bluuebunny/crossref_metadata_2025 huggingface dataset:
X-Ray Microtomography Analysis of Li-Sulfur Batteries with a Block Copolymer Electrolyte
Authors: Devaux Didier , Villaluenga Irune , Jiang Xi , Chang Yu Hao , Parkinson Dilworth Y. , Balsara Nitash P.
Published: December 2020

Li-ion batteries are the dominant solution for many applications, from small electronic devices up to hybrid and fully electric vehicles.[1] However, this technology is now mature and new chemistries are needed to reach high specific energy while ensuring safety. Despite a relatively low operating voltage, sulfur (S8) is an attractive cathode active material due to its high theoretical specific capacity; a factor of six higher than traditional LiCoO2 cathodes.[2] To realize high energy density systems, the S8 cathode must be paired with a Li metal anode. Many challenges remain to be addressed to effectively couple a Li metal with a S8 cathode such as the low S8 utilization, the strong volume change of active material upon cycling, the insulating nature of S8 and of the final product Li2S, the solubility of polysulfides in the electrolyte.[3] This issues lead to poor capacity retention, limited cycle life, and low Coulombic efficiency. To address the polysulfide dissolution problem one approach consists in confining S8 within mesoporous and nanoporous carbon.[4] However, conventional liquid electrolytes are not stable against Li metal. A solution is then to use a solid polymer electrolytes, such as polystyrene-b-poly(ethylene oxide) (SEO) block copolymer doped with LiTFSI salt, known to stabilize Li metal.[5]

The goal of this study is to understand the behavior of Li-S8 batteries comprising a SEO electrolyte. The cathode is a composite made of carbon, SEO electrolyte and sulfur-impregnated carbon nanospheres.[6] The cells were cycled and exhibited significant capacity fade. We thus used hard X-ray microtomography to determine the reason for this capacity fade. Figure 1 represents tomography images prior and after cycling. In addition to polysulfide dissolution, our observations indicate that the battery failure in our system is also due to strong changes at the Li/SEO interface.

References

[1] J. B. Goodenough, K.-S. Park, J. Am. Chem. Soc., 135 (2013) 1167 (2013).

[2] P. G. Bruce, S. A. Freunberger, L. J. Hardwick, J.-M. Tarascon, Nat. Mater., 11 (2012) 19.

[3] S. S. Zhang, J. Power Sources, 231, 153 (2013).

[4] X. Fan, W. Sun, F. Meng, A. Xing, J. Liu, Green Energy Environ., 3 (2018) 2.

[5] D. T. Hallinan, S. A. Mullin, G. M. Stone, and N. P. Balsara, J. Electrochem. Soc., 160, (2013) A464.

[6] D. Devaux, I. Villaluenga, X. Jiang, Y. H. Chang, D. Y. Parkinson, N. P. Balsara, J. Electrochem. Soc., 167 (2020) 060506

Figure 1
A Study on the Kinetics of the Phase Transformation in Silicon Anodes in Lithium Ion Batteries - in-Situ Experiments and a Computational Model
Authors: Rezazadeh Kalehbasti Shaghayegh , Maris Humphrey J , Bower Allan F , Guduru Pradeep R.
Published: December 2020

Being one of the major incentives in advancing technologies, characterizing the phase transformation in materials is yet far from reaching a fully comprehended subject. Understanding the mechanics, thermodynamics, and kinetics of the phase transformation serves a significant role in modeling the performance of materials. In this talk, we introduce a non-destructive in situ method for monitoring the advancement of the reaction front with a resolution of ~10 nm. We combine Picosecond Ultrasonics with Atomic Force Microscopy to study the velocity of the phase boundary propagation and the corresponding volumetric strain. Picosecond Ultrasonics is a pump and probe technique that can measure the thickness of the internal layers of material using ultrasounds that are generated and detected optically. Crystalline silicon is chosen as our model system due to its characteristic phase transformation behavior during its reaction with lithium. Using this technique, we have examined the diffusion of lithium atoms through different crystallographic orientations under various galvanostatic and potentiostatic conditions. Based on these experimental results, we have calibrated a modified Cahn-Hilliard type of phase field model of a moving phase boundary problem. In contrast to the classical formulation, the mobility of the interface can be determined using this modified Cahn-Hilliard model. The relevant thermodynamic and kinetic parameters for the phase transformation due to diffusion of Li in crystalline Si for the two crystallographic orientations are extracted. The extracted model parameters can facilitate the simulation of phase transformation in more complex structures with multiple crystallographic facets.
A Model-Based Insight into Electrolyte Behaviour in Aqueous Zinc-Ion Batteries
Authors: Borchers Niklas , Horstmann Birger
Published: December 2020

Next-generation batteries strive for the optimal fit in performance, cost, and environmental safety. Within recent times, a whole playground of different material systems and working principles were investigated. Consumer alkaline batteries with a metallic zinc anode and manganese dioxide cathode achieve excellent energy densities of [1], yet their development stalled due to their limited rechargeability. Switching the aqueous electrolyte from alkaline KOH to, for example, mild electrolytes, however, showed a reversible charge/discharge mechanism at the cathode [2]. This achievement highly increased the research interest in zinc-ion batteries in the last decade, and many successful systems were proposed [3], [4].

Aqueous metal batteries face a series of challenges. The limited stability window of water, as well as unwanted precipitation reactions, deteriorate the battery performance and increase aging reactions. The electrolytes composition and the concentration-dependent complex formation governs its performance. Within Zinc-air batteries, we performed model-based optimization studies of pH adjusted electrolytes [5].

