Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Na”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Tuning Methanol Transformation Pathways for Sustainable Steam Reforming: Na-Promotion Effects on Ag/m-ZrO 2 Catalysts

This work investigates the influence of sodium promotion on Ag/m-ZrO 2 catalysts for methanol steam reforming (MSR), focusing on activity, selectivity, surface chemistry, and mechanistic pathways. Temperature programmed reduction (TPR), XANES/EXAFS, CO 2 TPD, DRIFTS, and temperature programmed surface reaction methods were combined with fixed bed MSR testing to develop an integrated structure–function understanding of Na-modified Ag-ZrO 2 interfaces. Na addition systematically increases surface basicity, stabilizes strongly basic O 2− sites, and weakens the ν(CH) vibrational mode of surface formate, thereby facilitating C–H bond scission and accelerating decarboxylation to CO 2 . At moderate promoter levels (0.5–1.0 wt.% Na), the catalysts show significantly enhanced CO 2 selectivity and increased conversion relative to unpromoted Ag/m-ZrO 2 , while CH 4 formation remains negligible. Excessive Na (≥1.8 wt.%) leads to slower formate decomposition, greater carbonate stabilization, and suppressed conversion, revealing a narrow optimum around 1 wt.% Na. Short-term stability testing demonstrates steady conversion and product selectivity for both unpromoted and Na-promoted catalysts, with the latter maintaining markedly higher CO 2 selectivity. Although Pt/YSZ retains far superior intrinsic activity at ~10× higher space velocity, Ag offers a cost-advantaged alternative where lower cost metals are desirable. Collectively, these findings show that Na promotion enables tunable MSR selectivity on Ag/m-ZrO 2 by directing formate decomposition toward the CO 2 -forming pathway.

CO2 selectivity↗
DOE OSTI2025

Production of Radioactive 22 Na in Core-collapse Supernovae: The Ne-E(L) Component in Presolar Grains and Its Possible Consequences on Supernova Observations

Presolar graphite grains carry the isotopic signatures of their parent stars. A significant fraction of presolar graphites show isotopic abundance anomalies relative to solar for elements such as O, Si, Mg, and Ca, which are compatible with nucleosynthesis in core-collapse supernovae (CCSNe). Therefore, they must have condensed from CCSN ejecta before the formation of the Sun. Their most puzzling abundance signature is the 22 Ne-enriched component Ne-E(L), interpreted as the effect of the radioactive decay of 22 Na (T 1/2 = 2.6 yr). Previous works have shown that if H is ingested into the He shell and not fully destroyed before the explosion, the CCSN shock in the He-shell material produces large amounts of 22 Na. Here we focus on such CCSN models, showing a radioactive 26 Al production compatible with grain measurements, and analyze the conditions of 22Na nucleosynthesis. In these models, 22 Na is mostly made in the He shell, with a total ejected mass varying between 2.6 × 10 −3 M ⊙ and 1.9 × 10 −6 M ⊙ . We show that such 22 Na may already impact the CCSN light curve 500 days after the explosion, and at later stages it can be the main source powering the CCSN light curve for up to a few years before 44 Ti decay becomes dominant. Based on the CCSN yields above, the 1274.53 keV γ-ray flux due to 22 Na decay could be observable for years after the first CCSN light is detected, depending on the distance. This makes CCSNe possible sites to detect a 22 Na γ-ray signature consistently with the Ne-E(L) component found in presolar graphites. Finally, we discuss the potential contribution from 22 Na decay to the Galactic positron annihilation rate.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1994

