JP3403858B2 - Organic electrolyte 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 high capacity and high voltage organic electrolyte battery using a carbon material for a negative electrode and a metal oxide for a positive electrode.

[0002]

2. Description of the Related Art In recent years, a secondary battery using a conductive polymer, a transition metal oxide or the like as a positive electrode and a lithium metal or a lithium alloy as a negative electrode has a high energy density.
It has been proposed as a battery replacing i-Cd batteries and lead batteries. However, when these secondary batteries are repeatedly charged and discharged, the capacity is greatly reduced due to deterioration of the positive electrode or the negative electrode, and there is a problem in practical use. In particular, the deterioration of the negative electrode involves the formation of moss-like lithium crystals called dentite, and the repetition of charging and discharging eventually causes the dentite to penetrate the separator, causing a short circuit inside the battery, and in some cases, the battery exploding There was also a problem in terms of safety.

In recent years, in order to solve the above-mentioned problems, a battery using a carbon material such as graphite for a negative electrode and using a lithium-containing metal oxide such as LiCoO _{2 for} a positive electrode has been proposed. The battery is a so-called rocking chair type battery in which lithium is supplied to the negative electrode from the lithium-containing metal oxide of the positive electrode by charging after the battery is assembled, and the negative electrode lithium is returned to the positive electrode in discharging. Although the battery is characterized by a high voltage and a high capacity, the capacity still has an unsatisfactory point.

[0004]

In view of the above problems, the present inventors have made intensive studies and completed the present invention. An object of the present invention is to provide a secondary battery having a high capacity and a high voltage. To provide batteries. Another object of the present invention is to provide a secondary battery which can be charged and discharged for a long period of time and is excellent in safety. Still another object of the present invention is to provide a secondary battery having a low internal resistance. Still another object of the present invention is to provide a secondary battery which is easy to manufacture. Further objects of the present invention will become clear from the description below.

[0005]

Means for Solving the Problems The present inventors have completed the present invention by using a metal oxide for the positive electrode and a carbon material for the negative electrode, and selecting a method for supporting lithium (doping method) derived from the negative electrode. That is, the present invention relates to an organic electrolyte battery provided with a positive electrode, a negative electrode, and an aprotic organic solvent solution of a lithium salt as an electrolytic solution, wherein the positive electrode contains a lithium-containing metal oxide, the negative electrode is a carbon material, are those obtained by supporting the lithium from the positive electrode of lithium-containing metal oxide after battery assembly to the carbon material, and the electrode cross-sectional side in the battery to the positive electrode
An organic electrolyte battery characterized by carrying lithium more than lithium arranged in the direction .

[0006] As the carbon material in the present invention, any carbon material used in this type of secondary battery can be used. For example, a carbon material obtained by carbonizing pitch, tar, or the like, graphite, or the like can be used. Further, the present invention is effective for a carbon material whose efficiency in the first charge / discharge is 80% or less.

[0007] The negative electrode of the present invention is made of the above-mentioned carbon material, and is formed by molding a carbon material having a shape which is easy to mold such as powder, granules and short fibers with a binder. As the binder, a fluorinated resin such as polytetrafluoroethylene or polyvinylidene fluoride, or a thermoplastic resin such as polypropylene or polyethylene can be used, and a fluorinated binder is preferable.

[0008] As the positive electrode of the organic electrolyte battery of the present invention,
Li _X CoO _2, Li _X NiO _2, Li _X MnO ₂ , L
i _X FeO _2, etc. Li _X M _y O _Z (M is a metal, may also be in two or more metals) may be represented by the general formula, electrochemically doped, de-doped Lithium-containing metal oxide of lithium Use things. Particularly, a lithium-containing oxide having a voltage of 4 V or more with respect to lithium metal is preferable. Among them, lithium-containing cobalt oxide and lithium-containing nickel oxide are preferable. The positive electrode in the present invention is formed by adding the above-mentioned active material and, if necessary, a conductive material and a binder, and the type and composition of the conductive material and the binder may be appropriately set.