Yet, to our knowledge, there is no modelling work done for zinc-ion batteries. Within our contribution, we combine a description of complex formation with a dynamic cell model. The electrolyte speciation significantly influences the transport properties of the electrolyte as well as its stability. With our cell model, we predict the performance and rate-dependent behavior of commonly used materials. With this, we identify system-requirements and pitfalls in the ongoing optimization of aqueous zinc-ion batteries.

This work is supported by the Federal Ministry of Education and Research (BMBF) via the project ZIB.

Literature

[1] S. Clark, N. Borchers, Z. Jusys, R. J. Behm, and B. Horstmann, Aqueous Zinc Batteries. 2020.

[2] C. Xu, B. Li, H. Du, and F. Kang, “Energetic Zinc Ion Chemistry: The Rechargeable Zinc Ion Battery,” Angew. Chemie Int. Ed., vol. 51, no. 4, pp. 933–935, Jan. 2012, doi: 10.1002/anie.201106307.

[3] B. Tang, L. Shan, S. Liang, and J. Zhou, “Issues and Opportunities Facing Aqueous Zinc-ion Batteries,” Energy Environ. Sci., pp. 3288–3304, 2019, doi: 10.1039/c9ee02526j.

[4] J. Huang, Z. Guo, Y. Ma, D. Bin, Y. Wang, and Y. Xia, “Recent Progress of Rechargeable Batteries Using Mild Aqueous Electrolytes,” Small Methods, vol. 3, no. 1, p. 1800272, Jan. 2019, doi: 10.1002/smtd.201800272.

[5] S. Clark et al., “Designing Aqueous Organic Electrolytes for Zinc-Air Batteries: Method, Simulation, and Validation,” Adv. Energy Mater., vol. 10, no. 10, p. 1903470, Mar. 2020, doi: 10.1002/aenm.201903470.

Figure 1: Schematic of the interaction of the evaluation of electrolyte composition and the cell model. Illustration on the left adapted from [1]

Figure 1
(Invited) Theoretical Study on the Energy Storage Mechanism of Transition-Metal-Carbide MXene By Quantum-Classical Hybrid Simulation
Authors: Ando Yasunobu
Published: December 2020

Two-dimensional transition-metal carbide MXenes has been known as a promising material of high-performance electrode for energy storage applications with both non-aqueous and aqueous electrolytes because it has electronic conductivity, ion capability in interlayer nanospace, and the redox activity of Ti. Especially, as an electrode of electrochemical capacitors, MXenes have a unique dependence of capacitance on intercalated cation species and a distinctive behavior that is both capacitive and pseudocapacitive depending on the electrolyte. To better understand electrochemical mechanism of these behaviors, we performed a microscopic theoretical analysis of the electric-double layer (EDL) in the interlayer nanospace of the MXene electrode by combining first-principles calculations based on density functional theory (DFT) and classical implicit solvation theory named three dimensional reference-site interaction model (3D-RISM) method [1]. By using the quantum-classical hybrid simulation, solvation effect at the interlayer nanospace of MXene electrode was taken into consideration appropriately with low computational cost comparable with conventional DFT simulation.

For the unique dependence of capacitance on intercalated cation species, our simulation results showed that the capacitance of EDL capacitors can be enhanced by a factor of 1.8, when the water molecules are strongly confined into the two-dimensional nanoslits of titanium carbide MXene electrode. This is because that dipolar polarization of strongly confined water overscreens an external electric field applied on the EDL and enhances capacitance with a characteristically negative dielectric constant of a water molecule [2, 3].

Another investigated feature is the distinctive behavior that is both capacitive and pseudocapacitive depending on the electrolyte. As a result of their electronic states simulated via the quantum-classical hybrid simulation, it was found that the hydration shell of intercalated ions prevents orbital coupling between MXene and the intercalated ions, which leads to the formation of an EDL and capacitive behavior. However, once the cations are partially dehydrated and adsorbed onto the MXene surface directly, because of orbital coupling of the cation states with the MXene states, particularly for surface-termination groups, charge transfer occurs and results in a pseudocapacitive behavior [4].

References

[1] S. Nishihara, and M. Otani, Phys. Rev. B 96, 115429 (2017).

[2] A. Sugahara, Y. Ando, S. Kajiyama, K. Gotoh, K. Yazawa, M. Otani, M. Okubo, and A. Yamada, Nat. Commun. 10, 850 (2019).

[3] K. Kim, Y. Ando, A. Sugahara, S. Ko, Y. Yamada, M. Otani, M. Okubo, and A. Yamada, Chem. Mater. 31, 5190 (2019).

[4] Y. Ando, M. Okubo, A. Yamada, and M. Otani, Adv. Func. Mater. accepted (2020).
Density Functional Tight Binding Modelling of Lithium Intercalated Graphite with Machine-Learned Repulsive Potential
Authors: Panosetti Chiara , Anniés Simon , Grosu Cristina , Scheurer Christoph
Published: December 2020

Lithium ion batteries have been a central part of consumer electronics for decades. More recently, they have also become critical components in the quickly arising technological fields of electric mobility and intermittent renewable energy storage. However, many fundamental principles and mechanisms are not yet understood to a sufficient extent to fully realize the potential of the incorporated materials.