A high-resolution survey of interstellar Na I D1 lines

We present high-resolution (0.5 km/s) spectra, obtained with the McDonald Observatory 2.7 m coude echelle spectrograph, of interstellar Na I D1 absorption toward 38 bright stars. Numerous narrow, closely blended absorption components, showing resolved Na I hyperfine structure, are evident in these spectra; such narrow components appear in both low halo and quite local gas, as well as in gas toward more distant disk stars. We have used the method of profile fitting in an attempt to determine column densities, line widths, and velocities for the individual interstellar clouds contributing to the observed absorption lines. The resulting sample of 276 clouds is significantly larger, and likely more complete, than several previous samples of 'individual' interstellar clouds, and allows more precise investigation of various statistical properties. We find that the cloud column density (N) and line width parameter (b) are not correlated, for 0.3 km/s approximately less than b approximately less than 1.5 km/s and 10.0/sq cm approximately less than log (N(Na I)) approximately less than 11.6/sq cm. The median b is about 0.73 km/s, the median log N is about 11.09/sq cm, and the median separation between adjacent components is about 2.0 km/s. All these are overestimates of the true median values, however, due to our inability to completely resolve all the component structure present in some cases; even at a resolution of 0.5 km/s, we may have discerned only 60% of the full number of individual components actually present. The one-dimensional dispersion of component velocities, in the local standard of rest, is approximately 8.6 km/s; the distribution of velocities is broader and displaced to more negative velocities for the weaker components. If 80 K is a representative temperature for the interstellar clouds seen in Na I absorption, then at least 38% (and probably the majority) of the clouds have subsonic internal turbulent motions. The range in N(H I) observed at a given N(Na I) increases as N(Na I) decreases below about 10(exp 11)/sq cm, so that N(Na I) becomes a less reliable predictor of N(H I) at low column densities. These spectra will be quite useful in future detailed studies of these lines of sight with the Hubble Space Telescope (HST) Goddard High Resolution Spectrograph (GHRS) echelle -- to determine accurate velocities and to reveal the detailed interstellar component structures that cannot be discerned at the 3.5 km/s resolution available with the GHRS.

Welty, Daniel E.↗
DOE OSTI2020

Materials Data on Na(FeO2)2 by Materials Project

Na(FeO2)2 is Spinel structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Na is bonded to four O atoms to form NaO4 tetrahedra that share corners with twelve FeO6 octahedra. The corner-sharing octahedra tilt angles range from 57–65°. There are two shorter (2.14 Å) and two longer (2.18 Å) Na–O bond lengths. There are three inequivalent Fe sites. In the first Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six equivalent NaO4 tetrahedra and edges with six FeO6 octahedra. There are four shorter (2.06 Å) and two longer (2.08 Å) Fe–O bond lengths. In the second Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six equivalent NaO4 tetrahedra and edges with six FeO6 octahedra. There is two shorter (1.92 Å) and four longer (1.98 Å) Fe–O bond length. In the third Fe site, Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six equivalent NaO4 tetrahedra and edges with six FeO6 octahedra. There is two shorter (1.92 Å) and four longer (1.97 Å) Fe–O bond length. There are three inequivalent O sites. In the first O site, O is bonded to one Na and three Fe atoms to form a mixture of edge and corner-sharing ONaFe3 tetrahedra. In the second O site, O is bonded to one Na and three Fe atoms to form a mixture of distorted edge and corner-sharing ONaFe3 tetrahedra. In the third O site, O is bonded to one Na and three Fe atoms to form a mixture of edge and corner-sharing ONaFe3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(Mg4Al3)4 by Materials Project

Na(Mg4Al3)4 crystallizes in the cubic I-43m space group. The structure is three-dimensional. Na is bonded in a 4-coordinate geometry to four equivalent Mg and twelve equivalent Al atoms. All Na–Mg bond lengths are 3.17 Å. All Na–Al bond lengths are 3.24 Å. There are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 10-coordinate geometry to one Na, three equivalent Mg, and six equivalent Al atoms. All Mg–Mg bond lengths are 3.06 Å. All Mg–Al bond lengths are 3.13 Å. In the second Mg site, Mg is bonded in a 12-coordinate geometry to seven Mg and five equivalent Al atoms. There are two shorter (3.14 Å) and four longer (3.17 Å) Mg–Mg bond lengths. There are a spread of Mg–Al bond distances ranging from 2.88–3.18 Å. Al is bonded in a 11-coordinate geometry to one Na, seven Mg, and three equivalent Al atoms. There are one shorter (2.72 Å) and two longer (2.80 Å) Al–Al bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(SO3)2 by Materials Project

Na(SO3)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Na is bonded in an octahedral geometry to six O atoms. There are a spread of Na–O bond distances ranging from 2.38–2.43 Å. S is bonded in a trigonal planar geometry to three O atoms. All S–O bond lengths are 1.46 Å. There are three inequivalent O sites. In the first O site, O is bonded in a distorted bent 120 degrees geometry to one Na and one S atom. In the second O site, O is bonded in a bent 120 degrees geometry to one Na and one S atom. In the third O site, O is bonded in a bent 150 degrees geometry to one Na and one S atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(SeO3)2 by Materials Project

