bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding the Role of Cu Electocatalyst, Binder, and Membrane Interfaces in CO2 Electrolyzer Durability
Authors: Hendershot John C , Bello Mustapha , Dauda Monsuru Olatunji , Flake John C.
Published: September 2023

Carbon dioxide electrolyzers capable of maintaining stable performance for thousands of hours are necessary for commercial electrochemical reduction of CO2 to two-carbon products such as ethanol and ethylene. Currently, most studies containing CO2 reduction to two-carbon products have been for durations of under 20h. Only a few (<5) instances of CO2 reduction to two-carbon products at durations over 100h have been reported. Common cell failure mechanisms, such as carbonate salt precipitation and cathode flooding, can be mitigated by tuning the operating conditions of the reactor. Beyond these modes of failure, there are practical limitations related to materials' durabilities and long-term stabilities, including ionomeric membranes' operating lifetimes, gas diffusion cathodes, anodes, and other MEA components.

In this presentation, we explore the role of CO2, water, and ion transport on cell performance over extended periods of operation. The polymeric anion exchange membrane and conductive binder have been identified as crucial components in tuning the transport properties of electrolyzer systems and, thus, will be the focus of this study. We consider several types of anion exchange membranes (e.g., imidazolium, ammonium, piperindinium) and conductive binders (e.g., Nafion, PVDF, PTFE, PSMIM) for use in the direct reduction of CO2 to two-carbon products at nanoscale Cu electrodes (150mA/cm2, 0.01M KHCO3 anolyte). This work improves upon previous analysis of membrane and binder transport properties by testing a wider variety of materials for >100h durations and reporting specific cell failure times and causes. We will discuss the balances between carbonate precipitation, flooding, and other membrane or electrode failures as a function of materials, MEA preparation, and operating conditions. A comprehensive set of failure standards based on electrolyzer performance (pressure, outlet mass flow, two-carbon product Faradaic efficiencies, energy efficiency, carbon efficiency) is introduced, and electrolyzer configurations are tested in triplicate to produce statistically significant failure data. Overall, this provides insight into CO2, ion, and water transport's role in electrolyzer cell performance and failure mechanisms.

Figure 1
Effects of Low-Temperature Pre-Cycling on High-Temperature Degradation of Lithium-Ion Cells
Authors: Carter Muriel , Poudel Pragati , Gober Megan , Liaw Boryann (Bor Yann) , Nelson George J. , Zhang Guangsheng
Published: September 2023

Lithium-ion (Li-ion) batteries suffer accelerated degradation when the operating temperature is beyond the optimal range1, 2, about 20 °C to 35 °C. At lower temperatures and higher temperatures, lithium plating and solid-electrolyte interface (SEI) growth are dominating degradation mechanisms, respectively1. A previous work by our group3 showed interestingly that pre-cycling Li-ion cells at 5 °C reduced degradation during cycling at higher temperatures of 45 °C and 60 °C. The observation suggested that low-temperature pre-cycling has significant effects on high-temperature degradation of Li-ion cells. The previous work was based on small cells that consisted of a single pair of electrodes. To confirm if the phenomenon also exists in large cells that consist of multiple pairs of electrodes, commercially available 3-Ah pouch cells are tested. It is found that pre-cycling of these large cells at 5 °C also significantly reduces their degradation at 45 °C. However, this effect is observed only when the cells are compressed. Without compression, cells pre-cycled at 5 °C degrade much faster than baseline cells cycled only at 45 °C. Further analysis of the results, such as cell internal resistance analysis and electrochemical impedance spectroscopy, is performed to better understand the effects of low-temperature pre-cycling on high-temperature degradation behaviors of Li-ion cells.

References:

T. Waldmann, M. Wilka, M. Kasper, M. Fleischhammer and M. Wohlfahrt-Mehrens, Journal of Power Sources, 262, 129 (2014).

F. Leng, C. M. Tan and M. Pecht, Scientific Reports, 5, 12967 (2015).

P. Poudel, Z. Du, B. Liaw, T. Iriyama and G. Zhang, ECS Meeting Abstracts, MA2022-01, 443 (2022).
Performance Limitations in Ni-Rich, High-Energy Lithium-Ion-Battery Cathodes
Authors: Lindner Adrian , Both Svenja , Abdolhosseini Saeed , Menesklou Wolfgang , Danner Timo , Latz Arnulf , Krewer Ulrike
Published: September 2023

Lithium-ion batteries with Ni-rich stoichiometries such as LiNi0.8Mn0.1Co0.1O2 (NMC811) have gained

importance due to the reduction of critical resources such as cobalt. While these cathode materials

with high nickel content offer high specific capacity [1], their rate capability is significantly reduced

compared to other chemistries. In the present work, the combination of large-volume FIB/SEM

tomography, structurally-resolved simulation, and electrochemical half-cell analysis is used to

characterize the cathode microstructure of a commercial high-energy cell. Detailed structural data

were obtained by FIB/SEM tomography and used to optimize the simulation approach to accurately

describe the discharge capacity and electrode impedance simultaneously. Poor electrical conductivity

is identified as the main cause of power loss. An optimized, artificial structure with up to 10% higher

1C discharge capacity compared to the original structure is developed by increasing and homogenizing

the conductive binder network. This tool enables further understanding of structural aging and

degradation effects by correlating structural changes with performance losses.

