JP3222949B2 - Non-aqueous secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous secondary battery, and more particularly to an improvement of a positive electrode current collector for improving charge / discharge cycle characteristics.

[0002]

2. Description of the Related Art
Current collector material for positive electrode of non-aqueous secondary battery, especially LiNi
Aluminum is generally used as a current collector material of a positive electrode of a non-aqueous secondary battery capable of extracting a high voltage, using a metal oxide such as O ₂ or LiCoO ₂ as a positive electrode active material. This is because aluminum has excellent corrosion resistance,
This is because even during charging when the positive electrode has a high potential, it does not elute into the electrolytic solution.

However, this conventional nonaqueous secondary battery has poor adhesion between the aluminum molded body as the positive electrode current collector and the positive electrode active material. And the discharge capacity gradually decreases.

The above-mentioned contact resistance can be reduced to some extent by applying a carbon layer having excellent conductivity to the surface of the aluminum molded body, but the adhesion between the aluminum molded body and the carbon layer is not good. Further, as shown in Examples described later, when charging and discharging are repeatedly performed, the contact resistance increases and the battery capacity gradually decreases. It has been found that it is difficult to obtain a battery having characteristics.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a battery having a small contact resistance at the interface between a positive electrode current collector and a positive electrode active material and having excellent charge-discharge cycle characteristics. A non-aqueous secondary battery is provided.

[0006]

In order to achieve the above object, a non-aqueous secondary battery according to the present invention (hereinafter referred to as "battery of the present invention")
Called. ) Is a non-aqueous secondary battery using lithium metal or a substance capable of inserting and extracting lithium as a negative electrode material,
A conductive carbon material-containing aluminum molded body obtained by mixing a conductive carbon material with aluminum and then forming the mixture is used as a positive electrode current collector.

In the battery of the present invention, an aluminum molded body (a foil or a plate) containing a conductive carbon material is used as a positive electrode current collector. As the number of times increases, the adhesion between the positive electrode current collector and the positive electrode active material decreases, the contact resistance increases, and as a result, the problem that the battery capacity gradually decreases is solved.

[0008] As the negative electrode material in the battery of the present invention, metallic lithium or a substance capable of inserting and extracting lithium is used. Examples of the substance capable of inserting and extracting lithium include lithium alloys and carbon materials such as coke and graphite.
A powder material such as a carbon material is used as a negative electrode mixture by kneading with a binder such as polytetrafluoroethylene.

The positive electrode material (positive electrode active material) is not particularly limited. However, since aluminum used as a current collector material of the positive electrode is mainly a current collector material for a high-voltage non-aqueous battery, the negative electrode side A metal oxide exhibiting a high potential with respect to a lithium unipolar potential is exemplified as a typical positive electrode material.
Such a metal oxide is represented by a general formula Li _x MO _y (M is at least one metal element selected from the group consisting of Co, Ni, Mn and Fe; 0 ≦ x ≦ 2; 1 ≦ y ≦ 5). Of the metal M to be formed or a composite oxide of the metal M and Li. Specific examples include modified MnO ₂ , L
iNiO ₂ , LiCoO ₂ , LiMnO ₂ , LiMn ₂
O ₄ is mentioned. The powdery positive electrode material is used as a positive electrode mixture by kneading with a binder.

The conductive carbon material-containing aluminum molded body in the battery of the present invention can be obtained by, for example, mixing a conductive carbon material with heat-melted aluminum and subjecting it to a molding method such as rolling or mold molding by a conventional method, or an aluminum powder. It can be obtained by, for example, a method of hot-forming a mixture of a carbon material and a conductive carbon material.

[0011] The conductive carbon material has conductivity,
It is not particularly limited as long as it is a conductive carbon material capable of reducing the contact resistance at the interface between the positive electrode current collector and the positive electrode active material. Specific examples thereof include amorphous carbon such as acetylene black and carbon black. , Coke, graphite and the like. The shape is not particularly limited, such as powder, fibrous, and whisker.

