Supporting Information. First-Principles Study: Tuning the Redox Behavior of Li-Rich

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1 Supporting Information First-Principles Study: Tuning the Redox Behavior of Li-Rich Layered Oxides by Chlorine Doping Huijun Yan 1, Biao Li 1, Zhen Yu 2, Wangsheng Chu 2, Dingguo Xia 1* 1 Beijing Key Laboratory of Theory and Technology for Advanced Batteries Materials, College of Engineering, Peking University, Beijing , P. R. China; 2 National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei , P. R. China. * dgxia@pku.edu.cn A supercell LiNiO 2 (Li 27 Ni 27 O 54 ) with R 3 m space group is constructed. For the determination of structure of Li-rich Li 1.11 Ni 0.89 O 2 (Li 30 Ni 24 O 54 ), we replaced three Ni atoms with Li atoms. The distributed positions of Li atoms in TM-layer are in analogy to that in Li 2 MnO 3. The lithium atoms in transition layers are uniformly distributed in the systems. Several Li 1.11 Ni 0.89 O 2 (Li 27 [Li 3 Ni 24 ]O 54 ) configurations were relaxed, and the lowest energy configuration was selected. Similarly, the Li 1.11 Ni 0.89 O 1.89 A 0.11 (Li 27 [Li 3 Ni 24 ]O 51 A 3 ) (A=F, Cl, Br) were constructed by replacing some oxygen atoms with F/Cl/Br atoms. Firstly, we investigated the structure of Li 27 [Li 3 Ni 24 ]O 53 Cl 1, and S1

found that chlorine atom is inclined to occupy the oxygen site linked with lithium ion in TM-layer. Due to the small anion doping concentration, the dopant uniformly distribute in the system.

2 found that chlorine atom is inclined to occupy the oxygen site linked with lithium ion in TM-layer. Due to the small anion doping concentration, the dopant uniformly distribute in the system. By this analogy, several possible configurations were considered, and the lowest energy configuration Li 1.11 Ni 0.89 O 1.89 Cl 0.11 (Li 27 [Li 3 Ni 24 ]O 51 Cl 3 ) was selected. To the Li 1.11 Ni 0.89 O 2-y Cl y (y=0.22, 0.33, 0.44) and Li 1.11 Ni 0.89 O 1.89 A 0.11 (A=F, Br), the same construction approach was used. Figure S1. The optimized structures of Li 1.11 Ni 0.89 O 2-y Cl y (y=0.22, 0.33, 0.44). The layered structures still maintain well after chlorine introduction. S2

3 Figure S2. The relaxed structures of Li 1.11 Ni 0.89 O 1.89 F 0.11 (a) and Li 1.11 Ni 0.89 O 1.89 Br 0.11 (b). The layered structures still maintain well after F/Br doping. S3

4 Figure S3. The valence state of each Ni atom in Li 1.11 Ni 0.89 O 2 (Li 30 Ni 24 O 54 ) (a), Li 1.11 Ni 0.89 O 1.89 Cl 0.11 (Li 30 Ni 24 O 51 Cl 3 ) (b) and Li 1.11 Ni 0.89 O 1.78 Cl 0.22 (Li 30 Ni 24 O 48 Cl 6 ) (c). For the sake of simple and clear clarity, we only give the schematic diagram of atoms in TM-layer. Blue and purple atoms are nickel and hydrogen, respectively. The valence states of some nickel ions keep unchanged after chlorine introduction. S4

5 Table S1. The average charge of each element in Li 1.11 Ni 0.89 O 2-y Cl y and full delithiated Ni 0.89 O 2-y Cl y through bader charge analysis. y The average bader charge in Ni The average bader charge in O The average bader charge in Cl Li 0.8 Ni 0.89 O 2-y Ni 0.89O 2-yCl y Li 1.11Ni 0.89O 2-y Cl 3 Cl y Ni 0.89 O 2-y Cl y Li 1.11 Ni 0.89 O 2-y Cl y Ni 0.89 O 2-y Cl y It is peculiar when we come to check the bader charge of Ni ions, which shows little change upon delithiation, and is inconsistent with the calculated magnetic moment evolution (Figure 7 in manuscript) and the charge difference maps (Figure R1), as well as the DOS evolution (Figure R2). We speculate that this inconsistency is strongly correlated with the examined system which generates electron distribution with high complexity. It should be noted that previous bader analysis of Ir in Li 2 IrO 3 by Tarascon et al. [Science 350, 6267 (2015)] also demonstrates clear deviation compared with experimental evidence. S5

