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Lithium Ion Rechargeable Batteries
Tracing the Origins of Research and Development- Focus on the History of Negative-Electrode Material Development
Tokio Yamabe

Professor Emeritus, Kyoto University/
Professor, Nagasaki Institute of Applied Science

In the fall of 2015, Japan was again buzzing with media reports about theNobel Prize awarded to Japanese scientists. Unfortunately, there was no
Japanese win in the field of chemistry, but one area of this category where
Japan is seen as a strong contender for the prize is in lithium ion rechargeable
batteries, where Japanese researchers have made great contributions. The
names of Japanese candidates featured prominently in newspapers and othermedia in the expectation that this might be the year when they would clinch it.
But although the names of certain candidates may be put forward, taking acloser look, it is not always easy to work out who created the lithium ion
rechargeable battery and through what sequence of processes. In particular,
there are many uncertainties relating to the development of the negativeelectrode material．
In this interview, we speak with Tokio Yamabe, Professor Emeritus at Kyoto
University, who has been involved from the start in fundamental research intolithium ion capacitors and lithium ion rechargeable batteries. Since he is alsofamiliar with the key figures in the development of rechargeable batteries,
Professor Yamabe was able to fill us in on some of the ‘unrevealed‛ facts.
Tokio Yamabe ●1959: Graduated from Kyoto University Faculty ofEngineering
1981: P rofessor, Kyoto University Faculty ofEngineering
2000: P rofessor Emeritus, Kyoto University
2000: Director of Institute for Fundamental Chemistry2001: P resident of Nagasaki Institute of Applied
Science (NiAS)
2005: Director of Institute for Innovative Science andTechnology, NiAS
2013: Professor of Institute for Innovative Science andTechnology,N iAS
1

INTERVIEW

It all started with research on polyacetylene.
— Thinking about the origins of the lithium ion rechargeable battery, would you agree that it had its
beginnings in fundamental research on conductive polymers (polyacetylenes)?
Yamabe: That certainly applies when it comes to negative-electrode development. In the fall of 1977, aninternational conference on molecular conducting materials was held in New York, at which Professor
Hideki Shirakawa (Nobel Prize laureate in Chemistry 2000) presented his surprising discovery that apolyacetylene film close to a synthesized insulator displayed metallic conductivities when doped. It was thefirst demonstration of the highly conducting polyacetylene (CH)x, for which he was awarded the Nobel
Prize, and I still remember clearly that I became very excited because I realized immediately that thispolyacetylene would be a great subject for the quantum chemistry of nano-materials.
After that, having the opportunity to undertake joint research with Professor Shirakawa, I made further
progress, while focusing on (CH)x, in the study of the electronic properties and material design of conductive
polymers, through the use of quantum chemistry. As I recall now, there was already some talk at the time of
applying polyacetylene to use in rechargeable batteries.

— That would have been around 1980?
Yamabe: Yes, the first people to mention it were A. MacDiarmid and A. Heeger (both Nobel Prize laureates in
Chemistry 2000). In 1980, soon after the discovery of conductive polymers (1977), they presented its further
application to rechargeable batteries using electrochemical doping at the International Conference on Scienceand Technology of Synthetic Metals (held in August at Helsingör, Denmark). Their
presentation, which suggested the possibility of a very lightweight storage battery, attracted
much attention. For this, they used doped lithium using polyacetylene for positive- andnegative-electrodes. All of this is explained in detail in the journal Gosei Kinzoku (synthetic
metals), a special issue of the journal Kagaku (chemistry), Kagaku Zokan 87, edited by
Hideki Shirakawa and Tokio Yamabe, Kagaku-Dojin Publishing Company, Inc., publishedin 1980)＊1, which I compiled together with you around 35 years ago.

— Is that so? I had completely forgotten (laughs)．
Yamabe: Then, the next year, 1981, they obtained a patent under the title “Secondary batteries based onreversible electrochemical doping of conjugated polymers”. This patent was many pages long and was very
thorough in its content and certainly demonstrated their enthusiasm. Without doubt, they were the first people
to consider applying polyacetylene to use in rechargeable batteries. Of course, they didn’t just acquire the patent,
they also wrote scientific papers＊2.

