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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Modeling of Lithium Nucleation and Plating Kinetics Under Fast Charge Conditions

The onset of lithium nucleation and subsequent plating on the graphite particles is a challenging problem in the design of fast charging batteries. Here, a variational phase field formulation has been developed to initiate the nucleation of lithium particles based on the local plating overpotential conditions and allowing to predict the lithium plating under fast charge conditions. The model demonstrates that (1) at small charging current density, there is no nucleation and plating of metallic lithium, and no effect on the intercalation kinetics; (2) at intermediate charging current densities, initially a stagnated growth from isolated lithium nuclei is observed followed by a continuous growth of metallic lithium; (3) at large charging current densities, a continuous growth of metallic lithium resulting from coalescence of small nuclei into large nuclei decreases the excess interfacial energy, which in turn slows down the intercalation kinetics. The formulation sets the stage for predicting and evaluating the influence of various electrolyte compositions, graphite particle morphologies and electrode loadings on the nucleation and plating dynamics under fast charge conditions.

25 ENERGY STORAGE↗
DOE OSTI2023

Highly Reversible Lithiation of Additive Free T‐Nb 2 O 5 for a Quarter of a Million Cycles

Abstract Fast energy storage via intercalation requires quick ionic diffusion and often results in pseudocapacitive behavior. The cycling stability of such energy storage materials remains understudied despite the relevance to lifetime cost. Orthorhombic niobium oxide (T‐Nb 2 O 5 ) is a rapid ion intercalation material with a theoretical capacity of 201.7 mAh g −1 (Li 2 Nb 2 O 5 ) and good cycling stability due to the minimal unit cell strain during (de)intercalation. Prior reports of T‐Nb 2 O 5 cycling between 1.3–3.1 V versus Li/Li + noted a 50% loss in capacity after 10 000 cycles. Here, cyclic voltammetry is used to identify the role of the voltage window, state of charge, and potentiostatic holds on the cycling stability of mesoporous T‐Nb 2 O 5 thin films. Films cycled between 1.2–3.0 V versus Li/Li + without voltage holds (Li 1.1 Nb 2 O 5 ) exhibited extreme cycling stability with 90.8% capacity retention after 0.25 million cycles without detectable morphological/crystallographic changes. In contrast, the inclusion of 60 s voltage holds (Li 2.18 Nb 2 O 5 ) led to rapid capacity loss with 61.6% retention after 10 000 cycles with corresponding X‐ray diffraction evidence of amorphization. Cycling with other limited voltage windows identifies that most crystallographic degradation occurs at higher extents of lithiation. These results reveal remarkable stability over limited conditions and suggest that T‐Nb 2 O 5 amorphization is associated with high extents of lithiation.

25 ENERGY STORAGE↗
NASA NTRS2006

4-Vinyl-1,3-Dioxolane-2-One as an Additive for Li-Ion Cells

Electrolyte additive 4-vinyl-1,3-dioxolane-2-one has been found to be promising for rechargeable lithium-ion electrochemical cells. This and other additives, along with advanced electrolytes comprising solutions of LiPF6 in various mixtures of carbonate solvents, have been investigated in a continuing effort to improve the performances of rechargeable lithium-ion electrochemical cells, especially at low temperatures. In contrast to work by other researchers who have investigated the use of this additive to improve the high-temperature resilience of Li-ion cells, the current work involves the incorporation of 4-vinyl-1,3-dioxolane-2-one into quaternary carbonate electrolyte mixtures, previously optimized for low-temperature applications, resulting in improved low-temperature performance. The benefit afforded by 4-vinyl-1,3- dioxolane-2-one can be better understood in the light of relevant information from a number of prior NASA Tech Briefs articles about electrolytes and additives for such cells. To recapitulate: The loss of performance with decreasing temperature is attributable largely to a decrease of ionic conductivity and the increase in viscosity of the electrolyte. What is needed to extend the lower limit of operating temperature is a stable electrolyte solution with relatively small lowtemperature viscosity, a large electric permittivity, adequate coordination behavior, and appropriate ranges of solubilities of liquid and salt constituents. Whether the anode is made of graphitic or non-graphitic carbon, a film on the surface of the anode acts as a solid/electrolyte interface (SEI), the nature of which is critical to low-temperature performance. Desirably, the surface film should exert a chemically protective (passivating) effect on both the anode and the electrolyte, yet should remain conductive to lithium ions to facilitate intercalation and de-intercalation of the ions into and out of the carbon during discharging and charging, respectively. The additives investigated previously include alkyl pyrocarbonates. Those additives help to improve low-temperature performances by giving rise to the formation of SEIs having desired properties. The formation of the SEIs is believed to be facilitated by products (e.g., CO2) of the decomposition of these additives. These decomposition products are believed to react to form Li2CO3-based films on the carbon electrodes. The present additive, 4-vinyl-1,3-dioxolane-2-one, also helps to improve lowtemperature performance by contributing to the formation of SEIs having desired properties, but probably in a different manner: It is believed that, as part of the decomposition process, the compound polymerizes on the surfaces of carbon electrodes.

