JPH1074519A - Alkali metal secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high voltage discharge battery with excellent charge/ discharge characteristic. SOLUTION: An alkali metal secondary battery is formed of alkali metal (A) containing double oxide A2 PtO3 as positive electrode active material 6, lithium metal or lithium ion storage/release possible material as negative electrode active material 4 and material, in which alkali metal ions can be moved for electrochemical reaction with the positive electrode active material and negative electrode active material, as electrolyte. In this way, a great capacity non-aqueous electrolyte secondary battery can be constituted and is advantageously used in various fields.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an alkaline metal secondary battery,
More specifically, the present invention relates to a chargeable / dischargeable non-aqueous electrolyte secondary battery, and more particularly to a positive electrode active material that provides a battery having a high discharge voltage.

[0002]

2. Description of the Related Art A non-aqueous electrolyte battery using an alkali metal such as lithium or an alloy or compound thereof as a negative electrode active material is produced by an insertion or an intercalation reaction of a negative electrode metal ion into a positive electrode active material. It has both large discharge capacity and charge reversibility. Hitherto, layered oxides such as LiCoO ₂ and LiNiO ₂ have been proposed for these positive electrode active materials. However, since the specific gravity is small, the specific volume capacity is not as good as the specific weight capacity. Due to the structure, when deep charging is performed, electrostatic repulsion between oxygen layers increases, and the solid matrix is disturbed, so that a large-capacity charge / discharge cycle is practically difficult.

[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 high-voltage dischargeable battery having excellent charge-discharge characteristics. To provide.

[0004]

Means for Solving the Problems In order to achieve the above object, the alkali metal secondary battery of the present invention contains an alkali metal (A) -containing double oxide A ₂ PtO ₃ as a positive electrode active material, and contains lithium metal or lithium metal. A material capable of occluding and releasing lithium ions is used as a negative electrode active material, and a material capable of performing an electrochemical reaction of the alkali metal ions with the positive electrode active material and the negative electrode active material is used as an electrolyte. Features.

The present invention will be described in more detail.

[0006] AMO, such as LiCoO ₂ and LiNiO _{2 2}
(M: transition metal) has an A-O-M-O layer structure,
At the end of charging, the electrostatic repulsion between the layers is increased, and the solid matrix is disturbed, resulting in a reduction in capacity. On the other hand, A ₂ PtO ₃
It has a structure similar to AMO ₂ layered oxide, and A [A _1/3 Pt
_2/3 ] O ₂ (M = A _1/3 Pt _2/3 ). Since there is a layer in which lithium ions and platinum ions are mixed, at the end of charging, the electrostatic repulsion between the layers is weakened, and a capacity corresponding to the theoretical capacity can be expected.

In order to form a positive electrode using this positive electrode active material, a mixture of the compound powder and a binder powder such as polytetrafluoroethylene is compression-formed on a support such as stainless steel, or Mixing a conductive powder such as acetylene black to impart conductivity to the active material, further adding a binder powder such as polytetrafluoroethylene as necessary, and putting the mixture in a metal container, Alternatively, it is formed by means such as press-molding the above-mentioned mixture on a support such as stainless steel, or dispersing the above-mentioned mixture in a solvent such as an organic solvent to form a slurry and applying the slurry on a metal substrate.

[0008] Lithium, which is a negative electrode active material, is formed into a sheet in the same manner as that of a general lithium battery, and the sheet is pressure-bonded to a conductive net made of nickel, stainless steel or the like to form a negative electrode. In addition, as the negative electrode active material, in addition to lithium, lithium alloys and compounds, conventionally known alkali metals such as sodium, potassium, and magnesium, and their alkali metal alloys and carbon materials capable of occluding and releasing alkali metal ions, etc. Can be used.

Examples of the electrolyte 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. Alternatively, a non-aqueous electrolyte solvent, a molten salt, or a solid electrolyte in which a Lewis acid containing an alkali metal ion is dissolved 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.

[0011]

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 an argon atmosphere.

[0012]

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.

Li ₂ PtO _3, which is obtained by weighing and mixing lithium carbonate and platinum black according to the following reaction formula, firing at 800 ° C. for 24 hours in the open air, as a positive electrode active material:
Was used.

Reaction formula: Li ₂ CO ₃ + Pt + O ₂ → Li ₂ P
tO ₃ + CO ₂

FIG. 2 shows an X-ray diffraction pattern of the obtained powder sample. The X-ray diffraction pattern is exactly the space group P31
(JCPDS # 29-08)
20).

This sample is designated as a.

The sample a was 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 (0.5 mm thick, 0.5 mm thick). (Diameter 15 mm).

Next, the positive electrode mixture pellet 6 is placed on the positive electrode case 3.
Is placed under pressure, the separator 5 is placed on the net, and propylene carbonate (PC) is used as the electrolytic solution.
And a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 1: 1: 2 was injected with an appropriate amount of a 1 N solution of LiPF ₆ and impregnated with the mixture. A negative electrode 4 of metallic lithium is placed on a stainless steel sealing plate 1 inserted in the recess of FIG.
Was pressed and covered to form a coin-type lithium battery having a thickness of 2 mm and a diameter of 23 mm.

