bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring a New, Scalable Synthesis Route to Disordered Rock Salt (DRX) Cathode Materials
Authors: Chambers Matthew S. , Self Ethan , Armstrong Beth L. , Keum Jong
Published: August 2024

The global demand for lithium-ion batteries (LIBs) is ever-increasing as many nations seek to achieve a net carbon neutrality by the late 2030s. LiNi
x
Mn
y
Co1–x–y
O2, (NMC) is one of the most widely-used Li-ion cathode active materials. Despite its excellent performance (e.g., reversible capacities up to ~220 mA h g–1 and 500+ cycles), NMC contains both Ni and Co, which are expensive and have vulnerable supply chains. Li-excess disordered rock salt (DRX) materials are promising new cathode materials that utilize earth-abundant transition metals such as Mn and Ti. Through a combination of cationic and anionic charge compensation, DRX materials can attain specific energies ≥700 Wh kg–1. Doping F– into the DRX structure (Li1+x
Mn
y
Ti2–1–x–y
O2–z
F
z
) has been reported to improve the material’s cycling stability. Despite their promising properties, most DRX cathodes are prepared through solid-state synthesis routes which require high-energy milling, provide little-to-no control over the particle morphology, and are difficult to scale.

In this work, we developed a scalable combustion synthesis route (the glycine nitrate process) to produce high purity, high performance DRX cathodes. More specifically, we prepared two DRX precursors with nominal compositions of Li1.2Mn0.5Ti0.3O1.95 and Li1.2Mn0.7Ti0.1O1.85. When the precursors were heated under Ar to 1000 °C for 1 – 4 h, only 50% Li1.2Mn0.5Ti0.3O1.95 adopted a DRX structure, and no DRX formed for Li1.2Mn0.7Ti0.1O1.85. However, adding LiF to the precursors facilitates DRX phase formation during annealing and yields high purity DRX powders with the nominal compositions Li1.25Mn0.5Ti0.3O1.95F0.05 and Li1.35Mn0.7Ti0.1O1.85F0.15. In situ X-ray diffraction was employed to study the synthesis process, revealing DRX begins to form at just 600 °C, which is much lower than traditional solid-state routes. Furthermore, electrochemical tests on the Li1.35Mn0.7Ti0.1O1.85F0.15 cathode reveal these materials attain excellent performance with initial reversible capacities up to 215 mA h g–1 and stable cycling performance. These promising results demonstrate that combustion synthesis is a viable method for the scale-up of DRX materials.

This research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and was sponsored by the Vehicle Technologies Office (VTO) under the Office of Energy Efficiency and Renewable Energy (EERE). Some measurements were conducted at the Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility.
Non-Flammable Electrolyte for Large-Scale Ni-Rich Li-Ion Batteries: Reducing Thermal Runaway Risks
Authors: Sangsanit Thitiphum , Homlamai Kan , Joraleechanchai Nattanon , Prempluem Surat , Tejangkura Worapol , Sawangphruk Montree
Published: August 2024

This research explores the properties and applications of flame-retardant esters (FREs), specifically triethyl phosphate (TEP) and tributyl phosphate (TBP), within electrolyte systems. The investigation assesses their roles as additives (30%v/v) and primary solvents (80%v/v) in conjunction with carbonate-based electrolytes (1.0 M LiPF6 in EC:DEC:EMC) and a novel non-flammable electrolyte formulation (1.2 M LiPF6 in 70%v/v TEP with 30%v/v fluoroethylene carbonate, FEC). Results indicate that incorporating FREs as additives adversely affects cell performance and maintain flammability risks, necessitating alternative strategies for achieving nonflammability. However, utilizing FREs as primary solvents alongside carbonate solvents shows promise for developing non-flammable electrolytes, despite concerns such as reductive decomposition that may limit suitability for certain battery cells. Conversely, the incorporation of 70%v/v FREs with 30%v/v FEC in the new electrolyte formulation yields a stable solid electrolyte interface, inhibiting FRE decomposition and sustaining battery cycling performance. This combination offers a potential solution for producing non-flammable electrolytes, serving as a viable alternative to solid-state electrolytes. The compatibility of the 1.2 M LiPF6 in TEP:FEC, 70:30 %v/v formulation with existing battery manufacturing processes further enhances its applicability.

Figure 1
(Invited) Near-Field Optics and Its Applications in Nanoscale Materials: A Review
Authors: Fanchini Giovanni , Stocek Noah B. , Wong Victor
Published: August 2024

In this presentation, we first offer an overview of aperture-type scanning near field optical microscopy –a family of super-resolution imaging techniques based on evanescent waves, which can be combined with atomic force microscopy and are capable of subwavelength resolution nano-optical imaging. In the second part of this review, we will discuss a few applications in which our group capitalized on the super-resolution resolving power of SNOM to design specific nano-optical and nano-photonic systems for light harvesting, resistive memory device applications and nanoscale thermo-optical management, as well as to characterize nanoscale luminescent materials. Specific case studies that will be presented include the characterization of weakly photoluminescent and curved carbon dots for memory device applications, the three-dimensional characterization of plasmon-enhanced nanophotonic devices, as well as the development of near-field thermoreflectance imaging for nanophotonic-based thermal management applications. Collectively, our study well represents the versability of SNOM as a unique super-resolution nanophotonic tool for the investigation of light-matter interaction at the nanoscale.
(Invited) Design of Photoactive Inorganic Nanomaterials for Environmental Challenges
Authors: Moretti Elisa , Bordin Matteo , Liccardo Letizia , Lushaj Edlind
Published: August 2024

Nowadays, one of the main technological challenges that we are facing is the ability to provide a sustainable supply of clean energy and, among all renewable sources, solar energy displays the greatest potential. Recently, the development of novel synthetic strategies has led to the preparation of nanostructured materials displaying unique properties compared to the bulk counterpart systems, with controlled and tunable morphologies able to enhance the activity and selectivity of a catalytic process. In particular, nanostructured materials synthesized via the bottom–up approach present an opportunity for future generation manufacturing of devices.

