bluuebunny/crossref_metadata_2025 huggingface dataset:
Definition of Redox Centers in Reactions of Lithium Intercalation in Li3RuO4 Polymorphs
Authors: Li Haifeng , Ramakrishnan Srini , Freeland John , McCloskey Bryan D. , Cabana Jordi
Published: December 2020

Cathodes based on layered LiMO2 are the limiting components in the path toward Li-ion batteries with energy densities suitable for electric vehicles. Introducing an over-stoichiometry of Li increases storage capacity beyond a conventional mechanism of formal transition metal redox. Yet the role and fate of the oxide ligands in such intriguing additional capacity remain unclear. This reactivity was predicted in Li3Ru5+O4, making it a valuable model system. A comprehensive analysis of the redox activity of both Ru and O under different electrochemical conditions was carried out, and the effect of Li/Ru ordering was evaluated. Li3RuO4 displays highly reversible Li intercalation to Li4RuO4 below 2.5 V vs. Li+/Li0, with conventional reactivity through the formal Ru5+-Ru4+ couple. In turn, it can also undergo anodic Li extraction at 3.9 V, which involves of O states to a much greater extent than Ru. This reaction competes with side processes such as electrolyte decomposition and, to a much lesser extent, oxygen loss. Although the associated capacity is reversible, re-intercalation unlocks a different, conventional pathway also involving the formal Ru5+-Ru4+ couple despite operating above 2.5 V, leading to chemical hysteresis. This new pathway is both chemically and electrochemically reversible in subsequent cycles. This work exemplifies both the challenge of stabilizing highly depleted O states, even with 4d metals, and the ability of solids to access the same redox couple at two very different potential windows depending on the underlying structural changes. It highlights the importance of properly defining the covalency of oxides when defining charge compensation in view of the design of materials with high capacity for Li storage.
Cr-Doped Na3V2(PO4)3/C Nanocomposite with High Power Capability for Advanced Sodium-Ion Batteries
Authors: Lee Jun , Lee Indeok , Song Moonsoo , Park Young , Hwang Jang-Yeon , Kim Jaekook
Published: December 2020

NASICON-structured Na3V2(PO4)3 (NVP) is one of the most promising cathode materials for rechargeable sodium-ion batteries. In this study, Na3V2-x
Crx(PO4)3@C samples with different concentrations of substituted chromium (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, and 1.0) were fabricated using a low-cost pyro synthesis technique with the advantage of self-carbon-coating, which is essential for phosphate-based cathodes. The electrochemical properties of the Cr-substituted NVP samples were analyzed to evaluate the structural improvements and enhanced sodium storage among the synthesized samples. The rhombohedral structures of the NVP and Cr-doped NVP samples were confirmed by X-ray diffraction (XRD) analysis. Notably, phase change did not occur upon Cr doping. The introduction of Cr in NVP significantly enhanced the electrochemical performances. The NVP structure with x = 0.4 provided a superior discharge capacity of 49 mA h g-1 at a high rate of 70 C. An in-situ XRD investigation demonstrates the high structural stability of the doped sample during the Na+-ion intercalation/deintercalation. An ex-situ X-ray photoelectron spectroscopy analysis shows changes in the oxidation state of vanadium during charging/discharging.
Characterization of Cathode/Electrolyte Interfacial Processes By Scanning Electrochemical Microscopy
Authors: Huang Di , Engtrakul Chaiwat , Nanayakkara Sanjini U. , Luo Hongmei , Tenent Robert
Published: December 2020

Lithium transition metal oxides (LiMn2O4 and LiMO2 where M=Ni, Mn, Co, etc.) are widely applied in lithium ion batteries due to their considerable capacity and energy density. Multiple processes occurring at the cathode/electrolyte interface lead to performance degradation, one of which is the dissolution of transition metals. While transition metal dissolution has been known to occur for some time, open questions remain about mechanistic details of these processes. This work uses the scanning electrochemical microscope (SECM) to observe active cathode degradation processes in situ and immediately at the cathode/electrolyte interface. These results are also paired with complementary analysis employing inductively coupled plasma (ICP) and electron paramagnetic resonance (EPR) spectroscopies to yield insight into the properties of cathode degradation products and their reactivity.

This work focuses on studies of LiMn2O4 thin films as model cathodes and characterizes products of the Mn dissolution process. The degradation process of binder-free LiMn2O4 thin films prepared by polymer assisted deposition was investigated in varied electrolytes. The properties of Mn dissolution products from cathode degradation is compared to Mn salt solutions introduced into complementary electrolytes. Our results appear to indicate substantial variations between the properties of dissolved Mn salts and actual cathode degradation products. Moreover, electrolyte composition appears to affect the electrochemical behavior of metal dissolution products significantly. This likely indicates that the LiMn2O4 degradation mechanism in differing electrolytes undergo different degradation reaction pathways.
Anion Reactivity in Cation-Disordered Rocksalt Cathode Materials: The Influence of Fluorine Substitution
Authors: Crafton Matthew , Yue Yuan , Tong Wei , McCloskey Bryan D.
Published: December 2020

