bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Enabling Fast Charging of Lithium-Ion Batteries without Lithium Plating
Authors: Dasgupta Neil P.
Published: July 2022

Today’s Li-ion technology is highly optimized for performance at relatively slow charging operation. However, significant challenges still present for fast charging conditions (> 4C). In state-of-the-art Li-ion batteries (LIBs) with high energy densities, the electrodes are relatively thick (> 100 μm), which leads to a tradeoff between energy density and high-power performance. In addition, the electrochemical potential of the anode can easily become more negative than Li/Li+ during fast charging, resulting in Li plating [1]. Therefore, new approaches are needed to overcome these energy/power tradeoffs in LIBs

In this talk, I will introduce three strategies to enable fast charging LIBs, using industrially-relevant pouch cells with thick (>3 mAh/cm2) electrode loadings. In the first strategy, vertical channels are introduced into post-calendared electrodes using laser ablation patterning [2]. The resulting 3-D anode architecture consists of a hexagonal close-packed array of vertical channels that serve as linear pathways for rapid ionic diffusion through the electrode thickness. This allows for a more homogeneous flux of Li throughout the volume of the electrode. As a result, the accessible capacity of the electrode during fast charging increases, and Li plating is eliminated.

In the second strategy, the energy/power tradeoffs in carbonaceous anode materials are overcome by forming hybrid blends of graphite and hard carbon [3]. This allows for a balance between the higher energy density of graphite with the faster rate performance of hard carbon. By controlling the graphite/hard carbon ratio, we identify an optimal blend for fast charging.

In the third strategy, we demonstrate the potential to eliminate Li plating and enabling 4C fast charging purely through interfacial control. This is achieved by coating the surface of graphite with a solid-state electrolyte material using Atomic Layer Deposition (ALD) [4]. These coatings eliminate electrolyte decomposition during the formation cycle, resulting in an “artificial SEI” with a resistance that is 75% lower than the natural SEI that forms in carbonate electrolytes. This challenges the fundamental assumption that fast charging of thick graphite anodes must be solved by improving mass transport, highlighting the critical role of the SEI on fast-charge performance.

[1] Y. Chen, K.-H. Chen, A. J. Sanchez, E. Kazyak, V. Goel, Y. Gorlin, J. Christensen, K. Thornton, N. P. Dasgupta, J. Mater Chem. A
9, 23522 (2021).

[2] K.-H. Chen, M. Namkoong, V. Goel, C. Yang, S. Kazemiabnavi, S. M. Mortuza, E. Kazyak, J. Mazumder, K. Thornton, J. Sakamoto, N. P. Dasgupta, J. Power Sources
471, 228475 (2020).

[3] K.-H. Chen, V. Goel, M. J. Namkoong, M. Wied, S. Müller, V. Wood, J. Sakamoto, K. Thornton, N. P. Dasgupta, Adv. Energy Mater.
11, 2003336 (2020).

[4] E. Kazyak, K.-H. Chen, Y. Chen, T. H. Cho, N. P. Dasgupta, Adv. Energy Mater, In Press (2021).
Preventing Degradation of NMC811 with Bimetallic Oxide Coatings
Authors: Slaughter Jonathan , Chen Richard L. B. , Wright Dominic S. , Grey Clare P.
Published: July 2022

High nickel-content cathodes such as NMC811 (LiNi0.8Mn0.1Co0.1O2) offer high practical capacities but undergo rapid degradation during cycling due to multiple mechanisms, such as surface phase transformations, reactive oxygen release and transition metal dissolution. Coatings using metal oxides have been proposed to provide surface protection against these processes. In this work we have used bespoke bimetallic alkoxide precursors to deliver unique bimetallic oxide coatings onto NMC811 secondary particles. Bimetallic combinations of lithium and zirconium or magnesium and zirconium showed enhanced electrochemical performance compared to uncoated NMC811 and only zirconium-based coatings, particularly at high charging voltages (4.6 V). Examining the cathodes post-cycling with XPS revealed a significant difference in the cathode electrolyte interface (CEI) of the different coated cathodes, suggesting different surface chemical reactions occur with different coating materials. These bimetallic coatings could offer a route to accessing further capacity available only at higher potentials.

Figure 1
(Digital Presentation) Measuring Thermal Behavior of Lithium Metal Solid State Microcells with Differential Scanning Calorimetry
Authors: Bhargava Bhuvsmita , Johnson Nathan B , Chang Jonathan , Albertus Paul
Published: July 2022

Research efforts in developing solid-state batteries with lithium metal anode have been on the rise owing to the high specific energy density cells using lithium metal. An all solid-state battery is often assumed to be safer compared to a Li-ion battery with an organic liquid electrolyte. If the energy density of a cell is increased through the introduction of Li metal, the potential temperature rise of the cell also increases, leading to a reduction in cell safety. In particular, during self-heating Li metal has the potential to react with the cathode itself and/or oxygen released from the cathode upon heating, as well as the solid electrolyte. The rate and extent of exothermic reactions in a specific battery chemistry and configuration determine whether self-heating could be created in a cell, as well as its onset temperature and rate. To quantify the thermal behavior of the reactions that occur within a Li metal solid state cell upon heating, we use differential scanning calorimetry (DSC). For the DSC measurements, we assemble all cell layers inside hermetically sealed stainless sealed pans, which allows us to carry out the analysis in an inert environment. With this platform, multiple cell chemistries and configurations can be tested, and the calorimetry of the reactions taking place among all cell components can be quantified. In this presentation, we will discuss our DSC measurements on select cell chemistries including with LiCoO2 and LiNi0.8Mn0.1Co0.1O2 cathodes at different states of charge, Li7La3Zr2O12 and Li3PS4 solid electrolytes, and a Li metal anode.
Plasma Enabled Lithophilic Host for Lithium Anodes
Authors: McNally Dylan P , Zhang Wei , Ban Chunmei
Published: July 2022