This talk will focus on the importance of tuning the morphological features of a catalyst as a strategy to improve its optical and photocatalytic properties, focusing on how rationally designing inorganic materials at the nanoscale can lead to morphologies and structures suitable to enhance the performance of industrially and environmentally important processes. The talk will discuss some environmental applications that can be addressed by photoactive multi-component oxide systems synthesized via the bottom–up approach, highlighting their structure-reactivity relationship. Water contamination, in particular, is one of the upfront issues to be solved and complex organic molecules and pharmaceuticals, including antibiotics, are gaining attention due to their abuse and their low degradability. Photocatalytic drugs degradation will be presented as a successful case history [1-3] to provide inspiration to produce cheap, environmentally friendly, stable, and efficient photocatalysts, which hold a great potential for the development of new technologies not only for water remediation applications but also for energy applications in the field of solar fuel production.

[1] E. Moretti, L. Storaro, A. Talon, P. Riello, A. Infantes Molina, E. Rodríguez-Castellón, Appl. Catal. B: Environmental 168 (2015) 385.

[2] M. Telkhozhayeva, B. Hirsch, R. Konar, E. Teblum, R. Lavi, M. Weitman, B. Malik, E. Moretti, G.D. Nessim, Appl. Catal. B: Environmental 318 (2022) 121872.

[3] L. Liccardo, M. Bordin, P.M. Sheverdyaeva, M. Belli, P. Moras, A. Vomiero, E. Moretti, Adv. Funct. Mater. 33 (2023) 2212486.
Enhanced Quantum Efficiency of Near-IR Perovskite Light Emitting Diodes Via Dual Interfacial Modification
Authors: Bae Yu Bean , Jung Jae Woong
Published: August 2024

Near-infrared (NIR) light-emitting diodes play a crucial role in a wide range of applications, including sensors, night vision displays, security systems, medicine, spectroscopy, and military applications. The potential for high-performance NIR perovskite light-emitting diodes (NIR-PeLEDs) has been highlighted with the impressive advancement of fluorescent perovskite thin films. These PeLEDs exhibit promising features such as a tunable band gap, high color purity, and low non-radiative recombination rates. Despite these advantages, the current state-of-the-art NIR-PeLEDs faces challenges primarily related to poor film quality and increased defect states, leading to limitations in external quantum efficiency (EQE) and operational stability. In addressing these issues, we present a novel dual interfacial modification approach involving the incorporation of fluorinated phenethylammonium iodide (F-PEAI), a bulky organic cation, at both the bottom and top interfaces of perovskite emitting films. The modified interfaces result in perovskite films with a smoother surface morphology, complete coverage, and high crystallinity, leading to a red-shifted fluorescence band extending toward 800 nm. Furthermore, the introduction of F-PEAI facilitates the formation of compact and fine grains in perovskite films, contributing to an enhanced photoluminescence quantum yield (PLQY). Consequently, NIR-PeLEDs modified with F-PEAI demonstrate improved EQE values coupled with enhanced operational stability. The combination of electrical, optical, and physical analyses of both films and devices underscores the effectiveness of the dual interface modification in developing efficient NIR perovskite LEDs suitable for practical applications.
Improved Wide Temperature and Rate Performance in Li-Ion Batteries with Fluorinated Electrolyte Solvents
Authors: Usrey Monica Lee , Guillot Sarah Lucienne , Kerber Brian M , Du Peng , Zhou Liu (Amy) , Sriramulu Suresh
Published: August 2024

Commercial electrolytes include organic solvents unable to withstand the conditions required for the rapidly growing Li-ion battery industry, such as extreme temperatures and charge rates. The thermal and electrochemical stability limits of these solvents restrict the development of Li-ion batteries needed to sustain automotive electrification and other industrial applications. Further efforts are needed to enable electrolyte formulations suited for the operational demands in the market.

Koura has designed a series of fluorinated materials for use in Li-ion electrolytes that demonstrate improved performance and safety over conventional commercial electrolytes. The impact of Koura’s fluorinated solvents on performance in 4.3V Gr/NMC811 was examined, with a particular focus on benefits seen on extreme temperature and rate performance. Testing included cycling and rate performance across a range of temperatures from -20 °C to 45 °C and cycling conditions from C/2 to 4C. It has been found that these materials improve low temperature performance and reduce gassing and increase capacity retention during high-temperature and fast charge cycling. Where appropriate, performance of Koura materials is compared to common commercial solvents.

To elucidate the mechanisms responsible for the observed improvements, comprehensive post-test analysis has been conducted, including gas composition analysis and quantification via gas chromatography, bulk electrolyte composition analysis via NMR spectroscopy, and surface layer characterization via XPS and SEM. Bulk transport properties of the materials and electrolytes, including conductivity, viscosity, and Li+ solvation, are correlated to performance benefits.

