JPH11111291A - Positive electrode material for nonaqueous secondary battery and battery using this - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance capacity of a battery, reduce self-discharge at high temperature preserving time, improve a cycle characteristic at a high temperature, and restrain generation of gas by using lithium manganese compound oxide as a positive electrode material. SOLUTION: Spinel compound oxide used as a positive electrode material is expressed by a general formula (Li1+ AMn2 A+2 BMBO4 CXC). Here, M represents one or more kinds of elements among Cr, Fe, Co and Ni, and A, B and C respectively represent (0.02<A<=0.2, and 0.02<B<=0.2, and 0.01<=C<=0.2), and X represents a halogen element. In order to obtain particularly suitable compound oxide, a mixture of an Mn compound such as electrolytic manganese dioxide, a Cr compound such as chromium oxide, an Fe compound such as iron oxide, a Co compound such as cobalt oxide, an Ni compound such as nickel oxide, an Li compound such as Li2 Co3 and a fluorine compound such as LiF, is heat- treated at 600 to 900 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positive electrode material for a non-aqueous secondary battery and a non-aqueous secondary battery using the same as a positive electrode.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable tendency for electronic equipment to become smaller, thinner, and lighter. Accordingly, a battery as a power source has been made smaller, thinner, lighter, regardless of whether it is for driving or backup. Demand for higher energy density is increasing.
Lithium ion secondary batteries have recently been widely used in portable devices such as mobile phones and notebook personal computers because of the ability to reduce the size and weight of the devices.

At present, generally available lithium ion secondary batteries use lithium cobalt oxide as a positive electrode active material and carbon as a negative electrode active material. However, lithium cobalt oxide as the positive electrode active material may be short in the future because cobalt is expensive and reserves are small. On the other hand, recently, spinel-based lithium-containing manganese oxides have attracted attention as a positive electrode active material that is inexpensive, has abundant reserves, and can store and release lithium at the same high voltage as lithium cobalt oxide. Research has been done.

[0004]

However, the conventional spinel-based lithium manganese oxide has the following problems.

The spinel lithium manganese composite oxide has poor cycle characteristics, and it has been proposed to replace a part of manganese with lithium as disclosed in JP-A-5-205744 in order to improve the cycle characteristics. I have. Although this improves cycleability, there is a problem that self-discharge, particularly self-discharge at a high temperature, is large.

On the other hand, JP-A-7-37617 and JP-A-7-254403 disclose that fluorine is introduced into a spinel-based lithium manganese composite oxide, and in particular, JP-A-7-254403. Discloses that self-discharge at high temperatures is improved. However, although the self-discharge during high-temperature storage is improved by such a method, the cycleability at high temperatures is inferior, and the internal pressure of the battery increases due to the large amount of gas generated internally during high-temperature storage. There is a point.

An object of the present invention is to provide a non-aqueous secondary battery having high capacity, low self-discharge during high-temperature storage, excellent cyclability at high temperature and low gas generation, and a cathode material thereof.

[0008]

The present inventors have made intensive studies and as a result, they have found that the above-mentioned problems can be solved by using a spinel lithium manganese oxide having a specific composition as a positive electrode active material. Was completed.

The invention of the positive electrode material for a non-aqueous secondary battery according to claim 1 based on the above findings is based on the general formula Li _{(1 + A)} Mn
_{[2- (A + B)]} M B O (4-C) X C ( although, M is Cr, F
e, Co, Ni and the like, and one or more elements among them, A, B,
C is 0.02 <A ≦ 0.2 and 0.02 <B ≦ 0.
2, 0.01 ≦ C ≦ 0.2, X is a halogen element)
It is characterized by being represented by

A second aspect of the invention for a positive electrode material for a non-aqueous secondary battery is to provide a manganese compound, a lithium compound, and at least one compound such as a chromium compound, an iron compound, a cobalt compound, a nickel compound, and fluorine. It is characterized by being obtained by calcining a mixture with a compound at 600 to 900 ° C.

