bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved Electrochemical Performance of Lithium Air Batteries with N-Methyl-2-Pyrrolidone Based Composite Polymer Electrolytes
Authors: Tokur Mahmud , Algül Hasan , Cetinkaya Tugrul , Akkbulut Ahsen , Uysal Mehmet , Guler Mehmet Oguz , Akbulut Hatem 
Published: February 2020

Lithium air batteries are able to have higher energy density because of the lighter cathode and the fact that oxygen is freely available in the environment. This causes a great interest on these type of batteries. However, the performance of Li-air batteries is affected by many factors such as type of catalysts and electrolyte composition. The stability of electrolytes is a significant limitation for cycle life performance in Li-air batteries. In recent years, most efforts have focused on the development of stable electrolytes to improve cycle life and capacity of rechargeable Li-air batteries. Therefore, stability of the polymer composite electrolytes against the reduced oxygen species generated during the discharge process was investigated. Since Li2O2 is generated at the cathode surface during cycling, an investigation of the thermal stability, conductivity and resistance of electrolytes with Li2O2 was conducted. The other challenge of the stability of Li-air batteries is degradation of lithium anode. For this reason, great efforts of this study focused on improving lifetime and recycleability through, obtaining stable electrolyte with polymeric and inorganic additives.
For this aim, 1 M LiPF6 and LiBF4 salts dissolved in N-methyl-2-pyrrolidone (NMP) aprotic solvent and selected amount of polyvinylidene fluoride (PVDF) and polyethylene oxide (PEO), which is mostly used as binders for air electrodes in Li-air batteries and Al2O3 nanoparticles added into the electrolyte to improve thermal stability, provide highly reversible Li-O2 reaction during charging/discharging and prevent clogging of the porous structure of the cathode. In order to investigate electrochemical performance of the produced nanocomposite electrolytes, ECC-Air test cell was assembled in Ar-filled glove box. The lithium foil was used as anode, Sigracet 24BC gas diffusion layer (GDL) was used as the cathode and prepared nanocomposite solutions were used as the electrolyte. The anode and cathode was separated with a glass fiber separator. Differential scanning calorimetry (DSC) and derivative thermagravimetry (TG) measurements were used for thermal stability studies for the electrolytes. The cells were cyclically tested using 0.1 mA/cm2 current density over a voltage range of 2.15–4.1 V. Electrochemical impedance spectroscopy (EIS) measurements was carried out to investigate the effect of the PVDF, PeO and Al2O3 additives on the resistivity of the electrolyte. After the electrochemical cycling test, the surface of the cathode (GDL) was characterized using environmental scanning electron microscopy, X-ray diffraction patterns and Raman spectroscopy to investigate deposited lithium compounds such as LiO2, Li2O2 and Li2CO3 on the cathode during cycling test.
Metallic MoS2 Nanosheets As Electrodes with High Volumetric Energy and Power Densities
Authors: Acerce Muharrem , Voiry Damien , Chhowalla Manish 
Published: February 2020

In the past few years, considerable effort has been devoted to the study of graphene as energy storage material for supercapacitors. More recently other 2D materials have emerged such as MXenes and transition metal dichalcogenides. In this study, chemically exfoliated and restacked nanosheets of metallic 1T phase MoS2 has been introduced as a supercapacitor electrode and its electrochemical charge storage mechanism has been investigated in aqueous and organic electrolytes. High volumetric capacitance values (650F/cm3) have been obtained with 1T phase MoS2 even at high scan rates. High volumetric energy density (0.1Wh/cm3) and power density (51W/cm3) values were measured with organic electrolytes. During chemical exfoliation and restacking process, structural, chemical and electronic properties of MoS2 change via phase transformation from semiconducting 2H MoS2 to metallic 1T MoS2. High charge storage performances can be explained with the distinct structural and electronic properties of metallic 1T phase MoS2. The good electrical conductivity of the 1T phase enables thicker and binder free film fabrication. Interestingly the capacitance obtained from 1T MoS2 is surprisingly high comparing the modest surface area of MoS2. In order to understand the charge storage mechanism, ex-situ XRD measurements were conducted. Our results demonstrate that cations (Proton, Li+, Na+, K+, TEA+) intercalate to the two dimensional MoS2 flakes and enhance the accessible surfaces for the charge storage. Charge storage performance is stable over 5000cycles (97% capacitance retention). Our study provides insight into the electrochemical behavior of the phase engineered exfoliated and restacked nanosheets.
Enhanced Charge Transport and Storage of Two-Dimensional Vanadium Pentoxide
Authors: Rhodes Christopher , Lambdin Nicole , Patel Radica , Zaleski Audrey 
Published: February 2020