The battery manufactured in this manner was charged at 0.5 mA /
FIG. 3 shows a charge / discharge curve of the first cycle when initially charged to 4.5 V at a current density of ² cm ² and charged and discharged at a similar current density in a voltage range of 3.5 V to 4.5 V. FIG. 4 shows the cycle dependency of the charge / discharge capacity. By initial charge,
Lithium ions in the crystal structure of Li ₂ PtO _{3 as} the positive electrode active material were desorbed, and in the subsequent discharge process, a flat discharge of 4 V or more was possible with the insertion of lithium ions.

FIG. 5 shows a structural change accompanying charge and discharge of Li ₂ PtO _3. XRD measurement (X-Ray Di)
From the (fraction (X-ray diffraction)) result, the change in the interlayer distance can be found by following the change in the d (003) diffraction line corresponding to the interlayer distance. When charging (●) proceeds (horizontal axis x
The reversible result was obtained in which the interlayer distance was decreased (in the direction in which X increased from 0) and the interlayer distance was increased in the discharge (（) (in the direction in which the horizontal axis x decreased). From the above, it was observed that "the interlayer distance is reversibly expanded and contracted". That is, by XRD measurement accompanying charge / discharge, it was observed that the interlayer distance was reversibly expanded and contracted, and it was confirmed that this charge / discharge reaction was a Li intercalation reaction between Li ₂ PtO ₃ layers. It can be seen that a reversible lithium secondary battery is configured by the method of the present invention.

After initial charging to 4.5 V at a very small current density of 0.05 mA / cm ² ,
FIG. 6 shows a charge / discharge curve when charging / discharging was performed in a voltage range of 3.5 V to 4.5 V. Li ₂ PtO ₃ has a relatively weak electrostatic repulsion between layers even when lithium ions are desorbed.
A charge capacity corresponding to the amount of almost all lithium ions desorbed from the lithium ion single layer is obtained, and it is expected that the present invention can increase the capacity of the positive electrode active material.

[0022]

Example 2 Li ₂ PtO ₃ (sample a) was used as a positive electrode active material, initially charged to 4.5 V at a current density of 0.5 mA / cm ² , and then 3.5 V-4 at a similar current density. Table 1 shows the capacity when the battery was charged and discharged in a voltage range of 0.5 V. In addition, as an electrolyte, propylene carbonate (PC)
A 1N solution in which 1 mol of iClO ₄ was dissolved was used.

[0023]

Example 3 LiNaPtO ₃ (sample b) as a positive electrode active material
, And initially charged to 4.5 V at a current density of 0.5 mA / cm ² , as in sample a, and then at the same current density,
Table 1 shows the capacity when the battery was charged and discharged in a voltage range of 3.5 V to 4.5 V. In addition, a 1N solution in which 0.5 mol of LiClO ₄ and NaClO ₄ was dissolved in a propylene carbonate (PC) solvent was used as the electrolytic solution.

[0024]

Example 4 Using Na ₂ PtO ₃ (sample c) as a positive electrode active material, similarly to sample a, after initial charging to 4.5 V at a current density of 0.5 mA / cm ² , at the same current density, 3.
Table 1 shows the capacity when charged and discharged in a voltage range of 5V to 4.5V.
Shown in Note that, as the electrolytic solution, a 1 N solution in which 1 mol of NaClO ₄ was dissolved in a propylene carbonate (PC) solvent was used.

According to the present invention, the alkali metal ions in the crystal structure of the positive electrode active material are desorbed and inserted, and it can be seen that the present invention constitutes a reversible nonaqueous electrolyte battery.

[0026]

[Table 1]

[0027]

As described above, according to the present invention,
A large-capacity nonaqueous electrolyte secondary battery can be formed, and has an advantage that it can be used 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 a view showing an X-ray diffraction pattern of Li ₂ PtO ₃ which is an example of the present invention.

FIG. 3 is a diagram showing a charge / discharge curve of a first cycle of Li ₂ PtO ₃ which is an example of the present invention.

FIG. 4 is a diagram showing the cycle dependence of the charge / discharge capacity of Li ₂ PtO _{3 according to} one embodiment of the present invention.

FIG. 5 is a diagram showing a structural change accompanying charge and discharge of Li ₂ PtO ₃ which is an example of the present invention.

FIG. 6 is a diagram showing the charge / discharge capacity of Li ₂ PtO _{3 according to} one embodiment of the present invention.

[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 (2)

[Claims] An alkali metal (A) -containing complex oxide represented by the general formula, A ₂ PtO ₃ , is contained as a positive electrode active material, and an alkali metal or a substance capable of occluding and releasing an alkali metal is used as a negative electrode active material. An alkali metal secondary battery, wherein a substance capable of causing an ion of an alkali metal to undergo an electrochemical reaction with the positive electrode active material and the negative electrode active material is used as an electrolyte material. 2. The alkali metal (A) -containing double oxide, A
₂ PtO ₃ is a substance constituted by containing at least one of lithium and sodium as A;
_{2. The} method according to claim 1, wherein the composite oxide provided as Li _2-x Na _x PtO ₃ (0 ≦ x ≦ 2) is contained as a positive electrode active material.
The alkaline metal secondary battery as described in the above.