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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Size-Selective Nanoporous Atomically Thin Graphene Separators for Lithium–Sulfur Batteries

Lithium–sulfur batteries (LSBs) are extensively researched for their high energy densities but are hindered by the lithium polysulfide (LiPS) shuttling effect, which results in poor cyclability. A popular mitigation strategy is separator modification, where a LiPS trapping material is slurry-coated onto a conventional microporous polypropylene (PP) separator. This additional mass and volume unfortunately compromise the overall energy density of the LSB. This study aims to take a separator modification approach that avoids this issue. Nanoporous atomically thin membranes (NATMs) made of graphene are gaining attention for their scalable synthesis, tunable pore size, and negligible pore length. Herein, we apply a well-characterized graphene NATM for reasons similar to those of a size-selective interlayer in LSBs. The tailored pore size of ∼0.7–1.0 nm and atomic thinness facilitate the passage of Li + (solvated ionic diameters ∼0.54–1.26 nm) and blockage of larger LiPS (solvated ionic diameters ∼0.81–1.69 nm) without adding significant impedances or mass. The sulfur confinement is confirmed through scanning electron microscopy and energy-dispersive X-ray spectroscopy elemental analysis of the Li anode. An LSB with a NATM@PP separator shows virtually no capacity loss over 150 cycles, demonstrating efficacy of size-selective molecular sieving using NATMs in LSBs.

battery separator↗
DOE OSTI2025

Delineating the Factors Impacting the Electrochemical Behavior of Single-Crystal High-Nickel Layered Oxide Cathodes

High-nickel (Ni) (≥80%) single-crystal LiNi 1-x-y Mn x Co y O 2 (NMCs) have garnered recent interest as cathodes in lithium (Li)-ion batteries (LIBs). However, capacity fade at high voltages, particularly after the onset of the H2–H3 phase transition, hampers their viability. In this study, single-crystal LiNi 0.8 Mn x Co 0.2-x O 2 (x = 0.2, 0.1, 0) are synthesized and tested in LiPF 6 in ethyl methyl carbonate-based electrolytes, with and without monofluoroethylene carbonate and LiF 2 PO 2 additives, to clarify the effects of Co/Mn ratio and surface stabilization on high-voltage cycling degradation. By imposing a kinetic barrier to the accessible H2–H3 capacity, surface reconstruction is identified as the primary driver of high-voltage capacity loss, being greater in the Co-free cathode and in the absence of fluorinated electrolyte components. This is attributed to a synergy between increased mechanical stress due to worsened bulk and interfacial H2–H3 kinetics and decreased interfacial stability due to the poor passivating capability of the electrolyte. Here, the findings highlight the importance of limiting cathode impedance growth during high-voltage cycling, which can be achieved by tuning bulk dopants and electrolyte chemistry.

25 ENERGY STORAGE↗
DOE OSTI2020

Quantification of Inactive Lithium and Solid–Electrolyte Interphase Species on Graphite Electrodes after Fast Charging

Rapid charging of Li-ion batteries is limited by lithium plating on graphite anodes, whereby Li+ ions are reduced to Li metal on the graphite particle surface instead of inserting between graphitic layers, which directly contributes to cell capacity loss because of the low reversibility of the Li plating/stripping process. Furthermore, precisely identifying the onset and amount of Li plating is therefore vital in order to remedy these issues. We demonstrate a titration technique with a detection limit of 20 nmol (5 × 10 –4 mAh) of Li that can be used to quantify inactive Li that remains on the graphite electrode after fast charging. The titration is extended to quantify the total amount of solid carbonate species and lithium acetylide (Li 2 C 2 ) within the solid–electrolyte interphase (SEI), and electrochemical modeling is used to determine the Li plating exchange current density (10 A/m 2 ) and stripping efficiency (65%) of plated Li metal on graphite. These techniques provide a highly accurate measure of the onset of Li plating and quantitative insight into graphite SEI evolution during fast charging.

