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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

A low-cost, fluorine-free electrolyte for improved sodium batteries

Sodium batteries are an attractive alternative to lithium-ion technologies due to sodium’s lower cost and natural abundance—over 1,000 times greater than lithium, comprising approximately 2.4% of the Earth’s crust. However, most current electrolytes rely on fluorine-containing components, which raise economic and environmental concerns. This study explores fluorine-free, borate-based electrolytes that offer improved cycling stability and significant cost and sustainability benefits. We demonstrate stable sodium metal stripping and plating on aluminum foil, enabling anode-free cell configurations with over 50% capacity retention after 700 cycles. Spectroscopic and electrochemical analyses reveal the effects of solvents and salt composition on solvation, ionic conductivity, and oxidative stability. In full-cell configurations, the fluorine-free electrolyte maintains more than 98% capacity retention after 400 cycles. Furthermore, these findings represent a critical step toward the development of cost-effective, environmentally friendly, and high-performance sodium battery systems suitable for future electrification.

anode-free sodium batteries↗
DOE OSTI2026

Tuning Solid Electrolyte Interphase Formation before Plating Onset in Anode-Free Sodium Batteries

Sodium (Na) batteries are of growing interest due to the higher earth abundance of sodium than lithium, as well as their promising theoretical energy density when metallic Na anodes are used. However, Na plating and stripping are heavily influenced by the physicochemical properties of the solid electrolyte interphase (SEI), which is directly influenced by the solvent and salt used for the electrolyte. While most studies focus on the SEI that forms on the surface of Na metal after plating, we expand this analysis by identifying a nanoscale “pre-plating” SEI that forms on the current collector (CC) prior to the onset of Na plating. Here, we systematically investigate an array of Na salt and glyme solvents in the electrolyte and determine the associated impacts on pre-plating SEI formation on aluminum CCs. By combining analytical electrochemistry approaches with a multimodal suite of spectroscopy techniques (X-ray, infrared, and Raman), supported by density functional theory calculations, we reveal a direct correlation between the Na + coordination environment and pre-plating SEI composition. We find that longer-chain glymes produce larger proportions of organic alkoxide products in the interphase, consistent with increased Na + −glyme interactions, while the fraction of salt-derived inorganic products (e.g., NaF) correlates with Na + −anion coordination. These insights highlight the critical influence of electrolyte composition particularly solvent identity and Na + coordination on the initial SEI formation in anode-free Na batteries.

anode-free batteries↗
DOE OSTI2024

A New Class of Oxyhalide Solid Electrolytes NaNbCl 6‐2x O x for Solid‐state Sodium Batteries

Abstract Sodium‐based batteries are gaining momentum due to the abundance and lower cost of sodium compared to lithium. Solid‐state sodium batteries can also provide further safety advantages. However, sodium‐based solid‐state electrolytes (SSEs) that meet all the rigorous requirements, such as high ionic conductivity, oxidative stability with the cathode, and ease of processability, are lacking. We present here a new class of sodium‐based oxyhalide electrolytes NaNbCl 6‐2x O x with a facile mechanochemical synthesis. The oxyhalide NaNbCl 4 O exhibits close to two orders of magnitude higher ambient‐temperature sodium‐ion conductivity (1.03×10 −4 S cm −1 ) compared to the halide counterpart NaNbCl 6 (3×10 −6 S cm −1 ). Structural motifs unique to the oxygen content in NaNbCl 6‐2x O x are identified with 23 Na and 93 Nb magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and x‐ray diffraction (XRD). Solid‐state sodium batteries assembled with NaNbCl 4 O electrolyte and the cobalt‐ and nickel‐free layered Na 0.70 Fe 0.3 Mn 0.65 Al 0.05 O 2 cathode exhibit a maximum discharge capacity of 155 mAh g −1 with good cycle life at ambient temperature.

Kmiec, Steven↗
DOE OSTI2024

A New Class of Oxyhalide Solid Electrolytes NaNbCl 6‐2x O x for Solid‐state Sodium Batteries

Abstract Sodium‐based batteries are gaining momentum due to the abundance and lower cost of sodium compared to lithium. Solid‐state sodium batteries can also provide further safety advantages. However, sodium‐based solid‐state electrolytes (SSEs) that meet all the rigorous requirements, such as high ionic conductivity, oxidative stability with the cathode, and ease of processability, are lacking. We present here a new class of sodium‐based oxyhalide electrolytes NaNbCl 6‐2x O x with a facile mechanochemical synthesis. The oxyhalide NaNbCl 4 O exhibits close to two orders of magnitude higher ambient‐temperature sodium‐ion conductivity (1.03×10 −4 S cm −1 ) compared to the halide counterpart NaNbCl 6 (3×10 −6 S cm −1 ). Structural motifs unique to the oxygen content in NaNbCl 6‐2x O x are identified with 23 Na and 93 Nb magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and x‐ray diffraction (XRD). Solid‐state sodium batteries assembled with NaNbCl 4 O electrolyte and the cobalt‐ and nickel‐free layered Na 0.70 Fe 0.3 Mn 0.65 Al 0.05 O 2 cathode exhibit a maximum discharge capacity of 155 mAh g −1 with good cycle life at ambient temperature.

