bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Ultrahigh Efficiency Excitonic Micro-LEDs
Authors: Mi Zetian
Published: August 2024

To date, it has remained challenging to achieve high efficiency micro-LEDs, which are desired for next generation displays and virtual/augmented reality. The performance degradation with reducing dimensions for conventional LEDs has been largely attributed to the plasma damage induced on the mesa sidewalls. Here, we show such a fundamental challenge can be overcome by developing nanowire excitonic LEDs. In this study, InGaN/GaN nanowire LED heterostructures were grown on N-polar GaN-on-sapphire substrates utilizing selective area epitaxy. Studies have shown that the exciton binding energy in strain-relaxed InGaN nanostructures can be dramatically enhanced. Due to the strong Coulombic interaction between electrons and holes, the impact of nonradiative SRH recombination on the performance of an excitonic LED is significantly reduced. By exploiting the large exciton oscillator strength of quantum-confined nanostructures, we have achieved an external quantum efficiency (EQE) exceeding 25% for a green-emitting device with lateral dimensions less than 1 micrometer, which is the highest value reported for any LEDs of this size to the best of our knowledge. It is further observed that the EQE and output power of the excitonic LED show a significantly faster rising trend with current injection, compared to conventional devices. We have identified several important factors for achieving high efficiency excitonic LEDs, including the epitaxy of nanostructures to achieve strain relaxation and reduced dislocation densities and the formation of three-dimensional quantum-confinement to enhance electron-hole wavefunction overlap. We have further investigated the effect of Mg incorporation in p-GaN layer on the device performance. We found out that an optimized Mg dopant incorporation in nanowire structures can contribute significantly to the efficiency of micro-LEDs. We have measured significantly enhanced performance by optimizing Mg dopant incorporation, which leads to reduced leakage current and improved EQE. For example, for a red-emitting micro-LED, a peak external quantum efficiency of >8% was measured for a device with a lateral dimension less than one micrometer by optimizing Mg-dopant incorporation. Through these studies, we show that by harnessing the exciton oscillator strength of nearly dislocation-free nanostructures, together with a careful optimization of p-doping in the contact layer, the efficiency bottleneck of micro-LEDs can be addressed.

Conflict of interest: Some IP related to this work has been licensed to NS Nanotech, Inc., which was co-founded by Z. Mi. The University of Michigan and Mi have a financial interest in the company.
(Invited) Near-Infrared Triggered Theranostics
Authors: Vetrone Fiorenzo
Published: August 2024

In the last decade, the field of luminescent lanthanide doped nanoparticles has had a meteoric rise, progressing from the basic understanding of the photophysical properties governing their nanoscale luminescence, in particular upconversion, to their use in a plethora of applications, with considerable focus in biology and medicine. This interest stems primarily from the ability to stimulate these luminescent nanoparticles with near-infrared (NIR) light as well as their diverse emission wavelengths spanning the UV to the NIR. Therefore, with a single NIR excitation wavelength, it is possible to observe higher energy multiphoton luminescence, known as upconversion, or single photon NIR emission (known as down-shifted luminescence). The former upconversion process proceeds through the sequential absorption of multiple NIR photons through the long-lived 4f electronic energy states of the tri-positive lanthanide ions. As a result, upconversion is several of orders more efficient than conventional multiphoton absorption processes. This is especially interesting for applications in theranostics (therapy + diagnostics on the same platform) where the upconverted light can be used to trigger another light activated modality (therapy) while the NIR luminescence can be used for bioimaging and nanothermometry (diagnostics). Here, we present our work on the synthesis and development of various NIR excited (and emitting) core/shell lanthanide-doped nanostructures/nanoplatforms and demonstrate how their various emissions could be harnessed for applications in biology and nanomedicine.
Thiourea-Induced Cocrystallization of Mixed-Halide Perovskite Thin Films for High-Performance Pure Blue Perovskite Light Emitting Diodes
Authors: Lee Hyo Jae , Jung Jae Woong
Published: August 2024

Metal halide perovskite light-emitting diodes (PeLEDs) are gaining significant attention towards next-generation display materials owing to their advantageous properties, including color tunability, exceptionally narrow bandwidth, and high luminescence. Recent studies have successfully achieved over 20% external quantum efficiencies (EQE) in green and red PeLEDs. However, the blue PeLEDs lag far behind those of green or red PeLEDs because unstable phase stability in mixed halide perovskite thin films under high turn-on voltage (Von). In specific, the blue emission usually possesses halide ions with smaller ionic radius (Cl- or Br-), which easily migrates under high operative bias generating significant halogen vacancies and phase-transformation. In this context, we suggest thiourea as a promising additive for stabilizing defective perovskite thin films. Thiourea is a well-known hydrogen bond donor to halogens, which allows potential coordination complex of thiourea-halide ions to encompass well-dispersed mixed halides in co-crystallized perovskite lattices. In addition, the strong coordination of the C=S···Pb2+ was also demonstrated the thiourea-incorporated perovskite films, which effectively passivated undercoordinated Pb2+ antisites. Consequently, the thiourea-incorporated perovskite films exhibited stable deep-blue emission within 460 nm, demonstrating excellent luminance and quantum efficiency in pure blue PeLEDs. Moreover, the addition of thiourea achieved decreased Von and excellent spectral stability of pure blue PeLEDs at high applied bias, leading to significant advancements in pure blue perovskite display technology.
Development of a Thin-Film NMC System for the Investigation and Suppression of Harmful Reactions Occurring on the Surface of Cathode Materials in Li-Ion Batteries
Authors: Rodrigues Sameer R.J. , De Taeye Louis , Vereecken Philippe M.
Published: August 2024

