bluuebunny/crossref_metadata_2025 huggingface dataset:
Anodic Dissolution in Dual-Ion Batteries: Development of Protection Layers for Current Collectors
Authors: Teucher Georg , Van Gestel Tim , Uhlenbruck Sven , Guillon Olivier , Eichel Rüdiger-Albrecht , Meister Paul , Winter Martin
Published: February 2020

One aspect of the current research on lithium ion batteries is the increase of the cell voltage to improve the energy density. In innovative dual-ion cells, graphite intercalation compounds are used for both electrodes. Consequently, a simultaneous intercalation of lithium ions into the anode and the corresponding salt anions into the cathode is possible and enables voltage values above 5 V vs. Li/Li+. Established liquid electrolytes, consisting of carbonates and lithium hexafluorophosphate, do not resist these conditions. Therefore, we replace this mixture by ethyl methanesulfonate and organic lithium salts, having a good electrochemical performance also at higher temperatures. Now, it is the challenge to overcome the anodic dissolution of the aluminum current collector triggered by fluorinated anions like bis(trifluoromethylsulfonyl)imide (TFSI-). Our approach to protect the metal against anodic dissolution is the deposition of an only electronically conductive, defect-free and mechanically as well as electrochemically stable layer. We test different material compositions in the range of oxidic ceramics. First of all semiconductors like alumina doped zinc oxide show promising results to meet the requirements.  The preparation is based on a sol-gel route combined with several wet-chemical coating methods, because these are easily adjustable to different substrate dimensions. Ceramic thin layers of around 100 nm thickness are deposited on aluminum foil and mainly investigated by scanning electron microscopy, X-ray diffraction and secondary ion mass spectrometry. Additionally, we present conductivity measurements and the electrochemical performance tested with cyclic voltammetry.
Voltage Fade in Lmr-NMC Oxides Cycled below the Activation Plateau
Authors: Bareno Javier , Li Yan , Bettge Martin , Benedek Roy , Iddir Hakim , Chen Zonghai , Bloom Ira , Abraham Daniel P
Published: February 2020

A common feature of lithium-excess layered oxides, nominally of composition xLi2MnO3
•(1-x)LiMO2 (M = transition metal) is a high-voltage plateau (~4.5 V vs. Li/Li+) in their capacity-voltage profile during the first delithiation cycle.  This plateau is believed to result from activation of the Li2MnO3 component, which makes additional lithium available for electrochemical cycling.  Once activated (i.e., cycled beyond the activation plateau) the voltage v. capacity characteristic of LMR-NMC oxides is known to decrease continuously with cycling, resulting in a progressive loss of energy density.  This phenomenon is commonly referred to as voltage fade.

In this talk we show evidence of voltage fade well below the activation plateau.  We argue that this voltage fade results from a gradual accumulation of spinel environments in the crystal structure. Some of these spinel sites result from lithium deficiencies during oxide synthesis and are likely to be at the particle surfaces; other sites result from the migration of transition metal atoms in the partially-delithiated LiMO2 component into the lithium planes during electrochemical cycling.
(Invited) Electrolytes for Li-Ion Batteries Based on High Voltage Cathodes
Authors: Jow T. Richard , Delp Samuel A. , Allen Joshua L. , Allen Jan L. , Borodin Oleg , Olguin Marco
Published: February 2020

The electrolyte is a critical part of today’s Li-ion batteries. The state-of-the-art Li-ion batteries, which are made of cathodes such as 4.1 V LiCoO2 and 3.4 V LiFePO4 and graphite anode, function well in the state-of-the-art electrolytes made of LiPF6 in carbonate solvent mixtures such as EC and EMC with additive such as VC. The reason for this compatibility is attributed to the facts that the cathodes are within the stability range of the electrolytes and the ability of the electrolyte for forming a solid electrolyte interphase (SEI) layer on graphite, protecting the graphite anode from reacting with the electrolytes.

When developing higher energy density Li-ion batteries based on higher voltage cathodes such as 4.7 V LiNi0.5Mn1.5O4 (LNMO) and 4.8 V LiCoPO4 (LCP), the oxidative stability of the state-of-the-art electrolytes is in question. Furthermore, the stability of the high voltage cathodes themselves is also not certain. Efforts in improving the stability of LNMO and LCP through substitutions have yielded better performing cathodes in terms of improved capacity retention and coulombic efficiency.1, 2

The search for electrolytes that work with the high voltage cathodes has been intensive. Molecular modeling to understand the oxidative stability of Li-ion electrolytes has been active.3 This paper will review our recent efforts on electrolyte development for improving the electrochemical performance of the high voltage cathodes in Li-ion batteries.

References

A. Manthiram, Phys.Chem. Lett. 2011, 2, 176-184.

J. L. Allen, T. R. Jow, J. Wolfenstine, J. Power Sources 2011, 196, 8656.

O. Borodin, W. Behl, T. R. Jow, J. Phys. Chem. C 2013, 117, 8661-8682.
Comparative Study on Li Depletion for Li-O2 Batteries Using Carbonate and Ether Solvents
Authors: Jang Il-Chan , Ishihara Tatsumi
Published: February 2020

Recently, many researchers have interest on the Li-O2 rechargeable battery as a promising energy storage system because of its extremely large theoretical energy density. Due to its highly negative redox potential and an extremely large specific capacity, Li metal is essential for this system. However, Li metal has some drawbacks as an anode material for rechargeable batteries such as dendrite formation in charging process, surface passivation layer formation resulting in a loss of Li amount. Li loss by dendrites and SEI layers attribute depletion of energy sources, and therefore, significantly deteriorate cycleability of cells. In spite of its high importance, in previous studies, researches about Li metal are not studied in details especially in Li-O2 batteries. In this study, we investigate the Li depletion and its influence on cyclestability of cells depending on solvents including EC/DEC and TEGDME which is representative solvents in Li‒O2 batteries. Although ether based solvent is considered for good candidates as it has a fairly low vapor pressure with higher stability against oxidation, we confirmed serious dendrites with newly developed SEI layer of ROLi by XPS and ATR-FTIR analysis. This indicates increased Li depletion for TEGDME based cells and consequently influence on cycle stability.

