Diffusion of Li Atoms in LiMn2O4 with a Disordered Spinel Structure
|
Accession number;06A0198119
|
| Title;Diffusion of Li Atoms in LiMn2O4 with a Disordered Spinel Structure |
| Author;
ISHIZAWA NOBUO
(Nagoya Inst. of Technol.)
TATEISHI KENJI
(Nagoya Inst. of Technol.)
|
Journal Title;Journal of the Crystallographic Society of Japan
|
Journal Code:G0232A
|
ISSN:0369-4585
|
|
VOL.48;NO.1;PAGE.17-24(2006)
|
| Figure&Table&Reference;FIG.12, REF.9 |
| Pub. Country;Japan |
| Language;Japanese |
| Abstract;Crystals of LiMn2O4 undergo a first order structural phase transition near the room temperature. The high temperature (HT) form adopts a normal spinel-type structure (cubic, Fd3m) with the octahedral sites populated statistically with heterovalent Mn'III' and Mn'IV' in the equal ratio. The low temperature (LT) form adopts a 3*3*1 superstructure (orthorhombic, Fddd) with respect to the HT form, containing Mn1'III', Mn3'III', Mn4'IV', Mn5'IV' and intervalent Mn2 atoms. The synchrotron X-ray single-crystal electron-density analysis revealed a bond-length fluctuation along the pseudo-tetragonal Jahn-Teller distortion parallel to the a axis in the heterocubane Mn24O94 cluster which presumably shares three electrons among four e-parentage orbitals of Mn2 and behaves as a core of Zener polaron. The heterocubane Mn24O94 clusters are isolated with each other and embedded in an ordered way in the charge-ordered matrix containing Mn1'III', Mn3'III', Mn4'IV' and Mn5'IV'. The transition between the LT and HT forms of LiMn2O4 can thus be regarded as an order-disorder transition of the Zener polarons. The molecular dynamics (MD) studies revealed that a periodical random switching of Mn valences, reflecting the e-parentage electron hopping model, greatly facilitates the Li-ion self-diffusion. Two distinct but coexistent processes have been proposed for the diffusion of Li atoms in the HT form of LiMn2O4. (author abst.) |
|
|
|
Related Articles;
|
|
