bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel BCC Anode Materials for High-Power Alkaline MH-Air Batteries
Authors: Tan Hongjin , Weadock Nick , Fultz Brent , Bugga Ratnakumar V
Published: February 2020

Aqueous metal hydride air batteries (MH-Air) offer an inexpensive and safe alternative to the Li-ion batteries for electric vehicles.  To be competitive with Li-ion batteries, the energy density of a metal hydride battery system can be improved by introducing a low-mass bifunctional air cathode and developing a higher capacity anode material. V-based BCC alloys are promising high-capacity anode materials, and discharge capacities of greater than 450 mAh/g have been reported for TiV2.1-xCrxNi0.3 alloys.1 V-based BCC alloys containing Ti and Ni have been shown to separate chemically into a two-phase mixture with a minority Ni-Ti phase within a V-rich matrix,2 and we report the effects of this unmixing on electrochemical properties. 

The Ti-V-Cr-Ni BCC electrode materials were prepared by arc melting and rapid cooling with an Edmund Buhler compact MAM-1 with an attached suction casting crucible. The control samples were made by conventional arc melting under Ar. As-cast ingots were pulverized by hydriding in a Sievert’s apparatus. The samples were analyzed by x-ray diffractometry (XRD), scanning and transmission electron microscopy (SEM, TEM) and energy-dispersive x-ray spectrometry (EDS). The anode was prepared by pressing a mixture of alloy and Ni powders onto Ni mesh. Electrochemical cycling experiments were conducted in a half cell containing  30% aqueous KOH electrolyte, a Ni(OH)2 counter electrode and an Hg/HgO reference electrode. The electrode was charged at 100mA/g and discharged three times at 167mA/g, 50mA/g, and 10mA/g; each to a cut-off voltage of -0.7V vs. Hg/HgO.

EDS mapping showed, as expected,2 a Ti-Ni rich secondary phase in the arc melted sample that permeates the micron-scale primary V phase. (Fig. 1, top, Ni phase in green.) No phase segregation is resolved by EDS for the suction cast alloy. (Fig. 1, bottom). For the first 100 charge-discharge cycles, both materials gave similar capacities. However, at each cycle, the suction cast alloy consistently discharges with 20%-40% more capacity during the high-rate step (167mA/g, ~C/3, 1st step in Fig. 2).

It has been argued that the Ni-Ti phase is important for the electrocatalytic dissociation of H2 molecules during charge, and the matrix V-rich phase is the storage region for hydrogen.2 Reducing the length scale of the phase segregation of the Ni-Ti regions by rapid cooling may therefore improve the kinetics of the material by reducing the hydrogen diffusion length and by increasing surface area for electrocatalysis.

Inoue, et al. Electrochimica Acta, (2012), 59, 23-31.

Tsukahara, et al., J. Alloys Comp. (1997), 253-4, 583-6.

Figure 1
A Systematic Study on Sodium Doped Strontium Silicate for SOFC Application
Authors: Jee Youngseok , Xiong Xiaolei , Tong Jingjing , Si Fengzhan , Wang Jie , Fang Jie , Huang Kevin
Published: February 2020

1. Introduction

High temperature (HT) operation at 800 – 1000 °C causes many problems such as the thermal mismatch between membrane electrode assembly (MEA) components, expensive bipolar plates, micro structural changes, inter-diffusions, slow start-up time, decreasing system power density due to heat insulators. In order to overcome this main commercialization obstacle of solid oxide fuel cells (SOFCs), a lot of intermediate temperature (IT) electrolyte materials (Doped ceria, LSGM, ScSZ and so on) which can substitute for conventional YSZ have been proposed. And various thin film deposition techniques (Screen printing, Dip-coating, Magnetron sputtering, Pulsed Laser Deposition, Chemical Vapor Deposition and Atomic Layer Deposition) were applied to this research field. The goal of both types of approaches is minimizing the ionic resistance at decreased temperature.

Recently, the sodium doped strontium silicate (Sr1-xNaxSiO3-0.5x) is gathering attentions as a fast ion conductor.[1] And Wei et al. confirmed a good SOFC performance using this electrolyte material at 500 and 600 °C. [2] In this study, we investigated on this promising material to get the optimal fabrication conditions with composition and to minimize several problems on this material.

