JPH05343076A - Nonaqueous electrolyte battery - Google Patents

Abstract

PURPOSE:To improve a preserving characteristic and a charge and discharge cycle characteristic. CONSTITUTION:In a nonaqueous electrolyte battery having a positive electrode, a negative electrode mainly composed of a material capable of storing and releasing lithium metal or lithium, a separator to separate and isolate these both electrodes from each other and nonaqueous electrolyte, the nonaqueous electrolyte contains vasophenanthroline and/or 2,2'-dipyridyl. Since the nonaqueous electrolyte containing a specific unsaturated nitrogen contained heterocyclic compound is used, decomposition caused by a lithium ion of a solvent molecule in the nonaqueous electrolyte is restrained, so that a preserving characteristic or a charge and discharge characteristic can be improved in a secondary battery.

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, and more particularly to improvement of a non-aqueous electrolyte solution for the purpose of improving storage characteristics and cycle characteristics.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
As an electrolytic solution for a non-aqueous electrolytic solution battery, a non-aqueous electrolytic solution in which an electrolyte solute such as LiPF ₆ or LiClO ₄ is dissolved in a solvent such as propylene carbonate or dimethyl carbonate is generally used.

However, in such a conventional non-aqueous electrolyte solution, the solvent molecules are easily decomposed by lithium ions (Li ⁺ ), so that the storage characteristics are not good, and especially in the case of secondary batteries, only batteries having a short cycle life are used. There was a problem that it was difficult to obtain.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a non-aqueous electrolyte battery having excellent storage characteristics and charge / discharge cycle characteristics.

[0005]

A non-aqueous electrolyte battery according to the present invention (hereinafter, referred to as "the present battery") for achieving the above object is capable of inserting and extracting a positive electrode and lithium metal or lithium. A negative electrode mainly composed of a substance, a separator separating these electrodes, a non-aqueous electrolyte battery comprising a non-aqueous electrolyte, the non-aqueous electrolyte,
It is characterized by containing bathophenanthroline represented by the following chemical formula 1 and / or 2,2′-dipyridyl represented by the following chemical formula 2.

[0006]

[Chemical 1]

[0007]

[Chemical 2]

As described above, in the battery of the present invention, the non-aqueous electrolyte solution to which the specific unsaturated nitrogen-containing heterocyclic compound is added is used, which causes a problem in the conventional non-aqueous electrolyte battery. The deterioration of the non-aqueous electrolytic solution caused by the decomposition of the above-described solvent is suppressed.

In other words, in the battery of the present invention, a specific unsaturated nitrogen-containing heterocyclic compound is solvated with lithium ion (Li ⁺ ) to inactivate the lithium ion with respect to other solvent molecules. Thus, the stabilization of the solvent and the prevention of deterioration of the non-aqueous electrolyte solution are realized.

FIG. 1 is an explanatory view schematically showing the state of this solvation by taking 2,2'-dipyridyl as an example. A plurality of (three as shown in the figure) lithium ion ions are usually surrounded. It shows that the 2,2′-dipyridyl molecule is chelated in the state where the —N═C—C═N— bond portion having a higher electronegativity than the ring carbon atom is exposed to the lithium ion. . Thus, when the non-aqueous electrolyte solution of the present invention is used, since bathophenanthroline or 2,2′-dipyridyl is coordinated around the lithium ion (chelation), the lithium ion is stabilized and other The decomposition reaction of the solvent molecule of is suppressed.

The suitable addition amount of bathophenanthroline and / or 2,2'-dipyridyl in the present invention to the non-aqueous electrolytic solution is in the range of 0.5 to 10% by weight. If it is less than 0.5% by weight, the effect of suppressing the decomposition of solvent molecules is not sufficiently exhibited because it is too small, and if it exceeds 10% by weight, the concentration of addition is too high and the unsaturated nitrogen-containing heterocyclic ring is present. The formula compounds are likely to be decomposed on the positive electrode side, and the cycle characteristics tend to be rather deteriorated.

As the solvent of the non-aqueous electrolyte in the present invention, propylene carbonate, ethylene carbonate,
Examples include organic solvents such as 1,2-butylene carbonate, dimethyl carbonate, and diethyl carbonate, and mixed solvents of these with a low-boiling solvent, and examples of solutes include LiPF ₆ , LiClO ₄ , and LiCF ₃ SO _3. Since the non-aqueous electrolyte solution of the present invention contains a solvent which is easily decomposed by lithium ions, the effect intended by the present invention can be achieved by adding bathophenanthroline or 2,2′-dipyridyl, Not limited to.

Members other than the non-aqueous electrolyte of the battery of the present invention are not particularly limited, and various materials conventionally used for non-aqueous electrolyte batteries can be used.

That is, as the positive electrode material (active material),
Metal oxides (MnO ₂ , modified MnO ₂ , heavy Mn
O ₂ , MoO ₂ , CuO, Cr ₂ O ₃ , CrO ₃ , V ₂
O ₅ , LiCoO ₂ , LiNiO ₂ , NiOOH, etc.); metal sulfides (FeS, TiS ₂ , or MoS _2, etc.); metal selenides (TiSe _2, etc.); from the group consisting of chromium, manganese, iron, cobalt and nickel. A complex oxide of at least one selected metal and Li,
Various materials can be used.

