Science on Interfacial Ion Dynamics for Solid State Ionics Devices

Newsletter Vol.5
March 2022

Interface lonics toward
Sustainable Society
2019 – 2023 Japan Society for the Promotion of Science
Grant-in-Aid for Scientific Research on Innovative Areas

2

Preface | Contents

Preface
The postponed Olympics and Paralympic Games Tokyo 2020 were held inthe summer of 2021, and a variety of electric vehicles with modern forms
supported Tokyo 2020. In September, an electric car that led the marathon
course was powered by an all-solid-state battery, and its driving movie wasreleased. At the same time, the electrode–solid electrolyte interface issues
affecting the lifespan of all-solid-state batteries (SSBs) were highlighted. The
COP26 meeting held in November outlined a target that all new vehicle sales
by 2040 should be “Zero Emission” like electric vehicle that emit no CO2
during the driving. We hope that our achievements of Interface IONICS willcontribute to the further improvement of SSBs and then sustainable society.
While the vaccination rate is increasing, the global end of COVID-19 may takemore time because of the emergence of new mutant strains. We would like tocontinue our domestic and international collaborative research activities via
online and limited face-to-face meetings.
Yasutoshi Iriyama, Principal Investigator
Nagoya University

Contents

Member Introductions
		 Researchers

3		 Research Assistants

4

Research Achievements
		 Model Interface (Gp-A01)
Advanced Analysis (Gp-A02)

5
6

		 Computational & Data Science (Gp-A03)

7

Design of Functional Interface (Gp-A04)

8

Activity Reports
		 Conferences Partially Supported
		 by the Interface IONICS Project9

Symposiums and Seminars

9International Training Program Reports

10

Domestic Training Program Reports

11Member Introductions 3

Member Introductions
Researchers
Gp-A02

Hirofumi Tsukasaki
Osaka Prefecture Univ. Specially-appointed
Associate Professor (Mori Gr.)
/ Transmission electron microscopy
I obtained my PhD in 2016 from Waseda University, where I analyzed thedomain structure of ferroelectrics using transmission electron microscopy(TEM). Thereafter, I moved to materials science research at Osaka
Prefecture University as a postdoctoral fellow under Professor Shigeo
Mori. Since April 2021, I have been involved in the Interface IONICS project
as a specially appointed associate professor. My current research focuses
on glass and glass ceramics, whose physical properties are affected bytheir crystallite size, crystallinity, and crystal/amorphous interface
structure. To understand their ionic conduction mechanism, I am
currently analyzing the microstructure of glasses and glass ceramics by
TEM. Figure 1 shows a high-resolution TEM image of Li3PS4 glass, where
Li3PS4 nanocrystallites are dispersed in an amorphous matrix. Figure 2
shows dark-field images capturing the crystallization process of Li10 GeP2S12
glass. Nanocrystallites precipitate upon heat-treatment of the glass, as
denoted by the bright contrast. I would like to contribute to thedevelopment of materials for all-solid-state batteries by utilizing various
TEM observation techniques.

Figure 1. High-resolution TEM image of Li3PS 4 glass.

Figure 2. Dark-field images of the Li10 GeP 2S12 glass
heated in a TEM.

Gp-A04

Wataru Namiki
NIMS Postdoctoral Researcher (Tsuchiya Gr.)
/ Solid state ionics
I received my PhD from Tokyo University of Science in 2021. My research
focuses on nanoionic devices with magnetic properties, for memorystorage and artificial intelligence. In my PhD course, I fabricated an allsolid-state redox device with a solid-state Li-ion conductor (Fig. 1); thisdevice could manipulate the magnetic anisotropy in situ. I also establisheda quantitative method to analyze the direction of spontaneous
magnetization in a stacked device structure. The developed techniquerepresented a breakthrough new manipulation method that enables therotation of magnetization vectors (56°) at room temperature. In addition,
substantial manipulation of the magnetic anisotropy could also be
achieved (lowered as much as 40%) (Fig. 2). Such technology is applicable
to new-generation devices with spin dynamics, e.g., spin–torque oscillatorsand spin-wave waveguides. At present, I am actively involved in the studyof artificial intelligence with nanoionic devices.

