JP2002110185A - Electric cell with non-aqueous electrolyte solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric cell with non-aqueous electrolyte solution whose internal resistance is not increased significantly even if it has been left for a long time ranging from several months to several years after a partial discharge. SOLUTION: In the electric cell with non-aqueous electrolyte solution which cell comprises a negative electrode having metallic lithium or lithium alloy as active material, there is used, as a non-aqueous electrolyte solution, a non- aqueous solution containing lithium salt and at least a salt of the aluminum salts represented by the formulas, Al[N(CxF2x+1A)(CyF2y+1A)]3, Al[C(CxF2x+1 A)(CyF2y+1A)(CzF2z+1A)]3, and Al[CR(CxF2x+1A)(CyF2y+1A)]3, where A is CO or SO2, R is an alkyl group, and x, y, and z are the natural numbers of 1-4.

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 a non-aqueous electrolyte battery capable of suppressing an increase in internal resistance after discharging a part of battery capacity.

[0002]

2. Description of the Related Art In recent years, there has been a demand for the development of a battery having a small size, light weight and high energy density as a power source for various electronic devices. Non-aqueous electrolyte batteries using manganese dioxide, fluorinated graphite or the like as a positive electrode active material have come to be used.

[0003] This type of battery has a disadvantage that the internal resistance of the battery increases when it is stored for a long time after being discharged from the initial state. In particular, when the battery is stored for a long time in a state where about 70% or more of the battery capacity is discharged, the internal resistance is particularly increased. This is because the solvent component (especially a low boiling point solvent) in the electrolytic solution is decomposed by the catalytic action of MnO ₂ (Li) in the positive electrode active material generated at the time of discharge, and the decomposed product moves to the negative electrode side However, it is conceivable that an inert film is formed by reacting with lithium on the surface of the negative electrode to hinder the movement of lithium ions. Such an increase in internal resistance
This will impair the reliability of the battery.

In order to suppress such an increase in internal resistance, for example, an aluminum foil is pressed on the surface of a negative electrode made of metallic lithium to form a lithium-aluminum alloy layer, and an inert film is formed on the surface of the negative electrode. There is a method of suppressing such a situation. According to this method, the frequency of contact of the decomposition product with lithium is reduced, so that a reduction reaction on the negative electrode surface is suppressed, and as a result, an increase in internal resistance can be suppressed. However, this method
The alloying reaction takes a long time, and the surface of the formed alloy layer becomes fine powder, so that there is a problem that a problem such as breaking through the separator may occur.

Further, Japanese Patent Application Laid-Open No. 1-124960 discloses a method of adding aluminum trifluoromethanesulfonate [Al (CF ₃ SO ₃ ) ₃ ] to a non-aqueous electrolyte. According to this method, a lithium-aluminum alloy layer can be formed on the surface of the negative electrode made of metallic lithium, so that an increase in internal resistance can be suppressed as described above. However, the battery to which this method is applied can suppress the increase in the internal resistance for a certain period of time (about several months), but has a problem that the internal resistance greatly increases after that period. Was required.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above, and has been made in view of the above circumstances. Its purpose is to provide.

[0007]

Means for Solving the Problems To solve the above problems, the invention according to claim 1 comprises a negative electrode using lithium metal or a lithium alloy as an active material, a positive electrode, and a non-aqueous electrolyte. In a non-aqueous electrolyte battery, the non-aqueous electrolyte is
The solute is characterized by containing a lithium salt and at least one of aluminum salts represented by the following chemical formulas (1) to (3).

[0008]

Embedded image

When a lithium salt and the specific aluminum salt are used as a solute as in the above configuration, a lithium-aluminum alloy layer is formed on the surface of the negative electrode by the specific aluminum salt, and the ionic composition in the electrolytic solution is as follows: It mainly becomes lithium ions, anions derived from lithium salts and anions derived from the specific aluminum salts. for that reason,
Even if the battery is left for a long time after the partial discharge, the internal resistance of the battery does not increase significantly. Although the reason for this is not necessarily clear, the degree of dissociation is high because the anion of the specific aluminum salt has a large number of electron-withdrawing groups as compared with the aluminum trifluoromethanesulfonate, and this anion is stable in the electrolytic solution. It's easy to do. For this reason, the aluminum ions dissociated from the aluminum salt smoothly move to the negative electrode surface, and a dense and aluminum-rich alloy layer is formed. As a result, the formation of an inert film is further suppressed. In addition, a synergistic effect is conceivable in which the stable anion derived from the specific aluminum salt suppresses the decomposition of the electrolytic solution on the positive electrode surface.

