bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of Electrochemical Performance of Li-O2 Batteries Using Catalyst Containing Carbon Nanotube Cathodes
Authors: Chawla Neha , Chamaani Amir , Safa Meer , El-Zahab Bilal 
Published: February 2020

Batteries with high specific energy densities have attracted a lot of attention due to their demand in electric vehicles (EVs). Due to the increase in demand for energy storage devices for applications such as load-levelling of electrical energy supply and demand propulsion for electric vehicles and microelectro-mechanical devices, the research for new classes of electrode materials that provide high energy, high power and cycle life longer than lithium-ion batteries is being motivated. Lithium air batteries have high specific energy density and they can achieve four times higher energy density than the current lithium ion batteries. The search for high energy density batteries has motivated the research in lithium-air batteries.
Catalysts have been shown to improve both the battery capacity and the recyclability of these batteries when used in cathodes. Several catalysts have been discovered for lithium air batteries. Debart et al. used several catalysts for lithium oxygen batteries with non-aqueous electrolyte. The electro-catalysts used by them included Pt, La0.8Sr0.2MnO3, Fe2O3, NiO, CuO, CoFe2O4. Co3O4 exhibited highest discharge capacity and best cycling performance. Later Debart et al. examined manganese oxides as catalysts for lithium oxygen batteries. Mn3O4, bulk Mn2O3, bulk α, β, λ, γ-MnO2, α-MnO2 nanowires and β-MnO2 nanowires were used as catalysts. The air cathode with α-MnO2 as the catalyst showed the highest capacity of about 3000 mAh/g (carbon) Lu et al. reported ORR studies on polycrystalline metal catalysts of palladium, platinum, ruthenium, gold and glassy carbon surfaces in non-aqueous electrolyte.
In our study, we investigate various modes of loading palladium-based catalysts and their effect on the capacity and round-trip efficiency of lithium-air batteries. Our aim is to increase the first discharge capacity, improve the recyclability, increase capacity retention and improve the recyclability of the battery. The loading and morphology the catalyst-CNT cathode is studied using transmission electron microscopy. Electrochemical testing using electrochemical impedance spectroscopy and charge-discharge cycling is also investigated. Voltammetry, Raman spectroscopy, FTIR, XRD, UV/Vis spectroscopy and visual inspection of the discharge products using scanning electron microscopy confirms the increased stability of the electrolyte due to this encapsulation and suggest that this approach could lead the increasing Li-O2 battery capacity and cyclability performance.
Uniformly Thin and Large Surface Modification of Lithium Anode for Improving Cycling Performance of Lithium Metal Batteries
Authors: Moon Yong-Bok , Kim Jae-Hong , Woo Hyun-Sik , Kim Dong-Won 
Published: February 2020

Rechargeable lithium batteries using lithium metal as a negative electrode are attractive candidates for high energy density power sources, because the lithium metal offers a high specific capacity and possesses a low electrochemical potential.1,2 However, the development of rechargeable lithium metal batteries has been hindered for several decades by the high reactivity of lithium metal toward liquid electrolytes and the occurrence of dendrite growth during charge and discharge cycles. The formation and growth of lithium dendrites result in safety and cycle life problems. Additionally, continuous generation of the new solid electrolyte interphase (SEI) layer on lithium metal causes uncontrolled reductive decomposition of the organic electrolyte and gradual loss in capacity and cycling efficiency with repeated cycling. Therefore, protection of lithium metal and the formation of a stable SEI layer on the lithium electrode are very important for developing lithium metal batteries with good capacity retention and enhanced safety. In this work, a prospective approach for protecting a lithium metal is presented by spray coating with a conductive poly(3,4-ethylenedioxythiohene)-co-poly(ethylene glycol) (PEDOT-co-PEG) and inorganic particles (AlF3), which allows for lithium ion diffusion and restricts the access of the reactive solvents to the lithium surface. The protective composite layer played a positive role in reducing the reductive decomposition of the electrolyte and suppressing the dendrite growth of lithium during cycling. As a result, the surface modification of lithium electrode with PEDOT-co-PEG and AlF3 significantly improved the cycling stability of the lithium metal batteries.

