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At least 19 records

Topotactic Phase Transformation of Lithiated Spinel to Layered LiMn0.5Ni0.5O2: The Interaction of 3-D and 2-D Li-ion Diffusion

This study investigates the structural evolution of LiMn0.5Ni0.5O2 cathode materials for Li-ion batteries as a function of synthesis temperature and its effect on electrochemical performance. It is demonstrated that, as the synthesis temperature increases from 400 to 900 ?C, a gradual topotactic transformation occurs between a lithiated spinel structure, denoted herein as “lithium-excess spinel” LxS-LiMn0.5Ni0.5O2 (or LxS-LMNO), and the well-known layered LiMn0.5Ni0.5O2 structure prepared at high temperature, HT-LiMn0.5Ni0.5O2 (HT-LMNO). The electrochemical capacity of the LiMn0.5Ni0.5O2 electrodes follows a parabolic trend with increasing synthesis temperature, which is attributed primarily to the gradual transformation of 3-dimensional (3-D) to 2-dimensional (2-D) diffusion pathways for the Li ions. When synthesized at 400 °C, LxS-LiMn0.5Ni0.5O2 electrodes perform well, benefitting from the 3-D network of channels within the LxS structure. By contrast, when prepared at 500-700 °C, LiMn0.5Ni0.5O2 electrodes operate poorly, which is attributed to the formation of locally disordered structural arrangements that impede Li-ion diffusion. Such an increase in local disorder in the mid-temperature synthesis range is attributed to the structural frustration between the lithium-excess spinal and layered end-members. The transformation from the locally disordered to more ordered layered components between 700 °C and 900 °C enhances electrochemical performance. The study opens new avenues for designing next-generation Mn-rich cathode materials by fine-tuning the synthesis conditions as well as the composition and structure of LxS-LMNO electrodes.

energy storage

Chemo-Mechanics of α-V 2 O 5 During Lithiation and Implications for Rechargeable Battery Cathodes

Chemo-mechanical degradation of layered oxide electrodes is strongly influenced by crystallographic anisotropy, local stress evolution, and ion insertion, yet the intrinsic mechanical response of layered materials remains incompletely understood. Indeed, most prior studies have focused on polycrystalline materials but single crystals enable direct observation of coupling between anisotropic ion diffusion and mechanical response. This study aims to determine how crystallographic anisotropy and lithiation affect deformation, fracture, and mechanical properties in single-crystal V 2 O 5 , and compares this behavior with polycrystalline counterparts. Polycrystalline V 2 O 5 thin films and single-crystal α-V 2 O 5 were studied using nanoindentation, scanning electron microscopy, focused ion beam cross-sectioning, and Raman spectroscopy. Single crystals were tested in pristine and chemically lithiated states, including experiments in which crystals were first plastically deformed via nanoindentation and subsequently lithiated. Polycrystalline films exhibited significantly higher hardness and elastic modulus than single crystals. Single crystals indented normal to the exposed (001) basal plane exhibited pronounced anisotropic deformation, including directional slip, crystallographically-guided cracking, anisotropic crack propagation, interlayer separation, and shear localization. Lithiation caused substantial softening, reduced hardness and modulus, and suppressed displacement bursts during nanoindentation, while previously indented regions showed crack formation and growth upon lithiation. Mechanical behavior of α-V 2 O 5 is strongly governed by crystallographic anisotropy and further altered by lithiation, with pre-existing deformation serving as a strong driver of fracture during ion insertion. These findings illuminate the coupling among ion insertion, deformation, and fracture in layered oxides and provide a basis for understanding and mitigating mechanical failure in electrochemical energy-storage materials.