The anion generated from the specific aluminum salt is stably present in the electrolytic solution, so that more lithium ions contribute to the battery reaction. for that reason,
By including the specific aluminum salt, the battery performance does not decrease.

According to a second aspect of the present invention, in the first aspect of the invention, the active material of the positive electrode is manganese dioxide.

When manganese dioxide is used as the positive electrode active material, as described above, MnO _{2, which is} highly reactive due to discharge,
Although (Li) is generated on the positive electrode side, according to the present invention, since an alloy layer is formed on the negative electrode surface, the decomposition product of the solvent due to MnO ₂ (Li) comes into contact with the negative electrode and reacts to form an inert film. Formation can be prevented. Therefore, a non-aqueous electrolyte battery in which an increase in internal resistance is suppressed is obtained.

According to a third aspect of the present invention, in the first or second aspect, the non-aqueous electrolytic solution contains at least a low-boiling solvent as a solvent.

Since the low boiling point solvent is easily decomposed by reacting with MnO ₂ (Li) or the like, the improvement effect of the present invention is high when such a low boiling point solvent is used.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the lithium salt is different from the aluminum salt represented by the chemical formulas (1) to (3). It is a lithium salt having an anion.

Even with the combination of the lithium salt and the aluminum salt as described above, the degree of dissociation of the specific aluminum salt does not decrease, and the aluminum ions can smoothly form the alloy layer with the negative electrode lithium. Provided. Therefore, the battery can suppress an increase in internal resistance after storage.

According to a fifth aspect of the present invention, there is provided the method according to any one of the first to fourth aspects, wherein the chemical formula (1)
The compounding ratio of the aluminum salt represented by (3) in the whole nonaqueous electrolyte is 0.005 to 10% by mass.

When the mixing ratio of the specific aluminum salt is within the above range, a high quality alloy film is formed, and the ionic composition in the electrolytic solution becomes appropriate. Therefore, it is effective to increase the internal resistance of the battery. Can be suppressed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings, taking a cylindrical lithium battery as an example. FIG.
FIG. 1 is a schematic sectional view showing the configuration of this battery.

As shown in FIG. 1, this battery comprises a bottomed cylindrical outer can (negative electrode can) 1, a positive electrode 2 containing manganese dioxide as an active material, and a negative electrode 3 containing metallic lithium as an active material. ,
A spiral electrode body 5 formed by winding a separator 4 made of a polyethylene porous film is housed therein. A sealing lid 7 serving also as a positive electrode terminal is caulked and fixed to the opening of the outer can 1 via an insulating gasket 6. A negative electrode current collector lead plate 8 electrically connected to the negative electrode 3 is attached to the inner bottom surface of the outer can 1, and the positive electrode 2 is electrically connected to the inner bottom surface of the sealing lid 7. The positive electrode current collecting lead plate 9 is attached. In the drawing, reference numeral 10 denotes a negative electrode current collector lead plate fixing insulating tape, 11 denotes an upper insulating plate, and 12 denotes a lower insulating plate.

Here, in the separator 4, a mixed solvent of propylene carbonate (PC) and 1,2-dimethoxyethane (DME) is mixed with LiCF ₃ SO ₃ and Al
[N (CF ₃ SO ₂ ) ₂ ] ₃ is impregnated with a non-aqueous electrolyte solution.

A lithium battery having the above structure was manufactured as follows.

[Preparation of Positive Electrode] First, manganese dioxide as a positive electrode active material and artificial graphite as a conductive agent were mixed at a mass ratio of 9: 1 to prepare a positive electrode mixture. Next, 5 mass% of a fluororesin (polytetrafluoroethylene) as a binder and water as a dispersion medium were added to the positive electrode mixture, and mixed to prepare a slurry. Thereafter, this slurry was applied to a positive electrode core made of a thin aluminum plate, further compressed and dried to produce a positive electrode. afterwards,
A part of the positive electrode was peeled off, and a positive electrode current collector lead plate made of stainless steel was joined to the positive electrode core exposed from the part by spot welding.

[Preparation of Negative Electrode] A metal lithium plate was cut into a predetermined size to prepare a negative electrode. Thereafter, a negative electrode current collecting lead plate made of a nickel thin plate was pressure-bonded to a part of the negative electrode.

[Preparation of Non-Aqueous Electrolyte] LiCF ₃ SO ₃ and Al [N (CF) were mixed in an equal volume mixed solvent of propylene carbonate (PC) and 1,2-dimethoxyethane (DME).
₃ SO ₂ ) ₂ ] _{3 in a} ratio of 1: 1 (mass ratio), and a solute obtained by dissolving the aluminum salt in an amount of 5 mass% (combination ratio in the entire electrolytic solution) to form a non-aqueous electrolyte. A liquid was prepared.

