JP2002104827A - Spinel type lithium manganese compound oxide and its manufacturing method and lithium ion secondary battery esing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new spinel type lithium manganese compound oxide superior in electrical charge or discharge capacity and electrical charge or discharge cycle property and dense packing property as a cathode material for a lithium ion secondary battery. SOLUTION: The compositional formula of the spinel type lithium manganese compound oxide is shown as LixMn2-yMyOz (M is at least one kind among metal elements except Li and Mn, and 1.0<=x<=1.2, 0<=y<=0.5, 3.8<=z<=4.4). The average primary particle diameter is 0.01 μm or more and 0.2 μm or less. The average secondary particle diameter is 0.2 μm or more and 100 μm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a novel spinel-type lithium manganese composite oxide which is useful as a positive electrode material of a lithium ion secondary battery and has excellent charge / discharge capacity, charge / discharge cycle characteristics, and high filling properties. The present invention relates to a method for manufacturing the same and a lithium ion secondary battery using the same.

[0002]

2. Description of the Related Art In recent years, with the rapid spread of portable electronic devices, there has been an increasing demand for inexpensive secondary batteries which are small, lightweight, have a high energy density and are used as power supplies. In the future, it is expected to be used in large quantities as batteries for electric vehicles. Under such circumstances, expectations for a lithium ion secondary battery having a high voltage and a high energy density are increasing.

[0003] Positive electrode materials for lithium ion secondary batteries include:
Conventionally, LiCoO ₂ is mainly used, but the cobalt compound as a raw material is expensive and the supply amount is small. On the other hand, spinel-type lithium manganese composite oxides are cheaper in manganese compound as the main raw material than cobalt compounds, have a large supply, and are environmentally friendly. Expectations are great.

The spinel-type lithium manganese oxide LiMn
₂ O ₄ has been known for a long time, and has recently attracted attention as a positive electrode material for lithium ion secondary batteries. For example, JP-A-63-114605 discloses an organic electrolyte secondary battery comprising a negative electrode containing lithium, a positive electrode mainly composed of LiMn ₂ O ₄ , and an organic electrolyte. The publication discloses a negative electrode using lithium or a lithium alloy as an active material, and a positive electrode using spinel-type lithium manganese oxide, λ-type manganese dioxide, or a manganese oxide having an intermediate crystalline structure as the active material. Non-aqueous secondary batteries have been proposed.

[0005] Spinel type lithium manganese oxide
LiMn ₂ O ₄ is obtained by mixing a low-melting lithium compound and a manganese compound and firing the mixture. For example, JP 63
In the -114605 publication, lithium carbonate and manganese dioxide are heated and reacted at 400 ° C. in a nitrogen atmosphere,
In JP-A-63-187659, it is obtained by mixing Mn ₂ O ₃ and lithium carbonate and performing heat treatment in air at 650 ° C. for 6 hours and at 850 ° C. for 14 hours. However, the spinel-type lithium manganese oxide obtained by these methods has insufficient charge / discharge characteristics (for example, charge / discharge capacity).

[0006] In Japanese Patent No. 2870741, manganese oxyhydroxide is dispersed in an aqueous solution of lithium hydroxide and then subjected to a heat treatment, so that the average primary particle size is 0.1 to 5 μm and the secondary particles are Of lithium manganate having an average particle size of 1 to 100 μm and a specific surface area of 0.1 to 10 m ² / g, the X-ray diffraction peak of the lithium manganese composite oxide obtained in the example is LiMnO _This indicates that the performance was deteriorated due to repeated charging and discharging, and the charging and discharging characteristics were not sufficient. Furthermore, since manganese oxyhydroxide is used as a starting material, there is a problem in that the production cost increases due to energy loss due to moisture generated during firing and damage to the firing furnace.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and has excellent charge / discharge capacity, charge / discharge cycle characteristics, and high filling properties as a positive electrode material of a lithium ion secondary battery. An object of the present invention is to provide a novel spinel-type lithium-manganese composite oxide, a method for producing the same, and a lithium-ion secondary battery using the same.

