bluuebunny/crossref_metadata_2025 huggingface dataset:
Fermi Potential across Working Solid Oxide Cells with Zirconia or Ceria Electrolytes
Authors: Jacobsen Torben , Chatzichristodoulou Christodoulos , Mogensen Mogens Bjerg
Published: February 2020

A solid electrolyte will always possess a finite electronic conductivity, in particular electrolytes like doped ceria that easily get reduced and become mixed ionic and electronic conductors. This given rise too high leak currents through the solid oxide cell (SOC). Especially, problems have been observed for ceria based electrolytes, but also in case of solid oxide electrolyser cells (SOEC) with yttria stabilized zirconia (YSZ) big electronic leak currents have been observed for very high overvoltages on one or both electrodes.

Furthermore, it is important to realize that the potential gradient driving the O2-ions is not the Fermi potential, which is the potential of the electrons, but the Galvani potential (or inner potential) (1). The concepts of potentials describing the electrical situation of a solid electrolyte is shown i Fig. 1, and an example of the Fermi potential (π) and Galvani potential (φ) profiles are shown in Fig. 2. The Fermi potential will be affected directly by the Galvani potential, whereas the Galvani potential need not necessarily be affected by the Fermi potential because the concentration of “free” electrons may be very low.

The paper gives illustrative examples at various temperatures and operation conditions. Furthermore, the situation within cells based on gadolinia doped ceria (CGO) and on YSZ electrolytes are compared. Finally, it is discussed how the Fermi potential and electron conductivity will be affected by the various parameters including operation conditions.

Reference

[1] T. Jacobsen and M. Mogensen, ECS Transactions, 13 (no.26), 259 (2008).
The Role of Nonstoichiometry on the Electrocatalytic Properties of TiO2-δ towards the Conversion of Carbon Dioxide to Fuels
Authors: Sharma Pranav P. , Ke Fu-Sheng , Zhou Xiao-Dong
Published: February 2020

Crystalline titanium oxide (TiO2), which exists in the three ubiquitous phases: rutile, anatase and brookite, possesses a direct wide band gap (Eg
~ 3.3 eV at 300 K) similar to that of GaN (Eg
~ 3.4 eV at 300 K), is under consideration as an alternative material to replace GaN for optoelectronic applications. It's known that reduced titanium dioxides (TiO2-x and TiO) exhibit some unique chemical activities towards water oxidation. In this presentation, we will report our recent studies of using TiO2-x and TiO as the electrocatalysts to convert carbon dioxide to fuels by incorporating the electrocatalysts into a polymer exchange membrane fuel cell (PEMFC) based full electrochemical cell. Nonstoichiometric Ti3O5 was prepared by reducing TiO2 at high temperature in the presence of high pressure hydrogen. X-ray diffraction and thermogravimetric analysis were used to analyze the phase and nonstoichiometry of TiO and Ti3O5. Ti3O5 exhibits the highest Faradaic efficiency (~ 12%) towards the formation of formate, comparing to < 2% for both TiO and TiO2 P25. X-ray photoelectron spectroscopy (XPS) measurements of the Ti3O5 gas diffusion electrodes (GDEs) before and after electrolysis also suggest the presence of surface defects such as Ti3+ and oxygen vacancies which significantly influence the electrocatalytic activity for CO2 reduction.
Understanding Membrane Degradation Mechanisms Under Heavy Duty Fuel Cell Conditions: A Multi-Disciplinary Approach
Authors: Malek Kourosh , Kjeang Erik , Holdcroft Steven , Eikerling Michael , Djilali Ned , Knights Shanna
Published: February 2020

The Automotive Partnership of Canada (APC) project on Next-Gen Heavy Duty Fuel Cell Buses is a government supported three-year project dedicated to research and product development of next generation heavy duty fuel cell buses in Canada (www.apc-hdfc.ca). The project represents a collaborative effort between Ballard Power Systems, Simon Fraser University and University of Victoria in British Columbia, Canada. The overarching objective is fundamental understanding of membrane degradation mechanisms, degradation rates, and failure modes under drive cycles and conditions that are typical for heavy duty vehicle operation. The aim is to help develop next generation fuel cell technology that is equivalent to or surpasses incumbent diesel engines in terms of durability and reliability, while reducing capital and warranty costs.

In order to develop new durable membrane technologies and devise mitigation strategies to reach desired membrane lifetime, empirical and physical models need to be developed and employed. In this context, understanding the relationship between operation mode and membrane degradation under heavy duty fuel cell conditions is of vital importance. Apart from mechanical degradation such as thinning and pinhole formations, chemical and electrochemical degradation could also take place in perfluorosulfonated acid (PFSA) ionomer membranes. Due to complexity of the underlying processes, degradation mechanisms and their dependence on relevant operating conditions are not generally well established.

We present results from an extensive effort that integrates multi-scale, multi-disciplinary modeling with large–scale accelerated degradation testing data. Results are analysed in view of the relative importance of various membrane degradation mechanisms via various chemical and mechanical processes. The versatile multi-scale modeling framework includes structure formation at molecular/meso-scales, water sorption characteristics, kinetics, as well as continuum modelling of chemical and mechanical degradation processes.

References

[1] F. de Bruijn, et al., Fuel Cells 8(1), 2008, 3–22

[2] Cheng Chen, T. F. Fuller, Modeling of Hydrogen Peroxide Formation in PEMFCs, Electrochim. Acta, 54, 3984-3995 (2009).

[3] N. Macauley, L. Ghassemzadeh, C. Lim, M. Watson, J. Kolodziej, M. Lauritzen, S. Holdcroft, E. Kjeang, “Pt Band Formation Enhances the Stability of Fuel Cell Membranes”, ECS Electrochemistry Letters, 2(4) (2013) F1-F3.