Figure 1
Graphene Folding in Si Rich Carbon Nanofibers for Highly Stable, High Capacity Li-Ion Battery Anodes
Authors: Fei Ling , Joo Yong Lak
Published: February 2020

Silicon has received tremendous attention as lithium ion battery anode due to its high theoretical capacity) and low working potential versus Li+/Li. The major problems associated with Si are its poor conductivity and large volume change during the lithium insertion and extraction process. Previously, we prepared Si/carbon nanofibers with improved electrochemical performance of Si via environmental-friendly and cost-effective water-based electrospinning procedure [1]. In this work, we continued our effort to further improve the system. Graphene, possessing excellent mechanical property, high conductivity, and good stability, has been widely applied in the energy storage field. Herein, graphene was introduced to the Si/C nanofibers for the first time. It was found increasing graphene amount helps keep the fibers morphology after carbonization. And the fiber cross section images reveal that micrometer graphene is heavily folded into the nanometer fibers during electrospinning, while Si NPs are incorporated into the folds with nanospace inbetween. When applied as the anode material in LIBs, the composites show a high reversible capacity of ~1600 mAh g-1 at a charging rate of 100 mA/g and a stable capacity of 890 mAh g-1 at 1A/g after 50 cycles with 98% capacity retention. The interconnected graphene network not only ensures excellent conductivity, but also serves as a buffering matrix for the mechanic stress caused by volume change; the nanospace between Si NPs and graphene provides the space needed for volume expansion.

1. Y.S. Kim, K.W. Kim, D. Cho, N.S. Hansen, J. Lee, and Y.L. Joo, "Silicon-Rich Carbon Hybrid Nanofibers from Water-Based Spinning: The Synergy Between Silicon and Carbon for Li-ion Battery Anode Application", ChemElectroChem 1, 220-226 (2014).
Using X-Ray Diffraction to Map the Electrochemical Spatial Inhomogeneity within Li-Ion Batteries
Authors: Okasinski John , Abraham Daniel P
Published: February 2020

Many limitations of current lithium-ion battery technologies originate from the degradation of the battery’s active materials, with micromechanical fatigue damage playing a critical role. This microstructural damage results from mechanical strains and stresses induced by volume changes during the extraction and insertion of lithium ions.  In addition, structural changes that result from composition-induced phase changes and interfacial reactions with the electrolyte also contribute to the build-up of mechanical stresses.  The specific challenge undertaken is the characterization of the spatial inhomogeneity within the battery cell electrodes during electrochemical cycling via x-ray diffraction.

The Li1+xTM1-xO2compounds are leading candidates for the next generation of lithium batteries.  Due to constraints imposed by the complex electrode morphology, the mechanical stresses often lead to cracking within, and at the boundaries between, oxide particles.  We have conducted a systematic experimental study to determine the evolution in these oxide materials as a function of electrode cycling, position in the battery cell, and aging conditions. 

High-energy x-rays are able to penetrate through large amounts of material so that the diffraction signal probes the entire depth of the battery cells, including multiple layers of aluminum and copper current collectors and transition-metal laden electrodes.  The diffraction signal provides information on the lattice parameters for the active materials, which changes as the battery cell is cycled.  Results for a study of the spatial inhomogeneity that is present in a NMC523(+)/Graphite(-) battery with a prismatic form factor will be discussed.
Si/Mnooh Composite with Superior Lithium Storage Property
Authors: Zhan Hui , Zhong Hai , Yang Yanbo , Zhou Yunhong
Published: February 2020

High energy/power density Li-ion batteries have been pursued since the commercialization of Graphite/LiCoO2 LiBs, among all the cathode/anode combinations, LiBs with Si anode attracts more attention due to its potential high energy density. Nowadays, silicon have triggered much efforts due to the largest theoretical capacity (Li22Si5, ~4200 mAh g-1), and relatively lower electrochemical alloy/de-alloy reaction voltage (~0.4 V vs. Li/Li+). However, the repeated large volume changes during Li insertion and extraction can lead to electrode failure. The failure mechanism is believed to involve the particle pulverization, the electric contact deterioration which will finally cause the electrode disintegration and the rapid capacity fading. Recent research also prove that the solid-electrolyte interphase (SEI) degradation is another reason for the Si anode failure. A number of strategies have been implemented to suppress the volume change and enhance or maintain the electric contact between silicon and the conductive agent. Examples typically are the Si or Si/C composite with specially designed architecture, such as silicon nanowires, silicon nanorods, porous silicon and York-shell silicon/C composite, and they present the expected capacity performance and cycling stability. However, the relatively complicated multi-step synthesis and very fluffy, insufficiently compressible product powder brings the concerns on the cost and electrode fabrication. Except the material or architecture design, binder optimization or SEI additive has also been proposed to enhance the property of Si anode, and Carboxymethylcellulose (CMC) or Alginate binder and Fluoro-ethylene carbonate (FEC) additive are now been widely used in the researches on Si anode.

