bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Investigation of Na2MnSiO4, a Novel Cathode Material for Rechargeable Sodium Ion Batteries
Authors: Murphy Denissa Tjiadarma , Schmid Siegbert
Published: February 2020

Lithium ion batteries dominate the world’s requirements of portable power storage due to their superior energy and power capability. However, as the focus of battery applications shifts towards larger scale energy storage, placing pressure on the declining amount of usable lithium, research interests shift towards the development of sodium ion batteries. Recently, various sodium based cathode materials have been based on structures that allow lithium insertion. Mixed-polyanion lithium compounds have been shown to be suitable precursors as they have the structural stability required for the complete exchange of lithium with sodium.1 The silicates Li2
MSiO4, (M = Mn and Fe), fulfil today’s requirements of safe, cheap and sustainable cathode materials especially due to the abundance of iron, manganese and silicon. The relatively higher theoretical capacities for these materials arise due to the possible extraction of two lithium ions accessing the M
2+/M
3+ and M
3+/M
4+ redox couples.2 The clear advantages of Li2
MSiO4, (M = Mn and Fe), over other lithium insertion compounds have made these materials attractive as possible analogues for cathode materials in Na-ion batteries.

While the structure of Na2MnSiO4 (monoclinic, space group Pn) has been reported previously employing conventional X-ray diffraction technique,3 the possibility of this compound to be utilised as a cathode material in sodium ion batteries has not been explored. To date, we have been able to synthesise the Na2MnSiO4 and investigated the structural parameters of the compounds through the combination of synchrotron X-ray and neutron powder diffraction studies. This contribution will also address the electrochemical behaviour of this compound, including structural changes which occur in Na2MnSiO4during electrochemical cycling and the connection of these structural changes to the observed properties.

References:

[1] Zhu, Y.; Xu, Y.; Liu, Y.; Luo, C.; Wang, C. Nanoscale, 2013, 5, 780.

[2] Islam, M. S.; Dominko, R.; Masquelier, C.; Sirisopanaporn, C.; Armstrong, A. R.; Bruce, P. G. Journal of Materials Chemistry, 2011, 21, 9811.

[3] Duncan, H.; Kondamreddy, A.; Mercier, P. H. J.; Le Page, Y.; Abu-Lebdeh, Y.; Couillard, M.; Whitfield, P. S.; Davidson, I. J. Chemistry of Materials, 2011, 23, 5446.
Synthesis and Electrochemical Characterization of NaxMO2 as Electrode Materials for Sodium-Ion Batteries
Authors: Huynh L.T. Nguyen , Ramos J.P. Pereira , Baddour-Hadjean Rita , Nguyen V. Hoang , Tran V. Man , Le Phung My Loan
Published: February 2020

Nowadays, Na-ion batteries have been largely investigated for large scale applications such as grid storage and transportation because of the huge availability of sodium, its low cost and the similarity of both Li and Na insertion chemistries[[i]]. Some efforts have also been devoted to meet requirements in electric and portable devices such as cell phone or laptop. To do this, we must solve problems involving structural collapse due to high volume change during insertion/deinsertion. A good way to design the sodium electrode materials is by starting with analogue ones that function well for Li-ion batteries[i]. Layer structure of NaxMO2 composition seem to be greatly promising[i] due to its high capacity as well as good structural stability.

This work presents structure study and electrochemical behaviors of NaxMO2 (M = Mn, Ni and Co) as positive electrode materials synthesized by solid state reaction at 800oC. X-ray diffraction showed that structure of cobalt-based compound was the same as layer P2-Na0.74CoO2
[[ii]]. The single phase of Na0.44MnO2 was obtained by using difference manganese precursors (carbonate, acetate and electrolytic manganese dioxide) and the compound used acetate precursor revealed the best crystallinity. Ni-based compound could not form without O2 oxidation atmosphere. Cyclic voltammetry and charge/discharge testing in Swagelok cell with Na metal as anode between 2 - 3.8 V vs Na+/Na exhibited a series of phase transitions. We also determined the diffusion of sodium ion into tunnel structure by GITT Technique. The results will be further discussed.

Acknowledgements

This work was supported by National Foundation for Science and Technology Development (Nafosted) through Project Fund granted of 104.03-2012.46.

References

[i] Simon Engelke, Storage4, 2013, 1, 1.

[ii] J.J. Ding, Y.N. Zhou, Q. Sun, X.Q. Yu, X.Q. Yang, Z.W. Fu, Electrochemica Acta, 87, (2013), 488-393.
Ionic Liquid Based Electrolyte Systems Enabling Operation of High Voltage Cathode Materials
Authors: Snook Graeme Andrew , Huynh Thuy Diem , Ruether Thomas , Best Adam Samuel
Published: February 2020

Lithium batteries are becoming increasingly important in hybrid and electric vehicle applications. The common cathode materials for these batteries, when based on metal oxides, are reaching their limits in terms of gravimetric capacity (mAh/g). In an effort to push the boundaries in energy density (Wh/kg) for these devices, there is an increasing push to higher voltage cathode materials such as LiMn0.33Ni0.33Co0.33O2 and the LiNi0.5Mn1.5O4 type materials, where the highest capacities of the materials are accessed at potentials greater than 4.6 V vs. Li|Li+. With this push for higher energy and higher voltage there is a limit to the types of electrolytes that are compatible with these materials and allow for the higher operating voltages. Standard battery electrolytes such as (1.2 M LiPF6 in EC/DMC) are well known to be unstable at these high voltages as well allowing severe Aluminium current collector corrosion. A key enabler to increasing the energy density of a lithium battery is an improved electrolyte.

