JPH10223225A - Electrode active material, and alkali metallic non-aqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte battery for a large battery, having battery characteristics superior in charging/discharging characteristic at a low cost by using the electrode active material consisting of a transition metal borate complex, using Fe, Mn, Ti, etc., for the positive or negative active material. SOLUTION: At least one kind of Fe, Mn and Ti is contained as M of a transition metal borate complex, given by the general formula M3 BO6 (M is a transition metal). In M3 BO6 , the oxide or hydroxide of M, and B2 O3 are blended in the stoichiometric composition or with more B2 O3 by about 5%, and the mixture is temporarily baked for six hours at approximately 700 deg.C in the atmosphere, baked for about two days at approximately 900 deg.C, and then rapidly cooled and synthesized. The transition metal borate complex is used as the electrode active material. The electrode active material can constitute a positive or a negative electrode, and a counter electrodes is formed of including alkali metal, in particular, lithium, and an alkali metal non-aqueous electrolyte secondary battery which is good in practicability is provided at a low cost, using the electrolyte containing the non-aqueous solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode active material and an alkali metal non-aqueous electrolyte secondary battery, and more particularly to a chargeable / dischargeable electrode active material and a non-aqueous electrolyte secondary battery, and particularly to iron, manganese, and titanium. It is intended to realize an inexpensive secondary battery by using an electrode active material mainly composed of a double salt, and the like, and using this electrode active material.

[0002]

2. Description of the Related Art A non-aqueous electrolyte battery using an alkali metal such as lithium and an alloy or compound thereof as a negative electrode active material is produced by insertion or intercalation reaction of negative metal ions into the positive electrode active material. It has both large discharge capacity and charge reversibility. Conventionally, as a secondary battery using lithium as a negative electrode active material, V _{2 which} can be an intercalation host for lithium has been used.
A battery using a layered or tunnel-shaped oxide such as O ₅ , LiCoO _2, or LiNiO ₂ as a positive electrode has been proposed. However, since these metal oxides use a rare metal having an extremely small Clark number as a central metal, However, there are practical difficulties in terms of cost.

[0003]

SUMMARY OF THE INVENTION The present invention has been proposed to improve the above-mentioned problems, and an object of the present invention is to provide a non-aqueous electrolyte battery for a large battery having battery characteristics excellent in charge / discharge characteristics. At low cost.

[0004]

[Means for Solving the Problems] To achieve the above object, an electrode active material according to the present invention has a general formula: M ₃ BO
_{6 An} electrode active material comprising a transition metal borate complex given by (M: transition metal) is characterized in that M includes at least one of Fe, Mn, and Ti.

The present invention also provides an alkali metal nonaqueous electrolyte secondary battery using the above-mentioned electrode active material, and comprises a transition metal borane represented by the general formula: M ₃ BO ₆ (M: transition metal). An electrode active material comprising an acid complex, wherein the electrode active material comprises a transition metal borate complex including at least one of Fe, Mn, and Ti as M as a positive electrode active material or a negative electrode active material. It is characterized by being performed.

That is, in the electrode active material and the alkali metal non-aqueous electrolyte secondary battery of the present invention, the composition formula M ₃ BO ₆ (where M is a transition metal and M In the case where iron or the like is the main component), a material represented by the formula (I) is contained as a positive electrode active material or a negative electrode active material, and an alkali metal or a material capable of occluding and releasing an alkali metal is used as a counter electrode active material. A material capable of performing an electrochemical reaction with the positive electrode active material or the negative electrode active material is used as an electrolyte material.

The present invention will be described in more detail.

For example, Fe ₃ BO as an electrode active material
No. ₆ is composed of ferric oxide α-Fe ₂ O ₃ and boric acid B ₂ O ₃ in a stoichiometric composition or a small amount of boric acid (about 5%) in order to compensate for the loss due to volatilization of the boron component. After weighing and mixing,
After calcination at 700 ° C. for 6 hours in the air, 900
After baking at 2 ° C. for 2 days, it can be synthesized by rapid cooling. The synthesis method and synthesis conditions are not limited to these, and γ
Synthesis from other starting materials such as Fe ₂ O ₃ , Fe ₃ O ₄ , or FeO, or a mixture of these iron oxides or ferric hydroxide is also possible. The same applies when Mn or Ti is used instead of iron.

There are the following methods for forming an electrode using this active material. First, there is a method in which a mixture of the compound powder and a binder powder such as polytetrafluoroethylene is compression-molded on a support such as stainless steel. Alternatively, a conductive powder such as acetylene black is mixed to impart conductivity to the mixture powder, and a binder powder such as polytetrafluoroethylene is further added as necessary, and the mixture is added to a metal container. How to enter,
Alternatively, there is a method in which the above-mentioned mixture is compression-molded on a support such as stainless steel, or a method in which the above-mentioned mixture is dispersed in a solvent such as an organic solvent to be formed into a slurry and coated on a metal substrate.

When lithium metal is used as the negative electrode active material, the lithium metal is formed into a sheet, and the sheet is pressed against a conductive net made of nickel, stainless steel or the like to form a negative electrode. In addition, as the negative electrode active material, other than lithium, a lithium alloy, a lithium compound, other sodium,
Conventionally known alkali metals such as potassium and magnesium, their alkali metal alloys, and carbon materials capable of occluding and releasing alkali metal ions can be used.

