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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Electrolyte Compatible Separator Materials for Sodium-Ion Battery

Sodium-ion batteries (NIBs) have emerged as an alternative electrochemical energy storage to replace lithium-ion batteries (LIBs). Separator is one of the key components that dictates the cell performance of NIB. Significant progress has been made in electrolyte research, however for most cases glass fiber has been used as separator due to its remarkable electrolyte wettability despite its many disadvantages. In this study, we evaluated commercially available porous materials as separator material for NIB. Porous polyvinylidene fluoride (PVDF) membrane stands out as a universal separator which exhibits high compatibility with a wide range of electrolytes and electrodes and demonstrates high electrochemical stability evaluated in hard carbon/Na half cells and NaNi 1/3 Fe 1/3 Mn 1/3 O 2 (NFM111)/hard carbon full cells. This research highlights the PVDF membrane as a viable separator for advancing NIB research, enabling the development of new electrolyte materials without the separator constraints of wetting limitations or excessive electrolyte consumption.

Wostoupal, Owen S. [Argonne National Laboratory (A↗
DOE OSTI2023

Enhanced Optical Contrast and Switching in Near‐Infrared Electrochromic Devices by Optimizing Conjugated Polymer Oligo(Ethylene Glycol) Sidechain Content and Gel Electrolyte Composition

Abstract A detailed investigation addressing the effects of functionalizing conjugated polymers with oligo(ethylene glycol) (EG n ) sidechains on the performance and polymer‐electrolyte compatibility of electrochromic devices (ECDs) is reported. The electrochemistry for a series of donor‐acceptor copolymers having near‐infrared (NIR)‐optical absorption, where the donor fragment is 3,4‐ethylenedioxythiophene (EDOT) or an EG n functionalized bithiophene (g2T) and the acceptor fragment is diketopyrrolopyrrole (DPP) functionalized with branched alkyl or EG n sidechains, is extensively probed. ECDs are next fabricated and it is found that EG n sidechain incorporation must be finely balanced to promote polymer‐electrolyte compatibility and provide efficient ion exchange. Proper electrolyte‐cation pairing and polymer structural tuning affords a 2x increase in optical contrast (from 12% to 24%) and >60x reduction in switching time (from 20 to 0.3 s). Atomic force microscopy (AFM)/grazing incidence wide‐angle X‐ray scattering (GIWAXS) characterization of the polymer film morphology/microstructure reveals that an over‐abundance of EG n sidechains generates large polymer crystallites, which can suppress ion exchange. Lastly, time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) indicates sidechain/electrolyte identity does not influence the electrolyte penetration depth into the films, and EG n sidechain inclusion increases electrolyte cation uptake. The material structural design insight and guidelines regarding the polymer‐electrolyte ion insertion/expulsion dynamics reported here should be of significant utility for developing next‐generation mixed ionic‐electronic conducting materials.

Chemistry↗
DOE OSTI2020

Improving Lithium Metal Composite Anodes with Seeding and Pillaring Effects of Silicon Nanoparticles

Metallic lithium (Li) anodes are crucial for the development of high specific energy batteries yet plagued by their poor cycling efficiency. Electrode architecture engineering is vital for maintaining a stable anode volume and suppress Li corrosion during cycling. In this paper, a reduced graphene oxide “host” framework for Li metal anodes is further optimized by embedding silicon (Si) nanoparticles between the graphene layers. They serve as Li nucleation seeds to promote Li deposition within the framework even without pre-stored Li. Meanwhile, the LixSi alloy particles serve as supporting “pillars” between the graphene layers, enabling a minimized thickness shrinkage after full stripping of metallic Li. Combined with a Li compatible electrolyte, 99.4% Coulombic efficiency over ~600 cycles is achieved, and stable cycling of a Li||NMC532 full cell for ~380 cycles with negligible capacity decay is realized.

Wang, Hansen↗
DOE OSTI2021

Systematic Evaluation of Carbon Hosts for High-Energy Rechargeable Lithium-Metal Batteries