25 ENERGY STORAGE↗
DOE OSTI2024

In Situ and Operando Observation of Zinc Moss Growth and Dissolution in Alkaline Electrolyte for Zinc–Air Batteries

As a promising battery technology, zinc–air batteries still face significant challenges, including the formation of a mossy structure on the zinc metal anode in alkaline electrolyte. Because a similar phenomenon also plagues lithium and sodium metal batteries, elucidating its mechanism has important implications for progress in energy storage. Herein, operando X-ray nanotomography was employed to visualize zinc moss growth and dissolution at the individual colony level. By tracking its microstructure evolution, zinc moss was found to display irreversible plating/stripping behavior. While zinc moss exhibits self-limiting growth and zinc deposition occurs mainly in its outer region, zinc dissolution is more uniformly distributed inside the moss colony upon stripping, leading to the formation of “dead” zinc and capacity loss. A direct correlation is established between the moss amount and zinc plating/stripping efficiency. Finally, results from this study offer new insights into mitigating the unstable zinc plating morphology and improving the cycle life of aqueous zinc–air batteries.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Reactive Suspension Electrolytes for Lithium Metal Batteries

Lithium metal batteries (LMBs) suffer from dendrite growth and capacity loss, which compromise safety and cycle life. Here, we present a simple reactive suspension electrolyte (RSE) strategy. When metal oxide (MO x ) nanoparticles are dispersed in the liquid electrolyte, in situ formation of Li 2 O and Li–M phases occurs at the lithium metal anode. By studying two different types of RSEs, Type 1 RSEs (i.e., CuO RSE) without metal-Li alloying and Type 2 RSEs (i.e., ZnO RSE and In 2 O 3 RSE) with metal-Li alloying capability, we elucidate the roles of each reaction compound. Here, we find that Li 2 O can improve reversibility of Li metal anode by stabilizing the interphase while Li–M alloy phases guide uniform Li metal plating. Compared to the carbonate-type reference electrolyte, RSEs demonstrate reduced nucleation overpotential, lower interfacial impedance, and higher Coulombic efficiency, leading to an extended cycle life in Li|Li 1 Ni 0.8 Co 0.1 Mn 0.1 O 2 full cells.

Lee, Junyoung [Stanford Univ., CA (United States)]↗
DOE OSTI2025

Parasitic structure defect blights sustainability of cobalt-free single crystalline cathodes

Abstract Recent efforts to reduce battery costs and enhance sustainability have focused on eliminating Cobalt (Co) from cathode materials. While Co-free designs have shown notable success in polycrystalline cathodes, their impact on single crystalline (SC) cathodes remains less understood due to the significantly extended lithium diffusion pathways and the higher-temperature synthesis involved. Here, we reveal that removing Co from SC cathodes is structurally and electrochemically unfavorable, exhibiting unusual voltage fade behavior. Using multiscale diffraction and imaging techniques, we identify lithium-rich nanodomains (LRNDs) as a heterogeneous phase within the layered structure of Co-free SC cathodes. These LRNDs act as critical tipping points, inducing significant chemo-mechanical lattice strain and irreversible structural degradation, which exacerbates the voltage and capacity loss in electrochemical performance. Our findings highlight the considerable challenges of developing Co-free SC cathodes compared to polycrystalline ones and emphasize the need for new strategies to balance the interplay between cost, sustainability, and performance.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Chemical factors controlling the behaviour of oxide cathodes in batteries

Oxide cathodes enable high-energy lithium-ion and sodium-ion batteries, with their performances fundamentally governed by three interrelated chemical factors: electronic configuration, chemical bonding, and chemical reactivity. Here, we illustrate how these factors dictate the redox energy, structural stability, ionic and electronic transport, and interfacial behavior in both layered oxide and polyanion oxide cathodes. We discuss how crystal-field effects and octahedral-site stabilization energies influence cation migration, and how inductive effects tune bond covalency and operating voltages. We also explain how chemical bonding governs thermal stability, gas evolution, and first-cycle capacity loss, and how alignment of transition-metal redox band with the oxygen 2p band determines electrolyte reactivity. Comparison between lithium and sodium layered oxides further reveals how differences in Li-O and Na-O bond ionicity affect chemical reactivity. Finally, we outline strategies including compositional tuning, surface doping, and electrolyte optimization, and emphasize how high-throughput, data-driven approaches in guiding the design of next-generation oxide cathodes.