At CSIRO, we have been at the forefront of developing new ionic liquid based electrolytes to enable the next generation of high voltage electrodes. The key factors to consider besides essential properties such as solution conductivity, Lithium ion diffusivity, viscosity, etc are the electrochemical windows of these solvents (i.e. stability at high cathodic voltages), the stability of the Aluminium current collector (i.e. limited corrosion in the solvent) and the compatibility of the high voltage cathode materials in these electrolytes (i.e. limited solubility of charge/discharge products in the solvent). At this time, there is a significant effort to identify solvents (blends), lithium salts and / or additives that can stabilize the cathode in contact with the electrolyte and preclude Aluminium current collector corrosion.

Specifically described in this work is our progress in developing ionic liquids electrolytes as well as blends of these with other solvents and additives for high voltage cathode applications. SECM characterisation to detect cathode dissolution and current collector corrosion has been carried out, as well as long term cycling of lithium cells incorporating the high voltage cathodes.
Modeling Lithium Stripping and Plating
Authors: Horstmann Birger , Hein Simon , Latz Arnulf
Published: February 2020

Lithium-metal anodes are an indispensable ingredient of next-generation lithium battery concepts, as they offer energy densities comparable to those of new cathode chemistries, e.g., Li-O2 and Li-S. However, lithium-metal anodes undergo morphologic changes during battery cycling which reduces battery performance and safety. Lithium plating on standard graphite anodes is a related phenomenon. At low temperatures or high rates, lithium can deposit on the graphite surface as metal instead of intercalating.

Here, we approach crystallization of lithium metal from two directions. On a mesoscopic level, we model the dissolution of lithium metal. Experimentally, droplet formation, i.e., lithium stripping, was observed during the dissolution of lithium dendrites [1]. Based on our models for electrochemically-driven surface growth [2–4] inspired by phase-field modeling [5], we accurately describe lithium dendrite dissolution. In our model, the interaction between SEI and lithium metal is responsible for the nucleation of a Rayleigh-Jeans instability leading to droplet formation [6] driven by the lithium metal surface energy.

On a macroscopic level, we model lithium plating in a three-dimensional thermal transport and reaction model of the full battery cell. Our model accounts for consistent transport [7] and reaction [4] kinetics in electrolyte and electrode particles in order to understand the influence of inhomogeneous nucleation of lithium metal in a graphite anode on the battery performance.

Literature

[1] J. Steiger, D. Kramer, and R. Mönig, To Be Submitt. (2013).

[2] B. Horstmann, B. Gallant, R. Mitchell, W. G. Bessler, Y. Shao-Horn, and M. Z. Bazant, J. Phys. Chem. Lett. 4, 4217–4222 (2013).

[3] M. Z. Bazant, Acc. Chem. Res. (2013).

[4] A. Latz and J. Zausch, Electrochim. Acta 110, 358–362 (2013).

[5] L. Liang, Y. Qi, F. Xue, S. Bhattacharya, S. J. Harris, and L.-Q. Chen, Phys. Rev. E 86, 051609 (2012).

[6] J. Eggers, Rev. Mod. Phys. 69, 865–929 (1997).

[7] A. Latz and J. Zausch, J. Power Sources 196, 3296 (2011).
In Operando Nanoscale Imaging for Lithium and Sodium Intercalation Compounds
Authors: Meng Shirley , Ulvestad Andrew , Shpyrko Oleg , Cho Hyung-Man , Qian Danna
Published: February 2020

Coherent x-ray diffractive imaging (CXDI), a lensless form of microscopy capable of discerning electron density and strain with 20 nm resolution, is used to map the strain evolution of a single cathode particle in a functional battery as it is cycled in-situ. The evolution of compressive/tensile strain reveals a number of interesting phenomena. For instance, a strain front nucleates and propagates inward/outward during discharge/charge. Strain can be quantitativley correlated to the Lithium amount in the initial cycles, eventually becoming uncorrelated upon longterm cycling. We demonstrate that CXDI is a powerful diagnostic tool to reveal correlation between strain and electrochemistry at the single particle level and offers valuable information for electrode/battery modeling and future battery design. Scanning electron microsocpy and electron energy loss spectroscopy (STEM/EELS) offers unprecendented spatial resolution, which has enabled nanoscale imaging and chemical anslysis of the interfaces, ground boundaries and phase boundaries. By combinign electron based and X-ray based novel imaging techniques, we showcase the state-of-the-art diagnostic tools developed for probling functional battery materials in operando.
Influence of the Electrode Morphology on Lithium-Ion Battery Performance
Authors: Indrikova Maira , Golks Frederik , Kwade Arno
Published: February 2020

In the future the application of lithium ion batteries as an energy carrier for electric and hybrid electric vehicles will become important field in automotive industry. To achieve this aim, the power density, energy density and long term stability of a battery have to be increased. Sophisticated mixing processes as well as the calendaring process (electrode compression) are known to significantly affect the above mentioned criteria, in particular the electrochemical cell performance [1-3]. However, the underlying cause-effect relationships are to a large extend still unclear.

