Dynamics of coupled lithium/electron diffusion in TiO2 polymorphs

Journal Article · Thu Dec 10 04:00:00 EST 2009 · Journal of Physical Chemistry C, 113(49):20998–21007

DOI:https://doi.org/10.1021/jp9064517· OSTI ID:969609

Kerisit, Sebastien N; Rosso, Kevin M; Yang, Zhenguo; Liu, Jun

Molecular dynamics simulations were performed with a potential shell model to investigate the diffusion of lithium ions and electron polarons in rutile and anatase. Simulations of an isolated lithium ion in rutile predict fast diffusion in the c channels with an activation energy of 0.05 eV, which corresponds to a jump rate of 4×1011 s-1 and a diffusion coefficient of 9×10-5 cm2·s-1 at room temperature. In anatase, the activation energies for intra- and inter-octahedron lithium hopping are 0.02 and 0.39 eV, respectively, and the lithium diffusion coefficient is four to five orders of magnitude slower than in rutile. When in the presence of an electron polaron, lithium hopping is predicted to be affected up to four hops away. The effects are more pronounced in rutile; whereby the first energy minimum along the c direction is absent due to the strong lithium-electron electrostatic interactions along the open c channels. Combining the lithium hopping and electron transfer rates, a coupled diffusion mechanism emerges whereby the electron polarons diffuse rapidly back and forth around the lithium ions. This process can lead to the occurrence of an instantaneous driving force for lithium hopping. The lithium ion-electron polaron binding energies are found to be large, with a stronger binding in rutile than in anatase: 0.45 and 0.28 eV, respectively, suggesting that, at low lithium mole fractions, lithium ions and electron polarons will form strongly correlated pairs.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 969609
• Report Number(s): PNNL-SA-66930
• Journal Information: Journal of Physical Chemistry C, 113(49):20998–21007, Journal Name: Journal of Physical Chemistry C, 113(49):20998–21007 Journal Issue: 49 Vol. 113; ISSN 1932-7447
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
74 ATOMIC AND MOLECULAR PHYSICS
ACTIVATION ENERGY
DIFFUSION
ELECTRON TRANSFER
ELECTRONS
ELECTROSTATICS
LITHIUM
LITHIUM IONS
Li-ion batteries
POLARONS
RUTILE
SHELL MODELS
electron diffusion
lithium insertion
molecular dynamics
polymorphs
titania