Search NASA⌕ Search

SEARCH · Search NASA

Results for “oxidation capacity”

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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Advanced Microscopy and Spectroscopy for Probing and Optimizing Electrode-Electrolyte Interphases in High Energy Lithium Batteries (Final Scientific/Technical Report)

The earliest developed LiCoO 2 layered oxide cathode material sparked the development of other layered cathode materials, dominating the positive electrode materials for lithium ion batteries. Within the practical operating conditions of today, the current generation layered oxide materials do not meet the future energy storage demands of 350 Wh kg -1 at cell level. Li-rich layered oxide (LRLO) materials have the potential to meet the high energy demands. Unlike the classical layered oxides, LRLO materials exhibit capacities that go beyond conventional topotactic mechanistic theoretical values. Despite its high capacities, this material has several challenges (voltage fading, structural instability, sluggish kinetics, cathode electrolyte interphase instability, etc.) that must be overcome in order to reach commercialization. In the past five years, our research group has made great progress on developing advanced characterization techniques coupled with atomic scale modeling to properly characterize the dynamic phenomena that govern the performance limitations of LRLO materials. Furthermore, our efforts have guided the material synthesis and surface modification to improve capacity retention. By carefully controlling the oxygen activities through the creation of uniform oxygen vacancies, we were able to avoid structural decomposition in LRLO. Our materials deliver a discharge capacity as high as 306 mAh g -1 with an initial coulombic efficiency of 90.6%. Furthermore, they do not exhibit obvious capacity decay with a reversible capacity over 300 mAh g -1 after 100 cycles at 0.1 C-rate. Our approach demonstrates the critical needs for advanced diagnosis and characterization. It is through the in-depth understanding of these high voltage cathode materials at atomistic and molecular level and their dynamic changes during the operation of batteries; we can successfully formulate strategies to further optimize this class of cathode materials, especially for the voltage instabilities. The diagnostic tools developed here can also be leveraged to study anode materials such as Li metal anode. The challenge of probing Li metal is the low dose tolerance (high beam sensitivity) of Li metal. We will have to apply cryogenic method (low-temperature) and low-dose electron microscopy and specialized camera to enable the characterization of the lithium metal.

25 ENERGY STORAGE↗
DOE OSTI2021

Combined Technologies for In Situ Remediation of Tc-99 and U in Subsurface Sediments

In this study, combinations of chemical remedies were tested in bench-scale batch experiments to evaluate a two-step reduction-sequestration approach to effectively stabilize high concentrations of inorganic contaminant mixtures. Bench tests simulated contaminant and geochemical conditions of a perched aquifer located within the Central Plateau at the Hanford Site, located in southeastern Washington State (USA). Pairwise combinations of a reductant [e.g., zero valent iron, sulfur modified iron (SMI), or calcium polysulfide] and a sequestering agent [e.g., calcite, apatite, or dilute alkaline solution (e.g., NaOH)] were evaluated for immobilization and stabilization of technetium (Tc) (50,000 pCi/L), uranium (U) (150 mg/L), and nitrate (NO 3 ) (200 mg/L) in high ionic strength groundwater. The results of these batch studies demonstrated that reduction by SMI and sequestration in apatite or calcite are the most effective combination for these contaminant mixtures and conditions. Aqueous concentrations of Tc and U decreased by 95.6% ± 2.5% and 101.1% ± 5.2%, respectively, with SMI-apatite and 98.3% ± 0.0% and 101.2% ± 5.2%, respectively, with SMI-calcite. Sequential extractions showed that sequestered contaminants had limited capacity for re-oxidation; in fact, less than 10% of immobilized Tc and U was recovered by selective extraction of mineral phases most susceptible to oxidation. In addition, X-ray absorption near edge structure analysis of the sediment samples treated with SMI-calcite showed the presence of only U(IV), while both U(IV) and U(VI) were present in the SMI apatite combination [ratio of 0.43 U(IV):0.59 U(VI)].This study describes preliminary results that a two-step approach for stabilizing contaminant mixtures of long-lived radionuclides can be effective at reducing contaminant fluxes to groundwater from vadose and perched water zones.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Definition of Redox Centers in Reactions of Lithium Intercalation in Li 3 RuO 4 Polymorphs

