bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrocatalysis Approach to Lithium Polysulfides Redox Chemistry
Authors: Arava Leela mohana reddy 
Published: February 2020

Stabilizing polysulfide-shuttle process while ensuring high sulfur loading holds the key to realize high theoretical energy density (2500 Wh/kg) of lithium-sulfur (Li-S) batteries. Though several carbon based porous materials have been used as host structures for sulfur and its intermediate polysulfides, the week adsorption of polysulfides on carbon surface and its poor reaction kinetics limits them from practical application. Here, we preset a novel ‘electcatalysis’ approach to stabilize polysulfide shuttle process and also enhance its red-ox kinetics. Nature of electrocatalyst, pore-size distribution, concentration of polysulfides, temperature of the cell etc., on electrochemical properties will be discussed. 1, 2 We reveal substantial improvement in electrochemical properties such as specific capacity, rate capability, coulombic efficiency etc. and corroborate our findings with systematic experimental studies. Interaction between electrocatalyst and polysulfides has been evaluated by conducting X-ray photoelectron spectroscopy and electron microscopy studies at various electrochemical conditions. Thus, introducing a catalyst in the Li−S system will open a new avenue for improving electrochemical performance.
1. Al Salem, H.; Babu, G.; V. Rao, C.; Arava, L. M. R. Journal of the American Chemical Society
2015,137, (36), 11542-11545.
2. Babu, G.; Ababtain, K.; Ng, K. Y. S.; Arava, L. M. R. Scientific Reports
2015,5, 8763.
The Li Ion Diffusion Kinetics Study of Beta LiVOPO4 As Cathode Material for Lithium Ion Batteries
Authors: Ryu Kwang-Sun , Park Da jeong 
Published: February 2020

Lithium vanadyl phosphate (LiVOPO4) is an attractive cathode for lithium ion batteries with a high operating voltage 4.0V in phosphate poly-anion cathode materials and good theoretical capacity of 166mAh/g. LiVOPO4 exist mainly in two different crystallographic phases, one is orthorhombic β-LiVOPO4 another is triclinic α-LiVOPO4. Among these phases, β-LiVOPO4 is widely studied in view of lithium ion intercalation, and it shows better electrochemical performance than α-LiVOPO4. K. Nagamine et al. presented that the orthorhombic crystals have a three-dimensional Li ion pathway consisting of interconnected VO6 octahedral and PO4 tetrahedral units that consequently create channels for Li+ion movement. However, the main defects such as poor electrical conductivity and low lithium ionic conductivity are drawback for its application in lithium ion batteries. To improve the poor electrical conductivity, many researches have been studied by carbon coating and composite method.
While, the studies are extremely rate to enhance lithium ion conductivity and lithium ion diffusion coefficient technique. In this study, we have investigated that the diffusion coefficient of lithium ion in β-LiVOPO4 by SSCV (slow scan cyclic voltammetry), EIS (Electrochemical impedance spectroscopy), GITT (Galvanostatic intermittent titration technique) and PITT (Potentiostatic intermittent titration technique) to compare lithium diffusion value according to four techniques. And we have optimized diffusion technique in β-LiVOPO4. The synthesis of β-LiVOPO4 was carried out by sol-gel method. Firstly, oxalic acid and V2O5 in stoichiometric ratio were dissolved in deionized water with magnetic stirring at 70°C. After a clear blue solution formed, a mixture of stoichiometric NH4H2PO4 and LiNO3 was added to the solution while stirring for 4h and the green gel formed. Finally, the dried gel was decomposed at 300°C for 4h and the obtained product was sintered at 500 °C for 4h in air. As a result, SSCV, GITT, PITT techniques relatively indicated similar lithium ion diffusion coefficient value. But, low lithium ion diffusion coefficient value was obtained by EIS technique. Due to the accuracy for calculating needed. The chemical diffusion coefficient of EIS depends on the fitting of experimental impedance with an equivalent circuit model. While, the GITT and PITT techniques were obtained under deviation from equilibrium conditions. Because the between current and voltage and time more exactly reflected the diffusion property. So, among the four techniques, GITT and PITT were more reliable in β-LiVOPO4 cathode material.
Computational Insights to the Layered-to-Spinel Structural Transformation in Ni-Rich Lithiated Transition Metals Oxide Materials (LiNixCoyMnzO2)
Authors: Dixit Mudit , Schipper Florian , Markovsky Boris , Aurbach Doron , Major Dan Thomas 
Published: February 2020

