JP3381634B2 - Lithium secondary battery and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a structure of a lithium secondary battery.

[0002]

2. Description of the Related Art Conventional lithium secondary batteries generally consist of (1) a negative electrode using lithium metal as an active material, (2) a metal oxide,
A positive electrode coated with a positive electrode active material such as a sulfide, chloride, or halogen carbon compound, and It is composed of an electrolyte solution dissolved in salt.

The lithium secondary battery is repeatedly charged and discharged.

[0004]

However, according to such a lithium secondary battery using the above lithium metal as an active material, the lithium metal of the negative electrode and the electrolytic solution react undesirably at the time of charging, and lithium carbonate, Precipitate lithium oxide. Then, it is deposited on the lithium metal surface of the negative electrode. Therefore, the charging / discharging efficiency gradually decreases. Therefore, there is a problem of shortening the battery life.

An object of the present invention is to provide a lithium secondary battery which suppresses an undesired reaction between lithium metal and an electrolytic solution and extends the battery life.

[0006]

In order to achieve the above object, the invention according to claim 1 comprises lithium metal and an electrolytic solution.
In a lithium secondary battery in a battery can,
Suppresses undesired reactions between the lithium metal and the electrolyte
1ppm to 1000ppm hydrogen sulfide and 1ppm to 1
It is specially made by enclosing a mixed gas with water of 000ppm.
A lithium secondary battery is provided. Make this structure
By suppressing the reaction between lithium metal and electrolyte,
You can prolong your life. The invention according to claim 2 is 1 ppm to 1000 ppm hydrogen sulfide and 1 ppm to 1
In an atmosphere containing 000ppm of water, put the battery part in a battery can.
Made of lithium secondary battery characterized by incorporating materials
A manufacturing method is provided. With such a manufacturing method, lithium
Lithuium that suppresses the reaction between metal and electrolyte and prolongs battery life
A secondary battery can be manufactured.

Next, in the invention described in claim 2, the gas for suppressing an undesired reaction between the lithium metal according to claim 1 and the electrolytic solution contains hydrogen sulfide or water of 10 ppm to 500 ppm in the battery can. A lithium secondary battery is provided. With this structure, the reaction between the lithium metal and the electrolytic solution can be suppressed. Further, the invention according to claim 3 is characterized in that a battery member is incorporated into a battery can in an atmosphere containing either hydrogen sulfide or moisture or a mixed gas of hydrogen sulfide and moisture. A method for manufacturing the same is provided. With such a manufacturing method, it is possible to manufacture a lithium secondary battery that suppresses the reaction between the lithium metal and the electrolytic solution and extends the battery life.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The gist of the present invention will be described in detail below with reference to the embodiments shown in the drawings. <First Embodiment> FIG. 1 is a block diagram showing a coin-type cell of a lithium secondary battery according to an embodiment of the present invention.

1 is a lithium secondary battery, 11 is a positive electrode body, 1
2 is a positive electrode battery can, 13 is a gasket, 21 is a negative electrode body, 2
2 is a negative electrode battery can, 23 is a spring, 31 is a separator, 32
Is an electrolyte holding material. The lithium secondary battery 1 is specifically a coin cell 2032 type battery. The battery member in the battery can has the following structure.

The positive electrode battery can 12 is in contact with the positive electrode 11,
A gasket 13 is provided on the edge of the positive electrode battery can 12. A spring 23 is provided on the surface of the negative electrode battery can 22, and the negative electrode 21 is configured so that the spring 23 presses and contacts the negative electrode 21. Then, the electrolytic solution holding material 3 is formed on both front and back surfaces of the separator 31.
Two are provided. The electrolyte holding material 32 is impregnated with the electrolyte. In addition, the positive electrode 11
And the negative electrode 21 face each other. Then, the positive electrode battery can 12 and the negative electrode battery can 22 are fitted and sealed. Therefore, all the members in the battery are pressed against each other by the spring 23.

The inside of the can of the lithium secondary battery 1 has a space of about 0.2 CC to about 0.3 CC excluding the battery member. The electrolyte solution is generally composed of an organic solvent and a solute. This organic solvent is composed of a high dielectric constant solvent and a low viscosity solvent, and the solute is a lithium salt. The high dielectric constant solvent has, for example, 2 to 2 carbon atoms such as ethylene carbonate (hereinafter abbreviated as EC), propylene carbonate (hereinafter abbreviated as PC), butylene carbonate (hereinafter abbreviated as BC), and the like.
It is a cyclic carbonate of 4 (excluding carbonyl carbon).

