Science on Interfacial Ion Dynamics for Solid State Ionics Devices

Newsletter Vol.6
September 2022

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

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Preface | Contents

Preface
The fourth year of Interface IONICS started in April 2022, and 22
researchers from 17 universities or institutes joined the project as “publicly
offered research” members, conducting research for two years. The
Interface IONICS program continues to promote the fusion of different
academic research fields, promote the careers of young researchers, foster
international friendship, and collaborate with national projects currently
underway.
Finally, we hope that all of you maintain good health under these very
difficult conditions.
Yasutoshi Iriyama, Principal Investigator
Nagoya University

Contents

New Members
Publicly Offered Researchers / 2022.4-2024.3
		 Model Interface (Gp-A01)
Advanced Analysis (Gp-A02)

3
4

		 Computational & Data Science (Gp-A03)

5

Design of Functional Interface (Gp-A04)

5

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

7
8

		 Computational & Data Science (Gp-A03)

9

Design of Functional Interface (Gp-A04)

10

Activity Reports
		 Interface IONICS Online Symposium 2022

11

		 The 3rd Interface IONICS Seminar

11

New Members 3

New Members
Publicly Offered Researchers2022.4-2024.3
In April 2022, we welcomed 22 “publicly offered researchers,” who will contribute to our project with their
proposal-based research.

Gp-A01 Model Interface
Yuki Maruyama
Assistant Professor / Univ. Yamanashi / Crystal growth
Bulk single crystals are useful for our understanding interfacial properties. The purposeof my study is to grow bulk single crystals of Li+-ion conductors by the floating-zone method
and to clarify their basic physical properties such as their anisotropic ionic conductivity.

Yuta Maeyoshi
Researcher / AIST / Electrochemistry
I aim to develop organic solid electrolytes and design electrolyte/Li-metal interfaces thatexhibit high ion transport and accumulation properties to facilitate dense Li deposition, highLi plating/stripping efficiency, and long cycle life of Li-metal anodes.

Yuta Kimura
Assistant Professor / Tohoku Univ. / Solid state ionics
Mechanical stress can strongly affect the interfacial properties of solid state ionics
materials (SSIMs). In this study, I aim to quantitatively evaluate the influence of stress onmaterial–interfacial properties of SSIMs and to provide deeper insights into the interfacial
phenomena in SSIMs.

Takayuki Doi
Professor / Doshisha Univ. / Electrochemistry
We introduce a solid electrolyte interphase between a Si thick-film electrode and a solid
electrolyte to facilitate interfacial Li+-ion transfer. The morphology, structure, andcomposition of the interphase are investigated to elucidate factors that enable the rapid
interfacial transfer and high-density storage of Li+ ions.

Wataru Norimatsu
Associate Professor / Nagoya Univ. / Surface-structure physics and properties
I investigate the intercalation and desorption phenomena of Li+ ions in high-quality
samples of large-area epitaxial graphene. Using atomic-force microscopy and Raman
spectroscopy, I plan to reveal how and from where Li+ ions are intercalated.

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New Members

Munekazu Motoyama
Associate Professor / Kyushu Univ. / Electrochemistry
My goal is to understand how stable Li plating/stripping cycles via Li/oxide–solidelectrolyte interfaces are possible under hydrostatic pressures on the order of 102 MPa,
which are much greater than the yield strength of Li (approximately 1 MPa).

Gp-A02 Advanced Analysis
Takahiro Ito
Associate Professor / Nagoya Univ. / Photoemission spectroscopy
The purpose of my study is to elucidate the electronic structure of solid state ionicmaterials (bulk solid-electrolyte single crystals) using angle-resolved photoemission
spectroscopy. Photo- or electric-field-induced modulations will also be investigated to gain
insights into the mechanism of the ion-conduction process.