Atomically thin two-dimensional (2D) materials have a number of key features for electrochemical charge storage including significant available surface area, quantum confinement in two dimensions, and distinct local structures (e.g. surface states, edge sites). Vanadium pentoxide (V2O5) is a useful charge storage material based on its multiple available oxidation states which allows the material to store multiple ions and electrons within its structure during electrochemical cycling. V2O5 has a high theoretical specific capacity of 294 mAh/g based on the two-electron charge storage process, and this capacity is significantly higher than the capacity of current commercial cathode materials (~160 mAh/g). However, typical forms of V2O5 exhibit severe capacity fading upon cycling. We have explored 2D forms of V2O5 to provide cathode materials with high capacities and improved cycling stability. Two-dimensional V2O5 nanosheets were prepared from drying suspensions of ion-exchanged sodium metavanadate solutions. The synthesis, structural characterization, and electrochemical testing of 2D V2O5 will be presented to show the effect of various parameters (e.g. composition, particle size, aggregation, orientation) on the electrical and electrochemical properties. The ability to control the structure and properties of 2D materials allows the development of improved charge transport and storage materials for batteries, supercapacitors, and other electrochemical applications.
Ion-Transport Characteristics of Alkaline Battery Cathodes Containing Different Graphitic Additives
Authors: Forouzan M. Mehdi , Robertson Logan , Wray Michael , Wheeler Dean 
Published: February 2020

Yearly demand for primary alkaline batteries is around US$5 billion. Even though it is a mature technology, continued performance improvement is still possible. In common with other types of batteries, the performance of alkaline batteries is strongly affected by the composition and microstructure of the electrodes, especially the cathode. Naturally, in trying to optimize an electrode there are trade-offs between the capacity or amount of active material, and the volume fractions of conductive additive (carbon) and pores, which are each needed to transport charge.
This work builds on our prior work in directly measuring transport properties of electrodes [1-2]. We focus on understanding ion transport in the alkaline cathode, which is composed of EMD (electrolytic manganese dioxide), graphitic carbon, and electrolyte-filled pores. The effects of varying carbon type, carbon amount, and overall porosity on the ionic conductivity and tortuosity were studied. The correlations between ion transport and the microstructure and electronic conductivity were investigated as well. Tested carbons included a variety of common graphite additives from TIMCAL as well as graphene. Multiple analysis tools were used, including SEM/FIB determination of microstructure, ion-transport experiments, and multi-probe determination of electronic conductivities. It was found that highly compressible expanded graphites like BNB90 actually have a more deleterious effect on overall ionic conductivity that do other additives. This suggests a tradeoff between ionic and electronic conductivity performance in the choice of graphitic additive.
Furthermore, the degree of anisotropy of ion transport in the cathode for different conditions was investigated for samples containing EMD and BNB90 additive. Anisotropy of the structure of the graphite, caused by pellet compression, was observed by SEM. It was found that tortuosity is lower and ionic conductivity is higher in the direction orthogonal to the direction of compression.
[1] Zacharias et al., J. Electrochem. Soc. 160, A306-A311 (2013).
[2] Peterson and Wheeler, J. Electrochem. Soc. 161, A2175-A2181 (2014).