[4] L. Ghassemzadeh, S. Holdcroft, "Quantifying the structural changes of PFSA ionomer upon reaction with hydroxy radicals”, JACS, 2013, 135 (22) (2013), 8181-8184.

[5] R. M.H. Khorasany et al., “On the Constitutive Relations for Catalyst Coated Membrane Applied to In-Situ Fuel Cell Modeling”, 2013, submitted.

Fig. 1: APC project on heavy duty bus fuel cells (www.apc-hdfc.ca).
The Study of Indirect Electroreductive Cyclisation of Propargyl Derivatives Using [Ni(tmc)]Br2 As Catalyst in Ionic Liquids
Authors: Medeiros M. J. , Neto M. J. , Esperança J.M. S.S. , Esteves A. P. , Silva M. M.
Published: February 2020

Five-membered heterocyclic compounds are among the most important natural biologically active compounds. X-heterocycles (X = O, N) are usually synthesised by radical cyclisation methodology [1] based on organotin hydrides which are toxic and also troublesome to separate from the reaction products.

A convenient alternative to synthetic methods involving organometallic hydrides is the use of electrogenerated nickel(I) complexes as mediators for cathodic intramolecular cyclisations [2]. This methodology proved to be successful in the formation of carbocyclic products and substituted tetrahydrofurans. Such work has largely used aprotic organic solvents such as DMF which presents some toxicity.

Due to an increasingly “green”-conscious industrial community, researchers have started to examine more eco-friendly and sustainable chemical processes. Ionic liquids (ILs) represent a class of alternative solvents currently receiving serious consideration with the promise of both environmental and technological benefits [3].

A number of room-temperature ILs has been synthesized, characterized and applied in organic synthesis and catalyzed processes. Their characteristics render them promising replacements for volatile organic solvents (VOCs), which are a source of environmental problems.

In the present work, the reductive intramolecular cyclisation of bromopropargyloxy esters catalysed by electrogenerated (1,4,8,11-tetramethyl-1,4,8,11-tetraaza-cyclotetradecane)nickel(I), [Ni(tmc)]+ as the catalysts in ILs, N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide, [N1 1 1 2(OH)][NTf2] and 1-ethyl-3-methylimidazolium ethylsulfate, [C2mim][C2SO4] has been investigated by cyclic voltammetry and controlled-potential electrolysis. During controlled-potential electrolyses of solutions of Ni(II) complexes in the presence of bromopropargyloxy and bromoallyl derivatives, catalytic reduction of the latter proceeds via cleavage of the carbon–bromine bond to form a radical intermediate that undergoes cyclization to afford the substituted tetrahydrofurans [4].

ACKNOWLEDGEMENTS

We are grateful to the Fundação para a Ciência e Tecnologia (PEst-C/QUI/UI0686/2011) for financial support of this work.

REFERENCES

[1] B. Giese, “Radicals in Organic Synthesis: Formation of Carbon-Carbon Bonds”, Pergamon Press, Oxford, 1986.

[2] E. Dunach, M.J. Medeiros, S. Olivero, New J. Chem., 30, 1534 (2006).

[3] Ionic liquids IIIB: Fundamentals, Process, Challenges, and Opportunities, ACS Symp. Ser. (Eds.: R. D. Rogers and K. R. Seddon), ACS, Washington DC, 2005.

[4] 5. P.K. Mandal, G. Maiti, S.C. Roy, J. Org.
Chem., 63, 2829 (1998).
Effect of Temperature on Characteristic of Carbon Nanotube Nano-Composite Electrode Supercapacitor
Authors: Huang Naibao , Don Kirk , Thorpe Steven J. , Liang Chenghao , Xu Lishuang , Zhang Shuchun , Li Wan , Sun Min
Published: February 2020

In order to evaluate the effect of temperature on the performance of supercapacitors using coconut shell activated carbon (AC)/carbon nanotubes (CNTs) as nano-composite electrodes, the supercapacitor’s properties were tested in 1mol/L KOH solution at 35°C~60°C.The results indicated, when temperature increased from 35°C to 60°C, the resistance decreased from 0.83Ω to 0.78Ω by 6% and the capacitance increased from 93.32F/g to 104.36F/g by 11.8%. The effects were due to increased conductivity and carbon connectivity provided by the addition of CNTs. These results indicated that CNTs-based nano-composite electrode had good performance at high moderate temperature, and would be a promising material for use in low-cost electrical energy storage device.
Electrode Materials Away from Equilibrium for Lithium-Ion Intercalation
Authors: Cao Guozhong
Published: February 2020

Lithium-ion batteries store electrical energy in the form of chemical potential, the same as that in primary batteries; however, the charge-discharge process in lithium-ion batteries is more complex as it involves not only Faradaic reactions at the interface between electrodes and electrolyte, but also is accompanied with mass and charge transport and volume change of the electrodes that commonly possess low electrical conductivity. Electrodes away from thermodynamic equilibrium include nanostructures with high surface energy, poor-crystalline materials, and materials with significant surface or bulk defects. Such materials are in higher energy state and, thus, easier for phase transfer and nucleation; such materials also have less closely packed structure, permitting faster mass transport and accommodating more lithium-ions as well as tolerating more volume change. This presentation will take vanadium pentoxide and lithium titanate as two model materials to illustrate the influences of doping, surface defects and carbon coating, and nanostructures on the lithium-ion intercalation properties.
Optimization and Constant Capacity Cycling of the Core-Shell Carbon Silicon Composite Anode for Lithium Ion Batteries
Authors: Wen Hao , Soltis Richard , Karulkar Mohan
Published: February 2020

Accommodating the 3-fold volume expansion of silicon during lithiation is necessary to take advantage of its 10-fold larger capacity compared to industry-standard graphite. 1In this report, we describe recent experiments at using core- -shell C-Si composites that showed significant improvements in cycling performance over conventional C-Si composites.

