bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrospun Nanofiber-Based Cathodes for Lithium-Sulfur Batteries
Authors: Kalra Vibha
Published: May 2020

Lithium-Sulfur is a next generation battery chemistry that offers a theoretical capacity of 1,675 mAh/g, an order of magnitude higher than that of the currently used Li-ion battery cathodes. However, a serious challenge that has plagued the development of this technology is the dissolution and shuttle of intermediate polysulfides (Li2Sx, x=4-8) in the electrolyte resulting in loss of active material and rapid capacity fade during cycling. I will present two projects from my group both centred around Li-S batteries. In the first part of my talk, I will discuss our work on stabilization of titanium monoxide (TiO) nanoparticles in carbon nanofibers (CNF) through electrospinning and carbothermal processes and their unique bi-functionality – high conductivity and ability to bind polysulfides via Lewis acid-base interactions–as sulfur hosts. The developed 3-D TiO/CNF architecture with the inherent inter-fiber macropores of nanofiber mats provides a much higher surface area (~427 m2 g-1) and overcomes the challenges associated with the use of highly dense powdered Ti-based suboxides/monoxide materials, thereby allowing for high active sulfur loading among other benefits. The developed TiO/CNF-S cathodes exhibit high initial discharge capacities of ~1080 mAh g-1, ~975 mAh g-1, and ~791 mAh g-1 at 0.1C, 0.2C, and 0.5C rates, respectively with long-term cycling. Furthermore, free-standing TiO/CNF-S cathodes developed with rapid sulfur melt infiltration (~5 sec) eradicate the need of inactive elements viz. binders, additional current collectors (Al-foil) and additives. Using postmortem XPS and Raman analysis, this study reveals the presence of strong Lewis acid-base interaction between TiO (3d2) and Sx
2- through the coordinate covalent Ti-S bond formation. In the second part, I will discuss our work on in-situ infrared spectroelectrochemistry to understand redox mechanisms – a critical step for rational design of cathode systems for Li-S batteries. Specifically, I will discuss the use of sulfur-rich copolymers as active cathode materials and demonstrate in-situ FTIR with attenuated total reflection (ATR) to monitor polysulfide (PS) speciation (S
x

2-, 2 ≤ x ≤ 8) and polymeric signature evolution while simultaneously discharging/charging a full battery coin cell.
Onion Peel Based Porous Carbons As Cathode Components for Lis Battery
Authors: Arie Arenst Andreas , Susanti Ratna Frida , Kristianto Hans , Lee Joong Kee
Published: May 2020

In recent years, Lithium-sulfur (LiS) battery has emerged as promising energy storage systems to replace the conventional lithium ion battery. This battery system uses elemental sulfur as cathodes and Li metal as anodes and possess a higher specific capacity (1675 mAh/g) compared to that of lithium ion battery. However, some technical problems such as the low conductivity of sulfur, huge volume expansion during cycling and the shuttle effect of polysulfide have prevented this kind of battery system to be commercialized. One method to solve those problems is by using carbon materials as cathode component together with sulfur to form Carbon-sulfur composite cathodes. Carbon materials could improve the electrochemical performance of LiS battery due to the electrical conductivity and highly porous structure. Biomass derived conductive carbon materials have attracted increasing attention on account of their abundance, sustainability, and easy accessibility. Here, onion peel waste has been utilized to synthesize amorphous porous carbon (OPC) as cathode component for LiS battery. Porous carbons were prepared by using hydrothermal carbonization followed by the chemical activation process using KOH. The carbon-sulfur composites were then obtained after sulfur loading using the melt diffusion method. As obtained OPC/S composite demonstrates stable coulombic efficiencies of 98% and a reversible specific capacity of 432 mAh/g after 100 cycles at current density of 0.1 C when used for LiS battery. These improved electrochemical performances may be attributed to the structure of OPC showing mesoporous structure with defect carbon structure and high specific surface areas. These results show the potential and promising application of onion peel waste based porous carbon in LiS battery.
Conditioning-Free MgCl2/AlCl3 Electrolyte for Magnesium Batteries By Chemical Formation of Solvated Chloride
Authors: Kim Seong Shik (Steve) , Bevilacqua Sarah , See Kimberly A
Published: May 2020

Mg metal is a promising alternative anode material that offers higher theoretical specific capacity than conventional Li-ion batteries (LIBs), and the high natural abundance of Mg makes it more economically appealing than other post-LIB anode materials. The greater energy density hinges on a Mg-metal anode, and reversible Mg electrodeposition and stripping require an effective Mg electrolyte. Various electrolyte systems that support reversible have been introduced, but many of them contain drawbacks, such as narrow electrochemical window, reactivity with electrode materials, or poor Coulombic efficiency. In addition, challenges remain in understanding the relationship between electrochemistry at the Mg anode and the electrolyte composition due to the complicated interface of Mg metal and the electrolyte.

To probe the effect of the interface on Mg electrodeposition, an electrolyte with a known solution phase composition, the magnesium aluminum chloride complex (MACC) electrolyte, is explored. The MACC electrolyte undergoes electrolytic conditioning to support reversible Mg electrodeposition and stripping. During conditioning, free Cl- is released electrolytically while Al3+ is irreversibly deposited, and the concentration of the active species [Mg2(µ−Cl)3·6(THF)]+ increases, activating the MACC electrolyte.

