JP2002343435A - Polymer electrolyte and battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid state or gel-state polymer electrolyte having high ionic conductivity, and to provide a high-output polymer electrolyte battery using the same. SOLUTION: A condensation polycyclic aromatic compound or its derivative of 12 wt.% or more is contained in this polymer electrolyte which is made to contain at least a polymer and an electrolytic salt. Preferably, at least one kind selected from among a group comprising naphthalene, pyrene, anthracene, and phenanthrene, is used as the aromatic compound. The polymer electrolyte battery is formed, by using the polymer electrolyte containing the aromatic compound or its derivative, a positive electrode, and a negative electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polymer electrolyte and a battery using the same.

[0002]

2. Description of the Related Art Although an organic electrolyte battery represented by a lithium ion battery has a high capacity, there is a danger of fire or the like when a liquid leaks. Therefore, a solid or gel polymer electrolyte is used. It has been proposed to increase the reliability and safety of the battery by using it. Also, for mobile devices, further miniaturization and weight reduction of batteries are desired,
It has become difficult for batteries using an electrolyte (liquid electrolyte) to meet such demands, and practical use of polymer electrolyte batteries is expected as an alternative.

However, since the ionic conductivity of the polymer electrolyte is lower than that of the electrolyte, it is difficult to obtain a high output, and the polymer electrolyte battery has characteristics comparable to those of the electrolyte battery. The challenge is how to make it possible.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a solid or gel-like polymer electrolyte having high ionic conductivity, and using the same, a solid or gel-like electrolyte system having a high power and high output. It is an object to provide a molecular electrolyte battery.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, when a polymer electrolyte contains 12% by weight or more of a condensed polycyclic aromatic compound or a derivative thereof, The inventors have found that the ionic conductivity of the polymer electrolyte can be improved, and have completed the present invention.

In the present invention, the reason why the ionic conductivity of the polymer electrolyte can be increased by including a condensed polycyclic aromatic compound or a derivative thereof in the polymer electrolyte is not necessarily clear at present. The π-conjugated electron cloud of the condensed polycyclic aromatic compound or a derivative thereof contains lithium ions (the lithium salt is generally used as the electrolyte salt, and therefore, lithium will be described as an example of the constituent metal of the electrolyte salt). It is presumed that the lithium ions can move along the electron cloud, so that the lithium ions can move without depending on the thermal vibration of the polymer. Conventionally, condensed polycyclic aromatic compounds and their derivatives have been used as additives to electrolytes, but their purpose is to eliminate the irreversible capacity of the negative electrode and to improve safety during overcharge. And the amount of addition was up to several weight% with respect to the electrolyte (Japanese Patent Application Laid-Open Nos. 9-17431, 11-185809, 2000).
195551). This is because if the condensed polycyclic aromatic compound or its derivative is present in a large amount in the liquid electrolyte, the condensed polycyclic aromatic compound or its derivative becomes an ion carrier and causes self-discharge. In a solid or gelled polymer electrolyte, the movement of the condensed polycyclic aromatic compound or its derivative is limited,
The addition at a high concentration becomes possible, and the ionic conductivity can be improved without adverse effects.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the condensed polycyclic aromatic compound is not particularly limited, and various compounds can be used. For example, naphthalene, pyrene, anthracene, phenanthrene and the like are relatively inexpensive. It is preferable because it can be obtained in large quantities. Further, a derivative of a condensed polycyclic aromatic compound in which a functional group is added to naphthalene, pyrene, anthracene, phenanthrene or the like can be used in the same manner. As such a functional group, for example, a hydrocarbon group such as a methyl group, an ethyl group, a vinyl group, and a phenyl group is preferable. These condensed polycyclic aromatic compounds and derivatives thereof may be used alone or in combination of two or more.

[0008] The content of the above-mentioned condensed polycyclic aromatic compound or its derivative in the polymer electrolyte is 12% by weight or more in the polymer electrolyte (that is, a high content containing the condensed polycyclic aromatic compound or its derivative). (Condensed polycyclic aromatic compound or its derivative is 12 parts by weight or more in 100 parts by weight of the molecular electrolyte). This is because when the content of the condensed polycyclic aromatic compound or its derivative in the polymer electrolyte is less than 12% by weight, the ionic conductivity of the polymer electrolyte cannot be sufficiently improved. When the content of the condensed polycyclic aromatic compound or its derivative in the polymer electrolyte increases, the ionic conductivity of the polymer electrolyte increases, so that the content in the polymer electrolyte is 20% by weight or more. However, if the amount is too large, the strength as a polymer film cannot be maintained. Therefore, the amount is preferably 70% by weight or less, more preferably 60% by weight or less.

