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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

The Critical Stack Pressure to Alter Void Generation at Li/Solid-Electrolyte Interfaces during Stripping

The lithium stripping process generates vacancies, which may accumulate as voids and lead to uneven current distribution and dendrite growth in the following plating cycles. A stack pressure is typically required during stripping, but how to optimize the stack pressure is not clear. In this work, extremely lithiophilic Li/Li 2 O and lithiophobic Li/LiF interfaces were used to reveal the combining effect of interface interaction and stack pressure induced lithium creep on the stripping critical current density (CCD). A multiscale simulation scheme with Density Functional Theory (DFT), kinetic Monte Carlo (KMC) simulations, and an analytical model was developed. The analytical model predicted lithiophobic interfaces require a higher stack pressure than lithiophilic interfaces to reach the same CCD. The KMC simulations also showed higher stack pressure is needed at lithiophobic interfaces to accelerate Li vacancy diffusion into the bulk and maintain a flat surface. This stack pressure needs to be high enough to alter the Li forward-and-backward hopping barriers at the interface. This multiscale simulation scheme illustrates the importance to include the chemical-mechanical effects during Li stripping morphology evolution. It can be used to design ideal interlayer coating materials to maintain a flat Li surface during cycling.

25 ENERGY STORAGE↗
DOE OSTI2023

Sulfur Polymers as Flexible Interfacial Additives for Low Stack-Pressure Solid-State Lithium-Ion Batteries

Solid-state batteries (SSBs) fabricated using sulfide solid electrolytes (SSEs) typically require cell stack-pressures in the range of tens to hundreds of megapascals to maintain effective interfacial contact and lithium-ion mobility across the full cell stack. These relatively high cell stack-pressures necessarily require additional cell components that reduce the delivered volumetric and gravimetric capacities of SSBs. This work has developed a novel sulfur polymer (polyS) that improves lithium-ion conductivity in SSBs at low cell stack-pressures, thereby directly targeting this technological limitation. Specifically, this work shows that polyS can be combined with the argyrodite Li6PS5Cl (LPSC) to form a stable composite SSE. By combining LPSC particles with a flexible additive that enhances interfacial contact at low pressures, this new polyS LPSC composite SSE material greatly improves ionic conductivity at cell stack-pressures below 2.0 MPa in comparison to conventional LPSC composites. Furthermore, this polyS LPSC composite can be used to fabricate a full SSB that cycles reversibly at only 1.6 MPa. Finally, this composite SSE exhibits self-healing behavior when combined with a lithium metal electrode, wherein lithium dendrites are oxidized to form passivating Li2S species that recover the cell from shorting.

ENERGY STORAGE↗
DOE OSTI2022

Benchmarking Solid-State Batteries Containing Sulfide Separators: Effects of Electrode Composition and Stack Pressure

Integrating sulfide separators into solid-state batteries (SSBs) containing high energy cathodes typically requires one or more materials and engineering solutions including: (i) applying interfacial coatings to mitigate electrolyte decomposition, (ii) applying high stack pressures to form robust solid-solid contacts, and (iii) using alloying anodes to avoid Li dendrite formation. Despite the promise of these approaches, a lack of standardized testing protocols makes it difficult to directly compare results among different studies. To address this problem, the present work benchmarks the performance of SSBs containing β-Li 3 PS 4 (LPS) separators and composite cathodes. By systematically varying the anode/cathode composition and stack pressure, this work demonstrates that cathode design is a major bottleneck for solid-state cells cycled at low rates (<100 µA cm -2 ). Operando stack pressure measurements show that, while mechanical confinement generally promotes higher active material utilization and cycling stability, this strategy alone does not address interfacial reactivity between LPS and high voltage cathodes. Here, these results also demonstrate that stress evolution during cycling is dominated by volume changes at the Li metal anode. Finally, we show that FeS 2 cathodes with moderate operating voltages (<3 V vs Li/Li + ) exhibit superior cycling performance compared to high voltage cathodes by facilitating formation of stable cathode/electrolyte interfaces.

25 ENERGY STORAGE↗
DOE OSTI2022

Operating High-Energy Lithium-Metal Pouch Cells with Reduced Stack Pressure Through a Rational Lithium-Host Design

Transitioning from a liquid electrolyte to an inorganic solid electrolyte offers a potential pathway to enable highly reversible lithium-metal anodes. However, the solid-electrolyte-protected lithium-metal anode suffers from poor interfacial ionic contacts and requires an impractically high stack pressure (>1.0 MPa) to maintain the interfacial contacts. It is demonstrated here that combining a hollow silver/carbon fiber scaffold and an inorganic/organic composite electrolyte enables a highly reversible lithium-metal anode. Since the high surface area of the electrode provides intimate contact and the hollow structure of the electrode relieves the lithium plating-induced stress, the electrode/electrolyte interface remains stable during cycling even under mild stack pressure. This unconventional structural design is validated in practical pouch cells assembled with the 3D lithium host containing a onefold excess of lithium and a high-nickel cathode. At a mild stack pressure of 320 kPa, the pouch cell displays 83% capacity retention for 200 cycles. This work illustrates that combining a hollow electrode architecture and a robust solid electrolyte offers a practical pathway toward rechargeable lithium-metal anodes.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Electrochemo-mechanics unlocks hidden dynamics of lithium plating under stacking pressure