Here, we show that a small concentration of Mg(HMDS)2 to the MACC electrolyte suppresses Al3+ deposition and promotes reversible Mg electrodeposition and stripping on the first cycle. Such a drastic change from a small concentration suggests that changes are localized at the electrode-electrolyte interface. We show spectroscopically that Mg(HMDS)2 scavenges trace water in the solution. Spectroscopic results also suggest that Mg(HMDS)2 reacts with AlCl4
- in the MACC electrolyte to form free Cl-. Based on the spectroscopic and electrochemical results, we suggest that the formation of Cl- is the primary cause for improved behavior on cycle one, highlighting the role of Cl- in Mg deposition and stripping.
(Invited) Layered and Spinel Hosts for Li, Na, K and Mg-Ion Batteries
Authors: Van der Ven Anton , Kaufman Jonas , Kolli Sanjeev Krishna , Vinckeviciute Julija
Published: May 2020

Layered and spinel intercalation compounds have proven to be excellent electrode materials for Li-ion batteries. They are also promising electrode materials for Na, K and Mg-ion batteries. The electrochemical properties of an intercalation compound are very sensitive to the host crystal structure and guest cation chemistry. A systematic first-principles study of the electrochemical properties of layered and spinel forms of AxMO2 and AxMS2 was performed where A = Li, Na, K, Mg and where M are different transition metals. Differences in predicted voltage profiles and transport behavior emerge due to variations in guest ion radius and the degree of ionic bonding within the host. Statistical mechanics studies predict that phase stability, ordering tendencies and diffusion mechanisms change dramatically when varying the guest cation. In contrast to Li and Mg, the intercalation of the larger Na and K cations in layered compounds induces numerous stacking sequence phase transformations and results in complex ordering patterns. Variations in composition in layered intercalation compounds containing Na and K are realized by maintaining well-ordered domains that are interrupted by anti-phase boundaries. These ordering patterns have important consequences for diffusion mechanisms. Kinetic Monte Carlo simulations of diffusion show that the topology of the host structure plays an important role in affecting correlated diffusion, which usually leads to significant drops in diffusion coefficients.
Theory of Coupled Ion-Electron Transfer Kinetics in Ion Intercalation Materials
Authors: Fraggedakis Dimitrios , Zhang Yirui , Bazant Martin Z. , Shao-Horn Yang
Published: May 2020

Intercalation materials are commonly used in energy storage applications and more specifically in Li-ion batteries. At every cycle, Li ions are transferred between the anode and cathode of the battery. The intercalation process involves the transfer of solvated Li ions in the intercalation matrix and the electrochemical reduction of the reaction site. Until recently, electrochemical ion intercalation has been described using the phenomenological Butler-Volmer (BV) equation. However, there have been cases where its predictions deviate from the experimentally observed rates. In this work, we consider a novel theoretical approach, where we describe the intercalation process with coupled ion-electron transfer kinetics. More specifically, the classical picture of Marcus electron transfer is generalized to describe the ion insertion kinetics in solids. This coupling leads to ion concentration dependencies on the activation barrier of ion intercalation. We validate our theoretical prediction against Tafel plot measurements on Li intercalation in layered oxides (LiCoO2, NCM111), and also on rate capability measurements for several intercalation materials used in Li-ion batteries. This work opens the way to better understand and engineer the interfacial kinetics in energy storage applications.
(Invited) Kerr Gated Raman Spectroscopy to Investigate Aging Processes on Lithium-Ion Electrode Interfaces
Authors: Hardwick Laurence J. , Cabo-Fernandez Laura , Neale Alex Ryan , Braga Filipe , Kostecki Robert , Sazanovich Igor
Published: May 2020

Aging mechanisms have a great impact into batteries calendar life and performance. A better understanding of these complex processes is critical to improve the lifetime of the battery. Electrolyte aging plays a key role in the decrease of capacity since insoluble species and gas by-products are formed during the electrochemical cycling of the battery. Fluorescent species are formed during cycling of lithium ion batteries as a result of electrolyte decomposition due to the instability of the non-aqueous electrolytes and side reactions that occur at the electrode surface. The increase in the background fluorescence due to the presence of these components makes it harder to analyze data due to the spectroscopic overlap of Raman scattering and fluorescence. Herein we will demonstrate Kerr gated Raman spectroscopy as an effective technique for the isolation of the scattering effect from the fluorescence enabling the collection of the Raman spectra of LiPF6 salt and LiPF6-based organic carbonate electrolyte, without the interference of the fluorescence component. A comparison will be made with FT-Raman using a Laser excitation at 1064 nm, where we show that it is possible to obtain Raman spectra of Li-ion battery relevant materials above a diminished fluorescence background, but with a much lower sensitivity compared to using Kerr Gated Raman with an excitation at 400 nm. Kerr gated Raman was able to identify POF3 on the LiPF6 particle surface [1], after the addition of trace water and the degradation of graphitic carbon electrodes with respect to number of cycles.

[1] L. Cabo-Fernandez, A.R. Neale, F. Braga, I.V. Sazanovich, R. Kostecki, L.J. Hardwick,
Phys. Chem. Chem. Phys
.
, 2019,21, 23833-23842

Figure 1
Microstructural Analysis of Lithium-Ion Battery Cathodes Using Tomography Methods - Possibilities and Limitations
Authors: Joos Jochen , Kelly Steve T , Volkenandt Tobias , Freitag Stefanie , Weber André , Ivers-Tiffée Ellen
Published: May 2020

A deep knowledge of the 3D microstructure is essential for optimizing performance in Lithium ion battery electrodes. Tomography methods like focused ion beam-secondary electron microscopy (FIB-SEM) and X-ray tomography are the most frequently used 3D characterization techniques for battery electrodes. While each method has advantages and disadvantages, understanding the complex morphology of electrodes requires a complementary, multi-scale 3D approach.