Anisotropy

Depth-Resolved Lithiated Gradients in Pristine and Laser-Ablated Anodes During Fast Charging

Laser ablating 3D electrode microstructures is a technique to improve Li-ion battery fast-charge performance. This technique has been theoretically proposed and electrochemically validated previously in the literature. The fundamental principle underlying laser ablation is that the ablated features reduce Li-ion transport pathways, improving access to the electrode active material near the current collector. This, in turn, promotes more homogeneous electrode utilization. The present study seeks to directly affirm the physics attributed to laser ablation using operando high-speed synchrotron X-ray diffraction. In this study, depth-resolved graphite lithiation gradients are measured operando during high-rate (15 min) charging. The depth-resolved lithiation dynamics of both ablated and non-ablated anodes are compared. The results highlight that the laser-ablated graphite electrode has notably more homogeneous utilization as compared to the non-ablated electrode. Additionally, the ablated electrode has a significant delay in reaching the maximum graphite lithiation at the separator, indicating less propensity for lithium plating. During low rate delithiation/discharge (2 hr), the two cells' lithiation gradients converge. Notably, a calibrated physics-based electrochemical model accurately reflects experimental findings, suggesting the potential to use pseudo-4D models not only to optimize laser ablation parameters in fast-charge capable electrodes but also to guide fast charging protocols that avoid lithium plating.

25 ENERGY STORAGE

Reversible Disorder-to-Order Transition Induced by Aqueous Lithiation in Vanadate Electrode Materials

Vanadium-based oxides are intriguing electrode materials in aqueous electrochemical systems owing to their low cost and high theoretical capacity for alkali storage, especially lithium (Li) ions. However, a sequence of phase transformations and irreversible structure distortion upon Li-ion intercalation causes structural instability and has been a lingering problem for vanadium oxide electrodes. Here, in this work, we investigate lithium vanadate (Li–V 3 O 8 ) for aqueous Li-ion intercalation and deintercalation processes. Unlike its crystalline V 2 O 5 polymorph, Li–V 3 O 8 retains monophasic lithiation, which is attributed to its disordered crystalline nature and large interplanar distance. Importantly, we show a unique and reversible sequence of disorder-to-order structural transition induced by the extent of lithiation, which indicates sequential interlayer and intralayer lithiation process, and vice versa in delithiation process, supported by electrokinetic analysis, in situ X-ray diffraction (XRD), and Debye scattering simulations. The absence of distortive phase transitions and multilithiation pathways facilitates Li-ion diffusion across the vanadate electrode materials to improve storage capacity. This work opens a new dimension for vanadium-based disordered oxides, accelerating the development of low-cost, aqueous electrochemical systems.

36 MATERIALS SCIENCE

Probing the role of local tunnel variations in early-stage lithiation of α-MnO₂ nanowires via in situ TEM

Understanding lithium-ion transport in tunnel-structured manganese oxides is essential for designing high-performance lithium-ion battery electrode materials. Here, we elucidate the early-stage lithiation mechanism of potassium-stabilized α-MnO 2 nanowires using in situ transmission electron microscopy (TEM) coupled with electron energy-loss spectroscopy (EELS), high-resolution TEM (HRTEM), and geometric phase analysis (GPA). Real-time TEM imaging reveals clear volume expansion at the reaction front, while EELS analysis uncovers lithium-ion diffusion far beyond this region, where no visible expansion is observed, indicating fast, defect-assisted transport. GPA and HRTEM analyses show that localized tensile and compressive strain fields, originating from pre-existing local tunnel structural variations, persist after lithiation. The tensile-strained regions enable lithium-ion insertion with minimal lattice distortion, offering additional free volume that facilitates rapid lithium-ion accommodation ahead of the structural transformation. Our results demonstrate a local tunnel variation-mediated fast diffusion pathway that precedes bulk reaction, underscoring the critical role of local strain in enabling early-stage lithium transport. Given the structural versatility of MnO 2 and its ability to accommodate diverse atomic arrangements beyond the well-known tunnel phases (β-, γ-, δ-, λ-, R-phases), our findings highlight the importance of understanding and engineering local structural environments. This work provides fundamental insights into the interplay between defects, strain, and ion dynamics, and presents defect engineering as a promising approach to enhance both rate performance and structural stability in manganese-based cathodes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND

Substitution-Mediated Calcination of Nickel-Based Cathodes: Decoupling Lithiation and Crystallization