Ryotaro Aso
Associate Professor / Kyushu Univ. / Electron microscopy
The objective of my study is to reveal the relation between structural strain/distortionand ion diffusion at solid-state ionic interfaces using a combination of operando
atomic-resolution scanning transmission electron microscopy, energy-dispersive X-ray
spectroscopy, and electron energy-loss spectroscopy.

Yasuto Noda
Assistant Professor / Kyoto Univ. / Magnetic resonance (NMR and NQR)
The purpose of my study is to develop a magnetic resonance method that enables
noncontact and nondestructive probing of the electric field involving the conduction andaccumulation of ions at the interface of an ionic conductor by using the nuclear spins as aspy.

Takuya Majima
Associate Professor / Kyoto Univ. / Ion-beam science
To reveal the ion transport and storage behavior near the interfaces of solid state ionics
materials (SSIMs), we directly observe the spatial (depth) distribution of Li atoms and ionsnear the interface using time-of-flight elastic recoil detection analysis (TOF-ERDA) with
MeV-energy heavy-ion beams.

Kentaro Yamamoto
Associate Professor / Nara Women’s Univ. / Inorganic materials chemistry
The purpose of my study is to use operando time-resolved X-ray reflectivity to observe
structural changes at solid–solid interfaces during ion transport reactions and to clarify the
relationship between the structural changes and the ion transport at the interfaces.

New Members 5

Gp-A03 Computational & Data Science
Shusuke Kasamatsu
Associate Professor / Yamagata Univ. /Ab initio thermodynamics
My research aim is to provide a consistent picture of electrochemical solid–solidinterfaces by considering the huge configurational degrees of freedom of carriers anddopants as well as the electrochemical potential of ions and electrons in electrodes.

Ryo Kobayashi
Assistant Professor / Nagoya Inst. of Tech. / Computational materials science
The goal of my project is to understand the mechanism of grain-boundary resistance toion migration in solid-state electrolyte materials from an atomistic perspective. We havedeveloped a high-throughput method of producing force fields and will use it to perform
molecular dynamics simulations.

Koji Shimizu
Assistant Professor / Univ. of Tokyo / Density functional theory calculations
With the aid of DFT calculations and machine learning potentials, we will investigate theion dynamics across electrode–solid-electrolyte interfaces. By analyzing structural factors
and compositional variations, we will clarify the atomic-scale origin of the interface
resistance.

Gp-A04 Design of Functional Interface
Atsunori Ikezawa
Assistant Professor / Tokyo Inst. of Tech. / Electrochemistry
We develop reference electrodes applicable to solid electrolytes and construct
all-solid-state four-electrode cells to investigate Li+-ion transfer at solid–solid interfaces
using electrochemical measurements such as cyclic voltammetry and AC impedance
spectroscopy.

Kazuhiro Hikima
Assistant Professor / Toyohashi Univ. Tech. / Inorganic materials chemistry
My research topic is to synthesize sulfide-type solid electrolytes using a liquid-phasemethod with control of crystalline–amorphous interfaces. A secondary objective is toprepare a cathode composite containing a cathode active material and solid-electrolyte
solution via a liquid-phase process for an all-solid-state battery.

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New Members

Daisuke Mori
Associate Professor / Mie Univ. / Solid-state chemistry
Both high electronic conductivity and high ionic conductivity of an electrode are desired
to improve the input–output characteristics of all-solid-state batteries. In this study, acathode material with high electronic conductivity is investigated to develop a cathode/electrolyte composite with high capacity and good input–output characteristics.

Saneyuki Ohno
Assistant Professor / Kyushu Univ. / Materials science
Although fast carrier transport within an electrode is paramount for energy storage
devices, carrier mobility in solid state composite electrodes with a high interfacial area
density is surprisingly slow. My research aims to better understand the origin of such sluggish
transport, with the objective of opening a path for the use of insulating active materials.

