JP2000294239A - Manufacture of spinel type lithium manganate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of spinel type lithium manganate restraining a manganese elution quantity and improving battery characteristics at a high temperature such as high temperature storage characteristics and high temperature charge/discharge cycle characteristics. SOLUTION: Electrodeposited manganese dioxide is neutralized by lithium hydroxide. After neutralization, electrolytic manganese dioxide containing 0.02-0.5 wt.% of lithium is mixed with a lithium raw material, and then is fired. The manganese dioxide is crushed before or after neutralization by the lithium hydroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing spinel-type lithium manganate, and more particularly, to a method for producing a positive electrode material for a non-aqueous electrolyte secondary battery, which suppresses the amount of manganese eluted, provides high-temperature storage characteristics, The present invention relates to a method for producing a spinel type lithium manganate having improved high-temperature characteristics of a battery such as characteristics.

[0002]

2. Description of the Related Art With the rapid progress of portable and cordless personal computers and telephones in recent years, the demand for secondary batteries as power sources for driving them has been increasing. Among them, non-aqueous electrolyte secondary batteries are particularly expected because they have the smallest size and high energy density. The positive electrode material of a nonaqueous electrolyte secondary battery that satisfies the above requirements lithium cobaltate (LiCoO _2), lithium nickelate (LiNiO _2), and the like of lithium manganate (LiMn ₂ O _4). Since these composite oxides have a voltage of 4 V or more with respect to lithium,
A battery having a high energy density can be obtained.

[0003] Among the above composite oxides, LiCoO ₂ , L
While iNiO ₂ has a theoretical capacity of about 280 mAh / g, LiMn ₂ O ₄ is as small as 148 mAh / g, but is rich in manganese oxide as a raw material and is inexpensive.
Since there is no thermal instability during charging unlike LiNiO ₂ , it is considered to be suitable for EV applications.

However, since lithium manganate (LiMn ₂ O ₄ ) elutes Mn at a high temperature, there is a problem that the battery characteristics at a high temperature such as a high temperature storage property and a high temperature cycle characteristic are inferior.

Accordingly, an object of the present invention is to provide a positive electrode material for a non-aqueous electrolyte secondary battery, which suppresses the amount of manganese eluted during charging and improves battery characteristics at high temperatures such as high-temperature preservability and high-temperature cycle characteristics. Method for producing spinel-type lithium manganate and a cathode material comprising the lithium manganate,
Another object of the present invention is to provide a non-aqueous electrolyte secondary battery using the positive electrode material.

[0006]

Since electrolytic manganese dioxide is inexpensive and abundant, it is suitable as a manganese raw material for spinel-type lithium manganate. Normally, electrolytic manganese dioxide is subjected to soda neutralization for alkaline manganese battery applications after electrolysis. It is known that a small amount of sodium remains in soda neutralized electrolytic manganese dioxide, and the amount of sodium depends on neutralization conditions. Similarly, when neutralization is performed with lithium, a small amount of lithium remains in the electrolytic manganese dioxide, and the amount depends on the neutralization conditions.

The present inventors have focused on the neutralization conditions for electrolytic manganese dioxide, and by specifying the conditions, have found that the obtained spinel-type lithium manganate can achieve the above object, although the reason is unknown. I learned.

[0008] The invention of the method for producing spinel-type lithium manganate according to claim 1 based on such knowledge is to neutralize electrolytically deposited manganese dioxide with lithium hydroxide, and to neutralize lithium by 0.02 to 0.02. A method for producing spinel-type lithium manganate, comprising mixing and calcining electrolytic manganese dioxide containing 0.5% by weight with a lithium raw material.

The invention of claim 2 is characterized in that, in claim 1, manganese dioxide is pulverized either before or after the neutralization with lithium hydroxide.

The invention according to claim 3 is the method according to claim 2, wherein the manganese dioxide after pulverization has an average particle size of 5 to 30.
μm.

A fourth aspect of the present invention is characterized in that, in any one of the first to third aspects, the calcination is performed at 750 ° C. or higher.

[0012] [5] The invention of a cathode material for a non-aqueous electrolyte secondary battery according to [5] is characterized by comprising a spinel-type lithium manganate obtained by the production method according to any one of the above-mentioned [1] to [4].

[0013] The invention of a non-aqueous electrolyte secondary battery according to claim 6 provides a positive electrode using the positive electrode material according to claim 5, a lithium alloy or a negative electrode capable of inserting and extracting lithium and a non-aqueous electrolyte. Characterized by the following.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the present invention, electrolytic manganese dioxide is used as a manganese raw material for spinel-type lithium manganate.

