bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Ionic Liquid Anion Type in the Performance of Solid Polymer Electrolytes Based on Poly(vinylidene fluoride-trifluoroethylene)
Authors: Costa C. M. , Leones R. , Machado A. V. , Esperança J.M. S.S. , Silva M. M. , Lanceros-Méndez Senentxu 
Published: February 2020

Solid polymer electrolytes (SPEs) or ionic conductors were proposed by Gray in 1997 and are typically composed by polymer with salts in its constitution, finding applications in the areas of batteries, sensors/actuators and supercapacitors, among others. Recently, salts have been substituted by ionic liquid (ILs) due to their excellent properties, including high ionic conductivity (~10-3 – 10-2 S.cm-1), almost null volatility, null flammability, thermal stability, wide electrochemical windows (~4-6 V) and being environmental friendly [1-2].
The excellent properties of poly(vinylidene fluoride-co-trifluoroethylene), P(VDF-TrFE), as solid polymer electrolyte with (N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide, [N111 2(OH)][NTf2] where demonstrated in [3], where the addition of the ILs affects the microstructure, thermal stability and ionic conductivity of the polymer membrane.
In this work, the effect of different anions within the ionic liquid for the development of SPE based on P(VDF-TrFE) has been investigated. 1-ethyl-3-methylimidazolium acetate, [C2mim][OAc], 1-ethyl-3-methylimidazolium triflate, [C2mim][(CF3SO3)3], 1-ethyl-3-methylimidazolium lactate, [C2mim][Lactate], 1-ethyl-3-methylimidazolium thiocyanate, [C2mim][SNC] and 1-ethyl-3-methylimidazolium hydrogen sulphate [C2mim][HSO4] have been used for this purpose and the SPE were prepared by thermaly induced phase separation (TIPS). The thermal and electrical properties of the SPE strongly depend on the selected IL through their different interactions with the polymer matrix. The room temperature ionic conductivity increasing in the following way for the different anions: [SNC] > [CF3SO3)3] > [HSO4] > [Lactate] > [OAc].

Acknowledgments

This work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PEST-C/FIS/UI607/2011, PEST-C/QUI/UI0686/2013, PEST-OE/EQB/LA0004/2011, and grants SFRH/BD/68499/2010 (C.M.C.) and SRFH/BD/90366/2012 (R.L.). The authors also thank funding from Matepro –Optimizing Materials and Processes”, ref. NORTE-07-0124-FEDER-000037”, co-funded by the “Programa Operacional Regional do Norte” (ON.2 – O Novo Norte), under the “Quadro de Referência Estratégico Nacional” (QREN), through the “Fundo Europeu de Desenvolvimento Regional” (FEDER). The authors thank Solvay for kindly supplying the high quality materials.

References

[1] F.M. Gray, Solid Polymer Electrolytes: Fundamentals and Technological Applications, VCH Publishers Inc., 1991.
[2] J.M. Tarascon, M. Armand, Nature
414 (2001) (6861) 359.
[3] R. Leones, C.M. Costa, A.V. Machado, J.M.S.S. Esperança, M.M. Silva, S. Lanceros-Méndez, Solid State Ionics 253 (2013) 143.
Underlying Mechanisms of Plasmon-Enhanced Photocatalysis and Photoelectrochemical Performance
Authors: Wu Nick , Cushing Scott Kevin , Li Jiangtian 
Published: February 2020

Plasmonic metal-semiconductor composite photocatalysts and photoelectrodes have received extensive attention of researchers. This talk describes how surface plasmon resonance (SPR) enhances the light absorption and transfers the plasmonic energy from the metal to the semiconductor, which induces the charge separation and refrains the charge recombination in the semiconductor. This talk will present three plasmon-enhanced photocatalysis mechanisms: photonic enhancement, direct electron transfer (DET) and plasmon-induced resonance energy transfer (PIRET) mechanism. The talk will give an example of solar hydrogen generation by plasmonic metal-semiconductor composites.

References

[1] J. Li, S. K. Cushing, J. Bright, F. Meng, T. R. Senty, P. Zheng, A. D. Bristow, N. Q. Wu, ACS Catalysis, 3 (2013), 47-51
[2] S. K. Cushing*, L. A. Hornak, J. Lankford, Y. Liu, N.Q. Wu, Applied Physics A, 103 (2011), 955-958.
[3] Li, J.; Cushing, S. K.; Zheng, P.; Meng, F.; Chu, D.; Wu, N. Q. Nature Communications, 2013, 4, 2651, DOI: 10.1038/ncomms3651.