Rechargeable lithium batteries (RLBs) have attracted wide attention for achieving high energy and low cost, but the poor stability of the Li anode has remained as a large challenge. In the last several years, great efforts have been made to develop carbon anode structures for RLB applications. A wide range of carbon structures as well as many chemical modification strategies have been investigated to improve the Coulombic efficiency and extend the cycle life of the anodes or the cells. However, currently there is no clear conclusion on key factors that determine the performance of such the types of carbon structures due to the wide range of experimental conditions used in such studies. In this study, we systematically evaluated and compared the electrochemical properties of representative carbon anode materials as well as chemically functionalized carbon materials in different electrolytes. We have found that chemical functionalization, metallic loading, and the types of micro or nano-structures all have an effect on Li deposition/stripping process, but by far the most critical factor is the nature of the electrolytes. All carbon materials produced poor Coulombic efficiency and cycle life in conventional carbonate or ether-based electrolytes. However, when a Li metal compatible is used, the average Coulombic efficiency of Li metal deposition on all carbon structures is increased to 99% or higher. This study provides critical lessons on the directions for carbon anodes for RLBs. Based on these findings, we constructed Li metal coin cells using prelithiated hard carbon, LiNi0.6Mn0.2Co0.2O2 (NMC622) cathode, and compatible electrolyte and tested the cells under conditions of lean electrolyte, lean Li metal and high cathode loading required for more than 300 Wh kg-1 specific energy. More than 200 stable cycles were demonstrated with over 80% capacity retention. Furthermore, the existing challenges and potential approaches have been discussed to further extend the cyclability of lithium-metal batteries under practical conditions.

Liu, Yao↗
DOE OSTI2024

Condensation-based redox flow battery rebalancing

In a redox flow battery (RFB), the base solvent of the electrolytes tends to migrate across the barrier layer from one electrode toward the other. This can result in a volume and concentration imbalance between the electrolytes that is detrimental to battery efficiency and capacity. Compatible electrolytes can be mixed to rebalance the system, but for incompatible electrolytes mixing is not a viable option. To this end, the RFB herein includes a separator that recovers base solvent from the vapor phase of one of the electrolytes and returns the recovered base solvent to the other electrolyte to thereby reverse the imbalance.

Saraidaridis, James D.↗
DOE OSTI2022

A Carboranyl Electrolyte Enabling Highly Reversible Sodium Metal Anodes via a “Fluorine‐Free” SEI

Abstract Realization of practical sodium metal batteries (SMBs) is hindered due to lack of compatible electrolyte components, dendrite propagation, and poor understanding of anodic interphasial chemistries. Chemically robust liquid electrolytes that facilitate both favorable sodium metal deposition and a stable solid‐electrolyte interphase (SEI) are ideal to enable sodium metal and anode‐free cells. Herein we present advanced characterization of a novel fluorine‐free electrolyte utilizing the [HCB 11 H 11 ] 1− anion. Symmetrical Na cells operated with this electrolyte exhibit a remarkably low overpotential of 0.032 V at a current density of 2.0 mA cm −2 and a high coulombic efficiency of 99.5 % in half‐cell configurations. Surface characterization of electrodes post‐operation reveals the absence of dendritic sodium nucleation and a surprisingly stable fluorine‐free SEI. Furthermore, weak ion‐pairing is identified as key towards the successful development of fluorine‐free sodium electrolytes.

Tomich, Anton W.↗
DOE OSTI2022

A Carboranyl Electrolyte Enabling Highly Reversible Sodium Metal Anodes via a “Fluorine-Free” SEI

Realization of practical sodium metal batteries (SMBs) is hindered due to lack of compatible electrolyte components, dendrite propagation, and poor understanding of anodic interphasial chemistries. Chemically robust liquid electrolytes that facilitate both favorable sodium metal deposition and a stable solid-electrolyte interphase (SEI) are ideal to enable sodium metal and anode-free cells. Herein we present advanced characterization of a novel fluorine-free electrolyte utilizing the [HCB 11 H 11 ] 1- anion. Symmetrical Na cells operated with this electrolyte exhibit a remarkably low overpotential of 0.032 V at a current density of 2.0 mA cm -2 and a high coulombic efficiency of 99.5 % in half-cell configurations. Additionally, surface characterization of electrodes post-operation reveals the absence of dendritic sodium nucleation and a surprisingly stable fluorine-free SEI. Furthermore, weak ion-pairing is identified as key towards the successful development of fluorine-free sodium electrolytes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Balancing Interfacial Reactions to Achieve Long Cycle Life in High Energy Lithium Metal Batteries

