JP2001273930A - Manufacturing method of polymer battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a polymer battery which allows flexibility in the shape of a battery. SOLUTION: This is the manufacturing method equipped with the first process to house a battery element group composed of a positive electrode, a negative electrode and a solid polyelectrolyte in a flexible sheath body, the second process in which the inside of the flexible sheath body is sealed under a reducing pressure less than atmospheric pressure, and the third process in which the positive electrode, the negative electrode and the solid electrolyte and heat welded. Otherwise, this is the manufacturing method in which a heat press bonding is made after having returned the third process to the atmosphere of higher than the atmospheric pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a polymer battery capable of establishing a degree of freedom in battery shape.

[0002]

2. Description of the Related Art In recent years, portable electronic devices have become more portable.
Cordless technology is rapidly advancing. Furthermore, the concept of wearable attachment to the body is also in progress. Accordingly, there is an increasing demand for a small, lightweight, thin, free-form, and high-energy-density secondary battery serving as a driving power supply. From this point of view, non-aqueous secondary batteries, especially lithium polymer secondary batteries, are expected to be highly developed as batteries that have high voltage, high energy density, and can be made thinner and more flexible in shape. I'm in a hurry.

[0003]

The structure of a lithium polymer secondary battery is roughly divided into the following three types.

Type 1. A type in which the positive and negative electrodes containing a polymer are heat-welded in advance and gelled in the battery.

Type 2. A type in which an electrolyte containing a polymer or monomer is injected into the battery and gelled in the battery.

[0006] Type 3. A type in which a polymer solid electrolyte sheet formed in advance is sandwiched between the positive electrode and the negative electrode, and heat-sealed.

Type 1 and Type 2 both form a positive electrode, a negative electrode, and a separator, and then cause the electrolyte to gel in the battery. Therefore, the in-plane uniformity of the distance between the positive electrode and the negative electrode, the uniformity of the gel, and the uniformity are particularly large in the area. There was a problem with sex.

[0008] In Type 3, since the solid electrolyte sheet is formed in advance, the in-plane uniformity of the distance between the positive electrode and the negative electrode and the uniformity and homogeneity of the electrolyte gel can be maintained. In this case, the size of the battery element was limited by the hot roll device and the flat plate pressing device, and it was difficult to completely liberalize the shape.

Therefore, in the conventional manufacturing method, it is difficult to liberalize the shape. In particular, since it is necessary to bend a three-dimensional shape formed in two dimensions, there is a problem of a short circuit at a bent portion, which is more difficult. there were.

[0010] It is an object of the present invention to provide a method of manufacturing a polymer battery which solves such a problem relating to the manufacture of a polymer battery and realizes a degree of freedom in shape of the battery.

[0011]

According to the first aspect of the present invention, there is provided a first step of housing a battery element group including a positive electrode, a negative electrode, and a solid polymer electrolyte in a flexible package. A method for producing a polymer battery, comprising: a second step of closing the flexible outer casing after reducing the pressure to below atmospheric pressure, and a third step of heat-welding the positive electrode, the negative electrode, and the solid electrolyte. .

[0012] The invention according to claim 2 is a first step of accommodating a battery element group comprising a positive electrode, a negative electrode, and a polymer solid electrolyte in a flexible outer casing; And a third step of heat-welding the positive electrode, the negative electrode, and the solid electrolyte after returning to an atmosphere at or above atmospheric pressure. .

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION As a polymer solid electrolyte usable in the present invention, a gel polymer solid electrolyte in which an organic polymer compound and an electrolytic solution are integrated by gelation is desirable.

As the organic polymer compound constituting the gel polymer solid electrolyte, a polyvinylidene fluoride resin, a polyacrylonitrile resin, a polyacrylate resin or the like having a high ionic conductivity is preferable.

The non-aqueous electrolyte solvent constituting the gelled polymer solid electrolyte contains cyclic carbonate and chain carbonate as main components, and the cyclic carbonate includes ethylene carbonate (EC) and propylene carbonate (PC). And at least one selected from butylene carbonate (BC). Examples of the chain carbonate include dimethyl carbonate (DMC) and diethyl carbonate (DE).
C) and at least one selected from the group consisting of ethyl methyl carbonate (EMC) and the like.

As the non-aqueous electrolyte solute constituting the gel polymer solid electrolyte, a lithium salt having a strong electron-withdrawing property, for example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAs
F ₆ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN
(SO ₂ C ₂ F ₅ ) ₂ , LiC (SO ₂ CF ₃ ) _{3 and the} like are preferable, and these solutes may be used alone or in combination of two or more. It is preferable that these solutes are dissolved in the non-aqueous solvent at a concentration of 0.5M to 1.5M.

