Papers - TANIBATA Naoto
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Optimization of force-field potential parameters using conditional variational autoencoder Reviewed
Koki Matsunoshita, Yudai Yamaguchi, Masato Hamaie, Motoki Horibe, Naoto Tanibata, Hayami Takeda, Masanobu Nakayama, Masayuki Karasuyama, Ryo Kobayashi
Science and Technology of Advanced Materials: Methods 3 ( 1 ) 2023.09
Language：English Publishing type：Research paper (scientific journal) Publisher：Informa UK Limited
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Increasing the Sodium Metal Electrode Compatibility with the Na<sub>3</sub>PS<sub>4</sub> Solid‐State Electrolyte through Heteroatom Substitution Reviewed
Lieven Bekaert, Suzuno Akatsuka, Naoto Tanibata, Frank De Proft, Annick Hubin, Mesfin Haile Mamme, Masanobu Nakayama
ChemSusChem 16 ( 20 ) 2023.08
Language：English Publishing type：Research paper (scientific journal) Publisher：Wiley
Abstract
Rechargeable batteries are essential to the global shift towards renewable energy sources and their storage. At present, improvements in their safety and sustainability are of great importance as part of global sustainable development goals. A major contender in this shift are rechargeable solid‐state sodium batteries, as a low‐cost, safe, and sustainable alternative to conventional lithium‐ion batteries. Recently, solid‐state electrolytes with a high ionic conductivity and low flammability have been developed. However, these still face challenges with the highly reactive sodium metal electrode. The study of these electrolyte‐electrode interfaces is challenging from a computational and experimental point of view, but recent advances in molecular dynamics neural‐network potentials are finally enabling access to these environments compared to more computationally expensive conventional ab‐initio techniques. In this study, heteroatom‐substituted Na<sub>3</sub>PS<sub>3</sub>X<sub>1</sub> analogues, where X is sulfur, oxygen, selenium, tellurium, nitrogen, chlorine, and fluorine, are investigated using total‐trajectory analysis and neural‐network molecular dynamics. It was found that inductive electron‐withdrawing and electron‐donating effects, alongside differences in heteroatom atomic radius, electronegativity, and valency, influenced the electrolyte reactivity. The Na<sub>3</sub>PS<sub>3</sub>O<sub>1</sub> oxygen analogue was found to have superior chemical stability against the sodium metal electrode, paving the way towards high‐performance, long lifetime and reliable rechargeable solid‐state sodium batteries. -
Assessing the Reactivity of the Na<sub>3</sub>PS<sub>4</sub> Solid-State Electrolyte with the Sodium Metal Negative Electrode Using Total Trajectory Analysis with Neural-Network Potential Molecular Dynamics Reviewed
Lieven Bekaert, Suzuno Akatsuka, Naoto Tanibata, Frank De Proft, Annick Hubin, Mesfin Haile Mamme, Masanobu Nakayama
The Journal of Physical Chemistry C 127 ( 18 ) 8503 - 8514 2023.05
Language：English Publishing type：Research paper (scientific journal) Publisher：American Chemical Society (ACS)
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Screening chloride Li-ion conductors using high-throughput force-field molecular dynamics Reviewed
Shin Aizu, Shuta Takimoto, Naoto Tanibata, Hayami Takeda, Masanobu Nakayama, Ryo Kobayashi
JOURNAL OF THE AMERICAN CERAMIC SOCIETY 106 ( 5 ) 3035 - 3044 2023.05
Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY
The realization of high-energy-density all-solid-state Li-ion batteries requires materials exhibiting both high Li-ion conductivity and high deformability, as exemplified by Li3MCl6-type chlorides. Herein, we optimized the classical force-field (FF) parameters for 36 Li- and Cl-containing compounds to reproduce the results of high-precision first-principles calculations and performed rapid FF molecular dynamics (MD) calculations to determine their Li-ion conductivities. In addition, shear moduli were evaluated by first-principles calculations and used as a deformability index. Li4Mn3Cl10 was selected based on its Li-ion conductivity, stiffness, and thermodynamic stability. In accordance with the low calculated shear modulus (11.7 GPa), the cold-pressed compact had a high relative density of 98%, which indicated good deformability. The room-temperature conductivity (3.9 mS cm(-1)) was similar to that (1.6 mS cm(-1)) obtained by high-precision first-principles MD calculations. The Li-ion conductivity of synthesized Li4Mn3Cl10 (18 mu S cm(-1)) was relatively rather high compared to those of known chloride materials but much lower than the calculated value, which was ascribed to the fact that calculations were performed for the high-temperature phase, whereas synthesis yielded the low-temperature phase. The material screening method greatly increases the speed of material exploration and expands the application possibilities of chloride materials for all-solid-state batteries.