[0013] The invention of a non-aqueous secondary battery according to claim 3 provides a negative electrode active material capable of inserting and extracting lithium ions and a positive electrode active material comprising a lithium-containing composite oxide capable of inserting and extracting lithium ions. In a non-aqueous secondary battery provided with a non-aqueous electrolyte having lithium ion conductivity, the lithium-containing composite oxide is the positive electrode material according to claim 1 or 2.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The present invention is a general formula _{Li (1 + A) Mn [} 2- (A + B)] M B
O _(4-C) X _C (where M is at least one element such as Cr, Fe, Co, Ni, etc .; A, B, and C are each 0.02
<A ≦ 0.2, 0.02 <B ≦ 0.2, 0.01 ≦ C ≦
0.2, and X is a halogen element), and a non-aqueous secondary battery using the spinel-based lithium-manganese composite oxide.

Lithium-manganese composite oxide represented by stoichiometric composition LiMn ₂ O ₄ , when exposed to high temperature during charge / discharge or storage, manganese is eluted, the crystal structure is destroyed, and the capacity as a battery is reduced. descend. In contrast, those in which part of manganese is replaced by at least one of lithium and elements such as chromium, iron, cobalt, and nickel stabilize the crystal, reduce the elution of manganese, and increase the capacity during cycling at high temperatures. Is less reduced. This effect is Li _{(1 + A)}
Mn in _{[2- (A + B)]} M B O (4-C) X C, A, appears when B both 0.02 greater, more preferably 0.0
The effect is large at 4 or more, and is remarkably exhibited at 0.05 or more. However, when part of manganese is replaced with at least one of elements such as lithium and chromium, iron, cobalt, and nickel, the capacity as an active material is reduced according to the amount. Therefore, in order to obtain a high capacity as a battery, A + B is preferably set to 0.4 or less, more preferably 0.3 or less.

However, as described above, although the cycling characteristics at high temperature are improved by merely replacing a part of manganese with at least one of elements such as lithium and chromium, iron, cobalt, nickel, etc., it is not sufficient. And self-discharge during high-temperature storage is large, and gas generation is also large. Therefore, after mixing a fluorine compound with a starting material of a lithium manganese composite oxide in which part of such manganese is replaced with at least one of elements such as lithium and chromium, iron, cobalt, and nickel, the mixture is calcined, and the fluorine is reduced. When introduced, the crystals are stabilized, the collapse of the crystals during storage at high temperatures and the accompanying generation of oxygen are suppressed, and the decomposition of the solvent due to desorbed oxygen is suppressed, so that gas generation is reduced. Further, by substituting oxygen with fluorine, the average valence of manganese decreases, and the initial capacity also increases. In other words, the initial properties and high-temperature storage properties are improved due to the synergistic effect of replacing part of manganese with at least one of elements such as lithium and chromium, iron, cobalt, and nickel, and stabilizing the crystal by introducing fluorine. Is done.

In the present invention, the introduction amount C of fluorine as a halogen element is preferably 0.01 or more and 0.2 or less,
0.02 or more and 0.2 or less are more preferable. this is,
If it is less than 0.01, the effect is not sufficient, while if it is more than 0.2, the capacity is reduced, and not only a high capacity is not obtained when the battery is used, but also the stability of the crystal is rather reduced, and self-discharge and gas This is because the occurrence of the occurrence increases.

In order to suitably obtain the lithium-manganese composite oxide of the present invention, a manganese compound, a chromium compound, an iron compound, a cobalt compound, a nickel compound, a lithium compound and a fluorine compound are mixed and then heat-treated. In order to synthesize the crystalline phase and obtain sufficient effects on the initial characteristics and high-temperature characteristics, it is necessary to appropriately perform heat treatment. In the present invention,
As the heat treatment of the mixture of the manganese compound, the chromium compound, the iron compound, the cobalt compound, the nickel compound, the lithium compound, and the fluorine compound, it is preferable to perform the heat treatment at a specific temperature of 600 to 900 ° C. Here, the temperature is 6
The reason why the temperature is specified to be from 00 to 900 ° C. is that unreacted substances remain below 600 ° C., whereas if it exceeds 900 ° C., decomposition occurs and a single phase cannot be obtained.