The electrolytic manganese dioxide in the present invention is obtained by the following method. For example, a manganese sulfate solution having a predetermined concentration is used as an electrolytic solution, a carbon plate is used as a cathode, and a titanium plate is used as an anode. Electrolysis is performed at a constant current density while heating to deposit manganese dioxide on the cathode. Next, the deposited manganese dioxide is peeled off from the anode and pulverized to a predetermined particle size, preferably an average particle size of 5 to 30 μm.

In a non-aqueous electrolyte secondary battery, since the positive electrode material is processed into a thick film having a thickness of about 100 μm, if the particle size is too large, cracks or the like are generated, and it is difficult to form a uniform thick film. Therefore, when spinel-type lithium manganate is synthesized from electrolytic manganese dioxide having an average particle size of 5 to 30 μm as a raw material, a positive electrode material suitable for film formation can be obtained without additional grinding. It is presumed that neutralizing fine electrolytic manganese dioxide with lithium in this way facilitates more uniform distribution of lithium.

The electrolytic manganese dioxide pulverized to a predetermined particle size is neutralized with lithium, washed with water and dried. Specifically, the lithium is neutralized with lithium hydroxide.
The order of pulverization and neutralization is not particularly limited, and pulverization may be performed after neutralization.

The amount of lithium in the neutralized electrolytic manganese dioxide is preferably 0.02 to 0.5% by weight. If it exceeds 0.5% by weight, the amount of manganese eluted at a high temperature is reduced. The capacity is reduced. If the amount is less than 0.02% by weight, the effect is insufficient.

In the present invention, this electrolytic manganese dioxide is
It is mixed with a raw material of chromium and calcined to produce spinel-type manganese oxide.
Obtains titanium. As a lithium raw material, lithium carbonate
(Li _TwoCO_Three), Lithium nitrate (LiNO_Three), Hydroxyl
Lithium oxide (LiOH) and the like. Electrolytic dioxide
The Li / Mn molar ratio of manganese to lithium raw material is 0.50
0.60 is preferred.

These electrolytic manganese dioxide and lithium raw materials are preferably ground before or after mixing the raw materials in order to obtain a larger reaction area. The weighed and mixed raw materials may be used as they are or may be granulated. The granulation method may be wet or dry, and may be extrusion granulation, tumbling granulation, fluidized granulation, mixing granulation, spray drying granulation, pressure molding granulation, or flake granulation using a roll or the like. .

The raw material thus obtained is put into a firing furnace and fired at 600 to 1000 ° C. to obtain a spinel type lithium manganate. A temperature of about 600 ° C. is sufficient to obtain a single-phase spinel-type lithium manganese oxide, but a firing temperature of 750 ° C. or higher, preferably 850 ° C. or higher is necessary because a low firing temperature does not promote the growth of grains. Becomes Examples of the firing furnace used here include a rotary kiln and a stationary furnace. The firing time is 1 hour or more, preferably 5 to 20 hours, to obtain a uniform reaction. This spinel-type lithium manganate is used as a positive electrode material of a non-aqueous electrolyte secondary battery.

In the non-aqueous electrolyte secondary battery of the present invention, the positive electrode material, a conductive material such as carbon black, and a binder such as Teflon (polytetrafluoroethylene) binder are mixed to form a positive electrode mixture. For the negative electrode, a lithium alloy or a material capable of occluding and desorbing lithium such as carbon is used. As the non-aqueous electrolyte, a lithium salt such as lithium hexafluorophosphate (LiPF ₈ ) is ethylene carbonate-dimethyl. A solution dissolved in a mixed solvent such as carbonate or a solution obtained by using them as a gel electrolyte is used, but is not particularly limited.

Since the non-aqueous electrolyte secondary battery of the present invention can suppress the elution of manganese in a charged state, battery characteristics at high temperatures such as high-temperature storage and high-temperature cycle characteristics can be improved.

[0024]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and the like, but the present invention is not particularly limited thereto.

Example 1 A manganese sulfate aqueous solution having a sulfuric acid concentration of 50 g / l and a manganese concentration of 40 g / l was prepared as a manganese electrolytic solution. The temperature of the electrolytic solution was heated to 95 ° C., and electrolysis was performed at a current density of 60 A / m ² using a carbon plate as a cathode and a titanium plate as an anode. Next, the manganese dioxide electrodeposited on the anode was peeled off, and 7 mm
The following chips were pulverized, and the chips were further pulverized to an average particle size of about 20 μm.