The presented work investigates the influence of the electrode morphology on the electrochemical performance of the lithium ion battery, aiming at a model which correlates the intrinsic electrode design with characteristics, influence and dependencies of the electrode conductive paths. The performed experiments focused on the observation of changes in the electrode morphology upon external compression force using a novel analytical method, “quasi in-situ” compression scanning electron microscopy. For instance, direct insight into changes of particle-particle distances or pore volumes and their distribution may be obtained. Apart from electrode morphology analysis the electronic conductivity at the same compression pressure is investigated. Exemplary, figure 1a illustrates the changes of the electronic conductivity of the electrode as a function of pressure, as measured with the setup shown in figure 1b. While the porosity of the coating is decreased from initially 45% to 40%, the electronic conductivity increases significantly. Additional determination of the electrode compound performance in an electrochemical half cell (discharge rate test, average discharge potential and lifetime) for different compression forces is made. From the entire data set, a model is derived which correlates the morphological changes e.g., conductive additive network change with the resulting electrochemical performance.

Fig.1: (a) Measurement of electrode conductivity for varying force and a schematic illustration of compressed and uncompressed electrode (b)Experimental setup of conductivity measurements for varying force F; a small current (10 mA) is applied to the system, the response in voltage is recorded.

References

[1] H. Y. Tran, G. Greco, C. Täubert, M. Wohlfahrt-Mehrens, W. Haselrieder, A. Kwade, Journal of Power Sources 210 (2012), 276

[2] Y. H. Chen, C. W. Wang, X. Zhang, A. M. Sastry, Journal of Power Sources 195 (2010), 2851

[3] H. Zheng, J. Li, X. Song, G. Liu, V.S. Battaglia, Electrochimica Acta 71 (2012), 258
All-Solid Lithium Metal Polymer Batteries; Effect of LiFePO4 Cathode Density and Thickness on Electrochemical Performance
Authors: Jeong Jiseon , Lee Hoogil , Shin Gyuho , Ryou Mhyung-Hyun , Lee Yong Min
Published: February 2020

All-solid lithium metal polymer batteries (LMPBs) consisting of lithium transition metal cathode, polymer electrolyte and Li metal anode have been investigated for achieving much higher energy density than lithium-ion batteries (LIBs) or providing special design properties such as flexibility[1-2]. Unfortunately, commercially available LMPBs failed to go to market, because solid polymer electrolytes (SPEs) show low ionic conductivity and poor interfacial stability towards electrodes comparing to liquid electrolytes. However, most of researches on SPEs have been focused for electrolytes themselves without broad cell performance data such as cycle life and rate capability. Moreover, even though the cathode should be developed or optimized for LMPB systems, few researches on cathodes (for example, cathode thickness, density, or composition) unlike LIBs have been done systematically for LMPBs up to now [3].

So, in this work, we investigate the room temperature electrochemical properties of all-solid LMPBs while changing cathode thicknesses and densities. The LMPBs consist of LiFePO4/SPE/Li metal, in which SPEs for electrolyte and cathode binder are manufactured by in-situ thermal polymerization after cathode/high porous separator/Li cell assembly. The optimum thickness and density of LiFePO4 cathodes could be found by evaluating cycle performances at room temperatures and rate capability. At the same time, morphological changes within the cathode and electrochemical changes before and after polymerization are also compared precisely.

Acknowledgements

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government(MEST)(2010-0025738).

References

[1] J.Y. Lee et al., Journal Solid State Electrochem 14 (2010) 1445–1449

[2] J.Y. Lee et al., Journal of Power Sources 174 (2007) 603–606

[3] J.C. Choi et al., Journal of Electrochemical Science and Technology 4 (2013) 27-33
Microstructural X-Ray Tomographic Analysis of Commercial Lib Electrodes
Authors: Eller Jens , Ebner Martin , Wood Vanessa
Published: February 2020

Systematic characterization, understanding, and improvement of Lithium Ion Battery (LIB) electrodes at the micro- and nanometer scales is essential to improving LIB capacity, safety and lifetime. The visualization and quantification of LIB electrode microstructures using X-ray tomographic microscopy (XTM) of ex-situ electrode samples [1-4] and using in-operando setups [5] has proved highly valuable for electrode micro-structure understanding and optimization.

Here we present the XTM structural analysis of different commercial carbon based anode LIB electrodes. Electrode samples have been scanned in absorption contrast mode at the TOMCAT beamline of the Swiss Light Source at Paul Scherrer Intitute in Switzerland resulting in voxel edge length of 0.33 micrometer. The segmented XTM data sets were analyzed for the distributions of porosity, tortuosity, effective relative diffusivity, and pore space constrictions.

The cross sections of four different commercial anodes are shown in Figure a) and display distinct microstructures. As shown in the histograms in Figure b), these differences can be quantified by assessing the spread in through-plane (perpendicular to current collector) and in-plane (parallel to current collector) tortuosities calculated for multiple 1050 μm2regions throughout the cell. Such analysis of the electrode microstructure is linked to the corresponding rate capability that is determined using half-cell based three-dimensional electrochemical modeling [6]. Furthermore, because electrodes typically fail at localized weak points, special focus is put on quantifying constrictions in the pore structure and understanding their potential impact on electrochemical performance and cell life.

