bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Colloidal Quantum Dot Laser Diodes: Three Decades in the Making
Authors: Klimov Victor I.
Published: August 2024

It has been 30 years since the first demonstration of lasing with semiconductor nanocrystals embedded in glass matrices1 – the samples akin to standard colored glass filters. Following this discovery, it took three years to realize lasing with epitaxial QDs2 and six more years to demonstrate the effect of amplified spontaneous emission (ASE) – a precursor of lasing – with colloidal QDs.3

So far, all reported studies into colloidal QD lasing have utilized optically excited samples. However, most of the prospective technological applications require electrically pumped devices, that is, laser diodes. The realization of such devices is complicated by multiple problems, widely deemed insurmountable. These include extremely fast nonradiative Auger recombination of optical-gain-active multicarrier states, poor stability of QD films under high current densities required for lasing, and unfavorable balance between optical gain and optical losses in electroluminescent (EL) devices wherein a gain-active QD medium is a small fraction of an overall device stack comprising multiple optically lossy charge-transport layers.

Here we resolve these problems and achieve strong ASE with electrically driven QDs.4 To demonstrate this effect, we employ compact, continuously graded QDs with strongly suppressed Auger recombination incorporated into a low-loss photonic waveguide integrated into a pulsed light-emitting diode capable of operating at current densities of up to ~2000 A cm-2. These prototype ASE-type laser diodes exhibit strong, broad-band optical gain and demonstrate low-threshold, room-temperature ASE which leads to intense, edge-emitted EL whose instantaneous power reaches ~200 mW.

1. Vandyshev, Y. V., Dneprovskii, V. S., Klimov, V. I. & Okorokov, D. K. Lasing on a transition between quantum-well levels in a quantum dot. JETP Lett.
54, 442-445 (1991).

2. Kistaedter, N., Ledentsov, N. N., Grundmann, M., Bimberg, D., Ustinov, V. M., Ruvimov, S. S., Maximov, M. V., Kopev, P. S., Alferov, Z. I. & Richter, U. Low threshold, large To injection laser emission from (InGa)As quantum dots. Electron. Lett.
30, 1416 (1994).

3. Klimov, V. I., Mikhailovsky, A. A., Xu, S., Malko, A., Hollingsworth, J. A., Leatherdale, C. A., Eisler, H. J. & Bawendi, M. G. Optical gain and stimulated emission in nanocrystal quantum dots. Science
290, 314-317 (2000).

4. Ahn, N., Livache, C., Pinchetti, V., Jung, H., Jin, H., Hahm, D., Park, Y.-S. & Klimov, V. I. Electrically driven amplified spontaneous emission from colloidal quantum dots. Nature
617, 79-85 (2023).
(Invited) Photoluminescence Properties of Single InAsP Quantum Dots Embedded in InP Nanowires
Authors: Haffouz Sofiane , Poole Philip J , Northeast David , Williams Robin L. , Dalacu Dan
Published: August 2024

Non-classical light emitters that can generate single photons with a negligible multiphoton probability are one of the key components for quantum information technologies. Deterministically grown III-V semiconductor nanowires containing quantum dots are gaining interest as a viable platform for quantum key distribution applications. In this talk, we will report on our recent development of the fabrication of InAsP single quantum dots embedded within InP photonic waveguide nanowires. In particular, we outline the importance of the photonic waveguide design for optimum photon generation and coupling to external optics [1]. The measured count rate dependence on normalized wire diameter, D/λ (figure 1) of the nanowire sources is consistent with calculations of the spontaneous emission rate into the fundamental HE11 nanowire waveguide mode (ΓHE11). Manipulating dot growth conditions and engineering the band structure around the dot (dot-in-a-rod configuration) are applied [2] to enhance the photoluminescence emission rate at 1310 nm and 1550 nm. Single photon emission with very low multiple photon probability is demonstrated at O- and C-band [3,4]. Temperature dependent, second-order correlation measurements on the 1310 nm source show that these nanowire sources can generate single photons up to temperatures of 220 K [3].

[1] S. Haffouz, et al., Nano Letters, 18, 3047 (2018).

[2] S. Haffouz, et al., Applied Physics Letters, 117, 113101 (2020).

[3] P. Laferriére, et al., Nano Letters, 23, 962 (2023).

[4] A.N. Wakileh, et al., arXiv:2309.13381 (2023).

Figure 1
(Dielectric Science & Technology Thomas Callinan Award) Rare-Earth Luminescence in Silicon-Based Thin Film Structures
Authors: Azmi Fahmida , Khatami Zahra , Mascher Peter
Published: August 2024

For Si-based materials to be used in solid-state lighting and silicon photonics schemes it is necessary to have precise control of the optical emission from these materials. This can be accomplished using rare earth dopants such as Ce, Tb, and Eu to obtain blue, green, and red emissions, respectively. In this talk, we first will provide a review of our work in this field and then focus on Eu-doped films, which are particularly attractive for silicon photonic applications due to their intense emission in the visible spectral region [1]. We will also discuss the benefits of introducing a novel hybrid radio frequency (RF) magnetron sputtering source in the electron cyclotron resonance (ECR) plasma enhanced chemical vapour deposition (PECVD) reactor chamber [2], using the example of Tb-doped SiON films [3]. This approach contrasts with traditional doping methods which use metal-organic precursors or ion implantation to introduce rare-earth dopant species into the host matrix.