Figure 1. Schematic of an all-solid-state redox device.

Figure 2. Distributions of magnetic anisotropy variations
at various gate voltages.

4Member Introductions

Research Assistants

Gp-A01

Satoshi Yamamoto
Nagoya Univ. M2 (Iriyama Gr.)/ Electrochemistry, Solid state ionics
My research subject is the elucidation of Li+ insertion/extraction
mechanisms in the graphene/LiPON (lithium phosphorus oxynitride glass)system. The Li+ desolvation reaction is the rate-limiting process for the Li+
insertion reaction into graphite in an organic liquid electrolyte, and thisreaction is absent in a solid electrolyte such as LiPON.
Epitaxial graphene with controlled layer numbers can be synthesized bythermal decomposition of single-crystalline SiC. Hence, using SiC-derived
graphene with an amorphous LiPON electrolyte enables the study of amodel interface of graphite (graphene)/solid-state electrolyte.
I often visit Prof. Norimatsu’s group (A01) at Nagoya University to
prepare graphene samples and also collaborate with Prof. Kumatani’sgroup (A02) at Tohoku University on scanning electrochemical microscopy
experiments. Visiting other labs is very exciting for me, and I am grateful tohave had the opportunity to participate in this project. There are still
numerous aspects of my research that I feel I do not fully understand, but I
intend to do my best while enjoying research.

Figure. Instrument for preparing epitaxial graphenesamples via thermal decomposition of SiC.

Gp-A02

Masaki Abe
Tohoku Univ. M2 (Takahashi Gr.)/ X-ray microscopy
Since I was assigned to the Takahashi group in 2020, I have beenworking on developing an X-ray ptychographic measurement system foruse in the “tender” X-ray region (2–5 keV). X-ray ptychography using
coherent X-rays is a lensless microscopy technique that provides realspace sample images with a resolution of several tens of nanometers or
better. We can also obtain chemical-state images of a sample by analyzing
the spatially resolved absorption spectra obtained using ptychographic
measurements at continuous energies near the absorption edge of thetarget elements. We are the first group to establish a ptychographic
measurement system in the tender X-ray region and have successfully
obtained spatially resolved absorption spectra (~24 × 24 nm2 ) of sulfurcontaining polymer particles at the S K-edge (~2.47 keV) (right figure).
One of the promising applications of this method is cathode-active
materials of lithium–sulfur batteries, and we aim to elucidate the reaction
and degradation mechanisms of these materials during the charge–
discharge process by conducting operando measurements.

Figure. Reconstructed image of a sulfur-containing
polymer particle (top) and the spatially resolved
absorption spectrum (~24 × 24 nm 2) obtained from theimage (bottom).

Research Achievements 5

Research Achievements
2021.7– 2021.12

Gp-A01 Model Interface
Gp-A01 has provided model electrode materials
such as epitaxial thin-film electrodes and singlecrystalline solid electrolytes to its members, andcollaborative research with Gp-A02 and Gp-A03, in
addition to that within Gp-A01, has progressed
continually. A low-resistive graphene–solid electrolyte

interface was realized by eliminating the desolvation
process commonly observed in organic liquid electrolyte
systems. In addition, a standard solid-state battery
fabricated using NASICON-structured LATP combinedwith Fe2(MoO4)3 electrodes that can be treated even in air
was proposed. The results are highlighted as follows.