In this work, the possibilities and limitations for both 3D techniques, X-ray and FIB-SEM tomography, are studied using the example of a LiNiCoAlO2-LiCoO2 blend cathode from a commercial cell. The same cathode sample was analyzed with both techniques and moreover with different devices to enable a comparison of the obtained data quality. The material fractions, porosity, surface area and tortuosity are calculated from the different data sets and the results are compared with special emphasis on the differentiation of the different active materials and the carbon-binder phase. The reliable determination of these parameters is essential because they are needed, for example, to compare different electrode structures or to study the influence of the microstructure on the electrode performance to optimize the electrode structure.

Figure 1
Corelative Imaging of Battery Heterogeneities: Ionic Transport, Electronic Structure and Chemistry
Authors: Zhou Jigang
Published: May 2020

Deeper understanding of the heterogeneities, an intrinsic characteristic in batteries, including ionic transport, and chemical and electronic structures at interface and bulk of active materials and its dependence on other components in a battery is crucial for developing better performance batteries, especially for electric transportation purposes. Element specific X-ray absorption near-edge structures (XANES) spectroscopy, explores detailed information on the local chemistry and electronic states of the absorbing atom which makes it an excellent tool to understand chemical bonding, electronic structure, and surface and bulk chemistry difference in batteries. XANES with nano-focused X-ray beam (STXM) and surface sensitive field-imaging X-PEEM can collect chemical imaging of high chemical sensitivity with good spatial resolutions. In this talk I will show nanoscale chemical imaging studies of battery materials by STXM and X-PEEM at CLS. The emphasis is imaging inhomogeneity under “normal” or abusive conditions in a commercial like electrode with preserved interface structure. The studies show that the battery heterogeneity is an interplay of local environment, morphology and facet orientation of electrode active materials. Such novel characterization tools shall lead new insights on battery engineering toward a better battery with high performance, long service life and high safety.
(Invited) Power Performance of Lithium-Ion Batteries.
Authors: Schougaard Steen Brian
Published: May 2020

“We need more power Scotty!”. In STAR TREK as in lithium-ion batteries for transportation, power, is a major issue. The battery size in electric vehicles is generally increasing while it is clear that for most consumers, most of the time, the extra capacity will sit idle. This extra capacity, entails higher cost, higher energy consumption and higher environmental impact. Yet, consumers request longer driving autonomy, most likely since charging is still a comparably slow process. Thus, we need faster charging which translate into improved power performance.

A strong tool to analyse and optimize power performance is numerical modeling. However, modeling requires a series of input geometric and materials parameters, some of which until now have been very difficult to obtain reliably. In this talk we will cover our recent advances to measuring these parameters and how these may help improve optimization of power performance. Specifically, in situtechniques based on scanning probes and synchrotron X-rays, as well as new battery chemistries will be discussed.
(Invited) Novel Fluoride Batteries, Fluoride Shuttle Batteries, and Their Positive Electrodes
Authors: Ogumi Zempachi , Abe Takeshi
Published: May 2020

Progress of battery technology has opened new applications, which requires development of batteries of high performances, especially high energy density. There are two directions to improve the energy densities, i.e., enhancing cell voltage and increasing capacity of active materials. High cell voltage meets, however, the difficulty of stability of electrolyte.

Batteries based on rocking-chair type reactions are limited in their capacity due to requirement of host lattice. On the other hand, conversion type active materials including traditional dissolution-deposition type ones can give higher capacity by using multi electron reactions. Anion mediating system may be able to be operated various metal electrodes using the common charge carrier. Among anion mediating systems, fluoride mediating systems, fluoride shuttle batteries (FSBs), give high capacity because metal fluoride is generally low formal weight.

The authors’ group has focused on developing FSBs based on reactions of metal fluoride and metal, MFm/M. Metal fluoride are usually insulator, while some metal fluorides show ionic conductivity for F-. In this talk BiF3 and CuF2 are focused as positive active material. Electrolyte is a key material for activation of MFm/M electrodes. Solid electrolyte, liquid electrolyte including IL, and polymer electrolyte have been examined.

Addition of anion acceptors to organic electrolyte enhances charge and discharge performances of BiF3/Bi electrode. The selection of adding anion acceptors is critical for each MFm/M electrode. The addition of anion acceptor, fluorobis(2,4,6-trimethylphenyl)borane, in tetragryme-CsF electrolyte increases remarkably the capacity and cyclability of BiF3/Bi electrode1). Copper fluoride is known as a typical insulator and when Cu electrode is oxidized to CuF2 only the skin-layer of Cu metal, ca. 6 nm, is oxidized to CuF2 and is passivated using lanthanum fluoride solid electrolyte operated at 140 oC. The addition of BaF2 to CuF2 powder activates CuF2/Cu electrode2).

Konishi, T. Minato, T. Abe, Z. Ogumi, J. Electrochem. Soc., 2017 161, A3702.