The surge in electric vehicles and portable electronics has sparked increased demand for high-energy-density, rechargeable batteries. Lithium (Li) metal is sought after as the highest energy density anodes. However, Li metal suffers from many challenges including dendritic growth during stripping and plating and safety issues. This talk aims to discuss strategies to mitigate dendritic growth by using a 3D carbon-based host, as well as scalable fabrication techniques to integrate Li metal into a desirable 3D matrix. Electron microscopy and X-ray photoelectron spectrometers are combined to investigate the surface chemistry and morphology, in order to better understand the interaction between the Li metal and 3D carbon-based host material. Identified shifts in the C1s and O1s peaks demonstrate added surface functional groups in the carbon-based host material. With surface functionalization, the proposed Li-metal anode demonstrates significantly improved stability of stripping and plating when compared with lithium metal foil. As a result, the cells assembled with our proposed Li metal anode and the LiNixMnyCozO2 (x+y+z=1) cathode displays enhanced cycling reversibility as compared to the cells assembled with the Li metal foil.
(Invited) Engineered Electrode Materials Via Dry Processing
Authors: Obrovac Mark
Published: July 2022

Dry bulk processing methods can offer surprising control of particle shape, size, internal composition, and surface morphology. Mechanofusion is a method that can be used to smooth, spheronize, coat, and embed particles [1–4]. Dry particle microgranulation (DPMG) is a newly developed mechanofusion method in which ~50 μm speres are added to the process as "templating" media [5]. Here it will be shown that DPMG and new applications of mechanofusion offer unprecedented control in particle shape, internal porosity, and internal composition variation, enabling the creation of never before possible highly engineered particles, including:

consolidating submicron particles into dense and uniform ~10 μm particles that are spherical or tetrahedral in shape

spontaneous formation of core/shell particles from a mixture of submicron particles with different compositions

creating spherical graphite particles from fine flake graphite

embedding nanoparticles within the core of ~10 μm host particles

applying fused dense oxide particle coatings

smoothing the surface of polycrystalline particles to lower their surface area

Such methods can produce no waste and operate at 100 % yields, greatly reducing environmental impact and cost compared to other commercial particle production methods. This offers tremendous opportunity for creating sustainable advanced battery materials. Examples of new cathode and anode materials synthesized by these methods and opportunities for new materials will be discussed.

References

[1] L. Zheng, T.D. Hatchard, M.N. Obrovac, A high-quality mechanofusion coating for enhancing lithium-ion battery cathode material performance, MRS Commun. 9 (2019) 245–250. doi:10.1557/mrc.2018.209.

[2] Y. Cao, T.D. Hatchard, R.A. Dunlap, M.N. Obrovac, Mechanofusion-derived Si-alloy/graphite composite electrode materials for Li-ion batteries, J. Mater. Chem. A. 7 (2019) 8335–8343. doi:10.1039/C9TA00132H.

[3] L. Zheng, C. Wei, M.D.L. Garayt, J. MacInnis, M.N. Obrovac, Spherically Smooth Cathode Particles by Mechanofusion Processing, J. Electrochem. Soc. 166 (2019) A2924–A2927. doi:10.1149/2.0681913jes.

[4] Y. Liu, M. Charlton, J. Wang, J.C. Bennett, M.N. Obrovac, Si 85 Fe 15 O x Alloy Anode Materials with High Thermal Stability for Lithium Ion Batteries, J. Electrochem. Soc. 168 (2021) 110521. doi:10.1149/1945-7111/ac3163.

[5] M.N. Obrovac, L. Zheng, M.D.L. Garayt, Engineered Particle Synthesis by Dry Particle Microgranulation, Cell Reports Phys. Sci. 1 (2020) 100063. doi:10.1016/j.xcrp.2020.100063.
Upscaling of the Laser Structuring of Lithium-Ion Battery Electrodes - Process Development and Electrochemical Properties As a Function of Design Patterns
Authors: Sterzl Yannic , Pfleging Wilhelm
Published: July 2022

Structuring of electrodes for lithium-ion batteries by using ultrashort pulsed laser ablation is a quite promising approach to significantly increase the electrochemical performance of lithium-ion batteries. The main impact of such 3D electrodes is due to shortening of lithium-ion diffusion pathways and improving the electrolyte wetting of composite electrodes The latter is reducing the electrolyte filling process time and saving the need for warm aging in the manufacturing process. The 3D electrode concept, in combination with an increase in electrode layer thickness, facilitates an increase in energy and power density of batteries at the same time. To implement the laser structuring process in industrial cell manufacturing, an adaptation of the ultrafast laser technology to the coating speed has to be established.