The vast majority of concurrent lithium ion batteries make use of graphite anodes. Their working principle is based on intercalation–the embedding and ordering of (lithium-) ions in the two-dimensional spaces between the graphene sheets. This important process–it yields the upper bound to a battery's charging speed and plays a decisive role for its longevity–is characterized by multiple phase transitions, ordered and disordered domains, as well as non-equilibrium phenomena, and therefore quite complex. Such complexity emerges particularly at low states of charge (SOC), and complicates both the interpretation of experiments and the computational modelling.

From a computational standpoint, targeted system sizes compatible with the SOC range of interest are inaccessible to first-principles calculations, yet require first-principles treatment of key effects such as dispersion and long-range electrostatics. Density Functional Tight Binding (DFTB), a semi-empirical approximation to DFT, offers a high-quality trade-off between accuracy and speed. However, this advantage comes at the cost–or rather initial investment–of pairwise parametrization.

As no Li-C DFTB parameters were publicly available yet, we produced a parameter set specifically tailored to this system, employing a parametrization strategy [1] that combines global optimization of electronic parameters via Particle Swarm Optimization (PSO) [2] with our recently developed approach that uses Gaussian Process Regression (GPR) [3] to machine-learn the repulsive potential.

Using the resulting parametrization, we are able to reproduce experimental reference structures at a level of accuracy which is in no way inferior to much more costly ab initio methods. We present structural properties and diffusion barriers for some exemplary system states. Additionally, we are able for the first time to resolve the full Potential Energy Surface (PES) of Li motion in stage-I and stage-II LiC108 (SOC 5%). The PES contains information that enables us to implement, and in perspective discuss, both kinetic Monte Carlo (kMC) models of Li-ion mobility in the graphite host, and free-energy sampling which ultimately yields the computed voltage profile of the anode.

[1] Panosetti et al., https://arxiv.org/abs/1904.13351

[2] Chou et al., J. Chem. Theory Comput. 2016, 12, 1, 53–64

[3] Panosetti et al., J. Chem. Theory Comput. 2020, 16, 4, 2181–2191

Figure 1
(Invited) Strategic Development of Functional Electrode Materials and Electrolytes for Multivalent Ion Storage
Authors: Ha Jung Hoon , Lee Boeun , Oh Si Hyoung
Published: December 2020

As the global markets for electric vehicles (EVs) and commercial electricity storage systems (ESS) grow rapidly, the demand for more cost-effective and safe alternative to Li-ion technology (LIB) is ever-increasing. The multivalent ion storage based on Mg, Zn and Al metals offers promising candidates for viable energy storage mechanism, since raw materials of these metals are abundant in the earth-crust, environmentally-benign, and safe to handle with. The major technical challenges for rechargeable batteries using multivalent ion storage include lethargic electrode kinetics associated with multivalent cation diffusion through the intercalation hosts, and the development of functional electrolytes equipped with a high reversibility on metal plating-stripping, and a large electrochemical window. In this work, we present a couple of conversion-based electrode materials for facile multivalent ion storage, showing a large reversible capacity and a long-term cycle stability even in the high-current rate [1]. We also demonstrate a series of new electrolytes for Mg-ion batteries based on conventional Grignard reagents containing ionic liquids with allyl-functional group, which shows a fast reaction kinetics on the negative electrode and a high oxidative stability [2].

Reference

[1] J. H. Ha, B. Lee, J. H. Kim, B. W. Cho, S.-O. Kim, S. H. Oh, Energy Storage Mater. 27 (2020) 459-465

[2] B. Lee, j.-H. Cho, H. R. Seo, S. B. Na, J. H. Kim, B. W. Cho, T. Yim, S. H. Oh, J. Mater. Chem. A 7 (2019) 3126-3133.

Acknowledgement

This work was supported by KIST institutional program (2E30211)
(Invited) Designing Organic and Organometallic Materials for Next-Generation Redox Flow Batteries
Authors: Byon Hye Ryung
Published: December 2020

Redox flow batteries (RFBs) are an exciting target for storing renewable energy at a large scale. Currently available commercial RFBs relying on vanadium as the redox material have suffered from high cost to be scale to a grid-level size. Such a challenge could be reduced if redox-active organic molecules could be used instead of vanadium. In addition, the design of redox molecules with various functionalities can tune the molecular properties, which eventually allows for improving the solubility and controlling the redox potentials to optimize their performance. However, there are very few candidates that could serve as organic redox materials and almost all of them act as a single-electron carrier. For increasing the energy density, the effective strategies are (1) increasing voltage gap as the redox materials reversibly respond more negative/positive potentials for negolyte/posolyte, respectively, (2) increasing solubility, and (3) designing redox materials capable of two (or more)-electron storage, which instantly doubles the energy density. Here we present some research results which have been done in my laboratory for the target of increasing energy density. We show a new class of organic material of naphthalene diimide (NDI) that can reversibly store two electrons at neutral pH in aqueous solution. By decorating with glycinate, the solubility of n-type organic semiconducting NDI was improved in aqueous solution. We studied the fundamental two-electron redox behavior from experimental and computational analyses and displayed a prototype RFB containing [K2-BNDI] negolyte and 4-OH-TEMPO posolyte with reasonable cyclability, energy efficiency and excellent stability. To improve the stability of redox materials, we also attempted to use redox-active organometallic molecules such as pseudo-octahedral Co-polypyridyl complexes, and developed rational strategies for enhancing the robustness, namely, the spin-crossover between low and high-spin states and the chelation effect emerging from replacing three bidentate ligands with two tridentate analogues.
3D-Printed Energy Storage Devices
Authors: Ragones Heftsi , Vinegrad Adi , Goor Meital , Ardel Gilat , Dorfman Moty Marcos , Kamir Yosi , Golodnitsky Diana
Published: December 2020

