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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Hydrous Nickel–Iron Turnbull’s Blue as a High-Rate and Low-Temperature Proton Electrode

Proton batteries are emerging as a promising solution for energy storage; however, their development has been hindered by the lack of suitable cathode materials. Herein, a hydrous Turnbull’s blue analogue (TBA) of Ni[Fe(CN) 6 ] 2/3 ·4H 2 O has been investigated as a viable proton cathode. Particularly, it shows an extremely high rate performance up to 6000 C (390 A g –1 ) at room temperature and delivers good capacity values at a low temperature of -40 °C in an aqueous electrolyte. The excellent rate capability is also amenable to high mass loadings of 10 mg cm –2 . Such fast and low-temperature rate behavior likely stems from the fast proton conduction that is afforded by the Grotthuss mechanism inside the TBA structure. Furthermore, advanced characterization, including in operando synchrotron X-ray diffraction (XRD), and X-ray absorption near-edge structure (XANES) were employed to understand the changes of crystal structures and the oxidation-states of metal elements of the electrodes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Impact of Mg Substitution on the Structure, Stability, and Properties of the Na 2 Fe 2 F 7 Weberite Cathode

Of the few weberite-type Na-ion cathodes explored to date, Na 2 Fe 2 F 7 exhibits the best performance, with capacities up to 184 mAh/g and energy densities up to 550 Wh/kg reported for this material. However, the development of robust structure–property relationships for this material is complicated by its tendency to form as a mixture of metastable polymorphs, and transform to a lower-energy Na y FeF 3 perovskite compound during electrochemical cycling. Our first-principles-guided exploration of Fe-based weberite solid solutions with redox-inactive Mg 2+ and Al 3+ predicts an enhanced thermodynamic stability of Na 2 Mg x Fe 2–x F 7 as the Mg content is increased, and the x = 0.125 composition is selected for further exploration. We demonstrate that the monoclinic polymorph (space group C2/c) of Na 2 Fe 2 F 7 (Mg0) and of a new Mg-substituted weberite composition, Na 2 Mg 0.125 Fe 1.875 F 7 (Mg0.125), can be isolated using an optimized synthesis protocol. The impact of Mg substitution on the stability of the weberite phase during electrochemical cycling, and on the extent and rate of Na (de)intercalation, is examined. Irrespective of the Mg content, we find that the weberite phase is retained when cycling over a narrow voltage window (2.8–4.0 V vs Na/Na+). Over a wider voltage range (1.9–4.0 V), Mg0 shows steady capacity fade due to its transformation to the NayFeF3 perovskite phase, while Mg0.125 displays more reversible cycling and a reduced phase transformation. Yet, Mg incorporation also leads to kinetically limited Na extraction and a reduced overall capacity. These findings highlight the need for the continued compositional optimization of weberite cathodes to improve their structural stability while maximizing their energy density.

25 ENERGY STORAGE↗
DOE OSTI2023

Intercalation-type catalyst for non-aqueous room temperature sodium-sulfur batteries

Abstract Ambient-temperature sodium-sulfur (Na-S) batteries are potential attractive alternatives to lithium-ion batteries owing to their high theoretical specific energy of 1,274 Wh kg −1 based on the mass of Na 2 S and abundant sulfur resources. However, their practical viability is impeded by sodium polysulfide shuttling. Here, we report an intercalation-conversion hybrid positive electrode material by coupling the intercalation-type catalyst, MoTe 2 , with the conversion-type active material, sulfur. In addition, MoTe 2 nanosheets vertically grown on graphene flakes offer abundant active catalytic sites, further boosting the catalytic activity for sulfur redox. When used as a composite positive electrode and assembled in a coin cell with excess Na, a discharge capacity of 1,081 mA h g s −1 based on the mass of S with a capacity fade rate of 0.05% per cycle over 350 cycles at 0.1 C rate in a voltage range of 0.8 to 2.8 V is realized under a high sulfur loading of 3.5 mg cm −2 and a lean electrolyte condition with an electrolyte-to-sulfur ratio of 7 μL mg −1 . A fundamental understanding of the electrocatalysis of MoTe 2 is further revealed by in-situ synchrotron-based operando X-ray diffraction and ex-situ time-of-flight secondary ion mass spectrometry.