Acknowledgements

This work was funded by the German Ministry for Education and Research under the reference number

03XP0317D.

References

[1] A. Butt, G. Ali, K. Tul Kubra, R. Sharif, A. Salman, M. Bashir and S. Jamil, Energy Tech, 10(3),

2100775 (2022).

Figure 1: Virtual representations of a commercial cathode based on FIB/SEM tomography data. Three-dimensional analysis

allows for evaluation of volumetric phase contents, pore network diffusion and grain size distribution. Additionally, 3D data

acts as simulation domain for structurally resolved continuum simulations.

Figure 1
Development of Electrolyte Additives to Enable High-Voltage LiNi0.5Mn1.5O4 Lithium Ion Batteries
Authors: Cavers Heather , Wang Yajie , Kwade Arno
Published: September 2023

Electrochemical energy storage (EES) is still key to realize wide spread use of renewable energies. For large-scale EES production, the development of high energy density, non-toxic, cost-effective materials is necessary. In this study, a cobalt free active material, Lithium Nickel Manganese Oxide, LiNi0.5Mn1.5O4 (LNMO), was employed in the production of cathodes for high voltage lithium ion battery (LIB) applications. LNMO is an attractive cathode active material due to its high operating potential (~4.7 vs. Li/Li+ [1]), non-toxicity and low cost. The practical application of LNMO cathodes in LIBs has been relatively limited, especially for large scale application, due challenges associated with the material (i.e. electrolyte decomposition at high voltage, self-discharge and dissolution of the transition metals [2]).

Electrolyte additives are an effective way to address these challenges, without major cost increase or changes to the production approach. In this study the role of different electrolyte additives in high-voltage full-cell LIBs with both graphite and silicon-graphite anodes is investigated. Additives known for their solid electrolyte interphase (SEI) forming ability (i.e. vinylene carbonate (VC) and fluoroethylene carbonate (FEC)), as well as additives that play additional roles such as cathode electrolyte interface formation or HF scavenging (i.e. tris(trimethylsilyl) phosphite (TMSP) and succinate anhydride (SA)), are used [3]. Galvanostatic cycling measurements were performed in 3-electrode cells in order to investigate the rate capability and long term cycling stability of LMNO/Gr and LMNO/Gr-Si full-cells with different electrolyte additives. The electrochemical characterization was verified with post mortem analysis to confirm the SEI composition, chemical and mechanical stability of the electrodes and lack of lithium plating. Post mortem investigations were done with Raman spectroscopy, scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX) and optical microscopy. Improved rate performance and better long term cycling stability of both full-cell chemistries was achieved for electrolytes containing the TMSP additive.

References:

[1] G. Gabrielli, M. Marinaro, M. Mancini, P. Axmann and M. Wohlfahrt-Mehrens, J. Power Sources 351 (2017) 35-44.

[2] R. Amin, N. Muralidharan, R. K. Petla, H. Ben Yahia, S. A. Jassim Al-Hail, R. Essehli, C. Daniel, M. A. Khaleel, I. Belharouak, J. Power Sources, 467 (2020) 228318.

[3] K. Kim, H. Ma, S. Park, N.-S. Choi, ACS Energy Lett., 5 (2020) 1537-1553.
Formation and Suppression of Toxic Organofluorophosphates in Lithium Ion Batteries: Making the High-Voltage Additive Lithium Difluorophosphate Viable for Commercial Applications
Authors: Nowak Sascha , Kubot Maximilian , Winter Martin , Kasnatscheew Johannes , Muschiol Elisabeth
Published: September 2023

Organofluorophosphates (OFPs) are one of the major concerns regarding the safety of Lithium Ion Batteries (LIBs) due to their neurotoxic properties. The formation through the hydrolysis of the conducting salt LiPF6 and subsequent reactions (reductive/oxidative) with the cyclic and linear carbonates is a major drawback in terms of commercial application of LIBs. The additive Lithium Difluorophosphate, which is literature known and beneficial for high-voltage LIBs due to its transition metal (TM) capturing abilities, accelerates the formation of toxic OFPs even further as it also is a hydrolysis product of LiPF6. The suppression of the formation of toxic OFPs through a synergetic dual additive approach with fluoroethylene carbonate (FEC) is presented in this study. Here, the thermal- and electrochemical formation of OFPs are successfully inhibited with the addition of 2 wt.% of FEC to the electrolyte containing LiDFP (1 wt.%). Characterization of OFPs is conducted via high performance liquid chromatography mass spectrometry and the toxicological capabilities of the aged electrolyte is assed through an inhibition-evaluation of Acetylcholinesterase lyophilizate. Combined, these two methods illustrate the successful inhibition of OFP formation in FEC/LiDFP dual-additive electrolytes. Further, this dual-additive approach does not deteriorate the performance of LiDFP as single additive making the FEC/LiDFP additive combination a possible new benchmark for high-voltage LIBs.
Uncovering the Mechanism of Reactive Oxygen Species Scavenging by Organosilicon Lithium-Ion Battery Electrolyte Additives Using Fundamental Kinetic Analysis
Authors: Morris Louis Vincent , Ortiz-Ledon Cesar , Hamers Robert J
Published: September 2023