The manganese compound used in the present invention includes electrolytic manganese dioxide, chemically synthesized manganese dioxide, γ
-MnOOH, or the like can be used MnCO _3.
As the chromium compound, chromium oxide (such as Cr ₂ O ₃ ), chromium carbonate, chromium hydroxide and the like can be used. Iron oxides (Fe ₂ O ₃ , Fe ₃ O _4, etc.);
Iron hydroxide or the like can be used. As the cobalt compound, cobalt oxide (Co ₃ O ₄ , CoO, etc.), cobalt carbonate, cobalt hydroxide and the like can be used. As the nickel compound, nickel oxide (NiO or the like), nickel carbonate, nickel hydroxide, or the like can be used.
As the lithium compound, Li ₂ CO ₃ , LiOH, L
iNO ₃ , CH ₃ COOLi, or the like can be used.

As the fluorine compound used in the present invention, for example, LiF can be used.

The negative electrode used in combination with the positive electrode of the present invention comprising a spinel-based lithium manganese composite oxide into which a transition element such as cobalt or the like and fluorine have been introduced is usually a material used in this type of nonaqueous electrolyte secondary battery. Can be used, and there is no particular limitation. Examples of the negative electrode include metallic lithium, lithium alloy,
A metal oxide such as SnSiO _3, a metal nitride such as LiCoN _2, or a carbon material can be used. Also,
Coke, natural graphite, artificial graphite, non-graphitizable carbon, and the like can be used as the carbon material. As the electrolyte,
An electrolyte obtained by dissolving a lithium salt in a non-aqueous solvent can be used. As the electrolyte, LiClO ₄ , LiAsF
₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , Li
A conventionally known material such as (CF ₃ SO ₂ ) ₂ N is used.

The organic solvent is not particularly limited.
Carbonates, lactones, ethers and the like, for example, ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate,
Methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran,
Solvents such as 1,3-dioxolan and γ-butyrolactone can be used alone or as a mixture of two or more. The concentration of the electrolyte dissolved in these solvents is 0.5 to
It can be used at 2.0 mol / l.

In addition to the above, a solid or viscous body in which the above-mentioned electrolyte is uniformly dispersed in a polymer matrix, or a solid or viscous body impregnated with a non-aqueous solvent can also be used.
As the polymer matrix, for example, polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyvinylidene fluoride and the like can be used.
Further, a separator for preventing short circuit between the positive electrode and the negative electrode can be provided. Examples of the separator include a porous sheet of a material such as polyethylene, polypropylene, and cellulose, and a nonwoven fabric.

The positive electrode active material of the present invention is represented by the general formula L
_{i (1 + A) Mn [} 2- (A + B)] M B O (4-C) X C ( however, M
Is one or more elements such as Cr, Fe, Co, Ni, etc., and A, B, and C are respectively 0.02 <A ≦ 0.2, 0.02
(B ≦ 0.2, 0.01 ≦ C ≦ 0.2, and X is a halogen element) As a raw material of the halogen element (X) of the spinel-based lithium manganese composite oxide represented by Although LiF is shown as a typical example, the present invention is not limited to this. For example, LiCl, L
iBr or the like can also be used, and even in that case, the same effects as those of the following examples using LiF can be obtained.

[0023]

Hereinafter, embodiments of the present invention will be described in detail.
The present invention is not limited to this.

(Example 1) Electrolytic manganese dioxide, cobalt carbonate, Li ₂ CO ₃ and LiF were mixed at a composition ratio of [L
i] / ([Li] -1+ [Mn] + [Co]) = 0.5
2 and Mn: Co = 1.86: 0.1 and [Li
_LiF ] / ([Li _Li2CO3 ] + [Li _LiF ]) = 0.1 and mixed in the _composition shown in Table 1 in air at 800 ° C.
For 20 hours to obtain a positive electrode active material. Here, [L
i] represents the total molar amount of lithium, and [Li _{Li F} ] represents the molar amount of Li in LiF. After mixing 3 parts by weight of acetylene black and 3 parts by weight of flaky graphite as conductive agents with respect to 100 parts by weight of the lithium manganese composite oxide, 3 parts by weight of polyvinylidene fluoride as a binder were added to the total weight, and N was added. -Methylpyrrolidone (NMP) was added and wet mixed to obtain a paste. Next, this paste was uniformly applied to both sides of a 20 μm-thick aluminum foil serving as a positive electrode current collector and dried, and then pressure-formed with a roller press machine heated to 150 ° C. to obtain a belt-shaped positive electrode.

