JPH11260404A - Nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve charge/discharge performances in a high temperature, a shelf performance and safety in an abnormally-high temperature, by including polycyclic alicyclic hydrocarbons or derivatives thereof in an electrolyte a polymer gel electrolyte or a polymer solid electrolyte. SOLUTION: Polycyclic alicyclic hydrocarbons to be included are, preferably, pinene, canphene, bicyclo-octene, bicyclo-octane, bornene, fenchene, or ester/ether compounds having these skeletons. Especially, pinene or canphene in a mono- terpene group or its derivatives such as Nopylacetate or the like are preferable. These compounds trap radicals, which are produced in a high temperature and may become a cause of decomposition deterioration of an electrolyte or spontaneous ignition, and change them into inactive forms. These compounds are used as a solvent component of an electrolysis solution or a polymer gel electrolyte, or a plasticizer component of a polymer solid electrolyte, and a sub-solvent is also used. Also, polymer material forming a polymer gel electrolyte or a solid electrolyte may contain these compounds as its component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte battery such as a lithium battery and a lithium ion battery. Particularly, the present invention relates to a battery having excellent high-temperature resistance and excellent safety at high temperatures.

[0002]

2. Description of the Related Art An electrolyte of a lithium primary battery or a secondary battery using lithium, a lithium alloy or a lithium insertion compound as a negative electrode is obtained by dissolving a lithium salt in a non-aqueous solvent or polymer. The main solvents constituting the electrolytic solution are propylene carbonate (PC) and ethylene carbonate (E
Cyclic carbonates such as C), chain carbonates such as diethyl carbonate (DEC) and dimethyl carbonate (DMC), chain ethers such as dimethoxyethane, cyclic ethers such as tetrahydrofuran (THF), and gamma butyrolactone (γBL). Lactones, generally a mixture thereof. Such solvents include lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), and lithium hexafluorophosphate (LiP
F ₆ ), lithium trifluorometasulfonate (Li
A solution in which a lithium salt such as CF ₃ SO ₃ ) is dissolved is used as an electrolyte.

In the polymer solid electrolyte and the polymer gel electrolyte, examples of the polymer material include those having a polyethylene oxide (PEO) skeleton, a polysiloxane skeleton, and polyacrylonitrile (PAN). In the plasticizer of the polymer solid electrolyte or the solvent of the gel electrolyte, the ester,
Examples include ether and lactone solvents.

[0004]

The above-mentioned conventional non-aqueous electrolyte battery has the following problems. That is, the carbonates, ethers, and lactones, which are the main solvents of the electrolytic solution, do not have sufficient oxidation resistance at high temperatures.
When operated at a high temperature such as 80 ° C. or left unattended, the capacity is greatly reduced. Further, there is a danger of ignition and combustion when placed at an abnormally high temperature exceeding 200 ° C.

[0005]

According to the present invention, in order to solve the above-mentioned problems, an electrolyte, a polymer gel electrolyte or a polymer solid electrolyte contains a polycyclic alicyclic hydrocarbon or a derivative thereof as an additive. More preferably, the main solvent of the electrolytic solution, or the main solvent and the polymer material constituting the solid polymer electrolyte and the gel electrolyte are polycyclic alicyclic hydrocarbons or derivatives thereof. Among them, electrolytes containing monoterpenes or derivatives thereof have excellent stability at high temperatures,
In addition, they have found that they are superior to conventional electrolytes in flame retardancy, and have reached the present invention. It is not clear how the polycyclic alicyclic hydrocarbons act, but it is thought that radicals generated in the electrolyte at high temperatures may cause degradation and ignition of the electrolyte, and the above-mentioned polycyclic alicyclic hydrocarbons may be affected. It is thought that hydrogen acts to trap generated radicals and convert them to an inactive form.

[0006]

FIG. 1 is a sectional view showing an example of the battery of the present invention. In FIG. 1, reference numeral 1 denotes a positive electrode. The positive electrode is an active material such as lithium cobalt oxide (LiCoO ₂ ) or lithium manganate (LiMn ₂ O ₄ ), a conductive auxiliary material such as graphite or carbon black, polyvinylidene fluoride (PVDF)
Etc., and an electrolytic solution described later. Or P
Instead of VDF, it is composed of a polymer gel electrolyte or a polymer solid electrolyte having both functions of a binder and an electrolyte. The positive electrode 1 is supported on a current collector 3 such as an aluminum (Al) foil. 2 is a negative electrode. The negative electrode is composed of an active material made of a lithium-insertable material such as various carbon materials and transition metal oxide materials, a binder such as PVDF, and an electrolyte. Alternatively, similarly to the positive electrode, it is composed of a polymer gel electrolyte or a polymer solid electrolyte instead of PVDF. The negative electrode 2 is supported on a current collector 4 such as a copper foil. Reference numeral 5 denotes a separator made of a microporous polyethylene (PE) film containing an electrolyte, a polymer solid electrolyte film described later, or a polymer gel electrolyte.