Though many composites have been successfully synthesized and with good property, most of them use carbon or conductive polymer as the component with the consideration of enhancing the electrical contact or buffering the volume expansion. Here we report a new Si/MnOOH composite which shows an improved Li-ion storage performance. Hydrothermally prepared g-MnOOH was ball milled with silicon to form Si/MnOOH composite. The obtained Si/MnOOH composite exhibits an initial charge capacity of 3058 mAh g-1 with a coulombic efficiency of 78.2% at a rate of 0.1 A g-1 between 1.5 and 0.01 V. An excellent rate capability has been obtained on the composite, which shows a capacity of 1200 mAh g-1 at 12 A g-1 and 700 mAh g-1
at 20 A g-1. In addition, the Si/MnOOH composite presents a very stable cycling with more than 1000 mAh g-1 after 1500 cycles. The superior electro-activity toward lithium of the Si/MnOOH electrode should be attributed to the positive effect of γ-MnOOH on the alloying/de-alloying reaction between lithium and silicon. The results supplies a new strategy to enhance the electrochemical performance of Si anode, and the facile preparation offers a new way to obtain mass-producible Si anode material with perfect Li+ storage property.

Figure 1
About Microwave Solvothermal Synthesis of Solid Solutions LiFexMn1-xPO4/C and Their Electrochemical Properties
Authors: Handel Patricia , Stangl Christoph , God Colin , Filzwieser Monika , Uhlig Frank , Schroettner Hartmuth , Koller Stefan
Published: February 2020

In 1997, Goodenough and coworkers (1) discovered phospho-olivines LiMPO4 (M = Fe, Mn, Ni, Co) as promising positive electrode material for rechargeable lithium-ion batteries. Due to their flat voltage profile, high theoretical capacity (170 mAh*g-1 for LiFePO4), excellent thermal stability and environmental friendliness they attracted attention for both portable devices and automotive applications. Most research activities focused on the improvement of the electrochemical performance of LiFePO4, since LiMnPO4suffers from worse lithium-ion diffusion kinetics and Jahn-Teller distortion of its crystal lattice (2).

It is believed that the formation of solid solutions (3) between LiFePO4 and LiMnPO4 (LiFexMn1-xPO4) remarkably improves the electronic conductivity. This strategy seems auspicious, since the higher potential of LiMnPO4 (4.1V vs. Li/Li+) compared to LiFePO4 (3.5V vs. Li/Li+) leads to a superior energy density of the resulting lithium-ion battery.

Therefore, we report a microwave solvothermal synthesis of phospho-olivines LiMPO4(M= Fe, Mn, Co, Ni) and mixtures thereof within 10 minutes of reaction time. It is common for increasing the electronic conductivity of phospho-olivines to use one of the following problem-solving approaches: Coating with a conducting phase (4), minimizing of the particles in size (5) and doping with positive divalent\trivalent metal ions and\or fluorine (6).

Morphology of the samples is analyzed by scanning electron microscopy (SEM) as shown in figure 1. Additionally all powders are analyzed by X-ray powder diffraction (XRD), energy dispersive X-ray analysis (EDX), cyclic voltammetry (CV) and galvanostatic cycling (CC) experiments.

The occurrence of Fe and Mn in the phospho-olivine and their influence on the cell performance will be discussed (cf. figure 2). Furthermore, Mg is incorporated into the lattice and its influence on electrochemical behavior will be shown as well (cf. figure 3).

Acknowledgement

Herbert Quandt Foundation is gratefully acknowledged for funding.

References

1. A.K. Padhi, K.S. Nanjundaswamy, J.B. Goodenough, J. Electrochem. Soc., 144, 1188 (1997).

2. J. Hong, F. Wang, X. Wang, J. Graetz, J. Power Sources, 196, 3659 (2011).

3. C.-K. Back, R.-Z. Yin, Y.-S. Kim, J. Electrochem. Soc., 160, A1551 (2013).

4. H.C. Shin, W.I. Cho, H. Jang, Electrochim.
Acta, 52, 1472 (2006).

5. I. Bilecka, A. Hintennach, M. D. Rossell, D. Vie, P. Novák, M. Niederberger, J. Mater. Chem., 21, 5881 (2011).

6. Y. Huang, Y. Xu, X. Yang, Electrochim. Acta, 113, 156 (2013).

Figure 1
Effect of Liquid Phase Sintering of Composite Electrode Containing 0.44LiBO2·0.56LiF Solid Electrolyte for All-Solid-State Batteries
Authors: Lee Seokhee , Woo Sungpil , Yoon Youngsoo , Kim Dong-Joo
Published: February 2020

All-solid-state batteries have received significant attention around the world because of high safety, reliability and energy density [1]. Over the past 20 years, all-solid-state batteries fabricated by using thin film techniques have been thoroughly investigated [2, 3]. These batteries are developed as micro-batteries because typically their total thickness is approximately 15 μm, including the protective packaging. Their specific capacities are only between 5 and 100 μAh cm-2, depending on the thickness of electrodes [4]. The main challenge facing all-solid-state batteries is to enhance the surface capacity influenced by the thickness of cathode electrode. However, many attempts to increase the electrode thickness have not been successful because micro-cracks between the components are formed due to the stress generated at the solid electrode-electrolyte interface. Strong kinetic limitations due to the low mobility of the ions and electrons in the increased electrode is also another problem. To overcome these problems, a composite electrode made of multifunctional materials can be used as cathode electrode. The composite electrode should contain the electrochemically active material and should be able to transport electrons and ions in the electrode. In this study, a 0.44LiBO2∙0.56LiF solid electrolyte was used for Li+ conduction pathway in the composite electrode because it has a low melting point (> 700 °C) [5] and is expected to act as a bonding material at the interface resulted from liquid phase sintering. The composite electrode with a strong mechanically framework was fabricated by a simple one-step spark plasma sintering (SPS) technique. The composite formulation as well as sintering parameters were determined by the electrical properties and sintering behaviors of electrode materials. The composite electrode was very dense with very few voids visible in the TEM images (Fig. 1.). The 0.44LiBO2∙0.56LiF solid electrolyte was in close contact with the active materials due to liquid phase sintering. A Li-ion conduction path was formed along the electrode particles. In order to analyze the effects of liquid phase sintering systematically, the electrochemical performance of composite electrode is discussed in detail.