This presentation will show Koura’s efforts to fill a major gap in the demands of the Li-ion battery industry today through the design of fluorinated materials and optimization of advanced electrolyte formulations. Specifically, we will present data highlighting the performance of fluorinated compounds on improving battery performance under strenuous conditions with respect to both temperature and cycling rate. Results from fundamental mechanistic studies will be discussed to highlight the mechanisms underlying the observed performance improvements.
A Case of Inverted Crosstalk in High-Voltage Lithium-Ion Batteries with Carbonate-Based Electrolytes and LiNi0.5Mn1.5O4 Cathodes
Authors: Curcio Antonino , Walid Dachraoui , Dahl Øystein , Wagner Nils Peter , Battaglia Corsin , Kuehnel Ruben-Simon
Published: August 2024

The deployment of spinel LiNi0.5Mn1.5O4 (LNMO) cathodes can be key to develop lithium-ion batteries (LIBs) with higher energy density and lower costs. However, the most common carbonate-based electrolytes for LIBs suffer from severe degradation at high potentials, potentially causing cell failure and safety hazards.[1,2] Therefore, investigating the degradation mechanisms in battery cells employing high-voltage battery cathodes such as LNMO is paramount. In this work [3], we studied the influence of linear carbonates on cycling and interfacial stability. Electrolytes consisting of LiPF6 dissolved in a mixture of cyclic (ethylene carbonate, EC), and linear carbonates (diethyl carbonate, DEC, or dimethyl carbonate, DMC), in a 3:7 EC:DEC/DMC weight ratio, were compared. Galvanostatic cycling and electrochemical impedance spectroscopy data of LNMO||Li cells indicate that the linear carbonate plays a fundamental role in cell failure. Specifically, cells with DEC-based electrolyte show early rollover failure, reaching 80% and 20% state of health at cycle 31 and 55, respectively. In contrast, cells with DMC-containing electrolyte have better stability, keeping 80% state of health until cycle 92, as shown in Figure 1. Three-electrode measurements and further characterizations, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), unveil that cell failure occurs due to instability of the cathode-electrolyte interface; when DEC-based electrolytes are used, a huge impedance build-up is correlated with the formation of a spotty deposit on LNMO particles. In contrast, these deposits are absent in cathodes cycled in the DMC-based electrolyte. These deposits can be explained as originating from electrolyte reduction products forming on the anode side as shown previously for layered oxide||Li cells.[4] Overall, this study provides an insightful discussion on an "inverted crosstalk", i.e., from anode to cathode, degradation mechanism. Importantly, improved cycling stability with DMC compared to DEC is also found for LNMO||graphite cells.

[1] V. Nilsson, S. Liu, C. Battaglia, R.-S. Kühnel, Electrochim. Acta 427, 2022, 140867.

[2] S. Liu, M. Becker, Y. Huang-Joos, H. Lai, G. Homann, R. Grissa, K. Egorov, F. Fu, C. Battaglia, R.-S. Kühnel, Batteries Supercaps 6, 2023, e202300220.

[3] A. Curcio, W. Dachraoui, Ø. Dahl, N. P. Wagner, C. Battaglia, R.-S. Kühnel, submitted.

[4] H.-J. Peng, C. Villevieille, S. Trabesinger, H. Wolf, K. Leitner, P. Novák, J. Power Sources 335, 2016, 91-97.

Figure 1
The Impact of PTFE:PVDF Ratio on the Fabrication of Free-Standing Electrodes for Solvent-Free Dry Electrodes in Libs
Authors: Cha Jeong-Hwan , KIM Minjae , OH Eun-Suok , Jung Jung Min Chan , Gendensuren Bolormaa
Published: August 2024

The current wet process of LIB electrode fabrication presents several challenges, including the use of the environmentally toxic and harmful N-methyl-2-pyrrolidone (NMP) solvent and non-uniform binder distribution due to the capillary force of the drying process. In addition, it is difficult to increase the thickness of the electrode and leads to relatively low-capacity electrodes. To address these issues, solvent-free dry electrode processes are promising. In the dry electrode process, binders play crucial roles in free-standing electrode formation. Fibrillization of Polytetrafluoroethylene(PTFE) occurs at a temperature of about 19 ℃, and the shear force of high temperature and high pressure helps to maintain the shape of the free-standing electrode.

In this study, we performed a comparative analysis through the physical blending of PTFE and PVDF polymer binders with different ratios. A variety of characterization tools are used to investigate the optimal ratio that ensures good cycle performance for high-loading cathode electrodes while maintaining free-standing electrodes: 180° peel test, sheet-resistance test, SAICAS, FE-SEM, and electrochemical performance tests

Keywords: Solvent-free, Dry electrode; electrode fabrication; PTFE polymer binder, Fibrillization, Lithium ion batteries

Figure 1
(Invited) Design Criteria of Ether Electrolytes and Stable Interphase Toward Reversible Intercalation Chemistry of Graphite Anode in Li-Ion Batteries
Authors: Xia Dawei , Tao Lei , Lin Feng
Published: August 2024

