bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Dynamic Change of the Pore Size Distribution in Porous Electrodes of Lithium-Oxygen Batteries during Discharging
Authors: Li Xianglin 
Published: February 2020

The specific energy of lithium-oxygen (Li-O2) battery is usually less than 10% of the theoretical specific energy due to the limitation of mass (particularly oxygen) transfer in the porous electrode. The insoluble Li2O2 generated/depleted during the battery discharging/charging significantly changes the pore size distribution, mass transfer properties of the porous electrode, and the specific energy of the battery. This study develops a two dimensional, transient, and non-isothermal computational fluid dynamics model to simulate the mass transfer and electrochemical reactions within the battery and quantitatively calculate the change of the pore size distribution at various locations of the porous electrode of the battery.
The pore size distribution of a home-made gas diffusional electrode (GDE) is measured by nitrogen adsorption and mercury intrusion tests and the distribution is fitted with a log normal distribution. The scale factor of and the shape factor of the fitted log normal distribution are -2.5 and 0.5, respectively. The corresponding mean value of the pore size is 93 nm. To make the model manageable, the infinite pore sizes are binned into 7 bins and each bin has a cumulative distribution function (CDF) to describe the probability of a pore in the electrode that has the size defined by the bin. The number of bins has also been increased to 10 and 15 to make sure that the results are independent from the number of bins.
The solid products from the oxygen reduction reaction (ORR), which are mainly Li2O2, deposits on the electrode surface and redistributes the pore size in the electrode. Since the Li2O2 is generated non-uniformly in the electrode, properties of the porous electrode such as the average pore size, effective surface area, permeability, and electrical conductive resistance change non-uniformly in the electrode. This model simulates the discharging of a Li-O2 battery at 0.2 mA/cm2 for 520 hours, which equivalents to the specific energy density of about 2300 mAh/gcarbon, and can capture the non-uniform property change in the porous electrode. The model results show that properties of pores close to the air side change the most due to fast reactions in these pores. The permeability of pores close to the air side decreases from 7.92×10-15 m2 to 4.46×10-15 m2 and the average pore size decreases from 93 nm to 61 nm after the discharging.
Development of Novel Lithium Ion Battery Electrolytes for Silicon Anodes
Authors: Strand Dee , Zhu Ye , Caldwell Marissa , Cheng Gang 
Published: February 2020

Wildcat Discovery Technologies is developing novel electrolyte additives and noncarbonate formulations that yield improved solid electrolyte interphase (SEI) layers on silicon anodes. The large volumetric changes in silicon during charge/discharge cycles result in mechanical disruption of conventional SEI’s leading to rapid capacity fade as the cell cycles. Novel additives are demonstrated to improve cycle life of silicon based materials by forming less brittle, more mechanically robust SEI passivation layers. Since propylene carbonate (PC) is not expected to form an effective SEI layer, the additives are tested with PC to determine their efficacy. Wildcat’s high throughput electrolyte formulation, cell assembly, and test capabilities enable the evaluation of hundreds of additives in a very short timeframe.
Once effective SEI additives are identified in a PC-based formulation, other non-SEI forming solvents can be evaluated. Since the additives are effective without solvent participation in SEI formation, solvents can be considered that may not be reductively stable on the anode – and also opens the possibility to more oxidatively stable or less flammable solvents. Wildcat has evaluated hundreds of combinations of noncarbonate solvents with its initial silicon anode SEI additives.
This presentation will focus on the results of the additive improvement to cycle life in NMC//Si full cells, and illustrate the opportunities for novel solvent combinations.
Hetro-Atom Doped CNTs As Metal Free Electrocatalyst for Oxygen Reduction Reaction in Alkaline Fuel Cell
Authors: Nandan Ravi , Nanda Karuna Kar 
Published: February 2020

