JP3122854B2 - Battery impregnation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for impregnating a battery.

More specifically, the present invention relates to a method for impregnating an electrolytic solution in a process of manufacturing a non-aqueous secondary battery.

[0003]

2. Description of the Related Art In recent years, lithium-transition metal composite oxides capable of dedoping and doping lithium ions as disclosed in, for example, JP-A-62-90863 have been used as a positive electrode active material. A battery characterized by using a carbonaceous material that can be doped and dedoped as a negative electrode active material has attracted attention as a small, lightweight, high-capacity, and safe secondary battery. The battery is
The maximum electromotive force is about 4 V, which is more than three times that of a conventional nickel-cadmium battery. For this reason, an aqueous electrolyte cannot be used because it causes electrolysis, and a non-aqueous electrolyte must be used.

In general, since non-aqueous electrolytes have low ionic conductivity, it is necessary to increase the electrode surface area in this type of battery so as to maintain high output so that more current can be taken out for a certain period of time. For this purpose, it is effective to use a thin polyolefin-based porous membrane or nonwoven fabric as a separator.

However, since the non-aqueous electrolyte has a very high polarity and a large surface tension, it is difficult for a non-polar polyolefin-based separator to get wet. In the battery, the electrolyte is applied to the electrode and the electrode body composed of the separator. The process of uniformly impregnating took a very long time.

As disclosed in JP-A-2-244568, the addition of a surfactant is effective for increasing the impregnation speed, but the impregnation effect is still insufficient with the usual impregnation method. Can't expect. JP-A-2-172
No. 158 discloses a vacuum pressure impregnation method in which a liquid reservoir is provided at the opening of a can. However, it is difficult to maintain close contact between the liquid reservoir and the can, and a complicated mechanism is required for mass production. Becomes In addition, a quantitative dispensing method using a dispenser is also possible, but the apparatus and piping are complicated and not suitable for mass production.

Furthermore, the non-aqueous electrolyte has a high hygroscopicity, and the mixed water significantly impairs the characteristics of the battery, so that the impregnation operation must be performed sufficiently quickly.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for manufacturing a non-aqueous secondary battery in which positive and negative electrodes are disposed opposite to each other with a separator interposed therebetween and stored in a battery can. The purpose is to ensure impregnation.

[0009] In order to achieve the above object, the present invention is lithium
Lithium that can be undoped and doped
A positive electrode using a transfer metal composite oxide as a positive electrode active material;
Carbonaceous material that can be doped and de-doped
Negative electrode used as negative electrode active material
Electrode and rolled up into a cylindrical battery
Crush the electrode inserted in the can or the electrode body and make it square
Or the positive and negative electrodes inserted in the battery can
Are placed opposite each other via a separator, and
What is inserted in the pond can is immersed in an electrolytic solution under reduced pressure with the open end facing down, and then pressurized.

Hereinafter, the present invention will be described in detail.

First, the air in the battery can is removed by placing the battery can in an impregnation tank capable of being decompressed and pressurized, preferably under a reduced pressure of 30 mmHg or less.

Further, the battery can is introduced into the impregnating tank with the open end of the battery can facing downward, or the battery can is lowered into the electrolytic solution of the tank in which the electrolyte has been previously stored. By immersing the opening in the electrolyte and then applying pressure, the electrolyte quickly enters the battery can under reduced pressure.
After a certain time, the electrolyte in the impregnation tank is discharged out of the tank, or the battery can is pulled up from the electrolyte,
Excess electrolyte remaining on the opening end side of the battery can is recovered, and rapid impregnation is completed.

According to the present invention, the problem that the electrolytic solution absorbs moisture can be solved by eliminating the leakage of the impregnation tank and dehumidifying the pressurizing gas in advance. Furthermore,
It is preferable that the electrolytic solution is always brought into contact with a desiccant such as molecular sieves to perform further dehumidification.

When the portion of the battery can immersed in the electrolyte is limited to the vicinity of the open end of the battery can, the adhesion of the electrolyte to the outer wall of the battery can can be reduced. The labor for wiping off the attached electrolyte can be greatly reduced. The smaller the immersed portion, the smaller the amount of electrolyte attached to the outer wall of the battery can.However, if the immersed portion is too small, the pressurized gas enters the battery can during pressurization, causing insufficient impregnation. . The most preferable immersion depth is 5 to 10 mm from the open end of the battery can.