Highlight 1 A01-A02 joint paper

An appropriate reference and counter electrode in an all-solid-statebattery using NASICON-structured solid electrolyte
Y. Kee, Y. Suzuki, N. Ishigaki, M. Motoyama, Y. Kimura, K. Amezawa, Y. Iriyama.
Electrochem commun vol. 130, 107108 (2021)
https://doi.org/10.1016/j.elecom.2021.107108

Abstract
Anti-NASICON-structured Fe2(MoO4)3 (FMO) thinfilms are formed on NASICON-structured LATP solidstate electrolyte by pulsed laser deposition. The FMO
thin films operate at 3.0 V flat voltage vs. Li/Li+ within
the potential window of LATP. The FMO thin films on
LATP operates as with that in conventional organic
liquid electrolyte. Combining crystalline electrodesolid electrolytes with a similar framework structure at
relatively low temperatures will play an important role
in realizing reversible electrode reactions. An all-solidstate battery, FMO/LATP/LiCoO2, is developed toHighlight 2

apply the FMO as a reference and counter electrode,and the SSB operates at 1.0 V without visible capacity
fading. [Reproduced with permission of Elsevier]

A01 Research Gp Public Offering joint paper

Charge/discharge reactions via LiPON/multilayer-graphene interfaces
without Li+ desolvation/solvation processes
M. Motoyama, K. Miyoshi, S. Yamamoto, R. Sakakibara, Y. Yamamoto, T. Yamamoto, W. Norimatsu, Y. Iriyama.
ACS Appl. Energy Mater. vol. 4, 10442 (2021)
https://doi.org/10.1021/acsaem.1c00628

Abstract
Li+ desolvation process has been regarded as therate-limiting process in Li+ insertion reaction withgraphite anode in lithium-ion batteries. In contrast,
Li+ desolvation process is absent in solid-statebatteries. We fabricated thin-film all-solid-state cells bydepositing lithium phosphorus oxynitride glass (LiPON)
electrolyte onto a multilayer-graphene (MGr) film by
RF magnetron sputtering and measured the charge/
discharge performance of the cells. The charge transfer
resistance at the LiPON/MGr interface was significantly
small, although the LiPON/MGr interface was supposed
to have inorganic solid electrolyte interphase resulting

from the LiPON reduction decomposition. Consequently,
the dominant factor for the overall overpotential was theohmic loss for LiPON, and hence the capacity retention
was still maintained at 60% even at nearly 900C whenthe LiPON film thickness was 4 μm. [Reproduced withpermission of the American Chemical Society.]6

Research Achievements

Gp-A02 Advanced Analysis
This group aims to understand unique ion transport/
storage phenomena at solid-state interfaces throughcomprehensive analyses. We have been establishing/
improving various novel and advanced analytical techniquesand systematically applying them to typical model solidstate interfaces, such as a well-defined film electrode on asolid electrolyte and glass-ceramic electrolytes, which were
supplied by Gp-A01 and Gp-A04, respectively. Based on theobtained results, together with assistance from theoretical
calculations and simulations conducted by Gp-A03, we will
establish scientific principles that enable the design of highperformance solid-state interfaces.

Highlight 3

Structural characterization of the delithiated noncrystalline phase in a
Li-rich Li2VO2F cathode material
S. Hiroi, K. Ohara, O. Sakata.
Chem. Mater. vol. 33, pp. 5943–5950 (2021)
https://doi.org/10.1021/acs.chemmater.1c01466

Abstract
As a cathode material for lithium-ion batteries, thedisordered rock-salt-type Li2VO2F has a high theoretical
capacity of 462 mA h/g; however, this capacity fades
rapidly upon cycling. The atomic pair distributionfunction obtained from the X-ray total scattering
measurements indicates that the disordered rock-salt
crystal partially transforms to an amorphous phase on
delithiation. Using the extracted structural informationof the amorphous phase, a three-dimensional atomic
configuration was modeled by a combination of thedensity functional theory and reverse Monte Carlo
method. The structural model constructed thetetrahedral or pyramidal structure by V and anions.

These polyhedral structures are likely to involve theanion transfer between the crystalline and amorphous
phases. It induces the concentration fluctuation ofanions, O and F, in the crystalline phase and might be afactor for capacity fading of the Li2VO2F cathodematerial. [Reproduced with permission of the American
Chemical Society.]