Cathodes based on layered LiMO 2 are the limiting components in the path toward Li-ion batteries with energy densities suitable for electric vehicles. Introducing an over-stoichiometry of Li increases storage capacity beyond a conventional mechanism of formal transition metal redox. However, the role and fate of the oxide ligands in such intriguing additional capacity remain unclear. This reactivity was predicted in Li 3 RuO 4 , making it a valuable model system. For this study, a comprehensive analysis of the redox activity of both Ru and O under different electrochemical conditions was carried out, and the effect of Li/Ru ordering was evaluated. Li 3 RuO 4 displays highly reversible Li intercalation to Li 4 RuO 4 below 2.5 V vs Li + /Li 0 , with conventional reactivity through the formal Ru 5+ -Ru 4+ couple. In turn, it can also undergo anodic Li extraction at 3.9 V, which involves O states to a much greater extent than Ru. This reaction competes with side processes such as electrolyte decomposition and, to a much lesser extent, oxygen loss. Although the associated capacity is reversible, reintercalation unlocks a different, conventional pathway also involving the formal Ru 5+ -Ru 4+ couple despite operating above 2.5 V, leading to chemical hysteresis. This new pathway is both chemically and electrochemically reversible in subsequent cycles. This work exemplifies both the challenge of stabilizing highly depleted O states, even with 4d metals, and the ability of solids to access the same redox couple at two very different potential windows depending on the underlying structural changes. It highlights the importance of properly defining the covalency of oxides when defining charge compensation in view of the design of materials with high capacity for Li storage.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Unraveling Na and F coupling effects in stabilizing Li, Mn-rich layered oxide cathodes via local ordering modification

Regardless of the prevailing capacity and energy density of lithium, manganese-rich layered oxide (LMR-NMC) cathodes, continuous decay of voltage and overall energy density during cycling hinders this material from commercialization in Li-ion batteries. Although significant work focuses on single doping of Na and F, analysis in portraying the benefit of these ions in diminishing the structural distortion during activation cycle is in doubt. In this study, the effects of co-doping Na and F into the LMR-NMC structure in stabilizing the structure and mitigating oxygen loss during the first cycle are closely examined via in situ x-ray measurements. Na and F co-doping shows a 30% lower degree of Li + /Ni 2+ mixing in the Li layer (C2/m structure), 50% reduced Debye-Waller factor of Mn-O bonding, increase reversible TM migration, and faster Li diffusion relative to the pristine material. Due to the utilization of Ni redox chemistry below 4.4 V, less oxygen redox is required for charge compensation at high voltage. This study offers the first instance to quantitatively evaluate the effects of co-doping Na and F in LMR-NMC cathode in order to minimize voltage degradation by altering the local ordering of O3-type structure, which may rationalize strategies to overcome the issues of the material.

25 ENERGY STORAGE↗
DOE OSTI2025

Modulating Surface Anionic Redox Chemistry toward Highly Stable Li-Rich Cathodes with Negligible Oxygen Loss

Low initial Coulombic efficiency and severe capacity/voltage fading during cycling caused by serious irreversible oxygen release, especially in the initial cycle, and resultantly induced unstable electrode/electrolyte interfacial chemistry, largely prohibit the commercial application of high-capacity Li-rich layered oxide cathodes (LLOs). Here, in this work, a dual reductive gas interface cotreatment strategy is applied to regulate the lattice oxygen redox activity and reversibility with a multiple defective structure design including Li/O/TM (TM = transition metal) vacancies and the intrinsic TM doping as well as a full-surface protective layer, which can suppress the irreversible TM migration and then undesirable phase transformation, resisting the corrosion of electrolyte during cycling effectively. Importantly, the introduced reversible SO 3 2- /SO 4 2- redox couple that provides extra capacity compensation could alleviate the distortion of oxygen-central octahedral structure and structural collapse caused by immoderate oxygen oxidation. Thus, the lattice oxygen redox chemistry is optimized, with negligible oxygen loss during the initial cycle. And the designed AS-LLO cathode with greatly enhanced structure stability shows high-capacity retentions of 99.2% at 0.3C after 100 cycles and 82.4% even after 1000 cycles at 5C. This work provides a guideline for manipulating the oxygen redox chemistry to achieve long-lifespan Li-rich layered oxide cathodes for high-energy-density lithium batteries.