Search for eco-friendly sustainable solutions to the alarming energy calamity on both the small and large scale for portable electronic to automobile industry has become one of the most critical challenges on the way to decrease our dependence on traditional fossil fuels based energy sources. In this regard fuel cells provide an alternative solution for clean and green approach. The oxygen reduction reaction (ORR) a half cell reaction taking place at cathode being sluggish in nature requires catalyst to enhance the kinetics. ORR plays a vital role in controlling the performance of a fuel cell. Hence there is a huge demand to develop efficient ORR electrocatalysts for practical applications of the fuel cells. Traditionally, Pt-based electrocatalysts are most suitable for ORR because of their relatively low overpotential and high current density. But the limitation arises because they suffer from serious intermediate tolerance, anode crossover, poor operating stability in an aggressive electrochemical environment. Furthermore, high cost and limited supply hinder wide spread commercialization. This has driven the extensive search for alternative low-cost and high-performance ORR electrocatalysts.
Here, we report a facile one-step synthesis of nitrogen-, boron-doped and nitrogen & boron co-doped carbon nanotubes (CNTs) by pyrolysis and used as platinum-free cathode catalyst in direct methanol fuel cell (DMFC). Doped CNTs show excellent catalytic activity and methanol tolerance towards ORR which prompted us to study its fuel cell application. Doped CNTs used as cathode catalyst in DMFC shows comparable performance with the reported results based on state of art commercial platinum catalyst. Overall, the excellent methanol tolerance and good durability of doped CNTs based DMFC suggest a potential to replace platinum for making fuel-cell technology commercially viable.
Novel Flexible Sulfur Wire Fabrics (FSF) for Lithium-Sulfur Batteries
Authors: Jampani Hanumantha Prashanth , Shanthi Pavithra Murugavel , Gattu Bharat , Kumta Prashant N 
Published: February 2020

Introduction

Lithium sulfur and lithium-air batteries hold much promise for the future of batteries on account of their theoretical capacities of 2567 and 3505 Wh/kg respectively(1). The dissolution of sulfur through the formation of soluble polysulfides and the poor electronic conductivity of sulfur are however, major problems hindering Li-S battery progress (1-3). In addition, particle fracture and delamination as a result of repeated volumetric expansion and contraction have also been identified as factors responsible for poor long term performance(4, 5). In our previous work on lithium-sulfur batteries, we have shown the effectiveness of using a thin Li-ion conducting barrier layer in improving the cycling characteristics(6).
In this work, we develop a unique strategy to directly prepare sulfur wire mattes (Figure 1) capable of being spun as yarn and thereupon being used directly in the form of ‘textile fabric batteries’. Using these wires, we generate two other morphologies to specifically tackle fade and conductivity issues existing in sulfur cathodes. This results in sulfur cathodes with high electronic conductivity, minimal volumetric expansion and improved rate capabilities and cyclability. In addition, the electrodes that we use in this study allow us to obtain high areal capacities. Figure 1 shows SEM and EDAX map of the same. Results of these studies will be presented and discussed.

Captions

Figure 1:(a) Scanning electron microscopy image of the sulfur wires (b) EDAX map indicating the Sulfur distribution.

References

1. P. G. Bruce, S. A. Freunberger, L. J. Hardwick and J.-M. Tarascon, Nature Materials, 11, 19 (2012).
2. J. Cabana, L. Monconduit, D. Larcher and M. Rosa Palacin, Advanced Materials, 22, E170 (2010).
3. B. Scrosati and J. Garche, Journal of Power Sources, 195, 2419 (2010).
4. L. Ji, M. Rao, S. Aloni, L. Wang, E. J. Cairns and Y. Zhang, Energy & Environmental Science, 4, 5053 (2011).
5. Z. Wei Seh, W. Li, J. J. Cha, G. Zheng, Y. Yang, M. T. McDowell, P.-C. Hsu and Y. Cui, Nat Commun, 4, 1331 (2013).
6. P. J. Hanumantha, B. Gattu, O. Velikokhatnyi, M. K. Datta, S. S. Damle and P. N. Kumta, Journal of The Electrochemical Society, 161, A1173 (2014).

