Synthesis, Crystal Structure Analysis, and Electrochemical Properties

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Synthesis, Crystal Structure Analysis, and Electrochemical Properties of Rock-Salt Type MgxNiyCozO2 as a Cathode Material for Mg Rechargeable Batteries Yasushi Idemoto,*,† Tsukiko Takahashi,† Naoya Ishida,† Masanobu Nakayama,‡ and Naoto Kitamura† Inorg. Chem. Downloaded from pubs.acs.org by UNIV OF LOUISIANA AT LAFAYETTE on 04/17/19. For personal use only.

†

Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510, Japan Frontier Research Institute for Materials Science (FRIMS), Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555, Japan

‡

S Supporting Information *

ABSTRACT: Research has recently been focused on highperformance next-generation batteries to replace secondary batteries due to capacity limitations and safety concerns. The Mg secondary battery is one candidate to realize high energy density storage batteries for practical applications. Ni and Co typically exhibit desirable electrochemical characteristics; therefore, we have attempted to synthesize new rock-salt compositions, MgxNiyCozO2 (x + y + z ≤ 2.0), as cathode materials for Mg rechargeable batteries, and investigated their crystal structures and electrochemical characteristics. The materials were synthesized by the reverse coprecipitation method. Powder X-ray diffraction and transmission electron microscopy analyses showed the obtained samples were a single phase of the rock-salt structure with the space group Fm3̅m. The vacancies at the metal sites were estimated by Rietveld analysis to determine the new chemical composition of MgxNiyCoz□2‑x‑y‑zO2 (0.41 < x < 0.64, 0.82 < y < 1.23, 0.24 < z < 0.61). Charge−discharge tests indicated the discharge characteristics varied according to the Mg composition and the Ni/Co ratio. The Co and Mg compositions were considered to facilitate the insertion/deinsertion of Mg2+. The present new material has the potential to be a superior cathode material for Mg secondary batteries by first-principles calculations.

1. INTRODUCTION The introduction of photovoltaic power and wind power generation has recently been promoted to alleviate global warming. However, the amount of power generation fluctuates due to changes in wind speed and solar radiation. Therefore, to offset these fluctuating power supplies, a reliable power storage system is required. In the smart grid concept aimed at the effective use of such electric power, power storage systems are increasingly important for the collective management of electric power. In these systems, high energy density and long life are important, but also inexpensive batteries are required, especially for construction on a large scale. Thus, from the viewpoint of resource supply and economics, it is necessary to construct systems with careful selection of appropriate materials. Research on batteries, such as lithium ion and sodium ion, has been focused on improvements in energy density, safety, cycle performance, and durability; however, greater cost-effectiveness has become a more recent focus of study. Next-generation batteries based on polyvalent cations, such as magnesium ions as carriers, have also gained attention. Magnesium is a relatively safe metal, even when exposed to the air, and it has a low © XXXX American Chemical Society

standard electrode potential (−2.356 V vs SHE), which is 0.689 V higher than that for lithium metal (−3.045 V vs SHE).1,2 The theoretical capacity of magnesium metal is as high as about 2200 mAh g−1 or about 3832 mAh cm−3. Therefore, if a magnesium metal anode can be used, the realization of a magnesium rechargeable battery (MRB) with high energy density can be expected. However, there are many problems with the MRB, for example, there are few types of electrolytes capable of magnesium metal electrodeposition, the potential window of the electrolyte is narrow, and it is difficult to realize a cathode material with a high redox potential.3,4 In addition, magnesium ions have high charge density; therefore, it is difficult to diffuse in a solid or to dissolve and precipitate in an electrolytic solution.5 Research and development aimed at breakthroughs for MRBs has been active in recent years, and it is necessary to search for a new cathode material capable of repetitive insertion and deinsertion of Mg2+. Layered rock salt-type LiNi0.8Co0.2O2 has already been applied practically as a cathode material in Li-ion Received: December 29, 2018

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DOI: 10.1021/acs.inorgchem.8b03638 Inorg. Chem. XXXX, XXX, XXX−XXX

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structure was allowed, and the final energies of the optimized structural geometries were recalculated to correct for changes in the plane-wave basis during relaxation. An energy cutoff of 500 eV and a k-point mesh were selected such that the product of the number of k-points and the number of atoms in the unit cell was larger than 500. The arrangement of Mg, Ni and Co cations in the rock-salt structure is determined by selecting the most energetically stable structure among about 100 symmetrically distinct candidates. Mg and vacancy arrangements for the Mg-deintercalated phase were similarly determined. Candidate structures were generated using ATAT software.18,19

batteries, and the influence of the average/local structure on battery characteristics has been reported.6,7 Here, we examine the rock-salt type MgxNiyCozO2 (x + y + z ≤ 2.0), which is a novel composition regarded as Co-substituted MgNiO2 with some vacancies. The purpose of this study was to synthesize and evaluate the electrochemical properties of MgxNiyCozO2 as a MRB cathode, and conduct a crystal/electronic structure analysis.