The global demand for energy storage technology has created a tremendous need for Li-ion batteries that are lightweight, low cost, and sustainable. Research in the field of lithium-rich cathode materials has led to the development a new class of lithium-excess, cation-disordered rocksalt (DRX) materials. DRX materials display exciting promise as potential cathodes in lithium-ion batteries, owing to their high capacity and resource-friendly composition. Despite these exciting characteristics, these materials suffer from capacity loss over extended cycling due to deleterious side reactions that occur at high potentials, such as O2 loss. It has been shown that oxygen loss can be suppressed by partial substitution of the lattice oxygen for fluorine, but the role of fluorine in the material remains unclear. In this study, we examine the impact of fluorination on the anionic reactivity of DRX materials. We first use Differential Electrochemical Mass Spectrometry (DEMS) and Titration Mass Spectrometry to map first-charge electrochemistry in DRX cathodes. Comparing the results of this analysis for a DRX oxide and a DRX oxyfluoride, we observe that fluorination increases the transition metal capacity and reduces the oxygen redox capacity. These two effects influence the total material capacity in opposite ways, shifting the balance between transition metal redox and oxygen redox without strongly affecting the total charge capacity. We also adapt an existing technique that couples DEMS with a fluoride-scavenging additive, using it for the first time to show that small amounts of fluorine dissolve from DRX oxyfluorides during charging to high potentials. Finally, we extend these techniques over the first several cycles to study the reversibility of the redox processes and the stability of the materials during cycling. We demonstrate that while oxygen redox remains mostly reversible from cycle to cycle, electrolyte degradation and fluoride dissolution also continue to occur to a diminishing extent during cycling. These conclusions motivate surface passivation to control interfacial reactivity as an important direction to improve cycling stability.
(Invited) Lessons Learnt and Challenges Ahead the Development of Ca-Based Batteries
Authors: Palacin M.
Published: December 2020

The aim to develop batteries based in multivalent metal anodes has recently reemerged as part of the worldwide quest for new energy storage technologies with high energy density. Indeed, figures of merit attainable at the cell level computed using simple models indicate that the theoretical energy densities could easily top the state-of-the-art Li-ion, with costs being potentially much lower.

The viability of a rechargeable technology based on calcium has only been considered recently, after reversible plating/stripping in organic electrolytes was achieved. In the quest for suitable positive electrode materials for multivalent ions, both traditional intercalation hosts, such as TiS2 or V2O5, and alternative materials have been investigated. While V2O5 has so far attracted most attention, the interpretation of results is controversial, as changes in the diffraction pattern upon reduction might be related to the presence of water/protons in the electrolyte. Electrochemical extraction of calcium in Ca3Co2O6 is feasible but the only compound for which reversible electrochemical calcium insertion/extraction has reliably been shown to date is TiS2, despite the process being complex and non-practically viable as a result of solvent co-intercalation and high cell overpotential.

Overall, there is a long and winding road to follow before reliable proof-of-concept can be achieved and technological prospects evaluated. Development of reliable experimental setups, including reference and counter electrodes, coupled to complementary characterization techniques, as well as computational tools, is mandatory if steady progress is to be achieved.

Figure 1
(Keynote) Passivity at High Resolution: Insight from the Surface Science Approach
Authors: Maurice Vincent , Marcus Philippe
Published: December 2020

Passivity is a key property for the durable use of metals and alloys since it provides nanometer-thick, long-term self-protection against corrosion thanks to the formation at the surface of a self-healing oxide film, the passive film. High resolution insight into the mechanisms of self‐protection against corrosion of metals and alloys by oxide passive films can be achieved with a surface science approach, applying surface analytical methods to model solid/liquid interfaces corroding under well‐controlled conditions. This will be illustrated by several examples drawn from the research work performed over the years in the research group led by Philippe Marcus. The review will cover the nucleation and growth of 2D passive layers of adsorbed hydroxide ions, the nanostructure and atomic structure of 3D passive films, the dissolution mechanisms of passivated surfaces and structural aspects of localized corrosion initiation at the nanometer and sub‐nanometer scales. Recent progress made on the understanding of the mechanisms governing chromium enrichment in passive films formed on Cr-bearing alloys such as stainless steel will be highlighted with data on nucleation and growth of the surface oxide obtained at both space and time high resolution.

Some of this research has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (ERC Advanced Grant No. 741123, Corrosion Initiation Mechanisms at the Nanometric and Atomic Scales: CIMNAS).
(Invited) Micro- and Nano-Structure of Passive Film Formed on High Strengthen Steel Surface in pH 6.5 Boric Acid-Borate Buffer Solution
Authors: Fushimi Koji , Higa Kanta , Kitagawa Yuichi , Hasegawa Yasuchika , Katayama Hideki
Published: December 2020

Passivity of high strengthen (HS) steel in pH 6.5 boric acid-borate buffer at 1.5 V(RHE) was investigated by electrochemical technique and scanning transmission electron microscopy (STEM). A larger passivity maintaining current flowed through the HS steel compared with S45C carbon steel. A charge transfer resistance of passive HS steel surface was also larger than that of S45C steel. It was indicating that the passive film formed on the HS steel has a resistance less than that on the S45C steel. STEM revealed that the passive film formed on the HS steel was relatively thick and varied depending on the substrate structure, especially retained austenite. It was concluded that micro-structure and/or chemical composition of the substrate structure strongly affect the formation of oxide film and the conductive property of passive film formed on the HS steel.
(Invited) FTIR Spectroscopical Imaging of the Substrate / Polymer Interface upon Exposure to Corrosive Environments
Authors: Thierry Dominique , Persson Dan
Published: December 2020