The core- -shell structure is evident in FESEM, as shown in Figure 1. The ~100 nm Si cores are encapsulated inside larger carbon shells, leaving ~50 nm of hollow space. Previous studies showed that these structures are capable of accommodating the volume expansion of Si during lithiation without distorting the carbon shell, while maintaining a stable SEI layer.2Thermal gravimetric analysis showed that Si constitutes 75 wt% of the composite, close to the nominal 77 wt% as calculated from synthesis procedure.

Cycling to a fixed capacity of 1000 mAh/g, the cycling efficiency of the composite anode was mostly above 90% after the initial SEI formation, as shown in Figure 2. After the first cycle, subsequent cycling loops appeared to have a consistent shape, indicating reversible reaction chemistry.

Optimization of the core-hollow-shell composite is achieved by fine-tuning the fabrication process and cycling conditions. Constant capacity cycling controls the state of charge by limiting the integrated charge flow into the cell. The cutoff state of charge and the current density both have a significant effect on the cell performance. XRD reveals factors contributing to the irreversible charge loss at every cycle.

Improvement of the homogeneity of chemical coating and mixing was also studied. The precursor polymer used to produce the coating of carbon on the silicon nanoparticles directly impacts the geometry of the final product. The procedure for etching away the silicon dioxide shell with hydrofluoric acid was improved as well.

Reference

1. Li, X. & Zhi, L. Managing voids of Si anodes in lithium ion batteries. Nanoscale(2013). doi:10.1039/c3nr03197g

2. Liu, N. et al. A yolk-shell design for stabilized and scalable li-ion battery alloy anodes. Nano Lett.
12, 3315–21 (2012).
Silicon Nanowires and Nanotrees Electrodes for Pseudocapacitors
Authors: Sadki Said , Thissandier Fleur , Aradilla David , Berton Nicolas , Gentile Pascal , Bidan Gérard , Brousse Thierry
Published: February 2020

Supercapacitors integration in micro-electronic circuit should improve portable devices efficiency [1] and be easier with silicon (Si) electrodes. In our previous work we have realized highly doped Si nanowires (SiNWs) micro-supercapacitor (µ-SC) electrodes showing quasi ideal capacitive behavior [2, 3]. This works studies the elaboration and characterization of highly doped Si nanotrees (SiNTrs) µ-SC and SiNWs micro-pseudocapacitors electrodes. It focuses on our recent advances on SiNTrs growth and use in µ-SC.

SiNWs and SiNTrs are grown by CVD on highly doped Si via localized gold catalysis. SiNTrs are grown either by two CVD growths separated by a new gold deposition, or by a single growth in which an annealing (gold pours along NWs) separates trunks and branches growths [4, 5]. Electrochemical properties are evaluated in organic electrolyte (1M, NEt4BF4, PC) and ionic liquid (EMI-TFSI) by EIS, cyclic voltametry and galvanostatic charge/discharge. For PC PEDOT films was electrodeposited on SiNWs.

As seen previously, electrode capacity increases with the electrode developed surface, i.e. SiNWs length, density and SiNTrs branches. SiNTrs are tuned by fitting HCl gas ratio during trunk growth, annealing time and temperature. Doping gas/silane ratio monitors their doping level. Highly doped, dense, hyperbranched (L ≈ 3 µm, Ø ≈ 30 nm), 40 µm long SiNTrs electrodes have a 950 µF.cm-2 capacity, i.e. about 158 fold bulk Si one and twice 50µm long SiNWs electrode one. SiNTrs/SiNTrs µ-SCs show highly stable cycle efficiency (97 %) and capacity over at least 100 000 cycles for current densities ranging from 5 to 500 µA.cm-2. Using ionic liquid as electrolyte improves devices voltage and thus performances.

[1] J.R. Miller, P. Simon, Science, 2008, 321, 651

[2] F. Thissandier, and al, Electrochem. Comm., 2012, 25, 109

[3] F. Thissandier, and al, Nanoscale Res. Lett., 2012, accepted

[4] P. Gentile, and al, Nanotechnol., 2008, 19, 125608

[5] R. Maboudian, and al, J. Mater.
Chem., 2008, 18, 5376
Improvements in Li Air Batteries through Electrocatalysts, Electrode Structure Design and Modelling
Authors: Scott Keith , Cheng Hua , Sahapatsombut Ukrit
Published: February 2020

Rechargeable Li-air batteries allow Li+ and e- in the cell to react with O2 from the air and enable an increase in storage capacities up to 10 times cf. with Li ion. The air cathode is a new challenge for the battery. New nanostructured air cathode materials were fabricated, characterised by using XRD, TEM and SEM and tested as cathodes in rechargeable Li-air batteries. Such 3D nanomaterials displayed high capacity (up to 3000 mAhg-1). The superior performance of the nanomaterials was attributed to their structures which acted as transport pores The relationship between composition, especially ratios of catalyst to carbon, structure, properties and performance shall be discussed. Measures to tackle technical barriers in battery design and engineering will also be addressed. We have investigated the use of bifunctional MnO2/Au catalysts. This has provided significant improvement in its stability (stable cycling > 100) as well as a great improvement in the lithium air cell capacity (10,000mAh/g).