DOI： 10.1111/jace.18991
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Reaction Kinetics of Carbonation at the Surface of Garnet-Type Li<sub>7</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub> as Solid Electrolytes for All-Solid-State Li Ion Batteries Reviewed
Masanobu Nakayama, Takuya Horie, Ryosuke Natsume, Shogo Hashimura, Naoto Tanibata, Hayami Takeda, Hirotaka Maeda, Masashi Kotobuki
The Journal of Physical Chemistry C 127 ( 16 ) 7595 - 7601 2023.04
Language：English Publishing type：Research paper (scientific journal) Publisher：American Chemical Society (ACS)
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Computational studies on defect chemistry and Li-ion conductivity of spinel-type LiAl5O8 as coating material for Li-metal electrode. Reviewed International journal
Shuntaro Miyakawa, Shogo Matsuda, Naoto Tanibata, Hayami Takeda, Masanobu Nakayama, Takaya Saito, Svetlana Fukuchi
Scientific reports 12 ( 1 ) 16672 - 16672 2022.10
Language：English Publishing type：Research paper (scientific journal)
Li-metal rechargeable batteries are an attractive option for devices that require an extremely high specific energy density, high robustness, and long-term durability, such as high-altitude platform stations. However, Li dendrite growth during charge-discharge cycling causes short-circuit problems. One technical solution is to form an intermediate layer between the Li metal and electrolyte. This interfacial layer should possess mechanical strength, electrochemical stability in the presence of Li, and Li-ion conductivity. In this study, the Li-ion conductivity of spinel-type LiAl5O8 was investigated using first-principles density functional theory and force field molecular dynamics calculations. The calculation results confirmed that stoichiometric LiAl5O8 compounds do not exhibit Li-ion conductivity, whereas off-stoichiometric compounds with excess Li show long-range Li-ion diffusion. The evaluated activation energy was 0.28 eV, which is as low as that of well-known fast Li-ion conductors, such as garnet-type Li7La3Zr2O12. However, the extrapolated Li-ion conductivity at 298 K was relatively low (~ 10-6 S/cm) owing to the limited formation of migration pathways.
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Process optimisation for NASICON-type solid electrolyte synthesis using a combination of experiments and bayesian optimisation Reviewed
Hayami Takeda, Hiroko Fukuda, Koki Nakano, Syogo Hashimura, Naoto Tanibata, Masanobu Nakayama, Yasuharu Ono, Takaaki Natori
MATERIALS ADVANCES 2022.10
Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY
Na superionic conductor (NASICON)-type LiZr2(PO4)(3) (LZP) is an oxide-based solid electrolyte candidate for use in all-solid-state Li-ion batteries. However, as the ionic conductivity is insufficient, doping with aliovalent cations has been carried out to improve the Li-ion conductivity by controlling the composition and crystal structure. Li-ion conductivity is also affected by the microstructural properties of a sintered body, such as density, morphology, and elemental distribution, and thus, controlling process parameters, such as heating conditions during the solid-state reaction, improves conductivity. Using an exhaustive experimental approach, Ca and Si co-doped Li-rich NASICON-type LZP was synthesised via solid-state reactions under various two-step heating conditions to yield the highest Li-ion conductivity by optimising the conditions. The highest total Li-ion conductivity of 3.3 x 10(-5) S cm(-1) was obtained when the sample was first heated at 1050 degrees C and then heated at 1250 degrees C. The crystal structures, relative densities, micromorphologies, and Li-ion conductivities of the materials were characterised, and their relationships were investigated. These relationships were complex, and intuitively determining the optimal conditions was challenging with only a few experiments. Instead, as a proof-of-concept study, the collected data were used to demonstrate that Bayesian optimisation (BO) efficiently improved the experimental determination of the optimal heating conditions. The BO-guided experimental investigation determined the optimal conditions more rapidly compared to conventional trial-and-error approaches employed in the materials industry. The efficiency factor was approximately double that of the exhaustive search.