The positive electrode of the battery of the present invention is obtained by, for example, kneading the positive electrode material described above with a conductive agent such as acetylene black or carbon black and a binder such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVdF). After forming a mixture, this positive electrode mixture is rolled into a foil or lath plate made of aluminum or stainless steel as a current collector,
It is produced by heat treatment under vacuum at a temperature of about 250 ° C. for about 2 hours.

Examples of the negative electrode material include lithium metal, lithium alloys, carbon materials, and other substances capable of inserting and extracting lithium. A powder material such as a carbon material is kneaded with a binder such as polytetrafluoroethylene and used as a negative electrode mixture.

[0017]

In the battery of the present invention, the non-aqueous electrolytic solution contains bathophenanthroline and / or 2,2'-dipyridyl, and these unsaturated nitrogen-containing heterocyclic compounds are chelated around lithium ions. Coordinate. As a result, the contact between the other solvent molecules in the non-aqueous electrolyte solution and the lithium ions is cut off, and the decomposition degradation of the solvent molecules is suppressed.

[0018]

EXAMPLES The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to the following examples, and various modifications can be made without departing from the scope of the invention. Is possible.

Example 1 A flat non-aqueous electrolyte primary battery (the battery of the present invention) was produced.

[Preparation of Positive Electrode] Manganese dioxide as an active material, acetylene black as a conductive agent, and a fluororesin as a binder for both of them are mixed at a weight ratio of 80: 1.
The mixture was mixed at 0:10 to obtain a positive electrode mixture. This positive electrode mixture was molded into a disc-shaped positive electrode.

[Production of Negative Electrode] A disk-shaped negative electrode made of lithium metal was produced by rolling and punching.

[Preparation of Non-Aqueous Electrolyte] Ethylene carbonate (EC) and 1,2-butylene carbonate (BC)
Volume ratio of 1,2-dimethoxyethane (DME) to 1:
Lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ) was dissolved in a mixed solvent of 1: 3 at a concentration of 1 mol / liter, and bathophenanthroline was further added so as to be 5% by weight based on the total weight of the non-aqueous electrolyte solution. A non-aqueous electrolyte solution was prepared by mixing.

[Production of Battery] A flat primary battery (battery size: diameter 20) using the positive and negative electrodes and the non-aqueous electrolyte solution described above.
mm, thickness: 2.5 mm). As the separator, a microporous thin film made of polypropylene was used, which was impregnated with the above-mentioned non-aqueous electrolytic solution.

FIG. 2 shows the manufactured flat type battery BA1 of the present invention.
FIG. 2 is a cross-sectional view schematically showing the battery B of the present invention shown in FIG.
A1 includes a positive electrode 1, a negative electrode 2, a separator 3 separating these two electrodes, a positive electrode can 4, a negative electrode can 5, a positive electrode current collector 6, a negative electrode current collector 7 and an insulating packing 8 made of polypropylene. The positive electrode 1 and the negative electrode 2 are housed in a battery case formed by positive and negative bipolar cans 4 and 5 facing each other with a separator 3 impregnated with a non-aqueous electrolyte interposed therebetween, and the positive electrode 1 is interposed via a positive electrode current collector 6. The negative electrode 2 is connected to the positive electrode can 4 and the negative electrode 2 is connected to the negative electrode can 5 via the negative electrode current collector 7, and the chemical energy generated inside the battery BA1 of the present invention is output as electrical energy from both terminals of the positive electrode can 4 and the negative electrode can 5. You can take it out.

Comparative Example 1 A comparative battery BC1 was prepared in the same manner as in Example 1 except that bathophenanthroline was not added in the preparation of the non-aqueous electrolyte solution.

(Initial discharge characteristic test) For each of the battery BA1 of the present invention and the comparative battery BC1 immediately after production, 3
A constant resistance discharge of 00 ohm was performed to examine the initial discharge characteristics. The results are shown in Fig. 3.

FIG. 3 is a graph showing the discharge characteristics of each battery, with the vertical axis representing the battery voltage (V) and the horizontal axis representing the discharge time (h). It can be seen that there is no significant difference in discharge characteristics between the present battery BA1 and the comparative battery BC1.

(Discharge characteristics test after storage) 60 ° C after fabrication
Inventive Battery BA1 and Comparative Battery B after 3 months storage at
Each C1 was subjected to a constant resistance discharge of 300 ohms and the discharge characteristics were examined. The results are shown in Fig. 4.

FIG. 4 is a graph similar to the graph shown in FIG. 3, showing the discharge characteristics of each battery after storage. From FIG. 4, the battery BA1 of the present invention was compared after storage for 3 months. It can be seen that the discharge characteristic is clearly superior to that of the battery BC1.

Example 2 A flat type non-aqueous electrolyte secondary battery (the battery of the present invention) was produced.

