scholarly journals Spin polarization in the phase diagram of a Li–Fe–S system

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Tsuyoshi Takami ◽  
Tomonari Takeuchi ◽  
Toshiharu Fukunaga
Keyword(s):  
Spin Polarization ◽  
Density Functional ◽  
Inorganic Compounds ◽  
Density Functional Theory Calculations ◽  
Phase Changes ◽  
Electrochemical Technique ◽  
Functional Theory ◽  
Li Ion ◽  
Fe Ions ◽  
Li Content

AbstractDivalent and trivalent states of Fe ions are known to be stable in inorganic compounds. We focus a novel LixFeS5 cathode, in which the Li content (x) changes from 2 to 10 by an electrochemical technique. As x increases from 2, a Pauli paramagnetic conductive Li2FeS5 phase changes into a superparamagnetic insulating Li10FeS5 phase. Density functional theory calculations suggest that Fe+ ions in a high-x phase are responsible for ferromagnetic spin polarization. Reaching the monovalent Fe ion is significant for understanding microscopic chemistry behind operation as Li-ion batteries and the original physical properties resulting from the unique local structure.

scholarly journals Evidence for a Solid-Electrolyte Inductive Effect in Superionic Conductors

2020 ◽  
Author(s):  
Sean Culver ◽  
Alex Squires ◽  
Nicolo Minafra ◽  
Callum Armstrong ◽  
Thorben Krauskopf ◽  
...  
Keyword(s):  
Solid Electrolyte ◽  
Solid Electrolytes ◽  
Density Functional ◽  
Inductive Effect ◽  
Ionic Conductivities ◽  
Lithium Ion ◽  
Density Functional Theory Calculations ◽  
Ion Diffusion ◽  
Functional Theory ◽  
Li Ion

<p>Identifying and optimizing highly-conducting lithium-ion solid electrolytes is a critical step towards the realization of commercial all–solid-state lithium-ion batteries. Strategies to enhance ionic conductivities in solid electrolytes typically focus on the effects of modifying their crystal structures or of tuning mobile-ion stoichiometries. A less-explored approach is to modulate the chemical-bonding interactions within a material to promote fast lithium-ion diffusion. Recently, the idea of a solid-electrolyte inductive effect was proposed, whereby changes in bonding within the solid-electrolyte host-framework modify the potential-energy landscape for the mobile ions, resulting in an enhanced ionic conductivity. This concept has since been invoked to explain anomalous conductivity trends in a number of solid electrolytes. Direct evidence for a solid-electrolyte inductive effect, however, is lacking—in part because of the challenge of quantifying changes in local bonding interactions within a solid-electrolyte host-framework. <a></a><a>Here, we consider the evidence for a solid-electrolyte inductive effect in the archetypal superionic lithium-ion conductor Li<sub>10</sub>Ge<sub>1−<i>x</i></sub>Sn<i><sub>x</sub></i>P<sub>2</sub>S<sub>12</sub>, using Rietveld refinements against high-resolution temperature-dependent neutron-diffraction data, Raman spectroscopy, and density functional theory calculations.</a> Substituting Ge for Sn weakens the {Ge,Sn}–S bonding interactions and increases the charge-density associated with the S<sup>2-</sup> ions. This charge redistribution modifies the Li<sup>+</sup> substructure causing Li<sup>+</sup> ions to bind more strongly to the host-framework S anions; which in turn modulates the Li-ion potential-energy surface, increasing local barriers for Li-ion diffusion. Each of these effects is consistent with the predictions of the solid-electrolyte inductive effect model. Density functional theory calculations further predict that this inductive effect occurs even in the absence of changes to the host-framework geometry due to Ge → Sn substitution. These results provide direct evidence in support of a measurable solid-electrolyte inductive effect and demonstrate its application as a practical strategy for tuning ionic conductivities in superionic lithium-ion conductors.</p>

scholarly journals Nanometer-size Na cluster formation in micropore of hard carbon as origin of higher-capacity Na-ion battery

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Yong Youn ◽  
Bo Gao ◽  
Azusa Kamiyama ◽  
Kei Kubota ◽  
Shinichi Komaba ◽  
...  
Keyword(s):  
Density Functional ◽  
Cluster Formation ◽  
High Capacity ◽  
Density Functional Theory Calculations ◽  
High Energy ◽  
High Energy Density ◽  
Hard Carbon ◽  
Functional Theory ◽  
Nanometer Size ◽  
Li Ion