25 ENERGY STORAGE↗
DOE OSTI2021

Physiological, genomic, and sulfur isotopic characterization of methanol metabolism by Desulfovibrio carbinolicus

Methanol is often considered as a non-competitive substrate for methanogenic archaea, but an increasing number of sulfate-reducing microorganisms (SRMs) have been reported to be capable of respiring with methanol as an electron donor. A better understanding of the fate of methanol in natural or artificial anaerobic systems thus requires knowledge of the methanol dissimilation by SRMs. In this study, we describe the growth kinetics and sulfur isotope effects of Desulfovibrio carbinolicus, a methanol-oxidizing sulfate-reducing deltaproteobacterium, together with its genome sequence and annotation. D. carbinolicus can grow with a series of alcohols from methanol to butanol. Compared to longer-chain alcohols, however, specific growth and respiration rates decrease by several fold with methanol as an electron donor. Larger sulfur isotope fractionation accompanies slowed growth kinetics, indicating low chemical potential at terminal reductive steps of respiration. In a medium containing both ethanol and methanol, D. carbinolicus does not consume methanol even after the cessation of growth on ethanol. Among the two known methanol dissimilatory systems, the genome of D. carbinolicus contains the genes coding for alcohol dehydrogenase but lacks enzymes analogous to methanol methyltransferase. We analyzed the genomes of 52 additional species of sulfate-reducing bacteria that have been tested for methanol oxidation. There is no apparent relationship between phylogeny and methanol metabolizing capacity, but most gram-negative methanol oxidizers grow poorly, and none carry homologs for methyltransferase (mtaB). Although the amount of available data is limited, it is notable that more than half of the known gram-positive methanol oxidizers have both enzymatic systems, showing enhanced growth relative to the SRMs containing only alcohol dehydrogenase genes. Thus, physiological, genomic, and sulfur isotopic results suggest that D. carbinolicus and close relatives have the ability to metabolize methanol but likely play a limited role in methanol degradation in most natural environments.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

Rinse-Free, Sodium-Efficient Synthesis of O3-Type Layered Oxide Materials Enabled by Acetate Precursors

Sodium-ion batteries (SIBs) are a sustainable alternative to lithium-ion systems for global electrification, with O3-type layered oxide cathodes offering high specific capacity and feasibility of scalable synthesis. Industrial co-precipitation synthesis of these cathodes typically uses transition metal sulfates, requiring extensive water rinsing to remove Na 2 SO 4 impurities, a process that consumes significant water and risks residual inactive phases if incomplete. Here, this work introduces a rinse-free, resource-efficient approach using metal acetate precursors. Residual sodium acetate in non-rinsed precursors decomposes during sintering to generate Na 2 CO 3 in situ, partially substituting an external sodium resource (e.g., NaOH and Na 2 CO 3 ) and reducing its consumption by ∼18–20%. Phase-pure O3-Na 1.0 Ni 1/3 Fe 1/3 Mn 1/3 O 2 (NFM111) cathodes synthesized via this method exhibit microstructure and electrochemical performance comparable to rinsed sulfate-derived counterparts, with initial capacities of 141 mAh g −1 at C/20 (7.5 mA g −1 ). By eliminating rinsing and minimizing sodium reagent use, this acetate-based route enhances sustainability and scalability of layered oxide production for SIBs.

acetate vs. sulfate↗
DOE OSTI2024

Copper and bismuth-based sorbent characterization in simulated iodine off-gas streams