References

[1] Shearing, P. R., Howard, L. E., Jørgensen, P. S., Brandon, N. P., Harris, S.J., Electrochem. Comm., Vol. 12 (2010), pp. 374-377. [2] Kehrwald, D., Shearing, P. R., Shinha, P. K., Brandon, N. P., Harris, S. J., J. Electrochem. Soc., Vol. 158 (2011), pp. A1393-A1399. [3] Ebner, M., Geldmacher, F., Marone, F., Stampanoni, M. and Wood, V., Adv. Energy Mater., Vol. 3 (2013), pp. 845-850. [4] Ebner, M., Chung, D.-W., García, R. E. and Wood, V., Adv. Energy Mater, (2013). doi: 10.1002/aenm.201301278 [5] Ebner M, Marone F, Stampanoni M, Wood V., Science, Vol. 342 (2013), pp. 716-720. [6] Latz, A. and Zausch, J.,
J. Power Sources, 2011, Vol. 196(6), pp. 3296-3302.
Detailed Comparison of Lib and SIB Electrolytes Via DFT Calculations
Authors: Jónsson Erlendur , Johansson Patrik
Published: February 2020

While electrolytes for lithium-ion batteries (LIB) have been explored extensively, this is not (yet) the case for sodium-ion battery (SIB) electrolytes – especially true when it comes to detailed modelling efforts.

We have studied both LIB and SIB electrolytes using density functional theory (DFT), both to understand the dissociation ability of the salts used [1] and the solvation of the cations in the electrolyte solvents in detail [2]. By studying these properties for both LIB and SIB electrolytes, the major differences between the two systems can be outlined, and used for further rational design of new electrolytes and to explain experimental features. Here the main observations will be presented and recommendations given on areas to focus on, pertaining to the fundamental differences between LIB and SIB electrolytes. In general we find that the Na-salts have a higher tendency to dissociate into charge carrying species than Li-salts – from a pure ion-ion interaction strength point of view. A set of >50 different salts, i.e. choices of anions, were evaluated against Li+ and Na+. However, when the coordination and solvation of the respective cation, Li+ or Na+, explicitly by carbonate solvents, is taken into account, the ion-solvent interaction is similarly lowered. These observations thus lead almost to a status quo situation, but we stress that some nuances are worthy to consider for further development of SIB electrolytes and batteries.

[1] E. Jónsson, P. Johansson, Phys. Chem. Chem. Phys., 2012, 14, 10774-10779

[2] E. Jónsson, P. Johansson, submitted
Gas Solubility and Vapor Pressure of Electrolytes Based on Alkylcarbonates Containing Litfsi, Lifap, and LiPF6 Lithium Salt: Measurement and Prediction
Authors: Dougassa Yvon rodrigue , Porion Patrice , Jacquemin Johan , El watani Loubna , Tessier Cécile , Anouti Mérièm
Published: February 2020

Most liquid electrolytes used in commercial lithium-ion batteries are composed by alkylcarbonate mixture containing lithium salt. The decomposition of these solvents by oxidation or reduction during cycling of the cell, induce generation of gases (CO2, CH4, C2H4, CO …) increasing of pressure in the sealed cell, which causes a safety problem [1]. The prior understanding of parameters, such as structure and nature of salt, temperature pressure, concentration, salting effects and solvation parameters, which influence gas solubility and vapor pressure of electrolytes is required to formulate safer and suitable electrolytes especially at high temperature.

We present in this work the CO2, CH4, C2H4, CO solubility in different pure alkyl-carbonate solvents (PC, DMC, EMC, DEC) and their binary or ternary mixtures as well as the effect of temperature and lithium salt LiX (X = LiPF6, LiTFSI or LiFAP) structure and concentration on these properties. Furthermore, in order to understand parameters that influence the choice of the structure of the solvents and their ability to dissolve gas through the addition of a salt, we firstly analyzed experimentally the transport properties (Self diffusion coefficient (D), fluidity (h

-1
), and conductivity (s) and lithium transport number (tLi
) using the Stock-Einstein, and extended Jones-Dole equations [2]. Furthermore, measured data for the of CO2, C2H4, CH4 and CO solubility in pure alkylcarbonates and their mixtures containing LiPF6; LiFAP; LiTFSI salt, are reported as a function of temperature and concentration in salt. Based on experimental solubility data, the Henry’s law constant of gases in these solvents and electrolytes was then deduced and compared with values predicted by using COSMO-RS methodology within COSMOthermX software. From these results, the molar thermodynamic functions of dissolution such as the standard Gibbs energy, the enthalpy, and the entropy, as well as the mixing enthalpy of the solvents and electrolytes with the gases in its hypothetical liquid state were calculated and discussed [3]. Finally, the analysis of the CO2 solubility variations with the salt addition was then evaluated by determining specific ion parameters Hi
by using the Setchenov coefficients in solution. This study showed that the gas solubility is entropy driven and can been influenced by the shape, charge density, and size of the anions in lithium salt.

References

[1] S.A. Freunberger, Y. Chen, Z. Peng, J.M. Griffin, L.J. Hardwick, F. Bardé, P. Novák, P.G. Bruce, Journal of the American Chemical Society 133 (2011) 8040-8047.

[2] P. Porion, Y.R. Dougassa, C. Tessier, L. El Ouatani, J. Jacquemin, M. Anouti, Electrochimica Acta 114 (2013) 95-104.

[3] Y.R. Dougassa, C. Tessier, L. El Ouatani, M. Anouti, J. Jacquemin, The Journal of Chemical Thermodynamics 61 (2013) 32-44.
XRF-Microanalysis of Electrodes for Li-Ion Batteries
Authors: Boesenberg Ulrike , Falk Mareike , Menzel Magnus , Janek Jürgen , Falkenberg Gerald , Fittschen Ursula Fittschen Elisabeth
Published: February 2020

Spatial correlation between morphological properties and chemical phase visualizes transport mechanism and phase transformations, e.g. in electrodes for Li-ion batteries. This can help to find origin of aging and failure mechanism and finally, to build better batteries. Quasi nondestructive micro X-ray fluorescence analysis allows for in operandoand intermediate stages investigations such as elemental migration and can reveal structure-properties relationships while keeping the sample in a well-protected environment. Making use of the fairly large penetration length of the X-rays, representative volumes of the electrodes can be studied. The method is extremely suitable to correlate the spatial distribution of two or more elements.