Highlight 4

Lattice oxygen instability in oxide-based intercalation cathodes: A casestudy of layered LiNi1/3Co1/3Mn1/3O2
X. Hou, K. Ohta, Y. Kimura, Y. Tamenori, K. Tsuruta, K. Amezawa, T. Nakamura.
Adv. Energy Mater. vol. 11, pp. 2101005 (2021)
https://doi.org/10.1002/aenm.202101005

Abstract
Lattice oxygen stability in layered rock-salt
LiNi 1/3 Co 1/3 Mn 1/3 O 2−δ is investigated with a focus
on oxygen release behavior and relevant changes incrystal and electronic structures. Release of latticeoxygen facilitates cation mixing, transition metal slab
expansion, and Li slab contraction, thus deteriorating
the layered structure. As is revealed by X-ray
absorption spectroscopy, in the beginning stage ofoxygen release, the charge balance is compensatedby selective reduction of Ni3+. This suggests that highvalent Ni generated by delithiation or negative defectspecies, that is, lithium at the transition metal site,
aggravates oxygen release severely. These findings

provide a new research direction and guidelines forthe stabilization of lattice oxygen in oxide-based
intercalation cathodes. [Reproduced with permissionof the Wiley-VCH GmbH.]

Research Achievements

Gp-A03 Computational & Data Science
To construct a new theoretical framework forInterface IONICS, Gp-A03 has introduced two
strategies: a computational approach and a data
science approach. With the development of several
novel techniques and deep collaboration with the otherexperimental groups (Gp-A01, -A02, and -A04), we

have achieved a new understanding of interfacial
phenomena. Recently, two molecular dynamics studies
based on machine-learning potential provided novel
insights into the mixing and migration of atoms andions, leading to a deeper understanding of ionics.

Highlight 5Phase stability of Au-Li binary systems studied using neural network
potential
K. Shimizu, E.F. Arguelles, W. Li, Y. Ando, E. Minamitani, S. Watanabe.
Phys. Rev. B vol. 103, pp. 094112 (2021)
https://doi.org/10.1103/PhysRevB.103.094112

Abstract
The miscibility of Au and Li exhibits a potential
application as an adhesion layer and electrode material
in secondary batteries. To explore alloying properties,
we constructed a neural network potential (NNP) of
Au-Li binary systems based on density functional
theory (DFT) calculations. Using the constructed NNP,
we investigated the mixing energy of Au1-xLix with finecomposition grids, showing excellent agreement withDFT verifications. We found the existence of various
compositions with structures on and slightly above theconvex hull. Moreover, we found other stable phases.

Finally, we examined the alloying process starting fromthe phase separated structure to the complete mixing
phase. We found that when multiple adjacent Au atoms
dissolved into Li, the alloying of the entire Au/Li interface
started from the dissolved region. [Reproduced basedon Creative Commons license (CC BY 4.0).]

Highlight 6

Exploring the diffusion mechanism of Li ions in different modulated
arrangements of La(1-X)/3LixNbO3 with fitted force fields obtained via ametaheuristic algorithm
Z. Yang, R. E. Ward, N. Tanibata, H. Takeda, M. Nakayama, R. Kobyashi.
Solid State Ion vol. 366-367, pp. 115662 (2021)
https://doi.org/10.1016/j.ssi.2021.115662

Abstract
Li ion conductivity of A-sites deficient perovskite-type
LixLa(1-x)/3NbO3 (LLNO) has been investigated by materials
simulation. Our previous reports revealed that two typesof modulated structures, namely closed and striped
structures, derived from cation/vacancy arrangements
coexist in the La-rich layer, which affects Li-ion migration.
In this study, DFT-derived force-field molecular dynamics(FFMD) simulations were performed to investigate theeffect of a modulated structure on the migration behaviorof Li ions in LLNO compounds. The results indicate thatthe type of modulated arrangements of La/Vac has asignificant 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 inthe ab plane appeared to be much lower than along thec-axis, controlling the modulated arrangement of
LLNO is beneficial to eliminate La-ion blockage duringlong-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. [Reproduced based on Creative Commonslicense (CC BY 4.0).]7

