TY - JOUR

T1 - Lithium Diffusion Mechanisms in β-LiMO2 (M = Al, Ga)

T2 - A Combined Experimental and Theoretical Study

AU - Islam, Mazharul M.

AU - Uhlendorf, Johanna

AU - Witt, Elena

AU - Schmidt, Harald

AU - Heitjans, Paul

AU - Bredow, Thomas

N1 - Funding Information: We thank Dr. R. Ücker and Dr. C. Vinod Chandran for fruitful discussion. Financial support from the Deutsche Forschungs-gemeinschaft (DFG) in the framework of the Research Unit 1277 “molife” (Schm 1569/18-2, He 1574/13-2, BR1768/5-2) is gratefully acknowledged. P.H. is grateful for a Niedersachsen Professorship. Publisher Copyright: © 2017 American Chemical Society. Copyright: Copyright 2018 Elsevier B.V., All rights reserved.

PY - 2017/12/21

Y1 - 2017/12/21

N2 - Lithium diffusion mechanisms in β-LiMO2 (M = Al, Ga) were studied in a combined experimental and theoretical approach based on Li tracer diffusion experiments and climbing-image nudged-elastic-band (cNEB) calculations at density functional theory (DFT) level, respectively. Secondary ion mass spectrometry (SIMS) investigations were carried out for β-LiAlO2 and β-LiGaO2 polycrystalline films in the temperature range between 473 and 773 K. A thin layer of ion-beam sputtered isotope-enriched 6LiAlO2 or 6LiGaO2 was used as a tracer source. The diffusivities of β-LiGaO2 polycrystalline films are in good agreement with those measured on single crystals of the same type. The diffusivities of β-LiAlO2 are higher than in β-LiGaO2 by almost 2 orders of magnitude. This can be traced back to a lower activation energy for diffusion in β-LiAlO2. Our computational study shows that the formation energy of a Li vacancy (VLi) is much higher than that of the Li Frenkel pair (VLi + Lii) showing that Li vacancies are not abundant in both systems. Irrespective of the defect types, the defect formation energy values are smaller in β-LiAlO2 than in β-LiGaO2, indicating that Li ion migration could be facile for the former case. In both systems, the most likely Li migration pathways involve Li diffusion from a regular LiO4 tetrahedral location to the first and/or second nearest tetrahedral sites by octahedral interstitial sites. On the basis of calculated activation energies it is concluded that Li diffusion is faster in LiAlO2 than in LiGaO2. Our calculated data are in good accord with the experiments.

AB - Lithium diffusion mechanisms in β-LiMO2 (M = Al, Ga) were studied in a combined experimental and theoretical approach based on Li tracer diffusion experiments and climbing-image nudged-elastic-band (cNEB) calculations at density functional theory (DFT) level, respectively. Secondary ion mass spectrometry (SIMS) investigations were carried out for β-LiAlO2 and β-LiGaO2 polycrystalline films in the temperature range between 473 and 773 K. A thin layer of ion-beam sputtered isotope-enriched 6LiAlO2 or 6LiGaO2 was used as a tracer source. The diffusivities of β-LiGaO2 polycrystalline films are in good agreement with those measured on single crystals of the same type. The diffusivities of β-LiAlO2 are higher than in β-LiGaO2 by almost 2 orders of magnitude. This can be traced back to a lower activation energy for diffusion in β-LiAlO2. Our computational study shows that the formation energy of a Li vacancy (VLi) is much higher than that of the Li Frenkel pair (VLi + Lii) showing that Li vacancies are not abundant in both systems. Irrespective of the defect types, the defect formation energy values are smaller in β-LiAlO2 than in β-LiGaO2, indicating that Li ion migration could be facile for the former case. In both systems, the most likely Li migration pathways involve Li diffusion from a regular LiO4 tetrahedral location to the first and/or second nearest tetrahedral sites by octahedral interstitial sites. On the basis of calculated activation energies it is concluded that Li diffusion is faster in LiAlO2 than in LiGaO2. Our calculated data are in good accord with the experiments.

UR - http://www.scopus.com/inward/record.url?scp=85037561968&partnerID=8YFLogxK

U2 - 10.1021/acs.jpcc.7b06460

DO - 10.1021/acs.jpcc.7b06460

M3 - Article

AN - SCOPUS:85037561968

VL - 121

SP - 27788

EP - 27796

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7447

IS - 50

ER -