bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anodic Stability of Electrolyte Solvents and Additives at the Ni-Rich NMC Cathode-Electrolyte Interface in Li-Ion Batteries
Authors: Dose Wesley M. , Allen Jennifer P. , O'Keefe Christopher A. , Temprano Israel , Björklund Erik , Weatherup Robert S. , Grey Clare P. , De Volder Michael F. L. 
Published: July 2021

One of the key challenges facing Li-ion batteries with Ni-rich layered cathodes is the poor interfacial stability at both electrodes. Several recent reports have investigated the reactivity of the electrolyte at the surface of LiNixMnyCo1-x-yO2 (NMC) as a function of Ni content and electrolyte composition,1,2 but many of the complex processes taking place are not fully understood. In this work, we use a rapid electrochemical-based screening protocol3 to quantify the anodic stability of single-solvent electrolytes and additive-containing electrolyte solutions with respect to the fraction of Ni in the NMC cathode. The current that flows during a high voltage hold at 4.6 V vs Li/Li+ is found to be sensitive to the NMC surface chemistry, the degree of delithiation, and the composition of the electrolyte. Post-test XPS, solution NMR, and online electrochemical mass spectroscopy (OEMS) are combined to study the electrode- and electrolyte-dependent degradation products that are insoluble on the surface of the electrode, soluble in the electrolyte, and released as gas. The insights from quantification of the electrolyte anodic stability and the degradation signatures identified through this work highlight the importance of developing unique solutions to lower the interfacial reactivity of Ni-rich cathodes, which is a critical step to prolong the cycle life of high-energy Li-ion batteries.
References

Y. Zhang, Y. Katayama, R. Tatara, L. Giordano, Y. Yu, D. Fraggedakis, J. G. Sun, F. Maglia, R. Jung, M. Z. Bazant, Y. Shao-Horn, Energy Environ. Sci., 13, 183, 2020.

J. Wandt, A. T. S. Freiberg, A. Ogrodnik, H. A. Gasteiger, Mater. Today, 21, 825, 2018.

A. Tornheim, S. E. Trask, Z. Zhang, J. Electrochem. Soc., 163, A1717, 2016.
Optimization of 2-D Spatial Distributions of Pore Sizes, Platinum Content, and Nafion Amount in PEMFC
Authors: Lamb James , Andrei Petru 
Published: July 2021

Proton exchange membrane fuel cells (PEMFCs) provide a key technology to enable the transition to a zero-emission economy. In transportation applications, PEMFCs allow high-efficiency conversion of fuel to electricity, long range, and rapid refueling, all without pollution, noise, or other undesirable effects. However, cost remains one of the largest barriers to widespread adoption of PEMFC technologies. The goal of our research is to reduce PEMFC cost by optimizing the performance of the cell.
In this presentation we focus on the numerical optimization of the microstructure of the anode and cathode catalyst and gas diffusion layers in low-temperature PEMFCs. Our approach consists of discretizing realistic PEMFC structures numerically and solving the following optimization problem on a finite element grid [1]:

max
V(μPt, μN, μC, μ∈)

μPt(r), μN(r),

μC(r), μ∈(r)

where V is the voltage of the cell at a specified current density, μPt, μN, μC, and μ∈ are the two-dimensional spatial distributions of the platinum, nafion, and carbon contents, and porosity, respectively. The above problem is solved using a modified steepest descent method in which the gradients of the cell voltage with respect to the local values of the platinum, nafion, carbon, and porosity distributions are computed efficiently using an adjoint method [2, 3]. The numerical algorithm is implemented in our finite element simulator, RandFlux [4], in which the derivatives of transport equations with respect to the state variables and the adjoint operator are computed efficiently using automatic differentiation.
The figures present the optimized distribution of the platinum, nafion, pore fraction, and carbon as a function of the location in the cathode catalyst layer for a standard PEMFC with a membrane thickness of 25 mm, GDL thicknesses of 250 mm, and catalyst layer thicknesses of 15 mm. The 2-dimensional PEMFC is symmetric with respect to y=0.5 mm, has the opening between y=0.25 mm and 0.75 mm; the membrane is toward the left side of each figure, the gas diffusion layer (GDL) is toward the right side. The optimization was performed in order to increase the polarization of the cell at a current density of 0.5 A/cm2. We observe that it is optimum to increase the density of the platinum particles and the amount of the electrolyte near the membrane side of the catalyst layer and, in the same time, increase the porosity and carbon fraction near the gas diffusion layer. More results about the technique, the numerical implementation, and a number of fully optimized cells will be presented at the meeting.
References

Lamb and P. Andrei, ECS Transactions, 98, 67 (2020).