Understanding and mitigating lithium plating remains one of the most pressing challenges in advancing the safety and longevity of lithium-ion batteries (LIBs). Here, we present a novel integrative framework that combines in-operando swelling force measurements with a physics-based electro-chemo-mechanical model to uncover previously inaccessible insights into lithium plating dynamics under mechanical constraints. Unlike existing approaches that focus primarily on electrochemical signatures, our approach captures the coupled mechanical responses of commercial pouch cells during cycling, revealing how mechanical constraints fundamentally alter degradation pathways. We demonstrate that the use of a moderate stacking pressure suppresses lithium plating and enhances lithium stripping. This mechanically driven structural effect, coupled with the electrochemical process, significantly extends the linear aging regime in LIBs. Intriguingly, intermittent capacity recovery events that were observed during the battery cycling suggest dynamic lithium reactivation, a phenomenon rarely captured in real-time. This study pioneers a stress-aware methodology for diagnosing and managing lithium plating, establishing a new paradigm for real-time battery health monitoring. The findings offer transformative implications for the design of durable, high-performance LIB systems, opening new avenues for intelligent control strategies in battery management systems.

Bhowmick, Amit↗
DOE OSTI2022

Sulfide glass solid-state electrolyte separators for Li metal batteries: using an interlayer to increase rate performance and reduce stack pressure

We report on the solubility of (Li 2 S) 60 (SiS 2 ) x (P 2 S 5 ) 40–x , (0 ≤ x ≤ 40) sulfide glass solid-state electrolytes in the 1:1 (v/v) DME:DOL solvent mixture, a popular choice for lithium metal battery liquid electrolytes. SiS 2 -rich glasses within the compositional range of (Li 2 S) 60 (SiS 2 ) x (P 2 S 5 ) 40–x (28 ≤ x ≤ 40) were found to be functionally insoluble in DME:DOL. Hybrid symmetric test cells with a thin liquid electrolyte layer (0.6 M LiTFSI + 0.4 M LiNO 3 in 1:1 (v/v) DME:DOL) at the interface between lithium metal electrodes and an insoluble (Li 2 S) 60 (SiS 2 ) 28 (P 2 S 5 ) 12 glass wafer were tested. Hybrid test cells delivered a critical current density of 3.0 mA cm –2 at 25 °C and 0.1 MPa, which is nearly double the CCD of comparable dry symmetric test cells cycled at 10× higher stack pressure.

25 ENERGY STORAGE↗
DOE OSTI2021

A Power-Law Decrease in Interfacial Resistance Between Li 7 La 3 Zr 2 O 12 and Lithium Metal After Removing Stack Pressure

The high interfacial resistance between solid electrolytes and lithium metal is a hurdle to developing all solid-state batteries. External pressure applied on the lithium and solid electrolyte interface prior to electrochemical cycling is known to effectively lower the interfacial resistance. Here we report that the interfacial resistance between Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) and lithium metal decreases over time even after removing the external pressure. The irreversible decrease of interfacial resistance can be understood by a gradual reduction of the total energy of the system, including strain energy and interfacial energy. Under external pressure exceeding ~25 MPa, however, lithium can be squeezed into LLZTO, fracturing the ceramic solid electrolyte. As a result, these observations can help improve the understanding of lithium metal creep and the interactions between garnet-type solid electrolytes and lithium metal.

25 ENERGY STORAGE↗
DOE OSTI2025

Pressure-Induced Stacking of Rhodamine 6G Molecules

Extended conjugation of molecular π systems are of great significance for solar cells and organic light-emitting diodes as these can serve as new light absorbing and emitting chromophores. This research demonstrates the potential of using pressure and solvent environment to create larger assemblies of molecular π-conjugated systems. Here, we selected rhodamine 6G (Rh6G) to study the pressure-induced stacking of molecules in three different solvents: methanol (MeOH), isopropanol (IPA), and 16:3:1 mixture of methanol: ethanol: water (MEW). Absorption, emission, and fluorescence lifetime were studied at pressures up to 11.38 GPa. We found that pressure-induced stacking mechanisms can present solvent dependence: high pressures tend to create emissive Haggregates in MeOH and MEW, but excimers in IPA. This work guides and demonstrates routes to stacking of organic molecules using high pressures and provides fundamental insights into the formation of extended conjugation π systems.

