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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Conformal Lithium Fluoride Protection Layer on Three-Dimensional Lithium by Nonhazardous Gaseous Reagent Freon

Research on lithium (Li) metal chemistry has been rapidly gaining momentum nowadays not only because of the appealing high theoretical capacity, but also its indispensable role in the next-generation Li–S and Li–air batteries. However, two root problems of Li metal, namely high reactivity and infinite relative volume change during cycling, bring about numerous other challenges that impede its practical applications. In the past, extensive studies have targeted these two root causes by either improving interfacial stability or constructing a stable host. However, efficient surface passivation on three-dimensional (3D) Li is still absent. Here in this paper, we develop a conformal LiF coating technique on Li surface with commercial Freon R134a as the reagent. In contrast to solid/liquid reagents, gaseous Freon exhibits not only nontoxicity and well-controlled reactivity, but also much better permeability that enables a uniform LiF coating even on 3D Li. By applying a LiF coating onto 3D layered Li-reduced graphene oxide (Li-rGO) electrodes, highly reduced side reactions and enhanced cycling stability without overpotential augment for over 200 cycles were proven in symmetric cells. Furthermore, Li–S cells with LiF protected Li-rGO exhibit significantly improved cyclability and Coulombic efficiency, while excellent rate capability (~800 mAh g -1 at 2 C) can still be retained.

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

Lithium Acetylide: A Spectroscopic Marker for Lithium Deposition During Fast Charging of Li-Ion Cells

Rapid charging of lithium-ion batteries being developed for electric vehicles is a formidable challenge. Electrochemical polarization of cells during fast charging favors deposition of metallic Li onto the surface of the graphite electrode, and this Li plating compromises safety and accelerates performance degradation. Observing the onset of Li nucleation is essential for elucidation of mechanisms and defining conditions favoring this Li plating, but presently available methods are not sufficiently sensitive and selective while also allowing satisfactory spatial resolution. We demonstrate the use of Raman spectroscopy as a sensitive means to identify Li nucleation and map Li deposition. Metallic Li is detected indirectly by probing the vibrations in an acetylide species (represented as Li—C≡C—X) that is formed on the exposed surface of Li nuclei in contact with the solid electrolyte interphase on graphite. Surface-enhanced Raman scattering (SERS) involving this species on Li nuclei appears to dramatically increase sensitivity and selectivity of this detection, making our method an excellent complement to the existing spectroscopy and microscopy approaches for determining Li deposition.

25 ENERGY STORAGE↗
DOE OSTI2021

Zinc-Doped High-Nickel, Low-Cobalt Layered Oxide Cathodes for High-Energy-Density Lithium-Ion Batteries

High-Ni layered oxides with Ni contents greater than 90% are promising cathode candidates for high-energy-density Li-ion batteries. However, drastic electrode-electrolyte reactions and mechanical degradation issues limit their cycle life and practical viability. We demonstrate here that LiNi 0.94 Co 0.04 Zn 0.02 O 1.99 (NCZ), obtained by incorporating 2 mol% Zn 2+ into an ultrahigh-Ni baseline cathode material LiNi 0.94 Co 0.06 O 2 (NC), delivers superior cell performance. NCZ retains 74% of the initial capacity after 500 cycles in full cell assembled with graphite anode, outperforming NC (62% retention). NCZ also possesses a higher average discharge voltage relative to NC with an outstanding average voltage retention of over 99% after 130 cycles in half cells. Bulk structural investigations unveil that Zn doping promotes a smoother phase transition, suppresses anisotropic lattice distortion, and maintains the mechanical integrity of cathode particles. Furthermore, NCZ shows an enhanced interphase stability after long-term cycling, in contrast to the seriously degraded surface chemistry in NC. Finally, this work provides a practically viable approach for designing higher-energy-density high-Ni layered oxide cathodes for lithium-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2021

Influence of Calendering on the Electrochemical Performance of LiNi 0.9 Mn 0.05 Al 0.05 O 2 Cathodes in Lithium-Ion Cells

Electrode calendering is a necessary process used in industry to improve the volumetric capacity of lithium-ion batteries. However, calendering high-nickel cathodes leads to electrode particle pulverization, raising concerns of a reduced cycle life due to parasitic side reactions. We present here an investigation of the impact of calendering on the morphology and electrochemical performance of the cobalt-free layered oxide cathode LiNi 0.9 Mn 0.05 Al 0.05 O 2 (NMA-90). We find that secondary particle pulverization and fusion simultaneously occur at sufficiently high pressures. The initial surface area of the cathode is shown to increase with the degree of calendering, despite the higher likelihood of secondary particle fusion. Long-term cycling of full coin cells assembled with the NMA-90 cathode and the graphite anode indicates that cells with higher degrees of cathode calendering exhibit lower capacity fade compared to uncalendered cathodes. Hybrid pulse-power tests demonstrate that the usable capacity range of cells with calendered cathodes far exceeds those with uncalendered cells after long-term cycling. The improved capacity retention and pulse-power performance are attributed to the enhanced mechanical properties of the electrode after calendering that prevents loss of the primary particle contact during long-term cycling. As a result, we find that calendering high-nickel NMA-90 to industrially relevant densities does not have a detrimental effect on capacity fade, marking an important step toward commercial adoption.

