JPH11121038A - Lithium battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery having large capacity density and a long cycle life by dipping extremely fine porous polyolefin film in high polymer electrolytic solution of a specific density for a prescribed time and by surface treating it. SOLUTION: Extremely fine porous polyolefin film is dipped in high polymer electrolytic solution of the density 0.01-10 wt.% for 0.5-3 hours. It is preferable to use such a film that, after the extremely fine porous polyolefin film is dipped in silane coupling agent solution of the density 0.01-10 wt.% for 0.3-3 hours, taken out therefrom, and dried, it is dipped again in the high polymer electrolytic solution of the density 0.01-10 wt.% for 0.3-3 hours and is surface treated. It is preferable to use such a film that the extremely fine porous polyolefin film is dipped in oxazoline compound solution of the density 0.01-10 wt.% for 0.5-3 hours, taken out therefrom, and is surface treated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lithium battery and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, when an electrolytic solution obtained by dissolving a lithium electrolyte salt in a solvent such as propylene carbonate or ethylene carbonate is used as an electrolyte for a battery, an ultra-microporous polypropylene film is used as a separator. The separator is used to prevent the positive electrode and the negative electrode from coming into contact with each other.

FIG. 3 is a conceptual view of a conventional lithium battery, in which an aluminum foil 1 on which LiCoO ₃ is adhered is used as a positive electrode, and is opposed to the aluminum foil 1 at a predetermined distance to form a copper. The foil 3 to which graphite 4 is adhered is used as the negative electrode. A film 5 made of polypropylene is disposed in the middle of the film 5 and is ultra-porous and has many small holes 5a. The space between the positive electrode and the negative electrode is filled with an electrolyte solution obtained by dissolving LiClO ₄ in ethylene carbonate or polycarbonate. f represents a solution of this ethylene carbonate or polycarbonate, and Li plus ions generated by dissolving in the solution are 6, while ClO ₄ minus ions are represented by 7.

[0004] The polypropylene film 5 functions as an insulating material for preventing the positive electrode and the negative electrode from sticking to each other. In this case, the separator 5 hinders the mobility of ions, so that the capacity of the battery is reduced. ing. On the other hand, an all-solid lithium ion is used as a separator electrolyte, which is a solid electrolyte containing a lithium electrolyte salt in a solid polymer electrolyte such as polyethylene oxide or a solid polymer electrolyte with an improved ionic conductivity by impregnating and swelling the electrolyte. Batteries have been proposed, but their thickness must be increased to some extent, which results in higher resistance and lower battery capacity.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a lithium battery having a large battery capacity and a method of manufacturing the same, by preventing the separator from hindering the mobility of lithium ions.

[0006]

An object of the present invention is to provide a film obtained by dipping a microporous polyolefin film in a 0.01 to 10% by weight solution of a polymer electrolyte for 0.5 to 3 hours. The problem is solved by using a lithium battery.

Alternatively, the microporous polyolefin film is dipped in a silane coupling agent solution having a concentration of 0.01 to 10% by weight for 0.3 to 3 hours, taken out, dried, and then dried at 0.01 to 10% by weight. A lithium battery characterized by using a film which has been surface-treated by dipping in a polymer electrolyte solution having a concentration of 0.3 to 3 hours.

Alternatively, the microporous polyolefin film is dipped in an oxazoline compound solution having a concentration of 0.01 to 10% by weight for 0.5 to 3 hours, taken out and dried,
0.5 to 10% by weight in the polymer electrolyte at a concentration of 0.01 to 10% by weight.
The problem is solved by a lithium battery characterized by using a film that has been surface-treated by dipping for 3 hours.

Alternatively, a method for producing a lithium battery, characterized in that the ultramicroporous polyolefin film is surface-treated by dipping in a 0.01 to 10% by weight solution of a polymer electrolyte for 0.5 to 3 hours. , Is solved by.