Figure 1
Bond Pathway Analysis of NMR Spectra for Li1.2Mn0.4Co0.4O2: Pristine Material
Authors: Iddir Hakim , Key Baris , Dogan Fulya , Russell John , Long Brandon R. , Bareno Javier , Benedek Roy 
Published: February 2020

NMR has been applied extensively to lithium ion battery cathode materials, of which layered-layered composites xLi2MnO3•(1-x)LiMO2 (M=Mn,Co,Ni) are of particular interest, owing to their high energy density. In this work, NMR spectra are measured for the model layered-layered system xLi2MnO3•(1-x)LiCoO2 and Bond-Pathway-model analysis is applied to elucidate the atomic arrangement and domain structure of this material (in its pristine state, before electrochemical cycling). The simplest structural element of a domain consists of a stripe of composition LiMn2 parallel to an in-layer crystallographic axis in a metal layer of the composite. A simple model of the composite structure may be constructed by a superposition of such stripes in an LiCoO2 background. We show that such a model can account for most of the features of the observed NMR spectra.
Support from the Vehicle Technologies Program U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy.
In Situ Raman Microscopy of Metal Chloride Formation for Metal-Chloride Batteries
Authors: Hardwick Laurence J , Hughes Stephen , Heavens Steve 
Published: February 2020

Recently there has been a revived interest in high temperature molten salt battery systems, particularly sodium-sulphur and sodium metal-chloride, SMC. In particular SMC batteries have high theoretical specific energies and open circuit potentials (787 Whkg-1 and 2.58 V for Ni cell chemistry). They comprise a liquid Na anode, solid beta-alumina electrolyte and a metal chloride cathode which also contains sodium tetrachloroaluminate, NaAlCl4 as a secondary electrolyte [1]. However, battery performance is constrained by cathode underperformance resulting in obtainable specific energies in the region of 120 Wh kg-1 [2]. The best performing cathode formulations contain both Fe and Ni as active cathode materials, with an excess of Ni to prevent Cl2 liberation on overcharge. The excess Ni and NaAlCl4 increase the weight of the battery, while not contributing to the output, therefore reducing the specific energy. Additional reductions in performance are attributed to the cell chemistry occurring in the cathode. Alternative cathode formulations could enhance the performance of this battery technology and enable its application for grid storage. This should be achieved while maintaining the existing technologies high abundance of raw materials used in the manufacturing process.
This talk presents our research on the chemical processes occurring in the cathode for cell chemistries based on various transition metals, particularly Fe, Co, Ni, Zn and Cu, over the temperature range 200°C to 400°C. Cyclic voltammetry on polished coated wire tip electrodes have been used to determine the diffusion coefficients of the metal ions diffusing through their respective metal chloride layers. In situ Raman spectroscopy has been undertaken to develop a better understanding of the processes occurring to form the metal chlorides.
[1] J. Coetzer, J. Power Sources (1986) 18 377
[2] R.C. Galloway & S. Haslam, J. Power Sources (1999) 80 164
A Novel Model of Water Hydration in PEM Fuel Cell in Dynamic Operations
Authors: Liso Vincenzo , Nielsen Mads Pagh 
Published: February 2020

Polymer membrane (PEM) fuel cell requires good hydration in order to deliver high performance and ensure long life operation. Water is essential for membrane proton conductivity which increases by nearly six orders of magnitude from dry to fully hydrated. Adequate water management in PEM fuel cell is crucial in order to avoid an imbalance between water production and water removal from the fuel cell.
In the present study, a novel mathematical zero-dimensional model has been formulated for the water mass balance and hydration of a polymer electrolyte membrane. This model incorporates all the essential fundamental physical and electrochemical processes occurring in the membrane electrolyte and considers the water adsorption/desorption phenomena in the membrane. The effect of diffusivity model, surface roughness and water content driving force is considered. The model is validated against available experimental data.
In the results it is shown that the fuel cell water balance calculated by this model display better fit with experimental data-points compared with model where only water transport equilibrium were considered. We conclude that this discrepancy is due a different rate of water transport when membrane absorption/ desorption is considered in the model. The model becomes useful when studying fuel cells in dynamic conditions.
Coating Ti-V-Cr Thin Film on the Anode Gas Diffusion Layer to Improve the Performance of Proton Exchange Membrane Fuel Cells
Authors: Fang Sheng-Yu , Huang Rong-Hsin , Teoh Lay Gaik , Hsueh Kan-Lin , Chao Wen-Kai , Tsai Du-Cheng , Yang Tse-Ning , Shieu Fuh-Sheng 
Published: February 2020