2. EXPERIMENTAL SECTION 2.1. Synthesis. MgxNiyCozO2 (x + y + z ≤ 2.0) nominal compositions were synthesized by the reverse coprecipitation method, similar to that used for MgNiO2.8 Mg(NO3)2·6H2O (98%, Wako Pure Chemical Industries Ltd.), Ni(NO3)2·6H2O (98%, Wako Pure Chemical Industries Ltd.), and Co(NO3)2·6H2O (98%, Wako Pure Chemical Industries Ltd.) were stoichiometrically weighed and then dissolved in distilled water to obtain an aqueous solution with 0.080 M of each nitrate solution. The Mg−Ni−Co solution was added dropwise into 0.07 M Na2CO3 solution to form precipitates. The precursor was obtained by washing, filtering and drying the precipitates at 100 °C in air for 24 h. The precursor was calcined at 750 °C in air for 24 h to obtain the objective material. All the solutions were processed while maintaining the temperature at 80 °C. 2.2. Characterization. Identification of the obtained samples was performed using powder X-ray diffraction (XRD) measurement (X’Pert Pro, PANalytical, Cu Kα, 45 kV, 40 mA). The lattice parameters were calculated from a least-squares fit to the d-values. The composition of the metal components of the samples was determined using inductively coupled plasma atomic emission spectroscopy (ICP-AES; ICPE-9000, Shimadzu Seisakusho). Scanning transmission electron microscopyenergy dispersive X-ray spectroscopy (STEM-EDX; JEM-2100F/JED2300T, JEOL, 200 kV) was used to observe particle morphology, particle shape, and to conduct lattice imaging and elemental analysis. Crystal structure analysis was performed using the Rietveld method with synchrotron X-ray diffraction data (SPring-8, BL02B2, BL19B2) using RIETAN-FP software.9 2.3. Electrochemical Measurement. A coin-type cell (HS cell, Hohsen Ltd.) and a three-electrode cell (Toyo System Co., Ltd.) were used for electrochemical measurements. As the cathode, the synthesized material was mixed with conductive carbon (SuperC65, TIMCAL) and polytetrafluoroethylene (PTFE) as a binder in a weight ratio of 5:5:1, pressed onto an Al mesh at about 20 MPa and vacuumdried at 120 °C overnight. For some samples, pulverization was conducted using a planetary ball mill (300 rpm, 2 h) before the cathode assembly. Mg alloy (AZ31, Mg/Al/Zn = 96:3:1 w/w) was used as the anode material. A 0.5 M Mg[N(SO2CF3)2]2/acetonitrile solution or 1.0 M Mg[N(SO2CF3)2]2/triglyme solution (Kishida Chemical Co., Ltd.) was used as an electrolyte, and a polypropylene film (Celgard #2400) or glass-fiber separator (Tokyo Roshi Kaisha, Ltd.) was used as a separator. In the two-electrode HS cell, the charge termination voltage was 3.7 V versus AZ31 anode and the discharge termination voltage was 0 V versus anode with a current density of 5 mA·g−1. On the other hand, the charge and discharge termination voltages for the three-electrode cell were 0.345 and −1.955 V versus Ag/Ag+, respectively, that is, from 3.5 to 1.2 V versus Mg/Mg2+. Both cells were constructed in an argon-filled glovebox. The charge/discharge cycle tests were performed at 60 °C (thermostat) or 70 °C (hot plate) using a cell tester (HJ-SD8, Hokuto Denko, Co., Ltd.). The results of electrochemical measurement were shown in Supporting Information. 2.4. Computational Method. First-principles calculations were conducted based on density functional theory (DFT) for rock salt-type MgNi0.75Co0.25O2, MgNi0.83Co0.17O2, MgNi0.5Co0.5O2, and their Mgdeintercalated compounds. The Vienna ab initio simulation package (VASP)10,11 was utilized with the modified Perdew−Burke−Ernzerhof generalized gradient approximation (PBEsol-GGA) + U12−15 and projector-augmented wave (PAW) methods.16 For the GGA + U calculations, the U values for the d orbitals of Ni and Co were set to 6.0 and 3.4 eV, according to previous reports.17 Relaxation of the crystal

