Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2001-05-11
2004-01-27
Robertson, Jeffrey B. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S447000, C429S047000, C429S303000, C429S313000, C429S321000, C429S322000, C429S323000, C524S401000, C524S406000, C524S408000, C524S413000, C524S588000, C524S779000, C524S861000, C524S862000, C252S062200, C252S299200, C252S521300
Reexamination Certificate
active
06682823
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a curable composition for polymer electrolyte as well as a polymer electrolyte produced therefrom and a polymer battery in which the same is used.
BACKGROUND ART
For a polymer electrolyte to be usable in lithium ion batteries or electrochemical devices, it is essential that it shows a high ionic conductivity in a wide temperature range, from low to high temperatures, and shows no crystallinity. However, any polymer electrolyte meeting such necessary performance characteristics requirements collectively has not yet been developed.
In the art, such organic solvent as propylene carbonate and ethyl methyl carbonate, for instance, are widely used in polymer electrolytes to be used in polymer batteries and the like. From the boiling point/vapor pressure viewpoint, however, they generally impose limitations on the use in a high temperature range of 70 to 90° C.
Recently, polymer electrolytes, typically polyethylene oxide (hereinafter referred to as “PEO”), have been studied as means for improving the safety of such organic solvents. PEO forms complexes with salts of metals belonging to the group 1 or 2 of the periodic table of the elements, for example LiCF
3
SO
3
, LiClO
4
, NaCF
3
SO
3
and LiI, to show relatively good levels of ionic conductivity in a temperature range not lower than room temperature and, further, shows good storage stability. However, the ionic conductivity of PEO is highly dependent on the temperature and, while it shows good ionic conductivity at 60° C. or above, the ionic conductivity markedly lowers at temperatures not higher than 20° C. Therefore, it is difficult to incorporate it in general-purpose products which may be used at low temperatures.
As a means of improving the ionic conductivity using low-molecular PEO, a method of introducing low-molecular PEO into side chains of a vinyl polymer has been reported by D. J. Banistar et al. in Polymer, 25, 1600 (1984). Although this high-molecular material forms complexes with lithium salts, the ionic conductivity at low temperatures is not satisfactory.
Further, materials derived from polysiloxanes by introduction of low-molecular PEO onto side chains thereof are described in Journal of Power Source, 20, 327 (1987), Japanese Kokai Publication Sho-63-136409 and Japanese Kokai Publication Hei-02-265927. They are, however, insufficient in ionic conductivity, are not noncrystalline, are not easy to synthesize, occur as liquids and are poor in workability or moldability, and are insufficient in mechanical strength. For these and other reasons, they have not been put to practical use.
A hydrosilylated crosslinked compound derived from a PEO side chain- and SiH group-containing polysiloxane and an olefin having polyethylene oxide in its main chain is described in Japanese Kokai Publication Hei-03-115359. However, the ionic conductivity thereof is considerably low, namely about 4.9×10
−6
S·cm
−1
, and this is not satisfactory.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a curable composition capable of giving a polymer electrolyte showing a high level of ionic conductivity and excellent in mechanical strength as well. Another object is to provide a polymer battery excellent in electrochemical characteristics.
The invention provides a curable composition for polymer electrolyte;
which comprises the following constituents (A) to (D) as an essential constituent:
(A) a SiH group-containing polysiloxane;
(B) a compound having at least one structure selected from the group consisting of a phenylene unit, a siloxy linkage, an Si—N bond, a carbonyl group, an amide linkage and an amino group and having two or more alkenyl groups;
(C) a hydrosilylation catalyst; and
(D) an electrolyte salt compound.
In a preferred embodiment of the invention, the curable composition for polymer electrolyte comprises the following constituents (A) to (D) as an essential constituent:
(A) a polysiloxane having a polyethylene oxide structure-containing group and/or a cyclic carbonate structure-containing group as a substituent on a silicon atom and having two or more SiH groups;
(B) a compound having at least one structure selected from the group consisting of a phenylene unit, a siloxy linkage, an Si—N bond, a carbonyl group, an amide linkage and an amino group and having two or more alkenyl groups;
(C) a hydrosilylation catalyst; and
(D) an electrolyte salt compound.
The invention also provides a polymer electrolyte obtained from the above curable composition for polymer electrolyte as well as a polymer battery having a structure such that the above polymer electrolyte is disposed between an anode and a cathode.
DETAILED DISCLOSURE OF THE INVENTION
Constituent A
In the practice of the invention, any of those SiH group-containing polysiloxanes which are known in the art can be used as the constituent (A), without any limitation.
The constituent (A) polysiloxane preferably has a polyethylene oxide structure-containing group, a cyclic carbonate structure-containing group and/or a cyclic ether structure-containing group as a substituent on a silicon atom and further has two or more SiH groups. The one having a polyethylene oxide structure-containing group and/or a cyclic carbonate structure-containing group as a substituent on a silicon atom and further having two or more SiH groups is more preferred among others. In particular, from the high ionic conductivity viewpoint, the one having a polyethylene oxide structure-containing group and having two or more SiH groups is more preferred. In cases where the polymer electrolyte of the invention is used in combination with a carbonate, which is to serve as an electrolyte, the one having a polyethylene oxide structure-containing group and a cyclic carbonate structure-containing group and further having two or more SiH groups is still more preferred.
The polyethylene oxide structure-containing group so referred to herein is not particularly restricted but may be any of oxyethylene unit-containing univalent groups. The oxyethylene unit(s) may be bonded to a silicon atom either directly or via a bivalent organic group. The cyclic carbonate structure-containing group or cyclic ether structure-containing group is not particularly restricted but may be any of cyclic carbonate- or cyclic ether-containing univalent groups. The cyclic carbonate or cyclic ether may be bonded to a silicon atom either directly or via a bivalent organic group.
In cases where the constituent (A) polysiloxane has a polyethylene oxide structure-containing group as a substituent on a silicon atom, it is desirable, from the low crystallinity viewpoint, that 10 to 95% of all silicon atoms in the constituent (A) polysiloxane each has, as a substituent thereon, a polyethylene oxide structure-containing group with a degree of polymerization of the oxyethylene unit of 1 to 12 and it is more desirable that 40 to 90% of all silicon atoms in the constituent (A) polysiloxane each has, as a substituent thereon, a polyethylene oxide structure-containing group with a degree of polymerization of the oxyethylene unit of 1 to 12.
When the constituent (A) polysiloxane has a polyethylene oxide structure-containing group as a substituent on a silicon atom, the constituent (A) is preferably represented by the following structural formula:
wherein m and n each is an integer of not less than 1, p is an integer of 1 to 12 and R represents a hydrogen atom or a hydrocarbon group containing 1 to 20 carbon atoms and, when n is not less than 2, the each R may be the same or different, provided that at least one of the R's is a hydrogen atom; the arrangement of the m repeating units and n repeating units may be not in order.
When the constituent (A) is represented by the above formula, the polyethylene oxide introduction percentage (%, hereinafter referred to as G) defined below is preferably 10 to 95%, more preferably 40 to 90%.
G=[m
/(
m+n
+2)]×100.
The values of m and n can be calculated with ease by determining the substituent
Connely Bove Lodge & Hutz LLP
Kaneka Corporation
Robertson Jeffrey B.
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