JPH09330701A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a practical nonaqueous electrolyte secondary battery with high capacity and excellent charge and discharge cycle performance in which the density can be increased even when a positive electrode is pressure molded into a sheet for higher performance of smaller size by providing a positive electrode active material formed of LixMnOy obtained from electrolyzed manganese dioxide and a different kind of transition metal added thereto. SOLUTION: In a coin type nonaqueous electrolyte secondary battery 1, a positive electrode 3 is put in a battery can 2, a separator 4 is placed thereon, a nonaqueous electrolyte injected to the battery can, the battery can is covered with a battery lid 6 having a negative electrode 5 on the inside after a nonaqueous electrolyte is injected thereto, and a gasket 7 is interposed to the clearance between the battery lid 6 and the battery can 25 followed by caulking and sealing. The positive electrode 3 is obtained by filling a positive electrode mix 9 onto a positive electrode current collector 8 followed by pressure molding. The positive electrode active material in the positive electrode mix 9 is formed of LixMnOy obtained from electrolyzed manganese dioxide and a different kind of transition metal added thereto. This battery is applicable to other various types of batteries without being limited to coil type battery.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery, and more specifically, it uses LixMnOy as a positive electrode material and a lithium material, a lithium alloy, or a carbon material capable of being doped or dedoped with lithium as a negative electrode material. The present invention relates to a non-aqueous electrolyte secondary battery using.

[0002]

2. Description of the Related Art In recent years, due to advances in electronic technology and the like, various electronic devices (for example, headphone stereos, CD players, personal computers, etc.) have been improved in performance, downsized, and portable, and have been used as power sources for these electronic devices. There is also a strong demand for higher performance and smaller size of secondary batteries used.

Conventionally, there are nickel-cadmium batteries, lead batteries, etc. as secondary batteries used as a power source for these electronic devices. Recently, lithium ion secondary batteries belonging to non-aqueous electrolyte secondary batteries have been put into practical use. It has been.

In particular, the lithium ion secondary battery is the most promising secondary battery that can be made compact and lightweight. This lithium ion battery uses Li as a positive electrode active material.
A secondary battery in which CoO ₂ or LiNiO ₂ is used, a carbon material capable of being doped or dedoped with lithium is used as a negative electrode active material, a resin microporous film is used as a separator, and a nonaqueous electrolytic solution is used as an electrolytic solution. . However, at present, this lithium-ion battery is difficult to obtain the material, and the price is high.

On the other hand, fine powder LiMn ₂ O _{4 is} used as the positive electrode active material because the material is easily available and the price is low.
Research and development of non-aqueous electrolyte secondary batteries using a carbon material capable of being doped and dedoped with lithium as a negative electrode active material have also been carried out.

[0006]

However, as described above, when LiMn ₂ O ₄ which is a fine powder is used as the positive electrode material, when the positive electrode which is the electrode is pressure-molded into a sheet shape, the properties of this powder are improved. Therefore, it is difficult to form a positive electrode having a large capacity and flexibility because the density cannot be increased and it is hard, and a practical electrode cannot be manufactured. In addition, the charge / discharge cycle performance was significantly degraded after several tens of charge / discharge cycles, and the charge / discharge performance was rapidly lost as lithium moved from the positive electrode side to the negative electrode side. I was scarce.

[0007] Therefore, research is being conducted to use LiMn ₂ O ₄ obtained from electrolytic manganese dioxide having a large particle size as the positive electrode active material instead of the fine powder of LiMn ₂ O ₄ positive electrode active material. In this case, the positive electrode having a large capacity and flexibility can be formed even if the positive electrode is pressure-molded into a sheet, but in order to improve the conductivity, the conductive material mixed with the positive electrode active material is 10 It is required to be more than 10% by weight, and when the charge and discharge cycle is performed, the resistance increases, the conductivity cannot be maintained, and the capacity decreases, which is not practical.

The present invention has been made in view of the above points, and an object thereof is to provide a practical non-aqueous electrolyte secondary battery having a high capacity and excellent charge / discharge cycle performance.

