bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efficient "on-the-Fly" Calculation of Raman Spectra from Ab-Initio Molecular Dynamics: Application to Lithium-Sulfur Batteries
Authors: Partovi-Azar Pouya , Kühne Thomas D. , Kaghazchi Payam 
Published: February 2020

We present a novel computational method to accurately calculate Raman spectra from first principles. Together with an extension of the second-generation Car-Parrinello ab-initio molecular dynamics (AIMD) method to propagate maximally localized Wannier functions along with the nuclei, a speed-up of one order of magnitude can be obtained. Due to expression of the total polarizability as a sum of Wannier polarizabilities, the method also enable us to find partial Raman activities corresponding to local vibrations of different fragments in the system.
We have used this method to investigate the Raman spectra of (Li2S4)𝑛, 𝑛=1,4,8 clusters which are believed to be the last intermediates in the S8→Li2S transition in lithium-sulfur (Li-S) batteries, during the discharge cycle. However, it is not fully established whether or not any other products coexist with the Li2S crystal in the discharged state. In this study, we have observed a clear evidence of Li2S4→Li2S2 transition by investigating the systematic changes in the simulated Raman spectra as the cluster size increases. In line with recent experiments, we found that the Raman-active sulfur-sulfur stretching mode at 440 cm-1 can be considered as a signature of covalent bonding between two and more sulfur atoms per formula. We have also demonstrated that the transition is mainly due to the strong electrostatic interactions between polar Li2S4 monomers which result in energy lowering by arranging the local dipole moments in anti-parallel fashion. This arrangement result in the formation of crystal-like Li2S2 structures at the interfaces of Li2S4 monomers.
Furthermore, through minimum-energy conformation search combined with AIMD simulations, we have shown that upon carbonization of polyacrylonitrile in early discharge stages of Li-S batteries and further exposure of the product to octasulfur, S2 groups form a bridge between two consecutive nitrogen atom on the edge of carbon fiber. Moreover, our Raman simulations reveal a characteristic Raman activity for these -N-S-S-N- groups in 300 - 400 cm-1 frequency range, in form of two distinct peaks which researchers could not experimentally assign before. Finally, we will discuss our recent studies on structure of complex cathode materials using our approach together with experimental measurements.
Potential-Dependent Mechanism of Li Diffusion in Li2s for Li-S Batteries
Authors: Moradabadi Ashkan , Kaghazchi Payam 
Published: February 2020

Li2S is the final product of lithiation of sulfur cathode in Li-S batteries. Mechanism of Li diffusion in Li2S has not been studied so far. Such a study can help us to understand the origin of (measured) lower capacity of sulfur cathodes in comparison with the theoretical capacity. In this presentation, I will discuss formation energies of a variety of possible defects and their diffusion mechanisms in Li2S. We found that the pathway and energy barrier of Li diffusion in Li2S is potential dependent.
To our knowledge, such a result has not been reported so far in any other electrode materials. Our results show that Li(2-δ)S (Li-vacancy-rich) is the most favorable defective structure of Li2S for the voltage ranges between 0.93 V and 2.03 V (widely-used operating voltage range of Li-S batteries). In this case, the vacant sites are dominant defect sites and Li diffusion occurs via single vacancy with relatively low energy barrier of 270 meV. However, Li(2+δ)S (interstitial-Li-rich) may also exist as a metastable phase at high cycling rates (far from equilibrium). Considering the fact that the lithiation of S cathodes is an intraparticle two-phase (core/shell S/Li2S) growth process, we conclude that lithiation of metastable S/Li(2+δ)S particles may be strongly hindered because of the high energy barrier of 450 meV for Li diffusion (via the exchange mechanism) within the Li(2+δ)S shells.