25 ENERGY STORAGE↗
DOE OSTI2021

High-performing commercial Fe–N–C cathode electrocatalyst for anion-exchange membrane fuel cells

Here, to reduce the cost of fuel cell stacks and systems, it is important to create commercial catalysts that are free of platinum group metals (PGMs). To do this, such catalysts must have very high activity, but also have the correct microstructure to facilitate the transport of reactants and products. Here, we show a high-performing commercial oxygen reduction catalyst that was specifically developed for operation in alkaline media and is demonstrated in the cathode of operating anion-exchange membrane fuel cells (AEMFCs). With H 2 /O 2 reacting gases, AEMFCs made with Fe–N–C cathodes achieved a peak power density exceeding 2 W cm –2 (>1 W cm –2 with H 2 /air) and operated with very good voltage durability for more than 150 h. These AEMFCs also realized an iR-corrected current density at 0.9 V of 100 mA cm –2 . Finally, in a second configuration, Fe–N–C cathodes paired with low-loading PtRu/C anodes (0.125 mg PtRu per cm 2 , 0.08 mg Pt per cm 2 ) demonstrated a specific power of 10.4 W per mg PGM (16.25 W per mg Pt).

25 ENERGY STORAGE↗
DOE OSTI2025

Operando Neutron Imaging of Lithium Flux and Gradient Cathode Design for Enhanced Kinetics in High‐Loading All‐Solid‐State Li─S Batteries

All-solid-state Li–sulfur batteries (ASSLSBs) are considered promising candidates for next-generation energy storage owing to their inherent safety, high energy density, and abundant sulfur resources. However, slow redox kinetics greatly limit sulfur utilization during solid-solid sulfur reactions, leading to significant challenges to achieve efficient performance in high-mass-loading ASSLSBs. Here, operando neutron image is employed to directly visualize, for the first time, that sluggish Li + transport kinetics and the uneven distribution of Li + during cathodic reactions are critical factors limiting sulfur conversion. To address this issue, gradient cathode architectures comprising three and five layers are designed, in which catholyte concentrations are strategically varied to optimize Li-ion flux and enhance ionic conductivity of the whole composite cathode electrode. Operando neutron imaging distinctly visualizes and confirms that three-layer gradient approach significantly enhances Li-ion mobility, resulting in more uniform redox reactions and greatly improved sulfur utilization compared to traditional non-gradient structures. Consequently, the three-layer gradient cathode achieves superior rate performance and reduced electrode polarization at high sulfur mass loadings of 4.5 and 6.0 mg cm −2 . Furthermore, the applicability and scalability of this design are demonstrated in a five-layer gradient cathode architecture, achieving an impressive discharge specific capacity increase from 656 mAh g −1 (three-layer gradient) to 1232 mAh g −1 at 1/20 C for ultra-high sulfur loading of 7.5 mg cm −2 . In conclusion, this innovative gradient cathode design offers substantial advancements in understanding and overcoming Li-ion transport limitations, paving the way toward practical, high-energy-density ASSLSBs.

25 ENERGY STORAGE↗
DOE OSTI2026

Modulating Li + and Polysulfide Solvation with Low-Density Moderately Solvating Electrolytes for Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries show great promise as the next-generation rechargeable batteries, yet they still suffer from polysulfide shuttling and interphasial instability. Electrolyte, as the medium for ion transport and sulfur conversion, plays a crucial role in overcoming these challenges. Here, we introduce a moderately solvating electrolyte (MSE) based on low-density, low-viscosity, and nonfluorinated ether co-solvents that balances polysulfide suppression, Li metal stabilization, and redox kinetics. Through multiple solvent–solvent and solvent-ion interactions, the optimized MSE weakens Li + -solvent pairing while strengthening cation–anion interactions, thereby lowering the desolvation barrier and promoting the formation of a favorable solid–electrolyte interphase (SEI). Meanwhile, MSE limits the polysulfide dissolution but improves the accessibility of active material through better wettability and tailored solvation environment, leading to an altered sulfur deposition mechanism with β – α conversion. This approach enables a stable cycling of high-mass loading Li–S cells (> 3.5 mg cm -2 ) at both room temperature and 45 °C (where shuttling and side reactions are severer), and demonstrates a pouch cell with lean electrolyte content (4.5 µL mg s -1 ). This work highlights a practical route to develop high-performance electrolyte for Li–S cells and provides mechanistic insights into their operation.