The manganese dioxide (10 kg) was washed with 20 liters of water, and after washing water was discharged, 20 liters of water was added again. 35 g of lithium hydroxide was dissolved therein, neutralized for 24 hours while stirring, washed with water, filtered, and dried (50 ° C., 12 hours). Table 1 shows the lithium content of the obtained powder.

To 1 kg of manganese dioxide having an average particle size of about 20 μm, lithium carbonate was added and mixed so that the Li / Mn molar ratio was 0.54, and the mixture was baked in a box furnace at 800 ° C. for 20 hours to obtain a spinel type. Lithium manganate was obtained.

A positive electrode mixture is prepared by mixing 80 parts by weight of the thus obtained spinel type lithium manganate, 15 parts by weight of carbon plaque as a conductive agent and 5 parts by weight of polytetrafluoroethylene as a binder. did.

Using this positive electrode mixture, a coin-type nonaqueous electrolyte secondary battery shown in FIG. 1 was produced. That is, the current collector 3 also made of stainless steel is spot-welded to the inside of the positive electrode case 1 made of stainless steel having organic electrolyte resistance.
On the upper surface of the current collector 3, a positive electrode 5 made of the above positive electrode mixture is pressed. On the upper surface of the positive electrode 5, a separator 6 made of microporous polypropylene resin impregnated with an electrolytic solution is arranged. At the opening of the positive electrode case 1, a sealing plate 2 to which a negative electrode 4 made of metallic lithium is joined is disposed below a gasket 7 made of polypropylene, whereby the battery is sealed. The sealing plate 2 also serves as a negative electrode terminal,
It is made of the same stainless steel as the positive electrode case 1. The diameter of the battery is 20 mm, and the total height of the battery is 1.6 mm. As an electrolytic solution, a solution obtained by mixing ethylene carbonate and 1,3-dimethoxyethane in equal volumes was used as a solvent, and a solution obtained by dissolving 1 mol / liter of lithium hexafluorophosphate using this as a solute was used.

The battery thus obtained was subjected to a charge / discharge test. The charge / discharge test is performed at 20 ° C.
The current density was 0.5 mA / cm ² and the voltage was in the range of 4.3 V to 3.0 V. The batteries were charged at 4.3 V and stored in an environment of 80 ° C. for 3 days, and the storage characteristics of the batteries were checked using the discharge capacity of these batteries as the capacity retention ratio. Table 1 shows the measurement results of the initial discharge capacity and the high-temperature storage capacity retention rate.

Example 2 A spinel-type lithium manganate was synthesized in the same manner as in Example 1, except that the amount of lithium hydroxide added during the neutralization of electrolytic manganese dioxide was 55 g. Table 1 shows the lithium content. In addition, a coin-type nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 using this spinel-type lithium manganate as a positive electrode material, and the initial discharge capacity and the high-temperature storage capacity retention ratio were measured. Show.

Example 3 A spinel-type lithium manganate was synthesized in the same manner as in Example 1, except that the amount of lithium hydroxide added during neutralization of electrolytic manganese dioxide was changed to 85 g. Table 1 shows the lithium content. In addition, a coin-type nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 using this spinel-type lithium manganate as a positive electrode material, and the initial discharge capacity and the high-temperature storage capacity retention ratio were measured. Show.

Example 4 A spinel-type lithium manganate was synthesized in the same manner as in Example 1 except that the amount of lithium hydroxide added during the neutralization of electrolytic manganese dioxide was changed to 130 g. Table 1 shows the lithium content. In addition, a coin-type nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 using this spinel-type lithium manganate as a positive electrode material, and the initial discharge capacity and the high-temperature storage capacity retention ratio were measured. Show.

Example 5 A spinel-type lithium manganate was synthesized in the same manner as in Example 1, except that the amount of lithium hydroxide added during the neutralization of electrolytic manganese dioxide was changed to 180 g. Table 1 shows the lithium content. In addition, a coin-type nonaqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 using this spinel-type lithium manganate as a positive electrode material, and the initial discharge capacity and the high-temperature storage capacity retention ratio were measured. Show.

Example 6 A spinel-type lithium manganate was synthesized in the same manner as in Example 2 except that the sintering temperature was 900 ° C. Table 1 shows the lithium content. Also,
Using this spinel-type lithium manganate as a positive electrode material, a coin-type nonaqueous electrolyte secondary battery was prepared in the same manner as in Example 1, and the initial discharge capacity and high-temperature storage capacity retention were measured.
Table 1 shows the results.