3. RESULTS AND DISCUSSION 3.1. Characterization. The objective materials were synthesized as nominal (Mg:Ni:Co) compositions of (1:0.8:0.2), (2:0.8:0.2), (3:0.8:0.2), (1:0.6:0.4), (2:0.6:0.4), (3:0.6:0.4), and (2:0.5:0.5), which are denoted as MNC182, MNC282, MNC382, MNC164, MNC264, MNC364, and MNC255, respectively. XRD patterns for the synthesized specimens are shown in Figure 1, where all peaks were assigned

Figure 1. Powder X-ray diffraction patterns for Mgx Ni yCozO2 (MNCxyz), where x, y, and z represented the nominal composition: (a) MNC182, (b) MNC282, (c) MNC382, (d) MNC164, (e) MNC264, (f) MNC364, and (g) MNC255 (○ peaks assigned to Co3O4).

to the rock salt-type structure with space group Fm3̅m, except for MNC255. The solid-solubility limit of Co was lower than 0.5 atoms per formula unit (apfu) because a subphase was generated at the substitution of Co with 0.5 apfu. Table 1 shows the calculated lattice constants using synchrotron XRD and the nominal compositions for the present specimens. Chemical analyses with ICP-AES were performed to determine the metal compositions of the obtained materials. Table 2 shows the ICP-AES results for the monophase Table 1. Nominal Compositions of MgxNiyCozO2 and the Lattice Parameters Determined from Synchrotron XRD Measurements

MNC182 MNC164 MNC282 MNC264 MNC255 MNC382 MNC364 B

x

y

z

lattice parameter (nm)

1.0 1.0 2.0 2.0 2.0 3.0 3.0

0.8 0.6 0.8 0.6 0.5 0.8 0.6

0.2 0.4 0.2 0.4 0.5 0.2 0.4

0.419578(1) 0.420853(2) 0.419719(1) 0.420882(1) 0.419791(1) 0.420950(2) DOI: 10.1021/acs.inorgchem.8b03638 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry Table 2. Metal Compositions of MgxNiyCozO2 Determined by ICP-AES MNC182 MNC164 MNC282 MNC264 MNC382 MNC364

Mg

Ni

Co

0.3030(7) 0.274(1) 0.5010(4) 0.420(1) 0.3603(8) 0.443(1)

0.833(1) 0.602330(0) 0.798993(0) 0.604(1) 0.7944(9) 0.605(1)

0.1665(3) 0.397669(0) 0.2010(1) 0.39518(0) 0.2055(1) 0.394(1)

Table 3. STEM-EDX Quantitative Analysis of MNC182 at the Corresponding Area in Figure 2 whole tick position thin position outside center

Mg

Ni

Co

0.269 0.274 0.253 0.268 0.269

0.836 0.831 0.841 0.834 0.835

0.164 0.169 0.159 0.166 0.165

refined occupancy of Mg, Ni, or Co and was retained the ratio of metal composition. The analysis results are shown in Figure 3a and b for MNC282 and MNC264, respectively. The crystallographic parameters for all the specimens are summarized in Table 4. For all of the present samples, excellent fitting was achieved with some vacancies at 4a metal sites. Although the ionic radius of Co2+ is shorter than that of Ni2+ in octahedral coordination (Ni2+: 0.069 nm; Co2+: 0.065 nm),20 the lattice constants increased with Co-substitution. The difference in the lattice constants was considered to be due to cation deficiencies because more vacancies were characterized in MNC282 than in MNC264. The chemical formula, including defects, is represented as MgxNiyCoz□2‑x‑y‑zO2 for the present rock-salt materials. 3.3. Electron Density Distribution Obtained by the Maximum Entropy Method (MEM). The electronic structures for the present specimens were obtained by MEM for the structural model based on the Rietveld analysis. The electron density distributions and the electron distributions in line profiles between 4a−4b are shown in Figure 4. Although similar electronic distributions among the samples were obtained, the saddle point of MNC282 was located only at lower electron density. The Mg composition of MNC282 was the highest of all the present materials; therefore, the covalency of M−O (M: Mg, Ni, Co) was considered to be weak. The decrease in the covalency that accompanies the increase in the Mg composition was also confirmed for the other samples. The difference in covalency was considered to be the difference in the total electrons among Mg, Ni, and Co.