8Research Achievements

Gp-A04 Design of Functional Interface
Gp-A04 designs innovative solid-state ionics
materials (SSIMs) through interface engineering. Withan increase in the concentration of grain boundaries,
charge carriers are efficiently accumulated in SSIMs,
resulting in new structures and functionalities. Suchfunctionalities have been applied to new solid-state
ionics devices. Collaborative studies with members of
Gp-A02 and Gp-A03 have further accelerated thedevelopment of new solid-state devices.

Highlight 7

Mechanochemical synthesis and characterization of Na3–xP1–xWxS4 solid
electrolytes
F. Tsujia, A. Nasua, A. Sakuda, M. Tatsumisago, A. Hayashi.
J. Power Sources vol. 506, 230100 (2021)
https://doi.org/10.1016/j.jpowsour.2021.230100

AbstractAll-solid-state sodium batteries are attracting
attention as next-generation batteries, owing to theirimproved safety and abundance of sodium resources.
To realize all-solid-state sodium batteries, solid
electrolytes with high sodium-ion conductivities are
required. In this study, Na3PS4 electrolytes with partial
substitution of P5+ with W6+ were investigated. The
Na3–xP1–xWxS4 sulfide-based solid electrolytes wereprepared via a mechanochemical process andconsecutive heat treatment. The Na2.85P0.85W0.15S4
electrolyte with Na vacancies exhibited an ionic
conductivity of 8.8 × 10−3 S cm−1 at 25 °C, which was
higher than that of Na3PS4 solid elect rolyte. The

all-solid-state batteries (Na-Sn/Na2.85P0.85W0.15S4/
TiS2) exhibited a reversible capacity of 140 mA h g−1
at a current density of 0.038 mA cm−2 and retained
the capacity of 115 mAh g−1 for 40 cycles at 0.130 mA
cm−2 at 25 °C. The Na3–xP1–xWxS4 samples prepared
via mechanochemistry are homogeneous electrolytes
free of crystalline WS2 impurities and are effective
for application to all-solid-state sodium batteries.
[Reproduced with permission of Elsevier.]

Highlight 8

The electric double layer effect and its strong suppression at Li+ solid
electrolyte/hydrogenated diamond interfaces
T. Tsuchiya, M. Takayanagi, K. Mitsuishi, M. Imura, S. Ueda, Y. Koide, T. Higuchi, K. Terabe.
Commun. Chem. vol. 4, 117 (2021)
https://doi.org/10.1038/s42004-021-00554-7

Abstract
The electric double layer (EDL) effect at solid
electrolyte/electrode interfaces has been a key topic
in many energy and nanoelectronics applications (e.g.,
all-solid-state Li+ batteries and memristors). However,its characterization remains difficult in comparison
with liquid electrolytes. Herein, we use a novel method
to show that the EDL effect, and its suppression at
solid electrolyte/electronic material interfaces, can becharacterized on the basis of the electric conduction
characteristics of hydrogenated diamond (H-diamond)based EDL transistors (EDLTs). Whereas H-diamondbased EDLT with a Li-Si-Zr-O Li+ solid electrolyte
showed EDL-induced hole density modulation over arange of up to three orders of magnitude, EDLT with a
Li-La-Ti-O (LLTO) Li+ solid electrolyte showed negligible

enhancement, which indicates strong suppressionof the EDL effect. Such suppression is attributed tocharge neutralization in the LLTO, which is due tovariation in the valence state of the Ti ions present.
The method described is useful for quantitatively
evaluating the EDL effect in various solid electrolytes.
[Reproduced with permission of Springer Nature.]Activity Reports

Activity Reports
Conferences Partially Supported by the Interface IONICS Project

Co-organized Symposium “Science on Interfacial Ion Dynamics for Solid
State Devices” of the 82nd Autumn Meeting of the Japan Society ofApplied Physics (Online)
Prof. Yasutoshi Iriyama, Nagoya Univ.
Sep. 11, 2021

Prof. Daisuke Kan, Kyoto Univ.
Prof. Wataru Norimatsu, Nagoya Univ.