Kmiec, Steven↗
DOE OSTI2025

Fast oxygen redox enabled by flexible Al–O bonds in P2-type layered oxides for sodium batteries

Sodium-ion batteries (SIBs) exhibit significant potential for large-scale energy storage systems due to the abundance and low cost of sodium resources. Triggering lattice oxygen redox (LOR) in P2-type transition metal oxides is considered a promising approach to enhance energy density in SIB cathodes, providing high operating potential and substantial capacity. However, irreversible phase transitions associated with LOR, particularly from prisms (P-type stacking) to octahedrons (O-type stacking), lead to severe structural distortions and sluggish Na + diffusion kinetics. In this work, an Al-substitution strategy is proposed to suppress the formation of O-type stacking and instead promote the formation of a beneficial Z phase. Furthermore, the flexible Al-O bonds accommodate asymmetric variations in their occupied states during the sodiation process, mitigating local structural distortions through Al-O bond contraction. Stabilization of the local structure ensures the maintenance of a robust Na + diffusion pathway. As a result, the Al-substituted cathode achieves a low Na + diffusion barrier of 0.47 eV and delivers a capacity of 86 mAh/g even at a high current density of 1 A/g within 1.5–4.5 V, maintaining 62.5% capacity retention over 100 cycles.

36 MATERIALS SCIENCE↗
DOE OSTI2026

A high power, low temperature molten sodium battery

Low temperature molten sodium batteries promise low-cost, grid-scale energy storage using earth-abundant materials. To be economically viable, they must demonstrate high current (power) at relevant discharge times. Here a low temperature (135 °C) molten sodium battery with a NaI–AlCl 3 molten salt catholyte and NaSICON separator is explored, minimizing cell ohmic resistances and avoiding precipitation reactions in the molten salt catholyte. Operating currents were increased by as much as 100× compared to the energy-dense baseline design (197 Wh kg −1 and 248 mAh cm −2 ). Cells were cycled 100 times at 50 mA cm −2 (150 mW cm −2 ), averaging 99.8% coulombic efficiency and 79.7% energy efficiency for 30% of the theoretical capacity. Charging currents up to 250 mA cm −2 (1070 mW cm −2 ) are demonstrated for 10% of the theoretical capacity. Toward extending the accessible capacity in these high current systems, the volume ratio of catholyte molten salt to a graphite felt current collector was varied, altering (1) the local current density in the graphite felt and (2) the discharge time at a fixed current density. Optimizing the catholyte : felt ratio dramatically increased capacity utilization to 60% (102 mAh cm −2 ) at 50 mA cm −2 (150 mW cm −2 ) charge and 10 mA cm −2 discharge. This catholyte : felt ratio of 1.4 significantly decreased the cell impedance, minimizing electrode blocking effects seen previously in NaI–AlCl 3 catholytes. Together, these high areal loadings and impressive power outputs demonstrate how low temperature molten sodium batteries can compete with commercialized sodium systems operating at more than twice the temperature.

NaSICON↗
DOE OSTI2025

A Reductively Stable Electrolyte Realizes Deep Cycling Behavior in Anode‐free Sodium Batteries

For anode‐free sodium batteries to achieve practical consideration, highly reversible chemistries require exceptional ≥99.95% coulombic efficiencies that maintain over prolonged cycling periods. To do so, consumption of this severely limited sodium inventory must be restricted while metal nucleation processes that comprise the in situ formed metal anode are improved. Herein, we describe a fluorine‐free carborane electrolyte that satisfies these criteria by emphasizing reductive stability and weakly coordinating anion behavior as design principles. We find this approach promotes the development of a thin, robust SEI chemistry rich in both organic speciation and boron. The electrolyte described herein exhibits ideal metal nucleation behavior on one‐micron thin carbonaceous current collector surfaces and achieves a metal deposition/stripping efficiency near parity for 400 cycles. This novel anode chemistry is introduced to anode‐free full cell configurations where 87% of the initial discharge capacity is retained after 1000 cycles at 2.0 C. In conclusion, post‐test characterization of deep‐cycled anode‐free cells reveals suppressed capacity fade in these systems is attributed to the chemical stability of the carborane anion.

anode-free↗
DOE OSTI2021

Materials to improve the performance of lithium and sodium batteries

A lithium or sodium battery includes a cathode containing manganese; an anode containing an active anode material; a separator; an electrolyte; and a transition metal ion sequestration agent; wherein the transition metal ion sequestration agent contains a micron or nano-sized inorganic compound and the transition metal ion sequestration agent is located on and/or within the separator; on and/or within the anode; in the electrolyte; or any combination thereof.