Acknowledgement:

This work was supported by the National Science Foundation (CBET-1233795). The resource and facilities used in this work were partially supported by Research Challenge Grant from the State of West Virginia (EPS08-01), NSF (EPS 1003907), and the West Virginia University Research Corporation and the West Virginia EPSCoR Office. The use of WVU shared facilities is greatly appreciated.
Light Management in Extremely Thin Photoelectrode Architectures
Authors: Doiron Curtis , Bahauddin Shah M , Robatjazi Hossein , Thomann Isabell 
Published: February 2020

Concepts from metamaterials, plasmonics and nanophotonics are expected to be highly beneficial for the design of future solar energy conversion devices. Here, I will describe how we use these concepts to design advanced photoelectrode architectures for two challenging photocatalytic reactions: water splitting and CO2 reduction. We focus on the light management aspect in extremely thin absorber structures to achieve broadband omnidirectional solar absorption while carefully choosing materials systems that allow for efficient charge separation and catalytic activity.
I will discuss the benefits of employing thin-film absorber photoelectrodes, which include the potential for enhanced charge carrier extraction, increased photovoltages and the possibility to exploit hot carriers for purposes of driving chemical reactions. I will also discuss our analytical models and three-dimensional electromagnetic simulations that we employ to meticulously engineer light absorption in two-dimensional materials and plasmonic metal nanostructures. Complementing these materials and device design efforts, we are developing an experimental characterization toolbox, including photoelectrochemical techniques and ultrafast spectroscopic techniques that will allow us to analyze the influence of distinct plasmon-induced effects (e.g., near-field concentration, hot charge carriers, heat generation) and non-plasmonic effects (e.g., sample morphology, catalytic and electronic effects, charge separation and recombination) on photocatalysis.
High Power Density Vanadium Flow Batteries with Laser-Cut Flow Field Patterns on Carbon Paper Electrodes
Authors: Agar Ertan , Dennison Christopher R , Kumbur Emin Caglan 
Published: February 2020

A major technical issue that limits the commercialization of vanadium redox flow batteries (VRFBs) is their relatively low power density which often results in higher cost [1-2]. Recently, significant research has been focused on exploring new electrode materials, which is the key component affecting the power density of these systems. Recently, Mench and co-workers utilized carbon paper as a potential electrode material for these systems due to its reduced thickness and high active surface area (as compared to conventional carbon felt electrodes), which enables reduced resistance with improved limiting current and power density. Using carbon paper electrodes, they were able to demonstrate a peak power of 557 mW cm-2, which is significantly higher than what had previously been reported in literature [3-5].
Although they provide higher power density, one drawback of carbon paper electrodes is that they have a lower porosity and reduced pore size, which can potential promote mass transport limitations. In a recent study, our group investigated the effects of macro-scale circular perforations on the power density and performance of the carbon paper electrodes to explore possible mitigation strategies for minimizing mass transport losses [6]. We observed that laser-perforation of carbon paper electrodes improved the power density and performance of the VRFB cell up to 30 % when compared to raw (non-perforated) carbon paper, despite a loss in total surface area.
Motivated by the results of our previous work, in this study, we go beyond simple circular perforations and utilize laser manufacturing techniques to produce more complicated geometries and flow patterns on carbon paper electrodes to identify an optimum perforation geometry that would further minimize the transport losses and yield higher power density. Specifically, we study several common flow field patterns, varying the design and geometry of the transport channels. The effect of flow field pattern on the peak power density and limiting current is investigated with the goal of providing further understanding of the coupling between the surface area, performance and mass transport losses in VRFB electrodes.
References
[1] N. Trung, R. F. Savinell. J. Electrochem. Soc.19 (2010) 54-56.
[2] E. Agar, C. R. Dennison, K. W. Knehr, E. C. Kumbur, J. Power Sources. 225 (2013) 89-94.
[3] D. S. Aaron, Q. Lui, Z. Tang, G. M. Grim, A. B. Papandrew, A. Turhan, T. A. Zawodzinski, M. M. Mench, J. Power Sources. 206 (2012) 450-453.
[4] Q. H. Lui, G. M. Grim, A. B. Papandrew, A. Turhan, T. A. Zawodzinski, M. M. Mench. J. Electrochem. Soc. 159 (2012) 1246-1252.
[5] M. P. Manahan, Q. H. Lui, M. L. Gross, M. M. Mench, J. Power Sources. 222 (2013) 498-502.
[6] I. Mayrhuber, C. R. Dennison, V. Kalra, E. C. Kumbur, J. Power Sources. In press, DOI: 10.1016/j.jpowsour.2014.03.007.
GPU-Accelerated Pore-Scale Transport Resolved Model for Flow-Assisted Battery Design
Authors: Andersen Charles , Qiu Gang , Kandasamy Nagarajan , Sun Ying 
Published: February 2020