When the content of the conductive carbon material is excessive, the mechanical strength of the current collector tends to decrease. Therefore,
The preferred content is foil, plate, punching, etc.
Although it depends on the shape of the current collector, it cannot be regulated unconditionally, but in general, the range is preferably 1 to 50 parts by weight with respect to 100 parts by weight of aluminum.

The other members constituting the battery of the present invention are not particularly limited, and various materials conventionally used or proposed for non-aqueous secondary batteries can be used.

For example, as a solvent of the non-aqueous electrolyte,
Propylene carbonate, ethylene carbonate, 1,
Organic solvents such as 2-butylene carbonate, and dimethyl carbonate, diethyl carbonate, 1,2
A mixed solvent with a low-boiling solvent having a boiling point of 150 ° C. or lower, such as dimethokiethane, 1,2-diethoxyethane, ethoxymethoxyethane, etc .;
F ₆ and LiClO ₄ are exemplified.

[0015]

In the battery of the present invention, an aluminum molded body containing a conductive carbon material obtained by mixing aluminum with a conductive carbon material as a contact resistance reducing agent is used as a positive electrode current collector, so that the positive electrode active material is used. The contact resistance at the interface between the substance and the current collector is small, and the contact resistance is unlikely to increase even if charge and discharge are repeated.

[0016]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples, and may be carried out by appropriately changing the scope of the present invention. Is possible.

(Example 1) A cylindrical non-aqueous secondary battery (battery of the present invention) was manufactured.

[Preparation of positive electrode] LiN as positive electrode active material
iO ₂ , carbon black as a conductive agent, and polyethylene terephthalate (P
And TFE) at a weight ratio of 85: 10: 5 to prepare a positive electrode mixture. Further, 90 parts by weight of the aluminum melt was mixed with 10 parts by weight of carbon powder and rolled to prepare an aluminum foil containing a conductive carbon material having a foil thickness of 20 μm. Next, the positive electrode mixture was applied and rolled on both surfaces of the conductive carbon material-containing aluminum foil (positive electrode current collector) to produce a positive electrode.

[Preparation of Negative Electrode] A kneaded product of graphite powder and polyethylene terephthalate was applied and rolled on both sides of a copper foil as a negative electrode current collector to prepare a negative electrode.

[Preparation of Non-Aqueous Electrolyte] LiPF as a solute in ethylene carbonate (EC) as a solvent
₆ (Lithium hexafluorophosphate) was dissolved at 1 mol / L to prepare a non-aqueous electrolyte.

[Preparation of Non-Aqueous Secondary Battery] A cylindrical battery BA1 of the present invention was prepared using the above positive and negative electrodes and a non-aqueous electrolyte (battery dimensions: diameter 14.2 mm; length 50.0).
mm). As a separator, a microporous thin film made of polypropylene (manufactured by Polyplastics Co., Ltd., trade name "Celgard 3401") was used and impregnated with the above-mentioned non-aqueous electrolyte.

FIG. 1 is a schematic cross-sectional view of the battery BA1 of the invention produced. The battery BA1 of the invention includes a positive electrode 1 and a negative electrode 2, a separator 3 separating these electrodes, a positive electrode lead 4, and a negative electrode lead 5. , A positive electrode external terminal 6, a negative electrode can 7, and the like. The positive electrode 1 and the negative electrode 2 are housed in a negative electrode can 7 while being spirally wound through a separator 3 into which an electrolytic solution has been injected. The positive electrode 1 is connected to a positive electrode external terminal 6 through a positive electrode lead 4. The negative electrode 2 is connected to a negative electrode can 7 via a negative electrode lead 5, so that chemical energy generated inside the battery BA1 can be taken out as electric energy.