The effective capture of volatile radioiodine, a fission product present in used nuclear fuel (UNF), is of paramount importance for development of used fuel reprocessing schemes to prevent release of radioiodine during unit operations and to meet regulatory standards for air emissions. A well-studied method for iodine capture in off-gas streams is the use of silver-functionalized zeolite phases (AgZ), which exploit chemisorption of I to Ag. Advances into other Ag-functionalized materials, including aerogels and metal organic frameworks (MOFs), are underway [1]. Additional metals with the capability to chemisorb iodine, including Cu, Bi, and Sn, [1] are being evaluated as alternatives to Ag for potential applicability to iodine management in off-gas systems. The design of novel functionalized sorbents with Cu and Bi, including composites with metal particles embedded in PAN substrates [2] and composites with metal sulfides embedded in PAN [3], is an ongoing area of study for improved iodine capture. Previously reported work on novel PAN-based metal sorbents has provided the synthesis, characterization, and iodine capture efficiency of this new class of sorbent. Specifically, the metal sulfide PAN composites are found to be easy to produce and reproduce, as well as having a high iodine loading potential under static conditions [3]. Due to the favorable testing previously performed with metal sulfide PAN composites, further testing into the performance of these composites under gas streams containing I2(g) in combination with NO2(g) and H2O(g) is needed. Humid streams of NO2(g) may arise from dissolver off-gas streams, when used fuel is dissolved in HNO3(aq) [4]. NO2(g) has been found to reduce AgZ sorption capacity for I because of oxidation of Ag, the chemisorbing agent, to Ag2O [5]. It follows that performance evaluation of novel sorbents under highly oxidizing conditions such as NO2(g) streams is critical. Therefore, the objective of this study is to determine the effect of flowing NO2(g) and H2O(g) streams on iodine sorption capacity and sorbent performance. This work utilizes custom-built gas handling capabilities for sorbent exposure along with solid-state characterization techniques to assess the physical and chemical properties of sorbents before and after exposure.

copper, bismuth, iodine capture, iodine sorbent, p↗
DOE OSTI2022

Phosphate adsorption kinetics and equilibria on natural iron and manganese oxide composites

We report that it is well known that phosphate retention in soils and sediments is strongly influenced by binding to secondary iron oxides, there have been relatively few studies examining its adsorption/desorption behavior on multicomponent particles of realistic natural complexity. In this study, natural Mn-rich limonite (LM), was used to prepare naturally complex Fe- and Mn-oxide composite materials to examine phosphate adsorption/desorption. To clarify the role of the Mn-oxides, results for the LM sample were compared to those for an acid treated version (LAT), in which the acid-extractable Mn-oxide fraction has been selectively eliminated while leaving the Fe-oxide fraction intact. The saturated adsorption capacity on LAT was almost double that on LM, suggesting that phosphate adsorption to the iron oxides is strongly occluded by the Mn-oxide fraction. This result is reinforced by the comparing the pH dependence and fits to adsorption isotherms, and by desorption experiments and STEM-EDS mapping showing that phosphate loading on Mn-oxides was limited. Hence, although the collective results confirm that phosphate uptake and strong binding is selectively controlled by the Fe-oxide fraction, our study reveals that the Mn-oxide fraction strongly interferes with this process. Therefore, phosphate uptake behavior on metal oxides cannot be predicted solely on the basis of the Fe-oxide fraction present, but instead must take into account the deleterious impacts of other intimately associated phases. For co-diagenetic Fe/Mn-oxide composites in particular, Mn-oxides appear to severely limit phosphate uptake on the Fe-oxide fraction, either by hindering access to binding sites on the Fe-oxide or by lowering their affinity for P.

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

Comprehensively Strengthened Metal‐Oxygen Bonds for Reversible Anionic Redox Reaction

Introducing anionic redox in layered oxides is an effective approach to breaking the capacity limit of conventional cationic redox. However, the anionic redox reaction generally suffers from excessive oxidation of lattice oxygen to O 2 and O 2 release, resulting in local structural deterioration and rapid capacity/voltage decay. Here, a Na 0.71 Li 0.22 Al 0.05 Mn 0.73 O 2 (NLAM) cathode material is developed by introducing Al 3+ into the transition metal (TM) sites. Thanks to the strong Al–O bonding strength and small Al 3+ radius, the TMO 2 skeleton and the holistic TM–O bonds in NLAM are comprehensively strengthened, which inhibits the excessive lattice oxygen oxidation. The obtained NLAM exhibits a high reversible capacity of 194.4 mAh g —1 at 20 mA g —1 and decent cyclability with 98.6% capacity retention over 200 cycles at 200 mA g —1 . In situ characterizations reveal that the NLAM experiences phase transitions with an intermediate OP4 phase during the charge–discharge. Theoretical calculations further confirm that the Al substitution strategy is beneficial for improving the overlap between Mn 3d and O 2p orbitals. Importantly, this finding sheds light on the design of layered oxide cathodes with highly reversible anionic redox for sodium storage.

