Impact Objectives• Undertake research on the synthesis of core-shellparticles that combine functional materials• Optimise various structurally controlled catalyst
particles on the electrodes of metal-air secondary
batteries and water electrolysis cells

Power and more
Professor Tomoya Ohno and Associate Professor Shigeto Hirai discuss their novel approach to materials
science and how to combine the field with chemistry to overcome technological barriers

Professor
Tomoya Ohno

Associate Professor
Shigeto Hirai

Can you talk a little about your researchbackground in inorganic materials
engineering?
TO: I belonged to the research groupof Professor Hisao Suzuki of Shizuoka
University, Japan, and Professor Marija
Kosec, Professor Barbara Malič of Jožef
Stefan Institute, Slovenia, and we conducted
research on the chemical solution depositionof piezoelectric thin films. By combining themolecular design technology in the chemicalsolution process and powder engineeringthat I have cultivated so far, I developed
research on the synthesis of core-shellparticles that combine functional materials.
SH: I researched my PhD in Professor
Paul Attfield’s group at the University ofEdinburgh, UK. Since 2015 at the Kitami
Institute of Technology, I have beenconducting research on electrochemical
catalysts centred on the Oxygen Evolution
Reaction (OER). Meanwhile, I was fascinatedby the great potential of structural control ofnanocoating and catalyst particles. Therefore,
I started joint research with Professor
Tomoya Ohno. As a result of investigating
the effect of chemical molecular designon oxygen evolution catalytic ability, we
succeeded in enhancing both OER activity
and stability in Ca1-xSrxRuO3. Currently,
we are mounting and optimising various
structurally controlled catalyst particles on
the electrodes of rechargeable metal-airbatteries and water electrolysis cells.
Your latest research is developing core-shell
nanomaterials for energy storage devices
using chemical solution methods. Briefly,
can you explain in layperson terms what thisinvolves?

micrometre order materials. However, thechemical reaction-based coating I developed
is able to coat nanoparticles with functional
materials containing composite metal oxides
at the nano level. Therefore, we are currently
using this technology for the creation ofbattery materials, but in the future, we believethat it can be applied to the development ofa wide range of functional materials, such as
magnetic materials and optical materials.
In what ways can you progress your findings
to be applied to industrial applications?

TO: These core-shell nanomaterials are
essential for the catalysis of certain key
reactions in next generation batteries.
However, the active sites of the catalystmaterial may elute into the electrolyte
solution during repeated charging anddischarging. If prevented, it will be possible
to create a battery that can be used for a longtime. We are aiming to create this protection
by coating the catalyst particle surface ina thin film. However, when a coating isapplied, the catalytic activity may become
lower even if dissolution can be prevented.
To anticipate these effects, it is necessary todesign the precursor of the coating material
at the molecular level and develop core-shellparticles with appropriate structure.

TO: Currently, there are many hurdles
in applying the synthesis of core-shell
nanoparticles from the laboratory level tomass production processes. At present, myresearch group is talking with a Japanesemachine maker about the development ofequipment that can apply the process that
I have proposed for mass production. Ifsuch a device will be realised, we believethat the material proposed this time may be
implemented in industrial applications. We
hope that the development of all solid-state
rechargeable lithium-ion batteries, which
we are currently researching, will lead to thecreation of large batteries that are expected
to be installed in automobiles, etc., in thefuture.

What is the ultimate impact of your studies?

SH: We are also continuously searching
for, and implementing, electrode catalysts
with high durability and low-cost synthesis
methods and starting materials with the aimof next generation metal-air battery for cellphones that require less frequent charging.

TO: Many of the currently reported
technologies for coating particles aredesigned for coating basic materials such as
silica and core particles are often targeted atwww.impact.pub 43

Group members of the Inorganic Materials Chemistry Laboratory

Ohno and Hirai are using their combined
expertise to overcome the issues of catalysis
and stability of the cathode. Ohno has
extensive experience in the coating offunctional complex metal oxide materials.
‘I came to realise that the coating of thecatalyst at the metal-air battery cathodemight hold the key to stabilising its function,’
highlights Ohno. Hirai brings the knowledgeof the electrochemistry underlying therechargeable metal-air battery. This means
he is best placed to suggest candidate
coating compounds that will act as effective
catalysts. It’s this interaction between
traditional materials science and chemistry
that’s driving the success of Ohno and Hirai’swork. ‘We are using the power of chemistry
to develop various high-performance

Overcoming
technological blocks
Material scientists at the Kitami Institute of Technology have developed novel processes by which metalair batteries may become the energy storage cornerstone of the 21st century

The material sciences constitute one of
the cornerstones of modern technology.
This broad field concerns the preparation,modification and application of complex
materials and compounds. The knowledge
required covers physics, chemistry andengineering which work in concert to create
the key components, surfaces and devices.
These include everything from the key
surfaces inside of batteries to the physicalarchitecture of electronics, and even thespecial coatings employed on touchscreens.
The breadth of the field also accounts forthe wide range of specialisms within thediscipline. This is necessary due to thecomplexity and unpredictability of manyof the novel materials and techniques
being deployed. It requires significant
knowledge and experience to understandhow an additional element might interact ina catalyst or how a particular compound will
behave when coating another material.
COLLABORATION FOSTERS RESULTS
Professor Tomoya Ohno and Associate
Professor Shigeto Hirai are examples ofthe broad range of expertise required forsuccessful materials science. Whilst they arebased at the Kitami Institute of Technology,
44 www.impact.pub