Discovery of PAS with outstanding doping characteristics
Yamabe: The problem was that it gradually became clear that polyacetylene was unstable and unsuitable for use
in an electrode. So, a worldwide quest began to research and design a new conductive polymer and unknown
carbon material with its skeletal structure extending two-dimensionally to replace it. Among the materials westudied during the course of our research, there were the PAS (see framed article on next page) that we
discovered and which were later used as a negative-electrode material in the lithium ion rechargeable battery.
— About when would that have been?
Yamabe: That was around the beginning of the 1980s. The main substances explored as negative-electrodes
included a wide range of carbon materials, from conductive polymers to graphite. It was 1980 when I first started

2

Lithium Ion Rechargeable Batteries Tracing the Origins of Research and Development

COLUMN● How was the key material PAS discovered ! ●— How was this key material PAS discovered ?
Yamabe: Actually there are a few interesting stories
concerning that. It was in 1982 when we published thefirst research paper that pursued this polyacene-type
carbonaceous material from a theoretical point of view.
Although this material was predicted from material design
based on the analysis of quantum chemistry, by fortunate
coincidence, it was discovered at almost the same time by
my research collaborator, Dr. Shizukuni Yata of Kanebo,
Ltd., that it can be obtained through the pyrolysis ofphenol-formaldehyde resins. At the time, Kanebo, Ltd.
was also engaged in research and development of carbon
materials. During experiments in the heat treatment ofphenol-formaldehyde resins to obtain carbonaceous
materials, they happened to take out materials at thetemperature of 400~700°C, lower than planned, and foundthat they had unexpectedly obtained this black solid
substance with a metallic sheen. This is what we now callpolyacenic semiconductive material (PAS), which could
be described as a kind of synthetic metal (Figure 1).

2～4nm

Crystals

Space between crystals

Fig. 2 Model structure of nano-graphene blocks

ordered polyacene skeletal structure according to the resultsfrom the X-ray diffraction analysis. It is a hardgraphitizable amorphous carbon mainly comprising thenano-sized polyacene structure, and so can be regarded as aform of amorphous carbon. In current terminology, I
suppose they would be described as aggregates of “nanographene blocks” (Figure 2). This structure enables quite
easy lithium ion transfer and the technique of pre-doping.
In the pyrolysis of phenol-formaldehyde resins, bycontrolling the temperature and time of the heat treatment, it
is possible to obtain PAS materials with a wide range of H/
C ratios, specific surface areas, interlayer distance, andconductivity rates. In Dr. Yata’s 1984 patent, H/C ratio is
set at between 0.05 and 0.5. In that sense, PAS arecarbonaceous materials occupying a range from polyacenes(H/C = 0.5) to near to graphite (H/C = 0), and thosegenerated by pyrolysis of phenol-formaldehyde resin can beseen as a promising prototype thereof.

— Is that serendipity, too?．
Yamabe: As it was coincidental, I suppose you could say so.
Straight away, we began careful and thorough investigationof its fundamental properties as a semiconductive electronicmaterial using magnetic measurement, solid-state NMR,
electrochemistry and other techniques. Specifically, weinvestigated the structure, electrical transport properties, andp- and n-type doping properties. It was around 1982 that we
finally established that it was a nano-sized non-crystalline
semiconductor with excellent doping and undoping
properties, and very high lithium ion capacity. Later, it wasalso used as the negative-electrode material in the lithium
ion rechargeable battery.