Organic coating is an efficient method to protect metal surfaces from corrosive atmospheres but is dependent on the presence of a stable interface between the substrate and the polymer coating. However, coatings based on polymers have mostly only limited barrier properties for water and oxygen. Transport of water to the interfacial region is for most coatings inevitable upon prolonged exposure in aqueous environments. Ingress of water molecules can destabilize the substrate / polymer interface and lead to delamination of the polymer coating and initiation of corrosion processes. In this work was spectrochemical imaging of the substrate / polymer interfacial region using a FTIR-microscope with a focal plane array (FPA) detector is performed in order to follow the water up-take at the substrate / polymer interfacial region with micrometer sized lateral resolution. Chemical imaging of the interfacial region between substrates, such as Ge and Ge with thin Zn metallic layers, and organic coatings was performed during exposure to 0.1 M NaCl and humid air (95 %RH). The water uptake and water induced alterations in the substrate / polymer interfacial region on the microscale was followed. Simultaneous electrochemical impedance measurements allowed correlation of electrochemical information from the coated metal with the chemical imaging of the interfacial region.
(Invited) Corrosion Kinetics and Pit Morphology of Pure Aluminum during Atmospheric Corrosion By in-Operando Microtomography
Authors: Melia Michael Anthony , Noell Philip , Schindelholz Eric John
Published: December 2020

Predicting the kinetics and morphology of localized damage produced during corrosion of passive alloys is a foundational challenge in the development of robust damage models. This is especially the case for atmospheric corrosion, wherein the complex mechanistic interrelationships between environment, material microstructure, and the electrochemical processes driving corrosion are still little understood. This work shows the first results of long-term, in-situ characterization of atmospheric corrosion pits in commercially pure aluminum using x-ray microtomography to address the following questions: 1) how fast do individual pits in this material grow and what controls this growth rate? 2) how does the morphology of pits in this material evolve over time? 3) what is the relationship between pit morphology, the evolving electrolyte on the metal surface, and the microstructure? The mechanism involving the stifling of pit growth will also be discussed.

SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
(Invited) Detection of Anodic Partial Current of Mg Dissolution by Gas-Chromatographic Analysis
Authors: Hoshi Yoshinao , Hirayama Yusuke , Watanabe Hikari , Shitanda Isao , Itagaki Masayuki
Published: December 2020

Magnesium (Mg) and its alloys are attractive materials as the battery electrodes, biomaterials and structural materials because they have high strength-to-weight ratios. However, they actively dissolve in aqueous solution and hydrogen evolution is observed. The hydrogen evolution rate of Mg is increased with increasing anodic polarization above the open circuit potential, which is commonly known as the negative difference effect1,2. The reaction mechanisms of this behavior are unknown and various kinds of electrochemical methods have been developed to clarify them4-7.

We have developed an in-situ detection method of hydrogen gas evolved from Mg during electrochemical measurement6. In this method, an electrochemical cell was connected to a gas chromatograph, namely, the hydrogen gas evolved from dissolving Mg is delivered to the gas chromatograph with the argon carrier gas during electrochemical measurement. The hydrogen evolution rate could be determined by calculating from the volume of hydrogen gas estimated by gas-chromatographic analysis. In our previous work6, the hydrogen evolution rate could be determined under potentiostatic polarization of Mg successively.

In the present study, we applied the developed method6 to the detection of anodic partial current of Mg dissolution. The cathodic current related to the hydrogen evolution reaction was estimated from the volume of hydrogen gas obtained by gas-chromatographic analysis during anodic polarization measurement of Mg. The partial anodic current at each polarization potential could be estimated by the sum of the measured anodic current and absolute value of cathodic current associated with the hydrogen evolution reaction, namely, the partial anodic polarization curve could be obtained by the plots of partial anodic current at each polarization potential. The characteristics of measured anodic polarization curve of Mg and partial anodic polarization curve obtained by the developed method were discussed.

References

1. G. Song, A. Atrens, D. St John, X. Wu and J. Nairn, Corros. Sci., 39, 1981 (1997).

2. G. S. Frankel, A. Samaniego and N. Birbilis, Corros. Sci., 70, 104 (2013).

3. M. Curioni, Electrochim. Acta, 120, 284 (2014).

4. S. Lebouil, A. Duboin, F. Monti, P. Tabeling, P. Volovitch and K. Ogle, Electrochim. Acta, 124, 176 (2014).

5. S. Fajardo and G. S. Frankel, Electrochim. Acta, 165, 255 (2015).

6. Y. Hoshi, R. Takemiya, I. Shitanda and M. Itagaki, J. Electrochem. Soc., 163, C303 (2016).

7. Y. Hoshi, K. Miyazawa, I. Shitanda and M. Itagaki, J. Electrochem. Soc., 165, C243 (2018).
(Invited) Passivity and Pitting Corrosion Behavior of Additive Manufactured 17-4PH Stainless Steel
Authors: Barroux Adrien , Ducommun Nadège , Nivet Eric , Delgado Julien , Laffont Lydia , Blanc Christine
Published: December 2020

Conventionaly manufactured, i.e. wrought, 17-4PH martensitic stainless steel (MSS) is widely used in a large variety of applications, going from biomedical ustensils to large turbine blades. Recently, it appeared as a good candidate for additive manufacturing processes, e.g. laser beam melting (LBM), which is certainly the most common and developed process at this time. The specific microstructures generated by LBM have been well discussed in the literature for many types of materials. Nevertheless, these peculiarities can also affect the durability of the LBM-manufactured parts and specifically their corrosion behavior.

