bluuebunny/crossref_metadata_2025_split huggingface dataset:
Engineering Photovoltaic Waste Kerf-Loss Silicon into a Practically Applicable Anode for Lithium Ion Battery
Authors: Selvaraj Baskar , Huang Tzu-Yang , Wu Nae-Lih 
Published: February 2020

Silicon has been extensively studied as a lithium ion battery anode due to its high capacity and abundant in nature. Huge volume expansion (>300%) and relatively low electrical conductivity of this material resulted in pulverization, unstable SEI formation and poor cycling stability. Preparation of silicon nanomaterials (nanoparticles, nanowires, nanotubes and porous silicon) combined with carbon (carbon nanotubes, graphene and carbon coating) has significant achievements in addressing these problems but lacking in satisfying the requirements of practical application cost, high mass loading to have high capacity per unit area and simple method for the mass production. Fast growing solar industry produces tons of valuable crystalline silicon containing kerf loss (Kf) waste during slicing of the silicon ingots. Utilization of this Kf as a silicon source will provide an environmental friendly cheap constant source for the lithium ion battery anode and complement each other in the aspect of power generation and storage.
Kf silicon source with simple industrially mature high-energy ball milling (HEBM) is used here as a method for the material preparation. Instead of separating robust non-conductive abrasive SiC particles from Kf, it is adopted as millers to reduce Si particle size and skeleton to accommodate silicon volume expansion. In addition to SiC, nickel is added further to absorb volume expansion and to serve as electrical conductor along with the small amount of carbon black. Milling and calcination of Kf, nickel oxide and carbon black leads to the formation of micrometer sized agglomerates (~ 10 µm) composed of nanometer sized silicon, silicon carbide, nickel and carbon black (SSNC) ternary composite particles. This reduction of Si particle size with agglomerates formation gives rise to high particle tap-density and helped to achieve high mass loading on the electrode. This SSNC ternary composite has exhibited high reversible capacity > 800 mAh/g with comparably low first-cycle irreversibility. Reduction of silicon and engineering of its surface with non-conductive SiC and conductive nickel and carbon composite successfully reduced the volume expansion, leading to substantially enhanced cycle stability.

Figure 1
Designing Sandwich Structured Cu/SnCu/Cu Film and Its Use As Negative Electrode for Lithium Ion Batteries
Authors: Bilici Burcin , Polat Deniz Billur , Keles Ozgul 
Published: February 2020

We demonstrate the design and the fabrication of Cu/SnCu/Cu sandwich-like structured film by electrochemical deposition method. The Cu layer at the current collector/electrode interface increases the adhesion of the film. And the Cu layer at the electrode/electrolyte interface is believed to hold the electrode together to prevent the delamination and promotes a stable interface formation to optimize the electrochemical performance of the electrode. Moreover, Cu atoms in the SnCu layer of the Cu/SnCu/Cu sandwich-like film serve as conductive pathways to support an effictive lithiation/delithiation reactions between Sn and Li, plus act as buffer to tolerate the mechanical stress induced in the galvanostatic test. Herein it is important to note that possible intermetallics formation between Cu and Si might enhance the reversibility of the lithiation reaction of Sn with Li.
Therefore to promote the intermetallic formation in the film, a heat treatment (200˚C, 48h under vacuum atmosphere) has been applied. The galvanostatic test result shows that a remarkable improvement is noted when heat treated Cu/SnCu/Cu film is used as anode.
Understanding the Factors That Improve the Cycling Performance of Silicon Anode for Li-Ion Batteries
Authors: Alvarado Judith , Schroder Kjell W , Yersak Thomas A. , Stevenson Keith J. , Meng Ying Shirley 
Published: February 2020