Next, 1 part by weight of carboxymethylcellulose and 2 parts by weight of styrene butadiene rubber were added to a mixture of 95 parts by weight of graphitized mesocarbon fiber and 5 parts by weight of flake graphite,
Purified water was added as a solvent and wet-mixed to obtain a paste. This paste was uniformly applied on both sides of a copper foil having a thickness of 12 μm as a negative electrode current collector, dried, and then press-formed to prepare a strip-shaped negative electrode. A 25 μm-thick polyethylene microporous membrane was sandwiched as a separator between the strip-shaped positive electrode and the strip-shaped negative electrode to form a roll.

An insulating film was inserted into the bottom of a square iron can, and the wound body was crushed and inserted. Next, the negative electrode tab taken out from the wound body was welded to the closing lid, and the positive electrode tab was welded to the positive electrode pin of the closing lid. An electrolyte obtained by dissolving LiPF ₆ at a concentration of 1 mol / L in a 1: 2 mixed solvent of ethylene carbonate and diethyl carbonate was injected into the battery can, and then the closure lid was welded to a thickness of 8.6 m.
m, a width of 34 mm and a height of 48 mm were produced.

Example 2 Electrolytic manganese dioxide, cobalt carbonate, Li ₂ CO ₃ and LiF were mixed at a composition ratio [L
i] / ([Li] -1+ [Mn] + [Co]) = 0.5
5 and Mn: Co = 1.8: 0.1 and [L
i _LiF ] / ([Li _Li2CO3 ] + [Li _LiF ]) = 0.1
And mixed in the composition shown in Table 1 in air.
Heat treatment was performed at 20 ° C. for 20 hours. Using the obtained lithium manganese composite oxide, a battery can was produced in the same manner as in Example 1.

Example 3 Electrolytic manganese dioxide, cobalt carbonate, Li ₂ CO ₃ and LiF were mixed at a composition ratio of [L
i] / ([Li] -1+ [Mn] + [Co]) = 0.6
0 and Mn: Co = 1.7: 0.1 and [L
i _LiF ] / ([Li _Li2CO3 ] + [Li _LiF ]) = 0.1
And mixed in the composition shown in Table 1 in air.
Heat treatment was performed at 20 ° C. for 20 hours. Using the obtained lithium manganese composite oxide, a battery can was produced in the same manner as in Example 1.

Example 4 Electrolytic manganese dioxide, cobalt carbonate, Li ₂ CO ₃ and LiF were mixed at a composition ratio of [L
i] / ([Li] -1+ [Mn] + [Co]) = 0.5
5 and Mn: Co = 1.87: 0.03 and [Li
_LiF ] / ([Li _Li2CO3 ] + [Li _LiF ]) = 0.1 and mixed in the _composition shown in Table 1 in air at 800 ° C.
For 20 hours. Using the obtained lithium manganese composite oxide, a battery can was produced in the same manner as in Example 1.

Example 5 Electrolytic manganese dioxide, cobalt carbonate, Li ₂ CO ₃ and LiF were mixed at a composition ratio of [L
i] / ([Li] -1+ [Mn] + [Co]) = 0.5
5 and Mn: Co = 1.7: 0.2 and [L
i _LiF ] / [Li _Li2CO3 ] + [Li _LiF ]) = 0.1 and mixed in the _composition shown in Table 1 in air at 800 ° C.
For 20 hours. Using the obtained lithium manganese composite oxide, a battery can was produced in the same manner as in Example 1.

Example 6 Electrolytic manganese dioxide, cobalt carbonate, Li ₂ CO ₃ and LiF were mixed at a composition ratio of [L
i] / ([Li] -1+ [Mn] + [Co]) = 0.5
5 and Mn: Co = 1.8: 0.1 and [L
i _LiF ] / ([Li _Li2CO3 ] + [Li _LiF ]) = 0.1
And mixed in the composition shown in Table 1 in air.
Heat treatment was performed at 20 ° C. for 20 hours. Using the obtained lithium manganese composite oxide, a battery can was produced in the same manner as in Example 1.