[0008]

SUMMARY OF THE INVENTION The present invention solves such a problem, and the gist of the present invention is to provide a composition formula LixM
n _2-y M _y O _z (M is a metal element other than Li and Mn, 1.0 ≦ x ≦ 1.2, 0
≦ y ≦ 0.5, 3.8 ≦ z ≦ 4.4)
The average particle diameter of the primary particles is 0.01 μm or more and 0.2 μm or less, and the average particle diameter of the secondary particles of the lithium manganese composite oxide is 0.2 μm or more and 100 μm or less. It is a composite oxide. In addition, the present invention provides fine particles mainly composed of manganese oxide having an average particle diameter of 0.01 μm or more and 0.2 μm or less, lithium-containing compounds and metal compounds (excluding manganese and lithium).
Mixture or primary particle size average particle size is 0.01μm
As described above, there is provided a method for producing a spinel-type lithium-manganese composite oxide, which comprises heat-treating a mixture of a composite fine particle oxide of manganese and another metal having a particle size of 0.2 μm or less and a lithium compound. Further, the present invention is a lithium ion secondary battery characterized in that the above spinel type lithium manganese oxide is used as a positive electrode material.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The spinel-type lithium manganese composite oxide of the present invention has a composition formula of Li _x Mn _2-y M _y O _z (M is at least one or more metal elements other than Li and Mn, 1.0 ≦ x ≦ 1.2, 0 ≦ y ≦ 0.5 , 3.8 ≦ z ≦ 4.
4), x = 1.0, y = 0, may be LiMn ₂ O ₄ which is a spinel type lithium manganese oxide with z = 4, and 1.0 ≦ x ≦ 1.2, 0 ≦ y ≦ Any spinel-type lithium manganese composite oxide corresponding to the range of 0.5, 3.8 ≦ z ≦ 4.4 may be used. When x, y, and z exceed the above ranges, the charge / discharge capacity of the secondary battery decreases, and the charge / discharge cycle characteristics also deteriorate due to the unstable structure.

The above-mentioned metal elements are metal elements other than Li and Mn, and specifically, B, Mg, Al, Si, Sc, Ti, V, Cr,
Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Sn, S
b, La, Ce, Pr, Nd, Hf, Ta, and at least one element selected from the group consisting of Pb, and may include two or more elements. The spinel-type lithium manganese composite oxide has a spinel structure, and its X-ray diffraction pattern is the same as that of LiMn ₂ O ₄ described in JCPDS card No. 35-0782.

The average particle size of the primary particles of the spinel-type lithium manganese composite oxide of the present invention is 0.01 μm or more and 0.2 μm or less, preferably 0.02 μm or more and 0.1 μm or less. The primary particles are the smallest units that can be confirmed as particles when observed with an electron microscope.The spinel-type lithium manganese composite oxide of the present invention is irradiated with ultrasonic waves in a solvent such as water, or a homogenizer. When re-dispersed by applying an external force such as a strong shear force with various mills,
Some of them can be dispersed in the primary particles. The average particle diameter of the primary particles is a number average particle diameter, which is an average of 100 or more primary particle diameters from an electron micrograph. When the average particle size of the primary particles is less than 0.01 μm, when used as a positive electrode material for a lithium ion secondary battery, the reactivity becomes extremely high, and performance degradation due to elution of manganese or the like occurs. The average particle size of the primary particles is 0.2
If it exceeds μm, the movement of lithium ions during charge / discharge is not sufficiently performed, and the charge / discharge capacity is reduced.

The average particle size of the secondary particles of the spinel-type lithium manganese composite oxide of the present invention is from 0.2 μm to 100 μm, preferably from 0.5 μm to 50 μm, more preferably from 1.0 μm to 40 μm. It is as follows. Secondary particles are those in which primary particles are physically or chemically aggregated or aggregated when observed with an electron microscope,
The average particle size is a number average particle size of 100 or more. When the average particle diameter of the secondary particles is less than 0.2 μm, when the secondary particles are used as a positive electrode material of a lithium ion secondary battery, the filling rate is low, and the electric capacity per unit volume of the battery is low. When the average particle size of the secondary particles exceeds 100 μm, the particles damage the separator of the lithium ion secondary battery,
An electrical short circuit may occur.