References

[1] C.W. Ahn, J.J. Choi, J.H. Ryu, B.D. Hahn, J.W. Kim, W.H. Yoon, J.H. Choi, J.S. Lee, D.S. Park, J. Power Sources 272 (2014) 554-558.

[2] N.J. Dudney, Y. I. Jang, J. Power Sources, 119-121 (2003) 300-304.

[3] Y.N. Zhou, M.Z. Xue, Z.W. Fu, J. Power Sources 234 (2013) 310-332.

[4] A. Patil, V. Patil, D. W. Shin, J. W. Choi, D. S. Paik, S. J. Yoon, Mater. Res. Bull., 43 (2008) 1913-1916.

[5] K. Chen, Y. Shen, Y. Zhang, Y. Lin, C. Nan, J. Power Sources 249 (2014) 306-310.

Figure 1
Phase Field Modeling of the Li2O2 Growth in a Porous Cathode in Li-Air Batteries with Organic Electrolytes
Authors: Liang Linyun , Stan Marius , Anitescu Mihai
Published: February 2020

The electrochemistry of the Li-air batteries is based on a reversible reaction of 2Li++2e- +O2 = Li2O2 with forward direction describing the discharge of the cell. As the discharge proceeds, the pores of air cathodes become increasingly filled with Li2O2 precipitates, which eventually blocks oxygen from diffusing to the reaction sites. Therefore, the materials and architecture of air electrode influence its performance significantly. The optimization of the cathode microstructure by changing its specific surface area, thickness, and pore size distribution is an important aspect for developing efficient batteries. Beside, different ratios of carbon and electrolyte, wettablility of electrolytes, the effective electrochemical interface, result in variable electrochemical performance. To this end, a phase field model was developed to simulate and predict the Li2O2 crystalline growth in a three-dimensional electrolyte-filled porous carbon cathode in Li-air batteries. The model is able to capture the three-phase (carbon, electrolyte, and Li2O2) morphologies and their microstructural evolutions during the cell operation. The nucleation and growth of Li2O2 on the carbon surface is observed. The effects of oxygen pressure, interfacial energies, carbon substrate properties such as pore size and its distribution, thickness and volume fraction on the cathode performance will be discussed. The model provides useful information to optimize the electrode microstructure to enhance the battery performance.

Figure 1
The Porous Carbon Matrix for High Rate Performance Lithium-Sulfur Battery
Authors: Kang Hyo-Seok , Shin Hwang Dong , Lee Dong-Ju , Sun Yang-Kook
Published: February 2020

As the demand for sustainable, clean energy technologies increases, rechargeable lithium-ion batteries remain one of the most feasible alternatives for the future.1 However, the ability to deliver safe and high-energy density components at low cost is a major obstacles for Li-ion batteries for use in electric vehicles (EVs) and energy storage systems (ESS).2 Lithium-Sulfur batteries, one of the alternatives, has a large theoretical specific capacity of 1675 mAh g-1 and an energy density of 2600 Wh kg-1.3 Sulfur is also abundant in nature, inexpensive and eco-friendly. In spite of these benefits, Li-S cells have reached their limits due to their intrinsic characteristics. Firstly, sulfur has an insulating nature. Secondly, the resulting product, lithium polysulfide, is easily dissolved in the electrolyte, which causes active material loss. Lastly, slow kinetics occur at a lower plateau during charging-discharging processes. There are several approaches to overcome the slow kinetics and dissolution of lithium polysulfide, such as employing mesoporous carbon or a graphene oxide coating on sulfur. However, the utilization of sulfur is still a challenge due to the slow kinetics. One approach to address this issue is to limit the voltage range to reduce the formation of Li2S2 and Li2S. The lower plateau region (Li2S4 ↔ Li2S) has slow kinetics due to the phase transformation from a liquid to solid state by the Li2S growth mechanism.4 Moreover, the Li2S species that accumulate on the electrode surface may reduce the cycle life due to poor conductivity. We previously limited the voltage range of the upper plateau region (~2.1V vs Li+/Li); known as the fast kinetics region (S8 ↔ Li2S4) with a theoretical capacity of 419 mAh g-1,5 so as to hinder the formation of insoluble species (Li2S2, Li2S). Herein, we simply upgrade the structure with a porous cathode material ( activated carbon, AC) with a gas diffusion layer (GDL); this porous carbon GDL (PCG) was compared with the conventional Al foil current collector (porous carbon Al foil, PCA) through an electrochemical performance test. This unique porous structure enhanced the facile transportation of the Li-ion in the liquid state Li-S cells so that the rate capability of the Li-S cells was increased.