[0009]

In order to achieve the above object, the present invention is characterized in that the positive electrode active material is constituted by adding a different transition metal to LixMnOy obtained from electrolytic manganese dioxide. A water electrolyte secondary battery is provided.

According to the above structure, since the positive electrode active material has LixMnOy obtained from electrolytic manganese dioxide as a main constituent, it is possible to increase the density even when the positive electrode is pressure-molded into a sheet. Thus, a high capacity non-aqueous electrolyte secondary battery can be obtained. Further, since the positive electrode active material contains a different transition metal, the conductivity can be improved and the charge / discharge cycle performance can be maintained for a long period of time.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a preferred embodiment,
The content of the different transition metal is 0.003 to 0.015 of transition metal / manganese with respect to the LixMnOy.

Further, in a preferred embodiment, the different transition metal is any one of Ni, Co and Fe.

Further, in a preferred embodiment,
LixMnOy obtained from the electrolytic manganese dioxide
Are LiMn ₂ O ₄ and LiMn ₂ O ₃ obtained from electrolytic manganese dioxide having a specific surface area of 0.5 to ² m ² .

[0014]

EXAMPLE FIG. 1 is an overall structural view showing an example of implementation of a non-aqueous electrolyte secondary battery according to the present invention. This battery 1 is a coin type non-aqueous electrolyte secondary battery. In this battery 1, a positive electrode 3 is put in a battery can 2 and a separator 4 is placed on the positive electrode 3.
After injecting the non-aqueous electrolytic solution, a battery lid 6 having a negative electrode 5 inside is covered, a gasket 7 is inserted in a gap between the battery lid 6 and the battery can 2, and the caulking is performed to seal. . The positive electrode 3 is obtained by filling the positive electrode current collector 8 with the positive electrode mixture 9 and pressurizing. The battery of this example is a coin battery, but can be applied to any battery such as a cylindrical spiral battery, a flat plate rectangular battery, and an inside-out cylindrical battery. It can also be applied to large batteries.

The feature of the present invention is that the positive electrode active material in the positive electrode mixture is LixMnO obtained by electrolytic manganese dioxide.
That is, a different transition metal is added to y. LixMnOy obtained from this electrolytic manganese dioxide is
LiMn ₂ O ₄ and LiMn ₂ O ₃ obtained from electrolytic manganese dioxide having a specific surface area of 0.5 to ² m ² are preferable. However, in addition to electrolytic manganese dioxide, any material having a high filling property such as manganese dioxide, manganese dioxide, 2 manganese oxide, and 3 manganese oxide can be used. The different transition metal is preferably any one of Ni, Co, and Fe, and the content thereof is preferably 0.003 to 0.015 with respect to the electrolytic manganese dioxide. As a method of containing a different transition metal,
In addition to a method of depositing particles from a solution and re-heat treatment, a chemical vapor deposition replacement method (CVD), an electroless plating method, an adsorption method, or the like can be used. As the negative electrode material, lithium metal, lithium alloy, carbon material capable of being doped or dedoped with lithium, and the like can be used.

The electrolytic solution is a solution prepared by dissolving 0.5 to 1.5 mol / L (liter) of an electrolyte in an organic solvent alone or in a mixed solvent. As the organic solvent, propylene carbonate, ethylene carbonate, butylene carbonate, γ-butyrolactone,
Dimethyl carbonate, ethyl methyl carbonate, acetic acid ester compound, propionic acid ester compound, diacetic acid ester compound, dimethoxyethane, diethoxyethane, dimethoxypropane, diethoxypropane, tetrahydrofuran,
A single solvent or a mixed solvent such as dioxolane is used. Further, as the electrolyte, lithium perchlorate, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, 6
Lithium fluorophosphate, lithium hexafluoroarsenate, or the like is used.

Next, the non-aqueous electrolyte secondary battery was used as the coin battery of FIG. 1, and the positive electrode active material in the positive electrode mixture was LiMn ₂ O ₄ obtained from electrolytic manganese dioxide and N which was a different transition metal.
i, Co, or Fe is added,
A battery performance test when the negative electrode material is a carbon material that can be doped and dedoped with lithium will be described.