The high gravimetric capacity of lithiated silicon has motivated research as a potential anode for lithium ion batteries; however, major challenges remain for the implementation of silicon in commercial devices. During the lithiation process, a portion of the Li ions are consumed as the electrolyte is reduced to inactive side products from parasitic reactions, forming a solid electrolyte interphase (SEI). The SEI components should be electronically insulating and passivate the active material’s surface from further solvent reduction.1 However, due to the mechanical instability of silicon during lithiation, it prohibits the formation of a stable SEI causing capacity loss during cycling. In order to solve this issue, fluoroethylene carbonate (FEC) electrolyte additive has been widely used.2 However, the connection between SEI stability and FEC needs to be further investigated on a silicon model system.
Herein, SEI formed from LiPF6-carbonate based electrolytes, with and without FEC were investigated on 50nm amorphous silicon thin film electrodes. Figure 1 (a) demonstrates the excellent cycling performance of FEC over prolonged cycles compared to its counterpart. Anhydrous and anoxic X-ray photoelectron spectroscopy (Figure 2 (b)) and time-of-flight secondary ion mass spectrometry depth profiling techniques were used to accurately characterize the SEI structure and composition. These results show that FEC reduction leads to fluoride ion and LiF formation, consistent with previous results.3 We believe that the effectiveness of FEC at improving the Coulombic efficiency and capacity retention is due to fluoride ion formation from reduction of the electrolyte, which leads to the formation of a kinetically stable SEI comprised of predominately inorganic compounds. This work is funded by the Office of Vehicle Technologies, U.S. Department of Energy under the Advanced Battery Materials Research (BMR) Program.
Reference:
[1] Verma, P.; Maire, P.; Novák, P. Electrochim. Acta 55 (2010) 6332–6341.
[2] Xu, C.; Lindgren, F.; Philippe, B.; Gorgoi, M.; Björefors, F.; Edstrom, K.; Gustafsson, T. Chem. Mater. 27 (2015) 2591-2599.
[3] Leung, K.; Rempe, S. B.; Foster, M. E.; Ma, Y.; Martinez del la Hoz, J. M.; Sai, N.; Balbuena, P. B. J. Electrochem. Soc. 161 (2013) A213–A221.

Figure 1
Visualizing the Solid Electrolyte Interphase Layer Evolution in Silicon Electrode
Authors: Sina Mahsa , Alvarado Judith , Shobukawa Hitoshi , Meng Ying Shirley 
Published: February 2020

Silicon is a promising anode candidate in Li-ion batteries with a theoretical capacity more than ten times that of the commercial graphite anodes (372 mAh/g). However, Si electrodes suffer from rapid capacity fade during electrochemical cycling. One of the more successful strategies for dealing with the capacity loss and continuous solid electrolyte interphase (SEI) formation on Si electrodes has been the use of battery electrolyte additives such as fluoroethylene carbonate (FEC) [1-4]. In this work we used a combination of Annular Dark Field - Scanning Transmission Electron Microscope (ADF-STEM) imaging and Electron Energy Loss Spectroscopy (EELS) techniques in order to understand the effect of FEC on the chemical and morphology evolution of Silicon and SEI layer during cycling. We observed that upon lithiation crystalline Si converted into the amorphous LixSi alloy and two layers formed on the outermost surface of the electrode including: 1- SEI and 2- LixSiOy. It was found that the presence of FEC suppresses the formation of LixSiOy layer and leads to the formation of uniform SEI layer around the LixSi particles with high LiF content. Such STEM/EELS study correlates the morphology and chemistry of the Silicon and SEI layer for the first time and provides valuable insights into the electrochemicalperformance of Si electrodes.
Acknowledgements
This research is funded by the Office of Vehicle Technologies, U.S. Department of Energy under the Advanced Battery materials Research (BMR) Program.
References
[1] Philippe B., G. G. (2013), Chemistry of Materials, 25: 394-404.
[2] Xu C., F., et. al. (2015), Chemistry of Materials, 27:2591-2599..
[3McDowell M. T., et al. (2012), Advanced Materials 24: 6034-6041.
[4] Sina M., et al. (2015), Journal of Phys. Chem. C, 119: 9762–9775.
(Invited) Polyarylations of Heterofullerenes
Authors: Hirsch Andreas 
Published: February 2020

We will report on a variety of new arylation reactions leading to well defined oligoadducts of the heteofullerene C59N. These adducts contain an integral pyroll subunit. On the way the full arylation a variety of mono- and bishydrides could be isolated as well. All new compounds were fully characterized including x-ray crystallography. Based on the experimental data a convinving reaction mechanism describing the formation of these new fullerene adducts was proposed.
(Invited) C70 As a Photocatalyst for Oxidation of Benzylamines to Imines
Authors: Kumar Rakesh , Yamakoshi Yoko 
Published: February 2020

