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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

A polymeric composite protective layer for stable Li metal anodes

Lithium (Li) metal is a promising anode for high-performance secondary lithium batteries with high energy density due to its highest theoretical specific capacity and lowest electrochemical potential among anode materials. However, the dendritic growth and detrimental reactions with electrolyte during Li plating raise safety concerns and lead to premature failure. Herein, we report that a homogeneous nanocomposite protective layer, prepared by uniformly dispersing AlPO 4 nanoparticles into the vinylidene fluoride-co-hexafluoropropylene matrix, can effectively prevent dendrite growth and lead to superior cycling performance due to synergistic influence of homogeneous Li plating and electronic insulation of polymeric layer. The results reveal that the protected Li anode is able to sustain repeated Li plating/stripping for >750 cycles under a high current density of 3 mA cm -2 and under a practical specific capacity of 2 mAh cm -2 . Moreover, full-cell Li-ion battery is constructed by using LiFePO 4 and protected Li as a cathode and anode, respectively, rendering a stable capacity after 400 charge/discharge cycles. The current work presents a promising approach to stabilize Li metal anodes for next-generation Li secondary batteries.

25 ENERGY STORAGE↗
DOE OSTI2021

Silicon-Based Anodes for Long-Cycle-Life Lithium-ion Batteries

CVD process has been studied and optimized to achieve 2x scale up of porous Si anode materials with a clean process. The roles of CVD temperature, duration, C 2 H 2 gas pressure, and carrier gas have been optimized. It is found that LHCE (LHCE-1 and LHCE-4) can lead to more than 50% increase in the cycling stability of Si||NMC622 cells. LHCE-4 can also lead to smaller impedance increase and longer calendar life when tested in single layer pouch cells. These results are very helpful in the understanding of the Si based anode and further development of Si based Li ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2021

Advanced strategies for the development of porous carbon as a Li host/current collector for lithium metal batteries

Lithium metal is considered a promising anode material for high-energy-density rechargeable batteries because of its high specific theoretical capacity (3860 mAh g -1 , low mass density (0.534 g cm -3 ), and low electrochemical redox potential (-3.04 V vs. the standard hydrogen electrode). However, the high reactivity of Li with the electrolyte leads to the formation of an unstable solid electrolyte interphase (SEI) and continuous side reactions. Also, the non-uniform lithium-ion flux and infinite volume expansion of Li metal cause the growth of Li dendrites. These pose significant safety challenges and cause rapid capacity fading of the lithium metal batteries (LiMBs). To resolve these issues, a low-cost, easily processed, lightweight, high-performance carbon-based porous matrix is considered promising to host Li metal deposition. The three-dimensional (3D) porous nano/microstructured carbon provides sufficient space for Li accommodation during Li plating, buffers the volume changes during Li plating/stripping, and lowers the effective current density contributing to dendrite-free Li deposition. Besides, the outstanding electrochemical and mechanical stability, flexibility and the high electronic conductivity enable the nano/microstructured carbon to serve as both Li host and current collector. The development of 3D carbon/Li composite by mechanical roll-press techniques not only eliminates the complex and risky procedure of making carbon/Li composite based on Li plating or molten Li infusion but also stabilizes the capacity at higher Li plating/stripping rates. Recently, there is an advancement in the lithiophilic decorations of 3D structure to introduce sufficient nucleation sites and the development of artificial SEI on top of the 3D matrix to suppress Li dendrite formation. Such 3D structural modifications create a uniform electric field, lower the Li nucleation overpotential, provide strong mechanical and chemical stability, and stabilize the interface thereby inhibiting the degradation of lithium and the electrolyte. Here we summarize the research progress on porous carbon/Li composites in terms of materials type, structure, fabrication technique, their electrochemical battery performance, and identify the critical challenges that need to be addressed for high-energy-density practical LiMBs.