2. Experimental

The starting raw powders of SrCO3 (Sigma-Aldrich 99.9%), Na2CO3 (Alfa Aesar, 99.9%) and SiO2(Alfa Aesar 99.9%) were mixed and ball milled. The Na doping percentages on strontium site were 0 to 100 %. We varied calcination temperature from 600 °C to 1000 °C. After ball milling step, we also varied sintering temperature (800 – 1150 °C) and time (10, 20 and 100 h). 

Conductivity tests were conducted in the air environment and the furnace was controlled from 400 to 750 °C. Sample pellet was prepared to get the thickness of 1.5 mm using low speed saw. Then, we pasted silver electrodes with current collecting meshes on both sides of  pellets and connected wires to electrochemical impedance spectrometer (Solartron 1287 and 1260, UK). The micro structural images were captured using a field emission scanning electron microscope (FESEM, Zeiss Ultra) equipped with an energy dispersive X-ray spectroscopy (EDS) analyzer, respectively. The phase check was done using an X-ray diffractometer (D/max-A, Rigaku, Japan) with CuKα radiation (λ=1.5418 Å). The scan range was 2θ = 10 – 70 °at a rate of 5 ° min-1.

From this study, we found out the optimal fabrication conditions (sintering at 900 °C for 10 h) for 45 % sodium doped strontium silicate electrolyte which was known as the best ionic conductor. Moreover, we could guess the origin of this high conductivity was from the amorphous sodium silicate.

Reference

[1] P. Singh and J. B. Goodenough, J. Am. Chem. Soc., 2013, 135, 10149–10154

[2] T. Wei, P.Singh, Y. Gong, J.B. Goodenough, Y. Huang and K. Huang, Energy Environ. Sci., 2014, 7, 1680-1684

Figure 1
Nanostructured Ni-YSZ Anode By Atomic Layer Deposition for Solid Oxide Fuel Cells
Authors: Cui Xiaodan , Zdunek Alan D. , Takoudis Christos G
Published: February 2020

Nickel yttria-stabilized zirconia (Ni-YSZ) is the most commonly used anode for solid oxide fuel cells (SOFCs). The electrochemical performance of Ni-YSZ anodes can be improved when the size of constituent particles is reduced. However, under SOFC operating environment, nano-sized Ni particles suffer from sintering; nanoscale Ni-YSZ anodes can undergo structure changes, which constrain the development of nanoscale Ni-YSZ anodes.

In this work, nanoscale nanostructured Ni-YSZ anode was successfully fabricated by combining atomic layer deposition (ALD) and glancing angle deposition (GLAD). Prior to atomic layer deposition of YSZ, the porous Ni nanorod electrode was firstly prepared by GLAD. ALD was applied to deposit a uniform nanoscale YSZ coating layer over the nickel nanorods. The morphology of the nanostructured Ni-YSZ anode was examined with scanning electron microscopy (SEM). The surface area was increased to more than 3 times as large as plane area and the triple phase boundary (TPB) extended to the entire nickel surface. The surface composition was examined with X-ray photoelectron spectroscopy (XPS). The atomic composition of YSZ film was controlled by the ALD process and not affected by the post-deposition annealing process. ALD coating approach combined ionic conductive YSZ electrolyte phase with electrical conductive Ni phase flexibly and controlled the porosity of the nano-composite electrode just through deposition and post-deposition annealing process. Electrical conductivity measurements were performed using a 4-point probe method. The Ni-YSZ anodes maintained resistivity in the 10-4 cm·S-1 magnitude, which is sufficiently conductive as an SOFC anode. The ALD YSZ coating layer showed sintering-resistance on the nanostructured electrode with an as thin as 1.9 nm YSZ coating layer and excellent anode performance under SOFC operating conditions.
Electrochemical Properties of Nanocrystalline Li4Mn5O12 for Hybrid Capacitor
Authors: Man Tran Van , Huynh Nguyen Le Thanh , Le Thang Van , Phung LE My Loan
Published: February 2020

The hybrid capacitor or asymmetric capacitor is the hybridization of electrochemical capacitor and rechargeable batteries. The device is developed by hybridization on the electrode level; therefore, it is based on a battery anode (charged by faradic reaction) and electrochemical capacitor electrode (charge stored in the electrochemical double layer) [1]. Sometimes, the name “lithium-ion” capacitor was introduce to described a device using a graphite negative electrode and activated carbon (AC) based positive electrode in combination with a Li+ containing electrolyte [2].