Photosensitivity is one of the most important physico-chemical properties of fullerenes. Photoexcited C60 and C70 can cause the electron transfer (type I)1 or energy transfer (type II)2,3 reaction under visible light irradiation in quite high quantum yields (quantitative). These reactions have been used to develop new functional materials for the application of photovoltaic devices and photodynamic therapy agents. Especially in the latter application, generation of reactive oxygen species (ROSs)4 such as 1O2 and O2•–
5,6is used to affect the biological molecules.
The generation of 1O2 has been also used in the organic reaction. Using fullerenes as photocatalyst, oxidation of olefins,7 phenols8 and sulfides9 were reported. In this study, we used C70 for the oxidation of benzylamines. Compared to C60 and other commonly used photosensitizers such as tetraphenylporphyrin (TPP),10,11 C70 could catalyze the oxidation of benzylamines to corresponding imines efficiently with lower catalyst loading (0.01 mol %). The reaction worked also under the lower energy of lights using blue (max 470 nm) and green (max 520 nm) diodes. Reaction processed in clean manner without any significant amount of side product, and removal of the C70catalyst was carried out easily by just simple precipitation and filtration.
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1991, 95, 11. (3) Arbogast, J. W.; Foote, C. S. J. Am. Chem. Soc.
1991, 113, 8886. (4) Tokuyama, H.; Yamago, S.; Nakamura, E.; Shiraki, T.; Sugiura, Y. J. Am. Chem. Soc.
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1998, 120, 12363. (6) Yamakoshi, Y.; Umezawa, N.; Ryu, A.; Arakane, K.; Miyata, N.; Goda, Y.; Masumizu, T.; Nagano, T. J. Am. Chem. Soc.
2003, 125, 12803. (7) Tokuyama, H.; Nakamura, E. J. Org. Chem.
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(Invited) Chemically Modified Two-Dimensional Nanoelectronic Heterostructures
Authors: Hersam Mark C. 
Published: February 2020

The outstanding properties of graphene have been established on pristine samples in idealized conditions. However, for most applications, graphene needs to be chemically functionalized in a manner that either preserves its intrinsic properties or modifies its properties in a manner that enhances functionality. Towards these ends, several noncovalent chemistries have been demonstrated and characterized at the molecular scale with ultra-high vacuum scanning tunneling microscopy including 3,4,9,10-perylenetetracarboxylic dianhydride and 10,12 pentacosadiynoic acid. These self-assembled monolayers are shown to be effective atomic layer deposition seeding layers for dielectrics (e.g., Al2O3, HfO2, and ZnO), which allows for substantial improvements in the uniformity and reliability of metal-oxide-graphene electronic devices. On the other hand, covalent modification schemes based on free radical chemistries allow for more fundamental changes to the electronic and chemical properties of graphene. In particular, atomic oxygen has been established as an effective method for homogeneously and reversibly functionalizing graphene with epoxide groups. In addition to chemically doping graphene, epoxidation yields local modification of the graphene bandstructure and provides pathways for further chemical functionalization, thereby expanding the suite of chemically modified graphene heterostructures. Finally, this talk will conclude with ongoing work in our laboratory to extend the chemical modification strategies for graphene to other two-dimensional materials including ultrathin silicon [1,2], black phosphorus [3,4], and transition metal dichalcogenides [5].
[1] A. J. Mannix, B. Kiraly, B. L. Fisher, M. C. Hersam, and N. P. Guisinger, “Silicon growth at the two-dimensional limit on Ag(111),” ACS Nano, 8, 7538 (2014).
[2] B. Kiraly, A. J. Mannix, M. C. Hersam, and N. P. Guisinger, “Graphene-silicon heterostructures at the two-dimensional limit,” Chem. Mater., 27, 6085 (2015).
[3] J. D. Wood, S. A. Wells, D. Jariwala, K.-S. Chen, E. Cho, V. K. Sangwan, X. Liu, L. J. Lauhon, T. J. Marks, and M. C. Hersam, “Effective passivation of exfoliated black phosphorus transistors against ambient degradation,” Nano Lett., 14, 6964 (2014).
[4] X. Liu, J. D. Wood, K.-S. Chen, E. Cho, and M. C. Hersam, “In situ thermal decomposition of exfoliated two-dimensional black phosphorus,” J. Phys. Chem. Lett., 6, 773 (2015).
[5] X. Liu, I. Balla, H. Bergeron, G. P. Campbell, M. J. Bedzyk, and M. C. Hersam, “Rotationally commensurate growth of MoS2 on epitaxial graphene,” ACS Nano, DOI: 10.1021/acsnano.5b06398 (2015).
Photoelectronic Effects with Graphene Channels Interfaced with Quantum Dots Arrays
Authors: Miao Xin , Trivedi Samarth , Grebel Haim 
Published: February 2020