References

1. J.M.Tarascon and M.Armand, Nature, 539, 414 (2001).
2. D.Linden and T.B.Reddy, Handbook of Batteries, 3rd Edition, McGraw-Hill, New York (2003).
Intrinsic Conductivity in Magnesium-Oxygen Battery Discharge Products: MgO and MgO2
Authors: Smith Jeffrey Gordon , Naruse Junichi , Hiramatsu Hidehiko , Siegel Donald J 
Published: February 2020

Non-aqueous magnesium-oxygen (or ‘Mg-air’) batteries are attractive next generation energy storage devices due to their high theoretical energy densities, low cost, and potential for rechargeability. Prior experiments identified magnesium oxide, MgO, and magnesium peroxide, MgO2, as the primary discharge products in a Mg/O2 cell. Charge transport within these nominally-insulating compounds is expected to limit battery performance, yet these transport mechanisms are either incompletely understood (MgO2) or remain a matter of debate (MgO). The present study characterizes the conductivity associated with intrinsic (point) defects within both compounds using first-principles calculations. For MgO, negative Mg vacancies and hole polarons localized on oxygen anions were identified as the dominant charge carriers. Nevertheless, the large formation energies associated with these carriers suggest that their equilibrium concentrations are low. Furthermore, a large asymmetry exists in the carrier mobility: Mg vacancies are essentially immobile at room temperature, while hole polarons are highly mobile. Importantly, the calculated formation and mobility data for MgO are in remarkable agreement with the three “Arrhenius branches” observed in conductivity experiments, and thus clarify the long-debated transport mechanisms within these regimes. In the case of MgO2, electronic charge carriers alone – electron and hole polarons – are the most prevalent. Similar to MgO, the concentration of carriers in MgO2 is low, and poor mobility further limits conductivity. We conclude that: (i.) sluggish charge transport in MgO or MgO2 will limit battery performance when these compounds cover the cathode support, and (ii.) what little conductivity exists is primarily electronic in nature (i.e., polaron hopping). Artificially increasing the carrier concentration is suggested as a strategy for improving battery performance.
Calculating Anisotropic Correlated Chemical Expansion of Oxygen and Lithium Vacancies in Li2MnO3 to Determine Vacancy Concentrations
Authors: James Christine , Nation Leah , Li Juchuan , Dudney Nancy J , Sheldon Brian W. , Qi Yue 
Published: February 2020

Lithium-excess layered cathode materials for lithium-ion batteries of the form Li2MnO3-LiMO2 (M=transition metal(s)) show high capacities (>200 mAhg-1) due to the activation of the Li2MnO3 component.1 This activation process occurs during the first cycle at >4.4V, where it is widely accepted that oxygen is removed from the Li2MnO3 component. Thus, Li2-XMnO3-δ is formed upon cycling, creating a structure with both oxygen vacancies (VO) and lithium vacancies (VLi). It has been shown previously that the VLi and VO interact and that it is energetically favorable for VLi to form near VO.2 VO concentration in the Li2-XMnO3-δ is believed to be dilute, although the exact amount of VO(δ) is unclear.
To estimate the VO concentrations, calculations of the chemical expansion coefficient for vacancies in Li2MnO3 are combined with experimental stress measurements of a lithium-excess layered cathode material. The coupled VO and VLi have previously been shown to exhibit correlated anisotropic chemical expansion in Li2-XMnO3-δ at dilute concentrations.3 Thus, the chemical expansion coefficients for VO and VLi in the system are broken down into a dilute component for coupled VO and VLi and a component to capture the rest of the VLi which are far away from VO and contribute to the high capacity of these materials. The computational results are used to interpret stress measurements from a multibeam optical stress sensor (MOSS) on Li1.2Mn0.55Ni0.125Co0.125O2.
1. Thackeray, M. M.; et al., Journal of Materials Chemistry
2007,
17(30), 3112-3125.
2. James, C.; et al., Solid State Ionics
2016,
289, 87-94.
3. James, C.; et al., MRS Advances
2016, 1(15), 1037-1042. doi:10.1557/adv.2016.48.
A Statistical Mechanical Model Incorporating Coupled Concentration-Strain Effects in Lithium Ion Battery Electrode
Authors: Chen Hongjiang , Huang Hsiao-Ying Shadow 
Published: February 2020