References

1. J. B. Goodenough, Y. Kim, Chem. Mater., 22, 587 (2010).

2. J. M, Tarascon, M. Armand, Nature, 414, 359 (2001).

3. P.G. Bruce, S. A. Freunbergeg. L. J. Hardwich, J. M. Tarascon, Nat. Mater., 11, 19 (2012)

4. X. L. Ji, K. T. Lee L. F. Nazar, Nat. Mater., 8, 500 (2009)

5. C. Barchasz, F. Molton, C. Duboc, J. -C. Leprêtre, S. Patoux, F. Alloin, Anal. Chem., 84, 3973 (2012)
Synergistic Effect of Dual-Doping of Graphene Nanosheets on the Electrochemical Performance of Lithium-Air Cells
Authors: G Kannan Aravindaraj , Kim Jae-Hong , Kim Dong-Won
Published: February 2020

Rechargeable lithium-air battery is considered as one of the promising next-generation energy storage systems for application in electric vehicles due to its high theoretical energy density. In general, the performance of lithium-air cells in non-aqueous electrolyte is significantly affected by the large polarization in air cathode due to the deposition of discharge products as well as the ineffective electrocatalytic activity of electrode materials during oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). To address these issues, noble metals are being used as catalysts, which may increase the cost of lithium-air cells. Recently, graphene nanosheets with a two-dimensional sp2-hybridized carbon structure have been actively explored as metal-free air cathode due to their superior electronic conductivity, mechanical strength, chemical stability, high surface-to-volume ratio and structural flexibility. The edge sites and other defect sites present in the basal plane of graphene prepared by chemical method have been demonstrated as catalytic sites for ORR.1 Furthermore, doping of graphene with heteroatoms such as nitrogen, boron, sulfur and phosphorus breaks the charge neutrality of carbon atoms and acts as catalytic centers.2  In this study, we demonstrate the synergistic effect of dual-doping of graphene nanosheets on the performance of lithium-air cells. Chemical and morphological characterization of the dual-doped graphene nanosheets along with their enhanced electrochemical performance over the single-heteroatom doped graphene as metal-free air-cathode will be presented.

References

1.   E. Yoo and H. Zhou, ACS Nano, 5, 3020 (2011).

2.   L. Lai, J. R. Potts, D. Zhan, L. Wang, C. K. Poh, C. Tang, H. Gong, Z. Shen, J. Lin and R. S. Ruoff, Energy Environ. Sci., 5, 7936 (2012).
Conducting Polymer-Coated Carbon Nanotubes As High Rate Anode Material for Rechargeable Aqueous Electrolyte Battery
Authors: Lim Hana , Lee Min Hyung , Lee Ho-Nyun , Kim Hyun-Jong
Published: February 2020

Among various energy storage systems, the rechargeable battery has been proposed as one of the most promising strategy for grid-scale energy storage because of flexible power and energy characteristics, high energy conversion efficiency, and low maintenance. And, their compact size makes them well suited for use at distributed location to control the output fluctuations in local power generation.

Lithium-ion batteries are being considered as one of the most promising power sources for smart grids because of their high energy density and long cycling life. However, safety and fast charging performance are still two challenging issues to be solved for their use as large-scale systems. An attractive approach to circumvent this problem is to use an aqueous electrolyte for lithium-ion batteries, which adopt a ‘rocking-chair’ concept similar to the organic lithium-ion battery. In the mid 1990s, an aqueous lithium-ion battery was proposed that uses VO2 as the anode and LiMn2O4 as the cathode. By this combination, the safety problem of the organic electrolyte is fundamentally resolved. Furthermore, since the rigorous assembly conditions are avoided, the cost is reduced greatly, compared with the non-aqueous lithium-ion battery.

In this study, polypyrrole-coated carbon nanotube(CNT) was prepared by chemical oxidation polymerization of pyrrole on the surface-functionalized carbon nanotube in the presence of FeCl3. As increasing the concentration of pyrrole, the thickness of polypyrrole layer on the surface of CNT was gradually increased.

Polypyrrole was very stable during the lithium and sodium doping/dedoping processes in the aqueous solution without evolution of hydrogen. When the polymers were dispersed on the surface of carbon, the discharge capacity was highly improved due to the enhanced surface area and decreased diffusion length. In the charging-discharging experiments, the decay of capacity was greatly decreased although the charging/discharging rate was increased to 10C. The conducting polymer-coated CNT showed very promising charge-discharge characteristics at high-rate region in the aqueous sodium electrolyte.
Synthesis, Tailoring and Characterization of V2O5-Cathodes for High Performance Li+-, Na+- and Mg2+-Ion Batteries
Authors: Seidl Lukas , Ma Jiwei , Martens Sladjana , Mostafa Ehab , Schneider Oliver , Stimming Ulrich , Si Huinan , Qiu Xinping
Published: February 2020

Battery technology based  electric energy storage devices are inevitable on the way to electromobility and the widespread application of renewable energies like wind- or solar-power.1 Until now, Li+-ion batteries represent the state of art technology meeting best the demands of high energy- and power-densities. However issues related to high costs and safety still require improvement. 2,3 One strategy to tackle those issues is to replace the costly Li-metal by other, more abundant metals, such as Na or Mg.4 Due to the different ionic, electronic and chemical properties of Li+-, Na+- and Mg2+-ions, not every Li+-ion host material is suitable for the other ions. One exception is V2O5, which recently was successfully used as high voltage cathode for Na+- and Mg2+-ion intercalation.5,6

Similar to the research on Li-ion battery electrode materials, where people pursue the strategy of electrode nanostructuring in order to increase the rate capability and hence the power density, a wide variety of synthesis techniques was applied to obtain nano-V2O5, including top-down and bottom-up techniques.7 In this work, V2O5-nanofibres were synthesized by ultrasonication and electrochemical deposition. Anodization of vanadium metal yielded V2O5-nanotubes, while hydrothermal synthesis results in hollow V2O5-nanospheres. In order to characterize and specify the different electrode morphologies and performances, electrochemical, spectroscopic and microscopic techniques were applied (see Figure 1). In addition, fundamental studies on V2O5 and its interaction with Li+-, Na+- and Mg2+-ions were conducted making use of Scanning Tunneling Microscopy (STM) and the Electrochemical Quartz Crystal Microbalance technique (EQCM).

