JPH11149916A - Organic electrolytic battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electrolytic battery having high adhesion strength between a collector and an active material layer and excellent battery properties by binding a conductive coating on the surface of the collector. SOLUTION: In an organic electrolytic battery comprising a positive electrode, an negative electrode, a polymer electrolyte, a mixture of a conductive carbon material 7 and polyvinylidene fluoride is applied to the surface of a collector 6 to be used for the positive electrode or the negative electrode. Consequently, the adhesion strength between the active material layer and the collector 6 is kept even after impregnation with an organic electrolytic solution and an organic electrolytic battery with excellent battery properties can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an organic electrolyte battery,
In particular, it relates to improvement of contact resistance and adhesion between the current collector and the active material layer.

[0002]

2. Description of the Related Art The trend toward smaller, lighter and thinner portable telephones and notebook personal computers is increasing year by year, and there is an increasing demand for smaller, lighter and thinner batteries as power sources. In such a trend, lithium batteries are receiving attention, and in particular, lithium-polymer secondary batteries, which are organic electrolyte batteries using a polymer material as an electrolyte, are attracting attention as a method for reducing the thickness. Bellcore, a national research and development organization, used a copolymer of vinylidene fluoride (VDF) and propylene hexafluoride (HFP) (P (VDF-HFP)) as a polymer material for this lithium-polymer secondary battery. Polymer ion secondary battery was developed and is expected as the battery system closest to practical use. This battery system is characterized by using the same P (VDF-HFP) for the positive electrode, the negative electrode, the electrolyte and the separator, and integrating the separator and the positive electrode and the negative electrode by heat fusion.

[0003] However, the above-mentioned lithium polymer secondary battery contains a large amount of polymer in the positive electrode and the negative electrode, and thus has a lower capacity than the lithium-ion secondary battery currently commercialized. For this reason, in order to increase the capacity of the lithium polymer secondary battery, it is necessary to reduce the amount of polymer in the electrode plate within a range where integration is possible. However, when the amount of the polymer is reduced, there is a problem that the adhesion between the active material layer and the current collector is reduced, and the contact resistance is increased. In order to solve this problem, a method using a metal current collector which is obtained by removing an insulator on the current collector surface and binding with an adhesive conductive polymer composition,
It has been proposed to bind a polymer obtained by adding a conductive substance to P (VDF-HFP) after removing an insulator on the surface of an electric body (for example, US Pat. No. 5,554,459).

[0004]

However, in the current collector using P (VDF-HFP) as the conventional polymer, when the electrolyte is impregnated in the battery, the binding bonded to the surface of the current collector is performed. The layer had a drawback that the layer was swollen by the electrolyte and peeled off from the current collector surface. For this reason, the electrical contact between the current collector and the binding layer is deteriorated, and deterioration due to charge and discharge of the battery occurs.
This caused the cycle life to decrease.

An object of the present invention is to solve such a conventional problem, and an object of the present invention is to provide an organic electrolyte battery having good cycle characteristics while maintaining the adhesion between the current collector and the active material layer. It is.

[0006]

In order to solve the above-mentioned problems, at least one of the positive electrode and the negative electrode comprises at least an active material, a conductive material, a non-aqueous electrolyte and a non-aqueous electrolyte. The active material layer is made of a polymer that absorbs and retains, and a current collector is formed by binding a mixture of a conductive carbon material and polyvinylidene fluoride. With such a configuration, the conductive carbon material can be firmly bound to the current collector, and the adhesion between the active material layer and the current collector can be increased.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, at least one of a positive electrode and a negative electrode has at least one of an active material, a conductive material, a non-aqueous electrolyte, and an active material layer made of a polymer absorbing and retaining the non-aqueous electrolyte. An organic electrolyte battery comprising a current collector to which a mixture of a material and polyvinylidene fluoride is bound. By using polyvinylidene fluoride, which is a polymer that has a high affinity for the polymer in the active material layer and has a very low swelling due to the electrolyte, it can be separated from the current collector even in the presence of the electrolyte. To obtain an organic electrolyte battery with good cycle characteristics, by firmly binding the conductive carbon material to the current collector and improving the adhesion between the active material layer and the current collector. Can be.