Kitami, Japan, Ohno specialises in surface
coatings and powder technology whilst
Hirai is an expert in electro- and solid-statechemistry. Together they started collaborating
on research concerning the compositionand coating of catalysts used in rechargeable
metal-air batteries. All batteries rely heavily
on both their electrochemistry and thematerial composition of their catalysts,
so such work is a natural fit for Ohno andHirai’s specialisms. ‘We are developing
long-life, high-performance bi-functional
catalyst particles that can be mounted onrechargeable metal-air batteries, as well as
proposing positive particles coated with asolid electrolyte which are intended for use inall-solid state lithium-ion batteries,’ outlines
Ohno.
Metal-air batteries, unlike traditional battery
designs, have an anode made of a puremetal and a cathode that is, functionally, theair. Whilst, chemically, the cathode is the air
itself, there is typically a cathode material
that catalyses the oxygen evolution reactionthat is a core part of the process,’ explains
Ohno. ‘The major advantage of the metal-air
battery is the extremely high energy density
associated with its design.’ This means thatthe battery design has the potential to store

a lot more energy than most conventional
batteries. Consequently, metal-air batteries
have the potential for widespread use inelectric cars, national grid energy storage
and, of course, in all devices that require
regular charging. In the former, such anincreased battery life would be transformative
for the industry.
NEXT GENERATION ENERGY STORAGE
Whilst metal-air batteries have a potential
energy capacity which is up to 30 times thatof conventional lithium-ion batteries, its
technology is still in progress. ‘The mainconcern of metal air batteries is the reliabilityof the cathode, particularly the rate of theoxygen reduction and oxygen evolution
reaction,’ explains Ohno. ‘This means thatbattery discharge is not reliable enough for
power-heavy uses. At the same time, it also
makes the recharging process inefficient,’ hesays. Another issue with metal-air batteries
has been the harsh effects of charging athigh cathodic potentials, potentially causing
irreversible damage to it. Whilst there areother issues, the greatest issues preventing
the broad application of metal-air batteries lie
in its cathode.

were able to identify a calcium-strontiumruthenium-oxide with a protected layer that
had the potential to be the catalyst theyneeded.
Once the compound was identified,formulated and coated onto the material thatwill catalyse the reaction at the cathode, it
was, of course, necessary to test its potential
in an actual metal-air battery. The results
have been extremely encouraging. The
new material was able to improve both thecharge and discharge capacity of the battery.
‘The coating of the protective layer on thebi-functional catalyst particles that weremounted on the metal-air secondary battery
did not impede the catalytic activity, instead
it significantly improved the stability, as we

We are now well positioned to upscale the testing andseek out industrial partners capable of scaling up
manufacture and further testingmaterials,’ confirms Ohno. ‘In chemistry, it
is very common that the reaction will notproceed ideally, but occasionally we are able
to realise what we originally envisioned andhave reaffirmed the power of chemistry inmaterials science.’
THE IMPORTANCE OF NANO
Broadly speaking, Ohno and Hirai are usingchemical reaction and powder engineering
techniques to add thin films of protective
materials for the potential catalysts that could
help stabilise the cathode. This is a liquid
phase technique that uses the principlesof deposition to evenly coat extremely finelayers of a compound onto a target structure.
The thickness and structural regularity of thecoating is essential and so the underlying
nanostructure of the coated material is also
important. ‘To examine these structures,
we make use of electron microscopy andnitrogen adsorption experiments,’ confirms
Ohno. After extensive research and oldfashioned trial and error, Hirai and Ohno

TEM image of TiO2 nano-coated particle

had designed,’ enthuses Ohno. ‘We have also
confirmed that the effect differs dependingon the structure of the coating layer,’ he says.
The immediate next step will be to apply
the same principles to anode. However,
the results already represent an important
breakthrough in the potential application ofrechargeable metal-air batteries.
MACRO FUTURE
Ohno and Hirai’s work doesn’t justrepresent a breakthrough in metal-air battery
technology. Their methods, particularly thatof coating important compounds at a nanoscale. Ohno believes that this principle
and their processes have a huge range ofpotential applications. ‘The source of thistechnology lies in the design of precursor
molecules for inorganic materials. It is atechnology that can be applied to material
systems other than the materials that wehave proposed so far,’ enthuses Ohno.
‘We expect our work will be expanded into
various fields such as magnetic materials,optical materials and electronic materials
by selecting the combination of materials
relevant to each case,’ he confirms. Ohno
calls on other academics as well as industry
to make use of the principles they haveoutlined. It is clear that this team has openeda new path in materials science that may help
break many of the technological barriers. l

Project Insights
FUNDING• Grants-in-Aid for Scientific Research(20K05657)• New Energy and Industrial Technology
Development Organization (NEDO),‘Development of Fundamental
technologies for All Solid State Battery
applied to Electric Vehicles’COLLABORATORS
Associate Professor Naonori Sakamoto,Shizuoka University
TEAM MEMBERS
Jeevan Kumar Padarti (Post-doctoralfellow)
CONTACT
Professor Tomoya Ohno
T: +81 157 26 9456
E: ohno@mail.kitami-it.ac.jp
W: http://www.mtrl.kitami-it.ac.jp/
catalyst/
BIOS
Professor Tomoya Ohno studied
Materials Science at Shizuoka University.
He has worked at the Kitami Instituteof Technology since 2005, and in 2017
he became Full Professor. His researcharea is materials science and particle
technology. He is the Councillor of theSociety of Powder Technology, Japan, andthe editorial board member of Advanced
Powder Technology.
Associate Professor Shigeto Hirai
is based at the Kitami Institute ofTechnology and is an executive officerof the Materials Science Society ofJapan. Hirai’s current research is centredon electrochemistry and solid-statechemistry of energy-related materials.

TEM image of BaTiO3 nano-coated particle
www.impact.pub 45