In such device, different types of materials have been proposed for faradic component. Lithium insertion compounds used in lithium-ion batteries have attracted a lot of interest due to high specific charge. They have been typically used in organic electrolyte but the aqueous solutions are not missing [3,4]. In this work, nanocrystalline Li4Mn5O12 was low-temperature synthesized by sol-gel method with citric acid as a chelating agent. Various initial synthesis conditions were studied such as: pH of solution, the ratio of citric acid to total metal ions, the precursor of lithium salts. The structure, morphology and electrochemical properties of materials are characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), cyclic voltammetry (CV) and galvanostatic cycling with potential limit (GCPL). The stoichiometric of formula was exactly determined by reduction-oxidation titration and flame atomic absorption spectrophotoscopy (FAAS).

The resulting materials exhibited the particles size of 50 – 100 nm. The electrochemical results showed that Li4Mn5O12 synthesized at pH = 9 and the ratio of citric acid to total metal ions 1:1 exhibited the best electrochemical capacitive performance within potential range of  0 – 1.4 V in 1M Li2SO4. A maximum specific capacitance of 20 F.g-1 during 200 cycles was obtained for hybrid capacitor for AC/Li4Mn5O12 at high discharge rate of 5 A.g-1.

Acknowledgements

The authors would like to thank Office of Naval Research Global (ONRG) for the grant N62909-13-1-N235. The authors acknowledge funding from VNU-HCM under the grants HS2013-76-01.

 

References

 [1]. D. Cericola, Electrochimica Acta 72 (2010) A536.

[2]. O. Hatozaki,  Proc. Advanced Capacitor World Summit 2008,  San Diego, CA, USA, 2008.

[3]. Y.J. Hao,Y.Y. Wang, Q.Y. Lai, Z. Zhao, L.M. Chen, X.Y. Ji, Journal of Solid State Electrochemistry, 13 (2009) 905. 

[4]. K. Naoi, S. Ishimoto,Y. Isobe, S. Aoyagi, Journal of Power Sources 195 (2010) 6250.
High Volumetric Capacitance and Mechanisms of Electrochemical Charge Storage in Two-Dimensional Ti3C2-Based Mxene
Authors: Lukatskaya Maria R. , Ghidiu Michael , Mashtalir Olha , Ren Chang E. , Zhao Meng-Qiang , Dall'Agnese Yohan , Barsoum Michel W. , Gogotsi Yury
Published: February 2020

MXenes, a recently discovered large family of two-dimensional (2D) early transition metal carbides and carbonitrides, have shown much promise in electrochemical energy storage applications, such as battery and supercapacitor electrodes. Here we report on large volumetric capacitance and high rate capability of Ti3C2Tx – the most studied MXene to date.

Spontaneous intercalation of a variety of single- and multiply charged cations (such as Li+, Na+, K+, NH4
+, Mg2+, and Al3+
), together with highly reversible electrochemical insertion of the same cations, has been demonstrated for Ti3C2Tx in aqueous electrolytes. Perfect capacitive behavior was observed for Ti3C2Tx MXene even at quite high charge and discharge rates, contradicting to slow intercalation of ions in a specific potential range, which is usually observed in layered materials used in battery applications. In order to understand the mechanism of capacitive charge storage in MXenes, we performed characterization of the material using in-situ spectroscopy, X-ray diffraction and other techniques.
Cathodic Deposition of Metal Sulfide Nanostructures As Active Materials for High-Performance Supercapacitors
Authors: Chou Shu-Wei , Lin Jeng-Yu
Published: February 2020

Supercapacitors (SCs) have been widely recognized in a wide range of energy storage applications over the past decade due to their higher specific power density, faster charge/discharge rates and longer cycle life compared to batteries. Hydrous ruthenium oxide (RuO2) has been the most promising material with the high specific capacitance (>720 F g-1). However, the low abundance and high prices restrict the application of RuO2 in SCs. Hence, several alternatives have been proposed to be capable of the RuO2such as metal oxide and conducting polymer. In addition, nanostructured metal sulfides have been widely investigated as SCs electroactive materials. In recent years, nanostructured metal sulfides have been widely synthesized by chemical precipitation and hydrothermal. Nevertheless, the aforementioned metal sulfides still needed polymer binder, conducting agent and high pressure coating on the conductive substrate, which could contribute extra contact resistance. In this way, electrodeposition seems to be a great approach to prepare the electroactive materials on conductive substrates since the active materials can be directly growth on substrates without using any polymer binder, conducting agent and high pressure, and the weight and thickness of electroactive materials can easily controlled by adjusting the deposition conditions.

