bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring the Kinetics of Oxygen Reduction Reaction in Relation to Pitting Corrosion Resistance in Fe-Cr Alloys
Authors: Wang Ying , Blackwood Daniel John
Published: August 2024

Pitting corrosion, a major concern in materials science and engineering, threatens critical metallic structures and components. Its implications reach across daily life and industries such as energy, transportation, and infrastructure, potentially causing environmental harm, economic losses, and even loss of life. This complex process is influenced by factors including material composition, local environment, and mechanical stresses.1 Once initiated, pit propagation rates are largely dependent on the magnitude of the supporting cathodic current available from the oxygen reduction reaction (ORR) occurring on the external passive film.2 In Fe-Cr alloys, the ORR occurs on this film, undergoing a mixed diffusion and kinetic-controlled process. The number of electrons involved and the corrosion rate are determined by the thermodynamically stable state of the passive film.

This research studies the ORR kinetics on FeCr alloys fabricated by arc-melting, using both computational and experimental methods. The rotating disc electrode technique was employed across various Fe:Cr alloys in alkaline and neutral electrolytes. The Koutecky-Levich analysis showed a dominant four-electron ORR pathway in all tested Fe-Cr alloys, with the ORR significantly inhibited by higher proportions of Cr2O3 in the film, suggesting a correlation with high chromium content. Experimental ORR overpotentials, when combined with theoretical potential-pH (Pourbaix) diagrams, helped discern the likely characteristics of the passive films on the alloys. It was deduced that the catalytic properties of potential passive films increased in the order Cr2O3 < Fe3O4 < Fe2O3 < FeCr2O4. These findings, excellently aligned with density functional theory (DFT) modelling, underscore the role of increased chromium levels in slowing pitting progression by suppressing the ORR.

In summary, this research offers distinctive insights into the correlation between the kinetics of the ORR and the resistance to localized corrosion in Fe-Cr alloys, which enhances our understanding of the underlying mechanisms of pitting corrosion.

Keywords

FeCr alloy, pitting corrosion, ORR, rotating disc electrode, DFT

Reference

[1] B. Zhang, J. Wang, B. Wu, X. W. Guo, Y. J. Wang, D. Chen, Y. C. Zhang, K. Du, E. E. Oguzie, and X. L. Ma, Nat. Commun. (2018) 9, 2559.

[2] G. T. Burstein, P. C. Pistorius, and S. P. Mattin, Corros. Sci. (1993) 35, 57.
Modeling Silver Corrosion Mechanisms in Marine Atmospheric Environments
Authors: Policastro Steven A , Sanders Christine E. , Johnson Alexander , Santucci Raymond J , Hammond Mark H.
Published: August 2024

Measures that can assess the severity of the local environment are an important tool for combating atmospheric corrosion. One approach for determining the environmental severity employs electrochemical analysis alongside surface characterization on silver coupons exposed to the environment for varying durations. However, despite the long use of silver as an environmental severity monitor, the underlying reaction mechanisms that give rise to the observed corrosion products are not well understood. In addition, the measured ratios of silver corrosion products appear to be unique to the location where the silver coupons were exposed.

The goal of this work is to develop models of silver oxidation reactions that can explore pathways for the formation of silver corrosion products. We use density functional theory (DFT) calculations in nudged elastic band (NEB) approximations to determine electrochemical and chemical reaction along with surface diffusion energy barriers. An example reaction is shown in Figure 1a and b, in which an O2 molecule is adsorbed on an ‘on-top’ site on a relaxed Ag (100) crystal structure with periodic boundary conditions in the x and y-planes. The O2 molecule then dissociates into individual O atoms. The reaction pathway is approximated using the NEB approach to determine the dissociation energy barrier in Figure 1c. These reaction energy barriers are incorporated into a kinetic Monte Carlo (KMC) model of silver reactions to estimate the corrosion products present in marine atmospheric environments for comparison with experimental data.

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(Invited) Experimentally Measuring the Role of Ion-Phonon and Ion-Electron Correlations in Solid-State Li Ion Conductors
Authors: Cushing Scott K , Pham Kim , See Kimberly
Published: August 2024

In superionic conductors, ion hopping involves a complex interplay of ion-phonon, ion-electron, and ion-ion correlations that is challenging to measure experimentally. In this presentation, we present a new experimental technique that can directly measure ultrafast ion hopping on its inherent picosecond and longer timescale. The technique works by measuring the time-resolved perturbation to a GHz impedance signal when potential ion-coupling interactions are driven with UV to THz irradiation. High-bandwidth, real-time electronics allow synchronization of the impedance measurement to ultrafast laser pulses for varying carrier frequencies. The result of the measurement is the relative strength of different correlations in the many-body ion hopping Hamiltonian. We demonstrate the technique on Li0.5La0.5TiO3 (LLTO) and single crystalline Li7La3Zr2O12 (LLZO), both solid-state Li+ conductors. The ultrafast laser-driven impedance measurements reveal that the dominant ion hopping mechanism in LLTO is through a coupled phonon-ion THz rocking mode. Although this higher frequency mode is less than one-quarter of the overall phonon density of states, it leads to the majority of ion hops as compared to other optical and acoustic phonon modes. Metastable states lasting tens of minutes were also measured for ion-electron perturbations. Further work on extending the technique to measure ion-ion correlations is currently underway. In general, the new technique applies to any complex ion conducting system such as polymers, fuel cells, supercapacitors, and membranes.
(Invited) Model-Based BMS for Current and Next-Generation Batteries
Authors: Subramanian Venkat R.
Published: August 2024

Fast charging is researched heavily for the widespread implementation of lithium-ion batteries for electric vehicles. However, charging at high currents accelerates several parasitic reactions that lead to the degradation of the cell, affecting its lifetime. These reactions lead to loss of lithium inventory, loss of active material, and increased impedance in the cell. Examples of these side reactions include the growth of the solid-electrolyte interphase (SEI) layer, transition metal dissolution and deposition, lithium plating, solvent oxidation, etc. These mechanisms degrade the cell and reduce its cycle life.