Smart, Marshall↗
DOE OSTI2022

Meshfree Methods for Modeling Chemo-Mechanical Cathode Cracking in Li-Ion Batteries

Through repeated charging and discharging, the electrodes of a Li-ion battery experience cyclic loading causing swelling and contraction due to the movement of lithium, also known as intercalation. This research focuses specifically on the chemo-mechanical cracking in the cathode. Because cathode particles are comprised of many randomly-oriented grains, which have highly anisotropic material properties, the expansion and contraction is very non-uniform. As a result, stress concentrations tend to form between grains, which necessitates the modeling of crack propagation largely along grain boundaries. Chemo-mechanical models are simulated mainly by two methods: the cohesive zone model (CZM) and the continuous damage model (CDM). The CZM is more accurate at capturing the sharp discontinuities of a crack but is very computationally expensive and intractable for large-scale models as a result. Conversely, the CDM is easily computed but not well-suited to easily allow for discontinuous field variables, which are inherent across a crack. This study aims to improve the CDM's ability to capture discontinuous cracks. Current versions of the CDM use the finite element method (FEM), which is one of the most widely used approaches for spatial discretization. This research investigates the use of the Reproducing Kernel Particle Method (RKPM), a meshfree method, for spatial discretization and aims to achieve a chemo-mechanical crack propagation model that achieves both intermediate accuracy and computational time between a CDM and CZM. To gain a better understanding of how the meshfree model compares to the current FEM model in capturing cathode crack propagation, further investigation is needed.

cathode cracking↗
DOE OSTI2023

Meshfree Multiphysics Damage Modeling of Li-ion Battery Materials

Through repeated charging and discharging cycles, the electrodes of a Li-ion battery experience significant swelling and contraction due to the movement of lithium, also known as intercalation. This research focuses specifically on the chemo-mechanical cracking in the cathode. Because cathode particles are comprised of many randomly-oriented grains, which have highly anisotropic material properties, the expansion and contraction is very non-uniform. As a result, stress concentrations tend to form between grains, which necessitates the modeling of crack propagation largely along grain boundaries and material interfaces. Chemo-mechanical damage models are generally simulated by one of two methods: the cohesive zone model (CZM) and the continuous damage model (CDM). The CZM is more accurate at capturing the sharp discontinuities of a crack but is very computationally expensive and intractable for large-scale models as a result. Conversely, the CDM is easily computed but not well-suited to easily allow for discontinuous field variables, which are inherent across a crack. This study aims to improve the CDM's ability to capture discontinuous cracks. Current versions of the CDM use the finite element method (FEM), which is one of the most widely used approaches for spatial discretization. This research investigates the use of the Reproducing Kernel Particle Method (RKPM), a meshfree method, for spatial discretization and aims to achieve a coupled chemo-mechanical crack propagation model that enhances accuracy while maintaining high computational efficiency. This model features a fully coupled, iterative electrochemistry solution, which informs the meshfree damage model of impending crack formation. To gain a better understanding of how the meshfree model compares to the current FEM model in capturing cathode crack propagation, further investigation is needed.

damage modeling↗
NASA NTRS2007

Reversible Intercalation of Fluoride-Anion Receptor Complexes in Graphite

We have demonstrated a route to reversibly intercalate fluoride-anion receptor complexes in graphite via a nonaqueous electrochemical process. This approach may find application for a rechargeable lithium-fluoride dual-ion intercalating battery with high specific energy. The cell chemistry presented here uses graphite cathodes with LiF dissolved in a nonaqueous solvent through the aid of anion receptors. Cells have been demonstrated with reversible cathode specific capacity of approximately 80 mAh/g at discharge plateaus of upward of 4.8 V, with graphite staging of the intercalant observed via in situ synchrotron X-ray diffraction during charging. Electrochemical impedance spectroscopy and B-11 nuclear magnetic resonance studies suggest that cointercalation of the anion receptor with the fluoride occurs during charging, which likely limits the cathode specific capacity. The anion receptor type dictates the extent of graphite fluorination, and must be further optimized to realize high theoretical fluorination levels. To find these optimal anion receptors, we have designed an ab initio calculations-based scheme aimed at identifying receptors with favorable fluoride binding and release properties.