Materials with the stoichiometry Li(NixMnyCoz)O2 (NMC) have emerged as promising candidates for use as cathodes in Li-ion batteries for electric vehicles. This is primarily due to their high capacity, which increases with the nickel content (Ni-rich NMC). However, the increase in nickel also leads to a decrease in the stability of the material, hindering market introduction [1]. Much of these stability issues emanate from the surface of the material and move subsurface towards the bulk during battery operation [2]. The internal electrode architecture of traditional composite battery cathodes, containing active materials, carbon additives, and binders, complicates the study of the surface reactions. For this reason, we developed a thin-film model system of Ni-rich NMC with a high surface area-to-volume ratio to exacerbate the effect of the surface reactions, enabling easier characterization of the surface without influence of the bulk.

The interfacial reactions occurring when NMC is exposed to air was investigated using the thin-film system. These experiments were supported by thermodynamic calculations to propose a mechanism of what reactions occur on the surface. Our study showed that the surface of NMC is stable in inert environments, however, when exposed to air (in particular H2O and CO2) the active material at the surface reacts to form Li2CO3, coinciding with loss of Li2O and protonation of the material, forming transition metal oxyhydroxides. We found that this phenomenon can be reversed by performing a heat treatment, moving Li2O back into the film. However, during the annealing process, an additional reaction between the film and substrate takes place. This, once again, leads to the active material being deficient in Li2O. To compensate for this deficiency, Li2CO3 was deposited onto NMC prior to annealing. The thermodynamical properties of each film were approximated from their electrochemical behavior. It was found that the film treated with Li2CO3 before annealing was thermodynamically similar to what is expected for an NMC cathode. These results contribute to the understanding of the interfacial reactions that take place on the surface of NMC cathodes. Additionally, the study proposes strategies to mitigate and compensate for these reactions.

References:

[1] Noh et al. Journal of Power Sources 233 (2013)

[2] Lin et al. Nat Commun 5, 3529 (2014)
(Invited) Origin of Structural Degradation in Li-Rich Layered Oxide Cathode
Authors: Liu Tongchao
Published: August 2024

Li and Mn-rich cathode materials (LMR) that utilize both cation and anion redox can yield substantial increases in battery energy density. However, even though voltage decay issues cause continuous energy loss and impedes its commercialization, prerequisite driving force for this phenomena are a mystery. Here, with in-situ nanoscale sensitive coherent X-ray diffraction imaging (BCDI) techniques, we reveal that nanostrain and lattice displacement accumulate continuously during cell operation. Evidence unequivocally shows that this effect is the driving force for both structure degradations and oxygen loss that triggers the well-known rapid voltage decay in LMR. By further leveraging micro to macro length characterizations that span atomic structure, primary particle, multi-particle and electrode level, we demonstrate that the heterogeneous nature of LMR cathodes inevitably causes pernicious phase displacement/strain which cannot be eliminated by conventional doping or coating methods. These results affirm that lattice displacement and nano-strain, which represent commonly occurred but less detectable dynamic structure evolutions, play an undeniable role in structure decomposition and voltage fade. With these fundamental discoveries, we propose mesostructural design as a strategy to mitigate lattice displacement and inhomogeneous electrochemical/structural evolutions, thereby achieving stable voltage and capacity profiles. These findings highlight the significance of lattice strain/displacement in causing voltage decay and will inspire a wave of efforts to unlock the potential of the broad-scale commercialization of LMR cathode material.
Dynamic Coupling of Internal Strain Field and Lithium Pathway within Individual Battery Particles in Solid State Batteries
Authors: Chung Jinkyu , Bae Junho , Choi Hanbi , Nam Chihyun , Lee Danwon , Koo Bonho , Kim Namdong , Lim Jongwoo
Published: August 2024

In all-solid-state batteries (ASSBs), (electro)chemo-mechanical aspects such as uneven interfaces, cathode-electrolyte interphase formation, delamination, fracture, defects, etc., are the major factors in capacity fade but remain largely unknown.

Nonhomogeneous transfer of lithium ions can cause significant variations in strain and stress within battery electrodes, leading to degradation in battery performance. In all-solid-state batteries (ASSBs), the lithium pathway and the associated strain/stress field become more intricate due to the (electro)chemo-mechanical reaction at the electrode-electrolyte interfaces. The dynamic volume change in active particles are heavily influencing by strength of the solid electrolyte and interfacial conformality. This can continually alter the lithium pathway and the internal stress field, leading to recurrent redefinitions of (electro)chemo-mechanical environment.