In this study, cobalt sulfide and nickel sulfide nanostructures can be directly grown on Ni foam substrate as electroactive materials for high-performance supercapacitors by simply using a facile potentiodynamic deposition method. The Ni3S2 and CoS electrodes showed a high specific capacitance as well as 717 F g−
1 at 2 A g−
1 and 1471 F g−
1 at 4 A g−
1, as shown in Fig. 1(a) and Fig.1(b). As a result, nickel sulfides and cobalt sulfides can be considered as promising electrode materials for high-performance supercapacitors.

Figure 1
Facile Fabrication of Co3O4@C@Tnas Heterojunction Composites with Enhanced Electrochemical Performance for Supercapacitors
Authors: Yu Cui-Ping , Wang Yan , Zhang Jian-Fang , Shu Xia , Cui Jie-Wu , Xie Kui , Chen Zhong , Xie Ting , Wu Yu-Cheng
Published: February 2020

A new type of supercapacitors based on the well aligned TiO2 nanotube arrays (TNAs) modified with

 amorphous carbon and Co3O4 nanoparticles was prepared in this paper. Carbon-doped TNAs (C@TNAs) were fabricated by anodic oxidation of a pure titanium sheet in an aqueous 

solution containing 0.25M NH4F and 7vol% H2O directly, then followed by annealing 

the prepared TNAs samples in the Ar atmosphere, with the residual ethylene glycol absorbed on the

 TNAs wall during anodization as the carbon source. The C@TNAs were chosen as the 3D framework

 with larger surface area, easier access for the ions in the solution as well as the highly chemical

 stability, and the amorphous carbon could enhance the electric conductivity of TNAs. 

Co3O4 nanoparticles with the size of less than 15 nm were synthesized via the simple process of

 chemical bath deposition of cobalt acetate aqueous solution, which was as a result of the hydrolysis

 of Co2+ and simultaneously heterogeneous growth of Co3O4 nanoparticles on both the outer and

 inner surfaces of C@TNAs. The morphology, component and electrochemical property of 

Co3O4@C@ TNAs were characterized by field emission scanning electron microscope (FESEM),

 transmission electron microscope (TEM), X-ray diffraction (XRD), Raman spectrum, X-ray photoelectron 

spectroscopy (XPS), cyclic voltammetry (CV) and amperometry charge and discharge (CD), respectively.

 The influence of amorphous carbon on promoting electrochemical properties was discussed in this paper

 through comparing the CV of Co3O4 @ TNAs and Co3O4@C@ TNAs. After doped with amorphous carbon,

 a maximum specific capacitance of 689 F g-1 has been obtained in 2M KOH aqueous electrolyte at current

 density of 1 A g-1 with a potential window from 0 to 0.45 V (vs. Ag/AgCl). Furthermore, the specific 

capacitance retains 84 % based on the initial capacitance after 4000 cycles under high current density of 

10 A g-1, revealing the excellent long term electrochemical stability of the sample even at high cycling rate. 

Co3O4@C@TNAs heterostructure composites will hode promise for one of the best electrode systems for high 

performance supercapacitors.
GdBaM2-xFexO6-

δ
(M = Co, Mn) Perovskite-type Oxides as SOFCs Cathodes: Influence of Ordering Effects on the Crystal Structure and Properties
Authors: Garcia-Martin Susana , Muñoz-Gil Daniel , Urones-Garrote Esteban , Avila-Brande David , Martínez de Irujo Xabier
Published: February 2020

Perovskites of general formula A1-xA’
xM1-yM’yO3-δ (A = lanthanide atom, A’ = alkali earth atom and M, M’ = transition metal atom) are promising candidates as electrodes for solid oxide fuel cells (SOFCs) [1, 2]. Among them, A-site ordered perovskites as for instance GdBaCo2O5+δ, also called layered-type perovskites, show better electrochemical behaviour than materials with random distribution of the cations. The high oxygen mobility in these layered-type perovskites seems to be related to the A-cation ordering [3, 4].