Na(SeO3)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Na is bonded in an octahedral geometry to six O atoms. There are a spread of Na–O bond distances ranging from 2.41–2.47 Å. Se is bonded in a trigonal non-coplanar geometry to three O atoms. There is one shorter (1.66 Å) and two longer (1.67 Å) Se–O bond length. There are three inequivalent O sites. In the first O site, O is bonded in a bent 120 degrees geometry to one Na and one Se atom. In the second O site, O is bonded in a bent 120 degrees geometry to one Na and one Se atom. In the third O site, O is bonded in a bent 120 degrees geometry to one Na and one Se atom.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Synergistic Coupling Effect of Electronic Conductivity and Interphase Compatibility on High-Voltage Na 3 V 2 (PO 4 ) 2 F 3 Cathodes

Na 3 V 2 (PO 4 ) 2 F 3 (NVPF) has been considered an up-and-coming cathode material candidate for sodium (Na) ion batteries in light of its high specific capacity and working voltage. However, an erratic cathode/electrolyte interface layer is inevitably formed, accompanied by continuous electrolyte decomposition on the NVPF surface, when the voltage exceeds 4.2 V vs Na + /Na. Herein, the interphase features of NVPF are obviously enhanced owing to the ameliorated electronic conductivity obtained by combining it with carbon nanotubes (CNT). The NVPF with 3 wt % CNT (NVPF@3% CNT) reduces the Na + diffusion kinetic energy barrier and electron transport resistance. Furthermore, the conducting network formed by CNT with sturdy structure strength can promptly accommodate the volumetric changes during sequential Na + extraction/insertion and thus effectively improve the long-term cyclic performance of NVPF/hard carbon full cells. The initial discharge capacity approaches 105 mA h g –1 at 0.5C, and it retains 94% capacity retention after 200 cycles at the temperature of –10 °C. The cathode/electrolyte interphase characterization results further demonstrate that the interphase layer on the NVPF@3% CNT cathode is thinner and more compact compared with pristine samples. Here, this research provides a competitive strategy to facilitate the interfacial compatibility between the NVPF and electrolytes and accelerate the commercialization of high-performance Na-ion batteries.

25 ENERGY STORAGE↗
NASA NTRS1998

Reduced levels of skeletal muscle Na+K+ -ATPase in McArdle disease

We evaluated the hypothesis that impaired sarcolemmal function associated with exaggerated potassium release, impaired potassium uptake, or both may contribute to exertional fatigue and abnormal circulatory responses to exercise in McArdle disease (MD). The cellular mechanism of exertional fatigue and muscle injury in MD is unknown but likely involves impaired function of the ATPases that couple ATP hydrolysis to cellular work, including the muscle sodium potassium pump (Na+K+-ATPase). However, the concentration of muscle Na+K+ pumps in MD is not known, and no studies have related exercise increases in blood potassium concentrations to muscle Na+K+ pump levels. We measured muscle Na+K+ pumps (3H-ouabain binding) and plasma K+ in response to 20 minutes of cycle exercise in six patients with MD and in six sex-, age-, and weight-matched sedentary individuals. MD patients had lower levels of 3H-ouabain binding (231 +/- 18 pmol/g w.w., mean +/- SD, range, 210 to 251) than control subjects (317 +/- 37, range, 266 to 371, p < 0.0004), higher peak increases in plasma potassium in response to 45 +/- 7 W cycle exercise (MD, 1.00 +/- 0.15 mmol/L; control subjects, 0.48 +/- 0.09; p < 0.0001), and mean exercise heart rate responses to exercise that were 45 +/- 12 bpm greater than control subjects. Our results indicate that Na+K+ pump levels are low in MD patients compared with healthy subjects and identify a limitation of potassium reuptake that could result in sarcolemmal failure during peak rates of membrane activation and may promote exaggerated potassium-activated circulatory responses to submaximal exercise. The mechanism of the low Na+K+ pump concentrations in MD is unknown but may relate to deconditioning or to disruption of a close functional relationship between membrane ion transport and glycolysis.