Example 7 Electrolytic manganese dioxide, cobalt carbonate, Li ₂ CO ₃ and LiF were mixed at a composition ratio [L
i] / ([Li] -1+ [Mn] + [Co]) = 0.5
5 and Mn: Co = 1.8: 0.1 and [L
i _LiF ] / ([Li _Li2CO3 ] + [Li _LiF ]) = 0.2
And mixed in the composition shown in Table 1 in air.
Heat treatment was performed at 20 ° C. for 20 hours. Using the obtained lithium manganese composite oxide, a battery can was produced in the same manner as in Example 1.

Comparative Example 1 Electrolytic manganese dioxide, cobalt carbonate, Li ₂ CO ₃ and LiF were mixed at a composition ratio of [L
i] / ([Li] -1+ [Mn] + [Co]) = 0.5
1 and Mn: Co = 1.88: 0.1 and [Li
_LiF ] / ([Li _Li2CO3 ] + [Li _LiF ]) = 0.1 and mixed in the _composition shown in Table 1 in air at 800 ° C.
For 20 hours. Using the obtained lithium manganese composite oxide, a battery can was produced in the same manner as in Example 1.

Comparative Example 2 Electrolytic manganese dioxide, cobalt carbonate, Li ₂ CO ₃ and LiF were mixed at a composition ratio of [L
i] / ([Li] -1+ [Mn] + [Co]) = 0.6
3 and Mn: Co = 1.64: 0.1 and [Li
_LiF ] / ([Li _Li2CO3 ] + [Li _LiF ]) = 0.1 and mixed in the _composition shown in Table 1 in air at 800 ° C.
For 20 hours. Using the obtained lithium manganese composite oxide, a battery can was produced in the same manner as in Example 1.

(Comparative Example 3) Electrolytic manganese dioxide, cobalt carbonate, Li ₂ CO ₃ and LiF were mixed at a composition ratio of [L
i] / ([Li] -1+ [Mn] + [Co]) = 0.5
5 and Mn: Co = 1.88: 0.02 and [Li
_LiF ] / ([Li _Li2CO3 ] + [Li _LiF ]) = 0.1 and mixed in the _composition shown in Table 1 in air at 800 ° C.
For 20 hours. Using the obtained lithium manganese composite oxide, a battery can was produced in the same manner as in Example 1.

Comparative Example 4 Electrolytic manganese dioxide, cobalt carbonate, Li ₂ CO ₃ and LiF were mixed at a composition ratio [L
i] / ([Li] -1+ [Mn] + [Co]) = 0.5
5 and Mn: Co = 1.65: 0.25 and [Li
_LiF ] / ([Li _Li2CO3 ] + [Li _LiF ]) = 0.1 and mixed in the _composition shown in Table 1 in air at 800 ° C.
For 20 hours. Using the obtained lithium manganese composite oxide, a battery can was produced in the same manner as in Example 1.

Comparative Example 5 Electrolytic manganese dioxide, cobalt carbonate, Li ₂ CO ₃ and LiF were mixed at a composition ratio [L
i] / ([Li] -1+ [Mn] + [Co]) = 0.5
5 and Mn: Co = 1.8: 0.1 and [L
i _LiF ] / ([Li _Li2CO3 ] + [Li _LiF ]) = 0.0
08 and mixed in the composition shown in Table 1 in air.
Heat treatment was performed at 00 ° C. for 20 hours. Using the obtained lithium manganese composite oxide, a battery can was produced in the same manner as in Example 1.

Comparative Example 6 Electrolytic manganese dioxide, cobalt carbonate, Li ₂ CO ₃ and LiF were mixed at a composition ratio of [L
i] / ([Li] -1+ [Mn] + [Co]) = 0.5
5 and Mn: Co = 1.8: 0.1 and [L
i _LiF ] / ([Li _Li2CO3 ] + [Li _LiF ]) = 0.2
5 and mixed in the composition shown in Table 1 in air.
Heat treatment was performed at 0 ° C. for 20 hours. Using the obtained lithium manganese composite oxide, a battery can was produced in the same manner as in Example 1.