Reactive oxygen species, among them radical anions, have been a subject of numerous investigations within the lithium-ion battery and lithium-air battery communities because of their capacity for destructive side reactions with both solvent and electrolyte components of their chemistries. Electrolyte additive components which can control these destructive species represent an opportunity for technical innovation. Such innovation, however, is hampered by a lack of fundamental understanding of the reactive pathways that these reactive compounds might take in systems as complex as battery electrolyte. With this in mind, we have explored a family of structurally related reactive oxygen species scavenging electrolyte additive molecules and quantified their fundamental reactivity with the superoxide radical anion. These experiments have also allowed us to determine the mechanism of action by which these additives scavenge radical anions, thereby supporting the rational design of future additives aimed at reactive oxygen species suppression in battery contexts.
Development of Binder for Fast-Charging for Li-Ion Battery
Authors: Lee Go Eun , Oh Sae Wook , Kwon Se Man
Published: September 2023

In the recent years, fast-charging is a battery technology that continues to be in demand for portable devices, electric vehicles and grid storage. Especially, fast charging capability has become one of the key features targeted by battery and EV industries. However, charging at high rates has been shown to accelerate degradation, causing both the capacity and power capability of batteries to deteriorate. In addition, the efficiency of fast charging depends on the materials and current in the battery, but also ambient temperature is emerging as an important issue. When the ambient temperature decreases, there is a decrease in performance and battery stability problems. This is the reason that the diffusion of Li-ion is slower in the electrodes and the electrolyte at low temperatures due to sluggish kinetics of interaction. Therefore, it is recommended to use low charging speed and voltage at low ambient temperature. In order to increase the fast charging efficiency, the material and battery design must be well designed, and among them, by improving the ionic conductivity of the binder, the resistance of the entire battery is lowered and the fast charging efficiency is improved. In addition, the resistance of material change at low temperature and its effect on fast-charging were also examined.
(Invited) Deciphering the Interplay between Thermodynamics and Kinetics during Cathode Calcination
Authors: Barai Pallab , Garcia Juan , Kinnibrugh Tiffany , Chen Ke , Wolfman Mark , Wang Xiaoping , Fister Tim , WANG Feng , Iddir Hakim , Srinivasan Venkat
Published: September 2023

Synthesis of the cathode materials used in lithium ion batteries involve the two steps, coprecipitation and calcination, where in the first step cathode precursors are formed, and later in the second step lithium ions are inserted into these cathode particles through chemical routes. During calcination, the cathode precursors obtained from the coprecipitation is mixed with lithium salt (LiOH or Li2CO3) and heated at high temperatures (~ 650°C – 1000°C) where oxidation and lithiation of the cathode particles take place. Calcination is considered to be of major significance in determining the final state of the cathode particles because it not only determines the extent of oxidation and lithiation experienced by the cathodes, but also substantially influences its morphology (for example, primary particle size, internal porosity, etc.). Significant surface modification of the cathode particles is also possible during calcination, which can impact its charge transfer resistance. Before the oxidation and lithiation of the cathode precursors, removal of water or CO2 is observed. All these chemical changes within the cathode precursors lead to change in its lattice volume, which is reflected as variation in the size of the primary particles. Apart from this, sintering induced change in particle size is also observed during the calcination process.

In order to decipher the structural and morphological variations that occur during the calcination of cathode precursors, detailed experimental characterization is conducted in the present context using in situ X-ray diffraction (XRD) and thermogravimetric analysis (TGA) techniques. Atomistic simulations are conducted to decipher the feasibility of different chemical reactions that can possibly occur under elevated temperatures. Impact of reaction rate constant and mass transport in determining the extent of the oxidation and lithiation experienced by the cathode particles is analyzed by using a mesoscale level computational technique. Sintering induced grain growth experienced by the cathode primary particles is also investigated at the mesoscale level, which is demonstrated in Figure 1. Overall, a thorough understanding of the various physicochemical phenomena that occur during the calcination of cathode precursors has been developed using a combination of experimental and computational techniques, which will be discussed in detail.

Figure 1
Novel Theories for Modeling the Surface Stabilization and Dendrite Suppression for Lithium-Metal Anode Based on Piezoelectric Effect
Authors: Gao Tianhan , Lu Wei
Published: September 2023

During electrodeposition, a small perturbation can cause the metal surface to lose its stability and form dendrite. Lithium dendrite is a key barrier that has impeded the commercialization of lithium metal batteries as well as fast charging. We find a piezoelectric mechanism to suppress dendrites, whose effect measured by over-potential can easily be 106 stronger than mechanically blocking dendrite with a stiff film. We first expanded the classical electrochemical reaction kinetics by incorporating the effect of stress and thin film piezoelectricity. We then developed a novel theory that couples the fields of electrochemistry, piezoelectricity and thin film mechanics. We then developed a rigorous stability analysis approach to reveal the effect of surface tension, mechanical blocking and piezoelectric mechanism on the stability of electrodeposition. We finally developed a theoretical expression of the critical wavelength, which provides useful guidance on achieving stable electrodeposition for various systems [1].