The increasing demand for multifunctional portable/wearable electronic devices, including wireless sensors and implantable medical devices is continuously growing. Such devices need rechargeable batteries with dimensions on the scale of 1–10 mm3 (few to tens mm2 footprint area of substrate) including all the components and all the associated packing. Thus, in the past decade, along with the developments in battery materials, the focus has been shifting more and more towards innovative fabrication processes, unconventional configurations, and designs with multi-functional components. 3D printing technologies enable a well-controlled creation of functional materials with three-dimensional architectures, representing a promising approach for fabrication of next-generation electrochemical energy storage (EES) devices with high performance due to a higher electrode/electrolyte interfacial area.

In this work, we demonstrate a novel design and a novel approach of 3D printing of batteries of different shapes and size by using filaments composed of active electrode materials bound with polymers. The electrodes were printed by fused-filament fabrication (FFF) method. We demonstrated a reversible electrochemical cycling of 3D printed lithium iron phosphate (LFP) and lithium titanate (LTO) composite polymer electrodes vs. lithium metal anode with high performance and capacity in cells containing both conventional non-aqueous and ionic-liquid electrolytes.

In addition, the development and fabrication of a novel 3D-printed solid-state or quasi-solid electrolyte by FFF has been accomplished. The electrolytes are composed primarily of polyethylene oxide (PEO) and polyethylene glycol (PEG) which are known ionic conductors, and polylactic acid (PLA) for enhanced mechanical properties and high temperature durability.

Our research introduces novel thick-layer 3D batteries, thus reducing cost related to high mass loading per battery footprint of smart 3D structures with the help of low-cost fabrication method.

References

[1] H. Ragones et al. "Towards smart free form-factor 3D printable batteries." Sustainable Energy & Fuels 2.7 (2018): 1542-1549.

[2] H Ragones et al. On the Road to a Multi-Coaxial-Cable Battery: Development of a Novel 3D-Printed Composite Solid Electrolyte Journal of The Electrochemical Society 2019 ,167 (7), 070503.
2D Ti3C2Tz MXene Synthesized By Water-Free Etching of Ti3AlC2 in Polar Organic Solvents
Authors: Natu Varun , Pai Rahul , Sokol Maxim , Carey Michael , Kalra Vibha , Barsoum Michel W.
Published: December 2020

MXene is a recently discovered family of two-dimensional transition metal carbides, nitrides and carbonitrides that have shown a lot of promise in the field of energy storage with applications ranging from high capacity anodes for lithium, sodium, potassium and aluminum ion batteries, supercapacitors and catalysts for hydrogen evolution, among several others. The first MXene ,Ti3C2Tz, discovered in 2011, was synthesized by etching out the ‘Al’ atomic layers from the parent MAX phase, Ti3AlC2, in a solution of concentrated hydrofluoric acid. Several new ways of synthesizing MXenes at near ambient temperatures, incorporating chemical etching using hydrochloric acid and lithium fluoride and electrochemical etching in varying electrolytes have been developed since 2011. The majority of these etching methods, however, use water as their main solvent limiting direct use of MXenes in water sensitive applications such as Li and Na-ion batteries that use organic electrolytes. In this work, we demonstrate etching and delamination of MXenes in complete absence of water, by using organic polar solvents in the presence of ammonium dihydrogen fluoride. As importantly, we show that that electrodes made from Ti3C2Tz etched in propylene carbonate, resulted in Na-ion battery anodes with twice the capacity to those etched in water. The absence of water during etching also minimized the O and OH terminations relative to F.
High Mass-Loading Sulfur-Composite Cathode for Lithium-Sulfur Batteries
Authors: Baikalov Nurzhan , Serik Nurassyl , Kalybekkyzy Sandugash , Mentbayeva Almagul , Bakenov Zhumabay
Published: December 2020

The development of electric vehicles and portable devices require high power and high energy density batteries. In this regard, among the existing energy storage systems, the lithium-ion batteries (LIBs) play a key role. However, the energy and power densities of conventional LIBs are reaching the limited theoretical values and cannot fulfill requirements for new generation portable devices and electric vehicles. Sulfur is a promising replacement for intercalated cathode materials, since it has high theoretical capacity of 1672 mAh g-1 and high gravimetric energy density of 2600 Wh kg-1.1 Moreover sulfur has several advantages such as low cost, environmental friendliness and abundance.2 However, commercialization of lithium-sulfur batteries faces several difficulties related to low conductivity of sulfur, polysulfide dissolution and lithium dendrite growth.3,4 The aim of this research was to increase mass loading of sulfur in the electrode, which in turn requires improvement in the bulk conductivity. For that reason, high sulfur loading S/DPAN/CNT composite cathode was prepared by a simple and efficient way of designing micro and nano level 3D carbon networks. The covalent bonding between pyrolyzed PAN and sulfur diminishes polysulfide dissolution, while CNT maintains structural integrity, acting as nanoscale interwoven skeleton and ensures electron transfer within and between S/DPAN granules.5 Then S/DPAN/CNT was impregnated into pores of commercial carbon fiber paper (CFP), which in its turn provides bulk electron conductivity in macro level. As a result, mass loading of sulfur was increased up to 5 mg cm-2while maintaining a high initial specific capacity of 1400 mAh g-1 and stable cyclability.