specimens. The ratios of metal compositions were calculated as unity for the sum of the Ni and Co contents. The Ni/Co ratios were approximately controlled, while Mg was not dissolved in the specimens up to the nominal composition. The appropriate basic concentration used with the reverse coprecipitation method should thus be further examined with respect to Mg precipitation. Elemental mapping and lattice imaging for MNC182 were performed using STEM-EDX. The mapping results are shown in Figure 2 and confirm the homogeneous distribution of the metal atoms (Mg, Ni and Co). Quantitative analysis results from STEM-EDX are summarized in Table 3, where the atomic ratios of metals in a single particle are shown. The atomic ratio corresponded to the ICP-AES results and indicated the Ni and Co compositions were controlled, whereas there was a lack of Mg with respect to the nominal composition. Figure 2 shows a TEM image that gives lattice distances of 0.24 and 0.22 nm, which correspond to the (111) and (200) d-spacings, respectively. Therefore, the rock salt phase was successfully synthesized with homogeneous Mg, Ni, and Co distributions. 3.2. Crystal Structure Analysis Using Synchrotron XRD. The lattice parameters, atomic displacement parameters, and occupancies of the synthesized materials were refined by Rietveld analysis using synchrotron XRD data. In the rock salt structure, metal atoms occupied the same sites (4a in Wyckoff notation) and were constrained to satisfy the metal composition determined by chemical analysis (Table 2) to refine only the occupancy of vacancies. The vacancy was estimated by [1 − g(Mg) + g(Ni) + g(Co)], where g(M) was represented as the

Figure 2. (a) TEM image and STEM-EDX maps of (b) Mg K-edge, (c) Ni K-edge, and (d) Co K-edge, and lattice spacing of (e) d111 and (f) d200 observed for MNC182. C

DOI: 10.1021/acs.inorgchem.8b03638 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 3. Rietveld analyses for (a) MNC282 and (b) MNC264 synchrotron X-ray diffraction patterns. Plus marks indicate observed diffraction patterns and a solid line represents calculated intensities. The vertical marks indicate positions of allowed Bragg reflections. The curve at the bottom is the difference between the observed and calculated intensities on the same scale.

Table 4. Final Results of Rietveld Refinements for MgxNiyCozO2 from Synchrotron XRD Resultsa a (nm) Rwp (%) Rp (%) Re (%) 102 × B (nm2) at 4a (Mg, Ni, Co) 102 × B (nm2) at 4b (O) occupancy of Mg occupancy of Ni occupancy of Co occupancy of O

MNC182

MNC164

MNC282

MNC264

MNC382

MNC364

0.419578(1) 1.62 1.20 1.98 0.183(5) 0.374(6) 0.2235(2) 0.6148 0.1229 1

0.420853(2) 2.48 2.02 2.58 0.189(2) 0.380(8) 0.2095(3) 0.4605 0.3040 1

0.419719(1) 2.71 1.72 3.00 0.171(2) 0.373(8) 0.319(2) 0.5100 0.1283 1

0.420882(1) 2.22 1.87 2.47 0.160(2) 0.337(8) 0.2861(5) 0.4115 0.2692 1

0.419791(1) 2.33 2.22 2.90 0.177(2) 0.334(6) 0.2557(3) 0.5638 0.1459 1

0.420950(2) 2.39 1.66 3.01 0.223(2) 0.350(7) 0.3018(4) 0.4122 0.2685 1

a

The 4a (0,0,0) and 4b (1/2,1/2,1/2) sites were occupied by M (Mg, Ni, Co) and O, respectively.

3.4.4. Computational Approach. The resulting structures presented in Figure 5a−c exhibit formation energies of various Mg/vacancy arrangements as a function of Mg-deintercalation (Figure 5d−f). The formation energies, ΔEf, are defined as

where E0(X) is the total energy of X. The formation energy minima for each of the compositions are negative in Mg1−x(Ni,Co)O2, which indicates that the solid-solution mechanism or the formation of a superstructure at intermittent compositions due to Mg/vacancy ordered arrangement occurs during the charge−discharge reactions. Figure 5g−i shows the variation of cell volume with x. The Mg deintercalation reaction reduces the cell volume almost linearly