— In that sense, you could say that those carbonaceous
materials developed by various companies at the time converge
on the PAS in question….
Yamabe: I think so. That is exactly where the basis lies for— Could you explain the properties of PAS as a substance inasserting the priority of PAS. There is also a scientifica little more detail?
report which states this in academic terms (1997 Chem.
†
Yamabe: In general, the polyacene group is a collective term Rev. ). For instance, it has been stated clearly that the
carbonaceous
material of the negative-electrode for thefor the materials of the so-called nano-sized graphite groupthat includes polyphenantrenes, polyarylenes, etc. of which lithium ion rechargeable battery that was released on thethe structure is formed through condensation of the benzene market by Sony Corporation can be regarded as identical toring, like that of polyacene. However, the materials obtained PAS.
— So does that mean that PAS can be seen as
by the heat treatment of phenol-formaldehyde resins in an
the origin of research and development ofinert atmosphere are found not to have formed a regularly
negative-electrode material for the lithium ion
rechargeable batteries today?
Pyrolysis
Polyacenic
PhenolCrossMolding
400～700℃
semiconductive
formaldehyde
Yamabe: You can certainly think so. It is
Linkedresinmaterial（PAS）
probably a corporate secret, but as one canNon-oxidativeresin
atmosphereimagine, a graphite structure that is fragmented
to make it easy for lithium ions to move in andout but which is resistant to the formation ofdendrites, that is precisely the structure of PAS.
Molar ratio H/ C＝3/ 7≒0.43

Molar ratio H/C＝1/7≒0.14

Fig. 1 Production method of polyacene-based semiconductive materials

3† P. Novák, K. Müller, K. S. V. Santhanam,
O. Haas, “Electrochemically Active Polymers
for Rechargeable Batteries,” Chem. Rev., 97,
207（1997）．

INTERVIEW

researching PAS with Dr. Shizukuni Yata et al., who at the time worked for Kanebo, Ltd. We presented our
findings at a scientific conference in March 1982 (spring convention of the Physical Society of Japan) and inJune of the same year, we published a scientific paper on PAS＊3. At the same time, Dr. Yata applied for apatent＊4 which described that we had succeeded for the first time in doping lithium ions into a negativeelectrode made of PAS, and demonstrated the efficacy of this carbonaceous negative-electrode material andadapted it for use in a rechargeable battery.
At the time, it was generally not thought possible to perform stable electrochemical doping and undoping oflithium into carbon material using an organic electrolyte solution (in most cases propylene carbonate). In
particular, experiments with graphite were challenging as it involved decomposition of the electrolyte solution.
PAS, in contrast, was effective even with a propylene carbonate electrolyte solution, realizing a smootherlithium doping and undoping process.

— That is a very important point, but was lithium ion doping the key to adapting this substance for use
in rechargeable batteries, as it had been with polyacetylene?
Yamabe: Yes, the essential point was whether lithium ions could be doped into the negative-electrode. In
carbonaceous negative-electrodes, we had known for some time that graphite forms intercalational
compounds with alkaline metals, and in 1975 it was reported that it forms intercalational compounds withlithium. The research of M. Armand et al. in 1977＊5 was based on this finding, and in 1981 Hironosuke Ikeda
of SANYO Electric Co., Ltd. filed a patent application for a graphite negative-electrode.Then in 1982, R.
Yazami reported that electrochemical insertion and desorption of lithium ions was possible to and from agraphite (HOPG)＊6 within solid electrolytes (polyethylene oxides), at over 60°C. These solid electrolytes differ
from regular organic electrolyte solutions. Generally for lithium ion batteries, an organic electrolyte solution isapplied because of its high ionic conductivity. But solid electrolyte at room temperature has no practical ionic
conductivity. And regrettably, none of the above was sufficient for practical use．
As you know, there were two main trends in the research and development of negative-electrode materials
for lithium ion rechargeable batteries. One was the approach from the field of electrochemistry centering ongraphite intercalation compounds, and the other was the approach from the field of new nano- carbonaceous
materials that had originated in polyacetylene. In the move toward practical application, I would say, in
conclusion, it was the latter that played the leading role.