Rechargeable lithium (Li) metal batteries have attracted wide attentions as the next generation energy storage technologies. However, simultaneously achieving high cell-level energy density and long cycle life in realistic batteries is still a great challenge. Here we investigate the cell degradation mechanisms of Li||LiNi0.6Mn0.2Co0.2O2 pouch cells using different, but representative cell configurations to understand the fundamental linkage among Li thickness, electrolyte depletion and the structure evolution of solid electrolyte interphase (SEI) layers. Different cell failure modes were discovered when tuning the anode to cathode capacity (N/P) ratio in compatible electrolyte. With a thick-Li anode (N/P ratio = 2.5), initial stable cycling is obtained because of the abundant Li supply from the anode together with an artificially inflated high Coulombic Efficiency, followed by a premature sudden cell death appears due to the enrichment of “ineffective SEI” which does not participate in the electrochemical reactions but keep increasing cell impedance. The anode-free cell (N/P 0:1) displays a steady capacity decay because cathode Li loss dominates from the beginning to the end of cell cycle life. An optimized thin-Li (N/P 1:1) well balances the Li consumption rate with the impedance buildup by minimizing the growth of ineffective SEI layer, thus decelerates cell polarization increasing and extends cycling. Contrary to conventional wisdoms, long cycle life is observed by using ultra thin-Li (20 µm) in balanced cells. A prototype 350 Wh kg-1 pouch cell (2.0 Ah) achieves over 600 long stable cycles with 76% capacity retention without sudden cell death.

Niu, Chaojiang↗
DOE OSTI2022

Closo ‐Borate Gel Polymer Electrolyte with Remarkable Electrochemical Stability and a Wide Operating Temperature Window

Abstract A major challenge in the pursuit of higher‐energy‐density lithium batteries for carbon‐neutral‐mobility is electrolyte compatibility with a lithium metal electrode. This study demonstrates the robust and stable nature of a closo ‐borate based gel polymer electrolyte (GPE), which enables outstanding electrochemical stability and capacity retention upon extensive cycling. The GPE developed herein has an ionic conductivity of 7.3 × 10 −4 S cm −2 at room temperature and stability over a wide temperature range from −35 to 80 °C with a high lithium transference number ( = 0.51). Multinuclear nuclear magnetic resonance and Fourier transform infrared are used to understand the solvation environment and interaction between the GPE components. Density functional theory calculations are leveraged to gain additional insight into the coordination environment and support spectroscopic interpretations. The GPE is also established to be a suitable electrolyte for extended cycling with four different active electrode materials when paired with a lithium metal electrode. The GPE can also be incorporated into a flexible battery that is capable of being cut and still functional. The incorporation of a closo ‐borate into a gel polymer matrix represents a new direction for enhancing the electrochemical and physical properties of this class of materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Critical Insights into Solvent Choice for High-Voltage Organosulfur Electrolytes

Organosulfur electrolytes are promising candidates for enabling high-voltage cathodes due to their superior oxidative stability compared to conventional carbonate-based systems. However, their viscous nature and inability to passivate the anode necessitate the use of passivating agents and diluents to achieve meaningful charge/discharge rates. In this study, we investigate the use of cyclic fluorinated carbonates (CFCs) to form passivating interphases on electrode surfaces, aiming to optimize electrolyte performance in high-voltage systems. Electrolyte formulations containing 1.2 M LiPF 6 in a CFC:sulfone:1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether (TTE) mixture (2/5/3 V/V/V) were assessed in full-cell configurations with a LiNi 0.8 Mn 0.1 Co 0.1 O 2 (FCG-NMC) cathode and a 4.5 V upper cutoff potential. The results reveal that 3-3-3-trifluoropropylene carbonate (TFPC) combined with ethyl methyl sulfone (EMS) optimizes electrolyte performance, resulting in lower resistance buildup and reduced capacity loss compared to commercial electrolytes. We also explore the failure mechanisms of several carbonate/sulfone mixtures and identify key considerations for electrolyte compatibility in high-voltage systems. TFPC enhances cycling stability and lowers overall cell resistance, while fluoroethylene carbonate (FEC) formulations, despite higher ionic conductivity, fail to form adequate passivation layers, leading to rapid capacity loss. Additionally, EMS provides superior physical properties that avoid common failure modes seen with other sulfone solvents like methyl isopropyl sulfone and tetramethylene sulfone. Furthermore, this study underscores the importance of carefully selecting passivating carbonates and sulfone solvents to improve electrolyte performance and expand the viability of high-voltage electrolyte systems.