Figure 1
Investigating Novel Electrolytes to Suppress Dendrite Growth in Li-Air Batteries
Authors: Ryan Emily M , Tan Jinwang , Sokolinski Tatiana , Ferris Kim 
Published: February 2020

This research focuses on improving the performance and durability of advanced lithium air (Li-air) battery technologies through computational modeling and materials informatics. In particular, the issue of dendrite growth at the anode-electrolyte interface was investigated through physical models and a materials informatics approach to identify novel electrolyte materials for Li-air batteries.
Dendrites form on the anode surface over multiple charge and discharge cycles, causing a decrease in performance and safety concerns due to short circuiting. Dendrite growth depends strongly on the reactive transport near the anode-electrolyte interface and heterogeneities on the anode surface. To reduce dendrite growth, we investigated increasing the mixing near the anode-electrolyte interface through novel electrolyte designs that directionally affect the transport properties of the electrolyte solution. The research was divided into two main tasks: physical modeling of dendrite growth and morphology, and development of a materials informatics approach for identifying novel electrolyte materials.
Dendrite growth was investigated using the meso-scale smoothed particle hydrodynamics (SPH) method. SPH is a mesh-free technique that uses a Lagrangian framework to model the simulation domain as a discrete system of particles. SPH particles are used as interpolation points to discretize and solve the governing partial differential equations of a system based on the SPH smoothing function. Due to its Lagrangian nature, SPH does not require explicit boundary tracking, which allows for simple implementation of complex geometries and moving boundaries, such as the dendrite formation at the anode-electrolyte interface.
A materials informatics approach was used in a discovery mode to identify promising material combinations for the electrolyte. Our research focused on developing the materials informatics framework for electrolyte solutions. The developed framework is general and is applicable to other materials systems for batteries and for other application areas. The informatics techniques have predictive capabilities based upon an electrolyte materials knowledge base, allowing us to evaluate materials based on their thermodynamic properties and the desired properties needed for a specific application.
Modeling Diffusivity in Catalyst Layer of a PEMFC Based on a Unit Cell Approach
Authors: Salari Sina , McCague Claire , Tam Mickey , Stumper Jürgen , Bahrami Majid 
Published: February 2020

Polymer electrolyte membrane fuel cells (PEMFC) convert the reaction energy of hydrogen and air to electricity without harmful emissions. PEMFC rely on a membrane-electrode assembly (MEA) constructed from multiple layers of micro/nano porous materials and associated interfaces. The MEA includes a polymer electrolyte membrane (PEM) that conducts protons, a composite nano-structured catalyst layer (CL), and a fibrous gas diffusion layer (GDL) that distributes reactant gases and collects current. The production cost and limited durability of the platinum catalyst layer is a significant challenge for the commercialization of hydrogen fuel cells. The greater the activity of the Pt nanoparticles, the lower the required Pt loading on the carbon support, and the lower the production costs for the catalyst layer. Hydrogen and oxygen reactants diffuse to the catalyst Pt particles. Existing models for the diffusivity of CL are either not accurate or computationally demanding, making them difficult to use for CL optimization. In this study, the CL is represented by unit cells based on porosimetry and analysis of SEM images of CL structure. The mass diffusion problem is analytically solved for the unit cell to calculate effective diffusivity of CL. Unlike other simple models which use porosity as the only input to calculate diffusivity the proposed model considers the pore size distribution as well as structure of CL, which improves the accuracy. The model presented in this study shows results within acceptable accuracy respect to published experimental data.
Self-Assembly of Nanoparticle and Block Polymer Electrolytes
Authors: Villaluenga Irune , Inceoglu Sebnem , Jiang Xi , Chen Xi chelsea , Devaux Didier , Balsara Nitash P. 
Published: February 2020

Electrolytes used in rechargeable lithium-ion batteries are mixtures of lithium salts and alkyl carbonate solvents. The high ionic conductivity of these electrolytes is well-suited for several applications including cellphones and laptops. Unfortunately, these electrolytes are flammable and this limits our ability to use lithium batteries in large devices like electric vehicles. Solid block copolymer electrolytes are inherently less flammable and thus better suited for large scale applications.1 The ionic conductivity of block copolymer electrolytes is governed by the tortuosity of the conductive pathways, which is related to the morphology of block copolymers.2,3 Therefore, the ionic conductivity can be controlled by tuning the morphology. One approach consists in the addition of nanoparticles to block copolymer electrolytes. The morphology of these systems depends on the arrangement and the location of the nanoparticles in the block copolymer.4