The main goal of this work was to propose a detailed study of the pitting corrosion behavior of a 17-4PH MSS manufactured by LBM. In this framework, LBM parts were built from 17-4PH MSS powder, using optimized machine parameters. Samples of a commercial counterpart (CM –MSS) machined from a wrought cylindrical bar were studied as references. The pitting corrosion behavior of both MSSs was studied in chloride-containing solutions by combining linear potentiokinetic polarization associated with the determination of pitting potentials, and a statistical analysis of the current transients observed during potentiostatic experiments for metastable pitting. Significant differences were observed between the LBM and CM MSSs. They were explained considering the passive film composition, structure and morphology evaluated by combining transmission electron microscopy (TEM), scanning TEM (STEM) using the high-angle annular dark field (HAADF) mode, and Energy dispersive X-ray Spectroscopy (EDS) analyses. Results were related to the specific microstructure of the LBM samples as compared to that of the CM MSS, both microstructures being characterized by TEM, STEM and EDS.
(Invited) Quantifying Outgassing, Surface Oxygen Depletion and Solid Carbonate Evolution to Understand Interfacial Reactivity in Cathode Active Materials
Authors: McCloskey Bryan D. , Ramakrishnan Srinivasan , Renfrew Sara E
Published: December 2020

Complex degradation processes at the cathode-electrolyte interface limit the high voltage application of conventional and emerging cathode materials (e.g., Li or Ni-rich LiMO2, M= Li, Ni, Mn, Co, (NMC) layered oxides and Li-excess disordered rocksalt materials). We will present results in which quantitative gas evolution and acid titrations are used to identify key contributions to these high voltage instabilities in Ni-rich and Li-rich NMC materials, including electrolyte degradation evolution and the impact that residual solid carbonate has on parasitic reactions.1-2 This presentation will emphasize the need to accurately quantify these minor side reactions to fully understand their large influence on battery performance. We show that by using a short aqueous rinse on NMC powders prior to their integration into porous electrodes, adventitious carbonates are removed from the material surface, which also undergoes a structural change. Both of these effects dramatically reduce parasitic gas evolution from the materials and, in certain cases, improve the active material’s long term cyclability without compromising its capacity.3-4

References

1. Renfrew, S. E.; McCloskey, B. D. Quantification of surface oxygen depletion and solid carbonate evolution on the first cycle of LiNi0.6Mn0.2Co0.2O2 electrodes. ACS Applied Energy Materials 2019, 2, 3762-3772. 10.1021/acsaem.9b00459

2. Renfrew, S. E.; McCloskey, B. D. Residual lithium carbonate predominantly accounts for first cycle CO2 and CO outgassing of Li-stoichiometric and Li-rich layered transition-metal oxides. Journal of the American Chemical Society 2017, 139, 17853-17860. 10.1021/jacs.7b08461

3. Renfrew, S. E.; Kaufman, L. A.; McCloskey, B. D. Altering surface contaminants and defects influences the first-cycle outgassing and irreversible transformations of LiNi0.6Mn0.2Co0.2O2. ACS Applied Materials & Interfaces 2019, 11, 34913-34921. 10.1021/acsami.9b09992

4. Ramakrishnan, S.; Park, B.; Wu, J.; Yang, W.; McCloskey, B. D. Extended interfacial stability through simple acid rinsing in a Li-rich oxide cathode material. Journal of the American Chemical Society 2020, 142, 8522-8531. 10.1021/jacs.0c02859
(Invited) Atmospheric Corrosion of Magnesium Alloys: Influence of Aluminium Content
Authors: Thierry Dominique , Persson Dan
Published: December 2020

Magnesium has gained considerable interest as a structural material for automotive and aerospace applications due to its low density and high specific strength. The use of magnesium alloys in engineering applications is, however, mainly limited by their unsatisfactory surface properties and their poor corrosion resistance. In recent years, significant improvements have been made in achieving a better corrosion resistance particularly by reducing the contents of impurities such as Fe, Cu, and Ni. Intermetallic phases, a result of the casting process, play an important role in the corrosion process. The role of these intermetallic phases has been addressed in a number of papers [1–3]. The role of aluminum in the atmospheric corrosion of magnesium alloys has less addressed in the literature [4]. Esmaily et al have shown recently that the rate of corrosion of magnesium alloys decreased when increasing the Al content. However these experiments were performed on commercial magnesium alloys produced high pressure die casting under constant RH exposure at 90% RH.

In our work the corrosion behavior of binary Mg-Al alloys as well as that of commercial magnesium alloys with different aluminum contents have studied both under cyclic corrosion exposure in the laboratory and in field exposures in France and in Vietnam. Analyses of corrosion products have also been conducted. Additional in-situ measurements have been performed in order to better understand the atmospheric corrosion mechanisms of Mg alloys.