To date, it is extensively believed that ether electrolytes are incompatible with graphite anode in Li-ion batteries due to detrimental solvent co-intercalation and exfoliation. Here, we provide design criteria of ether electrolytes for reversible graphite anode without the high salt concentration. In short, for ether electrolytes, the reductive stability of anions (or their solvated complex) and the solid-electrolyte interphase (SEI) govern the reversibility of graphite anode. Exfoliation and co-intercalation are not the root cause of as-documented cell failures using graphite anodes. While reductive-instable lithium bis(fluorosulfonyl)imide (LiFSI) is the optimal salt paired with DOL, reductive-stable LiBF4 finds applications with DME. Individual 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) based electrolytes can enable ~99.9% Coulombic efficiency with excellent capacity retention and fast-charge capability using natural graphite. In DOL electrolytes, weakened Li-solvent interaction and preferential reduction of FSI anion coordinated with Li-ion contribute to homogeneous SEI enriched with inorganic species, for example, LiF. Therefore, electrolyte reduction and Li-DOL co-intercalation are inhibited. In DME electrolytes, we show that LiBF4 has limited reduction, majorly on the edge site. We discover that a self-terminating, heterogeneous interphase based on grainy LiF proves to be desirable for operating Li-solvent co-intercalation. Taking advantage of the anisotropic characteristics of natural graphite, we conducted a holistic investigation into the nature, function, and formation of the heterogeneous SEI. In these studies, we clarify a long-lasting confusing issue in LIBs community-that is, the compatibility between ether electrolytes and graphite anode. Our findings not only shed light on the enigmatic interphase formed by ether electrolytes but also offer critical insights into future electrolyte design for graphite anodes operated under extreme conditions.
Utilizing FeS2 Deposition on 3D Printed Carbon Microlattices as Free-Standing Electrodes in Lithium-Ion Batteries
Authors: Romero Cameron Taj , Liu Zhi , Gordon Kenneth , Fei Ling
Published: August 2024

Free-standing electrodes are a great alternative to slurry-coated battery electrodes as they eliminate the need for inactive components and shorten the fabrication process. In this work, carbon microlattice templates are designed and fabricated through the use of 3D stereolithography followed by pyrolysis to create a well-defined carbon template with a resolution >35 µm. Iron disulfide, a material with a high specific theoretical capacity, is then deposited on the surface and used as electrode material in lithium-ion batteries. To date, there have been no reports of FeS2 combined with 3D printed free-standing electrodes. The design utilizes controlled microchannels along the thickness direction to facilitate efficient ion transfer and interconnected carbon skeletons for electron transfer throughout the entire electrode. When directly applied in a lithium-ion battery, the composite material displayed a specific capacity of 562.5 mAh g-1 after 200 cycles with a current density of 500 mA g-1. A high-rate capability was also achieved. Stepwise cyclic voltammetry and Dunn Method confirm that the dominant mechanism guiding the excellent electrochemical performance is diffusion-controlled process, further highlighting the benefits of the organized microchannels. These results will advance the development of composite electrodes as well as shine light on the immense potential to develop high energy density batteries utilizing 3D printing, advocating for sustainable energy from both a research-driven and practical stance.
(Invited) Synthetic Strategies to Lower the Barrier for Making High Quality Quantum Dot Probes
Authors: Han Hee-Sun
Published: August 2024

Quantum dot (QD)-based bioimaging requires QDs with exceptional optical quality and well-controlled surface properties. Although extensive research has been carried out to produce high-quality nanocrystals and to design biocompatible ligands, significant expertise is required to synthesize the best quality QDs and ligands reported. Commercially available QDs often fail to meet the required quality and suffer from irreproducibility in their performance. These restrictions have limited the wide adoption of QDs for biomedical imaging in non-expert groups. My group strives to lower the barrier to preparing high-quality QD probes in a wide range of wavelengths. In this talk, I will discuss the synthetic strategies that we have developed to systematically grow high-quality nanocrystals of various sizes and materials with minimal human intervention and simplify the synthesis of polyimidazole ligands without compromising their quality. By lowering the synthetic barrier to high-quality QDs, we envision unleashing the full potential of QDs in various fields.
(Keynote) Engineering Lead Halide Perovskite Nanocrystals for Fast Single-Particle and Collective Light Emission
Authors: Kovalenko Maksym V.
Published: August 2024

Colloidal lead halide perovskite (LHP) nanocrystals (NCs), with bright and spectrally narrow photoluminescence (PL) tunable over the entire visible spectral range, are of immense interest as classical and quantum light sources. Fast (bright) and pure single-photon emission is key for many quantum technologies, from optical quantum computing to quantum key distribution and quantum imaging.The brightness of an emitter is ultimately described by Fermi’s golden rule, with a radiative rate proportional to its oscillator strength (intrinsic emitter property) times the local density of photonic states (photonic engineering, i.e. cavity). With perovskite NCs, we present a record-low sub-100 ps radiative decay time for CsPb(Br/Cl)3, almost as short as the reported exciton coherence time, by the NC size increase to 30 nm. The characteristic dependence of radiative rates on QD size, composition, and temperature suggests the formation of giant transition dipoles, as confirmed by effective-mass calculations for the case of the giant oscillator strength. Importantly, the fast radiative rate is achieved along with the single-photon emission despite the NC size being ten times larger than the exciton Bohr radius.