Non-NASA Center↗
DOE OSTI2023

Electrolytes with Solvating Inner Sheath Engineering for Practical Na–S Batteries

Sodium–sulfur (Na–S) batteries with durable Na-metal stability, shuttle-free cyclability, and long lifespan are promising to large-scale energy storages. However, meeting these stringent requirements poses huge challenges with the existing electrolytes. Herein, a localized saturated electrolyte (LSE) is proposed with 2-methyltetrahydrofuran (MeTHF) as an inner sheath solvent, which represents a new category of electrolyte for Na–S system. Unlike the traditional high concentration electrolytes, the LSE is realized with a low salt-to-solvent ratio and low diluent-to-solvent ratio, which pushes the limit of localized high concentration electrolyte (LHCE). The appropriate molecular structure and solvation ability of MeTHF regulate a saturated inner sheath, which features a reinforced coordination of Na + to anions, enlarged Na + -solvent distance, and weakened anion-diluent interaction. Such electrolyte configuration is found to be the key to build a sustainable interphase and a quasi-solid–solid sulfur redox process, making a dendrite-inhibited and shuttle-free Na–S battery possible. With this electrolyte, pouch cells with decent cycling performance under rather demanding conditions are demonstrated.

25 ENERGY STORAGE↗
DOE OSTI2020

A High-Energy NASICON-Type Cathode Material for Na-Ion Batteries

Over the last decade, Na-ion batteries have been extensively studied as low-cost alternatives to Li-ion batteries for large-scale grid storage applications; however, the development of high-energy positive electrodes remains a major challenge. Materials with a polyanionic framework, such as Na superionic conductor (NASICON)-structured cathodes with formula Na x M 2 (PO 4 ) 3 , have attracted considerable attention because of their stable 3D crystal structure and high operating potential. Herein, a novel NASICON-type compound, Na 4 MnCr(PO 4 ) 3 , is reported as a promising cathode material for Na-ion batteries that deliver a high specific capacity of 130 mAh g –1 during discharge utilizing high-voltage Mn 2+/3+ (3.5 V), Mn 3+/4+ (4.0 V), and Cr 3+/4+ (4.35 V) transition metal redox. In addition, Na 4 MnCr(PO 4 ) 3 exhibits a high rate capability (97 mAh g –1 at 5 C) and excellent all-temperature performance. In situ X-ray diffraction and synchrotron X-ray diffraction analyses reveal reversible structural evolution for both charge and discharge.

25 ENERGY STORAGE↗
DOE OSTI2021

New Mechanistic and Reaction Pathway Insights for Oxidative Coupling of Methane (OCM) over Supported Na 2 WO 4 /SiO 2 Catalysts

Abstract The complex structure of the catalytic active phase, and surface‐gas reaction networks have hindered understanding of the oxidative coupling of methane (OCM) reaction mechanism by supported Na 2 WO 4 /SiO 2 catalysts. The present study demonstrates, with the aid of in situ Raman spectroscopy and chemical probe (H 2 ‐TPR, TAP and steady‐state kinetics) experiments, that the long speculated crystalline Na 2 WO 4 active phase is unstable and melts under OCM reaction conditions, partially transforming to thermally stable surface Na‐WO x sites. Kinetic analysis via temporal analysis of products (TAP) and steady‐state OCM reaction studies demonstrate that ( i ) surface Na‐WO x sites are responsible for selectively activating CH 4 to C 2 H x and over‐oxidizing CH y to CO and ( ii ) molten Na 2 WO 4 phase is mainly responsible for over‐oxidation of CH 4 to CO 2 and also assists in oxidative dehydrogenation of C 2 H 6 to C 2 H 4 . These new insights reveal the nature of catalytic active sites and resolve the OCM reaction mechanism over supported Na 2 WO 4 /SiO 2 catalysts.

Sourav, Sagar↗
DOE OSTI2021

New Mechanistic and Reaction Pathway Insights for Oxidative Coupling of Methane (OCM) over Supported Na 2 WO 4 /SiO 2 Catalysts

Abstract The complex structure of the catalytic active phase, and surface‐gas reaction networks have hindered understanding of the oxidative coupling of methane (OCM) reaction mechanism by supported Na 2 WO 4 /SiO 2 catalysts. The present study demonstrates, with the aid of in situ Raman spectroscopy and chemical probe (H 2 ‐TPR, TAP and steady‐state kinetics) experiments, that the long speculated crystalline Na 2 WO 4 active phase is unstable and melts under OCM reaction conditions, partially transforming to thermally stable surface Na‐WO x sites. Kinetic analysis via temporal analysis of products (TAP) and steady‐state OCM reaction studies demonstrate that ( i ) surface Na‐WO x sites are responsible for selectively activating CH 4 to C 2 H x and over‐oxidizing CH y to CO and ( ii ) molten Na 2 WO 4 phase is mainly responsible for over‐oxidation of CH 4 to CO 2 and also assists in oxidative dehydrogenation of C 2 H 6 to C 2 H 4 . These new insights reveal the nature of catalytic active sites and resolve the OCM reaction mechanism over supported Na 2 WO 4 /SiO 2 catalysts.