Johnson, Kade [Univ. of Texas at San Antonio, TX (↗
DOE OSTI2024

A multiscale model to understand the interface chemistry, contacts, and dynamics during lithium stripping

A reversible Li-metal electrode, paired with a solid electrolyte, is critical for attaining higher energy density and safer batteries beyond the current lithium-ion cells. A stable stripping process may be even harder to attain as the stripping process will remove Li-atoms from the surface, and naturally reduce surface contact area, if not self-corrected by other mechanisms, such as diffusion and plastic deformation under an applied external stack pressure. Here, we capture these mechanisms occurring at multiple length- and time- scales, i.e., interface interactions, vacancy hopping, and plastic deformation, by integrating density functional theory (DFT) simulations, kinetic Monte Carlo (KMC), and continuum finite element method (FEM). By assuming the self-affine nature of multiscale contacts, we predict the steady-state contact area as a function of stripping current density, interface wettability, and stack pressure. We further estimate the exponential increase of overpotential due to contact area loss to maintain the same stripping current density. We demonstrate that a lithiophilic interface requires less stack pressure to reach the same steady-state contact area fraction than a lithiophobic interface. A “tolerable steady-state” contact area loss for maintaining stable stripping is estimated at 20 %, corresponding to a 10 % increase in overpotential. To constrain contact loss within the tolerance, the required stack pressure is 0.1, 0.5, and 2 times the yield strength of lithium metal for three distinct interfaces, lithiophilic Li/lithium oxide(Li2O), Li/lithium lanthanum zirconium oxide(LLZO), and lithiophoblic Li/lithium fluoride(LiF), respectively. The modeling results agree with experiments on the impact of the stack pressure quantitatively, while the discrepancy in stripping rate sensitivity is attributed to the simplifying interface interaction in our simulations. Overall, this multiscale simulation framework demonstrates the importance of electrochemical-mechanical coupling in understanding the dynamics of the Li/SE interface during stripping.

Feng, Min↗
DOE OSTI2022

Conformal Pressure and Fast-Charging Li-Ion Batteries

Batteries capable of extreme fast-charging (XFC) are a necessity for the deployment of electric vehicles. Material properties of electrodes and electrolytes along with cell parameters such as stack pressure and temperature have coupled, synergistic, and sometimes deleterious effects on fast-charging performance. We develop a new experimental testbed that allows precise and conformal application of electrode stack pressure. We focus on cell capacity degradation using single-layer pouch cells with graphite anodes, LiNi 0.5 Mn 0.3 Co 0.2 O 2 (NMC532) cathodes, and carbonate-based electrolyte. In the tested range (10–125 psi), cells cycled at higher pressure show higher capacity and less capacity fading. Additionally, Li plating decreases with increasing pressure as observed with scanning electron microscopy (SEM) and optical imaging. While the loss of Li inventory from Li plating is the largest contributor to capacity fade, electrochemical and SEM examination of the NMC cathodes after XFC experiments show increased secondary particle damage at lower pressure. We infer that the better performance at higher pressure is due to more homogeneous reactions of active materials across the electrode and less polarization through the electrode thickness. Our study emphasizes the importance of electrode stack pressure in XFC batteries and highlights its subtle role in cell conditions.

25 ENERGY STORAGE↗
DOE OSTI2025

Linking Pressure to Electrochemical Evolution in Solid-State Conversion Cathode Composites

Conversion-type cathodes, such as sulfur, FeS 2 , and FeF 3 , offer high theoretical capacities in solid-state lithium batteries but are hindered by substantial volume changes during cycling, leading to interfacial contact loss, crack formation, and microstructural degradation. Here, we investigate the relationships between electrochemical, mechanical, and structural evolution in solid-state electrode composites with these three active materials. Using real-time stack-pressure monitoring, synchrotron X-ray absorption spectroscopy, and electrokinetic modeling, we elucidate how stress evolution is linked to reversible and irreversible redox reactions. Nonlinear stack pressure evolution in cells with sulfur, FeS 2 , and FeF 3 electrode composites is found to arise from material-specific volume changes, the balance of volume change between the working and counter electrode, and the formation of distinct reaction intermediates. The three materials exhibit distinct stack pressure evolution, which is closely related to the different reaction processes in the materials, as demonstrated with X-ray absorption spectroscopy measurements. Through mesoscale modeling, we relate the experimental measurements to species evolution at the particle scale and track the dynamic coexistence of intermediate phases. Our findings highlight the importance of designing for volume changes of a given active material in solid-state battery systems.

batteries↗
DOE OSTI2026

Pressure Heterogeneity and Material Utilization in Thin-Film Solid-State Cathodes