Ni-rich lithiated transition metal oxides of layered structure (R-3m space group) LiNixCoyMnzO2 (NCMs, x>0.5) represent a family of promising materials for positive electrodes of advanced lithium-ion batteries (LIB). These materials demonstrate reversible capacities around 160 – 190 mAh/g in the potential range of 2.8 – 4.3 V. Despite of the considerable research on improvement of these materials’ performance by lattice doping with cations, the molecular level of understanding the effect of dopants on the electronic structure, voltages, and ion diffusion is very limited. However, the above information is essential for the design of new and efficient positive electrode materials for LIB. For example, atomistic resolution parameters, such as the diffusion of lithium ions within the layers, are responsible for the power of the battery. The electronic structure, on the other hand, dictates the electro-conductivity. Although many studies suggest improved performance of doped NCM cathode materials, the mechanism of the enhanced behavior still remains unclear. In this work, we present the computational study using ab-initio modeling of the role of Zr-doping on the electrochemical performance and structure of LiNi0.6Co0.2Mn0.2O2 (NCM-622) electrode material. We show that how doping influences on the Li+/Ni2+ mixing, charge distribution among transition metals, and lattice constants. In particular, we reveal that Ni+2 ions migration upon Li-deintercalation (charge) can initiate layered-to-spinel structural transformation. We also demonstrate the role of Zr+4 cations on limiting this transformation by investigating the electronic structure and possible Ni+2 migration pathways and mechanisms. In this presentation, the role of other multivalent dopant cations on the structural stability of NCM will be discussed.
First Principles Study on Lithium Transport through Crystalline and Amorphous Materials for Discovery of Battery Coatings
Authors: Lu Zhi , Hao Shiqiang , Yao Zhenpeng , Aykol Muratahan , Morgan Dane , Wolverton Chris 
Published: February 2020

A widely used remedy to slow down the degradation of the electrochemical performances of lithium-ion batteries is to apply coating materials on cathode surfaces.[1] Such coatings can serve as physical barriers to inhibit electrode-electrolyte side reactions, and they can also possess an additional functionality such as scavenging the detrimental acids (e.g., the hydrofluoric acid, HF) in electrolytes. Following our previous thermodynamics high-throughput search for functional cathode coatings,[2] we recently further built on our framework for understanding the battery performance improvement associated with coatings by studying and predicting lithium transport through a number of various crystalline and amorphous coating materials using density functional theory (DFT) calculations.
In the current work, we first investigated the Li diffusion in top candidates of crystalline metal oxides from our thermodynamics screening. With the help of MINT (software developed by our group), we found unique Li interstitial sites and corresponding migration pathway in these crystalline metal oxides. After that, DFT based Nudge Elastic Band (NEB) method was applied to calculate the migration barrier and corresponding Li diffusivity for each material was obtained by Kinetic Monte Carlo (KMC) simulation. Since many reports in the literature show coatings are likely to be in an amorphous form, we further studied the Li transport in a variety amorphous oxides and fluorides by methods that combine first principles density functional theory calculations and statistical mechanics.
In above diffusivity calculations, only dilute Li concentrations is taken into account, since at high Li concentration, phase transitions are likely to occur. Knowing that the Li diffusivity can be improved at high Li concentration, we extended our kinetical framework to some Li-contained metal oxides. All these metal oxides, fluorides and Li-contained metal oxides are top coating candidates examined from previous thermodynamic calculations. After all this kinetical calculation of Li transport, a ranking list is predicted and some materials are suggested as good coating materials in terms of Li diffusivity, which is one of the key factors influencing the rate performance of Li ion battery.
This work is one part of a framework for understanding the battery performance improvement associated with coatings and should aid in the future discovery of functional coating materials.