Morita, T. Abe, Z. Ogumi, et al., in preparation
Electrochemical Behavior and Structural Change of Spinel-LiMn2-XNixO4 (x = 0, 0.5) Cathode in Potassium Cells
Authors: Baddour-Hadjean Rita , Bhatia Ankush , Emery Nicolas , Laïk Barbara , Pereira-Ramos Jean-Pierre
Published: May 2020

On the recent research front for the next generation secondary batteries beyond Li, potassium insertion into graphite in non-aqueous cells has brought new insights into the electrochemical K+ intercalation behavior and introduced advantageous benefits from potassium. Since potassium resources are much abundant and the standard potential of K+/K is 0.13 V below that of Li+/Li, potassium-ion batteries can be regarded as an appealing alternative to LIBs to realize high voltage systems with low cost. The crucial issue is the development of cathode materials able to accommodate the large K-ion without displaying detrimental structural changes toward cycle life and rate capability performance. The 4.7 V LiMn1.5Ni0.5O4 spinel is already a promising cathode for the next generation of high voltage LIBs, and its host structure, λ-Mn0.75Ni0.25O2, could be of great interest for K-ion batteries.

Here, we investigate for the first time the potassium insertion properties into electrochemically prepared λ-MnO2 (λ-MO) and λ-Mn0.75Ni0.25O2 (λ-MNO) spinels. Lithium ions in LiMn2O4 and LiMn1.5Ni0.5O4 samples are electrochemically extracted in lithium containing electrolyte solution, forming λ-Mn1- xNixO2 (x = 0, 0.25) by first oxidation process. Potassium ions are then inserted into the lithium extracted spinel phases. From structural analysis by X-ray diffraction and Raman spectroscopy, it is found that the original λ-Mn0.75Ni0.25O2 spinel phase converts into a layered phase, K~0.5Mn0.75Ni0.25O2. Then, K~0.5Mn0.75Ni0.25O2 can deliver a high reversible capacity of 90 mAh g-1 at C/20 in the 2 V- 4.6 V vs K+/K voltage range with 78% retention for 60 cycles at C/20 (Fig. 1). Promising rate performance are also evidenced with an initial capacity of 60 mAh g-1 at C/5 (Fig. 1), and 65% retention after 300 cycles at C/5. The origin of the attractive electrochemical performances of λ-MNO is investigated by XRD , Raman and EDS experiments after discharge and charge cycles. These results open the possibility of using inexpensive and high-capacity Mn-based active materials for potassium-ion batteries.

Figure 1. Electrochemical properties of λ-Mn0.75Ni0.25O2 in a potassium cell. 1M KF6 /EC:PC 1:1 electrolyte, 2% vol. FEC. Voltage window 4.5 V- 2 V.

Figure 1
Chemical Bonding Effect on Crystallinity and Electrochemical Properties in Germanium Selenide/Nano-Carbon Composite As an Anode Materials for Potassium Ion Batteries
Authors: Lee Geon-Woo , Park Byung-Hoon , Kim Young-Hwan , Kim Kwang-Bum
Published: May 2020

Recently, as a promising alternatives to lithium ion batteries (LIBs), sodium-ion batteries (NIBs) and potassium-ion batteries (KIBs) have received considerable attention due to the abundance and low cost of sodium and potassium compared to those of lithium resources.

Recently, similar to graphite, layered metal chalcogenide compounds (LMCs) have been received significant attention as promising anode materials for KIBs, because of their large interlayer space for potassium ion intercalation and also narrow-bandgap semiconductor characteristic.

Germanium selenide (GeSe), one of the LMCs family, shows similar crystal structure to that of graphite lamellar with neighboring layers stacked together via weak van der Waals interlayer interactions along the one axis. The interlayer distance of GeSe (5.41 Å) is large that enables the convenient diffusion of alkali metals with large size without significant structural distortion. The potential multielectron transfer per formula unit is one of the main advantages of GeSe, which is beneficial for exceptionally high energy density in chemical energy storage. However, to the best of our knowledge, the layered GeSe applied as KIBs anode materials and its charge storage mechanism remain unexplored.

Unfortunately, LMCs family materials undergo a large volume expansion after the insertion of large-sized K+ ion which causes active material pulverization, electrical contact loss, and the formation of unstable solid electrolyte interfaces (SEIs), ultimately resulting in drastic capacity fading. Designing composites with carbon is one of the effective strategies to improve the electrochemical performances of LMCs.

However, their packing density is relatively low (0.58~0.83 g cm-3) due to the surplus inner void space, leading to low volumetric energy and power densities of batteries. To satisfy the demand for maximizing the energy density in limited loading spaces, volumetric energy density is becoming a more crucial factor for future KIBs applications than the gravimetric counterpart. In addition, the large surface area of nanomaterials will give rise to severe side reactions and poor thermal stability between electrode and electrolyte interfaces, thus leading to unfavorable cycle reversibility and safety hazard.

Herein, we for the first-time report GeSe/nano-carbon composite with a high tap-density as a novel anode material for KIBs. And the effect of chemical bonding induced by various ball-milling condition and CNT amounts on the crystal structure and carbon structure, so that we can figure out the effect of chemical bonding effect on the electrochemical properties of GeSe/nano-carbon composite. GeSe/nano-carbon composite showed reversible charge/discharge profiles with ~400 mA h g−1 at 0.05 A g−1 from the second cycle on. Further results will be presented in the conference.
Electrochemomechanical Properties of Red Phosphorus with Lithium, Sodium and Potassium
Authors: Capone Isaac , Pasta Mauro
Published: May 2020

