 O 12 (“x” = 0, 0.1, 0.15, and 0.2) micrometer-scale spheres have been successfully prepared for the first time using a simple and reproducible hydrothermal reaction followed by a short calcination process. The products were experimentally characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) mapping, inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge testing. Calcium dopant ions were shown to be uniformly distributed within the LTO structure without altering the underlying “flower-like” morphology. The largest lattice expansion and the highest Ti 3+ ratios were noted with XRD and XPS, respectively, whereas increased charge transfer conductivity and decreased Li + -ion diffusion coefficients were displayed in EIS for the Li 4–x Ca x Ti 5 O 12 (“x” = 0.2) sample. The “x” = 0.2 sample yielded a higher rate capability, an excellent reversibility, and a superior cycling stability, delivering 151 and 143 mAh/g under discharge rates of 20C and 40C at cycles 60 and 70, respectively. In addition, a high cycling stability was demonstrated with a capacity retention of 92% after 300 cycles at a very high discharge rate of 20C. In addition, first-principles calculations based on density functional theory (DFT) were conducted with the goal of further elucidating and understanding the nature of the doping mechanism in this study. The DFT calculations not only determined the structure of the Ca-doped Li 4 Ti 5 O 12 , which was found to be in accordance with the experimentally measured XPD pattern, but also yielded valuable insights into the doping-induced effect on both the atomic and electronic structures of Li 4 Ti 5 O 12 .

25 ENERGY STORAGE↗
DOE OSTI2023

Green Needle Coke Production from Pyrolysis Biocrude toward Bio-based Anode Material Manufacture: Biochar Fines Addition Effect as “Physical Template” on the Crystalline Order

Here, a new method for producing green needle coke (GNC) is developed by replacing the “heavy fraction” of petroleum pitch delayed coking with fast pyrolysis biocrude. A series of alternative biocrude distillation, carbonization, and calcination conditions were investigated to determine the influence of these processing parameters onto the crystalline structure of the resulting graphitized material. For the first time, the addition of biochar fines was found to serve as a “physical template” to increase the graphitic nature of the final product. During the initial biocrude carbonization (350–450 °C), volatile compounds are released, and aromatics in pyrolysis biocrude experience condensation, resulting in GNC solids with carbon contents above 95 wt % and some early lamellar structure. In the second stage of the thermal process (25–1500 °C), there are additional thermal decomposition reactions with an increase in the aromatic nature of the graphitized solid. It was found that systematic addition of biochar fines induces a nucleating effect during the GNC development. Thermogravimetric analysis suggests that biochar fines promote polycondensation reactions by modifying the biopitch structure and molecular weight, while elemental analysis (CHN) shows a reduction in both H/C and O/C ratios which are consistent with the increase in aromaticity and removal of oxygenated compounds as thermal treatment evolves. The effects of different bio-based pitch materials (after distillation) and GNC intermediates were evaluated by pyrolysis-gas chromatography mass spectrometry and Fourier transform infrared, displaying slight changes on product yields and quality. X-ray diffraction patterns taken after graphitization evidence an increase in the graphitic order with the addition of biochar fines. Transmittance electron microscopy depicts an improvement on graphitic morphology as biochar fine content increases. The use of biochar fines showed a significant increase in graphitic ordering at addition levels above 0.01 wt %. These results show that thermally treated biocrude/biochar fine systems can produce graphitic structures (hard carbon-like) that might be suitable for the manufacture of sodium-ion batteries.

09 BIOMASS FUELS↗