Sourav, Sagar↗
DOE OSTI2024

The role of Li doping in layered/layered Na x Li y Ni 0.4 Fe 0.2 Mn 0.4 O 2 intergrowth electrodes for sodium ion batteries

Here, the layered NaTMO 2 (TM = Ni, Fe, Mn) materials with the O3-type structure are attractive as positive electrodes for sodium ion batteries because of their high theoretical capacity. Additionally, Li doping in these materials has been shown to offer substantial enhancements to their electrochemical properties by promoting the formation of intergrowth structures, which are combinations of specific phases. However, the mechanism by which the intergrowth modifies the electrochemical properties is often unclear. Systematic variation of Li content in Na x Li y Ni 0.4 Fe 0.2 Mn 0.4 O 2 (NFM-Li y ) was conducted to identify its role in structural modification and electrochemical performance. Li contents of 0.15 and greater generate a layered/layered Na-O3/Li-O’3 intergrowth structure. 7 Li and 23 Na nuclear magnetic resonance and x-ray absorption spectroscopy identify that when the total solubility for alkali ions in the layered structure is exceeded, Li continues to form the Li-O’3 phase while the excess Na forms residual sodium compounds such as Na 2 O. Higher Li content is associated with improved capacity retention in the initial cycles from the superior stability of the mechanically linked NaO3/Li-O’3 structure that suppresses the P3 to OP2 phase transition during charge. However, high Li contents are associated with increased rates of parasitic side reactions that reduce long-term cycling stability. These side reactions are associated with the instability of the cathode-electrolyte interphase, which can be partially mitigated by atomic layer deposition (ALD) coating with alumina, which significantly enhances the capacity retention and Coulombic efficiency over many cycles. Overall, we find that the layered/layered Na-O3/Li-O’3 intergrowth structure is able to provide structural stability and suppress undesired phase transformations but is overwhelmed by the increased reactivity of the surface if not protected by surface coating.

25 ENERGY STORAGE↗
DOE OSTI2020

Enumeration as a Tool for Structure Solution: A Materials Genomic Approach to Solving the Cation-Ordered Structure of Na 3 V 2 (PO 4 ) 2 F 3

While powder diffraction methods are routinely utilized to optimize structural models for compounds whose crystal structures are known, the determination of unknown structures is far more challenging. When the unknown structure is large, structure solution can become a virtually intractable problem using standard structure solution methodologies, especially when the space group cannot be unambiguously resolved. One such system is the promising Na-ion battery cathode material Na 3 V 2 (PO 4 ) 2 F 3 whose high temperature and room temperature structures were previously solved, but whose more complex low-temperature structure could not be determined. Here, a novel materials genomic approach is demonstrated for the solution of the unknown 100 K structure of Na 3 V 2 (PO 4 ) 2 F 3 in which enumeration methods are first used to generate a large number (~3,000) of trial structures based on plausible orderings of Na ions and then automated Rietveld refinements are carried out to optimize each of these trial structures. Based on both the analysis of the ensemble of optimized trial structures and the density functional theory energy minimization of selected trial structures, the 100 K structure of Na 3 V 2 (PO 4 ) 2 F 3 is best described as belonging to the space group A2 1 am with unit cell dimensions of a = 9.01928(4), b = 27.1379(1), c = 10.73307(5). The 100 K unit cell has a large volume of 2627.07(2) Å 3 with Z = 12 and 33 independent crystallographic sites (9 Na, 3 V, 3 P, 12 O, and 6 F) that is 3x and 6x larger than the room- and high-temperature polymorphs of this phase, respectively. Finally, the novel methods described here will be generally applicable for the solution of the complex cation-ordered structures that commonly occur for battery materials.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Evidence of Zintl Intermediate Phase and Its Impacts on Li and Na Storage Performance of Pb-Based Alloying Anodes