electrolytes↗
DOE OSTI2020

A disordered rock salt anode for fast-charging lithium-ion batteries

Rechargeable lithium-ion batteries with high energy density that can be safely charged and discharged at high rates are desirable for electrified transportation and other applications. However, the sub-optimal intercalation potentials of current anodes result in a trade-off between energy density, power and safety. In this paper we report that disordered rock salt Li 3+ x V 2 O 5 can be used as a fast-charging anode that can reversibly cycle two lithium ions at an average voltage of about 0.6 volts versus a Li/Li + reference electrode. The increased potential compared to graphite reduces the likelihood of lithium metal plating if proper charging controls are used, alleviating a major safety concern (short-circuiting related to Li dendrite growth). In addition, a lithium-ion battery with a disordered rock salt Li 3 V 2 O 5 anode yields a cell voltage much higher than does a battery using a commercial fast-charging lithium titanate anode or other intercalation anode candidates (Li 3 VO 4 and LiV 0.5 Ti 0.5 S 2 ). Further, disordered rock salt Li 3 V 2 O 5 can perform over 1,000 charge–discharge cycles with negligible capacity decay and exhibits exceptional rate capability, delivering over 40 per cent of its capacity in 20 seconds. We attribute the low voltage and high rate capability of disordered rock salt Li 3 V 2 O 5 to a redistributive lithium intercalation mechanism with low energy barriers revealed via ab initio calculations. This low-potential, high-rate intercalation reaction can be used to identify other metal oxide anodes for fast-charging, long-life lithium-ion batteries.

25 ENERGY STORAGE↗
NASA NTRS2013

Li-Ion Battery and Supercapacitor Hybrid Design for Long Extravehicular Activities

With the need for long periods of extravehicular activities (EVAs) on the Moon or Mars or a near-asteroid, the need for long-performance batteries has increased significantly. The energy requirements for the EVA suit, as well as surface systems such as rovers, have increased significantly due to the number of applications they need to power at the same time. However, even with the best state-of-the-art Li-ion batteries, it is not possible to power the suit or the rovers for the extended period of performance. Carrying a charging system along with the batteries makes it cumbersome and requires a self-contained power source for the charging system that is usually not possible. An innovative method to charge and use the Li-ion batteries for long periods seems to be necessary and hence, with the advent of the Li-ion supercapacitors, a method has been developed to extend the performance period of the Li-ion power system for future exploration applications. The Li-ion supercapacitors have a working voltage range of 3.8 to 2.5 V, and are different from a traditional supercapacitor that typically has a working voltage of 1 V. The innovation is to use this Li-ion supercapacitor to charge Liion battery systems on an as-needed basis. The supercapacitors are charged using solar arrays and have battery systems of low capacity in parallel to be able to charge any one battery system while they provide power to the application. Supercapacitors can safely take up fast charge since the electrochemical process involved is still based on charge separation rather than the intercalation process seen in Li-ion batteries, thus preventing lithium metal deposition on the anodes. The lack of intercalation and eliminating wear of the supercapacitors allows for them to be charged and discharged safely for a few tens of thousands of cycles. The Li-ion supercapacitors can be charged from the solar cells during the day during an extended EVA. The Liion battery used can be half the capacity required for a nominal EVA. The small Li-ion battery can be divided into two parallel modules with independent charging ports that would allow the supercapacitors to charge one battery while the other is providing power to the rover or suit.

Jeevarajan, Judith↗
NASA NTRS2007

Hazards, Safety and Design Considerations for Commercial Lithium-ion Cells and Batteries

This viewgraph presentation reviews the features of the Lithium-ion batteries, particularly in reference to the hazards and safety of the battery. Some of the characteristics of the Lithium-ion cell are: Highest Energy Density of Rechargeable Battery Chemistries, No metallic lithium, Leading edge technology, Contains flammable electrolyte, Charge cut-off voltage is critical (overcharge can result in fire), Open circuit voltage higher than metallic lithium anode types with similar organic electrolytes. Intercalation is a process that places small ions in crystal lattice. Small ions (such as lithium, sodium, and the other alkali metals) can fit in the interstitial spaces in a graphite lattice. These metallic ions can go farther and force the graphitic planes apart to fit two, three, or more layers of metallic ions between the carbon sheets. Other features of the battery/cell are: The graphite is conductive, Very high energy density compared to NiMH or NiCd, Corrosion of aluminum occurs very quickly in the presence of air and electrolyte due to the formation of HF from LiPF6 and HF is highly corrosive. Slides showing the Intercalation/Deintercalation and the chemical reactions are shown along with the typical charge/discharge for a cylindrical cell. There are several graphs that review the hazards of the cells.