DOI： 10.1039/d2ma00731b
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Bayesian optimisation with transfer learning for NASICON-type solid electrolytes for all-solid-state Li-metal batteries Reviewed
Hiroko Fukuda, Shunya Kusakawa, Koki Nakano, Naoto Tanibata, Hayami Takeda, Masanobu Nakayama, Masayuki Karasuyama, Ichiro Takeuchi, Takaaki Natori, Yasuharu Ono
RSC Advances 12 ( 47 ) 30696 - 30703 2022.10
Language：English Publishing type：Research paper (scientific journal) Publisher：Royal Society of Chemistry (RSC)
Demonstrate BO approaches to search for optimal composition with high ionic conductivity efficiently.
DOI： 10.1039/D2RA04539G
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Growth Mechanism of Spiky Nb2O5 Nanoparticles and their Electrochemical Property Reviewed
Teruaki Fuchigami, Hayato Yamamoto, Naoto Tanibata, Masanobu Nakayama, Ken-ichi Kakimoto
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 259 ( 9 ) 2022.09
Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH
Spiky nanoarchitecture composed of numerous nanorods and a spherical core has applications in various fields because of its high performance and durability. However, controlling the spiky structure is challenging because of an unclear formation mechanism. This study investigates the growth mechanism of spiky nanostructure by hydrothermally synthesizing Nb2O5 with various conditions and additives, and it is shown that adsorption and gradual decomposition of ligands promote the formation of the spiky shape. Using oxalic acid as an additive and synthesizing at 160 degrees C, which is below oxalic acid's decomposition temperature, spherical Nb2O5 with a rough surface that consists of a nanostructure with less than 5 nm size forms, and its surface is protected by oxalate ions. When the synthesis temperature increases to 180 degrees C, oxalate ions are decomposed, and nanorods grow on the spherical particles. The results show that oxalate ions suppress particle growth, promote self-assembly, and control subsequent particle growth, resulting in complex nanostructures. When used as anode material in lithium-ion batteries, the spiky Nb2O5 nanoparticles show a higher capacity (143 mAh g(-1)) than collapsed spiky particles (92 mAh g(-1)) and nanorods (37 mAh g(-1)) because of fast lithium-ion diffusion on the surface nanostructure and high dispersibility.
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Na superionic conductor-type LiZr2(PO4)3 as a promising solid electrolyte for use in all-solid-state Li metal batteries Reviewed International journal
Masanobu Nakayama, Koki Nakano, Maho Harada, Naoto Tanibata, Hayami Takeda, Yusuke Noda, Ryo Kobayashi, Masayuki Karasuyama, Ichiro Takeuchi, Masashi Kotobuki
Chemical Communications 58 ( 67 ) 9328 - 9340 2022.08
Language：English Publishing type：Research paper (scientific journal)
All-solid-state Li-ion batteries are of considerable interest as safer alternatives to Li-ion batteries containing flammable organic electrolytes. To date, however, achieving sufficient charging and discharging rates, in addition to capacity, at room temperature using these all-solid-state batteries has been challenging. To overcome these issues, material simulations and informatics investigations of a relatively new Na superionic conductor (NASICON)-type LiZr2(PO4)3 (LZP) electrolyte were conducted to elucidate its characteristics and material functions. The following thermodynamic and/or kinetic properties of NASICON-type Li-ion conductive oxides were investigated with respect to the crystal structure mainly using material simulation and informatics approaches: (1) the electrochemical stabilities of LZP materials with respect to Li metal and (2) Li-ion conductivities in the bulk and at the grain boundaries. An efficient materials informatics search method was employed to optimise the material functions of the LZP electrolyte via Bayesian optimisation. This study should promote the application of LZP in all-solid-state batteries for use in technologies such as mobile devices and electric vehicles and enable more complex composition and process control.
DOI： 10.1039/D2CC01526A
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Chemical Composition Data-Driven Machine-Learning Prediction for Phase Stability and Materials Properties of Inorganic Crystalline Solids Reviewed
Taruto Atsumi, Kosei Sato, Yudai Yamaguchi, Masato Hamaie, Risa Yasuda, Naoto Tanibata, Hayami Takeda, Masanobu Nakayama, Masayuki Karasuyama, Ichiro Takeuchi
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 2022.02
Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH
Materials informatics has attracted significant attention toward the efficient discovery and development of new functional materials. Machine-learning regression techniques have often been used to establish a link between properties. In this respect, precise and rational regression is contingent on the choice of descriptors used to represent both composition and structural information. The usage of structure-derived descriptors restricts the prediction range to the registered materials in the crystal structure database owing to the structural information requirements. Conversely, machine-learning regression based only on compositional descriptors is free from this restriction, despite the fact that the prediction performance may diminish. Herein, their prediction performance is improved using compositional descriptors with histograms, and detailed surveys are performed on their ability to extrapolate. The proposed model achieves a high prediction accuracy based on the area under the receiver operating characteristic (ROC) curve (specifically, AUC > 0.9).