Battery performance is still affected by loss in capacity after repeated cycling due to instability of certain solvents and cathode carbon supports and ingress of CO2. A micro-macro homogeneous mathematical model was developed for the cycling operation of a porous Li-air cathode using concentrated binary electrolyte theory. The model includes mechanism for solvent degradation and production of Li carbonates. The physical and chemical property data is carefully applied in this model to predict the time dependance of electrolyte concentration, non-uniform porosity and reaction rate and loss of capacity after cycling. Alternative modes of battery operation are explored to improve power and energy density performance
Phase II SBIR Double Layer Electrode Technology for Advanced Space Power Technologies
Authors: Reich David , Nakahara Hiroshi
Published: February 2020

Under Phase II of this SBIR, Quallion is continuing development of its double-layer electrode technology for lithium ion batteries. The double-layer electrode technology increases adhesion of active materials to improve mechanical strength and the increased surface area increases conductivity. Quallion will refine its electrode design based on lessons learned in Phase I by adjusting the composition of coating materials and the electrode coating process, and incorporating the double-layer electrode into commercial satellite cell designs. Quallion is building prototype cells and will perform testing to validate their performance and to generate data for further analysis. Quallion will present initial data which will include rate capability, capacity, and cycle life characterization on test cells.
Comparison Study of Various Anode Materials for Li-Ion Capacitors
Authors: Tropy Nolan Lance , Cao Wanjun , Zheng Jim P.
Published: February 2020

Lithium-ion Capacitors (LICs) have attracted much attention as a new power source due to its high energy density compared to conventional electric double-layer capacitors (EDLCs), and its high power density compared to batteries as well as having the long cycle life. Recently, some research work1-2 in our group has been done on LICs. In this abstract, various carbon material anode electrode including hard carbon, soft carbon and graphite were studied and compared for the Li-ion Capacitors application.

To compare the hard carbon, soft carbon and graphite, three Li-ion capacitor full cells with these carbon electrodes were assembled to compare the power and cycle performance. Figure 1 presents the voltage profiles of the LIC full cells with various carbon electrodes. It can be seen that the swing potential of hard carbon and soft carbon anode electrodes is in a wider range than graphite electrodes. The swing potential range of hard carbon and soft carbon negative electrodes is 0.2-0.4 and 0.4-0.7 V vs. Li/Li+, respectively; which are above 0 V vs. Li/Li+ and can suppress the formation of lithium dendrites in anode to a large extent. On the other side, the potential plateau of graphite anode electrode is near 0 V vs. Li/Li+, which increases the possibility for lithium dendrites to form and short the LIC cells.

The LIC full cells with various carbon electrodes were also tested in Figure 2. This was done in order to compare the energy, power and cycle performance. It can be obviously observed from Figure 2(a) that LIC full cell with hard carbon electrode displays both higher energy density and higher power density than the cells with soft carbon and graphite. For the cycle performance as shown in Figure 2(b), after 1000 cycles, the LIC cell with hard carbon can retain up to 100% while the LIC cells with soft carbon and graphite only retain up to 80% and 78% of the initial discharge energy density, respectively. Based on the evaluation of the electrochemical properties including energy, power and cycle performance of the various carbon electrodes, it is concluded that hard carbon is the best option for negative electrode, as it displays a higher energy density, power density and longer cycle life implemented in two-electrode Li-ion capacitor systems.

References

1. W.J. Cao, J.P. Zheng, J. Power Sources, 213, 180 (2012).

2. W.J. Cao and J.P. Zheng, J. Electrochem. Soc. 160, A1572 (2013).
Molybdenum Doping of Li4Ti5O12 in a Reducing Atmosphere for High-Power Lithium Ion Batteries
Authors: Yoo Dongseok , Choi Jihwan , Kim Yong-tae
Published: February 2020

Li4Ti5O12 (LTO) is recognized as being one of the most promising anode materials for high power Li ion batteries; however, its insulating nature is a major drawback. In recent years, a simple thermal treatment carried out in a reducing atmosphere has been shown to generate oxygen vacancies for increasing the electronic conductivity of this material. Such structural defects, however, lead to re-oxidization over time, causing serious deterioration in anode performance. Herein, we report a unique approach to increasing the electronic conductivity with simultaneous improvement in structural stability. Doping of LTO with Mo in a reducing atmosphere resulted in extra charges at Ti sites caused by charge compensation by the homogeneously distributed Mo6+ ions, being delocalized over the entire lattice, with fewer oxygen vacancies generated. Using this simple method, a marked increase in electronic conductivity was achieved, in addition to an extremely high rate capability, with no performance deterioration over time.
A Combined Investigation into the Effect of Ni/Mn/Co Ions on Lithium-Ion Battery Anodes Using X-Ray Photoelectron Spectroscopy and Secondary Ion Mass Spectrometry
Authors: Nitta Naoki , Benson Jim , Lee Jung Tae , Kovalenko Igor , Tighe Sean , Fuller Thomas F. , Yushin Gleb
Published: February 2020

Nickel Cobalt Manganese (NCM) cathodes utilize the combination of transition metal ions to achieve good specific capacity, voltage, and safety characteristics, and are among the best performing of industrially produced cathode materials. However, Mn is known to escape the cathode via a disproportionation reaction as Mn2+, and has been detected on the anode solid electrolyte interface (SEI). Furthermore, batteries incorporating Mn in the cathode are known to have a reduced cycle life due to increased impedance (1). A recent study of Lithium Manganese Oxide (LMO) cathodes reveals the Mn to stay in the 2+ oxidation state (2), but little is otherwise known about the role of Mn in the SEI layer.