Nickel-based layered cathodes such as LiNiO 2 offer high energy density for lithium-ion batteries, yet improvements in cycling performance and safety are required for practical use–often achieved through manganese and cobalt substitution as in LiNi 0.80 Mn 0.10 Co 0.10 O 2 (NMC811). However, how such substitution impacts calcination, the key process that governs lithiation, structural ordering, crystallization, and ultimately the resulting material properties, remains unclear. Here, in this study, we investigate substitution-mediated calcination dynamics in NMC811 compared to LiNiO 2 using multiscale-correlated in situ spectroscopy and atomistic-to-mesoscale modeling. While both systems progress through the same sequence of intermediates toward the thermodynamically favored layered phase, NMC811 exhibits an earlier onset of layering, concurrent with hydroxide decomposition followed by sluggish crystallization. Modeling reveals that Mn and Co lower the energy barrier for lithium incorporation and ordering but increase the penalty for interlayer gliding, thereby slowing crystal growth at elevated temperatures. This substitution-mediated decoupling of lithiation and crystallization explains the fine-grained microstructure observed in NMC811 versus coarsened particles in LiNiO 2 and establishes a mechanistic framework for predictive microstructure engineering of Ni-based cathodes.

Calcination

Structural, Electrochemical, and (De)lithiation Mechanism Investigation of Cation-Disordered Rocksalt and Spinel Hybrid Nanomaterials in Lithium-Ion Batteries

Significant demand for lithium-ion batteries necessitates alternatives to Co- and Ni-based cathode materials. Cation-disordered materials using earth-abundant elements are being explored as promising candidates. Here, in this paper, we demonstrate a coprecipitation synthetic approach that allows direct preparation of disordered rocksalt Li 2.4 Fe 1.0 Ti 1.0 O 4.7 (r-LFTO·C) and spinel structured hybrid Li 0.5 Fe 1.0 Ti 0.9 O 3.2 ·C (s-LFTO·C) nanoparticles with a conformal conductive carbon coating. High-angle annular dark-field imaging coupled with electron energy loss spectroscopy mapping shows uniform Fe/Ti distribution with minor compositional variation among particles. Cation disorder was confirmed for both of the materials at an atomic level, with a short-range order more pronounced in r-LFTO·C. Operando X-ray absorption spectroscopy, ex situ hard X-ray photoelectron spectroscopy, ex situ soft X-ray absorption spectroscopy, and ex situ synchrotron X-ray diffraction were used to investigate (de)lithiation in the bulk and at the surface. Structurally, the r-LFTO·C demonstrated reversible partial Fe center migration between octahedral and tetrahedral sites during (de)lithiation. The r-LFTO·C evidenced that the redox of O was coincident with iron redox during initial electrochemical cycling, while iron redox dominated later cycling. In contrast, s-LFTO·C electrochemistry involved iron redox throughout the cycling process. The findings rationalize the differences in the electrochemistry where r-LFTO·C shows higher initial capacity yet poorer capacity retention over a voltage window where O redox can be accessed, while the s-LFTO·C shows lower initial capacity yet improved capacity retention.

25 ENERGY STORAGE

Deuterium retention in pre-lithiated samples and Li–D co-deposits in the DIII-D tokamak

Divertor designs involving liquid lithium have been proposed as an alternative to solid designs and wall conditioning techniques. However, Li affinity with tritium poses a risk for the fuel cycle. This study investigates deuterium retention in pre-lithiated samples and Li–D co-deposits in the DIII-D tokamak, making for the first time a direct comparison between Li–D co-deposits and pre-deposited Li films. Samples were exposed to H-mode plasmas in the far scrape-off layer (SOL), and Li powder was injected in-situ with the impurity powder dropper to study the uniformity of Li coatings, and the dependence of fuel retention on Li thickness. The results show that at temperatures below the melting point of lithium, deuterium retention is independent of the thickness of pre-deposited Li layers, with Li–D co-deposits being the primary factor for fuel retention. Both pre-deposited and in-situ deposited Li showed lower erosion than predicted by sputtering yield calculations. These results suggest that fuel retention in fusion reactors using lithium in the divertor will likely be dominated by co-deposits rather than in the divertor itself. If one desires to use Li to achieve flatter temperature profiles, operando Li injection is advantageous over pre-deposited Li films, at least at temperatures below the melting point of lithium.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Voltage Mining for (De)lithiation-Stabilized Cathodes and a Machine Learning Model for Li-Ion Cathode Voltage