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Octahedral Tilting and Modulation Structure in Perovskite‐Related Compound La 1/3 NbO 3 Reviewed
Yusuke Sakai, Daisuke Urushihara, Toru Asaka, Koichiro Fukuda, Zijian Yang, Naoto Tanibata, Hayami Takeda, Masanobu Nakayama
physica status solidi (b) 259 ( 9 ) 2022.01
Language：English Publishing type：Research paper (scientific journal) Publisher：Wiley
The crystal structure of the A-site-deficient perovskite La1/3NbO3 is investigated using X-ray powder diffraction, transmission electron microscopy (TEM), and computational methods. The NbO6 octahedral tilting is observed and confirmed to be in an a (-) b (0) c (0) manner in Glazer's notation. An incommensurate modulation structure in La1/3NbO3 is observed. Using scanning TEM (STEM) analyses and Monte Carlo simulations, the modulated structure is shown to originate from a striped arrangement of La and vacancies. The satellite reflections arising from the modulation structure are observed as a diffuse scatter in the electron diffraction patterns. By analyses with STEM and molecular dynamics calculations, it is concluded that the origin of diffuse scattering is the existence of nanoscale twin variants with different crystal orientations. The Nb ions in NbO6 octahedra represent an off-center shift like a pseudo-Jahn-Teller distortion. The shift of Nb ions is found to be cooperative with the concentration modulation of La ions.
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Density Functional Theory Studies on Li Metal Electrode/Garnet-Type Li7La3Zr2O12 Solid Electrolyte Interfaces for Application in All-Solid-State Batteries Reviewed
Ripon Iwasaki, Kunihiro Ishida, Risa Yasuda, Koki Nakano, Naoto Tanibata, Hayami Takeda, Masanobu Nakayama, Naoki Watanabe
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 2022.01
Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH
Garnet-type Li7La3Zr2O12 (LLZ) and its analogs are considered potential candidates as solid electrolytes for all-solid-state Li metal batteries because their fast Li-ion conductivity and chemical stability against Li metal anodes result in both safe and large energy densities. To date, several computational and experimental studies have been performed to obtain a more detailed understanding of the nonreactivity of garnet-type LLZ with Li metal and related phenomena. Herein, first-principles calculations based on the density functional theory approach are performed for Li metal/LLZ interfaces to elucidate the electronic and atomistic level aspects. It is confirmed that the valence band maximum and the conduction band minimum for the LLZ phase do not cross the Fermi level corresponding to the Li 2s band. In addition, it is found that the defect formation energies associated with both Li vacancy formation and interstitial Li formation are largely reduced. In particular, the formation energy associated with interstitial Li sites, i.e., Li+ insertion into the LLZ phase, is negative, indicating that spontaneous Li insertion is likely to proceed in the vicinity of the Li/LLZ interface. This new suggestion may help further elucidation of the reported interfacial behavior.
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Density Functional Theory and Machine Learning-Based Analyses for Improved Surface Stability of a BaTiO3-Coated LiCoO2 Positive Electrode Material Reviewed
Kunihiro Ishida, Naoto Tanibata, Hayami Takeda, Masanobu Nakayama, Takashi Teranishi, Naoki Watanabe
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 259 ( 9 ) 2021.12
Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH
The application of oxide coating on the surfaces of active cathode materials is an effective method for improving the electrochemical durability of lithium-ion batteries because it suppresses oxygen gas release from the surface of the cathode material. This report summarizes a study conducted on verifying the suppression of oxygen release from a LiCoO2 cathode material using BaTiO3 (BT), which has recently attracted attention as a new coating material. The use of first-principles calculations and machine learning as verification methods is described. In addition to the discussion of interfacial properties based on atomic- and electronic-level considerations, comprehensive verification of the interface with several junction patterns is described. The verification results suggest that the desorption of oxygen from the surface of the active material is hindered by the oxide coating, indicating the effectiveness of BT as a coating material.