Comparative Example 1 A kneaded mixture of carbon powder and polyethylene terephthalate in a weight ratio of 85:15 was prepared with a foil thickness of 20 μm.
m and coated on both sides of an aluminum foil to prepare a positive electrode current collector. The thickness of each carbon layer comprising the rolled carbon powder and the binder was 5 μm, and the ratio of aluminum to the carbon powder was about 90:10 by weight. Comparative battery BC was prepared in the same manner as in Example 1 except that the thus-prepared positive electrode current collector having a carbon layer formed on both surfaces was used in place of the aluminum foil containing a conductive carbon material.
1 was produced.

Comparative Example 2 Foil thickness 2 not containing carbon powder
Comparative Battery BC in the same manner as in Example 1 except that the aluminum foil of 0 μm was used as it was as the positive electrode current collector.
2 was produced.

(Charge-discharge cycle test) Battery BA1 of the present invention
And for the comparative batteries BC1 and BC2, the charging condition 0.5
C (full charge in 2 hours) at 4.1 V
After discharging the battery to a discharge end voltage of 2.5 V under a discharge condition of 0.5 C (the battery is fully discharged in 2 hours),
A charge / discharge cycle test as a cycle was performed, and a change in capacity of each battery when the charge / discharge cycle was repeated was examined. The results are shown in FIG.

FIG. 2 shows the charge / discharge cycle characteristics of each battery.
It is a graph showing the battery capacity (mAh) on the vertical axis and the number of cycles (times) on the horizontal axis.

As shown in the figure, in the battery BA1 of the present invention,
The contact resistance between the positive electrode current collector and the positive electrode active material is small, and
Since the battery capacity does not increase, the initial battery capacity of 400 mAh is maintained even at the 400th cycle, and the capacity is not reduced at all, whereas the positive electrode active material is simply pressed against the aluminum foil. Battery BC2
In the (conventional battery), since the adhesion between the two is not very good, the contact resistance sharply increases as the number of cycles increases, and the battery capacity reaches 1 at the 300th cycle.
It turns out that it falls to less than 00 mAh.

Further, in the comparative battery BC1 having the carbon layer provided on the aluminum foil, although the contact resistance is somewhat smaller than that of the comparative battery BC due to the formation of the carbon layer, the charge / discharge cycle characteristics are slightly better. As the number increases, the adhesion between the aluminum foil and the carbon layer gradually decreases, and the contact resistance increases. Therefore, it can be seen that the battery capacity decreases to slightly less than 150 mAh at the 400th cycle.

In the above embodiment, a specific example in which the present invention is applied to a cylindrical non-aqueous secondary battery has been described.
The shape of the battery is not particularly limited, and the present invention can be applied to non-aqueous secondary batteries of various shapes such as a flat type and a square type.

[0030]

According to the battery of the present invention, an aluminum molded article containing a conductive carbon material is used as a positive electrode current collector. Therefore, the contact resistance between the positive electrode active material and the positive electrode current collector is small, and the charge / discharge cycle is reduced. The present invention has excellent unique effects such as excellent characteristics.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a cylindrical battery of the present invention.

FIG. 2 is a charge / discharge cycle characteristic diagram of a battery of the present invention and a comparative battery.

[Explanation of symbols]

 BA1 Battery of the present invention 1 Positive electrode 2 Negative electrode 3 Separator

──────────────────────────────────────────────────続 き Continuing on the front page (72) Mayumi Uehara 2-18-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Koji Nishio 2-18-18 Keihanhondori, Moriguchi-shi, Osaka (72) Inventor Toshihiko Saito 2-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-50-91719 (JP, A) JP-A-59- 134560 (JP, A) JP-A-64-1220 (JP, A) JP-A-60-253157 (JP, A) JP-A-63-121272 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/02-4/04 H01M 4/64-4/84 H01M 10/40

Claims (1)

(57) [Claims] 1. A non-aqueous secondary battery using lithium metal or a substance capable of inserting and extracting lithium as a negative electrode material, wherein the conductive carbon material is mixed with aluminum to form a conductive carbon material-containing aluminum. A non-aqueous secondary battery, wherein the molded article is used as a positive electrode current collector.