Here, we describe the effect of the addition of functionalized silsesquioxane nanoparticles on the morphology and electrochemical properties of polystyrene-b-poly(ethylene oxide) diblock copolymer electrolytes.
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2007, 40, 4578.
[3] Hallinan, D. T.; Balsara, N. P. Annu.
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[4] Warren, S. C.; DiSalvo, F. J.; Wiesner, U. B. Nat. Mater.
2007, 6, 156.
(Invited) A Visible Light-Active Titania Photocatalyst with Rhodium As a Built-in Redox Mediator
Authors: Ohtani Bunsho , Kuncewicz Joanna 
Published: February 2020

Titanium(IV) oxide (titania) constitutes one of the most common base for highly active photocatalysts due to the proper electronic structure and physicochemical properties. The main drawback of this wide bandgap semiconductor is the range of the effective light which is limited to ultraviolet radiation. Bulk modification of titania with some of the transition metal ions allows to extend its photocatalytic activity toward visible light, however, the origin of the modification is often not sufficiently explained. Although a lot of studies were devoted to bulk modification of titania, the questions of the essential conditions for true doping and its influence on the photocatalytic activity still remain.
Utilization of rhodium (Rh) species for titania modification brings attention because of the similarity in ionic radius of Rh with that of titanium (Ti) with equivalent valency. Trivalent Rh may also strongly influence the light absorption properties of titania and several titania-based photocatalysts prepared by impregnation or doping with Rh species have been already reported [1-4]. Present work reports detailed studies on properties and photocatalytic activity of Rh-modified titania with respect to nature of modification depending on Rh content and preparation conditions.
Rh-modified titania (Rh-TiO2) was obtained by impregnation of titania (Showa Titanium FP-6, anatase) with Rh(III) chloride followed by calcination in air or oxygen at various temperatures. The preparation process led to the improvement of visible-light (> 420 nm) photocatalytic activity of base titania for oxidative decomposition of acetaldehyde (AcH) in air. The titania crystalline structure, photoabsorption properties and photocatalytic performance depended strongly on the Rh content. Figure 1 shows the activity of Rh-TiO2 as a function of molar ratio of rhodium/titanium (Rh/Ti). At extremely low Rh concentration, the activity was improved, presumably due to the participation of visible light-induced interfacial electron transition from isolated Rh(III) to conduction band of titania. In the middle range of Rh concentration, the activity was rather reduced by possible hindrance of photoabsorption of titania in its absorption edge with deposition of rhodium oxide. Relatively higher concentration (1mol%) induced enhancement of the activity, which might be attributed to "true" doping, substitution of Ti with Rh in titania.
The results of detailed studies on influence of rhodium amount and calcination conditions on anatase to rutile transformation and visible light induced photocatalytic activity, including photo-sensitization mechanism, will be discussed [5].
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[4] S. Kitano, K. Hashimoto, H. Kominami, Catal. Today, 164 (2011) 404.
[5] J. Kuncewicz, B. Ohtani, Chem. Commun., in press.
(Invited) Fabrication of Micro- and Nanostructures for High Efficiency Energy Conversion By Using Anodic Porous Alumina
Authors: Masuda Hideki , Kondo Toshiaki , Yanagishita Takashi 
Published: February 2020