25 ENERGY STORAGE↗
DOE OSTI2016

Li 3 PO 4 Matrix Enables a Long Cycle Life and High Energy Efficiency Bismuth-Based Battery

Bismuth is a lithium-ion battery anode material that can operate at an equilibrium potential higher than graphite and provide a capacity twice as high as that of Li 4 Ti 5 O 12 , making it intrinsically free from lithium plating that may cause catastrophic battery failure. However, the potential of bismuth is hampered by its inferior cyclability (limited to tens of cycles). Here, we propose an “ion conductive solid-state matrix” approach to address this issue. By homogeneously confining bismuth nanoparticles in a solid-state γ-Li 3 PO 4 matrix that is electrochemically formed in situ, the resulting composite anode exhibits a reversible capacity of 280 mA hours per gram (mA h/g) at a rate of 100 mA/g and a record cyclability among bismuth-based anodes up to 500 cycles with a capacity decay rate of merely 0.071% per cycle. We further show that full-cell batteries fabricated from this composite anode and commercial LiFePO 4 cathode deliver a stable cell voltage of ~2.5 V and remarkable energy efficiency up to 86.3%, on par with practical batteries (80–90%). This work paves a way for harnessing bismuth-based battery chemistry for the design of high capacity, safer lithium-ion batteries to meet demanding applications such as electric vehicles.

25 ENERGY STORAGE↗
DOE OSTI2018

Synergistic effect of hierarchical SnO2 nanorods/Fe2O3 hexahedrons with enhanced performance as lithium ion battery anodes

Highlights: • SnO{sub 2}-Fe{sub 2}O{sub 3} nanocomposites were fabricated by a two-step hydrothermal method. • SnO{sub 2}-Fe{sub 2}O{sub 3} nanocomposites show high capacity and excellent cycling stability. • The enhanced performances benefit from the synergistic effect of SnO{sub 2} and Fe{sub 2}O{sub 3}. • The reduced Fe nanoparticles facilitate the fully conversion reaction of SnO{sub 2}. - Abstract: Hierarchical SnO{sub 2}-Fe{sub 2}O{sub 3} nanocomposites composed of SnO{sub 2} nanorods and Fe{sub 2}O{sub 3} hexahedrons are successfully prepared by a two-step hydrothermal method. The lithium ion batteries (LIBs) based on as-synthesized products are fabricated to investigate their electrochemical performance. As an anode material for LIBs, SnO{sub 2}-Fe{sub 2}O{sub 3} nanocomposites deliver a high capacity of 1022 mAh g{sup −1} at 100 mA g{sup −1} after 100 cycles. The cycling stability and rate performance of the nanocomposites are significantly improved. The enhanced performances benefit from the synergistic effect of SnO{sub 2} nanorods and Fe{sub 2}O{sub 3} hexahedrons. The iron (Fe) nanoparticles reduced from Fe{sub 2}O{sub 3} not only facilitate the conversion reaction of SnO{sub 2}, resulting in the high capacity, but also increase the conductivity of the material. In addition, SnO{sub 2} serves as a matrix to protect Fe{sub 2}O{sub 3} from agglomeration, and the hierarchical structure effectively buffers volume changes, thus enhancing the cycling life of LIBs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Sub-5 nm edge-rich 1T'-ReSe 2 as bifunctional materials for hydrogen evolution and sodium-ion storage