One keynote lecture from Dr. Takada (NIMS); four
invited lectures from Prof. Suzuki (Tokyo Institute ofTechnology), Dr. Tsuchiya (NIMS), Dr. Yamamoto(JFCC), and Prof. Inoue (Kyushu University); and six
general lectures were presented. The number ofparticipants was approximately 80. The symposiumprovided a good opportunity to introduce the activities
of Interface IONICS to researchers closely associatedwith the Japan Society of Applied Physics.

Symposiums and Seminars

The 3rd Public Symposium on Interface IONICS (Online)
Sep. 16, 2021
The 3rd Public Symposium on Interface IONICS was
held online on Sep. 16, 2021. More than 300 people
registered for the symposium, which provided an
opportunity for scientists, engineers, and students todiscuss the diverse aspects of interfacial phenomena
related to solid-state chemistry, science, andtechnology. The conference featured three invited
talks from the academic and industrial communities.
Four representatives from each group in the Interface
IONICS project also delivered talks on recent researchadvances in the project. In addition, a poster session
was held from all members of Interface IONICS using
Zoom breakout rooms. These presentations triggered
detailed and exciting discussions throughout the
symposium.
Our first invited speaker, Dr. Mikinari Shimada, whois the director of LIBTEC, delivered a presentation
related to the development of solid-state batteries in
LIBTEC. Our second speaker, Prof. Kiyoshi Kanamura,
who is a distinguished professor studying the technology

Prof. Naoaki Yabuuchi, Yokohama National Univ.
of lithium-ion batteries, presented a history of theresearch progress on batteries, especially those with ametallic Li electrode. Finally, our third invited speaker,
Dr. Masayuki Nagamine, who is a chief scientist at
Murata Manufacturing Co., Ltd. delivered a talk on thehistory and development of Li-ion batteries in his
company and future prospects for the development ofsolid-state Li-ion batteries.

910

Activity Reports

International Training Program Reports

Visiting the Liquid Structure Research Group in the Wigner ResearchCentre for Physics, Budapest, Hungary
Oct. 17–Dec. 9, 2021

Dr. Hiroki Yamada, Japan Synchrotron Radiation Research Inst.

I visited the Liquid Structure Research Group in the
Wigner Research Centre for Physics in Budapest,
Hungary. The purpose of this visit was to reveal thestructural differences between Li3PS4 electrolytes
prepared by a typical mechanical milling method(denoted as “Glass”) and by mechanical milling under
different conditions (denoted as “MM”). These twomaterials have the same composition and density, but
MM exhibits greater Li-ion conductivity than Glass;thus, understanding their structural differences isimportant. For this reason, I worked with Dr. Laszlo
Puztai and Dr. Laszlo Temleitner, who are leading
developers of the Reverse Monte Carlo (RMC) softwareand specialists in analyzing amorphous/liquidmaterials.
During my visit, I was interested in combining
machine-learning potential (MLP) with RMC simulationand focused on developing this new method. In aprevious study, the structure of Li3PS4 electrolytes wasinvestigated by using the density functional theory(DFT) method. However, because of the associatedcalculation costs, this method is difficult to apply tolarger models (e.g., those with more than 1000 atoms
in total) for comparison with experimental data.
However, classical RMC sometimes produces a large
structure that compares favorably with experimental
results but has a thermodynamically unfavorable local
structure. This thermodynamically unfavorable local
structure hinders deep understanding of certain
aspects of materials, such as their physical properties.
Therefore, combining RMC with MLP, whose calculation
cost is much lower than that of DFT but provides
comparable results, is considered a promising
approach to overcoming these limitations.