Advances in lithium-metal anodes have inspired interest in discovery of Li-free cathodes, most of which are natively found in their charged state. This is in contrast to today's commercial lithium-ion battery cathodes, which are more stable in their discharged state. In this study, we combine calculated cathode voltage information from both categories of cathode materials, covering 5577 and 2423 total unique structure pairs, respectively. The resulting voltage distributions with respect to the redox pairs and anion types for both classes of compounds emphasize design principles for high-voltage cathodes, which favor later Period 4 transition metals in their higher oxidation states and more electronegative anions like fluorine or polyanion groups. Generally, cathodes that are found in their charged, delithiated state are shown to exhibit voltages lower than those that are most stable in their lithiated state, in agreement with thermodynamic expectations. Deviations from this trend are found to originate from different anion distributions between redox pairs. In addition, a machine learning model for voltage prediction based on chemical formulas is trained and shows state-of-the-art performance when compared to two established composition-based ML models for material properties predictions, Roost and CrabNet.

25 ENERGY STORAGE

Decoupling Li out-diffusion and surface diffusion in the lithiation-assisted epitaxial growth of lithium tungstate

Lithiation-assisted epitaxy offers a flexible and robust approach for synthesizing high-quality Li-containing materials and interfaces with precise control. Here, in this study, we use lithium tungstate (Li x WO 3+x/2 , where x = 0 to 2) as a model system to investigate the intertwined effects of Li out-diffusion-induced compositional changes and surface-diffusion-induced morphological changes. By systematically varying synthesis and processing conditions, we uncover their impact on lithium tungstate film formation. Comprehensive characterizations, including X-ray diffraction, atomic force microscopy, X-ray photoemission spectroscopy and time-of-flight secondary ion mass spectrometry, reveal that low-temperature growth (< 300 °C) followed by high-temperature annealing yields continuous lithium tungstate films with significantly reduced surface roughness. In contrast, high-temperature deposition (≥ 300 °C) accelerates surface diffusion and Li out-diffusion, leading to island formation. Furthermore, in situ scanning transmission electron microscopy demonstrates the beam sensitivity of Li 2 WO 4 and reveals a phase transition from Li 2 WO 4 to LiWO 3.5 under prolonged electron beam exposure. These findings deepen our understanding of how to control composition and morphology of Li-containing films, providing valuable insights for the design and integration of energy materials.

Shi, Jueli [Pacific Northwest National Laboratory

The Sensitivity of Nickel Substitution in the Structural Design of Manganese-Based Layered and Lithiated Spinel Electrodes for Li-Ion Batteries

A concerted effort is being made at Argonne National Laboratory to explore and develop high-performance lithium-manganese-nickel-oxide cathode materials for the lithium battery industry. They are both energy- and cost-competitive relative to cobalt- and nickel-rich systems, such as LiCoO 2 , LiNi 0.8 Co 0.15 Al 0.05 O 2 , and LiNi 0.8 Mn 0.1 Co 0.1 O 2 . The recent discovery of the structural versatility of LiNi 0.5 Mn 0.5 O 2 , has revealed that it can exist in three configurations: lithiated spinel, partially disordered layered, and completely disordered rock salt within a common cubic-close-packed oxygen array. This versatility opens up the possibility of designing structurally integrated electrode components with interlinking 2-D (layered) and 3-D (spinel) channels for Li-ion transport. This paper highlights the sensitivity of Ni substitution and synthesis temperature on the structural and electrochemical properties of LiNi 0.50 Mn 0.50 O 2 , LiNi 0.53 Mn 0.47 O 2 , LiNi 0.47 Mn 0.53 O 2 , and LiNi 0.25 Mn 0.75 O 2 electrodes, as well as a cobalt-containing composition, LiNi 0.333 Mn 0.333 Co 0.333 O 2 , when synthesized at a relatively low temperature of 400 °C.