The rhenium-based transition metal dichalcogenides (TMDs), as new members in the TMDs family, have raised great interests recently. Due to the anisotropic structure and unique photoelectric properties, they have potential applications for electrochemical energy conversion and storage. In this work, we performed density functional theory (DFT) calculations on pristine 1T'-ReSe 2 toward hydrogen evolution reaction (HER). The results indicated that the Gibbs free energy of the 1T'-ReSe 2 edge site for HER could be as small as 0.01 eV, superior to other reported TMDs. Experimentally, we developed a strategy to fabricate sub-5 nm sized 1T'-ReSe 2 nanoflakes on carbon nanotubes. Such a small size for the nanoflakes brought abundant edge exposure, which boosted the catalytic activity in the HER. Specifically, the 1T'-ReSe 2 nanoflakes needed only 23 and 60 mV overpotentials to achieve –1 and –10 mA cm –2 current densities, along with a low Tafel slope of 37 mV dec –1 and a high exchange current density of 0.3 mA cm –2 . The edge-rich and layered 1T'-ReSe 2 was also explored as an anode for sodium ion battery. The in operando X-ray absorption near edge structure (XANES) technique was applied to investigate the TMD behavior in real-time during the sodiation/desodiation process. Furthermore, the in situ results revealed that the nanosized 1T'-ReSe 2 is electrchemically reversible during discharge/charge cycles. The electrochemical test results demonstrated that 1T'-ReSe 2 could be a promising anode material for alkaline batteries.

25 ENERGY STORAGE↗
DOE OSTI2014

Stress effects on the initial lithiation of crystalline silicon nanowires: Reactive molecular dynamics simulations using ReaxFF

Silicon (Si) has been recognized as a promising anode material for the next-generation high-capacity lithium (Li)-ion batteries because of its high theoretical energy density. Recent in situ transmission electron microscopy (TEM) revealed that the electrochemical lithiation of crystalline Si nanowires (c-SiNWs) proceeds by the migration of the interface between the lithiated Si (LixSi) shell and the pristine unlithiated core, accompanied by solid-state amorphization. The underlying atomic mechanisms of Li insertion into c-Si remain poorly understood. In this research, we perform molecular dynamics (MD) simulations using the reactive force field (ReaxFF) to characterize the lithiation process of c-SiNWs. Our calculations show that ReaxFF can accurately reproduce the energy barriers of Li migration from DFT calculations in both crystalline (c-Si) and amorphous Si (a-Si). The ReaxFF-based MD simulations reveal that Li insertion into interlayer spacing between two adjacent (111) planes results in the peeling-off of the (111) facets and subsequent amorphization, in agreement with experimental observations. We find that breaking of the Si–Si bonds between (111)-bilayers requires a rather high local Li concentration, which explains the atomically sharp amorphous–crystalline interface (ACI). Our stress analysis shows that lithiation induces compressive stress at the ACI layer, causing retardation or even the stagnation of the reaction front, also in good agreement with TEM observations. Lithiation at high temperatures (e.g. 1200 K) shows that Li insertion into c-SiNW results in an amorphous to crystalline phase transformation at Li : Si composition of ~4.2:1. In conclusion, our modeling results provide a comprehensive picture of the effects of reaction and diffusion-induced stress on the interfacial dynamics and mechanical degradation of SiNW anodes under chemo-mechanical lithiation.