The type of the conductive agent may be a metal powder such as metallic nickel, but a carbon-based material such as activated carbon, carbon black, acetylene black, and graphite is particularly preferable. The mixing ratio varies depending on the electric conductivity of the active material, the shape of the electrode, and the like, but it is appropriate to add 2 to 40% to the active material. Further, the kind of the binder may be any one that is insoluble in the electrolytic solution used in the present invention described later, for example, a rubber-based binder such as SBR, polytetrafluoroethylene, a fluorinated resin such as polyvinylidene fluoride, Thermoplastic resins such as polypropylene and polyethylene are preferable, and the mixing ratio is preferably 20% or less.

The positive electrode and the negative electrode used in the present invention have the following electrode shapes.
Depending on the intended battery, various shapes such as a plate shape, a film shape, a column shape, or a shape formed on a metal foil can be adopted. In particular, those formed on a metal foil are preferable because they can be applied to various batteries as a current collector integrated electrode.

In the present invention, lithium derived from the negative electrode is
When the battery is completed, it is lithium contained in the negative electrode carbon material,
After the electrolyte is injected and the battery is assembled, lithium is supported on the negative electrode carbon material from the positive electrode lithium-containing oxide using an electrochemical method such as constant current or constant voltage. The positive electrode carries lithium electrochemically from lithium metal. Specifically, for example, when assembling a cylindrical battery, the positive electrode and the negative electrode are wound through a separator, the electrolytic solution is injected, and then the lithium is carried on the positive electrode by electrochemical contact between the positive electrode and lithium. The positive electrode and lithium are preferably connected by a resistor. The resistor can be used to control the current flowing between the positive electrode and lithium.The resistance value varies depending on the battery capacity and battery shape, but if it is too large, the current value becomes small and lithium is carried on the positive electrode. It takes a long time, and when it is too small, the current value becomes large and metallic lithium may be deposited. Preferably 0.1 to 10000Ω
Although a commercially available fixed resistor or the like may be used, for example, a stainless wire having a small wire diameter may be used for a length corresponding to a predetermined resistance. Further, lithium to be connected to the positive electrode is preferably arranged in the electrode cross-sectional direction.For example, when a cylindrical battery is formed by winding the positive electrode, the separator, and the negative electrode, the upper part of the winding electrode unit, or the lower part, When assembling a battery by laminating a positive electrode, a separator, and a negative electrode as shown in FIG. 1, when the electrode surface is a lower surface or an upper surface, there are four directions of side surfaces A, B, C, and D. As the lithium metal current collector, a conductive substance having resistance to both oxidation and reduction is preferably used. For example, stainless steel, platinum, or the like can be used. In addition, the lithium metal current collector
It is preferable that at least a part of the lithium metal electrode plate is disposed at a position farthest from the electrode plate because lithium can be smoothly carried. Also, as lithium,
For example, it is preferable to use lithium metal embedded in a conductor having a mesh shape, a mesh shape, a porous body, or the like, or to use a spirally wound lithium metal material for smoothly supporting lithium. When lithium is carried on the positive electrode in the battery case, lithium corresponding to a predetermined lithium amount is disposed.
The time from the injection of the electrolytic solution to the start of supporting lithium on the negative electrode carbon material from the positive electrode lithium-containing oxide is desirably earlier, preferably within one day, and preferably within one hour. The amount of lithium derived from the negative electrode is not particularly limited, but is preferably larger than the amount of lithium arranged in the electrode cross-sectional direction. Normally, this series of operations is performed at room temperature, but when the temperature becomes high, for example, about 40 ° C., the operation can be performed in a short time. In the present invention, the battery is completed when lithium has been supported by the lithium-containing oxide on the positive electrode by connection of the lithium and the positive electrode. As a method of supporting negative electrode lithium, there is a method of supporting the battery before assembling the battery, that is, a method of supporting the negative electrode carbon material in advance with a predetermined amount of lithium, and then assembling the battery. Is not preferred. Further, there is a method of short-circuiting lithium and the negative electrode carbon material in the battery. However, it is not preferable because lithium loading time on the negative electrode carbon material becomes long.

In the present invention, the amount of lithium derived from the negative electrode is:
Depending on the type of carbon material, 2
It is 0 mAh / g or more, preferably 50 mAh / g or more. If the amount is too small, sufficient capacity cannot be obtained. In the present invention, the amount of lithium supplied to the positive electrode is preferably equal to or smaller than that of lithium derived from the negative electrode.