— I see. So at the time, were you mainly focused on exploring negative-electrode materials?
Yamabe: There was also the issue of the positive-electrode, of course, but the negative-electrode was more
important in terms of storing electricity. As you know, the metallic lithium that had been used until then in thenegative-electrode is highly active and there were safety issues＊7. This is why battery researchers at the time
were eagerly seeking a new material to replace metallic lithium.
That was precisely the situation from the late 1970s into the early 1980s. Looking back now, this period,
which saw the concentration of scientific papers being published and patents being issued, was the dawning of
the lithium ion rechargeable battery and lithium ion capacitor. In light of the findings of Professors Shirakawa
and MacDiarmid, new developments had been under way, and it was just around then that the next set ofachievements (patents and scientific papers) had started to appear.

— Amid all that activity, it’s not easy to pinpoint which invention was first made by which scientist, is it?
Yamabe: Yes, you’re exactly right. There are scientific papers, presentations at academic conferences, andpatents, each of which has different aims and different procedures, so it really is difficult to decide who got
there first. However, as far as the negative-electrode is concerned, I think that the first time when stable
lithium doping and undoping — viewed as an absolute prerequisite for a lithium ion rechargeable battery —was demonstrated to be possible with a carbon-based material using a non-aqueous organic electrolyte wasprobably in our research with PAS. This was not just about the patent, but was also properly backed up by
scientific papers.
4Lithium Ion Rechargeable Batteries Tracing the Origins of Research and Development

Development of a PAS-based electric storage device— These details are certainly not very well known. How did your joint research with Dr. Yata proceed in practice?
Yamabe: The research at Kanebo, Ltd. progressed with myself in charge offundamental research and my collaborator Dr. Yata mainly in charge of appliedresearch for product commercialization. I first met Dr. Yata in 1980 when he came tolisten to my lecture on polyacetylenes. In this lecture, I touched briefly on thepolyacenes that we mentioned just now as a promising substance that could be
predicted based on quantum chemistry. This subject apparently captured Dr. Yata’s
interest, and we came up with the idea that something like a ‘polyacene’ could be
produced by the heat treatment of polymer. That was why we decided to work together.

— Prior to this, did you have a theoretical prediction concerning polyacene?

Dr. Shizukuni Yata

Yamabe: Yes, that’s right, that prediction was possible through analysis based on quantum chemistry. And,
when Dr. Yata showed me the samples after the heat treatment of phenol-formaldehyde resin in his
experiments, it looked like a shiny black thin chocolate bar, nothing like the thin film of polyacetylene with ametallic shine. We were determined to somehow or other make a success of the project and so we carried onwith our joint research. Almost all of my scientific papers concerning PAS were co-authored with Dr. Yata andhis group＊8. Sadly, however, he passed away in March 2012.

Photograph 1 PAS battery (left)
and lithium ion capacitor (right)
Source: website of Taiyo Yuden Co., Ltd.

— When was commercialization actually realized?
Yamabe: Taking advantage of the outstanding characteristics of PAS, Kanebo, Ltd. commercialized two types ofstorage battery products. One was known as the “PAS battery”, commercialized in 1989, which used PAS for the
positive- and negative-electrodes (Photograph 1, left). Operated like a capacitor, it had compact dimensions andhigh capacity, and was highly reliable. It is still in widespread use today around the world as a backup power source
for mobile telephones and other consumer appliances. This can be seen as the first product in which a conductive
carbonaceous material was used for the electrode of an electric storage device.
The other type used PAS also in both electrodes, but the PAS used in the negative-electrode was subject tolithium ions doped in advance. Dr. Yata led the world in the development of this technology, which is known
as the lithium ion pre-doping technique. Simply attaching a lithium sheet to PAS enabled the easy insertion oflithium ions. This allows the negative-electrode to operate in the same way as a lithium ion rechargeable
battery. In other words, it is a highly unique device in which the positive-electrode operates as a capacitor andthe negative-electrode as a rechargeable battery. This product was commercialized as a "lithium ion
capacitor" (Photograph 1, right) in 1991, which was exactly the same year as the lithium ion rechargeable
battery was released on the market. Today it is still used widely around the world in mobile telephones, IC
memory cards, and other information and communication devices.
5

