JPH0878019A - Nonaqueous electrolyte battery - Google Patents

Abstract

PURPOSE: To provide a nonaqueous electrolyte battery having practically usable large discharge capacity by using a lithium-containing iron oxide having a specified specific surface area or a specified average particle size as a positive electrode active material. CONSTITUTION: A nonaqueous electrolyte battery has a negative electrode using a material capable of absorbing/desorbing a lithium ion or metallic lithium as a negative electrode material and a positive electrode using a lithium- containing iron oxide represented by a composition formula of Lix FeOy (0<x<=1.5, 1.8<y<2.2) as a positive electrode active material. The lithium- containing iron oxide is required to have a BET specific surface area of 0.5 to 20.5m<2> /g, preferably 12 to 20m<2> /g. When average particle size is limited, the average particle size as determined by laser diffraction is 0.4 to 10μm, preferably 0.5 to 3μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte battery, and more particularly, to an inexpensive non-aqueous electrolyte battery using a lithium-containing iron oxide as a positive electrode active material and having a large discharge capacity. And an improvement of lithium-containing iron oxide.

[0002]

2. Description of the Related Art In recent years,
As one of the positive electrode active materials for non-aqueous electrolyte batteries, the composition formula Li
_The lithium-containing iron oxide represented by _x FeO _y (0 <x ≦ 1.5, 1.8 <y <2.2) is LiCoO ₂ , Li.
Since the raw material cost is lower than that of NiO ₂ etc., it is being reviewed. Thus, conventionally, a lithium-containing iron oxide having a considerably large specific surface area (21 m ² / g or more) has been used. However, a conventional non-aqueous electrolyte battery using such a lithium-containing iron oxide as a positive electrode active material cannot be put into practical use because the discharge capacity per unit weight of the positive electrode active material is about 20 to 30 mAh / g. There was a problem.

The present invention has been made to solve this problem, and an object thereof is to provide a positive electrode using a lithium-containing iron oxide having a practically large discharge capacity as a positive electrode active material. It is to provide a non-aqueous electrolyte battery provided.

[0004]

[Means for Solving the Problems] The non-aqueous electrolyte battery according to the present invention (hereinafter, referred to as "the present battery") for achieving the above object.
Called. ) Is a substance capable of inserting and extracting lithium ions or a negative electrode using metallic lithium as a negative electrode material, and a composition formula Li _x FeO _y (0 <x ≦ 1.5, 1.8 <
In a non-aqueous electrolyte battery including a positive electrode using a lithium-containing iron oxide represented by y <2.2) as a positive electrode active material, the lithium-containing iron oxide has a specific surface area of 0.5 to 20 according to the BET method. It is characterized in that it is 0.5 m ² / g.

The BET (Brunauer-Emmett-Teller) method is a method in which the adsorption amount of a monomolecular layer is determined on the adsorption isotherm and the surface area is determined from the cross-sectional area of the adsorbed molecule to calculate the specific surface area.

The specific surface area of the lithium-containing iron oxide in the present invention is limited to 0.5 to 20.5 m ² / g.
This is because a large discharge capacity can be obtained when a material having a specific surface area within this range is used, as shown in Examples described later. A suitable specific surface area is 12 to ²⁰ m ² / g.

The lithium-containing iron oxide having a specific surface area of 0.5 to 20.5 m ² / g has an average particle size of 0.4 to 10 μm, and the lithium-containing iron oxide has a specific surface area of 12 to ²⁰ m ² / g. The average particle size of the oxide is 0.5 to 3 μm.

The above average particle diameter is an average particle diameter on a 50% volume basis, which is determined by a laser diffraction method by regarding each particle as a spherical shape.

The larger the specific surface area, that is, the smaller the average particle diameter, the larger the reaction area per unit weight with the non-aqueous electrolyte, so that a large discharge capacity tends to be obtained. The reason why the discharge capacity decreases when the specific surface area exceeds 20.5 m ² / g, that is, when the average particle size is less than 0.4 μm is not necessarily clear to the present inventors, but If the surface area exceeds 20.5 m ² / g and becomes too large (that is, the average particle size becomes too small, less than 0.4 μm), the lithium-containing iron oxide reacts with the electrolytic solution to decompose the electrolytic solution. It is supposed to be because.

The lithium-containing iron oxide in the present invention is
For example, lithium carbonate (Li ₂ CO ₃ ) and iron (III) oxide
(Fe ₂ O ₃ ) was mixed at a predetermined molar ratio and then heat-treated in air, and the specific surface area was 0.5.
~ 20.5 m ² / g, that is, the average particle size is 0.4 to 10
It is obtained by pulverizing so as to be in the range of μm.

The positive electrode in the present invention includes, for example, a lithium-containing iron oxide having a specific surface area or average particle diameter within a specific range, a conductive agent such as acetylene black or carbon black, polytetrafluoroethylene (PTFE), Usually, a binder such as polyvinylidene fluoride (PVdF)
Produced by mixing at a weight ratio of 80 to 90: 5 to 15: 4 to 15 to form a positive electrode mixture, and then pressure molding at a predetermined pressure (usually 0.5 to 2.5 tons / cm ² ). To be done.