Figure 1
In Situ Characterization of Li Transport with Neutrons
Authors: Liu Danny X. , Co Anne C. , Lyons Daniel Joseph , Cao Lei Raymond 
Published: February 2020

We have recently developed a nondestructive method to visualize and quantify Li atom position in real-time using neutrons by a method referred to as neutron depth profiling (NDP). In situ NDP is an ideal technique for probing Li complex formation, accumulation and transport within the battery material during charge/discharge. Currently, our work is focused on understanding the effect of an electrochemical event to the materials’ storage properties. Specifically we report our recent work on the preferential Li nucleation, Li trapping and Li transport in intermetallic materials like LixSny, LixSiy and LixAly and intercalating materials like LiNiMnCoO3.
High Performance Iron-Doped LiMnPO4 Cathode Material for Lithium-Ion Batteries
Authors: Wang Liguang , Zuo Pengjian , Yin Geping , Wang Jiajun , Wang Jun 
Published: February 2020

Olivine-type LiMPO4 (M = Fe, Mn, Co, Ni) has become of great interest as cathodes for next-generation high-power lithium-ion batteries. LiMnPO4, possessing a moderate working voltage compatible to the present electrolyte systems, can provide a higher energy density than LiFePO4 on account of its higher redox potential of Mn3+/Mn2+ (4.1 V) than Fe3+/Fe2+ (3.5 V). However, the electrochemical performance of LiMnPO4 is poor due to the slow lithium diffusion kinetics within the grains and the low intrinsic electronic conductivity, even much worse than those of LiFePO4. Up to now, low electronic conductivity can be successfully overcome by modifying the LiMnPO4 particles with carbon and minimizing particle size. The mesoporous and hollow sphere structure can further improve the electrochemical performance of olivine-type LiMnPO4 material.
Here, we synthesized the mesoporous hollow sphere LiMn0.8Fe0.2PO4/C composite by a solvothermal method using spherical Li3PO4 as the precursor. The small crystalline size of (~50 nm) LiMn0.8Fe0.2PO4 can reduce the diffusion length for lithium ion transport leading to the enhanced rate capability. The mesoporous and hollow sphere structure offers high surface area, which can enhance the electrochemical performance of LiMn0.8Fe0.2PO4/C composite as show in Figure 1. The material exhibits an ultra-long cycle life exceeding 1000 cycles with an extremely low capacity decay of 0.0068 mAh·g-1 loss per cycle, which is the best cycling performance to our knowledge. The results exhibit that the mesoporous hollow sphere LiMn0.8Fe0.2PO4/C composite is a promising cathode material for lithium ion batteries.

Figure 1
Binder Free Mesoporous Spinel Oxides As an Anode Materials for High Performance Li-Ion Battery
Authors: Jadhav Harsharaj S. , Thorat Gaurav M. , Seo Jeong Gil 
Published: February 2020

The development of anode material with high specific capacity is the key issue in present lithium ion batteries (LIBs) technology. Recently, transition metal oxides (TMOs), especially cobalt-based oxides with spinel structure have attracted much attention as an anode material for LIBs due to its high theoretical capacity (~700 mAh g-1), long cycle life and high rate performances. In view of the high cost of Co, ternary cobalt oxides via partially substituting Co with less expensive metals, such as Cu, Zn, Ni, Fe, Ni, and Mn, are more practical anode materials for applications. Among these Cu and Zn not only less expensive, but also electrochemically active and contributes to the charge storage. Nevertheless, operation stability and high rating performance are two critical issues needing improvement before wide application of MCo2O4 (M=Cu, Zn) can be realized. However, the limitations of TMO materials could be possibly overcome by tailoring morphology and pore size distribution to sustain structural disintegration during cycling and promote lithium ion storage. Herein, flower-like and microsphere MCo2O4 (M=Cu, Zn) were synthesized by hydrothermal strategy with porous structure.
A facile urea-assisted hydrothermal method and subsequent calcination for 2 h was pursued to obtain pure flower-like and microsphere MCo2O4 (M=Cu, Zn) samples. The Ni-foam was used as substrate for in-situ deposition MCo2O4 (M=Cu, Zn). The obtained flower-like and microspheres morphology was assembled by nanorods, and the nanorods were comprised of interconnected particles with a porous structure. The important properties of electrode material such as morphology, size, surface area, porosity, pore size distribution highly desirable for its high performance. The desirable electrochemical performance of MCo2O4 (M=Cu, Zn) clearly indicates it is promising candidates as an anode material for LIB. This work was supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Education (Grant number: NRF-2013R1A1A2060638 and No. 2009-0093816).
High Capacity Li-Ion Anodes with Tunable Rate Capability Comprised of Si-Ge Branched Nanowire Heterostructures
Authors: Kennedy Tadhg , Ryan Kevin M 
Published: February 2020