NC self-assembly is a versatile platform for materials engineering, particularly for attaining collective phenomena with perovskite NCs, such as superfluorescence in perovskite NC superlattices. Thus far, LHP NCs have been co-assembled with building blocks that acted solely as spacers to promote the tuning of the mutual arrangement of LHP nanocubes [2]. However, the functionality of the second SL component can give rise to the enhancement of the LHP NCs properties or the emergence of new collective effects. We present the formation of multicomponent SLs made from the CsPbBr3 NCs of two different sizes. The diversity of obtained SLs encompassed the binary ABO6-, ABO3-, and NaCl-type structures, all of which contained orientationally and positionally confined NCs. For the selected model system, the ABO6-type SL, we observed efficient NC coupling and Förster-like energy transfer from strongly confined 5.3 nm CsPbBr3 NCs to weakly confined 17.6 nm CsPbBr3 NCs. Exciton spatiotemporal dynamics measurements reveal that binary SLs exhibit enhanced exciton diffusivity compared to one-component SLs across the entire temperature range (from 5 K to 298 K). Observed incoherent NC coupling and controllable excitonic transport within the solid NC SLs hold promise for potential applications in optoelectronic devices.

[1]C. Zhu, S. C. Boehme, L. G. Feld, A. Moskalenko, D. N. Dirin, R. F. Mahrt, T. Stöferle, M. I. Bodnarchuk, A. L. Efros, P. C. Sercel, M. V. Kovalenko, G. Rainò. In review.

[2] Ihor Cherniukh et al. Nature, 2021, 593, 535–542.

[3] T. Sekh et al. Submitted
(Invited) Redox Chemistries for Vacancy Modulation in Copper Phosphide Nanocrystals
Authors: Schimpf Alina , Rachkov Alexander
Published: August 2024

Copper phosphide has been proposed as an anode material for lithium-ion batteries due to the ability to accommodate the electrochemical insertion of Li ions without substantial reorganization of the P-sublattice. We present three copper-coupled redox chemistries that allow post-synthetic modulation of the delocalized hole concentrations in colloidal copper phosphide nanocrystals. Changes in the structural, optical, and compositional properties are evaluated by powder X-ray diffraction, electronic absorption spectroscopy, solid-state nuclear magnetic resonance spectroscopy and elemental analysis. The redox chemistries presented herein can be used to obtain nanocrystals with Cu/P ratios of ~2.66–2.93, a larger range than has been possible through purely synthetic tuning. Importantly, oxidation with a divalent metal halide and trioctylphosphine allows access to a uniquely Cu-deficient composition. Copper phosphide nanocrystal thin-films oxidized in this way would be ideal candidates for fundamental electrochemical lithiation studies.
(Invited) Enhanced Catalysis of Surface-Activated Metallic WSe2 Nanosheets By Single-Atom Pt for High-Performance Li-O2 Battery
Authors: Jeong Sohee , Lee Gwang-Hee
Published: August 2024

Layered materials, such as TMDCs, exhibit various electronic structures attributed to their polymorphism and can be further modificated at the atomic level through chemical treatments. TMDCs in the metallic phase (1T or 1T’ phase) have gained attention as efficient electrocatalystic materials, due to their exceptional transport properties compared to TMDCs in the semiconducting phase (2H phase). TMDCs with the metallic phase have been prepared by atomic-scale post-treatments, such as an intercalation and single-atom doping. However, the precise role of these post-treatments in the catalytic performance of TMDCs is still ambiguous, as it is uncertain whether the enhanced properties arise from charge transfer kinetics in metallic phase or electrochemical properties induced by the post-treatment.

Herein, we present a straightforward approach fabrication for fabricating metallic WSe2 nanosheets, which serve as an excellent support for single-atom Pt doping. The incorporation of single-atom Pt into WSe2 nanosheets was achieved using a simple solution method at room temperature. Extensive measurements were conducted, including XAS, XPS, and XPDF to investigate the local coordination structure of Pt-WSe2. These measurements confirmed the presentce of single-atom Pt doping within WSe2 layers. The introduction of single-atom Pt significantly enhanced the kinetics of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), leading to improved performance of Li-O2 batteries. Experimental measurements and DFT calculations provided evidence that the enhanced catalytic abilities of Pt-WSe2 originated from the improved interaction between oxygen and the Se vacancy on basal planes of WSe2. Consequently, the Li-O2 battery incorporating the Pt-WSe2 catalyst exhibited a stable discharge and charge cycle for up to 350 cycles, demonstrating its superior durability.
(Invited) Designing Quantum Dots for Multiplexed Deep-Tissue Imaging in the NIR-II
Authors: Dennis Allison M
Published: August 2024

The combination of bright, tunable semiconductor quantum dots (QDs) emitting in the shortwave infrared or second near infrared window (SWIR/NIR-II, 1000 – 1600 nm) and InGaAs camera-equipped preclinical imagers opens the door to non-invasive, multiplexed, deep tissue imaging in live mice. While imaging in the NIR-I is like imaging through fog due to highly scattering tissue, imaging in the SWIR/NIR-II is more like imaging through pond water, enabling deeper imaging with much improved resolution. We synthesized multiple PbS/CdS core/shell QDs with emission wavelengths spanning 1000-1600 nm. These particles have been encapsulated in lipid-PEG micelles and up to three colors (so far) dosed into nude mice for imaging on a Photon Etc IR VIVO imager equipped with a hyperspectral Bragg grating and 6 bandpass filters, enabling demixing of the discrete colors. We have obtained exceptionally clear images of lymphatic drainage and the vasculature system, including visualization of lymphatic valve opening in videos. Interestingly, following intravascular injection, the liver and spleen are very visible and distinct, enabling the non-invasive visualization of a key nanomedicine drug delivery parameter (i.e., are the nanoparticles accumulating in the liver or the spleen?). Image processing investigations are expanding our ability to demix colors as well as to determine the average depth of the contrast agent, based on the wavelength-dependent attenuation of the photoluminescence based on water absorption. In addition to the photophysical advantages of using QDs for NIR-II, elemental analysis of blood and tissue samples enables quantitative biodistribution and pharmacokinetic studies. Ongoing work involves the application of this imaging approach to assess the impact nanomaterial surface properties and route of delivery on their pharmacokinetics and the use of deep tissue paired agent imaging for non-invasive “optical biopsy” of orthotopic tumors. Current data are already visually stunning, and ongoing imaging highlights new opportunities for research with every experiment!