We further developed a theory for a bulk porous piezoelectric medium which couples electrochemistry, piezoelectricity, and mechanics. Specifically, we derived a piezoelectric overpotential, which reveals a fundamental relation to surface charge density, dielectric property of the medium, electrolyte concentration and diffusivity, and the reaction coefficient. Our simulation results show that piezoelectric medium can effectively suppresses electrodeposition on any protrusion, leading to a flat, dendrite-free surface [2].

References:

[1] T. Gao, G. Liu, W. Lu, A theory that couples electrochemistry and thin film piezoelectricity with stability analysis for electrodeposition, J. Mech. Phys. Solids. 162 (2022) 104827. doi:10.1016/j.jmps.2022.104827.

[2] T. Gao, D. Barnes, W. Lu, Theory of Coupled Electrochemistry and Piezoelectricity in a Porous Medium, Phys. Rev. Lett. 128 (2022) 68301. doi:10.1103/PhysRevLett.128.068301.
Parametric Reduced-Order Modeling of Battery Thermal Management Systems for Varying Rates of Cooling Liquid Flow
Authors: Xiang Linyan , Lee Cheol W , Zikanov Oleg , Hsu Chih-Cheng
Published: September 2023

The thermal management system in battery packs for electrical/hybrid electric vehicles plays an important role in maintaining good performance and health of battery cells. In order to optimize the thermal management system design, computational fluid dynamics (CFD) simulations are often used. The CFD is a powerful tool that can accurately simulate the thermal behavior of the system using numerical computation techniques such as finite volume method. However, the days-long computational expense means that the CFD-based simulations are still unsuitable for situations when rapid results are required, for example for online predictive control or fast-pace optimization design.

A new method of reduced-order modeling of battery thermal management systems (BTMS) was presented in [1]. Given a CFD model, the algorithm based on projection on Krylov-subspace yields a reduced-order model (ROM). The ROM accurately predicts the system’s transient response to arbitrary internal heating of individual batteries and temperature of cooling liquid at inlet. Unlike conventional Krylov-subspace approaches, the algorithm does not require the system matrix of the CFD model. Therefore, the method is more suitable for use with commercial CFD software which does not allow access to such internal information. The ROM uses a drastically reduced number of degrees of freedom requiring drastically reduced simulation time.

This paper extends our ROM by including the mass flow rate of cooling liquid as a model parameter. The task is accomplished by interpolating the system matrices after several local reduced-order models are constructed at discrete mass flow rates (MFR). In order to interpolate the local ROMs, we first need to transform the local ROMs onto a common subspace. The transformation matrix is obtained by applying the singular value decomposition (SVD) to the local projection matrices. In this paper, three local ROMs are built at 3 different MFRs. After these local ROMs are transformed according to the above procedure, a parametric reduced-order model (pROM) is constructed via quadratic interpolation.

The constructed pROM is tested against the new MFRs different from those used for building the local ROMs. For each new MFR, the pROM produced a transient response that is almost indistinguishable from that of the CFD model (e.g., see Figure 1). The several thousand core-hour computational time needed for CFD simulations is replaced by a few tens of seconds using the pROM on a personal computer. The low computing load of the pROM is deemed adequate for on-board applications.

Reference

[1] Xiang L, Lee CW, Zikanov O, Hsu C-C. Efficient reduced order model for heat transfer in a battery pack of an electric vehicle. Applied Thermal Engineering. 2022; 201:117641.

Figure 1

Figure 1
Accelerated Prediction and Analysis of Lithium-Ion Battery Lifetime Using Efficient Electrochemical Models
Authors: Uppaluri Maitri , Subramaniam Akshay , Lim Jin-hyung , Subramanian Venkat R.
Published: September 2023

Lithium-ion batteries degrade over their lifetime due to several parasitic reactions that occur in the cell. These reactions lead to loss of lithium inventory, loss of active material, mechanical and thermal damage to the cell’s component. Predicting cell aging and capacity fade is crucial for battery management systems (BMS) to monitor and control the battery's state of health. Physics-based models are valuable in battery management systems (BMS) to monitor the battery’s state of health and predict battery failure. BMS algorithms require fast codes that can predict and estimate battery parameters in real-time and control the battery’s performance under different loads.1 Common reduced-order models, such as the SPM (Single Particle Model) consider approximations that may not be valid as the cell ages. The Tanks-in-Series model is a model developed by Subramaniam et al., where the governing equations from the full-order ‘pseudo-2-D’ (p2D) model are volume-averaged over each cell region.2 This ensures that the physics captured by the mass and charge conservation equations are maintained without loss of accuracy while providing simulation solutions at a few milliseconds. The Tanks-in-Series model is ideal for predicting cell aging due to its reduced computation speed and predictability beyond other reduced-order models.

This work combines the Tanks-in-Series model with governing equations for several degradation mechanisms, including the growth of the SEI layer, lithium plating, particle cracking, etc. A comprehensive analysis of capacity fade predictions is shown, with comparisons to predictions from the P2D model.