Physics-based multi-scale battery models solve for equations that govern the charge and mass balances within the cell. Using these detailed mathematical models, it is possible to study material degradation mechanisms and predict their impact on capacity loss under several operating conditions. These models can be used to design new batteries with appropriate materials and design parameters suited for any given purpose.

More critically, these models can be integrated with battery management systems (BMS) to control the cell’s performance. These models can further be used to design novel charging protocols that enable safe and optimal cell performance and suppress cell material degradation. The BMS monitors and maintains the voltage, current, and temperature and estimates the internal states of the cell. Model-based BMS algorithms require fast codes that can predict and estimate battery parameters in real-time and control the battery’s performance under different loads.

Currently, the BMS implements equivalent circuit models that inadequately predict the cell’s performance for various conditions and design parameters. This talk presents the current efforts to move the models for BMS for current and next-generation batteries for single-cell to pack-level simulations.

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(Digital Presentation) Reactive Evaporation of Cr Vapors from Chromia-Alkaline Oxide Mixtures Generated in 800℃ Air and Subsequent Condensation Onto Aluminosilicate Fibers
Authors: van Leeuwen Travis Kent , Guerrero Amberly , Dowdy Ryan , Satritama Bima , Rhamdhani Akbar , Will Geoffrey , Gannon Paul
Published: August 2024

This research aims to improve fundamental understanding of the reactive evaporation and condensation of Chromium (Cr) vapors, which are generated from Cr containing alloys used in many high-temperature (>500℃) process environments and can form potentially problematic condensed hexavalent (Cr(VI)) species downstream. This study focuses on the effects of alkaline oxides present in the Cr source on the resultant Cr evaporation and condensation. Vapor species were generated by flowing high-temperature (800℃) air containing 3% water vapor over chromia (Cr2O3) and mixtures of chromia with calcium oxide (CaO) or magnesium oxide (MgO) powders. Lab-grade quartz and alumina fiber samples were positioned downstream from the Cr-alkaline oxide source where the temperature decreases (<500℃) to collect condensed vapor species. Total condensed Cr and ratios of oxidation states were measured using inductively coupled plasma optical emission spectroscopy (ICP-OES) and diphenyl carbazide (DPC) colorimetric/direct UV-VIS spectrophotometric analyses. Preliminary results indicate a decrease in partial pressures of generated Cr vapor species as well as a decrease in condensed Cr species on the aluminosilicate fibers when alkaline oxides are present in the Cr source compared to a pure Cr source. These results also indicate presence of hexavalent Cr (Cr(VI)) species condensed on all samples investigated. Computational thermodynamic equilibrium modelling corroborated the experimental results showing partial pressures of produced vapor species in the presence of alkaline oxides as well as stabilities of condensed Cr compounds on the fiber samples. Comparative results and analyses are presented and discussed to help inform mechanistic understanding and future related research and engineering efforts.

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CMP: Four Decades of Innovation and a Promising Future
Authors: Canaperi Donald
Published: August 2024

The invention of CMP by IBM in 1983 represents an inflection point in the evolution of semiconductors. It was a bold and risky idea to mechanically apply abrasives to the surface of a wafer, but this new process for restoring a wafer to a planar state was the key to continued areal scaling and increased device complexity. Initially applied to a simple application for filling trenches with insulator, the potential of this technique was evident. Through understanding of material properties and subsequent manipulation of slurry chemistry, CMP was applied to enable the more challenging and technically critical processes for Shallow Trench Isolation and Tungsten contacts. The late 1990’s saw the introduction of copper interconnects. IBM was first to market this technology which continues to support conductors down to lines widths on the order of 10 nanometers! The CMP process required for copper interconnects demanded a thorough understanding of the materials present and potential surface phenomena for exploitation. For this need, a new and complex mechanism for copper planarization was invented. Equally challenging was the need for a subsequent non-selective barrier removal step. For this a unique, self-balancing approach was also invented, borrowing some elements from previous STI technology.

Device architecture has progressed from planar geometry to FINFETs to Gate All Around, or Nanosheet technology. This evolution has required increasingly more CMP process steps with a concurrent demand for increased process control. Gate height control for Nanosheeets is currently paramount for performance, affected by many CMP steps in the process flow. A typical requirement is less than 1nm added variability per CMP step!

Looking forward, CMP continues to be tapped to enable technology evolution. Polish steps are becoming part of the patterning process to enable pitch splitting for upcoming nodes. A VTFET integration approach can enable further area scaling but presents integration challenges; CMP is being asked to enable “third color” schemes for the protection of NFET vs PFET devices which is necessary at various points in the in the VTFET process flow. Heterogeneous Integration is demanding nanometer control of topography across large contact pads and large lateral distances. Finally, extreme scaling is creating fundamental challenges for metal polish at the contact and interconnect levels. CMP tool architecture currently does not provide for control of ambient conditions at the wafer surface during wet transport and post CMP cleaning. Subsequently, unwanted metal dissolution is observed. New tool designs will be needed to control wafer surface conditions, and particularly oxygen exposure through all steps within the CMP tool.