Alternatively, the microporous polyolefin film is dipped in a silane coupling agent solution having a concentration of 0.01 to 10% by weight for 0.3 to 3 hours, taken out, dried, and then dried at 0.01 to 10% by weight. And a surface treatment by dipping in a polymer electrolyte solution having a concentration of 0.3 to 3 hours.

Alternatively, the microporous polyolefin film is dipped in an oxazoline compound solution having a concentration of 0.01 to 10% by weight for 0.5 to 3 hours, taken out and dried,
0.5 to 10% by weight in the polymer electrolyte at a concentration of 0.01 to 10% by weight.
A method for producing a lithium battery, characterized in that the surface is treated by dipping for 3 hours.

With the above structure, it is possible to obtain a lithium ion battery in which the wettability with the electrolytic solution is improved and the mobility of lithium ions is increased, and the lithium electrolytic solution is added to the surface-treated ultra-microporous polyolefin film. By using a surface treated polymer solid electrolyte film with a lithium ion mobility of a micron order thickness consisting of an impregnated surface gel polymer electrolyte membrane, a lithium battery with a large capacity density and a long cycle life can be obtained. it can.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a conceptual view or a principle view of a lithium battery according to a first embodiment. The separator 5 of this battery is made of a microporous polypropylene film and has a thickness similar to the conventional one. Is a separator having excellent insulating properties on the order of microns and having a large number of ultramicropores 5a on the order of millimicrons and relatively high ion mobility. However, this alone improves the fact that the ion mobility is not sufficiently large as described with reference to FIG. 3 and therefore the resistance is large and the capacity density is small, according to the present invention.

That is, the polypropylene film 5
Is subjected to a surface treatment by dipping (immersion) in a solution obtained by dissolving polyethylene oxide in a solvent of propylene carbonate or ethylene carbonate at a concentration of 0.01 to 10% by weight for 0.5 to 3 hours. As a result, as shown in the figure, on the surface of the microporous polypropylene film 5 and around the micropores 5a, the polyethylene oxide 20
Adsorbs. It has excellent ionic conductivity,
The wettability with the LiClO ₄ electrolyte can be greatly improved. Therefore, while acting as a separator in the electrolyte solution f, the mobility of lithium ions can be greatly increased.

The polyethylene oxide solution concentration is 0.01
If the amount is less than 10% by weight, the amount of adsorption is reduced and the improvement of the wettability of the electrolytic solution cannot be obtained. Rather, it lowers the mobility of lithium ions. In addition, when the dipping time is 0.5 hours or less, the amount of adsorption is small, and when the dipping time is 3 hours or more, the amount of adsorption is too large.
However, it is not possible to improve the lithium ion conductivity by closing the micropores 5a.

FIG. 2 shows a solid-state lithium battery according to a second embodiment of the present invention. As shown in FIG. 1, a polyethylene oxide 20 is formed on a polypropylene film 5 by cat whiskers. As shown in FIG. 1, a film obtained by dissolving a lithium electrolyte such as LiClO ₄ or LiAsF _{6 in} a solvent such as propylene carbonate or ethylene carbonate is adsorbed on a film obtained by adsorbing the film as shown in FIG. Molecule 20
Impregnated. This makes the electrolyte thickness as a surface gel-like polymer electrolyte membrane a thickness on the order of microns, and the positive electrode,
The negative electrode is directly adhered to this. A battery with a large lithium ion concentration can be obtained by this, but in this case, the polypropylene film 5 functions as a reinforcing material, and the solid type has conventionally had to increase the thickness of the battery. This increases the resistance and reduces the capacity. However, according to the present invention, the polypropylene film 5, which originally works as a separator, can have a large mechanical strength and a small thickness, thereby providing a high-density all-solid-state lithium-ion battery. be able to.

