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Discovering a First-Order Phase Transition in the Li-CeO 2 System.

Authors :: Li K
Zhou X
Nie A
Sun S
He YB
Ren W
Li B
Kang F
Kim JK
Zhang TY
Source :: Nano letters [Nano Lett] 2017 Feb 08; Vol. 17 (2), pp. 1282-1288. Date of Electronic Publication: 2017 Jan 05.
Publication Year :: 2017
Abstract: An in-depth understanding of (de)lithiation induced phase transition in electrode materials is crucial to grasp their structure-property relationships and provide guidance to the design of more desirable electrodes. By operando synchrotron XRD (SXRD) measurement and Density Functional Theory (DFT) based calculations, we discover a reversible first-order phase transition for the first time during (de)lithiation of CeO <subscript>2</subscript> nanoparticles. The Li <subscript>x</subscript> CeO <subscript>2</subscript> compound phase is identified to possess the same fluorite crystal structure with FM3M space group as that of the pristine CeO <subscript>2</subscript> nanoparticles. The SXRD determined lattice constant of the Li <subscript>x</subscript> CeO <subscript>2</subscript> compound phase is 0.551 nm, larger than that of 0.541 nm of the pristine CeO <subscript>2</subscript> phase. The DFT calculations further reveal that the Li induced redistribution of electrons causes the increase in the Ce-O covalent bonding, the shuffling of Ce and O atoms, and the jump expansion of lattice constant, thereby resulting in the first-order phase transition. Discovering the new phase transition throws light upon the reaction between lithium and CeO <subscript>2</subscript> , and provides opportunities to the further investigation of properties and potential applications of Li <subscript>x</subscript> CeO <subscript>2</subscript> .