The electrical and photo-electronic properties of graphene-based field effect transistors (GFETs) were studied when the single layer graphene served as the transistor channel, while interfaced with well organized, isolated semiconductor quantum dots (QD) array. The photoluminescence (PL) of the QDs as a function of the drain-source (Vds) and the gate-source (Vgs) bias was studied.
Graphene, a two-dimensional, single layer thick crystalline form of carbon atoms, has outstanding physical properties, such as high conductivity, chemical inertness, mechanical robustness and unusual dispersion relations [1]. In the past, we studied graphene layer(s) when suspended over nano-pore structures [2-6]. Here we used anodized aluminum oxide (AAO) as the perforated substrate, and core/shell CdSe/ZnS semiconductor quantum dots (QD) as the photo-sensitive material. The QD were imbedded in the AAO pores.
The GFETs were fabricated by transferring a single layer of graphene on top of the QD imbedded AAO. The array of holes on the AAO substrate were 25-30 nm in diameter and with a pitch of 100 nm. For the photoluminescence (PL) measurements, a 10 mW Ar ion laser at 488 nm was used in confocal arrangement. Coupling of the incident and/or emitted light with the surface Plasmon/Polariton (SPP) mode was observed as a peak in PL curve as a function of the sample's tilt angle with respect to the incident optical beam. The fluorescence peak of the QDs decreased monotonously as a function of Vgs and Vds alluding to the control of PL by the biasing potentials. The effect of white-light intensity on the sample conductivity was studied, as well: the difference in Ids between illuminated and non-illuminated cases was substantially affected by the biasing potentials.
[1] K.S. Novoselov, A.K. Geim, S.V. Morozov, D. Jiang, Y. Zhang, S.V. Dubonos, I.V. Grigorieva and A.A. Firsov, “ Electric Field Effect in Atomically Thin Carbon Films”, Science, 306, 666 (2004).
[2] A. Banerjee, R. Li and H. Grebel, “Surface Enhanced Raman with Graphenated Anodized Aluminum Oxide Substrates: the Effect of Sub-Wavelength Patterns”, Nanotechnology, 20 (29), art. no. 295502 (2009).
[3] A. Banerjee and H. Grebel, “Depositing Graphene Films on Solid and Perforated Substrates”, Nanotechnology, 19 1-5 art. no. 365303 (2008).
[4] Ruiqiong Li, and Grebel Haim, “Surface Enhanced Fluorescence”, IEEE Sensors, 10(3), 465-468 (2010) doi: 10.1109/JSEN.2009.2038513.
[5] R. Li, A. Banerjee and H. Grebel, “The possibility for surface plasmon lasers”, Optics Express, 17, 1622-1627 (2009).
[6] A. Banerjee, R. Li and H. Grebel, "Surface plasmon lasers with quantum dots as gain media", Appl. Phys. Letts., 95, 251106 (2009); doi:10.1063/1.3276273.
Band Gap Tuning of Germanene Nanoribbon Using Chemical Functionalization
Authors: Monshi Md Monirojjaman , Mehdi Aghaei Sadegh , Calizo Irene 
Published: February 2020