Vissers, Daniel R.↗
DOE OSTI2026

Unveiling the High‐Voltage Reactivity and Gas Evolution With Aluminum‐Based Chloride and Oxychloride Catholytes in Solid‐State Sodium Batteries

All-solid-state sodium batteries (ASSBs) employing halide solid electrolytes (SEs) offer a cost-effective and energy-dense alternative to conventional liquid electrolyte systems. However, their high voltage (>4 V vs. Na/Na + ) performance remains limited by interfacial instability between the cathode active material (CAM) and the SE. We present here the electrochemical and interfacial behaviors of crystalline NaAlCl 4 and amorphous sodium–aluminum–oxychloride (NACO) SEs when combined with NaNi 0.5 Mn 0.5 O 2 cathode. While oxygen incorporation in NACO enhances ionic conductivity by nearly three orders of magnitude relative to NaAlCl 4 , it does not improve high-voltage cycling stability. Cells employing NACO exhibit accelerated capacity fade, increased cell impedance growth, and intrinsic oxygen evolution above 4.5 V vs. Na 3 Sn, as revealed by operando electrochemical mass spectrometry. In contrast, the NaAlCl 4 -based cells show no detectable gas release, underscoring their superior high-voltage stability and safety. Time-of-flight secondary-ion mass spectrometry confirms the formation of Al─O and Ni/Mn─Cl species, respectively, in the SE and CAM, indicating redox-driven anion exchange that contributes to kinetic hindrance of high-voltage phase transitions. The findings establish that while oxygen incorporation enhances ionic transport, it can compromise interfacial stability, suggesting pure chloride SEs may offer a more robust and intrinsically safer pathway for developing high-energy ASSBs.

25 ENERGY STORAGE↗
DOE OSTI2024

Low temperature sodium battery comprising an electrochemically active molten inorganic catholyte

A high-performance electrochemically active sodium molten salt catholyte enables a dramatic reduction in molten sodium battery operating temperature from near 300° C. to less than 120° C. As an example, stable electrochemical cycling was demonstrated in a high voltage (3.65 V) sodium battery comprising a sodium iodide-gallium chloride (NaI—GaCl 3 ) molten salt catholyte for over 8 months at 110° C. The combination of high voltage, stable cycling behavior, and practical current densities supported by a molten catholyte enables a new generation of transformative high performance, low temperature molten sodium batteries.

Spoerke, Erik D.↗
DOE OSTI2022

Task-Specific Phosphonium Iongels by Fast UV-Photopolymerization for Solid-State Sodium Metal Batteries

Sodium metal batteries are an emerging technology that shows promise in terms of materials availability with respect to lithium batteries. Solid electrolytes are needed to tackle the safety issues related to sodium metal. In this work, a simple method to prepare a mechanically robust and efficient soft solid electrolyte for sodium batteries is demonstrated. A task-specific iongel electrolyte was prepared by combining in a simple process the excellent performance of sodium metal electrodes of an ionic liquid electrolyte and the mechanical properties of polymers. The iongel was synthesized by fast (<1 min) UV photopolymerization of poly(ethylene glycol) diacrylate (PEGDA) in the presence of a saturated 42%mol solution of sodium bis(fluorosulfonyl)imide (NaFSI) in trimethyl iso-butyl phosphonium bis(fluorosulfonyl)imide (P111i4FSI). The resulting soft solid electrolytes showed high ionic conductivity at room temperature (≥10 -3 S cm -1 ) and tunable storage modulus (10 4 –10 7 Pa). Iongel with the best ionic conductivity and good mechanical properties (Iongel10) showed excellent battery performance: Na/iongel/NaFePO 4 full cells delivered a high specific capacity of 140 mAh g -1 at 0.1 C and 120 mAh g -1 at 1 C with good capacity retention after 30 cycles.