According to the third embodiment of the present invention, although not shown, a solution-type ultra-porous polypropylene film 5 is prepared by adding a silane coupling agent having a concentration of 0.01 to 10% by weight to a methanol solution. In a solution obtained by dissolving in water.
By dipping for 5 to 3 hours and taking out and drying, the adsorbability of polyethylene oxide 20 was further improved as compared with FIG. The surface is further dipped in a 0.01 to 10% by weight polyethylene oxide solution for 0.5 to 3 hours.
Therefore, it is possible to provide a lithium ion battery in which the wettability of the polyethylene oxide to the electrolytic solution is further improved and the mobility of lithium ions is further increased.

According to a fourth embodiment of the present invention, a surface gel polymer electrolyte obtained by impregnating a lithium electrolyte solution into a microporous polypropylene film surface-treated as described above (not shown) It provides a solid-state lithium battery with a membrane having a thickness on the order of microns, but has a high mobility of lithium ions.In the present invention, the polypropylene film also functions as a reinforcing agent. To prevent,
An object of the present invention is to provide a solid battery that is superior to the related art.

According to the fifth embodiment of the present invention, although not shown, the ultra-porous polypropylene film 5 is prepared by dissolving an oxazoline compound at a concentration of 0.01 to 10% by weight in a methanol solution. A surface-treated polypropylene film is obtained by dipping for 5 to 3 hours and drying to obtain a surface-treated polypropylene film, which has a higher polyethylene oxide adsorptivity, and has a concentration of 0.01 to 10% by weight. By performing surface treatment by dipping in a polyethylene oxide solution of 0.5 to 3 hours for 0.5 to 3 hours, it is possible to provide a solution-type lithium ion battery having a high lithium ion mobility and having improved wettability with a lithium electrolyte. .

Further, according to a sixth embodiment of the present invention,
A solid type with high lithium ion mobility, in which the surface gelled polymer electrolyte membrane obtained as described above is impregnated with a lithium electrolyte solution into an ultra-microporous polypropylene film whose surface has been treated as described above and has a thickness on the order of microns. Can be provided. In the present solid-type lithium-ion battery, the separator that originally prevented the contact between the negative electrode and the positive electrode also functions as a matter of course.
In other words, a thin lithium ion battery that functions as a reinforcing agent and has a large capacity can be provided.

[0021]

Example 1 As in the first embodiment, as shown in FIG. 1, an ultra-microporous polypropylene film (Celgard 3401 manufactured by Celanese Corporation) 5 was prepared by adding polyethylene oxide at a concentration of 0.01% by weight. The surface is treated by dipping for 3 hours in a solution obtained by dissolving in propylene carbonate as a solvent. Polyethylene oxide 20 having excellent ionic conductivity can be adsorbed on the surface of the microporous polypropylene film 5 surface-treated in this way and around the micropores 5a, thereby improving the wettability with the lithium electrolyte. It is possible to obtain a lithium ion battery in which the mobility of lithium ions is increased while improving the function as a separator in the electrolytic solution.

Such a separator is made of LiClO ₄ -dissolved propylene carbonate and ethylene carbonate 3/2.
In a state of being immersed in the solution of, a positive electrode material composed of LiCoO ₃ and acetylene black as a conductive material and a polytetrafluoroethylene binder is applied to an aluminum foil to form a positive electrode,
In addition, a negative electrode material composed of graphite and a binder was applied to a copper foil to form a negative electrode, and a button battery was formed with the above-mentioned polypropylene film interposed therebetween. The charge / discharge capacity and cycle life are shown in Table 1 in comparison with the conventional example.

Similarly, a separator obtained by dipping an ultra-microporous polypropylene film (Celgard 3401 manufactured by Celanese) at a concentration of 1% by weight in a solution of polyethylene oxide in propylene carbonate for 1 hour and subjecting the resulting separator to a button battery as described above is obtained. The charge / discharge capacity and cycle life are also shown in Table 1.

