JP2001338643A - Lithium battery - Google Patents

Abstract

(57) [Summary] [Problem] To suppress a sharp drop in discharge voltage at the end of discharge,
Provide high capacity lithium batteries. SOLUTION: In a lithium battery, a mixture of a substance that decomposes from a substance before discharge into two or more substances by a discharge reaction and a substance into which Li ions can be inserted or a substance that can bond to Li ions by a discharge reaction is included. Use a positive electrode.
As the substance that decomposes into two or more kinds of substances by the above-described discharge reaction, CuO or a composite oxide containing Cu and another metal is preferable, and a substance into which Li ions can be inserted is B,
Al, Si, Ti, V, Mn, Fe, Co, Ni, Z
An oxide of at least one metal of n, Ga, Ge, Zr, Nb, Mo, W, and Bi, and a composite oxide containing another metal or Li are preferable. As a substance that binds to Li ions, Sn, Pb , Al, Au, Pt, Zn, Cd, A
g, Mg, a metal containing at least one of Si, an oxide,
Nitride or carbide is preferred.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium battery, and more particularly, to improvement of a positive electrode active material.

[0002]

2. Description of the Related Art Hitherto, as a lithium battery having a high capacity density, a lithium battery using copper oxide (CuO) as a positive electrode active material (hereinafter, referred to as "Li / CuO-based battery") has been proposed [for example, Broussley M .; , J
Umel Y, and Cabano J. P. (19
77) 152 ^nd Electrochemical S
ocietyy Meeting, Atlanta].

Further, it has also been clarified that the formation of a composite oxide composed of CuO as a base and another metal increases the discharge voltage. For example, Cu ₃ B ₂ O ₆
Is reported to discharge at about 2.0 V (Japanese Patent No. 1418068). This Cu ₃ B ₂ O ₆ is a two-electron reaction in which Cu is reduced by a discharge reaction to generate metallic Cu and Li oxide, resulting in a large capacity and excellent flatness of discharge voltage. have.

[0004]

However, the above L
An i / CuO-based battery and a Li / Cu ₃ B ₂ O _6- based battery decompose into metal Cu and Li oxide as the discharge proceeds, and the total volume of the positive and negative electrodes decreases significantly before and after the discharge. In the last stage, there was a problem that the positive electrode peeled off from the current collector or peeled off. Therefore, when a positive electrode using such a positive electrode active material is applied to a coin-type lithium battery or the like, there has been a problem that the positive electrode separates from the current collector at the end of discharge and the discharge voltage drops sharply.

The present invention solves the above-mentioned problems of the prior art and suppresses a sharp drop in discharge voltage at the end of discharge.
An object is to provide a high-capacity lithium battery.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a positive electrode active material in a lithium battery, a material that decomposes from a material before discharge into two or more substances by a discharge reaction, and a material into which Li ions can be inserted by a discharge reaction. Alternatively, the above problem has been solved by using a mixture of a substance capable of binding to Li ions.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Two or more types of the above-mentioned discharge reactions
Examples of the substance that decomposes into CuO or CuO
A composite oxide containing Cu and another metal is exemplified.
Such composite oxides containing Cu and other metals include:
For example, Cu_ThreeB_TwoO₆, Cu_Three(PO_Four)_Two, Cu_Four
O (PO_Four)_Two, Cu_FiveO_Two(PO_Four)_Two, Cu_TwoV_Two
O₇, CuFe_TwoO_Four, CuV_TwoO₆, Cu_FiveO_Two(V
O_Four)_Two, CuSiO_Three, Cu _ThreeteO₆, Cu_ThreeMo
_TwoO₉, Cu_ThreeNb_TwoO₈, CuB_TwoO_Four, CuAl_Two
O_Four, CuMn_TwoO_Four, Cu_TwoFeBO_Five, Cu_TwoMn
BO_FiveAnd the like.