Atsushi Inoishi
Assistant Professor / Kyushu Univ. / Inorganic materials
Conversion-type electrodes such as MgH2 form the electrolyte LiH during lithiation.
Understanding the mechanism of this in situ electrolyte formation enables the developmentof a solid-state battery with a high energy density. I study the details of the mechanism (e.g.,
the redox couple and the distribution of the formed electrolyte) in this type of electrode.

Teruo Kanki
Associate Professor / Osaka Univ. / Nanomaterials physics
My research objective is the development and analysis of an exotic transistor in which
proton motion is controlled by an electric field at a VO2 channel interface. This control leads
to both switching and memory functions, accompanied by a structural transformation
between insulating HVO2 and metal-like VO2.

Takashi Tsuchiya
Principal Researcher / National Inst. Materials Science / Solid state ionics
In my study, I will tackle the development of novel physical-property tuning devices basedon the principles of solid state ionics by focusing on electric carrier accumulation
mechanisms (e.g., redox and electric-double-layer effects) in the vicinity of solid(electrode)–solid-electrolyte interfaces.

Kan Hatakeyama-Sato
Assistant Professor / Waseda Univ. / Polymer chemistry
My research focuses on emerging glassy-type solid-polymer electrolytes composed ofcharge-transfer complexes. Although these electrolytes’ ion-transport processes have notyet been revealed, optimal interface design should be a key to obtaining organic conductors
with superionic properties.

Research Achievements 7

Research Achievements
2022.1–2022.6

Gp-A01 Model Interface
Gp-A01 has been conducting fundamental research on model interfaces using thin-film and single-crystal materials.
Some of their recent topics are highlighted as follows.

Highlight 1 A01 and A04 joint paper

Reaction mechanism of Li2MnO3 electrodes in an all-solid-state thin-film
battery analyzed by operando hard X-ray photoelectron spectroscopy
K. Hikima, K. Shimizu, H. Kiuchi, Y. Hinuma, K. Suzuki, M. Hirayama, E. Matsubara, R. Kanno.
J. Am. Chem. Soc. vol. 144, pp. 236–247 (2022)
https://doi.org/10.1021/jacs.1c09087

Abstract
Li2MnO3 is a promising cathode candidate for Li-ion
batteries because of its high discharge capacity;
however, its reaction mechanism during cycling has
not been sufficiently explicated. Observations of Mn
and O binding energy shifts in operando hard X-ray
photoelectron spectroscopy measurements enabled
us to determine the charge-compensation mechanismof Li2MnO3. The O 1s peak splits at an early stage during
the first charge, and the concentration of lower-valence
O changes reversibly with cycling, indicating theformation of a low-valence O species that intrinsicallyparticipates in the redox reaction. [Reproduced withpermission of the American Chemical Society. ]Highlight 2 A01 and ALCA-SPRING joint paper

In-situ X-ray diffraction of LiCoO2 in thin-film batteries under high-voltage
charging
T. Ohnishi, K. Mitsuishi, K. Takada.
ACS Appl. Energy Mater. vol. 4, pp. 14372–14379 (2021)
https://doi.org/10.1021/acsaem.1c03046

Abstract
LiCoO2 has been used as the cathode material
employed in lithium-ion batteries since their birth, andefforts to improve its performance are still in progress.
For example, complete use of lithium provides
the theoretical capacity as high as 274 mAh g−1; however,charge-discharge cycling with such a high capacity
leads to rapid degradation. The degradation mechanism
has been intensively studied in order to increase thepractical capacity. Although phase transitions taking
place in high-voltage charging has been considered toaffect the cycling performance, side reactions inducedby the high-voltage charging always overlap to blur theeffects of phase transitions on the electrode properties.
This study has unveiled the relation between the phasetransition and electrode properties by employing a solid
electrolyte that suppresses the side reactions
efficiently. Electrochemical impedance spectroscopy
combined with in-situ X-ray diffraction shows the clear
correlation between phase transition from O3 to H1-3
and drastic increase in the electrode resistance. The
increasing resistance is attributable to formation of
narrow interlayers with gallery height of 4.2 Å that
impede lithium-ion diffusion. [Reproduced withpermission of the American Chemical Society.]8Research 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 analyticaltechniques and systematically applying them to typicalsolid state interfaces, such as a well-defined film
electrode on a solid electrolyte and glass-ceramicelectrolytes, which were supplied by Gp-A01 and
Gp-A04. On the basis of the obtained results, together
with assistance from theoretical calculations andsimulations conducted by Gp-A03, we will establish
scientific principles that enable the design ofhigh-performance solid state interfaces.