Further, an ultramicroporous polypropylene film (Celgard 3401 manufactured by Celanese Corporation) was dipped at a concentration of 10% by weight in a propylene carbonate solution of polyethylene oxide for 0.5 hour to perform a surface treatment. The separator thus obtained was formed as a button battery in the same manner as described above, and its charge / discharge capacity and cycle life were evaluated. Also shown in Table 1.

Further, an electrolyte comprising a 3/2 solution of propylene carbonate and lithium carbonate of lithium electrolyte of LiClO ₄ is impregnated into a microporous polypropylene film on which polyethylene oxide molecules are adsorbed to form a surface gel polymer electrolyte membrane, This was made into a micron-order thickness to form a solid-state lithium-ion battery. As a result, a polypropylene film having a high lithium ion mobility and excellent mechanical strength as a separator can provide a solid-state lithium ion battery thinner than the conventional one. This performance is also shown in Table 1.

Further, a positive electrode composed of LiCoO ₃ , acetylene black as a conductive material and a polytetrafluoroethylene binder is applied to an aluminum foil to form a positive electrode, while a negative electrode composed of graphite and a binder is applied to a copper foil. Thus, a negative electrode was formed, and a button battery was formed with the above-described separator interposed therebetween. Table 1 shows the charge / discharge capacity and cycle life.

The comparative example in Table 1 has the structure shown in FIG. 3, but has an ultra-microporous polypropylene film without surface treatment (Celgardens 3401 manufactured by Celanese Corporation).
5 is an evaluation of charge / discharge capacity and cycle life.

[0028]

[Table 1]

As is clear from Table 1, the capacity density and the cycle life are significantly improved compared to the conventional case.

Example 2 An ultra-microporous polypropylene film (Celgard 3401 manufactured by Celanese Corporation) was dipped in a methanol solution of 0.01% by weight of a silane coupling agent γ-aminopropyltriethoxyoxysilane for 3 hours. Remove and dry. As a result, a film having good polyethylene oxide adsorbability can be obtained.
The surface was treated by dipping in a polyethylene oxide solution having a concentration of 01% by weight for 3 hours. As in Example 1, a lithium ion battery with improved lithium ion mobility and improved wettability of the polyethylene oxide with the electrolytic solution can be formed. Table 2 shows the charge / discharge capacity and cycle life.

Similarly, a microporous polypropylene film (Celgard 3401 manufactured by Celanese Corporation) is dipped in a 1% by weight methanol solution of a silane coupling agent γ-aminopropyltriethoxyoxysilane for 1 hour and dried. As a result, a film having good polyethylene oxide adsorbability can be obtained. This is surface-treated by dipping for 1 hour in a 1% by weight polyethylene oxide solution. As in Example 1, the wettability of the polyethylene oxide with the electrolytic solution is improved, and a lithium ion battery with increased lithium ion mobility can be obtained. Table 2 shows the charge / discharge capacity and cycle life.

Similarly, an ultra-microporous polypropylene film (Celgard 3401 manufactured by Celanese Corporation) is dipped in a 10% by weight methanol solution of a silane coupling agent γ-aminopropyltriethoxyoxysilane for 0.5 hour, taken out and dried. . Therefore, a film having a high polyethylene oxide adsorbing property is obtained. The film is dipped in a polyethylene oxide solution having a concentration of 10% by weight for 0.5 hour to perform a surface treatment. Thus, as in Example 1, a lithium ion battery having improved lithium ion mobility and improved wettability of the electrolyte with polyethylene oxide can be obtained. Table 2 shows the charge / discharge capacity and cycle life.

Further, the ultra-porous polypropylene film surface-treated as described above was treated with an electrolyte comprising a 3/2 solution of propylene carbonate and ethylene carbonate of lithium electrolyte of LiClO ₄ and adsorbed on a polyethylene oxide molecule as described above. An ultra-porous polypropylene film is impregnated to obtain a surface gel polymer electrolyte membrane. This thickness is set to a thickness on the order of microns. Even in this case, the polypropylene film has a sufficient strength despite this thinness and can withstand normal use, and a solid-state lithium ion battery having high lithium ion mobility can be obtained. This performance is shown in Table 2.

