JPH09213348A - Non-aqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the preserving characteristics of a non-aqueous electrolyte battery which uses lithium as a negative electrode active material by adding a specific quantity of 2-picoline or the like to non-aqueous electrolytic solution. SOLUTION: A non-aqueous electrolyte battery is composed of a positive electrode, a negative electrode using lithium as active material, and a non- aqueous electrolytic solution, wherein at least one of the 2-picoline, 3-picoline, 4-picoline, 2,4-dimethylpyridine, piperazine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, and 1,2,4,5-tetrazine is added in an amount of 0.01-20.0wt.% of the electrolyte. When the battery is in storage, its self-discharging is inhibited so that the preserving characteristics are enhanced.

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 using lithium as a negative electrode active material, that is, an improvement in storage characteristics of a lithium battery.

[0002]

2. Description of the Related Art A lithium battery using, for example, lithium as a negative electrode active material has attracted attention as a high energy density battery, and has been actively studied.

Generally, in this type of battery, as a solvent constituting the non-aqueous electrolyte, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, sulfolane, 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane. Etc. are used alone, binary or ternary mixtures. Then, as solutes dissolved in this, LiPF ₆ , L
iBF ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiA _S F ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiCF
₃ (CF ₂ ) ₃ SO ₃ etc. can be enumerated.

By the way, in such a non-aqueous electrolyte consisting of a single solvent, a binary or ternary mixed solvent, and a solute, a solvent and a negative electrode using lithium as an active material cause a chemical reaction, so that the battery after storage is stored. There is a problem of reduced capacity.
Therefore, suppressing self-discharge during storage is an important issue in the practical application of this type of battery. For example,
As disclosed in JP-A-49-108525, there is a method of adding pyridine to the electrolytic solution in order to improve the storage characteristics, but even in this method, sufficient characteristics have not yet been obtained, and thus improved. There is room for

[0005]

DISCLOSURE OF THE INVENTION The present invention proposes an excellent non-aqueous electrolyte solution which suppresses self-discharge when a battery of this kind is stored and improves storage characteristics.

[0006]

The present invention is a non-aqueous electrolyte battery comprising a positive electrode, a negative electrode using lithium as an active material, and a non-aqueous electrolyte solution, which comprises 2-picoline, 3-picoline, Four-
Picoline, 2,4-dimethylpyridine, piperazine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, 1,2,
At least one additive selected from the group consisting of 4,5-tetrazine was added to the non-aqueous electrolyte solution in the range of 0.01% to 20.0% by weight based on the weight of the non-aqueous electrolyte solution. The effect of addition is confirmed in this range.

Here, the chemical formula of 2-picoline is shown in Chemical formula 1.

[0008]

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Chemical formula 2 shows the structural formula of 3-picoline.

[0010]

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Chemical formula 3 shows the structural formula of 4-picoline.

[0012]

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[Chemical Formula 4] shows the structural formula of 2,4-dimethylpyridine.

[0014]

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In chemical formula 5, the structural formula of piperazine is shown.

[0016]

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Chemical formula 6 shows the structural formula of pyridazine.

[0018]

[Chemical 6]

Chemical formula 7 shows the structural formula of pyrimidine.

[0020]

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Chemical formula 8 shows the structural formula of pyrazine.

[0022]

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[Chemical Formula 9] shows the structural formula of 1,3,5-triazine.

[0024]

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[Chemical Formula 10] shows the structural formula of 1,2,4,5-tetrazine.

[0026]

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Among the above additives, one of 2-picoline, pyrazine and 1,3,5-triazine is considered to form an optimum film on the negative electrode and is particularly preferable. The reason for this is
This is because the structures represented by Chemical formula 1, Chemical formula 8 and Chemical formula 9 have a structure that is easily accessible to and reacts with lithium.
Alternatively, it is presumed that the electron distribution of each structure has a form that easily reacts with lithium metal. As a result, in these, the self-discharge rate can be further suppressed.

The amount of the additive added is more preferably in the range of 0.01% by weight to 10.0% by weight with respect to the weight of the non-aqueous electrolyte solution, and this kind of non-aqueous electrolyte battery is stored. It is preferable from the viewpoint of suppressing the subsequent decrease in discharge capacity.

The solute of this type of battery is LiPF ₆ , LiB
_{F 4, LiClO 4, LiCF 3} SO 3, LiA S F 6, LiN (CF 3 SO 2) 2, LiCF
₃ (CF ₂ ) ₃ SO _{3 and the} like can be used, but the present invention is not limited thereto.

Solvents for this type of battery include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate,
Sulfolane, 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane and the like can be used.

As the positive electrode of this type of battery, a metal oxide containing at least one of manganese, cobalt, nickel, vanadium and niobium can be used, but the present invention is not limited to this.