LiNi0.8Mn0.1Co0.1O2 cathode↗
DOE OSTI2025

In Situ Synthesis of Phosphate-Based CelloMOF as a Promising Separator for Li–Ion Batteries

Nowadays, battery separators play a critical role in determining the sustainability, electrochemical efficiency, and safety of lithium-ion batteries (LIBs). In this contribution, we developed fire-resistant composite membranes called CelloMOF by in situ grafting of metal-organic framework, ZIF-67, onto phosphorylated cellulose nanofibers (P-CNFs) followed by a vacuum filtration process akin to papermaking. The hybrid ZIF-67@P-CNF membrane exhibits superior properties than a polyolefin-based commercial separator (CS) in terms of enhanced thermal and dimensional stability, flame-retardant properties, better surface wettability, and improved electrolyte uptake. Thermal dimensional stability tests revealed that the ZIF-67@P-CNF separator maintained its structure even at 200 °C, whereas CS suffered severe shrinkage, potentially leading to internal short circuits. Combustion tests showed a peak heat release rate (PHRR) of 34.5 W/g and a total heat release (THR) of 1.61 kJ/g for ZIF-67@P-CNF, significantly lower than the PHRR (1111.82 W/g) and THR (40.89 kJ/g) of CS. The composite separator also demonstrated significantly improved wettability, with a contact angle of 32 ± 1.04°, compared to 92 ± 1.07° for CS, highlighting its hydrophilic nature. Electrochemical evaluations in LiFePO 4 /Li half-cells indicated a higher discharge capacity of 149 mA h g -1 at 0.2 C and superior capacity retention of 86% after 50 cycles, outperforming CS (145 mA h g -1 and 84%, respectively). In conclusion, these results underscore the potential of the ZIF-67@P-CNF membrane to advance safe, high-performance LIBs by addressing critical challenges in thermal stability, flame retardancy, and electrolyte compatibility.

ZIF-67↗
DOE OSTI2025

Locally Confined Polysulfide-Reactive Electrolytes for Shuttle-Free Sodium–Sulfur Batteries

Sodium-sulfur batteries promise high-energy-density and sustainable electrochemical energy storage but suffer from uncontrolled polysulfides dissolution and high sodium reactivity. These challenges fundamentally originate from poor electrolyte-electrode compatibility. Current electrolyte research inadequately addresses the trade-off between minimal polysulfides solvation and stabilizing sodium interfaces. Here, we present a locally-confined polysulfide-reactive electrolyte strategy that mediates the polysulfide dissolution dynamics and sodium stability by leveraging an electrophilic solvating species with a localized high-concentration electrolyte. This design enables shuttle-free cell operation by synergistically restricting the global solvating power of the electrolyte through intermolecular interactions and locally scavenging sparingly dissolved polysulfides via electrolyte electrophilicity. The precisely confined surface reaction facilitates a protective cathode-electrolyte interface, realizing a quasi-solid-state sulfur conversion in our liquid ether-based electrolyte, which crucially avoids crossover-induced catastrophic sodium-metal degradation. The proposed electrolyte demonstrates long-term cycling of high-mass-loading sulfur cathodes (> 3 mg S cm −2 with commercial carbon host and 70 wt% sulfur content), which afford 710 mA h g −1 over 400 cycles in coin cells and steady pouch cell operation over 180 cycles. Furthermore, this work establishes a scalable electrolyte design protocol that regulates the reaction chemistry of highly reactive electrodes, offering a pathway toward sustainable renewable energy storage.

25 ENERGY STORAGE↗
DOE OSTI2025

CO2 upgrading into bioproducts using a two-step abiotic–biotic system

The valorization of CO2 to chemicals beyond C1-2 products is receiving significant interest; however, the direct electrosynthesis of Cn molecules (n > 4) remains a challenge. Here, we present a two-step abiotic-biotic system for upgrading CO2 into the biopolymer, poly(3-hydroxybutyrate). In the electrolysis system, CO2 is converted into C2 oxygenates using a Cu-Ag tandem electrocatalyst. The electrolysis process generates a liquid stream containing ~ 200 mM acetate in a bio-compatible electrolyte. This electrosynthesized acetate is then fed to a bioreactor, where the substrate is upgraded by Cupriavidus necator to biopolymer with a maximum rate of 32 ± 3.5 mg L-1 h-1. We further demonstrate the purification of the resulting biopolymer into a powder. The high productivity of the abiotic-biotic system demonstrates its feasibility for sustainable chemical manufacturing.

CO2 upgrading↗
DOE OSTI2023

Multielectrode electrochemical cell for in situ structural characterization of amorphous thin-film catalysts using high-energy X-ray scattering

A multielectrode-based electrochemical cell allows the structural characterization of an amorphous thin-film water oxidation catalyst under various electrochemical potentials using high-energy X-ray scattering and atomic pair distribution function (PDF) techniques. A multielectrode with five electrodes provides a sufficiently low background signal to enable high-energy X-ray scattering (HEXS) measurements and amplifies the extremely low HEXS signals from samples for high-resolution PDF analysis of in situ data from thin-film catalysts. Glassy carbon (GC) creates a relatively low intensity HEXS pattern and is used as a working electrode. Instead of a three-dimensional (3D) porous electrode architecture, the flat geometry of the electrode enables various deposition techniques to be used for the preparation of a highly conductive metal oxide layer. PDF analysis demonstrates high spatial resolution for a 230 nm thick amorphous iridium oxide film deposited on two roughened 60 µm thick GC electrodes. The PDF analysis resolves the domain size and distinguishes changes in fine structure which are directly correlated with the structure and function of the catalysts. In conclusion, the results bring the opportunity to analyze the structure of nanometre-scale amorphous thin-film catalysts in an electrolyte-compatible and compact 3D-printed electrochemical cell in a three-electrode configuration.

