JPH0620672A - Separator for nonaqueous battery - Google Patents

Abstract

PURPOSE:To make the impregnating property to separator of electrolyte excellent and enhance impregnating speed by using a polyolefin fine porous film treated with a specified phosphor compound in a separator. CONSTITUTION:A polyolefin fine porous film of polyethylene or polypropylene is treated with at least one kind of phosphor compounds selected from the group shown by the formulae I, II, III, for example, tributhylphosphate, to form a separator for nonaqueous battery. In the formulae, R1-R6 and R8, R9 represent C4-C30 alkyl, aryl, allyl, aralkyl or halogenated alkyl groups, and R7 represents a C1-C30 alkyl, aryl, allyl, aralkyl or halogenated alkyl group.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a separator for non-aqueous batteries.

[0002]

2. Description of the Related Art In recent years, it has been desired to reduce the size and capacity of primary batteries and secondary batteries. Attempts have been made to reduce the size and capacity of positive and negative active materials, electrolytic solutions, battery structures, etc. There is. Selection of the separator is extremely important for realizing such a small size and high capacity. That is, the volume of the separator in the battery volume is naturally proportional to the thickness of the separator used. Conventionally, paper, woven cloth, non-woven cloth, glass mat, etc. have been used as separators, but these must have a certain thickness or more due to problems with strength, short circuit prevention, performance problems, etc. It was

On the other hand, in order to improve such a defect,
It is becoming mainstream to use thin and uniform microporous membranes such as polyethylene and polypropylene for the separator.
However, there is a big problem in using the microporous membrane. This is because the impregnation property of the electrolytic solution is poor, and the impregnation process is extremely complicated in the manufacturing process, and problems such as variations in battery performance occur due to impregnation defects and the like.

Particularly, in recent years, when a solvent such as a cyclic ester carbonate such as propylene carbonate or a cyclic ester such as γ-butyrolactone which is about to be used by withstanding a high voltage is used, the influence thereof is particularly large. Until now, measures such as addition of a surfactant have been proposed in order to solve such a drawback, but the adverse effect on the battery performance cannot be remarkably used.

Therefore, in Japanese Patent Laid-Open No. 2-244565, by using a non-aqueous electrolyte containing such a phosphorus compound, the impregnating property of the separator is excellent, the battery capacity is large, and the non-aqueous electrolyte having a large battery voltage is used. It is described that a battery is obtained. In this case, the adverse effect on the battery performance was small, and the impregnation property of the electrolytic solution into the separator was excellent, and although great progress was made, the improvement of the impregnation speed into the separator was not entirely satisfactory.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a separator which is excellent in impregnation property with an electrolytic solution and has a high impregnation rate.

[0007]

Means for Solving the Problems As a result of intensive studies made by the present inventors in order to solve the drawbacks of the conventional method, a polyolefin-based microporous membrane treated with such a phosphorus-based compound was used as a separator for a non-aqueous battery. It has been found that the use of the electrolyte as a separator makes it possible to improve the impregnation property of the electrolytic solution into the separator and to increase the impregnation speed.

That is, according to the present invention, the microporous polyolefin film is at least one phosphorous compound selected from the group of the general formulas (1), (2) and (3) represented by the following chemical formulas 4, 5, and 6. A separator for a non-aqueous battery, which is treated with a compound.

[0009]

[Chemical 4]

[0010]

[Chemical 5]

[0011]

[Chemical 6]

In the present invention, the polyolefin microporous membrane is not particularly limited, but for example, it has a network structure composed of fine communication holes as described in JP-A-54-52167. Examples of the microporous film include: The material may be polyethylene, polypropylene, polybutene, a mixture thereof, or a copolymer of two or more kinds of ethylene, propylene, butene and hexene.

In the present invention, the phosphorus compound for treating the polyolefin microporous membrane is a compound represented by the general formula (1):
Represented by (2) and (3), for example, tributyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, trilauryl phosphate, tricetyl phosphate, tristearyl phosphate, triphenyl phosphate, tricresyl phosphate. , Cresyl diphenyl phosphate, trichlorobutyl phosphate, triphenyl phosphite, tris tridecyl phosphite, dibutyl ethylphosphonate, dibutyl butylphosphonate and the like.