Our procedure for using RMC-MLP in this manner is
described as follows. First, classical RMC wasconducted to fit both X-ray and neutron scattering
patterns. After a constant number of movements, theenergy difference between the models before and after
RMC was calculated using MLP and the program
decided whether these movements generated by RMC
were acceptable. From a continuous loop of RMC andenergy evaluations, structure models satisfying boththe experimental results and the thermodynamic
requirements were obtained at the end of thesimulation. The latest results will be presented at the
3rd Meeting for Young Scientists in the Interface
IONICS Project.
Using this new RMC-MLP approach, structure
models of MM and Glass were obtained. From these
sophisticated models, a slight difference in bondlengths was observed, consistent with the results
related to Li-ion conductivity. In the next step, thisapproach will be used to analyze the interface between
amorphous electrolytes, which can be characterizedusing X-ray/neutron/electron diffraction measurements
at the region of interest. The experimental data fromthese analytic methods might be noisy because of thesmaller beam and higher background. However, by
tuning the potential and experimental weight in the
RMC-MLP to minimize the effects from experimental
errors, we expect to extract the essential structuralfeatures of the interface.
I am grateful for this opportunity to participate in
the international training program of the Interface
IONICS project and to gain valuable experience incollaborating with prominent researchers abroad.

Photos of the meeting to share the latest results. In addition to the group members, Prof. Eckhard Spohr (University of Duisburg-Essen) and Prof. Philippe Bopp
(Université Bordeaux) kindly attended the meeting and provided helpful comments.

Activity Reports

Domestic Training Program Reports

Visiting the Kan group at Kyoto University
Jul. 7–9, 2021
I visited Prof. Kan’s group at Kyoto University with
Prof. Yabuuchi, who is my supervisor at Yokohama
National University, to learn high-pressure synthesis
methods for metal oxides. I am currently studying
high-capacity positive electrode materials, andthe larger reversible capacity for these electrodematerials originates from an anionic redox reaction.
This conclusion (i.e., charge compensation by anionicspecies), was made on the basis of experimental
observations using X-ray absorption spectroscopy
at the oxygen K-edge region. Nevertheless, the lackof a reference material for anionic redox, i.e., stablematerials in the ambient condition with holes (orradicals on oxygen), hinders clear understanding of
the electronic structures for oxygen in high-capacity
electrode materials. Therefore, a reference material
is necessary. High-pressure synthesis enables us tosynthesize such a unique material, e.g., SrFeO3. We
expect that the high-pressure method can be used
to synthesize reference materials for spectroscopic

Ms. Nanaka Shimada, Yokohama National Univ.
studies of oxygen. We are grateful to the Interface
IONICS project for providing excellent collaboration
opportunities.

Domestic Training Program Reports

Visiting the Nakayama’s laboratory in Nagoya Institute of Technology
Nov. 11–12, 2021
I visited Prof. Nakayama’s laboratory at Nagoya
Institute of Technology to learn machine learningtechniques. Machine learning is an information
processing technology based on statistical mathematics
and has become a promising analytical tool in thematerials science field. Applying machine learning toexperimental data enables experimental scientists todevelop battery materials and attain new findings inbattery research.
On the first day, Prof. Nakayama gave an overview
of materials’ descriptors for machine learning (e.g.,

Assist. Prof. Kosuke Kawai, Waseda Univ.
composition, structure, and physical properties) andBayesian optimization. After his lecture, students in thelaboratory taught me how to use Python scripts, which
they had developed, through hands-on training. On thesecond day, I built a programing environment on mylaptop by installing software and revising the scripts forour datasets. We hope that the machine learningtechniques will be useful for developing battery materials
in our laboratory. I am grateful to the Interface IONICS
project for providing such beneficial collaboration
opportunities.

11

Newsletter vol.5
Publisher/Contact
Office for Scientific Research on Innovative Areas:
Science on Interfacial Ion Dynamics for Solid State Ionics Devices
TEL: +81-52-789-3576
E-mail: office@int-ionics.material.nagoya-u.ac.jp
https://interface-ionics.jp/en/index.html

Date of issue: March 2022