An important decrease in the maximum pit depth can be observed after different laboratory exposures when increasing the aluminum content in the material. Similar results have been obtained after 9 months exposure in Field. Hence, from these results it is obvious that an increase of the aluminum concentration in Mg-Al alloys decreased the corrosion rate of the alloy. This lead in lower mass loss and less deep corrosion attacks in the magnesium grains. The analyses of corrosion products formed after the cyclic corrosion tests and field exposures revealed the presence of Magnesium carbonate and MgCO3(OH)4,4H20, respectively. In both cases magnesium hydroxide (Mg(OH)2 was also found in the corrosion products. The results will be discussed in relation with the microstructure of the cast materials.

O. Lunder, J.E. Lein, S.M. Hesjevik, T.K. Aune, K. Nisancioglu, Werkstoffe und Korrosion 45 (6)

(1994) 331–340.

O. Lunder, J.H. Nordlien, K. Nisangliou, Corrosion Reviews 15 (3–4) (1997) 439–469.

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M. Esmailly, D.B. Blucher, J.E. Svensson, M. Halvarson and LG Johansson, Scripta Materiala, 115 (2016), 91-96
Smart Coatings for Corrosion Protection: On the Need for New Coating Concepts
Authors: Rohwerder Michael
Published: December 2020

Ideally smart coatings for corrosion protection have to be able to protect the underlying metal from corrosion by providing excellent barrier properties, at the same time showing a fast and efficient self-healing in case a defect down to the metal is inflicted into them, while being as delamination resistant as possible.

These seem to be basically incompatible properties, as either mobility of species is high or the coating is highly impermeable, i.e. it is difficult to envisage a coating that can be both at the same time. In fact, in recent works we have shown that for excellent self-healing performance especially the resistance against cathodic delamination of a coating should be significantly weakened [1, 2]. Using conductive polymer additions to non-conductive coatings, both high self-healing activity [1-3] as well as high resistance against cathodic delamination [4, 5] can be controlled in a wide range.

Based on an in-depth understanding of the underlying mechanisms we are currently working on strategies for developing coatings that show excellent active as well as passive protection properties. Latest progress of the research on this topic well be presented and the implication will be discussed.

[1] M. Uebel, L. Exbrayat, M. rabe, T.H. Tran, D. Crespy, M. Rohwerder, On the Role of Trigger Signal Spreading Velocity for Efficient Self-Healing Coatings for Corrosion Protection, Electrochem. Soc. 165 (2018) C1017-C1027

[2] H. Tran , A. Vimalanandan , G.Genchev , J. Fickert , K. Landfester, D. Crespy , M.Rohwerder, Regenerative Nano-Hybrid Coating Tailored for Autonomous Corrosion Protection, Advanced Materials 27(25) (2015) 3825-3830

[3] A. Vimalanandan, L.P. Lv, T.H. Tran, K. Landfester, D. Crespy, M. Rohwerder, Redox-Responsive Self-Healing for Corrosion Protection, Advanced Materials 25(48) (2013) 6980-6984

[4] Anna Merz, Matthias Uebel, Michael Rohwerder, The Protection Zone: A Long-Range Corrosion Protection Mechanism around Conducting Polymer Particles in Composite Coatings: Part I. Polyaniline and Polypyrrole, Electrochem. Soc. 166 (2019) C304-C313

[5] Anna Merz, Michael Rohwerder, The Protection Zone: A Long-Range Corrosion Protection Mechanism around Conducting Polymer Particles in Composite Coatings: Part II. PEDOT:PSS, Electrochem. Soc. 166 (2019) C314-C320
Cathodic Corrosion Protection of Steel with Electroplated Aluminum Alloys
Authors: Bottcher Rene , Ispas Adriana , Bund Andreas
Published: December 2020

Aluminum has excellent corrosion properties due to the formation of a dense oxide layer. This layer spontaneously forms in contact with air and protects the bulk material from further oxidation. Unfortunately, the formation of the natural oxide layer renders pure aluminum passive so that it is not a good candidate for the corrosion protection of a more noble substrate like steel. Therefore, for applications as a corrosion protection layer aluminum should be alloyed with other elements to prevent complete passivation.

Electrodeposition is an elegant and cost-efficient method to apply thin coatings on various substrates with complex geometries. The layer properties can be easily controlled by adjusting the deposition parameters (current density, temperature, electrolyte composition). Aluminum cannot be deposited from aqueous electrolytes because of its negative Nernst potential (-1.66 V vs. NHE). Ionic liquids (ILs) are suitable electrolytes for the deposition of reactive metals, such as Al, Nb and Ta. They have a broad electrochemical window (> 3 V) and high electrical conductivity, and show good solubility for many metal salts.