This talk is dedicated to the special session in honor of Professor S.V. Babu
(Invited) Doping Mechanisms and Defect Passivation of p-Type SnOx for Tfts and Bipolar Devices
Authors: Lee Dong Hun , Song Han Wook , Lee Sunghwan
Published: August 2024

Despite the outstanding achievements in multiple areas such as displays and energy, oxide electronics has been limited to single-polar (n-type) applications due to the facile generation of oxygen vacancies as native donors. On the contrary, the processing of p-type oxides is restrained due to the high formation energy of native acceptors. Furthermore, the oxygen 2p orbitals of the majority of oxide semiconductors are anisotropic and localized to the valence band maximum (VBM), resulting in a large effective mass of holes and hence low carrier mobility.

Hybrid orbital electronic configurations with cation d10 (closed shell structure) and cation s2 (pseudo-closed structure) have been suggested initially in complex oxides (e.g., CuMO2 where M= Al, Ga, and In; and SrCu2O2) to delocalize the oxygen 2p orbitals from the VBM. However, these complex oxides require high temperatures to process and are difficult to engineer the electrical properties of carrier density and carrier mobility due to the correlated nature of multi-cation species. Several single-cation p-type oxides such as PbO, Bi2O3, and SnO have emerged as well, where the energy level of a unique s-orbital of cations is similar to oxygen 2p orbitals, forming strong hybrid structures. In addition, a simpler single-cation structure leads to easier control of electrical properties required in practical device applications such as thin film transistors (TFT) and complementary logic inverters.

We previously reported scalable processing of p-type SnOx through thermodynamic-based interfacial reactions as well as reactive sputtering.1 More recently, we also suggested multi-modal encapsulation to enhance TFT on- and off-state behaviors and identified a defect complex as an effective p-type doping agent.2 However, challenges remain since the TFT off-state current is large, and the defect/trap state density is high.

In this presentation, we share our approaches to engineer the off-state current and passivate the defect/trap states. In addition to channel thickness optimization, intrinsic (Sn vacancy or oxygen interstitial) and extrinsic (H-related species) doping strategies to adjust channel carrier density will be compared. The performance of several surface treatments (oxygen plasma and UV) and TFT back channel encapsulations (SiO2 and Al2O3) will be systematically compared. Then, the device performance of optimized p-type SnO TFTs and complementary inverters with n-type InZnO TFTs will be discussed.

References

Lee et al., ACS Applied Materials & Interfaces, 13 (46), 55676–55686 (2021)

Lee et al., ACS Applied Materials & Interfaces, 14 (48), 53999–54011 (2022)

Acknowledgments

This work was partially supported by National Science Foundation, Award number ECCS-1931088 and CBET-2207302.
(Invited) Nitrogen Based Solid State Magneto-Ionics
Authors: Jensen Christopher , Chen Zhijie , Quintana Alberto , Quarterman Patrick , Grutter Alexander , Balakrishnan Purnima , Zhang Huairuo , Davydov Albert , Liu Chen , Zhang Xixiang , Liu Kai
Published: August 2024

Solid-state magneto-ionic (MI) effects have shown promise for energy-efficient nanoelectronics, where ionic migration may be used to achieve atomic-scale control of interfaces in magnetic nanostructures. To date, magneto-ionics have been mostly explored in oxygen-based systems [1-4], while there is a surge of interest in alternative ionic systems due to their different ionic migration mechanisms and characteristics [5-7].

We have recently demonstrated effective MI control of magnetic functionalities using a variety of ionic species, particularly nitrogen. In nitride-based Ta/CoFe/MnN/Ta films, the chemically induced MI effect is combined with the electric field driving of nitrogen to electrically manipulate exchange bias [8]. Upon field-cooling the heterostructure, ionic diffusion of nitrogen from MnN into the Ta layers occurs. A significant exchange bias is observed, which can be further enhanced by ~ 20% after voltage conditioning (Figs. 1a-1e). This enhancement can be reversed by voltage conditioning with an opposite polarity. Nitrogen migration within the MnN layer and into the Ta capping layer causes the enhancement in exchange bias, which is observed in polarized neutron reflectometry studies.

We have also achieved all-nitride-based magneto-ionic systems [9]. Thin films of (001)-ordered Mn4N are grown by sputtering Mn onto Mn3N2 seed layer on Si (100) substrate. Nitrogen ion migration across the Mn3N2 /Mn layers leads to a continuous evolution of the layers to Mn3N2 /Mn4N, Mn2N/Mn4N, and eventually Mn4N alone (Figs. 1f-1g). Furthermore, we have demonstrated MI control of the exchange bias effect in an all-nitride Mn4N/MnNx system, where the field-trained exchange field can be varied up to ten times by introducing or extracting nitrogen from the nitride system. This is achieved by adjusting the nitrogen gas partial pressure during deposition or varying annealing temperature after deposition.