To analyze the effect of the SEI on the degradation of NCM full cells, the authors previously analyzed anodes taken from commercial NCM batteries of varying degrees of degradation (3). X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) were used along with other techniques to analyze the presence of elements in the SEI as a function of depth. However, analysis of chemical species was complicated by the presence of PVDF binder, air exposure of the sample, and ion implantation/chemical decomposition due to exposure to a high energy ion beam.

In this study, the effect of temperature, cycling, and the presence of transition metal ions were studied in thin film half cells. Ni2+, Mn2+, and Co2+ion salts were each introduced, as these ions all dissolve into the electrolyte from NCM cathodes and have been detected in the SEI (4,5). A thin film carbon anode was used to obviate the binder, and allow clearer chemical analysis and depth profiling. XPS analysis was used to reveal chemical information about the SEI, while SIMS was used to provide a depth profile.

XPS analysis showed an increase in LiF composition with the number of charge/discharge cycles for all cells, but otherwise indicated a chemically different SEI when the salts are added. SIMS analysis showed the presence of Ni/Co/Mn ions and other species through the depth of the SEI layer. By combining these two methods, the character of the SEI with and without the transition metal ions was hypothesized.

REFERENCES

M. Wohlfahrt-Mehrens, C. Vogler, J. Garche, J. Power Sources
127, 58-64 (2004).

C. Zhan, J. Lu, A. Jeremy Kropf, T. Wu, A. N. Jansen, Y.-K. Sun, X. Qiu, K. Amine, Nat. Commun.
4, (2013).

J. T. Lee, N. Nitta, J. Benson, A. Magasinski, T. F. Fuller, G. Yushin, Carbon
52, 388-397 (2012).

D. P. Abraham, T. Spila, M. M. Furczon, E. Sammann, Electrochem. Solid-State Lett.
11, A226-A228 (2008).

H. Zheng, Q. Sun, G. Liu, X. Song, V. S. Battaglia, J. Power Sources
207, 134-140 (2012).
Spinel NiCo2O4 As a Promising Electrode Material for Li-Ion and Li-O2 Batteries
Authors: Jadhav Harsharaj S. , Park Chan-Jin
Published: February 2020

Secondary Li-ion batteries have played an important role as an energy storage device for portable electronics and electric/hybrid electric vehicles (EV/HEV). However, the energy density of conventional Li-ion battery is not sufficient, and thus a Li-O2 battery can be a potential alternative to Li-ion batteries due to its much higher energy density.

In addition, transition metal oxides with nanostructural characteristics have shown good performance due to their advantage of high surface to volume ratio and short length for Li-ion diffusion in comparison with their bulk counterparts. Previous studies showed that the spinel NiCo2O4 is an excellent candidate as an electrode material for Li-ion and Li-air batteries. NiCo2O4, a well-known cobalt-nickel spinel oxide, owns two solid-state redox couples (Co3+/ Co2+ and Ni3+/Ni2+) in the structure, which enables to exhibit a remarkable elctrocatalytic activity. In the present study, we have investigated the electrochemical performance of spinel NiCo2O4, as an anode material for Li-ion battery and cathode material for Li-O2 battery.

In the present study, spinel NiCo2O4 has been synthesized by simple and inexpensive urea assisted co-precipitation method and subsequent annealing at 400 oC for 2h.The TG and DSC analysis was carried out to analyze the weight loss during heat treatment. The spinel structure of NiCo2O4 was confirmed by the X-ray diffraction (XRD) analysis. The FE-SEM analysis reveals the formation of spinel NiCo2O4 with urchin like structure, composed of several nanorods. The nanorods are highly porous consisting of interconnected nanoparticles confirmed by TEM analysis. The N2 adsorption-desorption was carried out to investigate the surface area and porosity of spinel NiCo2O4. The electrochemical investigation of spinel NiCo2O4 as an anode material for Li-ion showed excellent cyclability (~1020 mAh.g-1 at 0.2C upto 200 cycles) and superior rate capability. The use of spinel NiCo2O4 as cathode material in Li-O2 cell, exhibit an excellent performance reasonable specific capacity, and lower overpotential. In conclusion, Spinel NiCo2O4 can be a potential candidate as an electrode material for Li-ion and Li-air batteries.
Synthesis of ZnO@Ni(OH)2 Nanostructures for Application in High-Performance Supercapacitors
Authors: Luo Yi-Hsiang , Liao Yun-Wen , Wang Jun-Yi , Huang Jin-Hua
Published: February 2020

Recently, supercapacitor has become a preferred energy storage device because it has higher power density than batteries and higher energy density than conventional capacitors and fast charge/discharge rates. Among the often used supercapacitor electrode materials, pseudocapacitive metal oxide exhibits much high capacitance, but the poor electrical conductivity limits its performance. In order to overcome this disadvantage, one dimensional ZnO nanowires (NWs) are widely employed because they can serve as a direct electrical pathway for electrons and provide a larger surface area for loading metal oxide. [1]

Base on above considerations, in this work, we fabricated the Ni(OH)2 coated ZnO electrodes for use in supercapacitors. As shown in Fig. 1, the Ni(OH)2 coated ZnO electrode consists of upstanding nanowires (NWs) and outstretched Ni(OH)2flakes grown all over each nanowire.

First, ZnO NWs was grown by immersing the seeded FTO substrate in aqueous solutions containing 0.01 M zinc acetate dihydrate and 0.01 M hexamethylenetetramine (HMTA) at 90 oC for 5 h. These ZnO NWs were then used as the trunks for the growth of Ni(OH)2 flakes. The Ni(OH)2 flakes were synthesized by the pulse galvanostatic electrodeposition onto the surface of ZnO NWs in aqueous solution of 5 mM nickel nitrate hexahydrate for 2 min at room temperature. The parameters of pulse galvanostatic electrodeposition include current density, pulse time (ton), and relaxation time (toff), the optimized conditions for pulse galvanostatic electrodeposition are 1 mA/cm2, 1 s, and 10 s respectively.