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Molecular Dynamics Simulation of Li-Ion Conduction at Grain Boundaries in NASICON-Type LiZr2(PO4)3 Solid Electrolytes Reviewed
Koki Nakano, Naoto Tanibata, Hayami Takeda, Ryo Kobayashi, Masanobu Nakayama, Naoki Watanabe
The Journal of Physical Chemistry C 125 ( 43 ) 23604 - 23612 2021.11
Language：English Publishing type：Research paper (scientific journal) Publisher：American Chemical Society (ACS)
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Exploring the diffusion mechanism of Li ions in different modulated arrangements of La(1-X)/3LixNbO3 with fitted force fields obtained via a metaheuristic algorithm
Zijian Yang, Robyn E. Ward, Naoto Tanibata, Hayami Takeda, Masanobu Nakayama, Ryo Kobayashi
SOLID STATE IONICS 366 2021.08
Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER
As a potential solid-state electrolyte material, Li-containing A-site deficient perovskite oxides have attracted the attention of researchers because of their high Li-ion conductivity and the relationship between Li-ion conduction and structural characteristics, which has been intensively investigated. We have recently confirmed a quasiperiodic ordered arrangement of La and vacancies (Vac) at the perovskite A-sites of La(1-X)/3LixNbO3 (LLNO) using a combination of density functional theory (DFT), Monte Carlo simulations, and electron diffraction. Interestingly, two types of modulated arrangements, namely closed and striped structures, coexist in the La-rich layer, which affect Li-ion migration. In this study, DFT-derived force-field molecular dynamics (FFMD) simulations were performed to investigate the effect of a modulated structure on the migration behavior of Li ions in LLNO compounds. The results indicate that the type of modulated arrangements of La/Vac has a significant influence on the migration of Li ions. Moreover, the estimated diffusion coefficients of the modulated structures are higher by a factor of 10 than those of La/Vac disordered models at 800 K. The migration energy in the ab plane appeared to be much lower than along the c-axis, controlling the modulated arrangement of LLNO is beneficial to eliminate La-ion blockage during long-distance migration. Accordingly, the present study reveals that the controlling cation/Vac arrangement at perovskite A-sites is crucial for achieving high Li-ion conductivity. At the same time, the research scheme of this work is also applicable to other solid electrolyte materials, which provides research guidance for high-throughput material retrieval.
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First-principles study of the morphology and surface structure of LaCoO3 and La0.5Sr0.5Fe0.5Co0.5O3 perovskites as air electrodes for solid oxide fuel cells Reviewed
Masanobu Nakayama, Katsuya Nishii, Kentaro Watanabe, Naoto Tanibata, Hayami Takeda, Takanori Itoh, Toru Asaka
Science and Technology of Advanced Materials 1 ( 1 ) 24 - 33 2021.03
Language：English Publishing type：Research paper (scientific journal) Publisher：Informa UK Limited
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Efficient Experimental Search for Discovering a Fast Li-Ion Conductor from a Perovskite-Type LixLa(1-x)/3NbO3 (LLNO) Solid-State Electrolyte Using Bayesian Optimization
Zijian Yang, Shinya Suzuki, Naoto Tanibata, Hayami Takeda, Masanobu Nakayama, Masayuki Karasuyama, Ichiro Takeuchi
JOURNAL OF PHYSICAL CHEMISTRY C 125 ( 1 ) 152 - 160 2021.01
Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC
LixLa(l -x)/3NbO3 (LLNO) is an A-site-deficient perovskite material that has a larger unit cell volume, a lower La3+ concentration, and a higher intrinsic vacancy concentration than (LixLa(2-x)/3TiO3), which is known to be one of the fastest Li-ion conductive oxides. These advantages make LLNO a potential oxide-based solid electrolyte candidate for allsolid-state Li-ion batteries. The A-site and B-site elements in this perovskite-type material can be substituted by ions with various charges and radii in a wide range of ways to form complicated solid solutions; hence, this type of material can be adapted to a variety of application requirements. Doping with monovalent or divalent metal compounds is a promising method for improving the ionic conductance of this perovskite-type material. In this study, the (LiyLa(1-y/3)(1-x)Sr0.5xNbO3 (0 <= 0.5 x <= 0.15, 0 <= y <= 0.3) composition formed by co-doping with Li2CO3 and SrCO3 was optimized using an exhaustive experimental approach. Sixty-four samples with different compositions were structurally analyzed, and their electrochemical performance was experimentally characterized, which revealed that the co-doped samples have higher ionic conductivities and superior sintered morphologies compared to those prepared by single doping. Because Li+ and Sr2+ doping improves the ionic conductivity for different reasons, and many factors, such as higher carrier concentrations, enhancements through sintering, and changes in the microstructure, play important roles, it is difficult or inefficient to determine the best composition using only traditional trial-and-error or intuitive searching. Instead, as a proof-of-concept study, we show that the Bayesian optimization (BO) method efficiently searches for the best composition and that material retrieval during experimental exploration can benefit from BO because it significantly reduces the high workload associated with the trial-and-error approach employed by the materials industry.