References

[1] Z. Chen, Y. Qin, K. Amine, Y.-K. Sun, J. Mater. Chem. 2010, 20, 7606.
[2] M. Aykol, S. Kirklin, C. Wolverton, Adv. Energy Mater. 2014, 4, 1400690

Acknowledgement

This computational research work was supported by The DOW Chemical Company.
The Effects of Co-Substitution and Al-Doping on the Structural Stability of LiNiO2
Authors: Lee Eunseok , Iddir Hakim , Benedek Roy 
Published: February 2020

Developing advanced cathode materials that provide high specific energy and power is essential for the commercialization of Li-ion batteries for electric vehicles. The layered LiNi0.8Co0.15Al0.05O2 (NCA) has received attentions as a promising candidate due to its cheaper material cost than LiCoO2, competitive electrochemical performance, and improved structural stability than LiNiO2. Thorough understanding of the origin of structural instability of Ni-based cathodes and the mechanism of Co-substitution and Al-doping will enable further improvement of Ni-based cathodes and other types of cathode materials as well. In this talk, we present our computational work on the structural stability of NCA, with emphasis on the effect of magnetic ions.
LiNi1-yCoyO2 (NC) was studied first. Atom-spin coupled cluster expansion (CE) based on the density functional theory (DFT) calculations was performed to find stable atom-spin configurations of NC. The cationic mixing was accounted for by assuming that each cationic lattice site can be occupied by any of Li, Co, or Ni. The result predicted three stable configurations at zero temperature: LiNi0.8Co0.2O2, LiNi0.67Co0.33O2, and LiNi0.5Co0.5O2, as well as several more configurations at finite temperature, especially at y < 1/3, which agreed to the experimental observation on the range of solid-solution phase NC. Interestingly, the configurations of solid-solution phase NC had Ni ions in Li-layer (Ni-defects). We also found that that the solid-solution phase NC became less dominant when the Co content increased, which suggested that Co substitution might have suppressed the formation of Ni-defects.
DFT calculations with HSE06 functional were additionally performed to investigate the mechanism of Co substitution associated with the suppression of Ni-defects formation. The oxidation state of each ion was obtained by analyzing the magnetic moment and agreed well with experimental observations. We found that a Ni-defect tended to be Ni2+ by oxidizing one Ni ion in TM layer to Ni4+ when they formed the nearest neighbor pair. In this case, the antiferromagnetic spin distribution was possible for all pairs of paramagnetic Ni ions (Ni2+ and Ni3+), which implies the configurations with Ni-defects (Ni ions in Li layer) are thermodynamically more favorable than non-defective configurations where such the antiferromagnetic spin distribution is not possible due to magnetic frustration. When Co is substitued for Ni, the oxidation state of Co is Co3+, which is diamagnetic like Ni4+. Then the antiferromagnetic spin distribution for all paramagnetic ions is also possible even without creating Ni-defects and we will demonstrate that the most ideal case is when y=1/3.
We performed further calculations to find stable NCA configurations by replacing a portion of Co in NC with Al. By comparing NC and NCA, the effect of Al-doping to the structural stability will be also discussed.
Scaling Effects of the Synthesis of Lithium- and Manganese-Rich Cathode Materials Via Carbonate Co-Precipitation
Authors: Kenkel Alexander , Kloepsch Richard , Wang Jun , Li Jie 
Published: February 2020