We have achieved a high specific capacitance 1827 F/g at a discharge current density of 2 A/g, corresponding discharge curves are shown in Fig. 2. Fig. 3 reveals the highest energy density and power density are 185.0 Wh/kg and 9.0 kW/kg, respectively. Effects of current density, ton, toff, and deposition time on the performance of supercapacitors were investigated.

Reference

Y. B. He, G. R. Li, Z. L. Wang, C. Y. Su, Y. X. Tong, Energy Environ. Sci., 2011, 4, 1288-1292.
Structure Design and Doping Modification of Li4Ti5O12 for Lithium Lion Batteries
Authors: Fan Li-Zhen , Ni Haifang
Published: February 2020

Because of its extreme safety and outstanding cycle life, spinel Li4Ti5O12
has been regarded as one of the most promising anode materials for lithium-ion batteries [1]. However, Li4Ti5O12 suffers from poor electronic conductivity, making it a challenge to achieve high capacity at high rates. Due to the superior electron mobility, high surface area and structural stability, carbon materials are expected to be a potential alternative for the conductive phase in lithium ion batteries.

Here, we describe a new strategy to the synthesis of three-dimensional (3D) hybrid-structure Li4Ti5O12/carbon for high-performance lithium-ion batteries by liquid deposition technique using carbon nanotubes (CNTs) [2], graphite oxide (GO) [3], porous carbon (PC) [4], carbon black (CB) as matrix, respectively. The intimate contact between the carbon framework and Li4Ti5O12 nanoparticles suppresses the agglomeration and growth of Li4Ti5O12 nanoparticles, and affords a highly conductive matrix for the rapid ionic and electronic conductions.Thereby, the as-prepared Li4Ti5O12/carbon composites exhibit greatly improved electrochemical performance compared with bulk Li4Ti5O12, showing excellent rate capability (120~150 mAh g-1 at 20 C) and cycling performance. The good performance is due to the short diffusion lengths of the Li4Ti5O12 nanoparticles uniformly dispersed on the highly conductive 3D carbon matrix.

In addition, Br-doped Li4Ti5O12 in the form of Li4Ti5Br
x
O12-x
(x= 0, 0.1, 0.2, 0.3, 0.4) was synthesized, the effects of Br doping on the structures and electrochemical properties of Li4Ti5O12 were extensively studied. Although Br doping did not change the phase composition, obvious effects on the particles morphology and size were observed. The as-synthesized Li4Ti5O11.8Br0.2 electrode presents much higher discharge capacity (161 mAh g-1 at 5C) and better cycle stability than that of other electrodes.

References

1. T. Ohzuku, A. Ueda, and N. Yamamoto, J. Electrochem. Soc.,
142, 143 (1995).

2. H.F. Ni, and L.-Z Fan, J. Power Sources, 214, 195 (2012).

3. L.F. Shen, C.Z. Yuan, H.J. Luo, X.G. Zhang, S.D. Yang, and X.G. Lu, Nanoscale, 3, 572 (2011).

4. L.F. Shen, X.G. Zhang, E. Uchaker, C.Z. Yuan, and G. Z. Cao, Adv. Ener. Mater.,
2, 691 (2012).
Highly Doped Conjugated Polymers for Electrochemical Energy Storage
Authors: Lutkenhaus Jodie , Jeon Ju-Won , Mike Jared
Published: February 2020

Electrodes composed of conjugated polymers (CPs) offer the potential of high-capacity, high-energy density electrochemical energy storage. CP electrodes are conductive, have high Coulombic efficiency, and are synthetically versatile. These materials store charge through electrochemical reduction and oxidation, otherwise known as de-doping and doping, respectively. Commonly explored CP electrodes, such as polyaniline or polypyrrole, can only achieve doping levels of 0.3-0.5, which result in only modest capacities and energies. Here, several routes to achieve doping levels as high as 0.9 are presented, wherein the result is a CP electrode that bears a capacity 90% of its theoretical value. It should be noted that even higher doping levels are possible with the addition of redox-active side chains. In the first route, aniline is synthesized in the presence of a polyacid to achieve a water-dispersible polyaniline:polyacid colloid. The polyacid acts as the dopant and provides non-covalent interactions that stabilize polyaniline in its most highly doped state, pernigraniline salt. Because of this stability, polyaniline can be reversibly reduced and oxidized up to 4.5 V vs. Li/Li+. The implementation of polyaniline:polyacid in a layer-by-layer electrode is also presented. The second route to high doping levels focuses upon electron-rich polymers, such as poly(dithienopyrroles), or poly(DTPs). Side chains are used to modify the poly(DTP)’s interaction with electrolyte, the backbone’s planarity, and the resultant conjugation. In the long term, high-capacity, high-energy CP electrodes potentially enable the formation of flexible energy and power for use in flexible electronics and other applications requiring unconventional shapes and form factors.
Microscopic Origin of the Ionic Transport Behaviors in Solid Electrolytes for Li Batteries
Authors: Ma Cheng , Liang Chengdu , More Karren , Chi Miaofang
Published: February 2020