In the presented study, the use of an ultrashort pulsed laser system of high power up to 300 W and high repetition rate in the MHz regime was evaluated regarding processing speed for patterning of graphite and silicon/graphite anodes. For composite graphite anodes (film thickness > 76 µm) with an areal capacity of about 2.5 – 4.0 mAh/cm2 and a thick-film silicon/graphite anode with 5 wt.% silicon content (film thickness 80 µm, areal capacity 4.3 mAh/cm2) the laser and process parameters and processing speed were evaluated and optimized. Furthermore, different structure patterns including hole, grid and line pattern, were studied regarding upscaling in roll-to-roll processing. The different types of patterns were evaluated with respect to accessible electrochemical properties. Prior to cell assembly and during post-mortem studies, the quality of structured electrodes was examined by profilometry and scanning electron microscopy. Debris formation and a thermal impact to active material and current collector could be avoided. To evaluate the electrochemical properties such as high rate capability, cell impedance, and cell lifetime, coin cells and pouch cells were manufactured. For this purpose, NMC 622 cathodes were prepared as the respective counter-electrodes and a cell balancing in the range of 1.1-1.2 was ensured.
Regulating Lithium Metal Deposition for Safe Cell Operation and to Extend Cyclic Performance of an Anode-Free Lithium Metal Battery
Authors: Weldeyohannes Haile Hisho , Su Wei-Nien , Hwang Bing-Joe
Published: July 2022

Using the ideal Lithium metal (Li) as an anode material for Lithium metal batteries (LMBs) displays considerable potential in enlightening energy density and power density than conventional lithium-ion batteries (LIBs). Nevertheless, the low Coulombic efficiency, significant volume changes during operation, which reduces electrode mechanical stability, and Lithium (Li) dendrites formed and growth from nonuniform Li deposition during cell operation causes safety issues and limits potential uses of Li as an anode material for LMBs. Recently, anode free (Lithium free) lithium metal batteries (AFLMBs) protocol have got great attention due to their higher energy density, reduces cell weight, costs effectiveness, easy fabrication, and safety during the process of cell manufacture. Nevertheless, in AFLMBs, the uncontrolled plating of lithium on bare copper foil imposes a more severe lithium dendrite growth. Hence, planning proper design on an anode current collector which is appropriate for AFLMBs is essential. Herein, we handle the growth of lithium dendrite by guiding lithium metal deposition site to the backside of the gold-sputtered perforated polyimide film (PI@Au), which used as an anode current collector. Hence, metallic lithium (Li) starts to plate on the modified PI@Au surface, and sequentially, growth of Li takes place in the direction away from the separator face (ASF). This backside deposition and growth approach allow the battery to operate safely, even when lithium dendrite exists. . Surprisingly, the dendrite-free surface on the separator-facing side (SF) of PI@Au anode reveals significantly improved cycling stability. As a result PI@Au//Li cell (2 mAh/cm2 and 0.5 mA/cm2) offers stable cycling performance for 1400 h without significant voltage polarization. Conversely, Cu//Li cell cycling with results higher voltage hysteresis and face short-circuit below 600 h at same working conditions. Besides, PI@Au//LFP anode-free full cell configuration maintained 20 % capacity retention (CR) with average Coulombic efficiency of 98.7 % after 340 cycles (0.5 mA/cm2). On the contrary, the Cu//LFP full cell runs only for 165 cycles under the same value of CR. Guiding the plating of Li to the backside of perforated polyimide film insights into an innovative technique for developing ultra-safe AFLMBs and also proves the viability of the electrical insulator substrates as anode current collectors by improving their conductivity and lithiophilicity.
The Role of Gas Evolution in Particle Surface Cracking in Nickel-Rich Lithium-Ion Cathode Materials
Authors: Kaufman Lori A. , Lee Dong hun , Huang Tzu-Yang , McCloskey Bryan D.
Published: July 2022

Nickel-rich layered oxide cathode materials (LiNixTM(1-x)O2 where x > 0.8) are of great interest because they offer increased capacity compared to current commercial materials while maintaining compatibility with supply chain and production processes already in place. However, recent studies have shown that these materials in their current form are unsuitable for commercial applications due to the accelerated degradation caused by replacing more stable transition metals with the relatively unstable nickel. While various strategies have already been proposed to mitigate this issue, the fundamental degradation mechanism still needs to be better understood to inform the design of the next generation of nickel-rich cathode materials. In this work, differential electrochemical mass spectrometry (DEMS) is combined with titration mass spectrometry (TiMS) to measure gases evolved in a lithium half-cell during cycling as well as surface species which evolve gas upon addition of strong acid to an extracted cathode. Along with qualitative observations of particle cracking by scanning electron microscopy (SEM), these results reveal correlations between particle cracking, electrolyte reactivity, and carbonate oxidation and deposition on the changing cathode surface in nickel-rich cathode materials.
Evaluating the Gassing and Swelling Behavior of Lithium-Ion Pouch Cells Using in-Situ Pressure Analysis
Authors: Stock Sandro , Diller Felix , Daub Rüdiger
Published: July 2022

The goal to reduce cost-intensive and rare elements in Lithium-ion batteries promotes the use of high-energy, nickel-rich cathodes. These materials are characterized by a high specific capacity but show an increased gas evolution during initial cycling. The main sources for the gas generation are the decomposition of electrolyte solvents at both electrodes when forming the SEI and CEI, as well as the structural release of oxygen at the cathode. A pronounced gas evolution imposes a high hazard potential during operation due to high pressures within the cell. Hence, analyzing the gas volume and the gassing period is crucial to determine optimal formation protocols and degassing steps. Existing optical or mechanical gas detection methods lack the in-situ applicability in a high-throughput production and are error-prone due to the overlaying effects of gassing and swelling. This work presents a novel method to evaluate both gassing and swelling independently to determine the gassing behavior of pouch cells with volume resolutions below 100 µl. In-situ pressure analysis is performed using an expansion cell bracket that provides a constant force on the cell, thus providing realistic and reproducible formation conditions. The method is validated using the established immersion bath measurement and three different cell chemistries are quantified: NMC/Graphite, LNMO/Graphite, and NCA/Si-Graphite. Pouch cells containing LNMO and NCA exhibited a 30 and 20 times higher gas evolution volume than conventional NMC/graphite cells, respectively. As a consequence, multi-cycle formation protocols are required as gas evolution continues within the first five charging and discharging cycles. Conclusively, a procedure to adapt the formation protocol to the gassing behavior is proposed, thus reducing processing time and ensuring the ideal degassing point.
Modelling Investigation of the Impact of Several Process Parameters on the Growth of the Viscous Layer during the Electropolishing
Authors: Boucher Aurelien , Fedi Baptiste , Doche Marie-Laure , Exbrayat Loic , Hihn Jean-Yves
Published: July 2022