As the negative electrode of this type of battery, a substance capable of electrochemically absorbing and desorbing lithium ions,
Alternatively, a material using metallic lithium as an electrode material is exemplified.
Examples of the substance capable of electrochemically absorbing and desorbing lithium ions include carbon materials such as graphite, coke, and organic material calcined products, and lithium-aluminum alloys, lithium-magnesium alloys, lithium-indium alloys, lithium-tin. Alloy, Lithium-Thallium alloy, Lithium-
Examples are lead alloys and lithium alloys such as lithium-bismuth alloys.

Among them, carbon materials are particularly preferable in that there is no fear of internal short circuit due to growth of dendritic electrodeposited lithium, and graphite is most preferable among carbon materials in terms of high capacity. .

By the way, 2-picoline as an additive, 3
-Non-aqueous system containing a specific amount of one of picoline, 4-picoline, 2,4-dimethylpyridine, piperazine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, and 1,2,4,5-tetrazine When an electrolytic solution is used, this additive reacts with lithium to form a good quality coating on the negative electrode. This coating suppresses direct contact between lithium and the solvent, and thus suppresses decomposition of the non-aqueous electrolytic solution due to contact between lithium and the electrolytic solution. In this way, the storage characteristics of the battery can be improved.

[0035]

Embodiments of the present invention will be described in detail below. (Experiment 1) FIG. 1 shows a half cross-sectional view of a flat non-aqueous electrolyte battery as one embodiment of the present invention. The negative electrode 1 made of lithium metal is pressure-bonded to the inner surface of the negative electrode current collector 2, and the negative electrode current collector 2 is fixed to the inner bottom surface of the U-shaped negative electrode can 3 made of ferritic stainless steel (SUS430). Has been done. The peripheral end of the negative electrode can 3 is fixed inside an insulating packing 4 made of polypropylene, and the outer periphery of the insulating packing 4 is made of stainless steel and has a U-shaped cross section in a direction opposite to the negative electrode can 3. 5 is fixed. A positive electrode current collector 6 is fixed to the inner bottom surface of the positive electrode can 5.
The positive electrode 7 is fixed to the inner surface of the positive electrode current collector 6.
A separator 8 impregnated with a non-aqueous electrolytic solution, which is the main feature of the present invention, is interposed between the positive electrode 7 and the negative electrode 1.

By the way, the positive electrode 7 uses manganese dioxide heat-treated at a temperature of 400 ° C. as an active material. The heat treatment can be changed in the temperature range of 350 to 430 ° C. This manganese dioxide, carbon powder as a conductive agent, and fluororesin powder as a binder are mixed in a weight ratio of 85: 10: 5, respectively. Next, this mixture was pressure-molded and then dried at 300 ° C. to prepare a positive electrode 7. This drying process can be set and changed in the temperature range of 250 to 350 ° C.

On the other hand, the negative electrode 1 is produced by punching a rolled lithium plate into a predetermined size.

Then, a mixed solvent of propylene carbonate (PC) and 1,2-dimethoxyethane (DME) (volume ratio 5: 5) was used as an electrolytic solution, and lithium trifluoromethanesulfonate was used as a solute at a ratio of 1 mol / l. 2-picoline as an additive is added to the solution dissolved in step 1 in a proportion of 0.5% by weight to obtain a non-aqueous electrolyte solution. Using this non-aqueous electrolyte,
A battery A of the invention having an outer diameter of 20.0 mm and a thickness of 2.5 mm was produced. Example 2 A battery B of the present invention was produced in the same manner as in Example 1, except that 3-picoline was used as an additive instead of 2-picoline used in Example 1. (Example 3) A battery C of the present invention was produced in the same manner as in Example 1 except that 4-picoline was used as an additive instead of 2-picoline used in Example 1. (Example 4) A battery D of the present invention was produced in the same manner except that 2,4-dimethylpyridine was used as an additive instead of the 2-picoline used in Example 1. (Example 5) A battery E of the present invention was produced in the same manner except that piperazine was used as an additive instead of the 2-picoline used in Example 1. (Example 6) A battery F of the present invention was produced in the same manner except that pyridazine was used as an additive instead of the 2-picoline used in Example 1. (Example 7) A battery G of the present invention was produced in the same manner except that pyrimidine was used as an additive instead of the 2-picoline used in Example 1. (Example 8) A battery H of the present invention was produced in the same manner except that pyrazine was used as an additive instead of the 2-picoline used in Example 1. (Example 9) A battery I of the present invention was produced in the same manner except that 1,3,5-triazine was used as an additive in place of the 2-picoline used in Example 1. (Example 10) A battery J of the present invention was produced in the same manner except that 1,2,4,5-tetrazine was used as an additive in place of the 2-picoline used in Example 1 above. (Comparative Example 1) As a comparative example, a similar battery was prepared by using an electrolytic solution without addition of 2-picoline or the like.
And (Comparative Example 2) A similar battery was prepared by using an electrolytic solution to which pyridine was added instead of 2-picoline in Example 1, and this was designated as Comparative Battery Y. This battery is
This is close to the technical idea disclosed in Japanese Patent Publication No. 49-108525.

