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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 91 records · Page 5

Characterization of Electrochemical Behavior for Aqueous Organic Redox Flow Batteries

Use of aqueous redox flow batteries with organic redox-active materials holds great promise for large-scale and sustainable energy storage. The development of low-cost, highly efficient aqueous redox flow batteries lies in a comprehensive understanding of the electrochemical behaviors of redox-active compounds. In this work, an alkaline redox battery with organic dihydroxyphenazine sulfonate (DHPS) anolyte and ferro-/ferricyanide (Fe(CN) 6 ) catholyte is investigated as a typical example of aqueous redox flow batteries using organic redox-active materials. The electrochemical kinetics of DHPS and Fe(CN) 6 are separately characterized using the symmetrical cell design. The resistance components are calculated directly from the experimental measurement. The key kinetic parameters are extracted and compared for DHPS and Fe(CN) 6 electrolytes. The extracted parameters are validated with symmetrical and full flow cell simulations at different operating conditions. Key parameters and internal loss are also compared with all-vanadium redox flow batteries, representing current state of the art. In addition, our extracted key parameters from a symmetrical flow cell are compared with the measured key parameters by cyclic voltammetry, a widely deployed electroanalytical technique. The cell performance prediction of DHPS anolyte on a 780 cm 2 interdigitated cell is made and found the power density is peaked at 475 mW cm -2 at our measurement condition.

25 ENERGY STORAGE↗

Membrane–Electrolyte System Approach to Understanding Ionic Conductivity and Crossover in Alkaline Flow Cells

Membrane transport properties are crucial for electrochemical devices, and these properties are influenced by the composition and concentration of the electrolyte in contact with the membrane. We apply this general membrane-electrolyte system approach to alkaline flow batteries, studying conductivity and ferricyanide crossover of Nafion and E-620. We report undetectable crossover for as-received Nafion and E-620 after both sodium and potassium exchange, but high ferricyanide permeability of 10 –7 to 10 –8 cm2 s –1 for Nafion subjected to pre-treatment prevalent in the flow battery literature. We show how the electrolyte mass fraction in hydrated membranes regulates the influence of ion concentration on membrane conductivity, identifying that increasing electrolyte concentration may not increase 1 membrane conductivity even when it increases electrolyte conductivity. To illustrate this behavior we introduce a new metric, the membrane penalty, as the ratio of the conductivity of the electrolyte to that of the membrane equilibrated with the electrolyte. We discuss the tradeoff between flow battery volumetric capacity and areal power density that arises from these findings. Finally, we apply insights from this approach to provide recommendations for use of membranes in alkaline flow cells, and electrochemical reactors in general.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

A reversible four-electron Sn metal aqueous battery

Sn is a promising metal anode for aqueous batteries, with up to four-electron redox available per atom (903 mAh g −1 Sn ). However, practically harnessing the four-electron Sn(OH) 6 2− /Sn reversibility remains challenging due to limited mechanistic understanding. Here, in this study, we reveal a kinetically asymmetric redox pathway involving a successive four-electron plating and a stepwise 2 + 2 electron stripping through a Sn(OH) 3 − intermediate. The crossover of Sn(OH) 3 − induces a reversible self-discharge that reduces Coulombic efficiency but does not impact cyclability, demonstrated by four-electron Sn-Ni full cells that sustain >800 h of stable cycling. By tuning the ion selectivity of the separator to suppress Sn(OH) 3 − crossover while allowing OH − transport, we further demonstrate high Sn utilization (67%) and high energy density (143.1 Wh L −1 cell). The results provide key understandings of the tradeoffs in engineering reversible multi-electron metal anodes and define a new benchmark for practical energy density that exceeds any Sn-based aqueous batteries to date.