Comparative Example 7 Electrolytic manganese dioxide, Li ₂
CO ₃ and LiF were mixed at a composition ratio of [Li] / ([Li]
-1+ [Mn] = 0.55 and [Li _LiF ] / ([L
i _Li2CO3 ] + [Li _LiF ]) = 0.1, and the mixture was heat-treated at 800 ° C. for 20 hours in air. Using the obtained lithium manganese composite oxide, a battery can was produced in the same manner as in Example 1.

(Test Results) The batteries produced in Examples and Comparative Examples were evaluated as follows. After charging for 5 hours at a charging voltage of 4.2 V, the battery was discharged at a constant current of 800 mA to 2.7 V to obtain a battery capacity. After repeating this charge / discharge cycle for 5 cycles, the battery was charged, stored at 85 ° C. for 120 hours in a 4.2 V charged state, cooled to room temperature, and discharged. The self-discharge rate was determined by {1- (discharge amount at sixth cycle / discharge amount at fifth cycle)} × 100. At this time, the thickness of the battery can was measured. Further, using another battery produced at the same time, the battery was charged at a charging voltage of 4.2 V for 5 hours and then discharged at a constant current of 800 mA to 2.7 V at 60 ° C. for 100 cycles.
The ratio of the discharge capacity at the 100th cycle to the discharge capacity at the first cycle was determined, and the ratio was taken as the cycle capacity retention rate at 60 ° C. The above results are shown in Table 1.

[0041]

[Table 1]

As shown in Table 1, Li _{(1 + A)} Mn
_{[2- (A + B)]} M B O (4-C) X C ( however, A, B, C are each 0.02 <A ≦ 0.2,0.02 <B ≦ 0.2,0 ≤
C ≦ 0.2, 0.01 ≦ D ≦ 0.2, and X is a halogen element), by using a spinel-based lithium manganese composite oxide represented by It has been found that a non-aqueous secondary battery having excellent cycle characteristics and high-temperature storage characteristics can be obtained.

[0043]

As described above, the present invention provides Li _{(1 + A)
Mn [2- (A + B)} ] M B O (4-C) X C ( however, A, B, C
Are respectively 0.02 <A ≦ 0.2, 0.02 <B ≦ 0.2,
By using a spinel-based lithium manganese composite oxide represented by the following formula (0.01 ≦ C ≦ 0.2, X is a halogen element) as a positive electrode active material, high capacity, high temperature cycle characteristics, and high temperature storage characteristics An excellent battery can be obtained. Furthermore, compared to a lithium manganese composite oxide in which only fluorine is introduced, a battery with less gas generation and excellent storage stability can be obtained. A non-aqueous electrolyte secondary that is comparable to the case of using a suitable lithium-cobalt composite oxide can be provided, and its industrial value is extremely large.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Fumio Nishikawa 1-3-1, Yoko, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Asahi Kasei Kogyo Co., Ltd. No. 1 Asahi Kasei Kogyo Co., Ltd.

Claims (3)

[Claims] [Claim 1] The general formula is Li _{(1 + A)} Mn _{[2- (A + B)]} M _B
O _(4-C) X _C (where M is at least one element such as Cr, Fe, Co, Ni, etc .; A, B, and C are each 0.02
<A ≦ 0.2, 0.02 <B ≦ 0.2, 0.01 ≦ C ≦
0.2, and X is a halogen element). 2. A mixture of at least one of a manganese compound, a lithium compound, a chromium compound, an iron compound, a cobalt compound, a nickel compound and the like, and a fluorine compound, which is obtained by firing at 600 to 900 ° C. The positive electrode material for a non-aqueous secondary battery according to claim 1, wherein 3. A negative electrode comprising a negative electrode active material capable of inserting and extracting lithium ions, a positive electrode active material comprising a lithium-containing composite oxide capable of inserting and extracting lithium ions, and a lithium ion conductive non-aqueous electrolyte. 3. The water secondary battery according to claim 1, wherein the lithium-containing composite oxide is used.
A non-aqueous secondary battery, which is the positive electrode material according to 1.