The above-mentioned substances into which Li ions can be inserted include, for example, B, Al, Si, Ti, V, Mn,
Fe, Co, Ni, Zn, Ga, Ge, Zr, Nb, M
at least one oxide selected from the group consisting of o, W, and Bi; a composite oxide of at least one selected from these metals and another metal; or at least one selected from these metals. A composite oxide containing Li may be used. Specific examples of these include, for example, V ₂ O ₅ ,
Nb ₂ O ₅ , TiO ₂ , MnO ₂ , MoO ₃ , WO ₃ ,
LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn
Examples include ₂ O ₄ and LiFeO ₂ .

[0009] Substances that bind to the above-mentioned Li ions include Sn, Pb, Al, Au, Pt, Zn, C
At least one metal selected from d, Ag, Mg, and Si, an oxide, a nitride, or a carbide is exemplified. Specific examples of these include Sn, Al, S
i, SnO, SiO, Si ₃ N ₄ , SiC and the like.

The positive electrode is composed of a substance which decomposes from a substance before discharge into two or more kinds of substances by the above-mentioned discharge reaction and L
Positive electrode active material composed of a substance into which i-ion can be inserted or a substance capable of binding to Li-ion, if necessary, for example, a conductive auxiliary such as acetylene black, graphite, or the like, for example, polytetrafluoroethylene, polyvinylidene fluoride, etc. The positive electrode mixture is prepared by adding and mixing the above binder, and the obtained positive electrode mixture is molded by an appropriate means.

In the lithium battery of the present invention, lithium or a lithium-containing substance is used for the negative electrode. Examples of the above-mentioned lithium-containing substance include a lithium alloy such as a lithium-aluminum alloy, a carbon material such as lithium-carbon, and the like, which can be appropriately used depending on required characteristics for a battery and its use. However, the lithium-containing material does not need to contain lithium immediately after production, and may be in a state containing lithium when acting as an active material of the negative electrode. Further, in order to improve storage characteristics, a negative electrode regulated battery in which the capacity of the negative electrode is made smaller than the capacity of the positive electrode active material may be used.

As the electrolytic solution, for example, LiCF ₃ SO
₃ , LiClO ₄ , LiPF ₆ , LiBF ₄ , LiC ₄
One or more electrolytes such as F ₉ SO ₃
One or a mixture of two or more organic solvents such as 2-dimethoxyethane, 1,2-diethoxyethane, propylene carbonate, ethylene carbonate, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolan, diethyl carbonate, and methyl ethyl carbonate. What is dissolved in a solvent is used, and it can be appropriately used depending on the required characteristics of the battery and its use.

Conventionally known Li / CuO-based batteries and Li / C
Unlike the u ₃ B ₂ O ₆ battery, for example, the Li / Cu ₃ B ₂ O ₅ + Nb ₂ O ₅ battery according to the present invention has a Cu ₃
Although B ₂ O ₅ is decomposed by discharge and the total volume decreases, Nb ₂ O ₅ has Li ions inserted between its lattices to increase the interstitial distance, and the particle volume expands accordingly. . Therefore, in the positive electrode using these together,
Since the change in volume before and after the discharge is reduced, a sharp decrease in the discharge voltage at the end of the discharge is suppressed, and a high capacity can be obtained.

In synthesizing a substance which decomposes from a substance before discharge into two or more kinds of substances by the above-mentioned discharge reaction, a substance into which Li ions can be inserted by the discharge reaction, or a substance which can combine with Li ions, Cu, B, Al , Si, Ti,
V, Mn, Fe, Co, Ni, Zn, Ga, Ge, Z
r, Nb, Mo, W, Bi, Sn, Pb, Au, Pt,
As raw materials such as Cd, Ag, Mg, and Si, oxides, halides, and carbonates thereof are preferably used.

The synthesis can be carried out, for example, by firing the above-mentioned raw material powder mixture in the air. The firing temperature is not particularly limited, but generally, a temperature in the range of 500 to 2000 ° C. is suitably adopted. The firing time is not particularly limited, but generally, a firing time in the range of several tens of minutes to several hours is suitably adopted.

As the conductive auxiliary used in preparing the positive electrode mixture, any electronic conductive material which does not cause a chemical change in the constructed battery may be used. For example, natural graphite (flaky graphite) may be used. , Earth graphite, etc.),
Artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber and metal powder (powder of copper, nickel, aluminum, silver, etc.), metal fiber or polyphenylene derivative (JP-A-59-20971)
And the like can be used as one kind or a mixture thereof.