Example 1 First, electrolytic manganese dioxide and lithium carbonate were weighed so that the atomic ratio of Mn: Li was 1: 0.5, mixed using a mortar, pressure-molded, and further mortar. Crush roughly with. Next, it is placed in an alumina crucible and heat-treated in an oxygen furnace in an oxygen atmosphere at 350 ° C. for 2 hours and 750 ° C. for 16 hours, and then cooled to room temperature to prepare LiMn ₂ O ₄ . This LiMn ₂ O ₄ had a peak corresponding to spinel type LiMn ₂ O ₄ in X-ray diffraction measurement. When the particle size distribution of this compound was measured with a laser measuring instrument, the 50% cumulative size was about 35 μm. In addition,
Comparative Example 1 was a case where this LiMn ₂ O ₄ was used as it was as a positive electrode active material.

Next, nickel nitrate is added in an amount of 0.005 mol / L.
It was dissolved in water to a concentration so that 500 ml was prepared.
29 g of the LiMn ₂ O ₄ is weighed and put into a nickel solution. While stirring this aqueous solution using a stirrer, a 5% LiOH aqueous solution was gradually added to adjust the pH of the solution to 9.0. In this state, stirring is continued for 1 hour. Next, this mixed liquid was filtered using a glass filter, the filtered solid portion was taken out, and dried at 100 ° C. for 12 hours under reduced pressure with a vacuum dryer. The obtained solid substance was further heat-treated at 500 to 700 ° C. for 10 hours to remove the residual hydroxyl group. In this manner we obtain a positive electrode active material Ni-LiMn ₂ O ₄ of Example 1.

Example 2 In the same steps as in Example 1, nickel nitrate was dissolved in water to a concentration of 0.015 mol / L to prepare 500 ml, and 29 g of LiMn ₂ O ₄ was treated. It is vacuumed and dried, and the positive electrode active material Ni-L of Example 2 is used.
iMn ₂ O ₄ is obtained.

<Example 3> In the same process as in Example 1, nickel nitrate was dissolved in water to a concentration of 0.003 mol / L to prepare 500 ml, and 29 g of LiMn ₂ O ₄ was treated, The positive electrode active material Ni-L of Example 3 after vacuum drying.
iMn ₂ O ₄ is obtained.

Comparative Example 2 In the same process as in Example 1, nickel nitrate was dissolved in water to a concentration of 0.02 mol / L to prepare 500 ml, and 29 g of LiMn ₂ O ₄ was treated. It is vacuumed and dried, and the positive electrode active material of Comparative Example 2 is Ni-Li.
Mn ₂ O ₄ is obtained.

Example 4 First, cobalt nitrate was added to 0.0
Dissolve in water to a concentration of 05 mol / L, 500m
1 was prepared. LiMn produced in the same manner as in Example 1
29 g of ₂ O ₄ is weighed and put into a cobalt solution. While stirring this aqueous solution using a stirrer, 5% Li
The pH of the solution was adjusted to 9.0 by slowly adding an OH aqueous solution. In this state, stirring is continued for about 1 hour. Next, this mixed liquid was filtered using a glass filter, the filtered solid portion was taken out, and dried at 100 ° C. for 12 hours under reduced pressure with a vacuum dryer. The obtained solid is further 500 to 70.
Heat treatment was performed at 0 ° C. for 10 hours to remove the residual hydroxyl group. Thus, the positive electrode active material Ni-Li of Example 4 was prepared.
Mn ₂ O ₄ is obtained.

Example 5 First, iron nitrate was dissolved in water to a concentration of 0.005 mol / L to prepare 500 ml. 29 g of LiMn ₂ O ₄ produced in the same manner as in Example 1 is weighed and charged into the iron solution. While stirring this aqueous solution using a stirrer, a 5% LiOH aqueous solution was gradually added to adjust the pH of the solution to 9.0. In this state, stirring is continued for about 1 hour. Next, this mixed liquid was filtered using a glass filter, the filtered solid portion was taken out, and dried at 100 ° C. for 12 hours under reduced pressure with a vacuum dryer. The obtained solid is 10 at 500 to 700 ° C.
Heat treatment was carried out for a period of time to remove the residual hydroxyl group. In this manner we obtain a positive electrode active material Ni-LiMn ₂ O ₄ of Example 5.