The spinel-type lithium manganese composite oxide of the present invention has an average primary particle diameter of 0.01 μm or more and 0.2 μm
Fine particles containing manganese oxide as the main component and a lithium-containing compound, manganese, or a heat-treated metal compound other than lithium, or manganese having an average primary particle diameter of 0.01 μm or more and 0.2 μm or less. It can be produced by heat-treating a composite fine particle oxide of another metal and a lithium-containing compound.

Oxidized manganese used in the production method of the present invention
Fine particles mainly containing manganese are mainly composed of manganese oxides.
And manganese oxide.
Is Mn _ThreeO_Four, Mn_TwoO_Three, MnO, MnO_TwoAnd Mn_ThreeO_FourAnd
MnO_TwoIs preferably used. In addition, the primary particles of fine particles
The average particle size is from 0.01 μm to 0.2 μm. Average particle size
Means more than 100 particles when observed with an electron microscope
Is the number average particle size. Average particle size of fine particles is less than 0.01μm
In the case of, because of its high surface activity, obtained by heat treatment
Spinel-type lithium manganese composite oxide has primary particles
Easy to grow, difficult to reduce average particle size below 0.2μm
And when the average particle diameter of the fine particles exceeds 0.2 μm.
Primary particles of spinel-type lithium manganese composite oxide
Has a mean particle size of more than 0.2 μm.

As the lithium-containing compound used in the production method of the present invention, there can be mentioned a compound containing lithium hydroxide, lithium carbonate or the like as a main component.

Manganese used in the production method of the present invention,
Compounds of metals other than lithium include B, Mg, Al, Si, S
c, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, M
o, Ru, Sn, Sb, La, Ce, Pr, Nd, Hf, Ta and a compound containing at least one metal element selected from the group consisting of Ta and Pb, including two or more metal elements It may be.

The composite oxide fine particles used in the present invention include manganese and B, Mg, Al, Si, Sc, Ti, V, Cr, Fe, C
o, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ru, Sn, Sb, La,
Fine particles of a composite oxide containing at least one metal element selected from the group consisting of Ce, Pr, Nd, Hf, Ta and Pb, and may contain three or more metal elements .

The fine particles mainly composed of manganese oxide and the fine particles of a composite oxide of manganese and another metal element used in the present invention have an average particle size of 0.01 μm or more and 0.2 μm or less, and the average particle size is determined by an electron microscope. It is the number average particle diameter of 100 or more fine particles when observed.

In the method for producing a spinel-type lithium manganese composite oxide according to the present invention, the fine particles containing manganese oxide as a main component, a lithium-containing compound and a metal compound are mixed and heat-treated. Heat treatment conditions, the heating temperature such that the average primary particle diameter of the spinel-type lithium manganese composite oxide does not exceed 0.2μm,
The heating time is determined. The actual heating temperature is from 250 ° C to 900 ° C, preferably from 350 ° C to 850 ° C. If the temperature is lower than 250 ° C., a spinel-type lithium manganese composite oxide cannot be obtained. In some cases, it is difficult to reduce the average particle size of the primary particles to 0.2 μm or less. The heating time is not particularly limited, but if the spinel-type lithium manganese composite oxide can be synthesized, the shorter the heating time is, the more advantageous from the viewpoint of manufacturing cost. In the heat treatment, the material that has been compressed into pellets before the heat treatment may be heated. After the heat treatment, when the obtained spinel-type lithium manganese composite oxide forms a large aggregate, pulverization is performed until the average particle size of the secondary particles becomes 100 μm or less.