[1] F. Azmi et al., “Tunable Emission from Eu:SiOxNy Thin Films Prepared by Integrated Magnetron Sputtering and Plasma Enhanced Chemical Vapor Deposition”, J. Vac. Sci. Technol. A 40, 043402 (2022); DOI: 10.1116/6.0001761

[2] J.W. Miller et al., “Integrated ECR-PECVD and Magnetron Sputtering System for Rare-Earth-Doped Si-Based Materials”, Surface and Coatings Technology 336, 99 (2018); DOI: 10.1016/j.surfcoat.2017.08.051

[3] Z. Khatami et al., "A comprehensive calibration of integrated magnetron sputtering and plasma enhanced chemical vapor deposition for rare-earth doped thin films", J. Mater. Res. (2023); DOI: 10.1557/s43578-023-01207-2
(Invited) Exploring and Manipulating Luminescence Centers in Lead Halide Perovskites through Hydrostatic Pressure
Authors: Bao Jiming
Published: August 2024

The application of hydrostatic pressure to materials induces changes in lattice constants, vibrational spectra, and electron-phonon interactions, thereby altering the optoelectronic properties of semiconductors. Consequently, hydrostatic pressure has become a widely utilized tool for investigating and enhancing the optical properties of organic/inorganic halide perovskites and their nanostructures. In this presentation, I will discuss the impact of hydrostatic pressure on two distinct types of luminescence centers in perovskite materials. The first type of luminescence centers originates from excitons within perovskite nanocrystals. I will discuss how hydrostatic pressure serves as a valuable tool for elucidating the origin of luminescence in low-dimensional perovskites, including 2D CsPb2Br5, 0D Cs4PbBr6, and 2D Ruddlesden-Popper Hybrid Perovskite Crystals. The second type of luminescence centers exhibit broadband optical emission from self-trapped excitons in low-dimensional perovskites. I will present our findings on the observation of strong exciton-phonon coupling and demonstrate how hydrostatic pressure can be employed to modulate electron-phonon coupling, offering a means to finely tune the broad emission spectrum.

References:

[1] J. Bao, V. G. Hadjiev, “Origin of Luminescent Centers and Edge States in Low-Dimensional Lead Halide Perovskites: Controversies, Challenges and Instructive Approaches”. Nano-Micro Lett. 11,
26 (2019).

[2] Chong Wang, Yanan Wang, Xinghua Su, Viktor G. Hadjiev, Shenyu Dai, Zhaojun Qin, Hector A Calderon Benavides, Yizhou Ni, Qiang Li, Jie Jian, Md Kamrul Alam, Haiyan Wang, Francisco C. Robles-Hernandez, Yan Yao, Shuo Chen, Qingkai Yu, Guoying Feng, Zhiming Wang, Jiming Bao, “Extrinsic Green Photoluminescence from the Edges of Two-dimensional Cesium Lead Halides”, Advanced Materials
31, 1902492 (2019).

[3] Zhaojun Qin, Shenyu Dai, Viktor G. Hadjiev, Chong Wang, Lixin Xie, Yizhou Ni, Chunzheng Wu, Guang Yang, Shuo Chen, Liangzi Deng, Qingkai Yu, Guoying Feng, Zhiming M. Wang, Jiming Bao, “Revealing the Origin of Luminescence Center in 0D Cs4PbBr6 Perovskite”, Chem. Mater.
31, 9098-9104 (2019).

[4] Zhaojun Qin, Shenyu Dai, Chalapathi Charan Gajjela, Chong Wang, Viktor G Hadjiev, Guang Yang, Jiabing Li, Xin Zhong, Zhongjia Tang, Yan Yao, Arnold M Guloy, Rohith Reddy, David Mayerich, Liangzi Deng, Qingkai Yu, Guoying Feng, Hector A Calderon, Francisco C Robles Hernandez, Zhiming M Wang, Jiming Bao, “Spontaneous Formation of 2D/3D Heterostructures on the Edges of 2D Ruddlesden-Popper Hybrid Perovskite Crystals”, Chem. Mater. 32, 5009 (2020).

[5] Shenyu Dai, Xinxin Xing, Viktor G. Hadjiev, Zhaojun Qin, Tian Tong, Guang Yang, Chong Wang, Lijuan Hou, Liangzi Deng, Zhiming Wang, Guoying Feng, Jiming Bao, “Theory and experiments of pressure-tunable broadband light emission from self-trapped excitons in metal halide crystals”, Materials Today Physics
30, 100926 (2023).
Probing Interfacial Degradation in Solid-State Batteries Using Machine Learning Force Fields
Authors: Kim Kwangnam , Yuan Suyue , Dive Aniruddha Mukund , Grieder Andrew , Adelstein Nicole , Kang Shinyoung , Wood Brandon C. , Wan Liwen
Published: August 2024

Solid-state batteries (SSBs) are next-generation energy storage technologies with improved safety and potentially higher energy densities compared to conventional Li-ion batteries, which is enabled by using fast ion-conducting solid electrolytes (SEs). However, practical applications of SSBs are hindered by the electro-chemo-mechanical instabilities at interfaces within the SEs (grain boundaries (GBs)) and between SEs and the electrodes, which deteriorates Li transport and the chemical and mechanical integrity of the cell. To mitigate, fundamental understanding of the intrinsic physico-chemical properties at interfaces is required. To this end, we directly probe atomic structures of the interfaces and GBs by performing large-scale atomistic simulations, enabled by validated machine-learning force fields (MLFFs) and resolve the structure-property relationship at complex interfaces that governs Li-ion transport and stability of SSBs.

In this talk, we will discuss the characteristics of garnet Li7La3Zr2O12 (LLZO) SE/LiCoO2 (LCO) cathode interfaces as well as the internal interfaces within the LLZO (GBs). It is observed from our simulations that the propensities for interfacial degradation strongly depend on the surface chemistry of LLZO and LCO. Doping LLZO is found to have a segregation effect at the LLZL GBs, here we will discuss its implication towards secondary phase formation and Li transport kinetics. At last, we will address the impact of interfaces on micro-crack propagation behavior in the LLZO-LCO system. In summary, our results reveal how atomic details of the dynamically evolving interfaces dictate the performance of SSBs, and provide guidance for processing and interface design to achieve desired performance .