Cutting edge instrumentation in this field is the MAIA fluorescence detector which allows for ultra fast mapping of areas of multiple mm² area with sub-micron resolution within minutes. This allows examination of full electrodes. The backscattering geometry of the detector enables easy mounting of flat samples such as electrodes or pouch-cells. By variation of the energy in the vicinity of an absorption edge, conclusions on local variations of the state of charge can be drawn, probing the oxidation state of the redox-active element.

For the present study, samples of LiNi0.5Mn1.5O4 electrodes cycled vs. Li were investigated at beamline P06 at DESY, Hamburg Germany. The experiment revealed significant inhomogeneities in the local Ni/Mn ratio upon cycling which is correlated to thinning of the electrode. Higher cycling rates showed an increased impact and higher material losses. Inhomogeneities in the phase transformation were also found during the charge and discharge process. This method is by no means limited to the investigated material, but is easily applicable to other transition metals.
Facile Polymer/Carbon Electrodes Fabrication for Low-Cost, High-Energy Supercapacitors
Authors: Arcila-Velez Margarita Rosa , Roberts Mark E.
Published: February 2020

Due to their potential for combined high power and high energy, supercapacitors provide exciting opportunities for future energy storage systems. Limitations in material performance and processing must be overcome to achieve large-scale manufacturing and utilization. Activated carbon has found application in supercapacitors due to its large surface area and chemical stability, however their energy density is limited by their electrochemical double layer capacitance, which depends on surface area. Conducting polymers (CPs), on the other hand, can store charge through Faradaic processes, which allows more efficient material utilization. Commercial application requires advances in continuous manufacturing methods and material performance, including cycle stability, charge capacity and operating potential.

In the past decade, research on CPs has focused on achieving nanostructured electrodes by modifying the synthesis processes to increase mechanical, electrical and electrochemical properties. An alternative is to incorporate a complementary material to reinforce the polymer structure, and carbon nanotubes (CNTs) provide a suitable option due to their superior mechanical properties, electronic conductivity and chemical stability. Composite materials can be engineered with CPs and CNTs to achieve significant property enhancement. The combination of conducting polymers with carbon materials has been studied in the past to enable the use of CPs in commercial supercapacitors, by making electrode material more stable, lighter, stronger and tougher. CNTs improve the cycle life and mechanical properties of CP since they can adapt easily to changes in volume, and also introduce new electronic properties based on interactions between the two compounds. On the other hand, CPs enhance the charge storage capacity and capacitance of CNT materials and can help overcome their bundling and aggregation.

In this work, we prepared free-standing CNTs/CP composite electrodes in a fast and scalable process by dispersing CNTs and CPs in suspension, filtering the mixture through a membrane and peeling off the dried filtrate. This process eliminates the need for a binder, substrate or additional processing and pressing, which can affect the properties of the material. These composite electrodes showed specific capacitances as high as 366 F/g. CNTs work well as both anode and cathode materials for supercapacitor devices due to their wide potential stability, and when combined with the appropriate redox polymer, high performances can be obtained. Asymmetric CNTs/CP supercapacitor cells fabricated with polymer-CNT cathodes and anodes exhibited high power and high energy densities, especially when compared to pure CNT and good cycling stability. Given the process simplicity, relatively low cost and high throughput, the present composites have great potential for large-scale CP/CNTs supercapacitor production.
Low Cost, Low Surface Area Activated Carbon As Anode Material for Neutral pH Aqueous Asymmetric Supercapacitor Applications Via a Simple Surface Modification
Authors: Shanbhag Sneha , Whitacre Jay
Published: February 2020

Surface modified activated carbon has been developed for use as a low-cost electrode material in aqueous asymmetric electrochemical supercapacitors.  Specifically, wood-based activated carbon with a surface area of under 500 m2/g was modified using an intermediate temperature acid exposure step that more than doubled the specific capacitance in a neutral aqueous electrolyte. After the modification step, the carbon was analyzed using x-ray photoelectron spectroscopy, BET, and combustion analysis. The material thus developed gave approximately 200% improvement in the specific capacitance in 1 M Na2SO4; namely 109 F/g when compared against the precursor activated carbon which showed 38 F/g. To prove the possible utility of this material, full asymmetric energy storage cells were made using the modified carbon as the anode active material and Lithium Manganese Oxide as the cathode active material and Na2SO4 aqueous electrolyte.  The test cells displayed excellent reversible capacity greater than 40 Ah/kg of activated carbon in anode for over 1000 cycles, which is an effective capacitance of approximately 160 F/g delivered over relatively slow  charge/discharge rates.   A Simple economic analysis shows that this material is over an order of magnitude more cost effective on a $/Ah basis than off-the-shelf electrochemical double-layer capacitor materials.  These encouraging results show great promise in developing low cost energy storage devices while incorporating non-toxic and environmentally benign materials.

Figure 1
An Efficient Solar Energy Storage System: All Vanadium Redox Photoelectrochemical Cell
Authors: Wei Zi , Liu Dong , Chia-jen Hsu , Shen Yi , Liu Fuqiang
Published: February 2020

Environmental pollution has been a severe issue for mankind and the immediate impact on our lives includes global warming as well as poor air quality. Besides, energy crisis attracts a lot concern as our demands for energy increase while the available energy resources are near depletion. 