[0015] When the impregnation is completed and surplus electrolytic solution remains in the battery can at a distance from the electrolyte reservoir, the excess electrolytic solution should be removed to reduce the weight of the battery can. is there. Further, when gas is generated in the battery can by charging the battery with an abnormally high voltage or the like, the space after removing the excessive electrolyte effectively functions as a gas reservoir. In the present invention, it is particularly preferable to use a method in which the opening of the battery can is separated from the electrolyte solution reservoir after the impregnation and the pressure is reduced again to discharge the excess electrolyte solution.

When it is necessary to remove the electrolytic solution adhering to the outer wall of the battery can after impregnation with the electrolytic solution, the electrolytic solution adhering to the outer wall of the battery can collects as droplets when the compressed gas is blown at a high speed, Further, it is effective to blow the compressed gas to the outer wall of the battery can using the property of scattering in a mist state. The flow rate of the compressed gas is preferably about 500 m / sec, and the diameter of the compressed gas is about 0.1 m / sec.
It is efficient to spray obliquely downward from the nozzle opening of about 5 mm toward the battery can. By pre-dehumidifying the compressed gas to be blown, it is possible to prevent moisture absorption and to proceed to the next step more quickly.

The structure of a battery to which the impregnation method of the present invention can be applied.
Are arranged opposite to the positive and negative electrodes with a separator
Insert the rolled-up electrode body into a cylindrical battery can
Or a square battery can by crushing the electrode body
Or the positive and negative electrodes are separated
And placed in a folded square battery can
It is entered.

The separator of the battery used in the present invention is not particularly limited, but the effect of the present invention is remarkable when a separator made of polyethylene or polypropylene is used. Specifically, examples thereof include a porous film of polypropylene, a porous film of polyethylene, a nonwoven fabric of polypropylene, a nonwoven fabric of polyethylene, and a laminate of these.

Examples of the non-aqueous electrolyte include ethers, ketones, lactones, nitriles, amines, amides, sulfur compounds, chlorinated hydrocarbons, esters, carbonates, nitro compounds, and the like. Phosphate ester compounds, sulfolane compounds and the like can be used, and among them, ethers, ketones, nitriles, chlorinated hydrocarbons, carbonates, and sulfolane compounds are preferable. More preferred are cyclic carbonates.

Typical examples thereof include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, anisole, monoglyme, acetonitrile, propionitrile, 4-methyl-2-pentanone, butyronitrile, valeronitrile, benzonitrile, , 2-
Dichloroethane, γ-butyrolactone, dimethoxyethane, methylformate, propylene carbonate, ethylene carbonate, vinylene carbonate, dimethylformamide, dimethylsulfoxide, dimethylthioformamide, sulfolane, 3-methyl-sulfolane, trimethyl phosphate, triethyl phosphate and these ethyl salts Examples thereof include a mixed solvent, but are not necessarily limited thereto.

The electrolyte of the non-aqueous electrolyte is not particularly limited. For example, LiClO ₄ , LiBF ₄ , L
iAsF ₆ , CF ₃ SO ₃ Li, LiPF ₆ , LiI,
LiAlCl ₄ , NaClO ₄ , NaBF ₄ , NaI,
^{_{(N-Bu) 4 N +}} ClO 4, (n-Bu) 4 N + BF 4
, KPF _{6 and the} like.

[0022]

Next, the present invention will be described in more detail by way of examples, which do not limit the scope of the present invention.

Example 1 A positive electrode was prepared by adding the same amount of a 5% DMF solution of polyvinylidene fluoride to a compound obtained by adding 5% of a carbon-based conductive additive to LiCoSn _0.02 O _{2 as} an active material. This is uniformly applied to both surfaces of an aluminum foil having a thickness of 15 μm at 300 g / m ² and dried.

The negative electrode has an average particle diameter of 1 as an active material.
The same amount of a 5% solution of polyvinylidene fluoride in DMF is added to 0 μm needle coke to obtain a dispersion, which is uniformly applied to both surfaces of a 10 μm thick stainless steel 304 foil at 150 g / m ² each and dried.