Redox flow batteries (RFBs) have emerged as grid-scale energy storage technology used in intermittent renewable energy resource applications due to their decoupled power and energy sizing and long life cycles. However, redox flow batteries suffer from low energy and power densities, which may be resolved by improving electrode design. As such, gaining insight into the effect of the electrode microstructure by using computer simulations is paramount in improving RFB performance. Such design optimization would not be possible through experimental procedure due to cost, time, or availability of materials.
Existing volume-averaged models treat the electrode/electrolyte matrix as a homogenous medium of uniform porosity. By contrast, we have developed a pore-scale simulation that distinctly accounts for the separate electrode/electrolyte phases. Our model requires no simplification or assumptions regarding the electrode morphology, and enables us to carry out detailed studies into the effects of the precise electrode microstructure with unprecedented fidelity. A comparison between the two approaches is shown in plots of electrode overpotential in a smooth distribution of a volume averaged model (Fig. 1a) and in a detailed 3D surface distribution of our pore-scale model (Fig. 1b). To simulate our system we use realistic carbon fiber geometry as an input to our simulation. X-ray computed tomography images of carbon fibers (Fig. 2a) are segmented in 2D images and then stacked as a 3D image (Fig. 2b) to create the virtual volume (Fig. 2c) from which we may take a selection of desired porosity. This model may be extended to the treatment of many different flow battery system configurations including all Vanadium, Vanadium/Bromide, and other novel VRB systems.
The primary drawback of a pore-scale approach is the high computational resources required. To overcome this challenge, in lieu of a traditional implementation with Message Passing Interface, which uses many central processing units to divide the computational effort of a simulation, as an alternative we employ the use of Graphics Processing Units (GPUs) which have been shown well suited for solving problems in computational fluid dynamics.
In this work we present an application using GPUs to increase the speedup of our simulations in order to simulate realistic length and time scales not possible using traditional methods (Fig. 3). Computational techniques for efficiently simulating RFB systems are examined along with the effect of domain size and number of processors on scalability and speedup.
Invited Presentation: NMR and Diffraction Studies of Electrode Reactions: The Effect of Structure, Rate and Electrode Formulations on Reaction Mechanisms
Authors: Grey Clare P. , Liu Hao , Strobridge Fiona , Zhou Lina , Leskes Michal , Hu Yan-Yan 
Published: February 2020

A full understanding of the operation of a battery requires that we utilize methods that allow devices or materials to be probed while they are operating (i.e., in-situ). This allows, for example, the transformations of the various cell components to be followed under realistic conditions without having to disassemble and take apart the cell. To this end, the application of new in and ex-situ Nuclear Magnetic Resonance (NMR) and X-ray diffraction (XRD) approaches to correlate structure and dynamics with function in lithium-ion batteries will be described. The in-situ approach allows processes to be captured, which are very difficult to detect directly by ex-situ methods. For example, we can detect side reactions involving the electrolyte and electrode materials and non-equilibrium processes that can occur during extremely fast charging and discharging. Ex-situ NMR investigations allow more detailed structural studies to be performed to correlate local and long-range structure with performance in battery materials.
In this talk, I will describe the use of NMR spectroscopy and X-ray diffraction to probe local structure changes in lithium ion batteries focusing on our work on olivines, spinels and lithium air cathodes. In the olivine work, we show how the use of fast charging allows us to capture metastable/non-equilibrium states. Mapping of the electrodes allows the distribution of the reaction front across the electrode to be followed. Second, the development of new NMR approaches to investigate paramagnetic battery materials, both in and ex situ, will be discussed, the approach making use of both theory and experiment. Although it is difficult to achieve high-resolution spectra from these paramagnetic materials (see for example the Li1.08-xMn1.92O4 resonance in Figure 1) in the in situ experiments, measurements of the relaxation time allow access to the dynamics of the lithium ions in real time as a function of state of charge.