SN anode↗

Controlling Surface Phase Transition and Chemical Reactivity of O3-Layered Metal Oxide Cathodes for High-Performance Na-Ion Batteries

O3-layered metal oxides are promising cathode materials for high-energy Na-ion batteries (SIBs); however, they suffer from fast capacity fade. In this work, we develop a high-performance O3-NaNi 0.68 Mn 0.22 Co 0.10 O 2 cathode for SIBs toward practical applications by suppressing the formation of a rock salt layer at the cathode surface with an advanced electrolyte. The cathode can deliver a high specific capacity of ~196 mAh g –1 and demonstrates >80% capacity retention over 1000 cycles. NaNi 0.68 Mn 0.22 Co 0.10 O 2 –hard carbon full-cells with practical loading (>2.5 mAh cm –2 ) and lean electrolyte (~40 μL) demonstrate ~82% capacity retention after 450 cycles. A 60 mAh single-layer pouch cell has also been fabricated and demonstrated stable performance. This work represents a significant leap in SIB development and brings new insights to the development of advanced layered metal oxide cathodes for alkaline-ion batteries.

25 ENERGY STORAGE↗

Mono-/Bimetallic Doped and Heterostructure Engineering for Electrochemical Energy Applications

Designing efficient materials is crucial to meeting specific requirements in various electrochemical energy applications. Mono-/bimetallic doped and heterostructure engineering have attracted considerable research interest due to their unique functionalities and potential for electrochemical energy conversion and storage. However, addressing material imperfections such as low conductivity and poor active sites requires a strategic approach to design. This review explores the latest advancements in materials modified by mono-/bimetallic doped and heterojunction strategies for electrochemical energy applications. It can be subdivided into three key points: (i) the regulatory mechanisms of metal doping and heterostructure engineering for materials; (ii) the preparation methods of materials with various engineering strategies; and (iii) the synergistic effects of two engineering approaches, further highlighting their applications in supercapacitors, alkaline ion batteries, and electrocatalysis. Finally, the review concludes with perspectives and recommendations for further research to advance these technologies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Sulfide electrolyte additive enables multi-ionic transfer pathways in alkaline iron redox

Traditional alkaline iron (Fe) batteries rely on the conversion reaction between Fe and Fe(OH) 2 but suffer from hydrogen generation upon Fe formation on charging. Fe 2+ /Fe 3+ redox is a promising anode reaction for alkaline Fe batteries, as it alleviates the formation of hydrogen gas during charging. However, achieving complete Fe 2+ /Fe 3+ redox with a one-electron transfer reaction is challenging due to the formation of electrochemically inert Fe 3 O 4 materials. Here, we demonstrate that an alkaline sulfide-containing electrolyte facilitates the reversible multi-ion transfer and transport pathways within (and beyond) the Fe 2+ /Fe 3+ redox system, including Fe(OH) 2 /Fe 3 O 4 conversion, intercalation of hydrosulfide into layered Fe(OH) 2 , and hydrogen deposition, mediated by hydroxyl ions, hydrosulfide anions, and protons, respectively. This multi-ionic charge storage mechanism delivers a compelling discharge capacity of up to 330 mA h g −1 , as determined by chronopotentiometry measurements at a current density of 0.1 A g −1 , exceeding the theoretical iron redox capacity solely relying on Fe 2+ /Fe 3+ redox (∼299 mA h g −1 ). Our study will highlight the potential of alkaline iron redox as a green anode reaction for various aqueous energy storage systems by utilizing a scalable and low-concentration hydrosulfide electrolyte additive.

36 MATERIALS SCIENCE↗

Salts for multivalent ion batteries

Methods for preparing electrolyte salts for alkaline earth metal-ion batteries (e.g., calcium and magnesium ion batteries) are described. The electrolyte salts comprise alkaline earth metal (e.g., Mg or Ca) salts of 3,4-dicyano-2-trifluoromethylimidazole (TDI). The methods comprise contacting TDI with an alkaline earth metal bis(trifluoroacetate) salt in trifluoroacetic acid.

25 ENERGY STORAGE↗

Modeling High Current Pulsed Discharge in AA Battery Cathodes: The Effect of Localized Charging during Rest

During high current operation, substantial heterogeneity develops within battery cathodes, particularly when their thickness is large. Heterogeneity relaxation during subsequent rest is important for understanding battery performance under pulsed conditions. Localized charge balancing phenomena within batteries at zero net current are not well understood and merit investigation. In this work, the heterogeneity within cathodes of commercial alkaline Zn–MnO 2 batteries is measured during discharge and monitored during rest using energy dispersive X-ray diffraction (EDXRD). Significant gradients in protonation form during discharge and partially relax under rest. It is demonstrated that the proton gradient relaxation is through local redox activity at zero net current, where local (de)protonation works to redistribute charge across the cathode thickness. To support this redox-based relaxation, a fundamental kinetic study on prismatic MnO 2 cathodes is conducted to determine an appropriate model to describe both discharge and charge kinetics of MnO 2 . These kinetics are incorporated into a computational model to simulate the proton gradient formation and partial relaxation under identical discharge conditions as the operando EDXRD experiments. Model and experimental data are found to be in excellent agreement, correctly predicting localized charge balancing at rest.