25 ENERGY STORAGE↗
DOE OSTI2021

MPC-based double-layer real-time conditional cSelf-restoration for interconnected microgrids

In this report, we propose a novel model predictive control(MPC)-based real-time conditional self-restoration energy management system (CSR-EMS) for interconnected microgrids (IMGs) integrated with renewable energy sources (RESs) and energy storage systems (ESSs). Superior to the existing IMG self-restoration methods, the “conditionality” of the proposed CSR-EMS can economically realize self-restoration and grid-assisted restoration during energy deficiency or faults, in both islanded and grid-connected modes. Cost minimization is implemented as the objective function to judge in real-time which restoration mode is economically preferred. The proposed CSR-EMS comprises two layers–the lower layer operates locally to eliminate electricity fluctuations created by RESs and ensure economic effectiveness within an MG, whereas the upper layer oversees the real-time operational status of the IMG system and determines power exchange among microgrids (MGs) during abnormalities. In detail, when a microgrid inside the IMG system experiences an energy deficiency, the CSR-EMS, on an MPC basis, intelligently optimizes power production from each dispatchable distributed generator (DG), ESS, power imported from the main grid, and power exchange among the IMGs to maintain the demand–supply balance, while considering system recovery cost, state of charge (SoC) of ESSs and operation modes of the IMGs (i.e., grid-connected or islanded mode). Simulation results and comparisons with existing IMG self-healing EMSs demonstrate the economic efficacy of the proposed CSR-EMS strategy during normal and abnormal operations, which can be used as an energy control framework for modern power systems with multiple interconnected microgrids.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2020

In Silico Discovery of Covalent Organic Frameworks for Carbon Capture

We screen a database of more than 69 000 hypothetical covalent organic frameworks (COFs) for carbon capture using parasitic energy as a metric. To compute CO 2 –framework interactions in molecular simulations, we develop a genetic algorithm to tune the charge equilibration method and derive accurate framework partial charges. Nearly 400 COFs are identified with parasitic energy lower than that of an amine scrubbing process using monoethanolamine; more than 70 are better performers than the best experimental COFs and several perform similarly to Mg-MOF-74. We analyze the effect of pore topology on carbon capture performance to guide the development of improved carbon capture materials.

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

Ionic Dynamics of the Charge Carrier in Layered Solid Materials for Mg Rechargeable Batteries

Multivalent-ion batteries have attracted growing attention due to their high theoretical energy density that potentially outperforms Li-ion batteries. One of the critical challenges of realizing a multivalent-ion battery is the strong polarization that results in the sluggish intercalation of ions in the host lattice, which motivates a fundamental understanding of multivalent-ion dynamics in solid-state materials. In this contribution, we investigate the diffusion mechanisms of divalent ions in a novel Mg anode coating, BiOCl, using first-principles informed learning-on-the-fly molecular dynamics. Based on nanosecond-scale dynamics observations, we gained insights into the concerted diffusion mechanism of Mg cation site-to-site hopping facilitated by synchronous anion rotational motion. Furthermore, we compute the Mg-ion diffusion in additional candidate host structures screened from available layered materials space. Here, the results suggest the co-operative divalent cation-anion motion is likely a common phenomenon in layered oxyhalide structures. Our findings provide a new perspective on how to enhance multivalent-ion diffusion in layered materials.

25 ENERGY STORAGE↗
DOE OSTI2026

Lithium–Sulfur Batteries Enabled by Fluorine-Free Electrolytes with a Compressed Solvation Structure

In this paper, a fluorine-free aromatic cosolvent strategy is presented to regulate electrolyte solvation chemistry in Li-S batteries with sulfurized polyacrylonitrile (SPAN) cathodes. Assisted by the Uni-ELF AI tool and experimental validation, toluene is identified as an optimal weakly solvating cosolvent. Its incorporation compresses the Li⁺ solvation sheath and induces an anion-dominated solvation structure, thereby enhancing interfacial ion transport and sulfur redox kinetics through controlled π-π interactions with polysulfides. Consequently, Li || Li symmetric cells exhibit stable cycling for over 1,000 cycles at a current density of 1 mA cm⁻². Meanwhile, Li-S cells employing high-loading SPAN cathodes retain more than 75% of their initial capacity after 250 cycles at -10 °C. Additionally, a practical pouch cell with high SPAN loading and a low electrolyte-to-SPAN ratio of 3 µL mg⁻¹ delivers an initial capacity of around 600 mAh gSPAN⁻¹, underscoring the potential of fluorine-free electrolytes for practical metal-sulfur batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