The electrolytic solution is a solution in which various lithium salts as supporting salts are dissolved in a non-aqueous solvent described later. As the lithium salt applied here, LiCF ₃ SO ₃ ,
LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ )
₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), Li
C (CF ₃ SO ₂ ) ₃ , LiBF ₄ , LiPF _{6 and the} like. The solvent of the electrolytic solution is the above-mentioned ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate or the like. The polymer component of the polymer gel electrolyte is a fluororesin such as polyvinylidene fluoride, polypropylene hexafluoride, or polyacrylonitrile. The polymer gel electrolyte is a gel composed of these polymer components and the electrolyte component. The polymer component of the polymer solid electrolyte is polyethylene oxide, polysiloxane, polyphosphazene, or the like. The polymer solid electrolyte is obtained by dissolving the lithium salt in a polymer having these polarities. In the polymer solid electrolyte, propylene carbonate, ethylene carbonate, γ-butyrolactone, or the like may be added as a plasticizer.

In the first embodiment, the electrolyte, the polymer gel electrolyte or the polymer solid electrolyte contains a polycyclic alicyclic hydrocarbon or a derivative thereof as an additive. Specifically, it is pinene, camphene, bornene, fenken, bicyclooctane, bicyclooctaene, or an ester or ether compound having a skeleton of these. Examples of the derivative include an alicyclic compound such as alkyl acetate, carbonate, and alkyl ether. Among them, pinene and camphene belonging to monoterpenes or nopyr acetate which is a derivative thereof are preferable. The content of these additives in the electrolyte solution, polymer gel electrolyte and polymer solid electrolyte is suitably from 1 to 10% by weight, and more preferably from 2 to 6% by weight.

In the second embodiment, the main solvent of the electrolytic solution, the main liquid component constituting the polymer gel electrolyte, and the main plasticizer of the plasticizer-containing polymer solid electrolyte are polycyclic alicyclic hydrocarbons or polycyclic alicyclic hydrocarbons. It is a derivative. Specifically, it is a pinene acetate or the like. The derivative ratio of the polycyclic alicyclic hydrocarbon in the whole solvent is at least 60 vol. %, And 80 vol. % Or more is desirable. As a co-solvent,
The aforementioned cyclic esters such as PC and EC, chain esters, butyrolactone, cyclic ethers and chain ethers can be used. The concentration of the lithium salt is suitably 0.5 to 2.0 M / l.

In the third embodiment, the polymer material constituting the polymer solid electrolyte or the polymer gel electrolyte contains a component having a polycyclic alicyclic skeleton structure. The polymer material may be a polymer consisting of a polycyclic alicyclic hydrocarbon or a derivative thereof alone, or a polymer gel electrolyte may be a copolymer or a mixture with a conventional fluororesin or polyacrylonitrile. In the polymer solid electrolyte, a copolymer or a mixture with a conventional polyethylene oxide or the like may be used. The proportion of the polycyclic alicyclic hydrocarbon or its derivative constituting the polymer is suitably at least 40% by weight. Furthermore, 60
% By weight or more is desirable. To give specific examples of derivatives of polycyclic alicyclic hydrocarbon applied as a polymer component,
It is a terpene derivative having an acrylate group at both terminals or a vinyl polymer having an alicyclic hydrocarbon derivative group as a pendant. Other examples include compounds having a structure in which a plurality of polycyclic alicyclic hydrocarbons are linked. The polymer solid electrolyte may be of a type containing a plasticizer, and a derivative of the polycyclic alicyclic hydrocarbon described in the solvent of the electrolytic solution is applied to the main plasticizer.

In the case where the solvent of the liquid electrolyte is a polycyclic alicyclic hydrocarbon, for example, the positive electrode is composed of 85% by weight of LiCoO ₂ , 10% by weight of carbon black, and 5% by weight of PVDF. , On an aluminum foil current collector. The thickness of the mixture layer is about 100 μm. The negative electrode is graphite 9
It consists of 5% by weight and 5% by weight of PVDF and is supported on a Cu foil current collector. The thickness of the mixture layer is about 100 μm. The separator is a PE microporous film having a thickness of 25 μm. The electrolyte is a solution of a terpene derivative in which LiPF ₆ having a concentration of 1 M is dissolved. An example of a derivative of a terpene derivative is one kind of nopyr acetate of a derivative of pinene.

The polymer solid electrolyte and the polymer gel electrolyte will be described as examples. Examples of the polymer material include a polymer of terpene diphenol diacrylate. The polymer solid electrolyte is a solid solution composed of 10% by weight of LiPF _{6 and} 90% by weight of the polymer. The polymer gel electrolyte contains 70% by weight of the above-mentioned 1 M LiPF ₆ nopyr acetate solution,
This is a polymer gel comprising 30% by weight of a polymer of terpene diphenol diacrylate. The positive electrode is LiCoO ₂ 67
The composite electrode is composed of 25% by weight, 8% by weight of acetylene black, and 25% by weight of a polymer solid electrolyte or a polymer gel electrolyte, and is supported on a positive electrode current collector made of Al foil. The thickness of the mixture layer is about 100 μm. The negative electrode is a composite electrode composed of 80% by weight of graphite and 20% by weight of a polymer solid electrolyte or a polymer gel electrolyte, and is supported on a negative electrode current collector made of Cu foil.
The thickness of the mixture layer is about 100 μm. The separator is a polymer solid electrolyte or polymer gel electrolyte film having a thickness of about 30 μm. Table 1 is a table comparing the self-discharge amount of the battery according to the present invention and the conventional battery at 60 ° C. for one month.