These effects demonstrate contrasts with oxygen-based MI effects in terms of operating principles, switching speed, and reversibility. Such MI systems are valuable platforms to gain quantitative understanding at buried interfaces. They also offer potentials for device applications based on electric modulation of magnetic functionalities.

This work has been supported in part by the NSF (ECCS-2151809, DMR-2005108, DMR-1828420), SRC/NIST SMART Center, and KAUST.

[1] U. Bauer et al., Nat. Mater. 14, 174 (2015).

[2] C. Bi et al., Phys. Rev. Lett. 113, 267202 (2014).

[3] D. A. Gilbert et al., Nat. Commun. 7, 11050 (2016).

[4] G. Chen et al., Sci. Adv. 6, eaba4924 (2020).

[5] A. J. Tan et al., Nat. Mater. 18, 35 (2019).

[6] G. Chen et al., Phys. Rev. X 11, 021015 (2021).

[7] J. de Rojas et al., Nat. Commun. 11, 5871 (2020).

[8] C. J. Jensen et al., ACS Nano 17, 6745 (2023).

[9] Z. J. Chen et al., Appl. Phys. Lett. 123, 082403 (2023).

Figure 1
Mechanistic Understanding of the Role of Bis(4-nitrophenyl) Carbonate (BNC) As Additive on the Solvation Structure and Polysulfides Shuttling Effect Towards Capacity Improvement in Lithium-Sulfur Batteries
Authors: Dai Huidong , Bak Seongmin , Gomes Luisa Larissa Arnaldo , Yang Kevin , Maxwell Derrick , Badhrinathan Srinidi , Du Yonghua , Pandey Gaind P. , Mukerjee Sanjeev
Published: August 2024

The lithium-sulfur (Li-S) batteries are considered as one of the most promising devices for next-generation energy storage applications, owing to its exceptional theoretical capacity and energy density. However, persistent challenges have hampered its performance, notably the sluggish polysulfides conversion kinetics and the polysulfides shuttling phenomenon. These issues lead to irreversible active material loss, rapid capacity decay, low coulombic efficiency, and a limited cycle life. This study demonstrates that bis(4-nitrophenyl) carbonate (BNC) can serve as an effective agent in anchoring dissolved polysulfides, thereby preventing their migration to the anode. Furthermore, this investigation indicates that BNC has the capability to modify the solvation structure of polysulfides in the electrolyte. The presence of 0.01M BNC induces a downfield shift in the 7Li NMR spectrum, signifying a strengthened solvation structure on Li-ion. This solvation modification results in altered kinetics, specifically a reduced Li2S2/Li2S conversion without sacrificing capacity, as confirmed by operando X-ray absorption spectroscopy (XAS). Operando Raman spectroscopy reveals the suppression of long-chain polysulfides (at 400 cm-1) and intermediate polysulfides (at 453 cm-1) with 0.01M BNC, mitigating sulfur shuttling to the anode. This observation is corroborated by X-ray fluorescence (XRF) mapping. Analysis of the corresponding X-ray absorption near-edge structure (XANES) demonstrates that both anodes and cathodes with 0.01M BNC exhibit lower levels of unconverted polysulfides over extended cycles. This improvement is attributed to the kinetic consequences resulting from solvation structure alteration. However, this investigation cautions against an indiscriminate increase in BNC concentration, as higher concentrations may lead to the over-conversion of soluble polysulfides. This nuanced understanding of the solvation structure's intrinsic mechanism, coupled with chemical reactions, provides valuable insights for practical design of Li-S batteries

Figure 1
(Invited) From Inside Out: How Synthesis-Structure Correlations Conspire to Determine Photoluminescence Traits and Operational Robustness in Non-Blinking Giant Quantum Dots
Authors: Hollingsworth Jennifer Ann
Published: August 2024

“Giant” or thick-shell core/shell quantum dots (gQDs) are an important class of solid-state quantum emitter. Without any encapsulation gQDs are characterized by strongly suppressed blinking, or even non-blinking behavior, and resistance to photobleaching at room temperature. In addition, non-radiative Auger processes are significantly reduced in this class of luminescent nanomaterial. Together, these qualities lead to novel functionality as photon sources for a range of ensemble and single-emitter applications, including down-conversion phosphors, direct excitation light-emitting diodes, single-biomolecule tracking, and single-photon generation. For many applications, operation at elevated temperature and under intense photon flux is also desired, and we have shown that gQDs outperform other emitters in this key metric of operational robustness. Interestingly, performance under these conditions is strongly dependent on the synthetic method employed for shell growth. Previously we revealed the mechanistic pathways responsible for thermally-assisted photodegradation, distinguishing effects of hot-carrier trapping and QD charging (ACS Nano 2018, 12, 5, 4206), and subsequently used solid-state spectroscopy to obtain kinetic and thermodynamic parameters of the photothermal degradation process (ACS Appl. Mater. Interfaces 2020, 12, 27, 30695). Here, I will discuss a comprehensive analysis of gQD structural properties from the inside of the nanocrystal to its surface and demonstrate correlations between specific structural features and both causal synthetic parameters and resulting performance metrics. Two synthetic methods—successive-ionic-layer-adsorption-and-reaction and high-temperature continuous-injection—will be compared. Investigated structural features will include interfacial alloying, stacking-fault density and surface-ligand identity, while correlated functionalities will address quantum yield, single-gQD photoluminescence under thermal/photo-stress, charging behavior and quantum-optical properties. I will show several unexpected conclusions, including the surprising finding that while interfacial alloying is the strongest indicator of gQD stability under stress, the parameter is not the determining factor for Auger suppression. Furthermore, quantum yield is strongly influenced by surface chemistry and can approach unity even in the case of a gQD comprising a thick shell with a high defect density with proper choice of excitation wavelength. Interestingly, we find a strong correlation between the existence of zinc-blende stacking faults and whether the gQD exhibits charged-state or purely excitonic emission, and the interplay between charged emission and excitonic emission can be precisely tuned by “mixing” shell-growth methods (Small Sci. 2023,3, 2300092).
(Invited) Epitaxial III-V Nanomaterials on the Si Platform for Quantum and Data Communications
Authors: Lewis Ryan B.
Published: August 2024