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract number DEAC52-07NA27344. Authors acknowledge funding support from the Vehicle Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy and computational resource support from the Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program. This research used resources of the Argonne Leadership Computing Facility, which is a DOE Office of Science User Facility supported under Contract DE-AC02-06CH11357.
(Invited) Stabilizing Graphite Anode in Electrolytes with Micelle-Like Nanostructures for High-Rate Lithium Storage
Authors: Xie Jian , Yu Yikang , Xu Jiayi , Duanmu Kaining , Shutthanandan Shuttha , Yang Zhenzhen , Qian Kun , Li Tao , Liu Cong , Murugesan Vijay
Published: August 2024

Graphite stands out as the preferred anode material in commercial lithium-ion batteries (LIBs). However, its limited compatibility with diverse solvent molecules poses a significant challenge in selecting electrolyte solvents for LIBs. The issue arises from the co-intercalation of solvent molecules into the graphite layer alongside Li ions, resulting in layer exfoliation. This constraint has left few alternatives, primarily relying on ethylene carbonate (EC)-based mixed solvents. Consequently, the translation of electrolyte advancements from the past three decades into practical LIBs has been hindered. In this study, we present electrolytes exhibiting a micelle-like structure designed at nanoscale to impede the liquid-phase exfoliation of the graphite layer. The micelle-like electrolyte structure, derived from concentrated long-chain lithium salts, effectively segregates Li ions from free diethylene carbonate (DOL) solvent molecules. This segregation mitigates interactions between graphite particles and free solvent molecules during Li intercalation. Our proposed mechanism provides refreshed insights, highlighting the significance of the concentrated long-chain lithium salts (LiTFSI) for the graphite stability rather than the widely accepted Li coordination structure or solid electrolyte interphase. These findings offer a pivotal guideline for enhancing LIB performance by overcoming electrolyte limitations on graphite anodes.
A Coupled NMR and Differential Capacity Study of the Consumption of Electrolyte and Additive Components during the Formation Cycle of Li-Ion Pouch Cells
Authors: Gauthier Roby , Lin Hongyi , Viswanathan Venkat , Whitacre Jay F
Published: August 2024

Understanding the side reactions occurring inside lithium-ion cells remain a significant challenge, presenting opportunities for innovation. In this context, we developed a coupled 1H NMR (nuclear magnetic resonance) and dQ/dV (differential capacity) analysis method aimed at enhancing our understanding of these reactions during the formation cycle. Using deuterated acetonitrile as an extraction solvent, we measured the relative consumption of electrolyte components inside different electrolyte, including in 1.2M LiPF6 EC:EMC 3:7 2% VC and 1.2M LiPF6 EC:EMC 3:7 2% VC + 1% DTD electrolytes at different voltage. Our NMR observations were subsequently compared with electrochemical data to better understand and validate the results. These findings offer valuable insights into lithium-ion cell dynamics and mark a significant step towards the advancement of diagnostic techniques.
Stable Hydroborate Solid-State Lithium Battery with High-Voltage NMC811 Cathode
Authors: Braun Hugo , Asakura Ryo , Remhof Arndt , Battaglia Corsin
Published: August 2024

Hydroborate solid electrolytes offer high ionic conductivity and are stable in contact with alkali metal anodes, but are challenging to integrate into batteries with high-voltage cathodes [1-3]. Here, we demonstrate stable dis-/charge cycling of solid-state lithium-ion batteries combining a Li3(CB11H12)2(CB9H10) hydroborate electrolyte with a 4 V-class LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode, exploiting the enhanced kinetic stability of the LiCB11H12-rich and LiCB9H10-poor electrolyte composition [4]. Cells with lithium metal and indium/lithium anodes achieve a discharge capacity at C/10 of ~145 mAh g–1 at room temperature and ~175 mAh g–1 at 60 °C. Indium/lithium cells retain 98% of their initial discharge capacity after 100 cycles at C/5 and 70% after 1000 cycles at C/2. Capacity retention of 97% after 100 cycles at C/5 and 75% after 350 cycles at C/2 is also achieved with a graphite anode without any excess lithium. The energy density per cathode composite weight of 460 Wh kg–1 is on par with the best solid-state batteries reported to date.

[1] L. Duchêne, A. Remhof, H. Hagemann, D. Battaglia, Energy Storage Materials, 2020, 225, 782

[2] L. Duchêne, R.-S. Kühnel, E. Stilp, E. Cuervo Reyes, A. Remhof, H. Hagemann, C. Battaglia, Energy & Environ. Science, 2017, 10, 2609

[3] R. Asakura, D. Reber, L. Duchêne, S. Payandeh, A. Remhof, H. Hagemann, C. Battaglia, Energy & Environ. Science, 2020, 13, 5048

[4] H. Braun, Ryo Asakura, A. Remhof, C. Battaglia, ACS Energy Lett. in press
Understanding Surface Degradation Mechanisms in Ni-Rich Cathodes for Li-Ion Batteries
Authors: Nayak Debasis , Sayed Farheen , Lovett Adam J , Joo Se Hun , Daramalla Venkateswarlu , Mahadevegowda Amoghavarsha , Nagle-Cocco Liam A. V. , Ducati Caterina , Spencer Ben , Pickard Christopher , Grey Clare P. , Driscoll Judith L. , Dutton Sian
Published: August 2024

High Ni-rich layered cathodes, such as; LiNi0.8Co0.15Al0.05O2 (NCA) and LiNi0.8Mn0.1Co0.1O2 (NMC811) materials, offer very high capacity and excellent rate capability fulfilling the pressing priorities. However, the cyclic performance is poor compared to other cathodes with lower Ni content. Due to high surface reactivity, first-cycle irreversibility is quite high in all these Ni-rich cathodes. Such surface reactions lead to different electrochemically inactive phases and reduce cyclic performance. Herein, we report a comprehensive analysis of plane selective cathode and electrolyte interface reactions and link the relationship between the formation of different cathode-electrolyte interphase (CEI) by-products with surface reconstruction mechanisms. Moreover, we established a guiding principle of coating strategy to enhance plane selective surface properties. Both bulk and thin-film Ni-rich NMC811 electrodes were used to investigate the surface properties. We fabricated epitaxial thin films of Ni-rich NMC811 cathodes of different orientations, such as; (104), (018), and (003). Al2O3 was chosen as a model coating material to understand how it modulates surface properties. The surface by-products depend highly on the surface charge and subsequently change with Al2O3 coating. Likewise, the surface reconstruction depends on these crystallographic planes and the coating layer exposed to the electrolyte.