Li-alloying nanowires (NWs) are promising anode materials for next generation lithium-ion batteries due to their large maximum theoretical capacity when compared with conventional graphitic based materials (372 mAh/g). Ge NWs, in particular, have shown great promise, exhibiting stable capacities of 900 mAh/g over 1000s of cycles and excellent rate capability due to the high rate of diffusivity of Li in Ge and its inherent high conductivity.1, 2 The superior capacity retention of Ge is attributed to the complete restructuring of the NWs that occurs within the ﬁrst 100 cycles to form a continuous porous network that is mechanically robust. The possibility of incorporating Si into this stable network of Ge is very appealing, combining the very high capacity of Si with the excellent rate characteristics and capacity retention of Ge.
Here we report the formation of high-performance and high-capacity lithium-ion battery anodes from high-density Si-Ge heterostructure nanowire arrays grown directly from the current collector.3 The unique morphology of the active material consists of Si NW branches grown from a Ge NW backbone. By tuning the ratio of Si to Ge in the material it is possible to design electrodes for either high-capacity applications (high Si : Ge mass ratio) or high rate capability applications (high Ge : Si mass ratio). We show by ex-situ high-resolution transmission electron microscopy (HRTEM) and high-resolution scanning electron microscopy (HRSEM) studies that the NW array transforms into a mechanically robust, porous network of Si and Ge ligaments. Once this network is formed it is highly stable, maintaining capacities of 1700 mAh/g over 100 cycles. The electrode material described here also has the advantage of being formed in a low energy, rapid synthetic protocol. Using a very simple reaction protocol, NW growth occurs by thermolytic decomposition of an organometallic precursor onto a preheated substrate in an inert atmosphere.
1. Kennedy, T.; Mullane, E.; Geaney, H.; Osiak, M.; O’Dwyer, C.; Ryan, K. M. Nano Lett.
2014, 14, (2), 716-723.
2. Mullane, E.; Kennedy, T.; Geaney, H.; Ryan, K. M. ACS Appl. Mater. Interfaces
2014, 6, (21), 18800-18807.
3. Kennedy, T.; Bezuidenhout, M.; Palaniappan, K.; Killian Stokes; Brandon, M.; Ryan, K. M. ACS Nano
2015, 9, 7456–7465.

Figure 1
Ultra-Thick Electrodes for Li-Ion Battery
Authors: Zolin Lorenzo , Jimenez-Manero Pablo , Gaubicher Joël , Porcher Willy , Lestriez Bernard 
Published: February 2020

In order to meet the challenge of a transition from fossil fuels to green energies, the rapid development of technology is crucial. A characteristic of energy produced from renewable sources is to be discontinuous in time (e. g. photovoltaic or wind turbines). So, as a result of the development of this kind of systems, it is really important to establish a reliable electric energy storage grid. Nowadays, advanced devices that convert and store energy are the focus of intensive attentions and lithium-ion batteries hold the promise of effective solution for a clean electric future.
Nevertheless, the needs to improve performances and reduce costs of Li-ion batteries encourage different research strategies. Among them, an increase in the basis weight of the electrodes active material allows to improve the energy density and to reduce the costs associated with the electrochemical inactive materials (current collectors and separator). The maximum loading achievable by the current industrial reference process, the coating, is limited by the migration of the binder during solvent evaporation phase. Thus, an innovative and effective process, the filtration, is here proposed for the production of ultra-thick electrodes (> 20 mAh / cm² or > 50 mg / cm²). In particular, this research is focused on the adaptation of filtration with the aim to obtain Li-ion battery electrodes and on the development of a pseudo 3D current collector. This innovative current collector is suitable for the filtration process, participates in the transversal electrical conductivity and improves the adhesion of the active layer. The active materials used in this research are commercial LiNiMnCo (NMC) for the cathode and graphite for the anode.
The mechanical properties of ultra-thick electrodes are, of course, critical and will be discussed. Moreover, the remarkable mechanical stability along with the improved adhesion of active material layer with the metallic current collector allows electrodes to be pressed and to attain low porosity, resulting in improved energy density and increased electrical conductivity due to a better contact between particles. The electrochemical performances of electrodes based on NMC/graphite and of a full cells composed of these ultra-thick electrodes will be presented.
These ultra-thick electrodes feature a volumetric energy density greater than the state of art Li-ion electrodes, making them particularly suitable for stock energy produced from renewable and natural sources, giving the possibility to increase the capacity of future electricity grid.
Fig. 1: Ambient temperature galvanostatic cycling behavior of a NMC/graphite ultra-thick cell at different C-rate. Inset shows typical potential vs. specific capacity profile.