25 ENERGY STORAGE↗
DOE OSTI2021

Dynamic spatial progression of isolated lithium during battery operations

The increasing demand for next-generation energy storage systems necessitates the development of high-performance lithium batteries. Unfortunately, current Li anodes exhibit rapid capacity decay and a short cycle life, owing to the continuous generation of solid electrolyte interface and isolated Li (i-Li). The formation of i-Li during the nonuniform dissolution of Li dendrites leads to a substantial capacity loss in lithium batteries under most testing conditions. Because i-Li loses electrical connection with the current collector, it has been considered electrochemically inactive or ‘dead’ in batteries. In this work, contradicting this commonly accepted presumption, we show that i-Li is highly responsive to battery operations, owing to its dynamic polarization to the electric field in the electrolyte. Simultaneous Li deposition and dissolution occurs on two ends of the i-Li, leading to its spatial progression toward the cathode (anode) during charge (discharge). Revealed by our simulation results, the progression rate of i-Li is mainly affected by its length, orientation and the applied current density. Moreover, we successfully demonstrate the recovery of i-Li in Cu–Li cells with >100% Coulombic efficiency and realize LiNi 0.5 Mn 0.3 Co 0.2 O 2 (NMC)–Li full cells with extended cycle life.

25 ENERGY STORAGE↗
DOE OSTI2021

Decomposition pathways and mitigation strategies for highly-stable hydroxyphenazine flow battery anolytes

Aqueous organic redox flow batteries are a promising technology for large-scale energy storage. The stability of the redox active organic molecules is increasingly being recognized as one of the major hurdles. Upon extended flow battery cycling, 7,8-dihydroxyphenazine-2 sulfonic acid (DHPS) undergoes desulfonation and reduction of a phenolic C–O bond to yield a mixture of 7/8-hydroxyphenazine-2-sulfonic acid, as well as hydrogenation of the aromatic ring system. Density functional theory (DFT) analysis of the charged DHPS, its ring-hydrogenated products, and variably substituted hydroxy phenazines has led to the development of a series of dihydroxylated phenazine isomers which provide insight into the effects of substitution pattern on solubility and stability. Seven dihydroxyphenazine (DHP) isomers were synthesized and their solubilities, electrochemical properties, flow battery cycling performance, and degradation pathways have been investigated. Based on theoretical and experimental results, hydroxyl substitution at the 1, 4, 6 and 9 positions yields highly stable derivatives, while substitution at the 2, 3, 7, and 8 positions results in unstable derivatives. Flow cells of 1,4- and 1,6-DHPs coupled with ferro/ferricyanide achieved high stabilities, with temporal capacity loss of 0.029 and 0.031% per day, respectively. Decomposition of 1,8- and 2,7-DHPs were found to arise from irreversible hydrogen rearrangement (tautomerization), yielding redox-inactive species. These results provide a detailed understanding of decomposition pathways and mitigation strategies for phenazine-based anolytes, and can provide general design guidelines for the development of stable redox-active organics.

25 ENERGY STORAGE↗
DOE OSTI2022

Incorporation of free halide ions stabilizes metal–organic frameworks (MOFs) against pore collapse and renders large-pore Zr-MOFs functional for water harvesting

Chemically and hydrolytically stable MOFs have shown promising water-vapor adsorption properties. However, MOFs that can simultaneously satisfy the following three requirements for effective water harvesting from low-humidity air are quite rare: (1) high water-uptake capacity; (2) hydrolytic and mechanical stability; (3) complete uptake at ~20–30% relative humidity (RH). Here we show that incorporating free halide ions is effective for enabling a representative Zr-MOF to meet these requirements for water harvesting. As-synthesized MOF-808 initially exhibits very good capacity at RH ≥ 30%, but quickly suffers large capacity losses due to water-evacuation-induced pore collapse. Via a framework-charging and free counter-ion inclusion approach, we were able to replace node-ligated formate anions with charge-neutral aqua ligands and site desired water-sorbing free-halide ions within the large pores of MOF-808 . In this study, altered samples show increased gravimetric water uptake, show beneficial shifts of water sorption isotherms toward lower water-vapor partial pressure, eliminate undesirable sorption/desorption isotherm hysteresis, and render MOF-808-Br indefinitely recyclable for ambient-temperature uptake of water vapor and lower-temperature liquid-water release.

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

Mesolytic cleavage of homobenzylic ethers for programmable end-of-life function in redoxmers