Further, in the present invention, the current collector is laminated or buried in the active material layer. As described above, the current collector having the conductive binding layer can be more effectively obtained by adopting a configuration in which the current collector and the active material layer have good current collection properties.

Further, in the present invention, the conductive carbon material is at least one selected from the group consisting of acetylene black, Ketjen black and carbon fiber, and the mixture of the conductive carbon material and the binder contains carbon material. The percentage is between 20 and 50% by weight of the mixture. These carbon materials are preferable as the conductive agent. When the content of the conductive agent is 20% by weight or less, the effect as the conductive agent is small, and when the content is 50% by weight or more, the binding force is reduced.

With these configurations, the organic electrolyte battery of the present invention can be used in an organic electrolyte battery having a high capacity by reducing the amount of polymer in the active material layer by binding a conductive carbon material to the surface of the current collector. Good adhesion and electrical contact can be realized, and excellent battery characteristics can be obtained.

(Embodiment 1) The structure of an organic electrolyte battery according to the present invention will be described with reference to FIG. The positive electrode plate has a structure in which a positive electrode active material layer 1 and a positive electrode current collector 2 are stacked or a current collector is embedded in the positive electrode active material layer. Similarly, the negative electrode plate has a structure in which the negative electrode active material layer 5 and the negative electrode current collector 4 are laminated or the current collector is embedded in the negative electrode active material layer. The polymer electrolyte 3 is provided between the positive electrode plate and the negative electrode plate, and is integrated with the positive electrode and the negative electrode by a heat fusion method or a casting method.

The positive electrode current collector 2 is made of a punching metal or a lath metal such as an aluminum metal or a conductive material coated with aluminum, and has acetylene black, ketjen black or carbon fiber as a conductive carbon material on its surface. A mixture of polyvinylidene fluoride as a binder is bound.

The negative electrode current collector 4 is made of a punching metal or a lath metal such as a copper, nickel metal or a conductive material coated with copper or nickel, and has acetylene black, ketjen black or a conductive carbon material on the surface. A mixture of carbon fibers and polyvinylidene fluoride as a binder is bound.

As a method of binding the conductive carbon material to the current collector, for example, a material obtained by dispersing acetylene black in an N-methylpyrrolidone solution of polyvinylidene fluoride is directly applied to the current collector, and then the solvent is applied. Of N-methylpyrrolidone is removed by drying.

The positive electrode active material layer 1 and the negative electrode active material layer 5
Is prepared by applying a paste composed of an active material, a conductive material and a polymer solution on a glass plate, and then removing the solvent by drying.

Further, the positive electrode active material layer 1 and the positive electrode current collector 2 and the negative electrode active material layer 5 and the negative electrode current collector 4 are heat-sealed with a heat roller to form a positive electrode plate and a negative electrode plate. A battery is manufactured by heat-sealing a polymer electrolyte 3 sandwiched between a positive electrode plate and a negative electrode plate with a heat roller.

[0017]

EXAMPLES Example 1 28 g of a copolymer of vinylidene fluoride and propylene hexafluoride (P (VDF-HFP), propylene hexafluoride ratio 12% by weight) was dissolved in 144 g of acetone.
A mixed solution to which 28 g of di-n-butyl phthalate (DBP) was added was prepared. This solution is applied on a glass plate with a thickness of 0.5 m.
m, and then acetone was removed by drying to a thickness of 0.08.
A polymer electrolyte sheet having a size of 30 mm × 50 mm is prepared.

The positive electrode sheet was prepared by dissolving 71 g of P (VDF-HFP) in 1130 g of acetone and lithium cobalt oxide 100
0 g, acetylene black 53 g, and DBP 110 g were mixed and the paste was adjusted on a glass plate to a thickness of 0.9 mm.
After coating with acetone, the acetone is dried and removed to a thickness of 0.1.
A sheet having a size of 3 mm and a size of 27 mm × 43 mm is obtained.