25 ENERGY STORAGE

Lithium–Divertor Interactions and Helium/Hydrogen Trapping in Lithiated Metals (Final Technical Report)

The goal of this project was to develop a fundamental understanding of helium and hydrogen behavior in lithium, both in bulk and at interfaces with tungsten, in order to inform the design of lithium based plasma facing components for fusion devices. Over the course of the award, the project produced the first comprehensive, peer reviewed dataset describing helium energetics, migration behaviors, and defect interactions in lithium. The research demonstrated that helium behaves in ways not previously observed in any other body centered cubic (BCC) metal: its interstitial configurations are more stable than substitutional ones, and its migration barriers are extraordinarily low, in some cases more than an order of magnitude below those in tungsten or iron. These discoveries reveal that helium in lithium diffuses so rapidly that its transport may be dominated by translational motion rather than the vibrationally activated mechanisms that underpin conventional solid state diffusion. This work lays a scientific foundation for understanding gas retention, bubble formation, and wall evolution in lithium based fusion environments and provides new computational tools, most notably a newly developed Li–He interatomic potential, for advancing future modeling efforts.

36 MATERIALS SCIENCE

Solid‐State Prealkylation of Electrode Architectures (SPEAR): Direct Control of Prelithiation Levels in Silicon Anodes and Electrochemical Cycling

The Solid-state Prealkylation of Electrode ARchitectures (SPEAR) is different than traditional electrochemical prealkylation processes. Through SPEAR, alkylation is driven by solid-state diffusion without the simultaneous SEI formation concomitant with polarization. Here, we investigate the prelithiation of 80 wt. % Si-based anodes to varying amounts (up to Li 1.38 Si) to understand the trade-off between improved Li capacity and expansion-induced stress. Through dilatometry, we found that solid-state lithiation led to filling of the electrode pores through silicon expansion. This swelling changed the SEI formation process and accessibility of the silicon compared to an electrochemically lithiated electrode. Indeed, optimal prelithiation to Li 0.82 Si increases the initial C/3 cycling capacity post-SEI formation up to 43%, consistent with deeper Si activation through the electrode bulk. Prelithiation and cycling cells prelithiated beyond Li 0.82 Si results in a state of charge (SOC) close to 100% which facilitates parasitic degradation mechanisms and volume expansion of the Si electrode. The results demonstrate a pathway to modify silicon activation/SEI formation to enable high-energy electrodes.

Musgrove, Amanda L. [Oak Ridge National Laboratory

Thermodynamic and Kinetic Mechanisms Governing the Synthesis of Nickel-Poor Cathodes

A deeper understanding of the thermodynamics and kinetics governing the lithiation and layering mechanisms of NMC cathode materials (LiNixMnyCozO 2 , where x + y + z = 1) offers valuable insights for enhancing synthesis methods and improving cathode performance. By employing atomistic and mesoscale approaches informed by in situ powder X-ray diffraction (PXRD) experiments, critical parameters for comprehending lithiation and layering processes and reaction rates were identified. The mesoscale approach captured the evolution of the phases and crystallite size observed in the in situ PXRD, revealing the differences in reaction rates with the use of different lithium salts and starting precursors. Ab initio molecular dynamics (AIMD) underscored the importance of vacancies and structural defects in promoting ion mobility and facilitating the nucleation of a layered domain. This nucleation disrupts the symmetry of disordered phases, ultimately creating a strained phase that serves as a buffer between layered and disordered regions. The lithiation and layering processes reflect a dynamic balance between the thermodynamic drive for a low-energy layered structure and the kinetic of diffusion, which is influenced by temperature and lithium vacancy concentration. Overall, reaction mechanisms are driven by the inherent defects of the intermediate phase that differ for NMC cathode materials. The lithium salts impact the rates of lithiation and layering, with a much slower process for Li 2 CO 3 .

25 ENERGY STORAGE

Compositionally Complex Spinel Oxides as Conversion Anodes for Lithium-Ion Batteries

Four different compositionally complex multicomponent M 3 O 4 spinels containing 5–8 distinct metals were prepared by a rapid combustion synthesis method or solvothermal synthesis. High resolution synchrotron X-ray diffraction patterns show that the materials consist primarily of spinel phases with small amounts of rock salt impurities, and, in several samples, a minor amount of contracted spinel phase. Materials were investigated as conversion anodes in lithium half-cells and delivered significantly higher capacities than two-component MgFe 2 O 4 made by combustion synthesis. X-ray absorption near-edge structure (XANES) was used to estimate the oxidation states of the metals in the pristine, lithiated (discharged) and delithiated (charged) materials to better understand the redox processes in half cells that led to the improvement. Co, Ni, and Zn are reduced to low oxidation states during lithiation (cell discharge) but are only partially oxidized. The presence of a conductive metallic network that forms after lithiation is thought to account for the improved electrochemical characteristics. Interestingly, in most of the samples, iron is not fully reduced during initial lithiation unlike what happens with a set of related high entropy spinel ferrites studied previously. Finally, the improved electrochemical properties of these materials illustrates both the advantages of complexity and the difficulties in predicting their behavior.