References

V. Ramadesigan et al., J. Electrochem. Soc., 159, R31–R45 (2012).

A. Subramaniam et al., J. Electrochem. Soc., 167, 013534 (2020).
Understanding the Processability of Graphite Blend Electrodes with Silicon Nanoparticles
Authors: Zapata Dominguez Diana , Mondal Brinti , A. Franco Alejandro
Published: September 2023

Li-ion batteries (LiBs) are one of the best solutions for energy storage due to their high capacity, high power, and cyclability1,2. The increasing need for energy storage to supply electric vehicles demands continuous innovation to optimize the LiBs, specifically the manufacturing parameters to fabricate these devices. The battery production requests improved materials, cell designs, greener manufacturing processes, and recycling3,4. For instance, developing an improved anode material could be a good approach for optimizing the LiB energy density. A blend of graphite and silicon is a promising negative electrode due to the combined stability of graphite with the high theoretical capacity of silicon5,6. Since adding silicon changes the manufacturing parameters already established for commercial graphite electrode fabrication, our goal is to understand the impact of the manufacturing process, such as the calendaring effect on the properties of the silicon/graphite blend electrodes. These electrodes were prepared with two different silicon percentages, 8%, and 15%, compared to pure graphite. We investigate the morphological changes, electrochemical aging, and tortuosity when decreasing the porosity from 55% to 30% for both electrodes to evidence the porosity threshold for obtaining adequate electrode properties. Manufacturing optimization is time and cost-consuming. Modeling approaches are an excellent choice to decrease LiB fabrication scraps. We are developing machine learning and physical models of the 3D silicon-graphite electrode fabrication process within our ARTISTIC project7, and these optimization results will help to validate them.

S. Chu and A. Majumdar, Nature, 488, 294–303 (2012).

J. B. Goodenough and K.-S. Park, J. Am. Chem. Soc., 135, 1167–1176 (2013).

J. Li, J. Fleetwood, W. B. Hawley, and W. Kays, Chem. Rev., 122, 903–956 (2022).

F. M. Zanotto et al., Batter. Supercaps, 5 (2022).

M. T. McDowell, S. W. Lee, W. D. Nix, and Y. Cui, Adv. Mater., 25, 4966–4985 (2013).

F. Jeschull et al., J. Electrochem. Soc., 167, 100535 (2020).

C. Liu, O. Arcelus, T. Lombardo, H. Oularbi, and A. A. Franco, J. Power Sources, 512, 230486 (2021).
(Digital Presentation) Experimental Investigation of Thermal Runaway of Single 21700 Li-Ion Cell and Runaway Propagation in a Battery Module
Authors: Ahamad Salahuddin , R Gowda Ramith , Sundaramaan K. V.
Published: September 2023

Li-ion battery is an integral part for the electric or hybrid electric vehicles, as they provide high energy density and power density with extended cycle-life compared to their closest rivals, Ni-MH batteries [1]. As the Li-ion batteries gained significant success in the automotive sector, safety issues, pertaining to the fire and explosion accidents caused by thermal runaway (TR) have become a critical issue obstructing their applications. Therefore, the Li-ion battery thermal runaway has attracted an increasing attention of the research community worldwide. Thermal runaway is a self-accelerated degradation process of Li-ion batteries, [2] it can be brought by abuse [3] or internal cell failure due to defects [4]. During the TR, a significant amount of burnable and harmful gas and a large amount of heat are generated, which substantially increase the temperature of batteries [5]. Currently, most of the research work on the TR characteristics are conducted under different triggering modes at the cell level. However, the research on the large lithium battery pack is quite scarce. Therefore, several important issues need to be identified to reveal the critical conditions of the fire propagation, and precisely predict the fire risk of Li-ion battery pack fire.

In this work, thermal failure experiments were performed using commercial cylindrical 21700 Li-ion single cell and a module by external heating, to analyze the casing rupture and the TR propagation behaviors in the pack based on the fire test apparatus. The critical parameters including the temperature, and heat release rate will be carefully analyzed to reveal the fire propagation hazards of battery packs.

References:

D. Rahn, and C. Y. Wang, Battery Systems Engineering, Wiley, State College, PA (2013).

Wen, Y. Yu, and C. Chen, Mater. Express, 2, 197 (2012).

W. Golubkov, D. Fuchs, J. Wagner, H. Wiltsche, C. Stangl, G. Fauler, G. Voitic, A. Thaler, and V. Hacker, RSC Adv., 4, 3633 (2014).

Feng, M. Ouyang, X. Liu, L. Lu, Y. Xia, and X. He, Energy Storage Mater., 10, 246 (2018).

Fu, S. Lu, K. Li, C. Liu, X. Cheng, and H. Zhang, J. Power Sources, 273, 216 (2015).
Polymer Electrolytes for Printed 2-D Microcapacitors with Silver Electrodes
Authors: Virya Alvin , Wang Guan Ying , Wang Zhi Yi , Chu Ta-Ya , Graddage Neil , Lian Keryn
Published: September 2023

The next generations of wearable electronics require high-performance, low-cost, thin, and flexible 2-D electronic components, e.g. capacitors and transistors. The commercial feasibility of these technologies relies on printable, high throughput, highly electronically-conductive, and inexpensive silver electrodes/current collectors to replace gold counterparts. However, silver-based devices are prone to failure due to corrosion forming resistive oxides or dendrites in aqueous environments (as shown in Figure 1a). Polymer electrolytes, possessing high ionic conductivity and enabled double layer capacitance at electrode interface, are highly tunable to minimize the dendritic growth and can be a promising technology for these 2-D devices.