Figure 1: 7Li in situ NMR of Li1.08Mn1.92O4 during galvanostatic cycling (electrochemistry shown on the left). The red arrows indicate the evolution of the resonance from the tetrahedral sites in Li1.08-xMn1.92O4. Short recycle delays are used so as to suppress the resonance from the electrolyte. Note the apparent increase in intensity at the end of the 4.0 V process/beginning of 4.2 V process on charge and the end of the 4.2 V process on discharge. The behaviour originates from a change in spin-spin relaxation behaviour and indicates a slowing down of the cation/electron mobility. This phenomena has been explored as a function of temperature and spinel stoichiometry.
Na-Fe-S-O System As Cathode Materials for Na-Ion Batteries: An Ab Initio Study
Authors: Chung Sai-Cheong , Nishimura Shinichi , Yamada Atsuo 
Published: February 2020

Sodium-ion rechargeable batteries have been attracting increasing interest as a cost effective alternative to lithium-ion batteries, particular for larger energy storage systems. However, sodium system has the intrinsic drawback of having lower voltage than lithium one. Exploration of cathode materials containing polyanions can led to high voltages and therefore is a meaningful remedy. Experiences gained in the studies of lithium battery show that sulphates (Li2Fe(SO4)2) deliver the highest voltage (3.83 V vs Li/Li+) among polyanions such as phosphates and silicates due to the high formal charge of S and inductive effects[1]. The Na-Fe-S-O system also has the advantage of composing of elements high in natural abundances and low in costs.
In exploring the Na-Fe-S-O system, our group found some new phases[2]. One of these can extract nearly all the Na atoms in the formula unit at an average voltage of 3.6 V vs Na/Na+. This is a significant improvement over the known Fe2(SO4)3 in the Nasicon phase[3], where only one Na atom can be inserted and at a lower voltage of 3.4 V vs Na/Na+. The rate capability and cycling performance are also very satisfactory. The new structure consists of peculiar edge sharing Fe2O10subunits forming tunnel spaces partially occupied by Na ions.
In order to understand the structural origin of the excellent performance of this material we carried out ab initio study employing density functional theory. Migration activation energy (Ea
) calculations found that Na ions are very mobile in the structure with Ea
as low as 0.14 eV (Figure). This accounts for the high rate performance and hints at the application as solid-state electrolytes. On the voltage aspect, emphasis will be put on the origin of the higher voltage of the present system in comparison to the Nasicon phase. Theory for the trend of voltage in cathode material employing different polyanions is well known, however, it is highly controversial for polymorphs of compounds with the same chemical compositions. Phase behavior at different state of charge will also be discussed.

References

[1] J.B. Goodenough in H Reiss (Ed.) Progress in Solid State Chemistry, Vol 5. Pergamon Press, 1971, pp 145-387
[2] A. Yamada, P. Barpanda, S. Nishimura, G. Oyama, Patent JP-2013-187914 (2013).
[3] A.K. Padhi, V. Manivannan, J.B. Goodenough, J. Electrochem. Soc. , 145(5), 1518 (1998).
Polypyrrole Coated LiMn0.15Fe0.85 PO4 Olivine As High Capacity Cathode Electrode for the Lithium-Ion Battery
Authors: Gao Xuanwen , Wang Jiazhao , Liu Hua Kun , Chou Shulei , Chen Guohua , Deng Yuanfu , Shi Zhicong 
Published: February 2020