Jeevarajan, Judith↗
DOE OSTI2022

Effect of crystallite geometries on electrochemical performance of porous intercalation electrodes by multiscale operando investigation

Lithium-ion batteries are yet to realize their full promise because of challenges in the design and construction of electrode architectures that allow for their entire interior volumes to be reversibly accessible for ion storage. Electrodes constructed from the same material and with the same specifications, which differ only in terms of dimensions and geometries of the constituent particles, can show surprising differences in polarization, stress accumulation and capacity fade. Here, using operando synchrotron X-ray diffraction and energy dispersive X-ray diffraction (EDXRD), we probe the mechanistic origins of the remarkable particle geometry-dependent modification of lithiation-induced phase transformations in V2O5 as a model phase-transforming cathode. A pronounced modulation of phase coexistence regimes is observed as a function of particle geometry. Specifically, a metastable phase is stabilized for nanometre-sized spherical V2O5 particles, to circumvent the formation of large misfit strains. Spatially resolved EDXRD measurements demonstrate that particle geometries strongly modify the tortuosity of the porous cathode architecture. Greater ion-transport limitations in electrode architectures comprising micrometre-sized platelets result in considerable lithiation heterogeneities across the thickness of the electrode. These insights establish particle geometry-dependent modification of metastable phase regimes and electrode tortuosity as key design principles for realizing the promise of intercalation cathodes. Designing electrode architectures for Li-ion batteries that can be reversibly accessible for ion storage can be challenging. Using operando techniques the mechanistic origin of lithiation-induced phase transformations in a V2O5 model cathode is now clarified.

Luo, Yuting↗
DOE OSTI2024

Rechargeable Li-ion battery with halogen intercalated graphite electrode

The disclosure provides rechargeable lithium ion batteries comprising at least one lithium salt-graphite composite electrode. In particular, the disclosure provides a rechargeable “water-in-bisalt” lithium ion battery with a high potential where at least a portion of the lithium salt is phase separated from the aqueous electrolyte, and where the anionic-redox reaction occurs within the graphitic lattice.

Wang, Chunsheng↗
DOE OSTI2022

Amorphization of Pseudocapacitive T−Nb 2 O 5 Accelerates Lithium Diffusivity as Revealed Using Tunable Isomorphic Architectures

Abstract Intercalation pseudocapacitance can combine capacitor‐like power densities with battery‐like energy densities. Such surface‐limited behavior requires rapid diffusion where amorphization can increase solid‐state diffusivity. Here intercalation pseudocapacitive materials with tailored extents of amorphization in T‐Nb 2 O 5 are first reported. Amorphization was characterized with WAXS, XPS, XAFS, and EPR which suggested a peroxide‐rich (O 2 2− ) surface that was consistent with DFT predictions. A series of tunable isomorphic architectures enabled comparisons while independently varying transport parameters. Through process of elimination, solid‐state lithium diffusion was identified as the dominant diffusive‐constraint dictating the maximum voltage sweep rate for surface‐limited kinetics ( v SLT ), termed the Surface‐Limited Threshold (SLT). The v SLT increased with amorphization however stable cycling required crystalline T‐Nb 2 O 5 . A current‐response model using series‐impedances well‐matched these observations. This perspective revealed that amorphization of T‐Nb 2 O 5 enhanced solid‐state diffusion by 12.2 % and increased surface‐limitations by 17.0 % (stable samples). This approach enabled retaining 95 % lithiation capacity at ∼800 mV s −1 (1,600 C‐rate equivalent).

25 ENERGY STORAGE↗
DOE OSTI2020

Cathode Interface Compatibility of Amorphous LiMn 2 O 4 (LMO) and Li 7 La 3 Zr 2 O 12 (LLZO) Characterized with Thin-Film Solid-State Electrochemical Cells

Solid-state lithium-ion batteries are a hopeful successor to traditional Li-ion cells that use liquid electrolytes. While a growing body of work has characterized the interfaces between various solid electrolytes and the lithium metal, interfaces with common cathode intercalation compounds are comparatively less understood. In this contribution, the influence of polarization and temperature on interfacial stability between LiMn 2 O 4 (LMO) and Li 7 La 3 Zr 2 O 12 (LLZO) are investigated. Sputtered thin-film LMO electrodes are utilized to permit high-capacity cycling while retaining a large ratio of interfacial area to electrode bulk. Electrochemical impedance spectroscopy (EIS) is compared across a set of full (LMO|LLZO|Li) and symmetric (LMO|LLZO|LMO, Li|LLZO|Li, and Au|LLZO|Au) cells to delineate impedance features that are specific to the evolution of the cathode interface. Furthermore, additional X-ray photoelectron spectroscopy (XPS) provides evidence of a limited interfacial reaction between LMO and LLZO that coincides with an increase in the impedance of the LMO–LLZO interface.