Further, a positive electrode material is composed of LiCoO ₃ , acetylene black as a conductive material and polytetrafluoroethylene as a binder, and this is applied to an aluminum foil to form a positive electrode. On the other hand, a negative electrode material composed of graphite and a binder is applied to a copper foil to form a negative electrode. A button battery is formed with the above-described separator interposed therebetween. Table 2 shows the charge / discharge capacity and cycle life.

[0035]

[Table 2]

As is clear from Table 2, the battery of the present invention has greatly improved capacity density and cycle life as compared with the conventional battery.

(Example 3) An ultramicroporous polypropylene film (Celgard 3401 manufactured by Celanese Corporation) is dipped in a solution obtained by dissolving a 0.01% by weight oxazoline compound phenyloxazoline in methanol as a solvent for 3 hours. Remove and dry. As a result, a film having a good polyethylene oxide adsorbing property is obtained. The film is dipped in a 0.01% by weight polyethylene oxide solution for 3 hours to be surface-treated. As in Example 1, a lithium ion battery having high lithium ion mobility and improved wettability of the polyethylene oxide with the electrolytic solution can be obtained. Table 3 shows the charge / discharge capacity and cycle life.

Similarly, an ultra-microporous polypropylene film (Celgard 3401 manufactured by Celanese) is dipped in a solution obtained by dissolving a 1% by weight oxazoline compound phenyloxazoline in methanol as a solvent for 1 hour. Remove and dry. As a result, a film having good polyethylene oxide adsorbability can be obtained. This film is dipped in a 1% by weight solution of polyethylene oxide for 1 hour for surface treatment. As in Embodiment 1, a lithium ion battery having improved lithium ion mobility and improved wettability of the electrolyte with polyethylene oxide can be obtained. Table 3 shows the charge / discharge capacity and cycle life.
Shown in

Similarly, an ultramicroporous polypropylene film (Celgard 3401 manufactured by Celanese) is dipped in a solution obtained by dissolving a 10% by weight oxazoline compound phenyloxazoline in methanol as a solvent for 0.5 hour. Remove and dry. After improving the adsorption of polyethylene oxide in this way, 10% by weight
The surface is treated by dipping in a polyethylene oxide solution having a concentration of 0.5 hour. As in Example 1, a lithium ion battery having improved lithium ion mobility and improved wettability of the electrolyte with polyethylene oxide can be obtained. Table 3 shows the charge / discharge capacity and cycle life.

Further, the ultra-porous polypropylene film surface-treated as described above is impregnated in LiClO ₄ with an electrolyte comprising a 3/2 solution of propylene carbonate and ethylene carbonate as lithium electrolytes, and a surface gel polymer electrolyte membrane is formed. Get. By setting the thickness of the electrolyte to a thickness on the order of microns, a solid-state lithium-ion battery having high lithium-ion mobility can be obtained. It is a skillful use of the mechanical strength of a polypropylene film other than as a separator.

Further, a positive electrode material is composed of LiCoO ₃ , acetylene black as a conductive material and polytetrafluoroethylene as a binder, and this is applied to an aluminum foil to form a positive electrode. On the other hand, a negative electrode material composed of graphite and a binder is applied to a copper foil to form a negative electrode. A button battery is formed with the above-described separator interposed therebetween. Table 3 shows the charge / discharge capacity and cycle life.

[0042]

[Table 3]

As is clear from Table 3, the lithium battery of the present invention has improved capacity density and cycle life as compared with the conventional lithium battery.

Although the embodiments of the present invention have been described above, the present invention is, of course, not limited to these, and various modifications can be made based on the technical concept of the present invention.

For example, although the microporous polypropylene film has been described as the separator, another polyolefin film, for example, a polyethylene film or a polyacrylate film may be used instead. In addition, although ethylene carbonate and propylene carbonate have been described as solvents, other solvents may be used.