Highlight 3 A02 and A04 joint paper

Crystallization behaviors in superionic conductor Na3PS4
H. Nakajima, H. Tsukasaki, J. Ding, T. Kimura, T. Nakano, A. Nasu, A. Hirata, A. Sakuda, A. Hayashi, S. Mori
J. Power Sources. vol. 511, 230444 (2021)
https://doi.org/10.1016/j.jpowsour.2021.230444

AbstractAll-solid-state batteries based on sodium compounds are regarded aspromising candidates for next-generation rechargeable batteries. A practicalsodium battery requires an electrolyte with high conductivity. Cubic Na3PS4
exhibiting high conductivity of over 10−4 S cm−1 is obtained by crystallizing
amorphous. Amorphous Na3PS4 crystallizes in a cubic structure andsubsequently is transformed into a tetragonal phase around 350ºC uponheating. In-situ observation by transmission electron microscopy (TEM)
demonstrates that the crystallite size rapidly increases during the cubic totetragonal phase transition. Moreover, electron diffraction analyses revealthat amorphous domains and nano-sized crystallites coexist in the cubic
phase, while the tetragonal phase contains micro-sized crystallites. The
nano-sized crystallites and the composite formed by crystallites andamorphous domains are most likely attributed to the increase in ionic
conductivity in the cubic phase. [Reproduced with permission of Elsevier.]

Highlight 4 A02 and ALCA-SPRING joint paper

Ion dynamics of the LixMn2O4 cathode in thin-film solid-state batteries
revealed by in situ Raman spectroscopy
N. Kuwata, Y. Matsuda, T. Okawa, G. Hasegawa, O. Kamishima, J. Kawamura.
Solid State Ion. vol. 380, 115925 (2022)
https://doi.org/10.1016/j.ssi.2022.115925

Abstract
In situ Raman spectroscopy of thin-film batteries isused to study the structural changes of LixMn2O4
during battery operation. Thin-film batteries with
Li/Li3PO4/LiMn2O4 structures are fabricated, and insitu Raman measurements are performed from boththe front and back sides of the thin-film battery.
The LixMn2O4 in the thin-film batteries presentcharacteristic Raman spectra originating from the α, β,and λ phases. Notably, the Raman intensity of LixMn2O4
shows hysteresis during charging and discharging
when observed from the front-surface configuration,
whereas only small hysteresis is observed whenmeasured from the back surface. This behavior is
explained by the lithium diffusion and phase transition
behavior in LixMn2O4. [Copyright 2022 The Authors,with permission from CC BY-NC-ND 4.0.]

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

new techniques and through deep collaboration withthe experimental groups (Gp-A01, -A02, and -A04), we
have achieved new understanding of interfacial
phenomena.

Highlight 5

Simulation of the compaction of an all-solid-state battery cathode withcoated particles using the discrete element method
M. So, G. Inoue, K. Park, K. Nunoshita, S. Ishikawa, Y. Tsuge.
J. Power Sources. vol. 530, 231279 (2022)
https://doi.org/10.1016/j.jpowsour.2022.231279

Abstract
The simulation of a cold-pressed electrode, which
consists of active material (AM) particles coated with asolid electrolyte (SE), of an all-solid-state battery, ispresented. The aim of this study is to elucidate theeffect of the SE coating structure. The new method wedeveloped to simulate the SE-coated AM particles isbased on a discrete element method. Simulation of the
AM as clustered particles held together by fusion
bonding allows the mechanical damage to the AM to be
reproduced simultaneously. For a ductile SE material,
new fusion bonding contacts with other particles could
develop when pressure is applied. Our simulations
suggest that the SE coating promotes more effective

ionic transport, in contrast to conventional particle
mixture, owing to the superior percolating network. At
low mold pressures, electron transport between the
AM particles is disrupted because of the shielding
effect of the SE coating. This effect vanishes at higher
mold pressures. Both types of electrodes have similar
damage profiles, with damage concentrated near thecurrent collector. [Reproduced with permission of
Elsevier.]