Keywords:
NMC811; Thin film; Epitaxial; CEI; Surface reconstruction
Understanding Ni-Rich Layered Cathode Materials for Fast-Charging Li-Ion Batteries
Authors: Ryu Hoon-Hee , Murugan Vivekanantha , Chen Guoying
Published: August 2024

The market for electric vehicles (EVs) has experienced significant growth, and this trend is expected to continue in the coming years. While the lithium-ion battery (LIB) technologies for EVs have made significant progress so far, they still face several disadvantages compared to the internal combustion engines. A predominate challenge is reducing battery charging time. [1]

Traditional LIBs typically use Li[Ni1-x-yCox(Mn and/or Al)y]O2 as cathode materials. To improve the driving range of EVs, energy density has been the focus of research and development in the past decade, which led to the wide adoption of Ni-rich (Ni content > 80%) layered oxide cathodes in LIBs.[2] With increasing Ni content, however, the structural changes that the cathode material undergoes during electrochemical reactions also become more severe, which negatively impact their fast-charging performances.[3-5]

It is evident that addressing the fast charging limitations requires a deep understanding of the active materials. In this presentation, we show our recent effort in improving fast charging performances of Ni-rich layered cathodes. As the reactivity of Li[Ni1-x-yCox(Mn and/or Al)y]O2 cathodes vary with the states of dis/charges, their fast charging performances are directly linked to the charging/discharging protocol. In addition, we report how various physical properties of the cathode materials, such as microstructures and facets, can affect kinetics and charging rates. Our perspectives on future development strategies for fast charging Ni-rich layered cathode materials will also be discussed.

[1] X. Wang, Y.-L. Ding, Y.-P. Deng, Z. Chen, Adv. Energy Mater. 2020, 10, 1903864.

[2] S.-T. Myung; F. Maglia; K.-J. Park; C. S. Yoon; P. Lamp; S.-J. Kim; Y.-K. Sun, ACS Energy Lett. 2017, 2, 196.

[3] F. Schipper; E. M. Erickson; C. Erk; J.-Y. Shin; F. F. Chesneau; D. Aurbach, J. Electrochem. Soc. 2017, 164, A6220.

[4] H.-H. Ryu, K.-J. Park, C. S. Yoon, Y.-K. Sun, Chem. Mater. 2018, 30, 1155.

[5] J. Park, H. Zhao, S. D. Kang, K. Lim, C.-C. Chen, Y.-S. Yu, R. D. Braatz, D. A. Shapiro, J. Hong, M. F. Toney, M. Z. Bazant, W. C. Chueh, Nat. Mater. 2021, 20, 991.
Effect of Water–Soluble Polyimide (w-PI) Type Binders on the Performance of High-Capacity Silicon Anodes of Lithium-Ion Batteries
Authors: Cheon Sehwa , Park Eun-jin , Park Se-Jin , Lee Ho-bong , Gendensuren Bolormaa , OH Eun-Suok
Published: August 2024

In order to enhance rapid charging and driving range for electric vehicles, the high-capacity of lithium-ion batteries (LIBs) is imperative. Commercially available graphite as an anode material has long cycle life, abundance, and low cost. However, it has a limitation in its theoretical specific capacity (372 mAh g−1).

To overcome this limitation, much attention has been paid to silicon (Si), which offers a high theoretical specific capacity of 4,200 mAh g−1. Nevertheless, silicon suffers from excessive volume expansion, resulting in issues such as pulverization of active alloy particles, delamination, and the formation of an unstable Solid Electrolyte Interphase layer. This lead to a limitation to use the silicon in large amount in an electrode. A polymeric binder has a critical role in improving the high-capacity Si anode. Conventional polyimide (PI), one of various super-engineering plastics, was applied to the Si anodes, but it is still challenged to water-insolublity and high temperature imidization process around 300 oC. In this study, a water-soluble PI (w-PI) is designed by the polycondensation between dianhydrides and diamine in water environment. In addition, a relatviely low-temperature imidization temperature below 200 oC will be appled by the introduction of dimethylimidazole. This study will briefly outline the direction for implementing a w-PI binder and improving electrochemical performance of high-capacity anode compared to conventional binders such as PVdF and CMC/SBR.

Keyword: high-capacity Si anode; dianhydrides and diamine; Polyimide (PI); and water-soluble PI

Figure 1
Lead Zirconate Titanate As an Anode for Li-Ion Batteries
Authors: Bhattarai Mohan , Shweta Shweta , Choudhary Sunny , Prasad Thapaliya Bishnu , Weiner Brad R , Katiyar Ram S , Morell Gerardo
Published: August 2024

Graphite, a successfully commercialized anode for lithium-ion batteries (LIBs), faces multipronged challenges, including an unsustainable supply chain and sluggish rate capabilities, underscoring the necessity of alternative anode materials for LIBs. Herein, the potential of lead zirconate titanate (PZT) as an anode material for LIBs has been investigated. Synthesis of bulk PZT materials was accomplished through a solid-state reaction, and the electrochemical performance of PZT anodes was investigated. The electrochemical characterization reveals that diffusion-controlled intercalation is the predominant charge storage mechanism in the PZT anode. Overall, the electrochemical performance of PZT indicates that it could be an alternative anode material for LIBs.
Investigating of Carbon Agent Distribution Using Long-Chain Alkyl in Grafted Binder for High-Capacity SiOx/Graphite Anode
Authors: Gendensuren Bolormaa , KIM Minjae , Sugartseren Nyambayar , OH Eun-Souk
Published: August 2024

A small amount of the conductive carbon agent in lithium-ion battery (LIB) formulation has a significantly impact on the rate capability performance of battery but the distribution problem of the carbon conductive material is issued in the electrode slurry due to its hydrophobic and inert characteristics. To overcome this problem, the use of dispersant agent was proposed in the electrode fabrication process.