INTERVIEW— By the way what is the difference between this capacitor and a rechargeable battery?
Yamabe: In the lithium ion capacitor, the positive- and negative-electrodes were each based on different principles,giving it a hybrid structure combining the oxidation-reduction reaction of a lithium ion rechargeable battery at thenegative-electrode and the physical adsorption reaction of an electric double-layer capacitor at the positive-electrode.
As for the negative-electrode, it is basically the same as a lithium ion rechargeable battery, but the difference is that
one gives out the stored electricity quickly and the other does it slowly. It has outstanding characteristics including
long-life, high capacity density, and higher safety than the lithium ion rechargeable battery. In the future, it has great
growth potential in automotive use and as a supplementary device for renewable energy sources such as solar
photovoltaics.

Where do the origins of the lithium ion rechargeable battery lie?
— The most standard lithium ion rechargeable battery currently on the market (see Table 1) uses lithium
cobalt oxide (LiCoO2) in the positive-electrode and not a literal graphite but a carbonaceous material in thenegative-electrode, but there are a number of different opinions as to how this came about and somequestionable data has certainly become mixed up in it. Particularly regarding the carbonaceous material forthe negative-electrode, each company had its own strategic approach…．
Yamabe: Each company has a position to defend, and it has to be admitted that the information has become confused.
As with many industrial products, the lithium ion rechargeable battery was certainly not an exception in that it was notcreated by a single inventor, but was an achievement based on the findings of many different researchers. That’s true
particularly concerning the negative-electrode, where the story goes back quite a long way, with various efforts andcumulated research carried out by researchers, mainly in the fields of electrochemistry and materials science.
However, as I said earlier, at the beginning of the 1980s, it was generally thought not possible to perform stableelectrochemical doping and undoping of lithium ions into graphite using an organic electrolyte solution. Nevertheless,we found that with our polyacene-based material (PAS), it was possible to do so both smoothly and stably.
Name
Polyethylene（CH2）xPolyacetylene（CH）xStructural formula
H

H

H

H

C

C

C

C

C

H

H

H

H

C

C

H
H

H
C

H
H

2

H
C

C

H

1

H

0.5
H

H

H

H

H

H

H

H

H

Polyacenoacene
（C3H）
x
H

H

H

H

H

H H

H

H

H

H

0.1

H

0.33

H

H

H

Polyacene
（C2H）
x
H

H/C ratio

Carbon（C10H）x

H
H

Structural formula

H

H

H
C

Name

H/C ratio

Graphite

H

H

H

H H

H

H

H

H

0

H

Fig. 3 Structures of the polyacene family (those on color ground) and H/C ratio
H/C ratio represents the molar ratio of hydrogen (H) and carbon (C) comprising carbonaceous materials. First introduced
by T. Yamabe et al., this index came to play a vital role for the evaluation of carbonaceous materials subsequently used forthe negative-electrode.

6Lithium Ion Rechargeable Batteries Tracing the Origins of Research and Development— Around that time, carbonaceous materials close to graphite were being explored by many researchers. Was
it your findings that provided the impetus?
Yamabe: Actually, the PAS patent filed in 1982 (see Table 2) was published in December 1983. I have theimpression that various companies that saw it wanted to somehow avoid infringing the patent rights
and therefore started to extend the scope of their research to include materials close to graphite with alow hydrogen to carbon ratio (Figure 3).
Then, in the mid-1980s, by combining such carbonaceous material for a negative-electrode and LiCoO2
for a positive-electrode, the ancestor of the current lithium ion rechargeable battery that does not use metallic
lithium for the negative-electrode was drawn up. The LiCoO2 for a positive-electrode was of course developedin 1980 by J. B. Goodenough et al. through their research on transition-metal oxides. In its development, large
contributions were made by Dr. Akira Yoshino of Asahi Kasei Corp. and Mr. Yoshio Nishi of Sony
Corporation.