Understanding and applying coulombic efficiency in lithium metal batteries

Coulombic Efficiency (CE) has been widely used in battery research as a quantifiable monitor to compare the properties and performances of materials, electrolytes, interfaces and the entire electrochemical cells. While CE with ultra high precision effectively predicts the lifespan and health for lithium ion (Li-ion) batteries, it is not necessarily true in rechargeable lithium (Li) metal batteries. A large variation of CE is often seen even from the same materials and electrolytes in Li metal cells. This work discusses the fundamental definition of CE in different configurations of Li metal-based cells. The similarities and differences of CE in Li-ion and Li metal cells have been clarified and used to understand the relevance/irrelevance between CE and cycling. Long-standing goal of this study is to help rational design of cell testing protocols and elaborate electrochemical results. The insights from this work are broadly applicable in many other rechargeable metal cells e.g., Zn, Mg and Na batteries to accelerate reseach innovation.

Xiao, Jie↗
DOE OSTI2024

Optimizing high energy density sulfur cathodes: A multivariate approach to electrode formulation and processing

Lithium-sulfur (Li-S) batteries involve complex solid-liquid-solid phase transformations during both discharging and charging processes, where cathode materials, formulation, and structure play a crucial role. Here, a design of experiments (DoE) methodology and an empirical model are developed to systematically explore the interactions and trade-offs among cathode factors and process variables, and to obtain generalizable effects estimates for the multivariate system. Compared to the conventional one-factor-at-a-time (OFAT) approach, this work demonstrates advantages in both efficiency and accuracy by allowing the data to guide future research and decisions. Further, an optimized cathode formulation and processing parameters are predicted and validated experimentally, achieving over 1000 mAh g -1 in discharge capacity and improved cycling under practical lean electrolyte (4 µL mg -1 S) and high S-loading cathodes (>4 mg cm -2 ) conditions. The optimized cathode was scaled up and assembled into Li-S pouch cells, achieving 316 Wh kg -1 in cell-level energy, proving that the comprehensive and rigorous framework for optimizing complex systems with DoE leads to improved performance in a practical pouch cell system.

25 ENERGY STORAGE↗
DOE OSTI2023

Morphology Evolution in Self-Healing Liquid-Gallium-Based Mg-Ion Battery Anode

Conventional solid battery anodes suffer from dendrite growth and volume changes, resulting in poor cycling performances. Self-healing electrodes made of liquid metals and alloys can overcome these issues by reversibly undergoing liquid–solid phase transformations during (dis)charging. Just recently, we achieved 1000 cycles in Mg-ion battery anodes using liquid Ga as the active material, which reversibly transformed into solid Mg 2 Ga 5 during (de)magnesiation. However, the fundamental mechanism behind this liquid–solid phase transformation remains unclear. In this follow-up work, cryogenic focused ion beam electron microscopy is used to elucidate the morphology evolution when liquid Ga embedded in a carbon-binder matrix transforms into solid Mg 2 Ga 5 during cycling. We found that liquid Ga gradually diffuses into the surrounding matrix, increasing the contact area between active material and electrolyte, facilitating the charge transfer process. These new insights will help understand the performance of alkali- and alkaline-earth-metal batteries based on liquid anodes.