An aprotic organic solvent is used as a solvent constituting the electrolytic solution used in the present invention. Examples of the aprotic organic solvent include, for example, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, tetrahydrofuran, dioxolan, methylene chloride, sulfolane, and the like.
A mixture of two or more of these aprotic organic solvents can also be used.

The electrolyte mixed or dissolved in a single solvent may be any electrolyte capable of generating lithium ions. As such an electrolyte, for example, Li
I, LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiP
F ₆ , LiHF _{2 and the} like. The electrolyte and the solvent are mixed in a sufficiently dehydrated state to form an electrolyte. The concentration of the electrolyte in the electrolyte is at least 0.1 mol / l or more in order to reduce the internal resistance due to the electrolyte. It is preferable that the amount is usually 0.2 to 1.5 mol / l.

A current collector for extracting a current outside the battery;
Alternatively, as the lead terminal, for example, carbon, platinum, nickel, stainless steel, aluminum, copper, or the like can be used.When a foil-shaped or net-shaped current collector is used, an electrode is formed on the current collector. It can also be used as a current collector integrated electrode.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a diagram illustrating the basic configuration of the battery according to the present invention. In FIG. 2, (1) is a positive electrode, and (2) is a negative electrode. (3) and (3 ') are current collectors, and the electrodes are formed on the current collectors. Lead terminal (8),
(8 ') is connected to the current collector so as not to cause a voltage drop, and one end thereof is connected to the battery case (6) and the top lid (7). (9) is a lithium unit, (10) is a lithium current collector of the lithium unit, connected to the positive electrode current collector (3) via the resistor (11), and the positive electrode (1) and the lithium metal ( During 9), the electrolyte is filled. (5) is a separator impregnated with an electrolytic solution, in which the aforementioned compound capable of generating ions that can be doped is dissolved in an aprotic organic solvent. The electrolyte is usually in a liquid state and is impregnated in the separator. However, the electrolyte may be used in a gel or solid state without a separator to prevent liquid leakage. (4) is an insulating packing arranged to prevent contact between the positive and negative electrodes (battery case and top lid).

[0017] The separator is a porous material having continuous holes for the electrolyte or the electrode active material and having no electron conductivity, and is usually made of glass fiber, polyethylene or polypropylene cloth, non-woven cloth. Alternatively, a porous body is used. Preferably, it is a nonwoven fabric or a porous separator made of glass fiber, polyethylene, polypropylene, or the like having three-dimensionally connected pores, and has an effect of shortening the lithium carrying time. The thickness of the separator is preferably thin in order to reduce the internal resistance of the battery, but is determined in consideration of the amount of retained electrolyte, flowability, strength, and the like. The positive and negative electrodes and the separator are fixed in the battery case (6) so that there is no practical problem. The shape, size, and the like of the electrode are appropriately determined depending on the shape and performance of the intended battery. FIG. 3 is a diagram illustrating the basic configuration of the lithium unit of the battery according to the present invention. In FIG. 3, (12) is lithium metal,
(10) is the current collector. (13) is (1)
It is an insulating cap for preventing the lithium metal of 2) from directly contacting the positive electrode (1), the negative electrode (2) and the battery case (6). The current collector (10) and the positive electrode terminal (3) are connected via a resistor (11). Further, a porous polypropylene nonwoven fabric holding an electrolyte may be inserted between the electrode unit and the lithium metal (12).
As shown by the arrow E, a hole having a diameter of about 4 mm is formed in the center of the lithium unit to weld the negative electrode terminal (8 ') and the lower part of the battery case (6). A commercially available fixed resistor or the like may be used for the resistor (11). For example, as shown in FIG. 4, a stainless wire (15) having a small wire diameter may be used for a predetermined length.
At this time, since the wire is thin and easily comes into contact with the battery case (6) and the electrode, it is better to cover with an insulating sealing tape (16) for both reinforcement and insulation. The shape of the battery of the present invention is not limited to the cylindrical shape as exemplified above, but includes a square shape, a box shape, and the like, and the shape is not particularly limited.

[0018]

The organic electrolyte battery of the present invention uses a carbon material for the negative electrode, a metal oxide for the positive electrode, appropriately controls both the amount of lithium derived from the negative electrode, and a method for supporting lithium derived from the negative electrode. By proper selection, the battery has a high capacity, a high voltage and a low internal resistance, and is a battery that is easy to manufacture. Hereinafter, the present invention will be described specifically with reference to examples.