Here, we have developed an operando coherent X-ray imaging platform and associated analysis methodologies. This technology can track the nanoscale transport of lithium and the strain evolution of individual electrode particles in ASSBs. With this platform, we gained a comprehensive electrochemical and mechanical understanding of the cycling properties of single electrode particles in ASSBs.
(Invited) Developing Periodically-Aligned Fibrous Structures to Suppress Lithium Dendrites for Anode-Free Batteries
Authors: Kim Jae Chul
Published: August 2024

We have developed electrospinning-based manufacturing capability for dendrite-free anode-free and anode-less batteries. Electrospinning is a widely used, feasible manufacturing approach to create nano- and micro-porous layers of functional fibers. By tailoring fiber compositions, the electrospun layers can afford a wide variety of functionalities applicable to biomedical templates, separation membranes, and energy storage. Its manufacturing capability is, however, limited to producing randomly oriented fibrous structures. Topology and tortuosity of the electrospun fibrous layers are poorly controlled, making it difficult to systematically investigate structure-property relationships for any given applications, especially electrochemical systems.

In this presentation, we will demonstrate how to improve the controllability of fiber construction geometry by electrospinning. Unlike conventional electrospinning, our approach employs a mobile stage that allows precise alignment of fibers. Produced fibrous structures will be used to construct current collectors of the anode-free batteries, one of the proposed beyond-lithium (Li)-ion battery systems for high energy density. While direct, yet reversible, Li plating and stripping on and from the current collector has proven difficult due to uncontrolled dendrite growth, we found that the flat copper foil reinforced by the three-dimensional fibrous structure can enhance Li storage efficiency over an extended number of cycles, outperforming the planar case. We will discuss the effect of fiber compositions and controlled geometrical configurations on stabilizing Li plating and stripping morphologies to suppress Li dendrite growth and provide a fundamental design principle to construct anode-free and anode-less battery cells. Battery manufacturing advanced by this work will offer a systematic strategy to develop next-generation energy storage systems for a sustainable energy future.
An Integrated New Method for the Characterisation of Thickness Changes in Battery Active Materials during Cyclisation Under Pressure
Authors: Bugenhagen Bernhard Eberhard Christian , Baumann Annika
Published: August 2024

Measuring thickness-changes in a battery stack (dilation) during cyclisation is paramount for the characterisation of chemo-mechanical properties of battery materials. A variety of approaches to achieve these measurements is available, either for measuring the whole stack or individual active materials. Another topic of great interest is the cyclisation of batteries under an applied pressure. These pressures range from a few kPa to hundreds of MPa. Especially the research of solid-state battery materials requires measurements of electrochemical properties under pressure.

In light of this, characterising chemo-mechanical properties under an applied pressure is a natural demand. However, to the best of our knowledge, no commercially available integrated solution to measure the dilation in a battery stack under any significant amount of applied pressure has been reported yet.

We therefore present a convenient and reproducible method to derive thickness changes of a whole cell stack under defined pressures during cycling. For that, the commercially available PAT-Cell-Force was used (Image 1, left). The PAT-Cell-Force allows the application of a force of up to 1500 N on a cell stack of a diameter of 18 mm. This translates to a pressure of up to ~6 MPa. Additionally, the PAT-Cell-Force is equipped with a strain gauge sensor, allowing the measurement of the force during the experiment. While cycling, periodic fluctuations in the force signal are observed that are correlated to the cell voltage (Image 1, right).

Through technical modifications of the PAT-Cell-Force, the dilation of the cell-stack Δd has been derived from the amplitude of the force signal ΔF, reproducibly and in very good agreement to the expected values. This has been achieved for applied forces of up to F0 ~ 100 N, corresponding to Pressures of approximately P0 ~ 400 kPa. Tests for higher pressures are currently pending.

Figure 1
(Invited) Multiscale Modeling and Machine Learning Investigation of Battery Interphase Dynamics
Authors: Cheng Tao
Published: August 2024

In recent years, the solid electrolyte interphase (SEI) has emerged as a critical component in the development of efficient and durable electrochemical storage systems. Understanding the dynamics and properties of SEI is paramount for the enhancement of battery performance and longevity. This study presents a novel multi-scale simulation approach, incorporating Hybrid Ab Initio Reactive Molecular Dynamics (HAIR), to elucidate the intricate mechanisms governing SEI formation and evolution. Our methodology involves simulation under operando conditions, closely mimicking real-world scenarios, to provide insights into the molecular interactions and structural changes within the SEI layer. By leveraging HAIR, we bridge the gap between quantum mechanical precision and the expansive temporal-spatial scales of molecular dynamics, facilitating a more comprehensive understanding of SEI behavior [1,2]. Furthermore, we integrate machine learning (ML) techniques to refine our predictive models. These ML algorithms are trained on a rich dataset derived from HAIR simulations, enabling the prediction of key electrochemical properties, including chemical composition and electronic structure. The application of machine learning significantly enhances our ability to forecast SEI evolution under various operational conditions. A critical aspect of our research is the prediction of X-ray photoelectron spectroscopy (XPS) and Coulombic Efficiency (CE) outcomes [3]. By simulating these properties, we provide valuable predictions that align closely with experimental data, thereby validating our simulation framework.

In summary, our study offers a groundbreaking perspective on SEI analysis, merging the fidelity of HAIR with the predictive power of machine learning. This approach not only deepens our fundamental understanding of SEI properties but also paves the way for the development of more efficient and durable electrochemical storage systems. Our findings hold significant implications for the future of battery technology and underscore the importance of advanced simulation techniques in electrochemical research.