25 ENERGY STORAGE↗
DOE OSTI2022

Synthesis of Fluorine-Doped Lithium Argyrodite Solid Electrolytes for Solid-State Lithium Metal Batteries

Solid-state lithium metal batteries (SSLMBs) that utilize novel solid electrolytes (SEs) have garnered much attention because of their potential to yield safe and high-energy-density batteries. Sulfide-based argyrodite-class SEs are an attractive option because of their impressive ionic conductivity. Recent studies have shown that LiF at the interface between Li and SE enhances electrochemical stability. However, the synthesis of F-doped argyrodites has remained challenging because of the high temperatures used in the state-of-the-art solid-state synthesis methods. In this work, for the f irst time, we report F-doped Li 5+y PS 5 F y argyrodites with a tunable doping content and dual dopants (F-/Cl- and F-/Br-) that were synthesized through a solvent-based approach. Among all compositions, Li 6 PS 5 F 0.5 C l0.5 exhibits the highest Li-ion conductivity of 3.5 x 10 -4 S cm -1 at room temperature (RT). Furthermore, Li symmetric cells using Li 6 PS 5 F 0.5 Cl 0.5 show the best cycling performance among the tested cells. X-ray photoelectron spectroscopy and ab initio molecular dynamics simulations revealed that the enhanced interfacial stability of Li 6 PS 5 F 0.5 C l0.5 SE against Li metal can be attributed to the formation of a stable solid electrolyte interphase (SEI)-containing conductive species (Li 3 P), alongside LiCl and LiF. These findings open new opportunities to develop high-performance SSLMBs using a novel class of F-doped argyrodite electrolytes.

25 ENERGY STORAGE↗
DOE OSTI2019

Prospect of Thermal Shock Induced Healing of Lithium Dendrite

Dendritic growth plagues the development of rechargeable lithium metal anodes. Recently, it has been reported that self-heating of the cell provides a mitigation strategy for suppressing dendrites. In order to study this phenomenon, we extend our recently developed nonlinear phase-field model to incorporate an energy balance equation allowing a full thermally coupled electrodeposition model using the open-source software package MOOSE. In this study, we consider the interplay between ionic transport and electrochemical reaction rate as a function of temperature and explore the possibility of using thermal shock induced dendrite suppression. We discover that, depending on the electrochemical reaction barrier and ionic diffusion barrier, self-heating could accelerate (larger reaction barrier) or decelerate (larger diffusion barrier) dendrite formation. Given that the electrolyte constituents can be used to tune both barriers, this study could provide an important avenue to exploit the self-heating effect favorably through electrolyte engineering.

25 ENERGY STORAGE↗
DOE OSTI2019

Stable Li Metal Anode by a Hybrid Lithium Polysulfidophosphate/Polymer Crosslinking Film

The practical application of rechargeable lithium (Li) metal batteries has long been hindered by the unstable Li metal anode with problems like Li dendrite growth, low Coulombic efficiency (CE), and short cycle life. Here, we demonstrate a multifunctional sulfur-containing hybrid Li polysulfidophosphate and poly(2-chloroethyl acrylate) cross-linking film that can provide effective protection for Li metal anode. This film can facilitate Li metal anode generating a stable organic/inorganic hybrid solid electrolyte interphase (SEI) layer containing multiple components such as polymer-tethered organo(poly)sulfide, inorganic Li polysulfidophosphate, Li sulfides, and Li salts. Thanks to this hybrid robust SEI layer, dendrite-free Li deposition and stable cycling of Li metal anode can be achieved (e.g. CE >98.7% over 950 cycles). We demonstrated this Li protection technique enables both the protected Li metal anode and Li-metal-free anode cycling with significantly improved CEs and stability in full cells using LiFePO 4 (~2.4 mAh/cm 2 ) cathode.

25 ENERGY STORAGE↗
DOE OSTI2021

Pressure-tailored lithium deposition and dissolution in lithium metal batteries

Unregulated lithium (Li) growth is the major cause of low Coulombic efficiency, short cycle life and safety hazards for rechargeable Li metal batteries. Strategies that aim to achieve large granular Li deposits have been extensively explored, and yet it remains a challenge to achieve the ideal Li deposits, which consist of large Li particles that are seamlessly packed on the electrode and can be reversibly deposited and stripped. In this work, we report a dense Li deposition (99.49% electrode density) with an ideal columnar structure that is achieved by controlling the uniaxial stack pressure during battery operation. Using multiscale characterization and simulation, we elucidate the critical role of stack pressure on Li nucleation, growth and dissolution processes and propose a Li-reservoir-testing protocol to maintain the ideal Li morphology during extended cycling. The precise manipulation of Li deposition and dissolution is a critical step to enable fast charging and a low-temperature operation for Li metal batteries.

25 ENERGY STORAGE↗
DOE OSTI2014

Determining the refractive index of shocked [100] lithium fluoride to the limit of transmissibility

Lithium fluoride (LiF) is a common window material used in shock- and ramp-compression experiments because it displays a host of positive attributes in these applications. Most commonly, it is used to maintain stress at an interface and velocimetry techniques are used to record the particle velocity at that interface. In this application, LiF remains transparent to stresses up to 200 GPa. In this stress range, LiF has an elastic-plastic response with a very low (<0.5 GPa) elastic precursor and exhibits no known solid-solid phase transformations. However, because the density dependence of the refractive index of LiF does not follow the Gladstone-Dale relation, the measured particle velocity at this interface is not the true particle velocity and must be corrected. For that reason, the measured velocity is often referred to as the apparent velocity in these types of experiments. In this article, we describe a series of shock-compression experiments that have been performed to determine the refractive index of LiF at the two most commonly used wavelengths (532 nm and 1550 nm) between 35 and 200 GPa to high precision. A modified form of the Gladstone-Dale relation was found to work best to fit the determined values of refractive index. In addition, we provide a direct relationship between the apparent and true particle velocity to correct experimentally obtained wave profiles by others using these velocimetry techniques.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