The negative electrode sheet was prepared by dissolving 35 g of P (VDF-HFP) in 321 g of acetone and spherical graphite (MC manufactured by Osaka Gas Co., Ltd.).
MB) 245 g, carbon fiber (VGCF made by Osaka Gas) 2
A paste prepared by mixing 0 g and 54 g of DBP was applied on a glass plate at a coating thickness of 1.2 mm, and acetone was dried and removed to obtain a 0.35 mm thick and 27 mm size.
A 43 mm sheet is obtained.

The mixture of the conductive carbon material and the binder to be applied to the current collector is prepared by dispersing and mixing 30 g of acetylene black and an N-methylpyrrolidone solution of polyvinylidene fluoride (12% by weight). This mixture was added to a thickness of 0.06.
mm of aluminum and copper lath metal, respectively, and then the N-methylpyrrolidone is dried and removed at a temperature of 80 ° C. or more to bind the mixture comprising the conductive carbon material of the present invention and polyvinylidene fluoride. Make a body.

A laminate of the positive electrode sheet and the aluminum current collector is sandwiched between polytetrafluoroethylene sheets (PTFE, 0.05 mm thick), and heated and pressed through two rollers heated to 150 ° C. Heat fusion. PTFE is used to prevent the active material layer from adhering to the roller, and other materials such as copper foil and aluminum foil may be used.

In the same manner, a negative electrode plate is prepared using the negative electrode sheet and the copper current collector. Finally, the polymer electrolyte is sandwiched between a positive electrode plate and a negative electrode plate, and heated and pressed by two rollers heated to 120 ° C. to produce a heat-fused integrated battery.

The above integrated battery was immersed in diethyl ether to extract and remove DBP, dried in vacuum at 50 ° C., and immersed in an electrolyte to obtain the battery of the present invention. Here, the electrolyte used was a solution prepared by dissolving lithium hexafluorophosphate in an equal volume mixture of ethylene carbonate and ethyl methyl carbonate. (Comparative Example 1) The battery of Comparative Example 1 was prepared in the same manner as in Example 1 except that a mixture of acetylene black was used as the conductive carbon material applied to the current collector and P (VDF-HFP) was used as the binder. Was prepared. (Comparative Example 2) The same procedure as in Example 1 was carried out except that a current collector of aluminum and copper, in which the mixture of the conductive carbon material and the binder was not bound to the current collector, was used for the positive electrode and the negative electrode, respectively. A battery of Comparative Example 2 was produced.

The internal resistance of the batteries of the obtained Example and Comparative Examples 1 and 2 was measured by using the AC impedance method. As a result, in the battery of Example, the internal resistance was 10
Ω · cm 2, whereas the battery of Comparative Example 1 had an internal resistance of 70 Ω · cm 2 and the battery of Comparative Example 2 had an internal resistance of 110 Ω · cm 2.
Cm 2, indicating that the internal resistance of the battery of Example was significantly reduced, and that the electrical contact between the current collector and the active material layer was dramatically improved.

Next, a cycle test was conducted in which the battery was charged at a charging current of 30 mA and then discharged at a discharging current of 30 mA, and the discharge capacities at the first cycle and the 20th cycle were measured. As a result, the discharge capacity in the first cycle was 142
mAh, 135 mAh for the battery of Comparative Example 1, 105 mAh for the battery of Comparative Example 2, and the discharge capacity at the 20th cycle was 140 mAh for the battery of Example 1, 30 mAh for the battery of Comparative Example 1, and 21 mAh for the battery of Comparative Example 2. Met. From this result, in the batteries of Example and Comparative Example 1,
It was found that good adhesion and electrical contact between the current collector and the active material layer can be realized by binding the conductive carbon material to the current collector surface. However, the capacity of the battery of Comparative Example 1 was reduced as the cycle progressed, and the capacity difference was increased at 20 cycles.