Reference

1. Liu Y; Yu PP; Sun QT; Wu Y; Xie M; Yang H; Cheng T*; Goddard WA; ACS Energy Lett.
2021, 6, 2320.

2. Liu Y; Sun QT; Yue BT; Zhang YY; Cheng T*; J. Mater. Chem. A
2023, 11, 14640.

3. Sun QT; Xiang Y; Liu Y; Xu L; Leng TL; Ye YF; Fortunelli A*; Goddard WA*; Cheng T*; J. Phys. Chem. Lett. 2022, 13, 8047.

Figure 1
Accurate Ionic Conductivity Calculations of Battery Electrolytes at High Salt Concentration Using Molecular Dynamics Simulations
Authors: Bhati Manav , Agarwal Garvit , Banik Suvo , Browning Andrea R , Halls Mathew D
Published: August 2024

The ionic conductivity of an electrolyte formulation is a crucial property influencing battery performance. The dependence of ionic conductivity on multiple parameters, such as salt and solvent type, concentration, and temperature complicates the design of next-generation electrolytes. Efficient design of superior electrolytes requires methods capable of accurately and rapidly predicting ionic conductivity. Such methods would enable high-throughput screening of electrolyte chemistries to establish structure-property relationships.

The simple Nernst-Einstein approximation is widely used in the literature to estimate ionic conductivity of electrolytes using the measured self-diffusivity. However, the failure of this approximation for concentrated solutions due to stronger intermolecular interactions requires incorporating a rigorous concentrated solution theory, such as Maxwell-Stefan (MS) diffusivity. Here, we present a molecular dynamics (MD) simulation workflow for calculating the ionic conductivity of liquid electrolytes utilizing the ion-correlated MS diffusion approach. We explore the sensitivity of calculated ionic conductivity to various simulation parameters and various methods in the literature to guide a standardized simulation protocol. Through rigorous benchmarking across a diverse range of electrolyte systems, we validate the model's accuracy by directly comparing the calculated ionic conductivities against experiments and existing literature. This work is a significant step toward a more unified and comprehensive evaluation procedure for ionic conductivity, accelerating the development of advanced electrolytes for improved battery performance.
Interrogating Internal Temperature Evolution in Li-Ion Cells
Authors: Alujjage Anuththara , Vishnugopi Bairav Sabarish , Barsukov Yevgen , Magee David , Mukherjee Partha P.
Published: August 2024

Li-ion batteries have become indispensable today as the energy landscape shifts towards more sustainable options through electrification. A critical aspect of enhancing their cycle life while maintaining safety and performance lies in the effective thermal management of the battery. Currently, most battery management systems (BMS) rely on external temperature sensors to estimate internal temperatures. However, rapid internal heat generation can lead to a significant disparity between external and internal temperatures, particularly during extreme operating conditions. This study delves into operando monitoring of internal temperatures during cycling of Li-ion cells at various operating temperatures and C-rates. This offers insights into the evolution of internal temperatures throughout cycling and the difference between external and internal temperatures. This information can be instrumental in developing computational models that can predict internal temperatures more accurately using non-invasive techniques in the future.
(Keynote) Automated / Autonomous Platforms for Synthesis, Purification, and Characterization of Quantum Dots
Authors: Kenis Paul J.A , Vikram Ajit , Xu Rui Hua Jeff
Published: August 2024

Controlling composition, structure, and thus properties of nanomaterials continues to be of importance to numerous fields. For example, applications of quantum dots range from displays and bioimaging, to metal nanoparticles for (electro-) catalytic conversions. The vastness of synthesis parameter space, in combination with still limited understanding of the nucleation and growth mechanisms for many quantum dots systems still hampers progress in identifying nanomaterials with desired properties for existing and newly envisioned purposes. Furthermore, the identification of optimal synthesis recipes for these nanostructures remains a major hurdle.

This presentation will report on the development and application a number of enabling capabilities for the synthesis and characterization of quantum dots, achieved through reactor engineering. We demonstrate how the use of automated flow reactors not only helps in run-to-run reproducibility but also in uncovering mechanistic information. Examples include reactors with dedicated nucleation, growth, and shell formation zones, and investigation that revealed mechanistic insight of how water concentration affects QD synthesis outcome. We also employed an autonomous flow reactor system to map synthesis parameter space of specific QD systems, a project that relied on fast, fully automated in-situ characterization using UV-vis or photo-luminescence in combination with multi-step machine learning workflows The utility of flow reactors, however, is limited when considering chemistries with longer reaction times. Hence, more recently we developed a fully automated batch reactor for parameter space mapping of QD synthesis via hot injection, the most frequently used method in both QD research and production at scale. This batch platform is being augmented with purification capabilities, to address some of the challenges of in-line, in-situ characterization of raw reaction mixtures, and to enable using advanced optical and structural characterization methods to provide insight into the actual structure of the QD materials.
(Invited) Synthesis of Ultra-Bright Colloidal Silicon Quantum Dots (PLQY~80%) and Highly Efficient LEDs (EQE>10%)
Authors: Saitow Ken-ichi
Published: August 2024

Silicon is the second most abundant element in the Earth’s crust and could be considered an environmentally benign material. Silicon has been widely used in electronic devices and solar cells, and it has dominated the semiconductor research and development. However, the photoluminescence (PL) of the bulk material shows an invisible NIR wavelength (λ ~ 1100 nm). In addition, the PL quantum yield (PLQY) of bulk crystal Si is ~0.01% owing to the indirect transition nature. In contrast, silicon quantum dots show PL in the entire visible spectral region [1]. Furthermore, colloidal silicon quantum dots demonstrate PLQYs of 60% [2], and thereby they give highly impact as environmentally benign and heavy-metal-free quantum dots (i.e., In, Cd, and Pb free) for displays, lighting, and biomedical imaging via solution processing. Indeed, silicon quantum dot LEDs have recently been produced from a natural substance, by upcycling discarded rice husks [3].