As Si-based integrated photonic components begin to replace older technologies for optical data communications, the need for better integration of semiconductor lasers on the Si platform is greater than ever. In addition, emerging interest in integrated-photonic-based quantum computing and quantum sensing presents a further need for quantum light emitters—entangled and single-photon—on Si. III-V quantum dots represent a promising solution, both for the active region of telecommunications-wavelength lasers and for quantum emitters. However, epitaxial quantum dots grown on conventional (100) substrates typically lack the high symmetry required for entangled-photon emission.

This presentation will discuss our recent work to develop a novel approach for III-V direct growth on Si via an ultrathin (<10 nm) single crystal strain relieving buffer layer, realized by the selective oxidation and condensation of an amorphous SiGe surface layer. The fabrication and properties of this novel Ge-rich buffer layer, as well as its use for subsequent III-V organometallic vapor-phase epitaxy will be presented.

The second part of the talk will present our recent work on the epitaxial growth and characterization of (In,Ga)As quantum dots for the above-mentioned applications. Specifically, I will show that surface-energy-modifying surfactants (Sb, Bi) present the possibility to externally direct quantum dot formation “on-demand” in strained InAs layers on GaAs(111) substrates, where quantum dot formation by the Stranski–Krastanov process does not naturally occur. These nanostructures are prospective for high-symmetry entangled-photon emitters. The three-dimensional (3D) composition profile of InAs quantum dot layers is characterized by atom-probe microscopy (APT), elucidating the real-world quantum dot matrix. This 3D composition data is input into a finite element solver to determine the quantum dot energies and wavefunctions for electrons and holes. The modeling reveals that in high-density quantum dot layers, the electron and hole states are hybridized between multiple quantum dots in the matrix. This has important consequences for design of quantum dot light emitters. The predicted transition energies are in agreement with low-temperature photoluminescence. This work constitutes a promising approach for integrating telecommunications-wavelength quantum dot lasers and entangled photon emitters on the Si integrated photonics platform.
(Invited) Quantitative Photonic Characterization and Modelling of Light Emission, Confinement, and Enhancement in Nanostructured Materials
Authors: Zapien J Antonio , Foo Yishu , Phoo May Thawda , Huqe Md Rashedul , Zhang Yun , Kwong Yee Man
Published: August 2024

Optical spectroscopy and imaging provide non-destructive, contactless, and fast strategies to study the nature and technological aspects of thin films and nanostructured materials for photonic and optoelectronic applications. Furthermore, the design, engineering, and optimization of such devices requires quantitative information with high-precision standards in measuring and modelling as is the case, for example, in the determination of the optical critical dimension (OCD) in the semiconductor industry. Our application of these strategies to the study of tunable self-assembled nanolasers, hybrid photonic-plasmonic sensors, and photovoltaic devices, among many other materials and devices has led us to the development of i) new modelling strategies based on the Finite-Difference Time-Domain (FDTD) method, and ii) home-made customizable characterization strategies based on spectroscopic ellipsometry (SE). The advantages of the FDTD method include its ability to i) obtain a wide spectral response from one time-domain simulation, ii) model single non-periodic structures, and iii) flexibility and generality to include, for example, non-linear and thermal effects. On its part, SE stands out from other optical techniques because, as a self-referenced and phase sensitive strategy, it can deliver extreme precision and sensitivity and has demonstrated flexibility that has been implemented in multiple spectral ranges and operation conditions. With this in mind, our group has systematically demonstrated the synergic use of FDTD-SE strategy, with complementary strengths and close-matched precision, in a range of materials and devices. We will report the fundamentals, status of our on-going efforts, and a critical review of the perceived limitations and expected outcomes of the FDTD-SE strategy as a quantitative tool for photonic and plasmonic subwavelength structures of interest in optoelectronic, sensing, and energy applications.

We gratefully acknowledge the financial support from the RGC (Projects CityU - 11210218, 11219919, 11215121 and 11310122) and ITC (Project ITS/461/18) of HKSAR, China.
(Invited) Chiral Metamaterials for Polarized Photoluminescence
Authors: Ferry Vivian
Published: August 2024

Metasurfaces offer compact routes to spatial and polarization control of luminescence from nearby emitters, enabling applications ranging from document security to stereoscopic displays to sensing.

Most of the time, light-emitters are distributed evenly across the surface. This talk will discuss an alternate approach, where we use direct-write electron beam lithography to pattern semiconductor nanocrystals into targeted shapes and locations, creating a highly tailored metasurface. We use a combination of nanoscale fabrication, Fourier-space photoluminescence measurements, and computational methods to study the circularly polarized photoluminescence from these designer structures.