This paper will discuss the deposition of binary aluminum alloys from imidazolium-based ILs and their corrosion behaviour. Results from potentiodynamic polarization experiments will be compared with results from salt spray tests and long-term environmental exposure experiments (> 1 year) to assess the suitability of the alloys for cathodic corrosion protection of steel.
(Invited) Performance and (de)lithiation Mechanism of Lithium-Lead (Pb) Anode for Li Battery
Authors: Johnson Christopher S. , Han Jinhyup , Park Jehee , Bak Seongmin , Son Seoung-Bum , Gim Jihyeon , Villa Cesar , Hu Xiaobing , Dravid Vinayak P. , Su Chi Cheung , Kim Youngsik , Lee Eungje
Published: December 2020

This talk will describe a new, high-performance Pb-based nanocomposite anode material for lithium-ion batteries. A unique nanocomposite structure of core-shell Pb@PbO nanoparticles and carbon matrix was able to be obtained by a simple high energy ball milling method using the low-cost PbO and carbon black starting materilas. The electrochemical performance tests showed the excellent reversible capacity (ca. 600 mAh/g) and cycle stability (92% retention at 100th cycle), which are the best performances ever reported for Pb-based anodes in the literature. Synchrotron X-ray diffraction and absorption techniques revealed the detailed lithium storage mechanisms that can be highlihghted with the unexpectedly wide reversible Pb redox range (between Pb2+ and Pb4-) and the evolution of Zintl-type LiyPb structures during the electrochemical lithium reaction. Our results provide new insights into the lithium storage mechanism of the Pb-based materials and their potential as low-cost, high-performance anodes.
(Invited) The Life and Death of Anode-Free Lithium Metal Cells
Authors: Louli Alex , Eldesoky Ahmed , Weber Rochelle , Genovese Matthew , Coon Matt , deGooyer Jack , Deng Zhe , White Robin T , Lee Jaehan , Rodgers Thomass , Dahn Jeff R.
Published: December 2020

Anode-free lithium metal cells store 60% more energy per volume than conventional lithium ion cells. Such high energy density cells will enable electric vehicles with increased range and decreased cost. The anode-free strategy of using zero excess lithium presents a number of advantages and challenges over conventional lithium metal cells. Anode-free cells exhibit ultra-high stack energy density >1200 Wh/L for the NMC532 and 811 cells investigated in this work. Lithium metal cells, on the other hand, with lithium foils thicker than 60 µm are actually less energy dense than lithium ion cells. Challenges associated with manufacturing thin lithium foils and their incorporation in cell production are avoided in anode-free cells. Safety is a concern for any cell with metallic lithium, although this often remains unaddressed in the literature. However, with no excess lithium, anode-free cells suffer from rapid capacity loss. Lifetimes of fewer than 40 cycles to 80% capacity are common. Increasing cycle life to hundreds of cycles is necessary to produce viable anode-free cells for electric vehicles.

Recently, we demonstrated state-of-the-art cycle life for anode-free cells utilizing a dual-salt carbonate-based electrolyte.1 This liquid electrolyte enabled a pristine lithium morphology of tightly packed lithium grains forming a smooth lithium mosaic, shown in Fig. 1a-b. In this present work, we probe the lithium morphology at different states of charge and conclude that this morphology is composed of lithium columns (Fig. 1c-e). Incredibly, the columnar lithium enabled by dual-salt electrolyte forms a matrix of dead lithium which facilitates reversible lithium deposition.

Unfortunately, this pristine morphology is not maintained. In this work, we characterize the degradation of anode-free cells with dual-salt electrolyte. We probe the deterioration of lithium morphology during aging with SEM and correlate this to electrolyte degradation. We observe increased lithium porosity via x-ray tomography and use acoustic transmission imaging to demonstrate electrolyte depletion. For safety characterization, we measure the temperature of cells during penetration with a nail and compare to cells made with other electrolytes promoted in the literature. Finally, we use the insights gained here to build anode-free cells that deliver a greater energy density than lithium ion cells for over 200 cycles. Although lifetime must still be increased, we believe anode-free lithium metal cells with liquid electrolyte present the most straightforward and lowest cost path towards viable high energy density lithium batteries.

Reference
s
:

[1] Rochelle Weber, Matthew Genovese, A. J. Louli, Samuel Hames, Cameron Martin, Ian G. Hill and J. R. Dahn, Nat. Energy, 4 (2019) 683-689.

Figure 1
(Invited) Computational Modeling of the Anode-Electrolyte Interface of Ca Ion Batteries
Authors: Smeu Manuel
Published: December 2020

Rechargeable batteries are critical components of portable electronics, electric vehicles and grid storage. Li-ion is the dominant technology because of its low weight, large voltage and high capacity, but the demand for raw materials is putting strain on the supply chain, and there are several safety, ethical and environmental concerns. Therefore, developing adequate alternatives to Li-ion batteries is an active research area around the world. Multivalent ion batteries (MVIBs), utilizing Mg, Ca, Zn and Al, are promising due to being based on earth-abundant materials, and their higher weight can be compensated by their multivalent nature, which allows their ions to carry multiple charges. We are particularly interested in Ca ion batteries, which have received relatively little attention compared to Mg and Al, yet they are predicted to provide the largest voltage for a multivalent ion. However, their development has been limited by challenges in identifying adequate electrolytes to reversibly plate and strip metal Ca anodes. While there have been some encouraging recent developments, a systematic understanding of the interactions between electrolytes and Ca is needed. For example, it is not clear how the electrolyte (e.g., ethylene carbonate) decomposes at a Ca metal surface, nor are the structure and composition known of the solid-electrolyte interphase (SEI) that forms between the metal anode and the electrolyte. Furthermore, the diffusion of Ca2+ ions through the SEI is not well understood.