J. Lamb, G. Mixon and P. Andrei, Journal of The Electrochemical Society, 164, E3232 (2017).

J. Lamb and P. Andrei, ECS Transactions, 97, 671 (2020).

RandFlux, Florida A&M University and Florida State University, http://www.eng.famu.fsu.edu/ms/RandFlux.

Figure 1
Molecular Dynamics of Electrostatic Channeling on the Surface of Malate Dehydrogenase-Citrate Synthase
Authors: Xie Yan , Calabrese Barton Scott 
Published: July 2021

Multi-enzyme catalytic cascade reactions exist in many metabolic pathways in nature; the benefits of these reactions include high efficiency and reduced time and labor costs [1].The design and application of efficient cascade reactions in biofuel cells, sensors, and chemical conversion requires an understanding of intermediate channeling between adjacent cascade active sites. Electrostatic channeling, for example, utilizes electrostatic force to control the direct transfer of charged intermediates [2]. Here, we study the electrostatic channeling of an oxaloacetate (OAA) intermediate between malate dehydrogenase (MDH) and citrate synthase (CS) active sites within the tricarboxylic acid (TCA) cycle.
The MDH-CS supramolecular assembly includes a positively charged surface between neighboring active sites that guides the movement of the negatively charged oxaloacetate, thus improving the transfer efficiency [3].To study the interaction between OAA and the charged enzyme surface and identify OAA’s transfer pathways, we simulated this system using molecular dynamics (MD). Specifically, since both MDH and CS have two identical subunits and thus two active sites, we ran 50 MD simulations for 10 ns near each of the four active sites, resulting in 200 parallel runs of simulations. Then we analyzed the resulting MD dataset with a Markov State Model (MSM) [4].We identified multiple energy basins in MSM, including four active site basins, a desorption basin, and an intermediate basin. MSM successfully predicted the the transition rates between those energy basins and identified the dominant transport pathways of OAA from MDH to CS. The visualization demonstrates that the dominant transport pathway crosses Arg65, providing further support for the experimental observation that Arg65 plays an critical role in the electrostatic transport process of OAA [3].This study improves the field’s understanding of natural substrate channeling mechanisms and can help with the design of artificial cascade reactions.

References

K. C. Nicolaou, D. J. Edmonds, and P. G. Bulger, Angew. Chemie - Int. Ed., 45, 7134–7186 (2006). doi:10.1002/anie.200601872.

I. Wheeldon, S. D. Minteer, S. Banta, S. Calabrese Barton, P. Atanassov, and M. Sigman, Nat. Chem (2016). doi:10.1038/NCHEM.2459

B. Bulutoglu, K. E. Garcia, F. Wu, S. D. Minteer, and S. Banta, ACS Chem. Biol., 11, 2847–2853 (2016). doi:10.1021/acschembio.6b00523

F. Noé, C. Schütte, E. Vanden-Eijnden, L. Reich, and T. R. Weikl, Proc. Natl. Acad. Sci. U. S. A., 106, 19011–19016 (2009). doi:10.1073/pnas.0905466106

Figure 1
Coupled Simulation of Electric Flight Dynamics and Physics Based Battery Model for Electric Aircraft Battery Pack Sizing Analysis
Authors: Kolluri Suryanarayana , Shah Krishna , Wang Mengyuan , Mesbahi Mehran , Subramanian Venkat R. 
Published: July 2021

