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 Atomistic Simulations of the Defect Chemistry and Self-Diffusion of Li-ion in LiAlO2

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2895 ◽  
Author(s):  
N. Kuganathan ◽  
J. Dark ◽  
E.N. Sgourou ◽  
Y. Panayiotatos ◽  
A. Chroneos
Keyword(s):  
Atomistic Simulation ◽  
Three Dimensional ◽  
Atomistic Simulations ◽  
Intrinsic Defect ◽  
Lithium Content ◽  
Frenkel Defect ◽  
Self Diffusion ◽  
Simulation Techniques ◽  
Lithium Diffusion ◽  
Li Ion

Lithium aluminate, LiAlO2, is a material that is presently being considered as a tritium breeder material in fusion reactors and coating material in Li-conducting electrodes. Here, we employ atomistic simulation techniques to show that the lowest energy intrinsic defect process is the cation anti-site defect (1.10 eV per defect). This was followed closely by the lithium Frenkel defect (1.44 eV per defect), which ensures a high lithium content in the material and inclination for lithium diffusion from formation of vacancies. Li self-diffusion is three dimensional and exhibits a curved pathway with a migration barrier of 0.53 eV. We considered a variety of dopants with charges +1 (Na, K and Rb), +2 (Mg, Ca, Sr and Ba), +3 (Ga, Fe, Co, Ni, Mn, Sc, Y and La) and +4 (Si, Ge, Ti, Zr and Ce) on the Al site. Dopants Mg2+ and Ge4+ can facilitate the formation of Li interstitials and Li vacancies, respectively. Trivalent dopants Fe3+, Ni3+ and Mn3+ prefer to occupy the Al site with exoergic solution energies meaning that they are candidate dopants for the synthesis of Li (Al, M) O2 (M = Fe, Ni and Mn) compounds.

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 A Computational Study of Defects, Li-Ion Migration and Dopants in Li2ZnSiO4 Polymorphs

Crystals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 563 ◽  
Author(s):  
Dilki Perera ◽  
Sashikesh Ganeshalingam ◽  
Navaratnarajah Kuganathan ◽  
Alexander Chroneos
Keyword(s):  
Long Range ◽  
Atomistic Simulation ◽  
Computational Study ◽  
Orthorhombic Phase ◽  
Activation Energies ◽  
Intrinsic Defect ◽  
Li Ion Batteries ◽  
Ion Migration ◽  
Simulation Techniques ◽  
Li Ion

Lithium zinc silicate, Li2ZnSiO4, is a promising ceramic solid electrolyte material for Li-ion batteries. In this study, atomistic simulation techniques were employed to examine intrinsic defect processes; long range Li-ion migration paths, together with activation energies; and candidate substitutional dopants at the Zn and the Si sites in both monoclinic and orthorhombic Li2ZnSiO4 phases. The Li-Zn anti-site defect is the most energetically favourable defect in both phases, suggesting that a small amount of cation mixing would be observed. The Li Frenkel is the second lowest energy process. Long range Li-ion migration is observed in the ac plane in the monoclinic phase and the bc plane in the orthorhombic phase with activation energies of 0.88 eV and 0.90 eV, respectively, suggesting that Li-ion diffusivities in both phases are moderate. Furthermore, we show that Fe3+ is a promising dopant to increase Li vacancies required for vacancy-mediated Li-ion migration, and that Al3+ is the best dopant to introduce additional Li in the lattice required for increasing the capacity of this material. The favourable isovalent dopants are Fe2+ at the Zn site and Ge4+ at the Si 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.

Role of divalent cation (Ba) substitution in the Li+ ion conductor LiTi2(PO4)3: a molecular dynamics study

2020 ◽  
Vol 22 (26) ◽  
pp. 14471-14479
Author(s):  
Kartik Sau ◽  
Tamio Ikeshoji ◽  
Supriya Roy
Keyword(s):  
Molecular Dynamics ◽  
Divalent Cation ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Ion Diffusion ◽  
Ion Conductor ◽  
Li Ion ◽  
Ba Substitution

Influence of Ba2+ ordering on cationic diffusion: (a) three-dimensional low Li+ ion diffusion using randomly substituted Ba2+, and (b) two-dimensional layered type high Li+ ion diffusion using specifically ordered substitution of Ba2+.

scholarly journals Defect, Diffusion and Dopant Properties of NaNiO2: Atomistic Simulation Study