Lithium iron phosphate has become the subject of great interest as storage cathodes for rechargeable lithium-ion batteries. Unfortunately, its intrinsic low electronic conductivity and low energy density still prevent it from practical commercialization [1]. In the past decade, Padhi et al [2] pioneered interest in the LiFe1-yMnyPO4 olivine system, showing the occupation of some percentage of octahedral 4c sites of LiFePO4 by Mn combines the advantages of the low toxicity of LiFePO4 and the relatively high operating voltage of LiMnPO4 (~4.1 V). This ability to increase the energy density of conventional LiFePO4 has been the driving force for extensive research on LiFe1-XMnxPO4 [3]. Nevertheless, besides the fundamentally low electronic conductivity of olivine, the Mn3+ doping may lead to another drawback, which is Mn3+ dissolution. It is generally accepted that Mn3+ causes serious mechanical stress and its disproportionation results in Mn2+dissolution from the surface by Jahn-Teller distortion [4]. Therefore, there have been many efforts to overcome these obstacles, for instance by decreasing the crystallite size and changing the morphology or providing a conductive matrix (e.g. carbon).
In this work, we present the application of a composite LiMn0.15Fe0.85PO4 coated with conductive polypyrrole (PPy) as cathode electrode for the Li-ion battery. The effects of the PPy coating on the physicochemical and electrochemical properties have been extensively studied. SEM and TEM images show that the PPy is uniformly coated on the surface of LiMn0.15Fe0.85PO4. The LiMn0.15Fe0.85PO4 electrode with 9 wt. % PPy coating exhibits a high discharge capacity and good cycle life at room temperature. This electrode delivers a discharge capacity of 135 mAh/g at 1/2 C, and after 100 cycles, the discharge capacity still reaches 126 mAh/g. In contrast, the discharge capacity of the pristine LiMn0.15Fe0.85PO4 is only around 128 mAh/g under the same conditions, and 114 mAh/g remains after 100 cycles, as shown in Fig. 1a. Electrochemical impedance spectroscopy verified the improved electrochemical conductivity of LiMn0.15Fe0.85PO4/PPy electrode. In addition, analysis of the counter electrode (Li film) confirmed that the PPy coating can protect the electrode from HF attack, and thus lead to reduction of Mn3+ dissolution in the LiMn0.15Fe0.85PO4-PPy electrode (Fig. 1b).
[1] A. Yamada, S. C. Chung, K. Hinokuma, Journal of the Electrochemical Society, 148 (2001) A224-A229.
[2] A. K. Padhi, K. S. Nanjundaswamy, J. B. Goodenough, Journal of the Electrochemical Society, 144 (1997) 1188-1194.
[3] S. Y. Chung, J. T. Bloking, Y. M. Chiang, Nat. Mater., 1 (2002) 123-128.
[4] R. Von Hagen, H. Lorrmann, K. C. Möller, S. Mathur, Advanced Energy Materials, 2 (2012) 553-559.
Cathode Properties of Rocksalt-type LiFeOF for Li-Ion Batteries
Authors: Kitajou Ayuko , Kidera Takafumi , Okada Shigeto 
Published: February 2020

The iron-based conversion-type cathode materials attract attention due to the low cost and the high theoretical capacity. Among them, Fe2O3 has the highest theoretical capacity; FeF3 has the highest discharge voltage, and FeOF shows the highest energy density. However, these conversion-type cathodes can’t use in Li-ion type cell with carbonaceous anode, because they don’t include lithium-ion in the initial composition. Recently, K. Kang group reported LiF-FeF2 nano-composite can be used as cathode for Li-ion batteries [1]. Actually, LiF-FeF2 nanocomposite showed that the reversible specific capacity was ca. 190 mAh/g with the average voltage of 3.6 V. In this research, we tried to prepare LiF-FeO composite as the novel cathode materials for Li-ion batteries by dry mechanical ball-milling method. Moreover, the cathode properties of LiF-FeO nanocomposite were evaluated against lithium metal or Li4Ti5O12 (LTO).
LiF-FeO was prepared by mixing of LiF and FeO with a molar ratio of LiF : FeO = 1.2 : 1. The mixture was dry ball-milled in Ar for 24, 48 and 72 h, respectively. After mechanical ball milling, 5 wt % acetylene black (AB) was added to 70 wt % mixture in Ar for 24 h. Then, the 75 wt % obtained LiF-FeO/carbon composite power was also mixed with 20 wt % AB and 5 wt % PTFE teflon binder and punched in the form of disks (10 mm in diameter). The electrochemical performance was evaluated with a 2032 coin-type cell using a non-aqueous electrolyte (1M LiPF6 in EC:DMC=1:1 in volume) against Li metal anode or LTO anode.
Rocksalt-type LiFeOF was obtained from LiF and FeO by the dry ball-milling method under ambient pressure. The reversible capacity of LiFeOF was 292 mAh/g with an average voltage of 2.5 V and an energy density over 700 mWh/g, which is higher than the theoretical energy density of LiFePO4 (Fig. 1). In addition, we confirmed that a LiFeOF can actually work as cathode in Li-ion type cell with LTO anode. The initial charge and discharge capacities per cathode weight were 180 mAh/g and 149 mAh/g with an 83% discharge/charge efficiency. The discharge capacity was 130 mAh/g even after 30 cycles, and the cycling efficiency of LiFeOF was 87%. The reversibly expansion and contraction of structure of LiFeOF during cycling was measured with XRD.