scholarly journals Simulation-Based Defect Engineering in “α-Spodumene”

2021 ◽  
Vol 5 (3) ◽  
pp. 57
Author(s):  
Sivanujan Suthaharan ◽  
Poobalasuntharam Iyngaran ◽  
Navaratnarajah Kuganathan
Keyword(s):  
Density Functional ◽  
Lithium Ion ◽  
Defect Cluster ◽  
Intrinsic Defect ◽  
Ion Diffusion ◽  
Defect Engineering ◽  
Functional Theory ◽  
Pair Potentials ◽  
Simulation Based ◽  
Defect Process

Naturally occurring lithium-rich α-spodumene (α-LiAlSi2O6) is a technologically important mineral that has attracted considerable attention in ceramics, polymer industries, and rechargeable lithium ion batteries (LIBs). The defect chemistry and dopant properties of this material are studied using a well-established atomistic simulation technique based on classical pair-potentials. The most favorable intrinsic defect process is the Al-Si anti-site defect cluster (1.08 eV/defect). The second most favorable defect process is the Li-Al anti-site defect cluster (1.17 eV/defect). The Li-Frenkel is higher in energy by 0.33 eV than the Al-Si anti-site defect cluster. This process would ensure the formation of Li vacancies required for the Li diffusion via the vacancy-assisted mechanism. The Li-ion diffusion in this material is slow, with an activation energy of 2.62 eV. The most promising isovalent dopants on the Li, Al, and Si sites are found to be Na, Ga, and Ge, respectively. The formation of both Li interstitials and oxygen vacancies can be facilitated by doping of Ga on the Si site. The incorporation of lithium is studied using density functional theory simulations and the electronic structures of resultant complexes are discussed.

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>

Enhanced ion diffusion induced by structural transition of Li-modified borophosphene

2020 ◽  
Vol 22 (37) ◽  
pp. 21326-21333
Author(s):  
Shiping Wang ◽  
Wei Zhang ◽  
Cai Lu ◽  
Yanhuai Ding ◽  
Jiuren Yin ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Lithium Ion Batteries ◽  
Density Functional ◽  
Structural Transition ◽  
Lithium Ion ◽  
Ion Diffusion ◽  
Functional Theory

Density functional theory (DFT) calculations have been carried out to investigate the performance of borophosphene in lithium-ion batteries.

scholarly journals Defects and Calcium Diffusion in Wollastonite

Chemistry ◽  
2020 ◽  
Vol 2 (4) ◽  
pp. 937-946
Author(s):  
Sumudu Nimasha ◽  
Sashikesh Ganeshalingam ◽  
Navaratnarajah Kuganathan ◽  
Konstantinos Davazoglou ◽  
Alexander Chroneos
Keyword(s):  
Activation Energy ◽  
Defect Cluster ◽  
Slow Diffusion ◽  
Pair Potentials ◽  
Simulation Based ◽  
Calcium Diffusion ◽  
Engineering Strategy ◽  
Ca Ions ◽  
Defect Process

Wollastonite (CaSiO3) is an important mineral that is widely used in ceramics and polymer industries. Defect energetics, diffusion of Ca ions and a solution of dopants are studied using atomistic-scale simulation based on the classical pair potentials. The energetically favourable defect process is calculated to be the Ca-Si anti-site defect cluster in which both Ca and Si swap their atomic positions simultaneously. It is calculated that the Ca ion migrates in the ab plane with an activation energy of 1.59 eV, inferring its slow diffusion. Favourable isovalent dopants on the Ca and Si sites are Sr2+ and Ge4+, respectively. Subvalent doping by Al on the Si site is a favourable process to incorporate additional Ca in the form of interstitials in CaSiO3. This engineering strategy would increase the capacity of this material.

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 Structural and Defect Properties of LiTi2(PO4)3

2021 ◽  
Vol 11 (5) ◽  
pp. 13268-13275
Keyword(s):  
Atomistic Simulation ◽  
Three Dimensional ◽  
Intrinsic Defect ◽  
Ion Diffusion ◽  
Ion Migration ◽  
Pair Potentials ◽  
Simulation Based ◽  
Engineering Strategy ◽  
Li Ion ◽  
High Chemical Stability

LiTi2(PO4)3 is an attractive electrolyte material in Li-ion batteries' application due to its high ionic conductivity and high chemical stability. Here we employ atomistic simulation based on the classical pair potentials to examine the intrinsic defect processes, Li-ion migration, and solution of various dopants in LiTi2(PO4)3. The Li-Frenkel (0.73 eV) is calculated to be the most favorable defect energy process ensuring the formation of Li vacancies required for the vacancy-assisted Li-ion migration. Long-range three-dimensional lithium vacancy migration was observed with a low activation energy of 0.36 eV, inferring fast Li-ion diffusion. The most favorable isovalent dopants on the Li and Ti sites are Na and Si, respectively. Li interstitials' formation in these materials is favored by doping of Ga on the Ti site. This engineering strategy can be of interest to improve the capacity of LiTi2(PO4)3.

scholarly journals Defect Process, Dopant Behaviour and Li Ion Mobility in the Li2MnO3 Cathode Material