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

Interfacial Issues and Modification of Solid Electrolyte Interphase for Li Metal Anode in Liquid and Solid Electrolytes

Abstract The high energy density required for the next generation of lithium batteries will likely be enabled by a shift toward lithium metal anode from the conventional intercalation‐based anode such as graphite. However, several critical challenges for Li metal originate from its highly reactive nature and the hostless reaction of deposition and stripping impede the practical use of Li metal as an anode. The role of the solid electrolyte interphase (SEI) is very important for the Li metal anode where the SEI must protect the dynamically changing surface of the Li metal. Since the SEI‐generating reaction mechanisms for the two different electrolyte systems, liquid and solid, are considerably different, the SEI layers formed between the Li metal and the electrolytes in the two electrolyte systems have substantially different properties, causing different interfacial issues. Inhibition of the interfacial problems requires different strategies to reinforce the SEI layer for each of the electrolyte systems. However, the differences in the two electrolyte systems have not been clearly compared in the prior literature. In this report, the interfacial issues for the two different electrolyte systems are compared and different strategies for SEI modification are provided to overcome the issues.

25 ENERGY STORAGE↗
DOE OSTI2021

Defect–Concentration–Mediated T–Nb 2 O 5 Anodes for Durable and Fast–Charging Li–Ion Batteries

Metastable orthorhombic niobium pentoxide (T-Nb 2 O 5 ) is a promising anode to fulfill the requirements for high-rate Li-ion batteries (LIBs). Stoichiometric T-Nb 2 O 5 is plagued by low electric conductivity and particle pulverization after repeated charge/discharge processes. In this work, oxygen vacancies are implanted into T-Nb 2 O 5 particles via acid immersion of Nb 2 O 5 ·nH 2 O with the formation of Lewis acid sites. The multiple characterizations and simulations reveal the lengthening of Nb–O bonds, and the transformation from NbO 7 pentagonal bipyramids and NbO 6 tetragonal bipyramids in T-Nb 2 O 5–x . The enrichment of oxygen vacancies endows T-Nb 2 O 5–x with higher electric conductivity, better electrochemical kinetics, larger pseudocapacitive contribution. O-doped graphitic C 3 N 4 is creatively proposed as a trace oxygen pump to repair excessive oxygen vacancies, and it also serves as a sacrifice template for Nb 2 O 5–x growth to construct a porous and monolithic electrode network. Defect-modulated Nb 2 O 5–x displays extraordinary cycling stability (164 mAh g –1 at 5 C after 1100 cycles), high capacity retention (104 mAh g –1 ) at an ultrahigh rate (25 C), and large areal capacity (0.74 mAh cm –2 ) under high mass loading (4 mg cm –2 ). The practical prospect is proved by Nb 2 O 5–x /LiNi 0.8 Co 0.1 Mn 0.1 O 2 full cells with high average platform (2.12 V) and high specific capacity (229 mAh g –1 ). Finally, the oxygen-defect modulation strategy on oxide anodes provides an alternative solution to fast-charging and durable LIBs.

25 ENERGY STORAGE↗
DOE OSTI2022

ϵ-VOPO 4 cathode for lithium ion batteries

The epsilon polymorph of vanadyl phosphate, ε-VOPO 4 , made from the solvothermally synthesized H 2 VOPO 4 , is a high density cathode material for lithium-ion batteries optimized to reversibly intercalate two Li-ions to reach the full theoretical capacity at least 50 cycles with a coulombic efficiency of 98%. This material adopts a stable 3D tunnel structure and can extract two Li-ions per vanadium ion, giving a theoretical capacity of 305 mAh/g, with an upper charge/discharge plateau at around 4.0 V, and one lower at around 2.5 V.

25 ENERGY STORAGE↗
DOE OSTI2023

ϵ-VOPO 4 cathode for lithium ion batteries

The epsilon polymorph of vanadyl phosphate, ε-VOPO 4 , made from the solvothermally synthesized H 2 VOPO 4 , is a high density cathode material for lithium-ion batteries optimized to reversibly intercalate two Li-ions to reach the full theoretical capacity at least 50 cycles with a coulombic efficiency of 98%. This material adopts a stable 3D tunnel structure and can extract two Li-ions per vanadium ion, giving a theoretical capacity of 305 mAh/g, with an upper charge/discharge plateau at around 4.0 V, and one lower at around 2.5 V.

25 ENERGY STORAGE↗