In this study, the grafting of adhesive acrylamide monomer (AM) and a long-chain alkyl monomer onto carboxymethyl cellulose (CMC) is applied to binder to improve the conductive agent distribution in a high-capacity SiOx/C anode. The long alkyl chain in the monomer of the graft copolymer binder exhibits good dispersibility of the carbon agent and improved conductive matrix compared to the binder with no alkyl monomer. This may be explained by CH-π integration between the alkyl monomer in graft polymer and carbon agent. The high-capacity SiOx/C anode with the long-alkyl chain introduced graft binder is examined in the slurry level with rheology and dispersion stability, in the electrode sheet level with electric resistance, peel-off, and coin-cell level with various electrochemical performance, charge/discharge performance.

Keywords: Silicon oxide; Graphite; Carbon agent distribution, long-chain alkyl monomer; Acrylamide; Graft copolymer

Figure 1
Rapid in-Situ Electrochemical Formation of Partially Disordered Spinel from Mn-Rich Disordered Rocksalt Cathodes
Authors: Holstun Tucker , Mishra Tara , Huang Liliang , Yang Xiaochen , Ceder Gerbrand
Published: August 2024

We present the development of an electrochemical formation method that enables rapid and in-situ formation of a partially disordered spinel phase from an initially disordered rocksalt (DRX) cathode. Recent studies on Mn-rich DRX materials have demonstrated the emergence of a spinel-like phase during cycling, resulting in improved capacity retention, energy density, and rate capability compared to materials which do not transform1,2,3. However, this transformation process typically requires weeks of cycling at relatively low rates, posing significant challenges for the commercialization of such materials.

To gain a deeper understanding of this transformation process, we carry-out a systematic study to determine whether the formation process of these spinel-like materials can be accelerated through a precycling formation process. By employing a novel electrochemical approach to purposefully stimulate the transformation, we successfully reduce the time required from several weeks to as little as one day for Mn-rich DRX. Extended cycling and synchrotron X-ray diffraction confirm that these materials exhibit both equivalent performance and resulting structure to those obtained through conventional cycling over a much longer duration. Further characterization of this material using HAADF and 4-D STEM reveals the complex local structure of the spinel-like partial ordering. It is hoped that such a practical electrochemical formation method will allow for an acceleration of research on these earth-abundant and energy-dense materials.

Li, L.; Lun, Z.; Chen, D.; Yue, Y.; Tong, W.; Chen, G.; Ceder, G.; Wang, C. Fluorination-Enhanced Surface Stability of Cation-Disordered Rocksalt Cathodes for Li-Ion Batteries. Adv Funct Mater 2021, 31 (25), 2101888. https://doi.org/10.1002/adfm.202101888.

Ahn, J.; Giovine, R.; Wu, V. C.; Koirala, K. P.; Wang, C.; Clément, R. J.; Chen, G. Ultrahigh-Capacity Rocksalt Cathodes Enabled by Cycling-Activated Structural Changes. Adv. Energy Mater. 2023. https://doi.org/10.1002/aenm.202300221.

Cai, Z.; Ouyang, B.; Hau, H.-M.; Chen, T.; Giovine, R.; Koirala, K. P.; Li, L.; Ji, H.; Ha, Y.; Sun, Y.; Huang, J.; Chen, Y.; Wu, V.; Yang, W.; Wang, C.; Clément, R. J.; Lun, Z.; Ceder, G. In Situ Formed Partially Disordered Phases as Earth-Abundant Mn-Rich Cathode Materials. Nat. Energy 2023, 1–10. https://doi.org/10.1038/s41560-023-01375-9.
Low-Temperature Anodization: An Electrochemical Route to Tailored Nanostructures in Heavily Doped p-Type Silicon for Forming Quantum Dots
Authors: Chiou Yu-Sheng , Liu Cheng-Ying , Wu Chun-Huang , Li Shu-Cheng , Huang Wei-Chi , Cheng Chao-Chia , Lee Benjamin T.-H.
Published: August 2024

This study presents a pioneering electrochemical approach to tailor the anodization outcomes of heavily doped p-type silicon, a subset of low-resistivity semiconductor materials, via low-temperature anodization. Conventionally, anodizing such silicon in hydrofluoric acid at room temperature leads to the formation of coarse porous silicon with negligible photoluminescence (PL) upon exposure to ultraviolet (UV) radiation.

In this investigation, we embark on an unconventional path by conducting the anodization process at an exceptionally low temperature of -20°C. This seemingly subtle adjustment, however, triggers a remarkable transformation in the optical characteristics of the silicon substrate. Strikingly, the anodized surface, when illuminated with UV radiation, emits a vibrant and distinct red PL signal (Figure 1), signifying the emergence of quantum confinement effects attributable to nanocrystals, i.e., quantum dots.

To substantiate the existence of these nanostructures, we employ advanced characterization techniques, with a focus on transmission electron microscopy (TEM). These rigorous analyses confirm the presence of well-defined silicon nanocrystals, typically measuring within the 3~4 nm range (Figure 2), meeting the prerequisites for quantum confinement effects. Notably, it is worth mentioning that the formation of such nanostructures is unattainable on heavily boron-doped silicon due to its high etching rate.

