Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From sulfur-containing reactant
Reexamination Certificate
2001-05-05
2003-08-05
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From sulfur-containing reactant
C528S332000, C528S422000, C528S423000, C528S424000, C428S402000, C429S129000, C429S199000, C429S304000, C429S317000
Reexamination Certificate
active
06602976
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to gel or polymer electrolytes containing a poly or oligo carbonate group as a main component, which is formed by condensation and/or ion exchange reactions, which can be used in electrochemical devices such as a battery, a capacitor, and a sensor.
BACKGROUND OF THE INVENTION
With the recent increasing demand for reduction in size and weight of electronic equipment, electrochemical devices have been attracting attention. Electrochemical devices are composed of a variety of constituent materials, and improvement is shown in the respective constituent materials. Of those constituent materials, an electrolyte solution is one of the main materials making up lithium batteries. The electrolyte solution generally comprises an organic solvent, such as propylene carbonate or ethylene carbonate in combination with other solvents, and an ionic salt, such as lithium hexafluorophosphate, as a solute, while it depends on matching with positive and negative electrodes. Use of such an electrolytic solution, however, involves many problems in, for example, leakage of liquid, safety, and the like. A polymer having dispersed therein a compound whose ions are easily movable or transportable, and a polyelectrolyte layer comprising a cross-linked polymer comprising polyethylene oxide as a main component, have been proposed However, their performance is insufficient as yet in terms of flexibility at low temperatures or stability. Thus, a satisfactory polymer electrolyte is not yet obtained. It has therefore been demanded to develop an effective polyelectrolyte that overcomes the above problems and will contribute to further advancement of technology while still having the properties of a gel or solid electrolyte.
The one main disadvantage of the lithium and lithium-ion polymer electrolyte battery is that since the gel or polymer electrolyte is very viscous or essentially a solid with liquid channels, the conductivity and internal resistance (or impedance) are reduced by a factor of 10 to 1000 times compared to lithium batteries with a liquid electrolyte. The conductivities for liquid lithium battery electrolytes for rechargeable lithium-ion batteries are usually in the 3 to 12 mS range at room temperature. On the other hand, the conductivities for true lithium in polymer or gel electrolytes range from 0.01 to 0.6 mS. Although several recent patents have claimed improvements up to about 1 mS. Both the rate of discharge and rate of charge are dependent on the conductivity and also low temperature performance is more negatively effected by the lower conductivities in the polymer electrolytes.
It is known that the best solvents for rechargeable lithium-ion battery performance are based on mixtures of ethylene carbonate (m.p. 35° C.) with other lower molecular weight dialkyl carbonates, which lower the liquidus range of the ethylene carbonate, such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc. Solutions of lithium salts such as the hexafluorophosphate, perchlorate, triflate, tetrafluoroborate, bis(trifluoromethylsulfonyl) imide, etc. at about one molar concentrations give conductivities in the range of 3 to 12 mS at room temperature.
In order to maximize the conductivity of the polymer electrolyte, the solvation of the lithium cation must be maximized, and therefore the amount of organic carbonate structure in the gel or polymer must be maximized according to the present invention there is provided.
U.S. Pat. No. 6,180,287 to Watanabe et al., which is herein incorporated by reference, discloses a solid polymer electrolyte by a polyether copolymer having a main chain derived from ethylene oxide and a side chain having two oligo-oxethylene groups and an electrolyte salt.
U.S. Pat. No. 6,190,805 to Takeuchi et al., which is herein incorporated by reference, discloses an ion conductive solid polymer electrolyte using a composite material derived from a (meth) acrylate prepolymer having a urethane bond and containing an oxyalkylene group, and an electrolyte salt.
JP-A4-253771 proposes to use a polyphosphazene-base polymer compound as an ion conductive material of a battery or electric double layer capacitor. The battery or electric double layer capacitor using a solid ion conductive material mainly comprising such a polymer compound is advantageous in that the output voltage is high as compared with those using an inorganic ion conductive material and it can be formed into various shapes and easily sealed. However, in this case, the ion conductivity of the solid polymer electrolyte is not sufficiently high and it is approximately from 10
−4
to 10
−6
S/cm, as a result, the takeout current is disadvantageously small. Furthermore, in assembling a solid electrolyte together with polarizable electrodes in a capacitor, it is difficult to uniformly compound the solid electrolyte with the carbon material having a large specific area because the materials mixed are both a solid.
J. Phys. Chem.,
Vol. 89, page 987 (1984) describes an example where oligoxyethylene is added to the side chain of polymethacrylic acid and an alkali metal salt is compounded thereto. Further,
J. Am. Chem.
Soc., Vol. 106, page 6854 (1984) describes polyphosphazene having an oligooxyethylene side chain, compounded with an alkali metal salt, however, the ion conductivity is about 1I0O S/cm and still insufficient.
SUMMARY OF THE INVENTION
The present invention relates to gel or polymer electrolytes prepared by condensation or ester exchange reactions, which are useful in electrochemical devices.
More particularly there is provided a series of polymers and oligomers, which use carbonate groups as the backbone of the polymer having the structure:
H[—(CHR)
z
CH
2
O(C═O)OCH
2
(Q)
v
(CHR)
n
O(C═O)OCH
2
(CHR)
z
—]
x
H
Where n is 1, 2, or 3, z is 0 to 6, R is hydrogen, methyl, ethyl, —CHR″O(C═O)O—M, where R″ is hydrogen, methyl, ethyl, or bridging group; M is a cross linking bond to another part of the molecule, methyl, ethyl, or propyl group or a mix thereof, Q is —(CH2OCH2)—,
or —CH2NRCH2—, and V is 0, 1, 2 or3.
A preferred polymer or oligomer of the invention has the following structure:
H[—(CHR)
z
CH
2
O(C═O)OCH
2
(CHR)
n
O(C═O)OCH
2
(CHR)
z
—]
x
H
Wherein Z is 2, N is 2, or 3, and R is hydrogen, methyl, ethyl, —CHR″O(C═O)O—M, where R″ is hydrogen, methyl, ethyl or bridging group; and M is a cross linking bond to another part of the molecule or a methyl or propyl or a mix of these groups.
It is general object of the invention to provide novel polymers and oligomers that can be useful for electrolytes in electrochemical devices.
It is another object of the invention to provide polymers that can be blended with high boiling organic carbonates to form gels.
It is a further object of the invention to provide electrolytes having high conductivity.
It is yet another object of the invention to provide a process for preparing polymers and oligomers for use in preparing high conductive electrolytes.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
According to the present invention there is provided a series of polymers and oligomers, which actually use the carbonate group as the backbone of the polymer and the actual condensing group rather an activated double bond in a special monomer. Accordingly, one is able to maximize the actual organic carbonate content of the polymer and maximize the conductivity of the polymer electrolyte.
Furthermore, it has been found that conductivities of about 0.5 to 2 mS can be obtained with lithium salts in these polymers and polymer gels formed by the condensation and/or polymerization of organic carbonates to form higher molecular weight molecules that maximize the primary organic carbonate content in the oligomer or polymer structure.
These polymers are formed by condensation and/or ester exchange reactions.
There is a continuum of these subject oligomers and polymers with respect to structure and physical properties. These polymers and oligomers exhibit enhance
McCloskey Joel
Smith W. Novis
Boykin Terressa M.
Lezdey John
Lithdyne International
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