25 ENERGY STORAGE↗
DOE OSTI2023

Stabilizing the Deep Sodiation Process in Layered Sodium Manganese Cathodes by Anchoring Boron Ions

Advanced high-energy-density sodium-ion batteries (SIBs) are inseparable from cathode materials with high specific capacities. Layered manganese-rich oxides (Na x MnO 2 , 0.6 ≤ x ≤1) are promising cathode materials owing to their ease of intercalation and extraction of a considerable amount of sodium ions. However, lattice interactions, especially electrostatic repulsive forces and anisotropic stresses, are usually caused by deep desodiatin/sodiation process, resulting in intragranular cracks and capacity degradation in SIBs. Here, boron ions are introduced into the layered structure to build up B-O-Mn bonds. Further, the regulated electronic structure in Na 0.637 B 0.038 MnO 2 (B-NMO) materials inhibits the deformation of MnO 6 octahedra, which finally achieves a gentle structural transition during the deep sodiation process. B-NMO electrode exhibits a high capacity (141 mAh g –1 ) at 1 C with a capacity retention of 81% after 100 cycles. Therefore, anchoring boron to manganese-rich materials inhibits the detrimental structural evolution of deep sodiation and can be used to obtain excellent cathode materials for SIBs.

25 ENERGY STORAGE↗
DOE OSTI2021

Highly efficient Pt catalyst on newly designed CeO 2 -ZrO 2 -Al 2 O 3 support for catalytic removal of pollutants from vehicle exhaust

Pt-CeO 2 catalysts have been widely studied for the vehicle emission control. Designing novel CeO 2 based supports with improved physical-chemical properties has become a research hotspot to further promote the catalytic performance and stability of Pt-CeO 2 catalysts. In this work, through utilizing a unique, two-step incipient wetness impregnation (T-IWI) method for ceria-zirconia-alumina (CZA-T) support preparation, a Pt single site catalyst (Pt/CZA-T) with excellent thermal stability was synthesized. Higher oxidation activity and Oxygen storage capacity (OSC) were achieved on activated Pt/CZA-T, comparing to Pt catalysts on regular CeO 2 /Al 2 O 3 (Pt/CA) and one-step prepared CeZrO x /Al 2 O 3 (Pt/CZA). Via the modification of hydrophilic/hydrophobic properties of γ-Al 2 O 3 by this unique T-IWI method, finer Ce 0.9 Zr 0.1 O 2 particles with higher density of surface defects were formed on CZA-T, on which a higher Pt dispersion and stronger Pt-O-Ce interaction were achieved. Upon activation, smaller, well-dispersed Pt clusters on CZA-T were generated. It was concluded that the CO oxidation performance and OSC were highly related to the size of Pt clusters on different supports that we have developed. Finally, more Pt sites located at Pt cluster-CeZrO x interfaces, which were the real active sites, were responsible for the highest OSC function and CO oxidation activity of activated Pt/CZA-T catalyst.

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

The Role of Catholyte Modulation in Suppressing the Initial Capacity Fade of Zinc Electrolytic Manganese Dioxide Coin Cells

Despite its potential for zinc–manganese oxide batteries, electrolytic manganese dioxide (EMD) can experience capacity fade due to a deficiency in the Mn 2+ supply at the cathode electrolyte interphase (CEI) from side reactions, even in the presence of an electrolyte additive. In this work, electrolyte loading modulation at the cathode electrolyte interface (CEI) was correlated with Zn∥EMD cell capacity retention and cycling performance, as a proposed measure to curb the initial capacity fade observed in EMD. Initial galvanostatic charge/discharge cycling, with varied electrolyte loading, revealed severe capacity fade (from ~188 to 10 mAh g –1 for the highest loading of 200 μL) within the first 15 cycles. Such a decrease in cell capacity is correlated with the formation of a Mn 4+ deposit on the current collector and consequently, the Mn 2+ depletion at CEI, as was supported by elemental and Raman analyses. Interestingly, confinement of the electrolyte to the CEI at a lower (≤15 μL) electrolyte loading mitigated Mn 4+ side-deposition, maintaining the cell capacity at >80% over the first 15 cycles. Interfacial Mn supply/depletion could be monitored via voltammetric analysis based on changes of the Zn 2+ insertionreduction peak. Additional galvanostatic experiments corroborated the voltammetric interpretation and the proposed degradation pathway in the studied cell conditions. The outcomes of this work provide practical insight into coin-cell design and configuration strategies for developing Zn∥EMD batteries.