Electrochemical polishing (EP) is of great interest because it is able to deal with small parts exhibiting high complex shapes and/or material hard to be polished. Electropolishing is an electrolytic process based on the anodic dissolution of the workpiece under constant current or potential. Previous work done on stainless steel 316L shows the ability of the process to obtain smooth and bright surfaces [1]. The mechanisms describing EP are not yet fully understood, but several mechanisms can be taken into account for its description and prediction. Jacquet’s theory is based on the influence of an electric resistance gradient [2]. Elmore will then complete it with the gradient of concentration in metal cation [3,4]. Diard and al proposed the role of so called “acceptor” species [5]. While Hoar and Mowat’s work are based on the formation of an oxide layer on the surface [6]. All theories have in common the establishment of a viscous layer (solid or liquid) that governs the process. On this basis, it is possible to propose a numerical approach for the simulation of the viscous layer formation during electropolishing of stainless steel 316L and Inconel parts. The objective is to demonstrate the impact of various process parameters (electrochemical parameters, electrolyte nature and concentration as well as hydrodynamic conditions) on the growth and the stability of this layer.

The figure illustrate the simulation of the viscous layer growth during the electropolishing of a plate at the bottom taking into account the circulation of the electrolyte from the left to the right.

[1] C. Rotty, A. Mandroyan, M-L Doche, J-Y Hihn, Surface & Coatings Technology vol.307 p125–135 (2016).

[2] JACQUET, P.A., Electrolytic method for obtaining bright copper surfaces, Nature 135 (1935) 1076.

[3] ELMORE, W.C., Electrolytic Polishing, J. Appl. Phys. 10 (1939) 724–727, http://dx.doi.org/10.1063/1.1707257.

[4] ELMORE, W.C., Electrolytic Polishing II, J. Appl. Phys. 11 (1940) 797–799, http://dx.doi.org/10.1063/1.1712738.

[5] DIARD, J.P., LANDAUD, P., LE CANUT, J.-M., LE GORREC, B., Interprétation cinétique du palier de polissage électrochimique des métaux, 6ème forum sur les impédances électrochimiques, Montrouge, 1992.

[6] HOAR, T.P., MOWAT, J.A.S., Mechanism of electropolishing, Nature 165 (1950) 64–65.

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Effect of N2-Anneal Temperature on Silicon Nitride Film: (I) Time-Dependent Dielectric Breakdown and ESR Evaluations
Authors: Kurita Hisatsugu , Nakamura Masataka , Miyagawa Hayato , Kamigaki Yoshiaki
Published: July 2022

Silicon Nitride (SiN) film has been used as insulating material in many electronic devices such as capacitors and memories . In this report, the effect of N2 anneal temperature on charge break down (Qbd) of LP-CVD SiN film was electrically evaluated using the time-dependent dielectric breakdown (TDDB) test method, and the variation and the density of defects which exist in SiN film, in the oxide layer between SiN and Si substrate, and at the surface of Si substrate, were investigated using an Electron Spin Resonance (ESR) to reveal the defect behavior related to the trigger of Qbd.

SiN metal-insulator-metal (MIM) capacitors were fabricated to evaluate TDDB. A 54 nm dielectric layer of SiN film was deposited at 700 degree-C, using a mixture of dichlorosilane（SiH2Cl2）and ammonia (NH3) gasses, by a LP-CVD vertical furnace. For the lower and upper electrode, a 400 nm polycrystalline silicon films were deposited using a LP-CVD. In order to evaluate the effect of anneal temperature on SiN film breakdown frequency, these samples were annealed in nitrogen atmosphere at temperatures between 700 and 1150 degree-C for 1 hour, using a vertical furnace.

Breakdown voltage was measured with a current-voltage tester (HP4071A, Hewlett Packard) for each SiN MIM capacitor. The breakdown frequency was defined as the ratio of failed capacitors to tested capacitors. For the TDDB measurements, a constant current stress of 1.33 A/cm2 was applied to the MIM capacitors with the area of 0.00375cm2, 0.0075cm2, 0.015cm2 and 0.03cm2. For each area, 100 chips were made from one wafer and measured.

In Fig.1, SiN film breakdown frequency increases toward a peak at around the N2 anneal temperature of 900 degree-C, then decreases at 1000 degree-C, and at more than 1100 degree-C, the frequency increases again drastically at 1150 degree-C.

SiN films for ESR study were fabricated on Si wafer in the same LP-CVD process, and annealed in nitrogen atmosphere at temperatures between 700 and 1150 degree-C for 1 hour, using a vertical furnace.

The ESR measurements were performed at room temperature using an X-band spectrometer (JES-RE1X). To improve the signal-to-noise ratio of an ESR signal waveform, we set the accumulation number of magnetic-field (H) sweep about 300 times. Mn2+/ MgO hyperfine lines were used for the g marker, and spin densities were determined by using the standard of known spin content.