Examples of the electrolytic solution include dimethoxyethane, 2-methyltetrahydrofuran, ethylene carbonate, methyl formate, dimethyl sulfoxide, propylene carbonate, acetonitrile, butyrolactone, dimethylformamide, dimethyl carbonate, diethyl carbonate, sulfolane, ethyl methyl carbonate and the like. A nonaqueous electrolyte solvent in which a Lewis acid containing an alkali metal ion is dissolved, or a solid electrolyte can be used.

As for other elements such as a structural material such as a separator and a battery case, various conventionally known materials can be used, and there is no particular limitation.

[0013]

EXAMPLES The method of the present invention will be described more specifically with reference to the following examples, but the present invention is not limited thereto. In the examples, preparation and measurement of the battery were performed in a dry box under an argon atmosphere.

[0014]

Embodiment 1 FIG. 1 is a cross-sectional view of a coin-type battery which is a specific example of a battery according to the present invention, wherein 1 is a sealing plate, 2 is a gasket, 3 is a positive electrode case, 4 is a negative electrode, and 5 is a separator. And 6 indicate positive electrode material mixture pellets.

The positive electrode active material includes ferric oxide α-Fe ₂ O ₃
And boric acid B ₂ O ₃ were weighed and mixed at a composition ratio of 3: 1 according to the following reaction formula, and fired in air at 700 ° C. for 6 hours, further fired at 900 ° C. for 2 days, and quenched Fe obtained
₃ BO ₆ was used.

Reaction formula: 3Fe ₂ O ₃ + B ₂ O ₃ → 2Fe ₃ BO ₆

FIG. 2 shows an X-ray diffraction pattern of the obtained powder sample. Its X-ray diffraction pattern is exactly the space group Pnm
a was identified as Fe ₃ BO ₆ (JCPDS # 18-0636).

This sample is pulverized into a powder, mixed with a conductive agent (acetylene black) and a binder (polytetrafluoroethylene), and then roll-formed to form a positive electrode mixture pellet 6 (thickness 0.5 mm, diameter: 0.5 mm). 15 mm).

Next, a negative electrode 4 made of metallic lithium is placed under pressure on a sealing plate 1 made of stainless steel, and inserted into a concave portion of a gasket 2 made of polypropylene. The positive electrode mixture pellets 6 are arranged in this order, and as an electrolyte, a proper amount of a 1 N solution of LiPF ₆ dissolved in a mixed solvent of ethylene carbonate and dimethyl carbonate in a volume ratio of 1: 2 is injected and impregnated. A coin-type lithium battery having a thickness of 2 mm and a diameter of 23 mm was produced by covering and caulking the stainless steel positive electrode case 3.

[0020] As an example showing the cycle reversibility of the present invention, 1.2V-2 at a current density of 0.5 mA / cm ^2.
FIG. 3 shows a charge / discharge curve in the second cycle of the 5V voltage regulation charge / discharge cycle test. Since its discharge curve is flat and its average discharge voltage is about 1.5 V, it is a low-cost electrode that is voltage-compatible with conventional aqueous secondary batteries such as nickel-cadmium batteries, nickel-metal hydride batteries, or dry batteries. It turns out that it is a material.

[0021]

Example 2 Using a coin-type lithium battery manufactured in the same manner as in Example 1, Fe _x Ti _1-x BO ₆ or Mn _x
0.5 mA / cm ^{2 of} Fe _1-x BO ₆ and Ti _x Mn _1-x BO ₆
Table 1 shows the reversible capacity at a current density of. According to the present invention,
These complexes, like Fe ₃ BO ₆ , were found to be electrode materials exhibiting large capacities.

[0022]

[Table 1]

[0023]

As described above, according to the present invention,
A low-cost, high-capacity, high-capacity non-aqueous electrolyte secondary battery can be configured, and has the advantage of being usable in various fields.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration example of a coin-type battery according to one embodiment of the present invention.

FIG. 2 is an X-ray diffraction pattern of Fe ₃ BO _{6 according to} one embodiment of the present invention.

FIG. 3 shows 1.2 V of Fe ₃ BO _{6 according to} an embodiment of the present invention.
FIG. 4 is a characteristic diagram showing a charge / discharge curve at the time of one 2.5 V voltage regulation test.

[Explanation of symbols]

 1 Stainless steel sealing plate 2 Polypropylene gasket 3 Stainless steel positive electrode case 4 Lithium negative electrode 5 Polypropylene separator 6 Positive electrode material pellet

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Junichi Yamaki Nippon Telegraph and Telephone Corporation 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo

Claims (5)

[Claims] 1. An electrode active material comprising a transition metal borate complex represented by the general formula: M ₃ BO ₆ (M: transition metal), wherein M includes at least one of Fe, Mn, and Ti. Electrode active material. 2. An electrode active material comprising a transition metal borate complex represented by the general formula: M ₃ BO ₆ (M: transition metal), wherein M comprises at least one of Fe, Mn, and Ti. An alkali metal nonaqueous electrolyte secondary battery comprising an electrode active material comprising a transition metal borate complex as a positive electrode active material or a negative electrode active material. 3. The electrode active material according to claim 2 as a positive electrode, a material containing an alkali metal as a negative electrode,
An alkali metal nonaqueous electrolyte secondary battery comprising a nonaqueous solvent as an electrolyte. 4. An electrode active material according to claim 2 as a negative electrode, a material containing an alkali metal as a positive electrode,
An alkali metal nonaqueous electrolyte secondary battery comprising a nonaqueous solvent as an electrolyte. 5. An alkali metal non-aqueous electrolyte secondary battery, wherein the alkali metal according to claim 3 is lithium.