Further, the gelled polymer solid electrolyte may include a microporous membrane made of a polyolefin resin, and a separator made of a woven or nonwoven fabric.

As the flexible outer package usable in the present invention, an aluminum laminated film having an aluminum foil as an intermediate layer, a polypropylene film on the inner side, and a polyethylene terephthalate film and a nylon film integrated on the outer side, respectively, is used. preferable.

In the battery element manufactured according to the present invention, since the inside of the battery is in a reduced pressure state below the atmospheric pressure, the pressure is uniformly applied to the battery element when the pressure is returned to a state higher than the atmospheric pressure during thermal welding. The uniform distance and good adhesion are maintained. Due to this, high-rate discharge, unevenness of the distance between the positive electrode and the negative electrode during charge / discharge cycles and poor adhesion,
It is possible to suppress deterioration of the active material due to concentration of a load on a part of the electrode plate.

The reduced pressure state below the atmospheric pressure means 100
Pa or less, and preferably in the range of 10 Pa to 100 Pa.

The state above the atmospheric pressure is 100,000 Pa or more, preferably 100,000 to 130,000 Pa.
Within the range, the polymer solid electrolyte layer becomes thinner,
It is preferable that the short circuit between the positive electrode and the negative electrode does not occur.

The conditions for heat welding are as follows:
C. to 105.degree. C. for about 1 to 3 hours are preferable.

Further, the battery element manufactured according to the present invention comprises a pre-formed flexible casing, a positive electrode,
Since the negative electrode and the polymer solid electrolyte sheet are inserted according to the shape of the flexible outer package and then heat-welded, short-circuit failure due to a short distance between the positive electrode and the negative electrode in the curved portion can be suppressed, and the battery Is possible.

The components other than the solid polymer electrolyte constituting the secondary battery are not particularly limited, and conventionally used components can be used.

For example, a lithium-containing transition metal compound capable of accepting lithium ions as a guest is used as the positive electrode active material. For example, a composite metal oxide of lithium and at least one metal selected from the group consisting of cobalt, manganese, nickel, chromium, iron and vanadium, LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiC
_{o x Ni (1-x)} O 2 (0 <x <1), LiCrO 2, αLi
FeO ₂ , LiVO _{2, and the} like.

As the negative electrode active material, a material containing graphite having a graphite type crystal structure capable of inserting and extracting lithium ions, for example, natural graphite and artificial graphite is used. In particular, the spacing (d ₀₀₂ ) of the lattice plane ( ₀₀₂ ) is 3.350.
It is preferable to use a carbon material having a graphite type crystal structure of about 3.400 °.

[0027]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but these do not limit the present invention in any way.

FIGS. 1, 2 and 3 are a top view and a sectional view of a lithium polymer battery according to an embodiment of the present invention.

1. Preparation of Positive Electrode The positive electrode 1 has a current collector 1a made of lath-processed aluminum foil, and has LiCoO _{2 as a} positive electrode active material, acetylene black as a conductive agent, and a polymer as a binder, for example, vinylidene fluoride (VDF) P) (VDF-H) with hexafluoropropylene (HFP)
A paste in which FP) is kneaded and dispersed in an organic solvent, for example, N-methyl-2-pyrrolidone, is applied, dried, and rolled to form a positive electrode mixture layer 1b to obtain a positive electrode plate.

2. Preparation of Negative Electrode Plate The negative electrode 2 was formed of a lath-processed copper foil as a current collector 2a, and artificial graphite (d ₀₀₂ = 3.355) as a negative electrode active material was formed on both surfaces thereof
Å) and a paste in which the powder of P (VDF-HFP) is kneaded and dispersed in an organic solvent, for example, N-methyl-2-pyrrolidone, is applied, and dried and rolled to form a negative electrode mixture layer 2b to form a negative electrode plate. .

3. Preparation of Polymer Electrolyte The polymer electrolyte 3 was prepared by adding the P (VDF-HFP) resin.
It is made into a sheet by hot extrusion molding,
Ethylene carbonate (EC) and diethyl carbonate as the medium
1: 3 weight ratio with Bonate (DEC), electrolyte solute
As LiPF ₆Was added to and mixed with 1 M of the above electrolyte solution.
Electrolysis by holding the sheet resin at 95 ° C for 1 hour
The polymer electrolyte is integrated by gelation of the liquid.

4. Preparation of Battery Element A polymer electrolyte 3 is disposed between the two positive electrode plates 1 prepared as described above, and a negative electrode plate 2 is disposed between the polymer electrolytes 3 and the whole is laminated as shown in FIG. Battery element 4
Is configured.