As the binder, for example, starch,
Polyvinyl alcohol, carboxymethyl cellulose,
Hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl pyrrolidone, tetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, polybutadiene,
Polysaccharides such as fluorine rubber and polyethylene oxide, thermoplastic resins, polymers having rubber elasticity, and the like are used alone or as a mixture thereof.

As the electrolyte, for example, propylene car
Bonate, ethylene carbonate, butylene carbonate
Dimethyl carbonate, diethyl carbonate,
Tyl ethyl carbonate, γ-butyrolactone, 1,2
-Dimethoxyethane, tetrahydrofuran, 2-methyl
Tetrahydrofuran, dimethyl sulfoxide, 1,3
-Dioxolane, formamide, dimethylformamid
, Acetonitrile, nitromethane, methyl formate, acetic acid
Methyl, phosphoric acid triester, trimethoxymethane, geo
Xolan derivatives, sulfolane, 3-methyl-2-oxa
Zolidinone, propylene carbonate derivative, tetrahi
Drofuran derivative, diethyl ether, 1,3-propa
In aprotic organic solvents such as sodium salt, for example, L
iCLO_Four, LiBF₆, LiPF₆, LiCF_ThreeSO
_Three, LiCF_ThreeCO_Two, LiAsF ₆, LiSbF₆,
LiB_TenCl_Ten, Lithium lower aliphatic carboxylate, Li
AlCl_Four, LiCl, LiBr, LiI, chlorobora
Electrolytes such as lithium lithium and lithium tetraphenylborate
A solution in which at least one kind is dissolved is used. Those
Among them, propylene carbonate and 1,2-dimethoxy
Cietan and / or diethyl carbonate and / or
Or LiC in a mixed solvent of methyl ethyl carbonate
10_Four, LiBF₆, LiPF₆, LiCF_ThreeSO_Threeof
Preferably, at least one of them is dissolved. This electrolysis
The amount of the solution added to the battery is not particularly limited,
Required depending on the amount of polar active material and negative electrode active material and battery size
The amount may be used. The concentration of the electrolyte in the electrolyte is
Is not limited to 0.2 to 3.0 mol / l
Is preferred.

[0019]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

Example 1 The following positive electrode mixture raw materials were prepared by mixing 40 mg of copper oxide (CuO), 8 mg of niobium oxide (Nb ₂ O ₅ ), 10 mg of acetylene black and 2 mg of polytetrafluoroethylene. The obtained positive electrode mixture was filled in a mold, and pressed into a disk having a diameter of 10 mm at a pressure of 1 t / cm ² to obtain a positive electrode.

In this positive electrode, the active material is
A substance that uses copper oxide (CuO) and niobium oxide (Nb ₂ O ₅ ) and decomposes a substance before discharge into two or more substances by a discharge reaction from the copper oxide (CuO);
Niobium oxide (Nb ₂ O ₅ ) is a substance into which Li ions can be inserted. That is, copper oxide (CuO) is decomposed into Cu and Li ₂ O by a discharge reaction, and niobium oxide (Nb ₂ O ₅ )
Li ions are inserted into the lattice by a discharge reaction.

A lithium foil was used for the negative electrode together with the positive electrode, and 1.2 mol / l of LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 1: 2 for the electrolytic solution. Using this, a coin-shaped lithium battery having a diameter of 20 mm and a thickness of 1.6 mm was produced.

Here, the structure of the coin-shaped lithium battery will be described with reference to FIG. 1. Reference numeral 1 denotes the positive electrode, and the positive electrode 1 has copper oxide (CuO) as a positive electrode active material as described above.
And niobium oxide (Nb ₂ O ₅ ). Negative electrode 2
Is made of lithium foil as described above, and is disposed to face the positive electrode 1 via the separator 3 made of a microporous polyethylene film. The positive electrode can 4 is made of stainless steel,
The current collector on the positive electrode side also serves as a terminal, and the negative electrode can 5 is also made of stainless steel. The negative electrode can 5 also serves as a current collector on the negative electrode side and a terminal. 6 is an annular gasket made of polypropylene, which is not shown in this battery,
The aforementioned electrolyte is injected.