Electrification of aircraft and aviation systems is a thriving area of research and technology development in recent years1. According to the Airbus Global Market Forecast, air traffic will double every 15 years, leading to increasing fuel consumption causing severe impact due to greenhouse gases and carbon emission2. Besides the environmental impact, as the international demand for fuel increases, and the fact that petroleum resources are limited, fuel prices are projected to rise. On the other side, the drop in the cost of lithium ion batteries makes electric aircraft feasible to commercialize now. This necessitates studying the battery pack sizing problem to build efficient Energy Management System (EMS) for electric aircraft.
There is a significant amount of research on EMS for electric aircraft. Most of the current literature related to electric aircraft modeling considers the battery voltage to be linear3. This may lead to inaccurate estimation of state of charge (SOC), a key state variable for batteries and battery pack. In this work, we perform coupled simulation studies of the longitudinal flight dynamics and physics-based battery model (single particle model)4
,5. This coupling enables accurate estimation of battery pack state of charge. The simulation studies are performed to understand the interplay between battery pack configuration/design parameters and variables/parameters related to flight dynamics, such as altitude, distance, flight path angle, and velocity. We also compare the SOC prediction of the battery pack using single particle model and dynamic empirical battery model. This work will be extended to develop efficient and robust EMS for electric aircraft.

Acknowledgements

This research was supported by the Texas Materials Institute (TMI) at The University of Texas at Austin.

References

J. A. Rosero, J. A. Ortega, E. Aldabas, and L. Romeral, IEEE Aerosp. Electron. Syst. Mag., 22, 3–9 (2007).

Airbus global market forecase. [Online]., https://www.airbus.com/aircraft/market/global-market-forecast.html.

M. Kaptsov and L. Rodrigues, J. Guid. Control. Dyn., 41, 285–290 (2018).

S. Santhanagopalan, Q. Guo, P. Ramadass, and R. E. White, J. Power Sources, 156, 620–628 (2006).

V. Ramadesigan, P. W. C. Northrop, S. De, S. Santhanagopalan, R. D. Braatz, and V. R. Subramanian, J. Electrochem. Soc., 159, R31–R45 (2012).
The Importance of Li-Ion Nature and Stacking in Layered Cathode Materials for Aqueous Ion Batteries: From Bulk to Surface Models
Authors: Posada Perez Sergio , Rignanese Gian-Marco , Hautier Geoffroy 
Published: July 2021

The performance of aqueous ion batteries has been demonstrated since the foundational work from Dahn et al. who combined an anode of VO2 and a cathode of LiMn2O4 in an aqueous electrolyte. The use of aqueous electrolytes opens the possibility of proton co-insertion, one of the common assumptions to explain performance issues in aqueous electrolytes. Experimental and computational works compared the feasibility of several cathode materials to be intercalated by H+ concluding likewise that non-layered cathode materials are less prone to proton intercalation than layered materials.
Therefore, layered compounds should not be good candidates as cathodes of aqueous batteries, although Li+ insertion/extraction using high concentrated LiNO3 aqueous solution as electrolyte, show results consistent with the Li (de)intercalation in organic electrolytes between the ranges from x equals 0.5-1.0 in layered LixCoO2. Thus, could layered materials have a good performance in aqueous environment despite of their tendency to accommodate protons?
In this work, we use ab-initio computations to investigate the behavior of LixCoO2 in aqueous electrolytes analyzing the proton insertion to determine which specific chemical and structural features lead to electrochemically stable materials for aqueous batteries by means of bulk and surface models. The investigations have concerned layered NaxCoO2 in order to investigate the role of stacking and ion material.
Our simulations reveal the excellent performance of LixCoO2 in contrast to NaxCoO2. By means of DFT calculations, the H+/ion exchange have been studied and the grand potential phase diagram and voltage-composition curves have been built considering different phases of LixCoO2 and NaxCoO2. Our simulations predicts the CoO(OH) as the most stable insertion/extraction product at battery operation conditions, due to the formation of O-H-O bonds. However, LixCoO2 is not affected by the presence of protons since they co-existence is not stable in comparison to full lithiated and full protonated systems. Our computations reveal that H+ could have a secondary role as surface detrimental agent, without compromising the battery performance. Nevertheless, the nature of Na and the stacking of NaxCoO2 favors the accommodation of protons, showing different performance than LixCoO2, due to the different stacking and different behavior of Na.
Our work suggests that to be layered is not enough justification to be discarded as cathode material for aqueous electrolytes. We suggest that the stacking, the alkali-proton repulsion, and specially the operation conditions (voltage window, pH...) are key factors to investigate the suitability or not of a layered material as positive electrode for ion aqueous batteries.
(Invited) Doping Considerations for Finfet, Gate-All-Around, and Nanosheet Based Devices
Authors: Duffy Ray 
Published: July 2021