In this study, some high-performance aqueous polymer electrolytes that have previously been demonstrated for supercapacitors were compared and modified for better integration into printed interdigitated devices with silver electrodes. The polymer electrolytes were evaluated for their apparent ionic conductivities, capacitance, and corrosion properties using cyclic voltammetry and electrochemical impedance spectroscopy. Polymer electrolytes can effectively inhibit dendritic formation as shown via optical microscope in Fig. 1b. The optimized electrolytes possessed (i) high ionic conductivity (>1 mS cm-1) at ambient, (ii) good ability to maintain well-dissociated ions enabling double layer capacitance formation (Fig. 1c), with capacitance >100 μF cm-2 and (iii) good compatibility with silver electrodes. Overall, the optimized polymer electrolytes can be a low-cost, viable alternative in printed electronics requiring high dielectric materials, such as microcapacitors and low-powered field-effect transistors.

Figure 1
(Invited) Design and Modeling of Resistive Switching Devices for Neuromorphic Applications
Authors: Sasikumar Renjith , Kolla Lakshmi Ganapathi , Misra Durgamadhab , Padmanabhan Revathy
Published: September 2023

Resistive switching devices are a critical component for the realization of computational systems that mimic biological neural systems. In biological systems, connection weights between the neurons are dependent on the time lapse between the neurons’ action potentials. Resistive switching devices (memristors) with multiple conductance states can mimic this biological spike-time-dependent plasticity (STDP) behaviour, with multiple conductance states being analogous to different synaptic weights. Additionally, memristors are one of the contenders as storage elements in non-volatile memories. The change in conductance in memristors can be broadly attributed to vacancy migration inside the switching layer (valence change memory) or the formation of metallic filaments inside the switching layer (electrochemical metallization).

Electrochemical metallization-based memristors with vertical transport and small inter-electrode distances have been reported recently. Their device characteristics exhibit multiple conductance states with relatively low switching voltages, which makes them well-suited for low-power neuromorphic applications. Our work models the transport in these memristors, focusing on explaining and capturing their current-voltage characteristics. Our model also captures the switching dynamics (with an emphasis on estimating switching energies and delays) and explains the experimentally observed STDP behaviour in these devices. We have proposed models for filament growth and dissolution along one dimension (axial) and two dimensions (axial and radial). The simulation results obtained using our model (and implemented in Verilog-A) have been validated with experimental data from multiple sources. Our work demonstrates the flexibility of including different transport mechanisms in a unified framework.

We have characterized valence change memory (VCM) memristors with HfO2 and HfZrO2 as switching layers. They exhibit bipolar switching, negative differential resistance, multiple conductance states, and STDP behaviour, which have been analyzed. We have also modeled the transport in these VCM-based memristors, and simulated the I-V and dynamic switching characteristics, and STDP behaviour in these devices. We have simulated arrays of, both, ECM and VCM devices using the proposed models, and tried to demonstrate a typical pattern classification problem using in-memory computation. We believe that our models provide useful insight into the design of memristors for neuromorphic and memory applications.
In Memory Energy Application for Electrochemical Random Access Memory
Authors: Nguyen Ngoc Anh , Melfi Massimiliano , Allain Marjolaine , Hellion Clemence , Lamy Yann , Oukassi Sami
Published: September 2023

This work explores the innovative concept of a hybrid dual-behavior device, based on emerging nonvolatile memory technology, for both data retention and energy storage. Electrochemical random access memory (ECRAM) is considered a major candidate as next-generation memory, thanks to its promising performances in terms of scalability and CMOS process compatibility. In particular, three-terminal synaptic transistors (SynT) offer an ion conductor-gated control from which ion doping content can be monitored with high energy efficiency via redox reactions, thus decoupling write-read actions and improving the linearity of programming states for neuromorphic computing1. Its working mechanisms, based on faradaic processes, motivate the study on the feasibility of operating ECRAM also as energy storage element.

To evaluate the energy capability, various electrochemical characterizations are presented. Cyclic voltammetry tests reveal that the cells behave as standard electrochemical storage elements when investigating the impact of the scan rate, maximum positive voltage, and area on the reduction peak. Storage capability amounts up to 1.5µAh.cm-2 have been obtained, two decades higher than deep trench capacitor existing solutions, while showing outstanding synaptic behavior: A nonvolatile conductance modulation (<75 nS) is achieved through reversible lithium intercalation into the channel, and synaptic functions, such as long-term potentiation/depression involve ultralow switching energy of 2 fJ μm−2. Moreover, this SynT shows excellent endurance (>105 weight updates) and recognition accuracy (>95% on the MNIST data test using crossbar simulations). Finally, design concepts are proposed, where ECRAM “in-memory energy” technology would be a newfangled approach to meet the needs of various emerging and standard applications.

Reference

Nguyen, N. et al. An Ultralow Power Li x TiO 2 -Based Synaptic Transistor for Scalable Neuromorphic Computing. Adv. Electron. Mater.
2200607, 2200607 (2022).