In Fig.2, Dangling bond density at silicon interface (Pb center) has a peak at 900 degree-C, and those in SiO2 (E’ center) and SiN film (K center) increase with increasing temperature from 1000 to 1150 degree-C. The former phenomena of Pb center coincides with the peak of SiN film breakdown frequency at 900 degree-C, and the latter one of E’ center and K center coincides with the tendency of increasing Qbd frequency at more than 1000 degree-C.

Figure 1
(Invited) Direct Band Gap Emission from Hexagonal Si-Ge
Authors: Bakkers Erik
Published: July 2022

Silicon and germanium cannot emit light efficiently due to their indirect bandgap, hampering the development of Si-based photonics. However, alloys of SiGe in the hexagonal phase are predicted to have a direct band gap. In this work, we exploit the unique feature of the nanowire growth mechanism to control the crystal structure by tuning the contact angle of the catalyst particle. A wurtzite wire is used as an epitaxial template to realise hexagonal Ge, SiGe, or pure Si (see accompanying Figure).1,2 We show efficient light emission up to room temperature accompanied by a short radiative life time, the hallmarks of a direct band gap material.3 The band gap energy is tunable in the range of 0.35 till 0.7eV by the chemical composition, opening a plethora of new applications. In addition, first signatures of lasing from hexagonal SiGe are obtained using an external cavity. We finally discuss possible routes to integrate this material in Si- technology.

1H.I.T Hauge et al.,
Nano Letters
15, 5855 (2015).

2H.I.T Hauge et al.,
Nano Letters
17, 85 (2017).

3E.M.T. Fadaly et al.,
Nature
580, 205 (2020).

Figure 1
(Invited) 2D Dimensional Quantum Materials for CMOS and Beyond CMOS Devices
Authors: Jariwala Deep
Published: July 2022

The isolation of a growing number of two-dimensional (2D) materials has inspired worldwide efforts to integrate distinct 2D materials into van der Waals (vdW) heterostructures. While a tremendous amount of research activity has occurred in assembling disparate 2D materials into “all-2D” van der Waals heterostructures and making outstanding progress on fundamental studies, practical applications of 2D materials will require a broader integration strategy. I will present our ongoing and recent work on integration of 2D materials with 3D electronic materials to realize logic switches and memory devices with novel functionality that can potentially augment the performance and functionality of Silicon technology. First, I will present our recent work on gate-tunable diode1 and tunnel junction devices2 based on integration of 2D chalcogenides with Si and GaN. Following this I will present our recent work on non-volatile memories based on Ferroelectric Field Effect Transistors (FE-FETs) made using a heterostructure of MoS2/AlScN3 and I also will present our work on Ferroelectric Diode (ferrodiode) devices4 also based on thin AlScN.

If time permits, I will also cover our ongoing efforts in scaling FE-FETs based on MoS2 and AlScN to < 100 nm channel lengths over large areas and also discuss in-memory computing using ferrodiode devices and also touch upon our efforts in photonics and light trapping using 2D semiconductors. I will end by giving a broad perspective on future opportunities of 2D semiconductors in micro and nanoelectronics.

References:

Miao, J.; Liu, X.; Jo, K.; He, K.; Saxena, R.; Song, B.; Zhang, H.; He, J.; Han, M.-G.; Hu, W.; Jariwala, D.
Nano Letters
2020, 20, (4), 2907-2915.

Miao, J.; Leblanc, C.; Liu, X.; Song, B.; Zhang, H.; Krylyuk, S.; Davydov, A. V.; Back, T.; Glavin, N. R.; Jariwala, D.,2D Metal Selenide-Silicon Steep Sub-Threshold Heterojunction Triodes with High On-Current Density arXiv:2111.06396

Liu, X.; Wang, D.; Zheng, J.; Musavigharavi, P.; Miao, J.; Stach, E. A.; Olsson III, R. H.; Jariwala, D.
Nano Letters
2021, 21, 3753–3761.

Liu, X.; Zheng, J.; Wang, D.; Musavigharavi, P.; Stach, E. A.; Olsson III, R.; Jariwala, D.
Applied Physics Letters
2021, 118, 202901
(Digital Presentation) CeOx Capping for Ferroelectric Y:HfO2 Films
Authors: Mizutani Kazuto , Hoshii Takuya , Wakabayashi Hitoshi , Tsutsui Kazuo , Kakushima Kuniyuki
Published: July 2022

In recent years, HfO2 has been paid a lot of attention as a ferroelectric material due to its excellent scalability and complementary-metal-oxide-semiconductor (CMOS) process compatibility [1]. Some of the issues of ferroelectric HfO2 are wake-up and fatigue effect, increase and decrease of remanent polarization (P
r) along with switching cycles, and low endurance. Generally, these phenomena are understood as a result of the increase and redistribution of oxygen vacancies (VO) in HfO2 films [2]. By the way, it is reported that CeOx can release and absorb oxygen from adjacent oxides [3]. In this study, we propose the stacking structure of CeOx and ferroelectric HfO2 to improve endurance and investigate electric properties and voltage application sequence to suppress the fatigue effect.