25 ENERGY STORAGE↗
DOE OSTI2019

Tin Nitride Atomic Layer Deposition Using N2H4

There is substantial lag in the development of atomic layer deposition (ALD) processes for nitrides compared to the high-quality, conformal oxides for which ALD has become the standard. A major factor in this disparity is the ready availability of highly reactive oxygen sources (mainly H2O, O2, and H2O2). High-energy nitrogen precursors are similarly required for the efficient incorporation of nitrogen in a film. Ammonia has often been used in conjunction with metal chlorides but requires relatively high temperatures for thermal ALD. Plasma-enhanced ALD can utilize molecular nitrogen as a precursor but can reduce film conformality on complex supports and damage the underlying substrate. Hydrazine (N2H4) is an alternative precursor which has been rarely explored for the fabrication of nitrides in ALD, but which is experiencing a surge in popularity due to its high reactivity, which enables the deposition of nitrides as-yet undemonstrated by ALD.(1) The added reactivity and volatility of liquid hydrazine may enable new reaction mechanisms, lower deposition temperatures, and conformality for high aspect ratio applications. Sn3N4 is a metastable semiconductor which shares a crystal structure with its analog, Si3N4; unlike Si3N4, Sn3N4 has only recently been grown by ALD,(2) being synthesized much more often through reactive sputtering.(3) As a binary, Sn3N4 has applications as a battery anode material, for photoelectrochemistry, and optoelectronic devices. We will report progress on the deposition of SnxNy films from tetrakis(dimethylamido) tin (TDMASn) and N2H4. Growth per cycle of this material (determined by x-ray reflectivity) is 0.4 A at 200 C, similar to the sole report of Sn3N4 from PE-ALD,(2) despite films being substantially Sn-rich. Identification of ALD growth window and self-limiting deposition characteristics are underway; initial testing indicates a competing chemical vapor deposition process which can be eliminated with adequate tuning of pulse/purge characteristics. A comparison of film conductivity and optical absorption at different growth temperatures will be presented. General issues of N2H4 purity and routes to prevent or control oxynitride formation will be discussed. (1) Du, L., et al. The First Atomic Layer Deposition Process for FexN Films. Chem. Comm., 2019, ASAP. DOI: 10.1039/C8CC10175B. (2) Stewart, D. M., et al. Tin Oxynitride Anodes by Atomic Layer Deposition for Solid-State Batteries. Chem. Mater. 2018, 30, 2526-34. (3) Caskey, C. M., et al. Semiconducting Properties of Spinel Tin Nitride and Other IV3N4 Polymorphs. J. Mater. Chem. C 2015, 3, 1389-96.

14 SOLAR ENERGY↗
DOE OSTI2023

Critical Contribution of Imbalanced Charge Loss to Performance Deterioration of Si-Based Lithium-Ion Cells during Calendar Aging

Increasing the energy density of lithium-ion batteries, and thereby reducing costs, is a major target for industry and academic research. One of the best opportunities is to replace the traditional graphite anode with a high-capacity anode material, such as silicon. However, Si-based lithium-ion batteries have been widely reported to suffer from a limited calendar life for automobile applications. Heretofore, there lacks a fundamental understanding of calendar aging for rationally developing mitigation strategies. Both open-circuit voltage and voltage-hold aging protocols were utilized to characterize the aging behavior of Si-based cells. Particularly, a high-precision leakage current measurement was applied to quantitatively measure the rate of parasitic reactions at the electrode/electrolyte interface. The rate of parasitic reactions at the Si anode was found 5 times and 15 times faster than those of LiNi 0.8 Mn 0.1 Co 0.1 O 2 and LiFePO 4 cathodes, respectively. Here, the imbalanced charge loss from parasitic reactions plays a critical role in exacerbating performance deterioration. In addition, a linear relationship between capacity loss and charge consumption from parasitic reactions provides fundamental support to assess calendar life through voltage-hold tests. These new findings imply that longer calendar life can be achieved by suppressing parasitic reactions at the Si anode to balance charge consumption during calendar aging.

25 ENERGY STORAGE↗
DOE OSTI2020

Improving Interface Stability of Si Anodes by Mg Coating in Li-Ion Batteries

Silicon (Si) is a promising anode material for high-energy-density lithium-ion batteries (LIBs), but its short calendar life and poor cycling performance prevent its large-scale adoption. Introducing magnesium (Mg) salt into the electrolyte has been recently shown to form a ternary Li–Mg–Si Zintl phase upon lithiation of Si and improve the cycling performance. However, the ternary Zintl phase formation mechanism and its impact on the solid electrolyte interphase (SEI) are not yet well understood. In this work, we demonstrate the formation of a ternary Li–Mg–Si Zintl phase by Mg coating of the Si anode, where Mg diffuses into the Si film upon deposition and intermixes further during the lithiation process. The presence of the Zintl phase improves the interface stability, alters the nature of the SEI, and enhances the cycling performance of the Si anode. This study provides insights into the formation mechanism of the ternary Zintl phase and guidelines for the future design of Si anodes.