6 Figure S4. The charge density differences between Li 1.11 Ni 0.89 O 2-y Cl y and Ni 0.89 O 2-y Cl y (y=0.11, 0.22, 0.33 and 0.44) for samples were shown in a-d, respectively. The isosurface level was set to be In Figure S4c and S4d, some chlorine ions marked by red circle provide small electrons, while some other not. S6

7 Figure S5. The optimized structure of Li 1.11-z Ni 0.89 O 1.89 Br 0.11 (z=0.77). Br-O bonds are formed in the charging process of Li 1.11-z Ni 0.89 O 1.89 Br 0.11, indicating that the structure is not stable. The lengths of Br-O bonds measured in angstrom were also labeled. S7

8 Figure S6. The O-2p and Ni-3d orbital density of states in Li 1.11 Ni 0.89 O 2-y Cl y (y=0, 0.11, 0.22). The Fermi energy was set to be 0eV. The bule dotted line and the green dotted line were marked the main O-2p and Ni-3d orbital density of states, respectively. Due to the chlorine introduction, the O-2p orbital density of states are more closer to the Fermi level, meaning that anion oxygen would lose electrons more easily. In other words, the oxidation potential of anion oxygen in Li 1.11 Ni 0.89 O 2-y Cl y (y=0.11 and 0.22) would be lowered. For the cationic nickel, the oxidation potential in Li 1.11 Ni 0.89 O 2-y Cl y (y=0.11 and 0.22) is also lowered. S8

9 Figure S7. The total density of states in Li 1.11 Ni 0.89 O 1.78 Cl The Fermi energy is set to be 0eV. S9

Figure S8. The possible Li migration paths in Li 1.11 Ni 0.89 O 2 (a,b) and Li 1.11 Ni 0.89 O 1.89 Cl 0.11 (c,d); the Li ion diffusion barrier of the corresponding each path (e).

10 Figure S8. The possible Li migration paths in Li 1.11 Ni 0.89 O 2 (a,b) and Li 1.11 Ni 0.89 O 1.89 Cl 0.11 (c,d); the Li ion diffusion barrier of the corresponding each path (e). Note that Path 1-5 are the lithium migration paths in Li-layer. Path 6-7 represent the lithium hops between TM-layer and Li-layer. Chlorine doping has little effect on the lithium diffusion barrier in Li-layer, while has a big effect on the diffusions of Li ion from TM-layer to Li-layer. In undoped system, the Li + migration barriers for Path 6 and Path 7 are the same. However, the Li + diffusion barrier of Path 7 decreases to 0.30eV after chlorine doping, which is lower than that in undoped system. Though the diffusion barrier of Path 6 increases after doping, lithium ions are generally considered to migrate along paths with smaller diffusion barrier, that Path 7 should be S10

11 considered rather than Path 6 after the doping. Therefore, chlorine doping reduces the Li + migration barrier along c direction, which is favor of the improvement of rate performance. S11

12 Figure S9. The structures with anti-site defect in Li 1.11 Ni 0.89 O 2 (a) and Li 1.11 Ni 0.89 O 1.89 Cl 0.11 (b). Due to the similar ionic radius between Ni 2+ and Li +, one Ni 2+ may be exchanged site with the nearest neighbor Li +, and three possible structures with anti-site defect are formed. One end of the yellow bond is Ni 2+. The other side of yellow bond is three lithium ions with the nearest neighbor Ni 2+. In Li 1.11 Ni 0.89 O 2, the lowest energy structure with the anti-site defect is the case when the Ni 2+ was exchanged with number-2 Li +. In Li 1.11 Ni 0.89 O 1.89 Cl 0.11, the lowest energy structure with the anti-site defect is the case when the Ni 2+ was exchanged with number-3 Li +. We defined the Li + /Ni 2+ antisite defect formation energy as follows: E f = E( defect) E( perfect) E(perfect) and E(defect) were the energy of Li 1.11 Ni 0.89 O 2-y Cl y (y=0, 0.11) without and with the Li + /Ni 2+ anti-site defect, respectively. S12