ΔEf [Mg1 − x(Ni, Co)O2 ] = E0[Mg1 − x(Ni, Co)O2 ] − (1 − x)E0[Mg(Ni, Co)O2 ] − xE0[(Ni, Co)O2 ]

(1) D

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Figure 4. Electron density distributions along the (001) section of (a) MNC182, (b) MNC282, (c) MNC382, (d) MNC164, (e) MNC264, and (f) MNC364, and (g) the line profiles between 4a (metal) and 4b (oxygen) sites.

with x, regardless of the Ni/Co ratio, and the cell shrinks to about 80% of the original cell volume by complete Mg deintercalation. The Mg deintercalation voltage is also evaluated according to

electronic structures were determined from synchrotron XRD measurements and MEM, respectively. XRD and ICP-AES measurements revealed that the synthesized materials had the rock-salt structure with a new chemical composition regarded as MgNiO2 substituted by Co. The solubility limit of Co in the materials was lower than 0.5 per formula unit. The Mg compositions were not included up to the nominal or objective composition of x = 1.0. The vacancies at the metal sites were estimated by Rietveld analysis to determine the new chemical composition of MgxNiyCoz□2‑x‑y‑zO2 (0.41 < x < 0.64, 0.82 < y < 1.23, 0.24 < z < 0.61). The Co and Mg compositions were considered to facilitate the insertion/deinsertion of Mg2+ due to the different covalency. Furthermore, the first-principles calculations showed possible charge−discharge behavior and to expect the suitable cathode materials for Mg rechargeable batteries.

V (x) = −[E0(Mg1 − x(Ni, Co)O2 ) − E0(Mg1 − (x + y)(Ni, Co)O2 ) − yE0(Mg)]/2yF

(2)

where F is the Faraday constant. E0(x + y) and E0(Mg) correspond to the total energy of the compounds with composition x + y and that of Mg metal, respectively. Figure 6 shows that the calculated voltages for MgNi0.75Co0.25O2 and MgNi0.5Co0.5O2 are in the range from about 2.2 to 3.0 V, whereas that for MgNi0.83Co0.17O2 has a slightly higher voltage of 2.5 to 3.2 V.

4. CONCLUSION Newly synthesized MgxNiyCozO2 (x + y + z ≤ 2.0) rock-salt materials were characterized and investigated as cathode materials for Mg rechargeable batteries. The crystal and E

DOI: 10.1021/acs.inorgchem.8b03638 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 5. Energetically stable structures for (a) MgNi0.75Co0.25O2, (b) MgNi0.83Co0.17O2, and (c) MgNi0.5Co0.5O2. (d−f) Formation energies for various Mg/vacancy arrangements as a function of the Mg-deintercalated structures and variation of cell volumes for (g) Mg1−xNi0.75Co0.25O2, (h) Mg1−xNi0.83Co0.17O2, and (i) Mg1−xNi0.5Co0.5O2 with demagnesiation, x.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.8b03638.

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Charge−discharge tests under several conditions to estimate the electrochemical properties as a cathode material for Mg rechargeable batteries (cathode active material, the synthesized materials; anode, AZ31 alloy; PDF)

AUTHOR INFORMATION

Corresponding Author

*Tel.: +81-4-7122-9493. Fax: +81-4-7125-7761. E-mail: [email protected].

Figure 6. Calculated voltages for (a) Mg1−xNi0.75Co0.25O2, (b) Mg1−xNi0.83Co0.17O2, and (c) Mg1−xNi0.5Co0.5O2 with demagnesiation, x.

ORCID

Yasushi Idemoto: 0000-0003-3832-2139 F

DOI: 10.1021/acs.inorgchem.8b03638 Inorg. Chem. XXXX, XXX, XXX−XXX

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(17) Jain, A.; Hautier, G.; Ong, S. P.; Moore, C. J.; Fischer, C. C.; Persson, K. A.; Ceder, G. Formation enthalpies by mixing GGA and GGA+U calculations. Phys. Rev. B: Condens. Matter Mater. Phys. 2011, 84, 045115. (18) van de Walle, A.; Asta, M.; Ceder, G. The Alloy Theoretic Automated Toolkit: A User Guide. CALPHAD: Comput. Coupling Phase Diagrams Thermochem. 2002, 26, 539−553. (19) van de Walle, A. Multicomponent multisublattice alloys, nonconfigurational entropy and other additions to the Alloy Theoretic Automated Toolkit. CALPHAD: Comput. Coupling Phase Diagrams Thermochem. 2009, 33, 266−278. (20) Jia, Y. Q. Crystal radii and effective ionic radii of the rare earth ions. J. Solid State Chem. 1991, 95, 184−187.

