JP2001250548A - Nonaqueous electrolyte battery and method of preparing positive electrode material for the nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a 3 V nonaqueous electrolyte battery, having a large discharging capacity and improved cycle characteristic. SOLUTION: The nonaqueous electrolyte battery comprises a positive electrode, containing a lithium ion storing and releasing material. The positive electrode material contains a compound, which is represented by general formula Ni1-xCoxO2Hn, where 0<x<0.55, 0.4<n<1.2, and a cobalt oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-aqueous electrolyte battery and a method for producing a cathode material for a non-aqueous electrolyte battery.

[0002]

2. Description of the Related Art In recent years, with the spread of various small portable electronic devices such as a cellular phone and a portable electronic terminal, a secondary battery as a power source for such portable electronic devices has played an important role. In particular, lithium-ion batteries have a higher energy density than aqueous batteries such as nickel-cadmium batteries or nickel-metal hydride batteries,
It is in the spotlight.

[0003] At present, commercially available lithium ion batteries include a positive electrode plate containing a positive electrode material composed of a transition metal composite oxide such as lithium cobalt oxide and a negative electrode containing a negative electrode active material composed of a carbon-based material such as graphite. Board and
Separator such as polyethylene or polypropylene and various carbonates such as ethylene carbonate
The battery comprises an electrolyte in which a lithium salt such as iPF ₆ is dissolved. The operating voltage of this battery is about 4 V, which is a so-called 4 V nonaqueous electrolyte battery.

[0004] On the other hand, from the viewpoint of the development of ICs operating at a low voltage of 3 V or less and the viewpoint of battery safety, it is estimated that the demand for 3 V non-aqueous electrolyte batteries will increase in the future. As the cathode material for the 3V-based nonaqueous electrolyte battery,
Although there are LiMnO ₂ and V ₂ O _5, there are many problems in terms of discharge capacity and cycle life characteristics, so they are currently used only for limited applications such as memory backup. It is. Recently, it has been proposed that an oxyhydroxide mainly composed of nickel can be used as a positive electrode material for a 3V-based nonaqueous electrolyte secondary battery, and its performance has been improved.

[0005]

An oxyhydroxide mainly composed of nickel can be used as a cathode material for a 3V non-aqueous electrolyte secondary battery. Although the initial discharge capacity is a high value, there is a problem that the discharge capacity decreases as the charge / discharge cycle progresses, and it is desired to solve it.

Accordingly, as a result of earnest studies on the cause, the present inventors have found that adding a cobalt oxide to a positive electrode plate together with an active material mainly composed of nickel;
It has been conceived that the above problem can be solved by using a compound containing nickel and cobalt in a solid state at 0 to 210 ° C. as an active material.

The present invention has been made on the basis of such knowledge, and it is an object of the present invention to provide a non-volatile semiconductor device having excellent cycle characteristics because the discharge capacity is large and the capacity does not decrease with the progress of charge / discharge cycles. An object of the present invention is to provide an aqueous electrolyte battery.

[0008]

According to the present invention, there is provided a non-aqueous electrolyte battery provided with a positive electrode containing a substance that occludes / releases lithium ions, wherein the positive electrode material has a general formula Ni _1-x Co _x O ₂
H _n (where 0 <x <0.55, 0.4 <n <1.2
) And a cobalt oxide.

Further, the present invention is characterized in that in the above positive electrode material, the ratio of the number of moles of cobalt to the total number of moles of nickel and cobalt (Co / (Ni + Co)) is 0.5 or less.

Further, the present invention provides a method of manufacturing a composition comprising the steps of: providing a molar ratio of cobalt to the total number of moles of nickel and cobalt (Co / (Co + N);
i)) a mixture of a nickel salt and a cobalt salt having 0.5 or less, 1) a step of melting by heating at 60 to 100 ° C., 2) a step of heating to a solid state by heating at 150 to 210 ° C., 3) a step of treating with an aqueous alkali solution, 4) a washing step for removing alkali components, and 5) an oxidation step. The salt and the cobalt salt are characterized in that they are at least one selected from the group consisting of nitrates, sulfates, phosphates, acetates, and hydrochlorides.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a paste obtained by kneading a cathode material powder, a conductive agent, a binder and a solvent is used.
It is produced as a positive electrode plate for a non-aqueous electrolyte battery by a method such as coating, drying, and pressing on a conductive core material such as an aluminum foil.

The cathode material has the general formula Ni _1-x Co _x O ₂
H _n (where, 0 <x <0.55,0.4 <n < and 1.2) that contains a compound represented by the cobalt oxide is used. Further, as the cobalt oxide, C
oO, Co ₃ O _{4 and the} like. By using this positive electrode material, a nonaqueous electrolyte battery having a large discharge capacity and not causing a decrease in capacity with the progress of a charge / discharge cycle can be obtained.

Furthermore, the ratio of the number of moles of cobalt to the total number of moles of nickel and cobalt in the cathode material (= Co /
(Ni + Co)) of 0.5 or less is used. If the ratio exceeds 0.5, the discharge capacity becomes small, which is not preferable.