The lithium ion secondary battery of the present invention uses the spinel-type lithium manganese composite oxide of the present invention as a positive electrode material. More specifically, for the positive electrode, a material obtained by mixing the above-described spinel-type lithium manganese composite oxide, a conductive material, a binder, a filler, and the like is used. Materials are used. In addition, as the electrolyte, a solution in which a lithium salt is dissolved in an organic solvent such as carbonates, sulfolane, lactones, and ethers, and a solid electrolyte having lithium ion conductivity are used.

[0021]

EXAMPLES Examples will be described below, but the present invention is not limited to these examples.

(A) Average particle size of primary particles and secondary particles From a photograph taken with a transmission electron microscope, 100
The particle size of the primary or secondary particles was measured and averaged. (b) Battery discharge capacity 50 mg of spinel-type lithium manganese composite oxide, 10 mg of acetylene black and 10 mg of polytetrafluoroethylene were mixed and kneaded, pressed on a titanium mesh with a pressure of 80 MPa, and dried under reduced pressure at 200 ° C. for 24 hours. This was performed to produce a positive electrode.
Next, this positive electrode material was accommodated in a three-electrode cell, and a lithium ion secondary battery was constructed using lithium foil for the negative electrode and LiClO ₄ for the electrolyte. Using this battery, charging and discharging were repeated at a constant current of 40 μA / cm ² at a battery voltage of 4.3 to 3.0 V, and the discharge capacity was measured. (c) Filling property In order to evaluate the filling property of the battery, the tap density was measured. That is, the density after tapping for 60 minutes under the condition of 6 times / 10 seconds using a powder property measuring device multi-tester MT-1000 manufactured by Seishin Enterprise Co., Ltd. was defined as the tap density.

Example 1 15.2 g of manganese tetroxide (Nanotech manufactured by CI Kasei Co., Ltd.) having an average primary particle size of 0.04 μm and 3.7 g of lithium carbonate (special grade manufactured by Ishizu Pharmaceutical Co., Ltd.) were mixed, and the mixture was mixed with a press machine.
The product molded under a load of 0 MPa was fired in an electric furnace at 750 ° C. for 12 hours in an air atmosphere, and then pulverized in a mortar to obtain a fine powder. From the results of X-ray diffraction measurement (FIG. 1), this fine powder was found to be spinel-type lithium manganese composite oxide (LiMn
₂ O ₄ ). The average particle size, tap density,
Table 1 shows the discharge capacities of the lithium ion secondary batteries.

Example 2 The procedure of Example 1 was repeated except that 15.2 g of manganese tetroxide (Brownox X, manufactured by Tosoh Corporation) having an average primary particle size of 0.08 μm was used. The results are shown in Table 1. Was.

Example 3 0.05 mol / L of sodium hydroxide aqueous solution was added to 50 L of 0.01 mol / L manganese (II) sulfate for about 50 L.
After adding 1 liter and adjusting to pH = 12, the mixture was stirred for 1 hour while bubbling 50 liter / min of air in the liquid with an air pump to obtain a brown precipitate, which was filtered by a conventional method.・ After washing, drying at 150 ° C for 1 day, 35 g of manganese tetroxide with an average primary particle size of 26 nm
I got Except for using 15.2 g of this manganese tetroxide,
The procedure was performed in the same manner as in Example 1, and the results are shown in Table 1.

Example 4 14.5 g of manganese tetroxide (Nanotec manufactured by C-I Kasei Co., Ltd.) having an average primary particle size of 0.04 μm, 0.8 g of cobalt oxide (Nano Tech manufactured by C-I Kasei Co., Ltd.) and lithium carbonate (special grade manufactured by Ishizu Pharmaceutical Co., Ltd.) ) Was carried out in the same manner as in Example 1 except for mixing 3.7 g), and the results are shown in Table 1.