— These are of course names that are known, Dr. Yoshino as the inventor of the lithium ion rechargeable
battery and Mr. Nishi as the engineer who was the first to commercialize it (see Table 1).
Yamabe: The fact that I am able to sit here today talking about this is thanks to the efforts and achievementsof these two researchers and the many others who worked for practical realization and commercialization. At
that time, the field was a hive of activity, and since Dr. Yoshino was a student in the same department of thefaculty of Kyoto University as I, from the beginning of the 1980s he often visited my laboratory. It was after I
told him about the existence of polyacetylene that he began polyacetylene research, and developed it to anelectrode for the lithium ion rechargeable battery.

— It seems that you and Dr. Yoshino were researching in close proximity. If you don’t mind me asking again,
what ultimately was the origin of that research?
Yamabe: Looking at the major streams in research development that I have spoken of so far, you could
perhaps say that the negative-electrode of today’s lithium ion rechargeable battery has its origins in our PASderived lithium ion capacitor technology. If you seek the origin beyond this, the discovery of conductive
polymers by Professor Shirakawa and his group, as I mentioned earlier, triggered the process, and it could
also be seen as having started from the polyacetylene lithium ion battery developed by MacDiarmid andHeeger et al. Of course, the positive-electrode was Goodenough’s achievement.

What determines the originality of the battery?
— What factor do you think determines the originality of this lithium ion rechargeable battery?
Yamabe: If only one person had single-handedly created the lithium ion rechargeable battery including both
positive- and negative-electrodes, then there could be no objection to calling that person the inventor. But in thepresent case, each science behind the materials used in the positive- and negative-electrodes, in other words, theinvention and creation of such materials should perhaps be considered separately. In this respect, I have alreadyexplained, and the remaining question is who first put them together. Actually, there is one opinion that it could
easily have occurred to any battery researcher who had read Goodenough’s papers to construct a lithium ion
rechargeable battery using graphite for the negative-electrode.

— Do you mean that neither the development of the negative-electrode material, nor the ingenious
combination of the positive- and negative-electrodes was totally irrelevant?
Yamabe: That opinion I cited just now was an extreme opinion. I think it is undeniable that the firstcombination of the positive-electrode (LiCoO2) and negative-electrode (carbonaceous material) was what led tothe creation of the lithium ion rechargeable battery. But, if you want to claim superiority for this combination,then you need to have both a correspondingly clear scientific basis and evidence.
7

INTERVIEW— Certainly we sometimes hear it said that a patent alone is insufficient as a scientific basis.
Yamabe: In the sense of definite scientific evidence, the patent by itself will not do. It is essential to publish aproperly researched scientific paper. In the world of science, the final judgment rests on the scientific paper. In
the case of the development of the lithium ion rechargeable battery, there is one more important point thatdefinitely ought to be mentioned. If the product is to be serviceable, then the question of how to establish safety isabsolutely essential. Even today, the question of how to minimize the risk of ignition and explosion with thelithium ion rechargeable battery is an important issue. The reason why this product has survived is that there wereengineers who tackled this issue head-on and resolved it in the early stage of development. This is something thatdeserves high praise. However superior the performance, a dangerous device will not survive as a widely adopted
product. This safety question is an essential issue that cannot be ignored.

— Thanks to your explanation, the uncertainty surrounding development of the lithium ion rechargeable
battery has become a lot clearer. Could I ask you to give a final comment?
Yamabe: Whoever the original inventor may have been, it remains true that the technology of the lithium ion
rechargeable battery originated in Japan. This is a point I really want to stress. One more point is that looking
back on the negative-electrode development process illustrates strongly the profundity of the discipline which
we might call “carbon sciences” in Japan＊9. Japan definitely leads the world here, as demonstrated for example
in the area of carbon fibers. It was because of such academic support and the highly mature environment that
we were able to develop our unique and original technology while achieving breakthroughs. Still having an
unknown nature, carbon is a very interesting material with the potential for greater development in the 21st
century.
(Interview and text: Yuko Taira, Chief Editor, Kagaku)

Table 1 Superficially overviewed history of development of the lithium ion rechargeable battery
Year

Main events

1977

Hideki Shirakawa et al. discovered that chemical doping increases the conductivity of polyacetylene.

