DFT study of anisotropic elastic property of LiCoO2 during lithium - PowerPoint PPT Presentation

MSE 69700 Project Report, 12/06/2018 DFT study of anisotropic elastic property of LiCoO2 during lithium intercalation and deintercalation process Lingbin Meng Department of Mechanical and Energy Engineering Indiana University - Purdue University Indianapolis (IUPUI)

Introduction • Lithium cobalt oxide (LiCoO 2 ) is a popular cathode material of lithium-ion batteries due to its excellent electrochemical properties [1]. • LiCoO 2 consists of layers of lithium that lie between slabs of octahedron formed by cobalt and oxygen atoms. • During charging-discharging, LiCoO 2 Unit cell of LiCoO 2 , with small black balls being Li, small white balls being O becomes Li x CoO 2 while x ranges from 0 and big grey balls being Co [2]. (discharging) to 1 (charging). [1] B. Huang, Y. I. Jang, Y. M. Chiang, and D. R. Sadoway, “Electrochemical evaluation of LiCoO2 synthesized by decomposition and intercalation of hydroxides for lithium-ion battery applications,” J. Appl. Electrochem. 28, 1365–1369 (1998). [2] L. Wu, J. Zhang, “Ab initio study of anisotropic mechanical properties of LiCoO2 during lithium intercalation and deintercalation 2 process,” J. Appl. Phys. 118, 225101 (2015).

Motivations • Performance of LiCoO 2 are sensitive to number of charge-discharge cycles and working environment. • Large volume expansion, phase transition, and associated Li diffusion-induced stresses within electrode materials can lead to their fracture and failure, which result in battery capacity loss and power fade [2]. • From experiment, it is reported that the mechanical properties of LiCoO2 will degrade after dozens of charge-discharge cycles [3, 4]. • To insure the performance of LiCoO 2 based lithium-ion batteries, it is imperative to understand the mechanical properties of LiCoO 2 during lithium intercalation and deintercalation process. [2] L. Wu, J. Zhang, “Ab initio study of anisotropic mechanical properties of LiCoO2 during lithium intercalation and deintercalation process,” J. Appl. Phys. 118, 225101 (2015). [3] W.-S. Yoon, K.-B. Kim, M.-G. Kim, M.-K. Lee, H.-J. Shin, J.-M. Lee et al., “Oxygen contribution on Li-ion intercalation-deintercalation in LiCoO2 investigated by O K-edge and Co L-edge x-ray absorption spectroscopy,” J. Phys. Chem. B 106, 2526–2532 (2002). 3 [4] H. Wang, Y. I. Jang, B. Huang, D. R. Sadoway, and Y. M. Chiang, “TEM study of electrochemical cycling-induced damage and disorder in LiCoO2 cathodes for rechargeable lithium batteries,” J. Electrochem. Soc. 146, 473–480 (1999).

Objective • Test the hypothesis that the anisotropic elastic behavior of Li x CoO 2 will be alleviated with higher lithium concentration • Obtain initial unit cell structures of CoO 2 and LiCoO 2 from literature • Fully relax the unit cells using VASP • Compute their elastic constants, �� and �� using nanoMATERIALS SeqQuest DFT • Compare the ratio of �� and �� between CoO 2 and LiCoO 2 • Test the hypothesis that LDA tends to predict harder bond than GGA • Use both LDA and GGA, and compare final results 4

Initial structures of LiCoO 2 from literature Cell Vectors [2]: 2.4595121500000000 -1.4200000000000000 0.0000000000000000 0.0000000000000000 2.8400000000000000 0.0000000000000000 0.0000000000000000 0.0000000000000000 14.1600000000000000 Atomic Structure (Fractional) [2]: Li 0.0000000000000000 0.0000000000000000 -0.0000000000000000 Li 0.6666666666666643 0.3333333333333357 0.3333333333333357 Li 0.3333333333333357 0.6666666666666643 0.6666666666666643 O 0.0000000000000000 0.0000000000000000 0.2390065962445188 O 0.6666666666666643 0.3333333333333357 0.5723399295778544 O 0.3333333333333357 0.6666666666666643 0.9056732629111830 O -0.0000000000000000 -0.0000000000000000 0.7609934037554813 O 0.6666666666666643 0.3333333333333357 0.0943267370888169 O 0.3333333333333357 0.6666666666666643 0.4276600704221455 Co 0.0000000000000000 0.0000000000000000 0.5000000000000000 Co 0.6666666666666643 0.3333333333333357 0.8333333333333357 Co 0.3333333333333357 0.6666666666666643 0.1666666666666643 [2] L. Wu, J. Zhang, “Ab initio study of anisotropic mechanical properties of LiCoO2 during lithium intercalation and deintercalation process,” J. Appl. Phys. 118, 225101 (2015). 5