A popular candidate that can be a solution for the above-mentioned problems is solar energy, a typical kind of renewable energy resource. The current obstacle to fully utilize sun light is the lack of efficient method to store it due to its intermittent nature. [1]

In this study, we demonstrated a novel solar energy storage system — an all vanadium redox photoelectrochemical storage (All-V-PECs) cell, which could be a viable solution for sustainable storage & utilization of solar energy. Herein, we combined an all vanadium redox flow battery with a photoelectrochemical cell in an All-V-PECs cell, where vanadium redox species served as the energy storage media while photoelectrochemical reactions on a semiconductor (e.g., TiO2) converted solar energy into electrochemical energy. When sun light strikes the TiO2 semiconductor, the photogenerated holes oxidized VO2+ into VO2
+ at the photoanode; meanwhile the photogenerated electrons reduced V3+ to V2+ at the at the counter electrode. The oxidized form of VO2
+ and reduced form of V2+ thus retain the chemical energy and can be converted to electricity via a reverse reaction (i.e., a discharge process); this process is similar to that in an all vanadium flow battery. [2]

Our preliminary results of photo charging indicated 95% faradic efficiency. This design could be a promising approach for efficient and regenerative solar energy storage. [3]

Reference:

[1] M.G. Walter, E.L. Warren, J.R. McKone, S.W. Boettcher, Q. Mi, E.A. Santori, N.S. Lewis, Solar water splitting cells, Chemical reviews, 110 (2010) 6446-6473.

[2] L. Li, S. Kim, W. Wang, Z. Yang, Advanced Redox Flow Batteries for Stationary Electrical Energy Storage, US Department of Energy, (2012).

[3] Z. Wei, D. Liu, C. Hsu, F. Liu, All-vanadium redox photoelectrochemical cell: An approach to store solar energy, Electrochemistry Communications, 45 (2014) 79-82.

Figure 1
Sn Thin Films and Their Application in Sodium Ion Battery
Authors: Xaba Nqobile , Modibedi Remegia Mmalewane , Mathe Mkhulu K. , Khotseng Lindiwe Eudora , Ozoemena Kenneth I.
Published: February 2020

Secondary batteries provide a more convenient way of storing energy generated from solar or wind power plants.  Lithium ion battery is the most developed battery system with applications in portable electronics and potentially electric vehicles.  The increased applications of lithium ion batteries would impact the reserves of lithium and therefore increase the cost of lithium ion battery.  In order to avoid this situation, an alternative to lithium ion battery needs to be developed.  Sodium, as the fourth most abundant element on earth, can be used in applications where energy density is not critical instead of lithium based batteries due to its low cost.  Moreover, the technology to develop sodium ion batteries (NIBs) is available due to similarities with lithium ion battery.  The challenge to developing NIBs is finding a suitable low cost anode material.  Thin films of Sn were prepared using electrochemical atomic layer deposition (EC-ALD) on Au slides, Cu foil and Ni foam substrate/current collectors to be used as anode material in sodium ion battery.  The deposition parameters were optimized using cyclic voltammetry.  The morphology, thickness and elemental mapping was done using FIB-SEM, AFM and SEM/EDS.  Electrochemical tests were conducted using cyclic voltammetry and impedance spectroscopy.  Charge and discharge tests were done to determine the best performing material.

Key words: Sn, EC-ALD, thin films, current collector, Sodium ion battery

 

References

[1] M. D. Slater, D. Kim, E. Lee, C. S. Johnson, Advanced Functional Material 23.8 (2013) 947-958.

[2] S. Y. Hong, Y. Kim, Y. Park, A. Choi, N.S. Choi,  K. T. Lee, Energy & Environmental Science 6.7 (2013) 2067-2081.

[3] V. Palomares, P. Serras, I. Villaluenga, K. B. Hueso, J. Carretero-González, T. Rojo, Energy & Environmental Science 5.3 (2012) 5884-5901.
Development of highly durable Ni-MH batteries through introduction of highly conductive Co compound-coated Ni (OH) 2 technology
Authors: Shigekazu Yasuoka , Takuya Kai , Yuzo Imoto , Takeshi Ito , Takayuki Yano , Kazuta Takeno , Hirofumi Yanagawa , Shuichi Doi
Published: February 2020

New L.S.D.(Low Self-Discharge)type Ni-MH batteries, such as  eneloop Ni-MH batteries,  were developed by introducing two major and original technological innovations. The first is a super-lattice hydrogen absorbing alloy technology, which results in higher capacity and longer cycle life. The second is HCN: highly conductive Co compound-coated Ni (OH) 2 technology, which results in higher capacity and higher durability. Even if HCN is charged and discharged in a cell, it maintains the same crystal structure as the raw material, Co valence differs from CoOOH which Co(OH)2 is clearly charged in the cell, it’s crystal structure  is less apt to collapse and over-discharge characteristics are improved. By optimizing HCN manufacturing method, we succeeded in developing a more highly durable positive electrode and cell.