25 ENERGY STORAGE↗
DOE OSTI2018

Operando Synchrotron Measurement of Strain Evolution in Individual Alloying Anode Particles within Lithium Batteries

Alloying anode materials offer high capacity for next-generation batteries, but the performance of these materials often decays rapidly with cycling because of volume changes and associated mechanical degradation or fracture. The direct measurement of crystallographic strain evolution in individual particles has not been reported, however, and this level of insight is critical for designing mechanically resilient materials. Here, we use operando X-ray diffraction to investigate strain evolution in individual germanium microparticles during electrochemical reaction with lithium. The diffraction peak was observed to shift in position and diminish in intensity during reaction because of the disappearance of the crystalline Ge phase. The compressive strain along the [111] direction was found to increase monotonically to a value of -0.21%. This finding is in agreement with a mechanical model that considers expansion and plastic deformation during reaction. As a result, this new insight into the mechanics of large-volume-change transformations in alloying anodes is important for improving the durability of high-capacity batteries.

25 ENERGY STORAGE↗
DOE OSTI2016

Transition-Metal Carbodiimides as Molecular Negative Electrode Materials for Lithium- and Sodium-Ion Batteries with Excellent Cycling Properties

Here we report evidence for the electrochemical activity of transition-metal carbodiimides versus lithium and sodium. In particular, iron carbodiimide, FeNCN, can be efficiently used as a negative electrode material for alkali-metal-ion batteries, similar to its oxide analogue FeO. Based on 57 Fe M ssbauer and infrared spectroscopy (IR) data, the electrochemical reaction mechanism can be explained by the reversible transformation of the Fe NCN into Li/Na NCN bonds during discharge and charge. These new electrode materials exhibit higher capacity compared to well-established negative electrode references such as graphite or hard carbon. Contrary to its oxide analogue, iron carbodiimide does not require heavy treatments (nanoscale tailoring, sophisticated textures, coating etc.) to obtain long cycle life with density current as high as 9 A/g -1 for hundreds of charge/discharge cycles. Similar to the iron compound, several other transition-metal carbodiimides M x (NCN) y with M = Mn, Cr, Zn can cycle successfully versus lithium and sodium. Ultimately, their electrochemical activity and performances open the way to the design of a novel family of anode materials.

25 ENERGY STORAGE↗
DOE OSTI2020

Spontaneous and reversible hollowing of alloy anode nanocrystals for stable battery cycling

High-capacity alloy anode materials for Li-ion batteries have long been held back by limited cyclability caused by the large volume changes during lithium insertion and removal. Hollow and yolk-shell nanostructures have been used to increase the cycling stability by providing an inner void space to accommodate volume changes and a mechanically and dimensionally stable outer surface. These materials, however, require complex synthesis procedures. Here, using in situ transmission electron microscopy, we show that sufficiently small antimony nanocrystals spontaneously form uniform voids on the removal of lithium, which are then reversibly filled and vacated during cycling. This behaviour is found to arise from a resilient native oxide layer that allows for an initial expansion during lithiation but mechanically prevents shrinkage as antimony forms voids during delithiation. In this work, we developed a chemomechanical model that explains these observations, and we demonstrate that this behaviour is size dependent. Thus, antimony naturally evolves to form optimal nanostructures for alloy anodes, as we show through electrochemical experiments in a half-cell configuration in which 15-nm antimony nanocrystals have a consistently higher Coulombic efficiency than larger nanoparticles.