Example 7 A spinel-type lithium manganate was synthesized in the same manner as in Example 2 except that the sintering temperature was 700 ° C. Table 1 shows the lithium content. Also,
Using this spinel-type lithium manganate as a positive electrode material, a coin-type nonaqueous electrolyte secondary battery was prepared in the same manner as in Example 1, and the initial discharge capacity and high-temperature storage capacity retention were measured.
Table 1 shows the results.

Comparative Example 1 Spinel-type lithium manganate was prepared in the same manner as in Example 1 except that the electrolytic manganese dioxide was not neutralized (the amount of lithium hydroxide added was 0 g). Table 1 shows the lithium content. Further, the spinel-type lithium manganate was used as a cathode material in Example 1
A coin-type non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 1 and the initial discharge capacity and the high-temperature storage capacity retention rate were measured. The results are shown in Table 1.

[0038]

[Table 1]

Example 8 A spinel-type lithium manganate was synthesized in the same manner as in Example 1, except that the average particle size of the electrolytic manganese dioxide during pulverization was 5 μm. Using this spinel-type lithium manganate as a positive electrode material, a coin-type nonaqueous electrolyte secondary battery was prepared in the same manner as in Example 1, and evaluated at two types of current densities, 0.5 mA / cm ² and 1.0 mA / cm ² . And the discharge capacity at a current density of 0.5 mA / cm ² is 1
The discharge capacity ratio at 1.0 mA / cm ² was represented as a current load ratio. Table 2 shows the current load ratio.

Example 9 The same evaluation as in Example 8 was performed on the coin-type nonaqueous electrolyte secondary battery manufactured in Example 1. Table 2 shows the current load ratio. Example 10 Except that the average particle size of pulverized electrolytic manganese dioxide was 30 μm,
In the same manner as in Example 1, spinel-type lithium manganate was synthesized. A coin-type nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 using this spinel-type lithium manganate as a positive electrode material, and the same evaluation as in Example 8 was performed. Table 2 shows the current load ratio.

Example 11 A spinel-type lithium manganate was synthesized in the same manner as in Example 1 except that the average particle size of the electrolytic manganese dioxide during pulverization was 35 μm. Using this spinel-type lithium manganate as a positive electrode material, a coin-type nonaqueous electrolyte secondary battery was prepared in the same manner as in Example 1,
The same evaluation as in Example 8 was performed. Table 2 shows the current load ratio.

[0042]

[Table 2]

[0043]

As described above, by using the spinel-type lithium manganate obtained by the production method of the present invention as a positive electrode material for a non-aqueous electrolyte secondary battery, the amount of manganese eluted during charging can be suppressed, Battery characteristics at high temperatures such as high-temperature storage characteristics and high-temperature cycle characteristics can be improved, and the current load factor can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a coin-type nonaqueous electrolyte secondary battery of an example and a comparative example.

[Description of Signs] 1 Positive electrode case 2 Sealing plate 3 Current collector 4 Metal lithium negative electrode 5 Positive electrode 6 Separator 7 Gasket

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Takuya Nakajima 1006 Kadoma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. F term (reference) 4G048 AA04 AB02 AB05 AC06 AD04 AD06 AE05 5H003 AA03 AA04 BA01 BA03 BA04 BA07 BB05 BC06 BD01 BD02 BD04

Claims (6)

[Claims] 1. The method according to claim 1, wherein the manganese dioxide electrolytically deposited is neutralized with lithium hydroxide.
Weight percent electrolytic manganese dioxide mixed with lithium raw material,
A method for producing spinel-type lithium manganate, which comprises firing. 2. The method for producing spinel-type lithium manganate according to claim 1, wherein manganese dioxide is pulverized before or after neutralization with lithium hydroxide. 3. The method according to claim 2, wherein the crushed manganese dioxide has an average particle size of 5 to 30 μm.
A method for producing spinel-type lithium manganate, characterized in that: 4. The method according to claim 1, wherein the calcination is performed at 750 ° C. or higher. 5. A positive electrode material for a non-aqueous electrolyte secondary battery, comprising a spinel-type lithium manganate obtained by the production method according to any one of claims 1 to 4. 6. A non-aqueous electrolyte secondary battery comprising a positive electrode using the positive electrode material according to claim 5, a lithium alloy or a negative electrode capable of inserting and extracting lithium, and a non-aqueous electrolyte. .