25 ENERGY STORAGE↗
DOE OSTI2026

Rational Design of Weakly‐Solvating Molecules for Salt‐In‐Pre‐Ionic‐Liquid Electrolytes for Li Metal Batteries

Lithium metal batteries (LMBs) promise step‐changes in energy densities but suffer from poor cycle life due to unstable electrolyte‐lithium interfaces. Conventional carbonate electrolytes exhibit excessive lithium‐ion solvation and low oxidative stability, leading to rapid capacity loss. Herein, we report a rationally designed weakly‐solvating cyclic sulfonamide, 1‐trifluoromethanesulfonyl)amide pyrrolidine (TFMSPyr), which integrates an electron‐withdrawing trifluoromethanesulfonyl functional group at pyrrolidinic‐N. TFMSPyr acts as a pre‐ionic‐liquid solvent that forms intrinsically localized, anion‐dominated solvation, coupling molecular architecture, solvation topology, and transport dynamics. As a result, LiFSI based salt‐in‐pre‐ionic‐liquid (SIPIL) electrolytes exhibit high lithium‐ion transference number, oxidative stability > 5 V versus Li/Li + and anion‐derived solid electrolyte interphases (SEI). Li||Cu cells with SIPIL deliver a first cycle Coulombic efficiency (CE) of ≈ 99% with average CE of 99.2% for 100 cycles, and lithium half‐cells with lithium iron phosphate (LFP) cathode exhibit 82% capacity retention after 400 cycles with CE of 99.98%. In anode‐free full cells, 95% of initial capacity is retained after 63 cycles with an average CE of 99.5%. These results demonstrate that molecular engineering of solvents offers a powerful pathway to stabilize lithium metal interfaces and enable practical Anodeless LMBs.

25 ENERGY STORAGE↗
DOE OSTI2023

Structure and lithium insertion in oxides of molybdenum

Oxides of molybdenum, MoO x , have a rich structural chemistry arising from the accommodation of oxygen deficiency as MoO 3 is reduced and varied redox behavior arising from the ability of Mo to take on several different oxidation states. We review MoO 3 , MoO 2 , and all the reduced Mo oxides with intermediate compositions for their performance as Li-ion battery electrode materials. These reduced oxides are perhaps the most structurally diverse in the field of energy storage materials, taking on structures ranging from ones with crystallographic shear to bronze-like structures and distorted rutile. The crystal structure can have a significant impact on the performance of battery materials, which makes the reduced Mo oxides a promising domain of study. Electrochemical studies of these oxides from as early as 1971 to as recently as 2022 are compiled, and characteristics of capacity, capacity retention, and rate performance are compared. We find that certain oxides indeed display promising and highly reversible capacities for Li + storage. Typical redox voltages for Mo oxides lie in a regime that hinders maximizing energy density when they are paired with higher-voltage cathodes or lower-voltage anodes. The possibility of decreasing the redox voltage in the future will expand the promise of these materials while offering an alternative to more critical elements such as Nb.

25 ENERGY STORAGE↗
DOE OSTI2025

Interface-engineered (AlMnCoNiZn) 3 O 4 @PPy nanocomposites for superior lithium storage: Mechanism and performance