Figure 1. Schematic view of the elaborated SynT, and corresponding dual energy and data storage properties: vertical gate stack is a nanobattery with energy storage function while lateral architecture allows for conductance modulation and data storage.

Figure 1
(Invited) Understanding Photoelectrocatalysis on Epitaxial Oxide Surfaces
Authors: Stoerzinger Kelsey A
Published: September 2023

The intermittent nature of renewable energy sources requires a clean, scalable means of converting and storing energy. One Earth abundant storage option is water electrolysis, storing energy in the bonds of O2 and H2. Photoelectrochemical (PEC) cells based on semiconductor/liquid interfaces can convert sunlight to chemical fuels without external circuitry, such as “splitting” water into O2 and H2 upon illumination. The efficacy of conversion depends in part on the location of the semiconductor band edges, dictating absorption, and also the rectifying properties of semiconductor–electrolyte junctions, which drives the separation of electron–hole pairs.

We will present studies of model oxide La(1-x)SrxFeO3 photoelectrodes grown by molecular beam epitaxy (MBE) and pulsed laser deposition (PLD) that display a known crystallographic orientation, surface area, path for charge transport, and strain. Aliovalent doping can tune the transition metal redox properties as well as the material band gap and conductivity, resulting in a rich phase space of possible water-oxidation photoanodes. Comparing the photooxidation of a fast redox couple to the slugging water oxidation reaction demonstrates the potential of electronic states that must be filled prior to oxygen evolution. Measurements of the surface speciation in a humid environment demonstrate that Sr incorporation also promotes hydroxylation, suggesting that water oxidation proceeds through the oxidation of FeIII-OH states, which is facilitated by Sr incorporation and results in an increased photovoltage. Surface-sensitive measurement of the valence band and unoccupied states (via O K-edge X-ray absorption spectroscopy) under humid conditions further support this picture. This fundamental insight builds understanding necessary for the design of active, earth-abundant photocatalysts that can be integrated into PEC devices for efficient conversion of solar energy into chemical fuels.
High-Vacuum Chemical Vapor Deposition of Monolayer Hexagonal Boron Nitride on Ge(001) from Borazine
Authors: Su Katherine Anna , Li Songying , Arnold Michael Scott
Published: September 2023

Hexagonal boron nitride (h-BN) has played significant roles in enhancing the optoelectronic and electronic properties of a host of two-dimensional materials. These include reducing charge scattering in field-effect transistors, increasing exciton emission efficiency in valleytronics, controlling interlayer excitons, and serving as a tunneling barrier. While the synthesis of h-BN on metallic substrates has been studied extensively, the synthesis of h-BN on CMOS-compatible substrates like Ge has not. Here, we report the growth of h-BN on Ge(001) from borazine via high-vacuum chemical vapor deposition. We find that the sublimation of Ge under high vacuum inhibits h-BN growth. To overcome this challenge, we place two Ge substrates face-to-face with a thin gap in between and tune the gap thickness to control h-BN nucleation density and island size. In addition, we systematically investigate the effects of growth temperature and precursor partial pressure on h-BN growth.

Figure 1
One-Dimensional Van Der Waals Helical Crystals with an Irrational Twist
Authors: Arguilla Maxx , Cordova Dmitri Leo Mesoza , Chua Kenneth
Published: September 2023

Long-range helicity in condensed materials has sternly relied on the precise ordering of cooperative intra- and inter-molecular bonding interactions. The exclusivity of these interactions in natural, organic, or molecular systems has limited the conclusive demonstration of aperiodic helical motifs in densely packed solid state lattices. In this talk, we will present a class of 1D van der Waals solids that crystallize as weakly bound helical chains that possess atomic scale order consistent with an aperiodic tetrahelix. We will describe how precise atomic level control of the local coordination environment in these 1D vdW lattices induces helical aperiodicity in periodic helical motifs based on repeating screw axis symmetry motifs. We will also highlight herein that the modularity of vdW lattices allows for the systematic engineering of helical attributes (radius, rise, and twist angle) and band gap energies across the visible to the near-UV spectral window. Owing to the intrinsic non-centrosymmetry of aperiodic helices, we will show that these 1D vdW tetrahelices exhibit visible range second harmonic generation in freestanding crystals from the bulk down to the nanoscale. Lastly, we will demonstrate that the weak vdW interchain interactions in these 1D vdW tetrahelices enables the micromechanical exfoliation into single ~1 nm diameter chiral helical chains. The realization of exfoliable 1D vdW tetrahelices presents a unique materials platform towards understanding the synthetic design rules towards helicity and chirality in low-dimensional solids. Atomically-precise helicity along these length scales will facilitate new opportunities in designing solid state materials towards sub-nanoscale nonlinear chiroptics, long-range spin polarization via chiral-induced spin selectivity, and 1D topological helicoid quantum states.
Estimation of Size and Lattice Strain of ZnO/Ag Nanowires Based on Williamson-Hall Analysis
Authors: Younsi Chahra
Published: September 2023