Batteries↗

Dynamics of disordered intermediates during the two-electron alkaline MnO 2 conversion reaction for grid-scale batteries

Battery technologies beyond Li-ion are likely needed for extensive integration of grid-scale storage. The rechargeable Zn-MnO 2 chemistry has the potential for high sustainability, high safety, and low cost, using Earth-abundant basis materials. In an alkaline electrolyte, the MnO 2 cathode can cycle reversibly if modified by including a Bi-containing additive, although the cycling mechanism remains mostly unknown. This work presents an account of the intermediate species involved in the electrochemical transformation from layered δ-MnO 2 to Mn(OH) 2 and back. During charge, a disordered intermediate with a structure resembling layered β-MnOOH exists stably for an extended period, corresponding to a regime known to have unexpected electrochemical activity of Bi. During discharge, β-MnOOH exists only briefly and is never the majority material, revealing that the cycling mechanism is asymmetric. In conclusion, these findings represent a significant advance in mechanistic knowledge and can enable engineering to develop the system for commercial use.

36 MATERIALS SCIENCE↗

Unlocking High Capacity and Reversible Alkaline Iron Redox Using Silicate-Sodium Hydroxide Hybrid Electrolytes

Alkaline iron (Fe) batteries are attractive due to the high abundance, low cost, and multiple valent states of Fe but show limited columbic efficiency and storage capacity when forming electrochemically inert Fe 3 O 4 on discharging and parasitic H 2 on charging. Herein, sodium silicate is found to promote Fe(OH) 2 /FeOOH against Fe(OH) 2 /Fe 3 O 4 conversions. Electrochemical experiments, operando X-ray characterization, and atomistic simulations reveal that improved Fe(OH) 2 /FeOOH conversion originates from (i) strong interaction between sodium silicate and iron oxide and (ii) silicate-induced strengthening of hydrogen-bond networks in electrolytes that inhibits water transport. Furthermore, the silicate additive suppresses hydrogen evolution by impairing energetics of water dissociation and hydroxyl de-sorption on iron surfaces. In conclusion, this new silicate-assisted redox chemistry mitigates H 2 and Fe 3 O 4 formation, improving storage capacity (199 mAh g -1 in half-cells) and coulombic efficiency (94 % after 400 full-cell cycles), paving a path to realizing green battery systems built from earth-abundant materials.

36 MATERIALS SCIENCE↗

Degradation Mechanism of Phosphate‐Based Li‐NASICON Conductors in Alkaline Environment

NASICON-type Li conductors (Li-NASICON) have traditionally been regarded as promising candidates for solid-state Li-air battery applications because of their stability in water and ambient air. However, the presence of water in the cathode of a Li-air battery can induce a highly alkaline environment by modifying the discharge product from Li 2 O 2 to LiOH which can potentially degrade cathode and separator materials. This study investigates the alkaline stability of common Li-NASICON chemistries through a systematic experimental study of LiTi x Ge 2-x (PO 4 ) 3 (LTGP) with varying x = 0–2.0. Density functional theory calculations are combined to gain a mechanistic understanding of the alkaline instability. It is demonstrated that the instability of LTGP in an alkaline environment is mainly driven by the dissolution of PO 4 3– groups, which subsequently precipitate as Li 3 PO 4 . The introduction of Ti facilitates the formation of a Ti-rich compound on the surface that eventually passivates the material, but only after significant bulk degradation. Consequently, phosphate-based Li-NASICON materials exhibit limited alkaline stability, raising concerns about their viability in humid Li-air batteries.

