Phase Separation and d Electronic Orbitals on Cyclic Degradation in Li-Mn-O Compounds: First-Principles Multiscale Modeling and Experimental Observations.
A combined study involving experiments and multiscale computational approaches is conducted to propose a theoretical solution for the suppression of the Jahn-Teller distortion which causes severe cyclic degradation. As-synthesized pristine and Al-doped Mn spinel compounds are the focus to understand the mechanism of the cyclic degradation in terms of the Jahn-Teller distortion, and the electrochemical performance of the Al-doped sample shows enhanced cyclic performance compared with that of the pristine one. Considering the electronic structures of the two systems using first-principles calculations, the pristine spinel suffers entirely from the Jahn-Teller distortion by Mn(3+), indicating an anisotropic electronic structure, but the Al-doped spinel exhibits an isotropic electronic structure, which means the suppressed Jahn-Teller distortion. A multiscale phase field model in nanodomain shows that the phase separation of the pristine spinel occurs to inactive Li0Mn2O4 (i.e., fully delithiated) gradually during cycles. In contrast, the Al-doped spinel does not show phase separation to an inactive phase. This explains why the Al-doped spinel maintains the capacity of the first charge during the subsequent cycles. On the basis of the mechanistic understanding of the origins and mechanism of the suppression of the Jahn-Teller distortion, fundamental insight for making tremendous cuts in the cyclic degradation could be provided for the Li-Mn-O compounds of Li-ion batteries.
Department of Mechanical and Aerospace Engineering, Seoul National University , Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea.
Duho
D
Kim
Department of Mechanical and Aerospace Engineering, Seoul National University , Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea.
Jin-Myoung
JM
Lim
Department of Advanced Materials Engineering for Information and Electronics, Kyung Hee University , 1732 Deogyeong-daero, Giheung-gu, Yongin 17104, Republic of Korea.
Min-Sik
MS
Park
Department of Materials Science and Engineering and Department of Physics, University of Texas at Dallas , Richardson, Texas 75080, United States.
Kyeongjae
K
Cho
Department of Mechanical and Aerospace Engineering, Seoul National University , Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea.
Maenghyo
M
Cho
Jahn−Teller distortion; Li−Mn−O compounds; first-principles calculation; multiscale modeling; phase field model