Figure 1. SEM images of (a) hollow V2O5-nanospheres, (b) electrodeposited V2O5 and (c) ultrasonicated V2O5

 

1B. Dunn, H. Kamath, J.-M. Tarascon, Science, 334 (2011) 928

2M. Armand, J.-M. Tarascon, Nature, 451 (2008) 652

3J. B. Goodenough, J. Solid State Electrochem., 16 (2012) 2019

4J. O. Besenhard, M. Winter, ChemPhysChem, 3 (2002) 155

5G. Gershinsky, H. D. Yoo, Y. Gofer, D. Aurbach, Langmuir, 29 (2013) 10964

6D. W. Su, S. X. Dou, G. X. Wang, J. Mater. Chem., 2 (2014) 11185

7A. S. Arico, P.Bruce, B. Scrosati, J.-M. Tarascon, W. van Schalkwijk, Nature, 4 (2005) 366

Figure 1
Comparative Study on Active Material in Solid and Liquid Form for Li-S Battery
Authors: Sawas Abdulrazzag , Ganguli Babu , Arava Leela mohana reddy , Bentley Jaron
Published: February 2020

Li-ion battery materials use intercalation chemistry that imposes limitations on the energy density that can be stored. Alternatively, chemistries labelled beyond lithium ion batteries such as lithium/sulfur (Li/S) and Li-air batteries have gained paramount importance. In particular, Li-S systems have attracted widely due to their high theoretical capacity of 1675 mAh/g of sulfur cathode, and low cost. However, Li-S batteries have complications such as (i) the low active material utilization due to the insulating nature of sulfur and its intermediate byproducts, (ii) dissolution of intermediate lithium polysulfides (LiPS) in the electrolyte and thereby deposition on to the Li anode, and (iii) large volume changes between S and Li2S (end product) upon complete discharge. Current research efforts to address these issues can be broadly classified into two types; one being loading maximum amount of active solid sulfur into conducting carbon matrix and other being liquid cathode known as catholyte (such as Li2S8) as a starting material. It is believed that both Li-S battery configurations eventually morph itself into a liquid electrochemical cell due to the formation of intermediate polysulfides at the very beginning of the discharge step. However, the systematic comparison of electrochemical performance of these two configurations for a fixed electrode morphology is missing. In order to understand the effect of nature of cathode material (solid vs liquid) on electrochemical properties, we have carried out systematic study on solid sulfur and dissolved lithium polysulfide in electrolyte (0.6 M Li2S8) as an active component for a Li-S cell containing carbon paper as cathode/current collector in an electrolyte containing 1M solution of LiTFSI in tetraethylene glycol dimethyle ether (TEGDME).  Coin cells were fabricated and tested for cyclic voltammograms (CV) in the potential range 1.5 ~3.0 V with different scan rates from 0.2 to 1.0 mV s-1 and impedance (EIS) studies from 100 KHz to 200 mHz. Charge- discharge studies at different current rates (0.2 and 0.5 C rate) were carried out in the potential range of 1.5 ~ 3.0 V. Cyclic stability and discharge capacity values for both configurations were compared by keeping all other parameters content.
Silicides and Novel Alloys with Open Tetrahedral Framework Structures Hosting Lithium Atoms
Authors: Fässler Thomas Friedrich
Published: February 2020

Alloys and intermetallic compounds are emerging as new generation anode materials with high lithium storage capacity [1].Due to the higher density of alloys Li insertion results in a higher energy density . Further is the operating voltage of alloy anodes well above the potential of metallic Li and there are less solvent intercalations for alloys.

It is well known that (semi)metals and alloys undergo several phase changes during the intercalation process. For example, the lithitation/delithiation process of Si is highly complex, involving crystalline-to-amorphous phase transitions and various amorphous phases. For a long time Li3.75Si (78.9 atom % Li) had been considered to be the fully lithiated state in a typical electrochemical reaction. Depending on the applied discharge voltage and the design of the Si anode amorphous Li3.75Si can undergo a transition to a crystalline but metastable phase Li15Si4. During our re-investigation of the Li-Si phase diagram we established Li4.25Si as the Li-richest phase, and found the novel high-temperature phase Li4.11Si. Further we report that the metastable Li3.75Si transforms to a stable phase through addition of Al [2].

In the course of our studies we searches for alternatives to pure silicon and have now synthesized novel framework structures consisting of boron and silicon, Zn and Sn, Zn and Ge as well as Ag and Ge which offer all tetrahedral framework structures that host Lithium atoms [3,4].

[1] W. J. Zhang, J. Power Sources 196 (2011) 13. M. N. Obrovac, L. Christensen, Electrochem. Solid-State Lett. 7 (2004) A93.

[2] M.Zeilinger, D. Benson, U. Häussermann, T. F. Fässler, Chem. Mater. 25 (2013) 1960−1967

[3] M. Zeilinger, L. van Wüllen, D. Benson, V. F. Kranak, S. Konar, T. F. Fässler, U. Häussermann, Angew. Chem. Int. Ed. 52 (2013) 5978 –5982

[4]  S. Stegmaier, T. F. Fässler, Inorg. Chem. 52 (2013) 2809-2816.
A Novel Li-Battery Cathode Material: Synthesis and Characterization of Li(Mn1-xCox)BO3
Authors: Le Roux Barbara , Bourbon Carole , Colin Jean François , Lebedev Oleg , Pralong Valérie
Published: February 2020

LiFePO4 is very attractive as positive electrode material for lithium-ion batteries especially for its safety and low cost. However, its specific capacity is limited to 170 mAh/g. LiMBO3 (M=Fe, Mn, Co) could be good alternatives to phosphates by having a higher theoretical specific capacity (>210 mAh/g) keeping the advantage of safety [1]. Moreover, borate compounds are expected to suffer from very low volume change upon cycling which is very interesting for the cycle life of the battery.