As the low viscosity solvent, dimethyl carbonate (hereinafter abbreviated as DMC), diethyl carbonate (hereinafter abbreviated as DEC), dipropyl carbonate (hereinafter DP)
C), methyl ethyl carbonate (hereinafter abbreviated as MEC) and other chain carbonates having 2 to 8 carbon atoms (excluding carbonyl carbon), 1,2-dimethoxyethane (hereinafter abbreviated as DME), 1, 2 -Diethoxyethane (hereinafter abbreviated as DEE), 1,2-dibutoxyethane (hereinafter D)
Abbreviated as BE), etc., chain ether, tetrahydrofuran,
They are cyclic ethers such as 2-methyltetrahydrofuran, esters such as methyl formate, methyl acetate and methyl propionate, and aromatic hydrocarbons such as benzene (hereinafter abbreviated as Bz), toluene and xylene.

These high dielectric constant solvents and low viscosity solvents may be used alone or in combination of two or more. Specific examples of the combination of the high dielectric constant solvent and the low viscosity solvent include EC-DMC, EC-DEC,
Two-component solvent system such as PC-DMC, PC-DEC, PC-MEC, EC-DMC-Bz, EC-DEC-Bz, P
C-DMC-Bz, PC-DEC-Bz, EC-PC-
Three-component solvent system such as DMC, EC-PC-DEC, EC-
4 such as PC-DMC-Bz, EC-PC-DEC-Bz
It is a component solvent system. The volume ratio of the high dielectric constant solvent and the low viscosity solvent is usually 1: 4 to 2:
The ratio is 1, preferably 1: 2 to 1: 1.

As the lithium salt, for example, LiPF6,
LiClO4, LiAsF6, LiBF4, LiAlC
Inorganic salts such as l4, LiCl, LiBr, CH3 SO3 L
i, CF3 SO3 Li, LiB (C6 H5) 4, CF3
It is an organic salt such as COOLi. These lithium salts may be used alone or in combination, and the concentration is usually 0.5 to 3 (1 mol / l), preferably 1 to 1.5 (1 mol / l) in the organic solvent. The following were used in this example:

The electrolytic solution was prepared by dissolving LiPF6 (lithium hexafluorophosphate) at a concentration of 1 mol / liter, and the volume ratio was 1 :.
2 is a mixed solution of EC (ethylene carbonate) and DEC (diethyl carbonate). The negative electrode 4 has a diameter of 15
mm disk-shaped foil-shaped lithium metal Li with a thickness of 70 μm
Is.

The positive electrode 5 is about 30 mg of LiCoO powder.
2 is pressure-coated on a disk-shaped stainless steel plate having a diameter of 15 mm. As the positive electrode active material applied to the positive electrode 5, for example, polymer polyaniline, polyacetylene, poly-p-
There are polymer derivatives such as phenylene, polybenzene, polypyridine, polyaniline, polyacetylene, polypyrrole, anthracene, polynaphthalene and derivatives thereof.

Further, as the inorganic oxide, manganese dioxide,
Vanadium pentoxide, molybdenum trioxide, chromium trioxide,
Examples include metal oxides such as cupric oxide. Inorganic sulfides include metal sulfides such as molybdenum trisulfide, titanium disulfide, and iron trisulfide. Others include fluorocarbon.

Lithium cobalt oxide (LiCoO2) was used as the positive electrode active material in this embodiment. The separator is a strip made of polypropylene. Next, a method for manufacturing a lithium secondary battery will be described. The lithium secondary battery is manufactured in a closed device, specifically, in a glove box. The atmosphere of this glove box keeps moisture in the atmosphere at a constant value of 1 ppm.

Then, the battery member is assembled to the battery can according to the following procedure. 1) The negative electrode body 21 is placed on the spring 23 provided on the inner surface of the negative electrode battery can 22. 2) A separator 31 having both surfaces sandwiched by an electrolyte holding material 32 is placed on the negative electrode body 21. 3) The positive electrode body 11 is placed on the separator 31. 4) Place the positive electrode battery can 12 on the positive electrode body 11. 5) The electrolytic solution is injected to impregnate the electrolytic solution holding material 32. 6) The positive electrode battery can 12 and the negative electrode battery can 22 are fitted and sealed.