The IEEE International Roadmap for Devices and Systems (IRDS) for More Moore devices summarises the Logic Device state of play very effectively; the FinFET is the key device architecture that could enable logic device scaling until 2025. Increasing fin height while reducing number of fins at unit footprint area is an effective solution to improve performance. It is forecasted that the parasitics will remain as a dominant term in the performance of critical paths. For reduced supply voltage, a transition to gate-all-around (GAA) structures such as lateral nanowires or nanosheets will be necessary to improve electrostatics. Lateral GAA structure would eventually evolve in to the vertical GAA structure to gain back the performance loss due to increasing parasitics at tighter pitches. In this review we will consider doping techniques based on ion implant, solid-source in-diffusion, liquid-source in-diffusion, and gas-source in-diffusion for these device technologies.
The problem of doping source-drain regions in Si MOS devices usually boils down to the problem of (1) getting the dopant into the target structure or wafer, (2) activating the dopant by a thermal treatment, (3) controlling the crystal damage and diffusion. In these advanced device architectures, in essence, the surface is a trapping site for dopants. This isn’t too much of a problem if ions are implanted past the surface by beam-line or by plasma-assisted doping processes, however with the in-diffusion based techniques this is a severe issue.
(Invited) Atomic-Layer-Deposition of in-Situ Crystallized Ge2Sb2Te5 Alloy and Gete/Sb2Te3 Superlattice, and Their Phase-Change Performances
Authors: Hwang Cheol 
Published: July 2021

This paper introduces a new atomic layer deposition process for highly conformal, nanocrystalline-as-deposited GeTe-Sb2Te3 pseudo-binary film growth at a deposition temperature of 130 °C. The process utilizes Ge(II)-guanidinate, Te(Si(CH3)3)2, and Sb(OC2H5)3 with the NH3 co-reagent. The alternative GeTe and Sb2Te3 subcycles produced various film compositions, all consistent with the GeTe-Sb2Te3 tie lines, owing to the stoichiometric reactions between the precursors without involvement of undesirable side reactions. The density of the nanocrystalline Ge2Sb2Te5 (GST225) films was 6.2 g/cm3, similar to the density of the bulk crystalline material. The crystallization behaviors indicated that the distribution of the constituent elements of the GST225 films was highly uniform at the atomic level, as opposed to the case of the low-temperature (100 °C)-deposited films. The cubic to hexagonal transition at 350 °C upon post-annealing produced (0001) hexagonal planes highly aligned along the substrate. The demonstration of the phase change memory device achieved high cycling endurance (>107).
The same ALD process was further exploited to grow the GeTe/Sb2Te3 superlattice structure, which might be an even more energy-efficient phase change material. It was found that the Sb2Te3 layer could be grown in highly c-axis oriented manner on SiO2 surface, which then can be used as the template layer for the subsequent growth of also highly c-axis oriented GeTe layer. Direct growth of the GeTe layer on SiO2 did not result in the similar optimal results. However, a certain intermixing occurs during the alternating growth of the Sb2Te3 and GeTe layers, of which details are dependent on the thickness ratio of the two layers. Interestingly, the intermixed layers still showed a certain type of layered structure, which appeared to be related to the van der Waals nature of the Sb2Te3 layer. However, such a layered structure could hardly be achieved on metallic surface such as TiN. This might be related with the highly interacting chemical nature of the TiN surface as well as the relatively rough surface topography. Adopting graphene or ultra-thin SiO2 layer on the TiN recovered the highly c-axis aligned growth behavior.
(Invited) Scratch Controled Electrochemical Production of Macropores in Silicon
Authors: Quiroga-Gonzalez Enrique 
Published: July 2021