Highlight 6 A03 and A01 joint paper

STEM-EELS spectrum imaging of an aerosol-deposited NASICON-type
LATP solid electrolyte and LCO cathode interface
S. Muto, Y. Yamamoto, M. Sakakura, H.-K. Tian, Y. Tateyama, Y. Iriyama.
ACS Appl. Energy Mater. vol. 5, pp. 98–107 (2022)
https://doi.org/10.1021/acsaem.1c02512

AbstractAll-solid-state batteries (ASSBs) are promising
candidates for application as next-generation
high-power supply in electric vehicles. ASSBs offer;
however, the high interfacial resistance between
the positive electrode and solid electrolyte due tosolid−solid contact reactions at elevated temperatures
limits their applications. To address these issues, theeffect of thermal annealing on the interfacial structure
between a NASICON-type LATP solid electrolyte and a
LCO cathode in an ASSB fabricated by aerosol
deposition was investigated, using STEM-EELS
spectral imaging. Metastable degraded low-density
transition layers were formed between LATP and LCO
in the as-deposited sample. A significant reduction ininterfacial resistance was achieved after thermal
annealing at 250−300 °C, which was mainly attributed

to structural recovery in this temperature range.
However, thermal annealing at 400 °C resulted inincreased interfacial resistance due to the formation ofa Co3O4-like spinel blocking layer at the LATP/LCO
interface. These findings were consistent withtheoretical predictions of Li and O transfer between
the layers due to thermal annealing. [Reproduced
based on Creative Commons license (CC BY 4.0).]910Research 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 in 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 A04 and A02 joint paper

Nanosized and metastable molybdenum oxides as negative electrodematerials for durable high-energy aqueous Li-ion batteries
J. Yuna, R. Sagehashi, Y. Sato, T. Masuda, S. Hoshino, H. B. Rajendra,
K. Okuno, A. Hosoe, A. S. Bandarenka, N. Yabuuchi.
Proc. Natl. Acad. Sci. U.S.A. vol. 118, e2024969118 (2021)
https://doi.org/10.1073/pnas.2024969118

Abstract
The development of inherently safe energy
devices is a key challenge, and aqueous Li-ion
batteries draw large attention for this purpose.
Herein, a type of a negative electrode material (i.e.,
LixNb2/7Mo3/7O2) is proposed for high-energy aqueous
Li-ion batteries. LixNb2/7Mo3/7O2 delivers a large
capacity of ~170 mA h g−1 with a low operating potential
range of 1.9 to 2.8 versus Li/Li+ in 21 m lithiumbis(trifluoromethanesulfonyl)amide (LiTFSA) aqueous
electrolyte. A full cell consisting of Li1.05Mn1.95O4/
Li9/7Nb2/7Mo3/7O2 presents high energy density of
107 W h kg−1 as the maximum value in 21 m LiTFSA
aqueous electrolyte, and 73% in capacity retention

is achieved after 2,000 cycles. Furthermore, hard
X-ray photoelectron spectroscopy study reveals thata protective surface layer is formed at the surfaceof the negative electrode, by which the high-energy
and durable aqueous batteries are realized with
LixNb2/7Mo3/7O2. [Reproduced with permission of
National Academy of Science.]