1980

J. B. Goodenough et al. at Oxford University announced the use of lithium cobalt oxide (LiCoO2) for the
positive-electrode.

1981

Hironosuke Ikeda of SANYO Electric Co., Ltd. and his group filed a patent application for a rechargeable lithium
battery using graphite for the negative-electrode.

1982

R. Yazami et al. at the French National Centre for Scientific Research reported that lithium ions can be electrochemicallyinserted to and desorbed from a graphite negative-electrode in solid electrolytes at high temperature.

1983

Akira Yoshino of Asahi Kasei Corp. and his group filed a patent application for a rechargeable battery using lithium
cobalt oxide and polyacetylene for the positive- and negative-electrodes respectively.，

1985

Akira Yoshino et al. filed a patent application for a new rechargeable battery (prototype of the lithium ion rechargeable
battery) using lithium cobalt oxide and carbon materials for the positive- and negative-electrodes respectively.

1991

Yoshio Nishi of Sony Corporation and his group commercialized a lithium ion battery.

8

Lithium Ion Rechargeable Batteries Tracing the Origins of Research and Development

Table 2 Main approved patents related to the lithium ion rechargeable battery
Application date

Main patents

1979 (April 5), EP

J. B. Goodenough et al.: Electrochemical cell and method of making ion conductors for saidcell1981 (February 28), EP

A. Heeger, A. MacDiarmid et al.: Secondary batteries based on reversible electrochemical
doping of conjugated polymers

1981 (June 18), JP

Hironosuke Ikeda et al. of SANYO Electric Co.: Rechargeable lithium battery using graphite
for the negative-electrode1982 (May 31), JP

Shizukuni Yata et al. of Kanebo, Ltd.: Organic electrolyte battery, a rechargeable battery with apolyacene negative-electrode doped with lithium ion

1985 (April 30) (PD), JP

Kazuya Hiratsuka et al. of Toshiba Battery Co., Ltd.: Non-aqueous solvent rechargeable battery,
consisting of the positive-electrode with metal chalcogenide compounds etc. and carbonaceous
material with quasi-graphite structure

1985 (May 10) (PD), JP

Akira Yoshino et al. of Asahi Kasei Corp.: Non-aqueous rechargeable battery with lithium cobalt
oxide and carbon materials for the positive- and negative-electrodes respectively

1990 (February 21), JP

Yoshio Nishi et al. of Sony Corporation: Carbonaceous material and its manufacturingmethod, and resulting non-aqueous electrolyte rechargeable battery(PD): Priority date

＊1.

＊2.
＊3.
＊4.
＊5.

＊6.

“The University of Pennsylvania group attracted attention after releasing its findings, i.e. application of polyacetylene toa rechargeable battery through the use of electrochemical doping. For example, when both electrodes each consisting of
0.1 mm-thick polyacetylene film are submerged in a THF solution containing lithium iodide and connected to a 9-volt
DC power source, the lithium iodide is electrolyzed, the polyacetylene of the positive-electrode becomes doped withiodine, and the negative-electrode becomes doped with lithium. This doping in electrolyte is equivalent to the charging
process. When an electric charge is connected to the two doped electrodes, the lithium ions and iodine ions react andelectric power is generated”. (main text, p.171)
P. J. Nigrey, D. Maclnnes Jr., D. P. Nairns, A. G. MacDiarmid, A. J. Heeger. Lightweight Rechargeable Storage Batteries
Using Polyacetylene (CH)x as the Cathode-Active Material. J. Electrochem. Soc., 128, 1651 (1981).
T. Yamabe, K. Tanaka, K. Ohzeki, S. Yata. Electronic Structure of Polyacenacene. A One-Dimensional Graphite. Solid
State Commun., 44, 823 (1982).