In the present invention, the amount of the phosphorus compound attached to the polyolefin microporous membrane is not particularly limited, but is preferably 0.01 g (phosphorus compound) /
m ² (microporous membrane) to 6 g / m ^{2 and} more preferably 0.0
^{5g / m 2 ~3g / m 2} , particularly preferably 0.1 g / m
It is in the range of ^{2 to 2} g / m ² . Adhesion amount is 0.01g / m
If less than ² , impregnating property of the electrolytic solution into the separator is poor, or because the impregnation rate is slow, the impregnation step becomes complicated, and it is time-consuming and unfavorable.
Poor impregnation causes deterioration of battery performance and variations, which is not preferable. When the adhesion amount exceeds 6 g / m ² , it is difficult to obtain a battery having good performance due to deterioration of cycleability and high load characteristics.

In the present invention, the method of treating the polyolefin microporous membrane with such a phosphorus compound is not particularly limited, but one example thereof is various methods using an oily dispersion of a phosphorus compound. The polyolefin-based microporous membrane can be impregnated and applied by an impregnation method, a coating method, or the like, and then dried at a temperature at which the polyolefin-based microporous membrane is not significantly deformed.

The battery using the separator of the present invention as a separator is not particularly limited, but examples of the positive electrode active material include TiS ₂ and Ti.
S ₃ , MoS ₃ , FeS ₂ , Li _(1-x) MnO ₂ , Li
_(1-x) CoO ₂ , Li _(1-x) NiO ₂ , V ₂ O ₅ , V ₆
O _{13 and the} like can be mentioned. Examples of the negative electrode active material include lithium, lithium alloys, carbonaceous materials, conductive polymers and the like.

As the electrolyte of the non-aqueous electrolyte, for example, L
iClO ₄ , LlBF ₄ , LlAsF ₆ , CF ₃ SO ₃
Li, LiPF ₆ , LiI, LiAlCl ₄ , NaCl
O ₄ , NaBF ₄ , NaI and the like can be mentioned. The organic solvent used in the electrolytic solution is, for example, ethers,
Although ketones, nitriles, chlorinated hydrocarbons, carbonates, sulfolane compounds, etc. can be used,
As typical examples of these, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, anisole, monoglyme, acetonitrile, propionitrile, 4-methyl-2-pentane, butyronitrile, valeronitrile, benzonitrile, 1,2- Examples thereof include dichloroethane, γ-butyrolactone, dimethoxyethane, methyl formate, propylene carbonate, ethylene carbonate, vinylene carbonate, dimethylformamide, dimethylsulfoxide, dimethylthioformamide, sulfolane, 3-methyl-sulfolane, and mixed solvents thereof. .

In particular, when high-boiling point solvents and mixed solvents such as cyclic carbonic acid esters such as propylene carbonate and ethylene carbonate, cyclic esters such as γ-butyrolactone, and sulfoxides such as dimethyl sulfoxide are used, Among them, impregnating property obtained by using a separator for a non-aqueous battery, which is treated with a phosphorus-based compound, when a cyclic ester carbonate and a cyclic ester and a mixed solvent thereof are used, which are described in JP-A-2-215059. And, the effect of improving the impregnation speed is very remarkable. Further, even if a small amount of the phosphorus-based compound is added to these electrolytes, it does not matter at all, and conversely, the effect of impregnating the electrolyte with respect to the separator and the impregnation speed are improved as compared with the case of not adding.

[0019]

EXAMPLES Examples will be shown below for illustrating the present invention in detail, but the present invention is not limited to the following examples.

[0020]

Example 1 This example shows a treatment example in which a phosphorus compound is attached to a polyolefin microporous film. Hypore 4030U, a microporous polyethylene membrane [Asahi Kasei Corporation
Made by trade name] in a 1% by weight methanol solution of trioctyl phosphate by a dipping method.
It was dried with hot air at 0 ° C. to obtain a separator having an adhesion amount of 0.3 g / m ² .

[0021]

Examples 2 to 7 The same operation as in Example 1 was carried out except that the concentrations of the phosphorus compound and its methanol solution were changed as shown in Table 1. Table 1 also shows the amount of adhesion at that time.

[0022]

[Example 9] As the electrolytic solution 1, a solution prepared by adjusting lithium borofluoride to a concentration of 1.0 M in propylene carbonate was used.
mm, width 15 mm, the lower end 5 mm was put into the electrolytic solution, and the length up to the liquid surface swelled in 10 minutes was measured to obtain the impregnation speed (mm / 10 min). The results are shown in Table 2.