5 mol% Y-doped HfO2 (Y:HfO2) and CeOx capping layers of metal-ferroelectric-metal (MFM) capacitors were deposited by atomic-layer-deposition (ALD) with W bottom and top electrodes by sputtering. Post metallization annealing (PMA) was performed at 450 and 500oC for the various duration. Figure 1 shows hysteresis loops of the capacitors with and without CeOx capping annealed at 450oC for 20 minutes. Large hysteresis on CeOx capping is observed even same annealing temperature and duration. Enhancement of transformation to ferroelectric phase can be explained as tensile stress to Y:HfO2 due to the difference of coefficient of thermal expansion (CTE) between CeOx and Y:HfO2. Variation of switching polarization (P
SW), the difference between positive and negative P
r, as a function of the number of switching cycles is also investigated and shown in figure 2. Both capacitors are annealed at 500oC for 100 minutes to crystallize. In the case of without CeOx capping, continuous wake-up effect and breakdown over 3×107 times switching are observed. On the other hand, the capacitor with CeOx capping shows a slight wake-up effect and fatigue after 106 times switching, additionally, endurance is improved to 3×109 times switching. The reason why fatigue and prolonging endurance occur is suspected that oxygen ions in the CeOx layer pin polarization domains and compensate VO in Y:HfO2. To suppress fatigue, we propose the recovery process by positive DC voltage application to top electrodes. In figure 3, hysteresis loops of the capacitor with CeOx capping before and after recovery voltage application. One can observe the larger hysteresis after recovery.

This work was supported by JST-COI (JPMJCE1309). One of the authors, Kazuto Mizutani, was supported by The FUTABA Foundation.

[1] T. S. Boscke, et al., Appl. Phys. Lett., 99, 102903 (2011). [2] M. Pesic, et al., Adv. Funct. Mater., 26, pp. 4601–4612 (2016). [3] M. Mamatrishat, et al., Vacuum, 86, pp. 1513-1513 (2012).

Figure 1
(Invited) Recent Progress on Molecular Beam Epitaxy of AlGaN Nanowires for Deep Ultraviolet Light Emitting Devices
Authors: Zhao Songrui , Zhang Qihua , Parimoo Heemal , Yin Xue
Published: July 2022

Aluminum gallium nitride (AlGaN) ultrawide bandgap semiconductors have been attractive for their applications to disinfection, material identification, and ultraviolet (UV) curing, and for their potential to replace conventional mercury lamp based light sources. Remarkable progress has been made in the past decades from understanding material fundamentals to device performance improvement. Nonetheless, the enduring challenges related to high dislocation densities and poor p-type doping, among others, make AlGaN nanowires an alternative appealing platform. In this talk, I will discuss our recent development on the molecular beam epitaxy of AlGaN nanowires for deep UV light emitting devices.

First, I will show that by exploiting the compositional fluctuations in high Al content AlGaN nanowires in nitrogen-rich environment, electroluminescence (EL) at 207 nm can be obtained. Such EL emission is measured from the device top surface. As today it has remained challenging to obtain EL emission from the surface around this wavelength (i.e., near vacuum UV), such nanowires could offer an interesting approach to obtain surface emitting at near vacuum UV. I will further show that, by using graphene contact, the light output of surface emitting AlGaN nanowire deep UV LEDs can be improved. It is found that comparing to conventional metal contact, by using graphene contact the light output can be improved by a factor of two and the peak external quantum efficiency can be improved by a factor of four. Lastly, I will show that, by using nanowire template on Si substrate, AlN epilayers with a relatively smooth surface can be obtained, which further enables the formation of AlGaN epilayers with various Al contents on top. Such AlGaN epilayers are found to have high internal quantum efficiency, presumably due to a strong carrier localization effect. Current progress on device development using such an AlN on Si template will also be discussed.
(Invited) Designing Microscale Structures for Enhanced Function of Electrocatalysts for Alkaline Water Electrolysis
Authors: Gates Byron D.
Published: July 2022

Water electrolysis has already been implemented for many decades on an industrial scale. It does, however, remain an active area of research and development for the pursuit of materials that have enhanced electrocatalytic performance and prolonged durability. For example, the accumulation of gas bubbles on the surfaces of electrodes during water electrolysis remains a challenge. Persistent bubbles on the surfaces of electrocatalysts can block electrolyte access to the electrode and reduce the electrochemically active surface area. At current densities that are relevant to industrial applications an extensive portion of the electrode can become covered with bubbles. There are a range of solutions that are being utilized in industrial settings, but also additional solutions being sought to optimize the efficiency of these systems. These solutions include applied shear flows across the surfaces of the electrodes, the implementation of ultrasonic induced cavitation, and an increase in electrolyte temperature. These solutions require further expenditures of energy and decrease the overall energy efficiency of the system. Alternative approaches may yield a lower energy demand for maintaining accessibility of the electrolyte to the electrochemically active surface area. One approach is through the design of electrode surface architectures that can assist with the removal of gas bubbles during water electrolysis. This work includes a review of the progress made in preparing structured electrodes for the alkaline based water electrolysis and specifically for the oxygen evolution reaction. These structures can influence the dynamics that occur at the electrode-electrolyte interface, such as the growth, coalescence, and release of oxygen gas bubbles. Understanding the correlations between the structures on the electrodes and their influence on the function of these materials towards the gas evolution are sought to guide the future development of optimal surface structures that are self-cleaning. Designs of electrode surface architectures are sought that can improve the efficiency of electrodes toward this and other gas evolution reactions.
The Microkinetic Performance Barriers of Ruthenium and Iridium Oxides during the Electrocatalytic Oxygen Evolution Reaction
Authors: Geppert Janis , Röse Philipp , Krewer Ulrike
Published: July 2022

Electrocatalytic water splitting is currently one of the most promising reactions to produce green hydrogen in a de-fossilized energy system.[1] The performance of PEM electrolyzers is substantially determined by the sluggish reaction kinetics of the oxygen evolution reaction (OER). Even highly active catalysts such as nanoparticulated transition metal oxides IrO2, RuO2 and their mixtures IrxRu1-xO2 exhibit overpotentials up to several hundreds of millivolts.[2] Dynamic microkinetic modeling is a powerful tool to analyze the single reactions and their interplay during OER at the electrode surface.[3] Quantitative insight into process-limiting steps on different active sites on the material surface can be used to suggest ways to improve dynamic OER operation.