5. 1. Production of Lithium Polymer Battery As shown in FIG. 1, 1c of the battery element produced as described above is a lead attachment portion provided on a positive electrode current collector, and an aluminum foil positive electrode lead 5 is welded here. . Reference numeral 2c denotes a lead mounting portion provided on the current collector of the negative electrode, to which a copper foil negative electrode lead 6 is welded. Reference numeral 7 denotes a flexible exterior body formed of an aluminum laminate film in which an aluminum foil is used as an intermediate layer, a polypropylene film is laminated on the inside, and a polyethylene terephthalate film and a nylon film are laminated on the outside. The battery element 4 accommodated in the aluminum laminate bag 7 has the positive electrode lead 5 and the negative electrode lead 6 drawn out of the bag, and the leading ends thereof are input / output terminals 8 and 9. Reference numerals 10 and 11 denote insulating protective films provided at intermediate portions of the leads 5 and 6, which are used to seal the opening of the aluminum laminate bag 7 by heat sealing or the like.
6 to ensure electrical insulation and airtightness. The aluminum laminate bag 7 is obtained by cutting the above-described aluminum laminate film into a strip shape, folding the aluminum laminate film at a central portion T in the longitudinal direction thereof, and heat-sealing the upper and lower sides P1 and P2 in advance. The battery element 4 is inserted from the P3 portion of the remaining one side.

Example 1 After reducing the pressure in the aluminum laminate bag 7 containing the battery element 4 to 100 Pa, the P3 portion is heat-sealed. Thereafter, the battery element 4 was left in a constant temperature bath at 100 ° C. for 1 hour, and the battery element 4 was integrated by heat welding to obtain a battery element a of Example 1.

(Example 2) The aluminum laminate bag 7 containing the battery element 4 is placed in a vacuum device, the pressure is reduced to 50 Pa, and the P3 portion is heat-sealed. Thereafter, the battery element 4 was taken out from the vacuum apparatus, left in a thermostat at 90 ° C. for 1 hour while being pressurized to 100,000 Pa, and the battery element 4 was integrated by heat welding to obtain a battery element b of Example 2.

(Embodiment 3) FIG. 3 including the battery element 4
After the pressure inside the aluminum laminate bag 7 having the shape shown in FIG. 7 is reduced to 100 Pa, the P3 portion is heat-sealed. Then 100 ° C
A battery element c of Example 3 was left in a thermostat for 1 hour, and the battery element 4 was integrated by heat welding.

(Embodiment 4) FIG. 3 including the battery element 4
Put the aluminum laminate bag 7 of the shape shown in
After reducing the pressure to 100 Pa, the P3 portion is heat-sealed. Thereafter, the battery element 4 was taken out of the vacuum apparatus, left in a thermostat at 100 ° C. for 1 hour, and the battery element 4 was integrated by heat welding to obtain a battery element d of Example 4.

(Comparative Example 1) The portion P3 is heat-sealed in the aluminum laminate bag 7 containing the battery element 4 without reducing the pressure. Thereafter, the battery element 4 was left in a thermostat at 100 ° C. for 1 hour, and the battery element 4 was integrated by heat welding to obtain a battery element e of Comparative Example 1.

(Comparative Example 2) The aluminum laminate bag 7 containing the battery element 4 was put in a vacuum device, the pressure was reduced to 100 Pa, and the P3 portion was heat-sealed. Thereafter, the battery element 4 was taken out from the vacuum apparatus, left in a constant temperature bath at 100 ° C. for 1 hour while being pressurized to 100,000 Pa, integrated with the battery element 4 by heat welding, and further bent into the same shape as in FIG. Element f.

The nominal capacity of the lithium polymer batteries thus produced in Examples 1 to 4 and Comparative Examples 1 and 2 is 500 mAh.

6. Test a. Internal micro short-circuit confirmation test The lithium polymer battery thus manufactured was charged in a constant temperature bath at 20 ° C with a charging current of 300 mA (0.6 C) until the battery voltage reached 4.2 V, and then a constant voltage of 4.2 V was applied. To charge the battery until the charging current becomes 50 mA (0.1 C) to make the battery fully charged. A fully charged battery in this manner
C., placed in a thermostat, taken out after 72 hours, left in a thermostat at 25.degree. C. for 2 hours, and measured the battery voltage. The results shown in Table 1 were obtained.

B. Cycle Characteristics The lithium polymer battery thus prepared was charged in a constant temperature bath at 20 ° C. with a charging current of 300 mA (0.6 C) until the battery voltage reached 4.2 V, and then charged at a constant voltage of 4.2 V. Until it reaches 50 mA (0.1 C),
Next, at a discharge current of 500 mA (1 C), the cutoff voltage becomes 3.0.
And the charge and discharge were repeated. Table 1 shows the discharge capacity retention ratio at 100 cycles when the initial discharge capacity was 100%.