Red phosphorus is a promising anode material thanks to its ability to form alloys with lithium, sodium and potassium, thus achieving high theoretical capacity (2596 mAh g-1 with Li and Na and 865 mAh g-1 with K). However, it suffers from its low electronic conductivity and a huge volume expansion that leads to the formation of stress with consequent fracture and pulverization of the particle. In this work, red phosphorus particles have been analyzed with in-situ TEM techniques in order to study the mechanism of the crack formation during the volume expansion with lithium, sodium and potassium. This experiment is coupled with computational modelling of the particles and the simulation of the diffusion of the ions through the particles to understand the development of stresses that can lead to the nucleation of the crack and the failure of the particle.
Molecular-Scale Understanding of Charge Storage Mechanisms in Positive Electrode Materials for Rechargeable Aluminum Metal Batteries
Authors: Messinger Robert J. , Jadhav Ankur L. , Gordon Leo W. , Xu Jeffrey H. , Turney Damon E. , Jay Rahul
Published: May 2020

Rechargeable aluminum metal batteries are an emerging energy storage technology with great promise: aluminum has among the highest capacities of common metal electrodes and is low cost, earth abundant, environmentally friendly, and inherently safe. Despite these opportunities, their technological development has been hindered due to fundamental challenges associated with aluminum electrochemistry. Few electrolytes enable the reversible electrodeposition of aluminum metal at room temperature, while few positive electrode materials have been demonstrated that exhibit high energy density and cycle life in those electrolytes. Here, recent progress will be discussed in the development and characterization of positive electrode materials for rechargeable aluminum metal batteries, including graphites, organic materials, sulfur, and crystalline transition metal compounds. Molecular-scale understanding of their charge storage mechanisms will be elucidated, revealed by a combination of electrochemical, spectroscopic, diffraction, imaging, and theoretical methods, such as multi-dimensional solid-state nuclear magnetic resonance (NMR) spectroscopy, in operando X-ray diffraction (XRD), electron microscopy, and density functional theory (DFT). The diversity of electrochemical charge storage mechanisms possible for aluminum battery chemistries will be highlighted. Overall, the results are aimed at developing next-generation rechargeable aluminum metal batteries for diverse energy storage applications.
(Invited) Heterogeneous Electronics Packaging Innovations Based on Silicon Technology
Authors: Iyer Subramanian S
Published: May 2020

Electronics Packaging refers to the electrical interconnection of heterogeneous dies using a hierarchy of packaging constructs. Today’s packaging is based on organic substrates called FR4 – glass reinforced epoxy laminate material with coarse pitches and solder-based connections. which have not shrunk over the last several decades. More recently however, packaging is undergoing materials and integration innovations that promise to usher in an era of package and board level scaling. These borrow extensively from silicon technology. We will address two such approaches: The Silicon Interconnect Fabric (Si IF), where we attempt to replace the PCB with a Silicon wafer that has fine wires and directly connects to heterogeneous dielets using solderless thermal compression bonding, to build large heterogeneous Systems on Wafers; and Flextratetm, a PDMS based flexible biocompatible substrate, that uses a fan-out wafer level processing approach to similar things. The talk will address the materials and processing challenges of these approaches.
Non-Polar Selector Operation Brought about By Coo/ITO Double Layer Structures
Authors: Kinoshita Kentaro , Saitoh Syuuhei
Published: May 2020

As memory devices get more and more highly integrated, the development of selectors that enables 3D crossbar structures is required, to suppress the current leakage called ’sneak path current’ that flows through unselected cells and half-selected cells. In this paper, we investigated a p-type semiconductor of CoO deposited on tin-doped indium oxide (ITO). We confirmed that non-polar, volatile, and very fast threshold resistance switching with a small dispersion of threshold voltage.
Interferometric Optical Isolator with Si Guiding Layer Operated in Unidirectional Magnetic Field
Authors: Yokoi Hideki , Yumoto Atsushi , Hasegawa Hiroyujki , Matsuzaki Shingo
Published: May 2020

INTRODUCTION

In optical communication systems, an optical isolator is indispensable in protecting active photonic devices from unwanted reflected light. An optical isolator with a Si guiding layer is a significant device for silicon photonic integrated circuits. In this paper, the authors report on an interferometric optical isolator with a Si guiding layer which can be operated in unidirectional magnetic field.

DEVICE STRUCTURE

Figure 1 shows an interferometric optical isolator with a Si guiding layer employing a nonreciprocal phase shift [1]. The nonreciprocal phase shift occurs in transverse-magnetic (TM) modes that travel in magneto-optic waveguides in which magnetization is aligned transverse to the light propagation direction in the film plane. The optical isolator employing the nonreciprocal phase shift is attractive because the device utilizes TM modes only so that there is no need for phase matching. The optical isolator includes an optical interferometer that consists of two coupling devices, a nonreciprocal phase shifter and a reciprocal phase shifter. In Fig. 1, one arm in the optical interferometer has a magnetic garnet cladding layer. When the interferometer has distinct layer structures, the optical isolator can be operated in a unidirectional magnetic field.

The optical isolator employing the nonreciprocal phase shift was designed at 1.55 μm. The nonreciprocal phase shifts in the magneto-optic waveguides with a magnetic-garnet/Si/SiO2 structure were calculated. The multimode interference (MMI) coupler and the reciprocal phase shifter were also designed. As a preliminary experiment, deposition of the magnetic garnet crystals were investigated on various substrates.

ACKNOWLEDGMENT

This work was partially supported by the SIT Research Center for Green Innovation.