In this work, we present the analysis of an experimentally validated microkinetic model. It allows to study the electrocatalytic reaction mechanism including the coverage of emerging surface species (e.g. *OH, *O, *OOH and *OO) for a wide potential range including OER. We show that there is a correlation between performance and the Ir:Ru ratio, that can be explained by two different potential determining deprotonation steps. In particular, the highest equilibrium potentials of 1.44 V and 1.58 V are quantified for the production of the adsorbate species *OOH on rutile RuO2 and *OO on IrO2, respectively. During OER at a potential of >1.5 V, adsorbed oxygen *O covers >40 % of the active sites, suggesting that subsequent water adsorption is the major process limitation. The surface of the oxide mixtures IrxRu1-xO2, is found to consist of actives sites of both Ir and Ru on which the OER mechanism is processed independently and at different overpotentials. Compared to the pure oxides, the mixtures reveal reduced reaction energies of the potential determining deprotonation processes. One can conclude that incorporating Ru into IrO2 provides higher overall performance while stability is remained. Dynamic microkinetic modelling is therefore a viable method to study catalytic surface processes as well as their limitations and to make suggestions for improving the performance of electrocatalytic systems.

[1] K. Kalz et al., ChemCatChem, 2017, 9, 17.

[2] D. Escalera-López et al., ACS Catalysis, 2021, 11, 15, 9300.

[3] J. Geppert et al., Electrochimica Acta, 2021, 380, 137902.
Ru-Loaded Graphitized Porous Carbon for High Performance Electrochemical Hydrogen Evolution
Authors: Shin Choel-Hwan , Lee Ha-Young , Yu Ted , Goddard William , Yu Jong-Sung
Published: July 2022

The performance of electrocatalysts is closely related to their supporting materials since their properties such as heteroatom doping, porosity, graphiticity, and electrical conductivity play a decisive role on catalyst performance. We report here the preparation of N-doped highly graphitized porous network-structured carbon (N-HGC) as a catalyst support for Ru nanoparticles (NPs) catalytically active for hydrogen evolution reaction (HER) using pyrolysis of g-C3N4. The as-prepared N-HGC shows high graphiticity confirmed by XRD and Raman analyses, high electrical conductivity, and large surface area along with large amount of open mesopores, containing the proper amount of N doping rich with high pyrrolic-N content for homogeneous distribution of Ru NPs. This Ru/N-HGC catalyst shows a remarkably low overpotential of 9.6 mV (vs RHE) at 10 mA/cm2, which is near ideal and far better than state-of-the-art Pt/C. It also illustrates superb stability, maintaining the HER activity for 200 h and 10k CV cycles without any significant degradation. This superb HER performance is attributed to the robust N-HGC support featuring thin carbon structure, high electrical conductivity, suitable porosity, and N pyrrolic doping. The atomistic basis for the low overpotential is explained via Grand Canonical Quantum Mechanics (GC-QM) calculations. These calculations show that the pyrrolic-N in the support strengthens the coupling to Ru NP and weakens the binding of H to Ru NP, improving the rate determining Tafel reaction.
3D Structured Au(NiMo)/Ti Catalysts for Hydrogen Evolution Reaction
Authors: Balciunaite Aldona , Barua Sukomol , Tamasiunaite Loreta , Vaičiūnienė Jūratė , Norkus Eugenijus
Published: July 2022

Hydrogen generation via water splitting in alkaline media is the most promising, alternative, clean, and next-generation technology that can fulfill the future energy demands and overcome the challenge of global warming. The kinetics of hydrogen generation via water splitting through electrochemical process mainly rely on hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Material selection and material design are the keys to developing highly active, low-cost, and stable non-noble metal electrocatalysts but also are of great challenge.

The Au(NiMo)/Ti-based catalysts were prepared via chemical and electrochemical methods in this study. Initially, the NiMo coatings on the Ti surface (1x1cm) were electrodeposited from a bath containing 0.01 M Na2MoO4 and 0.01, 0.1, and 0.5 M NiSO4 in an acidic condition. The process of electrochemical deposition was carried out at the current of 0.1 mA and 1 mAfor 3 min. The gold nanoparticles were deposited on the previously prepared NiMo/Ti electrodes by galvanic displacement through their immersion into an acidic Au-containing solution for 10s. The morphology and composition of the newly prepared catalysts have been investigated via SEM, XRD, EDS, and ICP-OES. The investigation of electrocatalytic properties of the prepared catalysts was performed by recording linear sweep voltammograms in 1M NaOH solution at a potential scan rate of 10 mVs-1 at 25-75⁰C temperature range.

It was observed that the power densities for the newly prepared Au(NiMo)/Ti catalysts with the Au loading from 2 up to 4 µgAucm-2 were 1.3 to 1.8 times higher than using NiMo/Ti catalysts for HER.