Graphene as a 2D carbon nanostructure has drawn tremendous interest worldwide because of its extremely high mobility and unique electronic, magnetic, and surface properties but opening a band gap remains challenging. Other 2D materials have emerged as promising materials that may be more easily altered to have a band gap, high mobility, and on/off ratio. Germanene with its buckled two-dimensional structure exhibits extremely high mobility, massless fermions behavior, and strong spin-orbit coupling which has drawn tremendous interest for high performance devices. However, it has no intrinsic band gap and low structural stability which are needed for logic and switching devices. Despite numerous attractive features in germanene it, like graphene, exhibits a semi-metallic zero band gap. Applying electric field, chemisorption of adatom species, introducing periodic nanoholes, doping and edge functionalization are all techniques aimed at opening a bandgap in germanene. Here we present a density functional theory based study of the influence of edge-functionalization using hydrogen (-H and -2H) and halogen (- F, -Cl, -Br, -I, -2F,-2Cl, -2Br, -2I), -S atoms and –SH, -OH, -CH3 groups termination. An overview is given of the influence of these edge-functional groups attached to different germanene nanoribbon (GNR) structures of varying width ranging from 6 to 19, focusing primarily on band gap. Additionally, the dependence of armchair GNR band gap on functionalization and ribbon width is explored. We found that edge functionalized armchair germanene nanoribbon (AGeNR) opened a band gap as small as 0.012 eV when functionalized by -2H and could be as high as 0.84 eV when functionalized with -2I. Nanoribbons could be classified into three families according to width as follows, W = 3K, 3K+1, and 3K+2. For mono-hydrogenated, fluorinated, chlorinated, hydroxyl termination, the band gap varied as EG (3K+2) < EG (3K) < EG (3K+1). For di-hydrogenated, fluorinated, and chlorinated we found band gap follwed the periodicity EG (3K+ 1) < EG (3K +2) < EG (3K ). Formation energy studies revealed that the AGeNR produced a more stable structure with fluorine functionalization and -SH, -OH, -CH3 group’s termination also provides similar result with sizable band gaps. Simulation results suggest that the electronic structure of germanene is similar to graphene and silicene. Energy band gap tuning of AGeNR using edge functionalization may provide a new means of integrating germanene in optoelectronics, low power and high performance switching devices.
Low Cost Fabrication of Graphene Oxide Films As Efficient Counter Electrode for Dye-Sensitized Solar Cells (DSSC)
Authors: Devarepally Kishore Kumar 
Published: February 2020

Graphene-oxide was prepared by screen printing to validate as an alternative counter electrode material to platinum in dye sensitized solar cells. The synthesis of graphene oxide was carried out by modified Hummer’s method using graphite flakes. Subsequently, graphene oxide paste was prepared by mixing α-terpineol and ethyl cellulose, which was screen-printed on FTO glass (TEC8) substrates. The screen printed films were subjected to annealing at 450°C for 30 minutes. The graphene oxide films were characterised by X-Ray Diffraction, Scanning Electron Microscopy and Raman spectroscopy for the required identification. The device fabrication was carried out by coupling TiO2 films soaked in N719 dye with Surlyn as the spacer between the electrodes.
The J-V measurements were carried out with the help of the solar Simulator AM1.5G condition under standard one Sun illumination. The DSSC fabricated with graphene oxide as counter electrode exhibited photoconversion efficiency of 5.58% whereas, platinum based devices showed photoconversion efficiency of 7.57%. The catalytic properties of graphene oxide films are being investigated by cyclic voltammetry and electrochemical Impedance spectroscopy. The present study suggests that graphene oxide counter electrodes can be considered as a promising alternative to platinum, with further optimisation, which clearly has advantages in terms of its abundance and low cost processing towards industrial prospects.
Covalent Functionalization of Graphene on Surfaces and in Solution
Authors: Hirsch Andreas 
Published: February 2020

We will present a series of new covalent functionalization sequences for graphene. For this purpose we reductively actived graphite. The resulting gaphenides were treated with electrophiles such as diazonium compounds in solution or on surfaces. This allowed for the first time to investigate the topicity (monotopic versus ditopic) of covalent graphene functionalization. The reaction products were fully characterized using state-of-the-art methods such as Scanning-Raman-Microscopy (SRM), TGA/MS/GC and electron microscopy.