In this study, a TiVCr hydrogen storage alloy was coated onto the anode gas diffusion layer (GDL) of proton exchange membrane fuel cells (PEMFCs) by direct-current sputtering to improve cell performance and durability. Scanning electron microscopy analysis indicated that the GDLs are well coated and that the TiVCr coating shows pyramidal protrusions. The single-cell performance of PEMFCs, in which the GDLs were coated with TiVCr hydrogen storage alloy as the anode, was investigated at cell temperatures of 25 and 65 °C (non-humidification and full-humidification conditions, respectively). The membrane-electrode assembly (MEA) with TiVCr hydrogen storage alloy-coated GDL (10 min sputtering time) exhibited optimal performance at 25 and 65 °C, with power densities 18.49% and 43.67%, respectively, higher than that without TiVCr hydrogen storage alloy coating. The MEA with the TiVCr-coated GDL obtained by 60 min of sputtering exhibited 90.6% greater durability under no-hydrogen flow conditions than the MEA without the TiVCr hydrogen storage alloy coating. These results demonstrate for the first time that GDLs coated with a hydrogen storage alloy such as TiVCr may be applied in PEMFCs to improve their performance and durability.
A Phosphonium Bis(fluorosulfonyl)Imide-Based Ionic Liquid Electrolyte for Lithium Batteries: Tailoring Composition and Performance
Authors: Girard Gaetan Marc-Antoine , Hilder Matthias , Whitbread Kristina , Nucciarone Donato , Zavorine Serguei , Moser Michael , Forsyth Maria , MacFarlane Douglas R , Howlett Patrick C 
Published: February 2020

The electrolyte is one of the key components of an energy storage device required to achieve high reliability and safety as well as high energy density. Lithium batteries have become one of the most common technologies for portable electronics and are making their way into electric vehicles and stationary storage.
The interaction of a phosphonium-based room temperature ionic liquid (RTIL) with a lithium salt, lithium bis(fluorosulfonyl)imide, as a function of temperature and concentration has been evaluated and correlated with the mechanism of lithium transport. The formulated system could be a potential safe electrolyte for lithium batteries to meet the challenges presented by emerging battery technologies. We have found that the highly conductive and fluid phosphonium ionic liquid based on FSI anion gives excellent performance for lithium batteries, particularly for electrolytes containing higher lithium salt concentrations. The relationship between the physical properties and the mobility of the species present in solution has also been investigated.
A combination of differential scanning calorimetry (DSC), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), nuclear magnetic resonance (NMR) and X-Ray Photoelectron (XPS) spectroscopy techniques were used to characterise these novel electrolytes. Impedance spectroscopy measurements established that the addition of lithium bis(fluorosulfonyl)imide to the ionic liquid decreased the ionic conductivity over a range of temperatures (from -20 to 120°C) and this was related to an increase of the dynamic viscosity. Interestingly, the mechanism of lithium transport is dependent on the lithium concentration. It is also evident from EIS and NMR that the mobility of the species in solution is dependent on lithium salt concentration, and this impacts the electrolyte transport properties and mechanism. These data give an insight into the fluidity of the species when introducing lithium into the system.
In terms of lithium electrodeposition, cyclic voltammetry (CV) is a powerful tool to better understand the electrochemical stability of lithium metal in the electrolyte to demonstrate the viability of using a lithium based anode in a battery. Cyclic voltammetry measurements showed that reversible electrodeposition of lithium at a nickel electrode could be observed at very high lithium salt concentrations (up to 3.8 mol.kg-1 of lithium salt) at 25°C. An increase of lithium concentration also revealed an improved efficiency and electrochemical stability at more negative potentials. These data provided an insight into the fundamental mechanism of lithium transport. The results suggest that the binary systems behave as a potential electrolyte including improved safety and stability.
(Invited) Push-Pull
p
-Extended porphyrins for Solar Energy Conversion
Authors: Wang Hong , Jinadasa Raja Gabadage , Matus Alex , Zou Shouzhong , Kerr Lei 
Published: February 2020