Initial structures of CoO 2 from literature Cell Vectors [2]: 2.883956181 0.000000000 0.000000000 -1.416978091 2.484278046 0.000000000 0.000000000 0.000000000 4.596576611 Atomic Structure (Fractional) [2]: O 0.3333333333333357 0.6666666666666643 0.2037769783220773 O 0.6666666666666643 0.3333333333333357 0.7962230216779227 Co -0.0000000000000000 0.0000000000000000 0.0000000000000000 [2] L. Wu, J. Zhang, “Ab initio study of anisotropic mechanical properties of LiCoO2 during lithium intercalation and deintercalation process,” J. Appl. Phys. 118, 225101 (2015). 6

Relaxation • Using VASP to fully relax the structure • VASP predicts more accurate lattice parameters, which can be seen later. This helps us start with reliable unit cell structures • For CoO2, number of K-points in all directions is 12. • For LiCoO2, number of K-points in x, y, z directions is 6, 6, 2, respectively. • The INCAR file is shown below • ISIF = 3 means both cell shape and cell volume are allowed to change to minimize the total energy • ENCUT is the KE cutoff in eV 7

Relaxation (cont.) • Insert initial structure, GGA potentials, number of kpoints into POSCAR, POTCAR and KPOINTS files in correct format, and use the INCAR in the previous slide, the computation can be started in VASP • Read results in CONTCAR: 8

Lattice parameters of LiCoO 2 comparison • The result is similar to experimental result and other DFT results. V (Å 3 ) a & b (Å) c (Å) This work (GGA) 2.85 14.04 33.02 Experiment [5] 2.82 14.05 32.23 Wu et al. (GGA) [2] 2.84 14.16 32.96 Xiong et al. (GGA) [6] 2.84 14.17 32.99 Qi et al. (HSE06) [7] 2.80 14.07 31.84 [2] L. Wu, J. Zhang, “Ab initio study of anisotropic mechanical properties of LiCoO2 during lithium intercalation and deintercalation process,” J. Appl. Phys. 118, 225101 (2015). [5] T. Motohashi, Y. Katsumata, T. Ono, R. Kanno, M. Karppinen, and H. Yamauchi, “Synthesis and properties of CoO2, the x ¼ 0 end member of the LixCoO2 and NaxCoO2 systems,” Chem. Mater. 19, 5063–5066 (2007). [6] F. Xiong, H. J. Yan, Y. Chen, B. Xu, J. X. Le, and C. Y. Ouyang, “The atomic and electronic structure changes upon delithiation of LiCoO2: From first principles calculations,” Int. J. Electrochem. Sci. 7, 9390 (2012). 9 [7] Y. Qi, L. G. Hector, C. James, and K. J. Kim, “Lithium concentration dependent elastic properties of battery electrode materials from first principles calculations,” J. Electrochem. Soc. 161, F3010–F3018 (2014).

Input geometry • The rest of the project will based on nanoMATERIALS SeqQuest DFT [8] tool at https://nanohub.org/tools/nmst_dft. • The input geometries are shown below: [8] R. P. Kumar Vedula, G. Bechtol, Benjamin. P. Haley, A. Strachan (2016), "nanoMATERIALS SeqQuest 10 DFT," https://nanohub.org/resources/nmst_dft. (DOI: 10.4231/D3K931744).

Energy expression • The following image shows the setting for LiCoO 2 . For CoO2, change the number of K-points to 12-12-12. 11

k-points convergence test • The next step is to compute the elastic constants by applying some strain to the structure and computing for stress or energy. • To make sure that the current K-point set is reliable, it is necessary to test the total energy and stress of the system will converge at current K-point set (12, 12, 12 for CoO 2 and 6, 6, 2 for LiCoO 2 ). • The 6-6-2 k-point set for LiCoO 2 converges well, whereas the 12-12-12 K- point set still has small fluctuation. But more k-points will lead to out-of- memory issue in the tool. Stress (GPa) Stress (GPa) CoO 2 Energy (Ryd) LiCoO 2 Energy (Ryd) xx yy zz zy zx yx xx yy zz zy zx yx kpoints 3-3-1 -7.4195 -8.5868 -6.4538 -0.2781 0.1605 1.0230 -848.8639 kpoints 3-3-3 -5.3889 -4.0528 -4.5506 -0.2212 -0.1100 2.9322 -281.7845 kpoints 5-5-2 -7.4735 -8.3797 -6.4120 0.1356 -0.0783 0.7824 -848.8667 kpoints 5-5-5 -3.9842 -5.1338 -6.0261 0.0378 -0.4830 0.5706 -281.7831 kpoints 6-6-2 -7.4611 -8.3973 -6.3796 0.1324 -0.0765 0.8075 -848.8665 kpoints 8-8-8 -4.0614 -5.0113 -5.5457 -0.3226 0.0950 0.8454 -281.7842 kpoints 8-8-3 -7.4554 -8.3980 -6.3850 0.1364 -0.0787 0.8137 -848.8665 kpoints 10-10-10 -4.0903 -5.0065 -5.5160 -0.3808 0.1945 0.9046 -281.7844 kpoints 12-12-12 -4.0788 -5.0507 -5.5647 -0.3195 0.0769 0.8485 -281.7843 12