Recently Li-ion-conducting solid electrolytes have received intensive research interest, as they provide solutions for issues associated with the organic liquid electrolytes in conventional Li-ion batteries. However, despite the relatively high bulk conductivity achieved in many solid electrolytes, the grain-boundary conductivity is frequently low and limits the application. Detailed atomic structure and elemental distribution on the grain boundaries in these materials must be revealed in order to fundamentally understand the origin of large grain-boundary resistance. Such studies, however, are currently very rare. Here we present a detailed atomic scale study on the conduction behaviors of an extensively studied solid electrolyte (Li3x
La2/3-x
)TiO3 (LLTO). Using aberration-corrected scanning transmission electron microscopy (STEM) and the associated electron energy loss spectroscopy (EELS) analysis, we found that the large grain-boundary resistance of LLTO arose from the intrinsic local structural reconstruction, which is energetically not favorable for Li accommodation. Therefore, large flux of charge carriers was unlikely to occur both along and across the grain boundary, leading to the poor grain-boundary conductivity. The relationship among the processing condition, microstructure, and ionic conductivity was established. And the ionic transport behavior in LLTO is further compared to that in garnet-type Li7La3Zr2O12. These results paved the way for further improvement of the Li-ion-conducting solid electrolytes.
Atomic-Level Manipulation of Multivalent Ion Intercalation Materials for High-Density Energy Storage
Authors: Yao Yan , Liang Yanliang , Li Yifei
Published: February 2020

Energy density and safety are key elements to transportation batteries, which are required to be weight/space efficient and should sustain harsh environments. Batteries based on multivalent metal cations, such as rechargeable magnesium batteries, are a promising technique for the pursuit of ultra-high-density energy storage which will deliver over four times higher volumetric energy densities than those of state-of-the-art lithium-ion batteries. Since multivalent cations are typically highly polarizing, they form large complex ions with solvent molecules and have strong electronic interaction with intercalation host materials, leading to inferior electrode performance. In this talk, I will present a general methodology of tailoring established lithium-intercalation hosts for multivalent metal cations. By combining theoretical modeling, chemical engineering, and electrochemical characterization, we have demonstrated that the ion intercalation and diffusion kinetics can be effectively improved by atomic-level manipulation of intercalation materials. This strategy enables a family of electrode materials for intercalation of multivalent cations, which are previously perceived as not suitable for the purpose.
Elucidation of Electrode-Electrolyte Interfaces Using Neutrons
Authors: Veith Gabriel M , Browning James F , Baggetto Loic
Published: February 2020

This presentation will describe experimental characterization of the thickness and composition of the reaction products on silicon anode materials and aluminum current collectors measured using neutron reflectometry. NR is a neutron scattering technique highly sensitive to morphological and compositional changes occurring across surfaces and interfaces, including buried interfaces. It can be used to study such changes over lengths scales extending 1 nm to hundreds-of-nanometers. Neutrons, by virtue of their nature, are deeply penetrating and therefore ideally suited as a probe to study materials in complicated environments, such as electrochemical cells. Unlike x-rays, neutrons interact with the nuclear potential of constituent element and are sensitive to light elements like Li and H.

We will show that the SiOx surface of silicon materials react irreversibly with the electrolyte 1.2M LiPF6-3:7 wt% ethylene carbonate:dimethyl carbonate. The reaction product is a complex mixture of Si-O-F-C species. It is dense and homogenous and has a thickness of about 3.5 nm. Similar reaction chemistry is observed for Al current collectors. Insights from these measurements will provide a framework to understand capacity losses with cycling of high energy density materials.

Acknowledgement:

This research was supported by the Materials Sciences and Engineering Division, Office of Basic Energy Sciences, U.S. Department of Energy under contract with UT-Battelle, LLC (LB, GMV). This Research at Oak Ridge National Laboratory's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U. S. Department of Energy.
Structure Evolution and Kinetics Study of Layered LiNixMnyCozO2 (x+y+z=1) Cathode Materials during Charge Using Synchrotron X-Ray Techniques
Authors: Zhou Yongning , Cho Sung-Jin , Bak Seong-Min , Yu Xiqian , Nam Kyung-Wan , Yang Xiao-Qing
Published: February 2020

Layer structured mixed transition metal oxides LiNixMnyCoyO2 (x+y+z=1, NMC) have been widely studied as promising cathode materials for Li-ion batteries due to their superior properties, better thermal stability, lower cost and higher capacity comparing to LiCoO2, which is the widely used cathode material for Li-ion cells. A typical NMC cathode with a composition of 1:1:1 (LiNi1/3Mn1/3Co1/3O2) is already being used in commercial lithium-ion battery cells. However, more systematic studies on the structure-performance relationship of the NCM materials are needed. It is critical to understand the role of each element in electrochemical performance in terms of the capacity, rate capability, cycling and calendar lifes as well as safety characteristics. In this regard, we present here a systematic study on the structural changes that occur in the NMC cathode materials with several different compositions such as NMC = 333, 433, 532, 622 and 811 during charge using combined in-situ synchrotron based X-ray techniques.

While in situ X-ray diffraction (XRD) was used to track the average bulk crystal structural changes, in situ X-ray absorption spectroscopy (XAS) was applied to monitor the electronic structure and local structure changes around each transition metal element (Ni, Mn and Co) in the NMC cathode during charge. In addition, time-resolved XRD and Quick-EXAFS were also used for monitoring its structural changes and kinetic property of each transition metal upon charge at different C rates (C/10 to 30C). Detailed results including in situ XRD and XAS on the NMC materials with various NMC compositions during charge will be present.

Acknowledgement

The work done at Brookhaven National Lab. was supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies under Contract Number DEAC02-98CH10886.
Investigation of Rare-Earth Electrochemistry in Molten Oxides
Authors: Lambotte Guillaume , DeLucas Rachel , Allanore Antoine
Published: February 2020

Molten oxides have successfully been used as electrolyte for the extraction of relatively noble metals in their liquid phase [1], offering a new paradigm in metal extraction that can mitigate GHG emissions thanks to the use of C-free electricity as well as the development of new inert anode materials [2,3].