Irreparable chemical damage to redox-active monomers, oligomers, and polymers (i.e. redoxmers) limits the lifetime of energy storage devices (e.g. redox flow batteries) by causing electrode and membrane fouling, as well as irreversible capacity loss. To predictably restore device and materials performance, it is desirable to add programmed destruction capabilities into these damage-prone materials. Here, we report the use of triggerable retrograde reactions to achieve programmable end-of-life function in redoxmers. Retrograde reactions are intended to break up damaged redoxmer materials into more soluble small-molecule constituents to prevent irreparably fouling battery interfaces. We investigated the redox-triggered mesolytic cleavage of homobenzylic ethers (HBEs) for this purpose. Combining experimental methods with simulations, we probed the influence of ring substituents on the programmable bond-scission behavior of HBEs. Variation of para-substituents on the HBEs allowed us to modify the oxidation potential, degradation pathway, and electrochemical mechanisms of the generated products. Given its ideal oxidation potential, we selected the para-methoxy-based HBE as the cleavage scaffold and integrated it with dialkoxybenzene, TEMPO, viologen, and para-nitrobenzene redox centers for compatibility, bulk deconstruction, and electrode defouling tests. Upon applying a high oxidation potential, the redox-active pendant is cleaved from the backbone via HBE bonds; of the four redox centers tested, three of them remained fully redox active. Viologen-appended redox active polymers with HBE linkers were cleaved to fully separate the redox centers from the backbone. Polymer-filmed electrodes were partially restored following HBE oxidation defouling. Here these studies highlight the co-design of new materials functions for developing sustainable energy storage materials.

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

Exploring Electrode-Level State-of-Charge and State-of-Health Dynamics in Lithium-Ion Battery Cells: Modeling and Experimental Identification

A computationally efficient model serves as a critical prerequisite for battery performance analysis and advanced battery management algorithm design. Although battery models that capture cell-level behavior have been widely explored in existing literature, electrode-level battery models have received much lesser attention till to date. However, such electrode-level models can significantly increase battery performance and life by enabling electrode-level health-conscious control. Such electrode-level control can effectively expand usable energy and power limits of the battery cells by utilizing the knowledge of individual electrodes' charge and health. In this context, this paper presents a comprehensive battery model developed with a reference electrode insertion that captures (i) electrode-level charge/discharge dynamics, (ii) stoichiometric and temporal dependencies of electrode-level resistances, (iii) solid electrolyte interface (SEI) layer growth as key degradation phenomenon, and (iv) capacity fade and resistance rise in each electrode due to nominal battery aging. The proposed model is identified, and a preliminary validation is performed utilizing terminal voltage and negative electrode potential data collected from a pouch cell under one continuous cycling and accelerated aging conditions where the cell experienced 14% capacity loss.

aging↗
DOE OSTI2024

Solvent-mediated oxide hydrogenation in layered cathodes

Self-discharge and chemically induced mechanical effects degrade calendar and cycle life in intercalation-based electrochromic and electrochemical energy storage devices. In rechargeable lithium-ion batteries, self-discharge in cathodes causes voltage and capacity loss over time. The prevailing self-discharge model centers on the diffusion of lithium ions from the electrolyte into the cathode. Here, we demonstrate an alternative pathway, where hydrogenation of layered transition metal oxide cathodes induces self-discharge through hydrogen transfer from carbonate solvents to delithiated oxides. In self-discharged cathodes, we further observe opposing proton and lithium ion concentration gradients, which contribute to chemical and structural heterogeneities within delithiated cathodes, accelerating degradation. Hydrogenation occurring in delithiated cathodes may affect the chemo-mechanical coupling of layered cathodes as well as the calendar life of lithium-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

Imaging Cycle-Induced Damage of MnO 2 Microparticles

MnO 2 has been proposed as an electrode material in electrochemical energy storage devices. However, poor cycle life, especially in aqueous electrolytes, remains a detriment to commercialization. Prior studies have suggested a number of explanations for this capacity loss; however, experiments aimed at elucidating the details of the degradation process (es) are sparse. We describe here a microtube-membrane construct that allows for electrodeposition of monodisperse MnO 2 microparticles distributed across the membrane surface, and for subsequent electrochemical cycling of these MnO 2 particles. This allowed for a detailed analysis of the effect of cycling on the MnO 2 , by simply imaging the membrane surface before and after cycling. When an aqueous electrolyte was used, gross changes in particle shape, size and morphology were observed over the course of 500 cycles. Partial dissolution occurred as well. No such changes were observed when the MnO 2 particles were cycled (up to 500 times) in a propylene carbonate electrolyte solution.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Understanding the Selective Deposition of Li Metal on Nonuniform Electrode Surfaces Using Atomic Force Microscopy

The use of lithium metal in secondary batteries has been impeded by its tendency to form dendrites: branching conductive structures of metal that can lead to capacity loss and, ultimately, internal shorts in the battery. Patterned electrodes, in addition to artificially increasing the current density of cells by increasing the surface area available for reaction, also generate a nonuniform electric field in the vicinity of the electrode surface. This nonuniform electric field, though rapidly screened by the electrolyte, can promote inhomogeneous deposition and Solid Electrolyte Interphase formation. As the consequence of these effects is not theoretically apparent since Solid Electrolyte Interphase volume and conductivity changes can, in principle, offset variations in local current density, we have performed experiments to examine the deposition of Li on nonuniform electrode surfaces using Atomic Force Microscopy. In this work, we measure the local variations in topography, SEI thickness, and composition, and discuss their implications for the formation of dendrites in Li metal.