The title of the patent was “Liquid organic electrolyte battery”.
In 1977, M. Armand et al. published the concept of a storage battery combining a graphite intercalational compoundwith metallic lithium foil, but no liquid suitable electrolyte solution was found.
M. Armand, P. Touzain, Mater. Sci. Eng., 31, 319 (1977)
Highly oriented pyrolytic graphite ; HOPG has excellent features like natural graphite, but is very expensive becauseof the complexity of the productive process and the necessity of high temperature heat treatment over 3000°C.

＊7.

At the time, a lithium non-rechargeable battery had already been commercialized that used manganese dioxide for the
positive-electrode and metallic lithium for the negative-electrode. As an extension of this, development of the lithium
rechargeable battery was also carried out. However, when metallic lithium was used for the negative-electrode, dendrite
crystals of lithium grew on the electrodes after charging and discharging, causing a short-circuit with the risk ofignition, explosion, and other safety issues.

＊8.

There are approximately 60 PAS-related research papers. The representative papers are as follows:8-1) Electronic Structure of Polyacenacene. A One-Dimensional Graphite, T. Yamabe, K. Tanaka, K. Ohzeki, andS. Yata, Solid State Commun., 44, 823 (1982).
8-2) Electric Conductivity of Polyacenic System Toward One-Dimensional Graphite, T. Yamabe, K. Tanaka, K.
Ohzeki, and S. Yata, Journal de Physique, 44, 645 (1983).

9

INTERVIEW

8-3) Electrical Transport in Pristine and Heavily Doped Polyacenic Materials, K. Tanaka, S. Yamanaka, T. Koike, T.
Yamabe, K. Yoshino, G. Ishii, and S. Yata, Phys. Rev. B, 32, 6675 (1985).
8-4) Electrical Conductivity and Thermoelectric Power in Polyacenic Materials, H. Ueno, G. Ishii, K. Yoshino,
K. Tanaka, T. Yamabe, and S. Yata, Syn. Met., 18, 515 (1987).
8-5) Studies of Porous Polyacenic Semiconductors toward Application, S. Yata, Y. Hato, K. Sakurai, H. Satake, K.
Mukai, K. Tanaka, and T. Yamabe, Syn. Met., 38, 169 -193(1990) .
8-6) Structure and Properties of Deeply N-Doped Polyacenic Semiconductor (PAS), S. Yata, H.Kinoshita,
M.Komori, N.Ando,T.Kashiwamura,T.Harada,K.Tanaka,andT.Yamabe, Proceedings of the Symposium on
New Saled Rechageable batteries and Supercapacitors 92-93, 502 (1993 )8-7) Polyacenic Semiconductor Materials (Application to Rechargeable Batteries), Polymeric Materials
Encyclopedia, K. Tanaka, T. Yamabe, and S. Yata, CRC Press. Inc., 5308 (1996).
＊9.

An influential publication called “Tanso-gaku (carbon sciences)” (edited by Kazuyoshi Tanaka, Hidekazu Touhara,and Hisanori Shinohara, 2011) was issued by Kagaku-Dojin Publishing. This is a high-quality specialist book full of
thought-provoking content that gives a systematic overview of the current state of carbon science, and carbon
material research/application.

Acknowledgment
I received highly valuable comments from Professor Nobuaki Murakami. In particular, the information on
patents was very thought-provoking. I take this opportunity to express my sincere gratitude.
Tokio Yamabe

This article is a translation of the journal Kagaku, Vol. 70, No. 12, 40 - 46 (2015). For
permission to translate and publish, we are very grateful to Kagaku-Dojin Publishing
Company, Inc. and Chief Editor, Yuko Taira who was also the interviewer for this article.
Tokio Yamabe, Nobuaki Murakami
Nagasaki Institute of Applied Science（c）2015-2016 Kagaku-Dojin Publishing Company, Inc.

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