We aim to address some of these points with computational modeling that combines density functional theory (DFT) with ab initio molecular dynamics (AIMD). We investigated the electrolyte decomposition of ethylene carbonate, with and without salt, at the Ca metal interface. We then compare this process to those occurring at Li and Al metal surfaces. The DFT calculations reveal the mechanism and energy barriers associated with the possible electrolyte decomposition pathways, while the AIMD trajectories show how quickly molecules decompose and their location. Next, we investigate the electron conductivity of the anode-electrolyte interface region at various stages of SEI layer formation. We accomplish this with the non-equilibrium Green’s function technique combined with DFT (NEGF-DFT), which not only tells us the conductivity but also the electron pathway through the interface. Finally, we investigate the possibility of protecting the electrolyte from reacting with the anode by separating them with an artificial SEI that still allows Ca2+ ions to diffuse through it. We propose that this strategy can aid in the development of rechargeable Ca ion batteries by bypassing the formation of an ionically insulating SEI as a result of electrolyte decomposition.
Graphene Functionalization As a Seed for Dielectric Passivation
Authors: Wyndaele Pieter-Jan , de Marneffe Jean-Francois , De Gendt Stefan
Published: December 2020

Two-dimensional (2D) semiconductor materials like Transition Metal Dichalcogenides (TMDCs) are prominent candidates to replace silicon (Si) as channel material in the future (Si-based) transistors. However, to fully exploit the superior properties of 2D TMDCs, their inherent problem of basal-plane inertness needs to be resolved to enable dielectric passivation layer growth. Therefore, the objective of this work is to explore innovative options to enable high-k growth on 2D materials.

A literature study is provided, setting out how 2D materials became of interest to the microelectronic industry as a results of continuous device downscaling. To overcome the issue of basal plane inertness, a single layer graphene is used that acts as a sacrificial growth template. This graphene layer is deposited on top of a base layer (e.g. 2D material), whereby the graphene layer is chemically activated via a dry UV/ozone treatment, while preserving the properties of the underlying 2D layer.

Initial experiments focus on the removal of polymer-based transfer residues that typically remain on the graphene surface after transfer. Mechanical scratching atomic force microscopy shows that hydrogen plasma treatments are an effective and time-efficient method to remove polymer transfer residues. However, the plasma exposure also induces surface modifications as demonstrated by Raman characterization.

Next, the growth template is chemically activated by gently oxidizing the graphene layer via a dry UV/ozone treatment. The UV/ozone process characteristics are explored in function of the graphene cleaning treatments developed in the previous stage. For as-received graphene an operating window of 2-5 minutes of UV/ozone exposure is defined in order to maximize the oxidation degree, and thus nucleation sites. Activation is in balance with graphene layer damage or removal. The process is evaluated based on contact angle measurements, Raman and conductivity atomic force microscopy characterization.

Lastly, an atomic layer deposition study is carried out that focuses on high-k deposition on the activated single layer graphene to provide a proof-of-concept of enhanced dielectric growth in function cleaning and activation treatments developed in the preceding stages. Rutherford backscattering spectroscopy demonstrates the importance of a well-functionalized surface to achieve good material growth.
Underlying Mechanisms on Tunable Electronic Structures of Graphene Quantum Dots Doped with Nitrogen and Sulfur Heteroatoms
Authors: Guo Qian , Feng Jianguang , Dong Lifeng
Published: December 2020

Graphene quantum dots (GQDs) are a new class of quantum dots with unique chemical and physical properties, and significant developments have been made on their electronic characteristic structures for wide applications in electronics, energy conversion and storage devices. Doping heteroatoms into graphene nanostructures is an efficient way to tune electronic structures. However, different synthesis methods have resulted in different doping configurations to affect electronic properties and thereby hindered systematically understanding the mechanisms of GQDs doped with heteroatoms. Herein, the electronic mechanism of GQDs doped with N and S was studied by density functional theory (DFT). The formation energies, electronic structures, and electrostatic potentials of the doped GQDs were calculated to reveal effects of different doping types on electronic properties. For the N/S co-doped GQDs, graphitic N and pyridine N were considered to substitute carbon atoms in the plane while the -C-S-C- and -C-SO2-C- at the edge. The formation energy calculated by DFT indicates that heteroatom doping tends to be doped at the basal plane. And surface doping could increase charge density of carbon atoms connected to nitrogen atoms. The introduction of -C-S-C- into the graphitic N and pyridine N structures reduces the energy difference between the highest occupied molecular orbital (HOMO) and the lowest occupied molecular orbital (LUMO). However, the addition of oxidized S into the N-doped structure increases the HOMO–LUMO energy gap. For the electrostatic potential diagram, the introduction of sulfur-containing groups can enhance the charge density around nitrogen, which suggests that heteroatom co-doped GQDs have improved electron transports. Therefore, this work provides valuable information on understanding electronic properties of N/S co-doped GQDs for the applications in nanoelectronic devices and give guidance for developing methods to controllably synthesize GQDs with well-defined and desirable properties towards specific purposes.
Routes to Novel Dielectric and Semiconductor Devices Using Cyclohexasilane
Authors: Elgammal Ramez Ahmed
Published: December 2020

A newly developed “liquid silicon” precursor will be discussed. Cyclohexasilane (CHS; Si6H12) has been used to make silicon-based films (such as polysilicon, silicon nitride, silicon carbide and others), as well as silicon nanowires and quantum dots. CHS offers a more versatile, lower-cost and safer pathway to a variety of silicon based products being considered for flexible and printable electronics.