Figure 1
Micro-Macroscopic Modeling of a Lithium-Ion Cell By Considering Grain Boundaries of Active Materials
Authors: Hoffmann John Alexander , Park Jonghyun 
Published: February 2020

Many important properties of electrode materials are profoundly sensitive to deviations from the crystalline perfection. Among them are grain boundaries that play an important role on battery performance by changing the ions distribution inside particles and corresponding stress level change. This paper explores the mechanical and microstructural aspect of battery behavior by developing a cell-level model that incorporates grain boundary diffusion in the electrode particles for the anode and cathode electrodes. The developed model is compared against the grainless model at various operating conditions to understand how grain boundaries influence capacity and stress generation. The results show an appreciable effect of grain boundary diffusion on the voltage profile for the cell for the parameters tested and, overall, a significant reduction in the maximum induced stress experienced in the cell. Stress behavior between the anode and cathode differ significantly, and show that the effective diffusivity of a particle might matter much more significantly than its location in the cell.
First-Principles Modeling of the Initial Stages of Ethylene Carbonate Decomposition on LixCoO2 (110) Surfaces
Authors: Qin Xueping , Shao Minhua 
Published: February 2020

Lithium ion batteries (LIBs) have been widely used in electric vehicles. At the same time, high capacities of batteries are required desperately, which could be realized by increasing the operational voltage of LIBs. However, side reactions occur under these high voltages at the cathode-electrolyte interface because of the instability of electrolyte components1-3, leading to electrode degradation, capacity fade and poor cycling stability of batteries and also some safety issues. Therefore, it is meaningful to understand the decomposition mechanism of organic solvents in LIBs, which could pave the way for electrode material design and battery design.
In this study, first-principles calculations were performed to investigate the initial stage of ethylene carbonate (EC) decomposition on the stable (110)4 surface of LixCoO2 (LCO, x=0.67, 1). For the possible initial decomposition reactions of EC on cathode surfaces, H-abstraction reaction and ring opening reaction have been proposed5, 6 and investigated on LixMnO2 surfaces7, 8. For the adsorption models of EC on LCO (110) slab, parallel (Fig. 1a) and Oc-upward (Fig. 1b) configurations were adopted, and the corresponding reaction barriers of possible reactions in two configurations were calculated by density functional theory (DFT) calculations. Climbing image nudged elastic band (CINEB) method was used to search the transition state (TS) and minimum energy path (MEP) of certain reactions.
Based on the calculation results, H-abstraction reaction (ΔEbarrier = 0.96 eV) is prone to occurring in a parallel configuration on LCO (110), while ring opening reaction (ΔEbarrier = 0.89 eV) is favored in Oc-upward configuration. These predicted EC decomposition fragments may not be the final products of side reactions, which could also react with other adsorbed fragments, leading to the SEI formation. The following reactions are considered and discussed in the presentation.

References

1. Aurbach, D.; Gofer, Y.; Langzam, J. Journal of the Electrochemical Society
1989,136, (11), 3198-3205.
2. Etacheri, V.; Marom, R.; Elazari, R.; Salitra, G.; Aurbach, D. Energy & Environmental Science
2011,4, (9), 3243-3262.
3. Peled, E.; Gabano, J. AP
1983.
4. Daheron, L.; Martinez, H.; Dedryvere, R.; Baraille, I.; Ménétrier, M.; Denage, C.; Delmas, C.; Gonbeau, D. The Journal of Physical Chemistry C
2009,113, (14), 5843-5852.
5. Borodin, O.; Olguin, M.; Spear, C. E.; Leiter, K. W.; Knap, J. Nanotechnology
2015,26, (35), 354003.
6. Gauthier, M.; Carney, T. J.; Grimaud, A.; Giordano, L.; Pour, N.; Chang, H.-H.; Fenning, D. P.; Lux, S. F.; Paschos, O.; Bauer, C. The journal of physical chemistry letters
2015,6, (22), 4653-4672.
7. Leung, K. The Journal of Physical Chemistry C
2012,116, (18), 9852-9861.
8. Kumar, N.; Leung, K.; Siegel, D. J. Journal of The Electrochemical Society
2014,161, (8), E3059-E3065.
Fig. 1. Adsorption models of EC on LCO (110) in a parallel configuration (a) and Oc-upward configuration (b).