The negative electrode material in the present invention is a substance or metallic lithium capable of inserting and extracting lithium ions. Examples of substances capable of inserting and extracting lithium ions include Li-Al alloys, Li-Sn alloys,
Examples include lithium alloys such as Li-Pb alloys; carbon materials such as graphite and coke; and metal oxides having a low potential with respect to the positive electrode such as lithium-niobium composite oxides and lithium-titanium composite oxides. The powder of a carbon material or the like may be prepared by, for example, adding this, a binder, and a conductive agent added if necessary,
Usually, the mixture is used at a weight ratio of 80 to 90: 6 to 15: 4 to 10 and used as a negative electrode mixture.

As described above, the present invention is characterized in that a lithium-containing iron oxide having a specific surface area or average particle diameter within a specific range is used as the positive electrode active material. Therefore, for other members constituting the battery such as the non-aqueous electrolyte and the separator (when the liquid electrolyte is used), various materials conventionally used or proposed for the non-aqueous electrolyte battery are used. be able to.

For example, as the solvent for the non-aqueous electrolyte, organic solvents such as ethylene carbonate, vinylene carbonate and propylene carbonate, and these and diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, A mixed solvent with a low boiling point solvent such as ethoxymethoxyethane is exemplified. It is also possible to use a solid electrolyte.

[0015]

In the battery of the present invention, the lithium-containing iron oxide having a specific surface area or average particle size is used as the positive electrode active material, so that the positive electrode has a large amount of occlusion and release of lithium ions.

[0016]

EXAMPLES The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to the following examples, and various modifications may be made without departing from the scope of the invention. Is possible.

Example 1 [Preparation of Positive Electrode] Lithium carbonate (Li ₂ CO ₃ ) and iron oxide
(III) (Fe ₂ O ₃ ) was mixed at a molar ratio of 1: 1 and then heat-treated in air at 850 ° C. for 20 hours to obtain massive LiFeO ₂ (lithium-containing iron oxide). .

This LiFeO ₂ was pulverized for 8 hours in an Ishikawa type mortar mortar to obtain LiFeO ₂ powder having an average particle size of 0.4 μm (specific surface area by BET method: 20.5 m ² / g).

For measuring the specific surface area, a specific surface area measuring apparatus Model 2200 (capacity method, manufactured by Shimadzu Micromeritex Co., Ltd.
The nitrogen adsorption method at the boiling point of liquid nitrogen) was used.

The above LiFeO ₂ powder, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder were mixed at a weight ratio of 90: 6: 4 to prepare a positive electrode mixture, and this positive electrode mixture was prepared. With a pressure of 2 tons / cm ² and a diameter of 2
After pressure-molding into a 0 mm disk shape, heat treatment was performed at 250 ° C. for 2 hours to produce a positive electrode.

[Preparation of Negative Electrode] A rolled lithium plate having a diameter of 20
A negative electrode was produced by punching out into a disc shape of mm.

[Preparation of Electrolyte Solution] Lithium perchlorate (LiClO ₄ ) was dissolved in a mixed solvent of equal volume of propylene carbonate (PC) and 1,2-dimethoxyethane (DME) at a ratio of 1 mol / liter. A non-aqueous electrolyte was prepared.

[Assembly of Non-Aqueous Electrolyte Battery] A flat non-aqueous electrolyte battery (battery of the present invention) BA1 (battery size: diameter 24.0 mm, using the positive and negative electrodes and the non-aqueous electrolyte solution)
Thickness 3.0 mm) was assembled. As the separator, a polypropylene microporous film was used, which was impregnated with the above non-aqueous electrolyte solution.

FIG. 1 is a sectional view of the assembled battery BA1 of the present invention. The battery BA1 of the present invention shown in FIG.
The negative electrode 2, a separator 3 separating them from each other, a positive electrode can 4, a negative electrode can 5, a positive electrode current collector 6, a negative electrode current collector 7, an insulating packing 8 made of polypropylene, and the like.

The positive electrode 1 and the negative electrode 2 are housed in a battery case formed by positive and negative electrode cans 4 and 5 facing each other with a separator 3 impregnated with a non-aqueous electrolytic solution interposed therebetween. The positive electrode 1 is a positive electrode current collector. 6 to the positive electrode can 4 and the negative electrode 2 to the negative electrode current collector 7
It is connected to the negative electrode can 5 via the so that the chemical energy generated inside the battery can be taken out as electric energy from both terminals of the positive electrode can 4 and the negative electrode can 5.

(Examples 2 to 8) The grinding time was 6, 5,
4, 3, 2, 1, 0.5 hours, and the average particle size is 0.5, 1, 2, 3, 5, 8, 10 μm in order (specific surface area:
20, 18, 15, 12, 8, ^2, 0.5m ² /
g) LiFeO ₂ powder was prepared, and these were made into LiFeO having an average particle size of 0.4 μm (specific surface area 20.5 m ² / g).
Inventive batteries BA2 to BA8 were sequentially manufactured in the same manner as in Example 1 except that ₂ powders were used instead.