In conclusion, our findings underscore the potential of low-temperature anodization as a versatile tool to tailor the luminescent properties of porous silicon at the nanoscale. This breakthrough not only advances our fundamental comprehension of semiconductor electrochemistry but also holds the promise of driving progress in electrochemical fabricating semiconductor quantum dots and optoelectronics.

Figure 1
(Invited) Reshaping Light with Hybrid Quantum Dot: Molecule Systems
Authors: Cadena Danielle M. , Wu Xinyi , Baraazandeh Maryan , Wang Honghao , Wang Kefu , Cline R. Peyton , Schwan Joseph , Mangolini Lorenzo , Eaves Joel D. , Tang Ming Lee , Roberts Sean T.
Published: August 2024

Photon upconversion is an energy conversion process wherein a material absorbs two or more low-energy photons and uses their energy to generate high-energy photons. Upconversion systems that convert near-infrared light into the visible range can address current challenges in solar energy capture and near-infrared sensor design while materials that operate at higher energy, producing UV photons from visible light, can enable applications in photocatalysis and light-based 3D printing. Due to their high extinction coefficients and size-tunable optical properties, quantum dots have emerged as ideal photosensitizers for photon upconversion systems. In these systems, light absorbed by a quantum dot is passed to a molecule at its surface, placing the molecule into a spin-triplet state. Upconversion is achieved when two molecules in their triplet state encounter one another and undergo triplet fusion, a process that deexcites one molecule and promotes the other to a high-energy, emissive spin-singlet state. In this presentation, I will present spectroscopic measurements and electronic structure calculations that identify energy transfer rates and key intermediates involved in two quantum dot systems that respectively demonstrate red-to-blue and blue-to-UV photon upconversion. In the first system, which consists of silicon quantum dots functionalized with anthracene ligands, we find that by controlling the chemical structure of molecular tethers that covalently link anthracene to silicon, we can produce strongly coupled states wherein excited charge carriers are shared between silicon and anthracene. By controlling the energy of these states, we can optimize the system’s performance, achieving an upconversion quantum yield of 17.2%. In the second system, we use CsPbBr3 perovskite quantum dots to drive triplet energy transfer to naphthalene ligands. This energy transfer process is found to be highly sensitive to the structure of the chemical linker that binds naphthalene to CsPbBr3, which we attribute to modulation of the degree of wavefunction overlap between the states of the quantum dot energy donor and naphthalene energy acceptor.
Lead-Free Nanocrystal Inks for Flexible Optoelectronic Devices
Authors: Greytak Andrew B , Shaker Abdulla E , Ahmed Fiaz , Abiodun Sakiru L , Adhikari Bishal
Published: August 2024

The exploration of AgBiS2 quantum dots (QDs) as an environmentally friendly alternative to previously-explored infrared-absorbing QDs has continued to gain interest in the past few years. Applications in optoelectronic devices are facilitated by colloidally stable inks that can be used to deposit films with favorable material properties on diverse substrates, including flexible substrates applicable to lightweight and wearable sensors. Here, we demonstrate that a rapid biphasic ligand exchange process can be used to make a AgBiS2 QD ink. The properties of deposited films are explored in lateral photoconductive devices and in heterojunction photovoltaic devices. In addition to this, we also demonstrated the use of this environmentally benign QD ink in flexible devices: the photo response was unchanged when the device was flat or bent. These results demonstrate the versatility of solution-phase ligand exchange approaches to QD-based optoelectronic devices.
(Invited) Heavy-Metal-Free Quantum Dot Thin-Film Photodetectors for SWIR Imaging: A Comprehensive Analysis for Performance Enhancement
Authors: Lieberman Itai
Published: August 2024

Various emerging technologies investigate the ability to sense and detect light in the shortwave infrared spectrum (wavelengths between 1100nm and 2500nm). Autonomous cars, smart agriculture, eye tracking for AR and VR applications, face recognition, surveillance, machine vision and new microscopy techniques can take advantage of additional information found in SWIR.

Thin film photodetectors, based on quantum dot photodiodes, show promise in bringing SWIR sensing to the mass markets by offering simpler and cheaper processes and higher resolution than existing technologies. However, the prevalent use of lead (Pb), Cadmium (Cd) and mercury (Hg) in existing quantum dot thin film photodetectors poses safety, environmental and regulatory challenges, limiting their widespread adoption.

InAs quantum dots emerge as a leading alternative, offering a heavy metal free solution and paving the way for the next generation of SWIR imaging devices. Nevertheless, a nuanced understanding of InAs-based devices is imperative for unlocking their full potential and optimizing performance. This work presents a meticulous and extensive analysis conducted in our laboratories, encompassing both devices and materials. The resulting insights empower an agile and informed redesign of the photodiode, showcasing tangible improvements in performance metrics.
(Invited) Development of Ag- and Sn-Based Colloidal Quantum Dots for Near Infrared Photodetection
Authors: Ouyang Jianying , Graddage Neil , Lu Jianping , Martin Barbara , Davidson-Hall Tyler , Tao Ye , Ding Jianfu , Malenfant Patrick
Published: August 2024