Further, considering the content of the condensed polycyclic aromatic compound or its derivative in the polymer electrolyte in relation to the electrolyte salt such as lithium salt in the polymer electrolyte, the molar concentration of the electrolyte salt is 0.1%. 5 times or more is preferable, and 1 time or more is more preferable. This is because, as described above, in order to increase the ionic conductivity of the polymer electrolyte, a certain amount or more of a condensed polycyclic aromatic compound or a derivative thereof is required for lithium ions.

[0010] The polymer electrolyte in the present invention is prepared in a solid or gel form, and the polymer (polymer) constituting the polymer electrolyte may be a conventionally used polymer without any particular limitation. it can. Examples of such a polymer include a vinylidene fluoride compound,
Acrylonitrile compounds, styrene compounds, alkyl methacrylate / alkyl acrylate compounds, urethane acrylate compounds, acrylamide / methacrylamide compounds, N-vinylamide compounds, alkyl vinyl ether compounds and monomers used in the synthesis of the compounds exemplified above. And the like, but are not limited to those exemplified.

As an electrolyte salt, for example, LiCl
O_Four, LiPF₆, LiBF_Four, LiAsF₆, LiS
bF₆, LiCF_ThreeSO_Three, LiC_FourF₉SO_Three, Li
CF_ThreeCO_Two, Li_TwoC_TwoF_Four(SO_Three)_Two, LiN
(CF_ThreeSO_Two)_Two, LiC (CF _ThreeSO_Two)_Three, Li
C_nF_{2n + 1}SO_Three(N ≧ 2), LiN (RfOSO_Two)
_Two[Where Rf is a fluoroalkyl group]
Salts are preferably used, and these electrolyte salts are each used alone.
Can also be used, or a mixture of two or more
You can also. Polymer components and electrolysis in polymer electrolytes
In order to obtain a certain level of ionic conductivity.
Indicates that the electrolyte salt is 5% by weight or more based on the weight of the polymer (Po
(Electrolyte salt is 5 parts by weight or more based on 100 parts by weight of rimer)
And preferably at least 10% by weight.
And more preferably 20% by weight or more.
However, if the amount is too large, ions do not dissociate.
Below, preferably 40% by weight or less.
More preferred.

The polymer electrolyte of the present invention is prepared by using the above-exemplified polymer and electrolyte salt as basic constituents, and further containing a condensed polycyclic aromatic compound or a derivative thereof. In the case of being performed, it is prepared in a solid state.In the present invention, an organic solvent may be added to such a solid state polymer electrolyte and mixed to form a gelled polymer electrolyte, or An organic solvent may be added during the preparation of the polymer electrolyte to prepare a gel polymer electrolyte. Examples of the organic solvent used for gelling the polymer electrolyte include, for example, 1,2-dimethoxyethane, 1,2-diethoxyethane, propylene carbonate, ethylene carbonate, γ-butyrolactone, tetrahydrofuran, 1,3 -Dioxolan,
Diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate and the like, which can be used alone or in combination of two or more,
They are not limited to them.

A battery is constructed using the polymer electrolyte of the present invention.
In this case, as the active material of the positive electrode, for example, LiC
oO_TwoSuch as lithium cobalt oxide, LiMn_TwoO_Four
Such as lithium manganese oxide, LiNiO_TwoSuch as
Titanium nickel oxide, LiNiO_TwoPart of Ni in C
LiNi substituted with o_1-xCo_xO_Two, Manganese dioxide
Oxides, such as vanadium pentoxide and chromium oxide
Or metal sulfides such as titanium disulfide and molybdenum disulfide
One or two or more of the products are used. The positive electrode of the above example
Among the active materials, LiNiO_Two, LiNi_1-xCo_xO
_Two, LiMn_TwoO _FourOpen circuit voltage during charging of Li etc. is Li standard
When using lithium composite oxide showing 4V or more at
Is particularly preferable since a high energy density can be obtained.

The positive electrode may be added to the positive electrode active material, if necessary, with a conductive additive such as flake graphite, carbon black, and acetylene black, and a binder such as polyvinylidene fluoride and polytetrafluoroethylene. The positive electrode mixture prepared by mixing and mixing is pressed or molded, or the positive electrode mixture is dispersed in a solvent to prepare a paste containing the positive electrode mixture (in this case, the binder is previously dissolved or dissolved in the solvent. The paste may be mixed with the positive electrode active material after dispersing), and the paste containing the positive electrode mixture is applied to a positive electrode current collector made of aluminum foil or the like,
It is manufactured by drying and forming a positive electrode mixture layer and, if necessary, passing through a step of rolling. However, the method for producing the positive electrode is not limited to the method exemplified above,
Other methods may be used.

The material used for the negative electrode may be any material capable of doping and undoping lithium ions. In the present invention, such a material is referred to as a negative electrode active material. , For example, graphite,
Carbon compounds such as pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesocarbon microbeads, carbon fibers, activated carbon and the like. Also, S
An alloy such as i, Sn, In, or a compound such as an oxide which can be charged and discharged at a low potential close to Li can also be used as the negative electrode active material.