In the production conditions of the cathode material, the temperature condition in step 1) is desirably 60 to 100 ° C. If the temperature is lower than 60 ° C., it may be difficult to obtain a molten state. If the temperature is higher than 100 ° C., part of the crystallization water is lost, which is not preferable. The temperature condition in step 2) is desirably 150 to 210 ° C. If the temperature is lower than 150 ° C., it takes a long time to change to a solid state, which is not practical. If the temperature exceeds 210 ° C., the nickel salt is decomposed. A more preferable temperature range is 180 to 200 ° C.

In the positive electrode material thus obtained, the ratio y (= Co / (Ni + Co)) of the mole number of cobalt to the total mole number of nickel and cobalt is desirably 0.5 or less. . When the amount of cobalt increases and the ratio becomes 0.6 or more, the discharge capacity decreases. A preferable range of the amount of cobalt in the positive electrode material is 0.0
2 to 0.5.

As the alkaline aqueous solution used in step 3), an aqueous solution of KOH, NaOH, LiOH or the like or a mixture thereof is used. The washing in the step 4) can be performed under normal pressure or reduced pressure using generated water.

The oxidizing method in step 5 includes a method of chemically oxidizing using an oxidizing agent such as peroxodisulfate, perchlorate and ozone, and a method of electrochemical anodic oxidation.

When a non-aqueous electrolyte battery is constructed using the positive electrode plate, the negative electrode plate, the separator, the electrolytic solution and the like manufactured as described above, a 3V non-aqueous electrolyte battery having high energy density and good cycle characteristics can be obtained. Obtainable.

It should be noted that the cathode material in the present invention includes those to which other metal elements such as aluminum, zinc, and rare earth elements are added in addition to nickel and cobalt in order to improve the performance. However, adding a large amount of these metal elements is not preferable because the energy density of the active material decreases. The preferred range of the amount added is
The ratio of the number of moles of the added metal to the total number of moles of the metal in the positive electrode material is 0.3 or less, more preferably 0.2 or less.

Examples of the solvent of the nonaqueous electrolyte used in the present invention include cyclic carbonates such as ethylene carbonate and propylene carbonate, chain carbonates such as dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate, γ-butyrolactone, sulfolane and dimethyl carbonate. Sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran,
A polar solvent such as 2-methyltetrahydrofuran, dioxolan, methyl acetate, or a mixture thereof can be used.

The lithium salts dissolved in the non-aqueous solvent include LiPF ₆ , LiBF ₄ , LiAsF ₆ and LiCF ₃
CO ₂ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , Li
Salts such as N (SO ₂ CF ₂ CF ₃ ) ₂ , LiN (COCF ₃ ) ₂ and LiN (COCF ₂ CF ₃ ) ₂ or a mixture thereof may be used.

As the separator, an insulating polyolefin microporous membrane such as polyethylene or polypropylene,
A solid polymer electrolyte, a gel electrolyte in which an electrolyte solution is contained in a solid polymer electrolyte, and the like can also be used. Further, an insulating microporous film and a solid polymer electrolyte may be used in combination. Further, when a porous solid polymer electrolyte membrane is used as the solid polymer electrolyte, the electrolyte contained in the polymer and the electrolyte contained in the pores may be different.

Further, as the negative electrode active material, Al, S
alloy of lithium with i, Pb, Sn, Zn, Cd, etc., L
transition metal oxides such as iFe2O3, WO2, MoO2,
Carbonaceous materials such as graphite and carbon, Li5 (Li
Lithium nitride such as 3N), metallic lithium, or a mixture thereof may be used.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below using preferred embodiments.

Example 1 First, a method for producing a positive electrode material will be described. After weighing nickel nitrate hexahydrate and cobalt nitrate hexahydrate so that the molar ratio of Ni and Co becomes a predetermined value, the mixture is held in a Teflon beaker, and heated at 80 ° C. in a hot air drier. Hold for 1 hour. Next, the temperature in the hot air dryer was raised to 180 ° C., and heat treatment was performed at that temperature for 10 hours to obtain a solid state. After this was collected and ground in an agate mortar, a large amount of NaOH aqueous solution (specific gravity was about 1.2)
5) and stirred for 1 hour. Subsequently, after washing with a large amount of purified water to remove adhered alkali components,
And dried in a hot air dryer to obtain a positive electrode material precursor powder.

Next, 100 parts by weight of the above-mentioned cathode material precursor powder was added to a sufficient amount of an aqueous sodium hydroxide solution (specific gravity: about 1.25). While stirring this aqueous solution,
151 parts by weight of sodium peroxodisulfate powder was added and stirred for about 10 hours. Subsequently, after washing with a large amount of purified water to remove attached alkali components, the resultant was dried in a hot-air dryer at 80 ° C. to obtain a cathode material powder of the present invention.

As an example, FIG. 1 shows an X-ray diffraction pattern of a cathode material containing 30 mol% of cobalt. In FIG. 1, the symbol ◎ indicates nickel oxyhydroxide (β-NiOOH).
And the symbol ▼ indicates a peak belonging to Co ₃ O ₄ . From FIG. 1, in the X-ray diffraction pattern of the obtained cathode material, the peak attributed to nickel oxyhydroxide and C
A peak belonging to o ₃ O ₄ was observed. The valence of this active material was about 2.95.