Electrochemical storage system such as Lithium-ion batteries have been widely used from power tools and portable electronics to recent PHEV/EV. However, Li-ion batteries’ low power density and cycling capability have limited many potential applications. Many studies have shown that mechanical deformation plays a significant role in these drawbacks. To understand the influence of mechanical deformation on electrochemical reactions and phase transition in electrodes, studies have used the phase field method to model the mechanical stresses/strains or Li-ion concentration profiles. Yet few of them have considered “coupling effects” of these two factors, and resulting in inaccurate simulation results. In this study, we use statistical mechanics and transition state theory to develop constitutive equations of electrodes that include the concentration-strain coupling effects. Specifically, we relate the activation energy change of microscopic particles of electrode components with materials’ strain energy density. Further, we model microscopic processes of electrodes’ deformation by describing the behavior of activated particles and their probability relationship with all local particles in electrodes. By combining the phase field method, our generalized constitutive equations could provide much more accurate simulation results of the concentration field and/or phases distributions, which could be used to design better electrodes structure and improve batteries’ power/cycling performance.
NaVO3: A Surprising Cathode Material for Rechargeable Na-Ion Battery
Authors: Zhang Jiaolong , Yu Denis Yau Wai 
Published: February 2020

In the past few years, Na-ion batteries (NIBs) have attracted much attention as an alternative energy storage device because Na is abundant and evenly-distributed in the world. However, commercialization of Na-ion batteries that have performances similar to existing lithium-ion batteries (LIBs) still requires the discovery and optimization of new high-capacity high-voltage electrode materials. NaVO3, which has been studied as anode for NIB based on the redox reaction of V5+/V4+
[1
,

2
], is evaluated as cathode material for NIB for the first time in this work.
Commercial NaVO3 shows no capacity at all when tested between 1.5 V and 4.5 V vs. Na/Na+, since the initial valence state of vanadium in NaVO3 is 5+ and the V5+/V4+ reaction occurs below 1.5 V. However, when the charging potential is increased to 4.9 V, capacities of 72.0 and 28.4 mAh g-1 are obtained from charge and discharge, respectively (see Figure 1(a)). Electrolyte decomposition alone during charging cannot account for the observed non-zero discharge capacity, so there has to be other mechanisms that can compensate for the charge transfer. We note that the second charging profile is different from that of the first charging profile. This result reassembles that of Li2MnO3 in LIB, which also shows electrochemical activity after a high-voltage activation process. We suspect NaVO3 undergoes a similar reaction mechanism as Li2MnO3, possibly a participation of oxygen redox-couple during the charge/discharge processes. Further work is being carried out to elaborate on the charge-discharge mechanism of NaVO3. When the commercial NaVO3 material is subjected to cycling, the capacity continues to increase, and eventually stabilizes at around 47 mAh g-1 after 50 cycles (see Figure 1(d)). This indicates that the charge-discharge process is reversible.
The theoretical capacity of NaVO3 is 220 mAh g-1 if one Na is removed from the lattice. Yet, the obtained capacity from commercial NaVO3 is only about 50 mAh g-1. The low capacity is partly attributed to the insulating nature of the material. We found that the available capacity from the material depends on particle size and electrical conductivity. Figures 1(b) shows the charge-discharge curves of ball-milled NaVO3 sample, which exhibits similar storage behavior to the pristine NaVO3, but delivers a higher capacity. Further ball-milling with carbon (acetylene black) increases the initial charge and discharge capacities to above 100 mAh g-1, but capacity degradation is severe. More results on the charge-discharge mechanism and stability of the material will be presented during the meeting.
Reference:
[1] G. Venkatesh, V. Pralong, O. I. Lebedev, V. Caignaert, P. Bazin and B. Raveau, Electrochemistry Communications, 40, 100 (2014).
[2] X. Liu, Y. Zhao, Y. Dong, Q. Kuang, Q. Fan, Z. Jing, S. Hou, J. Solid State Electroche
m,

20, 1803 (2016).