25 ENERGY STORAGE↗

DEVELOPMENT OF STABLE ANODE AND CATHODE MATERIALS FOR RECHARGEABLE BATTERIES

Batteries have been employed in a variety of applications, such as portable electronics, electric vehicles (EVs), and stationary energy storage to preserve energy from other renewable sources (like wind or solar energy). The ultimate goal is to develop high energy density, long life span, better safety, and low cost of the batteries. However, current commercialized batteries (like lead-acid, zinc-alkaline, lithium-ion batteries (LIBs)) could not fulfill all the demands of diversified applications. LIBs predominate the market because of their high energy density. To achieve a higher capacity of the cell, high-nickel layered (Ni > 90%) cathode materials are promising candidates since they compose high specific capacity and discharge voltage. In chapter 1, an introduction to cell energy density and the development of high-nickel layered cathode materials along with associated obstacles of poor cycling stability and thermal stability have been discussed. Associated works like doping or surface coating have also been mentioned in this section. In chapter 2, Al doping in high-nickel layered cathode materials to enhance the structural and thermal stability was introduced. Uniform incorporation of Al doping is achieved by mechanical fusion and calcination processes. The Al doping not only decreased the Li/Ni mixing ratio but also enhance the thermal resistance to oxygen evolution because of strong Al-O bonding, which leads to elevated electrochemical and thermal stability. In chapter 3, TiN is implemented as a Ti dopant for high-nickel layered cathode materials to improve the electrochemical performance in the LIBs. The Ti not only diffused within the bulk structure but also formed segregation on the surface, which improved the structural stability and led to better cycling performance. Although LIBs deliver high energy density, safety concerns of flammable organic electrolytes have not been resolved yet. Therefore, the aqueous rechargeable zinc-ion batteries (ZIB) have been praised for their safe, low-cost, eco-friendly stationary energy storage, which is considered as a complementary system to LIBs. In chapter 4, the mechanism, advantages, and challenges of ZIBs would be given and the strategies for solving the zinc metal anode issues have been discussed in this section. In chapter 5, a polymer coating method was reported to facilitate Zn deposition/ stripping by coordination with Zn2+ and prevented direct contact with aqueous electrolyte to block corrosion side-reactions. With this coating, a boost in a lifetime (up to 400 hours) and lower polarization under extremely high current conditions (10 mA cm-2) have been achieved in repeated Zn deposition/ stripping cycling.

25 ENERGY STORAGE↗

A rechargeable zinc-air battery based on zinc peroxide chemistry

When two is better than four Batteries based on the reaction of zinc and oxygen have been used for more than a century, but these have been primary (that is, nonrechargeable) cells. These batteries use an alkaline electrolyte and require a four-electron reduction of oxygen to water, which is a slow process. Sun et al. show that with the right choice of nonalkaline electrolyte, the battery can operate using a two-electron zinc-oxygen/zinc peroxide chemistry that is far more reversible. By making the electrolyte hydrophobic, water is excluded from the near surface of the cathode, thus preventing the four-electron reduction. These batteries also show higher energy density and better cycling stability. Science , this issue p. 46

Science & Technology - Other Topics↗

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

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

25 ENERGY STORAGE↗

Metallic and complex hydride-based electrochemical storage of energy

Abstract The development of efficient storage systems is one of the keys to the success of the energy transition. There are many ways to store energy, but among them, electrochemical storage is particularly valuable because it can store electrons produced by renewable energies with a very good efficiency. However, the solutions currently available on the market remain unsuitable in terms of storage capacity, recharging kinetics, durability, and cost. Technological breakthroughs are therefore expected to meet the growing need for energy storage. Within the framework of the Hydrogen Technology Collaboration Program—H 2 TCP Task-40, IEA’s expert researchers have developed innovative materials based on hydrides (metallic or complex) offering new solutions in the field of solid electrolytes and anodes for alkaline and ionic batteries. This review presents the state of the art of research in this field, from the most fundamental aspects to the applications in battery prototypes.