The fabrication of micro - and nanostructured materials with controlled geometrical structures has attracted increasing interest for the preparation of various types of energy conversion devices with high efficiencies. The use of the material, which has naturally occurring ordered structures, is effective for the fabrication of the micro- and nanostructures of various kinds of materials. Anodic porous alumina, which is formed by anodization of Al in acidic solution, is a promising candidate for the fabrication of micro- and nanostructured materials with controlled geometrical structures1,2. One of commonly used process for the fabrication of micro- and nanostructures using anodic porous alumina is a template synthesis3,4. This process can generate the micro- and nanostructures with controlled geometrical structures, which are useful for the fabrication of high efficient energy conversion devices. However, the problem of the usual template synthesis is the low throughput due to the difficulty of the repeated use of the template. To solve this problem, we have been studying the new types of processes, which allow the high throughput formation of micro- and nanostructures. In the present report, recent results concerning the high throughput fabrication process for the micro- and nanostructures of metals and metal oxides, which can be applied to the energy conversion devices. The processes include the molding fabrication process for metal nanowires, and the membrane emulsification for uniform sized nanoparticles of metal oxides5,6 by using anodic porous alumina. These processes allow the high throughput fabrication of micro- and nanostructures because the starting structures of anodic porous alumina can be used many times. The obtained micro- and nanostructures will be useful for the fabrication of energy conversion devices with high efficiency due to their precisely controlled geometrical fine structures.
1. T. Yanagishita, K. Nishio, and H. Masuda, Appl. Phys. Express, 1, 067004 (2008).
2. H. Masuda and K. Fukuda, Science, 268, 1466 (1995).
3. K. Yasui, T. Morikawa, K. Nishio, and H. Masuda, Jpn. J. Appl. Phys., 15, L469 (2005).
4. T. Kondo, T. Fukushima, K. Nishio, and H. Masuda, Appl. Phys. Express, 2, 125001 (2009).
5. T. Yanagishita, R. Fujimura, K. Nishio, and H. Masuda, Langmuir, 26, 1516 (2009).
6. T. Yanagishita, Y. Maejima, K. Nishio, and H. Masuda, RSC Adv., 4, 1538 (2014).
A New Binding Mode in the Dynamic Coordination Chemistry of Porphyrins
Authors: Boitrel Bernard , Le Gac Stéphane , Ndoyom Victoria 
Published: February 2020

In our on-going research program dedicated to the coordination of various cations of medical interests, we have been studying different types of porphyrinic architectures.1 Among these cations, bismuth appears as a plausible candidate for alpha-radiotherapy.2 Considering the decay scheme of its 213 isotope, it is obvious that the coordination chemistry of bismuth3 and lead4 and to some extent, thallium are somehow related and exhibit some similarities.
For instance, we have shown that an unprecedented transmetalation mechanism involving a daughter radionuclide is expected to increase the rate of 213Bi incorporation leading to 1Bi.5

Moreover, we will detail and demonstrate that this peculiar behaviour is rationalized by a translocation-coupled transmetalation mechanism, leading to the formation of a dinuclear complex in which coexist the long-known out-of-plane (OOP) coordination mode and the newly reported hanging-atop (HAT) coordination mode.6

This HAT binding mode is found in both homo- and heterobimetallic complexes with lead and bismuth (see both X-ray structures above) and represents the prerequisite for metal migration processes according to which these dinuclear complexes behave as allosteric Newton’s Cradle-like devices (NCD).7 This NCD behaviour can be extended to other metal complexes and controlled and/or initiated in different ways.8

1. Lemon, CM; Brothers PJ.; Boitrel B. Dalton Trans.
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4. Halime Z; Michaudet L; Lachkar M; Brossier P; Boitrel B. Bioconjugate Chem., 2004, 15, 1193-1200.
5. Le Gac, S.; Najjari, B.; Motreff, N.; Remaud-Le Saec, P.; Faivre-Chauvet, A.; Dimanche-Boitrel, M.-T.; Morgenstern, A.; Bruchertseifer, F.; Lachkar, M.; Boitrel, B. Chem. Commun.
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6. Le Gac S.; Najjari B.; Fusaro L.; Roisnel T.; Dorcet V.; Luhmer M.; Furet E.; Halet J.-F.; Boitrel B. Chem. Commun., 2012, 48, 3724-3726.
7. Najjari B.; Le Gac S.; Roisnel T.; Dorcet V.; Boitrel B. J. Am. Chem. Soc.,
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8.
a) Le Gac, S.; Dorcet, V.; Fusaro, L.; Boitrel, B., Chem. Eur. J.
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19, 13376-13386. b) Le Gac, S.; Najjari, B.; Dorcet, V.; Roisnel, T.; Fusaro, L.; Luhmer, M.; Furet, E.; Halet, J.-F.; Boitrel, B., Chem. Eur. J.
2013,
19, 11021-11038. c) Le Gac, S.; Fusaro, L.; Roisnel, T.; Boitrel, B., J. Am. Chem. Soc.
2014,
136, 6698-6715.

Figure 1