Figure 1
Supercapacitor Stack Built from Monolithic Porous Glassy Carbon Electrodes
Authors: Braun Artur 
Published: February 2020

The inherent high porosity of glassy carbon, a monolithic carbon form, can be opened by various oxidation processes. I present a gasphase thermal oxidation process which has been shown easy and successful for the opening and connecting of IUPAC micropores in the nanometer range. The precise control of this carbon "actication" process allows for the engineering of monlithic bipolar electrode assemblies with high porosity carbon films on top and bottom with an electroncilly conducting and ionically blocking layer inbetween. Stacks of several such electrodes have been built and tested for 100,000 cycles.
I will also show the detailed pore building and connection process which was assessed with small angle xray scattering and cyclic voltametry and impedance spectropscopy. The charge carrier dynamics follows consequently the evolution of the pore space. A mathematical model is presented which precisely reflects the evolution of porous film thickness, pore growth and double layer capacity.
[1] A. Braun, J. Ilavsky, S. Seifert, Highly porous activated glassy carbon film sandwich structure for electrochemical energy storage in ultracapacitor applications: Study of the porous film structure and gradient, J. Mater. Res. (2010) 25(8) 1532-1540.
Vertical Aligned Graphene/Metal Sulfides/N-Doped Carbon Ternary Sandwich Hierarchical Structure for Sodium Storage
Authors: Xie Dong , Xia Xinhui , Tu Jiangping 
Published: February 2020

Nowadays, sodium ion batteries (SIBs), one of the realistic promising alternatives to the lithium ion batteries (LIBs), have drawn increasing attention because of the high availability, the low cost and the intercalation chemical similarity of sodium compared with lithium. However, many active materials in application of LIBs are invalid for SIBs as far as the different ionic radium (Na+ ,1.06 Å vs. Li+ ,0.76 Å). Thus, much effort has been taken to explore suitable host material to allow reversible and rapid sodium ion insertion or extraction, especially for advanced anode materials.
Fortunately, the transition metal dichalcogenides (TMDs) with the formula MoX2 (S or Se) and graphene-like structure are widely studied as anode materials for SIBs due to the unique two-dimensional layered structure and high specific capacity. Nevertheless, the practical application of the graphene-like TMDs is impeded by its inherent limitations. First, layered TMDs nanosheets are so easy to restack with the van der Waals interaction, resulting into the decrease of accessible active sites for sodium ions. Second, compared with carbon-based materials, especially, graphene or carbon nanotubes, the TMDs have lower electrical conductivity, which is not favor electrode reactions. Third, the volume change and structural variation during discharge-charge process cause the pulverization and loose contact of the active materials, resulting rapid capacity fading. Fourth, the TMDs-based anodes face the dissolution issue of polysulfides or polyselenides, resulting in fast capacity fading and low Coulombic efficiency during the discharger-charge process. To combat the aforementioned problems, in this present work, we have made double modifications on the MoX2 by introducing the vertical aligned graphene (VG) as support backbone and nitrogen-doped carbon (N-C) coating as outer protective layer via a simple two-step process. The curved MoX2 nanoflakes are controlled deposited on the VG skeleton, which the cloth fabric server as current collector, via a facile hydrothermal method; subsequently, the N-C layer uniformly coats on the MoX2 nanoflakes by self-polymerizing dopamine followed by a post carbonization process. These samples are directly assembled into SIBs without any binders or conductive materials, and exhibit excellent electrochemical performance for SIBs. For example, our synthesized VG/MoSe2/N-C ternary composite exhibits superior storage sodium performance, with high capacity (540 mAh g-1), enhanced high rate capability and long-term cycling stability (298 mAh g-1 at 2.0 A g-1 after 1000 cycles). These designed ternary sandwich VG/MoX2/N-C ternary sandwichhierarchical structures, which provide a flexible vertical aligned graphene to accommodate volume changes, introduces large efficient active areas, good conductivity, and omnibearing paths for sodium ion and electrons, contributes to their superior performances and enables its application in energy storage.
Theoretical Investigation of Oxygen- and Bromine-Functionalized Model Carbon Structures for Li-Redox Activity
Authors: Rawal Saurin Hiren , Dathar Gopi Krishna Phani , Shelton William A , Xu Ye 
Published: February 2020