Acknowledgements

This research was supported by the targeted state program BR05236524 “Innovative Materials and Systems for Energy Conversion and Storage” from the Ministry of Education and Science of the Republic of Kazakhstan for 2018-2020.

References:

[1] K.H. Shin, K.-B. Kim, C.S. Jin, W. Ahn, K.N. Jung, J. Power Sources 202 (2011) 394–399.

[2] Y. Zhang, Y. Zhao, T. N. L. Doan, A. Konarov, D. Gosselink, H. G. Soboleski, P. Chen, Solid State Ionics 238 (2013) 30–35.

[3] M. Li, R. Carter, A. Douglas, L. Oakes, C. L. Pint, ACS Nano 11 (2017) 4877–4884.

[4] Z. Nie, J.-G. Zhang, N. D. Browning, Q. Li, L. B. Mehdi, X. Xie, J. Liu, G. L. Graff, J. Zheng, S. Ferrara, Adv. Energy Mater. 5 (2015) 1402290.
The Interplay between Thermodynamics and Kinetics in the Solid-State Synthesis of Layered Oxides
Authors: Bianchini Matteo , Wang Jingyang , Clément Raphaële J. , Ouyang Bin , Xiao Penghao , Kitchaev Daniil , Shi Tan , Zhang Yaqian , Wang Yan Eric , Kim Haegyeom , Zhang Mingjian , Bai Jianming , Wang Feng , Sun Wenhao , Ceder Gerbrand
Published: December 2020

To design a synthesis route for energy storage materials, the phase diagram is a useful starting point. However, non-equilibrium intermediates often appear during synthesis—which are difficult to anticipate and often persist as impurities in the final reaction product. In addition, intermediate phases may template the morphology of particles. Thus, being able to rationalize and predict which metastable intermediates form during solid-state reactions is crucial towards developing rational frameworks in which to create predictive ceramic synthesis approaches.

Guided by real-time in situ synchrotron observations of materials formation, we develop a new theory to model the reactions between ceramic precursors to form NaxMO2 layered oxides (M = Co, Mn), which are important cathode materials for Na-batteries. These layered oxides form in two polytypes: a two-layer (P2) stacking, and a three-layer (O3 or P3) stacking. Even though phase diagrams determine that P2 is the stable phase at Na0.66CoO2 composition, synthesis using a nominal 0.33 Na2O2 + CoO precursor mixture is observed to first form the O3-NaCoO2. The reaction then proceeds sequentially through non-equilibrium O3’and P3 phases, with the equilibrium P2-Na0.66CoO2 only obtained after long time at high temperature. This raises the fundamental question—how do thermodynamic driving forces and kinetic mechanisms conspire to create phases that are not thermodynamic stable, and why can some phases, which are thermodynamically favored at all temperatures, only be formed after long times at high temperature? We show that the first phase to form from the precursors is actually the compound which consumes the most reaction energy, irrespective of whether this compound is at the target stoichiometry. After this initial compound forms, a combination of fast topotactic reactions and slow nucleation and growth processes slowly bring the system to the equilibrium phase.

Based on this insight we can now predict how different precursors change the reaction pathway, driving the crystallization pathway through different intermediates. As an example, we show how P2-Na0.66MnO2 can be formed through very different reaction pathways by changing the precursors. This rationalization of the first phase to form creates a valuable design handle by which reaction paths can be tailored to go through, or circumvent, specific non-equilibrium intermediates. Our combined computational and experimental approach offers a predictive framework for the synthesis design of new energy materials.
(Invited) Area-Selective Atomic Layer Deposition of Manganese Oxides on Metal−Dielectric Patterns
Authors: Li Yicheng , Cao Kun , Chen Rong
Published: December 2020

Area-selective atomic layer deposition (ALD) is a kind of high-precision deposition technologies where it happens only on designed areas. It is a very promising technology for scaling-down of nanodevices because of the characteristics of sub-nanoscale thickness control and bottom-up self-alignment. In this work, we report inherently selective ALD of MnOx on Pt/SiO2 substrates by adjusting the ALD processes parameters. Mn precursors with different ligands are introduced, namely Mn(thd)3 and Mn(EtCp)2. Through temperature and precursor pulse etc. regulation, an appropriate selective process windows are approached. During the first few ALD cycles, there is a nucleation delay on SiO2 surface, while it grows linearly on metal surface. The results of selectivity may come from the active oxygen on the platinum surface which promoted the reaction, while the dielectric surface has a nucleation delay. Through first-principles calculation, the reaction path and energy barrier are analyzed to explain the selective growth. The study broadens the family of selective deposition and provides guidance for specific applications, such as integrated circuits, optoelectronic devices, etc.

Figure 1
(Invited) Reactions on Metal Surface and Diketone Induced By Gas Cluster Ions during Atomic Layer Etching
Authors: Toyoda Noriaki
Published: December 2020