25 ENERGY STORAGE↗
DOE OSTI2022

An electrochemically stable homogeneous glassy electrolyte formed at room temperature for all-solid-state sodium batteries

All-solid-state sodium batteries (ASSSBs) are promising candidates for grid-scale energy storage. However, there are no commercialized ASSSBs yet, in part due to the lack of a low-cost, simple-to-fabricate solid electrolyte (SE) with electrochemical stability towards Na metal. In this work, we report a family of oxysulfide glass SEs (Na 3 PS 4-x O x , where 0 < x ≤ 60) that not only exhibit the highest critical current density among all Na-ion conducting sulfide-based SEs, but also enable high-performance ambient-temperature sodium-sulfur batteries. By forming bridging oxygen units, the Na 3 PS 4-x Ox SEs undergo pressure-induced sintering at room temperature, resulting in a fully homogeneous glass structure with robust mechanical properties. Furthermore, the self-passivating solid electrolyte interphase at the Na|SE interface is critical for interface stabilization and reversible Na plating and stripping. The new structural and compositional design strategies presented here provide a new paradigm in the development of safe, low-cost, energy-dense, and long-lifetime ASSSBs.

25 ENERGY STORAGE↗
DOE OSTI2024

Research Progress and Perspectives on Pre‐Sodiation Strategies for Sodium‐Ion Batteries

Sodium‐ion batteries (SIBs) with abundant elements have garnered significant attention from researches as a promise compensation to lithium‐ion batteries (LIBs). However, the large‐scale commercial application of SIBs is partially hindered by the limited initial coulombic efficiency (ICE) due to the irreversible formation of solid electrolyte interphase (SEI) and intercalation into the defects in the anode. Similar to pre‐lithiation techniques, pre‐sodiation approaches are considered to be one of the most direct and effective way to compensate for the loss of active sodium at the anode side of SIBs during the initial cycle. In this context, additional sodium ions are pre‐injected to the cathode/anode material by chemical/electrochemical methods, aiming to improve battery span life and energy density. Here, this review delves into the necessity and impact of pre‐sodiation techniques, compiling the latest research progress, for instance, self‐sacrificing cathode additives, over‐sodiated cathode materials, direct contact and solution chemical pre‐sodiation. Notably, the research mechanisms underlying solution chemical pre‐sodiation are highlighted. This comprehensive overview aims to foster a deeper understanding of the pre‐sodiation techniques and expects to provide guidance for realizing the commercial application of high energy density sodium‐ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2022

Combining Experimental and Theoretical Techniques to Gain an Atomic Level Understanding of the Defect Binding Mechanism in Hard Carbon Anodes for Sodium Ion Batteries

Sodium ion batteries (NIBs) are an attractive alternative to lithium–ion batteries in applications that require large–scale energy storage due to sodium's high natural abundance and low cost. Hard carbon (HC) is the most promising anode material for NIBs; however, there is a knowledge gap in the understanding of the sodium binding mechanism that prevents a rational design of HC. This study tunes sucrose–derived HC via synthesis temperature then evaluates the structural, physical, and electrochemical properties. Neutron total scattering is used to generate structural models by fitting pair distribution functions (PDF) with a combination of molecular dynamics and reverse Monte Carlo methods. From this model, the number and type of structural features are identified, quantified, and correlated to the galvanostatic charge/discharge. A method of PDF “fingerprinting” binding sites using Na probe atoms is developed and analyzing these PDFs reveals an atomistic view of ion binding sites responsible for “defect” storage mechanisms. Combining these techniques results in an atomic–level study that provides a big picture of the Na–binding mechanism in NIBs, which allows for more precise tuning of the structure–property relationships in the future. Finally, the methodologies developed will also enable new strategies for the analysis of amorphous functional materials.

25 ENERGY STORAGE↗
DOE OSTI2023

A Self‐Healing Chemistry‐Enabled Organic Cathode for Sustainable and Stable Sodium‐Ion Batteries

Sodium‐on batteries (SIBs) are promising alternatives to lithium‐ion batteries (LIBs) because of the low cost, abundance, and high sustainability of sodium resources. Analogous to LIBs, the high‐capacity electrodes in SIBs always suffer from rapid capacity decay upon long‐term cycling due to the particle pulverization induced by a large volume change. Circumventing particle pulverization plays a critical role in developing high‐energy and long‐life SIBs. Herein, tetrahydroxy‐1,4‐benzoquinone disodium salt (TBDS) that can self‐heal the cracks by hydrogen bonding between hydroxyl group and carbonyl group is employed as a cathode for sustainable and stable SIBs. The self‐healing TBDS exhibits long cycle life of 1000 cycles with a high rate capability up to 2 A g −1 due to the fast Na‐ion diffusion reaction in the TBDS cathode. The intermolecular hydrogen bonding has been comprehensively characterized to understand the self‐healing mechanism. The hydrogen bonding‐enabled self‐healing organic materials are promising for developing high‐energy and long‐cycle‐life SIBs.

25 ENERGY STORAGE↗