Zinc oxide (ZnO) is known as an important semiconductor which has been studied extensively in the past few years due to its fundamental and technological importance, Its

many attractive properties, such as wide bandgap (3.37 eV), large exciton binding energy and excellent chemical stability, suggest a great many possible practical applications such as in gas sensors, ceramics, field-emission devices and luminescent materials and therapeutic , size and crystal morphology play important roles in these applications, which have driven researchers to focus on the synthesis of nanocrystalline ZnO. This work is aimed to the development and characterization of zinc oxyde nanowires for therapeutic applications. ZnO nanowires are elaborated by hydrothermal method using a novel synthesized protocol. The elaboration hydrothermal conditions were optimized in order to have the longest nanowires with the lowest diameter. The structural, morphological and elementary analysis of the growth NWs was carried out by X-ray Diffraction (DRX), Scanning Electron Microscopy (SEM) and Energy Dispersive spectroscopy (EDS). The XRD results revealed that the sample product was crystalline with a hexagonal wurtzite phase. transmission electron microscopy (TEM) showed single-crystal ZnO NPs with nearly wires shapes. The crystalline development in the ZnO-Nws was investigated by X-ray peak broadening. The Williamsone Hall (W_H) analysis and sizee strain plot method were used to study the individual contributions of crystallite sizes and lattice strain on the peak broadening of the ZnO-Nws.
(Invited) Fabrication and Device Performance of 2.7 Kv/2.5A NiO/Ga2O3 Heterojunction Power Rectifiers
Authors: Xia Xinyi , Li Jian-Sian , Chiang Chao-Ching , Ren Fan , Pearton Stephen J
Published: September 2023

In this study, The fabrication of a p-n junction NiO/Ga2O3 rectifier in which we employ a bilayer NiO structure with two different doping levels to achieve both high breakdown voltage and low on-state resistance was described. The band alignment of the NiO to the Ga2O3 was measured. Selective wet and dry etch processes for removing NiO from the underlying Ga2O3 was developed. Finally, the dc and switching performance of the rectifiers was characterized. The maximum breakdown voltage was 2.7 kV for a 1 mm diameter rectifier, with 2.5 A forward current and on/off ratio > 108 over a broad range of switching voltages. The reverse recovery time was limited by the measurement circuit but was < 100 µs. These results show the promise of heterojunction rectifiers based on Ga2O3 for future generations of power switching applications.

Figure 1
A Flexible and Stretchable Temperature Sensor Based on Contact Electrification for Robotic Sensing
Authors: Lim Kee Chin , Chen Shuo-Wen , Chen Yung-Hsin , Huang Yan-Tsz , Pal Arnab , Lin Zong-Hong
Published: September 2023

With the rapid development of robotic systems, an increasing number of various sensitive sensors are needed to meet the requirement of data collection for unmanned detection and monitoring technology. Among various external stimuli information, temperature sensing is an essential important function that can avoid high-temperature scalding injuries, achieve robot detection of environmental, and human-machine interfaces applications. However, most of the existing temperature sensors for robotic sensing are realized by rigid materials, which have the disadvantage of not being able to adapt to an arbitrarily curved surface. Also, most of the sensors are thermistor-based approaches, which faces challenges in developing a low-cost robotic system since external power is required to obtain the sensing signal. In this work, a self-powered and stretchable temperature sensor based on Triboelectric Nanogenerator (TENG) technology was developed. The principle of TENG is the coupling effect of triboelectric charge transfer and electrostatic induction effects, which can generate different magnitudes of electrical signals when subjected to external stimuli, including temperature. To this end, this study is a pilot effort toward validating the sensitivity of TENG electrical output on different temperature effects. The surface potential of materials is explored under different temperatures by Kelvin probe force microscopy (KPFM), which shows the feasibility of self-powered temperature sensor. The proposed temperature sensor is composed of highly resilient materials physiological saline as liquid electrode encapsulated with Ecoflex as triboelectric layer, which has the advantage of biocompatibility. The temperature sensing performance was successfully maintained at 200% stretch. Owing to its flexible, bendable and stretchable characteristics, the self-powered temperature-sensitive sensor has been successfully demonstrated on a robot hand, which can read the information and respond to different temperatures through the feedback system. Overall, this self-powered temperature-sensitive sensor has great potential to be an emerging tool for human-robot interaction and automatic detection.
(Invited) scalable Manufacturing and Biomedical Applications of Biocompatible Piezoelectric Materials
Authors: Wang Xudong
Published: September 2023

Piezoelectric materials are a group of important functional building blocks that interfacing the human body by coupling biomechanical energy and electricity. So far, many technology innovations have advanced piezoelectric materials and composites toward a broad range of biomedical applications, which possess unique biocompatibility and flexibility. Fundamentally, materials design and engineering draw the boundary where this technology may advance. In this talk, I introduce our most recent development of piezoelectric materials and composites that are particularly designed for implantable nanogenerator applications. First, I present our wafer-scale approach to creating piezoelectric biomaterial thin films based on γ glycine crystals. The self-assembled sandwich film structure enabled both strong piezoelectricity and largely improved flexibility. Then, new ferroelectric composites are presented as a new material used in 3D printing for directly manufacturing of piezoelectric architectures with tunable piezoelectric and mechanical properties. Toward the end, novel applications of implantable piezoelectric materials are introduced, which enable the closed-loop electrostimulations for many biomedical therapeutics.