Cuevas, Fermin (ORCID:0000000290555880)↗

Morphology and Dynamics in Hydroxide-Conducting Polysulfones

In alkaline zinc–manganese dioxide batteries, there is a need for selective polymeric separators that have good hydroxide ion conductivity but that prevent the transport of zincate (Zn(OH) 4 ) 2- . Here we investigate the nanoscale structure and hydroxide transport in two cationic polysulfones that are promising for these separators. We present the synthesis and characterization for a tetraethylammonium-functionalized polysulfone (TEA-PSU) and compare it to our previous work on an N-butylimidazolium-functionalized polysulfone (NBI-PSU). We perform atomistic molecular dynamics (MD) simulations of both polymers at experimentally relevant water contents. The MD simulations show that both polymers develop well phase separated nanoscale water domains that percolate through the polymer. Calculation of the total scattering intensity from the MD simulations reveal weak or nonexistent ionomer peaks at low wave vectors. The lack of an ionomer peak is due to a loss of contrast in the scattering. The small water domains in both polymers, with median diameters on the order of 0.5–0.7 nm, lead to hydroxide and water diffusion constants that are 1–2 orders of magnitude smaller than their values in bulk water. This confinement lowers the conductivity but also may explain the strong exclusion of zincate from the PSU membranes seen experimentally.

25 ENERGY STORAGE↗

Material Failure Mechanisms of Alkaline Zn Rechargeable Conversion Electrodes

Zinc (Zn) alkaline electrodes hold great importance and promise in the battery technology community, yet their behavior in real-world applications is still poorly understood. Here, we report a study of failure mechanisms and material evolution during cycling of 27 zinc–manganese dioxide (Zn–MnO 2 ) cells wherein the percent utilization of the Zn electroactive material is systematically varied between 1 and 16%. Cell fabrication is kept typical of the prevailing industrial cell design. The cycle life ranges from 2800 to 60, depending inversely on the Zn utilization. In all cases, the Zn material microstructure sheds the polytetrafluoroethylene (PTFE) binder and forms zinc oxide (ZnO) rods, with longer rods formed by lower current per Zn mass. Irreversible side reactions such as the hydrogen evolution reaction (HER), short circuits, or gas crossover cause the Zn anode’s charging efficiency to average 92% (as low as 86%), which in turn causes the baseload of metallic Zn to gradually disappear. Cell failure occurs after the baseload of metallic Zn is exhausted. The total lifetime discharge capacity remains constant near 12 ± 5 Ah/g Zn invariant of Zn utilization, which suggests that the aforementioned processes of Zn microstructural evolution and side-reaction destruction of baseload metallic zinc both progress linearly with cell capacity throughput. Manual reproduction of individual Zn failure mechanisms is performed in 22 fresh cells. Tight packing of the microstructure can lead to poor mass transfer, which causes supersaturation of soluble Zn and finally produces a high overvoltage during discharge. Here, the low charging current density yields poor coulombic efficiency due either to the competitive HER or soft short circuits.

25 ENERGY STORAGE↗

Interfacial and Kinetic Origins of Voltage Loss in Neutral Zinc‐Air Batteries

Rechargeable zinc-air batteries are promising candidates for grid-scale energy storage; however, their practical deployment is limited by oxygen electrocatalysis inefficiencies and interfacial instabilities, particularly outside conventional alkaline electrolytes. Here, in this work, zinc-air batteries operating under neutral electrolyte conditions using ZnCl 2 soaked KC-PAA-PAM gel polymer electrolytes and electrochemically synthesized Ni/Fe layered double hydroxide electrocatalysts is investigated. Ni/Fe-LDH is intentionally employed as an OER-biased benchmark catalyst to diagnose electrolyte and interface driven limitations rather than as a bifunctional ORR/OER solution. Full cells exhibit highly stable cycling over hundreds of hours, yet operate at substantially suppressed charge and discharge voltages relative to the thermodynamic value. Electrochemical impedance analysis shows that ohmic losses contribute only minimally to this voltage suppression. Post-mortem X-ray photoelectron spectroscopy reveals metallic zinc accumulation on the air cathode and chloride-containing species on the anode, indicating parasitic interfacial processes. Synchrotron-based soft X-ray absorption spectroscopy confirms stable Ni 2+ and Fe 3+ oxidation states during cycling, consistent with OER-biased catalytic behavior, while neutral-electrolyte oxygen evolution measurements demonstrate strong electrolyte-induced suppression of oxygen kinetics. Together, these results show that electrolyte chemistry and cathode-side parasitic processes, rather than catalyst identity alone, dominate voltage losses in neutral zinc-air batteries, providing mechanistic insight into the fundamental challenges associated with neutral electrolyte operation.

Long duration energy storage↗