Figure 1
Numerical Investigation of Membrane Dehydration Based on PEM Stack Transient Simulation
Authors: Jia Xiao
Published: February 2020

In this work, a three-dimensional, serpentine channel, four-cell PEM Stack model including current collector, gas diffusion layer, catalyst layer and membrane has been developed and is used to investigate the effects of membrane dehydration on PEM Stack performance. This numerical study is conducted using finite element method and computational fluid dynamics (CFD) code. To characterize the effects of membrane dehydration, the settings of operating and boundary conditions are not uniform throughout the whole period of simulation. The simulation condition is originally preferable, indicating a normally running stack in healthy status. Further transient simulation has been conducted under four failure conditions with different reactant humidity to monitor the variation of membrane water content and PEM Stack output voltage. The relatively drier reactants carry away more production water, causing the dehydration of membrane and reducing the protonic conductivity. Under a specific demand current, the output voltage of the stack decreases with the process of membrane dehydration, curtailing the maximum power that can be derived from the stack. Based on the simulation results, it is noticed that inlet reactants humidity has a great impact on the water management of stack. An improper operation on reactants supply can cause failures in PEM Stack, even components material degradation. Meanwhile, the simulation of stack output voltage and interior characteristics, as well as comparison of different levels of drying are prepared for further model-based study of identification and diagnosis of failures caused by improper water management and reactants starvation.
Highly Durable and Efficient Pore Filling Type Ion Exchange Membranes for Reverse Electrodialysis
Authors: Choi Young-Woo , Lee Mi-Soon , Kim Chan-Soo , Kim Han-Ki , Nahm KeeSuk
Published: February 2020

Highly durable ion exchange pore filling membranes (cation exchange membranes and anion exchange membranes) with high ion transfer coefficients have been developed for reverse electrodialysis as an energy conversion system. The polymer electrolytes in both cases of cation exchangeable and anion exchangeable ones consisting of the whole hydrocarbon materials were introduced into porous hydrocarbon substrates and crosslinked by radical polymerization in this work. The thickness of the prepared pore filling membranes was controlled between 20 and 25 micrometers to extremely lower membrane resistance and to increase ion transfer. The prepared ion exchange pore filling membranes were characterized by using dimensional stability, membrane area resistance, ion transport number, and phisico-chemical stability. Also the thermal and the structural properties of the prepared membranes were determined. Meanwhile, all the properties of the prepared membranes were compared with commercial membranes obtained from Tokuyama, Fuji, and Fuma-Tech. Furthermore, RED cell performance and energy efficiency using the prepared pore filling membranes were also evaluated. Finallly we obtained a world best cell power density when comparing to the result reported in elsewhere.
Dye-Sensitized Solar Cells with Reduced Graphene Oxideas the Counter Electrode Prepared By a Greenphotothermal Reduction Process
Authors: Yeh Min-Hsin , Lin Lu-Yin , Chang Ling-Yu , Leu Yow-An , Cheng Wan-Yu , Lin Jiang-Jen , Ho Kuo-Chuan
Published: February 2020

Highly conductive reduced graphene oxide (rGO) with good electrocatalytic ability for reducing triiodide ions (I3
-) is a promising catalyst for the counter electrode (CE) of dye-sensitized solar cells (DSSCs). However, hazardous chemical reducing agents or energy-consuming thermal treatments are required for preparing rGO from graphene oxide (GO). Therefore, it is necessary to find other effective and green reduction processes for the preparation of rGO and to fabricate rGO-based DSSCs. In this study, GO was prepared using a modified Hummers method from graphite powder, and further reduced to rGO through a photothermal reduction process (to give P-rGO). P-rGO shows better electrocatalytic ability due mainly to its high standard heterogeneous rate constant for I3
- reduction and in part to its considerable electrochemical surface area. The corresponding DSSC shows a higher cell efficiency (η) of 7.62% than that of the cell with a GO-based CE (η= 0.03%). When the low-temperature photothermal reduction process is applied to all-flexible plastic DSSCs, the DSSC with a P-rGO CE shows an η of 4.16%.
Optical Studies of Dry and Wet Reformed Methane on Solid Oxide Fuel Cell Anodes
Authors: Qadri Syed Noorullah , Kirtley John D. , Steinhurst Daniel A , Walker Robert A , Pomfret Michael B , Owrutsky Jeffrey C
Published: February 2020

The presently limited understanding of solid oxide fuel cell (SOFC) anode mechanisms is due to a lack of experimental techniques that can probe species and component materials directly during operation, or in operando. Previous investigations on the efficiency of Ni-YSZ-based electrode materials in different reforming conditions have been performed using post-mortem and in situ electrochemical analyses with little information on specific mechanisms that lead to fuel oxidation and cell degradation. An ensemble of non-invasive optical methods consisting of near infrared thermal imaging (NIRTI), Raman spectroscopy, and Fourier-transform infrared emission spectroscopy (FTIRES) is utilized to correlate the chemistry of fuel oxidation and carbon formation with traditional electrochemical measurements for methane and simulated biogas fuels in operating SOFCs.

Different reforming conditions for methane including plain, wet (steam), and dry (carbon dioxide) are investigated on anode- and electrolyte-supported cells. NIRTI results demonstrate that cooling on the anode surface due to endothermic hydrocarbon cracking for dry reforming or simulated biogas is significantly greater than for unreformed methane on both types of cells. Raman and FTIRES both show that more carbon is deposited with methane than with biogas. The small amount of carbon formed is limited to lower temperatures with simulated biogas whereas carbon formation occurs to a great extent at all temperatures with methane. Exhaust gas analysis with ex situ FTIR absorption measurements and mass spectrometry are combined with in operando measurements to further characterize and quantify the species involved. These findings serve as benchmark data for a better understanding of the mechanisms responsible for performance and degradation of SOFCs.
Peanut Shell Hybrid Sodium Ion Capacitor with Extreme Energy - Power Rivals Lithium Ion Capacitors
Authors: Mitlin David
Published: February 2020