Herein, red PL with a PLQY of 60–80% and LEDs with an external quantum efficiency of >10% were obtained at 1/3600th of the cost of existing methods. This was achieved by using trichlorosilane and an organic solvent to prepare a hydrogen silsesquioxane (HSQ) polymer, and by optimizing the LED optoelectric properties. Based on many silicon quantum dots synthesized in our study, each of them enabled us to quantitative the relationships HSQ polymer structure, PLQY, and LED efficiency, exhibiting the critical parameters that governed their performances. Moreover, the simple and cost-effective methods proposed here could prove invaluable for the synthesis and characterization of silicon quantum dots in the near future.

References

[1] Canham, L. Faraday Discuss. 2020, 222, 10–81; [2] Ono, T.; Xu, Y.; Sakata, T.; Saitow, K. I. ACS Appl. Mater. Interfaces 2022, 14, 1373–1388; [3] Terada, S.; Ueda, H.; Ono, T.; Saitow, K. ACS Sustainable Chem. Eng. 2022, 10, 1765–1776.
(Keynote) Macroscopic Materials Synthesized from Nanoparticle Superlattices
Authors: Macfarlane Robert
Published: August 2024

One of the promises of nanotechnology in its early developmental stages was the ability to make designer materials with precise control over individual building block composition and organization in 3D space. In recent years, material synthesis methods have advanced to be able to create a multitude of nanoparticles of varying sizes, shapes, and compositions, providing a vast array of building blocks to use as materials fabrication components. Additionally, processing methods have been developed to arrange these nanoparticles into ordered arrays, to dry them into thin films, and even to sinter them into more complex bulk solids. However, the fundamental promise of being able to build a material with controlled hierarchical structure across all length scales (atomic crystal structure, molecular composition; nanoscale feature size, shape, and organization; microstructure; macroscopic form) has been challenging to realize. A materials synthesis and processing route that could create free-standing, macroscopic materials or arbitrary three-dimensional shapes with precisely controlled nanoparticle positions across the entirety of the material composition would therefore be a major advancement. Here, we demonstrate a nanoparticle-based building block called a “Nanocomposite Tecton (NCT)” that enables a self-assembly route to fabricating free-standing 3D solids of arbitrary macroscopic shapes that can utilize a multitude of different nanoparticle compositions, and also possess specifically programmed nanoscale particle arrangements and controlled microstructure. This talk will outline the key synthesis and processing steps that enable this method of making materials with programmed material structure across ~7 orders of magnitude in length scale, thereby realizing a long-standing goal of nanomaterials fabrication.
(Invited) Towards Non-Blinking Strongly Confined Perovskite Quantum Dots
Authors: Mi Chenjia , Gee Gavin , Atteberry Mattew , Dong Yitong
Published: August 2024

Quantum information science has shown its capabilities to enable secure quantum communications. Single photon emitters (SPEs) that emit photons one at a time are fundamental elements of such transformative technologies. Colloidal cesium lead halide (CsPbX3, X=Br, I) perovskite QDs are ideal for next-generation SPEs because of their high room-temperature luminescence efficiency and low-cost, scalable syntheses. Unfortunately, individual perovskite QDs show insufficient photostability and severe photoluminescence (PL) intensity fluctuations (also called blinking). This has greatly limited the spectroscopic studies of perovskite QDs for SPE developments. One major roadblock toward non-blinking, photostable perovskite QDs is their highly ionic crystal structure. When preparing single perovskite QD samples, QD colloids often need to be diluted. During this process ligands can detach from the QD, introducing defects. This is particularly detrimental to strongly confined perovskite QDs since exciton-surface lattice interaction is greatly enhanced. As a result, strongly size confined perovskite QDs are experiencing severe PL blinking with large PL “OFF” occurrences.

To suppress perovskite QD blinking and photodegradation, we embedded QDs in an organic crystal matrix consists of Phenethylammonium bromide (PEABr) salts. The bromide rich surface of a QD can be epitaxially anchored onto the PEABr crystals and therefore be stabilized. Individual strongly confined CsPbBr3 QDs in our matrix show nearly non-blinking behavior under non-resonant laser excitations at room temperature. These QDs remain photostable without PL intensity decrease and spectral shift after more than 12 hours of continues excitations. We anticipate that these QDs will lead to more accurate and detailed study of exciton dynamics and structural-optical property relationships in strongly confined perovskite QDs.
Mixed Electronic-Ionic Conductive Polymer Binder for Silicon-Based Solid-State Battery
Authors: Li Defu , Ahmed Faiz , Liu Gao
Published: August 2024

Silicon has attracted extensive research attention in lithium-ion battery (LIB) field due to its high theoretical specific capacity (~3600 mAh/g) and cost-effectiveness. In recent years, silicon has emerged as a viable candidate for anode material for solid-state battery (SSB) technology. Similar to its application in LIBs, silicon utilizing in SSBs encounters challenges, such as significant volume variation (~300%) during cycling and poor cycling performance. In addition, the utilization of silicon in SSB faces another critical bottleneck in ionic conductivity due to the absence of liquid electrolyte. To address these challenges, various pioneering studies have explored potential solutions, including controlling the thickness of silicon anode to be below 150 nm,(1) fabricating electrodes with a combination of silicon and solid-state electrolyte (e.g, Garnet-type electrolyte(2) and sulfide electrolyte(3)), subjecting SSBs to a high pressure (10-50 MPa)(4).