Gas cluster ion beams (GCIB), which consists of several thousands of gaseous atoms or molecules, have been used as novel low-energy ion beams for surface processing and analysis. Since thousands of low-energy (several eV) atoms bombard a surface at the same time and the same position, the bombarded area experiences transient high-temperature and high-pressure conditions, which enhance sputtering of atoms or enhance surface reactions. In recent years, we have been investigating to apply GCIB as energetic ions for atomic layer etching. We have reported ALE of transition metals (Cu and Ni) with GCIB irradiations and diketone (acetylacetone and hexafluoroacetone). We separated each etching step as following; (1) adsorption of diketone molecules on metal oxide, (2) evacuation of residual vapor, (3) irradiation of oxygen GCIB to remove metal oxide. By using 5 keV oxygen GCIB (~ 2eV/molecules), thin layer of nickel oxide with adsorbed acetylacetone is removed. There is no physical sputtering at this energy region, which realizes self-limiting ALE process. From in-situ XPS study, Ni oxide with adsorbed diketone molecules can be removed by Ar-GCIB irradiation. It means that other oxidation method can be used to form metal oxide, and Ar-GCIB can be used for the removal steps. In this talk, we will report surface reactions between metals and diketone induced by gas cluster ion irradiations, and etching characteristics of various metals using GCIB irradiation and diketone.
(Invited) Elucidating the Mechanisms for Atomic Layer Growth through in Situ Studies
Authors: Elam Jeffrey W.
Published: December 2020

Atomic Layer Deposition (ALD) provides exquisite control over film thickness and composition and yields excellent conformality over large areas and within nanostructures. These desirable attributes derive from self-limiting surface chemistry, and can disappear if the self-limitation is removed. Understanding the surface chemical reactions, i.e. the ALD mechanism, can provide insight into the limits of self-limitation allowing better control, successful scale up, and the invention of new processes. In situ measurements are very effective for elucidating ALD growth mechanisms. In this presentation, I will describe investigations into the growth mechanisms of ALD nanocomposite films comprised of conducting (e.g. W, Mo and Re) and insulating (e.g. Al2O3, ZrO2 and TiO2) components using in situ measurements. These ALD nanocomposites have applications in particle detection, energy storage, and solar power. We have performed extensive in situ studies using quartz crystal microbalance (QCM), quadrupole mass spectrometry (QMS), Fourier transform infrared (FTIR) absorption spectroscopy, and current-voltage measurements. These measurements reveal unusual ALD chemistry occurring upon transitioning between the ALD processes for the two components. This results in unique reaction products that affect the properties of the films in beneficial ways. The knowledge gained from our in situ studies of the ALD nanocomposite films has helped us to overcome problems encountered when we scaled up the ALD processes to large area substrates. Beyond fundamental understanding, in situ measurements are extremely effective in ALD process development and process monitoring. I will end my talk by describing our recent work combining in situ measurements and machine learning to accelerate ALD process development.
(Invited) ALD Enabling High-Efficiency Solar Cells
Authors: Hoex Bram
Published: December 2020

Atomic layer deposition (ALD) can synthesize materials with atomic-scale precision. The ability to tune the material composition, film thickness with excellent conformality, low-temperature processing, and in-situ real-time monitoring makes this technique very appealing for a wide range of applications. In this contribution, we will show that ALD is already widely used in the manufacturing of industrial silicon solar cells, where ALD aluminum oxide is used for the passivation of the rear of PERC (Passivated Emitter and Rear Contact) solar cells. ALD aluminum oxide layers can also be used to reduce the contact resistance and firing temperature for phosphorous diffused surfaces. We will show that ALD layers can also avoid potential induced degradation (PID, a possible failure mode for large photovoltaic systems) at the solar cell level. ALD capping layers can also be used to reduce light and elevated temperature induced degradation (LeTID), which is a recently identified failure mode for high-efficiency solar cells, by acting as a blocking layer for hydrogen. Finally, we will show that ALD layers are enabling world-record CZTS (copper-zinc-tin-sulphide) solar cells.
Low-Temperature Deposition of Large-Grained Polycrystalline AlN Using Trisdimethylamido Aluminum (TDMAA) and Anhydrous Hydrazine
Authors: Ueda Scott , McLeod Aaron , Alvarez Daniel , Kummel Andrew C
Published: December 2020

High quality, large-grained AlN films are of interest for use as either heat spreading layers or as a buffer/templating layer for further film growth. As the typical deposition temperature for high-quality crystalline AlN is usually in excess of 800 oC, there is a large amount of thermal strain in the films and it is advantageous to develop processes to lower the deposition temperature so that it is compatible with back end of line (BEOL) processing. In this work, the low-temperature (<400 oC) deposition of polycrystalline AlN films is demonstrated by atomic layer annealing (ALA) which is a variant of ALD that utilizes a third pulse of low-energy inert gas ions in addition to the usual metal and co-reactant pulses [1].

Using trimethyl aluminum (TMA) or tris(dimethylamido) aluminum (TDMAA) with the highly reactive nitrogen-containing precursor hydrazine (N2H4), AlN can be deposited at ~200 oC [2]; however, these films are amorphous and would have low thermal conductivity due to a high degree of phonon scattering. Using TDMAA with N2H4 or NH3 at temperatures >350 oC, polycrystalline films can be deposited in a purely thermal process; however, the reported grain sizes are small (<5 nm) or there is a mixture of polycrystalline and amorphous phases [3-4]. ALA has been used to deposit crystalline films such as AlN [1,5] and GaN [6] on a near lattice-matched substrate (sapphire) at low temperatures, but a nitrogen-containing plasma was used.

In the present study of AlN ALA on Si (111) (a non-lattice matched substrate), two metal precursors (TMA and TDMAA) were compared using ultra-high purity anhydrous N2H4 as a co-reactant and argon ions with tuned energy for the third pulse. It was found that deposition using TDMAA as the Al precursor resulted in high-quality AlN films with large grain size (>20 nm) and low C/O contamination (<1.5%) whereas films deposited using TMA had much higher carbon content (>5%), owing to its thermal instability at 400 oC. Transmission electron micrographs for a 40 nm film grown using TDMAA and N2H4 show vertical grain structure with grains spanning the entire thickness of the film. As heat spreading layers often need to be in excess of 1 micron thick in order to be relevant for use in high volume manufacturing, it is also demonstrated that these 40 nm films successfully transfer the large grain size of the ALA film to a thick sputtered AlN film (which can be deposited relatively quickly) by acting as a template layer.