Low-cost photodetectors with sensitivity in the second near-infrared window (NIR-II, 1000–1700 nm) are highly demanded. Recently, we made the first demonstration of an Ag2Se colloidal quantum dots (QDs) photodiode with sensitivity up to 1200 nm. By employing secondary phosphine to elevate the precursor reactivity, the Ag2Se QDs with a distinct excitonic absorption peak was achieved. These nanocrystals were deposited from solution into a mesoporous TiO2 scaffold to increase the light absorption and charge separation and reduce the exciton diffusion length. By incorporating a suitable hole-transporting layer between the active layer and Ag anode, the resulting devices showed a responsivity of 4.17 mA/W at 1200 nm.1 Also, Ag2Te QDs are excellent for advancing the detection wavelength. Their synthesis with desired particle sizes, narrow size distribution and high photoluminescence quantum yield (PL QY) is challenging. We systematically investigate critical parameters affecting the synthesis in an organic phase. It shows that high Ag/Te feed ratio leads to smaller size and higher PL QY; under 4:1 Ag/Te feed molar ratio, addition of secondary phosphine leads to narrower size distribution and excellent colloidal stability; under 6:1 Ag/Te feed molar ratio, excess 1-dodecanethiol as a strong ligand slows the nucleation and results in fewer nuclei, leading to a broad size distribution and poor optical properties; additional n-trioctyl phosphine as a weak ligand provides better colloidal stability; and another weak ligand n-tributylphosphine improves Ag2Te QD colloidal stability, focuses size distribution, and enhances PL QY. After optimization relatively large Ag2Te QDs with distinct excitonic absorption peaks (~1050 – 1450 nm) and PL emission peak 1.3 – 1.7 µm (QY up to 6.2%) were obtained. NIR-II photodetection has been demonstrated with a responsivity of ~1.5 mA/W at 1400 nm.2 More recently, we have been developing Sn-based chalcogenide QDs and obtained preliminary photodetection results. These results demonstrate that Ag and Sn chalcogenide QDs offer a low-toxicity route for low-cost fabrication of NIR-II photodetection.

Reference:

[1] Graddage N, Ouyang J, Lu J, Chu TY, Zhang Y, Li Z, Wu X, Malenfant PRL, Tao Y. Near-Infrared-II Photodetectors Based on Silver Selenide Quantum Dots on Mesoporous TiO2 Scaffolds. ACS Applied Nano Materials 2020, 3: 12209–12217.

[2] Ouyang J, Graddage N, Lu J, Zhong Y, Chu TY, Zhang Y, Wu X, Kodra O, Li Z, Tao Y, Ding J. Ag2Te Colloidal Quantum Dots for Near-Infrared-II Photodetectors. ACS Applied Nano Materials 2021, 4: 13587–13601.

Keywords: Environmentally Friendly; Near Infrared; Quantum Dots; Photodetection.
(Invited) Surface State Modulation of Colloidal Quantum Dots and Construction of Quantum Dot Based Infrared Detectors
Authors: Ning Zhijun
Published: August 2024

Near-infrared photodetection and imaging devices play an important role in fields such as biological detection, information communication, military meteorology, etc. Traditional imaging devices require integration with readout circuits, and the complex integration process limits the development of infrared imaging systems. Lead sulfide colloidal quantum dots have excellent photoelectric properties in the infrared region, with a tunable bandgap width ranging from 0.4 to 1.5 eV, and spectral response covering below 2400 nm. Lead sulfide quantum dot films exhibit high absorption coefficients in the infrared region and excellent carrier mobility. In recent years, the performance of infrared detectors based on quantum dot systems has rapidly improved, and they are expected to develop into a new type of infrared detection and imaging technology. The speaker's team has combined infrared quantum dots with visible light quantum dots to prepare a simple, low-cost, and efficient infrared upconversion imaging device. By using the method of inducing band bending through interface electron storage, the efficiency of carrier tunneling and photon conversion has been improved, and the application of this technology in biological imaging has been preliminarily demonstrated. This report will introduce the development of quantum dot infrared detection materials and devices in recent years, as well as the research progress of the speaker's team in this area.
Study of Electronic and Optical Properties of Low-Dimensional Nanosystems by First Principles Calculations
Authors: Marri Ivan , Ganesapandian Sudha Priyanka
Published: August 2024

The development of new techniques for material manipulation at the nanoscale, as well as advanced numerical tools for material design, has opened up new prospects in the engineering of novel low-dimensional systems with properties specifically designed for applications in different fields, from photonics to energy conversion. Zero-, one-, and two-dimensional nanosystems show unique electronic, optical, and transport properties that can be tuned, for instance, by size reduction, passivation, and doping. In this talk, we discuss ab-initio results obtained in the study of structural, electronic, and optical properties of low-dimensional systems, in particular focusing on silicon, germanium, and silicon/germanium nanostructures. The analysis of mechanisms that can be exploited to tune Auger recombination and carrier multiplication processes, as well as of those that affect the formation of the band offset (Type I and Type II) at the nanoscale, will be discussed. At the end, effects induced by anion ordering on electronic and optical properties of metal oxynitrides will be analyzed.
Monitoring the Solid-Electrolyte Interphase Formation in Bis(fluorosulfonyl)Amide Ionic Liquid Electrolyte Using a Redox Probe Method
Authors: Katayama Yasushi , Okazaki Sho , Serizawa Nobuyuki
Published: August 2024

The solid-electrolyte interphase (SEI) has been considered to be formed on the negative electrode surface by reductive decomposition of electrolyte components. In the case of the electrolytes containing lithium ions, the SEI can be regarded as the Li+ conductor that enables the negative electrode reactions and prevents the further decomposition of the electrolytes. The structure of the SEI is often explained by the mosaic model, in which the SEI is a composite of several different inorganic and organic domains [1]. On the other hand, we have proposed the formation of the gelled SEI in bis(fluorosulfonyl)amide (FSA–) ionic liquid electrolytes containing a high concentration of LiFSA [2,3]. Furthermore, we have reported that the SEI formation can be detected by monitoring the redox reaction of ferrocene (Fc) and ferrocenium (Fc+) [4,5]. In the present study, the time-dependent transition of the SEI formed on a Pt electrode was investigated by the redox probe method in BMPFSA (BMP+ = 1-butyl-1-methylpyrrolidinium) containing LiFSA.