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High Formability and Fast Lithium Diffusivity in Metastable Spinel Chloride for Rechargeable All‐Solid‐State Lithium‐Ion Batteries Reviewed
Naoto Tanibata, Masashi Kato, Shuta Takimoto, Hayami Takeda, Masanobu Nakayama, Hirofumi Sumi
Advanced Energy and Sustainability Research 1 ( 1 ) 2000025 - 2000025 2020.10
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：Wiley
Materials with high formability and Li-ion diffusivity are desired to realize safe bulk-type all-solid-state Li-ion batteries with high energy density. Spinel-type Li2FeCl4, which is expected as a Li-ion-conductive electrode, adopts the high-temperature cubic phase (space group: Fd-3m) by a mechanochemical synthesis method. The powder-compressed pellet shows a high relative density of 92% and large neck formation between the particles. An analysis of the distribution of relaxation times from the AC impedance results indicates that the contribution of the grain boundary impedance is almost negligible (≈3%) in the powder-compressed pellet. Even the Li diffusion coefficient, which is underestimated by the Nernst–Einstein equation, is several orders of magnitude higher than those of conventional oxide and sulfide electrode materials. Analyzing the diffusion pathways using a classical force field calculation suggests that stabilizing the high-temperature phase at room temperature delocalizes Li ions in the diffusion pathway, thus realizing high Li-ion diffusivity. The Li2FeCl4 green compact containing 10 wt% carbon as an electron-conductive additive shows a one-electron charge reaction with a capacity of 126 mAh g−1, with no large overpotential at a high operating voltage of 3.6 V versus Li/Li+ at 30 °C.
Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/aesr.202000025
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Bayesian-optimization-guided experimental search of NASICON-type solid electrolytes for all-solid-state Li-ion batteries Reviewed
Maho Harada, Hayami Takeda, Shinya Suzuki, Koki Nakano, Naoto Tanibata, Masanobu Nakayama, Masayuki Karasuyama, Ichiro Takeuchi
JOURNAL OF MATERIALS CHEMISTRY A 8 ( 30 ) 15103 - 15109 2020.08
Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY
Divalent- or trivalent-metal-oxide-doped NASICON-type LiZr2(PO4)(3)(LZP) is an attractive oxide-based solid electrolyte for all-solid-state Li-ion batteries owing to its high Li-ion conductivity and stable charge-discharge cycling. Using an extensive experimental approach, the composition of CaO- and Y2O3-co-doped Li-rich NASICON-type LZP of the composition Li(1+x+2y)Z(r2-x-y)Y(x)Ca(y)(PO4)(3)(0 <= x <= 0.376, 0 <= y <= 0.376) was optimized. A number of 49 compositions were synthesized and their crystal structures, relative density of the sintered material, and Li-ion conductivity characterized. The co-doped compositions had a higher Li-ion conductivity than those doped with CaO or Y(2)O(3)alone. Furthermore, diffraction studies revealed that two phases and an impurity phase existed depending on the composition. Adding CaO significantly changed the relative density of the sintered material. Thus, to identify compositional dependencies among the Li-ion conductivity, phase stability, and relative density was complicated, and intuitively searching for the best composition was difficult. As a proof-of-concept, the collected data were used to demonstrate that the Bayesian optimization (BO) significantly improved the experimental search for the best oxide-based electrolyte composition. Multi-objective BO (MOBO), which considers more than two target performances, was also carried out. It was validated that the BO-guided experimental search determined more rapidly the best composition compared to conventional trial-and-error approaches employed in the materials industry.
DOI： 10.1039/d0ta04441e