AbstractDevelopment of high-energy-density anode is crucial for practical application of Na-ion battery as a post Li-ion battery. Hard carbon (HC), though a promising anode candidate, still has bottlenecks of insufficient capacity and unclear microscopic picture. Usage of the micropore has been recently discussed, however, the underlying sodiation mechanism is still controversial. Herein we examined the origin for the high-capacity sodiation of HC, based on density functional theory calculations. We demonstrated that nanometer-size Na cluster with 3–6 layers is energetically stable between two sheets of graphene, a model micropore, in addition to the adsorption and intercalation mechanisms. The finding well explains the extended capacity over typical 300 mAhg−1, up to 478 mAhg−1 recently found in the MgO-templated HC. We also clarified that the MgO-template can produce suitable nanometer-size micropores with slightly defective graphitic domains in HC. The present study considerably promotes the atomistic theory of sodiation mechanism and complicated HC science.

scholarly journals Evidence for a Solid-Electrolyte Inductive Effect in Superionic Conductors

2020 ◽  
Author(s):  
Sean Culver ◽  
Alex Squires ◽  
Nicolo Minafra ◽  
Callum Armstrong ◽  
Thorben Krauskopf ◽  
...  
Keyword(s):  
Solid Electrolyte ◽  
Solid Electrolytes ◽  
Density Functional ◽  
Inductive Effect ◽  
Ionic Conductivities ◽  
Lithium Ion ◽  
Density Functional Theory Calculations ◽  
Ion Diffusion ◽  
Functional Theory ◽  
Li Ion

<p>Identifying and optimizing highly-conducting lithium-ion solid electrolytes is a critical step towards the realization of commercial all–solid-state lithium-ion batteries. Strategies to enhance ionic conductivities in solid electrolytes typically focus on the effects of modifying their crystal structures or of tuning mobile-ion stoichiometries. A less-explored approach is to modulate the chemical-bonding interactions within a material to promote fast lithium-ion diffusion. Recently, the idea of a solid-electrolyte inductive effect was proposed, whereby changes in bonding within the solid-electrolyte host-framework modify the potential-energy landscape for the mobile ions, resulting in an enhanced ionic conductivity. This concept has since been invoked to explain anomalous conductivity trends in a number of solid electrolytes. Direct evidence for a solid-electrolyte inductive effect, however, is lacking—in part because of the challenge of quantifying changes in local bonding interactions within a solid-electrolyte host-framework. <a></a><a>Here, we consider the evidence for a solid-electrolyte inductive effect in the archetypal superionic lithium-ion conductor Li<sub>10</sub>Ge<sub>1−<i>x</i></sub>Sn<i><sub>x</sub></i>P<sub>2</sub>S<sub>12</sub>, using Rietveld refinements against high-resolution temperature-dependent neutron-diffraction data, Raman spectroscopy, and density functional theory calculations.</a> Substituting Ge for Sn weakens the {Ge,Sn}–S bonding interactions and increases the charge-density associated with the S<sup>2-</sup> ions. This charge redistribution modifies the Li<sup>+</sup> substructure causing Li<sup>+</sup> ions to bind more strongly to the host-framework S anions; which in turn modulates the Li-ion potential-energy surface, increasing local barriers for Li-ion diffusion. Each of these effects is consistent with the predictions of the solid-electrolyte inductive effect model. Density functional theory calculations further predict that this inductive effect occurs even in the absence of changes to the host-framework geometry due to Ge → Sn substitution. These results provide direct evidence in support of a measurable solid-electrolyte inductive effect and demonstrate its application as a practical strategy for tuning ionic conductivities in superionic lithium-ion conductors.</p>

Density functional theory calculations of NO molecule adsorption on monolayer MoS2 doped by Fe atom

2015 ◽  
Vol 29 (27) ◽  
pp. 1550160 ◽  
Author(s):  
Yanhua Wang ◽  
Xiaoyu Shang ◽  
Xiaowei Wang ◽  
Jianying Tong ◽  
Jingcheng Xu
Keyword(s):  
Density Functional Theory ◽  
Spin Polarization ◽  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
First Principles Calculations ◽  
Monolayer Mos2 ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
No Absorption

Functionalization of [Formula: see text] monolayer doped by the transition-metal Fe adatom [Formula: see text]–[Formula: see text] and NO absorption on [Formula: see text]–[Formula: see text] has been investigated computationally using first-principles calculations based on the density functional theory. We found that the system of [Formula: see text]–[Formula: see text] remains a semiconductor, with spin polarization at the Fermi level. However, for the system with absorption of NO molecule on the surface of [Formula: see text]–[Formula: see text] monolayer, its spin polarization is turned over at the Femi level, which provides a promising material for spintronic sensors.

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