Asahi Chemical has recently acquired three
important basic patents in Japan related to lithium ion rechargeable
batteries (LIB), bringing the total number of LIB patents
held in Japan and overseas to about 40. The company has decided
to make these patents broadly available by licensing to other
LIB makers.
Background
The spread of portable electronic devices,
such as mobile telephones and laptop computers, has been
accompanied by rapidly growing demand for small rechargeable
batteries. The LIB, introduced only a few years ago, is
quickly becoming the preferred rechargeable battery due
to its unmatched performance and absence of environmentally
hazardous substances. For 1996, LIB use nearly tripled from
the previous year, and such rapid growth is widely expected
to continue.
Asahi Chemical was the first company to
grasp the potential of the LIB, and launched the development
effort in 1982. The company has applied for over 300 patents
in Japan and overseas based on the results of this development
effort. Several of these relate to basic elements of the
LIB, and the three patents recently acquired are especially
important basic patents.
The patents
In brief, the three new patents can be summarized
as follows:
1. The use of carbonaceous negative electrode
material in combination with lithiated cobalt oxide as positive
electrode material. This is a particularly fundamental patent,
as it covers the combination of the optimum positive electrode
material, lithiated cobalt oxide, with the ubiquitous negative
electrode material, carbon.
2. The use of aluminum as the current collector
in positive electrodes using lithiated cobalt oxides. This
patent is important because aluminum is the optimum current
collector for positive electrodes using lithiated cobalt
oxide.
3. The use of an internal separator in
which the micropores close when a certain temperature is
reached. This patent is important because the use of membrane
separators having this function is indispensable in ensuring
the safety of an LIB.
The three patents were applied for early
on, and cover key elements of the LIB. It is believed that
the LIBs produced by the many makers are covered by these
patents. Other leading-edge developments at Asahi Chemical
have led to a number of other patents related to positive
and negative electrode materials, binders, and protective
elements.
Licensing
Asahi Chemical has concluded licensing agreements
with A&T Battery Corp., the LIB joint venture with the Toshiba
Group, under the three new patents. The company has decided
to make all of its LIB related patents available for licensing
by other LIB makers.
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