Highlight 8

Electrochemical control and protonation of the strontium iron oxide
SrFeOy by using proton-conducting electrolyte
Y. Isoda, D. Kan, Y. Ogura, T. Majima, T. Tsuchiya, Y. Shimakawa.
Appl. Phys. Lett. 120, 091601 (2022)
https://doi.org/10.1063/5.0083209

Abstract
To electrochemically control structural and transport
properties of oxygen-deficient perovskite SrFeOy(2.5 ≦ y ≦ 3) (SFO) epitaxial films, we employedelectric-field-effect transistor structures in which
the proton-conducting solid electrolyte Nafion
is used as a gate insulator. When a positive gate
voltage (VGS) is applied and protons are injected
toward the film channel layer, the SFO films areelectrochemically reduced, leading to increases in
the channel resistance. On the other hand, when anegative VGS is applied and protons are removed, theSFO films are oxidized, and as a result, the channel
resistances decrease. In addition, we found that theelectrochemically reduced SFO films accommodate

protons, forming the proton-containing oxide HxSrFeO2.5
whose proton concentration is determined by elastic
recoil detection analysis to be x ~0.11. Our results
indicate the usefulness of the proton-conducting solid
electrolyte for electrochemically controlling transition
metal oxides and for exploring proton-containingoxides. [Reproduced with permission of the American
Institute of Physics.]

Activity Reports

Activity Reports
Symposiums and Seminars

Interface IONICS Online Symposium 2022
Mar. 29, 2022

Dr. Yoshitaka Tateyama, NIMS

The Interface IONICS International Online Symposium2022 was held on March 29, 2022. The focus was“solid electrolyte ionics” and “cathodes for higher
energy density,” and two California professors who aretheorists were invited. Prof. Shyue Ping Ong (UC San
Diego) talked about the cutting-edge computational
analysis of room-temperature ion conductivity, including
works based on machine-learning potentials. Prof.
Hayashi and Prof. Kobayashi presented their recent
studies on ion diffusion in sulfide electrolytes and ion
diffusion around grain boundaries, respectively. Prof.
Anton Van der Ven (UC Santa Barbara) introduced thelatest works on positive electrode mechanisms,
including oxygen redox phenomena. Prof. Okubo andProf. Yabuuchi then provided their observations andtheories on the oxygen redox mechanisms in Li-rich
positive electrode materials. Intensive debates ensued
about the interpretation of the calculation results andthe underlying mechanisms in both topics. We thank allof the speakers and participants for the active andsubstantial discussion and look forward to our next
opportunity to host a topical international symposium.

Symposiums and Seminars

The 3rd Interface IONICS SeminarJan. 6–7, 2022

Assoc. Prof. Gen Inoue, Kyushu Univ.

The 3 rd Interface IONICS seminar was held as a
hybrid meeting on January 6 and 7, 2022. We had 51
in-person and 24 virtual attendees in total. The plenary
lectures were delivered by Dr. Hikari Sakaebe (AIST)
and Prof. Naoaki Yabuuchi (Yokohama National University).
Moreover, Dr. Hiroki Yamada (JASRI) reported on his

interesting experience in the “International Training
Program” in Budapest, Hungary. From the oralpresentations by students/postdocs, two outstanding
young researchers were awarded Interface IONICS
awards.

Interface IONICS Award Winners
Keisuke Yoshikawa
Iriyama Lab, Nagoya Univ.
Interfacial reactions at anti-perovskite-structured Li2OHBr/electrode interfaces

Makoto Takayanagi
Higuchi Lab, NIMS and Tokyo Univ. of Sci.
In-situ observations of oxygen transfer behaviors at various Li+-conducting solid-stateelectrolyte/electrode interfaces

11Newsletter vol.6
Publisher/Contact
Office for Scientific Research on Innovative Areas:
Science on Interfacial Ion Dynamics for Solid State Ionics Devices
TEL: +81-52-789-3235
E-mail: office@int-ionics.material.nagoya-u.ac.jp
https://interface-ionics.jp/en/index.html

Date of issue: September 2022