Nevertheless, the lithium intercalation potentials in borate compounds are lower than in phosphates which will limit their energy density [2]. Theoretically, LiCoBO3 is the most interesting borate compound in term of operating voltage and specific capacity; however, approaching its theoretical capacity seems difficult due to the structural/chemical instability of fully delithiated LiCoBO3 [3].

In order to have both reversible capacity and relatively high voltage, new Li(Mn1-xCox)BO3 have been explored. These materials have been synthesized for the first time by a multiple-step process. This one includes the synthesis of two intermediates essential to prevent the formation of metallic cobalt and Mn3+during the heat treatment.

Powders X-Ray diffraction patterns of Li(Mn1-xCox)BO3 and the evolution of lattice parameters with the cobalt content will be presented. TEM and neutron powder diffraction were carried out on these materials. Interestingly, ED patterns indicate that the C2/c space group previously reported for m-LiMnBO3 [4] and LiCoBO3 [5] cannot describe Li(Mn1-xCox)BO3 compounds. Neutron diffraction helps with the complete resolution of the structure and will be discussed during the presentation.

Electrochemical characterizations were also carried out on Li(Mn1-xCox)BO3 (0 ≤ x ≤ 1). Each material shows electrochemical activity, without in situ carbon coating. In order to improve performances of these compounds, an optimized synthesis has been developed and will be presented.

References:

[1] V. Legagneur et al., Solid State Ionics 139 (2001) 37

[2] D-H. Seo et al., Physical Review B 83, 205127 (2011)

[3] Y. Yamashita et al., ECS Electrochemistry Letters, 2 (8) A75-A77 (2013)

[4] O.S. Bondareva et al., Sov. Phys. Crystallogr. 23 (1978) 269

[5] Y. Piffard et al., Acta Cryst. (1998) C54, 1561-1563

Figure 1
Optical Impedance Spectroscopy - a Technique for Characterizing the Lithium Intercalation Process in a Porous Graphite Electrode
Authors: Manka Daniel , Schindler Stefan , Berg Philipp , Ivers-Tiffée Ellen
Published: February 2020

Graphite is the most commonly used anode material in Lithium-ion batteries. It allows high energy and power densities (depending on material parameters). Lithium intercalation losses can be reduced by fine-tuning anode design. In previous literature, several electrochemical models (1-4) were proposed to better understand and simulate this process.

The challenge is to parameterize and unambiguously validate these models. This would require electrochemical investigations e.g. electrochemical impedance spectroscopy (EIS) in half cell setups under a variation of boundary conditions, namely state of charge (SOC) or temperature (1,5). However, it can be difficult to get sufficient information for parameterization. Some parameters, e.g. electrical and ionic conductivity, show similar dependencies in their physical equations.

Lithium intercalation decreases the electrode potential and changes the diffusive reflectance. This is due to SOC dependent photo-molecular interactions, e.g. intraband transitions (6). In this work we present a new optical cell setup with a Lithium ring reference electrode. This innovation allows simultaneous in-situ optical and electrical measurements. We can now observe the dynamic behavior of the macroscopic anode surface reflectance. We demonstrate the excitation by using a modulated voltage signal to measure the reflectance as a response signal. With this new measurement method, we mapped an optical impedance spectrum (OIS), revealing further information about the Lithium intercalation process.

Conventional electrochemical models usually only contain electrical measurement figures. The most appropriate model assumption for porous graphite electrodes is based on a transmission line (1,7). In this study, the transmission line model is extended so that it reproduces both the EIS and OIS measurements. It is thereby possible to investigate different model assumptions using a combined electro-optical parameterization (Fig. 1). It becomes apparent that combined electro-optical parameterization can reduce ambiguities in the electrochemical model. It will be demonstrated that the OIS is highly sensitive to changes in ionic and electronic conductivities; ergo, these parameters can be reliably determined.

Figure 1
Geometrical Magnetoresistance in Multi-Gate FDSOI Structures
Authors: Navarro Carlos , Chang Sung-Jae , Bawedin Maryline , Andrieu François , Sagnes Bruno , Cristoloveanu Sorin
Published: February 2020

Mobility characterization is very challenging on SOI multi-gate transistors where several channels coexist and interact [1-3]. Among all mobility determination procedures, only the geometrical magnetoresistance yields accurate values free of any assumption (channel length, oxide and film thickness, doping, strain, etc). 

     Magnetoresistance is a direct consequence of carrier deflection by a magnetic field. When carriers do not follow the shortest path from source to drain, the channel resistance increases. The relation between the resistances obtained when the magnetic field is present or not yields:

            RB = R0 ( 1 + μMR
2 B2 )

     The carrier deviation by the Lorentz force is shown in Fig. 1a. The deviation is modulated by the device geometry. If the transistor is long and narrow (W/L  < 1) the Hall field opposes to the Lorentz force and the magnetoresistance is weak. However, when the sample is wide and short (W/L  >> 1) the Hall field is short-circuited by the end contacts and the Lorentz force is not compensated. Hence, carriers are deviated and the magnetoresistance is maximum. Fig. 2 illustrates the simulated electron mobility against the aspect ratio (W/L) for several magnetic field orientations. The magnetoresistance is much higher for normal magnetic fields (and W/L > 5) than for transversal fields as fully documented by experimental data [4].