There is a need for a silicon precursor that is not only cost effective, but one that can be readily chemically functionalized to develop advanced materials. CHS is one such silicon precursor that is a liquid at room temperature allowing for easier storage and handling. Cyclohexasilane has a moderate boiling point, 80 °C at 15 torr. It has long been considered to be the preeminent silicon precursor for a variety of applications including semiconductor devices and can create thin films of β-SiC on a variety of substrates under mild conditions including conventional CVD; but also LPCVD, APCVD, and laser assisted CVD. The growth rate of β-SiC using CHS is an order of magnitude faster compared to other silicon precursors and the crystalline quality should rival materials grown by MBE.

Aside from those advantages, CHS allows for facile p-doping of materials into the β-SiC films such as aluminum and due to the methods of deposition and the deposition conditions amenable to a reagent such as CHS, continuous growth with the suppression of unintentional secondary deposits may be readily achieved. Moreover, it may be possible to use CHS to achieve solution growth to deliver high structural quality SiC with significantly decreased capital and operational costs.

The use of CHS across a wide range of industries and applications will be discussed as will the advantages of this material over incumbent technologies.
Dummy Gate Footing Problems in Scaling Down of FinFET Structures
Authors: Jiang Changcheng , Xiao Xingyu , Ke Xing , Wang Yanliang , Li Yuchen , Chen Zhuofan , Wang Yan , Zhang Hai-Yang
Published: December 2020

The use of sacrificial dummy gate has been a standard process for HKMG in planar CMOS and subsequent FinFET technologies. However, the scaling down of FinFET design has led to a significant increase for the aspect ratio of gate structure. The profile of the dummy gate is of great importance for device performance and control of the dummy gate footing has become a prominent challenge. Here we studied dummy gate footing during high aspect ratio gate etch and its influence on device performance using virtual fabrication methods. At 7/5 nm FinFET technology node (as defined in IRDS 2018), the channel capacitance of the HKMG, which contributes to the AC performance, is showing to have percentage level differences respect to the existence/absence of dummy gate footing. Other problems posed by the dummy gate footing for subsequent procedures are also discussed.

Figure 1
Effect of Cobalt Content on Charge Compensation Mechanism of LiNixMnyCozO2 Cathode for Lithium Ion Battery
Authors: Morita Yoshiyuki , Nakanishi Koji , Aubin Megan , Ogasa Hiroshi , Fujiwara Yoshiya , Kushima Akihiro
Published: December 2020

LiCoO2 (LCO) is commonly used as a cathode for Li-ion batteries (LiBs) owing to its excellent intercalation nature, high voltage, and cyclic performance [1, 2]. However, LCO has issues due to the potential risk of future price increases of Co [3, 4]. Many efforts have been made to reduce the amount of Co in the cathode by replacing it with Ni and/or Mn, and LiNixMnyCozO2 (NMC) has been developed. NMC622, which contains 60 mol % of Ni in the transition metal composition, is now adopted in the majority of the electric vehicle battery chemistry. Although Ni-rich NMC is a promising alternative to low-Co cathodes, it is not clear whether the amount of Co can be further reduced from the present NMC622 without degrading cyclic stability. To further reduce the amount of Co, it is necessary to clarify the role of Co in the charge compensation mechanism and replace it with alternative elements with functions similar to those of Co.

In this study, we conducted XAFS, XRD and first-principles calculations for the NMC cathode with various transition metal composition ratios to clarify that the roles of Co, Ni, Mn, and O in the charge compensation mechanism. Synchrotron X-ray experiments were performed at SPring-8 and NewSUBARU synchrotron radiation facility in Japan. The first-principles calculations were carried out with Vienna Ab-initio Simulation Package (VASP) [5, 6], which uses plane-wave basis sets.

Fig. 1 shows the oxygen K-edge XANES spectra collected by the partial fluorescence yield (PFY) method at different states of charge (SOCs). As for the LCO, the peak intensity around 528 eV changed along with the SOC, suggesting that oxygen contributes to the charge compensation. Similar spectral changes were also observed with NMC111, NMC622, and slightly with NMC 811. In contrast, the white line energy in the Co L3-edge absorption hardly changed at any transition metal composition. Although there are various theories about the role of Co and oxygen in the charge compensation [7], our results show that there is no obvious change in the charge state of Co and oxygen contributes the most to the charge compensation in the LCO system. Detailed analysis including first-principles calculations will be discussed at the meeting.

[1] K. Mizushima et al., Mater. Res. Bull. 15, 783 (1980).

[2] A. Du Pasquier et al., J. Power Sources 115, 171 (2003).

[3] P.A. Nelson et al., Modeling the Performance and Cost of Lithium-Ion Batteries for Electric-Drive Vehicles, Argonne National Laboratory, 2012.

[4] Elsa A. Olivetti e
t al., Joule 1, 229 (2017).

[5] P. E. Blöch, Phys. Rev. B 50, 17953 (1994).

[6] G. Kresse et al., Phys. Rev. B 59, 1758 (1999).

[7] B. Li et al., Adv. Mater. 29, 1701054 (2017)

Figure 1