We will discuss the influence of patterning on the resulting optical properties, including the effects of spatial averaging and dipole orientation. We will then show an optimization strategy to produce highly polarized light at chosen angles of outcoupling. The final part of the talk will discuss adding layers of complexity, including the chirality of the underlying pattern, and creating light-emitting solids from intrinsically chiral semiconductor nanocrystals.
Development of High-Performance Cathodes for Inorganic Halide All-Solid-State Li-Ion Batteries
Authors: Deng Sixu
Published: August 2024

Electric vehicles (EVs), representing the future of transportation, are predicted to be one of the ultimate solutions to eliminate greenhouse gas emissions. Li-ion batteries (LIBs), as the most promising sustainable energy devices, are critical for the development of EVs because of their higher operating voltages compared to other energy storage technologies. However, the development of conventional LIBs touched the ceiling because of three main challenges. (1) The use of flammable and toxic liquid electrolytes brings high safety risks. (2) The limited energy density of LIBs cannot satisfy the requirement for long-range EVs. (3) The increasing market demand for LIBs will cause resource shortage and rise of cost.[1] Accordingly, all-solid-state Li-ion batteries (ASSLIBs) have recently emerged as promising alternative batteries for next-generation EVs because of their ability to overcome the drawbacks of conventional LIBs. Among the developed solid-state electrolytes (SSEs), inorganic SSEs (e.g., sulfide SSEs, halide SSEs) have high Li+ conductivity at 10-3 S cm-1 and improved interfacial stability, demonstrating stable cycling performance in ASSLIBs.[2] However, inorganic ASSLIBs still face some key challenges hindering their application in EVs. For example, the rate capability of inorganic ASSLIBs still falls far below the requirements of fast-charging EVs (full-charged in 15 min). In addition to the effect of Li+ conductivity in SSEs, Li+/e- transfer kinetics at the cathode interface and in cathode materials are also critically important for the high-rate capability of inorganic ASSLIBs. In this talk, I will first review our previous studies on cathode interface in inorganic ASSLIBs.[3-7] After that, I will introduce our most recent research on unveiling the kinetic limitation of cathode interfaces in inorganic ASSLIBs by synchrotron-based spectromicroscopy. Our research suggests that poor Li+/e- transfer kinetics at the cathode/SSE interface and in the cathode bulk structure are the key limitation for the low capacity of inorganic ASSLIBs under high-rate charge-discharge cycles.

References

[1] H. Li, Joule, 3 (2019) 911-914.

[2] S. Randau, D.A. Weber, O. Kötz, R. Koerver, P. Braun, A. Weber, E. Ivers-Tiffée, T. Adermann, J. Kulisch, W.G. Zeier, Nature Energy, 5 (2020) 259-270.

[3] S. Deng, X. Li, Z. Ren, W. Li, J. Luo, J. Liang, J. Liang, M.N. Banis, M. Li, Y. Zhao, Energy Storage Materials, 27 (2020) 117-123.

[4] S. Deng, Y. Sun, X. Li, Z. Ren, J. Liang, K. Doyle-Davis, J. Liang, W. Li, M. Norouzi Banis, Q. Sun, ACS Energy Letters, 5 (2020) 1243-1251.

[5] S. Deng, Q. Sun, M. Li, K. Adair, C. Yu, J. Li, W. Li, J. Fu, X. Li, R. Li, Energy Storage Materials, 35 (2021) 661-668.

[6] S. Deng, M. Jiang, N. Chen, W. Li, M. Zheng, W. Chen, R. Li, H. Huang, J. Wang, C.V. Singh, Advanced Functional Materials, 32 (2022) 2205594.

[7] S. Deng, M. Jiang, A. Rao, X. Lin, K. Doyle‐Davis, J. Liang, C. Yu, R. Li, S. Zhao, L. Zhang, Advanced Functional Materials, 32 (2022) 2200767.
Development of High-Performance LLZO Separators for Solid-State Batteries: Balancing Li Loss, Stability, and Morphology in a Tape Casting Process
Authors: Touidjine Kaouther , Rosen Melanie Finsterbusch , Kiyek Vivien , Ganapathy Swapna , Finsterbusch Martin , Guillon Olivier , Huijben Mark , Kelder Erik , Wagemaker Marnix , Fattakhova-Rohlfing Dina
Published: August 2024

Ceramic solid-state batteries (SSBs) are considered a viable alternative to lithium-ion batteries with liquid electrolytes, as they offer greater safety at the cell level. The Li7La3Zr2O12 garnet (LLZO) is a promising solid electrolyte for SSBs due to its stability with lithium metal anode and its good ionic conductivity of up to 2 mS cm-1. However, scalable and economically feasible techniques for producing LLZO-based batteries are required to make them competitive in the market.

Tape casting is an industrially scalable process for producing customizable ceramic components. Successful implementation of this method requires a deep understanding of the transformation of the LLZO powder during the whole process chain, especially the effects of Li loss due to air and protic solvents interaction as well as Li evaporation during sintering.