Here, we introduced an alternative approach to mitigate these challenges by designing anodes through incorporating silicon with mixed electronic-ionic conductive (MEIC) hierarchically ordered structure (HOS) polymer binders. These multifunctional HOS polymer binders effectively preserve the structural integrity of electrode materials, even when silicon materials experiences significant volume expansion and shrinkage during the charging-discharging process. Owing to establishments of covalent bonds between silicon surface and the polymer binders, the resulting SSBs exhibited excellent resilience and only required hand-tightening force (<1 ton) for operation. These polymer binders effectively maintained continuous electronic and ionic pathways within silicon-based anodes without the need of additional additives, such as carbon material and solid-state electrolytes. Utilizing these versatile polymer binders, the resultant SSBs featured an outstanding cycling performance over 100 cycles in full cells, with an average Coulombic efficiency exceeding 97%.

Reference

A. Song, W. Zhang, H. Guo, L. Dong, T. Jin, C. Shen and K. Xie, Advanced Energy Materials, 13, 2301464 (2023).

W. Ping, C. Yang, Y. Bao, C. Wang, H. Xie, E. Hitz, J. Cheng, T. Li and L. Hu, Energy Storage Materials, 21, 246 (2019).

M. Rana, Y. Rudel, P. Heuer, E. Schlautmann, C. Rosenbach, M. Y. Ali, H. Wiggers, A. Bielefeld and W. G. Zeier, ACS Energy Letters, 8, 3196 (2023).

D. H. Tan, Y.-T. Chen, H. Yang, W. Bao, B. Sreenarayanan, J.-M. Doux, W. Li, B. Lu, S.-Y. Ham and B. Sayahpour, Science, 373, 1494 (2021).
Solid-State Lithium-Ion Superionic Electrolytes with Reduced Moisture Sensitivity
Authors: Bahmani Farzaneh , Rodmyre Collin , Smirnova Alevtina W
Published: August 2024

The remarkable safety and high energy density of solid-state batteries (SSBs) created significant advantages in the development of next-generation energy storage. The properties of these batteries are highly dependent on the characteristics of solid-state electrolytes (SSEs), making them a crucial material in the development of such batteries. Following diverse principles of material design, lithium halide SSEs, particularly Li3InCl6, open new opportunities in the development of SSBs due to their unique properties including broad electrochemical stability window, high lithium-ion conductivity, and excellent deformability. Through a mechano-thermal synthesis approach, Li3InCl6 demonstrates substantial ionic conductivity at room temperature. We studied the temperature-dependent behavior of Li3InCl6 by using in-situ/operando techniques such as XRD and XPS. However, its susceptibility to moisture poses a significant challenge for practical implementation in SSBs. To overcome this limitation, this research is focused on a novel solution: hafnium doping of Li3InCl6. Integrating hafnium into the Li3InCl6 structure results in a substantial improvement in electrochemical performance. The Li2.6In0.6Hf0.4Cl6 solid-state electrolyte not only showcases heightened ionic conductivity but also demonstrates improved resistance to moisture. The achieved ionic conductivity reaches approximately 1 mS cm-1, marking a significant 3.5-fold increase compared to Li3InCl6. Noteworthy is the fact that, after 5 hours of exposure to air with 15% humidity, the observed reduction in ionic conductivity for Li2.6In0.6Hf0.4Cl6 is 37%, a notably lower decrease compared to the 57% reduction seen in Li3InCl6.

The efficacy of hafnium doping provides a crucial advancement in the field of solid-state electrolytes, promising a transformative impact on next-generation energy storage systems.
Enhancing Shelf-Life of Electrolytes with LiPF6 By Increasing Stability Under Commercially Relevant Storage Conditions
Authors: Usrey Monica Lee , Guillot Sarah Lucienne , Hennek Matthew , Garg Shipra , Homa Arthur , Sriramulu Suresh
Published: August 2024

Lithium hexafluorophosphate (LiPF6) salt is the most commonly used lithium salt in commercial Li-ion batteries due to its high conductivity, passivation of Al current collectors for positive electrodes, and participation in SEI layer formation at graphite anodes.1 However, LiPF6 suffers from poor thermal stability and poor stability toward protic species (like water) leading to decomposition that can significantly reduce Li-ion battery performance especially under the extreme conditions demanded by today’s industrial applications. Specifically, LiPF6 decomposition leads to HF generation, especially in the presence of water2, which results in multiple negative outcomes in Li-ion cells including dissolution of cathode materials and gas generation.3 Conditions during electrolyte blending, transport, and/or storage often exacerbate LiPF6 instability and increase HF generation.