REFERENCES

1. H. Yokoi, T. Mizumoto and Y. Shoji, Appl. Opt., 42, 6605 (2003).

Figure 1
(Invited) Binary Stochastic Neurons and Compound Synapses from Nano-Magnets
Authors: Appenzeller Joerg
Published: May 2020

In this presentation I will introduce the nCORE center CAPSL’s activities towards a probabilistic spin logic for Boolean and Non-Boolean computing. While magnetic materials in storage devices are part of our electronic world since many decades and are explored more recently by the semiconductor industry for memory applications such as Spin-transfer torque magnetic random-access memory (STT-RAM), spin based devices for logic applications are still in their infancies. Mimicking a CMOS type logic with magnets requires a “Write” and a “Read” unit as well as proper input/output isolation. Based on this, a device concept in which charge-to-spin conversion occurs through the Giant Spin Hall Effect (GSHE) [1], dipolar coupling mediates the information transfer from a magnet in the Write unit to another one in the Read unit, and a magnetic tunnel junction (MTJ) is used as the Read unit was proposed in 2012 under the name charge spin logic (CSL) [2]. Next, I will explain in how far the use of low-barrier magnets cannot only help to reduce power consumption of CSL devices but introduces a conceptually new way of computing through the introduction of “tunable randomness”. This idea, that is also known as probabilistic spin logic (PSL), was introduced in 2017 [3] and uses a counterintuitive aspect of magnets, namely their capability of creating a truly random magnetic signal if low-barrier circular nano-magnets are used. In particular, I will connect PSL with activities in the realm of quantum computing as well as neural networks.

[1] L. Liu, C.-F. Pai, Y. Li, H. W. Tseng, D. C. Ralph, and R. a. Buhrman, Science 336, 555 (2012).

[2] S. Datta, S. Salahuddin, and B. Behin-Aein, Applied Physics Letters 101, 252411 (2012).

[3] K. Y. Camsari, R. Faria, B. Sutton and S. Datta. Physical Review X 7, 031014 (2017).
Improved Electrochemical Performance of Al2O3 and ZrO2 Coated LiNi0.6Mn0.2Co0.2O2 Cathodes By Atomic Layer Deposition
Authors: Wang Xin , Liu Yongqiang , Li Jianlin , Meng Xiangbo
Published: May 2020

There has been an increasing demand on high-energy and low-cost lithium-ion batteries (LIBs) in order to power future transportation. In this context, LiNi1-x-yMnxCoyO2 (NMC) cathodes are particularly attractive, due to their higher capacity and lower cost compared to the traditional LiCoO2 cathodes [1]. Among the NMC cathodes, LiNi0.6Co0.2Mn0.2O2 (NMC622) is one of the most promising cathode materials undergoing extensive investigations, but it still suffers from a series of technical issues, such as dissolution of transition metal elements, and structural instability [2]. Aimed at addressing these issues, we recently applied Al2O3 and ZrO2 coatings on NMC622 using atomic layer deposition (ALD). We coated the composite electrode directly and it revealed that the ALD Al2O3 and ZrO2 coatings can improve the cyclability and sustainable capacity of the NMC622 cathodes at different cutoff voltages. In the study, we investigated the effects of ALD Al2O3 and ZrO2 coatings using X-ray diffraction, X-ray photoelectron spectroscopy, impedance spectroscopy, scanning electron microscopy, and transmission electron microscopy. Our study demonstrated that ALD remains an important tool to tackle technical issues in LIBs [3].

1. Manthiram, A., B. Song, and W. Li, A perspective on nickel-rich layered oxide cathodes for lithium-ion batteries. Energy Storage Materials, 2017. 6: p. 125-139.

2. Hou, P., et al., Surface/Interfacial Structure and Chemistry of High-Energy Nickel-Rich Layered Oxide Cathodes: Advances and Perspectives. Small, 2017. 13(45): p. 1701802.

3. Meng, X., X.-Q. Yang, and X. Sun, Emerging applications of atomic layer deposition for lithium-ion battery studies. Advanced Materials, 2012. 24(27): p. 3589-3615.
A Novel Multi-Functional Electrolyte Additive for Ni-Rich Cathode Materials
Authors: Pham Hieu Quang , Trabesinger Sigita
Published: May 2020

Ni-rich layer oxides Li[Ni
x
CoyMn1−x−y
]O2 (x ≥ 0.8, NCMs) are promising advanced cathode materials for high-energy Li-ion batteries because of their high specific capacity (≥ 200 mAh g−1) with an average discharge voltage of 3.8 V vs Li+/Li, as compared to the commercialized cathode materials (e.g. LiCoO2, LiFePO4).1 However, the instability of cathode–electrolyte interface causes the structural degradation of cathode active material and the electrolyte consumption, as well as gas evolution due to oxidative decomposition of electrolyte, resulting in a rapid capacity fading.2

Thus, improvement in the stability of cathode–electrolyte interphase is a key requirement to inhibit their structural degradation and enhance their electrochemical properties. The formation of a protective surface film via electrolyte additives is considered a cost-effective and reliable way to improve the cathode–electrolyte interfacial stability, as the stable surface film, uniformly distributed over the entire cathode surface, would prevent direct contact of oxide with the electrolyte, still allowing Li+ transport between the cathode and electrolyte.3 In this work, we report the high-performance NCM cathode through interfacial stabilization using a novel electrolyte additive. The details of surface film stability and formation mechanism, and their relation to gas evolution as well as cycling performance would be discussed.