[Production of Positive Electrode] Lithium-containing manganese dioxide (lithium salt and manganese dioxide 3
Which is heat-treated at 75 ° C. to occlude lithium in the pores of manganese dioxide), acetylene black as a conductive agent, and a fluororesin as a binder for both of these,
A weight ratio of 80:10:10 was mixed to obtain a positive electrode mixture. This positive electrode mixture was molded into a disc-shaped positive electrode.

[Production of Negative Electrode] A disk-shaped negative electrode made of lithium metal was produced by rolling and punching.

[Preparation of Non-Aqueous Electrolyte Solution] LiPF ₆ was added to a mixed solvent of ethylene carbonate, propylene carbonate and 1,2-dimethoxyethane in a volume ratio of 3: 3: 4.
A non-aqueous electrolyte solution was prepared by further adding and mixing 2,2′-dipyridyl in an amount of 0.1 mol / liter to the dissolved solution.

[Production of Battery] Using the above-mentioned positive and negative electrodes and the non-aqueous electrolyte solution, a flat type battery of the present invention (secondary battery) BA
2 to BA14 were produced (battery size: diameter 24 mm, length 3.0 mm). As the separator, a microporous thin film made of polypropylene was used, which was impregnated with the non-aqueous electrolyte solution described above.

Comparative Example 2 A comparative battery BC2 was prepared in the same manner as in Example 2 except that 2,2′-dipyridyl was not added.

Example 3 Instead of a mixed solvent of ethylene carbonate, propylene carbonate and 1,2-dimethoxyethane in a volume ratio of 3: 3: 4, an equal volume mixture of ethylene carbonate and 1,2-dimethoxyethane was used. A battery BA3 of the present invention was produced in the same manner as in Example 2 except that a solvent was used and pasophenanthroline was used at 1 mol / liter instead of 2,2′-dipyridyl.

Comparative Example 3 A comparative battery BC3 was produced in the same manner as in Example 3 except that pasophenanthroline was not added.

Example 4 Instead of a mixed solvent of ethylene carbonate, propylene carbonate and 1,2-dimethoxyethane in a volume ratio of 3: 3: 4, ethylene carbonate, 1,2-butylene carbonate and 1,2- The battery BA4 of the present invention was prepared in the same manner as in Example 2 except that a mixed solvent with dimethoxyethane in a volume ratio of 3: 3: 4 was used and LiCF ₃ SO ₃ was used in place of LiPF ₆ at 1 mol / liter. Was produced.

(Comparative Example 4) A comparative battery BC4 was prepared in the same manner as in Example 4 except that 2,2'-dipyridyl was not added.

(Charge / Discharge Cycle Test) Battery BA2 of the Present Invention
~ BA4 and comparative batteries BC2 to BC4 were subjected to a charge / discharge cycle test. The results are shown in Table 1. In the charge / discharge cycle test, charging and discharging were performed at 2 mA for 4 hours each, and this was regarded as one cycle.
The cycle life was defined as the number of cycles (times) until the battery voltage dropped to 1.8 V during discharge.

[0041]

[Table 1]

From Table 1, the batteries BA2 to BA4 of the present invention are
It can be seen that the cycle life is generally longer than that of the comparative batteries BC2 to BC4.

In the above embodiments, specific examples in which the present invention is applied to a flat type battery have been described, but the shape of the battery is not particularly limited, and the present invention has various shapes such as a cylindrical type and a square type. It can be applied to non-aqueous electrolyte batteries.

[0044]

INDUSTRIAL APPLICABILITY In the battery of the present invention, since a non-aqueous electrolyte containing a specific unsaturated nitrogen-containing heterocyclic compound is used, decomposition of other solvent molecules in the non-aqueous electrolyte by lithium ions Therefore, the present invention has excellent peculiar effects such as excellent storage characteristics and charge / discharge cycle characteristics.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a schematic cross-sectional view of a flat type battery of the present invention.

FIG. 3 is an initial discharge characteristic diagram of a battery of the present invention and a comparative battery.

FIG. 4 is a discharge characteristic diagram of the battery of the present invention and the comparative battery after storage at 60 ° C. for 3 months.

[Explanation of symbols]

 BA1 battery of the present invention 1 positive electrode 2 negative electrode 3 separator

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Ryuji Oshita 2-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Atsushi Suemori 2-18-2 Keihanhondori, Moriguchi-shi, Osaka Sanyo (72) Inventor Norihiro Furukawa 2-18 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. (72) Inventor Koji Nishio 2-18 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (2)

[Claims] 1. A non-aqueous electrolyte battery comprising a positive electrode, a negative electrode containing lithium metal or a substance capable of inserting and extracting lithium as a main material, a separator separating these electrodes, and a non-aqueous electrolyte solution. The non-aqueous electrolyte battery, wherein the non-aqueous electrolyte solution contains bathophenanthroline and / or 2,2′-dipyridyl. 2. The non-aqueous electrolyte battery according to claim 1, wherein the non-aqueous electrolyte solution contains bathophenanthroline and / or 2,2′-dipyridyl in an amount of 0.5 to 10% by weight.