In this talk, a novel approach for fabricating thin LLZO ceramic separators by tape casting will be presented, in which lithium saltis used as a lithium mediator source in different process steps to optimize the separator properties. Using XRD, Raman spectroscopy, NMR spectroscopy, and SEM, we systematically investigate the effects of material composition and process conditions on the compositional and electrochemical performance of tape-cast LLZO separators in symmetric cells. This research provides important insights for optimizing the manufacturing process and enables the development of high-performance LLZO ceramic separators for all-solid-state batteries.
Ab Initio Tomography Analysis of Lithium Incorporation and Diffusion in Multidomain Silicon Suboxide Anode Materials
Authors: Chae Somin , Lim Hyung-Kyu , Lee Sangheon
Published: August 2024

Silicon is considered a promising anode material to supplant conventional graphite materials in lithium-ion batteries due to its higher theoretical energy-storage capacity compared to graphite. However, the widespread application of Si anodes has been hindered because the capacity of Si anodes decreases rapidly as the charge/discharge cycle proceeds. The controlled incorporation of oxygen into Si is often considered as a feasible approach for employing Si as an anode material in the form of silicon suboxide. Silicon suboxide exhibits a lower energy capacity compared to pure Si, but offers enhanced stability against volume expansion. Consequently, silicon suboxide materials have been commercialized by blending them with graphite. However, the blending ratio of silicon suboxide with graphite is limited to low levels due to its poor first-cycle efficiency, so-called initial Coulombic efficiency. In-depth understanding of the lithium interaction characteristics within multidomain silicon suboxide is indispensable for optimizing the electrochemical performance of silicon suboxide anode materials for lithium-ion batteries. In this study, we investigate the domain-dependent thermodynamic and kinetic properties of lithium atoms within systematically designed multidomain silicon suboxide models composed of Si, SiO2, and Si/SiO2 interface by performing a series of computational simulations combined with a unique tomography-like sampling scheme. We find that the Si/SiO2 interfacial region exhibits preferential thermodynamics and kinetics for lithiation and can serve as a critical lithium transport channel during charge-discharge cycles, while the SiO2 domain is likely to be excluded from lithiation due to its high resistance to lithium diffusion. Consequently, a significant fraction of lithium is expected to be trapped at the Si/SiO2 interface during the discharge process, which ultimately contributes to a low initial Coulombic efficiency. This theoretical understanding suggests that the formation of continuously connected lithium-transportable Si/SiO2 interfacial channels surrounding the Si domains, along with a well-structured shallow SiO2 framework through the use of appropriate synthesis methods, is essential for maximizing the electrochemical performance of silicon suboxide anode materials. Our theoretical approach offers new insights into the atomistic characteristics of silicon suboxide during lithiation/delithiation processes, ultimately enabling the identification of the origin of low ICE and strategies for addressing it.

References

(1) Chae, S.; Lim, H.-K.; Lee, S. Energy Landscapes for Lithium Incorporation and Diffusion in Multidomain Silicon Suboxide Anode Materials. ACS Applied Materials & Interfaces
2023, 15 (49), 57059-57069. DOI: 10.1021/acsami.3c12846.

Figure 1
Boron-Doped Carbon Scaffold Hosts for Li Metal Batteries
Authors: Freyman Megan C. , Li Sichi , Zhu Cheng , Wang Bo , Xiao Yiran , Wood Marissa
Published: August 2024

Lithium metal anodes offer the promise of higher energy density batteries. However, the formation of lithium dendrites due to non-uniform plating and stripping of the lithium metal has proven to be a major hurdle for this technology, decreasing the lifetime of the device and causing safety hazards. Utilizing a carbon scaffold host for the lithium metal anode can limit dendrite formation by providing a more uniform electric field and numerous lithium nucleation sites to encourage uniform plating and stripping. In this poster, we present our work developing carbon scaffold hosts for lithium metal anodes. We synthesized scaffolds with various architectures and microstructures using different carbon materials. Our atomistic simulations demonstrated that the addition of boron to the carbon results in stronger binding of lithium to the carbon surface, further improving the lithiophilicity. Therefore, we also prepared boron-doped carbon scaffolds to test this experimentally. Boron was introduced using boric acid and incorporated into the carbon structure during carbonization under nitrogen, and these samples were characterized by XPS, SEM, and BET to try and correlate scaffold properties with performance. In addition, we are investigating other dopants (such as nitrogen), which have also been reported to increase the lithiophilicity of carbon materials. Utilizing these doped carbon scaffolds can help increase the lifetime of lithium metal batteries by improving the cycling uniformity.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344
The Effect of Heat Treatment on PFO-Based Graphite Structure for High-Performance Anode Material
Authors: Lee Jong Dae
Published: August 2024