[1] H-Y. Shih et al, Scientific Reports 7:39717.

[2] M. Mizuta et al, Japanese J. Appl. Phys. 25(12), L945-L948 (1986).

[3] R. G. Gordon, U. Riaz, and D. M. Hoffman, J. Mater. Res., 7(7) (1992).

[4] A. I. Abdulagatov et al Russian Microelec. 47(2), 118-130 (2018).

[5] W-C. Kao et al, RSC Adv. 9, 12226-12231 (2019).

[6] W-H. Lee et al ACS Sustainable Chem. Eng. 7,1, 487-495 (2019).

This work was supported in part by the Semiconductor Research Corporation.

Figure 1
Growth and Electrical Characteristics of PE-ALD Germanium Sulfide for 3D Cross-Point Memory
Authors: Kim Myoungsub , Kim Youngjun , Sohn Inkyu , Kim Hyungjun
Published: December 2020

The 3D cross-point memory, known to contain chalcogenide material-based ovonic threshold switching (OTS) selector, is bringing new changes to the memory hierarchy of DRAM and NAND flash memory. The cross-point memory of current planar 3D structures, meanwhile, is already expected to limit scaling in terms of number of critical masks and normalized cost, so it is necessary to prepare a vertical 3D structures [1]. Atomic layer deposition (ALD) process, which is essential to realize vertical 3D structures, has been mostly studied for phase change materials (PCM) based on GeSbTe but OTS selector research is still in its early stage. So, we have studied plasma enhanced-ALD (PE-ALD) of germanium sulfide (GeS) films containing sulfur chalcogenide element with higher optical bandgap than Te and Se for low off current OTS selector for larger array implementation [2] [3]. The PE-ALD of GeS amorphous chalcogenide films was synthesized using commercially available GeCl4 precursor with H2S plasma reactant. The Ge1S2 film was identified quantitative composition and impurities through AES depth profile analysis, and excellent thermal stability up to 600 ℃ was studied by In-situ high temperature X-ray diffraction (HT-XRD). And PE-ALD Ge1S2 has confirmed the superior step coverage in the vertical 3D structure through FIB-TEM compared to chemical vapor deposited GeS film. In addition, the devices of the 50 nm bottom electrode contact size using PE-ALD Ge1S2 films demonstrated OTS characteristic with of remarkable high threshold field 3.0 MV/cm, and low normalized off-current of 25 nA at half threshold voltage. The achievement of PE-ALD research on simple binary Ge1S2 amorphous chalcogenide will contribute to development the future 3D cross-point memory scaling.

Acknowledgments

This paper was result of the research project supported by SK Hynix Inc.

Reference

[1] T. Kim and S. Lee, “Evolution of Phase-Change Memory for the Storage-Class Memory and Beyond,” IEEE Trans. Electron Devices, vol. 1, pp. 1–13, 2020.

[2] C. C. Wu, C. H. Ho, J. Y. Wu, S. L. Lin, and Y. S. Huang, “Characterization of Ge(Se1-xSx)2 series layered crystals grown by vertical Bridgman method,” J. Cryst. Growth, vol. 281, no. 2–4, pp. 377–383, Aug. 2005.

[3] J. W. Park et al., “Optical properties of pseudobinary GeTe, Ge2 Sb2 Te5, GeSb2 Te4, GeSb4 Te7, and Sb2 Te3 from ellipsometry and density functional theory,” Phys. Rev. B - Condens. Matter Mater. Phys., vol. 80, no. 11, Sep. 2009.
Investigation of Hydrogen Effect on Ferroelectricity of Atomic Layer Deposited Hf0.5Zr0.5O2 Thin Film
Authors: Jung Yong Chan , Mohan Jaidah , Kim Harrison Sejoon , Hernandez-Arriaga Heber , Onaya Takashi , Kim Kihyun , Kim Namhun , Kim Si Joon , Ogura Atsushi , Choi Rino , Ahn Jinho , Kim Jiyoung
Published: December 2020

Ferroelectrics have retrieved great interest since the discovery of a ferroelectric phase in HfO2.1 Especially, ferroelectric Hf0.5Zr0.5O2 (HZO) thin films have studied for application as a non-volatile memory and field-effect transistor, due to their high scalability and compatibility with CMOS process.2 In our previous work, we have achieved a low thermal budget process (400 °C) by controlling the tensile stress from the TiN electrode during the annealing process.3 Moreover, the TiN electrode can act as a barrier layer against hydrogen diffusion, therefore, the HZO films using the TiN electrodes can prevent degradation of the ferroelectric properties from hydrogen incorporation. However, during the deposition of HZO film using atomic layer deposition (ALD), the choice of oxygen source can affect the residue in the deposited film. When hydrogen-related substances are used as the oxygen source, the ferroelectric properties can be altered by the residues remaining in the HZO film.