References:

1 S.-T. Myung, F. Maglia, K.-J. Park, C. S. Yoon, P. Lamp, S.-J. Kim, Y.-K. Sun, ACS Energy Lett. 2017, 2, 196

2 H. Q. Pham, E.-H. Hwang, Y.-G. Kwon, S.-W. Song, Chem. Commun., 2019, 55, 1256

3 K. Kim, Y. Kim, S. Parka, H. J. Yang, S. J. Park, K. Shin, J.-Je Woo, S. Kim, S. Y. Hong, N.-S. Choi, J. Power Sources 2018, 396, 276.
(Invited) Some Progress in Understanding the Chemical and Charge Distribution in Layered Oxides
Authors: Xu Zhengrui , Yang Zhijie , Rahman Muhammad Mominur , Mu Linqin , Lin Feng
Published: May 2020

Layered oxides have dominated the development of cathode materials for lithium and sodium ion batteries. To date, most studies of layered oxides have focused on controlling the global structural and chemical properties rather than improving the local chemical and charge distribution. We believe that there is a large space to improve the performance of these decades-old cathode materials from a different perspective. Can we improve the utility of battery particles throughout the electrode? Can we improve the %utilization of individual battery particles? Answering these questions lead us to investigate battery materials with particle specificity. In this presentation, we will discuss our recent progress in (1) controlling the chemical distribution in primary and secondary particles, and (2) probing the charge distribution with sensitivity to the grain crystallographic orientation in polycrystalline layered oxides. For the first one, we will highlight that tailoring the dopant distribution in Co-free Li layered cathodes can maximize the functions of individual doping elements, improving the bulk and surface stability. In addition, we will discuss how engineering the distribution of transition metals in secondary particles may provide some unexpected performance outcomes. For the second one, we will elucidate the spatially resolved charge distribution in lithium layered oxides with different grain crystallographic arrangements and establish a model to quantify their charge distributions. We will highlight that the crystallographic orientation-guided redox reaction governs the charge distribution in the local charged nanodomains.
Organic Cathode Based on Quinone-Sulfide Polymer for Both Li and Mg Batteries
Authors: Tran Ngoc Anh , Leprêtre Jean-Claude , Berthelot Romain , Alloin Fannie
Published: May 2020

The undeniable benefit of lithium-ion (LIB) batteries for the development of a more environmentally friendly economy was recognized by the 2019 Nobel Prize in Chemistry. However, relying only on LIBs to energy storage will put considerable strain on lithium and cobalt resources used in these batteries. Therefore, alternative battery technologies other than LIBs are desirable to satisfy our growing demand for energy. Magnesium-ion batteries offer many distinct advantages over LIBs, including the high earth-abundance of magnesium, its high energy density and reversible dendrite-free Mg deposition1. In parallel, organic materials are receiving an increasing amount of attention as electrode materials for future post lithium-ion batteries due to their versatility and sustainability2. In order to propose organic cathode with both high potential and specific capacity, new polymer based on hydroquinone sulfide, poly(benzoquinone disulfide) (PBQDS), were prepared in view to be applied in both lithium and magnesium batteries. Diglyme and sulfolane solvents associated with both LiTFSI (lithium bistrifluomethane sulfonimide) and Mg(TFSI)2 salts were selected, as electrolytes, in order to evaluate the potentiality of the active material3. First of all, the electrochemical responses of PBQDS in lithium and magnesium based electrolytes was performed in a cavity micro-electrode. Whereas in both case the cyclic voltammetry exhibit a close to reversible redox stem (Fig. 1a), The electrochemical characteristics of the material are very similar in term of potential and ΔEpeak in both lithium and magnesium systems at a relative high scan rate i.e. 1 mV s-1. An improvement of the redox couple reversibility seems to be observed in Mg form, with a ΔEpeak= 400 mV at E° of 0.3 V vs Fc+/Fc (3.5 vs Li+/Li). Given this interesting behavior, PBQDS in a coin cell configuration using glyme + LiTFSI electrolyte, was analyzed. . A stable capacity of 160 mAh g-1 was obtained at C/10 after 70 cycles, whereas a value of 120 mAh g-1 was maintained at C rate (Fig. 1b). In order to improve, the electrochemical performances, especially at high C-rate, the impact of the particle sizes (controlled grinding) of the cathodic material is in progress in view to approach its theoretical capacity value. In addition, the electrochemical investigations in both Mg and Li based electrolytes will be presented in regard to the electrolyte nature and the PBQDS morphology.

1. H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour, D. Aurbach, Energy Environ. Sci., 2013, 6, 2265–2279.

2. P. Poizot, F. Dolhem, Energy Environ. Sci., 2011, 4, 2003

3. H. Dong, Y. Liang, O. Tutusaus, R. Mohtadi, Y. Zhang, F. Hao, Y. Yao, Joule 2019, 3, 1–12

Figure 1
Preparation and Electrochemical Studies of Metal Fluorides for Lithium Batteries
Authors: VenkatashamyReddy MogalahalliVenkatesh , Abdulrahman Shahul Hameed , Karim Zaghib
Published: May 2020