The negative electrode may contain the same binder as in the case of the positive electrode, if necessary, added to the negative electrode active material.
The negative electrode mixture layer prepared by mixing is pressure-formed, or the negative electrode mixture is dispersed in a solvent to prepare a paste containing the negative electrode mixture (in this case, the binder is dissolved or dispersed before dispersing). The paste containing the negative electrode mixture may be applied to a negative electrode current collector made of copper foil or the like, and dried to form a negative electrode mixture layer, and optionally subjected to a rolling treatment. It is produced by going through a process. However, the method for manufacturing the negative electrode is not limited to the method described above, and may be another method.

[0017]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

Example 1 1.2 mol / l LiB of a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 2
F ₄ and Solution 70 parts by volume, Dai-ichi Kogyo Seiyaku Co. Erekuseru TA-140 [trade name, trifunctional crosslinkable polyethylene oxide monomers (termini acrylic)] was mixed with 30 parts by volume, the naphthalene To this mixture 17% by weight (Li
(About twice the number of moles of BF ₄ ) and mixed (ie, added so that naphthalene accounts for 17% by weight of the whole) and further added as a polymerization initiator.
After adding and mixing 00 ppm of benzoyl peroxide, the mixture was poured into an electric conductivity measurement cell and kept at 80 ° C. for 30 minutes to obtain a gel-like naphthalene-containing polymer electrolyte.

Comparative Example 1 1.2 mol / l LiB of a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 2
After mixing 70 parts by volume of the F ₄ solution and 30 parts by volume of Elexel TA-140 (described above) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and adding and mixing 3000 ppm of benzoyl peroxide as a polymerization initiator to the mixture, The mixture was poured into an electric conductivity measurement cell and kept at 80 ° C. for 30 minutes to obtain a gel polymer electrolyte.

Comparative Example 2 1.2 mol / l LiB of a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 2
70 parts by volume of the F ₄ solution and 30 parts by volume of Elexel TA-140 (described above) manufactured by Daiichi Kogyo Seiyaku Co., Ltd. were mixed, and naphthalene was added to this mixture to be 5% by weight and mixed.
Furthermore, after adding and mixing 3000 ppm of benzoyl peroxide as a polymerization initiator, the mixture was poured into an electric conductivity measurement cell, and kept at 80 ° C. for 30 minutes to obtain a gel polymer electrolyte.

With respect to the polymer electrolytes of Example 1 and Comparative Examples 1 and 2, their electric conductivities at -20 ° C, 0 ° C and 20 ° C were measured. Table 1 shows the results. The measurement of the electric conductivity was performed by an AC impedance method at a frequency of 100 kHz.

[0022]

[Table 1]

As shown in Table 1, the polymer electrolyte of Example 1 has a higher electric conductivity in the range of -20 ° C. to 20 ° C. than the polymer electrolyte of Comparative Example 1 corresponding to a conventional polymer electrolyte. I was able to get the degree. Further, even when naphthalene was contained, the polymer electrolyte of Comparative Example 2 having a small content thereof could not obtain a sufficient improvement in electric conductivity as compared with the polymer electrolyte of Example 1.

In the above embodiment, the electric conductivity was measured without measuring the ionic conductivity of the polymer electrolyte because it was difficult to measure the ionic conductivity because The degree and the electrical conductivity have a correlation, and the higher the electrical conductivity, the higher the ionic conductivity.

[0025]

As described above, according to the present invention,
A polymer electrolyte having high ionic conductivity can be obtained, and a high-output polymer electrolyte battery can be provided by using the polymer electrolyte.

Continued on the front page F-term (reference) 4J002 BC011 BD141 BE041 BG041 BG051 BG071 BG101 BG131 BJ001 BQ001 DD006 DE196 DH006 DK006 EA067 EH006 EV216 EV236 FD116 GQ02 5H024 AA06 AA09 FF11 FF21 FF23 ALH HJ01

Claims (4)

[Claims] Claims: 1. An apparatus comprising at least a polymer and an electrolyte salt,
A polymer electrolyte comprising a condensed polycyclic aromatic compound or a derivative thereof in an amount of 12% by weight or more. 2. The fused polycyclic aromatic compound comprises naphthalene,
The polymer electrolyte according to claim 1, wherein the polymer electrolyte is at least one selected from the group consisting of pyrene, anthracene, and phenanthrene. 3. The polymer electrolyte according to claim 1, wherein the content of the condensed polycyclic aromatic compound or a derivative thereof is at least 0.5 times the molar concentration of the electrolyte salt in molar concentration. . 4. A battery comprising at least a positive electrode, a negative electrode, and the polymer electrolyte according to claim 1.