25 ENERGY STORAGE↗
DOE OSTI2018

Fabrication of hollow carbonaceous nanospheres and their applications in lithium-ion batteries

Highlights: • SiO{sub 2}@SiO{sub 2}/RF resin composite nanospheres are prepared via a dual-templating method. • Hollow carbon nanospheres with large surface area are obtained after carbonization. • Hollow C/SiC composite nanospheres are produced after magnesiothermic reduction. • The carbonaceous nanospheres show superior electrochemical performance. • SiC nanomaterials can serve as candidate for LIBs anode materials. - Abstract: This paper presents a facile method for preparing hollow carbonaceous nanospheres for use in advanced Li-ion batteries (LIBs). Core–shell-structured silica@resin/silica nanosphere composites were used as the starting material. Hollow carbon nanospheres with a high specific surface area, i.e., 1389 m{sup 2} g{sup −1}, and C/SiC composite nanospheres composed of 24.4 wt.% amorphous carbon and 75.6 wt.% cubic β-SiC were obtained. Electrochemical measurements showed that the hollow carbon nanospheres delivered a reversible capacity of 553.5 mA h g{sup −1} after 100 cycles, which is higher than the theoretical capacity of graphite. A C/SiC composite nanosphere electrode gave a reversible capacity of 296 mA h g{sup −1} after 500 cycles. The results show that these nanospheres are promising candidates for use in LIB anodes.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Superior metal storage behavior of Zn-containing porous carbon nanostructures for Na and Li metal batteries

Na and Li metals are ideal anodes for high-energy rechargeable batteries. However, their poor coulombic efficiency and the associated safety issues due to dendritic metal deposition and large volume changes during metallic plating/stripping are the major causes that persistently hinder their practical energy-storage applications. Herein, Zn-containing carbon nanostructures derived from typical zeolitic imidazolate framework-8 (ZIF-8) are proposed as advanced metal anode materials for both Na and Li metal batteries. In this study; the three-dimensional interconnected porous surfaces confine metallic Na and Li within the nanostructures, filling the carbon scaffold, and covering the electrode surface to form stable solid electrolyte interphases. Based on the metal nucleation and growth results obtained through various electrochemical tests, Zn incorporation and pore morphology have been revealed to be the key factors that regulate the metal nucleation and metallic plating/stripping during cycling. Thus, the incorporation of Zn in the closed pores of a carbon nanostructure improves the cycle performance, even in carbonate electrolytes, and produces stable Na and Li metallic anodes for next-generation rechargeable batteries.

25 ENERGY STORAGE↗
NASA NTRS1991

Advances in Li-TiS2 cell technology

JPL is involved in a NASA sponsored program to develop ambient temperature secondary cells for future space missions. After several years of research on various cathode materials, Titanium Disulfide (TiS2) was selected in view of its intrinsic reversibility and high faradaic utilization. In the last two years, the efforts were focused on improving the cycle life of the system and developing 1 Ah cells. Several approaches including the use of mixed solvent electrolytes, the operation of cells at low temperature, and the cycling of cells under different voltage limits, were initially examined to improve the cycle life performance of the Li-TiS2 system. Spiral wound 1 Ah cells fabricated incorporating the improvements from the above studies have delivered more than 600 cycles at 50% DOD. Work is in progress to identify alternate anode materials that can improve the cycle life of the cells to 1000 cycles at 50% DOD. This paper summarizes the advances made in the Li-TiS technology at JPL since 1989.

S Surampudi↗
DOE OSTI2020

Ambient Temperature Graphitization Based on Mechanochemical Synthesis

Graphite has become a critical material because of its high supply risk and essential applications in energy industries. Its present synthesis still relies on an energy-intensive thermal treatment pathway (Acheson process) at about 3000 °C. Herein, a mechanochemical approach is demonstrated to afford highly crystalline graphite nanosheets at ambient temperature. The key to the success of our methodology lies in the successive decomposition and rearrangement of a carbon nitride framework driven by a denitriding reaction in the presence of magnesium. The afforded graphite features high crystallinity, a high degree of graphitization, a thin nanosheet architecture, and a small flake size, which endow it with superior efficiency in lithium-ion batteries as an anode material in terms of rate capacity and cycle stability. Finally, the mild and cost-effective pathway used in this study could be a promising alternative for graphite production.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