The formation of SEI by holding a Pt electrode at a negative potential was confirmed by a shift in the anodic peak potential of the cyclic voltammogram for Fc+/Fc couple in LiFSA/BMPFSA. The anodic peak disappeared when the electrode was held at the negative potential for a few hours, indicating the formation of a thick SEI. However, the anodic peak was observed again after keeping the electrode at the open circuit potential for a few hours, indicating the disappearance of the SEI. These results suggest that the SEI is formed by dissolution and/or dispersion of the decomposed products, which form at the electrode surface and diffuse into the electrolyte. Thus, the SEI formed at the potential is considered to exist as a metastable phase in the balance between the formation and diffusion of the decomposition products.

This work was partly supported by GteX Program Japan Grant Number JPMJGX23S0.

[1] E. Peled, D. Golodnitsky, and G. Ardel, J. Electrochem. Soc., 144, L208 (1997).

[2] R. Furuya, T. Hara, T. Fukunaga, K. Kawakami, N. Serizawa, and Y. Katayama, J. Electrochem. Soc., 168, 100516 (2021).

[3] N. Serizawa, R. Yamashita, and Y. Katayama, J. Phys. Chem. C, 127, 10434 (2023).

[4] S. Kato, N. Serizawa, and Y. Katayama, J. Electrochem. Soc., 169, 076509 (2022).

[5] S. Kato, N. Serizawa, and Y. Katayama, J. Electrochem. Soc., 170, 056504 (2023).
(Invited) Atomic-Scale Modeling of Charge-Transfer Kinetics at LixCoO2 Cathode-Electrolyte Interfaces
Authors: Halldin Stenlid Joakim , Lawson John W
Published: August 2024

In the search for Li-ion batteries with improved performance, interface engineering is a comparably underexplored area with significant opportunities for innovation. Ion transport across interfaces is, for instance, a significant bottleneck for fast charging/discharging. At electrode interfaces, it is often essential to capture the coupled motion of ions and electrons in order to provide accurate computational input for interfacial design. In this work we employ the recently proposed theory of coupled ion-electron transfer kinetics[1,2] in conjugation with constrained and constant-potential density functional theory to examine Li+ transfer across battery electrolyte-cathode interfaces at the atomic scale. Here, we focus on the common Li
x
CoO2 intercalation-type cathode material and liquid-state organic electrolytes. We establish trends in transport kinetics for different states-of-charge (SOC, i.e., varied degree of lithiation, x), types of electrolytes, and counterions that closely reproduces experimentally observed trends. From our modeling, we can identify a few key descriptors to predict performance metrics in Li-ion transport of a given electrolyte-cathode combination. These include the Li-ion free energy of adsorption, the free energies of reorganization of the cathode material and electrolyte upon the addition/removal of electrons, as well as the electronic coupling between electron acceptor and donor states. As these quantities can be relatively straightforwardly estimated for any given electrode-electrolyte pair, we envisage broad applications of our modeling approach in the interfacial design for batteries and related fields.

[1] Fraggedakis et al., Electrochimica Acta, 367, 137432 (2021)

[2] Bazant, Faraday Discussion, 246, 60 (2023)
Accelerating Measurement Times by Correlating Electrode/Electrolyte Interface Properties with Cycle and Calendar Lifetimes
Authors: Carroll Gerard Michael , Veith Gabriel M. , Schulze Maxwell C. , Doeren Ryan
Published: August 2024

Electrochemical performance measurements on novel battery technologies are slow and require substantial resources. For example, a common metric for assessing the cycle lifetime of a cell is by charging and discharging at a rate of one cycle every six hours (C/3) for 1000 cycles and reporting the remaining capacity after the measurement. At this rate, a single measurement takes eight months to acquire useful data. Even worse, the benchmark for an acceptable shelf-life (calendar life) is to retain 80% of the initial cell capacity through 10 years. As of now, the only reliable method for acquiring this value is to hold the cell at open circuit for the duration of the time (10 years) while performing intermittent reference performance tests. The ability to quickly screen new chemistries for LIB applications offers tremendous value for accelerating discovery. Here, I will present an electrochemical impedance technique that measures a key parameter of the solid|electrolyte interface. This method uses the Helmholtz and Gouy-Chapman-Stern models of electrochemical interfaces to approximate the ‘health’ of the anode|electrolyte interface. These measurements strongly correlate to the average Coulombic efficiency of batteries with different cell chemistries which may offer predictive power for assessing the long-term cycle and calendar lifetimes.
Optimizing the Electrolyte Additive Content in Practical Li-Ion Cells with Si-Dominant Anodes
Authors: Stehle Philipp , Rutz Daniel , Vrankovic Dragoljub , Anjass Montaha
Published: August 2024

Due to their high capacity, Silicon (Si) anodes are very promising for the next generation of lithium-ion batteries. However, Si materials suffer from a high volume expansion, which cause cracking and accumulated growth of the solid electrolyte interphase (SEI), resulting in low coulombic efficiencies and lifetime of the Si anodes. Applying additives in the electrolyte is a facile and straightforward approach to improve the composition of the SEI and reduce cracking. For Si-containing anodes, fluoroethylene carbonate (FEC) and vinylene carbonate (VC) are considered the most effective electrolyte additives. The salt lithium difluorophosphate (LiDFP) is known to improve the interphases of cathode materials and graphite when applied as additive, but has been poorly investigated for Si anodes. In our study, we combine VC, FEC, and a variation of LiDFP concentrations to investigate the effect on Si-dominant anodes in detail. We conducted detailed electrochemical testing in half coin cells and Si/NCM pouch cells, including long-term cycling, rate capability tests, potential monitoring of the anode and electrochemical impedance spectroscopy. For the latter two, we applied a novel perforated reference electrode concept, which allows for broad and precise measurement in pouch cells, while avoiding a blocking effect of the lithium ions. Furthermore, post-mortem analysis was conducted to gain detailed insights into the SEI formation and microstructure influenced by the different additive concentrations.