Anode materials based on conversion and alloying reactions are promising to achieve high energy density of advanced sodium-ion batteries (SIBs). While the chemical similarities between sodium and lithium as alkali elements make the benchmarking strategy practical in developing new high-performance anodes, simply borrowing the anode material from one system to the other does not always guarantee success unless it is based on sound understanding of both Li- and Na-reaction mechanisms. In this work, we report the Na storage performance of a Pb-based anode and its fundamental reaction dynamics. In contrast to its excellent electrochemical performances in Li cells (reversible ~600 mAh/g), the newly developed Pb@PbO–C nanocomposite anode has limited electrochemical Na reaction properties showing moderate capacity and rate performances (~300 mAh/g at 20 mA/g). Synchrotron-based X-ray diffraction and absorption spectroscopy studies reveal the fundamental differences in the Na and Li reaction mechanism of the Pb-based anode. Further, unlike Li reaction, the unique Na reaction mechanism involves the formation of a highly ionic NaPb Zintl phase, which comprises tetrahedral Pb 4 clusters, as an intermediate phase. The strong covalent character of the Pb 4 Zintl clusters adversely affects the electronic conductivity and thus limits the electrochemical performance of the Pb-based anode in Na cells. These findings provide new insights applicable to developing high-performance alloying anode materials.

25 ENERGY STORAGE↗
DOE OSTI2025

Probing Operando Electrochemical Strain Generation in α-NaFeO 2 Composite Cathodes during Cycling of Na-Ion Batteries

The transition metal oxide (TMO) cathodes in Na-ion batteries suffer from low-capacity retention. Chemo-mechanical instabilities lead to the deterioration of the electrochemical performance of TMO cathodes in Li-ion batteries. However, there is not much known about the chemo-mechanical instabilities in the TMO cathodes for Na-ion batteries. Understanding the governing forces behind the interplay between the electrochemical performance and mechanical stability in TMO cathodes is critical for the development of Na-ion batteries. Here, we synchronize the digital image correlation (DIC) technique with electrochemical analysis to capture the real-time deformation behavior of the α-NaFeO 2 cathodes during cycling. When the charge cutoff voltage is 3.6 V, the cathode experiences reversible deformations (except for the first cycle). There is negative strain (shrinkage) generation during Na extraction and positive strain (expansion) generation during the subsequent Na insertion. A detailed analysis of the potential-dependent strain rate evolution points out complicated phase transformations and nonequilibrium conditions in the α-NaFeO 2 cathodes during cycling. When the charge cutoff voltage was increased to 4.2 V, there was a rapid capacity loss and large plastic deformations in the α-NaFeO 2 cathodes. We provide an in-depth discussion about the possible mechanisms behind the chemo-mechanical instabilities in the α-NaFeO 2 . In conclusion, the correlation is critical to develop material-based strategies to mitigate instability mechanisms in TMO cathodes for Na-ion batteries.

Wable, Minal [University of Maryland Baltimore Cou↗
DOE OSTI2023

Calorimetric Study of Mixed Phosphates Na 4 M 3 (PO 4 ) 2 P 2 O 7 (M = Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ ) to Evaluate the Electrochemical Trends

Mixed polyanionic compounds have been studied extensively as viable cathode materials for sodium-ion batteries. Mixed phosphates, Na 4 M 3 (PO 4 ) 2 P 2 O 7 (M = Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ ), provide a low barrier for Na-ion diffusion, being advantageous in comparison to phosphates and pyrophosphates. The reported order of sodium extraction is ambiguous and remains unclear. Despite being structurally similar, electrochemical performance differs for all four analogues with different degrees of (de)sodiation, according to the transition element present. High-temperature oxide melt solution calorimetry has been used to establish the relation between thermodynamic phase stability and observed capacity for this series of mixed phosphates. Thermodynamic phase stability largely depends on the kind of structure, type of bonding, and size of the cations present. So, according to our results, the thermodynamic phase stability follows the order Na 4 Mn 3 (PO 4 ) 2 P 2 O 7 > Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 > Na 4 Co 3 (PO 4 ) 2 P 2 O 7 > Na 4 Ni 3 (PO 4 ) 2 P 2 O 7 . The thermodynamic studies serve as guidelines for the selection of compositions with the potential for fabricating advanced cathode materials with maximum performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