With respect to the battery of Example 1, when discharged at room temperature at a discharge current value of 1.0 mA / cm ² to a final voltage of 0.5 V, the amount of discharged electricity was 760 mAh / g.

FIG. 2 shows a discharge characteristic diagram of the battery of Example 1 under the above conditions.

Example 2 A positive electrode mixture was prepared in the same manner as in Example 1 except that CuO in the raw material of the positive electrode mixture of Example 1 was changed as follows. Cu ₃ B ₂ O ₆ 40mg

A positive electrode was prepared in the same manner as in Example 1 except that the obtained positive electrode mixture was used, and a coin-shaped lithium battery was prepared in the same manner as in Example 1 except that the positive electrode was used. Then, the obtained battery was discharged at a discharge current value of 1.0 mA / cm ² at room temperature in the same manner as in Example 1.
The amount of discharge electricity when discharged to 700 mAh / g.

Comparative Example 1 The following positive electrode mixture raw material was prepared except that a positive electrode mixture was prepared by mixing 48 mg of copper oxide (CuO), 10 mg of acetylene black, and 2 mg of polytetrafluoroethylene, and using the obtained positive electrode mixture. A positive electrode was produced in the same manner as in Example 1, and a coin-shaped lithium battery was produced in the same manner as in Example 1 except that the positive electrode was used. And about the obtained battery, Example 1
Similarly, when discharged at room temperature to a final voltage of 0.5 V at a discharge current value of 1.0 mA / cm ² , the amount of discharged electricity is 620.
mAh / g.

FIG. 3 shows a discharge characteristic diagram of the battery of Comparative Example 1 under the above conditions.

As is clear from a comparison between FIG. 2 showing the discharge characteristics of the battery of Example 1 and FIG. 3 showing the discharge characteristics of the battery of Comparative Example 1, the battery of Comparative Example 1 has a sharp discharge at the end of discharge. Although the voltage was lowered and the amount of discharged electricity was reduced to 620 mAh / g as described above, the battery of Example 1 was different from the battery of Comparative Example 1 in the sharp discharge voltage at the end of discharge. , As a result, as described above,
The discharge current value increased to 760 mAh / g.

[0031]

As described above, according to the present invention, it is possible to provide a high-capacity lithium battery by suppressing a sharp drop in discharge voltage at the end of discharge.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a lithium battery according to the present invention.

FIG. 2 is a discharge characteristic diagram of the battery of Example 1.

FIG. 3 is a discharge characteristic diagram of the battery of Comparative Example 1.

[Explanation of symbols]

 1 positive electrode 2 negative electrode 3 separator

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H024 AA02 AA03 CC03 DD14 FF15 FF16 FF17 FF18 FF20 HH00 5H050 AA08 BA17 CA07 CB08 CB09 CB12 DA09 EA02 EA10 EA12 EA23 EA24 FA17 GA10 HA02

Claims (4)

[Claims] 1. A lithium battery using lithium or a lithium-containing substance for a negative electrode and using an organic solvent-based electrolyte, a substance which decomposes a substance before discharge into two or more substances by a discharge reaction, and a lithium which is decomposed by a discharge reaction. A lithium battery using a positive electrode including a mixture of a substance capable of inserting ions or a substance capable of binding to Li ions. 2. The lithium battery according to claim 1, wherein the substance decomposed into two or more kinds of substances by the discharge reaction is CuO or a composite oxide containing Cu and another metal. 3. The substance into which the Li ion can be inserted,
B, Al, Si, Ti, V, Mn, Fe, Co, Ni,
Oxide of at least one metal selected from Zn, Ga, Ge, Zr, Nb, Mo, W, Bi, or composite oxide containing at least one selected from these metals and another metal Or a composite oxide containing at least one selected from the metals and Li.
The lithium battery as described. 4. The method according to claim 1, wherein the substance binding to the Li ion is S
n, Pb, Al, Au, Pt, Zn, Cd, Ag, M
g, a metal containing at least one selected from Si,
The lithium battery according to claim 1, which is an oxide, a nitride, or a carbide.