[0019]

【Example】

Example 1 A petroleum pitch was fired at 1200 ° C. and pulverized with a disk mill to obtain a carbon material powder having an average particle size of about 15 μm. Next, 100 parts by weight of the carbon material powder and 110 parts by weight of a solution obtained by dissolving 10 parts by weight of polyvinylidene fluoride powder in 90 parts by weight of N, N-dimethylformamide were sufficiently mixed to obtain a slurry. The slurry was applied on a 10 μm-thick copper foil (negative electrode current collector) using an applicator, dried, pressed, and coated with a carbon material on both surfaces.
A carbon material negative electrode of 0 μm was obtained. LiCoO ₂ 100 parts,
5 parts of graphite, polyvinylidene fluoride powder 10
A slurry was obtained by sufficiently mixing 50 parts by weight of a solution dissolved in 90 parts by weight of N, N-dimethylformamide. Thick the slurry using an applicator to a thickness of 2
Coated on a 0 μm aluminum foil (positive electrode current collector), dried and pressed, coated with LiCoO ₂ on both sides to a thickness of 150 μm
Of positive electrode 1 was obtained.

The positive electrode 1 (5.0 × 50 cm ² ) and the negative electrode (5.2 × 54 cm ² ) were used. As the separator, a polypropylene separator having a thickness of 25 μm and a width of 5.2 cm was used as shown in FIG. A cylindrical battery was assembled with a proper positional relationship between the positive electrode, the separator, and the negative electrode. An aluminum terminal having a thickness of 150 μm and a width of 5 mm was used as a positive electrode terminal, and nickel having the same size as the positive electrode terminal was used as a negative electrode terminal. In addition, a lithium unit was installed at the lower part of the battery case (the position shown in FIG. 2), which was the cross-sectional direction of the electrode unit. As shown in FIG. 3, the lithium unit has a hole with a diameter of 15 mm and a diameter of 4 mm at the center,
A lithium metal having a hole of 15 mm in diameter and a diameter of 4 mm at the center is press-bonded to a stainless steel mesh having a terminal of 10 mm in length and 5 mm in width (100 mAh with respect to the negative electrode carbon material).
/ G), and a 300 μm-thick polypropylene cap (having a hole with a diameter of 15 mm at the center) covering the bottom surface and height direction of the lithium portion. The terminal of the lithium part and the positive electrode terminal were connected by a resistor having a resistance value of 1000 and 2000 Ω, and cells 1 and 2 were obtained, respectively. Two cells were assembled in each case. The wire including the resistor connecting the lithium terminal and the positive electrode terminal was covered with a Teflon tape so as not to short-circuit with the battery case and the electrode. As the electrolyte, ethylene carbonate and diethyl carbonate are in a ratio of 1: 1 (weight ratio).
A solution in which LiPF ₆ was dissolved at a concentration of 1 mol / l was used for the mixed solution. One hour after the electrolyte was injected into the battery, at a constant current of 0.25 mA / cm ² , 120 mAh / g of lithium was passed through the anode carbon material by passing an amount of electricity corresponding to 120 mAh / g to the anode carbon material. Was doped from the positive electrode. When the cell 1 was disassembled 10 days after assembly, no lithium was deposited and lithium was completely lost. When the cell 2 was disassembled 20 days after assembly, no lithium was deposited and lithium was completely lost. ^3. The battery voltage was set to 4.25 at a constant current of 0.25 mA / cm ² .
The battery was charged to 3 V, and then discharged at a constant current of 0.25 mA / cm ² until the battery voltage reached 2.5 V. This cycle of 4.3 V-2.5 V was repeated, and the third discharge was evaluated by volume capacity (mAh / cc).
As a volume reference, a total including the volume of lithium metal in addition to the electrode volume, the separator volume, and the current collector volume was used. Table 1 shows the results.