To date, efforts to replace LiPF6 have not proven to be commercially successful, therefore strategies to improve the stability of LiPF6 electrolytes under relevant storage conditions are critical to support the deployment of Li-ion batteries. Koura has extensively characterized the degradation of LiPF6 as a function of multiple conditions, including temperature, water content, and electrolyte composition to inform the design of strategies to improve stability.

This presentation will summarize Koura’s efforts to understand LiPF6 decomposition under conditions relevant to the Li-ion electrolyte supply chain. Specifically, we will present data showing a series of fluorinated materials that improve the thermal stability of LiPF6 electrolyte through the elimination of existing HF and suppression of additional formation.

References:

Sascha Nowak and Martin Winter 2015 J. Electrochem. Soc. 162 A2500

Hui Yang et al 2006 J. Power Sources 161 573

Weishan Li 2020 J. Electrochem. Soc. 167 090514
Optimizing Silicon Nanostructures for Enhanced Li-Ion Storage: Microstructure, Binder and Production Technology
Authors: Kamali Ali Reza
Published: August 2024

The utilization of silicon nanostructures as anodes in lithium-ion batteries (LIBs) presents a promising avenue for improving device performance. However challenges related to prolonged cycling, energy density, and costs need to be addressed. This presentation outlines three strategies employed within the E2MC framework to overcome these challenges: (a) By incorporating high-quality graphene nanosheets, produced through a low-cost and scalable molten salt method, common silicon nanoparticles (generated by commercially available pyrolysis-based methods) can be enveloped in graphene layers with a controllable chemical composition. The graphene-encapsulated silicon nanoparticles exhibit stable electrochemical lithiation/delithiation performance, showcasing significantly improved energy density, even after numerous Li-insertion and extraction cycles, outperforming bare Si nanoparticles; (b) Thermally modified polyimide (PI) is introduced as an efficient binder to enhance the Li-ion storage performance of silicon nanoparticles. An optimized thermal treatment of the electrodes containing Si nanoparticles and PI binder produces an effective charge transfer complex (CTC) structure, improving the electrochemical performance by forming a compact structure that reduces charge transfer impedance. This enhancement significantly boosts the cycling performance of the silicon anode; (c) An ultra-fast shock-wave combustion synthesis approach is introduced for the rapid and low-cost preparation of Si nanostructures using naturally available SiO2 as the silicon feedstock. Completed at an ignition temperature of approximately 550 °C, this method requires virtually no dwell time. The resulting nanostructured Si product exhibits a mesoporous integrated sheet-like morphology, demonstrating excellent and stable Li-ion storage performance. This approach contributes to a more sustainable and cost-effective utilization of elemental Si nanoparticles in LIB applications.
Early-Stage Evaluation of Battery Safety Based on Materials, Component, and Microcell Calorimetry Measurements
Authors: Albertus Paul , Bhargava Bhuvsmita , Wang Zixuan , Ogundipe Taiwo , Zaman Samaa
Published: August 2024

There are numerous “beyond lithium ion” battery chemistries under development at universities, national labs, companies, and other organizations. Early-stage battery chemistry work typically focuses on demonstrating performance at the materials, coin, and pouch cell level, with evaluation and design for safety left for later stages.1 In this talk, we will describe the opportunities for assessing the safety of a battery chemistry at the earliest stages of its development, as soon as the active materials and electrolyte have been identified.2 With carefully designed and quantitative experiments, key information such as the amounts of heat released by the reactions of and among cell components, the temperatures at which that heat is released, the release of toxic or otherwise dangerous gases, the material heat capacities, and other key properties can be measured with differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and other approaches. We have demonstrated the value of this approach for a LixCoO2+C+PVDF cathode sheet /LLZO/Li metal material set, where we identified the previously under-appreciated role of the cathode sheet conductive additive and binder in the reaction pathways upon heating to 500°C in a DSC pan.3 Despite this material set containing no liquid electrolyte, delithiated LixCoO2 releases oxygen upon heating to >~230°C, and that oxygen can react exothermically with the Li metal and conductive carbon. In addition, PVDF binder releases HF gas at >400°C, which can also react exothermically with Li metal.

This talk will focus on the methodology required to obtain accurate measurements on milligram-scale samples, with an emphasis on the sample preparation and DSC methods to obtain accurate, repeatable results. Approaches associated with DSC baselining and integration methods will be presented. The talk will also present results from our recent work on material sets that are more commercially relevant for electric vehicle applications than the LixCoO2 cathode sheet/ LLZO / Li material set. In particular, results from material sets such as NMC532 cathode sheet / LLZO / Li, NMC811 cathode sheet / LLZO / Li, and NMC811 cathode sheet / LPSCl / Li metal will be presented. Finally, we will discuss the implications of our early-stage, material-scale work for future large-format cells.