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3094 ◽  
Author(s):  
Ruwani Kaushalya ◽  
Poobalasuntharam Iyngaran ◽  
Navaratnarajah Kuganathan ◽  
Alexander Chroneos
Keyword(s):  
Atomistic Simulation ◽  
High Capacity ◽  
Sodium Ion ◽  
Intrinsic Defect ◽  
Sodium Ion Batteries ◽  
Ion Diffusion ◽  
Defect Diffusion ◽  
Simulation Techniques ◽  
Defect Process ◽  
Isovalent Dopant

Sodium nickelate, NaNiO2, is a candidate cathode material for sodium ion batteries due to its high volumetric and gravimetric energy density. The use of atomistic simulation techniques allows the examination of the defect energetics, Na-ion diffusion and dopant properties within the crystal. Here, we show that the lowest energy intrinsic defect process is the Na-Ni anti-site. The Na Frenkel, which introduces Na vacancies in the lattice, is found to be the second most favourable defect process and this process is higher in energy only by 0.16 eV than the anti-site defect. Favourable Na-ion diffusion barrier of 0.67 eV in the ab plane indicates that the Na-ion diffusion in this material is relatively fast. Favourable divalent dopant on the Ni site is Co2+ that increases additional Na, leading to high capacity. The formation of Na vacancies can be facilitated by doping Ti4+ on the Ni site. The promising isovalent dopant on the Ni site is Ga3+.

scholarly journals Defects, Diffusion, and Dopants in Li2Ti6O13: Atomistic Simulation Study

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2851 ◽  
Author(s):  
Navaratnarajah Kuganathan ◽  
Sashikesh Ganeshalingam ◽  
Alexander Chroneos
Keyword(s):  
Electronic Structures ◽  
Atomistic Simulation ◽  
Density Functional ◽  
High Capacity ◽  
Ion Diffusion ◽  
Functional Theory ◽  
Energy Process ◽  
Defect Energy ◽  
Li Ion ◽  
Isovalent Dopant

In this study, force field-based simulations are employed to examine the defects in Li-ion diffusion pathways together with activation energies and a solution of dopants in Li2Ti6O13. The lowest defect energy process is found to be the Li Frenkel (0.66 eV/defect), inferring that this defect process is most likely to occur. This study further identifies that cation exchange (Li–Ti) disorder is the second lowest defect energy process. Long-range diffusion of Li-ion is observed in the bc-plane with activation energy of 0.25 eV, inferring that Li ions move fast in this material. The most promising trivalent dopant at the Ti site is Co3+, which would create more Li interstitials in the lattice required for high capacity. The favorable isovalent dopant is the Ge4+ at the Ti site, which may alter the mechanical property of this material. The electronic structures of the favorable dopants are analyzed using density functional theory (DFT) calculations.

scholarly journals Mg6MnO8 as a Magnesium-Ion Battery Material: Defects, Dopants and Mg-Ion Transport

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3213 ◽  
Author(s):  
Navaratnarajah Kuganathan ◽  
Evangelos I. Gkanas ◽  
Alexander Chroneos
Keyword(s):  
Ion Transport ◽  
High Performance ◽  
Electrode Materials ◽  
Three Dimensional ◽  
Intrinsic Defect ◽  
Magnesium Ion ◽  
Ion Migration ◽  
Solution Enthalpy ◽  
Magnesium Ion Batteries ◽  
Battery Material

Rechargeable magnesium ion batteries have recently received considerable attention as an alternative to Li- or Na-ion batteries. Understanding defects and ion transport is a key step in designing high performance electrode materials for Mg-ion batteries. Here we present a classical potential-based atomistic simulation study of defects, dopants and Mg-ion transport in Mg6MnO8. The formation of the Mg–Mn anti-site defect cluster is calculated to be the lowest energy process (1.73 eV/defect). The Mg Frenkel is calculated to be the second most favourable intrinsic defect and its formation energy is 2.84 eV/defect. A three-dimensional long-range Mg-ion migration path with overall activation energy of 0.82 eV is observed, suggesting that the diffusion of Mg-ions in this material is moderate. Substitutional doping of Ga on the Mn site can increase the capacity of this material in the form of Mg interstitials. The most energetically favourable isovalent dopant for Mg is found to be Fe. Interestingly, Si and Ge exhibit exoergic solution enthalpy for doping on the Mn site, requiring experimental verification.

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.

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