Next, a method for manufacturing a positive electrode plate will be described. A solution composed of 93 parts by weight of the positive electrode material powder obtained above and 7 parts by weight of acetylene black powder as a conductive agent is composed of polyvinylidene fluoride (binder) and N-methylpyrrolidone (NMP) as a solvent. Was added and kneaded to prepare a paste, and a predetermined amount of the paste was applied to both surfaces of an aluminum foil having a thickness of 20 μm, followed by drying and pressing to obtain a positive electrode plate.

Further, a method of manufacturing a test battery will be described. Each one of the various positive plates manufactured as described above,
Two lithium metal plates having the same size as the counter electrode, a lithium metal piece as the reference electrode, and 50 ml of a mixed solvent of 1: 1 by volume of ethylene carbonate and diethyl carbonate containing 1 M lithium perchlorate as the electrolytic solution. Various test batteries were manufactured using the test batteries.

Next, a charge / discharge test will be described. Each test battery was discharged at a current density of 0.1 mA / cm ² to 1.5 V at 25 ° C., and the initial discharge capacity was measured. Then charge to 4.2V at the same current density, 1.
A 10-cycle charge / discharge test was performed under the condition of discharging to 5V.

FIG. 2 shows the relationship between the first cycle discharge capacity of each test battery and the amount of cobalt added. By adding cobalt, the discharge capacity is increased. Particularly, when the ratio of the number of moles of cobalt to the total number of moles of nickel and cobalt (Co / (Ni + Co)) is 0.1 to 0.5, the discharge capacity becomes large. It can be seen that it can be obtained. Further, when the ratio of the number of moles of cobalt to the total number of moles of nickel and cobalt (Co / (Ni + Co)) exceeds 0.5, the discharge capacity tends to decrease, and the addition of a large amount of cobalt is not effective. all right.

The ratio of the discharge capacity at the 10th cycle to the discharge capacity at the 1st cycle in the charge / discharge cycle test is defined as a capacity retention rate. FIG. 3 shows the relationship between the capacity retention of each test battery and the amount of cobalt added. It was found that the capacity retention was high when the ratio of the number of moles of cobalt to the total number of moles of nickel and cobalt (Co / (Ni + Co)) was 0.5 or less.

The cathode material containing nickel and cobalt according to the present invention has the following properties in order to improve its performance.
Those to which other metal elements such as zinc, aluminum, and rare earth elements are added can also be used. In the embodiment of the present invention, acetylene black is used as the conductive agent, polyvinylidene fluoride is used as the binder, and NM is used as the solvent.
Although P was used, other things could be used.

[0034]

According to the present invention, the general formula Ni _1-x Co _x O ₂ H _n (where 0 <x <0.55, 0.
4 <n <1.2) and the use of a cathode material containing a cobalt oxide can provide a 3V nonaqueous electrolyte battery having a large discharge capacity and excellent cycle characteristics. Therefore, its industrial value is extremely large.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an X-ray diffraction pattern of a cathode material according to the present invention.

FIG. 2 shows the cobalt content in the positive electrode material of the test electrode and 1
The figure which showed the relationship with the discharge capacity at the cycle.

FIG. 3 is a view showing a relationship between a cobalt content in a positive electrode material and a capacity retention of a test electrode.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4G048 AA03 AB02 AB05 AC06 AE05 AE07 5H029 AJ03 AJ05 AK03 AL01 AL06 AL12 AM03 AM04 AM05 AM07 CJ02 CJ12 CJ14 DJ16 HJ02 HJ14 5H050 AA07 AA08 BA17 CA08 CB01 GA12 GA12 GA12 DA HA02 HA14

Claims (4)

[Claims] 1. A non-aqueous electrolyte battery provided with a positive electrode containing a substance that absorbs and releases lithium ions, wherein the positive electrode substance has a general formula of Ni _1-x Co _x O ₂ H _n (where 0 < x <
0.55, 0.4 <n <1.2) and a cobalt oxide. 2. The ratio of the number of moles of cobalt to the total number of moles of nickel and cobalt in the cathode material (Co / (Ni +
Co)) is 0.5 or less.
The non-aqueous electrolyte battery according to the above. 3. A method for producing a cathode material for a non-aqueous electrolyte battery, comprising: a nickel salt having a molar ratio (Co / (Co + Ni)) of cobalt to a total molar number of nickel and cobalt of 0.5 or less; 1) 6
Step of heating and melting at 0 to 100 ° C., 2) 150 to 2
A non-aqueous electrolyte battery characterized by passing through a step of heating at 10 ° C. to a solid state, a step of treating with an alkaline aqueous solution, a step of washing to remove alkali components, and a step of oxidizing. A method for producing a positive electrode material. 4. The nickel salt and the cobalt salt are at least one selected from the group consisting of nitrates, sulfates, phosphates, acetates and hydrochlorides.
The method for producing a positive electrode material for a nonaqueous electrolyte battery according to the above.