Conventional positive (cathodes) electrode materials for lithium batteries, use mixed-conducting lithium containing transition metal oxides, metal phosphates etc. which are able to store both lithium and electrons by changing their oxidation state. In this presentation, we discuss the facile synthesis of materials suitable for alternative electrode concepts including Transition metal fluorides MF2 (M=Fe, Mn, Zn) were obtained by reacting Fe, Mn, Zn-Metal salts with fumaric acid as a one-dimensional metal organic framework, and a polymer (PVDF) as Fluorine source, final products are obtained by heating at 600°C, 6h in Ar gas. The MOF were initially prepared by a simple chimie douce method. Incorporation of the MOF with a fluorinated polymer and the eventual decomposition lead to carbon coated metal fluoride nanoparticles of high surface area of >200 m2/g for FeF2. The obtained materials will be characterized in detail by X-ray diffraction, Scanning and Transmission electron microscope (SEM/TEM) are used to evaluate the structure and morphology, X-ray photoelectron spectroscopy are used understand structure, vibrational bands and oxidation state of the materials and BET surface area method. Electrochemical studies were carried out in the voltage, range 4 to 1.0 vs. Li, at current rate of 50 mA/g (0.1 C) using 1MLiPF6 (EC;DEC) as liquid electrolyte and tested with Li-metal as a counter and reference electrodes. The cyclic voltammetry at scan rate of 0.075 mV/sec at room temperature (24°C). Galvanostatic cycling of FeF2 demonstrates that the material exhibit stable and good reversible capacity of 580 mAh/g during the first cycle and slight capacity fading has been observed after 20 cycles. Further studies on rate performance is being carried up to 2.5 C rate. Whereas MnF2 and ZnF2 showed reversible capacity of 220 and 200 mAh/g and retained a capacity around 100 mAh/g after 20 cycles and showed lower capacity than FeF2. Discuss the structural, reaction mechanism of FeF2 during charge-discharge cycling by in situ/operando X-ray diffraction and electrochemical impedance spectroscopy studies discuss in detail.

Keywords: Metal fluorides (MF2 M=Fe, Zn, Mn); Electrochemical properties; Insitu studies; Electrochemical impedance spectroscopy; energy storage
Carbon Nanosphere-Encapsulated LiNi0.8Co0.15Al0.05O2 Cathode By Solvent-Free Mechanofusion Process for High Stable 18650 Lithium-Ion Batteries
Authors: Wutthiprom Wutthiprom , Phattharasupakun Nutthaphon , Sawangphruk Montree
Published: May 2020

LiNi0.8Co0.15Al0.05O2 namely NCA is one of the most promising Nickel-rich cathode materials since Panasonic and Tesla have been utilizing it in the electric vehicles (EVs) due to its high energy density (up to ~250 Wh kg-1). However, the unsolved problems of using NCA still hinder its electrochemical performance including (i) the severe capacity fading during cycling owing to side reactions of Ni4+ and carbonate-based electrolyte, (ii) low thermal stability, (iii) poor ionic conductivity, and (iv) microcracks at grain boundaries after long testing. Herein, NCA particles were mechanically encapsulated with nanosized-carbon black spheres (20-50 nm) as the core-shell structure (NCA@C) via a solvent-free mechanofusion process. In order to access the highest utilization of NCA@C, it was prepared as the cathode for cylindrical 18650 batteries coupled with commercial graphite anode. The embedded carbon nanospheres on the NCA surface can act as the buffer layers protecting the direct contact with electrolyte inhibiting the microcrack generation improving the long-term stability. The cell electrochemical performances were investigated using CCCV charge-CV discharge at 0.1C and followed by a long-term stability at 1.0C. The ex situ FE-SEM and EDX mapping after the charge-discharge and cycling were further evaluated in order to study the comparative structural changes of NCA cathode with and without carbon protective shell. The novel core-shell of Ni-rich material produced by the scalable dry-synthesized process can be one of the alternative cathode materials providing high energy and stability for 18650 batteries which are beneficial for future EV applications.
Elucidating the Redox Mechanism of Battery Cathode Materials Made from Earth-Abundant Elements
Authors: Hirsh Hayley S , Richardson Sabrina , Tan Darren Huan Shen , Wynn Thomas Andrew , Li Yixuan , Zhang Minghao , Meng Ying Shirley
Published: May 2020

Sodium ion batteries (NIBs) are a promising technology for grid storage due to the natural abundance, low cost, and suitable redox potential (-2.71 V vs. SHE) of Na. Exploration of NIB cathode materials that include abundant and inexpensive elements, has led to the investigation of sodium iron manganese oxides. However, these materials suffer from low electrochemical reversibility during cycling, and their reaction mechanisms are unresolved, presenting an obstacle for their further optimization. In literature, three different reaction mechanisms have been reported for sodium iron manganese cathodes including 1) Fe 2+/3+, 2) Fe 3+/4+, and 3) oxygen redox. Additionally, the reported redox measurements are ex situ, which leaves uncertainty if the oxidation state of these materials changes between electrochemical cycling and redox measurement. Herein, for the first time we combine operando x-ray absorption spectroscopy (XAS) and computation method to report the redox mechanisms of P2-Na2/3FexMn1-xO2 (x=1/4, 1/3, 1/2). The redox mechanism and capacity retention of these cathode materials is found to be dependent on the Fe content. When x=1/4, 1/3 the redox mechanism is Fe 2+/3+ and Mn 3+/4+, and the material exhibits high capacity retention. When x=1/2, the redox mechanism is Fe 3+/4+ and Mn 3+/ 4+, and the material shows poor capacity retention. These results indicate that improved reversibility of sodium iron manganese oxides can be obtained by limiting the amount of the Fe 3+/4+ redox through reducing the Fe content. These results will contribute to the rational design of long lifetime cathode materials made from earth-abundant elements.

Figure 1