Next, as the electrolytic solution 2, a solution prepared by adjusting lithium borofluoride to a concentration of 1.0 M in a mixed solvent of propylene carbonate, ethylene carbonate and γ-butyrolactone (volume ratio = 1: 1: 2) is used. The same operation was performed thereafter. The results are shown in Table 2. Further, as the electrolytic solution 3, a solution obtained by adding 0.5% by weight of trioctyl phosphate to the above ternary mixed electrolytic solution was used, and the same operation was performed. The results are shown in Table 2.

[0024]

Examples 10 to 16 As a separator, Examples 2 to
The same operation as in Example 9 was performed except that the product obtained in 8 was used. The results are shown in Table 2.

[0025]

[Comparative Example 1] The same operation as in Example 9 was carried out except that, as a separator, a polyethylene microporous membrane, Hypore 4030U (trade name, manufactured by Asahi Kasei Kogyo KK) was not treated with trioctyl phosphate. The results are shown in Table 2.

[0026]

Example 17 A commercially available petroleum-based needle coke [KOA-SJ COKE manufactured by Koa Oil Co., Ltd.] was crushed with a ball mill to an average particle size of 10 μm. The BET surface area of this needle coke was 11 m ² / g and the true density was 2.1.
3 g / cm ³ , surface spacing d ₀₀₂ , L obtained by X-ray diffraction
The c ₍₀₀₂₎ was 3.44Å and 52Å, respectively. After mixing 1 part by weight of this powder with 1 part by weight of a solution of polyacrylonitrile in dimethylformamide (concentration 4% by weight),
A film having a thickness of 75 μm was formed on both surfaces of a 10 μm copper foil.

On the other hand, after pulverizing LiCoO ₂ into a ball mill having an average particle size of 3 μm, 0.05 part by weight of graphite, 0.05 part by weight of acetylene black, and a solution of polyvinylidene fluoride in dimethylformamide (concentration: 1 part by weight of this powder). After mixing 1 part by weight (2% by weight), a film having a thickness of 100 μm was formed on both sides of a 15 μm aluminum foil. A cylindrical electrode coil having a diameter of 19 mm and a height of 78 mm is produced by using the needle coke coating film as a negative electrode, the LiCoO ₂ coating film as a positive electrode, and the one obtained in Example 1 as a separator.

Next, the above cylindrical electrode coil was inserted into a glass container having an inner diameter of 19 mm at the tip shown in FIG. 1, and after evacuation to a vacuum degree of 20 Torr, the electrolytic solution 1 in Example 9 was operated by a cock operation. Inject 7.5 ml, then
The inside of the container was returned to atmospheric pressure. The impregnation time was measured by measuring the time from the injection of the electrolytic solution to the time when the solution completely permeated into the electrode coil. The results are shown in Table 3.

Next, the electrolytic solution was used as the electrolytic solution 2 in Example 9.
Then, the same operation was performed. The results are shown in Table 3. Furthermore, the same operation was performed using the electrolytic solution 3 of Example 9 as the electrolytic solution. The results are shown in Table 3.

[0030]

Examples 18 to 24 As a separator, Examples 2 to
The same operation as in Example 17 was performed except that the product obtained in 8 was used. The results are shown in Table 3.

[0031]

[Comparative Example 2] Hypore 403, which is a polyethylene microporous membrane not treated with a phosphorus compound, as a separator
0 U [Asahi Kasei Kogyo KK, trade name] was used,
The same operation as in Example 17 was performed. The results are shown in Table 3.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

EFFECTS OF THE INVENTION According to the present invention, the impregnating property of the electrolytic solution into the separator is excellent, and the impregnation speed is also high, and therefore it is very useful as a separator for a non-aqueous battery.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an electrode coil impregnating apparatus used in Examples and Comparative Examples of the present invention (electrolyte solution and electrode coil are also shown).

[Explanation of symbols]

 1 Electrode Coil 2 Glass Container 3 Electrolyte 4A, 4B Cock

Claims (1)

[Claims] 1. A microporous polyolefin film is represented by the following chemical formula 1,
A separator for a non-aqueous battery, which is treated with at least one phosphorus compound selected from the group of formulas (1), (2) and (3) shown in Chemical formulas 2 and 3. [Chemical 1] [Chemical 2] [Chemical 3]