[0013]

[Table 1]

In Table 1, the basic structure of the battery is such that the positive electrode is Li
CoO ₂ and graphite are all the same for graphite but the electrolyte is different. A and B are batteries in which the electrolyte is liquid. A is a battery according to the present invention, and the composition of the electrolyte is a nopyr acetate solution in which 1M LiPF ₆ is dissolved. B is a conventional battery, and the composition of the electrolyte was EC / in which 1 M LiPF ₆ was dissolved.
It is a DMC / DEC mixed solution. C and D are polymer gel electrolyte batteries. C is a battery according to the present invention, in which the composition of the electrolyte is obtained by polymerizing terpene diphenyl diacrylate containing a nopyr acetate solution in which 1M LiPF ₆ is dissolved. D is a conventional battery and the composition of the electrolyte is 1
PAN containing an EC / DMC / DEC mixed solution in which M LiPF ₆ is dissolved. E and F are polymer solid electrolyte batteries. E is a battery according to the present invention, in which the composition of the electrolyte is obtained by polymerizing 90% by weight of terpene diphenol diacrylate containing 10% by weight of LiPF ₆ . F
Is a conventional battery in which the composition of the electrolyte is 90% by weight of PEO containing 10% by weight of LiPF ₆ .

As is clear from Table 1, the battery of the present invention has better self-discharge performance than the conventional battery.

FIG. 2 is a graph showing cycle characteristics when the battery A according to the present invention having a liquid electrolyte and the conventional battery B are repeatedly charged and discharged at a temperature of 60 ° C. The charging rate is 0.
2C, charge end voltage is 4.2V, discharge rate is 0.2
C, the discharge end voltage was 2.7 V. See Table 1 for battery categories.
It is the same as the category indicated by. From FIG. 1, it can be seen that the battery A according to the present invention has a smaller capacity decrease with the passage of cycles and has excellent characteristics as compared with the conventional battery B.

FIG. 3 shows batteries C and E according to the present invention and a conventional battery D having a polymer gel electrolyte and a polymer solid electrolyte, respectively.
FIG. 9 is a diagram comparing charge-discharge cycle characteristics of F at a temperature of 60 ° C. The conditions for both charging and discharging are the same as those shown in FIG. The battery classification is the same as that shown in Table 1.
As is clear from comparison between C and D and between E and F, the battery according to the present invention has a small decrease in capacity with the passage of cycles and has excellent characteristics.

Table 2 shows a comparison of safety when the battery according to the present invention and the conventional battery are fully charged and the temperature is raised to 250 ° C. All batteries have a capacity of 1000 mAh. The battery classification is the same as in Table 1 above.

[0019]

[Table 2]

As apparent from Table 2, the battery of the present invention has higher safety than the conventional battery.

[0021]

EFFECT OF THE INVENTION The nonaqueous electrolyte battery according to the present invention has excellent industrial value because it is excellent in charge / discharge performance at high temperatures, leaving performance at high temperatures, and safety when exposed to abnormal high temperatures. Things.

[Brief description of the drawings]

FIG. 1 is a sectional view of a nonaqueous electrolyte battery according to the present invention.

FIG. 2 is a diagram comparing charge / discharge cycle characteristics at 60 ° C. of a nonaqueous electrolyte secondary battery according to the present invention and a conventional secondary battery.

FIG. 3 is a diagram comparing charge / discharge cycle characteristics at 60 ° C. of a secondary battery having a polymer gel electrolyte and a polymer solid electrolyte according to the present invention and a conventional secondary battery.

Claims (5)

[Claims] 1. A non-aqueous electrolyte battery, wherein the electrolyte, the polymer gel electrolyte or the polymer solid electrolyte contains a polycyclic alicyclic hydrocarbon or a derivative thereof. 2. The method according to claim 1, wherein the polycyclic alicyclic hydrocarbon or a derivative thereof is a solvent component of an electrolytic solution, a polymer gel electrolyte, or a plasticizer component of a polymer solid electrolyte. Water electrolyte battery. 3. The non-aqueous electrolyte battery according to claim 1, wherein the polymer material constituting the polymer gel electrolyte or the polymer solid electrolyte contains a polycyclic alicyclic hydrocarbon or a derivative thereof as a component. . 4. The non-aqueous electrolyte battery according to claim 1, wherein the polycyclic alicyclic hydrocarbon has a basic structure represented by the following chemical formula. Embedded image Embedded image Embedded image Embedded image Embedded image 5. The non-aqueous electrolyte battery according to claim 1, wherein the derivative of the polycyclic alicyclic hydrocarbon is an ester or an ether.