The practical application of graphite anodes in lithium-ion batteries (LIBs) is constrained by low specific capacity (372 mAh g -1 ) and sluggish kinetics. Here, to address these limitations, our present study focuses on high-entropy oxides (HEOs), which offer high theoretical capacity and structural stability. We synthesized spinel-structured (AlMnCoNiZn) 3 O 4 nanoparticles via a solution combustion method and fabricated an (AlMnCoNiZn) 3 O 4 @polypyrrole (PPy) nanocomposite through in-situ polymerization. Our electrochemical tests demonstrate that the PPy modification significantly enhances performance. While the pristine (AlMnCoNiZn) 3 O 4 delivered 445 mAh g −1 after 100 cycles at 100 mA g −1 and 350 mAh g −1 after 1000 cycles at 1000 mA g −1 , the (AlMnCoNiZn) 3 O 4 @PPy composite achieved 695 mAh g −1 after 100 cycles and maintained 675 mAh g −1 after 1000 cycles. Furthermore, the composite improved rate capacity at 1000 mA g −1 from 211 mAh g −1 to 403 mAh g −1 . This work highlights how conductive and flexible polymer modifications can dramatically improve the electrochemical properties of HEOs. The developed (AlMnCoNiZn) 3 O 4 @PPy composite provides a promising direction for designing advanced anodes to meet next-generation energy storage demands.

Anodes material↗
DOE OSTI2025

Impact of SO 2 on NiFe Nanoparticle Exsolution and Dissolution from LaFe 0.9 Ni 0.1 O 3 Perovskite Oxides

Ni-doped LaFeO 3 perovskite oxide is a promising cathode material for solid oxide electrolysis cells (SOECs) designed for CO 2 /H 2 O coelectrolysis. Here, the performance of LaFe 0.9 Ni 0.1 O 3 is being investigated under real-world conditions that include exposure to acid gases, such as SO 2 , relevant to SOEC operation. Experiments show that LaFe 0.9 Ni 0.1 O 3 exsolves NiFe nanoparticles, along with the formation of surface SO 4 2– and SO 3 2– after being exposed to 200 ppm of SO 2 . This suggests that the ionic diffusion of Ni 3+ and Fe 3+ between the bulk and the surface remains unaffected throughout the exsolution–dissolution–exsolution cycle. Thermochemical water splitting has been employed as a probe reaction to evaluate the catalytic properties of the exsolved NiFe nanoparticles. These nanoparticles demonstrated improved hydrogen production compared to bare perovskite oxide substrates. However, after exposure to SO 2 , the formation of Fe-rich NiFe nanoparticles led to poor thermocatalytic performance and rapid deactivation of the perovskite at elevated temperatures. Density functional theory (DFT) analysis was utilized to validate the experimental findings, indicating a significantly negative reaction energy for water splitting over exsolved Fe, as well as stronger binding of SO 2 to Fe than to Ni. Computational analysis further suggests that the presence of surface sulfate promotes the formation of Fe-rich NiFe nanoparticles, aligning with the experimental results. Overall, this study clarifies how SO 2 affects the structure of SOEC perovskite oxide candidate materials. Future engineering efforts should focus on enhancing nanoparticle exsolution and sulfur resistance, which is crucial for improving the hydrogen production capacity of La-based perovskite oxides for electro- and thermocatalytic water splitting in real environments containing acid gases.

Najimu, Musa [Univ. of Southern California, Los An↗
DOE OSTI2020

Li-rich cathodes for rechargeable Li-based batteries: reaction mechanisms and advanced characterization techniques

Due to their high specific capacities beyond 250 mA h g -1 , lithium-rich oxides have been considered as promising cathodes for the next generation power batteries, bridging the capacity gap between traditional layered-oxide based lithium-ion batteries and future lithium metal batteries such as lithium sulfur and lithium air batteries. However, the practical application of Li-rich oxides has been hindered by formidable challenges. To address these challenges, the understanding of their electrochemical behaviors becomes critical and is expected to offer effective guidance for both materials and cell development. This work aims to provide fundamental insights into the reaction mechanisms, electrochemical challenges and modification strategies of lithium-rich oxides. We first summarize the research history, the pristine structures, and the classification of lithium-rich oxides. Then we review the critical reaction mechanisms that are closely related to their electrochemical features and performances, such as lattice oxygen oxidation, oxygen vacancy formation, transition-metal migration, layered to spinel transitions, ‘two-phase mechanism’, and lattice evolution. These discussions are coupled with state-of-the-art characterization techniques. As a comparison, the anionic redox reactions of layered sodium transition metal oxides are also discussed. Finally, after a brief overview of the correlation among the aforementioned mechanisms, we provide perspectives on the rational design of lithium-rich oxides with high energy densities and long-term cycling stability.

25 ENERGY STORAGE↗