Carbon materials such as graphene, nanotubes and even aromatic compounds1-3 are being widely considered as active electrode materials in Li-ion batteries owing to their light weight and low cost. The functionalization of carbon appears to be the key to enabling faradaic electrochemical activity. We are investigating the possibility of bromine-functionalized carbon materials as redox active with Li ions. We have shown that carbon functionalized with oxygen groups can undergo redox reaction with Li at a range of potentials, including some that are sufficiently high for such structures to be appropriate for use at cathodes.4 Some such structures may also be able to catalyze the oxygen reduction reaction in Li (Li-ORR). Furthermore we are carrying out density functional theory calculations coupled with electrochemical modeling to investigate the redox properties of bromine-functionalized carbon moieties. We find that under-coordinated carbon atoms can form certain stable brominated structures that can undergo redox reaction with Li. Local chemical environments plays an important role in efficient electrochemical reactivity of the carbon structures.5, 6 Our results provides insights at the atomic scale on the functionalizations required for activating carbon for these important electrochemical reactions.
References
1. B. Z. Jang, C. Liu, D. Neff, Z. Yu, M. C. Wang, W. Xiong and A. Zhamu, Nano letters, 11, 3785 (2011).
2. S. W. Lee, N. Yabuuchi, B. M. Gallant, S. Chen, B.-S. Kim, P. T. Hammond and Y. Shao-Horn, Nature Nanotechnology, 5, 531 (2010).
3. H. Chen, M. Armand, G. Demailly, F. Dolhem, P. Poizot and J. M. Tarascon, ChemSusChem, 1, 348 (2008).
4. Y. Xu and W. A. Shelton, Journal of the Electrochemical Society, 158, A1177 (2011).
5. Y. Zhao, Y. Ding, J. Song, L. Peng, J. B. Goodenough and G. Yu, Energy & Environmental Science, 7, 1990 (2014).
6. P. Bai and M. Z. Bazant, Electrochimica Acta, 202, 216 (2016).
Freestanding Graphene-Coated Carbon Nanotube Aerogels Decorated with Metal Nanoparticles As High Performance Electrodes for Ethanol Oxidation
Authors: Xie Minghao , Islam Mohammad F. 
Published: February 2020

There has been increasing demand to develop sustainable energy sources with high energy-conversion efficiency. Direct ethanol fuel cells (DEFCs) are one type of clean power source that is promising for a variety of applications. DEFCs typically consist of an anodic chamber that oxidizes ethanol and transfers electrons via an external circuit to a cathodic chamber that reduces oxygen. Nobel metals such as platinum (Pt) and palladium (Pd) are often used as electrocatalysts for the ethanol oxidation reaction (EOR) in the DEFC anode because of their intrinsic electrochemical properties. Unfortunately, cost and poor market supply require manipulating structural features of catalysts including shapes, sizes, and compositions to achieve optimal benefit from Pt and Pd. Further, to realize the utility of DEFCs in these applications, they must be cheap, lightweight, highly efficient, and stable over long operation lifetimes. We have developed DEFCs with enhanced electrochemical performance using three different electrocatalysts (Pt, Pd, and Pd-Pt core-shell nanoparticles) supported on graphene-coated carbon nanotube aerogels. These three-dimensional, porous aerogels are lightweight, and provide easy transport pathways for fuel and ions. The ultrahigh surface area of the aerogels allows deposition of small catalyst nanoparticles, while the graphene coating hinders coarsening of the nanoparticles during operation, improving the DEFC lifetime. The catalysts are spherical nanoparticles of diameter ≈ 5 nm (Pt), ≈ 8 nm (Pd), and ≈ 9 nm (Pd-Pt core-shell). The current densities of our DEFCs in alkaline media are ≈ 118 mA/cm2 with Pt, ≈ 150 mA/cm2 with Pd, and ≈ 283 mA/cm2 with Pd-Pt core-shell electrocatalysts, which are at least an order of magnitude larger than that of DEFCs that utilize commercially available electrodes, typically comprised of Pd nanoparticles supported on carbon black. Further, the performance of our DEFCs shows minimal degradation of 30–60% over 1,000 cycles. This work has been partially supported by the NSF through Grant CMMI 1335417 and US Army Research Office through grant W911NF-14-1-0651.