Example 5 A mixture of 50 liters of 0.01 mol / l manganese (II) sulfate and 4.5 liters of 0.01 mol / l cobalt (II) sulfate was mixed with about 55 liters of a 0.02 mol / l sodium hydroxide aqueous solution. After adding to adjust the pH to 12, the mixture was stirred for 1 hour while bubbling 50 liters / min of air in the liquid with an air pump to obtain a brown precipitate, which was filtered and filtered by a conventional method. After washing, 150 ℃
For 1 day to obtain 38.5 g of a composite oxide having an average primary particle size of 30 nm. A composition analysis of this composite oxide revealed Co / Mn = 11.9 wt%. This composite oxide 15.
The procedure was performed in the same manner as in Example 1 except that 3 g and 3.7 g of lithium carbonate (special grade manufactured by Ishizu Pharmaceutical Co., Ltd.) were mixed. The results are shown in Table 1.

Comparative Example 1 To 50 liters of 1 mol / l manganese (II) sulfate
About 50 liters of a 2 mol / l sodium hydroxide aqueous solution was added to adjust the pH to 12, and then 50
While bubbling air through the liquid at 1 liter / min.
Stirring was carried out for a time to obtain a brown precipitate, which was filtered and washed by a conventional method, and dried at 150 ° C. for one day to obtain trimanganese oxide having an average primary particle size of 250 nm. .
Example 1 except that 15.2 g of this manganese tetroxide was used.
And the results are shown in Table 1.

[0029]

[Table 1]

As shown in Table 1, the batteries of Examples 1 to 5 showed good results in all of the discharge capacity, charge / discharge cycle characteristics, and fillability. In the comparative example, the discharge capacity was low.

[0031]

According to the present invention, it has become possible to provide a spinel-type lithium manganese composite oxide having excellent discharge capacity, charge / discharge cycle characteristics, and filling properties.
A lithium ion secondary battery using the spinel-type lithium manganese composite oxide of the present invention as a positive electrode material has high capacity and high performance, which leads to miniaturization of electronic devices and improvement of battery life.

[Brief description of the drawings]

FIG. 1 is a view showing the results of X-ray diffraction measurement of a spinel-type lithium manganese composite oxide of the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshinari Ikegami 329 Sakagoshi, Ako-shi, Hyogo Prefecture Inside Ako Kasei Co., Ltd. (72) Inventor Hiroshi Nakajima 329 Sakakoshi, Ako-shi, Hyogo Prefecture Inside Ako Kasei Co., Ltd. (72) Inventor Yoshinobu Uozumi 329 Sakagoe, Ako-shi, Hyogo Aka Kasei Co., Ltd. (72) Inventor Yoshiyuki Takahara 329, Sakagoe, Ako-shi, Hyogo Ako Kasei Co., Ltd.F-term (reference) 4G048 AA04 AB06 AC06 AD04 AD06 5H029 AJ03 AJ05 AK03 AL06 AL12 AM03 AM04 AM06 AM07 AM12 AM16 CJ02 CJ08 DJ17 EJ03 EJ05 HJ02 HJ05 5H050 AA07 AA08 BA17 CA09 DA02 FA17 FA19 GA02 GA10 HA02 HA05

Claims (4)

[Claims] The composition formula Li _x Mn _2-y M _y O _z (M is at least one metal element other than Li and Mn, 1.0 ≦ x ≦ 1.2, 0 ≦ y ≦
0.5, 3.8 ≤ z ≤ 4.4) oxide, the average particle size of the primary particles is 0.01μm or more, 0.2μm or less, the average particle size of the secondary particles is 0.2μm or more, 100μm or less A spinel-type lithium manganese composite oxide, characterized in that: 2. The method according to claim 1, wherein the primary particles have an average particle size of 0.01 μm or more,
micron-based manganese oxide-based fine particles,
The method for producing a spinel-type lithium-manganese composite oxide according to claim 1, wherein the lithium-containing compound and a compound of a metal other than manganese and lithium are subjected to heat treatment. 3. The method according to claim 1, wherein the primary particles have an average particle size of 0.01 μm or more,
The method for producing a spinel-type lithium-manganese composite oxide according to claim 1, wherein the lithium-containing compound and a composite oxide fine particle of manganese and another metal element having a size of not more than μm are heat-treated. 4. A lithium ion secondary battery using the spinel-type lithium manganese composite oxide according to claim 1 as a cathode material.