Figure 1
(Invited) In Situ and Operando Scattering Studies on Quantum Dot-Based Devices
Authors: Müller-Buschbaum Peter
Published: August 2024

Colloidal quantum dots (QDs) made e.g. of PbS are attractive for various optoelectronic applications due to their tunable band gap with a large absorption wavelength range from the visible to the near-infrared region. Moreover, due to the high intrinsic permittivity, the exciton binding energy of PbS is smaller than in cadmium chalcogenide QDs and polymer materials, which is beneficial for devices driven by charge carrier generation and transport, e.g. photovoltaics and photodetectors.

In this work, we introduce wet chemical deposition methods beyond spin coating such as printing and spray deposition of QDs as a facile and potentially large-scale deposition method for high-performance photodetectors. The inner structures including the inter-dot distance of neighboring QDs and the structure, in the deposited QD solids, are studied by grazing-incidence small-angle X-ray scattering (GISAXS). In addition, the facet orientation of the QDs in the QD solids is characterized by grazing-incidence wide-angle X-ray scattering (GIWAXS). In particular, in situ GISAXS/GIWAXS studies during film formation are able to provide detailed information about the complex kinetic processes [1,2]. Operando GISAXS/GIWAXS studies on QD-based devices such as solar cells bring an in-depth understanding of the degradation mechanisms, which is key for improving the device stability and thereby bringing these novel materials into real-world applications [3]. Superlattice deformation in QD films on flexible substrates via uniaxial strain is followed in situ with GISAXS, providing a fundamental understanding of the impact of strain on the performance of flexible devices based on QD films, such as wearable electronics and next-generation solar cells on flexible substrates [4].

Nanoscale Horiz. 5, 880-885 (2020)

Nano Energy 78, 105254 (2020)

Energy Environ. Sci. 14, 3420-3429 (2021)

Mater. Horizon 8, 383-395 (2023)
(Invited) Electronic Trap Characterization in QD Devices Using Impedance Analysis Techniques
Authors: Park Taehwan , Hwang Gyuweon
Published: August 2024

Colloidal quantum dots (QDs) are semiconductor nanocrystals with dimensions in the range of tens of nanometers. They exhibit unique optical and electronic properties, such as a size-dependent band gap and high absorption cross-section. These properties make them attractive for optoelectronic applications such as photovoltaics, light-emitting diodes (LEDs), and photodetectors. However, QD optoelectronics pose significant challenges due to trap states, which mainly originate from the surface states of nanocrystals. Therefore, it is necessary to analyze the trap states of QDs to understand their electronic properties and optimize their performance in optoelectronic applications. With this understanding, we want to correlate the cause of the trap states with the chemical defect to design better passivation strategies.

In this discussion, we will explore the principles of electronic trap analysis in colloidal quantum dots based on impedance analysis techniques as a complementary method to spectroscopy. We will provide examples of electronic trap analysis in PbS QD photovoltaics and InP QD LEDs to demonstrate the effectiveness of this approach. We can electrically probe the QD layers in the device using an impedance analyzer to analyze the energy level and density of trap states. By combining chemical analysis and a theoretical approach with this technique, we attempted to correlate the trap states and chemical defects.
On the Electroluminescence of InP Quantum Dots with Varied ZnSe/ZnS Shell Thickness
Authors: Lin Yu-Sian , Ma Yi-Chun , Hoang Minh-Son , Chen Hsueh-Shih
Published: August 2024

Quantum dots (QDs) have emerged as a highly promising material for future display applications, offering advantages such as tunable emission wavelengths, narrow linewidths, and the ability to cover a broad color gamut. Traditionally, cadmium selenide (CdSe) QDs have dominated the electroluminescence (EL) QD light-emitting Diode (QLED) landscape. However, the presence of toxic metal cadmium in CdSe QDs has raised environmental and safety concerns. In recent years, indium phosphide (InP) materials, free from heavy metals, have become a focal point in EL QLED research. For InP EL QLED, the shell structure of InP/ZnSe/ZnS core/shell/shell QDs plays a crucial role in influencing carrier behavior and device performance. In this study, we prepare InP QDs with three different shell thickness, including ZnSeS shell with thickness of more than 6 nm (InP/ZnSe/ZnS QD size > 15 nm), and explore their EL properties. The research aims to investigate the potential mechanisms governing the interplay between shell thickness and carrier recombination, contributing to the optimization of InP QLEDs.

Figure 1
Camphor-Based CVD Graphene Integrating CsPbBr3 Quantum Dots for High-Temperature Endurance, High Flexibility, and Fast Optical Switch Photodetection
Authors: HU Yu-CHI , You Ziran , Ci Ji-Wei , Hsiao Ming-Hsiang , Wang Chong-An , Tsai Meng-Lin , Chuang Chia-Shain , Tsai Dung-Sheng
Published: August 2024

Photodetectors (PDs) based on camphor-based CVD graphene integrating CsPbBr3 quantum dots (QDs) have been fabricated on mica substrates successfully, showing temperature resistant, foldable, and fast response properties. The graphene synthesized from eco-friendly camphor was transferred onto mica substrates, and then the CsPbBr3 QDs were coated onto the graphene surface to form CsPbBr3 QDs/graphene composition on a flexible mica substrate.