Lithium-ion batteries (LIBs) have strong advantages due to their outstanding energy density levels, high-voltage capabilities, and lightweight composition. One of the most commonly used anode materials in LIBs is graphite, which exhibits high electrical conductivity, good thermal conductivity, and electrochemical stability and can exist in either its natural or artificial form. The charge/discharge characteristics and the capacity retention rate of a carbon anode in a LIB system were studied, considering the impact of heat treatment temperature on a carbon structure. First, the carbon anode is synthesized by heat treatment of petroleum fuel oil (PFO), at 440 ℃ for 1 hour in a domestic refinery to prepare a carbon precursor (4401P), followed by the heat treatment of the pitch at the temperature ranging from 1,000 to 2,400 ℃. The PFO-based pitch was carbonized to a soft carbon in the temperature range from 1,000 to 1,700 ℃, whereas the PFO-based pitch was graphitized in the temperature range from 2,100 to 2,400 ℃. Next, the structural properties of the preparedPFO-based carbon anode are analyzed by ex-situ XRD patterns to investigate Li-ion intercalation/de-intercalation with different charging C-rates. The carbonized anode produced at 1200 ℃ had an amorphous structure and cavities on the surface. Since most of the lithium ions were conserved in cavities and defects, there was a small structural change so that the discharge capacity of the carbonized anode decreased by 13 % from 0.1 C to 20 C. On the other hand, the discharge capacity of the graphitized anode produced at 2,400 ℃ decreased by 40 % from 0.1 C to 20 C due to different structural behavior of the graphitized anode. The graphitized anode formed an interlayer structure where 91 % lithium ions are inserted between the layers of the graphite at 0.1 C so that the thickness of a stack expanded from 286.96 Å to 346.28 Å, whereas the structure of the graphitized anode did not change at 20 C. Furthermore, the cycle retention of the carbon anodes with different heat treatment temperatures is at 1 C for 100 cycles. The carbonized anode produced at 1,200 ℃ and the graphitized anode produced at 2,400 ℃ showed cycle retention performance of 73 % and 90 %, respectively, indicating the high stability of the graphitized anode.
The Voltage-Based Implementation of the Tunneling Mechanism in Aging Models for Lithium-Ion Batteries
Authors: Wang Zhenya , Danilov Dmitri L. , Eichel Rudiger-A , Notten Peter H.L.
Published: August 2024

Lithium-ion batteries (LIBs) have become one of the most crucial power sources for electronics and electric vehicles due to high energy density, long cycle life, environmental friendliness, etc. Precise explanation and prediction of the aging behavior of LIBs is quickly becoming a hotspot. A solid electrolyte interface (SEI) growth is regarded as the dominant factor of capacity losses in LIBs. However, the previous SEI growth and aging models were based on energy levels. That means the energy barrier related to the Fermi level of SEI and electrode was used as the input parameter. It is not straightforward to implement, especially for industrial applications. Furthermore, the state-of-charge (SoC) and the energy barrier were usually assumed to be constant during (dis)charging, contradicting common sense and affecting the calculations' accuracy.

The present work proposes and experimentally validates an advanced voltage-based aging model. The voltage of the anode electrode is adopted as an input parameter in this model. It is easier to introduce dependence of aging on the voltage/SoC of the electrode with this model. It is found that deep delithiation of the anodes and lower SoC of LIBs will mitigate electron tunneling, lower SEI growth, and reduce calendar aging. Commonly used anode materials, such as graphite, Li4Ti5O12, and blended Si/C, are presented as interesting cases to investigate the effects of different electrode materials on the tunneling current profiles during (dis)charging for the first time. The model is instructive and can predict aging in LIBs with various electrode materials. This model and related analyses are beneficial for further optimizing LIB's electronic and electrode properties and as interesting limiting cases for testing battery modeling software.
Surface Modified Natural Graphite for Fast Charging Li-Ion Batteries
Authors: Tran Yen Hai Thi , Kang Dongguk , An Kihun , Song Seok Hyun , Kim Chunjoong , Kim Hyungsub , Song Seung-Wan
Published: August 2024

Graphite is a widely used anode active material in the vast majority of commercial Li-ion batteries (LIBs), but it retards charge due to intrinsically sluggish Li+ intercalation, which typically taking the battery’s full charging about three hours. In addition, fast charging of LIBs is hindered by the occurrence of Li metal plating and dendrites growth unless other a stable solid electrolyte interphase (SEI) form. Converting traditional graphite to a fast charging one provides new opportunities for the development and design of better performing batteries. In this presentation, we will report a breakthrough in boosting Li+ diffusion kinetics via surface modification of natural graphite for fast charging, which was obtained through a simple, scalable, and inexpensive method. We demonstrate that our surface modified natural graphite yields an unprecedented minute-scale charge speed, high capacity, cycle life and safety without Li plating and dendrites. This development holds significant promise for next-generation LIB.

Acknowledgements

This research was supported by the National Research Foundation grant funded by the Ministry of Science and ICT (2021M3H4A3A02086211, RS-2023-00217581) of Korea.
(Invited) Transformation Mechanism of Quantum-Sized Semiconductor Nanocrystals Revealed by in Situ Transmission Electron Microscopy
Authors: Yang Jiwoong
Published: August 2024

Semiconductor nanocrystal quantum dots are renowned for their remarkable properties, including tunable bandgap, pure color emission with exceptionally narrow bandwidths, and high luminescence efficiency. A thorough understanding of the transformation mechanism of quantum-sized semiconductor nanocrystals is essential for their practical application, as their properties are determined by their structure. This presentation will focus on exploring these mechanisms using in-situ transmission electron microscopy (TEM). The first part of the talk will examine the moisture-induced degradation of quantum-sized semiconductor nanocrystals, highlighting a notable finding: the formation of amorphous intermediates on the surfaces of these nanocrystals during degradation. This insight is crucial for developing strategies to enhance the stability and durability of nanocrystals, thereby extending their practical application. Next, I will discuss the crystal phase transition mechanism in II-VI semiconductor nanocrystals, triggered by off-stoichiometry. This discussion will shed light on the determinants of the crystal phase in these nanocrystals, a key to understanding their functionality. Lastly, the presentation introduces the application of in-situ X-ray scattering. This technique offers structural insights that complement those obtained from in-situ TEM, significantly enriching our understanding of the structural dynamics in semiconductor nanocrystals.