Dye-sensitized solar-cells (DSSCs) have emerged as one of the most promising photovoltaic technologies in solar energy conversion.1-3 Despite of the advances in the last two decades, organic dyes having better overlap with the solar spectrum and high thermostability are still in high demands. p-Extended porphyrins appear to be ideal candidates to satisfy these criteria as sensitizer for DSSCs. In this work, a novel class of push-pull
p-extended porphyrins was prepared. To our knowledge, the porphyrins presented here represent the first examples of pull-pull
p-extended porphyrins. The push-pull functional groups installed at the extended porphyrin periphery are expected to facilitate intramolecular and intermolecular electron transfer. Red-shifted and broadened absorptions are also expected due to the push-pull groups along with the p-extension. The design and synthesis of these organic materials take advantage of the chemistry of bromoporphyrins4,5 and a palladium (0) catalyzed cascade reaction developed in the Wang group.6-8 The electronic and optical properties of these p-extended porphyrins were measured using UV-Vis spectroscopy, life-time and steady state fluorescence spectroscopy, and cyclic voltammetry. DFT calculations were also performed for these porphyrins. The solar to electricity conversion efficiency of these porphyrins in DSSC were evaluated.

Reference

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L. Jiang, R. A. Zaenglein, J. T. Engle, C. Mittal, C. S. Hartley, C. J. Ziegler, H. Wang, Chem. Commun. 2012, 48, 6927-6929

L. Jiang, J. T. Engle, L. Sirk, C. S. Hartley, C. J. Ziegler, H. Wang, Org. Lett., 2011, 13, 3020-3023.
(Invited) Uniform Nanostructures for Highly Efficient and Reproducible Perovskite Solar Cells
Authors: Han Liyuan , WU Yongzhen , Yang Xudong , Chen Han , Islam Ashraful 
Published: February 2020

Organo-lead trihalide perovskites (CH3NH3PbX3, X = I, Br or Cl) as light absorption materials have attracted great attention recently in photovoltaic research. By virtue of their high absorptivity and long carrier diffusion length, the power conversion efficiency (PCE) was rapidly increased from 3.8% to above 17% within the short five years. In this presentation, I will report some our latest researches in this field.
Firstly, the hole-blocking layer is required to prevent holes formed in the perovskie or HTL layer from reaching the FTO electrode, which would otherwise short-circuit the cell. Optimization of the blocking layer is a key factor for improving the device performance of perovskite solar cells. We systematically examined the different blocking layer fabricated by three different methods. The surface morphology and film resistance shows that atomic layer deposition (ALD) based TiO2 compact layer contains much lower density of nano-scaled pinholes with respect to spin-coating and spray pyrolysis ones. The ALD-TiO2 layer acts as an efficient hole-blocking layer in perovskite solar cells, which offers a large shunt resistance and enables a high power conversion efficiency of 12.56%.
Secondly, uniform, highly crystalline perovskite film is important for sequential deposition processed perovskite solar cells. We develop a new method to enable an efficient deposition of perovskite film with enhanced conversion rate and surface morphology. By this approach, the energy conversion efficiency of mesoporous-free perovskite solar cells was twice as high as that of using traditional method.

Figure 1