According to the Raman spectrum, the structure of camphor-based CVD graphene is multilayer. The photoresponse of CsPbBr3 QDs/graphene composition was revealed by temperature-dependent (ranging from 300 K to 523 K) I-V measurements with/without white light illumination (light intensity: 112 mW/cm2). To highlight the temperature resistance of PDs based on CsPbBr3 QDs/graphene composition, a photo-to-dark current ratio (PDCR) of at 5 V is estimated at different temperatures. The PDCR of the CsPbBr3 QDs/graphene composition-based PD decreased from 3.2 to 0.74 with increasing temperature from 300 K to 523 K. Moreover, after 0 to 300 bending cycles, the vibration of PDCR value at 5 V is small (from 4.3 to 3.7), showing the high flexibility of the CsPbBr3 QDs/graphene composition-based PD. Furthermore, we found that the rise and fall times of the CsPbBr3 QDs/graphene composition-based PDs when we switched the illumination source ON and OFF are ~ 2 and ~1 ms, respectively, indicating fast optical switch behavior.

In this study, camphor-based CVD graphene incorporating CsPbBr3 QDs composition-based PD is demonstrated to exhibit high-temperature resistance, high flexibility, and fast response photodetection.

Keywords: Camphor, graphene, CsPbBr3 quantum dots, flexible photodetectors
Protective Layers to Improve the Durability of Lithium Anode
Authors: Peng Zhe , Wang Deyu
Published: August 2024

Lithium metal anode possesses the advantages of high theoretic special capacity (3860 mAh g-1), low redox potential (-3.04 V vs. S.H.E.) and abundant lithium source. Therefore, tremendous efforts have been paid to explore the remedies of practical utilization. Its applications were seriously hindered by the severely side reactions between the electrolyte solvents and Li metal due to the mismatched energy-gap and large volumetric variation of lithium deposition layer. To address this challenge, various strategies were developed in whole world to prolong the operational life of lithium metal anode.

Our group focused on the development of Li+ filtrated membrane to isolate the fresh Li metal from the solvents. Firstly, we established the transplantable LiF-rich membrane via NiF2 film during formation to significantly improve the durability of lithium metal anode.[1] Then, we prepared a Li-filtrated film via a homemade stacked grapheme (SG), which possesses the higher Li nucleation over-potential than that on rational nano-structured copper scaffold (NCS-SG).[2] Additionally, an advanced SEI-functional membrane derived from LiF decorated SG were proposed to protect lithium anode by retarding electron transfer via C-Fx to avoid lithium deposition on the film surface.[3] Finally, the approaches on compatible electrolytes would be proposed.[4-5]

In summary, the durability of lithium metal anode could be significantly prolonged by the appropriate protective strategies.

Acknowledgement

This work was supported by the National Natural Science Foundation of China (Grant No. 22179052) and the Excellent Discipline Cultivation Project by JHUN (2023XKZ013).

Reference

[1] Z. Peng, N. Zhao, Z. Zhang, et al., Nano Energy, 2017, 39: 662-672.

[2] F. Ren, Z. Peng, M. Wang, et al., Energy Storage Materials, 2019, 16: 364-373.

[3] M. Wang, Z. Peng, D. Wang, Advanced Energy Mater., 2019, 1802912.

[4] Y. Qin, D. Wang, M. Liu, et al., ACS Appl. Mater. Interfaces, 2021, 13, 49445−49452.

[5] Y. Qin, D. Wang, Submitted to Advanced Mater.
A Direct Comparison of a Power and an Energy-Optimized Li-Ion Pouch Cell: Characterization, Ageing and Modelling
Authors: Wind Julia , Vie Preben J. S. , Ostrander John , Shearing Paul R
Published: August 2024

Driven by the incredible transformation of the energy sector over the past 30 years lithium-ion batteries (LIBs) have seen continuous development and incredible improvements in terms of energy density, lifetime and power performance. Depending on their applications, Li-ion cells are normally optimized for either supplying as much power as possible or storing as much energy as possible, or a compromise between the two. A power optimized cell has typically a lower energy density and thinner electrode layers, compared to an energy optimized cell with higher energy density and thicker electrodes. One pathway to increase the performance of the modern LIBs is to move from conventional to thick electrode designs: this will result in an increased ratio of active components (anode/cathode) to inactive components (current collector, separator, casings) delivering improved energy densities. However, increasing the electrode thickness leads to several new challenges, such as e.g., reduced mechanical strength, higher tortuosity, and poorer rate performance, significantly affecting cell performance and ageing characteristics.

In this study we aim to develop a fundamental understanding of electrode performance and limitations through the evaluation of both, high-energy and high-power electrodes from state-of-the-art commercial LIBs. For this purpose, we selected two renowned large-scale commercial Li-ion pouch cells with similar geometry, chemistry, and capacity: one optimized for power and the other for energy.

Both cell types were tested following a test matrix including different temperatures, currents, and State-of-Charge limits as well as with and without mechanical compression of the cell during cycling. A large dataset with diagnostic data was recorded during ageing. This included, e.g., dQ/dV (Incremental capacity analysis, ICA), DC resistances and entropy changes. An especially strong influence of the current on the cycle life was observed for the energy-optimized cells. Cells without mechanical pressure had considerably shorter cycle life compared to cells cycled with mechanical pressure. Detailed monitoring of the pressure evolution across the pouch surface revealed significant pressure increases and thus electrode expansion throughout the cycling.