13 Equations involved in the article: (1) The average delithiated voltage of Li 1.11 Ni 0.89 O 1.89 A 0.11 (Li 30 Ni 24 O 51 A 3 ) (A=F, Cl, Br) was calculated by the following equation: [1] E( Li Ni24O54) E( Ni24O54) V ave = 30e 30 30E( Li) E( Li30Ni24O51A3 ) E( Ni24O51A3 ) 30E( Li) V ave = (A=F, Cl, Br) 30e E ( Li Ni ) 54 / E Li Ni O ) and E Ni O 24 ) / E Ni O ) are the calculated 30 24O ( A3 ( 54 energy with and without Li concentration, respectively. E (Li) is the total energy of the lithium metal. S13 ( 24 51A3 (2) Formation energies E f of configurations with different Li content in Li 1.11 Ni 0.89 O 1.89 Cl 0.11 (Li 30 Ni 24 O 51 Cl 3 ) were described as follows: [2] z z E f ( z) = E( Li30 zni24o54) E( Ni24O54) (1 ) E( Li30Ni24O54) z z E f ( z) = E( Li30 zni24o51cl3) E( Ni24O51Cl3) (1 ) E( Li30Ni24O51Cl3) E ( Li Ni ) 54 and E Li Ni O ) are the calculated total energy of 30 24O ( Cl3 Li 30 Ni 24 O 54 and Li 30 Ni 24 O 51 Cl 3, respectively. E ( Ni O ) and ) E Ni O are the calculated energy of delithiated state ( 24 51Cl3 Ni 24 O 54 and Ni 24 O 51 Cl 3, respectively. E ( Li30 O54 z Ni24 ) and E( Li30 z Ni24O51Cl3) were the calculated energy of different Li content. z represented different amount of delithiated with fixed intervals (z=3, 6, 9,..30)

14 (3)The averaged redox potential with the different Li concentration in Li 1.11 Ni 0.89 O 1.89 Cl 0.11 (Li 30 Ni 24 O 51 Cl 3 ) can be estimated as: V V E ave ave E( Li ( z z z ) = 1 2 E( Li ( z z z ) = 1 ( Li30 z Ni 1 24O54) 2 30 z1 30 z1 Ni Ni O 54 ) E( Li ( z 30 z2 O Cl ) E( Li Ni z ) e ( z 1 30 z O Ni z ) e ) ( z 2 z ) E( Li) 1 O Cl ) ( z z ) E( Li) and E( Li z Ni 24O54 ) are the calculated energy with different delithiated concentration z 1 and z 2 in Li 30 Ni 24 O 54, respectively. E( Li z Ni24O51Cl3 ) and E( Li z Ni 24O51Cl3 ) are the calculated energy with different delithiated concentration z 1 and z 2 in Li 30 Ni 24 O 51 Cl 3, respectively. E (Li) is the total energy of the lithium metal. The formation energy and the redox voltage with different Li concentration in Li 1.11 Ni 0.89 O 1.78 Cl 0.22 (Li 30 Ni 24 O 48 Cl 6 ) were also described as the same as Li 1.11 Ni 0.89 O 1.89 Cl 0.11 (Li 30 Ni 24 O 51 Cl 3 ). References: [1] Aydinol M. K.; Kohan A. F.; Ceder G.; Cho K.; Joannopoulos J. Ab initio Study of Lithium Intercalation in Metal Oxides and Metal Dichalcogenides. Phys. Rev. B 1997, 56, [2] Xiao, R.; Li H.; Chen L. Density Functional Investigation on Li 2 MnO 3. Chem. Mater. 2012, 24, S14

First-principles studies of cation-doped spinel LiMn 2 O 4 for lithium ion batteries

First-principles studies of cation-doped spinel LiMn 2 O 4 for lithium ion batteries Siqi Shi, 1 Ding-sheng Wang, 2 Sheng Meng, 2 Liquan Chen, 1 and Xuejie Huang 1, * 1 Nanoscale Physics and Devices Laboratory,