(Comparative Examples 1 and 2) Grinding time was 10 hours,
Change to 20 minutes, average particle size 0.3, 12 μm,
(Specific surface areas are 21, 0.3 m ² / g in that order) LiFe
Comparative battery BC1 was prepared in the same manner as in Example 1 except that O ₂ powder was prepared and used in place of LiFeO ₂ powder having an average particle size of 0.4 μm (specific surface area 20.5 m ² / g). , BC2 were produced.

[Discharge Capacity] Batteries BA1 to BA8 of the present invention,
Regarding Comparative Batteries BC1 and BC2, 1 g of a positive electrode active material (LiFeO ₂ powder) in the case of charging to a final voltage of 4.3 V at 1 mA and then discharging to a final voltage of 3.0 V at 1 mA
The discharge capacity per hit was examined. The results are shown in FIGS. 2 and 3.

FIG. 2 is a graph in which the vertical axis represents the discharge capacity (mAh / g) per 1 g of the positive electrode active material, and the horizontal axis represents the average particle size (μm) of the positive electrode active material. Also, FIG.
Is the discharge capacity per 1 g of the positive electrode active material (mAh /
g), and the horizontal axis indicates the specific surface area of the positive electrode active material (m ² /
It is the graph which took and represented g).

From FIG. 2, the average particle size is 0.4 to 10 μm,
That is, LiF having a specific surface area of 0.5 to 20.5 m ² / g
eO ₂ powder present battery using BA1~BA8, the average particle size or than the comparative batteries BC1, BC2 having a specific surface area were used LiFeO ₂ powder outside this range, it can be seen discharge capacity is large.

Further, referring to FIGS. 2 and 3, the battery B of the present invention is obtained.
Among A1 to BA8, the average particle size is 0.5 to 3 μm,
That is, a specific surface area of 12 to ²⁰ m ² / g of LiFeO ₂
The batteries BA2 to BA5 of the present invention using powder are 130 m
It can be seen that it has an extremely large discharge capacity of Ah / g. Table 1 collectively shows the above results.

[0032]

[Table 1]

In the above examples, the case where LiFeO ₂ powder is used as the positive electrode active material has been described as an example, but when other lithium-containing iron oxides regulated by the above formula are used as the positive electrode active material. Also obtained similar results.

Further, in the above embodiments, the case where the present invention is applied to the flat type non-aqueous electrolyte battery has been described, but the shape of the battery is not particularly limited, and the present invention is a cylindrical type, a square type, a film type or the like. It can be applied to non-aqueous electrolyte batteries of various shapes.

Further, although the liquid electrolyte (non-aqueous electrolyte) is used in the above embodiment, it is also possible to use a solid electrolyte. By using the solid electrolyte, there is no fear of liquid leakage, Free and reliable battery can be obtained.

Furthermore, the present invention is applicable to both primary batteries and secondary batteries.

[0037]

Since the lithium-containing iron oxide having a specific average particle diameter or specific surface area is used as the positive electrode active material, the battery of the present invention has a practically large discharge capacity.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a flat type non-aqueous electrolyte battery assembled in an example.

FIG. 2 is a graph showing the relationship between the average particle size of lithium-containing iron oxide (LiFeO ₂ ) powder and the discharge capacity.

FIG. 3 is a graph showing the relationship between the specific surface area of lithium-containing iron oxide (LiFeO ₂ ) powder and the discharge capacity.

[Explanation of symbols]

 BA1 flat type non-aqueous electrolyte battery (battery of the present invention) 1 positive electrode 2 negative electrode

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Koji Nishio 2-5-5 Keihan Hondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Toshihiko Saito 2-chome, Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd.

Claims (4)

[Claims] 1. A negative electrode using, as a negative electrode material, a substance capable of inserting and extracting lithium ions or metallic lithium.
Composition formula Li _x FeO _y (0 <x ≦ 1.5, 1.8 <y <
In a non-aqueous electrolyte battery including a positive electrode using a lithium-containing iron oxide represented by 2.2) as a positive electrode active material, the lithium-containing iron oxide has a specific surface area of 0.5 according to the BET method.
~ 20.5 m ² / g Non-aqueous electrolyte battery characterized by the above. 2. The non-aqueous electrolyte battery according to claim 1, wherein the specific surface area is 12 to ²⁰ m ² / g. 3. A negative electrode using a substance capable of inserting and extracting lithium ions or metallic lithium as a negative electrode material,
Composition formula Li _x FeO _y (0 <x ≦ 1.5, 1.8 <y <
In a non-aqueous electrolyte battery including a positive electrode having a lithium-containing iron oxide represented by 2.2) as a positive electrode active material, the lithium-containing iron oxide has an average particle size of 0.4 to 10 μm measured by a laser diffraction method. And a non-aqueous electrolyte battery. 4. The non-aqueous electrolyte battery according to claim 3, wherein the average particle size is 0.5 to 3 μm.