Intimate interfacial contact between the solid electrolyte and the cathode active material is critical for maximizing cathode utilization in solid-state batteries. However, volume changes during electrochemical cycling induce internal stresses that drive interfacial degradation, particularly under nonuniform stack pressure. In this study, we employ in situ energy-dispersive X-ray diffraction tomography to visualize and quantify reaction heterogeneities across a 3 mm-diameter solid-state cathode with a well-defined interface. Our results reveal that regions under a lower stack pressure exhibit reduced material utilization and reversibility, which negatively affect the high-pressure regions. Interfacial degradation further impedes lithium-ion transport and amplifies microscale reaction heterogeneity. These findings highlight the critical role of stack pressure distribution in governing interfacial stability and electrochemical performance, offering important design insights into practical solid-state battery systems.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Deciphering volume changes in Li-S solid-state battery components during cycling: Implication for advanced battery design

Here, in this work, we developed custom fixtures to investigate the mechanical and electrochemical behavior of all-solid-state lithium batteries during cycling under constant pressure and constant volume conditions. We successfully monitored vertical displacements during constant pressure cycling and pressure variations during constant volume cycling, allowing us decouple volume changes in the sulfur, Li 2 S cathodes, LixIn anode, and solid-state electrolyte. Scanning electron microscopy and electrochemical impedance spectroscopy confirmed that two structural changes occur during ASSLB cycling: (1) irreversible fractures in the active material particles, and (2) void formation within the electrode matrix. While the fractures in primary particles are permanent, void formation can be mitigated through stack pressure, which promotes particle rearrangement in the electrode matrix. Our findings emphasize the importance of stack pressure in maintaining the microscale integrity of all-solid-state lithium batteries, preventing void formation and enhance battery performance and durability.

Cell Design↗
DOE OSTI2024

Transient Chemo‐Mechanical Model of Lithium Plating Impacted by External Pressure

Abstract Lithium anodes show great promise in commercial applications, but are hindered by lithium plating and dendrite growth which cause safety concerns during long‐term cell operation. Stack pressure is experimentally observed to improve cell lifetime; however, the relationship between stress and lithium deposition has remained difficult to elucidate. In this work, a transient, 3D, finite‐element model of the evolution of a lithium anode due to stripping and plating is developed. The evolution of a microscale protrusion on the anode surface is tracked over one charge‐discharge cycle with respect to stack pressure and lithium yield strength. Lithium plastic deformation, nonconformal anode‐separator contact, and separator porosity effects are accounted for. Over the course of several hours of stripping/plating, the anode surface evolves to a similar morphology under pressure regardless of the initial conditions due to lithium plastic deformation and hardening. The rate of this evolution highly depends on the applied pressure and assumed lithium yield strength.

25 ENERGY STORAGE↗
DOE OSTI2021

Pressure-tailored lithium deposition and dissolution in lithium metal batteries

Unregulated lithium (Li) growth is the major cause of low Coulombic efficiency, short cycle life and safety hazards for rechargeable Li metal batteries. Strategies that aim to achieve large granular Li deposits have been extensively explored, and yet it remains a challenge to achieve the ideal Li deposits, which consist of large Li particles that are seamlessly packed on the electrode and can be reversibly deposited and stripped. In this work, we report a dense Li deposition (99.49% electrode density) with an ideal columnar structure that is achieved by controlling the uniaxial stack pressure during battery operation. Using multiscale characterization and simulation, we elucidate the critical role of stack pressure on Li nucleation, growth and dissolution processes and propose a Li-reservoir-testing protocol to maintain the ideal Li morphology during extended cycling. The precise manipulation of Li deposition and dissolution is a critical step to enable fast charging and a low-temperature operation for Li metal batteries.

25 ENERGY STORAGE↗
DOE OSTI2024

Evaluating Pressure‐dependent Discharge Behavior of Foil Versus In situ Plated Lithium Metal Anodes in Solid‐State Batteries

Abstract Anode‐free manufacturing of solid‐state batteries (SSBs) shows promise to maximize energy density by eliminating excess lithium (Li) and simplifying battery production. However, high reversibility during discharge (stripping of Li) is necessary for long‐lifetime SSBs with a limited Li reservoir. Further, the plastic flow of Li changes depending on the Li thickness, leading to possible differences in discharge performance under stack pressure. This work investigates the pressure‐dependent discharge performance of anode‐free manufactured SSBs with in situ plated Li and compares the performance to that of conventional thick Li foil cells. Distinct stripping behavior is observed at low pressures (0–1 MPa), where Li diffusivity and initial interfacial contact may control accessible capacity, compared to high pressures (3–10 MPa) where mechanical deformation of Li likely governs stripping behavior. Analysis of impedance spectra collected during stripping shows that additional stack pressure delays the formation of deep, as opposed to lateral, voids in the Li anode. These results provide insights to guide the transition from thick Li foil anodes to anode‐free manufactured SSBs.

Haslam, Catherine G.↗