Coin cell 20 made as described above
Moisture can be maintained at a constant value of 1 ppm in the space of 0.2 to 0.3 CC in the can of 32 type battery. After that, change the atmosphere of the glove box to 10ppm, 100ppm, 500
Six types of battery cans were assembled in place of ppm, 1000 ppm, 2000 ppm and 5000 ppm. <Second Embodiment> Next, a battery was manufactured in the second embodiment. However, the difference from the first embodiment is that the atmosphere of the glove box is 1 ppm, 10 ppm, 5 ppm of hydrogen sulfide in the atmosphere.
0ppm, 100ppm, 500ppm, 1000ppm, 20
Eight types of battery cans are assembled in the atmosphere of 00ppm and 5000ppm. Except for this point, the method is the same as that of the first embodiment. <Third Example> Further, a battery was manufactured in the third example. However, the point different from the first embodiment is that the battery can is assembled by keeping the mixed gas of hydrogen sulfide and water at a constant value in the atmosphere of the glove box. After that, 16 types of battery cans with different ratios of mixed gas of hydrogen sulfide and water are assembled. Except for this point, the method is the same as that of the first embodiment.

Next, the following types of batteries were subjected to the following charge / discharge tests to determine the life of the 31 types of batteries produced in Examples 1, 2, and 3 above. <Safety test> The charge / discharge test was performed under the following conditions in all of the first, second and third examples. 1) Charge: 4.2 V cutoff, charging current density 1 mA / square cm 2) Pause; 1 minute 3) Discharge: 3.0 V cutoff, discharge current density 1 mA / square
cm 4) Pause; 1 minute 5) The above 1 to 4 were repeated to examine the capacity and the number of charge / discharge cycles of each battery. <Charge / Discharge Test Results> Table 1 shows the relationship between the gas concentration and the number of cycles in Examples 1 and 2.

[0022]

[Table 1]

Table 2 shows the relationship between the ratio of the mixed gas of Example 3 and the number of cycles.

[0024]

[Table 2] Charge / discharge test results

Here, the battery manufactured in Example 1 with a water content of 1 ppm corresponds to a conventional battery. If the battery life is defined as 60% of the initial capacity, 10 pp of Examples 1 and 2
The battery life was remarkably improved in the range of m to 500 ppm. Example 1 was able to be increased from about 1.1 to about 1.4 times. Further, in Example 2, it was possible to improve about 1.1 to about 1.2 times. In Example 3, the mixed gas of 100 ppm of water and 1000 ppm of hydrogen sulfide was about 1.3 times as large as 1 ppm of water and 1000 pp.
It could be improved to about 1.4 by mixing gas with m 2 of hydrogen sulfide.

[0026]

As described above, according to the present invention described in detail, it is possible to suppress an undesired reaction between the lithium metal and the electrolytic solution and improve the battery life.

[Brief description of drawings]

FIG. 1 is an exploded side view of a lithium secondary battery of the present invention.

[Explanation of symbols] 1 lithium secondary battery, 11 positive electrode body, 12 positive electrode battery can, 13 gaskets, 21 negative electrode body, 22 negative electrode battery can, 23 springs, 31 separator, 32 Electrolyte holding material.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-63649 (JP, A) JP-A-10-64523 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 10/40

Claims (2)

(57) [Claims] 1. A lithium secondary battery having a lithium metal and an electrolytic solution in a battery can, wherein 1 to 1000 ppm of hydrogen sulfide that suppresses an undesired reaction between the lithium metal and the electrolytic solution is contained in the can. 1 pp
A lithium secondary battery characterized by being filled with a mixed gas of m to 1000 ppm of water . 2. A battery member containing lithium metal and an electrolytic solution.
In the manufacturing method of the lithium secondary battery contained in the battery can
Te, from 1000ppm hydrogen sulfide and 1ppm from 1ppm 100
In an atmosphere containing a mixed gas of water 0 ppm, a manufacturing method of a lithium secondary battery, which comprises incorporation the battery member to the battery can.