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1329 ◽  
Author(s):  
Navaratnarajah Kuganathan ◽  
Efstratia Sgourou ◽  
Yerassimos Panayiotatos ◽  
Alexander Chroneos
Keyword(s):  
Cathode Material ◽  
Low Cost ◽  
Lithium Ion ◽  
Intrinsic Defect ◽  
Ion Diffusion ◽  
Simulation Techniques ◽  
Low Toxicity ◽  
Li Ion ◽  
Defect Process ◽  
Lithium Ion Diffusion

Lithium manganite, Li2MnO3, is an attractive cathode material for rechargeable lithium ion batteries due to its large capacity, low cost and low toxicity. We employed well-established atomistic simulation techniques to examine defect processes, favourable dopants on the Mn site and lithium ion diffusion pathways in Li2MnO3. The Li Frenkel, which is necessary for the formation of Li vacancies in vacancy-assisted Li ion diffusion, is calculated to be the most favourable intrinsic defect (1.21 eV/defect). The cation intermixing is calculated to be the second most favourable defect process. High lithium ionic conductivity with a low activation energy of 0.44 eV indicates that a Li ion can be extracted easily in this material. To increase the capacity, trivalent dopants (Al3+, Co3+, Ga3+, Sc3+, In3+, Y3+, Gd3+ and La3+) were considered to create extra Li in Li2MnO3. The present calculations show that Al3+ is an ideal dopant for this strategy and that this is in agreement with the experiential study of Al-doped Li2MnO3. The favourable isovalent dopants are found to be the Si4+ and the Ge4+ on the Mn site.

scholarly journals Defect Properties and Lithium Incorporation in Li2ZrO3

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3963
Author(s):  
Kobiny Antony Rex ◽  
Poobalasuntharam Iyngaran ◽  
Navaratnarajah Kuganathan ◽  
Alexander Chroneos
Keyword(s):  
Atomistic Simulation ◽  
Density Functional ◽  
Functional Theory ◽  
Lithium Zirconate ◽  
Simulation Based ◽  
Electrochemical Devices ◽  
Li Ion ◽  
Cluster Energy ◽  
Experimental Values ◽  
Lithium Incorporation

Lithium zirconate is a candidate material in the design of electrochemical devices and tritium breeding blankets. Here we employ an atomistic simulation based on the classical pair-wise potentials to examine the defect energetics, diffusion of Li-ions, and solution of dopants. The Li-Frenkel is the lowest defect energy process. The Li-Zr anti-site defect cluster energy is slightly higher than the Li-Frenkel. The Li-ion diffuses along the c axis with an activation energy of 0.55 eV agreeing with experimental values. The most favorable isovalent dopants on the Li and Zr sites were Na and Ti respectively. The formation of additional Li in this material can be processed by doping of Ga on the Zr site. Incorporation of Li was studied using density functional theory simulation. Li incorporation is exoergic with respect to isolated gas phase Li. Furthermore, the semiconducting nature of LZO turns metallic upon Li incorporation.

scholarly journals Predicting the new carbon nanocages, fullerynes: a DFT study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohammad Qasemnazhand ◽  
Farhad Khoeini ◽  
Farah Marsusi
Keyword(s):  
Density Functional Theory ◽  
Lithium Ion Batteries ◽  
Density Functional ◽  
Lithium Ion ◽  
The Other ◽  
Electron Affinities ◽  
Chemical Formula ◽  
Functional Theory ◽  
Triple Bonds ◽  
Structural And Electronic Properties

AbstractIn this study, based on density functional theory, we propose a new branch of pseudo-fullerenes which contain triple bonds with sp hybridization. We call these new nanostructures fullerynes, according to IUPAC. We present four samples with the chemical formula of C4nHn, and the structures derived from fulleranes. We compare the structural and electronic properties of these structures with those of two common fullerenes and fulleranes systems. The calculated electron affinities of the sampled fullerynes are negative, and much smaller than those of fullerenes, so they should be chemically more stable than fullerenes. Although fulleranes also exhibit higher chemical stability than fullerynes, but pentagon or hexagon of the fullerane structures cannot pass ions and molecules. Applications of fullerynes can be included in the storage of ions and gases at the nanoscale. On the other hand, they can also be used as cathode/anode electrodes in lithium-ion batteries.

scholarly journals Na-ion diffusion in a NASICON-type solid electrolyte: a density functional study

2016 ◽  
Vol 18 (39) ◽  
pp. 27226-27231 ◽  
Author(s):  
Kieu My Bui ◽  
Van An Dinh ◽  
Susumu Okada ◽  
Takahisa Ohno
Keyword(s):  
Density Functional Theory ◽  
Solid Electrolyte ◽  
Electronic Structures ◽  
Density Functional ◽  
Diffusion Mechanism ◽  
Functional Study ◽  
Ion Diffusion ◽  
Functional Theory ◽  
Density Functional Study ◽  
Nasicon Type

Based on density functional theory, we have systematically studied the crystal and electronic structures, and the diffusion mechanism of the NASICON-type solid electrolyte Na3Zr2Si2PO12.

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