36 MATERIALS SCIENCE↗
DOE OSTI2021

NREL's HydroGEN Photoreactor Platform Design and Characterization

This technical report details the design, fabrication, and construction of a flow-through photoreactor developed at The National Renewable Energy Laboratory (NREL). The photoreactor is designed to facilitate indoor or outdoor testing on photoelectrochemical or integrated solar water splitting devices. The photoreactor design described here is based on a previous demonstration. The photoreactor version described herein contains several advanced design features that include: 1) Chassis-chuck two-part design, 2) Separable counter electrode compartments (here, the counter electrodes are anodes), 3) Reduced electrode separation to reduce electrolyte resistance, 4) Improved flow pattern for bubble removal, 5) Mounting for spectroradiometer receptor, 6) Fresnel lens and collimating tube attachments. The photoreactor presented here was designed primarily to accommodate photocathode materials in an illuminated compartment and a dark anode as the oxygen evolution catalyst. The build materials were thus chosen to for acid electrolyte compatibility. Other embodiments could accommodate a photoanode with dark hydrogen evolution catalyst and other build materials for alkaline compatibility.

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

Critical role of acceptor dopants in designing highly stable and compatible proton-conducting electrolytes for reversible solid oxide cells

Proton-conducting electrolytes are receiving increasing attention due to their high ionic conductivity at intermediate temperatures, enabling the operation of solid oxide cells with high energy efficiency at low cost. However, the effect of B-site dopants on the properties of doped barium hafnate-cerate electrolyte materials, especially in single cells under operating conditions, has not been systematically studied. Here we report our findings in the development of a series of proton-conducting electrolytes with a general formula of BaHf 0.1 Ce 0.7 R 0.2 O 3–δ (BHCR172, R = Yb, Er, Y, Gd, Sm). Here, the results reveal that electrical conductivity, ionic transference number, chemical stability against steam and CO 2 , and compatibility with NiO during sintering are all closely correlated with the dopant size. In particular, the reaction with NiO is found to strongly affect the properties of the electrolytes and hence cell performance. Among all tested compositions, BaHf 0.1 Ce 0.7 Yb 0.2 O 3–δ (BHCYb172) shows excellent chemical stability and minimal reactivity towards NiO, as predicted from density functional theory (DFT)-based calculations and confirmed by experimental results. In addition, proton-conducting reversible solid oxide cells (P-ReSOCs) based on the optimized electrolyte composition, BHCYb172, demonstrate exceptional performance and stability, achieving a remarkable peak power density of 1.74 W cm –2 (O 2 as the oxidant) at 600 °C in the fuel cell mode and a high current density of 2.0 A cm –2 at 1.3 V and 600 °C in the steam electrolysis mode while maintaining excellent durability for over 1000 h.

25 ENERGY STORAGE↗
DOE OSTI2022

The Role of Electrolyte Composition in Enabling Li Metal‐Iron Fluoride Full‐Cell Batteries

Abstract FeF 3 conversion cathodes, paired with Li metal, are promising for use in next‐generation secondary batteries and offer a remarkable theoretical energy density of 1947 Wh kg −1 compared to 690 Wh kg −1 for LiNi 0.5 Mn 1.5 O 4 ; however, many successful studies on FeF 3 cathodes are performed in cells with a large (>90‐fold) excess of Li that disguises the effects of tested variables on the anode and decreases the practical energy density of the battery. Herein, it is demonstrated that for full‐cell compatibility, the electrolyte must produce both a protective solid‐electrolyte interphase and cathode‐electrolyte interphase and that an electrolyte composed of 1:1.3:3 (m/m) LiFSI, 1,2‐dimethoxyethane, and 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether fulfills both these requirements. This work demonstrates the importance of verifying electrode level solutions on the full‐cell level when developing new battery chemistries and represents the first full cell demonstration of a Li/FeF 3 cell, with both limited Li and high capacity FeF 3 utilization.

25 ENERGY STORAGE↗