We are studying the influence of the crystal structure, in particular of the ion ordering effects, on the electrochemical properties of doubled perovskites with composition

GdBaM2-xFexO6-
δ (M = Co, Mn). The synthesis conditions affect both the oxygen stoichiometry and cation and/or anion vacancies ordering in the crystal structure of the materials.  We study the crystal structure of the compounds by Selected Area Electron Diffraction (SAED), High Resolution Transmission Electron Microscopy (HRTEM), Scanning Transmission Electron Microscopy (STEM) (High Angle Annular Dark Field HAADF-STEM and Annular Bright Field ABF-STEM) and Electron Energy-Loss Spectroscopy (EELS). The use of aberration-corrected transmission electron microscopy techniques provides atomic resolution information. We have found cation ordering (mainly associated to the A cations, although B-cation ordering has also been observed) and anion vacancies ordering in some of these perovskites. HAADF-STEM images (also called Z-contrast images) confirm the layered-type ordering of the A cations. Direct imaging of the oxygen sublattice is obtained by ABF-STEM images and the phase image of the restored exit wave, which allows location of the oxygen vacancies in the structure.

We study the electrochemical behavior of the materials on symmetrical two-electrode cells using Ce0.9Gd0.1O2-δ as electrolyte. Area specific resistance (ASR) associated to the electrode polarisation process at different temperatures is determined by AC impedance spectroscopy. We found that ordering effects of the crystal structure of the materials have a great impact on ASR values. In general, layered-type ordering of Gd and Ba in the structure decreases ASR values but different types of ordering of anion vacancies also play an important role in the physical properties of these materials.   

References:

A. Aguadero, L. Fawcett, S. Taub, R. Woolley, K. T. Wu, N. Xu, J. A. Kilner and S. J. Skinner, J. Mater. Sci. 47 (2012) 3925-3948.

E. Kendrick, P. R. Slater, Annu. Rep. Prog. Chem., Sect. A: Inorg. Chem 109 (2013) 396-420.

A. A. Taskin, A. N. Lavrov and Y. Ando, Appl. Phys. Letters. 86 (2005) 091910.

A. A. Taskin, A. N. Lavrov and Y. Ando, Progress in Solid State Chem. 35 (2007) 481-490.
The Influence of Water in Montmorillonite Clay on the Performance As Electrode Material for Li-Ion Battery/Capacitor
Authors: Chen Chunhui , Shah Gautam , Wang Chunlei
Published: February 2020

Recently, 2D materials have attracted great attention as electrode materials for lithium ion batteries due to their special electochemical properties. Clays are nature abundant materials which have 2D layered structures. Montmorillonite (MMT) is one of them and composed of units made up of two silica tetrahedral sheets with a central alumina octahedral sheet. The cation and water content in inter layer varies with source. Unlike graphene related materials, electrochemical properties of MMT has rarely been studied. Our recent research shows that MMT could be used as a green electrode material for Li-ion battery/capacitor. Here in this study, we will exam the influence of water in MMT clay on the electrochemical performance.

The performance of various status of MMT, in nature or dehydrated, will be exam. Conductive agent will also be added to improve conductivity of MMT electrode. Both traditional slurry casting and electrostatic spray deposition (ESD) will be used to fabricate the electrode. Fig. 1(a) shows the TEM image of nature MMT clay and (b) cyclic voltammetry (CV) curves of slurry casting MMT electrode. More detailed results will be shown during the meeting.

Figure 1
Investigation of Treated Graphene Oxides for Vanadium Redox Flow Battery
Authors: Di Blasi Alessandra , Di Blasi Orazio , Briguglio Nicola , Busacca Concetta , Antonucci Vincenzo
Published: February 2020

Thermically treated graphene oxides (TT-GOs) are obtained at different temperatures, 100°C, 150°C, 200°C and 300°C in reduced environment. Physico-chemical characterizations were carried out to evaluate the electrochemical results in terms of reversibility and electrochemical impedance spectroscopy (EIS) in a three electrode half-cell. The TT-GO sample treated at 100°C (TT-GO-100), characterized by the presence of hydroxyl (-OH) and carboxyl (-COOH) species, shows an higher reversibility towards the VO2+/VO2
+ redox reactions with respect to the all investigated samples. The electrochemical performance results confirm how the hydroxyl and carboxyl species prevalence play a fundamental role as active sites for the [VO]2+/[VO2]+ redox reaction process. The TT-GO-150, TT-GO-200 and TT-GO-300 sample, characterized by the prevalence of carbonyl species, phenolic (C-OH) and epoxide groups (C-O-C) on the basal plane of the structure, show a lower reversibility attributable to the higher ohmic and charge transfer resistances.
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. Jaquinod,  R. G. Khoury, K. M. Shea, K. M. Smith, Tetrahedron, 1999, 55, 13151-13158.