In this study, we adopted various oxygen sources such as H2O, deuterium oxide (D2O), and O3, for the investigation of hydrogen effect on the ferroelectric properties of the ALD-HZO films. The HZO films were deposited on the TiN bottom electrode by ALD using Hf[N(CH3)2]4 (TDMA-Hf) and Zr[N(CH3)2]4 (TDMA-Zr) as the precursors of Hf and Zr, while H2O, D2O, or O3 as the oxidant. After the TiN top electrode was deposited, rapid thermal annealing was done, and metal-insulator-metal capacitors were fabricated using a Pd/Au hard mask and wet etch process.

The HZO films exhibited the formation of a non-centrosymmetric orthorhombic phase which is origin of the ferroelectricity, without consideration for the oxygen sources.4 However, it was confirmed that the ferroelectricity of the HZO film deposited with the oxygen source including hydrogen such as H2O and D2O, was degraded due to the more incorporation with hydrogen. As a result, the ferroelectric polarization of H2O-, and D2O-based HZO was lower than that of O3-based HZO. Simultaneously, the H2O- and D2O-based HZO exhibited higher leakage current than that of O3-based HZO. The results strongly suggest that the suppression of hydrogen incorporation is important to apply ALD-HZO films for next-generation memory application.

This work is supported by the National Research Foundation of Korea (NRF) grant (No. NRF-2019R1F1A1059972), Brain Pool Program (No. 2019H1D3A2A01101691), and the Fostering Global Talents for Innovative Growth Program (No. P0008750).

1 T. S. Böscke, et al., Appl. Phys. Lett. 99, 102903 (2011).

2 S.J. Kim, et al., Appl. Phys. Lett. 113, 182903 (2018).

3 S.J. Kim, et al., Appl. Phys. Lett. 111, 242901 (2017).

4 S.J. Kim, et al., JOM 71, 246 (2019).

Figure 1
(Invited) High Throughput Atomic Layer Deposition Manufacturing Processes for Improved Batteries
Authors: Dameron Arrelaine A , Martinez Madison , Dumont Jaime , Herbert-Walters Meghan N. , Valceschini Annette M. , Ragonesi James , Hughes Barbara K.
Published: December 2020

Commercial adoption of EVs requires that we overcome consumer angst around battery range by enabling fast charge and increasing specific capacity, while also significantly decreasing cost ($/kWh). Achieving these objectives requires higher voltage and higher charge rate operation of high capacity cathodes and anodes and process intensification to minimize processing costs. The major challenge of high-capacity cathode materials paired with low-cost graphite anodes is their propensity for transition metal dissolution and crossover, and gas generation, which stems from electrochemical decomposition of the electrolyte solvent at electrode-electrolyte interfaces. This is exacerbated by increased voltage operation which not only requires voltage tolerant electrode materials and high voltage electrolytes but also requires advanced separators that minimize leakage current and maintain safe utilization under the more reactive conditions of high voltage (>4.5V vs Li+/Li). Equally destructive, fast charge operation adds rapid structural changes and cracking of both the cathode and anode materials due to rapid de-intercalation, transport, and intercalation of lithium ions from the cathode to the anode.

Forge Nano has demonstrated that atomic layer deposition (ALD) is effective at maintaining the structural integrity of high energy cathode materials at charge rates up to 6C and up to 4.6V top of charge with greater than twice the lifetime under accelerated conditions. Advanced nanoengineered surface treatments on anodes, particularly ionically conductive coatings, also prevent lithium plating and mitigate anode degradation during fast charge.

ALD is a platform technology that has been widely demonstrated as a laboratory method to modify interfaces to the benefit of a breadth of applications. While ALD is ubiquitous throughout the semiconductor industry, ALD is not yet widely accepted for modification of high surface area materials and few have demonstrated ALD on powder manufacturability. This talk highlights the impacts of ALD when applied to cathodes anodes and separators on battery performance, the various methods for scaling these ALD coatings to meet battery manufacturing requirements and the net pack-cost savings of ALD integration.
Does Spinel Serve As a Rigid Framework for Oxygen Redox?
Authors: Shi Xiang-Mei , Watanabe Eriko , Okubo Masashi , Yamada Atsuo
Published: December 2020

A major challenge for the development of lithium-ion batteries with high energy densities is to discover a large-capacity cathode material, and an additional oxygen redox capacity has recently been regarded as a new impetus. From the electronic-structure viewpoint, the best-studied oxygen-redox cathode materials, lithium-rich layered oxides possess oxide ions with nonbonding O 2p states along the Li-O-Li coordination axis, which provide the oxygen redox activity. After oxygen oxidation, either a π-type M t
2g-O 2p interaction (M: transition metal) or an O-O bond formation stabilizes the oxidized oxide ions, allowing for reaction reversibility. However, the layered structure is generally unstable after extracting an excess amount of Li ions, leading to the degradation of both capacity and voltage during charge/discharge cycles. It is therefore particularly important to implement oxide ions with nonbonding O 2p states into a stable host framework against excess Li-ion extraction to achieve reversible oxygen-redox capacity. As spinel oxides have a stable three-dimensional framework, it is attractive to explore for spinel oxides capable of the oxygen-redox reactions.

Here, we theoretically diagnose the oxygen-redox activity of spinel oxides using density functional theory (DFT) calculations. LiMg0.5Mn1.5O4 is employed as a model material, as its spinel structure is expected to have oxide ions with nonbonding O 2p state owing to the existence of ionic Mg2+ in the framework. The electronic structure change during the oxygen-redox reaction of LiMg0.5Mn1.5O4 is compared with that of a typical Li-rich layered oxide (Li2MnO3), revealing the lability of oxidized oxide ions in a spinel oxide.