Origins and mechanism of phase transformation in bulk Li 2 MnO 3 : First-principles calculation and experimental study

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1 Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A. This journal is The Royal Society of Chemistry 2015 Electronic Supplementary Information Origins and mechanism of phase transformation in bulk Li 2 MnO 3 : First-principles calculation and experimental study Jin-Myoung Lim, a Duho Kim, a Young-Geun Lim, b Min-Sik Park, b, * Young-Jun Kim, b Maenghyo Cho, a, * a, c,* and Kyeongjae Cho * Description of equations in the main article. 1) Enthalpy of formation E f (x) with decreasing Li content, 2 - x, in Li 2-x MnO 3 x x E f x E Li MnO 1 E Li MnO Li MnO 2 2 2x SPI like (1) All the calculations of this work were conducted along with the decrease in Li content to describe a delithiated state of Li 2 MnO 3 during the charge process. The enthalpy of formation E f was calculated based on the relative structural stabilities of structure (x = 0) and a SPI-like structure (x = 2). E Li MnO 2 x 3 E Li MnO 2 3 E Li MnO 0 3 : Calculated energy of Li 2-x MnO 3 of target structure from DFT SPI like : Calculated energy of Li 2 MnO 3 of structure from DFT : Calculated energy of Li 0 MnO 3 of SPI-like structure from DFT 2) Enthalpy of oxygen defect E O (x) with decreasing Li content, 2 - x, in Li 2-x MnO 3

2 2 O 2x x (2) E x E Li MnO E Li MnO E O 2, where E(Li 2-x MnO 3 ) are the energy obtained by the structure of ground state configured in Fig. 1b, and E(Li 2-x MnO 2.75 ) are calculated energy acquired by total configuration of oxygen-defected structures from ground state structure in Fig. 1b. E Li E Li E O MnO 2 x 2.75 MnO 2 x 3 2 : Calculated energy of Li 2-x MnO 2.75 of target structure from DFT : Calculated energy of Li 2-x MnO 3 of target structure from DFT : Calculated energy of O 2 gas for reference energy of oxygen from DFT i 3) and 4) The residual Li content R in Li Li 2 MnO 3 in the i-th cycle under the CC charging mode was calculated using eqn. 3 and 4 by obtaining the cumulative irreversible capacity of Li 2 MnO 3 during each cycle. i 1 i i 1 i 1 0 res res ch dis res th C C C C C C (3) R i Li i Cres 100 % (4) C th i C : Residual capacity at i-th cycle calculated by eqn. 3 res C : Charge capacity at (i+1)-th cycle observed by charge-discharge curve i 1 ch C : Discharge capacity at (i+1)-th cycle observed by charge-discharge curve i 1 dis C : Theoretical capacity th

3 Table S1. Comparison of lattice parameters of Li 2 MnO 3 obtained from experiment and density functional theory calculation. a b c β [Å] [Å] [Å] [ ] Experiment DFT (DFT) Koyama et al. a) (Exp.) Lei et al. b) a) Y. Koyama, I. Tanaka, M. Nagao and R. Kanno, J Power Sources, 2009, 189, b) C. H. Lei, J. G. Wen, M. Sardela, J. Bareno, I. Petrov, S.-H. Kang, and D. P. Abraham, J Mater Sci, 2009, 44,

4 (a) Voltage / V (Cal.) LA-like (Cal.) SPI-like (Cal.) 1st charge (Exp.) 2nd charge (Exp.) Capacity / mah g -1 (b) Charge variation bet. Li 2 MnO 3 to Li 1.75 MnO Mn O LA-like SPI-like Figure S1. (a) Calculated voltages of (black-solid line), LA-like (red-solid line), and SPI-like (bluesolid line) structures, as well as experimental voltages of 1st (green-solid line) and 2nd (green-dashed line) charge processes with constant-current charging method at C/20. (b) Charge variation of Mn (black-filled circles) and O (red-unfilled inverse triangles) ions obtained by bader charge analysis between Li 2 MnO 3 to Li 1.75 MnO 3 for three different structures.

5 Enthalpy of oxygen defect / ev LA-like SPI-like Inverse Li content x in Li 2-x MnO 2.75 Figure S2. Enthalpies of oxygen defect for three different structures with respect to inverse Li content x in Li 2- xmno 3 (black-filled circles are structure, red-unfilled inverse triangles are LA-like structure, and blue-unfilled triangles are SPI-like structure).

6 Figure S3. Partial density of statess (PDOS) of Mn ion in 4g site and surrounding O ions in the Li 2 MnO 3 structure with respect to inverse Li content x in Li 2-x MnO 3 ; (a) 0, ( b) 0.25, (c) 0..5, (d) 0.75, (e) 1.0, and (f) 1.25.

7 Figure S4. Partial density of states ( PDOS) of thee migrated Mn ion and surrounding O ions of LA-like (subscript L) and SPI-like (subscript S) structures with respect to inverse Li content x in Li 2-x MnOO 3 ; (a) 0.25, (b) 0.5, (c) 0.75, (d) 1.0, and (e) 1.25.

8 (a) Average net charge of O ions / e LA-like SPI-like (b) Average net charge of Mn ions / e LA-like SPI-like Inverse Li contents x in Li 2-x MnO 3 Inverse Li contents x in Li 2-x MnO 3 Figure S5. (a) Average net charge of O ions and (b) net charge of a migrated Mn ion calculated by bader analysis of (black-filled circle), LA-like (red-unfilled inverse triangle), and SPI-like (blue-unfilled triangle) structures with various inverse Li content x in Li 2-x MnO 3.

9 Figure S6. (a) Powder X-ray diffraction (XRD) pattern of synthesized Li 2 MnO 3 powder with a reference (JCPDS ). Field-emission scanning electron microscope (FESEM) images off the Li 2 MnO 3 at low magnification (b) and high magnification (c).

10 Figure S7. (a) Atomic model of Lii 2 MnO 3 structure and additional Mn migration paths. Path-iv represents the migration of Mn in 4g site to 2c site, and Path-v Path-iv and (c) Path-v with w respect too normalized migration describes the migration of Mn in 4h site. Detail description of migration barriers off each path; (b) path at different inverse Li content x in Li 2-x MnO 3 3.