Masaki Yoshio talks with
ScienceWatch.com and answers a few questions about
this month's Fast Moving Front in the field of Materials
Article: Mixed silicon-graphite composites as anode
material for lithium ion batteries influence of preparation
conditions on the properties of the material
Authors: Dimov, N;Kugino,
Journal: J POWER SOURCES, 136 (1): 108-114 SEP 10
Addresses: Saga Univ, Dept Appl Chem, 1 Honjo, Saga
Saga Univ, Dept Appl Chem, Saga 8408502, Japan.
Why do you think your paper is highly
The relationship between overall anode capacity and both: (1) silicon
content in the Si-based composite anode and (2) mole fraction of lithium
(x) in the LixSi alloy, was derived for the first time in a clear and
straightforward manner in this paper. This derivation took into account the
unique electrochemistry of silicon and served as a guidance rule for many
works that followed in this area. This helps explain the paper's high
Does it describe a new discovery, methodology, or
synthesis of knowledge?
There is one severe problem with the application of Si (or metal alloy)
anodes, i.e., the big volume change during lithium
intercalation/deintercalation, which causes capacity fading with
charge/discharge cycles. Our discovery was that carbon materials work as a
buffer matrix against the volume change of Si.
"At the very beginning our
methodology was misunderstood and sometimes
criticized by other
The paper introduces, in a quantitative manner, a new methodology to study
composite Si anodes, namely a constant capacity cycling test. Such a
methodology, systematically implemented in subsequent publications, has
helped us to better understand the behavior of these anodes, and to find
and develop better binder formulations and electrode preparation
Would you summarize the significance of your paper
in layman's terms?
At the very beginning, our methodology was misunderstood and sometimes
criticized by other researchers. The basis of our quantitative approach was
clearly described and explained in this paper. From this viewpoint, our
paper paved the way for a rethinking of the research paradigm in this field
and led to the discovery of new binding formulations which allow cycling of
anodes undergoing large volumetric variation over the course of
How did you become involved in this research and
were any particular problems encountered along the way?
A decade after the commercialization of lithium ion batteries it seemed
that the only way to improve their performance was to implement
high-capacity anode materials. This is why we focused our efforts on this
It might be somewhat surprising, but the main problem we faced along the
way was related to the stereotypical research methodology widely accepted
among researchers working in the field of the lithium ion batteries.
Virtually everyone involved in such studies has followed the same research
strategy for over two decades—to study the crystal lattice of the
host material and modify it with respect to some properties of interest,
for example: rate performance, capacity, cycle life, etc.
Silicon-related materials are exceptional because the silicon parent
crystal lattice breaks down and forms an amorphous LixSi alloy over the
first cycle and the methodology mentioned above simply cannot be followed.
Despite this, many of the research groups were still trying to attack the
problem from the viewpoint of the crystal lattice, its conservation, and
modification. Therefore, the lack of a single clear strategy to follow was
actually the main problem, which had to be overtaken by a new research
Where do you see your research leading in the
The ultimate goal of any applied research is its practical implementation
and, therefore, the best result would be to develop silicon anodes which
meet present-day industrial standards.
Do you foresee any social or political implications
for your research?
Speaking generally, battery technology might become one of the key
technologies in the near future. Successful implementation of
high-performance batteries, particularly in hybrid electric vehicles,
electric vehicles, and load-leveling systems, may help sustain the
development of an environmentally friendly and sustainable society.
Masaki Yoshio, Professor Emeritus
Advanced Research Center