[Preparation of Battery] First, the positive electrode and the negative electrode were wound through a separator made of a porous film made of polypropylene to prepare a spiral electrode body. Thereafter, the spiral electrode body is inserted into a bottomed cylindrical outer can (negative electrode can),
Further, the non-aqueous electrolyte was injected into the outer can. And
A sealing lid (positive electrode terminal) is swaged and fixed to the opening of the outer can via a polypropylene insulating gasket to form a cylindrical lithium battery (battery capacity: 1400 m).
Ah, diameter 17 mm, height 33.5 mm).

[Other Matters] In the above example, Al [N (CF ₃ SO ₂ ) ₂ ] ₃ was used as the specific aluminum salt, but the present invention is not limited to this. Various aluminum salts represented by 1) to (3) can be used. These may be used alone or in combination of two or more.

[0028]

Embedded image

Examples of the alkyl group represented by R in the above formula (3) include a methyl group, an ethyl group and a propyl group.

Specific examples of the above aluminum salt include A
l [N (CF ₃ SO ₂ ) ₂ ] ₃ , Al [N (C ₂ F ₅ S
O ₂ ) ₂ ] ₃ , Al [N (CF ₃ SO ₂ ) (C ₂ F ₅ SO ₂ )]
₃ , Al [C (CF ₃ SO ₂ ) ₃ ] ₃ , Al [CCH ₃ (CF
₃ SO ₂ ) ₂ ] _{3 and the} like.

The proportion of the aluminum salt occupied in the entire electrolytic solution is preferably in the range of 0.005 to 10% by mass in consideration of the formation of the alloy film and the ionic composition of the electrolytic solution.
Particularly preferably, it is in the range of 0.01 to 5% by mass.

In addition, other aluminum salts that can be alloyed with lithium may be used in combination with the above-mentioned specific aluminum salt. For example, Al (CF
₃ SO ₃ ) ₃ or the like can be used. In addition, Al (CF ₃
If SO ₃ ) ₃ is used together with a specific aluminum salt, it is advantageous in terms of cost and production.

In the above example, the lithium salt is L
Although iCF ₃ SO ₃ was used, the present invention is not limited to this. For example, LiN (CF ₃ SO ₂ ) ₂ , Li
N (C ₂ F ₅ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ ,
LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆
Etc. can be used. These may be used alone or in combination of two or more.

As the solvent for the non-aqueous electrolyte, the above-mentioned P
In addition to C and DME, for example, a high dielectric constant non-aqueous organic solvent having a dielectric constant (25 ° C.) of 20 or more, such as ethylene carbonate, butylene carbonate, and γ-butyrolactone, dimethyl carbonate, dioxolan, tetrahydrofuran, ethoxymethoxyethane, and the like And a low-boiling non-aqueous organic solvent having a boiling point of 100 ° C. or lower can be used. These may be used alone or in combination of two or more.

The nonaqueous electrolyte battery of the present invention is not limited to the structure shown in FIG. 1, and the positive electrode, the negative electrode and the like are not limited to those described above. Other positive electrode active materials include, for example, lithium-containing metal oxides such as lithium-containing cobalt composite oxide, lithium-containing nickel composite oxide, and lithium-containing manganese composite oxide, and metal oxides such as niobium oxide and vanadium oxide. Alternatively, a metal chalcogenide such as molybdenum disulfide can be used. As the negative electrode active material other than the above, a lithium alloy such as a lithium-aluminum alloy can be used.

[0036]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

(Example 1) In Example 1, a lithium battery manufactured by the same method as that described in the above embodiment mode was used.

Example 2 A lithium battery was manufactured in the same manner as in Example 1 except that Al [C (CF ₃ SO ₂ ) ₃ ] ₃ was used as a specific aluminum salt.

Example 3 Except that Al [CCH ₃ (CF ₃ SO ₂ ) ₂ ] ₃ was used as a specific aluminum salt,
A lithium battery was manufactured in the same manner as in Example 1.

Example 4 As a solute of the non-aqueous electrolyte, LiCF ₃ SO ₃ as a lithium salt, Al [N (CF ₃ SO ₂ ) ₂ ] _{3 as} a specific aluminum salt, and other aluminum salts And Al (CF ₃ SO ₂ ) ₃ in a mass ratio of 2:
A lithium battery was manufactured in the same manner as in Example 1, except that a mixture of 2: 1 was used, and a non-aqueous electrolyte solution in which a specific aluminum salt was dissolved to 3% by mass was used. .