R. Deshpande, L. Jiang, G. Schmidt, J. Rakovan, X. P. Wang, K. Wheeler, H. Wang, Org. lett 2009, 11, 4251-4253

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) Impact of Indiumand Gallium Doping on the Photovoltaic Performance of CdSe Quantum Dot Hybrid Solar Cells
Authors: Chikan Viktor , Ren Shenqiang , Kirkeminde Alec , Scott Randall , Gong Maogang , Totleben Jennifer , Tuinenga Christopher , Lewis Christopher , Luo Hongfu , Higgins Daniel
Published: February 2020

Colloidal CdSe quantum dots show great promise for fabrication of hybrid solar cells with enhanced power conversion efficiency, yet controlling the doping on the atomic length scale is challenging. Here, we demonstrate that gallium-, indium-, tin-doped CdSe quantum dots show significantly improved conductivity and charge carrier density, and also temperature dependent behavior. Furthermore, the doped CdSe hybrid solar cells greatly enhance photocurrent and photovoltage, in which the gallium doped CdSe quantum dots and P3HT bi-layer heterojunction solar cells leads to a maximum power conversion efficiency of 2.0% at elevated temperatures under AM 1.5 solar illumination. All the doped samples exhibit inverted temperature dependent power conversion of the photovoltaic cells, which could be effectively utilized in solar concentrators. The approach presented can be applied to a wide range of doped quantum dots and polymer hybrids and is compatible with solution processing, thereby offering a general tactic for improving the efficiency of quantum dot based solar cells.
(Invited) Optimization of the Thin-Film Making Process for Highly Efficient and Stable Polymer Solar Cells with Zinc Oxide Nanoparticles
Authors: Hayakawa Akinobu , Sagawa Takashi
Published: February 2020

There have been numerous reports on electron transporting ZnO-layer inserted polymer solar cells in order to rectify the directions of charge transport and stabilize the organic thin-films against the oxidative degradation of the organic components such as fullerene derivatives and conducting polymers. In spite of the remarkable progress of the power conversion efficiencies (PCEs) from 1% to over 10%, tuning of the thin-film making process is still uncertain in terms of desirable charge transport and collection through the photovoltaic performance. In this context, we investigated appropriate dispersing agents for inter-diffusion of zinc oxide nanoparticles in the active layer of the polymer solar cells of glass-ITO/PEDOT:PSS/P3HT-ZnO/ZnO/Al. Through the band-gap matching, the solubility test, the quenching of the emission of P3HT by addition of ZnO, and the evaluation of photovoltaic performance of the hybrid cells with various dispersing agents such as 1-4, it was found that asymmetric molecular structure with appropriate dipole moment of the dispersing agent shows good dispersion property of the ZnO nanoparticles and higher PCE with 1.5 times enhancement. We also investigated the impedance analyses to clarify the resistance (R
p) of the grain boundaries of the ZnO nanoparticles with various thicknesses of the ZnO layers and found the thickness dependence of the R
p. Effects of the particle size, aspect ratio (viz. morphology) of the ZnO nanostructures had also examined and obtained results also supported smaller grain boundaries of the ZnO reduced the R
s and attained the improved fill factor of 0.60. Durability test of the above hybrid cells sealed by glass and UV cut-off film under 1 sun at 63°C in 50% humidity revealed that the deterioration of the device is ascribed to the loss of the open-circuit voltage (V
oc). On the contrary, unsealed devices exposed to the air (viz. oxygen) effectively kept their V
ocs for more than one week under the dark and atmospheric conditions. The loss of V
oc is ascribed to the increase of the intrinsic carrier density of ZnO under the UV irradiation without oxygen, while such increment might be effectively suppressed by oxygen in the dark. Durability improvement with relatively constant V
oc by the Sn-doping into ZnO also supported above consideration.

Figure 1
(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