These invention batteries A to J and comparative battery X
And Y were used to compare the storage characteristics of the batteries. The experimental conditions were as follows: after each battery was manufactured and stored at 80 ° C for 2 months, the actual discharge of the battery was compared with the capacity before storage, and the difference was expressed as a percentage of the capacity before storage. Self-discharge rate (%) Was set. Table 1 shows the results.

[0040]

[Table 1]

It can be seen from Table 1 that the batteries A to J of the present invention have a smaller self-discharge rate than the comparative batteries X and Y and the decrease in the battery capacity during storage is suppressed, and the self-discharge is suppressed. I understand.

Further, the present invention battery A using 2-picoline as an additive, the present invention battery H using pyrazine, and
The battery I of the present invention using 1,3,5-triazine has a self-discharge rate of 2.8%, 2.4% and
It can be understood that it is 2.6%, which is extremely small and has excellent storage characteristics. (Experiment 2) A battery having the same structure as the battery A of the present invention of Example 1 was prepared, and the amount of 2-picoline added to the non-aqueous electrolyte solution was changed to compare the discharge capacities of the batteries after storage. did. Under this experimental condition, each battery was manufactured and stored at 80 ° C. for 2 months, and the discharge capacity (mAh) of the battery was measured.

The results are shown in Table 2. Table 2 shows the relationship between the amount of 2-picoline added and the self-discharge rate (%) relative to the weight of the non-aqueous electrolyte solution. The calculation of the self-discharge rate is the same as in Experiment 1 above.

[0044]

[Table 2]

From these results, it was confirmed that the addition amount of 2-picoline was in the range of 0.01% by weight to 20.0% by weight with respect to the weight of the non-aqueous electrolytic solution, and the decrease in battery capacity after storage was suppressed. doing. The amount of addition is preferably in the range of 0.01% by weight to 10.0% by weight from the viewpoint of not reducing the discharge capacity of the battery after storage.

Further, the addition amount is from 0.05% by weight to 5.0%.
In the range of weight%, the self-discharge rate is 5.2% or less, which is optimum.

In Experiment 2, the amount of 2-picoline added was changed, but other additives such as 3-picoline, 4-picoline, 2,4-dimethylpyridine, piperazine, pyridazine,
A similar tendency is observed in batteries using pyrimidine, pyrazine, 1,3,5-triazine and 1,2,4,5-tetrazine.

In each of the above embodiments, the non-aqueous electrolyte solution is used.
As a solute to be dissolved, trifluoromethanesulfonic acid
Tium LiCF_ThreeSO_Three, But LiPF₆, LiClO_Four, LiBF_Four, Li
N (CF _ThreeSO_Two)_Two, LiAsF₆Needless to say, can be used.
In addition, propylene carbonate and 1,2-diene as organic solvents
A mixed solvent of methoxyethane was shown as an example.
Germany, butylene carbonate, ethylene carbonate, vinyl
Nylene carbonate, dimethyl carbonate, diethyl
Carbonate, ethyl methyl carbonate, tetrahydr
Uses lofran, 1,3-dioxolane, and mixtures thereof.
It is possible to use

[0049]

As described above, in the non-aqueous electrolyte solution, the additives 2-picoline, 3-picoline, 4-picoline, 2,4-dimethylpyridine, piperazine, pyridazine, pyrimidine,
By adding a specific amount of one of pyrazine, 1,3,5-triazine and 1,2,4,5-tetrazine, the storage characteristics of this type of battery can be improved. And, as the additive, one of 2-picoline, pyrazine and 1,3,5-triazine is particularly suitable. Furthermore, among the specific addition amounts, 0.01% by weight based on the weight of the non-aqueous electrolyte solution
If the additive is added in the range of 1 to 10.0% by weight, the storage characteristics of the battery can be remarkably improved and its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a half sectional view of a battery of the present invention.

[Explanation of symbols]

 Reference Signs List 1 negative electrode 2 negative electrode current collector 3 negative electrode can 4 insulating packing 5 positive electrode can 6 positive electrode current collector 7 positive electrode 8 separator

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiyuki Noma 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Koji Nishio 2-chome Keihanhondori, Moriguchi-shi, Osaka No. 5-5 in Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. A non-aqueous electrolytic solution battery comprising a positive electrode, a negative electrode using lithium as an active material, and a non-aqueous electrolytic solution, comprising 2-picoline, 3-picoline, 4-picoline, and 2,4-dimethylpyridine. At least one additive selected from the group consisting of, piperazine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine and 1,2,4,5-tetrazine relative to the weight of the non-aqueous electrolyte solution. The non-aqueous electrolyte battery is added to the non-aqueous electrolyte solution in an amount of 0.01% to 20.0% by weight. 2. The additive is 2-picoline, pyrazine,
The non-aqueous electrolyte battery according to claim 1, which is one of 1,3,5-triazine. 3. The non-aqueous electrolyte battery according to claim 1, wherein the amount of the additive added is in the range of 0.01% by weight to 10.0% by weight with respect to the weight of the non-aqueous electrolyte. .