Naoya Ishida: 0000-0003-3707-6781 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors wish to gratefully acknowledge Dr. K. Sugimoto, Dr. S. Kawaguchi, and Dr. K. Osaka of the Japan Synchrotron Radiation Research Institute (JASRI) with regard to synchrotron XRD measurements (SPring-8; Proposal Nos. 2014B1457, 2015A1541, and 2016A1509). The authors thank Dr. T. Ichihashi for conducting the TEM analysis. This study was supported by the ALCA-SPRING project of the Japan Science and Technology Agency (JST).

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REFERENCES

(1) Latimer, W. M. The Oxidation States of the Elements and their Potentials in Aqueous Solutions, 2nd ed.; Prentice-Hall, Inc.: Englewood Cliffs, NJ, 1959. (2) Pourbaix, M. Atlas of Electrochemical Equilibria in Aqueous Solutions; Cebelcor: Brussel, 1966; 384. (3) Levi, E.; Gofer, Y.; Aurbach, D. On the Way to Rechargeable Mg Batteries: The Challenge of New Cathode Materials. Chem. Mater. 2010, 22, 860−868. (4) Levi, E.; Levi, M. D.; Chasid, O.; Aurbach, D. A review on the problems of the solid state ions diffusion in cathodes for rechargeable Mg batteries. J. Electroceram. 2009, 22, 13−19. (5) Yagi, S.; Tanaka, A.; Ichikawa, Y.; Ichitsubo, T.; Matsubara, E. Electrochemical Stability of Magnesium Battery Current Collectors in a Grignard Reagent-Based Electrolyte. J. Electrochem. Soc. 2013, 160 (3), C83−C88. (6) Idemoto, Y.; Tsukada, Y.; Kitamura, N.; Hoshikawa, A.; Ishigaki, T. Change in Crystal Structure of LiNi0.8Co0.19Cu0.01O2 Cathode during Charge of Coin Cell Observed by Ex Situ Time-of-flight Neutron Diffraction. Chem. Lett. 2011, 40, 168−170. (7) Idemoto, Y.; Horie, A.; Ishida, N.; Kitamura, N. Crystal Structure Analysis in the Charge and Discharge Process of Li-ion Battery Cathode-material LiNi0.8Co0.2O2. Electrochemistry 2016, 84 (10), 802− 807. (8) Yagi, S.; Ichikawa, Y.; Yamada, I.; Doi, T.; Ichitsubo, T.; Matsubara, E. Synthesis of Binary Magnesium−Transition Metal Oxides via Inverse Coprecipitation. Jpn. J. Appl. Phys. 2013, 52, 025501−6. (9) Izumi, F.; Momma, K. Three-Dimensional Visualization in Powder Diffraction. Solid State Phenom. 2007, 130, 15−20. (10) Kresse, G.; Furthmuller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B: Condens. Matter Mater. Phys. 1996, 54, 11169−11186. (11) Kresse, G.; Furthmuller, F. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput. Mater. Sci. 1996, 6, 15−50. (12) Perdew, J. P.; Chevary, J. A.; Vosko, S. H.; Jackson, K. A.; Pederson, M. R.; Singh, D. J.; Fiolhais, C. Atoms, molecules, solids, and surfaces: Applications of the generalized gradient approximation for exchange and correlation. Phys. Rev. B: Condens. Matter Mater. Phys. 1992, 46, 6671. (13) Perdew, J. P.; Wang, Y. Accurate and simple analytic representation of the electron-gas correlation energy. Phys. Rev. B: Condens. Matter Mater. Phys. 1992, 45, 13244. (14) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865. (15) Perdew, J. P.; Ruzsinszky, A.; Csonka, G. I.; Vydrov, O. A.; Scuseria, G. E.; Constantin, L. A.; Zhou, X.; Burke, K. Restoring the Density-Gradient Expansion for Exchange in Solids and Surfaces. Phys. Rev. Lett. 2008, 100, 136406. (16) Blochl, P. E. Projector augmented-wave method. Phys. Rev. B: Condens. Matter Mater. Phys. 1994, 50, 17953. G

DOI: 10.1021/acs.inorgchem.8b03638 Inorg. Chem. XXXX, XXX, XXX−XXX