1. See Category 3 in the ARPA-E EVS4ALL program, https://arpa-e.energy.gov/technologies/programs/evs4all

2. Joule 6, 742–755, April 20, 2022.

3. ACS Appl. Mater. Interfaces 2023, 15, 49, 57134–57143
Polymerized Acrylonitrile Artificial SEI for Long-Life Li-Metal Battery and Enhanced Stability for Li/Li10GeP2S12 Interface
Authors: Hoang Binh , Lin Chuan-Fu , Damircheli Roya , Brausch Madison , Ferrari Victoria
Published: August 2024

Lithium metal anode batteries have attracted significant attention as a promising energy storage technology, offering a high theoretical specific capacity and low electrochemical potential. Utilizing lithium metal as the anode material can substantially increase energy density compared to conventional lithium-ion batteries. However, the practical application of lithium metal anodes has encountered notable challenges, primarily due to the formation of dendritic structures during cycling. These dendrites pose safety risks and degrade battery performance. Addressing these challenges necessitates the development of a reliable and effective protection layer for lithium metal. This study presents a cost-effective and convenient method to produce lithium metal protective layers by creating ex-situ polymer layers using acrylonitrile (AN). This method extends the lifetime of lithium metal anodes by a remarkable factor of six under high current (1 mA/cm²) cycling conditions. While the cycle life of bare lithium metal is approximately 150 hours under high current conditions, AN-treated lithium metal anodes exhibit an impressive longevity of over 900 hours.

Furthermore, with the increasing attentions on solid-state electrolytes – which address the safety concerns and energy density limitations associated with conventional liquid electrolytes in lithium-ion batteries, the interface between Li metal and solid-state electrolytes has been the major challenges. For example, Li10GeP2S12 (LGPS) stands out among these solid electrolyte materials, boasting high ionic conductivity (1 x 10⁻² S cm⁻¹). Nonetheless, the severe instability of the interface between lithium metal anodes and solid electrolytes, including dendrite formation and electrolyte degradation, hindering their practical implementation. This work also goes deeply to explore the stability and performance of Li | LGPS systems by utilizing a polymerized acrylonitrile interfacial. By elucidating the mechanisms governing the interfacial layers, this low-cost fabrication of AN-treated lithium metal holds significant potential for advancing the commercialization of future lithium-metal batteries, surpassing the capabilities of traditional lithium-ion batteries.
Influence of Transition-Metal Order of LNMO Spinel on the Li Ion Diffusion
Authors: Glibo Albina , Cupid Damian Marlon , Kahr Juergen
Published: August 2024

Cathode materials contribute a substantial portion to the weight, cost, and environmentally sustainability of LIBs. A key strategy to enhance energy density at reduced cost and improved sustainability is to develop more cost-effective, cobalt-free, higher-energy-density alternatives. Among the Co-free electrode cathode chemistries, the LiNi0.5Mn1.5O4 (LNMO) spinel stands out as most promising. It exhibits a high specific energy density of 650 Wh/kg, attributed to its elevated operating voltage of approximately 4.7 V vs. Li+/Li. Furthermore, LNMO is more thermally stable than NMC and has high ionic conductivity. However, LNMO suffers from rapid capacity decay leading to short battery life, and high-voltage electrolytes that are resistant to decomposition at the higher operating voltages are required.

LNMO forms two phases depending on the ordering of transition metals (TM). In the disordered phase, Ni and Mn ions are randomly distributed on the 16d sites of the Fd3̅m cubic unit cell, whereas in the ordered phase, the which Ni and Mn atoms occupy 4b sites and 12d sites of the P4332 cubic cell, respectively. In this work, the impact of TM ordering on fundamental parameters such as the unit cell size, electrode expansion, and Li-ion diffusion coefficients at different states of charge were explored using techniques such as in-operando x-ray diffraction, in-situ dilatometry, galvanostatic intermittent titration technique, and electrochemical impedance spectroscopy. The electrodes for these studies were prepared using both PVDF and water-based binders such as CMC in order to gain key insights into the effect of aqueous electrode processing on the Li+-ion transport parameters, interface resistances, and electrode expansion during cycling.
Real-Time Monitoring of Electrochemical Reactions in All-Solid-State Lithium Batteries by Simultaneous Grazing-Incidence Small-Angle/Wide-Angle X-Ray Scattering
Authors: Liang Yuxin , Zheng Tianle , Sun Kun , Xu Zhuijun , Guan Tianfu , Apfelbeck Fabian A.C. , Ding Pan , Sharp Ian D. , Cheng Yajun , Schwartzkopf Matthias , Roth Stephan Volkher , Müller-Buschbaum Peter
Published: August 2024

Polyethylene oxide (PEO)-based composite electrolytes (PCEs) are considered as the promising candidates for next generation lithium metal batteries due to its high safety, easy fabrication and good electrochemical stability. However, the material suffers from low conductivity and high crystallinity of the ethylene oxide (EO) chain, which inhibits its commercialization. Therefore, it is crucial to understand the electrochemcial process as well as Li+ transfer pathway within PEO-based batteries. Using operando grazing-incidence small-angle and wide-angle X-ray scattering (GISAXS and GIWAXS) in Li||Cu cell framework, we find that the electrochemical reaction within the PCE is highly correlated with the evolution of the buried morphology and crystalline structure evolution of the PCE. This two irreversible reactions, PEO-Li+ reduction and TFSI- decomposition, cause changes in both the crystalline structure and morphology of the PCE. In addition, the reversible Li plating/stripping process alters the inner morphology, especially the PEO-LiTFSI domain radius, rather than causing crystalline structure changes. This work provides a new path to monitor a working battery in real time, thereby enabling detailed understanding of electrochemically-induced changes of the microscopic morphology and crystalline structure of PCE, which is essential for developing high transferable and interface stable PCE-based lithium metal batteries.

Figure 1