Cell-tear-down analysis was done to reveal differences in battery design, especially electrode structure and thicknesses. The extracted materials were structurally characterized by, e.g., SEM, XRD, and x-ray computed tomography, and assessed electrochemically in coin full- and half-cells. The obtained data was then used to fully parameterize a P2D electrochemical model.

The combination of detailed experiments coupled to P2D modelling provided valuable insights into influence of electrode thickness and morphology on battery performance and ageing, as well as degradation mechanisms specific to electrodes with increased thicknesses.
Modeling Pseudo-Capacitance as Parallel Electrochemical Reactions
Authors: Brady Nicholas
Published: August 2024

Pseudo-capacitors are attractive electrochemical energy storage devices for their superior rate performance over conventional batteries, and higher energy storage capacity over traditional capacitors. Despite the importance of these types of devices, their hybrid physics makes it difficult to simulate their performance; as such, a general and well-established physics-based mathematical model does not exist. Using MnO2 as a model pseudo-capacitive electrode, this work describes the electrochemical performance of the MnO2 electrode as two parallel redox reactions with independent exchange-current densities and thermodynamic relationships. One of the reactions mimics the fast time-constant of the near-surface reaction (typical in a pseudo-capacitor), while the second reaction has a larger time-constant, characteristic of insertion reactions. Both redox reactions could be parameterized through Butler-Volmer kinetics, and the time-constant of each reaction was controlled by its exchange current density, , and the sensitivity of the thermodynamic potential to the charge passed, . Because of this model’s simplicity and reliance on well-established mathematical descriptions of electrochemical kinetics and mass-transfer, it may have utility in modeling pseudo-capacitors in general, not just MnO2. In addition, the mathematical descriptions of the physics can be directly implemented with porous electrode theory, which is more amenable to mathematical device and component optimization.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and was supported by the LLNL-LDRD program under project 23-SI-002.
Impact of Fast-Charging Rates on Electrode Degradation in NMC/Gr Pouch Cells
Authors: Luo Mei , Gao Xiang , Mijailovic Aleksandar S , Wang Guanyi , Jansen Andrew N. , Yang Zhenzhen , Wu Qingliu , Sheldon Brian W. , Xu Jun , Lu Wenquan
Published: August 2024

With the rapid expansion of the electric vehicles market, fast charging lithium-ion batteries has become increasingly imperative and inevitable. However, as fast-charging technologies entering electric vehicle market, persistent challenges related to safety issue and cell degradation, such as lithium dendrite growth, thermal runaway etc. necessitate meticulous consideration. In this study, we investigated fast-charging rate effects on electrode degradation in 1.6 Ah pouch cells using LiNi0.5Mn 0.3Co 0.2O2 cathode and graphite anode provided by Nanoramic Laboratories. Our investigation involves a comparative analysis of the aging behavior of NMC/Gr cells subjected to various charging rates — 0.5C, 2C, 4C, and 6C. Notably, we observed that pouch cells charged at rates of 0.5C and 2C could persist 80% capacity retention over 1000 cycles while cells using 4C and 6C can survive no more than 400 cycles with 80% retention. Through a series of post-mortem characterizations, including electrochemical impedance spectroscopy (EIS), Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), we scrutinized the harvested NMC and graphite electrodes. As expected, more dendrite formation was observed on graphite anodes with 4C and 6C fast charging rates. The deterioration of cell performance primarily resulted from the degradation of the graphite anode. This degradation could be attributed to distinct dendrite morphologies at the graphite anode under varying charging rates (see Fig. 1). In addition to dendrite formation on graphite electrodes, we observed more severe pulverization of NMC secondary particles under higher charging rates despite their lower cycle numbers. This investigation provides a comprehensive understanding of how NMC and graphite degrade under different charging rates, offering valuable insights into the practical impacts of charging rates on cell lifespan and highlighting potential challenges that need to be addressed.

Acknowledgement

This material is based upon work supported by the U. S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Advanced Manufacturing Office, award number DE-EE0009111. Argonne National Laboratory is operated for DOE Office of Science by UChicago Argonne, LLC under contract number DE-AC02-06CH11357

Figure 1
Experimental Investigation on the Temperature Dependence of Open-Circuit Voltage Hysteresis in LiFePO4 Lithium-Ion Batteries
Authors: Chen Yupeng , Mitsubori Kunihiko
Published: August 2024

A commercial LiFePO4 Lithium-ion (LFP-LIB) cell was adopted to investigate hysteresis of open circuit voltage (OCV) in Lithium-ion batteries. Experiments were conducted within the typical operating temperature range of 0℃, 10℃, 20℃, 30℃, 40℃ and 45℃, covering state of charge (SOC) from 0% to 100%. The results showed that (i) OCV hysteresis is dependence on temperature and increases as the temperature decreases, and (ii) bimodality appears in certain SOCs. Comparing the impedances confirmed by electrochemical impedance spectroscopy (EIS), we found that charge-transfer resistance (Rct) increases significantly as the temperature decreases. This means that the LFP-LIB operating at lower temperatures suffers a higher polarization. This result indicates that identification of OCV hysteresis is essential for accurate SOC estimation.

Figure 1