Figure 1
Silver Oxide-Cobalt Phosphate Nanoparticle/ Nanoflake As a High Performance Supercapattery Electrode
Authors: Shao Han , Narayanasamy Padmanathan , McNulty David , O'Dwyer Colm , Razeeb Kafil M. 
Published: February 2020

Artificial cardiac pacemaker as an electronic device, can deliver the electrical impulses to regulate the heartbeats during emergency. In order to prevent the unnecessary injury caused by battery-replacement surgery, there is an urgent need to have a better energy storage device that could store enough energy with an excellent lifetime for 20 years. Supercapattery is a hybrid energy storage device, which combines the best of both battery and supercapacitor worlds and should be able to store enough energy like a battery with cyclability and specific power similar to a supercapacitor. Thereby, we are fabricating novel nanomaterials based electrodes for the development of these hybrid energy storage devices.1-2

In this work, a heterostructure of silver oxide - cobalt phosphate nanoparticle/ nanoflake was synthesized on nickel foam (NF) via simple hydrothermal method. The electrode was analyzed by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscope (TEM) to study the composition, structure and morphology of the heterostructure. The silver oxide nanoparticle enhanced the surface area of the electrode and improved electrochemical performance. The heterostructured electrode showed a wide potential window of 0.75 V in 3.0 M KOH solution and delivered a maximum specific capacity of 282.4 mAh g-1, which is equivalent to 1355.3 F g-1with no decay after 1,000 charge-discharge cycles. The performance of this heterostructure will be reported as a positive electrode in a complete supercapattery device configuration.

Acknowledgment

The authors acknowledge financial support from EU FP7 project MANpower (Contract 604360) to carry out this work.

Corresponding author's email address: kafil.mahmood@tyndall.ie

Reference

[1] Shao H.; Padmanathan, N.; McNulty, D.; O'Dwyer, C.; Razeeb, K. M., Supercapattery based on binder-free Co3(PO4)2·8H2O multilayer nano/ microflakes on nickel foam. ACS applied materials & interfaces
2016, 8, pp. 28592-28598.
[2] Padmanathan, N.; Shao, H.; McNulty, D.; O'Dwyer, C.; Razeeb, K. M., Hierarchical NiO–In2O3 microflower (3D)/ nanorod (1D) hetero-architecture as a supercapattery electrode with excellent cyclic stability. J. Mater. Chem. A
2016,
4(13), pp. 4820-4830.
Figure 1. SEM image of silver oxide-cobalt phosphate electrode.

Figure 1
Nanostructure Silicon-Based Hierarchical Architectures for High-Performance Lithium-Ion Battery Anode
Authors: Ambrosio Zanin Maria Helena , Li Xuemin , Bender Guido , Son Seoung-Bum , Ban Chunmei 
Published: February 2020

Silicon (Si) has the highest specific capacity (4200 mAhg-1) and volumetric capacity (9786 mAh cm-3) among the material candidates, which makes it the most promising material for the Lithium Ion Battery (LIB). However, the drastic volume fluctuation (~400%) during the lithiation/delithiation process reduces the battery cyclability and affects the battery reversibility. To overcome these limitations, different architectures have been developed for incorporating Si to accommodate the volumetric changes within the conductive matrix.
The combination of electrospinning and electrospray processes has been used to fabricate three different hierarchical network architectures based on nanoscale Si and Polyacrylonitrile (PAN). Among these hierarchical architectures, the core-shell Si/PAN structure and the Si/PAN multilayer structure have significantly improved the cycling performance with high capacity and good capacity retention. Cyclization has also been performed to form the hierarchical conductive framework, which provides a continuous electron transport network and high porosity to address the volume expansion during electrochemical reactions. By integrating electrospray process in the synthesis process, a greatly improved capacity is achieved with a high reversible area capacity over 2mAh/cm2. This work will present the results of our systematic investigation on structure-property relationships in the Si/PAN hierarchical architectures.