Table 1 shows Examples 1 to 5 and Comparative Examples 1 to 2 above.
2 is a table showing the positive electrode active material.

[0026]

[Table 1]

Using the positive electrode active material shown in Table 1, a charge / discharge test was conducted on a coin type battery. The coin type test battery in this case has a diameter of 20 mm and a height of 2.5 mm.
This coin type test battery was manufactured as follows. First, as a negative electrode, lithium metal having a thickness of 1.6 mm was punched into a diameter of 17 mm and pressed against the battery lid using a press machine.
Next, each positive electrode mixture was put into a battery can together with an aluminum net as a current collector in a pressure press device with a diameter of 15 m.
Put the positive electrode molded into m. In this case, each positive electrode mixture is prepared by mixing 90 parts by weight of each positive electrode active material, 7 parts by weight of graphite which is a conductive material, and 3 parts by weight of polyvinylidene fluoride which is a binder. Next, on the positive electrode, a polypropylene separator (Celguard # 250
2) is placed, and LiP is used as an electrolyte in a mixed organic solvent of propylene carbonate: diethyl carbonate = 1: 1.
A non-aqueous electrolyte solution in which 1 mol / L of F ₆ was dissolved was poured, covered with the battery lid, caulked with a gasket, and sealed to manufacture each coin-type test battery.

The batteries thus produced are shown in Table 2.

[0029]

[Table 2]

The following tests were carried out using the batteries shown in Table 2.

First, the battery was charged at a current of 0.5 mA / cm ² and an upper limit voltage of 4.2 V for 12 hours, and then discharged at a current of 0.5 mA / cm ² to 3.0 V. Next, the current is 1 mA / cm ² ,
Charged at the upper limit voltage of 4.2V for 5.5 hours, current 1mA / c
The cycle of discharging to 3.0 V at m ² was repeated 5 times. Two batteries are prepared for each battery, and after repeating the charge / discharge cycle 5 times as described above, one battery is
As a discharge load performance test, the battery was charged at a current of 1 mA / cm ² and an upper limit voltage of 4.2 V for 5.5 hours, and a current of 0.5 to 5 mA /
The test of discharging to 3.0 V in cm ² was repeated 5 times. As another charge / discharge cycle test, the other battery was repeatedly charged with a current of 1 mA / cm ² and an upper limit voltage of 4.2 V for 5.5 hours and then discharged to 3.0 V at a current of 1 mA / cm ² repeatedly. .

FIG. 2 shows the results of the discharge load performance test,
FIG. 3 shows the result of the charge / discharge cycle test.

As is apparent from FIGS. 2 and 3, a positive electrode active material obtained by adding an appropriate amount of any one of different transition metals Ni, Co and Fe to LiMn ₂ O ₄ obtained from electrolytic manganese dioxide was used. The non-aqueous electrolyte secondary battery used was Li
Non-aqueous electrolyte secondary battery using a positive electrode active material containing only Mn ₂ O ₄ or non-aqueous electrolyte using a positive electrode active material obtained by adding LiMn ₂ O ₄ to Ni, Co or Fe in an inappropriate amount. It can be seen that the discharge load performance and the charge / discharge cycle performance (performance for maintaining a high capacity) are superior to the electrolytic solution secondary battery. The reason for this is that the spinel-type LiMn ₂ O ₄ has the property as an oxide that it functions as a resistor when lithium moves, but by adding an appropriate amount of a different kind of transition metal, the surface of LiMn ₂ O ₄ can be added. It is presumed that a compound similar to lithium nickelate, lithium cobaltate, etc. is formed and the properties can be greatly improved. Also, Ni, C
O and Fe are extremely effective in terms of conductivity as compared with manganese compounds.