Li-rich cathode materials with the general formula Li1+x

M
1-x
O2 (M = Mn, Ni, Co; x <= 0.2) are very promising cathode materials for lithium ion batteries, particularly due to their significantly higher specific capacity (>200 mAh g-1) compared to state of the art cathode materials.[1] Popular members of the Li-rich family, like Li1.2Mn0.56Ni0.16Co0.08O2 [2] and the Co-free compound Li1.2Mn0.6Ni0.2O2 have already been structurally and electrochemically investigated, but mostly on laboratory scale. Thus, in order to obtain larger amounts of high-quality Li-rich cathode materials, the upscaling effects of the established co-precipitation synthesis route were thoroughly investigated in this work, specifically for the above mentioned stoichiometries. With regard to the upscaling process, the impact of the synthesis parameters (e.g. stirring speed and type, pH value, reaction time) on the resulting morphology of the precursor as well as that of the final oxide and consequently, its electrochemical performance was analyzed. For each material three differently sized batches were synthesized, one in a laboratory scale of 4 g and two larger batches up to 75 g.
For the Co-free materials a significant upscaling effect was observed (see Fig. 1): The faster stirring of the larger batches lead to larger, spherically shaped precursor particles. However, these large precursor particles form more inhomogeneous target materials upon calcination, which consequently resulted in an inferior electrochemical performance. The more homogeneous cathode particles of the small batches show very promising electrochemical properties with regard to both rate capability and capacity retention.
References:
[1] M.M.Thackeray, S.-H. Kang, C.S. Johnson, J.T. Vaughey, R. Benedek, S.A. Hackney, Journal of Materials Chemistry, 17 (2007) 3112-3125.
[2] J. Li, R. Klöpsch, S. Nowak, M. Kunze, M. Winter, S. Passerini, Journal of Power Sources, 196 (2011) 4821-4825.

Figure 1
Reaction Mechanism and Dynamics of Selenium As Cathode for High Energy Density Lithium-Ion Battery
Authors: Li Qianqian , Wu Jinsong , Liu Heguang , Dravid Vinayak 
Published: February 2020

Selenium, with similar chemical properties as sulfur, has recently attracted much research attention as potential electrodes for high energy density lithium-ion batteries. Unlike sulfur cathode with poor cycling performance due to the instability of Li-S compounds formed in lithiation and delithiation, Se is promising in regards to improvement in the cycling stability. We have used in situ transmission electron microscopy (TEM) to investigate the reaction mechanism and dynamics in the lithiation and delithiation cycles. We observe that single crystalline structure of pristine selenium nanowire gradually transformed to a polycrystalline structure as lithium continue insertion without intermediate amorphous phase formed during the whole lithiation process. And Li2Se phase with a polycrystalline structure finally forms after full lithiation. Li-Se alloying reaction accompanies with dramatic volume expansion, including both elongation along axil direction and expansion in radial direction. High density of stress and strain occurs at reaction front region, and then these stresses and strains rapidly glide to unreacted region, and move out of the nanowire from the surface and edge eventually. This process efficiently drives large amount of lithium ions to move forward. For comparison, we studied also the structural evolutions in the sodiation and desodiation which may have great implications for the development of sodium-ion batteries. These observations and experiments not only can help to deeply understand the reaction mechanism and reaction process, but favor to design novel nanostructure of electrodes with excellent electrochemical performance.
This work was supported as part of the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DEAC02-06CH11357, and the Initiative for Sustainability and Energy at Northwestern (ISEN). This work was also supported by the NUANCE Center, and made use of the EPIC facility (NUANCE Center-Northwestern University), which has received support from the MRSEC program (NSF DMR-1121262) at the Materials Research Center; the International Institute for Nanotechnology (IIN); and the State of Illinois, through the IIN.
First Principles Design of Hybrid Cathode Architectures Based on LiMn2O4 Spinel Oxides
Authors: Kim Soo , Aykol Muratahan , Wolverton Chris 
Published: February 2020