Comparative Example 1 A petroleum pitch was fired at 1200 ° C. and pulverized by a disk mill to obtain a carbon material powder having an average particle size of about 15 μm. Next, 100 parts by weight of the carbon material powder and 110 parts by weight of a solution obtained by dissolving 10 parts by weight of polyvinylidene fluoride powder in 90 parts by weight of N, N-dimethylformamide were sufficiently mixed to obtain a slurry. The slurry was applied on a 10 μm-thick copper foil (negative electrode current collector) using an applicator, dried, pressed, and coated with a carbon material on both surfaces.
A carbon material negative electrode of 0 μm was obtained. LiCoO ₂ 100 parts,
5 parts of graphite, polyvinylidene fluoride powder 10
A slurry was obtained by sufficiently mixing 50 parts by weight of a solution dissolved in 90 parts by weight of N, N-dimethylformamide. Thick the slurry using an applicator to a thickness of 2
200 μm thick coated on 0 μm aluminum foil (positive electrode current collector), dried and pressed, and coated with LiCoO ₂ on both sides
Of positive electrode 2 was obtained.

Using the positive electrode 2 (5.5 × 44 cm ² ) and the negative electrode (5.7 × 49 cm ² ), and using a polypropylene separator having a thickness of 25 μm and a width of 5.7 cm as a separator, a cylindrical battery was used. Assembled cell 3 was obtained. As the electrolyte, a 1: 1 (weight ratio) mixture of ethylene carbonate and diethyl carbonate was used to adjust the concentration of Li to 1 mol / l.
Using a solution of PF _6. 0.25m for the above battery
The battery was charged at a constant current of A / cm ² until the battery voltage reached 4.3 V, and subsequently discharged at a constant current of 0.25 mA / cm ² until the battery voltage reached 2.5 V. This 4.3V-2.5
The cycle of V was repeated, and in the third discharge, evaluation was made by volume capacity (mAh / cc). As a volume standard, the total of the electrode volume, the separator volume, and the current collector volume was used. Table 1 shows the results.

When lithium derived from the negative electrode was 0, sufficient capacity was not obtained.

Comparative Example 2 In Example 1, the lithium portion (10
A two-cell battery 4 was formed in the same manner as the cell 1 of Example 1 except that the negative electrode terminal was connected to the negative electrode terminal with a resistor of 1000Ω instead of the positive electrode terminal instead of the positive electrode terminal. When 50 pieces were decomposed 50 days after the injection of the electrolytic solution, no lithium was precipitated and lithium was completely lost. The capacity was measured in the same manner as in Example 1. Table 1 shows the results
Shown in

Although it is possible to directly carry lithium derived from the negative electrode by connection with lithium disposed in the cross-sectional direction of the electrode unit, it is not industrially preferable because it takes time. It is also industrially important to select an appropriate resistor for connection with lithium arranged in the electrode unit cross-sectional direction.

[0026]

[Table 1]

[Brief description of the drawings]

FIG. 1 is an explanatory view of an electrode cross section according to the present invention.

FIG. 2 is an explanatory diagram of a basic configuration of a battery according to the present invention.

FIG. 3 is an explanatory diagram of a basic configuration of a lithium unit according to the present invention.

FIG. 4 is an explanatory diagram of a basic configuration of a resistor according to the present invention.

[Explanation of symbols]

1 positive electrode 2 Negative electrode 3 Current collector (positive electrode) 3 'current collector (negative electrode) 4 Insulation packing 5 Separator 6 Battery case 7 Top lid 8 terminals (positive electrode) 8 'terminal (negative electrode) 9 lithium unit 10 Current collector (lithium metal) 11 Resistance 12 Lithium metal 13 Insulation cap 14 Separator 15 Stainless wire 16 Insulation sealing tape

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shizukuni Yada 2-6-113 Miyanishi, Harima-cho, Kako-gun, Hyogo (56) References JP-A-5-151994 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 10/40

Claims (2)

(57) [Claims] 1. An organic electrolyte battery comprising a positive electrode, a negative electrode, and a solution of a lithium salt in an aprotic organic solvent as an electrolyte, wherein the positive electrode contains a lithium-containing metal oxide, the negative electrode is a carbon material, An organic electrolyte battery comprising a material in which lithium is supported by a positive electrode lithium-containing metal oxide after battery assembly, and a positive electrode in which lithium is supported by lithium disposed in a cross-sectional direction of the electrode in the battery. 2. The organic electrolyte battery according to claim 1, wherein the positive electrode and lithium disposed in the electrode cross-sectional direction are connected by a resistor.