Acknowledgment

This project has received funding from European Social Fund (project No 09.3.3-LMT-K-712-19-0138) under a grant agreement with the Research Council of Lithuania (LMTLT).
(Invited) Aqueous Zinc Ion Systems for Large Scale Electrochemical Energy Storage: Progress and Opportunities
Authors: Marschilok Amy C.
Published: July 2022

Aqueous zinc ion batteries are appealing for large scale electrochemical energy storage systems due to their inherent low cost, innate safety, and environmentally friendly nature. However new materials, electrolytes and electrode fabrication approaches are required to achieve AZIB with the needed lifetime for grid scale use. Progress toward understanding and improving the function of AZIB systems will be described in this presentation, highlighting in situ and operando characterization approaches spanning multiple chemistries.
(Digital Presentation) Electrolyte Optimisation for Copper Deposition and Dissolution in Redox Flow Batteries
Authors: Rohan James F. , Casey Declan P , Lacarbonara Giampaolo , Faggiano Luigi , Porcu Stefania , Ricci Pier Carlo , Badenhorst Wouter Dirk D , Murtomaki Lasse , Sanz Laura , Arbizzani Catia
Published: July 2022

Aqueous copper redox flow batteries (CuRFB) based systems offer an alternative, more sustainable, redox flow battery to those based on vanadium for stationary renewable energy storage. Copper is an abundant material (~20 million tonnes/ year), that can be easily recycled and is significantly lower cost (6.5 € kg -1), by comparison with vanadium technology (20 € kg-1)[i]. CuRFBs can also be operated without perfluorinated membranes required in the vanadium redox flow batteries (VRFB). The CuRFB system takes advantage of the three stable oxidation states of copper Cu(0)-Cu(I)–Cu(II) in which the cuprous species are oxidised to cupric species in the positive half-cell and electrochemically deposited as copper on the negative electrode. The electrolyte system investigated in this work is based on chloride salts which are soluble up to 2.5 M[ii]
,[iii]
. This concentration level enables high current densities to be achieved assisting with high power delivery. The present study was focussed on the electrolyte optimisation including the use of ammonium salts as an alternative to calcium salts to provide a higher conductivity chloride based electrolyte with lower overpotential and better reversibility of the copper deposition and dissolution reaction. Other smaller (mM level) quantity bismuth based chemical additives were also found to improve the coulombic efficiency of the copper deposition and dissolution reaction in extended cycling.

[i] E. Sánchez-Díez, E. Ventosa, M. Guarnieri, A. Trovò, C. Flox, R. Marcilla, F. Soavi, P. Mazur, E. Aranzabe, R. Ferret, Redox flow batteries: Status and perspective towards sustainable stationary energy storage, Journal of Power Sources, 481, (2021), 228804,

[ii] G. Lacarbonara, L. Faggiano, S. Porcu, P.C. Ricci, S. Rapino, D.P. Casey, J.F. Rohan, C. Arbizzani Copper chloro-complexes concentrated solutions: an electrochemical study, Batteries, 7 (2021) 83

[iii] L. Faggiano, G. Lacarbonara, W.D. Badenhorst, L. Murtomäki, L. Sanz, C. Arbizzani, Short thermal treatment of carbon felts for copper-based redox flow batteries, Journal of Power Sources, 520, (2022), 230846

Figure 1
Engineering and Testing of CCM Modifications for Improved Operational Flexibility, Durability and Performance of Fuel Cells and Electrolyzers
Authors: Wilkinson David P. , Bonakdarpour Arman , Kwan Jason T.H. , Daniel Lius
Published: July 2022

The performance, durability and cost of PEM fuel cell and electrolyzer systems still requires further improvements before they can be widely adopted. Along with improved electrocatalysts, low cost interface modifications and intermediate layers are important to improve the operation of catalyst coated membranes (CCMs) and meet commercial requirements. In this presentation we present some examples of the modification of conventional commercial CCM and MEA modifications with performance benefits. This would include for example the effect of improving the microporous layer (MPL) / catalyst layer (CL) interface by reducing the gaps to improve power density1, the improvement of cross-over and operational flexibility with a thin electrolessly deposited catalyst layer at the membrane surface 2, and modification of the porous transport layer (PTL) / catalyst interface3.

A new testing method for the evaluation of commercial CCMs was used in this work which can accelerate design and testing of these new and modified CCMs. This new method uses a Modified Rotating Disk Electrode (MRDE)4 which allows electrodes and CCMs to be tested up to high current densities, e.g., 2 A/cm2, and eliminates the variability and issues associated with thin film RDE testing. Figure 1 shows an example of testing the oxygen evolution reaction (OER) performance for different PTLs with a commercial CCM using the MRDE. The MRDE testing is also useful for carrying out accelerated degradation (ADT) testing of CCMs for fuel cell or electrolyzer applications5 and has the potential to be used as a quality control tool for CCM manufacturing lines.

References:

L. Daniel, A. Bonakdarpour and D.P. Wilkinson, Fuel Cells, 20(2), F1-F7 (2020)

L.Daniel, A. Bonakdarpour and D.P. Wilkinson, ACS Applied Nano Materials, 2, 3127-3137 (2019); J. of Power Sources, 471, 228418 (2020)

M. Kroschel, A. Bonakdarpour, J.T.H. Kwan, P. Strasser and D.P. Wilkinson, Electrochim.
Acta, 317, 722-736 (2019)

J. T. H. Kwan, A. Bonakdarpour, G. Afonso, and D. P. Wilkinson, Electrochim. Acta, 258, 208–219 (2017).

P.J. Petzold, J.T.H. Kwan, A. Bonakdarpour, and D.P. Wilkinson, J. Electrochem. Soc., 168(2), 026507 (2021)

Figure 1: The effect of different titanium current collector meshes on OER performance using a commercial IrO2-based CCM obtained by the MRDE tool. Inset shows the pictures of different Ti meshes examined.

Figure 1