LiMn2O4 (LMO) can deliver a reasonable discharge capacity of ~130 mAh g-1, where the three-dimensional lithium ions diffusion channel in the spinel structure allows a rapid de-/intercalation reaction. There are several drawbacks of the spinel LMO including a severe capacity fade during cycling due to a Jahn-Teller (JT) distortion and Mn2+ dissolution. This Mn dissolution presumably starts at the particle surface; and therefore, it is essential to completely understand of the surface structure and its stability. We have recently constructed the thermodynamic stability diagram of LMO using density functional calculations (DFT) to investigate how stability of bulk LMO and LMO surfaces correlate as a function of oxygen and lithium chemical potentials.1 We have also suggested that Li-excess environments and too high temperatures should be avoided upon synthesis to yield particles with less (001) LMO facet, i.e., the surface that is more prone to Mn dissolution.
Furthermore, we have recently provided a novel strategy to suppress Mn dissolution and the JT distortion by investigating the spinel LMO (001) surface with a single layer of graphene using DFT.2 Our theoretical calculation in Ref. 2 suggests that the interaction between the graphene sheet and the LMO (001) surface suppresses the Mn3+ disproportionation reaction into Mn2+ and Mn4+. While all surface Mn atoms at the LMO (001) have an oxidation state of +3, we find that the (001) Mn atom that chemically bonds with graphene adopts an electron configuration that has a clear +4 character with an empty eg
band. By analyzing the (001) LMO surface Mn-O bond distance, we observe that the JT distortion is reduced as the oxidation state of surface Mn shifts to Mn4+ in the presence of the graphene sheet. A chemical bonding between graphene and LMO on the (001) surfaces provides an underlying mechanism that electronically modifies the LMO (001) surfaces, and subsequently stabilizes them against Mn3+ disproportionation reaction and the JT distortion by converting (001) surface Mn3+ to Mn4+. Our advanced first-principles computations shed lights on the development of alternative hybrid Mn-cathode architecture approaches that can overcome the key shortcomings in these cathode materials.

References

[1] S. Kim, M. Aykol, and C. Wolverton. Phys. Rev. B, 92, 115411.
[2] L. Jaber-Ansari, K. P. Puntambekar, S. Kim, M. Aykol, L. Luo, J. Wu, B. D. Myers, H. Iddir, J. T. Russell, S. J. Saldaña, R. Kumar, M. M. Thackeray, L. A. Curtiss, V. P. Dravid, C. Wolverton, and M. C. Hersam.
Adv. Energy. Mater.
5 (2015) 1500646

Acknowledgement

This computational research work was supported by Northwestern-Argonne Institute of Science and Engineering (NAISE) and the Dow Chemical Company.

Figure Caption: Hybrid Cathode Architectures: Graphene-stabilized LiMn2O4 (001) Li-terminated Surface.

Figure 1
The Nanode 3D Tin Anode for High Energy and High Rate
Authors: Moroz Stephanie , Wieser Manuel , Brown Melanie , Gamboa Kristine 
Published: February 2020

The Nanode is a nanoporous conductive membrane that provides a three dimensional matrix as a low cost support for electrodes. It is fabricated using commodity raw materials and chemicals, and manufacturing processes are in development for production on a roll-to-roll line.
The Nanode is combined with tin and tin alloys to form high energy anodes for lithium ion batteries. A thin film of active material is applied to the extremely high surface area of the conductive substrate which acts as the current collector. This has been shown to achieve greater energy at higher discharge rates compared to graphite anodes. Testing has been performed from 1 to 10C discharge rates at 100% depth of discharge paired with commercial NCM cathodes.
In addition, the nanoporous structure accommodates the expansion of the thin film of tin within its pores, reducing the overall electrode expansion/contraction occurring on charge/discharge of the anode.
Altogether, the low cost production, high energy at high rate, and reduced expansion of this anode provide a beneficial combination of features for future lithium ion batteries.
The Nanode technology also shows promise for applications beyond traditional lithium ion batteries, using alternative battery chemistries. This is made possible by the Nanode’s complex yet versatile electrode structure supported by a flexible manufacturing process that allows for the deposition of a range of metallic thin films of different compositions. These applications hold the potential to improve the energy density of rechargeable batteries beyond the limits of the traditional foil/particle approach, and they could reduce the cost of energy storage.