Electrochemical etching of macropores in Si can be done either randomly (wild pores) or lithographically defined. When the points to be etched are not defined, the etching process starts at defects, or statistically distributed on the surface, just limited by the space-charge-region created in the semiconductor as effect of the electric field applied [1]. Ordered pores are usually accomplished by lithography plus a preliminary etching step for the formation of inverted pyramids [2]. At the pits of the pyramids the electric field is more intense during the electrochemical etching process, causing that the probability to etch pores is higher at those points. Defining the positions where pores are etched is necessary for different applications, where order is important. However, this makes the process to produce pores, which is not necessarily clean, more expensive with the need clean-room appliances (masking layer deposition and lithography).
In order to simplify the production of ordered micropores, in this work it is proposed to take advantage of the increased probability of surface defects to act as nucleation points of growing pores. An electronic grade single side polished p-type Si wafer, with resistivity of 20 Ωcm was used as starting material. The electrolyte was a 10 % (v/v) HF solution in DMF. The wafer was scratched with fine sand paper previous to the etching process. Electrochemical etching was performed aplying a current density of 20 mA/cm^2 for 10 min. Macropores grew mainly along the scratches (see Figure). The spacing between pores depends on the distances between scratches. The regions without scratches have a lower probability to be etched. However, if the defects introduced by the sand paper are cured by a short chemical etching process in KOH, the probability to electrochemically etch those sections is further increased, in comparison with the sections with scratches and no KOH treatment. With the observations, it is straight to think that it is possible to do deffect engingineering to tune the electrochemical etching of micropores in Si.
[1] E. Quiroga-González, H. Föll, book chapter "Chapter 2: Fundamentals of Silicon Porosification via Electrochemical Etching", in "Porous Silicon: Formation and Properties, Volume 1", editor G. Korotcenkov, CRC Press. (2015). ISBN: 9781482264548.
[2] E. Quiroga-González, E. Ossei-Wusu, J. Carstensen, H. Föll, J. Electrochem. Soc. 158(11) E119 (2011).

Figure 1
(Invited) Polymer-Based Electronics: Infrared Detectors and Supercapacitors
Authors: Ng Tse Nga 
Published: July 2021

The shortwave infrared spectral region is particularly powerful for health monitoring and medical diagnostics, because biological tissues show low absorbance and minimal infrared auto-fluorescence, enabling greater penetration depth and improved resolution in comparison to visible light. Here I will discuss my lab’s development of organic infrared photodetectors using a new generation of semiconducting polymers extending to 1600 nm. Several demonstrations will show the various potential applications including blood pulse measurements, spectroscopic identification, and image reconstruction. Furthermore, we have implemented upconversion imagers that combine photo-sensing and display in a compact structure, to extend the capability of human and machine vision to 1400 nm.
In addition, the same infrared polymers are narrow bandgap and present opportunities to create energy dense supercapacitors. Here we present promising n-type polymers that retained 90% of initial capacitance after 2000 charge-discharge cycles. Through current-voltage and spectroscopic measurements, we infer the mechanisms that lead to capacitance fade and suggests structural and electrochemical strategies to realize high-endurance energy storage devices for flexible printed systems.
(Invited) Theoretical Frequency Limit of Organic Rectifier Diodes
Authors: Jung Sungyeop , Horowitz Gilles , Bonnassieux Yvan 
Published: July 2021

In this communication, a new theoretical model for the ac transit frequency of organic rectifier diodes is proposed. The model is built upon a full description of the drift-diffusion current in the rectifier diode for the entire forward bias regime. Such a method precisely correlates the transit frequency to a number of materials, geometrical, and operational parameters in particular the charge-Injection barriers. By systematic variation of parameters, it is found that a rectifier operating beyond 1 GHz is observable only with a highly injecting anode. Other parameters to reach that regime of operation are discussed.
This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2018R1D1AB07048877), and by Materials, Components & Equipment Research Program funded by the Gyeonggi Province.