[0043]

[Table 1]

As is clear from Table 1, the cycle characteristics of Comparative Example 1 in which the battery element was not thermally welded under reduced pressure was 82.3%, and Example 1 in which the battery element was thermally welded under reduced pressure. , 99.2%, 91.2%, and 99.9%, which are the cycle characteristics of Examples 2, 3, and 4, respectively.
It was inferior to 0.0% and 90.8%.

From this, the method of heat welding after reducing the pressure in the battery is because the load is concentrated on a part of the electrode plate due to the uniform distance between the positive electrode and the negative electrode and the improvement of the adhesion. This shows that active material deterioration can be suppressed.

Further, as is apparent from Table 1 above, the voltage of the small short-circuit confirmation test of Comparative Example 2 in which the battery element was thermally welded and then bent was 3.98 V, and the battery element was folded and then thermally welded. Compared with the voltages of the small short-circuit confirmation tests of Example 3 and Example 4, which are 4.15 V and 4.15 V, respectively, Comparative Example 2 indicates that there is a minute short-circuit.

From the above, it is shown that the method of heat-welding after bending the battery element can suppress a short circuit failure due to a short distance between the positive electrode and the negative electrode in the curved portion.

It should be noted that the present invention is not limited to the described embodiments, and various combinations that can be easily replaced from the gist of the invention are possible. In particular, the combination of the organic polymer compound of the polymer solid electrolyte, the electrolyte solvent, and the electrolyte solute in the above embodiment is not limited.

[0049]

As described above, according to the present invention, the first step of housing the battery element group including the positive electrode, the negative electrode, and the polymer solid electrolyte in the flexible outer casing, and the step of reducing the pressure of the flexible outer casing to below atmospheric pressure. A manufacturing method comprising: a second step of sealing; and a third step of heat-welding the positive electrode, the negative electrode, and the solid electrolyte. Alternatively, it is possible to provide a polymer battery realizing a degree of freedom in battery shape by a manufacturing method of performing thermocompression bonding after returning the third step to an atmosphere of an atmospheric pressure or higher.

[Brief description of the drawings]

FIG. 1 is a top view of a battery according to an embodiment of the present invention.

FIG. 2 is a sectional view of the battery.

FIG. 3 is a sectional view of a three-dimensional battery according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view of a three-dimensional battery according to an embodiment of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 1a Positive electrode collector 1b Positive electrode mixture layer 1c Positive electrode lead attachment part 2 Negative electrode 2a Negative electrode collector 2b Negative electrode mixture layer 2c Negative electrode lead attaching part 3 Polymer solid electrolyte 4 Battery element 5 Positive electrode lead 6 Negative electrode lead 7 Aluminum Laminate bag 8 Positive electrode output terminal 9 Negative electrode output terminal 10 Positive electrode lead insulation protection film 11 Negative electrode lead insulation protection film P1 Aluminum laminated film heat welded part P2 Aluminum laminated film heat welded part P3 Aluminum laminated film heat welded part T Aluminum laminated film bent part

Continued on the front page F term (reference) 5H011 AA00 CC02 CC06 CC10 DD05 FF02 JJ25 5H029 AJ00 AK03 AL07 AM00 AM03 AM07 AM16 BJ04 BJ12 CJ02 CJ05 CJ06 CJ28 DJ02 DJ08 DJ09 DJ11 DJ13 DJ14 DJ16 EJ01 EJ12 EJ14

Claims (7)

[Claims] A first step of accommodating a battery element group comprising a positive electrode, a negative electrode, and a polymer solid electrolyte in a flexible outer casing, a second step of reducing the pressure of the flexible outer casing to below atmospheric pressure, and closing the flexible outer casing; A method for producing a polymer battery, comprising a third step of thermally welding a positive electrode, the negative electrode, and the solid electrolyte. 2. A first step of housing a battery element group including a positive electrode, a negative electrode, and a polymer solid electrolyte in a flexible outer casing, and a second step of sealing the flexible outer casing containing the battery element in an atmosphere under atmospheric pressure. And a third step of heat-welding the positive electrode, the negative electrode, and the solid electrolyte after returning to an atmosphere at or above atmospheric pressure. 3. The method for producing a polymer battery according to claim 1, wherein the polymer solid electrolyte is obtained by integrating an organic polymer compound and an electrolytic solution by gelation. . 4. The method according to claim 3, wherein the organic polymer compound is a fluororesin. 5. The method according to claim 3, wherein the organic polymer compound is a fluororesin having closed cells and / or through holes. 6. The method for producing a polymer battery according to claim 1, wherein at least one of the positive electrode and the negative electrode has a structure having an active material particle layer bound by a binder. 7. The method for producing a polymer battery according to claim 1, wherein the flexible exterior body is formed in a three-dimensional shape in advance.