25 ENERGY STORAGE↗
DOE OSTI2020

Dendrite Growth Morphology Modeling in Liquid and Solid Electrolytes

The main goal of this project is to develop a multi-scale modeling approach that connects micron-scale phase-field models and atomic-scale density functional theory (DFT)-based simulations via parameter- and relationship-passing in order to predict Li-metal dendrite morphology evolution, in both liquid and solid electrolytes. The key hypothesis of the DFT-informed phase-field multiscale modeling approach is that it can capture the electrochemical-mechanical driving forces and incorporate the roles of nano-meter-thin solid electrolyte interphase (SEI) in liquid electrolytes as well as of the microstructures of micro-meter-thick solid electrolytes (SEs) for all-solid-state batteries. In this project, we have formulated and implemented phase-field models to incorporate the electrochemical driving forces in liquid electrolytes and then incorporate mechanical driving forces to simulate dendrite growth in solid electrolytes with resolved microstructures. We have implemented two treatments for the SEI: an explicit model to include the microstructure of the SE or SEI in the phase field model and an implicit model to simulate the impact of nano-meter thick SEI in liquid electrolytes by varying the electrode/electrolyte interfacial properties. The key interfacial properties, including the electronic and ionic transport properties, the charge transfer reaction kinetics, and mechanical properties, were computed by DFT-based calculations. At the DFT-based model, one key advancement is to directly predict the charge transfer reaction kinetics at a complex Li/SEI/electrolyte interface by linking DFT with density functional tight binding (DFTB) calculations. As the main accomplishments, we have demonstrated two successful predictions in both solid electrolyte and liquid electrolyte based on this multiscale approach. The predicted intergranular Li dendrite growth in LLZO revealed the importance of trapped electrons at internal interfaces in the microstructure of LLZO. The predicted electroplating morphology of mossy Li and faceted Mg agreed well with experiments. The insights provided by the multiscale model and the model enabled electrolyte and SEI design will accelerate the development of Li-metal electrode for high energy density batteries, that meet DOE’s target on cell density (>350 Wh/kg) and cost below $100/kWhuse for EV applications.

25 ENERGY STORAGE↗
DOE OSTI2020

Electrochemical generation of hexacyanoferrate and hexacyanoruthanate electroactive films at nickel electrode surfaces: A promising synthetic approach for new electrode materials in metal ion batteries and supercapacitors

Prussian blue analogues (PBAs) have been recently investigated as promising electrode materials for battery and supercapacitor applications. While most explorations have focused on PBA nanoparticles, very little attention has been focused on PBA films deposited on a metallic support. In this work, we have examined electrogenerating hexacyanoferrate (HCF) and hexacyanoruthenate (HCR) films on nickel surfaces via cyclic voltammetry. We found that the total material deposited was influenced by the metal cation present in the electrolyte solution and that, on average, the rate of deposition of the surface adsorbed/immobilized species was dependent on the species in solution. In particular, films electrogenerated in the presence of Na + and K + had the highest deposition rates. The cyclic voltammetric profiles exhibited dramatic differences depending on the cation present in the electrolyte solution. In addition, we found that all films were electrochemically irreversible in the presence of Li + and Mg 2+ containing electrolyte solutions. Further, and as a proof of concept, we modified high surface area nickel electrodes with HCF in sodium-based electrolytes, finding that these electrodes could operate reversibly at equivalent C-rates as high as 1667C.

25 ENERGY STORAGE↗
DOE OSTI2020

Rational Design of a Ni 3 N 0.85 Electrocatalyst to Accelerate Polysulfide Conversion in Lithium–Sulfur Batteries

Slow kinetics of polysulfide conversion reactions lead to severe issues for lithium–sulfur (Li–S) batteries, for example, low rate capability, polysulfide migration, and low Coulombic efficiencies. These challenges hinder the practical applications of Li–S batteries. Here, we proposed a rational strategy of tuning the d-band of catalysts to accelerate the conversion of polysulfides. Nitrogen vacancies were engineered in hexagonal Ni 3 N (space group P 6 3 22) to tune its d-band center, leading to the strong interaction between polysulfides and Ni 3 N. Because of the greater electron population in the lowest occupied molecular orbital of Li 2 S 4 , the terminal S–S bonds were weakened for breaking. Temperature-dependent experiments confirm that Ni 3 N 0.85 demonstrates a much low activation energy, thereby accelerating the conversion of polysulfides. A Li–S cell using Ni 3 N 0.85 can deliver a high initial discharge capacity of 1445.9 mAh g –1 (at 0.02 C) and low decay per cycle (0.039%). The Ni 3 N 0.85 cell can also demonstrate an initial capacity of 1200.4 mAh g –1 for up to 100 cycles at a high loading of 5.2 mg cm –2 . The high efficiency of rationally designed Ni 3 N 0.85 demonstrates the effectiveness of the d-band tuning strategy to develop low-activation-energy catalysts and to promote the atomic understanding of polysulfide conversion in Li–S batteries.

25 ENERGY STORAGE↗