25 ENERGY STORAGE↗
DOE OSTI2021

Critical Barriers to Successful Implementation of Earth-Abundant, Mn-Rich Cathodes for Vehicle Applications and Beyond: A Detailed Study of Low SOC Impedance

We report that earth-abundant, sustainable cathode chemistries based on Mn are increasingly attractive for enabling a broader portfolio of cathode oxides. The well-known class of lithium- and manganese-rich cathodes still represents very viable options. However, despite the important work on understanding the mechanisms of voltage fade, hysteresis, and oxygen activity, relatively little attention has been given to understanding the impedance characteristics of these electrodes. In particular, an anomalous rise in area specific impedance at lower states of charge, as well as overall impedance rise and surface damage due to electrolyte interactions, represent critical barriers to implementation. This work presents a comprehensive study of impedance behavior in cobalt-free, lithium- and manganese-rich electrodes. The use of a robust surface treatment allows for long-term behavior to be probed in the absence of surface damage, capacity loss, and impedance rise due to electrolyte interactions. The anomalous rise in impedance could not be correlated to surface changes, or surface phase formation, but could be directly correlated with the bulk processes of voltage fade and voltage hysteresis. The activated material can be explained as a percolating network of higher-voltage, layered-type sites having facile Li diffusion. Interspersed throughout this network are lower-voltage, disordered sites that represent a significant barrier.

25 ENERGY STORAGE↗
DOE OSTI2022

Across-Depth Heterogeneity and Irreversibility of Fast-Charge-Driven Lithium Plating

Enabling fast charging in lithium-ion batteries (LIBs) is a key factor for resolving consumers’ “range anxiety” concerns in choosing an electric vehicle over a gasoline-powered one. The best-known issue in the fast charging of current LIBs (based on LiNi x Mn y Co 1–x–y O 2 /graphite) is lithium plating, which is barely reversible and is accompanied by capacity loss over time. Therefore, understanding the reasons for the irreversibility of lithium plating driven by fast charging is critical to enhancing the fast-charging capability of LIBs. Here, a study of the irreversibility and heterogeneity of lithium plating is carried out by using electrochemical analyses, inductively coupled plasma mass spectroscopy, and X-ray photoelectron spectroscopy. Further, the study shows that the majority of the lithium plated during fast charging remains inactive even with very slow discharging rates, implying that most of the plated lithium is irreversibly lost. The study also reveals that chemical compounds such as LiF, Li 2 O and Li 2 (CO 3 ) are formed heterogeneously within the lithium plating and are responsible for some of the irreversibility of the plated lithium.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2023

Electrolyte Role in SEI Evolution at Si in the Pre-lithiation Stage vs the Post-lithiation Stage

The formation and evolution of the dynamic solid electrolyte interphase (SEI) at the Si anode/electrolyte interface are yet to be completely understood to solve irreversible capacity loss and increase battery cycle life. Herein, the evolution of SEI and its dynamic properties at the Si anode/electrolyte interface are investigated in two electrolyte systems, a 1.2 M LiPF6 in EC: EMC 3:7 (wt%) electrolyte (referred to as Gen2) and a 1.2 M LiTFSI in EC: EMC 3:7 (wt%) electrolyte (referred to as LiTFSI). Two lithiation stages are studied: the pre-lithiation (pre-Li) SEI stage and the post-lithiation (post-Li) stage. Findings reveal at the pre-Li, SEI formation starts at an early potential and contributes to the greater mass gain in the Si/Gen2, and it is dominated by the formation of a non-uniform F- and P-rich layer in Si/Gen2, in contrast to a homogeneous F- and C-containing layer at the Si/LiTFSI interphase. The initially formed SEI in LiTFSI further benefits the charge transfer kinetics. At the post-Li stage, a more substantial SEI evolution is observed at Si/LiTFSI. This paper offers a foundational understanding of the SEI dynamic evolution with electrolyte dependence. Findings from this report offer important insights into solving the complex SEI stability issues on Si.

25 ENERGY STORAGE↗