When the batteries of these Examples and Comparative Example 1 were disassembled, the cross section of the current collector of the battery of the present invention was such that the conductive carbon material 7 was bonded to the current collector 6 as schematically shown in FIG. In contrast, the cross section of the current collector of the battery of Comparative Example 1 was in a state where the conductive carbon material 7 was peeled off from the current collector 6 as shown in the schematic diagram of FIG.

By bonding the conductive carbon material to the surface of the current collector as described above, even in a lithium polymer secondary battery in which the amount of the polymer in the active material layer is reduced and the capacity is increased, good adhesion and electric power are obtained. Contact was achieved, and excellent battery characteristics were obtained. Example 2 A battery was prepared in the same manner as in Example 1 except that Ketjen Black or carbon fiber was used instead of acetylene black as the conductive carbon material.
The internal resistance was measured and the cycle characteristics were examined in the same manner as in the above.

As a result, the same effect as when acetylene black was used was obtained. (Example 3) A battery was produced in the same manner as in Example 1 except that the content of acetylene black in the mixture of acetylene black and a binder applied to the current collector was changed.

With respect to the obtained battery, the internal resistance of the battery was measured by using the AC impedance method. FIG. 4 shows the results. Further, after charging at a charging current of 30 mA, a cycle test of discharging at a discharging current of 30 mA was performed, and discharge capacities at the first cycle and the 20th cycle were measured. The result is shown in FIG.

FIG. 4 shows that when the content of acetylene black was 20% by weight or less, the internal resistance was increased, and the effect of the addition of the conductive agent was not obtained. Also, from the results of FIG. 5, the content of acetylene black was 20% by weight or less and 50% by weight.
Above, the capacity decrease in the 20th cycle with respect to the first cycle was remarkable. At 20% by weight or less, the effect of the addition of the conductive agent was not obtained, and at 50% by weight or less, the binding property was deteriorated and the capacity was significantly reduced. .

[0031]

As described above, according to the present invention, since the conductive carbon material and polyvinylidene fluoride are bonded to the surface of the current collector, the adhesion to the active material layer and the electrical contact are improved. Even if the amount of the polymer in the active material layer is reduced, a lithium-polymer battery having good battery characteristics and good cycle characteristics can be manufactured. In addition, by reducing the amount of the polymer, the capacity of the electrode plate can be increased, and the improvement of the battery capacity, which has been a problem of the polymer secondary battery, can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a power generation element portion of a polymer battery according to the present invention.

FIG. 2 is a schematic cross-sectional view of a current collector of the present invention.

FIG. 3 is a schematic cross-sectional view of a conventional current collector.

FIG. 4 is a diagram showing the relationship between the content of a conductive carbon material and internal resistance.

FIG. 5 is a diagram showing the relationship between the content of a conductive carbon material and the capacity of one cycle and 20 cycles.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 positive electrode active material layer 2 positive electrode current collector 3 polymer electrolyte 4 negative electrode active material layer 5 negative electrode current collector 6 current collector 7 conductive carbon material

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yasuo Yoshihara 1006 Odakadoma, Kadoma-shi, Osaka, Japan Matsushita Electric Industrial Co., Ltd. (72) Inventor Masahiko Ogawa 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Nobuo Eda 1006 Odaka Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] In an organic electrolyte battery comprising a positive electrode, a negative electrode and a polymer electrolyte, at least one of the positive electrode and the negative electrode has at least one of an active material, a conductive material, a non-aqueous electrolyte and a polymer which absorbs and retains the non-aqueous electrolyte. A material layer,
An organic electrolyte battery comprising a current collector having a mixture of a conductive carbon material and polyvinylidene fluoride bound to the surface. 2. The organic electrolyte battery according to claim 1, wherein the current collector is laminated or embedded in an active material layer. 3. The organic electrolyte battery according to claim 1, wherein the conductive carbon material is at least one selected from the group consisting of acetylene black, Ketjen black, and carbon fibers. 4. The mixture of the conductive carbon material and the binder,
The organic electrolyte battery according to claim 1, wherein the content of the carbon material is 20 to 50% by weight in the mixture.