Comparative Example 1 As a solute of a nonaqueous electrolyte, a lithium salt of LiCF ₃ SO ₃ and another aluminum salt of Al (CF ₃ SO ₃ ) ₃ were mixed at a mass ratio of 1: 1. A lithium battery was manufactured in the same manner as in Example 1, except that the mixture prepared in Example 1 was used, and a nonaqueous electrolyte solution in which a lithium salt was dissolved to 0.5 mol / L was used.

Comparative Example 2 As a solute of a non-aqueous electrolyte, a lithium salt, LiCF ₃ SO _3, was used, and a non-aqueous electrolyte in which the salt was dissolved to a concentration of 0.5 mol / liter was used. Other than that was carried out similarly to Example 1, and manufactured the lithium battery.

Each of the lithium batteries thus obtained was discharged for 70% of its battery capacity and stored for one year at room temperature (20 ° C.). The internal resistance before storage, the internal resistance after storage for 6 months, and the internal resistance after storage for one year were measured. The results are shown in Table 1 below.

[0044]

[Table 1]

From Table 1 above, it was found that the battery using the specific aluminum salt together with the lithium salt suppressed the increase in the internal resistance after storage for one year as compared with other batteries. Specifically, the internal resistance of the battery of Example 1 after storage for one year increased only by 0.14Ω compared to that before storage, whereas the battery of Comparative Example 1 was 0.72Ω and the battery of Comparative Example 2 was 8 .4
Since Ω also increased, it was found that the use of a specific aluminum salt can particularly suppress an increase in internal resistance.
In the battery of Comparative Example 1, the internal resistance only increased by 0.21Ω after storage for 6 months, but increased by 0.51Ω after storage for 6 months. ₃ SO ₃ ) ₃ was found to have an abrupt increase in internal resistance.

Accordingly, it has been found that it is necessary to use a specific aluminum salt in order to suppress an increase in internal resistance when the battery is stored for a long time after the partial discharge.

From the results of Example 4, it was found that an increase in internal resistance can be suppressed even when a specific aluminum salt and Al (CF ₃ SO ₃ ) ₃ are used together.

[0048]

The present invention has a great feature in that a specific aluminum salt is used together with a lithium salt as a solute of a non-aqueous electrolyte. According to the present invention, even if the battery is stored for a long time after discharge, A non-aqueous electrolyte battery in which the internal resistance does not increase significantly can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration of a cylindrical lithium battery as an example of the present invention.

[Explanation of symbols]

 Reference Signs List 1 outer can (negative electrode can) 2 positive electrode 3 negative electrode 4 separator 5 spiral electrode body 6 insulating gasket 7 sealing lid (positive electrode terminal) 8 negative electrode current collecting lead plate 9 positive electrode current collecting lead plate 10 negative electrode current collecting lead plate fixing insulating tape 11 upper part Insulating plate 12 Lower insulating plate

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Hiromitsu Suwa, 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Shinichiro Sakaguchi 2-5-2, Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. F-term (reference) 5H024 AA03 AA12 CC02 CC12 FF19 FF20 FF38 HH02 5H029 AJ04 AJ06 AK02 AK03 AL12 AM03 AM04 AM05 AM07 BJ02 BJ14 DJ09 HJ01 HJ02 5H050 AA09 AA12 CA06 CA05 FA05 HA01 HA02

Claims (5)

[Claims] 1. A non-aqueous electrolyte battery comprising a negative electrode using metal lithium or a lithium alloy as an active material, a positive electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises a lithium salt as a solute and A non-aqueous electrolyte battery comprising at least one of the aluminum salts represented by the chemical formulas (1) to (3). Embedded image 2. The non-aqueous electrolyte battery according to claim 1, wherein the active material of the positive electrode is manganese dioxide. 3. The non-aqueous electrolyte battery according to claim 1, wherein the non-aqueous electrolyte contains at least a low-boiling solvent as a solvent. 4. The method according to claim 1, wherein the lithium salt has the formula (1)
The nonaqueous electrolyte battery according to any one of claims 1 to 3, which is a lithium salt having an anion different from the aluminum salt represented by any one of (1) to (3). 5. The aluminum salt represented by any one of the chemical formulas (1) to (3), wherein the proportion of the aluminum salt in the whole nonaqueous electrolyte is 0.005 to 10% by mass. 2. The non-aqueous electrolyte battery according to claim 1.