Such developments have been possible thanks to the commensurable knowledge gained on well-established molten oxide systems that have a key role in pyrometallurgy, glassmaking or magma chemistry. Unfortunately, the perspective of extending such concept to more reactive metals extraction like the rare-earths is rapidly challenged by a surprising reality: there are only a limited amount of thermodynamic data available to describe rare-earth oxide chemistry in molten oxides.

The present paper therefore offers to discuss the recent thermodynamic and electrochemical developments achieved in our laboratory on rare-earth oxides chemistry in such electrolytes. In particular, the methodology behind electrolyte design, and the results obtained in the prediction of the corresponding phase diagrams will be discussed. Recent electrochemical results obtained with the identified systems will be presented.

[1] D. Wang, A.J. Gmitter, and D.R. Sadoway, J. Electrochem. Soc., 158 (6), E51-E54 (2011)

[2] A. Allanore, L. Yin and D.R. Sadoway, Nature, 497 (7449), 353–356, (2013)

[3] A. Allanore, Electrochimica Acta, 110, 587-592, (2013)
Voltammetric Analysis of Antispasmodic Drug Drotaverine Hydrochloride in Pharmaceutical Preparations Andbiological Medium
Authors: Jadon Nimsha , Jain Rajeev
Published: February 2020

Drotaverine hydrochloride is an antispasmodic drug widely used to relieve cramps or spasms of the stomach, intestines, and bladder.The electro reductive behavior of drotaverine has been investigated and one irreversible well-defined cathodic peak was observed at -1.04 V vs. Ag/AgCl (3M KCl). The electrochemical reduction and adsorption of drotaverine hydrochloride was studied in phosphate buffer medium by cyclic voltammetric (CV), differential pulse cathodic adsorptive stripping voltammetric (DPCAdSV) and square-wave cathodic adsorptive stripping voltammetric (SWCAdSV) techniques at hanging mercury drop electrode (HMDE). A fully validated, sensitive and reproducible cathodic adsorptive stripping voltammetric procedure for the trace determination of the bulk drug in pharmaceutical formulation and in biological medium has been developed.

The peak current showed a linear dependence with the drug concentration over the range 50 ng/mL to 25.6 µg/mL for SWCAdSV and 0.2 µg/mL to 51.8 µg/mL for DPCAdSV. The achieved LOD and LOQ were 7.1 ng/mL and 23.7 ng/mL by SWCAdSV and 33.84 ng/mL and 112.8 ng/mL by DPCAdSV respectively. The procedure was applied to the assay of the drug in tablets form with mean percentage recoveries of 100.4% with SWCAdSV and 100.2% with DPCAdSV. Applicability to assay the drug in spiked urine and serum samples were illustrated and minimum detectability were found to be 32.66 ng/mL and 49.83 ng/mL respectively.
Anodic Stripping Voltammetry Using Nanoelectrodes
Authors: Freeman Neville J , Kay Nicola J , Sultana Reshma , Hick Camilla , Boxall Colin , Ferrer-Huerta Miriam
Published: February 2020

Anodic stripping voltammetry is an important technique for the detection of trace metals. The technique is very sensitive but requires careful control of a range of parameters including the conditioning of the working electrode, the temperature and the hydrodyanamics. In theory nanoelectrodes are immune to stirring and thus this parameter ought to be of far less consequence in the analysis protocol. In this paper we report of preliminary studies of trace metal analysis using a commercial nanoelectrode structure and examine the robustness of the overall analytical technique.
Rapid Voltammetric Determination of Traces of Zn2+ in 105 Excess of Ni2
Authors: Zlatev Roumen , Stoytcheva Margarita , Medina Pablo Alberto Romero , Reyes Ana Luisa , Valdes Benjamin
Published: February 2020

The impurities determination in Ni electrolysis baths is of a great importance for the quality of the Ni electroplating protective and decorative coatings. Inclusions having more negative potential than Ni form corrosion anodic zones in the presence of humidity, corrupting the Ni layer protective properties. One of the most dangerous inclusions is Zn.

Zn often appears in the Ni coatings deposited on brass, as a result of the brass detail dissolution in the low pH Ni baths before the beginning of the electrolysis: the deposition of the first Ni layer.

As known, the maintenance of the Zn2+ concentration in the Ni bath bellow 3 ppm can prevent Zn inclusions formation in the Ni coatings, which requires on-line Zn2+ determination. Nevertheless, spectral analytical methods such as AAS and ICP cannot be applied after Zn2+ extraction from the high concentrated matrix, because the huge Ni2+ concentration will provoke crystallization in the nebulizer area corrupting the analysis. The direct application of some voltammetric techniques also cannot yield any results, because of the very small difference of the E½ of the two species, which will cause peak overlapping. Some specific properties of the Ni2+ and Zn2+ ions however can be used to avoid the interferences. It is known that Zn2+ forms soluble hydroxyl complex in the presence of excess of OH-, while Ni2+ forms the very stable Ni(OH)2 precipitation product. Thus, KOH or NaOH can be applied as a supporting electrolyte, in which a well defined peak of Zn2+ is registered as shown in Fig. 1, while no peak of Ni2+will appear because of its precipitation.

The effect of the NaOH concentration applied as a supporting electrolyte, of the Zn2+ adsorption by the formed Ni(OH)2 precipitation product, and of the Ni2+/Zn2+ concentration ratio on the analytical characteristics of the Zn2+ determination are the subject of this study. The results are presented and discussed. It is demonstrated that the developed method consisting in adding of a small volume of Ni electroplating bath solution to the NaOH supporting electrolyte, followed by DPV determination can be applied for the on-line Zn2+ determination.