L obtained from electrolytic manganese dioxide
By using the technique of the present invention in which iMn ₂ O ₄ is added with an appropriate amount of any one of different kinds of transition metals, Ni, Co, and Fe, alteration of the positive electrode active material itself due to charge / discharge cycles and deterioration of the surface thereof. It is estimated that this can be effectively suppressed. In particular, since the spinel type manganese compound has a tunnel structure, it is considered that the crystal structure easily serves as a resistance layer when lithium is transferred, which is one of the causes of structural deterioration.

If the reheat treatment temperature is too high after the treatment with the transition metal compound, in addition to the removal of the remaining hydroxyl groups, the transition metal oxide layer is promoted near the surface to easily form an insulating layer. Therefore, it is considered that the oxidation of the additional element and the conversion to the lithium compound can be effectively promoted by treating the reheat treatment temperature at a temperature lower by 100 to 200 ° C. than the initial heat treatment temperature.

When a large amount of the transition metal is treated, the capacity is lowered and the effect of reducing the resistance of the doped / dedoped surface of lithium is offset, and if the amount of the treatment is too small, the performance cannot be expected and the untreated surface is the same. turn into. Therefore, as described above, it is necessary to treat the transition metal in an appropriate amount.

The positive electrode active material does not necessarily have to be produced from electrolytic manganese dioxide, and may be produced from manganese oxides thereof by using manganese oxyhydroxide, manganese nitrate, manganese carbonate, or the like. The effect of can be expected. 150 μm when using these materials
It is effective to remove the above large particles.

In particular, when electrolytic manganese dioxide is used, there are great merits in terms of cost and significant improvement in filling property (high density, high capacity). . Specifically, the tap density of chemically synthesized manganese dioxide is 1.8, whereas the tap density of electrolytic manganese dioxide can be 2.1 or more.

[0039]

As described above, in the present invention, the positive electrode active material is L obtained from electrolytic manganese dioxide.
Since a different transition metal is added to ixMnOy, the density can be increased even when the positive electrode is pressure-molded into a sheet for high performance and size reduction of the battery. A high capacity non-aqueous electrolyte secondary battery can be obtained by using the active material.

Since the positive electrode active material contains a different transition metal, the conductivity can be improved, and the non-aqueous electrolyte secondary battery using this positive electrode active material has a long charge / discharge cycle performance. Can be maintained for a period of time. Further, as shown in the examples, the performance of the binder can be sufficiently exhibited at 5 to 8%.

Furthermore, a non-aqueous electrolyte secondary battery having the same performance as that of a high-priced lithium ion battery can be provided at low cost.

[Brief description of drawings]

FIG. 1 is an overall structural diagram showing an example of implementation of a non-aqueous electrolyte secondary battery according to the present invention.

FIG. 2 is a graph showing the results of a discharge load performance test of a non-aqueous electrolyte secondary battery.

FIG. 3 is a graph showing the results of a charge / discharge cycle test of a non-aqueous electrolyte secondary battery.

[Explanation of symbols]

1: Non-aqueous electrolyte secondary battery, 2: Battery can, 3: Positive electrode, 4:
Separator, 5: negative electrode, 6: battery lid, 7: gasket,
8: Positive electrode current collector, 9: Positive electrode mixture

Claims (4)

[Claims] 1. A non-aqueous electrolyte secondary battery, wherein the positive electrode active material has a structure in which a different transition metal is added to LixMnOy obtained from electrolytic manganese dioxide. 2. The content of the different transition metal is the Li
0.003 to 0.003 of transition metal / manganese with respect to xMnOy
The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery is 0.015. 3. The different transition metal is Ni, Co, Fe.
The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery is any one of the above. 4. L obtained from the electrolytic manganese dioxide
ixMnOy is LiMn ₂ O ₄ or LiMn obtained from electrolytic manganese dioxide having a specific surface area of 0.5 to ² m ^2.
The non-aqueous electrolyte secondary battery according to claim 1, which is ₂ O ₃ .