This is the first report of a hybrid sodium ion capacitor (NIC) with the active materials in both the anode and the cathode being derived entirely from a single precursor: peanut shells, which are a green and highly economical waste globally generated at over 6 million tons per year. The electrodes push the envelope of performance, delivering among the most promising sodiation capacity - rate capability - cycling retention combinations reported in literature for each materials class. Hence the resultant NIC also offers a state-of-the-art cyclically stable combination of energy and power, not only in respect to previously published NICs but also as compared to Li ion capacitors (LICs). The ion adsorption cathode based on Peanut Shell Nanosheet Carbon (PSNC) displays a hierarchically porous architecture, a sheet-like morphology down to 15 nm in thickness, a surface area on par with graphene materials (up to 2396 m2g-1) and high levels of oxygen doping (up to 13.51 wt%). Scanned from 1.5 - 4.2 V vs. Na/Na+ PSNC delivers a specific capacity of 161 mAhg-1 at 0.1A g-1 and 73 mAhg-1 at 25.6 Ag-1. A low surface area Peanut Shell Ordered Carbon (PSOC) is employed as an ion intercalation anode. PSOC delivers a total capacity of 315 mAhg-1 with a flat plateau of 181 mAhg-1 occurring below 0.1 V (tested at 0.1 Ag-1), and is stable at 10,000 cycles (tested at 3.2 Ag-1). The assembled NIC operates within a wide temperature range (0 - 65°C), yielding at room temperature (by active mass) 201, 76 and 50 Wh kg-1 at 285, 8500 and 16500 W kg-1, respectively. At 1.5 - 3.5 V, the hybrid device achieved 72% capacity retention after 10,000 cycles tested at 6.4 Ag-1, and 88% after 100,000 cycles at 51.2 Ag-1.
Novel Aluminum Air Ionic Liquid Based Battery
Authors: Gelman Danny , Shvartsev Boris , Ein-Eli Yair
Published: February 2020

The changing and expanding needs in the energy market, ranging from power grid energy storage systems to portable power sources, dictates the development of efficient, inexpensive, and high performance battery systems. These advanced electrochemical systems should better deal with the challenges posed by the nascent green economy and non-oil based transport systems. One of the promising avenues for achieving these goals is the development of battery systems based on aluminum (Al) and its alloys as anodes. The main advantages of such systems are the low equivalent weight of Al, its high natural abundance in the earth’s crust, (leading to a rather low price), and its safety characteristics. In addition, Al and its by-products are non-toxic and environmental friendly. Aluminum battery systems cover a wide range of applications; from field-portable emergency power supply to remote power applications and batteries for transportation. Theoretically Al contains approximately one-half the energy content of gasoline per unit weight (8,100 Wh/kg for Al-air and 13,000 Wh/kg for gasoline) and three times the energy per unit volume (21,870 Wh/l for Al-air  and  9,700 Wh/l for gasoline). Currently, the best practical utilization of gasoline for automotive applications can reach approximately 1,700 Wh/Kg and for aqueous Al-air batteries the values are 300-500 Wh/Kg. Nevertheless, the utilization of Al-air batteries as a sustainable energy storage device is hampered by some severe problems. High corrosion rate of the Al anode in aqueous alkaline solution is of great concern in terms of Al utilization and safety. On the other hand, Al surface activation is somewhat problematic in non-aqueous electrolytes, limiting substantially the possibility to utilize any power output. In this study, a newly developed non-aqueous Al-air battery is presented. The battery configuration utilizes 1-ethyl-3-methylimidazolium oligo-fluoro-hydrogenate (EMIm(HF)2.3F) room temperature ionic liquid (RTIL). The battery shows the ability to sustain current densities up to 1.5 mA/cm2, producing a capacity of 140 mAh/cm2 and thus, utilizing above 70% of the theoretical Al capacity. This is equivalent to an outstanding energy densities of 2,300 Wh/Kg and 6,200 Wh/L. Al2O3is detected at the air electrode as the battery discharge product, being the main cathodic reaction of oxygen reduction coupled with Al ions migrated to the air electrode.

* Equally contributed to the presented study

Figure 1
Modelling of Radical Reactions at Platinum Deposits in Polymer Electrolyte Membranes
Authors: Eslamibidgoli Mohammad J. , Eikerling Michael
Published: February 2020

Hydroxyl radicals are the leading cause of chemical degradation observed in polymer electrolyte membranes (PEM). Recent experimental studies have shown that Pt nano-deposits in the PEM (PITM), which originate from Pt dissolution in the catalyst layer, could play a dual role in radical-initiated membrane degradation [1]. Surface reactions at Pt particles could facilitate the formation as well as the scavenging of radicals. The net effect of Pt surface processes on the radical balance depends on the local equilibrium conditions around the Pt nano-deposits, specifically, their equivalent local electrode potential [2]. In this presentation, we will first discuss the potential distribution at PITM as a function of externally controlled thermodynamic conditions. Thereafter, we will present a Density Functional Theory investigation of the surface reactions at the Pt(111)|water interface that involve O2, H2O, H2O2 and OH radical species. We calculate the effective rates of radical production at PITM by incorporating the local conditions obtained in the above steps. The results are compared to experimental measurements of fluoride emission under varying pressure settings in Pt impregnated PEMs. 

References:

[1] M. P. Rodgers et al., J. Electrochem. Soc.
160 (10)  F1123-F1128 (2013)

[2] M. J. Eslamibidgoli et al., J. Phys. Chem. C. Submitted.