[0046]

As described above, according to the lithium battery and the method of manufacturing the same according to the present invention, a lithium ion battery having a larger capacity density and a longer cycle life than conventional ones can be obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a liquid lithium battery according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram of a solid-state lithium battery according to a second embodiment of the present invention.

FIG. 3 is a conceptual diagram of a conventional lithium battery.

[Explanation of symbols]

 5 Ultra-microporous polypropylene film 5a Micropore 20 Polyethylene oxide

Claims (16)

[Claims] 1. An ultra-microporous polyolefin film having a thickness of 0.1
0.5 to 10% by weight of a polymer electrolyte solution.
A lithium battery using a film that has been surface-treated by dipping for up to 3 hours. 2. An ultra-microporous polyolefin film having a thickness of 0.1
After being dipped in a silane coupling agent solution having a concentration of 01 to 10% by weight for 0.3 to 3 hours and dried,
0.1 to 10% by weight of the polymer electrolyte solution.
A lithium battery using a film that has been surface-treated by dipping for 3 to 3 hours. 3. An ultra-microporous polyolefin film having a thickness of 0.
After dipping in an oxazoline compound solution having a concentration of 0.1 to 10% by weight for 0.5 to 3 hours, taking out and drying, the solution is dried.
A lithium battery using a film which has been surface-treated by dipping in a polymer electrolyte having a concentration of 01 to 10% by weight for 0.5 to 3 hours. 4. A surface-gelled polymer electrolyte membrane in which a lithium electrolyte solution is impregnated into the surface-treated ultra-microporous polyolefin film.
4. The lithium battery according to any one of items 1 to 3. 5. The lithium battery according to claim 1, wherein the surface-treated microporous polyolefin film is used as a separator. 6. The lithium battery according to claim 4, wherein the surface gel polymer electrolyte membrane is used as a separator. 7. The polyolefin is polypropylene,
7. The lithium battery according to claim 1, wherein the lithium battery is one of polyethylene, polyisoprene, and polyisobutylene. 8. The lithium battery according to claim 1, wherein the polymer electrolyte is one of polyethylene oxide, polyethylene adipate, polyethylene succinate and polyphosphazene. 9. An ultra-microporous polyolefin film having a thickness of 0.
0.5 to 10% by weight of a polymer electrolyte solution.
A method for producing a lithium battery, which comprises performing a surface treatment by dipping for up to 3 hours. 10. A microporous polyolefin film is dipped into a silane coupling agent solution having a concentration of 0.01 to 10% by weight for 0.3 to 3 hours, taken out and dried, and then dried at 0.01 to 10% by weight. A method for producing a lithium battery, comprising: dipping in a polymer electrolyte solution having a concentration of 0.3 to 3 hours to perform surface treatment. 11. An ultramicroporous polyolefin film is dipped in an oxazoline compound solution having a concentration of 0.01 to 10% by weight for 0.5 to 3 hours, taken out and dried,
0.5 to 10% by weight in the polymer electrolyte at a concentration of 0.01 to 10% by weight.
A method for producing a lithium battery, wherein the surface is treated by dipping for 3 hours. 12. The surface-gelled polymer electrolyte membrane obtained by impregnating the surface-treated ultra-microporous polyolefin film with a lithium electrolyte solution.
12. The method for producing a lithium battery according to any one of items 1 to 11. 13. The method for producing a lithium battery according to claim 9, wherein the surface-treated microporous polyolefin film is used as a separator. 14. The method according to claim 12, wherein the surface gel polymer electrolyte membrane is used as a separator. 15. The method according to claim 9, wherein the polyolefin is one of polypropylene, polyethylene, polyisoprene and polyisobutylene.
The method for producing a lithium battery according to any one of the above. 16. The method for manufacturing a lithium battery according to claim 9, wherein the polymer electrolyte is one of polyethylene oxide, polyethylene adipate, polyethylene succinate and polyphosphazene.