     On the other hand, in double-gate FinFETs (Fig. 1b), the magnetoresistance is high even in narrow samples (W ~ L). This surprising result was explained by the lateral gate action which cancels the Hall voltage so preventing the compensation of the Lorentz force and resulting in the magnetoresistance [4].

     TCAD numerical simulations [5] were carried out to clarify the carrier deflection and magnetoresistance mobility in FinFETs. The impact of the device architecture, thicknesses, gate biasing scheme, and magnetic field orientation is documented and explained.

     References

[1] S. Cristoloveanu and S. S. Li, Electrical characterization of silicon-on-insulator materials and devices, Kluwer Academic Publishers, 1995.

[2] L. Pham-Nguyen, C. Fenouillet-Beranger, A. Vandooren, T. Skotnicki, G. Ghibaudo and S. Cristoloveanu, “In-situ comparison of Si/High-K and Si/SiO2 channels properties in SOI MOSFETs,” IEEE Electron Device Letts., vol. 30 (10), pp. 1075-1077, 2004.

[3] F. Dauge, J. Pretet, S. Cristoloveanu, A. Vandooren, L. Mathew, J. Jomaah and B.-Y. Nguyen, “Coupling effects and channels separation in FinFETs,” Solid-State Electron., vol. 48, pp. 535-542, 2004.

[4] S.-J. Chang, M. Bawedin and S. Cristoloveanu, “Mobility Investigation by Geometrical Magnetoresistance in Fully Depleted MOSFETs and FinFETs,” Electron Devices, IEEE Transactions on , vol.61(6), pp.1979-1986, 2014.

[5] Synopsys TCAD, Sentaurus Workbench Advanced, Version H-2013.10, Synopsys, Inc.

Figure 1
Influence of Substrate on Hafnium Silicate Metal-Insulator-Metal Capacitors Grown by Atomic Layer Deposition
Authors: Hutchinson B J , Teodorescu V S , Negrea R , Sheehan B , Carolan P , O'Brien S , Modreanu M , Pemble M E , Povey I. M
Published: February 2020

Metal insulator metal (MIM) capacitors are fundamental components of the electronic circuitry commonly found in many devices in areas such as analogue to digital conversion, micro-electromechanical systems, medical, automotive and memory applications [1-4]. Current MIMCAPS generally employ optimised low dielectric constant (k) materials (k~3.9 - 7) to attain the target electrical properties of high breakdown field and low current leakage. However, device scaling is limited due to the low k value of these materials and this presents a significant challenge to the future development of these technologies [5]. Many high k materials are under investigation to replace these lower k dielectrics to substantially increase the maximum capacitance density and reduce the area associated with the integration of MIM structures.

In this work we investigate the growth of hafnium silicate films by plasma assisted atomic layer deposition on a metal electrode. The hafnium silicate film was deposited using Tetrakis(dimethylamino)hafnium (TDMAHf) and Tetrakis(dimethylamino)silane (TDMASi) precursors at 250oC with a remote oxygen plasma (300 W).  From HR-TEM analysis and Raman spectroscopy it has been observed that the main crystalline phase is monoclinic HfO2. This crystallographic phase appears to be templated by the underlying titanium adhesion (10 nm) layer through the platinum electrode (200 nm).

The HR TEM analysis also reveals the presence of nanoparticles, located primarily towards the lower platinum metal layer. Based on electron energy loss spectroscopy (EELS) analysis the nanoparticles are consistent with silicon oxide inclusions, located at HfO2 grain boundaries.  In addition, the presence of additional phases was detected; these included a super-cell structure within the bulk and an amorphous phase. No hysteresis was observed in the capacitance voltage measurements and the material was observed to exhibit a k value of ~18.

References

[1] C. Zhu et al., IEDM Tech. Dig., 879–882 (2003).

[2] S. J. Kim et al., IEEE Elec. Dev. Lett., 25 (8), 538–540 (2006).

[3] F. El Kamel et al., Appl. Phys. Lett., 91 (17), 172 909 (2007).

[4] A. Hastings, “The Art of Analog Layout”, Prentice Hall, New Jersey, 2001.

[5] C. H. Ng et al., IEEE Elec. Dev. Lett. 24 (8), 506 (2003).
Atomic Resolution Study of VO2 Metal-Insulator Transition As Field-Effect Transistors
Authors: Asayesh-Ardakani Hasti , Nie Anmin , Marley Peter , Zhu Yihan , Sambandamurthy Ganapathy , Banerjee Sarbajit , Klie Robert F , Odegard Gregory , Shahbzian-Yassar Reza
Published: February 2020

There has been long-standing interest in ultra-fast Metal-Insulator Transition (MIT) in VO2 because of their possible applications in data processing systems specially field-effect transistors. The MIT in VO2 is associated with a structural phase transition, sharp resistivity and optical transparency changes by several orders of magnitudes, which happens close to room temperature (at ~ 340 K). The phase transition occurs from a monoclinic (M) structure to a tetragonal rutile (R) structure. The present work investigates the effect of W dopants in MIT of individual single-crystalline VO2 nanowires by use of aberration corrected scanning transition electron microscopy and in situ TEM. In this study different doping concentration of W were used, which corresponds to different transition temperatures around 340 K. The atomic scale Z-contrast imaging of individual single-crystalline W
x
V1-x
O2 nanowires indicates W dopant atoms and the strain caused by W atoms in in the structure. The localized strain caused by dopants play critical role in metal-insulator phase transition and control of electrical property of doped VO2.