After sizing these positive and negative electrodes to a width of 40 mm, attaching a lead tab, a spiral coil is formed through a polyethylene microporous membrane separator having a thickness of 35 μm.

The coil has a diameter of 15.5 mm and is inserted into a stainless steel can having an inner diameter of 15.6 mm and a length of 49.5 mm.

The electrolytic solution is a three-component solution of propylene carbonate, ethylene carbonate and γ-butyrolactone at 1 mol / l of LiBF ₄ .

FIGS. 1 and 2 are conceptual diagrams of an impregnating device and a droplet removing mechanism used in this embodiment, respectively.

The battery can 4 is held by the work holding jig 3,
The battery can 4 is set in the impregnation tank 1 with the open end facing downward. In this state, the open end of the battery can 4 has not yet touched the electrolyte stored at the bottom of the impregnation tank 1. The electrolytic solution is supplied from the electrolytic solution tank 6 through the dehydration column 5 by the pump 7, and the surplus returns to the electrolytic solution tank 6 under natural flow to keep the level in the electrolytic solution tank 1 constant.

After the battery can 4 is set, the flow path of the electrolytic solution is shut off, the impregnation tank 1 is evacuated to 30 Pa, and the air in the battery can is removed. After about 2 minutes, the elevating mechanism 2 is operated to lower the battery can 4, and as shown in FIG. 1, the open end of the battery can 4 is immersed in the electrolyte to a depth of 5 mm from the open end. Next, the exhaust path is shut off, air having a dew point of −50 ° C. is sent to the impregnation tank 1, and the pressure is increased to ² kgG / cm ² and held for about 5 minutes. During this time, the electrolytic solution is sucked up into the battery can 4, and rapid impregnation is performed.

Next, the pressure of the impregnation tank 1 is returned to normal pressure, and
The pressure is reduced to mmHg, and the excess electrolyte in the battery can is discharged. Next, the impregnation tank 1 is returned to normal pressure, and the battery can 4 is transferred to the droplet removing mechanism shown in FIG. The droplet removing mechanism is provided with a nozzle 8 for blowing air having a dew point of −50 ° C. toward the center of the opening end of the battery can 4.
Approximately 30 seconds after the battery can 4 is set, 6 l / min of air is blown from the nozzle 8 having a diameter of 0.5 mm to the electrolyte adhered to the outer wall of the opening end of the battery can 4. At this time, it is more effective to move the work holding jig 3 in parallel so that the air is uniformly applied. The electrolyte adhering to the outer wall of the battery can 4 is blown by the air flow, forms large droplets, collects at the open end of the battery can 4, and finally scatters in a mist. The scattered electrolytic solution is collected by a mist separator attached to the lower part of the droplet removing device and discarded.

Next, the battery can is completed by closing the battery can.

When 100 batteries were impregnated, the amount of impregnating liquid was in the range of 4.15 to 4.51 g / cell.
The performance as a battery was also good. When the battery immediately after the impregnation was disassembled, the electrolytic solution was uniformly stained on the entire surface of the separator.

[0034]

As described above, according to the impregnation method of the present invention, even in the case of mass production, the dispersion of the electrolyte impregnation amount can be made extremely small, and the entire surface of the separator can be uniformly impregnated. In addition, since the impregnation can be performed very quickly, it is possible to prevent the electrolyte solution from absorbing moisture that adversely affects the battery characteristics.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an impregnation device used in an example.

FIG. 2 is a conceptual diagram of a droplet removing mechanism used in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Impregnation tank 2 Elevating mechanism 3 Work holding jig 4 Battery can 5 Dehydration column 6 Electrolyte tank 7 Pump 8 Nozzle

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 2/36 103 H01M 10/40

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein the lithium ions are undoped.
Lithium-transition metal composite oxide is used as a positive electrode active material.
Positive electrode, and doping and dedoping lithium ions
A negative electrode using a carbonaceous material that can be used as a negative electrode active material is disposed to face through a separator, and is wound up in a roll shape.
An electrode body inserted into a cylindrical battery can or an electrode
A crushed body inserted into a square battery can, or
Is arranged so that the positive and negative electrodes are opposed to each other via a separator.
A method of impregnating a battery , comprising: inserting the battery inserted in a folded-type battery can into an electrolytic solution under reduced pressure with the open end facing downward; and then pressurizing the battery.