25 ENERGY STORAGE

Importance of $\delta B_{\|}$ on ETG stability, turbulence, and transport in NSTX

This study employs electron-scale gyrokinetic simulations to investigate the electron temperature gradient (ETG) driven instabilities, turbulence, and transport in the pedestal region of the National Spherical Torus Experiment, comparing non-lithiated (narrow pedestal) and lithiated (wide pedestal) scenarios. Our findings reveal that, in the non-lithiated case, a branch of strongly unstable ETG modes exhibiting finite parallel magnetic field fluctuations ($\delta B_{\parallel} \neq 0$) emerges at the pedestal top and upper density pedestal region. This branch is uncovered only when $\delta B_{\parallel}$ is retained in the simulations and is associated with substantial electrostatic electron heat flux. This region of strong ETG transport corresponds to the only region in the plasma where the pressure gradient is far below the critical gradient for kinetic ballooning modes. We investigated the origin of this finite $\delta B_{\parallel}$ ETG branch by analyzing the gyrokinetic field equations. Nonlinear saturation is also analyzed and contrasted for simulations with and without $\delta B_{\parallel}$. In contrast with the nonlithiated case, ETG modes in the lithiated case produce substantial transport in the steep gradient region, but are negligible at the pedestal top.

ETG

Superionic Surface Li-Ion Transport in Carbonaceous Materials

Unlike Li-ion transport in the bulk of carbonaceous materials, little is known about Li-ion diffusion on their surface. Here, in this study, we have discovered an ultrafast Li-ion transport phenomenon on the surface of carbonaceous materials with limited reversible Li insertion capacity and high surface area. An ionic conductivity of 18.1 mS cm –1 at room temperature is observed in lithiated Ketjen black (KB), far exceeding those of most solid-state ion conductors. Theoretical calculations reveal low diffusion barriers for the surface Li species. As a result, lithiated KB functions effectively as an interlayer between Li and solid-state electrolytes (SSEs) to mitigate dendrite growth. Further, lithiated KB acts as a high-performance mixed ionic–electronic conductor and replaces solid electrolytes to enhance graphite anode performance, demonstrating full utilization with ∼85% capacity retention over 300 cycles. The discovery of this surface-mediated ultrafast Li-ion transport mechanism provides new directions for the design of solid-state ion conductors and solid-state batteries.

Li metal batteries

Recent Developments in Lithium-Manganese-Nickel Oxide Electrochemistry: The Alchemy of LiMn 0.5 Ni 0.5 O 2

Efforts have been underway for some time at Argonne National Laboratory to design structurally integrated and stabilized lithium-manganese-nickel-oxide cathode materials. The goal has been to find a cobalt-free, high-capacity cathode for a Li-ion battery that is competitive, both cost- and energy-wise, with lithium-nickel-manganese-cobalt-oxide (NMC) and lithium-iron-phosphate (LFP) products. This brief synopsis highlights the remarkable alchemy of LiMn 0.5 Ni 0.5 O 2 resulting from its well-known, slightly disordered layered structure and the recently discovered lithiated spinel phase and totally disordered rock-salt configurations. All three arrangements share a structurally compatible cubic-close-packed oxygen array. The lithiated spinel and layered components provide an intersecting network of two- and three-dimensional channels that facilitate Li + -ion transport, while a minor amount of an extensively disordered rock-salt component likely serves to enhance the structural and electrochemical stability of the electrode. The synopsis also encompasses the historical development of lithiated spinel electrode materials and structurally integrated systems.

Thackeray, Michael M. [Argonne National Laboratory